Soil Taxonomy
A Basic System of Soil Classification for
Making and Interpreting Soil Surveys
Second Edition, 1999
United States Department of Agriculture
Natural Resources Conservation Service
Soil Taxonomy
A Basic System of Soil Classification for Making
and Interpreting Soil Surveys
Second Edition, 1999
By Soil Survey Staff
United States Department of Agriculture Agriculture Handbook
Natural Resources Conservation Service Number 436
4
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5
Table of Contents
Foreword.................................................................................................................................... 7
Chapter 1: The Soils That We Classify ...................................................................................9
Chapter 2: Soil Taxonomy and Soil Classification ................................................................. 15
Chapter 3: Differentiae for Mineral Soils and Organic Soils .................................................19
Chapter 4: Horizons and Characteristics Diagnostic for the Higher Categories ...................21
Chapter 5: Application of Soil Taxonomy to Soil Surveys .................................................. 115
Chapter 6: The Categories of Soil Taxonomy...................................................................... 119
Chapter 7: Nomenclature .................................................................................................... 125
Chapter 8: Identification of the Taxonomic Class of a Soil.................................................. 159
Chapter 9: Alfisols .............................................................................................................. 163
Chapter 10: Andisols.............................................................................................................. 271
Chapter 11: Aridisols ............................................................................................................ 329
Chapter 12: Entisols.............................................................................................................. 389
Chapter 13: Gelisols .............................................................................................................. 445
Chapter 14: Histosols ........................................................................................................... 473
Chapter 15: Inceptisols ......................................................................................................... 489
Chapter 16: Mollisols ........................................................................................................... 555
Chapter 17: Oxisols ............................................................................................................... 655
Chapter 18: Spodosols ......................................................................................................... 695
Chapter 19: Ultisols .............................................................................................................. 721
Chapter 20: Vertisols ............................................................................................................. 783
Chapter 21: Family and Series Differentiae and Names ........................................................ 819
Chapter 22: Soils of the United States .................................................................................. 837
Chapter 23: World Distribution of Orders and Suborders .................................................... 851
Appendix ................................................................................................................................ 857
Index ....................................................................................................................................... 863
Maps of the United States and of the World
7
The second edition of Soil Taxonomy: A Basic System of
Soil Classification for Making and Interpreting Soil Surveys is
the result of the collective experience and contributions of
thousands of pedologists from around the world.
This new edition includes many improvements. Two new
soil orders, Andisols and Gelisols, are added. Low-activity
clays are defined, and taxa are developed. The Aridisol,
Alfisol, Histosol, Inceptisol, Mollisol, Oxisol, Spodosol, and
Vertisol orders are updated. Aquic conditions, episaturation,
and oxyaquic subgroups are defined. Additions and
improvements are made at the family level.
We are indebted to our many colleagues throughout the
world who contributed soil descriptions and data, comments,
suggestions, and criticisms. We are especially grateful to all of
those who organized and hosted workshops and training
sessions. Many pedologists provided input to the International
Committees (ICOM’s), and we are thankful for their
participation. Although we cannot list everyone who offered
assistance, we do want to acknowledge the chairpersons of the
various ICOM’s.
ICOM Chairperson Institute
Low Activity
Clays ................ Frank Moormann............. Univ. of Utrecht
Oxisols ............... Stan Buol ......................... North Carolina
State Univ.
Andisols ............. Frank Leamy.................... Soil Bureau,
Lower Hutt
Aquic Soils ........ Johan Bouma ................... Agricultural Univ.,
Wageningen
Spodosols ........... Robert Rouke ................... Univ. of Maine
Vertisols ............. Juan Comerma ................. Univ. Centro
Venezuela
Aridisols ............ Ahmed Osman ................. Arab Center for
the Studies of
Arid Zones and
Dry Lands
Soil Families...... Ben Hajek ........................ Auburn Univ.
Gelisols .............. James Bockheim .............. Univ. of Wisconsin
Although many improvements have been made since
Dr. Guy Smith headed the effort to publish the first edition of
Soil Taxonomy, there are still areas that will require a
concerted effort to improve. The taxonomic system will
continue to evolve as the science matures.
The taxonomic system does not adequately address the
anthropogenic effects on soils. Soils in urban/industrial areas
can be drastically altered by landfills, farming, earth
movement, and heavy metal contamination. Agricultural areas
have undergone erosion, ripping, and land leveling. Drastically
disturbed soils are common in regions where precious metals,
rock aggregate, and fossil fuels have been mined. The
International Committee on Anthropogenic Soils
(ICOMANTH), chaired by Dr. Ray Bryant, is currently
meeting the challenge of developing appropriate taxa for these
unique soils.
Soil moisture regimes and intergrades of soil moisture
regimes need to be better defined. Some of the temperature
regimes need refinement. The International Committee on Soil
Moisture and Temperature Regimes (ICOMMOTR), chaired by
Dr. Ron Paetzold, is gathering data to make needed
improvements.
The system of soil taxonomy currently does not provide for
paleosols formed under remarkably different
paleoenvironments. With age, the properties of soils from
paleo and contemporaneous environments become welded.
Yet, when paleosols are well preserved, they are valuable
proxies of the biological and physiochemical evolution of the
earth. Many paleosols are deeper than the 2 m limit set by the
current system of soil taxonomy. There is now and will
continue to be pressure to observe and classify soils beyond the
2 m limit.
Many pedologists developed proposals, made comments and
suggestions, and reviewed chapters for this second edition.
Because of the concerted effort of many, the author of this
publication is identified as the “Soil Survey Staff.”
We would like to acknowledge those who helped write
chapters or provide data for figures, maps, and tables. They
include Dr. Arnt Bronger, Dr. Hari Eswaran, Dr. Samuel
Indorante, Dr. John Kimble, Henry Mount, Loyal Quandt, Paul
Reich, Sharon Waltman, and Dr. John Witty. Dr. Stanley
Anderson had the arduous task of editing the second edition.
Suzann Meierdierks and Dr. Patricia West provided their able
assistance in the editing and formatting process. Adrian Smith,
Foreword
8
Christopher Roll, and Nathan Kress provided invaluable GIS
expertise. Lastly, Dr. Robert Ahrens coordinated the effort. He
and Robert Engel worked tirelessly during the past few years to
prepare this edition.
Assistance in acquiring photographs for this publication was
provided by the Kentucky Association of Soil Classifiers; the
Washington Society of Professional Soil Scientists; the
University of Nebraska Press and Andrew A. Aandahl; the
Alaska/Yukon Society of Professional Soil Scientists; the
Florida Association of Professional Soil Classifiers; the Society
of Soil Scientists of Southern New England—Massachusetts;
the Kansas Association of Professional Soil Classifiers; the Soil
Classifiers Association of Michigan; the Professional Soil
Classifiers Association of Alabama; the Professional Soil
Scientists Association of Texas; and members of the National
Cooperative Soil Survey.
Horace Smith
Director, Soil Survey Division
9
The word “soil,” like many common words, has several
meanings. In its traditional meaning, soil is the natural
medium for the growth of land plants, whether or not it has
discernible soil horizons. This meaning is still the common
understanding of the word, and the greatest interest in soil is
centered on this meaning. People consider soil important
because it supports plants that supply food, fibers, drugs, and
other wants of humans and because it filters water and recycles
wastes. Soil covers the earth’s surface as a continuum, except on
bare rock, in areas of perpetual frost or deep water, or on the
bare ice of glaciers. In this sense, soil has a thickness that is
determined by the rooting depth of plants.
About 1870, a new concept of soil was introduced by the
Russian school led by Dokuchaiev (Glinka, 1927). Soils were
conceived to be independent natural bodies, each with a unique
morphology resulting from a unique combination of climate,
living matter, earthy parent materials, relief, and age of
landforms. The morphology of each soil, as expressed by a
vertical section through the differing horizons, reflects the
combined effects of the particular set of genetic factors
responsible for its development.
This was a revolutionary concept. One did not need to
depend wholly on inferences from the underlying rocks, the
climate, or other environmental factors, considered singly or
collectively; rather, the soil scientist could go directly to the soil
itself and see the integrated expression of all these in its
morphology. This concept made it not only possible but also
necessary to consider all soil characteristics collectively, in
terms of a complete, integrated, natural body, rather than
individually. Thus, the effect of any one characteristic or a
difference in any one depends on the others in the combination.
Experience has shown that no useful generalizations about
single characteristics can be made for all soils. Characteristics
are given weight according to the knowledge gained through
research and experience in soil genesis and the responses of soil
to management or manipulation. Both research in genesis and
the responses of soils have vital roles, but they are themselves
one step removed from the taxonomy of the soil, which is based
on combinations of soil characteristics. In short, the new
concept made pedology possible.
The Russian view of soils as independent natural bodies that
have genetic horizons led to a concept of soil as the part of the
earth’s crust that has properties reflecting the effects of local
and regional soil-forming agents. The solum in that concept is
the set of genetic horizons developed by soil-building forces,
but the parent material beneath is nonsoil. This concept has
limitations. If a solum is 1 or 2 m thick, there is little conflict
between the concept of soil as solum and the concept of soil as
the natural medium for the growth of terrestrial plants. If genetic
horizons are thin or absent and unconsolidated parent material
lies at or only a few centimeters below the surface, there is
serious conflict between the concepts. Dokuchaiev realized this
conflict and, despite the lack of horizons, included young
alluvium and peat in his classification of soil.
Soil in this text is a natural body comprised of solids
(minerals and organic matter), liquid, and gases that occurs on
the land surface, occupies space, and is characterized by one or
both of the following: horizons, or layers, that are
distinguishable from the initial material as a result of additions,
losses, transfers, and transformations of energy and matter or
the ability to support rooted plants in a natural environment.
This definition is expanded from the previous version of Soil
Taxonomy to include soils in areas of Antarctica where
pedogenesis occurs but where the climate is too harsh to
support the higher plant forms.
The upper limit of soil is the boundary between soil and air,
shallow water, live plants, or plant materials that have not begun
to decompose. Areas are not considered to have soil if the
surface is permanently covered by water too deep (typically
more than 2.5 m) for the growth of rooted plants. The horizontal
boundaries of soil are areas where the soil grades to deep water,
barren areas, rock, or ice. In some places the separation between
soil and nonsoil is so gradual that clear distinctions cannot be
made.
The lower boundary that separates soil from the nonsoil
underneath is most difficult to define. Soil consists of the
horizons near the earth’s surface that, in contrast to the
underlying parent material, have been altered by the
interactions of climate, relief, and living organisms over time.
Commonly, soil grades at its lower boundary to hard rock or to
earthy materials virtually devoid of animals, roots, or other
marks of biological activity. The lowest depth of biological
activity, however, is difficult to discern and is often gradual.
For purposes of classification, the lower boundary of soil is
arbitrarily set at 200 cm. In soils where either biological
activity or current pedogenic processes extend to depths greater
than 200 cm, the lower limit of the soil for classification
purposes is still 200 cm. In some instances the more weakly
cemented bedrocks (paralithic materials, defined later) have
been described and used to differentiate soil series (series
The Soils That We Classify
CHAPTER 1
10 Soil Taxonomy
control section, defined later), even though the paralithic
materials below a paralithic contact are not considered soil in
the true sense. In areas where soil has thin cemented horizons
that are impermeable to roots, the soil extends as deep as the
deepest cemented horizon, but not below 200 cm. For certain
management goals, layers deeper than the lower boundary of the
soil that is classified (200 cm) must also be described if they
affect the content and movement of water and air or other
interpretative concerns.
In the humid tropics, earthy materials may extend to a depth
of many meters with no obvious changes below the upper 1 or 2
m, except for an occasional stone line. In many wet soils, gleyed
soil material may begin a few centimeters below the surface and,
in some areas, continue down for several meters apparently
unchanged with increasing depth. The latter condition can arise
through the gradual filling of a wet basin in which the A horizon
is gradually added to the surface and becomes gleyed beneath.
Finally, the A horizon rests on a thick mass of gleyed material
that may be relatively uniform. In both of these situations, there
is no alternative but to set the lower limit of soil at the arbitrary
limitof200cm.
Soil, as defined in this text, does not need to have discernible
horizons, although the presence or absence of horizons and
their nature are of extreme importance in soil classification.
Plants can be grown under glass in pots filled with earthy
materials, such as peat or sand, or even in water. Under proper
conditions all these media are productive for plants, but they are
nonsoil here in the sense that they cannot be classified in the
same system that is used for the soils of a survey area, county,
or even nation. Plants even grow on trees, but trees are regarded
as nonsoil.
Soil has many properties that fluctuate with the seasons. It
may be alternately cold and warm or dry and moist. Biological
activity is slowed or stopped if the soil becomes too cold or too
dry. The soil receives flushes of organic matter when leaves fall
or grasses die. Soil is not static. The pH, soluble salts, amount of
organic matter and carbon-nitrogen ratio, numbers of microorganisms,
soil fauna, temperature, and moisture all change with
the seasons as well as with more extended periods of time. Soil
must be viewed from both the short-term and long-term
perspective.
Buried Soils
A buried soil is covered with a surface mantle of new soil
material that either is 50 cm or more thick or is 30 to 50 cm thick
and has a thickness that equals at least half the total thickness
of the named diagnostic horizons that are preserved in the
buried soil. A surface mantle of new material that does not have
the required thickness for buried soils can be used to establish a
phase of the mantled soil or even another soil series if the mantle
affects the use of the soil.
Any horizons or layers underlying a plaggen epipedon are
considered to be buried.
A surface mantle of new material, as defined here, is largely
unaltered, at least in the lower part. It may have a diagnostic
surface horizon (epipedon) and/or a cambic horizon, but it has
no other diagnostic subsurface horizons, all defined later.
However, there remains a layer 7.5 cm or more thick that fails the
requirements for all diagnostic horizons, as defined later,
overlying a horizon sequence that can be clearly identified as
the solum of a buried soil in at least half of each pedon. The
recognition of a surface mantle should not be based only on
studies of associated soils.
The Pedon, a Unit of Sampling
Few soil properties can be determined from the surface. To
determine the nature of a soil, one must study its horizons, or
layers. This study requires pits or some means of extracting
samples of material from the surface to the base of the soil. The
visible and tactile properties of samples can be studied in the
field. Soil moisture and temperature regimes are studied by
observations of changes over time at points selected to be
representative. Other properties of a soil must be learned by
studies of samples in an appropriate place, usually a laboratory.
In other words, one learns about most of the properties of a soil
by studying samples extracted to represent a sampling unit, not
by study of the whole soil body that is classified. A concept of
what to sample must be developed before soils can be classified
in a manner that meets the needs of the soil survey, and different
concepts might lead to different classifications. The concept
presented in this text is not the only one possible, and, in fact,
its logic has been scrutinized (Holmgren, 1988).
A soil commonly is not uniform in all its properties. Variability
may be due to accidents; events that lack definite order, such as
the development of fractures in a hard rock; variations in
deposits left by running water; or the placement of seeds by
wind or by animals. The influence of the biotic factors tends to
produce many examples of variability in a soil. Burrowing
animals, taprooted plants, falling trees, and plants that collect
different elements do not operate uniformly over large areas. A
filled burrow or a trace left by a taproot can result in holes in
horizons filled by contrasting materials. Salts collected by a
desert shrub remain concentrated below the shrub until it dies.
Shrink-swell and freeze-thaw processes are other factors that
contribute to soil variability.
The transition between two soils that differ in a particular
property or set of properties may be of at least two kinds.
Normally, a given horizon of one soil disappears over
horizontal distance by a gradual weakening of its expression.
However, in some places the horizons become intermittent
either with or without a marked decrease in the strength of
expression. The transitional forms having discontinuous
horizons or horizons that vary greatly in thickness or other
properties are not the rule, but the soils have been troublesome
to classify. One must decide whether the area is one soil in
which a horizon is discontinuous or variable, or two soils.
The Soils That We Classify 11
Trouble cannot be avoided by arbitrarily saying that two soils
are present if a diagnostic property or horizon is present in
some spots and not present in others. Some limit of area must
be set. If one sets no limit, a vertical hole made by a burrowing
animal would be considered “nonsoil.” It would become a soil
when filled or, if a coating were present, the coating would be
considered a soil. This would be absurd. Such a soil could not
support plants, could not have structure, and could not be
sampled for determination of its properties. The view that a
minimum areal limit of “a soil” cannot be set, if carried to the
extreme, leads to other odd conclusions. For example, if
columns or prisms were present, the exteriors of the prisms
would be different soils from the interiors wherever there are
coatings on the exteriors. In a structureless soil, a definition of
the smallest area of “a soil” as equivalent to the size of the
largest ped would have no meaning. No escape from a
minimum limit to the area of “a soil” seems possible. The
concept of the pedon (Gr. pedon, ground; rhymes with head on)
offers a partial solution to this problem and provides a clear
basis for soil descriptions and for the selection of soil samples.
A pedon has the smallest volume for which one should
describe and sample the soil to represent the nature and
arrangement of its horizons and variability in the properties that
are preserved in samples. A pedon is comparable in some ways
to the unit cell of a crystal. It has three dimensions. Its lower
limit is the somewhat vague limit between the soil and “nonsoil”
below. Its lateral dimensions are large enough to represent the
nature of any horizons and variability that may be present. A
horizon may vary in thickness or in composition, or it may be
discontinuous. The minimal horizontal area of a pedon is
arbitrarily set at 1 m2
, but it ranges to 10 m2
, depending on the
variability in the soil.
In the usual situation, where all horizons are continuous and
of nearly uniform thickness and composition, the pedon has a
horizontal area of about 1 m2
. Photo 1 shows the normal
situation in which horizons are continuous and relatively
Photo 1.—A soil that has continuous horizons, in an area of Wyoming.
12 Soil Taxonomy
uniform in thickness over considerable areas. The mollic
epipedon and calcic horizon extend for hundreds of meters in
areas of this Wyoming landscape. Each pedon includes the
range of variability that is present in a small volume. The pedon
is roughly polygonal. One lateral dimension does not differ
greatly from any other. The size of a pedon can be determined
only by examination of a volume that is appreciably larger than
the pedon.
Where horizons are intermittent or cyclic and recur in linear
intervals of 2 to 7 m (roughly 7 to 23 ft), the pedon includes onehalf
the cycle. Thus, each pedon includes the range of variability
that occurs within these small areas, but not necessarily the total
variability included in other similar pedons studied over a large
area. Where the cycle is less than 2 m, the horizontal area of a
pedon is the minimum size, 1 m2
.
Depending on the concept of soil and of the pedon, there
could be different classifications of the soils. With the concept
of soil and of the pedon that is outlined here, the pedons of
some soils may include markedly differing sequences of
horizons. The following examples clarify the concept of a pedon
that has intermittent horizons.
Photo 2 illustrates a soil near Brugge, Belgium, in an area that
is covered by eolian sand of Wisconsin (Wurm) age. The plow
layer, 35 cm thick, is very dark brown fine sand or loamy fine
sand. Most sand grains are free of visible coatings. The lower
boundary of the plow layer is abrupt and irregular and shows
many clear spade marks.
The next layer is a discontinuous B horizon that consists of
at least three materials. The first of these is dark brown (7.5YR
3/4, moist) fine sand with nodules. The nodules range from
about 5 to 20 cm in diameter and are firm or friable in the interior
but have a very firm crust about one-half cm thick. The crust has
stronger chroma and redder hue than the interior, suggesting the
segregation of iron. The interiors of the nodules are free of
roots.
The second material is very friable, massive, grayish brown
(10YR 5/2, moist) fine sand that has many fine fibrous roots. It
would normally be considered parent material, the C horizon,
Photo 2.—A sandy soil near Brugge, Belgium.
The Soils That We Classify 13
where it underlies the nodules of the B horizon; however, it
surrounds the nodules and continues down with little change to
a thin layer of buried muck that has been dated by radiocarbon
as Allerod (Two Creeks), about 11,000 years B.P.
The third material is very friable, massive fine sand that is
present in gross, more or less tubular forms as much as 60 cm in
diameter. The sand is similar to the second material in color but
has many weak, fine dark gray and very dark gray lamellae or
fibers that are comparable to those in or below the B horizon of
the sandy soils formed under heath.
The history of this soil has been studied by the staff of the
Institute for Soil Survey, IRSIA, Ghent.1
While under forest,
the soil was brown and had no clearly expressed eluvial or
illuvial horizons. After clearing of the forest and invasion of
the heather (Calluna vulgaris), a dark colored illuvial horizon
that contained amorphous compounds or mixtures of organic
matter, iron, and aluminum (see spodic horizon) formed.
During the 17th and 18th centuries, flax became an important
crop in Flanders, and the linen was woven in the farm homes
1
Personal communication from R. Tavernier.
Photo 3.—A soil in the Yukon Territory of Canada.
in the winter. To obtain high yields of high-quality flax, large
amounts of manure and chalk were applied to the fields. The
influence of the calcium and nitrogen was to destroy the B
horizon of amorphous materials, first in spots and then
completely. Photo 2 shows that the B horizon has been partly
destroyed. Because discontinuous horizons recur at intervals of
less than 1 m, the pedon has an area of 1 m2
.
The processes of either formation or destruction of many
horizons may not operate uniformly and may first produce
intermittent horizons. In places the forces operate with
remarkable uniformity and produce faint but continuous
horizons. Genetically, therefore, the discontinuous horizons can
have significance equivalent to weakly expressed but
continuous horizons.
Many cold soils are subject to physical disturbance as a
result of freezing and thawing. The forces generated through
freezing often produce cyclic or intermittent horizons. Photo 3
shows a soil from the Yukon Territory of Canada. The small
orange squares mark the boundary between permafrost and the
active layer. The organic layer is about 40 cm thick in the lowlying
areas and about 20 cm thick in the areas of higher
14
microrelief. This pattern is repeated at linear intervals of about
1 m. The pedon in photo 3 is 1 m2
. Soil taxonomy has taxa at
the subgroup level of Gelisols to deal with the range in
thickness of the organic layers.
Although every pedon can be classified, not every pedon
need be classified. The pedon should represent a segment of the
landscape. Sometimes, pedons that represent a segment of the
landscape are referred to as polypedons. Soil scientists should
try to sample, characterize, and classify representative pedons.
Soil taxonomy provides a means of comparing, describing, and
differentiating these various pedons.
Summary
Since the genesis of a soil may not be understood or may be
disputed, it can be used only as a guide to our thinking in
selecting criteria and forming concepts. Generally, a more or
less arbitrary definition of a pedon serves the purpose of
classification better at this time than a genetic one. For that
reason, the following definition is used: A pedon is a threedimensional
body of soil that has lateral dimensions large
enough to include representative variations in the shape and
relation of horizons and in the composition of the soil. Its
horizontal area ranges from 1 to 10 m2
, depending on the
nature of the variability in the soil, and its volume varies,
depending on the depth of the soil. Where the cycle of
variations is less than 2 m long and where all horizons are
continuous and of nearly uniform thickness, the pedon has a
horizontal area of approximately 1 m2
. Where horizons or
other properties are intermittent or cyclic and recur at linear
intervals of 2 to 7 m, the pedon includes one-half of the cycle.
If horizons are cyclic but recur at intervals of more than 7 m,
the pedon reverts to an area of approximately 1 m2
and more
than one soil is usually represented in each cycle.
Literature Cited
Glinka, K.D. 1927. Dokuchaiev’s Ideas in the Development
of Pedology and Cognate Sciences. 32 p. In Russian Pedology.
Invest. I. Acad. Sci. USSR, Leningrad.
Holmgren, G.G.S. 1988. The Point Representation of Soil.
SoilSci.Soc.Am.J.52:712-716.
15
The primary objective of soil taxonomy is to establish
hierarchies of classes that permit us to understand, as
fully as possible, the relationship among soils and between
soils and the factors responsible for their character. A second
objective is to provide a means of communication for the
discipline of soil science. Soil taxonomy was originally
developed to serve the purposes of soil survey. During the last
few decades, it has evolved into a means of communication in
soil science.
Taxonomy is a narrower term than classification.
Classification includes taxonomy, but it also includes the
grouping of soils according to limitations that affect specific
practical purposes, such as the soil limitations affecting the
foundations of buildings. Taxonomy is the part of classification
that is concerned primarily with relationships. Classifications
are contrivances made by humans to suit their purposes. They
are not themselves truths that can be discovered. A perfect
classification would have no drawbacks when used for the
purpose intended. Each distinctly different purpose, to be
served best, demands a different classification.
For the different purposes of the soil survey, classes are
needed that can be grouped or subdivided and regrouped to
permit the largest number and the most precise predictions
possible about responses to management and manipulation.
Consequently, not one but many classifications can be drawn
from the basic taxonomy. Flexibility in the classes of the
taxonomic system is achieved by the use of phases and by the
nomenclature. The phases are used to subdivide taxa according
to the practical needs for the purposes of a particular survey or
interpretation. They are discussed later in this chapter.
Flexibility in the hierarchy permits grouping taxa into
successively smaller numbers as one goes from lower to higher
categories. For some purposes it is useful to group taxa that
have been separated at a higher level in the system. For
example, one might want a group that includes all soils that
are waterlogged for extended periods. For other purposes one
might want a group comprised of all soils that have a B
horizon affected by sodium or of all soils that have a fragipan
or permafrost. Some soils might be in several of these groups,
so that no matter how a single hierarchy is arranged, it is not
possible to have all desired groups. Therefore, no single
hierarchy can best serve all our purposes. The way we attain
flexibility in the hierarchy is explained in the discussion of the
nomenclature.
As knowledge expands, new facts or closer approximations
of truths not only make improvements in classification possible
but also make some changes imperative. Thus, classifications
are not static but require change as knowledge expands.
Since the original edition of Soil Taxonomy was published in
1975, eight international committees have made proposals
that have been approved and incorporated. These committees
include the International Committee on Low Activity Clays
(ICOMLAC), the International Committee on Oxisols
(ICOMOX), the International Committee on Andisols
(ICOMAND), the International Committee on Spodosols
(ICOMOD), the International Committee on Aquic Moisture
Regimes (ICOMAQ), the International Committee on Vertisols
(ICOMERT), the International Committee on Aridisols
(ICOMID), the International Committee on Families
(ICOMFAM), and the International Committee on PermafrostAffected
Soils (ICOMPAS).
Taxonomy of soils is a controversial subject. In part,
controversy reflects differences in the purposes for which
taxonomic classifications are made and differences in concepts
of soil as well as differences in opinion about the taxonomy of
soils. One cannot say that one taxonomic classification is better
than another without reference to the purposes for which both
were made, and comparisons of the merits of taxonomies made
for different purposes can be useless.
The Attributes of Soil Taxonomy
Soil surveys require many nontaxonomic classifications that
can be related to the real bodies of soil and that facilitate
comparisons of both similarities and differences among them
for a great variety of purposes. These classifications are used to
determine whether experience at one location is applicable to
the soils of other locations. The classifications may have to be
used by a pedologist to apply the experience of others for soils
that are unfamiliar. Many persons with diverse backgrounds
and training are expected to use the classifications accurately to
transfer experience with the behavior of soils under a variety of
uses. These intended uses of the classifications impose some
specific requirements on the taxonomy that stands behind the
classifications. The attributes of soil taxonomy are described in
the following paragraphs.
First, the definition of each taxon carries as nearly as
possible the same meaning to each user. Definitions in soil
taxonomy are operational. It is insufficient to say that the soils
in one taxon are differentiated from others by high organicCHAPTER
2
Soil Taxonomy and Soil Classification
16 Soil Taxonomy
matter content because what is considered high in one place
may be considered low in another. The disadvantage of
definitions, of course, is that distinctions are made that may
not be meaningful for every conceivable use of the soil. Only by
operational definitions can competent pedologists with diverse
backgrounds arrive at the same classification of the same kind
of soil.
Second, soil taxonomy is a multicategoric system. Many
taxa are needed in the lower categories because many
properties are important to the use of a soil. Specific properties
can vary independently of others, and their importance depends
on their combination with other properties. Taxa in the lower
categories, therefore, must be defined as specifically as possible
in terms of many properties. This requirement results in more
taxa in the lower categories than the mind can comprehend.
Consequently, the taxa must be grouped on some rational basis
into progressively smaller numbers of classes of higher
categories in a manner that permits the mind to grasp the
concepts and relationships of all taxa. The mind readily grasps
5 to 12 items, but it cannot deal simultaneously with 100 to
1,000 items without some ordering principle. Higher categories
are necessary for organizing and understanding the lower
categories and, in addition, they can be useful in comparing
soils of large areas. They have only limited value for
transferring experience to a specific site for a specific use.
Third, the taxa represent real bodies of soil that are known to
occupy geographic areas. Pedologists are concerned with
mapping real bodies of soil, and a classification related to these
real bodies facilitates the mapping (Cline, 1963). Soil taxonomy
does not try to provide for all possible combinations of
properties because the classification of kinds of soil that have
not been studied should not be prejudiced by a closed system
that covers all contingencies. Rather, soil taxonomy provides a
means to recognize new taxa when discovery leads to new
combinations of properties important to our purposes.
Fourth, differentiae are soil properties that can be observed
in the field or that can be inferred either from other properties
that are observable in the field or from the combined data of
soil science and other disciplines. Some of the most important
properties of the soil are chemical properties, and soil
taxonomy uses criteria in some taxa based on laboratory
measurements. Often data from laboratory measurements can
be interpolated to other areas, or pedologists discover physical
or morphological properties that reflect chemical
characteristics. Soil temperature, soil moisture, and other
properties that fluctuate with the seasons are difficult to use in
taxonomy unless they can be inferred by reasoning from the
combined data of soil science and other disciplines, such as
meteorology. Soil mineralogy can usually be inferred by
reasoning from the combined data of soil science and geology.
If there are no data that permit inferences about important but
invisible soil properties, it is probably best to defer classifying a
soil until some knowledge of its important properties is
available. A classification that is based on extremely limited
knowledge of an object has little utility.
Fifth, soil taxonomy is capable of modification to
accommodate new knowledge with a minimum of disturbance.
Taxa can be added or combined in any category without
disturbance of the rest of the system at the same or a higher
categorical level. If the highest category includes a number of
taxa defined by a variety of properties, the number can be
increased or decreased by combining or subdividing taxa
whenever experience convinces us that this is advisable. If one
taxon in the highest category is divided, no others in that
category need be affected. If two or parts of two are combined,
only those two or those parts are affected. Obviously,
combining taxa at a high level changes classes of lower
categories if they are members of those taxa. Adding taxa may
have no effect on the lower categories if the soils concerned
were not previously included in the system. If the addition is a
consequence of combining classes, it affects the lower
categories.
Sixth, the differentiae keep an undisturbed soil and its
cultivated or otherwise human-modified equivalents in the
same taxon insofar as possible. Changes produced by a single
or repeated plowing that mixes the surface soil to a depth of 18
to 25 cm (7 to 10 in), for example, have the least possible effect
on the placement of a soil in soil taxonomy. Truncation by
erosion does not change the classification of a soil until
horizons or diagnostic features important to the use or
identification of the soil have been lost. Consequently, insofar
as possible, the diagnostic horizons and features should be
those below the part of the soil affected by human activities.
However, significant changes in the nature of the soil by
humans cannot be ignored.
Seventh, soil taxonomy is capable of providing taxa for all
soils on a landscape. Soils form a continuum. The continuum
is broken into a reasonable number of segments that have
limited and defined ranges in properties so that quantitative
interpretations of soil behavior can be made.
Eighth, soil taxonomy provides for all soils that are known,
wherever they may be. Many kinds of soil are poorly
represented or are unknown in the United States. A system that
includes all known soils helps us to see the soils of the United
States in better perspective, particularly if a kind of soil is
poorly represented or is very extensive. It also helps us to draw
on experience in other countries with kinds of soil that are
poorly represented or are not extensive in the United States as a
whole but that are extensive locally.
Selection of Differentiae
To serve the purpose of the soil survey, the pedon should be
classified by its own properties and the taxa defined strictly in
terms of soil properties. In soil definitions, a given property,
such as particle-size distribution or pH, cannot be treated in an
Soil Taxonomy and Soil Classification 17
identical way for all soils. The significance of a difference in any
one property depends on the others in the combination that
makes a soil of a certain kind.
Soil color and the soil horizons are obvious properties that
have been used as differentiating characteristics at high
categoric levels in most taxonomies. Color per se seems to
have no accessory characteristics. For example, if one
considers all the soils that have brown color, no statement can
be made about them except that they are brown. There are
accessory characteristics for some colors in combination with
other properties, and the use of color as a differentiating
characteristic should be limited to these situations. A more
useful classification can be devised if properties that have more
accessory properties than color are used as differentiae in the
highest categories.
Soil horizons are the result of the dominance of one or more
sets of processes over other processes through time. The
processes themselves are not now suitable for use as
differentiae. The illuviation of clay, for example, cannot be
observed or measured in a soil. If illuviation has been a
significant process in the genesis of a soil, however, there
should be marks in the soil that indicate this process. These
marks need not be the same everywhere, but if the proper
marks are selected, the classification can reflect the dominance
of illuviation over other processes, such as those that mix
horizons and those that prevent the movement of clay.
The nature of the horizons is useful in defining the taxa of
soils that have horizons but is useless for soils that do not have
them. Of course, the absence of horizons is itself a mark of
significance. Many important properties of soils, however, are
not necessarily reflected by the combinations of horizons, and
many important processes do not themselves produce horizons.
Intensive mixing of soil by animals can destroy horizons. The
leaching of bases, particularly calcium, and the cycling of bases
by plants in humid climates can be reflected by changes in base
status with increasing depth but can be independent of the
kinds of horizons in a soil. The horizons, therefore, are not the
sole differentiating characteristics in defining taxa.
Some soil properties influence or control specific processes
and, through them, the genesis of the soil. Silicate clays cannot
form in a soil composed entirely of quartz, and apparently they
do not form if a soil is too cold. The soil moisture regime
influences the base status of a soil and the formation of
horizons with an accumulation of illuvial clay or of carbonates.
These are examples of soil properties that are causes of other
properties and that require consideration when properties are
selected to be used as differentiae for taxa.
The differentiae should be soil properties, but the most
useful properties for the higher categories may be either those
that result from soil genesis or those that affect soil genesis
because they have the greatest number of accessory properties.
For example, the clay percentage in soils commonly increases
and then decreases with increasing depth. In many soils
differences in the content of clay are the result of eluviation
and illuviation. In other soils they may be only the result of
stratification of the materials in which the soils developed. If
the horizons are genetic, they have accessory properties,
although the accessory properties may vary with the kind of
soil. If the climate is humid, the eluvial horizons and at least
part of the illuvial horizons are free of finely divided
carbonates because carbonates tend to immobilize clay and
because the leaching required to form an illuvial horizon is
greater than the leaching required to dissolve and remove the
carbonates. Time of the order of some thousands of years
without significant erosion is required. During this time there
is opportunity for nutrients used by plants to be systematically
concentrated in various horizons. In soils that formed under
grass in humid temperate regions, phosphorus seems to be
concentrated in the surface horizons, a considerable part of it
in organic compounds.
If the clay distribution in a soil is due solely to stratification
of parent materials, few other statements can be made about
that soil. The soil may be calcareous or acid. This example
illustrates why properties that are the result of soil genesis or
that affect soil genesis are important. They have accessory
properties. Some of the accessory properties are known, but it
is likely that many are still unknown.
In soil surveys the pedologist is commonly concerned with
finding the boundaries between map units. The boundaries are
in places where there has been or is a difference in one or more
of the factors that control soil genesis. The mapper learns to
look for these places and uses a knowledge of soil genesis to
improve the accuracy and efficiency of mapping. Genesis is
fundamental to soil taxonomy and to the soil survey. Genesis
itself, however, is unsuitable for direct use in soil taxonomy.
Because the genesis of a soil cannot be observed or measured,
pedologists may have widely differing opinions about it, and
the classification of a given pedon is affected by the
background of the pedologist.
Forming and Defining Taxa
When forming and defining the taxa, one must consider all
the known properties, although only a few can be
differentiating. The differentiating properties should be the
ones that are the most important for our purposes or that have
the most important accessory characteristics.
Research and experience indicate that some properties are
important to plant growth. Soil taxonomy attempts to make the
most important statements possible about the taxa. Those
properties that are important to plant growth and that result
from or influence soil genesis are considered in the higher
categories. Those that are important to plant growth but are
unrelated to genesis should be considered only for the lowest
categories. For example, in soils that are only slightly
weathered, the nature and amount of clay may be the result of
geologic accidents. If the differences are not extreme, the
course of soil genesis is not necessarily affected. Although the
18
difference between illite and smectite is important to plant
growth, it is used as a differentiating characteristic only at a
low category in the system, the family.
Determining the similarities among soils is not always a
simple matter. There may be similarity in particle-size
distribution to the members of one taxon and in base status to
the members of another. One must decide which property is the
more important, and this decision must rest on the nature of
the statements that one can make about the classes if the kind
of soil is grouped one way or the other. The best grouping
determines the definition; the definition does not determine the
grouping. If the grouping has imperfections, so does the
definition. The statements are about the nature of the soils and
the interpretations that can be made for the various phases of a
taxon. Interpretations are predictions of the consequences of
specific uses of soils, commonly in terms of plant growth under
specified systems of management but also in terms of
engineering soil behavior after a given manipulation.
Interpretations of the soils indicate the reasonable alternatives
for their use and management and the expected results. The
best grouping is one that helps us to make the most precise and
most important interpretations. Soil taxonomy must continue to
be tested by the nature of the interpretations that can be made.
The taxonomic classification used in soil surveys requires
flexibility in the classes. It is commonly necessary to subdivide
taxa and regroup those subdivisions into new classes of another
classification for the greatest number and most precise
interpretations possible. Soil taxonomy was designed to
facilitate interpretations, but the interpretations themselves
require at least one additional step of reasoning (Cline, 1963).
The interpretations may also require information that is not
available from the taxonomy. Slope and stoniness are soil
characteristics that must be known or assumed for one to
predict consequences of farming with heavy machinery.
Invasions of locusts, hurricanes, or frequent hailstorms are not
soil characteristics, but their probability must be known or
assumed when crop yields are predicted. These and other
important characteristics may be used as bases for defining
phases of taxa that are necessary for interpretations for
specific fields or farms. The phases are not a part of the
taxonomy. Their nature is determined by the foreseeable
uses of the soils in a particular survey area. Quite different
phases might be differentiated for the same soils in an area of
general farming in contrast to a national forest or an area
being developed for housing and in an irrigated area in
contrast to the desert grazing land that is above the irrigation
canal. The phases represent a number of classifications
superimposed on the taxonomic classification to give part of
the flexibility that is needed for the wide variety of uses made
of soil.
Inevitably, the conclusions of a large group of scientists
include some compromises of divergent points of view.
Members of a group representing unlike interests and
experience are likely to see soils differently. Different points
of view about soil produce different ideas about its
classification. Consequently, compromises between the
conflicting desires of a number of individuals not only are
necessary but also are likely to produce a system that has more
general utility than a system that represents a single point of
view. Compromise may not be the exact word. The truth has
many facets; each person has a somewhat different view of the
truth, and no person can see the whole truth clearly. Soil
taxonomy allows changes in the system as new information
about soils becomes available. Since its inception, soil
taxonomy has been amended many times. Probably, no one
person will approve of all the details of these changes; few will
be able to agree on all the changes.
Literature Cited
Cline, M.G. 1963. Logic of the New System of Soil
Classification. Soil Sci. 96: 17-22.
19
Soil taxonomy differentiates between mineral soils and
organic soils. To do this, first, it is necessary to
distinguish mineral soil material from organic soil material.
Second, it is necessary to define the minimum part of a soil
that should be mineral if a soil is to be classified as a mineral
soil and the minimum part that should be organic if the soil is
to be classified as an organic soil.
Nearly all soils contain more than traces of both mineral
and organic components in some horizons, but most soils are
dominantly one or the other. The horizons that are less than
about 20 to 35 percent organic matter, by weight, have
properties that are more nearly those of mineral than of organic
soils. Even with this separation, the volume of organic matter
at the upper limit exceeds that of the mineral material in the
fine-earth fraction.
Mineral Soil Material
Mineral soil material (less than 2.0 mm in diameter) either:
1. Is saturated with water for less than 30 days (cumulative)
per year in normal years and contains less than 20 percent (by
weight) organic carbon; or
2. Is saturated with water for 30 days or more cumulative in
normal years (or is artificially drained) and, excluding live
roots, has an organic carbon content (by weight) of:
a. Less than 18 percent if the mineral fraction contains 60
percent or more clay; or
b. Less than 12 percent if the mineral fraction contains no
clay; or
c. Less than 12 + (clay percentage multiplied by 0.1)
percent if the mineral fraction contains less than 60 percent
clay.
Organic Soil Material
Soil material that contains more than the amounts of
organic carbon described above for mineral soil material is
considered organic soil material.
In the definition of mineral soil material above, material
that has more organic carbon than in item 1 is intended to
include what has been called litter or an O horizon. Material
that has more organic carbon than in item 2 has been called
peat or muck. Not all organic soil material accumulates in or
under water. Leaf litter may rest on a lithic contact and support
forest vegetation. The soil in this situation is organic only in
the sense that the mineral fraction is appreciably less than half
the weight and is only a small percentage of the volume of the
soil.
Distinction Between Mineral Soils and Organic
Soils
Most soils are dominantly mineral material, but many
mineral soils have horizons of organic material. For simplicity
in writing definitions of taxa, a distinction between what is
meant by a mineral soil and an organic soil is useful. To apply
the definitions of many taxa, one must first decide whether the
soil is mineral or organic. An exception is the Andisols
(defined later). These generally are considered to consist of
mineral soils, but some may be organic if they meet other
criteria for Andisols. Those that exceed the organic carbon
limit defined for mineral soils have a colloidal fraction
dominated by short-range-order minerals or aluminum-humus
complexes. The mineral fraction in these soils is believed to
give more control to the soil properties than the organic
fraction. Therefore, the soils are included with the Andisols
rather than the organic soils defined later as Histosols.
If a soil has both organic and mineral horizons, the relative
thickness of the organic and mineral soil materials must be
considered. At some point one must decide that the mineral
horizons are more important. This point is arbitrary and
depends in part on the nature of the materials. A thick layer of
sphagnum has a very low bulk density and contains less
organic matter than a thinner layer of well-decomposed muck.
It is much easier to measure the thickness of layers in the field
than it is to determine tons of organic matter per hectare. The
definition of a mineral soil, therefore, is based on the thickness
of the horizons, or layers, but the limits of thickness must vary
with the kinds of materials. The definition that follows is
intended to classify as mineral soils those that have both thick
mineral soil layers and no more organic material than the
amount permitted in the histic epipedon, which is defined in
chapter 4.
In the determination of whether a soil is organic or mineral,
the thickness of horizons is measured from the surface of the
CHAPTER 3
Differentiae for Mineral Soils1
and Organic Soils
1
Mineral soils include all soils except the suborder Histels and the order Histosols.
20
soil whether that is the surface of a mineral or an organic
horizon, unless the soil is buried as defined in chapter 1. Thus,
any O horizon at the surface is considered an organic horizon
if it meets the requirements of organic soil material as defined
later, and its thickness is added to that of any other organic
horizons to determine the total thickness of organic soil
materials.
Definition of Mineral Soils
Mineral soils are soils that have either of the following:
1. Mineral soil materials that meet one or more of the
following:
a. Overlie cindery, fragmental, or pumiceous materials
and/or have voids2
that are filled with 10 percent or less
organic materials and directly below these materials have
either a densic, lithic, or paralithic contact; or
b. When added with underlying cindery, fragmental, or
pumiceous materials, total more than 10 cm between the soil
surface and a depth of 50 cm; or
c. Constitute more than one-third of the total thickness of
the soil to a densic, lithic, or paralithic contact or have a
total thickness of more than 10 cm; or
d. If they are saturated with water for 30 days or more per
year in normal years (or are artificially drained) and have
organic materials with an upper boundary within
40 cm of the soil surface, have a total thickness of either:
(1) Less than 60 cm if three-fourths or more of their
volume consists of moss fibers or if their bulk density,
moist, is less than 0.1 g/cm3
; or
(2) Less than 40 cm if they consist either of sapric or
hemic materials, or of fibric materials with less than
three-fourths (by volume) moss fibers and a bulk density,
moist, of 0.1 g/cm3
or more; or
2. More than 20 percent, by volume, mineral soil materials
from the soil surface to a depth of 50 cm or to a glacic layer or
a densic, lithic, or paralithic contact, whichever is shallowest;
and
a. Permafrost within 100 cm of the soil surface; or
b. Gelic materials within 100 cm of the soil surface and
permafrost within 200 cm of the soil surface.
Definition of Organic Soils
Organic soils have organic soil materials that:
1. Do not have andic soil properties in 60 percent or more of
the thickness between the soil surface and either a depth of 60
cm or a densic, lithic, or paralithic contact or duripan if
shallower; and
2. Meet one or more of the following:
a. Overlie cindery, fragmental, or pumiceous materials
and/or fill their interstices2
and directly below these
materials have a densic, lithic, or paralithic contact; or
b. When added with the underlying cindery, fragmental, or
pumiceous materials, total 40 cm or more between the soil
surface and a depth of 50 cm; or
c. Constitute two-thirds or more of the total thickness of
the soil to a densic, lithic, or paralithic contact and have no
mineral horizons or have mineral horizons with a total
thickness of 10 cm or less; or
d. Are saturated with water for 30 days or more per year in
normal years (or are artificially drained), have an upper
boundary within 40 cm of the soil surface, and have a total
thickness of either:
(1) 60 cm or more if three-fourths or more of their
volume consists of moss fibers or if their bulk density,
moist, is less than 0.1 g/cm3
; or
(2) 40 cm or more if they consist either of sapric or
hemic materials, or of fibric materials with less than
three-fourths (by volume) moss fibers and a bulk density,
moist, of 0.1 g/cm3
or more; or
e. Are 80 percent or more, by volume, from the soil
surface to a depth of 50 cm or to a glacic layer or a densic,
lithic, or paralithic contact, whichever is shallowest.
It is a general rule that a soil is classified as an organic soil
(Histosol) if more than half of the upper 80 cm (32 in) of the
soil is organic or if organic soil material of any thickness rests
on rock or on fragmental material having interstices filled with
organic materials.
2
Materials that meet the definition of cindery, fragmental, or pumiceous but have more
than 10 percent, by volume, voids that are filled with organic soil materials are considered to be
organic soil materials.
21
This chapter defines the horizons and characteristics of
both mineral and organic soils. It is divided into three
parts—horizons and characteristics diagnostic for mineral soils,
characteristics diagnostic for organic soils, and horizons and
characteristics diagnostic for both mineral and organic soils.
The four highest categories of this taxonomy, in order of
decreasing rank and increasing numbers of taxa, are
distinguished by the presence or absence or a variety of
combinations of diagnostic horizons and characteristics. The
categories themselves are described in chapter 6.
The horizons and characteristics defined below are not in a
key format. Some diagnostic horizons are mutually exclusive,
and some are not. An umbric epipedon, for example, could not
also be a mollic epipedon. A kandic horizon with clay films,
however, could also meet the definition of an argillic horizon.
A soil horizon is a layer that is commonly parallel to the soil
surface. In some orders, such as Gelisols, Vertisols, and
Spodosols, however, horizons are not always parallel to the
surface. A horizon has some set of properties that have been
produced by soil-forming processes, and it has some properties
that are not like those of the layers directly above and beneath
it (USDA, SCS, 1993). A soil horizon commonly is differentiated
from the horizons adjacent to it partly by characteristics that can
be seen or measured in the field, such as color, structure, texture,
rupture-resistance class, and the presence or absence of
carbonates. In identifying a soil horizon, however, measurements
in the laboratory are sometimes required to supplement field
observations. According to the criteria we use, horizons are
identified partly by their own morphology and partly by
properties that differ from those of the overlying and underlying
horizons.
Many of the layers that are differentiae for organic soils do
not meet the definition of soil horizons. Unlike the layers of
soil that are commonly called horizons, they are layers that
formed in differing environments during the period when the
materials that now constitute the soils accumulated. Some of
the layers that serve as differentiae are soil horizons, but there
are no operational methods that can always distinguish
between “horizons” and “layers” that have similar properties.
The importance of making a distinction between horizons and
layers of organic soils is unknown. In the discussion that
follows, the term “soil material” is commonly used as a
broader term that includes both horizons and layers in organic
soils.
The horizon designations used in this chapter are defined in
the Soil Survey Manual (USDA, SCS, 1993) and the Keys to Soil
Taxonomy (USDA, NRCS, 1998).
Horizons and Characteristics
Diagnostic for Mineral Soils
The criteria for some of the following horizons and
characteristics, such as histic and folistic epipedons, can be met
in organic soils. They are diagnostic, however, only for the
mineral soils.
Diagnostic Surface Horizons: The
Epipedon
The epipedon (Gr. epi, over, upon, and pedon, soil) is a
horizon that forms at or near the surface and in which most of
the rock structure has been destroyed. It is darkened by organic
matter or shows evidence of eluviation, or both. Rock structure
as used here and in other places in this taxonomy includes fine
stratification (less than 5 mm) in unconsolidated sediments
(eolian, alluvial, lacustrine, or marine) and saprolite derived
from consolidated rocks in which the unweathered minerals
and pseudomorphs of weathered minerals retain their relative
positions to each other.
Any horizon may be at the surface of a truncated soil. The
following section, however, is concerned with eight diagnostic
horizons that have formed at or near the soil surface. These
horizons can be covered by a surface mantle of new soil
material. If the surface mantle has rock structure, the top of the
epipedon is considered the soil surface unless the mantle meets
the definition of buried soils in chapter 1. If the soil includes a
buried soil, the epipedon, if any, is at the soil surface and the
epipedon of the buried soil is considered a buried epipedon and
is not considered in selecting taxa unless the keys specifically
indicate buried horizons, such as those in Thapto-Histic
subgroups. A soil with a mantle thick enough to have a buried
soil has no epipedon if the soil has rock structure to the
surface or has an Ap horizon less than 25 cm thick that is
underlain by soil material with rock structure. The melanic
epipedon (defined below) is unique among epipedons. It forms
commonly in volcanic deposits and can receive fresh deposits of
ash. Therefore, this horizon is permitted to have layers within
and above the epipedon that are not part of the melanic
epipedon.
CHAPTER 4
Horizons and Characteristics Diagnostic for the Higher Categories
22 Soil Taxonomy
A recent alluvial or eolian deposit that retains stratifications
(5 mm or less thick) or an Ap horizon directly underlain by such
stratified material is not included in the concept of the epipedon
because time has not been sufficient for soil-forming processes
to erase these transient marks of deposition and for diagnostic
and accessory properties to develop.
An epipedon is not the same as an A horizon. It may
include part or all of an illuvial B horizon if the darkening by
organic matter extends from the soil surface into or through the
B horizon.
Anthropic Epipedon
The anthropic epipedon has the same limits as the mollic
epipedon in color, structure, and organic-carbon content. It
formed during long-continued use of the soil by humans, either
as a place of residence or as a site for growing irrigated crops.
In the former case, disposal of bones and shells has supplied
calcium and phosphorus and the level of phosphorus in the
epipedon is too high for a mollic epipedon. Such epipedons
occur in the humid parts of Europe, the United States, and
South America and probably in other parts of the world, mostly
in kitchen middens. The high level of phosphorus in the
anthropic epipedons is not everywhere accompanied by a base
saturation of 50 percent or more, but it is accompanied by a
relatively high base saturation if compared with the adjacent
soils.
In arid regions some long-irrigated soils have an epipedon
that is like the mollic epipedon in most chemical and physical
properties. The properties of the epipedon in these areas are
clearly the consequence of irrigation by humans. Such an
epipedon is grouped with the anthropic epipedons, which
developed under human habitation. If not irrigated, such an
epipedon is dry in all its parts for more than 9 months in
normal years. Additional data about anthropic epipedons from
several parts of the world may permit future improvements in
this definition.
Required Characteristics
In summary, the anthropic epipedon shows some evidence of
disturbance by human activity and meets all of the
requirements for a mollic epipedon, except for one or both of
the following:
1. 1,500 milligrams per kilogram or more P2
O5
soluble in 1
percent citric acid and a regular decrease in P2
O5
to a depth of
125 cm; or
2. If the soil is not irrigated, all parts of the epipedon are dry
for 9 months or more in normal years.
Folistic Epipedon
The folistic epipedon consists of organic material (defined in
chapter 3), unless the soil has been plowed. This epipedon
normally is at the soil surface, although it can be buried. If the
soil has been plowed, the organic-carbon requirements are lower
than the requirements for organic soil material because of the
need to accommodate the oxidation that occurs when the soil is
plowed. Folistic epipedons occur primarily in cool, humid
regions of the world. They differ from histic epipedons because
they are saturated with water for less than 30 days (cumulative)
in normal years (and are not artificially drained). Taxa for soils
with folistic epipedons above the series level are not currently
recognized in this taxonomy. The folistic epipedon is used only
with mineral soils.
Required Characteristics
The folistic epipedon is defined as a layer (one or more
horizons) that is saturated for less than 30 days (cumulative) in
normal years (and is not artificially drained) and either:
1. Consists of organic soil material that:
a. Is 20 cm or more thick and either contains 75 percent or
more (by volume) Sphagnum fibers or has a bulk density,
moist, of less than 0.1; or
b. Is 15 cm or more thick; or
2. Is an Ap horizon that, when mixed to a depth of 25 cm,
has an organic-carbon content (by weight) of:
a. 16 percent or more if the mineral fraction contains 60
percent or more clay; or
b. 8 percent or more if the mineral fraction contains no
clay; or
c. 8 + (clay percentage divided by 7.5) percent or more
if the mineral fraction contains less than 60 percent
clay.
Most folistic epipedons consist of organic soil material
(defined in chapter 3). Item 2 provides for a folistic epipedon
that is an Ap horizon consisting of mineral soil material.
Histic Epipedon
The histic epipedon consists of organic soil material (peat or
muck) if the soil has not been plowed. If the soil has been
plowed, the epipedon normally has a high content of organic
matter that results from mixing organic soil material with some
mineral material. The histic epipedon either is characterized by
saturation and reduction for some time in normal years or has
been artificially drained. It is normally at the soil surface,
although it can be buried.
Photo 4 shows a very dark histic epipedon that is saturated
for long periods and meets criterion 1 below.
Required Characteristics
The histic epipedon is a layer (one or more horizons) that is
characterized by saturation (for 30 days or more, cumulative)
Horizons and Characteristics Diagnostic for the Higher Categories 23
and reduction for some time during normal years (or is artificially
drained) and either:
1. Consists of organic soil material that:
a. Is 20 to 60 cm thick and either contains 75 percent or
more (by volume) Sphagnum fibers or has a bulk density,
moist, of less than 0.1; or
b. Is 20 to 40 cm thick; or
2. Is an Ap horizon that, when mixed to a depth of 25 cm,
has an organic-carbon content (by weight) of:
a. 16 percent or more if the mineral fraction contains 60
percent or more clay; or
b. 8 percent or more if the mineral fraction contains no
clay; or
c. 8 + (clay percentage divided by 7.5) percent or more if
the mineral fraction contains less than 60 percent clay.
Most histic epipedons consist of organic soil material
(defined in chapter 3). Item 2 provides for a histic epipedon
that is an Ap horizon consisting of mineral soil material. A
histic epipedon consisting of mineral soil material can also be
part of a mollic or umbric epipedon.
Melanic Epipedon
The melanic epipedon is a thick, dark colored (commonly
black) horizon at or near the soil surface (photo 5). It has high
concentrations of organic carbon, generally associated with
short-range-order minerals or aluminum-humus complexes.
The intense dark colors are attributed to the accumulation of
organic matter from which “Type A” humic acids are
extracted. This organic matter is thought to result from large
amounts of root residues supplied by a gramineous vegetation
and can be distinguished from organic matter formed under
forest vegetation by the melanic index.
The suite of secondary minerals generally is dominated by
allophane, and the soil material has a low bulk density and a
high anion adsorption capacity.
Required Characteristics
The melanic epipedon has both of the following:
1. An upper boundary at, or within 30 cm of, either the
mineral soil surface or the upper boundary of an organic layer
with andic soil properties (defined below), whichever is
shallower; and
2. In layers with a cumulative thickness of 30 cm or more
within a total thickness of 40 cm, all of the following:
a. Andic soil properties throughout; and
b. A color value, moist, and chroma (Munsell
designations) of 2 or less throughout and a melanic index of
1.70 or less throughout; and
c. 6 percent or more organic carbon as a weighted average
and 4 percent or more organic carbon in all layers.
Mollic Epipedon
The mollic epipedon is a relatively thick, dark colored,
humus-rich surface horizon (or horizons) in which bivalent
cations are dominant on the exchange complex and the grade
of structure is weak to strong (photos 6 and 7). These properties
are common in the soils of the steppes in the Americas, Europe,
and Asia.
Properties
The mollic epipedon is defined in terms of its morphology
rather than its genesis. It consists of mineral soil material and
is at the soil surface, unless it underlies a histic epipedon or
thin surface mantle, as explained earlier in this chapter. If the
surface layer of organic material is so thick that the soil is
recognized as a Histosol (defined below), the horizon that at one
time was a mollic epipedon is considered to be buried and no
longer meets the definition of an epipedon.
The mollic epipedon has soil structure strong enough that
less than one-half of the volume of all parts has rock structure
and one-half or more of the horizon is not both hard, very
hard, or harder and massive when dry. In this definition very
coarse prisms, with a diameter of 30 cm or more, are treated as
if they were the same as massive unless there is secondary
structure within the prisms. The restriction against hardness
and structure applies only to those epipedons that become dry.
A mollic epipedon can directly overlie deposits with rock
structure, including fine stratifications, if the epipedon is 25
cm or more thick. The epipedon does not include any layer in
which one-half or more of the volume has rock structure,
including fine stratifications.
The mollic epipedon has dark color and low chroma in 50
percent or more of its matrix. It typically has a Munsell color
value of 3 or less when moist and of 5 or less when dry and
chroma of 3 or less when moist. If its structure is fine granular
or fine blocky, the sample, when broken, may show only the
color of the coatings of peds. The color of the matrix in such
situations can be determined only by crushing or briefly
rubbing the sample. Prolonged rubbing should be avoided
because it may cause darkening of a sample if soft ironmanganese
concretions are present. Crushing should be just
sufficient to mix the coatings with the matrix. The dry color
value should be determined after the crushed sample is dry
enough for continued drying to produce no further change and
the sample has been smoothed to eliminate shadows.
Normally, the color value is at least 1 Munsell unit lower or
the chroma at least 2 units lower (both moist and dry) than that
of the 1C horizon (if one occurs). Some parent materials, such
24 Soil Taxonomy
as loess, cinders, basalt, or carbonaceous shale, can also have
dark color and low chroma. Soils that formed in such materials
can accumulate appreciable amounts of organic matter but
commonly have no visible darkening in the epipedon. In these
dark colored materials, the requirement that the mollic
epipedon have a lower color value or chroma than the C
horizon is waived if the surface horizon(s) meets all of the
other requirements for a mollic epipedon and, in addition, has
at least 0.6 percent more organic carbon than the C horizon.
Finely divided CaCO3
acts as a white pigment and causes
soils to have a high color value, especially when dry. To
compensate for the color of the carbonates, the mollic epipedon
is allowed to have lighter color than normal if the epipedon
averages more than 15 percent carbonates.
If the fine-earth fraction has a calcium carbonate equivalent
of 15 to 40 percent, the limit for the dry color value is waived.
If it has a calcium carbonate equivalent of 40 percent or more,
the limit for the dry color value is waived and the moist color
value is 5 or less.
The mollic epipedon forms in the presence of bivalent
cations, particularly calcium. The base saturation by the
NH4
OAc method is required to be 50 percent or more
throughout the epipedon.
The mollic epipedon is thought to be formed mainly through
the underground decomposition of organic residues in the
presence of these cations. The residues that are decomposed are
partly roots and partly organic residues from the surface that
have been taken underground by animals. Accumulation and
turnover of the organic matter in the mollic epipedon probably
are rapid. The radiocarbon age (mean residence time) of the
organic carbon is mostly 100 to 1,000 years. A high percentage
of the organic matter is so-called “humic acid.” The minimum
organic-carbon content throughout the thickness of the mollic
epipedon is 0.6 percent in most mollic epipedons. Exceptions
are (1) a minimum of 2.5 percent organic carbon in epipedons
that have a color value, moist, of 4 or 5 and a fine-earth
fraction with a calcium carbonate equivalent of 40 percent or
more and (2) a minimum of 0.6 percent more organic carbon
than in the C horizon in epipedons in which the C horizon has
a color as dark as or darker than the color of the epipedon.
The maximum organic-carbon content of a mollic epipedon
is the same as for mineral soil material. Some Ap horizons that
approach the lower limit of a histic epipedon can be part of the
mollic epipedon.
The minimum thickness of the mollic epipedon depends on
the depth and texture of the soil. The minimum thickness is for
soils with an epipedon that is loamy very fine sand or finer and
that is directly above a densic, lithic, or paralithic contact, a
petrocalcic horizon, or a duripan. These soils have a minimum
thickness of 10 cm. Soils that are 10 to 18 cm deep have a
mollic epipedon if the whole soil meets all of the criteria for a
mollic epipedon when mixed.
The minimum thickness is 25 cm for: (1) all soils with a
texture throughout the epipedon of loamy fine sand or coarser;
(2) all soils that have no diagnostic horizons or features below
the epipedon; and (3) soils that are 75 cm or more deep to a
densic, lithic, or paralithic contact, a petrocalcic horizon, or a
duripan, are more than 75 cm deep to the upper boundary of
any identifiable secondary carbonates, and are more than 75
cm deep to the lower boundary of any argillic, cambic, kandic,
natric, oxic, or spodic horizon (all defined below).
The minimum thickness is one-third of the thickness from
the mineral soil surface to any of the features described in the
paragraph above if (1) the texture throughout the epipedon is
loamy very fine sand or finer and (2) depth to the feature
described in the paragraph above is between 54 and 75 cm.
The minimum thickness is 18 cm for all other soils.
The mollic epipedon has less than 1,500 milligrams per
kilogram of P2
O5
soluble in 1 percent citric acid or has an
irregular decrease in the amounts of P2
O5
with increasing depth
below the epipedon, or there are phosphate nodules within the
epipedon. This restriction is intended to exclude plow layers of
very old arable soils and kitchen middens that, under use, have
acquired the properties of a mollic epipedon and to include the
epipedon of a soil developed in highly phosphatic parent
material.
Some part of the epipedon is moist for 90 days or more
(cumulative) in normal years during times when the soil
temperature at a depth of 50 cm is 5 o
C or higher and the soil is
not irrigated.
Sediments that have been continuously under water since
they were deposited have a very high water content and are
unable to support livestock. Although many soils that have a
mollic epipedon are very poorly drained, the mollic epipedon is
required to have an n value (defined below) of less than 0.7.
Several accessory properties are common in soils that have a
mollic epipedon. Most natural environments (not made by
humans) that produce a mollic epipedon also produce 2:1
lattice clays from minerals that can be altered, preclude serious
toxicity from aluminum or manganese, and ensure a reasonable
reserve of calcium, magnesium, and potassium and of nitrogen
if the soil has not been cultivated for a long time. These are
accessory properties that are important to plant growth.
Permeability is another accessory property important to most
uses of the soil. The structure of the mollic epipedon facilitates
the movement of moisture and air whenever the soil is not
saturated with water.
The content of organic matter indicates that the soil has
received enough moisture to support fair to luxuriant plant
growth in normal years. The mollic epipedon must be moist in
at least some part for 90 days or more (cumulative) in normal
years at times when the soil temperature is 5 o
C or higher at a
depth of 50 cm and when the soil is not irrigated.
Although the mollic epipedon is a surface horizon that can
be truncated by erosion, its many important accessory
properties suggest its use as a diagnostic horizon at a high
categoric level. Some soils have eroded to the extent that the
epipedon is no longer thick enough to meet the requirements
Horizons and Characteristics Diagnostic for the Higher Categories 25
for a mollic epipedon. In this case human activities have altered
the surface horizon, changing a mollic epipedon into an ochric
epipedon (defined below).
Required Characteristics
The mollic epipedon consists of mineral soil materials and has
the following properties:
1. When dry, either or both:
a. Structural units with a diameter of 30 cm or less
or secondary structure with a diameter of 30 cm or less;
or
b. A moderately hard or softer rupture-resistance class;
and
2. Rock structure, including fine (less than 5 mm)
stratifications, in less than one-half of the volume of all parts;
and
3. One of the following:
a. All of the following:
(1) Colors with a value of 3 or less, moist, and of 5 or
less, dry; and
(2) Colors with chroma of 3 or less, moist; and
(3) If the soil has a C horizon, the mollic epipedon has
a color value at least 1 Munsell unit lower or chroma at
least 2 units lower (both moist and dry) than that of the C
horizon or the epipedon has at least 0.6 percent more
organic carbon than the C horizon; or
b. A fine-earth fraction that has a calcium carbonate
equivalent of 15 to 40 percent and colors with a value and
chroma of 3 or less, moist; or
c. A fine-earth fraction that has a calcium carbonate
equivalent of 40 percent or more and a color value, moist, of
5 or less; and
4. A base saturation (by NH4
OAc) of 50 percent or more; and
5. An organic-carbon content of:
a. 2.5 percent or more if the epipedon has a color value,
moist, of 4 or 5; or
b. 0.6 percent more than that of the C horizon (if one
occurs) if the mollic epipedon has a color value less than 1
Munsell unit lower or chroma less than 2 units lower (both
moist and dry) than the C horizon; or
c. 0.6 percent or more; and
6. After mixing of the upper 18 cm of the mineral soil or of
the whole mineral soil if its depth to a densic, lithic, or
paralithic contact, petrocalcic horizon, or duripan (all defined
below) is less than 18 cm, the minimum thickness of the
epipedon is as follows:
a. 10 cm or the depth of the noncemented soil if the
epipedon is loamy very fine sand or finer and is directly
above a densic, lithic, or paralithic contact, a petrocalcic
horizon, or a duripan that is within 18 cm of the mineral
soil surface; or
b. 25 cm or more if the epipedon is loamy fine sand or
coarser throughout or if there are no underlying diagnostic
horizons (defined below) and the organic-carbon content of
the underlying materials decreases irregularly with
increasing depth; or
c. 25 cm or more if all of the following are 75 cm or more
below the mineral soil surface:
(1) The upper boundary of any pedogenic lime that is
present as filaments, soft coatings, or soft nodules; and
(2) The lower boundary of any argillic, cambic, natric,
oxic, or spodic horizon (defined below); and
(3) The upper boundary of any petrocalcic horizon,
duripan, or fragipan; or
d. 18 cm if the epipedon is loamy very fine sand or finer in
some part and one-third or more of the total thickness
between the top of the epipedon and the shallowest of any
features listed in item 6-c is less than 75 cm below the
mineral soil surface; or
e. 18 cm or more if none of the above conditions apply;
and
7. Phosphate:
a. Content less than 1,500 milligrams per kilogram
soluble in 1 percent citric acid; or
b. Content decreasing irregularly with increasing depth
below the epipedon; or
c. Nodules are within the epipedon; and
8. Some part of the epipedon is moist for 90 days or more
(cumulative) in normal years during times when the soil
temperature at a depth of 50 cm is 5 o
C or higher, if the soil is
not irrigated; and
9. The n value (defined below) is less than 0.7.
OchricEpipedon
The ochric epipedon fails to meet the definitions for any of
the other seven epipedons because it is too thin or too dry, has
too high a color value or chroma, contains too little organic
carbon, has too high an n value or melanic index, or is both
massive and hard or harder when dry (photos 8 and 9). Many
ochric epipedons have either a Munsell color value of 4 or
more, moist, and 6 or more, dry, or chroma of 4 or more, or
they include an A or Ap horizon that has both low color values
and low chroma but is too thin to be recognized as a mollic or
26 Soil Taxonomy
umbric epipedon (and has less than 15 percent calcium
carbonate equivalent in the fine-earth fraction). Ochric
epipedons also include horizons of organic materials that are
too thin to meet the requirements for a histic or folistic
epipedon.
The ochric epipedon includes eluvial horizons that are at or
near the soil surface, and it extends to the first underlying
diagnostic illuvial horizon (defined below as an argillic,
kandic, natric, or spodic horizon). If the underlying horizon is
a B horizon of alteration (defined below as a cambic or oxic
horizon) and there is no surface horizon that is appreciably
darkened by humus, the lower limit of the ochric epipedon is
the lower boundary of the plow layer or an equivalent depth
(18 cm) in a soil that has not been plowed. Actually, the same
horizon in an unplowed soil may be both part of the epipedon
and part of the cambic horizon; the ochric epipedon and the
subsurface diagnostic horizons are not all mutually exclusive.
The ochric epipedon does not have rock structure and does not
include finely stratified fresh sediments, nor can it be an Ap
horizon directly overlying such deposits.
The ochric epipedon by itself has few or no accessory
characteristics, but an ochric epipedon in combination with
other diagnostic horizons and features has many accessory
characteristics. For example, if there is an underlying horizon
in which clay has accumulated (defined later as an argillic
horizon) and if the epipedon is seldom or never dry, carbonates
are absent and base saturation is moderate or low in the major
part of the epipedon unless the soil has been limed. If the
texture is loamy, the structure breaks down easily when the soil
is cultivated.
Plaggen Epipedon
The plaggen epipedon is a human-made surface layer 50 cm
or more thick that has been produced by long-continued
manuring (photo 10). In medieval times, sod or other materials
commonly were used for bedding livestock and the manure was
spread on fields being cultivated. The mineral materials
brought in by this kind of manuring eventually produced an
appreciably thickened Ap horizon (as much as 1 m or more
thick). In northwestern Europe this custom was associated with
the poorly fertile, sandy Spodosols. The practice more or less
ceased at the turn of the 19th century, when fertilizers became
available.
The color of a plaggen epipedon and its organic-carbon
content depend on the materials used for bedding. If the sod
was cut from the heath, the plaggen epipedon tends to be black
or very dark gray, to be rich in organic matter, and to have a
wide carbon-nitrogen ratio. If the sod came from forested soils,
the plaggen epipedon tends to be brown, to have less organic
matter, and to have a narrower carbon-nitrogen ratio.
Commonly, the organic-carbon content ranges from 1.5 to 4
percent. Values commonly range from 1 to 4, moist, and
chromas are 2 or less.
A plaggen epipedon can be identified by several means.
Commonly, it contains artifacts, such as bits of brick and
pottery, throughout its depth. There may be chunks of diverse
materials, such as black sand and light gray sand, as large as
the size held by a spade. The plaggen epipedon normally shows
spade marks throughout its depth and also remnants of thin
stratified beds of sand that were probably produced on the soil
surface by beating rains and were later buried by spading. A
map unit delineation of soils with plaggen epipedons would
tend to have straight-sided rectangular bodies that are higher
than the adjacent soils by as much as or more than the
thickness of the plaggen epipedon.
Umbric Epipedon
The umbric epipedon is a relatively thick, dark colored,
humus-rich surface horizon or horizons (photo 11). It cannot be
distinguished by the eye from a mollic epipedon, but laboratory
studies show that the base saturation is less than 50 percent (by
NH4
OAc) in some or all parts.
The umbric epipedon is used for defining taxa at different
levels. For those soils in which the content of organic matter is
roughly proportional to the darkness of the color, the most
satisfactory groupings appear to be those that assign soils with
a thick, dark colored surface horizon and soils with a light
colored or thin surface horizon to different suborders.
Structure, bulk density, cation-exchange capacity, and other
properties are related to the amount and type of organic matter
in these soils. In those kinds of soil where dark color is not
related to the content of organic matter, the soils that have light
colored epipedons are separated from the soils that have dark
colored epipedons only at lower categoric levels, if at all.
Properties
The umbric epipedon consists of mineral soil material and is
at the soil surface, unless it underlies either a recent deposit
that is less than 50 cm thick and has fine stratification if not
plowed or a thin layer of organic soil material. If the surface
layer of organic material is so thick that the soil is recognized
as a Histosol (defined below), the umbric epipedon is considered
to be buried.
The umbric epipedon has soil structure strong enough so
that one-half or more of the horizon is not both hard, very
hard, or harder and massive when dry. Very coarse prisms,
with a diameter of 30 cm or more, are treated as if they were
the same as massive if there is no secondary structure within
the prisms. The restriction against massive and hardness
applies only to those epipedons that become dry.
The umbric epipedon has dark color and low chroma in 50
percent or more of its matrix. It has a Munsell color value of 3
or less, moist, and of 5 or less, dry, and chroma of 3 or less. If
its structure is fine granular or fine blocky, the sample when
broken may show only the color of the coatings of peds. The
color of the matrix in such situations can be determined only
Horizons and Characteristics Diagnostic for the Higher Categories 27
by crushing or briefly rubbing the sample. Prolonged rubbing
should be avoided because it may cause darkening of a sample
if soft iron-manganese concretions are present. Crushing
should be just sufficient to mix the coatings with the matrix.
The dry color value should be determined after the crushed
sample is dry enough for continued drying to produce no
further change and the sample has been smoothed to eliminate
shadows.
Normally, the color value is at least 1 Munsell unit lower or
the chroma at least 2 units lower (both moist and dry) than that
of the C horizon (if present). Some parent materials, such as
loess, cinders, alluvium, or shale, can also have dark color and
low chroma. Soils that formed in such materials can
accumulate appreciable amounts of organic matter but
commonly show no visible darkening in the epipedon. In these
dark colored materials, the requirement that the umbric
epipedon have a lower color value or chroma than the C
horizon is waived if the surface horizon(s) meets all of the
other requirements for an umbric epipedon and, in addition,
has at least 0.6 percent more organic carbon than the C
horizon.
Base saturation by the NH4
OAc method is required to be
less than 50 percent in some or all parts of the epipedon.
The umbric epipedon is thought to be formed mainly by the
decomposition of organic residues. The residues that are
decomposed are partly roots and partly organic residues from
the surface that have been taken underground by animals.
Accumulation and turnover of the organic matter in the umbric
epipedon probably are slower than in the mollic epipedon. The
aluminum ions may be somewhat toxic to some kinds of soil
micro-organisms. The minimum organic-carbon content
throughout the thickness of the umbric epipedon is 0.6 percent.
The minimum thickness of the umbric epipedon is
dependent on the depth and texture of the soil. The minimum
thickness is for soils with an epipedon that is loamy very fine
sand or finer (when mixed) and that is directly above a densic,
lithic, or paralithic contact, a petrocalcic horizon, or a duripan.
These soils have a minimum thickness of 10 cm. Soils that are
10 to 18 cm deep have an umbric epipedon if the whole soil
meets all of the criteria for an umbric epipedon when mixed.
The minimum thickness is 25 cm for (1) all soils with a
texture throughout the epipedon of loamy fine sand or coarser;
(2) all soils that have no diagnostic horizons or features below
the epipedon; and (3) soils that are 75 cm or more deep to a
densic, lithic, or paralithic contact or a duripan and are more
than 75 cm deep to the lower boundary of any argillic, cambic,
kandic, natric, oxic, or spodic horizon (all defined below).
The minimum thickness is one-third of the thickness from
the mineral soil surface to any of the features in the paragraph
above if (1) the texture in some or all parts of the epipedon is
loamy very fine sand or finer and (2) depth to the feature listed
in the paragraph above is between 54 and 75 cm below the
mineral soil surface.
The minimum thickness is 18 cm for all other soils.
The umbric epipedon has less than 1,500 milligrams per
kilogram of P2
O5
soluble in 1 percent citric acid or has an
irregular decrease in the amounts of P2
O5
with increasing depth
below the epipedon, or there are phosphate nodules within the
epipedon. This restriction is intended to exclude plow layers of
very old arable soils and kitchen middens that, under use, have
acquired the properties of an umbric epipedon and to include
the epipedon of a soil developed in highly phosphatic parent
material.
Some part of the epipedon is moist for 90 days or more
(cumulative) in normal years during times when the soil
temperature at a depth of 50 cm is 5 o
C or higher and the soil is
not irrigated.
Sediments that have been continuously under water since
deposition have a very high water content and are unable to
support livestock. Although some soils that have an umbric
epipedon are very poorly drained, the umbric epipedon is
required to have an n value (defined below) of less than 0.7.
Several accessory properties are common in soils that have
an umbric epipedon. These soils have the potential for toxicity
from aluminum, and they are commonly low in calcium,
magnesium, and potassium if lime and fertilizer have not been
applied. These are accessory properties important to plant
growth. The structure of the umbric epipedon facilitates the
movement of moisture and air whenever the soil is not
saturated with water.
The content of organic matter indicates that the soil has
received enough moisture to support fair to luxuriant plant
growth in normal years. The umbric epipedon must be moist in
at least some part for 3 months or more (cumulative) in normal
years at times when the soil temperature is 5 o
C or higher at a
depth of 50 cm and when the soil is not irrigated.
Although the umbric epipedon is a surface horizon that can
be truncated by erosion, its many important accessory
properties suggest its use as a diagnostic horizon at a high
categoric level.
Some plaggen epipedons meet all of the requirements for an
umbric epipedon but also show evidence of a gradual addition
of materials during cultivation, whereas the umbric epipedon
does not have the artifacts, spade marks, and raised surfaces
that are characteristic of the plaggen epipedon.
Required Characteristics
The umbric epipedon consists of mineral soil materials and
has the following properties:
1. When dry, either or both:
a. Structural units with a diameter of 30 cm or less or
secondary structure with a diameter of 30 cm or less; or
b. A moderately hard or softer rupture-resistance class;
and
28 Soil Taxonomy
2. All of the following:
a. Colors with a value of 3 or less, moist, and of 5 or less,
dry; and
b. Colors with chroma of 3 or less; and
c. If the soil has a C horizon, the umbric epipedon has a
color value at least 1 Munsell unit lower or chroma at least
2 units lower (both moist and dry) than that of the C
horizon or the epipedon has at least 0.6 percent more
organic carbon than that of the C horizon; and
3. A base saturation (by NH4
OAc) of less than 50 percent in
some or all parts; and
4. An organic-carbon content of:
a. 0.6 percent more than that of the C horizon (if one
occurs) if the umbric epipedon has a color value less than 1
Munsell unit lower or chroma less than 2 units lower (both
moist and dry) than the C horizon; or
b. 0.6 percent or more; and
5. After mixing of the upper 18 cm of the mineral soil or of
the whole mineral soil if its depth to a densic, lithic, or
paralithic contact or a duripan (all defined below) is less than
18 cm, the minimum thickness of the epipedon is as follows:
a. 10 cm or the depth of the noncemented soil if the
epipedon is loamy very fine sand or finer and is directly
above a densic, lithic, or paralithic contact or a duripan that
is within 18 cm of the mineral soil surface; or
b. 25 cm or more if the epipedon is loamy fine sand or
coarser throughout or if there are no underlying diagnostic
horizons (defined below) and the organic-carbon content of
the underlying materials decreases irregularly with
increasing depth; or
c. 25 cm or more if the lower boundary of any argillic,
cambic, natric, oxic, or spodic horizon (defined below) is 75
cm or more below the mineral soil surface; or
d. 18 cm if the epipedon is loamy very fine sand or finer in
some part and one-third or more of the total thickness
between the top of the epipedon and the shallowest of any
features listed in item 5-c is less than 75 cm below the
mineral soil surface; or
e. 18 cm or more if none of the above conditions apply;
and
6. Phosphate:
a. Content less than 1,500 milligrams per kilogram
soluble in 1 percent citric acid; or
b. Content decreasing irregularly with increasing depth
below the epipedon; or
c. Nodules are within the epipedon; and
7. Some part of the epipedon is moist for 90 days or more
(cumulative) in normal years during times when the soil
temperature at a depth of 50 cm is 5 o
C or higher, if the soil is
not irrigated; and
8. The n value (defined below) is less than 0.7; and
9. The umbric epipedon does not have the artifacts, spade
marks, and raised surfaces that are characteristic of the
plaggen epipedon.
Diagnostic Subsurface Horizons
The horizons described in this section form below the surface
of the soil, although in some areas they form directly below a
layer of leaf litter. They may be exposed at the surface by
truncation of the soil. Some of these horizons are generally
regarded as B horizons, some are considered B horizons by
many but not all pedologists, and others are generally regarded
as parts of the A horizon.
Agric Horizon
The agric horizon is an illuvial horizon that has formed
under cultivation and contains significant amounts of illuvial
silt, clay, and humus. When a soil is brought under cultivation,
the vegetation and the soil fauna as a rule are changed
drastically. The plow layer is mixed periodically, and, in effect,
a new cycle of soil formation is started. Even where the
cultivated crops resemble the native vegetation, stirring of the
plow layer and the use of amendments, especially lime,
nitrogen, and phosphate, normally produce significant changes
in soil structure, flora, and fauna.
After a soil has been cultivated for a long time, changes in
the horizon directly below the plow layer become apparent and
cannot be ignored in classifying the soil. The large pores in the
plow layer and the absence of vegetation immediately after
plowing permit a turbulent flow of muddy water to the base of
the plow layer. The water can enter wormholes or fine cracks
between peds at the base of the plow layer, and the suspended
materials are deposited as the water is withdrawn into capillary
pores. The worm channels, root channels, and surfaces of peds
in the horizon underlying the plow layer become coated with a
dark colored mixture of organic matter, silt, and clay. The
accumulations on the sides of wormholes become thick and can
eventually fill the holes. If worms are scarce, the accumulations
may take the form of lamellae that range in thickness from a
few millimeters to about 1 cm. The lamellae and the coatings
on the sides of wormholes always have a lower color value and
chroma than the soil matrix.
The agric horizon can have somewhat different forms in
different climates if there are differences in soil fauna. In areas
of a humid, temperate climate where soils have a udic moisture
regime and a mesic soil temperature regime (defined below),
earthworms can become abundant. If there are wormholes that,
Horizons and Characteristics Diagnostic for the Higher Categories 29
including their coatings, constitute 5 percent or more (by
volume) of the horizon and if the coatings are 2 mm or more
thick and have a color value, moist, of 4 or less and chroma of
2 or less, the horizon is an agric horizon. After long
cultivation, the content of organic matter in the agric horizon
is not likely to be high, but the carbon-nitrogen ratio is low
(generally less than 8). The pH value of the agric horizon is
close to neutral (6 to 6.5).
In areas of a Mediterranean climate where soils have a xeric
soil moisture regime (defined below), earthworms are less
common and the illuvial materials accumulate as lamellae
directly below the Ap horizon. If these lamellae are 5 mm or
more thick, have a color value, moist, of 4 or less and chroma
of 2 or less, and constitute 5 percent or more (by volume) of a
horizon 10 cm or more thick, this horizon is an agric horizon.
The agric horizon in these xeric soils is also part of an
argillic horizon. An agric horizon may form in several of the
other diagnostic horizons, but not in a mollic or anthropic
epipedon. A soil in which an illuvial horizon has formed in the
mollic epipedon is distinguished by other means.
Required Characteristics
The agric horizon is directly below an Ap horizon and has the
following properties:
1. A thickness of 10 cm or more and either:
a. 5 percent or more (by volume) wormholes, including
coatings that are 2 mm or more thick and have a value,
moist, of 4 or less and chroma of 2 or less; or
b. 5 percent or more (by volume) lamellae that have a
thickness of 5 mm or more and have a value, moist, of 4 or
less and chroma of 2 or less.
AlbicHorizon
The albic horizon (photo 12) is an eluvial horizon, 1.0 cm or
more thick, that has 85 percent or more (by volume) albic
materials (defined below). It generally occurs below an A
horizon but may be at the mineral soil surface. Under the albic
horizon there generally is an argillic, cambic, kandic, natric, or
spodic horizon or a fragipan (defined below). The albic horizon
may lie between a spodic horizon and either a fragipan or an
argillic horizon, or it may be between an argillic or kandic
horizon and a fragipan. It may lie between a mollic epipedon
and an argillic or natric horizon or between a cambic horizon
and an argillic, kandic, or natric horizon or a fragipan. The
albic horizon may separate horizons that, if they were together,
would meet the requirements for a mollic epipedon. It may
separate lamellae that together meet the requirements for an
argillic horizon. These lamellae are not considered to be part of
the albic horizon.
In some soils the horizon underlying the albic horizon is too
sandy or too weakly developed to have the levels of
accumulation required for an argillic, kandic, natric, or spodic
horizon. Some soils have, directly below the albic horizon, either
a densic, lithic, or paralithic contact or another relatively
impervious layer that produces a perched water table with
stagnant or moving water.
ArgillicHorizon
An argillic horizon is normally a subsurface horizon with a
significantly higher percentage of phyllosilicate clay than the
overlying soil material (photo 13). It shows evidence of clay
illuviation. The argillic horizon forms below the soil surface,
but it may be exposed at the surface later by erosion.
Genesis
Because there is little or no evidence of illuvial clay
movement in soils on the youngest landscapes, soil scientists
have concluded that the formation of an argillic horizon
requires at least a few thousand years. On some latePleistocene
landscapes, argillic horizons are more strongly
expressed in soils under forest vegetation than in soils under
grass. Therefore, the kind of flora and associated fauna is
thought to have an influence on the rate of development or
degree of expression of the argillic horizon. Climate also is a
factor. There are few or no examples of clay films in soils with
perudic soil moisture regimes, such as the soils in parts of
southeastern Alaska, the Olympic Peninsula of Washington,
and the British highlands where water percolates through the
soils during all seasons. Argillic horizons are common on the
adjacent lowlands in Great Britain, under climates where the
soils undergo wetting and drying cycles.
Textural differentiation in soils with argillic horizons results
from one or more processes acting simultaneously or
sequentially, affecting surface horizons, subsurface horizons, or
both. The degree to which a process or several processes
operate varies widely from soil to soil. In some soils clay
illuviation is significant, while in others clay illuviation is
overshadowed by in situ weathering. Not all of the processes
are completely understood. The ones thought to be most
important are summarized in the following paragraphs.
1. Clay eluviation and illuviation.—Some suspended clay
is carried downward in the soil water. The movement of clay
can take place from one horizon to another or within a horizon.
There is a strong mineralogical similarity between the fine clay
in an eluvial horizon and that in a deeper illuvial horizon. This
similarity supports the idea that clay migrates dominantly as
clay rather than as the products of decomposition that were
later synthesized to form clay-sized particles.
Clay mobility is influenced by a number of factors. If clay
platelets are aggregated by sesquioxides or other cementing
agents, the cement must be dissolved prior to clay movement.
Phyllosilicates with thick, diffuse double layers of adsorbed
cations are dispersed more easily than those with thin double
layers. If the ionic strength of the soil solution is high, clays
tend to flocculate. Wetting a dry soil seems to lead to
30 Soil Taxonomy
disruption of the fabric and to dispersion of clay unless the ionic
concentration is high. Sodium ions in solution, between critical
limits of activity, increase clay dispersion. Optimal clay
dispersion occurs when the pH at the zero point of net charge
on the clay particle is distinctly different from the pH of the
soil solution. This dispersion commonly occurs between pH
values of 4.5 and 6.5.
In soils that are periodically dry, the clay suspension moves
downward and stops in the dry subsoil as the soil solution is
absorbed. During absorption of the soil solution, the surface of
the ped acts as a filter and keeps clays from entering the
interior of the ped. The clay platelets then coat the surface of
the ped or void wall and are oriented with their long axes
parallel to the surface on which they were deposited. They are
called clay films. These layers of oriented clay can be
distinguished from the rest of the clay through the use of a
petrographic microscope.
As soil solution enters unsaturated subsoils, water
movement occurs in fine pores. Pore water velocity is reduced
as a function of pore wall friction. Some clay deposition may
occur simply because fluid velocity is too low to keep the clay
suspended.
Capillarity affects water movement both downward and into
the peds. If a soil horizon is underlain by a horizon of
considerably coarser texture (i.e., larger pores), capillary
continuity is broken and water tends to remain in the fine
capillaries above the zone of contact. When water evaporates or
is withdrawn by roots, suspended and/or dissolved materials,
including clay, are left. This action accentuates the original
difference in pore-size distribution, and clay is deposited
directly above the coarse textured strata or lenses.
Clays that are deposited from suspension in sediments, such
as shale or glacial till, are commonly oriented parallel to the
depositional or stress surface. In contrast, clays formed in place
within the soil generally are oriented according to the crystal
structure of the original mineral grains from which they
formed. Neither the mineral grains nor the planes in the shale
or till are consistently oriented with respect to any pedogenic
features. Consequently, the thin sections of many soils indicate
layers of oriented clays in peds and on the surfaces of pores and
peds.
Accumulation of clay in some soils occurs predominantly
through flocculation. The dispersed clay stops moving
downward if a layer with different pH or electrolyte
concentration, or both, is present in the subsoil. The
flocculated clays will have little or no orientation with respect
to the features of the microfabric. Thus, distinguishing
flocculated clays from clays formed in situ is difficult.
The above discussion is not intended to imply that all of the
clay increase in an argillic horizon is the result of illuviation.
The conclusions of many studies range from those indicating
that most of the clay increase is the result of translocation to
those indicating that most of the clay formed in situ with
minimal translocation.
2. Clay dissolution in the epipedon.—Dissolution of claysized
phyllosilicates can lead to a loss of clay in soils. The loss
generally is greatest in the upper horizons, where weathering
processes are most intense. Because this process generally
affects surface horizons more than subsurface horizons, a
vertical textural differentiation can result.
3. Selective erosion.—Raindrop splash and subsequent
surface soil erosion cause the smaller soil particles to be moved
farther downslope than the larger particles. Eventually, part of
the fine fraction is eliminated from the surface layer of sloping
soils, leaving a concentration of the coarser textured part. The
speed of this process depends on many factors. In areas where
highly erosive rain falls on soils with little surface cover, the
process can occur rapidly. The surficial movement of clay
downslope seems to be widespread, and selective erosion likely
is a process that contributes to textural differentiation in some
soils.
4. In situ clay formation.—Vertical textural
differentiation is enhanced in some soils when the surface
horizon dries and evaporation ceases but the subsoil remains
moist. The presence of water allows hydrolysis in the subsoil
and the subsequent production of clay. This process is
important in many soils.
5. Clay destruction in a subsurface horizon.—Clay
destruction may occur in a soil through the process of
ferrolysis. Ferrolysis causes loss of clay from the upper
horizons by decomposition from the upper layers. The process
consists of a sequence of repetitive cycles involving an
oxidative phase and a reductive phase. During the reductive
phase, the ferrous iron displaces exchangeable cations, which
are then removed by leaching. During the oxidative stage,
oxidation of exchangeable ferrous iron produces exchangeable
hydrogen, part of which attacks the phyllosilicate. In every
cycle, cations are removed by leaching and part of the
phyllosilicate is destroyed. With continued ferrolysis, a
seasonally wet soil, even if base saturated, can develop a gray,
silty or sandy horizon with a low clay content and a low cationexchange
capacity. Ferrolysis is the process that may help to
develop albic material in a number of soils, including Albolls
and Albaqualfs.
Regardless of the process responsible for textural
differentiation, clay illuviation in one form or another is
common to all argillic horizons.
Significance to Soil Classification
The argillic horizon represents a time-landscape
relationship that is locally and regionally important. A taxon
that includes all soils that have an argillic horizon would have
very few other common properties. Yet, the horizon is a mark
of landscape stability with respect to the formation and
preservation of a finer textured subsurface horizon, as opposed
to processes that destroy or remove clay from the horizon or
that mix horizons. Because an argillic horizon forms at a
relatively slow rate, its presence indicates that the geomorphic
Horizons and Characteristics Diagnostic for the Higher Categories 31
surface has been relatively stable and that the period of stability
has been long.
If the argillic horizon occurs in an area of an aridic moisture
regime (defined below) and is rarely moist or has free carbonates
throughout, it probably indicates an old soil and stable
geomorphic surface of such great age that the climate has
changed since the formation of the horizon. In the present
environment, the precipitation is not sufficient to remove
carbonates from the soil or to translocate clay to the base of the
argillic horizon.
On the steppes, savannas, and grasslands in areas of
subhumid climates, the argillic horizon is a useful means of
distinguishing between surfaces of Holocene or late-Pleistocene
age and older surfaces.
In cool, humid regions the argillic horizon seems to be
impermanent. It forms slowly, but there is evidence that with
time it is moved to a greater depth in the soil and is finally
destroyed. In its place, a glossic or spodic horizon may form.
In humid, temperate and tropical regions, the presence of an
argillic horizon has other meanings. In humid, temperate
regions that are forested, the argillic horizon is mainly a mark
of a stable surface. In the humid tropics the clay fraction of the
argillic horizon commonly is low in silicon because of intense
weathering. The high degree of weathering is reflected by a
dominance of 1:1 layer lattice clays and oxyhydroxides of iron
and by a general absence of 2:1 layer lattice clays, except for
hydroxy-interlayered vermiculite. Gibbsite can occur in the
most weathered argillic horizons. In humid, temperate and
tropical regions where cycling of bases by plants is the chief
mechanism by which basic cations are retained against
leaching from the soils, the available nutrients of ped exteriors
relative to ped interiors are significant to root development. In
some of these soils, the roots do not enter the peds of the
argillic horizon but occur along faces of the peds. The peds are
coated by continuous clay films with significantly more
nitrogen, phosphorus, and potassium than the available
nutrients in the interior of the peds.
Identification
Since the argillic horizon can result from one or more
processes acting simultaneously or sequentially and affecting
surface horizons, subsurface horizons, or both, one or more sets
of properties can be used for its identification. Positive
identification of the argillic horizon is difficult in some
situations. No one feature is common to all argillic horizons
and absent from all other horizons. Nearly all argillic horizons
have at least two of the following features:
1. There is more silicate clay in the argillic horizon than in an
overlying horizon. The boundary between the eluvial horizon
and the argillic horizon is generally clear or abrupt, and
commonly it is irregular. The clay content (percent, by weight,
less than 2 micrometers, excluding clay-sized carbonates) of the
argillic horizon must be at least 1.2 times the clay content of an
overlying eluvial horizon, and generally the increase must be
larger to be consistently detected in the field. The required
increase in clay content occurs within a vertical distance of 15
cm in most pedons, but it can occur within a vertical distance as
great as 30 cm and still meet the requirements for an argillic
horizon.
2. There are coatings of oriented clay on the surfaces of pores
and peds or orientated clay as coatings or as bridges between
sand grains somewhere within many argillic horizons. An
experienced pedologist can often identify the layers of oriented
clay on the surfaces of peds and in pores, called clay films,
with a 10 X hand lens. The clay films used to identify an
argillic horizon should occur on more than just the vertical
sides of peds. Examination of the surfaces of peds and pores
under a 10- to 20-power hand lens usually discloses one or
more of the features common to most clay films. The films may
differ from the interiors of the peds in color as well as texture.
Clay films should also have an observable thickness, whereas
many pressure faces do not. Pores that are open on the lower
side of a ped can have irregular lips where the clay protrudes.
Commonly, the surfaces have an irregular shape and show
channels and flow lines that apparently were formed by soil
solution moving through the soil. Photo 14 shows a prominent
clay film in a pore and a faint clay film on the surface of a ped
of an argillic horizon in a medium textured soil under
magnification. The pore has a prominent, dark gray coating,
and the surface of the ped has a distinct, brownish coating. The
broken surface that reveals the interior of the ped, on the right,
has no coating. The scale is 2 mm. Photo 15 shows illuvial clay
in sand. The clay coats the sand grains, and an occasional pore
has a clay film. Very commonly, the coatings occur only in part
of the horizon. Some argillic horizons have clay films only
toward the base of the argillic horizon.
3. The ratio of fine clay (particles less than 0.2 micrometer in
diameter) to total clay can be larger in an argillic horizon than
in the overlying horizons. This difference is more common in
soils with higher amounts of 2:1 phyllosilicates than 1:1
phyllosilicates. The table “Clay Distribution and Ratio of Fine
Clay to Total Clay in Two Soils That Have Argillic Horizons”
illustrates the difference in the size of clay particles in the
various horizons. The ratio of fine clay to total clay is typically,
but not always, highest in the argillic horizons with 2:1
phyllosilicates.
4. Rock structure is evident in less than half of the volume of
the argillic horizon. In this context rock structure includes fine
stratification (less than 10 mm) in unconsolidated sediments
(eolian, alluvial, lacustrine, or marine) and saprolite derived
from consolidated rocks in which unweathered minerals and
pseudomorphs of weathered minerals retain their relative
positions to each other.
32 Soil Taxonomy
5. The argillic horizon is commonly parallel or nearly parallel to
the surface. If the epipedon has been truncated, the argillic
horizon can occur at the soil surface.
Special Problems
This section is divided into five parts: (1) soils that formed in
uniform parent materials with clay illuviation; (2) truncated soils,
cultivated soils, and soils that formed in stratified parent
materials; (3) problems associated with determining the top of
the argillic horizon; (4) problems associated with determining
the base of the argillic horizon; and (5) destruction of the
argillic horizon.
1. Soils that formed in uniform parent materials with
clay illuviation.—It is believed that many soils are derived
from multiple parent materials rather than a single, uniform
material. Argillic horizons forming in uniform parent
materials are described first because they are the least
complicated. In soils that formed in uniform parent material
and have 15 to 40 percent clay in the overlying eluvial horizon,
no truncation, and no Ap horizon directly above the illuvial
horizon, the clay content in the illuviated horizon is at least 1.2
times greater than the clay content in the eluvial horizon. The
thickness of the illuvial horizon must be at least one-tenth that
of the overlying horizons, but as a minimum an illuvial
horizon must be at least 7.5 cm thick before it is considered an
argillic horizon. The thickness of the transition zone from the
eluvial horizon to the argillic horizon must be 30 cm or less.
The ratio of fine clay to total clay in the argillic horizon is
commonly at least 1.2 times greater than the ratio in the eluvial
horizon.
In soils with less than 15 percent clay in any part of the
overlying eluvial horizon, the illuvial horizon can be either
continuous vertically or composed of lamellae (photo 16). The
required ratio of clay in the illuvial horizon to that in the
eluvial horizon is somewhat higher than is required in both
medium textured and clayey soils. Soils that have less than 15
percent clay in any part of the eluvial horizon must have at
least 3 percent (absolute) more clay in the illuvial horizon. For
example, if the eluvial horizon has 4 percent clay, then the
illuvial horizon must have at least 7 percent clay.
In soils with less than 15 percent clay, the illuvial horizon
must be 15 cm or more thick to be an argillic horizon. If the
argillic horizon is composed of lamellae, which can be spaced
at intervals ranging from a few centimeters to a few decimeters
or more, only the lamellae 0.5 cm or more thick are considered
in determining whether the horizon meets the clay content and
thickness requirements for an argillic horizon.
In soils that have at least 40 percent clay in the eluvial
horizon, that formed in uniform material, and have no
truncation, the difference in clay content between the eluvial
horizon and the illuvial horizon must be 8 percent (absolute
difference) or more. For example, if the eluvial horizon has 42
percent clay, the illuvial horizon must have at least 50 percent
clay before it can be considered an argillic horizon. The
thickness of the illuvial horizon should be at least one-tenth
that of the overlying horizons. As a minimum, the illuvial
horizon must be at least 7.5 cm thick.
In areas where climates have distinct wet and dry seasons
and illuvial horizons have clayey textures and expansive 2:1
phyllosilicates, appreciable interped pressures are generated as
the clays swell. The pressures produce irregular but smooth
surfaces of peds and a strong degree of stress orientation of
clay throughout the ped. In many such clayey horizons,
identifying clay films is difficult or impossible.
If the coefficient of linear extensibility of the horizon
exceeds 0.04 and there are periods with distinct differences in
moisture content, the evidence of clay illuviation is satisfied if
the ratio of fine clay to total clay in the illuvial horizon is
greater by 1.2 times or more than the ratio in an overlying
horizon.
2. Truncated soils, cultivated soils, and soils that
formed in stratified parent materials.—Soils that formed in
stratified parent materials and truncated soils in which the
eluvial horizon has been removed or the illuvial horizon has
been mixed into an Ap horizon present special problems in the
identification of the argillic horizon. If both the eluvial
Clay Distribution and Ratio of Fine Clay to Total Clay in Two
Soils That Have Argillic Horizons
(Data for the argillic horizons are printed in italic type)
Clay distribution
Depth (cm)
Less than
0.002 mm
0.002 to
0.0002 mm
Less than
0.0002 mm
Fine clay:
total clay
Percent PercentPercent Ratio
0-18 ......... 22.6 15.8 6.8 0.30
18-25 ......... 26.2 18.8 7.4 .28
25-36 ......... 45.3 25.1 20.2 .45
36-58 ......... 42.8 26.6 16.2 .38
58-74 ......... 34.7 25.2 9.5 .27
74-89 ......... 32.9 24.0 8.9 .27
0-18 ......... 33.1 24.6 8.5 .26
18-25 ......... 32.4 23.2 9.2 .28
25-40 ......... 40.4 24.6 15.8 .39
40-53 ......... 45.0 25.0 20.0 .45
53-71 ......... 41.4 23.3 18.1 .44
71-120....... 38.0 23.3 14.7 .39
120-140....... 20.5 15.6 4.9 .23
140-205....... 20.3 15.3 5.0 .25
205-250....... 12.3 9.5 2.8 .23
Horizons and Characteristics Diagnostic for the Higher Categories 33
horizons and the illuvial horizons formed in materials with
different amounts of clay initially, differences in clay content
between the horizons cannot always be used to identify the
argillic horizon. Likewise, in soils that have been cultivated
and in which the Ap horizon is directly above the argillic
horizon, the argillic horizon may not be recognizable on the
basis of a clay increase. The plow layer may contain the most
clayey part of the original argillic horizon.
For soils that have an Ap horizon and do not have a
sufficient clay increase between the Ap horizon and the illuvial
horizon (as described above), the argillic horizon is determined
by the identification of evidence of clay illuviation, such as clay
films, clay linings on pores, or oriented clay in thin sections of
the matrix in some subhorizon.
In soils that have a lithologic discontinuity at the boundary
between the eluvial horizon and the illuvial horizon, clay
illuviation is evidence of an argillic horizon. Since it is critical
in these soils, clay illuviation must be prominent enough to
obscure fine sand grains on at least 10 percent of the surfaces
of peds, the clay illuviation must be nearly continuous in some
pores, or thin sections must show oriented clay coatings on at
least 1 percent of the horizon before the horizon is considered
to be an argillic horizon.
3. The top of the argillic horizon.—The top of the
argillic horizon in soils that are not truncated and that have no
lithologic discontinuity between the eluvial and illuvial
horizons occurs at the depth where the requirement for clay
increase is met. Soils that have an abrupt or clear boundary
between the eluvial and illuvial horizons have an argillic
horizon that starts near the top of the illuvial layer. If
properties of an argillic horizon are present but the upper
boundary is gradual, the top of the argillic horizon is the depth
at which the percentage of clay exceeds that of a horizon
higher in the profile by the appropriate amount after fitting a
smooth curve. Although the top of the argillic horizon is
defined on the basis of a clay increase, there are other
properties that provide clues to its identification. In many soils
the argillic horizon has stronger chroma, redder hue, or larger
structural units than the eluvial horizon. Clay films may or
may not be present at the depth designated as the top of the
argillic horizon.
In soils where the argillic horizon is degrading, such as soils
that have a glossic horizon, the top of the argillic horizon is the
point where the clay increase is met after mixing. For example,
an E/Bt horizon may be part of the argillic horizon if its clay
content, after mixing, exceeds the clay content of the overlying
horizon by the required amount. More commonly, Bt/E
horizons rather than E/Bt horizons have the required clay
increase.
The top of the argillic horizon in truncated soils that do not
exhibit the required clay increase and that do not have a
lithologic discontinuity is the bottom of the Ap horizon.
For soils that have a lithologic discontinuity between the
eluvial horizon and the illuvial horizon and that do not have
the required clay increase described above, the top of the argillic
horizon is considered to be at the contact between the two
materials.
4. The base of the argillic horizon.—The base of the
argillic horizon is obvious in many soils that overlie rootlimiting
layers, such as duripans or bedrock. In other soils the
lower boundary of the argillic horizon is gradual and
commonly is irregular. In these soils describing the base of the
argillic horizon is difficult, but a definition is needed for
identification of proper taxa.
The bottom of argillic horizons that have clay films is at the
depth where the combination of both structure with mean
horizontal dimensions of 10 cm or less and clay illuviation are
no longer identifiable. In sandy soils that have argillic horizons
without structure, the bottom of the argillic horizon is at the
depth where clay bridging of the sand grains is no longer
identifiable. The base of the argillic horizon is allowed to have
less total clay than the eluvial horizon.
Argillic horizons that do not have clay films, such as some
of the argillic horizons with a high shrink-swell potential, have
different criteria. The base of the argillic horizon in soils with
a high shrink-swell potential and no clay films is at the depth
where both the pressure faces and structure with mean
horizontal dimensions of 10 cm or less are no longer
identifiable.
5. Destruction of the argillic horizon.—An argillic
horizon can be formed and later destroyed. Destruction of
argillic horizons can occur in many ways and is by no means
limited to the following examples.
Argillic horizons that formed in paleoenvironments with
more effective precipitation than that in the present
environment can be engulfed by carbonates and more soluble
salts. This process commonly occurs in areas that are presently
arid. As the argillic horizon is engulfed, salt crystals grow and
plug the horizon. Concurrently, the salt crystals disrupt the soil
fabric and the cutans, including the clay films. In time, the
entire argillic horizon could be engulfed by salts and all
evidence of clay illuviation could be destroyed.
Mixing of horizons by animals, by frost, or by shrinking and
swelling can destroy argillic horizons or inhibit their
formation. Humans can rapidly change a soil and in some cases
destroy an argillic horizon.
Detailed studies of the micromorphology of some soils that
have an argillic horizon (e.g., Glossudalfs) provide evidence of
the destruction of argillic horizons. Clay films are absent from
the surfaces of peds, and skeletans, which are bleached silt or
sand grains that result from the loss of clay and iron, are
common. Oriented clay within the peds apparently persists. In
a degrading argillic horizon, the clay films on surfaces of peds
or in pores commonly are most abundant in the lower part of
the argillic horizon and in the underlying transitional horizon.
In advanced stages of degradation, there may be no clay films
within or on peds in the upper part of the argillic horizon.
Normally, a degrading argillic horizon also has an irregular
34 Soil Taxonomy
upper boundary that is marked by narrow to broad penetrations
of the eluvial horizon. Small nodular remnants of the argillic
horizon commonly occur in the lower part of the present
eluvial horizon.
An argillic layer that is being degraded or is subject to
pedoturbation must meet the requirements for clay increase
outlined above before it is considered an argillic horizon.
Required Characteristics
1. All argillic horizons must meet both of the following
requirements:
a. One of the following:
(1) If the argillic horizon is coarse-loamy, fine-loamy,
coarse-silty, fine-silty, fine, or very-fine or is loamy or
clayey, including skeletal counterparts, it must be at least
7.5 cm thick or at least one-tenth as thick as the sum of
the thickness of all overlying horizons, whichever is
greater. For example, if the overlying horizons are more
than 150 cm thick, then the argillic horizon must be 15
cm or more thick; or
(2) If the argillic horizon is sandy or sandy-skeletal, it
must be at least 15 cm thick; or
(3) If the argillic horizon is composed entirely of
lamellae, the combined thickness of the lamellae that are
0.5 cm or more thick must be 15 cm or more; and
b. Evidence of clay illuviation in at least one of the
following forms:
(1) Oriented clay bridging the sand grains; or
(2) Clay films lining pores; or
(3) Clay films on both vertical and horizontal surfaces
of peds; or
(4) Thin sections with oriented clay bodies that are
more than 1 percent of the section; or
(5) If the coefficient of linear extensibility is 0.04 or
higher and the soil has distinct wet and dry seasons, then
the ratio of fine clay to total clay in the illuvial horizon is
greater by 1.2 times or more than the ratio in the eluvial
horizon; and
2. If an eluvial horizon remains and there is no lithologic
discontinuity between it and the illuvial horizon and no plow
layer directly above the illuvial layer, then the illuvial horizon
must contain more total clay than the eluvial horizon within a
vertical distance of 30 cm or less, as follows:
a. If any part of the eluvial horizon has less than 15
percent total clay in the fine-earth fraction, the argillic
horizon must contain at least 3 percent (absolute) more clay
(10 percent versus 13 percent, for example); or
b. If the eluvial horizon has 15 to 40 percent total clay in
the fine-earth fraction, the argillic horizon must have at least
1.2 times more clay than the eluvial horizon; or
c. If the eluvial horizon has 40 percent or more total clay in
the fine-earth fraction, the argillic horizon must contain at
least 8 percent (absolute) more clay (42 percent versus 50
percent, for example).
Calcic Horizon
The calcic horizon is an illuvial horizon in which secondary
calcium carbonate or other carbonates have accumulated to a
significant extent (photo 17). Calcic horizons must be 15 cm or
more thick. They must have 15 percent calcium carbonate
equivalent and either have at least 5 percent more calcium
carbonate equivalent than the underlying horizon or have 5
percent or more identifiable secondary carbonates unless the
particle-size class is sandy, sandy-skeletal, coarse-loamy, or
loamy-skeletal and the clay content is less than 18 percent. If
the clay content is less than 18 percent and the particle-size
class is sandy, sandy-skeletal, coarse-loamy, or loamy-skeletal,
there must be at least 5 percent more calcium carbonate
equivalent than in an underlying horizon. In order to indicate
pedogenic accumulations of calcium carbonate, calcic horizons
require either identifiable secondary carbonates or more
calcium carbonate equivalent than an underlying horizon. If a
horizon with secondary carbonates is indurated or cemented to
such a degree that it meets the requirements for a petrocalcic
horizon, it is considered a petrocalcic horizon (defined below).
A calcic horizon may occur in conjunction with various other
horizons, such as a mollic epipedon, an argillic horizon, or a
natric horizon.
Most calcic horizons have identifiable secondary carbonates.
For reasons not fully understood, accumulations of carbonate in
some soils do not form filaments but are disseminated.
Disseminated carbonates have been observed in soils that are
high in gypsum or sodium and in soils where accumulations of
carbonate form through capillary rise.
The genetic implications of a calcic horizon vary. In arid
and semiarid regions with parent materials, including the dust
that falls, high in calcium carbonate, the precipitation is
insufficient to leach bases and salts. In these situations
carbonates accumulate in the larger voids, often first as
filaments along root channels and as thin, discontinuous
coatings on the bottom of rock fragments. With time,
continuous coatings of carbonate form on the rock fragments,
the carbonate filaments enlarge, and carbonate nodules and
concretions can form. With continued deposition of carbonates,
the horizon becomes plugged with carbonates. Finally, some
parts of a calcic horizon may become cemented or indurated,
though typically air-dry fragments of a calcic horizon slake in
water, except for disconnected carbonate concretions and
pendants under rock and pararock fragments.
In soils where ground water near the surface contains
appreciable amounts of calcium bicarbonate, capillary rise and
Horizons and Characteristics Diagnostic for the Higher Categories 35
evaporation and transpiration cause precipitation of calcium
carbonate. Depending on the depth from the surface to the
capillary fringe, the top of the zone of calcium carbonate
accumulation may be from the surface to a depth of about 60
cm. In such soils, the accumulation of calcium carbonate is
comparable to the accumulation of more soluble salts in desert
playas. Depending on the position of the water table, these soils
may occupy depressions. If water was ponded, a soil that has a
calcic horizon commonly forms a circular outline around the
deeper depressions and can also occur on microhighs in the
depressions.
In the situations above, one might attach a high genetic
significance to a calcic horizon. In some other circumstances,
however, one can attach little genetic significance to the
absolute amount of carbonates in a horizon or layer of
carbonate accumulation. Deposition from ground water at a
depth of 3 m or more is likely a geologic rather than a
pedologic process. In soils that formed in calcareous materials
on steppes, the amount of calcium carbonate in horizons that
contain secondary calcium carbonate is a partial function of the
amount of calcium carbonate in the parent materials.
Some plant species growing in soils with calcic horizons
often exhibit “lime-induced chlorosis,” in which
micronutrients, such as iron, manganese, and zinc, are
rendered unavailable to the plants. Plant species that occur
naturally in arid environments frequently do not exhibit this
chlorosis, but many agriculturally grown plant species, such as
citrus, avocados, corn, and beans, are susceptible to
micronutrient deficiencies in calcareous soils.
Required Characteristics
The calcic horizon has all of the following properties:
1. Is 15 cm or more thick; and
2. Is not indurated or cemented to such a degree that it meets
the requirements for a petrocalcic horizon; and
3. Has one or more of the following:
a. 15 percent or more CaCO3
equivalent (see below), and
its CaCO3
equivalent is 5 percent or more (absolute) higher
than that of an underlying horizon; or
b. 15 percent or more CaCO3
equivalent and 5 percent or
more (by volume) identifiable secondary carbonates; or
c. 5 percent or more calcium carbonate equivalent and
has:
(1) Less than 18 percent clay in the fine-earth fraction;
and
(2) A sandy, sandy-skeletal, coarse-loamy, or loamyskeletal
particle-size class; and
(3) 5 percent or more (by volume) identifiable
secondary carbonates or a calcium carbonate equivalent
(by weight) that is 5 percent or more (absolute) higher
than that of an underlying horizon.
Cambic Horizon
A cambic horizon (photo 18) is the result of physical
alterations, chemical transformations, or removals or of a
combination of two or more of these processes.
Physical alterations are the result of the movement of soil
particles by freezing and thawing, shrinking and swelling, root
proliferation, wetting and drying, or animal activities
(including human activities) to such an extent as to destroy
one-half or more of the original rock structure or to form
aggregations of the soil particles into peds, or both. Rock
structure in this context includes fine stratification (less than 5
mm thick) in unconsolidated sediments (eolian, alluvial,
lacustrine, or marine) and saprolite or residuum derived from
bedrock in which the unweathered minerals and pseudomorphs
of weathered minerals retain their relative positions to each
other.
Chemical transformations in the cambic horizon are the
result of (1) hydrolysis of primary minerals, which forms clays
and liberates sesquioxides; (2) solution and redistribution or
removal of carbonates or gypsum; (3) reduction and
segregation or removal of iron; or (4) a combination of these
processes.
Alteration by the accumulation of silicate clay, sesquioxides,
or organic matter or by the removal of calcium carbonate or
gypsum can also produce a cambic horizon. The accumulation
of clay and sesquioxides can be identified by field or laboratory
tests. The accumulation must be too little or the layer too thin
to meet the requirements for any other diagnostic subsurface
horizon. The cambic horizon also excludes layers that are part
of an anthropic, plaggen, folistic, histic, melanic, mollic, or
umbric epipedon but can include parts of some ochric
epipedons in unplowed soils. The cambic horizon and the
ochric horizon are not necessarily mutually exclusive.
The cambic horizon is commonly a subsurface horizon. It
normally lies in the position of a B horizon and in most pedons
is considered to be a B horizon, but it can include some A, E,
and transitional horizons. The cambic horizon is considered
part of the solum, and it normally occurs within the zone that
is reached by the roots of native plants. Some truncated soils
have a cambic horizon at the surface. Otherwise, the cambic
horizon is below one of the diagnostic epipedons. Regardless of
its mode of formation or position in a soil, the cambic horizon
must be 15 cm or more thick. The thickness requirement can
be met by combining lamellae that are 0.5 cm or more thick if
the other required criteria are met. The cambic horizon can
also include the illuvial materials that occur between the
lamellae. Although a cambic horizon requires a thickness of
only 15 cm, the base of the horizon must be 25 cm for most
taxa. (See the “Key to Soil Orders” in chapter 8.)
36 Soil Taxonomy
Below many argillic and spodic horizons, there are BC and CB
horizons that are transitional to the C horizon and in which
weathering and alteration have occurred. The alteration of
these transitional horizons in many soils is comparable to that
of other cambic horizons. There are also transitional horizons,
such as AB, EB, or BA horizons between an A or E horizon
and an argillic or kandic horizon, that may have the diagnostic
properties of a cambic horizon. Such transitional horizons are
considered cambic horizons. These cambic horizons are not
considered diagnostic above the series level in this taxonomy.
Identification
Cambic horizons may have several somewhat contrasting
forms, but each of these grades in places imperceptibly into the
others. The genetic significance of the cambic horizon varies
somewhat with the kind of soil. The properties of a cambic
horizon consistently carry the implication of a horizon that has
been altered. One could define several kinds of cambic
horizons and give them distinctive names, but understanding
the limits of the transitional forms would be difficult. The
possible benefits of separating the contrasting forms do not
seem to justify the complications that would result if one tried
to distinguish clearly the transitional forms. Nevertheless, it is
important to understand that cambic horizons vary in
appearance and in genetic significance. The typical forms that
the cambic horizon may have under varying combinations of
the soil-forming factors are described in the following
paragraphs.
1. A cambic horizon can form in the presence of aquic
conditions. If the level of ground water fluctuates near the soil
surface, free iron generally is removed from the individual
particles of sand, silt, and clay. Either this iron is lost from the
horizon, or some of it is concentrated, forming redoximorphic
concentrations. Gray redox depletions and red, brown, and
black redox concentrations are associated with the fluctuating
ground water. Because these features can develop rapidly in a
wet soil, they alone do not indicate sufficient alteration for the
identification of a cambic horizon. The processes of reduction
or of reduction and segregation of the iron must have been
intense enough to produce a horizon dominated by low chroma.
In addition, there must be soil structure or rock structure in less
than one-half of the volume before a layer can be identified as a
cambic horizon.
A cambic horizon normally does not form if aquic
conditions are present in a horizon at all times. Soils that
formed under these conditions have a reduced matrix with
colors that are commonly neutral or consist of shades of green
or blue. Soils with a reduced matrix change color on exposure
to air. Ordinarily, these changes are visible within a few
minutes if a moist clod is briefly exposed to the air and then is
broken so that the colors of the interior and the exterior can be
compared. Horizons with a reduced matrix are excluded from
the concept of the cambic horizon on the assumption that losses
of iron have been negligible.
A horizon forming under aquic conditions is a cambic horizon
if it has fluctuating aquic conditions within 50 cm of the surface
or the soil is artificially drained and the dominant colors (moist)
on faces of peds or in the matrix are characterized by the
following:
a. No change in hue on exposure to air; and
b. A value of 3 or less and chroma of 0; or
c. A value of 4 or more and chroma of 1 or less; or
d. Any value, chroma of 2 or less, and redox
concentrations.
2. Cambic horizons that are in subhumid and humid,
temperate regions and do not have aquic conditions near the
surface normally are brownish. Because free iron oxides have
been liberated, the chroma commonly is higher or the hue is
redder in the cambic horizon than in the C horizon or the
overlying horizon. Feldspars, volcanic glass, and easily
weatherable minerals, such as biotite, some pyroxenes, and
some amphiboles, show evidence of alteration under the
microscope. Oxides of iron derived from iron removed from
primary minerals can form coatings on individual soil paticles.
These coatings may be responsible for brownish and reddish
colors in the horizon. In humid, tropical regions the colors
commonly are more reddish than brownish.
Considerable time is required for the partial destruction of
iron-bearing minerals necessary for the development of color or
for the formation of clay. Structure, however, can form in short
periods. If there is sufficient clay and the soil material has a
relatively high coefficient of linear extensibility, expression of
structure takes place within a few years of the deposition of
sediment. Illuviation is insufficient to meet the requirements
for diagnostic horizons, and the peds generally do not show
distinctive coatings. In thin sections the microfabric
characteristics may include some distinctive features, such as
stress-oriented plasma domains. Illuviation argillans are
generally rare in cambic horizons. If there is a marked change
in pH because of the presence of calcareous materials
underlying the horizon or there is saprolitic material
underlying the cambic horizon, however, these underlying
materials may have significant amounts of translocated clay.
The presence of this clay implies that clay movement has taken
place in the soil, but the B horizon is not characterized by an
accumulation of translocated clay.
3. A cambic horizon that forms under a humid or subhumid
climate and from highly calcareous material commonly has
granular structure produced by soil fauna. In areas of temperate
and warm climates, earthworms, in particular, are ordinarily
active in mixing material from different horizons.
Consequently, the soil commonly is calcareous throughout its
Horizons and Characteristics Diagnostic for the Higher Categories 37
thickness, even though there has been a considerable loss of
carbonates. In calcareous materials there may be little or no
evidence of the weathering of feldspars and other silicate
materials. Evidence of the loss of carbonates is furnished by
weathered remnants of limestone fragments, by solution pitting
that can be seen on the faces of limestone pebbles, or by an
increasing content of carbonates with increasing depth. In
addition, the percentage of silicate clay commonly decreases
gradually with increasing depth.
4. In areas of arid and semiarid climates, the cambic horizon
commonly has still other forms. Gypsum and, especially,
calcium carbonate are common but are not present everywhere.
Except in areas that have Cicadidae or other burrowing
insects, the soil fauna are less significant to soil structure than
in humid regions. Changes in volume accompanying seasonal
changes in moisture content tend to produce prismatic
structure, and in some soils the prisms are very coarse. In arid
regions the tops of the prisms commonly lie only a very few
centimeters below a platy surface horizon. Other things being
equal, it appears that, up to a point, the lower the mean annual
precipitation, the closer the prisms are to the surface. Rock
structure, including fine stratification of sediments, is absent in
at least one-half of the volume of the cambic horizon, primarily
because the materials have been moved by roots and by
animals. In addition to soil structure or the absence of rock
structure, the cambic horizon shows evidence of the
redistribution of carbonates or gypsum. The mere redistribution
of salts more soluble than gypsum is insufficient evidence of a
cambic horizon because salt removal and accumulation can
occur very rapidly and change with the season. Calcium
carbonate and/or gypsum in transit through the cambic horizon
may be reprecipitated there, particularly on the undersides of
rock fragments, in pores, and on the faces of peds.
If calcium carbonate and gypsum are absent from the parent
material and from the dust that falls, there may be no
secondary carbonates or gypsum in the soil. In this situation,
the cambic horizon is identified by soil structure or the absence
of rock structure in more than one-half of the volume of the
horizon and any combination of redder hues and higher
chromas than in the underlying material or accumulations of
clays or sesquioxides. The clay content commonly decreases
with increasing depth in cambic horizons. Because of the
presence of lithologic discontinuities, however, determining
whether clay has been formed in the soil is difficult.
Features Common to Cambic Horizons
In spite of the diversity in appearance of cambic horizons,
there are some common features.
The degree of alteration of primary minerals may be slight
to very strong, but some weatherable minerals are present in
most cambic horizons. These include the clay minerals that
have a 2:1 lattice and amorphous clays as well as the various
alterable minerals that yield bases or iron to the soil solution.
Cambic horizons normally have soil structure, but some are
structureless.
A cambic horizon does not include layers that are part of the
following diagnostic horizons—an anthropic, histic, folistic,
melanic, mollic, plaggen, or umbric epipedon; an argillic,
calcic, gypsic, natric, oxic, petrocalcic, petrogypsic, placic, or
spodic horizon; or a duripan or fragipan (all defined in this
chapter).
A cambic horizon can include layers that are part of the
following diagnostic horizons—an ochric epipedon and an
agric, albic, glossic, or sombric horizon.
Required Characteristics
In summary, the cambic horizon is an altered horizon 15 cm
or more thick. If it is composed of lamellae, the combined
thickness of the lamellae must be 15 cm or more. In addition,
the cambic horizon must meet all of the following:
1. Has a texture of very fine sand, loamy very fine sand, or
finer; and
2. Shows evidence of alteration in one of the following forms:
a. Aquic conditions within 50 cm of the soil surface or
artificial drainage and all of the following:
(1) Soil structure or the absence of rock structure in
more than one-half of the volume; and
(2) Colors that do not change on exposure to air; and
(3) Dominant color, moist, on faces of peds or in the
matrix as follows:
(a) Value of 3 or less and chroma of 0; or
(b) Value of 4 or more and chroma of 1 or less; or
(c) Any value, chroma of 2 or less, and redox
concentrations; or
b. Does not have the combination of aquic conditions
within 50 cm of the soil surface or artificial drainage and
colors, moist, as defined in item 2-a-(3) above, and has soil
structure or the absence of rock structure in more than onehalf
of the volume and one or more of the following
properties:
(1) Higher chroma, higher value, redder hue, or higher
clay content than the underlying horizon or an overlying
horizon; or
(2) Evidence of the removal of carbonates or gypsum;
and
3. Has properties that do not meet the requirements for an
anthropic, histic, folistic, melanic, mollic, plaggen, or umbric
epipedon, a duripan or fragipan, or an argillic, calcic, gypsic,
natric, oxic, petrocalcic, petrogypsic, placic, or spodic horizon;
and
38 Soil Taxonomy
4. Is not part of an Ap horizon and does not have a brittle
manner of failure in more than 60 percent of the matrix.
Duripan
A duripan (L. durus, hard; meaning hardpan) is a subsurface
horizon that is cemented by illuvial silica to the degree that less
than 50 percent of the volume of air-dry fragments slake in water
or during prolonged soaking in acid (HCl). See photos 19 and 20.
Duripans vary in the degree of cementation by silica. In addition,
they commonly contain accessory cements, chiefly calcium
carbonate. As a consequence, duripans vary in appearance.
They generally are very firm or firmer and are always brittle, even
after prolonged wetting. They grade into and can occur in
conjunction with petrocalcic horizons, mostly in semiarid and
arid regions. They also grade into noncemented earthy materials
and into the fragipans of humid regions.
Genesis
Duripans occur mostly in soils with a xeric or aridic moisture
regime (defined later), that is, in soils that are seasonally dry or
are usually dry. Most soils that have a duripan have a moisture
regime in which soluble silica might be expected to be
translocated into lower horizons but not out of the soils.
Geographically, duripans are largely in areas affected by
volcanism. Soils may show evidence of recent ash deposition,
or they may be forming in sediments derived from pyroclastic
materials, such as tuffs and ignimbrites. Many duripans occur
in soils that contain an appreciable amount of volcanic glass in
the overlying horizons, which suggests the importance of
soluble silica to the genesis. Glass tends to weather readily, and
the weathering can liberate soluble silicates at a rapid rate.
Duripans are not limited to soils derived from volcanic
materials. Weathering of ferromagnesian minerals and
feldspars may also contribute to the formation of a duripan.
The parent materials of many soils that have a duripan
contain only a small amount of calcium. If calcium is
abundant, a calcic or petrocalcic horizon tends to occur with
the duripan.
In the initial stages of duripan formation, much of the silica
cementation appears to occur at or close to the weathering site
of the mineral grain or glass chard. Monosilicic acid in the
solution is adsorbed on soil grains, polymerizes, and
precipitates as the soil dries. Silt- and clay-sized particles can
then be cemented to the grains by the precipitated silica,
forming microaggregates. These microaggregates can grow in
size.
Alternatively, silica is adsorbed to the surface of the soil
particles, forming bridges that cement grains without
completely plugging small voids between the grains. This
process continues until roots and the downward movement of
the soil solution are stopped. At this point laminar caps
composed dominantly of silica and calcite can develop.
Once formed, a duripan may become broken into blocky
fragments, perhaps by earthquakes or slight volume changes
resulting from wetting and drying. Before a layer can be
considered a duripan, the lateral spacing of cracks wide enough
to allow the entry of feeder roots must average 10 cm or more.
AppearanceinanAridClimate
The strongly cemented to indurated duripans in areas of arid
climates (an aridic moisture regime, defined later) have an abrupt
upper boundary and are commonly platy. The plates are roughly
1 to 15 cm thick. In many of these pans, the pores and the
surfaces of the plates are coated with opal and with some
birefringent material that is probably a microcrystalline form of
silica. Carbonates generally are present in small to large
amounts. Roots commonly are between the plates. More than
50 percent of the cementation can be destroyed by alternately
soaking fragments of the pan in acid and concentrated alkali.
The acid is used to destroy any cementation by carbonates. If
some of the cements are carbonates or if a petrocalcic horizon
is present, less than 50 percent of the cementation is destroyed
by soaking the fragments in acid, but more than 50 percent is
destroyed by soaking the fragments in concentrated alkali,
either as a single treatment or by alternating treatments with
acid. The presence of a thin, continuous layer of opal, which is
insoluble in acid, indicates enough cementation by silica to
satisfy the requirements for a duripan. A duripan and a
petrocalcic horizon can occur together within the same
horizon. If a horizon is cemented and meets the criteria for a
petrocalcic horizon, any continuous horizon within the
cemented layers that does not slake, in 50 percent or more of
the volume, in acid is also considered a duripan. Commonly, a
nearly continuous layer of secondary silica occurs in the part of
the horizon that does not slake in acid.
The forms of a duripan that are transitional to regolith in
arid regions are mostly massive and firm or very firm when
moist and are brittle at all moisture states. Laminar caps of
silica and coatings of silica on plates are uncommon. For a
horizon to be a duripan, more than 50 percent of the horizon
must not slake in water or in HCl and the horizon must have at
least (1) a few vertical opal coatings, (2) some opal or other
forms of silica partly filling interstices or forming bridges
between sand-sized mineral grains, or (3) some silica coatings
or pendants on the undersides of rock and pararock fragments.
Moistened specimens of these forms of the duripan commonly
show a dull glassy luster when viewed under a hand lens. The
most weakly cemented forms of these transitional duripans can
be penetrated with some difficulty by a hand-powered soil
auger. Under irrigation, such horizons commonly are slowly
permeable to water, and, except in cracks, they are virtually
impenetrable to the roots of most plants.
Horizons and Characteristics Diagnostic for the Higher Categories 39
AppearanceinaMediterraneanClimate
In areas of Mediterranean climates (a xeric moisture regime,
defined later), the pan commonly has an abrupt upper boundary
and is broken into very coarse prisms or into polyhedrons that
are roughly 30 cm to 3 m or more in diameter. Coatings of opal
partly line the faces of the prisms and many of the pores. Roots
are absent in the prisms, except in cracks, and are commonly
matted on the upper boundary of the pan and on the sides of the
prisms. The prisms may have been formed by the slight volume
changes that result from wetting and drying. This process of
formation is suggested by the absence of prisms in the duripans
of arid regions.
The more strongly cemented pans of Mediterranean regions
have opal coatings over the tops of the polyhedrons as well as
on the sides, and the coatings are thicker than in the more
weakly cemented pans. Water often perches on top of the pan
during the rainy season. Coatings of iron, manganese, and
oriented clay may be observed on many of these pans.
Subsequent deposits of opal could engulf such coatings and
give rise to a cementation that can be broken down only by
repeated alternating treatments with solutions of acid and
concentrated alkali. Carbonates may be present above the pan
or in any part of it, or they may be completely absent. These
observations indicate that carbonates are not an essential part
of the pans.
The most weakly cemented forms of the duripans in a
Mediterranean region are mostly transitional to regolith.
Brittleness is pronounced at all moisture states, but most of the
pans can be penetrated with some difficulty by a hand-powered
soil auger. When dry, most of the pans are very hard and are
slowly permeable.
In areas of more humid climates (a udic moisture regime,
defined later), many of the duripans are in soils that have andic
soil properties (defined later) in some overlying horizons. Some
have characteristics transitional to a fragipan (described
later). Some have redoximorphic features of gray and strong
brown. Secondary carbonates and salts are absent in these
pans. The cementation in the pan must be strong enough for
less than 50 percent of dry pan fragments to slake when placed
in water. Some horizons meet the requirements for a fragipan if
more than 50 percent of dry pan fragments slake when placed in
water.
Required Characteristics
A duripan is a silica-cemented subsurface horizon with or
without auxiliary cementing agents. It can occur in conjunction
with a petrocalcic horizon.
A duripan must meet all of the following requirements:
1. The pan is cemented or indurated in more than 50 percent
of the volume of some horizon; and
2. The pan shows evidence of the accumulation of opal or
other forms of silica, such as laminar caps, coatings, lenses,
partly filled interstices, bridges between sand-sized grains, or
coatings on rock and pararock fragments; and
3. Less than 50 percent of the volume of air-dry fragments
slakes in 1N HCl even during prolonged soaking, but more
than 50 percent slakes in concentrated KOH or NaOH or in
alternating acid and alkali; and
4. Because of lateral continuity, roots can penetrate the pan
only along vertical fractures with a horizontal spacing of 10 cm
or more.
Fragipan
A fragipan (modified from L. fragilis, brittle, and pan;
meaning brittle pan) is an altered subsurface horizon, 15 cm or
more thick, that restricts the entry of water and roots into the
soil matrix. It may, but does not necessarily, underlie an
argillic, cambic, albic, or spodic horizon. It is commonly
within an argillic horizon, but some are within an albic
horizon. The fragipan has strongly developed fragic properties
(defined below). Commonly, it has a relatively low content of
organic matter and a high bulk density relative to the horizons
above it. The fragipan has a hard or harder rupture-resistance
class when dry. When moist, it has a brittle manner of failure
in 60 percent or more of the volume. The term “manner of
failure” refers to the tendency of a ped or clod to rupture
suddenly rather than to undergo slow deformation when
pressure is applied. Air-dried fragments slake when submerged
in water.
Most fragipans have redoximorphic features, show evidence
of translocation of clay, and have low or very low saturated
hydraulic conductivity. Some fragipans consist of albic
materials (defined below).
Most fragipans have very coarse prismatic structure. Some
have weak to strong, thick platy or lenticular structure within
the prisms. In others, the secondary structure is more nearly
weak coarse blocky than platy. Some fragipans have
transitional structure between platy and blocky. Some have no
secondary structure, and some appear to be massive. Many
have bleached, roughly vertical faces or borders of prisms that
look like seams in vertical cross section. The spacing of any
separations or bleached seams that are between the structural
units and allow the entry of roots averages 10 cm or more on
the horizontal dimensions.
The seams commonly have less clay in the upper part than
in the lower part. They form a polygonal pattern in horizontal
cross section. Most commonly, a fragipan has an abrupt or
clear upper boundary at a depth of 50 to 100 cm below the
original soil surface. The pan ranges from about 15 to 200 cm
in thickness. The lower boundary commonly is gradual or
diffuse. A fragipan is virtually free of roots, except in the
bleached seams and on the faces of prisms. In many fragipans
the bleached materials are not brittle when moist, although
40 Soil Taxonomy
they may be hard when dry. Photo 21 shows a fragipan that
begins at a depth of about 50 cm and has bleached seams
between peds. Clay films are on the faces of peds or on pore
fillings. Oriented clay is in the matrix of some fragipans.
Fragipans consisting of albic materials commonly do not have
bodies of oriented clay.
Significance to Soil Classification
Any continuous horizon that impedes movement of water
and the growth of roots is important to soil classification,
particularly for interpretations of soils for plant growth and for
engineering manipulations. Water stands above the pan in a
level soil and moves laterally along the top of the pan in a
sloping soil. Even though the processes that produce fragipans
are imperfectly known, these pans are restricted in their
climatic range and natural vegetation and are believed to be
genetic.
Genesis
The genesis of fragipans is obscure (Grossman and Carlisle,
1969). The formation of the density and brittleness of a fragipan
has been variously attributed to physical ripening, the weight of
glaciers, permafrost processes, and other events during the
Pleistocene. Some of the properties of some fragipans are
inherited from buried paleosols. The authors cited in the review
by Grossman and Carlisle all consider fragipans to be pedogenic
soil horizons, regardless of whether or not the density and
brittleness are pedogenic, on the basis of the following
evidence:
1. Fragipans show evidence of pedogenesis, other than
density and brittleness, including one or more of the
following—oriented clay in the matrix or on the faces of peds,
albic materials or coatings of albic materials on the faces of
peds or in seams, soil structure, and redoximorphic features in
the matrix or on the faces of peds.
2. The fragipan is roughly parallel to the soil surface.
3. The upper boundary of most fragipans has a narrow depth
range of about 50 to 100 cm below the surface, if the soil is not
eroded. This range in depth has been observed in northern
Michigan, in southern Mississippi, in New Zealand, in
Scotland, and in Italy. The extreme range in depth from the
surface in soils that have not been eroded or buried seems to be
from about 25 to 150 cm. This narrow range would be a
remarkable coincidence if the fragipans were not soil horizons.
4. The parent materials have common features, including a
loamy texture, few or no carbonates, and an appreciable
content of silt or very fine sand.
5. Fragipans of similar morphology underlie a variety of
horizons, including spodic, argillic, cambic, and albic
horizons.
6. Fragipans form only in soils in which water moves
downward through the profile. They are commonly at depths
that rarely freeze.
7. If a soil has an E´ horizon and a B´t horizon, the fragipan
may be in the lower part of an argillic horizon or even in the
eluvial horizon that separates the two B horizons. Thus, it
occurs in otherwise eluvial or illuvial horizons.
8. Fragipans most commonly occur in soils that formed under
forest vegetation.
The polygonal network of bleached materials is formed by
reduction of free iron after water has saturated the cracks. The
bleached materials commonly are bounded by a thin zone in
which iron has been concentrated. Other things being equal,
the structural units are smallest in the finest textured materials.
For a given texture, structure tends to be larger if the dry
season is short or mild rather than long or intense. Structural
units, with bleached surfaces, are rare or absent in the coarsest
textured materials.
If an argillic horizon overlies a fragipan, movement of clay
down the faces of structural units generally is indicated by
relatively thick clay films on the lower parts of the structural
units and by pedotubules within the peds.
Examination of the interiors of prisms shows close packing
of the mineral grains and bodies of oriented clay. The close
packing is consistent with the high bulk density of the fragipan
relative to the density of the overlying horizons.
The hardness of the fragipan when dry is largely attributed
to the close packing and to binding by clay. Binding by clay
alone, however, does not account for the brittleness of the pan
when it is moist. The brittleness may be the result of weak
chemical binding by one or more agents, not necessarily the
same in all kinds of soil. The higher pH of a fragipan that
underlies a spodic horizon suggests some consistent difference.
Hydrogen bonding with amorphous aluminosilicates has been
suggested in the literature. One piece of field evidence
supporting the hypothesis of weak chemical binding is that one
can find fragipans in which the brittleness appears to have
been partly or completely destroyed. Some soils in very old
arable fields in Belgium lack brittleness, but they retain the
color pattern. A weak fragipan is present in the adjacent fields.
The patterns of polygonal bleaching can be very well
developed, but the brittleness may be observable in only a small
part of the horizon near the center of the prisms. Fine feeder
roots ramify the nonbrittle parts of the prisms. The amount of
nonbrittle materials ranges from none to well over two-thirds
of the volume of the horizon.
A second piece of field evidence for weak chemical binding
is that, when exposed on streambanks, at least some fragipans
seem more stable than either the overlying horizons or the
underlying materials. The overlying and underlying materials
commonly slump in the exposures, and the fragipan protrudes.
The bleached materials on the sides of the prisms in the
protruding fragipan are commonly washed out by rain, after
which the brittle parts are exposed as separated prisms. At this
Horizons and Characteristics Diagnostic for the Higher Categories 41
time, the evidence about the cause of the brittleness is
conflicting.
Where a fragipan formed in till, its relatively high bulk density
may be attributed partly to the weight of the glaciers, to physical
ripening, or to consolidation within a layer of permafrost. Yet,
many if not all of the fragipans seem to reflect the influence of
other factors. One factor is presumed to be pressure generated
by very slight shrinking and swelling. When dry, a pan normally
has very fine cracks between the prisms, and very fine sand, silt,
and clay might be washed into these cracks when the dry
season ends. Then, when the pan is remoistened, it swells very
slightly. The force of swelling, however, is opposed by the
materials that have moved into the cracks between the prisms
and by the weight of the soil above. The internal pressure thus
generated may be responsible for part of the compaction. A
second factor is the inertness of the pan. Swelling and shrinking
produce little soil movement. Soil fauna seem to be absent, and
roots, restricted to the bleached zones between the prisms, are
mostly oriented vertically and do not lift the soil as they grow.
The pressure generated by the growth of the woody tree roots is
lateral, not vertical. The common flattened shape of the roots
attests to the pressure. Freezing and thawing are minimal. In
areas that support native vegetation, it is doubtful that many
fragipans ever freeze. Freezing is unlikely because of the depth
of the fragipan and the insulation provided by the O horizons
and by snow.
Identification
Four factors are important in identifying a fragipan.
First, a fragipan must have a minimum thickness. A
thickness of 15 cm or more is thought to be thick enough to
impart the interpretations for plant growth and for engineering
manipulations and to separate the fragipan from plowpans,
other compacted surface layers, or compacted layers near the
surface.
Second, a fragipan shows evidence of pedogenesis, in
addition to density and brittleness. This evidence, in the
matrix, on faces of peds, or in seams, is in the form of bodies of
oriented clay, clay films, albic materials, and/or both
redoximorphic features and soil structure. The evidence of
pedogenesis is needed to separate the fragipan from dense
parent materials (densic materials), such as dense till and
volcanic mudflow material.
Third, a fragipan has a combination of properties that
restrict the penetration of roots and water from 60 percent or
more of the volume of the horizon. Roots are restricted, except
in nearly vertical zones that form the boundaries between very
coarse structural units. The structural units are commonly
polyhedral in horizontal cross section and average 10 cm or
more across. Material within the structural units is massive, is
platy, or has weak blocky structure and has a firm or firmer
rupture-resistance class and a brittle manner of failure at or
near field capacity. Some fragipans are massive and are
restrictive throughout the horizon.
Fourth, air-dry fragments of the natural soil fabric, 5 to 10
cm in diameter, from more than 50 percent of the horizon slake
when they are submerged in water. This property separates
fragipans from duripans and other cemented horizons.
In the United States, soils that have a small amount of
plinthite normally are brittle in at least some parts of the
horizons that contain the plinthite. Some of these horizons
meet the requirements for a fragipan. At this stage of
knowledge, it is not clear that such horizons should be
considered fragipans. Where they are at depths comparable to
those of fragipans in other soils, however, the effects on plants
and on engineering uses of the soils are the same. For
pragmatic reasons, therefore, such horizons that have an upper
boundary within 100 cm of the mineral soil surface are
considered fragipans.
Required Characteristics
To be identified as a fragipan, a layer must have all of the
following characteristics:
1. The layer is 15 cm or more thick; and
2. The layer shows evidence of pedogenesis within the
horizon or, at a minimum, on the faces of structural units; and
3. The layer has very coarse prismatic, columnar, or blocky
structure of any grade, has weak structure of any size, or is
massive. Separations between structural units that allow roots
to enter have an average spacing of 10 cm or more on the
horizontal dimensions; and
4. Air-dry fragments of the natural soil fabric, 5 to 10 cm in
diameter, from more than 50 percent of the horizon slake when
they are submerged in water; and
5. The layer has, in 60 percent or more of the volume, a firm
or firmer rupture-resistance class, a brittle manner of failure at
or near field capacity, and virtually no roots.
Glossic Horizon
The glossic horizon (Gr. glossa, tongue) develops as a result
of the degradation of an argillic, kandic, or natric horizon from
which clay and free iron oxides are removed (photo 22). The
material between the peds resulting from this removal is albic
material (defined below). The process of eluviation gradually
progresses from the exteriors of the peds to their interiors. In
the early stages of development, the peds of the remnant
argillic, kandic, or natric horizon still form structural units that
extend throughout the glossic horizon, constituting close to 85
percent of its volume. In this early stage, the albic materials,
when viewed in vertical cross section, resemble tongues
extending into the horizon from the top. In the later stages,
some of these structural units no longer extend throughout the
horizon, and in the most advanced stages of the degradation
process, remnant peds constitute little more than 15 percent (by
42 Soil Taxonomy
volume) of the glossic horizon and are completely surrounded
by albic materials. The boundary between the illuvial and eluvial
parts of the glossic horizon may be either abrupt or clear and
either irregular or broken.
A glossic horizon generally occurs between an overlying
albic horizon and an underlying argillic, kandic, or natric
horizon or fragipan. It can lie between an argillic, cambic, or
kandic horizon and a fragipan. In the early stages of the
degradation process described above, a glossic horizon can be
within an argillic, kandic, or natric horizon or within a
fragipan if the fragipan shows evidence of the degradation of
an argillic horizon. An albic horizon may be below, or between
subhorizons of, the glossic horizon.
Argillic horizons consisting of lamellae and intervening
albic materials are not within the concept of the glossic
horizon.
Required Characteristics
The glossic horizon is 5 cm or more thick and consists of:
1. An eluvial part, i.e., albic materials (defined below), which
constitute 15 to 85 percent (by volume) of the glossic horizon;
and
2. An illuvial part, i.e., remnants (pieces) of an argillic,
kandic, or natric horizon (defined below).
Gypsic Horizon
The gypsic horizon is an illuvial horizon in which
secondary gypsum has accumulated to a significant extent
(photo 23). Most gypsic horizons occur in arid environments
where the parent materials are rich in gypsum. In soils that
have ground water near the surface, capillary rise and
evaporation plus transpiration can result in significant
accumulations of gypsum.
Gypsum may accumulate uniformly throughout a matrix of
sand and finer textured material or as masses or clusters of
crystals. In gravelly or stony material, it may accumulate in
pendants below the rock fragments.
Because of its solubility, gypsum can dissolve in soils and
cause damage to buildings, roads, irrigation delivery systems,
earthen dams, and other structures.
Required Characteristics
A gypsic horizon has all of the following properties:
1. Is 15 cm or more thick; and
2. Is not cemented or indurated to such a degree that it meets
the requirements for a petrogypsic horizon; and
3. Is 5 percent or more gypsum and 1 percent or more (by
volume) secondary visible gypsum; and
4. Has a product of thickness, in cm, multiplied by the
gypsum content percentage of 150 or more.
Thus, a horizon 30 cm thick that is 5 percent gypsum
qualifies as a gypsic horizon if it is 1 percent or more (by
volume) visible gypsum and is not cemented or indurated to
such a degree that it meets the requirements for a petrogypsic
horizon.
The gypsum percentage can be calculated by multiplying the
milliequivalents of gypsum per 100 g soil by the
milliequivalent weight of CaSO4
.2H2
O, which is 0.086.
Kandic Horizon1
Genesis
A kandic horizon is a subsurface horizon that has a
significantly higher percentage of clay than the overlying
horizon or horizons and has an apparent CEC of 16 cmol(+) or
less per kg clay (by 1N NH4
OAc pH 7) and an apparent ECEC
of 12 cmol(+) or less per kg clay (sum of bases extracted with
1N NH4
OAc pH 7 plus 1N KCl-extractable Al) in 50 percent or
more of the soil volume in the upper 100 cm or to a densic,
lithic, paralithic, or petroferric contact if shallower. The claysized
fraction is composed predominantly of 1:1 layer silicate
clays, mainly kaolinite, with varying amounts of oxyhydroxides
of iron and aluminum. Clay films may or may not be present.
(The percentage of clay is either measured by the pipette
method or estimated to be 2.5 times [percent water retained at
1500 kPa tension minus percent organic carbon], whichever
value is higher, but no more than 100.)
Textural differentiation in pedons with kandic horizons may
result from one or more processes acting simultaneously or
sequentially, affecting surface horizons, subsurface horizons, or
both. These processes are not all clearly understood, although
the most important ones can be summarized as follows:
1. Clay eluviation and illuviation.—In some soils it is
often difficult to find clear evidence, even by
micromorphological analysis, that the higher clay content in
the B horizon is a result of accumulation by illuviation of layer
silicate clays. Specifically, clay films (cutans) may be
completely absent, or they may be present only at depths below
the control section used in classification. In other soils clay
films may have been destroyed by biological activity or
pedoturbation processes. High concentrations and strong
activity of soil fauna in soils of tropical and subtropical areas,
where kandic horizons are common, may cause the partial or
total disappearance of clay films to a considerable depth over
time.
Many of the soils with kandic horizons that probably have
formed by illuvial processes occur on stable geomorphic
surfaces. On stable surfaces the illuviation process may no
longer be operative or at least may be acting so slowly that
mixing by soil organisms is more rapid than the formation of
1
The concept of the kandic horizon and the “kandi” and “kanhapli” great groups of soils
represent the work of the International Committee on the Classification of Low Activity Clays
(ICOMLAC), chaired by Dr. Frank R. Moormann.
Horizons and Characteristics Diagnostic for the Higher Categories 43
clay films. Under these conditions, clay films may be evident in
some pedons but not in other nearby pedons that otherwise
have similar morphology. Even within the same horizon of a
single pedon, some peds may have clay films while others do
not.
2. Clay destruction in the epipedon.—Weathering of
layer silicates may lead to a relative loss of clay in soils. The
loss generally is greatest in the upper horizons, where
weathering processes are most intense. Elimination of bases
and some silica is enhanced by high surface soil temperatures
in well drained soils with high rates of leaching. Because this
process affects surface horizons more than subsoil horizons, a
vertical textural differentiation may result. This process may
also have resulted in the absence of clay films in the lower
horizons of highly weathered soils on old stable surfaces. A
related process that occurs in surface horizons that are
periodically wet may also result in similar textural
differentiation.
3. Selective erosion.—Raindrop splash and subsequent
surface soil erosion cause the smallest soil particles to be
moved farther downslope than the larger particles. Eventually,
part of the fine fraction may be eliminated from the surface
layer of sloping soils, leaving a coarser textured surface layer.
The speed of this process depends on many factors. It may be
very rapid in climates with highly erosive rains or on soils with
little plant cover. The surficial movement of clay downslope
seems to be widespread, and selective erosion probably is a
major process leading to textural differentiation. The process
appears to be enhanced by periodic fire or by intermittent
cultivation, such as the shifting cultivation practiced for
thousands of years in areas where these soils occur.
4. Sedimentation of coarse textured surface
materials.—Lithologic discontinuities are probable on stable
landscapes in many intertropical areas. In many of the soils of
these areas, the surface layer is coarser textured than the
subsoil. Because all of the soil material is highly weathered,
however, stratification is not evident. If the finer textured
subsoil fulfills the requirements for the kandic horizon and the
surface layer is not composed of fine strata of recent material,
the subsoil horizon is classified as a kandic horizon.
Significance to Soil Classification
The kandic horizon provides a basis for differentiation
among soils with clay accumulation in the subsoil. The argillic
horizon alone does not provide an adequate diagnostic criterion
to differentiate all Ultisols and Alfisols from Oxisols and
Inceptisols. The kandic horizon is a diagnostic horizon that
separates Ultisols and Alfisols in which the clay fraction has
clay minerals with low CEC, comparable to Oxisols, from
Ultisols and Alfisols that have clay minerals with high CEC.
Textural differentiation in most low-activity clay soils by itself
is believed to be sufficiently important for the understanding of
soil development and use and should be recognized at a high
level of the classification system. In soils with clayey surface
horizons, however, the textural differentiation loses much of its
significance. Most low-activity clay (LAC) soils that have, after
mixing of the upper 18 cm, more than 40 percent clay in the
surface horizon will be Oxisols, although a few that have LAC
and the clay increase necessary for an argillic or kandic
horizon but have significant amounts of weatherable minerals
will remain “kandi” Ultisols or Alfisols.
The presence of a kandic horizon indicates a high degree of
weathering of the mineral soil material, such as that in soils on
old surfaces where weathering has taken place under warm
climatic conditions with moderate to high precipitation. The
high degree of weathering is reflected by a dominance of 1:1
layer silicate clays and oxyhydroxides of iron and aluminum,
although small amounts of 2:1 layer silicate clays may also be
present. There is a general absence of short-range-order
minerals, such as allophane or imgolite. The composition of
the 0.02 to 0.2 mm fraction does not always reflect the same
degree of weathering, especially in soils that formed in
weathering products of crystalline rocks. Thus, no weatherable
mineral content is specified in the definition of the kandic
horizon.
Identification
The kandic horizon is a vertically continuous subsurface
horizon (not composed of lamellae) with a significantly finer
texture than the overlying horizon or horizons. It may underlie
an ochric, umbric, anthropic, or mollic epipedon. The upper
boundary normally is clear or gradual, although it may be
abrupt. It is never diffuse. The increase in clay content is
reached within a vertical distance of 15 cm or less.
The top of the kandic horizon is within one of the following
depths:
1. If the particle-size class throughout the upper 100 cm is
sandy, the upper boundary is at a depth between 100 and 200
cm from the soil surface in most of the pedon.
2. If the clay content of the surface horizon is less than 20
percent and the particle-size class (of part or all of the upper
100 cm) is finer than sandy, the upper boundary is at a depth of
less than 125 cm from the soil surface.
3. If the clay content of the surface horizon is 20 percent or
more, the upper boundary is at a depth of less than 100 cm
from the mineral soil surface.
Textures coarser than loamy very fine sand are excluded
from the definition of the kandic horizon. The presence or
absence of clay films, identified by field examination, or cutans
in thin sections, is not a differentiating characteristic for
kandic horizons.
Other field characteristics of kandic horizons are not
normally diagnostic, since these horizons may have properties
of the argillic, cambic, or oxic horizon. Some soils with kandic
horizons resemble those with argillic horizons in that they have
a well developed subangular blocky structure, while bleached
44 Soil Taxonomy
grains of sand and silt may be present in the overlying coarser
textured horizon or horizons. The ratio of fine clay (particles
smaller than 0.2 micrometer) to total clay may be larger in the
kandic horizon than in the overlying coarser textured horizon or
horizons but is not diagnostic.
Other kandic horizons have one or more properties of oxic
horizons and would be called oxic horizons if they did not have
a distinct increase in content of clay at the upper boundary.
This rationale is comparable to that used for pedons dominated
by more active clays where an argillic horizon would be called
a cambic horizon if it did not have the characteristic increase
in content of clay at the upper boundary.
A kandic horizon is not overlain by layers more than 30 cm
thick that show fine stratification and/or have an organiccarbon
content that decreases irregularly with increasing depth,
unless it is a buried horizon. The kandic horizon also does not
show fine stratification and/or have an organic-carbon content
that decreases irregularly with increasing depth.
Required Characteristics
The kandic horizon:
1. Is a vertically continuous subsurface horizon that underlies
a coarser textured surface horizon. The minimum thickness of
the surface horizon is 18 cm after mixing or 5 cm if the
textural transition to the kandic horizon is abrupt and there is
no densic, lithic, paralithic, or petroferric contact (defined
below) within 50 cm of the mineral soil surface; and
2. Has its upper boundary:
a. At the point where the clay percentage in the fine-earth
fraction, increasing with depth within a vertical distance of
15 cm or less, is either:
(1) 4 percent or more (absolute) higher than that in the
surface horizon if that horizon has less than 20 percent
total clay in the fine-earth fraction; or
(2) 20 percent or more (relative) higher than that in the
surface horizon if that horizon has 20 to 40 percent total
clay in the fine-earth fraction; or
(3) 8 percent or more (absolute) higher than that in the
surface horizon if that horizon has more than 40 percent
total clay in the fine-earth fraction; and
b. At a depth:
(1) Between 100 cm and 200 cm from the mineral soil
surface if the particle-size class is sandy or sandy-skeletal
throughout the upper 100 cm; or
(2) Within 100 cm from the mineral soil surface if the
clay content in the fine-earth fraction of the surface
horizon is 20 percent or more; or
(3) Within 125 cm from the mineral soil surface for all
other soils; and
3. Has a thickness of either:
a. 30 cm or more; or
b. 15 cm or more if there is a densic, lithic, paralithic, or
petroferric contact within 50 cm of the mineral soil surface
and the kandic horizon constitutes 60 percent or more of the
vertical distance between a depth of 18 cm and the contact;
and
4. Has a texture of loamy very fine sand or finer; and
5. Has an apparent CEC of 16 cmol(+) or less per kg clay (by
1N NH4
OAc pH 7) and an apparent ECEC of 12 cmol(+) or
less per kg clay (sum of bases extracted with 1N NH4
OAc pH 7
plus 1N KCl-extractable Al) in 50 percent or more of its
thickness between the point where the clay increase
requirements are met and either a depth of 100 cm below that
point or a densic, lithic, paralithic, or petroferric contact if
shallower. (The percentage of clay is either measured by the
pipette method or estimated to be 2.5 times [percent water
retained at 1500 kPa tension minus percent organic carbon],
whichever is higher, but no more than 100); and
6. Has a regular decrease in organic-carbon content with
increasing depth, no fine stratification, and no overlying layers
more than 30 cm thick that have fine stratification and/or an
organic-carbon content that decreases irregularly with
increasing depth.
Natric Horizon
The natric (modified from natrium, sodium; implying the
presence of sodium) horizon is a special kind of argillic
horizon (photo 24). The dispersive properties of sodium
accelerate clay illuviation. Research has shown that natric
horizons form in Holocene-age soils, even in arid or semiarid
environments.
The effect of sodium on dispersion of clay and on the
formation of a B horizon of illuvial clay has long been
recognized. The effect of magnesium ions on dispersion of clay,
however, is still inconclusive. Laboratory studies seem to show
but slight difference between the effects of magnesium and the
effects of calcium. Yet, it is common for soils with a large
amount of exchangeable magnesium to have poor physical
properties. The reasons for the poor physical condition are
uncertain. Magnesium is considered in the definition of the
natric horizon because, as sodium is removed, magnesium
follows in the leaching sequence if chlorides are low and
sulfates high. If leaching continues, the magnesium is
eventually replaced. When replacement reaches the point
where the amount of exchangeable sodium is less than 15
percent and the amount of magnesium and sodium is less than
that of calcium and exchange acidity in upper subhorizons that
have a total thickness of 40 cm or more, the horizon is no
longer considered natric. The remains of such former natric
horizons are evident in soils in which the columnar structure is
Horizons and Characteristics Diagnostic for the Higher Categories 45
clearly evident but all other properties have been altered
because of a greatly changed environment or continued
leaching.
Required Characteristics
The natric horizon has, in addition to the properties of the
argillic horizon:
1. Either:
a. Columns or prisms in some part (generally the upper
part), which may break to blocks; or
b. Both blocky structure and eluvial materials, which
contain uncoated silt or sand grains and extend more than
2.5 cm into the horizon; and
2. Either:
a. An exchangeable sodium percentage (ESP) of 15
percent or more (or a sodium adsorption ratio [SAR] of 13
or more) in one or more horizons within 40 cm of its upper
boundary; or
b. More exchangeable magnesium plus sodium than
calcium plus exchange acidity (at pH 8.2) in one or more
horizons within 40 cm of its upper boundary if the ESP is
15 or more (or the SAR is 13 or more) in one or more
horizons within 200 cm of the mineral soil surface.
Ortstein
Ortstein is a cemented horizon that consists of spodic
materials.
Ortstein has one of the following orientations:
1. As a relatively horizontal layer. This type of orientation
tends to be root restrictive and occurs primarily in Aquods.
2. As vertical to irregular columns, tongues, pillars, or
bridges. This orientation tends to be less root restrictive than
the horizontal orientation. Vertical orientation occurs primarily
in Orthods.
3. As nodules. These may be remnants of one of the
orientations listed above.
Ortstein is 25 mm or more thick and 50 percent or more (by
volume) cemented. Continuous ortstein is 90 percent or more
cemented and has lateral continuity. Because of this continuity,
roots can penetrate only along vertical fractures with a
horizontal spacing of 10 cm or more.
Ortstein is differentiated from a placic horizon within
spodic materials solely on the basis of thickness. Placic
horizons within spodic materials are less than 25 mm thick,
and ortstein is 25 mm or more thick.
Required Characteristics
Ortstein has all of the following:
1. Consists of spodic materials; and
2. Is in a layer that is 50 percent or more cemented; and
3. Is 25 mm or more thick.
Oxic Horizon
The oxic horizon is a mineral subsurface horizon of sandy
loam or a finer texture with a low cation-exchange capacity
and a low content of weatherable minerals. It is at least 30 cm
(12 in) thick. The clay-sized fraction generally is dominated by
kaolinite with or without iron and aluminum oxyhydrates and
with few or no other lattice silicate minerals, except for
hydroxy interlayered vermiculites. The silt and sand fraction of
the oxic horizon is generally dominated by quartz with some
other resistant minerals. Weatherable minerals that are
potential sources of plant nutrients (K, Ca, and Mg) may be
present only if they do not exceed 10 percent of the 50- to 200micron
fraction. Rock fragments or lithorelicts may be present
only if they are coated with sesquioxides or if the included
weatherable minerals are completely altered.
Where dispersion is a problem, 3 times (percent water
retained at 1500 kPa tension minus percent organic carbon) is
used to estimate clay content. The apparent CEC, by the 1N
NH4
OAc pH 7 method, is equal to or less than 16 cmol(+) per
kg of clay, and the apparent effective CEC (ECEC), as
determined by the sum of NH4
OAc displaced bases plus 1N
KCl-extractable aluminum, is equal to or less than 12 cmol(+)
per kg of clay. The mineralogy and charge characteristics
exclude horizons containing significant quantities of shortrange-order
minerals. The oxic horizon does not have andic
soil properties. Some oxiclike horizons may have high amounts
of low-charge illite, but they have more than 10 percent
muscovite in the 50- to 200-micron fraction and are thus
excluded from oxic horizons because muscovite is considered a
weatherable mineral.
The upper boundary of the oxic horizon is either 18 cm
below the mineral soil surface or at the lower boundary of an
Ap horizon, whichever is deeper, or it is at a greater depth
where mineralogical and charge characteristics meet the
requirements for the oxic horizon. Any increase in clay content
at the upper boundary must be diffuse. The lower boundary of
the oxic horizon is also defined by its mineralogical and charge
requirements and may, in addition, be defined by the presence
of saprolite with rock structure.
Significance to Soil Classification and Use
One important attribute of the oxic horizon is that it is
almost devoid of primary weatherable minerals. Thus, further
weathering will release few plant nutrients.
Another important attribute is that in many soils with oxic
horizons the clay content is relatively constant with increasing
depth, indicating little or no clay mobility, which suggests a
high order of stability in the clay fraction of these soils. This
46 Soil Taxonomy
stability has been attributed to cementation by sesquioxides.
Oxic horizons generally have only traces of water-dispersible
clay if their net charge is near zero, but this characteristic is
also shared by some other horizons.
A third attribute of most oxic horizons is a stable fine and
very fine granular structure and thus the friable and porous
nature of the horizon. Bulk densities are generally low,
commonly near 1 g/cm3
in fine and very-fine particle-size
classes. Macrostructure may be angular or subangular blocky,
but the grade of blocky structure is generally weak.
These and other attributes directly or indirectly influence
the performance of soils having oxic horizons. The very low
cation-exchange capacity is an important consideration in soil
management. In addition, some oxic horizons have a high
capacity to adsorb anions and make some of the anions,
especially phosphates, unavailable to plants. Large amounts of
phosphate may need to be added as an initial amendment to
overcome the fixation capacity. Cations may need to be added
frequently and in small amounts to compensate for leaching
losses. The low CEC, where dominated by exchangeable Al, is
often an advantage in that only small amounts of basic cations
are needed to increase the base saturation percentage. Further,
the ease with which basic cations are leached makes the
chemical deepening of the root zone feasible via continued
applications of lime or gypsum.
Although oxic horizons commonly contain high amounts of
clay, their tendency to form a strong grade of very fine or fine
granular structure may give them characteristics similar to
those of sands. The horizons have a low available waterholding
capacity because most of the pores are either very large
between the granules (and thus do not retain water against the
forces of gravity) or are very small within the granules (and
thus retain water at too great a tension to be extracted by
plants). Plants may show evidence of moisture stress after only
a week without rain. Although the low available water-holding
capacity is most limiting to shallow-rooted plants, yields of
deep-rooted trees, such as rubbertree and oil palm, are also
known to decline because of moisture stress.
It is considered desirable to identify soil horizons that are
nearly sterile mineralogically because they are unable to supply
basic cations through the continued weathering of primary
minerals. As such, the oxic horizon can be considered a
counterpart of the cambic horizon, which has a greater content
of weatherable minerals. As with the cambic horizon, the
exclusion of certain sandy textures is admittedly arbitrary. In
the case of the oxic horizon, however, it is considered
necessary to preserve the uniformity of the horizon with
materials that have enough clay to reflect the low CEC nature
and structural tendencies.
When considered in the vertical sequence of a soil profile,
an increase in clay content with increasing depth may be
associated with increased grades of blocky structure not
common to the central concept of the oxic horizon. Where the
increase in clay content is below coarser textured surface
horizons, a small increase in the amount of clay appears more
significant to moisture relationships than where the surface
horizon is clayey. This increase is especially significant in the
interpretation of soils that have been subject to accelerated
erosion. Where the coarser textured surface horizons are
eroded in cultivated areas and finer textured subsoil material
becomes incorporated into the plow layer, spatial heterogeneity
with respect to the characteristics of the plow layer develops.
Thus, this pattern is considered more closely related to soils
that have argillic horizons than to soils that do not have rather
abrupt increases in clay content with increasing depth.
Therefore, some horizons with many oxic horizon properties,
such as low CEC and an absence of weatherable minerals, are
classified as kandic horizons and may be part of Ultisols and
Alfisols rather than Oxisols if there is less than 40 percent clay
in the upper 18 cm.
The identification of an oxic horizon in most soils requires
that the increase in clay content with increasing depth not
exceed 1.2 times the clay content in the overlying horizons
within a vertical distance of 15 cm (gradual boundary limit) if
the surface horizon contains 20 to 40 percent clay. If the
surface horizon contains more than 40 percent clay, an oxic
horizon must have an absolute clay content increase of less
than 8 percent within a vertical distance of 15 cm. If the
surface horizon contains less than 20 percent clay, the oxic
horizon must have an absolute clay content increase of less
than 4 percent in a vertical distance of 15 cm. These are
admittedly arbitrary limits, but they lend themselves to
consistent identification in the field and rather easy verification
by laboratory techniques.
Genesis
Oxic horizons are generally in soils on very old stable
geomorphic surfaces. They may occur in soils on younger
surfaces if the parent rock is basalt, serpentine, or other easily
weathered rock or if the parent material is preweathered. Oxic
horizons are not common in soils on steep slopes where
rejuvenation of the soils takes place through erosion,
truncation, or lateral flow of base-enriched subsurface water.
Soils on old geomorphic surfaces that may date to the mid
or late Tertiary generally have been reworked. Many of the
surficial deposits are preweathered, transported over short
distances, and deposited, perhaps several times. After
deposition and stabilization of the landscape, weathering and
soil formation start anew. Stone lines composed of quartz or
petroplinthite are common in some of these soils if the original
material could supply the stones. Quartz veins may be traced
through the saprolite but end abruptly or taper off at the stone
line, indicating that the material above the stone line has been
transported. Particle-size sorting may take place during
transport and deposition, and lithologic discontinuities are
common, although materials are very similar.
Horizons and Characteristics Diagnostic for the Higher Categories 47
As was indicated earlier, the parent materials may be
strongly preweathered. Weathering continues after deposition.
The intensity of the weathering is a function of environmental
conditions. In areas of aridic climates, this is minimal, and it is
supposed that the oxic properties were attained during
previous, more humid phases of the climate or in poorly
drained environments or developed as the material weathered
in transport.
In the more easily weathered parent materials and when
climatic conditions are favorable, oxic horizons form in soils
on young surfaces and over a relatively short period. Leaching
and desilicification are the most important processes, resulting
in a deep solum. The weathering front moves rapidly down the
soils, and on many basic and ultrabasic rocks, there is no real
saprolitic zone because the oxic horizon rests on rock or on a
thin weathering crust. Primary minerals are altered to
kaolinite, and, simultaneously or at a later stage, gibbsite and
geothite also accumulate. Accidents of nature may occur,
leaving behind some partially weathered rock or mineral
fragments in the oxic horizon. These fragments are generally
rare and, if present, are frequently coated with sesquioxides.
Pseudomorphs of olivine and augite may be present in some
oxic horizons, but these are not considered indicators of a lack
of weathering.
On stable surfaces time has permitted homogenization of the
soil material by pedoturbation processes. It is also possible that
the active pedoturbation has disrupted and assimilated any
evidence of lessivage, such as clay films. Consequently, most
oxic horizons are uniform in color, texture, and other
mineralogical or chemical properties to great depths in the soil.
The pedoturbation processes have also disrupted any rock
structure. In some saprolites weathering results in a
pseudomorphic alteration of feldspar phenocrysts to gibbsite,
the aggregates of which retain the original fabric.
Mineralogically and chemically, the saprolite may meet the
requirements for an oxic horizon, but it is not considered an
oxic horizon if it retains more than 5 percent rock fabric.
Booklets of kaolinite that formed through the pseudomorphic
alteration of biotite are considered weatherable minerals. In an
oxic horizon, these are disrupted and assimilated in the soil
material.
Soils with oxic horizons frequently occupy the upper part of
the landscape. The silica potential is very low in such soils.
These soils have a leaching environment in which there is no
possibility for synthesis of 2:1 clay minerals. Even in the wet
soils with oxic horizons, the recharging water may be so low in
bases and silica that, despite a high water table, the soils are
continuously flushed and leached. Isohyperthermic soil
temperature regimes and udic or perudic soil moisture regimes
are often considered optimal for the formation of oxic horizons,
but soils with oxic horizons are common in areas with ustic
soil moisture regimes or with isothermic soil temperature
regimes. They are rare in areas with aridic soil moisture
regimes and isomesic soil temperature regimes. Some oxic
horizons are present in areas of soil temperature regimes other
than iso regimes, and, although paleoclimatic factors have been
attributed to their formation, parent material is also probably a
major contributor.
Required Characteristics
In summary, the oxic horizon is a subsurface horizon that
does not have andic soil properties (defined below) and has all
of the following characteristics:
1. A thickness of 30 cm or more; and
2. A texture of sandy loam or finer in the fine-earth fraction;
and
3. Less than 10 percent weatherable minerals in the 50to
200-micron fraction; and
4. Rock structure in less than 5 percent of its volume, unless
the lithorelicts with weatherable minerals are coated with
sesquioxides; and
5. A diffuse upper boundary, i.e., within a vertical distance
of 15 cm, a clay increase with increasing depth of:
a. Less than 4 percent (absolute) in its fine-earth fraction
if the fine-earth fraction of the surface horizon contains less
than 20 percent clay; or
b. Less than 20 percent (relative) in its fine-earth fraction
if the fine-earth fraction of the surface horizon contains 20
to 40 percent clay; or
c. Less than 8 percent (absolute) in its fine-earth fraction
if the fine-earth fraction of the surface horizon contains 40
percent or more clay); and
6. An apparent CEC of 16 cmol(+) or less per kg clay (by 1N
NH4
OAc pH 7) and an apparent ECEC of 12 cmol(+) or less
per kg clay (sum of bases extracted with 1N NH4
OAc pH 7 plus
1N KCl-extractable Al). (The percentage of clay is either
measured by the pipette method or estimated to be 3 times
[percent water retained at 1500 kPa tension minus percent
organic carbon], whichever value is higher, but no more than
100).
PetrocalcicHorizon
The petrocalcic horizon is an illuvial horizon in which
secondary calcium carbonate or other carbonates have
accumulated to the extent that the horizon is cemented or
indurated (photo 25).
In some soils forming in parent materials that are rich in
carbonates or that receive regular additions of carbonates in
dust, the calcic horizon tends in time to become plugged with
carbonates and cemented into a massive, continuous horizon.
There is also evidence that a petrocalcic horizon can form
through a process of limestone alteration by in situ dissolution
48 Soil Taxonomy
and reprecipitation of carbonates. Petrocalcic horizons are
mainly in soils older than the Holocene and seem to be a mark
of advanced soil evolution.
In areas with an abundant source of carbonates and silica,
petrocalcic horizons and duripans can occur within the same
pedon.
The petrocalcic horizon is indurated or cemented
throughout each pedon by calcium carbonate or, less
commonly, by calcium and magnesium carbonate, with or
without accessory silica, to such a degree that dry fragments do
not slake in water and roots cannot enter, except in cracks that
have a horizontal spacing of 10 cm or more. If the fragments
are soaked in acid, cementation of the petrocalcic horizon is
destroyed in half or more of its lateral extent in each pedon.
The horizon is commonly massive or platy and is very hard or
harder when dry and very firm or firmer when moist. Its
saturated hydraulic conductivity commonly is moderately low
to very low unless the horizon is fractured.
A laminar cap may be present but is not required. If one is
present, carbonates normally constitute half or more, by
weight, of the laminar horizon. Gravel, sand, and silt grains
have been separated by the crystallization of carbonates in at
least parts of the laminar subhorizon. Sand and gravel have
been largely pushed aside by crystallization of calcium
carbonate at the surface of the laminar horizon. Radiocarbon
dates of the organic and inorganic carbon indicate that this
laminar horizon is late Wisconsinan to Holocene in age and
that the cementation of the underlying gravel took place during
the late Pleistocene.
Required Characteristics
A petrocalcic horizon must meet the following
requirements:
1. The horizon is cemented or indurated by carbonates, with or
without silica or other cementing agents; and
2. Because of lateral continuity, roots can penetrate only
along vertical fractures with a horizontal spacing of 10 cm or
more; and
3. The horizon has a thickness of:
a. 10 cm or more; or
b. 1 cm or more if it consists of a laminar cap directly
underlain by bedrock.
Petrogypsic Horizon
The petrogypsic horizon is an illuvial horizon, 10 cm or
more thick, in which secondary gypsum has accumulated to the
extent that the horizon is cemented or indurated (photo 26). Dry
fragments do not slake in water, and roots cannot enter, except in
vertical fractures that have a horizontal spacing of 10 cm or
more. The minimum gypsum content is 5 percent, and the
product of the thickness, in cm, multiplied by the gypsum
content percentage is 150 or more. Commonly, the gypsum
content is far greater than the minimum requirements. In many
pedons it is 60 percent or more. Petrogypsic horizons are known
to occur only in arid regions and develop in parent materials that
are rich in gypsum. They are rare in the United States but are
common in parts of Africa and Asia
Required Characteristics
A petrogypsic horizon must meet the following
requirements:
1. The horizon is cemented or indurated by gypsum, with or
without other cementing agents; and
2. Because of lateral continuity, roots can penetrate only
along vertical fractures with a horizontal spacing of 10 cm or
more; and
3. The horizon is 10 cm or more thick; and
4. The horizon is 5 percent or more gypsum, and the product
of its thickness, in cm, multiplied by the gypsum content
percentage is 150 or more.
Placic Horizon
The placic horizon (Gr. base of plax, flat stone; meaning a
thin cemented pan) is a thin, black to dark reddish pan that is
cemented by iron (or iron and manganese) and organic matter.
It is generally between 2 and 10 mm thick but may be as thin
as 1 mm. The placic horizon has a maximum thickness of 25
mm where it is associated with spodic materials. Where not
associated with spodic materials, it has no maximum thickness.
It is often associated with stratification in parent materials,
such as an abrupt discontinuity of hydraulic conductivity
associated with different particle sizes in ash layers. The placic
horizon is commonly within 50 cm of the mineral soil surface
and is roughly parallel with the mineral soil surface. It has a
pronounced wavy or even convoluted form. Commonly, it
occurs as a single pan rather than as multiple sheets (one
underlying another), but it may be bifurcated. It is a barrier to
water and roots. Placic horizons have been described in
Andisols, Histosols, Inceptisols, and Spodosols. In New
Zealand they also have been reported in young alluvial soils.
Most placic horizons occur in areas of cool, moist climates
with low evapotranspiration. They are known to occur in the
British Isles, New Zealand, Canada, and southeastern Alaska.
They also have been reported in the Tropics.
Placic horizons range in color from dark red to black.
Chemical data indicate that carbon and iron are major
components and aluminum and manganese minor components
in most placic horizons. In some areas, however, manganese is
a significant constituent of the horizons. There appears to be
little relationship between the chemical composition and the
color of the placic horizon.
Horizons and Characteristics Diagnostic for the Higher Categories 49
Research on genesis suggests that placic horizons form from
iron that is reduced and mobilized in the surface horizons and
oxidized and precipitated in the B horizon, where it can adsorb
soluble organic matter. The iron, however, does not form organometallic
complexes. The most common forms of iron in the placic
horizon are ferrihydrite and poorly crystalline goethite. These
minerals have a large capacity for adsorbing anions, including
humic substances.
Conditions for the reduction and mobilization of iron are
favored in strongly leached, acid soils with organic surface
horizons containing anaerobic micro-organisms. In some soils
placic horizons form at the boundary between layers with
contrasting particle-size classes, which restrict the soil
solution. Placic horizons also can form above lithic, densic, or
paralithic contacts. They are by no means restricted to the
conditions described above.
Most placic horizons in the British Isles have formed within
the last 3,000 years, but there is evidence to support incipient
formation of placic horizons within 100 years.
Placic horizons form in material with a variety of textures
ranging from sands to clays. The native vegetation in the
different climates includes tropical rain forest, Sphagnum, and
other rain-loving plants. In the British Isles placic horizons
occur under peat-forming ericaceous or grassy seminatural
vegetation, which is subject to periodic burns and was likely
forest within the last 3,000 years.
Unless the thickness of the placic horizon is minimal,
identification of the horizon is seldom difficult because the
hard, brittle pan differs so much from the material in which it
occurs and is so close to the mineral soil surface. The presence
of organic carbon and the shape and position of the placic
horizon distinguish the horizon from the ironstone sheets that
may form where water hangs, or moves laterally, at a lithologic
discontinuity. Where placic horizons occur within spodic
materials, they are arbitrarily differentiated from ortstein by
thickness. Ortstein has a minimum thickness of 25 mm.
Required Characteristics
A placic horizon must meet the following requirements:
1. The horizon is cemented or indurated with iron or iron and
manganese and organic matter, with or without other cementing
agents; and
2. Because of lateral continuity, roots can penetrate only
along vertical fractures with a horizontal spacing of 10 cm or
more; and
3. The horizon has a minimum thickness of 1 mm and, where
associated with spodic materials, is less than 25 mm thick.
Salic Horizon
A salic horizon is a horizon of accumulation of salts that are
more soluble than gypsum in cold water (photo 27). A common
salt is halite, the crystalline form of sodium chloride. In some
areas soluble sulfates may also accumulate with the crystalline
forms, such as thernadite, hexahydrite, epsomite, and mirabilite.
Two of the commonly occurring bicarbonates are trona and
natron. Under extreme aridic conditions and at low temperatures,
evaporites of calcium chloride, nitrates, and other soluble salts
may accumulate. Identification of the kinds of crystalline salts
requires detailed mineralogical analyses.
In extremely arid areas, such as parts of Chile and
Antarctica, where measurable precipitation is rare, salic
horizons have a hard or rigid rupture-resistance class. These
types of salic horizons are physical barriers to roots, but they
slake in water and, therefore, are not considered cemented.
Required Characteristics
A salic horizon is 15 cm or more thick and has, for 90
consecutive days or more in normal years:
1. An electrical conductivity (EC) equal to or greater than 30
dS/m in the water extracted from a saturated paste; and
2. A product of the EC, in dS/m, and thickness, in cm,
equal to 900 or more.
Sombric Horizon
A sombric horizon (F. sombre, dark) is a subsurface horizon
in mineral soils that has formed under free drainage. It
contains illuvial humus that is neither associated with
aluminum, as is the humus in the spodic horizon, nor dispersed
by sodium, as is common in the natric horizon. Consequently,
the sombric horizon does not have the high cation-exchange
capacity in its clay that characterizes a spodic horizon and does
not have the high base saturation of a natric horizon. It does
not underlie an albic horizon.
Sombric horizons are thought to be restricted to the cool,
moist soils of high plateaus and mountains in tropical or
subtropical regions. Because of strong leaching, their base
saturation is low (less than 50 percent by NH4
OAc).
The sombric horizon has a lower color value or chroma, or
both, than the overlying horizon and commonly contains more
organic matter. It may have formed in an argillic, cambic, or
oxic horizon. If peds are present, the dark colors are most
pronounced on surfaces of peds.
In the field a sombric horizon is easily mistaken for a buried
A horizon. It can be distinguished from some buried epipedons
by lateral tracing. In thin sections the organic matter of a
sombric horizon appears more concentrated on peds and in
pores than uniformly dispersed throughout the matrix.
Spodic Horizon
A spodic horizon is an illuvial layer with 85 percent or more
spodic materials (defined below). Spodic materials contain
illuvial active amorphous materials composed of organic matter
and aluminum, with or without iron. The term “active” is used
50 Soil Taxonomy
here to describe materials that have a high pH-dependent
charge, a large surface area, and high water retention. In
uncultivated soils the spodic horizon normally lies below an
albic horizon (a light colored eluvial horizon defined earlier).
Less commonly, it either is under an ochric epipedon that does
not meet the color requirements for an albic horizon or is in or
under an umbric epipedon. In some soils the spodic horizon is
at the surface of the mineral soil, directly below a thin O
horizon. In cultivated soils it generally occurs directly below
the Ap horizon. Spodic materials may remain in some
cultivated soils where the spodic horizon has been destroyed. If
85 percent of the spodic materials remain in the Ap horizon
and the soil meets the other criteria listed in the “Key to Soil
Orders” in chapter 8, the soil is considered a Spodosol.
Genesis
Spodic horizons form only in a humid environment. They are
commonly associated with cold or temperate climates but also
occur in hot climates. They do not occur in an arid environment,
although some occur in Mediterranean climates that have long,
dry summers.
The types of vegetation and litter covering the surface are
important in the formation of spodic horizons. In cool climates
spodic horizons occur in soils that have had a heath vegetation
(Erica and Calluna) or forest (broadleaf or coniferous)
vegetation. In a mixed forest, the spodic horizon generally is
more strongly expressed under certain species, such as hemlock
(Tsuga canadensis) or kauri (Agathis australis), than under
other species. In warm climates spodic horizons occur under
savanna, palm trees, and mixed forests.
A spodic horizon forms mostly in sandy, sandy-skeletal,
coarse-loamy, loamy-skeletal, or coarse-silty materials or in
andic soil materials (defined below), but it occasionally
develops in finer textured material. Some spodic horizons that
are not associated with an albic horizon may have been
overlooked in the past. If the parent materials are rich in clay,
the formation of a spodic horizon is likely to be delayed until
eluviation or weathering has reduced the clay content below a
critical level. A spodic horizon then forms in the eluvial horizon,
and the underlying argillic horizon is either destroyed or moved
to a greater depth as the spodic horizon thickens. There seems
to be an antagonism between a spodic horizon and
phyllosilicates. If a spodic horizon and an argillic horizon occur
in the same soil, they generally are separated by an eluvial
horizon (E´), but under heath vegetation a spodic horizon may
rest directly on, and may tongue into, an argillic horizon. In
calcareous parent material, a spodic horizon does not begin to
develop until carbonates have been leached from the upper part
of the soil. A spodic horizon can form either in relatively fresh
parent material containing abundant weatherable minerals or in
nearly pure quartz sand.
A spodic horizon can form either in a well drained soil or in a
soil with a shallow, fluctuating level of ground water. If the
water table remains within the spodic horizon for long periods,
the horizon may contain little or no iron. A spodic horizon does
not seem to develop in a soil that is permanently saturated with
water.
Under optimum conditions, a spodic horizon can form within
a few hundred years. Its biological destruction can be equally
rapid, at least in some cultivated soils where lime and fertilizers
are applied.
Most spodic horizons are horizons in which organic matter,
aluminum, and iron have accumulated. As far as is known,
aluminum is always present and may be essential. Almost all
spodic horizons have a maximum content of organic matter,
iron, or aluminum in their upper few centimeters, although
iron may be absent in some, or the iron and aluminum maxima
may be below the organic-matter maximum, and the aluminum
maximum may be below the iron maximum. Most spodic
horizons have hue of 7.5YR or redder. The presence of hue of
7.5YR or redder in a spodic horizon that does not contain iron,
the persistence of the hue after reduction if iron is present, and,
if iron is absent, the destruction of the color by ignition suggest
that organic compounds are important to the color of the spodic
horizon.
The mobile sesquioxides in spodic horizons can result from
the dissolution of primary minerals and from cycling by plants.
In eluvial horizons that overlie spodic horizons, the
aluminosilicates appear pitted as if by solution. Pitting is
particularly evident on mafic minerals. In some soils a well
developed spodic horizon is the upper mineral horizon,
overlain only by an O horizon. Although mixing of horizons by
animals or by falling trees generally can be demonstrated in
such soils, more than one source of the materials accumulated
in the spodic horizon is possible.
Some older theories concerning the formation of spodic
horizons postulated a mutual flocculation of positively charged
colloidal sesquioxides and negatively charged colloidal organic
matter. Others assumed a flocculation of sesquioxides or of
organic matter by changes in the redox potential or pH with
increasing depth.
According to newer theories, an association between organic
matter and iron and aluminum is formed by chelation and
electrostatic bonding. The compounds thus formed are soluble
if the sesquioxide concentration is low, but they are
precipitated when the sesquioxide concentration reaches a
critical level. Other research has demonstrated that large
amounts of inorganic aluminum and iron in a Spodosol can be
translocated as a sol from an A horizon to a B horizon before
complexing with organic matter.
Consequently, if solutions of organic compounds or sols that
are moving through the soil pick up sesquioxides from primary
minerals and from part of the spodic horizon, the compounds
are eventually precipitated somewhere in the spodic horizon.
The movement either can be downward (as a result of gravity)
or can be lateral or upward. Upward movement resulting from
capillary forces is suggested by the black, humus-rich
subhorizon above and on the sides of tongues of the E horizon
Horizons and Characteristics Diagnostic for the Higher Categories 51
that commonly penetrate at various angles into the spodic
horizon. Immobilization of sesquioxides may also be the result of
a hydrolysis of the organometallic complex induced by changes
in pH or by biological destruction of organic ligands. Two of the
specific properties of the immobilized material that becomes the
active fraction of a spodic horizon are (1) high concentrations of
carboxyl and hydroxyl sites that are destroyed on heating and
(2) solubilization of organic matter and sesquioxides on
treatment with a strong complexing agent, such as ammonium
oxalate.
Distinctions Between Spodic Horizons and Andic Soil
Materials
The central concept of andic soil materials is that of a soil
developing in weatherable, silica-rich parent materials, such as
volcanic ejecta or volcaniclastic materials, which have a
colloidal fraction dominated by short-range-order minerals or
aluminum-humus complexes. Under some environmental
conditions, weathering of primary aluminosilicates in parent
materials of nonvolcanic origin may also lead to the formation
of short-range-order minerals. The dominant process in most
soils with andic soil materials is one of weathering and mineral
transformation. Translocation within the soils and
accumulation of the translocated compounds are normally
minimal.
The central concept of soils with spodic horizons is one of
aluminum, or aluminum and iron, and organic matter
illuviating and precipitating when critical levels are reached.
Some areas, for example some areas in Alaska, periodically
receive volcanic ejecta (photo 28). These areas also have
climatic and vegetative conditions conducive to the formation
of spodic materials. The soils in these areas of Alaska exhibit
features of both andic and spodic materials. Because it
represents evidence of eluviation, the albic horizon is used to
separate Andisols from Spodosols; however, a layer of volcanic
ash should not be mistaken for an albic horizon.
Distinctions Between Spodic and Argillic Horizons
Argillic horizons are illuvial, and so are spodic horizons. As
an argillic horizon forms, discrete crystalline clay particles are
moved from an eluvial horizon to an illuvial horizon.
Consequently, the clays in the eluvial and illuvial horizons of a
soil that has an argillic horizon are similar, except where one
kind of clay mineral has moved in preference to others. The
silica-sesquioxide (SiO2
to R2
O3
) ratio of the whole soil is at a
minimum in the argillic horizon, but that of the clay fraction
remains virtually constant throughout the profile.
In soils that have a spodic horizon, the dominant processes
are dissolution of primary minerals in any eluvial horizon;
movement of iron, aluminum, and organic matter; and
precipitation of complexes of amorphous organic matter and
metal. Typically, the clay mineralogy in the eluvial horizon
differs greatly from that in the illuvial horizons, and the ratio
of SiO2
to R2
O3
both in the whole soil and in the clay fraction is
at a minimum in the spodic horizon.
In a particle-size separation, at least some of the illuviated
iron and aluminum is dispersed and becomes part of the
measured clay fraction. Consequently, data commonly show a
clay maximum in the spodic horizon. Both the spodic horizon
and the argillic horizon may be a horizon of accumulation of
free iron. In well drained soils that have an argillic horizon,
the ratio of free iron to clay tends to be constant in all horizons.
In soils that have a spodic horizon, however, this ratio tends to
vary.
There are large differences in micromorphology between an
argillic horizon and a spodic horizon. The birefringent
crystalline clay coatings of the argillic horizon differ sharply
from the isotropic amorphous coatings of the spodic horizon.
Most spodic horizons, however, contain some illuviated
crystalline clay.
Distinctions Between Spodic and Cambic Horizons
A cambic horizon can be formed either by alteration of
parent materials in place, resulting in the release of iron and
the formation of structure, or by solution and removal or
accumulation of carbonates or gypsum. There is not enough
illuviation to form a spodic horizon. Two situations in which a
spodic horizon and a cambic horizon might be confused in the
field are possible. A cambic horizon may grade laterally by
imperceptible stages into a spodic horizon as a result of
increasing accumulation of complexes of organic matter and
sesquioxides. A very weakly developed spodic horizon,
however, contains more of these complexes relative to
phyllosilicates than a cambic horizon, and the two kinds of
horizons can be separated either on the basis of their
morphology or by chemical techniques described below, in the
section on spodic materials.
It may be difficult to distinguish a spodic horizon from a
cambic horizon in a soil that has developed in pyroclastic
materials in a cool, perhumid climatic region. Under those
conditions, part of the amorphous mineral material in a cambic
horizon may form complexes with organic matter that are
similar to those of a spodic horizon. In this situation, a
distinction may be made on the basis of evidence of eluviation
and the typical color pattern of a spodic horizon. If an
overlying eluvial (albic) horizon is present in more than 50
percent of the pedon, it can be inferred that the underlying
horizon is illuvial. Likewise, the presence of a spodic horizon
is suggested if, in a freely drained soil, there is an abrupt
boundary between an Ap horizon and an underlying horizon
that contains 85 percent or more spodic materials.
Morphology
A typical spodic horizon is easily recognized in the field by
its color and structure. Commonly, it has a sandy, sandyskeletal,
coarse-loamy, loamy-skeletal, or coarse-silty particle-
52 Soil Taxonomy
size class. The upper boundary of the horizon is commonly
abrupt, and the hue, color value, and chroma of the horizon
change markedly with increasing depth within a few centimeters
of its upper boundary. The lowest color value, the reddest hue,
and the lowest chroma occur in the upper part of the horizon.
The lower part of the spodic horizon, or the horizon directly
below it, has a higher chroma or a yellower hue than the main
part, or it has some combination of these colors. Structure is
either absent or is granular, platy, blocky, or prismatic. Cracked
coatings of an isotropic amorphous mixture of organic matter,
iron, and aluminum can be detected on mineral sand grains in a
sandy or coarse-loamy spodic horizon viewed under a 40- to 60power
lens.
Commonly, cracked coatings are dominant in the lower part
of the spodic horizon. If the coatings are very thick, the
horizon may be ortstein. In a dry soil the coatings may be
cracked. Clay films are not present on peds or in pores within a
spodic horizon. Coatings on sand grains in a spodic horizon
may not be distinguishable under a hand lens, however, from
thin clay coatings in an argillic horizon.
If an albic horizon overlies a spodic horizon, there is seldom
any difficulty in determining that the spodic horizon is of
illuvial origin. Commonly, there is a second maximum of
organic carbon in the spodic horizon. In some tropical and
subtropical areas, the albic horizon may be extremely thick and
the spodic horizon may occur at a depth of 200 cm or more
below the mineral soil surface. The presence of organic carbon
and the characteristics of the exchange complex distinguish a
cemented spodic horizon (ortstein) from the ironstone layer
(petroferric contact, defined below) at a lithologic discontinuity
below many soils. In undisturbed soils without an albic
horizon, there is commonly a thin, dark eluvial horizon in
which many of the sand grains are free of humus and of
sesquioxide coatings. Many spodic horizons, however, are so
close to the mineral soil surface that the horizons overlying
them are easily destroyed by plowing or even by the
disturbances associated with logging. In some soils the albic or
other overlying horizons seem to have been mixed with the
spodic horizon by falling trees or by animals or may never have
existed. In a disturbed soil it may be difficult or impossible to
establish the illuvial nature of the spodic horizon, although it
has all of the morphological, chemical, and physical properties
of a spodic horizon, which is clearly illuvial. The presence of
an overlying eluvial horizon is not required in the definition of
a spodic horizon, although its identification is facilitated by the
presence of an eluvial horizon.
Identification
A spodic horizon normally underlies an O, A, Ap, or E
horizon. The hue and chroma may remain constant with
increasing depth if the horizon is thin and overlies a densic,
lithic, or paralithic contact (defined below). Generally, the
subhorizon with the reddest hue or the lowest chroma, or both,
is near the top of the spodic horizon. The hue becomes
yellower or the chroma higher, or both, within subhorizons of
the spodic horizon or in an underlying BC, C, E´, or Bx
horizon.
Spodic horizons must contain at least 85 percent spodic
materials. There are many useful clues from field evidence to
help identify spodic materials. Among these are an albic horizon
in 50 percent or more of the pedon and amorphous aluminum (or
aluminum and iron), which, when present in sufficient amounts,
provides color clues to the existence of spodic materials. These
colors are listed in the section on spodic materials. Spodic
materials cannot be positively identified from field evidence
alone. They must also have a pH value of 5.9 or less and an
organic-carbon content of 0.6 percent or more. Not all soils with
spodic materials have albic horizons. When albic horizons are
absent, spodic materials must still meet specific color
requirements and have at least one additional feature. Such
features can be morphological or chemical, or both. The
additional morphological features include (1) ortstein that has a
horizontal continuity through 50 percent or more of the pedon
and a very firm or firmer rupture-resistance class and (2) cracked
coatings on 10 percent or more of the sand grains. In some soils
the presence of isotropic cracked coatings may have to be
confirmed with the aid of a petrographic microscope. Optical
identification may not be feasible if there are significant
inclusions of mica or of other anisotropic clay or if the presence
of volcanic glass or other pyroclastic materials leads one to
suspect that the horizon is a cambic horizon containing
amorphous clay.
If a pedon does not have an albic horizon, ortstein, or sand
grains with cracked coatings, then the definition of spodic
materials requires that specific color and chemical criteria be
met. Two chemical criteria are used to evaluate spodic
materials. If at least one of these, in addition to the color
requirements, is satisfied, the definition of spodic materials is
met.
The first chemical criterion is that the percentages of
ammonium-oxalate-extractable aluminum plus one-half the
ammonium-oxalate-extractable iron in spodic materials must
total 0.50 or more and must be 2 times or more the amounts
present in an overlying umbric (or subhorizon of an umbric)
epipedon or in an ochric epipedon or albic horizon. The
increase in ammonium-oxalate-extractable iron and aluminum
from an A and/or E horizon to a B horizon is indicative of the
illuvial process. Ammonium oxalate will extract both iron and
aluminum associated with humus and inorganic amorphous
compounds, and it will also dissolve magnetite and
ferrihydrite, both of which contribute to the ammoniumoxalate-extractable
iron values. Ferrihydrite is believed to be
associated with both spodic and nonspodic materials in soils
associated with wetness.
The second chemical criterion is that the optical-density-ofoxalate-extract
(ODOE) value should be 0.25 or more and at
least double from an eluvial horizon to the spodic horizon. The
ODOE is assumed to result mostly from extracted fulvic acids.
Horizons and Characteristics Diagnostic for the Higher Categories 53
Photo 4.—A histic epipedon.
54 Soil Taxonomy
Photo 5.—A melanic epipedon approximately 90 cm thick in a
Melanudand from Japan.
Photo 6.—A mollic epipedon approximately 25 cm thick over a
calcic horizon in a soil from Idaho.
Horizons and Characteristics Diagnostic for the Higher Categories 55
Photo 7.—A mollic epipedon approximately 57 cm thick in an
Argiustoll from Kansas.
Photo 8.—An ochric epipedon from an Oxisol in Hawaii. The
ochric epipedon has high value and chroma.
56 Soil Taxonomy
Photo 10.—A soil that has a plaggen epipedon about 90 cm (3 ft)
thick. The sod presumably came from the heath. Variations
caused by mixing of materials can be seen. This map unit has
straight boundaries, and it is higher than the surrounding
landscape. Plaggen epipedons are not known to occur in the
United States but are common in parts of Western Europe.
Photo 9.—A soil with an ochric epipedon about 15 cm thick. The
dark colored ochric epipedon is too thin to be a mollic or
umbric epipedon.
Horizons and Characteristics Diagnostic for the Higher Categories 57
Photo 11.—An umbric epipedon in an Xerept from Spain. Photo 12.—An albic horizon in an Argialboll from North Dakota.
58 Soil Taxonomy
Photo 13.—An argillic horizon that begins at about 5 cm in a
Haplustalf from Texas. This argillic horizon has strong
prismatic structure.
Photo 14.—A prominent clay film in a pore and a faint clay film
on the surface of a ped in an argillic horizon.
Horizons and Characteristics Diagnostic for the Higher Categories 59
Photo 15.—Clay films and bridges on sand grains, which
commonly occur in argillic horizons with associated eluvial
horizons that have less than 15 percent clay.
Photo 16.—An argillic horizon that consists of lamellae.
60 Soil Taxonomy
Photo 17.—A partially cemented Ustic Haplocalcid from New
Mexico.
Photo 18.—A cambic horizon below a mollic epipedon in an Ustoll
from Nebraska.
Horizons and Characteristics Diagnostic for the Higher Categories 61
Photo 19.—A duripan underlain by cinders in a Durustoll from Arizona.
62 Soil Taxonomy
Photo 20.—Close-up of a calcareous duripan.
Horizons and Characteristics Diagnostic for the Higher Categories 63
Photo 21.—A fragipan beginning at a depth of about 50 cm.
Bleached seams are between the peds.
Photo 22.—A glossic horizon that has more than 15 percent albic
material between the peds of a degrading argillic horizon.
64 Soil Taxonomy
Photo 23.—A gypsic horizon between depths of 26 and 165 cm in a
Gypsid from New Mexico.
Horizons and Characteristics Diagnostic for the Higher Categories 65
Photo 24.—A natric horizon with columnar structure in a Natrudoll from Argentina.
66 Soil Taxonomy
Photo 25.—A petrocalcic horizon that begins at a depth of about
63 cm in an Argic Petrocalcid from New Mexico.
Photo 26.—A petrogypsic horizon beginning at a depth of about 50
cm in a Petrogypsid from New Mexico.
Horizons and Characteristics Diagnostic for the Higher Categories 67
Photo 28.—A spodic horizon in a Haplocryod from Alaska. This
soil receives periodic deposits of volcanic ash.
Photo 27.—A salic horizon in an Aquisalid from Nevada.
68 Soil Taxonomy
Photo 29.—A pedon with andic soil properties between depths of
about 48 and 100 cm. The material above 48 cm is from the
1980 eruption of Mount St. Helens and has not weathered
sufficiently to meet the criteria for andic soil properties.
Horizons and Characteristics Diagnostic for the Higher Categories 69
Photo 30.—Identifiable secondary carbonates that have engulfed a calcic horizon.
70 Soil Taxonomy
Photo 31.—Lamellae below an argillic horizon.
Horizons and Characteristics Diagnostic for the Higher Categories 71
Photo 32.—Close-up of lamellae.
72 Soil Taxonomy
Photo 33.—Continuous plinthite in a Plinthic Paleudalf from
Texas.
Photo 34.—Slickensides.
Horizons and Characteristics Diagnostic for the Higher Categories 73
Photo 35.—A pedon with aquic conditions close to the surface.
74 Soil Taxonomy
Photo 36.—Peds from a gleyed horizon and the horizon directly below.
Horizons and Characteristics Diagnostic for the Higher Categories 75
Photo 37.—A Turbel from the Yukon Territory with cryoturbation in the subsoil.
76 Soil Taxonomy
Photo 38.—A Glacistel from the Yukon Territory with a glacic layer beginning at a depth of about 50 cm.
Horizons and Characteristics Diagnostic for the Higher Categories 77
Photo 39.—Fractured lithic contact. Vertical fractures are greater than 10 cm. Sandstone is below the lithic contact.
78 Soil Taxonomy
Photo 40.—Differential weathering in grus from a soil in South Africa. The paralithic contact is highly irregular in this pedon.
Horizons and Characteristics Diagnostic for the Higher Categories 79
When there are significantly higher quantities in an illuvial
horizon than in an eluvial horizon, it is concluded that spodic
materials are present.
Thickness of the Spodic Horizon
For a variety of reasons, some spodic horizons are thin or
otherwise weakly developed. Some soils, particularly those that
formed in calcareous parent materials in areas of cool, humid
climates, have two horizons of accumulation, the upper of
which contains an accumulation of amorphous materials,
whereas the lower contains phyllosilicates. The two are
separated by an eluvial horizon. This sequence of horizons is
defined as a bisequum. In this situation, a spodic horizon has
formed, or begun to form, in a clay-depleted eluvial horizon.
Other spodic horizons are thin because they rest on a fragipan
or on a densic, lithic, or paralithic contact. In areas of very
cold, humid climates, any illuvial horizon is normally
dominated by organic matter and amorphous sesquioxides and
may be thin. Very thin horizons of accumulation are easily
destroyed by plowing, trampling by livestock, or logging. To
prevent such minor disturbances from changing the
classification of a soil, a minimum depth to the lower boundary
of the spodic horizon is required for the Spodosol order,
depending on the soil temperature regime (defined below). If the
soil temperature regime is mesic or warmer, the spodic horizon
must extend to a depth of 25 cm from the mineral soil surface,
unless the soil is less than 25 cm deep. For soils that have either
a cryic or a pergelic soil temperature regime, or a frigid soil
temperature regime and a spodic horizon with a coarse-loamy,
loamy-skeletal, or finer particle-size class, depth limits are waived
because in these soils there is less prospect of a serious
disturbance of significant areas than in sandy and warmer soils.
Depth limits also are waived for soils that have a duripan or
fragipan or a petroferric, paralithic, densic, or lithic contact
within 25 cm of the mineral soil surface. If these soils are
disturbed, the whole soil is altered and the classification is likely
to be affected.
Required Characteristics
A spodic horizon is normally a subsurface horizon underlying
an O, A, Ap, or E horizon. It may, however, meet the definition of
an umbric epipedon.
A spodic horizon must have 85 percent or more spodic
materials (described below) in a layer 2.5 cm or more thick that
is not part of any Ap horizon.
Other Diagnostic Soil Characteristics
(Mineral Soils)
Diagnostic soil characteristics are features of the soil that
are used in various places in the keys or in definitions of
diagnostic horizons.
Abrupt Textural Change
An abrupt textural change is a specific kind of change that
may occur between an ochric epipedon or an albic horizon and
an argillic horizon. It is characterized by a considerable increase
in clay content within a very short vertical distance in the zone
of contact. If the clay content in the fine-earth fraction of the
ochric epipedon or albic horizon is less than 20 percent, it
doubles within a vertical distance of 7.5 cm or less. If the clay
content in the fine-earth fraction of the ochric epipedon or the
albic horizon is 20 percent or more, there is an increase of 20
percent or more (absolute) within a vertical distance of 7.5 cm or
less (e.g., an increase from 22 to 42 percent) and the clay content
in some part of the argillic horizon is 2 times or more the amount
contained in the overlying horizon.
Normally, there is no transitional horizon between an ochric
epipedon or an albic horizon and an argillic horizon, or the
transitional horizon is too thin to be sampled. Some soils,
however, have a glossic horizon or interfingering of albic
materials (defined below) in parts of the argillic horizon. The
upper boundary of such a horizon is irregular or even
discontinuous. Sampling this mixture as a single horizon
might create the impression of a relatively thick transitional
horizon, whereas the thickness of the actual transition at the
contact may be no more than 1 mm.
Albic Materials
Albic (L. albus, white) materials are soil materials with a color
that is largely determined by the color of primary sand and silt
particles rather than by the color of their coatings. This
definition implies that clay and/or free iron oxides have been
removed from the materials or that the oxides have been
segregated to such an extent that the color of the materials is
largely determined by the color of the primary particles.
Required Characteristics
Albic materials have one of the following colors:
1. Chroma of 2 or less; and either
a. A color value, moist, of 3 and a color value, dry, of 6 or
more; or
b. A color value, moist, of 4 or more and a color value,
dry, of 5 or more; or
2. Chroma of 3 or less; and either
a. A color value, moist, of 6 or more; or
b. A color value, dry, of 7 or more; or
3. Chroma that is controlled by the color of uncoated grains
of silt or sand, hue of 5YR or redder, and the color values listed
in item 1-a or 1-b above.
80 Soil Taxonomy
Relatively unaltered layers of light colored sand, volcanic
ash, or other materials deposited by wind or water are not
considered albic materials, although they may have the same
color and apparent morphology. These deposits are parent
materials that are not characterized by the removal of clay
and/or free iron and do not overlie an illuvial horizon or other
soil horizon, except for a buried soil. Light colored krotovinas
or filled root channels should be considered albic materials
only if they have no fine stratifications or lamellae, if any
sealing along the krotovina walls has been destroyed, and if
these intrusions have been leached of free iron oxides and/or
clay after deposition.
Andic Soil Properties
Andic soil properties result mainly from the presence of
significant amounts of allophane, imogolite, ferrihydrite, or
aluminum-humus complexes in soils (photo 29). These materials,
originally termed “amorphous” (but understood to contain
allophane) in the 1975 edition of Soil Taxonomy, are commonly
formed during the weathering of tephra and other parent
materials with a significant content of volcanic glass. Although
volcanic glass is or was a common component in many
Andisols, it is not a requirement of the Andisol order. Some soils
develop andic soil properties without the influence of volcanic
glass.
Volcanic glass is a significant component of fresh tephra. In
most environments the volcanic glass weathers to short-rangeorder
minerals. The concept of Andisols includes weakly
weathered soils with much volcanic glass as well as more
strongly weathered soils rich in short-range-order minerals.
Hence, the content of volcanic glass is one of the
characteristics used in defining andic soil properties. Volcanic
glass is defined as optically isotropic translucent glass or
pumice of any color, including glassy aggregates and glass
coatings on other mineral grains. Composite grains must have
at least 50 percent (by volume) volcanic glass to be counted as
volcanic glass. In most cases the method used to determine
volcanic glass is not critical. When accurate measurement is
required, however, the standard method, use of a polarizing
microscope, is recommended.
Most horizons that have andic soil properties consist of
mineral soil materials. Some consist of organic soil materials.
A layer or horizon must have less than 25 percent organic
carbon, however, before it is considered to have andic soil
properties.
Required Characteristics
To be recognized as having andic soil properties, soil
materials must contain less than 25 percent (by weight) organic
carbon and meet one or both of the following requirements:
1. In the fine-earth fraction, all of the following:
a. Aluminum plus 1
/2 iron percentages (by ammonium
oxalate) totaling 2.0 percent or more; and
b. A bulk density, measured at 33 kPa water retention, of
0.90 g/cm3
or less; and
c. A phosphate retention of 85 percent or more; or
2. In the fine-earth fraction, a phosphate retention of 25
percent or more, 30 percent or more particles 0.02 to 2.0 mm
in size, and one of the following:
a. Aluminum plus 1
/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more and, in the 0.02 to 2.0 mm
fraction, 30 percent or more volcanic glass; or
b. Aluminum plus 1
/2 iron percentages (by ammonium
oxalate) totaling 2.0 or more and, in the 0.02 to 2.0 mm
fraction, 5 percent or more volcanic glass; or
c. Aluminum plus 1
/2 iron percentages (by ammonium
oxalate) totaling between 0.40 and 2.0 and, in the 0.02 to
2.0 mm fraction, enough volcanic glass so that the glass
percentage, when plotted against the value obtained by
adding aluminum plus 1
/2 iron percentages in the fine-earth
fraction, falls within the shaded area of diagram 1.
AnhydrousConditions
Anhydrous conditions (Gr. anydros, waterless) refer to the
active layer in soils of cold deserts and other areas with
permafrost (often dry permafrost) and low precipitation
(usually less than 50 mm water equivalent). Anhydrous soil
conditions are similar to the aridic (torric) soil moisture
regimes, except that the soil temperature is less than 0 o
C.
Coefficient of Linear Extensibility (COLE)
The coefficient of linear extensibility (COLE) is the ratio of
the difference between the moist length and dry length of a
clod to its dry length. It is (Lm - Ld)/Ld, where Lm is the
length at 33 kPa tension and Ld is the length when dry. COLE
can be calculated from the differences in bulk density of the
clod when moist and when dry. An estimate of COLE can be
calculated in the field by measuring the distance between two
pins in a clod of undisturbed soil at field capacity and again
after the clod has dried. COLE does not apply if the shrinkage
is irreversible.
Durinodes
Durinodes (L. durus, hard, and nodus, knot) are weakly
cemented to indurated nodules with a diameter of 1 cm or
more. The cement is SiO2
, presumably opal and
microcrystalline forms of silica. Durinodes break down in hot
concentrated KOH after treatment with HCl to remove
Horizons and Characteristics Diagnostic for the Higher Categories 81
carbonates but do not break down with concentrated HCl alone.
Dry durinodes do not slake appreciably in water, but prolonged
soaking can result in spalling of very thin platelets. Durinodes
are firm or firmer and brittle when wet, both before and after
treatment with acid. Most durinodes are roughly concentric
when viewed in cross section, and concentric stringers of opal
are visible under a hand lens.
Fragic Soil Properties
Fragic soil properties are the essential properties of a
fragipan. They have neither the layer thickness nor volume
requirements for the fragipan. Fragic soil properties are in
subsurface horizons, although they can be at or near the surface
in truncated soils. Aggregates with fragic soil properties have a
firm or firmer rupture-resistance class and a brittle manner of
failure when soil water is at or near field capacity. Air-dry
fragments of the natural fabric, 5 to 10 cm in diameter, slake when
they are submerged in water. Aggregates with fragic soil
properties show evidence of pedogenesis, including one or more
of the following: oriented clay within the matrix or on faces of
peds, redoximorphic features within the matrix or on faces of
peds, strong or moderate soil structure, and coatings of albic
materials or uncoated silt and sand grains on faces of peds or in
seams. Peds with these properties are considered to have fragic
soil properties regardless of whether or not the density and
brittleness are pedogenic.
Soil aggregates with fragic soil properties must:
1. Show evidence of pedogenesis within the aggregates or, at a
minimum, on the faces of the aggregates; and
2. Slake when air-dry fragments of the natural fabric, 5 to 10 cm
in diameter, are submerged in water; and
3. Have a firm or firmer rupture-resistance class and a brittle
manner of failure when soil water is at or near field capacity;
and
4. Restrict the entry of roots into the matrix when soil water
is at or near field capacity.
Identifiable Secondary Carbonates
The term “identifiable secondary carbonates” is used in the
definitions of a number of taxa. It refers to translocated
authigenic calcium carbonate that has been precipitated in
place from the soil solution rather than inherited from a soil
parent material, such as a calcareous loess or till (photo 30).
Identifiable secondary carbonates either may disrupt the soil
structure or fabric, forming masses, nodules, concretions, or
spheroidal aggregates (white eyes) that are soft and powdery
when dry, or may be present as coatings in pores, on structural
faces, or on the undersides of rock or pararock fragments. If
present as coatings, the secondary carbonates cover a
significant part of the surfaces. Commonly, they coat all of the
surfaces to a thickness of 1 mm or more. If little calcium
carbonate is present in the soil, however, the surfaces may be
only partially coated. The coatings must be thick enough to be
visible when moist. Some horizons are entirely engulfed by
carbonates. The color of these horizons is largely determined
by the carbonates. The carbonates in these horizons are within
the concept of identifiable secondary carbonates.
The filaments commonly seen in a dry calcareous horizon
are within the meaning of identifiable secondary carbonates if
the filaments are thick enough to be visible when the soil is
moist. Filaments commonly branch on structural faces.
Interfingering of Albic Materials
The term “interfingering of albic materials” refers to albic
materials that penetrate 5 cm or more into an underlying
argillic, kandic, or natric horizon along vertical and, to a lesser
Diagram 1.—Soils that are plotted in the shaded area have andic
soil properties. A soil has these properties if the fraction less
than 2.0 mm in size has phosphate retention of more than 25
percent and the 0.02 to 2.0 mm fraction is at least 30 percent
of the fraction less than 2.0 mm in size.
82 Soil Taxonomy
degree, horizontal faces of peds. There need not be a
continuous overlying albic horizon. The albic materials
constitute less than 15 percent of the layer that they penetrate,
but they form continuous skeletans (ped coatings of clean silt or
sand defined by Brewer, 1976) 1 mm or more thick on the vertical
faces of peds, which means a total width of 2 mm or more
between abutting peds. Because quartz is such a common
constituent of silt and sand, these skeletans are usually light
gray when moist and nearly white when dry, but their color is
determined in large part by the color of the sand or silt
fraction.
Required Characteristics
Interfingering of albic materials is recognized if albic
materials:
1. Penetrate 5 cm or more into an underlying argillic or
natric horizon; and
2. Are 2 mm or more thick between vertical faces of abutting
peds; and
3. Constitute less than 15 percent (by volume) of the layer
that they penetrate.
Lamellae
A lamella is an illuvial horizon less than 7.5 cm thick
(photos 31 and 32). Each lamella contains an accumulation of
oriented silicate clay on or bridging sand and silt grains (and
rock fragments if any are present). A lamella has more silicate
clay than the overlying eluvial horizon.
The significance of lamellae to soil classification is not in the
single lamella but in the multiple number of lamellae, each with
an overlying eluvial horizon in a single pedon. A single lamella
may occur in a pedon, but more commonly there are several
lamellae separated by eluvial horizons.
A lamella 0.5 cm or more thick can be part of a cambic
horizon unless it is sandy (loamy fine sand or coarser). It can
be part of an argillic horizon. A lamella is required to have an
accumulation of oriented silicate clay, but no specific amount
of clay is required. A single lamella is too thin to be either a
cambic or an argillic horizon. A combination of lamellae 15
cm or more thick, however, can be either a cambic or an
argillic horizon if all of the other criteria are met.
Identification
A lamella typically has (but is not required to have) a higher
chroma, redder hue, or lower color value, or any combination
of these, than the overlying eluvial horizon. Some lamellae
have no color differences. All lamellae are required to have
more silicate clay than the overlying eluvial horizon.
In a vertical cross section of a pedon, a lamella appears as a
thin horizon and is often called a “band.” It actually is an
undulating layer, and it is not always continuous. The upper
and lower boundaries may be wavy, and the thickness may vary
from one point to another.
Lamellae commonly occur in sandy and sandy-skeletal
sediments and less commonly in coarse-loamy, loamy-skeletal,
and coarse-silty sediments. The texture of the fine-earth
fraction in lamellae is mostly loamy sand or sandy loam, but it
is known to range from sand to sandy clay loam, silt loam, and
clay loam. The content of rock fragments ranges from 0 to
more than 65 percent. Lamellae commonly are single grained
or granular, but in some pedons they are massive.
Laboratory data show that, in addition to silicate clay
accumulations, silt (particularly fine silt), sesquioxides, and
organic carbon accumulate in some lamellae. Where there is
recharge of carbonates, there may also be accumulations of
carbonates in lamellae.
Although lamellae most commonly occur in eolian and
alluvial sediments, they have also been observed in coarse
grained residuum, such as grus. It is likely that there were very
thin layers with finer soil particles and smaller pore spaces
than in the residuum either above or below them. These thin
layers would then be similar to the bedding planes in the eolian
or alluvial sediments. It is logical that lamellae in residuum
form in the same way as described below.
Origin
Lamellae form in coarse textured sediments (coarse silt or
coarser) of eolian or alluvial deposits that include very small
amounts of silicate clay. Evidence indicates that they form
initially in the bedding planes. The bedding planes, as used
here, are very thin layers with finer soil particles and smaller
pore spaces than the materials either above or below them.
These were deposited during a lull in the wind or a reduction
in the velocity of water. Before a wetting front can move
through these bedding planes to the larger pores in the
underlying strata, the finer pores must be nearly saturated. This
pause in the percolation flow may be sufficient for plant roots
to capture water leaving suspended clay. As a result, silicate
clay suspended in the soil solution can be deposited in the
pores and on the surfaces of the particles. This deposition
further reduces the pore size. With the passing of each
succeeding wetting front, the pore size is reduced even further
and lamellae form.
The lamellae thicken as additional fine particles are
deposited. It is thought that the lamellae may also begin to act
as a filter at this point in their development.
In a close examination of pedons with a large number of
lamellae, the lamellae nearer the soil surface generally have the
least concentration of clay and have the faintest color contrast
from the overlying eluvial horizon. Some sand grains are
devoid of clay, and some have only thin coatings. These
lamellae are generally more wavy and less continuous than
those in the other parts of the lamellae zone (the zone in which
lamellae form). The eluvial horizons overlying these lamellae
are generally the thickest of those in the lamellae zone.
Horizons and Characteristics Diagnostic for the Higher Categories 83
Lamellae in the middle part of the lamellae zone appear to
have the highest concentration of clay at the upper edge of the
lamellae, and the clay content decreases with increasing depth.
The color contrast is greatest at the upper edge of the lamellae,
adjacent to the overlying eluvial horizon. In the lower part of
these lamellae, some sand grains are devoid of clay and some
have only thin clay coatings. The lower part of these lamellae
appear to be very similar to the lamellae closest to the soil
surface. The lamellae in the middle part of the lamellae zone
are wavy but commonly are not so wavy as those in the upper
part of the lamellae zone.
The deepest lamellae are commonly very thin. They have a
color contrast that is nearly as great as that at the upper edge of
the lamellae in the middle part of the lamellae zone. The
deepest lamellae are not very wavy and are commonly parallel
with each other. The thickness of the overlying eluvial
horizons varies more than that in the other parts of the
lamellae zone.
These observations suggest that clay is being moved from
the upper few lamellae to the lower lamellae. Also, in the
lamellae in the middle part of the layer containing lamellae,
clay is being stripped from the lower part of one lamella and is
being redeposited in the top part of the next lower lamella. The
lamellae thicken as clay is added to the top of the lamellae. At
this point, a lamella begins to move away from the bedding
plane from which it originated. The stripping of clay from the
lower part of a lamella and the redeposition in the top part of
the next lower lamella continue this movement upward and
away from the bedding plane.
The movement upward of each lamella is not uniform
throughout its extent. Consequently, lamellae are wavy rather
than smooth, like the bedding planes from which they
originated. Occasionally, some lamellae appear to be branched.
This branching occurs where part of a lamella has moved up
more rapidly than the overlying part of the next higher lamella
and they become joined in this part. The branching is further
evidence that lamellae form upward and that the movement is
not uniform.
Required Characteristics
A lamella is an illuvial horizon less than 7.5 cm thick
formed in unconsolidated regolith more than 50 cm thick.
Each lamella contains an accumulation of oriented silicate clay
on or bridging the sand and silt grains (and coarse fragments if
any are present). Each lamella is required to have more silicate
clay than the overlying eluvial horizon.
Lamellae occur in a vertical series of two or more, and each
lamella must have an overlying eluvial horizon. (An eluvial
horizon is not required above the uppermost lamella if the soil
is truncated.)
Lamellae may meet the requirements for either a cambic or an
argillic horizon. A combination of two or more lamellae 15 cm or
more thick is a cambic horizon if the texture is very fine sand,
loamy very fine sand, or finer. A combination of two or more
lamellae meets the requirements for an argillic horizon if there is
15 cm or more cumulative thickness of lamellae that are 0.5 cm or
more thick and that have a clay content of either:
1. 3 percent or more (absolute) higher than in the overlying
eluvial horizon (e.g., 13 percent versus 10 percent) if any part
of the eluvial horizon has less than 15 percent clay in the fineearth
fraction; or
2. 20 percent or more (relative) higher than in the overlying
eluvial horizon (e.g., 24 percent versus 20 percent) if all parts
of the eluvial horizon have more than 15 percent clay in the
fine-earth fraction.
Linear Extensibility (LE)
Linear extensibility (LE) helps to predict the potential of a
soil to shrink and swell. The LE of a soil layer is the product of
the thickness, in cm, multiplied by the COLE of the layer in
question. The LE of a soil is the sum of these products for all
soil horizons.
Lithologic Discontinuities
Lithologic discontinuities are significant changes in particlesize
distribution or mineralogy that represent differences in
lithology within a soil. A lithologic discontinuity can also
denote an age difference. For information on using horizon
designations for lithologic discontinuities, see the Soil Survey
Manual(USDA, SCS, 1993).
Not everyone agrees on the degree of change required for a
lithologic discontinuity. No attempt is made to quantify
lithologic discontinuities. The discussion below is meant to
serve as a guideline.
Several lines of field evidence can be used to evaluate
lithologic discontinuities. In addition to mineralogical and
textural differences that may require laboratory studies, certain
observations can be made in the field. These include but are
not limited to the following:
1. Abrupt textural contacts.—An abrupt change in
particle-size distribution, which is not solely a change in clay
content resulting from pedogenesis, can often be observed.
2. Contrasting sand sizes.—Significant changes in sand
size can be detected. For exampe, if material containing mostly
medium sand or finer sand abruptly overlies material containing
mostly coarse sand and very coarse sand, one can assume that
there are two different materials. Although the materials may be
of the same mineralogy, the contrasting sand sizes result from
differences in energy at the time of deposition by water and/or
wind.
3. Bedrock lithology vs. rock fragment lithology in the
soil.—If a soil with rock fragments overlies a lithic contact,
one would expect the rock fragments to have a lithology
similar to that of the material below the lithic contact. If many
of the rock fragments do not have the same lithology as the
84 Soil Taxonomy
underlying bedrock, the soil is not derived completely from the
underlying bedrock.
4. Stone lines.—The occurrence of a horizontal line of rock
fragments in the vertical sequence of a soil indicates that the soil
may have developed in more than one kind of parent material.
The material above the stone line is most likely transported, and
the material below may be of different origin.
5. Inverse distribution of rock fragments.—A lithologic
discontinuity is often indicated by an erratic distribution of
rock fragments. The percentage of rock fragments decreases
with increasing depth. This line of evidence is useful in areas
of soils that have relatively unweathered rock fragments.
6. Rock fragment weathering rinds.—Horizons
containing rock fragments with no rinds that overlie horizons
containing rocks with rinds suggest that the upper material is
in part depositional and not related to the lower part in time
and perhaps in lithology.
7. Shape of rock fragments.—A soil with horizons
containing angular rock fragments overlying horizons
containing well rounded rock fragments may indicate a
discontinuity. This line of evidence represents different
mechanisms of transport (colluvial vs. alluvial) or even
different transport distances.
8. Soil color.—Abrupt changes in color that are not the
result of pedogenic processes can be used as indicators of
discontinuity.
9. Micromorphological features.—Marked differences in
the size and shape of resistant minerals in one horizon and not
in another are indicators of differences in materials.
Use of Laboratory Data
Discontinuities are not always readily apparent in the field.
In these cases laboratory data are necessary. Even with
laboratory data, detecting discontinuities may be difficult. The
decision is a qualitative or perhaps a partly quantitative
judgment. General concepts of lithology as a function of depth
might include:
1. Laboratory data—visual scan.—The array of
laboratory data is assessed in an attempt to determine if a fielddesignated
discontinuity is corroborated and if any data show
evidence of a discontinuity not observed in the field. One must
sort changes in lithology from changes caused by pedogenic
processes. In most cases the quantities of sand and coarser
fractions are not altered significantly by soil-forming processes.
Therefore, an abrupt change in sand size or sand mineralogy is
a clue to lithologic change. Gross soil mineralogy and the
resistant mineral suite are other clues.
2. Data on a clay-free basis.—A common manipulation
in assessing lithologic change is computation of sand and silt
separates on a carbonate-free, clay-free basis (percent fraction,
e.g., fine sand and very fine sand, divided by percent sand plus
silt, times 100). Clay distribution is subject to pedogenic
change and may either mask inherited lithologic differences or
produce differences that are not inherited from lithology. The
numerical array computed on a clay-free basis can be inspected
visually or plotted as a function of depth.
Another aid used to assess lithologic changes is computation
of the ratios of one sand separate to another. The ratios can be
computed and examined as a numerical array, or they can be
plotted. The ratios work well if sufficient quantities of the two
fractions are available. Low quantities magnify changes in
ratios, especially if the denominator is low.
n Value
The n value (Pons and Zonneveld, 1965) characterizes the
relation between the percentage of water in a soil under field
conditions and its percentages of inorganic clay and humus.
The n value is helpful in predicting whether a soil can be
grazed by livestock or can support other loads and in
predicting what degree of subsidence would occur after
drainage.
For mineral soil materials that are not thixotropic, the n
value can be calculated by the following formula:
n = (A - 0.2R)/(L + 3H)
In this formula, A is the percentage of water in the soil in
field condition, calculated on a dry-soil basis; R is the
percentage of silt plus sand; L is the percentage of clay; and H
is the percentage of organic matter (percent organic carbon
multiplied by 1.724).
This formula is based on experience with soil materials that
have humified organic matter and in which illite and other
nonexpanding clay minerals are predominant. There are
indications that the factor by which the organic matter is
multiplied should exceed 3 if the organic matter is
incompletely humified. The correction for the water held by the
organic matter becomes an increasing source of uncertainty as
the ratio of clay to organic matter becomes narrow. In this
taxonomy, the n value is used only to characterize mineral
soils.
Few data for calculations of the n value are available in the
United States, but the critical n value of 0.7 can be
approximated closely in the field by a simple test of squeezing
a soil sample in the hand. If the soil flows between the fingers
with difficulty, the n value is between 0.7 and 1.0 (slightly fluid
manner of failure class); if the soil flows easily between the
fingers, the n value is 1 or more (moderately fluid or very fluid
manner of failure class).
Soils in which the moisture content is periodically reduced
below field capacity seldom have an n value of 0.7 or more.
Most of the soils that have been permanently saturated are
likely to have a high n value. Consequently, high n values are
primarily in soils of tidal marshes, swamps, and shallow lakes.
The sediments in these areas have never been above the
capillary fringe during drought cycles. A high calculated n
value may also be characteristic of some soils that formed in
Horizons and Characteristics Diagnostic for the Higher Categories 85
volcanic ash in areas of a perhumid climate. These soils are
thixotropic, and the field test is more reliable than the formula
for estimating their bearing value.
Petroferric Contact
A petroferric (Gr. petra, rock, and L. ferrum, iron; implying
ironstone) contact is a boundary between soil and a continuous
layer of indurated material in which iron is an important
cement and organic matter is either absent or present only in
traces. The indurated layer must be continuous within the
limits of each pedon, but it may be fractured if the average
lateral distance between fractures is 10 cm or more. The fact
that this ironstone layer contains little or no organic matter
distinguishes it from a placic horizon and an indurated spodic
horizon (ortstein), both of which contain organic matter.
The purpose in choosing a petroferric contact as a
diagnostic feature distinct from a lithic contact is to identify
the shallow layers of hard ironstone that may have been called
hardened laterite and those that may have accumulated in a
hard form. Petroferric contacts are extensive in tropical and
subtropical regions. There may be shallow sandstone that is
cemented by iron in any climatic region. The contact with such
a layer is a lithic contact, not a petroferric contact.
Several features can aid in making the distinction between a
lithic contact and a petroferric contact. First, a petroferric
contact is roughly horizontal. Second, the material directly
below a petroferric contact contains a high amount of iron
(normally 30 percent or more Fe2
O3
). Third, the ironstone
sheets below a petroferric contact are thin; their thickness
ranges from a few centimeters to very few meters. Sandstone,
on the other hand, may be thin or very thick, may be levelbedded
or tilted, and may contain only a small percentage of
Fe2
O3
. In the Tropics, the ironstone is generally more or less
vesicular.
Plinthite
Plinthite (Gr. plinthos, brick) is an iron-rich, humus-poor
mixture of clay with quartz and other minerals (photo 33). It
commonly occurs as dark red redox concentrations that usually
form platy, polygonal, or reticulate patterns. Plinthite changes
irreversibly to an ironstone hardpan or to irregular aggregates
on exposure to repeated wetting and drying, especially if it is
also exposed to heat from the sun. The lower boundary of a
zone in which plinthite occurs generally is diffuse or gradual,
but it may be abrupt at a lithologic discontinuity.
Plinthite may occur as a constituent of a number of
horizons, such as an epipedon, a cambic horizon, an argillic
horizon, an oxic horizon, or a C horizon. It is one form of the
material that has been called laterite. It normally forms in a
horizon below the surface, but it may form at the surface in a
seepy area at the base of a slope.
From a genetic viewpoint, plinthite forms by segregation of
iron. In many places iron probably has been added from other
horizons or from the higher adjacent soils. Generally, plinthite
forms in a horizon that is saturated with water for some time
during the year. Initially, iron is normally segregated in the
form of soft, more or less clayey, red or dark red redox
concentrations. These concentrations are not considered
plinthite unless there has been enough segregation of iron to
permit their irreversible hardening on exposure to repeated
wetting and drying. Plinthite is firm or very firm when the soil
moisture content is near field capacity and hard when the
moisture content is below the wilting point. Plinthite does not
harden irreversibly as a result of a single cycle of drying and
rewetting. After a single drying, it will remoisten and then can
be dispersed in large part if one shakes it in water with a
dispersing agent.
In a moist soil, plinthite is soft enough to be cut with a
spade. After irreversible hardening, it is no longer considered
plinthite but is called ironstone. Indurated ironstone materials
can be broken or shattered with a spade but cannot be dispersed
if one shakes them in water with a dispersing agent.
A small amount of plinthite in the soil does not form a
continuous phase; that is, the individual redox concentrations
or aggregates are not connected with each other. If a large
amount of plinthite is present, it may form a continuous phase.
If a continuous layer becomes indurated, it is a massive
ironstone layer that has irregular, somewhat tubular inclusions
of yellowish, grayish, or white, clayey material. If the layer is
exposed, these inclusions may be washed out, leaving an
ironstone that has many coarse, tubular pores.
Much that has been called laterite is included in the
meaning of plinthite. Doughy and concretionary laterite that
has not hardened is an example. Hardened laterite, whether it
is vesicular or pisolitic, is not included in the definition of
plinthite.
Resistant Minerals
Several references are made to resistant minerals in this
taxonomy. Obviously, the stability of a mineral in the soil is a
partial function of the soil moisture regime. Where resistant
minerals are referred to in the definitions of diagnostic
horizons and of various taxa, a humid climate, past or present,
is always assumed.
Resistant minerals are durable minerals in the 0.02 to 2.0
mm fraction. Quartz is the most common resistant mineral in
soils. The less common ones include sphene, rutile, zircon,
tourmaline, and beryl.
Slickensides
Slickensides are polished and grooved surfaces and
generally have dimensions exceeding 5 cm (photo 34). They
are produced when one soil mass slides past another. Some
slickensides occur at the lower boundary of a slip surface where
86 Soil Taxonomy
a mass of soil moves downward on a relatively steep slope.
Slickensides result directly from the swelling of clay minerals
and shear failure. They are very common in swelling clays that
undergo marked changes in moisture content.
Spodic Materials
Spodic materials form in an illuvial horizon that normally
underlies a histic, ochric, or umbric epipedon or an albic
horizon. In most undisturbed areas, spodic materials underlie
an albic horizon. They may occur within an umbric epipedon
or an Ap horizon.
A horizon consisting of spodic materials normally has an
optical-density-of-oxalate-extract (ODOE) value of 0.25 or
more, and that value is commonly at least 2 times as high as
the ODOE value in an overlying eluvial horizon. This increase
in ODOE value indicates an accumulation of translocated
organic materials in an illuvial horizon. Soils with spodic
materials show evidence that organic materials and aluminum,
with or without iron, have been moved from an eluvial horizon
to an illuvial horizon.
Definition of Spodic Materials
Spodic materials are mineral soil materials that do not have
all of the properties of an argillic or kandic horizon; are
dominated by active amorphous materials that are illuvial and
are composed of organic matter and aluminum, with or without
iron; and have both of the following:
1. A pH value in water (1:1) of 5.9 or less and an organiccarbon
content of 0.6 percent or more; and
2. One or both of the following:
a. An overlying albic horizon that extends horizontally
through 50 percent or more of each pedon and, directly
under the albic horizon, colors, moist (crushed and
smoothed sample), as follows:
(1) Hue of 5YR or redder; or
(2) Hue of 7.5YR, color value of 5 or less, and chroma
of 4 or less; or
(3) Hue of 10YR or neutral and a color value and
chroma of 2 or less; or
(4) A color of 10YR 3/1; or
b. With or without an albic horizon and one of the colors
listed above or hue of 7.5YR, color value, moist, of 5 or less,
chroma of 5 or 6 (crushed and smoothed sample), and one
or more of the following morphological or chemical
properties:
(1) Cementation by organic matter and aluminum, with
or without iron, in 50 percent or more of each pedon and
a very firm or firmer rupture-resistance class in the
cemented part; or
(2) 10 percent or more cracked coatings on sand grains;
or
(3) Aluminum plus 1
/2 iron percentages (by ammonium
oxalate) totaling 0.50 or more, and half that amount or
less in an overlying umbric (or subhorizon of an umbric)
epipedon, ochric epipedon, or albic horizon; or
(4) An optical-density-of-oxalate-extract (ODOE) value
of 0.25 or more, and a value half as high or lower in an
overlying umbric (or subhorizon of an umbric) epipedon,
ochric epipedon, or albic horizon.
Weatherable Minerals
Several references are made to weatherable minerals in this
taxonomy. Obviously, the stability of a mineral in a soil is a
partial function of the soil moisture regime. Where weatherable
minerals are referred to in the definitions of diagnostic
horizons and of various taxa in this taxonomy, a humid
climate, either present or past, is always assumed. The
minerals that are included in the meaning of weatherable
minerals are as follows:
1. Clay minerals: All 2:1 lattice clays, except for one that is
currently considered to be an aluminum-interlayered chlorite.
Sepiolite, talc, and glauconite are also included in this group of
weatherable clay minerals, although they are not everywhere of
clay size.
2. Silt- and sand-sized minerals (0.02 to 0.2 mm in
diameter): Feldspars, feldspathoids, ferromagnesian minerals,
glass, micas, zeolites, and apatite.
Obviously, this definition of the term “weatherable
minerals” is restrictive. The intent is to include, in the
definitions of diagnostic horizons and various taxa, only those
weatherable minerals that are unstable in a humid climate
compared to other minerals, such as quartz and 1:1 lattice
clays, but that are more resistant to weathering than calcite.
Characteristics Diagnostic for
Organic Soils
Following is a description of the characteristics that are
used only with organic soils.
Kinds of Organic Soil Materials
Three different kinds of organic soil materials are
distinguished in this taxonomy, based on the degree of
decomposition of the plant materials from which the organic
materials are derived. The three kinds are (1) fibric, (2) hemic,
and (3) sapric. Because of the importance of fiber content in
the definitions of these materials, fibers are defined before the
kinds of organic soil materials.
Horizons and Characteristics Diagnostic for the Higher Categories 87
Fibers
Fibers are pieces of plant tissue in organic soil materials
(excluding live roots) that:
1. Are large enough to be retained on a 100-mesh sieve
(openings 0.15 mm across) when the materials are screened;
and
2. Show evidence of the cellular structure of the plants from
which they are derived; and
3. Either are 2 cm or less in their smallest dimension or are
decomposed enough to be crushed and shredded with the
fingers.
Pieces of wood that are larger than 2 cm in cross section and
are so undecomposed that they cannot be crushed and shredded
with the fingers, such as large branches, logs, and stumps, are
not considered fibers but are considered coarse fragments
(comparable to gravel, stones, and boulders in mineral soils).
The degree of decomposition of organic materials is
indicated by the content of fibers. If the organic materials are
highly decomposed, fibers are nearly absent. If the organic
materials are only slightly decomposed, more of the volume,
exclusive of the coarse fragments, normally consists of fibers.
If the organic materials are moderately decomposed, the fibers
may be largely preserved but are easily broken down by
rubbing between the thumb and fingers. The percentage of
fibers that do not break down when rubbed gives the most
realistic field estimate of the degree of decomposition. In
addition, the bulk density (and hence the amount of subsidence
after drainage) is more closely related to the content of fiber
after rubbing than to the content of fiber before rubbing. A
small volume of the wet material is rubbed between the thumb
and fingers about 10 times with firm pressure. In the laboratory
the material, after rubbing, is washed on a screen. In the field
the rubbed material may be molded into a spherical or rodshaped
mass and broken for examination under a hand lens of
10 power or more to estimate the fiber content.
The definitions of fibric, hemic, and sapric soil materials
that follow are based in part on the content of fibers after
rubbing and in part on the solubility of the materials in sodium
pyrophosphate.
Fibric Soil Materials
Fibric soil materials (L. fibra, fiber) are the least
decomposed of all of the organic soil materials. They contain
large amounts of fibers that are well preserved and can be
linked to botanical origin. They have a low bulk density and a
high water content when saturated. Fibric soil materials have a
wide geographic distribution, and they occur in environments
that are not conducive to processes of alteration and
decomposition. Examples of such environments are the cool or
cold, perhumid, boreal forest zones, where raised bogs and hill
peats are dominated by Sphagnum; land-locked depressions
that have Hypnum moss; and very flat, undrained areas that
support a variety of reeds, sedges, and grasses. Wet flatlands
occur in glaciated areas in the higher latitudes. Also, very wet
flatlands are in some semitropical and tropical areas. An
example is the sawgrass (sedge) bogs of the Everglades in
Florida. Fibric materials commonly have a bulk density of less
than 0.1; a fiber content (unrubbed) exceeding two-thirds of the
volume; and a water content, when saturated, ranging from
about 850 to more than 3,000 percent of the weight of ovendry
material. Fibric materials commonly are light yellowish brown,
dark brown, or reddish brown.
Fibric soil materials are organic soil materials that either:
1. Contain three-fourths or more (by volume) fibers after
rubbing, excluding coarse fragments; or
2. Contain two-fifths or more (by volume) fibers after
rubbing, excluding coarse fragments, and yield color values
and chromas of 7/1, 7/2, 8/1, 8/2, or 8/3 (diagram 2) on white
chromatographic or filter paper that is inserted into a paste
made of the soil materials in a saturated sodium-pyrophosphate
solution.
Hemic Soil Materials
Hemic soil materials (Gr. hemi, half; implying intermediate
decomposition) are intermediate in their degree of
decomposition between the less decomposed fibric and more
decomposed sapric materials. Their morphological features
give intermediate values for fiber content, bulk density, and
water content. Hemic soil materials are partly altered both
physically and biochemically. Their geographic distribution is
widespread. Colors are commonly dark grayish brown to dark
reddish brown. The fibers are largely destroyed when the wet
organic material is rubbed. The bulk density commonly is
between 0.07 and 0.18, the fiber content normally is between
one-third and two-thirds of the volume before rubbing, and the
maximum water content at saturation commonly ranges from
about 450 to 850 percent. Hemic materials do not meet both the
fiber content (after rubbing) and the sodium-pyrophosphate
solubility requirements for either fibric or sapric materials
(diagram2).
Sapric Soil Materials
Sapric soil materials (Gr. sapros, rotten) are the most highly
decomposed of the three kinds of organic soil materials. They
have the smallest amount of plant fiber, the highest bulk
density, and the lowest water content on a dry-weight basis at
saturation. Sapric soil materials are commonly very dark gray
to black. They are relatively stable; i.e., they change very little
physically and chemically with time in comparison to other
organic soil materials. Sapric materials have been exposed to
aerobic decomposition either naturally or because of artificial
88 Soil Taxonomy
drainage. In undrained bogs sapric materials occur at the
present surface or were previously at the surface and are now
buried. The bulk density of these materials commonly is 0.2 or
more, the fiber content averages less than one-third of the
volume before rubbing, and the maximum water content at
saturation normally is less than 450 percent on an ovendry
basis.
Sapric materials have the following characteristics:
1. The fiber content, after rubbing, is less than one-sixth (by
volume), excluding coarse fragments; and
2. The color of the sodium-pyrophosphate extract on white
chromatographic or filter paper is below or to the right of a
line drawn to exclude blocks 5/1, 6/2, and 7/3 (Munsell
designations, diagram 2). If few or no fibers can be detected and
the color of the pyrophosphate extract is to the left of or above
this line, the possibility that the material is limnic must be
considered.
Humilluvic Material
Humilluvic material, i.e., illuvial humus, accumulates in the
lower parts of some organic soils that are acid and have been
drained and cultivated. The humilluvic material has a C14
age
that is not older than the overlying organic materials. It has
very high solubility in sodium pyrophosphate and rewets very
slowly after drying. Most commonly, it accumulates near a
contact with a sandy mineral horizon.
To be recognized as a differentia in classification, the
humilluvic material must constitute one-half or more (by
volume) of a layer 2 cm or more thick. Because humilluvic
materials are recognized in few soils, there are not enough data
to develop a precise definition. Taxa with humilluvic material
are recognized in Histosols but not Histels.
Limnic Materials
The presence or absence of limnic deposits is taken into
account in the higher categories of Histosols but not Histels.
The nature of such deposits is considered in the lower
categories of Histosols. Limnic materials include both organic
and inorganic materials that were either (1) deposited in water
by precipitation or through the action of aquatic organisms,
such as algae or diatoms, or (2) derived from underwater and
floating aquatic plants and subsequently modified by aquatic
animals. They include coprogenous earth (sedimentary peat),
diatomaceous earth, and marl. Except for some of the
coprogenous earths that contain 30 percent or more organic
matter, most of these limnic materials are inorganic. Diatomite
is highly siliceous; marl is mainly calcium carbonate. Limnic
materials generally occur in the lower part of an organic soil
and were formed during an open-water stage of bog
development.
Coprogenous Earth
A layer of coprogenous earth (sedimentary peat) is a limnic
layer that:
1. Contains many fecal pellets with diameters between a few
hundredths and a few tenths of a millimeter; and
2. Has a color value, moist, of 4 or less; and
3. Either forms a slightly viscous water suspension and is
nonplastic or slightly plastic but not sticky, or shrinks upon
drying, forming clods that are difficult to rewet and often tend
to crack along horizontal planes; and
4. Either yields a saturated sodium-pyrophosphate extract on
Diagram 2.—Value and chroma of pyrophosphate solution of fibric
and sapric materials.
Horizons and Characteristics Diagnostic for the Higher Categories 89
white chromatographic or filter paper that has a color value of
7 or more and chroma of 2 or less (diagram 2) or has a cationexchange
capacity of less than 240 cmol(+) per kg organic
matter (measured by loss on ignition), or both.
Normally, layers of coprogenous earth contain almost no
visible fragments of plants. These layers have a range in
particle size and a C-N ratio (12 to 20) that are consistent with
advanced decomposition. Yet, they have both a low and a
narrow range in cation-exchange capacity (80 to 160 cmol(+)
per kg of organic matter), which indicates little decomposition
influenced by exposure to air. In places these layers have what
appears to be platy structure. The individual plates are a little
more than 0.5 mm thick and may be increments of annual
deposition. Such structure certainly is not pedogenic. Olive or
olive brown colors in organic layers of organic soils are
characteristic of coprogenous earth layers. The most common
colors are those with hue of 2.5Y or 5Y, value of 3 or 4, and
chroma of 2.
Diatomaceous Earth
A layer of diatomaceous earth is a limnic layer that:
1. If not previously dried, has a matrix color value of 3, 4,
or 5, which changes irreversibly on drying as a result of the
irreversible shrinkage of organic-matter coatings on diatoms
(identifiable by microscopic, 440 X, examination of dry
samples); and
2. Either yields a saturated sodium-pyrophosphate extract on
white chromatographic or filter paper that has a color value of
8 or more and chroma of 2 or less or has a cation-exchange
capacity of less than 240 cmol(+) per kg organic matter (by
loss on ignition), or both.
Layers of diatomaceous earth normally are more nearly
mineral than organic in composition.
Marl
A layer of marl is a limnic layer that:
1. Has a color value, moist, of 5 or more; and
2. Reacts with dilute HCl to evolve CO2
.
The color of marl usually does not change irreversibly
on drying because a layer of marl contains too little organic
matter, even before it has been shrunk by drying, to coat
the carbonate particles. Most of the samples of marl from
the United States studied to date have an organic-matter
content between 4 and 20 percent, inclusive, and, after
treatment with dilute HCl, some disintegrated plant remains
are evident.
Thickness of Organic Soil Materials
(Control Section of Histosols and Histels)
The thickness of organic materials over limnic materials,
mineral materials, water, or permafrost is used to define the
Histosols and Histels.
For practical reasons, an arbitrary control section has been
established for the classification of Histosols and Histels.
Depending on the kinds of soil material in the surface layer,
the control section has a thickness of either 130 cm or 160 cm
from the soil surface if there is no densic, lithic, or paralithic
contact, thick layer of water, or permafrost within the
respective limit. The thicker control section is used if the
surface layer to a depth of 60 cm either contains three-fourths
or more fibers derived from Sphagnum, Hypnum, or other
mosses or has a bulk density of less than 0.1. Layers of water,
which may be between a few centimeters and many meters
thick in these soils, are considered to be the lower boundary of
the control section only if the water extends below a depth of
130 or 160 cm, respectively. A densic, lithic, or paralithic
contact, if shallower than 130 or 160 cm, constitutes the lower
boundary of the control section. In some soils the lower
boundary is 25 cm below the upper limit of permafrost. An
unconsolidated mineral substratum shallower than those limits
does not change the lower boundary of the control section.
The control section of Histosols and Histels is divided
somewhat arbitrarily into three tiers—surface, subsurface, and
bottom tiers.
Surface Tier
The surface tier of a Histosol or Histel extends from the soil
surface to a depth of 60 cm if either (1) the materials within
that depth are fibric and three-fourths or more of the fiber
volume is derived from Sphagnum or other mosses or (2) the
materials have a bulk density of less than 0.1. Otherwise, the
surface tier extends from the soil surface to a depth of 30 cm.
Some organic soils have a mineral surface layer less than 40
cm thick as a result of flooding, volcanic eruptions, additions
of mineral materials to increase soil strength or reduce the
hazard of frost, or other causes. If such a mineral layer is less
than 30 cm thick, it constitutes the upper part of the surface
tier; if it is 30 to 40 cm thick, it constitutes the whole surface
tier and part of the subsurface tier.
Subsurface Tier
The subsurface tier is normally 60 cm thick. If the control
section ends at a shallower depth (at a densic, lithic, or
paralithic contact or a water layer or in permafrost), however,
90 Soil Taxonomy
the subsurface tier extends from the lower boundary of the
surface tier to the lower boundary of the control section. It
includes any unconsolidated mineral layers that may be present
within those depths.
Bottom Tier
The bottom tier is 40 cm thick unless the control section has
its lower boundary at a shallower depth (at a densic, lithic, or
paralithic contact or a water layer or in permafrost).
Thus, if the organic materials are thick, there are two
possible thicknesses of the control section, depending on the
presence or absence and the thickness of a surface mantle of
fibric moss or other organic material that has a low bulk
density (less than 0.1). If the fibric moss extends to a depth of
60 cm and is the dominant material within this depth (threefourths
or more of the volume), the control section is 160 cm
thick. If the fibric moss is thin or absent, the control section
extends to a depth of 130 cm.
Horizons and Characteristics
Diagnostic for Both Mineral and
Organic Soils
Following are descriptions of the horizons and
characteristics diagnostic for both mineral and organic soils.
Aquic Conditions2
Soils with aquic (L. aqua, water) conditions are those that
currently undergo continuous or periodic saturation and
reduction. The presence of these conditions is indicated by
redoximorphic features, except in Histosols and Histels, and
can be verified by measuring saturation and reduction, except
in artificially drained soils. Artificial drainage is defined here
as the removal of free water from soils having aquic conditions
by surface mounding, ditches, or subsurface tiles to the extent
that water table levels are changed significantly in connection
with specific types of land use. In the keys, artificially drained
soils are included with soils that have aquic conditions.
Elements of aquic conditions are as follows:
1. Saturation is characterized by zero or positive pressure in
the soil water and can generally be determined by observing
free water in an unlined auger hole. Problems may arise,
however, in clayey soils with peds, where an unlined auger
hole may fill with water flowing along faces of peds while the
soil matrix is and remains unsaturated (bypass flow). Such free
water may incorrectly suggest the presence of a water table,
while the actual water table occurs at greater depth. Use of well
sealed piezometers or tensiometers is therefore recommended
for measuring saturation. Problems may still occur, however, if
water runs into piezometer slits near the bottom of the
piezometer hole or if tensiometers with slowly reacting
manometers are used. The first problem can be overcome by
using piezometers with smaller slits and the second by using
transducer tensiometry, which reacts faster than manometers.
Soils are considered wet if they have pressure heads greater
than -1 kPa. Only macropores, such as cracks between peds or
channels, are then filled with air, while the soil matrix is
usually still saturated. Obviously, exact measurements of the
wet state can be obtained only with tensiometers. For
operational purposes, the use of piezometers is recommended
as a standard method.
The duration of saturation required for creating aquic
conditions varies, depending on the soil environment, and is
not specified.
Three types of saturation are defined:
a. Endosaturation.—The soil is saturated with water in all
layers from the upper boundary of saturation to a depth of
200 cm or more from the mineral soil surface.
b. Episaturation.—The soil is saturated with water in one
or more layers within 200 cm of the mineral soil surface and
also has one or more unsaturated layers, with an upper
boundary above a depth of 200 cm, below the saturated
layer. The zone of saturation, i.e., the water table, is perched
on top of a relatively impermeable layer.
c. Anthric saturation.—This term refers to a special kind
of aquic conditions that occur in soils that are cultivated and
irrigated (flood irrigation). Soils with anthraquic conditions
must meet the requirements for aquic conditions and in
addition have both of the following:
(1) A tilled surface layer and a directly underlying
slowly permeable layer that has, for 3 months or more in
normal years, both:
(a) Saturation and reduction; and
(b) Chroma of 2 or less in the matrix; and
(2) A subsurface horizon with one or more of the
following:
(a) Redox depletions with a color value, moist, of 4
or more and chroma of 2 or less in macropores; or
(b) Redox concentrations of iron; or
(c) 2 times or more the amount of iron (by dithionite
citrate) contained in the tilled surface layer.
2. The degree of reduction in a soil can be characterized by
the direct measurement of redox potentials. Direct
measurements should take into account chemical equilibria as
expressed by stability diagrams in standard soil textbooks.
2
In 1992, the term “aquic conditions” was introduced and other changes were made
throughout this taxonomy as a result of recommendations submitted to NRCS by the
International Committee on Aquic Moisture Regime (ICOMAQ), which was established in
1982 and was chaired initially by Dr. Frank Moormann, then by Dr. Johan Bouma.
Horizons and Characteristics Diagnostic for the Higher Categories 91
Reduction and oxidation processes are also a function of soil
pH. Obtaining accurate measurements of the degree of reduction
in a soil is difficult. In the context of this taxonomy, however,
only a degree of reduction that results in reduced iron is
considered, because it produces the visible redoximorphic
features that are identified in the keys. A simple field test is
available to determine if reduced iron ions are present. A freshly
broken surface of a field-wet soil sample is treated with
alpha,alpha-dipyridyl in neutral, 1-normal ammonium-acetate
solution. The appearance of a strong red color on the freshly
broken surface indicates the presence of reduced iron ions. A
positive reaction to the alpha,alpha-dipyridyl field test for
ferrous iron (Childs, 1981) may be used to confirm the existence
of reducing conditions and is especially useful in situations
where, despite saturation, normal morphological indicators of
such conditions are either absent or obscured (as by the dark
colors characteristic of melanic great groups). A negative
reaction, however, does not imply that reducing conditions are
always absent. It may only mean that the level of free iron in the
soil is below the sensitivity limit of the test or that the soil is in
an oxidized phase at the time of testing. Use of alpha,alphadipyridyl
in a 10 percent acetic-acid solution is not
recommended because the acid is likely to change soil
conditions, for example, by dissolving CaCO3
.
The duration of reduction required for creating aquic
conditions is not specified.
3. Redoximorphic features associated with wetness result
from alternating periods of reduction and oxidation of iron and
manganese compounds in the soil. Reduction occurs during
saturation with water, and oxidation occurs when the soil is not
saturated. The reduced iron and manganese ions are mobile
and may be transported by water as it moves through the soil.
Certain redox patterns occur as a function of the patterns in
which the ion-carrying water moves through the soil and as a
function of the location of aerated zones in the soil. Redox
patterns are also affected by the fact that manganese is reduced
more rapidly than iron, while iron oxidizes more rapidly upon
aeration. Characteristic color patterns are created by these
processes. The reduced iron and manganese ions may be
removed from a soil if vertical or lateral fluxes of water occur,
in which case there is no iron or manganese precipitation in
that soil. Wherever the iron and manganese are oxidized and
precipitated, they form either soft masses or hard concretions
or nodules. Movement of iron and manganese as a result of
redox processes in a soil may result in redoximorphic features
that are defined as follows:
a. Redox concentrations.—These are zones of apparent
accumulation of Fe-Mn oxides, including:
(1) Nodules and concretions, which are cemented
bodies that can be removed from the soil intact.
Concretions are distinguished from nodules on the basis
of internal organization. A concretion typically has
concentric layers that are visible to the naked eye.
Nodules do not have visible organized internal structure.
Boundaries commonly are diffuse if formed in situ and
sharp after pedoturbation. Sharp boundaries may be relict
features in some soils; and
(2) Masses, which are noncemented concentrations of
substances within the soil matrix; and
(3) Pore linings, i.e., zones of accumulation along
pores that may be either coatings on pore surfaces
or impregnations from the matrix adjacent to the
pores.
b. Redox depletions.—These are zones of low chroma
(chromas less than those in the matrix) where either Fe-Mn
oxides alone or both Fe-Mn oxides and clay have been
stripped out, including:
(1) Iron depletions, i.e., zones that contain low amounts
of Fe and Mn oxides but have a clay content similar to
that of the adjacent matrix (often referred to as albans or
neoalbans); and
(2) Clay depletions, i.e., zones that contain low
amounts of Fe, Mn, and clay (often referred to as silt
coatings or skeletans).
c. Reduced matrix.—This is a soil matrix that has low
chroma in situ but undergoes a change in hue or chroma
within 30 minutes after the soil material has been exposed
to air.
d. In soils that have no visible redoximorphic features, a
reaction to an alpha,alpha-dipyridyl solution satisfies the
requirement for redoximorphic features.
Photo 35 shows a pedon from Alaska with aquic conditions
close to the surface. When snow begins to melt in the spring,
the subsoil remains frozen and perches water in the gleyed
zone. Photo 36 shows peds from the gleyed horizon and the
horizon directly below. The gleyed horizon has redoximorphic
concentrations lining pores and redoximorphic depletions in
the matrix. The horizon below has redoximorphic depletions
lining pores and redoximorphic concentrations in the matrix.
Field experience indicates that it is not possible to define a
specific set of redoximorphic features that is uniquely
characteristic of all of the taxa in one particular category.
Therefore, color patterns that are unique to specific taxa are
referenced in the keys.
Anthraquic conditions are a variant of episaturation and
are associated with controlled flooding (for such crops as
wetland rice and cranberries), which causes reduction
processes in the saturated, puddled surface soil and oxidation
92 Soil Taxonomy
of reduced and mobilized iron and manganese in the unsaturated
subsoil.
Cryoturbation
Cryoturbation (frost churning) is the mixing of the soil matrix
within the pedon that results in irregular or broken horizons,
involutions, accumulation of organic matter on the permafrost
table, oriented rock fragments, and silt caps on rock fragments
(photo 37).
Densic Contact
A densic contact (L. densus, thick) is a contact between soil
and densic materials (defined below). It has no cracks, or the
spacing of cracks that roots can enter is 10 cm or more.
Densic Materials
Densic materials are relatively unaltered materials (do not
meet the requirements for any other named diagnostic horizons
or any other diagnostic soil characteristic) that have a
noncemented rupture-resistance class. The bulk density or the
organization is such that roots cannot enter, except in cracks.
These are mostly earthy materials, such as till, volcanic
mudflows, and some mechanically compacted materials, for
example, mine spoils. Some noncemented rocks can be densic
materials if they are dense or resistant enough to keep roots
from entering, except in cracks.
Densic materials are noncemented and thus differ from
paralithic materials and the material below a lithic contact,
both of which are cemented.
Densic materials have, at their upper boundary, a densic
contact if they have no cracks or if the spacing of cracks that
roots can enter is 10 cm or more. These materials can be used
to differentiate soil series if the materials are within the series
control section.
Gelic Materials
Gelic materials are mineral or organic soil materials that
show evidence of cryoturbation (frost churning) and/or ice
segregation in the active layer (seasonal thaw layer) and/or the
upper part of the permafrost. Cryoturbation is manifested by
irregular and broken horizons, involutions, accumulation of
organic matter on top of and within the permafrost, oriented
rock fragments, and silt-enriched layers. The characteristic
structures associated with gelic materials include platy, blocky,
or granular macrostructures; the structural results of sorting;
and orbiculic, conglomeric, banded, or vesicular microfabrics.
Ice segregation is manifested by ice lenses, vein ice, segregated
ice crystals, and ice wedges. Cryopedogenic processes that lead
to gelic materials are driven by the physical volume change of
water to ice, moisture migration along a thermal gradient in
the frozen system, or thermal contraction of the frozen material
by continued rapid cooling.
Glacic Layer
A glacic layer is massive ice or ground ice in the form of ice
lenses or wedges (photo 38). The layer is 30 cm or more thick
and contains 75 percent or more visible ice.
Lithic Contact
A lithic contact is the boundary between soil and a coherent
underlying material (photo 39). Except in Ruptic-Lithic
subgroups, the underlying material must be virtually
continuous within the limits of a pedon. Cracks that can be
penetrated by roots are few, and their horizontal spacing is 10
cm or more. The underlying material must be sufficiently
coherent when moist to make hand-digging with a spade
impractical, although the material may be chipped or scraped
with a spade. The material below a lithic contact must be in a
strongly cemented or more cemented rupture-resistance class.
Commonly, the material is indurated. The underlying material
considered here does not include diagnostic soil horizons, such
as a duripan or a petrocalcic horizon.
A lithic contact is diagnostic at the subgroup level if it is
within 125 cm of the mineral soil surface in Oxisols and within
50 cm of the mineral soil surface in all other mineral soils. In
organic soils the lithic contact must be within the control
section to be recognized at the subgroup level.
Paralithic Contact
A paralithic (lithiclike) contact is a contact between soil and
paralithic materials (defined below) where the paralithic
materials have no cracks or the spacing of cracks that roots can
enter is 10 cm or more (photo 40).
Paralithic Materials
Paralithic materials are relatively unaltered materials (do
not meet the requirements for any other named diagnostic
horizons or any other diagnostic soil characteristic) that have
an extremely weakly cemented to moderately cemented
rupture-resistance class. Cementation, bulk density, and the
organization are such that roots cannot enter, except in cracks.
Paralithic materials have, at their upper boundary, a paralithic
contact if they have no cracks or if the spacing of cracks that
roots can enter is 10 cm or more. Commonly, these materials
are partially weathered bedrock or weakly consolidated
bedrock, such as sandstone, siltstone, or shale. Paralithic
materials can be used to differentiate soil series if the materials
are within the series control section. Fragments of paralithic
materials 2.0 mm or more in diameter are referred to as
pararock fragments.
Horizons and Characteristics Diagnostic for the Higher Categories 93
Permafrost
Permafrost is defined as a thermal condition in which a
material (including soil material) remains below 0 o
C for 2 or
more years in succession. Those gelic materials having
permafrost contain the unfrozen soil solution that drives
cryopedogenic processes. Permafrost may be cemented by ice
or, in the case of insufficient interstitial water, may be dry. The
frozen layer has a variety of ice lenses, vein ice, segregated ice
crystals, and ice wedges. The permafrost table is in dynamic
equilibrium with the environment.
Soil Moisture Regimes
It has been conventional to identify three soil moisture
regimes. In one, the soil is saturated. In another, the amount of
water is enough to cause leaching. In the third, no leaching
occurs. In the leaching regime, some water moves through the
soil at some time during the year and moves on down to the
moist substratum. In the nonleaching regime, water moves into
the soil but is withdrawn by evapotranspiration, leaving
precipitated carbonates and more soluble salts. Between these
two regimes, there is another possible one in which there is
alternation from year to year; leaching occurs in some years but
not in all. For consideration of the losses of soluble materials
or their accumulation in horizons with k, y, or z suffixes, these
concepts are adequate. For the understanding of biological
processes, they leave much to be desired. A soil can be subject
to leaching during winter, when it is too cold for optimum
biological activity, and it can be too dry during most of the
summer for significant biological activity. The result is a
relatively wide carbon-nitrogen ratio.
The term “soil moisture regime” refers to the presence or
absence either of ground water or of water held at a tension of
less than 1500 kPa in the soil or in specific horizons during
periods of the year. Water held at a tension of 1500 kPa or
more is not available to keep most mesophytic plants alive. The
availability of water is also affected by dissolved salts. If a soil
is saturated with water that is too salty to be available to most
plants, it is considered salty rather than dry. Consequently, a
horizon is considered dry when the moisture tension is 1500
kPa or more and is considered moist if water is held at a
tension of less than 1500 kPa but more than zero. A soil may
be continuously moist in some or all horizons either throughout
the year or for some part of the year. It may be either moist in
winter and dry in summer or the reverse. In the Northern
Hemisphere, summer refers to June, July, and August and
winter refers to December, January, and February.
Significance to Soil Classification
The moisture regime of a soil is an important property of the
soil as well as a determinant of processes that can occur in the
soil. During geologic time there have been significant changes
in climate. Soils that could have formed only in a humid
climate are now preserved in an arid climate in some areas.
Such soils have relict features that reflect the former moisture
regime and other features that reflect the present moisture
regime.
The soil moisture regime is only partially a function of
climate. Most deep, permeable soils under high and well
distributed rainfall have water that is available to plants most
of the time. Soils in areas of an arid climate, however, are not
necessarily dry. They may be dry, moist, or saturated,
depending on their position on the landscape, because they
may receive water from sources other than the rain that falls on
them. The extra water may be runoff from rainfall on an
adjacent slope or on distant mountains, or it may come from
melting snow, seepage, or even natural artesian sources. In the
Northern Hemisphere, precipitation is more effective in soils
on north aspects than in soils on south aspects. In some areas
this difference is significant enough for there to be different
soil moisture regimes on north and south aspects. Soils may
also lose part or most of the water that falls on them,
particularly if they are sloping and the surface horizon has few
noncapillary pores. On any given landscape that has uniform
climate, adjacent soils may have different moisture regimes.
Each of the moisture regimes in the history of a soil is a
factor in the genesis of that soil and is the cause of many
accessory characteristics. Most of the accessory characteristics,
however, and those most important for interpretations are
associated with the present moisture regime, even if the present
regime differs widely from some of the earlier regimes. For
example, before an argillic horizon forms, enough water has to
pass through the soil to remove soluble materials, such as
finely divided carbonates. If the leaching and formation of the
argillic horizon took place under climatic conditions with more
effective precipitation than that of today, the present argillic
horizon is not necessarily free from carbonates or other soluble
materials. Soils with soluble salts or carbonates above and
within the argillic horizon have characteristics that reflect both
past and present climates. The argillic horizon formed under a
past climate, and the soluble salts and carbonates accumulated
under the present climate. Both climates have left markers that
can be observed in the soils today. The argillic horizon that
formed under more effective moisture may have formed under
precipitation similar to that of today but under cooler
temperatures, or it may have formed under temperatures
similar to those of today but under higher precipitation. There
is no precise measure of past climates, and an accurate
reconstruction of past climates is difficult. More importantly,
the present climate determines use and management of the soil.
It is a property of the soil. Furthermore, the moisture regimes
of most soils are inferred from the present climate, and smallscale
maps can be interpreted in terms of the many accessory
94 Soil Taxonomy
characteristics that are common to most of the soils that have a
common climate. These characteristics include the amount,
nature, and distribution of organic matter, the base status of the
soil, and the presence or absence of salts.
The most important of the soil interpretations are the
potentials for growing different plants and the cultural
practices required to grow them. Without soil climate as a
criterion at some level in the taxonomic system, for example,
Vertisols from Texas could be in the same taxonomic class as
Vertisols from North Dakota.
Normal Years
In the discussions that follow and throughout the keys, the
term “normal years” is used. A normal year is defined as a year
that has plus or minus one standard deviation of the long-term
mean annual precipitation. (Long-term refers to 30 years or
more.) Also, the mean monthly precipitation during a normal
year must be plus or minus one standard deviation of the longterm
monthly precipitation for 8 of the 12 months. For the
most part, normal years can be calculated from the mean
annual precipitation. When catastrophic events occur during a
year, however, the standard deviations of the monthly means
should also be calculated. The term “normal years” replaces
the terms “most years” and “6 out of 10 years,” which were
used in the previous edition of Soil Taxonomy (USDA, SCS,
1975).
Estimation
The landscape position of every soil is subject to extremes in
climate. While no 2 years have exactly the same weather
conditions, the moisture status of the soil must be characterized
by probability. Weather probabilities can be determined from
long-term weather records and observations of how each soil
responds to weather conditions as modified by its landscape
position.
A number of methods have been devised to relate soil
moisture to meteorological records. To date, all of these
methods have some shortcomings, even for gently sloping soils
that depend primarily on precipitation for their moisture. Dew
and fog can add appreciable amounts of moisture to some soils,
but quantitative data are rare.
The graphs in diagrams 3 to 16 are based on the average
values for precipitation, temperature, and potential
evapotranspiration. They give an oversimplified picture of the
moisture regime of the whole soil rather than of the moisture
control section. The data are based on the monthly
climatological values of temperature and precipitation for the
indicated number of years and the monthly potential
evapotranspiration (PE) normals taken from the large
Thornthwaite collection covering the world (Mather, 1964,
1965). No reduction from potential evapotranspiration was
made.
The following legend helps to explain the graphs in
diagrams 3 to 16. Numbers at the bottom of the graphs indicate
months of the year.
In diagram 3 the area between the line that joins all of the
precipitation normals and the one that joins all of the PE
normals indicates the status of soil moisture. Beginning at the
point where precipitation becomes greater than PE, the area to
the right shows recharge, the amount of moisture stored in the
soil. This area commonly extends to the extreme right of the
diagram. The amount of recharge is limited either by the
available water capacity (AWC) of the soil, in which case a
vertical line delimits the area as surplus, or by the fact that PE
again exceeds precipitation before the AWC has been filled.
The point where PE exceeds precipitation is utilization.
Utilization shows the amount of PE necessary to remove the
water held at a tension of less than 1500 kPa. Excess PE, if
any, before the time that recharge begins is called deficit and is
delimited by a vertical line.
The discussion of recharge, surplus, utilization, and deficit
in the preceding paragraph has implied the moisture regime of
a cool, moist region in the Northern Hemisphere, but many
other combinations of recharge, surplus, utilization, and deficit
can occur, including all surplus and all deficit.
For definitions of taxa, it is recognized that the accretion of
daily or monthly precipitation is depleted, linearly or
nonlinearly, by daily or monthly potential evapotranspiration.
An initial condition is set, and the sequence of subsequent
water balances shows whether critical parts of the soil profile
are likely to be moist, partly dry, or completely dry as the
seasons advance. Depending on one’s purposes, an assumption
of linear or of nonlinear depletion of soil moisture might be
best. To represent the probable soil moisture regime, the
estimate of evapotranspiration should be reduced as the soil
dries. To represent irrigation needs, evapotranspiration at the
full potential rate would give a better picture. Either procedure
gives a crude picture of both.
Soil Moisture Control Section
The intent in defining the soil moisture control section is to
facilitate estimation of soil moisture regimes from climatic
data. The upper boundary of this control section is the depth to
which a dry (tension of more than 1500 kPa, but not air-dry)
Horizons and Characteristics Diagnostic for the Higher Categories 95
soil will be moistened by 2.5 cm of water within 24 hours. The
lower boundary is the depth to which a dry soil will be
moistened by 7.5 cm of water within 48 hours. These depths do
not include the depth of moistening along any cracks or animal
burrows that are open to the surface.
The boundaries for the soil moisture control section
correspond to the rooting depths for many crops; however,
there are natural plant communities that have their roots either
above or below the control section. Attempts are currently
being made to improve the parameters of the soil moisture
control section.
If 7.5 cm of water moistens the soil to a densic, lithic,
paralithic, or petroferric contact or to a petrocalcic or
petrogypsic horizon or a duripan, the contact or the upper
boundary of the cemented horizon constitutes the lower
boundary of the soil moisture control section. If a soil is
moistened to one of these contacts or horizons by 2.5 cm of
water, the soil moisture control section is the boundary or the
contact itself. The control section of such a soil is considered
moist if the contact or upper boundary of the cemented horizon
has a thin film of water. If that upper boundary is dry, the
control section is considered dry.
The concept of the soil moisture control section does not
apply well to the cracking clays, because these clays remoisten
from both the surface and the bases of the cracks. The soil
moisture patterns of these soils are defined in terms of the
pattern of cracking over time.
Dry soils can remoisten unevenly for a variety of reasons
other than microrelief or the presence of cracks or holes that
are open at the surface. Water can be suspended by capillary
forces in a dry sandy soil (Rode, 1965). When the suspended
water exceeds a critical limit, it drains rapidly at some points
into lower soil layers. Water can be suspended in a dry or moist
soil if pore sizes increase with increasing depth, and similar
leaks may occur. Uneven moistening may result from
interception of rain by plants. Part of the rain reaches the soil
by flowing down the stem of the plant. Some plants, such as
mulga (Acacia aneura) in Australia, intercept virtually all of
the rain falling on them. In this situation, the soil is moistened
deeply around the stem but remains extremely dry under the
canopy of the mulga. In areas between the plants, rain
generally falls directly on the soil. Thus, within a very short
distance, there are three contrasting moisture regimes. In one,
the soil is deeply moistened; in the second, which surrounds
the first, the soil receives virtually no moisture; and in the
third, the soil is intermittently moist and dry.
If moistening occurs unevenly, the weighted average depth
of moistening in a pedon is used for the limits of the moisture
control section.
The moisture control section of a soil extends approximately
(1) from 10 to 30 cm below the soil surface if the particle-size
class of the soil is fine-loamy, coarse-silty, fine-silty, or clayey;
(2) from 20 to 60 cm if the particle-size class is coarse-loamy;
and (3) from 30 to 90 cm if the particle-size class is sandy. If
the soil contains rock and pararock fragments that do not
absorb and release water, the limits of the moisture control
section are deeper. The limits of the soil moisture control
section are affected not only by the particle-size class but also
by differences in soil structure or pore-size distribution or by
other factors that influence the movement and retention of
water in the soil.
The classification of the soil series in the United States
was determined in part by knowledge of the moisture
regimes. The definitions of soil moisture regimes that follow
were fitted to the boundaries. If future studies show that the
classifications of the soils are not in agreement with these
definitions, we are more likely to change the definitions than
the classifications. Over time, changes in both will doubtless
be made.
Classes of Soil Moisture Regimes
The soil moisture regimes are defined in terms of the level
of ground water and in terms of the seasonal presence or
absence of water held at a tension of less than 1500 kPa in the
moisture control section. It is assumed in the definitions that
the soil supports whatever vegetation it is capable of
supporting, i.e., crops, grass, or native vegetation, and that the
amount of stored moisture is not being increased by irrigation
Diagram 3.—Udic, frigid; St. Petersburg, Russia (formerly
Leningrad, U.S.S.R.).
96 Soil Taxonomy
or fallowing. These cultural practices affect the soil moisture
conditions as long as they are continued.
Aquic moisture regime.—The aquic (L. aqua, water)
moisture regime is a reducing regime in a soil that is virtually
free of dissolved oxygen because it is saturated by water. Some
soils are saturated with water at times while dissolved oxygen
is present, either because the water is moving or because the
environment is unfavorable for micro-organisms (e.g., if the
temperature is less than 1 o
C); such a regime is not considered
aquic.
It is not known how long a soil must be saturated before it is
said to have an aquic moisture regime, but the duration must
be at least a few days, because it is implicit in the concept that
dissolved oxygen is virtually absent. Because dissolved oxygen
is removed from ground water by respiration of microorganisms,
roots, and soil fauna, it is also implicit in the
concept that the soil temperature is above biologic zero for
some time while the soil is saturated. Biologic zero is defined
as 5 o
C in this taxonomy. In some of the very cold regions of
the world, however, biological activity occurs at temperatures
below 5 o
C.
Very commonly, the level of ground water fluctuates with
the seasons; it is highest in the rainy season or in fall, winter,
or spring if cold weather virtually stops evapotranspiration.
There are soils, however, in which the ground water is always
at or very close to the surface. Examples are soils in tidal
marshes or in closed, landlocked depressions fed by perennial
streams. Such soils are considered to have a peraquic moisture
regime. The distinction between the aquic moisture regime and
the peraquic moisture regime is not closely defined because
neither regime is used as a criterion for taxa above the series
level. These terms can be used in descriptions of taxa. Some
soils with an aquic moisture regime also have a xeric, ustic, or
aridic (torric) regime.
Although the aquic and peraquic moisture regimes are
not used as either criteria or formative elements for taxa,
they are used in taxon descriptions as an aid in understanding
genesis. The formative term “aqu” refers to aquic conditions,
not an aquic moisture regime. Some soils included in the
“Aqu” suborders may have aquic or peraquic moisture
regimes.
Aridic and torric (L. aridus, dry, and L. torridus, hot
and dry) moisture regimes.—These terms are used for the
same moisture regime but in different categories of the
taxonomy.
In the aridic (torric) moisture regime, the moisture control
section is, in normal years:
1. Dry in all parts for more than half of the cumulative days
per year when the soil temperature at a depth of 50 cm from the
soil surface is above 5 o
C; and
2. Moist in some or all parts for less than 90 consecutive
days when the soil temperature at a depth of 50 cm is above
8 o
C.
Soils that have an aridic (torric) moisture regime
normally occur in areas of arid climates. A few are in areas
of semiarid climates and either have physical properties that
keep them dry, such as a crusty surface that virtually
precludes the infiltration of water, or are on steep slopes where
runoff is high. There is little or no leaching in this moisture
regime, and soluble salts accumulate in the soils if there is a
source.
Diagrams 4 to 7 illustrate climatic data in a region where the
soils have an aridic (torric) moisture regime. Diagram 4 is an
example of an area with an aridic soil moisture regime and a
hyperthermic soil temperature regime. Diagram 5 is an
Diagram 4.—Aridic, hyperthermic; Jodhpur, India.
Horizons and Characteristics Diagnostic for the Higher Categories 97
example of an area with an aridic soil moisture regime and a
thermic temperature regime. Diagram 6 is an example of an area
with an aridic soil moisture regime and a mesic soil temperature
regime. Diagram 7 is an example of an area with an aridic soil
moisture regime that grades towards an ustic soil moisture
regime.
The limits set for soil temperature exclude from these moisture
regimes soils in the very cold and dry polar regions and in areas
at high elevations. Such soils are considered to have anhydrous
conditions (defined earlier).
Udic moisture regime.—The udic (L. udus, humid)
moisture regime is one in which the soil moisture control
section is not dry in any part for as long as 90 cumulative days
in normal years. If the mean annual soil temperature is lower
than 22 o
C and if the mean winter and mean summer soil
temperatures at a depth of 50 cm from the soil surface differ by
6 o
C or more, the soil moisture control section, in normal
years, is dry in all parts for less than 45 consecutive days
in the 4 months following the summer solstice. In addition,
the udic moisture regime requires, except for short periods, a
three-phase system, solid-liquid-gas, in part or all of the soil
moisture control section when the soil temperature is above
5o
C.
The udic moisture regime is common to the soils of humid
climates that have well distributed rainfall; have enough rain
in summer so that the amount of stored moisture plus rainfall
is approximately equal to, or exceeds, the amount of
evapotranspiration; or have adequate winter rains to recharge
the soils and cool, foggy summers, as in coastal areas. Water
moves downward through the soils at some time in normal
years.
In climates where precipitation exceeds evapotranspiration in
all months of normal years, the moisture tension rarely reaches
100 kPa in the soil moisture control section, although there are
occasional brief periods when some stored moisture
is used. The water moves through the soil in all months whenDiagram 5.—Aridic, thermic; Las Vegas, Nevada, United States.
Diagram 6.—Aridic, mesic; Lanzhou, China.
98 Soil Taxonomy
it is not frozen. Such an extremely wet moisture regime is
called perudic (L. per, throughout in time, and L. udus,
humid). In the names of most taxa, the formative element “ud”
is used to indicate either a udic or a perudic regime; the
formative element “per” is used in selected taxa. The
distinction between perudic and udic can always be made
at the series level.
Diagram 8 illustrates an area with a udic soil moisture regime
and an isohyperthermic soil temperature regime. Diagram 9
illustrates an area with a udic soil moisture regime and a thermic
temperature regime. Diagrams 10 and 11 are examples of areas
with a udic soil moisture regime and mesic and frigid temperature
regimes, respectively.
Diagram 12 illustrates a perudic soil moisture regime. Note
that the perudic regime shows a surplus every month of the
year. Obviously, if calculations were made on a daily basis,
there would be short periods of withdrawal.
Ustic moisture regime.—The ustic (L. ustus, burnt;
implying dryness) moisture regime is intermediate between
the aridic regime and the udic regime. Its concept is one of
moisture that is limited but is present at a time when
conditions are suitable for plant growth. The concept of
the ustic moisture regime is not applied to soils that have
permafrost or a cryic soil temperature regime (defined
below).
If the mean annual soil temperature is 22 o
C or higher or if
the mean summer and winter soil temperatures differ by less
than 6 o
C at a depth of 50 cm below the soil surface, the soil
moisture control section in areas of the ustic moisture regime is
dry in some or all parts for 90 or more cumulative days in
normal years. It is moist, however, in some part either for more
than 180 cumulative days per year or for 90 or more
consecutive days.
If the mean annual soil temperature is lower than 22 o
C and
Diagram 7.—Aridic, mesic; Odessa, Ukraine.
Diagram 8.—Udic, isohyperthermic; Rio de Janeiro, Brazil.
Horizons and Characteristics Diagnostic for the Higher Categories 99
if the mean summer and winter soil temperatures differ by 6 o
C
or more at a depth of 50 cm from the soil surface, the soil
moisture control section in areas of the ustic moisture regime is
dry in some or all parts for 90 or more cumulative days in
normal years, but it is not dry in all parts for more than half of
the cumulative days when the soil temperature at a depth of 50
cm is higher than 5 o
C. If in normal years the moisture control
section is moist in all parts for 45 or more consecutive days in
the 4 months following the winter solstice, the moisture control
section is dry in all parts for less than 45 consecutive days in
the 4 months following the summer solstice. Diagram 13
illustrates an area with an ustic soil moisture regime and a
thermic soil temperature regime. Diagram 14 illustrates an
area with an ustic soil moisture regime and a mesic soil
temperature regime.
In tropical and subtropical regions that have a monsoon
climate with either one or two dry seasons, summer and winter
seasons have little meaning. In those regions the moisture
regime is ustic if there is at least one rainy season of 3 months
or more. In temperate regions of subhumid or semiarid
climates, the rainy seasons are usually spring and summer or
spring and fall, but never winter. Native plants are mostly
annuals or plants that have a dormant period while the soil is
dry.
Xeric moisture regime.—The xeric (Gr. xeros, dry)
moisture regime is the typical moisture regime in areas of
Mediterranean climates, where winters are moist and cool and
summers are warm and dry. The moisture, which falls during
the winter, when potential evapotranspiration is at a minimum,
is particularly effective for leaching. In areas of a xeric
moisture regime, the soil moisture control section, in normal
years, is dry in all parts for 45 or more consecutive days in the
4 months following the summer solstice and moist in all parts
for 45 or more consecutive days in the 4 months following the
Diagram 9.—Udic, thermic; Buenos Aires, Argentina.
Diagram 10.—Udic, mesic; Sapporo, Japan.
100 Soil Taxonomy
winter solstice. Also, in normal years, the moisture control
section is moist in some part for more than half of the
cumulative days per year when the soil temperature at a depth
of 50 cm from the soil surface is higher than 6 o
C or for 90 or
more consecutive days when the soil temperature at a depth of
50 cm is higher than 8 o
C. The mean annual soil temperature is
lower than 22 o
C, and the mean summer and mean winter soil
temperatures differ by 6 o
C or more either at a depth of 50 cm
from the soil surface or at a densic, lithic, or paralithic contact
if shallower.
Diagram 15 illustrates an area with a xeric soil moisture regime
and a thermic soil temperature regime. Diagram 16 illustrates an
area with a xeric soil moisture regime and a mesic soil
temperature regime.
Soil Temperature Regimes
The temperature of a soil is one of its important properties.
Within limits, temperature controls the possibilities for plant
growth and for soil formation. Below the freezing point, there
is no biotic activity, water no longer moves as a liquid, and,
unless there is frost heaving, time stands still for the soil.
Between temperatures of 0 and 5 o
C, root growth of most plant
species and germination of most seeds are impossible. A
horizon as cold as 5 o
C is a thermal pan to the roots of most
plants.
Biological processes in the soil are controlled in large
measure by soil temperature and moisture. Each plant species
has its own temperature requirements. In the Antarctic, for
example, there is a microscopic plant that grows only at
temperatures below 7 o
C, temperatures at which most other
plants are inactive. At the other extreme, germination of seeds
of many tropical plant species requires a soil temperature of
24 o
C or higher. Plant species have one or more soil
temperature requirements that are met by the soils of their
native environment. Similarly, soil fauna have temperature
requirements for survival. Soil temperature, therefore, has an
important influence on biological, chemical, and physical
processes in the soil and on the adaptation of introduced plant
species.
At any moment the temperature within a soil varies fromDiagram 11.—Udic, frigid; Harbin, China.
Diagram 12.—Perudic, mesic; Zeehan, Australia (Tasmania) .
Horizons and Characteristics Diagnostic for the Higher Categories 101
horizon to horizon. The temperature near the surface fluctuates
with the hours of the day and with the seasons of the year. The
fluctuations may be very small or very large, depending on the
environment. Because temperature is so variable, or perhaps
because it is not preserved in samples, some pedologists have
thought that it is not a property of a soil. One is inclined to
notice the properties that differ among soils and to focus
attention on them.
Each pedon has a characteristic temperature regime that can
be measured and described. For most practical purposes, the
temperature regime can be described by the mean annual soil
temperature, the average seasonal fluctuations from that mean,
and the mean warm or cold seasonal soil temperature gradient
within the main root zone, which is the zone from a depth of 5
to 100 cm.
Mean Annual Soil Temperature
Each pedon has a mean annual temperature that is
essentially the same in all horizons at all depths in the soil and
at depths considerably below the soil. The measured mean
annual soil temperature is seldom the same in successive
depths at a given location, but the differences are so small that it
seems valid and useful to take a single value as the mean annual
temperature of a soil.
The mean annual soil temperature is related most closely
to the mean annual air temperature, but this relationship is
affected to some extent by the amount and distribution of
rain, the amount of snow, the protection provided by shade
and by O horizons in forests, the slope aspect and gradient,
and irrigation. Other factors, such as soil color, texture,
and content of organic matter, have negligible effects (Smith
etal.,1964).
Fluctuations of Soil Temperature
The mean annual temperature of a soil is not a single
reading but the average of a series of readings. Near the
surface, the readings may fluctuate from the mean fully as
much as those of the air temperature, especially if there is no
insulating cover. The fluctuations occur as daily and annual
cycles, which in most places are made somewhat irregular by
weather events. The fluctuations decrease with increasing
depth and are ultimately damped out in the substrata in a zoneDiagram 13.—Ustic, thermic; Haskell, Texas, United States.
Diagram 14.—Ustic, mesic; Halle, Germany.
102 Soil Taxonomy
where the temperature is constant and is the same as the mean
annual soil temperature.
Daily fluctuations.—Daily changes in air temperature
have a significant effect on the temperature of soil horizons
to a depth of about 50 cm. The fluctuations may be very
large, particularly in soils of dry climates where the daily
range in temperature of the upper 2.5 cm of the soils may
approach 55 o
C. At the other extreme, under melting snow,
the temperature at the soil surface may be constant
throughout the day. In a few places in high mountains
very near the Equator, the soils have virtually constant
temperature.
Daily fluctuations in soil temperature are affected by
clouds, vegetation, length of day, soil color, slope, soil
moisture, air circulation near the ground, and the temperature
of any rain that falls. Moisture can be exceedingly important
in reducing fluctuations in soil temperature. The specific heat
of water is roughly 4 times that of a dry surface horizon, and the
specific heat of a medium textured surface horizon at field
capacity is roughly one-half more than that at the wilting
point. Water increases the thermal conductivity of soils, and
it can also absorb or liberate heat by freezing and thawing
or by evaporating and condensing. All of these effects of
soil water reduce fluctuations in soil temperature at the
surface.
Fluctuations caused by changes in weather.—Soil
temperatures also fluctuate during short periods of belowaverage
or above-average air temperatures. The fluctuations
caused by weather extend to a greater depth than those of the
diurnal cycle. Periods of high or low temperature tend to last
a few days to a week in most of the United States. Like
weather patterns in general, however, they occur at irregular
intervals.
The soil temperature at a depth of 50 cm shows almost no
Diagram 15.—Xeric, thermic; Athens, Greece.
Diagram 16.—Xeric, mesic; Portland, Oregon, United States.
Horizons and Characteristics Diagnostic for the Higher Categories 103
daily fluctuation, but it reflects short-time weather patterns. Data
indicate that at shallow depths soil temperatures reflect daily
fluctuations in temperature.
Cold or warm rains may bring about rapid and marked
changes in the temperature of surface horizons. Generally, the
direct effect of a rain on soil temperature is not measurable 48
hours after the rain ends.
Seasonal fluctuations and soil temperature gradients in the
Tropics.—Seasonal fluctuations of soil temperature are
generally small in the intertropical regions between the Tropic of
Capricorn and the Tropic of Cancer. Mean annual soil
temperatures vary with elevation, but seasonal temperatures
vary primarily with clouds and rain. The warmest seasons may
be the dry seasons, for the effects of clouds and rain may
outweigh those of the angle of the sun’s rays.
Diagram 17 shows the soil temperature, air temperature,
rainfall, and percentage of possible sunshine at Yangambi, Zaire,
at an elevation of about 365 m (I.N.E.A.C., 1953). These data
indicate that the soil temperature is higher in winter than in
summer. Actually, the soil temperature fluctuates with cloud
cover and rain and appears to be most closely correlated with
the amount of sunshine. In the Tropics, differences between
summer and winter temperatures are small and may be in
either direction. The average temperature over a 3-month
season is virtually the same at all depths within the upper m of
the soil.
As the temperate region is approached, near the Tropic of
Cancer, for example, soil temperatures in summer are likely to be
higher than those in winter, but the differences between the
mean summer temperature and the mean winter temperature in
the upper m of the soil are usually less than 6 o
C.
Seasonal fluctuation and soil temperature gradients in
midlatitudes.—Soil temperatures in the 48 conterminous
States of the United States generally show marked seasonal
Diagram 17.—Mean monthly soil temperature at a depth of 50 cm for 1952 at Yangambi, Zaire, and the major factors that affect the soil
temperature.
104 Soil Taxonomy
fluctuations. To illustrate seasonal changes under a midlatitude
continental climate, such as that in much of the United States,
a good record of soil temperatures from Belgrade, Yugoslavia
(Chang, 1958b), has been selected. This record is shown
graphically in diagram 18. The annual cooling and heating
waves extend to a depth of 12 m, but the amplitude of variation
at this depth is only 0.1 o
C. At a depth of 14 m, the temperature
is constant and is the same as the mean annual soil temperature.
These records clearly show that seasonal temperature
fluctuations penetrate deeply into the earth, well below the limit
of soil.
The depth to the stratum that has constant temperature is not
the same in all soils. It is reduced by shallow ground water
because water has high specific heat. Records of well-water
temperature in the 48 conterminous States of the United States
show that, in the presence of ground water, the stratum of
constant soil temperature occurs at a depth of about 9 m.
Chang (1958a) has estimated that, in the absence of ground
water, seasonal fluctuations of soil temperature penetrate to a
depth of 20 m in Alaska, 15 m in midlatitudes, and 10 m in the
Tropics. In dry soils, thermal conductivity is low and, although
seasonal fluctuations in temperature may be very large, the
depth of penetration is no greater than in moist soils. At Jaipur,
India (lat. 27o
N.), the seasonal range in soil temperature at a
depth of 6 m was 2.7 o
C, but at a depth of 14 m, it was only
0.2 o
C (Chang, 1958b).
The amplitude of seasonal fluctuations and the timing of
periods of warm and cool soil temperature are primarily
functions of latitude and climate. In midlatitudes the angle of
the sun’s rays is most important, but clouds, rain, irrigation
water, snow cover, bodies of water, direction and angle of
slope, and presence or absence of shallow ground water and of
thick O horizons can all affect the amplitude of fluctuation.
Seasonal fluctuations in midlatitudes are generally in excess of
Diagram 18.—Mean monthly isotherms of ground temperature at Belgrade, Yugoslavia.
Horizons and Characteristics Diagnostic for the Higher Categories 105
6 o
C. That is, the average summer soil temperature is more
than 6 o
C higher than the average winter soil temperature in
the upper m of the soil.
Since the temperatures of soils at high elevations tend to
resemble those of soils at high latitudes, the discussion in this
section is confined to soils having mean annual temperatures of
8 o
C or higher. The cold soils at high elevations in the
midlatitudes are discussed with the soils of high latitudes.
Effect of depth.—In a given soil, the closer to the surface,
the greater the amplitude of fluctuation. Seasonal variations
of soil temperature are greatest at the surface and decrease
with increasing depth until, at a depth of 9 m or more, they
disappear (diagram 18). The mean summer, winter, and
annual soil temperatures (Chang, 1958b) are plotted in
diagram 19 as a function of depth together with air
temperatures for Ames, Iowa, which is in the midlatitudes. If
we disregard the upper few cm, the changes in the mean
seasonal soil temperature with increasing depth are nearly
linear, so nearly so that one must conclude that the mean
seasonal temperature of soil to any depth within the main
zone of rooting is very closely approximated by the mean
temperature at the midpoint in depth. The temperature gradient
is positive in winter and negative in summer. It is
approximately 0.5 o
C per 10 cm. The gradients seem very
similar in most midlatitude soils where records are available,
even in undrained peats.
Effect of vegetative cover.—In the humid midlatitudes, the
plant cover can have an important influence on seasonal
fluctuations of soil temperature. The differences among kinds
of plant cover, such as grass, crops, and trees, in shading or
insulating the soil are minor if O horizons are transient or
absent.
Diagram 19.—Soil temperature gradients with air temperatures for winter and summer in relation to mean annual temperatures at Ames,
Iowa.
106 Soil Taxonomy
Effect of irrigation.—Irrigation of dry soils can have a
marked effect on the soil temperature in summer. Both
evaporation and shade affect the temperature, but evaporation
is probably the more important. The reduction may exceed 8 o
C
in places.
Effect of ground water.—Because of its large latent and
specific heat, shallow ground water greatly affects seasonal
fluctuations of soil temperature in midlatitudes. The principal
effects occur during periods when the soil is freezing or
thawing because the latent heat of the freezing of water is
about 80 times the specific heat.
Effect of aspect and gradient of slope.—The aspect
(direction) and gradient of slope may affect the deviation of the
mean monthly soil temperatures from the annual mean. The
effect in winter is large compared to that in summer. In the
Northern Hemisphere, south-facing slopes have smaller
seasonal fluctuations from the annual mean than north-facing
slopes. The effects of aspect increase sharply in high latitudes.
Diagram 20 shows the relationship between soil temperature and
elevation on north and south aspects in the Great Basin of
Nevada (Jensen et al., 1989).
Seasonal fluctuations in high latitudes.—Soils in high
latitudes are cold, and the seasonal soil temperature fluctuations
do not approximate a simple sine curve as do those in
midlatitudes. Diagram 21 shows the mean monthly soil and air
temperatures at Mustiala, Finland (Chang, 1958b). The air
temperature follows a simple sine curve and is above the mean
for only 5 months and below it for 7 months. The asymmetrical
soil temperature fluctuations reflect the combined influence of
snow as an insulator during winter and the relatively high
insolation during summer months, when the sun is above the
horizon all or most of the time
Diagram 22 shows the mean annual seasonal soil
temperature at Mustiala, Finland, as a function of depth
Diagram 20.—Relationship between soil temperature and elevation on south and north aspects.
Horizons and Characteristics Diagnostic for the Higher Categories 107
(Chang, 1958b). The skewed seasonal fluctuations are indicated
by the closeness of the lines that show winter temperature and
mean annual temperature
In these latitudes, the soil temperature in summer is lower
than the air temperature. The temperature gradients with
increasing depth are similar to those in midlatitudes.
Effect of snow cover.—Diagram 23 shows the effect of
snow cover on soil temperature at various depths (Molga, 1958).
It indicates the difference in temperature between bare soil and
soil covered with snow (snow-covered plot minus bare plot).
From November through March, the snow-covered plot was
warmer at all depths. The average temperature difference for the
winter months, December through February, was 4 o
C
at a depth of 50 cm. In April, when the air temperature was
rising and snow was melting, the bare soil warmed more
rapidly and was warmer than the snow-covered plot to a depth
of 40 cm.
The effect of snow on soil temperature is not limited to high
latitudes and high altitudes. Snow cover is common but
intermittent for the most part in midlatitudes where the mean
annual soil temperature is less than 13 o
C.
Effect of vegetative cover.—The cover of litter and of moss in
areas of cold climates commonly is thicker than the cover in
areas of warm climates. As the cover thickens, it reduces the
amplitude of seasonal fluctuations of soil temperature because
it insulates the soil during the entire year.
Diagram 24 shows the mean monthly soil temperatures for a
cleared field versus a forested site at Delta Junction, Alaska
(Shur et al., 1993). Without the shade from trees and insulation
from litter and organic matter, the cleared field is colder in
winter and warmer in summer.
Differences in the type of vegetation can result in variations
in soil temperature. Diagram 25 illustrates differences between a
climax spruce forest with a thick organic layer and a less
insulated aspen forest in the Copper River area of Alaska
(Moore and Ping, 1989).
Diagram 21.—Mean monthly and annual soil and air temperatures at Mustiala, Finland.
108 Soil Taxonomy
Effect of ground water.—Because of its specific and latent
heat, ground water reduces seasonal fluctuations of soil
temperature. In diagram 26 the soil temperature at a depth of 50
cm is plotted for two soils at Flahult, Sweden (Chang, 1958b),
where the mean annual soil temperature is about 6 o
C. The soil in
the wet bog was warmer in winter and cooler in summer than the
sandy soil. The amplitude of fluctuations at a depth of 50 cm
was 4 o
C less in the wet bog than in the sandy soil.
Estimation of Soil Temperature
Soil temperature often can be estimated from climatological
data with a precision that is adequate for the present needs of
soil surveys. If we cannot make reasonably precise estimates,
the measurement of soil temperature need not be a difficult or a
time-consuming task.
Frequently, the mean annual soil temperature for much
of the United States is estimated by adding 1 o
C to the
mean annual air temperature. The table “Mean Annual
Soil Temperature (MAST) and Mean Annual Air Temperature
(MAAT)” shows the mean annual soil temperature from
various sites in the United States. It also shows the
difference between the mean annual soil temperature and
the mean annual air temperature at these sites. These data
indicate that for some areas in the United States the mean
annual soil temperature should be estimated by adding 2 or
even 3 o
C (rather than 1 o
C) to the mean annual air
temperature.
The mean summer soil temperature at a specific depth
also can be estimated. To make this estimate, we can take
the average summer temperatures of the upper 100 cm and
correct for the temperature-depth gradient by adding or
subtracting 0.6 o
C for each 10 cm above or below a depth of
50 cm. The mean winter temperature of many midlatitude
soils can be estimated from the difference between the mean
annual temperatures and the mean summer temperatures
because the differences are of the same magnitude but have
opposite signs.
The cooling wave at Belgrade extends to a depth of 12 m,
and at this depth the minimum temperature is reached about 10
months later than at a depth of 1 m (diagram 18). The amplitude
of variation at a depth of 12 m is less than 0.1 o
C. Thus, the
mean annual temperature of a soil in midlatitudes can be
Diagram 22.—Soil temperature gradients with air temperatures for winter and summer in relation to mean annual temperatures at
Mustiala, Finland.
Horizons and Characteristics Diagnostic for the Higher Categories 109
determined at any time by a single reading at a depth of 13 m. A
single reading at a depth of 10 m is within 0.1 o
C of the mean
annual soil temperature. A single reading at a depth of 6 m is
within 1 o
C of the mean annual temperature.
The mean annual temperature of soils underlain by deep
regolith can therefore be very closely approximated at any
season by measurement in a deep auger boring. In some areas
an even simpler method of determining the mean annual soil
temperature can be used. Dug wells generally range from 6 to
18 m in depth. If the water table stands between 9 and 18 m
and water is drawn from the well frequently, the temperature of
water in the well, which is in equilibrium with the soil
temperature, gives the mean annual soil temperature within a
margin of error of less than 1 o
C. The well must be in use, so
that water is moving into it from the ground. Unfortunately,
this method is suited only to humid regions where ground
water is shallow and is not frozen. Extensive records of wellwater
temperature have shown that the water temperature
between depths of 9 and 18 m is essentially constant
throughout the year.
If the soil is shallow and there are no wells, the mean
annual soil temperature can be measured over the four seasons
only by taking several readings at regular intervals of time. If
the soil is expected to be frozen deeply at the time of one or
Diagram 23.—Monthly soil temperature differences between bare and snow-covered plots at Leningrad, U.S.S.R. (now St. Petersburg,
Russia), and mean monthly air temperature and snow thickness.
Site name
MAST
(50 cm)
MAST
minus
MAAT
o
C o
C
Adams Ranch, New Mexico ............. 14.67 2.94
Crescent City, Minnesota ................. 7.30 1.39
Ellicott City, Maryland ..................... 12.23 1.14
Geneva, New York ............................ 9.60 1.20
Lind, Washington ............................. 11.12 1.70
Mandan, North Dakota..................... 7.13 2.84
Molly Caren, Ohio............................ 11.72 2.19
Nunn, Colorado ................................ 10.43 2.89
Prairie View, Texas ........................... 21.17 1.79
Rogers Farm, Nebraska .................... 11.25 1.84
Tidewater, North Carolina ............... 16.29 .72
Torrington, Wyoming ....................... 9.96 2.40
Wabeno, Wisconsin .......................... 6.14 2.10
Watkinsville, Georgia ....................... 17.20 2.14
Mean Annual Soil Temperature (MAST) and Mean Annual Air
Temperature (MAAT)
110 Soil Taxonomy
more readings, a special thermometer or a thermocouple can be
buried. If the temperature of a soil is measured at a depth
below the influence of the daily cycle of fluctuations, such as a
depth of 50 cm, four readings equally spaced throughout
the year give a very close approximation of the mean annual
temperature. For example, the average of readings taken
at a depth of 50 cm at Vauxhall, Alberta, on January 1,
April 1, July 1, and October 1, 1962, differs from the
average of two readings each day of the year by only 0.3 o
C.
Greater precision can be achieved by increasing either the
number or the depth of the readings. The mean annual soil
temperature computed for any one year will be close to the longterm
mean annual temperature, that is, the normal temperature.
At Ames, Iowa, for example, the standard deviation of the yearly
mean for a 13-year record at a depth of 50 cm is only 0.6 o
C.
Seasonal temperatures bear an almost linear relation to
depth within the limits of depth that usually concern soil
scientists. By selecting a suitable depth and measuring the
temperature on the 15th of June, July, and August, we can
derive the average soil temperature for the 3-month summer
period. The margin of error will be small only if measurements are
made at a depth below the daily temperature fluctuations, that is,
Diagram 24.—Mean monthly soil temperatures measured at 50 cm below the mineral soil surface during 1992 near Delta Junction,
Alaska, United States.
Diagram 25.—Relationship of mean annual soil temperature
(MAST) and vegetative cover for the Copper River series.
Sites are in close proximity on the same landform. The
spruce site is in a late seral stage. The aspen site is in an
early seral stage because of wildfire.
Horizons and Characteristics Diagnostic for the Higher Categories 111
at a depth of 50 cm or more. Measurements made at a depth of 50
cm give the average temperature in the upper m of the soil. A
test of this method at Vauxhall, Alberta, shows that the average
of three measurements taken at a depth of 50 cm on June 15, July
15, and August 15, 1962, is within 0.6 o
C of the mean summer
temperature computed from daily readings.
Greater precision can be achieved mainly by increasing the
number of readings. Readings of soil temperature at depths as
shallow as 50 cm should be deferred for at least 48 hours after a
heavy rain.
Classes of Soil Temperature Regimes
Following is a description of the soil temperature regimes
used in defining classes at various categoric levels in this
taxonomy.
Cryic (Gr. kryos, coldness; meaning very cold soils).—Soils
in this temperature regime have a mean annual temperature lower
than 8 o
C but do not have permafrost.
1. In mineral soils the mean summer soil temperature (June,
July, and August in the Northern Hemisphere and December,
January, and February in the Southern Hemisphere) either at a
depth of 50 cm from the soil surface or at a densic, lithic, or
paralithic contact, whichever is shallower, is as follows:
a. If the soil is not saturated with water during some part of
the summer and
(1) If there is no O horizon: lower than 15 o
C; or
(2) If there is an O horizon: lower than 8 o
C; or
b. If the soil is saturated with water during some part of the
summer and
(1) If there is no O horizon: lower than 13 o
C; or
(2) If there is an O horizon or a histic epipedon: lower
than 6 o
C.
2. In organic soils the mean annual soil temperature is lower
than 6 o
C.
Cryic soils that have an aquic moisture regime commonly are
churned by frost.
Isofrigid soils could also have a cryic temperature regime. A
few with organic materials in the upper part are exceptions.
The concepts of the soil temperature regimes described
Diagram 26.—Mean monthly and mean annual soil temperatures in a soil in a wet bog and in a sandy soil at Flahult, Sweden.
112 Soil Taxonomy
below are used in defining classes of soils in the low
categories.
Frigid.—A soil with a frigid temperature regime is
warmer in summer than a soil with a cryic regime, but its
mean annual temperature is lower than 8 o
C and the difference
between mean summer (June, July, and August) and mean
winter (December, January, and February) soil temperatures is
more than 6 o
C either at a depth of 50 cm from the soil surface
or at a densic, lithic, or paralithic contact, whichever is
shallower.
Mesic.—The mean annual soil temperature is 8 o
C or higher
but lower than 15 o
C, and the difference between mean summer
and mean winter soil temperatures is more than 6 o
C either at a
depth of 50 cm from the soil surface or at a densic, lithic, or
paralithic contact, whichever is shallower.
Thermic.—The mean annual soil temperature is 15 o
C or
higher but lower than 22 o
C, and the difference between mean
summer and mean winter soil temperatures is more than 6 o
C
either at a depth of 50 cm from the soil surface or at a densic,
lithic, or paralithic contact, whichever is shallower.
Hyperthermic.—The mean annual soil temperature is
22 o
C or higher, and the difference between mean summer and
mean winter soil temperatures is more than 6 o
C either at a
depth of 50 cm from the soil surface or at a densic, lithic, or
paralithic contact, whichever is shallower.
If the name of a soil temperature regime has the prefix iso,
the mean summer and mean winter soil temperatures differ by
less than 6 o
C at a depth of 50 cm or at a densic, lithic, or
paralithic contact, whichever is shallower.
Isofrigid.—The mean annual soil temperature is lower than
8 o
C.
Isomesic.—The mean annual soil temperature is 8 o
C or
higher but lower than 15 o
C.
Isothermic.—The mean annual soil temperature is 15 o
C or
higher but lower than 22 o
C.
Isohyperthermic.—The mean annual soil temperature is
22 o
C or higher.
Sulfidic Materials
Sulfidic materials contain oxidizable sulfur compounds. They
are mineral or organic soil materials that have a pH value of more
than 3.5 and that, if incubated as a layer 1 cm thick under moist
aerobic conditions (field capacity) at room temperature, show a
drop in pH of 0.5 or more units to a pH value of 4.0 or less (1:1
by weight in water or in a minimum of water to permit
measurement) within 8 weeks.
Sulfidic materials accumulate as a soil or sediment that is
permanently saturated, generally with brackish water. The
sulfates in the water are biologically reduced to sulfides as the
materials accumulate. Sulfidic materials most commonly
accumulate in coastal marshes near the mouth of rivers that
carry noncalcareous sediments, but they may occur in
freshwater marshes if there is sulfur in the water. Upland sulfidic
materials may have accumulated in a similar manner
in the geologic past.
If a soil containing sulfidic materials is drained or if sulfidic
materials are otherwise exposed to aerobic conditions, the
sulfides oxidize and form sulfuric acid. The pH value, which
normally is near neutrality before drainage or exposure, may
drop below 3. The acid may induce the formation of iron and
aluminum sulfates. The iron sulfate, jarosite, may segregate,
forming the yellow redoximorphic concentrations that
commonly characterize a sulfuric horizon. The transition from
sulfidic materials to a sulfuric horizon normally requires very
few years and may occur within a few weeks. A sample of
sulfidic materials, if air-dried slowly in shade for about 2
months with occasional remoistening, becomes extremely acid.
Sulfuric Horizon
Brackish water sediments frequently contain pyrite (rarely
marcasite), which is an iron sulfide. Pyrite forms from the
microbial decomposition of organic matter. Sulfur released
from the organic matter combines with the iron to crystallize
FeS. Characteristically, the pyrite crystals occur as nests or
framboids composed of bipyramidal crystals of pyrite. In an
oxidizing environment, pyrite oxidizes and the products of
oxidation are jarosite and sulfuric acid. The jarosite may
undergo slow hydrolysis, leading to further production of
sulfuric acid. Iron is precipitated as a reddish ochre precipitate,
commonly ferrihydrite, which later may crystallize as
maghemite, goethite, and even hematite. If free aluminum is
present, alunite may crystallize in addition to jarosite. The
jarosite has a straw-yellow color and frequently lines pores in
the soil. Jarosite concentrations are among the indicators of a
sulfuric horizon.
In some soils, the hydrolysis of jarosite is rapid and the
yellow redoximorphic concentrations may not be evident, even
though the soils are extremely acid (pH less than 3.5) or the
soil solution is high in soluble sulfur. The low pH and high
amount of soluble sulfur are indicators of a sulfuric horizon. A
soil can develop low pH values, however, from highly acidic
materials from other sources. Therefore, low pH and sulfuric
materials in the underlying layers also are indicators of a
sulfuric horizon. A quick test of sulfidic materials is a rapid
fall in pH on drying or after treatment with an oxidizing agent,
such as hydrogen peroxide.
A sulfuric horizon forms as a result of drainage (most
commonly artificial drainage) and oxidation of sulfide-rich or
organic soil materials. It can form in areas where sulfidic
materials have been exposed as a result of surface mining,
dredging, or other earth-moving operations. A sulfuric horizon
is detrimental to most plants.
Required Characteristics
The sulfuric (L. sulfur) horizon is 15 cm or more thick and is
composed of either mineral or organic soil material that has a pH
Horizons and Characteristics Diagnostic for the Higher Categories 113
value of 3.5 or less (1:1 by weight in water or in a minimum of
water to permit measurement) and shows evidence that the low
pH value is caused by sulfuric acid. The evidence is one or more
of the following:
1. Jarosite concentrations; or
2. Directly underlying sulfidic materials (defined above);
or
3. 0.05 percent or more water-soluble sulfate.
Literature Cited
Brewer, R. 1976. Fabric and Mineral Analysis of Soils.
Second edition. John Wiley and Sons, Inc. New York, New
York.
Chang, Jen Hu. 1958a. Ground Temperature. I. Blue Hill
Meteorol. Observ. Harvard Univ.
Chang, Jen Hu. 1958b. Ground Temperature. II. Blue Hill
Meteorol. Observ. Harvard Univ.
Childs, C.W. 1981. Field Test for Ferrous Iron and FerricOrganic
Complexes (on Exchange Sites or in Water-Soluble
Forms) in Soils. Austr. J. of Soil Res. 19: 175-180.
Grossman, R.B., and F.J. Carlisle. 1969. Fragipan Soils of the
Eastern United States. Advan. Agron. 21: 237-279.
Institut National pour l’etude Agronomique du Congo Belge
(I.N.E.A.C.). 1953. Bulletin Climatologique annuel du Congo
Belge et du Duanda-Urundi. Annee. Bur. Climatol. 7.
Jensen, M.E., G.H. Simonson, and R.E. Keane. 1989. Soil
Temperature and Moisture Regime Relationships Within Some
Rangelands of the Great Basin. Soil Sci. 147: 134-139.
Mather, J.R., ed. 1964. Average Climatic Water Balance Data
of the Continents, Parts V-VII. C.W. Thornthwaite Assoc. Lab.
Climatol.Publ.,Vol.XVII,No.1-3.
Mather, J.R., ed. 1965. Average Climatic Water Balance Data
of the Continents, Part VIII. C.W. Thornthwaite Assoc. Lab.
Climatol.Publ.,Vol.XVIII,No.2.
Molga, M. 1958. Agricultural Meteorology. Part II. Outline
of Agrometeorological Problems. Translated (from Polish)
reprint of Part II, pp. 218-517, by Centralny Instytut
Informacji. Naukowo-Technicznej i Ekonomicznej, Warsaw.
1962.
Moore, J.P., and C.L. Ping. 1989. Classification of Permafrost
Soils.SoilSurv.Horiz.30:98-104.
Pons, L.J., and I.S. Zonneveld. 1965. Soil Ripening and Soil
Classification. Initial Soil Formation in Alluvial Deposits and
a Classification of the Resulting Soils. Int. Inst. Land Reclam.
and Impr. Pub. 13. Wageningen, The Netherlands.
Rode, A.A. 1965. Theory of Soil Moisture. Vol. 1. Moisture
Properties of Soils and Movement of Soil Moisture. pp. 159-
202. (Translated from Russian, 1969). Israel Program Sci.
Transl., Jerusalem.
Shur, Y.L., G.J. Michaelson, and C.L. Ping. 1993. International
Correlation Meeting on Permafrost-Affected Soils. Suppl. Data
to the Guidebook—Alaska Portion.
Smith, G.D., D.F. Newhall, and L.H. Robbins. 1964. SoilTemperature
Regimes, Their Characteristics and Predictability.
U.S. Dep. Agric., Soil Conserv. Serv, SCS-TP-144.
United States Department of Agriculture, Natural Resources
Conservation Service. 1998. Keys to Soil Taxonomy. Eighth
edition. Soil Surv. Staff.
United States Department of Agriculture, Soil Conservation
Service. 1975. Soil Taxonomy: A Basic System of Soil
Classification for Making and Interpreting Soil Surveys. Soil
Surv. Staff. U.S. Dep. Agric. Handb. 436.
United States Department of Agriculture, Soil Conservation
Service. 1993. Soil Survey Manual. Soil Surv. Div. Staff. U.S.
Dep. Agric. Handb. 18.
115
The fundamental purposes of a soil survey are to show
the geographic distribution of soils and to make
predictions about the soils (USDA, SCS, 1951 and 1993). To
this end, a soil survey includes soil maps, map unit
descriptions, soil series descriptions, taxonomic classifications,
and interpretations for the use and management of the soils.
Soil surveys are made at several intensities and for many
uses. The procedures, standards, and uses are described in the
most recent revision of the Soil Survey Manual (USDA, SCS,
1993) and the most recent version of the National Soil Survey
Handbook (USDA, NRCS, 1997). The applications of soil survey
are numerous. They include interpretations for the growth of
plants, such as crops, forage species, trees, and ornamental
shrubs. They also include interpretations for urban, rural, and
recreational development and for conservation and wildlife
habitat planning.
Soil mapping and classification have evolved, and the
conceptual framework for mapping and classifying soils has
changed and will continue to change. Over the years soil
science literature has documented numerous concepts and
approaches to mapping, classifying, and interpreting soils at
various scales. The purpose of this chapter is not to present the
numerous concepts and approaches but to outline the
application of widely used and accepted soil-landscape models
and taxonomic models for mapping and labeling soil
geographic order in soil surveys at scales of 1:12,000 to
1:100,000 and in soil surveys at scales smaller than 1:100,000.
Mapping and Labeling Soil Geographic Order at
Large (1:12,000 to 1:31,680) and Intermediate
(1:31,680 to 1:100,000) Scales
Mapping Soil Geographic Order
A landscape is a portion of the land surface that the eye can
comprehend in a single view and is a collection of landforms
(Ruhe, 1969). Understanding landscapes and landforms and
their influence on soil distribution is critical in observing and
mapping soil geographic order (Peterson, 1981; Ruhe, 1969).
The tasks of a soil scientist who sets out to map soils and
produce a soil survey are to perceive a meaningful soil
geographic pattern at the landscape, landform, and landform
component levels and to record that pattern in a form that can
be retained and conveyed to others. The most common scales
for a large-scale soil map range from 1:12,000 to 1:31,680
(USDA, SCS, 1993). With intensive field investigation of areas
mapped within this scale range, soil geographic variation can
be readily observed and recorded cartographically at the
landscape, landform, and landform component levels. The
minimum-size delineation is commonly between 0.6 and 4 ha
(USDA,SCS,1993).
Intermediate-scale soil maps range from 1:31,680 to
1:100,000 and are commonly associated with lower intensity
field soil surveys (USDA, SCS, 1993). At this map scale and
with the lower intensity of field investigation, soil geographic
variation can be observed and recorded cartographically at the
multiple landscape, landscape, or landform level. The
minimum-size delineation for intermediate soil maps is
commonly between 4 and 250 ha (USDA, SCS, 1993).
In mapping soils at any scale, it is necessary to assume that
there is a pattern of order in the spatial distribution of soil
characteristics. The soil genesis model, which defines soil as a
function of parent material, climate, living organisms, relief,
and time, provides a basis for predicting order. A soil surveyor
quickly learns that the geographic distribution of soils is
related to the five soil-forming factors. A soil surveyor observes
and maps a geographic pattern of soils by grouping soils with
similar genesis and by separating soils where there is a change
in one or more of the soil-forming factors. Hudson (1990 and
1992) outlined the application of the catena concept (Milne,
1936) and the soil factor equation (Jenny, 1941) to soil survey as
a general model of perceiving and mapping soil geographic
order. Hudson (1992) has also summarized the soil-landscape
paradigm that has guided field soil surveys in the United States
for almost a century.
The Soil-Landscape Paradigm and Soil Survey
Soils are landscapes as well as profiles (USDA, SCS, 1951,
pp. 5-8; USDA, SCS, 1993, pp. 9-11). In soil survey, a soillandscape
unit can be thought of as a landscape unit
(landscape, landform, or landform component) further modified
by one or more of the soil-forming factors. Within a soillandscape
unit, the five factors of soil formation interact in a
distinctive manner. As a result, areas of a soil-landscape unit
have a relatively homogeneous soil pattern. A soil surveyor
perceives soil patterns by first conceptually dividing the
landscape into soil-landscape units. The boundaries between
dissimilar soil-landscape units are placed where one or more of
the soil-forming factors change within a short lateral distance.
The more rapid the change between one or more of the soilCHAPTER
5
Application of Soil Taxonomy to Soil Surveys
116 Soil Taxonomy
forming factors, the more abrupt the boundary between the
soil-landscape units and the easier it is for one to locate the
boundary. The slower the change between one or more of the
soil-forming factors, the more gradual the boundary between
the soil-landscape units and the more difficult it is for one to
locate the boundary. Generally, the closer the similarities
between two landscape units, the more gradual the change
between the landscape units and the more similar their
associated soils tend to be. Conversely, very dissimilar
landscape units tend to have abrupt boundaries between them
and have very dissimilar soils.
Identifying soil-landscape units provides the basis for
recognizing soils and then designing soil map units, which are
the basic units for identifying soil geographic order in a soil
survey. Soil-landscape units can be combined to form map
units that encompass broader ranges of soils, or subdividing
the soil-landscape units can identify the soils and soil
distribution within a map unit in greater detail. The degree to
which soil-landscape units are combined or subdivided to form
soil map units is primarily a function of the complexity of the
soil-landscape units, the detail required for the intended use of
the soil survey, and the ability of the soil scientist to
consistently identify the soils and map units through
application of the available knowledge and tools and within the
constraints of cost and time.
Labeling Soil Geographic Order With Soil Taxonomy
A soil delineation (soil map unit delineation) is an
individual polygon identified on a soil map by a map unit
symbol and/or name that defines a three-dimensional soil body
of a specified area, shape, and location on the landscape (Soil
Science Society of America, 1997). A map unit is an aggregate
of all soil delineations in a soil survey area that have a defined
set of similar soil characteristics (Van Wambeke and Forbes,
1986).
Once soil-landscape units and soil map units have been
delineated, some means of labeling and representing the kinds
of soil that occur in the map units is needed. The classification
system described in Soil Taxonomy (USDA, SCS, 1975) has
been used for many years in identifying and labeling soils that
occur within soil-landscape units and soil map units. Following
is a description of the application of the taxonomic system to
soil survey.
A class is a group of individuals or other units similar in
selected properties and distinguished from all other classes of
the same population by differences in these properties. Taxon
(pl. taxa) is a name used in classifications for a single class. It
may be broadly or narrowly defined according to the category.
A soil order is a taxon, as is a soil series, a family, or a great
group (Smith, 1963). The taxa of this soil classification are
conceptual and are defined as precisely as our present
knowledge permits. They give us common standards for soil
correlation, which includes the mapping, naming, and
interpretation of soils. In practice, soil scientists map soillandscape
units. Properties of these soil-landscape units
correspond to the concepts of the taxa. Relating the soil bodies
(soil-landscape units or soil delineations) represented on maps
to taxonomic classes at some level in a classification system is
accomplished through soil correlation (Simonson, 1963).
In large- and intermediate-scale soil surveys, if the concept of
a named series or other taxon corresponds to the properties of
the soil expected in a soil-landscape unit or soil map unit, we
normally use the name of that series or taxon to help identify the
soil properties of the delineation. If there is no named series or
taxon available and we believe that such a series or other taxon
would be useful, we define and establish a new series or other
taxon. Also, for the practical purposes of a soil survey, another
classification is superimposed on the series or taxa to identify
significant differences in slope, erosion, stoniness, or other
characteristics. The assignment of taxonomic names, such as the
name of a soil series, to label a map unit means that if we examine
the soil-landscape unit or soil map unit, we expect most
locations within the delineation to meet the criteria of the taxon
or taxa (Holmgren, 1988). The designing, naming, and describing
of soil map units, which are covered elsewhere (USDA, SCS,
1993; USDA, NRCS, 1997; Van Wambeke and Forbes, 1986), are
all critical elements in the understanding of soil geographic
patterns.
Soil Geographic Order and Soil Taxonomy in Soil Survey
It is commonly acknowledged that there is a disparity
between the entity that soil surveyors map and the entity that
they classify. Soil surveyors map soil bodies (soil-landscape
units and soil map units). Soil taxonomy, however, effectively
utilizes properties from samples taken within the soillandscape
units and soil map units to establish taxon
boundaries and classify soils (Holmgren, 1988). Time and the
fiscal constraints of a soil survey necessitate minimizing the
number of samples taken. In the past, this disparity between
sampling units and mapping units and the need for minimizing
the sampling effort was rationalized with the pedon and
polypedon. The pedon served as the sampling unit and was
defined as a three-dimensional soil volume with an area of 1 to
10 m2
and a depth that includes the entire solum (USDA, SCS,
1975). The polypedon was defined as a set of contiguous
pedons (USDA, SCS, 1975). It was intended to be used to
establish series level taxa and the map units delineated in the
soil survey.
Applying the pedon and polypedon concepts to mapping
and classification has been the subject of debate and a source of
misunderstanding in soil survey for decades (Hudson, 1990 and
1992; Holmgren, 1988). Some notable problems are that in
reality soil profiles rather than pedons (i.e., three-dimensional
volumes) are really sampled and classified (Holmgren, 1988),
that soil property variation prohibits the selection of one profile
or a few profiles to represent variation within delineated soil
bodies (Hudson, 1990), and that soil-landscape units and soil
map units are composed of more than one polypedon (as
Application of Soil Taxomony to Soil Surveys 117
defined by USDA, SCS, 1975) and contain soils with properties
outside the ranges of established taxa. Application of the soillandscape
paradigm (Hudson, 1990 and 1992), however, can
identify soil-landscape boundaries and soil map unit boundaries,
and then, through careful selection of soil profiles that best
represent soil conditions within soil-landscape and soil map unit
delineations, the soil map units can be labeled and described
and useful soil surveys can be produced.
Large- and intermediate-scale soil surveys can be used to
provide general information about soil properties within each
soil-landscape unit and soil map unit. These soil surveys,
however, cannot be used in predicting exact soil properties at
any particular location with statistical confidence, and soil
properties may exceed the ranges defined for the taxa used to
represent soil-landscape units and soil map units.
Recognizing Established Series and Establishing
New Series in a Soil Survey Area at Scales of
1:12,000 to 1:100,000
The standards for establishing series, recognizing
established series, and naming the map units within a soil
survey area have changed in the past and can be expected to
change in the future. The current standards are presented
elsewhere (USDA, SCS, 1993; USDA, NRCS, 1997; Van
Wambeke and Forbes, 1986), and the results of the various
international classification committees are readily available.
The factors that should be considered when recognizing
established soil series, establishing new soil series, and naming
the map units within a soil survey area are described in the
following paragraphs.
The soil series is the basic taxonomic class in soil survey
areas mapped at large and intermediate scales. As a taxonomic
class, a series is a group of soils that have horizons similar in
arrangement and in differentiating characteristics (USDA, SCS,
1993). When recognizing established series and establishing
new series in the field, we must consider the scale and the
degree of accuracy and precision at which we observe and plot
boundaries between soil-landscape units and soil map units. We
must also consider the ability of soil scientists to consistently
observe, determine, and record soil similarities and differences in
the field; the purpose of the soil survey; the nature of the
variability of the soils within a delineation; the importance of the
variations to planning; and the probable uses of the soils. An
example of the application of series differentiae is given in
chapter 21 of this publication.
The representation of soil distribution on a map is imperfect
to varying degrees. In the field, at large and intermediate
scales, soil scientists observe the boundaries between soillandscape
units and soil map units and then record the
boundaries on an aerial photo or an appropriate map base.
Inevitably, there are errors in the observation and placement of
these lines, in the sampling and identification of soils at the
boundaries, and in the sampling and identification of soils within
the boundaries of soil-landscape units and soil map units.
Because series have narrow ranges in their properties, most
soils within a soil-landscape unit or soil map unit can be sampled
and identified with reasonable accuracy, even though the
locations of some of the boundaries may be obscure or difficult
to place. There commonly are areas in which a soil in a
delineation does not fit an established series. In this case the
range in characteristics of the existing series could be
expanded, a new series could be established, or the soil could
be handled as a taxadjunct (USDA, SCS, 1993; Van Wambeke
and Forbes, 1986). There are also cases in which soils within a
soil-landscape unit or soil map unit occur as areas too small or
too intermingled to be delineated at the selected scale or in
which differences between soils are subtle and cannot be
consistently observed and mapped in the field. These cases can
be handled within the definitions of kinds of soil map units,
which include consociations, complexes, associations, and
undifferentiated groups, and in the map unit descriptions
(USDA, SCS, 1993; Van Wambeke and Forbes, 1986).
Labeling Soil Maps at Scales Smaller Than
1:100,000
As map scales become smaller, the degree of detail and
precision of the soil map decreases. This decrease is reflected
in the naming of map units and in the map unit descriptions.
Small-scale or general soil maps of individual survey areas in
published soil surveys in the United States commonly have
scales that range from about 1:100,000 to 1:250,000. The map
units delineated on these maps have been named as
associations of series. These generalized maps usually are
made by combining the delineations of detailed soil survey
maps to form broader map units (USDA, SCS, 1993). These
broader map units group similar map unit delineations and are
commonly named for the two or three most dominant soil
series or taxa. The map unit descriptions for these smaller scale
maps should reflect the greater degree of map generalization.
State and regional soil maps commonly are produced at
scales of 1:250,000 to 1:1,000,000. State and regional general
soil maps can be produced by further generalizing county soil
maps. These state and regional maps are typically at scales of
about 1:500,000, and the map units delineated on these maps
are associations of the dominant soil series or taxa on the
county general soil maps.
Schematic soil maps commonly are at a scale of 1:1,000,000
or smaller (USDA, SCS, 1993). These maps can be compiled from
information on more detailed soil maps, county and state general
soil maps, and regional soil maps. Other sources of soil
geographic information can also be used where little or no soil
mapping information is available. At these small scales, map
units commonly are associations or consociations of taxa at the
higher categories, such as Oxisols, Udalfs, and Epiaquepts.
118
Literature Cited
Holmgren, G.G.S. 1988. The Point Representation of Soil. Soil
Sci.Soc.Amer.J.52:712-716.
Hudson, B.D. 1990. Concepts of Soil Mapping and
Interpretation. Soil Surv. Horiz. 31: 63-72.
Hudson, B.D. 1992. The Soil Survey as Paradigm-Based
Science. Soil Sci. Soc. Amer. J. 56: 836-841.
Jenny, H. 1941. Factors of Soil Formation. McGraw-Hill, New
York.
Milne, G. 1936. A Provisional Map of East Africa. East
African Agric. Res. Stn. Amani Memoirs.
Peterson, F.F. 1981. Landforms of the Basin and Range
Province Defined for Soil Survey. Nevada Agric. Exp. Stn.
Tech. Bull. 28.
Ruhe, R.V. 1969. Quaternary Landscapes in Iowa. Iowa State
Univ. Press.
Simonson, R.W. 1963. Soil Correlation and the New
Classification System. Soil Sci. 96: 23-30.
Smith, G.D. 1963. Objectives and Basic Assumptions of the
New Classification System. Soil Sci. 96: 6-16.
Soil Science Society of America. 1997. Glossary of
Soil Science Terms.
United States Department of Agriculture, Natural
Resources Conservation Service. 1997. National Soil
Survey Handbook. Soil Surv. Staff.
United States Department of Agriculture, Soil
Conservation Service. 1951. Soil Survey Manual. Soil
Surv. Staff. U.S. Dep. Agric. Handb. 18.
United States Department of Agriculture, Soil
Conservation Service. 1975. Soil Taxonomy: A Basic
System of Soil Classification for Making and Interpreting
Soil Surveys. Soil Surv. Staff. U.S. Dep. Agric. Handb.
436.
United States Department of Agriculture, Soil
Conservation Service. 1993. Soil Survey Manual. Soil
Surv. Div. Staff. U.S. Dep. Agric. Handb. 18.
Van Wambeke, A., and T.R. Forbes, eds. 1986.
Guidelines for Using “Soil Taxonomy” in the Names
of Soil Map Units. Soil Manage. Support Serv. Tech.
Monogr. 10. U.S. Dep. Agric., Soil Conserv. Serv., and
Cornell Univ., Agron. Dep.
119
Acategory of soil taxonomy is a set of classes that is
defined approximately at the same level of
generalization or abstraction and that includes all soils. There
are six categories in soil taxonomy. In order of decreasing rank
and increasing number of differentiae and classes, the
categories are order, suborder, great group, subgroup, family,
and series.
In one sense, soil taxonomy is a sorting process. In the
highest category, one sorts all kinds of soil into a small number
of classes. The number of classes is small enough for one to
comprehend and remember them and to understand the
distinctions among them. The sorting must make distinctions
that are meaningful for our purposes. When all soils are sorted
into a very few classes, such as the 12 orders, each order is very
heterogeneous with respect to properties that are not considered
in the sorting and that are not accessory to the properties that
are considered. For some purposes, however, the order level
may provide sufficient information. As one continues to
classify a soil at lower and lower levels of soil taxonomy, more
information is conveyed about the soil. This method of
conveying information is one of the advantages of a
multicategoric classification system.
Reducing the heterogeneity requires another sorting in the
next lower category, the suborder. Again, the sorting must be
meaningful, but the sorting in one order may have little
meaning in another order. In soil taxonomy there are 64
suborders, a number larger than can be remembered
conveniently along with all the properties of the suborders. If
we focus on the suborders of a single order, however, we have,
at the most, seven suborders to understand and remember.
Each of the suborders in an order has the properties common to
the order plus the properties used for sorting into that suborder.
In each of the 64 suborders, there is still great heterogeneity, so
we must sort again to obtain, at the next lower level, a set of
meaningful great groups. There are more than 300 great
groups, more than one can remember. One need focus,
however, on only one suborder at a time.
The sorting process continues in the remaining categories
down to the soil series. The soils in any one series are nearly
homogeneous in that their range of properties is small and can
be readily understood. Collectively, the thousands of soil series
are far beyond our powers of comprehension, but they can be
sorted category by category, and one seldom needs to
comprehend more than a few of them at any one time.
Orders
There are 12 orders. They are differentiated by the presence
or absence of diagnostic horizons or features that reflect soilforming
processes. If the soils in a given taxon are thought to
have had significantly different genesis, the intent has been to
sort out the differences in the next lower category.
Soil properties are the consequences of a variety of processes
acting on parent materials over time. Distinctions among
orders aid in understanding soils and remembering them on a
grand scale. The processes that occur in soils must be orderly
in relation to the soil-forming factors, which are climate and
living organisms acting on parent materials over time, as
conditioned by relief. These factors, in turn, have geographic
order. The features of the soil-forming processes are clearly
visible, but the details of the processes can only be inferred.
The distinctions made in classifying soils cannot be based on
the processes themselves because new knowledge is certain to
change our ideas about the processes, but the features of the
processes are facts that can be observed and measured and used
as a basis for distinctions. Thus, the distinctions between
orders are based on the markers left by processes that
experience indicates are dominant forces in shaping the
character of the soil. In this framework, the lack of features or
the zero degree also is a logical criterion.
The 12 orders and the major properties that differentiate
them illustrate the nature of this category. Complete definitions
are given later in this publication.
These orders are not the only possible orders in the
taxonomy. In fact, two new orders, Andisols and Gelisols, have
been established since the first edition of Soil Taxonomy. The
hierarchy is flexible, and other ad hoc orders may be defined to
emphasize properties not considered in the 12 orders. The
method of defining ad hoc orders is described in connection
with nomenclature later in this publication.
Alfisols
The soils in this order have markers of processes that
translocate silicate clays without excessive depletion of bases
and without dominance of the processes that lead to the
formation of a mollic epipedon. The unique properties of
Alfisols are a combination of an ochric or umbric epipedon, an
argillic or natric horizon, a medium to high supply of bases in
the soils, and water available to mesophytic plants for more
CHAPTER 6
The Categories of Soil Taxonomy
120 Soil Taxonomy
than half the year or more than 3 consecutive months during a
warm season. Because these soils have water and bases, they
are, as a whole, intensively used.
Andisols
The unique property of Andisols is a dominance of shortrange-order
minerals or Al-humus complexes that result from
weathering and mineral transformation with a minimum of
translocation. The characteristics common to most Andisols
include a high phosphorus retention, available water capacity,
and cation-exchange capacity. Most Andisols formed in
volcanic ejecta or volcaniclastic materials. Andisols can form
in almost any environment, however, as long as suitable
temperature and adequate moisture are available to permit
weathering and the formation of short-range-order minerals.
The soils can have any diagnostic epipedon or subsurface
horizon as long as the unique property of Andisols is in 60
percent of the upper 60 cm of the soils, disregarding O
horizons that have 25 percent or more organic carbon.
Prior to 1989, the soils now classified as Andisols were
included with Inceptisols, mainly as Andepts and Andaquepts,
which were discontinued with the acceptance of Andisols as an
order in soil taxonomy.
Aridisols
The unique properties common to Aridisols are a
combination of a lack of water available to mesophytic plants
for very extended periods, one or more pedogenic horizons, a
surface horizon or horizons not significantly darkened by
humus, and absence of deep, wide cracks (see Vertisols) and
andic soil properties (see Andisols). Aridisols have no
available water during most of the time that the soils are warm
enough for plant growth (warmer than 5 o
C [41 o
F]), and they
never have water continuously available for as long as 90 days
when the soil temperature is above 8 o
C (47 o
F).
Aridisols are primarily soils of arid areas. They are in areas
that preclude much entry of water into the soils at present,
either under extremely scanty rainfall or under slight rainfall
that for one reason or another does not enter the soils. The
vegetation in many areas consists of scattered ephemeral
grasses and forbs, cacti, and xerophytic shrubs. Some Aridisols
furnish limited grazing. If irrigated, many of them are suitable
for a wide variety of crops.
Entisols
The unique properties common to Entisols are dominance of
mineral soil materials and absence of distinct pedogenic
horizons. The absence of features of any major set of soilforming
processes is itself an important distinction. There can
be no accessory characteristics. Entisols are soils in the sense
that they support plants, but they may be in any climate and
under any vegetation. The absence of pedogenic horizons may
be the result of an inert parent material, such as quartz sand, in
which horizons do not readily form; slowly soluble, hard rock,
such as limestone, which leaves little residue; insufficient time
for horizons to form, as in recent deposits of ash or alluvium;
occurrence on slopes where the rate of erosion exceeds the rate
of formation of pedogenic horizons; recent mixing of horizons
by animals or by plowing to a depth of 1 or 2 m; or the spoils
from deep excavations.
Gelisols
The unique property of Gelisols is the presence of
permafrost and soil features and properties associated with
freezing and thawing. These features include irregular or
broken horizons and incorporation of organic materials in the
lower horizons, especially along the top of the permafrost table.
Freezing and thawing produce granular, platy, and vesicular
structures in surface and subsurface horizons. The increases in
soil volume on freezing are considered a major soil-forming
process in Gelisols. These soils are confined to the higher
latitudes or high elevations, but they make up about 13 percent
of the soils in the world, second only to Aridisols.
Histosols
The unique properties of Histosols are a very high content of
organic matter in the upper 80 cm (32 in) of the soils and no
permafrost. The amount of organic matter is at least 20 to 30
percent in more than half of this thickness, or the horizon that
is rich in organic matter rests on rock or rock rubble. Most
Histosols are peats or mucks, which consist of more or less
decomposed plant remains that accumulated in water, but some
formed from forest litter or moss, or both, and are freely
drained. The freely drained Histosols are described in chapter
14.
Inceptisols
Inceptisols have a wide range in characteristics and occur in
a wide variety of climates. They can form in almost any
environment, except for an arid environment, and the
comparable differences in vegetation are great. Inceptisols can
grade toward any other soil order and occur on a variety of
landforms. The unique properties of Inceptisols are a
combination of water available to plants for more than half the
year or more than 3 consecutive months during a warm season
and one or more pedogenic horizons of alteration or
concentration with little accumulation of translocated materials
other than carbonates or amorphous silica. In addition,
Inceptisols do not have one or more of the unique properties of
Mollisols, which are a thick, dark surface horizon and a high
calcium supply, or the unique property of Andisols, which is
the dominance of short-range-order minerals or Al-humus
complexes.
Mollisols
The unique properties of Mollisols are a combination of a
very dark brown to black surface horizon (mollic epipedon)
that makes up more than one-third of the combined thickness
The Categories of Soil Taxonomy 121
of the A and B horizons or that is more than 25 cm thick and
that has structure or is not hard or very hard when dry; a
dominance of calcium among the extractable cations in the A
and B horizons; a dominance of crystalline clay minerals of
moderate or high cation-exchange capacity; and less than 30
percent clay in some horizon above 50 cm if the soils have
deep, wide cracks (1 cm or more wide) above this depth at
some season.
Mollisols characteristically form under grass in climates
that have a moderate to pronounced seasonal moisture deficit.
Some Mollisols, however, formed under a forest ecosystem, and
a few formed in marshes or in marls in humid climates.
Mollisols are extensive soils on the steppes of Europe, Asia,
North America, and South America.
Oxisols
The unique properties of Oxisols are extreme weathering of
most minerals other than quartz to kaolin and free oxides, very
low activity of the clay fraction, and a loamy or clayey texture
(sandy loam or finer).
Oxisols characteristically occur in tropical or subtropical
regions, on land surfaces that have been stable for a long time.
Generally, the surfaces are early Pleistocene or much older, but
Oxisols can occur on relatively young surfaces when weathered
soil material is redeposited. Oxisols developed in a humid
climate. Because climates change, however, some are now in
an arid environment.
Spodosols
Spodosols have markers in at least an upper sequum of
dominant processes that translocate humus and aluminum, or
humus, aluminum, and iron, as amorphous materials. The
unique property of Spodosols is a B horizon consisting of an
accumulation of black or reddish amorphous materials that
have a high cation-exchange capacity. This horizon is the
spodic horizon. In most undisturbed soils, an albic horizon
overlies the B horizon. The spodic horizon has accessory
characteristics of coarse texture, high pH-dependent charge,
and few bases. Commonly, the cation-exchange capacity is
related to the amount of organic carbon rather than to the clay.
Ultisols
Ultisols, like Alfisols, have markers of clay translocation,
but they also have markers of intensive leaching that are absent
in Alfisols. The unique properties common to Ultisols are an
argillic horizon and a low supply of bases, particularly in the
lower horizons.
The cation-exchange capacity in Ultisols is mostly moderate
or low. The decrease in base saturation with increasing depth
reflects cycling of bases by plants or additions in fertilizers. In
soils that have not been cultivated, the highest base saturation
is normally in the few centimeters directly beneath the surface.
Like Alfisols, Ultisols have water, but they have few bases.
Without applications of fertilizer, they can be used for shifting
cultivation. Because they are commonly warm and moist,
however, they can be made highly productive if fertilizer is
applied.
Vertisols
These soils have markers of processes related to the failure
of soil materials along shear planes (slickensides). Because the
soil material moves, the diagnostic properties have many
accessory properties. Among them are a high bulk density
when the soils are dry, low or very low hydraulic conductivity
when the soils are moist, an appreciable rise and fall of the soil
surface as the soils become moist and then dry, and rapid
drying as a result of open cracks. The unique properties
common to Vertisols are a high content of clay, pronounced
changes in volume with changes in moisture, cracks that open
and close periodically, and evidence of soil movement in the
form of slickensides and of wedge-shaped structural aggregates
that are tilted at an angle from the horizontal. The
development of eluvial/illuvial horizons in some Vertisols
suggests that pedoturbation is not rapid enough to preclude
long-term translocation processes.
Suborders
Sixty-four suborders currently are recognized. The
differentiae for the suborders vary with the order but can be
illustrated by examples from two orders. The Entisol order has
five suborders that distinguish the major reasons for absence of
horizon differentiation. One suborder includes soils that have
aquic conditions. These are the soils in areas of marshy recent
alluvium and the soils of coastal marshes that are saturated
with water and have a blue or green hue close to the surface.
This suborder segregates the wet varieties. A second suborder
includes soils that are not wet and that consist of recent
alluvium, which generally is stratified. This suborder
segregates the very young soils that do not have horizons
because there is continuing deposition of new sediments. A
third suborder includes soils on recently eroded slopes. This
suborder segregates soils that are kept young by removal of soil
materials at a rate that is more rapid than that of horizon
differentiation. A fourth suborder includes sands that may
range from recent to old. If old, they either lack the building
blocks for pedogenic horizons or do not have enough moisture.
Although the reasons for absence of horizons in the sands vary,
the sands have many common physical properties, such as a
low capacity for moisture retention, high hydraulic
conductivity, and susceptibility to soil blowing. The sorting of
these differences is continued in the lower categories. The fifth
suborder of Entisols includes soils in which horizons have been
mixed by deep plowing or other human activities that have
destroyed the pedogenic horizons as such but not the fragments
of the horizons.
Alfisols has five suborders. As in Entisols, one suborder
includes wet soils in which the colors are dominantly gray. A
122 Soil Taxonomy
second suborder includes Alfisols that are cold and have a
short growing season. A third suborder includes soils that have
a udic moisture regime and rarely do not have water available
for plants. A fourth suborder has an ustic moisture regime and
has extended or frequent periods when the soils do not have
water that is available to mesophytic plants in some or all
horizons. The fifth suborder includes the Alfisols that have a
xeric moisture regime. These soils are cool and moist in winter,
but they are dry for extended periods in summer.
The differentiae used in defining the suborders of Alfisols
include important properties that influence genesis and that are
extremely important to plant growth. The differentiae in six of
the other orders closely parallel those of Alfisols. In the
remaining orders, differentiae were selected to reflect what
seemed to be the most important variables within the orders.
Great Groups
There are more than 300 great groups. At as high a
categoric level as possible, it is desirable to consider all the
horizons and their nature collectively as well as the
temperature and moisture regimes. The moisture and
temperature regimes are causes of properties, and they also are
properties of the whole soil rather than of specific horizons. At
the order and suborder levels, only a few of the most important
horizons could be considered because there are few taxa in
those categories. At the great group level, the assemblage of
horizons and the most significant properties of the whole soil
are considered. Although the definition of a great group may
involve only a few differentiae, the accessory properties are
many times that number.
Differentiae in the great group category segregate soils that
have the following properties in common:
Close similarities in kind, arrangement, and degree of
expression of horizons.—Exceptions are made for some thin
surface horizons that would be mixed by plowing or lost by
erosion and for horizons that indicate transitions to other great
groups. For example, an argillic horizon that underlies the
spodic horizon is permitted in the Spodosol order because that
combination is considered to represent a kind of transition
between Spodosols on the one hand and Alfisols and Ultisols
on the other. Emphasis is placed on the upper sequum in the
great group category because it is thought to reflect the current
processes and is more critical to plant growth than the deeper
horizons.
Similarities in base status.—If the base status varies widely
within a suborder, the range is narrowed at the great group
level.
The suborders of Alfisols were defined on the basis of
moisture regimes. In addition to the argillic horizon that is
common to all Alfisols, other kinds of horizons may occur. A
fragipan or duripan restricts root development and water
movement, which in turn affect current processes of soil
formation. These horizons are used as one basis for defining
great groups. The argillic horizon may have a fine texture and
may be abruptly separated from an overlying albic horizon.
This combination also affects root development and water
movement, inducing shallow perched ground water and
intermittent reducing conditions in the soils. The horizons may
be thick as a result of very long periods of development. They
may be undergoing destruction, and the soils may have
developed a glossic horizon. These features also are used as
differentiae for great groups.
In contrast to Alfisols, emphasis in the Entisols was placed
on soil moisture and temperature regimes when the great
groups were differentiated. Because the various suborders occur
in all parts of the world, they have extreme ranges in moisture
and temperature regimes, and those regimes affect pedogenesis
as well as use and management of the soils.
Subgroups
There are more than 2,400 subgroups. Through the
categories of order, suborder, and great group, emphasis has
been placed on features or processes that appear to dominate
the course or degree of soil development. In addition to these
dominant features, many soils have properties that, although
apparently subordinate, are still markers of important sets of
processes. Some of these appear to be features of processes that
are dominant in some other great group, suborder, or order. In
a particular soil, however, they only modify the traits of other
processes. For example, some soils have aquic conditions and
have, throughout their depth, gray colors with reddish or
brownish redox concentrations. Other soils have aquic
conditions only in their lower horizons, and in those horizons
the dominant colors may be shades of brown, red, or yellow
with some gray redox depletions. The effects of ground water
are apparent in both sets of soils, but they have less importance
in the latter set.
Other properties are features of processes that are not used
as criteria of any taxon above the subgroup level. For example,
a Mollisol at the foot of a slope, where there has been a slow
accumulation of materials washed from the higher parts of the
slope, may have a greatly overthickened mollic epipedon.
Thus, there are three kinds of subgroups:
Typic subgroups.—These are not necessarily the most
extensive subgroups, nor do they necessarily represent the
central concept of the great group. In some taxa typic
subgroups simply represent the soils that do not have the
characteristics defined for the other subgroups.
Intergrades or transitional forms to other orders,
suborders, or great groups.—The properties may be the result
of processes that cause one kind of soil to develop from or
toward another kind of soil or otherwise to have intermediate
properties between those of two or three great groups. The
properties used to define the intergrades may be:
1. Horizons in addition to those definitive of the great
group, including an argillic horizon that underlies a spodic
The Categories of Soil Taxonomy 123
horizon and a buried horizon, such as a thick layer of
organic materials that is buried by a thin mineral soil; or
2. Intermittent horizons, such as those described in the
section of chapter 1 that deals with the pedon; or
3. Properties of one or more other great groups that are
expressed in part of the soils but are subordinate to the
properties of the great group of which the subgroup is a
member. One example of different depths of saturation and
reduction was given earlier. Another example might be an
Alfisol that has an ochric epipedon a little too thin or a little
too light in color to be a mollic epipedon. This feature could
result from an invasion of grassland by forest or the reverse,
from the coexistence of both grass and forest, or from the
erosion caused by human activities.
Extragrades.—These subgroups have some properties that
are not representative of the great group but that do not
indicate transitions to any other known kind of soil. One
example of an overthickened mollic epipedon was given
earlier. Other examples are soils that are very shallow over
rock (Lithic) or soils that have high amounts of organic carbon
(Humic).
Families
In this category, the intent has been to group the soils within
a subgroup having similar physical and chemical properties
that affect their responses to management and manipulation for
use. In some cases soil properties are used in this category
without regard to their significance as indicators of soilforming
processes.
The following are defined primarily to provide groupings of
mineral soils with restricted ranges in:
1. Particle-size classes in horizons of major biologic
activity below plow depth;
2. Mineralogy classes in the same horizons that are
considered in naming particle-size classes;
3. Cation-exchange activity classes of certain particle-size
and mineralogy classes in the same horizons that are
considered in naming particle-size classes;
4. Calcareous and reaction classes in horizons directly
below plow depth;
5. Soil temperature classes;
6. Thickness of the soil penetrable by roots; and
7. Classes of coatings, cracks, and rupture resistance used
in defining some families to produce the needed
homogeneity.
These properties carry important interpretive information,
including aeration and the movement and retention of water,
both of which affect the growth of plants and engineering
uses. The differentiae are described in more detail in chapter
21.
Series
The series is the lowest category in this system. More
than 19,000 series have been recognized in the United States.
The differentiae used for series generally are the same as
those used for classes in other categories, but the range
permitted for one or more properties is narrower than the
range permitted in a family or in some other higher category.
For several properties, a series may have virtually the full
range that is permitted in a family, but for one or more
properties, the range is restricted. The purpose of the series
category, like that of the family, is mainly pragmatic, and the
taxa in the series category are closely allied to interpretive uses
of the system.
Two kinds of distinctions, therefore, are made among series.
First, the distinctions among families and among classes of all
higher categories also are distinctions among series. A series
cannot range across the limits between two families or between
two classes of any higher category. Second, distinctions among
similar series within a family are restrictions in one or more
but not necessarily all of the ranges in properties of the family.
Taken collectively, the number of the latter kind of distinctions
is too large to be comprehended readily. One can only state the
basis for separating individual series. Diagnostic horizons and
features provide a framework for differentiating series, but
series differentiae need not be limited to the defined diagnostic
horizons and features.
The differentiae for series in the same family are expected to
meet three tests. The first is that properties serving as
differentiae can be observed or can be inferred with reasonable
assurance. The second is that the differentiae must create soil
series having a unique range of properties that is significantly
greater than the normal margin of errors made by qualified
pedologists when they measure, observe, or estimate the
properties. The third is that the differentiae must reflect a
property of the soils. This significance can be reflected in the
nature or degree of expression of one or more horizons. The
nature of horizons includes mineralogy, structure, ruptureresistance
class, texture of the subhorizons, and moisture and
temperature regimes. If color is accessory to some other
property, it too is included. Degree of horizon expression
includes thickness, contrast between horizons or subhorizons,
and the nature of boundaries. If horizons are absent, the nature
of the whole zone of major biologic activity is considered. The
series control section is defined in chapter 21.
Important differences, shown by experience or research to
condition or influence the nature of the statements that we can
make about the behavior of the soil, should be considered as
series differentiae.
124
A number of soil properties condition the statements made
about a soil or its use but are not series differentiae. A steep
slope or stones on the surface may be very important to the use
of a soil in mechanized farming, but they may have virtually no
importance to the growth of a forest, although they can hinder
timber harvesting. If it is assumed that these soil characteristics
are not reflected in the nature of the soil, or in the nature or
degree of expression of horizons explained earlier, then they
may be used as one of the bases of phases of soil series. The
phases provide for a utilitarian classification that can be
superimposed on soil taxonomy at any categoric level to permit
more precise interpretations and predictions of the consequence
of the various alternative uses of the soil.
The primary use of soil series in the classification system is
to relate the map units represented on detailed soil maps to the
taxa and to the interpretations that may follow. Map units are
named for one or more soil series. Map units are real things,
but series are conceptual. The Miami series, for example,
cannot be seen or touched, but the map units that are identified
as physical entities expressing the concept of the Miami series
can be seen and touched.
The names of soil series have several meanings that must be
kept in mind. First, the Miami series is a taxonomic class, a
concept of a narrowly defined kind of soil. Second, one may
examine a pedon and say, “This is Miami,” meaning that the
properties in the pedon are those of the Miami series and that
the pedon is a proper example. Third, “Miami” is used as part
of the name of a map unit in an area that is shown on a soil
map if the Miami series is dominant in that area. An example
of such a map unit is Miami silt loam, 2 to 6 percent slopes.
These are three common meanings of “Miami,” or of any series
name, and all are proper. It is essential, however, to keep in
mind that a series, as used in this taxonomy, is conceptual; the
meaning is not identical with the meaning intended on soil
maps because an area of Miami soil has inclusions of soils of
other series. Inclusions of Miami soil also are permitted in
areas named for other series. The application of this taxonomy
to soil surveys is described in chapter 5.
125
The nomenclature of soil taxonomy is based on the
following premises: Each taxon requires a name if it is
to be used in speech; a good name is short, easy to pronounce,
and distinctive in meaning; a name is connotative, that is,
capable of mnemonic attachment to the concept of the thing
itself (Heller, 1963); and it is useful if the name of a taxon
indicates its position in the classification, if similarities in
important properties are reflected by similarities in names, if
the mnemonic attachments hold in many languages, and if the
name fits into many languages without translation.
The name of each taxon above the category of series
indicates its class in all categories of which it is a member.
The name of a soil series indicates only the category of series.
Thus, a series name may be recognized as a series, but it does
not indicate the order, suborder, great group, subgroup, or
family.
The table “Example of Names of Taxa” shows the names of
taxa in each category from order to series for two soil series.
Because the assigned names are connotative and because most
formative elements carry the same meaning in any
combination, a name can convey a great deal of information
about a soil.
Recognition of Names
Orders
The names of orders can be recognized as such because the
name of each order ends in sol (L. solum, soil) with the
connecting vowel o for Greek roots and i for other roots, as is
indicated in the table “Formative Elements in Names of Soil
Orders.” Each name of an order contains a formative element
that begins with the vowel directly preceding the connecting
vowel and ends with the last consonant preceding the
connecting vowel. In the order name “Entisol,” the formative
element is ent. In the name “Aridisol,” it is id. These formative
elements are used as endings for the names of suborders, great
groups, and subgroups. Thus, the names of all taxa higher than
the series that are members of the Entisol order end in ent and
can be recognized as belonging to that order. Names ending in
id are the names of taxa belonging to the Aridisol order.
Suborders
The names of suborders have exactly two syllables. The first
syllable connotes something about the diagnostic properties of
the soils. The second is the formative element from the name of
the order. The 28 formative elements shown in the table
“Formative Elements in Names of Suborders” are used with the
12 formative elements from names of the orders to make the
names of 64 suborders. The suborder of Entisols that has aquic
conditions throughout is called Aquents (L. aqua, water, plus
ent from Entisol). The formative element aqu is used with this
meaning in 9 of the 12 orders. The suborder of Entisols that
consists of very young sediments is called Fluvents (L. fluvius,
river, plus ent from Entisol).
Great Groups
The name of a great group consists of the name of a
suborder and a prefix that consists of one or two formative
elements suggesting something about the diagnostic properties.
The formative elements are shown in the table “Formative
Elements in Names of Great Groups.” The names of great
groups, therefore, have three or four syllables and end with the
name of a suborder. Fluvents that have a cryic temperature
regime are called Cryofluvents (Gr. kryos, icy cold, plus
fluvent). Fluvents that have a torric moisture regime are called
Torrifluvents (L. toridus, hot and dry).
Subgroups
The name of a subgroup consists of the name of a great
group modified by one or more adjectives. In some instances,
the adjective Typic represents what is thought to typify the
great group. In other instances, Typic subgroups simply do not
have any of the characteristics used to define the other
subgroups in a great group. Each Typic subgroup has, in
clearly expressed form, all the diagnostic properties of the
order, suborder, and great group to which it belongs. Typic
subgroups also have no additional properties indicating a
transition to another great group. A Typic subgroup is not
necessarily the most extensive subgroup of a great group.
CHAPTER 7
Nomenclature1
1
This chapter was developed with the assistance of the late Prof. A.L. Leemans, Classic
Language Department, State University of Ghent, and the late Prof. John L. Heller, Department
of the Classics, University of Illinois.
126 Soil Taxonomy
Intergrade subgroups are those that belong to one great
group but have some properties of another order, suborder, or
great group. They are named by use of the adjectival form of
the name of the appropriate taxon as a modifier of the great
group name. Thus, the Torrifluvents that have some of the
properties of Vertisols or the properties closely associated with
Vertisols are called Vertic Torrifluvents. Vertic Torrifluvents
have some of the properties of Vertisols superimposed on the
complete set of diagnostic properties of Torrifluvents.
Extragrade subgroups are those that have important
properties that are not representative of the great group but that
do not indicate transitions to any other known kind of soil.
They are named by modifying the great group name with an
adjective that connotes something about the nature of the
aberrant properties. Thus, a Cryorthent that has bedrock that is
at least strongly cemented within 50 cm of the mineral soil
surface is called a Lithic Cryorthent (lithic, Gr. lithos, stone).
This subgroup is listed as an example in the table “Names of
Orders, Suborders, Great Groups, and Subgroups.”
Families
The names of families are polynomial. Each consists of the
name of a subgroup and descriptive terms, generally three or
more, that indicate the particle-size class (or combinations
thereof if strongly contrasting), the mineralogy (26 classes), the
cation-exchange activity (4 classes), the calcareous and
reaction class (4 classes), the temperature (8 classes), and, in a
few families, depth of the soil (3 classes), rupture resistance (2
classes), and classes of coatings and classes of cracks (3
classes). The names of most families have three to five
descriptive terms that modify the subgroup name, but a few
have only one or two and a few have as many as six. The
example given in the table “Example of Names of Taxa” is a
family of fine-loamy (particle-size class), mixed (mineralogy),
superactive (cation-exchange activity), calcareous (calcareous
and reaction), mesic (soil temperature) Typic Torrifluvents.
Series
The names of series as a rule are abstract place names. The
name generally is taken from a place near the one where the
series was first recognized. It may be the name of a town, a
county, or some local feature. Some series have coined names.
Many of the series names have been carried over from earlier
classifications. Some have been in use since 1900. The name of
a series carries no meaning to people who have no other source
of information about the soils in the series.
Entisols ...................... Fluvents .................... Torrifluvents ............. Typic Torrifluvents ... Fine-loamy, Jocity, Youngston.
mixed, superactive,
calcareous, mesic.
Example of Names of Taxa
Order Suborder Great Group Subgroup Family Series
Alfisols ........................................ Alf............................................... Meaningless syllable .................. Pedalfer.
Andisols ....................................... And ............................................. Modified from ando ................... Ando.
Aridisols ...................................... Id................................................. L. aridus, dry.............................. Arid.
Entisols ........................................ Ent .............................................. Meaningless syllable .................. Recent.
Gelisols ........................................ El ................................................ L. gelare, to freeze ..................... Jell.
Histosols ...................................... Ist ................................................ Gr. histos, tissue ......................... Histology.
Inceptisols .................................... Ept .............................................. L. inceptum, beginning .............. Inception.
Mollisols ...................................... Oll ............................................... L. mollis, soft ............................. Mollify.
Oxisols ......................................... Ox ............................................... F. oxide, oxide ............................ Oxide.
Spodosols ..................................... Od ............................................... Gr. spodos, wood ash ................. Odd.
Ultisols......................................... Ult ............................................... L. ultumus, last ........................... Ultimate.
Vertisols ....................................... Ert ............................................... L. verto, turn .............................. Invert.
Formative Elements in Names of Soil Orders
Name of order Formative element in name Derivation of formative element
Pronunciation of formative
element
Nomenclature 127
Meanings in the Names
The Jocity and Youngston series shown in the table
“Example of Names of Taxa” are two members of the fineloamy,
mixed, superactive, calcareous, mesic family of Typic
Torrifluvents. The meaning of each of these terms is defined as
follows:
Fine-loamy means that from a depth of 25 to 100 cm there
is no marked contrast in particle-size class, the content of clay
is between 18 and 35 percent, 15 percent or more of the
material is coarser than 0.1 mm in diameter (fine sand to very
coarse sand plus gravel), but less than 35 percent of the
material, by volume, is rock fragments 2.0 mm or more in
diameter (less than about 50 percent by weight). The average
texture, then, is likely to be loam, clay loam, or sandy clay
loam.
Mixed indicates a mixed mineralogy, that is, there is
less than 40 percent any one mineral other than quartz in the
fraction between 0.02 and 2.0 mm in diameter, less than 20
percent (by weight) glauconitic pellets in the fine-earth
fraction, a total of 5 percent or less iron plus gibbsite (by
|weight) in the fine-earth fraction, and a fine-earth fraction that
has at least one of the following: free carbonates, pH of a
suspension of 1 g soil in 50 ml 1 M NaF of 8.4 or less after 2
minutes, or a ratio of 1500 kPa water to measured clay of 0.6
or less.
Superactive means that the cation-exchange capacity divided
by the percent clay is 0.60 or more.
Calcareous means that the soils have free carbonates in all
parts from a depth of 25 to 50 cm and that, in this setting, they
probably are calcareous throughout.
Mesic indicates a mesic temperature regime, that is, the
mean annual soil temperature is between 8 and 15 o
C (47 and
59 o
F) and the soil temperature fluctuates more than 8 o
C
between summer and winter. In other words, the soils are
somewhere in the midlatitudes, summer is warm or hot, and
winter is cool or cold.
No term for soil depth is included in the family name of these
Alb ........................... L. albus, white ................................................................. Presence of an albic horizon.
Anthr ....................... Modified from Gr. anthropos, human ............................. Modified by humans.
Aqu .......................... L. aqua, water.................................................................. Aquic conditions.
Ar ............................. L. arare, to plow .............................................................. Mixed horizon.
Arg ........................... Modified from argillic horizon; L. argilla, white clay ... Presence of an argillic horizon.
Calc .......................... L. calcis, lime .................................................................. Presence of a calcic horizon.
Camb........................ L. cambiare, to exchange ................................................ Presence of a cambic horizon.
Cry ........................... Gr. kryos, icy cold............................................................ Cold.
Dur ........................... L. durus, hard .................................................................. Presence of a duripan.
Fibr .......................... L. fibra, fiber ................................................................... Least decomposed stage.
Fluv .......................... L. fluvius, river ................................................................ Flood plain.
Fol ............................ L. folia, leaf ..................................................................... Mass of leaves.
Gyps ......................... L. gypsum, gypsum .......................................................... Presence of a gypsic horizon.
Hem ......................... Gr. hemi, half ................................................................... Intermediate stage of decomposition.
Hist .......................... Gr. histos, tissue .............................................................. Presence of organic materials.
Hum ......................... L. humus, earth ................................................................ Presence of organic matter.
Orth ......................... Gr. orthos, true ................................................................ The common ones.
Per ............................ L. per, throughout in time ............................................... Perudic moisture regime.
Psamm ..................... Gr. psammos, sand........................................................... Sandy texture.
Rend......................... Modified from Rendzina ................................................. High carbonate content.
Sal ............................ L. base of sal, salt ............................................................ Presence of a salic horizon.
Sapr.......................... Gr. saprose, rotten ........................................................... Most decomposed stage.
Torr .......................... L. torridus, hot and dry ................................................... Torric moisture regime.
Turb ......................... L. turbidis, disturbed ....................................................... Presence of cryoturbation.
Ud ............................ L. udus, humid................................................................. Udic moisture regime.
Ust............................ L. ustus, burnt .................................................................. Ustic moisture regime.
Vitr ........................... L. vitrum, glass ................................................................ Presence of glass.
Xer ........................... Gr. xeros, dry ................................................................... Xeric moisture regime.
Formative Elements in Names of Suborders
Formative element Derivation Connotation
128 Soil Taxonomy
Acr ........................... Modified from Gr. arkos, at the end ............................... Extreme weathering.
Al ............................. Modified from aluminum ................................................ High aluminum, low iron.
Alb ........................... L. albus, white ................................................................. Presence of an albic horizon.
Anhy ........................ Gr. anydros, waterless ..................................................... Very dry.
Anthr ....................... Modified from Gr. anthropos, human ............................. An anthropic epipedon.
Aqu .......................... L. aqua, water.................................................................. Aquic conditions.
Argi .......................... Modified from argillic horizon; L. argilla, white clay ... Presence of an argillic horizon.
Calci, calc ................ L. calcis, lime .................................................................. A calcic horizon.
Cry ........................... Gr. kryos, icy cold............................................................ Cold.
Dur ........................... L. durus, hard .................................................................. A duripan.
Dystr, dys ................. Modified from Gr. dys, ill; dystrophic, infertile ............. Low base saturation.
Endo......................... Gr. endon, endo, within................................................... Implying a ground water table.
Epi ........................... Gr. epi, on, above ............................................................ Implying a perched water table.
Eutr .......................... Modified from Gr. eu, good; eutrophic, fertile ............... High base saturation.
Ferr .......................... L. ferrum, iron ................................................................. Presence of iron.
Fibr .......................... L. fibra, fiber ................................................................... Least decomposed stage.
Fluv .......................... L. fluvius, river ................................................................ Flood plain.
Fol ............................ L. folia, leaf ..................................................................... Mass of leaves.
Fragi ........................ Modified from L. fragilis, brittle .................................... Presence of a fragipan.
Fragloss ................... Compound of fra(g) and gloss ......................................... See the formative elements “frag” and “gloss.”
Fulv .......................... L. fulvus, dull brownish yellow ....................................... Dark brown color, presence of organic carbon.
Glac.......................... L. glacialis, icy ................................................................ Ice lenses or wedges.
Gyps ......................... L. gypsum, gypsum .......................................................... Presence of a gypsic horizon.
Gloss ........................ Gr. glossa, tongue............................................................ Presence of a glossic horizon.
Hal ........................... Gr. hals, salt..................................................................... Salty.
Hapl ......................... Gr. haplous, simple ......................................................... Minimum horizon development.
Hem ......................... Gr. hemi, half ................................................................... Intermediate stage of decomposition.
Hist .......................... Gr. histos, tissue .............................................................. Presence of organic materials.
Hum ......................... L. humus, earth ................................................................ Presence of organic matter.
Hydr ......................... Gr. hydor, water ............................................................... Presence of water.
Kand, kan ................ Modified from kandite..................................................... 1:1 layer silicate clays.
Luv ........................... Gr. louo, to wash ............................................................. Illuvial.
Melan ....................... Gr. melasanos, black ....................................................... Black, presence of organic carbon.
Moll ......................... L. mollis, soft ................................................................... Presence of a mollic epipedon.
Natr .......................... Modified from natrium, sodium ...................................... Presence of a natric horizon.
Pale .......................... Gr. paleos, old ................................................................. Excessive development.
Petr........................... Gr. comb. form of petra, rock ......................................... A cemented horizon.
Plac .......................... Gr. base of plax, flat stone ............................................... Presence of a thin pan.
Plagg ........................ Modified from Ger. plaggen, sod .................................... Presence of a plaggen epipedon.
Plinth ....................... Gr. plinthos, brick............................................................ Presence of plinthite.
Psamm ..................... Gr. psammos, sand........................................................... Sandy texture.
Quartz ...................... Ger. quarz, quartz ............................................................ High quartz content.
Rhod ........................ Gr. base of rhodon, rose .................................................. Dark red color.
Sal ............................ L. base of sal, salt ............................................................ Presence of a salic horizon.
Sapr.......................... Gr. saprose, rotten ........................................................... Most decomposed stage.
Somb ........................ F. sombre, dark ................................................................ Presence of a sombric horizon.
Sphagn ..................... Gr. sphagnos, bog ............................................................ Presence of sphagnum.
Sulf .......................... L. sulfur, sulfur ................................................................ Presence of sulfides or their oxidation products.
Torr .......................... L. torridus, hot and dry ................................................... Torric moisture regime.
Formative Elements in Names of Great Groups
Formative element Derivation Connotation
Nomenclature 129
Typic Torrifluvents, indicating that the soils are 50 cm or more
deep.
The meaning of Typic varies with the great group. Torri
indicates a torric (dry) moisture regime. Fluv indicates that the
sediments are probably alluvial rather than eolian because fresh
eolian sediments may be sandy, silty, or clayey but are rarely
fine-loamy. Ent, the final syllable, indicates that the soils are
Entisols. As such, they have no fragipan, duripan, permafrost,
or cambic, argillic, calcic, petrocalcic, gypsic, oxic,
petrogypsic, placic, salic, or spodic horizon within 100 cm of
the mineral soil surface; have no sulfuric horizon within 150
cm of the mineral soil surface; and have no histic, mollic,
plaggen, or umbric epipedon.
The terms describing these Typic Torrifluvents allow us to
visualize soils on flood plains or alluvial fans in an arid,
temperate climate. Although the soils may be a bit salty, they
cannot be extremely salty. They probably have stratification but
have no severe limitation for irrigation. Under irrigation, iron
chlorosis may be a problem in sensitive plants. Unless
irrigated, the soils can be used only for limited grazing.
Forming Names
Names of Orders, Suborders, and Great Groups
The names of the orders, suborders, and great groups that
are currently recognized are shown in the table “Names of
Orders, Suborders, Great Groups, and Subgroups.” The
formative elements used in these names are shown in the tables
“Formative Elements in Names of Soil Orders,” “Formative
Elements in Names of Suborders,” and “Formative Elements in
Names of Great Groups.”
Names of Subgroups
The name of a subgroup consists of the name of a great
group modified by one or more adjectives. As was explained
earlier, the adjective Typic is used for the subgroup that is
thought to typify the central concept of the great group or for
soils that fail to meet the criteria of the other subgroups defined
for a great group.
Intergrade subgroups that have, in addition to the properties
of their great group, some properties of another taxon carry the
name of the other taxon in the form of an adjective. The names of
orders, suborders, or great groups or any of the prior (first)
formative elements of those names may be used in the form of
an adjective in subgroup names. A few soils may have aberrant
properties of two great groups that belong in different orders or
suborders. For these, it is necessary to use two names of taxa as
adjectives in the subgroup name.
The names of extragrade subgroups include one or more
special descriptive adjectives that modify the name of the great
group and connote the nature of aberrant properties.
Names of Intergrades Toward Other Great Groups in the
Same Suborder
If the aberrant property of a soil is one that is characteristic
of another great group in the same suborder, only the
distinctive formative element of the great group name is used
to indicate the aberrant property. Thus, a Typic Argidurid is
defined in part as having an indurated or very strongly
cemented duripan. If the only aberrant feature of an Argidic
Argidurid is that the duripan is strongly cemented or less
cemented throughout, the soil is considered to intergrade
toward Argids. The name, however, is Argidic Argidurids, not
Haplargidic Argidurids. Only the prior (first) formative
element is used in adjectival form if the two great groups are in
the same suborder.
Names of Intergrades Toward a Great Group in the Same
Order but in a Different Suborder
Two kinds of names have been chosen to indicate
intergrades toward a great group in the same order but in a
different suborder. If the only aberrant features are color and
moisture regime and hue is too yellow or chroma is too high or
too low for the Typic subgroup, the adjectives Aeric and Aquic
are used.
If an Epiaquult has chroma too high for the Typic subgroup
but has no other aberrant feature, it is assigned to an Aeric
Ud ............................ L. udus, humid................................................................. Udic moisture regime.
Umbr ........................ L. umbra, shade ............................................................... Presence of an umbric epipedon.
Ust............................ L. ustus, burnt .................................................................. Ustic moisture regime.
Verm ........................ L. base of vermes, worm.................................................. Wormy or mixed by animals.
Vitr ........................... L. vitrum, glass ................................................................ Presence of glass.
Xer ........................... Gr. xeros, dry ................................................................... Xeric moisture regime.
Formative Elements in Names of Great Groups--Continued
Formative element Derivation Connotation
130 Soil Taxonomy
Alfisols ........ Aqualfs........Cryaqualfs ........ Typic.
Plinthaqualfs .... Typic.
Duraqualfs ........ Typic.
Natraqualfs ....... Vertic,
Vermic,
Albic Glossic,
Albic,
Glossic,
Mollic,
Typic.
Fragiaqualfs ..... Vermic,
Aeric,
Plinthic,
Humic,
Typic.
Kandiaqualfs .... Arenic,
Grossarenic,
Plinthic,
Aeric Umbric,
Aeric,
Umbric,
Typic.
Vermaqualfs ..... Natric,
Typic.
Albaqualfs ........ Arenic,
Aeric Vertic,
Chromic Vertic,
Vertic,
Udollic,
Aeric,
Aquandic,
Mollic,
Umbric,
Typic.
Glossaqualfs ..... Histic,
Arenic,
Aeric Fragic,
Fragic,
Aeric,
Mollic,
Typic.
Epiaqualfs ........ Aeric Chromic
Vertic,
Aeric Vertic,
Chromic Vertic,
Vertic,
Aquandic,
Aeric Fragic,
Fragic,
Arenic,
Grossarenic,
Aeric Umbric,
Udollic,
Aeric,
Mollic,
Umbric,
Typic.
Endoaqualfs...... Aquandic,
Chromic Vertic,
Vertic,
Aeric Fragic,
Fragic,
Arenic,
Grossarenic,
Udollic,
Aeric Umbric,
Aeric,
Mollic,
Umbric,
Typic.
Cryalfs.........Palecryalfs ........ Andic,
Vitrandic,
Aquic,
Oxyaquic,
Xeric,
Ustic,
Mollic,
Umbric,
Typic.
Glossocryalfs .... Lithic,
Vertic,
Andic,
Vitrandic,
Aquic,
Oxyaquic,
Fragic,
Xerollic,
Umbric Xeric,
Ustollic,
Xeric,
Ustic,
Mollic,
Umbric,
Eutric,
Typic.
Haplocryalfs ..... Lithic,
Vertic,
Andic,
Names of Orders, Suborders, Great Groups, and Subgroups
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 131
Vitrandic,
Aquic,
Oxyaquic,
Lamellic,
Psammentic,
Inceptic,
Xerollic,
Umbric Xeric,
Ustollic,
Xeric,
Ustic,
Mollic,
Umbric,
Eutric,
Typic.
Ustalfs ....... Durustalfs .......... Typic.
Plinthustalfs ...... Typic.
Natrustalfs ......... Salidic,
Leptic Torrertic,
Torrertic,
Aquertic,
Aridic Leptic,
Vertic,
Aquic Arenic,
Aquic,
Arenic,
Petrocalcic,
Leptic,
Haplargdic,
Aridic,
Mollic,
Typic.
Kandiustalfs ...... Grossarenic,
Aquic Arenic,
Plinthic,
Aquic,
Arenic Aridic,
Arenic,
Aridic,
Udic,
Rhodic,
Typic.
Kanhaplustalfs .. Lithic,
Aquic,
Aridic,
Udic,
Rhodic,
Typic.
Paleustalfs.......... Aquertic,
Oxyaquic Vertic,
Udertic,
Vertic,
Aquic Arenic,
Aquic,
Oxyaquic,
Lamellic,
Psammentic,
Arenic Aridic,
Grossarenic,
Arenic,
Plinthic,
Petrocalcic,
Calcidic,
Aridic,
Kandic,
Rhodic,
Ultic,
Udic,
Typic.
Rhodustalfs....... Lithic,
Kanhaplic,
Udic,
Typic.
Haplustalfs ....... Lithic,
Aquertic,
Oxyaquic Vertic,
Torrertic,
Udertic,
Vertic,
Aquic Arenic,
Aquultic,
Aquic,
Oxyaquic,
Vitrandic,
Lamellic,
Psammentic,
Arenic Aridic,
Arenic,
Calcidic,
Aridic,
Kanhaplic,
Inceptic,
Calcic Udic,
Ultic,
Calcic,
Udic,
Typic.
Xeralfs ........Durixeralfs ....... Natric,
OrderOrder Suborder Great Group Subgroup Suborder Great Group Subgroup
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
132 Soil Taxonomy
Durixeralfs
(continued) ..... Vertic,
Aquic,
Abruptic Haplic,
Abruptic,
Haplic,
Typic.
Natrixeralfs ...... Vertic,
Aquic,
Typic.
Fragixeralfs ...... Andic,
Vitrandic,
Mollic,
Aquic,
Inceptic,
Typic.
Plinthoxeralfs ... Typic.
Rhodoxeralfs .... Lithic,
Vertic,
Petrocalcic,
Calcic,
Inceptic,
Typic.
Palexeralfs ........ Vertic,
Aquandic,
Andic,
Vitrandic,
Fragiaquic,
Aquic,
Petrocalcic,
Lamellic,
Psammentic,
Arenic,
Natric,
Fragic,
Calcic,
Plinthic,
Ultic,
Haplic,
Mollic,
Typic.
Haploxeralfs ..... Lithic Mollic,
Lithic Ruptic-
Inceptic,
Lithic,
Vertic,
Aquandic,
Andic,
Vitrandic,
Fragiaquic,
Aquultic,
Aquic,
Natric,
Fragic,
Lamellic,
Psammentic,
Plinthic,
Calcic,
Inceptic,
Ultic,
Mollic,
Typic.
Udalfs ..........Natrudalfs......... Vertic,
Glossaquic,
Aquic,
Typic.
Ferrudalfs ......... Aquic,
Typic.
Fraglossudalfs .. Andic,
Vitrandic,
Aquic,
Oxyaquic,
Typic.
Fragiudalfs ....... Andic,
Vitrandic,
Aquic,
Oxyaquic,
Typic.
Kandiudalfs ...... Plinthaquic,
Aquic,
Oxyaquic,
Arenic Plinthic,
Grossarenic
Plinthic,
Arenic,
Grossarenic,
Plinthic,
Rhodic,
Mollic,
Typic.
Kanhapludalfs .. Lithic,
Aquic,
Oxyaquic,
Rhodic,
Typic.
Paleudalfs ......... Vertic,
Andic,
Vitrandic,
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 133
Fragiaquic,
Plinthaquic,
Glossaquic,
Albaquic,
Aquic,
Anthraquic,
Oxyaquic,
Fragic,
Arenic Plinthic,
Grossarenic
Plinthic,
Lamellic,
Psammentic,
Arenic,
Grossarenic,
Plinthic,
Glossic,
Rhodic,
Mollic,
Typic.
Rhodudalfs ....... Typic.
Glossudalfs ....... Aquertic,
Oxyaquic Vertic,
Vertic,
Aquandic,
Andic,
Vitrandic,
Fragiaquic,
Aquic,
Oxyaquic,
Fragic,
Arenic,
Haplic,
Typic.
Hapludalfs ........ Lithic,
Aquertic
Chromic,
Aquertic,
Oxyaquic Vertic,
Chromic Vertic,
Vertic,
Andic,
Vitrandic,
Fragiaquic,
Fragic Oxyaquic,
Aquic Arenic,
Albaquultic,
Albaquic,
Glossaquic,
Aquultic,
Aquollic,
Aquic,
Anthraquic,
Oxyaquic,
Fragic,
Lamellic,
Psammentic,
Arenic,
Glossic,
Inceptic,
Ultic,
Mollic,
Typic.
Andisols ....... Aquands ......Cryaquands ...... Lithic,
Histic,
Thaptic,
Typic.
Placaquands ..... Lithic,
Duric Histic,
Duric,
Histic,
Thaptic,
Typic.
Duraquands ...... Histic,
Acraquoxic,
Thaptic,
Typic.
Vitraquands ...... Lithic,
Duric,
Histic,
Thaptic,
Typic.
Melanaquands .. Lithic,
Acraquoxic,
Hydric Pachic,
Hydric,
Pachic,
Thaptic,
Typic.
Epiaquands....... Duric,
Histic,
Alic,
Hydric,
Thaptic,
Typic.
Endoaquands .... Lithic,
Duric,
Histic,
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
134 Soil Taxonomy
Xerands ..... Vitrixerands....... Lithic,
Aquic,
Thaptic,
Alfic Humic,
Ultic,
Alfic,
Humic,
Typic.
Melanoxerands .. Pachic,
Typic.
Haploxerands..... Lithic,
Aquic,
Thaptic,
Calcic,
Ultic,
Alfic Humic,
Alfic,
Humic,
Typic.
Vitrands .... Ustivitrands ....... Lithic,
Aquic,
Thaptic,
Calcic,
Humic,
Typic.
Udivitrands ........ Lithic,
Aquic,
Thaptic,
Ultic,
Alfic,
Humic,
Typic.
Ustands ..... Durustands ........ Aquic,
Thaptic,
Humic,
Typic.
Haplustands ....... Lithic,
Aquic,
Dystric Vitric,
Vitric,
Pachic,
Thaptic,
Calcic,
Dystric,
Oxic,
Ultic,
Alfic,
Humic,
Typic.
Endoaquands
(continued) ..... Alic,
Hydric,
Thaptic,
Typic.
Cryands .......Duricryands ...... Aquic,
Typic.
Hydrocryands .... Lithic,
Placic,
Aquic,
Thaptic,
Typic.
Melanocryands .. Lithic,
Vitric,
Typic.
Fulvicryands ...... Lithic,
Pachic,
Vitric,
Typic.
Vitricryands ....... Lithic,
Aquic,
Oxyaquic,
Thaptic,
Humic Xeric,
Xeric,
Ultic,
Alfic,
Humic,
Typic.
Haplocryands ..... Lithic,
Alic,
Aquic,
Acrudoxic,
Vitric,
Thaptic,
Xeric,
Typic.
Torrands .... Duritorrands ...... Petrocalcic,
Vitric,
Typic.
Vitritorrands ...... Lithic,
Duric,
Aquic,
Calcic,
Typic.
Haplotorrands .... Lithic,
Duric,
Calcic,
Typic.
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group SubgroupOrder Suborder Great Group Subgroup
Nomenclature 135
Udands ...... Placudands ........ Lithic,
Aquic,
Acrudoxic,
Hydric,
Typic.
Durudands ........ Aquic,
Acrudoxic,
Hydric,
Pachic,
Typic.
Melanudands .... Lithic,
Anthraquic,
Aquic,
Acrudoxic Vitric,
Acrudoxic
Hydric,
Acrudoxic,
Pachic Vitric,
Vitric,
Hydric Pachic,
Pachic,
Hydric,
Thaptic,
Ultic,
Eutric,
Typic.
Hydrudands ...... Lithic,
Aquic,
Acrudoxic
Thaptic,
Acrudoxic,
Thaptic,
Eutric,
Ultic,
Typic.
Fulvudands ....... Eutric Lithic,
Lithic,
Aquic,
Hydric,
Acrudoxic,
Ultic,
Eutric Pachic,
Eutric,
Pachic,
Thaptic,
Typic.
Hapludands ...... Lithic,
Anthraquic,
Aquic Duric,
Duric,
Alic,
Aquic,
Acrudoxic
Hydric,
Acrudoxic
Thaptic,
Acrudoxic Ultic,
Acrudoxic,
Vitric,
Hydric Thaptic,
Hydric,
Eutric Thaptic,
Thaptic,
Eutric,
Oxic,
Ultic,
Alfic,
Typic.
Aridisols ...... Cryids..........Salicryids.......... Aquic,
Typic.
Petrocryids........ Xereptic,
Duric Xeric,
Duric,
Petrogypsic,
Xeric,
Ustic,
Typic.
Gypsicryids....... Calcic,
Vitrixerandic,
Vitrandic,
Typic.
Argicryids......... Lithic,
Vertic,
Natric,
Vitrixerandic,
Vitrandic,
Xeric,
Ustic,
Typic.
Calcicryids ....... Lithic,
Vitrixerandic,
Vitrandic,
Xeric,
Ustic,
Typic.
Haplocryids ...... Lithic,
Vertic,
Vitrixerandic,
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
136 Soil Taxonomy
Haplocryids
(continued) ..... Vitrandic,
Xeric,
Ustic,
Typic.
Salids ..........Aquisalids ........ Gypsic,
Calcic,
Typic.
Haplosalids ....... Duric,
Petrogypsic,
Gypsic,
Calcic,
Typic.
Durids .........Natridurids ....... Vertic,
Aquic
Natrargidic,
Aquic,
Natrixeralfic,
Natrargidic,
Vitrixerandic,
Vitrandic,
Xeric,
Typic.
Argidurids ........ Vertic,
Aquic,
Abruptic Xeric,
Abruptic,
Haploxeralfic,
Argidic,
Vitrixerandic,
Vitrandic,
Xeric,
Ustic,
Typic.
Haplodurids ...... Aquicambidic,
Aquic,
Xereptic,
Cambidic,
Vitrixerandic,
Vitrandic,
Xeric,
Ustic,
Typic.
Gypsids .......Petrogypsids ..... Petrocalcic,
Calcic,
Vitrixerandic,
Vitrandic,
Xeric,
Ustic,
Typic.
Natrigypsids ..... Lithic,
Vertic,
Petronodic,
Vitrixerandic,
Vitrandic,
Xeric,
Ustic,
Typic.
Argigypsids ...... Lithic,
Vertic,
Calcic,
Petronodic,
Vitrixerandic,
Vitrandic,
Xeric,
Ustic,
Typic.
Calcigypsids ..... Lithic,
Petronodic,
Vitrixerandic,
Vitrandic,
Xeric,
Ustic,
Typic.
Haplogypsids .... Lithic,
Leptic,
Sodic,
Petronodic,
Vitrixerandic,
Vitrandic,
Xeric,
Ustic,
Typic.
Argids .........Petroargids ....... Petrogypsic Ustic,
Petrogypsic,
Duric Xeric,
Duric,
Natric,
Xeric,
Ustic,
Typic.
Natrargids ........ Lithic Xeric,
Lithic Ustic,
Lithic,
Vertic,
Aquic,
Durinodic Xeric,
Durinodic,
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 137
Petronodic,
Glossic Ustic,
Haplic Ustic,
Haploxeralfic,
Haplic,
Vitrixerandic,
Vitrandic,
Xeric,
Ustic,
Glossic,
Typic.
Paleargids ......... Vertic,
Aquic,
Arenic Ustic,
Arenic,
Calcic,
Durinodic Xeric,
Durinodic,
Petronodic Ustic,
Petronodic,
Vitrixerandic,
Vitrandic,
Xeric,
Ustic,
Typic.
Gypsiargids ...... Aquic,
Durinodic,
Vitrixerandic,
Vitrandic,
Xeric,
Ustic,
Typic.
Calciargids ....... Lithic,
Xerertic,
Ustertic,
Vertic,
Aquic,
Arenic Ustic,
Arenic,
Durinodic Xeric,
Durinodic,
Petronodic Xeric,
Petronodic Ustic,
Petronodic,
Vitrixerandic,
Vitrandic,
Xeric,
Ustic,
Typic.
Haplargids ........ Lithic Ruptic-
Entic,
Lithic Xeric,
Lithic Ustic,
Lithic,
Xerertic,
Ustertic,
Vertic,
Aquic,
Arenic Ustic,
Arenic,
Durinodic Xeric,
Durinodic,
Petronodic Ustic,
Petronodic,
Vitrixerandic,
Vitrandic,
Xeric,
Ustic,
Typic.
Calcids ........Petrocalcids ...... Aquic,
Natric,
Xeralfic,
Ustalfic,
Argic,
Calcic Lithic,
Calcic,
Xeric,
Ustic,
Typic.
Haplocalcids ..... Lithic Xeric,
Lithic Ustic,
Lithic,
Vertic,
Aquic Durinodic,
Aquic,
Duric Xeric,
Duric,
Durinodic Xeric,
Durinodic,
Petronodic Xeric,
Petronodic Ustic,
Petronodic,
Sodic Xeric,
Sodic Ustic,
Sodic,
Vitrixerandic,
Vitrandic,
Xeric,
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
138 Soil Taxonomy
Haplocalcids
(continued) ..... Ustic,
Typic.
Cambids ......Aquicambids .... Sodic,
Durinodic Xeric,
Durinodic,
Petronodic,
Vitrixerandic,
Vitrandic,
Fluventic,
Xeric,
Ustic,
Typic.
Petrocambids .... Sodic,
Vitrixerandic,
Vitrandic,
Xeric,
Ustic,
Typic.
Anthracambids .. Typic.
Haplocambids .... Lithic Xeric,
Lithic Ustic,
Lithic,
Xerertic,
Ustertic,
Vertic,
Durinodic Xeric,
Durinodic,
Petronodic Xeric,
Petronodic Ustic,
Petronodic,
Sodic Xeric,
Sodic Ustic,
Sodic,
Vitrixerandic,
Vitrandic,
Xerofluventic,
Ustifluventic,
Fluventic,
Xeric,
Ustic,
Typic.
Entisols ........ Aquents ..... Sulfaquents ........ Haplic,
Histic,
Thapto-Histic,
Typic.
Hydraquents ...... Sulfic,
Sodic,
Thaptic-Histic,
Typic.
Cryaquents......... Aquandic,
Typic.
Psammaquents... Lithic,
Sodic,
Spodic,
Humaqueptic,
Mollic,
Typic.
Fluvaquents ....... Sulfic,
Vertic,
Thapto-Histic,
Aquandic,
Aeric,
Humaqueptic,
Mollic,
Typic.
Epiaquents ......... Aeric,
Humaqueptic,
Mollic,
Typic.
Endoaquents ..... Sulfic,
Lithic,
Sodic,
Aeric,
Humaqueptic,
Mollic,
Typic.
Arents .........Ustarents .......... Haplic.
Xerarents .......... Sodic,
Duric,
Alfic,
Haplic.
Torriarents ........ Sodic,
Duric,
Haplic.
Udarents ........... Alfic,
Ultic,
Mollic,
Haplic.
Psamments ..Cryopsamments
..... Lithic,
Aquic,
Oxyaquic,
Vitrandic,
Spodic,
Lamellic,
Typic.
Subgroup
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group
Nomenclature 139
Torripsamments
..... Lithic,
Vitrandic,
Haploduridic,
Ustic,
Xeric,
Rhodic,
Typic.
Quartzipsamments
..... Lithic,
Aquodic,
Aquic,
Oxyaquic,
Ustoxic,
Udoxic,
Plinthic,
Lamellic Ustic,
Lamellic,
Ustic,
Xeric,
Spodic,
Typic.
Ustipsamments
..... Lithic,
Aquic,
Oxyaquic,
Aridic,
Lamellic,
Rhodic,
Typic.
Xeropsamments
..... Lithic,
Aquic Durinodic,
Aquic,
Oxyaquic,
Vitrandic,
Durinodic,
Lamellic,
Dystric,
Typic.
Udipsamments
..... Lithic,
Aquic,
Oxyaquic,
Spodic,
Lamellic,
Plagganthreptic,
Typic.
Fluvents ......Cryofluvents ..... Andic,
Vitrandic,
Aquic,
Oxyaquic,
Mollic,
Typic.
Xerofluvents ..... Vertic,
Aquandic,
Andic,
Vitrandic,
Aquic,
Oxyaquic,
Durinodic,
Mollic,
Typic.
Ustifluvents ...... Aquertic,
Torrertic,
Vertic,
Anthraquic,
Aquic,
Oxyaquic,
Aridic,
Udic,
Mollic,
Typic.
Torrifluvents..... Ustertic,
Vertic,
Vitrixerandic,
Vitrandic,
Aquic,
Oxyaquic,
Duric Xeric,
Duric,
Ustic,
Xeric,
Anthropic,
Typic.
Udifluvents ....... Aquertic,
Vertic,
Andic,
Vitrandic,
Aquic,
Oxyaquic,
Mollic,
Typic.
Orthents ......Cryorthents ----- Lithic,
Vitrandic,
Aquic,
Oxyaquic,
Lamellic,
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
140 Soil Taxonomy
Cryorthents
(continued) ..... Typic.
Torriorthents .... Lithic Ustic,
Lithic Xeric,
Lithic,
Xerertic,
Ustertic,
Vertic,
Vitrandic,
Aquic,
Oxyaquic,
Duric,
Ustic,
Xeric,
Typic.
Xerorthents ...... Lithic,
Vitrandic,
Aquic,
Oxyaquic,
Durinodic,
Dystric,
Typic.
Ustorthents ....... Aridic Lithic,
Lithic,
Torrertic,
Vertic,
Anthraquic,
Aquic,
Oxyaquic,
Durinodic,
Vitritorrandic,
Vitrandic,
Aridic,
Udic,
Vermic,
Typic.
Udorthents ........ Lithic,
Vitrandic,
Aquic,
Oxyaquic,
Vermic,
Typic.
Gelisols ........ Histels .........Folistels ............ Lithic,
Glacic,
Typic.
Glacistels .......... Hemic,
Sapric,
Typic.
Fibristels ........... Lithic,
Terric,
Fluvaquentic,
Sphagnic,
Typic.
Hemistels ........... Lithic,
Terric,
Fluvaquentic,
Typic.
Sapristels ........... Lithic,
Terric,
Fluvaquentic,
Typic.
Turbels ........Histoturbels ....... Lithic,
Glacic,
Ruptic,
Typic.
Aquiturbels........ Lithic,
Glacic,
Sulfuric,
Ruptic-Histic,
Psammentic,
Typic.
Anhyturbels ....... Lithic,
Glacic,
Petrogypsic,
Gypsic,
Nitric,
Salic,
Calcic,
Typic.
Molliturbels ....... Lithic,
Glacic,
Vertic,
Andic,
Vitrandic,
Cumulic,
Aquic,
Typic.
Umbriturbels ..... Lithic,
Glacic,
Vertic,
Andic,
Vitrandic,
Cumulic,
Aquic,
Typic.
Psammoturbels .. Lithic,
Glacic,
Spodic,
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 141
Typic.
Haploturbels ..... Lithic,
Glacic,
Aquic,
Typic.
Orthels ........Historthels ........ Lithic,
Glacic,
Ruptic,
Typic.
Aquorthels........ Lithic,
Glacic,
Sulfuric,
Ruptic-Histic,
Andic,
Vitrandic,
Salic,
Psammentic,
Typic.
Anhyorthels...... Lithic,
Glacic,
Petrogypsic,
Gypsic,
Nitric,
Salic,
Calcic,
Typic.
Mollorthels ....... Lithic,
Glacic,
Vertic,
Andic,
Vitrandic,
Cumulic,
Aquic,
Typic.
Umbrorthels ..... Lithic,
Glacic,
Vertic,
Andic,
Vitrandic,
Cumulic,
Aquic,
Typic.
Argiorthels ....... Lithic,
Glacic,
Natric,
Typic.
Psammorthels ... Lithic,
Glacic,
Spodic,
Typic.
Haplorthels ....... Lithic,
Glacic,
Aquic,
Typic.
Histosols ...... Folists..........Cryofolists ........ Lithic,
Typic.
Torrifolists ........ Lithic,
Typic.
Ustifolists ......... Lithic,
Typic.
Udifolists .......... Lithic,
Typic.
Fibrists ........Cryofibrists....... Hydric,
Lithic,
Terric,
Fluvaquentic,
Sphagnic,
Typic.
Sphagnofibrists.............
Hydric,
Lithic,
Limnic,
Terric,
Fluvaquentic,
Hemic,
Typic.
Haplofibrists ..... Hydric,
Lithic,
Limnic,
Terric,
Fluvaquentic,
Hemic,
Typic.
Saprists .......Sulfosaprists ..... Typic.
Sulfisaprists...... Terric,
Typic.
Cryosaprists...... Lithic,
Terric,
Fluvaquentic,
Typic.
Haplosaprists .... Lithic,
Limnic,
Halic Terric,
Halic,
Terric,
Fluvaquentic,
Hemic,
Typic.
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
142 Soil Taxonomy
Hemists .......Sulfohemists ..... Typic.
Sulfihemists...... Terric,
Typic.
Luvihemists ...... Typic.
Cryohemists ..... Hydric,
Lithic,
Terric,
Fluvaquentic,
Typic.
Haplohemists.... Hydric,
Lithic,
Limnic,
Terric,
Fluvaquentic,
Fibric,
Sapric,
Typic.
Inceptisols .... Aquepts .......Sulfaquepts ....... Salidic,
Hydraquentic,
Typic.
Petraquepts ....... Histic Placic,
Placic,
Plinthic,
Typic.
Halaquepts........ Vertic,
Aquandic,
Duric,
Aeric,
Typic.
Fragiaquepts ..... Aeric,
Humic,
Typic.
Cryaquepts ....... Sulfic,
Histic Lithic,
Lithic,
Vertic,
Histic,
Aquandic,
Fluvaquentic,
Aeric Humic,
Aeric,
Humic,
Typic.
Vermaquepts..... Sodic,
Typic.
Humaquepts ..... Hydraquentic,
Histic,
Aquandic,
Cumulic,
Fluvaquentic,
Aeric,
Typic.
Epiaquepts ........ Vertic,
Aquandic,
Fluvaquentic,
Fragic,
Aeric,
Humic,
Mollic,
Typic.
Endoaquepts ..... Sulfic,
Lithic,
Vertic,
Aquandic,
Fluvaquentic,
Fragic,
Aeric,
Humic,
Mollic,
Typic.
Anthrepts ....Plagganthrepts.........
Typic.
Haplanthrepts ... Typic.
Cryepts ........Eutrocryepts ..... Humic Lithic,
Lithic,
Andic,
Vitrandic,
Aquic,
Oxyaquic,
Lamellic,
Xeric,
Ustic,
Humic,
Typic.
Dystrocryepts.... Humic Lithic,
Lithic,
Andic,
Vitrandic,
Aquic,
Oxyaquic,
Lamellic,
Spodic,
Xeric,
Ustic,
Humic,
Typic.
Ustepts ........Durustepts ........ Typic.
Calciustepts ...... Lithic Petrocalcic,
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 143
Lithic,
Torrertic,
Vertic,
Petrocalcic,
Gypsic,
Aquic,
Aridic,
Udic,
Typic.
Dystrustepts...... Lithic,
Andic,
Vitrandic,
Aquic,
Fluventic,
Oxic,
Humic,
Typic.
Haplustepts ....... Aridic Lithic,
Lithic,
Udertic,
Torrertic,
Vertic,
Andic,
Vitrandic,
Anthraquic,
Aquic,
Oxyaquic,
Oxic,
Lamellic,
Torrifluventic,
Udifluventic,
Fluventic,
Gypsic,
Haplocalcidic,
Calcic Udic,
Calcic,
Aridic,
Dystric,
Udic,
Typic.
Xerepts ........Durixerepts....... Aquandic,
Andic,
Vitrandic,
Aquic,
Entic,
Typic.
Calcixerepts...... Lithic,
Vertic,
Petrocalcic,
Sodic,
Vitrandic,
Aquic,
Typic.
Fragixerepts ..... Andic,
Vitrandic,
Aquic,
Humic,
Typic.
Dystroxerepts ... Humic Lithic,
Lithic,
Aquandic,
Andic,
Vitrandic,
Fragiaquic,
Fluvaquentic,
Aquic,
Oxyaquic,
Fragic,
Fluventic Humic,
Fluventic,
Humic,
Typic.
Haploxerepts .... Humic Lithic,
Lithic,
Vertic,
Aquandic,
Andic,
Vitrandic,
Gypsic,
Aquic,
Lamellic,
Fragic,
Fluventic,
Calcic,
Humic,
Typic.
Udepts .........Sulfudepts......... Typic.
Durudepts ......... Aquandic,
Andic,
Vitrandic,
Aquic,
Typic.
Fragiudepts....... Andic,
Vitrandic,
Aquic,
Humic,
Typic.
Eutrudepts ........ Humic Lithic,
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
144 Soil Taxonomy
Eutrudepts
(continued) ..... Lithic,
Aquertic,
Vertic,
Andic,
Vitrandic,
Anthraquic,
Fragiaquic,
Fluvaquentic,
Aquic Dystric,
Aquic,
Oxyaquic,
Fragic,
Lamellic,
Dystric Fluventic,
Fluventic,
Arenic,
Dystric,
Rendollic,
Humic,
Ruptic-Alfic,
Typic.
Dystrudepts ...... Humic Lithic,
Lithic,
Vertic,
Aquandic,
Andic,
Vitrandic,
Fragiaquic,
Fluvaquentic,
Aquic Humic,
Aquic,
Oxyaquic,
Fragic,
Lamellic,
Humic
Psammentic,
Fluventic Humic,
Fluventic,
Spodic,
Oxic,
Humic Pachic,
Humic,
Ruptic-Alfic,
Ruptic-Ultic,
Typic.
Mollisols ...... Albolls.........Natralbolls ........ Leptic,
Typic.
Argialbolls........ Xerertic,
Vertic,
Argiaquic Xeric,
Argiaquic,
Xeric,
Aquandic,
Typic.
Aquolls........Cryaquolls ........ Vertic,
Histic,
Thapto-Histic,
Aquandic,
Argic,
Calcic,
Cumulic,
Typic.
Duraquolls ........ Natric,
Vertic,
Argic,
Typic.
Natraquolls ....... Vertic,
Typic.
Calciaquolls...... Petrocalcic,
Aeric,
Typic.
Argiaquolls....... Arenic,
Grossarenic,
Vertic,
Abruptic,
Typic.
Epiaquolls ........ Cumulic Vertic,
Fluvaquentic
Vertic,
Vertic,
Histic,
Thapto-Histic,
Aquandic,
Duric,
Cumulic,
Fluvaquentic,
Typic.
Endoaquolls ..... Lithic,
Cumulic Vertic,
Fluvaquentic
Vertic,
Vertic,
Histic,
Thapto-Histic,
Aquandic,
Duric,
Cumulic,
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 145
Fluvaquentic,
Typic.
Rendolls ......Cryrendolls....... Lithic,
Typic.
Haprendolls ...... Lithic,
Vertic,
Inceptic,
Entic,
Typic.
Cryolls.........Duricryolls ....... Argic,
Typic.
Natricryolls ...... Typic.
Palecryrolls....... Aquic,
Oxyaquic,
Abruptic,
Pachic,
Ustic,
Xeric,
Typic.
Argicryolls........ Lithic,
Vertic,
Andic,
Vitrandic,
Abruptic,
Aquic,
Oxyaquic,
Pachic,
Alfic,
Ustic,
Xeric,
Typic.
Calcicryolls ...... Lithic,
Petrocalcic,
Pachic,
Ustic,
Xeric,
Typic.
Haplocryolls ..... Lithic,
Vertic,
Andic,
Vitrandic,
Aquic Cumulic,
Cumulic,
Fluvaquentic,
Aquic,
Oxyaquic,
Calcic Pachic,
Pachic,
Fluventic,
Calcic,
Ustic,
Xeric,
Typic.
Xerolls ........Durixerolls ....... Vertic,
Vitritorrandic,
Vitrandic,
Aquic,
Paleargidic,
Abruptic
Argiduridic,
Cambidic,
Haploduridic,
Argidic,
Argiduridic,
Haplic
Palexerollic,
Palexerollic,
Haplic
Haploxerollic,
Haploxerollic,
Haplic,
Typic.
Natrixerolls ...... Vertic,
Aquic Duric,
Aquic,
Aridic,
Duric,
Typic.
Palexerolls ........ Vertic,
Vitrandic,
Aquic,
Pachic,
Petrocalcidic,
Duric,
Aridic,
Petrocalcic,
Ultic,
Haplic,
Typic.
Calcixerolls ...... Lithic,
Vertic,
Aquic,
Oxyaquic,
Pachic,
Vitrandic,
Aridic,
Vermic,
Typic.
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
146 Soil Taxonomy
Argixerolls ....... Lithic Ultic,
Lithic,
Torrertic,
Vertic,
Andic,
Vitritorrandic,
Vitrandic,
Aquultic,
Aquic,
Oxyaquic,
Alfic,
Calcic Pachic,
Pachic Ultic,
Pachic,
Argiduridic,
Duric,
Calciargidic,
Aridic,
Calcic,
Ultic,
Typic.
Haploxerolls ..... Lithic Ultic,
Lithic,
Torrertic,
Vertic,
Vitritorrandic,
Vitrandic,
Aquic Cumulic,
Cumulic Ultic,
Cumulic,
Fluvaquentic,
Aquic Duric,
Aquultic,
Aquic,
Oxyaquic,
Calcic Pachic,
Pachic Ultic,
Pachic,
Torrifluventic,
Duridic,
Calcidic,
Torripsammentic,
Torriorthentic,
Aridic,
Duric,
Psammentic,
Fluventic,
Vermic,
Calcic,
Entic Ultic,
Ultic,
Entic,
Typic.
Ustolls .........Durustolls ......... Natric,
Haploduridic,
Argiduridic,
Entic,
Haplic,
Typic.
Natrustolls ........ Leptic Torrertic,
Torrertic,
Leptic Vertic,
Glossic Vertic,
Vertic,
Aridic Leptic,
Leptic,
Aquic,
Aridic,
Duric,
Glossic,
Typic.
Calciustolls....... Salidic,
Lithic
Petrocalcic,
Lithic,
Torrertic,
Udertic,
Vertic,
Petrocalcic,
Gypsic,
Pachic,
Aquic,
Oxyaquic,
Aridic,
Udic,
Typic.
Paleustolls ........ Torrertic,
Udertic,
Vertic,
Pachic,
Aquic,
Petrocalcic,
Calcidic,
Aridic,
Udic,
Calcic,
Entic,
Typic.
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 147
Argiustolls ........ Aridic Lithic,
Alfic Lithic,
Lithic,
Torrertic,
Udertic,
Vertic,
Andic,
Vitritorrandic,
Vitrandic,
Pachic,
Aquic,
Oxyaquic,
Alfic,
Calcidic,
Aridic,
Udic,
Duric,
Typic.
Vermustolls ...... Lithic,
Aquic,
Pachic,
Entic,
Typic.
Haplustolls ....... Salidic,
Ruptic-Lithic,
Lithic,
Torrertic,
Pachic Udertic,
Udertic,
Vertic,
Torroxic,
Oxic,
Andic,
Vitritorrandic,
Vitrandic,
Aquic Cumulic,
Cumulic,
Anthraquic,
Fluvaquentic,
Pachic,
Aquic,
Oxyaquic,
Torrifluventic,
Torriorthentic,
Aridic,
Fluventic,
Duric,
Udorthentic,
Udic,
Entic,
Typic.
Udolls ..........Natrudolls......... Petrocalcic,
Leptic Vertic,
Glossic Vertic,
Vertic,
Leptic,
Glossic,
Calcic,
Typic.
Calciudolls ....... Lithic,
Vertic,
Aquic,
Fluventic,
Typic.
Paleudolls ......... Vertic,
Petrocalcic,
Aquic,
Pachic,
Oxyaquic,
Calcic,
Typic.
Argiudolls ........ Lithic,
Aquertic,
Oxyaquic Vertic,
Pachic Vertic,
Alfic Vertic,
Vertic,
Andic,
Vitrandic,
Aquic,
Pachic,
Oxyaquic,
Lamellic,
Psammentic,
Arenic,
Abruptic,
Alfic,
Oxic,
Calcic,
Typic.
Vermudolls ....... Lithic,
Haplic,
Typic.
Hapludolls ........ Lithic,
Aquertic,
Vertic,
Andic,
Vitrandic,
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
148 Soil Taxonomy
Hapludolls
(continued) ..... Aquic Cumulic,
Cumulic,
Fluvaquentic,
Aquic,
Pachic,
Oxyaquic,
Fluventic,
Vermic,
Calcic,
Entic,
Typic.
Oxisols ......... Aquox .........Acraquox .......... Plinthic,
Aeric,
Typic.
Plinthaquox ...... Aeric,
Typic.
Eutraquox ......... Histic,
Plinthic,
Aeric,
Humic,
Typic.
Haplaquox ........ Histic,
Plinthic,
Aeric,
Humic,
Typic.
Torrox .........Acrotorrox ........ Petroferric,
Lithic,
Typic.
Eutrotorrox ....... Petroferric,
Lithic,
Typic.
Haplotorrox ...... Petroferric,
Lithic,
Typic.
Ustox ...........Sombriustox ..... Petroferric,
Lithic,
Humic,
Typic.
Acrustox ........... Aquic Petroferric,
Petroferric,
Aquic Lithic,
Lithic,
Anionic Aquic,
Anionic,
Plinthic,
Aquic,
Eutric,
Humic Rhodic,
Humic Xanthic,
Humic,
Rhodic,
Xanthic,
Typic.
Eutrustox .......... Aquic Petroferric,
Petroferric,
Aquic Lithic,
Lithic,
Plinthaquic,
Plinthic,
Aquic,
Kandiustalfic,
Humic Inceptic,
Inceptic,
Humic Rhodic,
Humic Xanthic,
Humic,
Rhodic,
Xanthic,
Typic.
Kandiustox ....... Aquic Petroferric,
Petroferric,
Aquic Lithic,
Lithic,
Plinthaquic,
Plinthic,
Aquic,
Humic Rhodic,
Humic Xanthic,
Humic,
Rhodic,
Xanthic,
Typic.
Haplustox ......... Aquic Petroferric,
Petroferric,
Aquic Lithic,
Lithic,
Plinthaquic,
Plinthic,
Aqueptic,
Aquic,
Oxyaquic,
Inceptic,
Humic Rhodic,
Humic Xanthic,
Humic,
Rhodic,
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 149
Xanthic,
Typic.
Perox ...........Sombriperox ..... Petroferric,
Lithic,
Humic,
Typic.
Acroperox......... Aquic Petroferric,
Petroferric,
Aquic Lithic,
Lithic,
Anionic,
Plinthic,
Aquic,
Humic Rhodic,
Humic Xanthic,
Humic,
Rhodic,
Xanthic,
Typic.
Eutroperox........ Aquic Petroferric,
Petroferric,
Aquic Lithic,
Lithic,
Plinthaquic,
Plinthic,
Aquic,
Kandiudalfic,
Humic Inceptic,
Inceptic,
Humic Rhodic,
Humic Xanthic,
Humic,
Rhodic,
Xanthic,
Typic.
Kandiperox....... Aquic Petroferric,
Petroferric,
Aquic Lithic,
Lithic,
Plinthaquic,
Plinthic,
Aquic,
Andic,
Humic Rhodic,
Humic Xanthic,
Humic,
Rhodic,
Xanthic,
Typic.
Haploperox ....... Aquic Petroferric,
Petroferric,
Aquic Lithic,
Lithic,
Plinthaquic,
Plinthic,
Aquic,
Andic,
Humic Rhodic,
Humic Xanthic,
Humic,
Rhodic,
Xanthic,
Typic.
Udox............Sombriudox ...... Petroferric,
Lithic,
Humic,
Typic.
Acrudox............ Aquic Petroferric,
Petroferric,
Aquic Lithic,
Lithic,
Anionic Aquic,
Anionic,
Plinthic,
Aquic,
Eutric,
Humic Rhodic,
Humic Xanthic,
Humic,
Rhodic,
Xanthic,
Typic.
Eutrudox........... Aquic Petroferric,
Petroferric,
Aquic Lithic,
Lithic,
Plinthaquic,
Plinthic,
Aquic,
Kandiudalfic,
Humic Inceptic,
Inceptic,
Humic Rhodic,
Humic Xanthic,
Humic,
Rhodic,
Xanthic,
Typic.
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
150 Soil Taxonomy
Kandiudox ........ Aquic Petroferric,
Petroferric,
Aquic Lithic,
Lithic,
Plinthaquic,
Plinthic,
Aquic,
Andic,
Humic Rhodic,
Humic Xanthic,
Humic,
Rhodic,
Xanthic,
Typic.
Hapludox .......... Aquic Petroferric,
Petroferric,
Aquic Lithic,
Lithic,
Plinthaquic,
Plinthic,
Aquic,
Inceptic,
Andic,
Humic Rhodic,
Humic Xanthic,
Humic,
Rhodic,
Xanthic,
Typic.
Spodosols ..... Aquods ........Cryaquods ........ Lithic,
Placic,
Duric,
Andic,
Entic,
Typic.
Alaquods .......... Lithic,
Duric,
Histic,
Alfic Arenic,
Arenic Ultic,
Arenic Umbric,
Arenic,
Grossarenic,
Alfic,
Ultic,
Aeric,
Typic.
Fragiaquods ...... Histic,
Plagganthreptic,
Argic,
Typic.
Placaquods ....... Andic,
Typic.
Duraquods ........ Histic,
Andic,
Typic.
Epiaquods......... Lithic,
Histic,
Andic,
Alfic,
Ultic,
Umbric,
Typic.
Endoaquods ...... Lithic,
Histic,
Andic,
Argic,
Umbric,
Typic.
Cryods .........Placocryods ...... Andic,
Humic,
Typic.
Duricryods ........ Aquandic,
Andic,
Aquic,
Oxyaquic,
Humic,
Typic.
Humicryods ...... Lithic,
Aquandic,
Andic,
Aquic,
Oxyaquic,
Typic.
Haplocryods...... Lithic,
Aquandic,
Andic,
Aquic,
Oxyaquic,
Entic,
Typic.
Humods .......Placohumods .... Andic,
Typic.
Durihumods ..... Andic,
Typic.
Fragihumods .... Typic.
Haplohumods ... Lithic,
Andic,
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 151
Plagganthreptic,
Typic.
Orthods .......Placorthods....... Typic.
Durorthods ....... Andic,
Typic.
Fragiorthods ..... Aquic,
Alfic Oxyaquic,
Oxyaquic,
Plagganthreptic,
Alfic,
Ultic,
Entic,
Typic.
Alorthods.......... Oxyaquic,
Arenic Ultic,
Arenic,
Entic
Grossarenic,
Entic,
Grossarenic,
Plagganthreptic,
Alfic,
Ultic,
Typic.
Haplorthods ...... Entic Lithic,
Lithic,
Fragiaquic,
Aqualfic,
Aquentic,
Aquic,
Alfic Oxyaquic,
Oxyaquic Ultic,
Fragic,
Lamellic,
Oxyaquic,
Andic,
Alfic,
Ultic,
Entic,
Typic.
Ultisols......... Aquults .......Plinthaquults .... Kandic,
Typic.
Fragiaquults ..... Aeric,
Plinthic,
Umbric,
Typic.
Albaquults ........ Vertic,
Kandic,
Aeric,
Typic.
Kandiaquults .... Acraquoxic,
Arenic Plinthic,
Arenic Umbric,
Arenic,
Grossarenic,
Plinthic,
Aeric,
Umbric,
Typic.
Kanhaplaquults
............ Aquandic,
Plinthic,
Aeric Umbric,
Aeric,
Umbric,
Typic.
Paleaquults ....... Vertic,
Arenic Plinthic,
Arenic Umbric,
Arenic,
Grossarenic,
Plinthic,
Aeric,
Umbric,
Typic.
Umbraquults..... Plinthic,
Typic.
Epiaquults ........ Vertic,
Aeric Fragic,
Arenic,
Grossarenic,
Fragic,
Aeric,
Typic.
Endoaquults ..... Arenic,
Grossarenic,
Aeric,
Typic.
Humults ......Sombrihumults...........
Typic.
Plinthohumults...........
Typic.
Kandihumults... Andic
Ombroaquic,
Ustandic,
Andic,
Aquic,
Ombroaquic,
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
152 Soil Taxonomy
Kandihumults
(continued) ..... Plinthic,
Ustic,
Xeric,
Anthropic,
Typic.
Kanhaplohumults...........
Lithic,
Ustandic,
Andic,
Aquic,
Ombroaquic,
Ustic,
Xeric,
Anthropic,
Typic.
Palehumults...... Aquandic,
Andic,
Aquic,
Plinthic,
Oxyaquic,
Ustic,
Xeric,
Typic.
Haplohumults ... Lithic,
Aquandic,
Aquic,
Andic,
Plinthic,
Oxyaquic,
Ustic,
Xeric,
Typic.
Udults..........Plinthudults ...... Typic.
Fragiudults ....... Arenic,
Plinthaquic,
Glossaquic,
Aquic,
Plinthic,
Glossic,
Humic,
Typic.
Kandiudults ...... Arenic
Plinthaquic,
Aquic Arenic,
Arenic Plinthic,
Arenic Rhodic,
Arenic,
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Grossarenic
Plinthic,
Grossarenic,
Acrudoxic
Plinthic,
Acrudoxic,
Plinthaquic,
Aquandic,
Andic,
Aquic,
Plinthic,
Ombroaquic,
Oxyaquic,
Sombric,
Rhodic,
Typic.
Kanhapludults .. Lithic,
Plinthaquic,
Arenic Plinthic,
Arenic,
Acrudoxic,
Fragiaquic,
Andic,
Aquic,
Ombroaquic,
Oxyaquic,
Plinthic,
Fragic,
Rhodic,
Typic.
Paleudults ......... Vertic,
Spodic,
Arenic
Plinthaquic,
Aquic Arenic,
Plinthaquic,
Fragiaquic,
Aquic,
Anthraquic,
Oxyaquic,
Lamellic,
Arenic Plinthic,
Psammentic,
Grossarenic
Plinthic,
Plinthic,
Arenic Rhodic,
Arenic,
Nomenclature 153
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Grossarenic,
Fragic,
Rhodic,
Typic.
Rhodudults ....... Lithic,
Psammentic,
Typic.
Hapludults ........ Lithic Ruptic-
Entic,
Lithic,
Vertic,
Fragiaquic,
Aquic Arenic,
Aquic,
Fragic,
Oxyaquic,
Lamellic,
Psammentic,
Arenic,
Grossarenic,
Inceptic,
Humic,
Typic.
Ustults .........Plinthustults ..... Haplic,
Typic.
Kandiustults ..... Acrustoxic,
Aquic,
Arenic Plinthic,
Arenic,
Udandic,
Andic,
Plinthic,
Aridic,
Udic,
Rhodic,
Typic.
Kanhaplustults
............. Lithic,
Acrustoxic,
Aquic,
Arenic,
Udandic,
Andic,
Plinthic,
Ombroaquic,
Aridic,
Udic,
Rhodic,
Typic.
Paleustults ........ Typic.
Rhodustults ...... Lithic,
Psammentic,
Typic.
Haplustults ....... Lithic,
Petroferric,
Aquic,
Arenic,
Ombroaquic,
Plinthic,
Kanhaplic,
Typic.
Xerults ........Palexerults ........ Aquandic,
Aquic,
Andic,
Typic.
Haploxerults ..... Lithic Ruptic-
Inceptic,
Lithic,
Aquic,
Andic,
Lamellic,
Psammentic,
Arenic,
Grossarenic,
Typic.
Vertisols ....... Aquerts........Salaquerts ......... Aridic,
Ustic,
Leptic,
Entic,
Chromic,
Typic.
Duraquerts........ Aridic,
Xeric,
Ustic,
Aeric,
Chromic,
Typic.
Natraquerts....... Typic.
Calciaquerts ..... Aeric,
Typic.
Dystraquerts ..... Sulfaqueptic,
Aridic,
Ustic,
Aeric,
Leptic,
Entic,
Chromic,
Typic.
154 Soil Taxonomy
Epiaquerts ........ Halic,
Sodic,
Aridic,
Xeric,
Ustic,
Aeric,
Leptic,
Entic,
Chromic,
Typic.
Endoaquerts ..... Halic,
Sodic,
Aridic,
Xeric,
Ustic,
Aeric,
Leptic,
Entic,
Chromic,
Typic.
Cryerts ........Humicryerts ...... Sodic,
Typic.
Haplocryerts ..... Sodic,
Chromic,
Typic.
Xererts ........Durixererts ....... Halic,
Sodic,
Aquic,
Aridic,
Udic,
Haplic,
Chromic,
Typic.
Calcixererts ...... Lithic,
Petrocalcic,
Aridic,
Leptic,
Entic,
Chromic,
Typic.
Haploxererts ..... Lithic,
Halic,
Sodic,
Aridic,
Aquic,
Udic,
Leptic,
Entic,
Chromic,
Names of Orders, Suborders, Great Groups, and Subgroups--Continued
Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Typic.
Torrerts .......Salitorrerts........ Aquic,
Leptic,
Entic,
Chromic,
Typic.
Gypsitorrerts .... Chromic,
Typic.
Calcitorrerts ..... Petrocalcic,
Leptic,
Entic,
Chromic,
Typic.
Haplotorrerts .... Halic,
Sodic,
Leptic,
Entic,
Chromic,
Typic.
Usterts .........Dystrusterts ...... Lithic,
Aquic,
Aridic,
Udic,
Leptic,
Entic,
Chromic,
Typic.
Salusterts .......... Lithic,
Sodic,
Aquic,
Aridic,
Leptic,
Entic,
Chromic,
Typic.
Gypsiusterts...... Lithic,
Halic,
Sodic,
Aridic,
Udic,
Leptic,
Entic,
Chromic,
Typic.
Calciusterts....... Lithic,
Halic,
Sodic,
Petrocalcic,
Aridic,
Nomenclature 155
Names of Orders, Suborders, Great Groups,
and Subgroups--Continued
Order Suborder Great Group Subgroup
subgroup. Using an adjective taken from the suborder (“Udic”)
would not suggest that the difference is one of aeration alone.
If the only aberrant feature of a Hapludult is redoximorphic
features that are too shallow for a Typic Hapludult, the
adjective Aquic is used in the subgroup name. If redox
depletions (accompanied by aquic conditions unless the soils
are artificially drained) appear within the upper 60 cm of the
argillic horizon, the soil is called an Aquic Hapludult, not an
Aquultic Hapludult.
In other instances, the adjective in the subgroup name is
made from the first two formative elements of the appropriate
Udic,
Leptic,
Entic,
Chromic,
Typic.
Haplusterts ....... Lithic,
Halic,
Sodic,
Petrocalcic,
Gypsic,
Calcic,
Aridic Leptic,
Aridic,
Leptic Udic,
Entic Udic,
Chromic Udic,
Udic,
Leptic,
Entic,
Chromic,
Typic.
Uderts..........Dystruderts ....... Aquic,
Oxyaquic,
Leptic,
Entic,
Chromic,
Typic.
Hapluderts ........ Lithic,
Aquic,
Oxyaquic,
Leptic,
Entic,
Chromic,
Typic.
great group name in that suborder. For example, if a Paleudult
has both shallow redoximorphic features and some plinthite, it
is called a Plinthaquic Paleudult, not a Plinthaquultic
Paleudult. Note that the formative element for the order is not
repeated in the adjective if the two great groups are in the same
order.
NamesofIntergradesTowardGreatGroupsinOther
Orders
If a Hapludalf has a surface horizon that is too dark for a
Typic subgroup and approaches the properties of the surface
horizons of Mollisols, the soil is considered to intergrade to
one of the great groups of Mollisols. If the only aberrant feature
is the nature of the surface horizon, the soil is called a Mollic
Hapludalf. This soil has the feature that is common to all
Mollisols, and only the prior formative element of the order
name is used. If, in addition, the soil has gray redox depletions
in the upper part of the argillic horizon, it is considered an
intergrade toward Aquolls and is called an Aquollic Hapludalf.
Note that this name is simpler than “Aquic Mollic Hapludalf.”
The general rule is that the simplest possible name is used. If
there are several aberrant features, the adjectival forms of one
or more great group names may be required. An exception is
the adjective Argic when used in great groups of Aquods.
Rather than intergrading to one specific taxon, Argic
subgroups intergrade to orders that have argillic horizons,
specifically Alfisols and Ultisols.
Names of Subgroups not Intergrading Toward Any Known
Kind of Soil (Extragrades)
Some soils have aberrant properties that are not
characteristic of a class in a higher category of any order,
suborder, or great group. One example might be taken from the
concave pedons that are at the base of slopes, in depressions, or
in other areas where new soil material accumulates slowly on
the surface. In these soils material is added to the A horizon.
The presence of an overthickened A horizon is not used to
define any great group, but the soils lie outside the range of the
Typic subgroup and there is no class toward which they
intergrade. Hence, a descriptive adjective is required. For this
particular situation, the adjective Cumulic (L. cumulus, heap,
plus ic, Gr. ikos) is used to form the subgroup names. Pachic is
used to indicate an overthickened epipedon if there is no
evidence of new material at the surface.
Other soils lie outside the range of Typic subgroups in an
opposite direction. Such soils are, in effect, truncated by hard
rock and are shallow or are intermittent between rock outcrops.
They are, in effect, intergrades to nonsoil and are called Lithic
subgroups. The names of formative elements in groups of this
sort, which are called extragrades, are listed together with their
derivation in the table “Adjectives in Names of Extragrades and
Their Meaning.”
156 Soil Taxonomy
Adjectives in Names of Extragrades and Their Meaning
Adjective Derivation Connotation
Abruptic ................... L. abruptum, torn off ....................................................... Abrupt textural change.
Aeric1
....................... Gr. aerios, air .................................................................. Aeration.
Albic ........................ L. albus, white ................................................................. Presence of an albic horizon.
Alic .......................... Modified from aluminum ................................................ High Al3+
status.
Anionic .................... Gr. anion .......................................................................... Positively charged colloid.
Anthraquic............... Modified from Gr. anthropos, human, and
L. aqua, water................................................................ Controlled flooding.
Anthropic................. Modified from Gr. anthropos, human ............................. An anthropic epipedon.
Arenic ...................... L. arena, sand .................................................................. Sandy material between 50 and 100 cm thick.
Calcic ....................... L. calis, lime .................................................................... Presence of a calcic horizon.
Chromic ................... Gr. chroma, color............................................................. High chroma.
Cumulic ................... L. cumulus, heap.............................................................. Thickened epipedon.
Durinodic................. L. durus, hard .................................................................. Presence of durinodes.
Eutric ....................... Modified from Gr. eu, good; eutrophic, fertile ............... High base status.
Fragic ....................... Modified from L. fragilis, brittle .................................... Presence of fragic properties.
Glacic....................... L. glacialis, icy ................................................................ Presence of ice lenses or wedges.
Glossic ..................... Gr. glossa, tongue............................................................ Tongued horizon boundaries.
Grossarenic .............. L. grossus, thick, and L. arena, sand .............................. Thick sandy layer.
Gypsic ...................... L. gypsum, gypsum .......................................................... Presence of a gypsic horizon.
Halic ........................ Gr. hals, salt..................................................................... Salty.
Humic ...................... L. humus, earth ................................................................ Presence of organic matter.
Hydric ...................... Gr. hydor, water ............................................................... Presence of water.
Kandic ..................... Modified from kandite..................................................... Presence of 1:1 layer silicate clays.
Lamellic ................... L. lamella, dim ................................................................ Presence of lamellae.
Leptic ....................... Gr. leptos, thin................................................................. A thin soil.
Limnic ..................... Modified from Gr. limn, lake .......................................... Presence of a limnic layer.
Lithic ....................... Gr. lithos, stone ............................................................... Presence of a shallow lithic contact.
Natric ....................... Modified from natrium, sodium ...................................... Presence of sodium.
Nitric........................ Modified from nitron ....................................................... Presence of nitrate salts.
Ombroaquic ............. Gr. ombros, rain, and aquic............................................. Surface wetness.
Oxyaquic.................. Oxy, representing oxygen, and aquic .............................. Aerated.
Pachic ...................... Gr. pachys, thick.............................................................. A thick epipedon.
Petrocalcic ............... Gr. petra, rock, and calcic from calcium ........................ Presence of a petrocalcic horizon.
Petroferric ................ Gr. petra, rock, and L. ferrum, iron ................................ Presence of a petroferric contact (ironstone).
Petrogypsic .............. Gr. petra, rock, and L. gypsum, gypsum......................... Presence of a petrogypsic horizon.
Petronodic ................ Modified from petra, rock, and nodulus, a little knot .... Presence of concretions and/or nodules.
Placic ....................... Gr. base of plax, flat stone ............................................... Presence of a thin pan (placic horizon).
Plinthic .................... Modified from Gr. plinthos, brick ................................... Presence of plinthite.
Rhodic...................... Gr. base of rhodon, rose .................................................. Dark red color.
Ruptic1
..................... L. ruptum, broken ............................................................ Intermittent or broken horizons.
Sodic ........................ Modified from sodium ..................................................... Presence of sodium salts.
Sombric.................... F. sombre, dark ................................................................ Presence of a sombric horizon.
Sulfic........................ L. sulfur, sulfur ................................................................ Presence of sulfides or their oxidation products.
Terric ....................... L. terra, earth .................................................................. A mineral substratum.
Thapto(ic)1
............... Gr. thapto, buried............................................................ A buried soil.
Umbric ..................... L. base of umbra, shade................................................... Presence of an umbric epipedon.
Xanthic .................... Gr. xanthos ...................................................................... Yellow.
1
Not strictly an extragrade. Name used to indicate a special departure from the Typic subgroup.
Nomenclature 157
NamesofMultipleSubgroupsIntergradingBetweenTwoGiven
GreatGroups
Two or more subgroups in a given great group may be
intergrades to the same class of soil or even to nonsoil. In one
area, for example, the horizons may be continuous; in another,
discontinuous; and in a third, buried. Also, the properties of
two classes may be mixed in a single horizon in one area but
may be in separate horizons in another area. A soil of class X
may be developing from or toward class Y, producing subgroups
that have different properties.
If the intergrade is one in which horizons are intermittent,
the adjective Ruptic (L. ruptum, broken) is used in the
subgroup name. The substantive in the name is the one for the
kind of soil having the greatest area in the pedon; the
adjectives are formed from the names of the kinds that have the
lesser area, preceded by the adjective Ruptic and connected by
hyphens. Thus, if X is dominant and Y is minor, the soil is
named Ruptic-Yic X. For example, Ruptic-Lithic Haplustolls
have a lithic contact only in part of each pedon. If the entire
pedon were lithic and the argillic horizon of the Haploxerult
were intermittent, the name would be Lithic Ruptic-Inceptic
Haploxerults. The general rule is that modifiers are hyphenated
if they apply to only part of the pedon. No hyphens are used if
the modifier applies to the entire pedon.
If the subgroup is one in which a buried soil is an important
part of the present soil, the name includes Thapto (Gr. thapto,
buried) as a modifier of the name of the buried soil. Hyphens
are used to connect Thapto with the name of the buried soil,
except in the order Andisols, where the name of the buried soil
is omitted. In Thaptic subgroups of Andisols, the buried soil is
normally an Andisol. Thus, soil X that includes a buried soil,
Y, is called Thapto-Yic X. A Humaquept that has a histic
epipedon is called a Histic Humaquept, but a Fluvaquent in
which a Histosol or Histic epipedon has been buried is called a
Thapto-Histic Fluvaquent.
Arrangement of modifiers.—Modifiers are arranged
alphabetically, for example, Aquic Arenic Hapludults.
Names of Families
Each family requires one or more names. The technical
family name consists of a series of descriptive terms modifying
the subgroup name. For these terms we take the class names
that are given in chapter 21 for particle-size class, mineralogy,
and so on, in family differentiae. The descriptive terms in the
names of families are given in a consistent order, which is as
follows: particle-size class, mineralogy class, cation-exchange
activity class, calcareous and reaction class, soil temperature
class, soil depth class, rupture resistance class, classes of
coatings, and classes of cracks.
Redundancy in the names of families should be avoided.
Particle-size class and temperature classes should not be used
in the family name if they are specified above the family level.
Psamments, by definition, all have a sand or loamy sand texture
and are in a sandy particle-size class, unless they are ashy. It is
therefore redundant to specify a particle-size class for
Psamments, unless they are ashy.
Rules of Nomenclature
For uniformity, certain rules are followed.
First, the names are considered to be modern vernacular
nouns. They are treated as masculine nouns in languages that
have grammatical gender. While only the names of the orders
have a suffix meaning “soil,” this meaning is understood to be
included in all names. Thus, the names are not to be converted
to adjectives that modify the word “soil.” The prior (first)
formative elements of the names of suborders and great groups
can be converted to adjectives that modify the name of the
category. Thus, one may speak of Aquic great groups, referring
to all taxa of that rank with names that include the formative
element aqu.
Second, plural forms of the nouns conform to the rules of
the language in which the names are used. If a final vowel or
suffix allows the name to fit better into a particular language, it
can be added as needed.
Third, adjectives are formed by adding the suffix ikos (Gr.),
shortened or adapted to the modern vernaculars according to
the rules of the language used. For example, in English the
ending is ic; in French, ique; and in German, isch. Adjectival
forms are placed in the position that is normal for the language
in which they are used.
Fourth, the names of the orders, suborders, and great groups
are treated as proper nouns, and the first letter is capitalized.
The adjectival forms of these names may be capitalized or not,
depending on the conventions of printing in the language in
which they are used. In the United States, each word in a
subgroup name is capitalized.
Fifth, pronunciation of the names follows the rules of the
modern vernacular in the language in which the words are
used.
Use of Single Formative Elements
The names in the tables “Formative Elements in Names of Soil
Orders,” “Formative Elements in Names of Suborders,” and
“Formative Elements in Names of Great Groups” are not the only
possible names or uses of the formative elements. There is
considerable repetition in the use of a number of formative
elements. Aqu, for example, is the prior (first) formative element
in the names of nine suborders. In this position, it implies that
the soils are completely saturated with water at some season and
that they show the effects of permanent or periodic reduction of
iron to the ferrous state. If one wishes to specify all mineral soils
that are permanently or periodically wet, one may use the
appropriate formative element to modify the name of a category
158
and speak of Aquic suborders or Aquic great groups. Such a
use of Aquic is equivalent to creating an order with all these
suborders.
It is necessary, however, to specify the categoric level of the
taxa. Aquic also is used to define subgroups of soils that are not
in Aquic suborders but that have shallow ground water at some
period and have the required redox criteria at a depth generally
of more than 50 cm. Aquic subgroups are not so wet as Aquic
suborders. One should not speak of aquic soils if one means
Aquic suborders or Aquic subgroups.
If it serves one’s purpose, many formative elements that are
repeated in the names of taxa can be used to alter the hierarchy
for the moment and to call to mind all the soils with the
property one wishes to consider. The soils in the Cryic suborder
and Gelisol order bring together all the cold soils. Calcic great
groups bring together all the soils that have a horizon of
appreciable accumulation of carbonates, and so on. The
nomenclature permits a flexible classification in which
emphasis can be shifted as needed to any of a number of
important properties that are subordinated in the arrangement
shown in the table “Names of Orders, Suborders, Great
Groups, and Subgroups.”
Literature Cited
Heller, J.L. 1963. The Nomenclature of Soils or What’s in a
Name?SoilSci.Soc.Amer. Proc.27:216-220.
159
The taxonomic class of a specific soil can be determined
by using the keys that follow in this and other chapters.
It is assumed that the reader is familiar with the definitions of
diagnostic horizons and properties that are given in chapters 3
and 4 of this publication and with the meanings of the terms
used for describing soils given in the Soil Survey Manual. The
Index at the back of this publication indicates the pages on
which definitions of terms are given.
Standard rounding conventions should be used to determine
numerical values.
Soil colors (hue, value, and chroma) are used in many of
the criteria that follow. Soil colors typically change value and
some change hue and chroma, depending on the water state.
In many of the criteria of the keys, the water state is specified.
If no water state is specified, the soil is considered to meet
the criterion if it does so when moist or dry or both moist and
dry.
All of the keys in this taxonomy are designed in such a way
that the user can determine the correct classification of a soil
by going through the keys systematically. The user must start at
the beginning of the “Key to Soil Orders” and eliminate, one
by one, all classes that include criteria that do not fit the soil in
question. The soil belongs to the first class listed for which it
meets all the required criteria.
In classifying a specific soil, the user of soil taxonomy
begins by checking through the “Key to Soil Orders” to
determine the name of the first order that, according to the
criteria listed, includes the soil in question. The next step is
to go to the page indicated to find the “Key to Suborders” of
that particular order. Then the user systematically goes through
the key to identify the suborder that includes the soil, i.e., the
first in the list for which it meets all the required criteria. The
same procedure is used to find the great group class of the soil
in the “Key to Great Groups” of the identified suborder.
Likewise, going through the “Key to Subgroups” of that great
group, the user selects as the correct subgroup name the name
of the first taxon for which the soil meets all of the required
criteria.
The family level is determined, in a similar manner, after
the subgroup has been determined. Chapter 21 can be used, as
one would use other keys in this taxonomy, to determine which
components are part of the family. The family, however,
typically has more than one component, and therefore the entire
chapter must be used. The keys to control sections for classes
used as components of a family must be used to determine the
control section before use of the keys to classes.
The descriptions and definitions of individual soil series are
not included in this text. Definitions of the series and of the
control section and examples of the application are given in
chapter 21. The classification of the series and the list of
families and their included series for the soils of the 50 States,
Puerto Rico, and the Virgin Islands are given in another
publication (Soil Series of the United States, Including Puerto
Rico and the Virgin Islands: Their Taxonomic Classification).
That publication does not include the descriptions or
definitions of the series, but descriptions of specific series are
available on request from the Natural Resources Conservation
Service. No one publication includes descriptions of all the
series.
In the “Key to Soil Orders” and the other keys that follow,
the diagnostic horizons and the properties mentioned do not
include those below any densic, lithic, paralithic, or petroferric
contact. The properties of buried soils and the properties of a
surface mantle are considered on the basis of whether or not
the soil meets the meaning of the term “buried soil” given in
chapter 1.
If a soil has a surface mantle and is not a buried soil, the top
of the original surface layer is considered the “soil surface” for
determining depth to and thickness of diagnostic horizons and
most other diagnostic soil characteristics. The only properties
of the surface mantle that are considered are soil temperature,
soil moisture (including aquic conditions), and any andic or
vitrandic properties.
If a soil profile includes a buried soil, the present soil
surface is used to determine soil moisture and temperature as
well as depth to and thickness of diagnostic horizons and other
diagnostic soil characteristics. Diagnostic horizons of the
buried soil are not considered in selecting taxa unless the
criteria in the keys specifically indicate buried horizons, such
as in Thapto-Histic subgroups. Most other diagnostic soil
characteristics of the buried soil are not considered, but organic
carbon if of Holocene age, andic soil properties, base
saturation, and all properties used to determine family and
series placement are considered.
CHAPTER 8
Identification of the Taxonomic Class of a Soil
160 Soil Taxonomy
Key to Soil Orders
A. Soils that have:
1. Permafrost within 100 cm of the soil surface; or
2. Gelic materials within 100 cm of the soil surface and
permafrost within 200 cm of the soil surface.
Gelisols, p. 445
B. Other soils that:
1. Do not have andic soil properties in 60 percent or more
of the thickness between the soil surface and either a depth
of 60 cm or a densic, lithic, or paralithic contact or duripan
if shallower; and
2. Have organic soil materials that meet one or more of
the following:
a. Overlie cindery, fragmental, or pumiceous materials
and/or fill their interstices1
and directly below these
materials, have a densic, lithic, or paralithic contact;
or
b. When added with the underlying cindery,
fragmental, or pumiceous materials, total 40 cm or more
between the soil surface and a depth of 50 cm; or
c. Constitute two-thirds or more of the total thickness
of the soil to a densic, lithic, or paralithic contact and
have no mineral horizons or have mineral horizons with
a total thickness of 10 cm or less; or
d. Are saturated with water for 30 days or more per
year in normal years (or are artificially drained), have an
upper boundary within 40 cm of the soil surface, and
have a total thickness of either:
(1) 60 cm or more if three-fourths or more of their
volume consists of moss fibers or if their bulk density,
moist, is less than 0.1 g/cm3
; or
(2) 40 cm or more if they consist either of sapric or
hemic materials, or of fibric materials with less than
three-fourths (by volume) moss fibers and a bulk
density, moist, of 0.1 g/cm3
or more.
Histosols, p. 473
C. Other soils that do not have a plaggen epipedon or an
argillic or kandic horizon above a spodic horizon, and have
one or more of the following:
1. A spodic horizon, an albic horizon in 50 percent or
more of each pedon, and a cryic soil temperature regime;
or
2. An Ap horizon containing 85 percent or more spodic
materials; or
3. A spodic horizon with all of the following
characteristics:
a. One or more of the following:
(1) A thickness of 10 cm or more; or
(2) An overlying Ap horizon; or
(3) Cementation in 50 percent or more of each
pedon; or
(4) A coarse-loamy, loamy-skeletal, or finer particlesize
class and a frigid temperature regime in the soil;
or
(5) A cryic temperature regime in the soil; and
b. An upper boundary within the following depths from
the mineral soil surface: either
(1) Less than 50 cm; or
(2) Less than 200 cm if the soil has a sandy
particle-size class in at least some part between
the mineral soil surface and the spodic horizon;
and
c. A lower boundary as follows:
(1) Either at a depth of 25 cm or more below the
mineral soil surface or at the top of a duripan or
fragipan or at a densic, lithic, paralithic, or petroferric
contact, whichever is shallowest; or
(2) At any depth,
(a) If the spodic horizon has a coarse-loamy,
loamy-skeletal, or finer particle-size class and the
soil has a frigid temperature regime; or
(b) If the soil has a cryic temperature regime;
and
d. Either:
(1) A directly overlying albic horizon in 50 percent
or more of each pedon; or
(2) No andic soil properties in 60 percent or more of
the thickness either:
(a) Within 60 cm either of the mineral soil
surface or of the top of an organic layer with andic
soil properties, whichever is shallower, if there is
no densic, lithic, or paralithic contact, duripan, or
petrocalcic horizon within that depth; or
(b) Between either the mineral soil surface or the
top of an organic layer with andic soil properties,
whichever is shallower, and a densic, lithic, or
1
Materials that meet the definition of cindery, fragmental, or pumiceous but have more
than 10 percent, by volume, voids that are filled with organic soil materials are considered to be
organic soil materials.
Identification of the Taxonomic Class of a Soil 161
paralithic contact, a duripan, or a petrocalcic
horizon.
Spodosols, p. 695
D. Other soils that have andic soil properties in 60 percent or
more of the thickness either:
1. Within 60 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever
is shallower, if there is no densic, lithic, or paralithic
contact, duripan, or petrocalcic horizon within that depth;
or
2. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon.
Andisols, p. 271
E. Other soils that have either:
1. An oxic horizon that has its upper boundary within 150
cm of the mineral soil surface and no kandic horizon that
has its upper boundary within that depth; or
2. 40 percent or more (by weight) clay in the fine-earth
fraction between the mineral soil surface and a depth of 18
cm (after mixing) and a kandic horizon that has the
weatherable-mineral properties of an oxic horizon and has
its upper boundary within 100 cm of the mineral soil
surface.
Oxisols, p. 655
F. Other soils that have:
1. A layer 25 cm or more thick, with an upper boundary
within 100 cm of the mineral soil surface, that has either
slickensides or wedge-shaped peds that have their long axes
tilted 10 to 60 degrees from the horizontal; and
2. A weighted average of 30 percent or more clay in the
fine-earth fraction either between the mineral soil surface
and a depth of 18 cm or in an Ap horizon, whichever is
thicker, and 30 percent or more clay in the fine-earth
fraction of all horizons between a depth of 18 cm and either
a depth of 50 cm or a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon if shallower; and
3. Cracks2
that open and close periodically.
Vertisols, p. 783
G. Other soils that:
1. Have:
a. An aridic soil moisture regime; and
b. An ochric or anthropic epipedon; and
c. One or more of the following with the upper
boundary within 100 cm of the soil surface: a cambic
horizon with a lower depth of 25 cm or more; a cryic
temperature regime and a cambic horizon; a calcic,
gypsic, petrocalcic, petrogypsic, or salic horizon; or a
duripan; or
d. An argillic or natric horizon; or
2. Have a salic horizon; and
a. Saturation with water in one or more layers within
100 cm of the soil surface for 1 month or more during a
normal year; and
b. A moisture control section that is dry in some or all
parts at some time during normal years; and
c. No sulfuric horizon that has its upper boundary
within 150 cm of the mineral soil surface.
Aridisols, p. 329
H. Other soils that have either:
1. An argillic or kandic horizon, but no fragipan, and a
base saturation (by sum of cations) of less than 35 percent at
one of the following depths:
a. If the epipedon has a sandy or sandy-skeletal
particle-size class throughout, either:
(1) 125 cm below the upper boundary of the argillic
horizon (but no deeper than 200 cm below the mineral
soil surface) or 180 cm below the mineral soil surface,
whichever is deeper; or
(2) At a densic, lithic, paralithic, or petroferric
contact if shallower; or
b. The shallowest of the following depths:
(1) 125 cm below the upper boundary of the argillic
or kandic horizon; or
(2) 180 cm below the mineral soil surface; or
(3) At a densic, lithic, paralithic, or petroferric
contact; or
2. A fragipan and both of the following:
a. Either an argillic or a kandic horizon above, within,
or below it or clay films 1 mm or more thick in one or
more of its subhorizons; and
b. A base saturation (by sum of cations) of less than
35 percent at the shallowest of the following depths:
2
A crack is a separation between gross polyhedrons. If the surface is strongly selfmulching,
i.e., a mass of granules, or if the soil is cultivated while cracks are open, the cracks
may be filled mainly by granular materials from the surface, but they are open in the sense that
the polyhedrons are separated. A crack is regarded as open if it controls the infiltration and
percolation of water in a dry, clayey soil.
162
(1) 75 cm below the upper boundary of the fragipan;
or
(2) 200 cm below the mineral soil surface; or
(3) At a densic, lithic, paralithic, or petroferric
contact.
Ultisols, p. 721
I. Other soils that have both of the following:
1. Either:
a. A mollic epipedon; or
b. Both a surface horizon that meets all the
requirements for a mollic epipedon except thickness after
the soil has been mixed to a depth of 18 cm and a
subhorizon more than 7.5 cm thick, within the upper part
of an argillic, kandic, or natric horizon, that meets the
color, organic-carbon content, base saturation, and
structure requirements of a mollic epipedon but is
separated from the surface horizon by an albic horizon;
and
2. A base saturation of 50 percent or more (by NH4
OAc) in
all horizons either between the upper boundary of any
argillic, kandic, or natric horizon and a depth of 125 cm
below that boundary, or between the mineral soil surface
and a depth of 180 cm, or between the mineral soil surface
and a densic, lithic, or paralithic contact, whichever depth is
shallowest.
Mollisols, p. 555
J. Other soils that do not have a plaggen epipedon and that
have either:
1. An argillic, kandic, or natric horizon; or
2. A fragipan that has clay films 1 mm or more thick in
some part.
Alfisols, p. 163
K. Other soils that have either:
1. One or more of the following:
a. A cambic horizon with its upper boundary within
100 cm of the mineral soil surface and its lower boundary
at a depth of 25 cm or more below the mineral soil surface;
or
b. A calcic, petrocalcic, gypsic, petrogypsic, or
placic horizon or a duripan with an upper boundary within
a depth of 100 cm of the mineral soil surface; or
c. A fragipan or an oxic, sombric, or spodic horizon with
an upper boundary within 200 cm of the mineral soil
surface; or
d. A sulfuric horizon that has its upper boundary within
150 cm of the mineral soil surface; or
e. A cryic temperature regime and a cambic horizon; or
2. No sulfidic materials within 50 cm of the mineral soil
surface; and both:
a. In one or more horizons between 20 and 50 cm
below the mineral soil surface, either an n value of 0.7 or
less or less than 8 percent clay in the fine-earth fraction;
and
b. One or both of the following:
(1) A salic horizon or a histic, mollic, plaggen, or
umbric epipedon; or
(2) In 50 percent or more of the layers between the
mineral soil surface and a depth of 50 cm, an
exchangeable sodium percentage of 15 or more (or a
sodium adsorption ratio of 13 or more), which
decreases with increasing depth below 50 cm, and also
ground water within 100 cm of the mineral soil
surface at some time during the year when the soil is
not frozen in any part.
Inceptisols, p. 489
L. Other soils.
Entisols, p. 389
Literature Cited
United States Department of Agriculture, Soil Conservation
Service. 1990. Soil Series of the United States, Including Puerto
Rico and the Virgin Islands: Their Taxonomic Classification.
Misc. Pub. 1483.
163
The central concept of Alfisols is that of soils that have
an ochric epipedon, an argillic horizon, and moderate to
high base saturation and in which water is held at less than
1500 kPa tension during at least 3 months each year when the
soils are warm enough for plants to grow. Alfisols may also
have a fragipan, a duripan, a kandic horizon, a natric horizon,
a petrocalcic horizon, plinthite, or other features, and these
features are used in defining the great groups within the order.
A very few Alfisols that are very wet during part of the year
have an umbric epipedon.
Alfisols that have a thermic or warmer soil temperature
regime tend to form a belt between the Aridisols of arid regions
and the Inceptisols, Ultisols, and Oxisols in areas of warm,
humid climates. Where the soil temperature regime is mesic or
cooler, the Alfisols in the United States tend to form a belt
between the Mollisols of the grasslands and the Spodosols and
Inceptisols in areas of very humid climates.
In regions of mesic and frigid soil temperature regimes,
Alfisols are mostly on late-Pleistocene deposits or surfaces. In
warmer regions, they are on late-Pleistocene or older surfaces if
there are only infrequent years when the soils lose bases by
leaching or if there is an external source of bases, such as
calcareous dust from a desert.
Most Alfisols have a udic, ustic, or xeric moisture regime,
and many have aquic conditions. Alfisols are not known to
have a perudic moisture regime. Leaching of bases from the
soils may occur almost every year or may be infrequent.
Definition of Alfisols and Limits Between
Alfisols and Soils of Other Orders
The definition of Alfisols must provide criteria that separate
Alfisols from all other orders. The aggregate of these criteria
defines the limits of Alfisols in relation to all other known
soils.
Alfisols are mineral soils that meet all of the following:
1. Unlike Histosols, Alfisols do not have organic soil
materials that meet one or more of the following:
a. Overlie cindery, fragmental, or pumiceous materials
and/or fill their interstices1
and directly below these
materials have either a densic, lithic, or paralithic contact;
or
b. When added with the underlying cindery, fragmental, or
pumiceous materials, total 40 cm or more between the soil
surface and a depth of 50 cm; or
c. Constitute two-thirds or more of the total thickness of
the soil to a densic, lithic, or paralithic contact and have no
mineral horizons or have mineral horizons with a total
thickness of 10 cm or less; or
d. Are saturated with water for 30 days or more in normal
years (or are artificially drained), have an upper boundary
within 40 cm of the soil surface, and have a total thickness
of either:
(1) 60 cm or more if three-fourths or more of their
volume consists of moss fibers or if their bulk density,
moist, is less than 0.1 g/cm3
; or
(2) 40 cm or more if they consist either of sapric or
hemic materials, or of fibric materials with less than
three-fourths (by volume) moss fibers and a bulk density,
moist, of 0.1 g/cm3
or more;
2. Unlike Spodosols, Alfisols do not have a spodic horizon or
an Ap horizon containing 85 percent or more spodic materials
above the argillic, kandic, or natric horizon and do not have
one or more of the following:
a. An albic horizon in 50 percent or more of each pedon
and a cryic soil temperature regime; or
b. A spodic horizon with all of the following
characteristics:
(1) One or more of the following:
(a) A thickness of 10 cm or more; or
(b) An overlying Ap horizon; or
(c) Cementation in 50 percent or more of each
pedon; or
(d) A coarse-loamy, loamy-skeletal, or finer
particle-size class and a frigid soil temperature
regime; or
(e) A cryic soil temperature regime;
and
CHAPTER 9
Alfisols
1
Materials that meet the definition of cindery, fragmental, or pumiceous but have more
than 10 percent, by volume, voids that are filled with organic soil materials are considered to be
organic soil materials.
164 Soil Taxonomy
(2) An upper boundary within the following depths
from the mineral soil surface: either
(a) Less than 50 cm; or
(b) Less than 200 cm if the soil has a sandy particlesize
class between the mineral soil surface and the
spodic horizon; and
(3) A lower boundary as follows:
(a) Either at a depth of 25 cm or more below the
mineral soil surface or at the top of a duripan or
fragipan or at a densic, lithic, paralithic, or petroferric
contact, whichever is shallowest; or
(b) At any depth if the spodic horizon has a coarseloamy,
loamy-skeletal, or finer particle-size class and
the soil has a frigid temperature regime, or if the soil
has a cryic temperature regime;
3. Unlike Andisols, Alfisols have andic soil properties in less
than 60 percent of the thickness either:
a. Within 60 cm of either the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever
is shallower, if there is no densic, lithic, or paralithic
contact, duripan, or petrocalcic horizon within that depth;
or
b. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon;
4. Unlike Gelisols, Alfisols do not have:
a. Permafrost within 100 cm of the soil surface; or
b. Gelic materials within 100 cm of the soil surface and
permafrost within 200 cm of the soil surface;
5. Unlike Oxisols, Alfisols do not have:
a. An oxic horizon that has its upper boundary within 150
cm of the mineral soil surface, unless the soil also has both
an argillic or kandic horizon that has its upper boundary
within that depth and less than 40 percent (by weight) clay
in the fine-earth fraction between the mineral soil surface
and a depth of 18 cm (after mixing) or more than 10 percent
weatherable minerals; and
b. Both of the following: (1) a kandic horizon that has less
than 10 percent weatherable minerals and has an upper
boundary within 150 cm of the mineral soil surface and (2)
40 percent or more (by weight) clay in the fine-earth
fraction between the mineral soil surface and a depth of 18
cm (after mixing);
6. Unlike Vertisols, Alfisols do not have all of the following:
a. A layer 25 cm or more thick, with an upper boundary
within 100 cm of the mineral soil surface, that has either
slickensides close enough to intersect or wedge-shaped
aggregates that have their long axes tilted 10 to 60 degrees
from the horizontal; and
b. A weighted average of 30 percent or more clay in the
fine-earth fraction either between the mineral soil surface
and a depth of 18 cm or in an Ap horizon, whichever is
thicker, and 30 percent or more clay in the fine-earth
fraction of all horizons between a depth of 18 cm and either
a depth of 50 cm or a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon if shallower; and
c. Cracks2
that open and close periodically;
7. Unlike Aridisols, Alfisols do not have an aridic soil
moisture regime;
8. Unlike Ultisols, Alfisols have either:
a. An argillic or kandic horizon, but no fragipan, and a
base saturation (by sum of cations) of 35 percent or more at
one of the following depths:
(1) In an epipedon that has a sandy or sandy-skeletal
particle-size class throughout, either:
(a) 125 cm below the upper boundary of the argillic
or kandic horizon (but no deeper than 200 cm below
the mineral soil surface) or 180 cm below the mineral
soil surface, whichever is deeper; or
(b) At a densic, lithic, paralithic, or petroferric
contact if shallower; or
(2) The shallowest of the following depths:
(a) 125 cm below the upper boundary of the argillic
or kandic horizon; or
(b) 180 cm below the mineral soil surface; or
(c) At a densic, lithic, paralithic, or petroferric
contact; or
b. A fragipan and a base saturation (by sum of cations) of
35 percent or more at the shallowest of the following
depths:
(1) 75 cm below the upper boundary of the fragipan; or
(2) 200 cm below the mineral soil surface; or
(3) At a densic, lithic, paralithic, or petroferric contact;
9. Unlike Mollisols, Alfisols do not have both:
a. A mollic epipedon or both a surface horizon that meets
2
A crack is a separation between gross polyhedrons. If the surface is strongly selfmulching,
i.e., a mass of granules, or if the soil is cultivated while cracks are open, the cracks
may be filled mainly by granular materials from the surface, but they are open in the sense that
the polyhedrons are separated. A crack is regarded as open if it controls the infiltration and
percolation of water in a dry, clayey soil.
Alfisols 165
all of the requirements for a mollic epipedon except thickness
after the surface soil has been mixed to a
depth of 18 cm, and a subhorizon more than 7.5 cm thick,
within the upper part of an argillic, kandic, or natric
horizon, that meets the color, organic-carbon content, base
saturation, and structure requirements of a mollic epipedon
but is separated from the surface horizon by an albic
horizon; and
b. A base saturation of 50 percent or more (by NH4
OAc) in
all horizons either between the upper boundary of any
argillic, kandic, or natric horizon and a depth of 125 cm
below that boundary, or between the mineral soil surface
and a depth of 180 cm, or between the mineral soil surface
and a densic, lithic, or paralithic contact, whichever depth is
shallowest;
10. Unlike Inceptisols and Entisols, Alfisols have either:
a. An argillic, kandic, or natric horizon; or
b. A fragipan that has clay films 1 mm or more thick in
some part.
Representative Pedon and Data
Following is a description of a representative Alfisol. Data
for the pedon identified in this description are given in the
table “Characterization Data for an Alfisol.”
Classification: Fine, mixed, semiactive, isohyperthermic Typic
Haplustalf
Site identification number: 90P0621
Location: Killikulam Agriculture College, India
Latitude: 09 degrees, 00 minutes 00 seconds N.
Longitude: 78 degrees 00 minutes 00 seconds E.
Landscape: Plains
Microrelief: Land leveled or smooth
Slope: Plane
Elevation: 23 m above m.s.l.
Permeability class: Moderate
Drainage class: Well drained
Land use: Cropland
Vegetation: Foxtail millet
Hazard of erosion or deposition: Slight
Parent material: Alluvium derived from igneous material over
igneous rock
Diagnostic horizons: An ochric epipedon from a depth of 0 to
23 cm and an argillic horizon from a depth of 23 to 115
cm
Described by: M. Janakiraman, S. Ramu, and R.J. Engel
In the following pedon description, colors are for dry soil
unless otherwise indicated.
Ap—0 to 13 cm; yellowish red (5YR 5/6) sandy clay loam,
yellowish red (5YR 4/6) moist; weak fine subangular
blocky structure; hard, firm, sticky and plastic; common
fine roots throughout; many very fine and fine interstitial
and tubular pores; common medium rounded ironmanganese
concretions; 5 percent igneous pebbles; clear
smooth boundary.
BAt—13 to 23 cm; red (2.5YR 4/6) gravelly sandy clay loam,
dark red (2.5YR 3/6) moist; moderate fine subangular
blocky structure; slightly hard, friable, sticky and plastic;
few fine roots throughout; many fine and medium
interstitial and tubular pores; few faint clay films on faces
of peds and in pores; common medium rounded ironmanganese
concretions; 30 percent igneous pebbles;
abrupt smooth boundary.
Bt1—23 to 36 cm; dark reddish brown (2.5YR 3/4) sandy clay,
dark reddish brown (2.5YR 3/4) moist; strong fine
subangular blocky structure; friable, very sticky and
plastic; few fine roots throughout; common fine interstitial
and tubular pores; few faint clay films on faces of peds and
in pores; common medium rounded iron-manganese
concretions; 5 percent igneous pebbles; clear wavy
boundary.
Bt2—36 to 48 cm; dark reddish brown (2.5YR 3/4) sandy clay,
dark red (2.5YR 3/6) moist; strong medium angular blocky
structure; very friable, very sticky and plastic; few fine
roots throughout; common fine interstitial and tubular
pores; few faint clay films on faces of peds and in pores;
common medium rounded iron-manganese concretions; 10
percent igneous pebbles; clear smooth boundary.
Bt3—48 to 81 cm; dark reddish brown (2.5YR 3/4) very
gravelly sandy clay, dark red (2.5YR 3/6) moist; strong
medium subangular blocky structure; friable, very sticky
and plastic; few fine roots throughout; common fine and
medium interstitial and tubular pores; few faint clay films
on faces of peds and in pores; common medium rounded
iron-manganese concretions; 40 percent igneous pebbles;
gradual broken boundary.
BCt—81 to 115 cm; yellowish red (5YR 5/6) extremely
gravelly sandy clay and weathered bedrock, 50 percent
yellowish red (5YR 4/6) and 50 percent reddish yellow
(5YR 6/8) moist; moderate fine subangular blocky
structure; very friable, very sticky and plastic; few fine
roots throughout; common fine and medium interstitial
and tubular pores; few faint clay films on faces of peds and
in pores; common medium rounded iron-manganese
concretions; 65 percent igneous pebbles; clear broken
boundary.
Cr—115 to 130 cm; reddish yellow (5YR 6/8), moist,
weathered bedrock; massive.
Key to Suborders
JA. Alfisols that have, in one or more horizons within 50 cm
of the mineral soil surface, aquic conditions (other than
anthraquic conditions) for some time in normal years (or
artificial drainage) and have one or both of the following:
166 Soil Taxonomy
Characterization Data for an Alfisol
SITE IDENTIFICATION NO.: 90P0621
CLASSIFICATION: FINE, MIXED, SEMIACTIVE, ISOHYPERTHERMIC TYPIC HAPLUSTALF
GENERAL METHODS: 1B1A, 2A1, 2B
-1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-
-----------------------------------------------------------------------------------------------------------------------------------
(- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)
CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT
SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF
NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE
<- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL
90P3691 0- 13 Ap 28.0 12.3 59.7 21.4 6.6 5.7 12.5 15.8 12.4 11.5 7.5 8 TR -- 51 8
90P3692 13- 23 BAt 17.9 8.6 73.5 12.8 3.4 5.2 11.6 18.5 14.9 14.3 14.2 13 TR -- 67 13
90P3693 23- 36 Bt1 36.9 8.5 54.6 28.1 3.5 5.0 7.4 13.6 12.4 11.7 9.5 6 TR -- 50 6
90P3694 36- 48 Bt2 48.2 9.1 42.7 39.5 4.8 4.3 7.3 10.0 9.1 7.9 8.4 8 1 -- 41 9
90P3695 48- 81 Bt3 44.7 9.7 45.6 35.3 5.3 4.4 7.0 8.2 7.4 7.7 15.3 24 2 -- 55 26
90P3696 81-115 BCt 45.5 12.6 41.9 30.5 7.3 5.3 6.4 9.4 6.2 5.5 14.4 32 20 1 70 53
90P3697 115-130 Cr1 16.9 13.3 69.8 10.2 6.9 6.4 15.5 24.3 13.9 8.7 7.4 11 2 -- 60 13
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ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD
C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE
DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL
(cm) 6A1c 6B3a 6S3 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A3a 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1
Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm
0- 13 0.68 0.60 0.37 1.62 1.77 0.028 15.7 10.4 0.08
13- 23 0.15 0.40 0.37 1.67 1.77 0.018 13.2 6.7 0.10
23- 36 0.23 0.35 0.33 1.63 1.73 0.019 15.3 12.3 0.05
36- 48 0.22 0.35 0.34 1.59 1.77 0.034 20.5 16.3 0.06
48- 81 0.13 0.39 0.32 14.3
81-115 0.09 0.50 0.37 1.58 1.70 0.015 19.1 16.7 0.02
115-130 0.02 1.24 0.63 1.70 1.78 0.014 15.6 10.6 0.08
-----------------------------------------------------------------------------------------------------------------------------------
(- NH4OAc EXTRACTABLE BASES -) ACID- EXTR (- - - -CEC - - -) Al -BASE SAT- CO3 AS RES. COND.(- - - -PH - - -)
Ca Mg Na K SUM ITY Al SUM NH4- BASES SAT SUM NH4 CaCO3 ohms mmhos CaCl2 H2O
DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc + Al OAc <2mm /cm /cm .01M
(cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 6G9b 5A3a 5A8b 5A3b 5G1 5C3 5C1 6E1g 8E1 8I 8C1f 8C1f
<- - - - - - - - - - - -meq / 100 g - - - - - - - - - - -> <- - - - -Pct - - - -> 1:2 1:1
0- 13 12.5 5.5 0.2 0.6 18.8 2.5 21.3 16.8 88 100 TR 0.22 7.1 7.7
13- 23 5.8 2.3 0.2 0.2 8.5 1.4 9.9 7.2 86 100 TR 0.14 7.1 7.8
23- 36 10.0 4.1 0.4 0.2 14.7 2.5 17.2 12.9 85 100 TR 0.11 7.0 7.5
36- 48 13.1 6.3 0.6 0.3 20.3 2.7 23.0 16.7 88 100 -- 0.17 7.1 7.8
48- 81 12.5 6.3 0.6 0.3 19.7 2.3 22.0 17.6 90 100 TR 0.16 7.0 7.7
81-115 15.3 8.2 0.7 0.5 24.7 3.0 27.7 22.8 89 100 0.16 6.8 7.5
115-130 16.9 6.1 0.5 0.2 23.7 2.1 25.8 20.9 92 100 0.11 6.8 7.7
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< - - - - - - - - - - - - - - - - - - - - - - CLAY MINERALOGY (<.002mm) - - - - - - - - - - - - - - - - - - - - - - - >
FRAC- < - - - - - X-RAY - - - - - ->< - - - THERMAL - - - ->< - - - - - - - ELEMENTAL - - - - - - - ->< - -> EGME INTERSAMPLE
TION < >< - DTA - ->< - TGA - -> SiO2 Al2O3 Fe2O3 MgO CaO K2O Na2O < > RETN PRETA<
- - - - - 7A2i - - - - - ->< - 7A6 - >< - 7A4b - >< - - - - - - - - - 7C3 - - - - - - - - ->< > 7D2 TION
NUMBER <- - >< - - - - Peak size - - - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - -><mg/g>< - ->
90P3693 TCLY KK 3 MI 1 GE 1 HE 1 29.0 13.3 0.9
90P3695 TCLY KK 4 MT 2 GE 2 MI 1 HE 1 26.0 11.4 1.0
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The chemical data are based on the fraction less than 2 mm in size.
Fraction interpretation: TCLY, total clay, <0.002 mm.
Mineral interpretation: KK, kaolinite; MI, mica; GE, goethite; HE, hematite; MT, montmorillonite.
Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.
Pedon mineralogy based on clay: Mixed.
Family mineralogy: Mixed.
Alfisols 167
1. Redoximorphic features in all layers between either the
lower boundary of an Ap horizon or a depth of 25 cm below
the mineral soil surface, whichever is deeper, and a depth of
40 cm; and one of the following within the upper 12.5 cm of
the argillic, natric, glossic, or kandic horizon:
a. 50 percent or more redox depletions with chroma of 2
or less on faces of peds and redox concentrations within
peds; or
b. Redox concentrations and 50 percent or more redox
depletions with chroma of 2 or less in the matrix; or
c. 50 percent or more redox depletions with chroma of
1 or less on faces of peds or in the matrix, or both; or
2. In the horizons that have aquic conditions, enough
active ferrous iron to give a positive reaction to alpha,alphadipyridyl
at a time when the soil is not being irrigated.
Aqualfs, p. 167
JB. Other Alfisols that have a cryic or isofrigid temperature
regime.
Cryalfs, p. 189
JC. Other Alfisols that have an ustic moisture regime.
Ustalfs, p. 228
JD. Other Alfisols that have a xeric moisture regime.
Xeralfs, p. 253
JE. Other Alfisols.
Udalfs, p. 200
Aqualfs
Aqualfs are the Alfisols that have aquic conditions for some
time in normal years (or artificial drainage) at or near the soil
surface. Their appearance is normally controlled by gray redox
depletions and higher chroma redox concentrations. In some of
these soils, ground water is near the surface during a
considerable part of the year but drops to depths below the
argillic or kandic horizon in another part of the year. In others,
the ground water may be deep most of the year but horizons
that have low hydraulic conductivity restrict the downward
movement of water and extend the period of saturation.
Aqualfs occur in many parts of the world, mostly in small
areas of late-Pleistocene deposits. In either of these situations,
the fluctuating water table that seems essential to the genesis of
Aqualfs does not occur. The wetness of a few Aqualfs is the
result of seepage.
Most Aqualfs, except for those that have a frigid or cryic
temperature regime, have some artificial drainage or other
water control and are cultivated. Rice is a common crop on the
Aqualfs that have a thermic or warmer temperature regime.
Before they were cultivated, some of the Aqualfs were under
forest vegetation and others were under grass. Nearly all
Aqualfs are believed to have supported forest vegetation at
some time in the past.
Definition
Aqualfs are the Alfisols that have, within 50 cm of the
mineral soil surface, aquic conditions for some time in normal
years (or artificial drainage) and have one or both of the
following:
1. Redoximorphic features in all layers between either the lower
boundary of an Ap horizon or a depth of 25 cm below the
mineral soil surface, whichever is deeper, and a depth of 40 cm
or more; and one of the following:
a. 50 percent or more redox depletions with chroma of 2
or less on faces of peds, and redox concentrations within
peds, of the argillic, natric, or kandic horizon; or
b. 50 percent or more redox depletions with chroma of 2
or less, and redox concentrations, in the matrix of the
argillic, natric, or kandic horizon; or
c. 50 percent or more redox depletions with chroma of 1
or less either on faces of peds or in the matrix of the argillic,
natric, or kandic horizon; or
2. In the horizons that have aquic conditions, enough active
ferrous iron to give a positive reaction to alpha,alpha-dipyridyl
at a time when the soil is not being irrigated.
Key to Great Groups
JAA. Aqualfs that have a cryic temperature regime.
Cryaqualfs, p. 171
JAB. Other Aqualfs that have one or more horizons, at a
depth between 30 and 150 cm from the mineral soil surface, in
which plinthite either forms a continuous phase or constitutes
one-half or more of the volume.
Plinthaqualfs, p. 188
JAC. Other Aqualfs that have a duripan.
Duraqualfs, p. 171
JAD. Other Aqualfs that have a natric horizon.
Natraqualfs, p. 186
JAE. Other Aqualfs that have a fragipan with an upper
boundary within 100 cm of the mineral soil surface.
Fragiaqualfs, p. 181
JAF. Other Aqualfs that have a kandic horizon.
Kandiaqualfs, p. 184
JAG. Other Aqualfs that have one or more layers, at least 25
168 Soil Taxonomy
cm thick (cumulative) within 100 cm of the mineral soil surface,
that have 50 percent or more (by volume) recognizable
bioturbation, such as filled animal burrows, wormholes, or
casts.
Vermaqualfs, p. 188
JAH. Other Aqualfs that have an abrupt textural change
between the ochric epipedon or the albic horizon and the
argillic horizon and have a moderately low or lower saturated
hydraulic conductivity in the argillic horizon.
Albaqualfs, p. 168
JAI. Other Aqualfs that have a glossic horizon.
Glossaqualfs, p. 182
JAJ. Other Aqualfs that have episaturation.
Epiaqualfs, p. 175
JAK. Other Aqualfs.
Endoaqualfs, p. 171
Albaqualfs
These are the Aqualfs with ground water seasonally perched
above a slowly permeable argillic horizon. Commonly, an albic
horizon rests abruptly on the argillic horizon, with virtually no
transitional horizon between the two. The soil temperature
regime is frigid, isomesic, mesic, or warmer. Albaqualfs do not
have a kandic horizon, a natric horizon, a fragipan, or a
duripan. They have no horizon at a depth between 30 and 150
cm from the mineral soil surface in which plinthite either
forms a continuous phase or constitutes one-half or more of the
volume. Recognizable bioturbation, such as filled animal
burrows, wormholes, or casts, is less than 50 percent (by
volume) in all layers at least 25 cm thick (cumulative) within
100 cm of the mineral soil surface. In the United States, most
Albaqualfs have a mesic, thermic, or hyperthermic temperature
regime and, unless the soils are irrigated, the albic horizon is
dry for short periods in summer in normal years. The dryness
seems essential to the genesis. Thus, Aqualfs in which the albic
horizon is rarely dry are in great groups other than Albaqualfs.
Definition
Albaqualfs are the Aqualfs that:
1. Have an abrupt textural change between an ochric
epipedon or, more commonly, an albic horizon and the argillic
horizon and have moderately low or lower saturated hydraulic
conductivity in the argillic horizon;
2. Have a frigid, mesic, isomesic, or warmer temperature
regime;
3. Have no fragipan, no duripan, no kandic horizon, and no
natric horizon;
4. Do not have one or more layers, at least 25 cm thick
(cumulative) within 100 cm of the mineral soil surface, that
have 50 percent or more (by volume) recognizable
bioturbation, such as filled animal burrows, wormholes, or
casts;
5. Have, in all horizons at a depth between 30 and 150 cm from
the mineral soil surface, less than 50 percent (by volume)
plinthite.
Key to Subgroups
JAHA. Albaqualfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 cm or more below the mineral soil surface.
Arenic Albaqualfs
JAHB. Other Albaqualfs that have both of the following:
1. One or both:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. Chroma of 3 or more in 40 percent or more of the
matrix between the lower boundary of the A or Ap horizon
and a depth of 75 cm from the mineral soil surface.
Aeric Vertic Albaqualfs
JAHC. Other Albaqualfs that have both of the following:
1. One or both:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. An Ap horizon or materials between the mineral soil
surface and a depth of 18 cm that, after mixing, have one or
more of the following:
a. A color value, moist, of 4 or more; or
b. A color value, dry, of 6 or more; or
Alfisols 169
c. Chroma of 4 or more.
Chromic Vertic Albaqualfs
JAHD. Other Albaqualfs that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Albaqualfs
JAHE. Other Albaqualfs that have both:
1. Chroma of 3 or more in 40 percent or more of the
matrix between the lower boundary of the A or Ap horizon
and a depth of 75 cm from the mineral soil surface; and
2. A mollic epipedon, an Ap horizon that meets all of the
requirements for a mollic epipedon except thickness, or
materials between the soil surface and a depth of 18 cm that
meet these requirements after mixing.
Udollic Albaqualfs
JAHF. Other Albaqualfs that have chroma of 3 or more in 40
percent or more of the matrix between the lower boundary of
the A or Ap horizon and a depth of 75 cm from the mineral
soil surface.
Aeric Albaqualfs
JAHG. Other Albaqualfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or more of the following:
1. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
2. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
3. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Albaqualfs
JAHH. Other Albaqualfs that have a mollic epipedon, an
Ap horizon that meets all of the requirements for a mollic
epipedon except thickness, or materials between the soil
surface and a depth of 18 cm that meet these requirements
aftermixing.
MollicAlbaqualfs
JAHI. Other Albaqualfs that have an umbric epipedon, an Ap
horizon that meets all of the requirements for an umbric
epipedon except thickness, or materials between the soil
surface and a depth of 18 cm that meet these requirements after
mixing.
Umbric Albaqualfs
JAHJ. Other Albaqualfs.
Typic Albaqualfs
Definition of Typic Albaqualfs
Typic Albaqualfs are the Albaqualfs that:
1. Have a texture finer than loamy fine sand in one or more
subhorizons within 50 cm of the mineral soil surface;
2. Have chroma of 2 or less in 60 percent or more of the mass
between the bottom of the A or Ap horizon and a depth of 75
cm;
3. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
4. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density of 1.0 g/cm3
or less, measured at 33 kPa
water retention, in the fraction less than 2.0 mm in size and
acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
170 Soil Taxonomy
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is equal
to 30 or more; and
5. Do not have a mollic or umbric epipedon, an Ap horizon
that meets all of the requirements for a mollic or umbric
epipedon except thickness, or materials between the soil
surface and a depth of 18 cm that meet these requirements
aftermixing.
Description of Subgroups
Typic Albaqualfs.—The central concept or Typic subgroup of
Albaqualfs is fixed on soils that have dominantly low chroma
throughout the upper part to a depth of 75 cm or more; that have
relatively high color value in the plow layer, too high for a mollic
epipedon; that do not have a thick epipedon with a sandy or
sandy-skeletal particle-size class throughout; and that do not
have slickensides, wedge-shaped aggregates, a high linear
extensibility, or wide cracks. Chroma of 3 or more, if dominant in
the horizons directly below the A or Ap horizon, indicates
saturation with water for only short periods and is a defining
feature for Aeric Albaqualfs and other subgroups that
intergrade to freely drained soils.
An Ap horizon that has the color of a mollic epipedon and
similar upper horizons that would be mixed by plowing are
associated in some parts of the United States with a native
prairie vegetation. Horizons with such colors are used to define
intergrades to the Mollisols. Soils that have slickensides,
wedge-shaped aggregates, a high linear extensibility, or wide
cracks are assigned to Vertic or combination Vertic subgroups
because these properties are shared with Vertisols. Typic
Albaqualfs do not have a surface mantle or layer in the upper
75 cm that has both a low bulk density and a high content of
weakly crystalline minerals or that consists of slightly or
moderately weathered pyroclastic materials because these
properties are shared with Andisols. Typic Albaqualfs are
extensive in parts of the Mississippi Valley in Illinois,
Missouri, Arkansas, and Louisiana and in part of Oregon and
Florida. They are uncommon elsewhere in the United States.
These soils are nearly level and are difficult to drain. Some are
cultivated, but many are used as pasture or are in forests.
Aeric Albaqualfs.—Chroma in these soils is more than 2 in
more than 40 percent of the mass between the bottom of the A
or Ap horizon and a depth of 75 cm. Most commonly, the
chroma in the matrix of the argillic horizon is 3 or more. The
period of saturation with water in these soils is shorter than the
one characteristic of Typic Albaqualfs. Aeric Albaqualfs are
intergrades between Albaqualfs and Hapludalfs. They generally
are steep enough for water to run off the surface rather than
stand on the surface. They genarally are either cultivated or
used as pasture. If they are cultivated, erosion is commonly a
problem. These soils are not extensive. They occur mostly in
Louisiana and Missouri.
Aeric Vertic Albaqualfs.—These soils are like Typic
Albaqualfs, but they are high in content of expanding clays and
have cracks 5 mm or more wide, slickensides, wedge-shaped
aggregates, or a linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
These soils also have chroma of more than 2 in more than 40
percent of the mass between the bottom of the A or Ap horizon
and a depth of 75 cm. Most commonly, the chroma in the
matrix of the argillic horizon is 3 or more. These soils are
permitted, but not required, to have upper horizons that have a
color value of 3 or less, moist, and 5 or less, dry, or have these
colors after mixing to a depth of 15 cm. The period of
saturation with water in these soils is shorter than the one
characteristic of Typic Albaqualfs. Aeric Vertic Albaqualfs are
considered to be transitional to Uderts and are not extensive in
the United States.
Aquandic Albaqualfs.—These soils are like Typic Albaqualfs,
but they have a surface mantle or layer in the upper 75 cm that
has both a low bulk density and a high content of weakly
crystalline minerals or that consists of slightly or moderately
weathered pyroclastic materials. These soils are not known to
occur in the United States.
Arenic Albaqualfs.—Arenic Albaqualfs have a sandy or
sandy-skeletal particle-size class throughout a layer extending
from the mineral soil surface to the top of an argillic horizon at
a depth of 50 cm or more below the mineral soil surface. They
may have chroma of more than 2 in more than 40 percent of
the mass between the A or Ap horizon and a depth of 75 cm.
They may also either have an Ap horizon in which the color
value, moist, is less than 4 and the value, dry, is less than 6
after the soils have been crushed and smoothed or, if not
disturbed, have these colors to a depth of 18 cm, after mixing.
These soils are not extensive. They are most common in
Florida.
Chromic Vertic Albaqualfs.—These soils are like Typic
Albaqualfs, but they are high in content of expanding clays and
have cracks 5 mm or more wide, slickensides, wedge-shaped
aggregates, or a linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
These soils are one kind of intergrade between Albaqualfs and
Aquerts. Chromic Vertic Albaqualfs are not extensive.
Mollic Albaqualfs.—These soils are like Typic Albaqualfs,
but they have either a mollic epipedon or an Ap horizon that
meets all of the requirements for a mollic epipedon except
thickness or have materials between the soil surface and a
depth of 18 cm that meet these requirements after mixing.
Many of these soils had a prairie vegetation before they were
cultivated. Mollic Albaqualfs are intergrades between
Albaqualfs and Argialbolls or Argiaquolls. They are nearly
level and cannot be easily drained. They are most extensive in
Florida and are rare elsewhere in the United States. Most of
them are cultivated.
Udollic Albaqualfs.—These soils are like Typic Albaqualfs,
Alfisols 171
but they have either a mollic epipedon or an Ap horizon that
meets all of the requirements for a mollic epipedon except
thickness or have materials between the soil surface and a
depth of 18 cm that meet these requirements after mixing.
These soils also have chroma of more than 2 in more than 40
percent of the mass between the bottom of the A or Ap horizon
and a depth of 75 cm. Most commonly, the chroma in the
matrix of the argillic horizon is 3 or more. The period of
saturation with water in these soils is shorter than the one
characteristic of Typic Albaqualfs. Udollic Albaqualfs are
intergrades between Albaqualfs and Argiudolls and are of
very small extent in the United States.
Umbric Albaqualfs.—These soils are like Typic
Albaqualfs, but they have either an umbric epipedon or an Ap
horizon that meets all of the requirements for an umbric
epipedon except thickness or have materials between the soil
surface and a depth of 18 cm that meet these requirements after
mixing. They are nearly level and cannot be easily drained.
They are most common in Florida and are rare elsewhere in the
United States.
Vertic Albaqualfs.—These soils are like Typic Albaqualfs,
but they are high in content of expanding clays and have
cracks 5 mm or more wide, slickensides, wedge-shaped
aggregates, or a linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
They also have upper horizons that have a color value of 3 or
less, moist, and 5 or less, dry, or have these colors after mixing
to a depth of 15 cm. These soils are one kind of intergrade
between Albaqualfs and Aquerts. Vertic Albaqualfs are mostly
in the central part of the United States and are common in
parts of Illinois and Missouri. Their slopes are gentle. Most of
these soils have been cleared and are used as cropland. Some of
the soils are used as woodland or pasture.
Cryaqualfs
Cryaqualfs are the Aqualfs that have a cryic or isofrigid
temperature regime. These soils are not known to occur in the
United States. The group has been proposed for other
countries, but definitions of subgroups have not been
suggested.
Key to Subgroups
JAAA. All Cryaqualfs (provisionally).
TypicCryaqualfs
Duraqualfs
Duraqualfs are the Aqualfs that have a duripan and a frigid,
mesic, isomesic, or warmer temperature regime. These soils
have no horizon at a depth between 30 and 150 cm from the
mineral soil surface in which plinthite either forms a
continuous phase or constitutes one-half or more of the volume.
Duraqualfs are not known to occur in the United States. The
group has been proposed for other countries, but definitions of
subgroups have not been suggested.
KeytoSubgroups
JACA. All Duraqualfs (provisionally).
TypicDuraqualfs
Endoaqualfs
Endoaqualfs are the Aqualfs that have an epipedon that rests
on an argillic horizon without an abrupt textural change
if the argillic horizon has moderately low or lower saturated
hydraulic conductivity. These soils do not have a kandic
horizon, a natric horizon, a fragipan, or a duripan. The soil
temperature regime is frigid, isomesic, mesic, or warmer.
Endoaqualfs have no horizon at a depth between 30 and 150
cm from the mineral soil surface in which plinthite either
forms a continuous phase or constitutes one-half or more of
the volume. Recognizable bioturbation, such as filled animal
burrows, wormholes, or casts, is less than 50 percent (by
volume) in all layers at least 25 cm thick (cumulative)
within 100 cm of the mineral soil surface. Endoaqualfs
are characterized by endoaquic saturation. The ground
water fluctuates from a level near the soil surface to below
the argillic horizon and is sometimes below a depth of
200 cm.
Before cultivation, most Endoaqualfs supported either a
deciduous broadleaf or a coniferous forest. Generally,
Endoaqualfs are nearly level, and their parent materials are
typically late-Pleistocene sediments.
Definition
Endoaqualfs are the Aqualfs that:
1. Have endosaturation and a frigid, mesic, isomesic, or
warmer soil temperature regime; and
2. Do not have a glossic, kandic, or natric horizon or a
duripan; and
3. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface; and
4. Do not have an abrupt textural change between the albic
and argillic horizons if the saturated hydraulic conductivity of
the argillic horizon is moderately low or lower; and
5. Do not have one or more layers, at least 25 cm thick
(cumulative) within 100 cm of the mineral soil surface, that
have 50 percent or more (by volume) recognizable
bioturbation, such as filled animal burrows, wormholes, or
casts; and
6. Have, in all horizons at a depth between 30 and 150 cm
from the mineral soil surface, less than 50 percent (by volume)
plinthite.
172 Soil Taxonomy
KeytoSubgroups
JAKA. Endoaqualfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, one or more of the
following:
1. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
2. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
3. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Endoaqualfs
JAKB. Other Endoaqualfs that have both of the following:
1. One or both:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. An Ap horizon or materials between the mineral soil
surface and a depth of 18 cm that, after mixing, have one or
more of the following:
a. A color value, moist, of 4 or more; or
b. A color value, dry, of 6 or more; or
c. Chroma of 4 or more.
Chromic Vertic Endoaqualfs
JAKC. Other Endoaqualfs that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral soil
surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Endoaqualfs
JAKD. Other Endoaqualfs that have:
1. Fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm
of the mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm
or more thick; and
2. In one or more horizons between the A or Ap horizon
and a depth of 75 cm below the mineral soil surface, one or
a combination of the following colors:
a. Hue of 7.5YR or redder in 50 percent or more of the
matrix; and
(1) If peds are present, chroma of 2 or more on 50
percent or more of ped exteriors or no redox
depletions with chroma of 2 or less in ped interiors; or
(2) If peds are absent, chroma of 2 or more in 50
percent or more of the matrix; or
b. In 50 percent or more of the matrix, hue of 10YR or
yellower and either:
(1) Both a color value of 3 or more (moist) and
chroma of 3 or more (moist and dry); or
(2) Chroma of 2 or more if there are no redox
concentrations.
Aeric Fragic Endoaqualfs
JAKE. Other Endoaqualfs that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Endoaqualfs
JAKF. Other Endoaqualfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 to 100 cm below the mineral soil surface.
Arenic Endoaqualfs
JAKG. Other Endoaqualfs that have a sandy or sandyskeletal
particle-size class throughout a layer extending from
Alfisols 173
the mineral soil surface to the top of an argillic horizon at a depth
of 100 cm or more below the mineral soil surface.
GrossarenicEndoaqualfs
JAKH. Other Endoaqualfs that have both:
1. A mollic epipedon, an Ap horizon that meets all of the
requirements for a mollic epipedon except thickness, or
materials between the soil surface and a depth of 18 cm that
meet these requirements after mixing; and
2. In one or more horizons between the A or Ap horizon
and a depth of 75 cm below the mineral soil surface, one or
a combination of the following colors:
a. Hue of 7.5YR or redder in 50 percent or more of the
matrix; and
(1) If peds are present, chroma of 2 or more on 50
percent or more of ped exteriors or no redox
depletions with chroma of 2 or less in ped interiors; or
(2) If peds are absent, chroma of 2 or more in 50
percent or more of the matrix; or
b. In 50 percent or more of the matrix, hue of 10YR or
yellower and either:
(1) Both a color value of 3 or more (moist) and
chroma of 3 or more; or
(2) Chroma of 2 or more if there are no redox
concentrations.
Udollic Endoaqualfs
JAKI. Other Endoaqualfs that have both:
1. An umbric epipedon, an Ap horizon that meets all of
the requirements for an umbric epipedon except thickness,
or materials between the soil surface and a depth of 18 cm
that meet these requirements after mixing; and
2. In one or more horizons between the A or Ap horizon
and a depth of 75 cm below the mineral soil surface, one or
a combination of the following colors:
a. Hue of 7.5YR or redder in 50 percent or more of the
matrix; and
(1) If peds are present, chroma of 2 or more on 50
percent or more of ped exteriors or no redox
depletions with chroma of 2 or less in ped interiors; or
(2) If peds are absent, chroma of 2 or more in 50
percent or more of the matrix; or
b. In 50 percent or more of the matrix, hue of 10YR or
yellower and either:
(1) Both a color value of 3 or more (moist) and
chroma of 3 or more; or
(2) Chroma of 2 or more if there are no redox
concentrations.
Aeric Umbric Endoaqualfs
JAKJ. Other Endoaqualfs that have, in one or more horizons
between the A or Ap horizon and a depth of 75 cm below the
mineral soil surface, in 50 percent or more of the matrix, one
or a combination of the following colors:
1. Hue of 7.5YR or redder; and
a. If peds are present, chroma of 2 or more (both moist
and dry) on 50 percent or more of ped exteriors or no
redox depletions with chroma of 2 or less (both moist and
dry) in ped interiors; or
b. If peds are absent, chroma of 2 or more (both moist
and dry); or
2. Hue of 10YR or yellower and either:
a. Both a color value of 3 or more (moist) and chroma
of 3 or more (moist and dry); or
b. Chroma of 2 or more (both moist and dry) and no
redox concentrations.
Aeric Endoaqualfs
JAKK. Other Endoaqualfs that have a mollic epipedon, an
Ap horizon that meets all of the requirements for a mollic
epipedon except thickness, or materials between the soil
surface and a depth of 18 cm that meet these requirements after
mixing.
Mollic Endoaqualfs
JAKL. Other Endoaqualfs that have an umbric epipedon, an
Ap horizon that meets all of the requirements for an umbric
epipedon except thickness, or materials between the soil
surface and a depth of 18 cm that meet these requirements after
mixing.
Umbric Endoaqualfs
JAKM. Other Endoaqualfs.
Typic Endoaqualfs
Definition of Typic Endoaqualfs
Typic Endoaqualfs are the Endoaqualfs that:
1. Do not have, in any horizons between the A or Ap horizon
and a depth of 75 cm below the mineral soil surface, in 50
percent or more of the matrix, one or a combination of the
following: either
a. Hue of 7.5YR or redder; and
(1) If peds are present, either chroma of 2 or more on
50 percent or more of ped exteriors or no redox
depletions with chroma of 2 or less in ped interiors; or
174 Soil Taxonomy
(2) If peds are absent, chroma of 2 or more in 50 percent
or more of the matrix; or
b. Hue of 10YR or yellower and either:
(1) Both a color value of 3 or more (moist) and chroma of
3 or more (moist and dry); or
(2) Chroma of 2 or more (both moist and dry) and no
redox concentrations;
2. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, any of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
3. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
4. Do not have a mollic or umbric epipedon, an Ap horizon
that meets all of the requirements for a mollic or umbric
epipedon except thickness, or materials between the mineral
soil surface and a depth of 18 cm that meet these requirements
after mixing;
5. Do not have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of an argillic horizon at a depth of 50 cm or more;
6. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick.
Description of Subgroups
Typic Endoaqualfs.—The Typic subgroup of Endoaqualfs
is fixed on soils that have dominantly low chroma throughout
the upper part to a depth of 75 cm or more; that have relatively
high color value in the plow layer, too high for a mollic or
umbric epipedon; that do not have a thick epipedon with a
sandy or sandy-skeletal particle-size class throughout; and that
do not have slickensides, wedge-shaped aggregates, a high
linear extensibility, or wide cracks. Chroma of 3 or more, if
dominant in the horizons directly below the A or Ap horizon,
indicates saturation with water for only short periods and is a
defining feature for Aeric Endoaqualfs and other subgroups
that intergrade to freely drained soils.
Soils with a mollic or umbric epipedon, or an Ap horizon
and similar upper horizons that, when mixed, have the color of
a mollic or umbric epipedon, are associated in some parts of
the United States with a native prairie vegetation. Horizons
with such colors are used to define intergrades to Mollisols and
to define Umbric extragrades. Soils that have slickensides,
wedge-shaped aggregates, a high linear extensibility, or wide
cracks are assigned to Vertic or combination Vertic subgroups
because these properties are shared with Vertisols. Soils that
have fragic soil properties in a significant volume are assigned
to Fragic or combination Fragic subgroups because these
properties are shared with Fragiaqualfs and Fragiudalfs. Typic
Endoaqualfs do not have a surface mantle or layer in the upper
75 cm that has both a low bulk density and a high content of
weakly crystalline minerals or that consists of slightly or
moderately weathered pyroclastic materials because these
properties are shared with Andisols. A thick layer of sand or
loamy sand, starting at the mineral soil surface, is the basis for
defining the Arenic and Grossarenic subgroups. Typic
Endoaqualfs are moderately extensive. They are not extensive
in any one State but occur throughout a large part of the
Eastern United States and in Oregon and Washington. These
soils are nearly level. Most have been cleared and are used as
cropland, but some are used as pasture or are in forests.
Aeric Endoaqualfs.—Below the A or Ap horizon, these
soils have chroma that is too high for the Typic subgroup, but
they are otherwise like Typic Endoaqualfs in their defined
properties and in most other properties. The high chroma
commonly occurs in the matrix of the peds in the argillic
horizon. Aeric Endoaqualfs are moderately extensive in the
north-central part of the United States, which was covered by
Wisconsinan glaciers and their valley trains. Nearly all of the
soils have been cleared and are used as cropland.
Aeric Fragic Endoaqualfs.—These soils have fragic soil
properties in a significant volume but do not have a fragipan
unless it has its upper boundary at a depth of more than 100
cm below the mineral soil surface. Below the A or Ap horizon,
these soils have chroma that is too high for the Typic subgroup.
Alfisols 175
The high chroma commonly occurs in the matrix of the peds in
the argillic horizon. The soils are otherwise like Typic
Endoaqualfs in their defined properties and in most other
properties. Aeric Fragic Endoaqualfs are rare in the United
States.
Aeric Umbric Endoaqualfs.—These soils have an umbric
epipedon or a surface horizon that meets all of the
requirements for an umbric epipedon except thickness. Below
the A or Ap horizon, these soils have chroma that is too high
for the Typic subgroup. The high chroma commonly occurs in
the matrix of the peds in the argillic horizon. The soils are
otherwise like Typic Endoaqualfs in their defined properties
and in most other properties. Aeric Umbric Endoaqualfs are
rare in the United States.
Aquandic Endoaqualfs.—These soils are like Typic
Endoaqualfs, but they have a surface mantle or layer in the
upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. These
soils are rare in the United States and are known to occur only
in the Pacific Northwest. They are in forests or have been
cleared and are used as cropland or pasture.
Arenic Endoaqualfs.—These soils have a sandy or sandyskeletal
particle-size class throughout a layer extending from
the mineral soil surface to the top of an argillic horizon at a
depth of 50 to 100 cm below the mineral soil surface. The
upper part of the argillic horizon or the lower part of the
epipedon is permitted to have, in 50 percent or more of the
matrix, chroma that is too high for Typic Endoaqualfs. Arenic
Endoaqualfs may also have either an Ap horizon with a color
value, moist, of 3 or less and a color value, dry, of 5 or less
(crushed and smoothed sample) or, if undisturbed, materials
between the soil surface and a depth of 18 cm that have these
colors after mixing. These soils are otherwise like those of the
Typic subgroup in their defined properties, but their argillic
horizon generally is sandier than that of the Typic
Endoaqualfs. In the United States, Arenic Endoaqualfs occur
principally in Florida. Many have been cleared and drained
and are used as cropland.
Chromic Vertic Endoaqualfs.—These soils are like Typic
Endoaqualfs, but they are high in content of expanding clays
and have cracks 5 mm or more wide, slickensides, wedgeshaped
aggregates, or a high linear extensibility. These soils
may also have a somewhat higher chroma in the upper part of
the argillic horizon than Typic Endoaqualfs. Chromic Vertic
Endoaqualfs are rare in the United States.
Fragic Endoaqualfs.—These soils have fragic soil
properties in a significant volume but do not have a fragipan
unless it has its upper boundary at a depth of more than 100
cm below the mineral soil surface. The soils are otherwise like
Typic Endoaqualfs in their defined properties and in most other
properties. Fragic Endoaqualfs are rare in the United States.
Grossarenic Endoaqualfs.—The sandy or sandy-skeletal
layer is thicker in these soils than in Arenic Endoaqualfs.
Grossarenic Endoaqualfs are not known to occur in the United
States.
Mollic Endoaqualfs.—These soils have a mollic epipedon
or a surface horizon that meets all of the requirements for a
mollic epipedon except thickness but have a base saturation of
less than 50 percent (by NH4
OAc) in some part of the argillic
horizon. In the United States, the dark colored surface horizon
generally is too thin to be a mollic epipedon. These soils are
intergrades between Endoaqualfs and Argiaquolls. They are
extensive in the glaciated parts of the United States. Most of
them have been cleared and drained and are used as cropland.
Udollic Endoaqualfs.—These soils are like Typic
Endoaqualfs, but they have chroma in the upper part of the
argillic horizon that is too high for the Typic subgroup and
have a mollic epipedon or a surface horizon that meets all of
the requirements for a mollic epipedon except thickness. The
high chroma commonly occurs in the matrix of the peds in the
argillic horizon. Udollic Endoaqualfs are widely scattered in
the glaciated parts of the United States, particularly in the
north-central region. Most of them have been cleared and
drained and are used as cropland.
Umbric Endoaqualfs.—These soils are like Typic
Endoaqualfs, but they have an umbric epipedon or a surface
horizon that meets all of the requirements for an umbric
epipedon except thickness. These soils are rare in the United
States.
Vertic Endoaqualfs.—These soils are like Typic
Endoaqualfs, but they are high in content of expanding clays
and have cracks 5 mm or more wide, slickensides, wedgeshaped
aggregates, or a high linear extensibility. In addition,
because Vertisols can have a mollic epipedon, the soils in this
subgroup may have either an Ap horizon with a color value,
moist, of 3 or less and a color value, dry, of 5 or less or, if
undisturbed, materials between the mineral soil surface and a
depth of 18 cm that have these color values after mixing. A
mollic epipedon is permitted if some subhorizon of the argillic
horizon has a base saturation of less than 50 percent (by
NH4
OAc). Vertic Endoaqualfs may also have a somewhat higher
chroma than Typic Endoaqualfs.
Epiaqualfs
Epiaqualfs are the Aqualfs that have an epipedon that rests
on an argillic horizon without an abrupt textural change if the
argillic horizon has low saturated hydraulic conductivity. These
soils do not have a kandic horizon, a natric horizon, a
fragipan, or a duripan. The soil temperature regime is frigid,
isomesic, mesic, or warmer. The soils have no horizon at a
depth between 30 and 150 cm from the mineral soil surface in
which plinthite either forms a continuous phase or constitutes
one-half or more of the volume. Recognizable bioturbation,
such as filled animal burrows, wormholes, or casts, is less than
50 percent (by volume) in all layers at least 25 cm thick
(cumulative) within 100 cm of the mineral soil surface. The
176 Soil Taxonomy
soils have epiaquic saturation during some part of the year.
Ground water is commonly perched on horizons below the
argillic horizon. It fluctuates from a level near the soil surface to
below the argillic horizon and sometimes is not evident.
Before cultivation, most Epiaqualfs supported either a
deciduous broadleaf or a coniferous forest. Generally,
Epiaqualfs are nearly level, and their parent materials are
typically late-Pleistocene sediments.
Definition
Epiaqualfs are the Aqualfs that:
1. Have episaturation and a frigid, mesic, isomesic, or
warmer temperature regime;
2. Do not have a glossic, kandic, or natric horizon or a
duripan;
3. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface;
4. Do not have an abrupt textural change between the albic
and argillic horizons if the saturated hydraulic conductivity of
the argillic horizon is moderately low or lower;
5. Do not have one or more layers, at least 25 cm thick
(cumulative) within 100 cm of the mineral soil surface, that
have 50 percent or more (by volume) recognizable
bioturbation, such as filled animal burrows, wormholes, or
casts; and
6. Have, in all horizons at a depth between 30 and 150 cm
from the mineral soil surface, less than 50 percent (by volume)
plinthite.
Key to Subgroups
JAJA. Epiaqualfs that have all of the following:
1. One or both:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. In one or more horizons between the A or Ap horizon
and a depth of 75 cm below the mineral soil surface, in 50
percent or more of the matrix, one or a combination of the
following colors:
a. Hue of 7.5YR or redder; and
(1) If peds are present, chroma of 2 or more (both
moist and dry) on 50 percent or more of ped exteriors or
no redox depletions with chroma of 2 or less (both
moist and dry) in ped interiors; or
(2) If peds are absent, chroma of 2 or more (both
moist and dry); or
b. Hue of 10YR or yellower and either:
(1) Both a color value of 3 or more (moist) and
chroma of 3 or more (moist and dry); or
(2) Chroma of 2 or more (both moist and dry) and
no redox concentrations; and
3. An Ap horizon or materials between the mineral soil
surface and a depth of 18 cm that, after mixing, have one or
more of the following:
a. A color value, moist, of 4 or more; or
b. A color value, dry, of 6 or more; or
c. Chroma of 4 or more.
Aeric Chromic Vertic Epiaqualfs
JAJB. Other Epiaqualfs that have both of the following:
1. One or both:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. In one or more horizons between the A or Ap horizon
and a depth of 75 cm below the mineral soil surface, in 50
percent or more of the matrix, one or a combination of the
following colors:
a. Hue of 7.5YR or redder; and
(1) If peds are present, chroma of 2 or more (both
moist and dry) on 50 percent or more of ped exteriors
or no redox depletions with chroma of 2 or less (both
moist and dry) in ped interiors; or
(2) If peds are absent, chroma of 2 or more (both
moist and dry); or
b. Hue of 10YR or yellower and either:
(1) Both a color value of 3 or more (moist) and
chroma of 3 or more (moist and dry); or
Alfisols 177
(2) Chroma of 2 or more (both moist and dry) and no
redox concentrations.
Aeric Vertic Epiaqualfs
JAJC. Other Epiaqualfs that have both of the following:
1. One or both:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. An Ap horizon or materials between the mineral soil
surface and a depth of 18 cm that, after mixing, have one or
more of the following:
a. A color value, moist, of 4 or more; or
b. A color value, dry, of 6 or more; or
c. Chroma of 4 or more.
Chromic Vertic Epiaqualfs
JAJD. Other Epiaqualfs that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Epiaqualfs
JAJE. Other Epiaqualfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, one or more of the
following:
1. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
2. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
3. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Epiaqualfs
JAJF. Other Epiaqualfs that have:
1. Fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm
of the mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm
or more thick; and
2. In one or more horizons between the A or Ap horizon
and a depth of 75 cm below the mineral soil surface, in 50
percent or more of the matrix, one or a combination of the
following colors:
a. Hue of 7.5YR or redder; and
(1) If peds are present, chroma of 2 or more (both
moist and dry) on 50 percent or more of ped exteriors
or no redox depletions with chroma of 2 or less (both
moist and dry) in ped interiors; or
(2) If peds are absent, chroma of 2 or more (both
moist and dry); or
b. Hue of 10YR or yellower and either:
(1) Both a color value of 3 or more (moist) and
chroma of 3 or more (moist and dry); or
(2) Chroma of 2 or more (both moist and dry) and
no redox concentrations.
Aeric Fragic Epiaqualfs
JAJG. Other Epiaqualfs that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Epiaqualfs
JAJH. Other Epiaqualfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 to 100 cm below the mineral soil surface.
Arenic Epiaqualfs
178 Soil Taxonomy
JAJI. Other Epiaqualfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 100 cm or more below the mineral soil surface.
Grossarenic Epiaqualfs
JAJJ. Other Epiaqualfs that have:
1. An umbric epipedon, an Ap horizon that meets all of
the requirements for an umbric epipedon except thickness,
or materials between the soil surface and a depth of 18 cm
that meet these requirements after mixing; and
2. In one or more horizons between the A or Ap horizon
and a depth of 75 cm below the mineral soil surface, in 50
percent or more of the matrix, one or a combination of the
following colors:
a. Hue of 7.5YR or redder; and
(1) If peds are present, chroma of 2 or more (both
moist and dry) on 50 percent or more of ped exteriors
or no redox depletions with chroma of 2 or less (both
moist and dry) in ped interiors; or
(2) If peds are absent, chroma of 2 or more (both
moist and dry); or
b. Hue of 10YR or yellower and either:
(1) Both a color value of 3 or more (moist) and
chroma of 3 or more (moist and dry); or
(2) Chroma of 2 or more (both moist and dry) and
no redox concentrations.
Aeric Umbric Epiaqualfs
JAJK. Other Epiaqualfs that have both:
1. A mollic epipedon, an Ap horizon that meets all of the
requirements for a mollic epipedon except thickness, or
materials between the soil surface and a depth of 18 cm that
meet these requirements after mixing; and
2. In 50 percent or more of the matrix in one or more
horizons between the A or Ap horizon and a depth of 75 cm
below the mineral soil surface, one or a combination of the
following colors:
a. Hue of 7.5YR or redder; and
(1) If peds are present, chroma of 2 or more on 50
percent or more of ped exteriors or no redox
depletions with chroma of 2 or less in ped interiors; or
(2) If peds are absent, chroma of 2 or more in 50
percent or more of the matrix; or
b. Hue of 10YR or yellower and either:
(1) Both a color value of 3 or more (moist) and
chroma of 3 or more; or
(2) Chroma of 2 or more if there are no redox
concentrations.
Udollic Epiaqualfs
JAJL. Other Epiaqualfs that have, in one or more horizons
between the A or Ap horizon and a depth of 75 cm below the
mineral soil surface, in 50 percent or more of the matrix, one
or a combination of the following colors:
1. Hue of 7.5YR or redder; and
a. If peds are present, chroma of 2 or more (both moist
and dry) on 50 percent or more of ped exteriors or no
redox depletions with chroma of 2 or less (both moist and
dry) in ped interiors; or
b. If peds are absent, chroma of 2 or more (both moist
and dry); or
2. Hue of 10YR or yellower and either:
a. Both a color value of 3 or more (moist) and chroma
of 3 or more (moist and dry); or
b. Chroma of 2 or more (both moist and dry) and no
redox concentrations.
Aeric Epiaqualfs
JAJM. Other Epiaqualfs that have a mollic epipedon, an Ap
horizon that meets all of the requirements for a mollic
epipedon except thickness, or materials between the soil
surface and a depth of 18 cm that meet these requirements after
mixing.
Mollic Epiaqualfs
JAJN. Other Epiaqualfs that have an umbric epipedon, an Ap
horizon that meets all of the requirements for an umbric
epipedon except thickness, or materials between the soil
surface and a depth of 18 cm that meet these requirements after
mixing.
Umbric Epiaqualfs
JAJO. Other Epiaqualfs.
Typic Epiaqualfs
Definition of Typic Epiaqualfs
Typic Epiaqualfs are the Epiaqualfs that:
1. Do not have, in any horizons between the A or Ap horizon
and a depth of 75 cm below the mineral soil surface, in 50
percent or more of the matrix, one or a combination of the
following: either
a. Hue of 7.5YR or redder; and
(1) If peds are present, either chroma of 2 or more
on 50 percent or more of ped exteriors or no redox
depletions with chroma of 2 or less in ped interiors;
or
Alfisols 179
(2) If peds are absent, chroma of 2 or more in 50 percent
or more of the matrix; or
b. Hue of 10YR or yellower and either:
(1) Both a color value of 3 or more (moist) and chroma of
3 or more (moist and dry); or
(2) Chroma of 2 or more (both moist and dry) and no
redox concentrations;
2. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, any of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
3. Do not have a mollic or umbric epipedon, an Ap horizon
that meets all of the requirements for a mollic or umbric
epipedon except thickness, or materials between the mineral
soil surface and a depth of 18 cm that meet these requirements
after mixing;
4. Do not have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of an argillic horizon at a depth of 50 cm or more;
5. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
and
6. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick.
Description of Subgroups
Typic Epiaqualfs.—The central concept or Typic subgroup
of Epiaqualfs is fixed on soils that (1) have dominantly low
chroma between the A or Ap horizon and a depth of 75 cm or
more from the mineral soil surface; (2) have a lighter color
value, moist, in the plow layer, or in comparable horizons if
undisturbed, than in a mollic epipedon; and (3) do not have a
thick epipedon with a sandy or sandy-skeletal particle-size
class throughout. In addition, the soils have no surface mantle
affected by pyroclastic materials, have no cracks and
slickensides or wedge-shaped aggregates, and do not have a
linear extensibility of 6.0 cm or more to a depth of 100 cm
from the mineral soil surface.
Chroma higher than that of Typic Epiaqualfs is
characteristic of soils that are saturated for shorter periods and
serves to define intergrades to freely drained soils. Soils that
have slickensides, wedge-shaped aggregates, a high linear
extensibility, or wide cracks are assigned to Vertic or
combination Vertic subgroups because these properties are
shared with Vertisols. Soils that have fragic soil properties in a
significant volume are assigned to Fragic or combination
Fragic subgroups because these properties are shared with
Fragiaqualfs and Fragiudalfs. Typic Epiaqualfs do not have a
surface mantle or layer in the upper 75 cm that has both a low
bulk density and a high content of weakly crystalline minerals
or that consists of slightly or moderately weathered pyroclastic
materials because these properties are shared with Andisols.
Color values, moist, of 2 or 3 in a plow layer indicate a higherthan-normal
content of organic matter and form the basis for
defining intergrades to other great groups. A thick layer of
sand or loamy sand, starting at the mineral soil surface, is the
basis for defining the Arenic subgroup. Typic Epiaqualfs are
moderately extensive. They are not extensive in any one State
but occur throughout a large part of the Eastern United States
and in California and Texas. These soils are nearly level. Most
have been cleared and are used as cropland, but some are used
as pasture or are in forests.
Aeric Chromic Vertic Epiaqualfs.—These soils are like
Typic Epiaqualfs, but they are high in content of expanding
clays and have cracks 5 mm or more wide, slickensides,
wedge-shaped aggregates, or a high linear extensibility. Below
the A or Ap horizon, they have higher chroma than that in
Typic Epiaqualfs. The high chroma commonly occurs in the
matrix of the peds in the argillic horizon. Aeric Chromic Vertic
Epiaqualfs are rare in the United States.
Aeric Epiaqualfs.—Below the A or Ap horizon, these soils
have chroma that is too high for the Typic subgroup, but they
180 Soil Taxonomy
are otherwise like Typic Epiaqualfs in their defined properties
and in most other properties. The high chroma commonly
occurs in the matrix of the peds in the argillic horizon. In the
United States, Aeric Epiaqualfs are extensive in the northcentral
region, which was covered by Wisconsinan glaciers, but
are of small extent elsewhere. Nearly all have been cleared and
are used as cropland, but some are used as pasture or are in
forests.
Aeric Fragic Epiaqualfs.—These soils have fragic soil
properties in a significant volume but do not have a fragipan
unless it has its upper boundary at a depth of more than 100
cm below the mineral soil surface. Below the A or Ap horizon,
these soils have chroma that is too high for the Typic subgroup.
The high chroma commonly occurs in the matrix of the peds in
the argillic horizon. The soils are otherwise like Typic
Epiaqualfs in their defined properties and in most other
properties. Aeric Fragic Epiaqualfs are rare in the United
States.
Aeric Umbric Epiaqualfs.—These soils have an umbric
epipedon or a surface horizon that meets all of the
requirements for an umbric epipedon except thickness. Below
the A or Ap horizon, these soils have chroma that is too high
for the Typic subgroup. The high chroma commonly occurs in
the matrix of the peds in the argillic horizon. The soils are
otherwise like Typic Epiaqualfs in their defined properties and
in most other properties. Aeric Umbric Epiaqualfs are rare in
the United States.
Aeric Vertic Epiaqualfs.—These soils are like Typic
Epiaqualfs, but they are high in content of expanding clays and
have cracks 5 mm or more wide, slickensides, wedge-shaped
aggregates, or a high linear extensibility. Below the A or Ap
horizon, these soils have chroma that is too high for the Typic
subgroup. The high chroma commonly occurs in the matrix of
the peds in the argillic horizon. Aeric Vertic Epiaqualfs are
rare in the United States.
Aquandic Epiaqualfs.—These soils are like Typic
Epiaqualfs, but they have a surface mantle or layer in the upper
75 cm that has both a low bulk density and a high content of
weakly crystalline minerals or that consists of slightly or
moderately weathered pyroclastic materials. These soils are
rare in the United States and are known to occur only in the
Pacific Northwest. They are in forests or have been cleared and
are used as cropland or pasture.
Arenic Epiaqualfs.—These soils have a sandy or sandyskeletal
particle-size class throughout a layer extending from
the mineral soil surface to the top of an argillic horizon at a
depth of 50 to 100 cm below the mineral soil surface. The
upper part of the argillic horizon or the lower part of the
epipedon is permitted to have, in 50 percent or more of the
matrix, chroma that is too high for Typic Epiaqualfs. Arenic
Epiaqualfs may also have either an Ap horizon with a color
value, moist, of 3 or less and a color value, dry, of 5 or less
(crushed and smoothed sample) or, if undisturbed, materials
between the soil surface and a depth of 18 cm that have these
colors after mixing. These soils are otherwise like those of the
Typic subgroup in their defined properties. They are of small
extent in the United States and occur principally in Minnesota.
Chromic Vertic Epiaqualfs.—These soils are like Typic
Epiaqualfs, but they are high in content of expanding clays and
have cracks 5 mm or more wide, slickensides, wedge-shaped
aggregates, or a high linear extensibility. In the upper part of
the argillic horizon, they may also have somewhat higher
chroma than that in Typic Epiaqualfs. Chromic Vertic
Epiaqualfs are rare in the United States.
Fragic Epiaqualfs.—These soils have fragic soil properties
in a significant volume but do not have a fragipan unless it has
its upper boundary at a depth of more than 100 cm below the
mineral soil surface. The soils are otherwise like Typic
Epiaqualfs in their defined properties and in most other
properties. Fragic Epiaqualfs are rare in the United States.
Grossarenic Epiaqualfs.—These soils have a sandy or
sandy-skeletal particle-size class throughout a layer extending
from the mineral soil surface to the top of an argillic horizon at
a depth of 100 cm or more below the mineral soil surface.
These soils are not known to occur in the United States.
Mollic Epiaqualfs.—These soils have a mollic epipedon or
a surface horizon that meets all of the requirements for a
mollic epipedon except thickness. Soils with a mollic epipedon
have a base saturation of less than 50 percent (by NH4
OAc) in
some part of the argillic horizon. In the United States, the dark
colored surface horizon of these soils generally is too thin to be
a mollic epipedon. These soils are intergrades between
Epiaqualfs and Argiaquolls. They are moderately extensive in
the Great Lakes region of the United States. Most of them have
been cleared and drained and are used as cropland, but some
are used as pasture or are in forests.
Udollic Epiaqualfs.—These soils are like Typic Epiaqualfs,
but they have (1) in 50 percent or more of the matrix of some
horizon between the A or Ap horizon and a depth of 75 cm
from the mineral soil surface, chroma that is too high for Typic
Epiaqualfs, and (2) either a mollic epipedon or a surface
horizon that meets all of the requirements for a mollic
epipedon except thickness. A mollic epipedon is permitted in
this subgroup only if the base saturation in some part of the
argillic horizon is less than 50 percent (by NH4
OAc).
Udollic Epiaqualfs are moderately extensive in the Great
Lakes region of the United States. Most of them have been
cleared and drained and are used as cropland, but some are
used as pasture or are in forests.
Umbric Epiaqualfs.—These soils are like Typic Epiaqualfs,
but they have either an umbric epipedon, an Ap horizon that
meets all of the requirements for an umbric epipedon except
thickness, or materials between the soil surface and a depth of
18 cm that meet these requirements after mixing. These soils
are rare in the United States.
Vertic Epiaqualfs.—These soils are like Typic Epiaqualfs,
but they are high in content of expanding clays and have
cracks 5 mm or more wide, slickensides, wedge-shaped
Alfisols 181
aggregates, or a high linear extensibility. In addition, because
Typic Vertisols have a dark colored epipedon, Vertic Epiaqualfs
have either an Ap horizon with a color value, moist, of 3 or
less and a color value, dry, of 5 or less or, if undisturbed,
materials between the mineral soil surface and a depth of 18
cm that have these color values after mixing. A mollic
epipedon is permitted if some subhorizon of the argillic
horizon has a base saturation of less than 50 percent (by
NH4
OAc).
Vertic Epiaqualfs are moderately extensive. They are most
extensive in the Midwest but occur throughout a large part of
the Eastern United States. These soils are nearly level. Most
have been cleared and are used as cropland, but some are used
as pasture or are in forests.
Fragiaqualfs
Fragiaqualfs are the Aqualfs that have a fragipan within 100
cm of the mineral soil surface. Most of them have ground water
that is perched above a fragipan at some period and saturates
the soils at another period. These soils have no duripan or
natric horizon and do not have plinthite that forms a
continuous phase or constitutes more than one-half of the
matrix within some subhorizon at a depth between 30 and 150
cm from the soil surface. The soil temperature regime is frigid,
isomesic, mesic, or warmer. In the United States, the soils
generally have frigid to thermic temperature regimes. In
normal years, the albic horizon generally does not become dry,
but the ground water drops below the base of the fragipan
during summer and the soil moisture content is below field
capacity at some period. Most Fragiaqualfs in the United States
formed in Wisconsinan deposits of late-Pleistocene age and had
a broadleaf deciduous forest vegetation before they were
cultivated. Most of the soils are nearly level. Fragiaqualfs as a
group have lower base saturation than other Aqualfs.
Definition
Fragiaqualfs are the Aqualfs that:
1. Have a fragipan with an upper boundary within 100 cm of
the mineral soil surface;
2. Have a frigid, mesic, isomesic, or warmer temperature
regime;
3. Have no duripan or natric horizon;
4. Have, in all horizons at a depth between 30 and 150 cm
from the mineral soil surface, less than 50 percent (by volume)
plinthite.
Key to Subgroups
JAEA. Fragiaqualfs that have one or more layers, at least 25
cm thick (cumulative) within 100 cm of the mineral soil
surface, that have 25 percent or more (by volume) recognizable
bioturbation, such as filled animal burrows, wormholes, or
casts.
Vermic Fragiaqualfs
JAEB. Other Fragiaqualfs that have, between the A or Ap
horizon and a fragipan, a horizon with 50 percent or more
chroma of 3 or more if hue is 10YR or redder or of 4 or more if
hue is 2.5Y or yellower.
Aeric Fragiaqualfs
JAEC. Other Fragiaqualfs that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Fragiaqualfs
JAED. Other Fragiaqualfs that have an Ap horizon with a
color value, moist, of 3 or less and a color value, dry, of 5 or
less (crushed and smoothed sample) or materials between the
soil surface and a depth of 18 cm that have these color values
after mixing.
Humic Fragiaqualfs
JAEE. Other Fragiaqualfs.
Typic Fragiaqualfs
DefinitionofTypicFragiaqualfs
Typic Fragiaqualfs are the Fragiaqualfs that:
1. Have, in all horizons between the A or Ap horizon and
the fragipan, more than 50 percent chroma of 2 or less if
hue is 10YR or redder or of 3 or less if hue is 2.5Y or
yellower;
2. Have less than 5 percent (by volume) plinthite in all
subhorizons within 150 cm of the mineral soil surface;
3. Have an Ap horizon that has either or both a color value,
moist, of 4 or more or a color value, dry, of 6 or more after the
soil has been crushed and smoothed or have these color values
in the upper 18 cm after mixing; and
4. Do not have one or more layers, at least 25 cm thick
(cumulative) within 100 cm of the mineral soil surface, that
have 25 percent or more (by volume) recognizable
bioturbation, such as filled animal burrows, wormholes, or
casts.
Description of Subgroups
Typic Fragiaqualfs.—The central concept or Typic
subgroup of Fragiaqualfs is fixed on soils that have dominantly
low chroma in all horizons between the fragipan and the plow
layer, if one occurs, and that have a color value in the plow
layer that is lighter than that of an umbric epipedon. Typic
Fragiaqualfs have less than 5 percent (by volume) plinthite in
all subhorizons within 150 cm of the mineral soil surface and
182 Soil Taxonomy
have less than 25 percent (by volume) recognizable bioturbation,
such as filled animal burrows, wormholes, or casts, in all
subhorizons at least 25 cm thick (cumulative) within 100 cm of
the mineral soil surface. These soils are nearly level and are
saturated for long periods in winter and early spring. Most Typic
Fragiaqualfs in the United States are in the Central and
Northeastern States. Typic Fragiaqualfs are of moderate extent.
Most of them have been cleared and are used as cropland.
Artificial drainage is difficult, however, and some of the soils are
used as pasture or are in forests.
Aeric Fragiaqualfs.—These soils are like Typic Fragiaqualfs,
but, in some subhorizon between the A or Ap horizon and the
fragipan, they have chroma of 3 or more if hue is 10YR or redder
or chroma of 4 or more if hue is 2.5Y or yellower. The period of
saturation with water in these soils is shorter than that in the
Typic subgroup. In most areas the slope is slightly greater in
areas of Aeric Fragiaqualfs than in areas of Typic Fragiaqualfs.
Aeric Fragiaqualfs are considered intergrades between
Fragiaqualfs and Fragiudalfs.
Aeric Fragiaqualfs generally are steep enough for water to
run off the surface rather than stand on the surface. They are
extensive locally in the glaciated areas of the north-central
region of the United States but are rare elsewhere in the United
States. Most Aeric Fragiaqualfs in the United States have been
cleared and are used as cropland, but some are used as pasture
or are in forests.
Plinthic Fragiaqualfs.—These soils have 5 percent or more
(by volume) plinthite in one or more horizons within 150 cm of
the mineral soil surface. These soils are not known to occur in
the United States.
Humic Fragiaqualfs.—These soils have a mollic or umbric
epipedon or a plow layer or A horizon that meets all of the
requirements for a mollic or umbric epipedon except thickness.
These soils are known to occur only in Missouri. They had a
prairie vegetation before they were cultivated. Most of them are
now used as cropland.
Vermic Fragiaqualfs.—These soils have one or more
layers, at least 25 cm thick (cumulative) within 100 cm of the
mineral soil surface, that have 25 percent or more (by volume)
recognizable bioturbation, such as filled animal burrows,
wormholes, or casts. These soils are known to occur only in
Texas.
Glossaqualfs
Glossaqualfs are the Aqualfs that have a frigid, mesic,
isomesic, or warmer temperature regime and have a glossic
horizon. These soils do not have a fragipan, a duripan, a
kandic horizon, or a natric horizon. Plinthite constitutes less
than one-half of the volume of the matrix in all subhorizons at
a depth between 30 and 150 cm from the soil surface. The
glossic horizon is interpreted as evidence that the argillic
horizon has been partly destroyed. Tubular intrusions of albic
materials into the argillic horizon may be formed by filling of
burrows made by crayfish or of traces of taproots. Light colored
krotovinas or filled root channels should be considered albic
materials only if they have no fine stratifications and no
lamellae, if all sealing along krotovina walls has been
destroyed, and if these intrusions have, after deposition, been
leached of some free iron oxides and/or clay.
Characteristically, these soils have the most humid climates
of the Alfisols and the most water passing through the profile
and have a relatively low base saturation for soils of this order.
Before the soils were cultivated, the vegetation was mostly
deciduous hardwood forest. The parent materials are largely
basic or calcareous sediments of late-Pleistocene age. Slopes
are nearly level or concave.
Glossaqualfs are mostly in the most northern and southern
parts of the range of Aqualfs. They generally are in the Great
Lakes area and on the gulf coast. A few are in the Pacific
Northwest. Except where the temperature regime is frigid,
most of these soils have been drained and are used for
cultivated crops.
Definition
Glossaqualfs are the Aqualfs that:
1. Have a glossic horizon;
2. Have a frigid, mesic, isomesic, or warmer temperature
regime;
3. Have, in all horizons at a depth between 30 and 150 cm
from the mineral soil surface, less than 50 percent (by volume)
plinthite;
4. Do not have a fragipan, a duripan, a kandic horizon, or a
natric horizon;
5. Do not have one or more layers, at least 25 cm thick
(cumulative) within 100 cm of the mineral soil surface, that
have 50 percent or more (by volume) recognizable
bioturbation, such as filled animal burrows, wormholes, or
casts;
6. Do not have both an abrupt textural change between the
ochric epipedon or albic horizon and the argillic horizon and a
moderately low or lower saturated hydraulic conductivity in the
argillic horizon.
Key to Subgroups
JAIA. Glossaqualfs that have a histic epipedon.
Histic Glossaqualfs
JAIB. Other Glossaqualfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 cm or more below the mineral soil surface.
Arenic Glossaqualfs
JAIC. Other Glossaqualfs that have:
Alfisols 183
1. Fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of
the mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm or
more thick; and
2. In one or more horizons between the A or Ap horizon
and a depth of 75 cm below the mineral soil surface, one or
a combination of the following colors:
a. Hue of 7.5YR or redder in 50 percent or more of the
matrix; and
(1) If peds are present, chroma of 2 or more on 50
percent or more of ped exteriors or no redox
depletions with chroma of 2 or less in ped interiors; or
(2) If peds are absent, chroma of 2 or more in 50
percent or more of the matrix; or
b. In 50 percent or more of the matrix, hue of 10YR or
yellower and either:
(1) Both a color value of 3 or more (moist) and
chroma of 3 or more (moist and dry); or
(2) Chroma of 2 or more if there are no redox
concentrations.
Aeric Fragic Glossaqualfs
JAID. Other Glossaqualfs that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Glossaqualfs
JAIE. Other Glossaqualfs that have, in one or more horizons
between the A or Ap horizon and a depth of 75 cm below the
mineral soil surface, in 50 percent or more of the matrix, one
or a combination of the following colors:
1. Hue of 7.5YR or redder; and
a. If peds are present, chroma of 2 or more (both moist
and dry) on 50 percent or more of ped exteriors or no
redox depletions with chroma of 2 or less (both moist and
dry) in ped interiors; or
b. If peds are absent, chroma of 2 or more (both moist
and dry); or
2. Hue of 10YR or yellower and either:
a. Both a color value of 3 or more (moist) and chroma
of 3 or more (moist and dry); or
b. Chroma of 2 or more (both moist and dry) and no
redox concentrations.
Aeric Glossaqualfs
JAIF. Other Glossaqualfs that have a mollic epipedon, an Ap
horizon that meets all of the requirements for a mollic
epipedon except thickness, or materials between the soil
surface and a depth of 18 cm that meet these requirements after
mixing.
Mollic Glossaqualfs
JAIG. Other Glossaqualfs.
Typic Glossaqualfs
Definition of Typic Glossaqualfs
Typic Glossaqualfs are the Glossaqualfs that:
1. Do not have a histic epipedon;
2. Do not have, in any horizons between the A or Ap horizon
and a depth of 75 cm below the mineral soil surface, in 50
percent or more of the matrix, one or a combination of the
following: either
a. Hue of 7.5YR or redder; and
(1) If peds are present, either chroma of 2 or more on
50 percent or more of ped exteriors or no redox
depletions with chroma of 2 or less in ped interiors; or
(2) If peds are absent, chroma of 2 or more in 50
percent or more of the matrix; or
b. Hue of 10YR or yellower and either:
(1) Both a color value of 3 or more (moist) and chroma
of 3 or more (moist and dry); or
(2) Chroma of 2 or more (both moist and dry) and no
redox concentrations;
3. Have a texture finer than loamy fine sand in one or more
subhorizons within 50 cm of the mineral soil surface;
4. Do not have a mollic epipedon, an Ap horizon that meets
all of the requirements for a mollic epipedon except thickness,
or materials between the soil surface and a depth of 18 cm that
meet these requirements after mixing;
5. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick.
Description of Subgroups
Typic Glossaqualfs.—The central concept or Typic
subgroup of Glossaqualfs is fixed on soils that have dominantly
184 Soil Taxonomy
low chroma throughout the horizons below the A or Ap
horizon, to a depth of 75 cm or more. These soils do not have a
mollic epipedon, nor do they have a plow layer or an
equivalent horizon that meets all of the requirements for a
mollic epipedon except thickness. Soils that have a thick
epipedon with a sandy or sandy-skeletal particle-size class
throughout are assigned to the Arenic subgroup. Soils that
have fragic soil properties in a significant volume are assigned
to Fragic or combination Fragic subgroups because these
properties are shared with Fragiaqualfs and Fragiudalfs. Typic
Glossaqualfs are the wettest Glossaqualfs.
Higher chroma than that of Typic Glossaqualfs is
characteristic of the somewhat better drained Glossaqualfs and
is used to define the Aeric subgroup, which consists of
intergrades to Glossudalfs. Typic Glossaqualfs occur
throughout the areas of Glossaqualfs in the United States. Most
of them are cultivated.
Aeric Fragic Glossaqualfs.—These soils have fragic soil
properties in a significant volume but do not have a fragipan
unless it has its upper boundary at a depth of more than 100
cm below the mineral soil surface. Below the A or Ap horizon,
these soils have chroma that is too high for the Typic subgroup.
The high chroma commonly occurs in the matrix of the peds in
the argillic horizon. The soils are otherwise like Typic
Glossaqualfs in their defined properties and in most other
properties. Aeric Fragic Glossaqualfs are rare in the United
States.
Aeric Glossaqualfs.—These soils have some subhorizon
between the A or Ap horizon and a depth of 75 cm that has
chroma that is too high for Typic Glossaqualfs. The period of
saturation is somewhat shorter than that in soils of the Typic
subgroup. Aeric Glossaqualfs occur throughout the areas of
Glossaqualfs in the United States. Most of them are cultivated.
Arenic Glossaqualfs.—These soils have a sandy or sandyskeletal
layer, starting at the mineral soil surface, that is 50 cm
or more thick. The epipedon overlies an argillic horizon. The
chroma may or may not be higher than that in the Typic
subgroup. These soils occur in Florida but are not extensive in
the United States.
Fragic Glossaqualfs.—These soils have fragic soil
properties in a significant volume but do not have a fragipan
unless it has its upper boundary at a depth of more than 100
cm below the mineral soil surface. The soils are otherwise like
Typic Glossaqualfs in their defined properties and in most
other properties. Fragic Glossaqualfs are rare in the United
States.
Histic Glossaqualfs.—These soils have a Histic epipedon.
They occur near sea level and are thought to have had a lower
water table at the time the argillic horizon formed than they
have now. They are known to occur only in Florida in the
United States.
Mollic Glossaqualfs.—These soils have a mollic epipedon or
a plow layer or its equivalent, if not plowed, that meets all of the
requirements for a mollic epipedon except thickness. These
soils are known to occur only in Minnesota in the United
States.
Kandiaqualfs
These are the Aqualfs that have a frigid, mesic, isomesic, or
warmer temperature regime and a kandic horizon. These soils
do not have a fragipan, a duripan, or a natric horizon. Plinthite
constitutes less than half of the volume of the matrix in all
subhorizons at a depth between 30 and 150 cm from the soil
surface. The soils are allowed, but not required, to have a
glossic horizon. Characteristically, they have the most warm
and humid climates of the Aqualfs and the most water passing
through the profile and have a relatively low base saturation for
soils of this order. The vegetation is mostly tropical or
subtropical hardwood forest. Slopes are nearly level or concave.
Kandiaqualfs are mostly in tropical and subtropical areas.
They are rare in the United States.
Definition
Kandiaqualfs are the Aqualfs that:
1. Have a kandic horizon;
2. Have a frigid, mesic, isomesic, or warmer temperature
regime;
3. Do not have a natric horizon or a duripan;
4. Have, in all horizons at a depth between 30 and 150 cm
from the mineral soil surface, less than 50 percent (by volume)
plinthite;
5. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface.
Key to Subgroups
JAFA. Kandiaqualfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of a kandic horizon at a depth of
50 to 100 cm below the mineral soil surface.
Arenic Kandiaqualfs
JAFB. Other Kandiaqualfs that have a sandy or sandyskeletal
particle-size class throughout a layer extending from
the mineral soil surface to the top of a kandic horizon at a
depth of 100 cm or more below the mineral soil surface.
Grossarenic Kandiaqualfs
JAFC. Other Kandiaqualfs that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Kandiaqualfs
JAFD. Other Kandiaqualfs that have both:
1. An Ap horizon with a color value, moist, of 3 or less
Alfisols 185
and a color value, dry, of 5 or less (crushed and smoothed
sample) or materials between the soil surface and a depth of
18 cm that have these color values after mixing; and
2. In one or more horizons between the A or Ap horizon
and a depth of 75 cm below the mineral soil surface, in 50
percent or more of the matrix, one or a combination of the
following colors:
a. Hue of 7.5YR or redder; and
(1) If peds are present, chroma of 2 or more (both
moist and dry) on 50 percent or more of ped exteriors
or no redox depletions with chroma of 2 or less (both
moist and dry) in ped interiors; or
(2) If peds are absent, chroma of 2 or more (both
moist and dry); or
b. Hue of 10YR or yellower and either:
(1) Both a color value of 3 or more (moist) and
chroma of 3 or more (moist and dry); or
(2) Chroma of 2 or more (both moist and dry) and
no redox concentrations.
Aeric Umbric Kandiaqualfs
JAFE. Other Kandiaqualfs that have, in one or more horizons
between the A or Ap horizon and a depth of 75 cm below the
mineral soil surface, in 50 percent or more of the matrix, one
or a combination of the following colors:
1. Hue of 7.5YR or redder; and
a. If peds are present, chroma of 2 or more (both moist
and dry) on 50 percent or more of ped exteriors or no
redox depletions with chroma of 2 or less (both moist and
dry) in ped interiors; or
b. If peds are absent, chroma of 2 or more (both moist
and dry); or
2. Hue of 10YR or yellower and either:
a. Both a color value of 3 or more (moist) and chroma
of 3 or more (moist and dry); or
b. Chroma of 2 or more (both moist and dry) and no
redox concentrations.
Aeric Kandiaqualfs
JAFF. Other Kandiaqualfs that have an umbric epipedon, an
Ap horizon that meets all of the requirements for an umbric
epipedon except thickness, or materials between the soil
surface and a depth of 18 cm that meet these requirements after
mixing.
Umbric Kandiaqualfs
JAFG. Other Kandiaqualfs.
Typic Kandiaqualfs
DefinitionofTypicKandiaqualfs
Typic Kandiaqualfs are the Kandiaqualfs that:
1. Do not have, in any horizons between the A or Ap horizon
and a depth of 75 cm below the mineral soil surface, in 50
percent or more of the matrix, one or a combination of the
following: either
a. Hue of 7.5YR or redder; and
(1) If peds are present, either chroma of 2 or more on
50 percent or more of ped exteriors or no redox
depletions with chroma of 2 or less in ped interiors; or
(2) If peds are absent, chroma of 2 or more in 50
percent or more of the matrix; or
b. Hue of 10YR or yellower and either:
(1) Both a color value of 3 or more (moist) and chroma
of 3 or more (moist and dry); or
(2) Chroma of 2 or more (both moist and dry) and no
redox concentrations;
2. Have an Ap horizon that has either a color value, moist, of
4 or more or a color value, dry, of 6 or more after the soil has
been crushed or have these color values in the upper 18 cm
after mixing;
3. Have a texture finer than loamy fine sand in one or more
subhorizons within 50 cm of the mineral soil surface;
4. Do not have a horizon within 150 cm of the soil surface
that has 5 percent or more plinthite, by volume.
Description of Subgroups
Typic Kandiaqualfs.—The central concept or Typic
subgroup of Kandiaqualfs is fixed on soils that (1) have
dominantly low chroma between the A or Ap horizon and a
depth of 75 cm or more from the mineral soil surface; (2) have
a lighter color value, moist, in the plow layer, or in comparable
horizons if undisturbed, than in an umbric epipedon; and (3)
do not have a thick epipedon with a sandy or sandy-skeletal
particle-size class throughout.
Chroma higher than that of Typic Kandiaqualfs is
characteristic of soils that are saturated for shorter periods and
serves to define intergrades to freely drained soils. Color
values, moist, of 2 or 3 in a plow layer indicate a higher-thannormal
content of organic matter and form the basis for
defining intergrades to other great groups. A thick layer of
sand or loamy sand, starting at the mineral soil surface, is the
basis for defining the Arenic and Grossarenic subgroups. Typic
Kandiaqualfs are not known to occur in the United States.
Aeric Kandiaqualfs.—Below the A or Ap horizon, these
soils have chroma that is too high for the Typic subgroup, but
they are otherwise like Typic Kandiaqualfs in their defined
properties and in most other properties. Aeric Kandiaqualfs are
not known to occur in the United States.
186 Soil Taxonomy
Aeric Umbric Kandiaqualfs.—These soils have an umbric
epipedon or a surface horizon that meets all of the
requirements for an umbric epipedon except thickness. Below
the A or Ap horizon, these soils have chroma that is too high for
the Typic subgroup. They are otherwise like Typic Kandiaqualfs
in their defined properties and in most other properties. Aeric
Umbric Kandiaqualfs are not known to occur in the United
States.
Arenic Kandiaqualfs.—These soils have a sandy or sandyskeletal
particle-size class throughout a layer extending from
the mineral soil surface to the top of a kandic horizon at a
depth of 50 to 100 cm below the mineral soil surface. The
upper part of the kandic horizon or the lower part of the
epipedon is permitted to have, in 50 percent or more of the
matrix, chroma that is too high for Typic Kandiaqualfs. Arenic
Kandiaqualfs may also have either an Ap horizon with a color
value, moist, of 3 or less and a color value, dry, of 5 or less
(crushed and smoothed sample) or, if undisturbed, materials
between the soil surface and a depth of 18 cm that have these
colors after mixing. These soils are otherwise like those of the
Typic subgroup in their defined properties. Arenic
Kandiaqualfs are not known to occur in the United States.
Grossarenic Kandiaqualfs.—These soils have a sandy or
sandy-skeletal particle-size class throughout a layer extending
from the mineral soil surface to the top of a kandic horizon at a
depth of 100 cm or more below the mineral soil surface. These
soils are not known to occur in the United States.
Plinthic Kandiaqualfs.—These soils have 5 percent or
more (by volume) plinthite in one or more horizons within 150
cm of the mineral soil surface. These soils are not known to
occur in the United States.
Umbric Kandiaqualfs.—These soils have an umbric
epipedon or a plow layer or its equivalent, if not plowed, that
meets all of the requirements for an umbric epipedon except
thickness. These soils are not known to occur in the United
States.
Natraqualfs
Natraqualfs are the Aqualfs that have a natric horizon and
have a frigid, mesic, isomesic, or warmer temperature regime.
These soils do not have a duripan, and plinthite constitutes less
than one-half of the volume of the matrix in all subhorizons at
a depth between 30 and 150 cm from the soil surface.
Typically, ground water perches above the natric horizon at one
period and saturates the soils at another period. Natraqualfs are
allowed, but not required, to have a glossic horizon. In the
United States, most of these soils have a mesic, thermic, or
hyperthermic temperature regime, but a few are frigid. If
undisturbed, Natraqualfs commonly have a thin A horizon
overlying a thin albic horizon that, in turn, overlies the natric
horizon. If the soils are plowed, the two upper horizons and
part of the natric horizon or only part of the two upper
horizons may be mixed.
In the United States, the vegetation on Natraqualfs before
cultivation most commonly was grass or mixed grass and
drought-tolerant trees. In humid regions where the precipitation
is 100 cm or more, the presence of sodium generally is attributed
to very slow permeability in the natric horizon. The permeability
is so slow that there is thought to
be less leaching of sodium than there is release of sodium by
the weathering of feldspars. Many Natraqualfs in the United
States formed in loess or alluvium of Wisconsinan age.
Some Natraqualfs are in basins or on lowlands and are
subject to flooding, and the sodium in them may be supplied by
salty ground water or sea water. Characteristically, areas of
Natraqualfs are small.
Definition
Natraqualfs are the Aqualfs that:
1. Have a natric horizon;
2. Have a frigid, mesic, isomesic, or warmer temperature
regime;
3. Do not have a duripan;
4. Have, in all horizons at a depth between 30 and 150 cm
from the mineral soil surface, less than 50 percent (by volume)
plinthite.
Key to Subgroups
JADA. Natraqualfs that have one or both of the following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Natraqualfs
JADB. Other Natraqualfs that have one or more layers, at
least 25 cm thick (cumulative) within 100 cm of the mineral
soil surface, that have 25 percent or more (by volume)
recognizable bioturbation, such as filled animal burrows,
wormholes, or casts.
Vermic Natraqualfs
JADC. Other Natraqualfs that have both:
1. A glossic horizon or interfingering of albic materials
into the natric horizon; and
2. An exchangeable sodium percentage of less than 15 and
less magnesium plus sodium than calcium plus extractable
acidity either throughout the upper 15 cm of the natric
Alfisols 187
horizon or in all horizons within 40 cm of the mineral soil
surface, whichever is deeper.
Albic Glossic Natraqualfs
JADD. Other Natraqualfs that have an exchangeable sodium
percentage of less than 15 and less magnesium plus sodium than
calcium plus extractable acidity either throughout the upper 15
cm of the natric horizon or in all horizons within 40 cm of the
mineral soil surface, whichever is deeper.
Albic Natraqualfs
JADE. Other Natraqualfs that have a glossic horizon or
interfingering of albic materials into the natric horizon.
Glossic Natraqualfs
JADF. Other Natraqualfs that have a mollic epipedon, an Ap
horizon that meets all of the requirements for a mollic
epipedon except thickness, or materials between the soil
surface and a depth of 18 cm that meet these requirements after
mixing.
Mollic Natraqualfs
JADG. Other Natraqualfs.
Typic Natraqualfs
Definition of Typic Natraqualfs
Typic Natraqualfs are the Natraqualfs that:
1. Do not have a glossic horizon or interfingering of albic
materials more than 2.5 cm into the natric horizon;
2. Do not have a mollic epipedon, an Ap horizon that meets
all of the requirements for a mollic epipedon except thickness,
or materials between the soil surface and a depth of 18 cm that
meet these requirements after mixing;
3. Have, in some horizon within 40 cm of the soil surface or
within the upper 15 cm of the natric horizon, whichever is
deeper, 15 percent or more saturation with sodium or more
magnesium plus sodium than calcium plus extractable acidity;
4. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
and
5. Do not have one or more layers, at least 25 cm thick
(cumulative) within 100 cm of the mineral soil surface, that
have 25 percent or more (by volume) recognizable
bioturbation, such as filled animal burrows, wormholes, or
casts.
Description of Subgroups
Typic Natraqualfs.—The central concept or Typic
subgroup of Natraqualfs is fixed on soils that (1) have high
saturation with sodium or more magnesium and sodium than
calcium and extractable acidity in the upper part; (2) have
dominantly low chroma between the A or Ap horizon and a
depth of 75 cm or more from the mineral soil surface; (3) do
not have a glossic horizon or interfingering of albic materials
more than 2.5 cm into the natric horizon; (4) have an ochric
epipedon and do not meet any of the requirements for a mollic
epipedon, except for thickness, in the plow layer or in
comparable horizons if undisturbed; and (5) do not have both
cracks and slickensides, wedge-shaped aggregates, or a linear
extensibility of 6.0 cm or more to a depth of 100 cm from the
mineral soil surface.
Chroma higher than that of Typic Natraqualfs is characteristic
of soils that are saturated for shorter periods and serves to
define intergrades to freely drained soils. Soils that have
slickensides, wedge-shaped aggregates, a high linear
extensibility, or wide cracks are assigned to Vertic subgroups
because these properties are shared with Vertisols. Natraqualfs
that have a mollic epipedon or an epipedon that meets all of
the requirements for a mollic epipedon except thickness are
considered intergrades to Natraquolls and form the basis for
defining the Mollic subgroup. Typic Natraqualfs are not
extensive. The Typic subgroup is not necessarily the most
extensive, but it provides what seems to be the best base for
defining other subgroups. Many of these soils are in Texas, and
others are widely distributed in the United States. Because the
area of Typic Natraqualfs is small, their use generally is
determined by the use of the associated soils. Many Typic
Natraqualfs have been cleared and are used as cropland, but
some are used as pasture or are in forests. Some of these soils
are used for rice. The amount of calcium in some of these soils
is inadequate for some plants.
Albic Glossic Natraqualfs.—These soils have less than 15
percent sodium and less sodium plus magnesium than calcium
plus exchangeable acidity in the upper part of the natric
horizon or the upper part of the soils if the top of the natric
horizon is deep. These soils also have a glossic horizon or albic
materials interfingering into the natric horizon. There are
fewer problems of plant nutrition in these soils than in soils of
the Typic subgroup. Nevertheless, moisture relations as a rule
negatively affect the productivity of Albic Glossic Natraqualfs.
These soils are of small extent in the United States and are
mostly near the gulf coast. Commonly, they occur in small
areas, and the use of these soils is closely associated with the
use of the surrounding soils.
Albic Natraqualfs.—These soils have less than 15 percent
sodium and less sodium plus magnesium than calcium plus
exchangeable acidity in the upper part of the natric horizon or
188 Soil Taxonomy
the upper part of the soils if the top of the natric horizon is deep.
These soils are otherwise much like Typic Natraqualfs in defined
properties. There are fewer problems of plant nutrition in Albic
Natraqualfs than in soils of the Typic subgroup. Nevertheless,
moisture relations as a rule negatively affect the productivity of
Albic Natraqualfs. Commonly, the extent of these soils is small,
and the use of the soils is closely associated with the use of the
surrounding soils.
Glossic Natraqualfs.—These soils have a glossic horizon
or interfingering of albic materials in the upper part of the
natric horizon but are otherwise like Typic Natraqualfs in
defined properties. In general, the natric horizon is deeper in
soils of this subgroup than in Typic Natraqualfs. In the United
States, Glossic Natraqualfs are of only small extent. They occur
principally in the Mississippi River Valley, California, and
Montana. Their use generally is determined by the use of the
associated soils.
Mollic Natraqualfs.—These soils have a mollic epipedon
or a surface horizon that meets all of the requirements for a
mollic epipedon except thickness. The soils are intergrades to
Natraquolls. They are of very small extent in the United States.
Vermic Natraqualfs.—These soils have one or more layers,
at least 25 cm thick within 100 cm of the mineral soil surface,
that have 25 percent or more (by volume) recognizable
bioturbation, such as filled animal burrows, wormholes, or
casts. The soils are intergrades to Vermaqualfs. They are of
very small extent in the United States and are mainly in Texas.
Vertic Natraqualfs.—These soils are like Typic Natraqualfs,
but they are high in content of expanding clays and have cracks
5 mm or more wide, slickensides, wedge-shaped aggregates, or a
high linear extensibility. These soils are not extensive. They are
nearly level. Most have been cleared and are used as cropland,
but some are used as pasture or are in forests.
Plinthaqualfs
Plinthaqualfs are the Aqualfs that have a frigid, mesic,
isomesic, or warmer temperature regime. Plinthite constitutes
one-half or more of the volume of the matrix in some
subhorizon at a depth between 30 and 150 cm from the soil
surface. These soils are mainly in depressions in areas of wetdry
tropical and subtropical climates. They are not known to
occur in the United States, but they are reported to be extensive
in Africa south of the Sahara. They are perhaps the least used
of the Alfisols, at least in part because they tend to be too wet
in the rainy season and too dry in the dry season for most
crops. On most of these soils, the vegetation is or was savanna
or a deciduous broadleaf forest.
Definition
Plinthaqualfs are the Aqualfs that:
1. Have one or more horizons at a depth between 30 and 150
cm from the mineral soil surface in which plinthite either
forms a continuous phase or constitutes one-half or more of the
volume;
2. Have a frigid, mesic, isomesic, or warmer temperature regime.
KeytoSubgroups
JABA. All Plinthaqualfs (provisionally).
TypicPlinthaqualfs
Vermaqualfs
Vermaqualfs are the Aqualfs that have one or more layers,
at least 25 cm thick (cumulative) within 100 cm of the
mineral soil surface, that have 50 percent or more (by volume)
recognizable bioturbation, such as filled animal burrows,
wormholes, or casts. Bioturbation has destroyed less than
one-half of the volume of some part of the argillic horizon.
Krotovinas restrict water movement because they are dense,
massive, compact, and stratified. Soil horizons are obliterated
where the krotovinas occur. Significant amounts of krotovinas
in a soil affect soil morphology, soil hydrology, and soil
behavior. These soils are known to in areas occur along the
coastal plain of Texas where the bioturbation is caused by
crayfish.
Definition
Vermaqualfs are the Aqualfs that:
1. Have one or more layers, at least 25 cm thick (cumulative)
within 100 cm of the mineral soil surface, that have 50 percent
or more (by volume) recognizable bioturbation, such as filled
animal burrows, wormholes, or casts;
2. Have a frigid, mesic, isomesic, or warmer temperature
regime;
3. Have, in all horizons at a depth between 30 and 150 cm
from the mineral soil surface, less than 50 percent (by volume)
plinthite;
4. Do not have a duripan, a kandic horizon, or a natric
horizon;
5. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface.
Key to Subgroups
JAGA. Vermaqualfs that have an exchangeable sodium
percentage of 7 or more (or a sodium adsorption ratio of 6 or
more) either or both:
1. Throughout the upper 15 cm of the argillic horizon;
and/or
2. Throughout all horizons within 40 cm of the mineral
soil surface.
Natric Vermaqualfs
Alfisols 189
JAGB. Other Vermaqualfs.
TypicVermaqualfs
DefinitionofTypicVermaqualfs
Typic Vermaqualfs are the Vermaqualfs that have an
exchangeable sodium percentage of less than 7 throughout the
upper 15 cm of the argillic horizon and throughout all horizons
within 40 cm of the mineral soil surface.
Description of Subgroups
Typic Vermaqualfs.—Typic Vermaqualfs are the
Vermaqualfs that have an exchangeable sodium percentage of
less than 7 (and a sodium adsorption ratio of less than 6) both
in some part of the upper 15 cm of the argillic horizon and in
some horizon within 40 cm of the mineral soil surface.
Natric Vermaqualfs.—Natric Vermaqualfs are the
Vermaqualfs that have an exchangeable sodium percentage of 7
or more (and a sodium adsorption ratio of 6 or more) either in
some part of the upper 15 cm of the argillic horizon or in some
horizon within 40 cm of the mineral soil surface.
Cryalfs
Cryalfs are the more or less freely drained Alfisols of cold
regions. Nearly all of these soils have a cryic temperature
regime and normally have a udic moisture regime.
Cryalfs are not extensive. They formed in North America,
Eastern Europe, and Asia above 49o
N. latitude and in some
high mountains south of that latitude. In the mountains, they
tend to form below the Spodosols or Inceptisols. Most Cryalfs
are or have been under a coniferous forest. In North America
they are mainly in forests because of their short, cool growing
season.
Characteristically, Cryalfs have an O horizon, an albic
horizon, and an argillic horizon. In some areas they have a thin
A horizon. In regions of the least rainfall, they are neutral or
slightly acid in all horizons and a Bk horizon may underlie the
argillic horizon. In many of the more humid areas of their
occurrence, the lower part of the albic horizon and the upper
part of the argillic horizon are strongly or very strongly acid.
Cryalfs in the United States generally developed in
Pleistocene deposits, mostly of Wisconsinan age.
Definition
Cryalfs are the Alfisols that:
1. Do not have both aquic conditions and the colors defined
for Aqualfs; and
2. Have a cryic temperature regime.
Key to Great Groups
JBA. Cryalfs that have all of the following:
1. An argillic, kandic, or natric horizon that has its upper
boundary 60 cm or more below both:
a. The mineral soil surface; and
b. The lower boundary of any surface mantle containing
30 percent or more vitric volcanic ash, cinders, or other
vitric pyroclastic materials; and
2. A texture (in the fine-earth fraction) finer than loamy fine
sand in one or more horizons above the argillic, kandic, or
natric horizon; and
3. Either a glossic horizon or interfingering of albic materials
into the argillic, kandic, or natric horizon.
Palecryalfs, p. 198
JBB. Other Cryalfs that have a glossic horizon.
Glossocryalfs, p. 189
JBC. Other Cryalfs.
Haplocryalfs, p. 193
Glossocryalfs
Glossocryalfs are the Cryalfs that have a glossic horizon and
normally have an argillic horizon that has an upper boundary
within 60 cm of the mineral soil surface. The argillic, kandic,
or natric horizon has its upper boundary within 60 cm of the
soil surface, unless there is either a sandy or sandy-skeletal
particle-size class throughout the layers above the argillic,
kandic, or natric horizon or there is a surface mantle or layer in
the upper 75 cm consisting of slightly or moderately weathered
pyroclastic materials.
The glossic horizon commonly has tonguelike projections of
albic materials extending into the argillic horizon. These
projections are thought to indicate that the argillic horizon is
being moved deeper into the soils. In the areas where the soils
are transitional between Spodosols and Alfisols, some
Glossocryalfs have a cambic horizon that appears to be an
incipient spodic horizon. The cambic horizon is commonly
separated from the argillic horizon by an albic horizon. The
vegetation is mostly coniferous trees. A few Glossocryalfs have
been cleared and are used mostly as pasture.
Definition
Glossocryalfs are the Cryalfs that have:
1. A glossic horizon; and
2. One or more of the following:
a. An argillic, kandic, or natric horizon that has its upper
boundary at less than 60 cm below the mineral soil surface;
or
b. An argillic, kandic, or natric horizon that has its upper
190 Soil Taxonomy
boundary at less than 60 cm below the lower boundary of
any surface mantle containing 30 percent or more vitric
volcanic ash, cinders, or other vitric pyroclastic materials;
or
c. No texture (in the fine-earth fraction) finer than loamy fine
sand in any horizon above the argillic, kandic, or natric
horizon.
Key to Subgroups
JBBA. Glossocryalfs that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Glossocryalfs
JBBB. Other Glossocryalfs that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Glossocryalfs
JBBC. Other Glossocryalfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Glossocryalfs
JBBD. Other Glossocryalfs that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Glossocryalfs
JBBE. Other Glossocryalfs that have, in one or more
subhorizons within the upper 25 cm of the argillic, kandic, or
natric horizon, redox depletions with chroma of 2 or less
and also aquic conditions for some time in normal years
(or artificial drainage).
Aquic Glossocryalfs
JBBF. Other Glossocryalfs that are saturated with water in
one or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Glossocryalfs
JBBG. Other Glossocryalfs that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Glossocryalfs
JBBH. Other Glossocryalfs that have:
1. A xeric moisture regime; and
2. An Ap horizon with a color value, moist, of 3 or
less and a color value, dry, of 5 or less (crushed and
smoothed sample) or materials between the soil surface
and a depth of 18 cm that have these color values after
mixing; and
3. A base saturation of 50 percent or more (by NH4
OAc)
in all parts from the mineral soil surface to a depth of 180
cm or to a densic, lithic, or paralithic contact, whichever is
shallower.
Xerollic Glossocryalfs
JBBI. Other Glossocryalfs that have:
1. A xeric moisture regime; and
2. An Ap horizon with a color value, moist, of 3 or less
and a color value, dry, of 5 or less (crushed and smoothed
sample) or materials between the soil surface and a depth of
18 cm that have these color values after mixing.
Umbric Xeric Glossocryalfs
JBBJ. Other Glossocryalfs that:
1. Are dry in some part of the moisture control section for
45 or more days (cumulative) in normal years; and
2. Have an Ap horizon with a color value, moist, of 3 or
less and a color value, dry, of 5 or less (crushed and
smoothed sample) or materials between the soil surface and
a depth of 18 cm that have these color values after mixing;
and
Alfisols 191
3. Have a base saturation of 50 percent or more (by
NH4
OAc) in all parts from the mineral soil surface to a depth
of 180 cm or to a densic, lithic, or paralithic contact,
whichever is shallower.
Ustollic Glossocryalfs
JBBK. Other Glossocryalfs that have a xeric moisture
regime.
Xeric Glossocryalfs
JBBL. Other Glossocryalfs that are dry in some part of the
moisture control section for 45 or more days (cumulative) in
normal years.
Ustic Glossocryalfs
JBBM. Other Glossocryalfs that:
1. Have an Ap horizon with a color value, moist, of 3 or
less and a color value, dry, of 5 or less (crushed and
smoothed sample) or materials between the soil surface and
a depth of 18 cm that have these color values after mixing;
and
2. Have a base saturation of 50 percent or more (by
NH4
OAc) in all parts from the mineral soil surface to a
depth of 180 cm or to a densic, lithic, or paralithic contact,
whichever is shallower.
Mollic Glossocryalfs
JBBN. Other Glossocryalfs that have an Ap horizon with a
color value, moist, of 3 or less and a color value, dry, of 5 or
less (crushed and smoothed sample) or materials between the
soil surface and a depth of 18 cm that have these color values
after mixing.
Umbric Glossocryalfs
JBBO. Other Glossocryalfs that have a base saturation of 50
percent or more (by NH4
OAc) in all parts from the mineral soil
surface to a depth of 180 cm or to a densic, lithic, or paralithic
contact, whichever is shallower.
Eutric Glossocryalfs
JBBP. Other Glossocryalfs.
Typic Glossocryalfs
Definition of Typic Glossocryalfs
Typic Glossocryalfs are the Glossocryalfs that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have one or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
3. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
4. In any subhorizon within the upper 25 cm of the argillic,
kandic, or natric horizon, do not have redox depletions with
chroma of 2 or less and also aquic conditions;
5. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 7 or more consecutive days or 20 or
more cumulative days in normal years;
6. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick;
7. Have a udic moisture regime;
8. Are dry in some part of the moisture control section for
less than 45 days (cumulative) in normal years;
9. Have an Ap horizon with a color value, moist, of 4 or more
or a color value, dry, of 6 or more (crushed and smoothed
sample) or materials between the soil surface and a depth of 18
cm that have these color values after mixing;
10. Have a base saturation of less than 50 percent (by
192 Soil Taxonomy
NH4
OAc) in some part between the mineral soil surface and a
depth of 180 cm or a densic, lithic, or paralithic contact,
whichever is shallower.
Description of Subgroups
Typic Glossocryalfs.—The central concept or Typic
subgroup of Glossocryalfs is fixed on freely drained soils that
are deep or moderately deep to hard rock and that have a high
color value to a depth comparable to that of an Ap horizon.
The soils have a glossic horizon and are moist in all but short
periods during the growing season.
These soils do not have slickensides, wedge-shaped
aggregates, a high linear extensibility, or wide cracks because
these properties are shared with Vertisols. Soils that have both
a low bulk density and a high content of weakly crystalline
minerals or that have a high content of volcanic glass are
excluded from Typic Glossocryalfs because these properties are
shared with Andisols. Soils that have both redox depletions
with low chroma in the upper 25 cm of the argillic, kandic, or
natric horizon and ground water within this depth are excluded
from Typic Glossocryalfs because these properties are shared
with Aqualfs. Other soils that are saturated with water within
100 cm of the mineral soil surface for 20 or more consecutive
days or 30 or more cumulative days in normal years are
excluded because of importance to the use of these soils. Soils
with a layer having fragic soil properties also are excluded
because these properties are shared with Fraglossudalfs and
Fragiudalfs. Typic Glossocryalfs do not have a surface mantle
or layer in the upper 75 cm that has both a low bulk density
and a high content of weakly crystalline minerals or that
consists of slightly or moderately weathered pyroclastic
materials because these properties are shared with Andisols.
Soils that have a xeric moisture regime and other soils that are
dry for more than 45 days also are excluded because they share
properties with Xeralfs and Ustalfs. Soils that have a surface
horizon as thick as 15 cm that is dark enough to be near or
within the range of a mollic or umbric epipedon are recognized
as Mollic intergrades or Umbric extragrades.
Typic Glossocryalfs are in the mountains in the Western
United States. They generally are under a coniferous forest.
They have gentle to very steep slopes. They are of small extent
in the United States and are rare elsewhere.
Andic and Vitrandic Glossocryalfs.—These soils are like
Typic Glossocryalfs, but they have a surface mantle or layer in
the upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. These
soils occur in the high mountains of the Western United States.
They are permitted, but not required, to have redox depletions
and also a color value of 3 or less, moist, and 5 or less, dry, in
surface horizons, after mixing to a depth of 15 cm. They also
are permitted to be dry for more than 45 days. They are not
extensive. Most of them have moderate or strong slopes and
are used for limited summer grazing, as forest, or as wildlife
habitat.
Aquic Glossocryalfs.—These soils are like Typic
Glossocryalfs, but they have redox depletions with chroma of 2
or less and have horizons, within 75 cm of the surface, that are
saturated with water at some time during the year. The gray
redox depletions should not be confused with low chroma of
the glossic horizon. In addition to the redox depletions, Aquic
Glossocryalfs are permitted to have a color value of 3 or less,
moist, and 5 or less, dry, in surface horizons, after mixing to a
depth of 15 cm. The wetness is caused mainly by slowly
permeable materials in the lower horizons or the substratum.
These soils are rare in the United States.
Eutric Glossocryalfs.—These soils are like Typic
Glossocryalfs, but they have a base saturation of 50 percent or
more (by NH4
OAc) in all parts between the mineral soil surface
and a depth of 180 cm or a densic, lithic, or paralithic contact,
whichever is shallower. These soils formed mostly in
calcareous materials. They support range or coniferous forest
vegetation and have gentle to very steep slopes. They are of
small extent in the United States and are rare elsewhere.
Fragic Glossocryalfs.—These soils are like Typic
Glossocryalfs, but they have a fragipan or at least 30 percent
(by volume) peds with fragic soil properties in the upper part of
the argillic horizon. Fragic Glossocryalfs have not been
recognized in the United States.
Lithic Glossocryalfs.—These soils are permitted to have
any of the properties of Glossocryalfs. They are required to
have a lithic contact within 50 cm of the surface. These soils
are of small extent in the Western United States.
Mollic Glossocryalfs.—These soils are like Typic
Glossocryalfs, but their upper horizons have a color value of 3
or less, moist, and 5 or less, dry, after mixing to a depth of 15
cm. Mollic Glossocryalfs have a base saturation of 50 percent
or more (by NH4
OAc) in all parts from the mineral soil surface
to a depth of 180 cm or to a densic, lithic, or paralithic contact,
whichever is shallower. These soils commonly support a
coniferous forest in which the trees are more widely spaced
than is typical for Glossocryalfs. Mollic Glossocryalfs are not
extensive in the United States except very locally.
Oxyaquic Glossocryalfs.—These soils are like Typic
Glossocryalfs, but they are saturated with water within 100 cm
of the mineral soil surface for 20 or more consecutive days or
30 or more cumulative days in normal years. Oxyaquic
Glossocryalfs are permitted to have a color value of 3 or less,
moist, and 5 or less, dry, in surface horizons, after mixing to a
depth of 15 cm. The wetness is caused mainly by slowly
permeable materials in the lower horizons or the substratum.
These soils are rare in the United States.
Umbric Glossocryalfs.—These soils are like Typic
Glossocryalfs, but their upper horizons have a color value of 3
or less, moist, and 5 or less, dry, after mixing to a depth of 15
cm. These soils have a base saturation of less than 50 percent
Alfisols 193
(by NH4
OAc) in some part between the mineral soil surface and
a depth of 180 cm or to a densic, lithic, or paralithic contact,
whichever is shallower. The soils commonly support coniferous
forest. Some forests have widely spaced trees. In some areas
these soils are used as rangeland. The soils are not extensive in
the United States.
Umbric Xeric Glossocryalfs.—These soils are like Typic
Glossocryalfs, but they have a xeric moisture regime and their
upper horizons have a color value of 3 or less, moist, and 5 or
less, dry, after mixing to a depth of 15 cm. These soils have a
base saturation of less than 50 percent (by NH4
OAc) in some
part between the mineral soil surface and a depth of 180 cm or
a densic, lithic, or paralithic contact, whichever is shallower.
Umbric Xeric Glossocryalfs commonly support coniferous
forest. Some forests have widely spaced trees. In some areas
these soils are used as rangeland. They are not extensive in the
United States.
Ustic Glossocryalfs.—These soils are like Typic
Glossocryalfs, but they are dry in some part of the moisture
control section for 45 or more days (cumulative) in normal
years. They are considered to be transitional to Ustalfs. Ustic
Glossocryalfs commonly support a sparse coniferous forest with
widely spaced trees or are used as rangeland. They are not
extensive in the United States except very locally.
Ustollic Glossocryalfs.—These soils are like Typic
Glossocryalfs, but they are dry in some part of the moisture
control section for 45 or more days (cumulative) in normal
years and their upper horizons have a color value of 3 or less,
moist, and 5 or less, dry, after mixing to a depth of 15 cm.
These soils have a base saturation of 50 percent or more (by
NH4
OAc) in all parts from the mineral soil surface to a depth
of 180 cm or to a densic, lithic, or paralithic contact,
whichever is shallower. They are considered to be transitional
to Ustolls. They commonly support rangeland vegetation or a
sparse coniferous forest with widely spaced trees. They are not
extensive in the United States.
Vertic Glossocryalfs.—These soils are like Typic
Glossocryalfs, but they are high in content of expanding clays
and have cracks 5 mm or more wide, slickensides, wedgeshaped
aggregates, or a linear extensibility of 6.0 cm or more
between the mineral soil surface and either a depth of 100 cm
or a densic, lithic, or paralithic contact, whichever is shallower.
These soils are considered to be transitional to Vertisols. Vertic
Glossocryalfs support coniferous forest or are used as
rangeland. They are not extensive in the United States.
Xeric Glossocryalfs.—These soils are like Typic
Glossocryalfs, but they have a xeric moisture regime. They are
considered to be transitional to Xeralfs. Xeric Glossocryalfs
commonly support coniferous forest. Some forests have widely
spaced trees. In some areas Xeric Glossocryalfs are used as
rangeland. These soils are not extensive in the United States.
Xerollic Glossocryalfs.—These soils are like Typic
Glossocryalfs, but they have a xeric moisture regime and their
upper horizons have a color value of 3 or less, moist, and 5 or
less, dry, after mixing to a depth of 15 cm. These soils have a
base saturation of 50 percent or more (by NH4
OAc) in all parts
from the mineral soil surface to a depth of 180 cm or to a densic,
lithic, or paralithic contact, whichever is shallower. They are
considered to be transitional to Xerolls. Xerollic Glossocryalfs
commonly support a sparse coniferous forest with widely
spaced trees or support rangeland vegetation. They are not
extensive in the United States.
Haplocryalfs
These are the Cryalfs with no glossic horizon. Most of these
soils have no interfingering of albic materials into the argillic,
kandic, or natric horizon. Most have an argillic horizon that
has an upper boundary within 60 cm of the mineral soil
surface. The common sequence of horizons is an O horizon, an
albic horizon, and an argillic horizon. There also are
transitional horizons and a Bw, Btk, or Bk horizon in some
pedons.
The Haplocryalfs of the United States are in the mountains
of the Western States and have a cryic temperature regime.
Most support coniferous forest vegetation. Virtually none of
them are cultivated because their slopes are steep and the
growing season is short and cool. In other countries,
Haplocryalfs occur on mountains and also on plains nearly as
far north as the line of continuous permafrost. Some of the
associated soils on these landscapes are Gelisols on northfacing
slopes and Histosols.
Definition
Haplocryalfs are the Cryalfs that:
1. Do not have a glossic horizon; and
2. Have one or more of the following:
a. An argillic, kandic, or natric horizon that has its upper
boundary at less than 60 cm below the mineral soil surface;
or
b. An argillic, kandic, or natric horizon that has its upper
boundary at less than 60 cm below the lower boundary of
any surface mantle containing 30 percent or more vitric
volcanic ash, cinders, or other vitric pyroclastic materials;
or
c. No texture (in the fine-earth fraction) finer than loamy
fine sand in any horizon above the argillic, kandic, or natric
horizon; or
d. No interfingering of albic materials into the argillic or
natric horizon.
Key to Subgroups
JBCA. Haplocryalfs that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Haplocryalfs
194 Soil Taxonomy
JBCB. Other Haplocryalfs that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Haplocryalfs
JBCC. Other Haplocryalfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Haplocryalfs
JBCD. Other Haplocryalfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Haplocryalfs
JBCE. Other Haplocryalfs that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Haplocryalfs
JBCF. Other Haplocryalfs that are saturated with water in one
or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Haplocryalfs
JBCG. Other Haplocryalfs that have an argillic horizon that:
1. Consists entirely of lamellae; or
2. Is a combination of two or more lamellae and one or more
subhorizons with a thickness of 7.5 to 20 cm, each layer with
an overlying eluvial horizon; or
3. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
a. Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
horizon); or
b. A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon.
Lamellic Haplocryalfs
JBCH. Other Haplocryalfs that have a sandy or sandy-skeletal
particle-size class throughout the upper 75 cm of the argillic,
kandic, or natric horizon or throughout the entire argillic,
kandic, or natric horizon if it is less than 75 cm thick.
Psammentic Haplocryalfs
JBCI. Other Haplocryalfs that have:
1. An argillic, kandic, or natric horizon that is 35 cm or
less thick; and
2. No densic, lithic, or paralithic contact within 100 cm of
the mineral soil surface.
Inceptic Haplocryalfs
JBCJ. Other Haplocryalfs that have:
1. A xeric moisture regime; and
2. An Ap horizon with a color value, moist, of 3 or less
and a color value, dry, of 5 or less (crushed and smoothed
sample) or materials between the soil surface and a depth of
18 cm that have these color values after mixing; and
3. A base saturation of 50 percent or more (by NH4
OAc)
in all parts from the mineral soil surface to a depth of 180
cm or to a densic, lithic, or paralithic contact, whichever is
shallower.
Xerollic Haplocryalfs
JBCK. Other Haplocryalfs that have:
1. A xeric moisture regime; and
2. An Ap horizon with a color value, moist, of 3 or less
and a color value, dry, of 5 or less (crushed and smoothed
sample) or materials between the soil surface and a depth of
18 cm that have these color values after mixing.
Umbric Xeric Haplocryalfs
Alfisols 195
JBCL. Other Haplocryalfs that:
1. Are dry in some part of the moisture control section for
45 or more days (cumulative) in normal years; and
2. Have an Ap horizon with a color value, moist, of 3 or less
and a color value, dry, of 5 or less (crushed and smoothed
sample) or materials between the soil surface and a depth of
18 cm that have these color values after mixing; and
3. Have a base saturation of 50 percent or more (by
NH4
OAc) in all parts from the mineral soil surface to a
depth of 180 cm or to a densic, lithic, or paralithic contact,
whichever is shallower.
Ustollic Haplocryalfs
JBCM. Other Haplocryalfs that have a xeric moisture regime.
Xeric Haplocryalfs
JBCN. Other Haplocryalfs that are dry in some part of the
moisture control section for 45 or more days (cumulative) in
normal years.
Ustic Haplocryalfs
JBCO. Other Haplocryalfs that:
1. Have an Ap horizon with a color value, moist, of 3 or
less and a color value, dry, of 5 or less (crushed and
smoothed sample) or materials between the soil surface and
a depth of 18 cm that have these color values after mixing;
and
2. Have a base saturation of 50 percent or more (by
NH4
OAc) in all parts from the mineral soil surface to a
depth of 180 cm or to a densic, lithic, or paralithic contact,
whichever is shallower.
Mollic Haplocryalfs
JBCP. Other Haplocryalfs that have an Ap horizon with a
color value, moist, of 3 or less and a color value, dry, of 5 or
less (crushed and smoothed sample) or materials between the
soil surface and a depth of 18 cm that have these color values
after mixing.
Umbric Haplocryalfs
JBCQ. Other Haplocryalfs that have a base saturation of 50
percent or more (by NH4
OAc) in all parts from the mineral soil
surface to a depth of 180 cm or to a densic, lithic, or paralithic
contact, whichever is shallower.
Eutric Haplocryalfs
JBCR. Other Haplocryalfs.
Typic Haplocryalfs
Definition of Typic Haplocryalfs
Typic Haplocryalfs are the Haplocryalfs that:
1. Do not have a lithic contact within 50 cm of the mineral soil
surface;
2. Do not have one or both of the following:
a. Cracks within 125 cm of the mineral soil surface that are 5
mm or more wide through a thickness of 30 cm or more for
some time in normal years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has its upper
boundary within 125 cm of the mineral soil surface; or
b. A linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm
or a densic, lithic, or paralithic contact, whichever is
shallower;
3. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
4. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
5. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 7 or more consecutive days or 20 or
more cumulative days in normal years;
6. Have an argillic horizon that meets none of the following:
a. Consists entirely of lamellae; or
b. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
c. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
(1) Two or more lamellae with a combined thickness of 5
196 Soil Taxonomy
cm or more (that may or may not be part of the argillic
horizon); or
(2) A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon;
7. Have an argillic, kandic, or natric horizon that is finer
than the sandy or sandy-skeletal particle-size class in some part
of the upper 75 cm if the argillic, kandic, or natric horizon is
more than 75 cm thick or in any part if the argillic, kandic, or
natric horizon is less than 75 cm thick;
8. Have an argillic, kandic, or natric horizon that is more
than 35 cm thick;
9. Have a udic moisture regime;
10. Are dry in some part of the moisture control section for
less than 45 days (cumulative) in normal years;
11. Have an Ap horizon with a color value, moist, of 4 or
more or a color value, dry, of 6 or more (crushed and smoothed
sample) or materials between the soil surface and a depth of 18
cm that have these color values after mixing; and
12. Have a base saturation of less than 50 percent (by
NH4
OAc) in some part between the mineral soil surface and a
depth of 180 cm or a densic, lithic, or paralithic contact,
whichever is shallower.
Description of Subgroups
Typic Haplocryalfs.—The central concept or Typic
subgroup of Haplocryalfs is fixed on freely drained soils that
are deep or moderately deep to hard rock and that do not have
a glossic horizon. These soils have a high color value in an Ap
horizon or in a layer of comparable depth after mixing and
have a loamy or finer textured argillic horizon not composed
entirely of thin lamellae.
These soils do not have slickensides, wedge-shaped
aggregates, a high linear extensibility, or wide cracks because
these properties are shared with Vertisols. Soils with both a low
bulk density and a high content of weakly crystalline minerals
or that consist of thin layers of pyroclastic materials are
excluded from Typic Haplocryalfs because they have properties
that are shared with the Andisols. Redox depletions and
saturation with water within 100 cm of the surface for extended
periods cause a soil to be excluded from the Typic subgroup
because they are properties shared with Aqualfs. A shallow
lithic contact defines the Lithic subgroup, a convention used
throughout this taxonomy.
Soils that have a xeric moisture regime and other soils that
are dry for more than 45 days also are excluded because they
share properties with Xeralfs and Ustalfs. Soils that have a
surface horizon as thick as 15 cm that is dark enough to be
near or within the range of a mollic or umbric epipedon are
excluded from the Typic subgroup because the thick, dark
horizon is believed to indicate a transitional form to Mollisols or
an Umbric extragrade.
Haplocryalfs with an argillic, kandic, or natric horizon that has
a sandy or sandy-skeletal particle-size class are excluded from
the Typic subgroup and are assigned to the Psammentic
subgroup. Soils that have a base saturation of 50 percent or
more (by NH4
OAc) in all parts from the mineral soil surface to
a depth of 180 cm or to a root-limiting layer are considered
atypical and are assigned to the Eutric subgroup.
Typic Haplocryalfs are not extensive in the United States.
They are in the mountains of the Western States. Most of them
are under a coniferous forest. Slopes generally are moderately
steep to very steep.
Andic and Vitrandic Haplocryalfs.—These soils are like
Typic Haplocryalfs, but they have a surface mantle or layer in
the upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. These
soils occur in the high mountains of the Western United States.
They are permitted, but not required, to have redox depletions
and also color value of 3 or less, moist, and 5 or less, dry, in
surface horizons, after mixing to a depth of 15 cm. They also
are permitted to be dry for more than 45 days. They are not
extensive. Most of them have moderate or strong slopes and are
used for limited summer grazing, as forest, or as wildlife
habitat.
Aquic Haplocryalfs.—These soils are like Typic
Haplocryalfs, but they have redox depletions with chroma of 2
or less and have, within 75 cm of the surface, horizons that are
saturated with water at some time during the year. In addition
to the redox depletions, Aquic Haplocryalfs are permitted to
have a color value of 3 or less, moist, and 5 or less, dry, in
surface horizons, after mixing to a depth of 15 cm. The
wetness is caused mainly by slowly permeable materials in the
lower horizons or the substratum. These soils are rare in the
United States.
Eutric Haplocryalfs.—These soils are like Typic
Haplocryalfs, but they have a base saturation of 50 percent or
more (by NH4
OAc) in all parts between the mineral soil surface
and a depth of 180 cm or a densic, lithic, or paralithic contact,
whichever is shallower. Most of these soils formed in
calcareous materials. Eutric Haplocryalfs support range or
coniferous forest vegetation and have gentle to very steep
slopes. They are of small extent in the United States and are
rare elsewhere.
Inceptic Haplocryalfs.—These soils are like Typic
Haplocryalfs in defined properties, but they have an argillic,
kandic, or natric horizon that is 35 cm or less thick and have
no densic, lithic, or paralithic contact within 100 cm of the
mineral soil surface. These soils may also have an Ap horizon
that has a color value, moist, of 3 or less or upper horizons that
Alfisols 197
have a color value, moist, of less than 4 after the surface soil has
been mixed to a depth of 15 cm. These soils are not extensive in
the United States.
Lamellic Haplocryalfs.—These soils are like Typic
Haplocryalfs in defined properties, but they have an argillic
horizon that consists entirely or partially of lamellae. Most of
these soils have a sandy particle-size class, and the upper
boundary of the argillic horizon or the upper lamella may be
below a depth of 60 cm. The upper several lamellae are
commonly broken or discontinuous horizontally. These soils
may also have a glossic horizon, and they are allowed to have
an Ap horizon that has a color value, moist, of 3 or less or
upper horizons that have a color value, moist, of less than 4
after the surface soil has been mixed to a depth of 15 cm. These
soils are not extensive in the United States.
Lithic Haplocryalfs.—These soils are permitted to have
any of the properties of Haplocryalfs. They are required to have
a lithic contact within 50 cm of the surface. They are of small
extent in the Western United States.
Mollic Haplocryalfs.—These soils are like Typic
Haplocryalfs, but their upper horizons have a color value of 3
or less, moist, and 5 or less, dry, after mixing to a depth of 15
cm. These soils have a base saturation of 50 percent or more
(by NH4
OAc) in all parts from the mineral soil surface to a
depth of 180 cm or to a densic, lithic, or paralithic contact,
whichever is shallower. Mollic Haplocryalfs commonly support
a coniferous forest in which the trees are more widely spaced
than in areas of the Typic subgroup. These soils are not
extensive in the United States except very locally.
Oxyaquic Haplocryalfs.—These soils are like Typic
Haplocryalfs, but they are saturated with water within 100 cm
of the mineral soil surface for 20 or more consecutive days or
30 or more cumulative days in normal years. They are
permitted to have a color value of 3 or less, moist, and 5 or
less, dry, in surface horizons, after mixing to a depth of 15 cm.
The wetness is caused mainly by slowly permeable materials in
the lower horizons or the substratum. These soils are rare in
the United States.
Psammentic Haplocryalfs.—These soils are like Typic
Haplocryalfs in defined properties, but they have a sandy or
sandy-skeletal particle-size class throughout the upper 75 cm of
the argillic, kandic, or natric horizon or throughout the entire
argillic, kandic, or natric horizon if it is less than 75 cm thick.
These soils may also have a glossic horizon and an Ap horizon
that has a color value, moist, of 3 or less or upper horizons that
have a color value, moist, of less than 4 after the surface soil
has been mixed to a depth of 15 cm. These soils are not
extensive in the United States.
Umbric Haplocryalfs.—These soils are like Typic
Haplocryalfs, but their upper horizons have a color value of 3
or less, moist, and 5 or less, dry, after mixing to a depth of 15
cm. These soils have a base saturation of less than 50 percent
(by NH4
OAc) in some part between the mineral soil surface
and a depth of 180 cm or a root-limiting layer, whichever is
shallower. Umbric Haplocryalfs commonly support coniferous
forest. Some forests have widely spaced trees. In some areas
these soils are used as rangeland. The soils are not extensive in
the United States.
Umbric Xeric Haplocryalfs.—These soils are like Typic
Haplocryalfs, but they have a xeric moisture regime and their
upper horizons have a color value of 3 or less, moist, and 5 or
less, dry, after mixing to a depth of 15 cm. They also have a
base saturation of less than 50 percent (by NH4
OAc) in some
part between the mineral soil surface and a depth of 180 cm or
a densic, lithic, or paralithic contact, whichever is shallower.
Umbric Xeric Haplocryalfs commonly support coniferous
forest. Some forests have widely spaced trees. In some areas
these soils are used as rangeland. The soils are not extensive in
the United States.
Ustic Haplocryalfs.—These soils are like Typic
Haplocryalfs, but they are dry in some part of the moisture
control section for 45 or more days (cumulative) in normal
years. They are considered to be transitional to Ustalfs. Ustic
Haplocryalfs commonly support a sparse coniferous forest with
widely spaced trees or are used as rangeland. They are not
extensive in the United States except very locally.
Ustollic Haplocryalfs.—These soils are like Typic
Haplocryalfs, but they are dry in some part of the moisture
control section for 45 or more days (cumulative) in normal
years and their upper horizons have a color value of 3 or less,
moist, and 5 or less, dry, after mixing to a depth of 15 cm.
These soils have a base saturation of 50 percent or more (by
NH4
OAc) in all parts from the mineral soil surface to a depth
of 180 cm or to a densic, lithic, or paralithic contact,
whichever is shallower. They are considered to be transitional
to Ustolls. Ustollic Haplocryalfs commonly support rangeland
vegetation or a sparse coniferous forest with widely spaced
trees. They are not extensive in the United States.
Vertic Haplocryalfs.—These soils are like Typic
Haplocryalfs, but they are high in content of expanding clays
and have cracks 5 mm or more wide, slickensides, wedgeshaped
aggregates, or a linear extensibility of 6.0 cm or more
between the mineral soil surface and either a depth of 100 cm
or a densic, lithic, or paralithic contact, whichever is shallower.
These soils are considered to be transitional to Vertisols. They
support coniferous forest or are used as rangeland. They are not
extensive in the United States.
Xeric Haplocryalfs.—These soils are like Typic
Haplocryalfs, but they have a xeric moisture regime. They are
considered to be transitional to Xeralfs. Xeric Haplocryalfs
commonly support coniferous forest. Some forests have widely
spaced trees. In some areas these soils are used as rangeland.
The soils are not extensive in the United States.
Xerollic Haplocryalfs.—These soils are like Typic
Haplocryalfs, but they have a xeric moisture regime and their
upper horizons have a color value of 3 or less, moist, and 5 or
198 Soil Taxonomy
less, dry, after mixing to a depth of 15 cm. These soils have a
base saturation of 50 percent or more (by NH4
OAc) in all parts
from the mineral soil surface to a depth of 180 cm or to a densic,
lithic, or paralithic contact, whichever is shallower. They are
considered to be transitional to Xerolls. Xerollic Haplocryalfs
commonly support a sparse coniferous forest with widely
spaced trees or support rangeland vegetation. They are not
extensive in the United States.
Palecryalfs
Palecryalfs are the Cryalfs that have a thick epipedon and a
glossic horizon or interfingering of albic materials into the
argillic, kandic, or natric horizon. Most of these soils have an
albic horizon and a glossic horizon. The soils are thought to be
restricted to relatively stable surfaces in the mountains, many
of which are older than the Wisconsinan Glaciation. The
stability may be the result of stoniness. The vegetation on these
soils is mostly coniferous forest. The temperature regimes are
mostly cryic. The moisture regimes are mostly udic.
Definition
Palecryalfs are the Cryalfs that:
1. Have an argillic, kandic, or natric horizon that has its
upper boundary 60 cm or more below both:
a. The mineral soil surface; and
b. The lower boundary of any surface mantle containing
60 percent or more vitric volcanic ash, cinders, or other
vitric pyroclastic materials; and
2. Have a glossic horizon or interfingering of albic materials
in the argillic, kandic, or natric horizon; and
3. Have texture (in the fine-earth fraction) finer than loamy
fine sand in some subhorizon above the argillic, kandic, or
natric horizon.
Key to Subgroups
JBAA. Palecryalfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Palecryalfs
JBAB. Other Palecryalfs that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, one or both of the
following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Palecryalfs
JBAC. Other Palecryalfs that have, in one or more horizons
within 100 cm of the mineral soil surface, redox depletions
with chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Palecryalfs
JBAD. Other Palecryalfs that are saturated with water in one
or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Palecryalfs
JBAE. Other Palecryalfs that have a xeric moisture regime.
Xeric Palecryalfs
JBAF. Other Palecryalfs that are dry in some part of the
moisture control section for 45 or more days (cumulative) in
normal years.
Ustic Palecryalfs
JBAG. Other Palecryalfs that:
1. Have an Ap horizon with a color value, moist, of 3 or
less and a color value, dry, of 5 or less (crushed and
smoothed sample) or materials between the soil surface and
a depth of 18 cm that have these color values after mixing;
and
2. Have a base saturation of 50 percent or more (by
NH4
OAc) in all parts from the mineral soil surface to a
depth of 180 cm or to a densic, lithic, or paralithic contact,
whichever is shallower.
Mollic Palecryalfs
JBAH. Other Palecryalfs that have an Ap horizon with a
color value, moist, of 3 or less and a color value, dry, of 5 or
less (crushed and smoothed sample) or materials between the
soil surface and a depth of 18 cm that have these color values
after mixing.
Umbric Palecryalfs
JBAI. Other Palecryalfs.
Typic Palecryalfs
Alfisols 199
Definition of Typic Palecryalfs
Typic Palecryalfs are the Palecryalfs that:
1. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size, of
1.0 g/cm3
or less, measured at 33 kPa water retention, and
acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
2. Do not have, in any horizon within 100 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
3. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 7 or more consecutive days or 20 or
more cumulative days in normal years;
4. Have a udic moisture regime;
5. Are dry in some part of the moisture control section for
less than 45 days (cumulative) in normal years; and
6. Have an Ap horizon that has a color value, moist, of 4 or
more or a color value, dry, of 6 or more when crushed and
smoothed or have materials to a depth of 18 cm that have these
colors after mixing.
Description of Subgroups
Typic Palecryalfs.—The central concept or Typic subgroup
of Palecryalfs is fixed on freely drained soils that are deep to
the top of the argillic horizon and that have a glossic horizon.
These soils have a high color value in an Ap horizon or in a
layer of comparable depth after mixing and have a loamy or
finer texture above the argillic horizon.
Soils with both a low bulk density and a high content of
weakly crystalline minerals or that consist of thin layers of
pyroclastic materials are excluded from Typic Palecryalfs
because they have properties that are shared with Andisols.
Redox depletions and saturation with water within 100 cm of
the surface for extended periods cause a soil to be excluded from
the Typic subgroup because they are properties shared with
Aqualfs.
Soils that have a xeric moisture regime and other soils that
are dry for more than 45 days also are excluded because they
share properties with Xeralfs and Ustalfs. Soils that have a
surface horizon as thick as 15 cm that is dark enough to be
near or within the range of a mollic or umbric epipedon are
excluded from the Typic subgroup because the thick, dark
horizon is believed to indicate a transitional form to Mollisols
or an Umbric extragrade.
Typic Palecryalfs are not extensive in the United States.
They are in the mountains of the Western States. Most are
under a coniferous forest. Slopes generally are moderately steep
to very steep.
Andic and Vitrandic Palecryalfs.—These soils are like
Typic Palecryalfs, but they have a surface mantle or layer in the
upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. These
soils occur in the high mountains of the Western United States.
They are permitted, but not required, to have redox depletions
and also color value of 3 or less, moist, and 5 or less, dry, in
surface horizons, after mixing to a depth of 15 cm. They also
are permitted to be dry for more than 45 days. They are not
extensive. Most of them are moderately steep to very steep and
are used for limited summer grazing, as forest, or as wildlife
habitat.
Aquic Palecryalfs.—These soils are like Typic Palecryalfs,
but they have redox depletions with chroma of 2 or less and
have, within 75 cm of the surface, horizons that are saturated
with water at some time during the year. In addition to the
redox depletions, Aquic Palecryalfs are permitted to have a
color value of 3 or less, moist, and 5 or less, dry, in surface
horizons, after mixing to a depth of 15 cm. The wetness is
caused mainly by slowly permeable materials in the lower
horizons or the substratum. These soils are rare in the United
States.
Mollic Palecryalfs.—These soils are like Typic Palecryalfs,
but their upper horizons have a color value of 3 or less, moist,
and 5 or less, dry, after mixing to a depth of 15 cm. These soils
have a base saturation of 50 percent or more (by NH4
OAc) in
all parts from the mineral soil surface to a depth of 180 cm or
to a densic, lithic, or paralithic contact, whichever is shallower.
The soils commonly support a coniferous forest in which the
trees are more widely spaced than is typical for Palecryalfs.
Mollic Palecryalfs are not extensive in the United States.
Oxyaquic Palecryalfs.—These soils are like Typic
Palecryalfs, but they are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years. They are permitted
to have a color value of 3 or less, moist, and 5 or less, dry, in
200 Soil Taxonomy
surface horizons, after mixing to a depth of 15 cm. The wetness
is caused mainly by slowly permeable materials in the lower
horizons or the substratum. These soils are rare in the United
States.
Umbric Palecryalfs.—These soils are like Typic
Palecryalfs, but their upper horizons have a color value of 3 or
less, moist, and 5 or less, dry, after mixing to a depth of 15 cm.
These soils have a base saturation of less than 50 percent (by
NH4
OAc) in some part between the mineral soil surface and a
depth of 180 cm or a root-limiting layer, whichever is
shallower. They commonly support a coniferous forest. Some
forests have widely spaced trees. In some areas Umbric
Palecryalfs are used as rangeland. The soils are not extensive
in the United States.
Ustic Palecryalfs.—These soils are like Typic Palecryalfs,
but they are dry in some part of the moisture control section for
45 or more days (cumulative) in normal years. They are
considered to be transitional to Ustalfs. Ustic Palecryalfs
commonly support a sparse coniferous forest with widely
spaced trees or are used as rangeland. They are not extensive in
the United States.
Xeric Palecryalfs.—These soils are like Typic Palecryalfs,
but they have a xeric moisture regime. They are considered to
be transitional to Xeralfs. Xeric Palecryalfs commonly support
a coniferous forest. Some forests have widely spaced trees. In
some areas these soils are used as rangeland. The soils are not
extensive in the United States.
Udalfs
Udalfs are the more or less freely drained Alfisols that have a
udic moisture regime and a frigid, mesic, isomesic, or warmer
temperature regime. These soils are principally but not entirely in
areas of late-Pleistocene deposits and erosional surfaces of
about the same age. Some of the Udalfs that are on the older
surfaces are underlain by limestone or other calcareous
sediments.
Udalfs are very extensive in the United States and in
Western Europe. All of them are believed to have supported
forest vegetation at some time during development. Most
Udalfs with a mesic or warmer temperature regime have or had
deciduous forest vegetation, and many with a frigid
temperature regime have or had mixed coniferous and
deciduous forest vegetation.
Many Udalfs have been cleared of trees and are intensively
farmed. As a result of erosion, many now have only an argillic
or kandic horizon below an Ap horizon that is mostly material
once part of the argillic or kandic horizon. Other Udalfs are on
stable surfaces and retain most of their eluvial horizons above
the argillic or kandic horizon. Normally, the undisturbed soils
have a thin A horizon darkened by humus. A few Udalfs have a
natric horizon. Others have a fragipan in or below the argillic
or kandic horizon.
Definition
Udalfs are the Alfisols that:
1. Have a frigid, mesic, isomesic, or warmer temperature
regime;
2. Have a udic moisture regime; and
3. Have, in no horizon within 50 cm of the mineral soil surface,
both aquic conditions (other than anthraquic conditions) for
some time in normal years (or artificial drainage) and either of
the following:
a. Redoximorphic features in all layers between either the
lower boundary of an Ap horizon or a depth of 25 cm below
the mineral soil surface, whichever is deeper, and a depth of
40 cm; and one of the following within the upper 12.5 cm of
the argillic, kandic, natric, or glossic horizon:
(1) 50 percent or more redox depletions with chroma of
2 or less on faces of peds and redox concentrations
within peds; or
(2) Redox concentrations and 50 percent or more redox
depletions with chroma of 2 or less in the matrix; or
(3) 50 percent or more redox depletions with chroma of
1 or less on faces of peds or in the matrix, or both; or
b. In a horizon that has aquic conditions, enough active
ferrous iron to give a positive reaction to alpha,alphadipyridyl
at a time when the soil is not being irrigated.
Key to Great Groups
JEA. Udalfs that have a natric horizon.
Natrudalfs, p. 221
JEB. Other Udalfs that have:
1. A glossic horizon; and
2. In the argillic or kandic horizon, discrete nodules, 2.5
to 30 cm in diameter, that:
a. Are enriched with iron and extremely weakly
cemented to indurated; and
b. Have exteriors with either a redder hue or a higher
chroma than the interiors.
Ferrudalfs, p. 201
JEC. Other Udalfs that have both:
1. A glossic horizon; and
2. A fragipan with an upper boundary within 100 cm of
the mineral soil surface.
Fraglossudalfs, p. 203
Alfisols 201
JED. Other Udalfs that have a fragipan with an upper
boundary within 100 cm of the mineral soil surface.
Fragiudalfs, p. 202
JEE. Other Udalfs that:
1. Do not have a densic, lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface; and
2. Have a kandic horizon; and
3. Within 150 cm of the mineral soil surface, either:
a. Do not have a clay decrease with increasing depth of
20 percent or more (relative) from the maximum clay
content [Clay is measured noncarbonate clay or based on
the following formula: Clay % = 2.5(% water retained at
1500 kPa tension - % organic carbon), whichever value is
greater, but no more than 100]; or
b. Have 5 percent or more (by volume) skeletans on
faces of peds in the layer that has a 20 percent lower clay
content and, below that layer, a clay increase of 3 percent
or more (absolute) in the fine-earth fraction.
Kandiudalfs, p. 217
JEF. Other Udalfs that have a kandic horizon.
Kanhapludalfs, p. 219
JEG. Other Udalfs that:
1. Do not have a densic, lithic, or paralithic contact within
150 cm of the mineral soil surface; and
2. Within 150 cm of the mineral soil surface, either:
a. Do not have a clay decrease with increasing depth of
20 percent or more (relative) from the maximum clay
content [Clay is measured noncarbonate clay or based on
the following formula: Clay % = 2.5(% water retained at
1500 kPa tension - % organic carbon), whichever value is
greater, but no more than 100]; or
b. Have 5 percent or more (by volume) skeletans on
faces of peds in the layer that has a 20 percent lower clay
content and, below that layer, a clay increase of 3 percent
or more (absolute) in the fine-earth fraction; and
3. Have an argillic horizon with one or more of the
following:
a. In 50 percent or more of the matrix of one or more
subhorizons in its lower one-half, hue of 7.5YR or redder
and chroma of 5 or more; or
b. In 50 percent or more of the matrix of horizons that
total more than one-half the total thickness, hue of
2.5YR or redder, value, moist, of 3 or less, and value,
dry, of 4 or less; or
c. Many coarse redox concentrations with hue of 5YR or
redder or chroma of 6 or more, or both, in one or more
subhorizons; or
4. Have a frigid temperature regime and all of the
following:
a. An argillic horizon that has its upper boundary 60 cm
or more below both:
(1) The mineral soil surface; and
(2) The lower boundary of any surface mantle
containing 30 percent or more vitric volcanic ash,
cinders, or other vitric pyroclastic materials; and
b. A texture (in the fine-earth fraction) finer than
loamy fine sand in one or more horizons above the
argillic horizon; and
c. Either a glossic horizon or interfingering of albic
materials into the argillic horizon.
Paleudalfs, p. 222
JEH. Other Udalfs that have, in all subhorizons in the upper
100 cm of the argillic horizon or throughout the entire argillic
horizon if less than 100 cm thick, more than 50 percent colors
that have all of the following:
1. Hue of 2.5YR or redder; and
2. Value, moist, of 3 or less; and
3. Dry value no more than 1 unit higher than the moist
value.
Rhodudalfs, p. 228
JEI. Other Udalfs that have a glossic horizon.
Glossudalfs, p. 205
JEJ. Other Udalfs.
Hapludalfs, p. 208
Ferrudalfs
Ferrudalfs are the Udalfs that do not have a natric horizon
and have both a glossic horizon and an argillic or kandic
horizon that has been partially cemented by iron. In some areas
these soils formed under a heath vegetation. The heath
vegetation may have succeeded a forest following many years
of collection and removal of forest litter. Under the heath,
which is efficient in complexing iron and aluminum, the upper
part of the argillic horizon was destroyed and fragments of the
argillic horizon became coated and weakly cemented with iron.
Some Ferrudalfs have a fragipan at some depth, commonly
about 100 cm. Ferrudalfs are not known to occur in the United
States and are rare elsewhere. Only two subgroups are
provided.
202 Soil Taxonomy
Definition
Ferrudalfs are the Udalfs that:
1. Do not have a natric horizon;
2. Have a glossic horizon; and
3. In the argillic or kandic horizon, have discrete nodules, 2.5
to about 30 cm in diameter, that are enriched with iron, that
are extremely weakly cemented to indurated, and that have
exteriors with either a redder hue and/or a higher chroma than
the interiors.
KeytoSubgroups
JEBA. Ferrudalfs that have, in one or more horizons within 60
cm of the mineral soil surface, redox depletions with chroma of 2
or less and also aquic conditions for some time in normal years
(or artificial drainage).
Aquic Ferrudalfs
JEBB. Other Ferrudalfs.
Typic Ferrudalfs
Definition of Typic Ferrudalfs
Typic Ferrudalfs are the Ferrudalfs that do not have, in one
or more horizons within 60 cm of the mineral soil surface,
redox depletions with chroma of 2 or less and also aquic
conditions for some time in normal years.
Description of Subgroups
Typic Ferrudalfs.—These soils are the Ferrudalfs that do
not have, in any horizon within 60 cm of the mineral soil
surface, redox depletions with chroma of 2 or less and also
aquic conditions. These soils are not known to occur in the
United States.
Aquic Ferrudalfs.—These soils are like Typic Ferrudalfs,
but they have, in one or more horizons within 40 cm of the
mineral soil surface, redox depletions with chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage). These soils are intergrades between
Aqualfs and Ferrudalfs. They are not known to occur in the
United States.
Fragiudalfs
Fragiudalfs are the Udalfs that have a fragipan within 100
cm of the soil surface but do not have a glossic or natric
horizon. They commonly have an argillic or cambic horizon
above the fragipan. Redoximorphic features are in many
pedons, starting at a depth 50 to 100 cm below the mineral
soil surface. Ground water is perched seasonally above the
fragipan, and a thin eluvial horizon commonly is directly above
the fragipan.
Most Fragiudalfs in the United States are on gentle slopes
and formed, at least in part, in silty or loamy deposits. The
deposits are largely of late-Pleistocene age. The duripan formed
in an older buried soil in some areas. A duripan seems to form if
the burial was to a depth of about 50 to 75 cm. Temperature
regimes are mostly frigid, mesic, or thermic. In the United
States, the native vegetation on these soils was primarily a
broadleaf deciduous forest.
Definition
Fragiudalfs are the Udalfs that:
1. Have a fragipan with an upper boundary within 100 cm of
the mineral soil surface;
2. Do not have a natric horizon; and
3. Do not have a glossic horizon.
Key to Subgroups
JEDA. Fragiudalfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Fragiudalfs
JEDB. Other Fragiudalfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Fragiudalfs
JEDC. Other Fragiudalfs that have, in one or more horizons
within 40 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Fragiudalfs
JEDD. Other Fragiudalfs that are saturated with water in one
or more layers above the fragipan in normal years for either or
both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Fragiudalfs
Alfisols 203
JEDE. Other Fragiudalfs.
TypicFragiudalfs
Definition of Typic Fragiudalfs
Typic Fragiudalfs are the Fragiudalfs that:
1. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size, of
1.0 g/cm3
or less, measured at 33 kPa water retention, and
acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
2. Do not have, in any subhorizon within the upper 25 cm of
the argillic or kandic horizon, redox depletions with chroma of
2 or less and also aquic conditions; and
3. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 7 or more consecutive days or 20 or
more cumulative days in normal years.
Description of Subgroups
Typic Fragiudalfs.—The central concept or Typic subgroup
of Fragiudalfs is fixed on the most freely drained soils of this
great group. Typic Fragiudalfs are not the most extensive
subgroup, but they furnish the best basis for definition of
subgroups. No Fragiudalfs are freely drained because in all of
them ground water is perched above the fragipan in many
years. The perched water table is a probable cause of the very
common albic materials and bleached clay depletions directly
above the fragipan. Soils that have these features and also
redox depletions with low chroma at a shallow depth, normally
along with redox concentrations of high chroma or of reddish
hue, are considered to be intergrades toward Aqualfs. Typic
Fragiudalfs do not have a surface mantle or layer in the upper
75 cm that has both a low bulk density and a high content of
weakly crystalline minerals or that consists of slightly or
moderately weathered pyroclastic materials because these
properties are shared with Andisols.
Andic and Vitrandic Fragiudalfs.—These soils are like
Typic Fragiudalfs, but they have a surface mantle or layer in
the upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. These
soils occur in the foothills and mountains of the Western
United States. They are permitted, but not required, to have
redox depletions and to be saturated with water within 100 cm
of the mineral soil surface for 7 or more consecutive days or 20
or more cumulative days in normal years. They are not
extensive. They are used mainly as forest, but some have been
cleared and are used as cropland or pasture.
Aquic Fragiudalfs.—These soils are like Typic Fragiudalfs,
but they have, in one or more horizons within 40 cm of the
mineral soil surface, redox depletions with chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage). They are intergrades between Fragiaqualfs
and Fragiudalfs. In the United States, they are widely scattered
from Pennsylvania to Illinois and from Illinois to Louisiana.
They are moderately extensive locally within this area. They
have gentle slopes, and most of them are farmed.
Oxyaquic Fragiudalfs.—These soils are like Typic
Fragiudalfs, but they are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years. The wetness is
caused by slow permeability in the fragipan. These soils are
common in the United States. Most of them have been cleared
and are used for crops or pasture.
Fraglossudalfs
Fraglossudalfs have both a fragipan within 100 cm of the
soil surface and a glossic horizon. They do not have a natric
horizon or discrete iron-cemented nodules 2.5 to 30 cm in
diameter in an argillic or kandic horizon. The upper boundary
of the argillic or kandic horizon generally is broken. These
soils are not extensive in the United States. They are more
extensive in Europe.
Definition
Fraglossudalfs are the Udalfs that:
1. Have a glossic horizon;
2. Have a fragipan with an upper boundary within 100 cm of
the mineral soil surface;
3. Do not have a natric horizon; and
4. Do not have, in the argillic or kandic horizon, discrete
nodules, 2.5 to 30 cm in diameter, that have exteriors with
either a redder hue or a higher chroma than the interiors, that
are enriched with iron, and are extremely weakly cemented to
indurated.
Key to Subgroups
JECA. Fraglossudalfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
204 Soil Taxonomy
of the mineral soil surface, a fine-earth fraction with both a bulk
density of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and Al plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0.
Andic Fraglossudalfs
JECB. Other Fraglossudalfs that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Fraglossudalfs
JECC. Other Fraglossudalfs that have, in one or more
subhorizons within the upper 25 cm of the argillic or kandic
horizon, redox depletions with chroma of 2 or less and also
aquic conditions for some time in normal years (or artificial
drainage).
Aquic Fraglossudalfs
JECD. Other Fraglossudalfs that are saturated with water in
one or more layers above the fragipan in normal years for
either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Fraglossudalfs
JECE. Other Fraglossudalfs.
Typic Fraglossudalfs
Definition of Typic Fraglossudalfs
Typic Fraglossudalfs are the Fraglossudalfs that:
1. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more; and
2. Do not have, in any subhorizon within the upper 25 cm of
the argillic or kandic horizon, redox depletions with chroma of
2 or less and also aquic conditions; and
3. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 7 or more consecutive days or 20 or
more cumulative days in normal years.
Description of Subgroups
Typic Fraglossudalfs.—The central concept or Typic
subgroup of Fraglossudalfs is fixed on moderately well drained
soils that have a fragipan at a depth of 50 to 100 cm from the
mineral soil surface. These soils are more freely drained than
most soils in this great group. Typic Fraglossudalfs do not have
a surface mantle or layer in the upper 75 cm that has both a
low bulk density and a high content of weakly crystalline
minerals or that consists of slightly or moderately weathered
pyroclastic materials because these properties are shared with
Andisols. Typic Fraglossudalfs are rare in the United States.
Andic and Vitrandic Fraglossudalfs.—These soils are like
Typic Fraglossudalfs, but they have a surface mantle or layer in
the upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. These
soils occur in the foothills and mountains of the Western
United States. They are permitted, but not required, to have
redox depletions and to be saturated with water within 100 cm
of the mineral soil surface for 7 or more consecutive days or 20
or more cumulative days in normal years. They are not
extensive. They are used mainly as forest, but some have been
cleared and are used as cropland or pasture.
Aquic Fraglossudalfs.—These soils are like Typic
Fraglossudalfs, but they have, in one or more horizons within
40 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage). These soils are
intergrades between Fragiaqualfs and Fraglossudalfs. In the
United States, they are widely scattered from New York to
Louisiana and some are in Idaho. These soils are moderately
extensive locally within this area. They have gentle slopes, and
most of them are farmed.
Oxyaquic Fraglossudalfs.—These soils are like Typic
Fraglossudalfs, but they are saturated with water within 100
Alfisols 205
cm of the mineral soil surface for 20 or more consecutive days or
30 or more cumulative days in normal years. The wetness is
caused by slow permeability in the fragipan. These soils are
common in the United States. Most of them have been cleared
and are used for crops or pasture.
Glossudalfs
Glossudalfs do not have a fragipan, a kandic horizon, or a
natric horizon. They have an argillic horizon that shows
evidence of destruction in the form of a glossic horizon, but
they do not have discrete iron-cemented nodules 2.5 to 30 cm
in diameter. The glossic horizon extends through the argillic
horizon in some of these soils. Glossudalfs do not have very
dark red colors throughout the argillic horizon. They are more
extensive in Europe than in the United States.
Definition
Glossudalfs are the Udalfs that:
1. Have a glossic horizon;
2. Do not have, in the argillic horizon, discrete nodules, 2.5
to 30 cm in diameter, that have enriched exteriors and are
cemented or indurated with iron;
3. Do not have a natric or kandic horizon;
4. Do not have a fragipan within 100 cm of the soil surface;
5. Have an argillic horizon that in some part has hue of
5YR or yellower, a color value, moist, of 3.5 or more, or
a color value, dry, more than 1 unit higher than the moist
value.
Key to Subgroups
JEIA. Glossudalfs that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. Redox depletions with chroma of 2 or less in layers that
also have aquic conditions in normal years (or artificial
drainage) either:
a. Within the upper 25 cm of the argillic horizon if its
upper boundary is within 50 cm of the mineral soil
surface; or
b. Within 75 cm of the mineral soil surface if the upper
boundary of the argillic horizon is 50 cm or more below the
mineral soil surface.
Aquertic Glossudalfs
JEIB. Other Glossudalfs that have both:
1. Saturation with water in one or more layers within 100
cm of the mineral soil surface in normal years for either or
both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days; and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Oxyaquic Vertic Glossudalfs
JEIC. Other Glossudalfs that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Glossudalfs
JEID. Other Glossudalfs that have both:
1. In one or more subhorizons within the upper 25 cm of
the argillic horizon, redox depletions with chroma of 2 or
less and also aquic conditions for some time in normal years
(or artificial drainage); and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface,
one or more of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
206 Soil Taxonomy
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Glossudalfs
JEIE. Other Glossudalfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Glossudalfs
JEIF. Other Glossudalfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Glossudalfs
JEIG. Other Glossudalfs that have both:
1. Fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm
of the mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm
or more thick; and
2. Redox depletions with chroma of 2 or less in layers that
also have aquic conditions in normal years (or artificial
drainage) either:
a. Within the upper 25 cm of the argillic horizon if its
upper boundary is within 50 cm of the mineral soil
surface; or
b. Within 75 cm of the mineral soil surface if the upper
boundary of the argillic horizon is 50 cm or more below
the mineral soil surface.
Fragiaquic Glossudalfs
JEIH. Other Glossudalfs that have, in one or more
subhorizons within the upper 25 cm of the argillic horizon,
redox depletions with chroma of 2 or less and also aquic
conditions for some time in normal years (or artificial
drainage).
Aquic Glossudalfs
JEII. Other Glossudalfs that are saturated with water in one
or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Glossudalfs
JEIJ. Other Glossudalfs that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Glossudalfs
JEIK. Other Glossudalfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 cm or more below the mineral soil surface.
Arenic Glossudalfs
JEIL. Other Glossudalfs that have a glossic horizon less than
50 cm in total thickness.
Haplic Glossudalfs
JEIM. Other Glossudalfs.
Typic Glossudalfs
Definition of Typic Glossudalfs
Typic Glossudalfs are the Glossudalfs that:
1. Do not have cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a thickness of 30
cm or more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick that
has its upper boundary within 125 cm of the mineral soil
surface;
2. Have a linear extensibility of less than 6.0 cm between the
mineral soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact, whichever is shallower;
Alfisols 207
3. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, any of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
4. Do not have, in any subhorizon within the upper 25 cm of
the argillic horizon, redox depletions with chroma of 2 or less
and also aquic conditions;
5. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 7 or more consecutive days or 20 or
more cumulative days in normal years;
6. Do not have fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm or
more thick;
7. Do not have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of an argillic horizon at a depth of 50 cm or more below
the mineral soil surface;
8. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick; and
9. Have a glossic horizon that is 50 cm or more thick.
Description of Subgroups
Typic Glossudalfs.—The central concept or Typic subgroup
of Glossudalfs is fixed on freely drained soils that have a
glossic horizon that is at least 50 cm in total thickness. These
soils do not have slickensides, wedge-shaped aggregates, a
high linear extensibility, or wide cracks because these properties
are shared with Vertisols.
Soils with both a low bulk density and a high content of
weakly crystalline minerals or that consist of thin layers of
pyroclastic materials are excluded from Typic Glossudalfs
because they have properties that are shared with Andisols.
Redox depletions and saturation with water within 100 cm of
the surface for extended periods cause a soil to be excluded
from the Typic subgroup because these properties are shared
with Aqualfs. Typic Glossudalfs do not have fragic soil
properties in a large volume in any layer 15 cm or more thick
because these are properties shared with Fragiudalfs and
Fraglossudalfs. Typic Glossudalfs do not have a layer, starting
at the mineral soil surface, that has a texture of loamy fine sand
or coarser in all parts and that is more than 50 cm thick
because this property is used to define the Arenic subgroup.
Typic Glossudalfs are of small extent in the United States.
They occur in areas from Texas to Michigan.
Andic and Vitrandic Glossudalfs.—These soils are like
Typic Glossudalfs, but they have a surface mantle or layer in
the upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. These
soils occur in the foothills and mountains of the Western
United States. They are not extensive. Most of them have
gently sloping to steep slopes and are used as cropland, forest,
or pasture.
Aquandic Glossudalfs.—These soils are like Typic
Glossudalfs, but they have redox depletions with low chroma
and also aquic conditions at a shallow depth for some time in
normal years. In addition, they a surface mantle or layer in the
upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. These
soils occur in the foothills and mountains of the Western
United States. They are not extensive. Most of them are level to
gently sloping and are used as cropland, forest, or pasture.
Aquertic Glossudalfs.—These soils have redox depletions
with low chroma and also aquic conditions at a shallow depth
for some time in normal years. In addition, they have an
appreciable amount of swelling clays. The aquic conditions,
swelling clays, and low saturated hydraulic conductivity seem
to be the most important properties of the soils in this
subgroup. Most of the soils formed in clayey parent materials.
Aquertic Glossudalfs are of small extent. Slopes are gentle, but
the soils are highly erodible. Most of the soils are farmed, but
some of them are used as pasture or forest.
Aquic Glossudalfs.—These soils have redox depletions
with low chroma and also aquic conditions at a shallow depth
for some time in normal years. In addition, they are permitted
to have fragic soil properties. These soils are permitted, but not
required, to have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of an argillic horizon at a depth of 50 cm or more. In
208 Soil Taxonomy
the United States, these soils are moderately extensive on the
lower coastal plain along the Gulf of Mexico and are known to
occur elsewhere. Many of them are in forests, but much of the
acreage of these soils has been cleared and is used as cropland
or pasture.
Arenic Glossudalfs.—These soils have a layer that has a
sandy or sandy-skeletal particle-size class throughout and
extends from the mineral soil surface to the top of an argillic
horizon at a depth of 50 cm or more below the mineral soil
surface. These soils are known to occur only in Texas and
Michigan in the United States.
Fragiaquic Glossudalfs.—These soils are like Typic
Glossudalfs, but they have redox depletions with low chroma
and also aquic conditions at a shallow depth for some time in
normal years. In addition, they have fragic soil properties in 30
percent or more of the volume of a layer 15 cm or more thick
that has its upper boundary within 100 cm of the mineral soil
surface or in 60 percent or more of the volume of a layer 15 cm
or more thick anywhere in the soils. These soils are not
extensive in the United States.
Fragic Glossudalfs.—These soils are like Typic
Glossudalfs, but they have fragic soil properties in 30 percent
or more of the volume of a layer 15 cm or more thick that has
its upper boundary within 100 cm of the mineral soil surface or
in 60 percent or more of the volume of a layer 15 cm or more
thick anywhere in the soils. These soils are not extensive in the
United States.
Haplic Glossudalfs.—These soils are like Typic
Glossudalfs, but the glossic horizon is less than 50 cm thick.
Thus, the soils have some characteristics of Hapludalfs. They
occur locally in Michigan and Wisconsin and in the central
part of the Southern United States.
Oxyaquic Glossudalfs.—These soils are like Typic
Glossudalfs, but they are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years. The wetness is
caused mainly by slowly permeable materials in the lower
horizons or the substratum. These soils are of small extent and
are mostly in the south-central and north-central parts of the
United States.
Oxyaquic Vertic Glossudalfs.—These soils are like Typic
Glossudalfs, but they are high in content of expanding clays
and have cracks 5 mm or more wide, slickensides, wedgeshaped
aggregates, or a linear extensibility of 6.0 cm or more
between the mineral soil surface and either a depth of 100 cm
or a densic, lithic, or paralithic contact, whichever is shallower.
The soils also are saturated with water within 100 cm of the
mineral soil surface for 20 or more consecutive days or 30 or
more cumulative days in normal years. The wetness is caused
mainly by slowly permeable materials in the lower horizons or
the substratum. These soils are rare in the United States and
are considered to be transitional to Vertisols.
Vertic Glossudalfs.—These soils are like Typic
Glossudalfs, but they are high in content of expanding clays
and have cracks 5 mm or more wide, slickensides, wedge-shaped
aggregates, or a linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact, whichever is shallower. These soils
are rare in the United States and are considered to be transitional
to Vertisols.
Hapludalfs
Hapludalfs are the Udalfs that do not have a glossic, kandic,
or natric horizon or a fragipan within 100 cm of the mineral
soil surface. They do not have very dark red colors throughout
the argillic horizon. The base of the argillic horizon is
normally less than 150 cm below the soil surface and, in many
areas, is less than 100 cm below the surface. In an undisturbed
soil, there generally is a thin, very dark brown A horizon, 5 to
10 cm thick, over a lighter colored brownish eluvial horizon.
The eluvial horizon grades into a finer textured argillic
horizon, generally at a depth of about 30 to 45 cm in loamy
materials. Because the Hapludalfs have been cultivated
extensively, many of those on slopes have lost their eluvial
horizons.
These soils formed principally in late-Pleistocene deposits
or on a surface of comparable age. They are extensive soils in
the Northeastern States, excluding New England, and in
Europe, excluding most of Scandinavia.
The vegetation on Hapludalfs in the United States was a
deciduous broadleaf forest, but the soils are now mostly
farmed. Temperature regimes are mesic or thermic.
Definition
Hapludalfs are the Udalfs that:
1. Do not have a glossic, kandic, or natric horizon;
2. Have an argillic horizon that in some part has hue of 5YR
or yellower, a color value, moist, of 3.5 or more, or a color
value, dry, more than 1 unit higher than the moist value;
3. Do not have a fragipan within 100 cm of the mineral soil
surface;
4. Either have a densic, lithic, or paralithic contact within
150 cm of the soil surface or have a clay distribution in which
the clay content decreases with increasing depth by 20 percent
or more from its maximum within 150 cm of the soil surface
and, if there is a clay increase of 3 percent or more (absolute)
below that layer, less than 5 percent of the volume in the layer
where the clay content decreases consists of skeletans on faces
of peds, if:
a. Hue is redder than 10YR and chroma of more than 4 is
dominant;
b. Hue is 2.5YR or redder, the value, moist, is less than 4,
and the value, dry, is less than 5 throughout the major part
of the argillic horizon; or
Alfisols 209
c. There are many coarse redox concentrations that have
hue redder than 7.5YR or chroma of more than 5.
Key to Subgroups
JEJA. Hapludalfs that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Hapludalfs
JEJB. Other Hapludalfs that have all of the following:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. Redox depletions with chroma of 2 or less in layers that
also have aquic conditions in normal years (or artificial
drainage) either:
a. Within the upper 25 cm of the argillic horizon if its
upper boundary is within 50 cm of the mineral soil
surface; or
b. Within 75 cm of the mineral soil surface if the upper
boundary of the argillic horizon is 50 cm or more below
the mineral soil surface; and
3. An Ap horizon or materials between the mineral soil
surface and a depth of 18 cm that, after mixing, have one or
more of the following:
a. A color value, moist, of 4 or more; or
b. A color value, dry, of 6 or more; or
c. Chroma of 4 or more.
Aquertic Chromic Hapludalfs
JEJC. Other Hapludalfs that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. Redox depletions with chroma of 2 or less in layers that
also have aquic conditions in normal years (or artificial
drainage) either:
a. Within the upper 25 cm of the argillic horizon if its
upper boundary is within 50 cm of the mineral soil
surface; or
b. Within 75 cm of the mineral soil surface if the upper
boundary of the argillic horizon is 50 cm or more below
the mineral soil surface.
Aquertic Hapludalfs
JEJD. Other Hapludalfs that have both:
1. Saturation with water in one or more layers within 100
cm of the mineral soil surface in normal years for either or
both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days; and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Oxyaquic Vertic Hapludalfs
JEJE. Other Hapludalfs that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. An Ap horizon or materials between the mineral soil
210 Soil Taxonomy
surface and a depth of 18 cm that, after mixing, have one or
more of the following:
a. A color value, moist, of 4 or more; or
b. A color value, dry, of 6 or more; or
c. Chroma of 4 or more.
Chromic Vertic Hapludalfs
JEJF. Other Hapludalfs that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm or
a densic, lithic, or paralithic contact, whichever is
shallower.
Vertic Hapludalfs
JEJG. Other Hapludalfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Hapludalfs
JEJH. Other Hapludalfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Hapludalfs
JEJI. Other Hapludalfs that have both:
1. Fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm
of the mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm or
more thick; and
2. Redox depletions with chroma of 2 or less in layers that
also have aquic conditions in normal years (or artificial
drainage) either:
a. Within the upper 25 cm of the argillic horizon if its
upper boundary is within 50 cm of the mineral soil
surface; or
b. Within 75 cm of the mineral soil surface if the upper
boundary of the argillic horizon is 50 cm or more below
the mineral soil surface.
Fragiaquic Hapludalfs
JEJJ. Other Hapludalfs that have both:
1. Fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm
of the mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm
or more thick; and
2. Saturation with water in one or more layers within 100
cm of the mineral soil surface in normal years for either or
both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days.
Fragic Oxyaquic Hapludalfs
JEJK. Other Hapludalfs that have both:
1. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. A sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface
to the top of an argillic horizon at a depth of 50 cm or
more.
Aquic Arenic Hapludalfs
JEJL. Other Hapludalfs that have:
1. An abrupt textural change; and
2. Redox depletions with chroma of 2 or less in layers that
also have aquic conditions in normal years (or artificial
drainage) either:
a. Within the upper 25 cm of the argillic horizon if its
upper boundary is within 50 cm of the mineral soil
surface; or
b. Within 75 cm of the mineral soil surface if the upper
Alfisols 211
boundary of the argillic horizon is 50 cm or more below the
mineral soil surface; and
3. A base saturation (by sum of cations) of less than 60
percent at a depth of 125 cm from the top of the argillic
horizon, at a depth of 180 cm from the mineral soil surface,
or directly above a densic, lithic, or paralithic contact,
whichever is shallowest.
Albaquultic Hapludalfs
JEJM. Other Hapludalfs that have both:
1. An abrupt textural change; and
2. Redox depletions with chroma of 2 or less in layers that
also have aquic conditions in normal years (or artificial
drainage) either:
a. Within the upper 25 cm of the argillic horizon if its
upper boundary is within 50 cm of the mineral soil
surface; or
b. Within 75 cm of the mineral soil surface if the upper
boundary of the argillic horizon is 50 cm or more below
the mineral soil surface.
Albaquic Hapludalfs
JEJN. Other Hapludalfs that have both:
1. Interfingering of albic materials in the upper part of the
argillic horizon; and
2. Redox depletions with chroma of 2 or less in layers that
also have aquic conditions in normal years (or artificial
drainage) either:
a. Within the upper 25 cm of the argillic horizon if its
upper boundary is within 50 cm of the mineral soil
surface; or
b. Within 75 cm of the mineral soil surface if the upper
boundary of the argillic horizon is 50 cm or more below
the mineral soil surface.
Glossaquic Hapludalfs
JEJO. Other Hapludalfs that have both:
1. Redox depletions with chroma of 2 or less in layers that
also have aquic conditions in normal years (or artificial
drainage) either:
a. Within the upper 25 cm of the argillic horizon if its
upper boundary is within 50 cm of the mineral soil
surface; or
b. Within 75 cm of the mineral soil surface if the upper
boundary of the argillic horizon is 50 cm or more below
the mineral soil surface; and
2. A base saturation (by sum of cations) of less than 60
percent at a depth of 125 cm from the top of the argillic
horizon, at a depth of 180 cm from the mineral soil surface, or
directly above a densic, lithic, or paralithic contact, whichever
is shallowest.
Aquultic Hapludalfs
JEJP. Other Hapludalfs that have both:
1. An Ap horizon that has a color value, moist, of 3 or less
and a color value, dry, of 5 or less (crushed and smoothed
sample) or materials between the soil surface and a depth of
18 cm that have these color values after mixing; and
2. Redox depletions with chroma of 2 or less in layers that
also have aquic conditions in normal years (or artificial
drainage) either:
a. Within the upper 25 cm of the argillic horizon if its
upper boundary is within 50 cm of the mineral soil
surface; or
b. Within 75 cm of the mineral soil surface if the upper
boundary of the argillic horizon is 50 cm or more below
the mineral soil surface.
Aquollic Hapludalfs
JEJQ. Other Hapludalfs that have redox depletions with
chroma of 2 or less in layers that also have aquic conditions in
normal years (or artificial drainage) either:
1. Within the upper 25 cm of the argillic horizon if its
upper boundary is within 50 cm of the mineral soil surface;
or
2. Within 75 cm of the mineral soil surface if the upper
boundary of the argillic horizon is 50 cm or more below the
mineral soil surface.
Aquic Hapludalfs
JEJR. Other Hapludalfs that have anthraquic conditions.
Anthraquic Hapludalfs
JEJS. Other Hapludalfs that are saturated with water in one
or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Hapludalfs
JEJT. Other Hapludalfs that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Hapludalfs
212 Soil Taxonomy
JEJU. Other Hapludalfs that have an argillic horizon that:
1. Consists entirely of lamellae; or
2. Is a combination of two or more lamellae and one or more
subhorizons with a thickness of 7.5 to 20 cm, each layer with
an overlying eluvial horizon; or
3. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
a. Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
horizon); or
b. A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon.
Lamellic Hapludalfs
JEJV. Other Hapludalfs that have a sandy particle-size class
throughout the upper 75 cm of the argillic horizon or
throughout the entire argillic horizon if it is less than 75 cm
thick.
Psammentic Hapludalfs
JEJW. Other Hapludalfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 cm or more.
Arenic Hapludalfs
JEJX. Other Hapludalfs that have interfingering of
albic materials in one or more subhorizons of the argillic
horizon.
Glossic Hapludalfs
JEJY. Other Hapludalfs that have:
1. An argillic, kandic, or natric horizon that is 35 cm or
less thick; and
2. No densic, lithic, or paralithic contact within 100 cm of
the mineral soil surface.
Inceptic Hapludalfs
JEJZ. Other Hapludalfs that have a base saturation (by sum
of cations) of less than 60 percent at a depth of 125 cm below
the top of the argillic horizon, at a depth of 180 cm below the
mineral soil surface, or directly above a densic, lithic, or
paralithic contact, whichever is shallowest.
Ultic Hapludalfs
JEJZa. Other Hapludalfs that have a mollic epipedon, an Ap
horizon that meets all of the requirements for a mollic
epipedon except thickness, or materials between the soil
surface and a depth of 18 cm that meet these requirements after
mixing.
Mollic Hapludalfs
JEJZb. Other Hapludalfs.
Typic Hapludalfs
Definition of Typic Hapludalfs
Typic Hapludalfs are the Hapludalfs that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
3. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
4. Do not have redox depletions with chroma of 2 or less in
layers that also have aquic conditions in normal years (or
artificial drainage) either:
a. Within the upper 25 cm of the argillic horizon if its
upper boundary is within 50 cm of the mineral soil surface;
or
b. Within 75 cm of the mineral soil surface if the upper
boundary of the argillic horizon is 50 cm or more below the
mineral soil surface;
Alfisols 213
5. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 7 or more consecutive days or 20 or
more cumulative days in normal years;
6. Do not have anthraquic conditions;
7. Have a texture finer than loamy fine sand in one or more
subhorizons within 50 cm of the mineral soil surface;
8. Do not have a mollic epipedon, an Ap horizon that meets
all of the requirements for a mollic epipedon except thickness,
or materials between the soil surface and a depth of 18 cm that
meet these requirements after mixing;
9. Have an argillic horizon that is finer than the sandy
particle-size class in some part of the upper 75 cm if the
argillic horizon is more than 75 cm thick or in any part if the
argillic horizon is less than 75 cm thick;
10. Have a base saturation (by sum of cations) of 60 percent
or more at a depth of 125 cm below the top of the argillic
horizon, at a depth of 180 cm below the soil surface, or directly
above a densic, lithic, or paralithic contact, whichever is
shallowest;
11. Do not have interfingering of albic materials in any
subhorizon of the argillic horizon;
12. Have an argillic horizon that meets none of the following:
a. Consists entirely of lamellae; or
b. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
c. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
(1) Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
horizon); or
(2) A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon;
13. Have an argillic horizon that is more than 35 cm thick;
and
14. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick.
Description of Subgroups
Typic Hapludalfs.—The central concept or Typic subgroup of
Hapludalfs is fixed on freely drained soils that have an argillic
horizon that does not have an abrupt upper boundary, that does
not have interfingering of albic materials, that has a relatively
high base saturation, and that has a loamy or clayey texture and
is not composed entirely of thin lamellae. In addition, these soils
are deep or moderately deep to hard rock, have a light colored
plow layer, and do not have a thick epipedon with a sandy or
sandy-skeletal particle-size class throughout. They do not have
slickensides, wedge-shaped aggregates, a high linear
extensibility, or wide cracks.
An abrupt upper boundary of the argillic horizon and redox
concentrations in the argillic horizon are properties shared
with Albaqualfs and Albaquults and define intergrades to those
great groups.
If the upper 25 cm of the argillic horizon has aquic
conditions for some time in normal years (or artificial
drainage) and redox depletions with chroma of 2 or less, or
saturation with water within 100 cm of the surface for extended
periods, the soil is excluded from Typic Hapludalfs because
these properties are shared with Aqualfs.
A thick layer, starting at the mineral soil surface, that has a
sandy or sandy-skeletal particle-size class is considered
atypical and defines the Arenic subgroup. Interfingering of
albic materials in the argillic horizon causes a soil to be
excluded because this property is shared with Glossudalfs.
Typic Glossudalfs do not have a surface mantle or layer in the
upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials because
these properties are shared with Andisols.
A shallow lithic contact defines the Lithic subgroup, a
convention used throughout this taxonomy. Surface horizons
above a depth of 18 cm that, after mixing, have the color of a
mollic epipedon and a plow layer that has this color are
believed to indicate a transition to Mollisols.
An argillic horizon that has a sandy particle-size class or
that is composed entirely of thin lamellae is the basis for
defining the Lamellic and Psammentic subgroups. A relatively
low base saturation in the deeper horizons is a property shared
with Ultisols and is used to define the intergrades to that order.
Soils that have slickensides, wedge-shaped aggregates, a
high linear extensibility, or wide cracks are excluded from the
Typic Hapludalfs because these properties are shared with
Vertisols.
Albaquic Hapludalfs.—These soils have an abrupt textural
change between an eluvial horizon, commonly an albic
horizon, and the argillic horizon. They also have, in one or
more subhorizons within the upper 25 cm of the argillic
horizon, redox depletions with chroma of 2 or less and aquic
conditions for some time in normal years (or artificial
214 Soil Taxonomy
drainage). These soils are intergrades between Albaqualfs and
Hapludalfs. They are mostly in the Southern United States and
are widely distributed. Most of them are used as forest, but
some have been cleared and are used as pasture or cropland.
Some of them developed under grass and are used as
rangeland, pasture, or cropland.
Albaquultic Hapludalfs.—These soils are like Typic
Hapludalfs, but they have an abrupt textural change between an
eluvial horizon, commonly an albic horizon, and the argillic
horizon and have, in one or more subhorizons within the upper
25 cm of the argillic horizon, redox depletions with chroma of
2 or less and aquic conditions for some time in normal years
(or artificial drainage). They also have a base saturation (by
sum of cations) of less than 60 percent at a depth of 125 cm
below the top of the argillic horizon, at a depth of 180 cm
below the soil surface, or directly above a densic, lithic, or
paralithic contact, whichever is shallowest. They differ from
soils of the Albaquic subgroup because they have a lower base
saturation and from soils of the Aquultic subgroup because
they have an abrupt textural change at the top of the argillic
horizon. Albaquultic Hapludalfs are intergrades between
Albaquults and Hapludalfs. They are mostly on the coastal
plain bordering the Gulf of Mexico and are not extensive.
Nearly all of these soils are in forests.
Andic and Vitrandic Hapludalfs.—These soils are like
Typic Hapludalfs, but they have a surface mantle or layer in the
upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. These
soils occur in the foothills and mountains of the Western
United States. They are permitted, but not required, to have
redox depletions and to be saturated with water within 100 cm
of the mineral soil surface for 7 or more consecutive days or 20
or more cumulative days in normal years. These soils are of
very small extent but are locally important. They are used
mainly as forest, but some areas have been cleared and are used
as cropland or pasture.
Anthraquic Hapludalfs.—These soils are like Typic
Hapludalfs, but they have been irrigated for paddy rice
production for many years and have developed anthraquic
conditions. They are permitted, but not required, to have redox
depletions with chroma of 2 or less in layers that also have
aquic conditions in normal years either within the upper 25 cm
of the argillic horizon if its upper boundary is within 50 cm of
the mineral soil surface or within 75 cm of the mineral soil
surface if the upper boundary of the argillic horizon is deeper
than 50 cm. These soils are not extensive and are rare in the
United States. They have level or nearly level slopes.
Aquertic Hapludalfs.—These soils are like Typic
Hapludalfs, but they have redox depletions with low chroma,
aquic conditions at a shallow depth for some time in normal
years, and an appreciable amount of swelling clays. The Ap
horizon or the surface soil to a depth of 18 cm after mixing has
a color value of 3 or less, moist, and 5 or less, dry. A few of
these soils have a mollic epipedon, but the base saturation is
less than 50 percent (by NH4
OAc) in at least part of the argillic
horizon. The aquic conditions, swelling clays, and low
saturated hydraulic conductivity seem to be the most important
properties of the soils in this subgroup. Most of the soils
formed in clayey parent materials. Aquertic Hapludalfs are of
small extent. Slopes are gentle. Most of the soils have been
cleared and are used as cropland or pasture, but some of them
are used as forest. Some of the soils developed under grass
vegetation and are used as cropland or rangeland.
Aquertic Chromic Hapludalfs.—These soils are like Typic
Hapludalfs, but they have redox depletions with low chroma
and also have aquic conditions at a shallow depth for some
time in normal years. In addition, they have an appreciable
amount of swelling clays. The aquic conditions, swelling clays,
and low saturated hydraulic conductivity seem to be the most
important properties of the soils in this subgroup. Most of the
soils formed in clayey parent materials. Aquertic Chromic
Hapludalfs are of small extent. Slopes are gentle. Most of the
soils have been cleared and are used as cropland or pasture, but
some are used as forest.
Aquic Arenic Hapludalfs.—These soils have, in one or
more horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage). They
also have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of an argillic horizon at a depth of 50 cm or more. The
plow layer or the surface soil to a depth of 18 cm after mixing
is permitted, but not required, to have a color value of 3 or less,
moist, and 5 or less, dry. There is no restriction on the base
saturation other than that imposed by the definition of Alfisols.
Aquic Arenic Hapludalfs are not extensive in the United States.
They are mostly on the lake plains adjacent to the Great Lakes.
Their slopes are very gentle. Most of the soils have been
cleared and are used as cropland, but some of them are used as
pasture or forest.
Aquic Hapludalfs.—These soils are like Typic Hapludalfs,
but they have redox depletions with chroma of 2 or less in
layers that also have aquic conditions in normal years (or
artificial drainage) either within the upper 25 cm of the argillic
horizon if its upper boundary is within 50 cm of the mineral
soil surface or within 75 cm of the mineral soil surface if the
upper boundary of the argillic horizon is deeper than 50 cm.
These soils are intergrades between Aqualfs and Hapludalfs.
They are moderately extensive in the United States,
particularly in the glaciated areas of the north-central region.
Most of the soils have gentle slopes and have been cleared and
are used as cropland, but some of them are used as pasture or
forest.
Aquollic Hapludalfs.—These soils have, in one or more
subhorizons within the upper 25 cm of the argillic horizon,
redox depletions with chroma of 2 or less and also aquic
conditions for some time in normal years (or artificial
Alfisols 215
drainage). In addition, the Ap horizon or the surface soil to a
depth of 18 cm after mixing has a color value of 3 or less,
moist, and 5 or less, dry. These soils are intergrades between
Argiaquolls and Hapludalfs. They are moderately extensive in
the United States, particularly in the glaciated parts of the
north-central region. Slopes are very gentle. Nearly all of the
soils have been cleared and are used as cropland, but some of
them are used as pasture or forest.
Aquultic Hapludalfs.—These soils have, in one or more
subhorizons within the upper 25 cm of the argillic horizon,
redox depletions with chroma of 2 or less and also aquic
conditions for some time in normal years (or artificial
drainage). In addition, the base saturation (by sum of cations)
is less than 60 percent at a depth of 125 cm below the top of
the argillic horizon, at a depth of 180 cm below the soil
surface, or directly above a densic, lithic, or paralithic contact,
whichever is shallowest. The Ap horizon or the surface soil to
a depth of 18 cm after mixing may have any color value when
moist. These soils are intergrades between Aquults and
Hapludalfs. They are not extensive in the United States and are
known to occur only on the low Atlantic Coastal Plain. Their
slopes are very gentle. Many of the soils have been cleared and
are used as cropland, but some of them are used as pasture or
forest.
Arenic Hapludalfs.—These soils have a sandy or sandyskeletal
particle-size class in all subhorizons to the top of an
argillic horizon at a depth of 50 cm or more. The plow layer or
the surface soil to a depth of 18 cm after mixing is permitted,
but not required, to have a color value of 3 or less, moist, and 5
or less, dry. There is no restriction on the base saturation other
than that imposed by the definition of Alfisols. Arenic
Hapludalfs are not extensive in the United States. They occur
mostly in the glaciated parts of the north-central region of the
United States and in Florida. Their slopes are mostly gentle.
Where slopes are suitable, the soils have been cleared and are
used as cropland. Some of the soils are used as pasture or
forest.
Chromic Vertic Hapludalfs.—These soils are like Typic
Hapludalfs, but they have an appreciable amount of swelling
clays. The swelling clays and low saturated hydraulic
conductivity seem to be the most important properties of the
soils in this subgroup. Most of the soils formed in clayey parent
materials. Chromic Vertic Hapludalfs are of small extent.
Slopes are gentle to steep. Most of the less sloping soils have
been cleared and are used as cropland or pasture. Some of the
soils are used as forest.
Fragiaquic Hapludalfs.—These soils are like Typic
Hapludalfs, but they have redox depletions with low chroma
and also aquic conditions at a shallow depth for some time in
normal years. In addition, they have fragic soil properties in 30
percent or more of the volume of a layer 15 cm or more thick
that has its upper boundary within 100 cm of the mineral soil
surface or in 60 percent or more of the volume of a layer 15 cm
or more thick anywhere in the soils. These soils are considered
intergrades to Fraqiaqualfs. They are not extensive in the United
States.
Fragic Hapludalfs.—These soils are like Typic Hapludalfs,
but they have fragic soil properties in 30 percent or more of the
volume of a layer 15 cm or more thick that has its upper
boundary within 100 cm of the mineral soil surface or in 60
percent or more of the volume of a layer 15 cm or more thick
anywhere in the soils. These soils are considered intergrades to
Fraqiudalfs. They are not extensive in the United States.
Fragic Oxyaquic Hapludalfs.—These soils are like Typic
Hapludalfs, but they are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years. In addition, they
have fragic soil properties in 30 percent or more of the volume
of a layer 15 cm or more thick that has its upper boundary
within 100 cm of the mineral soil surface or in 60 percent or
more of the volume of a layer 15 cm or more thick anywhere in
the soils. These soils are considered intergrades to
Fraqiaqualfs. They are not extensive in the United States.
Glossaquic Hapludalfs.—These soils have, in one or more
subhorizons within the upper 25 cm of the argillic horizon,
redox depletions with chroma of 2 or less and also aquic
conditions for some time in normal years (or artificial
drainage). In addition, there is evidence of destruction of the
argillic horizon in the form of albic materials interfingering in
or into the argillic horizon. The Ap horizon or the surface soil
to a depth of 18 cm after mixing is permitted, but not required,
to have a color value, moist, of 3 or less. These soils are
intergrades between Glossaqualfs and Hapludalfs. They are
primarily in cool areas that were glaciated and along the gulf
coast of the United States. Where they have gentle slopes, most
of these soils have been cleared and are used as cropland or
pasture. Some of the soils are used as forest.
Glossic Hapludalfs.—These soils show evidence of
destruction of the argillic horizon in the form of albic materials
interfingering in or into the argillic horizon. The soils are
intergrades between Glossudalfs and Hapludalfs. The Ap
horizon or the surface soil to a depth of 18 cm after mixing is
permitted, but not required, to have a color value, moist, of 3 or
less. In most undisturbed areas of Glossic Hapludalfs, the color
value is 4 or more after the upper layers to a depth of 18 cm
have been mixed, but the cultivated soils have a darker Ap
horizon. Glossic Hapludalfs are moderately extensive in the
United States. They are primarily in cool areas that were
glaciated. Where they have gentle slopes, many of these soils
have been cleared and are used as cropland or pasture. Some of
the soils are used as forest.
Inceptic Hapludalfs.—These soils have an argillic horizon
that is less than 35 cm thick and have no densic, lithic, or
paralithic contact within 100 cm of the mineral soil surface.
They are permitted, but not required, to have a color value,
moist, of 3 or less in the Ap horizon or in the surface soil to a
depth of 18 cm after mixing and to have a base saturation (by
sum of cations) that is less than 60 percent. These soils are not
216 Soil Taxonomy
extensive in the United States. They are considered intergrades
between Udepts and Hapludalfs. They are of small extent in the
United States. Where slopes are suitable, many of these soils
have been cleared and are used as cropland or pasture. Some of
the soils, mostly the more sloping ones, are used as forest.
Lamellic Hapludalfs.—These soils are like Typic
Hapludalfs, but they have an argillic horizon that consists
entirely of lamellae or is a combination of two or more
lamellae and one or more subhorizons with a thickness of 7.5
to 20 cm, each layer with an overlying eluvial horizon. In some
of the soils, the argillic horizon consists of one or more
subhorizons that are more than 20 cm thick, each with an
overlying eluvial horizon, and above these horizons there are
either two or more lamellae with a combined thickness of 5 cm
or more or a combination of lamellae and one or more parts of
the argillic horizon 7.5 to 20 cm thick, each with an overlying
eluvial horizon. Lamellic Hapludalfs are permitted, but not
required, to have a color value, moist, of 3 or less in the Ap
horizon or in the surface soil to a depth of 18 cm after mixing
and to have a base saturation (by sum of cations) that is less
than 60 percent. The soils are not extensive in the United
States. They are intergrades between Psamments and
Hapludalfs. Many of the Lamellic Hapludalfs in the United
States are on lake plains adjacent to the Great Lakes. Where
they have gentle slopes, many of these soils have been cleared
and are used as cropland or pasture. Some of the soils are used
as forest.
Lithic Hapludalfs.—These soils have a lithic contact
within 50 cm of the mineral soil surface. They are permitted to
have any other property that is allowed in Hapludalfs. They can
have redox depletions with low chroma and aquic conditions at
a shallow depth for some time in normal years. There can be
evidence of destruction of the argillic horizon in the form of
albic materials interfingering in or into the argillic horizon.
The Ap horizon or the surface soil to a depth of 18 cm after
mixing is permitted, but not required, to have a color value,
moist, of 3 or less. These soils are not extensive in the United
States, and they are widely distributed. Their slopes range from
gentle to very steep. Most of the soils are used as pasture or
forest.
Mollic Hapludalfs.—These soils are like Typic Hapludalfs,
but they have a mollic epipedon, an Ap horizon that meets all
of the requirements for a mollic epipedon except thickness, or
materials between the soil surface and a depth of 18 cm that
meet these requirements after mixing. The soils that have a
mollic epipedon also have a base saturation of less than 50
percent (by NH4
OAc) in at least part of the argillic horizon.
Mollic Hapludalfs are mostly transitional in morphology and in
location to Udolls. They are moderately extensive in the United
States. Their slopes range from gentle to strong. Where slopes
are suitable, nearly all of these soils have been cleared and are
used as cropland or pasture. Some of the soils, mainly the most
sloping ones, are used as forest.
Oxyaquic Hapludalfs.—These soils are like Typic
Hapludalfs, but they are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years. In addition, the soils
are permitted, but not required, to have a color value, moist, of
3 or less in the Ap horizon or in the surface soil to a depth of
18 cm after mixing and to have a base saturation (by sum of
cations) that is less than 60 percent. These soils are moderately
extensive in the United States. They are considered intergrades
to Aqualfs. Slopes are gentle. Most Oxyaquic Hapludalfs have
been cleared and are used as cropland or pasture, but some of
them are used as forest.
Oxyaquic Vertic Hapludalfs.—These soils are like Typic
Hapludalfs, but they have an appreciable amount of swelling
clays and are saturated with water within 100 cm of the
mineral soil surface for 20 or more consecutive days or 30 or
more cumulative days in normal years. In addition, the soils
are permitted, but not required, to have a color value, moist, of
3 or less in the Ap horizon or in the surface soil to a depth of
18 cm after mixing and to have a base saturation (by sum of
cations) that is less than 60 percent. A few of these soils have a
mollic epipedon, but the base saturation is less than 50 percent
(by NH4
OAc) in at least part of the argillic horizon. The
swelling clays, saturation, and low saturated hydraulic
conductivity seem to be the most important properties of the
soils in this subgroup. Most of the soils formed in clayey parent
materials. Oxyaquic Vertic Hapludalfs are considered
intergrades to Aquerts. They are not extensive in the United
States. Slopes are gentle. Most of the soils have been cleared
and are used as cropland or pasture, but some of them are used
as forest.
Psammentic Hapludalfs.—These soils have a sandy
particle-size class throughout the upper 75 cm of the argillic
horizon or throughout the entire argillic horizon if it is less
than 75 cm thick. Depth to the argillic horizon may be more
than 100 cm. Generally, the depth is more than 50 cm, and all
horizons above the argillic horizon have a texture of loamy fine
sand or coarser. These soils are permitted, but not required, to
have a color value, moist, of 3 or less in the Ap horizon or in
the surface soil to a depth of 18 cm after mixing and to have a
base saturation (by sum of cations) that is less than 60 percent.
The soils are not extensive in the United States. They are
intergrades between Psamments and Hapludalfs. Most
Psammentic Hapludalfs are in the parts of the United States
that were glaciated, but a few are in Florida. Slopes generally
are gentle. Most of these soils have been cleared and are used
as cropland or pasture, but some of them are used as forest.
Ultic Hapludalfs.—These soils have a base saturation (by
sum of cations) that is less than 60 percent at a depth of 125
cm below the top of the argillic horizon, at a depth of 180 cm
below the soil surface, or directly above a densic, lithic, or
paralithic contact, whichever is shallowest. In addition, the Ap
horizon or the surface soil to a depth of 18 cm after mixing is
permitted, but not required, to have a color value, moist, of 3 or
less. Commonly, the argillic horizon has hue of 7.5YR or
Alfisols 217
redder or has chroma of more than 4. Some Typic Hapludalfs
have these same colors. Ultic Hapludalfs are intergrades
between Hapludults and Hapludalfs. They are moderately
extensive in the United States. Most of them developed from
weathered country rocks but not from acid rocks. Ultic
Hapludalfs are mostly in highly dissected areas where the
landscape is hilly or mountainous. Their slopes range from
gentle to strong. Where slopes are suitable, most of the soils
have been cleared and are used as cropland or pasture. Some of
the soils, mostly the most sloping ones, are used as forest.
Vertic Hapludalfs.—These soils have deep cracks and
appreciable amounts of swelling clays. The swelling clays and
low saturated hydraulic conductivity seem to be the most
important properties of the soils in this subgroup. Most of the
soils formed in clayey parent materials. Vertic Hapludalfs are
moderately extensive. Slopes are gentle to steep, and the soils
are highly erodible. Some of these soils have been cleared and
are used as cropland or pasture, and some, mainly the most
sloping ones, are used as forest.
Kandiudalfs
Kandiudalfs are the Udalfs that have a kandic horizon. These
soils have a clay distribution in which the content of clay does
not decrease from its maximum amount by 20 percent or more
within 150 cm of the soil surface or the layer with the decrease
has at least 5 percent of the volume consisting of skeletans on
faces of peds and there is at least a 3 percent (absolute) increase
in content of clay below this layer. Kandiudalfs do not have a
natric horizon, nor do they have a fragipan within 100 cm of the
mineral soil surface. They do not have both a glossic horizon
and discrete nodules, 2.5 to 30 cm in diameter, that are enriched
with iron and cemented to indurated. These soils are 150 cm or
more deep to a densic, lithic, paralithic, or petroferric contact.
The base of the kandic horizon is commonly more than 150 cm
below the soil surface and in some areas is more than 200 cm
below the surface. Most of these soils have a thermic or warmer
soil temperature regime. The natural vegetation was forest,
mostly deciduous, but many of the soils are now cleared and
used as cropland.
Definition
Kandiudalfs are the Udalfs that:
1. Have a kandic horizon;
2. Do not have a densic, lithic, paralithic, or petroferric contact
within 150 cm of the mineral soil surface;
3. Have a clay distribution in which the percentage of clay
does not decrease from its maximum amount by as much as 20
percent within 150 cm of the soil surface, or the layer in which
the clay percentage decreases by more than 20 percent has at
least 5 percent of the volume consisting of skeletans on faces of
peds and there is at least a 3 percent (absolute) increase in
content of clay below this layer;
4. Do not have a natric horizon;
5. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface;
6. Do not have both a glossic horizon and, in the kandic
horizon, discrete nodules, 2.5 to 30 cm in diameter, that have
enriched exteriors, are weakly cemented with iron, and have
exteriors with redder hue or higher chroma than the interiors.
Key to Subgroups
JEEA. Kandiudalfs that have both:
1. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Plinthaquic Kandiudalfs
JEEB. Other Kandiudalfs that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Kandiudalfs
JEEC. Other Kandiudalfs that are saturated with water in one
or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Kandiudalfs
JEED. Other Kandiudalfs that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
a kandic horizon at a depth of 50 to 100 cm; and
2. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Arenic Plinthic Kandiudalfs
JEEE. Other Kandiudalfs that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
a kandic horizon at a depth of 100 cm or more; and
2. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Grossarenic Plinthic Kandiudalfs
218 Soil Taxonomy
JEEF. Other Kandiudalfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of a kandic horizon at a depth of
50 to 100 cm.
Arenic Kandiudalfs
JEEG. Other Kandiudalfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of a kandic horizon at a depth of
100 cm or more.
Grossarenic Kandiudalfs
JEEH. Other Kandiudalfs that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Kandiudalfs
JEEI. Other Kandiudalfs that have, in all subhorizons in the
upper 100 cm of the kandic horizon or throughout the entire
kandic horizon if less than 100 cm thick, more than 50 percent
colors that have all of the following:
1. Hue of 2.5YR or redder; and
2. Value, moist, of 3 or less; and
3. Dry value no more than 1 unit higher than the moist
value.
Rhodic Kandiudalfs
JEEJ. Other Kandiudalfs that have a mollic epipedon, an Ap
horizon that meets all of the requirements for a mollic
epipedon except thickness, or materials between the soil
surface and a depth of 18 cm that meet these requirements after
mixing.
Mollic Kandiudalfs
JEEK. Other Kandiudalfs.
Typic Kandiudalfs
Definition of Typic Kandiudalfs
Typic Kandiudalfs are the Kandiudalfs that:
1. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
2. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years;
3. Have a texture finer than loamy fine sand in one or more
subhorizons within 50 cm of the mineral soil surface;
4. Do not have, in all subhorizons in the upper 100 cm of the
kandic horizon or throughout the entire kandic horizon if less
than 100 cm thick, more than 50 percent colors that have all of
the following:
a. Hue of 2.5YR or redder; and
b. Value, moist, of 3 or less; and
c. Dry value no more than 1 unit higher than the moist
value;
5. Have a kandic horizon that has a color value, dry, of 5 or
more in some subhorizon, or a color value, moist, that is less
than the value, dry, by more than 1 unit unless hue in some
part of the kandic horizon is 5YR or yellower;
6. Do not have a horizon within 150 cm of the surface that
has 5 percent or more plinthite, by volume; and
7. Do not have a mollic epipedon, an Ap horizon that meets
all of the requirements for a mollic epipedon except thickness,
or materials between the soil surface and a depth of 18 cm that
meet these requirements after mixing.
Description of Subgroups
Typic Kandiudalfs.—The central concept or Typic
subgroup of Kandiudalfs is fixed on freely drained soils that do
not have a thick epipedon with a sandy or sandy-skeletal
particle-size class throughout and that do not have the color of
a mollic epipedon in any Ap horizon or in subhorizons of
comparable thickness if the soils are undisturbed. The kandic
horizon has a color value, dry, of 4.5 or more in some
subhorizon, or the color values, moist and dry, differ by more
than 1 unit unless hue in some part of the kandic horizon is
5YR or yellower. The kandic horizon does not have an
appreciable amount of plinthite.
Soils that have shallow redox depletions with low chroma in
horizons that also have aquic conditions for some time in
normal years (or artificial drainage) are excluded from Typic
Kandiudalfs because these properties are shared with
Kandiaqualfs. A thick epipedon with a sandy or sandy-skeletal
particle-size class throughout is considered atypical and defines
the Arenic and Grossarenic subgroups. The color of a mollic
epipedon in the plow layer or, if the soils are undisturbed, in
surface horizons of comparable thickness is not typical and
defines the Mollic subgroup. Plinthite in appreciable volume
defines the Plinthic subgroup. Typic Kandiudalfs are rare in
the United States.
Aquic Kandiudalfs.—These soils are like Typic Kandiudalfs,
but they have, in one or more horizons within
75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time
in normal years (or artificial drainage). The soils are
permitted, but not required, to have a color value, moist, of
less than 4 and a color value, dry, of less than 6 in the Ap
horizon or in the upper 18 cm after mixing and to have a
sandy or sandy-skeletal particle-size class throughout a layer
extending from the mineral soil surface to the top of a kandic
horizon at a depth of 50 cm or more below the mineral soil
surface. The soils also are permitted to have 5 percent or
more (by volume) plinthite in some subhorizon within 150 cm
Alfisols 219
of the surface. They are not known to occur in the United
States.
Arenic Kandiudalfs.—These soils are like Typic Kandiudalfs,
but they have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to the
top of a kandic horizon at a depth of 50 to 100 cm below the
mineral soil surface. These soils are not known to occur in the
United States.
Arenic Plinthic Kandiudalfs.—These soils are like Typic
Kandiudalfs, but they have a sandy or sandy-skeletal particlesize
class throughout a layer extending from the mineral soil
surface to the top of a kandic horizon at a depth of 50 to 100
cm below the mineral soil surface. They also have 5 percent or
more (by volume) plinthite in some subhorizon within 150 cm
of the surface. During rainy seasons ground water tends to
perch above the horizon that contains plinthite. These soils are
not known to occur in the United States.
Grossarenic Kandiudalfs.—These soils are like Typic
Kandiudalfs, but they have a sandy or sandy-skeletal particlesize
class throughout a layer extending from the mineral soil
surface to the top of a kandic horizon at a depth of 100 cm or
more below the mineral soil surface. These soils are not known
to occur in the United States.
Grossarenic Plinthic Kandiudalfs.—These soils are like
Typic Kandiudalfs, but they have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of a kandic horizon at a depth of
100 cm or more below the mineral soil surface. They also have
5 percent or more (by volume) plinthite in some subhorizon
within 150 cm of the surface. During rainy seasons ground
water tends to perch above the horizon that contains plinthite.
These soils are not known to occur in the United States.
Mollic Kandiudalfs.—These soils are like Typic
Kandiudalfs, but they have a mollic epipedon, an Ap horizon
that meets all of the requirements for a mollic epipedon except
thickness, or materials between the soil surface and a depth of
18 cm that meet these requirements after mixing. These soils
are considered intergrades between Paleudolls and
Kandiudalfs. They are not known to occur in the United States.
Oxyaquic Kandiudalfs.—These soils are like Typic
Kandiudalfs, but they are saturated with water within 100 cm
of the mineral soil surface for 20 or more consecutive days or
30 or more cumulative days in normal years. In addition, the
soils are permitted, but not required, to have a color value,
moist, of 3 or less in the Ap horizon or in the surface soil to a
depth of 18 cm after mixing and to have a sandy or sandyskeletal
particle-size class throughout a layer extending from
the mineral soil surface to the top of a kandic horizon at a
depth of 50 cm or more below the mineral soil surface. They
also are permitted to have 5 percent or more (by volume)
plinthite in some subhorizon within 150 cm of the surface.
These soils are considered intergrades to Aqualfs.
Plinthaquic Kandiudalfs.—These soils are like Typic
Kandiudalfs, but they have, in one or more horizons within 75
cm of the mineral soil surface, redox depletions with chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). They have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of
the mineral soil surface. In addition, the soils are permitted,
but not required, to have a color value, moist, of 3 or less in
the Ap horizon or in the surface soil to a depth of 18 cm, after
mixing. These soils are intergrades between Plinthaqualfs and
Kandiudalfs. They are not known to occur in the United
States.
Plinthic Kandiudalfs.—These soils have 5 percent or more
(by volume) plinthite in some subhorizon within 150 cm of the
surface. In addition, they are permitted, but not required, to
have a color value, moist, of 3 or less in the Ap horizon or in
the surface soil to a depth of 18 cm, after mixing. During rainy
seasons ground water tends to perch above the horizons that
contain plinthite. These soils are not known to occur in the
United States.
Rhodic Kandiudalfs.—These soils are like Typic Kandiudalfs,
but all parts of the kandic horizon have a color value, moist, of
less than 3.5 and a dry color value no more than 1 unit higher
than the moist value and hue in the kandic horizon is redder than
5YR. In addition, the Ap horizon or the upper 18 cm after mixing
commonly has a color value, moist, of less than 3.5 and value,
dry, no more than 1 unit higher than the moist value. These soils
are rare in the United States.
Kanhapludalfs
Kanhapludalfs are the Udalfs that have a kandic horizon.
They do not have a natric horizon, nor do they have a fragipan
with an upper boundary within 100 cm of the mineral soil
surface. They do not have both a glossic horizon and discrete
nodules, 2.5 to 30 cm in diameter, that are enriched with iron
and cemented to indurated. The base of the kandic horizon is
less than 150 cm below the soil surface, or the kandic horizon
has a clay distribution in which the content of clay decreases
from its maximum amount by 20 percent or more within 150
cm of the soil surface, and the layer in which the percentage of
clay is less than the maximum has less than 5 percent of the
volume consisting of skeletans on faces of peds or there is less
than a 3 percent (absolute) increase in content of clay below
this layer. Most of these soils have a thermic or warmer soil
temperature regime. The natural vegetation on Kanhapludalfs
was forest, mostly deciduous, but many of the soils are now
cleared and used as cropland.
Definition
Kanhapludalfs are the Udalfs that:
1. Have a kandic horizon;
2. Have a clay distribution in which the content of clay
decreases from its maximum amount by 20 percent or more
within 150 cm of the soil surface, and the layer in which the
220 Soil Taxonomy
percentage of clay is less than the maximum has less than 5
percent of the volume consisting of skeletans on faces of peds
or there is less than a 3 percent (absolute) increase in content of
clay below this layer;
3. Do not have a natric horizon;
4. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface; and
5. Do not have both a glossic horizon and, in the kandic
horizon, discrete nodules, 2.5 to about 30 cm in diameter, that
are enriched with iron, are extremely weakly cemented to
indurated, and have exteriors with either redder hue and/or
higher chroma than the interiors.
Key to Subgroups
JEFA. Kanhapludalfs that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Kanhapludalfs
JEFB. Other Kanhapludalfs that have, in one or
more horizons within 75 cm of the mineral soil surface,
redox depletions with chroma of 2 or less and also aquic
conditions for some time in normal years (or artificial
drainage).
Aquic Kanhapludalfs
JEFC. Other Kanhapludalfs that are saturated with water in
one or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Kanhapludalfs
JEFD. Other Kanhapludalfs that have, in all subhorizons in
the upper 100 cm of the kandic horizon or throughout the
entire kandic horizon if less than 100 cm thick, more than 50
percent colors that have all of the following:
1. Hue of 2.5YR or redder; and
2. Value, moist, of 3 or less; and
3. Dry value no more than 1 unit higher than the moist
value.
Rhodic Kanhapludalfs
JEFE. Other Kanhapludalfs.
Typic Kanhapludalfs
Definition of Typic Kanhapludalfs
Typic Kanhapludalfs are the Kanhapludalfs that:
1. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
conditions;
2. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30 or
more cumulative days in normal years;
3. Do not have a lithic contact within 50 cm of the soil surface;
and
4. Do not have, in all subhorizons in the upper 100 cm of the
kandic horizon or throughout the entire kandic horizon if less
than 100 cm thick, more than 50 percent colors that have all of
the following:
a. Hue of 2.5YR or redder; and
b. Value, moist, of 3 or less; and
c. Dry value no more than 1 unit higher than the moist
value.
Description of Subgroups
Typic Kanhapludalfs.—The central concept or Typic
subgroup of Kanhapludalfs is fixed on freely drained soils that
are more than 50 cm deep to a lithic contact.
Soils with a kandic horizon that has 50 percent or more
colors with hue of 2.5YR or redder, value, dry, of 3 or less, and
color values, moist and dry, that differ by 1 or less than 1 unit
are excluded from Typic Kanhapludalfs because these
properties are shared with Rhodudalfs. Soils that have shallow
redox depletions with low chroma in horizons that also have
aquic conditions for some time in normal years (or artificial
drainage) are excluded from Typic Kanhapludalfs because
these properties are shared with Kandiaqualfs. Typic
Kanhapludalfs are rare in the United States.
Aquic Kanhapludalfs.—These soils are like Typic
Kanhapludalfs, but they have, in one or more horizons within
75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time
in normal years (or artificial drainage). The soils are
permitted, but not required, to have a kandic horizon that has
50 percent or more colors with hue of 2.5YR or redder, value,
dry, of 3 or less, and color values, moist and dry, that differ by
1 or less than 1 unit, and they are excluded from Typic
Kanhapludalfs because these properties are shared with
Rhodudalfs. Aquic Kanhapludalfs are not known to occur in
the United States.
Lithic Kanhapludalfs.—These soils have a lithic contact
within 50 cm of the mineral soil surface. In addition, they are
permitted to have any color, saturation, or redox feature
allowed in Kanhapludalfs. Lithic Kanhapludalfs are not known
to occur in the United States.
Oxyaquic Kanhapludalfs.—These soils are like Typic
Kanhapludalfs, but they are saturated with water within 100
cm of the mineral soil surface for 20 or more consecutive days
or 30 or more cumulative days in normal years. In addition,
these soils are permitted, but not required, to have a kandic
horizon that has 50 percent or more colors with hue of 2.5YR
or redder, value, dry, of 3 or less, and color values, moist and
Alfisols 221
dry, that differ by 1 or less than 1 unit, and they are excluded
from Typic Kanhapludalfs because these properties are shared
with Rhodudalfs. Oxyaquic Kanhapludalfs are considered
intergrades to Aqualfs. They are not known to occur in the
United States.
Rhodic Kanhapludalfs.—These soils are like Typic
Kanhapludalfs, but all parts of the kandic horizon have a color
value, moist, of less than 3.5 and a dry color value no more
than 1 unit higher than the moist value and hue in the kandic
horizon is redder than 5YR. In addition, the Ap horizon or the
upper 18 cm after mixing commonly has a color value, moist,
of less than 3.5 and value, dry, no more than 1 unit higher than
the moist value. These soils are considered intergrades to
Rhodudalfs. They are rare in the United States.
Natrudalfs
Natrudalfs are the Udalfs that have a natric horizon. Because
the natric horizon is slowly permeable, perched ground water is
common for short periods and the natric horizon commonly has
redoximorphic features. These soils are of small extent in the
United States. Some of the soils were forested. Some supported
open forests, and some supported grass. Most of the soils have
been cleared and are used as cropland or pasture. The soils are
not so productive as most Udalfs, but they generally are farmed
if they occur in very small areas and the associated soils are
productive.
KeytoSubgroups
JEAA. Natrudalfs that have one or both of the following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral soil
surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Natrudalfs
JEAB. Other Natrudalfs that have:
1. Either a glossic horizon or interfingering of albic
materials into the natric horizon; and
2. Redox depletions with chroma of 2 or less in layers that
also have aquic conditions in normal years (or artificial
drainage) either:
a. Within the upper 25 cm of the natric horizon if its
upper boundary is within 50 cm of the mineral soil
surface; or
b. Within 75 cm of the mineral soil surface if the upper
boundary of the natric horizon is 50 cm or more below the
mineral soil surface.
Glossaquic Natrudalfs
JEAC. Other Natrudalfs that have redox depletions with
chroma of 2 or less in layers that also have aquic conditions in
normal years (or artificial drainage) either:
1. Within the upper 25 cm of the natric horizon if its
upper boundary is within 50 cm of the mineral soil surface;
or
2. Within 75 cm of the mineral soil surface if the upper
boundary of the natric horizon is 50 cm or more below the
mineral soil surface.
Aquic Natrudalfs
JEAD. Other Natrudalfs.
Typic Natrudalfs
Definition of Typic Natrudalfs
Typic Natrudalfs are the Natrudalfs that:
1. Do not have redox depletions with chroma of 2 or less in
layers that also have aquic conditions in normal years (or
artificial drainage) either:
a. Within the upper 25 cm of the natric horizon if its
upper boundary is within 50 cm of the mineral soil surface;
or
b. Within 75 cm of the mineral soil surface if the upper
boundary of the natric horizon is 50 cm or more below the
mineral soil surface; and
2. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Description of Subgroups
Typic Natrudalfs.—Typic Natrudalfs are not the most
extensive subgroup, but they furnish the best basis for
definition of subgroups. Most Natrudalfs are not freely drained
because the ground water is perched above the natric horizon
in many years. The perched water table is a probable cause of
the very common albic materials and glossic horizon at the
upper boundary of the natric horizon. Soils that have redox
depletions with low chroma at a shallow depth and also have
aquic conditions are considered to be intergrades toward
222 Soil Taxonomy
Aqualfs. Soils that have cracks and slickensides or wedgeshaped
aggregates are excluded from the Typic subgroup
because these properties are shared with Vertisols.
Aquic Natrudalfs.—Aquic Natrudalfs are not so well
drained as Typic Natrudalfs because the natric horizon
commonly has low or very low saturated hydraulic
conductivity. Soils that have a glossic horizon and
interfingering of albic materials into the upper part of the
natric horizon are excluded from the aquic subgroup because
these properties are shared with Glossaqualfs.
Glossaquic Natrudalfs.—These soils are not so well
drained as Typic Natrudalfs because the natric horizon
commonly has low or very low saturated hydraulic
conductivity. Glossaquic Natrudalfs also have a glossic horizon
or albic materials that interfinger into the natric horizon,
mostly between columns or prisms, commonly to a depth of 10
to 20 cm below their tops. These soils are not extensive in the
United States.
Vertic Natrudalfs.—These soils are like Typic Natrudalfs, but
they are high in content of expanding clays and have cracks 5
mm or more wide, slickensides, wedge-shaped aggregates, or a
linear extensibility of 6.0 cm or more between the mineral soil
surface and either a depth of 100 cm or a densic, lithic, or
paralithic contact, whichever is shallower. Vertic Natrudalfs are
considered intergrades between Natrudalfs and Vertisols. They
are rare in the United States.
Paleudalfs
Paleudalfs are the Alfisols that have a thick solum. These
soils do not have a kandic or natric horizon, nor do they have a
fragipan within 100 cm of the mineral soil surface. Some have
an argillic horizon that shows evidence of destruction in the
form of a glossic horizon, but they do not have both a glossic
horizon and discrete iron-cemented nodules 2.5 to 30 cm in
diameter. Paleudalfs are on relatively stable surfaces. Most of
them are older than the Wisconsinan Glaciation. The time of
soil formation dates from the Sangamon interglacial period or
earlier. Base saturation commonly is lower than that in many
other Alfisols. Before cultivation, most Paleudalfs in the
United States had a vegetation of mixed deciduous hardwood
forest.
Definition
Paleudalfs are the Udalfs that:
1. Do not have a kandic or natric horizon;
2. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface;
3. Have a clay distribution in which the percentage of clay
does not decrease from its maximum amount by as much as 20
percent within 150 cm of the soil surface, or the layer in which
the clay percentage decreases by more than 20 percent has at
least 5 percent of the volume consisting of skeletans on faces of
peds and there is at least a 3 percent (absolute) increase in
content of clay below this layer;
4. Do not have a densic, lithic, or paralithic contact within
150 cm of the soil surface;
5. Have an argillic horizon with one or more of the
following:
a. In 50 percent or more of the matrix of one or more
subhorizons in its lower one-half, hue of 7.5YR or redder
and chroma of 5 or more; or
b. In 50 percent or more of the matrix of horizons that
total more than one-half the total thickness, hue of 2.5YR or
redder, value, moist, of 3 or less, and value, dry, of 4 or less;
or
c. Many coarse redox concentrations with hue of 5YR or
redder or chroma of 6 or more, or both, in one or more
subhorizons;
6. Do not have both a glossic horizon and, in the argillic
horizon, discrete nodules, 2.5 to 30 cm in diameter, that are
cemented or indurated with iron and that have exteriors with
redder hue or higher chroma than the interiors; and
7. Have a frigid temperature regime and all of the following:
a. An argillic horizon that has its upper boundary 60 cm
or more below both:
(1) The mineral soil surface; and
(2) The lower boundary of any surface mantle
containing 30 percent or more vitric volcanic ash,
cinders, or other vitric pyroclastic materials; and
b. A texture (in the fine-earth fraction) finer than loamy
fine sand in one or more horizons above the argillic
horizon; and
c. Either a glossic horizon or interfingering of albic
materials into the argillic horizon.
Key to Subgroups
JEGA. Paleudalfs that have one or both of the following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Paleudalfs
Alfisols 223
JEGB. Other Paleudalfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Paleudalfs
JEGC. Other Paleudalfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Paleudalfs
JEGD. Other Paleudalfs that have both:
1. Fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm
of the mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm
or more thick; and
2. Redox depletions with chroma of 2 or less in layers that
also have aquic conditions in normal years (or artificial
drainage) either:
a. Within the upper 25 cm of the argillic horizon if its
upper boundary is within 50 cm of the mineral soil
surface; or
b. Within 75 cm of the mineral soil surface if the upper
boundary of the argillic horizon is 50 cm or more below
the mineral soil surface.
Fragiaquic Paleudalfs
JEGE. Other Paleudalfs that have both:
1. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Plinthaquic Paleudalfs
JEGF. Other Paleudalfs that have both:
1. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. A glossic horizon or, in the upper part of the argillic
horizon, one or more subhorizons that have 5 percent or
more (by volume) clay depletions with chroma of 2 or less.
Glossaquic Paleudalfs
JEGG. Other Paleudalfs that have both:
1. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. A clay increase of 15 percent or more (absolute) in the
fine-earth fraction within a vertical distance of 2.5 cm at the
upper boundary of the argillic horizon.
Albaquic Paleudalfs
JEGH. Other Paleudalfs that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Paleudalfs
JEGI. Other Paleudalfs that have anthraquic conditions.
Anthraquic Paleudalfs
JEGJ. Other Paleudalfs that are saturated with water in one
or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Paleudalfs
JEGK. Other Paleudalfs that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Paleudalfs
224 Soil Taxonomy
JEGL. Other Paleudalfs that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
an argillic horizon at a depth of 50 to 100 cm; and
2. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Arenic Plinthic Paleudalfs
JEGM. Other Paleudalfs that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
an argillic horizon at a depth of 100 cm or more; and
2. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Grossarenic Plinthic Paleudalfs
JEGN. Other Paleudalfs that have an argillic horizon that:
1. Consists entirely of lamellae; or
2. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
3. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
a. Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
horizon); or
b. A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon.
Lamellic Paleudalfs
JEGO. Other Paleudalfs that have a sandy particle-size class
throughout the upper 75 cm of the argillic horizon or
throughout the entire argillic horizon if it is less than 75 cm
thick.
Psammentic Paleudalfs
JEGP. Other Paleudalfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 to 100 cm.
Arenic Paleudalfs
JEGQ. Other Paleudalfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 100 cm or more.
Grossarenic Paleudalfs
JEGR. Other Paleudalfs that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Paleudalfs
JEGS. Other Paleudalfs that have either:
1. A glossic horizon; or
2. In the upper part of the argillic horizon, one or more
subhorizons that have 5 percent or more (by volume)
skeletans with chroma of 2 or less; or
3. 5 percent or more (by volume) albic materials in some
subhorizon of the argillic horizon.
Glossic Paleudalfs
JEGT. Other Paleudalfs that have, in all subhorizons in the
upper 100 cm of the argillic horizon or throughout the entire
argillic horizon if less than 100 cm thick, more than 50 percent
colors that have all of the following:
1. Hue of 2.5YR or redder; and
2. Value, moist, of 3 or less; and
3. Dry value no more than 1 unit higher than the moist
value.
Rhodic Paleudalfs
JEGU. Other Paleudalfs that have a mollic epipedon, an Ap
horizon that meets all of the requirements for a mollic
epipedon except thickness, or materials between the soil
surface and a depth of 18 cm that meet these requirements after
mixing.
Mollic Paleudalfs
JEGV. Other Paleudalfs.
Typic Paleudalfs
Definition of Typic Paleudalfs
Typic Paleudalfs are the Paleudalfs that:
1. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
Alfisols 225
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
2. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions and do not have an increase of 15 percent or
more (absolute) clay within a vertical distance of 2.5 cm at the
upper boundary of the argillic horizon;
3. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years;
4. Do not have anthraquic conditions;
5. Have a texture finer than loamy fine sand in one or more
subhorizons within 50 cm of the mineral soil surface;
6. Do not have, in all subhorizons in the upper 100 cm of the
argillic horizon or throughout the entire argillic horizon if less
than 100 cm thick, more than 50 percent colors that have all of
the following:
a. Hue of 2.5YR or redder; and
b. Value, moist, of 3 or less; and
c. Dry value no more than 1 unit higher than the moist
value;
7. Have an argillic horizon that has a color value, dry, of 4.5
or more in some subhorizon, or a color value, moist, that is less
than the value, dry, by more than 1 unit unless hue in some
part of the argillic horizon is 5YR or yellower;
8. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
9. Have less than 5 percent (by volume) plinthite in all
subhorizons within 150 cm of the surface;
10. Have an argillic horizon that is finer than the sandy
particle-size class in some part of the upper 75 cm if the
argillic horizon is more than 75 cm thick or in any part if the
argillic horizon is less than 75 cm thick;
11. Do not have a glossic horizon or subhorizons in the upper
part of the argillic horizon that have clay depletions that:
a. Have moist chroma of 2 or less; and
b. Occupy 5 percent or more of the volume of the
subhorizon;
12. Do not have albic materials that constitute as much as 5
percent of any subhorizon of the argillic horizon;
13. Have an argillic horizon that meets none of the following:
a. Consists entirely of lamellae; or
b. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
c. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
(1) Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
horizon); or
(2) A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon;
14. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick;
15. Do not have a mollic epipedon, an Ap horizon that meets
all of the requirements for a mollic epipedon except thickness,
or materials between the soil surface and a depth of 18 cm that
meet these requirements after mixing.
Description of Subgroups
Typic Paleudalfs.—The central concept or Typic subgroup
of Paleudalfs is fixed on freely drained soils that do not have a
thick epipedon with a sandy or sandy-skeletal particle-size
class throughout. These soils do not have a mollic epipedon or
an Ap horizon or subhorizons of comparable thickness that
meet all of the requirements for a mollic epipedon except
thickness. The argillic horizon has a color value, dry, of 5 or
more in some subhorizon, or the color values, moist and dry,
differ by more than 1 unit unless hue in some part of the
argillic horizon is 5YR or yellower. The argillic horizon does
not have cracks and slickensides or wedge-shaped aggregates,
and it does not have an appreciable amount of plinthite or a
sandy texture throughout. These soils do not have albic
materials that constitute as much as 5 percent of any
subhorizon of the argillic horizon.
Soils that have shallow redox depletions with low chroma in
226 Soil Taxonomy
horizons that also have aquic conditions for some time in normal
years (or artificial drainage) are excluded from Typic Paleudalfs
because these properties are shared with Aqualfs. A thick
epipedon with a sandy or sandy-skeletal particle-size class
throughout is considered atypical and defines the Arenic and
Grossarenic subgroups. Typic Paleudalfs do not have a surface
mantle or layer in the upper 75 cm that has both a low bulk
density and a high content of weakly crystalline minerals or that
consists of slightly or moderately weathered pyroclastic
materials because these properties are shared with Andisols.
Soils that have a mollic epipedon or that meet all of the
requirements for a mollic epipedon, except for thickness, in the
plow layer or in surface horizons of comparable thickness are
considered atypical, and these properties define the Mollic
subgroup. Plinthite in appreciable volume defines the Plinthic
subgroup. An argillic horizon that has a sandy particle-size
class throughout its upper 75 cm is the basis for defining the
Psammentic subgroup. An argillic horizon that is composed
entirely of lamellae is the basis for defining the Lamellic
subgroup.
Typic Paleudalfs are moderately extensive in the United
States. Many are in the unglaciated areas of the Southern
States. Most of the soils that have gentle or moderate slopes
have been cleared of the original forests and are used as
cropland.
Albaquic Paleudalfs.—These soils are like Typic
Paleudalfs, but they have, in one or more horizons within 75
cm of the mineral soil surface, redox depletions with chroma of
2 or less and also aquic conditions for some time in normal
years (or artificial drainage). They have an increase of 15
percent or more in the amount of clay (absolute) within a
vertical distance of 2.5 cm at the top of the argillic horizon.
They are intergrades between Albaqualfs and Paleudalfs. They
are mainly in Oklahoma and are not extensive in the United
States.
Andic and Vitrandic Paleudalfs.—These soils are like
Typic Paleudalfs, but they have a surface mantle or layer in the
upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. These
soils occur in the foothills and mountains of the Western
United States. They are permitted, but not required, to have
redox depletions and to be saturated with water within 100 cm
of the mineral soil surface for 7 or more consecutive days or 20
or more cumulative days in normal years. The soils are
permitted, but not required, to have a mollic epipedon or an Ap
horizon or other subhorizons of comparable thickness that meet
all of the requirements for a mollic epipedon, except for
thickness, after mixing. These soils are of very small extent but
are locally important. They generally have a frigid temperature
regime and are used as forest. Some areas have been cleared
and are used as cropland or pasture.
Anthraquic Paleudalfs.—These soils are like Typic
Paleudalfs, but they have been irrigated for paddy rice
production for many years and have developed anthraquic
conditions. They are permitted, but not required, to have redox
depletions with chroma of 2 or less in layers that also have
aquic conditions in normal years either within the upper 25 cm
of the argillic horizon if its upper boundary is within 50 cm of
the mineral soil surface or within 75 cm of the mineral soil
surface if the upper boundary of the argillic horizon is deeper
than 50 cm. These soils are permitted, but not required, to have
a mollic epipedon or an Ap horizon that meets all of the
requirements for a mollic epipedon except thickness. They
have level or nearly level slopes. They are not extensive and
are not known to occur in the United States. They have been
cleared of the original forests and are used mostly for paddy
rice.
Aquic Paleudalfs.—These soils are like Typic Paleudalfs,
but they have, in one or more horizons within 75 cm of the
mineral soil surface, redox depletions with chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage). A gray, sandy albic horizon is not adequate
evidence of wetness. These soils are permitted, but not
required, to have a mollic epipedon or an Ap horizon or other
subhorizons of comparable thickness that meet all of the
requirements for a mollic epipedon, except for thickness, after
mixing. The soils are not extensive in the United States. Most
of them are in the Southern States. Slopes are gentle, and most
of the soils have been cleared of the original forests and are
used as cropland.
Arenic Paleudalfs.—These soils have a sandy or sandyskeletal
particle-size class throughout a layer extending from
the mineral soil surface to the top of an argillic horizon at a
depth of 50 to 100 cm below the mineral soil surface. The
argillic horizons are mostly loamy and tend to have more sand
than those in Typic Paleudalfs. Arenic Paleudalfs are rare in
the United States. They occur on plains and high terraces,
mostly in Texas and Oklahoma. Slopes are mostly gentle. Most
of these soils are used as pasture, but some are used as
cropland.
Arenic Plinthic Paleudalfs.—These soils have a sandy or
sandy-skeletal particle-size class throughout a layer extending
from the mineral soil surface to the top of an argillic horizon at
a depth of 50 to 100 cm below the mineral soil surface. They
have 5 percent or more (by volume) plinthite in some
subhorizon within 150 cm of the surface. During rainy seasons
ground water tends to perch above the horizon that contains
plinthite. These soils are rare in the United States. They are
mostly on the coastal plain in Texas. Most of the soils are in
forests.
Fragiaquic Paleudalfs.—These soils are like Typic
Paleudalfs, but they have redox depletions with low chroma
and also aquic conditions at a shallow depth for some time in
normal years. In addition, they have fragic soil properties in 30
percent or more of the volume of a layer 15 cm or more thick
that has its upper boundary within 100 cm of the mineral soil
surface or in 60 percent or more of the volume of a layer 15 cm
Alfisols 227
or more thick anywhere in the soils. These soils are permitted,
but not required, to have a mollic epipedon or an Ap horizon or
other subhorizons of comparable thickness that meet all of the
requirements for a mollic epipedon, except for thickness, after
mixing. These soils are considered intergrades to Fraqiaqualfs.
They are not extensive in the United States.
Fragic Paleudalfs.—These soils are like Typic Paleudalfs,
but they have fragic soil properties in 30 percent or more of the
volume of a layer 15 cm or more thick that has its upper
boundary within 100 cm of the mineral soil surface or in 60
percent or more of the volume of a layer 15 cm or more thick
anywhere in the soils. These soils are considered intergrades to
Fraqiudalfs. They are not extensive in the United States.
Glossaquic Paleudalfs.—These soils are like Typic
Paleudalfs, but they have, in one or more horizons within 75
cm of the mineral soil surface, redox depletions with chroma of
2 or less and also aquic conditions for some time in normal
years (or artificial drainage). In addition, they have a glossic
horizon or a subhorizon within the argillic horizon, commonly
25 cm or more below its upper boundary, that has thick
skeletans of low chroma. These soils are permitted, but not
required, to have a mollic epipedon or an Ap horizon or other
subhorizons of comparable thickness that meet all of the
requirements for a mollic epipedon, except for thickness, after
mixing. These soils are of minor extent in the central part of
the Southern United States.
Glossic Paleudalfs.—These soils have a glossic horizon or
a subhorizon within the argillic horizon, commonly 25 cm or
more below its upper boundary, that has thick skeletans of low
chroma that occupy an appreciable part of the mass of the
subhorizon. These soils are permitted, but not required, to have
a mollic epipedon or an Ap horizon or other subhorizons of
comparable thickness that meet all of the requirements for a
mollic epipedon, except for thickness, after mixing. The soils
are otherwise like Typic Paleudalfs in defined properties and in
accessory properties. They are not extensive in the United
States. They occur mostly in the central part of the Southern
United States. Slopes are very gentle, and most of the soils are
used as cropland.
Grossarenic Paleudalfs.—These soils have a sandy or
sandy-skeletal particle-size class throughout a layer extending
from the mineral soil surface to the top of an argillic horizon at
a depth of 100 cm or more below the mineral soil surface. The
argillic horizons are mostly loamy and tend to have more sand
than those in Typic Paleudalfs. Grossarenic Paleudalfs are of
small extent in the United States. They occur on the coastal
plain in Texas and Florida. Slopes are gentle. The soils are
used mainly as pasture, but some are used as cropland.
Grossarenic Plinthic Paleudalfs.—These soils have a
sandy or sandy-skeletal particle-size class throughout a layer
extending from the mineral soil surface to the top of an argillic
horizon at a depth of 100 cm or more below the mineral soil
surface. The argillic horizon contains some plinthite, and
ground water may be perched above the plinthite during rainy
seasons. These soils are rare in the United States. They are
mostly on the coastal plain in Texas. Slopes are gentle. Most of
these soils are used as forest.
Lamellic Paleudalfs.—These soils are like Typic
Paleudalfs, but they have an argillic horizon that consists
entirely of lamellae or is a combination of two or more
lamellae and one or more subhorizons with a thickness of 7.5
to 20 cm, each layer with an overlying eluvial horizon. In some
of the soils, the argillic horizon consists of one or more
subhorizons that are more than 20 cm thick, each with an
overlying eluvial horizon, and above these horizons there are
either two or more lamellae with a combined thickness of 5 cm
or more or a combination of lamellae and one or more parts of
the argillic horizon 7.5 to 20 cm thick, each with an overlying
eluvial horizon These soils are permitted, but not required, to
have a color value, moist, of 3 or less in the Ap horizon or in
the surface soil to a depth of 18 cm, after mixing. They are not
extensive in the United States.
Mollic Paleudalfs.—These soils are like Typic Paleudalfs,
but they have a mollic epipedon, an Ap horizon that meets all
of the requirements for a mollic epipedon except thickness, or
materials between the soil surface and a depth of 18 cm that
meet these requirements after mixing. Many of the Mollic
Paleudalfs in the United States had grass vegetation or open
forest vegetation before they were cultivated. Mollic Paleudalfs
are considered intergrades between Paleudalfs and Paleudolls.
They are not extensive in the United States. Most of them are
in the center of the country, from Wisconsin to Oklahoma and
the adjacent states. Slopes are mainly gentle, and most of the
soils are used as cropland.
Oxyaquic Paleudalfs.—These soils are like Typic
Paleudalfs, but they are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years. These soils are
permitted, but not required, to have a mollic epipedon or an Ap
horizon or other subhorizons of comparable thickness that meet
all of the requirements for a mollic epipedon, except for
thickness, after mixing. The soils are not extensive in the
United States.
Plinthaquic Paleudalfs.—These soils have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage). They
also have 5 percent or more (by volume) plinthite in some
subhorizon within 150 cm of the soil surface. These soils are
permitted, but not required, to have a mollic epipedon or an Ap
horizon or other subhorizons of comparable thickness that meet
all of the requirements for a mollic epipedon, except for
thickness, after mixing. They are of small extent, mostly in
Texas, in the United States.
Plinthic Paleudalfs.—These soils have 5 percent or more
(by volume) plinthite in some subhorizon within 150 cm of the
soil surface. During rainy seasons ground water tends to perch
for short periods above the horizons that contain plinthite.
228 Soil Taxonomy
These soils are not extensive in the United States. They occur
mainly along the gulf coast in Texas. Their slopes are mostly
gentle. Many of the soils are used as cropland, but some are in
forests.
Psammentic Paleudalfs.—These soils have an argillic
horizon that has a sandy particle-size class throughout the
upper 75 cm or throughout the entire thickness if it is less than
75 cm thick. The clay content of the argillic horizon
approaches that of a sandy loam in most of the soils.
Psammentic Paleudalfs commonly have an epipedon that has a
texture of loamy fine sand or coarser throughout its thickness
and that may be either more or less than 50 cm thick. The soils
are permitted, but not required, to have a mollic epipedon or an
Ap horizon or other subhorizons of comparable thickness that
meet all of the requirements for a mollic epipedon, except for
thickness, after mixing. These soils are considered intergrades
between Udipsamments and Paleudalfs. They are of small
extent in the United States. Most of them are used as forest, but
some have been cleared of trees and are used as pasture or
cropland.
Rhodic Paleudalfs.—These soils are like Typic Paleudalfs,
but all parts of the argillic horizon have a color value, moist, of
less than 3.5 and a dry color value no more than 1 unit higher
than the moist value and hue in the argillic horizon is 2.5YR
or redder. In addition, the Ap horizon or the upper 18 cm after
mixing normally has a color value, moist, of less than 3.5 and
value, dry, no more than 1 unit higher than the moist value.
These soils are of small extent in the United States. They occur
in the Southeastern States. Their slopes are mainly gentle.
Most of the soils have been cleared of trees and are used as
cropland or pasture.
Vertic Paleudalfs.—These soils are high in content of
expanding clays and have cracks 5 mm or more wide,
slickensides, wedge-shaped aggregates, or a linear extensibility
of 6.0 cm or more between the mineral soil surface and either a
depth of 100 cm or a densic, lithic, or paralithic contact,
whichever is shallower. They are permitted, but not required, to
have redox depletions and to be saturated with water within
100 cm of the mineral soil surface for 7 or more consecutive
days or 20 or more cumulative days in normal years. These
soils also are permitted, but not required, to have a mollic
epipedon or an Ap horizon or other subhorizons of comparable
thickness that meet all of the requirements for a mollic
epipedon, except for thickness, after mixing. The soils are of
small extent in the United States. Most of them are used as
forest or pasture, but some are used as cropland.
Rhodudalfs
Rhodudalfs are dark red Udalfs that have a thinner solum
than that of Paleudalfs. Rhodudalfs do not have a kandic or
natric horizon. They do not have a fragipan with an upper
boundary within 100 cm of the mineral soil surface. They do
not have both a glossic horizon and discrete nodules, 2.5 to 30
cm in diameter, that are enriched with iron and cemented to
indurated. Their parent materials are mostly basic. These soils
are rare in the United States, and definitions of subgroups have
not been developed.
Definition
Rhodudalfs are the Udalfs that:
1. Have, in all subhorizons in the upper 100 cm of the argillic
horizon or throughout the entire argillic horizon if less than 100
cm thick, more than 50 percent colors that have all of the
following:
a. Hue of 2.5YR or redder; and
b. Value, moist, of 3 or less; and
c. Dry value no more than 1 unit higher than the moist
value;
2. Do not have a kandic or natric horizon;
3. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface;
4. Do not have both a glossic horizon and, in the argillic
horizon, discrete nodules, 2.5 to about 30 cm in diameter, that
are enriched with iron, are extremely weakly cemented to
indurated, and that have exteriors with either redder hue
and/or higher chroma than the interiors; and
5. Have either a densic, lithic, or paralithic contact within
150 cm of the soil surface; or
a. Within 150 cm of the mineral soil surface, have both:
(1) A clay decrease with increasing depth of 20 percent
or more (relative) from the maximum clay content; and
(2) Less than 5 percent (by volume) skeletans on faces
of peds in the layer that has a 20 percent lower clay
content or, below that layer, a clay increase of less than 3
percent (absolute) in the fine-earth fraction.
Key to Subgroups
JEHA. All Rhodudalfs (provisionally).
TypicRhodudalfs
Ustalfs
Ustalfs are the Alfisols of subhumid to semiarid regions.
They have an ustic moisture regime and a frigid, mesic,
isomesic, or warmer temperature regime. They do not have,
near the soil surface, both redoximorphic features with low
chroma and aquic conditions (other than anthraquic
conditions) for some time in normal years. Moisture moves
through most of these soils to deeper layers only in occasional
years. If there are carbonates in the parent materials or in the
dust that settles on the surface, the soils tend to have a Bk or
calcic horizon below or in the argillic or kandic horizon. The
Alfisols 229
dry season or seasons are pronounced enough that trees are
either deciduous or xerophytic. Many of these soils have or
have had a savanna vegetation, and some were grasslands.
Most of the soils are used as cropland or for grazing. Some are
used as irrigated cropland. Sorghum, wheat, and cotton are the
most common crops. Droughts are common.
Ustalfs tend to form a belt between the Aridisols of arid
regions and the Udalfs, Ultisols, Oxisols, and Inceptisols of
humid regions. The temperature regimes of Ustalfs are mostly
thermic, isothermic, or warmer. These soils are extensive in the
world. In the United States, their area is moderate, but the soils
are extensive in the southern part of the Great Plains.
Ustalfs may be in areas of erosional surfaces or deposits of
late-Wisconsinan age, but a great many, and characteristically
those of warm regions, are on old surfaces. In the Ustalfs on
old surfaces, the minerals have been strongly weathered,
possibly in an environment more humid than the present one.
At least, the clays in many of these older soils are kaolinitic.
The base saturation in them at present probably reflects
additions of bases in dust and rain.
Definition
Ustalfs are the Alfisols that:
1. Have an ustic moisture regime;
2. Have chroma too high for Aqualfs or do not have aquic
conditions within 50 cm of the mineral soil surface for some
time in normal years; and
3. Have a frigid, mesic, isomesic, or warmer temperature
regime.
Key to Great Groups
JCA. Ustalfs that have a duripan that has its upper boundary
within 100 cm of the mineral soil surface.
Durustalfs, p. 230
JCB. Other Ustalfs that have one or more horizons within
150 cm of the mineral soil surface in which plinthite either
forms a continuous phase or constitutes one-half or more of the
volume.
Plinthustalfs, p. 252
JCC. Other Ustalfs that have a natric horizon.
Natrustalfs, p. 241
JCD. Other Ustalfs that:
1. Have a kandic horizon; and
2. Do not have a densic, lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface; and
3. Within 150 cm of the mineral soil surface, either:
a. Do not have a clay decrease with increasing depth of
20 percent or more (relative) from the maximum clay
content [Clay is measured noncarbonate clay or based on
the following formula: Clay % = 2.5(% water retained at
1500 kPa tension - % organic carbon), whichever value is
greater, but no more than 100]; or
b. Have 5 percent or more (by volume) skeletans on
faces of peds in the layer that has a 20 percent lower clay
content and, below that layer, a clay increase of 3 percent
or more (absolute) in the fine-earth fraction.
Kandiustalfs, p. 237
JCE. Other Ustalfs that have a kandic horizon.
Kanhaplustalfs, p. 240
JCF. Other Ustalfs that have one or more of the following:
1. A petrocalcic horizon that has its upper boundary
within 150 cm of the mineral soil surface; or
2. No densic, lithic, or paralithic contact within 150 cm of
the mineral soil surface and an argillic horizon that has
both:
a. Within 150 cm of the mineral soil surface, either:
(1) With increasing depth, no clay decrease of 20
percent or more (relative) from the maximum clay
content [Clay is measured noncarbonate clay or based
on the following formula: Clay % = 2.5(% water
retained at 1500 kPa tension - % organic carbon),
whichever value is greater, but no more than 100]; or
(2) 5 percent or more (by volume) skeletans on faces
of peds in the layer that has a 20 percent lower clay
content and, below that layer, a clay increase of 3
percent or more (absolute) in the fine-earth fraction;
and
b. In the lower one-half of the argillic horizon, one or
more subhorizons with either or both:
(1) Hue of 7.5YR or redder and chroma of 5 or more
in 50 percent or more of the matrix; or
(2) Common or many coarse redox concentrations
with hue of 7.5YR or redder or chroma of 6 or more,
or both; or
3. No densic, lithic, or paralithic contact within 50 cm of
the mineral soil surface and an argillic horizon that has
both:
a. A clayey or clayey-skeletal particle-size class
throughout one or more subhorizons in its upper part;
and
b. At its upper boundary, a clay increase (in the fineearth
fraction) of either 20 percent or more (absolute)
230 Soil Taxonomy
within a vertical distance of 7.5 cm or of 15 percent or more
(absolute) within a vertical distance of 2.5 cm.
Paleustalfs, p. 246
JCG. Other Ustalfs that have, in all subhorizons in the upper
100 cm of the argillic horizon or throughout the entire argillic
horizon if less than 100 cm thick, more than 50 percent colors
that have all of the following:
1. Hue of 2.5YR or redder; and
2. Value, moist, of 3 or less; and
3. Dry value no more than 1 unit higher than the moist
value.
Rhodustalfs, p. 252
JCH. Other Ustalfs.
Haplustalfs, p. 230
Durustalfs
Durustalfs are the Ustalfs that have a duripan that has its
upper boundary within 100 cm of the mineral soil surface.
They are not known to occur in the United States, but the great
group has been provided for use in other countries. Subgroups
have not been developed.
Key to Subgroups
JCAA. All Durustalfs (provisionally).
Typic Durustalfs
Haplustalfs
Haplustalfs are the Ustalfs that have an argillic horizon. They
do not have a kandic or natric horizon, do not have a duripan
that has its upper boundary within 100 cm of the surface, do not
have a petrocalcic horizon within 150 cm of the surface, and do
not have much plinthite. Many of these soils are relatively thin,
are reddish to yellowish brown, or have a significant clay
decrease within 150 cm of the surface. They are not dark red or
dusky red throughout the argillic horizon. The argillic horizon
does not have both a clayey or clayey-skeletal particle-size class
in some subhorizon in its upper part and an abrupt upper
boundary.
Haplustalfs are commonly in areas of relatively recent
erosional surfaces or deposits, most of them late Pleistocene in
age. Some of the soils have a monsoon climate. Others have
two more or less marked dry seasons during the year.
Definition
Haplustalfs are the Ustalfs that:
1. Have an argillic horizon but do not have a kandic or natric
horizon;
2. Do not have a duripan that has an upper boundary within
100 cm of the mineral soil surface;
3. Do not have a petrocalcic horizon that has an upper
boundary within 150 cm of the mineral soil surface;
4. Do not have plinthite that forms a continuous phase or
constitutes more than half the matrix within any subhorizon
of the argillic horizon within 125 cm of the mineral soil
surface;
5. Have an argillic horizon that in some part has hue no
redder than 5YR or value, moist, of 4 or more or value, dry,
more than 1 unit higher than the moist value;
6. Have a densic, lithic, or paralithic contact at a depth of less
than 150 cm below the mineral soil surface, or the argillic
horizon has either:
a. Within 150 cm of the mineral soil surface: either
(1) A clay decrease with increasing depth of 20 percent
or more (relative) from the maximum clay content; or
(2) Less than 5 percent (by volume) skeletans on faces
of peds in the layer that has a 20 percent lower clay
content or, below that layer, no clay increase of as much
as 3 percent (absolute) in the fine-earth fraction; or
b. All of the following:
(1) In 50 percent or more of the matrix of all
subhorizons in its lower one-half, hue of 10YR or
yellower or chroma of 4 or less; and
(2) In less than one-half of the total thickness,
subhorizons that have, in 50 percent or more of the
matrix, hue of 7.5YR or redder, a color value, moist, of 3
or less, and a color value, dry, of 4 or less; and
(3) In the matrix of all subhorizons in its lower onehalf,
few or no coarse redox concentrations with hue of
7.5YR or redder or chroma of 6 or more, or both;
7. Have a densic, lithic, or paralithic contact at a depth of less
than 50 cm below the mineral soil surface, or the argillic
horizon either:
a. Does not have a clayey or clayey-skeletal particle-size
class in some subhorizon in its upper part; or
b. At its upper boundary, has a clay increase, in the fineearth
fraction, of less than 15 percent (absolute) within a
vertical distance of 2.5 cm, and less than 20 percent
(absolute) within a vertical distance of 7.5 cm.
Key to Subgroups
JCHA. Haplustalfs that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Haplustalfs
Alfisols 231
JCHB. Other Haplustalfs that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage).
Aquertic Haplustalfs
JCHC. Other Haplustalfs that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. Saturation with water in one or more layers within 100
cm of the mineral soil surface in normal years for either or
both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days.
Oxyaquic Vertic Haplustalfs
JCHD. Other Haplustalfs that have both of the following:
1. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the cumulative days per
year when the soil temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for less than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
5 o
C;
2. One or both of the following:
a. Cracks within 125 cm of the soil surface that are 5
mm or more wide through a thickness of 30 cm or more
for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the soil
surface; or
b. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact, whichever is shallower.
Torrertic Haplustalfs
JCHE. Other Haplustalfs that have both:
1. When neither irrigated nor fallowed to store moisture,
either:
a. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for four-tenths or less of the cumulative days
per year when the temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C; or
b. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for less than 120
cumulative days per year when the temperature at a depth
of 50 cm below the soil surface is higher than 8 o
C; and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
232 Soil Taxonomy
densic, lithic, or paralithic contact, whichever is
shallower.
UderticHaplustalfs
JCHF. Other Haplustalfs that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Haplustalfs
JCHG. Other Haplustalfs that have both:
1. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
an argillic horizon at a depth of 50 to 100 cm.
Aquic Arenic Haplustalfs
JCHH. Other Haplustalfs that have both:
1. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. An argillic horizon that has a base saturation (by sum
of cations) of less than 75 percent throughout.
Aquultic Haplustalfs
JCHI. Other Haplustalfs that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Haplustalfs
JCHJ. Other Haplustalfs that are saturated with water in one
or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Haplustalfs
JCHK. Other Haplustalfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm of
the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser than
2.0 mm, of which more than 66 percent is cinders, pumice, and
pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Haplustalfs
JCHL. Other Haplustalfs that have an argillic horizon that:
1. Consists entirely of lamellae; or
2. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
3. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
a. Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
horizon); or
b. A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon.
Lamellic Haplustalfs
JCHM. Other Haplustalfs that have a sandy particle-size class
throughout the upper 75 cm of the argillic horizon or
throughout the entire argillic horizon if it is less than 75 cm
thick.
Psammentic Haplustalfs
JCHN. Other Haplustalfs that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
an argillic horizon at a depth of 50 cm or more; and
2. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
Alfisols 233
b. A mesic or thermic soil temperature regime
and a moisture control section that in normal years
is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature
at a depth of 50 cm below the soil surface is higher
than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for less than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
5 o
C.
Arenic Aridic Haplustalfs
JCHO. Other Haplustalfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 cm or more.
Arenic Haplustalfs
JCHP. Other Haplustalfs that have both:
1. A calcic horizon with its upper boundary within 100 cm
of the mineral soil surface; and
2. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for less than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
5o
C.
Calcidic Haplustalfs
JCHQ. Other Haplustalfs that, when neither irrigated nor
fallowed to store moisture, have one of the following:
1. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for four-tenths
or more of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for six-tenths or more of the cumulative days per year
when the soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
3. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
a. Is moist in some or all parts for less than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
b. Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 5 o
C.
Aridic Haplustalfs
JCHR. Other Haplustalfs that have a CEC of less than 24
cmol(+)/kg clay (by 1N NH4
OAc pH 7) in 50 percent or more
either of the argillic horizon if less than 100 cm thick or of its
upper 100 cm.
Kanhaplic Haplustalfs
JCHS. Other Haplustalfs that have:
1. An argillic, kandic, or natric horizon that is 35 cm or
less thick; and
2. No densic, lithic, or paralithic contact within 100 cm of
the mineral soil surface.
Inceptic Haplustalfs
JCHT. Other Haplustalfs that have both:
1. A calcic horizon with its upper boundary within 100 cm
of the mineral soil surface; and
2. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in some or all parts for
less than 105 cumulative days per year when the
234 Soil Taxonomy
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for four-tenths or less of the cumulative days
per year when the temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for less than 120
cumulative days per year when the temperature at a depth
of 50 cm below the soil surface is higher than 8 o
C.
Calcic Udic Haplustalfs
JCHU. Other Haplustalfs that have an argillic horizon with a
base saturation (by sum of cations) of less than 75 percent
throughout.
Ultic Haplustalfs
JCHV. Other Haplustalfs that have a calcic horizon with its
upper boundary within 100 cm of the mineral soil surface.
Calcic Haplustalfs
JCHW. Other Haplustalfs that, when neither irrigated nor
fallowed to store moisture, have one of the following:
1. A frigid temperature regime and a moisture control
section that in normal years is dry in some or all parts for
less than 105 cumulative days per year when the
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for four-tenths or less of the cumulative days per year
when the temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
3. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for less than 120
cumulative days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8 o
C.
Udic Haplustalfs
JCHX. Other Haplustalfs.
Typic Haplustalfs
Definition of Typic Haplustalfs
Typic Haplustalfs are the Haplustalfs that:
1. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
2. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30 or
more cumulative days in normal years;
3. Have a texture finer than loamy fine sand in one or more
subhorizons within 50 cm of the mineral soil surface;
4. Do not have a lithic contact within 50 cm of the soil
surface;
5. Have a CEC of 24 or more cmol(+)/kg clay (by 1N
NH4
OAc pH 7) in the major part of the argillic horizon or in
the major part of its upper 100 cm if the argillic horizon is
more than 100 cm thick;
6. Do not have a sandy particle-size class throughout the
upper 75 cm of the argillic horizon or throughout the entire
argillic horizon if it is less than 75 cm thick;
7. When neither irrigated nor fallowed to store moisture:
a. Have a frigid soil temperature regime and both are dry
in some or all parts of the soil moisture control section for
105 or more cumulative days and are dry in all parts of the
soil moisture control section for less than four-tenths of the
cumulative days per year in normal years and during a
period when the temperature at a depth of 50 cm below the
soil surface is higher than 5 o
C; or
b. Have a mesic or thermic soil temperature regime and
both are dry for more than four-tenths of the cumulative
days per year in some part of the moisture control section
and are dry for less than six-tenths of the time in some part
of the moisture control section (not necessarily the same
part) in normal years and during a period when the soil
temperature at a depth of 50 cm exceeds 5 o
C; or
c. Have a hyperthermic, isomesic, or warmer soil
temperature regime and:
(1) Are dry in some or all parts of the moisture control
section for 120 or more cumulative days per year; and
(2) Are moist in some or all parts of the moisture
control section for 90 or more consecutive days per year
both in normal years and during a period when the soil
temperature at a depth of 50 cm exceeds 8 o
C; and
(3) Are moist in some or all parts for six-tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C;
8. Have an argillic horizon that has a base saturation (by sum
of cations) of 75 percent or more in some part;
9. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
Alfisols 235
that has its upper boundary within 125 cm of the mineral soil
surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
10. Do not have a calcic horizon with its upper boundary
within 100 cm of the mineral soil surface;
11. Have an argillic horizon that meets none of the following:
a. Consists entirely of lamellae; or
b. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
c. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
(1) Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
horizon); or
(2) A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon;
12. Have an argillic horizon more than 35 cm thick; and
13. Do not have, throughout one or more horizons with a
total thickness of 18 cm or more within 75 cm of the mineral
soil surface, one or both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Description of Subgroups
Typic Haplustalfs.—The central concept or Typic subgroup
of Haplustalfs is fixed on freely drained soils that are
moderately deep or deep to hard rock; that have an argillic
horizon that has a loamy or clayey particle-size class, some 2:1
lattice clay, and high base saturation; that do not have deep,
wide cracks in normal years; that do not have a calcic horizon
at a moderate depth; and that are moist for an appreciable part
of a growing season.
Soils that have redox depletions with low chroma near the
surface in one or more horizons that also have aquic conditions
for some time in normal years (or artificial drainage) are
excluded from Typic Haplustalfs because these properties are
shared with Aqualfs. Soils that are saturated with water in one
or more layers within 100 cm of the mineral soil surface for 20
or more consecutive days or 30 or more cumulative days in
normal years are considered atypical and define the Oxyaquic
subgroup. A thick layer, starting at the mineral soil surface, of
sand or loamy sand is not considered normal and defines
Arenic subgroups, a convention used elsewhere in this
taxonomy. A shallow lithic contact defines the Lithic subgroup,
another convention used throughout this taxonomy. Clays that
have low activity suggest strong weathering and are used to
define the Kanhaplic subgroup. An argillic horizon that has a
texture of loamy fine sand or coarser is not considered normal
and defines the Psammentic subgroup. An argillic horizon that
is composed entirely of thin lamellae defines the Lamellic
subgroup.
A soil moisture regime that approaches the udic regime is
considered more moist than normal and defines the Udic
subgroup. A moderately low base saturation throughout the
argillic horizon is considered atypical and defines the Ultic
subgroup.
Cracks and slickensides or wedge-shaped aggregates are
properties shared with Vertisols and define Vertic subgroups. A
soil moisture regime that approaches the aridic regime is
considered drier than normal and defines Aridic subgroups.
Typic Haplustalfs are moderately extensive in the United
States. They are used mainly for grazing or as cropland.
Aquertic Haplustalfs.—These soils have a clayey texture
and have expanding clay in the argillic horizon. They also
have redox depletions with low chroma within 75 cm of the
mineral soil surface that are caused by periods of wetness.
These soils are in nearly level areas and may or may not have
calcic horizons or relatively low base saturation. They are rare
in the United States.
Aquic Arenic Haplustalfs.—These soils have, in one or
more horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage). In
addition, they have a layer, starting at the mineral soil surface,
that is between 50 and 100 cm thick and has a texture of loamy
fine sand or coarser. The presence or absence of a calcic
horizon or of relatively low base saturation is not definitive of
this subgroup. These soils are on gentle slopes and are rare in
the United States.
Aquic Haplustalfs.—These soils are like Typic Haplustalfs,
but they have redox depletions with low chroma within 75 cm
of the mineral soil surface that are caused by periods of
wetness. These soils are in nearly level areas and may or may
not have calcic horizons or relatively low base saturation. They
are locally important in the central part of the Southern United
States. They are used as cropland or for grazing.
Aquultic Haplustalfs.—These soils are like Typic
236 Soil Taxonomy
Haplustalfs, but they have redox depletions with low chroma
within 75 cm of the mineral soil surface that are caused by
periods of wetness. These soils are in nearly level areas and
have relatively low base saturation. They are rare in the United
States.
Arenic Aridic Haplustalfs.—These soils are like Typic
Haplustalfs, but they have a layer, 50 cm or more thick,
starting at the mineral soil surface, that has a texture of loamy
fine sand or coarser throughout its thickness. In addition, they
are drier than the Typic Haplustalfs and, because they have a
thick epipedon with a sandy or sandy-skeletal particle-size
class throughout, they are permitted, but not required, to have a
calcic horizon within the depths required for the Typic
subgroup. Arenic Aridic Haplustalfs are rare in the United
States.
Arenic Haplustalfs.—These soils are like Typic
Haplustalfs, but they have a layer, 50 cm or more thick,
starting at the mineral soil surface, that has a texture of loamy
fine sand or coarser throughout its thickness. There is no
restriction on base saturation in the argillic horizon, except for
the limit imposed by the definition of Alfisols. A calcic horizon
may be present at any depth but is not required. These soils are
of small extent but are locally important in the southern part of
the Great Plains in the United States. Their slopes are gentle.
Most of the soils are used as cropland.
Aridic Haplustalfs.—These soils are drier than Typic
Haplustalfs. They are intergrades between Haplargids and
Haplustalfs. They are extensive in the southern part of the
Great Plains of the United States. Slopes generally are gentle or
moderate. Many of these soils are used for grazing, and others
are used as cropland. Some of the cropland is irrigated, and
some is used for drought-tolerant crops.
Calcic Haplustalfs.—These soils are like Typic Haplustalfs,
but they have a calcic horizon that has its upper boundary
within 100 cm of the mineral soil surface. They are rare in the
United States.
Calcic Udic Haplustalfs.—These soils are like Typic
Haplustalfs, but they are dry in some part of the moisture
control section for less than four-tenths of the cumulative days
when the soil temperature at a depth of 50 cm exceeds 5 o
C if
the soil temperature regime is mesic or thermic and are dry in
some or all parts of the moisture control section for less than
90 days during a period when the soil temperature at a depth of
50 cm exceeds 8 o
C if the soil temperature regime is
hyperthermic, isomesic, or warmer. These soils also have a
calcic horizon that has its upper boundary within 100 cm of the
mineral soil surface. They are rare in the United States.
Calcidic Haplustalfs.—These soils are drier than Typic
Haplustalfs. They have a calcic horizon that has its upper
boundary within 100 cm of the mineral soil surface. These soils
are intergrades between Calcids or Calciargids and Haplustalfs.
They are rare in the United States.
Inceptic Haplustalfs.—These soils have an argillic horizon 35
cm or less thick and have no densic, lithic, or paralithic contact
within 100 cm of the mineral soil surface. In addition,
the base saturation of all parts of the argillic horizon is
permitted, but not required, to be lower than that in Typic
Haplustalfs. A calcic horizon also is permitted. These soils are
considered intergrades to Ustepts. They are rare in the United
States.
Kanhaplic Haplustalfs.—These soils are like Typic
Haplustalfs, but they have a cation-exchange capacity (by 1N
NH4
OAc pH 7) of less than 24 cmol(+)/kg clay. They are
permitted, but not required, to have a base saturation (by sum
of cations) that is less than 75 percent in all parts of the argillic
horizon and to have a calcic horizon or soft, powdery
secondary lime at any depth. The upper boundary of the argillic
horizon in these soils generally is gradual. Kanhaplic
Haplustalfs are intergrades between Haplustalfs and Ustox.
They are not known to occur on the United States mainland or
in Puerto Rico, but the subgroup is provided for use in other
countries.
Lamellic Haplustalfs.—These soils are like Typic
Haplustalfs in defined properties, but they have an argillic
horizon that consists of lamellae or partially of lamellae. Most
of these soils have a sandy particle-size class, and the upper
boundary of the argillic horizon or the upper lamella may be
below a depth of 60 cm. The upper several lamellae are
commonly broken or discontinuous horizontally. These soils
are not extensive in the United States.
Lithic Haplustalfs.—These soils have a lithic contact
within 50 cm of the soil surface. They are permitted to have
any of the other properties allowed in Haplustalfs. They are
common in the southwestern part of the United States. Their
slopes are moderate or strong. Most of the soils are used for
grazing.
Oxyaquic Haplustalfs.—These soils are like Typic
Haplustalfs, but they are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years. In addition, these
soils are permitted, but not required, to have a base saturation
(by sum of cations) that is less than 75 percent. They are
considered intergrades to Aqualfs. These soils are rare in the
United States.
Oxyaquic Vertic Haplustalfs.—These soils have a clayey
texture and have expanding clay in the argillic horizon. They
also have deep, wide cracks in normal years. In addition, they
are saturated with water within 100 cm of the mineral soil
surface for 20 or more consecutive days or 30 or more
cumulative days in normal years. These soils are not extensive
in the United States.
Psammentic Haplustalfs.—These soils have a sandy
particle-size class throughout the upper 75 cm of the argillic
horizon or throughout the entire argillic horizon if it is less
than 75 cm thick. In addition, the base saturation of the argillic
horizon is permitted, but not required, to be lower than that in
Typic Haplustalfs. A calcic horizon is permitted. These soils
are considered intergrades to Ustipsamments. They are of small
Alfisols 237
extent in the United States. Their slopes are mostly gentle. Most
of these soils are grazed, but some are used for drought-tolerant
crops.
Torrertic Haplustalfs.—These soils are drier than Typic
Haplustalfs. They also have a clayey texture and have
expanding clay in the argillic horizon. They have deep, wide
cracks in normal years. They are not extensive in the United
States.
Udertic Haplustalfs.—These soils are like Typic
Haplustalfs, but they have a clayey texture and have expanding
clay in the argillic horizon. They are dry in some part of the
moisture control section for less than four-tenths of the
cumulative days when the soil temperature at a depth of 50 cm
exceeds 5 o
C if the soil temperature regime is mesic or thermic
and are dry in some or all parts of the moisture control section
for less than 90 days during a period when the soil temperature
at a depth of 50 cm exceeds 8 o
C if the soil temperature regime
is hyperthermic, isomesic, or warmer. These soils are
intergrades between Uderts and Haplustalfs. They are of small
extent but are locally important in Texas and Oklahoma in the
United States. Their slopes are mostly gentle. Most of these
soils are used as cropland.
Udic Haplustalfs.—These soils are like Typic Haplustalfs,
but they are dry in some part of the moisture control section for
less than four-tenths of the cumulative days when the soil
temperature at a depth of 50 cm exceeds 5 o
C if the soil
temperature regime is mesic or thermic and are dry in some or
all parts of the moisture control section for less than 90 days
during a period when the soil temperature at a depth of 50 cm
exceeds 8 o
C if the soil temperature regime is hyperthermic,
isomesic, or warmer. These soils are intergrades between
Hapludalfs and Haplustalfs. They are extensive locally on the
Great Plains in the United States. Their slopes range from
gentle to strong. Where slopes are suitable, most of these soils
are used as cropland.
Ultic Haplustalfs.—These soils are like Typic Haplustalfs,
but they have a base saturation (by sum of cations) that is less
than 75 percent in all parts of the argillic horizon. These soils
are intergrades between Hapludults and Haplustalfs. They are
moderately extensive in California and Oklahoma in the
United States and are extensive in some parts of the world.
Their slopes are gentle to strong in the United States. Where
slopes are suitable, most of these soils are used as cropland.
Vertic Haplustalfs.—These soils have a clayey texture and
have expanding clay in the argillic horizon. They also have
deep, wide cracks in normal years. They are not extensive in
the United States. Their slopes are gentle or moderate. Most of
these soils are used for grazing.
Vitrandic Haplustalfs.—These are the Haplustalfs that
have significant amounts of volcanic ash, pumice, or glass in
one or more layers 18 cm or more thick within 75 cm of the
mineral soil surface. These soils do not have a high shrinkswell
potential and are not saturated within 100 cm of the
mineral soil surface for extended periods. They occur in New
Mexico and are used as rangeland or woodland.
Kandiustalfs
Kandiustalfs are the Ustalfs with thick argillic horizons that
have relatively high base saturation but a low cation-exchange
capacity. Many of these soils occur on the older surfaces in
warm, humid or semihumid areas. Kandiustalfs occur in Africa
and South America. They are commonly used as rangeland or
cropland.
Definition
Kandiustalfs are the Ustalfs that:
1. Have a kandic horizon;
2. Do not have a densic, lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface and do not
have a duripan within 100 cm of the mineral soil surface;
3. Have a clay distribution in which the percentage of clay
does not decrease from its maximum amount by as much as 20
percent within 150 cm of the soil surface, or the layer in which
the clay percentage decreases by more than 20 percent has at
least 5 percent of the volume consisting of skeletans on faces of
peds and there is at least a 3 percent (absolute) increase in
content of clay below this layer;
4. Do not have plinthite that forms a continuous phase or
constitutes more than half the volume of some subhorizon
within 150 cm of the mineral soil surface; and
5. Do not have a natric horizon.
Key to Subgroups
JCDA. Kandiustalfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of a kandic horizon at a depth of
100 cm or more.
Grossarenic Kandiustalfs
JCDB. Other Kandiustalfs that have both:
1. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
a kandic horizon at a depth of 50 to 100 cm.
Aquic Arenic Kandiustalfs
JCDC. Other Kandiustalfs that have 5 percent or more (by
238 Soil Taxonomy
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Kandiustalfs
JCDD. Other Kandiustalfs that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Kandiustalfs
JCDE. Other Kandiustalfs that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
a kandic horizon at a depth of 50 to 100 cm; and
2. When neither irrigated nor fallowed to store moisture,
either:
a. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
b. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for less than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
5 o
C.
Arenic Aridic Kandiustalfs
JCDF. Other Kandiustalfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of a kandic horizon at a depth of
50 to 100 cm.
Arenic Kandiustalfs
JCDG. Other Kandiustalfs that, when neither irrigated nor
fallowed to store moisture, have either:
1. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for six-tenths or more of the cumulative days per year
when the soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
2. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
a. Is moist in some or all parts for less than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
b. Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 5 o
C.
Aridic Kandiustalfs
JCDH. Other Kandiustalfs that, when neither irrigated nor
fallowed to store moisture, have either:
1. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for 135 cumulative days or less per year when the
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for less than 120
cumulative days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8 o
C.
Udic Kandiustalfs
JCDI. Other Kandiustalfs that have, in all subhorizons in the
upper 100 cm of the kandic horizon or throughout the entire
kandic horizon if less than 100 cm thick, more than 50 percent
colors that have all of the following:
1. Hue of 2.5YR or redder; and
2. Value, moist, of 3 or less; and
3. Dry value no more than 1 unit higher than the moist
value.
Rhodic Kandiustalfs
JCDJ. Other Kandiustalfs.
Typic Kandiustalfs
Definition of Typic Kandiustalfs
Typic Kandiustalfs are the Kandiustalfs that:
1. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
2. Have a texture finer than loamy fine sand in one or more
subhorizons within 50 cm of the mineral soil surface;
3. Have, in all horizons within 150 cm of the mineral soil
surface, less than 5 percent plinthite, by volume;
4. When neither irrigated nor fallowed to store moisture:
a. Have a mesic or thermic soil temperature regime and
both are dry in some part less than six-tenths of the time
Alfisols 239
and are dry for more than 135 cumulative days per year in
some part of the moisture control section (not necessarily the
same part) in normal years and during a period when the soil
temperature at a depth of 50 cm exceeds 5 o
C; or
b. Have a hyperthermic, isomesic, or warmer soil
temperature regime and:
(1) Are dry in some or all parts of the moisture control
section for 120 or more cumulative days per year; and
(2) Are moist in some or all parts of the moisture
control section for 90 or more consecutive days per year
both in normal years and during a period when the soil
temperature at a depth of 50 cm exceeds 8 o
C; and
(3) Are moist in some or all parts for six-tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C;
5. Do not have, in all subhorizons in the upper 100 cm of the
kandic horizon or throughout the entire kandic horizon if less
than 100 cm thick, more than 50 percent colors that have all of
the following:
a. Hue of 2.5YR or redder; and
b. Value, moist, of 3 or less; and
c. Dry value no more than 1 unit higher than the moist
value.
Description of Subgroups
Typic Kandiustalfs.—The central concept or Typic
subgroup of Kandiustalfs is fixed on freely drained soils that
are moderately deep or deep to hard rock, that have an argillic
horizon that has a loamy or clayey particle-size class and high
base saturation, and that are moist for an appreciable part of a
growing season.
Soils that have redox depletions with low chroma near the
surface in one or more horizons that also have aquic conditions
for some time in normal years (or artificial drainage) are
excluded from Typic Kandiustalfs because these properties are
shared with Aqualfs. A thick layer, starting at the mineral soil
surface, of sand or loamy sand is not considered normal and
defines Arenic and Grossarenic subgroups, a convention used
elsewhere in this taxonomy.
A soil moisture regime that approaches the udic regime is
considered more moist than normal and defines the Udic
subgroup.
A soil moisture regime that approaches the aridic regime is
considered drier than normal and defines Aridic subgroups.
Typic Kandiustalfs are not known to occur in the United
States. They are defined for use in other parts of the world.
Aquic Arenic Kandiustalfs.—These soils have, in one or
more horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage). In addition,
they have a layer, starting at the mineral soil surface, that is 50 to
100 cm thick and has a sandy or sandy-skeletal particle-size
class throughout. These soils are on gentle slopes. They are not
known to occur in the United States. They are defined for use in
other parts of the world.
Aquic Kandiustalfs.—These soils are like Typic
Kandiustalfs, but they have redox depletions with low chroma
within 75 cm of the mineral soil surface that are caused by
periods of wetness. The soils are in nearly level areas. They are
not known to occur in the United States. They are defined for
use in other parts of the world.
Arenic Aridic Kandiustalfs.—These soils are like Typic
Kandiustalfs, but they have a layer, 50 to 100 cm thick, starting
at the mineral soil surface, that has a sandy or sandy-skeletal
particle-size class throughout its thickness. In addition, they
are drier than the Typic Kandiustalfs. Arenic Aridic
Kandiustalfs are on gentle slopes. They are not known to occur
in the United States. They are defined for use in other parts of
the world.
Arenic Kandiustalfs.—These soils are like Typic
Kandiustalfs, but they have a layer, 50 to 100 cm thick, starting
at the mineral soil surface, that has a sandy or sandy-skeletal
particle-size class throughout its thickness. These soils are not
known to occur in the United States. They are defined for use
in other parts of the world.
Aridic Kandiustalfs.—These soils are drier than Typic
Kandiustalfs. They are intergrades between Argids and
Kandiustalfs. They are not known to occur in the United
States. They are defined for use in other parts of the world.
Grossarenic Kandiustalfs.—These soils are like Typic
Kandiustalfs, but they have a layer, 100 cm or more thick,
starting at the mineral soil surface, that has a sandy or sandyskeletal
particle-size class throughout its thickness. These soils
are not known to occur in the United States. They are defined
for use in other parts of the world.
Plinthic Kandiustalfs.—These soils are like Typic
Kandiustalfs, but they have 5 percent or more (by volume)
plinthite in one or more horizons within 150 cm of the mineral
soil surface. These soils are not known to occur in the United
States. They are defined for use in other parts of the world.
Rhodic Kandiustalfs.—These soils are like Typic
Kandiustalfs, but they have, in all subhorizons in the upper 100
cm of the kandic horizon or throughout the entire kandic
horizon if less than 100 cm thick, more than 50 percent colors
that have hue of 2.5YR or redder, value, moist, of 3 or less, and
dry value no more than 1 unit higher than the moist value.
These soils are not known to occur in the United States. They
are defined for use in other parts of the world.
Udic Kandiustalfs.—These soils are like Typic
Kandiustalfs, but they are dry in some part of the moisture
control section for less than four-tenths of the cumulative days
when the soil temperature at a depth of 50 cm exceeds 5 o
C if
the soil temperature regime is mesic or thermic and are dry in
240 Soil Taxonomy
some or all parts of the moisture control section for less than 90
days during a period when the soil temperature at a depth of 50
cm exceeds 8 o
C if the soil temperature regime is hyperthermic,
isomesic, or warmer. These soils are intergrades between
Kandiudalfs and Kandiustalfs. They are not known to occur in
the United States. They are defined for use in other parts of the
world.
Kanhaplustalfs
Kanhaplustalfs are the Ustalfs that have relatively high base
saturation but have a low cation-exchange capacity. These soils
do not have the thick argillic horizon characteristic of the
Kandiustalfs. Kanhaplustalfs commonly occur on the older
surfaces in warm, humid or semihumid areas. They are used
for livestock grazing or crop production.
Definition
Kanhaplustalfs are the Ustalfs that:
1. Have a kandic horizon;
2. Are more than 150 cm deep and have a clay distribution
in which the content of clay decreases from its maximum
amount by 20 percent or more within 150 cm of the soil
surface, and the layer in which the percentage of clay is less
than the maximum has less than 5 percent of the volume
consisting of skeletans on faces of peds or there is less than
a 3 percent (absolute) increase in content of clay below this
layer;
3. Do not have plinthite that forms a continuous phase or
constitutes more than half the volume of some subhorizon
within 150 cm of the soil surface;
4. Do not have a natric horizon; and
5. Do not have a duripan within 100 cm of the mineral soil
surface.
Key to Subgroups
JCEA. Kanhaplustalfs that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Kanhaplustalfs
JCEB. Other Kanhaplustalfs that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage).
Aquic Kanhaplustalfs
JCEC. Other Kanhaplustalfs that, when neither irrigated nor
fallowed to store moisture, have either:
1. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for six-tenths or more of the cumulative days per year
when the soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
2. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
a. Is moist in some or all parts for less than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
b. Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 5 o
C.
Aridic Kanhaplustalfs
JCED. Other Kanhaplustalfs that, when neither irrigated nor
fallowed to store moisture, have either:
1. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for 135 cumulative days or less per year when the
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for less than 120
cumulative days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8 o
C.
Udic Kanhaplustalfs
JCEE. Other Kanhaplustalfs that have, in all subhorizons in
the upper 100 cm of the kandic horizon or throughout the
entire kandic horizon if less than 100 cm thick, more than 50
percent colors that have all of the following:
1. Hue of 2.5YR or redder; and
2. Value, moist, of 3 or less; and
3. Dry value no more than 1 unit higher than the moist
value.
Rhodic Kanhaplustalfs
JCEF. Other Kanhaplustalfs.
Typic Kanhaplustalfs
Definition of Typic Kanhaplustalfs
Typic Kanhaplustalfs are the Kanhaplustalfs that:
1. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
2. Do not have a lithic contact within 50 cm of the soil
surface;
3. When neither irrigated nor fallowed to store moisture:
Alfisols 241
a. Have a mesic or thermic soil temperature regime and, in
one-half or more of the years, both are dry less than sixtenths
of the time and are dry for more than 135 cumulative
days in some part of the moisture control section (not
necessarily the same part) during a period when the soil
temperature at a depth of 50 cm exceeds 5 o
C; or
b. Have a hyperthermic, isomesic, or warmer soil
temperature regime and:
(1) Are dry in some or all parts of the moisture control
section for 120 or more cumulative days per year; and
(2) Are moist in some or all parts of the moisture
control section for 90 or more consecutive days per year
both in normal years and during a period when the soil
temperature at a depth of 50 cm exceeds 8 o
C; and
(3) Are moist in some or all parts for six-tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; and
4. Have, in all subhorizons in the upper 100 cm of the kandic
horizon or throughout the entire kandic horizon if less than
100 cm thick, more than 50 percent colors that have all of the
following:
a. Hue of 2.5YR or redder; and
b. Value, moist, of 3 or less; and
c. Dry value no more than 1 unit higher than the moist
value.
Description of Subgroups
Typic Kanhaplustalfs.—The central concept or Typic
subgroup of Kanhaplustalfs is fixed on freely drained soils that
are moderately deep or deep to hard rock and that are moist for
an appreciable part of a growing season.
Soils that have redox depletions with low chroma near the
surface in one or more horizons that also have aquic conditions
for some time in normal years (or artificial drainage) are
excluded from Typic Kanhaplustalfs because these properties
are shared with Aqualfs. A shallow lithic contact defines the
Lithic subgroup, a convention used throughout this taxonomy.
A soil moisture regime that approaches the udic regime is
considered more moist than normal and defines the Udic
subgroup. A soil moisture regime that approaches the aridic
regime is considered drier than normal and defines the Aridic
subgroup.
Typic Kanhaplustalfs are not known to occur in the United
States. They are defined for use in other parts of the world.
Aquic Kanhaplustalfs.—These soils are like Typic
Kanhaplustalfs, but they have redox depletions with low
chroma within 75 cm of the mineral soil surface that are
caused by periods of wetness. The soils are in nearly level areas
and may or may not have calcic horizons or relatively low base
saturation. Aquic Kanhaplustalfs are not known to occur in the
United States. They are defined for use in other parts of the
world.
Aridic Kanhaplustalfs.—These soils are drier than Typic
Kanhaplustalfs. They are intergrades between Haplargids and
Kanhaplustalfs. Aridic Kanhaplustalfs are not known to occur
in the United States. They are defined for use in other parts of
the world.
Lithic Kanhaplustalfs.—These soils have a lithic contact
within 50 cm of the soil surface. They are permitted to have
any of the other properties allowed in Kanhaplustalfs. They are
not known to occur in the United States. They are defined for
use in other parts of the world.
Rhodic Kanhaplustalfs.—These soils are like Typic
Kanhaplustalfs, but all of the kandic horizon or the upper 100
cm of the kandic horizon has a color with hue of 2.5YR or
redder, value, moist, of 3 or less, and a dry color value no more
than 1 unit higher than the moist value. Rhodic Kanhaplustalfs
are not known to occur in the United States. They are defined
for use in other parts of the world.
Udic Kanhaplustalfs.—These soils are like Typic
Kanhaplustalfs, but they are dry in some part of the moisture
control section for 135 or fewer cumulative days per year when
the soil temperature at a depth of 50 cm exceeds 5 o
C if the soil
temperature regime is mesic or thermic and are dry in some or
all parts of the moisture control section for less than 120
cumulative days per year during a period when the soil
temperature at a depth of 50 cm exceeds 8 o
C if the soil
temperature regime is hyperthermic, isomesic, or warmer.
These soils are intergrades between Kanhapludalfs and
Kanhaplustalfs. Udic Kanhaplustalfs are not known to occur in
the United States. They are defined for use in other parts of the
world.
Natrustalfs
Natrustalfs are the Ustalfs that have a natric horizon. They do
not have a duripan within 100 cm of the mineral soil surface, nor
do they have plinthite that forms a continuous phase or
constitutes more than half the volume of some subhorizon
within 150 cm of the soil surface. The epipedon is normally 10 to
20 cm thick. The natric horizon generally is underlain by a Bk or
calcic horizon at a depth between about 25 and 40 cm.
Natrustalfs were considered Solonetz soils, Soloth soils, and
transitional forms in the 1938 classification. Except for a few
parts of the Great Plains and mountain basins, they are not
extensive in the United States.
Definition
Natrustalfs are the Ustalfs that:
1. Have a natric horizon;
2. Do not have a duripan within 100 cm of the mineral soil
surface;
242 Soil Taxonomy
3. Do not have plinthite that forms a continuous phase or
constitutes more than half the volume of some subhorizon
within 150 cm of the soil surface.
KeytoSubgroups
JCCA. Natrustalfs that have a salic horizon that has its upper
boundary within 75 cm of the mineral soil surface.
Salidic Natrustalfs
JCCB. Other Natrustalfs that have all of the following:
1. Visible crystals of gypsum or other salts more soluble
than gypsum, or both, within 40 cm of the soil surface; and
2. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for less than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
5 o
C; and
3. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Leptic Torrertic Natrustalfs
JCCC. Other Natrustalfs that have both of the following:
1. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for less than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
5 o
C; and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Torrertic Natrustalfs
JCCD. Other Natrustalfs that have both:
1. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
Alfisols 243
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Aquertic Natrustalfs
JCCE. Other Natrustalfs that have both of the following:
1. Visible crystals of gypsum or other salts more soluble
than gypsum, or both, within 40 cm of the mineral soil
surface; and
2. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for less than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
5 o
C.
Aridic Leptic Natrustalfs
JCCF. Other Natrustalfs that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm or
a densic, lithic, or paralithic contact, whichever is
shallower.
Vertic Natrustalfs
JCCG. Other Natrustalfs that have both:
1. In one or more horizons within 75 cm of the mineral soil
surface, redox depletions with chroma of 2 or less and also
aquic conditions for some time in normal years (or artificial
drainage); and
2. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
an argillic horizon at a depth of 50 cm or more.
Aquic Arenic Natrustalfs
JCCH. Other Natrustalfs that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Natrustalfs
JCCI. Other Natrustalfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 cm or more.
Arenic Natrustalfs
JCCJ. Other Natrustalfs that have a petrocalcic horizon that
has its upper boundary within 150 cm of the mineral soil
surface.
Petrocalcic Natrustalfs
JCCK. Other Natrustalfs that have visible crystals of gypsum
or other salts more soluble than gypsum, or both, within 40 cm
of the mineral soil surface.
Leptic Natrustalfs
JCCL. Other Natrustalfs that have both of the following:
1. An exchangeable sodium percentage of less than 15 (or
a sodium adsorption ratio of less than 13) in 50 percent or
more of the natric horizon; and
2. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for less than 90
244 Soil Taxonomy
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
5 o
C.
Haplargidic Natrustalfs
JCCM. Other Natrustalfs that, when neither irrigated nor
fallowed to store moisture, have one of the following:
1. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for four-tenths
or more of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for six-tenths or more of the cumulative days per year
when the soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
3. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
a. Is moist in some or all parts for less than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
b. Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 5 o
C.
Aridic Natrustalfs
JCCN. Other Natrustalfs that have an Ap horizon with a
color value, moist, of 3 or less and a color value, dry, of 5 or
less (crushed and smoothed sample) or materials between the
soil surface and a depth of 18 cm that have these color values
after mixing.
Mollic Natrustalfs
JCCO. Other Natrustalfs.
Typic Natrustalfs
Definition of Typic Natrustalfs
Typic Natrustalfs are the Natrustalfs that:
1. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
2. Have an Ap horizon that has a color value, moist, of more
than 3, or the surface soil to a depth of 18 cm, after mixing, has a
color value, moist, of more than 3;
3. Do not have a salic horizon that has its upper boundary
within 75 cm of the soil surface;
4. Do not have a petrocalcic horizon that has its upper
boundary within 150 cm of the surface;
5. Have a texture finer than loamy fine sand in one or more
subhorizons within 50 cm of the mineral soil surface;
6. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
7. When neither irrigated nor fallowed to store moisture,
meet one of the following:
a. Have a frigid temperature regime and a moisture
control section that in normal years is dry in all parts for
less than four-tenths of the cumulative days per year when
the soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. Have a mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for less than six-tenths of the cumulative days per year
when the soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
c. Have a hyperthermic, isomesic, or warmer soil
temperature regime and:
(1) Are dry in some or all parts of the moisture control
section for 120 or more cumulative days per year; and
(2) Are moist in some or all parts of the moisture
control section for 90 or more consecutive days per year
both in normal years and during a period when the soil
temperature at a depth of 50 cm exceeds 8 o
C; and
(3) Are moist in some or all parts for six-tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C;
8. Have an exchangeable sodium percentage of 15 or more
(or a sodium adsorption ratio of 13 or more) in more than 50
percent of the natric horizon; and
9. Do not have visible crystals of gypsum or other salts more
Alfisols 245
soluble than gypsum, or both, within 40 cm of the mineral soil
surface.
Description of Subgroups
Typic Natrustalfs.—The central concept or Typic subgroup
of Natrustalfs is fixed on soils that are not so well drained as
most other Ustalfs because the natric horizon has virtually no
hydraulic conductivity. The plow layer, if one occurs, or the
equivalent subhorizons have a color value, moist, of more than
3, and there is no salic horizon within 75 cm and no
petrocalcic horizon within 150 cm of the surface. A thick
epipedon with a sandy or sandy-skeletal particle-size class
throughout is considered atypical and is used to define Arenic
subgroups. Visible crystals of gypsum or other salts more
soluble than gypsum are not within 40 cm of the mineral soil
surface. Surface horizons above a depth of 18 cm that, after
mixing, have the color of a mollic epipedon or a plow layer
that has this color is believed to indicate a transition to
Mollisols and define the Mollic subgroup.
Soils that have shallow redox depletions with low chroma in
horizons that also have aquic conditions for some time in
normal years (or artificial drainage) are excluded from the
Typic subgroup because these properties are shared with
Aqualfs. Soils that have a shallow salic horizon are excluded
because such a horizon is shared with Salids. A petrocalcic
horizon is considered atypical and is the basis for defining the
Petrocalcic subgroup.
The Typic Natrustalfs in the United States are most
commonly in depressions or on the margins of lakes or playas.
Their slopes are nearly level. Most of these soils are used for
grazing.
Aquertic Natrustalfs.—These soils are like Typic
Natrustalfs, but they have a clayey texture and have expanding
clay in the argillic horizon. They also have redox depletions
with low chroma within 75 cm of the mineral soil surface that
are caused by periods of wetness. In addition, the surface soil to
a depth of 18 cm after mixing or the Ap horizon is permitted,
but not required, to have a color value, moist, of 3 or less.
These soils are in nearly level areas. They are rare in the
United States.
Aquic Arenic Natrustalfs.—These soils have, in one or
more horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage). In
addition, they have a layer, starting at the mineral soil surface,
that is between 50 and 100 cm thick and has a texture of
loamy fine sand or coarser. The soils in this subgroup are
known to be locally extensive only in Texas in the United
States. Most are used for grazing. Slopes are nearly level to
gently undulating, suggesting some reworking by wind in the
late Pleistocene.
Aquic Natrustalfs.—These soils are like Typic Natrustalfs,
but they have, in one or more horizons within 75 cm of the
mineral soil surface, redox depletions with chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage). In addition, the surface soil to a depth of
18 cm after mixing or the Ap horizon is permitted, but not
required, to have a color value, moist, of 3 or less. These soils
are rare in the United States. Most of them are used for
grazing.
Arenic Natrustalfs.—These soils are like Typic Natrustalfs,
but they have a layer, starting at the mineral soil surface, 50 cm
or more thick, with a sandy or sandy-skeletal particle-size class
throughout its thickness. These soils are not extensive in the
United States. Their slopes are nearly level to gently
undulating, suggesting some reworking by wind.
Aridic Leptic Natrustalfs.—These soils are drier than
Typic Natrustalfs. In addition, they have visible crystals of
gypsum or other salts more soluble than gypsum within 40 cm
of the mineral soil surface. These soils are intergrades between
Natrargids and Natrustalfs. They are rare in the United States.
Aridic Natrustalfs.—These soils are drier than Typic
Natrustalfs. They are intergrades between Natrargids and
Natrustalfs. They are rare in the United States.
Haplargidic Natrustalfs.—These soils are drier than Typic
Natrustalfs. They also have an exchangeable sodium
percentage of less than 15 (or a sodium adsorption ratio of less
than 13) in 50 percent or more of the natric horizon. These
soils are intergrades between Haplargids and Natrustalfs. They
are rare in the United States.
Leptic Natrustalfs.—These soils have visible crystals of
gypsum or other salts more soluble than gypsum within 40 cm
of the mineral soil surface. They are rare in the United States.
Leptic Torrertic Natrustalfs.—These soils are drier than
Typic Natrustalfs. They have a clayey texture and have
expanding clay in the argillic horizon. They have deep, wide
cracks in normal years. These soils also have visible crystals of
gypsum or other salts more soluble than gypsum within 40 cm
of the mineral soil surface. They are rare in the United States.
Mollic Natrustalfs.—These soils are like Typic Natrustalfs,
but the Ap horizon or the upper 18 cm after mixing has a color
value, moist, of 3 or less, generally 3. These soils are of small
extent in the United States. Their slopes are nearly level, and
most of the soils are used for grazing.
Petrocalcic Natrustalfs.—These soils have a petrocalcic
horizon that is normally about 50 to 75 cm below the soil
surface but is very thin, about 5 to 10 cm thick. They are rare
in the United States.
Salidic Natrustalfs.—These soils are like Typic Natrustalfs,
but they have a salic horizon within 75 cm of the surface but in
or below the natric horizon. They are rare in the United States.
Ground water in these soils is relatively shallow and is salty.
The soils are used only for limited grazing.
Torrertic Natrustalfs.—These soils are drier than Typic
Natrustalfs. They have a clayey texture and have expanding
clay in the argillic horizon. They have deep, wide cracks in
normal years. They are rare in the United States.
Vertic Natrustalfs.—These soils are like Typic Natrustalfs,
246 Soil Taxonomy
but they have a clayey texture and have expanding clay in the
argillic horizon. In addition, the surface soil to a depth of 18 cm
after mixing or the Ap horizon is permitted, but not required, to
have a color value, moist, of 3 or less. These soils are in nearly
level areas. They are rare in the United States.
Paleustalfs
Paleustalfs are the reddish or red Ustalfs that are on old
surfaces. Many of them have some plinthite in their lower
horizons. Paleustalfs occur in relatively stable landscape
positions, their slopes are mostly gentle, and their genesis
began before the late Pleistocene. In the United States, they
typically have a Bk or calcic horizon in or below the argillic
horizon as a result of additions of atmospheric carbonates.
Commonly, secondary lime coats the surfaces of peds that have
noncalcareous interiors and the soils may be noncalcareous at a
depth of less than 200 cm. A few of these soils, near the
boundary where they join Aridisols, have received enough
calcareous dust to have a petrocalcic horizon. A few others,
near the boundary where they join Udults or Udalfs, do not
have a Bk horizon. Before cultivation, the vegetation on the
Paleustalfs in the United States included a mixture of grasses
and woody plants. These soils are moderately extensive in the
southern part of the Great Plains in the United States, and they
probably are extensive in Africa and southern Asia.
Definition
Paleustalfs are the Ustalfs that:
1. Do not have a duripan within 100 cm of the soil surface
and do not have a natric horizon;
2. Do not have plinthite that forms a continuous phase or
constitutes more than half the matrix within any subhorizon of
the argillic horizon within 150 cm of the soil surface; and
3. Meet one or more of the following:
a. Have a petrocalcic horizon that is in or below an argillic
horizon but that has an upper boundary within 150 cm of
the soil surface; or
b. Do not have a densic, lithic, or paralithic contact within
150 cm of the soil surface and have an argillic horizon that
has:
(1) A clay distribution in which the percentage of clay
does not decrease from its maximum amount by as much
as 20 percent from the soil surface to a depth of 150 cm,
or the layer in which the clay percentage decreases by
more than 20 percent has at least 5 percent of the volume
consisting of skeletans on faces of peds and there is at
least a 3 percent (absolute) increase in content of clay
below this layer; and
(2) One or more of the following:
(a) Hue of 7.5YR or redder and chroma of 5 or more in
50 percent or more of the matrix of one or more horizons
in its lower one-half;
(b) In 50 percent or more of the matrix of horizons that
total more than one-half the total thickness, hue of
7.5YR or redder, value, moist, of 3 or less, and value,
dry, of 4 or less; or
(c) In one or more horizons in its lower one-half,
common coarse redox concentrations that have hue of
7.5YR or redder or chroma of 6 or more, or both; or
c. Do not have a densic, lithic, or paralithic contact within
50 cm of the surface and have an argillic horizon that has:
(1) A clayey or clayey-skeletal particle-size class in its
upper part; and
(2) At its upper boundary, a clay increase of at least 20
percent (absolute) within a vertical distance of 7.5 cm or
of 15 percent (absolute) within a distance of 2.5 cm, in
the fine-earth fraction.
Although the restriction on depth to a densic, lithic, or
paralithic contact in the Paleustalfs is only 50 cm, it is rare that
such a contact is within a depth of 150 cm. A few of these
soils, however, have rock at a depth of less than 100 cm.
Key to Subgroups
JCFA. Paleustalfs that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage).
Aquertic Paleustalfs
JCFB. Other Paleustalfs that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
Alfisols 247
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
and
2. Saturation with water in one or more layers within 100
cm of the mineral soil surface in normal years for either or
both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days.
Oxyaquic Vertic Paleustalfs
JCFC. Other Paleustalfs that have both:
1. When neither irrigated nor fallowed to store moisture,
either:
a. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for four-tenths or less of the time (cumulative)
per year when the temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C; or
b. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for less than 120
cumulative days per year when the temperature at a depth
of 50 cm below the soil surface is higher than 8 o
C; and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Udertic Paleustalfs
JCFD. Other Paleustalfs that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact, whichever is shallower.
Vertic Paleustalfs
JCFE. Other Paleustalfs that have both:
1. In one or more horizons within 75 cm of the mineral soil
surface, redox depletions with chroma of 2 or less and also
aquic conditions for some time in normal years (or artificial
drainage); and
2. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
an argillic horizon at a depth of 50 to 100 cm.
Aquic Arenic Paleustalfs
JCFF. Other Paleustalfs that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Paleustalfs
JCFG. Other Paleustalfs that are saturated with water in one
or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Paleustalfs
JCFH. Other Paleustalfs that have an argillic horizon that:
1. Consists entirely of lamellae; or
2. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
3. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
a. Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
horizon); or
b. A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon.
Lamellic Paleustalfs
JCFI. Other Paleustalfs that have a sandy particle-size class
throughout the upper 75 cm of the argillic horizon or
throughout the entire argillic horizon if it is less than 75 cm
thick.
Psammentic Paleustalfs
248 Soil Taxonomy
JCFJ. Other Paleustalfs that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
an argillic horizon at a depth of 50 to 100 cm; and
2. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the time (cumulative) per year when
the soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the time (cumulative)
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for less than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
5 o
C.
Arenic Aridic Paleustalfs
JCFK. Other Paleustalfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 100 cm or more.
Grossarenic Paleustalfs
JCFL. Other Paleustalfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 to 100 cm.
Arenic Paleustalfs
JCFM. Other Paleustalfs that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Paleustalfs
JCFN. Other Paleustalfs that have a petrocalcic horizon that
has its upper boundary within 150 cm of the mineral soil
surface.
Petrocalcic Paleustalfs
JCFO. Other Paleustalfs that have both:
1. When neither irrigated nor fallowed to store moisture,
either:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the time (cumulative) per year when
the soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the time (cumulative)
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for less than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
5 o
C; and
2. A calcic horizon either within 100 cm of the mineral
soil surface if the weighted average particle-size class of the
upper 50 cm of the argillic horizon is sandy, or within 60
cm if it is loamy, or within 50 cm if it is clayey, and
carbonates in all horizons above the calcic horizon.
Calcidic Paleustalfs
JCFP. Other Paleustalfs that, when neither irrigated nor
fallowed to store moisture, have:
1. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for four-tenths
or more of the time (cumulative) per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for six-tenths or more of the time (cumulative) per year
when the soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
3. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
a. Is moist in some or all parts for less than 90
consecutive days per year when the temperature at a
Alfisols 249
depth of 50 cm below the soil surface is higher than 8 o
C;
and
b. Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 5 o
C.
Aridic Paleustalfs
JCFQ. Other Paleustalfs that have a CEC of less than 24
cmol(+)/kg clay (by 1N NH4
OAc pH 7) in 50 percent or more
either of the argillic horizon if less than 100 cm thick or of its
upper 100 cm.
Kandic Paleustalfs
JCFR. Other Paleustalfs that have, in all subhorizons in the
upper 100 cm of the argillic horizon or throughout the entire
argillic horizon if less than 100 cm thick, more than 50 percent
colors that have all of the following:
1. Hue of 2.5YR or redder; and
2. Value, moist, of 3 or less; and
3. Dry value no more than 1 unit higher than the moist
value.
Rhodic Paleustalfs
JCFS. Other Paleustalfs that have an argillic horizon with a
base saturation (by sum of cations) of less than 75 percent
throughout.
Ultic Paleustalfs
JCFT. Other Paleustalfs that, when neither irrigated nor
fallowed to store moisture, have either:
1. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for four-tenths or less of the time (cumulative) per year
when the temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
2. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for less than 120
cumulative days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8 o
C.
Udic Paleustalfs
JCFU. Other Paleustalfs.
Typic Paleustalfs
Definition of Typic Paleustalfs
Typic Paleustalfs are the Paleustalfs that:
1. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
2. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years;
3. Have a texture finer than loamy fine sand in one or more
subhorizons within 50 cm of the mineral soil surface;
4. Have less than 5 percent (by volume) plinthite in all
subhorizons within 150 cm of the soil surface;
5. When neither irrigated nor fallowed to store moisture:
a. Have a frigid temperature regime and a moisture
control section that in normal years is dry in all parts for
less than four-tenths of the time (cumulative) per year when
the soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. Have a mesic or thermic soil temperature regime and a
moisture control section that is dry in some part for more
than four-tenths but less than six-tenths of the time
(cumulative) when the soil temperature at a depth of 50 cm
exceeds 5 o
C; or
c. Have a hyperthermic, isomesic, or warmer soil
temperature regime and:
(1) Are dry in some or all parts of the moisture control
section for 120 or more cumulative days per year; and
(2) Are moist in some or all parts of the moisture
control section for 90 or more consecutive days per year
both in normal years and during a period when the soil
temperature at a depth of 50 cm exceeds 8 o
C; and
(3) Are moist in some or all parts for six-tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C;
6. Have an argillic horizon that has a base saturation (by sum
of cations) of 75 percent or more in some part;
7. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
8. Do not have a petrocalcic horizon that has its upper
boundary within 150 cm of the soil surface;
9. Do not have a calcic horizon that has an upper boundary
within 100 cm of the soil surface if the weighted average
250 Soil Taxonomy
particle-size class of the upper 50 cm of the argillic horizon is
sandy, or 60 cm if it is loamy, or 50 cm if it is clayey;
10. Have a CEC of 24 or more cmol(+)/kg clay (by 1N NH4
OAc
pH 7) in the major part of the argillic horizon or in the major part
of its upper 100 cm if it is thicker than 100 cm;
11. Have, in all subhorizons in the upper 100 cm of the argillic
horizon or throughout the entire argillic horizon if less than 100
cm thick, more than 50 percent colors that have all of the
following:
a. Hue of 2.5YR or redder; and
b. Value, moist, of 3 or less; and
c. Dry value no more than 1 unit higher than the moist
value;
12. Have an argillic horizon that is finer than the sandy
particle-size class in some part of the upper 75 cm if the
argillic horizon is more than 75 cm thick or in any part if the
argillic horizon is less than 75 cm thick;
13. Have an argillic horizon that meets none of the following:
a. Consists entirely of lamellae; or
b. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
c. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
(1) Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
horizon); or
(2) A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon.
Description of Subgroups
Typic Paleustalfs.—The central concept or Typic subgroup
of Paleustalfs is fixed on freely drained soils that have a thin or
loamy epipedon; that do not have cracks and slickensides or
wedge-shaped aggregates; that are moist for an appreciable
part of the growing season; and that have an argillic horizon
that contains some 2:1 lattice clays, has a loamy or clayey
particle-size class and high base saturation in at least some
part, and is not composed entirely of thin lamellae.
Soils that have shallow redox depletions with low chroma in
horizons that also have aquic conditions for some time in
normal years (or artificial drainage) are excluded from Typic
Paleustalfs because these properties are shared with Aqualfs. A
thick epipedon with a sandy or sandy-skeletal particle-size
class throughout is not considered normal and defines Arenic
and Grossarenic subgroups, a convention used elsewhere in
this taxonomy. Soils that have an appreciable amount of
plinthite are excluded because the presence of plinthite is a
property of Plinthustalfs. A soil moisture regime that is ustic
but borders on udic is more moist than normal and defines the
Udic subgroup. A moderately low base saturation throughout
the argillic horizon is considered atypical and defines the Ultic
subgroup.
Cracks and slickensides or wedge-shaped aggregates are
properties shared with Vertisols and define intergrades to that
order. A petrocalcic horizon causes a soil to be excluded from
the Typic subgroup, even though one is very common in
Paleustalfs, and its presence defines the Petrocalcic subgroup.
A soil moisture regime that approaches the aridic regime is
considered drier than normal and defines Aridic subgroups.
Clays that have low activity are considered evidence of
strong weathering, and their dominance is the basis for
defining the Kandic subgroup.
Typic Paleustalfs are not the most extensive subgroup of
Paleustalfs in the United States. They are mostly in Texas.
Some of them are used as cropland, and many of them are used
for grazing. The Typic subgroup was selected to provide a basis
for defining subgroups, and it is thought to be extensive in
some parts of the world.
Aquertic Paleustalfs.—These soils are like Typic
Paleustalfs, but they have, in one or more horizons within 75
cm of the mineral soil surface, redox depletions with chroma of
2 or less and also aquic conditions for some time in normal
years (or artificial drainage). In addition, they have cracks and
slickensides or wedge-shaped aggregates. The base saturation
(by sum of cations) may be less than 75 percent throughout the
argillic horizon. These soils are not extensive in the United
States. Their slopes are gentle, and most of the soils are used as
cropland.
Aquic Arenic Paleustalfs.—These soils have, in one or
more horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage). In
addition, they have a layer, starting at the mineral soil surface,
that is between 50 and 100 cm thick and has a sandy or sandyskeletal
particle-size class throughout its thickness. The base
saturation (by sum of cations) may be less than 75 percent
throughout the argillic horizon. These soils are moderately
extensive in some areas in the southern part of the Great
Plains in the United States. Their slopes are gentle or
moderate.
Aquic Paleustalfs.—These soils are like Typic Paleustalfs,
but they have, in one or more horizons within 75 cm of the
mineral soil surface, redox depletions with chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage). Skeletans with low chroma should not be
mistaken for redox depletions with low chroma, which are
caused by wetness. The base saturation (by sum of cations) may
be less than 75 percent throughout the argillic horizon. These
Alfisols 251
soils are of moderate extent in the United States. Most of them
are in Texas. Their slopes are gentle, and most of the soils are
used as cropland.
Arenic Aridic Paleustalfs.—These soils have a layer,
starting at the mineral soil surface, that is between 50 and 100
cm thick and has a sandy or sandy-skeletal particle-size class
throughout its thickness. They are drier than Typic Paleustalfs.
Some Arenic Aridic Paleustalfs have a calcic horizon or a
horizon that has identifiable secondary carbonates. Arenic
Aridic Paleustalfs are of small extent in the southern part of the
Great Plains in the United States. Their slopes are gentle. These
soils are used mainly for grazing.
Arenic Paleustalfs.—These soils have a layer, starting at
the mineral soil surface, that is between 50 and 100 cm thick
and has a sandy or sandy-skeletal particle-size class throughout
its thickness. These soils are not extensive in the United States.
Their slopes are mostly gentle or moderate. Some of the soils
are used as cropland, but most of them are used for grazing.
Aridic Paleustalfs.—These soils are like Typic Paleustalfs,
but they are drier. In addition, they do not have a calcic
horizon or are noncalcareous in some subhorizon above the
calcic horizon, or, if calcareous throughout, the calcic horizon
is deeper than 100 cm if the weighted average particle-size
class of the upper 50 cm of the argillic horizon is sandy, deeper
than 60 cm if the particle-size class is loamy, or 50 cm if the
particle-size class is clayey. The calcic horizon is normally in
the thick argillic horizon. These soils are thought to have been
recalcified since the argillic horizon formed. In the United
States, dust from the Aridisols to the west is a probable source
of some of the carbonates. Aridic Paleustalfs are extensive in
some areas in the southern part of the Great Plains. Their
slopes are gentle. Many of the soils are used as cropland. Some
are used for irrigated crops, mainly cotton, sorghum, and
wheat. Others are used for drought-tolerant crops or for
grazing.
Calcidic Paleustalfs.—These soils are calcareous in all
subhorizons; have a calcic horizon within 100 cm of the soil
surface, commonly within 50 cm; and are drier than Typic
Paleustalfs. The argillic horizon appears to have been largely
but not entirely disrupted by the deposition of carbonates, but it
is preserved in part below the calcic horizon. Calcidic
Paleustalfs are not extensive in the United States. They are
used mainly for grazing.
Grossarenic Paleustalfs.—These soils have an epipedon
that has a sandy or sandy-skeletal particle-size class throughout
and is more than 100 cm thick. The argillic horizon commonly
is sandy loam or sandy clay loam. The soils of this subgroup
are extensive only locally in Texas in the United States. Most
of them are used for grazing. Their slopes are gentle but
commonly are billowy, suggesting some reworking by wind at
some time during the late Pleistocene.
Kandic Paleustalfs.—These soils have an argillic horizon
that has a CEC (by 1N NH4
OAc pH 7) of less than 24 cmol(+)/
kg clay in the major part. The base saturation (by sum of
cations) is less than 75 percent in all parts of the argillic horizon
in some pedons. These soils are intergrades between Paleustalfs
and Kandiustalfs. They are not known to occur in the United
States but probably are moderately extensive in some other
countries.
Lamellic Paleustalfs.—These soils are like Typic
Paleustalfs in defined properties, but they have an argillic
horizon that consists of lamellae or partially of lamellae. Most
of these soils have a sandy particle-size class, and the upper
boundary of the argillic horizon or the upper lamella may be
below a depth of 60 cm. The upper several lamellae are
commonly broken or discontinuous horizontally. These soils
are not extensive in the United States.
Oxyaquic Paleustalfs.—These soils are like Typic
Paleustalfs, but they are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years. In addition, the soils
are permitted, but not required, to have a base saturation (by
sum of cations) that is less than 75 percent. They are
considered intergrades to Aqualfs. They are rare in the United
States.
Oxyaquic Vertic Paleustalfs.—These soils are like Typic
Paleustalfs, but they have a clayey texture and have expanding
clay in the argillic horizon. They also have deep, wide cracks
in normal years and are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years. These soils are not
extensive in the United States.
Petrocalcic Paleustalfs.—These soils have a petrocalcic
horizon, most commonly at a depth about 75 cm below the
surface, and are drier than Typic Paleustalfs. The upper part of
the argillic horizon is noncalcareous. Petrocalcic Paleustalfs
are locally extensive in the southern part of the Great Plains in
the United States. Some of them are used for crops, mainly
cotton, sorghum, and wheat. A few of the soils are irrigated.
Many are used for grazing.
Plinthic Paleustalfs.—These soils are like Typic
Paleustalfs, but they have 5 percent or more (by volume)
plinthite in one or more horizons within 150 cm of the mineral
soil surface. In addition, the soils are permitted, but not
required, to have a base saturation (by sum of cations) that is
less than 75 percent. These soils are rare in the United States.
Psammentic Paleustalfs.—These soils are like Typic
Paleustalfs, but they have a sandy particle-size class throughout
the upper 75 cm of the argillic horizon or throughout the entire
argillic horizon if it is less than 75 cm thick. In addition, the
epipedon is permitted to be, and generally is, more than 50 cm
thick, and its texture is permitted to be loamy fine sand or
coarser throughout its thickness. These soils are not extensive
in the United States. Their slopes are gentle to strong. Most of
the soils are used for grazing.
Rhodic Paleustalfs.—These soils are like Typic Paleustalfs,
but the argillic horizon has hue of 2.5YR or redder and has a
color value, moist, of 3 or less and a dry color value 1 unit or
252 Soil Taxonomy
less higher than the moist value. In addition, the base saturation
(by sum of cations) may be less than 75 percent throughout the
argillic horizon. These soils are not extensive in the United
States. Their slopes are gentle, and most of the soils are used for
grazing.
Udertic Paleustalfs.—These soils are like Typic Paleustalfs,
but they have cracks and slickensides or wedge-shaped
aggregates and are moist for longer periods. They are
intergrades between Hapluderts and Paleustalfs. They are
locally extensive in some areas in the southern part of the Great
Plains in the United States. Their slopes are gentle, and most of
the soils are used as cropland.
Udic Paleustalfs.—These soils are like Typic Paleustalfs,
but they are moist for longer periods. They are intergrades
between Paleudalfs and Paleustalfs. They are extensive in parts
of the United States. Their slopes are gentle, and most of the
soils are used as cropland.
Ultic Paleustalfs.—These soils are like Typic Paleustalfs,
but they have a base saturation (by sum of cations) that is less
than 75 percent in all subhorizons of the argillic horizon. Most
Ultic Paleustalfs do not have a calcic horizon or a horizon that
contains identifiable secondary carbonates. Ultic Paleustalfs are
intergrades between Paleudults or Paleustults and Paleustalfs.
They are locally extensive in Texas and Oklahoma in the
United States. Their slopes are gentle, and most of the soils are
used as cropland.
Vertic Paleustalfs.—These soils are like Typic Paleustalfs,
but they have cracks and slickensides or wedge-shaped
aggregates. Vertic Paleustalfs are intergrades between
Haplusterts and Paleustalfs. They are moderately extensive
locally in some areas in the southern part of the Great Plains
and in the southwestern part of the United States. Their slopes
are gentle, and most of the soils are used as cropland.
Plinthustalfs
Plinthustalfs are the Ustalfs that have one or more horizons
within 150 cm of the mineral soil surface in which plinthite
either forms a continuous phase or constitutes one-half or more
of the volume. These soils do not have a duripan that has its
upper boundary within 100 cm of the soil surface. There are no
soil series in the United States that are presently classified in
this great group, but the group is provided for use in other
parts of the world. Subgroups have not been developed.
Key to Subgroups
JCBA. All Plinthustalfs (provisionally).
Typic Plinthustalfs
Rhodustalfs
Rhodustalfs are dark red Ustalfs that have a thinner solum
than that in Paleustalfs. Rhodustalfs generally formed on
erosional surfaces or in deposits of late-Pleistocene age. In the
United States, their vegetation was mostly grass and scattered
woody shrubs and trees before the soils were cultivated. The
parent materials are basic. These soils are rare in the United
States.
Definition
Rhodustalfs are the Ustalfs that:
1. Have, in all subhorizons in the upper 100 cm of the
argillic horizon or throughout the entire argillic horizon if less
than 100 cm thick, more than 50 percent colors that have all of
the following:
a. Hue of 2.5YR or redder; and
b. Value, moist, of 3 or less; and
c. Dry value no more than 1 unit higher than the moist
value;
2. Do not have a natric or kandic horizon;
3. Do not have a duripan that has an upper boundary within
100 cm of the soil surface or a petrocalcic horizon that has an
upper boundary within 150 cm of the soil surface;
4. Do not have plinthite that forms a continuous phase or
constitutes more than half the matrix within any subhorizon of
the argillic horizon within 150 cm of the soil surface;
5. Either have a densic, lithic, or paralithic contact within
150 cm of the soil surface or have a clay distribution in the
argillic horizon in which the clay content decreases with
increasing depth by 20 percent or more from its maximum
within 150 cm of the soil surface and, if there is a clay increase
of 3 percent or more (absolute) below that layer, less than 5
percent of the volume in the layer where the clay content
decreases consists of skeletans on faces of peds; and
6. Have either:
a. A densic, lithic, or paralithic contact within 50 cm of
the soil surface; or
b. A particle-size class other than fine, very-fine, or
clayey-skeletal in the upper part of the argillic horizon; or
c. A fine, very-fine, or clayey-skeletal particle-size class in
the upper part of the argillic horizon and an increase of less
than 20 percent clay (absolute) within a vertical distance of
7.5 cm and of less than 15 percent within 2.5 cm of the
upper boundary of the argillic horizon.
Key to Subgroups
JCGA. Rhodustalfs that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Rhodustalfs
JCGB. Other Rhodustalfs that have a CEC of less than 24
cmol(+)/kg clay (by 1N NH4
OAc pH 7) in 50 percent or more
Alfisols 253
either of the argillic horizon if less than 100 cm thick or of its
upper 100 cm.
KanhaplicRhodustalfs
JCGC. Other Rhodustalfs that, when neither irrigated nor
fallowed to store moisture, have either:
1. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for four-tenths or less of the time (cumulative) per year
when the temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
2. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for less than 120
cumulative days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8 o
C.
Udic Rhodustalfs
JCGD. Other Rhodustalfs.
Typic Rhodustalfs
Definition of Typic Rhodustalfs
Typic Rhodustalfs are the Rhodustalfs that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Have a CEC of 24 or more cmol(+)/kg clay (by 1N
NH4
OAc pH 7) in the major part of the argillic horizon or the
major part of the upper 100 cm of the argillic horizon if the
argillic horizon is thicker than 100 cm; and
3. When neither irrigated nor fallowed to store moisture,
have:
a. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for more than four-tenths of the time (cumulative)
when the soil temperature at a depth of 50 cm exceeds 5 o
C;
or
b. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for 120 or more days
(cumulative) during a period when the soil temperature at a
depth of 50 cm exceeds 8 o
C.
Description of Subgroups
Typic Rhodustalfs.—The central concept or Typic subgroup
of Rhodustalfs is fixed on soils that are deep or moderately
deep to hard rock and that have some 2:1 lattice clays.
A shallow lithic contact defines the Lithic subgroup, a
convention used throughout this taxonomy. Low activity in the
clay fraction is thought to indicate stronger weathering than
normal and is used to define the Kanhaplic subgroup.
Rhodustalfs that are moist for longer periods than are described
for the Typic subgroup are assigned to the Udic subgroup.
Typic Rhodustalfs are rare in the United States. Their slopes
range from gentle to strong. Most of them are used for grazing.
Kanhaplic Rhodustalfs.—These soils are like Typic
Rhodustalfs, but their CEC is less than 24 cmol(+)/kg clay.
They are permitted, but not required, to have a calcic or Bk
horizon that contains identifiable secondary carbonates. These
soils are rare in the United States and are known to occur only in
Hawaii. Their slopes are strong, and most of the soils are used
for grazing.
Lithic Rhodustalfs.—These soils have a lithic contact
within 50 cm of the soil surface. They may have any of the
other properties allowed in Rhodustalfs. Lithic Rhodustalfs are
rare in the United States and are known to occur only in Texas.
Udic Rhodustalfs.—These soils are like Typic Rhodustalfs,
but they are moist for longer periods. They are rare in the
United States. Their slopes are moderate or strong, and most of
the soils are used for grazing.
Xeralfs
Xeralfs are the Alfisols in regions that have a
Mediterranean climate. As their name implies, they have a
xeric moisture regime. They are dry for extended periods in
summer, but in winter moisture moves through the soils to
deeper layers in at least occasional years, if not in normal
years. Small grain and other winter annuals are common crops
where there is no irrigation. Grapes and olives also are
common crops where the climate is thermic. With irrigation, a
wide variety of crops can be grown.
Xeralfs formed not only in the area around the
Mediterranean Sea but also in parts of South Africa, Chile,
western and southern Australia, and in the Western United
States. Most of these soils border the Mediterranean Sea or lie
to the east of an ocean at midlatitudes. The temperature regime
is thermic, mesic, or frigid. In the world as a whole, Xeralfs
are not extensive soils, but in the regions where they occur,
they are extensive. In the United States, they are moderately
extensive. Before the soils were farmed, the vegetation was a
mixture of annual grasses, forbs, and woody shrubs on the
warmest and driest Xeralfs and coniferous forest on the coolest
and most moist Xeralfs.
Xeralfs formed on surfaces that are of different ages. Some
formed on erosional surfaces or in deposits of late-Wisconsinan
age, and some, such as those in Australia, are on old surfaces
and have characteristics that probably reflect an environment
greatly different from the present one. In the oldest Xeralfs, the
boundary between the A and B horizons commonly is very
abrupt. The epipedon of some Xeralfs is hard and massive
when dry.
254 Soil Taxonomy
Definition
Xeralfs are the Alfisols that:
1. Have a xeric moisture regime;
2. Have a frigid, mesic, or thermic temperature regime;
3. Have, in no horizon within 50 cm of the mineral soil surface,
both aquic conditions (other than anthraquic conditions) for
some time in normal years (or artificial drainage) and either of
the following:
a. Redoximorphic features in all layers between either the
lower boundary of an Ap horizon or a depth of 25 cm below
the mineral soil surface, whichever is deeper, and a depth of
40 cm; and one of the following within the upper 12.5 cm of
the argillic, kandic, natric, or glossic horizon:
(1) 50 percent or more redox depletions with chroma of
2 or less on faces of peds and redox concentrations
within peds; or
(2) Redox concentrations and 50 percent or more redox
depletions with chroma of 2 or less in the matrix; or
(3) 50 percent or more redox depletions with chroma of
1 or less on faces of peds or in the matrix, or both; or
b. In a horizon that has aquic conditions, enough active
ferrous iron to give a positive reaction to alpha,alphadipyridyl
at a time when the soil is not being irrigated.
Key to Great Groups
JDA. Xeralfs that have a duripan that has its upper boundary
within 100 cm of the mineral soil surface.
Durixeralfs,p.254
JDB. Other Xeralfs that have a natric horizon.
Natrixeralfs,p.263
JDC. Other Xeralfs that have a fragipan with an upper
boundary within 100 cm of the mineral soil surface.
Fragixeralfs,p.256
JDD. Other Xeralfs that have one or more horizons within
150 cm of the mineral soil surface in which plinthite either
forms a continuous phase or constitutes one-half or more of the
volume.
Plinthoxeralfs, p. 269
JDE. Other Xeralfs that have, in all subhorizons in the upper
100 cm of the argillic or kandic horizon or throughout the
entire argillic or kandic horizon if less than 100 cm thick,
more than 50 percent colors that have all of the following:
1. Hue of 2.5YR or redder; and
2. Value, moist, of 3 or less; and
3. Dry value no more than 1 unit higher than the moist
value.
Rhodoxeralfs, p. 269
JDF. Other Xeralfs that have one or more of the following:
1. A petrocalcic horizon that has its upper boundary within
150 cm of the mineral soil surface; or
2. No densic, lithic, or paralithic contact within 150 cm of
the mineral soil surface and an argillic or kandic horizon
that has both:
a. Within 150 cm of the mineral soil surface, either:
(1) With increasing depth, no clay decrease of 20
percent or more (relative) from the maximum clay
content [Clay is measured noncarbonate clay or based
on the following formula: Clay % = 2.5(% water
retained at 1500 kPa tension - % organic carbon),
whichever value is greater, but no more than 100]; or
(2) 5 percent or more (by volume) skeletans on faces
of peds in the layer that has a 20 percent lower clay
content and, below that layer, a clay increase of 3
percent or more (absolute) in the fine-earth fraction;
and
b. A base at a depth of 150 cm or more; or
3. No densic, lithic, or paralithic contact within 50 cm of
the mineral soil surface and an argillic or kandic horizon
that has within 15 cm of its upper boundary both:
a. A clayey, clayey-skeletal, fine, or very-fine particlesize
class; and
b. A clay increase, in the fine-earth fraction, of either
20 percent or more (absolute) within a vertical distance
of 7.5 cm or of 15 percent or more (absolute) within a
vertical distance of 2.5 cm.
Palexeralfs,p.264
JDG. OtherXeralfs.
Haploxeralfs, p. 258
Durixeralfs
Durixeralfs are the Xeralfs that have a duripan that has an
upper boundary within 100 cm of the soil surface but below an
argillic or natric horizon. These soils are known to have
formed in California, Idaho, Nevada, Oregon, Chile, and Italy,
in areas of Pleistocene or earlier vulcanism. Some of the
Durixeralfs in the United States appear to be on very old
surfaces and have complex horizons that indicate polygenesis.
The oldest soils are commonly reddish and have kaolinitic
Alfisols 255
mineralogy. Other Durixeralfs appear to have formed in latePleistocene
sediments and are yellowish brown and have 2:1
lattice clays. The pan commonly has an upper boundary about
50 cm below the soil surface and has very coarse polyhedrons,
the tops and sides of which are coated with opal or chalcedony.
In undisturbed areas in the United States, a microrelief of about
10 to 100 cm or more is common. The microrelief is mainly
the result of differences in the thickness of horizons that are
above the duripan.
Durixeralfs are moderately extensive only in California and
Idaho in the United States.
Definition
Durixeralfs are the Xeralfs that have a duripan that has an
upper boundary within 100 cm of the mineral soil surface.
Key to Subgroups
JDAA. Durixeralfs that have a natric horizon.
Natric Durixeralfs
JDAB. Other Durixeralfs that have, above the duripan, one
or both of the following:
1. Cracks that are 5 mm or more wide through a thickness
of 30 cm or more for some time in normal years, and
slickensides or wedge-shaped aggregates in a layer 15 cm or
more thick; or
2. A linear extensibility of 6.0 cm or more.
Vertic Durixeralfs
JDAC. Other Durixeralfs that have, in one or more
subhorizons within the argillic horizon, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Durixeralfs
JDAD. Other Durixeralfs that have both:
1. An argillic horizon that has both:
a. A clayey, clayey-skeletal, fine, or very-fine particlesize
class throughout some subhorizon 7.5 cm or more
thick; and
b. At its upper boundary or within some part, a clay
increase either of 20 percent or more (absolute) within a
vertical distance of 7.5 cm or of 15 percent or more
(absolute) within a vertical distance of 2.5 cm, in the
fine-earth fraction; and
2. A duripan that is strongly cemented or less cemented in
all subhorizons.
Abruptic Haplic Durixeralfs
JDAE. Other Durixeralfs that have an argillic horizon that
has both:
1. A clayey, clayey-skeletal, fine, or very-fine particle-size
class throughout some subhorizon 7.5 cm or more thick;
and
2. At its upper boundary or within some part, a clay
increase either of 20 percent or more (absolute) within a
vertical distance of 7.5 cm or of 15 percent or more
(absolute) within a vertical distance of 2.5 cm, in the fineearth
fraction.
Abruptic Durixeralfs
JDAF. Other Durixeralfs that have a duripan that is strongly
cemented or less cemented in all subhorizons.
Haplic Durixeralfs
JDAG. Other Durixeralfs.
Typic Durixeralfs
Definition of Typic Durixeralfs
Typic Durixeralfs are the Durixeralfs that:
1. Have an argillic horizon that meets one or more of the
following:
a. Has less than 35 percent clay in all subhorizons that are
7.5 cm or thicker; or
b. Has an increase in clay content that is less than 15
percent (absolute) within a vertical distance of 2.5 cm and is
less than 20 percent (absolute) within a vertical distance of
7.5 cm at the upper boundary and within all parts;
2. Do not have, in any subhorizon within the argillic horizon,
redox depletions with chroma of 2 or less and also aquic
conditions;
3. Have a duripan that is very strongly cemented or indurated
in some part;
4. Do not have a natric horizon; and
5. Above the duripan, do not have either:
a. Cracks that are 5 mm or more wide through a thickness
of 30 cm or more for some time in normal years, and
slickensides or wedge-shaped aggregates in a layer 15 cm or
more thick; or
b. A linear extensibility of 6.0 cm or more.
Description of Subgroups
Typic Durixeralfs.—The central concept or Typic subgroup
is fixed on the most freely drained Durixeralfs that have a very
strongly cemented or indurated duripan and do not have a
natric horizon. These soils have an argillic horizon that either
has less than 35 percent clay or, if it has 35 percent or more
clay, has a relatively small increase in clay content or a
relatively thick transitional horizon between the epipedon and
the argillic horizon.
256 Soil Taxonomy
The Typic subgroup is not the most extensive subgroup, but
it was selected to provide what seems the best basis for
definition of the others.
An abrupt textural change at the upper boundary of the
argillic horizon or within the argillic horizon is very common,
and it defines Abruptic subgroups. Soils that have redox
depletions with low chroma and aquic conditions for some time
in normal years (or artificial drainage) in the argillic horizon are
excluded from the Typic subgroup. A duripan that does not
have a very strongly cemented or indurated subhorizon is
considered weakly expressed and is the basis for definition of
Haplic subgroups. A natric horizon is considered atypical and
is used to define the Natric subgroup.
Abruptic Durixeralfs.—These soils are like Typic
Durixeralfs, but the argillic horizon has a fine, very-fine,
clayey, or clayey-skeletal particle-size class in some
subhorizon, and at the upper boundary of the argillic horizon
or within the argillic horizon, there is a marked increase in
content of clay. These soils are moderately extensive in
California. In many of the soils, the argillic horizon appears to
have formed since the duripan developed. Slopes are gentle or
moderate. Most of the soils are used for grazing or for small
grain.
Abruptic Haplic Durixeralfs.—These soils have an argillic
horizon that has a fine, very-fine, clayey, or clayey-skeletal
particle-size class in some subhorizon and, at the upper
boundary of the argillic horizon or within the argillic horizon,
there is a marked increase in content of clay. In addition, the
duripan is strongly cemented or less cemented in all
subhorizons. It is not known whether the duripan is forming, is
being destroyed, or is only weakly developed. These soils are
not extensive. Their slopes are gentle. Most of the soils are
used for grazing.
Aquic Durixeralfs.—These soils are like Typic Durixeralfs,
but they have, in one or more horizons within 75 cm of the
mineral soil surface, redox depletions with chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage). These soils are not known to occur in the
United States.
Haplic Durixeralfs.—These soils are like Typic
Durixeralfs, but the duripan is strongly cemented or less
cemented in all subhorizons. It is not known whether the
duripan is forming, is being destroyed, or is only weakly
developed. In the United States, Haplic Durixeralfs are not
extensive, except locally in California. Their slopes are gentle
or moderate. Some of the soils are used for irrigated citrus
crops, some are used for small grain, and some are used as
pasture.
Natric Durixeralfs.—These soils have a natric horizon.
The duripan may or may not be indurated, and there may be
redox depletions with low chroma in the natric horizon, which
in some years may be saturated or may have ground water
perched above it. In the United States, these soils are extensive
only in the Central Valley of California. Commonly, they are
saline. After reclamation, they may be used for cultivated
crops. Otherwise, they provide only limited grazing unless
irrigated.
Vertic Durixeralfs.—These soils have, above the duripan,
cracks that are 5 mm or more wide through a thickness of 30
cm or more in normal years and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick or have a linear
extensibility of 6.0 cm or more. These soils are not known to
occur in the United States.
Fragixeralfs
Fragixeralfs are the Xeralfs that have a fragipan with an upper
boundary within 100 cm below the mineral soil surface.
Commonly, these soils have a brown argillic or kandic horizon
and have redoximorphic features and a perched water table that
is seasonally above the pan. Above the pan, some Fragixeralfs
have a thin eluvial horizon with peds that have gray clay
depletions.
Most Fragixeralfs in the United States are on gentle or
moderate slopes and formed, at least in part, in silty or loamy
late-Pleistocene deposits. Some are strongly sloping.
Temperature regimes are mesic or frigid. In the United States,
the native vegetation was primarily a coniferous forest. These
soils are of small extent in Idaho and Oregon.
Definition
Fragixeralfs are the Xeralfs that:
1. Have a fragipan with an upper boundary within 100 cm of
the mineral soil surface;
2. Do not have a duripan with an upper boundary within 100
cm of the mineral soil surface;
3. Do not have a natric horizon.
Key to Subgroups
JDCA. Fragixeralfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Fragixeralfs
JDCB. Other Fragixeralfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
Alfisols 257
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Fragixeralfs
JDCC. Other Fragixeralfs that have an Ap horizon with a color
value, moist, of 3 or less and a color value, dry, of 5 or less
(crushed and smoothed sample) or materials between the soil
surface and a depth of 18 cm that have these color values after
mixing.
Mollic Fragixeralfs
JDCD. Other Fragixeralfs that have, in one or more horizons
within 40 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Fragixeralfs
JDCE. Other Fragixeralfs that, above the fragipan, do not
have an argillic or kandic horizon with clay films on both
vertical and horizontal faces of any peds.
Inceptic Fragixeralfs
JDCF. Other Fragixeralfs.
Typic Fragixeralfs
Definition of Typic Fragixeralfs
Typic Fragixeralfs are the Fragixeralfs that:
1. Above the fragipan, have an argillic or kandic horizon that
has clay films on at least some vertical and horizontal faces of
primary or secondary peds, or both;
2. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is equal
to 30 or more;
3. Either have an Ap horizon that has a color value, moist, of 4
or more or a color value, dry, of 6 or more, when crushed and
smoothed, or have materials to a depth of 18 cm that have
these colors after mixing; and
4. Do not have, in any horizon within 40 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions.
Description of Subgroups
Typic Fragixeralfs.—The central concept or Typic
subgroup of Fragixeralfs is fixed on the soils of this great
group that are the most freely drained, that have an argillic or
kandic horizon above the fragipan, and that have a high color
value in an Ap horizon or in comparable layers if the soils are
undisturbed.
Typic Fragixeralfs are not the most extensive subgroup, but
they furnish the best basis for definition of subgroups. No
Fragixeralfs are freely drained because in all of them ground
water is perched above the fragipan in many years. The
perched water table is a probable cause of the very common
albic materials and gray clay depletions directly above the
fragipan. Soils that have these features and also redox
depletions with low chroma at a shallow depth together with
redox concentrations of high chroma or of reddish hue are
considered to be intergrades toward Aqualfs.
Typic Fragixeralfs do not have a surface mantle or layer in
the upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. An Ap
horizon or subhorizons of comparable thickness that have the
color of a mollic epipedon are considered atypical and define
the Mollic subgroup.
In many Fragixeralfs the fragipan is in the argillic horizon;
above the fragipan, there is a cambic horizon that is separated
from the pan by an eluvial horizon. These extra horizons form
the basis for defining intergrades to Fragixerepts.
Andic and Vitrandic Fragixeralfs.—These soils are like
Typic Fragixeralfs, but they have a surface mantle or layer in
the upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. In the
United States, these soils occur in Idaho. They are permitted,
but not required, to have redox depletions and also color value
of 3 or less, moist, and 5 or less, dry, in surface horizons, after
mixing to a depth of 15 cm. These soils are not extensive.
Aquic Fragixeralfs.—These soils are like Typic
Fragixeralfs, but they have, in one or more horizons within 40
cm of the mineral soil surface, redox depletions with chroma of
2 or less and also aquic conditions for some time in normal
years (or artificial drainage). Aquic Fragixeralfs are
258 Soil Taxonomy
intergrades between Fragiaqualfs and Fragixeralfs. They are rare
in the United States.
Inceptic Fragixeralfs.—These soils are like Typic
Fragixeralfs, but, above the fragipan, they do not have a distinct
argillic horizon that has clay films on some vertical and
horizontal faces of peds. They have, above the fragipan, a
brown or strong brown, unmottled horizon that seems more
like a cambic horizon than an argillic horizon. Directly above
the fragipan, there may be a thin eluvial horizon. The prism
faces of the fragipan have thick (more than 1 mm) clay films, or
the fragipan itself also is an argillic horizon.
Mollic Fragixeralfs.—These soils have an Ap horizon that
has a color value, moist, darker than 4 and a color vaue, dry,
darker than 6, or they have these color values to a depth of 18
cm, after mixing. These soils are permitted, but not required, to
have redox depletions that have chroma of 2 or less within 40
cm of the soil surface. The epipedon is mollic or approaches
the properties of a mollic epipedon.
Haploxeralfs
These are the Xeralfs that have an argillic or kandic horizon
that is relatively thin, has a clear or gradual upper boundary, or
has a loamy particle-size class throughout. These soils are not
dark red or dusky red throughout. They do not have a natric
horizon and do not have a duripan or fragipan with an upper
boundary within 100 cm of the mineral soil surface. They have
neither a petrocalcic horizon nor one or more horizons in
which plinthite either forms a continuous phase or constitutes
one-half or more of the volume within 150 cm of the soil
surface. Many Haploxeralfs formed in late-Pleistocene deposits
or on erosional surfaces of that age. Their parent materials may
be either acidic or basic. These soils are extensive in the areas
of Xeralfs in the Western United States.
Definition
Haploxeralfs are the Xeralfs that:
1. Do not have a natric horizon;
2. Do not have a duripan or fragipan with an upper boundary
within 100 cm of the mineral soil surface;
3. Do not have plinthite that forms a continuous phase or that
constitutes more than half the matrix within one or more
horizons within 150 cm of the mineral soil surface;
4. Do not have a petrocalcic horizon with its upper boundary
within 150 cm of the soil surface;
5. Have a densic, lithic, or paralithic contact within 150 cm
of the mineral soil surface or have an argillic or kandic horizon
that has either:
a. Within 150 cm of the mineral soil surface, either:
(1) A clay decrease with increasing depth of 20 percent
or more (relative) from the maximum clay content; or
(2) Less than 5 percent (by volume) skeletans on faces
of peds in the layer that has a 20 percent lower clay
content or, below that layer, a clay increase of less than 3
percent (absolute) in the fine-earth fraction; or
b. A base at a depth of less than 150 cm;
6. Have a densic, lithic, or paralithic contact within 50 cm of
the mineral soil surface or have an argillic or kandic horizon
that has:
a. Less than 35 percent clay in all parts; or
b. At its upper boundary, a clay increase, in the fine-earth
fraction, of both less than 20 percent (absolute) within a
vertical distance of 7.5 cm and of less than 15 percent
(absolute) within a vertical distance of 2.5 cm;
7. Have, in the upper 100 cm of the argillic or kandic horizon
or throughout the entire argillic or kandic horizon if less than
100 cm thick, less than 50 percent colors that have hue of
2.5YR or redder or one of the following:
a. Value, moist, of 4 or more; or
b. Dry value 2 or more units higher than the moist value.
Key to Subgroups
JDGA. Haploxeralfs that have both:
1. A lithic contact within 50 cm of the mineral soil
surface; and
2. A color value, moist, of 3 or less and 0.7 percent or
more organic carbon either throughout an Ap horizon or
throughout the upper 10 cm of an A horizon.
Lithic Mollic Haploxeralfs
JDGB. Other Haploxeralfs that have both:
1. A lithic contact within 50 cm of the mineral soil
surface; and
2. An argillic or kandic horizon that is discontinuous
horizontally in each pedon.
Lithic Ruptic-Inceptic Haploxeralfs
JDGC. Other Haploxeralfs that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Haploxeralfs
JDGD. Other Haploxeralfs that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
Alfisols 259
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick that
has its upper boundary within 125 cm of the mineral soil
surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact, whichever is shallower.
Vertic Haploxeralfs
JDGE. Other Haploxeralfs that have both:
1. In one or more horizons within 75 cm of the mineral soil
surface, redox depletions with chroma of 2 or less and also
aquic conditions for some time in normal years (or artificial
drainage); and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface,
one or more of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Haploxeralfs
JDGF. Other Haploxeralfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Haploxeralfs
JDGG. Other Haploxeralfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is equal
to 30 or more.
Vitrandic Haploxeralfs
JDGH. Other Haploxeralfs that have both:
1. Fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of
the mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm or
more thick; and
2. Redox depletions with chroma of 2 or less in layers that
also have aquic conditions in normal years (or artificial
drainage) either:
a. Within the upper 25 cm of the argillic or kandic
horizon if its upper boundary is within 50 cm of the
mineral soil surface; or
b. Within 75 cm of the mineral soil surface if the upper
boundary of the argillic or kandic horizon is 50 cm or
more below the mineral soil surface.
Fragiaquic Haploxeralfs
JDGI. Other Haploxeralfs that have both:
1. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. An argillic or kandic horizon that has a base saturation
(by sum of cations) of less than 75 percent in one or more
subhorizons within its upper 75 cm or above a densic, lithic,
or paralithic contact, whichever is shallower.
Aquultic Haploxeralfs
JDGJ. Other Haploxeralfs that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Haploxeralfs
JDGK. Other Haploxeralfs that have an exchangeable sodium
percentage of 15 or more (or a sodium adsorption ratio of 13 or
more) in one or more subhorizons of the argillic or kandic
horizon.
Natric Haploxeralfs
JDGL. Other Haploxeralfs that have fragic soil properties:
260 Soil Taxonomy
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Haploxeralfs
JDGM. Other Haploxeralfs that have an argillic horizon that:
1. Consists entirely of lamellae; or
2. Is a combination of two or more lamellae and one or more
subhorizons with a thickness of 7.5 to 20 cm, each layer with
an overlying eluvial horizon; or
3. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
a. Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
horizon); or
b. A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon.
Lamellic Haploxeralfs
JDGN. Other Haploxeralfs that have a sandy particle-size
class throughout the upper 75 cm of the argillic horizon or
throughout the entire argillic horizon if it is less than 75 cm
thick.
Psammentic Haploxeralfs
JDGO. Other Haploxeralfs that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Haploxeralfs
JDGP. Other Haploxeralfs that have a calcic horizon that has
its upper boundary within 100 cm of the mineral soil surface.
Calcic Haploxeralfs
JDGQ. Other Haploxeralfs that have:
1. An argillic, kandic, or natric horizon that is 35 cm or
less thick; and
2. No densic, lithic, or paralithic contact within 100 cm of
the mineral soil surface.
Inceptic Haploxeralfs
JDGR. Other Haploxeralfs that have an argillic or kandic
horizon that has a base saturation (by sum of cations) of less
than 75 percent in one or more subhorizons within its upper 75
cm or above a densic, lithic, or paralithic contact, whichever is
shallower.
Ultic Haploxeralfs
JDGS. Other Haploxeralfs that have a color value, moist, of 3
or less and 0.7 percent or more organic carbon either
throughout an Ap horizon or throughout the upper 10 cm of an
A horizon.
MollicHaploxeralfs
JDGT. Other Haploxeralfs.
Typic Haploxeralfs
Definition of Typic Haploxeralfs
Typic Haploxeralfs are the Haploxeralfs that:
1. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
2. Have an A horizon that, throughout its upper 10 cm, has a
color value, moist, of 4 or more or has less than 0.7 percent
organic carbon in some part or have an Ap horizon that has a
color value, moist, of 4 or more or contains less than 0.7
percent organic carbon;
3. Do not have a lithic contact within 50 cm of the soil
surface;
4. Have exchangeable sodium that is less than 15 percent of
the CEC (at pH 8.2) throughout the argillic horizon;
5. Have less than 5 percent (by volume) plinthite in all
subhorizons within 150 cm of the soil surface;
6. Have an argillic or kandic horizon that has a base
saturation (by sum of cations) of 75 percent or more throughout
the upper 75 cm or to a densic, lithic, or paralithic contact,
whichever is shallower;
7. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
8. Have an argillic or kandic horizon that is finer than the
sandy particle-size class in some part of the upper 75 cm if the
argillic or kandic horizon is more than 75 cm thick or in any
part if the argillic or kandic horizon is less than 75 cm thick;
9. Do not have a calcic horizon that has its upper boundary
within the upper 100 cm of the mineral soil surface;
Alfisols 261
10. Have an exchangeable sodium percentage of less than 15
(or a sodium adsorption ratio of less than 13) in all subhorizons
of the argillic or kandic horizon;
11. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention, and
acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
12. Do not have an argillic horizon that:
a. Consists entirely of lamellae; or
b. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
c. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
(1) Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
horizon); or
(2) A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon;
13. Have an argillic or kandic horizon that is more than 35
cm thick; and
14. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick.
Description of Subgroups
Typic Haploxeralfs.—The central concept or Typic subgroup
of Haploxeralfs is fixed on freely drained soils that are deep or
moderately deep to hard rock, that have high base saturation but
little sodium on the exchange complex, and that have little or no
plinthite. In addition, the argillic horizon is 35 cm or more thick,
does not consist of lamellae, and has a particle-size class finer
than sandy. Typic Haploxeralfs do not have cracks and
slickensides or wedge-shaped aggregates or a linear extensibility
of 6.0 cm or more.
Soils that have redox depletions with low chroma at a
shallow depth and that have ground water during the growing
season are excluded from Typic Haploxeralfs because these
properties are shared with Aqualfs. Soils that have a large
volume of fragic soil properties are excluded because they are
considered intergrades to Fragixeralfs. Soils that have an Ap
horizon or a moderately thick A horizon that has the color and
organic-matter content of a mollic epipedon are excluded
because these properties are shared with Mollisols. A shallow
lithic contact defines the Lithic subgroups, a convention used
throughout this taxonomy.
Soils that contain exchangeable sodium in the amount
adequate for a natric horizon are excluded from Typic
Haploxeralfs because this important property is shared with
Natrixeralfs. Soils that contain plinthite are excluded because
plinthite is a property of Plinthoxeralfs. A base saturation that
is only moderately high is considered atypical and defines the
Ultic subgroup. Soils that have cracks and slickensides or
wedge-shaped aggregates are excluded because these properties
are shared with Vertisols. An argillic horizon composed
entirely of thin lamellae is considered atypical and defines the
Psammentic subgroup. A moderately shallow calcic horizon
also is considered atypical and defines the Calcic subgroup.
Typic Haploxeralfs are extensive in the central and coastal
valleys and adjacent foothills of California in the United States.
They are on late-Pleistocene terraces and fans or dissected
upland surfaces. Where slopes are suitable, the soils are
irrigated and intensively farmed. Other areas are used for
grazing or woodland.
Andic and Vitrandic Haploxeralfs.—These soils are like
Typic Haploxeralfs, but they have a surface mantle or layer in
the upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. They
are permitted, but not required, to have a color value of 3 or
less, moist, and 5 or less, dry, in surface horizons, after mixing
to a depth of 15 cm. In the United States, these soils occur
mostly in Washington, Idaho, Oregon, and California. The
temperature regimes are mostly mesic or frigid. The native
vegetation was primarily a coniferous forest. These soils are
moderately extensive in the United States. They are used
262 Soil Taxonomy
mostly as forest, but some have been cleared and are used as
cropland or pasture.
Aquandic Haploxeralfs.—These soils are like Typic
Haploxeralfs, but they have a surface mantle or layer in the
upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. They
have, in one or more horizons within 75 cm of the mineral soil
surface, redox depletions with chroma of 2 or less and also
aquic conditions for some time in normal years (or artificial
drainage). They are permitted, but not required, to have a color
value of 3 or less, moist, and 5 or less, dry, in surface horizons,
after mixing to a depth of 15 cm. Aquandic Haploxeralfs are not
extensive.
Aquic Haploxeralfs.—These soils are like Typic
Haploxeralfs, but they have, in one or more horizons within 75
cm of the mineral soil surface, redox depletions with chroma of
2 or less and also aquic conditions for some time in normal
years (or artificial drainage). In addition, they are permitted,
but not required, to have an A horizon that, throughout the
upper 10 cm, has a color value, moist, of 3 or less and has more
than 0.7 percent organic carbon or to have an Ap horizon that
has a color value, moist, of 3 or less and has more than 0.7
percent organic carbon. These soils are not extensive. They are
mostly in California and Washington. Most of them have a
clayey argillic horizon that has low hydraulic conductivity.
Slopes range considerably. The native vegetation was primarily
a coniferous forest in Washington and grass and shrubs in
California. The soils that have suitable slopes are used mainly
as cropland.
Aquultic Haploxeralfs.—These soils are like Typic
Haploxeralfs, but they have, in one or more horizons within 75
cm of the mineral soil surface, redox depletions with chroma of
2 or less and also aquic conditions for some time in normal
years (or artificial drainage). They have a base saturation (by
sum of cations) that is less than 75 percent in some subhorizon
within 75 cm of the upper boundary of the argillic or kandic
horizon. In addition, they are permitted, but not required, to
have an A horizon that, throughout the upper 10 cm, has a
color value, moist, of 3 or less and has more than 0.7 percent
organic carbon or to have an Ap horizon that has a color value,
moist, of 3 or less and has more than 0.7 percent organic
carbon. These soils are of small extent, mostly in Oregon. They
are intergrades between Haploxeralfs and Aquults. Most
Aquultic Haploxeralfs have a clayey argillic horizon that has
low hydraulic conductivity. The native vegetation was
primarily forest. Slopes are mostly gentle, and many of the
soils have been cleared and are used as cropland.
Calcic Haploxeralfs.—These soils are like Typic
Haploxeralfs, but they have a calcic horizon that has its upper
boundary within 100 cm of the soil surface. They are known to
occur in Idaho and Utah in the United States. They are not
extensive.
Fragiaquic Haploxeralfs.—These soils are like Typic
Haploxeralfs, but they have redox depletions with low chroma
and aquic conditions at a shallow depth for some time in normal
years. In addition, they have fragic soil properties in 30 percent
or more of the volume of a layer 15 cm or more thick that has its
upper boundary within 100 cm of the mineral soil surface or in 60
percent or more of the volume of a layer 15 cm or more thick
anywhere in the soils. These soils are not extensive in the
United States.
Fragic Haploxeralfs.—These soils are like Typic
Haploxeralfs, but they have fragic soil properties in 30 percent
or more of the volume of a layer 15 cm or more thick that has
its upper boundary within 100 cm of the mineral soil surface or
in 60 percent or more of the volume of a layer 15 cm or more
thick anywhere in the soils. These soils are not extensive in the
United States.
Inceptic Haploxeralfs.—These soils are like Typic
Haploxeralfs in defined properties, but they have an argillic or
kandic horizon that is 35 cm or less thick and have no densic,
lithic, or paralithic contact within 100 cm of the soil surface.
They may also have an A horizon that, throughout its upper 10
cm, has a color value, moist, of 3 or less and has 0.7 percent or
more organic carbon or an Ap horizon that has both a color
value, moist, of 3 or less and 0.7 percent or more organic
carbon. These soils are not extensive in the United States.
Lamellic Haploxeralfs.—These soils are like Typic
Haploxeralfs in defined properties, but they have an argillic
horizon that consists of lamellae or partially of lamellae. Most
Lamellic Haploxeralfs have a sandy particle-size class. The
upper several lamellae are commonly broken or discontinuous
horizontally. Lamellic Haploxeralfs are allowed to have an Ap
horizon that has a color value, moist, of 3 or less or upper
horizons that have a color value, moist, of less than 4 after the
surface soil has been mixed to a depth of 15 cm. These soils are
not extensive in the United States.
Lithic Haploxeralfs.—These soils are like Typic
Haploxeralfs, but they have a lithic contact within 50 cm of the
soil surface. In addition, they are permitted, but not required,
to have a base saturation (by sum of cations) that is less than
75 percent in some subhorizon within 75 cm of the upper
boundary of the argillic or kandic horizon. These soils are not
extensive in the United States. They are mostly in California
and Idaho. The vegetation is mostly grasses and shrubs. Some
areas support widely spaced trees. These soils are used as
rangeland.
Lithic Mollic Haploxeralfs.—These soils are like Typic
Haploxeralfs, but they have a lithic contact within 50 cm of the
soil surface and also have an A horizon that, throughout its
upper 10 cm, has a color value, moist, of 3 or less and has 0.7
percent or more organic carbon; rarely, they have an Ap
horizon that has a color value, moist, of 3 or less and has 0.7
percent or more organic carbon. These soils are permitted, but
not required, to have a base saturation (by sum of cations) that
Alfisols 263
is less than 75 percent in some subhorizon within 75 cm of the
upper boundary of the argillic or kandic horizon. They are
mostly in California and Idaho in the United States. The
vegetation is mostly grasses and shrubs. Some areas support
widely spaced trees. These soils are used mainly as rangeland.
Lithic Ruptic-Inceptic Haploxeralfs.—These soils are like
Typic Haploxeralfs, but they have a lithic contact within 50 cm
of the soil surface. The upper boundary of the contact is
irregular. The major part of the pedon has an argillic or kandic
horizon. Where the lithic contact is closest to the soil surface,
however, only a cambic horizon is evident. These soils are rare
in the United States.
Mollic Haploxeralfs.—These soils are like Typic
Haploxeralfs, but they have an A horizon that, throughout its
upper 10 cm, has a color value, moist, of 3 or less and has 0.7
percent or more organic carbon; rarely, they have an Ap
horizon that has both a color value, moist, of 3 or less and 0.7
percent or more organic carbon. The epipedon of these soils
meets all of the requirements for a mollic epipedon as a rule,
but it is both massive and hard or very hard when dry. These
soils are extensive in the United States. They are intergrades
between Haploxeralfs and Argixerolls. Their slopes range from
nearly level to very strong. Where slopes are suitable, many of
the soils are cultivated. The soils that have strong slopes are
mainly under forest vegetation.
Natric Haploxeralfs.—These soils are like Typic
Haploxeralfs, but they have 15 percent or more saturation with
sodium in some part of the argillic horizon. The argillic
horizon would be a natric horizon if it had prismatic or
columnar structure or if it had blocky structure and albic
materials extending more than 2.5 cm into the horizon. These
soils are not extensive in the United States.
Plinthic Haploxeralfs.—These soils have 5 percent or more
(by volume) plinthite in one or more horizons within 150 cm of
the mineral soil surface. These soils are not known to occur in
the United States.
Psammentic Haploxeralfs.—These soils have an argillic
horizon that has a sandy particle-size class (loamy fine sand or
coarser) throughout the upper 75 cm of the argillic horizon or
throughout the entire argillic horizon if it is less than 75 cm
thick. These soils are rare in the United States. Most formed on
old stabilized sand dunes, and their slopes are gentle or
moderate. Most of the soils are used for grazing.
Ultic Haploxeralfs.—These soils are like Typic
Haploxeralfs, but they have a base saturation (by sum of
cations) that is less than 75 percent in some subhorizon within
75 cm of the upper boundary of the argillic or kandic horizon.
In addition, they are permitted, but not required, to have an A
horizon that, throughout its upper 10 cm, has a color value,
moist, of 3 or less and has 0.7 percent or more organic carbon
or to have an Ap horizon that has a color value, moist, of 3 or
less and has 0.7 percent or more organic carbon. These soils
are extensive. They are mostly in California, Oregon,
Washington, and Idaho. They occur in areas where Xeralfs
intergrade toward Ultisols and in areas where the parent
materials have a component of volcanic ash. Slopes range from
gentle to very strong. Most Ultic Haploxeralfs with strong or
very strong slopes are in forests and in some areas are grazed
for short periods. Many Ultic Haploxeralfs with gentle slopes
have been cleared and are used as cropland, but some are used
as pasture or are in forests.
Vertic Haploxeralfs.—These soils are like Typic Haploxeralfs,
but they are high in content of expanding clays and have cracks
5 mm or more wide, slickensides, wedge-shaped aggregates, or a
linear extensibility of 6.0 cm or more between the mineral soil
surface and either a depth of 100 cm or a densic, lithic, or
paralithic contact, whichever is shallower. These soils are rare in
the United States and are considered to be transitional to
Vertisols.
Natrixeralfs
Natrixeralfs are the Xeralfs that have a natric horizon but do
not have a duripan. They are not extensive. They support a
sparse vegetation that commonly consists of salt-tolerant
grasses and forbs. They were considered Solonetz soils, Soloth
soils, and transitional forms in the 1938 classification.
Definition
Natrixeralfs are the Xeralfs that:
1. Have a natric horizon;
2. Do not have a duripan within 100 cm of the soil surface.
Key to Subgroups
JDBA. Natrixeralfs that have one or both of the following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Natrixeralfs
JDBB. Other Natrixeralfs that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Natrixeralfs
JDBC. Other Natrixeralfs.
Typic Natrixeralfs
264 Soil Taxonomy
Definition of Typic Natrixeralfs
Typic Natrixeralfs are the Natrixeralfs that:
1. Do not have, in any horizon within 75 cm of the mineral soil
surface, redox depletions with chroma of 2 or less and also aquic
conditions; and
2. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that are 5
mm or more wide through a thickness of 30 cm or more for
some time in normal years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has its upper
boundary within 125 cm of the mineral soil surface; or
b. A linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm or
a densic, lithic, or paralithic contact, whichever is
shallower.
Description of Subgroups
Typic Natrixeralfs.—The central concept or Typic
subgroup of Natrixeralfs is fixed on the most freely drained
soils of this great group. None of these soils are freely drained
because their low hydraulic conductivity results in perched
ground water above the natric horizon in many years. Some
Natrixeralfs have ground water below as well as above the
natric horizon and have redox depletions with low chroma.
These features cause the soils to be excluded from the Typic
subgroup because they are properties shared with Aqualfs.
Typic Natrixeralfs are not extensive in the United States.
They are mostly in California and Montana. Their slopes are
mostly gentle. The soils developed under grass, shrubs, and
forbs. Some of the soils, mostly those in California, are
reclaimed and used as cropland. The native plants are used for
grazing.
Aquic Natrixeralfs.—These soils are like Typic
Natrixeralfs, but they have, in one or more horizons within 75
cm of the mineral soil surface, redox depletions with chroma of
2 or less and also aquic conditions for some time in normal
years (or artificial drainage). These soils are rare in the United
States. Their slopes are mostly nearly level. The soils
developed under grass, shrubs, and forbs. Some of the soils,
mostly those in California, are reclaimed and used as cropland.
The native plants are used for grazing.
Vertic Natrixeralfs.—These soils are like Typic
Natrixeralfs, but they are high in content of expanding clays
and have cracks 5 mm or more wide, slickensides, wedgeshaped
aggregates, or a linear extensibility of 6.0 cm or more
between the mineral soil surface and either a depth of 100 cm
or a densic, lithic, or paralithic contact, whichever is shallower.
These soils are rare in the United States. They are considered
to be transitional to Vertisols.
Palexeralfs
Palexeralfs are the Xeralfs that have a petrocalcic horizon or
an argillic or kandic horizon that is thick or that has, at its
upper boundary, both a clayey, clayey-skeletal, fine, or veryfine
particle-size class and a large clay increase. Many of these
soils have some plinthite in their lower horizons, but this
feature is rare in the United States. Palexeralfs are in relatively
stable landscape positions on gentle slopes, and most began
their genesis before the late Pleistocene. During pluvial periods
of the Pleistocene, carbonates appear to have been almost
completely removed from the argillic or kandic horizon of most
of these soils, but some of the soils appear to have been
recalcified later.
Most Palexeralfs formed in acid or in moderately basic parent
materials, but some formed in materials as basic as basalt. The
native vegetation on the warmest Palexeralfs in the United States
was a mixture of annual grasses, forbs, and woody shrubs. The
native vegetation on the coolest Palexeralfs was mostly a
coniferous forest. Palexeralfs are moderately extensive both in
the United States and in some other parts of the world.
Definition
Palexeralfs are the Xeralfs that:
1. Have a petrocalcic horizon that has its upper boundary
within 150 cm of the mineral soil surface;
2. Have no densic, lithic, or paralithic contact within 150 cm
of the mineral soil surface and have an argillic or kandic
horizon that has both:
a. Within 150 cm of the mineral soil surface, either:
(1) With increasing depth, no clay decrease of 20
percent or more (relative) from the maximum clay
content; or
(2) 5 percent or more (by volume) skeletans on faces of
peds in the layer that has a 20 percent lower clay content
and, below that layer, a clay increase of 3 percent or
more (absolute) in the fine-earth fraction; and
b. A base at a depth of 150 cm or more;
3. Have no densic, lithic, or paralithic contact within 50 cm
of the mineral soil surface and have an argillic or kandic
horizon that has within 15 cm of its upper boundary both:
a. A clayey, clayey-skeletal, fine, or very-fine particle-size
class; and
b. A clay increase, in the fine-earth fraction, of either 20
percent or more (absolute) within a vertical distance of 7.5
cm or of 15 percent or more (absolute) within a vertical
distance of 2.5 cm; and
Alfisols 265
4. Do not have a duripan or fragipan with an upper boundary
within 100 cm of the mineral soil surface;
5. Do not have a natric horizon;
6. Do not have plinthite that forms a continuous phase
or that constitutes more than one-half the matrix within
one or more horizons within 150 cm of the mineral soil
surface;
7. Have, in the upper 100 cm of the argillic or kandic horizon or
throughout the entire argillic or kandic horizon if less than 100
cm thick, less than 50 percent colors that have hue of 2.5YR or
redder or one of the following:
a. Value, moist, of 4 or more; or
b. Dry value 2 or more units higher than the moist value.
KeytoSubgroups
JDFA. Palexeralfs that have one or both of the following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Palexeralfs
JDFB. Other Palexeralfs that have both:
1. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface,
one or more of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Palexeralfs
JDFC. Other Palexeralfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Palexeralfs
JDFD. Other Palexeralfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Palexeralfs
JDFE. Other Palexeralfs that have both:
1. Fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm
of the mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm
or more thick; and
2. Redox depletions with chroma of 2 or less in layers that
also have aquic conditions in normal years (or artificial
drainage) either:
a. Within the upper 25 cm of the argillic or kandic
horizon if its upper boundary is within 50 cm of the
mineral soil surface; or
b. Within 75 cm of the mineral soil surface if the upper
boundary of the argillic or kandic horizon is 50 cm or
more below the mineral soil surface.
Fragiaquic Palexeralfs
JDFF. Other Palexeralfs that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
266 Soil Taxonomy
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Palexeralfs
JDFG. Other Palexeralfs that have a petrocalcic horizon that
has its upper boundary within 150 cm of the mineral soil
surface.
Petrocalcic Palexeralfs
JDFH. Other Palexeralfs that have an argillic horizon that:
1. Consists entirely of lamellae; or
2. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
3. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
a. Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
horizon); or
b. A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon.
Lamellic Palexeralfs
JDFI. Other Palexeralfs that have a sandy particle-size class
throughout the upper 75 cm of the argillic horizon or
throughout the entire argillic horizon if it is less than 75 cm
thick.
Psammentic Palexeralfs
JDFJ. Other Palexeralfs that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic or kandic horizon
at a depth of 50 cm or more.
Arenic Palexeralfs
JDFK. Other Palexeralfs that have an exchangeable sodium
percentage of 15 or more (or a sodium adsorption ratio of 13 or
more) in one or more horizons within 100 cm of the mineral
soil surface.
Natric Palexeralfs
JDFL. Other Palexeralfs that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Palexeralfs
JDFM. Other Palexeralfs that have a calcic horizon within 150
cm of the mineral soil surface.
Calcic Palexeralfs
JDFN. Other Palexeralfs that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Palexeralfs
JDFO. Other Palexeralfs that have an argillic or kandic
horizon that has a base saturation (by sum of cations) of less
than 75 percent throughout.
Ultic Palexeralfs
JDFP. Other Palexeralfs with an argillic or kandic horizon
that has, in the fine-earth fraction, either or both:
1. Less than 35 percent clay throughout all subhorizons
within 15 cm of its upper boundary; or
2. At its upper boundary, a clay increase of less than 20
percent (absolute) within a vertical distance of 7.5 cm and of
less than 15 percent (absolute) within a vertical distance of
2.5 cm.
Haplic Palexeralfs
JDFQ. Other Palexeralfs that have a color value, moist, of 3
or less and 0.7 percent or more organic carbon either
throughout an Ap horizon or throughout the upper 10 cm of an
A horizon.
Mollic Palexeralfs
JDFR. Other Palexeralfs.
Typic Palexeralfs
Definition of Typic Palexeralfs
Typic Palexeralfs are the Palexeralfs that:
1. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
2. Have neither a calcic nor a petrocalcic horizon within 150
cm of the soil surface;
3. Have an A horizon that, throughout its upper 10 cm, has a
color value, moist, of 4 or more or contains less than 0.7
percent organic carbon or have an Ap horizon that has a color
value, moist, of 4 or more or contains less than 0.7 percent
organic carbon;
4. Have an argillic or kandic horizon that has at least 75
percent base saturation (by sum of cations) in some part;
5. Have an argillic or kandic horizon in which some
subhorizon in the upper 15 cm has 35 percent or more
clay and there is an increase of at least 20 percent clay
(absolute) within a vertical distance of 7.5 cm or of at least
Alfisols 267
15 percent clay (absolute) within 2.5 cm at the upper
boundary;
6. Have less than 5 percent (by volume) plinthite in all
subhorizons within 150 cm of the soil surface;
7. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
8. Have less than 15 percent saturation with sodium in all
subhorizons within 100 cm of the soil surface;
9. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
10. Have an argillic horizon that meets none of the following:
a. Consists entirely of lamellae; or
b. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
c. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
(1) Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
horizon); or
(2) A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an overlying
eluvial horizon; and
11. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick.
Description of Subgroups
Typic Palexeralfs.—The central concept or Typic subgroup
of Palexeralfs is fixed on moderately deep or deep, freely
drained soils that have an argillic or kandic horizon that has an
abrupt upper boundary, 35 percent or more clay in the upper
part, and high base saturation. These soils have neither a calcic
nor a petrocalcic horizon within 150 cm of the mineral soil
surface. They also have little or no plinthite, and they do not
have cracks and slickensides or wedge-shaped aggregates.
Soils that have redox depletions with low chroma and
ground water at a moderate depth are excluded from the Typic
subgroup because these properties are shared with Aqualfs.
Soils that have a calcic or petrocalcic horizon are excluded
because these horizons are interpreted to be evidence of
recalcification of the soils. Soils that have a moderately thin A
horizon or an Ap horizon that has the color and organic-matter
content of a mollic epipedon are excluded because they
approach the properties of Mollisols. A moderately low base
saturation is associated with relatively high precipitation,
either past or present, and is used to define the Ultic subgroup.
A clear or gradual upper boundary of the argillic or kandic
horizon is considered atypical in Palexeralfs, and a soil that
has one is excluded from the Typic subgroup. Plinthite is a
property shared with Plinthoxeralfs, and a soil that contains
plinthite is excluded from the Typic subgroup, unless the
amount is very small. Cracks and slickensides or wedge-shaped
aggregates are properties shared with Vertisols and define the
Vertic subgroup. A thick epipedon with a sandy or sandyskeletal
particle-size class throughout is considered atypical
and causes soils to be excluded from the Typic subgroup, a
convention that is used elsewhere in this taxonomy.
Typic Palexeralfs are moderately extensive. They are on old
terraces and on foothills, mostly in California in the United
States. Slopes are gentle to steep. Most of these soils are used
as rangeland. Some are used as cropland.
Andic and Vitrandic Palexeralfs.—These soils are like
Typic Palexeralfs, but they have a surface mantle or layer in the
upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. These
soils are permitted, but not required, to have a color value of 3
or less, moist, and 5 or less, dry, in surface horizons, after
mixing to a depth of 15 cm. In the United States, these soils
268 Soil Taxonomy
occur mostly in Washington and California. The temperature
regimes are mostly mesic or frigid. The native vegetation was
primarily a coniferous forest. These soils are moderately
extensive in the United States. They are used mostly as forest,
but some have been cleared and are used as cropland or
pasture.
Aquandic Palexeralfs.—These soils are like Typic
Palexeralfs, but they have a surface mantle or layer in the
upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. These
soils have, in one or more horizons within 75 cm of the
mineral soil surface, redox depletions with chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage). They are permitted, but not required, to
have a color value of 3 or less, moist, and 5 or less, dry, in
surface horizons, after mixing to a depth of 15 cm. Aquandic
Palexeralfs are not extensive.
Arenic Palexeralfs.—These soils have a layer, starting at
the mineral soil surface, that is 50 cm or more thick and has a
sandy or sandy-skeletal particle-size class throughout its
thickness. These soils are not known to occur in the United
States. The subgroup has been established for use in other
countries.
Aquic Palexeralfs.—These soils are like Typic Palexeralfs,
but they have, in one or more horizons within 75 cm of the
mineral soil surface, redox depletions with chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage). In addition, they are permitted to have an
A horizon that, throughout its upper 10 cm, has a color value,
moist, of 3 or less and contains more than 0.7 percent organic
carbon or to have an Ap horizon that has a color value, moist,
of 3 or less and contains more than 0.7 percent organic
carbon. Aquic Palexeralfs are of small extent, mostly in
Washington and Oregon in the United States. Their slopes are
nearly level. The native vegetation is primarily a coniferous
forest.
Calcic Palexeralfs.—These soils are like Typic Palexeralfs,
but they have a calcic horizon that has its upper boundary
within 150 cm of the mineral soil surface. They are rare in the
United States and are known to occur only in California. The
subgroup may also be needed for use in other countries.
Fragiaquic Palexeralfs.—These soils are like Typic
Palexeralfs, but they have redox depletions with low chroma
and aquic conditions at a shallow depth for some time in
normal years. In addition, they have fragic soil properties in 30
percent or more of the volume of a layer 15 cm or more thick
that has its upper boundary within 100 cm of the mineral soil
surface or in 60 percent or more of the volume of a layer 15 cm
or more thick anywhere in the soils. These soils are not
extensive in the United States.
Fragic Palexeralfs.—These soils are like Typic Palexeralfs,
but they have fragic soil properties in 30 percent or more of the
volume of a layer 15 cm or more thick that has its upper
boundary within 100 cm of the mineral soil surface or in 60
percent or more of the volume of a layer 15 cm or more thick
anywhere in the soils. These soils are not extensive in the
United States.
Haplic Palexeralfs.—These soils are like Typic Palexeralfs,
but they do not have an argillic or kandic horizon that has an
abrupt upper boundary and 35 percent or more clay in the upper
part. These soils are not extensive in the United States.
Lamellic Palexeralfs.—These soils are like Typic Palexeralfs,
but they have an argillic horizon that consists of lamellae or
partially of lamellae. Most of these soils do not have an argillic
or kandic horizon that has an abrupt upper boundary and 35
percent or more clay in the upper part. The upper several
lamellae are commonly broken or discontinuous horizontally.
These soils are not extensive in the United States.
Mollic Palexeralfs.—These soils are like Typic Palexeralfs,
but they have an A horizon that, throughout its upper 10 cm,
has a color value, moist, of 3 or less and contains more than
0.7 percent organic carbon or have an Ap horizon that has a
color value, moist, of 3 or less and contains more than 0.7
percent organic carbon. Mollic Palexeralfs have an argillic or
kandic horizon that has an abrupt upper boundary, 35 percent
or more clay in the upper part, and high base saturation. They
are intergrades between Palexeralfs and Palexerolls. Their
slopes are gentle or moderate. The native vegetation is
primarily rangeland or savanna with widely spaced oak or
coniferous trees. Mollic Palexeralfs are of moderate extent in
the United States. Where slopes are suitable, some of these
soils are used as cropland. Many of the soils are used for
grazing.
Natric Palexeralfs.—These soils have 15 percent or more
saturation with sodium in one or more horizons within 100 cm
of the mineral soil surface. Some of these soils have columnar
or prismatic structure in the argillic horizon, but the horizon
that contains sodium is too deep in the soils to be a natric
horizon. Natric Palexeralfs are rare in the United States.
Petrocalcic Palexeralfs.—These soils are like Typic
Palexeralfs, but they have a petrocalcic horizon that has an
upper boundary within 150 cm of the soil surface. In addition,
the argillic or kandic horizon is permitted, but not required, to
have less than 35 percent clay in all subhorizons, and there
may be, at the upper boundary, an increase in clay content of
less than 20 percent (absolute) within a vertical distance of 7.5
cm and an increase of less than 15 percent clay (absolute)
within a vertical distance of 2.5 cm. These soils are rare in the
United States. The subgroup has been established for use in
other countries.
Plinthic Palexeralfs.—These soils have 5 percent or more
(by volume) plinthite in one or more horizons within 150 cm of
the mineral soil surface. They are not known to occur in the
United States.
Psammentic Palexeralfs.—These soils have an argillic
Alfisols 269
horizon that has a sandy particle-size class throughout the
upper 75 cm or throughout the entire argillic horizon if it is less
than 75 cm thick. They are rare in the United States.
Ultic Palexeralfs.—These soils are like Typic Palexeralfs,
but they have a base saturation that is less than 75 percent in
all parts of the argillic or kandic horizon. In addition, the
argillic or kandic horizon is permitted, but not required, to
have less than 35 percent clay in all subhorizons, and there
may be, at the upper boundary, an increase of less than 20
percent (absolute) in clay content within a vertical distance of
7.5 cm and an increase of less than 15 percent clay (absolute)
within a vertical distance of 2.5 cm. These soils also are
permitted to have an A horizon that, throughout its upper 10
cm, has a color value, moist, of 3 or less and contains more than
0.7 percent organic carbon or to have an Ap horizon that has a
color value, moist, of 3 or less and contains more than 0.7
percent organic carbon. Ultic Palexeralfs are moderately
extensive in California, Oregon, and Washington in the United
States. The native vegetation is primarily a coniferous forest but
is rangeland or savanna with widely spaced oak or coniferous
trees on the warmest and driest sites. Slopes are gentle to steep.
The primary uses of these soils are timber production and
grazing. Some of the soils are used as cropland, much of which
is irrigated.
Vertic Palexeralfs.—These soils are high in content of
expanding clays and have cracks 5 mm or more wide,
slickensides, wedge-shaped aggregates, or a linear extensibility
of 6.0 cm or more between the mineral soil surface and either a
depth of 100 cm or a densic, lithic, or paralithic contact,
whichever is shallower. These soils are considered to be
transitional to Vertisols. They are rare in the United States. The
subgroup has been established mainly for use in other
countries.
Plinthoxeralfs
Plinthoxeralfs are the Xeralfs that have one or more horizons
within 150 cm of the mineral soil surface in which plinthite either
forms a continuous phase or constitutes one-half or more of the
volume. There are few of these soils in the United States, but the
soils are moderately extensive in other parts of the world.
Subgroups have not been developed.
Definition
Plinthoxeralfs are the Xeralfs that:
1. Have one or more horizons within 150 cm of the mineral soil
surface in which plinthite either forms a continuous phase or
constitutes one-half or more of the volume;
2. Have neither a fragipan nor a duripan with an upper
boundary within 100 cm of the mineral soil surface;
3. Do not have a natric horizon.
KeytoSubgroups
JDDA. All Plinthoxeralfs (provisionally).
Typic Plinthoxeralfs
Rhodoxeralfs
Rhodoxeralfs are the more or less dark red Xeralfs that formed
in areas of limestone, basalt, and other highly basic parent
materials. As a group, these soils are remarkably uniform in
virtually all properties, except for depth to rock. A few that are
receiving carbonates may have a calcic or petrocalcic horizon
below the argillic or kandic horizon. Rhodoxeralfs are rare in the
United States.
Definition
Rhodoxeralfs are the Xeralfs that:
1. Have, in all subhorizons in the upper 100 cm of the argillic
or kandic horizon or throughout the entire argillic or kandic
horizon if less than 100 cm thick, more than 50 percent colors
that have all of the following:
a. Hue of 2.5YR or redder; and
b. Value, moist, of 3 or less; and
c. Dry value no more than 1 unit higher than the moist
value;
2. Have neither a fragipan nor a duripan that has its upper
boundary within 100 cm of the mineral soil surface;
3. Do not have a natric horizon;
4. Do not have, within 150 cm of the mineral soil surface,
plinthite forming a continuous phase or constituting one-half
or more of the volume.
Key to Subgroups
JDEA. Rhodoxeralfs that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Rhodoxeralfs
JDEB. Other Rhodoxeralfs that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Rhodoxeralfs
270
JDEC. Other Rhodoxeralfs that have a petrocalcic horizon
that has its upper boundary within 150 cm of the mineral soil
surface.
Petrocalcic Rhodoxeralfs
JDED. Other Rhodoxeralfs that have a calcic horizon that
has its upper boundary within 150 cm of the mineral soil
surface.
Calcic Rhodoxeralfs
JDEE. Other Rhodoxeralfs that have an argillic or kandic
horizon that is either less than 15 cm thick or is discontinuous
horizontally in each pedon.
Inceptic Rhodoxeralfs
JDEF. Other Rhodoxeralfs.
Typic Rhodoxeralfs
Definition of Typic Rhodoxeralfs
Typic Rhodoxeralfs are the Rhodoxeralfs that:
1. Have an argillic or kandic horizon that is more than 15 cm
thick and is horizontally continuous in each pedon;
2. Do not have a lithic contact within 50 cm of the mineral
soil surface;
3. Do not have a petrocalcic horizon that has an upper
boundary within 150 cm of the mineral soil surface;
4. Do not have a calcic horizon that has an upper boundary
within 150 cm of the mineral soil surface; and
5. Do not have one or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Description of Subgroups
Typic Rhodoxeralfs.—The central concept or Typic
subgroup of Rhodoxeralfs is fixed on moderately deep or
deep soils that have an argillic or kandic horizon that is
horizontally continuous throughout each pedon and that do
not have a calcic or petrocalcic horizon shallow enough to be
diagnostic.
Soils in which an argillic horizon is discontinuous
horizontally are excluded from the Typic subgroup because
such a horizon represents weak development. A shallow lithic
contact is used to define the Lithic subgroup, a convention
used throughout this taxonomy. Soils that have a calcic or
petrocalcic horizon are excluded from this subgroup because
these horizons are thought to indicate recalcification
through addition of carbonates that originated outside of the
soils.
Most of the Typic Rhodoxeralfs in the United States
are moderately sloping or strongly sloping and are in
forests or are used for grazing. A few are irrigated and
farmed.
Calcic Rhodoxeralfs.—These soils are like Typic
Rhodoxeralfs, but they have a calcic horizon that has an upper
boundary within 150 cm of the mineral soil surface. They are
not known to occur in the United States. The subgroup is
provided for use in other countries.
Inceptic Rhodoxeralfs.—These soils are like Typic
Rhodoxeralfs in defined properties, but they have an argillic or
kandic horizon that is 35 cm or less thick. They are not known
to occur in the United States. The subgroup is provided for use
in other countries.
Lithic Rhodoxeralfs.—These soils are like Typic
Rhodoxeralfs, but they have a lithic contact within 50 cm of
the mineral soil surface. They are not known to occur in the
United States. The subgroup is provided for use in other
countries.
Petrocalcic Rhodoxeralfs.—These soils are like Typic
Rhodoxeralfs, but they have a petrocalcic horizon that has an
upper boundary within 150 cm of the mineral soil surface.
They are not known to occur in the United States. The
subgroup is provided for use in other countries.
Vertic Rhodoxeralfs.—These soils are high in content of
expanding clays and have cracks 5 mm or more wide,
slickensides, wedge-shaped aggregates, or a linear extensibility
of 6.0 cm or more between the mineral soil surface and either a
depth of 100 cm or a densic, lithic, or paralithic contact,
whichever is shallower. These soils are considered to be
transitional to Vertisols. They are rare in the United States. The
subgroup has been established mainly for use in other
countries.
271
The central concept of an Andisol is that of a soil
developing in volcanic ejecta (such as volcanic ash,
pumice, cinders, and lava) and/or in volcaniclastic materials,
the colloidal fraction of which is dominated by short-rangeorder
minerals or Al-humus complexes. Under some
environmental conditions, weathering of primary aluminosilicates
in parent materials of nonvolcanic origin may also
lead to the formation of short-range-order minerals. Some of
these soils also are included in Andisols.
The dominant processes in most Andisols are weathering
and mineral transformation. Translocation within the soils and
accumulation of the translocated compounds are normally
minimal. The accumulation of organic matter, complexed with
aluminum, however, is characteristic of Andisols in some
regimes.
Weathering of primary alumino-silicates has proceeded only
to the point of formation of short-range-order minerals, such as
allophane, imogolite, and ferrihydrite. Commonly, this state
has been perceived as a stage in the transition from
unweathered to the more weathered volcanic material
characteristic of some other soil orders. Under some
conditions, however, the short-range-order minerals achieve a
stability that allows them to persist with little or only very slow
further alteration over long periods.
Andisols may have any diagnostic epipedon, provided that
the minimum requirements for the order are met in and/or
below the epipedon. Andisols may also have any soil moisture
regime and any soil temperature regime. They can occupy any
position on the landscape and can occur at any elevation.
Andisols have andic soil properties in 60 percent of a layer
in the upper part of the soils. The upper part is considered to
start at the mineral soil surface or at the surface of organic soil
materials with andic soil properties and end at a point 60 cm
below the starting point or at a densic, lithic, or paralithic
contact, a duripan, or a petrocalcic horizon, whichever is
shallowest. These soils may have many kinds of diagnostic
horizons below this layer. The soils are considered Andisols if
the criteria for thickness and position of the andic layer or
layers are met, irrespective of the nature of the underlying
material or horizons.
Cultivation of the soils, as in puddling of the surface layer
in areas used for rice paddies, may change some of the
physical properties of the upper part of the soils, such as bulk
density. A soil that, below this disturbed zone, has a layer, at
least 36 cm thick, with andic soil properties meets the
requirements for Andisols. Many Andisols, such as those that
formed in some loess or alluvium, are stratified. Before the
soils are considered Andisols, the layers that meet the
requirements for andic soil properties must have a cumulative
thickness of at least 36 cm within the upper 60 cm.
One of the outstanding features of Andisols is their high
natural productivity. There are exceptions to this very general
statement, but the dominance of physical properties that favor
the growth of most plants, allied to the most common
occurrence of the soils in areas of considerable rainfall, has
resulted in volcanic soils being generally regarded as highly
fertile soils.
Andisols cover more than 124 million hectares, or
approximately 0.8 percent of the earth’s surface. By far, the
most striking pattern in the distribution of Andisols follows the
circum-Pacific Ring of Fire—that concentration of active
tectonic zones and volcanoes along the western coast of the
American continents, both North and South, across the
Aleutian Islands, down the Kamchatka peninsula of Russia,
through Japan, the Philippine Islands, and Indonesia, across
Papua New Guinea, the Solomon Islands, and Vanuatu and
other Pacific Islands to New Zealand. Other distinctive patterns
are associated with the Rift Valley of Africa, the west coast of
Italy, the Hawaiian Islands, the West Indies, Iceland, the
Canary Islands, and other island locations.
Definition of Andisols and Limits Between
Andisols and Soils of Other Orders
Andisols are soils that:
1. Have andic soil properties in 60 percent or more of the
thickness either:
a. Within 60 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever
is shallower, if there is no densic, lithic, or paralithic
contact, duripan, or petrocalcic horizon within that depth;
or
b. Between either the mineral soil surface or the top of an
CHAPTER 10
Andisols1
1
This chapter builds on the preliminary Andisol Proposal (1978) by Guy D. Smith (New
Zealand Soil Bureau Record 96) and represents the work of the International Committee on the
Classification of Andisols (ICOMAND), chaired by Michael L. Leamy, New Zealand Soil
Bureau.
272 Soil Taxonomy
organic layer with andic soil properties, whichever is
shallower, and a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon;
2. Do not have organic soil materials that meet one or more
of the following:
a. Overlie cindery, fragmental, or pumiceous materials
and/or fill their interstices2
and directly below these
materials have either a densic, lithic, or paralithic contact;
or
b. When added with the underlying cindery, fragmental, or
pumiceous materials, total 40 cm or more between the soil
surface and a depth of 50 cm; or
c. Constitute two-thirds or more of the total thickness of
the soil to a densic, lithic, or paralithic contact and have no
mineral horizons or have mineral horizons with a total
thickness of 10 cm or less; or
d. Are saturated with water for 30 days or more in normal
years (or are artificially drained), have an upper boundary
within 40 cm of the soil surface, and have a total thickness
of either:
(1) 60 cm or more if three-fourths or more of their
volume consists of moss fibers or if their bulk density,
moist, is less than 0.1 g/cm3
; or
(2) 40 cm or more if they consist either of sapric or
hemic materials, or of fibric materials with less than
three-fourths (by volume) moss fibers and a bulk density,
moist, of 0.1 g/cm3
or more;
3. Do not have both a spodic horizon and an albic horizon in
50 percent or more of each pedon;
4. Do not have an Ap horizon containing 85 percent or more
spodic materials; and
5. Do not have:
a. Permafrost within 100 cm of the soil surface; or
b. Gelic materials within 100 cm of the soil surface and
permafrost within 200 cm of the soil surface.
Limits Between Andisols and Other Soil Orders
The definition of Andisols must provide criteria that
separate Andisols from all other soil orders. The aggregate of
these criteria defines the limits of Andisols in relation to all
other known kinds of soil.
1. Unlike Andisols, Gelisols have:
a. Permafrost within 100 cm of the soil surface; or
b. Gelic materials within 100 cm of the soil surface and
permafrost within 200 cm of the soil surface.
2. Unlike Andisols, Histosols are soils that:
a. Do not have andic soil properties in 60 percent or more
of the thickness between the soil surface and either a depth
of 60 cm or a densic, lithic, or paralithic contact or duripan
if shallower; and
b. Have organic soil materials that meet one or more of
the following:
(1) Overlie cindery, fragmental, or pumiceous materials
and/or fill their interstices2
and directly below these
materials have either a densic, lithic, or paralithic
contact; or
(2) When added with the underlying cindery,
fragmental, or pumiceous material, total 40 cm or more
between the soil surface and a depth of 50 cm; or
(3) Constitute two-thirds or more of the total thickness
of the soil to a densic, lithic, or paralithic contact and
have no mineral horizons or have mineral horizons with
a total thickness of 10 cm or less; or
(4) Are saturated with water for 30 days or more in
normal years (or are artificially drained), have an upper
boundary within 40 cm of the soil surface, and have a
total thickness of either:
(a) 60 cm if three-fourths or more of their volume
consists of moss fibers or if their bulk density, moist,
is less than 0.1 g/cm3
; or
(b) 40 cm or more if they consist either of sapric or
hemic materials, or of fibric materials with less than
three-fourths (by volume) moss fibers and a bulk
density, moist, of 0.1 g/cm3
or more.
3. Unlike Andisols, Spodosols have:
a. Both a spodic horizon and an albic horizon in 50
percent or more of each pedon; or
b. An Ap horizon containing 85 percent or more spodic
materials.
4. Andisols differ from Alfisols, Aridisols, Entisols,
Inceptisols, Mollisols, Oxisols, Ultisols, and Vertisols because
they have andic soil properties in 60 percent or more of the
thickness either:
a. Within 60 cm either of the mineral soil surface or the
top of an organic layer with andic soil properties, whichever
is shallower, if there is no densic, lithic, or paralithic
contact, duripan, or petrocalcic horizon within that depth;
or
2
Materials that meet the definition of cindery, fragmental, or pumiceous but have more
than 10 percent, by volume, voids that are filled with organic soil materials are considered to be
organic soil materials.
Andisols 273
b. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon.
Representative Pedon and Data
Following is a description of a representative Andisol. Data
for the pedon identified in this description are given in the
table “Characterization Data for an Andisol.”
Classification: Medial, amorphic, mesic Eutric Fulvudand
Site identification number: 83P0481
Location: Chile
Landform: Terrace
Slope: 1 percent, plane
Elevation: 17 m above m.s.l.
Annual precipitation: 205 cm
Soil moisture regime: Udic
Average annual air temperature: 13 o
C
Permeability class: Moderately rapid
Drainage class: Well drained
Depth to water table: More than 200 cm
Land use: Pasture
Stoniness class: 1
Particle-size control section: 0 to 100 cm
Parent material: Ejecta ash
Diagnostic features: An umbric epipedon from a depth of
0 to 27 cm, a cambic horizon from a depth of 27 to
98 cm, and andic soil properties from a depth of 0 to
200 cm
Field moisture: From a depth of 0 to 39 cm—dry; from a depth
of 39 to 200 cm—slightly moist
Described by: T. Cook, W. Luzio, R. Honorato, G. Galindo, W.
Vera, and R. Grez
In the following pedon description, colors are for moist soil
unless otherwise indicated. Field reaction was determined by
use of paper test strips.
Ap1—0 to 4 cm; very dark grayish brown (10YR 3/2) silt
loam, brown (10YR 4/3) dry; strong medium and coarse
granular structure; friable, weakly smeary, slightly sticky
and slightly plastic; many very fine and fine roots; many
very fine and fine interstitial pores; strongly acid (pH 5.3);
abrupt smooth boundary.
Ap2—4 to 27 cm; very dark brown (10YR 2/2) silt loam,
brown (10YR 4/3) dry; moderate very coarse subangular
blocky structure parting to weak coarse granular; friable,
moderately smeary, slightly sticky and slightly plastic;
many very fine and few medium roots; many very fine and
fine interstitial pores; strongly acid (pH 5.3); abrupt
smooth boundary.
2BA—27 to 39 cm; dark yellowish brown (10YR 3/4) silt
loam, brown (10YR 5/3) dry; weak coarse prismatic
structure; very friable, moderately smeary, slightly sticky
and slightly plastic; common very fine and few medium
roots; common coarse and common very fine tubular
pores; few fine cylindrical insect casts; moderately acid
(pH 5.7); 1 percent ejecta pebbles; clear smooth boundary.
2Bw1—39 to 73 cm; dark brown (7.5YR 3/4) silt loam; weak
coarse prismatic structure parting to moderate medium
and coarse subangular blocky; very friable, moderately
smeary, slightly sticky and slightly plastic; common very
fine roots; many very fine and few fine tubular pores;
few fine cylindrical insect casts; moderately acid (pH 5.7);
1 percent ejecta pebbles; clear smooth boundary.
2Bw2—73 to 98 cm; dark brown (10YR 3/3) silt loam;
moderate coarse prismatic structure parting to weak
medium subangular blocky; friable, moderately smeary,
slightly sticky and slightly plastic; few very fine roots;
many fine and medium tubular pores; patchy skeletans
(sand or silt) in root channels and/or pores; moderately
acid (pH 5.7); 1 percent ejecta pebbles; gradual smooth
boundary.
2C1—98 to 160 cm; dark yellowish brown (10YR 3/4) silt
loam; massive; friable, moderately smeary, slightly sticky
and slightly plastic; few very fine roots; many fine and
medium tubular pores; patchy skeletans (sand or silt) in
root channels and/or pores; moderately acid (pH 5.7); clear
irregular boundary.
3C2—160 to 200 cm; dark yellowish brown (10YR 4/4) silt
loam; massive; firm, moderately smeary, sticky and
slightly plastic; few very fine roots; many very fine and
fine and many medium tubular pores; a few thin seams
and masses of uncoated fine sand; moderately acid (pH
5.7).
Key to Suborders
DA. Andisols that have either:
1. A histic epipedon; or
2. In a layer above a densic, lithic, or paralithic contact or in
a layer at a depth between 40 and 50 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallowest, aquic
conditions for some time in normal years (or artificial
drainage) and one or more of the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on
faces of peds or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction
to alpha,alpha-dipyridyl at a time when the soil is not
being irrigated.
Aquands, p. 275
274 Soil Taxonomy
Characterization Data for an Andisol
SITE IDENTIFICATION NO.: 83P0481
CLASSIFICATION: MEDIAL, AMORPHIC, MESIC EUTRIC FULVUDAND
GENERAL METHODS: 1B1A, 2A1, 2B
-1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-
-----------------------------------------------------------------------------------------------------------------------------------
(- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)
CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT
SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF
NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE
<- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL
83P2246 0- 4 Ap1 10.4 68.8 20.8 44.4 24.4 10.5 5.1 2.2 2.7 0.3 TR -- -- 10 --
83P2247 4- 27 Ap2 5.9 72.7 21.4 45.1 27.6 13.7 5.4 1.2 0.9 0.2 TR TR -- 8 --
83P2248 27- 39 2BA 1.0 56.1 42.9 30.4 25.7 21.5 14.2 4.6 1.9 0.7 TR -- -- 21 --
83P2249 39- 73 2Bw1 -- 42.7 57.3 17.7 25.0 24.9 21.7 6.7 3.1 0.9 TR -- -- 32 --
83P2250 73- 98 2Bw2 3.6 36.7 59.7 17.4 19.3 20.9 21.6 10.4 5.7 1.1 TR TR -- 39 --
83P2251 98-129 2C1 4.7 35.0 60.3 16.7 18.3 21.8 20.8 10.9 6.2 0.6 TR -- -- 38 --
83P2252 129-160 2C1 2.2 29.0 68.8 13.5 15.5 24.9 24.3 11.6 6.6 1.4 TR -- -- 44 --
83P2253 160-200 3C2 3.7 46.9 49.4 27.7 19.2 11.4 8.9 7.0 10.1 12.0 TR -- -- 38 --
-----------------------------------------------------------------------------------------------------------------------------------
ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD
C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE
DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL
(cm) 6A1c 6B3a 6S3 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A3a 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1
Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm
0- 4 12.4 1.076 3.2 1.9 3.97 4.38 36.9
4- 27 8.61 0.668 3.8 2.3 5.37 5.78 0.70 0.81 0.050 55.5 29.4 0.15
27- 39 4.03 0.302 4.6 2.0 22.00 44.10 0.68 0.80 0.056 27.9
39- 73 2.43 4.9 1.8 0.87 0.87 24.9
73- 98 1.07 5.1 1.6 3.89 12.67 0.74 0.84 0.043 54.5 24.0 0.07
98-129 0.91 4.9 1.7 2.62 9.49 0.84 0.96 0.046 54.0 22.9 0.08
129-160 0.72 4.1 1.3 5.68 21.36 0.80 0.93 0.051 57.0 21.4 0.08
160-200 1.69 4.6 1.7 6.57 16.54 0.90 1.09 0.066 60.8 26.2
-----------------------------------------------------------------------------------------------------------------------------------
(- NH4OAc EXTRACTABLE BASES -) ACID- EXTR (- - - -CEC - - -) Al -BASE SAT- CO3 AS RES. COND.(- - - -PH - - -)
Ca Mg Na K SUM ITY Al SUM NH4- BASES SAT SUM NH4 CaCO3 ohms mmhos NaF CaCl2 H2O
DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc + Al OAc <2mm /cm /cm .01M
(cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 6G9a 5A3a 5A8b 5A3b 5G1 5C3 5C1 6E1g 8E1 8I 8C1d 8C1f 8C1f
<- - - - - - - - - - - -meq / 100 g - - - - - - - - - - -> <- - - - -Pct - - - -> 1:2 1:1
0- 4 11.4 3.0 0.8 0.6 15.8 47.5 0.3 63.3 41.3 16.1 2 25 38 10.4 5.2 5.6
4- 27 1.7 0.2 0.1 0.1 2.1 49.5 1.3 51.6 31.7 3.4 38 4 7 10.9 4.8 5.2
27- 39 0.9 0.1 0.1 -- 1.1 39.7 TR 40.8 22.0 3 5 11.1 5.4 5.7
39- 73 3.4 0.4 0.1 0.1 4.0 31.2 TR 35.2 18.6 11 22 10.7 5.6 5.9
73- 98 2.5 0.7 TR -- 3.2 23.6 -- 26.8 14.0 12 23 10.6 5.8 6.1
98-129 2.9 0.8 -- -- 3.7 22.4 -- 26.1 12.3 14 30 10.4 5.8 6.2
129-160 2.3 0.7 TR -- 3.0 23.7 TR 26.7 12.5 11 24 10.6 5.8 6.2
160-200 1.5 0.3 -- -- 1.8 33.2 0.1 35.0 24.3 1.9 5 5 7 10.8 5.7 5.9
-----------------------------------------------------------------------------------------------------------------------------------
ACID OXALATE EXTRACTION PHOSPHORUS KCl TOTAL (- -WATER CONTENT- - )(- - - - WATER DISPERSIBLE - - - - ) MIN AGGRT
OPT Fe Si Al CIT- Mn C 0.06 1- 2- 15 <- - PIPETTE - - >< - HYDROMETER - > SOIL STABL
DEN RET ACID BAR BAR BAR BAR CLAY SILT SAND CLAY SILT SAND CONT <5mm
SAMPLE HZ 8J 6C9a 6V2 6G12 6S4 6S5 6D3 6A2d 4B1c 4B1a 4B1a 4B2b <- - - 3A1c - - -><- - - SML - - -> 8F1 4G1
NO. NO <- P c t o f < 2 m m -><- p p m ->< - - - - - - - - - - P e r c e n t o f < 2 m m - - - - - - - - - - >< Pct>
83P2246 1 1.40 1.08 3.01 94 45.6
83P2247 2 1.39 1.18 3.54 99 34.1
83P2248 3 1.84 1.95 4.55 98 44.1
83P2249 4 2.13 2.13 4.68 98 51.7
83P2250 5 2.01 1.27 2.86 98 45.6
83P2251 6 2.01 1.27 2.64 97 44.6
83P2252 7 1.69 1.48 2.97 98 47.0
83P2253 8 2.50 2.83 5.77 98 61.2
-----------------------------------------------------------------------------------------------------------------------------------
Andisols 275
DB. Other Andisols that have a cryic soil temperature
regime.
Cryands, p. 285
DC. Other Andisols that have an aridic moisture regime.
Torrands, p. 294
DD. Other Andisols that have a xeric moisture regime.
Xerands, p. 323
DE. Other Andisols that have a 1500 kPa water retention of
less than 15 percent on air-dried samples and less than 30
percent on undried samples throughout 60 percent or more of
the thickness either:
1. Within 60 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever
is shallower, if there is no densic, lithic, or paralithic
contact, duripan, or petrocalcic horizon within that depth;
or
2. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon.
Vitrands, p. 319
DF. Other Andisols that have an ustic moisture regime.
Ustands, p. 315
DG. Other Andisols.
Udands, p. 297
Aquands
Aquands are the Andisols with aquic conditions at or near
the surface. Commonly, these soils have dark colored surface
horizons that meet the requirements for a histic, umbric, or
mollic epipedon. They occur in the lower landscape positions
and support forest or grass vegetation. Some have been drained
and are used for small grain or grass for livestock. Aquands
occur in the Pacific Northwest and in other areas that have a
volcanic influence.
Definition
Aquands are the Andisols that have either:
1. A histic epipedon; or
2. In a layer above a densic, lithic, or paralithic contact or in
a layer at a depth between 40 and 50 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, aquic conditions
for some time in normal years (or artificial drainage) and one
or more of the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or
Characterization Data for an Andisol--Continued
-1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-
-----------------------------------------------------------------------------------------------------------------------------------
< - - - - - - - - - - - - - - - - - - - - - - CLAY MINERALOGY (<.002mm) - - - - - - - - - - - - - - - - - - - - - - - >
FRAC- < - - - - - X-RAY - - - - - ->< - - - THERMAL - - - ->< - - - - - - - ELEMENTAL - - - - - - - ->< - -> EGME INTERSAMPLE
TION < >< - DTA - ->< - TGA - -> SiO2 Al2O3 Fe2O3 MgO CaO K2O Na2O < > RETN PRETA<
- - - - - 7A2i - - - - - ->< - 7A6 - >< - 7A4b - >< - - - - - - - - - 7C3 - - - - - - - - ->< > 7D2 TION
NUMBER <- - >< - - - - Peak size - - - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - -><mg/g>< - ->
83P2247 TCLY VR 1 NX 6 6.3 0.2
83P2248 TCLY GI 1 VR 1 NX 6 GI 1 5.7
83P2250 TCLY GI 2 KK 1 VR 1 NX 6 GI13 KK 2 10.2 0.1
83P2253 TCLY KK 1 GI 1 NX 6 KK 4 GI 3 9.7 0.2
-----------------------------------------------------------------------------------------------------------------------------------
< - - - - - - - - - - - - - - - - - - - - SAND - SILT MINERALOGY (2.0-0.002mm) - - - - - - - - - - - - - - - - - - - - >
FRAC- < - - - - - X-RAY - - ->< - - - THERMAL - - - ->< - - - - - - - OPTICAL - - - - - - - - >< >INTERSAMPLE
TION < >< - DTA - ->< - TGA - ->TOT RE< - - - - - GRAIN COUNT - - - - - ->< >PRETA<
- - - - 7A2i - - - - >< - 7A3b - >< - 7A4b - >< - - - - - - - - 7B1a - - - - - - - - ->< > TION
NUMBER < - ->< - - - Peak Size - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - - - - - - - ->< - ->
83P2248 VFS OT96 GS 4 GAtr
-----------------------------------------------------------------------------------------------------------------------------------
The chemical data are based on the fraction less than 2 mm in size.
Fraction interpretation: TCLY, total clay, <0.002 mm; VFS, very fine sand, 0.05-0.10 mm.
Mineral interpretation: VR, vermiculite; NX, noncrystalline; GA, glass aggregate; GI, gibbsite; OT, other; GS, glass; KK,
kaolinite.
Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.
276 Soil Taxonomy
more chroma of 2 or less either in redox depletions on faces of
peds or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Key to Great Groups
DAA. Aquands that have a cryic soil temperature regime.
Cryaquands, p. 276
DAB. Other Aquands that have, in half or more of each
pedon, a placic horizon within 100 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Placaquands, p. 282
DAC. Other Aquands that have, in 75 percent or more of
each pedon, a cemented horizon that has its upper boundary
within 100 cm either of the mineral soil surface or of the top of
an organic layer with andic soil properties, whichever is
shallower.
Duraquands, p. 277
DAD. Other Aquands that have a 1500 kPa water retention
of less than 15 percent on air-dried samples and less than 30
percent on undried samples throughout 60 percent or more of
the thickness either:
1. Within 60 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever
is shallower, if there is no densic, lithic, or paralithic
contact within that depth; or
2. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a densic, lithic, or paralithic contact.
Vitraquands, p. 283
DAE. Other Aquands that have a melanic epipedon.
Melanaquands, p. 281
DAF. Other Aquands that have episaturation.
Epiaquands, p. 279
DAG. Other Aquands.
Endoaquands, p. 278
Cryaquands
Cryaquands are the more or less poorly drained Andisols of
cold regions. They are not extensive. They formed in the
western part of North America and the northeastern part of
Asia above 49o
north latitude and in mountains south of that
latitude. Most of these soils formed under grassy meadow or
coniferous forest vegetation.
Characteristically, Cryaquands have a thin O horizon, a
mollic or umbric epipedon, and a cambic horizon with many
redox concentrations.
The Cryaquands in the United States generally developed in
late-Pleistocene or Holocene deposits.
Definition
Cryaquands are the Aquands that have a cryic soil
temperature regime.
Key to Subgroups
DAAA. Cryaquands that have a lithic contact within 50 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Lithic Cryaquands
DAAB. Other Cryaquands that have a histic epipedon.
Histic Cryaquands
DAAC. Other Cryaquands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Cryaquands
DAAD. Other Cryaquands.
Typic Cryaquands
Definition of Typic Cryaquands
Typic Cryaquands are the Cryaquands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have a histic epipedon; and
3. Do not have, between depths of 25 and 100 cm, a layer 10
cm or more thick with more than 3.0 percent organic carbon
and the colors of a mollic epipedon throughout, occurring
below a horizon or horizons 10 cm or more thick with a color
value 1 unit or more higher and an organic-carbon content 1
percent or more lower.
Description of Subgroups
Typic Cryaquands.—The central concept or Typic
subgroup of Cryaquands is fixed on soils that are moderately
deep or deeper and have a mollic or umbric epipedon and a
cambic horizon. Typic Cryaquands do not have a histic
Andisols 277
epipedon; a lithic contact within a depth of 50 cm; or, between
depths of 25 and 100 cm, a buried, dark colored layer 10 cm or
more thick.
These soils commonly support wet meadow vegetation, but
some support coniferous forest vegetation. Some forests have
widely spaced trees. Typic Cryaquands are not extensive in the
United States.
Histic Cryaquands.—These soils are like Typic
Cryaquands, but they have a histic epipedon. They are
considered intergrades to Histosols. They are rare in the United
States.
Lithic Cryaquands.—These soils are like Typic
Cryaquands, but they have a lithic contact within a depth of 50
cm. They are rare in the United States.
Thaptic Cryaquands.—These soils are like Typic
Cryaquands, but they have, between depths of 25 and 100 cm,
a buried, dark colored layer 10 cm or more thick below a
lighter colored horizon or horizons, 10 cm or more thick, with
a lower content of organic carbon. Thaptic Cryaquands are rare
in the United States.
Duraquands
Duraquands are the more or less poorly drained Andisols
that have, in 75 percent or more of each pedon, a cemented
horizon that has its upper boundary within 100 cm of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower. Duraquands are not
known to occur in the United States. They are established for
use in other countries.
Definition
Duraquands are the Aquands that:
1. In 75 percent or more of each pedon, have a cemented
horizon with its upper boundary within 100 cm of the mineral
soil surface or of the top of an organic layer that has andic soil
properties, whichever is shallower;
2. Do not have a cryic soil temperature regime; and
3. Do not have, in half or more of each pedon, a placic
horizon within 100 cm of the mineral soil surface or of the
upper boundary of an organic layer that has andic soil
properties, whichever is shallower.
Key to Subgroups
DACA. Duraquands that have a histic epipedon.
Histic Duraquands
DACB. Other Duraquands that have extractable bases (by
NH4
OAc) plus 1N KCl-extractable Al3+
totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more horizons
with a total thickness of 30 cm or more at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower.
Acraquoxic Duraquands
DACC. Other Duraquands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Duraquands
DACD. Other Duraquands.
Typic Duraquands
DefinitionofTypicDuraquands
Typic Duraquands are the Duraquands that:
1. Do not have a histic epipedon;
2. Do not have, between depths of 25 and 100 cm, a layer 10 cm
or more thick with more than 3.0 percent organic carbon and the
colors of a mollic epipedon throughout, occurring below a
horizon or horizons 10 cm or more thick with a color value 1 unit
or more higher and an organic-carbon content 1 percent or more
lower; and
3. Have extractable bases (by NH4
OAc) plus 1N KClextractable
Al3+
of 2.0 or more cmol(+) kg-1
in the fine-earth
fraction of all subhorizons 30 cm or more thick between depths
of 25 and 100 cm.
Description of Subgroups
Typic Duraquands.—The central concept or Typic
subgroup of Duraquands is fixed on soils that do not have a
histic epipedon, have extractable bases plus 1N KCl-extractable
Al3+
totaling 2.0 or more cmol(+)/kg, and do not have, between
depths of 25 and 100 cm, a buried, dark colored layer 10 cm or
more thick below a lighter colored horizon or horizons 10 cm
or more thick with a lower content of organic carbon.
These soils are not known to occur in the United States.
They are established for use in other countries.
Acraquoxic Duraquands.—These soils are like Typic
Duraquands, but they have very low extractable bases plus 1N
KCl-extractable Al3+
in the fine-earth fraction of one or more
horizons with a total thickness of 30 cm or more at a depth
between 25 and 100 cm either from the mineral soil surface or
from the top of an organic layer with andic soil properties,
whichever is shallower. Acraquoxic Duraquands are not known
to occur in the United States. They are established for use in
other countries.
Histic Duraquands.—These soils are like Typic
278 Soil Taxonomy
Duraquands, but they have a histic epipedon. They are not
known to occur in the United States. They are established for
use in other countries.
Thaptic Duraquands.—These soils are like Typic
Duraquands, but they have, between depths of 25 and 100 cm,
a buried, dark colored layer 10 cm or more thick below a
lighter colored horizon or horizons 10 cm or more thick with a
lower content of organic carbon. Thaptic Duraquands are not
known to occur in the United States. They are established for
use in other countries.
Endoaquands
Endoaquands are the more or less poorly drained Andisols
with no slowly permeable layers that cause unsaturated layers
to underlie saturated layers within 200 cm of the mineral soil
surface. Most of these soils formed under grassy meadow
vegetation, but some formed under coniferous forest vegetation.
Characteristically, Endoaquands have a thin O horizon, a
mollic or umbric epipedon, and a cambic horizon with many
redox concentrations.
The Endoaquands in the United States generally developed
in late-Pleistocene or Holocene deposits.
Definition
Endoaquands are the Aquands that:
1. Do not have, in 75 percent or more of each pedon, a
cemented horizon that has its upper boundary within 100 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower;
2. Do not have, in half or more of each pedon, a placic
horizon within 100 cm either of the mineral soil surface or of
the top of an organic layer with andic soil properties,
whichever is shallower;
3. Do not have a melanic epipedon;
4. Do not have a cryic soil temperature regime;
5. Have a 1500 kPa water retention either of 15 percent or
more on air-dried samples or of 30 percent or more on undried
samples throughout one or more layers with a total thickness of
more than 25 cm within 60 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower; and
6. Have endosaturation.
Key to Subgroups
DAGA. Endoaquands that have a lithic contact within 50 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Lithic Endoaquands
DAGB. Other Endoaquands that have a horizon 15 cm or
more thick that has 20 percent or more (by volume)
cemented soil material and has its upper boundary within
100 cm either of the mineral soil surface or of the top of
an organic layer with andic soil properties, whichever is
shallower.
DuricEndoaquands
DAGC. Other Endoaquands that have a histic epipedon.
Histic Endoaquands
DAGD. Other Endoaquands that have more than 2.0
cmol(+)/kg Al3+
(by 1N KCl) in the fine-earth fraction of one or
more horizons with a total thickness of 10 cm or more at a depth
between 25 and 50 cm either from the mineral soil surface or from
the top of an organic layer with andic soil properties, whichever
is shallower.
AlicEndoaquands
DAGE. Other Endoaquands that have, on undried samples, a
1500 kPa water retention of 70 percent or more throughout a
layer 35 cm or more thick within 100 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Hydric Endoaquands
DAGF. Other Endoaquands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Endoaquands
DAGG. Other Endoaquands.
Typic Endoaquands
DefinitionofTypicEndoaquands
Typic Endoaquands are the Endoaquands that:
1. Do not have a lithic contact within 50 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower;
2. Do not have a horizon with an upper boundary within 100
cm either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower, that is
more than 15 cm thick and has 20 percent or more (by volume)
cemented soil material;
3. Do not have a histic epipedon;
4. Do not have, at a depth between 25 and 100 cm either from
the mineral soil surface or from the top of an organic layer with
Andisols 279
andic soil properties, whichever is shallower, a layer 10 cm or
more thick with more than 3.0 percent organic carbon and the
colors of a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that have a color
value, moist, 1 unit or more higher and an organic-carbon
content 1 percent or more (absolute) lower;
5. Have 2.0 cmol(+)/kg or less Al3+
(by 1N KCl) in the fine-earth
fraction throughout a layer 10 cm or more thick at a depth
between 25 and 50 cm either from the mineral soil surface or from
the top of an organic layer with andic soil properties, whichever
is shallower; and
6. Have, on undried samples, a 1500 kPa water retention of less
than 70 percent throughout a layer 35 cm or more thick within
100 cm either of the mineral soil surface or of the upper
boundary of an organic layer with andic soil properties,
whichever is shallower.
Description of Subgroups
Typic Endoaquands.—The central concept or Typic
subgroup of Endoaquands is fixed on soils that do not have a
histic epipedon, that are moderately deep or deeper, and that do
not have, between depths of 25 and 100 cm, a buried, dark
colored layer 10 cm or more thick below a lighter colored
horizon or horizons 10 cm or more thick with a lower content
of organic carbon. Soils that have a horizon 15 cm or more
thick with 20 percent or more cemented soil material also are
excluded.
Endoaquands that have, on undried samples, a 1500 kPa
water retention of 70 percent or more throughout a layer 35 cm
or more thick in the upper part are assigned to the Hydric
subgroup. Soils with more than 2.0 cmol(+)/kg Al3+
(by 1N
KCl) in the fine-earth fraction of one or more horizons with a
total thickness of 10 cm or more also are excluded from the
Typic subgroup. Soils that have a lithic contact within a depth
of 50 cm are assigned to the Lithic subgroup. Soils that have a
histic epipedon are excluded from the Typic subgroup because
they are considered intergrades to Histosols.
Typic Endoaquands are not extensive in the United States.
They commonly support wet meadow vegetation, but some
support coniferous forest vegetation. Most Typic Endoaquands
are used as rangeland, but some have been drained and are
used as cropland or pasture.
Alic Endoaquands.—These soils are like Typic
Endoaquands, but they have more than 2.0 cmol(+)/kg Al3+
(by
1N KCl) in the fine-earth fraction of one or more horizons with
a total thickness of 10 cm or more at a depth between 25 and
50 cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower. These soils are rare in the United States.
Duric Endoaquands.—These soils are like Typic
Endoaquands, but they have a horizon 15 cm or more thick
that has 20 percent or more (by volume) cemented soil material
and has its upper boundary within 100 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower. These soils have not been
recognized in the United States.
Histic Endoaquands.—These soils are like Typic
Endoaquands, but they have a histic epipedon. They have not
been recognized in the United States.
Hydric Endoaquands.—These soils are like Typic
Endoaquands, but they have, on undried samples, a 1500 kPa
water retention of 70 percent or more throughout a layer 35 cm
or more thick within 100 cm either of the mineral soil surface
or of the top of an organic layer with andic soil properties,
whichever is shallower. These soils have not been recognized
in the United States.
Lithic Endoaquands.—These soils are like Typic
Endoaquands, but they have a lithic contact within a depth of
50 cm. They have not been recognized in the United States.
Thaptic Endoaquands.—These soils are like Typic
Endoaquands, but they have, between depths of 25 and 100 cm,
a buried, dark colored layer 10 cm or more thick below a
lighter colored horizon or horizons 10 cm or more thick with a
lower content of organic carbon. These soils are rare in the
United States.
Epiaquands
Epiaquands are the more or less poorly drained Andisols with
a slowly permeable layer that causes unsaturated layers to
underlie saturated layers within 200 cm of the mineral soil
surface. Most of these soils formed under grassy meadow
vegetation, but some formed under coniferous forest vegetation.
Characteristically, Epiaquands have a thin O horizon, a
mollic or umbric epipedon, and a cambic horizon with many
redox concentrations.
The Epiaquands in the United States generally developed in
late-Pleistocene or Holocene deposits.
Definition
Epiaquands are the Aquands that:
1. Do not have, in 75 percent or more of each pedon, a
cemented horizon that has its upper boundary within 100 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower;
2. Do not have, in half or more of each pedon, a placic
horizon within 100 cm either of the mineral soil surface or of
the top of an organic layer with andic soil properties,
whichever is shallower;
3. Do not have a melanic epipedon;
4. Do not have a cryic soil temperature regime;
5. Have a 1500 kPa water retention either of 15 percent or more
on air-dried samples or of 30 percent or more on undried samples
throughout one or more layers with a total thickness of more
280 Soil Taxonomy
than 25 cm within 60 cm either of the mineral soil surface or of
the top of an organic layer with andic soil properties, whichever
is shallower; and
6. Have episaturation.
KeytoSubgroups
DAFA. Epiaquands that have a horizon 15 cm or more thick
that has 20 percent or more (by volume) cemented soil material
and has its upper boundary within 100 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
DuricEpiaquands
DAFB. Other Epiaquands that have a histic epipedon.
Histic Epiaquands
DAFC. Other Epiaquands that have more than 2.0
cmol(+)/kg Al3+
(by 1N KCl) in the fine-earth fraction of one or
more horizons with a total thickness of 10 cm or more at a depth
between 25 and 50 cm either from the mineral soil surface or from
the top of an organic layer with andic soil properties, whichever
is shallower.
AlicEpiaquands
DAFD. Other Epiaquands that have, on undried samples, a
1500 kPa water retention of 70 percent or more throughout a
layer 35 cm or more thick within 100 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Hydric Epiaquands
DAFE. Other Epiaquands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Epiaquands
DAFF. Other Epiaquands.
Typic Epiaquands
Definition of Typic Epiaquands
Typic Epiaquands are the Epiaquands that:
1. Do not have a horizon with an upper boundary
within 100 cm either of the mineral soil surface or of
the top of an organic layer with andic soil properties,
whichever is shallower, that is more than 15 cm thick
and has 20 percent or more (by volume) cemented soil
material;
2. Do not have a histic epipedon;
3. Do not have, at a depth between 25 and 100 cm either from
the mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, a layer 10 cm or
more thick with more than 3.0 percent organic carbon and the
colors of a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that have a color
value, moist, 1 unit or more higher and an organic-carbon
content 1 percent or more (absolute) lower;
4. Have 2.0 cmol(+)/kg or less Al3+
(by 1N KCl) in the fine-earth
fraction throughout a layer 10 cm or more thick at a depth
between 25 and 50 cm either from the mineral soil surface or from
the top of an organic layer with andic soil properties, whichever
is shallower; and
5. Have, on undried samples, a 1500 kPa water retention of less
than 70 percent throughout a layer 35 cm or more thick within
100 cm either of the mineral soil surface or of the upper
boundary of an organic layer with andic soil properties,
whichever is shallower.
Description of Subgroups
Typic Epiaquands.—The central concept or Typic
subgroup of Epiaquands is fixed on moderately deep or deeper
soils that do not have a histic epipedon and do not have,
between depths of 25 and 100 cm, a buried, dark colored layer
10 cm or more thick below a lighter colored horizon or
horizons 10 cm or more thick with a lower content of organic
carbon. Soils that have a horizon 15 cm or more thick with 20
percent or more cemented soil material also are excluded.
Epiaquands that have, on undried samples, a 1500 kPa
water retention of 70 percent or more throughout a layer 35 cm
or more thick in the upper part are assigned to the Hydric
subgroup. Soils with more than 2.0 cmol(+)/kg Al3+
(by 1N
KCl) in the fine-earth fraction of one or more horizons with a
total thickness of 10 cm or more also are excluded from the
Typic subgroup. Soils that have a histic epipedon are excluded
from the Typic subgroup because they are considered
intergrades to Histosols.
Typic Epiaquands are rare in the United States. They
commonly support wet meadow vegetation, but some support
coniferous forest vegetation.
Alic Epiaquands.—These soils are like Typic Epiaquands,
but they have more than 2.0 cmol(+)/kg Al3+
(by 1N KCl) in
the fine-earth fraction of one or more horizons with a total
thickness of 10 cm or more at a depth between 25 and 50 cm
either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower. These soils are rare in the United States.
Andisols 281
Duric Epiaquands.—These soils are like Typic
Epiaquands, but they have a horizon 15 cm or more thick that
has 20 percent or more (by volume) cemented soil material and
has its upper boundary within 100 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower. These soils have not been
recognized in the United States.
Histic Epiaquands.—These soils are like Typic
Epiaquands, but they have a histic epipedon. They have not
been recognized in the United States.
Hydric Epiaquands.—These soils are like Typic
Epiaquands, but they have, on undried samples, a 1500 kPa
water retention of 70 percent or more throughout a layer 35 cm
or more thick within 100 cm either of the mineral soil surface
or of the top of an organic layer with andic soil properties,
whichever is shallower. These soils have not been recognized
in the United States.
Thaptic Epiaquands.—These soils are like Typic
Epiaquands, but they have, between depths of 25 and 100 cm, a
buried, dark colored layer 10 cm or more thick below a lighter
colored horizon or horizons 10 cm or more thick with a lower
content of organic carbon. These soils are rare in the United
States.
Melanaquands
Melanaquands are the more or less poorly drained Andisols
with a melanic epipedon. Most of these soils formed under
forest vegetation.
Characteristically, Melanaquands have a thin O horizon, a
thick melanic epipedon, and a cambic horizon with many
redox concentrations.
Definition
Melanaquands are the Aquands that:
1. Have a melanic epipedon;
2. Do not have, in 75 percent or more of each pedon, a
cemented horizon with its upper boundary within 100 cm
of the mineral soil surface or of the upper boundary of an
organic layer that has andic soil properties, whichever is
shallower;
3. Do not have a cryic soil temperature regime;
4. Do not have, in half or more of each pedon, a placic
horizon within 100 cm of the mineral soil surface or of the
upper boundary of an organic layer that has andic soil
properties, whichever is shallower; and
5. Have a 1500 kPa water retention of 15 percent or more
on air-dried samples or 30 percent or more on undried samples
throughout a thickness of more than 25 cm within 60 cm of
the mineral soil surface or of the upper boundary of an
organic layer with andic soil properties, whichever is
shallower.
KeytoSubgroups
DAEA. Melanaquands that have a lithic contact within 50 cm
either of the mineral soil surface or of the top of an organic layer
with andic soil properties, whichever is shallower.
Lithic Melanaquands
DAEB. Other Melanaquands that have extractable bases (by
NH4
OAc) plus 1N KCl-extractable Al3+
totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more horizons
with a total thickness of 30 cm or more at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower.
Acraquoxic Melanaquands
DAEC. Other Melanaquands that have both:
1. On undried samples, a 1500 kPa water retention of 70
percent or more throughout a layer 35 cm or more thick
within 100 cm either of the mineral soil surface or of the top
of an organic layer with andic soil properties, whichever is
shallower; and
2. More than 6.0 percent organic carbon and the colors of
a mollic epipedon throughout a layer 50 cm or more thick
within 60 cm either of the mineral soil surface or of the top
of an organic layer with andic soil properties, whichever is
shallower.
Hydric Pachic Melanaquands
DAED. Other Melanaquands that have, on undried samples,
a 1500 kPa water retention of 70 percent or more throughout a
layer 35 cm or more thick within 100 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Hydric Melanaquands
DAEE. Other Melanaquands that have more than 6.0 percent
organic carbon and the colors of a mollic epipedon throughout
a layer 50 cm or more thick within 60 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Pachic Melanaquands
DAEF. Other Melanaquands that have, at a depth between 40
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
282 Soil Taxonomy
thickness of 10 cm or more that have a color value, moist, 1 unit
or more higher and an organic-carbon content 1 percent or more
(absolute) lower.
ThapticMelanaquands
DAEG. Other Melanaquands.
Typic Melanaquands
Definition of Typic Melanaquands
Typic Melanaquands are the Melanaquands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. On undried samples, have a 1500 kPa water retention of
less than 70 percent throughout any continuous thickness of 35
cm or more within the upper 100 cm;
3. Do not have both more than 6.0 percent organic carbon
and the colors of a mollic epipedon throughout at least 50 cm
of the upper 60 cm;
4. Do not have, between depths of 40 and 100 cm, a layer 10
cm or more thick with more than 3.0 percent organic carbon
and the colors of a mollic epipedon throughout, occurring
below a horizon or horizons 10 cm or more thick with a color
value 1 unit or more higher and an organic-carbon content 1
percent or more lower; and
5. Have extractable bases (by NH4
OAc) plus 1N KClextractable
Al3+
of 2.0 or more cmol(+) kg-1
in the fine-earth
fraction of all subhorizons 30 cm or more thick between depths
of 25 and 100 cm.
Description of Subgroups
Typic Melanaquands.—The central concept or Typic
subgroup of Melanaquands is fixed on soils that have a melanic
epipedon less than 50 cm thick, are moderately deep or deeper,
and do not have, between depths of 25 and 100 cm, a buried,
dark colored layer 10 cm or more thick below a lighter colored
horizon or horizons 10 cm or more thick with a lower content
of organic carbon. Soils that have, on undried samples, a 1500
kPa water retention of 70 percent or more throughout a layer
35 cm or more thick in the upper part are assigned to the
Hydric subgroup. Soils that have a lithic contact within a depth
of 50 cm are assigned to the Lithic subgroup.
Typic Melanaquands are not extensive in the United States.
They commonly support coniferous forest vegetation. Most of
these soils are used as woodland or have been drained and are
used as cropland or pasture.
Acraquoxic Melanaquands.—These soils are like Typic
Melanaquands, but they have very low extractable bases plus
1N KCl-extractable Al3+
in the fine-earth fraction of one or
more horizons with a total thickness of 30 cm or more at a
depth between 25 and 100 cm either from the mineral soil
surface or from the top of an organic layer with andic soil
properties, whichever is shallower. These soils are not known
to occur in the United States. They are established for use in
other countries.
Hydric Melanaquands.—These soils are like Typic
Melanaquands, but they have, on undried samples, a 1500 kPa
water retention of 70 percent or more throughout a layer 35 cm
or more thick within 100 cm either of the mineral soil surface
or of the top of an organic layer with andic soil properties,
whichever is shallower. These soils have not been recognized
in the United States.
Hydric Pachic Melanaquands.—These soils are like Typic
Melanaquands, but they have both more than 6.0 percent
organic carbon and the colors of a mollic epipedon throughout
at least 50 cm of the upper 60 cm of the andic materials and,
on undried samples, a 1500 kPa water retention of 70 percent
or more throughout a layer 35 cm or more thick within 100 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower. Hydric
Pachic Melanaquands have not been recognized in the United
States.
Lithic Melanaquands.—These soils are like Typic
Melanaquands, but they have a lithic contact within a depth of
50 cm. They have not been recognized in the United States.
Pachic Melanaquands.—These soils are like Typic
Melanaquands, but they have more than 6.0 percent organic
carbon and the colors of a mollic epipedon throughout at least
50 cm of the upper 60 cm below the mineral soil surface or
below the top of an organic layer with andic soil properties,
whichever is shallower. These soils have not been recognized
in the United States.
Thaptic Melanaquands.—These soils are like Typic
Melanaquands, but they have, between depths of 25 and 100
cm, a buried, dark colored layer 10 cm or more thick below a
lighter colored horizon or horizons 10 cm or more thick with a
lower content of organic carbon. These soils have not been
recognized in the United States.
Placaquands
Placaquands are the more or less poorly drained Andisols
that have, in half or more of each pedon, a placic horizon
within 100 cm of the mineral soil surface or of the upper
boundary of an organic layer that has andic soil properties,
whichever is shallower. Most of these soils formed under
coniferous forest vegetation.
Characteristically, Placaquands have a thin O horizon and
an umbric or histic epipedon above the placic horizon. They
are rare in the United States.
Definition
Placaquands are the Aquands that:
1. In half or more of each pedon, have a placic horizon
within 100 cm of the mineral soil surface or of the upper
boundary of an organic layer that has andic soil properties,
whichever is shallower; and
Andisols 283
2. Do not have a cryic soil temperature regime.
KeytoSubgroups
DABA. Placaquands that have a lithic contact within 50 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Lithic Placaquands
DABB. Other Placaquands that have both:
1. A histic epipedon; and
2. A horizon 15 cm or more thick that has 20 percent or
more (by volume) cemented soil material and has its upper
boundary within 100 cm either of the mineral soil surface or
of the top of an organic layer with andic soil properties,
whichever is shallower.
Duric Histic Placaquands
DABC. Other Placaquands that have a horizon 15 cm or
more thick that has 20 percent or more (by volume) cemented
soil material and has its upper boundary within 100 cm either
of the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower.
Duric Placaquands
DABD. Other Placaquands that have a histic epipedon.
Histic Placaquands
DABE. Other Placaquands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Placaquands
DABF. Other Placaquands.
Typic Placaquands
Definition of Typic Placaquands
Typic Placaquands are the Placaquands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have a horizon with its upper boundary within 100
cm of the mineral soil surface or of the upper boundary of an
organic layer that has andic soil properties, whichever is
shallower, that is more than 15 cm thick and that has 20
percent or more (by volume) cemented soil material;
3. Do not have a histic epipedon; and
4. Do not have, between depths of 25 and 100 cm, a layer 10 cm
or more thick with more than 3.0 percent organic carbon and the
colors of a mollic epipedon throughout, occurring below a
horizon or horizons 10 cm or more thick with a color value 1 unit
or more higher and an organic-carbon content 1 percent or more
lower.
Description of Subgroups
Typic Placaquands.—The central concept or Typic
subgroup of Placaquands is fixed on soils that do not have a
histic epipedon, are moderately deep or deeper, and do not
have, between depths of 25 and 100 cm, a buried, dark colored
layer 10 cm or more thick below a lighter colored horizon or
horizons 10 cm or more thick with a lower content of organic
carbon. Soils that average 20 percent or more (by volume)
cemented soil material in a layer 15 cm or more thick are
assigned to the Duric subgroup. Soils that have a lithic contact
within a depth of 50 cm are assigned to the Lithic subgroup.
Typic Placaquands have not been recognized in the United
States.
Duric Histic Placaquands.—These soils are like Typic
Placaquands, but they have both a histic epipedon and a
horizon 15 cm or more thick that has 20 percent or more (by
volume) cemented soil material and has its upper boundary
within 100 cm either of the mineral soil surface or of the top of
an organic layer with andic soil properties, whichever is
shallower. These soils have not been recognized in the United
States.
Duric Placaquands.—These soils are like Typic
Placaquands, but they have a horizon 15 cm or more thick that
has 20 percent or more (by volume) cemented soil material and
has its upper boundary within 100 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower. These soils have not been
recognized in the United States.
Histic Placaquands.—These soils are like Typic
Placaquands, but they have a histic epipedon. They are rare in
the United States.
Lithic Placaquands.—These soils are like Typic
Placaquands, but they have a lithic contact within a depth of 50
cm. They have not been recognized in the United States.
Thaptic Placaquands.—These soils are like Typic
Placaquands, but they have, between depths of 25 and 100 cm,
a buried, dark colored layer 10 cm or more thick below a
lighter colored horizon or horizons 10 cm or more thick with a
lower content of organic carbon. These soils have not been
recognized in the United States.
Vitraquands
Vitraquands are the more or less poorly drained Andisols
with relatively coarse textures. Most of these soils have no
slowly permeable layer that causes unsaturated layers to
underlie saturated layers within 200 cm of the mineral soil
284 Soil Taxonomy
surface. Many of the soils formed under grassy or brushy
meadow vegetation, but some formed under coniferous forest
vegetation.
Characteristically, Vitraquands have a thin O horizon, a
mollic or umbric epipedon, and a cambic horizon with many
redox concentrations.
Most Vitraquands in the United States developed in
Holocene deposits.
Definition
Vitraquands are the Aquands that:
1. Have a 1500 kPa water retention of less than 15 percent on
air-dried samples and less than 30 percent on undried samples
throughout 60 percent or more of the thickness either:
a. Within 60 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever
is shallower, if there is no lithic or paralithic contact,
duripan, or petrocalcic horizon within that depth; or
b. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon;
2. Do not have a cryic soil temperature regime;
3. Do not have, in half or more of each pedon, a placic
horizon within 100 cm of the mineral soil surface or of the
upper boundary of an organic layer that has andic soil
properties, whichever is shallower; and
4. Do not have, in 75 percent or more of each pedon, a
cemented horizon with its upper boundary within 100 cm of
the mineral soil surface or of the upper boundary of an organic
layer that has andic soil properties, whichever is shallower.
Key to Subgroups
DADA. Vitraquands that have a lithic contact within 50 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Lithic Vitraquands
DADB. Other Vitraquands that have a horizon 15 cm or
more thick that has 20 percent or more (by volume) cemented
soil material and has its upper boundary within 100 cm either
of the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower.
Duric Vitraquands
DADC. Other Vitraquands that have a histic epipedon.
Histic Vitraquands
DADD. Other Vitraquands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
ThapticVitraquands
DADE. Other Vitraquands.
Typic Vitraquands
Definition of Typic Vitraquands
Typic Vitraquands are the Vitraquands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have a horizon with its upper boundary within 100
cm of the mineral soil surface or of the upper boundary of an
organic layer that has andic soil properties, whichever is
shallower, that is more than 15 cm thick and that has 20
percent or more (by volume) cemented soil material;
3. Do not have a histic epipedon; and
4. Do not have, between depths of 25 and 100 cm, a layer 10
cm or more thick with more than 3.0 percent organic carbon
and the colors of a mollic epipedon throughout, occurring
below a horizon or horizons 10 cm or more thick with a color
value 1 unit or more higher and an organic-carbon content 1
percent or more lower.
Description of Subgroups
Typic Vitraquands.—The central concept or Typic
subgroup of Vitraquands is fixed on soils that do not have a
histic epipedon, are moderately deep or deeper, and do not
have, between depths of 25 and 100 cm, a buried, dark colored
layer 10 cm or more thick below a lighter colored horizon or
horizons 10 cm or more thick with a lower content of organic
carbon. Soils that average 20 percent or more (by volume)
cemented soil material in a layer 15 cm or more thick are
assigned to the Duric subgroup. Soils that have a lithic
contact within a depth of 50 cm are assigned to the Lithic
subgroup. Typic Vitraquands are of small extent in the United
States.
Duric Vitraquands.—These soils are like Typic
Vitraquands, but they have a horizon 15 cm or more thick that
has 20 percent or more (by volume) cemented soil material and
has its upper boundary within 100 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower. These soils have not been
recognized in the United States.
Histic Vitraquands.—These soils are like Typic
Vitraquands, but they have a histic epipedon. They are of small
extent in the United States.
Lithic Vitraquands.—These soils are like Typic
Andisols 285
Vitraquands, but they have a lithic contact within a depth of 50
cm. They have not been recognized in the United States.
Thaptic Vitraquands.—These soils are like Typic
Vitraquands, but they have, between depths of 25 and 100 cm,
a buried, dark colored layer 10 cm or more thick below a
lighter colored horizon or horizons 10 cm or more thick with a
lower content of organic carbon. These soils have not been
recognized in the United States.
Cryands
Cryands are the more or less well drained Andisols of cold
regions. These soils are moderately extensive. They formed in
the western part of North America and the northeastern part of
Asia above 49o
north latitude and in mountains south of that
latitude. Most of the soils formed under coniferous forest
vegetation.
Characteristically, Cryands have a thin O horizon and a
cambic horizon. The epipedon ranges from ochric to melanic.
The Cryands in the United States generally developed in
late-Pleistocene or Holocene deposits.
Definition
Cryands are the Andisols that:
1. Have a cryic soil temperature regime; and
2. Do not have a histic epipedon or the aquic conditions
characteristic of Aquands.
Key to Great Groups
DBA. Cryands that have, in 75 percent or more of each
pedon, a cemented horizon that has its upper boundary within
100 cm either of the mineral soil surface or of the top of an
organic layer with andic soil properties, whichever is
shallower.
Duricryands, p. 285
DBB. Other Cryands that have, on undried samples, a 1500
kPa water retention of 100 percent or more, by weighted
average, throughout either:
1. One or more layers with a total thickness of 35 cm
between the mineral soil surface or the top of an organic
layer with andic soil properties, whichever is shallower,
and 100 cm from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever
is shallower, if there is no densic, lithic, or paralithic
contact, duripan, or petrocalcic horizon within that depth;
or
2. 60 percent or more of the horizon thickness between
either the mineral soil surface or the top of an organic layer
with andic soil properties, whichever is shallower, and a
densic, lithic, or paralithic contact, a duripan, or a petrocalcic
horizon.
Hydrocryands, p. 289
DBC. Other Cryands that have a melanic epipedon.
Melanocryands, p. 291
DBD. Other Cryands that have a layer that meets the depth,
thickness, and organic-carbon requirements for a melanic
epipedon.
Fulvicryands, p. 286
DBE. Other Cryands that have a 1500 kPa water retention of
less than 15 percent on air-dried samples and less than 30
percent on undried samples throughout 60 percent or more of
the thickness either:
1. Within 60 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever
is shallower, if there is no densic, lithic, or paralithic
contact, duripan, or petrocalcic horizon within that depth;
or
2. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon.
Vitricryands, p. 292
DBF. Other Cryands.
Haplocryands, p. 287
Duricryands
Duricryands are the Cryands that have, in 75 percent or
more of each pedon, a cemented horizon that has its upper
boundary within 100 cm either of the mineral soil surface or
of the top of an organic layer with andic soil properties,
whichever is shallower. Characteristically, Duricryands have a
thin O horizon and a cambic horizon above the cemented
horizon.
The Duricryands in the United States generally developed in
late-Pleistocene or Holocene deposits. Most formed under
coniferous forest vegetation.
Definition
Duricryands are the Cryands that have, in 75 percent or
more of each pedon, a cemented horizon that has its upper
boundary within 100 cm of either the mineral soil surface or of
the top of an organic layer with andic soil properties,
whichever is shallower.
Key to Subgroups
DBAA. Duricryands that have, in some subhorizon at a depth
between 50 and 100 cm either from the mineral soil surface or
286 Soil Taxonomy
from the top of an organic layer with andic soil properties,
whichever is shallower, aquic conditions for some time in
normal years (or artificial drainage) and one or more of the
following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent or more
chroma of 2 or less either in redox depletions on faces of peds
or in the matrix if peds are absent; or
3. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Duricryands
DBAB. Other Duricryands.
Typic Duricryands
Definition of Typic Duricryands
Typic Duricryands are the Duricryands that do not have, in
any horizon at a depth between 50 and 100 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, both aquic
conditions and any of the following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
3. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Description of Subgroups
Typic Duricryands.—The central concept or Typic
subgroup of Duricryands is fixed on soils that have relatively
high amounts of aluminum and low cation-exchange capacities
and do not have both aquic conditions and redox features in
any horizon at a depth between 50 and 100 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower.
These soils are not extensive in the United States. They
commonly support coniferous forest vegetation. Most of the
soils are used for timber production, but some are used as
recreational areas.
Aquic Duricryands.—These soils are like Typic
Duricryands, but they have both aquic conditions (or artificial
drainage) and redox features in a horizon at a depth between
50 and 100 cm either from the mineral soil surface or from the
top of an organic layer with andic soil properties, whichever is
shallower. These soils are rare in the United States. Most are
used for timber production, but some are used as recreational
areas.
Fulvicryands
Fulvicryands are the Cryands that do not have a melanic
epipedon but have a layer that meets the depth, thickness, and
organic-carbon requirements for a melanic epipedon. They do
not have, in 75 percent or more of each pedon, a cemented
horizon that has its upper boundary within 100 cm of either the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower.
Characteristically, Fulvicryands have a thin O horizon, an
umbric epipedon, and a cambic horizon.
The Fulvicryands in the United States generally developed
in late-Pleistocene or Holocene deposits. Most formed under
coniferous forest vegetation.
Definition
Fulvicryands are the Cryands that:
1. Have, in less than 75 percent of each pedon, a cemented
horizon that has its upper boundary within 100 cm of either the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower;
2. Do not have a melanic epipedon but have a layer that
meets the depth, thickness, and organic carbon requirements
for a melanic epipedon; and
3. Do not have, on undried samples, a 1500 kPa water
retention of 100 percent or more, by weighted average,
throughout either:
a. One or more layers with a total thickness of 35 cm
between the mineral soil surface or the top of an organic
layer with andic soil properties, whichever is shallower, and
100 cm from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, if there is no densic, lithic, or paralithic contact,
duripan, or petrocalcic horizon within that depth; or
b. 60 percent or more of the horizon thickness between
either the mineral soil surface or the top of an organic layer
with andic soil properties, whichever is shallower, and a
densic, lithic, or paralithic contact, a duripan, or a
petrocalcic horizon.
Key to Subgroups
DBDA. Fulvicryands that have a lithic contact within 50 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Lithic Fulvicryands
DBDB. Other Fulvicryands that have, throughout a layer 50
cm or more thick within 60 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower:
Andisols 287
1. More than 6.0 percent organic carbon, by weighted
average; and
2. More than 4.0 percent organic carbon in all parts.
Pachic Fulvicryands
DBDC. Other Fulvicryands that have a 1500 kPa water
retention of less than 15 percent on air-dried samples and less
than 30 percent on undried samples throughout one or more
layers that have andic soil properties and have a total thickness
of 25 cm or more within 100 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Vitric Fulvicryands
DBDD. Other Fulvicryands.
Typic Fulvicryands
Definition of Typic Fulvicryands
Typic Fulvicryands are the Fulvicryands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Have a 1500 kPa water retention of 15 percent or more on
air-dried samples or 30 percent or more on undried samples in
all subhorizons that meet the requirements for andic soil
properties and that are 25 cm or more thick and are within 100
cm of the mineral soil surface or of the upper boundary of an
organic layer that has andic soil properties, whichever is
shallower; and
3. Do not have throughout a layer 50 cm or more thick within
60 cm either of the mineral soil surface or of the top of an
organic layer with andic soil properties, whichever is
shallower:
a. More than 6.0 percent organic carbon, by weighted
average; and
b. More than 4.0 percent organic carbon in all parts.
Description of Subgroups
Typic Fulvicryands.—The central concept or Typic
subgroup of Fulvicryands is fixed on moderately deep or
deeper, more or less well drained soils that have a 1500 kPa
water retention of 15 percent or more on air-dried samples or
30 percent or more on undried samples in all subhorizons that
meet the requirements for andic soil properties and that are 25
cm or more thick and are within 100 cm of the mineral soil
surface or of the upper boundary of an organic layer that has
andic soil properties, whichever is shallower.
Typic Fulvicryands commonly have relatively high amounts
of aluminum and low cation-exchange capacities. These soils
are not extensive in the United States. They commonly support
coniferous forest vegetation. Most are used for timber
production, but some are used as recreational areas.
Lithic Fulvicryands.—These soils are like Typic
Fulvicryands, but they have a lithic contact within a depth of
50 cm. They have not been recognized in the United States.
Pachic Fulvicryands.—These soils are like Typic
Fulvicryands, but they have thicker, darker layers or horizons
at or near the surface. These soils are not extensive in the
United States. They commonly support coniferous forest
vegetation. Most are used for timber production, but some are
used as recreational areas.
Vitric Fulvicryands.—These soils are like Typic
Fulvicryands, but they have a 1500 kPa water retention of less
than 15 percent on air-dried samples and less than 30 percent
on undried samples in all subhorizons that meet the
requirements for andic soil properties and that are 25 cm or
more thick and are within 100 cm of the mineral soil surface or
of the upper boundary of an organic layer that has andic soil
properties, whichever is shallower. These soils are rare in the
United States. Most of the soils are used for timber production,
but some are used as recreational areas.
Haplocryands
Haplocryands are the Cryands that do not have a melanic
epipedon or a layer that meets the depth, thickness, and
organic-carbon requirements for a melanic epipedon. They do
not have, in 75 percent or more of each pedon, a cemented
horizon that has its upper boundary within 100 cm of either the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower. They have, on undried
samples, a 1500 kPa water retention of less than 100 percent,
by weighted average, throughout 60 percent or more of the
upper 60 cm of the andic materials. They also have a 1500 kPa
water retention of 30 percent or more on undried samples or of
15 percent or more on air-dried samples, by weighted average,
throughout 60 percent or more of the upper 60 cm of the andic
materials.
Characteristically, Haplocryands have a thin O horizon, an
umbric epipedon, and a cambic horizon.
The Haplocryands in the United States generally developed
in late-Pleistocene or Holocene deposits. Most formed under
coniferous forest vegetation.
Definition
Haplocryands are the Cryands that:
1. Have, in less than 75 percent of each pedon, a cemented
horizon that has its upper boundary within 100 cm of either the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower;
2. Do not have a melanic epipedon or an epipedon meeting
the depth, thickness, and organic-carbon requirements for a
melanic epipedon;
3. Have, on undried samples, a 1500 kPa water retention of
288 Soil Taxonomy
less than 100 percent, by weighted average, throughout more
than 40 percent of the horizon thickness between either the
mineral soil surface or the top of an organic layer with andic soil
properties, whichever is shallower, and a densic, lithic, or
paralithic contact, a duripan, a petrocalcic horizon, or a depth of
60 cm, whichever is shallowest; and
4. Have a 1500 kPa water retention of 30 percent or more on
undried samples or 15 percent or more on air-dried samples in
all subhorizons that meet the requirements for andic soil
properties and that are at least 25 cm thick and are within 100
cm of the mineral soil surface or of the upper boundary of an
organic layer that has andic soil properties, whichever is
shallower.
Key to Subgroups
DBFA. Haplocryands that have a lithic contact within 50 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Lithic Haplocryands
DBFB. Other Haplocryands that have more than 2.0
cmol(+)/kg Al3+
(by 1N KCl) in the fine-earth fraction of one
or more horizons with a total thickness of 10 cm or more at a
depth between 25 and 50 cm either from the mineral soil
surface or from the top of an organic layer with andic soil
properties, whichever is shallower.
Alic Haplocryands
DBFC. Other Haplocryands that have, in some subhorizon at
a depth between 50 and 100 cm either from the mineral soil
surface or from the top of an organic layer with andic soil
properties, whichever is shallower, aquic conditions for some
time in normal years (or artificial drainage) and one or more of
the following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
3. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Haplocryands
DBFD. Other Haplocryands that have extractable bases (by
NH4
OAc) plus 1N KCl-extractable Al3+
totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more horizons
with a total thickness of 30 cm or more at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower.
Acrudoxic Haplocryands
DBFE. Other Haplocryands that have a 1500 kPa water
retention of less than 15 percent on air-dried samples and less
than 30 percent on undried samples throughout one or more
layers that have andic soil properties and have a total thickness
of 25 cm or more within 100 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Vitric Haplocryands
DBFF. Other Haplocryands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Haplocryands
DBFG. Other Haplocryands that have a xeric moisture
regime.
Xeric Haplocryands
DBFH. Other Haplocryands.
Typic Haplocryands
Definition of Typic Haplocryands
Typic Haplocryands are the Haplocryands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have, in any horizon at a depth between 50
and 100 cm either from the mineral soil surface or from
the top of an organic layer with andic soil properties,
whichever is shallower, both aquic conditions and any of
the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated;
3. Have, on undried samples, 30 percent or more 1500 kPa
water retention in all subhorizons that meet the requirements
for andic soil properties and that are at least 25 cm thick and
are within 100 cm of the mineral soil surface or of the upper
boundary of an organic layer that has andic soil properties,
whichever is shallower;
4. Have 1N KCl-extractable Al3+
of 2.0 or less cmol(+) kg-1
in
Andisols 289
the fine-earth fraction throughout all layers 10 cm or more thick
between depths of 25 and 50 cm;
5. Do not have, between depths of 25 and 100 cm, a layer 10
cm or more thick with more than 3.0 percent organic carbon
and the colors of a mollic epipedon throughout, occurring
below a horizon or horizons 10 cm or more thick with a color
value 1 unit or more higher and an organic-carbon content 1
percent or more lower;
6. Have extractable bases (by NH4
OAc) plus 1N KClextractable
Al3+
of 2.0 or more cmol(+) kg-1
in the fine-earth
fraction of all subhorizons 30 cm or more thick between depths
of 25 and 100 cm; and
7. Do not have a xeric soil moisture regime.
Description of Subgroups
Typic Haplocryands.—The central concept or Typic
subgroup of Haplocryands is fixed on moderately deep or deep
soils that have a 1500 kPa water retention of 15 percent or
more on air-dried samples or 30 percent or more on undried
samples in all subhorizons that meet the requirements for andic
soil properties and that are 25 cm or more thick and are within
100 cm of the mineral soil surface or of the upper boundary of
an organic layer that has andic soil properties, whichever is
shallower.
Soils with more than 2.0 cmol(+)/kg Al3+
(by 1N KCl) in
the fine-earth fraction of one or more horizons with a total
thickness of 10 cm or more are excluded from the Typic
subgroup. Soils that have a lithic contact within a depth of 50
cm are assigned to the Lithic subgroup. Soils that have both
aquic conditions (or artificial drainage) and redox features in
any horizon at a depth between 50 and 100 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, are excluded
from the Typic subgroup and are considered intergrades to
Aquands.
Typic Haplocryands are moderately extensive in the United
States. They commonly support coniferous forest vegetation.
Most are used for timber production, but some are used as
recreational areas.
Acrudoxic Haplocryands.—These soils are like Typic
Haplocryands, but they have extractable bases plus 1N KClextractable
Al3+
totaling less than 2.0 cmol(+)/kg in the fineearth
fraction of one or more horizons with a total thickness of
30 cm or more at a depth between 25 and 100 cm either from
the mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower. These soils have
not been recognized in the United States.
Alic Haplocryands.—These soils are like Typic
Haplocryands, but they have more than 2.0 cmol(+)/kg Al3+
(by
1N KCl) in the fine-earth fraction of one or more horizons with
a total thickness of 10 cm or more at a depth between 25 and
50 cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower. These soils are mostly in Oregon and Washington
and are of small extent in the United States. Most of the soils
are used for timber production, but some are used as
recreational areas.
Aquic Haplocryands.—These soils are like Typic
Haplocryands, but they have both aquic conditions (or artificial
drainage) and redox features in a horizon at a depth between
50 and 100 cm either from the mineral soil surface or from the
top of an organic layer with andic soil properties, whichever is
shallower. These soils are rare in the United States. Most of the
soils are used for timber production, but some are used as
recreational areas.
Lithic Haplocryands.—These soils are like Typic
Haplocryands, but they have a lithic contact within a depth of
50 cm. They are mostly in Oregon and Washington and are of
small extent in the United States. Most of the soils are used for
timber production or as recreational areas.
Thaptic Haplocryands.—These soils are like Typic
Haplocryands, but they have, between depths of 25 and 100
cm, a buried, dark colored layer 10 cm or more thick below a
lighter colored horizon or horizons 10 cm or more thick with a
lower content of organic carbon. These soils have not been
recognized in the United States.
Vitric Haplocryands.—These soils are like Typic
Haplocryands, but they have a 1500 kPa water retention of less
than 15 percent on air-dried samples and less than 30 percent
on undried samples in some subhorizon that meets the
requirements for andic soil properties and that is 25 cm or
more thick and is within 100 cm of the mineral soil surface or
of the upper boundary of an organic layer that has andic soil
properties, whichever is shallower. These soils are mostly in
Idaho, Oregon, and Washington and are of small extent in the
United States. Most of the soils are used for timber production,
but some are used as recreational areas.
Xeric Haplocryands.—These soils are like Typic
Haplocryands, but they have a xeric moisture regime. They are
mostly in California and Idaho and are of small extent in the
United States. Most of the soils are used for timber production,
but some are used as recreational areas.
Hydrocryands
Hydrocryands have, on undried samples, a 1500 kPa water
retention of 100 percent or more, by weighted average,
throughout 60 percent or more of the upper part of the pedon.
They do not have, in 75 percent or more of each pedon, a
cemented horizon that has its upper boundary within 100 cm of
either the mineral soil surface or of the top of an organic layer
with andic soil properties, whichever is shallower.
Hydrocryands have not been recognized in the United
States. Most formed under coniferous forest vegetation.
290 Soil Taxonomy
Definition
Hydrocryands are the Cryands that:
1. Have, in less than 75 percent of each pedon, a cemented
horizon that has its upper boundary within 100 cm of either the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower; and
2. Have, on undried samples, a 1500 kPa water retention of
100 percent or more, by weighted average, throughout either:
a. One or more layers with a total thickness of 35 cm
between the mineral soil surface or the top of an organic
layer with andic soil properties, whichever is shallower, and
100 cm from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, if there is no densic, lithic, or paralithic contact,
duripan, or petrocalcic horizon within that depth; or
b. 60 percent or more of the horizon thickness between
either the mineral soil surface or the top of an organic layer
with andic soil properties, whichever is shallower, and a
densic, lithic, or paralithic contact, a duripan, or a
petrocalcic horizon.
Key to Subgroups
DBBA. Hydrocryands that have a lithic contact within 50 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Lithic Hydrocryands
DBBB. Other Hydrocryands that have a placic horizon within
100 cm either of the mineral soil surface or of the top of an
organic layer with andic soil properties, whichever is
shallower.
Placic Hydrocryands
DBBC. Other Hydrocryands that have, in one or more
horizons at a depth between 50 and 100 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, aquic conditions
for some time in normal years (or artificial drainage) and one
or more of the following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
3. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Hydrocryands
DBBD. Other Hydrocryands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Hydrocryands
DBBE. Other Hydrocryands.
Typic Hydrocryands
Definition of Typic Hydrocryands
Typic Hydrocryands are the Hydrocryands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have, in any horizon at a depth between 50 and 100
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, both aquic conditions and any of the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated;
3. Do not have a placic horizon within 100 cm of the soil
surface; and
4. Do not have, between depths of 25 and 100 cm, a layer 10
cm or more thick with more than 3.0 percent organic carbon
and the colors of a mollic epipedon throughout, occurring
below a horizon or horizons 10 cm or more thick with a color
value 1 unit or more higher and an organic-carbon content 1
percent or more lower.
Description of Subgroups
Typic Hydrocryands.—The central concept or Typic
subgroup of Hydrocryands is fixed on moderately deep or deep
soils that do not have a placic horizon within a depth of 100
cm and do not have, between depths of 25 and 100 cm, a
buried, dark colored layer 10 cm or more thick below a lighter
colored horizon or horizons 10 cm or more thick with a lower
content of organic carbon.
Soils that have a lithic contact within a depth of 50 cm are
assigned to the Lithic subgroup. Soils that have both aquic
conditions (or artificial drainage) and redox features in any
horizon at a depth between 50 and 100 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, are excluded
Andisols 291
from the Typic subgroup and are considered intergrades to
Aquands.
Typic Hydrocryands are not known to occur in the United
States.
Aquic Hydrocryands.—These soils are like Typic
Hydrocryands, but they have both aquic conditions (or artificial
drainage) and redox features in a horizon at a depth between
50 and 100 cm either from the mineral soil surface or from the
top of an organic layer with andic soil properties, whichever is
shallower. These soils are not known to occur in the United
States.
Lithic Hydrocryands.—These soils are like Typic
Hydrocryands, but they have a lithic contact within a depth of
50 cm. They are not known to occur in the United States.
Placic Hydrocryands.—These soils are like Typic
Hydrocryands, but they have a placic horizon within 100 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower. These
soils are not known to occur in the United States.
Thaptic Hydrocryands.—These soils are like Typic
Hydrocryands, but they have, between depths of 25 and 100
cm, a buried, dark colored layer 10 cm or more thick below a
lighter colored horizon or horizons 10 cm or more thick with a
lower content of organic carbon. These soils have not been
recognized in the United States.
Melanocryands
Melanocryands are the Cryands that have a melanic
epipedon but do not have, in 75 percent or more of each pedon,
a cemented horizon that has its upper boundary within 100 cm
of either the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower. These
soils also do not have the high water retention associated with
Hydrocryands. Melanocryands have not been recognized in the
United States.
Definition
Melanocryands are the Cryands that:
1. Have, in less than 75 percent of each pedon, a cemented
horizon that has its upper boundary within 100 cm of either the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower;
2. Have a melanic epipedon; and
3. Do not have, on undried samples, a 1500 kPa water
retention of 100 percent or more, by weighted average,
throughout either:
a. One or more layers with a total thickness of 35 cm
between the mineral soil surface or the top of an organic
layer with andic soil properties, whichever is shallower, and
100 cm from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, if there is no densic, lithic, or paralithic contact,
duripan, or petrocalcic horizon within that depth; or
b. 60 percent or more of the horizon thickness between
either the mineral soil surface or the top of an organic layer
with andic soil properties, whichever is shallower, and a
densic, lithic, or paralithic contact, a duripan, or a
petrocalcic horizon.
Key to Subgroups
DBCA. Melanocryands that have a lithic contact within
50 cm either of the mineral soil surface or of the top of an
organic layer that has andic soil properties, whichever is
shallower.
Lithic Melanocryands
DBCB. Other Melanocryands that have a 1500 kPa water
retention of less than 15 percent on air-dried samples and less
than 30 percent on undried samples throughout one or more
layers that have andic soil properties and have a total thickness
of 25 cm or more within 100 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Vitric Melanocryands
DBCC. Other Melanocryands.
Typic Melanocryands
Definition of Typic Melanocryands
Typic Melanocryands are the Melanocryands that:
1. Do not have a lithic contact within 50 cm of the soil
surface; and
2. Have, on undried samples, 30 percent or more 1500 kPa
water retention in all subhorizons that meet the requirements
for andic soil properties and that are at least 25 cm thick and
are within 100 cm of the mineral soil surface or of the upper
boundary of an organic layer that has andic soil properties,
whichever is shallower.
Description of Subgroups
Typic Melanocryands.—The central concept or Typic
subgroup of Melanocryands is fixed on moderately deep or
deeper soils that have a 1500 kPa water retention of 15 percent
or more on air-dried samples or 30 percent or more on undried
samples in all subhorizons that meet the requirements for andic
soil properties and that are 25 cm or more thick and are within
100 cm of the mineral soil surface or of the upper boundary of
an organic layer that has andic soil properties, whichever is
shallower.
Typic Melanocryands commonly have relatively high
amounts of aluminum. They have been recognized in the
Pacific Northwest.
Lithic Melanocryands.—These soils are like Typic
292 Soil Taxonomy
Melanocryands, but they have a lithic contact within a depth
of 50 cm. They have not been recognized in the United
States.
Vitric Melanocryands.—These soils are like Typic
Melanocryands, but they have a 1500 kPa water retention
of less than 15 percent on air-dried samples and less than
30 percent on undried samples in all subhorizons that meet
the requirements for andic soil properties and that are 25
cm or more thick and are within 100 cm of the mineral
soil surface or of the upper boundary of an organic layer
that has andic soil properties, whichever is shallower.
Vitric Melanocryands have not been recognized in the United
States.
Vitricryands
Vitricryands are the Cryands that have a 1500 kPa water
retention of less than 15 percent on air-dried samples and less
than 30 percent on undried samples throughout 60 percent or
more of the upper 60 cm of the andic materials. These soils do
not have a melanic epipedon or a layer that meets the depth,
thickness, and organic-carbon requirements for a melanic
epipedon. They do not have, in 75 percent or more of each
pedon, a cemented horizon that has its upper boundary within
100 cm of either the mineral soil surface or of the top of an
organic layer with andic soil properties, whichever is
shallower.
Characteristically, Vitricryands have a thin O horizon; an
ochric, mollic, or umbric epipedon; and a cambic horizon.
The Vitricryands in the United States generally developed in
Holocene deposits. Most formed under coniferous forest
vegetation.
Definition
Vitricryands are the Cryands that:
1. Have, in less than 75 percent of each pedon, a cemented
horizon that has its upper boundary within 100 cm of either the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower;
2. Do not have a melanic epipedon or an epipedon meeting
the depth, thickness, and organic-carbon requirements for a
melanic epipedon; and
3. Have a 1500 kPa water retention of less than 15 percent on
air-dried samples and less than 30 percent on undried samples
throughout 60 percent or more of the thickness either:
a. Within 60 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever
is shallower, if there is no densic, lithic, or paralithic
contact, duripan, or petrocalcic horizon within that depth;
or
b. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a densic, lithic, or paralithic contact, a duripan,
or a petrocalcic horizon.
KeytoSubgroups
DBEA. Vitricryands that have a lithic contact within
50 cm either of the mineral soil surface or of the top of an
organic layer that has andic soil properties, whichever is
shallower.
Lithic Vitricryands
DBEB. Other Vitricryands that have, in one or more horizons
at a depth between 50 and 100 cm either from the mineral soil
surface or from the top of an organic layer with andic soil
properties, whichever is shallower, aquic conditions for some
time in normal years (or artificial drainage) and one or more of
the following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
3. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Vitricryands
DBEC. Other Vitricryands that are saturated with water in
one or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Vitricryands
DBED. Other Vitricryands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Vitricryands
DBEE. Other Vitricryands that have a xeric moisture regime
and a mollic or umbric epipedon.
Humic Xeric Vitricryands
DBEF. Other Vitricryands that have a xeric moisture regime.
Xeric Vitricryands
DBEG. Other Vitricryands that have an argillic or kandic
horizon that has both:
Andisols 293
1. An upper boundary within 125 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower; and
2. A base saturation (by sum of cations) of less than 35
percent throughout the upper 50 cm or throughout the entire
argillic or kandic horizon if it is less than 50 cm thick.
Ultic Vitricryands
DBEH. Other Vitricryands that have an argillic or kandic
horizon that has its upper boundary within 125 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower.
Alfic Vitricryands
DBEI. Other Vitricryands that have a mollic or umbric
epipedon.
Humic Vitricryands
DBEJ. Other Vitricryands.
Typic Vitricryands
Definition of Typic Vitricryands
Typic Vitricryands are the Vitricryands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have, in any horizon at a depth between 50 and 100
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, both aquic conditions and any of the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated;
3. Do not have, between depths of 25 and 100 cm, a layer 10
cm or more thick with more than 3.0 percent organic carbon
and the colors of a mollic epipedon throughout, occurring
below a horizon or horizons 10 cm or more thick with a color
value 1 unit or more higher and an organic-carbon content 1
percent or more lower;
4. Do not have a xeric moisture regime;
5. Do not have an argillic or kandic horizon with its upper
boundary within 125 cm of the mineral soil surface or of the
upper boundary of an organic layer that has andic soil
properties, whichever is shallower;
6. Do not have a mollic or umbric epipedon; and
7. Are not saturated with water in one or more layers within
100 cm of the mineral soil surface for 20 or more consecutive
days or 30 or more cumulative days in normal years.
Description of Subgroups
Typic Vitricryands.—The central concept or Typic
subgroup of Vitricryands is fixed on moderately deep or deep,
more or less well drained soils that have an ochric epipedon
and a udic moisture regime. These soils do not have an argillic
horizon. They do not have, between depths of 25 and 100 cm, a
buried, dark colored layer 10 cm or more thick below a lighter
colored horizon or horizons 10 cm or more thick with a lower
content of organic carbon.
Soils that have a lithic contact within a depth of 50 cm are
assigned to the Lithic subgroup. Soils that are saturated with
water in one or more layers within 100 cm of the mineral soil
surface for 20 or more consecutive days or 30 or more
cumulative days in normal years are excluded from the Typic
subgroup and are considered intergrades to Aquands. Soils that
have both aquic conditions (or artificial drainage) and redox
features in any horizon at a depth between 50 and 100 cm
either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, also are excluded from the Typic subgroup and are
considered intergrades to Aquands.
Typic Vitricryands are moderately extensive in the United
States. They are mainly in Washington, Oregon, and Idaho.
They commonly support coniferous forest vegetation. Most are
used for timber production, but some are used as recreational
areas.
Alfic Vitricryands.—These soils are like Typic
Vitricryands, but they have both an argillic or kandic horizon
within 125 cm either of the mineral soil surface or of the top of
an organic layer with andic soil properties, whichever is
shallower, and a base saturation (by sum of cations) of 35
percent or more in some part of the argillic or kandic horizon.
These soils are of small extent in the United States. They are
mainly in Washington, Oregon, and Idaho. They commonly
support coniferous forest vegetation. Most are used for timber
production, but some are used as recreational areas.
Aquic Vitricryands.—These soils are like Typic
Vitricryands, but they have both aquic conditions (or artificial
drainage) and redox features in a horizon at a depth between
50 and 100 cm either from the mineral soil surface or from the
top of an organic layer with andic soil properties, whichever is
shallower. These soils are rare in the United States. Most are
used for timber production, but some are used as recreational
areas.
Humic Vitricryands.—These soils are like Typic
Vitricryands, but they have a mollic or umbric epipedon. They
are of small extent in the United States. They are mainly in
Alaska, Idaho, and Washington. They commonly support
grassy vegetation in Alaska and coniferous forest vegetation
elsewhere. Most of the soils are used as recreational areas or
for timber production.
294 Soil Taxonomy
Humic Xeric Vitricryands.—These soils are like Typic
Vitricryands, but they have both a mollic or umbric epipedon
and a xeric moisture regime. These soils are of small extent in
the United States. They are mainly in Washington. They
commonly support coniferous forest vegetation. Most are used
for timber production, but some are used as recreational areas.
Lithic Vitricryands.—These soils are like Typic
Vitricryands, but they have a lithic contact within a depth of 50
cm. They are mostly in Alaska and Washington and are of
small extent in the United States. They commonly support
grassy vegetation in Alaska and coniferous forest vegetation
elsewhere. Most of the soils are used as recreational areas or
for timber production.
Oxyaquic Vitricryands.—These soils are like Typic
Vitricryands, but they are saturated with water in one or more
layers within 100 cm of the mineral soil surface for 20 or more
consecutive days or 30 or more cumulative days in normal
years. These soils are rare in the United States.
Thaptic Vitricryands.—These soils are like Typic
Vitricryands, but they have, between depths of 25 and 100 cm,
a buried, dark colored layer 10 cm or more thick below a
lighter colored horizon or horizons 10 cm or more thick with a
lower content of organic carbon. These soils have not been
recognized in the United States.
Ultic Vitricryands.—These soils are like Typic
Vitricryands, but they have an argillic or kandic horizon that
has both an upper boundary within 125 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower, and a base saturation
(by sum of cations) of less than 35 percent throughout the
upper 50 cm or throughout the entire horizon if it is less than
50 cm thick. These soils have not been recognized in the
United States.
Xeric Vitricryands.—These soils are like Typic Vitricryands,
but they have a xeric moisture regime. They are moderately
extensive in the United States. They are mainly in Washington
and Oregon. They commonly support coniferous forest
vegetation. Most are used for timber production, but some are
used as recreational areas.
Torrands
Torrands are the more or less well drained Andisols of dry
regions. These soils are not extensive. Some formed in the
western part of North America, and some are known to occur
in Hawaii and other Pacific islands. Most of the soils formed
under grassy or shrub vegetation.
Characteristically, Torrands have an ochric or mollic
epipedon and a cambic horizon. Some have a duripan or a
petrocalcic horizon.
The Torrands in the United States generally developed in
late-Pleistocene or Holocene deposits.
Definition
Torrands are the Andisols that:
1. Have an aridic soil moisture regime;
2. Have a frigid or warmer soil temperature regime; and
3. Do not have a histic epipedon or the aquic conditions
characteristic of Aquands.
Key to Great Groups
DCA. Torrands that have, in 75 percent or more of each
pedon, a cemented horizon that has its upper boundary within
100 cm either of the mineral soil surface or of the top of an
organic layer with andic soil properties, whichever is
shallower.
Duritorrands, p. 294
DCB. Other Torrands that have, on air-dried samples, a 1500
kPa water retention of less than 15 percent throughout 60
percent or more of the thickness either:
1. Within 60 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever
is shallower, if there is no densic, lithic, or paralithic
contact, duripan, or petrocalcic horizon within that depth;
or
2. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon.
Vitritorrands, p. 296
DCC. Other Torrands.
Haplotorrands, p. 295
Duritorrands
Duritorrands are the Torrands that have, in 75 percent or
more of each pedon, a cemented horizon that has its upper
boundary within 100 cm either of the mineral soil surface or of
the top of an organic layer with andic soil properties, whichever
is shallower.
Characteristically, these soils have an ochric or mollic
epipedon and a cambic horizon above the cemented horizon.
The Duritorrands in the United States generally developed
in late-Pleistocene deposits. Most formed under grass or shrub
vegetation, and some have widely spaced trees.
Definition
Duritorrands are the Torrands that have, in 75 percent or
more of each pedon, a cemented horizon that has its upper
Andisols 295
boundary within 100 cm of either the mineral soil surface or of
the top of an organic layer with andic soil properties, whichever
is shallower.
KeytoSubgroups
DCAA. Duritorrands that have a petrocalcic horizon that has
its upper boundary within 100 cm of the mineral soil surface.
Petrocalcic Duritorrands
DCAB. Other Duritorrands that have, on air-dried samples, a
1500 kPa water retention of less than 15 percent throughout 60
percent or more of the thickness either:
1. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, if there is no paralithic contact or duripan within
that depth, and a point 60 cm below that depth; or
2. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a paralithic contact or a duripan.
Vitric Duritorrands
DCAC. Other Duritorrands.
Typic Duritorrands
Definition of Typic Duritorrands
Typic Duritorrands are the Duritorrands that:
1. Do not have a petrocalcic horizon with its upper boundary
within 100 cm of the mineral soil surface;
2. Do not have, on air-dried samples, a 1500 kPa water
retention of less than 15 percent throughout 60 percent or more
of the thickness either:
a. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, if there is no paralithic contact or duripan within
that depth, and a point 60 cm below that depth; or
b. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a paralithic contact or a duripan.
Description of Subgroups
Typic Duritorrands.—The central concept or Typic
subgroup of Duritorrands is fixed on soils that have a cemented
horizon, other than a petrocalcic horizon, that has its upper
boundary within 100 cm of the mineral soil surface.
Commonly, the cemented horizon is a duripan. These soils do
not have, on air-dried samples, a 1500 kPa water retention of
less than 15 percent throughout 60 percent or more of the
thickness between either the mineral soil surface or the top of
an organic layer with andic soil properties and a point 60 cm
below that depth, a paralithic contact, or a duripan, whichever
is shallowest.
These soils are known to occur only in Hawaii and are of
small extent in the United States. They commonly support
grassy or shrub vegetation. Most are used as rangeland, but
some are used as recreational areas.
Petrocalcic Duritorrands.—These soils are like Typic
Duritorrands, but they have a petrocalcic horizon that has its
upper boundary within 100 cm of the mineral soil surface.
These soils are known to occur only in Hawaii and are of small
extent in the United States. They commonly support grassy or
shrub vegetation. Most are used as rangeland, but some are
used as recreational areas.
Vitric Duritorrands.—These soils are like Typic
Duritorrands, but they have, on air-dried samples, a 1500 kPa
water retention of less than 15 percent throughout 60 percent
or more of the thickness between either the mineral soil surface
or the top of an organic layer with andic soil properties and a
point 60 cm below that depth, a paralithic contact, or a
duripan, whichever is shallowest.
These soils are known to occur only in Oregon and are of
small extent in the United States. They support grassy or shrub
vegetation, and some have widely spaced trees. Most of the
soils are used as rangeland, but some are used as recreational
areas.
Haplotorrands
Haplotorrands are the Torrands that do not have a cemented
horizon that has its upper boundary within 100 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower. These soils have, on
air-dried samples, a 1500 kPa water retention of 15 percent or
more throughout less than 60 percent of the thickness between
the mineral soil surface or the top of an organic layer with
andic soil properties, whichever is shallower, and a point 60
cm below the starting point or a densic, lithic, or paralithic
contact, whichever is shallower.
Characteristically, Haplotorrands have an ochric or mollic
epipedon and a cambic horizon.
The Haplotorrands in the United States generally developed
in late-Pleistocene deposits. Most formed under grass or shrub
vegetation, and some have widely spaced trees.
Definition
Haplotorrands are the Torrands that:
1. Do not have, in 75 percent or more of each pedon, a
cemented horizon that has its upper boundary within 100 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower;
2. Have, on air-dried samples, a 1500 kPa water retention of
15 percent or more throughout less than 60 percent of the
thickness either:
a. Within 60 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever
296 Soil Taxonomy
is shallower, if there is no densic, lithic, or paralithic
contact, duripan, or petrocalcic horizon within that depth;
or
b. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon.
Key to Subgroups
DCCA. Haplotorrands that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Haplotorrands
DCCB. Other Haplotorrands that have a horizon 15 cm or
more thick that has 20 percent or more (by volume) cemented
soil material and has its upper boundary within 100 cm of the
mineral soil surface.
Duric Haplotorrands
DCCC. Other Haplotorrands that have a calcic horizon that
has its upper boundary within 125 cm of the mineral soil
surface.
Calcic Haplotorrands
DCCD. Other Haplotorrands.
Typic Haplotorrands
Definition of Typic Haplotorrands
Typic Haplotorrands are the Haplotorrands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have 20 percent or more (by volume) cemented soil
material in a horizon that has its upper boundary within 100
cm of the mineral soil surface and is more than 15 cm thick;
3. Do not have a calcic horizon with its upper boundary
within 125 cm of the mineral soil surface.
Description of Subgroups
Typic Haplotorrands.—The central concept or Typic
subgroup of Haplotorrands is fixed on moderately deep or deep
soils that have no horizon 15 cm or more thick that has 20
percent or more (by volume) cemented soil material and has its
upper boundary within 100 cm of the mineral soil surface.
These soils do not have a calcic horizon that has its upper
boundary within 125 cm of the mineral soil surface. Soils that
have a lithic contact within a depth of 50 cm are assigned to
the Lithic subgroup.
Typic Haplotorrands are known to occur only in Hawaii and
are of small extent in the United States. They commonly
support grassy or shrub vegetation. Most are used as rangeland,
but some are used as recreational areas.
Calcic Haplotorrands.—These soils are like Typic
Haplotorrands, but they have a calcic horizon that has its upper
boundary within 125 cm of the mineral soil surface. They are
known to occur only in Hawaii and are of small extent in the
United States. They commonly support grassy or shrub
vegetation. Most of the soils are used as rangeland, but some
are used as recreational areas.
Duric Haplotorrands.—These soils are like Typic
Haplotorrands, but they have 20 percent or more (by volume)
cemented soil material in a horizon that has its upper boundary
within 100 cm of the mineral soil surface and is more than 15
cm thick. These soils are known to occur only in Hawaii and
are of small extent in the United States. They commonly
support grassy or shrub vegetation. Most of the soils are used
as rangeland, but some are used as recreational areas.
Lithic Haplotorrands.—These soils are like Typic
Haplotorrands, but they have a lithic contact within a depth of
50 cm. They have not been recognized in the United States.
Vitritorrands
Vitritorrands are the Torrands that do not have a cemented
horizon that has its upper boundary within 100 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower. They have, on air-dried
samples, a 1500 kPa water retention of less than 15 percent
throughout 60 percent or more of the thickness between the
mineral soil surface or the top of an organic layer with andic
soil properties, whichever is shallower, and a point 60 cm
below the starting point or a densic, lithic, or paralithic
contact, whichever is shallower.
Characteristically, Vitritorrands have an ochric or mollic
epipedon and a cambic horizon.
The Vitritorrands in the United States generally developed
in Holocene deposits. Most formed under grass or shrub
vegetation, and some have widely spaced trees.
Definition
Vitritorrands are the Torrands that:
1. Have, on air-dried samples, a 1500 kPa water retention of
less than 15 percent throughout 60 percent or more of the
thickness either:
a. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, if there is no paralithic contact or duripan within
that depth, and a point 60 cm below that depth; or
b. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a paralithic contact or a duripan; and
2. Do not have, in 75 percent or more of each pedon, a
cemented horizon that has its upper boundary within 100 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Andisols 297
KeytoSubgroups
DCBA. Vitritorrands that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Vitritorrands
DCBB. Other Vitritorrands that have a horizon 15 cm or
more thick that has 20 percent or more (by volume) cemented
soil material and has its upper boundary within 100 cm of the
mineral soil surface.
Duric Vitritorrands
DCBC. Other Vitritorrands that have, in one or more
horizons at a depth between 50 and 100 cm from the mineral
soil surface, aquic conditions for some time in normal years (or
artificial drainage) and one or more of the following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
3. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Vitritorrands
DCBD. Other Vitritorrands that have a calcic horizon that
has its upper boundary within 125 cm of the mineral soil
surface.
Calcic Vitritorrands
DCBE. Other Vitritorrands.
Typic Vitritorrands
Definition of Typic Vitritorrands
Typic Vitritorrands are the Vitritorrands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have 20 percent or more (by volume) cemented soil
material in a horizon that has its upper boundary within 100
cm of the mineral soil surface and is more than 15 cm thick;
3. Do not have, in any horizon at a depth between 50 and 100
cm from the mineral soil surface, both aquic conditions and
any of the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated; and
4. Do not have a calcic horizon with its upper boundary within
125 cm of the mineral soil surface.
Description of Subgroups
Typic Vitritorrands.—The central concept or Typic
subgroup of Vitritorrands is fixed on moderately deep or deep
soils that have no horizon 15 cm or more thick that has 20
percent or more (by volume) cemented soil material and has its
upper boundary within 100 cm of the mineral soil surface.
These soils do not have a calcic horizon that has its upper
boundary within 125 cm of the mineral soil surface. Soils that
have a lithic contact within a depth of 50 cm are assigned to
the Lithic subgroup.
Typic Vitritorrands are known to occur only in Oregon and
are of small extent in the United States. They commonly
support grassy or shrub vegetation and some widely spaced
trees. Most of the soils are used as rangeland, but some are
used as recreational areas.
Aquic Vitritorrands.—These soils are like Typic
Vitritorrands, but they have both aquic conditions (or artificial
drainage) and redox features in a horizon at a depth between
50 and 100 cm either from the mineral soil surface or from the
top of an organic layer with andic soil properties, whichever is
shallower. These soils are not known to occur in the United
States.
Calcic Vitritorrands.—These soils are like Typic
Vitritorrands, but they have a calcic horizon that has its upper
boundary within 125 cm of the mineral soil surface. These soils
are not known to occur in the United States.
Duric Vitritorrands.—These soils are like Typic
Vitritorrands, but they have 20 percent or more (by volume)
cemented soil material in a horizon that has its upper boundary
within 100 cm of the mineral soil surface and is more than 15
cm thick. These soils are not known to occur in the United
States.
Lithic Vitritorrands.—These soils are like Typic
Vitritorrands, but they have a lithic contact within a depth of
50 cm. They have not been recognized in the United States.
Udands
Udands are the more or less well drained Andisols of moist
regions. These soils are moderately extensive. They are mostly
on the Pacific rim, mainly in the western part of North
America and in Japan, New Zealand, the Philippines, and
Indonesia. Most of the Udands in the United States are in
Washington and Oregon, but some are in Hawaii. Most Udands
formed under forest vegetation.
Characteristically, Udands have an ochric or umbric
epipedon and a cambic horizon. Some have a duripan.
298 Soil Taxonomy
Most of the Udands in the United States developed in latePleistocene
or Holocene deposits.
Definition
Udands are the Andisols that:
1. Have a udic soil moisture regime;
2. Have a frigid or warmer soil temperature regime;
3. Do not have a histic epipedon or the aquic conditions
characteristic of Aquands; and
4. Have a 1500 kPa water retention of 15 percent or more on
air-dried samples and 30 percent or more on undried samples
throughout more than 40 percent of the thickness either:
a. Within 60 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever
is shallower, if there is no densic, lithic, or paralithic
contact, duripan, or petrocalcic horizon within that depth;
or
b. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon.
Key to Great Groups
DGA. Udands that have, in half or more of each pedon, a
placic horizon within 100 cm either of the mineral soil surface
or of the top of an organic layer with andic soil properties,
whichever is shallower.
Placudands, p. 314
DGB. Other Udands that have, in 75 percent or more of each
pedon, a cemented horizon that has its upper boundary within
100 cm either of the mineral soil surface or of the top of an
organic layer with andic soil properties, whichever is
shallower.
Durudands, p. 298
DGC. Other Udands that have a melanic epipedon.
Melanudands, p. 310
DGD. Other Udands that have, on undried samples, a 1500
kPa water retention of 100 percent or more, by weighted
average, throughout either:
1. One or more layers with a total thickness of 35 cm
between the mineral soil surface or the top of an organic
layer with andic soil properties, whichever is shallower, and
100 cm from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, if there is no densic, lithic, or paralithic contact,
duripan, or petrocalcic horizon within that depth; or
2. 60 percent or more of the horizon thickness between
either the mineral soil surface or the top of an organic layer
with andic soil properties, whichever is shallower, and a
densic, lithic, or paralithic contact, a duripan, or a
petrocalcic horizon.
Hydrudands, p. 308
DGE. Other Udands that have a layer that meets the depth,
thickness, and organic-carbon requirements for a melanic
epipedon.
Fulvudands, p. 300
DGF. Other Udands.
Hapludands, p. 303
Durudands
Durudands are moderately deep or shallow Udands that do
not have a placic horizon. In 75 percent or more of each pedon,
they have a cemented horizon that has its upper boundary
within 100 cm of the mineral soil surface or of the upper
boundary of an organic layer that has andic soil properties,
whichever is shallower.
Characteristically, Durudands have a thin O horizon, an
ochric or umbric epipedon, a cambic horizon, and a cemented
horizon.
The Durudands in the United States generally developed in
late-Pleistocene deposits. Most formed under coniferous forest
vegetation.
Definition
Durudands are the Udands that:
1. Do not have, in half or more of each pedon, a placic
horizon within 100 cm of the mineral soil surface or of the
upper boundary of an organic layer that has andic soil
properties, whichever is shallower; and
2. Have, in 75 percent or more of each pedon, a cemented
horizon with its upper boundary within 100 cm of the mineral
soil surface or of the upper boundary of an organic layer that
has andic soil properties, whichever is shallower.
Key to Subgroups
DGBA. Durudands that have, in one or more horizons above
the cemented horizon, aquic conditions for some time in
normal years (or artificial drainage) and one or more of the
following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
3. Enough active ferrous iron to give a positive reaction to
Andisols 299
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Durudands
DGBB. Other Durudands that have extractable bases (by
NH4
OAc) plus 1N KCl-extractable Al3+
totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more horizons
with a total thickness of 30 cm or more at a depth between 25
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, and the cemented horizon.
Acrudoxic Durudands
DGBC. Other Durudands that have, on undried samples, a
1500 kPa water retention of 70 percent or more throughout a
layer 35 cm or more thick above the cemented horizon.
Hydric Durudands
DGBD. Other Durudands that have more than 6.0 percent
organic carbon and the colors of a mollic epipedon throughout
a layer 50 cm or more thick within 60 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Pachic Durudands
DGBE. Other Durudands.
Typic Durudands
Definition of Typic Durudands
Typic Durudands are the Durudands that:
1. Do not have, in any horizon at a depth between 50 cm
either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, and the cemented horizon, both aquic conditions
and any of the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated;
2. Do not have, on undried samples, a 1500 kPa water
retention of 70 percent or more throughout a continuous
thickness of 35 cm or more above the cemented horizon;
3. Have extractable bases (by NH4
OAc) plus 1N KClextractable
Al3+
of 2.0 or more cmol(+) kg-1
in the fine-earth
fraction of all subhorizons 30 cm or more thick at a depth
between either 25 cm from the mineral soil surface or from the
top of an organic layer with andic soil properties, whichever is
shallower, and the cemented horizon; and
4. Do not have more than 6.0 percent organic carbon and the
colors of a mollic epipedon throughout a layer 50 cm or more
thick within 60 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Description of Subgroups
Typic Durudands.—The central concept or Typic subgroup
of Durudands is fixed on moderately deep or shallow soils that
have, on undried samples, a 1500 kPa water retention of less
than 70 percent throughout all layers 35 cm or more thick
above the cemented horizon.
Soils that have both aquic conditions (or artificial drainage)
and redox features in any horizon at a depth between 50 and
100 cm either from the mineral soil surface or from the top of
an organic layer with andic soil properties, whichever is
shallower, are excluded from the Typic subgroup and are
considered intergrades to Aquands. Soils that have more than
6.0 percent organic carbon and the colors of a mollic epipedon
throughout a layer 50 cm or more thick within 60 cm either of
the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower, also are
excluded.
Typic Durudands are moderately extensive in the United
States. They commonly support coniferous forest vegetation.
Most of these soils are used for timber production, but some are
used as recreational areas.
Acrudoxic Durudands.—These soils are like Typic
Durudands, but they have extractable bases plus 1N KClextractable
Al3+
totaling less than 2.0 cmol(+)/kg in the fineearth
fraction of one or more horizons with a total thickness of
30 cm or more at a depth between 25 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, and the cemented
horizon. These soils have not been recognized in the United
States.
Aquic Durudands.—These soils are like Typic Durudands,
but they have both aquic conditions (or artificial drainage) and
redox features in a horizon at a depth between 50 cm either
from the mineral soil surface or from the top of an organic
layer with andic soil properties, whichever is shallower, and
the cemented horizon. These soils are of small extent in the
State of Washington. Most of the soils are used for timber
production.
Hydric Durudands.—These soils are like Typic
Durudands, but they have, on undried samples, a 1500 kPa
water retention of 70 percent or more throughout a layer 35 cm
or more thick above the cemented horizon. These soils are rare
and are known to occur only in Hawaii.
Pachic Durudands.—These soils are like Typic Durudands,
but they have more than 6.0 percent organic carbon and the
colors of a mollic epipedon throughout a layer 50 cm or more
thick within 60 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
300 Soil Taxonomy
shallower. These soils are not known to occur in the United
States.
Fulvudands
Fulvudands are the Udands that do not have a melanic
epipedon but have a layer that meets the depth, thickness, and
organic-carbon requirements for a melanic epipedon. These
soils can have a lithic contact. In 75 percent or more of each
pedon, however, they do not have a placic horizon or any other
cemented horizon with its upper boundary within 100 cm of
the mineral soil surface or of the upper boundary of an organic
layer that has andic soil properties, whichever is shallower.
The soils have, on undried samples, a 1500 kPa water retention
of less than 100 percent, by weighted average, throughout the
major part of the andic materials.
Characteristically, Fulvudands have a thin O horizon, an
umbric epipedon, and a cambic horizon.
The Fulvudands in the United States generally developed in
late-Pleistocene deposits. Most formed under coniferous forest
vegetation.
Definition
Fulvudands are the Udands that:
1. Do not have, within 100 cm of the mineral soil surface or
of the upper boundary of an organic layer that has andic soil
properties, whichever is shallower, the upper boundary of a
placic horizon that occurs in half or more of each pedon and
can have a lithic contact but do not have any other cemented
horizon that occurs in 75 percent or more of each pedon within
these depths;
2. Do not have, on undried samples, a 1500 kPa water
retention of 100 percent or more, by weighted average,
throughout either:
a. One or more layers with a total thickness of 35 cm
between the mineral soil surface or the top of an organic
layer with andic soil properties, whichever is shallower, and
100 cm from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, if there is no densic, lithic, or paralithic contact,
duripan, or petrocalcic horizon within that depth; or
b. 60 percent or more of the horizon thickness between
either the mineral soil surface or the top of an organic layer
with andic soil properties, whichever is shallower, and a
densic, lithic, or paralithic contact, a duripan, or a
petrocalcic horizon; and
3. Do not have a melanic epipedon but have a layer that
meets the depth, thickness, and organic-carbon requirements
for a melanic epipedon.
Key to Subgroups
DGEA. Fulvudands that have both:
1. A lithic contact within 50 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower; and
2. No horizons with more than 2.0 cmol(+)/kg Al3+
(by 1N
KCl) in the fine-earth fraction and with a total thickness of
10 cm or more at a depth between 25 cm from the mineral
soil surface or from the top of an organic layer with andic
soil properties, whichever is shallower, and the lithic
contact.
Eutric Lithic Fulvudands
DGEB. Other Fulvudands that have a lithic contact within 50
cm either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Lithic Fulvudands
DGEC. Other Fulvudands that have, in one or more horizons
at a depth between 50 and 100 cm either from the mineral soil
surface or from the top of an organic layer with andic soil
properties, whichever is shallower, aquic conditions for some
time in normal years (or artificial drainage) and one or more of
the following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
3. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Fulvudands
DGED. Other Fulvudands that have, on undried samples, a
1500 kPa water retention of 70 percent or more throughout a
layer 35 cm or more thick within 100 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Hydric Fulvudands
DGEE. Other Fulvudands that have extractable bases (by
NH4
OAc) plus 1N KCl-extractable Al3+
totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more horizons
with a total thickness of 30 cm or more at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower.
Acrudoxic Fulvudands
DGEF. Other Fulvudands that have an argillic or kandic
horizon that has both:
1. An upper boundary within 125 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower; and
Andisols 301
2. A base saturation (by sum of cations) of less than 35
percent throughout its upper 50 cm.
Ultic Fulvudands
DGEG. Other Fulvudands that have both:
1. No horizons with more than 2.0 cmol(+)/kg Al3+
(by 1N
KCl) in the fine-earth fraction and with a total thickness of
10 cm or more at a depth between 25 and 50 cm either from
the mineral soil surface or from the top of an organic layer
with andic soil properties, whichever is shallower; and
2. Throughout a layer 50 cm or more thick within 60 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower:
a. More than 6.0 percent organic carbon, by weighted
average; and
b. More than 4.0 percent organic carbon in all parts.
Eutric Pachic Fulvudands
DGEH. Other Fulvudands that have no horizons with more
than 2.0 cmol(+)/kg Al3+
(by 1N KCl) in the fine-earth fraction
and with a total thickness of 10 cm or more at a depth between
25 and 50 cm either from the mineral soil surface or from the
top of an organic layer with andic soil properties, whichever is
shallower.
Eutric Fulvudands
DGEI. Other Fulvudands that have, throughout a layer 50 cm
or more thick within 60 cm either of the mineral soil surface or
of the top of an organic layer with andic soil properties,
whichever is shallower:
1. More than 6.0 percent organic carbon, by weighted
average; and
2. More than 4.0 percent organic carbon in all parts.
Pachic Fulvudands
DGEJ. Other Fulvudands that have, at a depth between 40
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Fulvudands
DGEK. Other Fulvudands.
Typic Fulvudands
Definition of Typic Fulvudands
Typic Fulvudands are the Fulvudands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have, in any horizon at a depth between 50 and 100
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, both aquic conditions and any of the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated;
3. Do not have throughout a layer 50 cm or more thick within
60 cm either of the mineral soil surface or of the top of an
organic layer with andic soil properties, whichever is
shallower, both:
a. More than 6.0 percent organic carbon, by weighted
average; and
b. More than 4.0 percent organic carbon in all parts;
4. On undried samples, have a 1500 kPa water retention of
less than 70 percent throughout all layers 35 cm or more thick
within the upper 100 cm;
5. Do not have, between depths of 40 and 100 cm, a layer 10
cm or more thick with more than 3.0 percent organic carbon
and the colors of a mollic epipedon throughout, occurring
below a horizon or horizons 10 cm or more thick with a color
value 1 unit or more higher and an organic-carbon content 1
percent or more lower;
6. Have an Al3+
(1N KCl extractable) of 2.0 cmol(+)/kg in the
fine-earth fraction throughout all layers 10 cm or more thick
between depths of 25 and 50 cm;
7. Have extractable bases (by NH4
OAc) plus 1N KClextractable
Al3+
of 2.0 or more cmol(+) kg-1
in the fine-earth
fraction of all subhorizons 30 cm or more thick between depths
of 25 and 100 cm; and
8. Do not have an argillic or kandic horizon that has its
upper boundary within 125 cm of the mineral soil surface or of
the upper boundary of an organic layer with andic soil
properties, whichever is shallower, and base saturation (by sum
of cations) of less than 35 percent throughout the upper 50 cm
of that horizon.
Description of Subgroups
Typic Fulvudands.—The central concept or Typic subgroup
of Fulvudands is fixed on moderately deep or deep soils that
have a relatively high amount of aluminum. These soils have,
on undried samples, a 1500 kPa water retention of less than 70
302 Soil Taxonomy
percent throughout all layers 35 cm or more thick within 100
cm either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower. Soils
that have, at a depth between 40 and 100 cm either from the
mineral soil surface or from the top of an organic layer with andic
soil properties, whichever is shallower, a dark colored layer 10
cm or more thick with more than 3.0 percent organic carbon,
underlying one or more lighter colored horizons with a total
thickness of 10 cm or more and a lower content of organic
carbon, are excluded from the Typic subgroup. The upper part
of Typic Fulvudands has extractable bases plus 1N KClextractable
Al3+
that total more than 2.0 cmol(+)/kg in the fineearth
fraction of one or more horizons with a total thickness of
30 cm or more.
Soils that have both aquic conditions (or artificial drainage)
and redox features in any horizon at a depth between 50 and
100 cm either from the mineral soil surface or from the top of
an organic layer with andic soil properties, whichever is
shallower, are excluded from the Typic subgroup and are
considered intergrades to Aquands. Soils that average more
than 6.0 percent organic carbon throughout a layer 50 cm or
more thick in the upper part also are excluded.
Typic Fulvudands are moderately extensive in the United
States. They commonly support coniferous forest vegetation.
Most of these soils are used for timber production, but some are
used as cropland.
Acrudoxic Fulvudands.—These soils are like Typic
Fulvudands, but they have extractable bases plus 1N KClextractable
Al3+
totaling less than 2.0 cmol(+)/kg in the fineearth
fraction of one or more horizons with a total thickness of
30 cm or more at a depth between 25 and 100 cm either from
the mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower. These soils are
not known to occur in the United States. They are established
for use in other countries.
Aquic Fulvudands.—These soils are like Typic Fulvudands,
but they have both aquic conditions (or artificial drainage) and
redox features in a horizon at a depth between 50 and 100 cm
either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower. These soils are of small extent and are known to
occur only in the State of Washington in the United States.
Most of the soils are used for timber production.
Eutric Fulvudands.—These soils are like Typic
Fulvudands, but they do not have one or more horizons with
more than 2.0 cmol(+)/kg Al3+
(by 1N KCl) in the fine-earth
fraction and with a total thickness of 10 cm or more at a depth
between 25 and 50 cm either from the mineral soil surface or
from the top of an organic layer with andic soil properties,
whichever is shallower. These soils are not known to occur in
the United States. They are established for use in other
countries.
Eutric Lithic Fulvudands.—These soils are like Typic
Fulvudands, but they have a lithic contact within 50 cm either
of the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower. They do not have
one or more horizons with more than 2.0 cmol(+)/kg Al3+
(by 1N
KCl) in the fine-earth fraction and with a total thickness of 10 cm
or more at a depth between 25 and 50 cm either from the mineral
soil surface or from the top of an organic layer with andic soil
properties, whichever is shallower. These soils are of small
extent and are known to occur only in the State of Washington
in the United States. Most of the soils are used for timber
production, but some are used as recreational areas.
Eutric Pachic Fulvudands.—These soils are like Typic
Fulvudands, but they do not have horizons with more than 2.0
cmol(+)/kg Al3+
(by 1N KCl) in the fine-earth fraction and with
a total thickness of 10 cm or more at a depth between 25 and
50 cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower. They have, throughout a layer 50 cm or more thick
within 60 cm either of the mineral soil surface or of the top of
an organic layer with andic soil properties, whichever is
shallower, both more than 6.0 percent organic carbon, by
weighted average, and more than 4.0 percent organic carbon in
all parts.
Hydric Fulvudands.—These soils are like Typic
Fulvudands, but they have, on undried samples, a 1500 kPa
water retention of 70 percent or more throughout a layer 35 cm
or more thick within 100 cm of the mineral soil surface or of
the top of an organic layer with andic soil properties,
whichever is shallower. These soils are not known to occur in
the United States. They are established for use in other
countries.
Lithic Fulvudands.—These soils are like Typic
Fulvudands, but they have a lithic contact within 50 cm either
of the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower. These soils are of
small extent and are known to occur only in the State of
Washington. Most of the soils are used for timber production,
but some are used as recreational areas.
Pachic Fulvudands.—These soils are like Typic
Fulvudands, but they have, throughout a layer 50 cm or more
thick within 60 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower, both more than 6.0 percent organic carbon, by
weighted average, and more than 4.0 percent organic carbon in
all parts. These soils are not known to occur in the United
States.
Thaptic Fulvudands.—These soils are like Typic
Fulvudands, but they have, between depths of 25 and 100 cm, a
buried, dark colored layer 10 cm or more thick below a lighter
colored horizon or horizons 10 cm or more thick with a lower
content of organic carbon. These soils have not been
recognized in the United States.
Ultic Fulvudands.—These are the Fulvudands that have an
argillic or kandic horizon with a base saturation of less than 35
percent throughout the upper 50 cm. These soils do not have a
Andisols 303
lithic contact within 50 cm of the mineral soil surface or aquic
conditions within 100 cm of the mineral soil surface. They occur
in the Pacific Northwest, where they formed under forest
vegetation.
Hapludands
Hapludands are the Udands that do not have a melanic
epipedon or a layer that meets the depth, thickness, and
organic-carbon requirements for a melanic epipedon. They do
not have a placic horizon with its upper boundary within 100
cm of the mineral soil surface or of the upper boundary of an
organic layer that has andic soil properties, whichever is
shallower. They can have a lithic contact but do not have any
other cemented horizon in 75 percent or more of each pedon
within these depths. They have, on undried samples, a 1500
kPa water retention of less than 100 percent, by weighted
average, throughout the major part of the andic materials.
Commonly, Hapludands have a thin O horizon, an ochric or
umbric epipedon, and a cambic horizon.
Most of the Hapludands in the United States developed in
late-Pleistocene or Holocene deposits. Most formed under
coniferous forest vegetation.
Definition
Hapludands are the Udands that:
1. Do not have, in half or more of each pedon, a placic
horizon within 100 cm of the mineral soil surface or of the
upper boundary of an organic layer that has andic soil
properties, whichever is shallower;
2. Do not have, in 75 percent or more of each pedon, a
cemented horizon with its upper boundary within 100 cm of
the mineral soil surface or of the upper boundary of an organic
layer that has andic soil properties, whichever is shallower;
3. Do not have a melanic epipedon or an epipedon meeting
the depth, thickness, and organic-carbon requirements for a
melanic epipedon; and
4. Have, on undried samples, a 1500 kPa water retention of
less than 100 percent, by weighted average, throughout all
layers 35 cm or more thick within 100 cm of the mineral soil
surface or of the upper boundary of an organic layer that has
andic soil properties, whichever is shallower.
Key to Subgroups
DGFA. Hapludands that have a lithic contact within 50 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Lithic Hapludands
DGFB. Other Hapludands that have anthraquic conditions.
Anthraquic Hapludands
DGFC. Other Hapludands that have both:
1. A horizon 15 cm or more thick that has 20 percent or more
(by volume) cemented soil material and has its upper
boundary within 100 cm either of the mineral soil surface or
of the top of an organic layer with andic soil properties,
whichever is shallower; and
2. In one or more horizons at a depth between 50 and 100
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, aquic conditions for some time in normal years
(or artificial drainage) and one or more of the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on
faces of peds or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction
to alpha,alpha-dipyridyl at a time when the soil is not
being irrigated.
Aquic Duric Hapludands
DGFD. Other Hapludands that have a horizon 15 cm or more
thick that has 20 percent or more (by volume) cemented soil
material and has its upper boundary within 100 cm either of
the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower.
Duric Hapludands
DGFE. Other Hapludands that have more than 2.0
cmol(+)/kg Al3+
(by 1N KCl) in the fine-earth fraction of one
or more horizons with a total thickness of 10 cm or more at a
depth between 25 and 50 cm either from the mineral soil
surface or from the top of an organic layer with andic soil
properties, whichever is shallower.
Alic Hapludands
DGFF. Other Hapludands that have, in one or more horizons
at a depth between 50 and 100 cm either from the mineral soil
surface or from the top of an organic layer with andic soil
properties, whichever is shallower, aquic conditions for some
time in normal years (or artificial drainage) and one or more of
the following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
3. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Hapludands
304 Soil Taxonomy
DGFG. Other Hapludands that have both:
1. Extractable bases (by NH4
OAc) plus 1N KClextractable
Al3+
totaling less than 2.0 cmol(+)/kg in the
fine-earth fraction of one or more horizons with a total
thickness of 30 cm or more at a depth between 25 and 100
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower; and
2. On undried samples, a 1500 kPa water retention of 70
percent or more throughout a layer 35 cm or more thick
within 100 cm either of the mineral soil surface or of the top
of an organic layer with andic soil properties, whichever is
shallower.
Acrudoxic Hydric Hapludands
DGFH. Other Hapludands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, both:
1. Extractable bases (by NH4
OAc) plus 1N KClextractable
Al3+
totaling less than 2.0 cmol(+)/kg in the
fine-earth fraction of one or more horizons with a total
thickness of 30 cm or more; and
2. A layer 10 cm or more thick with more than 3.0 percent
organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent
or more (absolute) lower.
Acrudoxic Thaptic Hapludands
DGFI. Other Hapludands that have both:
1. Extractable bases (by NH4
OAc) plus 1N KClextractable
Al3+
totaling less than 2.0 cmol(+)/kg in the
fine-earth fraction of one or more horizons with a total
thickness of 30 cm or more at a depth between 25 and 100
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower; and
2. An argillic or kandic horizon that has both:
a. An upper boundary within 125 cm either of the
mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower; and
b. A base saturation (by sum of cations) of less than 35
percent throughout its upper 50 cm.
Acrudoxic Ultic Hapludands
DGFJ. Other Hapludands that have extractable bases (by
NH4
OAc) plus 1N KCl-extractable Al3+
totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more horizons
with a total thickness of 30 cm or more at a depth between 25
and 100 cm either from the mineral soil surface or from the top of
an organic layer with andic soil properties, whichever is
shallower.
Acrudoxic Hapludands
DGFK. Other Hapludands that have a 1500 kPa water
retention of less than 15 percent on air-dried samples and less
than 30 percent on undried samples throughout one or more
layers that have andic soil properties and have a total thickness
of 25 cm or more within 100 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Vitric Hapludands
DGFL. Other Hapludands that have both:
1. On undried samples, a 1500 kPa water retention of 70
percent or more throughout a layer 35 cm or more thick
within 100 cm either of the mineral soil surface or of the top
of an organic layer with andic soil properties, whichever is
shallower; and
2. At a depth between 25 and 100 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, a layer 10 cm
or more thick with more than 3.0 percent organic carbon
and the colors of a mollic epipedon throughout, underlying
one or more horizons with a total thickness of 10 cm or
more that have a color value, moist, 1 unit or more higher
and an organic-carbon content 1 percent or more (absolute)
lower.
Hydric Thaptic Hapludands
DGFM. Other Hapludands that have, on undried samples, a
1500 kPa water retention of 70 percent or more throughout a
layer 35 cm or more thick within 100 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Hydric Hapludands
DGFN. Other Hapludands that have both:
1. A sum of extractable bases of more than 25.0
cmol(+)/kg in the fine-earth fraction throughout one or
more horizons with a total thickness of 15 cm or more at a
depth between 25 and 75 cm either from the mineral soil
surface or from the top of an organic layer with andic soil
properties, whichever is shallower; and
2. At a depth between 25 and 100 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, a layer 10 cm
or more thick with more than 3.0 percent organic carbon
and the colors of a mollic epipedon throughout, underlying
one or more horizons with a total thickness of 10 cm or
Andisols 305
more that have a color value, moist, 1 unit or more higher
and an organic-carbon content 1 percent or more (absolute)
lower.
EutricThapticHapludands
DGFO. Other Hapludands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Hapludands
DGFP. Other Hapludands that have a sum of extractable
bases of more than 25.0 cmol(+)/kg in the fine-earth fraction
throughout one or more horizons with a total thickness of 15
cm or more at a depth between 25 and 75 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower.
Eutric Hapludands
DGFQ. Other Hapludands that have an oxic horizon that has
its upper boundary within 125 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Oxic Hapludands
DGFR. Other Hapludands that have an argillic or kandic
horizon that has both:
1. An upper boundary within 125 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower; and
2. A base saturation (by sum of cations) of less than 35
percent throughout its upper 50 cm.
Ultic Hapludands
DGFS. Other Hapludands that have an argillic or kandic
horizon that has its upper boundary within 125 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower.
Alfic Hapludands
DGFT. Other Hapludands.
Typic Hapludands
Definition of Typic Hapludands
Typic Hapludands are the Hapludands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have a horizon with its upper boundary within 100
cm of the mineral soil surface or of the upper boundary of an
organic layer that has andic soil properties, whichever is
shallower, that is more than 15 cm thick and that has 20 percent
or more (by volume) cemented soil material;
3. Do not have, in any horizon at a depth between 50 and 100
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, both aquic conditions and any of the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated;
4. Do not have anthraquic conditions;
5. Have, on undried samples, a 1500 kPa water retention of
less than 70 percent throughout all layers 35 cm or more thick
within 100 cm either of the mineral soil surface or of the top of
an organic layer with andic soil properties, whichever is
shallower;
6. Have a 1500 kPa water retention of 15 percent or more on
air-dried samples or 30 percent or more on undried samples
throughout all layers that have andic soil properties and have a
total thickness of 25 cm or more within 100 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower;
7. Have 1N KCl-extractable Al3+
of 2.0 or less cmol(+) kg-1
in
the fine-earth fraction throughout all layers 10 cm or more
thick between depths of 25 and 50 cm;
8. Do not have, between depths of 25 and 100 cm, a layer 10
cm or more thick with more than 3.0 percent organic carbon
and the colors of a mollic epipedon throughout, occurring
below a horizon or horizons 10 cm or more thick with a color
value, moist, 1 unit or more higher and an organic-carbon
content 1 percent or more lower;
9. Have a sum of bases of 25.0 or less cmol(+) kg-1
in the
fine-earth fraction of one or more subhorizons 35 cm or more
thick between depths of 25 and 75 cm;
10. Have extractable bases (by NH4
OAc) plus 1N KClextractable
Al3+
of 2.0 or more cmol(+) kg-1
in the fine-earth
fraction of all subhorizons 30 cm or more thick between depths
of 25 and 100 cm; and
11. Do not have an argillic, kandic, or oxic horizon with its
upper boundary within 125 cm of the mineral soil surface or of
the upper boundary of an organic layer that has andic soil
properties, whichever is shallower.
306 Soil Taxonomy
Description of Subgroups
Typic Hapludands.—The central concept or Typic
subgroup of Hapludands is fixed on moderately deep or deep
soils that have 2.0 or less cmol(+)/kg Al3+
(by 1N KCl) in the
fine-earth fraction of a layer 10 cm or more thick at a depth
between 25 and 50 cm either from the mineral soil surface or
from the top of an organic layer with andic soil properties,
whichever is shallower. These soils have, within 100 cm either
of the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower, a 1500 kPa water
retention of 15 percent or more on air-dried samples
throughout all layers 25 cm or more thick and between 30 and
70 percent on undried samples throughout all layers 35 cm or
more thick. The sum of extractable bases is 25.0 cmol(+)/kg or
less throughout horizons with a total thickness of 15 cm or more
in the upper part of the soils.
Soils that have, at a depth between 40 and 100 cm either from
the mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, a dark colored layer
10 cm or more thick with more than 3.0 percent organic carbon,
underlying one or more lighter colored horizons with a total
thickness of 10 cm or more and a lower content of organic
carbon, are excluded from the Typic subgroup. Typic
Hapludands do not have a horizon 15 cm or more thick with 20
percent or more (by volume) cemented soil material in the upper
part. Extractable bases plus 1N KCl-extractable Al3+
total more
than 2.0 cmol(+)/kg in the fine-earth fraction of one or more
horizons with a total thickness of 30 cm or more in the upper part
of these soils.
Soils that have anthraquic conditions and soils with both
aquic conditions (or artificial drainage) and redox features in
any horizon at a depth between 50 and 100 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, are excluded
from the Typic subgroup and are considered intergrades to
Aquands. Soils that have a lithic contact within a depth of 50
cm are assigned to the Lithic subgroup.
Typic Hapludands are moderately extensive in the United
States. They commonly support coniferous forest vegetation.
Most of these soils are used for timber production, but some
have been cleared and are used as cropland.
Acrudoxic Hapludands.—These soils are like Typic
Hapludands, but they have extractable bases plus 1N KClextractable
Al3+
totaling less than 2.0 cmol(+)/kg in the fineearth
fraction of one or more horizons with a total thickness of
30 cm or more at a depth between 25 and 100 cm either from
the mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower. These soils are
not known to occur in the United States. They are established
for use in other countries.
Acrudoxic Hydric Hapludands.—These soils are like
Typic Hapludands, but they have extractable bases plus 1N
KCl-extractable Al3+
totaling less than 2.0 cmol(+)/kg in the
fine-earth fraction of one or more horizons with a total
thickness of 30 cm or more at a depth between 25 and 100 cm
either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower. They also have, on undried samples, a 1500 kPa
water retention of 70 percent or more throughout a layer 35 cm
or more thick within 100 cm of the mineral soil surface or of
the top of an organic layer with andic soil properties,
whichever is shallower. These soils are not known to occur in
the United States. They are established for use in other
countries.
Acrudoxic Thaptic Hapludands.—Thesesoilsarelike
Typic Hapludands, but they have, between depths of 25 and
100 cm, a buried, dark colored layer 10 cm or more thick
below a lighter colored horizon or horizons 10 cm or more
thick with a lower content of organic carbon. They also have
extractable bases plus 1N KCl-extractable Al3+
totaling less
than 2.0 cmol(+)/kg in the fine-earth fraction of one or more
horizons with a total thickness of 30 cm or more at a depth
between 25 and 100 cm either from the mineral soil surface or
from the top of an organic layer with andic soil properties,
whichever is shallower. These soils are not known to occur in
the United States. They are established for use in other
countries.
Acrudoxic Ultic Hapludands.—These soils are like Typic
Hapludands, but they have extractable bases plus 1N KClextractable
Al3+
totaling less than 2.0 cmol(+)/kg in the fineearth
fraction of one or more horizons with a total thickness of
30 cm or more at a depth between 25 and 100 cm either from
the mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower. They also have
an argillic or kandic horizon that has both an upper boundary
within 125 cm either of the mineral soil surface or of the top of
an organic layer with andic soil properties, whichever is
shallower, and a base saturation (by sum of cations) of less
than 35 percent throughout the upper 50 cm or throughout the
entire horizon if it is less than 50 cm thick. These soils are not
known to occur in the United States. They are established for
use in other countries.
Alfic Hapludands.—These soils are like Typic Hapludands,
but they have an argillic or kandic horizon that has both an
upper boundary within 125 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower, and a base saturation (by
sum of cations) of 35 percent or more in some part of the upper
50 cm or in the entire horizon if it is less than 50 cm thick.
These soils are not known to occur in the United States. They
are established for use in other countries.
Alic Hapludands.—These soils are like Typic Hapludands,
but they have more than 2.0 cmol(+)/kg Al3+
(by 1N KCl) in
the fine-earth fraction of one or more horizons with a total
thickness of 10 cm or more at a depth between 25 and 50 cm
either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
Andisols 307
shallower. These soils are moderately extensive in the United
States. They commonly support coniferous forest vegetation.
Most of the soils are used for timber production, but some have
been cleared and are used as cropland.
Anthraquic Hapludands.—These soils are like Typic
Hapludands, but they have anthraquic conditions. They are
used for the production of paddy rice. These soils are not
known to occur in the United States. They are established for
use in other countries.
Aquic Duric Hapludands.—These soils are like Typic
Hapludands, but they have both aquic conditions (or artificial
drainage) and redox features in a horizon at a depth between
50 and 100 cm either from the mineral soil surface or from the
top of an organic layer with andic soil properties, whichever is
shallower. These soils are not known to occur in the United
States. They are established for use in other countries.
Aquic Hapludands.—These soils are like Typic
Hapludands, but they have both aquic conditions (or artificial
drainage) and redox features in a horizon at a depth between
50 and 100 cm either from the mineral soil surface or from the
top of an organic layer with andic soil properties, whichever is
shallower. These soils are of small extent and are known to
occur only in the State of Washington. Most of the soils are
used for timber production.
Duric Hapludands.—These soils are like Typic
Hapludands, but they have a horizon 15 cm or more thick that
has 20 percent or more (by volume) cemented soil material and
has its upper boundary within 100 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower. These soils have not been
recognized in the United States.
Eutric Hapludands.—These soils are like Typic
Hapludands, but they have a sum of extractable bases of more
than 25.0 cmol(+)/kg in the fine-earth fraction throughout one
or more horizons with a total thickness of 15 cm or more at a
depth between 25 and 75 cm either from the mineral soil
surface or from the top of an organic layer with andic soil
properties, whichever is shallower. These soils are not known
to occur in the United States. They are established for use in
other countries.
Eutric Thaptic Hapludands.—These Hapludands have a
sum of extractable bases of more than 25.0 cmol(+)/kg in the
fine-earth fraction throughout one or more horizons with a
total thickness of 15 cm or more at a depth between 25 and 75
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower. These soils also have a buried mineral layer. They
do not have aquic conditions within a depth of 100 cm or high
amounts of aluminum. They are not known to occur in the
United States. They are established for use in other countries.
Hydric Hapludands.—These soils are like Typic
Hapludands, but they have, on undried samples, a 1500 kPa
water retention of 70 percent or more throughout a layer 35 cm
or more thick within 100 cm either of the mineral soil surface
or of the top of an organic layer with andic soil properties,
whichever is shallower. They also have, between depths of 25
and 100 cm, a buried, dark colored layer 10 cm or more thick
below a lighter colored horizon or horizons 10 cm or more
thick with a lower content of organic carbon. These soils are
rare and are known to occur only in Hawaii in the United
States.
Hydric Thaptic Hapludands.—These soils are like Typic
Hapludands, but they have, on undried samples, a 1500 kPa
water retention of 70 percent or more throughout a layer 35 cm
or more thick within 100 cm either of the mineral soil surface
or of the top of an organic layer with andic soil properties,
whichever is shallower. These soils have not been recognized
in the United States. They are established for use in other
countries.
Lithic Hapludands.—These soils are like Typic
Hapludands, but they have a lithic contact within 50 cm either
of the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower. These soils are of
small extent in Washington and Oregon in the United States.
Most are used for timber production, but some are used as
recreational areas.
Oxic Hapludands.—These soils are like Typic Hapludands,
but they have an oxic horizon that has its upper boundary
within 125 cm either of the mineral soil surface or of the top of
an organic layer with andic soil properties, whichever is
shallower. These soils are not known to occur in the United
States.
Thaptic Hapludands.—These soils are like Typic
Hapludands, but they have, between depths of 25 and 100 cm,
a buried, dark colored layer 10 cm or more thick below a
lighter colored horizon or horizons 10 cm or more thick with a
lower content of organic carbon. These soils have not been
recognized in the United States.
Ultic Hapludands.—These soils are like Typic Hapludands,
but they have an argillic or kandic horizon that has both an
upper boundary within 125 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower, and a base saturation (by
sum of cations) of less than 35 percent throughout the upper 50
cm or throughout the entire horizon if it is less than 50 cm
thick. These soils are not known to occur in the United States.
They are established for use in other countries.
Vitric Hapludands.—These soils are like Typic Hapludands,
but they have a 1500 kPa water retention of less than 15 percent
on air-dried samples and less than 30 percent on undried
samples throughout one or more layers that have andic soil
properties and have a total thickness of 25 cm or more within 100
cm either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower. These
soils are of small extent in Washington and Oregon in the United
States. Most are used for timber production. Some have been
cleared and are used as cropland, and some are used as
recreational areas.
308 Soil Taxonomy
Hydrudands
Hydrudands are the Udands that have, on undried samples,
a 1500 kPa water retention of 100 percent or more, by
weighted average, throughout the major part of the andic
materials. These soils do not have, in 75 percent or more of
each pedon, a melanic epipedon or a placic horizon or any
other cemented horizon with its upper boundary within 100 cm
of the mineral soil surface or of the upper boundary of an
organic layer that has andic soil properties, whichever is
shallower.
Commonly, Hydrudands have a thin O horizon, an ochric or
umbric epipedon, and a cambic horizon.
Most of the Hydrudands in the United States developed in
late-Pleistocene deposits and formed under forest vegetation.
Definition
Hydrudands are the Udands that:
1. Do not have, in half or more of each pedon, a placic
horizon within 100 cm of the mineral soil surface or of the
upper boundary of an organic layer that has andic soil
properties, whichever is shallower;
2. Do not have, in 75 percent or more of each pedon, a
cemented horizon with its upper boundary within 100 cm of
the mineral soil surface or of the upper boundary of an organic
layer that has andic soil properties, whichever is shallower;
3. Do not have a melanic epipedon; and
4. Have, on undried samples, a 1500 kPa water retention of
100 percent or more, by weighted average, throughout either:
a. One or more layers with a total thickness of 35 cm
between the mineral soil surface or the top of an organic
layer with andic soil properties, whichever is shallower, and
100 cm from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, if there is no densic, lithic, or paralithic contact,
duripan, or petrocalcic horizon within that depth; or
b. 60 percent or more of the horizon thickness between
either the mineral soil surface or the top of an organic layer
with andic soil properties, whichever is shallower, and a
densic, lithic, or paralithic contact, a duripan, or a
petrocalcic horizon.
Key to Subgroups
DGDA. Hydrudands that have a lithic contact within 50 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Lithic Hydrudands
DGDB. Other Hydrudands that have, in one or more
horizons at a depth between 50 and 100 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, aquic conditions
for some time in normal years (or artificial drainage) and one or
more of the following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent or more
chroma of 2 or less either in redox depletions on faces of peds
or in the matrix if peds are absent; or
3. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Hydrudands
DGDC. Other Hydrudands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, both:
1. Extractable bases (by NH4
OAc) plus 1N KClextractable
Al3+
totaling less than 2.0 cmol(+)/kg in the
fine-earth fraction of one or more horizons with a total
thickness of 30 cm or more; and
2. A layer 10 cm or more thick with more than 3.0 percent
organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent
or more (absolute) lower.
Acrudoxic Thaptic Hydrudands
DGDD. Other Hydrudands that have extractable bases (by
NH4
OAc) plus 1N KCl-extractable Al3+
totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more horizons
with a total thickness of 30 cm or more at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower.
Acrudoxic Hydrudands
DGDE. Other Hydrudands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Hydrudands
DGDF. Other Hydrudands that have a sum of extractable
bases of more than 25.0 cmol(+)/kg in the fine-earth fraction
throughout one or more horizons with a total thickness of 15
cm or more at a depth between 25 and 75 cm either from the
Andisols 309
mineral soil surface or from the top of an organic layer with andic
soil properties, whichever is shallower.
Eutric Hydrudands
DGDG. Other Hydrudands that have an argillic or kandic
horizon that has both:
1. An upper boundary within 125 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower; and
2. A base saturation (by sum of cations) of less than 35
percent throughout its upper 50 cm.
Ultic Hydrudands
DGDH. Other Hydrudands.
Typic Hydrudands
Definition of Typic Hydrudands
Typic Hydrudands are the Hydrudands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have, in any horizon at a depth between 50 and 100
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, both aquic conditions and any of the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated;
3. Do not have, between depths of 25 and 100 cm, a layer 10
cm or more thick with more than 3.0 percent organic carbon
and the colors of a mollic epipedon throughout, occurring
below a horizon or horizons 10 cm or more thick with a color
value, moist, 1 unit or more higher and an organic-carbon
content 1 percent or more lower;
4. Have a sum of bases of 25.0 or less cmol(+) kg-1
in the
fine-earth fraction of one or more subhorizons 35 cm or more
thick at a depth between 25 and 75 cm from the mineral soil
surface or from the upper boundary of an organic layer that has
andic soil properties, whichever is shallower;
5. Have extractable bases (by NH4
OAc) plus 1N KClextractable
Al3+
of 2.0 or more cmol(+) kg-1
in the fine-earth
fraction of all subhorizons 30 cm or more thick between depths
of 25 and 100 cm; and6. Do not have an argillic or kandic
horizon with its upper boundary within 125 cm of the mineral
soil surface or of the upper boundary of an organic layer that
has andic soil properties, whichever is shallower.
Description of Subgroups
Typic Hydrudands.—The central concept or Typic
subgroup of Hydrudands is fixed on more or less well drained,
moderately deep or deep soils that have extractable bases plus
1N KCl-extractable Al3+
totaling 2.0 or more cmol(+)/kg in the
fine-earth fraction of horizons with a total thickness of 30 cm
or more at a depth between 25 and 100 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower. These soils do
not have an argillic horizon with a base saturation (by sum of
cations) of less than 35 percent throughout its upper 50 cm.
The sum of extractable bases is 25.0 cmol(+)/kg or less
throughout horizons with a total thickness of 15 cm or more in
the upper part of the soils.
Soils that have, at a depth between 40 and 100 cm either
from the mineral soil surface or from the top of an organic
layer with andic soil properties, whichever is shallower, a dark
colored layer 10 cm or more thick with more than 3.0 percent
organic carbon, underlying one or more lighter colored
horizons with a total thickness of 10 cm or more and a lower
content of organic carbon, are excluded from the Typic
subgroup.
Soils that have both aquic conditions (or artificial drainage)
and redox features in any horizon at a depth between 50 and
100 cm either from the mineral soil surface or from the top of
an organic layer with andic soil properties, whichever is
shallower, are excluded from the Typic subgroup and are
considered intergrades to Aquands. Soils that have a lithic
contact within a depth of 50 cm are assigned to the Lithic
subgroup.
Typic Hydrudands are of moderate extent in Hawaii in
the United States. They supported forest vegetation. Most
of these soils have been cleared and are used as cropland or
pasture.
Acrudoxic Hydrudands.—These soils are like Typic
Hydrudands, but they have extractable bases plus 1N KClextractable
Al3+
totaling less than 2.0 cmol(+)/kg in the fineearth
fraction of one or more horizons with a total thickness of
30 cm or more at a depth between 25 and 100 cm either from
the mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower. These soils are
not known to occur in the United States. They are established
for use in other countries.
Acrudoxic Thaptic Hydrudands.—Thesesoilsarelike
Typic Hydrudands, but they have, between depths of 25 and
100 cm, a buried, dark colored layer 10 cm or more thick
below a lighter colored horizon or horizons 10 cm or more thick
with a lower content of organic carbon. They also have
extractable bases plus 1N KCl-extractable Al3+
totaling less
than 2.0 cmol(+)/kg in the fine-earth fraction of one or more
horizons with a total thickness of 30 cm or more at a depth
between 25 and 100 cm either from the mineral soil surface or
from the top of an organic layer with andic soil properties,
whichever is shallower. These soils are not known to occur in
310 Soil Taxonomy
the United States. They are established for use in other
countries.
Aquic Hydrudands.—These soils are like Typic
Hydrudands, but they have both aquic conditions (or artificial
drainage) and redox features in a horizon at a depth between
50 and 100 cm either from the mineral soil surface or from the
top of an organic layer with andic soil properties, whichever is
shallower. These soils are of small extent and are known to
occur only in Hawaii in the United States. Most of the soils
have been cleared and are used as cropland or pasture.
Eutric Hydrudands.—These soils are like Typic
Hydrudands, but they have a sum of extractable bases of more
than 25.0 cmol(+)/kg in the fine-earth fraction throughout one
or more horizons with a total thickness of 35 cm or more at a
depth between 25 and 75 cm either from the mineral soil surface
or from the top of an organic layer with andic soil properties,
whichever is shallower. These soils are not known to occur in
the United States. They are established for use in other
countries.
Lithic Hydrudands.—These soils are like Typic Hydrudands,
but they have a lithic contact within 50 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower. These soils are of small
extent in Hawaii in the United States. Most have been cleared
and are used as cropland or pasture, but some are used as
recreational areas.
Thaptic Hydrudands.—These soils are like Typic
Hydrudands, but they have, between depths of 25 and 100 cm,
a buried, dark colored layer 10 cm or more thick below a
lighter colored horizon or horizons 10 cm or more thick with a
lower content of organic carbon. These soils have not been
recognized in the United States. They are established for use in
other countries.
Ultic Hydrudands.—These soils are like Typic
Hydrudands, but they have an argillic or kandic horizon
that has both an upper boundary within 125 cm either of
the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower, and a base
saturation (by sum of cations) of less than 35 percent
throughout the upper 50 cm or throughout the entire horizon if it
is less than 50 cm thick. These soils are not known to occur in
the United States. They are established for use in other
countries.
Melanudands
These are the Udands that have a melanic epipedon. They
can have a lithic contact but do not have, in 75 percent or more
of each pedon, a placic horizon or any other cemented horizon
with its upper boundary within 100 cm of the mineral soil
surface or of the upper boundary of an organic layer with andic
soil properties, whichever is shallower. Characteristically,
Melanudands have a melanic epipedon and a cambic horizon.
The Melanudands in the United States generally developed
in late-Pleistocene deposits. Most formed under forest or
savanna vegetation.
Definition
Melanudands are the Udands that:
1. Do not have, in half or more of each pedon, a placic horizon
within 100 cm of the mineral soil surface or of the upper
boundary of an organic layer that has andic soil properties,
whichever is shallower;
2. Do not have, in 75 percent or more of each pedon, a
cemented horizon with its upper boundary within 100 cm of
the mineral soil surface or of the upper boundary of an organic
layer that has andic soil properties, whichever is shallower;
and
3. Have a melanic epipedon.
Key to Subgroups
DGCA. Melanudands that have a lithic contact within
50 cm either of the mineral soil surface or of the top of an
organic layer that has andic soil properties, whichever is
shallower.
Lithic Melanudands
DGCB. Other Melanudands that have anthraquic conditions.
Anthraquic Melanudands
DGCC. Other Melanudands that have, in one or more
horizons at a depth between 50 and 100 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, aquic conditions
for some time in normal years (or artificial drainage) and one
or more of the following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
3. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Melanudands
DGCD. Other Melanudands that have both:
1. Extractable bases (by NH4
OAc) plus 1N KClextractable
Al3+
totaling less than 2.0 cmol(+)/kg in the
fine-earth fraction of one or more horizons with a total
thickness of 30 cm or more at a depth between 25 and 100
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower; and
2. A 1500 kPa water retention of less than 15 percent on
Andisols 311
air-dried samples and less than 30 percent on undried
samples throughout one or more layers that have andic soil
properties and have a total thickness of 25 cm or more within
100 cm either of the mineral soil surface or of the top of an
organic layer with andic soil properties, whichever is
shallower.
Acrudoxic Vitric Melanudands
DGCE. Other Melanudands that have both:
1. Extractable bases (by NH4
OAc) plus 1N KClextractable
Al3+
totaling less than 2.0 cmol(+)/kg in the
fine-earth fraction of one or more horizons with a total
thickness of 30 cm or more at a depth between 25 and 100
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower; and
2. On undried samples, a 1500 kPa water retention of 70
percent or more throughout a layer 35 cm or more thick
within 100 cm either of the mineral soil surface or of the top
of an organic layer with andic soil properties, whichever is
shallower.
Acrudoxic Hydric Melanudands
DGCF. Other Melanudands that have extractable bases (by
NH4
OAc) plus 1N KCl-extractable Al3+
totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more horizons
with a total thickness of 30 cm or more at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower.
Acrudoxic Melanudands
DGCG. Other Melanudands that have both:
1. More than 6.0 percent organic carbon and the colors of
a mollic epipedon throughout a layer 50 cm or more thick
within 60 cm either of the mineral soil surface or of the top
of an organic layer with andic soil properties, whichever is
shallower; and
2. A 1500 kPa water retention of less than 15 percent on
air-dried samples and less than 30 percent on undried
samples throughout one or more layers that have andic soil
properties and have a total thickness of 25 cm or more
within 100 cm either of the mineral soil surface or of the top
of an organic layer with andic soil properties, whichever is
shallower.
Pachic Vitric Melanudands
DGCH. Other Melanudands that have a 1500 kPa water
retention of less than 15 percent on air-dried samples and less
than 30 percent on undried samples throughout one or more
layers that have andic soil properties and have a total thickness
of 25 cm or more within 100 cm either of the mineral soil surface
or of the top of an organic layer with andic soil properties,
whichever is shallower.
VitricMelanudands
DGCI. Other Melanudands that have both:
1. On undried samples, a 1500 kPa water retention of 70
percent or more throughout a layer 35 cm or more thick
within 100 cm either of the mineral soil surface or of the top
of an organic layer with andic soil properties, whichever is
shallower; and
2. More than 6.0 percent organic carbon and the colors of
a mollic epipedon throughout a layer 50 cm or more thick
within 60 cm either of the mineral soil surface or of the top
of an organic layer with andic soil properties, whichever is
shallower.
Hydric Pachic Melanudands
DGCJ. Other Melanudands that have more than 6.0 percent
organic carbon and the colors of a mollic epipedon throughout
a layer 50 cm or more thick within 60 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Pachic Melanudands
DGCK. Other Melanudands that have, on undried samples, a
1500 kPa water retention of 70 percent or more throughout a
layer 35 cm or more thick within 100 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Hydric Melanudands
DGCL. Other Melanudands that have, at a depth between 40
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Melanudands
DGCM. Other Melanudands that have an argillic or kandic
horizon that has both:
1. An upper boundary within 125 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower; and
2. A base saturation (by sum of cations) of less than 35
percent throughout its upper 50 cm.
Ultic Melanudands
312 Soil Taxonomy
DGCN. Other Melanudands that have a sum of extractable
bases of more than 25.0 cmol(+)/kg in the fine-earth fraction
throughout one or more horizons with a total thickness of 15
cm or more at a depth between 25 and 75 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower.
Eutric Melanudands
DGCO. Other Melanudands.
Typic Melanudands
DefinitionofTypicMelanudands
Typic Melanudands are the Melanudands that:
1. Do not have a lithic contact within 50 cm of the soil surface;
2. Do not have, in any horizon at a depth between 50 and 100
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, both aquic conditions and any of the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated;
3. Have, on undried samples, a 1500 kPa water retention of
less than 70 percent throughout all layers 35 cm or more thick
within 100 cm either of the mineral soil surface or of the top of
an organic layer with andic soil properties, whichever is
shallower;
4. Have a 1500 kPa water retention of 15 percent or more on
air-dried samples or 30 percent or more on undried samples
throughout all layers that have andic soil properties and have a
total thickness of 25 cm or more within 100 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower;
5. Do not have both more than 6.0 percent organic carbon
and the colors of a mollic epipedon throughout at least 50 cm
of the upper 60 cm, excluding any overlying layers that do not
have andic soil properties;
6. Do not have a sum of bases of more than 25.0 cmol(+) kg-1
in
the fine-earth fraction throughout some subhorizon 15 cm or
more thick at a depth between 25 and 75 cm either from mineral
soil surface or from the upper boundary of an organic layer that
has andic soil properties, whichever is shallower;
7. Do not have, between depths of 40 and 100 cm, a layer 10
cm or more thick with more than 3.0 percent organic carbon and
the colors of a mollic epipedon throughout, occurring below a
horizon or horizons 10 cm or more thick with a color value, moist,
1 unit or more higher and an organic-carbon content 1 percent or
more lower;
8. Have extractable bases (by NH4
OAc) plus 1N KClextractable
Al3+
of 2.0 or more cmol(+) kg-1
in the fine-earth
fraction of all subhorizons 30 cm or more thick at a depth
between 25 and 100 cm from the mineral soil surface or from
the upper boundary of an organic layer that has andic soil
properties, whichever is shallower;
9. Do not have an argillic or kandic horizon with a base
saturation (by sum of cations) of less than 35 percent
throughout its upper 50 cm and its upper boundary within 125
cm of the mineral soil surface or of the upper boundary of an
organic layer that has andic soil properties, whichever is
shallower; and
10. Do not have anthraquic conditions.
Description of Subgroups
Typic Melanudands.—The central concept or Typic
subgroup of Melanudands is fixed on moderately deep or
deeper soils that commonly have relatively high amounts of
aluminum. These soils have, within 100 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower, a 1500 kPa water
retention of 15 percent or more on air-dried samples
throughout all layers 25 cm or more thick and between 30 and
70 percent on undried samples throughout all layers 35 cm or
more thick. The sum of extractable bases is 25.0 cmol(+)/kg or
less throughout horizons with a total thickness of 15 cm or
more in the upper part of the soils.
Soils that have, at a depth between 40 and 100 cm either
from the mineral soil surface or from the top of an organic
layer with andic soil properties, whichever is shallower, a dark
colored layer 10 cm or more thick with more than 3.0 percent
organic carbon, underlying one or more lighter colored
horizons with a total thickness of 10 cm or more and a lower
content of organic carbon, are excluded from the Typic
subgroup. Extractable bases plus 1N-KCl-extractable Al3+
total
more than 2.0 cmol(+)/kg in the fine-earth fraction of one or
more horizons with a total thickness of 30 cm or more in the
upper part of the Typic Melanudands.
Soils that have anthraquic conditions and soils with both
aquic conditions (or artificial drainage) and redox features in
any horizon at a depth between 50 and 100 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, are excluded
from the Typic subgroup and are considered intergrades to
Aquands. Soils that have a lithic contact within a depth of 50
cm are assigned to the Lithic subgroup.
Typic Melanudands are not known to occur in the Pacific
Northwest.
Acrudoxic Hydric Melanudands.—These soils are like Typic
Andisols 313
Melanudands, but they have extractable bases plus 1N KClextractable
Al3+
totaling less than 2.0 cmol(+)/kg in the fine-earth
fraction of one or more horizons with a total thickness of 30 cm
or more at a depth between 25 and 100 cm either from the mineral
soil surface or from the top of an organic layer with andic soil
properties, whichever is shallower. They also have, on undried
samples, a 1500 kPa water retention of 70 percent or more
throughout a layer 35 cm or more thick within 100 cm of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower. These soils are not
known to occur in the United States. They are established for
use in other countries.
Acrudoxic Melanudands.—These soils are like Typic
Melanudands, but they have extractable bases plus 1N KClextractable
Al3+
totaling less than 2.0 cmol(+)/kg in the fineearth
fraction of one or more horizons with a total thickness of
30 cm or more at a depth between 25 and 100 cm either from
the mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower. These soils are
not known to occur in the United States. They are established
for use in other countries.
Acrudoxic Vitric Melanudands.—These soils are like Typic
Melanudands, but they have extractable bases plus 1N KClextractable
Al3+
totaling less than 2.0 cmol(+)/kg in the fine-earth
fraction of one or more horizons with a total thickness of 30 cm
or more at a depth between 25 and 100 cm either from the mineral
soil surface or from the top of an organic layer with andic soil
properties, whichever is shallower. They also have a 1500 kPa
water retention of less than 15 percent on air-dried samples and
less than 30 percent on undried samples throughout one or more
layers that have andic soil properties and have a total thickness
of 25 cm or more within 100 cm either of the mineral soil surface
or of the top of an organic layer with andic soil properties,
whichever is shallower. These soils are not known to occur in
the United States. They are established for use in other
countries.
Anthraquic Melanudands.—These soils are like Typic
Melanudands, but they have anthraquic conditions. They are
used for the production of paddy rice. These soils are not
known to occur in the United States. They are established for
use in other countries.
Aquic Melanudands.—These soils are like Typic
Melanudands, but they have both aquic conditions (or
artificial drainage) and redox features in a horizon at a depth
between 50 and 100 cm either from the mineral soil surface or
from the top of an organic layer with andic soil properties,
whichever is shallower. These soils are not known to occur in
the United States. They are established for use in other
countries.
Eutric Melanudands.—These soils are like Typic
Melanudands, but they have a sum of extractable bases of more
than 25.0 cmol(+)/kg in the fine-earth fraction throughout one
or more horizons with a total thickness of 35 cm or more at a
depth between 25 and 75 cm either from the mineral soil surface
or from the top of an organic layer with andic soil properties,
whichever is shallower. These soils are not known to occur in
the United States. They are established for use in other
countries.
Hydric Melanudands.—These soils are like Typic
Melanudands, but they have, on undried samples, a 1500 kPa
water retention of 70 percent or more throughout a layer 35 cm
or more thick within 100 cm either of the mineral soil surface
or of the top of an organic layer with andic soil properties,
whichever is shallower. These soils have not been recognized
in the United States. They are established for use in other
countries.
Hydric Pachic Melanudands.—These soils are like Typic
Melanudands, but they have, on undried samples, a 1500 kPa
water retention of 70 percent or more throughout a layer 35 cm
or more thick within 100 cm either of the mineral soil surface
or of the top of an organic layer with andic soil properties,
whichever is shallower. These soils also have both more than
6.0 percent organic carbon and the colors of a mollic epipedon
throughout at least 50 cm of the upper 60 cm of the andic
materials and have, on undried samples, a 1500 kPa water
retention of 70 percent or more throughout a layer 35 cm or
more thick within 100 cm either of the mineral soil surface or
of the top of an organic layer with andic soil properties,
whichever is shallower. The soils have not been recognized in
the United States. They are established for use in other
countries.
Lithic Melanudands.—These soils are like Typic
Melanudands, but they have a lithic contact within 50 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower. These
soils have not been recognized in the United States. They are
established for use in other countries.
Pachic Melanudands.—These soils are like Typic
Melanudands, but they have both more than 6.0 percent
organic carbon and the colors of a mollic epipedon throughout
at least 50 cm of the upper 60 cm of the andic materials and
have, on undried samples, a 1500 kPa water retention of 70
percent or more throughout a layer 35 cm or more thick within
100 cm either of the mineral soil surface or of the top of an
organic layer with andic soil properties, whichever is
shallower. These soils have not been recognized in the United
States. They are established for use in other countries.
Pachic Vitric Melanudands.—These soils are like Typic
Melanudands, but they have a 1500 kPa water retention of less
than 15 percent on air-dried samples and less than 30 percent
on undried samples throughout one or more layers that have
andic soil properties and have a total thickness of 25 cm or
more within 100 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower. These soils also have both more than 6.0 percent
organic carbon and the colors of a mollic epipedon throughout
at least 50 cm of the upper 60 cm of the andic materials and
have, on undried samples, a 1500 kPa water retention of 70
314 Soil Taxonomy
percent or more throughout a layer 35 cm or more thick within
100 cm either of the mineral soil surface or of the top of an
organic layer with andic soil properties, whichever is shallower.
The soils have not been recognized in the United States. They
are established for use in other countries.
Thaptic Melanudands.—These soils are like Typic
Melanudands, but they have, between depths of 25 and 100 cm,
a buried, dark colored layer 10 cm or more thick below a lighter
colored horizon or horizons 10 cm or more thick with a lower
content of organic carbon. These soils have not been
recognized in the United States. They are established for use in
other countries.
Ultic Melanudands.—These soils are like Typic
Melanudands, but they have an argillic or kandic horizon that
has both an upper boundary within 125 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower, and a base saturation
(by sum of cations) of less than 35 percent throughout the
upper 50 cm or throughout the entire horizon if it is less than
50 cm thick. These soils are not known to occur in the United
States. They are established for use in other countries.
Vitric Melanudands.—These soils are like Typic
Melanudands, but they have a 1500 kPa water retention of less
than 15 percent on air-dried samples and less than 30 percent
on undried samples throughout one or more layers that have
andic soil properties and have a total thickness of 25 cm or
more within 100 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower. These soils are not known to occur in the United
States. They are established for use in other countries.
Placudands
Placudands are the more or less well drained Udands that
have, in half or more of each pedon, a placic horizon within
100 cm either of the mineral soil surface or of the top of an
organic layer with andic soil properties, whichever is shallower.
Characteristically, Placudands have a thin O horizon and an
ochric or umbric epipedon above the placic horizon.
Placudands are rare in the United States. Most formed under
forest vegetation.
Definition
Placudands are the Udands that have, in half or more of
each pedon, a placic horizon within 100 cm of the mineral soil
surface or of the upper boundary of an organic layer that has
andic soil properties, whichever is shallower.
Key to Subgroups
DGAA. Placudands that have a lithic contact within
50 cm either of the mineral soil surface or of the top of an
organic layer that has andic soil properties, whichever is
shallower.
LithicPlacudands
DGAB. Other Placudands that have, in one or more
horizons at a depth between 50 cm either from the mineral
soil surface or from the top of an organic layer with andic
soil properties, whichever is shallower, and the placic
horizon, aquic conditions for some time in normal years
(or artificial drainage) and one or more of the following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent
or more chroma of 2 or less either in redox depletions
on faces of peds or in the matrix if peds are absent;
or
3. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Placudands
DGAC. Other Placudands that have extractable bases (by
NH4
OAc) plus 1N KCl-extractable Al3+
totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more horizons
with a total thickness of 30 cm or more at a depth between 25
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, and the placic horizon.
Acrudoxic Placudands
DGAD. Other Placudands that have, on undried samples, a
1500 kPa water retention of 70 percent or more throughout a
layer 35 cm or more thick within 100 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Hydric Placudands
DGAE. Other Placudands.
Typic Placudands
DefinitionofTypicPlacudands
Typic Placudands are the Placudands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have, in any horizon at a depth between 50 cm
either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is shallower,
and the placic horizon, both aquic conditions and any of the
following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or more
chroma of 2 or less either in redox depletions on faces of peds
or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction to
Andisols 315
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated;
3. Have extractable bases (by NH4
OAc) plus 1N KClextractable
Al3+
of 2.0 or more cmol(+) kg-1
in the fine-earth
fraction of all subhorizons 30 cm or more thick at a depth
between 25 cm from the mineral soil surface or from the
upper boundary of an organic layer that has andic soil
properties, whichever is shallower, and the placic horizon;
and
4. Do not have, on undried samples, a 1500 kPa water
retention of 70 percent or more throughout a layer 35 cm or more
thick within 100 cm either of the mineral soil surface or of the top
of an organic layer with andic soil properties, whichever is
shallower.
Description of Subgroups
Typic Placudands.—The central concept or Typic subgroup
of Placudands is fixed on moderately deep or shallow soils that
have, on undried samples, a 1500 kPa water retention of less
than 70 percent throughout all layers 35 cm or more thick
above the cemented horizon.
Soils that have both aquic conditions (or artificial drainage)
and redox features in any horizon at a depth between 50 cm
either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, are excluded from the Typic subgroup and are
considered intergrades to Aquands. Soils that have extractable
bases plus 1N KCl-extractable Al3+
totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more horizons
with a total thickness of 30 cm or more at a depth between 25
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, and the placic horizon also are excluded.
Typic Placudands are of very small extent in the United
States.
Acrudoxic Placudands.—These soils are like Typic
Placudands, but they have extractable bases plus 1N KClextractable
Al3+
totaling less than 2.0 cmol(+)/kg in the fineearth
fraction of one or more horizons with a total thickness of
30 cm or more at a depth between 25 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, and the placic
horizon. These soils have not been recognized in the United
States.
Aquic Placudands.—These soils are like Typic Placudands,
but they have both aquic conditions (or artificial drainage) and
redox features in a horizon at a depth between 50 cm either
from the mineral soil surface or from the top of an organic
layer with andic soil properties, whichever is shallower, and
the placic horizon. These soils have not been recognized in the
United States.
Hydric Placudands.—These soils are like Typic Placudands,
but they have, on undried samples, a 1500 kPa water retention
of 70 percent or more throughout a layer 35 cm or more thick
within 100 cm either of the mineral soil surface or of the top
of an organic layer with andic soil properties, whichever is
shallower. These soils have not been recognized in the United
States.
Lithic Placudands.—These soils are like Typic Placudands,
but they have a lithic contact within 50 cm of the mineral soil
surface.
Ustands
Ustands are the more or less well drained Andisols of
subhumid to semiarid regions. These soils are of relatively small
extent. They are mostly in Mexico, the western part of the United
States, the Pacific Islands, and the eastern part of Africa. Most
Ustands in the United States are in Hawaii, Arizona, and New
Mexico. Most formed under grass, shrub, or forest vegetation.
Characteristically, Ustands have an ochric or mollic epipedon
and a cambic horizon. Some have a duripan.
The Ustands in the United States generally developed in latePleistocene
or Holocene deposits.
Definition
Ustands are the Andisols that:
1. Have an ustic soil moisture regime;
2. Have a frigid or warmer soil temperature regime;
3. Do not have a histic epipedon or the periods of saturation
and reduction that are defined for Aquands; and
4. Do not have a 1500 kPa water retention of less than 15
percent on air-dried samples and less than 30 percent on
undried samples throughout 60 percent or more of the
thickness from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, to a point 60 cm below the starting point or to any
densic, lithic, or paralithic contact, duripan, or petrocalcic
horizon within that depth.
Key to Great Groups
DFA. Ustands that have, in 75 percent or more of each pedon,
a cemented horizon that has its upper boundary within 100 cm
either of the mineral soil surface or of the top of an organic layer
with andic soil properties, whichever is shallower.
Durustands, p. 316
DFB. Other Ustands.
Haplustands, p. 317
316 Soil Taxonomy
Durustands
Durustands are the Ustands that have, in 75 percent or more
of each pedon, a cemented horizon with its upper boundary
within 100 cm either of the mineral soil surface or of the top of
an organic layer with andic soil properties, whichever is
shallower.
Characteristically, Durustands have an ochric epipedon and a
cambic horizon above the cemented horizon.
The Durustands in the United States generally developed in
late-Pleistocene or Holocene deposits. Most formed under
coniferous/grass or shrub vegetation.
Definition
Durustands are the Ustands that have, in 75 percent or more
of each pedon, a cemented horizon with its upper boundary
within 100 cm of the mineral soil surface.
Key to Subgroups
DFAA. Durustands that have, in one or more horizons at a
depth between 50 and 100 cm either from the mineral soil
surface or from the top of an organic layer with andic soil
properties, whichever is shallower, aquic conditions for some
time in normal years (or artificial drainage) and one or more of
the following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
3. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Durustands
DFAB. Other Durustands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Durustands
DFAC. Other Durustands that have a melanic, mollic, or
umbric epipedon.
Humic Durustands
DFAD. Other Durustands.
Typic Durustands
Definition of Typic Durustands
Typic Durustands are the Durustands that:
1. Do not have, in any horizon at a depth between 50 and 100
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is shallower,
both aquic conditions and any of the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or more
chroma of 2 or less either in redox depletions on faces of peds
or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated;
2. Do not have, between depths of 25 and 100 cm, a layer 10
cm or more thick with more than 3.0 percent organic carbon
and the colors of a mollic epipedon throughout, occurring
below a horizon or horizons 10 cm or more thick with a color
value, moist, 1 unit or more higher and an organic-carbon
content 1 percent or more lower; and
3. Do not have a melanic, mollic, or umbric epipedon.
Description of Subgroups
Typic Durustands.—The central concept or Typic subgroup
of Durustands is fixed on moderately deep or shallow soils with
an ochric epipedon. These soils do not have both aquic
conditions (or artificial drainage) and redox features in any
horizon at a depth between 50 and 100 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower. They do not have,
between depths of 25 and 100 cm, a buried, dark colored layer
10 cm or more thick below a lighter colored horizon or
horizons 10 cm or more thick with a lower content of organic
carbon. These soils are not known to occur in the United
States. They are established for use in other countries.
Aquic Durustands.—These soils are like Typic Durustands,
but they have both aquic conditions (or artificial drainage) and
redox features in a horizon at a depth between 50 and 100 cm
either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower. These soils are not known to occur in the United
States. They are established for use in other countries.
Humic Durustands.—These soils are like Typic
Durustands, but they have a melanic, mollic, or umbric
epipedon. They are rare in the United States. Most of these
soils are used as rangeland, but some are used for timber
production or as recreational areas.
Thaptic Durustands.—These soils are like Typic
Durustands, but they have, between depths of 25 and 100 cm, a
buried, dark colored layer 10 cm or more thick below a lighter
Andisols 317
colored horizon or horizons 10 cm or more thick with a lower
content of organic carbon. These soils are not known to occur in
the United States. They are established for use in other
countries.
Haplustands
Haplustands are the Ustands that do not have, in 75 percent
or more of each pedon, a cemented horizon that has its upper
boundary within 100 cm either of the mineral soil surface or of
the top of an organic layer with andic soil properties,
whichever is shallower. Characteristically, Haplustands have an
ochric epipedon and a cambic horizon above the cemented
horizon.
The Haplustands in the United States generally developed in
late-Pleistocene or Holocene deposits. Most formed under
coniferous/grass or shrub vegetation.
Definition
Haplustands are the Ustands that do not have, in 75 percent
or more of each pedon, a cemented horizon with its upper
boundary within 100 cm of the mineral soil surface.
Key to Subgroups
DFBA. Haplustands that have a lithic contact within 50 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Lithic Haplustands
DFBB. Other Haplustands that have, in one or more horizons
at a depth between 50 and 100 cm either from the mineral soil
surface or from the top of an organic layer with andic soil
properties, whichever is shallower, aquic conditions for some
time in normal years (or artificial drainage) and one or more of
the following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
3. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Haplustands
DFBC. Other Haplustands that have both:
1. Extractable bases (by NH4
OAc) plus 1N KClextractable
Al3+
totaling less than 15.0 cmol(+)/kg in the
fine-earth fraction throughout one or more horizons with a
total thickness of 60 cm or more within 75 cm either of the
mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower; and
2. A 1500 kPa water retention of less than 15 percent on
air-dried samples and less than 30 percent on undried
samples throughout one or more layers that have andic soil
properties and have a total thickness of 25 cm or more within
100 cm either of the mineral soil surface or of the top of an
organic layer with andic soil properties, whichever is
shallower.
Dystric Vitric Haplustands
DFBD. Other Haplustands that have a 1500 kPa water
retention of less than 15 percent on air-dried samples and less
than 30 percent on undried samples throughout one or more
layers that have andic soil properties and have a total thickness
of 25 cm or more within 100 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Vitric Haplustands
DFBE. Other Haplustands that have more than 6.0 percent
organic carbon and the colors of a mollic epipedon throughout
a layer 50 cm or more thick within 60 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Pachic Haplustands
DFBF. Other Haplustands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Haplustands
DFBG. Other Haplustands that have a calcic horizon that has
its upper boundary within 125 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Calcic Haplustands
DFBH. Other Haplustands that have extractable bases (by
NH4
OAc) plus 1N KCl-extractable Al3+
totaling less than 15.0
cmol(+)/kg in the fine-earth fraction throughout one or more
horizons with a total thickness of 60 cm or more within 75 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Dystric Haplustands
318 Soil Taxonomy
DFBI. Other Haplustands that have an oxic horizon that has its
upper boundary within 125 cm either of the mineral soil surface
or of the top of an organic layer with andic soil properties,
whichever is shallower.
OxicHaplustands
DFBJ. Other Haplustands that have an argillic or kandic
horizon that has both:
1. An upper boundary within 125 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower; and
2. A base saturation (by sum of cations) of less than 35
percent throughout the upper 50 cm or throughout the entire
argillic or kandic horizon if it is less than 50 cm thick.
Ultic Haplustands
DFBK. Other Haplustands that have an argillic or kandic
horizon that has its upper boundary within 125 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower.
Alfic Haplustands
DFBL. Other Haplustands that have a melanic, mollic, or
umbric epipedon.
Humic Haplustands
DFBM. Other Haplustands.
Typic Haplustands
Definition of Typic Haplustands
Typic Haplustands are the Haplustands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have, in any horizon at a depth between 50 and 100
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, both aquic conditions and any of the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated;
3. Have, on undried samples, 30 percent or more 1500 kPa
water retention in all subhorizons that meet the requirements
for andic soil properties and that are at least 25 cm thick and
are within 100 cm of the mineral soil surface or of the upper
boundary of an organic layer that has andic soil properties,
whichever is shallower;
4. Do not have both more than 6.0 percent organic carbon and
the colors of a mollic epipedon throughout at least 50 cm of the
upper 60 cm, excluding any overlying layers that do not have
andic soil properties;
5. Do not have, between depths of 25 and 100 cm, a layer 10 cm
or more thick with more than 3.0 percent organic carbon and the
colors of a mollic epipedon throughout, occurring below a
horizon or horizons 10 cm or more thick with a color value, moist,
1 unit or more higher and an organic-carbon content 1 percent or
more lower;
6. Do not have a calcic horizon with its upper boundary within
125 cm of the mineral soil surface;
7. Have extractable bases (by NH4
OAc) plus 1N KClextractable
Al3+
of 15.0 or more cmol(+) kg-1
in the fine-earth
fraction throughout at least 60 cm of the upper 75 cm;
8. Do not have an oxic horizon with its upper boundary
within 125 cm of the mineral soil surface;
9. Do not have an argillic or kandic horizon with its upper
boundary within 125 cm of the mineral soil surface; and
10. Do not have a melanic, mollic, or umbric epipedon.
Description of Subgroups
Typic Haplustands.—The central concept or Typic
subgroup of Haplustands is fixed on moderately deep or deeper
soils that have an ochric epipedon and do not have a calcic,
argillic, or oxic horizon. These soils have extractable bases
plus 1N KCl-extractable Al3+
of 15.0 or more cmol(+) kg-1
in
the fine-earth fraction throughout at least 60 cm of the upper
75 cm. They have a 1500 kPa water retention of 15 percent or
more on air-dried samples and 30 percent or more on undried
samples throughout all layers 25 cm or more thick within 100
cm either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower. Soils
that have, at a depth between 40 and 100 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, a dark colored
layer 10 cm or more thick with more than 3.0 percent organic
carbon, underlying one or more lighter colored horizons with a
total thickness of 10 cm or more and a lower content of organic
carbon, are excluded from the Typic subgroup.
Soils that have both aquic conditions (or artificial drainage)
and redox features in any horizon at a depth between 50 and
100 cm either from the mineral soil surface or from the top of
an organic layer with andic soil properties, whichever is
shallower, are excluded from the Typic subgroup and are
considered intergrades to Aquands. Soils that have a lithic
Andisols 319
contact within a depth of 50 cm are assigned to the Lithic
subgroup.
Typic Haplustands are of small extent in the United States.
They commonly support grassland or forest vegetation. Most
are used as rangeland or for timber production, but some have
been cleared and are used as cropland.
Alfic Haplustands.—These soils are like Typic
Haplustands, but they have an argillic or kandic horizon that has
both an upper boundary within 125 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower, and a base saturation (by
sum of cations) of 35 percent or more in some part of the upper
50 cm or in the entire horizon if it is less than 50 cm thick. These
soils are not known to occur in the United States. They are
established for use in other countries.
Aquic Haplustands.—These soils are like Typic
Haplustands, but they have both aquic conditions (or artificial
drainage) and redox features in a horizon at a depth between
50 and 100 cm either from the mineral soil surface or from the
top of an organic layer with andic soil properties, whichever is
shallower. These soils are not known to occur in the United
States. They are established for use in other countries.
Calcic Haplustands.—These soils are like Typic
Haplustands, but they have a calcic horizon that has its upper
boundary within 125 cm either of the mineral soil surface or of
the top of an organic layer with andic soil properties,
whichever is shallower. These soils have not been recognized
in the United States.
Dystric Haplustands.—These soils are like Typic
Haplustands, but they have a sum of extractable bases plus
aluminum of less than 15.0 cmol(+)/kg in the fine-earth
fraction throughout one or more horizons with a total thickness
of 60 cm or more within 75 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower. These soils are not known
to occur in the United States. They are established for use in
other countries.
Dystric Vitric Haplustands.—These soils are like Typic
Haplustands, but they have a sum of extractable bases plus
aluminum of less than 15.0 cmol(+)/kg in the fine-earth
fraction throughout one or more horizons with a total thickness
of 60 cm or more within 75 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower. They also have a 1500 kPa
water retention of less than 15 percent on air-dried samples
and less than 30 percent on undried samples throughout one or
more layers that have andic soil properties and have a total
thickness of 25 cm or more within 100 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower. These soils are not known
to occur in the United States. They are established for use in
other countries.
Humic Haplustands.—These soils are like Typic
Haplustands, but they have a melanic, mollic, or umbric
epipedon. They are rare and are known to occur only in Hawaii
and Arizona in the United States.
Lithic Haplustands.—These soils are like Typic
Haplustands, but they have a lithic contact within 50 cm either
of the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower. These soils are of
small extent and occur mostly in Hawaii in the United States.
Most of the soils are used as cropland or as recreational areas.
Oxic Haplustands.—These soils are like Typic
Haplustands, but they have an oxic horizon that has its upper
boundary within 125 cm either of the mineral soil surface or of
the top of an organic layer with andic soil properties,
whichever is shallower. These soils are not known to occur in
the United States.
Pachic Haplustands.—These soils are like Typic
Haplustands, but they have more than 6.0 percent organic
carbon and the colors of a mollic epipedon throughout a layer
50 cm or more thick within 60 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower. These soils have not been
recognized in the United States.
Thaptic Haplustands.—These soils are like Typic
Haplustands, but they have, between depths of 25 and 100 cm,
a buried, dark colored layer 10 cm or more thick below a
lighter colored horizon or horizons 10 cm or more thick with a
lower content of organic carbon. These soils have not been
recognized in the United States.
Ultic Haplustands.—These soils are like Typic
Haplustands, but they have an argillic or kandic horizon that
has both an upper boundary within 125 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower, and a base saturation
(by sum of cations) of less than 35 percent throughout the
upper 50 cm or throughout the entire horizon if it is less than
50 cm thick. These soils are not known to occur in the United
States. They are established for use in other countries.
Vitric Haplustands.—These soils are like Typic
Haplustands, but they have a 1500 kPa water retention of less
than 15 percent on air-dried samples and less than 30 percent
on undried samples throughout one or more layers that have
andic soil properties and have a total thickness of 25 cm or
more within 100 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower. These soils are of small extent in Washington and
Oregon. Most are used for timber production. Some have been
cleared and are used as cropland, and some are used as
recreational areas.
Vitrands
Vitrands are the more or less well drained, coarse textured
Andisols. These are relatively young soils that occur mostly
320 Soil Taxonomy
near volcanoes. Most of the Vitrands in the United States are in
Oregon, Washington, and Idaho. Vitrands formed mainly under
coniferous forest vegetation.
Characteristically, Vitrands have an ochric or mollic epipedon
and a cambic horizon.
Most of the Vitrands in the United States developed in
Holocene deposits.
Definition
Vitrands are the Andisols that:
1. Have a frigid or warmer soil temperature regime;
2. Do not have a histic epipedon or the periods of saturation
and reduction that are defined for Aquands;
3. Have an ustic or udic moisture regime; and
4. Have a 1500 kPa water retention of less than 15 percent
on air-dried samples and less than 30 percent on undried
samples throughout 60 percent or more of the thickness
either:
a. Within 60 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever
is shallower, if there is no densic, lithic, or paralithic
contact, duripan, or petrocalcic horizon within that depth;
or
b. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon.
Key to Great Groups
DEA. Vitrands that have an ustic moisture regime.
Ustivitrands, p. 322
DEB. Other Vitrands.
Udivitrands, p. 320
Udivitrands
Udivitrands are the more or less well drained Vitrands that
have a udic moisture regime. Characteristically, these soils
have an ochric epipedon and a cambic horizon. Some have an
argillic horizon.
Most of the Udivitrands in the United States developed in
Holocene deposits under coniferous forest vegetation.
Definition
Udivitrands are the Vitrands that have a udic soil moisture
regime.
KeytoSubgroups
DEBA. Udivitrands that have a lithic contact within 50 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Lithic Udivitrands
DEBB. Other Udivitrands that have, in one or more horizons
at a depth between 50 and 100 cm either from the mineral soil
surface or from the top of an organic layer with andic soil
properties, whichever is shallower, aquic conditions for some
time in normal years (or artificial drainage) and one or more of
the following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
3. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Udivitrands
DEBC. Other Udivitrands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Udivitrands
DEBD. Other Udivitrands that have both:
1. An argillic or kandic horizon that has its upper
boundary within 125 cm of the mineral soil surface or of the
upper boundary of an organic layer with andic soil
properties, whichever is shallower; and
2. A base saturation (by sum of cations) of less than 35
percent throughout the upper 50 cm of the argillic or kandic
horizon.
Ultic Udivitrands
DEBE. Other Udivitrands that have an argillic or kandic
horizon that has its upper boundary within 125 cm of the
mineral soil surface or of the upper boundary of an organic
layer with andic soil properties, whichever is shallower.
Alfic Udivitrands
DEBF. Other Udivitrands that have a melanic, mollic, or
umbric epipedon.
Humic Udivitrands
Andisols 321
DEBG. Other Udivitrands.
TypicUdivitrands
DefinitionofTypicUdivitrands
Typic Udivitrands are the Udivitrands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have, in any horizon at a depth between 50 and 100
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is shallower,
both aquic conditions and any of the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or more
chroma of 2 or less either in redox depletions on faces of peds
or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated;
3. Do not have, between depths of 25 and 100 cm, a layer 10
cm or more thick with more than 3.0 percent organic carbon
and the colors of a mollic epipedon throughout, occurring
below a horizon or horizons 10 cm or more thick with a color
value, moist, 1 unit or more higher and an organic-carbon
content 1 percent or more lower;
4. Do not have an argillic or kandic horizon that has its
upper boundary within 125 cm of the mineral soil surface or of
the upper boundary of an organic layer with andic soil
properties, whichever is shallower; and
5. Do not have a melanic, mollic, or umbric epipedon.
Description of Subgroups
Typic Udivitrands.—The central concept or Typic
subgroup of Udivitrands is fixed on moderately deep or deeper
soils that have an ochric epipedon and do not have an argillic
horizon.
Soils that have both aquic conditions (or artificial drainage)
and redox features in any horizon at a depth between 50 and
100 cm either from the mineral soil surface or from the top of
an organic layer with andic soil properties, whichever is
shallower, are excluded from the Typic subgroup and are
considered intergrades to Aquands. Soils that have, at a depth
between 40 and 100 cm either from the mineral soil surface or
from the top of an organic layer with andic soil properties,
whichever is shallower, a dark colored layer 10 cm or more
thick with more than 3.0 percent organic carbon, underlying
one or more lighter colored horizons with a total thickness of
10 cm or more and a lower content of organic carbon, also are
excluded. Soils that have a lithic contact within a depth of 50
cm are assigned to the Lithic subgroup.
Typic Udivitrands are moderately extensive in the States of
Washington and Idaho. They commonly support coniferous
forest vegetation. Most of these soils are used for timber
production, but some have been cleared and are used as
cropland.
Alfic Udivitrands.—These soils are like Typic Udivitrands,
but they have an argillic or kandic horizon that has both an
upper boundary within 125 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower, and a base saturation (by
sum of cations) of 35 percent or more in some part of the upper
50 cm or in the entire horizon if it is less than 50 cm thick. These
soils are moderately extensive in Idaho and Oregon. They
commonly support coniferous forest vegetation. Most of the
soils are used for timber production, but some have been cleared
and are used as cropland.
Aquic Udivitrands.—These soils are like Typic
Udivitrands, but they have both aquic conditions (or artificial
drainage) and redox features in a horizon at a depth between
50 and 100 cm either from the mineral soil surface or from the
top of an organic layer with andic soil properties, whichever is
shallower. These soils are not known to occur in the United
States. They are established for use in other countries.
Humic Udivitrands.—These soils are like Typic
Udivitrands, but they have a melanic, mollic, or umbric
epipedon. They are of small extent and are known to occur
only in the State of Washington. They commonly support
coniferous forest vegetation. Most of the soils are used for
timber production, but some have been cleared and are used as
cropland.
Lithic Udivitrands.—These soils are like Typic
Udivitrands, but they have a lithic contact within 50 cm either
of the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower. These soils are of
small extent and occur mostly in Oregon, Montana, and
Washington. They commonly support coniferous forest
vegetation. Most of the soils are used for timber production, but
some are used as recreational areas.
Thaptic Udivitrands.—These soils are like Typic
Udivitrands, but they have, between depths of 25 and 100 cm, a
buried, dark colored layer 10 cm or more thick below a lighter
colored horizon or horizons 10 cm or more thick with a lower
content of organic carbon. These soils have not been
recognized in the United States.
Ultic Udivitrands.—These soils are like Typic Udivitrands,
but they have an argillic or kandic horizon that has both an
upper boundary within 125 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower, and a base saturation (by
sum of cations) of less than 35 percent throughout the upper 50
cm or throughout the entire horizon if it is less than 50 cm
thick. These soils are not known to occur in the United States.
They are established for use in other countries.
322 Soil Taxonomy
Ustivitrands
Ustivitrands are the more or less well drained Vitrands that
have an ustic moisture regime. Characteristically, Ustivitrands
have an ochric epipedon and a cambic horizon.
Ustivitrands are rare in the United States.
Definition
Ustivitrands are the Vitrands that have an ustic soil
moisture regime.
KeytoSubgroups
DEAA. Ustivitrands that have a lithic contact within 50 cm
either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Lithic Ustivitrands
DEAB. Other Ustivitrands that have, in one or more horizons
at a depth between 50 and 100 cm either from the mineral soil
surface or from the top of an organic layer with andic soil
properties, whichever is shallower, aquic conditions for some
time in normal years (or artificial drainage) and one or more of
the following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
3. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Ustivitrands
DEAC. Other Ustivitrands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the top
of an organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Ustivitrands
DEAD. Other Ustivitrands that have a calcic horizon that has
its upper boundary within 125 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Calcic Ustivitrands
DEAE. Other Ustivitrands that have a melanic, mollic, or
umbric epipedon.
Humic Ustivitrands
DEAF. Other Ustivitrands.
TypicUstivitrands
DefinitionofTypicUstivitrands
Typic Ustivitrands are the Ustivitrands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have, in any horizon at a depth between 50 and 100
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, both aquic conditions and any of the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or more
chroma of 2 or less either in redox depletions on faces of peds
or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated;
3. Do not have, between depths of 25 and 100 cm, a layer 10
cm or more thick with more than 3.0 percent organic carbon
and the colors of a mollic epipedon throughout, occurring
below a horizon or horizons 10 cm or more thick with a color
value, moist, 1 unit or more higher and an organic-carbon
content 1 percent or more lower;
4. Do not have a calcic horizon with its upper boundary
within 125 cm of the mineral soil surface; and
5. Do not have a melanic, mollic, or umbric epipedon.
Description of Subgroups
Typic Ustivitrands.—The central concept or Typic
subgroup of Ustivitrands is fixed on moderately deep or deep
soils that have an ochric epipedon and do not have an argillic
or calcic horizon. Soils that have, at a depth between 40 and
100 cm either from the mineral soil surface or from the top of
an organic layer with andic soil properties, whichever is
shallower, a dark colored layer 10 cm or more thick with more
than 3.0 percent organic carbon, underlying one or more
lighter colored horizons with a total thickness of 10 cm or
more and a lower content of organic carbon, are excluded from
the Typic subgroup.
Soils that have a lithic contact within a depth of 50 cm are
assigned to the Lithic subgroup. Soils that have both aquic
conditions (or artificial drainage) and redox features in any
horizon at a depth between 50 and 100 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, are excluded
from the Typic subgroup and are considered intergrades to
Aquands.
Typic Ustivitrands are of moderate extent. They are mostly
in California and Washington.
Andisols 323
Aquic Ustivitrands.—These soils are like Typic Ustivitrands,
but they have both aquic conditions (or artificial drainage) and
redox features in a horizon at a depth between 50 and 100 cm
either from the mineral soil surface or from the top of an organic
layer with andic soil properties, whichever is shallower. These
soils are not known to occur in the United States. They are
established for use in other countries.
Calcic Ustivitrands.—These soils are like Typic
Ustivitrands, but they have a calcic horizon that has its upper
boundary within 125 cm either of the mineral soil surface or of
the top of an organic layer with andic soil properties,
whichever is shallower. These soils have not been recognized
in the United States. They are established for use in other
countries.
Humic Ustivitrands.—These soils are like Typic
Ustivitrands, but they have a melanic, mollic, or umbric
epipedon. They are not known to occur in the United States.
They are established for use in other countries.
Lithic Ustivitrands.—These soils are like Typic
Ustivitrands, but they have a lithic contact within 50 cm either
of the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower. These soils are
not known to occur in the United States. They are established
for use in other countries.
Thaptic Ustivitrands.—These soils are like Typic
Ustivitrands, but they have, between depths of 25 and 100 cm,
a buried, dark colored layer 10 cm or more thick below a
lighter colored horizon or horizons 10 cm or more thick with a
lower content of organic carbon. These soils have not been
recognized in the United States. They are established for use in
other countries.
Xerands
Xerands are the more or less well drained Andisols that
have a xeric moisture regime and a frigid, mesic, or thermic
temperature regime. Most of the Xerands in the United States
are in Oregon, Washington, Idaho, and California. Most
Xerands have a frigid or mesic temperature regime and formed
under coniferous forest vegetation. Some formed under grass or
shrub vegetation.
Characteristically, Xerands have an ochric or mollic epipedon
and a cambic horizon.
Most of the Xerands in the United States developed in latePleistocene
or Holocene deposits.
Definition
Xerands are the Andisols that:
1. Have a xeric soil moisture regime;
2. Have a frigid, mesic, or thermic soil temperature regime;
and
3. Do not have a histic epipedon or the aquic conditions
characteristic of Aquands.
Key to Great Groups
DDA. Xerands that have a 1500 kPa water retention of less
than 15 percent on air-dried samples and less than 30 percent
on undried samples throughout 60 percent or more of the
thickness either:
1. Within 60 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever
is shallower, if there is no densic, lithic, or paralithic
contact, duripan, or petrocalcic horizon within that depth;
or
2. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon.
Vitrixerands,p.326
DDB. Other Xerands that have a melanic epipedon.
Melanoxerands, p. 325
DDC. Other Xerands.
Haploxerands, p. 323
Haploxerands
Haploxerands are the more or less well drained Xerands that
do not have a melanic epipedon. These soils have a 1500 kPa
water retention of 15 percent or more on air-dried samples and
30 percent or more on undried samples throughout more than
30 percent of the upper part.
Characteristically, Haploxerands have a thin O horizon, an
ochric or mollic epipedon, and a cambic horizon.
The Haploxerands in the United States generally developed
in late-Pleistocene or Holocene deposits. Most formed under
coniferous forest vegetation, but some formed under grass or
shrub vegetation.
Definition
Haploxerands are the Xerands that:
1. Do not have a 1500 kPa water retention of less than 15
percent on air-dried samples and less than 30 percent on
undried samples throughout 60 percent or more of the
thickness either:
a. Within 60 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever
is shallower, if there is no densic, lithic, or paralithic
contact, duripan, or petrocalcic horizon within that depth;
or
b. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon; and
324 Soil Taxonomy
2. Do not have a melanic epipedon.
KeytoSubgroups
DDCA. Haploxerands that have a lithic contact within 50 cm of
the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower.
Lithic Haploxerands
DDCB. Other Haploxerands that have, in one or more
horizons at a depth between 50 and 100 cm either from the
mineral soil surface or from the top of an organic layer with andic
soil properties, whichever is shallower, aquic conditions for
some time in normal years (or artificial drainage) and one or more
of the following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent or more
chroma of 2 or less either in redox depletions on faces of peds
or in the matrix if peds are absent; or
3. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Haploxerands
DDCC. Other Haploxerands that have, at a depth between 25
and 100 cm from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Haploxerands
DDCD. Other Haploxerands that have a calcic horizon that
has its upper boundary within 125 cm of the mineral soil
surface.
Calcic Haploxerands
DDCE. Other Haploxerands that have an argillic or kandic
horizon that has both:
1. An upper boundary within 125 cm of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower; and
2. A base saturation (by sum of cations) of less than 35
percent throughout its upper 50 cm.
Ultic Haploxerands
DDCF. Other Haploxerands that have both:
1. A mollic or umbric epipedon; and
2. An argillic or kandic horizon that has its upper
boundary within 125 cm of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever
is shallower.
Alfic Humic Haploxerands
DDCG. Other Haploxerands that have an argillic or kandic
horizon that has its upper boundary within 125 cm of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower.
Alfic Haploxerands
DDCH. Other Haploxerands that have a mollic or umbric
epipedon.
Humic Haploxerands
DDCI. Other Haploxerands.
Typic Haploxerands
Definition of Typic Haploxerands
Typic Haploxerands are the Haploxerands that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have, in any horizon at a depth between 50 and 100
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, both aquic conditions and any of the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated;
3. Do not have, between depths of 25 and 100 cm, a layer 10
cm or more thick with more than 3.0 percent organic carbon
and the colors of a mollic epipedon throughout, occurring
below a horizon or horizons 10 cm or more thick with a color
value, moist, 1 unit or more higher and an organic-carbon
content 1 percent or more lower;
4. Do not have a calcic horizon with its upper boundary
within 125 cm of the mineral soil surface;
5. Do not have an argillic or kandic horizon with its upper
boundary within 125 cm of the mineral soil surface or of the
upper boundary of an organic layer that has andic soil
properties, whichever is shallower; and
6. Do not have either a mollic or umbric epipedon.
Description of Subgroups
Typic Haploxerands.—The central concept or Typic
subgroup of Haploxerands is fixed on moderately deep or deep
Andisols 325
soils that have an ochric epipedon and do not have an argillic
horizon. Soils that have both aquic conditions (or artificial
drainage) and redox features in any horizon at a depth between
50 and 100 cm either from the mineral soil surface or from the
top of an organic layer with andic soil properties, whichever is
shallower, are excluded from the Typic subgroup and are
considered intergrades to Aquands. Soils that have, at a depth
between 40 and 100 cm either from the mineral soil surface or
from the top of an organic layer with andic soil properties,
whichever is shallower, a dark colored layer 10 cm or more
thick with more than 3.0 percent organic carbon, underlying one
or more lighter colored horizons with a total thickness of 10 cm
or more and a lower content of organic carbon, also are
excluded. Soils that have a lithic contact within a depth of 50
cm are assigned to the Lithic subgroup.
Typic Haploxerands commonly support coniferous forest
vegetation. Most of these soils are used for timber production,
but some have been cleared and are used as cropland.
Alfic Haploxerands.—These soils are like Typic
Haploxerands, but they have an argillic or kandic horizon that
has both an upper boundary within 125 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower, and a base saturation
(by sum of cations) of 35 percent or more in some part of the
upper 50 cm or in the entire horizon if it is less than 50 cm
thick. These soils are rare in the United States.
Alfic Humic Haploxerands.—These soils are like Typic
Haploxerands, but they have an argillic or kandic horizon that
has both an upper boundary within 125 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower, and a base saturation
(by sum of cations) of 35 percent or more in some part of the
upper 50 cm or in the entire horizon if it is less than 50 cm
thick. They also have a melanic, mollic, or umbric epipedon.
They are rare in the United States.
Aquic Haploxerands.—These soils are like Typic
Haploxerands, but they have both aquic conditions (or artificial
drainage) and redox features in a horizon at a depth between
50 and 100 cm either from the mineral soil surface or from the
top of an organic layer with andic soil properties, whichever is
shallower. These soils are rare in the United States. They are
known to occur in Washington and Oregon.
Calcic Haploxerands.—These soils are like Typic
Haploxerands, but they have a calcic horizon that has its upper
boundary within 125 cm either of the mineral soil surface or of
the top of an organic layer with andic soil properties,
whichever is shallower. These soils have not been recognized
in the United States. They are established for use in other
countries.
Humic Haploxerands.—These soils are like Typic
Haploxerands, but they have a melanic, mollic, or umbric
epipedon. They are of small extent in the United States. They
are known to occur in California and Washington.
Lithic Haploxerands.—These soils are like Typic
Haploxerands, but they have a lithic contact within 50 cm either
of the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower. These soils are of
small extent in the United States. They are known to occur in
California and Oregon.
Thaptic Haploxerands.—These soils are like Typic
Haploxerands, but they have, between depths of 25 and 100
cm, a buried, dark colored layer 10 cm or more thick below a
lighter colored horizon or horizons 10 cm or more thick with a
lower content of organic carbon. These soils have not been
recognized in the United States. They are established for use in
other countries.
Ultic Haploxerands.—These soils are like Typic
Haploxerands, but they have an argillic or kandic horizon that
has both an upper boundary within 125 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower, and a base saturation
(by sum of cations) of less than 35 percent throughout the
upper 50 cm or throughout the entire horizon if it is less than
50 cm thick. These soils are of small extent in the United
States. They are known to occur in California.
Melanoxerands
Melanoxerands are the Xerands that have a melanic epipedon
and a 1500 kPa water retention of 15 percent or more on air-dried
samples and 30 percent or more on undried samples throughout
more than 30 percent of the upper part.
Melanoxerands have a melanic epipedon and commonly
have a cambic horizon.
Most of the Melanoxerands in the United States developed
in late-Pleistocene or Holocene deposits. Most formed under
forest or savanna vegetation.
Definition
Melanoxerands are the Xerands that:
1. Have a melanic epipedon; and
2. Do not have a 1500 kPa water retention of less than 15
percent on air-dried samples and less than 30 percent on
undried samples throughout 60 percent or more of the
thickness either:
a. Within 60 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever
is shallower, if there is no densic, lithic, or paralithic
contact, duripan, or petrocalcic horizon within that depth;
or
b. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is
shallower, and a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon.
326 Soil Taxonomy
KeytoSubgroups
DDBA. Melanoxerands that have more than 6.0 percent
organic carbon and the colors of a mollic epipedon throughout
a layer 50 cm or more thick within 60 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Pachic Melanoxerands
DDBB. Other Melanoxerands.
Typic Melanoxerands
DefinitionofTypicMelanoxerands
Typic Melanoxerands are the Melanoxerands that do not
have both more than 6.0 percent organic carbon and the colors
of a mollic epipedon throughout at least 50 cm of the upper 60
cm, excluding any overlying layers that do not have andic soil
properties.
Description of Subgroups
Typic Melanoxerands.—The central concept or Typic
subgroup of Melanoxerands is fixed on soils that have a
melanic epipedon and do not have both more than 6.0 percent
organic carbon and the colors of a mollic epipedon throughout
at least 50 cm of the upper 60 cm below the mineral soil
surface or below the top of an organic layer with andic soil
properties, whichever is shallower.
These soils commonly support coniferous forest vegetation.
They are not extensive in the United States. They are known to
occur in Washington and California. Most of the soils are used
as woodland or have been cleared and are used as cropland or
pasture.
Pachic Melanoxerands.—These soils are like Typic
Melanoxerands, but they have both more than 6.0 percent
organic carbon and the colors of a mollic epipedon throughout
at least 50 cm of the upper 60 cm below the mineral soil
surface or below the top of an organic layer with andic soil
properties, whichever is shallower. These soils are of small
extent in the United States. They are known to occur in
Washington and California.
Vitrixerands
Vitrixerands are the relatively coarse textured Xerands. These
are relatively young soils that in many areas occur
near volcanoes. The soils are moderately extensive in the
United States. They are mostly in Oregon, Washington, and
Idaho. These soils formed mainly under coniferous forest
vegetation.
Commonly, Vitrixerands have an ochric or mollic epipedon
and a cambic horizon.
Most of the Vitrixerands in the United States developed in
Holocene or late-Pleistocene deposits.
Definition
Vitrixerands are the Xerands that have a 1500 kPa water
retention of less than 15 percent on air-dried samples and less
than 30 percent on undried samples throughout 60 percent or
more of the thickness either:
1. Within 60 cm either of the mineral soil surface or of
the top of an organic layer with andic soil properties,
whichever is shallower, if there is no densic, lithic, or
paralithic contact, duripan, or petrocalcic horizon within that
depth; or
2. Between either the mineral soil surface or the top of an
organic layer with andic soil properties, whichever is shallower,
and a densic, lithic, or paralithic contact, a duripan, or a
petrocalcic horizon.
KeytoSubgroups
DDAA. Vitrixerands that have a lithic contact within 50 cm of
the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower.
Lithic Vitrixerands
DDAB. Other Vitrixerands that have, in one or more
horizons at a depth between 50 and 100 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, aquic conditions
for some time in normal years (or artificial drainage) and one
or more of the following:
1. 2 percent or more redox concentrations; or
2. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
3. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Vitrixerands
DDAC. Other Vitrixerands that have, at a depth between 25
and 100 cm from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1
unit or more higher and an organic-carbon content 1 percent or
more (absolute) lower.
Thaptic Vitrixerands
DDAD. Other Vitrixerands that have both:
1. A melanic, mollic, or umbric epipedon; and
Andisols 327
2. An argillic or kandic horizon that has its upper boundary
within 125 cm of the mineral soil surface or of the top of an
organic layer with andic soil properties, whichever is
shallower.
Alfic Humic Vitrixerands
DDAE. Other Vitrixerands that have an argillic or kandic
horizon that has both:
1. An upper boundary within 125 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower; and
2. A base saturation (by sum of cations) of less than 35
percent throughout the upper 50 cm or throughout the entire
argillic or kandic horizon if it is less than 50 cm thick.
Ultic Vitrixerands
DDAF. Other Vitrixerands that have an argillic or kandic
horizon that has its upper boundary within 125 cm of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower.
Alfic Vitrixerands
DDAG. Other Vitrixerands that have a melanic, mollic, or
umbric epipedon.
Humic Vitrixerands
DDAH. Other Vitrixerands.
Typic Vitrixerands
Definition of Typic Vitrixerands
Typic Vitrixerands are the Vitrixerands that:
1. Do not have a lithic contact within 50 cm of the soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower;
2. Do not have, in any horizon at a depth between 50 and 100
cm either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, both aquic conditions and any of the following:
a. 2 percent or more redox concentrations; or
b. A color value, moist, of 4 or more and 50 percent or
more chroma of 2 or less either in redox depletions on faces
of peds or in the matrix if peds are absent; or
c. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated;
3. Do not have, at a depth between 25 and 100 cm from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, a layer 10 cm or
more thick with more than 3.0 percent organic carbon and the
colors of a mollic epipedon throughout, occurring below a
horizon or horizons 10 cm or more thick with a color value, moist,
1 unit or more higher and an organic-carbon content 1 percent or
more lower;
4. Do not have an argillic or kandic horizon that has its upper
boundary within 125 cm of the mineral soil surface or of the
upper boundary of an organic layer with andic soil properties,
whichever is shallower; and
5. Do not have a melanic, mollic, or umbric epipedon.
Description of Subgroups
Typic Vitrixerands.—The central concept or Typic
subgroup of Vitrixerands is fixed on moderately deep or deep
soils that have an ochric epipedon and do not have an argillic
horizon. Soils that have, at a depth between 40 and 100 cm
either from the mineral soil surface or from the top of an
organic layer with andic soil properties, whichever is
shallower, a dark colored layer 10 cm or more thick with more
than 3.0 percent organic carbon, underlying one or more lighter
colored horizons with a total thickness of 10 cm or more and a
lower content of organic carbon, are excluded from the Typic
subgroup.
Soils that have a lithic contact within a depth of 50 cm are
assigned to the Lithic subgroup. Soils that have both aquic
conditions (or artificial drainage) and redox features in any
horizon at a depth between 50 and 100 cm either from the
mineral soil surface or from the top of an organic layer with
andic soil properties, whichever is shallower, are excluded
from the Typic subgroup and are considered intergrades to
Aquands.
Typic Vitrixerands commonly support coniferous forest
vegetation. Most are used for timber production, but some have
been cleared and are used as cropland.
Alfic Vitrixerands.—These soils are like Typic
Vitrixerands, but they have an argillic or kandic horizon that
has both an upper boundary within 125 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower, and a base saturation
(by sum of cations) of 35 percent or more in some part of the
upper 50 cm or in the entire horizon if it is less than 50 cm
thick. These soils are rare in the United States.
Alfic Humic Vitrixerands.—These soils are like Typic
Vitrixerands, but they have an argillic or kandic horizon that
has both an upper boundary within 125 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower, and a base saturation
(by sum of cations) of 35 percent or more in some part of the
upper 50 cm or in the entire horizon if it is less than 50 cm
thick. They also have a melanic, mollic, or umbric epipedon.
These soils are rare in the United States.
Aquic Vitrixerands.—These soils are like Typic
Vitrixerands, but they have both aquic conditions (or artificial
drainage) and redox features in a horizon at a depth between
50 and 100 cm either from the mineral soil surface or from the
328
top of an organic layer with andic soil properties, whichever is
shallower. These soils are rare in the United States. They are
known to occur in Washington and Oregon.
Humic Vitrixerands.—These soils are like Typic
Vitrixerands, but they have a melanic, mollic, or umbric
epipedon. They are moderately extensive in the United States.
They are known to occur in Oregon, California, and
Washington.
Lithic Vitrixerands.—These soils are like Typic Vitrixerands,
but they have a lithic contact within 50 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower. These soils are of small
extent in the United States. They are known to occur in
California and Oregon.
Thaptic Vitrixerands.—These soils are like Typic
Vitrixerands, but they have, between depths of 25 and 100 cm, a
buried, dark colored layer 10 cm or more thick below a lighter
colored horizon or horizons 10 cm or more thick with a lower
content of organic carbon. These soils have not been
recognized in the United States. They are established for use in
other countries.
Ultic Vitrixerands.—These soils are like Typic
Vitrixerands, but they have an argillic or kandic horizon that
has both an upper boundary within 125 cm either of the
mineral soil surface or of the top of an organic layer with andic
soil properties, whichever is shallower, and a base saturation
(by sum of cations) of less than 35 percent throughout the upper
50 cm or throughout the entire horizon if it is less than 50 cm
thick. These soils are of small extent in the United States. They
are known to occur in California.
329
Aridisols, as their name implies, are soils in which water
is not available to mesophytic plants for long periods.
During most of the time when the soils are warm enough for
plants to grow, soil water is held at potentials less than the
permanent wilting point or has a content of soluble salts great
enough to limit the growth of plants other than halophytes, or
both. There is no period of 90 consecutive days when moisture
is continuously available for plant growth.
The concept of Aridisols is based on limited soil moisture
available for the growth of most plants. In areas bordering
deserts, the absolute precipitation may be sufficient for the
growth of some plants. Because of runoff or a very low storage
capacity of the soils, or both, however, the actual soil moisture
regime is aridic.
Soil moisture and to a lesser extent soil temperature regimes
control processes in soils. In the other soil orders, soil moisture
regimes are used at the suborder level or the lower categories,
but in the Aridisols they are used to define the order category.
The result is a rather homogeneous class in the sense that
additions, removals, transfers, and transformations within the
soils are strongly influenced by the lack of moisture. Aridisols
require a minimum degree of soil formation. This is commonly
expressed as a cambic horizon. Because the soil moisture
regime is the single most important constraint in the utilization
of these soils, this order delineates geographic areas that have
relatively uniform use.
Because of an extreme imbalance between
evapotranspiration and precipitation, many Aridisols contain
salts. The dominant process is one of accumulation and
concentration of weathering products. The accumulation of
salts is the second most important constraint to land use. Many
soluble precipitates may be eliminated or changed in
concentration through irrigation. In Aridisols, however, the
availability of adequate quality irrigation water is a
fundamental problem. Together with irrigation, a mechanism
for evacuation of the soluble precipitates must be provided or
there is a rapid buildup of salinity and/or sodicity. Irrigation
and drainage systems must be well maintained to keep the soils
from reverting to their original state.
The classification of Aridisols must include consideration of
these constraints or performance restrictive qualities at a high
categoric level. Some Aridisols are also situated on geologic
evaporites. It is frequently difficult to bring these substratum
conditions into a classification system, but care must be taken
to evaluate these deep-seated salt accumulations, particularly in
irrigation projects.
Some Aridisols have inherited features, such as an argillic
horizon, that may be attributed to past wetter paleoclimatic
conditions. There is evidence, however, that clay illuviation
has also occurred during the Holocene. These attributes, and
specifically an argillic horizon, significantly affect the use and
management of the soils.
In the definition of suborders, emphasis is given to the
redistribution of soluble materials and their accumulation. Four
of the seven suborders are defined on the basis of the
composition and accumulation of the soluble fraction.
Weathering and clay translocation also take place in Aridisols.
Two suborders reflect these processes. The seven suborders are:
1. Cryids—Aridisols in cold areas
2. Salids—accumulation of salts more soluble than
gypsum
3. Durids—accumulation of silica
4. Gypsids—accumulation of gypsum
5. Argids—accumulation of clay
6. Calcids—accumulation of carbonates
7. Cambids—translocation and/or transformation of
material
The great group level reflects the degree of expression of the
horizons of accumulation and/or the results of other processes
that are considered subordinate to the particular suborder. The
defining element is the degree of expression of the diagnostic
horizon.
Definition of Aridisols and Limits Between
Aridisols and Soils of Other Orders
1. Unlike Inceptisols and Entisols, Aridisols have:
a. An aridic soil moisture regime; and
b. An ochric or anthropic epipedon; and
c. One or more of the following with the upper boundary
within 100 cm of the soil surface: a cambic horizon with its
lower boundary at a depth of 25 cm or more; a cryic
CHAPTER 11
Aridisols1
1
This chapter was rewritten in 1994 following recommendations of the International
Committee on Aridisols (ICOMID), chaired by Dr. A. Osman. Major contributions were made
by Dr. H. Eswaran, J. Nichols, and Dr. Mohammad Ilaiwi.
330 Soil Taxonomy
temperature regime and a cambic horizon; a calcic, gypsic,
petrocalcic, petrogypsic, or salic horizon; or a duripan; or
d. An argillic or natric horizon; or
e. A salic horizon; and
(1) Saturation with water in one or more layers within
100 cm of the soil surface for 1 month or more in normal
years; and
(2) A moisture control section that is dry in some or all
parts at some time in normal years; and
(3) No sulfuric horizon that has its upper boundary
within 150 cm of the mineral soil surface;
2. Unlike Histosols, Aridisols do not have organic soil
materials that meet one or more of following:
a. Overlie cindery, fragmental, or pumiceous materials
and/or fill their interstices and directly below these
materials have either a densic, lithic, or paralithic contact;
or
b. When added with the underlying cindery, fragmental, or
pumiceous materials, total 40 cm or more between the soil
surface and a depth of 50 cm; or
c. Constitute two-thirds or more of the total thickness of
the soil to a densic, lithic, or paralithic contact and have no
mineral horizons or have mineral horizons with a total
thickness of 10 cm or less; or
d. Are saturated with water for 30 days or more in normal
years (or are artificially drained), have an upper boundary
within 40 cm of the soil surface, and have a total thickness
of either:
(1) 60 cm or more if three-fourths or more of their
volume consists of moss fibers or if their bulk density,
moist, is less than 0.1 g/cm3
; or
(2) 40 cm or more if they consist either of sapric or
hemic materials, or of fibric materials with less than
three-fourths (by volume) moss fibers and a bulk density,
moist, of 0.1 g/cm3
or more;
3. Unlike Gelisols, Aridisols do not have:
a. Permafrost within 100 cm of the soil surface; or
b. Gelic materials within 100 cm of the soil surface and
permafrost within 200 cm of the soil surface;
4. Unlike Spodosols, Aridisols do not have either:
a. A spodic horizon and an albic horizon in 50 percent or
more of each pedon; or
b. An Ap horizon containing 85 percent or more spodic
materials;
5. Unlike Andisols, Aridisols do not have andic soil
properties in 60 percent or more of the thickness between
either the mineral soil surface or the top of an organic layer
with andic soil properties, whichever is shallower, and a depth
of 60 cm or a densic, lithic, or paralithic contact, a duripan, or
a petrocalcic horizon, whichever is shallower;
6. Unlike Oxisols, Aridisols do not have within 150 cm of the
mineral soil surface either an oxic horizon or a kandic horizon
that meets the weatherable-mineral requirements for an oxic
horizon and also do not have 40 percent or more clay in the
surface 18 cm after mixing;
7. Unlike Vertisols, Aridisols do not have all of the following:
a. A layer 25 cm or more thick, with an upper boundary
within 100 cm of the mineral soil surface, that has either
slickensides or wedge-shaped aggregates that have their
long axes tilted 10 to 60 degrees from the horizontal; and
b. A weighted average of 30 percent or more clay in the
fine-earth fraction either between the mineral soil surface
and a depth of 18 cm or an Ap horizon, whichever is
thicker, and 30 percent or more clay in the fine-earth
fraction of all horizons between a depth of 18 cm and either
a depth of 50 cm or a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon if shallower; and
c. Cracks that open and close periodically;
8. Unlike Alfisols and Ultisols, Aridisols have an aridic soil
moisture regime;
9. Unlike Mollisols, Aridisols do not have a mollic epipedon.
Representative Pedon and Data
Following is a description of a representative Aridisol. Data
for the pedon identified in this description are given in the
table “Characterization Data for an Aridisol.”
Classification: Coarse-loamy, carbonatic, thermic Ustic
Haplocalcid
Site identification number: 40A3562
Location: Cochise County, Arizona; 5.6 km east and 22.5 km
south of Willcox, Arizona; 320 m north and 180 m east of
the S1
/4 corner of sec. 11, T. 16 S., R. 24 E.
Slope: 3 percent
Elevation: 1,293 m above m.s.l.
Annual precipitation: 280 mm
Soil moisture regime: Aridic
Air temperature: Average annual—14 o
C; summer—17 o
C;
winter—12 o
C
Drainage class: Well drained
Land use: Cropland
Runoff class: Low
Particle-size control section: 56 to 100 cm
Parent material: Mixed alluvium derived from andesite,
limestone, and quartzite
Aridisols 331
Diagnostic horizons: An ochric epipedon from a depth of 0 to 56
cm and a calcic horizon from a depth of 56 to 269 cm
Described by: J. Jay and M.L. Richardson
In the following pedon description, colors are for dry soil
unless otherwise indicated. Field determination of pH was
made by a colormetric method.
Ap1—0 to 33 cm; light brownish gray (10YR 6/2) loam, brown
(10YR 4/3) moist; moderate fine granular structure;
slightly hard, friable, slightly plastic; many fine to coarse
roots; many fine interstitial pores; continuous violent
effervescence; moderately alkaline (pH 8.2); gradual
smooth boundary.
Ap2—33 to 56 cm; light brownish gray (10YR 6/2) loam,
brown (10YR 4/3) moist; weak fine subangular blocky
structure; slightly hard, friable, slightly sticky and slightly
plastic; many fine to coarse roots; many fine interstitial
pores; continuous violent effervescence; moderately
alkaline (pH 8.2); abrupt irregular boundary.
Bk1—56 to 81 cm; pale brown (10YR 6/3) and white (10YR
8/2) loam, brown (10YR 5/3) and 1 percent pale brown
(10YR 6/3) moist; massive; extremely hard, firm,
nonsticky and slightly plastic; many fine to coarse roots;
many very fine and fine tubular pores; continuous violent
effervescence; 50 to 60 percent medium and large
carbonate masses that are extremely hard and slightly
rigid; strongly alkaline (pH 8.8); gradual smooth
boundary.
Bk2—81 to 107 cm; white (10YR 8/2) and pinkish gray
(7.5YR 7/2) clay loam, light brown (7.5YR 6/4) moist;
weak fine subangular blocky structure; very hard, friable,
slightly sticky and slightly plastic; many fine to coarse
roots; many very fine and fine tubular pores; continuous
violent effervescence; approximately 9 percent carbonate
masses that are extremely hard and slightly rigid; strongly
alkaline (pH 8.6); gradual smooth boundary.
Bk3—107 to 135 cm; pinkish white (7.5YR 8/2) loam, light
brown (7.5YR 6/4) and pink (7.5YR 7/4) moist; weak fine
subangular blocky structure parting to weak fine granular;
slightly hard, friable, slightly sticky and slightly plastic;
many fine to coarse roots; many very fine and fine tubular
pores; continuous violent effervescence; 50 to 60 percent
5- to 25-mm, rounded and irregularly shaped carbonate
masses; strongly alkaline (pH 8.6); clear smooth
boundary.
Bk4—135 to 269 cm; white (10YR 8/2) and pink (7.5YR 7/4)
clay loam, light brown (7.5YR 6/4) moist; weak fine
subangular blocky structure; very hard, extremely firm,
slightly sticky and plastic; many fine to coarse roots; many
very fine to medium tubular pores; continuous violent
effervescence; 10 to 15 percent 6- to 30-mm carbonate
masses; strongly alkaline (pH 8.8); clear irregular
boundary.
2C—269 to 279 cm; light brown (7.5YR 6/4) clay, brown (7.5YR
4/4) moist; common coarse distinct pink (7.5YR 7/4) mottles;
weak fine and medium subangular blocky structure; hard,
very firm, very plastic; many fine to coarse roots; common
medium and many very fine and fine tubular pores;
continuous violent effervescence; strongly alkaline (pH
8.6).
Key to Suborders
GA. Aridisols that have a cryic soil temperature regime.
Cryids, p. 365
GB. Other Aridisols that have a salic horizon that has its
upper boundary within 100 cm of the soil surface.
Salids, p. 387
GC. Other Aridisols that have a duripan that has its upper
boundary within 100 cm of the soil surface.
Durids, p. 372
GD. Other Aridisols that have a gypsic or petrogypsic horizon
that has its upper boundary within 100 cm of the soil surface
and do not have a petrocalcic horizon overlying these horizons.
Gypsids, p. 379
GE. Other Aridisols that have an argillic or natric
horizon (deleted text) and do not have a petrocalcic horizon
than has an upper boundary within 100 cm of the soil
surface.
Argids, p. 331
GF. Other Aridisols that have a calcic or petrocalcic horizon
that has its upper boundary within 100 cm of the soil surface.
Calcids, p. 351
GG. Other Aridisols.
Cambids, p. 357
Argids
These are the Aridisols that have an argillic or natric
horizon but do not have a duripan or a gypsic, petrocalcic,
petrogypsic, or salic horizon within 100 cm of the soil surface.
The low water flux and high concentration of salts in many
Aridisols hinder clay illuviation. The presence of an argillic
horizon commonly is attributed to a moister paleoclimate,
although there is evidence that clay illuviation occurred during
the Holocene in arid soils. Where the soil moisture regime
grades to ustic or xeric, evidence of clay translocation
commonly is more readily established. Most of the Argids
occur in North America. A few have been recognized in the
deserts of North Africa or the Near East.
332 Soil Taxonomy
Characterization Data for an Aridisol
SITE IDENTIFICATION NO.: 40A3562
CLASSIFICATION: COARSE-LOAMY, CARBONATIC, THERMIC USTIC HAPLOCALCID
GENERAL METHODS: 1B1A, 2A1, 2B
-1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-
-----------------------------------------------------------------------------------------------------------------------------------
(- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)
CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT
SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF
NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE
<- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL
4027472 0- 33 Ap1 17.2 32.4 50.4 5.0 17.9 14.5 10.9 17.2 8.4 9.8 4.1 -- -- -- 39 --
4027473 33- 56 Ap2 18.3 34.5 47.2 6.0 17.9 16.6 11.9 16.3 7.5 8.1 3.4 -- -- -- 35 --
4027474 56- 81 Bk1 29.2 32.9 37.9 15.0 19.8 13.1 9.2 11.6 5.5 7.5 4.1 -- -- -- 29 --
4027475 81-107 Bk2 38.1 36.2 25.7 24.0 23.7 12.5 7.3 8.4 3.5 4.1 2.4 -- -- -- 18 --
4027476 107-135 Bk3 45.1 31.6 23.3 29.0 20.4 11.2 6.1 8.8 3.2 3.4 1.8 -- -- -- 17 --
4027477 135-269 Bk4 50.2 29.4 20.4 33.0 21.1 8.3 5.9 6.6 2.7 3.5 1.7 -- -- -- 14 --
4027478 269-279 2C 40.2 34.1 25.7 13.0 24.6 9.5 10.3 9.3 2.8 2.3 1.0 -- -- 2 17 2
-----------------------------------------------------------------------------------------------------------------------------------
ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD
C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE
DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL
(cm) 6A1c 6B4a 6S3 6R3b 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A5 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1
Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm
0- 33 0.90 0.093 0.88 0.86 14.8
33- 56 0.60 0.067 0.79 0.85 15.6
56- 81 0.34 0.32 0.52 58 28 15.3
81-107 0.18 0.29 0.40 45 23 15.3
107-135 0.16 0.26 0.33 14.7
135-269 0.11 0.19 0.32 16.3
269-279 0.03 0.38 0.36 14.6
-----------------------------------------------------------------------------------------------------------------------------------
(- NH4OAc EXTRACTABLE BASES -) ACID- (- -CEC- -) EXCH SAR BASE CARBONATE CaSO4 AS (- - - -PH - - -)
Ca Mg Na K SUM ITY SUM NH4- Na SATURATION AS CaCO3 GYPSUM SAT CaCl2 H2O
DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc SUM NH4OAc <2mm <20mm <2mm <20mm PASTE .01M
(cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 5A3a 5A8b 55D2 5E 5C3 5C1 6E1g 6E4 6F1a 6F4 8C1b 8C1f 8C1f
<- - - - - - - - - -meq / 100 g - - - - - - - - - -> Pct <- -Pct- > <- -Pct -> <- -Pct -> 1:2 1:1
0- 33 3.2 1.0 1.7 15.1 4 2 100 100 27 7.8
33- 56 3.3 0.8 2.0 14.5 4 2 100 100 29 8.0
56- 81 3.9 0.8 1.6 9.4 7 2 100 100 46 8.1
81-107 3.6 1.0 1.3 10.9 8 2 100 100 60 8.1
107-135 3.9 1.1 1.5 11.5 7 2 100 100 55 8.1
135-269 4.7 0.9 1.5 9.6 7 2 100 100 58 8.1
269-279 4.7 0.9 2.0 15.4 5 2 100 100 29 8.0
-----------------------------------------------------------------------------------------------------------------------------------
(- - - - - - - - - - -WATER EXTRACTED FROM SATURATED PASTE- - - - - - - - - - - - - )PRED.
TOTAL ELEC. ELEC.
Ca Mg Na K CO3 HCO3 F Cl SO4 NO2 NO3 H2O SALTS COND. COND.
DEPTH EST. 8A3a 8I
(cm) 6N1b 6O1b 6P1b 6Q1b 6I1b 6J1b 6U1a 6K1c 6L1c 6W1a 6M1c 8A 8D5 mmhos mmhos
< - - - - - - - - - - - - - -meq / liter - - - - - - - - - - - -> <- -Pct- -> /cm /cm
0- 33 18.6 4.0 6.9 0.8 -- 2.2 5.0 51.8 0.1 2.83
33- 56 6.4 1.5 3.4 0.4 -- 2.3 2.5 54.3 TR 1.17
56- 81 5.4 2.0 3.2 0.8 -- 2.8 2.2 53.8 TR 1.13
81-107 2.8 2.2 3.4 0.8 -- 2.0 2.2 49.2 TR 1.13
107-135 5.5 2.6 5.0 1.0 -- 2.2 2.2 49.6 TR 1.40
135-269 5.6 2.2 4.4 1.2 -- 2.2 2.1 52.3 TR 1.37
269-279 4.9 2.0 3.2 0.8 -- 1.8 1.7 59.9 TR 1.09
-----------------------------------------------------------------------------------------------------------------------------------
The chemical data are based on the fraction less than 2 mm in size.
Aridisols 333
Definition
Argids are the Aridisols that:
1. Have a natric or argillic horizon (deleted text);
2. Have a soil temperature regime warmer than cryic;
3. Do not have a duripan or a gypsic, petrocalcic, petrogypsic,
or salic horizon that has its upper boundary within 100 cm of the
soil surface.
Key to Great Groups
GEA. Argids that have a duripan or a petrocalcic or
petrogypsic horizon that has its upper boundary within 150 cm
of the soil surface.
Petroargids, p. 350
GEB. Other Argids that have a natric horizon.
Natrargids, p. 343
GEC. Other Argids that do not have a densic, lithic, or
paralithic contact within 50 cm of the soil surface and have
either:
1. A clay increase of 15 percent or more (absolute) within
a vertical distance of 2.5 cm either within the argillic
horizon or at its upper boundary; or
2. An argillic horizon that extends to 150 cm or more
from the soil surface, that does not have a clay decrease with
increasing depth of 20 percent or more (relative) from the
maximum clay content, and that has, in 50 percent or more
of the matrix in some part between 100 and 150 cm, either:
a. Hue of 7.5YR or redder and chroma of 5 or more; or
b. Hue of 7.5YR or redder and value, moist, of 3 or less
and value, dry, of 4 or less.
Paleargids, p. 346
GED. Other Argids that have a gypsic horizon that has its
upper boundary within 150 cm of the soil surface.
Gypsiargids, p. 337
GEE. Other Argids that have a calcic horizon that has its
upper boundary within 150 cm of the soil surface.
Calciargids, p. 333
GEF. Other Argids.
Haplargids, p. 339
Calciargids
These are the Argids that, below the argillic horizon, have a
calcic horizon within 150 cm of the soil surface. These soils
have been recharged with calcium carbonate from dust.
Calciargids are commonly on late-Pleistocene erosional
surfaces or on gentle to steep slopes. Before the International
Committee on Aridisols (ICOMID) was established, these soils
were classified as Haplargids.
Definition
Calciargids are the Argids that:
1. Have a calcic horizon that has its upper boundary within 150
cm of the soil surface;
2. Do not have a natric horizon;
3. Do not have a duripan or a gypsic, petrocalcic, or
petrogypsic horizon that has its upper boundary within 150 cm
of the soil surface;
4. Have a densic, lithic, or paralithic contact within 50 cm of
the soil surface; or
a. A clay increase of less than 15 percent (absolute) within
a vertical distance of 2.5 cm either within the argillic
horizon or at its upper boundary; or
b. An argillic horizon that does not extend to 150 cm from
the soil surface, has a clay decrease with increasing depth of
20 percent or more (relative) from the maximum clay
content, or has either:
(1) Hue of 10YR or yellower or chroma of 4 or less in
the matrix of all horizons between depths of 100 and 150
cm; or
(2) Hue of 10YR or yellower and value, moist, of 4 or
more or value, dry, of 4 or less in less than 50 percent of
the matrix.
Key to Subgroups
GEEA. Calciargids that have a lithic contact within 50 cm of
the soil surface.
Lithic Calciargids
GEEB. Other Calciargids that have both:
1. One or both of the following:
a. Cracks within 125 cm of the soil surface that are 5
mm or more wide through a thickness of 30 cm or more
for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the soil
surface; or
b. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact if shallower; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
334 Soil Taxonomy
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric.
Xerertic Calciargids
GEEC. Other Calciargids that have both:
1. One or both of the following:
a. Cracks within 125 cm of the soil surface that are 5
mm or more wide through a thickness of 30 cm or more
for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the soil
surface; or
b. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact if shallower; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on ustic.
Ustertic Calciargids
GEED. Other Calciargids that have one or both of the
following:
1. Cracks within 125 cm of the soil surface that are 5 mm
or more wide through a thickness of 30 cm or more for some
time in normal years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has its upper
boundary within 125 cm of the soil surface; or
2. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic, lithic,
or paralithic contact if shallower.
Vertic Calciargids
GEEE. Other Calciargids that are either:
1. Irrigated and have aquic conditions for some time in
normal years in one or more layers within 100 cm of the soil
surface; or
2. Saturated with water in one or more layers within
100 cm of the soil surface for 1 month or more in normal
years.
Aquic Calciargids
GEEF. Other Calciargids that have:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the soil surface to the top of an
argillic horizon at a depth of 50 cm or more; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature at a depth of 50 cm is 5 o
C or higher and a
soil moisture regime that borders on ustic.
Arenic Ustic Calciargids
GEEG. Other Calciargids that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the soil
surface to the top of an argillic horizon at a depth of 50 cm or
more.
Arenic Calciargids
GEEH. Other Calciargids that have the following
combination of characteristics:
1. Have one or more horizons, within 100 cm of the soil
surface and with a combined thickness of 15 cm or more,
that contain 20 percent or more (by volume) durinodes or
are brittle and have at least a firm rupture-resistance class
when moist; and
2. Are dry in all parts of the moisture control section for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and
have a soil moisture regime that borders on xeric.
Durinodic Xeric Calciargids
GEEI. Other Calciargids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that contain 20 percent or more
(by volume) durinodes or are brittle and have at least a firm
rupture-resistance class when moist.
Durinodic Calciargids
GEEJ. Other Calciargids that:
1. Are dry in all parts of the moisture control section
for less than three-fourths of the time (cumulative) when
the soil temperature at a depth of 50 cm is 5 o
C or higher
and have a soil moisture regime that borders on xeric;
and
2. Have one or more horizons, within 100 cm of the soil
surface and with a combined thickness of 15 cm or more,
that contain 20 percent or more (by volume) nodules or
concretions.
Petronodic Xeric Calciargids
GEEK. Other Calciargids that:
1. Are dry in all parts of the moisture control section
for less than three-fourths of the time (cumulative) when
the soil temperature at a depth of 50 cm is 5 o
C or higher
and have a soil moisture regime that borders on ustic;
and
2. Have one or more horizons, within 100 cm of the soil
surface and with a combined thickness of 15 cm or more,
Aridisols 335
that contain 20 percent or more (by volume) nodules or
concretions.
Petronodic Ustic Calciargids
GEEL. Other Calciargids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that contain 20 percent or more
(by volume) nodules or concretions.
Petronodic Calciargids
GEEM. Other Calciargids that have both:
1. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Calciargids
GEEN. Other Calciargids that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Calciargids
GEEO. Other Calciargids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature at a depth of 50 cm is
5 o
C or higher and have a soil moisture regime that borders on
xeric.
Xeric Calciargids
GEEP. Other Calciargids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature at a depth of 50 cm is
5 o
C or higher and have a soil moisture regime that borders on
ustic.
Ustic Calciargids
GEEQ. Other Calciargids.
Typic Calciargids
Definition of Typic Calciargids
Typic Calciargids are the Calciargids that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Are not both irrigated and characterized by aquic
conditions for some time in normal years in one or more layers
within 100 cm of the soil surface and are not saturated with
water in one or more layers within 100 cm of the soil surface
for 1 month or more in normal years;
3. Do not have one or more horizons, within 100 cm of the
soil surface and with a combined thickness of more than 15
cm, that contain 20 percent or more (by volume) durinodes,
nodules, or concretions or are brittle and have at least a firm
rupture-resistance class when moist;
4. Are dry in all parts of the moisture control section for
three-fourths or more of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm;
5. Do not have a sandy or sandy-skeletal particle-size class in
all layers extending from the soil surface to the top of an
argillic horizon at a depth of 50 cm or more;
6. Have either:
a. No cracks within 125 cm of the soil surface that are
5 mm or more wide through a thickness of 30 cm or more
for some time in normal years, and no slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the soil
surface; or
b. A linear extensibility of less than 6.0 cm between the
soil surface and either a depth of 100 cm or a densic, lithic,
or paralithic contact, whichever is shallower;
7. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
336 Soil Taxonomy
Description of Subgroups
Typic Calciargids.—These soils are among the driest of the
Calciargids. Soils in which the soil moisture regime borders on
ustic or xeric are more moist and are the basis for the Ustic and
Xeric subgroups. Typic Calciargids do not have a high shrinkswell
potential or a lithic contact within 50 cm of the soil
surface. They do not have a significant amount of durinodes,
nodules, concretions, volcanic glass, cinders, pumice, or
pumicelike fragments. They do not have a layer that is partially
cemented by silica. They do not have a thick sandy surface
horizon and are not saturated for 1 month in normal years.
These soils occur in the deserts of the western part of the
United States and are used for grazing.
Aquic Calciargids.—These are the Calciargids that are
saturated within 100 cm of the soil surface for short periods but
are dry enough to meet the requirements of an aridic soil
moisture regime. These soils do not have a high shrink-swell
potential or a lithic contact within 50 cm of the soil surface.
They are rare in the world.
Arenic Calciargids.—These are the Calciargids that have a
sandy or sandy-skeletal particle-size class from the soil surface
to a depth of 50 cm or more and have a soil moisture regime
that does not border on ustic. These soils do not have a lithic
contact within 50 cm of the surface and are not saturated
within 100 cm of the soil surface. They are known to occur in
the desert of California.
Arenic Ustic Calciargids.—These are the Calciargids that
have a sandy or sandy-skeletal particle-size class from the
surface to a depth of 50 cm or more and have a soil moisture
regime that borders on ustic. These soils do not have a lithic
contact within 50 cm of the soil surface or aquic conditions for
more than 1 month per year within 100 cm of the soil surface.
Durinodic Calciargids.—These are the Calciargids that
have a horizon with 20 percent or more durinodes or are brittle
and have at least a firm rupture-resistance class. These soils do
not have a lithic contact within 50 cm of the soil surface and
are not saturated within 100 cm of the soil surface for 1 month
or more in normal years. Durinodic Calciargids do not have
thick sandy horizons from the surface to a depth of 50 cm or
more, nor do they have a high shrink-swell potential. These
soils occur in Nevada and Idaho and are used primarily for
grazing by livestock.
Durinodic Xeric Calciargids.—These are the Calciargids
that have a horizon with 20 percent or more durinodes or are
brittle and have at least a firm rupture-resistance class. These
soils have a soil moisture regime that borders on xeric. They do
not have a lithic contact within 50 cm of the soil surface and
are not saturated within 100 cm of the soil surface for 1 month
or more in normal years. Durinodic Xeric Calciargids do not
have thick sandy horizons from the surface to a depth of 50 cm
or more, nor do they have a high shrink-swell potential. These
soils occur in Nevada and Idaho and are used primarily for
grazing by livestock.
Lithic Calciargids.—These are the Calciargids that have a
lithic contact within 50 cm of the soil surface. These soils
occur in several States in the southwestern part of the United
States. They are commonly used for grazing by livestock.
Petronodic Calciargids.—These are the Calciargids that
have one or more horizons, 15 cm or more thick, that have 20
percent or more (by volume) nodules or concretions. The
nodules and concretions are not cemented by silica (durinodes).
These soils do not have a lithic contact within 50 cm of the soil
surface or a high shrink-swell potential. They are not saturated
within 100 cm of the soil surface, nor do they have thick sandy
layers starting at the soil surface. Petronodic Calciargids do not
have a soil moisture regime that borders on ustic or xeric.
These soils occur in California, Arizona, and New Mexico and
are used as rangeland.
Petronodic Ustic Calciargids.—These are the Calciargids
that have, in one or more horizons with a combined thickness
of 15 cm or more, 20 percent or more (by volume) nodules or
concretions and that have a soil moisture regime that borders
on ustic. These soils do not have a lithic contact within 50 cm
of the soil surface, a high shrink-swell potential, saturation
with water for 1 month or more within 100 cm of the soil
surface, or durinodes or brittleness. Petronodic Ustic
Calciargids occur in Arizona and New Mexico.
Petronodic Xeric Calciargids.—These are the Calciargids
that have a soil moisture regime that borders on xeric and have
one or more horizons, 15 cm or more thick, that have 20
percent or more (by volume) nodules or concretions. The
nodules and concretions are not cemented by silica (durinodes).
These soils do not have a lithic contact within 50 cm of the soil
surface or a high shrink-swell potential. Petronodic Xeric
Calciargids are not saturated within 100 cm of the soil surface,
nor do they have thick sandy layers starting at the soil surface.
These soils are moderately extensive in Idaho and are used as
irrigated cropland, pasture, or rangeland.
Ustertic Calciargids.—These are the Calciargids that have
a high shrink-swell potential and a soil moisture regime that
borders on ustic. These soils do not have a lithic contact within
50 cm of the soil surface. They occur in the southwestern part
of the United States and are commonly used as rangeland.
Ustic Calciargids.—These are the Calciargids that have a
soil moisture regime that borders on ustic. These soils do not
have many other distinguishing characteristics, such as a lithic
contact within 50 cm of the soil surface; a high shrink-swell
potential; an accumulation of durinodes, concretions, or
nodules; or a significant amount of volcanic glass, pumice,
cinders, or pumicelike fragments near the surface. These soils
occur in various States throughout the southwestern part of the
United States. They are extensive and are used as irrigated
cropland, pasture, or rangeland.
Vertic Calciargids.—These are the Calciargids that have
a high shrink-swell potential but do not have a soil moisture
regime that borders on ustic or xeric. These soils also do not
have a lithic contact within 50 cm of the soil surface. Vertic
Aridisols 337
Calciargids occur in the southwestern part of the United
States.
Vitrandic Calciargids.—These are the Calciargids that
have a layer 18 cm or more thick in the upper 75 cm with a
significant amount of volcanic glass, pumice, cinders, and
pumicelike fragments. These soils do not have a lithic contact
within 50 cm of the soil surface; a high shrink-swell potential;
an accumulation of nodules, concretions, or durinodes; or a soil
moisture regime that borders on xeric. These soils occur in the
southwestern part of the United States, in areas that have a
volcanic influence.
Vitrixerandic Calciargids.—These are the Calciargids that
have a layer 18 cm or more thick in the upper 75 cm with a
significant amount of volcanic glass, pumice, cinders, and
pumicelike fragments and have a soil moisture regime that
borders on xeric. These soils do not have a lithic contact within
50 cm of the soil surface; a high shrink-swell potential; or an
accumulation of nodules, concretions, or durinodes. They occur
in the southwestern part of the United States, in areas that have
a volcanic influence.
Xerertic Calciargids.—These are the Calciargids that have
a high shrink-swell potential and have a soil moisture regime
that borders on xeric. These soils do not have a lithic contact
within 50 cm of the soil surface.
Xeric Calciargids.—These are the Calciargids that have a
soil moisture regime that borders on xeric. These soils do not
have many other distinguishing characteristics, such as a lithic
contact within 50 cm of the soil surface; a high shrink-swell
potential; an accumulation of durinodes, concretions, or
nodules; or a significant amount of volcanic glass, pumice,
cinders, or pumicelike fragments near the surface. These soils
occur in various States throughout the western part of the
United States. They are extensive and are used as irrigated
cropland, pasture, or rangeland.
Gypsiargids
Gypsiargids are the Argids that have a gypsic horizon within
150 cm of the soil surface. Most of these soils are on latePleistocene
surfaces. In the United States, they are of minor
extent and are known to occur in northwestern New Mexico and
possibly in other States in the Four Corners area.
Definition
Gypsiargids are the Argids that:
1. Have a gypsic horizon that has its upper boundary within
150 cm of the soil surface;
2. Do not have a duripan or a petrocalcic or petrogypsic
horizon that has its upper boundary within 150 cm of the soil
surface;
3. Do not have a natric horizon;
4. Have a densic, lithic, or paralithic contact within 50 cm of the
soil surface; or
a. A clay increase of less than 15 percent (absolute) within
a vertical distance of 2.5 cm either within the argillic
horizon or at its upper boundary; or
b. An argillic horizon that does not extend to 150 cm from
the soil surface, has a clay decrease with increasing depth of
20 percent or more (relative) from the maximum clay
content, or has either:
(1) Hue of 10YR or yellower or chroma of 4 or less in
the matrix of all horizons between depths of 100 and 150
cm; or
(2) Hue of 10YR or yellower and value, moist, of 4 or
more or value, dry, of 4 or less in less than 50 percent of
the matrix.
Key to Subgroups
GEDA. Gypsiargids that are either:
1. Irrigated and have aquic conditions for some time in
normal years in one or more layers within 100 cm of the soil
surface; or
2. Are saturated with water in one or more layers within
100 cm of the soil surface for 1 month or more in normal
years.
Aquic Gypsiargids
GEDB. Other Gypsiargids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that either contain 20 percent or
more (by volume) durinodes or are brittle and have at least a
firm rupture-resistance class when moist.
Durinodic Gypsiargids
GEDC. Other Gypsiargids that have both:
1. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
338 Soil Taxonomy
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Gypsiargids
GEDD. Other Gypsiargids that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Gypsiargids
GEDE. Other Gypsiargids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature at a depth of 50 cm is
5 o
C or higher and have a soil moisture regime that borders on
xeric.
Xeric Gypsiargids
GEDF. Other Gypsiargids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
ustic.
Ustic Gypsiargids
GEDG. Other Gypsiargids.
Typic Gypsiargids
Definition of Typic Gypsiargids
Typic Gypsiargids are the Gypsiargids that:
1. Are not both irrigated and characterized by aquic
conditions for some time in normal years in one or more layers
within 100 cm of the soil surface and are not saturated with
water in one or more layers within 100 cm of the soil surface
for 1 month or more in normal years;
2. Do not have one or more horizons, within 100 cm of the
soil surface and with a combined thickness of more than 15
cm, that contain 20 percent or more (by volume) durinodes or
are brittle and have at least a firm rupture-resistance class
when moist;
3. Are dry in all parts of the moisture control section for
three-fourths or more of the time (cumulative) when the soil
temperature at a depth of 50 cm is 5 o
C or higher;
4. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Description of Subgroups
Typic Gypsiargids.—The Typic subgroup is centered on
the soils that are not saturated for 1 month or more within 100
cm of the soil surface in normal years, that do not have a soil
moisture regime that borders on ustic or xeric, that do not have
durinodes or brittleness, and that do not have a significant
amount of volcanic glass, pumice, cinders, or pumicelike
fragments close to the surface.
Aquic Gypsiargids.—These are the Gypsiargids that are
saturated for 1 month or more within 100 cm of the soil surface
in normal years. These soils are very rare in the world.
Durinodic Gypsiargids.—These are the Gypsiargids that
have one or more horizons, 15 cm or more thick, that have 20
percent or more durinodes or are brittle and firm when moist.
The brittleness and firm rupture-resistance class in these soils
are attributed to partial cementation by silica.
Ustic Gypsiargids.—These are the Gypsiargids that have a
soil moisture regime that borders on ustic. Because of the
added moisture, these soils are more productive than soils in
the Typic subgroup. Ustic Gypsiargids do not have an
accumulation of durinodes or brittleness; a significant amount
of volcanic glass, cinders, pumice, or pumicelike fragments
near the surface; or saturation for 1 month or more within 100
cm of the soil surface in normal years.
Vitrandic Gypsiargids.—These are the Gypsiargids that
have a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments but do not have a soil moisture regime
that borders on xeric. These soils are not saturated for 1 month
or more within 100 cm of the soil surface in normal years and
do not have brittleness or an accumulation of durinodes.
Vitrixerandic Gypsiargids.—These are the Gypsiargids
that have a significant amount of volcanic glass, cinders,
pumice, or pumicelike fragments and have a soil moisture
regime that borders on xeric. These soils are not saturated for 1
month or more within 100 cm of the soil surface in normal
years and do not have brittleness or durinodes.
Xeric Gypsiargids.—These are the Gypsiargids that have a
soil moisture regime that borders on xeric. These soils are not
saturated for 1 month or more within 100 cm of the soil surface
in normal years and do not have brittleness or an accumulation
Aridisols 339
of durinodes. They also do not have a significant amount of
volcanic glass, cinders, pumice, or pumicelike fragments.
Haplargids
These are the Argids that have an argillic horizon but do not
have a duripan or a petrocalcic, petrogypsic, calcic, gypsic, or
natric horizon. These soils commonly have calcium carbonate
accumulations within or below the argillic horizon. Haplargids
commonly occur on late-Pleistocene surfaces or sediments.
Definition
Haplargids are the Argids that:
1. Do not have a duripan or a petrocalcic, petrogypsic,
gypsic, or calcic horizon that has an upper boundary within
150 cm of the soil surface;
2. Do not have a natric horizon;
3. Have a densic, lithic, or paralithic contact within 50 cm of
the soil surface; or
a. A clay increase of less than 15 percent (absolute) within
a vertical distance of 2.5 cm either within the argillic
horizon or at its upper boundary; or
b. An argillic horizon that does not extend to 150 cm from
the soil surface, has a clay decrease with increasing depth of
20 percent or more (relative) from the maximum clay
content, or has either:
(1) Hue of 10YR or yellower or chroma of 4 or less in
the matrix of all horizons between depths of 100 and 150
cm; or
(2) Hue of 10YR or yellower and value, moist, of 4 or
more or value, dry, of 4 or less in less than 50 percent of
the matrix.
Key to Subgroups
GEFA. Haplargids that have:
1. A lithic contact within 50 cm of the soil surface; and
2. An argillic horizon that is discontinuous throughout
each pedon.
Lithic Ruptic-Entic Haplargids
GEFB. Other Haplargids that have:
1. A lithic contact within 50 cm of the soil surface;
and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric.
Lithic Xeric Haplargids
GEFC. Other Haplargids that have:
1. A lithic contact within 50 cm of the soil surface; and
2. A moisture control section that is dry in all parts for less
than three-fourths of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm and a soil
moisture regime that borders on ustic.
Lithic Ustic Haplargids
GEFD. Other Haplargids that have a lithic contact within 50
cm of the soil surface.
Lithic Haplargids
GEFE. Other Haplargids that have both:
1. One or both of the following:
a. Cracks within 125 cm of the soil surface that are 5
mm or more wide through a thickness of 30 cm or more
for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the soil
surface; or
b. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact if shallower; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric.
Xerertic Haplargids
GEFF. Other Haplargids that have both:
1. One or both of the following:
a. Cracks within 125 cm of the soil surface that are 5
mm or more wide through a thickness of 30 cm or more
for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the soil
surface; or
b. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact if shallower; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on ustic.
Ustertic Haplargids
GEFG. Other Haplargids that have one or both of the
following:
1. Cracks within 125 cm of the soil surface that are 5 mm
340 Soil Taxonomy
or more wide through a thickness of 30 cm or more for some
time in normal years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has its upper
boundary within 125 cm of the soil surface; or
2. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic, lithic,
or paralithic contact if shallower.
Vertic Haplargids
GEFH. Other Haplargids that are either:
1. Irrigated and have aquic conditions for some time in
normal years in one or more layers within 100 cm of the soil
surface; or
2. Saturated with water in one or more layers within 100
cm of the soil surface for 1 month or more in normal years.
Aquic Haplargids
GEFI. Other Haplargids that have:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the soil surface to the top of an
argillic horizon at a depth of 50 cm or more; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature at a depth of 50 cm is 5 o
C or higher and a
soil moisture regime that borders on ustic.
Arenic Ustic Haplargids
GEFJ. Other Haplargids that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the soil
surface to the top of an argillic horizon at a depth of 50 cm or
more.
Arenic Haplargids
GEFK. Other Haplargids that have:
1. One or more horizons, within 100 cm of the soil surface
and with a combined thickness of 15 cm or more, that
contain 20 percent or more (by volume) durinodes or are
brittle and have at least a firm rupture-resistance class when
moist; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric.
Durinodic Xeric Haplargids
GEFL. Other Haplargids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that contain 20 percent or more
(by volume) durinodes or are brittle and have at least a firm
rupture-resistance class when moist.
Durinodic Haplargids
GEFM. Other Haplargids that:
1. Have one or more horizons, within 100 cm of the soil
surface and with a combined thickness of 15 cm or more,
that contain 20 percent or more (by volume) nodules or
concretions; and
2. Are dry in all parts of the moisture control section for
less than three-fourths of the time (cumulative) when the
soil temperature at a depth of 50 cm is 5 o
C or higher and
have a soil moisture regime that borders on ustic.
Petronodic Ustic Haplargids
GEFN. Other Haplargids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that contain 20 percent or more
(by volume) nodules or concretions.
Petronodic Haplargids
GEFO. Other Haplargids that have both:
1. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Haplargids
GEFP. Other Haplargids that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Haplargids
GEFQ. Other Haplargids that are dry in all parts of the
moisture control section for less than three-fourths of the time
Aridisols 341
(cumulative) when the soil temperature at a depth of 50 cm is
5 o
C or higher and have a soil moisture regime that borders on
xeric.
Xeric Haplargids
GEFR. Other Haplargids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
ustic.
Ustic Haplargids
GEFS. Other Haplargids.
Typic Haplargids
Definition of Typic Haplargids
Typic Haplargids are the Haplargids that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Have an argillic horizon that is continuous throughout
each pedon;
3. Have a moisture control section that is dry in all parts for
three-fourths or more of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm;
4. Have:
a. No cracks within 125 cm of the soil surface that are
5 mm or more wide through a thickness of 30 cm or more
for some time in normal years, and no slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the soil
surface; and
b. A linear extensibility of less than 6.0 cm between the
soil surface and either a depth of 100 cm or a densic, lithic,
or paralithic contact if shallower;
5. Are not both irrigated and characterized by aquic
conditions for some time in normal years in one or more layers
within 100 cm of the soil surface and are not saturated with
water in one or more layers within 100 cm of the soil surface
for 1 month or more in normal years;
6. Do not have a sandy or sandy-skeletal particle-size class in
all layers extending from the soil surface to the top of an
argillic horizon at a depth of 50 cm or more;
7. Do not have one or more horizons, within 100 cm of the
soil surface and with a combined thickness of more than 15
cm, that contain 20 percent or more (by volume) durinodes,
nodules, or concretions or are brittle and have at least a firm
rupture-resistance class when moist;
8. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser than
2.0 mm, of which more than 66 percent is cinders, pumice, and
pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Description of Subgroups
Typic Haplargids.—The Typic subgroup is centered on
soils that are moderately deep or deeper and have a soil
moisture regime that borders on neither ustic nor xeric. These
soils do not have a high shrink-swell potential; saturation
within 100 cm of the soil surface for 1 month or more in
normal years; horizons with a sandy or sandy-skeletal particlesize
class from the soil surface to a depth of 50 cm; or horizons
with significant accumulations of durinodes, concretions,
nodules, volcanic glass, pumice, cinders, or pumicelike
fragments.
Aquic Haplargids.—These are the Haplargids that are
saturated within 100 cm of the soil surface for 1 month or more
in normal years but are dry for most of the year. These soils do
not have a lithic contact within 50 cm of the soil surface or a
high shrink-swell potential. They occur on stream terraces in
Idaho and California.
Arenic Haplargids.—These are the Haplargids that have a
sandy or sandy-skeletal particle-size class from the surface to a
depth of 50 cm or more and do not have a soil moisture regime
that borders on ustic. These soils do not have a lithic contact
within 50 cm of the soil surface or a high shrink-swell
potential. They are not saturated with water for 1 month or
more within 100 cm of the soil surface in normal years. These
soils occur in California and are used as rangeland.
Arenic Ustic Haplargids.—These are the Haplargids that
have a sandy or sandy-skeletal particle-size class from the
surface to a depth of 50 cm or more and have a soil moisture
regime that borders on ustic. These soils do not have a lithic
contact within 50 cm of the soil surface or a high shrink-swell
potential. They are not saturated with water for 1 month or
more within 100 cm of the soil surface in normal years. These
soils occur in Texas, New Mexico, and Colorado and are used
as rangeland.
Durinodic Haplargids.—These are the Haplargids that
have one or more horizons, at least 15 cm thick, that have 20
percent or more durinodes or are brittle and at least firm when
moist. These soils do not have a soil moisture regime that
borders on xeric and do not have a high shrink-swell potential.
They do not have a lithic contact within 50 cm of the soil
surface or thick sandy horizons from the soil surface to a depth
342 Soil Taxonomy
of 50 cm or more. They are not saturated for 1 month or more
within 100 cm of the soil surface in normal years. These soils
occur in Nevada and California. They are used primarily as
rangeland, but in some areas they are used for urban
development or irrigated cropland.
Durinodic Xeric Haplargids.—These are the Haplargids
that have one or more horizons, at least 15 cm thick, that have
20 percent or more durinodes or are brittle and at least firm
when moist. These soils have a soil moisture regime that
borders on xeric. They do not have a lithic contact within 50
cm of the soil surface; thick sandy horizons from the soil
surface to a depth of 50 cm or more; or a high shrink-swell
potential. They are not saturated for 1 month or more within
100 cm of the soil surface in normal years. These soils occur in
Nevada, Idaho, and California. They are used primarily as
rangeland, but in some areas they are used for urban
development or irrigated cropland.
Lithic Haplargids.—These are the Haplargids that have a
lithic contact within 50 cm of the soil surface. These soils have
a continuous argillic horizon and do not have a soil moisture
regime that borders on ustic or xeric. They occur in the hot to
cool deserts in the western part of the United States and are
used primarily as rangeland.
Lithic Ruptic-Entic Haplargids.—These are the
Haplargids that have a lithic contact within 50 cm of the soil
surface and have a discontinuous argillic horizon. These soils
occur in Nevada and are used primarily as rangeland.
Lithic Ustic Haplargids.—These are the Haplargids that
have a lithic contact within 50 cm of the soil surface, a
continuous argillic horizon, and a soil moisture regime that
borders on ustic. These soils occur in the deserts of the
southwestern part of the United States and are used primarily
as rangeland.
Lithic Xeric Haplargids.—These are the Haplargids that
have a lithic contact within 50 cm of the soil surface, a
continuous argillic horizon, and a soil moisture regime that
borders on xeric. These soils occur in Nevada, California, and
Idaho and are used primarily as rangeland.
Petronodic Haplargids.—These are the Haplargids that
have one or more horizons, 15 cm or more thick, that have 20
percent or more, by volume, nodules and concretions. These
soils do not have durinodes or brittleness and at least a firm
rupture-resistance class when moist. They do not have a lithic
contact within 50 cm of the surface or a high shrink-swell
potential. They are not sandy or sandy-skeletal from the soil
surface to a depth of 50 cm or more, do not have a soil
moisture regime that borders on ustic, and are not saturated for
1 month or more within 100 cm of the soil surface in normal
years. These soils occur in Arizona and New Mexico and are
used primarily as rangeland.
Petronodic Ustic Haplargids.—These are the Haplargids
that have, in one or more horizons with a total thickness of 15
cm or more, 20 percent or more nodules and concretions and
that have a soil moisture regime that borders on ustic. These
soils do not have a lithic contact within 50 cm of the mineral soil
surface, are not saturated with water for 1 month or more within
100 cm of the soil surface in normal years, and do not have
durinodes or brittleness. They occur in Arizona and New
Mexico.
Ustertic Haplargids.—These are the Haplargids that have
a high shrink-swell potential and have a soil moisture regime
that borders on ustic. These soils do not have a lithic contact
within 50 cm of the soil surface. They occur in the deserts of
the southwestern part of the United States and are used
primarily as rangeland.
Ustic Haplargids.—These are the Haplargids that have a
soil moisture regime that borders on ustic. These soils do not
have a lithic contact within 50 cm of the soil surface; a high
shrink-swell potential; a sandy or sandy-skeletal particle-size
class from the soil surface to a depth of 50 cm or more; or a
significant amount of volcanic glass, cinders, pumice,
pumicelike fragments, durinodes, concretions, or nodules.
Ustic Haplargids are not saturated for 1 month or more within
100 cm of the soil surface in normal years. These soils are
extensive in the southwestern part of the United States.
Vertic Haplargids.—These are the Haplargids that have a
high shrink-swell potential but do not have a soil moisture
regime that borders on xeric or ustic. These soils also do not
have a lithic contact within 50 cm of the soil surface. They
occur in the western part of the United States.
Vitrandic Haplargids.—These are the Haplargids that have
a significant amount of volcanic glass, pumice, cinders, or
pumicelike fragments in one or more horizons with a total
thickness of 18 cm within 75 cm of the soil surface. These soils
do not have a soil moisture regime that borders on xeric; a
lithic contact within 50 cm of the soil surface; a high shrinkswell
potential; a significant amount of durinodes, nodules, or
concretions; or a sandy or sandy-skeletal particle-size class
from the soil surface to a depth of 50 cm or more. These soils
are rare but occur in the western part of the United States, in
areas with a volcanic influence.
Vitrixerandic Haplargids.—These are the Haplargids that
have a significant amount of volcanic glass, pumice, cinders, or
pumicelike fragments in one or more horizons with a total
thickness of 18 cm within 75 cm of the soil surface and have a
soil moisture regime that borders on xeric. These soils do not
have a lithic contact within 50 cm of the soil surface; a high
shrink-swell potential; a significant amount of durinodes,
nodules, or concretions; or a sandy or sandy-skeletal particlesize
class from the soil surface to a depth of 50 cm or more.
They are rare but occur in the western part of the United States,
in areas with a volcanic influence.
Xerertic Haplargids.—These are the Haplargids that have
a high shrink-swell potential and have a soil moisture regime
that borders on xeric. These soils do not have a lithic contact
within 50 cm of the soil surface. They occur in Nevada and
Idaho and are used primarily as rangeland.
Xeric Haplargids.—These are the Haplargids that have a
Aridisols 343
soil moisture regime that borders on xeric. These soils do not
have a lithic contact within 50 cm of the soil surface; a high
shrink-swell potential; a sandy or sandy-skeletal particle-size
class from the soil surface to a depth of 50 cm or more; or a
significant amount of volcanic glass, durinodes, concretions, or
nodules. Xeric Haplargids are not saturated for 1 month or more
within 100 cm of the soil surface in normal years. They are
extensive in Oregon, Nevada, and Idaho.
Natrargids
These are the Argids that have a natric horizon but do not
have a duripan or a petrocalcic or petrogypsic horizon within
150 cm of the soil surface. Commonly, the natric horizon has
prismatic or columnar structure. Natrargids commonly contain
carbonates, soluble salts, or both. These soils formed in
sediments that range in age from Holocene to late-Pleistocene.
Most of them are nearly level to gently sloping. These soils
occur in the western part of the United States and on the
western edge of the Great Plains.
Definition
Natrargids are the Argids that:
1. Have a natric horizon;
2. Do not have a duripan or a petrocalcic or petrogypsic
horizon that has its upper boundary within 150 cm of the soil
surface.
Key to Subgroups
GEBA. Natrargids that have both of the following:
1. A lithic contact within 50 cm of the soil surface; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric.
Lithic Xeric Natrargids
GEBB. Other Natrargids that have both of the following:
1. A lithic contact within 50 cm of the soil surface; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on ustic.
Lithic Ustic Natrargids
GEBC. Other Natrargids that have a lithic contact within 50
cm of the soil surface.
Lithic Natrargids
GEBD. Other Natrargids that have one or both of the
following:
1. Cracks within 125 cm of the soil surface that are 5 mm or
more wide through a thickness of 30 cm or more for some time
in normal years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has its upper
boundary within 125 cm of the soil surface; or
2. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic, lithic,
or paralithic contact, whichever is shallower.
Vertic Natrargids
GEBE. Other Natrargids that are either:
1. Irrigated and have aquic conditions for some time in
normal years in one or more layers within 100 cm of the soil
surface; or
2. Saturated with water in one or more layers within
100 cm of the soil surface for 1 month or more in normal
years.
Aquic Natrargids
GEBF. Other Natrargids that meet both of the following:
1. Have one or more horizons, within 100 cm of the soil
surface and with a combined thickness of 15 cm or more,
that contain 20 percent or more (by volume) durinodes or
are brittle and have at least a firm rupture-resistance class
when moist; and
2. Are dry in all parts of the moisture control section for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and
have a soil moisture regime that borders on xeric.
Durinodic Xeric Natrargids
GEBG. Other Natrargids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that contain 20 percent or more
(by volume) durinodes or are brittle and have at least a firm
rupture-resistance class when moist.
Durinodic Natrargids
GEBH. Other Natrargids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that contain 20 percent or more
(by volume) nodules or concretions.
Petronodic Natrargids
GEBI. Other Natrargids that have:
1. Skeletans covering 10 percent or more of the surfaces of
344 Soil Taxonomy
peds at a depth 2.5 cm or more below the upper boundary of
the natric horizon; and
2. A moisture control section that is dry in all parts for less
than three-fourths of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm and a soil
moisture regime that borders on ustic.
Glossic Ustic Natrargids
GEBJ. Other Natrargids that have:
1. An exchangeable sodium percentage of less than 15 (or
an SAR of less than 13) in 50 percent or more of the natric
horizon; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on ustic.
Haplic Ustic Natrargids
GEBK. Other Natrargids that have:
1. An exchangeable sodium percentage of less than 15
(or an SAR of less than 13) in 50 percent or more of the
natric horizon; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric.
Haploxeralfic Natrargids
GEBL. Other Natrargids that have an exchangeable sodium
percentage of less than 15 (or an SAR of less than 13) in 50
percent or more of the natric horizon.
Haplic Natrargids
GEBM. Other Natrargids that have both:
1. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Natrargids
GEBN. Other Natrargids that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm of
the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser than
2.0 mm, of which more than 66 percent is cinders, pumice, and
pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Natrargids
GEBO. Other Natrargids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature at a depth of 50 cm is
5 o
C or higher and have a soil moisture regime that borders on
xeric.
Xeric Natrargids
GEBP. Other Natrargids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature at a depth of 50 cm is
5 o
C or higher and have a soil moisture regime that borders on
ustic.
Ustic Natrargids
GEBQ. Other Natrargids that have skeletans covering 10
percent or more of the surfaces of peds at a depth 2.5 cm or
more below the upper boundary of the natric horizon.
Glossic Natrargids
GEBR. Other Natrargids.
Typic Natrargids
Definition of Typic Natrargids
Typic Natrargids are the Natrargids that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Have either:
a. No cracks within 125 cm of the soil surface that are 5
mm or more wide through a thickness of 30 cm or more for
some time in normal years, and no slickensides or wedgeshaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the soil surface; or
b. A linear extensibility of less than 6.0 cm between the
soil surface and either a depth of 100 cm or a densic, lithic,
or paralithic contact, whichever is shallower;
3. Are not both irrigated and characterized by aquic
conditions for some time in normal years in one or more layers
within 100 cm of the soil surface and are not saturated with
Aridisols 345
water in one or more layers within 100 cm of the soil surface for 1
month or more in normal years;
4. Do not have one or more horizons, within 100 cm of the soil
surface and with a combined thickness of more than 15 cm, that
contain 20 percent or more (by volume) durinodes, nodules, or
concretions or are brittle and have at least a firm ruptureresistance
class when moist;
5. Are dry in all parts of the moisture control section for threefourths
or more of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm;
6. Have skeletans covering less than 10 percent of the
surfaces of peds at a depth 2.5 cm or more below the upper
boundary of the natric horizon;
7. Have an exchangeable sodium percentage of 15 or more
(or an SAR of 13 or more) in more than 50 percent of the
natric horizon;
8. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Description of Subgroups
Typic Natrargids.—The Typic subgroup is centered on
soils that are moderately deep or deeper and have a soil
moisture regime that borders on neither ustic nor xeric. These
soils have an exchangeable sodium percentage of 15 or more in
more than 50 percent of the natric horizon but do not have
more than 10 percent skeletans at a depth 2.5 cm or more
below the upper boundary of the natric horizon. They also do
not have a high shrink-swell potential; saturation within 100
cm of the soil surface for 1 month or more in normal years; or
horizons with significant accumulations of durinodes,
concretions, nodules, volcanic glass, pumice, cinders, or
pumicelike fragments. These soils occur in the southwestern
part of the United States as well as southern Argentina.
Aquic Natrargids.—These are the Natrargids that are
saturated within 100 cm of the soil surface for 1 month or more
in normal years but are dry for most of the year. These soils do
not have a lithic contact within 50 cm of the soil surface or a
high shrink-swell potential. They occur on stream terraces in
Nevada, Oregon, Colorado, Montana, Utah, and California.
Durinodic Natrargids.—These are the Natrargids that have
one or more horizons, at least 15 cm thick, that have 20
percent or more durinodes or are brittle and at least firm when
moist. These soils do not have a soil moisture regime that
borders on xeric and do not have a high shrink-swell potential.
They do not have a lithic contact within 50 cm of the soil
surface. These soils are not saturated for 1 month or more
within 100 cm of the soil surface in normal years. They occur
in Nevada and California. They are used primarily as
rangeland, but in some areas they are used for urban
development or irrigated cropland.
Durinodic Xeric Natrargids.—These are the Natrargids
that have one or more horizons, at least 15 cm thick, that have
20 percent or more durinodes or are brittle and at least firm
when moist. These soils have a soil moisture regime that
borders on xeric but do not have a high shrink-swell potential.
They do not have a lithic contact within 50 cm of the soil
surface. These soils are not saturated for 1 month or more
within 100 cm of the soil surface in normal years. They occur
in Nevada, Idaho, and California. They are used primarily as
rangeland, but in some areas they are used for urban
development or irrigated cropland.
Glossic Natrargids.—These are the Natrargids that have
skeletans covering 10 percent or more of the surfaces of peds at
a depth 2.5 cm or more below the upper boundary of the natric
horizon and have an exchangeable sodium percentage of 15 or
more in more than 50 percent of the natric horizon. These soils
do not have a soil moisture regime that borders on ustic or
xeric. They do not have a lithic contact within 50 cm of the soil
surface or a high shrink-swell potential. They are not saturated
for 1 month or more within 100 cm of the soil surface in
normal years. These soils do not have a significant amount of
volcanic glass, pumice, cinders, pumicelike fragments,
durinodes, nodules, or concretions.
Glossic Ustic Natrargids.—These are the Natrargids that
have skeletans covering 10 percent or more of the surfaces of
peds at a depth 2.5 cm or more below the upper boundary of
the natric horizon and have a soil moisture regime that borders
on ustic. These soils do not have a lithic contact within 50 cm
of the soil surface or a high shrink-swell potential. They are
not saturated for 1 month or more within 100 cm of the soil
surface in normal years. These soils do not have a significant
amount of durinodes, nodules, or concretions. They occur in
Montana. They are used as rangeland or irrigated cropland.
Haplic Natrargids.—These are the Natrargids that have an
exchangeable sodium percentage of less than 15 in 50 percent
or more of the natric horizon but do not have a soil moisture
regime that borders on ustic or xeric. These soils do not have a
lithic contact within 50 cm of the soil surface or a high shrinkswell
potential. They are not saturated for 1 month or more
within 100 cm of the soil surface. These soils do not have a
significant amount of durinodes, nodules, or concretions. They
occur in Nevada, New Mexico, and Arizona. They are used
primarily as rangeland.
Haplic Ustic Natrargids.—These are the Natrargids that
have an exchangeable sodium percentage of less than 15 in 50
346 Soil Taxonomy
percent or more of the natric horizon and have a soil moisture
regime that borders on ustic. These soils do not have a lithic
contact within 50 cm of the soil surface, a high shrink-swell
potential, or skeletans covering 10 percent or more of the
surfaces of peds at a depth 2.5 cm or more below the upper
boundary of the natric horizon. Haplic Ustic Natrargids are not
saturated for 1 month or more within 100 cm of the soil
surface. These soils do not have a significant amount of
durinodes, nodules, or concretions. They occur in Wyoming
and the Four Corners area of northwestern New Mexico,
northeastern Arizona, southeastern Utah, and southwestern
Colorado. They are used primarily as rangeland.
Haploxeralfic Natrargids.—These are the Natrargids that
have an exchangeable sodium percentage of less than 15 in 50
percent or more of the natric horizon and have a soil moisture
regime that borders on xeric. These soils do not have a lithic
contact within 50 cm of the soil surface, a high shrink-swell
potential, or skeletans covering 10 percent or more of the
surfaces of peds at a depth 2.5 cm or more below the upper
boundary of the natric horizon. Haploxeralfic Natrargids are
not saturated for 1 month or more within 100 cm of the soil
surface. They do not have a significant amount of durinodes,
nodules, or concretions. They occur in California and possibly
in Nevada. They are used primarily as rangeland.
Lithic Natrargids.—These are the Natrargids that have a
lithic contact within 50 cm of the soil surface. These soils do
not have a soil moisture regime that borders on ustic or xeric.
They occur in the hot to cool deserts in the western part of the
United States and are used primarily as rangeland.
Lithic Ustic Natrargids.—These are the Natrargids that
have a lithic contact within 50 cm of the soil surface and have
a soil moisture regime that borders on ustic. These soils occur
in the deserts of the southwestern part of the United States and
are used primarily as rangeland.
Lithic Xeric Natrargids.—These are the Natrargids that
have a lithic contact within 50 cm of the soil surface and have
a soil moisture regime that borders on xeric. These soils occur
in Nevada, California, and Idaho and are used primarily as
rangeland.
Petronodic Natrargids.—These are the Natrargids that
have one or more horizons, 15 cm or more thick, that have 20
percent or more, by volume, nodules and concretions. These
soils do not have durinodes or brittleness and at least a firm
rupture-resistance class when moist. They do not have a lithic
contact within 50 cm of the surface or a high shrink-swell
potential. Petronodic Natrargids are not saturated for 1 month
or more within 100 cm of the soil surface in normal years.
These soils occur in Arizona and New Mexico and are used
primarily as rangeland.
Ustic Natrargids.—These are the Natrargids that have a
soil moisture regime that borders on ustic. These soils do not
have a lithic contact within 50 cm of the soil surface; a high
shrink-swell potential; skeletans covering 10 percent or more
of the surfaces of peds at a depth 2.5 cm or more below the
upper boundary of the natric horizon; an exchangeable sodium
percentage of 15 or more in more than 50 percent of the natric
horizon; or a significant amount of volcanic glass, pumice,
cinders, pumicelike fragments, durinodes, concretions, or
nodules. Ustic Natrargids are not saturated for 1 month or
more within 100 cm of the soil surface in normal years. These
soils occur in the southwestern part of the United States as well
as southern Argentina.
Vertic Natrargids.—These are the Natrargids that have a
high shrink-swell potential. These soils do not have a lithic
contact within 50 cm of the soil surface. Because of a high
percentage of clay and sodium, these soils are difficult to
reclaim and manage. Most of the soils are used as rangeland.
Vitrandic Natrargids.—These are the Natrargids that have
a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments in one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface.
These soils do not have a soil moisture regime that borders on
xeric; a lithic contact within 50 cm of the soil surface; a high
shrink-swell potential; an exchangeable sodium percentage of
15 or more in more than 50 percent of the natric horizon; or a
significant amount of durinodes, concretions, or nodules.
Vitrandic Natrargids are not saturated for 1 month or more
within 100 cm of the soil surface in normal years.
Vitrixerandic Natrargids.—These are the Natrargids that
have a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments in one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface
and have a soil moisture regime that borders on xeric. These
soils do not have a lithic contact within 50 cm of the soil
surface; a high shrink-swell potential; an exchangeable sodium
percentage of 15 or more in more than 50 percent of the natric
horizon; or a significant amount of durinodes, concretions, or
nodules. Vitrixerandic Natrargids are not saturated for 1 month
or more within 100 cm of the soil surface in normal years.
Xeric Natrargids.—These are the Natrargids that have a soil
moisture regime that borders on xeric. These soils do not have a
lithic contact within 50 cm of the soil surface; a high shrink-swell
potential; an exchangeable sodium percentage of 15 or more in
more than 50 percent of the natric horizon; or a significant
amount of volcanic glass, pumice, cinders, pumicelike fragments,
durinodes, concretions, or nodules. Xeric Natrargids are not
saturated for 1 month or more within 100 cm of the soil surface in
normal years. These soils occur in Nevada, Utah, and Idaho and
in southern Argentina.
Paleargids
These are the Argids that are on stable land surfaces and
have an abrupt textural change or a clay distribution that does
not decrease significantly. Most of these soils formed in
sediments appreciably older than the late-Pleistocene. If
calcareous dust is present, some of these soils may be
calcareous in all horizons. Slopes are normally gentle.
Aridisols 347
Definition
Paleargids are the Argids that:
1. Do not have a densic, lithic, or paralithic contact within 50
cm of the soil surface and that have either:
a. A clay increase of 15 percent or more (absolute) within
a vertical distance of 2.5 cm either within the argillic
horizon or at its upper boundary; or
b. An argillic horizon that extends to 150 cm or more
from the soil surface, that does not have a clay decrease with
increasing depth of 20 percent or more (relative) from the
maximum clay content and has, in 50 percent or more of the
matrix in some part between depths of 100 and 150 cm,
either:
(1) Hue of 7.5YR or redder and chroma of 5 or more;
or
(2) Hue of 7.5YR or redder and value, moist, of 3 or
less and value, dry, of 4 or less; and
2. Do not have a duripan or a petrocalcic or petrogypsic
horizon that has its upper boundary within 150 cm of the soil
surface; and
3. Do not have a natric horizon.
Key to Subgroups
GECA. Paleargids that have one or both of the following:
1. Cracks within 125 cm of the soil surface that are 5 mm
or more wide through a thickness of 30 cm or more for some
time in normal years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has its upper
boundary within 125 cm of the soil surface; or
2. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic, lithic,
or paralithic contact, whichever is shallower.
Vertic Paleargids
GECB. Other Paleargids that are either:
1. Irrigated and have aquic conditions for some time in
normal years in one or more layers within 100 cm of the soil
surface; or
2. Saturated with water in one or more layers within 100
cm of the soil surface for 1 month or more in normal years.
Aquic Paleargids
GECC. Other Paleargids that have:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
an argillic horizon at a depth of 50 cm or more; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on ustic.
Arenic Ustic Paleargids
GECD. Other Paleargids that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 cm or more.
Arenic Paleargids
GECE. Other Paleargids that have a calcic horizon that has
its upper boundary within 150 cm of the soil surface.
Calcic Paleargids
GECF. Other Paleargids that have:
1. One or more horizons, within 100 cm of the soil surface
and with a combined thickness of 15 cm or more, that
contain 20 percent or more (by volume) durinodes or are
brittle and have at least a firm rupture-resistance class when
moist; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric.
Durinodic Xeric Paleargids
GECG. Other Paleargids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that contain 20 percent or more
(by volume) durinodes or are brittle and have at least a firm
rupture-resistance class when moist.
Durinodic Paleargids
GECH. Other Paleargids that:
1. Have one or more horizons, within 100 cm of the soil
surface and with a combined thickness of 15 cm or more,
that contain 20 percent or more (by volume) nodules or
concretions; and
2. Are dry in all parts of the moisture control section for
less than three-fourths of the time (cumulative) when the
soil temperature at a depth of 50 cm is 5 o
C or higher and
have a soil moisture regime that borders on ustic.
Petronodic Ustic Paleargids
GECI. Other Paleargids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that contain 20 percent or more
(by volume) nodules or concretions.
Petronodic Paleargids
GECJ. Other Paleargids that have both:
348 Soil Taxonomy
1. A moisture control section that is dry in all parts for less
than three-fourths of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm and a soil
moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Paleargids
GECK. Other Paleargids that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Paleargids
GECL. Other Paleargids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
xeric.
Xeric Paleargids
GECM. Other Paleargids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
ustic.
Ustic Paleargids
GECN. Other Paleargids.
Typic Paleargids
Definition of Typic Paleargids
Typic Paleargids are the Paleargids that:
1. Have both of the following:
a. No cracks within 125 cm of the soil surface that are 5
mm or more wide through a thickness of 30 cm or more for
some time in normal years, and no slickensides or wedgeshaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the soil surface; and
b. A linear extensibility of less than 6.0 cm between the
soil surface and either a depth of 100 cm or a densic, lithic,
or paralithic contact, whichever is shallower;
2. Are not both irrigated and characterized by aquic
conditions for some time in normal years in one or more layers
within 100 cm of the soil surface and are not saturated with
water in one or more layers within 100 cm of the soil surface
for 1 month or more in normal years;
3. Do not have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of an argillic horizon at a depth of 50 cm or more;
4. Have a moisture control section that is dry in all parts for
three-fourths or more of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm;
5. Do not have a calcic horizon that has its upper boundary
within 150 cm of the soil surface;
6. Do not have one or more horizons, within 100 cm of the
soil surface and with a combined thickness of more than 15
cm, that contain 20 percent or more (by volume) durinodes,
nodules, or concretions or are brittle and have at least a firm
rupture-resistance class when moist;
7. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Description of Subgroups
Typic Paleargids.—The Typic subgroup is centered on the
concept of dry soils that do not have a soil moisture regime that
borders on ustic or xeric. These soils do not have a high
shrink-swell potential; saturation with water for 1 month or
more within 100 cm of the soil surface; a sandy or sandyskeletal
particle-size class from the soil surface to a depth of 50
cm; a calcic horizon; or a significant amount of durinodes,
nodules, concretions, volcanic glass, pumice, cinders, or
pumicelike fragments. These soils are not the dominant
subgroup of Paleargids. They occur in the deserts of the
southwestern part of the United States and in southern
Argentina.
Aridisols 349
Aquic Paleargids.—These are the Paleargids that are
saturated for 1 month or more within 100 cm of the soil surface
in normal years. These soils do not have a high shrink-swell
potential. They commonly have some sodium associated with
them. They are rare in the world.
Arenic Paleargids.—These are the Paleargids that have a
sandy or sandy-skeletal particle-size class from the soil surface
to a depth of 50 cm or more. These soils do not have a soil
moisture regime that borders on ustic, do not have a high
shrink-swell potential, and are not saturated with water for 1
month or more within 100 cm of the soil surface in normal
years. They are rare in the world.
Arenic Ustic Paleargids.—These are the Paleargids that
have a sandy or sandy-skeletal particle-size class from the soil
surface to a depth of 50 cm or more and have a soil moisture
regime that borders on ustic. These soils do not have a high
shrink-swell potential and are not saturated with water for 1
month or more within 100 cm of the soil surface in normal
years. They are rare in the world.
Calcic Paleargids.—These are the Paleargids with a calcic
horizon that has its upper boundary within 150 cm of the soil
surface. These soils do not have a high shrink-swell potential,
a sandy or sandy-skeletal particle-size class from the soil
surface to a depth of 50 cm or more, or saturation with water
for 1 month or more within 100 cm of the soil surface in
normal years. These soils occur in Arizona, New Mexico, and
Texas.
Durinodic Paleargids.—These are the Paleargids that have
one or more horizons, with a combined thickness of 15 cm or
more, that contain 20 percent or more durinodes or are brittle
and have at least a firm rupture-resistance class. These soils do
not have a high shrink-swell potential, saturation with water
for 1 month or more within 100 cm of the soil surface in
normal years, a calcic horizon, a soil moisture regime that
borders on xeric, or a sandy or sandy-skeletal particle-size class
from the soil surface to a depth of 50 cm or more.
Durinodic Xeric Paleargids.—These are the Paleargids
that have one or more horizons, with a combined thickness of
15 cm or more, that contain 20 percent or more durinodes or
are brittle and have at least a firm rupture-resistance class.
These soils also have a soil moisture regime that borders on
xeric. They do not have a high shrink-swell potential,
saturation with water for 1 month or more within 100 cm of
the soil surface in normal years, a calcic horizon, or a sandy or
sandy-skeletal particle-size class from the soil surface to a
depth of 50 cm or more. These soils occur in Oregon.
Petronodic Paleargids.—These are the Paleargids that have
one or more horizons, with a combined thickness of 15 cm or
more, that contain 20 percent or more nodules or concretions
but do not have durinodes. These soils do not have a high
shrink-swell potential, a soil moisture regime that borders on
ustic, saturation with water for 1 month or more within 100 cm
of the soil surface in normal years, a calcic horizon, or a sandy
or sandy-skeletal particle-size class from the soil surface to a
depth of 50 cm or more. These soils occur in Arizona.
Petronodic Ustic Paleargids.—These are the Paleargids
that have, in one or more horizons with a combined thickness
of 15 cm or more, 20 percent or more nodules or concretions
and that have a soil moisture regime that borders on ustic.
These soils do not have a high shrink-swell potential,
saturation with water for 1 month or more within 100 cm of
the soil surface in normal years, a calcic horizon within 150
cm of the soil surface, or durinodes or brittleness within 100
cm of the soil surface. The soils occur mostly in Arizona and
NewMexico.
Ustic Paleargids.—These are the Paleargids that have a soil
moisture regime that borders on ustic. These soils do not have
a high shrink-swell potential; saturation with water for 1
month or more within 100 cm of the soil surface in normal
years; a calcic horizon; a sandy or sandy-skeletal particle-size
class from the soil surface to a depth of 50 cm or more; or a
significant amount of volcanic glass, pumice, cinders,
pumicelike fragments, durinodes, nodules, and concretions.
These soils occur in desert areas of the United States and
Argentina.
Vertic Paleargids.—These are the Paleargids that have a
high shrink-swell potential. They are known to occur in
California, Arizona, Nevada, Oregon, and Colorado.
Vitrandic Paleargids.—These are the Paleargids that have
a significant amount of volcanic glass, pumice, cinders, or
pumicelike fragments in one or more horizons with a total
thickness of 18 cm within 75 cm of the soil surface. These soils
do not have a soil moisture regime that borders on xeric; a high
shrink-swell potential; saturation with water for 1 month or
more within 100 cm of the soil surface in normal years; a
calcic horizon; a sandy or sandy-skeletal particle-size class
from the soil surface to a depth of 50 cm or more; or a
significant amount of durinodes, nodules, and concretions.
Vitrixerandic Paleargids.—These are the Paleargids that
have a significant amount of volcanic glass, pumice, cinders, or
pumicelike fragments in one or more horizons with a total
thickness of 18 cm within 75 cm of the soil surface and have a
soil moisture regime that borders on xeric. These soils do not
have a high shrink-swell potential; saturation with water for 1
month or more within 100 cm of the soil surface in normal
years; a calcic horizon; a sandy or sandy-skeletal particle-size
class from the soil surface to a depth of 50 cm or more; or a
significant amount of durinodes, nodules, and concretions.
Xeric Paleargids.—These are the Paleargids that have a
soil moisture regime that borders on xeric. These soils do not
have a high shrink-swell potential; saturation with water for 1
month or more within 100 cm of the soil surface in normal
years; a calcic horizon; a sandy or sandy-skeletal particle-size
class from the soil surface to a depth of 50 cm or more; or a
significant amount of volcanic glass, pumice, cinders,
pumicelike fragments, durinodes, nodules, and concretions.
350 Soil Taxonomy
These soils occur in desert areas of the United States and
Argentina.
Petroargids
These are the Argids that have a duripan or a petrocalcic or
petrogypsic horizon that has its upper boundary at a depth
between 100 and 150 cm from the soil surface. These soils
occur on stable landscapes in the western part of the United
States and in southern Argentina and western South Africa.
Definition
These are the Argids that have a duripan or a petrocalcic or
petrogypsic horizon that has its upper boundary within 150 cm
of the soil surface.
Key to Subgroups
GEAA. Petroargids that meet both of the following:
1. Have a petrogypsic horizon that has its upper boundary
within 150 cm of the soil surface; and
2. Are dry in all parts of the moisture control section for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and
have a soil moisture regime that borders on ustic.
Petrogypsic Ustic Petroargids
GEAB. Other Petroargids that have a petrogypsic horizon
that has its upper boundary within 150 cm of the soil surface.
Petrogypsic Petroargids
GEAC. Other Petroargids that have:
1. A duripan that has its upper boundary within 150 cm of
the soil surface; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric.
Duric Xeric Petroargids
GEAD. Other Petroargids that have a duripan that has its
upper boundary within 150 cm of the soil surface.
Duric Petroargids
GEAE. Other Petroargids that have a natric horizon.
Natric Petroargids
GEAF. Other Petroargids that have a moisture control section
that is dry in all parts for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
xeric.
Xeric Petroargids
GEAG. Other Petroargids that have a moisture control section
that is dry in all parts for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
ustic.
Ustic Petroargids
GEAH. Other Petroargids.
Typic Petroargids
Definition of Typic Petroargids
Typic Petroargids are the Petroargids that:
1. Have a petrocalcic horizon that has its upper boundary
within 150 cm of the soil surface;
2. Are dry in all parts of the moisture control section for
three-fourths or more of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm;
3. Do not have a duripan or a petrogypsic horizon that has its
upper boundary within 150 cm of the soil surface;
4. Do not have a natric horizon.
Description of Subgroups
Typic Petroargids.—These are the Petroargids that have a
petrocalcic horizon that has its upper boundary within 150 cm
of the soil surface. These soils do not have a soil moisture
regime that borders on ustic or xeric. They occur in the
southwestern part of the United States and in South Africa and
Argentina.
Duric Petroargids.—These are the Petroargids that have a
duripan. These soils do not have a soil moisture regime that
borders on xeric. Many of the soils occur in areas that have a
volcanic influence. Duric Petroargids occur in Nevada, New
Mexico, and Arizona in the United States and in Australia and
South Africa.
Duric Xeric Petroargids.—These are the Petroargids that
have a duripan and a soil moisture regime that borders on
xeric. Many of these soils occur in areas that have a volcanic
influence. Duric Xeric Petroargids occur in Nevada and Idaho.
Natric Petroargids.—These are the Petroargids that have
natric and petrocalcic horizons. These soils occur in Argentina
and are used mostly for grazing by livestock.
Petrogypsic Petroargids.—These are the Petroargids that
have a petrogypsic horizon but do not have a soil moisture
regime that borders on ustic. These soils occur in very dry parts
of the world where the parent materials are rich in gypsum.
They are known to occur in New Mexico as well as Iran and
Iraq.
Petrogypsic Ustic Petroargids.—These are the Petroargids
that have a petrogypsic horizon and have a soil moisture
regime that borders on ustic. These soils are rare in the world.
Ustic Petroargids.—These are the Petroargids that have a
petrocalcic horizon and have a soil moisture regime that
Aridisols 351
borders on ustic. These soils occur in Arizona and New Mexico
as well as Argentina.
Xeric Petroargids.—These are the Petroargids that have a
petrocalcic horizon and have a soil moisture regime that borders
on xeric. They are known to occur in Idaho.
Calcids
Calcids are the Aridisols with calcium carbonate that was in
the parent materials or was added as dust, or both.
Precipitation is insufficient to leach or even move the
carbonates to great depths. The upper boundary of the calcic or
petrocalcic horizon is normally within 50 cm of the soil
surface. If the soils are irrigated and cultivated, micronutrient
deficiencies are normal. These soils are extensive in the
western part of the United States and in other arid regions of
the world.
Definition
Calcids are the Aridisols that:
1. Have a petrocalcic or calcic horizon that has its upper
boundary within 100 cm of the soil surface and do not have an
argillic or natric horizon with its upper boundary within 100
cm of the soil surface, unless a petrocalcic horizon is within
100 cm of the soil surface;
2. Have a temperature regime warmer than cryic;
3. Do not have a duripan or a salic, gypsic, or petrogypsic
horizon that has its upper boundary within 100 cm of the soil
surface.
Key to Great Groups
GFA. Calcids that have a petrocalcic horizon that has its
upper boundary within 100 cm of the soil surface.
Petrocalcids, p. 355
GFB. Other Calcids.
Haplocalcids, p. 351
Haplocalcids
Haplocalcids are the Calcids that have a calcic horizon with
its upper boundary within 100 cm of the soil surface. These
soils do not have a duripan or an argillic, natric, or petrocalcic
horizon within 100 cm of the soil surface. Some of the soils
have a cambic horizon above the calcic horizon. Haplocalcids
are extensive.
Definition
Haplocalcids are the Calcids that:
1. Have a calcic horizon that has its upper boundary within 100
cm of the soil surface;
2. Do not have a petrocalcic horizon that has its upper
boundary within 100 cm of the soil surface.
KeytoSubgroups
GFBA. Haplocalcids that have:
1. A lithic contact within 50 cm of the soil surface; and
2. A moisture control section that is dry in all parts for less
than three-fourths of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm and a soil
moisture regime that borders on xeric.
Lithic Xeric Haplocalcids
GFBB. Other Haplocalcids that have:
1. A lithic contact within 50 cm of the soil surface; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on ustic.
Lithic Ustic Haplocalcids
GFBC. Other Haplocalcids that have a lithic contact within
50 cm of the soil surface.
Lithic Haplocalcids
GFBD. Other Haplocalcids that have:
1. Cracks within 125 cm of the soil surface that are 5 mm
or more wide through a thickness of 30 cm or more for some
time in normal years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has its upper
boundary within 125 cm of the soil surface; or
2. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic, lithic,
or paralithic contact, whichever is shallower.
Vertic Haplocalcids
GFBE. Other Haplocalcids that:
1. Are either:
a. Irrigated and have aquic conditions for some time in
normal years in one or more layers within 100 cm of the
soil surface; or
b. Saturated with water in one or more layers within
100 cm of the soil surface for 1 month or more in normal
years; and
2. Have one or more horizons, within 100 cm of the soil
surface and with a combined thickness of 15 cm or more,
352 Soil Taxonomy
that contain 20 percent or more (by volume) durinodes or are
brittle and have at least a firm rupture-resistance class when
moist.
AquicDurinodicHaplocalcids
GFBF. Other Haplocalcids that are either:
1. Irrigated and have aquic conditions for some time in
normal years in one or more layers within 100 cm of the soil
surface; or
2. Saturated with water in one or more layers within 100
cm of the soil surface for 1 month or more in normal years.
Aquic Haplocalcids
GFBG. Other Haplocalcids that have:
1. A duripan that has its upper boundary within 150 cm of
the surface; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric.
Duric Xeric Haplocalcids
GFBH. Other Haplocalcids that have a duripan that has its
upper boundary within 150 cm of the surface.
Duric Haplocalcids
GFBI. Other Haplocalcids that have:
1. One or more horizons, within 100 cm of the soil surface
and with a combined thickness of 15 cm or more, that
contain 20 percent or more (by volume) durinodes or are
brittle and have at least a firm rupture-resistance class when
moist; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric.
Durinodic Xeric Haplocalcids
GFBJ. Other Haplocalcids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that contain 20 percent or more
(by volume) durinodes or are brittle and have at least a firm
rupture-resistance class when moist.
Durinodic Haplocalcids
GFBK. Other Haplocalcids that have:
1. One or more horizons, within 100 cm of the soil surface
and with a combined thickness of 15 cm or more, that
contain 20 percent or more (by volume) nodules or
concretions; and
2. A moisture control section that is dry in all parts for less
than three-fourths of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm and a soil
moisture regime that borders on xeric.
Petronodic Xeric Haplocalcids
GFBL. Other Haplocalids that:
1. Have one or more horizons, within 100 cm of the soil
surface and with a combined thickness of 15 cm or more,
that contain 20 percent or more (by volume) nodules or
concretions; and
2. Are dry in all parts of the moisture control section for
less than three-fourths of the time (cumulative) when the
soil temperature at a depth of 50 cm is 5 o
C or higher and
have a soil moisture regime that borders on ustic.
Petronodic Ustic Haplocalcids
GFBM. Other Haplocalcids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that contain 20 percent or more
(by volume) nodules or concretions.
Petronodic Haplocalcids
GFBN. Other Haplocalcids that have both:
1. A horizon at least 25 cm thick within 100 cm of the soil
surface that has an exchangeable sodium percentage of 15
or more (or an SAR of 13 or more) during at least 1 month
in normal years; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature at a depth of 50 cm is 5 o
C or higher and a
soil moisture regime that borders on xeric.
Sodic Xeric Haplocalcids
GFBO. Other Haplocalcids that meet both of the following:
1. Have, in a horizon at least 25 cm thick within 100 cm
of the soil surface, an exchangeable sodium percentage of 15
or more (or an SAR of 13 or more) during at least 1 month
in normal years; and
2. Are dry in all parts of the moisture control section for
less than three-fourths of the time (cumulative) when the
soil temperature at a depth of 50 cm is 5 o
C or higher and
have a soil moisture regime that borders on ustic.
Sodic Ustic Haplocalcids
GFBP. Other Haplocalcids that have, in a horizon at least 25
cm thick within 100 cm of the mineral soil surface, an
exchangeable sodium percentage of 15 or more (or an SAR of
13 or more) during at least 1 month in normal years.
Sodic Haplocalcids
Aridisols 353
GFBQ. Other Haplocalcids that have both:
1. A moisture control section that is dry in all parts for less
than three-fourths of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm and a soil
moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Haplocalcids
GFBR. Other Haplocalcids that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Haplocalcids
GFBS. Other Haplocalcids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
xeric.
Xeric Haplocalcids
GFBT. Other Haplocalcids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
ustic.
Ustic Haplocalcids
GFBU. Other Haplocalcids.
Typic Haplocalcids
Definition of Typic Haplocalcids
Typic Haplocalcids are the Haplocalcids that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Are dry in all parts of the moisture control section for threefourths
or more of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm;
3. Have both of the following:
a. No cracks within 125 cm of the soil surface that are 5
mm or more wide through a thickness of 30 cm or more for
some time in normal years, and no slickensides or wedgeshaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the soil surface; and
b. A linear extensibility of less than 6.0 cm between the
soil surface and either a depth of 100 cm or a densic, lithic,
or paralithic contact, whichever is shallower;
4. Are not both irrigated and characterized by aquic
conditions for some time in normal years in one or more layers
within 100 cm of the soil surface and are not saturated with
water in one or more layers within 100 cm of the soil surface
for 1 month or more in normal years;
5. Do not have one or more horizons, within 100 cm of the
soil surface and with a combined thickness of more than 15
cm, that contain 20 percent or more (by volume) durinodes,
nodules, or concretions or are brittle and have at least a firm
rupture-resistance class when moist;
6. Do not have, in one or more horizons within 100 cm of the
mineral soil surface, an exchangeable sodium percentage of 15
or more (or an SAR of 13 or more) for 1 month or more in
normal years;
7. Do not have a duripan that has its upper boundary within
150 cm of the surface;
8. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Description of Subgroups
Typic Haplocalcids.—The Typic subgroup is centered on dry
soils that lack the features that define the other subgroups.
These soils do not have a lithic contact with its upper boundary
within 50 cm of the soil surface; a high shrink-swell potential;
saturation with water for 1 month or more within 100 cm of
354 Soil Taxonomy
the soil surface; a duripan within 150 cm of the soil surface; a
significant amount of durinodes or brittleness, nodules,
concretions, volcanic glass, pumice, cinders, or pumicelike
fragments; an accumulation of sodium; or a soil moisture regime
that borders on xeric or ustic. These soils are common in the
desert areas of the world.
Aquic Durinodic Haplocalcids.—These are the
Haplocalcids that are saturated with water for 1 month or more
within 100 cm of the soil surface in normal years and have a
significant amount of durinodes or brittleness. These soils do
not have a lithic contact within 50 cm of the soil surface or a
high shrink-swell potential. They are known to occur in
California and Nevada.
Aquic Haplocalcids.—These are the Haplocalcids that are
saturated with water for 1 month or more within 100 cm of the
soil surface in normal years. These soils do not have a lithic
contact within 50 cm of the soil surface, a high shrink-swell
potential, or a significant amount of durinodes or brittleness.
These soils occur in California, Nevada, Idaho, and Utah.
Duric Haplocalcids.—These are the Haplocalcids that have
a duripan with an upper boundary between depths of 100 and
150 cm but do not have a soil moisture regime that borders on
xeric. These soils do not have a lithic contact within 50 cm of
the soil surface or a high shrink-swell potential. They are not
saturated with water for 1 month or more within 100 cm of the
soil surface in normal years and do not have a significant
amount of durinodes or brittleness. These soils are rare in the
world.
Duric Xeric Haplocalcids.—These are the Haplocalcids
that have a duripan at a depth of 100 to 150 cm and have a soil
moisture regime that borders on xeric. These soils do not have
a lithic contact within 50 cm of the soil surface or a high
shrink-swell potential. Duric Haplocalcids are not saturated
with water for 1 month or more within 100 cm of the soil
surface in normal years and do not have a significant amount
of durinodes or brittleness. These soils are rare in the world.
Durinodic Haplocalcids.—These are the Haplocalcids that
have one or more horizons, within 100 cm of the soil surface
and with a combined thickness of 15 cm or more, that contain
20 percent or more durinodes or are brittle and have at least a
firm rupture-resistance class when moist. These soils do not
have a soil moisture regime that borders on xeric, a duripan
within 150 cm of the soil surface, a lithic contact within 50 cm
of the soil surface, or a high shrink-swell potential. They are
not saturated with water for 1 month or more within 100 cm of
the soil surface. They occur in Nevada, California, and
Arizona.
Durinodic Xeric Haplocalcids.—These are the
Haplocalcids that have one or more horizons, within 100 cm of
the soil surface and with a combined thickness of 15 cm or
more, that contain 20 percent or more durinodes or are brittle
and have at least a firm rupture-resistance class when moist.
These soils have a soil moisture regime that borders on xeric.
They do not have a duripan within 150 cm of the soil surface, a
lithic contact within 50 cm of the soil surface, a high shrink-swell
potential, or saturation with water for 1 month or more within 100
cm of the soil surface. They occur in Nevada, California, Idaho,
and Utah.
Lithic Haplocalcids.—These are the Haplocalcids that have
a lithic contact within 50 cm of the soil surface but do not have
a soil moisture regime that borders on either xeric or ustic.
These soils occur throughout the deserts of the world.
Lithic Ustic Haplocalcids.—These are the Haplocalcids
that have a lithic contact within 50 cm of the soil surface and a
soil moisture regime that borders on ustic. These soils are
common in the semiarid regions of the world. In the United
States, they occur in Texas, Utah, and Arizona.
Lithic Xeric Haplocalcids.—These are the Haplocalcids
that have a lithic contact within 50 cm of the soil surface and a
soil moisture regime that borders on xeric. In the United
States, these soils occur in Nevada, Utah, and Idaho.
Petronodic Haplocalcids.—These are the Haplocalcids that
have, in one or more horizons with a combined thickness of 15
cm or more, 20 percent or more nodules and concretions but do
not have a soil moisture regime that borders on ustic or xeric.
These soils do not have a lithic contact within 50 cm of the soil
surface, a high shrink-swell potential, saturation with water for
1 month or more within 100 cm of the soil surface, a duripan
within 150 cm of the soil surface, or durinodes or brittleness.
These soils occur in California, Arizona, Nevada, New Mexico,
and Idaho.
Petronodic Ustic Haplocalcids.—These are the
Haplocalcids that have, in one or more horizons with a
combined thickness of 15 cm or more, 20 percent or more
nodules and concretions and that have a soil moisture regime
that borders on ustic. These soils do not have a lithic contact
within 50 cm of the soil surface, a high shrink-swell potential,
saturation with water for 1 month or more within 100 cm of
the soil surface, a duripan within 150 cm of the soil surface, or
durinodes or brittleness. The soils occur in Arizona, New
Mexico, and Texas.
Petronodic Xeric Haplocalcids.—These are the
Haplocalcids that have, in one or more horizons with a
combined thickness of 15 cm or more, 20 percent or more
nodules and concretions and have a soil moisture regime that
borders on xeric. These soils do not have a lithic contact within
50 cm of the soil surface, a high shrink-swell potential,
saturation with water for 1 month or more within 100 cm of
the soil surface, a duripan within 150 cm of the soil surface, or
durinodes or brittleness. The soils occur in Nevada, Oregon,
and Idaho.
Sodic Haplocalcids.—These are the Haplocalcids that have,
in a horizon at least 25 cm thick within 100 cm of the soil
surface, an exchangeable sodium percentage of 15 or more
during at least 1 month in normal years and have a soil
moisture regime that does not border on either ustic or xeric.
These soils do not have a lithic contact within 50 cm of the soil
surface; a high shrink-swell potential; saturation with water for
Aridisols 355
1 month or more within 100 cm of the soil surface; a duripan
within 150 cm of the soil surface; or a significant amount of
durinodes, nodules, concretions, or brittleness. These soils
occur in California, Nevada, and Texas.
Sodic Ustic Haplocalcids.—These are the Haplocalcids that
have, in a horizon at least 25 cm thick within 100 cm of the
soil surface, an exchangeable sodium percentage of 15 or more
during at least 1 month in normal years and have a soil
moisture regime that borders on ustic. These soils do not have
a lithic contact within 50 cm of the soil surface; a high shrinkswell
potential; saturation with water for 1 month or more
within 100 cm of the soil surface; a duripan within 150 cm of
the soil surface; or a significant amount of durinodes, nodules,
concretions, or brittleness. These soils occur in Utah.
Sodic Xeric Haplocalcids.—These are the Haplocalcids
that have, in a horizon at least 25 cm thick within 100 cm of
the soil surface, an exchangeable sodium percentage of 15 or
more during at least 1 month in normal years and have a soil
moisture regime that borders on xeric. These soils do not have
a lithic contact within 50 cm of the soil surface; a high shrinkswell
potential; saturation with water for 1 month or more
within 100 cm of the soil surface; a duripan within 150 cm of
the soil surface; or a significant amount of durinodes, nodules,
concretions, or brittleness. These soils are known to occur in
Idaho, Oregon, and Utah.
Ustic Haplocalcids.—These are the Haplocalcids that have
a soil moisture regime that borders on ustic. These soils do not
have, in a horizon at least 25 cm thick within 100 cm of the
soil surface, an exchangeable sodium percentage of 15 or more
during at least 1 month in normal years and do not have a
lithic contact within 50 cm of the soil surface; a high shrinkswell
potential; saturation with water for 1 month or more
within 100 cm of the soil surface; a duripan within 150 cm of
the soil surface; or a significant amount of volcanic glass,
pumice, cinders, pumicelike fragments, durinodes, nodules,
concretions, or brittleness. These soils are common in the
semiarid deserts of the world.
Vertic Haplocalcids.—These are the Haplocalcids that have
a high shrink-swell potential. These soils do not have a lithic
contact within 50 cm of the soil surface. They are relatively
rare in the world.
Vitrandic Haplocalcids.—These are the Haplocalcids that
have a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments throughout one or more horizons with a
total thickness of 18 cm or more within 75 cm of the soil
surface and have a soil moisture regime that does not border on
xeric. These soils do not have, in a horizon at least 25 cm thick
within 100 cm of the soil surface, an exchangeable sodium
percentage of 15 or more during at least 1 month in normal
years and do not have a lithic contact within 50 cm of the soil
surface; a high shrink-swell potential; saturation with water for
1 month or more within 100 cm of the soil surface; a duripan
within 150 cm of the soil surface; or a significant amount of
durinodes, nodules, concretions, or brittleness. These soils are
not common in the world but occur in areas that have a volcanic
influence.
Vitrixerandic Haplocalcids.—These are the Haplocalcids
that have a significant amount of volcanic glass, cinders,
pumice, or pumicelike fragments throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the soil surface and have a soil moisture regime that borders
on xeric. These soils do not have, in a horizon at least 25 cm
thick within 100 cm of the soil surface, an exchangeable
sodium percentage of 15 or more during at least 1 month in
normal years and do not have a lithic contact within 50 cm of
the soil surface; a high shrink-swell potential; saturation with
water for 1 month or more within 100 cm of the soil surface; a
duripan within 150 cm of the soil surface; or a significant
amount of durinodes, nodules, concretions, or brittleness.
These soils are not common in the world but occur in areas
that have a volcanic influence.
Xeric Haplocalcids.—These are the Haplocalcids that have a
soil moisture regime that borders on xeric. These soils do not
have, in a horizon at least 25 cm thick within 100 cm of the
soil surface, an exchangeable sodium percentage of 15 or more
during at least 1 month in normal years and do not have a
lithic contact within 50 cm of the soil surface; a high shrinkswell
potential; saturation with water for 1 month or more
within 100 cm of the soil surface; a duripan within 150 cm of
the soil surface; or a significant amount of volcanic glass,
pumice, cinders, pumicelike fragments, durinodes, nodules,
concretions, or brittleness. These soils are common in the
semiarid deserts of the world where summers are dry and
winters are moist.
Petrocalcids
Petrocalcids are the Calcids that have a petrocalcic horizon
that has its upper boundary within 100 cm of the soil surface.
Normally, the upper boundary of the petrocalcic horizon is
close to the soil surface. Some of these soils show evidence of
former argillic horizons that are now engulfed with carbonates.
Generally, Petrocalcids are on gentle slopes that have been
stable for long periods. They occur on old landscapes in the
southwestern part of the United States and in other deserts of
the world.
Definition
Petrocalcids are the Calcids that have a petrocalcic
horizon that has its upper boundary within 100 cm of the
soil surface.
Key to Subgroups
GFAA. Petrocalcids that are either:
1. Irrigated and have aquic conditions for some time in
normal years in one or more layers within 100 cm of the soil
surface; or
356 Soil Taxonomy
2. Saturated with water in one or more layers within 100 cm
of the soil surface for 1 month or more in normal years.
Aquic Petrocalcids
GFAB. Other Petrocalcids that have a natric horizon.
Natric Petrocalcids
GFAC. Other Petrocalcids that have both of the following:
1. An argillic horizon that has its upper boundary within
100 cm of the soil surface; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric.
Xeralfic Petrocalcids
GFAD. Other Petrocalcids that have both of the following:
1. An argillic horizon that has its upper boundary within
100 cm of the soil surface; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on ustic.
Ustalfic Petrocalcids
GFAE. Other Petrocalcids that have an argillic horizon that
has its upper boundary within 100 cm of the soil surface.
Argic Petrocalcids
GFAF. Other Petrocalcids that have:
1. A calcic horizon overlying the petrocalcic horizon; and
2. A lithic contact within 50 cm of the soil surface.
Calcic Lithic Petrocalcids
GFAG. Other Petrocalcids that have a calcic horizon
overlying the petrocalcic horizon.
Calcic Petrocalcids
GFAH. Other Petrocalcids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
xeric.
Xeric Petrocalcids
GFAI. Other Petrocalcids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
ustic.
Ustic Petrocalcids
GFAJ. Other Petrocalcids.
Typic Petrocalcids
Definition of Typic Petrocalcids
Typic Petrocalcids are the Petrocalcids that:
1. Are not both irrigated and characterized by aquic conditions
for some time in normal years in one or more layers within 100 cm
of the soil surface and are not saturated with water in one or
more layers within 100 cm of the soil surface for 1 month or more
in normal years;
2. Do not have a natric horizon;
3. Do not have an argillic horizon that has its upper boundary
within 100 cm of the soil surface;
4. Do not have a calcic horizon overlying the petrocalcic
horizon;
5. Have a moisture control section that is dry in all parts for
three-fourths or more of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm.
Description of Subgroups
Typic Petrocalcids.—The Typic subgroup is centered on
dry soils that do not have any of the features associated with
the other subgroups. These soils do not have a natric, argillic,
or calcic horizon. They also do not have a soil moisture regime
that borders on xeric or ustic. They are saturated with water for
1 month or more in one or more layers within 100 cm of the
soil surface. These soils are widespread in the desert areas of
the world.
Aquic Petrocalcids.—These are the Petrocalcids that are
saturated with water for 1 month or more within 100 cm of the
soil surface in normal years. These soils can have other
diagnostic horizons. They are saturated for short periods and
dry for most of the year. They are rare but occur in Nevada.
Argic Petrocalcids.—These are the Petrocalcids that have
an argillic horizon and have a soil moisture regime that does
not border on ustic or xeric. These soils do not have a natric
horizon. They occur in the desert areas of several States in the
western part of the United States.
Calcic Lithic Petrocalcids.—These are the Petrocalcids
that have a calcic horizon, do not have an argillic or natric
horizon, and have a lithic contact within 50 cm of the soil
surface. These soils are not saturated for 1 month or more
within 100 cm of the soil surface in normal years. They occur
in Arizona, New Mexico, Texas, and other Western States.
Most of these soils are used as rangeland.
Calcic Petrocalcids.—These are the Petrocalcids that have
a calcic horizon but do not have an argillic or natric horizon.
These soils are not saturated for 1 month or more within 100
cm of the soil surface in normal years. They occur in Arizona,
California, Nevada, New Mexico, Texas, and Utah.
Natric Petrocalcids.—These are the Petrocalcids that have
Aridisols 357
a natric horizon. These soils are not saturated for 1 month or
more within 100 cm of the soil surface in normal years. They are
rare in the world.
Ustalfic Petrocalcids.—These are the Petrocalcids that have
an argillic horizon and have a soil moisture regime that borders
on ustic. These soils do not have a natric horizon and are not
saturated for 1 month or more within 100 cm of the soil surface
during the growing season. They occur in Nevada, New Mexico,
Arizona, and Utah.
Ustic Petrocalcids.—These are the Petrocalcids that have a
soil moisture regime that borders on ustic. These soils do not
have an argillic, calcic, or natric horizon. They are not
saturated for 1 month or more in normal years. These soils
occur in Arizona, Utah, and New Mexico and in other semiarid
areas of the world.
Xeralfic Petrocalcids.—These are the Petrocalcids that
have an argillic horizon and have a soil moisture regime that
borders on xeric. The soils do not have a natric horizon and are
not saturated with water for 1 month or more within 100 cm of
the soil surface. They are moist in winter and dry in summer.
Xeric Petrocalcids.—These are the Petrocalcids that have a
soil moisture regime that borders on xeric. These soils do not
have an argillic, calcic, or natric horizon. They are not
saturated for 1 month or more in normal years. These soils
occur in California, Utah, and Nevada.
Cambids
These are the Aridisols with the least degree of soil
development. These soils have a cambic horizon within 100 cm
of the soil surface. They may have other diagnostic horizons,
such as a petrocalcic, gypsic, or calcic horizon, but the upper
boundary of these horizons must be below 100 cm of the soil
surface. These soils are the most common Aridisols in the
United States.
Definition
Cambids are the Aridisols that:
1. Have a cambic horizon that has its upper boundary within
100 cm of the soil surface;
2. Have a soil temperature regime warmer than cryic;
3. Do not have a duripan or an argillic, calcic, natric,
petrocalcic, gypsic, petrogypsic, or salic horizon that has its
upper boundary within 100 cm of the soil surface.
Key to Great Groups
GGA. Cambids that are either:
1. Irrigated and have aquic conditions for some time in
normal years in one or more layers within 100 cm of the soil
surface; or
2. Saturated with water in one or more layers within 100 cm
of the soil surface for 1 month or more in normal years.
Aquicambids, p. 357
GGB. Other Cambids that have a duripan or a petrocalcic or
petrogypsic horizon that has its upper boundary within 150 cm
of the soil surface.
Petrocambids, p. 364
GGC. Other Cambids that have an anthropic epipedon.
Anthracambids, p. 357
GGD. OtherCambids.
Haplocambids, p. 359
Anthracambids
These are the Cambids that have an anthropic epipedon.
These soils generally have been irrigated for many centuries.
They are not known to occur in large areas of the United
States. The great group is provided for use elsewhere.
Definition
Anthracambids are the Cambids that:
1. Have an anthropic epipedon.
2. Are not both irrigated and characterized by aquic
conditions for some time in normal years in one or more layers
within 100 cm of the soil surface and are not saturated with
water in one or more layers within 100 cm of the soil surface
for 1 month or more in normal years.
3. Do not have a duripan or a petrocalcic or petrogypsic
horizon that has its upper boundary within 150 cm of the soil
surface.
Key to Subgroups
GGCA. All Anthracambids.
Typic Anthracambids
Definition of Typic Anthracambids
All Anthracambids are considered Typic.
Description of Subgroups
Typic Anthracambids.—All Anthracambids are considered
Typic. Few data are available for these soils. No soil series have
been established for these taxa in the United States. These soils
occur in small areas adjacent to Native American ruins.
Aquicambids
These are the Cambids that are saturated with water for
short periods in normal years. These soils commonly are
adjacent to playas and have accumulations of salts.
358 Soil Taxonomy
Aquicambids commonly have high pH values, which inhibit the
formation of redoximorphic features.
Definition
Aquicambids are the Cambids that are either irrigated and
have redoximorphic features in one or more layers within 100
cm of the soil surface or are saturated with water in one or
more layers within 100 cm of the soil surface for 1 month or
more in normal years.
Key to Subgroups
GGAA. Aquicambids that have, in a horizon at least 25 cm
thick within 100 cm of the soil surface, an exchangeable
sodium percentage of 15 or more (or an SAR of 13 or more)
during at least 1 month in normal years.
Sodic Aquicambids
GGAB. Other Aquicambids that:
1. Have one or more horizons, within 100 cm of the soil
surface and with a combined thickness of 15 cm or more,
that contain 20 percent or more (by volume) durinodes r are
brittle and have at least a firm rupture-resistance class when
moist; and
2. Are dry in all parts of the moisture control section for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and
have a soil moisture regime that borders on xeric.
Durinodic Xeric Aquicambids
GGAC. Other Aquicambids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that contain 20 percent or more
(by volume) durinodes or are brittle and have at least a firm
rupture-resistance class when moist.
Durinodic Aquicambids
GGAD. Other Aquicambids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that contain 20 percent or more
(by volume) nodules or concretions.
Petronodic Aquicambids
GGAE. Other Aquicambids that have both:
1. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Aquicambids
GGAF. Other Aquicambids that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Aquicambids
GGAG. Other Aquicambids that have an irregular decrease in
content of organic carbon from a depth of 25 cm either to a
depth of 125 cm or to a densic, lithic, or paralithic contact if
shallower.
Fluventic Aquicambids
GGAH. Other Aquicambids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
xeric.
Xeric Aquicambids
GGAI. Other Aquicambids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
ustic.
Ustic Aquicambids
GGAJ. Other Aquicambids.
Typic Aquicambids
Definition of Typic Aquicambids
Typic Aquicambids are the Aquicambids that:
1. Do not have, in a horizon at least 25 cm thick within 100
cm of the soil surface, an exchangeable sodium percentage of
15 or more (or an SAR of 13 or more) during at least 1 month
in normal years;
Aridisols 359
2. Do not have one or more horizons, within 100 cm of the soil
surface and with a combined thickness of more than 15 cm, that
contain 20 percent or more (by volume) durinodes, nodules, or
concretions or are brittle and have at least a firm ruptureresistance
class when moist;
3. Have a moisture control section that is dry in all parts for
three-fourths or more of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm;
4. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more;
5. Have a regular decrease in content of organic carbon from
a depth of 25 cm either to a depth of 125 cm or to a densic,
lithic, or paralithic contact if shallower.
Description of Subgroups
Typic Aquicambids.—The Typic subgroup is centered on
Aquicambids that do not have any of the features defined for
the other subgroups. These soils do not have an accumulation
of sodium; durinodes or brittleness; a significant amount of
nodules, concretions, volcanic glass, pumice, cinders, or
pumicelike fragments; an irregular decrease in content of
organic carbon below the cambic horizon; or a soil moisture
regime that borders on ustic or xeric.
Durinodic Aquicambids.—These are the Aquicambids that
have one or more horizons, within 100 cm of the soil surface
and with a cumulative thickness of 15 cm or more, that contain
20 percent or more durinodes or are brittle and have at least a
firm rupture-resistance class. These soils do not have, in a
horizon at least 25 cm thick, an exchangeable sodium
percentage of 15 or more. The soil moisture regime does not
border on xeric.
Durinodic Xeric Aquicambids.—These are the
Aquicambids that have a soil moisture regime that borders on
xeric and have one or more horizons, within 100 cm of the soil
surface and with a cumulative thickness of 15 cm or more, that
contain 20 percent or more durinodes or are brittle and have at
least a firm rupture-resistance class. These soils do not have, in
a horizon at least 25 cm thick, an exchangeable sodium
percentage of 15 or more.
Fluventic Aquicambids.—These are the Aquicambids that
have an irregular decrease in content of organic carbon below
the cambic horizon. These soils do not have a significant
amount of sodium, durinodes, nodules, concretions, volcanic
glass, pumice, cinders, or pumicelike fragments and are not
brittle.
Petronodic Aquicambids.—These are the Aquicambids
that have one or more horizons, within 100 cm of the soil
surface and with a combined thickness of 15 cm or more, that
contain 20 percent or more nodules and concretions. These soils
do not have a significant amount of sodium, durinodes, or
brittleness.
Sodic Aquicambids.—These are the Aquicambids that have,
in one or more horizons at least 25 cm thick within 100 cm of the
soil surface, an exchangeable sodium percentage of 15 or more
for at least 1 month in normal years. These soils occur in New
Mexico.
Ustic Aquicambids.—These are the Aquicambids that have
a soil moisture regime that borders on ustic. These soils do not
have a significant amount of sodium, durinodes, nodules,
concretions, volcanic glass, pumice, cinders, or pumicelike
fragments and are not brittle. They also do not have an
irregular decrease in content of organic carbon below the
cambic horizon.
Vitrandic Aquicambids.—These are the Aquicambids that
have a significant amount of volcanic glass, pumice, cinders, or
pumicelike fragments in one or more horizons 18 cm thick
within 75 cm of the soil surface but do not have a soil moisture
regime that borders on xeric. These soils do not have a
significant amount of sodium, durinodes, concretions, or
nodules and are not brittle.
Vitrixerandic Aquicambids.—These are the Aquicambids
that have a significant amount of volcanic glass, pumice,
cinders, or pumicelike fragments in one or more horizons 18
cm thick within 75 cm of the soil surface and have a soil
moisture regime that borders on xeric. These soils do not have
a significant amount of sodium, durinodes, concretions, or
nodules and are not brittle.
Xeric Aquicambids.—These are the Aquicambids that have a
soil moisture regime that borders on xeric. These soils do not
have a significant amount of sodium, durinodes, nodules,
concretions, volcanic glass, pumice, cinders, or pumicelike
fragments and are not brittle. They also do not have an
irregular decrease in content of organic carbon below the
cambic horizon.
Haplocambids
Haplocambids are the most commonly occurring of the
Cambids. These soils are characterized by minimal horizon
expression. Most Haplocambids have a redistribution of
carbonates below the cambic horizon. The amount of
carbonates, however, is insufficient to meet the definition of a
calcic horizon, or the upper boundary is more than 100 cm
below the soil surface. These soils occur on a variety of
landscapes, commonly on those that are younger than latePleistocene
in age.
360 Soil Taxonomy
Definition
Haplocambids are the Cambids that:
1. Are not both irrigated and characterized by aquic conditions
for some time in normal years in one or more layers within 100 cm
of the soil surface and are not saturated with water in one or
more layers within 100 cm of the soil surface for 1 month or more
in normal years;
2. Do not have a duripan or a petrocalcic or petrogypsic
horizon that has its upper boundary within 150 cm of the soil
surface;
3. Do not have an anthropic epipedon.
Key to Subgroups
GGDA. Haplocambids that have:
1. A lithic contact within 50 cm of the soil surface;
and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric.
Lithic Xeric Haplocambids
GGDB. Other Haplocambids that have:
1. A lithic contact within 50 cm of the soil surface; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on ustic.
Lithic Ustic Haplocambids
GGDC. Other Haplocambids that have a lithic contact within
50 cm of the soil surface.
Lithic Haplocambids
GGDD. Other Haplocambids that have:
1. One or both of the following:
a. Cracks within 125 cm of the soil surface that are 5
mm or more wide through a thickness of 30 cm or more
for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the soil
surface; or
b. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact if shallower; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm and a soil
moisture regime that borders on xeric.
Xerertic Haplocambids
GGDE. Other Haplocambids that have:
1. One or both of the following:
a. Cracks within 125 cm of the soil surface that are 5
mm or more wide through a thickness of 30 cm or more
for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the soil
surface; or
b. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact if shallower; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on ustic.
Ustertic Haplocambids
GGDF. Other Haplocambids that have at least one of the
following:
1. Cracks within 125 cm of the soil surface that are 5 mm
or more wide through a thickness of 30 cm or more for some
time in normal years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has its upper
boundary within 125 cm of the soil surface; or
2. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic, lithic,
or paralithic contact, whichever is shallower.
Vertic Haplocambids
GGDG. Other Haplocambids that have both of the following:
1. One or more horizons, within 100 cm of the soil surface
and with a combined thickness of 15 cm or more, that
contain 20 percent or more (by volume) durinodes or are
brittle and have at least a firm rupture-resistance class when
moist; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature at a depth of 50 cm is 5 o
C or higher and a
soil moisture regime that borders on xeric.
Durinodic Xeric Haplocambids
GGDH. Other Haplocambids that have one or more horizons,
within 100 cm of the soil surface and with a combined
Aridisols 361
thickness of 15 cm or more, that contain 20 percent or more (by
volume) durinodes or are brittle and have at least a firm ruptureresistance
class when moist.
Durinodic Haplocambids
GGDI. Other Haplocambids that have:
1. One or more horizons, within 100 cm of the soil surface
and with a combined thickness of 15 cm or more, that
contain 20 percent or more (by volume) nodules or
concretions; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature at a depth of 50 cm is 5 o
C or higher and a
soil moisture regime that borders on xeric.
Petronodic Xeric Haplocambids
GGDJ. Other Haplocambids that:
1. Have one or more horizons, within 100 cm of the soil
surface and with a combined thickness of 15 cm or more,
that contain 20 percent or more (by volume) nodules or
concretions; and
2. Are dry in all parts of the moisture control section for
less than three-fourths of the time (cumulative) when the
soil temperature at a depth of 50 cm is 5 o
C or higher and
have a soil moisture regime that borders on ustic.
Petronodic Ustic Haplocambids
GGDK. Other Haplocambids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that contain 20 percent or more
(by volume) nodules or concretions.
Petronodic Haplocambids
GGDL. Other Haplocambids that have both:
1. A horizon at least 25 cm thick within 100 cm of the soil
surface that has an exchangeable sodium percentage of 15
or more (or an SAR of 13 or more) during at least 1 month
in normal years; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature at a depth of 50 cm is 5 o
C or higher and a
soil moisture regime that borders on xeric.
Sodic Xeric Haplocambids
GGDM. Other Haplocambids that meet both of the following:
1. Have, in a horizon at least 25 cm thick within 100 cm
of the soil surface, an exchangeable sodium percentage of 15
or more (or an SAR of 13 or more) during at least 1 month
in normal years; and
2. Are dry in all parts of the moisture control section
for less than three-fourths of the time (cumulative) when
the soil temperature at a depth of 50 cm is 5 o
C or higher
and have a soil moisture regime that borders on ustic.
Sodic Ustic Haplocambids
GGDN. Other Haplocambids that have, in a horizon at least 25
cm thick within 100 cm of the soil surface, an exchangeable
sodium percentage of 15 or more (or an SAR of 13 or more)
during at least 1 month in normal years.
Sodic Haplocambids
GGDO. Other Haplocambids that have both:
1. A moisture control section that is dry in all parts
for less than three-fourths of the time (cumulative) when
the soil temperature is 5 o
C or higher at a depth of 50
cm and a soil moisture regime that borders on xeric;
and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Haplocambids
GGDP. Other Haplocambids that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Haplocambids
GGDQ. Other Haplocambids that:
1. Are dry in all parts of the moisture control section
for less than three-fourths of the time (cumulative) when
the soil temperature at a depth of 50 cm is 5 o
C or higher
and have a soil moisture regime that borders on xeric;
and
2. Have an irregular decrease in content of organic carbon
362 Soil Taxonomy
from a depth of 25 cm either to a depth of 125 cm or to a
densic, lithic, or paralithic contact if shallower.
XerofluventicHaplocambids
GGDR. Other Haplocambids that:
1. Are dry in all parts of the moisture control section for
less than three-fourths of the time (cumulative) when the
soil temperature at a depth of 50 cm is 5 o
C or higher and
have a soil moisture regime that borders on ustic; and
2. Have an irregular decrease in content of organic carbon
from a depth of 25 cm either to a depth of 125 cm or to a
densic, lithic, or paralithic contact if shallower.
Ustifluventic Haplocambids
GGDS. Other Haplocambids that have an irregular decrease
in content of organic carbon from a depth of 25 cm either to a
depth of 125 cm or to a densic, lithic, or paralithic contact if
shallower.
Fluventic Haplocambids
GGDT. Other Haplocambids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature at a depth of 50 cm is
5 o
C or higher and have a soil moisture regime that borders on
xeric.
Xeric Haplocambids
GGDU. Other Haplocambids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature at a depth of 50 cm is
5 o
C or higher and have a soil moisture regime that borders on
ustic.
Ustic Haplocambids
GGDV. Other Haplocambids.
Typic Haplocambids
Definition of Typic Haplocambids
Typic Haplocambids are the Haplocambids that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have one or more horizons, within 100 cm of the
soil surface and with a combined thickness of more than 15
cm, that contain 20 percent or more (by volume) durinodes,
nodules, or concretions or are brittle and have at least a firm
rupture-resistance class when moist;
3. Are dry in all parts of the moisture control section for
three-fourths or more of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm;
4. Have either:
a. No cracks within 125 cm of the soil surface that are 5
mm or more wide through a thickness of 30 cm or more for
some time in normal years, and no slickensides or wedgeshaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the soil surface; or
b. A linear extensibility of less than 6.0 cm between the soil
surface and either a depth of 100 cm or a densic, lithic, or
paralithic contact, whichever is shallower;
5. Do not have, in a horizon at least 25 cm thick within 100 cm
of the soil surface, an exchangeable sodium percentage of 15 or
more (or an SAR of 13 or more) during at least 1 month in normal
years;
6. Have a regular decrease in content of organic carbon from a
depth of 25 cm either to a depth of 125 cm or to a densic, lithic,
or paralithic contact if shallower;
7. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Description of Subgroups
Typic Haplocambids.—These are the Haplocambids that
do not have any of the features defined for the other subgroups.
These soils do not have any of the following: a lithic contact
within 50 cm of the soil surface; a high shrink-swell potential;
brittleness; a significant amount of sodium, durinodes, nodules,
concretions, volcanic glass, cinders, pumice, or pumicelike
fragments; a soil moisture regime that borders on ustic or
xeric; or an irregular decrease in content of organic carbon
below the cambic horizon.
Durinodic Haplocambids.—These are the Haplocambids
that have one or more horizons, within 100 cm of the soil
surface and with a combined thickness of 15 cm or more, that
contain 20 percent or more, by volume, durinodes or are brittle.
These soils do not have a soil moisture regime that borders on
xeric. They also do not have a lithic contact within 50 cm of
the soil surface or a high shrink-swell potential. They occur in
Nevada and California as well as other areas that have a source
of silica.
Durinodic Xeric Haplocambids.—These are the
Haplocambids that have one or more horizons, within 100 cm
of the soil surface and with a combined thickness of 15 cm or
more, that contain 20 percent or more, by volume, durinodes or
are brittle. These soils have a soil moisture regime that borders
on xeric. They do not have a lithic contact within 50 cm of the
Aridisols 363
soil surface or a high shrink-swell potential. They occur in
Nevada, Idaho, Oregon, and Washington as well as other areas
that have a source of silica.
Fluventic Haplocambids.—These are the Haplocambids
that have an irregular decrease in content of organic carbon
below the cambic horizon. These soils do not have a lithic
contact within 50 cm of the soil surface; a high shrink-swell
potential; a significant amount of sodium, durinodes, nodules,
concretions, volcanic glass, cinders, pumice, or pumicelike
fragments; or brittleness. These soils occur in Arizona and
New Mexico.
Lithic Haplocambids.—These are the Haplocambids that
have a lithic contact within 50 cm of the soil surface. These
soils do not have a soil moisture regime that borders on ustic or
xeric. They are common in the desert areas of the world.
Lithic Ustic Haplocambids.—These are the Haplocambids
that have a lithic contact within 50 cm of the soil surface and
have a soil moisture regime that borders on ustic.
Lithic Xeric Haplocambids.—These are the Haplocambids
that have a lithic contact within 50 cm of the soil surface and
have a soil moisture regime that borders on xeric.
Petronodic Haplocambids.—These are the Haplocambids
that have one or more horizons, within 100 cm of the soil
surface and with a combined thickness of 15 cm or more, that
contain 20 percent or more nodules and concretions. These
soils do not have a soil moisture regime that borders on ustic or
xeric, a lithic contact within 50 cm of the soil surface, a high
shrink-swell potential, a significant amount of durinodes, or
brittleness.
Petronodic Ustic Haplocambids.—These are the
Haplocambids that have one or more horizons, within 100 cm
of the soil surface and with a combined thickness of 15 cm or
more, that contain 20 percent or more nodules and concretions.
These soils have a soil moisture regime that borders on ustic.
They do not have a lithic contact within 50 cm of the soil
surface, a high shrink-swell potential, a significant amount of
durinodes, or brittleness. The soils occur in Arizona and New
Mexico.
Petronodic Xeric Haplocambids.—These are the
Haplocambids that have one or more horizons, within 100 cm
of the soil surface and with a combined thickness of 15 cm or
more, that contain 20 percent or more nodules and concretions.
These soils have a soil moisture regime that borders on xeric.
They do not have a lithic contact within 50 cm of the soil
surface, a high shrink-swell potential, a significant amount of
durinodes, or brittleness.
Sodic Haplocambids.—These are the Haplocambids that
have, in a horizon at least 25 cm thick within 100 cm of the
soil surface, an exchangeable sodium percentage of 15 or more
during at least 1 month in normal years but do not have a soil
moisture regime that borders on xeric or ustic. These soils do
not contain a significant amount of durinodes, nodules, or
concretions, nor are they brittle. They do not have a lithic
contact within 50 cm of the soil surface or a high shrink-swell
potential. They occur in Nevada, New Mexico, and California.
Sodic Ustic Haplocambids.—These are the Haplocambids
that have, in a horizon at least 25 cm thick within 100 cm of
the soil surface, an exchangeable sodium percentage of 15 or
more during at least 1 month in normal years and have a soil
moisture regime that borders on ustic. These soils do not
contain a significant amount of durinodes, nodules, or
concretions and are not brittle. They do not have a lithic
contact within 50 cm of the soil surface or a high shrink-swell
potential. They occur in Arizona, New Mexico, and Utah.
Sodic Xeric Haplocambids.—These are the Haplocambids
that have, in a horizon at least 25 cm thick within 100 cm of
the soil surface, an exchangeable sodium percentage of 15 or
more during at least 1 month in normal years and have a soil
moisture regime that borders on xeric. These soils do not
contain a significant amount of durinodes, nodules, or
concretions, nor are they brittle. They do not have a lithic
contact within 50 cm of the soil surface or a high shrink-swell
potential. They occur in Oregon, California, and Nevada.
Ustertic Haplocambids.—These are the Haplocambids that
have a high shrink-swell potential and have a soil moisture
regime that borders on ustic. Most of these soils formed in
parent materials rich in smectitic clays. These soils do not have
a lithic contact within 50 cm of the soil surface. They are
known to occur in Wyoming.
Ustic Haplocambids.—These are the Haplocambids that
have a soil moisture regime that borders on ustic. These soils
do not have a lithic contact within 50 cm of the soil surface; a
high shrink-swell potential; brittleness; a significant amount of
sodium, durinodes, nodules, concretions, volcanic glass,
cinders, pumice, or pumicelike fragments; or an irregular
decrease in content of organic carbon below the cambic
horizon. They occur in the deserts of the western part of the
United States and in other deserts of the world.
Ustifluventic Haplocambids.—These are the
Haplocambids that have a soil moisture regime that borders on
ustic and have an irregular decrease in content of organic
carbon below the cambic horizon. These soils do not have a
lithic contact within 50 cm of the soil surface; a high shrinkswell
potential; brittleness; or a significant amount of sodium,
durinodes, nodules, concretions, volcanic glass, cinders,
pumice, or pumicelike fragments. They are known to occur in
Arizona, Wyoming, New Mexico, and Texas.
Vertic Haplocambids.—These are the Haplocambids that
have a high shrink-swell potential but do not have a soil
moisture regime that borders on xeric or ustic. These soils do
not have a lithic contact within 50 cm of the soil surface.
Vitrandic Haplocambids.—These are the Haplocambids that
have a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments but do not have a soil moisture regime that
borders on xeric. These soils do not have a lithic contact within
50 cm of the soil surface; a high shrink-swell potential;
364 Soil Taxonomy
brittleness; or a significant amount of sodium, durinodes,
nodules, or concretions.
Vitrixerandic Haplocambids.—These are the Haplocambids
that have a significant amount of volcanic glass, cinders,
pumice, or pumicelike fragments and have a soil moisture regime
that borders on xeric. These soils do not have a lithic contact
within 50 cm of the soil surface; a high shrink-swell potential;
brittleness; or a significant amount of sodium, durinodes,
nodules, or concretions. These soils occur in California, Oregon,
Nevada, and Washington.
Xerertic Haplocambids.—These are the Haplocambids that
have a high shrink-swell potential and have a soil moisture
regime that borders on xeric. These soils do not have a lithic
contact within 50 cm of the soil surface. They occur in
Washington and Idaho.
Xeric Haplocambids.—These are the Haplocambids that
have a soil moisture regime that borders on xeric. These
soils do not have a lithic contact within 50 cm of the soil
surface; a high shrink-swell potential; brittleness; a significant
amount of sodium, durinodes, nodules, concretions, volcanic
glass, cinders, pumice, or pumicelike fragments; or an
irregular decrease in content of organic carbon below the
cambic horizon. They occur in many of the deserts in the
western part of the United States and in other deserts of the
world.
Xerofluventic Haplocambids.—These are the Haplocambids
that have a soil moisture regime that borders on xeric and have
an irregular decrease in content of organic carbon below the
cambic horizon. These soils do not have a lithic contact within
50 cm of the soil surface; a high shrink-swell potential;
brittleness; or a significant amount of sodium, durinodes,
nodules, concretions, volcanic glass, cinders, pumice, or
pumicelike fragments.
Petrocambids
These soils have a duripan or a petrocalcic or petrogypsic
horizon that has its upper boundary at a depth between 100 and
150 cm from the soil surface. These soils are not extensive
because most Aridisols have these diagnostic horizons at
shallower depths. Because of their importance to water
movement as well as interpretations, however, classes for these
types of soils are provided.
Definition
Petrocambids are the Cambids that:
1. Have a duripan or a petrocalcic or petrogypsic horizon
with an upper boundary within 150 cm of the soil surface;
2. Are not both irrigated and characterized by aquic
conditions for some time in normal years in one or more layers
within 100 cm of the soil surface and are not saturated with
water in one or more layers within 100 cm of the soil surface
for 1 month or more in normal years.
KeytoSubgroups
GGBA. Petrocambids that have, in a horizon at least 25 cm
thick within 100 cm of the soil surface, an exchangeable
sodium percentage of 15 or more (or an SAR of 13 or more)
during at least 1 month in normal years.
SodicPetrocambids
GGBB. Other Petrocambids that have both:
1. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Petrocambids
GGBC. Other Petrocambids that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Petrocambids
GGBD. Other Petrocambids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature at a depth of 50 cm is
5 o
C or higher and have a soil moisture regime that borders on
xeric.
Xeric Petrocambids
GGBE. Other Petrocambids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature at a depth of 50 cm is
5 o
C or higher and have a soil moisture regime that borders on
ustic.
Ustic Petrocambids
Aridisols 365
GGBF. Other Petrocambids.
Typic Petrocambids
Definition of Typic Petrocambids
Typic Petrocambids are the Petrocambids that:
1. Do not have, in a horizon at least 25 cm thick within 100 cm
of the soil surface, an exchangeable sodium percentage of 15 or
more (or an SAR of 13 or more) during at least 1 month in normal
years;
2. Are dry in all parts of the moisture control section for threefourths
or more of the time (cumulative) when the soil
temperature at a depth of 50 cm is 5 o
C or higher;
3. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Description of Subgroups
Typic Petrocambids.—These are the Petrocambids that do
not have a soil moisture regime that borders on ustic or xeric or
a significant amount of sodium, volcanic glass, cinders,
pumice, or pumicelike fragments.
Sodic Petrocambids.—These are the Petrocambids that
have, in a horizon at least 25 cm thick within 100 cm of the
soil surface, an exchangeable sodium percentage of 15 or more
during at least 1 month in normal years.
Ustic Petrocambids.—These are the Petrocambids that
have a soil moisture regime that borders on ustic. These soils
do not have a significant amount of sodium, volcanic glass,
cinders, pumice, or pumicelike fragments.
Vitrandic Petrocambids.—These are the Petrocambids that
have a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments throughout one or more horizons with a
total thickness of 18 cm or more within 75 cm of the soil
surface and do not have a soil moisture regime that borders on
xeric. These soils also do not have a significant amount of
sodium.
Vitrixerandic Petrocambids.—These are the Petrocambids
that have a significant amount of volcanic glass, cinders,
pumice, or pumicelike fragments throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the soil surface and have a soil moisture regime that borders
on xeric. These soils do not have a significant amount of
sodium.
Xeric Petrocambids.—These are the Petrocambids that
have a soil moisture regime that borders on xeric. These soils
do not have a significant amount of sodium, volcanic glass,
cinders, pumice, or pumicelike fragments. They occur in
Nevada.
Cryids
Cryids are the Aridisols of cold deserts. Short growing
seasons combined with arid conditions limit the use of these
soils. The soils are characteristically at high elevations,
dominantly in the mountain and basin areas in the United
States and Asia and in other parts of the world.
The cold deserts commonly have undergone alternating
periods of colder and warmer climates, which have resulted in
the expansion and contraction of alpine glaciers in the adjacent
mountains. The consequent variations in the sediment load
carried by mountain streams have resulted in relict landforms,
such as pediments, terraces, and alluvial fans. Cryids
commonly show evidence of periglacial features, such as icewedged
casts, ground wedges, and mounds.
Cryids may have a duripan or an argillic, calcic, cambic,
gypsic, natric, petrocalcic, petrogypsic, or salic horizon. These
horizons are the basis for great groups. Haplocryids are
characterized by minimal development. Some Cryids occur
near ustic or xeric soil moisture regimes, which are the basis
for subgroups.
Definition
Cryids are the Aridisols that have a cryic temperature
regime.
Key to Great Groups
GAA. Cryids that have a salic horizon that has its upper
boundary within 100 cm of the soil surface.
Salicryids, p. 372
GAB. Other Cryids that have a duripan or a petrocalcic or
petrogypsic horizon that has its upper boundary within 100 cm
of the soil surface.
Petrocryids, p. 371
GAC. Other Cryids that have a gypsic horizon that has its
upper boundary within 100 cm of the soil surface.
Gypsicryids, p. 368
GAD. Other Cryids that have an argillic or natric horizon.
Argicryids, p. 366
GAE. Other Cryids that have a calcic horizon that has its
upper boundary within 100 cm of the soil surface.
Calcicryids, p. 367
366 Soil Taxonomy
GAF. Other Cryids.
Haplocryids, p. 369
Argicryids
These are the Cryids that have an illuvial horizon in which
silicate clays have accumulated. In general, the Argicryids
without a natric horizon formed in areas of late-Pleistocene or
older sediments or surfaces. Many of these soils receive
increments of dust, which may be a source of clay-sized
particles. Argicryids may be on gentle or steep slopes. These
soils are not extensive.
Definition
Argicryids are the Cryids that:
1. Have an argillic or natric horizon;
2. Do not have a duripan or a gypsic, petrocalcic,
petrogypsic, or salic horizon with an upper boundary within
100 cm of the soil surface.
Key to Subgroups
GADA. Argicryids that have a lithic contact within 50 cm of
the soil surface.
Lithic Argicryids
GADB. Other Argicryids that have one or both of the
following:
1. Cracks within 125 cm of the soil surface that are 5 mm
or more wide throughout a thickness of 30 cm or more for
some time in normal years, and slickensides or wedgeshaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral soil
surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Argicryids
GADC. Other Argicryids that have a natric horizon that has
its upper boundary within 100 cm of the soil surface.
Natric Argicryids
GADD. Other Argicryids that have both:
1. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Argicryids
GADE. Other Argicryids that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Argicryids
GADF. Other Argicryids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
xeric.
Xeric Argicryids
GADG. Other Argicryids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
ustic.
Ustic Argicryids
GADH. Other Argicryids.
Typic Argicryids
Definition of Typic Argicryids
Typic Argicryids are the Argicryids that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Have either:
a. No cracks within 125 cm of the soil surface that are
5 mm or more wide through a thickness of 30 cm or more
for some time in normal years, and no slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the soil
surface; or
b. A linear extensibility of less than 6.0 cm between the
Aridisols 367
soil surface and either a depth of 100 cm or a densic, lithic, or
paralithic contact, whichever is shallower;
3. Do not have a natric horizon that has its upper boundary
within 100 cm of the soil surface;
4. Are dry in all parts of the moisture control section for
three-fourths or more of the time (cumulative) when the soil
temperature is 5 o
C at a depth of 50 cm;
5. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Description of Subgroups
Typic Argicryids.—The Typic subgroup is centered on soils
that do not have a soil moisture regime that borders on ustic or
xeric. These soils also do not have a high shrink-swell
potential; a lithic contact within 50 cm of the soil surface; a
natric horizon; or a significant amount of volcanic glass,
cinders, pumice, or pumicelike fragments.
Lithic Argicryids.—These are the Argicryids that have a
lithic contact within 50 cm of the soil surface. These soils can
have other features, such as a soil moisture regime that borders
on ustic or xeric or a natric horizon, but the lithic contact keys
first.
Natric Argicryids.—These are the Argicryids that have a
natric horizon that has its upper boundary within 100 cm of the
soil surface. These soils do not have a lithic contact within 50
cm of the soil surface or a high shrink-swell potential.
Ustic Argicryids.—These are the Argicryids that have a
soil moisture regime that borders on ustic. These soils do not
have a high shrink-swell potential; a lithic contact within 50
cm of the soil surface; a natric horizon; or a significant amount
of volcanic glass, cinders, pumice, or pumicelike fragments.
Vertic Argicryids.—These are the Argicryids that have a
high shrink-swell potential. These soils do not have a lithic
contact within 50 cm of the soil surface. They can have a soil
moisture regime that borders on ustic or xeric.
Vitrandic Argicryids.—These are the Argicryids that have
a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments. These soils do not have a soil moisture
regime that borders on xeric, a lithic contact within 50 cm of
the soil surface, a high shrink-swell potential, or a natric
horizon. They are associated with areas that have a volcanic
influence.
Vitrixerandic Argicryids.—These are the Argicryids that
have a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments and have a soil moisture regime that
borders on xeric. These soils do not have a lithic contact within
50 cm of the soil surface, a natric horizon, or a high shrink-swell
potential.
Xeric Argicryids.—These are the Argicryids that have a soil
moisture regime that borders on xeric. These soils do not have a
significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments; a lithic contact within 50 cm of the soil
surface; a natric horizon; or a high shrink-swell potential.
Calcicryids
These are the Cryids that are derived from parent materials
high in content of lime or that have had lime added as dust.
Precipitation is unable to remove the calcium carbonate to
substantial depths. These soils typically have an ochric
epipedon and a calcic horizon. Some have a cambic horizon
overlying the calcic horizon.
Definition
Calcicryids are the Cryids that:
1. Have a calcic horizon that has its upper boundary within
100 cm of the soil surface;
2. Do not have a duripan or a gypsic, petrocalcic,
petrogypsic, or salic horizon with an upper boundary within
100 cm of the soil surface;
3. Do not have an argillic or natric horizon.
Key to Subgroups
GAEA. Calcicryids that have a lithic contact within 50 cm of
the soil surface.
Lithic Calcicryids
GAEB. Other Calcicryids that have both:
1. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Calcicryids
368 Soil Taxonomy
GAEC. Other Calcicryids that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm of
the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser than
2.0 mm, of which more than 66 percent is cinders, pumice, and
pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Calcicryids
GAED. Other Calcicryids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
xeric.
Xeric Calcicryids
GAEE. Other Calcicryids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
ustic.
Ustic Calcicryids
GAEF. Other Calcicryids.
Typic Calcicryids
Definition of Typic Calcicryids
Typic Calcicryids are the Calcicryids that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Are dry in all parts of the moisture control section for
three-fourths or more of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm;
3. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Description of Subgroups
Typic Calcicryids.—The Typic subgroup is centered on the
Calcicryids that do not have the properties associated with the
other subgroups. These soils do not have a lithic contact within
50 cm of the soil surface; a soil moisture regime that borders
on ustic or xeric, or a significant amount of volcanic glass,
cinders, pumice, or pumicelike fragments.
Lithic Calcicryids.—These are the Calcicryids that have a
lithic contact within 50 cm of the soil surface.
Ustic Calcicryids.—These are the Calcicryids that have a
soil moisture regime that borders on ustic. These soils do not
have a lithic contact within 50 cm of the soil surface or a
significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments.
Vitrandic Calcicryids.—These are the Calcicryids that
have a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments but do not have a soil moisture regime
that borders on xeric. These soils do not have a lithic contact
within 50 cm of the soil surface.
Vitrixerandic Calcicryids.—These are the Calcicryids that
have a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments and have a soil moisture regime that
borders on xeric. These soils do not have a lithic contact within
50 cm of the soil surface.
Xeric Calcicryids.—These are the Calcicryids that have a
soil moisture regime that borders on xeric. These soils do not
have a lithic contact within 50 cm of the soil surface or a
significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments. They are known to occur in Idaho.
Gypsicryids
Gypsicryids are the Cryids that have a gypsic horizon. An
ochric epipedon and a cambic horizon commonly occur above
the gypsic horizon. These soils formed in parent materials rich
in gypsum. They are rare in the world.
Definition
Gypsicryids are the Cryids that:
1. Have a gypsic horizon that has its upper boundary within
100 cm of the soil surface;
2. Do not have a duripan or a petrocalcic, petrogypsic, or
salic horizon with an upper boundary within 100 cm of the soil
surface.
Key to Subgroups
GACA. Gypsicryids that have a calcic horizon.
Calcic Gypsicryids
GACB. Other Gypsicryids that have both:
Aridisols 369
1. A moisture control section that is dry in all parts for less
than three-fourths of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm and a soil
moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Gypsicryids
GACC. Other Gypsicryids that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Gypsicryids
GACD. Other Gypsicryids.
Typic Gypsicryids
Definition of Typic Gypsicryids
Typic Gypsicryids are the Gypsicryids that:
1. Do not have a calcic horizon;
2. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Description of Subgroups
Typic Gypsicryids.—These are the Gypsicryids that do not
have a calcic horizon or a significant amount of volcanic glass,
cinders, pumice, or pumicelike fragments.
Calcic Gypsicryids.—These are the Gypsicryids that have a
calcic horizon. These soils can have other diagnostic horizons
or features, but the calcic horizon keys first.
Vitrandic Gypsicryids.—These are the Gypsicryids that
have a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments but do not have a soil moisture regime
that borders on xeric.
Vitrixerandic Gypsicryids.—These are the Gypsicryids
that have a significant amount of volcanic glass, cinders,
pumice, and pumicelike fragments and have a soil moisture
regime that borders on xeric.
Haplocryids
These are the Cryids that have a cambic horizon. An ochric
epipedon is common. Other diagnostic horizons may occur
below a depth of 100 cm. These soils commonly have
accumulations of calcium carbonate below the cambic horizon.
They are rare in the world.
Definition
Haplocryids are the Cryids that:
1. Do not have an argillic or natric horizon;
2. Do not have a duripan or a calcic, gypsic, petrocalcic,
petrogypsic, or salic horizon that has an upper boundary within
100 cm of the soil surface.
Key to Subgroups
GAFA. Haplocryids that have a lithic contact within 50 cm of
the soil surface.
Lithic Haplocryids
GAFB. Other Haplocryids that have one or both of the
following:
1. Cracks within 125 cm of the soil surface that are 5 mm
or more wide throughout a thickness of 30 cm or more for
some time in normal years, and slickensides or wedgeshaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral soil
surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Haplocryids
370 Soil Taxonomy
GAFC. Other Haplocryids that have both:
1. A moisture control section that is dry in all parts for less
than three-fourths of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm and a soil
moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Haplocryids
GAFD. Other Haplocryids that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Haplocryids
GAFE. Other Haplocryids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
xeric.
Xeric Haplocryids
GAFF. Other Haplocryids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
ustic.
Ustic Haplocryids
GAFG. Other Haplocryids.
Typic Haplocryids
Definition of Typic Haplocryids
Typic Haplocryids are the Haplocryids that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Have either:
a. No cracks within 125 cm of the soil surface that are
5 mm or more wide through a thickness of 30 cm or more
for some time in normal years, and no slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the soil
surface; or
b. A linear extensibility of less than 6.0 cm between the
soil surface and either a depth of 100 cm or a densic, lithic,
or paralithic contact, whichever is shallower;
3. Are dry in all parts of the moisture control section for
three-fourths or more of the time (cumulative) when the soil
temperature is 5 o
C at a depth of 50 cm;
4. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Description of Subgroups
Typic Haplocryids.—The Typic subgroup of Haplocryids is
centered on features that are not defined for the other
subgroups. These soils do not have a lithic contact within 50
cm of the soil surface; a significant amount of volcanic glass,
cinders, pumice, and pumicelike fragments; a high shrinkswell
potential; or a soil moisture regime that borders on ustic
or xeric.
Lithic Haplocryids.—These are the Haplocryids that have
a lithic contact within 50 cm of the soil surface. These soils can
have other characteristics, but the lithic contact keys first.
Ustic Haplocryids.—These are the Haplocryids that have a
soil moisture regime that borders on ustic. These soils do not
have a lithic contact within 50 cm of the soil surface; a high
shrink-swell potential; or a significant amount of volcanic
glass, cinders, pumice, or pumicelike fragments.
Vertic Haplocryids.—These are the Haplocryids that have
a high shrink-swell potential. These soils do not have a lithic
contact within 50 cm of the soil surface.
Vitrandic Haplocryids.—These are the Haplocryids that
have a significant amount of volcanic glass, cinders, pumice,
and pumicelike fragments but do not have a soil moisture
Aridisols 371
regime that borders on xeric. These soils also do not have a lithic
contact within 50 cm of the soil surface or a high shrink-swell
potential.
Vitrixerandic Haplocryids.—These are the Haplocryids
that have a significant amount of volcanic glass, cinders,
pumice, and pumicelike fragments and have a soil moisture
regime that borders on xeric. These soils do not have a lithic
contact within 50 cm of the soil surface or a high shrink-swell
potential.
Xeric Haplocryids.—These are the Haplocryids that have a
soil moisture regime that borders on xeric. These soils do not
have a lithic contact within 50 cm of the soil surface; a high
shrink-swell potential; or a significant amount of volcanic
glass, cinders, pumice, or pumicelike fragments.
Petrocryids
These are the Cryids that have a duripan or a petrocalcic or
petrogypsic horizon. An argillic, cambic, or natric horizon may
occur above the cemented layer. These soils occur in the
mountains of Idaho and possibly Wyoming.
Definition
Petrocryids are the Cryids that:
1. Have a duripan or a petrocalcic or petrogypsic horizon
with an upper boundary within 100 cm of the soil surface;
2. Do not have a salic horizon that has its upper boundary
within 100 cm of the soil surface.
Key to Subgroups
GABA. Petrocryids that:
1. Have a duripan that is strongly cemented or less
cemented in all subhorizons and has its upper boundary
within 100 cm of the soil surface; and
2. Are dry in all parts of the moisture control section for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and
have a soil moisture regime that borders on xeric.
Xereptic Petrocryids
GABB. Other Petrocryids that:
1. Have a duripan that has its upper boundary within 100
cm of the soil surface; and
2. Are dry in all parts of the moisture control section for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and
have a soil moisture regime that borders on xeric.
Duric Xeric Petrocryids
GABC. Other Petrocryids that have a duripan that has its upper
boundary within 100 cm of the soil surface.
Duric Petrocryids
GABD. Other Petrocryids that have a petrogypsic horizon that
has its upper boundary within 100 cm of the soil surface.
Petrogypsic Petrocryids
GABE. Other Petrocryids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
xeric.
Xeric Petrocryids
GABF. Other Petrocryids that are dry in all parts of the
moisture control section for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
ustic.
Ustic Petrocryids
GABG. Other Petrocryids.
Typic Petrocryids
Definition of Typic Petrocryids
Typic Petrocryids are the Petrocryids that:
1. Have a petrocalcic horizon that has its upper boundary
within 100 cm of the soil surface;
2. Do not have a duripan or a petrogypsic horizon that has an
upper boundary within 100 cm of the soil surface;
3. Are dry in all parts of the moisture control section for
three-fourths or more of the time (cumulative) when the soil
temperature is 5 o
C at a depth of 50 cm.
Description of Subgroups
Typic Petrocryids.—The central concept of the Typic
subgroup is that of dry soils with a petrocalcic horizon. These
soils do not have a duripan, a petrogypsic horizon, or a soil
moisture regime that borders on ustic or xeric.
Duric Petrocryids.—These are the Petrocryids that have a
duripan that is very strongly cemented or indurated in at least
some part. These soils do not have a soil moisture regime that
borders on xeric.
Duric Xeric Petrocryids.—These are the Petrocryids that
have a duripan that is very strongly cemented or indurated and
have a soil moisture regime that borders on xeric. These soils
occur in Idaho.
Petrogypsic Petrocryids.—These are the Petrocryids that
have a petrogypsic horizon. These soils do not have a duripan.
372 Soil Taxonomy
Ustic Petrocryids.—These are the Petrocryids that have a
petrocalcic horizon and have a soil moisture regime that borders
on ustic. These soils do not have a petrogypsic horizon or a
duripan.
Xeric Petrocryids.—These are the Petrocryids that have a
petrocalcic horizon and have a soil moisture regime that
borders on xeric. These soils do not have a petrogypsic horizon
or a duripan.
Xereptic Petrocryids.—These are the Petrocryids that have a
duripan that is strongly cemented or less cemented and have a
soil moisture regime that borders on xeric. These soils occur in
Idaho.
Salicryids
Salicryids are the Cryids that have a salic horizon. These soils
can have other diagnostic horizons and characteristics, but the
presence of soluble salts is considered important to
interpretations. The soils occur in extremely arid, cold regions
of the world.
Definition
Salicryids are the Cryids that have a salic horizon that has
its upper boundary within 100 cm of the soil surface.
Key to Subgroups
GAAA. Salicryids that are saturated with water in one or
more layers within 100 cm of the soil surface for 1 month or
more in normal years.
Aquic Salicryids
GAAB. Other Salicryids.
Typic Salicryids
Definition of Typic Salicryids
Typic Salicryids are the Salicryids that are not saturated
with water in any layer within 100 cm of the soil surface for 1
month or more in normal years.
Description of Subgroups
Typic Salicryids.—These are the Salicryids that are not
saturated with water in one or more horizons within 100 cm of
the soil surface for at least 1 month in normal years.
Aquic Salicryids.—These are the Salicryids that are
saturated with water in one or more horizons for 1 month or
more in normal years.
Durids
Durids are the Aridisols that have a duripan that has an
upper boundary within 100 cm of the soil surface. In many
areas the duripan is within 50 cm of the soil surface. These
soils occur dominantly on gentle slopes and formed in
sediments that contain pyroclastics. The duripan is cemented
partly with opal or chalcedony. The soils commonly have
calcium carbonate. The duripan is a barrier to both roots and
water.
Some Durids have an argillic or natric horizon above
the duripan, and these horizons are the basis for great
groups. Where these soils occur in areas adjacent to an ustic
or xeric soil moisture regime, intergrades are recognized at
the subgroup level. Most of these soils are used for grazing.
The amount of forage is low where the duripan is shallow.
These soils occur in the western part of the United States,
particularly in Nevada. They are not known to occur outside
the United States.
Definition
Durids are the Aridisols that:
1. Have a duripan that has its upper boundary within 100 cm of
the surface;
2. Have a soil temperature regime warmer than cryic;
3. Do not have a salic horizon that has its upper boundary
within 100 cm of the soil surface.
Key to Great Groups
GCA. Durids that have a natric horizon above the duripan.
Natridurids, p. 377
GCB. Other Durids that have an argillic horizon above the
duripan.
Argidurids, p. 372
GCC. Other Durids.
Haplodurids, p. 375
Argidurids
These are the Durids with an argillic horizon above the
duripan. Commonly, the duripan is within 50 cm of the soil
surface. These soils are close to volcanic areas or formed in
eolian or alluvial sediments derived from pyroclastics.
Definition
Argidurids are the Durids that:
1. Have an argillic horizon above the duripan;
2. Do not have a natric horizon above the duripan.
Key to Subgroups
GCBA. Argidurids that have, above the duripan, one or both
of the following:
1. Cracks between the soil surface and the top of the
Aridisols 373
duripan that are 5 mm or more wide through a thickness of
30 cm or more for some time in normal years, and
slickensides or wedge-shaped aggregates in a layer 15 cm
or more thick that has its upper boundary above the duripan;
or
2. A linear extensibility of 6.0 cm or more between the soil
surface and the top of the duripan.
Vertic Argidurids
GCBB. Other Argidurids that are either:
1. Irrigated and have aquic conditions for some time in
normal years in one or more layers within 100 cm of the soil
surface; or
2. Saturated with water in one or more layers within 100
cm of the soil surface for 1 month or more in normal years.
Aquic Argidurids
GCBC. Other Argidurids that have the following combination
of characteristics:
1. An argillic horizon that has 35 percent or more clay in
the fine-earth fraction of some part; and either
a. A clay increase of 15 percent or more (absolute)
within a vertical distance of 2.5 cm either within the
argillic horizon or at its upper boundary; or
b. If there is an Ap horizon directly above the argillic
horizon, a clay increase of 10 percent or more (absolute)
at the upper boundary of the argillic horizon; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric.
Abruptic Xeric Argidurids
GCBD. Other Argidurids that have an argillic horizon that
has 35 percent or more clay in the fine-earth fraction of some
part; and either
1. A clay increase of 15 percent or more (absolute) within
a vertical distance of 2.5 cm within the argillic horizon or at
its upper boundary; or
2. If there is an Ap horizon directly above the argillic
horizon, a clay increase of 10 percent or more (absolute) at
the upper boundary of the argillic horizon.
Abruptic Argidurids
GCBE. Other Argidurids that have:
1. A duripan that is strongly cemented or less cemented in
all subhorizons; and
2. A moisture control section that is dry in all parts for less
than three-fourths of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm and a soil
moisture regime that borders on xeric.
Haploxeralfic Argidurids
GCBF. Other Argidurids that have a duripan that is strongly
cemented or less cemented in all subhorizons.
Argidic Argidurids
GCBG. Other Argidurids that have both:
1. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Argidurids
GCBH. Other Argidurids that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Argidurids
GCBI. Other Argidurids that have a moisture control section
that is dry in all parts for less than three-fourths of the time
(cumulative) when the soil temperature is 5 o
C or higher at a
depth of 50 cm and have a soil moisture regime that borders on
xeric.
Xeric Argidurids
GCBJ. Other Argidurids that have a moisture control section
374 Soil Taxonomy
that is dry in all parts for less than three-fourths of the time
(cumulative) when the soil temperature at a depth of 50 cm is
5 o
C or higher and have a soil moisture regime that borders on
ustic.
Ustic Argidurids
GCBK. Other Argidurids.
Typic Argidurids
Definition of Typic Argidurids
Typic Argidurids are the Argidurids that:
1. Do not have either of the following:
a. Cracks between the soil surface and the top of the
duripan that are 5 mm or more wide through a thickness of
30 cm or more for some time in normal years, or
slickensides or wedge-shaped aggregates in a layer 15 cm or
more thick that has its upper boundary above the duripan;
or
b. A linear extensibility of 6.0 cm or more between the soil
surface and the top of the duripan;
2. Are not both irrigated and characterized by aquic
conditions for some time in normal years in one or more layers
within 100 cm of the soil surface and are not saturated with
water in one or more layers within 100 cm of the soil surface
for 1 month or more in normal years;
3. Have an argillic horizon that has less than 35 percent clay
in the fine-earth fraction of some part; or
a. A clay increase of less than 15 percent (absolute) within
a vertical distance of 2.5 cm both within the argillic horizon
and at its upper boundary; or
b. If there is an Ap horizon directly above the argillic
horizon, a clay increase of less than 10 percent (absolute) at
the upper boundary of the argillic horizon;
4. Have a moisture control section that is dry in all parts for
three-fourths or more of the time (cumulative) when the soil
temperature at a depth of 50 cm is 5 o
C or higher;
5. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more;
6. Have a duripan that is strongly cemented or less cemented
in all subhorizons.
Description of Subgroups
Typic Argidurids.—The Typic subgroup of Argidurids is
defined in terms of characteristics that are not evident. It does
not have the following: a high shrink-swell potential;
saturation with water for 1 month or more within 100 cm of
the soil surface in normal years; a significant increase in
content of clay either within the argillic horizon or at its upper
boundary; a soil moisture regime that borders on ustic or xeric;
or a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments. These soils have a duripan that is very
strongly cemented or indurated in at least some part.
Abruptic Argidurids.—These are the Argidurids that have
a significant increase in content of clay within a short distance
either within the argillic horizon or at its upper boundary but
do not have a soil moisture regime that borders on xeric. The
abrupt increase in content of clay is important to water
movement. These soils do not have a high shrink-swell
potential and are not saturated with water for 1 month or more
within 100 cm of the soil surface in normal years. They are
known to occur in Arizona and Nevada.
Abruptic Xeric Argidurids.—These are the Argidurids
that have a significant increase in content of clay within a short
distance either within the argillic horizon or at its upper
boundary and have a soil moisture regime that borders on
xeric. The abrupt increase in content of clay is important to
water movement. These soils do not have a high shrink-swell
potential and are not saturated with water for 1 month or more
within 100 cm of the soil surface in normal years. They occur
in California, Oregon, and Nevada.
Aquic Argidurids.—These are the Argidurids that are
saturated with water for 1 month or more within 100 cm of the
soil surface in normal years. These soils are commonly
saturated by runoff from melting snow or from heavy rains.
They are dry for most of the year. They do not have a high
shrink-swell potential.
Argidic Argidurids.—These are the Argidurids that have a
duripan that is strongly cemented or less cemented in all
subhorizons and do not have a soil moisture regime that
borders on xeric. These soils do not have a high shrink-swell
potential, saturation with water for 1 month or more within
100 cm of the soil surface in normal years, or a significant
increase in content of clay within the argillic horizon or at its
upper boundary. These soils are known to occur in Nevada,
Oregon, and California.
Haploxeralfic Argidurids.—These are the Argidurids that
have a duripan that is strongly cemented or less cemented in
all subhorizons and have a soil moisture regime that borders on
xeric. These soils do not have a high shrink-swell potential,
saturation with water for 1 month or more within 100 cm of
the soil surface in normal years, or a significant increase in
Aridisols 375
content of clay within the argillic horizon or at its upper
boundary. These soils are known to occur in Nevada, Oregon,
Utah, Idaho, and California.
Ustic Argidurids.—These are the Argidurids that have a
soil moisture regime that borders on ustic and have a duripan
that is very strongly cemented or indurated in at least some
part. These soils do not have a high shrink-swell potential;
saturation with water for 1 month or more within 100 cm of
the soil surface in normal years; a significant increase in
content of clay either within the argillic horizon or at its upper
boundary; or a significant amount of volcanic glass, cinders,
pumice, or pumicelike fragments. These soils occur in Nevada.
Vertic Argidurids.—These are the Argidurids that have a
high shrink-swell potential. These soils occur in Nevada.
Vitrandic Argidurids.—These are the Argidurids that have
a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments but do not have a soil moisture regime
that borders on xeric. These soils have a duripan that is very
strongly cemented or indurated in at least some part. They do
not have an abrupt change in content of clay within the argillic
horizon or at its upper boundary, a high shrink-swell potential,
or saturation with water for 1 month or more within 100 cm of
the soil surface during the growing season.
Vitrixerandic Argidurids.—These are the Argidurids that
have a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments and have a soil moisture regime that
borders on xeric. These soils have a duripan that is very
strongly cemented or indurated in at least some part. They do
not have an abrupt change in content of clay within the argillic
horizon or at its upper boundary, a high shrink-swell potential,
or saturation with water for 1 month or more within 100 cm of
the soil surface during the growing season. These soils are
known to occur in Oregon.
Xeric Argidurids.—These are the Argidurids that have a soil
moisture regime that borders on xeric and have a duripan that is
very strongly cemented or indurated in at least some part. These
soils do not have a high shrink-swell potential; saturation with
water for 1 month or more within 100 cm of the soil surface in
normal years; a significant increase in content of clay either
within the argillic horizon or at its upper boundary; or a
significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments. These soils occur in Nevada, Oregon,
Idaho, Utah, and California.
Haplodurids
These are the Durids that do not have a natric or argillic
horizon. These soils formed in materials that have a pyroclastic
influence. Most Haplodurids are used for grazing.
Definition
Haplodurids are the Durids that do not have an argillic or
natric horizon above the duripan.
KeytoSubgroups
GCCA. Haplodurids that:
1. Have a duripan that is strongly cemented or less
cemented in all subhorizons; and
2. Are either:
a. Irrigated and have aquic conditions for some time in
normal years in one or more layers within 100 cm of the
soil surface; or
b. Saturated with water in one or more layers within
100 cm of the soil surface for 1 month or more in normal
years.
Aquicambidic Haplodurids
GCCB. Other Haplodurids that are either:
1. Irrigated and have aquic conditions for some time in
normal years in one or more layers within 100 cm of the soil
surface; or
2. Saturated with water in one or more layers within 100
cm of the soil surface for 1 month or more in normal years.
Aquic Haplodurids
GCCC. Other Haplodurids that have:
1. A duripan that is strongly cemented or less cemented in
all subhorizons; and
2. A mean annual soil temperature lower than 22 o
C, a
difference of 5 o
C or more between mean summer and mean
winter soil temperatures at a depth of 50 cm, and a soil
moisture regime that borders on xeric.
Xereptic Haplodurids
GCCD. Other Haplodurids that have a duripan that is
strongly cemented or less cemented in all subhorizons.
Cambidic Haplodurids
GCCE. Other Haplodurids that have:
1. A moisture control section that is dry in all parts for
three-fourths of the time (cumulative) or less when the soil
temperature at a depth of 50 cm is 5 o
C or higher and a soil
moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
376 Soil Taxonomy
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Haplodurids
GCCF. Other Haplodurids that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Haplodurids
GCCG. Other Haplodurids that have a mean annual soil
temperature lower than 22 o
C, a difference of 5 o
C or more
between mean summer and mean winter soil temperatures at a
depth of 50 cm, and a soil moisture regime that borders on
xeric.
Xeric Haplodurids
GCCH. Other Haplodurids that have a moisture control
section that is dry in all parts for less than three-fourths of the
time (cumulative) when the soil temperature at a depth of 50
cm is 5 o
C or higher and have a soil moisture regime that
borders on ustic.
Ustic Haplodurids
GCCI. Other Haplodurids.
Typic Haplodurids
Definition of Typic Haplodurids
Typic Haplodurids are the Durids that:
1. Are not both irrigated and characterized by aquic
conditions for some time in normal years in one or more layers
within 100 cm of the soil surface and are not saturated with
water in one or more layers within 100 cm of the soil surface
for 1 month or more in normal years;
2. Have a moisture control section that is dry in all parts for
three-fourths or more of the time (cumulative) when the soil
temperature at a depth of 50 cm is 5 o
C or higher;
3. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more;
4. Have a duripan that is indurated or very strongly cemented
in at least one subhorizon.
Description of Subgroups
Typic Haplodurids.—These are the Haplodurids that have
a duripan that is very strongly cemented or indurated in at least
some part. These soils do not have a soil moisture regime that
borders on ustic or xeric; saturation with water for 1 month or
more within 100 cm of the soil surface in normal years; or a
significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments.
Aquicambidic Haplodurids.—These are the Haplodurids
that are saturated with water for 1 month or more within 100
cm of the soil surface in normal years and have a duripan that
is strongly cemented or less cemented in all subhorizons. These
soils occur in California, Oregon, and Nevada.
Aquic Haplodurids.—These are the Haplodurids that are
saturated with water for 1 month or more within 100 cm of the
soil surface in normal years and have a duripan that is very
strongly cemented or indurated in at least some part. These
soils occur in California, Oregon, and Washington.
Cambidic Haplodurids.—These are the Haplodurids that
have a duripan that is strongly cemented or less cemented in
all subhorizons but do not have a soil moisture regime that
borders on xeric. These soils are not saturated with water for 1
month or more within 100 cm of the soil surface in normal
years. They occur in Nevada and California.
Ustic Haplodurids.—These are the Haplodurids that have a
soil moisture regime that borders on ustic and have a duripan
that is very strongly cemented or indurated in at least some
part. These soils are not saturated with water for 1 month or
more within 100 cm of the soil surface in normal years, nor do
they have a significant amount of volcanic glass, cinders,
pumice, or pumicelike fragments.
Vitrandic Haplodurids.—These are the Haplodurids that
have a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments but do not have a soil moisture regime
that borders on xeric. These soils have a duripan that is very
strongly cemented or indurated in at least some part. They are
not saturated with water for 1 month or more within 100 cm of
the soil surface in normal years. These soils are known to occur
in California.
Vitrixerandic Haplodurids.—These are the Haplodurids
that have a significant amount of volcanic glass, cinders,
pumice, or pumicelike fragments and have a soil moisture
regime that borders on xeric. These soils also have a duripan
that is very strongly cemented or indurated in at least some
part. They are not saturated with water for 1 month or more
Aridisols 377
within 100 cm of the soil surface in normal years. These soils are
known to occur in California and Oregon.
Xeric Haplodurids.—These are the Haplodurids that have
a soil moisture regime that borders on xeric and have a duripan
that is very strongly cemented or indurated in at least some
part. These soils are not saturated with water for 1 month or
more within 100 cm of the soil surface in normal years, nor do
they have a significant amount of volcanic glass, cinders,
pumice, or pumicelike fragments. They occur in a number of
Western States.
Xereptic Haplodurids.—These are the Haplodurids that
have a soil moisture regime that borders on xeric and have a
duripan that is strongly cemented or less cemented in all
subhorizons. These soils are not saturated with water for 1
month or more within 100 cm of the soil surface in normal
years. They occur in Nevada, Utah, Oregon, Washington, and
Idaho.
Natridurids
These are the Durids that have a natric horizon above the
duripan. Commonly, the duripan is within 50 cm of the soil
surface. In many areas it is plugged by calcium carbonate.
These soils are commonly on gently sloping landscapes and
formed in materials derived from pyroclastics. They are not
extensive and are used mostly for grazing.
Definition
Natridurids are the Durids that have a natric horizon above
the duripan.
Key to Subgroups
GCAA. Natridurids that have, above the duripan, one or both
of the following:
1. Cracks between the soil surface and the top of the
duripan that are 5 mm or more wide through a thickness of
30 cm or more for some time in normal years, and
slickensides or wedge-shaped aggregates in a layer 15 cm or
more thick that has its upper boundary above the duripan;
or
2. A linear extensibility of 6.0 cm or more between the
soil surface and the top of the duripan.
Vertic Natridurids
GCAB. Other Natridurids that meet both of the following:
1. Have a duripan that is strongly cemented or less
cemented in all subhorizons; and
2. Are either:
a. Irrigated and have aquic conditions for some time in
normal years in one or more layers within 100 cm of the
soil surface; or
b. Saturated with water in one or more layers within
100 cm of the soil surface for 1 month or more in normal
years.
AquicNatrargidicNatridurids
GCAC. Other Natridurids that are either:
1. Irrigated and have aquic conditions for some time in
normal years in one or more layers within 100 cm of the soil
surface; or
2. Saturated with water in one or more layers within 100
cm of the soil surface for 1 month or more in normal years.
Aquic Natridurids
GCAD. Other Natridurids that have the following
combination of characteristics:
1. A duripan that is strongly cemented or less cemented in
all subhorizons; and
2. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric.
Natrixeralfic Natridurids
GCAE. Other Natridurids that have a duripan that is strongly
cemented or less cemented in all subhorizons.
Natrargidic Natridurids
GCAF. Other Natridurids that have both:
1. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Natridurids
GCAG. Other Natridurids that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
378 Soil Taxonomy
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Natridurids
GCAH. Other Natridurids that have a moisture control
section that is dry in all parts for less than three-fourths of the
time (cumulative) when the soil temperature is 5 o
C or higher
at a depth of 50 cm and have a soil moisture regime that
borders on xeric.
Xeric Natridurids
GCAI. Other Natridurids.
Typic Natridurids
Definition of Typic Natridurids
Typic Natridurids are the Durids that:
1. Do not have either of the following:
a. Cracks between the soil surface and the top of the
duripan that are 5 mm or more wide through a thickness of
30 cm or more for some time in normal years, and
slickensides or wedge-shaped aggregates in a layer 15 cm or
more thick that has its upper boundary above the duripan;
or
b. A linear extensibility of 6.0 cm or more between the soil
surface and the top of the duripan;
2. Are not both irrigated and characterized by aquic
conditions for some time in normal years in one or more layers
within 100 cm of the soil surface and are not saturated with
water in one or more layers within 100 cm of the soil surface
for 1 month or more in normal years;
3. Have a moisture control section that is dry in all parts for
three-fourths or more of the time (cumulative) when the soil
temperature is 5 o
C or higher at a depth of 50 cm;
4. Have a duripan that is either indurated or very strongly
cemented in at least one subhorizon;
5. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Description of Subgroups
Typic Natridurids.—These are the Natridurids that have a
duripan that is very strongly cemented or indurated in at least
some part. These soils do not have a soil moisture regime that
borders on xeric, a high shrink-swell potential, or saturation
with water for 1 month or more within 100 cm of the soil
surface in normal years.
Aquic Natrargidic Natridurids.—These are the
Natridurids that are saturated with water for at least 1 month
within 100 cm of the soil surface in normal years and have a
duripan that is strongly cemented or less cemented in all
subhorizons. These soils do not have a high shrink-swell
potential. They occur in Nevada.
Aquic Natridurids.—These are the Natridurids that have a
duripan that is very strongly cemented or indurated in at least
some part and are saturated with water for at least 1 month
within 100 cm of the soil surface in normal years. These soils
do not have a high shrink-swell potential.
Natrargidic Natridurids.—These are the Natridurids that
have a duripan that is strongly cemented or less cemented in
all subhorizons and have a soil moisture regime that does not
border on xeric. These soils do not have a high shrink-swell
potential and are not saturated with water for 1 month or more
within 100 cm of the soil surface in normal years. They occur
in Nevada.
Natrixeralfic Natridurids.—These are the Natridurids that
have a duripan that is strongly cemented or less cemented in
all subhorizons and have a soil moisture regime that borders on
xeric. These soils do not have a high shrink-swell potential and
are not saturated with water for 1 month or more within 100
cm of the soil surface in normal years. They occur in Nevada
and California.
Vertic Natridurids.—These are the Natridurids that have a
high shrink-swell potential.
Vitrandic Natridurids.—These are the Natridurids that
have a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments and have a soil moisture regime that
does not border on xeric. These soils have a duripan that is
very strongly cemented or indurated in at least some part. They
do not have a high shrink-swell potential and are not saturated
with water for 1 month or more within 100 cm of the soil
surface in normal years.
Vitrixerandic Natridurids.—These are the Natridurids that
have a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments and have a soil moisture regime that
borders on xeric. These soils also have a duripan that is very
strongly cemented or indurated in at least some part. They do
not have a high shrink-swell potential and are not saturated
with water for 1 month or more within 100 cm of the soil
surface in normal years.
Xeric Natridurids.—These are the Natridurids that have a
Aridisols 379
duripan that is very strongly cemented or indurated in at least
some part and have a soil moisture regime that borders on xeric.
These soils do not have a high shrink-swell potential and are not
saturated with water for 1 month or more within 100 cm of the
soil surface in normal years.
Gypsids
Gypsids are the Aridisols that have a gypsic or petrogypsic
horizon within 100 cm of the soil surface. Accumulation of
gypsum takes place initially as crystal aggregates in the voids
of the soils. These aggregates grow by accretion, displacing the
enclosing soil material. When the gypsic horizon occurs as a
cemented impermeable layer, it is recognized as the
petrogypsic horizon. Each of these forms of gypsum
accumulation implies processes in the soils, and each presents
a constraint to soil use. One of the largest constraints is
dissolution of the gypsum, which plays havoc with structures,
roads, and irrigation delivery systems.
The presence of one or more of these horizons, with or
without other diagnostic horizons, defines the great groups of
the Gypsids. Gypsids occur in Iraq, Syria, Saudi Arabia, Iran,
Somalia, West Asia, and some of the most arid areas of the
western part of the United States.
Gypsids are on many segments of the landscape. Some of
them have calcic or related horizons that overlie the gypsic
horizon.
Definition
Gypsids are the Aridisols that:
1. Have a gypsic or petrogypsic horizon that has an upper
boundary within 100 cm of the soil surface;
2. Do not have a petrocalcic horizon overlying the gypsic or
petrogypsic horizon;
3. Have a soil temperature regime warmer than cryic;
4. Do not have a duripan or a salic horizon that has an upper
boundary within 100 cm of the soil surface.
Key to Great Groups
GDA. Gypsids that have a petrogypsic or petrocalcic horizon
that has its upper boundary within 100 cm of the soil surface.
Petrogypsids, p. 386
GDB. Other Gypsids that have a natric horizon that has its
upper boundary within 100 cm of the soil surface.
Natrigypsids, p. 384
GDC. Other Gypsids that have an argillic horizon that has its
upper boundary within 100 cm of the soil surface.
Argigypsids, p. 379
GDD. Other Gypsids that have a calcic horizon that has its
upper boundary within 100 cm of the soil surface.
Calcigypsids, p. 381
GDE. Other Gypsids.
Haplogypsids, p. 382
Argigypsids
Argigypsids are the Gypsids that have an argillic horizon.
These soils are known to occur in the Four Corners area of the
western part of the United States and in Texas. They are used
primarily for grazing.
Definition
Argigypsids are the Gypsids that:
1. Have an argillic horizon that has its upper boundary
within 100 cm of the soil surface;
2. Do not have a natric, petrocalcic, or petrogypsic horizon
with an upper boundary within 100 cm of the soil surface.
Key to Subgroups
GDCA. Argigypsids that have a lithic contact within 50 cm of
the soil surface.
Lithic Argigypsids
GDCB. Other Argigypsids that have:
1. Cracks within 125 cm of the soil surface that are 5 mm
or more wide through a thickness of 30 cm or more for some
time in normal years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has its upper
boundary within 125 cm of the soil surface; or
2. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic, lithic,
or paralithic contact, whichever is shallower.
Vertic Argigypsids
GDCC. Other Argigypsids that have a calcic horizon
overlying the gypsic horizon.
Calcic Argigypsids
GDCD. Other Argigypsids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that contain 20 percent or more
(by volume) durinodes, nodules, or concretions.
Petronodic Argigypsids
GDCE. Other Argigypsids that have both:
1. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric; and
380 Soil Taxonomy
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or both
of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Argigypsids
GDCF. Other Argigypsids that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 percent or more.
Vitrandic Argigypsids
GDCG. Other Argigypsids that have a moisture control
section that is dry in all parts for less than three-fourths of the
time (cumulative) when the soil temperature at a depth of 50
cm is 5 o
C or higher and have a soil moisture regime that
borders on xeric.
Xeric Argigypsids
GDCH. Other Argigypsids that have a moisture control
section that is dry in all parts for less than three-fourths of the
time (cumulative) when the soil temperature at a depth of 50
cm is 5 o
C or higher and have a soil moisture regime that
borders on ustic.
Ustic Argigypsids
GDCI. Other Argigypsids.
Typic Argigypsids
Definition of Typic Argigypsids
Typic Argigypsids are the Argigypsids that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Have either:
a. No cracks within 125 cm of the soil surface that are 5
mm or more wide through a thickness of 30 cm or more for
some time in normal years, and no slickensides or wedgeshaped
aggregates in a layer 15 cm or more thick that has its
upper boundary within 125 cm of the soil surface; or
b. A linear extensibility of less than 6.0 cm between the soil
surface and either a depth of 100 cm or a densic, lithic, or
paralithic contact, whichever is shallower;
3. Do not have a calcic horizon overlying the gypsic horizon;
4. Have a moisture control section that is dry in all parts for
three-fourths or more of the time (cumulative) when the soil
temperature at a depth of 50 cm is 5 o
C or higher;
5. Do not have one or more horizons, within 100 cm of the
soil surface and with a combined thickness of more than 15
cm, that contain 20 percent or more (by volume) durinodes,
nodules, or concretions;
6. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Description of Subgroups
Typic Argigypsids.—These are the Argigypsids that do not
have a lithic contact within 50 cm of the soil surface; a high
shrink-swell potential; a calcic horizon above the gypsic
horizon; a soil moisture regime that borders on xeric or ustic; a
significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments; or a significant amount of durinodes,
concretions, or nodules.
Calcic Argigypsids.—These are the Argigypsids that have
a calcic horizon over the gypsic horizon. These soils do not
have a lithic contact within 50 cm of the soil surface or a high
shrink-swell potential. They are known to occur in Arizona.
Lithic Argigypsids.—These are the Argigypsids that have a
lithic contact within 50 cm of the soil surface. They can have a
soil moisture regime that borders on ustic or xeric.
Petronodic Argigypsids.—These are the Argigypsids that
have a significant amount of durinodes, nodules, or
concretions. These soils do not have a calcic horizon above the
gypsic horizon, a lithic contact within 50 cm of the soil
surface, or a high shrink-swell potential.
Ustic Argigypsids.—These are the Argigypsids that have a
soil moisture regime that borders on ustic. These soils do not
have a lithic contact within 50 cm of the soil surface; a high
shrink-swell potential; a calcic horizon above the gypsic
Aridisols 381
horizon; a significant amount of volcanic glass, cinders, pumice,
or pumicelike fragments; or a significant amount of durinodes,
concretions, or nodules.
Vertic Argigypsids.—These are the moderately deep to
very deep Argigypsids that have a high shrink-swell potential.
They occur in Texas, where they are used as rangeland.
Vitrandic Argigypsids.—These are the Argigypsids that
have a significant amount of volcanic glass, cinders, pumice,
or pumicelike fragments but do not have a soil moisture
regime that borders on xeric. These soils also do not have
a lithic contact within 50 cm of the soil surface; a high
shrink-swell potential; a calcic horizon above the gypsic
horizon; or a significant amount of durinodes, nodules, or
concretions.
Vitrixerandic Argigypsids.—These are the Argigypsids
that have a significant amount of volcanic glass, cinders,
pumice, or pumicelike fragments and have a soil moisture
regime that borders on xeric. Vitrixerandic Argigypsids do not
have a lithic contact within 50 cm of the soil surface; a high
shrink-swell potential; a calcic horizon above the gypsic
horizon; or a significant amount of durinodes, nodules, or
concretions.
Xeric Argigypsids.—These are the Argigypsids that have a
soil moisture regime that borders on xeric. These soils do not
have a lithic contact within 50 cm of the soil surface; a high
shrink-swell potential; a calcic horizon above the gypsic
horizon; or a significant amount of volcanic glass, cinders,
pumice, pumicelike fragments, durinodes, concretions, or
nodules.
Calcigypsids
Calcigypsids are the Gypsids that have a calcic horizon.
Commonly, the calcic horizon is above the gypsic horizon
because of differences in the solubility of gypsum and calcium
carbonate. These soils are known to occur in New Mexico.
Most Calcigypsids are used for grazing.
Definition
Calcigypsids are the Gypsids that:
1. Have both a gypsic and calcic horizon that have their
upper boundary within 100 cm of the soil surface;
2. Do not have an argillic, natric, petrogypsic, or petrocalcic
horizon that has an upper boundary within 100 cm of the soil
surface.
Key to Subgroups
GDDA. Calcigypsids that have a lithic contact within 50 cm
of the soil surface.
Lithic Calcigypsids
GDDB. Other Calcigypsids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that contain 20 percent or more (by
volume) durinodes, nodules, or concretions.
Petronodic Calcigypsids
GDDC. Other Calcigypsids that have both:
1. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Calcigypsids
GDDD. Other Calcigypsids that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Calcigypsids
GDDE. Other Calcigypsids that have a moisture control
section that is dry in all parts for less than three-fourths of the
time (cumulative) when the soil temperature at a depth of 50
cm is 5 o
C or higher and have a soil moisture regime that
borders on xeric.
Xeric Calcigypsids
GDDF. Other Calcigypsids that have a moisture control
section that is dry in all parts for less than three-fourths of the
time (cumulative) when the soil temperature at a depth of 50
cm is 5 o
C or higher and have a soil moisture regime that
borders on ustic.
Ustic Calcigypsids
GDDG. Other Calcigypsids.
Typic Calcigypsids
382 Soil Taxonomy
Definition of Typic Calcigypsids
Typic Calcigypsids are the Calcigypsids that:
1. Have a moisture control section that is dry in all parts for
three-fourths or more of the time (cumulative) when the soil
temperature at a depth of 50 cm is 5 o
C or higher;
2. Do not have a lithic contact within 100 cm of the soil
surface;
3. Do not have one or more horizons, within 100 cm of the
soil surface and with a combined thickness of more than 15
cm, that contain 20 percent or more (by volume) durinodes,
nodules, or concretions;
4. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Description of Subgroups
Typic Calcigypsids.—These are the Calcigypsids that do
not have a lithic contact within 50 cm of the soil surface; a
significant amount of volcanic glass, cinders, pumice,
pumicelike fragments, durinodes, nodules, or concretions; or a
soil moisture regime that borders on ustic or xeric. These soils
are known to occur in Arizona, Texas, and New Mexico.
Lithic Calcigypsids.—These are the Calcigypsids that have
a lithic contact within 50 cm of the soil surface. These soils
occur in New Mexico and Arizona.
Petronodic Calcigypsids.—These are the Calcigypsids that
have a significant amount of durinodes, concretions, or
nodules. These soils do not have a lithic contact within 50 cm
of the soil surface. They occur in Arizona.
Ustic Calcigypsids.—These are the Calcigypsids that have
a soil moisture regime that borders on ustic. These soils do not
have a lithic contact within 50 cm of the soil surface or a
significant amount of volcanic glass, cinders, pumice,
pumicelike fragments, durinodes, nodules, or concretions.
These soils are known to occur in New Mexico and Texas.
Vitrandic Calcigypsids.—These are the Calcigypsids that
have a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments but do not have a soil moisture regime
that borders on xeric. These soils do not have a lithic contact
within 50 cm of the soil surface or a significant amount of
durinodes, concretions, or nodules.
Vitrixerandic Calcigypsids.—These are the Calcigypsids
that have a significant amount of volcanic glass, cinders,
pumice, or pumicelike fragments and have a soil moisture regime
that borders on xeric. These soils do not have a lithic contact
within 50 cm of the soil surface or a significant amount of
durinodes, concretions, or nodules.
Xeric Calcigypsids.—These are the Calcigypsids that have a
soil moisture regime that borders on xeric. These soils do not
have a lithic contact within 50 cm of the soil surface or a
significant amount of volcanic glass, cinders, pumice,
pumicelike fragments, durinodes, nodules, or concretions.
These soils are known to occur in Utah.
Haplogypsids
Haplogypsids are the Gypsids that have no petrogypsic,
natric, argillic, or calcic horizon that has an upper boundary
within 100 cm of the soil surface. Some Haplogypsids have a
cambic horizon overlying the gypsic horizon. These soils are
commonly very pale in color. They are not extensive in the
United States. The largest concentrations in the United States
are in New Mexico and Texas. The soils are more common in
other parts of the world.
Definition
Haplogypsids are the Gypsids that:
1. Do not have a petrogypsic or calcic horizon that has an
upper boundary within 100 cm of the soil surface;
2. Do not have an argillic or natric horizon that has an upper
boundary within 100 cm of the soil surface.
Key to Subgroups
GDEA. Haplogypsids that have a lithic contact within 50 cm
of the soil surface.
Lithic Haplogypsids
GDEB. Other Haplogypsids that have a gypsic horizon that
has its upper boundary within 18 cm of the soil surface.
Leptic Haplogypsids
GDEC. Other Haplogypsids that have, in a horizon at least
25 cm thick within 100 cm of the mineral soil surface, an
exchangeable sodium percentage of 15 or more (or an SAR of
13 or more) during at least 1 month in normal years.
Sodic Haplogypsids
GDED. Other Haplogypsids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that contain 20 percent or more
(by volume) durinodes, nodules, or concretions.
Petronodic Haplogypsids
GDEE. Other Haplogypsids that have both:
1. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
Aridisols 383
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Haplogypsids
GDEF. Other Haplogypsids that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Haplogypsids
GDEG. Other Haplogypsids that have a moisture control
section that is dry in all parts for less than three-fourths of the
time (cumulative) when the soil temperature at a depth of 50
cm is 5 o
C or higher and have a soil moisture regime that
borders on xeric.
Xeric Haplogypsids
GDEH. Other Haplogypsids that have a moisture control
section that is dry in all parts for less than three-fourths of the
time (cumulative) when the soil temperature at a depth of 50
cm is 5 o
C or higher and have a soil moisture regime that
borders on ustic.
Ustic Haplogypsids
GDEI. Other Haplogypsids.
Typic Haplogypsids
Definition of Typic Haplogypsids
Typic Haplogypsids are the Haplogypsids that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have a gypsic horizon that has its upper boundary
within 18 cm of the soil surface;
3. Do not have, in one or more horizons within 100 cm of the
soil surface, an exchangeable sodium percentage of 15 or more
(or an SAR of 13 or more) for 1 month or more in normal
years;
4. Have a moisture control section that is dry in all parts for
three-fourths of the time (cumulative) when the soil
temperature at a depth of 50 cm is 5 o
C or higher;
5. Do not have one or more horizons, within 100 cm of the
soil surface and with a combined thickness of more than 15
cm, that contain 20 percent or more (by volume) durinodes,
nodules, or concretions;
6. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Description of Subgroups
Typic Haplogypsids.—These are the Haplogypsids that do
not have a lithic contact within 50 cm of the soil surface; a
gypsic horizon within 18 cm of the soil surface; a significant
amount of sodium, durinodes, concretions, nodules, volcanic
glass, cinders, pumice, or pumicelike fragments; or a soil
moisture regime that borders on xeric or ustic. These soils
occur in California, New Mexico, Arizona, Texas, and Nevada.
Leptic Haplogypsids.— These are the Haplogypsids that
have a gypsic horizon with its upper boundary within 18 cm of
the soil surface. These soils do not have a lithic contact within
50 cm of the soil surface. They occur in Nevada, Arizona, and
New Mexico.
Lithic Haplogypsids.—These are the Haplogypsids that
have a lithic contact within 50 cm of the soil surface. These
soils can have characteristics that are common in the other
subgroups.
Petronodic Haplogypsids.—These are the Haplogypsids
that have a significant amount of durinodes, concretions, or
nodules. These soils do not have a lithic contact within 50 cm
of the soil surface, a gypsic horizon with its upper boundary
within 18 cm of the soil surface, or a significant amount of
sodium.
Sodic Haplogypsids.—These are the Haplogypsids that
have, in a horizon at least 25 cm thick within 100 cm of the
soil surface, an exchangeable sodium percentage of 15 or more.
These soils do not have a lithic contact within 50 cm of the soil
surface or a gypsic horizon that has its upper boundary within
18 cm of the soil surface.
384 Soil Taxonomy
Ustic Haplogypsids.—These are the Haplogypsids that
have a soil moisture regime that borders on ustic. These soils
do not have a lithic contact within 50 cm of the soil surface; a
gypsic horizon within 18 cm of the soil surface; or a significant
amount of sodium, durinodes, concretions, nodules, volcanic
glass, cinders, pumice, or pumicelike fragments. Ustic
Haplogypsids occur in Utah, Arizona, Colorado, New Mexico,
and Wyoming.
Vitrandic Haplogypsids.—These are the Haplogypsids that
have a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments but do not have a soil moisture regime
that borders on xeric. These soils do not have a lithic contact
within 50 cm of the soil surface; a gypsic horizon within 18 cm
of the soil surface; or a significant amount of sodium,
durinodes, concretions, or nodules.
Vitrixerandic Haplogypsids.—These are the Haplogypsids
that have a significant amount of volcanic glass, cinders,
pumice, or pumicelike fragments and have a soil moisture
regime that borders on xeric. These soils do not have a lithic
contact within 50 cm of the soil surface; a gypsic horizon
within 18 cm of the soil surface; or a significant amount of
sodium, durinodes, concretions, or nodules.
Xeric Haplogypsids.—These are the Haplogypsids that have
a soil moisture regime that borders on xeric. These soils do not
have a lithic contact within 50 cm of the soil surface; a gypsic
horizon within 18 cm of the soil surface; or a significant amount
of sodium, durinodes, concretions, nodules, volcanic glass,
cinders, pumice, or pumicelike fragments. Xeric Haplogypsids
occur in Utah and California.
Natrigypsids
Natrigypsids are the Gypsids that have a natric horizon and
have no petrogypsic or petrocalcic horizon within 100 cm of
the soil surface. The gypsic horizon is commonly below the
natric horizon. These soils formed in parent materials high in
content of gypsum and sodium, such as sedimentary materials
that were deposited in a marine environment. The soils are rare
but are known to occur in the Four Corners area of the western
part of the United States (northwestern New Mexico,
northeastern Arizona, southeastern Utah, and southwestern
Colorado). The soils are used primarily for grazing.
Definition
Natrigypsids are the Gypsids that:
1. Have a natric horizon that has its upper boundary within
100 cm of the soil surface;
2. Do not have a petrogypsic or petrocalcic horizon with an
upper boundary within 100 cm of the soil surface.
KeytoSubgroups
GDBA. Natrigypsids that have a lithic contact within 50 cm of
the soil surface.
Lithic Natrigypsids
GDBB. Other Natrigypsids that have:
1. Cracks within 125 cm of the soil surface that are 5
mm or more wide through a thickness of 30 cm or more
for some time in normal years, and slickensides or wedgeshaped
aggregates in a layer 15 cm or more thick that
has its upper boundary within 125 cm of the soil surface;
or
2. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic, lithic,
or paralithic contact, whichever is shallower.
Vertic Natrigypsids
GDBC. Other Natrigypsids that have one or more horizons,
within 100 cm of the soil surface and with a combined
thickness of 15 cm or more, that contain 20 percent or more
(by volume) durinodes, nodules, or concretions.
Petronodic Natrigypsids
GDBD. Other Natrigypsids that have both:
1. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Natrigypsids
GDBE. Other Natrigypsids that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
Aridisols 385
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Natrigypsids
GDBF. Other Natrigypsids that have a moisture control
section that is dry in all parts for less than three-fourths of the
time (cumulative) when the soil temperature at a depth of 50
cm is 5 o
C or higher and have a soil moisture regime that
borders on xeric.
Xeric Natrigypsids
GDBG. Other Natrigypsids that have a moisture control
section that is dry in all parts for less than three-fourths of the
time (cumulative) when the soil temperature at a depth of 50
cm is 5 o
C or higher and have a soil moisture regime that
borders on ustic.
Ustic Natrigypsids
GDBH. Other Natrigypsids.
Typic Natrigypsids
Definition of Typic Natrigypsids
Typic Natrigypsids are the Natrigypsids that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Have either:
a. No cracks within 125 cm of the soil surface that are 5
mm or more wide through a thickness of 30 cm or more for
some time in normal years, and no slickensides or wedgeshaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the soil surface; or
b. A linear extensibility of less than 6.0 cm between the
soil surface and either a depth of 100 cm or a densic, lithic,
or paralithic contact, whichever is shallower;
3. Have a moisture control section that is dry in all parts for
three-fourths or more of the time (cumulative) when the soil
temperature at a depth of 50 cm is 5 o
C or higher;
4. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more;
5. Do not have one or more horizons, within 100 cm of the soil
surface and with a combined thickness of more than 15 cm, that
contain 20 percent or more (by volume) durinodes, nodules, or
concretions.
Description of Subgroups
Typic Natrigypsids.—The Typic subgroup of Natrigypsids is
defined in terms of characteristics that are not evident. These
soils do not have a lithic contact within 50 cm of the soil
surface; a high shrink-swell potential; a soil moisture regime
that borders on xeric or ustic; or a significant amount of
durinodes, nodules, concretions, volcanic glass, cinders,
pumice, or pumicelike fragments.
Lithic Natrigypsids.—These are the Natrigypsids that have
a lithic contact within 50 cm of the soil surface. These soils can
have the characteristics defined for the other subgroups. The
presence of a lithic contact is considered important to
interpretations and keys first.
Petronodic Natrigypsids.—These are the Natrigypsids that
have a significant amount of durinodes, nodules, or
concretions. These soils do not have a lithic contact within 50
cm of the soil surface or a high shrink-swell potential.
Ustic Natrigypsids.—These are the Natrigypsids that have
a soil moisture regime that borders on ustic. These soils do not
have a lithic contact within 50 cm of the soil surface; a high
shrink-swell potential; or a significant amount of durinodes,
concretions, nodules, volcanic glass, cinders, pumice, or
pumicelike fragments.
Vertic Natrigypsids.—These are the Natrigypsids that have
a high shrink-swell potential. These soils do not have a lithic
contact within 50 cm of the soil surface.
Vitrandic Natrigypsids.—These are the Natrigypsids that
have a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments but do not have a soil moisture regime
that borders on xeric. These soils also do not have a lithic
contact within 50 cm of the soil surface; a high shrink-swell
potential; or a significant amount of durinodes, nodules, and
concretions.
Vitrixerandic Natrigypsids.—These are the Natrigypsids
that have a significant amount of volcanic glass, cinders,
pumice, or pumicelike fragments and have a soil moisture
regime that borders on xeric. These soils do not have a lithic
contact within 50 cm of the soil surface; a high shrink-swell
potential; or a significant amount of durinodes, nodules, and
concretions.
Xeric Natrigypsids.—These are the Natrigypsids that have
a soil moisture regime that borders on xeric. These soils do not
have a lithic contact within 50 cm of the soil surface; a high
shrink-swell potential; or a significant amount of durinodes,
concretions, nodules, volcanic glass, cinders, pumice, or
pumicelike fragments.
386 Soil Taxonomy
Petrogypsids
Petrogypsids are the Gypsids that have a petrogypsic or
petrocalcic horizon that has its upper boundary within 100 cm
of the soil surface. These soils occur in very arid areas of the
world where the parent material is high in content of gypsum.
When the petrogypsic horizon is close to the surface, crusting
forms pseudohexagonal patterns on the soil surface.
Petrogypsids occupy old surfaces. In Syria and Iraq, they are on
the highest terraces along the Tigris and Euphrates Rivers.
These soils are not extensive in the United States but are
extensive in other countries.
Definition
Petrogypsids are the Gypsids that have a petrogypsic or
petrocalcic horizon that has its upper boundary within 100 cm
of the soil surface.
Key to Subgroups
GDAA. Petrogypsids that have a petrocalcic horizon that has
its upper boundary within 100 cm of the soil surface.
Petrocalcic Petrogypsids
GDAB. Other Petrogypsids that have a calcic horizon
overlying the petrogypsic horizon.
Calcic Petrogypsids
GDAC. Other Petrogypsids that have both:
1. A moisture control section that is dry in all parts for
less than three-fourths of the time (cumulative) when the
soil temperature is 5 o
C or higher at a depth of 50 cm and a
soil moisture regime that borders on xeric; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the soil surface, one or
both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent
or more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrixerandic Petrogypsids
GDAD. Other Petrogypsids that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Vitrandic Petrogypsids
GDAE. Other Petrogypsids that have a moisture control
section that is dry in all parts for less than three-fourths of the
time (cumulative) when the soil temperature at a depth of 50
cm is 5 o
C or higher and have a soil moisture regime that
borders on xeric.
Xeric Petrogypsids
GDAF. Other Petrogypsids that have a moisture control
section that is dry in all parts for less than three-fourths of the
time (cumulative) when the soil temperature at a depth of 50
cm is 5 o
C or higher and have a soil moisture regime that
borders on ustic.
Ustic Petrogypsids
GDAG. Other Petrogypsids.
Typic Petrogypsids
Definition of Typic Petrogypsids
Typic Petrogypsids are the Petrogypsids that:
1. Do not have a petrocalcic horizon within 100 cm of the
soil surface;
2. Do not have a calcic horizon overlying the petrogypsic
horizon;
3. Have a moisture control section that is dry in all parts for
three-fourths or more of the time (cumulative) when the soil
temperature at a depth of 50 cm is 5 o
C or higher;
4. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is 30 or more.
Description of Subgroups
Typic Petrogypsids.—These are the Petrogypsids that have
a petrogypsic horizon. These soils do not have a calcic or
petrocalcic horizon above the petrogypsic horizon or a
significant amount of volcanic glass, cinders, pumice, or
Aridisols 387
pumicelike fragments. The moisture regime does not border on
ustic or xeric.
Calcic Petrogypsids.—These are the Petrogypsids that have
a calcic horizon above the petrogypsic horizon. These soils do
not have a petrocalcic horizon.
Petrocalcic Petrogypsids.—These are the Petrogypsids that
have a petrocalcic horizon. These soils are known to occur in
Nevada.
Ustic Petrogypsids.—These are the Petrogypsids that
have a petrogypsic horizon and have a soil moisture regime
that borders on ustic. These soils do not have a calcic or
petrocalcic horizon above the petrogypsic horizon or a
significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments.
Vitrandic Petrogypsids.—These are the Petrogypsids that
have a significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments but do not have a soil moisture regime
that borders on xeric. These soils do not have a calcic horizon
overlying the petrogypsic horizon and do not have a petrocalcic
horizon.
Vitrixerandic Petrogypsids.—These are the Petrogypsids
that have a significant amount of volcanic glass, cinders,
pumice, or pumicelike fragments and have a soil moisture
regime that borders on xeric. These soils do not have a calcic
horizon overlying the petrogypsic horizon and do not have a
petrocalcic horizon.
Xeric Petrogypsids.—These are the Petrogypsids that have
a petrogypsic horizon and have a soil moisture regime that
borders on xeric. These soils do not have a calcic horizon
above the petrogypsic horizon; a petrocalcic horizon; or a
significant amount of volcanic glass, cinders, pumice, or
pumicelike fragments.
Salids
Salids are most common in depressions (playas) in the
deserts or in closed basins in the wetter areas bordering the
deserts. In North Africa and in the Near East, such depressions
are referred to as Sebkhas or Chotts, depending on the presence
or absence of surface water for prolonged periods.
Under the arid environment and hot temperatures,
accumulation of salts commonly occurs when there is a supply
of salts and a net upward movement of water in the soils. In
some areas a salic horizon has formed in salty parent materials
without the presence of ground water. The most common form
of salt is sodium chloride (halite), but sulfates (thenardite,
mirabilite, and hexahydrite) and other salts may also occur.
The concept of Salids is one of accumulation of an excessive
amount of salts that are more soluble than gypsum. This is
implicit in the definition, which requires a minimum absolute
EC of 30 dS/m in 1:1 extract (about 2 percent salt) and a
product of EC and thickness of at least 900.
As a rule, Salids are unsuitable for agricultural use, unless
the salts are leached out. Leaching the salts is an expensive
undertaking, particularly if there is no natural outlet for the
drainage water.
Two great groups are recognized—Aquisalids, which are
saturated with water for 1 month or more during the year, and
Haplosalids, which are drier.
Definition
Salids are the Aridisols that have:
1. A salic horizon that has its upper boundary within 100 cm of
the soil surface;
2. A soil temperature regime warmer than cryic.
Key to Great Groups
GBA. Salids that are saturated with water in one or more layers
within 100 cm of the mineral soil surface for 1 month or more in
normal years.
Aquisalids, p. 387
GBB. Other Salids.
Haplosalids, p. 388
Aquisalids
These are the salty soils in wet areas in the deserts where
capillary rise and evaporation of water concentrate the salts
near the surface. Some of these soils have redoximorphic
depletions and concentrations. In other soils redoximorphic
features may not be evident because of a high pH and the
associated low redox potential, which inhibit iron and
manganese reduction. These soils occur dominantly in
depressional areas where ground water saturates the soils at
least part of the year. The vegetation on these soils generally is
sparse, consisting of salt-tolerant shrubs, grasses, and forbs.
Although these soils may hold water at a tension less than
1500 kPa, the dissolved salt content makes the soils
physiologically dry.
Definition
Aquisalids are the Salids that are saturated with water in
one or more layers within 100 cm of the mineral soil surface
for 1 month or more in normal years.
Key to Subgroups
GBAA. Aquisalids that have a gypsic or petrogypsic horizon
that has its upper boundary within 100 cm of the soil surface.
Gypsic Aquisalids
GBAB. Other Aquisalids that have a calcic or petrocalcic
388
horizon that has an upper boundary within 100 cm of the soil
surface.
Calcic Aquisalids
GBAC. Other Aquisalids.
Typic Aquisalids
Definition of Typic Aquisalids
Typic Aquisalids are the Aquisalids that do not have a calcic,
gypsic, petrocalcic, or petrogypsic horizon that has its upper
boundary within 100 cm of the soil surface.
Description of Subgroups
Typic Aquisalids.—These are the Aquisalids that do not
have a calcic, petrocalcic, gypsic, or petrogypsic horizon.
These soils occur in most States in the West.
Calcic Aquisalids.—These are the Aquisalids that have a
calcic or petrocalcic horizon within 100 cm of the soil surface.
These soils do not have a gypsic or petrogypsic horizon with an
upper boundary within 100 cm of the soil surface. They occur
in Nevada and Texas.
Gypsic Aquisalids.—These are the Aquisalids that have a
gypsic or petrogypsic horizon with an upper boundary within
100 cm of the soil surface. These soils occur in Texas and
Colorado.
Haplosalids
These are the Salids that have a high concentration of salts
but do not have the saturation that is associated with the
Aquisalids. Haplosalids may be saturated for shorter periods
than Aquisalids or may have had a water table associated with
a past climate. In the Four Corners area of the United States,
salic horizons have formed without the influence of a water
table in saline parent materials.
Definition
Haplosalids are the Salids that are not saturated with water
in one or more layers within 100 cm of the mineral soil surface
for 1 month or more in normal years.
Key to Subgroups
GBBA. Haplosalids that have a duripan that has its upper
boundary within 100 cm of the soil surface.
Duric Haplosalids
GBBB. Other Haplosalids that have a petrogypsic
horizon that has its upper boundary within 100 cm of
the soil surface.
Petrogypsic Haplosalids
GBBC. Other Haplosalids that have a gypsic horizon that has
its upper boundary within 100 cm of the soil surface.
Gypsic Haplosalids
GBBD. Other Haplosalids that have a calcic horizon that has
its upper boundary within 100 cm of the soil surface.
Calcic Haplosalids
GBBE. Other Haplosalids.
Typic Haplosalids
Definition of Typic Haplosalids
Typic Haplosalids are the Haplosalids that do not have a
calcic, gypsic, or petrogypsic horizon or a duripan that has an
upper boundary within 100 cm of the soil surface.
Description of Subgroups
Typic Haplosalids.—These are the Haplosalids that do not
have a calcic, gypsic, or petrogypsic horizon or a duripan with
an upper boundary within 100 cm of the soil surface. Before
1994, these soils were identified as Torriorthents if a salic
horizon was the only diagnostic horizon. These soils occur in
California.
Calcic Haplosalids.—These are the Haplosalids that have a
calcic horizon that has its upper boundary within 100 cm of the
soil surface. These soils do not have a gypsic or petrogypsic
horizon or a duripan with an upper boundary within 100 cm of
the soil surface. They occur in Arizona.
Duric Haplosalids.—These are the Haplosalids that have a
duripan with its upper boundary within 100 cm of the soil
surface.
Gypsic Haplosalids.—These are the Haplosalids that have
a gypsic horizon with its upper boundary within 100 cm of the
soil surface. These soils do not have a duripan. They occur in
California.
Petrogypsic Haplosalids.—These are the Haplosalids
that have a petrogypsic horizon that has its upper boundary
within 100 cm of the soil surface. These soils do not have a
duripan.
389
The central concept of Entisols is that of soils that have
little or no evidence of the development of pedogenic
horizons. Most Entisols have no diagnostic horizons other than
an ochric epipedon. Very few have an anthropic epipedon. A
few that have a sandy or sandy-skeletal particle-size class have
a horizon that would be a cambic horizon were it not for the
particle-size class exclusion. Very few Entisols have an albic
horizon. In coastal marshes some Entisols that have sulfidic
materials within 50 cm of the mineral soil surface have a histic
epipedon.
On many landscapes the soil material is not in place long
enough for pedogenic processes to form distinctive horizons.
Some of these soils are on steep, actively eroding slopes, and
others are on flood plains or glacial outwash plains that receive
new deposits of alluvium at frequent intervals. Some Entisols
are old enough to have formed diagnostic horizons, but they
consist mostly of quartz or other minerals that are resistant to
the weathering needed to form diagnostic horizons. Buried
diagnostic horizons are permitted in Entisols if they meet the
requirements for buried soil defined in chapter 1.
Entisols may have any mineral parent material, vegetation,
age, or moisture regime and any temperature regime, but they
do not have permafrost. The only features common to all soils
of the order are the virtual absence of diagnostic horizons and
the mineral nature of the soils.
Definition of Entisols and Limits Between
Entisols and Soils of Other Orders
Entisols are mineral soils that:
1. Do not have an Ap horizon containing 85 percent or more
spodic materials;
2. Do not have a fragipan or an argillic, kandic, natric, oxic,
or spodic horizon;
3. Do not have andic soil properties in 60 percent or more of
the thickness, whether buried or not, between either the
mineral soil surface or the top of an organic layer with andic
soil properties, whichever is shallower, and either a depth of 60
cm from the shallower of the above or a densic, lithic, or
paralithic contact if shallower than 60 cm;
4. Do not have permafrost within 100 cm of the soil surface
or both gelic materials within 100 cm of the soil surface and
permafrost within 200 cm of the soil surface;
5. Do not have all of the following:
a. A layer 25 cm or more thick, with an upper boundary
within 100 cm of the mineral soil surface, that has either
slickensides close enough to intersect or wedge-shaped
aggregates that have their long axes tilted 10 to 60 degrees
from the horizontal; and
b. A weighted average of 30 percent or more clay in the
fine-earth fraction either between the mineral soil surface
and a depth of 18 cm or in an Ap horizon, whichever is
thicker, and 30 percent or more clay in the fine-earth
fraction of all horizons between a depth of 18 cm and either
a depth of 50 cm or a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon if shallower; and
c. Cracks that open and close periodically;
6. Do not have both a salic horizon and an aridic moisture
regime;
7. Do not have all of the following:
a. A salic horizon; and
b. A moisture control section that is dry at some time in
normal years; and
c. Saturation with water in one or more layers within
100 cm of the soil surface for 1 month or more in normal
years;
8. Do not have both a mollic epipedon and a base saturation
(by NH4
OAc) of 50 percent or more in all horizons either
between the mineral soil surface and a depth of 180 cm or
between the mineral soil surface and a densic, lithic, or
paralithic contact, whichever is shallower;
9. Do not have a cambic horizon with its upper boundary
within 100 cm of the mineral soil surface or its lower boundary
at a depth of 25 cm or more below the mineral soil surface;
10. Do not have both a cambic horizon and a cryic
temperature regime;
11. Do not have a duripan or a calcic, petrocalcic, gypsic,
petrogypsic, or placic horizon unless its upper boundary is
more than 100 cm below the mineral soil surface;
CHAPTER 12
Entisols
390 Soil Taxonomy
12. Do not have a sulfuric horizon unless its upper boundary
is more than 150 cm below the mineral soil surface; and
13. Unless the soil has either sulfidic materials within 50 cm
of the mineral soil surface or has, in one or more horizons at a
depth between 20 and 50 cm below the mineral soil surface,
both an n value of more than 0.7 and 8 percent or more clay in
the fine-earth fraction, do not have:
a. In 50 percent or more of the layers between the mineral
soil surface and a depth of 50 cm, an exchangeable sodium
percentage of 15 or more (or a sodium adsorption ratio of 13
or more), which decreases with increasing depth below 50
cm, and also ground water within 100 cm of the mineral
soil surface at some time during the year when the soil is
not frozen in any part; or
b. A histic, mollic, plaggen, or umbric epipedon.
Limits Between Entisols and Soils of Other Orders
The definition of Entisols must provide criteria that separate
Entisols from all other orders. These criteria define the limits
of Entisols in relation to all other known kinds of soil.
1. Unlike Alfisols, Entisols must not have an argillic, natric,
or kandic horizon.
2. Unlike Andisols, Entisols must not have andic soil
properties in 60 percent or more of the thickness, whether
buried or not, between either the mineral soil surface or the top
of an organic layer with andic soil properties, whichever is
shallower, and either a depth of 60 cm from the shallower of
the above or a densic, lithic, or paralithic contact if shallower
than 60 cm.
3. Unlike Aridisols, Entisols must not have:
a. All of the following:
(1) A salic horizon; and
(2) A moisture control section that is dry at some time
in normal years; and
(3) Saturation with water in one or more layers within
100 cm of the soil surface for 1 month or more in normal
years; or
b. Both an anthropic or ochric epipedon and an aridic
moisture regime; and
(1) An argillic or natric horizon; or
(2) A cambic horizon with its lower boundary below 25
cm or its upper boundary within 100 cm of the soil
surface; or
(3) A calcic, petrocalcic, gypsic, petrogypsic, or salic
horizon or a duripan with its upper boundary within 100
cm of the soil surface.
4. Unlike Gelisols, Entisols do not have permafrost within
100 cm of the soil surface, nor do they have both gelic
materials within 100 cm of the soil surface and permafrost
within 200 cm of the soil surface.
5. Unlike Inceptisols, Entisols:
a. Must not have any of the following:
(1) A cambic horizon with its upper boundary within
100 cm of the mineral soil surface or its lower boundary
at a depth of 25 cm or more below the mineral soil
surface;
(2) A duripan or a calcic, petrocalcic, gypsic,
petrogypsic, or placic horizon unless its upper boundary
is more than 100 cm below the mineral soil surface;
(3) A fragipan or an oxic or spodic horizon;
(4) A sulfuric horizon unless its upper boundary is
more than 150 cm below the mineral soil surface;
(5) Both a cambic horizon and a cryic temperature
regime; and
b. Have either sulfidic materials within 50 cm of the
mineral soil surface or have, in one or more horizons at a
depth between 20 and 50 cm below the mineral soil surface,
both an n value of more than 0.7 and 8 percent or more clay
in the fine-earth fraction, if they have:
(1) In 50 percent or more of the layers between the
mineral soil surface and a depth of 50 cm, an
exchangeable sodium percentage of 15 or more (or a
sodium adsorption ratio of 13 or more), which decreases
with increasing depth below 50 cm, and also ground
water within 100 cm of the mineral soil surface at some
time during the year when the soil is not frozen in any
part; or
(2) A histic, mollic, plaggen, or umbric epipedon.
6. Unlike Histosols, Entisols must meet the definition of
mineral soils.
7. Unlike Mollisols, Entisols must not have a mollic
epipedon unless they also either have sulfidic materials within
50 cm of the mineral soil surface or have, in one or more
horizons at a depth between 20 and 50 cm below the mineral
soil surface, both an n value of more than 0.7 and 8 percent or
more clay in the fine-earth fraction.
8. Unlike Oxisols, Entisols must not have an oxic or kandic
horizon.
9. Unlike Spodosols, Entisols must not have a spodic horizon
or an Ap horizon consisting of 85 percent or more spodic
materials.
10. Unlike Ultisols, Entisols must not have an argillic or
kandic horizon.
Entisols 391
11. Unlike Vertisols, Entisols must not have all of the
following:
a. A layer 25 cm or more thick, with an upper boundary
within 100 cm of the mineral soil surface, that has either
slickensides close enough to intersect or wedge-shaped
aggregates that have their long axes tilted 10 to 60 degrees
from the horizontal; and
b. A weighted average of 30 percent or more clay in the
fine-earth fraction either between the mineral soil surface
and a depth of 18 cm or in an Ap horizon, whichever is
thicker, and 30 percent or more clay in all horizons between
a depth of 18 cm and either a depth of 50 cm or a densic,
lithic, or paralithic contact, a duripan, or a petrocalcic
horizon if shallower; and
c. Cracks that open and close periodically.
Representative Pedon and Data
Following is a description of a representative Entisol. Data
for the pedon identified in this description are given in the
table “Characterization Data for an Entisol.”
Classification: Mixed, mesic Typic Ustipsamment
Site identification number: 87P0168
Location: Blaine County, Nebraska; 520 m north and 90 m
west of the southeast corner of sec. 9, T. 22 N., R. 22 E.
Landscape: Sandhills
Landform: Dune
Slope: 19 percent, north facing
Elevation: 778 m above m.s.l.
Soil moisture regime: Ustic
Soil temperature regime: Mesic
Permeability class: Rapid
Drainage class: Excessively drained
Depth to water table: More than 150 cm
Land use: Rangeland (grazed)
Hazard of erosion or deposition: Slight
Parent material: Sandy eolian material
Described by: Shurtliff
In the following pedon description, colors are for dry soil
unless otherwise indicated.
A—0 to 13 cm; grayish brown (10YR 5/2) fine sand, very dark
grayish brown (10YR 3/2) moist; weak fine granular
structure; soft, very friable; many fine and medium roots;
slightly acid (pH 6.3); clear smooth boundary.
AC—13 to 28 cm; light brownish gray (10YR 6/2) fine sand,
dark grayish brown (10YR 4/2) moist; single grain; loose;
common fine and medium roots; neutral (pH 7.0); clear
smooth boundary.
C1—28 to 64 cm; pale brown (10YR 6/3) fine sand, brown
(10YR 5/3) moist; single grain; loose; few or common fine
roots; neutral (pH 7.0); clear smooth boundary.
C2—64 to 152 cm; very pale brown (10YR 7/3) fine sand, pale
brown (10YR 6/3) moist; single grain; loose; few fine
roots; neutral (pH 7.0).
Key to Suborders
LA. Entisols that have one or more of the following:
1. Aquic conditions and sulfidic materials within 50 cm of
the mineral soil surface; or
2. Permanent saturation with water and a reduced
matrix in all horizons below 25 cm from the mineral soil
surface; or
3. In a layer above a densic, lithic, or paralithic contact or
in a layer at a depth between 40 and 50 cm below the
mineral soil surface, whichever is shallower, aquic
conditions for some time in normal years (or artificial
drainage) and one or more of the following:
a. A texture finer than loamy fine sand and, in 50
percent or more of the matrix, one or more of the
following:
(1) Chroma of 0; or
(2) Chroma of 1 or less and a color value, moist,
of 4 or more; or
(3) Chroma of 2 or less and redox concentrations;
or
b. A texture of loamy fine sand or coarser and, in 50
percent or more of the matrix, one or more of the
following:
(1) Chroma of 0; or
(2) Hue of 10YR or redder, a color value, moist, of 4
or more, and chroma of 1; or
(3) Hue of 10YR or redder, chroma of 2 or less, and
redox concentrations; or
(4) Hue of 2.5Y or yellower, chroma of 3 or less, and
distinct or prominent redox concentrations; or
(5) Hue of 2.5Y or yellower and chroma of 1; or
(6) Hue of 5GY, 5G, 5BG, or 5B; or
(7) Any color if it results from uncoated sand grains;
or
c. Enough active ferrous iron to give a positive reaction
to alpha,alpha-dipyridyl at a time when the soil is not
being irrigated.
Aquents, p. 393
LB. Other Entisols that have, in one or more layers at a depth
between 25 and 100 cm below the mineral soil surface, 3
392 Soil Taxonomy
Characterization Data for an Entisol
SITE IDENTIFICATION NO.: 87P0168
CLASSIFICATION: MIXED, MESIC TYPIC USTIPSAMMENT
GENERAL METHODS: 1B1A, 2A1, 2B
-1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-
-----------------------------------------------------------------------------------------------------------------------------------
(- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)
CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT
SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF
NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE
<- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL
87P 904 0- 13 A 3.5 3.2 93.3 0.7 2.5 19.9 66.0 7.1 0.3 -- -- -- -- 73 --
87P 905 13- 28 AC 2.8 2.1 95.1 0.5 1.6 18.8 67.6 8.5 0.2 -- -- -- -- 76 --
87P 906 28- 64 C1 2.5 1.2 96.3 0.2 1.0 16.4 72.4 7.3 0.2 -- -- -- -- 80 --
87P 907 64-152 C2 2.5 1.0 96.5 -- 1.0 13.0 73.0 10.2 0.3 -- -- -- -- 83 --
-----------------------------------------------------------------------------------------------------------------------------------
ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD
C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE
DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL
(cm) 6A1c 6B3a 6S3 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A3a 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1
Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm
0- 13 0.58 0.049 1.20 0.86 3.0
13- 28 0.35 0.033 1.29 0.79 2.2
28- 64 0.09 1.20 0.64 1.6
64-152 0.06 1.00 0.56 1.4
-----------------------------------------------------------------------------------------------------------------------------------
(- NH4OAc EXTRACTABLE BASES -) ACID- EXTR (- - - -CEC - - -) Al -BASE SAT- CO3 AS RES. COND.(- - - -PH - - -)
Ca Mg Na K SUM ITY Al SUM NH4- BASES SAT SUM NH4 CaCO3 ohms mmhos CaCl2 H2O
DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc + Al OAc <2mm /cm /cm .01M
(cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 6G9b 5A3a 5A8b 5A3b 5G1 5C3 5C1 6E1g 8E1 8I 8C1f 8C1f
<- - - - - - - - - - - -meq / 100 g - - - - - - - - - - -> <- - - - -Pct - - - -> 1:2 1:1
0- 13 3.0 0.6 TR 0.3 3.9 1.5 5.4 4.2 72 93 5.2 5.8
13- 28 2.7 0.5 TR 0.2 3.4 0.8 4.2 3.6 81 94 5.4 6.1
28- 64 2.2 0.5 TR 0.1 2.8 0.7 3.5 3.0 80 93 5.6 6.3
64-152 1.8 0.4 TR 0.1 2.3 0.3 2.6 2.5 88 92 5.6 6.4
-----------------------------------------------------------------------------------------------------------------------------------
< - - - - - - - - - - - - - - - - - - - - SAND - SILT MINERALOGY (2.0-0.002mm) - - - - - - - - - - - - - - - - - - - - >
FRAC- < - - - - - X-RAY - - ->< - - - THERMAL - - - ->< - - - - - - - OPTICAL - - - - - - - - >< >INTERSAMPLE
TION < >< - DTA - ->< - TGA - ->TOT RE< - - - - - GRAIN COUNT - - - - - ->< >PRETA<
- - - - 7A2i - - - - >< - 7A3c - >< - 7A4c - >< - - - - - - - - 7B1a - - - - - - - - ->< > TION
NUMBER < - ->< - - - Peak Size - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - - - - - - - ->< - ->
87P 905 FS 66 QZ61 FK20 FP 9 AR 6 CD 5 PRtr
87P 905 FS TMtr FEtr HNtr GStr GNtr
87P 906 FS 76 QZ68 FK12 CD 8 FP 7 AR 5 GStr
87P 906 FS PRtr OPtr HNtr
87P 907 FS 68 QZ63 FK18 FP10 CD 5 AR 4 PRtr
87P 907 FS HNtr GNtr POtr
-----------------------------------------------------------------------------------------------------------------------------------
The chemical data are based on the fraction less than 2 mm in size.
Fraction interpretation: FS, fine sand, 0.1-0.25 mm.
Mineral interpretation: QZ, quartz; FK, potassium feldspar; FP, plagioclase feldspar; AR, weathered aggregate; CD, chalcedony;
PR, pyroxene; TM, tourmaline; FE, iron oxides; HN, hornblende; GS, glass; GN, garnet; OP, opaques; PO, plant opal.
Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.
Entisols 393
2. Permanent saturation with water and a reduced matrix in all
horizons below 25 cm from the mineral soil surface; or
3. In a layer above a densic, lithic, or paralithic contact or in a
layer at a depth between 40 and 50 cm below the mineral soil
surface, whichever is shallower, aquic conditions for some time
in normal years (or artificial drainage) and either:
a. A texture finer than loamy fine sand and, in 50 percent
or more of the matrix, either:
(1) Chroma of 0; or
(2) Chroma of 2 or less if there are redox
concentrations; or
(3) Chroma of 1 or less and a color value, moist, of 4 or
more if there are no redox concentrations; or
b. A texture of loamy fine sand or coarser and, in 50
percent or more of the matrix, either:
(1) Chroma of 0; or
(2) Hue of 10YR or redder, a color value, moist, of 4 or
more, and chroma of 1; or
(3) Hue of 10YR or redder and chroma of 2 or less if
there are redox concentrations; or
(4) Hue of 2.5Y or yellower and chroma of 3 or less if
there are distinct or prominent redox concentrations; or
(5) Hue of 2.5Y or yellower and chroma of 1; or
(6) Hue of 5GY, 5G, 5BG, or 5B; or
(7) Any color if it results from uncoated sand grains; or
c. Enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Key to Great Groups
LAA. Aquents that have sulfidic materials within 50 cm of
the mineral soil surface.
Sulfaquents, p. 403
LAB. Other Aquents that have, in all horizons at a depth
between 20 and 50 cm below the mineral soil surface, both an
n value of more than 0.7 and 8 percent or more clay in the fineearth
fraction.
Hydraquents, p. 400
LAC. Other Aquents that have a cryic soil temperature
regime.
Cryaquents, p. 394
LAD. Other Aquents that have less than 35 percent (by
percent or more (by volume) fragments of diagnostic horizons
that are not arranged in any discernible order.
Arents, p. 403
LC. Other Entisols that have less than 35 percent (by volume)
rock fragments and a texture of loamy fine sand or coarser in all
layers within the particle-size control section.
Psamments, p. 432
LD. Other Entisols that do not have a densic, lithic, or
paralithic contact within 25 cm of the mineral soil surface and
have:
1. A slope of less than 25 percent; and
2. Either 0.2 percent or more organic carbon of Holocene
age at a depth of 125 cm below the mineral soil surface or
an irregular decrease in content of organic carbon from a
depth of 25 cm to a depth of 125 cm or to a densic, lithic, or
paralithic contact if shallower; and
3. A soil temperature regime:
a. That is warmer than cryic; or
b. That is cryic and the soil has:
(1) No gelic material; and
(2) Either a slope of less than 5 percent or less than
15 percent volcanic glass in the 0.02 to 2.0 mm
fraction in some part of the particle-size control
section.
Fluvents, p. 406
LE. Other Entisols.
Orthents, p. 420
Aquents
These are the wet Entisols. They may be in tidal marshes,
on deltas, on the margins of lakes where the soils are
continuously saturated with water, on flood plains along
streams where the soils are saturated at some time of the year,
or in areas of wet, sandy deposits. Many Aquents have bluish
or grayish colors and redoximorphic features. They may have
any temperature regime. Most of them formed in recent
sediments, and they support vegetation that tolerates
permanent or periodic wetness.
Definition
Aquents are the Entisols that have one or more of the
following:
1. Aquic conditions and sulfidic materials within 50 cm of
the mineral soil surface; or
394 Soil Taxonomy
volume) rock fragments and a texture of loamy fine sand or
coarser in all layers within the particle-size control section.
Psammaquents, p. 401
LAE. Other Aquents that have either 0.2 percent or more
organic carbon of Holocene age at a depth of 125 cm below the
mineral soil surface or an irregular decrease in content of
organic carbon from a depth of 25 cm to a depth of 125 cm or
to a densic, lithic, or paralithic contact if shallower.
Fluvaquents, p. 397
LAF. Other Aquents that have episaturation.
Epiaquents, p. 396
LAG. Other Aquents.
Endoaquents, p. 395
Cryaquents
These are the cold, wet soils in high mountains or of high
latitudes. Cryaquents are on flood plains, in depressional areas,
and in coastal marshes. Many are grayish and stratified. Those
in coastal marshes commonly have greenish to bluish hues.
Because they are both cold and wet, Cryaquents have low
potential for farming. The major areas of these soils in the
United States are in Alaska, where they are in coastal marshes,
on outwash plains, and on flood plains. The soils formed in
recent sediments and are extensive in Alaska south of the
permafrost zone. Most Cryaquents support mixed forest,
shrub, or grassy vegetation. Many are nearly level, and their
parent materials are typically Holocene or late-Pleistocene
sediments.
Definition
Cryaquents are the Aquents that:
1. Have a cryic soil temperature regime;
2. Do not have sulfidic materials within 50 cm of the mineral
soil surface;
3. Do not have, in all horizons at a depth between 20 and
50 cm below the mineral soil surface, both an n value of
more than 0.7 and 8 percent or more clay in the fine-earth
fraction.
Key to Subgroups
LACA. Cryaquents that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or more of the following:
1. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
2. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
3. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Cryaquents
LACB. Other Cryaquents.
Typic Cryaquents
Definition of Typic Cryaquents
Typic Cryaquents are the Cryaquents that do not have,
throughout a cumulative thickness of 18 cm or more and
within a depth of 75 cm, one or more of the following:
1. A bulk density, in the fraction less than 2.0 mm in size, of
1.0 g/cm3
or less, measured at 33 kPa water retention, and
acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
2. Fragments coarser than 2.0 mm constituting more than 35
percent of the whole soil and cinders, pumice, and pumicelike
fragments making up more than 66 percent of these fragments;
or
3. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is equal
to 30 or more.
Description of Subgroups
Typic Cryaquents.—More variability in properties is
permitted in this subgroup than in most Typic subgroups
because the soils are both cold and wet. There are no
restrictions on particle size, organic carbon, and other
properties that are used to distinguish taxa in many places in
this taxonomy. These soils are of moderate extent in the United
States, occurring mostly on wet flood plains in Alaska and in
the high mountains of the Western States. Most of the Typic
Cryaquents are under their native vegetation and have a thin O
horizon.
Aquandic Cryaquents.—These soils have a layer in the
upper 75 cm that is 18 cm or more thick and is rich in
pyroclastics. The clays in this layer normally do not disperse
well and have a high pH-dependent charge. These soils are rare
in the United States and are known to occur only on wet flood
plains in Alaska.
Entisols 395
Endoaquents
Endoaquents are the Aquents that have an isofrigid, frigid, or
warmer temperature regime and endoaquic saturation. The
ground water fluctuates from a level near or above the soil
surface to about 100 cm below the soil surface and is
sometimes below 200 cm.
Many Endoaquents support either a deciduous or coniferous
forest. Some have been cleared and are used as cropland or
pasture. Generally, Endoaquents are nearly level, and their
parent materials are typically late-Pleistocene or Holocene
sediments.
Definition
Endoaquents are the Aquents that:
1. Do not have sulfidic materials within 50 cm of the mineral
soil surface;
2. Do not have a cryic soil temperature regime;
3. Have either an n value of 0.7 or less or less than 8 percent
clay in some or all horizons at a depth between 20 and 50 cm
below the mineral soil surface;
4. In some part of the particle-size control section, have
either:
a. A texture finer than loamy fine sand; or
b. 35 percent or more (by volume) rock fragments;
5. Have less than 0.2 percent organic carbon of Holocene age
at a depth of 125 cm below the mineral soil surface and a
regular decrease in content of organic carbon from a depth of
25 cm to a depth of 125 cm or to a densic, lithic, or paralithic
contact if shallower; and
6. Have endosaturation.
Key to Subgroups
LAGA. Endoaquents that have, within 100 cm of the mineral
soil surface, one or both of the following:
1. Sulfidic materials; or
2. A horizon 15 cm or more thick that has all of the
characteristics of a sulfuric horizon, except that it has a pH
value between 3.5 and 4.0.
Sulfic Endoaquents
LAGB. Other Endoaquents that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Endoaquents
LAGC. Other Endoaquents that have, in one or more
horizons within 100 cm of the mineral soil surface, an
exchangeable sodium percentage of 15 or more (or a sodium
adsorption ratio of 13 or more) for 6 or more months in normal
years.
SodicEndoaquents
LAGD. Other Endoaquents that have, in one or more
horizons between either the Ap horizon or a depth of 25 cm
from the mineral soil surface, whichever is deeper, and a depth
of 75 cm, colors in 50 percent or more of the matrix as follows:
1. Hue of 2.5Y or redder, a color value, moist, of 6 or
more, and chroma of 3 or more; or
2. Hue of 2.5Y or redder, a color value, moist, of 5 or less,
and chroma of 2 or more; or
3. Hue of 5Y and chroma of 3 or more; or
4. Hue of 5Y or redder and chroma of 2 or more if there
are no redox concentrations.
Aeric Endoaquents
LAGE. Other Endoaquents that have both:
1. An Ap horizon that has a color value, moist, of 3 or less
and a color value, dry, of 5 or less (crushed and smoothed)
or materials in the upper 15 cm that have these colors after
mixing; and
2. A base saturation (by NH4
OAc) of less than 50 percent
in some part within 100 cm of the mineral soil surface.
Humaqueptic Endoaquents
LAGF. Other Endoaquents that have either an Ap horizon
that has a color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed) or materials in the upper
15 cm that have these colors after mixing.
Mollic Endoaquents
LAGG. Other Endoaquents.
Typic Endoaquents
Definition of Typic Endoaquents
Typic Endoaquents are the Endoaquents that:
1. Have, in one or more horizons between either the Ap
horizon or a depth of 25 cm from the mineral soil surface,
whichever is deeper, and a depth of 75 cm, colors in 50 percent
or more of the matrix as follows:
a. If there are redox concentrations, either:
(1) Hue of 2.5Y or redder, a color value, moist, of 6 or
more, and chroma of 2 or less; or
(2) Hue less yellow and less red than 5Y; or
(3) Hue of 5Y and chroma of 2 or less; or
b. Chroma of 1 or less;
396 Soil Taxonomy
2. Have an Ap horizon that has a color value, moist, of 4 or
more or a color value, dry, of 6 or more (crushed and
smoothed) and materials in the upper 15 cm that have one or
more of these colors after mixing;
3. Do not have a lithic contact within 50 cm of the mineral
soil surface;
4. Do not have, within 100 cm of the mineral soil surface,
either:
a. Sulfidic materials; or
b. A horizon 15 cm or more thick that has all of the
characteristics of a sulfuric horizon, except that it has a pH
value between 3.5 and 4.0; and
5. Do not have, in one or more horizons within 100 cm of the
mineral soil surface, an exchangeable sodium percentage of 15
or more (or a sodium adsorption ratio of 13 or more) for 6 or
more months in normal years.
Description of Subgroups
Typic Endoaquents.—The central concept or Typic
subgroup of Endoaquents is centered on moderately deep or
deeper soils with low chroma throughout the layer at a depth
between 25 and 75 cm below the mineral soil surface. These
soils have an Ap horizon that has a color value, moist, of 4 or
more or a color value, dry, of 6 or more (crushed and
smoothed) or have materials in the upper 15 cm that have these
colors after mixing. The soils do not have, within 100 cm of
the mineral soil surface, a horizon with an exchangeable
sodium percentage of 15 or more, sulfidic materials, or any
horizon 15 cm or more thick that has all of the characteristics
of a sulfuric horizon, except that it has a pH value between 3.5
and 4.0.
Soils that have a shallow lithic contact are excluded from
the Typic subgroup. Typic Endoaquents are of small extent in
the United States. They are widely distributed, mostly in the
humid parts of the country.
Aeric Endoaquents.—These soils are like Typic
Endoaquents, but they have some subhorizon at a depth
between 25 and 75 cm in which hue is redder or chroma is
higher than is typical for Endoaquents or there are no redox
concentrations. These colors are thought to reflect a level of
ground water that is not so shallow as the level in the Typic
subgroup or is shallow for a shorter period. These soils are of
small extent in the United States. They are widely distributed,
mostly in the humid parts of the country.
Humaqueptic Endoaquents.—These soils are like Typic
Endoaquents, but they have an Ap horizon that has a color
value, moist, of 3 or less and a color value, dry, of 5 or less
(crushed and smoothed) or have materials in the upper 15 cm
that have these colors after mixing. These soils are considered
intergrades to Humaquepts. They are mainly in the northcentral
part of the United States. They are of small extent in
the United States.
Lithic Endoaquents.—These soils are like Typic
Endoaquents, but they have a lithic contact within 50 cm of the
soil surface. They are of small extent in the United States.
Mollic Endoaquents.—These soils are like Typic
Endoaquents, but they have an Ap horizon that has a color
value, moist, of 3 or less and a color value, dry, of 5 or less
(crushed and smoothed) or have materials in the upper 15 cm
that have these colors after mixing. These soils are considered
intergrades to Aquolls. They are mainly in the north-central
part of the United States.
Sodic Endoaquents.—These soils are like Typic
Endoaquents, but they have, within 100 cm of the mineral soil
surface, an exchangeable sodium percentage of 15 or more for
6 or more months in normal years. These soils are of small
extent and are known to occur only in tidal-influenced areas on
the gulf coast in the United States. They support mostly grassy
vegetation.
Sulfic Endoaquents.—These soils are like Typic
Endoaquents, but they have sulfidic materials at a depth
between 50 and 100 cm below the mineral soil surface. These
soils are not known to occur in the United States. The subgroup
has been established for use in other countries.
Epiaquents
Epiaquents are the Aquents that have an isofrigid, frigid,
isomesic, mesic, or warmer temperature regime and epiaquic
saturation. The ground water is perched during some periods
in these soils and fluctuates from a level near or above the soil
surface in wet seasons. The water table does not occur in the
upper 200 cm during some periods in some of these soils.
Many Epiaquents support either a deciduous or a coniferous
forest. Some have been cleared and are used as cropland or
pasture. Generally, Epiaquents are nearly level, and their
parent materials are typically late-Pleistocene or Holocene
sediments.
Definition
Epiaquents are the Aquents that:
1. Do not have sulfidic materials within 50 cm of the mineral
soil surface;
2. Do not have a cryic soil temperature regime;
3. Have either an n value of 0.7 or less or less than 8 percent
clay in some or all horizons at a depth between 20 and 50 cm
below the mineral soil surface;
4. In some part of the particle-size control section, have
either:
a. A texture finer than loamy fine sand; or
b. 35 percent or more (by volume) rock fragments;
5. Have less than 0.2 percent organic carbon of Holocene age
at a depth of 125 cm below the mineral soil surface and a
Entisols 397
regular decrease in content of organic carbon from a depth of 25
cm to a depth of 125 cm or to a densic, lithic, or paralithic contact
if shallower; and
6. Have episaturation.
KeytoSubgroups
LAFA. Epiaquents that have, in one or more horizons between
either the Ap horizon or a depth of 25 cm from the mineral soil
surface, whichever is deeper, and a depth of 75 cm, colors in 50
percent or more of the matrix as follows:
1. Hue of 2.5Y or redder, a color value, moist, of 6 or more,
and chroma of 3 or more; or
2. Hue of 2.5Y or redder, a color value, moist, of 5 or less,
and chroma of 2 or more; or
3. Hue of 5Y and chroma of 3 or more; or
4. Chroma of 2 or more if there are no redox
concentrations.
Aeric Epiaquents
LAFB. Other Epiaquents that have both:
1. An Ap horizon that has a color value, moist, of 3 or less
and a color value, dry, of 5 or less (crushed and smoothed)
or materials in the upper 15 cm that have these colors after
mixing; and
2. A base saturation (by NH4
OAc) of less than 50 percent
in some part within 100 cm of the mineral soil surface.
Humaqueptic Epiaquents
LAFC. Other Epiaquents that have either an Ap horizon that
has a color value, moist, of 3 or less and a color value, dry, of 5
or less (crushed and smoothed) or materials in the upper 15 cm
that have these colors after mixing.
Mollic Epiaquents
LAFD. Other Epiaquents.
Typic Epiaquents
Definition of Typic Epiaquents
Typic Epiaquents are the Epiaquents that have:
1. In one or more horizons between either the Ap horizon or
a depth of 25 cm from the mineral soil surface, whichever is
deeper, and a depth of 75 cm, colors in 50 percent or more of
the matrix as follows:
a. If there are redox concentrations, either:
(1) Hue of 2.5Y or redder, a color value, moist, of 6 or
more, and chroma of 2 or less; or
(2) Hue less yellow or less red than 5Y; or
(3) Hue of 5Y and chroma of 2 or less; or
b. Chroma of 1 or less; and
2. An Ap horizon that has a color value, moist, of 4 or more or
a color value, dry, of 6 or more (crushed and smoothed) or
materials in the upper 15 cm that have these colors after
mixing.
Description of Subgroups
Typic Epiaquents.—The Typic subgroup of Epiaquents is
centered on soils with low chroma throughout the layer at a
depth between 25 and 75 cm below the mineral soil surface.
These soils have an Ap horizon that has a color value, moist, of
4 or more or a color value, dry, of 6 or more (crushed and
smoothed) or have materials in the upper 15 cm that have these
colors after mixing. The soils are of small extent in the United
States. They are widely distributed, mostly in the humid parts
of the country.
Aeric Epiaquents.—These soils are like Typic Epiaquents,
but they have some subhorizon at a depth between 25 and 75
cm in which hue is redder or chroma is higher than is typical
for Epiaquents or there are no redox concentrations. These
colors are thought to reflect a level of ground water that is not
so shallow as the level in the Typic subgroup or is shallow for a
shorter period. These soils are of small extent in the United
States. They are widely distributed, mostly in the humid parts
of the country.
Humaqueptic Epiaquents.—These soils are like Typic
Epiaquents, but they have an Ap horizon that has a color value,
moist, of 3 or less and a color value, dry, of 5 or less (crushed
and smoothed) or have materials in the upper 15 cm that have
these colors after mixing. These soils are considered
intergrades to Humaquepts. They are of small extent in the
United States. They occur mainly in the north-central part of
the country.
Mollic Epiaquents.—These soils are like Typic Epiaquents,
but they have an Ap horizon that has a color value, moist, of 3
or less and a color value, dry, of 5 or less (crushed and
smoothed) or have materials in the upper 15 cm that have these
colors after mixing. These soils are considered intergrades to
Aquolls. They are mainly in the north-central part of the
United States.
Fluvaquents
Fluvaquents are primarily the stratified, wet soils on flood
plains and deltas of middle and low latitudes. The stratification
reflects deposition of sediments under changing currents and in
shifting channels. The sediments are of Holocene age and have
a relatively high content of organic carbon at a considerable
depth when compared with many other wet, mineral soils. The
materials have dried or have partially dried from time to time
as they accumulated, and the n values are low. These soils are
extensive along large rivers, particularly in humid areas. The
ground water fluctuates from a level near or above the soil
surface to about 100 cm below the soil surface and is
398 Soil Taxonomy
sometimes below 200 cm. Generally, Fluvaquents are nearly
level.
Many Fluvaquents support either a deciduous or a
coniferous forest. Some have been cleared and protected from
flooding and are used as cropland or pasture.
Definition
Fluvaquents are the Aquents that:
1. Have a soil temperature regime warmer than cryic;
2. Have an n value of 0.7 or less or have less than 8 percent
clay in some or all subhorizons between depths of 20 and 50
cm;
3. Have either a texture finer than loamy fine sand or 35
percent or more (by volume) rock fragments in some or in all
parts of the particle-size control section;
4. Have a content of Holocene-age organic carbon that
decreases irregularly with increasing depth below 25 cm or that
remains more than 0.2 percent to a depth of 125 cm (thin strata
of sand may have less organic carbon if the finer sediments at a
depth of 125 cm or below have 0.2 percent organic carbon or
more); and
5. Do not have sulfidic materials within 50 cm of the mineral
soil surface.
Key to Subgroups
LAEA. Fluvaquents that have, within 100 cm of the mineral
soil surface, one or both of the following:
1. Sulfidic materials; or
2. A horizon 15 cm or more thick that has all of the
characteristics of a sulfuric horizon, except that it has a pH
value between 3.5 and 4.0.
Sulfic Fluvaquents
LAEB. Other Fluvaquents that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Fluvaquents
LAEC. Other Fluvaquents that have a buried layer of organic
soil materials, 20 cm or more thick, that has its upper boundary
within 100 cm of the mineral soil surface.
Thapto-Histic Fluvaquents
LAED. Other Fluvaquents that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm of
the mineral soil surface, one or more of the following:
1. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
2. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
3. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Fluvaquents
LAEE. Other Fluvaquents that have, in one or more horizons
between either the Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and a depth of 75
cm, colors in 50 percent or more of the matrix as follows:
1. Hue of 2.5Y or redder, a color value, moist, of 6 or
more, and chroma of 3 or more; or
2. Hue of 2.5Y or redder, a color value, moist, of 5 or less,
and chroma of 2 or more; or
3. Hue of 5Y and chroma of 3 or more; or
4. Chroma of 2 or more if there are no redox
concentrations.
Aeric Fluvaquents
LAEF. Other Fluvaquents that have both:
1. An Ap horizon that has a color value, moist, of 3 or less
and a color value, dry, of 5 or less (crushed and smoothed)
or materials in the upper 15 cm that have these colors after
mixing; and
2. A base saturation (by NH4
OAc) of less than 50 percent
in some part within 100 cm of the mineral soil surface.
Humaqueptic Fluvaquents
LAEG. Other Fluvaquents that have either an Ap horizon
that has a color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed) or materials in the upper
15 cm that have these colors after mixing.
Mollic Fluvaquents
LAEH. Other Fluvaquents.
Typic Fluvaquents
Entisols 399
DefinitionofTypicFluvaquents
Typic Fluvaquents are the Fluvaquents that:
1. Have, in one or more horizons between either the Ap
horizon or a depth of 25 cm from the mineral soil surface,
whichever is deeper, and a depth of 75 cm, colors in 50 percent
or more of the matrix as follows:
a. If there are redox concentrations, either:
(1) Hue of 2.5Y or redder, a color value, moist, of 6 or
more, and chroma of 2 or less; or
(2) Hue less yellow and less red than 5Y; or
(3) Hue of 5Y and chroma of 2 or less; or
b. Chroma of 1 or less;
2. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
3. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
4. Have an Ap horizon that has a color value, moist, of 4 or
more or a color value, dry, of 6 or more (crushed and
smoothed) or materials in the upper 15 cm that have these
colors after mixing;
5. Do not have a buried layer of organic soil materials, 20 cm
or more thick, that has its upper boundary within 100 cm of the
soil surface; and
6. Do not have, within 100 cm of the mineral soil surface,
either:
a. Sulfidic materials; or
b. A horizon 15 cm or more thick that has all of the
characteristics of a sulfuric horizon, except that it has a pH
value between 3.5 and 4.0.
Description of Subgroups
Typic Fluvaquents.—The concept of Typic Fluvaquents is
centered almost exclusively on very young water-laid deposits
that are mostly in wet areas on flood plains. These soils have
fine strata at a shallow depth, or they show too little evidence
of alteration to have a cambic horizon. Redoximorphic features
in the soils extend downward from a point very close to the
surface, and the water table is at or close to the surface most of
the year unless artificial drainage has been provided. The soils
do not have a layer of fine pyroclastic materials that is as thick
as or thicker than 18 cm and that is within 75 cm of the
surface. They do not have a buried Histosol or a buried histic
epipedon within a depth of 100 cm. They do not have a dark
surface horizon or, if one occurs, it is thin. These
characteristics were selected for the Typic subgroup not
because they are most common but because they represent the
wettest and most recent Fluvaquents. As horizons begin to
develop, the soils are classified in intergrade subgroups that
indicate their nature.
Most Typic Fluvaquents are nearly level, and their parent
materials are Holocene sediments. Many support forest
vegetation, but some support shrub or grassy vegetation. Some
areas have been cleared, drained, and protected from flooding
and are used as cropland or pasture.
Aeric Fluvaquents.—These soils are like Typic
Fluvaquents, but they have some subhorizon at a depth between
25 and 75 cm in which chroma is higher than that of soils in
the Typic subgroup, reflecting a level of ground water that is
not so shallow as in the Typic subgroup or is shallow a shorter
period.
Most Aeric Fluvaquents are nearly level. Most support forest
vegetation, but some support shrub or grassy vegetation. Many
areas have been cleared, drained, and protected from flooding
and are used as cropland or pasture.
Aquandic Fluvaquents.—These soils are similar to Typic
Fluvaquents, but they have a layer of pyroclastic materials that
is 18 cm or more thick and that is in the upper 75 cm. In the
United States, these soils occur in western Washington but are
not extensive. Most Aquandic Fluvaquents are nearly level and
support forest vegetation. Many areas have been cleared,
drained, and protected from flooding and are used as hayland
or pasture.
Humaqueptic Fluvaquents.—These soils have a surface
400 Soil Taxonomy
horizon that has the color and other properties of an umbric
epipedon, except for thickness. In the United States, these soils
occur on nearly level flood plains in areas where Ultisols or
other soils that have low base saturation are the dominant
upland soils. Most Humaqueptic Fluvaquents are forested.
Some are pastured, and a few have been drained and are
cultivated. Humaqueptic Fluvaquents are not extensive soils.
Mollic Fluvaquents.—These soils have a surface horizon
that has the color and other properties of a mollic epipedon,
except for thickness. The epipedon is less than 25 cm thick.
These soils are otherwise like Typic Fluvaquents in defined
properties. They have high base saturation, and some of them
are calcareous. Many of them are on flood plains along streams
in areas where Mollisols are extensive soils on uplands. Mollic
Fluvaquents are moderately extensive soils in the United
States. Nearly all have been cleared, drained, and protected
from flooding and are used as cropland or pasture.
Sulfic Fluvaquents.—These soils have sulfidic materials at
a depth between 50 and 100 cm below the mineral soil surface.
They are of small extent in the States of Washington and
California in the United States.
Thapto-Histic Fluvaquents.—These soils are similar to
Typic Fluvaquents, but they have a buried Histosol or a buried
histic epipedon that has its upper boundary within 100 cm of
the soil surface. Many Thapto-Histic Fluvaquents in the United
States formed within the last 100 to 150 years as a result of
erosion on hillsides and the deposition of sediment on a
Histosol. In the United States, Thapto-Histic Fluvaquents are of
moderately small extent and in many areas are farmed or
pastured. In other parts of the world, these soils occur near
streams in coastal marshes.
Vertic Fluvaquents.—These soils are like Typic Fluvaquents,
but they either have cracks and slickensides or wedge-shaped
aggregates or have a linear extensibility of 6.0 or more within 100
cm of the mineral soil surface. These soils are mainly in
backswamps on flood plains where water stands for long
periods unless the soils have been artificially drained. Because
there are no restrictions on the color value of Vertisols, Vertic
Fluvaquents are permitted, but not required, to have a lower
color value than the soils of the Typic subgroup. Vertic
Fluvaquents have fine strata near the surface. They are of
moderate extent in the United States. They are nearly level and
support forest, shrub, or grassy vegetation. Many areas have
been cleared, drained, and protected from flooding and are
used as cropland or pasture.
Hydraquents
These are loamy and clayey soils in tidal marshes that are
permanently saturated with water. Hydraquents formed in
sediments that were deposited under water and have a low bulk
density, commonly about 0.6 g/cc, and a high water content,
commonly more than 100 percent of the dry weight. If the soils
are drained, the loss of water is irreversible and the bulk
density increases as water is withdrawn. The soils deposited in
tidal marshes retain their high water content. Hydraquents
never have been dry, and consequently the bulk density is low
and the water content is very high. The soils typically have
reduced matrices, and their colors mostly are bluish gray to
greenish gray and change to shades of brown when the soils
are exposed to air. A color change normally can be seen within
a matter of seconds or a few minutes but may not be complete
until some weeks have passed.
Because the water content is high, the soil strength is low,
commonly too low for the soils to support grazing animals.
Nevertheless, some Hydraquents may be grazed if the water
content in the surface layer is relatively low or if vegetation
adds strength to the surface layer.
Hydraquents are extensive in tidal marshes. In the United
States, they are largely confined to the Atlantic and gulf coasts,
although a few are on the northern Pacific coast and near San
Francisco Bay.
Definition
Hydraquents are the Aquents that:
1. Do not have sulfidic materials within 50 cm of the mineral
soil surface; and
2. Have, in all subhorizons at a depth between 20 and 50 cm
below the mineral soil surface, both an n value of more than
0.7 and 8 percent or more clay.
Key to Subgroups
LABA. Hydraquents that have, within 100 cm of the mineral
soil surface, one or both of the following:
1. Sulfidic materials; or
2. A horizon 15 cm or more thick that has all of the
characteristics of a sulfuric horizon, except that it has a pH
value between 3.5 and 4.0.
Sulfic Hydraquents
LABB. Other Hydraquents that have, in one or more
horizons within 100 cm of the mineral soil surface, an
exchangeable sodium percentage of 15 or more (or a sodium
adsorption ratio of 13 or more) for 6 or more months in normal
years.
Sodic Hydraquents
LABC. Other Hydraquents that have a buried layer of organic
soil materials, 20 cm or more thick, that has its upper boundary
within 100 cm of the mineral soil surface.
Thapto-Histic Hydraquents
LABD. Other Hydraquents.
Typic Hydraquents
Entisols 401
DefinitionofTypicHydraquents
Typic Hydraquents are the Hydraquents that:
1. Do not have, within 100 cm of the mineral soil surface, one
or both of the following:
a. Sulfidic materials; or
b. A horizon 15 cm or more thick that has all of the
characteristics of a sulfuric horizon, except that it has a pH
value between 3.5 and 4.0;
2. Do not have, in one or more horizons within 100 cm of the
mineral soil surface, an exchangeable sodium percentage of 15
or more (or a sodium adsorption ratio of 13 or more) for 6 or
more months in normal years; and
3. Do not have a buried layer of organic soil materials, 20 cm
or more thick, that has its upper boundary within 100 cm of the
mineral soil surface.
Description of Subgroups
Typic Hydraquents.—These are the Hydraquents that,
within 100 cm of the soil surface, do not have any horizon 15
cm or more thick that has all of the characteristics of a sulfuric
horizon, except that it has a pH value between 3.5 and 4.0, and
do not have sulfidic materials or an exchangeable sodium
percentage of 15 or more. These soils have neither a buried
Histosol nor a buried histic epipedon that has its upper
boundary within 100 cm of the mineral soil surface.
Typic Hydraquents are of moderate extent in the United
States. They are nearly level and support swamp forest, shrub,
or grassy vegetation. Most of these soils are used as wildlife
habitat.
Sodic Hydraquents.—These are the Hydraquents that,
within 100 cm of the soil surface, have an exchangeable
sodium percentage of 15 or more. They do not have, within
100 cm of the soil surface, any sulfidic materials or any
horizon 15 cm or more thick that has a pH value of 3.5 to 4.0
and any other characteristics of a sulfuric horizon.
Sodic Hydraquents are of small extent in the United States,
occurring mostly in the Mississippi delta and westward along
the gulf coast. They are nearly level and support mostly grassy
and forb vegetation. Most of these soils are used as wildlife
habitat.
Sulfic Hydraquents.—These are the Hydraquents that,
within 100 cm of the soil surface, have sulfidic materials or a
horizon 15 cm or more thick that has all of the characteristics
of a sulfuric horizon, except that it has a pH value between 3.5
and 4.0. The soils are of small extent in the United States.
They are nearly level and support mostly grassy and forb
vegetation. Most of these soils are used as wildlife habitat.
Thapto-Histic Hydraquents.—These soils are like Typic
Hydraquents, but they have a buried Histosol or a buried histic
epipedon that has its upper boundary within 100 cm of the
mineral soil surface. Within 100 cm of the soil surface, they do
not have any sulfidic materials or any horizon 15 cm or more
thick that has a pH value of 3.5 to 4.0 and any other
characteristics of a sulfuric horizon and do not have an
exchangeable sodium percentage of 15 or more.
Thapto-Histic Hydraquents are of small extent in the United
States. They are nearly level and support swamp forest, shrub,
or grassy vegetation. Most of these soils are used as wildlife
habitat.
Psammaquents
These Aquents have a sandy texture and commonly are gray,
with or without redox concentrations. The water table is at or
near the surface for long periods unless artificial drainage has
been provided. Most of these soils formed in late-Pleistocene to
recent sediments. Most do not have distinctive features, but a
few have a B horizon that is similar to the one in Spodosols but
is too weakly developed to be a spodic horizon. Others show
some darkening and accumulation of organic matter in an A
horizon but too little for a mollic or umbric epipedon.
Definition
Psammaquents are the Aquents that:
1. Do not have sulfidic materials within 50 cm of the mineral
soil surface;
2. Do not have, in any horizon at a depth between 20 and 50
cm below the mineral soil surface, both an n value of more
than 0.7 and 8 percent or more clay in the fine-earth fraction;
3. Do not have a cryic soil temperature regime;
4. Have less than 35 percent (by volume) rock fragments and
a texture of loamy fine sand or coarser in all layers within the
control section for the family particle-size class.
Key to Subgroups
LADA. Psammaquents that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Psammaquents
LADB. Other Psammaquents that have, in one or more
horizons within 100 cm of the mineral soil surface, an
exchangeable sodium percentage of 15 or more (or a sodium
adsorption ratio of 13 or more) for 6 or more months in normal
years.
Sodic Psammaquents
LADC. Other Psammaquents that have a horizon, 5 cm or
more thick, either below an Ap horizon or at a depth of 18 cm
or more from the mineral soil surface, whichever is deeper, that
has one or more of the following:
1. In 25 percent or more of each pedon, cementation by
organic matter and aluminum, with or without iron; or
402 Soil Taxonomy
2. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
3. An ODOE value of 0.12 or more, and a value half as
high or lower in an overlying horizon.
Spodic Psammaquents
LADD. Other Psammaquents that have both:
1. An Ap horizon that has a color value, moist, of 3 or less
and a color value, dry, of 5 or less (crushed and smoothed)
or materials in the upper 15 cm that have these colors after
mixing; and
2. A base saturation (by NH4
OAc) of less than 50 percent
in some part within 100 cm of the mineral soil surface.
Humaqueptic Psammaquents
LADE. Other Psammaquents that have either an Ap horizon
that has a color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed) or materials in the upper
15 cm that have these colors after mixing.
Mollic Psammaquents
LADF. Other Psammaquents.
Typic Psammaquents
Definition of Typic Psammaquents
Typic Psammaquents are the Psammaquents that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Have an Ap horizon that has a color value, moist, of 4 or
more or a color value, dry, of 6 or more (crushed and
smoothed) and materials in the upper 15 cm that have these
colors after mixing;
3. Do not have a horizon, 5 cm or more thick, either below
an Ap horizon or at a depth of 18 cm or more from the mineral
soil surface, whichever is deeper, that has one or more of the
following:
a. In 25 percent or more of each pedon, cementation by
organic matter and aluminum, with or without iron; or
b. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
c. An ODOE value of 0.12 or more, and a value half as
high or lower in an overlying horizon; and
4. Do not have, in one or more horizons within 100 cm of the
mineral soil surface, an exchangeable sodium percentage of 15
or more (or a sodium adsorption ratio of 13 or more) for 6 or
more months in normal years.
Description of Subgroups
Typic Psammaquents.—The central concept or Typic
subgroup of Psammaquents is fixed on moderately deep or
deeper soils that have an Ap horizon that has a color value,
moist, of 4 or more or a color value, dry, of 6 or more or that
have materials in the upper 15 cm that have these colors after
mixing. These soils do not have an exchangeable sodium
percentage of 15 or more within 100 cm of the mineral soil
surface. They do not have a horizon that approaches the
criteria for a spodic horizon. They are saturated with water part
of the time. A range in the length of the periods of saturation is
permitted.
Typic Psammaquents are locally extensive in the United
States, particularly on the coastal plains and in areas covered
by Wisconsinan outwash. Few of them are farmed. Most are
used for grazing or forest, depending on their natural
vegetation.
Humaqueptic Psammaquents.—These soils are like Typic
Psammaquents, but the A or Ap horizon resembles an umbric
epipedon but is less than 25 cm thick. The base saturation (by
NH4
OAc) is less than 50 percent in some part of the soils
within the upper 100 cm. In the United States, these soils are
of small extent. Most support mixed forest vegetation. Some
have been cleared and drained and are used as cropland,
hayland, or pasture.
Lithic Psammaquents.—These soils are like Typic
Psammaquents, but they have a lithic contact within 50 cm of
the soil surface. They are of small extent in the United States.
Mollic Psammaquents.—These soils are like Typic
Psammaquents, but the A or Ap horizon resembles a mollic
epipedon but is less than 25 cm thick. They have a base
saturation of 50 percent or more in all horizons within 100 cm
of the soil surface. These soils are moderately extensive in the
United States, mostly in areas of Wisconsinan outwash. The A
horizon generally is black or very dark gray but is too thin to
meet the requirements for a mollic epipedon, which in sands
must be at least 25 cm thick. Many of these soils support
hardwood forest, and some support grass or grass and widely
scattered trees. Mollic Psammaquents are used for grazing or
forest, depending on their natural vegetation. Some of the soils
have been cleared and drained and are used as cropland or
pasture.
Sodic Psammaquents.—These soils have, in one or more
horizons within 100 cm of the mineral soil surface, an
exchangeable sodium percentage of 15 or more. They are not
extensive in the United States. They are mostly on the low
coastal plains in Texas. Most of them support their native
vegetation of grasses and forbs and are used as rangeland.
Spodic Psammaquents.—These soils have a weak
accumulation of amorphous materials, mostly humus. They are
not extensive in the United States. They are in Florida, on the
low coastal plains along the Atlantic Ocean and the Gulf of
Mexico. Most of them still have their native vegetation of
Entisols 403
forest or shrubs and grasses. Some have been cleared and
drained and are used as cropland or pasture.
Sulfaquents
These are the Aquents that have an appreciable amount of
sulfides close to the mineral soil surface and have few or no
carbonates. The sulfides are close enough to the surface for the
soils to become extremely acid and virtually sterile if drained.
These soils are largely restricted to coastal marshes where the
water is brackish. Tidal marshes at the mouth of rivers
normally have areas of these soils unless the river sediments
are rich in carbonates. Coastal marshes that are not near rivers
also may have areas of these soils if storms periodically flood
them with salt water.
Sulfaquents are permanently saturated at or near the
surface, and many are nearly neutral in reaction. The n value
typically is high, commonly more than 1 in most horizons. A
histic epipedon composed of organic soil materials is common.
These soils can have any mineral particle-size class, but those
with less than 8 percent clay are not considered typical. If the
soils are drained, the sulfides oxidize and the soils change
rapidly to Sulfaquepts.
Sulfaquents commonly are not used as cropland, but some
are used for the production of rice. The areas used for rice are
kept flooded at all times, except for a very brief period while
the crop is harvested.
Sulfaquents are extensive along coasts and bays from the
Equator to high latitudes. They are moderately extensive on the
east coast of the United States, where they border the Atlantic
Ocean in areas not protected by barrier islands.
Definition
Sulfaquents are the Aquents that have sulfidic materials
within 50 cm of the mineral soil surface.
Key to Subgroups
LAAA. Sulfaquents that have, in some horizons at a depth
between 20 and 50 cm below the mineral soil surface, either or
both:
1. An n value of 0.7 or less; or
2. Less than 8 percent clay in the fine-earth fraction.
Haplic Sulfaquents
LAAB. Other Sulfaquents that have a histic epipedon.
Histic Sulfaquents
LAAC. Other Sulfaquents that have a buried layer of organic
soil materials, 20 cm or more thick, that has its upper boundary
within 100 cm of the mineral soil surface.
Thapto-Histic Sulfaquents
LAAD. Other Sulfaquents.
Typic Sulfaquents
Definition of Typic Sulfaquents
Typic Sulfaquents are the Sulfaquents that:
1. Do not have, in one or more horizons at a depth between 20
and 50 cm below the mineral soil surface, either or both:
a. Less than 8 percent clay in the fine-earth fraction; or
b. An n value of 0.7 or less;
2. Do not have a histic epipedon;
3. Do not have a buried layer of organic soil materials, 20 cm or
more thick, that has its upper boundary within 100 cm of the
mineral soil surface.
Description of Subgroups
Typic Sulfaquents.—The central concept or Typic subgroup
of Sulfaquents is fixed on soils that have, in all horizons at a
depth between 20 and 50 cm below the mineral soil surface,
both an n value of more than 0.7 and 8 percent or more clay in
the fine-earth fraction. These soils do not have a histic
epipedon or a buried histic epipedon. They are extensive in the
coastal marshes along the Atlantic seaboard but are not
extensive elsewhere in the United States. They are nearly level
and support mostly grassy and forb vegetation. Most of the
soils are used as wildlife habitat.
Haplic Sulfaquents.—These are the Sulfaquents that have,
in one or more horizons at a depth between 20 and 50 cm
below the mineral soil surface, either or both less than 8
percent clay in the fine-earth fraction or an n value of 0.7 or
less. These soils are of small extent in the United States. They
are nearly level and support mostly grassy and forb vegetation.
Most of these soils are used as wildlife habitat.
Histic Sulfaquents.—These soils are like Typic
Sulfaquents, but they have a histic epipedon. They are of small
extent in the United States. They are nearly level and support
mostly grassy and forb vegetation. Most of these soils are used
as wildlife habitat.
Thapto-Histic Sulfaquents.—These are the Sulfaquents
that have a buried Histosol or a buried histic epipedon with its
upper boundary within 100 cm of the soil surface. These soils
do not have n values above 0.7. They occur in New Jersey,
Maryland, and Delaware.
Arents
These are the Entisols that do not have horizons because
they have been deeply mixed by plowing, spading, or other
methods of moving by humans. The soils retain fragments that
can be identified as parts of a former spodic or argillic horizon,
404 Soil Taxonomy
a duripan, and so on, but the fragments do not themselves form
horizons. Rather, they are scattered through the soils and are
mixed with the materials of other horizons. Some of these soils
are the result of deliberate soil modification intended to break
or remove a pan. Some are the result of replacing the soil
profile after strip-mining. Others have resulted from cuts and
fills made to shape the surface or even from the accident of
location in an area of intensive bombardment during a war.
Arents are not extensive in the United States. Their area is
increasing, however, because of increased use of modern power
machinery to modify soils for high-intensity crop production.
Arents form a unique suborder in that there are no Typic
subgroups. Subgroups of Arents are intergrades to other orders,
suborders, or great groups, according to the nature of the
fragments that can be identified. The Arents that do not meet
other subgroup criteria are assigned to the Haplic subgroup.
Definition
Arents are the Entisols that:
1. Have 3 percent or more, by volume, fragments of diagnostic
horizons in one or more subhorizons at a depth between 25 and
100 cm below the soil surface, and the fragments are not
arranged in a discernible order; and
2. Do not have, within 50 cm of the mineral soil surface, aquic
conditions; and
a. The colors defined for Aquents; or
b. Sulfidic materials; or
c. A positive reaction to alpha,alpha-dipyridyl when the soil
is not being irrigated.
Key to Great Groups
LBA. Arents that have an ustic moisture regime.
Ustarents, p. 405
LBB. Other Arents that have a xeric moisture regime.
Xerarents, p. 406
LBC. Other Arents that have an aridic (or torric) moisture
regime.
Torriarents, p. 404
LBD. Other Arents.
Udarents, p. 404
Torriarents
These are the Arents of arid regions. They have an aridic (or
torric) moisture regime. Generally, they are neutral or more
alkaline, and many are calcareous. Many have gentle slopes.
Most have been modified for irrigated agriculture. Torriarents
are extensive in California but occur throughout the Western
United States.
Definition
Torriarents are the Arents that have an aridic soil moisture
regime.
Key to Subgroups
LBCA. Torriarents that have, in one or more horizons within
100 cm of the mineral soil surface, 3 percent or more
fragments of a natric horizon.
Sodic Torriarents
LBCB. Other Torriarents that have, within 100 cm of the
mineral soil surface, 3 percent or more fragments of a duripan
or a petrocalcic horizon;
Duric Torriarents
LBCC. Other Torriarents.
Haplic Torriarents
Description of Subgroups
Haplic Torriarents.—The Haplic subgroup of Torriarents
is centered on soils that have 3 percent or more fragments of an
argillic or cambic horizon. These soils are permitted to have
fragments of any diagnostic horizon, but they cannot have, in
any horizon within 100 cm of the mineral soil surface,
fragments of a duripan or a petrocalcic or natric horizon. Many
of the soils have gentle slopes. Most have been modified for
irrigated agriculture. Haplic Torriarents are used as irrigated
cropland. They are of moderately small extent. They are mostly
in California but occur throughout the Western United States.
Duric Torriarents.—The Duric subgroup of Torriarents is
centered on soils that have, in some horizon within 100 cm of
the mineral soil surface, 3 percent or more fragments of a
duripan or a petrocalcic horizon. Many of these soils have
gentle slopes. Most have been modified for irrigated
agriculture. Duric Torriarents are used as irrigated cropland.
They are of moderate extent. They are mostly in California but
occur throughout the Western United States.
Sodic Torriarents.—The Sodic subgroup of Torriarents is
centered on soils that have, in some horizon within 100 cm of
the mineral soil surface, 3 percent or more fragments of a
natric horizon. Many of these soils have gentle slopes. Most
have been modified for irrigated agriculture. Sodic Torriarents
are used as irrigated cropland. They are of small extent. They
are known to occur only in California in the United States.
Udarents
These are the Arents of moist regions. They have a udic
moisture regime. Many have gentle slopes. Many have been
modified in the process of strip-mining. The top part of the soil
profile was removed and then replaced after the mining was
Entisols 405
completed. Some of these soils have a densic contact with
compacted layers of soil materials. Some formed in fill
material. Udarents are moderately extensive in the United
States. They are used mostly as pasture, but some are used as
woodland, cropland, or homesites.
Definition
Udarents are the Arents that have a udic soil moisture
regime.
Key to Subgroups
LBDA. Udarents that have 3 percent or more fragments of an
argillic horizon in some horizon within 100 cm of the mineral
soil surface and have a base saturation (by sum of cations) of
35 percent or more in all parts within 100 cm of the mineral
soil surface.
Alfic Udarents
LBDB. Other Udarents that have 3 percent or more
fragments of an argillic horizon in some horizon within 100
cm of the mineral soil surface.
Ultic Udarents
LBDC. Other Udarents that have 3 percent or more
fragments of a mollic epipedon in some horizon within 100 cm
of the mineral soil surface and have a base saturation (by sum
of cations) of 35 percent or more in all parts within 100 cm of
the mineral soil surface.
Mollic Udarents
LBDD. Other Udarents.
Haplic Udarents
Description of Subgroups
Haplic Udarents.—The Haplic subgroup of Udarents is
centered on soils that have 3 percent or more fragments of a
cambic horizon in some horizon within 100 cm of the mineral
soil surface. These soils are permitted to have fragments of
other diagnostic horizons, but they cannot have, in any horizon
within 100 cm of the mineral soil surface, 3 percent or more
fragments of an argillic horizon. They cannot have 3 percent or
more fragments of a mollic epipedon unless some horizon
within 100 cm of the mineral soil surface has a base saturation
of less than 35 percent. Commonly, these soils have gentle
slopes. They formed in a number of ways. Some have been
modified in the process of strip-mining. The top part of the soil
profile was removed and then replaced after the mining was
completed. Some of the soils have a densic contact with
compacted layers of soil materials. Haplic Udarents are of
small extent in the United States.
Alfic Udarents.—The Alfic subgroup of Udarents is fixed
on soils that have 3 percent or more fragments of an argillic
horizon in some horizon and have a base saturation (by sum of
cations) of 35 percent or more in all parts within 100 cm of the
mineral soil surface. These soils are permitted to have
fragments of other diagnostic horizons. Many of the soils have
gentle slopes. Alfic Udarents formed in a number of ways.
Many have been modified in the process of strip-mining. The
top part of the soil profile was removed and then replaced after
the mining was completed. Some of these soils have a densic
contact with compacted layers of soil materials. Alfic Udarents
are moderately extensive in the United States. They are used
mostly as pasture or cropland. Some are used as woodland and
some as homesites.
Mollic Udarents.—The Mollic subgroup of Udarents is
fixed on soils that have 3 percent or more fragments of a mollic
epipedon in some horizon within 100 cm of the mineral soil
surface and have a base saturation (by sum of cations) of 35
percent or more in all parts within 100 cm of the mineral soil
surface. These soils are permitted to have fragments of other
diagnostic horizons, but they cannot have, in any horizon
within 100 cm of the mineral soil surface, 3 percent or more
fragments of an argillic horizon. Many of the soils have gentle
slopes. Mollic Udarents formed in a number of ways. Some
have been modified in the process of strip-mining. The top
part of the soil profile was removed and then replaced after
the mining was completed. Some of the soils have a densic
contact with compacted layers of soil materials. Mollic
Udarents are of small extent in the United States. They are
used mostly as pasture or cropland, but some are used as
homesites.
Ultic Udarents.—The Ultic subgroup of Udarents is fixed
on soils that have 3 percent or more fragments of an argillic
horizon and have a base saturation (by sum of cations) of less
than 35 percent in some part within 100 cm of the mineral soil
surface. These soils are permitted to have fragments of other
diagnostic horizons. Many have gentle slopes. Ultic Udarents
formed in a number of ways. A few have been modified in the
process of strip-mining. The top part of the soil profile was
removed and then replaced after the mining was completed.
Some of these soils have a densic contact with compacted
layers of soil materials. Ultic Udarents are of small extent in the
United States. They are used mostly as pasture, woodland, or
cropland.
Ustarents
These are the Arents that have an ustic moisture regime.
Many of these soils have gentle slopes. Most formed in fill
material. Some have a densic contact with compacted layers of
soil materials. Ustarents are of small extent in the United
States. They are used mostly as pasture or are idle.
Definition
Ustarents are the Arents that have an ustic soil moisture
regime.
406 Soil Taxonomy
KeytoSubgroups
LBAA. All Ustarents.
Haplic Utarents
Description of Subgroups
Haplic Ustarents.—The Haplic subgroup of Ustarents is
the only subgroup recognized. These soils have, in some
horizon within 100 cm of the mineral soil surface, 3 percent or
more fragments of a diagnostic horizon. They are permitted to
have fragments of any diagnostic horizon. Commonly, they
have gentle slopes. Most formed in fill material. Some have a
densic contact with compacted layers of soil materials. Haplic
Ustarents are of small extent in the United States. They are
used mostly as pasture or are idle.
Xerarents
These are the Arents that have a xeric moisture regime. Most
of these soils have been modified for irrigated agriculture. Many
have gentle slopes. Xerarents occur mostly in California in the
United States.
Definition
Xerarents are the Arents that have a xeric soil moisture
regime.
Key to Subgroups
LBBA. Xerarents that have, in one or more horizons within
100 cm of the mineral soil surface, 3 percent or more
fragments of a natric horizon.
Sodic Xerarents
LBBB. Other Xerarents that have, within 100 cm of the
mineral soil surface, 3 percent or more fragments of a duripan
or a petrocalcic horizon.
Duric Xerarents
LBBC. Other Xerarents that have fragments of an argillic
horizon with a base saturation (by sum of cations) of 35 percent
or more within 100 cm of the mineral soil surface.
Alfic Xerarents
LBBD. Other Xerarents.
Haplic Xerarents
Description of Subgroups
Haplic Xerarents.—The Haplic subgroup of Xerarents is
centered on soils that have 3 percent or more fragments of a
cambic horizon or another diagnostic horizon. These soils are
not permitted to have, in any horizon within 100 cm of the
mineral soil surface, 3 percent or more fragments of a duripan
or an argillic or natric horizon. Many of the soils have gentle
slopes. Most have been modified for irrigated agriculture.
Haplic Xerarents are used as irrigated cropland. They are of
small extent, mostly in California.
Alfic Xerarents.—The Alfic subgroup of Xerarents is
centered on soils that have 3 percent or more fragments of an
argillic horizon in some horizon and have a base saturation (by
sum of cations) of 35 percent or more in all parts within 100
cm of the mineral soil surface. These soils are not permitted to
have, in any horizon within 100 cm of the mineral soil surface,
3 percent or more fragments of a duripan or a petrocalcic or
natric horizon. They are permitted to have fragments of other
diagnostic horizons. Many of the soils have gentle slopes. Most
have been modified for irrigated agriculture. Alfic Xerarents
are used as irrigated cropland. They are of moderate extent,
mostly in California.
Duric Xerarents.—The Duric subgroup of Xerarents is
centered on soils that have, in some horizon within 100 cm of
the mineral soil surface, 3 percent or more fragments of a
duripan or a natric or petrocalcic horizon. Many of these soils
have gentle slopes. Most have been modified for irrigated
agriculture. Duric Xerarents are used as irrigated cropland.
They are of moderate extent, mostly in California.
Sodic Xerarents.—The Sodic subgroup of Xerarents is
centered on soils that have, in some horizon within 100 cm of
the mineral soil surface, 3 percent or more fragments of a
natric horizon. Many of these soils have gentle slopes. Most
have been modified for irrigated agriculture. Sodic Xerarents
are used as irrigated cropland. They are of small extent and are
known to occur only in California in the United States.
Fluvents
These are mostly brownish to reddish soils that formed in
recent water-deposited sediments, mainly on flood plains, fans,
and deltas of rivers and small streams but not in backswamps
where drainage is poor. The age of the sediments in humid
regions commonly is a few years or decades or a very few
hundred years. In arid regions it may be somewhat more. Many
Fluvents are frequently flooded unless they are protected by
dams or levees. Stratification of the materials is normal. Most
of the alluvial sediments are derived from eroding soils or
streambanks and contain an appreciable amount of organic
carbon, which is mainly in the clay fraction. Strata of clayey or
loamy materials commonly have more organic carbon than the
overlying more sandy strata. Thus, the percentage of organic
carbon of Holocene age decreases irregularly with increasing
depth if the materials are stratified. If the texture is
homogeneous, the content of organic carbon decreases
regularly with increasing depth. Because the deposits generally
are loamy and recent, however, the percentage of carbon in the
deep layers is higher than in soils that formed in parent
materials other than alluvium. This difference in content of
organic carbon is the basis for the definition of Fluvents that
follows. Fluvents can have any vegetation and any temperature
regime. They can have any moisture regime that does not meet
Entisols 407
the criteria for Aquents. Soils that formed in recent alluvium
and have a permanently frozen substratum are grouped with
Gelisols. Some soils that formed in volcanic tephra and some
that have gelic materials are excluded from Fluvents because
they have a different mode of formation and different
interpretations.
Definition
Fluvents are the Entisols that:
1. Have 35 percent or more (by volume) rock fragments or a
texture of loamy very fine sand or finer in some part of the
particle-size control section;
2. Do not have, in one or more layers at a depth between 25
and 100 cm below the mineral soil surface, 3 percent or more
(by volume) fragments of diagnostic horizons that can be
identified and that occur more or less without a discernible
order;
3. Have a slope of less than 25 percent;
4. Have a content of Holocene-age organic carbon that
decreases irregularly with increasing depth or that is 0.2
percent or more at a depth of 125 cm or at a densic, lithic, or
paralithic contact if shallower;
5. Do not have, within 50 cm of the mineral soil surface,
aquic conditions; and
a. The colors defined for Aquents; or
b. Sulfidic materials; or
c. A positive reaction to alpha,alpha-dipyridyl when the
soil is not being irrigated;
6. Do not have both permanent saturation with water and a
reduced matrix in all horizons below 25 cm from the mineral
soil surface;
7. Have a soil temperature regime:
a. That is warmer than cryic; or
b. That is cryic and the soil has:
(1) No gelic material; and
(2) Either a slope of less than 5 percent or less than 15
percent volcanic glass in the 0.02 to 2.0 mm fraction in
some part of the particle-size control section; and
8. Do not have a densic, lithic, or paralithic contact within 25
cm of the soil surface.
Key to Great Groups
LDA. Fluvents that have a cryic soil temperature regime.
Cryofluvents, p. 407
LDB. Other Fluvents that have a xeric moisture regime.
Xerofluvents, p. 417
LDC. Other Fluvents that have an ustic moisture regime.
Ustifluvents, p. 414
LDD. Other Fluvents that have an aridic (or torric) moisture
regime.
Torrifluvents, p. 408
LDE. Other Fluvents.
Udifluvents, p. 411
Cryofluvents
These are the cold Fluvents. They do not have permafrost or
gelic materials, but the growing season is short and cool. The
vegetation typically is a coniferous or mixed forest. In the
United States, these soils are mostly in Alaska, but some are in
mountain valleys in the West. Cryofluvents are moderately
extensive.
Definition
Cryofluvents are the Fluvents that have a cryic temperature
regime.
Key to Subgroups
LDAA. Cryofluvents that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and percent aluminum plus 1
/2 the iron percentage
(by ammonium oxalate) totaling more than 1.0.
Andic Cryofluvents
LDAB. Other Cryofluvents that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Cryofluvents
LDAC. Other Cryofluvents that have, in one or more
horizons within 50 cm of the mineral soil surface, redox
408 Soil Taxonomy
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage).
AquicCryofluvents
LDAD. Other Cryofluvents that are saturated with water in
one or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Cryofluvents
LDAE. Other Cryofluvents that have either an Ap horizon
that has a color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed) or materials in the upper
15 cm that have these colors after mixing.
Mollic Cryofluvents
LDAF. Other Cryofluvents.
Typic Cryofluvents
Definition of Typic Cryofluvents
Typic Cryofluvents are the Cryofluvents that:
1. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
2. Do not have, in any horizon within 50 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
3. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 1 month or more in normal years;
and
4. Have an A or Ap horizon that has a color value, moist,
of 4 or more or a color value, dry, of 6 or more when crushed
and smoothed or that is less than 15 cm thick.
Description of Subgroups
Typic Cryofluvents.—The Typic subgroup of Cryofluvents
is centered on soils without ground water within the upper 100
cm, except for short periods following floods. When these soils
thaw in spring, the soil above the layer that remains frozen
may be saturated and very soft, but the water drains out rapidly
when the frozen layer thaws. Redox depletions with chroma of
2 or less do not occur within 50 cm of the mineral soil surface.
The soils do not have, in the upper 75 cm, a deposit of
pyroclastic materials that is as thick as 18 cm. An O horizon at
the surface is normal, but the A horizon is thin or faint. Both
fine and coarse strata are common below a depth of a few
centimeters.
Andic and Vitrandic Cryofluvents.—These soils are like
Typic Cryofluvents, but they have a layer of pyroclastic
materials that is 18 cm or more thick and that is in the upper
75 cm. Andic and Vitrandic Cryofluvents have slopes of less
than 5 percent. They are of very minor extent, but they have
been observed in the State of Washington.
Aquic Cryofluvents.—These soils are like Typic
Cryofluvents, but they have some redox depletions with low
chroma (2 or less) within the upper 50 cm of the mineral soil
surface in horizons that also have aquic conditions for some
time in normal years (or artificial drainage). These soils are
intergrades to Aquents. They are not extensive even in Alaska.
Mollic Cryofluvents.—These soils have a surface horizon
that meets the criteria for a mollic epipedon, except that it is
too thin or finely stratified. The soils are not extensive. They
are along streams in areas where Cryolls occur, mainly at
intermediate elevations in the mountains of the Western United
States.
Oxyaquic Cryofluvents.—These soils are like Typic
Cryofluvents, but they are saturated with water in one or more
layers within 100 cm of the mineral soil surface for either or
both 20 or more consecutive days or 30 or more cumulative
days in normal years. Some of the soils have redox depletions
with low chroma (2 or less) below 50 cm from the mineral soil
surface. Oxyaquic Cryofluvents are considered intergrades to
Aquents. They are not extensive.
Torrifluvents
These are the Fluvents of arid climates. They have an aridic
(or torric) moisture regime and a temperature regime warmer
than cryic. Most of them have a high pH value and are
calcareous, and a few are somewhat salty. The soils are subject
to flooding, but most are not flooded frequently or for long
periods. The larger areas that have a favorable topography and
are close to a source of water commonly are irrigated. The
natural vegetation on the Torrifluvents in the United States
consisted mostly of grasses, xerophytic shrubs, and cacti, but in
some parts of the world the only vegetation on the soils has
been irrigated crops because the sediments accumulated while
the soils were being cultivated.
Entisols 409
Definition
Torrifluvents are the Fluvents that have an aridic (or torric)
moisture regime and a soil temperature regime warmer than
cryic.
Key to Subgroups
LDDA. Torrifluvents that have:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. A moisture control section that, in normal years, is dry
in all its parts for less than three-fourths of the cumulative
days per year when the soil temperature at a depth of 50 cm
from the soil surface is 5 o
C or higher; and
3. An aridic (or torric) moisture regime that borders on
ustic.
Ustertic Torrifluvents
LDDB. Other Torrifluvents that have one or both of the
following:
1. Cracks within 125 cm of the soil surface that are 5 mm
or more wide through a thickness of 30 cm or more for some
time in most normal years, and slickensides or wedgeshaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the soil surface; or
2. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic, lithic,
or paralithic contact, whichever is shallower.
Vertic Torrifluvents
LDDC. Other Torrifluvents that have:
1. A moisture control section that, in normal years, is dry
in all its parts for less than three-fourths of the cumulative
days per year when the soil temperature at a depth of 50 cm
from the soil surface is 5 o
C or higher; and
2. A thermic, mesic, or frigid soil temperature regime and
an aridic (or torric) moisture regime that borders on xeric;
and
3. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface,
one or both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrixerandic Torrifluvents
LDDD. Other Torrifluvents that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Torrifluvents
LDDE. Other Torrifluvents that have, in one or more
horizons within 100 cm of the soil surface, both redox
depletions with chroma of 2 or less and aquic conditions for
some time in normal years (or artificial drainage).
Aquic Torrifluvents
LDDF. Other Torrifluvents that are saturated with water in
one or more layers within 150 cm of the soil surface in normal
years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Torrifluvents
LDDG. Other Torrifluvents that have:
1. A horizon within 100 cm of the mineral soil surface
that is 15 cm or more thick and that either has 20 percent or
more (by volume) durinodes or is brittle and has a firm
rupture-resistance class when moist; and
2. A moisture control section that, in normal years, is dry
in all its parts for less than three-fourths of the cumulative
days per year when the soil temperature at a depth of 50 cm
from the soil surface is 5 o
C or higher; and
410 Soil Taxonomy
3. A thermic, mesic, or frigid soil temperature regime and an
aridic (or torric) moisture regime that borders on xeric.
Duric Xeric Torrifluvents
LDDH. Other Torrifluvents that have a horizon within 100
cm of the mineral soil surface that is 15 cm or more thick and
that either has 20 percent or more (by volume) durinodes or is
brittle and has a firm rupture-resistance class when moist.
Duric Torrifluvents
LDDI. Other Torrifluvents that have both:
1. A moisture control section that, in normal years, is dry
in all its parts for less than three-fourths of the cumulative
days per year when the soil temperature at a depth of 50 cm
from the soil surface is 5 o
C or higher; and
2. An aridic (or torric) moisture regime that borders on
ustic.
Ustic Torrifluvents
LDDJ. Other Torrifluvents that have both:
1. A moisture control section that, in normal years, is dry
in all its parts for less than three-fourths of the cumulative
days per year when the soil temperature at a depth of 50 cm
from the soil surface is 5 o
C or higher; and
2. A thermic, mesic, or frigid soil temperature regime and
an aridic (or torric) moisture regime that borders on xeric.
Xeric Torrifluvents
LDDK. Other Torrifluvents that have an anthropic epipedon.
Anthropic Torrifluvents
LDDL. Other Torrifluvents.
Typic Torrifluvents
Definition of Typic Torrifluvents
Typic Torrifluvents are the Torrifluvents that:
1. Do not have a horizon within 100 cm of the surface that is
more than 15 cm thick and that either has as much as 20
percent durinodes in a nonbrittle matrix or is brittle and has a
firm rupture-resistance class when moist;
2. Have neither:
a. Cracks within 125 cm of the soil surface that are 5 mm
or more wide through a thickness of 30 cm or more for some
time in normal years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has its upper
boundary within 125 cm of the soil surface; nor
b. A linear extensibility of 6.0 cm or more between the soil
surface and either a depth of 100 cm or a densic, lithic, or
paralithic contact, whichever is shallower;
3. Do not have an anthropic epipedon;
4. Are dry in all parts of the moisture control section for threefourths
or more of the time (cumulative) when the soil
temperature at a depth of 50 cm is 5 o
C or more;
5. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
6. Do not have, in any horizon within 100 cm of the soil
surface, both redox depletions with chroma of 2 or less and
aquic conditions; and
7. Are not saturated with water in any layer within 150 cm of
the soil surface for either or both 30 or more cumulative days
or 20 or more consecutive days in normal years.
Description of Subgroups
Typic Torrifluvents.—These are the driest Fluvents. They
are subject to flooding, but flooding is rare in some areas of the
soils.
Weak cementation by silica is excluded from the Typic
subgroup because it is considered to indicate the initial
development of a duripan. Cracks and slickensides or wedgeshaped
aggregates are properties shared with Vertisols and are
the basis for defining the Vertic subgroup. Typic Torrifluvents
do not have an anthropic epipedon or a water table within a
depth of 150 cm. They do not have, in the upper 75 cm, a
deposit of pyroclastic materials that is as thick as 18 cm.
The concept of the Typic subgroup is that of the drier part of
the range of Torrifluvents. Extra moisture coming as summer
rain or during summer floods is the basis for defining the Ustic
subgroup. Extra moisture coming as cool-season rain or during
winter floods is the basis for defining the Xeric subgroups.
Typic Torrifluvents are extensive soils in the intermountain
States of the United States. Many of them are irrigated. The
others furnish only a small amount of forage for grazing.
Anthropic Torrifluvents.—These soils are like Typic
Torrifluvents, but they have an anthropic epipedon. They have
been irrigated for many years or even many centuries. They are
not known to occur in the United States. They are mainly along
rivers flowing through deserts in parts of the world with a long
irrigation history.
Aquic Torrifluvents.—These soils have a water table
Entisols 411
within a depth of 100 cm. They have some redox depletions with
chroma of 2 or less within 100 cm of the mineral soil surface,
although chroma of 3 or more is commonly dominant to this
depth or deeper. These soils are intergrades between
Ustifluvents and Aquents. They are not extensive in the United
States as a whole but are locally important on the flood plains
along the larger rivers. Many Aquic Torrifluvents in the United
States are irrigated and cultivated. Some have a water table
that is partly or fully a result of excess irrigation water.
Duric Torrifluvents.—These soils have, within the upper
meter, a horizon that is partially cemented by silica. This
horizon is at least 15 cm thick. It has at least 20 percent
durinodes, by volume, or it is both brittle and firm when moist.
Either of these characteristics causes some interference with
water movement and root penetration. These soils are
intergrades between Fluvents and Durids. They are not
extensive in the United States, but they occur in Nevada. They
are used only as rangeland.
Duric Xeric Torrifluvents.—These soils have a moisture
regime that is marginal to xeric. The moisture control section
is regularly moist in winter and early in spring but is very dry
in summer. These soils have, within the upper meter, a horizon
that is partially cemented by silica. This horizon is 15 cm or
more thick. It has at least 20 percent durinodes, by volume, or
it is both brittle and firm when moist. Either of these
characteristics causes some interference with water movement
and root penetration. These soils are intergrades between
Fluvents and Durixerolls.
The moisture that is stored in winter results in better plant
growth on these soils than on the related Duric Torrifluvents,
which have a lower and less reliable supply of moisture. Duric
Xeric Torrifluvents are rare in the United States. They are used
mainly for winter and spring grazing.
Oxyaquic Torrifluvents.—These soils are like Typic
Torrifluvents, but they are saturated with water in one or more
layers within 150 cm of the mineral soil surface for either or
both 20 or more consecutive days or 30 or more cumulative
days in normal years. Some of the soils have redox depletions
with low chroma (2 or less) at a depth below 100 cm from the
mineral soil surface. Oxyaquic Torrifluvents are considered
intergrades to Aquents. They are not extensive. Some of the
soils have a water table that is partly or fully a result of excess
irrigation water. Oxyaquic Torrifluvents are used mainly as
cropland.
Ustertic Torrifluvents.—These soils have a high linear
extensibility and deep cracks. The moisture that closes the
cracks comes during a growing season when the soils are
warm. These soils are not extensive in the United States, but
they are widely scattered along the rivers in the drier parts of
the northern Great Plains. Some of the soils are irrigated and
used as cropland, and others are used for summer grazing.
Ustic Torrifluvents.—These soils are like Typic
Torrifluvents, but they have more available moisture during
summer or, in tropical regions, during rainy seasons. They
either receive more rainfall or are flooded more frequently than
the soils in the Typic subgroup. Ustic Torrifluvents are moist in
some or all parts of the moisture control section for more than
one-fourth of the time (cumulative) when the soil temperature
at a depth of 50 cm is 5 o
C or higher. These soils are extensive
along the rivers in the drier parts of the Great Plains in the
United States. Many of the soils are irrigated and used as
cropland, and the others are used for summer grazing.
Vertic Torrifluvents.—These soils are like Typic
Torrifluvents, but they have cracks and slickensides or wedgeshaped
aggregates and have many of the properties of Vertisols.
Vertic Torrifluvents are not extensive in the United States.
Some that have a low content of salts are irrigated. Others,
particularly those that are salty, furnish only a small amount of
forage for grazing.
Vitrandic Torrifluvents.—These soils are like Typic
Torrifluvents, but they have a layer of pyroclastic materials that
is 18 cm or more thick and that is in the upper 75 cm. These
soils are of minor extent, mostly in California.
Vitrixerandic Torrifluvents.—These soils are like Typic
Torrifluvents, but they have a moisture regime that is marginal
to xeric. The moisture control section is regularly moist in
winter and early in spring but is very dry in summer. These
soils have a layer of pyroclastic materials that is 18 cm or more
thick and that is in the upper 75 cm. The moisture stored in
winter results in better plant growth on these soils than on the
soils in the Typic subgroup. Vitrixerandic Torrifluvents are of
minor extent in the United States. They are used as rangeland
or cropland.
Xeric Torrifluvents.—These soils are like Typic
Torrifluvents, but they have a moisture regime that is marginal
to xeric. The moisture control section is regularly moist in
winter and early in spring but is very dry in summer. The
moisture stored in winter results in better plant growth on these
soils than on the soils in the Typic subgroup.
Xeric Torrifluvents are moderately extensive in the northern
intermountain States of the United States. Many of the soils are
irrigated and used as cropland, and the others are used for
winter and spring grazing.
Udifluvents
These are the Fluvents that have a udic moisture regime and
a temperature regime warmer than cryic. They are on flood
plains along streams and rivers, and they may be flooded
during almost any season. There is little or no evidence of
alteration of the fine stratification in the alluvium, although in
some Udifluvents that have a fine-silty or fine particle-size
class, identifying the stratification may be difficult. Some
Udifluvents formed under forest vegetation, but many have had
no vegetation other than pasture or cultivated crops because the
sediments in which the soils formed were deposited while the
soils were being used. Udifluvents are extensive in the United
States.
412 Soil Taxonomy
Definition
Udifluvents are the Fluvents that:
1. Have a udic moisture regime; and
2. Have a temperature regime warmer than cryic.
KeytoSubgroups
LDEA. Udifluvents that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. Either or both of the following:
a. In one or more horizons within 50 cm of the mineral
soil surface, redox depletions with chroma of 2 or less
and also aquic conditions for some time in normal years
(or artificial drainage); or
b. In one or more horizons within 100 cm of the
mineral soil surface, a color value, moist, of 4 or more
and either chroma of 0 or hue of 5GY, 5G, 5BG, or 5B
and also aquic conditions for some time in normal years
(or artificial drainage).
Aquertic Udifluvents
LDEB. Other Udifluvents that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm
or a densic, lithic, or paralithic contact, whichever is
shallower.
Vertic Udifluvents
LDEC. Other Udifluvents that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling more than 1.0.
Andic Udifluvents
LDED. Other Udifluvents that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Udifluvents
LDEE. Other Udifluvents that have either:
1. In one or more horizons within 50 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); or
2. In one or more horizons within 100 cm of the mineral
soil surface, a color value, moist, of 4 or more and either
chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic
conditions for some time in normal years (or artificial
drainage).
Aquic Udifluvents
LDEF. Other Udifluvents that are saturated with water in one
or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Udifluvents
LDEG. Other Udifluvents that have either an Ap horizon that
has a color value, moist, of 3 or less and a color value, dry, of 5
or less (crushed and smoothed) or materials in the upper 15 cm
that have these colors after mixing.
Mollic Udifluvents
LDEH. Other Udifluvents.
Typic Udifluvents
Definition of Typic Udifluvents
Typic Udifluvents are the Udifluvents that:
Entisols 413
1. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size, of
1.0 g/cm3
or less, measured at 33 kPa water retention, and
acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
2. Do not have either:
a. In any horizon within 50 cm of the mineral soil surface,
redox depletions with chroma of 2 or less or aquic
conditions; or
b. In any horizon within 100 cm of the mineral soil
surface, a color value, moist, of 4 or more and either chroma
of 0 or hue of 5GY, 5G, 5BG, or 5B or aquic conditions;
3. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for either or both 20 or more
consecutive days or 30 or more cumulative days;
4. Have either an Ap horizon that has a color value, moist,
of 4 or more or a color value, dry, of 6 or more when crushed
and smoothed or materials in the upper 15 cm thick that have
these colors after mixing; and
5. Do not have either of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Description of Subgroups
Typic Udifluvents.—These are the Udifluvents that have
moderately good or good drainage. They occur in relatively
high areas on flood plains, and the water table is deeper than
50 cm all of the time or enough of the time for there to be no
redox depletions with chroma of 2 or less or aquic conditions
within 50 cm of the mineral soil surface and no chroma of 0 or
hue bluer than 10Y or aquic conditions within a depth of 100
cm. The Typic subgroup excludes soils that have either cracks
and slickensides or wedge-shaped aggregates or a linear
extensibility of 6.0 or more within 100 cm of the mineral soil
surface. Typic Udifluvents are considered intergrades to
Vertisols. They do not have, in the upper 75 cm, a deposit of
pyroclastic materials that is as thick as 18 cm. They are
extensive along the rivers in the humid parts of the United
States and in many other countries. If redox depletions are
shallow, the soils are excluded from the Typic subgroup and are
considered intergrades to Aquents. Most of the Typic
Udifluvents in the United States are used as cropland if the
areas of the soils are large enough.
Andic and Vitrandic Udifluvents.—These soils are like
Typic Udifluvents, but they have a layer of pyroclastic
materials that is 18 cm or more thick and that is in the upper
75 cm. They are of minor extent, mostly in the States of
Washington and Oregon.
Aquertic Udifluvents.—These soils have either cracks and
slickensides or wedge-shaped aggregates or a linear
extensibility of 6.0 or more within 100 cm of the mineral soil
surface. They also have a water table that is shallower than the
one in Typic Udifluvents or that persists for longer periods
within a depth of 50 cm. They have some redox depletions with
chroma of 2 or less within 50 cm of the mineral soil surface,
although chroma of 3 or more is dominant to this depth or
deeper, or they have chroma of 0 or hue bluer than 10Y in one
or more horizons at a depth between 50 and 100 cm below the
mineral soil surface. In either situation, they have aquic
conditions for some time in normal years within these depths
(or artificial drainage). These soils are intergrades between
Udifluvents and Aquerts. They are not extensive in the United
States as a whole but are locally important on the flood plains
along some of the larger rivers. Most of the Aquertic
Udifluvents in the United States have been cleared and are used
as cropland.
Aquic Udifluvents.—These soils have a water table that is
shallower than the one in Typic Udifluvents or that persists for
longer periods within a depth of 50 cm. They have some redox
depletions with chroma of 2 or less within 50 cm of the
mineral soil surface, although chroma of 3 or more is dominant
to this depth or deeper, or they have chroma of 0 or hue bluer
than 10Y in one or more horizons at a depth between 50 and
100 cm below the mineral soil surface. In either situation, they
have aquic conditions for some time in normal years within
these depths (or artificial drainage). These soils are intergrades
between Udifluvents and Aquents. They are not extensive in
the United States as a whole but are locally extensive on the
flood plains along the larger rivers. Nearly all of the Aquic
Udifluvents in the United States are used as cropland.
Mollic Udifluvents.—These soils differ from Typic
414 Soil Taxonomy
Udifluvents in that the Ap horizon or the upper 15 cm, after
mixing, has colors as dark as those of a mollic epipedon. The
sediments below this depth are finely stratified and may have
dark colors. The soils have not been in place long enough for
mixing by roots and by burrowing animals and insects, volume
changes on wetting and drying, and frost action to have
obliterated the fine strata below the Ap horizon or a depth of
15 cm. Mollic Udifluvents are associated with Udolls in the
central part of the Northern United States. They are adjacent to
streams and are not extensive. Most of them are used as
cropland.
Oxyaquic Udifluvents.—These soils are like Typic
Udifluvents, but they are saturated with water in one or more
layers within 100 cm of the mineral soil surface for either or
both 20 or more consecutive days or 30 or more cumulative
days in normal years. Some of these soils have redox depletions
with low chroma (2 or less) at a depth below 100 cm from the
mineral soil surface. Oxyaquic Udifluvents are considered
intergrades to Aquents. They are not extensive.
Vertic Udifluvents.—These soils have either cracks
and slickensides or wedge-shaped aggregates or a linear
extensibility of 6.0 or more within 100 cm of the mineral
soil surface. The soils are intergrades between Udifluvents
and Uderts. They are not extensive in the United States as
a whole but are locally important on the flood plains along
some of the larger rivers. Most of the Vertic Udifluvents
in the United States have been cleared and are used as
cropland.
Ustifluvents
These are the Fluvents that have an ustic moisture regime
and a temperature regime warmer than cryic. These soils are
on flood plains along rivers and streams in areas of middle or
low latitudes. Flooding can occur in any season but is most
common in summer in the middle latitudes and during the
rainy season in the Tropics. A few of the soils are flooded
regularly in summer because of melting snow in high
mountains, even though the summer is rainless.
Definition
Ustifluvents are the Fluvents that:
1. Have an ustic moisture regime; and
2. Have a temperature regime warmer than cryic.
Key to Subgroups
LDCA. Ustifluvents that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. Either or both of the following:
a. In one or more horizons within 50 cm of the mineral
soil surface, redox depletions with chroma of 2 or less
and also aquic conditions for some time in normal years
(or artificial drainage); or
b. In one or more horizons within 150 cm of the
mineral soil surface, a color value, moist, of 4 or more
and either chroma of 0 or hue of 5GY, 5G, 5BG, or 5B
and also aquic conditions for some time in normal years
(or artificial drainage).
Aquertic Ustifluvents
LDCB. Other Ustifluvents that have both of the following:
1. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that, in normal years, is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that, in normal years, is dry in
some part for six-tenths or more of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that,
in normal years, remains moist in some or all parts for
less than 90 consecutive days per year when the
temperature at a depth of 50 cm below the soil surface is
higher than 8 o
C; and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Torrertic Ustifluvents
Entisols 415
LDCC. Other Ustifluvents that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Ustifluvents
LDCD. Other Ustifluvents that have anthraquic conditions.
Anthraquic Ustifluvents
LDCE. Other Ustifluvents that have either:
1. In one or more horizons within 50 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); or
2. In one or more horizons within 150 cm of the mineral
soil surface, a color value, moist, of 4 or more and either
chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic
conditions for some time in normal years (or artificial
drainage).
Aquic Ustifluvents
LDCF. Other Ustifluvents that are saturated with water in
one or more layers within 150 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Ustifluvents
LDCG. Other Ustifluvents that, when neither irrigated nor
fallowed to store moisture, have one of the following:
1. A frigid soil temperature regime and a moisture control
section that, in normal years, is dry in all parts for fourtenths
or more of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A mesic or thermic soil temperature regime and a
moisture control section that, in normal years, is dry in
some part for six-tenths or more of the cumulative days per
year when the soil temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C; or
3. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that, in
normal years, is moist in some or all parts for less than 180
cumulative days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8 o
C.
Aridic Ustifluvents
LDCH. Other Ustifluvents that, when neither irrigated nor
fallowed to store moisture, have one of the following:
1. A frigid soil temperature regime and a moisture control
section that, in normal years, is dry in some or all parts for
less than 105 cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A mesic or thermic soil temperature regime and a
moisture control section that, in normal years, is dry in
some part for less than four-tenths of the cumulative days
per year when the temperature at a depth of 50 cm below the
soil surface is higher than 5 o
C; or
3. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that, in
normal years, is dry in some or all parts for less than 120
cumulative days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8 o
C.
Udic Ustifluvents
LDCI. Other Ustifluvents that have either an Ap horizon that
has a color value, moist, of 3 or less and a color value, dry, of 5
or less (crushed and smoothed) or materials in the upper 15 cm
that have these colors after mixing.
Mollic Ustifluvents
LDCJ. Other Ustifluvents.
Typic Ustifluvents
Definition of Typic Ustifluvents
Typic Ustifluvents are the Ustifluvents that:
1. Do not have either:
a. In any horizon within 50 cm of the mineral soil surface,
redox depletions with chroma of 2 or less or aquic
conditions; or
b. In any horizon within 150 cm of the mineral soil
surface, a color value, moist, of 4 or more and either chroma
of 0 or hue of 5GY, 5G, 5BG, or 5B or aquic conditions;
2. Are not saturated with water in any layer within 150 cm of
the mineral soil surface for either or both 20 or more
consecutive days or 30 or more cumulative days;
3. Do not have anthraquic conditions;
4. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
416 Soil Taxonomy
wedge-shaped aggregates in a layer 15 cm or more thick that
has its upper boundary within 125 cm of the mineral soil
surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
5. Have either an Ap horizon that has a color value, moist, of
4 or more or a color value, dry, of 6 or more when crushed and
smoothed or materials in the upper 15 cm that have these
colors after mixing; and
6. When neither irrigated nor fallowed to store moisture,
have one of the following:
a. A frigid soil temperature regime and a moisture control
section that, in normal years, is dry in some or all parts for
105 or more cumulative days per year but is not dry in all
parts for four-tenths or more of the cumulative days per year
when the soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that, in normal years, is dry in
some part for four- to six-tenths of the cumulative days per
year when the temperature at a depth of 50 cm below the
soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that, in
normal years, is dry in some or all parts for 120 or more
cumulative days and moist for 180 or more cumulative days
per year when the temperature at a depth of 50 cm below the
soil surface is higher than 8 o
C.
Description of Subgroups
Typic Ustifluvents.—These are the Ustifluvents that have
good or moderately good drainage and that do not have a fine
particle-size class and clay of a swelling type in a major part of
the upper 125 cm. These soils occur in relatively high areas on
flood plains, and the water table is deeper than 100 cm, except
for very brief periods. There are no redox depletions with
chroma of 2 or less or aquic conditions within 50 cm of the
mineral soil surface and no chroma of 0 or hue bluer than 10Y
or aquic conditions within a depth of 100 cm.
There normally is little or no evidence of alteration of the
fine stratification in the alluvium. In some Typic Ustifluvents
that have a fine-silty or fine particle-size class, however,
stratification cannot be easily identified. Typic Ustifluvents are
extensive along streams in the subhumid or semiarid parts of
the Great Plains in the United States and also are extensive in
many other countries. Many of these soils are used as cropland,
with or without irrigation. Others are used for summer grazing.
Anthraquic Ustifluvents.—These soils are like Typic
Ustifluvents, but they have a human-made perched water table
near the soil surface. They commonly have some redox
depletions with chroma of 2 or less in the Ap horizon. They are
intergrades between Ustifluvents and Aquents. Anthraquic
Ustifluvents may or may not have an Ap horizon or material in
the upper 15 cm that would be a mollic epipedon, except that
the layer rests on finely stratified sediment. These soils are not
known to occur in the United States. They are irrigated and are
used for paddy rice.
Aquertic Ustifluvents.—These soils have aquic conditions
within 50 cm of the mineral soil surface for some time in
normal years and have a high shrink-swell potential. They are
of limited extent in the West and on the Great Plains in the
United States. They commonly are used as grazing land.
Aquic Ustifluvents.—These soils have a shallower water
table than that in Typic Ustifluvents or one that persists for
long periods within a depth of 150 cm. They commonly have
some redox depletions with chroma of 2 or less within 50 cm of
the mineral soil surface, or they have chroma of 0 or hue bluer
than 10Y at some depth between 50 and 150 cm. They are
intergrades between Ustifluvents and Aquents. Aquic
Ustifluvents may or may not have an Ap horizon or material in
the upper 15 cm that would be a mollic epipedon, except that
the layer rests on finely stratified sediment. These soils are not
extensive in the United States. Most of them are used as
cropland, some of which is irrigated.
Aridic Ustifluvents.—These soils are drier than Typic
Ustifluvents. They are intergrades between Ustifluvents and
Torrifluvents. They are moderately extensive in the southern
part of the Great Plains of the United States. Slopes in general
are gentle or moderate. Many of these soils are used for
grazing, and others are used as cropland. Some of the cropland
is irrigated, and some is used for drought-tolerant crops.
Mollic Ustifluvents.—These soils differ from Typic
Ustifluvents in that the Ap horizon or the upper 15 cm, after
mixing, has colors as dark as those of a mollic epipedon. The
sediments below this depth are finely stratified and may have
dark colors. The soils have not been in place long enough for
mixing by roots and by burrowing animals and insects, volume
changes on wetting and drying, and frost action to have
obliterated the fine strata below the Ap horizon or a depth of
15 cm. Mollic Ustifluvents are associated with Ustolls on the
Great Plains and in areas to the west in the United States. They
are adjacent to streams and are not extensive. They are used as
cropland or grazing land.
Oxyaquic Ustifluvents.—These soils have a shallower
water table than that in Typic Ustifluvents. The water table
persists for either or both 20 or more consecutive days or 30 or
more cumulative days within a depth of 150 cm. The soils
commonly have some redox depletions with chroma of 2 or less
at a depth between 50 and 150 cm below the mineral soil
surface. They are intergrades between Ustifluvents and
Aquents. They may or may not have an Ap horizon or material
in the upper 15 cm that would be a mollic epipedon, except
Entisols 417
that the layer rests on finely stratified sediment. These soils are
not extensive in the United States. Most of them are used as
cropland, with or without irrigation.
Torrertic Ustifluvents.—These soils are drier than Typic
Ustifluvents. They have cracks and high COLE values, which
are properties shared with Vertisols. They do not yet have the
properties that are diagnostic for Vertisols. Because there are
no restrictions on the color value of Vertisols, Torrertic
Ustifluvents are permitted, but not required, to have a lower
color value than the soils in the Typic subgroup. Torrertic
Ustifluvents are rare in the United States. Some of them are
used as cropland, with or without irrigation, and the others are
used as grazing land.
Udic Ustifluvents.—These soils are like Typic Ustifluvents,
but they are less dry. They are dry in some part of the moisture
control section for less than four-tenths of the cumulative days
when the soil temperature at a depth of 50 cm exceeds 5 o
C if
the soil temperature regime is mesic or thermic. They are dry
in some or all parts of the moisture control section for less than
90 days during a period when the soil temperature at a depth of
50 cm exceeds 8 o
C if the soil temperature regime is
hyperthermic, isomesic, or warmer. These soils are intergrades
between Ustifluvents and Udifluvents. They are moderately
extensive on the Great Plains in the United States. Their slopes
are gentle. Where areas are large, most of these soils are used
as cropland.
Vertic Ustifluvents.—These soils are like Typic
Ustifluvents, but they have cracks and high COLE values,
which are properties shared with Vertisols. They do not yet
have the properties that are diagnostic for Vertisols. Because
there are no restrictions on the color value of Vertisols, Vertic
Ustifluvents are permitted, but not required, to have a lower
color value than the soils in the Typic subgroup. Vertic
Ustifluvents are rare in the United States. Some of them are
used as cropland, with or without irrigation, and the others are
used as grazing land.
Xerofluvents
These are the Fluvents that have a xeric moisture regime
and a frigid, mesic, or thermic temperature regime. These soils
are on flood plains along rivers or streams or on alluvial fans,
mostly in areas with Mediterranean climates. Flooding is most
common in winter, but some of the soils are flooded in spring
because of melting snow in the nearby mountains. Not all
Fluvents in Mediterranean climates are Xerofluvents. Some are
flooded during summer because of melting snow in high
mountains. This flooding can supply moisture during the
summer. The vegetation on Xerofluvents is commonly mixed
forest or grass and shrubs. The Xerofluvents in the United
States are mostly in California and the Northwestern States.
The soils are moderately extensive.
Definition
Xerofluvents are the Fluvents that have a xeric moisture
regime and a frigid, mesic, or thermic soil temperature
regime.
Key to Subgroups
LDBA. Xerofluvents that have one or both of the following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Xerofluvents
LDBB. Other Xerofluvents that have:
1. In one or more horizons within 50 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); or
2. In one or more horizons within 150 cm of the mineral
soil surface, a color value, moist, of 4 or more and either
chroma of 0 or hue bluer than 10Y and also aquic
conditions for some time in normal years (or artificial
drainage); and
3. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface,
one or more of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Xerofluvents
418 Soil Taxonomy
LDBC. Other Xerofluvents that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm of
the mineral soil surface, a fine-earth fraction with both a bulk
density of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and Al plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0.
Andic Xerofluvents
LDBD. Other Xerofluvents that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Xerofluvents
LDBE. Other Xerofluvents that have either:
1. In one or more horizons within 50 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); or
2. In one or more horizons within 150 cm of the mineral
soil surface, a color value, moist, of 4 or more and either
chroma of 0 or hue of 5GY, 5G, 5BG, or 5B or aquic
conditions for some time in normal years.
Aquic Xerofluvents
LDBF. Other Xerofluvents that are saturated with water in
one or more layers within 150 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Xerofluvents
LDBG. Other Xerofluvents that have a horizon within 100
cm of the mineral soil surface that is 15 cm or more thick and
that either has 20 percent or more (by volume) durinodes or is
brittle and has a firm rupture-resistance class when moist.
Durinodic Xerofluvents
LDBH. Other Xerofluvents that have either an Ap horizon
that has a color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed) or materials in the upper 15
cm that have these colors after mixing.
Mollic Xerofluvents
LDBI. Other Xerofluvents.
Typic Xerofluvents
Definition of Typic Xerofluvents
Typic Xerofluvents are the Xerofluvents that:
1. Do not have either:
a. In any horizon within 50 cm of the mineral soil surface,
redox depletions with chroma of 2 or less or aquic
conditions; or
b. In any horizon within 150 cm of the mineral soil
surface, a color value, moist, of 4 or more and either chroma
of 0 or hue of 5GY, 5G, 5BG, or 5B or aquic conditions;
2. Are not saturated with water in any layer within 150 cm of
the mineral soil surface in normal years for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
3. Do not have a horizon within 100 cm of the surface that is
more than 15 cm thick and that either has 20 percent or more
durinodes or is brittle and has a firm rupture-resistance class
when moist;
4. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
5. Have either an Ap horizon that has a color value, moist,
of 4 or more or a color value, dry, of 6 or more when crushed
and smoothed or materials in the upper 15 cm that have these
colors after mixing; and
6. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, any of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
Entisols 419
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Description of Subgroups
Typic Xerofluvents.—The central concept or Typic
subgroup of Xerofluvents is fixed on soils that have good or
moderately good drainage, that show little or no evidence of
cementation by silica, and that do not have a fine particle-size
class and clay of a swelling type in the upper 100 cm. These
soils do not have, in the upper 75 cm, a deposit of pyroclastic
materials that is as thick as 18 cm. They are in relatively high
areas on flood plains, and the water table is deeper than 150
cm in normal years.
Partial cementation by silica causes soils to be excluded
from the Typic subgroup because this feature is considered to
indicate an intergrade to Durids or Durixerepts. Soils that have
cracks and slickensides or wedge-shaped aggregates are
excluded from the Typic subgroup because they have most of
the properties of Xererts. Presumably, the deposits are too
recent to have the evidence of movement that is necessary in
Vertisols.
Typic Xerofluvents are moderately extensive in the Western
United States. They are nearly level and are used mostly as
pasture or irrigated cropland.
Andic and Vitrandic Xerofluvents.—These soils are like
Typic Xerofluvents, but they have a surface mantle or layer in
the upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. These
soils occur on flood plains in the Western United States. They
are permitted, but not required, to have color value of 3 or less,
moist, and 5 or less, dry, in surface horizons, after mixing to a
depth of 15 cm. These soils are of small extent. Most have
gentle slopes, have been cleared and protected from flooding,
and are used as cropland. Some are used as forest or pasture.
Aquandic Xerofluvents.—These soils have, in one or more
horizons within 50 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage), or they
have, in one or more horizons within 150 cm of the mineral
soil surface, a color value, moist, of 4 or more and either
chroma of 0 or hue bluer than 10Y and also aquic conditions
for some time in normal years (or artificial drainage). The soils
have a surface mantle or layer in the upper 75 cm that has both
a low bulk density and a high content of weakly crystalline
minerals or that consists of slightly or moderately weathered
pyroclastic materials. These soils occur on flood plains in the
Western United States. They are permitted, but not required, to
have a color value of 3 or less, moist, and 5 or less, dry, in
surface horizons, after mixing to a depth of 15 cm. The soils
are not extensive. Most have gentle slopes, have been cleared
and protected from flooding, and are used as cropland. Some
are used as pasture or forest.
Aquic Xerofluvents.—These soils have, in one or more
horizons within 50 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage), or they
have, in one or more horizons within 150 cm of the mineral
soil surface, a color value, moist, of 4 or more and either
chroma of 0 or hue bluer than 10Y and also aquic conditions
for some time in normal years (or artificial drainage). The soils
are otherwise like Typic Xerofluvents in defined properties, but
they tend to have more salts bacause of capillary rise and
evapotranspiration. Aquic Xerofluvents are on nearly level
flood plains. They are used mostly as irrigated cropland or
pasture. Some are used for native pasture, hay, or grazing.
These soils are moderately extensive in the Western United
States.
Durinodic Xerofluvents.—These soils differ from Typic
Xerofluvents in that they are partially cemented by silica. They
are in relatively high areas on flood plains, and the water table
is deeper than 150 cm in normal years. Durinodic Xerofluvents
are intergrades to Durids or Durixerepts. They are nearly level
and are used for native pasture or irrigated crops. They are not
extensive in the United States.
Mollic Xerofluvents.—These soils differ from Typic
Xerofluvents in that the Ap horizon or the upper 15 cm, after
mixing, has colors as dark as those of a mollic epipedon. The
sediments below this depth are finely stratified and may have
dark colors. The soils have not been in place long enough for
mixing by roots and by burrowing animals and insects, wetting
and drying, and frost action to have obliterated the fine strata
below the Ap horizon or a depth of 15 cm. Mollic Xerofluvents
are associated with Xerolls in the Western United States. They
are adjacent to streams and are not extensive.
Oxyaquic Xerofluvents.—These soils are like Typic
Xerofluvents, but they are saturated with water in one or more
layers within 150 cm of the mineral soil surface for either or
both 20 or more consecutive days or 30 or more cumulative
days in normal years. Some of the soils have redox depletions
with low chroma (2 or less) at a depth below 100 cm from the
mineral soil surface. Oxyaquic Xerofluvents are considered
intergrades to Aquents. They are not extensive. Some have a
water table that is partly or fully a result of excess irrigation
water.
Vertic Xerofluvents.—These soils have a fine texture and
deep, wide cracks, but they do not yet have all of the properties
that are diagnostic for Vertisols. There is no restriction on the
presence of ground water above a depth of 150 cm. Vertic
420 Soil Taxonomy
Xerofluvents generally are in low areas on flood plains. They
are rare in the United States.
Orthents
These are primarily Entisols on recent erosional surfaces. The
erosion may be geologic or may have been induced by
cultivation, mining, or other factors. Any former soil that was
on the landscape has been completely removed or so truncated
that the diagnostic horizons for all other orders do not occur. A
few Orthents are in areas of recent loamy or fine eolian
deposits, in areas of solifluction or glacial deposits, or in areas
of debris from recent landslides and mudflows.
Orthents occur in any climate and under any vegetation.
They are do not occur in areas that have aquic conditions, a
high water table, and the colors defined for Aquents or on
shifting or stabilized sand dunes.
Definition
Orthents are the Entisols that:
1. Have a texture of loamy very fine sand or finer or 35
percent (by volume) or more rock fragments in some layer
within the particle-size control section;
2. Do not have fragments of diagnostic horizons that can be
identified and that occur more or less without a discernible
order below any Ap horizon but above a depth of 100 cm or
above a densic, lithic, or paralithic contact that is shallower
than 100 cm;
3. Have a slope of more than 25 percent or have a content of
Holocene-age organic carbon that decreases regularly with
increasing depth and reaches a level of 0.2 percent or less
within a depth of 125 cm; and
4. Do not have, within 50 cm of the mineral soil surface,
aquic conditions; and
a. The colors defined for Aquents; or
b. Sulfidic materials; or
c. A positive reaction to alpha,alpha-dipyridyl when the
soil is not being irrigated.
Key to Great Groups
LEA. Orthents that have a cryic soil temperature regime.
Cryorthents, p. 420
LEB. Other Orthents that have an aridic (or torric) moisture
regime.
Torriorthents, p. 421
LEC. Other Orthents that have a xeric moisture regime.
Xerorthents, p. 430
LED. Other Orthents that have an ustic moisture regime.
Ustorthents, p. 426
LEE. Other Orthents.
Udorthents, p. 425
Cryorthents
These are the Orthents of high mountains or high latitudes.
Most of them are sandy-skeletal, are on slopes where rock is
very shallow, or are in areas of recent solifluction or volcanic
deposits. The vegetation may be coniferous forest, tundra, or
even the sparse vegetation of very cold, dry areas. Few areas
are cultivated. These soils are of small extent in high
mountains and in areas of tundra vegetation in the United
States. Some of the soils are cold and dry, have a thin
efflorescence of salt on the surface during summer, and may be
dry in all horizons during some periods. Most of the
Cryorthents in the United States still support their native
vegetation.
Definition
Cryorthents are the Orthents that have a cryic soil
temperature regime.
Key to Subgroups
LEAA. Cryorthents that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Cryorthents
LEAB. Other Cryorthents that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Cryorthents
LEAC. Other Cryorthents that have, in one or more horizons
within 50 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Cryorthents
LEAD. Other Cryorthents that are saturated with water in
Entisols 421
one or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Cryorthents
LEAE. Other Cryorthents that have lamellae within 200 cm
of the mineral soil surface.
Lamellic Cryorthents
LEAF. Other Cryorthents.
Typic Cryorthents
Definition of Typic Cryorthents
Typic Cryorthents are the Cryorthents that:
1. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
2. Do not have, in any horizon within 50 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
3. Are not saturated with water in any layer within 100 cm of
the mineral soil surface in normal years for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
4. Do not have a lithic contact within 50 cm of the soil
surface; and
5. Do not have lamellae within 200 cm of the mineral soil
surface.
Description of Subgroups
Typic Cryorthents.—These are the Cryorthents that are not
saturated with water within a depth of 100 cm and that, in the
upper 75 cm, do not have a deposit of pyroclastic materials that
is as thick as 18 cm. Most of the soils are sandy-skeletal or
very shallow to a paralithic or densic contact. Most are in
forests, and they have an O horizon, a thin or sandy A horizon,
and a B horizon too sandy or too thin to be a cambic horizon.
Typic Cryorthents do not have diagnostic horizons other than
an ochric epipedon. Because cultivation is not likely in the
foreseeable future, the soils cannot have a cambic horizon even
if the base is at a depth of less than 25 cm below the mineral
soil surface. Typic Cryorthents are of small extent.
Aquic Cryorthents.—These soils are saturated with water
within 50 cm of the surface at some time during normal years
and have redox depletions with chroma of 2 or less within that
depth. The dominant chroma, however, is more than 2. These
soils are considered intergrades to Cryaquents. They are rare in
the United States.
Lamellic Cryorthents.—These soils have lamellae within
200 cm of the soil surface. The uppermost lamellae commonly
are within 75 cm of the soil surface, but other lamellae may be
as deep as 200 cm. These soils are of very small extent, mostly
in the mountains of the Western United States. They formed
under coniferous forest vegetation.
Lithic Cryorthents.—These soils have a lithic contact
within 50 cm of the soil surface and commonly at a depth
appreciably less than 50 cm. The soils may be saturated with
water above the lithic contact when snow melts. They are of
small extent, mostly in the mountains of the Western United
States. Some are in Alaska, and some are in the mountains of
the Northeastern United States. Lithic Cryorthents formed
under forest vegetation or under grasses and shrubs.
Oxyaquic Cryorthents.—These soils are saturated with
water within 100 cm of the surface at some time during normal
years. They can have redox depletions that have chroma of 2 or
less below a depth of 50 cm. These soils are considered
intergrades to Cryaquents. They are rare in the United States.
Vitrandic Cryorthents.—These soils formed in volcanic
deposits or have a deposit of fine pyroclastic materials near the
surface. Most of these deposits are of Holocene or historic age.
These soils are considered intergrades to Vitricryands. They are
of small extent, mostly in the mountains of the Western United
States.
Torriorthents
These are the dry Orthents of cool to hot, arid regions. They
have an aridic (or torric) moisture regime and a temperature
regime warmer than cryic. Generally, they are neutral or
calcareous and are on moderate to very steep slopes. A few are
on gentle slopes. Many of the gently sloping soils are on rock
pediments, are very shallow, have a sandy-skeletal particle-size
class, or are salty. Others are on fans where sediments are
recent but have little organic carbon. The vegetation on
Torriorthents commonly is sparse and consists mostly of
xerophytic shrubs and ephemeral grasses and forbs. The
vegetation on a few of the soils is saltgrass. Torriorthents are
422 Soil Taxonomy
used mainly for grazing. They are extensive in the Western
United States.
Definition
Torriorthents are the Orthents that have an aridic (or torric)
moisture regime and have a soil temperature regime warmer
than cryic.
Key to Subgroups
LEBA. Torriorthents that have:
1. A lithic contact within 50 cm of the soil surface; and
2. A moisture control section that, in normal years, is dry
in all its parts for less than three-fourths of the cumulative
days per year when the soil temperature at a depth of 50 cm
from the soil surface is 5 o
C or higher; and
3. A hyperthermic, thermic, mesic, frigid, or iso soil
temperature regime and an aridic (or torric) moisture
regime that borders on ustic.
Lithic Ustic Torriorthents
LEBB. Other Torriorthents that have:
1. A lithic contact within 50 cm of the soil surface; and
2. A moisture control section that, in normal years, is dry
in all its parts for less than three-fourths of the cumulative
days per year when the soil temperature at a depth of 50 cm
from the soil surface is 5 o
C or higher; and
3. A thermic, mesic, or rigid soil temperature regime and
an aridic (or torric) moisture regime that borders on xeric.
Lithic Xeric Torriorthents
LEBC. Other Torriorthents that have a lithic contact within
50 cm of the soil surface.
Lithic Torriorthents
LEBD. Other Torriorthents that have:
1. One or both of the following:
a. Cracks within 125 cm of the soil surface that are 5
mm or more wide through a thickness of 30 cm or more
for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the soil
surface; or
b. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact, whichever is shallower; and
2. A moisture control section that, in normal years, is dry
in all its parts for less than three-fourths of the cumulative
days per year when the soil temperature at a depth of 50 cm
from the soil surface is 5 o
C or higher; and
3. A thermic, mesic, or frigid soil temperature regime and an
aridic (or torric) moisture regime that borders on xeric.
Xerertic Torriorthents
LEBE. Other Torriorthents that have:
1. One or both of the following:
a. Cracks within 125 cm of the soil surface that are 5
mm or more wide through a thickness of 30 cm or more
for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the soil
surface; or
b. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact, whichever is shallower; and
2. A moisture control section that, in normal years, is dry
in all its parts for less than three-fourths of the cumulative
days per year when the soil temperature at a depth of 50 cm
from the soil surface is 5 o
C or higher; and
3. An aridic (or torric) moisture regime that borders on
ustic.
Ustertic Torriorthents
LEBF. Other Torriorthents that have one or both of the
following:
1. Cracks within 125 cm of the soil surface that are 5 mm
or more wide through a thickness of 30 cm or more for some
time in normal years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has its upper
boundary within 125 cm of the soil surface; or
2. A linear extensibility of 6.0 cm or more between the
soil surface and either a depth of 100 cm or a densic, lithic,
or paralithic contact, whichever is shallower.
Vertic Torriorthents
LEBG. Other Torriorthents that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Torriorthents
Entisols 423
LEBH. Other Torriorthents that have, in one or more horizons
within 100 cm of the soil surface, redox depletions with chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage).
Aquic Torriorthents
LEBI. Other Torriorthents that are saturated with water in
one or more layers within 150 cm of the soil surface in normal
years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Torriorthents
LEBJ. Other Torriorthents that have a horizon within 100 cm
of the soil surface that is 15 cm or more thick and that either
has 20 percent or more (by volume) durinodes or is brittle and
has a firm rupture-resistance class when moist.
Duric Torriorthents
LEBK. Other Torriorthents that have both:
1. A moisture control section that, in normal years, is dry
in all its parts for less than three-fourths of the cumulative
days per year when the soil temperature at a depth of 50 cm
from the soil surface is 5 o
C or higher; and
2. A hyperthermic, thermic, mesic, frigid, or iso soil
temperature regime and an aridic (or torric) moisture
regime that borders on ustic.
Ustic Torriorthents
LEBL. Other Torriorthents that have both:
1. A moisture control section that, in normal years, is dry
in all its parts for less than three-fourths of the cumulative
days per year when the soil temperature at a depth of 50 cm
from the soil surface is 5 o
C or higher; and
2. A thermic, mesic, or frigid soil temperature regime
and an aridic (or torric) moisture regime that borders on
xeric.
Xeric Torriorthents
LEBM. Other Torriorthents.
Typic Torriorthents
Definition of Typic Torriorthents
Typic Torriorthents are the Torriorthents that:
1. Do not have a horizon within 100 cm of the surface that is
more than 15 cm thick and that either has 20 percent or more
durinodes or is brittle and has a firm rupture-resistance class
when moist;
2. Do not have a lithic contact within 50 cm of the surface;
3. Do not have either:
a. Cracks within 125 cm of the soil surface that are 5 mm or
more wide through a thickness of 30 cm or more for some time
in normal years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has its upper
boundary within 125 cm of the soil surface; or
b. A linear extensibility of 6.0 cm or more between the soil
surface and either a depth of 100 cm or a densic, lithic, or
paralithic contact, whichever is shallower;
4. Are dry in all parts of the moisture control section for
three-fourths or more of the time (cumulative) when the soil
temperature at a depth of 50 cm is 5 o
C or higher;
5. Do not have, in any horizon within 100 cm of the soil
surface, redox depletionswith chroma of 2 or less and also
aquic conditions;
6. Are not saturated with water in any layer within 150 cm of
the soil surface for either or both 30 or more cumulative days
or 20 or more consecutive days in normal years; and
7. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Description of Subgroups
Typic Torriorthents.—The Typic subgroup is fixed on the
driest Torriorthents. Many of these soils are shallow to weakly
cemented rock. Some are moderately deep or deep to hard rock.
Soils that are partially cemented by silica are excluded from
the Typic subgroup because this feature is considered to
indicate the initial development of a duripan. The Torriorthents
that have a high linear extensibility or cracks and slickensides
or wedge-shaped aggregates also are excluded because they
share so many properties with Torrerts. Typic Torriorthents do
not have, in the upper 75 cm, a deposit of pyroclastic materials
that is as thick as 18 cm.
Typic Torriorthents are extensive soils in the intermountain
States of the United States. Most of them have moderate or
strong slopes and are used only for grazing. Others that have
gentle slopes are irrigated. The gently sloping soils are mostly
on fans or piedmont slopes where the sediments are recent and
have little organic carbon.
424 Soil Taxonomy
Aquic Torriorthents.—These soils have, in one or more
horizons within 100 cm of the soil surface, redox depletions
with chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage). The soils formed
mostly in recent alluvium, but they have too little organic
matter to meet the requirements for Fluvents. Ground water is
evident mostly during the high-water stages of streams. Most
Aquic Torriorthents have conductivity well in excess of 2 dS/m
as a result of salts that accumulate through capillary rise and
evapotranspiration. Soil moisture depends greatly on
subirrigation and is unpredictable, and there are no restrictions
on it in the definition. These soils are rare in the United States.
They have gentle slopes, and many of them are irrigated.
Duric Torriorthents.—These soils are partially cemented
by silica. In the soils in the United States, the cementation is in
the form of durinodes. Duric Torriorthents formed mostly in
rather recent alluvium, but they have too little organic matter
to meet the requirements for Fluvents. Most of the soils have
conductivity well in excess of 2 dS/m. The parent materials
were derived from rocks rich in pyroclastic materials. Duric
Torriorthents are rare in the United States.
Lithic Torriorthents.—These soils have a lithic contact
that is within 50 cm of the surface and commonly is at a depth
of less than 25 cm. They have a low moisture-storage capacity,
and they occur mostly in association with soils of other orders
or subgroups that have more moisture available to plants.
Lithic Torriorthents are of moderate extent in the United
States. They are used mostly for winter or spring grazing.
Lithic Ustic Torriorthents.—These soils have more
available moisture than Lithic Torriorthents during summer or,
if located in the Tropics, during the rainy seasons. They are
moist in some or all parts of the moisture control section for
more than one-fourth of the time (cumulative) when the soil
temperature at a depth of 50 cm exceeds 5 o
C. They have a
shallow or very shallow lithic contact, which limits the
moisture-storage capacity. Consequently, the soils commonly
are associated with the Ustalfs and Ustolls on more stable
surfaces. Lithic Ustic Torriorthents are of moderate extent in
the United States. They are used mostly for winter or spring
grazing.
Lithic Xeric Torriorthents.—These soils have a lithic
contact within 50 cm of the surface and have more available
moisture than the soils of the Lithic subgroup. They are in
regions that have enough winter precipitation for the moisture
control section to be moist in all parts during late winter or
early spring, but they are continuously dry in all parts of the
moisture control section for most of the summer in normal
years. The lithic contact commonly limits the moisture-storage
capacity of the moisture control section. Lithic Xeric
Torriorthents are of moderate extent in the United States. They
are used mostly for winter or spring grazing.
Oxyaquic Torriorthents.—These soils are like Typic
Torriorthents, but they are saturated with water in one or more
layers within 150 cm of the mineral soil surface for either or
both 20 or more consecutive days or 30 or more cumulative
days in normal years. Some of the soils have redox depletions
with low chroma (2 or less) at a depth below 100 cm from the
mineral soil surface. Oxyaquic Torriorthents are considered
intergrades to Aquents. They are not extensive. Some have a
water table that is partly or fully a result of excess irrigation
water.
Ustertic Torriorthents.—These soils have a high linear
extensibility or cracks and slickensides or wedge-shaped
aggregates. In the soils in the United States, the cracks are
closed in spring and periodically in summer. Most of the soils
have cracks and a high linear extensibility. Some have all of
the properties of Vertisols but have a densic or paralithic
contact at a shallow depth. Most are on flood plains on the
Great Plains. Ustertic Torriorthents are not extensive. Many of
them are used for summer grazing, and some are used as
cropland.
Ustic Torriorthents.—These soils have more available
moisture than Typic Torriorthents during summer or during
rainy seasons in the Tropics. They are moist in some or all
parts of the moisture control section for more than one-fourth
of the time (cumulative) when the soil temperature at a depth
of 50 cm exceeds 5 o
C. These soils can support somewhat more
vegetation than the soils in the Typic subgroup. They
commonly are associated with the Ustolls or Ustalfs on the
gentler slopes of the more stable surfaces. In many areas Ustic
Torriorthents lose an appreciable part of their precipitation as
runoff. These soils are extensive in the United States. They are
used mostly for grazing, but some are used as cropland.
Vertic Torriorthents.—These soils have a high linear
extensibility or cracks and slickensides or wedge-shaped
aggregates. They commonly have two short, undependable
rainy seasons. Slopes of the soils in the United States range
from nearly level to strong. Where slopes are suitable and
water is available, most of the soils are irrigated. Others are
used for grazing. Vertic Torriorthents are of small extent in the
Southwestern United States.
Vitrandic Torriorthents.—These soils are like Typic
Torriorthents, but they formed in volcanic deposits or have a
layer of pyroclastic materials that is 18 cm or more thick and
that is in the upper 75 cm. These soils are of small extent,
mostly in California, Oregon, and Nevada.
Xerertic Torriorthents.—These soils have a high linear
extensibility and cracks that regularly close during a cool or
cold season. They are in areas of winter precipitation and have
a moisture regime that approaches xeric. These soils can
produce more vegetation than the soils of the Typic or Ustic
subgroup because of the reliable supply of moisture stored in
winter. Xerertic Torriorthents are of small extent, mostly in
Utah. Most of these soils are used for grazing, but some are
used as irrigated cropland.
Xeric Torriorthents.—These soils are moist in some part of
the moisture control section for more than one-fourth of the
time when the soil temperature at a depth of 50 cm is 5 o
C or
Entisols 425
higher. They are in areas of winter precipitation and have a
moisture regime that approaches xeric. These soils can produce
more vegetation than the soils of the Typic or Ustic subgroup
because of the reliable supply of moisture stored in winter.
Xeric Torriorthents are extensive in the intermountain and
Pacific States of the United States. Some have moderate to very
steep slopes and formed mostly in weakly cemented country
rock. Others have gentle slopes and formed in alluvium that
had little organic matter. The gently sloping soils are mostly on
fans and piedmont slopes. Where slopes are suitable and water
is available, most of the Xeric Torriorthents are irrigated and
used as cropland. Those that are not irrigated are used mainly
for winter and spring grazing.
Udorthents
These are the Orthents of cool to hot, moist regions. They
have a udic moisture regime and a temperature regime warmer
than cryic. Generally, they are acid to neutral, but some are
calcareous. Slopes generally are moderate to steep but are
gentle in a few areas. Udorthents commonly occur in areas of
very recently exposed regolith, such as loess or till; in areas of
weakly cemented rocks, such as shale; or in areas of thin
regolith over hard rocks. Many of the gently sloping soils are
the result of mining or other earth-moving activities. Some
have a sandy-skeletal particle-size class. The vegetation is
commonly a deciduous forest, or the soils are used as pasture.
Udorthents are extensive soils on steep slopes in the humid
parts of the United States.
Definition
Udorthents are the Orthents that:
1. Have a udic moisture regime; and
2. Have a soil temperature regime warmer than cryic.
Key to Subgroups
LEEA. Udorthents that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Udorthents
LEEB. Other Udorthents that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is equal
to 30 or more.
VitrandicUdorthents
LEEC. Other Udorthents that have, in one or more horizons
within 100 cm of the mineral soil surface, redox depletions
with chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Udorthents
LEED. Other Udorthents that are saturated with water in one
or more layers within 150 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Udorthents
LEEE. Other Udorthents that have 50 percent or more (by
volume) wormholes, wormcasts, and filled animal burrows
between either the Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and either a depth of
100 cm or a densic, lithic, paralithic, or petroferric contact,
whichever is shallower.
Vermic Udorthents
LEEF. Other Udorthents.
Typic Udorthents
Definition of Typic Udorthents
Typic Udorthents are the Udorthents that:
1. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
2. Do not have, in any horizon within 100 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
3. Are not saturated with water in any layer within 150
cm of the mineral soil surface for either or both 30 or more
426 Soil Taxonomy
cumulative days or 20 or more consecutive days in normal
years;
4. Do not have a lithic contact within 50 cm of the mineral soil
surface; and
5. Have less than 50 percent (by volume) wormholes,
wormcasts, and filled animal burrows between the bottom of
the Ap horizon or a depth of 25 cm, whichever is deeper, and
either a depth of 100 cm or a densic, lithic, paralithic, or
petroferric contact if one occurs above a depth of 100 cm.
Description of Subgroups
Typic Udorthents.—The central concept or Typic subgroup
of Udorthents is fixed on soils that are shallow to weakly
cemented rock or deep or moderately deep to rock and that
have deep ground water and low animal activity. Many of these
soils formed in mine spoil or fill material. Some have a densic
contact with compacted layers of soil materials. Typic
Udorthents do not have, in the upper 75 cm, a deposit of
pyroclastic materials that is as thick as 18 cm. These soils are
used mostly as pasture or forest. A few are used as cropland,
and a few are idle.
Aquic Udorthents.—These soils have, in one or more
horizons within 100 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage). The soils
are not extensive in the United States. They have slopes that
range from nearly level to steep. They are used mostly for
grazing or forest, but some that are gently sloping are used for
cultivated crops.
Lithic Udorthents.—These soils have a lithic contact
within 50 cm of the surface. The lithic contact is at a depth of
less than 25 cm in most of the soils. Lithic Udorthents are
otherwise like Typic Udorthents, except that possibly some of
them have very high biological activity above the lithic contact.
Lithic Udorthents are of small extent in the United States.
They are used mostly as pasture or forest. A few of these soils
are used as wildlife habitat.
Oxyaquic Udorthents.—These soils are saturated with
water for 20 consecutive days and/or 30 cumulative days within
150 cm of the mineral soil surface during normal years. They
may or may not have redoximorphic features, but they do not
have redox depletions with chroma of 2 or less within 100 cm
of the mineral soil surface. These soils occur in the
Midwestern and Northeastern United States. The soils in the
Northeast commonly are forested, but some are used for hay
and pasture. The soils in the Midwest are used mostly for crop
production.
Vermic Udorthents.—These soils have been so completely
reworked by animals, generally by earthworms, that distinct
horizons cannot be identified. The soils have not been
identified in the United States but have been observed in other
countries.
Vitrandic Udorthents.—These soils formed in volcanic
deposits or have a deposit of fine pyroclastic material 18 cm
thick or thicker within the upper 75 cm and generally at the
surface. Most of these deposits are of Holocene or historic age.
These soils are considered intergrades to Vitrands. They are of
small extent, mostly in the mountains of the Western United
States.
Ustorthents
These are the Orthents of cool to hot regions. They have an
ustic moisture regime and a temperature regime warmer than
cryic. Generally, they are neutral to calcareous, but some are
acid. Slopes generally are moderate to steep but are gentle in a
few areas. Ustorthents commonly occur in areas of very
recently exposed regolith, mostly weakly cemented sedimentary
deposits, or in areas of thin regolith over hard rocks. The
vegetation in warm regions commonly is a deciduous forest or
savanna. The soils that have a mesic or frigid temperature
regime commonly support scattered grasses mixed with
xerophytic shrubs. Some of the soils that have been cultivated
for a long time probably now consist of what was the C horizon
of other soils, particularly Ustalfs. The cultivated soils probably
never had any vegetation, except for cultivated crops. A few of
the soils that are in areas of loamy-skeletal or sandy-skeletal
sediments, mostly alluvium, have gentle slopes. Ustorthents are
extensive in the United States, particularly on the Great Plains.
Definition
Ustorthents are the Orthents that:
1. Have a soil temperature regime warmer than cryic; and
2. Have an ustic soil moisture regime.
Key to Subgroups
LEDA. Ustorthents that have:
1. A lithic contact within 50 cm of the mineral soil
surface; and
2. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that, in normal years, is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that, in normal years, is dry in
some part for six-tenths or more of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
Entisols 427
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that,
in normal years, remains moist in some or all parts for
less than 90 consecutive days per year when the
temperature at a depth of 50 cm below the soil surface is
higher than 8 o
C.
Aridic Lithic Ustorthents
LEDB. Other Ustorthents that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Ustorthents
LEDC. Other Ustorthents that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that, in normal years, is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that, in normal years, is dry in
some part for six-tenths or more of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that,
in normal years, remains moist in some or all parts for
less than 90 consecutive days per year when the
temperature at a depth of 50 cm below the soil surface is
higher than 8 o
C.
Torrertic Ustorthents
LEDD. Other Ustorthents that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral soil
surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Ustorthents
LEDE. Other Ustorthents that have anthraquic conditions.
Anthraquic Ustorthents
LEDF. Other Ustorthents that have, in one or more horizons
within 100 cm of the mineral soil surface, redox depletions
with chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Ustorthents
LEDG. Other Ustorthents that are saturated with water in
one or more layers within 150 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Ustorthents
LEDH. Other Ustorthents that have a horizon within 100
cm of the mineral soil surface that is 15 cm or more thick
and that either has 20 percent or more (by volume) durinodes
or is brittle and has a firm rupture-resistance class when
moist.
Durinodic Ustorthents
LEDI. Other Ustorthents that have both:
1. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that, in normal years, is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that, in normal years, is dry in
some part for six-tenths or more of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that,
in normal years, remains moist in some or all parts for
less than 90 consecutive days per year when the
temperature at a depth of 50 cm below the soil surface is
higher than 8 o
C; and
2. Throughout one or more horizons with a total thickness
428 Soil Taxonomy
of 18 cm or more within 75 cm of the soil surface, one or both
of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitritorrandic Ustorthents
LEDJ. Other Ustorthents that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Ustorthents
LEDK. Other Ustorthents that, when neither irrigated nor
fallowed to store moisture, have one of the following:
1. A frigid soil temperature regime and a moisture control
section that, in normal years, is dry in all parts for fourtenths
or more of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A mesic or thermic soil temperature regime and a
moisture control section that, in normal years, is dry in
some part for six-tenths or more of the cumulative days per
year when the soil temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C; or
3. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that, in
normal years, is moist in some or all parts for less than 180
cumulative days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8 o
C.
Aridic Ustorthents
LEDL. Other Ustorthents that, when neither irrigated nor
fallowed to store moisture, have one of the following:
1. A frigid soil temperature regime and a moisture control
section that, in normal years, is dry in some or all parts for
less than 105 cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A mesic or thermic soil temperature regime and a
moisture control section that, in normal years, is dry in
some part for less than four-tenths of the cumulative days
per year when the temperature at a depth of 50 cm below the
soil surface is higher than 5 o
C; or
3. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that, in
normal years, is dry in some or all parts for less than 120
cumulative days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8 o
C.
Udic Ustorthents
LEDM. Other Ustorthents that have 50 percent or more (by
volume) wormholes, wormcasts, and filled animal burrows
between either the Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and either a depth of
100 cm or a densic, lithic, paralithic, or petroferric contact,
whichever is shallower.
Vermic Ustorthents
LEDN. Other Ustorthents.
Typic Ustorthents
Definition of Typic Ustorthents
Typic Ustorthents are the Ustorthents that:
1. Do not have, in any horizon within 100 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
2. Are not saturated with water in any layer within 150 cm of
the mineral soil surface for either or both 30 or more
cumulative days or 20 or more consecutive days in normal
years;
3. Do not have anthraquic conditions;
4. Do not have a horizon within 100 cm of the surface that is
more than 15 cm thick and that either has 20 percent or more
durinodes or is brittle and has a firm rupture-resistance class
when moist;
5. Do not have a lithic contact within 50 cm of the surface;
6. Have less than 50 percent (by volume) wormholes,
wormcasts, and filled animal burrows between the bottom of
the Ap horizon or a depth of 25 cm, whichever is deeper, and a
Entisols 429
depth of 100 cm or a densic, lithic, or paralithic or petroferric
contact, whichever is shallower;
7. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
8. When neither irrigated nor fallowed to store moisture,
have one of the following:
a. A frigid soil temperature regime and a moisture control
section that, in normal years, is dry in some or all parts for
105 or more cumulative days per year but is not dry in all
parts for four-tenths or more of the cumulative days per year
when the soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that, in normal years, is dry in
some part for four- to six-tenths of the cumulative days per
year when the temperature at a depth of 50 cm below the
soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that, in
normal years, is dry in some or all parts for 120 or more
cumulative days and moist for 180 or more cumulative days
per year when the temperature at a depth of 50 cm below the
soil surface is higher than 8 o
C; and
9. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the soil surface,
one or both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Description of Subgroups
Typic Ustorthents.—The central concept or Typic subgroup
of Ustorthents is fixed on soils that are deep or moderately deep
to hard rock and that do not have ground water within a depth
of 150 cm, do not have appreciable cementation by silica, do
not have high biologic activity, do not have a clayey texture
and a swelling type of clay, and do not have, in the upper 75
cm, a deposit of pyroclastic materials that is as thick as 18 cm.
The most common of these soils have a thin or very thin ochric
epipedon resting on weakly cemented rock or on sediments.
Some Typic Ustorthents formed in mine spoil or fill material.
Soils that have a shallow lithic contact are excluded from the
Typic subgroup, a convention used throughout this taxonomy.
Slopes of Typic Ustorthents range from nearly level to very
steep. These soils are used mostly for grazing, forest, or
catchments, but some are used for nonirrigated grain and a few
that have gentle slopes are used as irrigated cropland. Typic
Ustorthents are of moderate extent on the Great Plains in the
United States.
Anthraquic Ustorthents.—These soils are like Typic
Ustorthents, but they have a human-made perched water table
near the soil surface. They commonly have some redox
depletions with chroma of 2 or less in the Ap horizon. They are
intergrades between Ustorthents and Aquents. Anthraquic
Ustorthents are not known to occur in the United States. They
are irrigated and are used for paddy rice.
Aquic Ustorthents.—These soils have, in one or more
horizons within 100 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage). The soils
are on low terraces or fans, in areas of sediments that are partly
sandy and partly loamy. Ground water is shallow during wet
periods or during periods when snow melts on the adjacent
mountains. The water has a very low salt content. These soils
either are nearly level or are in depressions. They commonly
have been drained and are used for irrigated crops. They are
not extensive in the United States.
Aridic Lithic Ustorthents.—These are the Ustorthents that
are drier than the soils in the Typic subgroup and have a lithic
contact within 50 cm of the mineral soil surface. Aridic Lithic
Ustorthents occur in the more arid regions of the Great Plains
in the United States. They range from gently sloping to steep.
Most are used as rangeland and wildlife habitat.
Aridic Ustorthents.—These soils are drier than Typic
Ustorthents and do not have a lithic contact within 50 cm of
the mineral soil surface. They are intergrades between
Ustorthents and Torriorthents. They are moderately extensive
in the southern part of the Great Plains in the United States.
Slopes are gentle to steep. Many Aridic Ustorthents are used
for grazing. Some of the less sloping soils are used as cropland.
Some of the cropland is irrigated, and some is used for
drought-tolerant crops.
Durinodic Ustorthents.—These soils differ from Typic
Ustorthents in that they are partially cemented by silica. They
are intergrades to Durids or Durustepts. They are not known to
occur in the United States.
Lithic Ustorthents.—These soils have a lithic contact
430 Soil Taxonomy
within 50 cm of the soil surface. Generally, the lithic contact is
appreciably shallower than 50 cm and is most commonly at a
depth of less than 25 cm. These soils are otherwise like those
of the Typic subgroup in defined characteristics. Slopes range
from gentle to very steep. Lithic Ustorthents are used mostly as
grazing land and watersheds, but some areas are used as forest.
These soils are moderately extensive in parts of the Western
United States.
Oxyaquic Ustorthents.—These soils are like Typic
Ustorthents, but they are saturated with water in one or more
layers within 150 cm of the mineral soil surface for either or
both 20 or more consecutive days or 30 or more cumulative
days in normal years. Some of these soils have redox depletions
with low chroma (2 or less) at a depth of more than 100 cm
below the mineral soil surface. Oxyaquic Ustorthents are
considered intergrades to Aquents. They are not extensive.
Some of the soils have a water table that is partly or fully a
result of excess irrigation water.
Torrertic Ustorthents.—These soils have a high shrinkswell
potential and a soil moisture regime that borders on
aridic. They do not have a lithic contact within 50 cm of the
mineral soil surface. They occur in the western Dakotas as well
as Montana, Wyoming, Colorado, Arizona, and New Mexico.
They are used mostly as rangeland.
Udic Ustorthents.—These soils are like Typic Ustorthents,
but they are dry in some part of the moisture control section for
less than four-tenths of the cumulative days when the soil
temperature at a depth of 50 cm exceeds 5 o
C if the soil
temperature regime is mesic or thermic and are dry in some or
all parts of the moisture control section for less than 90 days
during a period when the soil temperature at a depth of 50 cm
exceeds 8 o
C if the soil temperature regime is hyperthermic,
isomesic, or warmer. These soils are intergrades between
Ustorthents and Udorthents. They are of very small extent in
the United States.
Vermic Ustorthents.—These soils have been so completely
reworked by animals, such as rodents, earthworms, and insects,
that diagnostic horizons cannot be identified. The soils have
not been identified in the United States but have been observed
in other countries.
Vertic Ustorthents.—These soils have high linear
extensibility or cracks and slickensides or wedge-shaped
aggregates. Slopes of the soils in the United States range from
nearly level to strong. Vertic Ustorthents are of small extent in
the United States. They are used mostly for grazing.
Vitrandic Ustorthents.—These soils are like Typic
Ustorthents, but they are composed of volcanic deposits or have
a layer of pyroclastic materials that is 18 cm or more thick and
is in the upper 75 cm. These soils are of minor extent, mostly
in the States of Arizona and New Mexico.
Vitritorrandic Ustorthents.—These soils are like Typic
Ustorthents, but they are composed of volcanic deposits or have
a layer of pyroclastic materials that is 18 cm or more thick and
is in the upper 75 cm. The soils have a moisture regime that is
marginal to aridic. They are of minor extent, mostly in the
States of Arizona and New Mexico.
Xerorthents
These are the Orthents of Mediterranean climates. They
have a xeric moisture regime and a frigid, mesic, or thermic
soil temperature regime. Generally, they are neutral to
moderately alkaline, but some are acid. Slopes are mostly
moderate to steep but are gentle in a few areas. Because many
of the soils are strongly sloping and lose water through runoff,
not all Orthents in a Mediterranean climate have a xeric
moisture regime, particularly if the regolith is thin. Winter
rains usually are gentle, summer drought is certain, and most
of the Orthents in a Mediterranean climate are Xerorthents.
The Xerorthents commonly are in sandy-skeletal families or
occur in areas of very recently exposed regolith, such as loess
or till; in areas of weakly cemented rocks, such as shale; or in
areas of very thin regolith over hard rocks. Some of these soils,
particularly those that have been cultivated for a long time or
reshaped for irrigation, consist of what was the C horizon of
other Xeric great groups, chiefly Xeralfs and Xerolls. The
vegetation is commonly trees or shrubs, or the soils are used
as pasture.
Definition
Xerorthents are the Orthents that have a xeric moisture
regime and a frigid, mesic, or thermic soil temperature regime.
Key to Subgroups
LECA. Xerorthents that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Xerorthents
LECB. Other Xerorthents that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Xerorthents
LECC. Other Xerorthents that have, in one or more horizons
Entisols 431
within 100 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Xerorthents
LECD. Other Xerorthents that are saturated with water in
one or more layers within 150 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Xerorthents
LECE. Other Xerorthents that have a horizon within 100 cm
of the mineral soil surface that is 15 cm or more thick and that
either has 20 percent or more (by volume) durinodes or is
brittle and has a firm rupture-resistance class when moist.
Durinodic Xerorthents
LECF. Other Xerorthents that have a base saturation (by
NH4
OAc) of less than 60 percent in all horizons at a depth
between 25 and 75 cm below the mineral soil surface.
Dystric Xerorthents
LECG. Other Xerorthents.
Typic Xerorthents
Definition of Typic Xerorthents
Typic Xerorthents are the Xerorthents that:
1. Do not have, in any horizon within 100 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
2. Are not saturated with water in any layer within 150 cm of
the mineral soil surface for either or both 30 or more
cumulative days or 20 or more consecutive days in normal
years;
3. Do not have a horizon within 100 cm of the surface that is
more than 15 cm thick and that either has 20 percent or more
durinodes or is brittle and has a firm rupture-resistance class
when moist;
4. Do not have a lithic contact within 50 cm of the soil
surface;
5. Have a base saturation (by NH4
OAc) of 60 percent or more
in some part at a depth between 25 and 75 cm below the soil
surface; and
6. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Description of Subgroups
Typic Xerorthents.—The central concept or Typic
subgroup of Xerorthents is fixed on soils that are moderately
deep or deep to hard rock, do not have ground water within a
depth of 150 cm, and are not partially cemented by silica.
These soils have a base saturation (by NH4
OAc) of 60 percent
or more in some part at a depth of between 25 and 75 cm below
the soil surface. Soils that have a shallow lithic contact are
excluded from the Typic subgroup, a convention used
throughout this taxonomy. Soils that are partially cemented by
silica are excluded because such soils are thought to represent
intergrades to Durixerepts.
Commonly, Typic Xerorthents are in a sandy-skeletal family
or have a thin ochric epipedon that rests on a densic or
paralithic contact with weakly cemented rock or dense
sediments. Some of these soils have been cultivated for a long
time or have been reshaped for irrigation and consist of what
was the C horizon of other soils, chiefly Xeralfs and Xerolls.
Typic Xerorthents are used mostly as forest or grazing land.
A few of these soils are used as cropland, and a few are idle.
Aquic Xerorthents.—These soils have, in one or more
horizons within 100 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage). The soils
are on low terraces in the western part of the United States and
are not extensive.
Durinodic Xerorthents.—These soils differ from the soils
in the Typic subgroup because they have, within 100 cm of the
mineral soil surface, a horizon that is more than 15 cm thick
and that either has 20 percent or more (by volume) durinodes
or is brittle and has a firm rupture-resistance class when moist.
The Durinodic Xerorthents in the United States occur mainly
in eastern Washington, where there is appreciable volcanic ash
in the loess. The soils are used for small grain or as grazing
land.
Dystric Xerorthents.—These are the Xerorthents that occur
in areas of relatively high rainfall. The soils have a base
saturation (by NH4
OAc) of less than 60 percent in some part at
a depth between 25 and 75 cm below the surface. They have
coarse textures, but they are excluded from Psamments because
they have a high content of rock fragments and from Xerepts
432 Soil Taxonomy
because the textures are coarser than is permitted in cambic
horizons. Dystric Xerorthents are of moderate extent in the
Western United States, mostly in California, Washington, and
Oregon. They are used mostly as forest, but some are used as
cropland.
Lithic Xerorthents.—These soils have a lithic contact
within 50 cm of the soil surface, normally within 25 cm of the
surface. Slopes range from gentle to very steep. Lithic
Xerorthents are used mostly as grazing land and watersheds,
but some areas are used as forest. These soils are moderately
extensive in parts of the Western United States.
Oxyaquic Xerorthents.—These soils are saturated with
water for 20 or more consecutive days and/or 30 or more
cumulative days within 100 cm of the mineral soil surface
during normal years. They do not have redox depletions with
chroma of 2 or less within 100 cm of the mineral soil surface.
These soils are of limited extent in California, Idaho, and
eastern Oregon. They are used as grazing land.
Vitrandic Xerorthents.—These soils are like Typic
Xerorthents, but they are composed of volcanic deposits or
have a layer of pyroclastic materials that is 18 cm or more
thick and is in the upper 75 cm. The soils are of minor
extent, mostly in the States of California, Oregon, and
Washington.
Psamments
These are the sandy Entisols. They are sandy in all layers
within the particle-size control section. Some formed in poorly
graded (well sorted) sands on shifting or stabilized sand dunes,
in cover sands, or in sandy parent materials that were sorted in
an earlier geologic cycle. Some formed in sands that were
sorted by water and are on outwash plains, lake plains, natural
levees, or beaches. A few Psamments formed in material
weathered from sandstone or granitic bedrock. Psamments
occur under any climate, but they cannot have permafrost
within 100 cm of the soil surface. They can have any
vegetation and are on surfaces of virtually any age from
recent historic to Pliocene or older. The Psamments on old
stable surfaces commonly consist of quartz sand. Ground
water typically is deeper than 50 cm and commonly is much
deeper.
Psamments have a relatively low water-holding capacity.
Those that are bare and become dry are subject to soil blowing
and drifting and cannot easily support wheeled vehicles.
Because very gravelly sands do not have the two qualities just
described, they are excluded from Psamments and are grouped
with Orthents. Thus, not all Entisols that have a sandy texture
are Psamments.
Definition
Psamments are the Entisols that:
1. Have have less than 35 percent (by volume) rock fragments
and a texture of loamy fine sand or coarser in all layers within
the particle-size control section;
2. Do not have, within 50 cm of the mineral soil surface, aquic
conditions; and
a. The colors defined for Aquents; or
b. Sulfidic materials; or
c. A positive reaction to alpha,alpha-dipyridyl when the soil
is not being irrigated;
3. Do not have fragments of diagnostic horizons that can be
identified and that occur more or less without a discernible
order below any Ap horizon but within the particle-size control
section; and
4. Do not have sulfidic materials within 50 cm of the mineral
soil surface or both the aquic conditions and colors defined for
Aquents.
Key to Great Groups
LCA. Psamments that have a cryic soil temperature
regime.
Cryopsamments, p. 432
LCB. Other Psamments that have an aridic (or torric)
moisture regime.
Torripsamments, p. 436
LCC. Other Psamments that have, in the 0.02 to 2.0 mm
fraction within the particle-size control section, a total of more
than 90 percent (by weighted average) resistant minerals.
Quartzipsamments, p. 434
LCD. Other Psamments that have an ustic moisture regime.
Ustipsamments, p. 439
LCE. Other Psamments that have a xeric moisture regime.
Xeropsamments, p. 441
LCF. Other Psamments.
Udipsamments, p. 438
Cryopsamments
These are the Psamments of cold areas. In the United States,
they are primarily in high mountains of the West and in
Alaska. Generally, they have, or had before they were
disturbed, a coniferous forest vegetation. They are of small
extent. Most of them formed in material weathered from
granitic rocks or in deposits of late-Pleistocene or recent age.
Some formed in recent volcanic deposits.
Entisols 433
Definition
Cryopsamments are the Psamments that have a cryic soil
temperature regime.
Key to Subgroups
LCAA. Cryopsamments that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Cryopsamments
LCAB. Other Cryopsamments that have, in one or more
horizons within 50 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage).
Aquic Cryopsamments
LCAC. Other Cryopsamments that are saturated with water
in one or more layers within 100 cm of the mineral soil surface
in normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Cryopsamments
LCAD. Other Cryopsamments that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction
containing 5 percent or more volcanic glass, and [(Al plus 1
/2
Fe, percent extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrandic Cryopsamments
LCAE. Other Cryopsamments that have a horizon 5 cm or
more thick that has one or more of the following:
1. In 25 percent or more of each pedon, cementation by
organic matter and aluminum, with or without iron; or
2. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
3. An ODOE value of 0.12 or more, and a value half as
high or lower in an overlying horizon.
Spodic Cryopsamments
LCAF. Other Cryopsamments that have lamellae within 200
cm of the mineral soil surface.
Lamellic Cryopsamments
LCAG. Other Cryopsamments.
Typic Cryopsamments
Definition of Typic Cryopsamments
Typic Cryopsamments are the Cryopsamments that:
1. Do not have lamellae within 200 cm of the soil surface;
2. Do not have, in any horizon within 50 cm of the mineral soil
surface, redox depletions with chroma of 2 or less and also aquic
conditions;
3. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for either or both 20 or more
consecutive days or 30 or more cumulative days in normal
years;
4. Do not have a lithic contact within 50 cm of the soil
surface;
5. Do not have a horizon, 5 cm or more thick, either below
an Ap horizon or at a depth of 18 cm or more from the mineral
soil surface, whichever is deeper, that has one or more of the
following:
a. In 25 percent or more of each pedon, cementation by
organic matter and aluminum, with or without iron; or
b. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
c. An ODOE value of 0.12 or more, and a value half as
high or lower in an overlying horizon; and
6. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, a fine-earth fraction containing 5 percent or more
volcanic glass, and [(Al plus 1
/2 Fe, percent extracted by
ammonium oxalate) times 60] plus the volcanic glass (percent)
is less than 30.
Description of Subgroups
Typic Cryopsamments.—The central concept or Typic
subgroup of Cryopsamments is fixed on deep sands that have
ground water deeper than 100 cm, that do not have a weak
accumulation of amorphous materials, and do not have
lamellae within 200 cm of the soil surface.
These soils do not have, in the upper 75 cm, a deposit of
pyroclastic materials that is as thick as 18 cm. Lamellae with
illuvial clay are considered to represent a transition to Cryalfs.
Shallow mottles with low chroma and short periods of
saturation in the mottled horizon are considered features of the
intergrades to Psammaquents. Soils that have a weak
accumulation of amorphous materials are considered
intergrades to Spodosols.
Typic Cryopsamments are of small extent. Most are in
Alaska, but some are in the mountains of other Western States.
Aquic Cryopsamments.—These soils have aquic
conditions for some time in normal years (or artificial
drainage) and redox depletions with chroma of 2 or less within
50 cm of the mineral soil surface. The soils have not been
identified as series in the United States, but the subgroup is
provided for use if needed.
Lamellic Cryopsamments.—These soils have lamellae
within 200 cm of the soil surface. An albic horizon normally is
434 Soil Taxonomy
below an O horizon or a thin A or Ap horizon in these soils.
The soils are rare in the United States and are at elevations
above 1,200 m. They are used as forest.
Lithic Cryopsamments.—These soils have a lithic contact
within a depth of 50 cm. They are permitted to have redox
depletions with low chroma (2 or less) above the lithic contact.
These soils are not known to occur in the United States.
Oxyaquic Cryopsamments.—These soils are like Typic
Cryopsamments, but they are saturated with water in one or
more layers within 100 cm of the mineral soil surface for either
or both 20 or more consecutive days or 30 or more cumulative
days in normal years. Some of these soils have redox depletions
with low chroma (2 or less) at a depth below 50 cm from the
mineral soil surface. Oxyaquic Cryopsamments are considered
intergrades to Aquents. They are not known to occur in the
United States.
Spodic Cryopsamments.—These soils have a weak
accumulation of amorphous materials. They are presumed to be
developing toward Spodosols, mainly Cryods, but are too
weakly developed to be classified as Spodosols. No series has
been established, but the subgroup is provided for use if
needed.
Vitrandic Cryopsamments.—These soils formed in volcanic
deposits or have a deposit of fine pyroclastic materials near the
surface. The soils are considered intergrades to Vitricryands.
They are of small extent, mostly in the mountains of the Western
United States.
Quartzipsamments
These are the freely drained Psamments that have more than
90 percent resistant minerals. They are in humid to semiarid,
cool to hot regions. They can have any temperature regime,
except for cryic, and any moisture regime, except for aridic (or
torric). These soils are high in content of quartz sand and are
white or stained with shades of brown, yellow, or red. Because
they commonly have virtually no minerals that can weather,
they can occur on some extremely old land surfaces. They also
occur on late-Pleistocene and younger surfaces. A spodic
horizon is known to lie beneath white sand, particularly in
tropical areas, at a depth of several meters, so deep that
determination of its presence or absence is not practical. The
most important properties in such areas are those of the upper
2 m or so that consists of uncoated quartz sand.
The vegetation on Quartzipsamments varies widely with
climate. Few of these soils are cultivated, except in Florida.
Quartzipsamments are extensive on the coastal plains in the
United States.
Definition
Quartzipsamments are the Psamments that:
1. Have a temperature regime warmer than cryic;
2. Have a moisture regime other than aridic (or torric); and
3. Average more than 90 percent resistant minerals in
the 0.02 to 2.0 mm fraction within the particle-size control
section.
Key to Subgroups
LCCA. Quartzipsamments that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Quartzipsamments
LCCB. Other Quartzipsamments that have both:
1. In one or more horizons within 100 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. A horizon, 5 cm or more thick, either below an Ap
horizon or at a depth of 18 cm or more from the mineral soil
surface, whichever is deeper, that has one or more of the
following:
a. In 25 percent or more of each pedon, cementation
by organic matter and aluminum, with or without iron;
or
b. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
c. An ODOE value of 0.12 or more, and a value half as
high or lower in an overlying horizon.
Aquodic Quartzipsamments
LCCC. Other Quartzipsamments that have, in one or more
horizons within 100 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage).
Aquic Quartzipsamments
LCCD. Other Quartzipsamments that are saturated with
water in one or more layers within 100 cm of the mineral soil
surface in normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Quartzipsamments
LCCE. Other Quartzipsamments that meet all of the
following:
1. Have an ustic moisture regime; and
2. Have a clay fraction with a CEC of 16 cmol(+) or less
per kg clay (by NH4
OAc pH 7); and
3. The sum of the weighted average silt plus 2 times
the weighted average clay (both by weight) is more than 5.
Ustoxic Quartzipsamments
Entisols 435
LCCF. Other Quartzipsamments that meet all of the
following:
1. Have a udic moisture regime; and
2. Have a clay fraction with a CEC of 16 cmol(+) or less per
kg clay (by NH4
OAc pH 7); and
3. The sum of the weighted average silt plus 2 times the
weighted average clay (both by weight) is more than 5.
Udoxic Quartzipsamments
LCCG. Other Quartzipsamments that have 5 percent or more
(by volume) plinthite in one or more horizons within 100 cm of
the mineral soil surface.
Plinthic Quartzipsamments
LCCH. Other Quartzipsamments that have both:
1. Lamellae within 200 cm of the mineral soil surface; and
2. An ustic moisture regime.
Lamellic Ustic Quartzipsamments
LCCI. Other Quartzipsamments that have lamellae within
200 cm of the mineral soil surface.
Lamellic Quartzipsamments
LCCJ. Other Quartzipsamments that have an ustic moisture
regime.
Ustic Quartzipsamments
LCCK. Other Quartzipsamments that have a xeric moisture
regime.
Xeric Quartzipsamments
LCCL. Other Quartzipsamments that have a horizon, 5 cm or
more thick, either below an Ap horizon or at a depth of 18 cm
or more from the mineral soil surface, whichever is deeper, that
has one or more of the following:
1. In 25 percent or more of each pedon, cementation by
organic matter and aluminum, with or without iron; or
2. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
3. An ODOE value of 0.12 or more, and a value half as
high or lower in an overlying horizon.
Spodic Quartzipsamments
LCCM. Other Quartzipsamments.
Typic Quartzipsamments
Definition of Typic Quartzipsamments
Typic Quartzipsamments are the Quartzipsamments that:
1. Do not have, in any horizon within 100 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
2. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 30 or more cumulative days or 20
or more consecutive days in normal years;
3. Do not have a horizon, 5 cm or more thick, either below
an Ap horizon or at a depth of 18 cm or more from the mineral
soil surface, whichever is deeper, that has one or more of the
following:
a. In 25 percent or more of each pedon, cementation by
organic matter and aluminum, with or without iron; or
b. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
c. An ODOE value of 0.12 or more, and a value half as
high or lower in an overlying horizon;
4. Do not have a lithic contact within 50 cm of the soil
surface;
5. Have a clay fraction with a CEC of more than 16 than
cmol(+) per kg clay (by NH4
OAc pH 7) if the sum of the
weighted average silt plus 2 times the weighted clay (both by
weight) is more than 5;
6. Have less than 5 percent plinthite in all horizons above a
depth of 100 cm;
7. Have a udic or perudic moisture regime; and
8. Do not have lamellae within 200 cm of the soil surface.
Description of Subgroups
Typic Quartzipsamments.—The Typic subgroup of
Quartzipsamments is centered on soils that have a udic or
perudic moisture regime, have deep ground water in all
seasons, do not have distinct color horizons, have a moderately
thick or thicker regolith, and have at least moderately active
clays or very little clay. These soils are extensive in the United
States. They are mostly in the Southeastern States. Most are
used as forest, but some are used as cropland or pasture.
Aquic Quartzipsamments.—These soils have, in one or
more horizons within 100 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage). The soils
are considered intergrades to Psammaquents. They are of small
extent in the United States.
Aquodic Quartzipsamments.—These soils have weak
accumulations of amorphous materials. They also have, in one
or more horizons within 100 cm of the mineral soil surface,
redox depletions with chroma of 2 or less and aquic conditions
for some time in normal years (or artificial drainage). These
soils are considered intergrades to Aquods. They are of small
extent in the United States.
436 Soil Taxonomy
Lamellic Quartzipsamments.—These soils have lamellae
within 200 cm of the soil surface. The Lamellic
Quartzipsamments in the United States have a udic moisture
regime, although the subgroup also allows soils with a xeric
regime. Because of the lamellae, Lamellic Quartzipsamments
have more moisture available for deep-rooted plants, such as
trees and perennial grasses, than Typic Quartzipsamments.
Lamellic Quartzipsamments are of small extent in the United
States.
Lamellic Ustic Quartzipsamments.—These soils have an
ustic moisture regime and have lamellae within 200 cm of the
soil surface. Because of the lamellae, these soils have more
moisture available for deep-rooted plants, such as trees and
perennial grasses, than other Quartzipsamments with an ustic
moisture regime. Lamellic Ustic Quartzipsamments are of
small extent in the United States.
Lithic Quartzipsamments.—These soils are shallow to a
lithic contact. They are of small extent in the United States.
Oxyaquic Quartzipsamments.—These soils are saturated
with water in one or more layers within 150 cm of the mineral
soil surface for either or both 20 or more consecutive days or
30 or more cumulative days in normal years. Some of the soils
have redox depletions with low chroma (2 or less) at a depth
below 100 cm from the mineral soil surface. Oxyaquic
Quartzipsamments are considered intergrades to Aquents. They
are of small extent in the United States.
Plinthic Quartzipsamments.—These soils have 5 percent
or more (by volume) plinthite in one or more horizons within
100 cm of the mineral soil surface. They are not known to
occur in the United States.
Spodic Quartzipsamments.—These soils are like Typic
Quartzipsamments, but they have a weak accumulation of
amorphous materials. The ground water is deeper than 100 cm
most of the year in the soils of this subgroup. These soils are of
small extent in the United States.
Udoxic Quartzipsamments.—These soils are like Typic
Quartzipsamments, but they have a clay fraction that meets the
CEC requirements for an oxic horizon, but the amount of clay
is too small for an oxic horizon. Udoxic Quartzipsamments are
not known to occur in the United States, but they are extensive
in the equatorial regions of Africa and South America.
Ustic Quartzipsamments.—These soils are like Typic
Quartzipsamments, but they have an ustic moisture regime.
They are of small extent in the United States.
Ustoxic Quartzipsamments.—These soils are like Typic
Quartzipsamments, but they have an ustic moisture regime and
have a clay fraction that meets the CEC requirements of clay in
an oxic horizon. The amount of clay is too small to meet the
requirements for an oxic horizon. These soils are not known to
occur in the United States, but they are extensive in Africa and
South America.
Xeric Quartzipsamments.—These soils are like Typic
Quartzipsamments, but they have a xeric moisture regime.
They are not known to occur in the United States.
Torripsamments
These are the cool to hot Psamments of arid climates. They
have an aridic (or torric) moisture regime and a temperature
regime warmer than cryic. Many of these soils are on stable
surfaces, some are on dunes, some are stabilized, and some are
moving. Torripsamments consist of quartz, mixed sands,
volcanic glass, or even gypsum and may have any color.
Generally, they are neutral or calcareous and are nearly level to
steep. The vegetation consists mostly of xerophytic shrubs,
grasses, and forbs. Many of these soils support more vegetation
than other soils with an aridic moisture regime, presumably
because they lose less water as runoff. Some of the soils on
dunes support a few ephemeral plants or have a partial cover of
xerophytic and ephemeral plants. The shifting dunes may be
devoid of plants in normal years. Most of the deposits are of
late-Pleistocene or younger age. These soils are used mainly for
grazing. They are extensive in the Western United States.
Definition
Torripsamments are the Psamments that have an aridic (or
torric) moisture regime and a soil temperature regime warmer
than cryic.
Key to Subgroups
LCBA. Torripsamments that have a lithic contact within 50
cm of the soil surface.
Lithic Torripsamments
LCBB. Other Torripsamments that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction
containing 5 percent or more volcanic glass, and [(Al plus 1
/2
Fe, percent extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrandic Torripsamments
LCBC. Other Torripsamments that have a horizon within
100 cm of the soil surface that is 15 cm or more thick and that
either has 20 percent or more (by volume) durinodes or is
brittle and has a firm rupture-resistance class when moist.
Haploduridic Torripsamments
LCBD. Other Torripsamments that have both:
1. A moisture control section that, in normal years, is dry
in all its parts for less than three-fourths of the cumulative
days per year when the soil temperature at a depth of 50 cm
from the soil surface is 5 o
C or higher; and
2. An aridic (or torric) moisture regime that borders on
ustic.
Ustic Torripsamments
LCBE. Other Torripsamments that have both:
Entisols 437
1. A moisture control section that, in normal years, is dry in
all its parts for less than three-fourths of the cumulative days
per year when the soil temperature at a depth of 50 cm from
the soil surface is 5 o
C or higher; and
2. A thermic, mesic, or frigid soil temperature regime and an
aridic (or torric) moisture regime that borders on xeric.
Xeric Torripsamments
LCBF. Other Torripsamments that have, in all horizons from
a depth of 25 to 100 cm, more than 50 percent colors that have
all of the following:
1. Hue of 2.5YR or redder; and
2. A color value, moist, of 3 or less; and
3. A dry value no more than 1 unit higher than the moist
value.
Rhodic Torripsamments
LCBG. Other Torripsamments.
Typic Torripsamments
Definition of Typic Torripsamments
Typic Torripsamments are the Torripsamments that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have a horizon within 100 cm of the surface that is
more than 15 cm thick and that either has 20 percent or more
durinodes or is brittle and has a firm rupture-resistance class
when moist;
3. Are dry in all parts of the moisture control section for
three-fourths or more of the time (cumulative) when the soil
temperature at a depth of 50 cm is 5 o
C or higher;
4. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, a fine-earth fraction containing 5 percent or more
volcanic glass, and [(Al plus 1
/2 Fe, percent extracted by
ammonium oxalate) times 60] plus the volcanic glass (percent)
is 30 or more; and
5. Do not have, in all horizons from a depth of 25 to 100 cm,
more than 50 percent colors that have all of the following:
1. Hue of 2.5YR or redder; and
2. A color value, moist, of 3 or less; and
3. A dry value no more than 1 unit higher than the moist
value.
Description of Subgroups
Typic Torripsamments.—The Typic subgroup consists of
the Torripsamments that are dry for more than three-fourths of
the time when the soil temperature is 5 o
C or higher. These
soils do not have evident cementation by silica and are
moderately deep or deep to a lithic contact. The limitation on
moisture restricts the subgroup to the drier part of the range of
the great group. The restriction against a lithic contact is the
same one that is applied in Typic subgroups throughout most of
this taxonomy. Many of these soils support more vegetation
than other soils with an aridic moisture regime, perhaps
because of rapid infiltration and a low available water capacity,
which cause the precipitation to moisten the soils to a greater
depth than in most other soils with an aridic moisture regime.
Some water is stored below the soil moisture control section.
Typic Torripsamments are moderately extensive in the Western
United States. They are used mainly for grazing.
Haploduridic Torripsamments.—These soils have, within
100 cm of the surface, a horizon that is more than 15 cm thick
and that either has 20 percent or more durinodes or is brittle
and has a firm rupture-resistance class when moist. The soils
are permitted to have a moisture regime that is not so dry as
that of the Typic subgroup. Some volcanic ash and other
pyroclastic materials are in some of these soils. Haploduridic
Torripsamments are not known to occur in the United States.
Lithic Torripsamments.—These soils are less than 50 cm
deep to a lithic contact. Because the soils are shallow, a wider
range in the moisture regime is permitted than in other
Torripsamments. Small areas of Lithic Torripsamments are in
the mountains in the Western United States and are used for
grazing.
Rhodic Torripsamments.—These soils have dark red
colors. They do not have a lithic contact within 50 cm of the
soil surface or a moisture regime that borders on ustic or xeric.
They are in areas of an isohyperthermic soil temperature
regime in India. Some of these soils are used for the production
of cashews.
Ustic Torripsamments.—These soils have an aridic
moisture regime that borders on ustic. Most of the soils in this
subgroup have two short rainy seasons and two long dry
seasons each year. The longer rainy season is less than 3
months, or it has only showers of erratic distribution, so that
the moisture control section dries between rains. Many of these
soils support more vegetation than other soils with an aridic
moisture regime that borders on ustic, perhaps because of rapid
infiltration and a low available water capacity, which cause the
precipitation to moisten the soils to a greater depth than in
most other soils with an aridic moisture regime. Some water is
stored below the soil moisture control section. Ustic
Torripsamments are extensive in the Western United States.
They are used mainly for grazing.
Vitrandic Torripsamments.—These soils have a
significant volcanic influence in one or more layers 18 cm or
more thick within 75 cm of the mineral soil surface. They are
in California and Oregon. Most are used as rangeland, but
some are mined for pumice or are irrigated and used for alfalfa.
Xeric Torripsamments.—These soils have an aridic
moisture regime that borders on xeric. The rainy season is in
438 Soil Taxonomy
winter, and summer is very dry. The supply of winter moisture
is dependable, however, and the soils can support more
vegetation than the soils of the Typic subgroup. The level of
organic matter may be higher than in Typic Torripsamments
but does not need to be higher in the soils on shifting dunes.
Many of the Xeric Torripsamments support more brushy
vegetation than other soils with an aridic moisture regime that
borders on xeric, perhaps because of rapid infiltration and a
low available water capacity, which cause the precipitation to
moisten the soils to a greater depth than in most other soils
with an aridic moisture regime. Some water is stored deep
below the soil moisture control section. Xeric Torripsamments
are moderately extensive in the Western United States. They
are used mainly for grazing. Some of the soils are used as
irrigated cropland.
Udipsamments
These are the Psamments that are of humid regions and have
a temperature regime warmer than cryic. The soils have a udic
moisture regime, and they average more than 10 percent
weatherable minerals (in the 0.02 to 2.0 mm fraction) in the
particle-size control section. They are predominantly in areas
of late-Pleistocene or more recent deposits and are mostly
brownish and freely drained. Most of the soils have supported
forest vegetation, but a few have been cultivated ever since the
sands were deposited. Others have been cultivated for a very
long time. Udipsamments are extensive in the United States.
Many are used as forest. Large areas, mostly with mesic or
warmer temperature regimes, have been cleared and are used
as cropland or pasture.
Definition
Udipsamments are the Psamments that:
1. Have a soil temperature regime warmer than cryic;
2. Have a udic moisture regime; and
3. Average less than 90 percent resistant minerals in the 0.02
to 2.0 mm fraction within the particle-size control section.
Key to Subgroups
LCFA. Udipsamments that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Udipsamments
LCFB. Other Udipsamments that have, in one or more
horizons within 100 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage).
Aquic Udipsamments
LCFC. Other Udipsamments that are saturated with water in
one or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Udipsamments
LCFD. Other Udipsamments that have a horizon, 5 cm or
more thick, either below an Ap horizon or at a depth of 18 cm
or more from the mineral soil surface, whichever is deeper, that
has one or more of the following:
1. In 25 percent or more of each pedon, cementation by
organic matter and aluminum, with or without iron; or
2. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
3. An ODOE value of 0.12 or more, and a value half as
high or lower in an overlying horizon.
Spodic Udipsamments
LCFE. Other Udipsamments that have lamellae within 200
cm of the mineral soil surface.
Lamellic Udipsamments
LCFF. Other Udipsamments that have a surface horizon
between 25 and 50 cm thick that meets all of the requirements
for a plaggen epipedon except thickness.
Plagganthreptic Udipsamments
LCFG. Other Udipsamments.
Typic Udipsamments
Definition of Typic Udipsamments
Typic Udipsamments are the Udipsamments that:
1. Do not have lamellae within 200 cm of the soil surface;
2. Do not have, in any horizon within 100 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
3. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 30 or more cumulative days or 20
or more consecutive days in normal years;
4. Do not have a lithic contact within a depth of 50 cm;
5. Do not have a horizon, 5 cm or more thick, either below
an Ap horizon or at a depth of 18 cm or more from the mineral
soil surface, whichever is deeper, that has one or more of the
following:
a. In 25 percent or more of each pedon, cementation
by organic matter and aluminum, with or without iron;
or
b. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
Entisols 439
c. An ODOE value of 0.12 or more, and a value half as high
or lower in an overlying horizon; and
6. Do not have a surface horizon between 25 and 50 cm thick
that meets all of the requirements for a plaggen epipedon
except thickness.
Description of Subgroups
Typic Udipsamments.—The Typic subgroup of
Udipsamments is centered on soils that are moderately deep or
deeper to a lithic contact, have deep ground water, do not have
a weak accumulation of amorphous materials, do not have
lamellae within 200 cm of the soil surface, and do not have an
epipedon (less than 50 cm thick) that meets all of the
requirements for a plaggen epipedon except thickness.
Soils that have a lithic contact within 50 cm of the soil
surface are excluded from the Typic subgroup, a convention
used throughout this taxonomy. Soils that are saturated with
water within a depth of 100 cm and have redox depletions with
low chroma (2 or less) are considered intergrades to
Psammaquents. Soils that have weak accumulations of
amorphous materials are considered intergrades to Spodosols.
In the United States, such soils are mostly intergrades to
Orthods. Lamellae are used as criteria for the Lamellic
subgroup and indicate a transition to Alfisols or Ultisols. A
thin surface mantle that meets all of the requirements for a
plaggen epipedon except thickness is considered a transition to
Plagganthrepts.
Typic Udipsamments are extensive in the Eastern United
States. They are used mainly as forest, but large areas have
been cleared and are used as cropland or pasture.
Aquic Udipsamments.—These soils are saturated with
water at some time of the year and have redox depletions with
low chroma (2 or less) within 100 cm of the soil surface, and
they are permitted, but not required, to have lamellae within
200 cm of the surface. They are otherwise like Typic
Udipsamments. Aquic Udipsamments are of moderate extent in
the Eastern United States. They are used mainly as forest, but
some areas have been cleared and are used as cropland or
pasture.
Lamellic Udipsamments.—These soils have lamellae in
which clay has accumulated as oriented coatings on sand
grains. These soils are of moderate extent in the Eastern
United States. They are used mainly as forest, but some have
been cleared and are used as cropland or pasture.
Lithic Udipsamments.—These soils have a lithic contact
within 50 cm of the soil surface but are otherwise like Typic
Udipsamments. Lithic Udipsamments are of very small extent
in the Eastern United States. They are used mainly as forest.
Oxyaquic Udipsamments.—These soils are saturated with
water for 20 or more consecutive days or 30 or more
cumulative days in normal years; do not have redox depletions
with low chroma (2 or less) within 100 cm of the soil surface;
and are permitted, but not required, to have lamellae within
200 cm of the surface. They are otherwise like Typic
Udipsamments. Oxyaquic Udipsamments are of moderately small
extent in the Eastern United States. They are used mainly as
forest, but some have been cleared and are used as cropland or
pasture.
Plagganthreptic Udipsamments.—These soils have a
surface horizon between 25 and 50 cm thick that meets all of
the requirements for a plaggen epipedon except thickness.
They are not known to occur in the United States, but the
subgroup is provided for use in other countries.
Spodic Udipsamments.—These soils have weak
accumulations of amorphous materials. They are considered to
be developing toward Spodosols or to be more or less in
equilibrium between Psamments and Spodosols, generally
Orthods in the United States. Spodic Udipsamments are of
small extent in the Eastern United States. They are used
mainly as forest, but some have been cleared and are used as
cropland or pasture.
Ustipsamments
These are the Psamments that have an ustic moisture
regime. They can have any temperature regime warmer than
cryic. These soils support mostly grass or savanna vegetation.
A few are in drought-tolerant forests of small, scattered trees.
Many support as much vegetation as or more vegetation than
other soils with an ustic moisture regime, perhaps because of
rapid infiltration and a low available water capacity, which cause
the precipitation to moisten the soils to a greater depth than in
most other soils with an ustic moisture regime. Some water is
stored below the soil moisture control section. Ustipsamments
are used mainly for grazing. Few of them are cultivated because
they are subject to soil blowing if they are cultivated.
Ustipsamments are extensive soils on the Great Plains in the
United States.
Definition
Ustipsamments are the Psamments that:
1. Have a soil temperature regime warmer than cryic;
2. Have an ustic soil moisture regime; and
3. Average less than 90 percent resistant minerals (in
the 0.02 to 2.0 mm fraction) in the particle-size control
section.
Key to Subgroups
LCDA. Ustipsamments that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Ustipsamments
LCDB. Other Ustipsamments that have, in one or more
horizons within 100 cm of the mineral soil surface, distinct or
prominent redox concentrations and also aquic conditions for
some time in normal years (or artificial drainage).
Aquic Ustipsamments
440 Soil Taxonomy
LCDC. Other Ustipsamments that are saturated with water in
one or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Ustipsamments
LCDD. Other Ustipsamments that, when neither irrigated
nor fallowed to store moisture, have one of the following:
1. A frigid soil temperature regime and a moisture control
section that, in normal years, is dry in all parts for fourtenths
or more of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A mesic or thermic soil temperature regime and a
moisture control section that, in normal years, is dry in
some part for six-tenths or more of the cumulative days per
year when the soil temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C; or
3. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that, in
normal years, is moist in some or all parts for less than 180
cumulative days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8 o
C.
Aridic Ustipsamments
LCDE. Other Ustipsamments that have lamellae within 200
cm of the mineral soil surface.
Lamellic Ustipsamments
LCDF. Other Ustipsamments that have, in all horizons from
a depth of 25 to 100 cm, more than 50 percent colors that have
all of the following:
1. Hue of 2.5YR or redder; and
2. A color value, moist, of 3 or less; and
3. A dry value no more than 1 unit higher than the moist
value.
Rhodic Ustipsamments
LCDG. Other Ustipsamments.
Typic Ustipsamments
Definition of Typic Ustipsamments
Typic Ustipsamments are the Ustipsamments that:
1. Do not have lamellae within 200 cm of the soil surface;
2. Do not have, in any horizon within 100 cm of the mineral
soil surface, distinct or prominent redox concentrations and
also aquic conditions;
3. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 30 or more cumulative days or 20 or
more consecutive days in normal years;
4. Do not have a lithic contact within 50 cm of the surface;
5. Are either irrigated or fallowed to store moisture or have one
of the following:
a. A frigid soil temperature regime and a moisture control
section that, in normal years, is dry in all parts for less than
four-tenths of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that, in normal years, is dry in
some part for less than six-tenths of the cumulative days per
year when the soil temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that, in
normal years, is moist in some or all parts for 180 or more
cumulative days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8 o
C; and
6. Do not have, in all horizons from a depth of 25 to 100 cm,
more than 50 percent colors that have all of the following:
1. Hue of 2.5YR or redder; and
2. A color value, moist, of 3 or less; and
3. A dry value no more than 1 unit higher than the moist
value.
Description of Subgroups
Typic Ustipsamments.—The central concept or Typic
subgroup of Ustipsamments is fixed on sands that have deep
ground water and a thick regolith and do not have lamellae
within 200 cm of the soil surface. Some of these soils are
shallow to a paralithic contact. Commonly, the sands are a
mixture of quartz and feldspars.
Soils that have lamellae in which silicate clays have
accumulated are excluded from the Typic subgroup because the
lamellae are considered to indicate intergrades to soils that
have an argillic horizon. Soils that have a lithic contact within
50 cm of the surface are excluded from the Typic subgroup, a
convention used throughout this taxonomy. Redoximorphic
features and the presence of ground water within 100 cm of the
surface at some time of the year cause soils to be excluded
because these features are considered to indicate intergrades to
Psammaquents.
Typic Ustipsamments are freely drained sands. They support
mostly grass or savanna vegetation. A few are in droughttolerant
forests of small, scattered trees. Many support as much
Entisols 441
vegetation as or more vegetation than other soils with an ustic
moisture regime, perhaps because of rapid infiltration and a
low available water capacity, which cause the precipitation to
moisten the soils to a greater depth than in most other soils
with an ustic moisture regime. Some water is stored below the
soil moisture control section. Typic Ustipsamments are
extensive on the Great Plains in the United States. They are
used mainly for grazing. Few of them are cultivated because
they are subject to soil blowing if they are cultivated.
Aquic Ustipsamments.—These soils are saturated with
water at some time of the year and have redoximorphic features
of low or high chroma within 100 cm of the soil surface. The
soils are otherwise like the soils of the Typic subgroup. They
are of small extent in the United States.
Aridic Ustipsamments.—These soils are drier than Typic
Ustipsamments. They are intergrades between Ustipsamments
and Torripsamments. They are moderately extensive in the
southern part of the Great Plains in the United States. Slopes
are gentle to steep. These soils are freely drained sands. They
support mostly grass or savanna vegetation. A few are in
drought-tolerant forests of small, scattered trees. Many support
as much vegetation as or more vegetation than other soils with
an ustic moisture regime, perhaps because of rapid infiltration
and a low available water capacity, which cause the
precipitation to moisten the soils to a greater depth than in
most other soils with an ustic moisture regime. Some water is
stored below the soil moisture control section. Most of the
Aridic Ustipsamments are used for grazing. Few of them are
cultivated because they are subject to soil blowing if they are
cultivated.
Lamellic Ustipsamments.—These soils have lamellae
within 200 cm of the soil surface. They are of small extent in
the United States. They are used mainly as rangeland. Few of
them are cultivated because they are subject to soil blowing if
they are cultivated.
Lithic Ustipsamments.—These soils have a lithic contact
within 50 cm of the soil surface. They support grass or savanna
vegetation. Small areas of these soils are known to occur in the
United States.
Oxyaquic Ustipsamments.—These soils are saturated
with water for 20 or more consecutive days or 30 or more
cumulative days in normal years; do not have redox
depletions with low chroma (2 or less) within 100 cm of the
soil surface; and are permitted, but not required, to have
lamellae within 200 cm of the surface. They are otherwise
like Typic Ustipsamments. Oxyaquic Ustipsamments are of
small extent in the United States. They are used mainly as
rangeland.
Rhodic Ustipsamments.—These soils have dark red colors.
They do not have a lithic contact within 50 cm of the soil
surface, lamellae, or a moisture regime that borders on aridic.
They are known to occur only in areas of an isohyperthermic
soil temperature regime in India. These soils commonly are
used for the production of cashews.
Xeropsamments
These are the Psamments that are of Mediterranean climates
and that have weatherable minerals, commonly feldspars, in
the sand fraction. These soils are moist in winter and dry in
summer. They have a frigid, mesic, or thermic temperature
regime. Most Xeropsamments formed in deposits of lateWisconsinan
or more recent age. Some are on terraces and
glacial outwash plains. Others are on dunes. Because the
supply of winter moisture is reliable, few of the dunes are
shifting. Some of these soils have supported a coniferous
vegetation, but most have supported and still support a mixture
of grasses and xerophytic shrubs or trees. Xeropsamments are
moderately extensive in parts of the Western United States.
Definition
Xeropsamments are the Psamments that:
1. Have a xeric moisture regime and a frigid, mesic, or
thermic soil temperature regime; and
2. Have, in the 0.02 to 2.0 mm fraction within the particlesize
control section, 90 percent or less (by weighted average)
resistant minerals.
Key to Subgroups
LCEA. Xeropsamments have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Xeropsamments
LCEB. Other Xeropsamments that have both:
1. In one or more horizons within 100 cm of the mineral
soil surface, distinct or prominent redox concentrations and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. A horizon within 100 cm of the mineral soil surface
that is 15 cm or more thick and that either has 20 percent or
more (by volume) durinodes or is brittle and has a firm
rupture-resistance class when moist.
Aquic Durinodic Xeropsamments
LCEC. Other Xeropsamments that have, in one or more
horizons within 100 cm of the mineral soil surface, distinct or
prominent redox concentrations and also aquic conditions for
some time in normal years (or artificial drainage).
Aquic Xeropsamments
LCED. Other Xeropsamments that are saturated with water
in one or more layers within 100 cm of the mineral soil surface
in normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Xeropsamments
442 Soil Taxonomy
LCEE. Other Xeropsamments that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction
containing 5 percent or more volcanic glass, and [(Al plus 1
/2
Fe, percent extracted by ammonium oxalate) times 60] plus the
volcanic glass (percent) is 30 or more.
Vitrandic Xeropsamments
LCEF. Other Xeropsamments that have a horizon within
100 cm of the mineral soil surface that is 15 cm or more thick
and that either has 20 percent or more (by volume) durinodes
or is brittle and has a firm rupture-resistance class when
moist.
Durinodic Xeropsamments
LCEG. Other Xeropsamments that have lamellae within 200
cm of the mineral soil surface.
Lamellic Xeropsamments
LCEH. Other Xeropsamments that have a base saturation (by
NH4
OAc) of less than 60 percent in all horizons at a depth
between 25 and 75 cm below the mineral soil surface.
Dystric Xeropsamments
LCEI. Other Xeropsamments.
Typic Xeropsamments
Definition of Typic Xeropsamments
Typic Xeropsamments are the Xeropsamments that:
1. Do not have lamellae within 200 cm of the soil surface;
2. Do not have, in any horizon within 100 cm of the mineral
soil surface, distinct or prominent redox concentrations and
also aquic conditions;
3. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 30 or more cumulative days or 20
or more consecutive days in normal years;
4. Do not have a horizon within 100 cm of the surface that is
more than 15 cm thick and that either has 20 percent or more
durinodes or is brittle and has a firm rupture-resistance class
when moist;
5. Do not have a lithic contact within 50 cm of the soil
surface;
6. Have a base saturation (by NH4
OAc) of 60 percent or more
in some part at a depth between 25 and 75 cm below the soil
surface; and
7. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, a fine-earth fraction containing 5 percent or more
volcanic glass, and [(Al plus 1
/2 Fe, percent extracted by
ammonium oxalate) times 60] plus the volcanic glass (percent)
is less than 30.
Description of Subgroups
Typic Xeropsamments.—The Typic subgroup of
Xeropsamments is centered on sands that have no ground
water within a depth of 100 cm, that do not have evident
cementation with silica, and that do not have lamellae in which
silicate clay has accumulated. These soils are more than 50 cm
deep to any lithic contact. Normally, the sands are deep and are
a mixture of quartz and feldspars and little volcanic glass.
These soils have no lamellae within 200 cm of the soil
surface because the lamellae are considered to indicate
intergrades to soils that have an argillic horizon, generally
Xeralfs. Soils that have a lithic contact within a depth of 50 cm
are excluded from the Typic subgroup, a convention used
throughout this taxonomy. Soils that have ground water within
100 cm of the surface at some time of the year are excluded
because they are considered to indicate intergrades to
Psammaquents. Partial cementation by silica is considered to
indicate intergrades to great groups that have duripans.
Typic Xeropsamments are of moderate extent in the Western
United States, mostly in California, Washington, and Nevada.
The soils that are frigid or mesic are used mostly as forest, but
some areas have been cleared and are used as cropland. The
soils that are thermic are used mostly as cropland or rangeland.
Aquic Durinodic Xeropsamments.—These soils show
evidence of weak cementation by silica in the form of
durinodes or of a horizon more than 15 cm thick that is brittle
and has a firm rupture-resistance class when moist. The soils
normally have an appreciable amount of pyroclastics in the
sand fraction. In addition, they are saturated with water at
some time during the year and have distinct or prominent
redox concentrations within 100 cm of the soil surface.
Aquic Xeropsamments.—These soils are saturated with
water at some time during the year and have distinct or
prominent redox concentrations within 100 cm of the soil
surface. They are not extensive soils in the United States.
Durinodic Xeropsamments.—These soils show evidence of
weak cementation by silica in the form of durinodes or of a
horizon more than 15 cm thick that is brittle and has a firm
rupture-resistance class when moist. The soils are not known to
occur in the United States.
Dystric Xeropsamments.—These soils receive relatively
high amounts of rainfall during the winter months. As a
consequence, the base saturation is lower than that in the soils
of the Typic subgroup. Dystric Xeropsamments are not
extensive. In the United States, they are mostly in California
and Washington, where they support forest vegetation.
Lamellic Xeropsamments.—These soils have lamellae
within 200 cm of the soil surface. They are not extensive. They
are mostly in California, Washington, and Idaho in the United
States. They are used mainly as forest.
Lithic Xeropsamments.—These soils have a lithic contact
within 50 cm of the surface. They are not extensive. They are
mostly in California, Oregon, and Idaho in the United States.
They are used mainly as forest.
Entisols 443
Oxyaquic Xeropsamments.—These soils are saturated with
water at some time during the year. The saturation occurs
within 100 cm of the soil surface. These soils are not extensive
in the United States.
Vitrandic Xeropsamments.—These soils consist of volcanic
deposits or have a layer of pyroclastic materials, 18 cm or more
thick, in the upper 75 cm. The soils are of minor extent, mostly in
California. They are used mainly as forest.
445
The central concept of Gelisols is that of soils with gelic
materials underlain by permafrost. Freezing and
thawing are important processes in Gelisols. Diagnostic
horizons may or may not be present. Permafrost influences
pedogenesis by acting as a barrier to the downward movement
of the soil solution.
Cryoturbation (frost mixing) is an important process in
many Gelisols and results in irregular or broken horizons,
involutions, organic matter accumulation on the permafrost
table, oriented rock fragments, and silt caps on rock fragments.
Cryoturbation occurs when two freezing fronts, one from the
surface and the other from the permafrost, merge during
freeze-back in the autumn. Ice segregation is an important
property of gelic materials and occurs when the soil solution
migrates toward ice, increasing the volume of ice. Volume
changes also occur as the water freezes. In the drier areas,
cryoturbation is less pronounced or does not occur, but the soils
still have gelic materials, as manifested by sand wedges and ice
crystals.
Diagnostic horizons, including ochric, mollic, umbric, and
histic epipedons and argillic, salic, gypsic, and calcic horizons,
have been observed in Gelisols. The importance of these
diagnostic horizons, however, is overshadowed by the
properties of the gelic materials and the associated permafrost.
In some Gelisols the effects of cryoturbation are so well
expressed that no diagnostic horizons are observed.
Definition of Gelisols and Limits Between
Gelisols and Soils of Other Orders
Gelisols are soils that have one or more of the following:
1. Permafrost within 100 cm of the soil surface; or
2. Gelic materials within 100 cm of the soil surface and
permafrost within 200 cm of the soil surface.
Limits Between Gelisols and Other Soil Orders
The definition of Gelisols must provide criteria that separate
Gelisols from all other orders. The aggregate of these criteria
defines the limits of Gelisols in relation to all other known
soils.
Unlike the other soil orders, Gelisols have one or both of the
following:
1. Permafrost within 100 cm of the soil surface; or
2. Gelic materials within 100 cm of the soil surface and
permafrost within 200 cm of the soil surface.
Representative Pedon and Data
Following is a description of a representative Gelisol. Data
for the pedon identified in this description are given in the
table “Characterization Data for a Gelisol.”
Classification: Loamy, mixed, superactive Typic Molliorthel
Site identification number: 94P0668
Location: Lower Kolymar, Russia
Latitude: 68 degrees 43 minutes 56 seconds N.
Longitude: 161 degrees 31 minutes 49 seconds E.
Slope: 3 percent
Aspect: 270 degrees
Horizontal shape: Convex
Vertical shape: Convex
Total slope length: 200 m, 30 m of which is above the sample
site
Elevation: 140 m
Landscape: Plains
Landform: Pediment
Annual precipitation: 190 mm
Soil moisture regime: Udic
Land use: Forest land (not grazed)
Permeability class: Moderate
Natural drainage class: Well drained
Parent material: Loess and moderately weathered local
colluvium derived from acidic schist and diorite
Particle-size control section: 25 to 100 cm
Diagnostic features: An mollic epipedon from a depth of 0 to
38 cm and permafrost at a depth of 94 cm
Notes: An ice-rich permafrost table is at a depth of 94 cm.
The frozen layer from a depth of 78 to 94 cm is thought to be
part of the active layer in some years. Charcoal is mixed to a
depth of 25 cm. Rock fragments are diorite.
CHAPTER 13
Gelisols1
1
This chapter is based on recommendations by the International Committee on
Permafrost-Affected Soils (ICOMPAS), chaired by Dr. James G. Bockheim, University of
Wisconsin.
446 Soil Taxonomy
Characterization Data for a Gelisol
SITE IDENTIFICATION NO.: 94P0668
CLASSIFICATION: LOAMY, MIXED, SUPERACTIVE TYPIC MOLLORTHEL
GENERAL METHODS: 1B1A, 2A1, 2B
-1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-
-----------------------------------------------------------------------------------------------------------------------------------
(- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)
CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT
SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF
NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE
<- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL
94P5015 0- 7 A 23.7 61.3 15.0 11.2 31.1 30.2 8.4 3.3 0.6 0.4 2.3 4 2 3V 15 9
94P5016 7- 12 AB 8.7 72.9 18.4 4.5 34.4 38.5 12.1 1.7 1.4 1.5 1.7 2 1 5V 14 8
94P5017 12- 38 Bw1 13.0 70.1 16.9 5.6 33.1 37.0 13.4 1.3 0.9 0.7 0.6 1 1 5V 10 7
94P5018 38- 59 Bw2 15.5 68.3 16.2 9.6 31.9 36.4 14.1 1.1 0.4 0.4 0.2 TR 1 5V 8 6
94P5019 59- 78 Bw3 15.4 68.9 15.7 8.1 29.8 39.1 14.0 1.1 0.2 0.3 0.1 TR TR 5V 7 5
94P5020 78- 94 Bw4 15.2 70.3 14.5 7.3 29.8 40.5 12.5 1.0 0.3 0.3 0.4 TR TR 5V 7 5
94P5021 94-110 Cf 13.5 75.6 10.9 6.7 29.1 46.5 9.7 0.6 0.2 0.2 0.2 TR 1 5V 7 6
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ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD
C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE
DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL
(cm) 6A1c 6B4a 6S3 6R3c 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A5 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1
Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm
0- 7 7.54 0.331 TR 1.25 0.95 0.73 1.04 0.121 38.3 22.5 0.11
7- 12 0.65 0.064 1 -- 1.4 0.1 TR 1.31 0.67 1.65 1.65 -- 18.5 5.8 0.20
12- 38 0.56 0.065 TR -- 1.6 0.1 TR 0.97 0.50 6.5
38- 59 0.48 0.065 1 -- 1.8 0.1 TR 0.95 0.57 8.8
59- 78 0.44 0.066 2 -- 1.7 0.1 TR 0.88 0.54 1.54 1.66 0.024 20.8 8.3 0.19
78- 94 0.44 0.068 1 -- 1.6 0.1 TR 0.86 0.51 1.73 1.79 0.011 18.3 7.7 0.18
94-110 0.39 0.059 1 -- 1.5 0.1 TR 0.83 0.51 6.9
-----------------------------------------------------------------------------------------------------------------------------------
(- NH4OAc EXTRACTABLE BASES -) ACID- EXTR (- - - -CEC - - -) Al -BASE SAT- CO3 AS RES. COND.(- - - -PH - - -)
Ca Mg Na K SUM ITY Al SUM NH4- BASES SAT SUM NH4 CaCO3 ohms mmhos KCl CaCl2 H2O
DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc + Al OAc <2mm /cm /cm IN .01M
(cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 6G9d 5A3a 5A8c 5A3b 5G1 5C3 5C1 6E1g 8E1 8I 8C1g 8C1f 8C1f
<- - - - - - - - - - - -meq / 100 g - - - - - - - - - - -> <- - - - -Pct - - - -> 1:2 1:1
0- 7 11.1 4.9 0.6 0.4 17.0 28.0 45.0 29.7 38 57 3.8 4.6 5.2
7- 12 6.0 2.8 0.3 0.1 9.2 7.5 0.3 16.7 11.4 9.5 3 55 81 4.1 4.9 5.7
12- 38 7.4 3.7 0.2 0.1 11.4 5.4 TR 16.8 12.6 68 90 4.7 5.6 6.6
38- 59 9.5 4.9 0.4 0.2 15.0 5.1 20.1 14.7 75 100 5.4 6.1 6.8
59- 78 9.2 4.6 0.2 0.2 14.2 3.8 18.0 13.5 79 100 5.6 6.3 6.8
78- 94 8.0 4.1 0.2 0.2 12.5 3.7 16.2 13.1 77 95 5.8 6.4 7.3
94-110 7.5 3.8 0.2 0.2 11.7 2.4 14.1 11.2 83 100 5.8 6.5 7.3
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ACID OXALATE EXTRACTION PHOSPHORUS KCl TOTAL (- -WATER CONTENT- - )(- - - - WATER DISPERSIBLE - - - - ) MIN AGGRT
OPT Fe Si Al CIT- Mn C 0.06 1- 2- 15 <- - PIPETTE - - >< - HYDROMETER - > SOIL STABL
DEN RET ACID BAR BAR BAR BAR CLAY SILT SAND CLAY SILT SAND CONT <5mm
SAMPLE HZ 8J 6C9b 6V2b 6G12b 6S4 6S5 6D3b 6A2e 4B1c 4B1a 4B1a 4B2b <- - - 3A1c - - -><- - - SML - - -> 8F1 4G1
NO. NO <- P c t o f < 2 m m -><- p p m ->< - - - - - - - - - - P e r c e n t o f < 2 m m - - - - - - - - - - >< Pct>
94P5015 1 30.8 90
94P5016 2 0.06 0.48 0.03 0.13 32 0.5 11.0
94P5017 3 0.05 0.42 0.05 0.14 31 0.6 12.3
94P5018 4 0.04 0.37 0.05 0.15 28 12.7
94P5019 5 0.04 0.36 0.06 0.15 23 12.5
94P5020 6 0.04 0.33 0.06 0.12 28 14.1
94P5021 7 0.03 0.28 0.06 0.11 28 10.7
-----------------------------------------------------------------------------------------------------------------------------------
< - - - - - - - - - - - - - - - - - - - - - - CLAY MINERALOGY (<.002mm) - - - - - - - - - - - - - - - - - - - - - - - >
FRAC- < - - - - - X-RAY - - - - - ->< - - - THERMAL - - - ->< - - - - - - - ELEMENTAL - - - - - - - ->< - -> EGME INTERSAMPLE
TION < >< - DTA - ->< - TGA - -> SiO2 Al2O3 Fe2O3 MgO CaO K2O Na2O < > RETN PRETA<
- - - - - 7A2i - - - - - ->< - 7A6b - >< - 7A4c - >< - - - - - - - - - 7C4a- - - - - - - - ->< > 7D2 TION
NUMBER <- - >< - - - - Peak size - - - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - -><mg/g>< - ->
94P5017 TCLY VR 3 MI 3 KK 2 QZ 2 FD 2
94P5017 VM 1
94P5019 TCLY MI 3 VR 3 KK 2 QZ 1 FD 1
94P5021 TCLY MI 3 VR 2 KK 2 QZ 1 FD 1
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Gelisols 447
Characterization Data for a Gelisol--Continued
-1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-
-----------------------------------------------------------------------------------------------------------------------------------
< - - - - - - - - - - - - - - - - - - - - SAND - SILT MINERALOGY (2.0-0.002mm) - - - - - - - - - - - - - - - - - - - - >
FRAC- < - - - - - X-RAY - - ->< - - - THERMAL - - - ->< - - - - - - - OPTICAL - - - - - - - - >< >INTERSAMPLE
TION < >< - DTA - ->< - TGA - ->TOT RE< - - - - - GRAIN COUNT - - - - - ->< >PRETA<
- - - - 7A2i - - - - >< - 7A3c - >< - 7A4c - >< - - - - - - - - 7B1a - - - - - - - - ->< > TION
NUMBER < - ->< - - - Peak Size - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - - - - - - - ->< - ->
94P5017 CSi 39 QZ38 FK25 AR19 FP 5 MS 4 CM 4
94P5017 CSi PR 2 HN 1 FE 1 OPtr POtr BYtr
94P5017 CSi GNtr RUtr GStr ZRtr APtr BYtr
94P5018 CSi 48 QZ46 FK22 AR17 FP 7 PR 2 HN 2
94P5018 CSi FE 2 MS 1 BT 1 CM 1 OPtr APtr
94P5018 CSi MZtr BYtr ZRtr RUtr GNtr GStr
94P5018 CSi FZtr ZEtr
94P5019 CSi 43 QZ42 AR24 FK15 FP 5 HN 4 MS 2
94P5019 CSi CM 2 FE 1 BT 1 PRtr OPtr FZtr
94P5019 CSi GNtr ZEtr CTtr BYtr ZRtr APtr
94P5019 CSi RUtr
94P5020 CSi 46 QZ46 AR19 FK17 FP 6 MS 4 CM 3
94P5020 CSi HN 3 PR 1 FEtr BTtr BYtr RUtr
94P5020 CSi OPtr APtr TMtr POtr GStr ZRtr
94P5020 CSi GNtr
94P5021 CSi 46 QZ45 FK20 AR20 FP 5 CM 4 HU 2
94P5021 CSi MS 1 BT 1 PR 1 FE 1 OPtr RUtr
94P5021 CSi ZRtr BYtr APtr GNtr
-----------------------------------------------------------------------------------------------------------------------------------
The chemical data are based on the fraction less than 2 mm in size.
V in tier 1, column 18, indicates volume estimates.
Fraction interpretation: TCLY, total clay, <0.002 mm; CSi, coarse silt, 0.02-0.05 mm.
Mineral interpretation: VR, vermiculite; MI, mica; KK, kaolinite; QZ, quartz; FD, feldspar; VM, vermiculite-mica; FK, potassium
feldspar; AR, weathered aggregate; FP, plagioclase feldspar; MS, muscovite; CM, chlorite-mica; PR, pyroxene; HN, hornblende;
FE, iron oxides; OP, opaques; PO, plant opal; BY, beryl; GN, garnet; RU, rutile; GS, glass; ZR, zircon; AP, apatite;
BT, biotite; MZ, monazite; FZ, feldspathoid; ZE, zeolite; CT cassiterite; TM, tourmaline.
Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.
Family mineralogy: Mixed.
In the following pedon description, colors are for moist soil
unless otherwise indicated.
A—0 to 7 cm; dark reddish brown (5YR 2/2) silt loam, dark
reddish brown (5YR 3/2) dry; weak thin platy and
moderate very fine subangular blocky structure; many very
fine roots throughout; 1 percent angular gravel; very
strongly acid; abrupt wavy boundary.
AB—7 to 12 cm; dark grayish brown (10YR 4/2) silt loam,
light olive brown (2.5Y 5/3) dry; weak thin platy and
moderate very fine subangular blocky structure; firm,
slightly sticky and slightly plastic; common very fine to
medium roots throughout; common fine high-continuity
tubular pores; 9.0 percent clay; 3 percent angular gravel;
very strongly acid; abrupt wavy boundary.
Bw1—12 to 38 cm; dark brown (10YR 3/3) silt loam, light
olive brown (2.5Y 5/3) dry; moderate thin platy and
moderate fine subangular blocky structure; friable, slightly
sticky and slightly plastic; common very fine to medium
roots throughout; many medium vesicular and many very
fine high-continuity tubular pores; 10.0 percent clay; 3
percent angular gravel; very strongly acid; clear wavy
boundary.
Bw2—38 to 59 cm; very dark grayish brown (10YR 3/2) silt loam,
light olive brown (2.5Y 5/3) dry; strong very fine subangular
blocky structure; very friable, slightly sticky and plastic;
common very fine to medium roots throughout; many very
fine and fine high-continuity tubular pores; 15.0 percent
clay; 3 percent angular gravel; very strongly acid; clear
wavy boundary.
Bw3—59 to 78 cm; very dark grayish brown (2.5Y 3/2) silt
loam, light olive brown (2.5Y 5/3) dry; moderate very thin
platy and moderate very fine subangular blocky structure;
friable, slightly sticky and plastic; 15.0 percent clay; 3
percent angular gravel; strongly acid; gradual wavy
boundary.
Bw4—78 to 94 cm; dark grayish brown (2.5Y 4/2) silt loam,
grayish brown (2.5Y 5/2) dry; strong medium platy and
moderate fine subangular blocky structure; extremely
firm, sticky and plastic; few very fine and fine roots;
common very fine and fine moderate-continuity tubular
pores; 17.0 percent clay; 2 percent angular cobbles and 3
percent angular gravel; strongly acid; clear wavy boundary.
448 Soil Taxonomy
Cf—94 to 110 cm; dark grayish brown (2.5Y 4/2) silt loam;
massive; extremely firm, sticky and plastic; 17.0 percent
clay; 2 percent angular cobbles and 3 percent angular
gravel; strongly acid.
Key to Suborders
AA. Gelisols that have organic soil materials that meet one or
more of the following:
1. Overlie cindery, fragmental, or pumiceous materials
and/or fill their interstices and directly below these
materials have either a densic, lithic, or paralithic contact;
or
2. When added with the underlying cindery, fragmental, or
pumiceous materials, total 40 cm or more between the soil
surface and a depth of 50 cm; or
3. Are saturated with water for 30 or more cumulative
days during normal years (or are artificially drained) and
have 80 percent or more, by volume, organic soil materials
from the soil surface to a depth of 50 cm or to a glacic layer
or a densic, lithic, or paralithic contact, whichever is
shallowest.
Histels, p. 448
AB. Other Gelisols that have one or more horizons showing
cryoturbation in the form of irregular, broken, or distorted
horizon boundaries, involutions, the accumulation of organic
matter on top of the permafrost, ice or sand wedges, and
oriented rock fragments.
Turbels, p. 462
AC. Other Gelisols.
Orthels, p. 452
Histels
These are the Gelisols with large amounts of organic carbon
that commonly accumulate under anaerobic conditions, or the
organic matter at least partially fills voids in fragmental,
cindery, or pumiceous materials. Cold temperatures contribute
to the accumulation of organic matter.
Definition
Histels are the Gelisols that have organic soil materials that
meet one or more of the following:
1. Overlie cindery, fragmental, or pumiceous materials and/or
fill their interstices and directly below these materials have
either a densic, lithic, or paralithic contact; or
2. When added with the underlying cindery, fragmental, or
pumiceous materials, total 40 cm or more between the soil
surface and a depth of 50 cm; or
3. Are saturated with water for 30 or more cumulative
days during normal years (or are artificially drained) and
have 80 percent or more, by volume, organic soil materials
from the soil surface to a depth of 50 cm or to a glacic layer
or a densic, lithic, or paralithic contact, whichever is
shallowest.
Key to Great Groups
AAA. Histels that are saturated with water for less than 30
cumulative days during normal years (and are not artificially
drained).
Folistels, p. 449
AAB. Other Histels that are saturated with water for 30 or
more cumulative days during normal years and that have both:
1. A glacic layer with its upper boundary within 100 cm of
the soil surface; and
2. Less than three-fourths (by volume) Sphagnum fibers in
the organic soil materials to a depth of 50 cm or to a densic,
lithic, or paralithic contact, whichever is shallower.
Glacistels, p. 450
AAC. Other Histels that have more thickness of fibric soil
materials than any other kind of organic soil material to a
depth of 50 cm or to a densic, lithic, or paralithic contact,
whichever is shallowest.
Fibristels, p. 448
AAD. Other Histels that have more thickness of hemic soil
materials than any other kind of organic soil material to a
depth of 50 cm or to a densic, lithic, or paralithic contact,
whichever is shallowest.
Hemistels, p. 450
AAE. Other Histels.
Sapristels, p. 451
Fibristels
These are wet Histels in which the organic materials are
slightly decomposed. Most of the fiber is not destroyed by
rubbing between the thumb and fingers. The botanical origin of
much of the materials can be readily determined.
Many Fibristels have ground water near the surface nearly
all the time. These soils are of small extent in Alaska, Canada,
and Siberia. They occur in depressional or level areas,
commonly to adjacent water bodies.
Gelisols 449
Definition
Fibristels are the Histels that:
1. Are saturated with water for 30 or more cumulative days
during normal years;
2. Do not have a glacic layer that has its upper boundary
within 100 cm of the soil surface; and
3. Have more thickness of fibric soil materials than any other
kind of organic soil material to a depth of 50 cm or to a densic,
lithic, or paralithic contact, whichever is shallowest.
Key to Subgroups
AACA. Fibristels that have a lithic contact within 100 cm of
the soil surface.
Lithic Fibristels
AACB. Other Fibristels that have a mineral layer 30 cm or
more thick within 100 cm of the soil surface.
Terric Fibristels
AACC. Other Fibristels that have, within the organic
materials, either one mineral layer 5 cm or more thick or two
or more layers of any thickness within 100 cm of the soil
surface.
Fluvaquentic Fibristels
AACD. Other Fibristels in which three-fourths or more of the
fibric material is derived from Sphagnum to a depth of 50 cm
or to a densic, lithic, or paralithic contact, whichever is
shallowest.
Sphagnic Fibristels
AACE. Other Fibristels.
Typic Fibristels
Definition of Typic Fibristels
Typic Fibristels are the Fibristels that:
1. Do not have a lithic contact within 100 cm of the soil
surface;
2. Do not have a mineral layer between 5 and 30 cm thick or
two or more thin, continuous mineral layers within 100 cm of
the soil surface;
3. Do not have a mineral layer 30 cm or more thick that has
its upper boundary within 100 cm of the soil surface; and
4. Have less than three-fourths of their fibric material derived
from Sphagnum to a depth of 50 cm or to a densic, lithic, or
paralithic contact, whichever is shallowest.
Description of Subgroups
Typic Fibristels.—The Typic subgroup is fixed on soils that
do not have a lithic contact within 100 cm of the soil surface
and are not composed largely of Sphagnum. A lithic contact is
used in classifying soils in lithic subgroups. Thick or thin
mineral layers as well as intermittent layers that are within 100
cm of the soil surface cause soils to be excluded from the Typic
subgroup. Typic Fibristels are of small extent in the world but
are known to occur in northern Russia and in Alaska and
Canada.
Fluvaquentic Fibristels.—These soils differ from the Typic
Fibristels because they have, within 100 cm of the soil surface,
either one mineral layer 5 to 30 cm thick or two or more
mineral layers of any thickness. These soils are relatively rare
but occur in Canada and Siberia.
Lithic Fibristels.—These soils differ from Typic Fibristels
because they have a lithic contact within 100 cm of the soil
surface.
Sphagnic Fibristels.—These soils differ from Typic
Fibristels because three-fourths or more of their fibric materials
is derived from Sphagnum to a depth of 50 cm. These soils
occur in Alaska, Siberia, and Canada.
Terric Fibristels.—These soils differ from Typic Fibristels
because they have a mineral layer 30 cm or more thick within
100 cm of the soil surface. These soils occur in Alaska,
Canada, and Siberia.
Folistels
These are the more or less freely drained Histels that consist
primarily of O horizons derived from plant litter resting on
rock or on fragmental materials that consist of gravel or larger
rock fragments in which the interstices are partly filled or
filled with organic materials. Plant roots grow in the organic
materials. These soils are rare in the world.
Definition
Folistels are the Histels that are saturated with water for less
than 30 cumulative days during normal years (and are not
artificially drained).
Key to Subgroups
AAAA. Folistels that have a lithic contact within 50 cm of
the soil surface.
Lithic Folistels
AAAB. Other Folistels that have a glacic layer with its upper
boundary within 100 cm of the soil surface.
Glacic Folistels
AAAC. Other Folistels.
Typic Folistels
Definition of Typic Folistels
Typic Folistels are the Folistels that:
1. Do not have a lithic contact within 50 cm of the soil
surface; and
450 Soil Taxonomy
2. Do not have a glacic layer that has its upper boundary
within 100 cm of the soil surface.
Description of Subgroups
Typic Folistels.—The concept of the Typic Folistels is that of
soils with organic materials that are filling or partially filling
interstices in fragmental materials. Typic Folistels do not have
either a glacic layer within 100 cm of the soil surface or a lithic
contact within 50 cm of the soil surface.
Glacic Folistels.—These are the Folistels that have a
layer of ice 30 cm or more thick within 100 cm of the soil
surface.
Lithic Folistels.—These are the Folistels that have organic
materials resting on a lithic contact within 50 cm of the soil
surface.
Glacistels
Glacistels are the Histels that have 30 cm or more of ice within
100 cm of the soil surface. Disturbance of the surface-insulating
layer causes the ice layer to melt and the soils to collapse. These
soils occur in Alaska, Canada, and Siberia.
Definition
Glacistels are the Histels that:
1. Are saturated with water for 30 or more cumulative days
during normal years;
2. Have a glacic layer with its upper boundary within 100 cm
of the soil surface; and
3. Have less than three-fourths (by volume) Sphagnum fibers
to a depth of 50 cm or to a densic, lithic, or paralithic contact,
whichever is shallowest.
Key to Subgroups
AABA. Glacistels that have more thickness of hemic
materials than any other kind of organic soil material in the
upper 50 cm.
Hemic Glacistels
AABB. Other Glacistels that have more thickness of sapric
materials than any other kind of organic soil material in the
upper 50 cm.
Sapric Glacistels
AABC. Other Glacistels
Typic Glacistels
Definition of Typic Glacistels
Typic Glacistels are the Glacistels that have more thickness
of fibric material than any other kind of organic material in the
upper 50 cm.
Description of Subgroups
Typic Glacistels.—These are the Glacistels that are
dominated by fibric materials. The Typic concept of Glacistels
is centered on a dominance of fibric material. The cold
temperature and high water tables associated with these soils
inhibit the breakdown of organic matter.
Hemic Glacistels.—These are the Glacistels that are
dominated by hemic materials. The botanical origin of much of
the material cannot be readily determined. Water is at or very
close to the surface of these soils much of the time, unless
drainage has been provided.
Sapric Glacistels.—These are the Glacistels that are
dominated by sapric materials. Although water is at or near the
surface for much of the year, the organic material is
decomposed to the degree that the original plant material is
unrecognizable.
Hemistels
These are wet Histels in which the organic materials are
moderately decomposed. The botanical origin of much of the
organic material is between one-sixth and two-thirds after
rubbing between the fingers. Water is at or very close to the
surface of these soils much of the time, unless artificial
drainage has been provided. The level of ground water may
fluctuate but seldom drops much below the surface tier.
Hemistels occur in depressional areas or the adjacent water
bodies. These soils are known to occur in Siberia, Canada, and
Alaska.
Definition
Hemistels are the Histels that:
1. Are saturated with water for 30 or more cumulative days
during normal years (and are not artificially drained);
2. Do not have a glacic layer that has its upper boundary
within 100 cm of the soil surface; and
3. Have more thickness of hemic soil materials than any
other kind of organic soil material to a depth of 50 cm or to a
densic, lithic, or paralithic contact, whichever is shallowest.
Key to Subgroups
AADA. Hemistels that have a lithic contact within 100 cm of
the soil surface.
Lithic Hemistels
AADB. Other Hemistels that have a mineral layer 30 cm or
more thick within 100 cm of the soil surface.
Terric Hemistels
AADC. Other Hemistels that have, within the organic
materials, either one mineral layer 5 cm or more thick or two
Gelisols 451
or more layers of any thickness within 100 cm of the soil
surface.
FluvaquenticHemistels
AADD. Other Hemistels.
Typic Hemistels
Definition of Typic Hemistels
Typic Hemistels are the Hemistels that:
1. Do not have a lithic contact within 100 cm of the soil
surface;
2. Do not have a mineral layer between 5 and 30 cm thick or
two or more thin, continuous mineral layers within 100 cm of
the soil surface; and
3. Do not have a mineral layer 30 cm or more thick that has
its upper boundary within 100 cm of the soil surface.
Description of Subgroups
Typic Hemistels.—These are the Hemistels that do not
have a lithic contact within 100 cm of the soil surface. These
soils also do not have thick or thin mineral layers within 100
cm of the soil surface. Typic Hemistels occur in Alaska,
Siberia, and Canada.
Fluvaquentic Hemistels.—These are the Hemistels that
have one or more thin layers of mineral soil material within
100 cm of the soil surface. The mineral soil material commonly
is deposited by floodwaters or ponded waters. These soils occur
in Alaska, Canada, and Siberia.
Lithic Hemistels.—These are the Hemistels that have a
lithic contact within 100 cm of the soil surface. These soils are
relatively rare in the world.
Terric Hemistels.—These are the Hemistels that have a
thick mineral layer within 100 cm of the soil surface. The thick
mineral layer may have been deposited under hydrologic
conditions that differ from those of the present. These soils
occur in Alaska, Canada, and Siberia.
Sapristels
These are wet Histels in which the organic materials are well
decomposed. The botanical origin of the organic material is
difficult to determine in most of these soils. The fiber content of
most of the organic material is less than one-sixth after rubbing
between the fingers.
Sapristels occur in areas where ground water tables tend to
fluctuate within the soils or where the soils were aerobic during
drier periods in the past. When drained, fibric and hemic
materials commonly decompose to form sapric materials.
Definition
Sapristels are the Histels that:
1. Are saturated with water for 30 or more cumulative days
during normal years (and are not artificially drained);
2. Do not have a glacic layer that has its upper boundary
within 100 cm of the soil surface; and
3. Have more thickness of sapric soil materials than any other
kind of organic soil material to a depth of 50 cm or to a densic,
lithic, or paralithic contact, whichever is shallowest.
Key to Subgroups
AAEA. Sapristels that have a lithic contact within 100 cm of
the soil surface.
Lithic Sapristels
AAEB. Other Sapristels that have a mineral layer 30 cm or
more thick within 100 cm of the soil surface.
Terric Sapristels
AAEC. Other Sapristels that have, within the organic
materials, either one mineral layer 5 cm or more thick or two
or more layers of any thickness within 100 cm of the soil
surface.
Fluvaquentic Sapristels
AAED. Other Sapristels.
Typic Sapristels
Definition of Typic Sapristels
Typic Sapristels are the Sapristels that:
1. Do not have a lithic contact within 100 cm of the soil
surface;
2. Do not have a mineral layer between 5 and 30 cm thick or
two or more thin, continuous mineral layers within 100 cm of
the soil surface; and
3. Do not have a mineral layer 30 cm or more thick that has
its upper boundary within 100 cm of the soil surface.
Description of Subgroups
Typic Sapristels.—These are the Sapristels that do not have
a lithic contact within 100 cm of the soil surface. These soils
also do not have thick or thin mineral layers within 100 cm of
the soil surface. Typic Sapristels occur in Alaska, Siberia, and
Canada.
Fluvaquentic Sapristels.—These are the Sapristels that
have one or more thin layers of mineral soil material within
100 cm of the soil surface. The mineral soil material commonly
is deposited by floodwaters or ponded waters. These soils occur
in Alaska, Canada, and Siberia.
Lithic Sapristels.—These are the Sapristels that have a
lithic contact within 100 cm of the soil surface. These soils are
relatively rare in the world.
452 Soil Taxonomy
Terric Sapristels.—These are the Sapristels that have a thick
mineral layer within 100 cm of the soil surface. The thick mineral
layer may have been deposited under hydrologic conditions that
differ from those of the present. These soils occur in Alaska,
Canada, and Siberia.
Orthels
Orthels are the Gelisols that show little or no evidence of
cryoturbation and are the second most abundant suborder of
Gelisols. These soils occur primarily within the zone of
widespread permafrost or in areas of coarse textured materials
in the continuous zone of permafrost. Orthels are generally
drier than Turbels and Histels. They occur in the southern
Andes and the high latitudes of the Northern Hemisphere.
Definition
Orthels are the Gelisols that:
1. Do not have organic soil materials that meet any of the
following:
a. Overlie cindery, fragmental, or pumiceous materials
and/or fill their interstices and directly below these
materials have either a densic, lithic, or paralithic contact;
or
b. When added with the underlying cindery, fragmental, or
pumiceous materials, total 40 cm or more between the soil
surface and a depth of 50 cm; or
c. Are saturated with water for 30 or more cumulative
days during normal years (or are artificially drained) and
have 80 percent or more, by volume, organic soil materials
from the soil surface to a depth of 50 cm or to a glacic layer
or a densic, lithic, or paralithic contact, whichever is
shallowest; and
2. Do not have any horizons showing cryoturbation in the
form of irregular, broken, or distorted horizon boundaries,
involutions, the accumulation of organic matter on top of the
permafrost, ice or sand wedges, and oriented rock fragments.
Key to Great Groups
ACA. Orthels that have in 30 percent or more of the pedon
more than 40 percent, by volume, organic materials from the
soil surface to a depth of 50 cm.
Historthels, p. 457
ACB. Other Orthels that have, within 50 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions during normal years (or artificial drainage).
Aquorthels, p. 453
ACC. Other Orthels that have anhydrous conditions.
Anhyorthels, p. 452
ACD. Other Orthels that have a mollic epipedon.
Mollorthels, p. 457
ACE. Other Orthels that have an umbric epipedon.
Umbrorthels, p. 460
ACF. Other Orthels that have an argillic horizon that has its
upper boundary within 100 cm of the mineral soil surface.
Argiorthels, p. 455
ACG. Other Orthels that have, below the Ap horizon or below
a depth of 25 cm, whichever is deeper, less than 35 percent (by
volume) rock fragments and have a texture of loamy fine sand or
coarser in the particle-size control section.
Psammorthels, p. 459
ACH. Other Orthels.
Haplorthels, p. 456
Anhyorthels
These are the Orthels that have anhydrous conditions. They
often have dry permafrost (i.e., insufficient moisture for
interstitial ice to occur). The cold deserts commonly receive
less than 30 mm of annual precipitation. These soils support
little or no vegetation.
These soils are limited in extent but are known to occur in
continental Antarctica, the High Arctic (northern Greenland
and Ellesmere Island), and the cold, dry mountains of Eurasia
at elevations of more than 3,700 m.
Definition
Anhyorthels are the Orthels that:
1. Have anhydrous conditions;
2. Do not have in 30 percent or more of the pedon more
than 40 percent, by volume, organic materials from the soil
surface to a depth of 50 cm; and
3. Do not have, within 50 cm of the mineral soil surface,
redox depletions with chroma of 2 or less and also aquic
conditions during normal years.
Key to Subgroups
ACCA. Anhyorthels that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Anhyorthels
ACCB. Other Anhyorthels that have a glacic layer that has
its upper boundary within 100 cm of the mineral soil surface.
Glacic Anhyorthels
Gelisols 453
ACCC. Other Anhyorthels that have a petrogypsic horizon
that has its upper boundary within 100 cm of the mineral soil
surface.
Petrogypsic Anhyorthels
ACCD. Other Anhyorthels that have a gypsic horizon that
has its upper boundary within 100 cm of the mineral soil
surface.
Gypsic Anhyorthels
ACCE. Other Anhyorthels that have a horizon 15 cm or
more thick that contains 12 cmol(-)/L in 1:5 soil:water nitrate
and in which the product of its thickness (in cm) and its nitrate
concentration is 3,500 or more.
Nitric Anhyorthels
ACCF. Other Anhyorthels that have a salic horizon that has
its upper boundary within 100 cm of the mineral soil surface.
Salic Anhyorthels
ACCG. Other Anhyorthels that have a calcic horizon with its
upper boundary within 100 cm of the mineral soil surface.
Calcic Anhyorthels
ACCH. Other Anhyorthels.
Typic Anhyorthels
Definition of Typic Anhyorthels
These are the Anhyorthels that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Do not have a glacic layer or a petrogypsic, gypsic, salic,
or calcic horizon with its upper boundary within 100 cm of the
mineral soil surface; and
3. Do not have a horizon 15 cm or more thick that has 12
cmol(-)/L nitrate in 1:5 soil:water extract and in which the
product of its thickness (in cm) and its nitrate concentration is
3,500 or more.
Description of Subgroups
Typic Anhyorthels.—These are the Anhyorthels that
commonly have accumulations of salts, including gypsum and
calcium carbonate, but insufficient quantities to meet the
criteria for a calcic, gypsic, petrogypsic, or salic horizon. These
soils also do not contain large amounts of nitrate. Typic
Anhyorthels do not have a lithic contact within 50 cm of the
mineral soil surface or a glacic layer with its upper boundary
within 100 cm of the mineral soil surface.
Calcic Anhyorthels.—These are the Anhyorthels that have
a calcic horizon within 100 cm of the mineral soil surface.
These soils commonly have other more soluble salts, but not in
sufficient quantity to meet the criteria for a petrogypsic, gypsic,
or salic horizon. These soils also lack sufficient quantities of
nitrate, a glacic layer, and a lithic contact.
Glacic Anhyorthels.—These are the Anhyorthels that have
a glacic layer with its upper boundary within 100 cm of the
mineral soil surface. These soils commonly have accumulations
of salts, including calcium carbonate and gypsum, but do not
have a lithic contact within 50 cm of the mineral soil surface.
Gypsic Anhyorthels.—These are the Anhyorthels that have
a gypsic horizon within 100 cm of the mineral soil surface.
They commonly have other salts, including calcium carbonate.
These soils do not have a lithic contact within 50 cm or a
glacic layer with its upper boundary within 100 cm of the
mineral soil surface.
Lithic Anhyorthels.—These are the Anhyorthels that have
a lithic contact within 50 cm of the mineral soil surface. They
commonly have accumulations of salts, including calcium
carbonate and gypsum.
Nitric Anhyorthels.—These are the Anhyorthels that have
large accumulations of nitrate. They commonly have
accumulations of other salts, but do not have gypsic or
petrogypsic horizons. Nitric Anhyorthels also do not have a
lithic contact within 50 cm or a glacic layer with an upper
boundary within 100 cm of the mineral soil surface.
Petrogypsic Anhyorthels.—These are the Anhyorthels that
have a petrogypsic horizon within 100 cm of the mineral soil
surface. They can have accumulations of other salts, but they
do not have a lithic contact within 50 cm or a glacic layer with
its upper boundary within 100 cm of the mineral soil surface.
Salic Anhyorthels.—These are the Anhyorthels that have a
salic horizon with or without a calcic horizon. These soils do
not have a lithic contact within 50 cm or a glacic layer with its
upper boundary within 100 cm of the mineral soil surface.
They also do not have gypsic or petrogypsic horizons or large
accumulations of nitrates within 100 cm of the mineral soil
surface.
Aquorthels
These are the Orthels that are saturated and reduced close to
the surface for at least part of the year. These soils have redox
depletions with chroma of 2 or less. Aquorthels do not have
high amounts of organic carbon at the surface. These soils are
common in the centers of large-scale, low-centered polygons
along the North Slope of the Brooks Range in Alaska.
Definition
Aquorthels are the Orthels that:
1. Have, within 50 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
during normal years; and
2. Do not have in 30 percent or more of the pedon more
than 40 percent, by volume, organic materials from the
mineral soil surface to a depth of 50 cm.
454 Soil Taxonomy
KeytoSubgroups
ACBA. Aquorthels that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Aquorthels
ACBB. Other Aquorthels that have a glacic layer that has its
upper boundary within 100 cm of the mineral soil surface.
Glacic Aquorthels
ACBC. Other Aquorthels that have a sulfuric horizon or
sulfidic materials with an upper boundary within 100 cm of the
mineral soil surface.
Sulfuric Aquorthels
ACBD. Other Aquorthels that have either:
1. Organic soil materials that are discontinuous at the
surface; or
2. Organic soil materials at the surface that change in
thickness fourfold or more within a pedon.
Ruptic-Histic Aquorthels
ACBE. Other Aquorthels that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Aquorthels
ACBF. Other Aquorthels that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Aquorthels
ACBG. Other Aquorthels that have a salic horizon that
has its upper boundary within 100 cm of the mineral soil
surface.
Salic Aquorthels
ACBH. Other Aquorthels that have less than 35 percent (by
volume) rock fragments and a texture of loamy fine sand or
coarser in all layers within the particle-size control section.
Psammentic Aquorthels
ACBI. Other Aquorthels.
Typic Aquorthels
Definition of Typic Aquorthels
These are the Aquorthels that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Do not have a glacic layer that has its upper boundary
within 100 cm of the mineral soil surface;
3. Do not have either:
a. Organic soil materials that are discontinuous at the
surface; or
b. Organic soil materials at the surface that change in
thickness fourfold or more within a pedon;
4. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, a fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al plus
1
/2 Fe percentages (by ammonium oxalate) totaling more than
1.0;
5. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, one or both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
6. Do not have a salic or sulfuric horizon or sulfidic materials
with an upper boundary within 100 cm of the mineral soil
surface; and
7. Have 35 percent (by volume) or more rock fragments or a
texture finer than loamy fine sand in at least one layer within
the particle-size control section.
Description of Subgroups
Typic Aquorthels.—The concept of Typic Aquorthels is
centered on soils without special characteristics. The Typic
Gelisols 455
subgroup does not have a lithic contact within 50 cm or a glacic
layer with an upper boundary within 100 cm of the mineral soil
surface. These soils also do not have salic or sulfuric horizons
or sulfidic materials within 100 cm of the mineral soil surface.
Textures are finer than loamy fine sand or are skeletal in at least
some layers of the particle-size control section. If these soils
have organic soil materials at the surface, the layer is continuous
and does not change much in thickness within a pedon. These
soils do have the andic soil properties or volcanic glass
associated with the Vitrandic Aquorthels.
Andic Aquorthels.—These are the Aquorthels that have,
throughout one or more horizons with a total thickness of 18
cm or more within 75 cm of the mineral soil surface, a fineearth
fraction with both a bulk density of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and Al plus 1
/2 Fe
percentages (by ammonium oxalate) totaling more than 1.0.
These soils do not have a lithic contact within 50 cm or a
glacic layer with an upper boundary within 100 cm of the
mineral soil surface. Andic Aquorthels are commonly in areas
that receive volcanic ejecta, but this is not required.
Glacic Aquorthels.—These are the Aquorthels that have a
glacic layer with an upper boundary within 100 cm of the
mineral soil surface. Commonly, these soils have organic soil
materials at the surface. Disturbance of the surface horizon
removes the insulating layer; the glacic layer then melts, and
the soil collapses.
Lithic Aquorthels.—These are the Aquorthels that have a
lithic contact within 50 cm of the mineral soil surface. These
soils are rare in the world.
Psammentic Aquorthels.—These are the sandy Aquorthels
that do not have a lithic contact within 50 cm of the mineral
soil surface or a glacic layer with its upper boundary within
100 cm of the mineral soil surface. They also do not have a
salic or sulfuric horizon or sulfidic materials with an upper
boundary within 100 cm of the mineral soil surface. These soils
commonly have thin organic layers and do not have andic soil
properties.
Ruptic-Histic Aquorthels.—These are the Aquorthels that
have an organic layer at the surface that is either discontinuous
or thins and thickens because of periglacial microrelief. These
soils are common in Alaska, Canada, and Siberia.
Salic Aquorthels.—These are the Aquorthels that have a
salic horizon with its upper boundary within 100 cm of the
mineral soil surface. These soils do not have a glacic layer, a
sulfuric horizon, or sulfidic materials with an upper boundary
within 100 cm or a lithic contact within 50 cm of the mineral
soil surface. Salic Aquorthels do not have an organic layer at
the surface that thins and thickens in relationship to
microrelief. These soils do not have andic soil properties.
Sulfuric Aquorthels.—These are the Aquorthels that have
a sulfuric horizon or sulfidic materials within 100 cm of the
mineral soil surface. They do not have a lithic contact within
50 cm of the mineral soil surface and do not have a glacic layer
within 100 cm of the mineral soil surface. These soils occur in
cold coastal areas of the world.
Vitrandic Aquorthels.—These are Aquorthels that have,
throughout one or more horizons with a total thickness of 18
cm or more within 75 cm of the mineral soil surface, one or
both of the following:
1. More than 35 percent (by volume) fragments coarser than
2.0 mm, of which more than 66 percent is cinders, pumice, and
pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Aquorthels are not so weathered as the Andic
Aquorthels. They do not have a lithic contact within 50 cm or a
glacic layer, a sulfuric horizon, or sulfidic materials with an
upper boundary within 100 cm of the mineral soil surface.
Argiorthels
These are the Orthels that have an argillic horizon. These
soils do not have a mollic or umbric epipedon or anhydrous
conditions. Argiorthels do not have the wet conditions
conducive to the accumulation of organic matter close to the
surface. The argillic horizon in these soils commonly is weakly
expressed. These soils are rare in the world but are known to
occur in northern Siberia.
Definition
Argiorthels are the Orthels that:
1. Have an argillic horizon that has its upper boundary
within 100 cm of the mineral soil surface;
2. Do not have in 30 percent or more of the pedon more
than 40 percent, by volume, organic materials from the soil
surface to a depth of 50 cm;
3. Do not have, within 50 cm of the mineral soil surface,
redox depletions with chroma of 2 or less and also aquic
conditions during normal years;
4. Do not have anhydrous conditions; and
5. Do not have a mollic or umbric epipedon.
Key to Subgroups
ACFA. Argiorthels that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Argiorthels
456 Soil Taxonomy
ACFB. Other Argiorthels that have a glacic layer that has its
upper boundary within 100 cm of the mineral soil surface.
Glacic Argiorthels
ACFC. Other Argiorthels that have a natric horizon.
Natric Argiorthels
ACFD. Other Argiorthels.
Typic Argiorthels
Definition of Typic Argiorthels
Typic Argiorthels are the Orthels that:
1. Do not have a lithic contact within 50 cm of the mineral soil
surface;
2. Do not have a glacic layer that has its upper boundary
within 100 cm of the mineral soil surface; and
3. Do not have a natric horizon.
Description of Subgroups
Typic Argiorthels.—These are the Argiorthels that have no
special characteristics. Commonly, the argillic horizon is
weakly developed in these soils. Typic Argiorthels do not have
a lithic contact within 50 cm or a glacic layer with an upper
boundary within 100 cm of the mineral soil surface. These
soils also do not have the sodium associated with natric
horizons. Typic Argiorthels are on stable surfaces with tundra
vegetation.
Glacic Argiorthels.—These are the Argiorthels that have a
glacic layer with its upper boundary within 100 cm of the
mineral soil surface. Glacic Argiorthels do not have a lithic
contact within 50 cm of the mineral soil surface. Disturbance
of the insulating surface layer causes the ice to melt and the
soil to collapse.
Lithic Argiorthels.—These are the Argiorthels that have a
lithic contact within 50 cm of the mineral soil surface. Lithic
Argiorthels are associated with stable, bedrock-controlled
landscapes.
Natric Argiorthels.—These are the Argiorthels that have a
natric horizon. Natric Argiorthels do not have a lithic contact
within 50 cm or a glacic layer with an upper boundary within
100 cm of the mineral soil surface. These soils commonly are
derived from sodium-rich marine deposits.
Haplorthels
Haplorthels are the Orthels that have an ochric epipedon and
commonly a cambic horizon but have insufficient moisture prior
to freezing to produce cryoturbation. These soils are not
sufficiently wet for the development of thick organic layers at
the surface. They are not sandy throughout the particle-size
control section. They occur in Alaska, Canada, and Siberia.
Definition
Haplorthels are the Orthels that:
1. Do not have in 30 percent or more of the pedon more
than 40 percent, by volume, organic materials from the soil
surface to a depth of 50 cm;
2. Do not have anhydrous conditions;
3. Do not have a mollic or umbric epipedon;
4. Do not have an argillic horizon that has its upper boundary
within 100 cm of the mineral soil surface;
5. Have 35 percent or more (by volume) rock fragments or a
texture finer than loamy fine sand in at least one layer within
the particle-size control section; and
6. Do not have, within 50 cm of the mineral soil surface,
redox depletions with chroma of 2 or less and also aquic
conditions during normal years.
Key to Subgroups
ACHA. Haplorthels that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Haplorthels
ACHB. Other Haplorthels that have a glacic layer that has its
upper boundary within 100 cm of the mineral soil surface.
Glacic Haplorthels
ACHC. Other Haplorthels that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time
during normal years (or artificial drainage).
Aquic Haplorthels
ACHD. Other Haplorthels.
Typic Haplorthels
Definition of Typic Haplorthels
Typic Haplorthels are the Orthels that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Do not have a glacic layer that has its upper boundary
within 100 cm of the mineral soil surface; and
3. Do not have, in one or more horizons within 100 cm of the
mineral soil surface, distinct or prominent redox
concentrations and also aquic conditions for some time during
normal years.
Description of Subgroups
Typic Haplorthels.—These are the Haplorthels that do not
have a lithic contact within 50 cm or a glacic layer with an
Gelisols 457
upper boundary within 100 cm of the mineral soil surface. The
Typic subgroup does not have the redoximorphic features
associated with the Aquic subgroup.
Aquic Haplorthels.—These are the Haplorthels that are
saturated and reduced for some time during normal years. They
do not have a lithic contact within 50 cm of the mineral soil
surface or a glacic layer with an upper boundary within 100 cm
of the mineral soil surface. These soils commonly have well
expressed features related to cryoturbation.
Glacic Haplorthels.—These are the Haplorthels that have
a glacic layer with an upper boundary within 100 cm of the
mineral soil surface. They do not have a lithic contact within
50 cm of the mineral soil surface. Disturbance of the surface
can cause the ice layer to melt and the soil to collapse.
Lithic Haplorthels.—These are the Haplorthels that have a
lithic contact within 50 cm of the mineral soil surface. These
soils are rare in the world.
Historthels
Historthels are the Orthels that have organic materials at the
surface. Commonly, the organic materials are thicker in the
lower positions on the landscape and thinner in the higher
positions. These soils are commonly saturated at or near the
surface for some time during normal years and have
redoximorphic features.
Definition
Historthels are the Orthels that have in 30 percent or more
of the pedon more than 40 percent, by volume, organic
materials from the soil surface to a depth of 50 cm.
Key to Subgroups
ACAA. Historthels that have a lithic contact within 50 cm of
the soil surface.
Lithic Historthels
ACAB. Other Historthels that have a glacic layer that has its
upper boundary within 100 cm of the soil surface.
Glacic Historthels
ACAC. Other Historthels that have more than 40 percent, by
volume, organic soil materials from the soil surface to a depth
of 50 cm in 75 percent or less of the pedon.
Ruptic Historthels
ACAD. Other Historthels.
Typic Historthels
Definition of Typic Historthels
Typic Historthels are the Orthels that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have a glacic layer that has its upper boundary
within 100 cm of the soil surface; and
3. Have more than 40 percent, by volume, organic soil
materials from the soil surface to a depth of 50 cm in more
than 75 percent of the pedon.
Description of Subgroups
Typic Historthels.—These are the Historthels that do not
have a glacic layer with an upper boundary within 100 cm or a
lithic contact within 50 cm of the soil surface. Commonly,
these soils have an organic layer at the surface that varies in
thickness and are saturated for at least brief periods during
normal years.
Glacic Historthels.—These are the Historthels that have a
glacic layer with an upper boundary within 100 cm of the soil
surface. These soils do not have a lithic contact within 50 cm
of the mineral soil surface. Disturbance of the insulating
organic layer causes the ice to melt and the soil to collapse.
Lithic Historthels.—These are the Historthels that have a
lithic contact within 50 cm of the soil surface. These soils are
rare in the world.
Ruptic Historthels.—These are the Historthels that have
organic layers at the surface that vary in thickness. Commonly,
the thickness is related to the position on the landscape. A
pattern of high and low areas repeats itself over relatively short
distances. These soils do not have a lithic contact within 50 cm
or a glacic layer with an upper boundary within 100 cm of the
soil surface.
Mollorthels
Mollorthels are the Orthels that have a mollic epipedon.
These soils are not wet for long periods and, unlike Historthels,
do not have organic materials at the surface. They are known to
occur in Alaska, Canada, and Siberia. On the North Slope of
the Brooks Range in Alaska, they support vegetation that
differs from that on Umbrorthels.
Definition
Mollorthels are the Orthels that:
1. Have a mollic epipedon;
2. Do not have anhydrous conditions;
3. Do not have in 30 percent or more of the pedon more
than 40 percent, by volume, organic materials from the soil
surface to a depth of 50 cm; and
4. Do not have, within 50 cm of the mineral soil surface,
458 Soil Taxonomy
redox depletions with chroma of 2 or less and aquic conditions
during normal years.
KeytoSubgroups
ACDA. Mollorthels that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Mollorthels
ACDB. Other Mollorthels that have a glacic layer that has its
upper boundary within 100 cm of the mineral soil surface.
Glacic Mollorthels
ACDC. Other Mollorthels that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time during normal years, and slickensides
or wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallowest.
Vertic Mollorthels
ACDD. Other Mollorthels that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Mollorthels
ACDE. Other Mollorthels that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Mollorthels
ACDF. Other Mollorthels that have:
1. A mollic epipedon 40 cm or more thick with a texture
finer than loamy fine sand; and
2. A slope of less than 25 percent.
Cumulic Mollorthels
ACDG. Other Mollorthels that have, in one or more horizons
within 100 cm of the mineral soil surface, distinct or
prominent redox concentrations and also aquic conditions for
some time during normal years (or artificial drainage).
Aquic Mollorthels
ACDH. Other Mollorthels.
Typic Mollorthels
Definition of Typic Mollorthels
Typic Mollorthels are the Mollorthels that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Do not have a glacic layer that has its upper boundary
within 100 cm of the mineral soil surface;
3. Do not have either of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time during normal years, and slickensides
or wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallowest;
4. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, a fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al plus
1
/2 Fe percentages (by ammonium oxalate) totaling more than
1.0;
5. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, one or both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
6. Have either:
Gelisols 459
a. A mollic epipedon that is less than 40 cm thick, unless
the texture is loamy fine sand or coarser; or
b. A slope of 25 percent or more; and
7. Do not have, in any horizon within 100 cm of the mineral
soil surface, distinct or prominent redox concentrations and
also aquic conditions for some time during normal years.
Description of Subgroups
Typic Mollorthels.—These are the Mollorthels without any
special features. These soils do not have a lithic contact within
50 cm or a glacic layer with an upper boundary within 100 cm
of the mineral soil surface. They do not have the potential to
shrink and swell characteristic of the Vertic Mollorthels and do
not have the volcanic glass or ammonium-extractable iron and
aluminum characteristic of the Andic and Vitrandic
Mollorthels. Typic Mollorthels have a mollic epipedon that is
less than 40 cm thick, unless they are on steep slopes or are
sandy, or both, and do not have evidence of wetness and
distinct or prominent redox concentrations within 100 cm of
the mineral soil surface.
Andic Mollorthels.—These are the Mollorthels that have,
throughout one or more horizons with a total thickness of 18
cm or more within 75 cm of the mineral soil surface, a fineearth
fraction with both a bulk density of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and Al plus 1
/2 Fe
percentages (by ammonium oxalate) totaling more than 1.0.
These soils do not have a lithic contact within 50 cm or a
glacic layer with an upper boundary within 100 cm of the
mineral soil surface. They also do not have the high shrinkswell
potential associated with the Vertic Mollorthels. Andic
Mollorthels are commonly in areas that receive volcanic ejecta,
but this is not required.
Aquic Mollorthels.—These are the Mollorthels with aquic
conditions and distinct or prominent redox concentrations
within 100 cm of the mineral soil surface. These soils do not
have a lithic contact within 50 cm or a glacic layer with an
upper boundary within 100 cm of the mineral soil surface.
They do not have the potential to shrink and swell
characteristic of the Vertic Mollorthels or the volcanic glass or
ammonium-extractable iron and aluminum characteristic of the
Andic and Vitrandic Mollorthels. Aquic Mollorthels have a
mollic epipedon that is less than 40 cm thick, unless they are
on steep slopes or are sandy, or both.
Cumulic Mollorthels.—These are the Mollorthels that have
a mollic epipedon that is 40 cm or more thick, a texture finer
than loamy fine sand, and a slope of less than 25 percent.
These soils do not have a lithic contact within 50 cm or a
glacic layer with an upper boundary within 100 cm of the
mineral soil surface. Cumulic Mollorthels do not have the
potential to shrink and swell characteristic of the Vertic
Mollorthels or the volcanic glass or ammonium-extractable
iron and aluminum characteristic of the Andic and Vitrandic
Mollorthels.
Glacic Mollorthels.—These are the Mollorthels that have a
glacic layer with an upper boundary within 100 cm of the
mineral soil surface. These soils do not have a lithic contact
with its upper boundary within 50 cm of the mineral soil
surface. Disturbance of the insulating surface layer causes the
ice to melt and the soil to collapse.
Lithic Mollorthels.—These are the Mollorthels that have a
lithic contact within 50 cm of the mineral soil surface.
Vertic Mollorthels.—These are the Mollorthels that show
physical evidence of high shrink-swell in the form of cracks
and slickensides or wedge-shaped aggregates or have the
potential to shrink and swell. This potential is determined by
the linear extensibility. These soils do not have a lithic contact
within 50 cm or a glacic layer with an upper boundary within
100 cm of the mineral soil surface.
Vitrandic Mollorthels.—These are the Mollorthels that
have, throughout one or more horizons with a total thickness of
18 cm or more within 75 cm of the mineral soil surface, one or
both of the following:
1. More than 35 percent (by volume) fragments coarser than
2.0 mm, of which more than 66 percent is cinders, pumice, and
pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Mollorthels are not so weathered as the Andic
Mollorthels, do not have the shrink-swell potential associated
with the Vertic Mollorthels, and do not have a lithic contact
within 50 cm or a glacic layer with an upper boundary within
100 cm of the mineral soil surface.
Psammorthels
Psammorthels are the Orthels that have less than 35 percent
(by volume) rock fragments and a texture of loamy fine sand or
coarser in all layers within the particle-size control section.
These soils commonly have an ochric epipedon but not an
umbric or mollic epipedon or an argillic horizon. Unlike
Historthels, Psammorthels do not have organic materials close
to the surface. They also do not have aquic conditions within
50 cm of the mineral soil surface or anhydrous conditions.
Definition
Psammorthels are the Orthels that:
1. Have less than 35 percent (by volume) rock fragments and
a texture of loamy fine sand or coarser in all layers within the
particle-size control section;
460 Soil Taxonomy
2. Do not have in 30 percent or more of the pedon more
than 40 percent, by volume, organic materials from the soil
surface to a depth of 50 cm;
3. Do not have an argillic horizon with its upper boundary
within 100 cm of the mineral soil surface;
4. Do not have anhydrous conditions;
5. Do not have a mollic or umbric epipedon; and
6. Do not have, within 50 cm of the mineral soil surface,
redox depletions with chroma of 2 or less and also aquic
conditions during normal years.
Key to Subgroups
ACGA. Psammorthels that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Psammorthels
ACGB. Other Psammorthels that have a glacic layer that
has its upper boundary within 100 cm of the mineral soil
surface.
Glacic Psammorthels
ACGC. Other Psammorthels that have a horizon 5 cm or
more thick that has one or more of the following:
1. In 25 percent or more of each pedon, cementation by
organic matter and aluminum, with or without iron; or
2. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
3. An ODOE value of 0.12 or more, and a value half as
high or lower in an overlying horizon.
Spodic Psammorthels
ACGD. Other Psammorthels.
Typic Psammorthels
Definition of Typic Psammorthels
Typic Psammorthels are the Psammorthels that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Do not have a glacic layer that has its upper boundary
within 100 cm of the mineral soil surface; and
3. Do not have a horizon 5 cm or more thick that has any of
the following:
a. In 25 percent or more of each pedon, cementation by
organic matter and aluminum, with or without iron; or
b. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
c. An ODOE value of 0.12 or more, and a value half as high
or lower in an overlying horizon.
Description of Subgroups
Typic Psammorthels.—These are the Psammorthels that do
not have a lithic contact within 50 cm or a glacic layer with its
upper boundary within 100 cm of the mineral soil surface.
Typic Psammorthels do not have accumulations of
sesquioxides.
Glacic Psammorthels.—These are the Psammorthels that
have a glacic layer with its upper boundary within 100 cm of
the mineral soil surface but do not have a lithic contact within
50 cm of the mineral soil surface. Disturbance of the surface
commonly thaws the ice layer, after which the soil collapses.
Lithic Psammorthels.—These are the Psammorthels that
have a lithic contact within 50 cm of the mineral soil surface.
Spodic Psammorthels.—These are the Psammorthels that
grade toward Spodosols. Spodic Psammorthels have an E
horizon and a B horizon with accumulations of organic matter,
aluminum, and iron. They do not have a lithic contact within
50 cm of the mineral soil surface or a glacic layer with an
upper boundary within 100 cm of the mineral soil surface.
Umbrorthels
Umbrorthels are the Orthels that have an umbric epipedon.
These soils are not wet for long periods, nor are they dry
throughout the growing season. Unlike Historthels,
Umbrorthels do not have organic materials at the surface. They
are known to occur in Alaska, Canada, and Siberia. On the
North Slope of the Brooks Range in Alaska, they support
vegetation that differs from that on Mollorthels.
Definition
Umbrorthels are the Orthels that:
1. Have an umbric epipedon;
2. Do not have in 30 percent or more of the pedon more
than 40 percent, by volume, organic materials from the soil
surface to a depth of 50 cm;
3. Do not have anhydrous conditions; and
4. Do not have, within 50 cm of the mineral soil surface,
redox depletions with chroma of 2 or less and also aquic
conditions during normal years.
Key to Subgroups
ACEA. Umbrorthels that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Umbrorthels
ACEB. Other Umbrorthels that have a glacic layer that has
its upper boundary within 100 cm of the mineral soil surface.
Glacic Umbrorthels
Gelisols 461
ACEC. Other Umbrorthels that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time during normal years, and slickensides
or wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallowest.
Vertic Umbrorthels
ACED. Other Umbrorthels that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm3
or less, measured at 33 kPa
water retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Umbrorthels
ACEE. Other Umbrorthels that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Umbrorthels
ACEF. Other Umbrorthels that have:
1. An umbric epipedon 40 cm or more thick with a texture
finer than loamy fine sand; and
2. A slope of less than 25 percent.
Cumulic Umbrorthels
ACEG. Other Umbrorthels that have, in one or more
horizons within 100 cm of the mineral soil surface, distinct or
prominent redox concentrations and also aquic conditions for
some time during normal years (or artificial drainage).
Aquic Umbrorthels
ACEH. Other Umbrorthels.
Typic Umbrorthels
DefinitionofTypicUmbrorthels
Typic Umbrorthels are the Umbrorthels that:
1. Do not have a lithic contact within 50 cm of the mineral soil
surface;
2. Do not have a glacic layer that has its upper boundary
within 100 cm of the mineral soil surface;
3. Have neither of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time during normal years, and slickensides
or wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; nor
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallowest;
4. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, a fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al plus
1
/2 Fe percentages (by ammonium oxalate) totaling more than
1.0;
5. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
6. Have either:
a. An umbric epipedon that is less than 40 cm thick,
unless the texture is loamy fine sand or coarser; or
b. A slope of 25 percent or more; and
7. Do not have, in any horizon within 100 cm of the mineral
soil surface, distinct or prominent redox concentrations and
also aquic conditions for some time during normal years.
Description of Subgroups
Typic Umbrorthels.—These are the Umbrorthels without
any special features. These soils do not have a lithic contact
462 Soil Taxonomy
within 50 cm or a glacic layer with its upper boundary within
100 cm of the mineral soil surface. They do not have the
potential to shrink and swell characteristic of the Vertic
Umbrorthels or the volcanic glass or ammonium-extractable
iron and aluminum characteristic of the Andic and Vitrandic
Umbrorthels. Typic Umbrorthels have an umbric epipedon that
is less than 40 cm thick, unless they are on steep slopes or are
sandy, or both, and do not have evidence of wetness and
distinct or prominent redox concentrations within 100 cm of
the mineral soil surface.
Andic Umbrorthels.—These are the Umbrorthels that
have, throughout one or more horizons with a total thickness of
18 cm or more within 75 cm of the mineral soil surface, a fineearth
fraction with both a bulk density of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and Al plus 1
/2 Fe
percentages (by ammonium oxalate) totaling more than 1.0.
These soils do not have a lithic contact within 50 cm or a
glacic layer with its upper boundary within 100 cm of the
mineral soil surface. They also do not have the high shrinkswell
potential associated with the Vertic Umbrorthels. Andic
Umbrorthels are commonly in areas that receive volcanic
ejecta, but this is not required.
Aquic Umbrorthels.—These are the Umbrorthels with aquic
conditions and distinct or prominent redox concentrations
within 100 cm of the mineral soil surface. These soils do not
have a lithic contact within 50 cm or a glacic layer with its upper
boundary within 100 cm of the mineral soil surface. They do not
have the potential to shrink and swell characteristic of the Vertic
Umbrorthels or the volcanic glass or ammonium-extractable iron
and aluminum characteristic of the Andic and Vitrandic
Umbrorthels. Aquic Umbrorthels have an umbric epipedon that
is less than 40 cm thick, unless they are on steep slopes or are
sandy, or both.
Cumulic Umbrorthels.—These are the Umbrorthels that
have an umbric epipedon that is 40 cm or more thick, a texture
finer than loamy fine sand, and a slope of less than 25 percent.
These soils do not have a lithic contact within 50 cm or a
glacic layer with its upper boundary within 100 cm of the
mineral soil surface. Cumulic Umbrorthels do not have the
potential to shrink and swell characteristic of the Vertic
Umbrorthels or the volcanic glass or ammonium-extractable
iron and aluminum characteristic of the Andic and Vitrandic
Umbrorthels.
Glacic Umbrorthels.—These are the Umbrorthels that have
a glacic layer with an upper boundary within 100 cm of the
mineral soil surface. These soils do not have a lithic contact
with its upper boundary within 50 cm of the mineral soil
surface. Disturbance of the insulating surface layer causes the
ice to melt and the soil to collapse.
Lithic Umbrorthels.—These are the Umbrorthels that have
a lithic contact within 50 cm of the mineral soil surface.
Vertic Umbrorthels.—These are the Umbrorthels that show
physical evidence of high shrink-swell in the form of cracks
and slickensides or wedge-shaped aggregates or have the
potential to shrink and swell. This potential is determined by the
linear extensibility. These soils do not have a lithic contact
within 50 cm or a glacic layer with an upper boundary within 100
cm of the mineral soil surface.
Vitrandic Umbrorthels.—These are the Umbrorthels that
have, throughout one or more horizons with a total thickness of
18 cm or more within 75 cm of the mineral soil surface, one or
both of the following:
1. More than 35 percent (by volume) fragments coarser than
2.0 mm, of which more than 66 percent is cinders, pumice, and
pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Umbrorthels are not so weathered as the Andic
Umbrorthels, do not have the shrink-swell potential associated
with the Vertic Umbrorthels, and do not have a lithic contact
within 50 cm or a glacic layer with an upper boundary within
100 cm of the mineral soil surface.
Turbels
These are the Gelisols that have one or more horizons with
evidence of cryoturbation in the form of irregular, broken, or
distorted horizon boundaries, involutions, the accumulation of
organic matter on top of the permafrost, ice or sand wedges,
and oriented rock fragments.
Cryoturbation occurs only in soils with sufficient moisture.
Cryoturbated horizons in soils that are dry for most of the year
likely were more moist in the past.
Turbels are the dominant suborder of Gelisols. They
account for about half the Gelisols on a global basis. These
soils are common in the High and Middle Arctic vegetation
regions of North America and Eurasia at latitudes of 65o
N. or
more.
Definition
Turbels are the Gelisols that:
1. Do not have organic soil materials that meet one or more
of the following:
a. Overlie cindery, fragmental, or pumiceous materials
and/or fill their interstices and directly below these
materials have either a densic, lithic, or paralithic contact;
or
b. When added with the underlying cindery, fragmental, or
Gelisols 463
pumiceous materials, total 40 cm or more between the soil
surface and a depth of 50 cm; or
c. Are saturated with water for 30 or more cumulative days
during normal years (or are artificially drained) and have 80
percent or more, by volume, organic soil materials from the
soil surface to a depth of 50 cm or to a glacic layer or a
densic, lithic, or paralithic contact, whichever is shallowest;
and
2. Have one or more horizons with evidence of cryoturbation
in the form of irregular, broken, or distorted horizon
boundaries, involutions, the accumulation of organic matter on
top of the permafrost, ice or sand wedges, and oriented rock
fragments.
Key to Great Groups
ABA. Turbels that have in 30 percent or more of the pedon
more than 40 percent, by volume, organic materials from the
soil surface to a depth of 50 cm.
Histoturbels, p. 466
ABB. Other Turbels that have, within 50 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions during normal years (or artificial drainage).
Aquiturbels, p. 464
ABC. Other Turbels that have anhydrous conditions.
Anhyturbels, p. 463
ABD. Other Turbels that have a mollic epipedon.
Molliturbels, p. 466
ABE. Other Turbels that have an umbric epipedon.
Umbriturbels, p. 469
ABF. Other Turbels that have less than 35 percent (by
volume) rock fragments and a texture of loamy fine sand or
coarser in all layers within the particle-size control section.
Psammoturbels, p. 468
ABG. Other Turbels.
Haploturbels, p. 465
Anhyturbels
These are the Turbels that have anhydrous conditions and
may have dry permafrost (i.e., insufficient moisture for
interstitial ice to occur). The cold deserts commonly receive
less than 30 mm of annual precipitation. These soils support
little or no vegetation.
Anhyturbels are limited in extent but occur in continental
Antarctica, northern Greenland, and the cold, dry mountains of
Eurasia at elevations of more than 3,700 m.
These soils have undergone climatic periods in the past when
more moisture was available.
Definition
Anhyturbels are the Turbels that:
1. Have anhydrous conditions;
2. Do not have in 30 percent or more of the pedon more
than 40 percent, by volume, organic materials from the soil
surface to a depth of 50 cm; and
3. Do not have, within 50 cm of the mineral soil surface,
redox depletions with chroma of 2 or less and also aquic
conditions during normal years.
Key to Subgroups
ABCA. Anhyturbels that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Anhyturbels
ABCB. Other Anhyturbels that have a glacic layer with its
upper boundary within 100 cm of the mineral soil surface.
Glacic Anhyturbels
ABCC. Other Anhyturbels that have a petrogypsic horizon
with its upper boundary within 100 cm of the mineral soil
surface.
Petrogypsic Anhyturbels
ABCD. Other Anhyturbels that have a gypsic horizon with
its upper boundary within 100 cm of the mineral soil surface.
Gypsic Anhyturbels
ABCE. Other Anhyturbels that have a horizon 15 cm or more
thick that contains 12 cmol(-)/L nitrate in 1:5 soil:water extract
and in which the product of its thickness (in cm) and its nitrate
concentration is 3,500 or more.
Nitric Anhyturbels
ABCF. Other Anhyturbels that have a salic horizon that has
its upper boundary within 100 cm of the mineral soil surface.
Salic Anhyturbels
ABCG. Other Anhyturbels that have a calcic horizon that has
its upper boundary within 100 cm of the mineral soil surface.
Calcic Anhyturbels
ABCH. Other Anhyturbels.
Typic Anhyturbels
Definition of Typic Anhyturbels
These are the Anhyturbels that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
464 Soil Taxonomy
2. Do not have a glacic layer or a petrogypsic, gypsic, salic, or
calcic horizon with its upper boundary within 100 cm of the
mineral soil surface; and
3. Do not have a horizon 15 cm or more thick that has 12
cmol(-)/L nitrate in 1:5 soil:water extract and in which the
product of its thickness (in cm) and its nitrate concentration is
3,500ormore.
Description of Subgroups
Typic Anhyturbels.—These are the Anhyturbels that
commonly have accumulations of salts, including gypsum and
calcium carbonate, but insufficient quantities to meet the
criteria for a calcic, gypsic, petrogypsic, or salic horizon. These
soils also do not contain large amounts of nitrate. They do not
have a lithic contact within 50 cm of the mineral soil surface or
a glacic layer with its upper boundary within 100 cm of the
mineral soil surface.
Calcic Anhyturbels.—These are the Anhyturbels that have
a calcic horizon within 100 cm of the mineral soil surface.
These soils commonly have other more soluble salts, but not in
sufficient quantity to meet the criteria for a petrogypsic, gypsic,
or salic horizon. The soils also lack sufficient quantities of
nitrate, a glacic layer, and a lithic contact.
Glacic Anhyturbels.—These are the Anhyturbels that have
a glacic layer with an upper boundary withi 100 cm of the
mineral soil surface. These soils commonly have accumulations
of salts, including calcium carbonate and gypsum, but do not
have a lithic contact within 50 cm of the mineral soil surface.
Gypsic Anhyturbels.—These are the Anhyturbels that have
a gypsic horizon within 100 cm of the mineral soil surface.
They commonly have other salts, including calcium carbonate.
These soils do not have a lithic contact within 50 cm or a
glacic layer with an upper boundary within 100 cm of the
mineral soil surface.
Lithic Anhyturbels.—These are the Anhyturbels that have
a lithic contact within 50 cm of the mineral soil surface. They
commonly have accumulations of salts, including calcium
carbonate and gypsum.
Nitric Anhyturbels.—These are the Anhyturbels that have
large accumulations of nitrate. They commonly have
accumulations of other salts, but they do not have gypsic or
petrogypsic horizons. They also do not have a lithic contact
within 50 cm or a glacic layer with an upper boundary within
100 cm of the mineral soil surface.
Petrogypsic Anhyturbels.—These are the Anhyturbels that
have a petrogypsic horizon within 100 cm of the mineral soil
surface. They can have accumulations of other salts, but they
do not have a lithic contact within 50 cm or a glacic layer with
an upper boundary within 100 cm of the mineral soil surface.
Salic Anhyturbels.—These are the Anhyturbels that have a
salic horizon with or without a calcic horizon. These soils do
not have a lithic contact within 50 cm or a glacic layer with an
upper boundary within 100 cm of the mineral soil surface. They
also do not have gypsic or petrogypsic horizons or large
accumulations of nitrates within 100 cm of the mineral soil
surface.
Aquiturbels
These are the Turbels that are saturated with water close to
the surface. Saturation commonly occurs in spring, when water
perches on the permafrost and temperatures are warm enough
for iron reduction to occur. These soils can have mollic,
umbric, or ochric epipedons. They occur in depressional areas
in Alaska, Canada, and Eurasia.
Definition
Aquiturbels are the Turbels that:
1. Have, within 50 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
during normal years (or artificial drainage); and
2. Do not have in 30 percent or more of the pedon more
than 40 percent, by volume, organic materials from the soil
surface to a depth of 50 cm.
Key to Subgroups
ABBA. Aquiturbels that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Aquiturbels
ABBB. Other Aquiturbels that have a glacic layer with its
upper boundary within 100 cm of the mineral soil surface.
Glacic Aquiturbels
ABBC. Other Aquiturbels that have a sulfuric horizon or
sulfidic materials with an upper boundary within 100 cm of the
mineral soil surface.
Sulfuric Aquiturbels
ABBD. Other Aquiturbels that have either:
1. Organic soil materials that are discontinous at the
surface; or
2. Organic soil materials at the surface that change in
thickness fourfold or more within a pedon.
Ruptic-Histic Aquiturbels
ABBE. Other Aquiturbels that have less than 35 percent (by
volume) rock fragments and a texture of loamy fine sand or
coarser in all layers within the particle-size control section.
Psammentic Aquiturbels
ABBF. Other Aquiturbels.
Typic Aquiturbels
Gelisols 465
Definition of Typic Aquiturbels
Typic Aquiturbels are the Turbels that:
1. Do not have a lithic contact within 50 cm of the mineral soil
surface;
2. Do not have a glacic layer that has its upper boundary
within 100 cm of the mineral soil surface;
3. Have neither of the following:
a. Organic soil materials that are discontinous at the
surface; nor
b. Organic soil materials at the surface that change in
thickness fourfold or more within a pedon;
4. Have neither a sulfuric horizon nor sulfidic materials with
an upper boundary within 100 cm of the mineral soil surface;
and
5. Have either 35 percent or more (by volume) rock
fragments or a texture finer than loamy fine sand in one or
more layers within the particle-size control section.
Description of Subgroups
Typic Aquiturbels.—The concept of Typic Aquiturbels is
centered on Aquiturbels without special characteristics. The
Typic subgroup does not have a lithic contact within 50 cm, a
glacic layer with an upper boundary within 100 cm of the
mineral soil surface, or a sulfuric horizon or sulfidic materials
within 100 cm of the mineral soil surface. Textures are finer
than loamy fine sand or are skeletal in at least some part of the
particle-size control section. If these soils have organic soil
materials at the surface, the layer is continuous and does not
change much in thickness within a pedon.
Glacic Aquiturbels.—These are the Aquiturbels that have a
glacic layer with an upper boundary within 100 cm of the
mineral soil surface. Commonly, these soils have organic soil
materials at the surface. Disturbance of the surface horizon
removes the insulating layer; the glacic layer then melts, and
the soil collapses.
Lithic Aquiturbels.—These are the Aquiturbels that have a
lithic contact within 50 cm of the mineral soil surface. These
soils are rare in the world.
Psammentic Aquiturbels.—These are the sandy
Aquiturbels that do not have a lithic contact within 50 cm of
the mineral soil surface or a glacic layer with an upper
boundary within 100 cm of the mineral soil surface. These soils
commonly have thin organic layers.
Ruptic-Histic Aquiturbels.—These are the Aquiturbels
that have an organic layer at the surface that is either
discontinuous or thins and thickens because of periglacial
microrelief. These soils are common in Alaska, Canada, and
Siberia.
Sulfuric Aquiturbels.—These are the Aquiturbels that have
a sulfuric horizon or sulfidic materials within 100 cm of the
mineral soil surface. These soils occur in cold coastal areas of
the world.
Haploturbels
Haploturbels are the Turbels that have an ochric epipedon
and have sufficient moisture to produce cryoturbation. These
soils are not sufficiently wet for the development of thick
organic layers at the surface or redox features. Haploturbels are
not sandy throughout the particle-size control section.
Commonly, the cryoturbation is not well expressed. These soils
occur in Alaska, Canada, and Siberia.
Definition
Haploturbels are the Turbels that:
1. Do not have in 30 percent or more of the pedon more than
40 percent, by volume, organic materials from the soil surface
to a depth of 50 cm;
2. Do not have, within 50 cm of the mineral soil surface,
redox depletions with chroma of 2 or less and also aquic
conditions during normal years;
3. Do not have anhydrous conditions;
4. Do not have a mollic or umbric epipedon; and
5. Have 35 percent or more (by volume) rock fragments or a
texture finer than loamy fine sand in at least one layer within
the particle-size control section.
Key to Subgroups
ABGA. Haploturbels that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Haploturbels
ABGB. Other Haploturbels that have a glacic layer that has
an upper boundary within 100 cm of the mineral soil surface.
Glacic Haploturbels
ABGC. Other Haploturbels that have, in one or more
horizons within 100 cm of the mineral soil surface, distinct or
prominent redox concentrations and also aquic conditions for
some time during normal years (or artificial drainage).
Aquic Haploturbels
ABGD. Other Haploturbels.
Typic Haploturbels
Definition of Typic Haploturbels
Typic Haploturbels are the Turbels that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Do not have a glacic layer that has its upper boundary
within 100 cm of the mineral soil surface; and
466 Soil Taxonomy
3. Do not have, in one or more horizons within 100 cm
of the mineral soil surface, distinct or prominent redox
concentrations and also aquic conditions for some time
during normal years.
Description of Subgroups
Typic Haploturbels.—These are the Haploturbels that do not
have a lithic contact within 50 cm or a glacic layer with an upper
boundary within 100 cm of the mineral soil surface. The Typic
subgroup does not have the redoximorphic features associated
with the Aquic subgroup.
Aquic Haploturbels.—These are the Haploturbels that are
saturated and reduced for some time during normal years.
These soils commonly have well expressed features related to
cryoturbation.
Glacic Haploturbels.—These are the Haploturbels that
have a glacic layer with an upper boundary within 100 cm of
the mineral soil surface. Disturbance of the surface can cause
the ice layer to melt and the soil to collapse.
Lithic Haploturbels.—These are the Haploturbels that have
a lithic contact within 50 cm of the mineral soil surface. These
soils are rare in the world.
Histoturbels
Histoturbels are the Turbels that have organic materials at the
surface. Commonly, the organic materials are thicker in the lower
positions on the landscape and thinner in the higher positions.
These soils are commonly saturated at or near the surface for
some time during normal years. They commonly have
redoximorphic features.
Definition
Histoturbels are the Turbels that have in 30 percent or more
of the pedon more than 40 percent, by volume, organic
materials from the soil surface to a depth of 50 cm.
Key to Subgroups
ABAA. Histoturbels that have a lithic contact within 50 cm
of the soil surface.
Lithic Histoturbels
ABAB. Other Histoturbels that have a glacic layer with its
upper boundary within 100 cm of the soil surface.
Glacic Histoturbels
ABAC. Other Histoturbels that have more than 40 percent,
by volume, organic soil materials from the soil surface to a
depth of 50 cm in 75 percent or less of the pedon.
Ruptic Histoturbels
ABAD. Other Histoturbels.
Typic Histoturbels
Definition of Typic Histoturbels
Typic Histoturbels are the Turbels that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have a glacic layer that has its upper boundary
within 100 cm of the soil surface; and
3. Have more than 40 percent, by volume, organic soil
materials from the soil surface to a depth of 50 cm in more
than 75 percent of the pedon.
Description of Subgroups
Typic Histoturbels.—These are the Histoturbels that do not
have a glacic layer with an upper boundary within 100 cm or a
lithic contact within 50 cm of the soil surface. Commonly,
these soils have an organic layer at the surface that varies in
thickness. These soils are saturated for at least brief periods
during normal years.
Glacic Histoturbels.—These are the Histoturbels that have
a glacic layer with an upper boundary within 100 cm of the soil
surface. They do not have a lithic contact within 50 cm of the
mineral soil surface. Disturbance of the insulating organic
layer causes the ice to melt and the soil to collapse.
Lithic Histoturbels.—These are the Histoturbels that have
a lithic contact within 50 cm of the soil surface. These soils are
rare in the world.
Ruptic Histoturbels.—These are the Histoturbels that have
organic layers at the surface that vary in thickness. Commonly,
the thickness is related to the position on the landscape. A
pattern of high and low areas repeats itself over relatively short
distances. These soils do not have a lithic contact within 50 cm
or a glacic layer with an upper boundary within 100 cm of the
soil surface.
Molliturbels
Molliturbels are the Turbels that have a mollic epipedon.
These soils are not wet for long periods and do not have the
redoximorphic features associated with Aquiturbels or the
organic materials at the surface associated with Histoturbels.
They are known to occur in Alaska, Canada, and Siberia. On
the North Slope of the Brooks Range in Alaska, they support
vegetation that differs from that on the more acid
Umbriturbels.
Definition
Molliturbels are the Turbels that:
1. Have a mollic epipedon;
2. Do not have anhydrous conditions;
3. Do not have in 30 percent or more of the pedon more
than 40 percent, by volume, organic materials from the soil
surface to a depth of 50 cm; and
Gelisols 467
4. Do not have, within 50 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
during normal years.
KeytoSubgroups
ABDA. Molliturbels that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Molliturbels
ABDB. Other Molliturbels that have a glacic layer that has
its upper boundary within 100 cm of the mineral soil surface.
Glacic Molliturbels
ABDC. Other Molliturbels that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time during normal years, and slickensides
or wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallowest.
Vertic Molliturbels
ABDD. Other Molliturbels that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Molliturbels
ABDE. Other Molliturbels that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Molliturbels
ABDF. Other Molliturbels that have:
1. A mollic epipedon 40 cm or more thick with a texture finer
than loamy fine sand; and
2. A slope of less than 25 percent.
Cumulic Molliturbels
ABDG. Other Molliturbels that have, in one or more
horizons within 100 cm of the mineral soil surface, distinct or
prominent redox concentrations and also aquic conditions for
some time during normal years (or artificial drainage).
Aquic Molliturbels
ABDH. Other Molliturbels.
Typic Molliturbels
Definition of Typic Molliturbels
Typic Molliturbels are the Molliturbels that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Do not have a glacic layer that has its upper boundary
within 100 cm of the mineral soil surface;
3. Do not have either of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time during normal years, and slickensides
or wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallowest;
4. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, a fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al plus
1
/2 Fe percentages (by ammonium oxalate) totaling more than
1.0;
5. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, one or both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
468 Soil Taxonomy
oxalate) times 60] plus the volcanic glass (percent) is equal
to 30 or more;
6. Have either:
a. A mollic epipedon that is less than 40 cm thick, unless
the texture is loamy fine sand or coarser; or
b. A slope of 25 percent or more; and
7. Do not have, in any horizon within 100 cm of the mineral
soil surface, distinct or prominent redox concentrations and
also aquic conditions for some time during normal years.
Description of Subgroups
Typic Molliturbels.—These are the Molliturbels without
any special features. These soils do not have a lithic contact
within 50 cm or a glacic layer with an upper boundary within
100 cm of the mineral soil surface. They do not have the
potential to shrink and swell characteristic of the Vertic
subgroup and do not have the volcanic glass or ammoniumextractable
iron and aluminum characteristic of the Andic and
Vitrandic subgroups. Typic Molliturbels have a mollic
epipedon that is less than 40 cm thick, unless they are on steep
slopes or are sandy, or both, and do not have evidence of
wetness and distinct or prominent redox concentrations within
100 cm of the mineral soil surface.
Andic Molliturbels.—These are the Molliturbels that have,
throughout one or more horizons with a total thickness of 18
cm or more within 75 cm of the mineral soil surface, a fineearth
fraction with both a bulk density of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and Al plus
1
/2 Fe percentages (by ammonium oxalate) totaling more than
1.0. These soils do not have a lithic contact within 50 cm or a
glacic layer with an upper boundary within 100 cm of the
mineral soil surface. They also do not have the high shrinkswell
potential associated with the Vertic subgroup. Andic
Molliturbels are commonly in areas that receive volcanic
ejecta, but this is not required.
Aquic Molliturbels.—These are the Molliturbels with aquic
conditions and distinct or prominent redox concentrations
within 100 cm of the mineral soil surface. These soils do not
have a lithic contact within 50 cm or a glacic layer with an
upper boundary within 100 cm of the surface. They do not have
the potential to shrink and swell characteristic of the Vertic
subgroup or the volcanic glass or ammonium-extractable iron
and aluminum characteristic of the Andic and Vitrandic
subgroups. Aquic Molliturbels have a mollic epipedon that is
less than 40 cm thick, unless they are sandy or on steep slopes.
Cumulic Molliturbels.—These are the Molliturbels that
have a mollic epipedon that is 40 cm or more thick, a texture
finer than loamy fine sand, and a slope of less than 25 percent.
These soils do not have a lithic contact within 50 cm or a
glacic layer with an upper boundary within 100 cm of the
surface. Cumulic Molliturbels do not have the potential to
shrink and swell characteristic of the Vertic subgroup or the
volcanic glass or ammonium-extractable iron and aluminum
characteristic of the Andic and Vitrandic subgroups.
Glacic Molliturbels.—These are the Molliturbels that have
a glacic layer with an upper boundary within 100 cm of the
mineral soil surface. These soils do not have a lithic contact
with its upper boundary within 50 cm of the mineral soil
surface. Disturbance of the insulating surface layer causes the
ice to melt and the soil to collapse.
Lithic Molliturbels.—These are the Molliturbels that have
a lithic contact within 50 cm of the mineral soil surface.
Vertic Molliturbels.—These are the Molliturbels that show
physical evidence of high shrink-swell in the form of cracks
and slickensides or wedge-shaped aggregates or have the
potential to shrink and swell. This potential is determined by
the linear extensibility. These soils do not have a lithic contact
within 50 cm or a glacic layer with an upper boundary within
100 cm of the mineral soil surface.
Vitrandic Molliturbels.—These are the Molliturbels that
have, throughout one or more horizons with a total thickness of
18 cm or more within 75 cm of the mineral soil surface, one or
both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is equal
to 30 or more.
Vitrandic Molliturbels are not so weathered as the Andic
subgroup, do not have the shrink-swell potential associated
with the Vertic subgroup, and do not have a lithic contact
within 50 cm or a glacic layer with an upper boundary within
100 cm of the mineral soil surface.
Psammoturbels
Psammoturbels are the Turbels that have less than 35 percent
(by volume) rock fragments and a texture of loamy fine sand or
coarser in all layers within the particle-size control section.
These soils commonly have an ochric epipedon but not an
umbric or mollic epipedon or anhydrous conditions.
Psammoturbels do not have the redoximorphic features
associated with Aquiturbels or the organic materials close to
the surface associated with Histoturbels.
Definition
Psammoturbels are the Turbels that:
1. Have less than 35 percent (by volume) rock fragments and
Gelisols 469
a texture of loamy fine sand or coarser in all layers within the
particle-size control section;
2. Do not have in 30 percent or more of the pedon more
than 40 percent, by volume, organic materials from the soil
surface to a depth of 50 cm;
3. Do not have, within 50 cm of the mineral soil surface,
redox depletions with chroma of 2 or less and also aquic
conditions during normal years;
4. Do not have anhydrous conditions; and
5. Do not have a mollic or umbric epipedon.
Key to Subgroups
ABFA. Psammoturbels that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Psammoturbels
ABFB. Other Psammoturbels that have a glacic layer that
has its upper boundary within 100 cm of the mineral soil
surface.
Glacic Psammoturbels
ABFC. Other Psammoturbels that have a horizon 5 cm or
more thick that has one or more of the following:
1. In 25 percent or more of each pedon, cementation
by organic matter and aluminum, with or without iron; or
2. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
3. An ODOE value of 0.12 or more, and a value half as
high or lower in an overlying horizon.
Spodic Psammoturbels
ABFD. Other Psammoturbels.
Typic Psammoturbels
Definition of Typic Psammoturbels
Typic Psammoturbels are the Psammoturbels that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Do not have a glacic layer that has its upper boundary
within 100 cm of the mineral soil surface; and
3. Do not have a horizon 5 cm or more thick that has any of
the following:
a. In 25 percent or more of each pedon, cementation by
organic matter and aluminum, with or without iron; or
b. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
c. An ODOE value of 0.12 or more, and a value half as high
or lower in an overlying horizon.
Description of Subgroups
Typic Psammoturbels.—These are the Psammoturbels that
do not have a lithic contact within 50 cm or a glacic layer with
an upper boundary within 100 cm of the mineral soil surface.
Typic Psammoturbels do not have the accumulations of
sesquioxides that are associated with the Spodic intergrade.
Glacic Psammoturbels.—These are the Psammoturbels
that have a glacic layer with an upper boundary within 100 cm
of the mineral soil surface but do not have a lithic contact
within 50 cm of the mineral soil surface. Disturbance of the
surface commonly thaws the ice layer, after which the soil
collapses.
Lithic Psammoturbels.—These are the Psammoturbels
that have a lithic contact within 50 cm of the mineral soil
surface.
Spodic Psammoturbels.—These are the Psammoturbels
that grade toward the Spodosols. They have an E horizon and a
B horizon with accumulations of organic matter, aluminum,
and iron. These soils do not have a lithic contact within 50 cm
or a glacic layer with an upper boundary within 100 cm of the
soil surface.
Umbriturbels
Umbriturbels are the Turbels that have an umbric epipedon.
These soils are not wet for long periods and do not have the
redoximorphic features associated with Aquiturbels, the
organic materials at the surface associated with Histoturbels, or
the anhydrous conditions associated with Anhyturbels.
Umbriturbels are known to occur in Alaska, Canada,
Greenland, and Siberia. On the North Slope of the Brooks
Range in Alaska, they support vegetation that differs from that
on Molliturbels.
Definition
Umbriturbels are the Turbels that:
1. Have an umbric epipedon;
2. Do not have in 30 percent or more of the pedon more
than 40 percent, by volume, organic materials from the soil
surface to a depth of 50 cm;
3. Do not have, within 50 cm of the mineral soil surface,
redox depletions with chroma of 2 or less and also aquic
conditions during normal years; and
4. Do not have anhydrous conditions.
Key to Subgroups
ABEA. Umbriturbels that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Umbriturbels
470 Soil Taxonomy
ABEB. Other Umbriturbels that have a glacic layer that has its
upper boundary within 100 cm of the mineral soil surface.
Glacic Umbriturbels
ABEC. Other Umbriturbels that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time during normal years, and slickensides
or wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm or
a densic, lithic, or paralithic contact, whichever is
shallowest.
Vertic Umbriturbels
ABED. Other Umbriturbels that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm3
or less, measured at 33 kPa
water retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Umbriturbels
ABEE. Other Umbriturbels that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, one or both of the
following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Umbriturbels
ABEF. Other Umbriturbels that have:
1. An umbric epipedon 40 cm or more thick with a texture
finer than loamy fine sand; and
2. A slope of less than 25 percent.
Cumulic Umbriturbels
ABEG. Other Umbriturbels that have, in one or more
horizons within 100 cm of the mineral soil surface, distinct or
prominent redox concentrations and also aquic conditions for
some time during normal years (or artificial drainage).
AquicUmbriturbels
ABEH. Other Umbriturbels.
Typic Umbriturbels
Definition of Typic Umbriturbels
Typic Umbriturbels are the Umbriturbels that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Do not have a glacic layer that has its upper boundary
within 100 cm of the mineral soil surface;
3. Have neither of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time during normal years, and slickensides
or wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; nor
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallowest;
4. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, a fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al plus
1
/2 Fe percentages (by ammonium oxalate) totaling more than
1.0;
5. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, either of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
6. Have either:
a. An umbric epipedon that is less than 40 cm thick,
unless the texture is loamy fine sand or coarser; or
b. A slope of 25 percent or more; and
Gelisols 471
7. Do not have, in any horizon within 100 cm of the mineral soil
surface, distinct or prominent redox concentrations and also
aquic conditions for some time during normal years.
Description of Subgroups
Typic Umbriturbels.—These are the Umbriturbels without
any special features. These soils do not have a lithic contact
within 50 cm or a glacic layer with an upper boundary within
100 cm of the mineral soil surface. They do not have the
potential to shrink and swell characteristic of the Vertic
subgroup or the volcanic glass or ammonium-extractable iron
and aluminum characteristic of the Andic and Vitrandic
subgroups. Typic Umbriturbels have an umbric epipedon that is
less than 40 cm thick, unless they are on steep slopes or are
sandy, or both, and do not have evidence of wetness and
distinct or prominent redox concentrations within 100 cm of
the mineral soil surface.
Andic Umbriturbels.—These are the Umbriturbels that
have, throughout one or more horizons with a total thickness of
18 cm or more within 75 cm of the mineral soil surface, a fineearth
fraction with both a bulk density of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and Al plus
1
/2 Fe percentages (by ammonium oxalate) totaling more than
1.0. These soils do not have a lithic contact within 50 cm or a
glacic layer with an upper boundary within 100 cm of the
mineral soil surface. They also do not have the high shrinkswell
potential associated with the Vertic subgroup. Andic
Umbriturbels are commonly in areas that receive volcanic
ejecta, but this is not required.
Aquic Umbriturbels.—These are the Umbriturbels with
aquic conditions and distinct or prominent redox
concentrations within 100 cm of the mineral soil surface.
These soils do not have a lithic contact within 50 cm or a
glacic layer with an upper boundary within 100 cm of the
mineral soil surface. They do not have the potential to shrink
and swell characteristic of the Vertic subgroup or the volcanic
glass or ammonium-extractable iron and aluminum
characteristic of the Andic and Vitrandic subgroups. Aquic
Umbriturbels have an umbric epipedon that is less than 40 cm
thick, unless they are on steep slopes or are sandy, or both.
Cumulic Umbriturbels.—These are the Umbriturbels that
have an umbric epipedon that is 40 cm or more thick, a texture
finer than loamy fine sand, and a slope of less than 25 percent.
These soils do not have a lithic contact within 50 cm or a
glacic layer with an upper boundary within 100 cm of the
mineral soil surface. Cumulic Umbriturbels do not have the
potential to shrink and swell characteristic of the Vertic
subgroup or the volcanic glass or ammonium-extractable iron
and aluminum characteristic of the Andic and Vitrandic
subgroups.
Glacic Umbriturbels.—These are the Umbriturbels that have
a glacic layer with an upper boundary within 100 cm of the
mineral soil surface. These soils do not have a lithic contact with
its upper boundary within 50 cm of the mineral soil surface.
Disturbance of the insulating surface layer causes the ice to melt
and the soil to collapse.
Lithic Umbriturbels.—These are the Umbriturbels that
have a lithic contact within 50 cm of the mineral soil surface.
Vertic Umbriturbels.—These are the Umbriturbels that
show physical evidence of high shrink-swell in the form of
cracks and slickensides or wedge-shaped aggregates or have
the potential to shrink and swell. This potential is determined
by the linear extensibility. These soils do not have a lithic
contact within 50 cm or a glacic layer with an upper boundary
within 100 cm of the mineral soil surface.
Vitrandic Umbriturbels.—These are the Umbriturbels that
have, throughout one or more horizons with a total thickness of
18 cm or more within 75 cm of the mineral soil surface, one or
both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Umbriturbels are not so weathered as the Andic
subgroup, do not have the shrink-swell potential associated
with the Vertic subgroup, and do not have a lithic contact
within 50 cm or a glacic layer with an upper boundary within
100 cm of the mineral soil surface.
473
The central concept of Histosols is that of soils forming
in organic soil materials. The general rule is that a soil
without permafrost is classified as a Histosol if half or more of
the upper 80 cm is organic. A soil is also classified as a
Histosol if the organic materials rest on rock or fill or partially
fill voids in fragmental, cindery, or pumiceous materials. If the
bulk density is very low, less than 0.1, three-fourths or more of
the upper 80 cm must be organic.
Definition of Histosols and Limits Between
Histosols and Soils of Other Orders
Histosols are soils that:
1. Do not have either of the following:
a. Permafrost within 100 cm of the soil surface; or
b. Gelic materials within 100 cm of the soil surface and
permafrost within 200 cm of the soil surface; and
2. Do not have andic soil properties in 60 percent or more of
the thickness between the soil surface and either a depth of 60
cm or a densic, lithic, or paralithic contact or duripan if
shallower; and
3. Have organic soil materials that meet one or more of the
following:
a. Overlie cindery, fragmental, or pumiceous materials
and/or fill their interstices and directly below these
materials have either a densic, lithic, or paralithic contact;
or
b. When added with the underlying cindery, fragmental, or
pumiceous materials, total 40 cm or more between the soil
surface and a depth of 50 cm; or
c. Constitute two-thirds or more of the total thickness of
the soil to a densic, lithic, or paralithic contact and have no
mineral horizons or have mineral horizons with a total
thickness of 10 cm or less; or
d. Are saturated with water for 30 or more cumulative
days during normal years (or are artificially drained), have
an upper boundary within 40 cm of the soil surface, and
have a total thickness of either:
(1) 60 cm or more if three-fourths or more of their
volume consists of moss fibers or if their bulk density,
moist, is less than 0.1 g/cm3
; or
(2) 40 cm or more if they consist either of sapric or
hemic materials, or of fibric materials with less than
three-fourths (by volume) moss fibers and a bulk density,
moist, of 0.1 g/cm3
or more.
Limits Between Histosols and Soils of Other
Orders
The definition of Histosols must provide criteria that
separate Histosols from all other orders. The aggregate of these
criteria defines the limits of Histosols in relation to all other
known soils.
1. Unlike Gelisols, Histosols do not have:
a. Permafrost within 100 cm of the soil surface; or
b. Gelic materials within 100 cm of the soil surface and
permafrost within 200 cm of the soil surface;
2. Unlike Andisols, Histosols do not have andic soil
properties in 60 percent or more of the thickness between the
soil surface and either a depth of 60 cm, or a densic, lithic, or
paralithic contact or duripan if shallower;
3. Unlike all other mineral soil orders, Histosols have organic
soil materials that meet one or more of the following:
a. Overlie cindery, fragmental, or pumiceous materials
and/or fill their interstices1
and directly below these
materials have either a densic, lithic, or paralithic contact;
or
b. When added with the underlying cindery, fragmental, or
pumiceous materials, total 40 cm or more between the soil
surface and a depth of 50 cm; or
c. Constitute two-thirds or more of the total thickness of
the soil to a densic, lithic, or paralithic contact and have no
mineral horizons or have mineral horizons with a total
thickness of 10 cm or less; or
d. Constitute two-thirds or more of the total thickness of
CHAPTER 14
Histosols
1
Materials that meet the definition of cindery, fragmental, or pumiceous but have more
than 10 percent, by volume, voids that are filled with organic soil materials are considered to be
organic soil materials.
474 Soil Taxonomy
the soil from the soil surface to 25 cm below the upper
boundary of permafrost and have no mineral horizons or
have mineral horizons with a total thickness of 10 cm or
less within that depth; or
e. Are saturated with water for 30 or more cumulative days
during normal years (or are artificially drained), have an upper
boundary within 40 cm of the soil surface, and have a total
thickness of either:
(1) 60 cm or more if three-fourths or more of their volume
consists of moss fibers or if their bulk density, moist, is
less than 0.1 g/cm3
; or
(2) 40 cm or more if they consist either of sapric or hemic
materials, or of fibric materials with less than three-fourths
(by volume) moss fibers and a bulk density, moist, of 0.1
g/cm3
or more.
Key to Suborders
BA. Histosols that are saturated with water for less than 30
cumulative days during normal years (and are not artificially
drained).
Folists, p. 478
BB. Other Histosols that:
1. Have more thickness of fibric soil materials than any
other kind of organic soil material either:
a. In the organic parts of the subsurface tier if there is
no continuous mineral layer 40 cm or more thick that has
its upper boundary within the subsurface tier; or
b. In the combined thickness of the organic parts of the
surface and subsurface tiers if there is a continuous
mineral layer 40 cm or more thick that has its upper
boundary within the subsurface tier; and
2. Do not have a sulfuric horizon that has its upper
boundary within 50 cm of the soil surface; and
3. Do not have sulfidic materials within 100 cm of the soil
surface.
Fibrists, p. 474
BC. Other Histosols that have more thickness of sapric
soil materials than any other kind of organic soil materials
either:
1. In the organic parts of the subsurface tier if there is no
continuous mineral layer 40 cm or more thick that has its
upper boundary within the subsurface tier; or
2. In the combined thickness of the organic parts of the
surface and subsurface tiers if there is a continuous mineral
layer 40 cm or more thick that has its upper boundary within
the subsurface tier.
Saprists, p. 484
BD. Other Histosols.
Hemists, p. 480
Fibrists
These are the wet Histosols in which the organic materials are
only slightly decomposed. More than two-thirds of the soil
consists of fibers that remain after rubbing between the thumb
and fingers. The botanic origin of the materials can be readily
determined. The bulk density is commonly less than 0.1 g/cm3
.
Many Fibrists have ground water near the soil surface nearly
all the time. A few areas of Fibrists are artificially drained. The
level of the ground water fluctuates but seldom drops much
below the bottom of the surface tier.
Fibrists are of relatively small extent but occur from the
Equator to latitudes with a cryic temperature regime. They are
in closed depressions and in broad flat areas, such as coastal
plains. Most are under natural vegetation.
Definition
Fibrists are the Histosols that:
1. Are saturated for 30 or more cumulative days or are
artificially drained; and
2. Have fibric soil materials that are:
a. Dominant in the organic part of the control section if
there is a mineral layer (or layers) 40 cm or more thick that
has its upper boundary in the subsurface tier, or if a densic,
lithic, or paralithic contact occurs in the subsurface tier;
or
b. Dominant in the subsurface tier if there is no
continuous mineral layer 40 cm or more thick that has its
upper boundary in that tier; and
3. Do not have a sulfuric horizon that has its upper boundary
within 50 cm of the soil surface; and
4. Do not have sulfidic materials within 100 cm of the soil
surface.
Key to Great Groups
BBA. Fibrists that have a cryic soil temperature regime.
Cryofibrists, p. 475
BBB. Other Fibrists in which fibric Sphagnum constitutes
three-fourths or more of the volume to either a depth of 90 cm
from the soil surface or to a densic, lithic, or paralithic contact,
Histosols 475
fragmental materials, or other mineral soil materials if at a depth
of less than 90 cm.
Sphagnofibrists, p. 477
BBC. Other Fibrists.
Haplofibrists, p. 476
Cryofibrists
These are cold Fibrists. The fibers may be derived from any
plant, woody or herbaceous. These soils may freeze during the
winter, or they may have a climate in which the soils do not
freeze during winter in normal years but are cold in summer.
In either situation, the low temperatures limit the use of the
soils. Most of these soils support native vegetation.
Definition
Cryofibrists are the Fibrists that have a cryic soil
temperature regime.
Key to Subgroups
BBAA. Cryofibrists that have a layer of water within the
control section, below the surface tier.
Hydric Cryofibrists
BBAB. Other Cryofibrists that have a lithic contact within
the control section.
Lithic Cryofibrists
BBAC. Other Cryofibrists that have a mineral layer 30 cm or
more thick that has its upper boundary within the control
section, below the surface tier.
Terric Cryofibrists
BBAD. Other Cryofibrists that have, within the organic
materials, either one mineral layer 5 cm or more thick or two
or more mineral layers of any thickness in the control section,
below the surface tier.
Fluvaquentic Cryofibrists
BBAE. Other Cryofibrists in which three-fourths or more of
the fiber volume in the surface tier is derived from Sphagnum.
Sphagnic Cryofibrists
BBAF. Other Cryofibrists.
Typic Cryofibrists
Definition of Typic Cryofibrists
Typic Cryofibrists are the Cryofibrists that:
1. Do not have a layer of water within the control section,
below the surface tier;
2. Have less than three-fourths of their fiber volume derived
from Sphagnum in the surface tier;
3. Do not have a lithic contact within the control section;
4. Do not have a mineral layer between 5 and 30 cm thick or
two or more thin, continuous mineral layers within the organic
materials in the control section, below the surface tier; and
5. Do not have a mineral layer 30 cm or more thick that has
its upper boundary below the surface tier and within the control
section.
Description of Subgroups
Typic Cryofibrists.—The central concept or Typic
subgroup of Cryofibrists is fixed on soils that do not have a
lithic contact and have less than three-fourths of the fiber
volume in the surface tier derived from Sphagnum.
A lithic contact is used in classifying lithic subgroups, as it
is throughout this taxonomy. In addition, thick or thin mineral
layers as well as intermittent mineral layers that are within the
control section, below the surface tier, cause soils to be
excluded from the Typic subgroup. The presence of layers that
are more decomposed than fibric materials is considered less
important in cold soils than in the warmer soils. The cold soils
are mostly in the State of Alaska in the United States and are
used as woodland or wildlife habitat.
Fluvaquentic Cryofibrists.—These soils differ from Typic
Cryofibrists because they have, within the organic materials,
either one mineral layer 5 to 30 cm thick or two or more
mineral layers of any thickness in the control section, below
the surface tier. These soils are not known to occur in the
United States.
Hydric Cryofibrists.—These soils differ from Typic
Cryofibrists because they have a layer of water within the
control section, below the surface tier. These soils are of small
extent, mostly in the State of Alaska in the United States, and
are used as wildlife habitat.
Lithic Cryofibrists.—These soils differ from Typic
Cryofibrists because they have a lithic contact within the
control section. These soils are not known to occur in the
United States.
Sphagnic Cryofibrists.—These soils differ from Typic
Cryofibrists because three-fourths or more of the fiber volume
in their surface tier is derived from Sphagnum. These soils are
of small extent, mostly in the State of Alaska in the United
States, and are used as woodland or wildlife habitat. The soils
are an important source of mulch for gardening, and some are
used as fuel.
Terric Cryofibrists.—These soils differ from Typic
Cryofibrists because they have a mineral layer 30 cm or more
thick that has its upper boundary within the control section,
below the surface tier. These soils are of small extent, mostly in
476 Soil Taxonomy
the State of Alaska in the United States, and are used as
woodland or wildlife habitat.
Haplofibrists
These are the Fibrists in which the temperature regime is
warmer than cryic and less than three-fourths of the fiber
volume is derived from Sphagnum. The fibers may have been
derived from wood, grasses, sedges, mosses, and other
herbaceous plants or from some combination of these. If these
soils are drained and cultivated under the present technology,
the organic materials will decompose either slowly or rapidly,
depending on the management used and the temperature.
Eventually, within some decades, the Haplofibrists that are
drained and cultivated will be replaced first by Hemists and
Saprists and then by mineral soils. Most of these soils in the
United States support native vegetation.
Definition
Haplofibrists are the Fibrists that:
1. Have a soil temperature regime warmer than cryic;
2. Have less than three-fourths of their fiber volume derived
from Sphagnum either in the upper 90 cm or more of the
control section or in the soil above a densic, lithic, or paralithic
contact, fragmental materials, or mineral soil materials
shallower than 90 cm.
Key to Subgroups
BBCA. Haplofibrists that have a layer of water within the
control section, below the surface tier.
Hydric Haplofibrists
BBCB. Other Haplofibrists that have a lithic contact within
the control section.
Lithic Haplofibrists
BBCC. Other Haplofibrists that have one or more limnic
layers with a total thickness of 5 cm or more within the control
section.
Limnic Haplofibrists
BBCD. Other Haplofibrists that have a mineral layer 30 cm
or more thick that has its upper boundary within the control
section, below the surface tier.
Terric Haplofibrists
BBCE. Other Haplofibrists that have, within the organic
materials, either one mineral layer 5 cm or more thick or two
or more mineral layers of any thickness in the control section,
below the surface tier.
Fluvaquentic Haplofibrists
BBCF. Other Haplofibrists that have one or more layers of
hemic and sapric materials with a total thickness of 25 cm or
more in the control section, below the surface tier.
Hemic Haplofibrists
BBCG. Other Haplofibrists.
Typic Haplofibrists
Definition of Typic Haplofibrists
Typic Haplofibrists are the Haplofibrists that:
1. Have a total of less than 25 cm hemic and sapric materials
below the surface tier;
2. Do not have a limnic layer(s) 5 cm or more thick within
the control section;
3. Do not have a lithic contact within the control section;
4. Do not have a mineral layer between 5 and 30 cm thick
or two or more thin, continuous mineral layers within the
organic materials in the control section, below the surface
tier;
5. Do not have a mineral layer 30 cm or more thick that has
its upper boundary within the control section, below the surface
tier; and
6. Do not have a layer of water within the control section,
below the surface tier.
Description of Subgroups
Typic Haplofibrists.—The central concept or Typic
subgroup of Haplofibrists is fixed on soils that do not have a
lithic contact and do not have a layer of water within the
control section, below the surface tier.
A lithic contact is used in classifying lithic subgroups, as it
is throughout this taxonomy. In addition, thick or thin mineral
layers as well as intermittent mineral layers that are within the
surface tier cause soils to be excluded from the Typic
subgroup. The presence of limnic materials and layers that
are more decomposed than fibric materials also excludes
soils from the Typic subgroup. Typic Haplofibrists are of
small extent in the United States and are used mostly as
wildlife habitat.
Fluvaquentic Haplofibrists.—These soils differ from Typic
Haplofibrists because they have, within the organic materials,
either one mineral layer 5 to 30 cm thick or two or more
mineral layers of any thickness in the control section, below
the surface tier. These soils are not known to occur in the
United States.
Hemic Haplofibrists.—These soils differ from Typic
Haplofibrists because they have one or more layers of hemic
and sapric materials with a total thickness of 25 cm or more
below the surface tier. These soils are not known to occur in
the United States.
Hydric Haplofibrists.—These soils differ from Typic
Haplofibrists because they have a layer of water within the
Histosols 477
control section, below the surface tier. These soils are of small
extent, mostly in the State of Alaska in the United States, and
are used as wildlife habitat.
Limnic Haplofibrists.—These soils differ from Typic
Haplofibrists because they have one or more limnic layers
with a total thickness of 5 cm or more within the control
section. These soils are not known to occur in the United
States.
Lithic Haplofibrists.—These soils differ from Typic
Haplofibrists because they have a lithic contact within the
control section. These soils are not known to occur in the
United States.
Terric Haplofibrists.—These soils differ from Typic
Haplofibrists because they have a mineral layer 30 cm or more
thick that has its upper boundary within the control section,
below the surface tier. These soils are of small extent, mostly in
the State of Alaska in the United States, and are used as
woodland or wildlife habitat.
Sphagnofibrists
These are the Fibrists that were derived mainly from the
various species of Sphagnum and associated herbaceous plants.
At least three-fourths of the fibers, by volume, are Sphagnum in
at least the upper 90 cm of the soil or throughout the soil if
there is a densic, lithic, or paralithic contact shallower than 90
cm. A few of these soils have a mesic soil temperature regime
that borders on frigid, but in general the soils are cool. Most of
them have a frigid temperature regime. The structure of
Sphagnum, with its water-holding cells, makes these soils
unique, and for that reason they are grouped as
Sphagnofibrists.
Definition
Sphagnofibrists are the Fibrists that:
1. Have three-fourths or more of their fiber volume
derived from Sphagnum in the upper 90 cm or more of
the control section, or above a densic, lithic, or paralithic
contact, fragmental materials, or mineral soil shallower than
90 cm;
2. Have a mean annual soil temperature that is warmer than
cryic.
Key to Subgroups
BBBA. Sphagnofibrists that have a layer of water within the
control section, below the surface tier.
Hydric Sphagnofibrists
BBBB. Other Sphagnofibrists that have a lithic contact
within the control section.
Lithic Sphagnofibrists
BBBC. Other Sphagnofibrists that have one or more limnic
layers with a total thickness of 5 cm or more within the control
section.
Limnic Sphagnofibrists
BBBD. Other Sphagnofibrists that have a mineral layer 30
cm or more thick that has its upper boundary within the control
section, below the surface tier.
Terric Sphagnofibrists
BBBE. Other Sphagnofibrists that have, within the organic
materials, either one mineral layer 5 cm or more thick or two
or more mineral layers of any thickness in the control section,
below the surface tier.
Fluvaquentic Sphagnofibrists
BBBF. Other Sphagnofibrists that have one or more layers of
hemic and sapric materials with a total thickness of 25 cm or
more in the control section, below the surface tier.
Hemic Sphagnofibrists
BBBG. Other Sphagnofibrists.
Typic Sphagnofibrists
Definition of Typic Sphagnofibrists
Typic Sphagnofibrists are the Sphagnofibrists that:
1. Do not have a mineral layer between 5 and 30 cm thick or
two or more thin, continuous mineral layers within the organic
materials in the control section, below the surface tier;
2. Have a total of less than 25 cm hemic and sapric materials
below the surface tier;
3. Do not have a layer of water within the control section,
below the surface tier;
4. Do not have a limnic layer(s) 5 cm or more thick within
the control section;
5. Do not have a lithic contact within the control section; and
6. Do not have a mineral layer 30 cm or more thick that has
its upper boundary in the control section, below the surface tier.
Description of Subgroups
Typic Sphagnofibrists.—The central concept or Typic
subgroup of Sphagnofibrists is fixed on thick, continuous fibric
organic materials that were derived primarily from Sphagnum.
These soils do not have a lithic contact and do not have a layer
of water within the control section, below the surface tier. At
least three-fourths of the fibric materials, by volume, were
derived from Sphagnum. These soils occur as raised bogs or
high moors in closed depressions and as blanket bogs on more
or less dissected landscapes.
Layers of organic material more decomposed than fibric
materials affect the movement of water and indicate an
intergrade to Hemists. Thin mineral layers normally affect the
478 Soil Taxonomy
movement of water drastically. These layers normally are alluvial
and define the Fluvaquentic subgroup. Thick mineral layers,
rock, limnic layers, and water within the control section are used
as bases for classifying terric, lithic, limnic, and hydric
extragrades, respectively.
Typic Sphagnofibrists are used mostly as wildlife habitat. A
few have been cleared and are used for specialty crops. These
soils are of small extent in the United States.
Fluvaquentic Sphagnofibrists.—These soils differ from
Typic Sphagnofibrists because they have, within the organic
materials, either one mineral layer 5 to 30 cm thick or two or
more mineral layers of any thickness in the control section,
below the surface tier. These soils are not known to occur in
the United States.
Hemic Sphagnofibrists.—These soils differ from Typic
Sphagnofibrists because they have one or more layers of hemic
and sapric materials with a total thickness of 25 cm or more
below the surface tier. These soils are of small extent in the
United States.
Hydric Sphagnofibrists.—These soils differ from Typic
Sphagnofibrists because they have a layer of water within the
control section, below the surface tier. These soils are not
known to occur in the United States.
Limnic Sphagnofibrists.—These soils differ from Typic
Sphagnofibrists because they have one or more limnic layers
with a total thickness of 5 cm or more within the control
section. These soils are not known to occur in the United
States.
Lithic Sphagnofibrists.—These soils differ from Typic
Sphagnofibrists because they have a lithic contact within the
control section. These soils are not known to occur in the
United States.
Terric Sphagnofibrists.—These soils differ from Typic
Sphagnofibrists because they have a mineral layer 30 cm
or more thick with its upper boundary within the control
section, below the surface tier. These soils are of small extent
in the United States and are used as woodland or wildlife
habitat.
Folists
These are the more or less freely drained Histosols that
consist primarily of O horizons derived from leaf litter, twigs,
and branches resting on rock or on fragmental materials that
consist of gravel, stones, and boulders in which the interstices
are filled or partly filled with organic materials. Plant roots
grow only in the organic materials. Many of these soils are in
very humid climates from the Tropics to high latitudes and
high elevations. Some have an ustic or aridic (or torric) soil
moisture regime. Most of the Folists in the United States are
in Hawaii and Alaska. There are some Folists in the
mountains in the western part of the United States, in the
northern Lake States, and in the northeastern part of the
United States.
Definition
Folists are the Histosols that are saturated with water for less
than 30 cumulative days during normal years (and are not
artificially drained).
Key to Great Groups
BAA. Folists that have a cryic soil temperature regime.
Cryofolists, p. 478
BAB. Other Folists that have an aridic (or torric) soil moisture
regime.
Torrifolists, p. 479
BAC. Other Folists that have an ustic or xeric soil moisture
regime.
Ustifolists, p. 479
BAD. Other Folists.
Udifolists, p. 479
Cryofolists
These are the cold Folists. In the United States they occur
mostly in southeastern Alaska, where the climate is cool,
oceanic, and very humid. They are on gentle to very steep
slopes. Their vegetation is primarily coniferous forests, and the
only part of the soils in which there are plant roots is the O
horizon. Beneath the O horizon, there may be a few
centimeters of mineral soil material or none on hard rock or
there may be fragmental materials consisting of gravel, stones,
and boulders with the interstices filled or partly filled with
organic materials.
Definition
Cryofolists are the Folists that have a cryic temperature
regime.
Key to Subgroups
BAAA. Cryofolists that have a lithic contact within 50 cm of
the soil surface.
Lithic Cryofolists
BAAB. Other Cryofolists.
Typic Cryofolists
Definition of Typic Cryofolists
Typic Cryofolists are the Cryofolists that do not have a lithic
contact within 50 cm of the surface.
Description of Subgroups
Typic Cryofolists.—The central concept or Typic subgroup
of Cryofolists is fixed on soils that have organic materials
resting on fragmental materials and filling or partly filling
Histosols 479
interstices in the fragmental materials, which consist of gravel,
stones, and boulders. The soils on fragmental materials are not
necessarily the most common in the great group, but they are
classified as the Typic subgroup because the presence of
shallow hard rock is used throughout this taxonomy to define
lithic subgroups.
Lithic Cryofolists.—The Lithic subgroup of Cryofolists
has organic materials that rest on a lithic contact within
50 cm of the soil surface. Lithic Cryofolists are of small
extent. They occur on the Olympic Peninsula in the United
States. These soils are used as either woodland or wildlife
habitat.
Torrifolists
These are the Folists that have a temperature regime warmer
than cryic and an aridic (or torric) soil moisture regime. They
occur in Hawaii, chiefly on lava flows in areas that receive little
rainfall. The vegetation is mostly fountaingrass mixed with
shrubs.
Definition
Torrifolists are the Folists that have a temperature regime
warmer than cryic and an aridic (or torric) soil moisture
regime.
Key to Subgroups
BABA. Torrifolists that have a lithic contact within 50 cm of
the soil surface.
Lithic Torrifolists
BABB. Other Torrifolists.
Typic Torrifolists
Definition of Typic Torrifolists
Typic Torrifolists are the Torrifolists that do not have a
lithic contact within 50 cm of the soil surface.
Description of Subgroups
Typic Torrifolists.—The central concept or Typic subgroup
of Torrifolists is fixed on soils that have organic materials
resting on fragmental materials and filling or partly filling
interstices in the fragmental materials, which consist of
gravel, stones, and boulders. The soils on fragmental materials
are not necessarily the most common in the great group, but
they are classified as the Typic subgroup because the presence
of shallow hard rock is used throughout this taxonomy to
define lithic subgroups. These soils are of small extent in the
State of Hawaii in the United States and are used as wildlife
habitat.
Lithic Torrifolists.—The Lithic subgroup of Torrifolists has
organic materials resting on a lithic contact within 50 cm of
the soil surface. These soils are of small extent in the State of
Hawaii in the United States and are used as wildlife habitat.
Udifolists
These are the Folists that have a temperature regime warmer
than cryic and a udic (or perudic) soil moisture regime. They
occur in Hawaii, chiefly on lava flows in areas that receive very
high amounts of well-distributed rainfall. The vegetation is
mostly forest mixed with tree ferns.
Definition
Udifolists are the Folists that have:
1. A temperature regime warmer than cryic;
2. A udic (or perudic) soil moisture regime.
KeytoSubgroups
BADA. Udifolists that have a lithic contact within 50 cm of the
soil surface.
Lithic Udifolists
BADB. Other Udifolists.
Typic Udifolists
Definition of Typic Udifolists
Typic Udifolists are the Udifolists that do not have a lithic
contact within 50 cm of the surface.
Description of Subgroups
Typic Udifolists.—The central concept or Typic subgroup
of Udifolists is fixed on soils that have organic materials
resting on fragmental materials and filling or partly filling
interstices in the fragmental materials, which consist of gravel,
stones, and boulders. The soils on fragmental materials are not
necessarily the most common in the great group, but they are
classified as the Typic subgroup because the presence of
shallow hard rock is used throughout this taxonomy to define
lithic subgroups. These soils are of small extent in the State of
Hawaii in the United States and are used as wildlife habitat.
Lithic Udifolists.—The Lithic subgroup of Udifolists has
organic materials resting on a lithic contact within 50 cm of
the soil surface. These soils are of small extent in the State of
Hawaii and on the Olympic Peninsula of Washington in the
United States and are used as wildlife habitat.
Ustifolists
These are the Folists that have a temperature regime
warmer than cryic and an ustic or xeric soil moisture regime.
These soils have an O horizon overlying or in fragmental
materials or directly overlying bedrock that is less than 50 cm
from the surface.
Definition
Ustifolists are the Folists that have a temperature regime
warmer than cryic and an ustic or xeric soil moisture regime.
480 Soil Taxonomy
KeytoSubgroups
BACA. Ustifolists that have a lithic contact within 50 cm of the
soil surface.
Lithic Ustifolists
BACB. Other Ustifolists.
Typic Ustifolists
Definition of Typic Ustifolists
Typic Ustifolists are the Ustifolists that do not have a lithic
contact within 50 cm of the surface.
Description of Subgroups
Typic Ustifolists.—The central concept or Typic subgroup
of Ustifolists is fixed on soils that have organic materials
resting on fragmental materials and filling or partly filling
interstices in the fragmental materials, which consist of gravel,
stones, and boulders. The soils on fragmental materials are not
necessarily the most common in the great group, but they are
classified as the Typic subgroup because the presence of
shallow hard rock is used throughout this taxonomy to define
lithic subgroups. These soils are of small extent in the State of
Hawaii in the United States and are used as wildlife habitat.
Lithic Ustifolists.—The Lithic subgroup of Ustifolists has
organic materials resting on a lithic contact within 50 cm of
the soil surface. These soils are of small extent in the State of
Hawaii in the United States and are used as wildlife habitat.
Hemists
These are wet Histosols in which the organic materials are
moderately decomposed. The botanic origin of much of the
organic material cannot be readily determined. The fiber
content of much of the organic material is between one-sixth
and two-thirds after rubbing between the thumb and fingers.
The bulk density commonly is between 0.1 and 0.2 g/cm3
.
Ground water is at or very close to the surface of these soils
much of the time unless artificial drainage has been provided.
The level of ground water may fluctuate but seldom drops
much below the bottom of the surface tier.
Hemists occur from the Equator to latitudes with a cryic
temperature regime. They are in closed depressions and in
broad flat areas, such as coastal plains and outwash plains.
Most Hemists are under natural vegetation and are used as
woodland, rangeland, or wildlife habitat. Some large areas of
Hemists are cleared, drained, and used as cropland.
Definition
Hemists are the Histosols that:
1. Are saturated with water for 30 or more cumulative days
during normal years (unless artificially drained);
2. Do not have more thickness of fibric soil materials and do
not have more thickness of sapric soil materials than any other
kind of organic soil material either:
a. In the organic parts of the subsurface tier if there is no
continuous mineral layer 40 cm or more thick that has its
upper boundary within the subsurface tier; or
b. In the combined thickness of the organic parts of the
surface and subsurface tiers if there is a continuous mineral
layer 40 cm or more thick that has its upper boundary
within the subsurface tier; or
3. Have a sulfuric horizon that has its upper boundary within
50 cm of the soil surface, or sulfidic materials within 100 cm
of the soil surface, and more thickness of fibric soil material
than any other kind of organic soil material either:
a. In the organic parts of the subsurface tier if there is no
continuous mineral layer 40 cm or more thick that has its
upper boundary within the subsurface tier; or
b. In the combined thickness of the organic parts of the
surface and subsurface tiers if there is a continuous mineral
layer 40 cm or more thick that has its upper boundary
within the subsurface tier.
Key to Great Groups
BDA. Hemists that have a sulfuric horizon that has its upper
boundary within 50 cm of the soil surface.
Sulfohemists, p. 483
BDB. Other Hemists that have sulfidic materials within 100
cm of the soil surface.
Sulfihemists, p. 483
BDC. Other Hemists that have a horizon 2 cm or more thick
in which humilluvic materials constitute one-half or more of
the volume.
Luvihemists, p. 483
BDD. Other Hemists that have a cryic temperature regime.
Cryohemists, p. 480
BDE. Other Hemists.
Haplohemists, p. 481
Cryohemists
These are the cold Hemists that do not have a sulfuric
horizon with its upper boundary within 50 cm of the soil
surface or sulfidic materials within 100 cm of the soil surface.
They have a cryic temperature regime. The fibers in these soils
are from many kinds of plant materials, including wood, moss,
grass, and herbaceous materials. Some of these soils freeze
during the winter, and some do not freeze. Those that do not
Histosols 481
freeze are insulated by snow cover or have a marine climate in
which winters are mild and summers are very cool. Low soil
temperatures in the summer limit the suitable crops where
these soils are used as cropland. Most of these soils support
native coniferous forest vegetation.
Definition
Cryohemists are the Hemists that:
1. Have a cryic temperature regime;
2. Do not have a sulfuric horizon that has its upper boundary
within 50 cm of the surface;
3. Do not have sulfidic materials within 100 cm of the
surface;
4. Do not have a horizon 2 cm or more thick in which
humilluvic materials constitute one-half or more of the volume.
Key to Subgroups
BDDA. Cryohemists that have a layer of water within the
control section, below the surface tier.
Hydric Cryohemists
BDDB. Other Cryohemists that have a lithic contact within
the control section.
Lithic Cryohemists
BDDC. Other Cryohemists that have a mineral layer 30 cm
or more thick that has its upper boundary within the control
section, below the surface tier.
Terric Cryohemists
BDDD. Other Cryohemists that have, within the organic
materials, either one mineral layer 5 cm or more thick or two
or more mineral layers of any thickness in the control section,
below the surface tier.
Fluvaquentic Cryohemists
BDDE. Other Cryohemists.
Typic Cryohemists
Definition of Typic Cryohemists
Typic Cryohemists are the Cryohemists that:
1. Do not have a layer of water within the control section,
below the surface tier;
2. Do not have a lithic contact within the control section;
3. Do not have a mineral layer 30 cm or more thick that has
its upper boundary in the control section, below the surface
tier; and
4. Do not have a mineral layer between 5 and 30 cm thick or
two or more thin, continuous mineral layers within the organic
materials in the control section, below the surface tier.
Description of Subgroups
Typic Cryohemists.—The central concept or Typic subgroup
of Cryohemists is fixed on soils that do not have a lithic contact
and do not have a layer of water within the control section,
below the surface tier.
A lithic contact is used in classifying the Lithic subgroup, as
it is throughout this taxonomy. In addition, thick or thin
mineral layers as well as intermittent mineral layers that are
below the surface tier cause soils to be excluded from the Typic
subgroup. The presence or absence of layers of materials either
more or less decomposed than hemic materials is considered
less important in the very cold soils than in other great groups
of Hemists. These soils are mostly in the State of Alaska in the
United States and are used mainly as woodland or wildlife
habitat.
Fluvaquentic Cryohemists.—These soils differ from Typic
Cryohemists because they have, within the organic materials,
either one mineral layer 5 to 30 cm thick or two or more
mineral layers of any thickness in the control section, below
the surface tier. These soils are not known to occur in the
United States.
Hydric Cryohemists.—These soils differ from Typic
Cryohemists because they have a layer of water within the
control section, below the surface tier. These soils are not
known to occur in the United States.
Lithic Cryohemists.—These soils differ from Typic
Cryohemists because they have a lithic contact within the
control section. These soils are of small extent, mostly in the
State of Alaska in the United States, and are used as woodland
or wildlife habitat.
Terric Cryohemists.—These soils differ from Typic
Cryohemists because they have a mineral layer 30 cm or more
thick that has its upper boundary within the control section,
below the surface tier. These soils are of small extent, mostly in
the State of Alaska in the United States, and are used as
woodland or wildlife habitat.
Haplohemists
These are the Hemists that have a temperature regime
warmer than cryic and that do not have a sulfuric horizon with
its upper boundary within 50 cm of the soil surface or sulfidic
materials within 100 cm of the soil surface. They are wet at the
base of the surface tier for more than 30 cumulative days during
normal years unless they have been drained. Most
Haplohemists are saturated for considerably longer than 30
days per year. The organic materials in these soils are from
many kinds of plant materials, including wood, moss, grass,
and herbaceous materials. These soils do not have a layer of
humilluvic materials 2 cm or more thick within 130 cm of the soil
surface.
If these soils are drained and cultivated under the present
technology, the organic materials decompose and disappear
slowly or rapidly, depending on the management used and the
482 Soil Taxonomy
temperature. Eventually, within some decades, the
Haplohemists that are drained and cultivated will be replaced
by Saprists and then by mineral soils. Most Haplohemists
support native vegetation, mostly forest plants or shrubs and
grasslike plants. Some large areas are cleared, drained, and used
as cropland.
Definition
Haplohemists are the Hemists that:
1. Have a soil temperature regime warmer than cryic;
2. Do not have a layer of humilluvic materials 2 cm or more
thick;
3. Do not have a sulfuric horizon that has its upper boundary
within 50 cm of the soil surface; and
4. Do not have sulfidic materials within 100 cm of the soil
surface.
Key to Subgroups
BDEA. Haplohemists that have a layer of water within the
control section, below the surface tier.
Hydric Haplohemists
BDEB. Other Haplohemists that have a lithic contact within
the control section.
Lithic Haplohemists
BDEC. Other Haplohemists that have one or more limnic
layers with a total thickness of 5 cm or more within the control
section.
Limnic Haplohemists
BDED. Other Haplohemists that have a mineral layer 30 cm
or more thick that has its upper boundary within the control
section, below the surface tier.
Terric Haplohemists
BDEE. Other Haplohemists that have, within the organic
materials, either one mineral layer 5 cm or more thick or two
or more mineral layers of any thickness in the control section,
below the surface tier.
Fluvaquentic Haplohemists
BDEF. Other Haplohemists that have one or more layers of
fibric materials with a total thickness of 25 cm or more in the
control section, below the surface tier.
Fibric Haplohemists
BDEG. Other Haplohemists that have one or more layers of
sapric materials with a total thickness of 25 cm or more below
the surface tier.
Sapric Haplohemists
BDEH. Other Haplohemists.
TypicHaplohemists
DefinitionofTypicHaplohemists
Typic Haplohemists are the Haplohemists that:
1. Do not have a mineral layer between 5 and 30 cm thick or
two or more thin, continuous mineral layers within the organic
materials in the control section, below the surface tier;
2. Have:
a. Less than 25 cm of fibric materials below the surface
tier; and
b. Less than 25 cm of sapric materials below the surface
tier;
3. Do not have a mineral layer 30 cm or more thick that has
its upper boundary in the control section, below the surface
tier;
4. Do not have a layer of water within the control section,
below the surface tier;
5. Do not have a limnic layer(s) 5 cm or more thick within
the control section; and
6. Do not have a lithic contact within the control section.
Description of Subgroups
Typic Haplohemists.—The central concept or Typic
subgroup of Haplohemists is fixed on soils that do not have a
lithic contact and do not have a layer of water within the
control section, below the surface tier.
A lithic contact is used in classifying the Lithic subgroup, as
it is throughout this taxonomy. In addition, thick or thin
mineral layers as well as intermittent mineral layers that are
below the surface tier cause soils to be excluded from the Typic
subgroup. The presence of layers of materials either more or
less decomposed than hemic materials is used as differentia for
the Fibric and Sapric subgroups, respectively. These soils are
widely distributed in the United States, mostly in the Eastern
States. They are used mainly as woodland, cropland, or wildlife
habitat.
Fibric Haplohemists.—These soils differ from Typic
Haplohemists because they have one or more layers of fibric
materials with a total thickness of 25 cm or more below the
surface tier. These soils are of very small extent in the United
States.
Fluvaquentic Haplohemists.—These soils differ from Typic
Haplohemists because they have, within the organic materials,
either one mineral layer 5 to 30 cm thick or two or more
mineral layers of any thickness in the control section, below
the surface tier. These soils are of very small extent in the
United States.
Hydric Haplohemists.—These soils differ from Typic
Histosols 483
Haplohemists because they have a layer of water within the
control section, below the surface tier. These soils are of small
extent in the United States.
Limnic Haplohemists.—These soils differ from Typic
Haplohemists because they have one or more limnic layers with
a total thickness of 5 cm or more within the control section.
These soils are of small extent but occur in a broad geographic
range from Puerto Rico to the Pacific Northwest. Many of the
soils support natural vegetation, but some are used as cropland
or for hay and pasture.
Lithic Haplohemists.—These soils differ from Typic
Haplohemists because they have a lithic contact within the
control section. These soils are of very small extent in the
United States.
Sapric Haplohemists.—These soils differ from Typic
Haplohemists because they have one or more layers of sapric
materials with a total thickness of 25 cm or more below the
surface tier. These soils are of very small extent in the United
States.
Terric Haplohemists.—These soils differ from Typic
Haplohemists because they have a mineral layer 30 cm or more
thick that has its upper boundary within the control section,
below the surface tier. These soils are widely distributed in the
United States, mostly in the Eastern States. They are used
mainly as woodland, cropland, or wildlife habitat.
Luvihemists
Luvihemists are not known to occur in the United States, but
the great group is provided tentatively for use in other countries
if needed. These are the Hemists that have, within the control
section, a horizon 2 cm or more thick in which humilluvic
materials constitute one-half or more of the volume. Because
Luvihemists cannot be studied in the United States, a precise
definition of these soils is not attempted here. It should be
noted, however, that they are normally acid and have been
cultivated for a long time.
Key to Subgroups
BDCA. All Luvihemists (provisionally).
TypicLuvihemists
Sulfihemists
These are the Hemists that have sulfidic materials within 100
cm of the surface. They are potentially extremely acid or ultra
acid. Most Sulfihemists will develop a sulfuric horizon and
become Sulfohemists if they are artificially drained to an extent
that allows oxygen to reach the sulfidic materials. These soils are
permitted to have more fiber than other Hemists. They are mainly
in coastal marshes near the mouths of rivers or in the deltas of
rivers that carry sediments having a low content of carbonates
and are locally extensive. Most Sulfihemists support native
vegetation, mainly forbs and grasslike plants.
Definition
Sulfihemists are the Hemists that:
1. Have sulfidic materials within 100 cm of the surface; and
2. Do not have a sulfuric horizon that has its upper boundary
within 50 cm of the soil surface.
Key to Subgroups
BDBA. Sulfihemists that have a mineral layer 30 cm or more
thick that has its upper boundary within the control section,
below the surface tier.
Terric Sulfihemists
BDBB. Other Sulfihemists.
Typic Sulfihemists
Definition of Typic Sulfihemists
Typic Sulfihemists are the Sulfihemists that do not have a
mineral layer 30 cm or more thick that has its upper boundary
in the control section, below the surface tier.
Description of Subgroups
Typic Sulfihemists.—The central concept or Typic
subgroup of Sulfihemists is fixed on soils that do not have a
mineral layer 30 cm or more thick that has its upper boundary
in the control section, below the surface tier. These soils are
widely distributed in the United States, mostly in the Eastern
States. They generally support native vegetation, mostly sparse
forbs and grasslike plants. They are used mainly as recreational
areas or wildlife habitat.
Terric Sulfihemists.—These soils differ from Typic
Sulfihemists because they have a mineral layer 30 cm or more
thick that has its upper boundary within the control section,
below the surface tier. They are mainly in coastal marshes near
the mouths of rivers or in the deltas of rivers on the east coast
of the United States. They are locally extensive. These soils
support native vegetation, mostly forbs and grasslike plants.
They are used mainly as recreational areas or wildlife habitat.
Sulfohemists
These are the Hemists that have a sulfuric horizon within 50
cm of the surface. The sulfuric horizon formed as a
consequence of draining the sulfidic materials. These soils are
extremely acid and are toxic to most plants. Most are nearly
black and have straw-colored redoximorphic concentrations of
iron sulfate (jarosite) within 50 cm of the surface. The soils are
mainly in drained coastal marshes or deltas near the mouths of
rivers that carry sediments having a low content of carbonates.
Most of the soils have an appreciable amount of mineral
material within the control section. These soils support sparse
vegetation, mostly forbs and grasslike plants. They are used
mainly as recreational areas or wildlife habitat.
484 Soil Taxonomy
Definition
Sulfohemists are the Hemists that have a sulfuric horizon that
has its upper boundary within 50 cm of the surface.
KeytoSubgroups
BDAA. All Sulfohemists (provisionally).
Typic Sulfohemists
Saprists
These are the wet Histosols in which the organic materials
are well decomposed. The botanic origin of the organic
material is difficult to determine in most of these soils. The
fiber content is less than one-sixth after rubbing between the
thumb and fingers. Most of these soils have a bulk density of
more than 0.2 g/cm3
.
Saprists occur in areas where the ground water table tends
to fluctuate within the soils or in areas where the soils were
aerobic during drier periods in the past. They consist of the
residue that remains after the aerobic decomposition of organic
matter. When drained, fibric and hemic materials commonly
decompose to form sapric materials. If the organic materials
are deep and are drained either artificially or naturally, the
Fibrists and Hemists are converted after some decades to
Saprists.
Definition
Saprists are the Histosols that:
1. Are saturated with water for 30 or more cumulative days
during normal years (unless artificially drained); and
2. Have more thickness of sapric soil materials than any other
kind of organic soil materials either:
a. In the organic parts of the subsurface tier if there is no
continuous mineral layer 40 cm or more thick that has its
upper boundary within the subsurface tier; or
b. In the combined thickness of the organic parts of the
surface and subsurface tiers if there is a continuous mineral
layer 40 cm or more thick that has its upper boundary
within the subsurface tier.
Key to Great Groups
BCA. Saprists that have a sulfuric horizon that has its upper
boundary within 50 cm of the soil surface.
Sulfosaprists, p. 487
BCB. Other Saprists that have sulfidic materials within 100
cm of the soil surface.
Sulfisaprists, p. 486
BCC. Other Saprists that have a cryic temperature regime.
Cryosaprists, p. 484
BCD. Other Saprists.
Haplosaprists, p. 485
Cryosaprists
These are the cold Saprists that do not have a sulfuric
horizon with its upper boundary within 50 cm of the soil
surface and do not have sulfidic materials within 100 cm of the
soil surface. They have a cryic temperature regime. These soils
formed from many kinds of plant materials, including wood,
moss, grass, and herbaceous materials. Some of these soils
freeze during the winter, and some do not freeze. Those that do
not freeze are insulated by snow cover or have a marine climate
in which winters are mild and summers are very cool. Low soil
temperatures in the summer limit the suitable crops where
these soils are used as cropland. Most of these soils support
native coniferous forest vegetation.
Definition
Cryosaprists are the Saprists that:
1. Have a cryic temperature regime; and
2. Do not have a sulfuric horizon that has its upper boundary
within 50 cm of the soil surface; and
3. Do not have sulfidic materials within 100 cm of the soil
surface.
Key to Subgroups
BCCA. Cryosaprists that have a lithic contact within the
control section.
Lithic Cryosaprists
BCCB. Other Cryosaprists that have a mineral layer 30 cm or
more thick that has its upper boundary within the control
section, below the surface tier.
Terric Cryosaprists
BCCC. Other Cryosaprists that have, within the organic
materials, either one mineral layer 5 cm or more thick or two
or more mineral layers of any thickness in the control section,
below the surface tier.
Fluvaquentic Cryosaprists
BCCD. Other Cryosaprists.
Typic Cryosaprists
Definition of Typic Cryosaprists
Typic Cryosaprists are the Cryosaprists that:
1. Do not have a lithic contact within the control section;
Histosols 485
2. Do not have a mineral layer 30 cm or more thick that has its
upper boundary in the control section, below the surface tier;
and
3. Do not have a mineral layer between 5 and 30 cm thick or
two or more thin, continuous mineral layers within the organic
materials in the control section, below the surface tier.
Description of Subgroups
Typic Cryosaprists.—The central concept or Typic
subgroup of Cryosaprists is fixed on soils that do not have a
lithic contact and do not have thick or thin mineral layers or
intermittent mineral layers below the surface tier.
A lithic contact is used in classifying the Lithic subgroup, as
it is throughout this taxonomy. In addition, thick or thin
mineral layers as well as intermittent mineral layers that are
below the surface tier cause soils to be excluded from the Typic
subgroup. The presence of layers of materials less decomposed
than sapric materials is considered less important in these cold
Saprists than in the other great groups. These soils are of small
extent, mostly in the State of Alaska in the United States, and
are used as woodland or wildlife habitat.
Fluvaquentic Cryosaprists.—These soils differ from Typic
Cryosaprists because they have, within the organic materials,
either one mineral layer 5 to 30 cm thick or two or more
mineral layers of any thickness in the control section, below
the surface tier. These soils are of small extent, mostly in the
State of Alaska in the United States, and are used as woodland
or wildlife habitat.
Lithic Cryosaprists.—These soils differ from Typic
Cryosaprists because they have a lithic contact within the
control section. These soils are of small extent, mostly in the
State of Alaska in the United States, and are used as woodland
or wildlife habitat.
Terric Cryosaprists.—These soils differ from Typic
Cryosaprists because they have a mineral layer 30 cm or more
thick that has its upper boundary within the control section,
below the surface tier. These soils are of small extent, mostly in
the State of Alaska in the United States, and are used as
woodland or wildlife habitat.
Haplosaprists
These are the Saprists that have a temperature regime
warmer than cryic and that do not have a sulfuric horizon with
its upper boundary within 50 cm of the soil surface or sulfidic
materials within 100 cm of the soil surface. These soils are wet
at the base of the surface tier for more than 30 cumulative days
during normal years unless they have been drained. The
organic materials in these soils are from many kinds of plant
materials, including wood, moss, grass, and herbaceous
materials.
If these soils are drained and cultivated under the present
technology, the organic materials decompose and disappear
slowly or rapidly, depending on the management used and the
temperature. Eventually, within some decades, the Haplosaprists
that are drained and cultivated will be replaced by mineral soils.
This conversion of some of the soils has been observed in the
United States. Many Haplosaprists support native vegetation,
mostly forest plants or shrubs and grasslike plants. Many areas
are cleared, drained, and used as cropland.
Definition
Haplosaprists are the Saprists that:
1. Do not have a sulfuric horizon that has its upper boundary
within 50 cm of the soil surface;
2. Do not have sulfidic materials within 100 cm of the soil
surface; and
3. Have a temperature regime warmer than cryic.
Key to Subgroups
BCDA. Haplosaprists that have a lithic contact within the
control section.
Lithic Haplosaprists
BCDB. Other Haplosaprists that have one or more limnic
layers with a total thickness of 5 cm or more within the control
section.
Limnic Haplosaprists
BCDC. Other Haplosaprists that have both:
1. Throughout a layer 30 cm or thick that has its upper
boundary within the control section, an electrical
conductivity of 30 dS/m or more (1:1 soil:water) for 6
months or more during normal years; and
2. A mineral layer 30 cm or more thick that has its upper
boundary within the control section, below the surface tier.
Halic Terric Haplosaprists
BCDD. Other Haplosaprists that have throughout a layer 30
cm or more thick within the control section, an electrical
conductivity of 30 dS/m or more (1:1 soil:water) for 6 months
or more during normal years.
Halic Haplosaprists
BCDE. Other Haplosaprists that have a mineral layer 30 cm
or more thick that has its upper boundary within the control
section, below the surface tier.
Terric Haplosaprists
BCDF. Other Haplosaprists that have, within the organic
materials, either one mineral layer 5 cm or more thick or two
or more mineral layers of any thickness in the control section,
below the surface tier.
Fluvaquentic Haplosaprists
486 Soil Taxonomy
BCDG. Other Haplosaprists that have one or more layers of
fibric or hemic materials with a total thickness of 25 cm or more in
the control section, below the surface tier.
HemicHaplosaprists
BCDH. Other Haplosaprists.
Typic Haplosaprists
Definition of Typic Haplosaprists
Typic Haplosaprists are the Haplosaprists that:
1. Do not have a mineral layer between 5 and 30 cm thick or
two or more thin, continuous mineral layers within the organic
materials in the control section, below the surface tier;
2. Have a total of less than 25 cm fibric and hemic materials
below the surface tier;
3. Do not have a mineral layer 30 cm or more thick that has
its upper boundary in the control section, below the surface
tier;
4. Do not have throughout a layer 30 cm or more thick within
the control section, an electrical conductivity of 30 dS/m or
more (1:1 soil:water) for 6 months or more during normal
years;
5. Do not have a limnic layer(s) 5 cm or more thick within
the control section; and
6. Do not have a lithic contact within the control section.
Description of Subgroups
Typic Haplosaprists.—The central concept or Typic
subgroup of Haplosaprists is fixed on soils that do not have a
lithic contact and do not have thick or thin mineral layers or
intermittent mineral layers below the surface tier.
A lithic contact is used in classifying the Lithic subgroup, as
it is throughout this taxonomy. In addition, thick or thin
mineral layers as well as intermittent mineral layers that are
below the surface tier cause soils to be excluded from the Typic
subgroup. The presence of layers of materials less decomposed
than sapric materials is used as differentia for the Hemic
subgroup. These soils are widely distributed in the United
States, mostly in the Eastern States. They are used mainly as
woodland, cropland, or wildlife habitat.
Fluvaquentic Haplosaprists.—These soils differ from
Typic Haplosaprists because they have, within the organic
materials, either one mineral layer 5 to 30 cm thick or two or
more mineral layers of any thickness in the control section,
below the surface tier. These soils are of very small extent in
the United States.
Halic Haplosaprists.—These are the Haplosaprists that
have an electrical conductivity of 30 dS/m or more in a layer
30 cm or more thick within 130 cm of the soil surface. These
soils do not have a lithic contact within a depth of 130 cm or
limnic layers. Halic Haplosaprists commonly occur near coastal
areas that are inundated by the ocean.
Halic Terric Haplosaprists.—These are the Haplosaprists
that have an electrical conductivity of 30 dS/m or more in a layer
30 cm or more thick within 130 cm of the soil surface and have a
mineral layer 30 cm or more thick. These soils do not have a lithic
contact within a depth of 130 cm or limnic layers. Halic Terric
Haplosaprists commonly occur near coastal areas that are
inundated by the ocean.
Hemic Haplosaprists.—These soils differ from Typic
Haplosaprists because they have one or more layers of fibric or
hemic materials with a total thickness of 25 cm or more below
the surface tier. These soils are of small extent, mostly in the
Lake States in the United States.
Limnic Haplosaprists.—These soils differ from Typic
Haplosaprists because they have one or more limnic layers with
a total thickness of 5 cm or more within the control section.
These soils are of small extent, mostly in the Lake States in the
United States.
Lithic Haplosaprists.—These soils differ from Typic
Haplosaprists because they have a lithic contact within the
control section. These soils are of very small extent in the
United States.
Terric Haplosaprists.—These soils differ from Typic
Haplosaprists because they have a mineral layer 30 cm or more
thick that has its upper boundary within the control section,
below the surface tier. These soils are widely distributed in the
United States, mostly in the Eastern States. They are used
mainly as woodland, cropland, or wildlife habitat.
Sulfisaprists
These are the potentially acid sulfate soils (cat clays) that
consist of organic soil materials. They have sulfidic materials
within 100 cm of the soil surface and have not been drained.
They occur mainly in coastal marshes near the mouths of rivers
or in the deltas of rivers that carry sediments with a low
content of carbonates. The soils are locally extensive in the
coastal marshes and deltas of some large rivers that drain
humid regions.
Definition
Sulfisaprists are the Saprists that:
1. Do not have a sulfuric horizon that has its upper boundary
within 50 cm of the soil surface; and
2. Have sulfidic materials within 100 cm of the soil surface.
Key to Subgroups
BCBA. Sulfisaprists that have a mineral layer 30 cm or more
thick that has its upper boundary within the control section,
below the surface tier.
Terric Sulfisaprists
Histosols 487
BCBB. Other Sulfisaprists.
Typic Sulfisaprists
Definition of Typic Sulfisaprists
Typic Sulfisaprists are the Sulfisaprists that do not have a
mineral layer 30 cm or more thick that has its upper boundary
in the control section, below the surface tier.
Description of Subgroups
Typic Sulfisaprists.—The central concept or Typic
subgroup of Sulfisaprists is fixed on soils that do not have a
mineral layer 30 cm or more thick that has its upper boundary
in the control section, below the surface tier. These soils are of
small extent in the United States, mostly in the Eastern States.
They generally support native vegetation, mostly sparse forbs
and grasslike plants. They are used mainly as recreational
areas or wildlife habitat.
Terric Sulfisaprists.—These soils differ from Typic
Sulfisaprists because they have a mineral layer 30 cm or more
thick that has its upper boundary within the control section,
below the surface tier. They are mainly in coastal marshes near
the mouths of rivers or in the deltas of rivers on the east coast
of the United States. They are of small extent. These soils
support native vegetation, mostly forbs and grasslike plants.
They are used mainly as recreational areas or wildlife habitat.
Sulfosaprists
These are the acid sulfate soils (cat clays) that consist of
organic soil materials. They have a sulfuric horizon that
formed as a consequence of draining the sulfidic materials.
They are extremely acid and are toxic to most plants. They are
mainly in drained coastal marshes or deltas near the mouths of
rivers that carry sediments containing few or no carbonates.
Most of these soils have an appreciable amount of mineral
material within the control section.
Definition
Sulfosaprists are the Saprists that have a sulfuric horizon
that has its upper boundary within 50 cm of the soil surface.
Key to Subgroups
BCAA. All Sulfosaprists (provisionally).
Typic Sulfosaprists
489
The central concept of Inceptisols is that of soils that are
of cool to very warm, humid and subhumid regions and
that have a cambic horizon and an ochric epipedon. The order
of Inceptisols includes a wide variety of soils. In some areas
Inceptisols are soils with minimal development, while in other
areas they are soils with diagnostic horizons that merely fail
the criteria of the other soil orders.
Inceptisols have many kinds of diagnostic horizons and
epipedons. They can have an anthropic, histic, mollic, ochric,
plaggen, or umbric epipedon. Only a very few Inceptisols,
however, have a mollic epipedon. The mollic epipedon is
restricted to soils with low base saturation below the epipedon.
The most common diagnostic horizons are ochric and umbric
epipedons, a cambic horizon, and a fragipan. The most
common horizon sequence is an ochric epipedon over a cambic
horizon, with or without an underlying fragipan. Some
Inceptisols have an umbric epipedon overlying a cambic
horizon, with or without an underlying duripan or fragipan. A
calcic or petrocalcic horizon or a duripan is common in
subhumid areas. All soils that have a plaggen epipedon are
Inceptisols, and any soil underlying the plaggen epipedon is
considered to be buried.
The definition of Inceptisols is necessarily complicated.
These soils range from very poorly drained to excessively
drained. If the epipedon is ochric or anthropic, a diagnostic
subsurface horizon or high exchangeable sodium also is
required. Inceptisols typically have a cambic horizon, but one
is not required if the soil has a mollic, umbric, histic, or
plaggen epipedon or if there is a fragipan or duripan or any
placic, calcic, petrocalcic, gypsic, petrogypsic, salic, or sulfuric
horizon. Inceptisols cannot have an argillic, kandic, or natric
horizon unless it is buried. An oxic horizon is permitted only if
the upper boundary is deeper than 150 cm. A spodic horizon is
permitted only if it is less than 10 cm thick or if the upper
boundary is deeper than 50 cm below the mineral soil surface
and none of the overlying layers have a sandy or sandy-skeletal
particle-size class.
Inceptisols occur from equatorial to tundra regions. Soils
that have permafrost within 100 cm of the soil surface are now
classified as Gelisols. Inceptisols cannot have an aridic (torric)
moisture regime. Soils with an aridic (torric) moisture regime
are recognized as Aridisols if they have a cambic or other
diagnostic horizon. Inceptisols commonly occur on landscapes
that are relatively active, such as mountain slopes, where
erosional processes are actively exposing unweathered
materials, and river valleys, where relatively unweathered
sediments are being deposited. Many of the Inceptisols in the
United States formed in late-Pleistocene glacial drift. If the
precipitation exceeds the potential evapotranspiration every
month, Inceptisols occur in areas of old as well as young
surfaces or deposits. If the soil temperature regime is frigid or
cryic in these humid regions, Inceptisols form mainly in the
more loamy and clayey parent materials and Spodosols and
Entisols (Psamments) form in the sandy materials.
Definition of Inceptisols and Limits
Between Inceptisols and Soils of Other
Orders
The definition of Inceptisols provides criteria that separate
Inceptisols from all other orders. The aggregate of these
criteria defines the limits of Inceptisols in relation to other soil
orders.
Inceptisols are mineral soils that meet all of the following:
1. Unlike Gelisols, Inceptisols do not have either of the
following:
a. Permafrost within 100 cm of the soil surface; or
b. Gelic materials within 100 cm of the soil surface and
permafrost within 200 cm of the soil surface;
2. Unlike Andisols, Inceptisols do not have andic soil
properties in 60 percent or more of the thickness between the
soil surface and either a depth of 60 cm or a densic, lithic, or
paralithic contact or duripan if shallower;
3. Unlike Histosols, Inceptisols do not have organic soil
materials that meet one or more of the following:
a. Overlie cindery, fragmental, or pumiceous materials
and/or fill their interstices and directly below these
materials have either a densic, lithic, or paralithic contact;
or
b. When added with the underlying cindery, fragmental, or
pumiceous materials, total 40 cm or more between the soil
surface and a depth of 50 cm; or
c. Constitute two-thirds or more of the total thickness of
CHAPTER 15
Inceptisols
490 Soil Taxonomy
the soil to a densic, lithic, or paralithic contact and have no
mineral horizons or have mineral horizons with a total
thickness of 10 cm or less; or
d. Are saturated with water for 30 days or more in normal
years (or are artificially drained), have an upper boundary
within 40 cm of the soil surface, and have a total thickness
of either:
(1) 60 cm or more if three-fourths or more of their
volume consists of moss fibers or if their bulk density,
moist, is less than 0.1 g/cm3
; or
(2) 40 cm or more if they consist either of sapric or
hemic materials, or of fibric materials with less than
three-fourths (by volume) moss fibers and a bulk density,
moist, of 0.1 g/cm3
or more;
4. Unlike Spodosols, Inceptisols do not have one or more of
the following:
a. A spodic horizon, an albic horizon in 50 percent or
more of each pedon, and a cryic or pergelic soil temperature
regime; or
b. An Ap horizon containing 85 percent or more spodic
materials; or
c. A spodic horizon with all of the following
characteristics:
(1) One or more of the following:
(a) A thickness of 10 cm or more; or
(b) An overlying Ap horizon; or
(c) Cementation in 50 percent or more of each
pedon; or
(d) A coarse-loamy, loamy-skeletal, or finer particlesize
class and a frigid temperature regime; or
(e) A cryic or pergelic temperature regime; and
(2) An upper boundary within the following depths
from the mineral soil surface: either
(a) Less than 50 cm; or
(b) Less than 200 cm if the soil has a sandy or
sandy-skeletal particle-size class in at least some part
between the mineral soil surface and the spodic
horizon; and
(3) A lower boundary as follows:
(a) Either at a depth of 25 cm or more below the
mineral soil surface, or at the top of a duripan or
fragipan, or at a densic, lithic, paralithic, or
petroferric contact, whichever is shallowest; or
(b) At any depth:
1) If the spodic horizon has a coarse-loamy,
loamy-skeletal, or finer particle-size class and the
soil has a frigid temperature regime; or
2) If the soil has a cryic or pergelic temperature
regime;
5. Unlike Oxisols, Inceptisols do not have an oxic horizon
that has its upper boundary within 150 cm of the mineral soil
surface;
6. Unlike Vertisols, Inceptisols do not have all of the
following:
a. A layer 25 cm or more thick, with an upper boundary
within 100 cm of the mineral soil surface, that has either
slickensides close enough to intersect or wedge-shaped
aggregates that have their long axes tilted 10 to 60 degrees
from the horizontal; and
b. A weighted average of 30 percent or more clay in the
fine-earth fraction either between the mineral soil surface
and a depth of 18 cm or in an Ap horizon, whichever is
thicker, and 30 percent or more clay in the fine-earth
fraction of all horizons between a depth of 18 cm and either
a depth of 50 cm or a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon if shallower; and
c. Cracks that open and close periodically;
7. Unlike Aridisols, Inceptisols do not have an aridic soil
moisture regime and meet all of the following criteria:
a. Do not have a salic horizon; and
b. Are not saturated with water in one or more layers
within 100 cm of the soil surface for 1 month or more in
normal years; and
c. Do not have a moisture control section that is dry in
some or all parts at some time in normal years; and
d. Have a sulfuric horizon that has its upper boundary
within 150 cm of the mineral soil surface;
8. Unlike Alfisols and Ultisols, Inceptisols do not have an
argillic, kandic, or natric horizon and do not have a fragipan
with clay films 1 mm or more thick in one or more of its
subhorizons;
9. Unlike Mollisols, Inceptisols do not have both of the
following:
a. Either:
(1) A mollic epipedon; or
(2) Both a surface horizon that meets all of the
requirements for a mollic epipedon, except for thickness,
Inceptisols 491
after the soil has been mixed to a depth of 18 cm, and a
subhorizon more than 7.5 cm thick, within the upper part
of an argillic, kandic, or natric horizon, that meets the
color, organic-carbon content, base saturation, and
structure requirements for a mollic epipedon but is
separated from the surface horizon by an albic horizon;
and
b. A base saturation of 50 percent or more (by NH4
OAc) in
all horizons either between the upper boundary of any
argillic, kandic, or natric horizon and a depth of 125 cm
below that boundary, or between the mineral soil surface
and a depth of 180 cm, or between the mineral soil surface
and a densic, lithic, or paralithic contact, whichever depth is
shallower; and
10. Unlike Entisols, Inceptisols have either:
a. One or more of the following:
(1) A cambic horizon with its upper boundary
within 100 cm of the mineral soil surface and its lower
boundary at a depth of 25 cm or more below the mineral
soil surface; or
(2) A calcic, petrocalcic, gypsic, petrogypsic, or placic
horizon or a duripan with an upper boundary within 100
cm of the mineral soil surface; or
(3) A fragipan or an oxic, sombric, or spodic horizon
with an upper boundary within 200 cm of the mineral
soil surface; or
(4) A sulfuric horizon that has its upper boundary
within 150 cm of the mineral soil surface; or
(5) A cryic or pergelic temperature regime and a
cambic horizon; or
b. No sulfidic materials within 50 cm of the mineral soil
surface; and both
(1) In one or more horizons at a depth between 20
and 50 cm below the mineral soil surface, either an n
value of 0.7 or less or less than 8 percent clay in the fineearth
fraction; and
(2) One or both of the following:
(a) A salic horizon or a histic, mollic, plaggen, or
umbric epipedon; or
(b) In 50 percent or more of the layers between the
mineral soil surface and a depth of 50 cm, an
exchangeable sodium percentage of 15 or more (or a
sodium adsorption ratio of 13 or more), which
decreases with increasing depth below 50 cm, and also
ground water within 100 cm of the mineral soil
surface at some time during the year when the soil is
not frozen in any part.
Representative Pedon and Data
Following is a description of a representative Inceptisol. Data
for the pedon identified in this description are given in the table
“Characterization Data for an Inceptisol.”
Classification: Coarse-loamy, isotic, frigid Typic Dystrudept
Site identification number: 87P0581
Location: Windsor County, Vermont; town of West Windsor;
30 m south of the Hartland town line and 2,280 m east of
the Reading town line
Latitude: 43 degrees 31 minutes 41 seconds N.
Longitude: 72 degrees 30 minutes 15 seconds W.
Landscape: Hills
Slope: 12 percent, complex, east facing
Elevation: 417 m above m.s.l.
Annual precipitation: 100 cm
Soil moisture regime: Udic
Average annual air temperature: 6 o
C
Average annual soil temperature: 7 o
C
Permeability class: Moderate
Drainage class: Well drained
Depth to water table: More than 150 cm
Land use: Pasture
Stoniness class: 1
Hazard of erosion: Slight
Runoff class: Medium
Particle-size control section: 25 to 73 cm
Parent material: Glacial till derived from schist and phyllite
Vegetation: Natural—mixed forest; cleared—native pasture
Diagnostic features: An ochric epipedon from a depth of 0 to
22 cm, a cambic horizon from a depth of 22 to 73 cm, and
a lithic contact at a depth of 73 cm
Described by: Villars, McLeese, Gourley, and Wheeler
In the following pedon description, colors are for moist soil
unless otherwise indicated.
Ap1—0 to 10 cm; very dark gray (10YR 3/1) silt loam, gray
(10YR 5/1) dry; moderate medium granular structure; very
friable, nonsticky and nonplastic; many very fine and
many fine roots throughout; common very fine interstitial
and tubular pores; neutral (pH 6.6); 1 percent
metamorphic pebbles; abrupt smooth boundary.
Ap2—10 to 22 cm; very dark grayish brown (10YR 3/2) silt
loam, light brownish gray (10YR 6/2) dry; weak fine
subangular blocky structure parting to weak fine granular;
friable, nonsticky and nonplastic; many very fine and
common fine roots throughout; common very fine
interstitial and tubular pores; common continuous faint
iron stains on sand grains and pebbles; sand grains are
coated with sesquioxides and have very few black
micropellets when viewed with a 10X and 20X hand lens
and a 100X microscope; slightly acid (pH 6.4); 1 percent
metamorphic pebbles; abrupt wavy boundary.
492 Soil Taxonomy
Characterization Data for an Inceptisol
SITE IDENTIFICATION NO: 87P0581
CLASSIFICATION: COARSE-LOAMY, ISOTIC, FRIGID TYPIC DYSTRUDEPT
GENERAL METHODS: 1B1A, 2A1, 2B
-1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-
-----------------------------------------------------------------------------------------------------------------------------------
(- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)
CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT
SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF
NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE
<- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL
87P3045 0- 10 Ap1 4.9 39.5 55.6 1.6 27.2 12.3 14.5 20.0 10.3 6.8 4.0 3 2 -- 44 5
87P3046 10- 22 Ap2 3.4 38.3 58.3 0.6 24.3 14.0 13.1 18.6 10.3 8.0 8.3 9 7 2 55 18
87P3047 22- 40 Bw 1.6 44.5 53.9 0.7 28.9 15.6 13.2 16.8 9.4 7.1 7.4 7 4 1 48 12
87P3048 40- 55 Bt 1.7 45.4 52.9 0.2 29.1 16.3 13.4 17.3 9.3 7.1 5.8 5 7 -- 47 15
87P3049 55- 73 BCt 1.0 39.6 59.4 -- 24.2 15.4 14.5 18.4 10.0 8.3 8.2 8 8 1 54 20
-----------------------------------------------------------------------------------------------------------------------------------
ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD
C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE
DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL
(cm) 6A1c 6B3a 6S3 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A3a 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1
Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm
0- 10 5.16 0.457 1.7 0.4 0.1 4.51 8.00 0.91 1.04 0.045 27.1 25.9 11.5
10- 22 2.17 0.186 1.7 0.5 0.1 3.09 2.18 1.38 1.38 -- 26.1 24.6 6.4 0.21
22- 40 1.29 0.100 1.7 0.5 0.1 4.50 6.00 1.24 1.26 0.005 33.1 28.1 5.6 0.22
40- 55 1.02 1.5 0.5 0.1 3.29 4.00 1.25 1.25 -- 29.8 25.1 4.6 0.22
55- 73 0.81 1.4 0.3 TR 4.90 3.70 3.7
-----------------------------------------------------------------------------------------------------------------------------------
(- NH4OAc EXTRACTABLE BASES -) ACID- EXTR (- - - -CEC - - -) Al -BASE SAT- CO3 AS RES. COND.(- - - -PH - - -)
Ca Mg Na K SUM ITY Al SUM NH4- BASES SAT SUM NH4 CaCO3 ohms mmhos NaF CaCl2 H2O
DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc + Al OAc <2mm /cm /cm .01M
(cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 6G9b 5A3a 5A8b 5A3b 5G1 5C3 5C1 6E1g 8E1 8I 8C1d 8C1f 8C1f
<- - - - - - - - - - - -meq / 100 g - - - - - - - - - - -> <- - - - -Pct - - - -> 1:2 1:1
0- 10 15.1 0.4 0.1 0.1 15.7 14.7 TR 30.4 22.1 52 71 9.7 5.3 5.6
10- 22 4.7 TR TR -- 4.7 11.0 15.7 10.5 30 45 10.4 5.3 5.8
22- 40 0.9 TR -- -- 0.9 11.6 1.1 12.5 7.2 2.0 55 7 13 10.9 4.8 5.4
40- 55 0.9 -- 0.1 -- 1.0 8.8 9.8 5.6 10 18 10.8 5.0 5.7
55- 73 1.2 TR TR -- 1.2 7.4 8.6 4.9 14 24 10.6 5.0 5.7
-----------------------------------------------------------------------------------------------------------------------------------
ACID OXALATE EXTRACTION PHOSPHORUS KCl TOTAL (- -WATER CONTENT- - )(- - - - WATER DISPERSIBLE - - - - ) MIN AGGRT
OPT Fe Si Al CIT- Mn C 0.06 1- 2- 15 <- - PIPETTE - - >< - HYDROMETER - > SOIL STABL
DEN RET ACID BAR BAR BAR BAR CLAY SILT SAND CLAY SILT SAND CONT <5mm
SAMPLE HZ 8J 6C9a 6V2 6G12 6S4 6S5 6D3 6A2d 4B1c 4B1a 4B1a 4B2b <- - - 3A1c - - -><- - - SML - - -> 8F1 4G1
NO. NO <- P c t o f < 2 m m -><- p p m ->< - - - - - - - - - - P e r c e n t o f < 2 m m - - - - - - - - - - >< Pct>
87P3045 1 0.27 0.72 0.05 0.44 52 5.30 39.2 95
87P3046 2 0.21 0.71 0.05 0.47 47 2.42 26.1 7.4 86
87P3047 3 0.16 0.65 0.08 0.59 56 1.63 33.1 9.6
87P3048 4 0.09 0.46 0.07 0.50 52 1.34 29.8 6.8
87P3049 5 0.09 0.49 0.05 0.37 44 1.08 39
-----------------------------------------------------------------------------------------------------------------------------------
< - - - - - - - - - - - - - - - - - - - - - - CLAY MINERALOGY (<.002mm) - - - - - - - - - - - - - - - - - - - - - - - >
FRAC- < - - - - - X-RAY - - - - - ->< - - - THERMAL - - - ->< - - - - - - - ELEMENTAL - - - - - - - ->< - -> EGME INTERSAMPLE
TION < >< - DTA - ->< - TGA - -> SiO2 Al2O3 Fe2O3 MgO CaO K2O Na2O < > RETN PRETA<
- - - - - 7A2i - - - - - ->< - 7A6 - >< - 7A4b - >< - - - - - - - - - 7C3 - - - - - - - - ->< > 7D2 TION
NUMBER <- - >< - - - - Peak size - - - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - -><mg/g>< - ->
87P3045 TCLY KK 1 VR 1 MI 1 7.1 0.8
87P3047 TCLY VR 1 KK 1 MI 1 GE 1 13.9 1.0
87P3049 TCLY MI 1 KK 1 VR 1 7.1 0.7
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Inceptisols 493
Characterization Data for an Inceptisol--Continued
-1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-
-----------------------------------------------------------------------------------------------------------------------------------
< - - - - - - - - - - - - - - - - - - - - SAND - SILT MINERALOGY (2.0-0.002mm) - - - - - - - - - - - - - - - - - - - - >
FRAC- < - - - - - X-RAY - - ->< - - - THERMAL - - - ->< - - - - - - - OPTICAL - - - - - - - - >< >INTERSAMPLE
TION < >< - DTA - ->< - TGA - ->TOT RE< - - - - - GRAIN COUNT - - - - - ->< >PRETA<
- - - - 7A2i - - - - >< - 7A3c - >< - 7A4c - >< - - - - - - - - 7B1a - - - - - - - - ->< > TION
NUMBER < - ->< - - - Peak Size - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - - - - - - - ->< - ->
87P3047 FS 66 QZ66 MS16 BT13 AR 2 FK 2 FP 1
87P3047 FS FEtr GNtr OPtr MZtr PRtr
87P3048 FS 72 QZ68 BT15 MS 7 FP 4 GN 3 AR 1
87P3048 FS OP 1 FK 1 PR 1 HNtr SPtr
87P3049 FS 64 QZ61 BT16 MS14 AR 3 FP 3 GN 2
87P3049 FS OP 1 FKtr PRtr HNtr SPtr
-----------------------------------------------------------------------------------------------------------------------------------
The chemical data are based on the fraction less than 2 mm in size.
Fraction interpretation: TCLY, total clay, <0.002 mm; FS, fine sand, 0.1-0.25 mm.
Mineral interpretation: KK, kaolinite; VR, vermiculite; MI, mica; GE, goethite; QZ, quartz; MS, muscovite; BT, biotite;
AR, weathered aggregate; FK, potassium feldspar; FP, plagioclase feldspar; FE, iron oxides; GN, garnet; OP, opaques;
MZ, monazite; PR, pyroxene; HN, hornblende; SP, sphene.
Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.
Bw—22 to 40 cm; dark brown (10YR 3/3) silt loam, pale brown
(10YR 6/3) dry; weak fine subangular blocky structure;
friable, weakly smeary, nonsticky and nonplastic; few fine
roots throughout; few very fine interstitial and tubular
pores; many continuous faint iron stains on sand grains
and pebbles; slightly acid (pH 6.0);
1 percent metamorphic pebbles; sand grains are thinly
coated with sesquioxides and have a few black
micropellets; clear wavy boundary.
Bt—40 to 55 cm; dark grayish brown (2.5Y 4/2) silt loam;
weak fine and medium subangular blocky structure;
friable, nonsticky and nonplastic; few fine and few
medium roots throughout; few very fine interstitial and
tubular pores; few faint clay films on sand grains and
pebbles; moderately acid (pH 5.8); 1 percent metamorphic
pebbles and 2 percent metamorphic cobbles; coated sand
grains; abrupt wavy boundary.
BCt—55 to 73 cm; dark grayish brown (2.5Y 4/2) silt loam;
weak medium subangular blocky structure; friable,
nonsticky and nonplastic; few fine roots throughout;
few very fine interstitial and tubular pores; very few
faint clay films on sand grains and pebbles; slightly acid
(pH 6.0); 1 percent metamorphic pebbles and 2 percent
metamorphic cobbles; coated sand grains; abrupt wavy
boundary.
2R—73 cm; schist or phyllite.
Key to Suborders
KA. Inceptisols that have one or more of the following:
1. In a layer above a densic, lithic, or paralithic contact or
in a layer at a depth between 40 and 50 cm from the mineral
soil surface, whichever is shallower, aquic conditions for
some time in normal years (or artificial drainage) and one or
more of the following:
a. A histic epipedon; or
b. A sulfuric horizon that has its upper boundary within
50 cm of the mineral soil surface; or
c. A layer directly under the epipedon, or within 50 cm
of the mineral soil surface, that has, on faces of peds or
in the matrix if peds are absent, 50 percent or more
chroma of either:
(1) 2 or less if there are redox concentrations; or
(2) 1 or less; or
d. Within 50 cm of the mineral soil surface, enough
active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated; or
2. An exchangeable sodium percentage (ESP) of 15 or
more (or a sodium adsorption ratio [SAR] of 13 or more) in
half or more of the soil volume within 50 cm of the mineral
soil surface, a decrease in ESP (or SAR) values with
increasing depth below 50 cm, and ground water within 100
cm of the mineral soil surface for some time during the year.
Aquepts, p. 494
KB. Other Inceptisols that have a plaggen or anthropic
epipedon.
Anthrepts, p. 494
KC. Other Inceptisols that have a cryic soil temperature
regime.
Cryepts, p. 512
494 Soil Taxonomy
KD. Other Inceptisols that have an ustic soil moisture
regime.
Ustepts, p. 530
KE. Other Inceptisols that have a xeric soil moisture regime.
Xerepts, p. 542
KF. Other Inceptisols that have a udic soil moisture regime.
Udepts, p. 516
Anthrepts
These are the more or less freely drained Inceptisols that
have either an anthropic or plaggen epipedon. Most of these
soils have been used as cropland or as sites for human
occupation for many years. Anthrepts can have almost any
temperature regime and almost any vegetation. Most have a
cambic horizon.
Definition
Anthrepts are the Inceptisols that:
1. Have an anthropic or plaggen epipedon; and
2. Do not have, in a layer above a densic, lithic, or paralithic
contact or in a layer at a depth between 40 and 50 cm from the
mineral soil surface, whichever is shallower, aquic conditions
for some time in normal years and one or more of the
following:
a. A histic epipedon; or
b. A sulfuric horizon that has its upper boundary within
50 cm of the mineral soil surface; or
c. A layer directly under the epipedon, or within 50 cm of
the mineral soil surface, that has, on faces of peds or in the
matrix if peds are absent, 50 percent or more chroma of
either:
(1) 2 or less if there are redox concentrations; or
(2) 1 or less; and
3. Do not have an exchangeable sodium percentage (ESP)
of 15 or more (or a sodium adsorption ratio [SAR] of 13 or
more) in half or more of the soil volume within 50 cm of the
mineral soil surface, an ESP (or SAR) below 50 cm that
decreases with increasing depth, and ground water within 100
cm of the mineral soil surface during some time of the year;
and
4. Do not have, within 50 cm of the mineral soil surface,
enough active ferrous iron to give a positive reaction to
alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Key to Great Groups
KBA. Anthrepts that have a plaggen epipedon.
Plagganthrepts, p. 494
KBB. Other Anthrepts.
Haplanthrepts, p. 494
Haplanthrepts
Haplanthrepts are the Anthrepts that have an anthropic
epipedon. Because Haplanthrepts are not extensive, their
classification has not been developed. Subgroups based on soil
moisture regimes may be needed. Most of these soils are in
Asia and North Africa. Haplanthrepts have gentle slopes and
are either farmed or used as homesites.
Key to Subgroups
KBBA. All Haplanthrepts (provisionally).
TypicHaplanthrepts
Plagganthrepts
Plagganthrepts are the Anthrepts that have a plaggen
epipedon. Because Plagganthrepts are not extensive, their
classification has not been developed beyond their grouping
into a single great group. These soils are known to occur only
in Europe, including the British Isles. They have a udic
moisture regime. They have gentle slopes and are used either
as cropland or as homesites. The buried soils under the plaggen
epipedon vary appreciably in morphology, but few of them had
high natural fertility.
Key to Subgroups
KBAA. All Plagganthrepts (provisionally).
Typic Plagganthrepts
Aquepts
These are the wet Inceptisols. The natural drainage is poor or
very poor and, if the soils have not been artificially drained,
ground water is at or near the soil surface at some time during
normal years but typically not at all seasons. These soils
generally have a gray to black surface horizon and a gray
subsurface horizon with redox concentrations that begins at a
depth of less than 50 cm. A few of the soils have a brownish
surface horizon that is less than 50 cm thick.
Most Aquepts formed in late-Pleistocene or younger
deposits in depressions, on nearly level plains, or on flood
plains. They occur from the Equator to latitudes with
discontinuous permafrost. The common features of most of
these soils are the grayish and reddish colors of redoximorphic
features at a depth of 50 cm or less and, unless the soils have
Inceptisols 495
been artificially drained, shallow ground water. Aquepts may
have almost any particle-size class except fragmental, any
reaction class, any temperature regime, and almost any
vegetation. Most of the soils have a cambic horizon, and some
have a fragipan. It is possible that some have a plaggen
epipedon.
Definition
Aquepts are the Inceptisols that have:
1. In a layer above a densic, lithic, or paralithic contact or in a
layer at a depth between 40 and 50 cm from the mineral soil
surface, whichever is shallower, aquic conditions for some time
in normal years (or artificial drainage) and one or more of the
following:
a. A histic epipedon; or
b. A sulfuric horizon that has its upper boundary within
50 cm of the mineral soil surface; or
c. A layer directly under the epipedon, or within 50 cm of
the mineral soil surface, that has, on faces of peds or in the
matrix if peds are absent, 50 percent or more chroma of
either:
(1) 2 or less if there are redox concentrations; or
(2) 1 or less; or
2. An exchangeable sodium percentage (ESP) of 15 or more
(or a sodium adsorption ratio [SAR] of 13 or more) in half or
more of the soil volume within 50 cm of the mineral soil
surface, an ESP (or SAR) below 50 cm that decreases with
increasing depth, and ground water within 100 cm of the
mineral soil surface during some time of the year; or
3. Within 50 cm of the mineral soil surface, enough active
ferrous iron to give a positive reaction to alpha,alpha-dipyridyl
at a time when the soil is not being irrigated.
Key to Great Groups
KAA. Aquepts that have a sulfuric horizon that has its upper
boundary within 50 cm of the mineral soil surface.
Sulfaquepts, p. 510
KAB. Other Aquepts that have, within 100 cm of the
mineral soil surface, one or more horizons in which plinthite
or a cemented or indurated diagnostic horizon either forms a
continuous phase or constitutes one-half or more of the
volume.
Petraquepts, p. 509
KAC. Other Aquepts that have either:
1. A salic horizon; or
2. In one or more horizons with a total thickness of 25 cm
or more within 50 cm of the mineral soil surface, an
exchangeable sodium percentage (ESP) of 15 or more (or a
sodium adsorption ratio [SAR] of 13 or more) and a
decrease in ESP (or SAR) values with increasing depth
below 50 cm.
Halaquepts, p. 505
KAD. Other Aquepts that have a fragipan with its upper
boundary within 100 cm of the mineral soil surface.
Fragiaquepts, p. 504
KAE. Other Aquepts that have a cryic soil temperature
regime.
Cryaquepts, p. 495
KAF. Other Aquepts that have, in one or more layers at least
25 cm thick (cumulative) within 100 cm of the mineral soil
surface, 25 percent or more (by volume) recognizable
bioturbation, such as filled animal burrows, wormholes, or
casts.
Vermaquepts, p. 511
KAG. Other Aquepts that have a histic, melanic, mollic, or
umbric epipedon.
Humaquepts, p. 507
KAH. Other Aquepts that have episaturation.
Epiaquepts, p. 502
KAI. Other Aquepts.
Endoaquepts, p. 498
Cryaquepts
These are the cold Aquepts. They are of moderate extent in
the high mountains and subarctic regions of North America
and Eurasia. They typically have an ochric or histic epipedon
over a cambic horizon. Cryaquepts are on flood plains, in
depressional areas, and on plains. Most have grayish subsoils,
and some are stratified. The major areas of the Cryaquepts in
the United States are on the outwash plains and flood plains of
Alaska. Cryaquepts formed mostly in late-Pleistocene or recent
sediments south of the continuous permafrost zone. Most
support mixed forest, shrub, or grassy vegetation. Many are
nearly level, but some in areas of high precipitation have
strong slopes. Because Cryaquepts are both cold and wet, they
have low potential for cropping.
Definition
Cryaquepts are the Aquepts that:
1. Have a cryic soil temperature regime;
496 Soil Taxonomy
2. Do not have a fragipan with its upper boundary within 100
cm of the mineral soil surface;
3. Do not have a sulfuric horizon that has its upper boundary
within 50 cm of the soil surface;
4. Do not have a cemented or indurated diagnostic horizon
within 100 cm of the mineral soil surface in half or more of
each pedon; and
5. Do not have either:
a. A salic horizon; or
b. In one or more horizons with a total thickness of 25 cm
or more within 50 cm of the mineral soil surface, an
exchangeable sodium percentage (ESP) of 15 or more (or a
sodium adsorption ratio [SAR] of 13 or more) and a
decrease in ESP (or SAR) values with increasing depth
below 50 cm.
Key to Subgroups
KAEA. Cryaquepts that have, within 150 cm of the mineral
soil surface, one or more of the following:
1. A sulfuric horizon; or
2. A horizon 15 cm or more thick that has all of the
characteristics of a sulfuric horizon, except that it has a pH
between 3.5 and 4.0; or
3. Sulfidic materials.
Sulfic Cryaquepts
KAEB. Other Cryaquepts that have both a histic epipedon
and a lithic contact within 50 cm of the mineral soil surface.
Histic Lithic Cryaquepts
KAEC. Other Cryaquepts that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Cryaquepts
KAED. Other Cryaquepts that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Cryaquepts
KAEE. Other Cryaquepts that have a histic epipedon.
Histic Cryaquepts
KAEF. Other Cryaquepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, one or more of the
following:
1. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
2. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
3. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Cryaquepts
KAEG. Other Cryaquepts that have a slope of less than 25
percent; and
1. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of 0.2 percent or
more and no densic, lithic, or paralithic contact within that
depth; or
2. An irregular decrease in organic-carbon content
(Holocene age) between a depth of 25 cm and either a depth
of 125 cm below the mineral soil surface or a densic, lithic,
or paralithic contact, whichever is shallower.
Fluvaquentic Cryaquepts
KAEH. Other Cryaquepts that have both:
1. Chroma of 3 or more in 40 percent or more of the
matrix of one or more horizons at a depth between 15 and
50 cm from the mineral soil surface; and
2. A mollic or umbric epipedon.
Aeric Humic Cryaquepts
KAEI. Other Cryaquepts that have chroma of 3 or more in
40 percent or more of the matrix of one or more horizons at a
depth between 15 and 50 cm from the mineral soil surface.
Aeric Cryaquepts
KAEJ. Other Cryaquepts that have a mollic or umbric
epipedon.
Humic Cryaquepts
KAEK. Other Cryaquepts.
Typic Cryaquepts
Inceptisols 497
DefinitionofTypicCryaquepts
Typic Cryaquepts are the Cryaquepts that:
1. Do not have, within 150 cm of the mineral soil surface, any
of the following:
a. A sulfuric horizon; or
b. A horizon 15 cm or more thick that has all of the
characteristics of a sulfuric horizon, except that it has a pH
between 3.5 and 4.0; or
c. Sulfidic materials;
2. Do not have a lithic contact within 50 cm of the mineral
soil surface;
3. Do not have a histic, umbric, or mollic epipedon;
4. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
5. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
6. Do not have both:
a. Either 0.2 percent or more organic carbon (Holocene
age) at a depth of 125 cm below the mineral soil surface or
an irregular decrease in organic-carbon content (Holocene
age) between a depth of 25 cm and either a depth of 125 cm
below the mineral soil surface or a densic, lithic, or paralithic
contact, whichever is shallower; and
b. A slope of less than 25 percent; and
7. Have chroma of 2 or less in 60 percent or more of the mass
of all horizons between depths of 15 and 50 cm.
Description of Subgroups
Typic Cryaquepts.—The central concept or Typic subgroup
of Cryaquepts is fixed on soils that have a thick, gray regolith
and an ochric epipedon and do not have a layer of materials
with andic soil properties that is as thick as 18 cm and is near
the surface.
Soils that have a lithic contact within a depth of 50 cm are
assigned to the Lithic subgroup. Soils that have a histic
epipedon are excluded from the Typic subgroup because they
are considered intergrades to Histosols. Soils that have an
umbric or mollic epipedon are excluded from the Typic
subgroup because they are considered intergrades to
Humaquepts and Aquolls, respectively. Soils that either have
0.2 percent or more organic carbon (Holocene age) at a depth
of 125 cm below the mineral soil surface or have an irregular
decrease in organic-carbon content (Holocene age) between a
depth of 25 cm and either a depth of 125 cm below the mineral
soil surface or a densic, lithic, or paralithic contact, whichever
is shallower, are considered intergrades to Fluvaquents.
Typic Cryaquepts are of moderate extent in the United
States. They occur mostly in southern Alaska, but some are in
the high mountains of the Western States. Most Typic
Cryaquepts support native vegetation and have a thin O
horizon.
Aeric Cryaquepts.—These soils have chroma of 3 or more
in 40 percent or more of some subhorizon within 50 cm of the
mineral soil surface. The high chroma is thought to reflect
either deeper ground water or a shorter period of saturation
than that in the Typic subgroup. The soils are otherwise like
Typic Cryaquepts. Aeric Cryaquepts are of small extent in the
United States and occur mostly in southern Alaska and in the
high mountains of the Western and Northern States. Most of
these soils support their native vegetation and have a thin O
horizon. Most support forest vegetation, but some support
water-tolerant grasses. Aeric Cryaquepts are used mainly as
forest and wildlife habitat. Some are used as pasture and some
as hayland.
Aeric Humic Cryaquepts.—These soils have a mollic or
umbric epipedon and also have chroma of 3 or more in 40
percent or more of some subhorizon within 50 cm of the
mineral soil surface. The high chroma is thought to reflect
either deeper ground water or a shorter period of saturation
than that in the Typic subgroup. The soils are otherwise like
Typic Cryaquepts. Aeric Humic Cryaquepts are of very small
extent in the United States and are known to occur only in
southern Alaska. They support native vegetation and have a
thin O horizon. The vegetation consists of water-tolerant trees,
498 Soil Taxonomy
shrubs, and grasses. These soils are used mainly as wildlife
habitat.
Aquandic Cryaquepts.—These soils have a layer in the
upper 75 cm that has some andic soil properties. This layer is
18 cm or more thick. The clays in this layer normally do not
disperse well and have a high pH-dependent charge. In the
Aquandic Cryaquepts in the United States, this layer normally
is at or very close to the soil surface. The epipedon commonly
is umbric, but this is not required. These soils are of small
extent in the United States and are known to occur in Alaska
and Oregon. Most support native vegetation. Most support
water-tolerant grasses, and some support forest vegetation.
Aquandic Cryaquepts are used mainly as wildlife habitat. Some
are used as pasture and some as hayland.
Fluvaquentic Cryaquepts.—These soils have either 0.2
percent or more organic carbon (Holocene age) at a depth of
125 cm below the mineral soil surface or an irregular decrease
in organic-carbon content (Holocene age) between a depth of
25 cm and either a depth of 125 cm below the mineral soil
surface or a densic, lithic, or paralithic contact, whichever is
shallower. They also have slopes of less than 25 percent. These
soils are of small extent in the United States. They are on flood
plains. Most support a native vegetation of water-tolerant trees
and grasses. Fluvaquentic Cryaquepts are used mainly as
wildlife habitat.
Histic Cryaquepts.—These soils have a histic epipedon but
otherwise are like Typic Cryaquepts. They tend to have ground
water at a higher level than in the soils of the Typic subgroup,
and shallow water stands for some time above the soil surface.
Histic Cryaquepts are considered intergrades to Histosols. They
are of small extent in the United States and occur mostly in
southern Alaska and in the high mountains of the
Northwestern States. Most of the Histic Cryaquepts support
native vegetation. They support forest vegetation or watertolerant
shrubs and grasses. Histic Cryaquepts are used mainly
as forest and wildlife habitat.
Histic Lithic Cryaquepts.—These soils have a histic
epipedon, and they have a lithic contact within 50 cm of the
mineral soil surface. They tend to have ground water at a
higher level than in the soils of the Typic subgroup, and very
shallow water stands for some time above the mineral soil
surface. Histic Lithic Cryaquepts are of very small extent in the
United States and are known to occur only in southern Alaska.
They support native vegetation, which consists of watertolerant
trees, shrubs, and grasses. These soils are used mainly
as wildlife habitat.
Humic Cryaquepts.—These soils have an umbric or mollic
epipedon but otherwise are like Typic Cryaquepts. They are
considered intergrades to Humaquepts. Humic Cryaquepts are
of small extent in the United States and occur mostly in
southern Alaska and in Idaho. Most of these soils support
native vegetation, which consists of trees or water-tolerant
shrubs and grasses. The soils are used mainly as forest and
wildlife habitat.
Lithic Cryaquepts.—These soils have a lithic contact within
50 cm of the mineral soil surface. They are not known to occur in
the United States. This subgroup is established for use in other
parts of the world.
Sulfic Cryaquepts.—These soils have a sulfuric horizon or
a horizon approaching a sulfuric horizon but otherwise are like
Typic Cryaquepts. They are considered intergrades to
Sulfaquepts. They are rare in the United States.
Vertic Cryaquepts.—These soils are like Typic Cryaquepts,
but they are high in expanding clays and have cracks 5 mm or
more wide, slickensides, wedge-shaped aggregates, or a linear
extensibility of 6.0 cm or more between the mineral soil surface
and either a depth of 100 cm or a densic, lithic, or paralithic
contact, whichever is shallower. These soils are considered to
be transitional to Vertisols. This subgroup is not known to
occur in the United States. It is established for use in other
parts of the world.
Endoaquepts
Endoaquepts are the Aquepts that have endosaturation. The
ground water commonly fluctuates from a level near the soil
surface to below a depth of 50 cm. These soils have a frigid or
warmer soil temperature regime and do not have any sulfuric,
placic, or salic horizon or a fragipan near the soil surface. They
do not have high exchangeable sodium near the soil surface
that becomes less with increasing depth below 50 cm. They
have no horizon within 100 cm of the mineral soil surface in
which plinthite or any other cemented or indurated diagnostic
horizon either forms a continuous phase or constitutes one-half
or more of the volume. Recognizable bioturbation, such as
filled animal burrows, wormholes, or casts, is less than 50
percent (by volume) in all layers that are 25 cm or more thick
(cumulative) within 100 cm of the mineral soil surface. Before
they were cultivated, most Endoaquepts supported forest
vegetation. Generally, Endoaquepts are nearly level, and their
parent materials are typically late-Pleistocene or younger
sediments.
Definition
Endoaquepts are the Aquepts that:
1. Do not have a sulfuric horizon that has its upper boundary
within 50 cm of the mineral soil surface;
2. Do not have, within 100 cm of the mineral soil surface,
one or more horizons in which plinthite or a cemented or
indurated diagnostic horizon forms either a continuous phase
or constitutes one-half or more of the volume;
3. Have an exchangeable sodium percentage (ESP) of less
than 15 (or a sodium adsorption ratio [SAR] of less than 13) in
half or more of the soil volume within 50 cm of the mineral
soil surface or an ESP (or SAR) below 50 cm that remains
constant or increases with increasing depth;
Inceptisols 499
4. Have neither a salic horizon nor a fragipan with its upper
boundary within 100 cm of the mineral soil surface;
5. Do not have a cryic soil temperature regime;
6. Do not have, in one or more layers at least 25 cm thick
(cumulative) within 100 cm of the mineral soil surface, 25
percent or more (by volume) recognizable bioturbation, such as
filled animal burrows, wormholes, or casts;
7. Do not have any histic, melanic, mollic, or umbric
epipedon; and
8. Have endosaturation.
Key to Subgroups
KAIA. Endoaquepts that have, within 150 cm of the mineral
soil surface, one or more of the following:
1. A sulfuric horizon; or
2. A horizon 15 cm or more thick that has all of the
characteristics of a sulfuric horizon, except that it has a pH
between 3.5 and 4.0; or
3. Sulfidic materials.
Sulfic Endoaquepts
KAIB. Other Endoaquepts that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Endoaquepts
KAIC. Other Endoaquepts that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Endoaquepts
KAID. Other Endoaquepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or more of the following:
1. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
2. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
3. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Endoaquepts
KAIE. Other Endoaquepts that have a slope of less than 25
percent; and
1. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of 0.2 percent or
more and no densic, lithic, or paralithic contact within that
depth; or
2. An irregular decrease in organic-carbon content
(Holocene age) between a depth of 25 cm and either a depth
of 125 cm below the mineral soil surface or a densic, lithic,
or paralithic contact, whichever is shallower.
Fluvaquentic Endoaquepts
KAIF. Other Endoaquepts that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Endoaquepts
KAIG. Other Endoaquepts that have, in one or more
horizons between the A or Ap horizon and a depth of 75 cm
below the mineral soil surface, one of the following colors:
1. Hue of 7.5YR or redder in 50 percent or more of the
matrix; and
a. If peds are present, either chroma of 2 or more on 50
percent or more of ped exteriors or no redox depletions
with chroma of 2 or less in ped interiors; or
b. If peds are absent, chroma of 2 or more in 50 percent
or more of the matrix; or
2. In 50 percent or more of the matrix, hue of 10YR or
yellower and either:
a. Both a color value, moist, and chroma of 3 or more;
or
b. Chroma of 2 or more if there are no redox
concentrations.
Aeric Endoaquepts
KAIH. Other Endoaquepts that have:
500 Soil Taxonomy
1. A color value, moist, of 3 or less and a color value, dry, of
5 or less (crushed and smoothed) in the Ap horizon or in the
upper 15 cm after mixing; and
2. A base saturation (by NH4
OAc) of less than 50 percent in
some part within 100 cm of the mineral soil surface.
Humic Endoaquepts
KAII. Other Endoaquepts that have a color value, moist, of 3
or less and a color value, dry, of 5 or less (crushed and
smoothed) either in the Ap horizon or in the upper 15 cm after
mixing.
Mollic Endoaquepts
KAIJ. Other Endoaquepts.
Typic Endoaquepts
Definition of Typic Endoaquepts
Typic Endoaquepts are the Endoaquepts that:
1. Do not have, within 150 cm of the mineral soil surface,
any sulfuric horizon, a horizon 15 cm or more thick that has
all of the characteristics of a sulfuric horizon, except that it has
a pH between 3.5 and 4.0, or sulfidic materials;
2. Do not have a lithic contact within 50 cm of the mineral
soil surface;
3. Do not have either:
a. Both cracks within 125 cm of the mineral soil surface
that are 5 mm or more wide through a thickness of 30 cm or
more for some time in most years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of less than 6.0 cm between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
4. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, one or more of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
5. Either have less than 0.2 percent organic carbon (Holocene
age) at a depth of 125 cm below the mineral soil surface and a
regular decrease in organic-carbon content (Holocene age)
between a depth of 25 cm and either a depth of 125 cm below
the mineral soil surface or a densic, lithic, or paralithic contact,
whichever is shallower, or have a slope of 25 percent or more;
6. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick;
7. Do not have, in one or more horizons between the A or Ap
horizon and a depth of 75 cm below the mineral soil surface,
one of the following colors:
a. Hue of 7.5YR or redder in 50 percent or more of the
matrix; and
(1) If peds are present, either chroma of 2 or more
on 50 percent or more of ped exteriors or no redox
depletions with chroma of 2 or less in ped interiors; or
(2) If peds are absent, chroma of 2 or more in 50
percent or more of the matrix; or
b. In 50 percent or more of the matrix, hue of 10YR or
yellower and either:
(1) Both a color value, moist, and chroma of 3 or more;
or
(2) Chroma of 2 or more if there are no redox
concentrations; and
8. Have a color value, moist, of 4 or more or a color value,
dry, of 6 or more (crushed and smoothed) in the Ap horizon or
in the upper 15 cm after mixing.
Description of Subgroups
Typic Endoaquepts.—The central concept or Typic
subgroup of Endoaquepts is fixed on dominantly gray soils
with endosaturation. High chroma in some subhorizon is the
basis for definition of the Aeric subgroup. Soils that have
layers with some andic soil properties are excluded from the
Typic subgroup because such layers indicate an intergrade to
Aquands. Typic Endoaquepts have both less than 0.2 percent
organic carbon (Holocene age) at a depth of 125 cm below the
mineral soil surface and a regular decrease in organic-carbon
content (Holocene age) between a depth of 25 cm and either a
depth of 125 cm below the mineral soil surface or a densic,
lithic, or paralithic contact, whichever is shallower, unless they
Inceptisols 501
have a slope of 25 percent or more. Soils that have fragic soil
properties in a layer 15 cm or more thick are considered
intergrades to Fragiaquepts. A lithic contact within a depth of
50 cm is the basis for definition of the Lithic subgroup. A high
shrink-swell potential or deep, wide cracks in expanding clays
indicate intergrades to Vertisols. Jarosite mottles, if associated
with a low pH value, indicate intergrades to Sulfaquepts. A
dark colored Ap horizon or a moderately thick, dark colored A
horizon is the basis for defining intergrades to Humaquepts or
to Aquolls, depending on the base status.
Typic Endoaquepts are extensive in the United States and
occur in all parts of the country, except for the coldest and the
driest parts. The native vegetation consists mostly of watertolerant
trees, shrubs, and grasses. Many of these soils have
been cleared and artificially drained and are used as cropland
or pasture. Some support their native vegetation.
Aeric Endoaquepts.—These soils have a horizon within
the upper 75 cm that has a chroma too high for Typic
Endoaquepts. The higher chroma is thought to indicate either a
shorter period of saturation of the whole soil with water or
somewhat deeper ground water than that in the soils of the
Typic subgroup. The correlation of color with soil drainage
classes is imperfect. A dark plow layer or a relatively thick,
dark A horizon is permitted, but neither is required. These
soils are extensive in the Eastern United States and occur in all
parts of the United States, except for the coldest and the driest
parts. The native vegetation consists mostly of water-tolerant
trees and shrubs. Many of these soils have been cleared and
artificially drained and are used as cropland or pasture. Some
support their native vegetation.
Aquandic Endoaquepts.—These soils have some andic soil
properties in a layer in the upper 75 cm that is 18 cm or more
thick. The clays in this layer normally do not disperse well and
have a high pH-dependent charge. Typically, this layer is at or
very close to the soil surface. These soils are of small extent in
the United States and are known to occur in California and
Idaho. Most supported water-tolerant grasses, and some
support forest vegetation. Most of the soils are artificially
drained and are used as cropland or hayland. Some are used as
rangeland and some as wildlife habitat.
Fluvaquentic Endoaquepts.—These soils have either 0.2
percent or more organic carbon (Holocene age) at a depth of
125 cm below the mineral soil surface or an irregular decrease
in organic-carbon content (Holocene age) between a depth of
25 cm and either a depth of 125 cm below the mineral soil
surface or a densic, lithic, or paralithic contact, whichever is
shallower. They also have slopes of less than 25 percent. These
soils are extensive in the United States. They are on flood
plains in all parts of the country, except for the coldest and the
driest parts. The native vegetation is mostly water-tolerant
trees and grasses. Some of these soils are used as forest, and
some have been cleared and artificially drained and are used as
cropland or pasture.
Fragic Endoaquepts.—These soils have a significant
volume of fragic soil properties, but they do not have a fragipan
unless the upper boundary is at a depth of more than 100 cm
below the mineral soil surface. The soils are rare in the United
States.
Humic Endoaquepts.—These soils have a darker surface
horizon than that in Typic Endoaquepts and have relatively low
base saturation. They are considered to be intermediate
between Typic Endoaquepts and Humaquepts. Humic
Endoaquepts are of small extent in the United States. They
occur mostly in the Eastern States. The native vegetation
consists mostly of water-tolerant trees and shrubs. Many of
these soils have been cleared and artificially drained and are
used as cropland or pasture. Some support native vegetation.
Lithic Endoaquepts.—These soils have a lithic contact
within 50 cm of the soil surface but otherwise are like Typic
Endoaquepts. Lithic Endoaquepts are of small extent in the
United States. They occur mostly in Florida and New York.
The native vegetation consists mostly of water-tolerant trees,
shrubs, and grasses. Some of these soils are used as forest, and
some have been cleared and artificially drained and are used as
cropland or pasture.
Mollic Endoaquepts.—These soils have a darker surface
horizon than that in Typic Endoaquepts and have relatively
high base saturation. They are considered to be intermediate
between Typic Endoaquepts and Endoaquolls. Mollic
Endoaquepts are moderately extensive in the United States.
They are mostly in the Eastern States. The native vegetation
consists mostly of water-tolerant trees, grasses, and shrubs.
Many of these soils have been cleared and artificially drained
and are used as cropland or pasture. Some support their native
vegetation.
Sulfic Endoaquepts.—These soils are mainly in drained
coastal marshes. Either they have jarosite mottles and a pH
(1:1 water, air-dried slowly in shade) between 3.5 and 4.0 in
some part within a depth of 50 cm, or they have jarosite
mottles and a pH of less than 4.0 (1:1 water, air-dried slowly in
shade) in some part at a depth between 50 and 150 cm from the
surface. The soils are considered intergrades to Sulfaquepts.
Sulfic Endoaquepts are mostly on tidal flats. Many of these
soils have been cleared and artificially drained. Because of the
acidity, however, they now support native vegetation. They
support sparse vegetation of water- and acid-tolerant shrubs
and grasses. They are used mainly as wildlife habitat.
Vertic Endoaquepts.—These soils are fine textured, and they
shrink and swell appreciably when their moisture content
changes. Most of the soils have a high content of smectite, and
some have a dry season in which potential evapotranspiration
exceeds precipitation. The soils are of moderate extent in the
United States and occur in all parts of the country, except for
the coldest and the driest parts. The native vegetation consists
mostly of water-tolerant trees, shrubs, and grasses. Many of
these soils have been cleared and artificially drained and are
used as cropland or pasture. Some support their native
vegetation.
502 Soil Taxonomy
Epiaquepts
Epiaquepts are the Aquepts that have episaturation. The
ground water commonly fluctuates from a level near the soil
surface to below a depth of 200 cm. These soils have a frigid or
warmer soil temperature regime and do not have any sulfuric,
placic, or salic horizon or a fragipan near the soil surface. They
do not have high exchangeable sodium near the soil surface
that becomes less with increasing depth below 50 cm. They
have no horizon within 100 cm of the mineral soil surface in
which plinthite or any other cemented or indurated diagnostic
horizon either forms a continuous phase or constitutes one-half
or more of the volume. Recognizable bioturbation, such as
filled animal burrows, wormholes, or casts, is less than 50
percent (by volume) in all layers at least 25 cm thick
(cumulative) within 100 cm of the mineral soil surface. Before
cultivation, most Epiaquepts supported forest vegetation.
Generally, Epiaquepts are nearly level or gently sloping, and
their parent materials are typically late-Pleistocene or younger
sediments.
Definition
Epiaquepts are the Aquepts that:
1. Do not have a sulfuric horizon that has its upper boundary
within 50 cm of the mineral soil surface;
2. Do not have, within 100 cm of the mineral soil surface,
one or more horizons in which plinthite or a cemented or
indurated diagnostic horizon either forms a continuous phase
or constitutes one-half or more of the volume;
3. Have an exchangeable sodium percentage (ESP) of less
than 15 (or a sodium adsorption ratio [SAR] of less than 13) in
half or more of the soil volume within 50 cm of the mineral
soil surface or an ESP (or SAR) below 50 cm that remains
constant or increases with increasing depth;
4. Have neither a salic horizon nor a fragipan with its upper
boundary within 100 cm of the mineral soil surface;
5. Do not have a cryic soil temperature regime;
6. Do not have, in one or more layers at least 25 cm thick
(cumulative) within 100 cm of the mineral soil surface, 25
percent or more (by volume) recognizable bioturbation, such as
filled animal burrows, wormholes, or casts;
7. Do not have a histic, melanic, mollic, or umbric epipedon;
and
8. Have episaturation.
Key to Subgroups
KAHA. Epiaquepts that have one or both of the following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Epiaquepts
KAHB. Other Epiaquepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or more of the following:
1. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
2. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
3. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Epiaquepts
KAHC. Other Epiaquepts that have a slope of less than 25
percent; and
1. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of 0.2 percent or
more and no densic, lithic, or paralithic contact within that
depth; or
2. An irregular decrease in organic-carbon content
(Holocene age) between a depth of 25 cm and either a depth
of 125 cm below the mineral soil surface or a densic, lithic,
or paralithic contact, whichever is shallower.
Fluvaquentic Epiaquepts
KAHD. Other Epiaquepts that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Epiaquepts
KAHE. Other Epiaquepts that have, in one or more horizons
Inceptisols 503
between the A or Ap horizon and a depth of 75 cm below the
mineral soil surface, one of the following colors:
1. Hue of 7.5YR or redder in 50 percent or more of the
matrix; and
a. If peds are present, either chroma of 2 or more on 50
percent or more of ped exteriors or no redox depletions
with chroma of 2 or less in ped interiors; or
b. If peds are absent, chroma of 2 or more in 50 percent
or more of the matrix; or
2. In 50 percent or more of the matrix, hue of 10YR or
yellower and either:
a. Both a color value, moist, and chroma of 3 or more;
or
b. Chroma of 2 or more if there are no redox
concentrations.
Aeric Epiaquepts
KAHF. Other Epiaquepts that have both:
1. A color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed) in the Ap horizon or in
the upper 15 cm after mixing; and
2. A base saturation (by NH4
OAc) of less than 50 percent
in some part within 100 cm of the mineral soil surface.
Humic Epiaquepts
KAHG. Other Epiaquepts that have a color value, moist, of 3
or less and a color value, dry, of 5 or less (crushed and
smoothed) either in the Ap horizon or in the upper 15 cm after
mixing.
Mollic Epiaquepts
KAHH. Other Epiaquepts.
Typic Epiaquepts
Definition of Typic Epiaquepts
Typic Epiaquepts are the Epiaquepts that:
1. Do not have both cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a thickness of 30
cm or more for some time in most years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick that
has its upper boundary within 125 cm of the mineral soil
surface;
2. Have a linear extensibility of less than 6.0 cm between the
mineral soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact, whichever is shallower;
3. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, one or more of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
4. Either have less than 0.2 percent organic carbon (Holocene
age) at a depth of 125 cm below the mineral soil surface and a
regular decrease in organic-carbon content (Holocene age)
between a depth of 25 cm and either a depth of 125 cm below
the mineral soil surface or a densic, lithic, or paralithic
contact, whichever is shallower, or have a slope of 25 percent
or more;
5. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick;
6. Do not have, in one or more horizons between the A or Ap
horizon and a depth of 75 cm below the mineral soil surface,
one of the following colors:
a. Hue of 7.5YR or redder in 50 percent or more of the
matrix; and
(1) If peds are present, either chroma of 2 or more
on 50 percent or more of ped exteriors or no redox
depletions with chroma of 2 or less in ped interiors; or
(2) If peds are absent, chroma of 2 or more in 50
percent or more of the matrix; or
b. In 50 percent or more of the matrix, hue of 10YR or
yellower and either:
(1) Both a color value, moist, and chroma of 3 or more;
or
(2) Chroma of 2 or more if there are no redox
concentrations; and
7. Have a color value, moist, of 4 or more or a color value,
dry, of 6 or more (crushed and smoothed) in the Ap horizon or
in the upper 15 cm after mixing.
504 Soil Taxonomy
Description of Subgroups
Typic Epiaquepts.—The central concept or Typic subgroup of
Epiaquepts is fixed on dominantly gray soils with episaturation.
High chroma in some subhorizon is the basis for definition of the
Aeric subgroup. Soils that have some andic soil properties in
layers that are near the surface are excluded from the Typic
subgroup because such layers indicate an intergrade to
Aquands. Typic Epiaquepts have both less than 0.2 percent
organic carbon (Holocene age) at a depth of 125 cm below the
mineral soil surface and a regular decrease in organic-carbon
content (Holocene age) between a depth of 25 cm and either a
depth of 125 cm below the mineral soil surface or a densic, lithic,
or paralithic contact, whichever is shallower, unless they have a
slope of 25 percent or more. Soils that have fragic soil properties
in a layer 15 cm or more thick are considered intergrades to
Fragiaquepts. Deep, wide cracks in expanding clays indicate
intergrades to Vertisols. A dark colored Ap horizon or a
moderately thick, dark colored A horizon is the basis for defining
intergrades to Humaquepts or to Aquolls, depending on the
base status.
Typic Epiaquepts are of small extent in the United States.
They are widely distributed and occur in all parts of the
country, except for the coldest and the driest parts. The native
vegetation consists mostly of water-tolerant trees, shrubs, and
grasses. Many of these soils have been cleared and artificially
drained and are used as cropland or pasture. Some support
native vegetation.
Aeric Epiaquepts.—These soils have a horizon within the
upper 75 cm that has a chroma too high for Typic Epiaquepts.
The higher chroma is thought to indicate either a shorter
period of saturation of the whole soil with water or somewhat
deeper ground water than that in the soils of the Typic
subgroup. The correlation of color with soil drainage classes is
imperfect. A dark plow layer or a relatively thick, dark A
horizon is permitted, but neither is required. Aeric Epiaquepts
are extensive in the Eastern United States. They occur in all
parts of the United States, except for the coldest and the driest
parts. The native vegetation consists mostly of water-tolerant
trees and shrubs. Many of these soils have been cleared and
artificially drained and are used as cropland or pasture. Some
support native vegetation.
Aquandic Epiaquepts.—These soils have some andic soil
properties in a layer in the upper 75 cm that is 18 cm or more
thick. The clays in this layer normally do not disperse well and
have a high pH-dependent charge. These soils are not known to
occur in the United States. The subgroup is provided for use
elsewhere.
Fluvaquentic Epiaquepts.—These soils have either 0.2
percent or more organic carbon (Holocene age) at a depth of
125 cm below the mineral soil surface or an irregular decrease
in organic-carbon content (Holocene age) between a depth of
25 cm and either a depth of 125 cm below the mineral soil
surface or a densic, lithic, or paralithic contact, whichever is
shallower. They also have slopes of less than 25 percent. They
are moderately extensive in the United States. They are on flood
plains in all parts of the country, except for the coldest and the
driest parts. The native vegetation is mostly water-tolerant trees
and grasses. Some of these soils are used as forest, and some
have been cleared and artificially drained and are used as
cropland or pasture.
Fragic Epiaquepts.—These soils have a significant volume
of fragic soil properties, but they do not have a fragipan unless
it has its upper boundary at a depth of more than 100 cm below
the mineral soil surface. The soils are of small extent in the
United States.
Humic Epiaquepts.—These soils have a darker surface
horizon than that in Typic Epiaquepts and have relatively low
base saturation. They are considered to be intermediate
between Typic Epiaquepts and Humaquepts. Humic Epiaquepts
are rare in the United States. The native vegetation consists
mostly of water-tolerant trees and shrubs.
Mollic Epiaquepts.—These soils have a darker surface
horizon than that in Typic Epiaquepts and have relatively high
base saturation. They are considered to be intermediate
between Typic Epiaquepts and Epiaquolls. Mollic Epiaquepts
are of small extent in the United States. They occur mostly in
the Northern and Eastern States. The native vegetation consists
mostly of water-tolerant trees, grasses, and shrubs. Many of
these soils have been cleared and artificially drained and are
used as cropland or pasture. Some support native vegetation.
Vertic Epiaquepts.—These soils are fine textured, and they
shrink and swell appreciably when their moisture content
changes. Most of them have a high content of smectite, and
some have a dry season in which potential evapotranspiration
exceeds precipitation. These soils are of moderate extent in the
United States. They occur in all parts of the country, except for
the coldest and the driest parts. The native vegetation consists
mostly of water-tolerant trees, shrubs, and grasses. Many of
these soils have been cleared and artificially drained and are
used as cropland or pasture. Some support native vegetation.
Fragiaquepts
These are the Aquepts that have a fragipan within 100 cm of
the mineral soil surface, commonly at a depth of 30 to 50 cm.
Typically, the soils have episaturation and the water table is
perched on the fragipan. The horizons above the pan are grayish
and are saturated with water during some periods in normal
years. Most of these soils have a forest vegetation, but a few
areas have been cleared. The trees have a shallow root system
and are particularly subject to windthrow. A distinct microrelief
of 50 to 60 cm or more is very common above the pan. The upper
surface of the pan generally is smooth. In many areas of these
soils, the horizons above the fragipan appear to have been mixed
by the uplift of the roots of falling trees. In some areas the
horizons above the pan consist of an O horizon, an ochric
epipedon, and an intermittent cambic horizon below the mounds.
In other areas the cambic horizon is continuous.
Inceptisols 505
The Fragiaquepts in the United States have mostly a frigid or
mesic soil temperature regime. They are moderately extensive in
parts of the Northeastern States, and a few of the soils occur in
Oregon and Washington. Fragiaquepts that have a temperature
regime marginal to cryic have been reported in other countries,
but no unique subgroups are provided for these soils. Most
Fragiaquepts are nearly level or gently sloping and developed in
Pleistocene-age sediments.
Definition
Fragiaquepts are the Aquepts that:
1. Have a fragipan with its upper boundary within 100 cm of
the mineral soil surface;
2. Do not have a sulfuric horizon that has its upper boundary
within 50 cm of the mineral soil surface;
3. Do not have, within 100 cm of the mineral soil surface,
one or more horizons in which plinthite or a cemented or
indurated diagnostic horizon either forms a continuous phase
or constitutes one-half or more of the volume;
4. Have an SAR of less than 13 (or less than 15 percent
saturation with sodium) in half or more of the upper 50 cm or
have an SAR (or saturation with sodium) that is constant or
increases with increasing depth below 50 cm; and
5. Do not have a salic horizon.
Key to Subgroups
KADA. Fragiaquepts that have, in 50 percent or more of the
matrix of one or more horizons either between the plow layer
and a depth of 75 cm below the mineral soil surface or, if there
is no plow layer, between depths of 15 and 75 cm, chroma of
either:
1. 3 or more; or
2. 2 or more if there are no redox concentrations.
Aeric Fragiaquepts
KADB. Other Fragiaquepts that have a histic, mollic, or
umbric epipedon.
Humic Fragiaquepts
KADC. Other Fragiaquepts.
Typic Fragiaquepts
Definition of Typic Fragiaquepts
Typic Fragiaquepts are the Fragiaquepts that:
1. Do not have a histic, mollic, or umbric epipedon;
and
2. Have, in more than 50 percent of the matrix of one or
more horizons either between the plow layer and 75 cm below
the mineral soil surface or, if there is no plow layer, between
depths of 15 and 75 cm, chroma of either:
a. 2 or less if redox concentrations are present; or
b. 1 or less.
Description of Subgroups
Typic Fragiaquepts.—The central concept or Typic subgroup
of Fragiaquepts is fixed on soils that have an ochric epipedon.
These soils have dominant chroma, in the matrix of all
subhorizons between the Ap horizon or a depth of 15 cm and a
depth of 75 cm below the mineral soil surface, of 2 or less if there
are redox concentrations or of 1 or less if there are no redox
concentrations. Chroma higher than these limits is considered
evidence of somewhat better aeration and is the basis for
defining the Aeric subgroup. An umbric or mollic epipedon is
the basis for defining the Humic subgroup.
Typic Fragiaquepts are of small extent in the United States.
They occur mostly in the Northern and Eastern States. The
native vegetation consists mostly of water-tolerant trees and
shrubs. Many of these soils support native vegetation, but some
have been cleared and artificially drained and are used as
cropland or pasture.
Aeric Fragiaquepts.—These soils have one or more
horizons that have chroma too high for the Typic subgroup but
are otherwise like Typic Fragiaquepts. Aeric Fragiaquepts are
of moderate extent in the United States. They occur mostly in
the Northern and Eastern States. The native vegetation consists
mostly of water-tolerant trees and shrubs. Many of these soils
have been cleared and artificially drained and are used as
cropland or pasture. Some support native vegetation.
Humic Fragiaquepts.—These soils have an umbric
epipedon or, rarely, a mollic epipedon that has been produced
by liming an umbric epipedon. The soils are otherwise like
Typic Fragiaquepts. Humic Fragiaquepts are rare in the United
States.
Halaquepts
These are saline or sodic soils that have both a seasonal high
water table and a season in which capillary rise and
evapotranspiration bring sodium or other salts to or near the
soil surface. Salt efflorescence on the soil surface is common in
dry seasons.
Halaquepts typically have grayish colors, and some have
redox concentrations from near the soil surface downward.
Nearly all are level and formed in Holocene alluvium. The
native vegetation is mostly sedges and salt-tolerant grasses and
shrubs, but some of the soils have been artificially drained and
are used as irrigated cropland. Halaquepts are not extensive in
the United States.
Definition
Halaquepts are the Aquepts that:
1. Have:
a. An SAR of 13 or more (or sodium saturation that is 15
506 Soil Taxonomy
percent or more), in half or more of the upper 50 cm, that
decreases with increasing depth below 50 cm and saturation
with water at some period within a depth of 100 cm; or
b. A salic horizon;
2. Do not have a sulfuric horizon that has its upper boundary
within 50 cm of the mineral soil surface; and
3. Do not have, within 100 cm of the mineral soil surface,
one or more horizons in which plinthite or a cemented or
indurated diagnostic horizon either forms a continuous phase
or constitutes one-half or more of the volume.
Key to Subgroups
KACA. Halaquepts that have one or both of the following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Halaquepts
KACB. Other Halaquepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or more of the following:
1. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
2. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
3. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Halaquepts
KACC. Other Halaquepts that have a horizon 15 cm or more
thick that has 20 percent or more (by volume) cemented or
indurated soil material and has its upper boundary within 100
cm either of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Duric Halaquepts
KACD. Other Halaquepts that have chroma of 3 or more
in 40 percent or more of the matrix of one or more horizons
at a depth between 15 and 75 cm from the mineral soil
surface.
Aeric Halaquepts
KACE. Other Halaquepts.
Typic Halaquepts
Definition of Typic Halaquepts
Typic Halaquepts are the Halaquepts that:
1. Have chroma of 2 or less in 60 percent or more of
the matrix in all subhorizons between depths of 15 and
75 cm;
2. Do not have a horizon 15 cm or more thick that has 20
percent or more (by volume) cemented or indurated soil
material and has its upper boundary within 100 cm either of
the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower;
3. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
and
4. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Inceptisols 507
Description of Subgroups
Typic Halaquepts.—The central concept or Typic subgroup
of Halaquepts is fixed on soils that have chroma of 2 or less in
all subhorizons between depths of 15 and 75 cm. These soils
have less than 20 percent cemented soil material in the upper
100 cm. Some of the soils have a salic horizon. Salinity
commonly varies with seasons in these soils, even under
irrigation. Most of the soils, however, have electrical
conductivity in excess of 2 dS/m in some horizon at some time
of the year. Commonly, the conductivity exceeds 15 dS/m.
Chroma of more than 2 in more than 40 percent of the matrix
of some subhorizon between depths of 15 and 75 cm is the
basis for definition of the Aeric subgroup.
Typic Halaquepts are of moderate extent in the Western
United States. The native vegetation consists mostly of waterand
salt-tolerant shrubs and grasses. Most of these soils
support native vegetation and are used as rangeland. Some
have been cleared and artificially drained and are used as
irrigated cropland or pasture.
Aeric Halaquepts.—These soils have chroma too high for
the Typic subgroup in some subhorizon between depths of 15
and 75 cm below the soil surface. The higher chroma is
thought to indicate a lower level of ground water and
somewhat better aeration. These soils are of moderate extent in
the Western United States. The native vegetation is mostly
water- and salt-tolerant shrubs and grasses. Most of these soils
are used as rangeland. Some have been cleared and artificially
drained and are used as irrigated cropland or pasture.
Aquandic Halaquepts.—These soils have some andic soil
properties in a layer in the upper 75 cm that is 18 cm or more
thick. The clays in this layer normally do not disperse well and
have a high pH-dependent charge. These soils are not known to
occur in the United States. The subgroup is provided for use
elsewhere.
Duric Halaquepts.—These soils have 20 percent or more
cemented or indurated soil material in a horizon 15 cm or more
thick that is in the upper 100 cm. The soils are of moderate
extent in the Western United States. They occur in the
semiarid, high valleys east of the Cascade Range in southern
Oregon. The native vegetation consists mostly of water- and
salt-tolerant shrubs and grasses. Most of these soils are used as
rangeland. Some have been cleared and artificially drained and
are used as irrigated cropland or pasture.
Vertic Halaquepts.—These soils are high in expanding
clays and have cracks 5 mm or more wide, slickensides,
wedge-shaped aggregates, or a linear extensibility of 6.0 cm or
more between the mineral soil surface and either a depth of
100 cm or a densic, lithic, or paralithic contact, whichever is
shallower. The soils are considered to be transitional to
Vertisols. Vertic Halaquepts are of small extent and occur in
the Western United States and in Puerto Rico.
Humaquepts
Humaquepts are the Aquepts that have a histic, melanic,
mollic, or umbric epipedon. The ground water commonly
fluctuates from a level near the soil surface to below a depth of
50 cm. These soils have a frigid or warmer soil temperature
regime and do not have any sulfuric, placic, or salic horizon or
a fragipan near the soil surface. They do not have high
exchangeable sodium near the soil surface that becomes less
with increasing depth below 50 cm. They have no horizon
within 100 cm of the mineral soil surface in which plinthite or
any other cemented or indurated diagnostic horizon either
forms a continuous phase or constitutes one-half or more of the
volume. Recognizable bioturbation, such as filled animal
burrows, wormholes, or casts, is less than 50 percent (by
volume) in all layers at least 25 cm thick (cumulative) within
100 cm of the mineral soil surface. Before they were cultivated,
most Humaquepts supported forest vegetation. Generally,
Humaquepts are nearly level, and their parent materials are
typically late-Pleistocene or younger sediments. These soils are
of small extent in the United States.
Definition
Humaquepts are the Aquepts that:
1. Have an umbric, mollic, melanic, or histic epipedon;
2. Do not have a sulfuric horizon that has its upper boundary
within 50 cm of the mineral soil surface;
3. Do not have, within 100 cm of the mineral soil surface,
one or more horizons in which plinthite or a cemented or
indurated diagnostic horizon either forms a continuous phase
or constitutes one-half or more of the volume;
4. Have an exchangeable sodium percentage (ESP) of less
than 15 (or a sodium adsorption ratio [SAR] of less than 13) in
half or more of the soil volume within 50 cm of the mineral
soil surface or an ESP (or SAR) below 50 cm that remains
constant or increases with increasing depth;
5. Have neither a salic horizon nor a fragipan with its upper
boundary within 100 cm of the mineral soil surface;
6. Do not have a cryic soil temperature regime; and
7. Do not have, in one or more layers at least 25 cm thick
(cumulative) within 100 cm of the mineral soil surface, 25
percent or more (by volume) recognizable bioturbation, such as
filled animal burrows, wormholes, or casts.
Key to Subgroups
KAGA. Humaquepts that have an n value of either:
1. More than 0.7 (and less than 8 percent clay) in one or
508 Soil Taxonomy
more layers at a depth between 20 and 50 cm from the mineral
soil surface; or
2. More than 0.9 in one or more layers at a depth
between 50 and 100 cm.
Hydraquentic Humaquepts
KAGB. Other Humaquepts that have a histic epipedon.
Histic Humaquepts
KAGC. Other Humaquepts that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, one or more of the following:
1. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
2. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
3. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Humaquepts
KAGD. Other Humaquepts that have a slope of less than 25
percent; and
1. An umbric or mollic epipedon 60 cm or more thick; and
either
2. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of 0.2 percent or
more and no densic, lithic, or paralithic contact within that
depth; or
3. An irregular decrease in organic-carbon content
(Holocene age) between a depth of 25 cm and either a depth
of 125 cm below the mineral soil surface or a densic, lithic,
or paralithic contact, whichever is shallower.
Cumulic Humaquepts
KAGE. Other Humaquepts that have a slope of less than 25
percent; and
1. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of 0.2 percent or
more and no densic, lithic, or paralithic contact within that
depth; or
2. An irregular decrease in organic-carbon content
(Holocene age) between a depth of 25 cm and either a depth
of 125 cm below the mineral soil surface or a densic, lithic,
or paralithic contact, whichever is shallower.
Fluvaquentic Humaquepts
KAGF. Other Humaquepts that have hue of 5Y or redder and
chroma of 3 or more in more than 40 percent of the matrix of
one or more subhorizons at a depth between 15 and 75 cm
from the mineral soil surface.
Aeric Humaquepts
KAGG. Other Humaquepts.
Typic Humaquepts
Definition of Typic Humaquepts
Typic Humaquepts are the Humaquepts that:
1. Have chroma of 2 or less, moist, or hue less red than 5Y
in 60 percent or more of the matrix in all subhorizons between
depths of 15 and 75 cm;
2. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
3. Have a content of organic carbon (Holocene age) that
decreases regularly with increasing depth and, unless a densic,
lithic, or paralithic contact occurs at a shallower depth, reaches
a level of 0.2 percent or less within 125 cm of the soil surface;
4. Do not have a histic epipedon; and
5. Have an n value of less than 0.9 between depths of 50
and 100 cm and of 0.7 or less in all layers between depths of
20 and 50 cm.
Description of Subgroups
Typic Humaquepts.—The central concept or Typic
subgroup of Humaquepts is fixed on very poorly drained soils
Inceptisols 509
that have an umbric epipedon that is between 25 and 60 cm
thick, have a low n value, have a regular decrease in organiccarbon
content (Holocene age) with increasing depth, and do
not have a significant amount of materials that have some
andic soil properties. A few of these soils have a mollic
epipedon.
An overthickened epipedon indicates addition of materials
at the surface and is the basis for definition of the Cumulic
subgroup. A histic epipedon indicates a transition to Histosols.
A high n value is characteristic of Hydraquents and causes
soils to be excluded from the Typic subgroup. An irregular
decrease in organic-carbon content (Holocene age) with
increasing depth indicates buried horizons and is the basis for
defining the Fluvaquentic subgroup.
Typic Humaquepts are of moderate extent in the United
States. They are widely distributed and commonly occur in the
most moist parts of the country. The native vegetation consists
mostly of water-tolerant trees, shrubs, and grasses. Many of
these soils have been cleared and artificially drained and are
used as cropland or pasture. Some support native vegetation.
Aeric Humaquepts.—These soils have a horizon within the
upper 75 cm that has a hue too red and a chroma too high for
Typic Humaquepts. The higher chroma is thought to indicate
either a shorter period of saturation of the whole soil with
water or somewhat deeper ground water than that in the soils
of the Typic subgroup. Aeric Humaquepts are not known to
occur in the United States.
Aquandic Humaquepts.—These soils have some andic soil
properties in a layer in the upper 75 cm that is 18 cm or more
thick. The clays in this layer normally do not disperse well and
have a high pH-dependent charge. Typically, this layer is at or
very close to the soil surface. An umbric epipedon is common
but is not required. These soils are of small extent in the
United States and are known to occur in Washington, Oregon,
and Idaho. Most of the soils supported water-tolerant forest
vegetation, and some supported water-tolerant grasses and
shrubs. Many of the soils are artificially drained and are used
as cropland or hayland, and many are used as forest. Some are
used as pasture and some as wildlife habitat.
Cumulic Humaquepts.—These soils have an irregular
decrease in organic-carbon content (Holocene age) with
increasing depth or have a relatively high amount of organic
carbon (Holocene age) in the deep layers. In addition, they
have a thick epipedon. These soils commonly are on flood
plains or at the margins of closed depressions where there has
been very slow deposition of new materials. The deposition has
been slow enough for new materials to have become part of the
epipedon. These soils are of moderate extent in the United
States. They are widely distributed and occur mostly in the
most moist parts of the country. The native vegetation consists
mostly of water-tolerant trees, shrubs, and grasses. Most of
these soils support native vegetation. Some have been cleared
and artificially drained and are used as cropland or pasture.
Fluvaquentic Humaquepts.—These soils have an irregular
decrease in organic-carbon content (Holocene age) with
increasing depth or have a relatively high amount of organic
carbon (Holocene age) in the deep layers. They are subject to
flooding by muddy water and have some of the properties of
Fluvents. Fluvaquentic Humaquepts are of small extent in the
United States. They are widely distributed and occur mostly in
the most moist parts of the country. The native vegetation
consists mostly of water-tolerant trees, shrubs, and grasses.
Most of these soils support their native vegetation. Some have
been cleared and artificially drained and are used as cropland
or pasture.
Histic Humaquepts.—These soils have a histic epipedon.
They are the wettest of the Humaquepts and are intergrades to
Histosols. The organic-carbon content (Holocene age) may be
relatively high in the deep layers. Histic Humaquepts are of
moderate extent in the United States and are widely distributed
mostly in the northern and eastern parts of the country. The
native vegetation consists mostly of water-tolerant trees,
shrubs, and grasses. Most of these soils support native
vegetation. A few of the soils have been cleared and artificially
drained and are used as cropland or pasture.
Hydraquentic Humaquepts.—These soils have an n value
of either more than 0.7 in one or more layers at a depth
between 20 and 50 cm from the mineral soil surface or of more
than 0.9 in one or more layers at a depth between 50 and 100
cm from the mineral soil surface. The soils are rare in the
United States. They are on tidal flats. The native vegetation
consists mostly of water-tolerant grasses, sedges, rushes, and
shrubs.
Petraquepts
These are the Aquepts that have one or more horizons,
within 100 cm of the mineral soil surface, in which plinthite or
a cemented or indurated diagnostic horizon either forms a
continuous phase or constitutes one-half or more of the volume.
A layer of plinthite and the placic horizon are the only
horizons known to occur in the Petraquepts in the United
States. A Typic subgroup is provided for Petraquepts with a
duripan or petrocalcic horizon. Petraquepts are soils in which
the ground water table fluctuates considerably during the year,
between a level at or near the soil surface during the rainy
season and a much lower level during less wet seasons. A
histic or umbric epipedon and a cambic horizon may be
present. In some of the soils, the placic horizon is so close to
the soil surface that there is no cambic horizon above it.
Petraquepts are in areas of very high rainfall. The
vegetation may be a rain forest, Sphagnum, or other waterloving
plants. The temperature regime is frigid to
isohyperthermic. Slopes generally are such that water does not
pond on the surface, but high rainfall keeps some of the soils
continuously wet. Petraquepts are rare in the world.
510 Soil Taxonomy
Definition
1. Petraquepts are the Aquepts that have, within 100 cm of the
mineral soil surface, one or more horizons in which plinthite or a
cemented or indurated diagnostic horizon either forms a
continuous phase or constitutes one-half or more of the volume;
and
2. Do not have a sulfuric horizon that has its upper boundary
within 50 cm of the mineral soil surface.
Key to Subgroups
KABA. Petraquepts that have both:
1. A histic epipedon; and
2. A placic horizon.
Histic Placic Petraquepts
KABB. Other Petraquepts that have a placic horizon.
Placic Petraquepts
KABC. Other Petraquepts that have one or more horizons
within 125 cm of the mineral soil surface in which plinthite
either forms a continuous phase or constitutes one-half or more
of the volume.
Plinthic Petraquepts
KABD. Other Petraquepts.
Typic Petraquepts
Definition of Typic Petraquepts
Typic Petraquepts are the Petraquepts that:
1. Do not have a placic horizon; and
2. Do not have one or more horizons within 125 cm of the
mineral soil surface in which plinthite either forms a
continuous phase or constitutes one-half or more of the volume.
Description of Subgroups
Typic Petraquepts.—The central concept or Typic
subgroup of Petraquepts is fixed on soils that have a duripan or
a petrocalcic horizon within 100 cm of the mineral soil surface.
These soils do not have a horizon within 125 cm of the mineral
soil surface in which plinthite either forms a continuous phase
or constitutes one-half or more of the volume and do not have a
placic horizon. They can have a histic epipedon if there is no
placic horizon. Typic Petraquepts are not the most common
Petraquepts and are not known to occur in the United States.
Histic Placic Petraquepts.—These soils have both a histic
epipedon and a placic horizon. They are like Typic Petraquepts
in other defined properties. Histic Placic Petraquepts are of
very small extent and occur only in Hawaii in the United
States. They are used as wildlife habitat and as water
catchments.
Placic Petraquepts.—These soils have a placic horizon but
do not have a histic epipedon. Normally, the placic horizon lies
within 25 to 50 cm of the mineral soil surface. These soils are
of very small extent and occur only in Hawaii in the United
States. They are used as wildlife habitat and as water
catchments.
Plinthic Petraquepts.—These soils have one or more
horizons within 125 cm of the mineral soil surface in which
plinthite either forms a continuous phase or constitutes onehalf
or more of the volume. These soils are not known to occur
in the United States. The subgroup has been established for use
in other countries.
Sulfaquepts
These are the acid sulfate soils (cat clays) that have been
drained and oxidized at some time. They are extremely acid
and toxic to most plants. They are mostly dark gray and have
straw-colored mottles of iron sulfate (jarosite) within 50 cm of
the soil surface. These soils are mainly in drained coastal
marshes near the mouths of rivers that carry sediments that are
free of carbonates or have a low content of carbonates. They
can have any texture, but most are loamy or clayey. The soils
contain an appreciable amount of organic carbon (Holocene
age). They are rare in the United States but occur elsewhere in
a few areas that have been used mainly for the production of
rice.
Definition
Sulfaquepts are the Aquepts that have a sulfuric horizon
that has its upper boundary within 50 cm of the soil surface.
Key to Subgroups
KAAA. Sulfaquepts that have a salic horizon within 75 cm of
the mineral soil surface.
Salidic Sulfaquepts
KAAB. Other Sulfaquepts that have an n value of either:
1. More than 0.7 (and less than 8 percent clay) in one or
more layers at a depth between 20 and 50 cm from the
mineral soil surface; or
2. More than 0.9 in one or more layers at a depth
between 50 and 100 cm from the mineral soil surface.
Hydraquentic Sulfaquepts
KAAC. Other Sulfaquepts.
Typic Sulfaquepts
Definition of Typic Sulfaquepts
Typic Sulfaquepts are the Sulfaquepts that:
1. Do not have a salic horizon within 75 cm of the mineral
soil surface; and
2. Have an n value both:
Inceptisols 511
a. Of 0.7 or less in all layers at a depth between 20 and 50
cm from the mineral soil surface; and
b. Of less than 0.9 in all layers at a depth between 50 and
100 cm from the mineral soil surface.
Description of Subgroups
Typic Sulfaquepts.—The central concept or Typic subgroup
of Sulfaquepts is fixed on very poorly drained soils that do not
have a salic horizon and have an n value of 0.7 or less in all
layers at a depth between 20 and 50 cm from the mineral soil
surface and of 0.9 or less in all layers at a depth between 50
and 100 cm from the mineral soil surface.
These soils are rare in the United States. They are on tidal
flats. The native vegetation is sparse and consists mostly of
water-tolerant grasses, sedges, rushes, and shrubs.
Hydraquentic Sulfaquepts.—These soils have an n value
of either more than 0.7 in one or more layers at a depth
between 20 and 50 cm from the mineral soil surface or of more
than 0.9 in one or more layers at a depth between 50 and 100
cm from the mineral soil surface. The soils are rare in the
United States. They are on tidal flats. The native vegetation is
sparse and consists of water-tolerant grasses, sedges, rushes,
and shrubs.
Salidic Sulfaquepts.—These soils have a salic horizon
within 75 cm of the mineral soil surface. They are rare in the
United States. They are on tidal flats. The native vegetation
consists of very sparse water- and salt-tolerant grasses, sedges,
rushes, and shrubs.
Vermaquepts
Vermaquepts are the Aquepts that have recognizable
bioturbation, such as filled animal burrows, wormholes, or
casts. It has been shown that because krotovinas are dense,
massive, compact, and stratified, they restrict water movement.
Significant amounts of krotovinas in a soil affect soil
morphology, soil hydrology, and soil behavior. These soils are
known to occur along the coastal plain of Texas as well as
other Southeastern States.
Definition
Vermaquepts are the Aquepts that:
1. Have, in one or more layers at least 25 cm thick
(cumulative) within 100 cm of the soil surface, 50 percent or
more (by volume) recognizable bioturbation, such as filled
animal burrows, wormholes, or casts;
2. Do not have a sulfuric horizon that has its upper boundary
within 50 cm of the soil surface;
3. Do not have, within 100 cm of the mineral soil surface,
one or more horizons in which plinthite or a cemented or
indurated diagnostic horizon either forms a continuous phase or
constitutes one-half or more of the volume;
4. Do not have, in one or more horizons with a total
thickness of 25 cm or more within 50 cm of the mineral soil
surface, an exchangeable sodium percentage (ESP) of 15 or
more (or a sodium adsorption ratio [SAR] of 13 or more) and a
decrease in ESP (or SAR) values with increasing depth below
50cm;
5. Do not have a fragipan with its upper boundary within 100
cm of the mineral soil surface;
6. Have a soil temperature regime warmer than cryic; and
7. Do not have a salic horizon.
Key to Subgroups
KAFA. Vermaquepts that have an exchangeable sodium
percentage of 7 or more (or a sodium adsorption ratio [SAR] of
6 or more) in one or more subhorizons within 100 cm of the
mineral soil surface.
Sodic Vermaquepts
KAFB. Other Vermaquepts.
Typic Vermaquepts
Definition of Typic Vermaquepts
Typic Vermaquepts are the Vermaquepts that do not have an
exchangeable sodium percentage of 7 or more (or a sodium
adsorption ratio [SAR] of 6 or more) in one or more
subhorizons within 100 cm of the mineral soil surface.
Description of Subgroups
Typic Vermaquepts.—The central concept or Typic
subgroup of Vermaquepts is fixed on poorly drained soils that
have an exchangeable sodium percentage of less than 7 (or a
sodium adsorption ratio [SAR] of less than 6) in all
subhorizons within 100 cm of the mineral soil surface. The
recognizable bioturbation in the soils is caused mainly by
crayfish. These soils are of small extent in the United States.
They occur mostly on the coastal plain in Texas. The native
vegetation consists mostly of water-tolerant trees and shrubs.
Most of these soils have been cleared and are used as cropland.
Rice is among the commonly grown crops. Crayfish are
sometimes raised on the crop residue.
Sodic Vermaquepts.—These soils have an exchangeable
sodium percentage of 7 or more (or a sodium adsorption ratio
[SAR] of 6 or more) in one or more subhorizons within 100 cm
of the mineral soil surface. The recognizable bioturbation in
the soils is caused mainly by crayfish. These soils are of small
extent in the United States. They occur mostly on the coastal
plain in Texas. The native vegetation consists mostly of watertolerant
trees and shrubs. Most of these soils have been cleared
512 Soil Taxonomy
and are used as cropland. Rice is among the commonly grown
crops. Crayfish are sometimes raised on the crop residue.
Cryepts
Cryepts are the cold Inceptisols of high mountains or high
latitudes. They cannot have permafrost within 100 cm of the
soil surface. The vegetation is mostly conifers or mixed
conifers and hardwoods. Few of the soils are cultivated.
Cryepts formed in loess, drift, or alluvium or in solifluction
deposits, mostly late Pleistocene or Holocene in age. The soils
commonly have a thin, dark brownish ochric epipedon and a
brownish cambic horizon. Some have bedrock within 100 cm
of the surface. Cryepts are moderately extensive in the United
States. They occur in the high mountains of the West and in
southern Alaska as well as in other mountainous areas of the
world.
Definition
Cryepts are the Inceptisols that:
1. Have a cryic temperature regime;
2. Do not have both aquic conditions and a histic epipedon,
the colors defined for Aquepts, or enough active ferrous iron to
give a positive reaction to alpha,alpha-dipyridyl at a time when
the soil is not being irrigated;
3. Do not have an exchangeable sodium percentage (ESP)
of 15 or more (or a sodium adsorption ratio [SAR] of 13 or
more) in half or more of the soil volume within 50 cm of the
mineral soil surface, an ESP (or SAR) below 50 cm that
decreases with increasing depth, and ground water within 100
cm of the mineral soil surface during some time of the year;
and
4. Have neither a plaggen nor an anthropic epipedon.
Key to Great Groups
KCA. Cryepts that have one or both of the following:
1. Free carbonates within the soils; or
2. A base saturation (by NH4
OAc) of 60 percent or more
in one or more horizons at a depth between 25 and 75 cm
from the mineral soil surface.
Eutrocryepts, p. 514
KCB. Other Cryepts.
Dystrocryepts, p. 512
Dystrocryepts
These are the Cryepts that do not have free carbonates and
have a base saturation (by NH4
OAc) of less than 60 percent in
all horizons at a depth between 25 and 75 cm from the mineral
soil surface. The vegetation is mostly conifers or mixed
conifers and hardwoods. Few of the soils are cultivated.
Dystrocryepts may have formed in loess, drift, or alluvium or
in solifluction deposits, mostly late Pleistocene or Holocene in
age. The soils commonly have a thin, dark brownish ochric
epipedon and a brownish cambic horizon. Some have an
umbric epipedon, and some have bedrock within 100 cm of the
surface. In the United States, Dystrocryepts are moderately
extensive in the high mountains of the West and in southern
Alaska. They also occur in other mountainous areas of the
world.
Definition
Dystrocryepts are the Cryepts that:
1. Do not have free carbonates within the soils; and
2. Have a base saturation (by NH4
OAc) of less than 60
percent in all horizons at a depth between 25 and 75 cm from
the mineral soil surface.
Key to Subgroups
KCBA. Dystrocryepts that have both:
1. An umbric or mollic epipedon; and
2. A lithic contact within 50 cm of the mineral soil
surface.
Humic Lithic Dystrocryepts
KCBB. Other Dystrocryepts that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Dystrocryepts
KCBC. Other Dystrocryepts that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm3
or less, measured at 33 kPa
water retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Dystrocryepts
KCBD. Other Dystrocryepts that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
Inceptisols 513
oxalate) times 60] plus the volcanic glass (percent) is equal
to 30 or more.
Vitrandic Dystrocryepts
KCBE. Other Dystrocryepts that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage).
Aquic Dystrocryepts
KCBF. Other Dystrocryepts that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Dystrocryepts
KCBG. Other Dystrocryepts that have lamellae (two or more)
within 200 cm of the mineral soil surface.
Lamellic Dystrocryepts
KCBH. Other Dystrocryepts that have a horizon 5 cm or
more thick that has one or more of the following:
1. In 25 percent or more of each pedon, cementation by
organic matter and aluminum, with or without iron; or
2. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
3. An ODOE value of 0.12 or more, and a value half as
high or lower in an overlying horizon.
Spodic Dystrocryepts
KCBI. Other Dystrocryepts that have a xeric moisture
regime.
Xeric Dystrocryepts
KCBJ. Other Dystrocryepts that are dry in some part of the
moisture control section for 45 or more days (cumulative) in
normal years.
Ustic Dystrocryepts
KCBK. Other Dystrocryepts that have an umbric or mollic
epipedon.
Humic Dystrocryepts
KCBL. Other Dystrocryepts.
Typic Dystrocryepts
Definition of Typic Dystrocryepts
Typic Dystrocryepts are the Dystrocryepts that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have, in any horizon within 75 cm of the mineral soil
surface, redox depletions with chroma of 2 or less and also aquic
conditions;
3. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years;
4. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
5. Have neither an umbric nor a mollic epipedon;
6. Do not have lamellae (two or more) within 200 cm of the
mineral soil surface;
7. Do not have a horizon 5 cm or more thick that has one or
more of the following:
a. In 25 percent or more of each pedon, cementation by
organic matter and aluminum, with or without iron; or
b. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
c. An ODOE value of 0.12 or more, and a value half as
high or lower in an overlying horizon;
8. Do not have a xeric moisture regime; and
9. Are dry in some part of the moisture control section for
less than 45 days (cumulative) in normal years.
Description of Subgroups
Typic Dystrocryepts.—The central concept or the Typic
subgroup of Dystrocryepts is fixed on deep, more or less freely
514 Soil Taxonomy
drained soils that have an ochric epipedon and that do not have
lamellae.
Soils that have lamellae in which silicate clay has
accumulated are excluded from the Typic subgroup because
they are considered to be intergrades to Alfisols. Shallow hard
rock is used to define the Lithic subgroup. Soils that have a
thin mantle or layer of materials that have some andic soil
properties are excluded from the Typic subgroup because they
are considered to be an intergrade to Andisols. A shallow water
table and redox depletions with low chroma indicate
intergrades to Aquepts. An umbric or mollic epipedon is not
considered typical and is used to define Humic and
combination Humic subgroups.
Typic Dystrocryepts are of large extent in the United States.
They are mostly in the mountains of the Western States and in
Alaska. The vegetation is mostly coniferous forest. The soils
are used mainly for timber production and wildlife habitat.
Andic and Vitrandic Dystrocryepts.—These soils have, in
the upper 75 cm, a layer that is 18 cm or more thick and that
has some andic soil properties or that consists of fine
pyroclastic materials. This layer is most commonly at the
mineral soil surface. Most of these soils have an ochric or
umbric epipedon and a cambic horizon. Andic and Vitrandic
Dystrocryepts are of large extent in the United States. They are
mostly in the mountains of the Western States. The vegetation
is mostly coniferous forest. The soils are used mainly for
timber production and wildlife habitat.
Aquic Dystrocryepts.—These soils have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage). In
addition, some of the soils have an umbric or mollic epipedon.
Aquic Dystrocryepts are of small extent in the United States.
They are mostly in Alaska, but a few are in the mountains of
other Western States. The vegetation is mostly coniferous
forest. The soils are used mainly for timber production and
wildlife habitat.
Humic Dystrocryepts.—These soils are like Typic
Dystrocryepts, but they have an umbric or mollic epipedon.
Many of the soils are in areas of higher precipitation than the
soils of the Typic subgroup. Humic Dystrocryepts are of
moderate extent in the United States. They are mostly in the
mountains of the Western States. The vegetation is mostly
coniferous forest. The soils are used mainly for timber
production and wildlife habitat.
Humic Lithic Dystrocryepts.—These soils have an umbric
or mollic epipedon and a lithic contact within 50 cm of the soil
surface. They are of moderate extent in the United States. They
are mostly in the mountains of the Western States. The
vegetation is mostly coniferous forest. The soils are used
mainly for timber production and wildlife habitat.
Lamellic Dystrocryepts.—These soils have two or more
lamellae. The top of the uppermost lamella is within 75 cm of
the soil surface, but others may be deeper. Most of these soils
have a coarse-loamy, coarse-silty, or loamy-skeletal particle-size
class. Lamellic Dystrocryepts are of small extent in the United
States. They are mostly in the mountains of the Western States.
The vegetation is mostly coniferous forest. The soils are used
mainly for timber production and wildlife habitat.
Lithic Dystrocryepts.—These soils have an ochric
epipedon and a lithic contact within 50 cm of the soil surface.
They are of moderate extent in the United States. They are
mostly in the mountains of the Western States. The vegetation
is mostly coniferous forest. The soils are used mainly for
timber production and wildlife habitat.
Oxyaquic Dystrocryepts.—These soils are saturated with
water in one or more layers within 100 cm of the mineral soil
surface for 20 consecutive days or 30 cumulative days in
normal years. The soils are of small extent in the United States.
They are mostly in Alaska and in the mountains of the Western
States. The vegetation is mostly coniferous forest. The soils are
used mainly for timber production and wildlife habitat.
Spodic Dystrocryepts.—These soils have a weak
accumulation of amorphous materials. They are presumed to be
developing toward Spodosols, mainly Cryods, but are too
weakly developed to be classified as Spodosols. Spodic
Dystrocryepts are of small extent in the United States. They are
in the mountains of the Western States.
Ustic Dystrocryepts.—These soils are like Typic
Dystrocryepts, but they are dry in some part of the moisture
control section for 45 or more days (cumulative) in normal
years. They are considered to be transitional to Ustepts. Ustic
Dystrocryepts commonly support a sparse coniferous forest
with widely spaced trees or are used as rangeland. They are not
extensive in the United States.
Xeric Dystrocryepts.—These soils are like Typic
Dystrocryepts, but they have a xeric moisture regime. They are
considered to be transitional to Xerepts. Xeric Dystrocryepts
commonly support coniferous forest vegetation. Some of the
forests have widely spaced trees. Some of the soils are used as
rangeland. Xeric Dystrocryepts are not extensive in the United
States.
Eutrocryepts
These are the Cryepts that have free carbonates or have a
base saturation (by NH4
OAc) of 60 percent or more in some
horizon at a depth between 25 and 75 cm from the mineral soil
surface. The vegetation is mostly mixed conifers and
hardwoods or shrubs, grass, and widely spaced trees. Few of
the soils are used as cropland. Eutrocryepts formed mostly in
drift, alluvium, or colluvium or in solifluction deposits, mostly
late Pleistocene or Holocene in age. The soils commonly have a
thin, dark brownish ochric epipedon and a brownish cambic
horizon. Some have an umbric epipedon, and some have
bedrock within 100 cm of the surface. In the United States,
Inceptisols 515
these soils are of small extent in the high mountains of the West.
They also occur in other parts of the world, mostly in
mountainous areas.
Definition
Eutrocryepts are the Cryepts that:
1. Have free carbonates within the soils; or
2. Have a base saturation (by NH4
OAc) of 60 percent or more
in one or more horizons at a depth between 25 and 75 cm from
the mineral soil surface.
Key to Subgroups
KCAA. Eutrocryepts that have both:
1. An umbric or mollic epipedon; and
2. A lithic contact within 50 cm of the mineral soil
surface.
Humic Lithic Eutrocryepts
KCAB. Other Eutrocryepts that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Eutrocryepts
KCAC. Other Eutrocryepts that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm3
or less, measured at 33 kPa
water retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Eutrocryepts
KCAD. Other Eutrocryepts that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Eutrocryepts
KCAE. Other Eutrocryepts that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage).
Aquic Eutrocryepts
KCAF. Other Eutrocryepts that in normal years are saturated
with water in one or more layers within 100 cm of the mineral soil
surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Eutrocryepts
KCAG. Other Eutrocryepts that have lamellae (two or more)
within 200 cm of the mineral soil surface.
Lamellic Eutrocryepts
KCAH. Other Eutrocryepts that have a xeric moisture
regime.
Xeric Eutrocryepts
KCAI. Other Eutrocryepts that are dry in some part of the
moisture control section for 45 or more days (cumulative) in
normal years.
Ustic Eutrocryepts
KCAJ. Other Eutrocryepts that have an umbric or mollic
epipedon.
Humic Eutrocryepts
KCAK. Other Eutrocryepts.
Typic Eutrocryepts
Definition of Typic Eutrocryepts
Typic Eutrocryepts are the Eutrocryepts that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
3. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years;
4. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
516 Soil Taxonomy
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
5. Do not have lamellae (two or more) within 200 cm of the
mineral soil surface;
6. Have neither an umbric nor a mollic epipedon;
7. Do not have a xeric moisture regime; and
8. Are dry in some part of the moisture control section for
less than 45 days (cumulative) in normal years.
Description of Subgroups
Typic Eutrocryepts.—The central concept or Typic
subgroup of Eutrocryepts is fixed on deep, more or less freely
drained soils that have an ochric epipedon and that do not have
lamellae.
Soils that have lamellae in which silicate clay has
accumulated are excluded from the Typic subgroup because
they are considered to be intergrades to Alfisols. Shallow hard
rock is used to define the Lithic subgroup. Soils that have a
thin mantle or layer of materials that have some andic soil
properties are excluded from the Typic subgroup because they
are considered to be an intergrade to Andisols. A shallow water
table and redox depletions with low chroma indicate
intergrades to Aquepts. An umbric or mollic epipedon is not
considered typical and is used to define Humic and
combination Humic subgroups.
Typic Eutrocryepts are of large extent in the United States
and occur mostly in the mountains of the Western States and in
southern Alaska. The vegetation is mostly coniferous forest.
The soils are used mainly for timber production and wildlife
habitat.
Andic and Vitrandic Eutrocryepts.—These soils have, in
the upper 75 cm, a layer 18 cm or more thick that has some
andic soil properties or consists of fine pyroclastic materials.
This layer is most commonly at the mineral soil surface. Most
of these soils have an ochric or umbric epipedon and a cambic
horizon. Andic and Vitrandic Eutrocryepts are of very small
extent in the United States. They are mostly in the mountains
of the Western States. The vegetation is mostly coniferous
forest. The soils are used mainly for timber production and
wildlife habitat.
Aquic Eutrocryepts.—These soils have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage). In
addition, some of the soils have an umbric or mollic epipedon.
Aquic Eutrocryepts are of small extent in the United States.
They are mostly in Alaska, but a few are in the mountains of
the Western States. The vegetation is mostly coniferous forest.
The soils are used mainly for timber production and wildlife
habitat.
Humic Eutrocryepts.—These soils have an umbric or
mollic epipedon. They are of very small extent in the United
States. They are mostly in the mountains of the Western States.
The vegetation is mostly coniferous forest. The soils are used
mainly for timber production and wildlife habitat.
Humic Lithic Eutrocryepts.—These soils have an umbric
or mollic epipedon and a lithic contact within 50 cm of the soil
surface. They are of very small extent in the United States.
They are mostly in the mountains of the Western States. The
vegetation is mostly coniferous forest. The soils are used
mainly for timber production and wildlife habitat.
Lamellic Eutrocryepts.—These soils have two or more
lamellae. The upper boundary of the uppermost lamella is
within 75 cm of the soil surface, but others may be deeper.
Most of these soils have a coarse-loamy, coarse-silty, or loamyskeletal
particle-size class. Lamellic Eutrocryepts are of small
extent in the mountains of the Western United States. The
vegetation is mostly coniferous forest. The soils are used
mainly for timber production and wildlife habitat.
Lithic Eutrocryepts.—These soils have an ochric epipedon
and a lithic contact within 50 cm of the soil surface. They are
of moderate extent in the United States. They are mostly in the
mountains of the Western States. The vegetation is mostly
coniferous forest. The soils are used mainly for timber
production and wildlife habitat.
Oxyaquic Eutrocryepts.—These soils are saturated with
water in one or more layers within 100 cm of the mineral soil
surface for 20 consecutive days or 30 cumulative days in
normal years. The soils are of small extent in the United States.
They are mostly in Alaska and in the mountains of the Western
States. The vegetation is mostly coniferous forest. The soils are
used mainly for timber production and wildlife habitat.
Ustic Eutrocryepts.—These soils are like Typic
Eutrocryepts, but they are dry in some part of the moisture
control section for 45 or more days (cumulative) in normal
years. They are considered to be transitional to Ustepts. Ustic
Eutrocryepts commonly support a sparse coniferous forest with
widely spaced trees or are used as pasture. They are not
extensive in the United States.
Xeric Eutrocryepts.—These soils are like Typic
Eutrocryepts, but they have a xeric moisture regime. They are
considered to be transitional to Xerepts. Xeric Eutrocryepts
commonly support coniferous forest. Some of the forests have
widely spaced trees. Some of the soils are used as pasture.
Xeric Eutrocryepts are not extensive in the United States.
Udepts
Udepts are mainly the more or less freely drained Inceptisols
that have a udic or perudic moisture regime. They formed on
nearly level to steep surfaces, mostly of late-Pleistocene or
Holocene age. Some of the soils, in areas where the soil
Inceptisols 517
moisture regime is perudic, formed in older deposits. Most of the
soils had or now have a forest vegetation, but some support
shrubs or grasses. A few formed from Mollisols by truncation
of the mollic epipedon, mostly under cultivation. Most of the
soils have an ochric or umbric epipedon and a cambic horizon.
Some also have a sulfuric horizon, a fragipan, or a duripan.
The Udepts in the United States are most extensive in the
Appalachian Mountains, on the Allegheny Plateau, and on the
west coast.
Definition
Udepts are the Inceptisols that:
1. Have a udic moisture regime;
2. Do not have both aquic conditions and a histic epipedon,
the colors defined for Aquepts, or enough active ferrous iron to
give a positive reaction to alpha,alpha-dipyridyl at a time when
the soil is not being irrigated;
3. Do not have an exchangeable sodium percentage (ESP)
of 15 or more (or a sodium adsorption ratio [SAR] of 13 or
more) in half or more of the soil volume within 50 cm of the
mineral soil surface, an ESP (or SAR) below 50 cm that
decreases with increasing depth, and ground water within 100
cm of the mineral soil surface during some time of the year;
4. Have neither a plaggen nor an anthropic epipedon; and
5. Have a soil temperature regime warmer than cryic.
Key to Great Groups
KFA. Udepts that have a sulfuric horizon within 50 cm of the
mineral soil surface.
Sulfudepts, p. 530
KFB. Other Udepts that have a duripan that has its upper
boundary within 100 cm of the mineral soil surface.
Durudepts, p. 517
KFC. Other Udepts that have a fragipan with its upper
boundary within 100 cm of the mineral soil surface.
Fragiudepts, p. 529
KFD. Other Udepts that have one or both of the following:
1. Free carbonates within the soils; or
2. A base saturation (by NH4
OAc) of 60 percent or more
in one or more horizons at a depth between 25 and 75 cm
from the mineral soil surface.
Eutrudepts, p. 524
KFE. Other Udepts.
Dystrudepts, p. 518
Durudepts
These are the Udepts that have a duripan that has its upper
boundary within 100 cm of the soil surface. Most of the Udepts
in the United States occur in areas that have a Mediterranean
climate but that have high precipitation. Commonly, the soils
have a perched water table above the duripan for part of winter
or early spring. The vegetation commonly is coniferous forest.
These soils are of very small extent in the United States.
Definition
Durudepts are the Udepts that:
1. Have a duripan that has its upper boundary within 100 cm
of the soil surface; and
2. Do not have a sulfuric horizon within 50 cm of the mineral
soil surface.
Key to Subgroups
KFBA. Durudepts that have both:
1. In one or more horizons above the duripan and
within 60 cm of the mineral soil surface, distinct or
prominent redox concentrations and also aquic conditions
for some time in normal years (or artificial drainage); and
2. Throughout one or more horizons with a total thickness
of 18 cm or more, above the duripan and within 75 cm of
the mineral soil surface, one or more of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Durudepts
KFBB. Other Durudepts that have, throughout one or more
horizons with a total thickness of 18 cm or more, above the
duripan and within 75 cm of the mineral soil surface, a fineearth
fraction with both a bulk density of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and Al plus 1
/2 Fe
percentages (by ammonium oxalate) totaling more than 1.0.
Andic Durudepts
518 Soil Taxonomy
KFBC. Other Durudepts that have, throughout one or more
horizons with a total thickness of 18 cm or more, above the
duripan and within 75 cm of the mineral soil surface, one or
both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Durudepts
KFBD. Other Durudepts that have, in one or more horizons
above the duripan and within 30 cm of the mineral soil surface,
distinct or prominent redox concentrations and also aquic
conditions for some time in normal years (or artificial
drainage).
Aquic Durudepts
KFBE. Other Durudepts.
Typic Durudepts
Definition of Typic Durudepts
Typic Durudepts are the Durudepts that:
1. Do not have, in any horizon above the duripan and
within 30 cm of the mineral soil surface, distinct or
prominent redox concentrations and also aquic conditions;
and
2. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, any of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Description of Subgroups
Typic Durudepts.—These are the Durudepts that are free of
redoximorphic features and that do not have a layer near the
surface that has many of the properties of Andisols. Typic
Durudepts are of very small extent in the United States. The
native vegetation is mostly coniferous forest. The soils are used
mainly as forest, cropland, or homesites.
Andic and Vitrandic Durudepts.—These soils have a layer
near the surface that is 18 cm or more thick and that has many
of the properties of Andisols. Andic and Vitrandic Durudepts
are of very small extent in the United States and are mostly in
western Washington. The native vegetation is mostly
coniferous forest. These soils are used mainly as forest,
cropland, pasture, or homesites.
Aquandic Durudepts.—These soils have a layer near the
surface that is 18 cm or more thick and that has many of the
properties of Andisols. Aquandic Durudepts also have redox
concentrations and aquic conditions and are wetter than Typic
Durudepts. They are rare in the United States.
Aquic Durudepts.—These soils have redox concentrations
and aquic conditions and are wetter than Typic Durudepts.
Commonly, they also have gentler slopes. Aquic Durudepts are
rare in the United States.
Dystrudepts
These are the acid Udepts of humid and perhumid regions.
They developed mostly in late-Pleistocene or Holocene
deposits. Some developed on older, steeply sloping surfaces.
The parent materials generally are acid, moderately or weakly
consolidated sedimentary or metamorphic rocks or acid
sediments. A few of the soils formed in saprolite derived from
igneous rocks. The vegetation was mostly deciduous trees.
Most of the Dystrudepts that formed in alluvium are now
cultivated, and many of the other Dystrudepts are used as
pasture.
The normal horizon sequence in Dystrudepts is an ochric
epipedon over a cambic horizon. Some of the steeper
Dystrudepts have a shallow densic, lithic, or paralithic contact.
Dystrudepts are extensive in the United States. They are mostly
in the Eastern and Southern States.
Definition
Dystrudepts are the Udepts that:
1. Do not have free carbonates within the soils;
2. Have a base saturation of less than 60 percent (by
NH4
OAc) in all subhorizons between depths of 25 and 75 cm
below the soil surface;
3. Do not have a fragipan or duripan that has an upper
boundary within 100 cm of the mineral soil surface; and
4. Do not have a sulfuric horizon within 50 cm of the mineral
soil surface.
Inceptisols 519
KeytoSubgroups
KFEA. Dystrudepts that have both:
1. A lithic contact within 50 cm of the mineral soil surface;
and
2. An umbric or mollic epipedon.
Humic Lithic Dystrudepts
KFEB. Other Dystrudepts that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Dystrudepts
KFEC. Other Dystrudepts that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm
or a densic, lithic, or paralithic contact, whichever is
shallower.
Vertic Dystrudepts
KFED. Other Dystrudepts that have both:
1. In one or more horizons within 60 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface,
one or more of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Dystrudepts
KFEE. Other Dystrudepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Dystrudepts
KFEF. Other Dystrudepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Dystrudepts
KFEG. Other Dystrudepts that have both:
1. Fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm
of the mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm
or more thick; and
2. In one or more horizons within 60 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions in normal years (or artificial
drainage).
Fragiaquic Dystrudepts
KFEH. Other Dystrudepts that have a slope of less than 25
percent; and
1. In one or more horizons within 60 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. Either:
a. At a depth of 125 cm below the mineral soil surface,
an organic-carbon content (Holocene age) of 0.2 percent
or more and no densic, lithic, or paralithic contact within
that depth; or
b. An irregular decrease in organic-carbon content
520 Soil Taxonomy
(Holocene age) between a depth of 25 cm and either a
depth of 125 cm below the mineral soil surface or a
densic, lithic, or paralithic contact, whichever is
shallower.
Fluvaquentic Dystrudepts
KFEI. Other Dystrudepts that have both:
1. An umbric or mollic epipedon; and
2. In one or more horizons within 60 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Humic Dystrudepts
KFEJ. Other Dystrudepts that have, in one or more horizons
within 60 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Dystrudepts
KFEK. Other Dystrudepts that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Dystrudepts
KFEL. Other Dystrudepts that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Dystrudepts
KFEM. Other Dystrudepts that have lamellae (two or more)
within 200 cm of the mineral soil surface.
Lamellic Dystrudepts
KFEN. Other Dystrudepts that have both:
1. An umbric or mollic epipedon; and
2. A sandy particle-size class throughout the particle-size
control section.
Humic Psammentic Dystrudepts
KFEO. Other Dystrudepts that have a slope of less than 25
percent; and
1. An umbric or mollic epipedon; and
2. Either:
a. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of 0.2 percent or
more and no densic, lithic, or paralithic contact within that
depth; or
b. An irregular decrease in organic-carbon content
(Holocene age) between a depth of 25 cm and either a
depth of 125 cm below the mineral soil surface or a
densic, lithic, or paralithic contact, whichever is
shallower.
Fluventic Humic Dystrudepts
KFEP. Other Dystrudepts that have a slope of less than 25
percent; and either
1. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of 0.2 percent or
more and no densic, lithic, or paralithic contact within that
depth; or
2. An irregular decrease in organic-carbon content
(Holocene age) between a depth of 25 cm and either a depth
of 125 cm below the mineral soil surface or a densic, lithic,
or paralithic contact, whichever is shallower.
Fluventic Dystrudepts
KEEQ. Other Dystrudepts that have a horizon 5 cm or more
thick that has one or more of the following:
1. In 25 percent or more of each pedon, cementation by
organic matter and aluminum, with or without iron; or
2. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
3. An ODOE value of 0.12 or more, and a value half as
high or lower in an overlying horizon.
Spodic Dystrudepts
KFER. Other Dystrudepts that have in 50 percent or more of
the soil volume between a depth of 25 cm from the mineral soil
surface and either a depth of 100 cm or a densic, lithic, or
paralithic contact if shallower:
1. A CEC (by 1N NH4
OAc pH 7) of less than 24 cmol(+)
per kg clay; or
2. Both a ratio of measured clay in the fine-earth fraction
to percent water retained at 1500 kPa tension of 0.6 or more
and the following: the CEC (by 1N NH4
OAc pH 7) divided
by the product of three times [percent water retained at 1500
kPa tension minus percent organic carbon (but no more than
1.00)] is less than 24.
Oxic Dystrudepts
Inceptisols 521
KFES. Other Dystrudepts that have an umbric or mollic
epipedon that is 50 cm or more thick.
Humic Pachic Dystrudepts
KFET. Other Dystrudepts that have an umbric or mollic
epipedon.
Humic Dystrudepts
KFEU. Other Dystrudepts that have both:
1. In each pedon a cambic horizon that includes 10 to 50
percent (by volume) illuvial parts that otherwise meet the
requirements for an argillic, kandic, or natric horizon; and
2. A base saturation (by sum of cations) of 35 percent or
more either at a depth of 125 cm from the top of the cambic
horizon or directly above a densic, lithic, or paralithic
contact if shallower.
Ruptic-Alfic Dystrudepts
KFEV. Other Dystrudepts that have in each pedon a cambic
horizon that includes 10 to 50 percent (by volume) illuvial
parts that otherwise meet the requirements for an argillic,
kandic, or natric horizon.
Ruptic-Ultic Dystrudepts
KFEW. Other Dystrudepts.
Typic Dystrudepts
Definition of Typic Dystrudepts
Typic Dystrudepts are the Dystrudepts that:
1. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
2. Do not have, in any horizon within 60 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
3. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years;
4. Have a slope of 25 percent or more; or
a. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of less than 0.2
percent or a densic, lithic, or paralithic contact within that
depth; or
b. A regular decrease in organic-carbon content (Holocene
age) between a depth of 25 cm and either a depth of 125 cm
below the mineral soil surface or a densic, lithic, or
paralithic contact, whichever is shallower;
5. Do not have a lithic contact within 50 cm of the mineral
soil surface;
6. Do not have a cambic horizon that includes 10 to 50
percent (by volume) illuvial parts that otherwise meet the
requirements for an argillic, kandic, or natric horizon;
7. Do not have an umbric or mollic epipedon;
8. Do not have lamellae (two or more) within 200 cm of the
soil surface;
9. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick;
10. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
and
11. Do not have, in 50 percent or more of the soil volume
between a depth of 25 cm from the mineral soil surface and
either a depth of 100 cm or a densic, lithic, or paralithic
contact if shallower, either:
a. A CEC (by 1N NH4
OAc pH 7) of less than 24 cmol(+)
per kg clay; or
522 Soil Taxonomy
b. Both a ratio of measured clay in the fine-earth fraction to
percent water retained at 1500 kPa tension of 0.6 or more and
the following: the CEC (by 1N NH4
OAc pH 7) divided by the
product of three times [percent water retained at 1500 kPa
tension minus percent organic carbon (but no more than
1.00)] is less than 24.
Description of Subgroups
Typic Dystrudepts.—The central concept or Typic
subgroup of Dystrudepts is fixed on soils that are moderately
deep or deep to hard rock, are freely drained and acid, have an
ochric epipedon, and do not have any intermittent argillic,
natric, or kandic horizon. In addition, the percentage of
organic carbon of Holocene age decreases regularly with
increasing depth and is very low at a depth of 125 cm.
Soils that have slickensides, wedge-shaped aggregates, a
high linear extensibility, or wide cracks are assigned to the
Vertic subgroup because these properties are shared with
Vertisols. If the percentage of carbon is relatively high at a
depth of 125 cm or if the percentage decreases irregularly with
increasing depth and slopes are gentle, the parent material
normally is recent Holocene alluvium. The soils that formed in
this alluvium are considered intergrades to Fluvents or to
Fluvaquents if the soils are also wet. A shallow water table and
redox depletions with low chroma indicate intergrades to
Aquepts. An intermittent argillic, natric, or kandic horizon is
considered evidence that the soil is developing toward Alfisols
or Ultisols, depending on the base saturation. A lithic contact
within a depth of 50 cm is the basis for defining the Lithic
subgroup. The presence of an umbric or mollic epipedon is
used to define Humic and combination Humic subgroups. Soils
that have a thin mantle or layer that has some andic soil
properties are excluded from the Typic subgroup because they
are considered to be an intergrade to Andisols. Soils with a low
CEC in the clay fraction are considered intergrades to Oxisols.
Typic Dystrudepts are extensive in the United States. They
are widely distributed. The largest concentration is in the
Northeastern States. The native vegetation consists mostly of
mixed forest. Most of these soils are used as forest. Many of the
less sloping soils have been cleared and are used as cropland or
pasture.
Andic and Vitrandic Dystrudepts.—These soils have some
andic soil properties in a layer in the upper part that is 18 cm
or more thick. Some of the soils contain a significant amount
of volcanic ash. Some have an umbric epipedon. Andic and
Vitrandic Dystrudepts are moderately extensive in the
Northwestern United States. The native vegetation consists
mostly of coniferous forest. Most of these soils support their
native vegetation and are used as forest. A few of the less
sloping soils have been cleared and are used as cropland or
pasture.
Aquandic Dystrudepts.—These soils have aquic conditions
and redox depletions with low chroma in the upper part of the
subsoil. They also have some andic soil properties in a layer in
the upper part that is 18 cm or more thick. Some of these soils
contain a significant amount of volcanic ash, and some have an
umbric epipedon. Ground water commonly is present in the
soils only during winter. These soils have gentle slopes. They
are of small extent in the United States and are mostly in the
State of Washington. The native vegetation consists mostly of
coniferous forest. Most of these soils support native vegetation
and are used as forest. Some have been cleared and are used as
pasture or cropland.
Aquic Dystrudepts.—These soils have redox depletions
with low chroma in a brownish or reddish matrix in the
subsoil. Most of the soils also have redox concentrations with
high chroma. Ground water commonly is present only during
wet periods. Most of the Aquic Dystrudepts in the United
States formed in late-Pleistocene sediments and have gentle
slopes. Some of the soils have an umbric epipedon. Aquic
Dystrudepts are moderately extensive in the United States.
They are widely distributed. The largest concentration is in the
Northeastern States. The native vegetation consists mostly of
mixed forest. Many of these soils have been cleared and are
used as cropland or pasture, and many are used as forest.
Aquic Humic Dystrudepts.—These soils have redox
depletions with low chroma in a brownish or reddish matrix in
the subsoil and have an umbric or mollic epipedon. Most also
have redox concentrations with high chroma. Most of the
Aquic Humic Dystrudepts in the United States formed in latePleistocene
sediments and have gentle slopes. Ground water
commonly is present only during wet periods unless the soils
are artificially drained. The native vegetation consists mostly
of mixed forest. Many of these soils are used as forest, and
many have been cleared and are used as cropland or pasture.
Fluvaquentic Dystrudepts.—These soils have redox
depletions with low chroma in a brownish matrix. They formed
in Holocene or recent alluvium. They are on flood plains along
rivers draining regions that have acid soils. During wet periods
ground water is present in the redox-depleted zone unless the
soils have been drained. Most of these soils are subject to
occasional flooding, but they receive little fresh sediment.
Some of the soils have an umbric epipedon. Fluvaquentic
Dystrudepts are moderately extensive in the United States.
They are widely distributed. The largest concentration is in the
Northeastern States. The native vegetation consists mostly of
mixed forest. Many of these soils have been cleared and are
used as cropland or pasture, and some are used as forest.
Fluventic Dystrudepts.—These soils are on flood plains
along rivers draining regions that have acid soils. They formed
in Holocene or recent alluvium. They are subject to occasional
flooding but receive little fresh alluvium. Fluventic Dystrudepts
are moderately extensive in the United States. They are widely
distributed. The largest concentration is in the Northeastern
States. The native vegetation consists mostly of mixed forest.
Most of these soils have been cleared and are used as cropland.
Some are used as pasture and some as forest.
Fluventic Humic Dystrudepts.—These soils are on flood
Inceptisols 523
plains along rivers draining regions that have acid soils. They
have an umbric or mollic epipedon and formed in Holocene or
recent alluvium. These soils are subject to occasional flooding
but receive little fresh alluvium. Fluventic Humic Dystrudepts
are of small extent in the United States. They are in Oregon
and the Nashville Basin and Appalachian valleys in the United
States. The native vegetation consists mostly of mixed forest.
Most of these soils have been cleared and are used as
intensively cultivated cropland. Some are used as pasture and
some as forest.
Fragiaquic Dystrudepts.—These soils are like Typic
Dystrudepts, but they have, at a shallow depth, redox
depletions with low chroma and also aquic conditions for some
time in normal years. In addition, they have fragic soil
properties in 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm of the
mineral soil surface or in 60 percent or more of the volume of a
layer 15 cm or more thick anywhere in the soils. These soils
are permitted to have a mollic or umbric epipedon. They are
considered intergrades to Fraqiaquepts. They are not extensive
in the United States.
Fragic Dystrudepts.—These soils have fragic soil
properties in 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm of the
mineral soil surface or in 60 percent or more of the volume of a
layer 15 cm or more thick anywhere in the soils. These soils
are considered intergrades to Fragiudepts. They are not
extensive in the United States.
Humic Dystrudepts.—These soils have an umbric or mollic
epipedon that is less than 50 cm thick. They are otherwise like
the soils of the Typic subgroup. Humic Dystrudepts are
moderately extensive in the United States. They are widely
distributed but are concentrated in the mountains of the
Eastern and Northwestern States. The native vegetation
consists mostly of mixed forest. Most of these soils are used as
forest. Many of the less sloping soils have been cleared and are
used as cropland or pasture.
Humic Lithic Dystrudepts.—These soils have a lithic
contact at a shallow depth and have an umbric or mollic
epipedon. They formed mostly in acid sedimentary or
metamorphic rocks. Most of the soils have moderate to steep
slopes. Humic Lithic Dystrudepts are moderately extensive in
the United States. They are widely distributed. The largest
concentration is in the Northwestern States. The native
vegetation consists mostly of coniferous forest. Most of these
soils are used as forest. Some of the less sloping soils have been
cleared and are used as pasture.
Humic Pachic Dystrudepts.—These soils have an umbric
or mollic epipedon 50 cm or more thick. They are otherwise
like the soils of the Typic subgroup. Humic Pachic Dystrudepts
are of small extent in the United States. They are widely
distributed but are concentrated in the mountains of the
Eastern and Northwestern States. The native vegetation
consists mostly of mixed forest. Most of these soils are used as
forest. Many of the less sloping soils have been cleared and are
used as cropland or pasture.
Humic Psammentic Dystrudepts.—These soils have an
umbric or mollic epipedon and a sandy particle-size class
throughout all layers at a depth between 25 and 100 cm below
the mineral soil surface. The soils are of small extent in the
United States. The native vegetation consists mostly of forest.
Most of these soils are used as forest. Some of the less sloping
soils have been cleared and are used as cropland or pasture.
Lamellic Dystrudepts.—These soils are like Typic
Dystrudepts, but they have two or more lamellae. They are not
extensive in the United States.
Lithic Dystrudepts.—These soils are like Typic
Dystrudepts, but they have a lithic contact at a shallow depth.
They formed mostly in acid sedimentary or metamorphic rocks.
Most of the soils have moderate to steep slopes. Lithic
Dystrudepts are extensive in the United States. They are widely
distributed. The largest concentration is in the Northeastern
States. The native vegetation consists mostly of mixed forest.
Most of these soils are used as forest. Some of the less sloping
soils have been cleared and are used as pasture.
Oxic Dystrudepts.—These soils have clays with a low
cation-exchange capacity dominant in the particle-size control
section. They are considered intergrades to Oxisols. Oxic
Dystrudepts are not extensive in the United States.
Oxyaquic Dystrudepts.—These soils are saturated with
water within 100 cm of the mineral soil surface for 20 or more
consecutive days or 30 or more cumulative days in normal
years. The soils are moderately extensive in the United States.
They are considered intergrades to Aquepts. Slopes are gentle.
Many Oxyaquic Dystrudepts have been cleared and are used as
cropland or pasture. Some are used as forest.
Ruptic-Alfic Dystrudepts.—These soils have a cambic
horizon that includes 10 to 50 percent (by volume) illuvial
parts that otherwise meet the requirements for an argillic,
natric, or kandic horizon, and they have a base saturation of 35
percent or more at a depth of 125 cm below the top of the
argillic horizon or directly above a densic, lithic, or paralithic
contact if one is shallower than that depth. Most of these soils
are strongly sloping to steeply sloping, and in most of them the
depth to rock is less than 125 cm. The soils are of very small
extent in the United States.
Ruptic-Ultic Dystrudepts.—These soils have a cambic
horizon that includes 10 to 50 percent (by volume) illuvial
parts that otherwise meet the requirements for an argillic,
natric, or kandic horizon. Most of the soils are shallow over
weakly consolidated sedimentary rock. Generally, the illuvial
part of the cambic horizon is where the rock is deepest. The
base saturation is less than 35 percent. The native vegetation is
mostly hardwood forest. These soils generally are steeply
sloping, and they are used as forest or pasture. They are of
small extent in the United States.
Spodic Dystrudepts.—These soils have a weak
accumulation of amorphous materials. They are presumed to be
524 Soil Taxonomy
developing toward Spodosols, mainly Orthods, but are too
weakly developed to be classified as Spodosols. Spodic
Dystrudepts are of moderate extent in the United States. They
are mainly in the Northeastern States.
Vertic Dystrudepts.—These soils are high in expanding clays
and have cracks 5 mm or more wide, slickensides, wedge-shaped
aggregates, or a linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact, whichever is shallower. The soils are
considered to be transitional to Vertisols. They are of very small
extent in the United States.
Eutrudepts
These are the base-rich Udepts of humid regions. Many
developed in Holocene or late-Pleistocene deposits. Some of the
soils that have steep slopes formed in older deposits. The
parent materials commonly are calcareous sediments or basic
sedimentary rocks. The vegetation was mostly deciduous
hardwoods, but the gently sloping soils are now cultivated and
many of the steeply sloping soils are used as pasture.
Eutrudepts are not extensive in the United States.
Definition
Eutrudepts are the Udepts that:
1. Have one or both of the following:
a. Free carbonates within the soils; or
b. A base saturation of 60 percent or more (by NH4
OAc) in
some subhorizon that is between depths of 25 and 75 cm
below the mineral soil surface;
2. Do not have a fragipan or duripan with its upper boundary
within 100 cm of the mineral soil surface; and
3. Do not have a sulfuric horizon with its upper boundary
within 50 cm of the mineral soil surface.
Key to Subgroups
KFDA. Eutrudepts that have both:
1. An umbric or mollic epipedon; and
2. A lithic contact within 50 cm of the mineral soil
surface.
Humic Lithic Eutrudepts
KFDB. Other Eutrudepts that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Eutrudepts
KFDC. Other Eutrudepts that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. In one or more horizons within 60 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage).
Aquertic Eutrudepts
KFDD. Other Eutrudepts that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Eutrudepts
KFDE. Other Eutrudepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Eutrudepts
KFDF. Other Eutrudepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Eutrudepts
Inceptisols 525
KFDG. Other Eutrudepts that have anthraquic conditions.
Anthraquic Eutrudepts
KFDH. Other Eutrudepts that have both:
1. Fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm
of the mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm
or more thick; and
2. In one or more horizons within 60 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions in normal years (or artificial
drainage).
Fragiaquic Eutrudepts
KFDI. Other Eutrudepts that have a slope of less than 25
percent; and
1. In one or more horizons within 60 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. Either:
a. At a depth of 125 cm below the mineral soil surface,
an organic-carbon content (Holocene age) of 0.2 percent
or more and no densic, lithic, or paralithic contact within
that depth; or
b. An irregular decrease in organic-carbon content
(Holocene age) between a depth of 25 cm and either a
depth of 125 cm below the mineral soil surface or a
densic, lithic, or paralithic contact, whichever is
shallower.
Fluvaquentic Eutrudepts
KFDJ. Other Eutrudepts that:
1. Have, in one or more horizons within 60 cm of the
mineral soil surface, redox depletions with chroma of 2 or
less and also aquic conditions for some time in normal years
(or artificial drainage); and
2. Do not have free carbonates throughout any horizon
within 100 cm of the mineral soil surface.
Aquic Dystric Eutrudepts
KFDK. Other Eutrudepts that have, in one or more horizons
within 60 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Eutrudepts
KFDL. Other Eutrudepts that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Eutrudepts
KFDM. Other Eutrudepts that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Eutrudepts
KFDN. Other Eutrudepts that have lamellae (two or more)
within 200 cm of the mineral soil surface.
Lamellic Eutrudepts
KFDO. Other Eutrudepts that have a slope of less than 25
percent; and
1. Do not have free carbonates throughout any horizon
within 100 cm of the mineral soil surface; and either
2. Have, at a depth of 125 cm below the mineral soil
surface, an organic-carbon content (Holocene age) of 0.2
percent or more and no densic, lithic, or paralithic contact
within that depth; or
3. Have an irregular decrease in organic-carbon content
(Holocene age) between a depth of 25 cm and either a depth
of 125 cm below the mineral soil surface or a densic, lithic,
or paralithic contact, whichever is shallower.
Dystric Fluventic Eutrudepts
KFDP. Other Eutrudepts that have a slope of less than 25
percent; and either
1. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of 0.2 percent or
more and no densic, lithic, or paralithic contact within that
depth; or
2. An irregular decrease in organic-carbon content
(Holocene Age) between a depth of 25 cm and either a depth
of 125 cm below the mineral soil surface or a densic, lithic,
or paralithic contact, whichever is shallower.
Fluventic Eutrudepts
KFDQ. Other Eutrudepts that have a sandy or sandy-skeletal
particle-size class in all horizons within 50 cm of the mineral
soil surface.
Arenic Eutrudepts
526 Soil Taxonomy
KFDR. Other Eutrudepts that do not have free carbonates
throughout any horizon within 100 cm of the mineral soil
surface.
Dystric Eutrudepts
KFDS. Other Eutrudepts that have 40 percent or more free
carbonates, including coarse fragments as much as 75 mm in
diameter, in all horizons between the top of the cambic horizon
and either a depth of 100 cm from the mineral soil surface or a
densic, lithic, or paralithic contact if shallower.
Rendollic Eutrudepts
KFDT. Other Eutrudepts that have an umbric or mollic
epipedon.
Humic Eutrudepts
KFDU. Other Eutrudepts that have a cambic horizon that
includes 10 to 50 percent (by volume) illuvial parts that
otherwise meet the requirements for an argillic, kandic, or
natric horizon.
Ruptic-Alfic Eutrudepts
KFDV. Other Eutrudepts.
Typic Eutrudepts
Definition of Typic Eutrudepts
Typic Eutrudepts are the Eutrudepts that:
1. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
2. Do not have, in any horizon within 60 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
3. Do not have anthraquic conditions;
4. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30 or
more cumulative days in normal years;
5. Have a texture of very fine sand or finer within 50 cm of the
soil surface;
6. Have free carbonates within 100 cm of the mineral soil
surface in some part of each pedon;
7. Have a slope of 25 percent or more or one or both of the
following:
a. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of less then 0.2
percent and no densic, lithic, or paralithic contact within
that depth; or
b. A regular decrease in organic-carbon content (Holocene
age) between a depth of 25 cm and either a depth of 125 cm
below the mineral soil surface or a densic, lithic, or
paralithic contact, whichever is shallower;
8. Do not have a lithic contact within 50 cm of the soil
surface;
9. Do not have a cambic horizon that includes 10 to 50
percent (by volume) illuvial parts that otherwise meet the
requirements for an argillic, kandic, or natric horizon;
10. Have neither an umbric nor a mollic epipedon;
11. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm or
a densic, lithic, or paralithic contact, whichever is
shallower;
12. Have less than 40 percent free carbonates, including
coarse fragments as much as 75 mm in diameter, in and below
the cambic horizon but above a densic, lithic, or paralithic
contact and above a depth of 100 cm from the mineral soil
surface;
13. Do not have lamellae (two or more) within 200 cm of the
soil surface; and
14. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick.
Inceptisols 527
Description of Subgroups
Typic Eutrudepts.—The central concept or Typic subgroup
of Eutrudepts is fixed on deep, more or less freely drained,
loamy or clayey soils that have an ochric epipedon and some
free carbonates, but not a large amount, within 100 cm of the
soil surface.
Soils that have a thin mantle or layer that has some andic
soil properties are excluded from the Typic subgroup because
they are considered to be an intergrade to Andisols. Soils that
have redox depletions with low chroma accompanied by
ground water at some time of the year or by artificial drainage
are excluded because they are intergrades to Aquepts. A surface
mantle of sand or loamy sand more than 50 cm thick is the
basis for defining the Arenic extragrade, a convention used in
many other taxa. Typic Eutrudepts have free carbonates above
a depth of 100 cm from the mineral soil surface. The absence
of free carbonates is used to define intergrades to Dystrudepts,
and the presence of 40 percent or more free carbonates
indicates a transition to Haprendolls. An irregular decrease in
content of organic carbon (Holocene age) with increasing depth
or a relatively high percentage in the deep layers is the basis
for defining intergrades to Fluvents or, if the soils are
periodically saturated with water, to Fluvaquents. A lithic
contact shallower than 50 cm defines the Lithic subgroup, a
convention used throughout this taxonomy. A cambic horizon
that includes 10 to 50 percent illuvial parts that otherwise meet
the requirements for an argillic, kandic, or natric horizon
indicates development toward Alfisols and defines the RupticAlfic
subgroup. A high content of swelling clays accompanied
by deep cracks indicates intergrades to Vertisols. An umbric or
mollic epipedon is not considered typical and is used to define
Humic and combination Humic subgroups.
Typic Eutrudepts are of moderate extent in the United
States. They are widely distributed. The native vegetation
consists mostly of hardwood or mixed forest. Most of the
strongly sloping soils are used as forest. Many of the less
sloping soils have been cleared and are used as cropland or
pasture.
Andic and Vitrandic Eutrudepts.—These soils have some
andic soil properties in a layer 18 cm or more thick in the
upper part. In some of the soils, this layer was derived at least
in part from pyroclastic materials. Andic and Vitrandic
Eutrudepts are of small extent in the United States. They are
known to occur only in western Montana. The native
vegetation consists of coniferous forest. Most of these soils are
used as forest.
Anthraquic Eutrudepts.—These soils have been irrigated
for the production of paddy rice for many years and have
developed anthraquic conditions. They are permitted, but not
required, to have redox depletions with chroma of 2 or less in
layers that in normal years also have aquic conditions within
75 cm of the mineral soil surface. These soils have level or
nearly level slopes. They are not extensive and are not known to
occur in the United States.
Aquertic Eutrudepts.—These soils have redox depletions
with low chroma within 60 cm of the soil surface and either are
artificially drained or are saturated with water within the
redox-depleted zone at some time of the year. They have a high
COLE and do not have a densic, lithic, or paralithic contact
within 50 cm of the soil surface. These soils are not known to
occur in the United States.
Aquic Dystric Eutrudepts.—These soils have redox
depletions with low chroma above a depth of 60 cm and either
are artificially drained or are saturated with water in the redoxdepleted
zone at some time of the year, usually in winter or
spring. In addition, they have no free carbonates to a depth of
100 cm below the mineral soil surface. These soils are of
moderate extent in the United States. Most formed in latePleistocene
or Holocene sediments and are in the north-central
and northeastern parts of the United States. The native
vegetation consisted of forest. Most of these soils are nearly
level and have been cleared and are used as cropland or
pasture.
Aquic Eutrudepts.—These soils have redox depletions with
low chroma within 60 cm of the soil surface and either are
artificially drained or are saturated with water within the
redox-depleted zone at some time of the year, usually in winter
or spring. The soils are of small extent in the United States.
Most formed in late-Pleistocene sediments and are in the
Northeastern United States. The native vegetation consisted of
forest. Most of these soils are nearly level and have been
cleared and are used as cropland or pasture.
Arenic Eutrudepts.—These soils have a surface mantle of
sand or loamy sand that is more than 50 cm thick and is
underlain by a cambic horizon. In the United States, they
formed in late-Pleistocene sediments and have gentle or
moderate slopes. These soils are of very small extent in the
United States and are known to occur only in Michigan. The
native vegetation consists of mixed forest. Most of these soils
are used as forest.
Dystric Eutrudepts.—These soils have no free carbonates
above a depth of 100 cm from the mineral soil surface. In the
United States, they formed mostly in late-Pleistocene or
Holocene sediments. Some of the soils that have steep slopes
formed in older deposits. Dystric Eutrudepts are moderately
extensive in the United States. They are widely distributed. The
largest concentration is in the Northeastern States. The native
vegetation consists mostly of mixed forest. Most of these soils
are used as forest. Most of the less sloping soils have been
cleared and are used as cropland or pasture.
Dystric Fluventic Eutrudepts.—These soils formed in
alluvium on flood plains along streams and rivers. They do not
have free carbonates above a depth of 100 cm from the mineral
soil surface. They are subject to occasional overflow but receive
little fresh sediment. These soils are of moderate extent in the
528 Soil Taxonomy
Eastern United States. The native vegetation consists mostly of
forest. Most of these soils have been cleared and are used as
cropland. Some are used as pasture and some as forest.
Fluvaquentic Eutrudepts.—These soils formed mostly in
Holocene alluvium along streams. They have redox depletions
with low chroma within the upper 60 cm, and they either are
artificially drained or are saturated with water at some time of
the year, mostly when the streams are at flood stage. The soils
are subject to occasional overflow but receive little fresh
sediment. They are of moderate extent in the Eastern United
States. The native vegetation consisted mostly of forest. Nearly
all of the Fluvaquentic Eutrudepts in the United States have
been cleared and are used as cropland.
Fluventic Eutrudepts.—These soils formed in alluvium on
flood plains along streams and rivers. The content of organic
carbon (Holocene age) decreases irregularly with increasing
depth or is relatively high at a depth of 125 cm. The soils have
some free carbonates above a depth of 100 cm from the mineral
soil surface. Most are nearly level. These soils are of small
extent in the Eastern United States. The native vegetation
consisted mostly of forest. Nearly all of the Fluventic
Eutrudepts in the United States have been cleared and are used
as cropland.
Fragiaquic Eutrudepts.—These soils have, at a shallow
depth, redox depletions with low chroma and also aquic
conditions for some time in normal years. In addition, they
have fragic soil properties in 30 percent or more of the volume
of a layer 15 cm or more thick that has its upper boundary
within 100 cm of the mineral soil surface or in 60 percent or
more of the volume of a layer 15 cm or more thick anywhere in
the soils. These soils are considered intergrades to
Fraqiaquepts. They are not extensive in the United States.
Fragic Eutrudepts.—These soils have fragic soil properties
in 30 percent or more of the volume of a layer 15 cm or more
thick that has its upper boundary within 100 cm of the mineral
soil surface or in 60 percent or more of the volume of a layer
15 cm or more thick anywhere in the soils. The soils are
considered intergrades to Fraqiudepts. They are not extensive
in the United States.
Humic Eutrudepts.—These soils have an umbric or mollic
epipedon but are otherwise like Typic Eutrudepts. Humic
Eutrudepts are of moderate extent in the United States. They
are widely distributed. The largest concentration is in the
Northwestern States. The native vegetation consists mostly of
coniferous forest. Most of these soils are used as forest. A few
of the less sloping soils have been cleared and are used as
cropland or pasture.
Humic Lithic Eutrudepts.—These soils have an umbric or
mollic epipedon and a lithic contact within 50 cm of the
mineral soil surface. They are of small extent in the United
States. They are widely distributed. The largest concentration
is in the Eastern States. The native vegetation consists mostly
of mixed forest. Most of these soils are used as forest. A few of
the less sloping soils have been cleared and are used as pasture.
Lamellic Eutrudepts.—These soils have two or more lamellae
within 200 cm of the mineral soil surface. They are not extensive
in the United States.
Lithic Eutrudepts.—These soils have an ochric epipedon
and a lithic contact within 50 cm of the mineral soil surface.
They are of small extent in the United States. They are widely
distributed. The largest concentration is in the Northeastern
States. The native vegetation consists mostly of mixed forest.
Most of these soils are used as forest. A few of the less sloping
soils have been cleared and are used as pasture.
Oxyaquic Eutrudepts.—These soils are saturated with
water within 100 cm of the mineral soil surface for 20 or more
consecutive days or 30 or more cumulative days in normal
years. They are of small extent in the United States. They are
considered intergrades to Aquepts. Slopes are gentle. Many
Oxyaquic Eutrudepts have been cleared and are used as
cropland or pasture. Some are used as forest.
Rendollic Eutrudepts.—These soils formed in marl, chalk,
shattered limestone, or shattered dolomite. They have more
than 40 percent calcium carbonate equivalent in some part
above 100 cm from the mineral soil surface. Fragments more
than 75 mm in diameter and solid limestone are excluded when
the content of carbonates is determined. These soils are
considered to be intergrades to Rendolls, and some of them
have developed from Haprendolls. Rendollic Eutrudepts are of
small extent in the United States. The native vegetation
consisted mostly of trees and grasses. Most the Rendollic
Eutrudepts in the United States have been cleared and are used
as hayland or pasture. Some of the soils, mostly the steeper
ones, are used as forest.
Ruptic-Alfic Eutrudepts.—These soils have a cambic
horizon that includes 10 to 50 percent illuvial parts that
otherwise meet the requirements for an argillic, kandic, or
natric horizon. The soils are moderately sloping or strongly
sloping and are shallow over calcareous, weakly consolidated
sedimentary rock or fractured limestone. The illuvial parts of
the cambic horizon are generally in the parts of the pedon
where the depth to rock is greatest. These soils are of small
extent in the United States. The native vegetation consisted
mostly of hardwood forest. Most of the Ruptic-Alfic Eutrudepts
in the United States have been cleared and are used as hayland
or pasture. Some of the soils, mostly the steeper ones, are used
as forest.
Vertic Eutrudepts.—These soils have a high COLE and do
not have a densic, lithic, or paralithic contact within 50 cm of
the soil surface. Most of the soils have gentle or moderate
slopes. Vertic Eutrudepts are of small extent in the United
States. The native vegetation consisted mostly of forest. Most
of the Vertic Eutrudepts in the United States have been cleared
and are used as cropland or pasture. Some are used as forest.
Inceptisols 529
Fragiudepts
These are the Udepts that have a fragipan within 100 cm of
the mineral soil surface. They do not have a sulfuric horizon
within 50 cm of the mineral soil surface. Commonly, they have
a brownish cambic horizon that is underlain, at a depth of
about 50 cm, by a fragipan. Most Fragiudepts have perched
water above the pan at some time of the year, and few roots
penetrate the pan. Consequently, plants tend to have shallow
root systems. Many Fragiudepts formed in late-Pleistocene or
Holocene deposits on gentle or moderate slopes. Some are
strongly sloping. The parent materials of most Fragiudepts are
loamy and either are acid or have only a small amount of free
carbonates. A few of the materials are sandy and have an
appreciable amount of fine sand and very fine sand. Most of
the Fragiudepts in the United States are in the Northeastern
States and the States bordering the Mississippi and Ohio
Rivers. A few are in the northern Lake States, and some are in
the humid parts of the Northwestern States. These soils are
extensive.
Definition
Fragiudepts are the Udepts that:
1. Have a fragipan within 100 cm of the mineral soil surface;
2. Do not have a sulfuric horizon within 50 cm of the mineral
soil surface; and
3. Do not have a duripan within 100 cm of the mineral soil
surface.
Key to Subgroups
KFCA. Fragiudepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Fragiudepts
KFCB. Other Fragiudepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is equal
to 30 or more.
VitrandicFragiudepts
KFCC. Other Fragiudepts that have, in one or more horizons
within 30 cm of the mineral soil surface, distinct or prominent
redox concentrations and also aquic conditions for some time
in normal years (or artificial drainage).
Aquic Fragiudepts
KFCD. Other Fragiudepts that have an umbric or mollic
epipedon.
Humic Fragiudepts
KFCE. Other Fragiudepts.
Typic Fragiudepts
Definition of Typic Fragiudepts
Typic Fragiudepts are the Fragiudepts that:
1. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
2. Do not have, in any horizon within 30 cm of the mineral
soil surface, distinct or prominent redox concentrations and
also aquic conditions; and
3. Do not have an umbric or mollic epipedon.
Description of Subgroups
Typic Fragiudepts.—The central concept or Typic
subgroup of Fragiudepts is fixed on soils that are free of
distinct or prominent redox concentrations in the upper 30 cm,
that have an ochric epipedon, and that do not have some andic
soil properties in a layer near the surface that is as thick as 18
cm.
530 Soil Taxonomy
A mantle of materials with andic soil properties between 18
and 35 cm thick indicates an intergrade to Andisols. Most
Typic Fragiudepts have perched ground water above the pan at
some time of the year. Shallow redox concentrations indicate
intergrades to Fragiaquepts and is the basis for defining the
Aquic subgroup.
Typic Fragiudepts are moderately extensive in the United
States. They occur mostly in the Northeastern States. The
native vegetation consists of mixed forest. Most of the less
sloping soils have been cleared and are used as cropland or
pasture. Some of the soils, mostly the steeper ones, are used as
forest.
Andic and Vitrandic Fragiudepts.—These soils have some
andic soil properties in a layer near the surface that is 18 cm or
more thick. This layer has many of the properties of Andisols.
Andic and Vitrandic Fragiudepts are not extensive and are not
known to occur in the United States.
Aquic Fragiudepts.—These soils have, at a shallow depth,
redox concentrations of medium or high contrast and are
somewhat wetter than Typic Fragiudepts. Commonly, they also
have gentler slopes. Aquic Fragiudepts are of small extent in
the United States. Most formed in late-Pleistocene sediments
and are in the Northeastern States. The native vegetation
consisted of forest. Most of these soils are nearly level and have
been cleared and are used as cropland or pasture.
Humic Fragiudepts.—These soils are like Typic Fragiudepts,
but they have a mollic or umbric epipedon. They are not
extensive and are rare in the United States.
Sulfudepts
These are extremely acid soils that formed in sulfidic materials
that have been exposed to aerobic conditions, mainly as a result
of surface mining, road construction, dredging, or other earthmoving
operations. These soils are of small extent in the United
States.
Definition
Sulfudepts are the Udepts that have a sulfuric horizon within
50 cm of the mineral soil surface.
KeytoSubgroups
KFAA. All Sulfudepts (provisionally).
TypicSulfudepts
Ustepts
Ustepts are mainly the more or less freely drained
Inceptisols that have an ustic moisture regime. They receive
dominantly summer precipitation, or they have an isomesic,
hyperthermic, or warmer temperature regime. They formed
mostly in Pleistocene or Holocene deposits. Some of the soils
that have steep slopes formed in older deposits. Some Ustepts
formed from Mollisols by truncation of the mollic epipedon,
mostly under cultivation. Most Ustepts have an ochric epipedon
and a cambic horizon. Many are calcareous at a shallow depth
and have a Bk or calcic horizon. A few have a duripan or an
umbric epipedon. The native vegetation commonly was grass,
but some of the soils supported trees. Most of the soils are used
as cropland or pasture. Ustepts are of moderate extent in the
United States. They are most common on the Great Plains,
mostly in Montana, Texas, and Oklahoma.
Definition
Ustepts are the Inceptisols that:
1. Have an ustic moisture regime;
2. Do not have, in a layer above a densic, lithic, or paralithic
contact or in a layer at a depth between 40 and 50 cm from the
mineral soil surface, whichever is shallower, aquic conditions
for some time in normal years and one or more of the
following:
a. A histic epipedon; or
b. A sulfuric horizon that has its upper boundary within
50 cm of the mineral soil surface; or
c. A layer directly under the epipedon, or within 50 cm of
the mineral soil surface, that has, on faces of peds or in the
matrix if peds are absent, 50 percent or more chroma of
either:
(1) 2 or less if there are redox concentrations; or
(2) 1 or less; or
d. Within 50 cm of the mineral soil surface, enough active
ferrous iron to give a positive reaction to alpha,alphadipyridyl
at a time when the soil is not being irrigated;
3. Do not have an exchangeable sodium percentage (ESP)
of 15 or more (or a sodium adsorption ratio [SAR] of 13 or
more) in half or more of the soil volume within 50 cm of the
mineral soil surface, a decrease in ESP (or SAR) values with
increasing depth below 50 cm, and ground water within 100
cm of the mineral soil surface for some time during the year;
4. Have neither a plaggen nor an anthropic epipedon; and
5. Have a soil temperature regime warmer than cryic.
Key to Great Groups
KDA. Ustepts that have a duripan that has its upper
boundary within 100 cm of the mineral soil surface.
Durustepts, p. 533
KDB. Other Ustepts that both:
1. Have a calcic horizon with its upper boundary
within 100 cm of the mineral soil surface or a petrocalcic
Inceptisols 531
horizon that has its upper boundary within 150 cm of the
mineral soil surface; and
2. Are either calcareous or have a texture of loamy fine sand
or coarser in all parts above the calcic or petrocalcic horizon,
after the soil between the mineral soil surface and a depth of
18 cm has been mixed.
Calciustepts, p. 531
KDC. Other Ustepts that have both of the following:
1. No free carbonates within 200 cm of the mineral soil
surface; and
2. A base saturation (by NH4
OAc) of less than 60 percent
in all horizons at a depth between 25 and 75 cm from the
mineral soil surface.
Dystrustepts, p. 534
KDD. Other Ustepts.
Haplustepts, p. 536
Calciustepts
These are the Ustepts that have a calcic or petrocalcic
horizon and that are calcareous or have a sandy particle-size
class in all overlying horizons. The soils do not have a duripan.
The precipitation has been insufficient to remove the
carbonates from the upper horizons, or there is a continuing
external source of carbonates in dust or water.
Calciustepts formed mostly in Pleistocene or older
materials. On the Calciustepts in the United States, the
vegetation was dominantly grass before the soils were
cultivated. The soils are most extensive on the Great Plains in
the United States, but some are in the intermountain valleys of
the Western States.
Definition
Calciustepts are the Ustepts that:
1. Have a calcic horizon that has its upper boundary
within 100 cm of the mineral soil surface or a petrocalcic
horizon that has its upper boundary within 150 cm of the
mineral soil surface and are calcareous in all parts of all
horizons above the calcic or petrocalcic horizon, after the
upper part of the soil to a depth of 18 cm has been mixed,
unless the texture is coarser than loamy very fine sand or very
fine sand; and
2. Do not have a duripan that has its upper boundary
within 100 cm of the mineral soil surface.
Key to Subgroups
KDBA. Calciustepts that have a petrocalcic horizon and a
lithic contact within 50 cm of the mineral soil surface.
Lithic Petrocalcic Calciustepts
KDBB. Other Calciustepts that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Calciustepts
KDBC. Other Calciustepts that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some or all parts for six-tenths or more of the cumulative
days per year when the temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some or all parts for six-tenths or more
of the cumulative days per year when the temperature
at a depth of 50 cm below the soil surface is higher
than 5 o
C.
Torrertic Calciustepts
KDBD. Other Calciustepts that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
532 Soil Taxonomy
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Calciustepts
KDBE. Other Calciustepts that have a petrocalcic horizon
that has its upper boundary within 100 cm of the mineral soil
surface.
Petrocalcic Calciustepts
KDBF. Other Calciustepts that have a gypsic horizon that has
its upper boundary within 100 cm of the mineral soil surface.
Gypsic Calciustepts
KDBG. Other Calciustepts that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage).
Aquic Calciustepts
KDBH. Other Calciustepts that have, when neither irrigated
nor fallowed to store moisture, one of the following:
1. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for four-tenths
or more of the cumulative days per year when the
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
or all parts for six-tenths or more of the cumulative days per
year when the temperature at a depth of 50 cm below the
soil surface is higher than 5 o
C; or
3. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
a. Is moist in some or all parts for fewer than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
b. Is dry in some or all parts for six-tenths or more of
the cumulative days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 5 o
C.
Aridic Calciustepts
KDBI. Other Calciustepts that have, when neither irrigated
nor fallowed to store moisture, either:
1. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
or all parts for four-tenths or less of the consecutive days per
year when the temperature at a depth of 50 cm below the
soil surface is higher than 5 o
C; or
2. A hyperthermic, isomesic, or warmer iso soil temperature
regime and a moisture control section that in normal years is
dry in some or all parts for fewer than 120 cumulative days
per year when the temperature at a depth of 50 cm below the
soil surface is higher than 8 o
C.
Udic Calciustepts
KDBJ. Other Calciustepts.
Typic Calciustepts
Definition of Typic Calciustepts
Typic Calciustepts are the Calciustepts that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have a petrocalcic horizon that has its upper
boundary within 100 cm of the mineral soil surface;
3. Do not have a gypsic horizon that has its upper boundary
within 100 cm of the mineral soil surface;
4. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
5. When neither irrigated nor fallowed to store moisture,
have one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for less than
four-tenths of the cumulative days per year when the
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
or all parts for more than four-tenths but less than six-tenths
of the cumulative days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is moist in some or all parts for 90 or more
consecutive days per year or is dry for less than six-tenths of
the cumulative days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C
and is dry for more than 120 cumulative days per year when
the temperature at a depth of 50 cm below the soil surface is
higher than 8 o
C; and
6. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
Inceptisols 533
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Description of Subgroups
Typic Calciustepts.—The central concept or Typic
subgroup of Calciustepts is fixed on more or less freely drained
soils that have a calcic rather than a petrocalcic horizon and
that do not have slickensides, wedge-shaped aggregates, a high
linear extensibility, or wide cracks in normal years.
Redox concentrations and a ground water table that
fluctuates within 75 cm of the mineral soil surface are
properties shared with Aquolls and define the Aquic subgroup.
A shallow lithic contact defines the Lithic subgroup, a
convention used throughout this taxonomy. A petrocalcic
horizon indicates development more intensive than normal and
defines the Petrocalcic subgroup. Slickensides, wedge-shaped
aggregates, a high linear extensibility, and wide cracks that are
evident in normal years are characteristics of Vertisols and are
used to define the Vertic subgroup.
Typic Calciustepts are of small extent in the United States.
They are mostly on the northern Great Plains, in Montana and
South Dakota. Many of these soils supported grasses and
shrubs. Most of the soils on plains are now used as cropland.
Aquic Calciustepts.—These soils have redox depletions
with low chroma and either have shallow ground water at some
time of the year or are artificially drained. Color value and
chroma of these soils commonly are lower than those of Typic
Calciustepts. Aquic Calciustepts developed mostly in nearly
level upland areas that commonly are concave. They are of very
small extent in the United States.
Aridic Calciustepts.—These soils are drier than Typic
Calciustepts. They generally receive less precipitation than the
soils of the Typic subgroup, or they lose more water through
runoff. Aridic Calciustepts are of moderately large extent and
are widely distributed in the Western United States. The largest
extent is in the western part of the Great Plains. Slopes range
from nearly level to steep. In the United States, many of the
soils that have suitable slopes are used as cropland. If the
temperature regime is frigid or mesic, many are fallowed in
alternate years to store moisture. Some are irrigated, and most
of the more sloping soils are used as pasture.
Gypsic Calciustepts.—These soils have a gypsic horizon in
addition to the calcic horizon. In most of these soils, the gypsic
horizon is in the lower part of or below the calcic horizon.
These soils are of very small extent in the United States. They
are mostly on the southern Great Plains.
Lithic Calciustepts.—These soils have a shallow lithic
contact. They are of small extent in the United States. They are
mostly in the Western States. They have moderate to very steep
slopes. The vegetation is mostly grass and shrubs, but a few of
the soils support forest vegetation. Lithic Calciustepts are used
mainly as pasture or forest.
Lithic Petrocalcic Calciustepts.—These soils have a
petrocalcic horizon overlying hard bedrock within a depth of
50 cm. Typically, the fractures in the underlying bedrock are
filled with cemented secondary carbonates. Most of these soils
are drier than Typic Calciustepts. Slopes are gentle. Lithic
Petrocalcic Calciustepts formed on surfaces older than the
Pleistocene. They occur locally in Texas. They are used mainly
as pasture.
Petrocalcic Calciustepts.—These soils have a petrocalcic
horizon. In some of the soils, depth to the petrocalcic horizon
is less than 50 cm. Some of the soils that have a petrocalcic
horizon below a depth of 50 cm are underlain by hard bedrock.
Petrocalcic Calciustepts are of small extent on the southern
Great Plains of the United States. The largest extent is in
Texas. Most of the soils are used as pasture.
Torrertic Calciustepts.—These soils have a clayey particlesize
class in a significant part, have expanding clays, and in
normal years have deep cracks. Also, the soils are drier than
Vertic Calciustepts. Torrertic Calciustepts are of very small
extent in the United States.
Udic Calciustepts.—These soils are more moist than Typic
Calciustepts and in most areas receive more precipitation. Udic
Calciustepts are of small extent and are known to occur only in
Texas. The native vegetation is mostly grasses and shrubs.
Slopes generally are gentle. Most of these soils are used as
cropland.
Vertic Calciustepts.—These soils have a clayey particle-size
class in a significant part, have expanding clays, and in normal
years have deep cracks. They formed mostly in
material weathered from smectite-rich shale or from limestone.
They are of small extent. The native vegetation was mostly
grasses.
Durustepts
These are the Ustepts that have a duripan with its upper
boundary within 100 cm of the soil surface. Commonly, these
soils formed in the vicinity of volcanic cinders and ash falls.
The parent materials are mainly volcanic tuffs, ash, cinders,
and volcanic rocks. In the United States, the native vegetation
is mostly grasses, shrubs, and trees. These soils are of small
extent. They formed mainly in areas of Pleistocene deposits.
They may be also on the leeward sides of some volcanic
islands.
Definition
Durustepts are the Ustepts that have a duripan that
has its upper boundary within 100 cm of the mineral soil
surface.
Key to Subgroups
KDAA. All Durustepts (provisionally).
TypicDurustepts
534 Soil Taxonomy
Dystrustepts
These are the acid Ustepts. They developed mostly in
Pleistocene or Holocene deposits. Some of the soils that have
steep slopes formed in older deposits. The parent materials
generally are acid, moderately or weakly consolidated
sedimentary or metamorphic rocks or acid sediments. The
vegetation was mostly forest. Most of these soils have a thermic
or warmer temperature regime.
A common horizon sequence in Dystrustepts is an ochric or
umbric epipedon over a cambic horizon. Some of the steeper
soils have a shallow densic, lithic, or paralithic contact.
Dystrustepts are of very small extent in the United States.
Definition
Dystrustepts are the Ustepts that:
1. Do not have free carbonates within the soils;
2. Have a base saturation of less than 60 percent (by
NH4
OAc) in all subhorizons between depths of 25 and 75 cm
below the soil surface;
3. Do not have a duripan that has an upper boundary
within 100 cm of the mineral soil surface; and
4. Do not meet both of the following:
a. Have a calcic horizon with its upper boundary within
100 cm of the mineral soil surface or a petrocalcic horizon
with its upper boundary within 150 cm of the mineral soil
surface; and
b. Either have a texture of loamy fine sand or coarser in
all parts above the calcic or petrocalcic horizon or are
calcareous after the soil between the mineral soil surface
and a depth of 18 cm has been mixed.
Key to Subgroups
KDCA. Dystrustepts that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Dystrustepts
KDCB. Other Dystrustepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Dystrustepts
KDCC. Other Dystrustepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Dystrustepts
KDCD. Other Dystrustepts that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage).
Aquic Dystrustepts
KDCE. Other Dystrustepts that have a slope of less than 25
percent; and either
1. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of 0.2 percent or
more and no densic, lithic, or paralithic contact within that
depth; or
2. An irregular decrease in organic-carbon content
(Holocene age) between a depth of 25 cm and either a depth
of 125 cm below the mineral soil surface or a densic, lithic,
or paralithic contact, whichever is shallower.
Fluventic Dystrustepts
KDCF. Other Dystrustepts that have in 50 percent or more of
the soil volume between a depth of 25 cm from the mineral soil
surface and either a depth of 100 cm or a densic, lithic, or
paralithic contact if shallower:
1. A CEC (by 1N NH4
OAc pH 7) of less than 24 cmol(+)
per kg clay; or
2. Both a ratio of measured clay in the fine-earth fraction
to percent water retained at 1500 kPa tension of 0.6 or more
and the following: the CEC (by 1N NH4
OAc pH 7) divided
by the product of three times [percent water retained at 1500
kPa tension minus percent organic carbon (but no more than
1.00)] is less than 24.
Oxic Dystrustepts
KDCG. Other Dystrustepts that have an umbric or mollic
epipedon.
Humic Dystrustepts
KDCH. Other Dystrustepts.
Typic Dystrustepts
Inceptisols 535
Definition of Typic Dystrustepts
Typic Dystrustepts are the Dystrustepts that:
1. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size, of
1.0 g/cm3
or less, measured at 33 kPa water retention, and
acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
2. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
3. Have a slope of 25 percent or more; or
a. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of less than 0.2
percent or a densic, lithic, or paralithic contact within that
depth; or
b. A regular decrease in organic-carbon content (Holocene
age) between a depth of 25 cm and either a depth of 125 cm
below the mineral soil surface or a densic, lithic, or
paralithic contact, whichever is shallower;
4. Do not have a lithic contact within 50 cm of the mineral
soil surface;
5. Do not have an umbric or mollic epipedon; and
6. Do not have, in 50 percent or more of the soil volume
between a depth of 25 cm from the mineral soil surface and
either a depth of 100 cm or a densic, lithic, or paralithic
contact if shallower, either:
a. A CEC (by 1N NH4
OAc pH 7) of less than 24 cmol(+)
per kg clay; or
b. Both a ratio of measured clay in the fine-earth fraction
to percent water retained at 1500 kPa tension of 0.6 or more
and the following: the CEC (by 1N NH4
OAc pH 7) divided
by the product of three times [percent water retained at 1500
kPa tension minus percent organic carbon (but no more than
1.00)] is less than 24.
Description of Subgroups
Typic Dystrustepts.—The central concept or Typic subgroup
of Dystrustepts is fixed on soils that are moderately deep or
deep to hard rock, are freely drained, are acid, and have an
ochric epipedon. In addition, the percentage of organic carbon
of Holocene age decreases regularly with increasing depth and
is very low at a depth of 125 cm.
If the percentage of organic carbon is relatively high at a
depth of 125 cm or if the percentage decreases irregularly with
increasing depth and slopes are gentle, the parent material
normally is recent Holocene alluvium. The soils that formed in
this alluvium are considered intergrades to Fluvents. A shallow
water table and redox depletions with low chroma indicate
intergrades to Aquepts. A lithic contact within a depth of 50
cm is the basis for defining the Lithic subgroup. The presence
of an umbric or mollic epipedon is used to define the Humic
subgroup. Soils that have a thin mantle or layer that has some
andic soil properties are excluded from the Typic subgroup
because they are considered to be an intergrade to Andisols.
Soils with a low CEC in the clay fraction are considered
intergrades to Oxisols.
Typic Dystrustepts are of very small extent in the United
States and are known to occur only on tropical islands.
Andic and Vitrandic Dystrustepts.—These soils have
some andic soil properties in a layer 18 cm or more thick in the
upper part. Some of the soils contain a significant amount of
volcanic ash, and some have an umbric epipedon. Andic and
Vitrandic Dystrustepts are not known to occur in the United
States.
Aquic Dystrustepts.—These soils have redox depletions
with low chroma in a brownish or reddish matrix in the
subsoil. Most of the soils also have concentrations with high
chroma. Ground water is present during wet periods unless the
soils are artificially drained. Some of these soils have an
umbric epipedon. Aquic Dystrustepts are not known to occur in
the United States.
Fluventic Dystrustepts.—These soils are on flood plains
along rivers draining regions that have acid soils. They formed
in Holocene or recent alluvium. They are subject to occasional
flooding but receive little fresh alluvium. These soils are rare
in the United States.
Humic Dystrustepts.—These soils have an umbric or
mollic epipedon but are otherwise like the soils of the Typic
subgroup. Humic Dystrustepts are known to occur only on
tropical islands in the United States.
Lithic Dystrustepts.—These soils have a lithic contact at a
shallow depth. They formed mostly in material weathered from
acid rocks. Most of the soils have moderate to steep slopes.
Lithic Dystrustepts are not known to occur in the United
States.
536 Soil Taxonomy
Oxic Dystrustepts.—These soils have clays with a low
cation-exchange capacity dominant in the particle-size control
section. They are considered intergrades to Oxisols. Oxic
Dystrustepts are not extensive in the United States.
Haplustepts
These are the more or less freely drained Ustepts that are
calcareous at some depth or have a high base status. Some of
the soils have a Bk or calcic horizon, but they do not have both
a calcic or petrocalcic horizon and a sandy particle-size class or
carbonates in all horizons above the calcic or petrocalcic
horizon. The native vegetation commonly was grass, but some
of the soils supported trees. Haplustepts are not extensive in the
United States, except locally on the Great Plains.
Definition
Haplustepts are the Ustepts that:
1. Do not have a duripan that has its upper boundary
within 100 cm of the mineral soil surface;
2. Do not have both:
a. A calcic horizon with its upper boundary within 100 cm
of the mineral soil surface or a petrocalcic horizon with its
upper boundary within 150 cm of the mineral soil surface;
and
b. Either free carbonates or a texture of loamy fine sand or
coarser in all parts above the calcic or petrocalcic horizon,
after the soil between the mineral soil surface and a depth of
18 cm has been mixed; and
3. Have:
a. Free carbonates within 200 cm of the mineral soil
surface; or
b. A base saturation (by NH4
OAc) of 60 percent or more in
some horizon at a depth between 25 and 75 cm from the
mineral soil surface.
Key to Subgroups
KDDA. Haplustepts that have:
1. A lithic contact within 50 cm of the mineral soil
surface; and
2. When neither irrigated nor fallowed to store moisture,
either:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the cumulative days per
year when the temperature at a depth of 50 cm below the
soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some part for six-tenths or more of the
cumulative days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
5 o
C.
Aridic Lithic Haplustepts
KDDB. Other Haplustepts that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Haplustepts
KDDC. Other Haplustepts that have both:
1. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid soil temperature regime and a moisture
control section that in normal years is dry in some or all
parts for fewer than 105 cumulative days per year when
the temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for less than four-tenths of the cumulative days
per year when the temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for fewer than
120 cumulative days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
Inceptisols 537
densic, lithic, or paralithic contact, whichever is
shallower.
UderticHaplustepts
KDDD. Other Haplustepts that have both:
1. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid soil temperature regime and a moisture
control section that in normal years is dry in all parts for
four-tenths or more of the cumulative days per year when
the temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the cumulative days
per year when the temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some part for six-tenths or more of the
cumulative days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
5 o
C; and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Torrertic Haplustepts
KDDE. Other Haplustepts that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Haplustepts
KDDF. Other Haplustepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Haplustepts
KDDG. Other Haplustepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Haplustepts
KDDH. Other Haplustepts that have anthraquic conditions.
Anthraquic Haplustepts
KDDI. Other Haplustepts that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Haplustepts
KDDJ. Other Haplustepts that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Haplustepts
KDDK. Other Haplustepts that have in 50 percent or more of
the soil volume between a depth of 25 cm from the mineral soil
surface and either a depth of 100 cm or a densic, lithic, or
paralithic contact if shallower:
1. A CEC (by 1N NH4
OAc pH 7) of less than 24 cmol(+)
per kg clay; or
538 Soil Taxonomy
2. Both a ratio of measured clay in the fine-earth fraction to
percent water retained at 1500 kPa tension of 0.6 or more and
the following: the CEC (by 1N NH4
OAc pH 7) divided by the
product of three times [percent water retained at 1500 kPa
tension minus percent organic carbon (but no more than
1.00)] is less than 24.
Oxic Haplustepts
KDDL. Other Haplustepts that have lamellae (two or more)
within 200 cm of the mineral soil surface.
Lamellic Haplustepts
KDDM. Other Haplustepts that have a slope of less than 25
percent; and
1. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid soil temperature regime and a moisture
control section that in normal years is dry in all parts for
four-tenths or more of the cumulative days per year when
the temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the cumulative days
per year when the temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some part for six-tenths or more of the
cumulative days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
5 o
C; and
2. Either:
a. At a depth of 125 cm below the mineral soil surface,
an organic-carbon content (Holocene age) of 0.2 percent
or more and no densic, lithic, or paralithic contact within
that depth; or
b. An irregular decrease in organic-carbon content
(Holocene age) between a depth of 25 cm and either a
depth of 125 cm below the mineral soil surface or a
densic, lithic, or paralithic contact, whichever is
shallower.
Torrifluventic Haplustepts
KDDN. Other Haplustepts that have a slope of less than 25
percent; and
1. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid soil temperature regime and a moisture control
section that in normal years is dry in some or all parts for
fewer than 105 cumulative days per year when the
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for less than four-tenths of the cumulative days
per year when the temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for fewer than
120 cumulative days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
2. Either:
a. At a depth of 125 cm below the mineral soil surface,
an organic-carbon content (Holocene age) of 0.2 percent
or more and no densic, lithic, or paralithic contact within
that depth; or
b. An irregular decrease in organic-carbon content
(Holocene age) between a depth of 25 cm and either a
depth of 125 cm below the mineral soil surface or a
densic, lithic, or paralithic contact, whichever is
shallower.
Udifluventic Haplustepts
KDDO. Other Haplustepts that have a slope of less than 25
percent; and either
1. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of 0.2 percent or
more and no densic, lithic, or paralithic contact within that
depth; or
2. An irregular decrease in organic-carbon content
(Holocene age) between a depth of 25 cm and either a depth
of 125 cm below the mineral soil surface or a densic, lithic,
or paralithic contact, whichever is shallower.
Fluventic Haplustepts
KDDP. Other Haplustepts that have a gypsic horizon that
has its upper boundary within 100 cm of the mineral soil
surface.
Gypsic Haplustepts
Inceptisols 539
KDDQ. Other Haplustepts that have both:
1. A calcic horizon that has its upper boundary within 100
cm of the mineral soil surface; and
2. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid soil temperature regime and a moisture
control section that in normal years is dry in all parts for
four-tenths or more of the cumulative days per year when
the temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the cumulative days
per year when the temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some part for six-tenths or more of the
cumulative days per year when the temperature at a
depth of 50 cm below the soil surface is higher than
5 o
C.
Haplocalcidic Haplustepts
KDDR. Other Haplustepts that have both:
1. A calcic horizon that has its upper boundary within 100
cm of the mineral soil surface; and
2. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid soil temperature regime and a moisture
control section that in normal years is dry in some or all
parts for fewer than 105 cumulative days per year when
the temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for less than four-tenths of the cumulative days
per year when the temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for fewer than
120 cumulative days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C.
Calcic Udic Haplustepts
KDDS. Other Haplustepts that have a calcic horizon that has
its upper boundary within 100 cm of the mineral soil surface.
Calcic Haplustepts
KDDT. Other Haplustepts that, when neither irrigated nor
fallowed to store moisture, have one of the following:
1. A frigid soil temperature regime and a moisture control
section that in normal years is dry in all parts for four-tenths
or more of the cumulative days per year when the
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for six-tenths or more of the cumulative days per year
when the temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
3. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
a. Is moist in some or all parts for fewer than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
b. Is dry in some part for six-tenths or more of the
cumulative days per year when the temperature at a depth
of 50 cm below the soil surface is higher than 5 o
C.
Aridic Haplustepts
KDDU. Other Haplustepts that have a base saturation (by
sum of cations) of less than 60 percent in some horizon
between either an Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and either a depth of
75 cm below the mineral soil surface or a densic, lithic, or
paralithic contact, whichever is shallower.
Dystric Haplustepts
KDDV. Other Haplustepts that, when neither irrigated nor
fallowed to store moisture, have one of the following:
1. A frigid soil temperature regime and a moisture control
section that in normal years is dry in some or all parts for
fewer than 105 cumulative days per year when the
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A mesic or thermic soil temperature regime and a moisture
control section that in normal years is dry in some part for
540 Soil Taxonomy
less than four-tenths of the cumulative days per year when
the temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
3. A hyperthermic, isomesic, or warmer iso soil temperature
regime and a moisture control section that in normal years is
dry in some or all parts for fewer than 120 cumulative days
per year when the temperature at a depth of 50 cm below the
soil surface is higher than 8 o
C.
Udic Haplustepts
KDDW. Other Haplustepts.
Typic Haplustepts
Definition of Typic Haplustepts
Typic Haplustepts are the Haplustepts that:
1. Either have a content of organic carbon (Holocene age)
that decreases regularly with increasing depth and, unless a
densic, lithic, or paralithic contact occurs at a shallower depth,
reaches a level of 0.2 percent or less within 125 cm of the soil
surface or have a slope of more than 25 percent;
2. Do not have a lithic contact within 50 cm of the surface;
3. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
4. Do not have anthraquic conditions;
5. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
6. When neither irrigated nor fallowed to store moisture,
have one of the following:
a. A frigid soil temperature regime and a moisture control
section that in normal years is dry in some or all parts for
105 or more cumulative days per year but is not dry in all
parts for four-tenths or more of the cumulative days per year
when the temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for four-tenths to six-tenths of the cumulative days per
year when the temperature at a depth of 50 cm below the
soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for 90 or more
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
(2) Is dry in some part for a period between 120
cumulative days and six-tenths of the cumulative days
per year when the temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C;
7. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
8. Have a base saturation (by sum of cations) of more than 60
percent in all horizons between either an Ap horizon or a depth
of 25 cm from the mineral soil surface, whichever is deeper,
and either a depth of 75 cm or a densic, lithic, or paralithic
contact, whichever is shallower;
9. Do not have a calcic horizon that has its upper boundary
within 100 cm of the mineral soil surface;
10. Do not have a gypsic horizon that has its upper boundary
within 100 cm of the mineral soil surface;
11. Do not have lamellae (two or more) within 200 cm of the
soil surface;
12. Have in less than 50 percent of the soil volume between a
depth of 25 cm from the mineral soil surface and either a depth
of 100 cm or a densic, lithic, or paralithic contact if shallower:
a. A CEC (by 1N NH4
OAc pH 7) of less than 24 cmol(+)
per kg clay; or
b. Both a ratio of measured clay in the fine-earth fraction
Inceptisols 541
to percent water retained at 1500 kPa tension of 0.6 or more
and the following: the CEC (by 1N NH4
OAc pH 7) divided by
the product of three times [percent water retained at 1500 kPa
tension minus percent organic carbon (but no more than
1.00)] is less than 24; and
13. Are not saturated with water in one or more layers
within 100 cm of the mineral soil surface for 20 or more
consecutive days or 30 or more cumulative days in normal
years.
Description of Subgroups
Typic Haplustepts.—The central concept or Typic
subgroup of Haplustepts is fixed on thick soils that have a high
base saturation throughout layers below the surface layer but do
not have a calcic horizon. The soils are dry for moderate
periods in normal years.
Gently sloping and nearly level Haplustepts are excluded
from the Typic subgroup if the content of organic carbon
(Holocene age) decreases irregularly with increasing depth or
remains relatively high in the deep layers. These soils have
some of the properties of Fluvents. Soils that have a lithic
contact shallower than 50 cm are excluded from the Typic
subgroup, a convention used throughout this taxonomy. Clayey
soils that have expanding clays and deep cracks are excluded
because they have some properties of Vertisols.
Typic Haplustepts are of large extent on the plains of the
Western United States. They are widely distributed from
Montana to Texas. Most of the soils are gently sloping to
strongly sloping. The native vegetation consists mostly of
grass, shrubs, and trees. Most of the strongly sloping soils are
used as rangeland or forest. Most of the less sloping soils have
been cleared and are used as cropland or pasture.
Andic and Vitrandic Haplustepts.—These soils have some
andic soil properties in a layer 18 cm or more thick in the
upper part and have many of the properties of Andisols. In
some of these soils, this layer was derived at least in part from
pyroclastic materials. Andic and Vitrandic Haplustepts are of
small extent in the United States. They are known to occur
only in western Montana. The native vegetation consists of
coniferous forest. Most of these soils are used as forest.
Anthraquic Haplustepts.—These soils have been irrigated
for the production of paddy rice for many years and have
developed redoximorphic features in the upper part. They are
permitted, but not required, to have redox depletions with
chroma of 2 or less in layers that also have aquic conditions in
normal years within 75 cm of the mineral soil surface. These
soils are not extensive and are not known to occur in the
United States. They have level or nearly level slopes.
Aquic Haplustepts.—These soils have redox depletions
with low chroma commonly in a brownish or reddish matrix in
the subsoil. Redox concentrations with high chroma also are
common. Most of the Aquic Haplustepts in the United States
have nearly level or gentle slopes. Ground water is present
during wet periods unless the soils are artificially drained. These
soils are of small extent in the United States and are widely
distributed on the Great Plains from Montana to Texas. The
native vegetation consists mostly of trees or widely spaced
trees and grass. Most of these soils have been cleared and are
used as pasture.
Aridic Haplustepts.—These soils receive less moisture
than the soils of the Typic subgroup but otherwise are like them
in defined properties. In general, the depth to carbonates is less
than that in the soils of the Typic subgroup. Aridic Haplustepts
are extensive in the western part of the Great Plains in the
United States. Slopes range from gentle to steep. Most of these
soils are used as rangeland. Where slopes are suitable, many of
the soils are used as cropland.
Aridic Lithic Haplustepts.—These soils have a lithic
contact within 50 cm of the soil surface and receive less
moisture than the soils of the Typic subgroup. The vegetation is
mostly grass and shrubs. Slopes are gentle to steep. Aridic
Lithic Haplustepts are used as rangeland or wildlife habitat.
Calcic Haplustepts.—These soils have a calcic horizon but
otherwise are like Typic Haplustepts in defined properties.
Calcic Haplustepts are of small extent on the Great Plains of
the United States. The native vegetation consists mostly of
grass and shrubs but in some areas is coniferous forest. Most of
these soils are used as rangeland or forest. Where slopes are
suitable, some of the soils are used as cropland or pasture.
Calcic Udic Haplustepts.—These soils receive more
moisture than the soils of the Typic subgroup and have a calcic
horizon. Calcic Udic Haplustepts are of small extent in the
southern part of the Great Plains in the United States. The
native vegetation consists mostly of grass, shrubs, and widely
spaced trees. Slopes generally are gentle. Most of these soils
are used as rangeland or pasture.
Dystric Haplustepts.—These soils have a base saturation of
less than 60 percent in some horizon between either an Ap
horizon or a depth of 25 cm from the mineral soil surface,
whichever is deeper, and a depth of 75 cm or a densic, lithic, or
paralithic contact, whichever is shallower. Some of the soils
have free carbonates at some depth within 200 cm of the soil
surface. Dystric Haplustepts are known to occur only on
tropical islands in the United States. They are of very small
extent.
Fluventic Haplustepts.—These soils formed in alluvium.
Slopes are gentle, and coarse stratification is common. These
soils are of small extent in the southern part of the Great Plains
in the United States. The native vegetation consisted mostly of
grass and widely spaced trees. Most of these soils are used as
cropland, rangeland, or pasture.
Gypsic Haplustepts.—These soils have a gypsic horizon
within 100 cm of the mineral soil surface. They are of very
small extent in the United States.
Haplocalcidic Haplustepts.—These soils receive less
moisture than the soils of the Typic subgroup and have a calcic
horizon. They are extensive in the western part of the Great
542 Soil Taxonomy
Plains and on foothills of the Rocky Mountains in the United
States. The native vegetation consists mostly of grass and
shrubs, but it includes pinyon pine and juniper trees in Arizona.
Slopes range from gentle to steep. Most of these soils are used
as rangeland or grazed forest. Where slopes are suitable, some
of the soils are used as cropland.
Lamellic Haplustepts.—These soils are like Typic
Haplustepts, but they have two or more lamellae. They are not
extensive in the United States.
Lithic Haplustepts.—These soils have a lithic contact
within 50 cm of the soil surface. Slopes are gentle to very
steep. These soils are of moderate extent on the plains and
foothills of the Western United States. They are widely
distributed from Montana to Texas. The native vegetation
consists mostly of grass, shrubs, and trees. Most of these soils
are used as rangeland or grazed forest. A few of the less
sloping soils have been cleared and are used as cropland or
pasture.
Oxic Haplustepts.—These soils have a cambic horizon that
approaches the properties of an oxic horizon but are otherwise
like Typic Haplustepts in defined properties. Oxic Haplustepts
are of very small extent in the United States. They occur mostly
on tropical or semitropical islands. The native vegetation
consists mostly of trees and shrubs. Most of these soils are used
as forest. Where slopes are suitable, some of the soils have been
cleared and are used as cropland or pasture.
Oxyaquic Haplustepts.—These soils are saturated with
water within 100 cm of the mineral soil surface for 20 or more
consecutive days or 30 or more cumulative days in normal
years. The soils are of very small extent in the United States.
They are considered intergrades to Aquepts.
Torrertic Haplustepts.—These soils receive less moisture
than the soils of the Typic subgroup. They are clayey and have
deep cracks at some season in most years, a property that is
shared with Torrerts. Torrertic Haplustepts generally are nearly
level or gently sloping. They are of small extent in the United
States and occur on the Great Plains from Montana to
Oklahoma. The native vegetation consists of grass and shrubs.
Most of these soils are used as rangeland, but some are used as
cropland, some of which is irrigated.
Torrifluventic Haplustepts.—These soils formed in
alluvium and receive less moisture than the soils of the
Fluventic and Typic subgroups. In general, the depth to free
carbonates is less than that in the soils in these subgroups.
Torrifluventic Haplustepts are of very small extent in the
United States. They are mostly in the western part of the Great
Plains.
Udertic Haplustepts.—These soils receive more moisture
than the soils of the Typic subgroup. They are clayey and have
deep cracks at some season in most years, a property that is
shared with Usterts. Udertic Haplustepts generally are nearly
level to sloping. They are of small extent and are known to
occur only in Texas in the United States. The native vegetation
consists of hardwood forest or grass and widely spaced trees.
Most of these soils are used as rangeland or hayland.
Udic Haplustepts.—These soils receive more moisture than
the soils of the Typic subgroup. They are otherwise like Typic
Haplustepts. Udic Haplustepts are of small extent in the United
States. They occur mostly on the southern Great Plains. Where
slopes are suitable, the soils are used mainly as cropland.
Udifluventic Haplustepts.—These soils formed in alluvium
and receive more moisture than the soils of the Typic subgroup.
Udifluventic Haplustepts are of small extent in the southern
part of the Great Plains in the United States. The native
vegetation consists of hardwood forest or grass and widely
spaced trees. Most of these soils are used as cropland or
rangeland or for pecan orchards.
Vertic Haplustepts.—These soils are clayey and have deep
cracks at some season in normal years, a property that is shared
with Usterts. Vertic Haplustepts generally are nearly level to
sloping. They are of moderate extent and occur on the Great
Plains from South Dakota to Texas in the United States. The
native vegetation consists mostly of grass and some shrubs and
widely spaced trees. Most of these soils are used as rangeland
or cropland.
Xerepts
Xerepts are mainly the more or less freely drained Inceptisols
that have a xeric moisture regime. They have a frigid, mesic, or
thermic temperature regime. They formed mostly in Pleistocene
or Holocene deposits. Some of the soils, mostly the ones that
have steep slopes, formed in older deposits. Most of the soils
have an ochric epipedon and a cambic horizon. Some have an
umbric epipedon or a duripan, and a few have a fragipan. Some
are calcareous at a shallow depth and have a Bk or calcic
horizon. The native vegetation commonly is coniferous forest on
the soils that have a frigid or mesic temperature regime and
shrubs, grass, and widely spaced trees on the soils that have a
thermic temperature regime.
Xerepts are of moderate extent in the United States. They
are most common in the States of California, Oregon,
Washington, Idaho, and Utah.
Definition
Xerepts are the Inceptisols that:
1. Have a xeric moisture regime;
2. Do not have, in a layer above a densic, lithic, or paralithic
contact or in a layer at a depth between 40 and 50 cm from the
mineral soil surface, whichever is shallower, aquic conditions
for some time in normal years and one or more of the
following:
a. A histic epipedon; or
Inceptisols 543
b. A sulfuric horizon that has its upper boundary within 50
cm of the mineral soil surface; or
c. A layer directly under the epipedon, or within 50 cm of
the mineral soil surface, that has, on faces of peds or in the
matrix if peds are absent, 50 percent or more chroma of
either:
(1) 2 or less if there are redox concentrations; or
(2) 1 or less; or
d. Within 50 cm of the mineral soil surface, enough active
ferrous iron to give a positive reaction to alpha,alphadipyridyl
at a time when the soil is not being irrigated;
3. Do not have an exchangeable sodium percentage (ESP)
of 15 or more (or a sodium adsorption ratio [SAR] of 13 or
more) in half or more of the soil volume within 50 cm of the
mineral soil surface, a decrease in ESP (or SAR) values with
increasing depth below 50 cm, and ground water within 100
cm of the mineral soil surface for some time during the year;
4. Have neither a plaggen nor an anthropic epipedon; and
5. Have a mesic, frigid, or thermic soil temperature regime.
Key to Great Groups
KEA. Xerepts that have a duripan that has its upper
boundary within 100 cm of the mineral soil surface.
Durixerepts, p. 545
KEB. Other Xerepts that both:
1. Have a calcic horizon with its upper boundary
within 100 cm of the mineral soil surface or a petrocalcic
horizon with its upper boundary within 150 cm of the
mineral soil surface; and
2. Are calcareous in all parts above the calcic or
petrocalcic horizon, after the soil between the mineral soil
surface and a depth of 18 cm has been mixed.
Calcixerepts, p. 543
KEC. Other Xerepts that have a fragipan that has its upper
boundary within 100 cm of the mineral soil surface.
Fragixerepts, p. 549
KED. Other Xerepts that have both of the following:
1. No free carbonates within 200 cm of the mineral soil
surface; and
2. A base saturation (by NH4
OAc) of less than 60 percent
in all horizons at a depth between 25 and 75 cm from the
mineral soil surface.
Dystroxerepts, p. 546
KEE. Other Xerepts.
Haploxerepts, p. 551
Calcixerepts
These are the Xerepts that do not have a duripan or a
fragipan but have a calcic or petrocalcic horizon and that are
calcareous in all overlying horizons. Either the parent
materials had more carbonates than the rainfall could remove
from the upper horizons, or there is a continuing external
source of carbonates in dust or water.
Calcixerepts formed mostly in Pleistocene sediments or
younger materials on surfaces of comparable age. In the United
States, the vegetation was dominantly grass and shrubs before
the soils were cultivated. These soils are most extensive in
California, Idaho, and Utah.
Definition
Calcixerepts are the Xerepts that:
1. Have a calcic horizon that has its upper boundary
within 100 cm of the mineral soil surface or a petrocalcic
horizon that has its upper boundary within 150 cm of the
mineral soil surface and are calcareous in all parts of all
horizons above the calcic or petrocalcic horizon; and
2. Do not have a duripan or fragipan that has its upper
boundary within 100 cm of the mineral soil surface.
Key to Subgroups
KEBA. Calcixerepts that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Calcixerepts
KEBB. Other Calcixerepts that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Calcixerepts
KEBC. Other Calcixerepts that have a petrocalcic horizon
that has its upper boundary within 100 cm of the mineral soil
surface.
Petrocalcic Calcixerepts
KEBD. Other Calcixerepts that have an exchangeable
544 Soil Taxonomy
sodium percentage of 15 or more (or a sodium adsorption ratio
[SAR] of 13 or more) in one or more subhorizons within 100 cm
of the mineral soil surface.
Sodic Calcixerepts
KEBE. Other Calcixerepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Calcixerepts
KEBF. Other Calcixerepts that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Calcixerepts
KEBG. Other Calcixerepts.
Typic Calcixerepts
Definition of Typic Calcixerepts
Typic Calcixerepts are the Calcixerepts that:
1. Do not have a lithic contact within 50 cm of the soil
surface;
2. Do not have a petrocalcic horizon that has its upper
boundary within 100 cm of the mineral soil surface;
3. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
4. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, one or both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is equal
to 30 or more;
5. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
and
6. Have an exchangeable sodium percentage of less than 15
(or a sodium adsorption ratio [SAR] of less than 13) in all
subhorizons within 100 cm of the mineral soil surface.
Description of Subgroups
Typic Calcixerepts.—The central concept or Typic
subgroup of Calcixerepts is fixed on more or less freely drained
soils that have a calcic rather than a petrocalcic horizon. These
soils do not have slickensides, wedge-shaped aggregates, a
high linear extensibility, or wide cracks in normal years.
Soils that have a thin mantle or layer of materials that have
some andic soil properties are excluded from the Typic
subgroup because they are considered to be an intergrade to
Andisols. Redox concentrations and a ground water table that
fluctuates within 75 cm of the mineral soil surface are
properties shared with Aquolls and define the Aquic subgroup.
A shallow lithic contact defines the Lithic subgroup, a
convention used throughout this taxonomy. A petrocalcic
horizon indicates development more intensive than normal and
is used to define the Petrocalcic subgroup. Slickensides, wedgeshaped
aggregates, a high linear extensibility, and wide cracks
that are evident in normal years are characteristics of Vertisols
and are used to define the Vertic subgroup.
Typic Calcixerepts are of small extent in the United States.
They are mostly in California, Utah, and Idaho. Many of these
soils supported grasses and shrubs and widely spaced trees.
Most are used as rangeland or irrigated cropland.
Aquic Calcixerepts.—These soils have redox depletions
with low chroma and either have shallow ground water at some
time of the year or are artificially drained. The soils are not
known to occur in the United States.
Lithic Calcixerepts.—These soils have a shallow lithic
contact. They are of very small extent in the Western United
States.
Petrocalcic Calcixerepts.—These soils have a petrocalcic
horizon. They are not known to occur in the United States.
Sodic Calcixerepts.—These soils have a high content of
Inceptisols 545
sodium in the upper part. They are of very small extent in the
United States.
Vertic Calcixerepts.—These soils have a clayey particle-size
class in a significant part, have expanding clays, and in normal
years have deep cracks. They are of very small extent in the
United States.
Vitrandic Calcixerepts.—These soils have some andic soil
properties in a layer 18 cm or more thick in the upper part and
have many of the properties of Andisols. In some areas this
layer was derived at least in part from pyroclastic materials.
Vitrandic Calcixerepts are of very small extent in the United
States.
Durixerepts
These are the Xerepts that have a duripan that has its upper
boundary within 100 cm of the soil surface. These soils have a
Mediterranean climate and receive a large part of their annual
precipitation in winter. Commonly, water is perched above the
duripan for part of winter or early spring. The vegetation was
commonly a coniferous forest or a mixture of grasses and
scattered trees. Durixerepts are not extensive in the United
States as a whole but are extensive locally.
Definition
Durixerepts are the Xerepts that have a duripan that has its
upper boundary within 100 cm of the soil surface.
Key to Subgroups
KEAA. Durixerepts that have both:
1. In one or more horizons above the duripan and
within 30 cm of the mineral soil surface, distinct or
prominent redox concentrations and also aquic conditions
for some time in normal years (or artificial drainage); and
2. Throughout one or more horizons with a total thickness
of 18 cm or more, above the duripan and within 75 cm of
the mineral soil surface, one or more of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
AquandicDurixerepts
KEAB. Other Durixerepts that have, throughout one or more
horizons with a total thickness of 18 cm or more, above the
duripan and within 75 cm of the mineral soil surface, a fineearth
fraction with both a bulk density of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and Al plus 1
/2 Fe
percentages (by ammonium oxalate) totaling more than 1.0.
Andic Durixerepts
KEAC. Other Durixerepts that have, throughout one or more
horizons with a total thickness of 18 cm or more, above the
duripan and within 75 cm of the mineral soil surface, one or
both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Durixerepts
KEAD. Other Durixerepts that have, in one or more horizons
above the duripan and within 30 cm of the mineral soil surface,
distinct or prominent redox concentrations and also aquic
conditions for some time in normal years (or artificial
drainage).
Aquic Durixerepts
KEAE. Other Durixerepts that have a duripan that is strongly
cemented or less cemented in all subhorizons.
Entic Durixerepts
KEAF. Other Durixerepts.
Typic Durixerepts
Definition of Typic Durixerepts
Typic Durixerepts are the Durixerepts that:
1. Have a duripan that is very strongly cemented or is
indurated;
2. Do not have, in any horizon above the duripan and
within 30 cm of the mineral soil surface, distinct or prominent
redox concentrations and also aquic conditions; and
546 Soil Taxonomy
3. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, any of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Description of Subgroups
Typic Durixerepts.—The central concept or Typic
subgroup of Durixerepts is fixed on soils that are free of
redoximorphic features and have a very strongly cemented or
indurated duripan. These soils do not have a layer near the
surface that has many of the properties of Andisols. The pan
generally has very coarse polyhedrons that are 100 cm or more
across. It commonly is within 50 cm of the mineral soil
surface. Soils that have a less strongly cemented duripan are
considered to be intergrades to Entisols.
Typic Durixerepts are of small extent in the United States.
The native vegetation is mostly shrubs and grass. These soils
are used mainly as rangeland or irrigated cropland. Some are
used as homesites.
Andic and Vitrandic Durixerepts.—These soils have many
of the properties of Andisols in a layer near the surface that is
18 cm or more thick. Andic and Vitrandic Durixerepts are of
small extent in the United States. They occur mostly in the
western part of Washington State. The native vegetation is
mostly coniferous forest, but in some areas it is shrubs and
grass. These soils are used mainly as forest. Some have been
cleared and are used as cropland, pasture, or homesites.
Aquandic Durixerepts.—These soils have many of the
properties of Andisols in a layer near the surface that is 18 cm
or more thick. Aquandic Durixerepts also have redox
concentrations and aquic conditions and are wetter than Typic
Durixerepts. They are rare in the United States.
Aquic Durixerepts.—These soils have redox concentrations
and aquic conditions and are wetter than Typic Durixerepts.
Commonly, they also have gentler slopes. Aquic Durixerepts
are rare in the United States.
Entic Durixerepts.—These soils have a duripan that is
cemented but is not very strongly cemented or indurated.
Because the pan is not very strongly cemented or indurated,
these soils are considered intergrades to Entisols. Entic
Durixerepts are of small extent in the United States. The
vegetation is mostly annual grasses and scattered trees on the
thermic soils and forest on the cooler soils.
Dystroxerepts
These are the acid Xerepts. They developed mostly in
Pleistocene or Holocene deposits. Some of the soils that have
steep slopes formed in older deposits. The normal horizon
sequence in Dystroxerepts is an ochric epipedon over a cambic
horizon. Some of the steep Dystroxerepts have a shallow
densic, lithic, or paralithic contact. The parent materials
generally are acid, moderately or weakly consolidated
sedimentary or metamorphic rocks or acid sediments,
commonly with additions of volcanic ash near the surface. A
few of the soils formed in saprolite derived from igneous rocks.
The vegetation was mostly coniferous trees. Most
Dystroxerepts are used as forest or pasture. Some of the soils,
mostly the least sloping ones, are used as cropland.
Dystroxerepts are extensive soils in the States of California,
Washington, and Oregon.
Definition
Dystroxerepts are the Xerepts that:
1. Do not have free carbonates within the soils;
2. Have a base saturation of less than 60 percent (by
NH4
OAc) in all subhorizons between depths of 25 and 75 cm
below the soil surface; and
3. Do not have a fragipan or duripan that has its upper
boundary within 100 cm of the mineral soil surface.
Key to Subgroups
KEDA. Dystroxerepts that have both:
1. A lithic contact within 50 cm of the mineral soil
surface; and
2. An umbric or mollic epipedon.
Humic Lithic Dystroxerepts
KEDB. Other Dystroxerepts that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Dystroxerepts
KEDC. Other Dystroxerepts that have both:
1. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface,
one or more of the following:
Inceptisols 547
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Dystroxerepts
KEDD. Other Dystroxerepts that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm3
or less, measured at 33 kPa
water retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Dystroxerepts
KEDE. Other Dystroxerepts that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Dystroxerepts
KEDF. Other Dystroxerepts that have both:
1. Fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm
of the mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm
or more thick; and
2. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions in normal years (or artificial
drainage).
Fragiaquic Dystroxerepts
KEDG. Other Dystroxerepts that have a slope of less than 25
percent; and
1. In one or more horizons within 75 cm of the mineral soil
surface, redox depletions with chroma of 2 or less and also
aquic conditions for some time in normal years (or artificial
drainage); and
2. Either:
a. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of 0.2 percent or
more and no densic, lithic, or paralithic contact within that
depth; or
b. An irregular decrease in organic-carbon content
(Holocene age) between a depth of 25 cm and either a
depth of 125 cm below the mineral soil surface or a
densic, lithic, or paralithic contact, whichever is
shallower.
Fluvaquentic Dystroxerepts
KEDH. Other Dystroxerepts that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage).
Aquic Dystroxerepts
KEDI. Other Dystroxerepts that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Dystroxerepts
KEDJ. Other Dystroxerepts that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Dystroxerepts
KEDK. Other Dystroxerepts that have a slope of less than 25
percent; and
1. An umbric or mollic epipedon; and
2. Either:
a. At a depth of 125 cm below the mineral soil surface,
an organic-carbon content (Holocene age) of 0.2 percent
548 Soil Taxonomy
or more and no densic, lithic, or paralithic contact within
that depth; or
b. An irregular decrease in organic-carbon content
(Holocene age) between a depth of 25 cm and either a
depth of 125 cm below the mineral soil surface or a
densic, lithic, or paralithic contact, whichever is
shallower.
Fluventic Humic Dystroxerepts
KEDL. Other Dystroxerepts that have a slope of less than 25
percent; and either
1. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of 0.2 percent or
more and no densic, lithic, or paralithic contact within that
depth; or
2. An irregular decrease in organic-carbon content
(Holocene age) between a depth of 25 cm and either a depth
of 125 cm below the mineral soil surface or a densic, lithic,
or paralithic contact, whichever is shallower.
Fluventic Dystroxerepts
KEDM. Other Dystroxerepts that have an umbric or mollic
epipedon.
Humic Dystroxerepts
KEDN. Other Dystroxerepts.
Typic Dystroxerepts
Definition of Typic Dystroxerepts
Typic Dystroxerepts are the Dystroxerepts that:
1. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
2. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
3. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years;
4. Have a slope of 25 percent or more; or
a. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of less than 0.2
percent or a densic, lithic, or paralithic contact within that
depth; or
b. A regular decrease in organic-carbon content (Holocene
age) between a depth of 25 cm and either a depth of 125 cm
below the mineral soil surface or a densic, lithic, or
paralithic contact, whichever is shallower;
5. Do not have a lithic contact within 50 cm of the mineral
soil surface;
6. Do not have an umbric or mollic epipedon; and
7. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick.
Description of Subgroups
Typic Dystroxerepts.—The central concept or Typic
subgroup of Dystroxerepts is fixed on soils that are moderately
deep or deeper to hard rock, are freely drained, are acid, and
have an ochric epipedon. In addition, the content of organic
carbon of Holocene age decreases regularly with increasing
depth and is very low at a depth of 125 cm.
If content of organic carbon is relatively high at a depth of
125 cm or if it decreases irregularly with increasing depth and
slopes are gentle, the parent material normally is recent
Holocene alluvium. The soils that formed in this alluvium are
considered intergrades to Fluvents or, if the soils have aquic
conditions near the surface, to Fluvaquents. A shallow water
table and redox depletions with low chroma indicate
intergrades to Aquepts. A lithic contact within a depth of 50
cm is the basis for defining the Lithic subgroup. The presence
of an umbric or mollic epipedon is used to define Humic and
combination Humic subgroups. Soils that have a thin mantle or
layer that has some andic soil properties are excluded from the
Typic subgroup because they are considered to be an intergrade
to Andisols.
Typic Dystroxerepts are of moderate extent in the United
States. They are mostly in the Northwestern States. The native
vegetation consists mostly of coniferous forest. Most of these
soils are used as forest. Some of the less sloping soils have been
cleared and are used as cropland or pasture.
Inceptisols 549
Andic and Vitrandic Dystroxerepts.—These soils have some
andic soil properties in a layer in the upper part that is 18 cm or
more thick. Some of the soils contain a significant amount of
volcanic ash. Some have an umbric epipedon. Andic and
Vitrandic Dystroxerepts are moderately extensive in the
Northwestern United States. The native vegetation consists
mostly of coniferous forest. Most of these soils support native
vegetation and are used as forest. A few of the less sloping soils
have been cleared and are used as cropland or pasture.
Aquandic Dystroxerepts.—These soils have aquic
conditions in the upper part of the subsoil and have some andic
soil properties in a layer in the upper part that is 18 cm or
more thick. Some of the soils contain a significant amount of
volcanic ash, and some have an umbric epipedon. Ground
water commonly is present only during winter unless the soils
are artificially drained. These soils have gentle slopes. They are
of small extent in the United States. They occur mostly in
Washington State. The native vegetation consists mostly of
coniferous forest. Most of these soils support native vegetation
and are used as forest. Some have been cleared and are used as
pasture or cropland.
Aquic Dystroxerepts.—These soils have redox depletions
with low chroma in a brownish or reddish matrix in the
subsoil. Many of the soils also have redox concentrations with
high chroma. Most of the Aquic Dystroxerepts in the United
States formed in late-Pleistocene sediments and have gentle
slopes. Ground water commonly is present only during wet
periods unless the soils are artificially drained. Some of these
soils have an umbric epipedon. Aquic Dystroxerepts are of
small extent in the United States. They occur mostly in
Washington State. The native vegetation consists mostly of
coniferous forest. Most of these soils are used as forest, but
some have been cleared and are used as cropland or pasture.
Fluvaquentic Dystroxerepts.—These soils have redox
depletions with low chroma in a brownish matrix and formed
in Holocene or recent alluvium. They are on flood plains.
During wet periods ground water is present in the redoxdepleted
zone unless the soils have been drained. Most of these
soils are subject to occasional flooding, but they receive little
fresh sediment. Some of the soils have an umbric epipedon.
Fluvaquentic Dystroxerepts are of very small extent in the
United States.
Fluventic Dystroxerepts.—These soils are on flood plains
along rivers and streams. They formed in Holocene or recent
alluvium. They are subject to occasional flooding but receive
little fresh alluvium. These soils are of very small extent in the
United States.
Fluventic Humic Dystroxerepts.—These soils are on flood
plains along rivers and streams. They have an umbric or mollic
epipedon. They formed in Holocene or recent alluvium. They
are subject to occasional flooding but receive little fresh
alluvium. These soils are of very small extent in the United
States.
Fragiaquic Dystroxerepts.—These soils have fragic soil
properties in 30 percent or more of a layer 15 cm or more thick
that has its upper boundary within 100 cm of the mineral soil
surface or in 60 percent or more of a layer 15 cm or more thick
anywhere in the soils. In addition, they have redox depletions
with low chroma in a brownish or reddish matrix in the
subsoil. Commonly, there are also redox concentrations with
high chroma. Ground water commonly is present in these soils
during winter. The soils are considered intergrades to
Fragiaquepts. They are not extensive in the United States.
Fragic Dystroxerepts.—These soils have fragic soil
properties in 30 percent or more of a layer 15 cm or more thick
that has its upper boundary within 100 cm of the mineral soil
surface or in 60 percent or more of a layer 15 cm or more thick
anywhere in the soils. These soils are considered intergrades to
Fragixerepts. They are not extensive in the United States.
Humic Dystroxerepts.—These soils have an umbric or
mollic epipedon but are otherwise like the soils of the Typic
subgroup. Humic Dystroxerepts are moderately extensive in the
United States. They are mostly in California and in the
Northwestern States. The native vegetation consists mostly of
coniferous forest. Most of these soils are used as forest. Many
of the less sloping soils have been cleared and are used as
cropland or pasture.
Humic Lithic Dystroxerepts.—These soils have a lithic
contact within 50 cm of the mineral soil surface and have a
mollic or umbric epipedon. An umbric epipedon is more
common than a mollic epipedon. These soils are of small
extent in the Northwestern United States.
Lithic Dystroxerepts.—These soils have a lithic contact at
a shallow depth. They formed mostly in acid sedimentary or
metamorphic rocks. Most of the soils have moderate to steep
slopes. Lithic Dystroxerepts are of small extent in the United
States. They are mostly in California and Oregon. The native
vegetation consists mostly of coniferous forest. Most of these
soils are used as forest.
Oxyaquic Dystroxerepts.—These soils are saturated with
water within 100 cm of the mineral soil surface for 20 or more
consecutive days or 30 or more cumulative days in normal
years. The soils are of small extent in the United States. They
are considered intergrades to Aquepts. Most Oxyaquic
Dystroxerepts are used as forest. Some have been cleared and
are used as cropland or pasture.
Fragixerepts
These are the Xerepts that have a fragipan within 100 cm of
the mineral soil surface. Commonly, these soils have a
brownish cambic horizon that is underlain by a fragipan at a
depth of about 70 cm. Most Fragixerepts have perched water
above the pan in winter, and few roots penetrate the pan.
Consequently, plants tend to have shallow root systems. Many
Fragixerepts formed in late-Pleistocene deposits. They have
mostly gentle or moderate slopes, but some are steep. Most of
these soils are loamy and have been leached of any free
550 Soil Taxonomy
carbonates. The Fragixerepts in the United States are mostly in
the States of Idaho and Oregon. They are of small extent.
Definition
Fragixerepts are the Xerepts that:
1. Have a fragipan within 100 cm of the mineral soil surface;
2. Do not have a duripan within 100 cm of the mineral soil
surface; and
3. Do not have both:
a. A calcic horizon with its upper boundary within 100 cm
of the mineral soil surface or a petrocalcic horizon with its
upper boundary within 150 cm of the mineral soil surface;
and
b. Calcareous materials in all parts above the calcic or
petrocalcic horizon, after the soil between the mineral soil
surface and a depth of 18 cm has been mixed.
Key to Subgroups
KECA. Fragixerepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Fragixerepts
KECB. Other Fragixerepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Fragixerepts
KECC. Other Fragixerepts that have, in one or more
horizons within 30 cm of the mineral soil surface, distinct or
prominent redox concentrations and also aquic conditions for
some time in normal years (or artificial drainage).
Aquic Fragixerepts
KECD. Other Fragixerepts that have an umbric or mollic
epipedon.
Humic Fragixerepts
KECE. Other Fragixerepts.
Typic Fragixerepts
Definition of Typic Fragixerepts
Typic Fragixerepts are the Fragixerepts that:
1. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
2. Do not have, in any horizon within 30 cm of the mineral
soil surface, distinct or prominent redox concentrations and
also aquic conditions; and
3. Do not have an umbric or mollic epipedon.
Description of Subgroups
Typic Fragixerepts.—The central concept or Typic
subgroup of Fragixerepts is fixed on soils that are free of
distinct or prominent redox concentrations in the upper 30 cm,
have an ochric epipedon, and do not have some andic soil
properties in a layer near the surface that is as thick as 18 cm.
A mantle of materials with andic soil properties between 18
and 35 cm thick indicates an intergrade to Andisols. Most
Typic Fragixerepts have a perched water table above the pan at
times during the winter. Shallow redox concentrations indicate
intergrades to Fragiaquepts and are the basis for defining the
Aquic subgroup.
Typic Fragixerepts are of small extent in the United States.
They occur mostly in the Northwestern States. The native
vegetation consists of mixed forest. Many of the less sloping
Inceptisols 551
soils have been cleared and are used as cropland or pasture.
Some of the soils, mostly the steeper ones, are used as forest.
Andic and Vitrandic Fragixerepts.—These soils have a
layer near the surface that is 18 cm or more thick and that
contains volcanic glass or has some andic soil properties. In
some soils this layer has many of the properties of Andisols.
Andic and Vitrandic Fragixerepts are not extensive and are not
known to occur in the United States.
Aquic Fragixerepts.—These soils have, at a shallow depth,
redox concentrations of medium or high contrast and are
somewhat wetter than Typic Fragixerepts. Commonly, they also
have gentler slopes. Aquic Fragixerepts are of very small
extent in the Northwestern United States. The native
vegetation consisted of forest. Most of these soils are nearly
level or gently sloping and have been cleared and are used as
cropland or pasture.
Humic Fragixerepts.—These soils are like Typic
Fragixerepts, but they have an umbric or mollic epipedon.
They are rare in the United States.
Haploxerepts
These are the more or less freely drained Xerepts that are
calcareous at some depth or have a high base status. Some of
the soils have a Bk or calcic horizon, but they do not have both
a calcic or petrocalcic horizon and free carbonates in all
horizons above the calcic or petrocalcic horizon. Haploxerepts
are moist in winter and into the spring but are thoroughly dry
for much of the summer. They have a frigid, mesic, or thermic
temperature regime. Slopes are gentle to very steep, and the
soils are shallow to very deep. The most common vegetation on
the Haploxerepts in the United States was coniferous forest on
the frigid and mesic soils and grass and widely spaced trees on
the thermic soils. Haploxerepts are in the Western United
States. They are moderately extensive.
Definition
Haploxerepts are the Xerepts that:
1. Have:
a. Free carbonates in some part within 200 cm of the
mineral soil surface; or
b. A base saturation (by NH4
OAc) of 60 percent or more in
some horizon at a depth between 25 and 75 cm from the
mineral soil surface;
2. Have neither a duripan nor a fragipan that has its upper
boundary within 100 cm of the mineral soil surface; and
3. Do not have both:
a. A calcic horizon with its upper boundary within 100 cm
of the mineral soil surface or a petrocalcic horizon with its
upper boundary within 150 cm of the mineral soil surface;
and
b. Free carbonates in all parts above the calcic or
petrocalcic horizon, after the soil between the mineral soil
surface and a depth of 18 cm has been mixed.
KeytoSubgroups
KEEA. Haploxerepts that have both:
1. A lithic contact within 50 cm of the mineral soil surface;
and
2. An umbric or mollic epipedon.
Humic Lithic Haploxerepts
KEEB. Other Haploxerepts that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Haploxerepts
KEEC. Other Haploxerepts that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Haploxerepts
KEED. Other Haploxerepts that have both:
1. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface,
one or more of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
552 Soil Taxonomy
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Haploxerepts
KEEE. Other Haploxerepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm of
the mineral soil surface, a fine-earth fraction with both a bulk
density of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and Al plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0.
Andic Haploxerepts
KEEF. Other Haploxerepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Haploxerepts
KEEG. Other Haploxerepts that have a gypsic horizon within
100 cm of the mineral soil surface.
Gypsic Haploxerepts
KEEH. Other Haploxerepts that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage).
Aquic Haploxerepts
KEEI. Other Haploxerepts that have lamellae (two or more)
within 200 cm of the mineral soil surface.
Lamellic Haploxerepts
KEEJ. Other Haploxerepts that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Haploxerepts
KEEK. Other Haploxerepts that have a slope of less than 25
percent; and either
1. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of 0.2 percent or
more and no densic, lithic, or paralithic contact within that
depth; or
2. An irregular decrease in organic-carbon content
(Holocene age) between a depth of 25 cm and either a depth
of 125 cm below the mineral soil surface or a densic, lithic,
or paralithic contact, whichever is shallower.
Fluventic Haploxerepts
KEEL. Other Haploxerepts that have a calcic horizon or
identifiable secondary carbonates within one of the following
particle-size class and depth combinations:
1. A sandy or sandy-skeletal particle-size class and
within 150 cm of the mineral soil surface; or
2. A clayey, clayey-skeletal, fine, or very-fine particle-size
class and within 90 cm of the mineral soil surface; or
3. Any other particle-size class and within 110 cm of the
mineral soil surface.
Calcic Haploxerepts
KEEM. Other Haploxerepts that have an umbric or mollic
epipedon.
Humic Haploxerepts
KEEN. Other Haploxerepts.
Typic Haploxerepts
Definition of Typic Haploxerepts
Typic Haploxerepts are the Haploxerepts that:
1. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
2. Do not have an umbric or mollic epipedon;
3. Have a slope of 25 percent or more; or
a. At a depth of 125 cm below the mineral soil surface, an
organic-carbon content (Holocene age) of less than 0.2
percent or a densic, lithic, or paralithic contact within that
depth; or
b. A regular decrease in organic-carbon content (Holocene
age) between a depth of 25 cm and either a depth of 125 cm
below the mineral soil surface or a densic, lithic, or
paralithic contact, whichever is shallower;
4. Do not have a lithic contact within 50 cm of the soil
surface in 10 percent or more of each pedon;
5. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
Inceptisols 553
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick that
has its upper boundary within 125 cm of the mineral soil
surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact, whichever is shallower;
6. Do not have a calcic horizon or identifiable secondary
carbonates within the following particle-size class and depth
combinations:
a. A sandy or sandy-skeletal particle-size class and within
150 cm of the mineral soil surface; or
b. A clayey, clayey-skeletal, fine, or very-fine particle-size
class and within 90 cm of the mineral soil surface; or
c. Any other particle-size class and within 110 cm of the
mineral soil surface;
7. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
8. Do not have a gypsic horizon within 100 cm of the soil
surface;
9. Do not have lamellae (two or more) within 200 cm of the
soil surface; and
10. Do not have fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Description of Subgroups
Typic Haploxerepts.—The central concept or Typic subgroup
of Haploxerepts is fixed on moderately deep or deeper, relatively
well drained soils that have an ochric epipedon. These soils do
not have a Bk or calcic horizon, unless it is deep, and do not
have a surface mantle that has some andic soil properties or a
high content of volcanic glass.
Soils that have shallow redox depletions with low chroma
and ground water in the depleted zone or artificial drainage are
excluded from the Typic subgroup because these properties
indicate intergrades to Aquepts and are the basis for
recognition of the Aquic subgroup. A layer or a surface mantle,
18 cm or more thick, that has some andic properties or a high
content of volcanic glass is excluded from the Typic subgroup
because it indicates a transition to Andisols and is used to
define Andic and Vitrandic subgroups. A shallow lithic contact
is the basis for recognition of the Lithic subgroup. Soils that
have a clayey texture accompanied by deep cracks are excluded
from the Typic subgroup because these characteristics indicate
intergrades to Vertisols and define the Vertic subgroup. Soils
that have an umbric or mollic epipedon are not considered
typical and are assigned to Humic and combination Humic
subgroups. Soils that have an organic-carbon content
(Holocene age) that decreases irregularly with increasing depth
or that remains relatively high in the deep layers are excluded
from the Typic subgroup and are considered intergrades to
Fluvents and Fluvaquents. Soils that have a shallow Bk or
calcic horizon are also excluded and are considered intergrades
to Calcixerepts.
Typic Haploxerepts are of moderate extent. They are in the
Western United States. Slopes are gentle to steep. The native
vegetation consists mostly of grass and shrubs. Most of the less
sloping soils are used as cropland. Some of the soils,
commonly the most sloping ones, support their native
vegetation and are used as rangeland.
Andic and Vitrandic Haploxerepts.—These soils have a
layer or a surface mantle, 18 cm or more thick, that has some
andic soil properties and that has many of the properties of
Andisols. In addition, some Andic and Vitrandic Haploxerepts
have an umbric epipedon. Andic and Vitrandic Haploxerepts
are of small extent. Slopes are gentle to very steep. The native
vegetation consists mostly of coniferous forest. Many of these
soils support their native vegetation and are used as forest.
Many of the less sloping soils have been cleared and are used
as cropland or pasture.
Aquandic Haploxerepts.—These soils have redox depletions
with low chroma (less than 2) within 75 cm of the soil surface
and either are artificially drained or are saturated with water in
the redox-depleted horizons at some time of the year, usually in
winter or early spring. The soils also have a layer or a surface
mantle, 18 cm or more thick, that has many of the properties of
Andisols. In addition, Aquandic Haploxerepts commonly have
554
an umbric epipedon. These soils are of very small extent in the
United States. They occur mostly in the State of Washington.
Slopes are gentle. The native vegetation consists mostly of
coniferous forest. Some of these soils have been cleared and are
used as cropland or pasture. Some support their native
vegetation and are used as forest.
Aquic Haploxerepts.—These soils have redox depletions
with low chroma (less than 2) within 75 cm of the soil surface
and either are artificially drained or are saturated with water in
the redox-depleted horizons at some time of the year, usually in
winter or spring. These soils are of small extent in the Western
United States. Slopes are gentle. The native vegetation consists
mostly of coniferous forest. Many of these soils have been
cleared and are used as cropland or pasture. Some support their
native vegetation and are used as forest.
Calcic Haploxerepts.—These soils have, in the upper part,
a calcic or Bk horizon that contains identifiable secondary
carbonates. These soils are of small extent in the United States.
They occur in the Western States. Slopes are gentle to very
steep. The native vegetation consists mostly of grass and
shrubs, but some of the soils support widely spaced trees. Most
Calcic Haploxerepts support their native vegetation and are
used as rangeland. Some of the less sloping soils are used as
cropland.
Fluventic Haploxerepts.—These soils formed in stratified
alluvium on gentle slopes. The soils are of small extent in the
Western United States. The native vegetation consists mostly of
grass and shrubs, but in some areas it is coniferous forest. Most
of these soils have been cleared and are used as cropland or
pasture. Some support their native vegetation and are used as
rangeland or forest.
Fragic Haploxerepts.—These soils have fragic soil
properties in 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm of the
mineral soil surface or in 60 percent or more of the volume of a
layer 15 cm or more thick anywhere in the soils. These soils
are considered intergrades to Fragixerepts. They are not
extensive in the United States.
Gypsic Haploxerepts.—These soils have a gypsic horizon
within 100 cm of the mineral soil surface. They are of very
small extent and are known to occur only in California in the
United States.
Humic Haploxerepts.—These soils have an umbric or
mollic epipedon. They are otherwise like the soils of the Typic
subgroup. The Humic Haploxerepts in the United States
formed mostly in materials weathered from rocks or in other
materials that have few or no free carbonates. Many of the soils
receive a relatively high amount of precipitation. Humic
Haploxerepts are of moderate extent in the Western United
States. Slopes are gentle to very steep. The native vegetation
consists mostly of coniferous forest. Many of these soils
support their native vegetation and are used as forest. Some are
cleared and are used as cropland or pasture.
Humic Lithic Haploxerepts.—These soils have an
umbric or mollic epipedon and have a shallow lithic contact. In
the United States, they formed mostly in materials that
weathered from rocks and have few or no free carbonates.
Many of the soils receive a relatively high amount of
precipitation. Humic Lithic Haploxerepts are of small extent in
the Western United States. Slopes are gentle to very steep. The
native vegetation consists mostly of coniferous forest. Many of
these soils support their native vegetation and are used as
forest.
Lamellic Haploxerepts.—These soils are like Typic
Haploxerepts, but they have two or more lamellae in the
subsoil. They are not extensive in the United States.
Lithic Haploxerepts.—These soils have a shallow lithic
contact. They are of moderate extent in the Western United
States. Slopes are gentle to very steep. The native vegetation
consists mostly of sparse coniferous forest. Many of these soils
support their native vegetation and are used as forest or
rangeland.
Vertic Haploxerepts.—These soils have a clayey texture
and have deep cracks in summer if they are not irrigated.
Vertic Haploxerepts are of small extent in the Western United
States. Slopes are gentle to moderately steep. The native
vegetation consists mostly of grass and shrubs. Most of the less
sloping soils are used as cropland. Some of the soils,
commonly the most sloping ones, support their native
vegetation and are used as rangeland.
555
Mollisols commonly are the very dark colored,
base-rich, mineral soils of the steppes. Nearly all of
these soils have a mollic epipedon. Many also have an argillic,
natric, or calcic horizon. A few have an albic horizon. Some
also have a duripan or a petrocalcic horizon.
Mollisols are extensive in subhumid to semiarid areas on
the plains of North America, Europe, Asia, and South
America. They lie generally between the Aridisols of arid
climates and the Spodosols or Alfisols of humid climates. They
are most extensive at mid latitudes, but they also occur at high
latitudes and high altitudes and in tropical regions.
Many of these soils developed under grass at some time,
although many apparently were forested at an earlier time.
Some of the soils that are in the mountains or that were derived
from highly calcareous parent material apparently formed
under forest vegetation. Mollisols may have any of the defined
temperature regimes but do not have permafrost. Soils with
mollic epipedons and permafrost are Gelisols. Mollisols can
have any moisture regime, but enough available moisture to
support perennial grasses seems to be essential.
Most Mollisols at high latitudes formed in late-Pleistocene
or Holocene deposits. Beyond the limits of glaciation, Mollisols
may be in areas of older deposits or on older surfaces dating
back perhaps to the mid Pleistocene or earlier, and these
commonly have an argillic horizon with a reddish hue.
In frigid or warmer areas where slopes are not too steep,
Mollisols are used mainly for small grain in the drier regions
and maize (corn) or soybeans in the warmer, humid regions.
Definition of Mollisols and Limits Between
Mollisols and Soils of Other Orders
Mollisols are mineral soils that either have a mollic
epipedon or have a surface horizon that, after mixing to a
depth of 18 cm, meets all of the requirements for a mollic
epipedon except thickness. They also have an upper subhorizon
that is more than 7.5 cm thick in an argillic or natric horizon
that meets the color, organic-carbon content, base saturation,
and structure requirements for a mollic epipedon but is
separated from the surface horizon by an albic horizon (the
combined thickness must meet the thickness requirements for a
mollic epipedon), and they meet all of the following:
1. Unlike Gelisols, Mollisols do not have either of the
following:
a. Permafrost within 100 cm of the soil surface; or
b. Gelic materials within 100 cm of the soil surface and
permafrost within 200 cm of the soil surface;
2. Unlike Histosols, Mollisols do not have organic soil
materials that meet one or more of the following:
a. Overlie cindery, fragmental, or pumiceous materials
and/or fill their interstices and directly below these
materials have either a densic, lithic, or paralithic contact;
or
b. When added with the underlying cindery, fragmental, or
pumiceous materials, total 40 cm or more between the soil
surface and a depth of 50 cm; or
c. Constitute two-thirds or more of the total thickness of
the soil to a densic, lithic, or paralithic contact and have no
mineral horizons or have mineral horizons with a total
thickness of 10 cm or less; or
d. Are saturated with water for 6 months or more in
normal years (or are artificially drained), have an upper
boundary within 40 cm of the soil surface, and have a total
thickness of either:
(1) 60 cm or more if three-fourths or more of their
volume consists of moss fibers or if their bulk density,
moist, is less than 0.1 g/cm3
; or
(2) 40 cm or more if they consist either of sapric or
hemic materials, or of fibric materials with less than
three-fourths (by volume) moss fibers and a bulk density,
moist, of 0.1 g/cm3
or more;
3. Unlike Spodosols, Mollisols do not have a spodic
horizon or an Ap horizon containing 85 percent or more
spodic materials and do not have one or more of the
following:
a. An albic horizon in 50 percent or more of each pedon
and a cryic soil temperature regime; or
b. A spodic horizon with all of the following
characteristics:
(1) One or more of the following:
(a) A thickness of 10 cm or more; or
(b) An overlying Ap horizon; or
CHAPTER 16
Mollisols
556 Soil Taxonomy
(c) Cementation in 50 percent or more of each
pedon; or
(d) A coarse-loamy, loamy-skeletal, or finer particlesize
class and a frigid temperature soil regime; or
(e) A cryic temperature soil regime; and
(2) An upper boundary within the following depths
from the mineral soil surface: either
(a) Less than 50 cm; or
(b) Less than 200 cm if the soil has a sandy particlesize
class between the mineral soil surface and the
spodic horizon; and
(3) A lower boundary as follows:
(a) Either at a depth of 25 cm or more below the
mineral soil surface, at the top of a duripan or
fragipan, or at a densic, lithic, paralithic, or
petroferric contact, whichever is shallowest; or
(b) At any depth if the spodic horizon has a coarseloamy,
loamy-skeletal, or finer particle-size class and
the soil has a frigid temperature regime or if the soil
has a cryic temperature regime;
4. Unlike Andisols, Mollisols must not have andic soil
properties in 60 percent or more of the thickness between
either the mineral soil surface or the top of an organic layer
with andic soil properties, whichever is shallower, and either a
depth of 60 cm from the shallower of the above or a densic,
lithic, or paralithic contact, a duripan, or a petrocalcic horizon
if shallower than 60 cm;
5. Unlike Oxisols, Mollisols must not have:
a. An oxic horizon within 150 cm of the soil surface; or
b. Both:
(1) 40 percent or more clay in the surface 18 cm of the
mineral soil after mixing; and
(2) A kandic horizon with less than 10 percent
weatherable minerals within 150 cm of the soil surface;
6. Unlike Vertisols, Mollisols must not have all of the
following:
a. A layer 25 cm or more thick, with an upper boundary
within 100 cm of the mineral soil surface, that has either
slickensides close enough to intersect or wedge-shaped
aggregates that have their long axes tilted 10 to 60 degrees
from the horizontal; and
b. A weighted average of 30 percent or more clay in the
fine-earth fraction either between the mineral soil surface
and a depth of 18 cm or in an Ap horizon, whichever is
thicker, and 30 percent or more clay in the fine-earth
fraction of all horizons between a depth of 18 cm and either
a depth of 50 cm or a densic, lithic, or paralithic contact,
duripan, or petrocalcic horizon if shallower; and
c. Cracks that open and close periodically;
7. Unlike Aridisols, Mollisols must:
a. Have a mollic epipedon; and
b. Not have a salic horizon if they also have all of the
following:
(1) Saturation with water in one or more layers
within 100 cm of the soil surface for 1 month or more
in normal years; and
(2) A moisture control section that is, in at least some
part, dry in normal years; and
(3) No sulfuric horizon that has its upper boundary
within 150 cm of the mineral soil surface;
8. Unlike Alfisols and Ultisols, Mollisols must have:
a. Either:
(1) A mollic epipedon; or
(2) Both a surface horizon that meets all of the
requirements for a mollic epipedon except thickness after
the soil has been mixed to a depth of 18 cm and a
subhorizon more than 7.5 cm thick, within the upper part
of an argillic, kandic, or natric horizon, that meets the
color, organic-carbon content, base saturation, and
structure requirements for a mollic epipedon but is
separated from the surface horizon by an albic horizon;
and
b. An argillic, kandic, or natric horizon that has a base
saturation of 50 percent or more (by NH4
OAc) in the upper
125 cm or in all subhorizons if the argillic horizon is less
than 125 cm thick; and
9. Unlike Inceptisols and Entisols, Mollisols have both a
mollic epipedon and a base saturation of 50 percent or more
(by NH4
OAc) in all subhorizons to a depth of 180 cm below the
mineral soil surface.
Representative Pedon and Data
Following is a description of a representative Mollisol. Data
for the pedon identified in this description are given in the
table “Characterization Data for a Mollisol.”
Classification: Fine-silty, mixed, superactive, mesic Pachic
Argiustoll
Site identification number: 79P0146
Location: Gosper County, Nebraska; 135 m east and 750 m
north of the southwest corner of sec. 7, T. 7 N., R. 22 W.
Mollisols 557
Landscape: Plains
Soil moisture regime: Ustic
Depth to water table: More than 150 cm
Permeability class: Moderate
Land use: Cropland
Parent material: Loess
Diagnostic horizons: A mollic epipedon from a depth of 0
to 71 cm and an argillic horizon from a depth of 30 to
91 cm
Described by: M. Dixon and S. Scheinost
In the following pedon description, colors are for dry soil
unless otherwise indicated.
Ap—0 to 18 cm; dark grayish brown (10YR 4/2) silt loam,
very dark grayish brown (10YR 3/2) moist; weak fine
granular structure; slightly hard, very friable, nonsticky;
common fine roots; abrupt smooth boundary.
A—18 to 30 cm; dark grayish brown (10YR 4/2) silt loam,
very dark grayish brown (10YR 3/2) moist; weak fine and
medium subangular blocky structure; slightly hard, very
friable, slightly sticky; common fine roots; clear smooth
boundary.
Bt1—30 to 49 cm; dark gray (10YR 4/1) silty clay loam, very
dark gray (10YR 3/1) moist; weak coarse prismatic
structure parting to moderate medium subangular blocky;
hard, friable, slightly sticky; common fine roots; common
faint clay films on faces of peds; clear smooth boundary.
Bt2—49 to 71 cm; dark grayish brown (10YR 4/2) silty clay
loam, very dark grayish brown (10YR 3/2) moist; weak
coarse prismatic structure parting to moderate medium
subangular blocky; slightly hard, friable, slightly sticky;
few fine roots; few fine tubular pores; common faint clay
films on faces of peds; clear wavy boundary.
Bt3—71 to 91 cm; dark grayish brown (10YR 4/2) silty clay
loam, dark grayish brown (10YR 4/2) moist; weak coarse
prismatic structure parting to moderate medium
subangular blocky; few clay films on faces of prisms; few
fine roots; gradual wavy boundary.
BC—91 to 117 cm; light brownish gray (10YR 6/2) silt loam,
grayish brown (10YR 5/2) moist; weak medium prismatic
structure parting to weak fine subangular blocky; slightly
hard, very friable, nonsticky; few fine tubular pores; few
old root channels; gradual wavy boundary.
BCk1—117 to 142 cm; pale brown (10YR 6/3) silt loam,
brown (10YR 5/3) moist; massive; slightly hard, very
friable, nonsticky; few very fine tubular pores; common
fine and medium concretions of lime; common old root
channels; slightly effervescent; diffuse wavy boundary.
BCk2—142 to 165 cm; pale brown (10YR 6/3) silt loam,
brown (10YR 5/3) moist; weak coarse prismatic structure;
slightly hard, very friable, nonsticky; coatings of lime or
carbonate on faces of peds and in pores; common fine and
medium soft masses of lime; slightly effervescent.
Key to Suborders
IA. Mollisols that have:
1. An argillic or natric horizon; and
2. An albic horizon that has chroma of 2 or less and is 2.5
cm or more thick, has its lower boundary 18 cm or more
below the mineral soil surface, and either lies directly below
the mollic epipedon or separates horizons that together meet
all of the requirements for a mollic epipedon; and
3. In one or more subhorizons of the albic horizon and/or
of the argillic or natric horizon and within 100 cm of the
mineral soil surface, redox concentrations in the form of
masses or concretions, or both, and also aquic conditions for
some time in normal years (or artificial drainage).
Albolls, p. 560
IB. Other Mollisols that have, in a layer above a densic,
lithic, or paralithic contact or in a layer at a depth between 40
and 50 cm from the mineral soil surface, whichever is
shallower, aquic conditions for some time in normal years (or
artificial drainage) and one or more of the following:
1. A histic epipedon overlying the mollic epipedon; or
2. An exchangeable sodium percentage (ESP) of 15 or
more (or a sodium adsorption ratio [SAR] of 13 or more) in
the upper part of the mollic epipedon and a decrease in ESP
(or SAR) values with increasing depth below 50 cm from
the mineral soil surface; or
3. A calcic or petrocalcic horizon that has its upper
boundary within 40 cm of the mineral soil surface; or
4. A mollic epipedon, with chroma of 1 or less, that
extends to a lithic contact within 30 cm of the mineral soil
surface; or
5. One of the following colors:
a. Chroma of 1 or less in the lower part of the mollic
epipedon;1
and either
(1) Distinct or prominent redox concentrations in
the lower part of the mollic epipedon; or
(2) Either directly below the mollic epipedon or
within 75 cm of the mineral soil surface if a calcic
horizon intervenes, a color value, moist, of 4 or more
and one of the following:
(a) 50 percent or more chroma of 1 on faces of
peds or in the matrix, hue of 10YR or redder, and
redox concentrations; or
1
If the mollic epipedon extends to a lithic contact within 30 cm of the mineral soil surface,
the requirement for redoximorphic features is waived.
558 Soil Taxonomy
Characterization Data for a Mollisol
SITE IDENTIFICATION NO.: 79P0146
CLASSIFICATION: FINE-SILTY, MIXED, SUPERACTIVE, MESIC PACHIC ARGIUSTOLL
GENERAL METHODS: 1B1A, 2A1, 2B
-1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-
-----------------------------------------------------------------------------------------------------------------------------------
(- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)
CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT
SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF
NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE
<- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL
79P 720 0- 18 Ap 21.1 61.0 17.9 14.8 21.6 39.4 16.9 0.4 0.3 0.1 0.2 -- -- -- 1 --
79P 721 18- 30 A 21.4 61.0 17.6 16.4 21.0 40.0 16.6 0.6 0.2 0.1 0.1 -- -- -- 1 --
79P 722 30- 49 Bt1 27.5 58.5 14.0 21.2 20.8 37.7 12.7 0.6 0.4 0.2 0.1 -- -- -- 1 --
79P 723 49- 71 Bt2 28.5 53.9 17.6 22.3 20.6 33.3 16.7 0.4 0.3 0.1 0.1 -- -- -- 1 --
79P 724 71- 91 Bt3 25.9 55.5 18.6 18.8 20.9 34.6 18.0 0.3 0.2 0.1 TR -- -- -- 1 --
79P 725 91-117 BC 21.7 56.5 21.8 13.0 20.9 35.6 20.9 0.6 0.2 0.1 TR -- -- -- 1 --
79P 726 117-142 BCk1 19.6 59.4 21.0 8.5 0.3 23.0 36.4 20.3 0.4 0.2 0.1 TR -- -- -- 1 --
79P 727 142-165 BCk2 18.4 56.3 25.3 7.3 22.2 34.1 24.6 0.4 0.2 0.1 TR -- -- -- 1 --
-----------------------------------------------------------------------------------------------------------------------------------
ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD
C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE
DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL
(cm) 6A1c 6B1b 6S1a 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A3a 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2 4C1
Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm
0- 18 1.52 0.149 0.4 0.1 TR 0.96 0.53 33 10 1.31 1.43 0.030 34.6 27.2 11.1 0.21
18- 30 1.14 0.122 0.4 0.1 TR 0.93 0.52 34 12 1.34 1.45 0.027 32.3 25.7 11.2 0.19
30- 49 0.99 0.097 0.5 0.1 TR 0.90 0.52 42 22 1.32 1.48 0.039 30.5 27.2 14.3 0.17
49- 71 0.61 0.067 0.5 0.1 TR 0.88 0.54 44 23 1.46 1.62 0.035 27.5 25.1 15.4 0.14
71- 91 0.40 0.049 0.5 0.1 TR 0.90 0.53 42 21 1.47 1.58 0.024 26.6 23.4 13.6 0.14
91-117 0.26 0.039 0.4 0.1 TR 1.00 0.53 34 13 1.41 1.49 0.019 28.4 22.7 11.6 0.16
117-142 0.18 0.027 0.4 0.1 TR 1.09 0.57 32 11 1.36 1.43 0.017 33.0 25.2 11.2 0.19
142-165 0.15 0.022 0.4 0.1 TR 1.13 0.57 32 9 1.32 1.38 0.015 37.1 23.8 10.4 0.18
-----------------------------------------------------------------------------------------------------------------------------------
(- NH4OAc EXTRACTABLE BASES -) ACID- (- -CEC- -) EXCH SAR BASE CO3 AS RES. CaSO4 AS (- - - -PH - - -)
Ca Mg Na K SUM ITY SUM NH4- Na SATURATION CaCO3 ohms GYPSUM SAT CaCl2 H2O
DEPTH 5B4a 5B4a 5B4a 5B4a BASES CATS OAc SUM NH4OAc <2mm /cm <2mm <20mm PASTE .01M
(cm) 6N2e 6O2d 6P2b 6Q2b 6H2b 5A3a 5A6a 5D2 5E 5C3 5C1 6E1b 8E1 6F1c 6F1c 8C1b 8C1e 8C1a
<- - - - - - - - - -meq / 100 g - - - - - - - - - -> Pct <- -Pct- > Pct <- -Pct -> 1:2 1:1
0- 18 12.0 3.0 TR 2.6 17.6 6.0 23.6 20.3 TR 75 87 5.7 6.3
18- 30 14.6 3.7 0.1 1.4 19.8 7.6 27.4 19.8 TR 72 100 TR 5.6 6.1
30- 49 18.1 5.7 0.1 1.0 24.9 4.1 29.0 24.7 TR 86 100 TR 6.4 7.0
49- 71 17.3 6.2 0.2 1.4 25.1 3.8 28.9 25.0 1 87 100 TR 6.5 7.1
71- 91 16.2 5.6 0.2 1.5 23.5 2.7 26.2 23.3 1 90 100 TR 6.9 7.4
91-117 18.3 5.6 0.2 1.8 25.9 1.7 27.6 21.8 1 TR 94 100 TR 2200 7.4 7.4 8.0
117-142 6.9 0.2 2.2 21.4 1 100 100 2 7.8 8.5
142-165 7.6 0.3 2.4 20.8 1 100 100 3 7.9 8.6
-----------------------------------------------------------------------------------------------------------------------------------
(- - - - - - - - - - -WATER EXTRACTED FROM SATURATED PASTE- - - - - - - - - - - - - )PRED.
TOTAL ELEC. ELEC.
Ca Mg Na K CO3 HCO3 F Cl SO4 NO2 NO3 H2O SALTS COND. COND.
DEPTH EST. 8A1a 8I
(cm) 6N1b 6O1b 6P1b 6Q1b 6I1b 6J1b 6U1a 6K1c 6L1c 6W1a 6M1c 8A 8D5 mmhos mmhos
< - - - - - - - - - - - - - -meq / liter - - - - - - - - - - - -> <- -Pct- -> /cm /cm
91-117 2.0 1.0 0.4 0.7 -- 3.4 -- 0.1 0.2 -- -- 74.0 TR 0.42
-----------------------------------------------------------------------------------------------------------------------------------
< - - - - - - - - - - - - - - - - - - - - - - CLAY MINERALOGY (<.002mm) - - - - - - - - - - - - - - - - - - - - - - - >
FRAC- < - - - - - X-RAY - - - - - ->< - - - THERMAL - - - ->< - - - - - - - ELEMENTAL - - - - - - - ->< - -> EGME INTERSAMPLE
TION < >< - DTA - ->< - TGA - -> SiO2 Al2O3 Fe2O3 MgO CaO K2O Na2O < > RETN PRETA<
- - - - - 7A2i - - - - - ->< - 7A6 - >< - 7A4b - >< - - - - - - - - - 7C3 - - - - - - - - ->< > 7D2 TION
NUMBER <- - >< - - - - Peak size - - - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - -><mg/g>< - ->
79P 720 TCLY MI 3 KK 2 MT 2 QZ 1 6.0 2.5
79P 721 TCLY MI 3 KK 2 MT 2 QZ 1 6.3 2.4
79P 722 TCLY MT 4 MI 3 KK 2 QZ 1 KK15 6.7 2.2
79P 723 TCLY MT 3 MI 2 KK 2 QZ 1 6.1 2.0
79P 724 TCLY MT 3 MI 3 KK 2 QZ 1 6.9 2.2
79P 725 TCLY MT 3 MI 2 KK 2 QZ 1 6.3 2.3
79P 726 TCLY MT 3 MI 2 KK 2 QZ 1 6.1 2.2
79P 727 TCLY MT 2 MI 1 KK 1 QZ 1 6.3 2.2
-----------------------------------------------------------------------------------------------------------------------------------
Mollisols 559
(b) 50 percent or more chroma of 2 or less on faces
of peds or in the matrix, hue of 2.5Y, and redox
concentrations; or
(c) 50 percent or more chroma of 1 on faces of
peds or in the matrix and hue of 2.5Y or yellower;
or
(d) 50 percent or more chroma of 3 or less on
faces of peds or in the matrix, hue of 5Y, and redox
concentrations; or
(e) 50 percent or more chroma of 0 on faces of
peds or in the matrix; or
(f) Hue of 5GY, 5G, 5BG, or 5B; or
(g) Any color if it results from uncoated sand
grains; or
b. Chroma of 2 in the lower part of the mollic
epipedon; and either
(1) Distinct or prominent redox concentrations in
the lower part of the mollic epipedon; or
(2) Directly below the mollic epipedon, one of the
following matrix colors:
(a) A color value, moist, of 4, chroma of 2, and
some redox depletions with a color value, moist, of
4 or more and chroma of 1 or less; or
(b) A color value, moist, of 5 or more, chroma of 2
or less, and redox concentrations; or
(c) A color value, moist, of 4 and chroma of 1 or
less; or
6. At a depth between 40 and 50 cm from the mineral soil
surface, enough active ferrous iron to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated.
Aquolls, p. 563
IC. Other Mollisols that:
1. Have a mollic epipedon less than 50 cm thick; and
2. Do not have an argillic or calcic horizon; and
3. Have, either within or directly below the mollic
epipedon, mineral soil materials less than 7.5 cm in
diameter that have a CaCO3
equivalent of 40 percent or
more; and
4. Have either or both a udic moisture regime or a cryic
soil temperature regime.
Rendolls, p. 584
ID. Other Mollisols that have a cryic soil temperature
regime.
Cryolls, p. 575
Characterization Data for a Mollisol--Continued
-1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-
-----------------------------------------------------------------------------------------------------------------------------------
< - - - - - - - - - - - - - - - - - - - - SAND - SILT MINERALOGY (2.0-0.002mm) - - - - - - - - - - - - - - - - - - - - >
FRAC- < - - - - - X-RAY - - ->< - - - THERMAL - - - ->< - - - - - - - OPTICAL - - - - - - - - >< >INTERSAMPLE
TION < >< - DTA - ->< - TGA - ->TOT RE< - - - - - GRAIN COUNT - - - - - ->< >PRETA<
- - - - 7A2i - - - - >< - 7A3c - >< - 7A4c - >< - - - - - - - - 7B1a - - - - - - - - ->< > TION
NUMBER < - ->< - - - Peak Size - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - - - - - - - ->< - ->
79P 722 CSi 61 QZ52 FK19 FP 7 GS 6 CD 4 PO 3
79P 722 CSi GA 2 HN 1 AR 1 FE 1 OP 1 MS 1
79P 722 CSi PR 1 BTtr BYtr STtr ZRtr RUtr
79P 722 CSi EPtr GNtr TMtr TEtr APtr
79P 723 CSi 60 QZ51 FK25 FP 7 CD 4 PO 3 GS 2
79P 723 CSi HN 2 AR 2 OP 1 MS 1 GA 1 TM 1
79P 723 CSi FEtr BTtr PRtr STtr ZEtr GNtr
79P 723 CSi CTtr APtr ZRtr BYtr TEtr
79P 724 CSi 61 QZ54 FK22 FP 7 CD 4 GS 3 AR 3
79P 724 CSi HN 2 MS 2 OP 2 PR 1 FE 1 POtr
79P 724 CSi BTtr ZRtr ZEtr FZtr CTtr GNtr
79P 724 CSi APtr BYtr RUtr TMtr
-----------------------------------------------------------------------------------------------------------------------------------
The chemical data are based on the fraction less than 2 mm in size.
Fraction interpretation: TCLY, total clay, <0.002 mm; CSi, coarse silt, 0.02-0.05 mm.
Mineral interpretation: MI, mica; KK, kaolinite; MT, montmorillonite; QZ, quartz; FK, potassium feldspar; FP, plagioclase feldspar;
GS, glass; CD, chalcedony; PO, plant opal; GA, glass aggregate; HN, hornblende; AR, weathered aggregate; FE, iron oxides; OP,
opaques; MS, muscovite; PR, pyroxene; BT, biotite; BY, beryl; ST, stilbite; ZR, zircon; RU, rutile; EP, epidote; GN, garnet;
TM, tourmaline; TE, tremolite; AP, apatite; ZE, zeolite; CT, cassiterite; FZ, feldspathoid.
Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.
560 Soil Taxonomy
IE. Other Mollisols that have either a xeric moisture regime or
an aridic moisture regime that borders on xeric.
Xerolls, p. 630
IF. Other Mollisols that have either an ustic moisture regime or
an aridic moisture regime that borders on ustic.
Ustolls, p. 601
IG. Other Mollisols.
Udolls, p. 586
Albolls
Albolls are the Mollisols that have an albic horizon and
fluctuating ground water. Most of these soils are saturated with
water to or near the soil surface at some time during winter or
spring in normal years. In summer ground water commonly is
not within a depth of 200 cm. Below the albic horizon, there is
either an argillic or, less commonly, a natric horizon. These
soils developed mostly on broad, nearly level to sloping ridges,
on back slopes, or in closed depressions. Most have
episaturation. In the United States, most Albolls are in areas of
late-Pleistocene deposits. Most Albolls developed under grass
or grass and shrub vegetation. In early stages of development,
some are thought to have had forest vegetation that was
replaced by grass. Because slopes are gentle, most of the
Albolls in the United States are now cultivated.
Definition
Albolls are the Mollisols that have all of the following:
1. An argillic or natric horizon; and
2. An albic horizon that has chroma of 2 or less and that
is 2.5 cm or more thick, has its lower boundary 18 cm or more
below the mineral soil surface, and either lies directly below
the mollic epipedon or separates horizons that together meet all
of the requirements for a mollic epipedon; and
3. In one or more subhorizons of the albic horizon and/or of
the argillic or natric horizon and within 100 cm of the mineral
soil surface, redox concentrations in the form of masses or
concretions, or both, and also aquic conditions for some time in
normal years (or artificial drainage).
Key to Great Groups
IAA. Albolls that have a natric horizon.
Natralbolls, p. 562
IAB. Other Albolls.
Argialbolls, p. 560
Argialbolls
These are the Albolls that have an argillic horizon but do not
have a natric horizon. Most of the soils have very dark gray to
black coatings of humus and clay on the peds in the upper part
of the argillic horizon. In the United States, these soils are most
extensive in the loess-covered areas of the Midwestern States
where temperature regimes are mesic. A very few of the soils
have a frigid or thermic temperature regime. A distinct moisture
deficit in summer and a moisture surplus in winter and spring
seem to be essential to the genesis of these soils. Argialbolls are
associated on the landscape with soils of all other suborders of
Mollisols, except possibly for Rendolls. Because they have
gentle slopes, most of the Argialbolls in the United States are
cultivated.
Definition
Argialbolls are the Albolls that have an argillic horizon but do
not have a natric horizon.
KeytoSubgroups
IABA. Argialbolls that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. If not irrigated, a moisture control section that in
normal years is dry in all parts for 45 or more consecutive
days during the 120 days following the summer solstice.
Xerertic Argialbolls
IABB. Other Argialbolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm
Mollisols 561
or a densic, lithic, or paralithic contact, whichever is
shallower.
Vertic Argialbolls
IABC. Other Argialbolls that:
1. Do not have an abrupt textural change from the albic to
the argillic horizon; and
2. If not irrigated, have a moisture control section that in
normal years is dry in all parts for 45 or more consecutive
days during the 120 days following the summer solstice.
Argiaquic Xeric Argialbolls
IABD. Other Argialbolls that do not have an abrupt textural
change from the albic to the argillic horizon.
Argiaquic Argialbolls
IABE. Other Argialbolls that, if not irrigated, have a
moisture control section that in normal years is dry in all parts
for 45 or more consecutive days during the 120 days following
the summer solstice.
Xeric Argialbolls
IABF. Other Argialbolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or more of the following:
1. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
2. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
3. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Argialbolls
IABG. Other Argialbolls.
Typic Argialbolls
Definition of Typic Argialbolls
Typic Argialbolls are the Argialbolls that:
1. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention, and
acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
2. Have an abrupt textural change from the albic to the
argillic horizon;
3. When not irrigated, have a moisture control section that in
normal years is not dry in all parts for as long as 45
consecutive days during the 120 days following the summer
solstice; and
4. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm
or a densic, lithic, or paralithic contact, whichever is
shallower.
Description of Subgroups
Typic Argialbolls.—The central concept or Typic subgroup
of Argialbolls is fixed on soils that are saturated with water at
some season long enough to have a low chroma dominant in
the albic horizon and that receive enough summer rainfall for
the moisture control section to be moistened, at least in some
part, at frequent intervals in normal years. In addition, the
argillic horizon has an abrupt upper boundary, has a markedly
greater percentage of clay than the albic horizon, and has the
accessory property of low or very low hydraulic conductivity
when the water content is at or above field capacity.
Prolonged dryness of the moisture control section occurs in
Mediterranean climates. It is a property of the Xeric suborder
of Mollisols and is the basis for defining the Xeric subgroups
of Argialbolls. A gradual upper boundary of the argillic
horizon or a small difference in the percentage of clay between
the albic and argillic horizons indicates an intergrade to
Argiaquolls. A surface mantle that shows the influence of
562 Soil Taxonomy
pyroclastic materials has many of the properties of Andisols and
is the basis for defining the Aquandic subgroup.
Typic Argialbolls are of moderate extent in the United
States and are mostly on the Great Plains. Most of these soils
supported water-tolerant grasses, sedges, and shrubs. Most are
used as cropland or hayland, and many are artificially drained.
Some are used as grazing land and some as wildlife habitat.
Aquandic Argialbolls.—These soils are like Typic
Argialbolls, but they have a layer in the upper 75 cm that is 18
cm or more thick and has some andic soil properties. The clays
in this layer normally do not disperse well and have a high pHdependent
charge. Typically, this layer is at or very close to the
soil surface. Aquandic Argialbolls are of very small extent in
the United States and are known to occur only in California
and Oregon.
Argiaquic Argialbolls.—These soils are like Typic
Argialbolls, but they do not have the abrupt textural change
required of Typic Argialbolls. They are considered to be
intergrades to Argiaquolls. The hydraulic conductivity in the
argillic horizon of soils in the Argiaquic subgroup normally is
greater than that of Typic Argialbolls. Most Argiaquic
Argialbolls supported water-tolerant grasses. Many have been
artificially drained and are used as cropland or hayland. Some
are used as grazing land and some as wildlife habitat.
Argiaquic Xeric Argialbolls.—These soils consistently
have long periods in summer when the moisture control section
is dry, and they do not have the abrupt textural change that
marks the Typic subgroup. In these properties they resemble
Xerolls and Argiaquolls. Argiaquic Xeric Argialbolls are of
small extent in the United States and are known to occur only
in Oregon, Idaho, and Montana. Some of these soils supported
trees, and some supported mostly water-tolerant grasses and
shrubs. Most of the soils are used as cropland, hayland, or
pasture. Some are used as rangeland.
Vertic Argialbolls.—These soils have a clayey particle-size
class in a significant part, have expanding clays, and in normal
years have deep cracks. They are of small extent in the United
States. They occur throughout the Great Plains. These soils
supported mostly water-tolerant grasses. Most are used as
cropland or hayland. Some have been artificially drained.
Some are used as grazing land and some as wildlife habitat.
Xerertic Argialbolls.—These soils have a clayey particlesize
class in a significant part, have expanding clays, and in
normal years have deep cracks. They consistently have long
periods in summer when the moisture control section is dry.
These soils are of small extent in the United States and are
known to occur only in Oregon and Idaho. Some of the soils
supported coniferous forest vegetation, and some supported
mostly water-tolerant grasses. Most of the soils are used as
cropland or hayland. Some are used as forest and some as
grazing land.
Xeric Argialbolls.—These soils consistently have long
periods in summer when the moisture control section is dry.
They are of moderate extent in the United States and occur
mostly in the Northwestern States. Most of these soils
supported water-tolerant grasses, and some supported
coniferous forest vegetation. Most are used as cropland or
hayland. Some are used as grazing land and some as forest.
Natralbolls
These are the Albolls that have a natric horizon. The natric
horizon normally lies very close to the surface. These soils
commonly have a thin epipedon overlying an albic horizon.
The color of the upper part of the soils, after mixing to a depth
of 18 cm, however, is dark enough for a mollic epipedon
because the epipedon and the natric horizon are dark colored.
Ground water is shallow during part of the year, and capillary
rise in many Natralbolls has concentrated salts, including
sodium salts, in the upper 50 cm of the soils.
Natralbolls are known to occur only in subhumid and humid
regions. They are in areas of late-Pleistocene till plains and
lacustrine deposits or Holocene deposits. The vegetation
consists of grasses and sedges. The soils are used as cropland
or rangeland, or the grasses are cut for hay.
Definition
Natralbolls are the Albolls that have a natric horizon.
Key to Subgroups
IAAA. Natralbolls that have visible crystals of gypsum
and/or more soluble salts within 40 cm of the mineral soil
surface.
Leptic Natralbolls
IAAB. Other Natralbolls.
Typic Natralbolls
Definition of Typic Natralbolls
Typic Natralbolls are the Natralbolls that do not have visible
crystals of gypsum and/or more soluble salts within 40 cm of
the mineral soil surface.
Description of Subgroups
Typic Natralbolls.—The central concept or Typic subgroup
of Natralbolls is fixed on soils that do not have visible crystals
of gypsum and/or more soluble salts within 40 cm of the
mineral soil surface. The salts adversely affect the use of these
soils and are the basis for defining the Leptic subgroup. These
soils are of very small extent in the United States. They are
mostly on the northern Great Plains. They supported mostly
salt-tolerant grasses and sedges. Slopes generally are gentle,
and many of these soils are cultivated. Some of the soils are
used as rangeland or hayland.
Leptic Natralbolls.—These soils have visible evidence of
salts at least as soluble as gypsum within 40 cm of the soil
surface. They have thinner sola than those of the Typic
subgroup, and the close proximity of the soluble salts to the
Mollisols 563
surface restricts plant growth. Leptic Natralbolls are
moderately extensive on the northern Great Plains of the
United States. They are on gentle slopes and are used
primarily as rangeland.
Aquolls
Aquolls are the Mollisols that are wet and that have
dominant low chroma, commonly in olive hues, and have highcontrast
redox depletions in or below the epipedon. These soils
commonly develop in low areas where water collects and
stands, but some are on broad flats or on seepy hillsides. Most
of the soils have had a vegetation of grasses, sedges, and forbs,
but a few also have had forest vegetation. In the United States,
Aquolls are most extensive in glaciated areas of the
Midwestern States where the drift or loess was calcareous. In a
layer above a densic, lithic, or paralithic contact or in a layer at
a depth between 40 and 50 cm from the mineral soil surface,
whichever is shallower, Aquolls have aquic conditions or are
artificially drained. They can have any temperature regime
from cryic to isohyperthermic.
Definition
Aquolls are the Mollisols that have, in a layer above a
densic, lithic, or paralithic contact or in a layer at a depth
between 40 and 50 cm from the mineral soil surface, whichever
is shallower, aquic conditions for some time in normal years
(or artificial drainage) and meet one or more of the following:
1. Have a histic epipedon overlying the mollic epipedon; or
2. Have an exchangeable sodium percentage (ESP) of 15 or
more (or a sodium adsorption ratio [SAR] of 13 or more) in the
upper part of the mollic epipedon and a decrease in ESP (or
SAR) values with increasing depth below 50 cm from the
mineral soil surface; or
3. Have a calcic or petrocalcic horizon that has its upper
boundary within 40 cm of the mineral soil surface; or
4. Have a mollic epipedon, with chroma of 1 or less, that
extends to a lithic contact within 30 cm of the mineral soil
surface; or
5. Have one of the following colors:
a. Chroma of 1 or less in the lower part of the mollic
epipedon; and either
(1) Distinct or prominent redox concentrations in the
lower part of the mollic epipedon; or
(2) Either directly below the mollic epipedon or
within 75 cm of the mineral soil surface if a calcic
horizon intervenes, a color value, moist, of 4 or more and
one of the following:
(a) 50 percent or more chroma of 1 on faces of peds
or in the matrix, hue of 10YR or redder, and redox
concentrations; or
(b) 50 percent or more chroma of 2 or less on faces of
peds or in the matrix, hue of 2.5Y, and redox
concentrations; or
(c) 50 percent or more chroma of 1 on faces of
peds or in the matrix and hue of 2.5Y or yellower;
or
(d) 50 percent or more chroma of 3 or less on faces
of peds or in the matrix, hue of 5Y, and redox
concentrations; or
(e) 50 percent or more chroma of 0 on faces of peds
or in the matrix; or
(f) Hue of 5GY, 5G, 5BG, or 5B; or
(g) Any color if it results from uncoated sand grains;
or
b. Chroma of 2 in the lower part of the mollic epipedon;
and either
(1) Distinct or prominent redox concentrations in the
lower part of the mollic epipedon; or
(2) Matrix colors directly below the mollic epipedon as
follows: either
(a) A color value, moist, of 4, chroma of 2, and some
redox depletions with a color value, moist, of 4 or
more and chroma of 1 or less; or
(b) A color value, moist, of 5 or more, chroma of 2
or less, and redox concentrations; or
(c) A color value, moist, of 4 and chroma of 1 or
less; or
6. At a depth between 40 and 50 cm from the mineral soil
surface, have enough active ferrous iron to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is not
being irrigated; and
7. Do not have both an albic horizon and, within 100 cm of
the mineral soil surface, any subhorizon of the albic horizon
and/or of the argillic or natric horizon that has redox
concentrations in the form of masses or concretions, or both,
and also aquic conditions.
Key to Great Groups
IBA. Aquolls that have a cryic soil temperature regime.
Cryaquolls, p. 566
IBB. Other Aquolls that have a duripan that has its upper
boundary within 100 cm of the mineral soil surface.
Duraquolls, p. 568
564 Soil Taxonomy
IBC. Other Aquolls that have a natric horizon.
Natraquolls, p. 574
IBD. Other Aquolls that have a calcic or gypsic horizon that
has its upper boundary within 40 cm of the mineral soil surface
but do not have an argillic horizon unless it is a buried
horizon.
Calciaquolls, p. 565
IBE. Other Aquolls that have an argillic horizon.
Argiaquolls, p. 564
IBF. Other Aquolls that have episaturation.
Epiaquolls, p. 571
IBG. Other Aquolls.
Endoaquolls, p. 569
Argiaquolls
These are the Aquolls that have both an argillic horizon and a
temperature regime warmer than cryic. In these soils the depth to
ground water fluctuates appreciably and commonly is shallow in
winter and spring but deep in summer. Most of the Argiaquolls
in the United States have been drained and are used as
cropland. They are extensive and are widely distributed
throughout the Midwest and the western parts of the country.
Definition
Argiaquolls are the Aquolls that:
1. Have an argillic horizon but do not have a natric horizon;
and
2. Do not have a duripan that has its upper boundary
within 100 cm of the mineral soil surface; and
3. Have a soil temperature regime that is warmer than cryic.
Key to Subgroups
IBEA. Argiaquolls that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 to 100 cm.
Arenic Argiaquolls
IBEB. Other Argiaquolls that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 100 cm or more.
Grossarenic Argiaquolls
IBEC. Other Argiaquolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Argiaquolls
IBED. Other Argiaquolls that have an argillic horizon that,
with increasing depth, has a clay increase of 20 percent or
more (absolute, in the fine-earth fraction) within its upper 7.5
cm.
Abruptic Argiaquolls
IBEE. Other Argiaquolls.
Typic Argiaquolls
Definition of Typic Argiaquolls
Typic Argiaquolls are the Argiaquolls that:
1. Do not have an argillic horizon that has an increase in clay
content of 20 percent (absolute) or more within a vertical
distance of 7.5 cm below the upper boundary;
2. Have a texture finer than loamy fine sand in some
subhorizon within 50 cm of the mineral soil surface; and
3. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Description of Subgroups
Typic Argiaquolls.—The central concept or Typic subgroup
of Argiaquolls is fixed on soils that have a gradual textural
change at the top of the argillic horizon, have a loamy or
clayey particle-size class close to the surface, but do not have
slickensides, wedge-shaped aggregates, a high linear
extensibility, or wide cracks. An abrupt textural change is the
basis for defining Abruptic extragrades of Argiaquolls. A sandy
surface layer more than 50 cm thick is the basis for defining
Arenic and Grossarenic extragrades. Deep cracks, slickensides,
wedge-shaped aggregates, and a high linear extensibility are
characteristics shared with Vertisols and are the basis for
defining the Vertic subgroup.
Typic Argiaquolls are extensive in the United States. They
Mollisols 565
are widely distributed, but the largest extent is in the Midwest
and on the Great Plains. These soils supported mostly watertolerant
grasses, sedges, and shrubs. Most have been artificially
drained and are used as cropland. Some are used as grazing
land or hayland and some as wildlife habitat.
Abruptic Argiaquolls.—These soils have an abrupt textural
change at the top of the argillic horizon. They become dry in
the moisture control section in normal years. They may be
intergrades to Argialbolls, but they show no clear evidence of
the development of an albic horizon. These soils are of small
extent in the United States and occur mostly on the Great
Plains. They supported mostly water-tolerant grasses, sedges,
and shrubs. Slopes are gentle, and most of the soils have been
artificially drained and are used as cropland or hayland. Some
of the soils are used as grazing land and some as wildlife
habitat.
Arenic Argiaquolls.—These soils have a sandy or sandyskeletal
particle-size class to a depth between 50 and 100 cm.
These soils are of very small extent in the United States and are
known to occur only in Florida.
Grossarenic Argiaquolls.—These soils have a sandy or
sandy-skeletal particle-size class to a depth of more than 100
cm. They are of very small extent in the United States and are
known to occur only in Florida.
Vertic Argiaquolls.—These soils are like Typic Argiaquolls,
but they are high in content of expanding clays and have cracks,
slickensides, wedge-shaped aggregates, or a high linear
extensibility. Most of the soils in this subgroup have a clayey
particle-size class in a significant part. These soils are of
moderate extent in the United States and occur mostly on the
Great Plains. They supported mostly water-tolerant grasses,
sedges, and shrubs. Most of the soils have been artificially
drained and are used as cropland or hayland. Some are used as
grazing land and some as wildlife habitat.
Calciaquolls
These are the Aquolls that have a shallow calcic or gypsic
horizon. They have a temperature regime warmer than cryic,
do not have a natric or argillic horizon, and do not have a
duripan that has its upper boundary within 100 cm of the
mineral soil surface. Capillary rise of calcium-rich water and
then evapotranspiration have been important processes in the
genesis of these soils. In the humid parts of the United States,
the soils commonly formed around the margins of shallow,
intermittent ponds in closed depressions left by glaciers. In
semiarid and arid areas, the soils are mainly on flood plains,
low terraces, and the margins of Pleistocene lakes where
ground water is shallow. A calcic horizon normally is at or
very close to the surface of the soils. Carbonates in high
concentrations act as a white pigment, and not all Calciaquolls
have a surface horizon that is dark colored when dry. Aquolls
with a gypsic horizon are included with Calciaquolls, but no
Calciaquolls with a gypsic horizon have been recognized in the
United States.
Calciaquolls are moderately extensive in the United States.
Most are calcareous from the surface downward, and problems
with plant chlorosis are common. In humid regions potassium
deficiency in plants can be severe. In arid regions salinity may
be a problem.
Definition
Calciaquolls are the Aquolls that:
1. Have a calcic or gypsic horizon that has its upper boundary
within 40 cm of the mineral soil surface;
2. Have a soil temperature regime warmer than cryic;
3. Do not have a natric or argillic horizon; and
4. Do not have a duripan that has its upper boundary
within 100 cm of the mineral soil surface.
Key to Subgroups
IBDA. Calciaquolls that have a petrocalcic horizon that has
its upper boundary within 100 cm of the mineral soil surface.
Petrocalcic Calciaquolls
IBDB. Other Calciaquolls that have 50 percent or more
chroma of 3 or more on faces of peds or in the matrix of one or
more horizons within 75 cm of the mineral soil surface or that
have the following colors directly below the mollic epipedon:
1. Hue of 2.5Y or yellower and chroma of 3 or more; or
2. Hue of 10YR or redder and chroma of 2 or more; or
3. Hue of 2.5Y or yellower and chroma of 2 or more if
there are no distinct or prominent redox concentrations.
Aeric Calciaquolls
IBDC. Other Calciaquolls.
Typic Calciaquolls
Definition of Typic Calciaquolls
Typic Calciaquolls are the Calciaquolls that:
1. Have more than 50 percent chroma of 2 or less on faces of
peds or in the matrix in all horizons within 75 cm of the
mineral soil surface or have the following colors directly below
the mollic epipedon:
a. Hue of 2.5Y or yellower, chroma of 2 or less, and
distinct or prominent redox concentrations; or
b. Hue of 2.5Y or yellower and chroma of 1; or
c. Hue of 10YR or redder and chroma of 1; or
d. Chroma of 0; and
566 Soil Taxonomy
2. Do not have a petrocalcic horizon that has its upper
boundary within 100 cm of the mineral soil surface.
Description of Subgroups
Typic Calciaquolls.—The central concept or Typic
subgroup of Calciaquolls is fixed on soils that have redox
concentrations with high chroma or have low chroma at a
shallow depth and that do not have a petrocalcic horizon
above a depth of 100 cm.
The absence of redox concentrations that have high chroma
and chroma in the matrix higher than that of the Typic
subgroup are evidence of somewhat better natural drainage
than that of the Typic subgroup, and these properties are the
basis for defining the Aeric subgroup. A shallow petrocalcic
horizon is known to occur only in arid climates and is not
considered normal. It is the basis for defining the Petrocalcic
subgroup. Calciaquolls that have a gypsic horizon are included
in the Typic subgroup, but none are known to occur in the
United States.
Typic Calciaquolls are moderately extensive in the United
States. They are widely distributed, but the largest extent is in
the Midwest and on the Great Plains. These soils supported
mostly water-tolerant grasses, sedges, and shrubs. Most are
used as grazing land or hayland. Some are used as cropland
and some as wildlife habitat.
Aeric Calciaquolls.—These soils have chroma higher than
that of Typic Calciaquolls and are deeper to redox
concentrations. Ground water is normally deeper than in soils
of the Typic subgroup. Aeric Calciaquolls are of moderate
extent in the United States, mostly on the Great Plains. They
supported mostly water-tolerant grasses and shrubs. Most of
the soils are used as cropland, grazing land, or hayland, but
some are used as wildlife habitat.
Petrocalcic Calciaquolls.—These soils have a petrocalcic
horizon within 100 cm of the mineral soil surface and
commonly within 50 cm. They are mostly on the margins of
Pleistocene lakes in arid regions. The processes that produced
the petrocalcic horizon are not understood. These soils are of
very small extent in the United States and are known to occur
only in Utah.
Cryaquolls
Cryaquolls are the cold Aquolls of high elevations or
high latitudes. Because they are both wet and cold, most
of these soils are not cultivated. The presence or absence
of horizons used to define the great groups of warmer soils
has less significance to the use of these soils, although the
processes that produced the horizons appear to be similar.
Cryaquolls may have an argillic or cambic horizon or a
shallow calcic horizon. In the United States, these soils are
mostly in high mountain valleys in the West, but they are not
extensive. They are used mostly for grazing, or the grasses are
cut for hay.
Definition
Cryaquolls are the Aquolls that have a cryic temperature
regime.
Key to Subgroups
IBAA. Cryaquolls that have one or both of the following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Cryaquolls
IBAB. Other Cryaquolls that have a histic epipedon.
Histic Cryaquolls
IBAC. Other Cryaquolls that have a buried layer of organic
soil materials, 20 cm or more thick, that has its upper
boundary within 100 cm of the mineral soil surface.
Thapto-Histic Cryaquolls
IBAD. Other Cryaquolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or more of the following:
1. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
2. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
3. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Cryaquolls
IBAE. Other Cryaquolls that have an argillic horizon.
Argic Cryaquolls
IBAF. Other Cryaquolls that have a calcic horizon either
within or directly below the mollic epipedon.
Calcic Cryaquolls
Mollisols 567
IBAG. Other Cryaquolls that have a mollic epipedon 50 cm or
more thick.
Cumulic Cryaquolls
IBAH. Other Cryaquolls.
Typic Cryaquolls
Definition of Typic Cryaquolls
Typic Cryaquolls are the Cryaquolls that:
1. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
2. Do not have an argillic horizon;
3. Do not have a calcic horizon within or directly below the
mollic epipedon;
4. Have a mollic epipedon that is less than 50 cm thick;
5. Do not have a histic epipedon;
6. Do not have a buried layer of organic soil materials, 20 cm
or more thick, that has its upper boundary within a depth of
100 cm; and
7. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Description of Subgroups
Typic Cryaquolls.—The central concept or Typic subgroup
of Cryaquolls is fixed on soils that have a mollic epipedon less
than 50 cm thick and that do not have a histic epipedon or an
argillic or calcic horizon. These soils do not have slickensides,
wedge-shaped aggregates, a high linear extensibility, or wide
cracks. They do not have a buried Histosol or a surface mantle
or layer in the upper 75 cm that has both a low bulk density
and a high content of weakly crystalline minerals or that
consists of slightly or moderately weathered pyroclastic
materials because these properties are shared with Andisols.
An argillic horizon in or below the mollic epipedon is rare
and is the basis for defining intergrades to Argiaquolls. A
calcic horizon in or directly below the epipedon is rare and is
the basis for defining intergrades to Calciaquolls. The
thickness of the mollic epipedon is normally less than 50 cm,
but in some Cryaquolls the thickness is quite variable within
distances of a few centimeters because of frost action. Tongues
of the mollic epipedon a few centimeters across may penetrate
the cambic horizon for a distance of more than 25 cm. If such
tongues are present, the average penetration is used to
determine the thickness of the epipedon. An overthickened
epipedon is the basis for defining the Cumulic extragrade.
The wettest Cryaquolls may have a histic epipedon, and they
are regarded as a transition to Histosols. A buried Histosol at a
depth of less than 100 cm is the basis for defining the ThaptoHistic
subgroup.
Typic Cryaquolls are of moderate extent in the United
States. They are mostly in mountain valleys in the Western
States. These soils supported mostly water-tolerant grasses,
sedges, and shrubs. Most of the soils are used as grazing land
or wildlife habitat.
Aquandic Cryaquolls.—These soils are like Typic
Cryaquolls, but they have a surface mantle or layer in the upper
75 cm that has both a low bulk density and a high content of
weakly crystalline minerals or that consists of slightly or
moderately weathered pyroclastic materials. These soils are of
small extent in the United States. They are in mountain valleys
in the Northwestern States. They supported mostly watertolerant
grasses, sedges, and shrubs. Most of the soils are used
as grazing land or wildlife habitat.
Argic Cryaquolls.—These soils have an argillic horizon
and are considered intergrades to Argiaquolls. They are of
small extent in the United States. They are mostly in mountain
valleys in the Western States. They supported mostly watertolerant
grasses, sedges, and shrubs. Most of the soils are used
as grazing land or wildlife habitat.
Calcic Cryaquolls.—These soils have a calcic horizon in or
directly below the mollic epipedon and are considered
intergrades to Calciaquolls. The water table usually is high
during the short summer, and the water results in enrichment
of the surface layer with carbonates by capillary rise and
568 Soil Taxonomy
evapotranspiration. These soils are of small extent in the United
States. They are mostly in mountain valleys in the Western
States. They supported mostly water-tolerant grasses, sedges,
and shrubs. Most of the soils are used as grazing land or wildlife
habitat.
Cumulic Cryaquolls.—These soils have an overthickened
mollic epipedon as a result of slow accumulation of material
washed from higher areas. They are subject to occasional
flooding when streams are high. These soils are of small extent
in the United States. They are mostly in narrow mountain
valleys in the Western States. They supported mostly watertolerant
grasses, sedges, shrubs, and trees. Most of the soils are
used as grazing land or wildlife habitat.
Histic Cryaquolls.—These soils have a histic epipedon and
are considered intergrades to Histosols. They are the wettest of
the Cryaquolls, and the level of ground water in them
fluctuates the least. Histic Cryaquolls are rare in the United
States. They are known to occur only in Colorado.
Thapto-Histic Cryaquolls.—These soils formed in mineral
deposits over a Histosol. The epipedon may extend to the
buried Histosol, which has its upper boundary within 100 cm
of the mineral soil surface. These soils are not known to occur
in the United States.
Vertic Cryaquolls.—These soils have a clayey particle-size
class in a significant part, have expanding clays, and in normal
years have deep cracks. They are dry periodically in at least the
upper part during normal years. They are not known to occur
in the United States.
Duraquolls
These are the Aquolls that have a duripan and a soil
temperature regime warmer than cryic. In the United States,
these soils are restricted to areas that have a Mediterranean
climate or to arid regions. All Duraquolls are near enough to
volcanoes to have received ash falls. They are wet in winter,
but most are quite dry in summer. The upper boundary of the
duripan most commonly lies about 50 to 75 cm below the soil
surface. These soils range from slightly acid to strongly
alkaline. They are of small extent.
Definition
Duraquolls are the Aquolls that:
1. Have a duripan that has its upper boundary within 100 cm
of the mineral soil surface; and
2. Have a soil temperature regime that is warmer than cryic.
Key to Subgroups
IBBA. Duraquolls that have a natric horizon.
Natric Duraquolls
IBBB. Other Duraquolls that have, above the duripan, one or
both of the following:
1. Cracks that are 5 mm or more wide through a thickness of
30 cm or more for some time in normal years, and slickensides
or wedge-shaped aggregates in a layer 15 cm or more thick;
or
2. A linear extensibility of 6.0 cm or more.
Vertic Duraquolls
IBBC. Other Duraquolls that have an argillic horizon.
Argic Duraquolls
IBBD. Other Duraquolls.
Typic Duraquolls
Definition of Typic Duraquolls
Typic Duraquolls are the Duraquolls that:
1. Do not have an argillic or natric horizon; and
2. Do not have either:
a. Cracks that for some time in normal years are 5 mm or
more wide throughout a layer 30 cm or more thick either
within 125 cm of the mineral soil surface or above a duripan
if shallower, and slickensides or wedge-shaped aggregates
in a layer 15 cm or more thick that has its upper boundary
within 125 cm of the mineral soil surface or above a duripan
if shallower; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact or a duripan, whichever
is shallower.
Description of Subgroups
Typic Duraquolls.—The central concept or Typic subgroup
of Duraquolls is fixed on soils that do not have an argillic
horizon and do not have a natric horizon. These soils do not
have deep cracks, slickensides, wedge-shaped aggregates, or a
high linear extensibility. The presence of an argillic or natric
horizon is the basis for defining intergrades to Argiaquolls and
Natraquolls, respectively. Typic Duraquolls are of small extent
in the United States. They are only in the Western States. They
supported mostly water-tolerant grasses, sedges, and shrubs.
Most of the soils are used as irrigated cropland, hayland, or
rangeland.
Argic Duraquolls.—These soils are like Typic Duraquolls,
but they have an argillic horizon. They are of very small extent
in the United States. They are known to occur only in
California and Oregon, where they are used mostly as
rangeland.
Natric Duraquolls.—These soils are like Typic Duraquolls,
but they have a natric horizon above the duripan. They are of
small extent in the United States. They are only in the Western
States. They supported mostly water-tolerant grasses, sedges,
and shrubs. Most of the soils are used as irrigated cropland,
hayland, or rangeland.
Mollisols 569
Vertic Duraquolls.—These soils are like Typic Duraquolls,
but they have a clayey particle-size class in a significant part,
have expanding clays, and in normal years have deep cracks.
They are of very small extent in the United States. They
supported mostly water-tolerant grasses.
Endoaquolls
These are the Aquolls that have both endosaturation and a
temperature regime warmer than cryic. They do not have an
argillic, natric, calcic, or gypsic horizon. The depth to ground
water fluctuates appreciably in these soils. Commonly, the
ground water is at or near the soil surface in winter and spring
but is deep in summer. Most of the Endoaquolls in the United
States have been artificially drained and are used as cropland.
They are extensive and are widely distributed throughout the
Midwest and the western parts of the country.
Definition
Endoaquolls are the Aquolls that:
1. Have endosaturation;
2. Have a soil temperature regime that is warmer than
cryic;
3. Do not have an argillic or natric horizon;
4. Do not have a duripan that has its upper boundary
within 100 cm of the mineral soil surface; and
5. Do not have a calcic or gypsic horizon that has its upper
boundary within 40 cm of the mineral soil surface.
Key to Subgroups
IBGA. Endoaquolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Endoaquolls
IBGB. Other Endoaquolls that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. A mollic epipedon 60 cm or more thick.
Cumulic Vertic Endoaquolls
IBGC. Other Endoaquolls that have both of the following:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. A slope of less than 25 percent; and either
a. An organic-carbon content of 0.3 percent or more in
all horizons within 125 cm of the mineral soil surface; or
b. An irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm or to a
densic, lithic, or paralithic contact if shallower.
Fluvaquentic Vertic Endoaquolls
IBGD. Other Endoaquolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Endoaquolls
IBGE. Other Endoaquolls that have a histic epipedon.
Histic Endoaquolls
IBGF. Other Endoaquolls that have a buried layer of organic
soil materials, 20 cm or more thick, that has its upper boundary
within 100 cm of the mineral soil surface.
Thapto-Histic Endoaquolls
IBGG. Other Endoaquolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or more of the following:
1. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
2. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
570 Soil Taxonomy
3. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Endoaquolls
IBGH. Other Endoaquolls that have a horizon, 15 cm or
more thick within 100 cm of the mineral soil surface, that
either has 20 percent or more (by volume) durinodes or is
brittle and has a firm rupture-resistance class when moist.
Duric Endoaquolls
IBGI. Other Endoaquolls that have a mollic epipedon 60 cm
or more thick.
Cumulic Endoaquolls
IBGJ. Other Endoaquolls that have a slope of less than 25
percent; and either
1. An organic-carbon content of 0.3 percent or more in all
horizons within 125 cm of the mineral soil surface; or
2. An irregular decrease in organic-carbon content from a
depth of 25 cm to a depth of 125 cm or to a densic, lithic, or
paralithic contact if shallower.
Fluvaquentic Endoaquolls
IBGK. Other Endoaquolls.
Typic Endoaquolls
Definition of Typic Endoaquolls
Typic Endoaquolls are the Endoaquolls that:
1. Do not have a histic epipedon;
2. Do not have a buried layer of organic soil materials, 20 cm
or more thick, that has its upper boundary within 100 cm of the
mineral soil surface;
3. Do not have a horizon, 15 cm or more thick within 100 cm
of the mineral soil surface, that has 20 percent or more (by
volume) durinodes or is brittle and has a firm ruptureresistance
class when moist;
4. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower;
5. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, any of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
6. Do not have a lithic contact within 50 cm of the mineral
soil surface;
7. Have a mollic epipedon that is less than 60 cm thick; and
8. Either have less than 0.3 percent organic carbon at a depth
of 125 cm below the mineral soil surface and a regular
decrease in organic-carbon content from a depth of 25 cm to a
depth of 125 cm or to a densic, lithic, or paralithic contact if
shallower or have a slope of 25 percent or more.
Description of Subgroups
Typic Endoaquolls.—The Typic subgroup of Endoaquolls is
fixed on deep soils that do not have slickensides, wedge-shaped
aggregates, a high linear extensibility, or wide cracks. These
soils have a mollic epipedon less than 60 cm thick and have
both a regular decrease in organic-carbon content with
increasing depth and an organic-carbon content of less than 0.3
percent in some horizon within 125 cm of the mineral soil
surface. They do not have a horizon within 100 cm of the
mineral soil surface that has 20 percent or more durinodes or is
brittle and has a firm rupture-resistance class when moist.
These soils do not have a lithic contact, a histic epipedon, or a
buried organic layer.
Soils that have slickensides, wedge-shaped aggregates, a
high linear extensibility, or wide cracks are assigned to Vertic
or combination Vertic subgroups because these properties are
shared with Vertisols. Typic Endoaquolls do not have a surface
mantle or layer in the upper 75 cm that has both a low bulk
density and a high content of weakly crystalline minerals or
that consists of slightly or moderately weathered pyroclastic
materials because these properties are shared with Andisols.
Mollisols 571
Typic Endoaquolls are extensive and occur throughout a
large part of the United States. They are most extensive in the
Midwestern States. They are nearly level. Most of the soils
have been artificially drained and are used as cropland, but
some are used as pasture or forest.
Aquandic Endoaquolls.—These soils have a surface mantle
or layer in the upper 75 cm that has both a low bulk density
and a high content of weakly crystalline minerals or that
consists of slightly or moderately weathered pyroclastic
materials. These soils are of small extent in the United States
and occur only in the Western States. They are used mostly as
pasture or have been artificially drained and are used as
cropland.
Cumulic Endoaquolls.—These soils have a mollic epipedon
60 cm or more thick. They commonly have an irregular
decrease in organic-carbon content with increasing depth. They
formed mostly in recent alluvium on flood plains or in closed
depressions. These soils are extensive and occur throughout a
large part of the United States. They are most extensive in the
Midwestern and Western States. Many of the soils have been
artificially drained and are used as cropland. Some are used as
pasture and some as woodland or wildlife habitat.
Cumulic Vertic Endoaquolls.—These soils are high in
content of expanding clays and have cracks 5 mm or more
wide, slickensides, wedge-shaped aggregates, or a high linear
extensibility. They also have a mollic epipedon 60 cm or more
thick. They formed mostly in recent alluvium on flood plains
or in closed depressions. These soils are of small extent and
occur mostly in the Midwestern States of the United States.
Many of the soils have been artificially drained and are used as
cropland. Some are used as pasture and some as woodland or
wildlife habitat.
Duric Endoaquolls.—These soils have a horizon, 15 cm or
more thick within 100 cm of the mineral soil surface, that has
20 percent or more (by volume) durinodes or is brittle and has
a firm rupture-resistance class when moist. These soils are rare
in the United States.
Fluvaquentic Endoaquolls.—These soils are like Typic
Endoaquolls, but they have an irregular decrease in organiccarbon
content with increasing depth or have an organiccarbon
content of 0.3 percent or more in all horizons within
125 cm of the mineral soil surface. The soils formed mostly in
recent alluvium on flood plains. They are extensive and occur
throughout a large part of the United States. Many of the soils
have been artificially drained and are used as cropland. Some
are used as pasture and some as woodland or wildlife habitat.
Fluvaquentic Vertic Endoaquolls.—These soils are high in
content of expanding clays and have cracks 5 mm or more
wide, slickensides, wedge-shaped aggregates, or a high linear
extensibility. They also have an irregular decrease in organiccarbon
content with increasing depth or have an organiccarbon
content of 0.3 percent or more in all horizons within
125 cm of the mineral soil surface. These soils formed mostly
in recent alluvium on flood plains. They are of small extent in
the United States. Many of the soils have been artificially
drained and are used as cropland. Some are used as pasture and
some as woodland or wildlife habitat.
Histic Endoaquolls.—These soils are like Typic
Endoaquolls, but they have a histic epipedon. They are more
poorly drained than Typic Endoaquolls. Histic Endoaquolls are
rare in the United States.
Lithic Endoaquolls.—These soils are like Typic
Endoaquolls, but they have a lithic contact within 50 cm of the
mineral soil surface. They are rare in the United States.
Thapto-Histic Endoaquolls.—These soils are like Typic
Endoaquolls, but they have a buried Histosol with its upper
boundary within 100 cm of the mineral soil surface. They are
not known to occur in the United States.
Vertic Endoaquolls.—These soils are like Typic Endoaquolls,
but they are high in content of expanding clays and have cracks,
slickensides, wedge-shaped aggregates, or a high linear
extensibility. They formed mostly in late-Pleistocene or Holocene
deposits. Vertic Endoaquolls are of moderate extent in the United
States, mostly in the Midwest and on the Great Plains. Many of
the soils have been artificially drained and are used as cropland.
Some are used as pasture and some as woodland, rangeland, or
wildlife habitat.
Epiaquolls
These are the Aquolls that have both episaturation and a
temperature regime warmer than cryic. They do not have an
argillic or natric horizon. The depth to ground water fluctuates
appreciably in these soils. A perched water table is at or near
the soil surface during wet periods, mostly in winter and early
spring, but commonly does not occur during dry periods in
summer. Most of the Epiaquolls in the United States have
some artificial drainage, mostly surface drainage, and are
used as cropland. The soils are extensive and are widely
distributed throughout the Midwest and the western parts of
the country.
Definition
Epiaquolls are the Aquolls that:
1. Have episaturation;
2. Have a soil temperature regime that is warmer than cryic;
3. Do not have an argillic or natric horizon;
4. Do not have a duripan that has its upper boundary
within 100 cm of the mineral soil surface; and
5. Do not have a calcic horizon that has its upper boundary
within 40 cm of the mineral soil surface.
Key to Subgroups
IBFA. Epiaquolls that have both of the following:
1. One or both of the following:
572 Soil Taxonomy
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. A mollic epipedon 60 cm or more thick.
Cumulic Vertic Epiaquolls
IBFB. Other Epiaquolls that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. A slope of less than 25 percent; and either
a. An organic-carbon content of 0.3 percent or more in
all horizons within 125 cm of the mineral soil surface; or
b. An irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm or to a
densic, lithic, or paralithic contact if shallower.
Fluvaquentic Vertic Epiaquolls
IBFC. Other Epiaquolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Epiaquolls
IBFD. Other Epiaquolls that have a histic epipedon.
Histic Epiaquolls
IBFE. Other Epiaquolls that have a buried layer of organic soil
materials, 20 cm or more thick, that has its upper boundary
within 100 cm of the mineral soil surface.
Thapto-Histic Epiaquolls
IBFF. Other Epiaquolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or more of the following:
1. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
2. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
3. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Epiaquolls
IBFG. Other Epiaquolls that have a horizon, 15 cm or more
thick within 100 cm of the mineral soil surface, that either has
20 percent or more (by volume) durinodes or is brittle and has
a firm rupture-resistance class when moist.
Duric Epiaquolls
IBFH. Other Epiaquolls that have a mollic epipedon 60 cm or
more thick.
Cumulic Epiaquolls
IBFI. Other Epiaquolls that have a slope of less than 25
percent; and either
1. An organic-carbon content of 0.3 percent or more in all
horizons within 125 cm of the mineral soil surface; or
2. An irregular decrease in organic-carbon content from a
depth of 25 cm to a depth of 125 cm or to a densic, lithic, or
paralithic contact if shallower.
Fluvaquentic Epiaquolls
IBFJ. Other Epiaquolls.
Typic Epiaquolls
Definition of Typic Epiaquolls
Typic Epiaquolls are the Epiaquolls that:
1. Do not have a histic epipedon;
Mollisols 573
2. Do not have a buried layer of organic soil materials, 20 cm or
more thick, that has its upper boundary within 100 cm of the
mineral soil surface;
3. Do not have a horizon, 15 cm or more thick within 100 cm
of the mineral soil surface, that has 20 percent or more (by
volume) durinodes or is brittle and has a firm ruptureresistance
class when moist;
4. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, any of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
5. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
6. Have a mollic epipedon less than 60 cm thick; and
7. Either have less than 0.3 percent organic carbon at a depth
of 125 cm below the mineral soil surface and a regular
decrease in organic-carbon content from a depth of 25 cm to a
depth of 125 cm or to a densic, lithic, or paralithic contact if
shallower or have a slope of 25 percent or more.
Description of Subgroups
Typic Epiaquolls.—The Typic subgroup of Epiaquolls is
centered on deep soils that do not have slickensides, wedgeshaped
aggregates, a high linear extensibility, or wide cracks.
These soils have a mollic epipedon that is less than 60 cm
thick and have both a regular decrease in organic-carbon
content with increasing depth and an organic-carbon content of
less than 0.3 percent in some horizon within 125 cm of the
mineral soil surface. They do not have a horizon within 100
cm of the mineral soil surface that has 20 percent or more
durinodes or is brittle and has a firm rupture-resistance class
when moist.
Soils that have slickensides, wedge-shaped aggregates, a
high linear extensibility, or wide cracks are assigned to Vertic
and combination Vertic subgroups because these properties are
shared with Vertisols. Typic Epiaquolls do not have a surface
mantle or layer in the upper 75 cm that has both a low bulk
density and a high content of weakly crystalline minerals or
that consists of slightly or moderately weathered pyroclastic
materials because these properties are shared with Andisols.
Typic Epiaquolls are moderately extensive in the United
States and are mostly in the Midwestern States. These soils are
nearly level. Most have been artificially drained and are used
as cropland. Some are used as pasture and some as forest.
Aquandic Epiaquolls.—These soils are like Typic
Epiaquolls, but they have a surface mantle or layer in the upper
75 cm that has both a low bulk density and a high content of
weakly crystalline minerals or that consists of slightly or
moderately weathered pyroclastic materials. Aquandic
Epiaquolls are not known to occur in the United States.
Cumulic Epiaquolls.—These soils are like Typic
Epiaquolls, but they have a mollic epipedon 60 cm or more
thick. They commonly have an irregular decrease in organiccarbon
content with increasing depth. They formed mostly in
recent alluvium on flood plains or in closed depressions.
Cumulic Epiaquolls are of very small extent.
Cumulic Vertic Epiaquolls.—These soils are like Typic
Epiaquolls, but they are high in content of expanding clays and
have cracks 5 mm or more wide, slickensides, wedge-shaped
aggregates, or a high linear extensibility. They also have a
mollic epipedon 60 cm or more thick. These soils formed
mostly in recent alluvium on flood plains or in closed
depressions. They are of small extent in the United States.
They are nearly level. Most of the soils have been artificially
drained and are used as cropland. Some are used as pasture and
some as forest.
Duric Epiaquolls.—These soils have a horizon, 15 cm or
more thick within 100 cm of the mineral soil surface, that has
20 percent or more (by volume) durinodes or is brittle and has
a firm rupture-resistance class when moist. They are otherwise
like Typic Epiaquolls in their defined properties and in most
other properties. Duric Epiaquolls are not known to occur in
the United States.
Fluvaquentic Epiaquolls.—These soils are like Typic
Epiaquolls, but they have an irregular decrease in organiccarbon
content with increasing depth or have an organiccarbon
content of 0.3 percent or more in all horizons within
574 Soil Taxonomy
125 cm of the mineral soil surface. These soils formed mostly in
recent alluvium on flood plains. They are not known to occur in
the United States.
Fluvaquentic Vertic Epiaquolls.—These soils are like
Typic Epiaquolls, but they are high in content of expanding
clays and have cracks 5 mm or more wide, slickensides,
wedge-shaped aggregates, or a high linear extensibility. They
also have an irregular decrease in organic-carbon content with
increasing depth or have an organic-carbon content of 0.3
percent or more in all horizons within 125 cm of the mineral
soil surface. These soils formed mostly in recent alluvium on
flood plains. They are not known to occur in the United States.
Histic Epiaquolls.—These soils are like Typic Epiaquolls,
but they have a histic epipedon. They are more poorly drained
than Typic Epiaquolls. Histic Epiaquolls are rare in the United
States.
Thapto-Histic Epiaquolls.—These soils are like Typic
Epiaquolls, but they have a buried Histosol with its upper
boundary within 100 cm of the mineral soil surface. These soils
are not known to occur in the United States.
Vertic Epiaquolls.—These soils are like Typic Epiaquolls, but
they are high in content of expanding clays and have cracks 5
mm or more wide, slickensides, wedge-shaped aggregates, or a
high linear extensibility. These soils formed mostly in latePleistocene
or Holocene deposits. They are of moderate extent
in the United States, mostly in the Midwest and on the Great
Plains. Many of the soils have been artificially drained and are
used as cropland. Some are used as pasture and some as
woodland, rangeland, or wildlife habitat.
Natraquolls
These are the Aquolls that have a temperature regime warmer
than cryic and have a natric horizon. They do not have a duripan
within 100 cm of the mineral soil surface. The natric horizon
normally lies very close to the surface. The thin overlying
horizon commonly has a dry color that is too light for a mollic
epipedon. The color of the upper part of the soils, after mixing to
a depth of 18 cm, however, is dark enough for a mollic epipedon
because the natric horizon is nearly black. Ground water is
shallow during most of the year, and capillary rise in many
Natraquolls has concentrated salts, including sodium salts, in
the upper 50 cm of the soils.
Natraquolls are known to occur only in subhumid to arid
regions. They are on flood plains and on the margins of lakes.
They formed in late-Pleistocene or Holocene deposits. The
vegetation consists of grasses, sedges, and shrubs. The soils are
used as rangeland, or the grasses are cut for hay. The soils are
rarely cultivated. They are rare in the United States.
Definition
Natraquolls are the Aquolls that:
1. Have a natric horizon;
2. Have a soil temperature regime that is warmer than cryic;
and
3. Do not have a duripan that has its upper boundary
within 100 cm of the soil surface.
Key to Subgroups
IBCA. Natraquolls that have one or both of the following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Natraquolls
IBCB. Other Natraquolls.
Typic Natraquolls
Definition of Typic Natraquolls
Typic Natraquolls are the Natraquolls that do not have
either:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or more
for some time in normal years, and slickensides or wedgeshaped
aggregates in a layer 15 cm or more thick that has its
upper boundary within 125 cm of the mineral soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact, whichever is shallower.
Description of Subgroups
Typic Natraquolls.—The central concept or Typic subgroup
of Natraquolls is fixed on soils that do not have slickensides,
wedge-shaped aggregates, a high linear extensibility, or wide
cracks. Deep cracks, slickensides, wedge-shaped aggregates,
and a high linear extensibility are characteristics shared with
Vertisols and are the basis for defining the Vertic subgroup.
Typic Natraquolls are of small extent in the United States.
They are widely distributed throughout the Western United
States. These soils supported mostly salt-tolerant grasses,
sedges, and shrubs. Some of the soils have been artificially
drained and are used as cropland. Some are used as grazing
land or hayland and some as wildlife habitat.
Vertic Natraquolls.—These soils are like Typic
Natraquolls, but they have a clayey particle-size class in a
significant part, have expanding clays, and in normal years
have deep cracks. They are of small extent in the United States.
They are recognized only in South Dakota. These soils
Mollisols 575
supported mostly salt-tolerant grasses, sedges, and shrubs.
Most are used as hayland or grazing land.
Cryolls
Cryolls are the cool or cold, more or less freely drained
Mollisols. They are moderately extensive in the high
mountains of the Western United States. They also are
extensive on the plains and mountains of Eastern Europe and
in Asia. On the plains they are mainly in areas of latePleistocene
or Holocene deposits. In the mountains of the
Western States, some of the soils may be on older surfaces, but
the geomorphology of these areas has had little study.
Cryolls have a cryic temperature regime and a udic, ustic, or
xeric moisture regime.
The vegetation on the Cryolls on the plains was mostly
grasses. The Cryolls in the mountains have either forest or
grass vegetation. On the Cryolls in Alaska, spruce, birch, and
aspen trees are common.
Definition
Cryolls are the Mollisols that:
1. Have a cryic soil temperature regime;
2. Do not have all of the following:
a. An argillic or natric horizon; and
b. An albic horizon that has chroma of 2 or less, that has
its lower boundary 18 cm or more below the mineral soil
surface, and either lies directly below the mollic epipedon or
separates horizons that together meet all of the requirements
for a mollic epipedon; and
c. In one or more subhorizons of the albic horizon and/or
of the argillic or natric horizon and within 100 cm of the
mineral soil surface, redox concentrations in the form of
masses or concretions, or both, and also aquic conditions for
some time in normal years (or artificial drainage);
3. Do not have the characteristics defined for Aquolls; and
4. Have one or more of the following:
a. Either within or directly below the mollic epipedon,
mineral soil materials less than 7.5 cm in diameter that
have a CaCO3
equivalent of less than 40 percent; or
b. A mollic epipedon 50 cm or more thick; or
c. An argillic or calcic horizon.
Key to Great Groups
IDA. Cryolls that have a duripan that has its upper boundary
within 100 cm of the mineral soil surface.
Duricryolls, p. 579
IDB. Other Cryolls that have a natric horizon.
Natricryolls, p. 582
IDC. Other Cryolls that have both:
1. An argillic horizon that has its upper boundary 60 cm or
more below the mineral soil surface; and
2. A texture finer than loamy fine sand in all horizons above
the argillic horizon.
Palecryolls, p. 583
IDD. Other Cryolls that have an argillic horizon.
Argicryolls, p. 575
IDE. Other Cryolls that:
1. Have a calcic or petrocalcic horizon that has its upper
boundary within 100 cm of the mineral soil surface; and
2. In all parts above the calcic or petrocalcic horizon, after
the materials between the soil surface and a depth of 18 cm
have been mixed, either are calcareous or have a texture of
loamy fine sand or coarser.
Calcicryolls, p. 578
IDF. Other Cryolls.
Haplocryolls, p. 579
Argicryolls
These are the Cryolls that have an argillic horizon close to the
surface. Commonly, the upper part of the argillic horizon is in the
mollic epipedon. Some of these soils have a Bk horizon below
the argillic horizon. Argicryolls do not have a natric horizon or a
duripan.
Argicryolls formed mainly in Pleistocene or Holocene
deposits or are on surfaces of equivalent ages. They have cool
or short summers.
Most Argicryolls in the United States are in the mountains
of the Western States. A few are in Alaska. In other countries
at high latitudes, Argicryolls also developed on plains. In the
United States, the vegetation at the time of settlement was
either forest or grass. Many of the soils had grasses and
scattered conifer trees. Most of the soils are used as rangeland
or forest. Some are cultivated and used for small grain or for
hay.
Definition
Argicryolls are the Cryolls that:
1. Have an argillic horizon that has its upper boundary less
than 60 cm below the mineral soil surface or have a texture of
loamy fine sand or coarser in all horizons above the argillic
horizon;
2. Do not have a natric horizon; and
576 Soil Taxonomy
3. Do not have a duripan that has its upper boundary
within 100 cm of the mineral soil surface.
Key to Subgroups
IDDA. Argicryolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Argicryolls
IDDB. Other Argicryolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Argicryolls
IDDC. Other Argicryolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Argicryolls
IDDD. Other Argicryolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Argicryolls
IDDE. Other Argicryolls that have an argillic horizon that,
with increasing depth, has a clay increase of 20 percent or
more (absolute, in the fine-earth fraction) within its upper
7.5 cm.
Abruptic Argicryolls
IDDF. Other Argicryolls that have, in one or more horizons
within 100 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Argicryolls
IDDG. Other Argicryolls that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Argicryolls
IDDH. Other Argicryolls that have a mollic epipedon that is
40 cm or more thick and has a texture finer than loamy fine
sand.
Pachic Argicryolls
IDDI. Other Argicryolls that have either:
1. Above the argillic horizon, an albic horizon or a
horizon that has color values too high for a mollic epipedon
and chroma too high for an albic horizon; or
2. A glossic horizon, or interfingering of albic materials
into the upper part of the argillic horizon, or skeletans of
clean silt and sand covering 50 percent or more of the faces
of peds in the upper 5 cm of the argillic horizon.
Alfic Argicryolls
IDDJ. Other Argicryolls that have an ustic moisture regime.
Ustic Argicryolls
IDDK. Other Argicryolls that have a xeric moisture regime.
Xeric Argicryolls
IDDL. Other Argicryolls.
Typic Argicryolls
Definition of Typic Argicryolls
Typic Argicryolls are the Argicryolls that:
1. Do not have an argillic horizon that has an increase in clay
content of 20 percent (absolute) or more within a vertical
distance of 7.5 cm below the upper boundary;
2. Do not have either:
a. An albic horizon or another horizon above the argillic
horizon that has a color value too high for a mollic epipedon
and chroma too high for an albic horizon; or
b. A glossic horizon, or interfingering of albic materials in
the upper part of the argillic horizon, or skeletans of clean
silt and sand covering 50 percent or more of the faces of
peds in the upper 5 cm or more of the argillic horizon;
3. Do not have, throughout a cumulative thickness of 18 cm
Mollisols 577
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
4. Do not have, in any horizon within 100 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
5. In normal years are not saturated with water in any layer
within 100 cm of the mineral soil surface for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
6. Do not have a lithic contact within 50 cm of the mineral
soil surface;
7. Have a udic moisture regime;
8. Have a mollic epipedon that is less than 40 cm thick or has
a texture of loamy fine sand or coarser; and
9. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Description of Subgroups
Typic Argicryolls.—The central concept or Typic subgroup
of Argicryolls is fixed on freely drained soils that have a udic
moisture regime and have a mollic epipedon less than 40 cm
thick. These soils do not have an albic horizon or an abrupt
boundary to the argillic horizon and do not have a surface
mantle or layer in the upper 75 cm that has both a low bulk
density and a high content of weakly crystalline minerals or
that consists of slightly or moderately weathered pyroclastic
materials.
An albic horizon indicates that the soils had forest
vegetation and is the basis for defining intergrades to Alfisols.
Redox concentrations and shallow ground water are properties
of Aquolls and are the basis for defining the Aquic subgroup.
A thick mollic epipedon is the basis for defining the Pachic
subgroup. The vegetation on the Argicryolls on broad plains
was mostly grasses. The Argicryolls in the mountains have
either forest or grass vegetation. Most Argicryolls are used as
rangeland, forest, or wildlife habitat.
Abruptic Argicryolls.—These soils have an abrupt textural
change at the top of the argillic horizon, and most also have an
albic horizon. In the Abruptic Argicryolls in the United States,
the argillic horizon commonly has columnar structure but does
not have the sodium or magnesium necessary for a natric
horizon. The vegetation is mostly grass and shrubs. Slopes are
gentle to moderately steep. Most of the soils are used as
rangeland, pasture, or wildlife habitat.
Alfic Argicryolls.—These soils have an albic horizon or a
horizon that has color values too high for a mollic epipedon
and chroma too high for an albic horizon above the argillic
horizon, or they have a glossic horizon in the upper part of the
argillic horizon. They either have a gradual transition between
those horizons or have only a moderate contrast between the
percentages of clay in the two horizons. These soils are of
moderate extent in the mountains of the Western United States.
Slopes range from gentle to steep. Some of these soils currently
have forest vegetation, but others support mostly grass. Alfic
Argicryolls are used mostly as forest or rangeland, but a few
are used as hayland.
Andic and Vitrandic Argicryolls.—These soils have a
surface mantle or layer in the upper 75 cm that has both a low
bulk density and a high content of weakly crystalline minerals
or that consists of slightly or moderately weathered pyroclastic
materials. These soils are of very small extent in the mountains
of the Western United States. The vegetation is mostly forest or
grass and widely spaced trees. Most of the soils are used as
forest, rangeland, or wildlife habitat.
Aquic Argicryolls.—Ground water fluctuates at some depth
in these soils, and redox concentrations are in the horizons that
are saturated part of the time. These soils are of small extent in
the mountains of the Western United States. The vegetation is
mostly forest or grass and widely spaced trees. Most of the soils
are used as forest, rangeland, or wildlife habitat.
Lithic Argicryolls.—These soils have a lithic contact
within 50 cm of the mineral soil surface. Slopes are gentle to
steep. The vegetation on these soils is mostly grass and shrubs,
but some of the soils support forest vegetation. Most of the soils
are used as rangeland.
Oxyaquic Argicryolls.—These soils are saturated with water
within 100 cm of the mineral soil surface for 20 or more
578 Soil Taxonomy
consecutive days or 30 or more cumulative days in normal
years. They are not known to occur in the United States.
Pachic Argicryolls.—These soils have a thick mollic
epipedon. The argillic horizon generally is in the lower part of
the mollic epipedon. Slopes of the Pachic Argicryolls in the
United States range from gentle to steep. The soils are
extensive in the high mountains of the Western States. Most of
the soils are used for summer grazing, but some are used as
forest.
Ustic Argicryolls.—These soils have an ustic moisture
regime. They are considered to be transitional to Ustolls. They
commonly are used as rangeland or are in sparse forests with
widely spaced trees. They are of small extent in the United
States.
Vertic Argicryolls.—These soils have a clayey particle-size
class in a significant part, have expanding clays, and in normal
years have deep cracks. The thickness of the mollic epipedon,
the distribution of organic carbon in the epipedon, and the
presence of redoximorphic features or other evidence of
wetness are not definitive of this subgroup. These soils are of
small extent in the mountains of the Western United States.
Xeric Argicryolls.—These soils have a xeric moisture
regime. They are considered to be transitional to Xerolls. They
commonly are in forests with widely spaced trees. They are of
small extent in the United States.
Calcicryolls
These are the Cryolls that have a calcic or petrocalcic
horizon that has its upper boundary within 100 cm of the
mineral soil surface. They are calcareous, or would be
calcareous if plowed, in all parts of the pedon above the calcic
horizon, or they have a texture of loamy fine sand or coarser in
all parts above the calcic or petrocalcic horizon. The mollic
epipedon commonly includes part of the calcic horizon. These
soils formed in materials that have a moderate to high
percentage of carbonates. Many of the soils are in areas of
deposits that originated from limestone.
Calcicryolls occur in areas of cool or short summers. In the
United States, the vegetation at the time of settlement was
either grass or forest. The soils are of moderate extent in the
mountains of the Western United States. Most of the soils are
used as rangeland, forest, or wildlife habitat. A few areas are
cultivated and used for small grain or hay.
Definition
Calcicryolls are the Cryolls that:
1. Have a calcic or petrocalcic horizon that has its upper
boundary within 100 cm of the mineral soil surface;
2. Either are calcareous or have a texture of loamy fine sand
or coarser in all parts above the calcic or petrocalcic horizon
after the materials between the soil surface and a depth of 18
cm have been mixed;
3. Do not have a duripan that has its upper boundary
within 100 cm of the mineral soil surface; and
4. Do not have a natric or argillic horizon.
KeytoSubgroups
IDEA. Calcicryolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Calcicryolls
IDEB. Other Calcicryolls that have a petrocalcic horizon that
has its upper boundary within 100 cm of the mineral soil
surface.
Petrocalcic Calcicryolls
IDEC. Other Calcicryolls that have a mollic epipedon that is
40 cm or more thick and has a texture finer than loamy fine
sand.
Pachic Calcicryolls
IDED. Other Calcicryolls that have an ustic moisture regime.
Ustic Calcicryolls
IDEE. Other Calcicryolls that have a xeric moisture regime.
Xeric Calcicryolls
IDEF. Other Calcicryolls.
Typic Calcicryolls
Definition of Typic Calcicryolls
Typic Calcicryolls are the Calcicryolls that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Have a mollic epipedon that is less than 40 cm thick or has
a texture of loamy fine sand or coarser;
3. Have a udic moisture regime; and
4. Do not have a petrocalcic horizon with its upper boundary
within 100 cm of the mineral soil surface.
Description of Subgroups
Typic Calcicryolls.—The central concept or Typic
subgroup of Calcicryolls is fixed on soils that have a udic
moisture regime and have a mollic epipedon less than 40 cm
thick. These soils do not have a lithic contact within 50 cm of
the mineral soil surface. A thick mollic epipedon is the basis
for defining the Pachic subgroup. The vegetation on the Typic
Calcicryolls on broad plains was mostly grasses and shrubs.
The Typic Calcicryolls in the mountains have either grass or
forest vegetation. Most Typic Calcicryolls are used as
rangeland or forest, but a few are used as cropland.
Lithic Calcicryolls.—These soils have a lithic contact
within 50 cm of the mineral soil surface. They are of small
extent in the mountains of the Western United States. Their
Mollisols 579
slopes are gentle to steep. The vegetation on these soils is
mostly grass and shrubs, but some of the soils support widely
spaced trees. Most of the soils are used as rangeland.
Pachic Calcicryolls.—These soils have a thick, calcareous
mollic epipedon that extends into the calcic horizon or is
directly underlain by the calcic horizon. They formed mainly in
calcareous sediments. The vegetation in broad areas is mostly
grasses and shrubs. The more sloping soils in the mountains
have either grass or forest vegetation. Most of the soils are used
as rangeland, but a few are used as forest or cropland.
Petrocalcic Calcicryolls.—These soils have a petrocalcic
horizon with its upper boundary within 100 cm of the mineral
soil surface. They do not have a lithic contact within 50 cm of
the mineral soil surface. They are of limited extent in the
Western United States. They are used for grazing by livestock.
Ustic Calcicryolls.—These soils are like Typic Calcicryolls,
but they have an ustic moisture regime. They are considered to
be transitional to Calciustolls. Ustic Calcicryolls commonly are
used as rangeland or are in forests with widely spaced trees.
They are of small extent in the United States.
Xeric Calcicryolls.—These soils are like Typic Calcicryolls,
but they have a xeric moisture regime. They are considered to be
transitional to Calcixerolls. Xeric Calcicryolls commonly are in
forests with widely spaced trees. They are of small extent in the
United States.
Duricryolls
These are the Cryolls that have a duripan that has its upper
boundary within 100 cm of the mineral soil surface. They are
of small extent in mountain valleys of the Western United
States. Many had grasses and widely spaced conifer trees. Most
of the soils are used as rangeland or forest.
Definition
Duricryolls are the Cryolls that have a duripan that has its
upper boundary within 100 cm of the mineral soil surface.
Key to Subgroups
IDAA. Duricryolls that have an argillic horizon.
Argic Duricryolls
IDAB. Other Duricryolls.
Typic Duricryolls
Definition of Typic Duricryolls
Typic Duricryolls are the Duricryolls that do not have an
argillic horizon.
Description of Subgroups
Typic Duricryolls.—The central concept or Typic subgroup
of Duricryolls is fixed on soils that do not have an argillic
horizon above the duripan. These soils are of small extent.
They are at high elevations in the Western United States. The
natural vegetation is either grass and shrubs or trees. The soils
are used as rangeland or forest.
Argic Duricryolls.—These soils are like the Typic subgroup
of Duricryolls, but they have an argillic horizon above the
duripan. Argic Duricryolls are of small extent. They are at high
elevations in the Western United States. The natural vegetation
is either grass and shrubs or trees. These soils are used as
rangeland or forest.
Haplocryolls
These are the Cryolls that do not have an argillic or natric
horizon. Most Haplocryolls have a cambic horizon. Some have
a calcic horizon. Haplocryolls do not have a duripan that has
its upper boundary within 100 cm of the mineral soil surface.
They do not have a calcic or petrocalcic horizon that has its
upper boundary within 100 cm of the mineral soil surface
unless some part of the soil above the calcic or petrocalcic
horizon, after the materials between the soil surface and a
depth of 18 cm have been mixed, either is not calcareous or has
a texture finer than loamy fine sand.
Haplocryolls formed mainly in Pleistocene or Holocene
deposits or on surfaces of equivalent ages. They have cool or
short summers. They are extensive in the United States. The
vegetation at the time of settlement was either forest or grass.
Many of the soils had grasses and scattered conifer trees. Most
of the soils are used as rangeland or forest. Some are cultivated
and used for small grain or hay.
Definition
Haplocryolls are the Cryolls that:
1. Do not have a duripan that has its upper boundary
within 100 cm of the mineral soil surface;
2. Do not have a natric or argillic horizon; and
3. Do not meet both of the following:
a. Have a calcic or petrocalcic horizon that has its upper
boundary within 100 cm of the mineral soil surface; and
b. In all parts above the calcic or petrocalcic horizon, after
the materials between the soil surface and a depth of 18 cm
have been mixed, either are calcareous or have a texture of
loamy fine sand or coarser.
Key to Subgroups
IDFA. Haplocryolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Haplocryolls
IDFB. Other Haplocryolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
580 Soil Taxonomy
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick that
has its upper boundary within 125 cm of the mineral soil
surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Haplocryolls
IDFC. Other Haplocryolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Haplocryolls
IDFD. Other Haplocryolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Haplocryolls
IDFE. Other Haplocryolls that have:
1. A mollic epipedon that is 40 cm or more thick and has
a texture finer than loamy fine sand; and
2. An irregular decrease in organic-carbon content from a
depth of 25 cm below the mineral soil surface to a depth of
125 cm or to a densic, lithic, or paralithic contact if
shallower; and
3. A slope of less than 25 percent; and
4. In one or more horizons within 100 cm of the mineral
soil surface, distinct or prominent redox concentrations and
also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Cumulic Haplocryolls
IDFF. Other Haplocryolls that have:
1. A mollic epipedon that is 40 cm or more thick and has
a texture finer than loamy fine sand; and
2. An irregular decrease in organic-carbon content from a
depth of 25 cm below the mineral soil surface to a depth of
125 cm or to a densic, lithic, or paralithic contact if
shallower; and
3. A slope of less than 25 percent.
Cumulic Haplocryolls
IDFG. Other Haplocryolls that have both:
1. A slope of less than 25 percent; and either
a. An organic-carbon content of 0.3 percent or more
at a depth of 125 cm below the mineral soil surface;
or
b. An irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm or to a
densic, lithic, or paralithic contact if shallower; and
2. In one or more horizons within 100 cm of the mineral
soil surface, distinct or prominent redox concentrations and
also aquic conditions for some time in normal years (or
artificial drainage).
Fluvaquentic Haplocryolls
IDFH. Other Haplocryolls that have, in one or more horizons
within 100 cm of the mineral soil surface, distinct or
prominent redox concentrations and also aquic conditions for
some time in normal years (or artificial drainage).
Aquic Haplocryolls
IDFI. Other Haplocryolls that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Haplocryolls
IDFJ. Other Haplocryolls that have both:
1. A mollic epipedon that is 40 cm or more thick and has
a texture finer than loamy fine sand; and
2. A calcic horizon either within or directly below the
mollic epipedon, but no argillic horizon in the lower part of
the mollic epipedon.
Calcic Pachic Haplocryolls
IDFK. Other Haplocryolls that have a mollic epipedon that is
40 cm or more thick and has a texture finer than loamy fine
sand.
Pachic Haplocryolls
IDFL. Other Haplocryolls that have a slope of less than 25
percent; and either
Mollisols 581
1. An organic-carbon content of 0.3 percent or more at a
depth of 125 cm below the mineral soil surface; or
2. An irregular decrease in organic-carbon content from a
depth of 25 cm to a depth of 125 cm or to a densic, lithic, or
paralithic contact if shallower.
Fluventic Haplocryolls
IDFM. Other Haplocryolls that have a calcic horizon within
100 cm of the mineral soil surface.
Calcic Haplocryolls
IDFN. Other Haplocryolls that have an ustic moisture
regime.
Ustic Haplocryolls
IDFO. Other Haplocryolls that have a xeric moisture regime.
Xeric Haplocryolls
IDFP. Other Haplocryolls.
Typic Haplocryolls
Definition of Typic Haplocryolls
Typic Haplocryolls are the Haplocryolls that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
3. Do not have, in any horizon within 100 cm of the mineral
soil surface, distinct or prominent redox concentrations and
also aquic conditions;
4. In normal years are not saturated with water in any layer
within 100 cm of the mineral soil surface for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
5. Do not have a calcic horizon within 100 cm of the mineral
soil surface;
6. Have a mollic epipedon that is less than 40 cm thick or
that has a texture of loamy fine sand or coarser;
7. Have a udic soil moisture regime;
8. Either have a regular decrease in organic-carbon content
with increasing depth and, unless a densic, lithic, or paralithic
contact is at some depth between 50 and 125 cm below the soil
surface, have an organic-carbon content of 0.3 percent or less
at a depth within 125 cm of the mineral soil surface or have a
slope of 25 percent or more; and
9. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Description of Subgroups
Typic Haplocryolls.—The central concept or Typic
subgroup of Haplocryolls is fixed on freely drained soils that
have a udic soil moisture regime and that do not have a calcic
horizon within 100 cm or hard rock within 50 cm of the soil
surface. The horizon sequence is normally a noncalcareous
mollic epipedon of moderate thickness over a cambic horizon.
These soils do not have a surface mantle or layer in the
upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals or that consists of
slightly or moderately weathered pyroclastic materials. In
addition, they do not have a high shrink-swell potential, a
thick mollic epipedon, or an irregular decrease in organiccarbon
content.
Redox concentrations and shallow ground water are
properties of Aquolls and are the basis for defining Aquic and
combination Aquic subgroups. A calcic horizon within a depth
of 100 cm is characteristic of Calcicryolls and is the basis for
defining Calcic and combination Calcic subgroups. A thick
mollic epipedon is the basis for defining Pachic and
combination Pachic subgroups.
The vegetation on the Typic Haplocryolls on broad plains
was mostly grasses. The Typic Haplocryolls in the mountains
have either forest or grass vegetation. Most Typic Haplocryolls
are used as rangeland, forest, or wildlife habitat.
Andic and Vitrandic Haplocryolls.—These soils have a
surface mantle or layer in the upper 75 cm that has both a low
bulk density and a high content of weakly crystalline minerals
582 Soil Taxonomy
or that consists of slightly or moderately weathered pyroclastic
materials. These soils are of very small extent in the mountains
of the Western United States. The vegetation is mostly forest or
grass and widely spaced trees. Most of these soils are used as
forest, rangeland, or wildlife habitat.
Aquic Cumulic Haplocryolls.—Ground water fluctuates at
some depth in these soils, and redox concentrations are in the
horizons that are saturated part of the time. The soils have a
thick mollic epipedon, and their content of organic carbon
decreases irregularly with increasing depth. The soils are of
small extent in mountain valleys of the Western United States.
The vegetation is mostly grass, shrubs, and widely spaced
trees. Most of these soils are used as rangeland, pasture, or
cropland, but some are used as forest or wildlife habitat.
Aquic Haplocryolls.—Ground water fluctuates at some
depth in these soils, and redox concentrations are in the
horizons that are saturated part of the time. These soils are of
small extent in mountain valleys of the Western United States.
The vegetation is mostly forest or grass and widely spaced
trees. Most of the soils are used as forest, rangeland, or wildlife
habitat.
Calcic Haplocryolls.—These soils have a calcic horizon
within 100 cm of the mineral soil surface, but they are
otherwise like Typic Haplocryolls. Calcic Haplocryolls are of
small extent. The vegetation is mostly forest or grass and
widely spaced trees. Most of these soils are used as forest,
rangeland, or wildlife habitat, but a few are used as cropland.
Calcic Pachic Haplocryolls.—These soils have a thick
mollic epipedon and a calcic horizon within 100 cm of the
mineral soil surface. They are of small extent. The vegetation
is mostly forest or grass and widely spaced trees. Most of these
soils are used as forest, rangeland, or wildlife habitat, but a few
are used as cropland.
Cumulic Haplocryolls.—These soils have a thick mollic
epipedon, and their content of organic carbon decreases
irregularly with increasing depth. The soils formed in positions
where they receive fresh sediments at a rate slow enough for
this material to become incorporated in the mollic epipedon.
These soils are on flood plains or have concave slopes. They
are of small extent in Alaska and in mountain valleys of the
Western United States. The vegetation is mostly grass, shrubs,
and widely spaced trees. Most of these soils are used as
rangeland, pasture, or cropland, but some are used as forest or
wildlife habitat.
Fluvaquentic Haplocryolls.—These soils are like Typic
Haplocryolls, but ground water fluctuates at some depth in the
soils and redox concentrations are in the horizons that are
saturated part of the time. Fluvaquentic Haplocryolls have an
irregular decrease in organic-carbon content with increasing
depth or have an organic-carbon content of 0.3 percent or more
in all horizons within 125 cm of the mineral soil surface.
These soils formed mostly in recent alluvium on flood plains.
They are of small extent in mountain valleys of the Western
United States. The vegetation is mostly grass, shrubs, and
widely spaced trees. Most of the soils are used as rangeland or
pasture, but some are used as wildlife habitat.
Fluventic Haplocryolls.—These soils are like Typic
Haplocryolls, but they have an irregular decrease in organiccarbon
content with increasing depth or have an organiccarbon
content of 0.3 percent or more in all horizons within
125 cm of the mineral soil surface. These soils are not known
to occur in the United States.
Lithic Haplocryolls.—These soils have a shallow lithic
contact. They are of moderate extent in the mountains of the
Western United States. Their slopes are gentle to steep. The
vegetation is mostly grass and shrubs, but some of the soils
support forest vegetation. Lithic Haplocryolls are used mostly
as rangeland or forest.
Oxyaquic Haplocryolls.—These soils are like Typic
Haplocryolls, but they are saturated with water within 100 cm
of the mineral soil surface for 20 or more consecutive days or
30 or more cumulative days in normal years. These soils are
not known to occur in the United States.
Pachic Haplocryolls.—These soils are like Typic
Haplocryolls, but they have a thick mollic epipedon. Slopes of
the Pachic Haplocryolls in the United States range from gentle
to steep. The soils commonly are used as rangeland or support
forest vegetation. Some support grass and widely spaced trees.
The soils are extensive in the high mountains of the Western
States. They are used mostly as rangeland or forest. A few of
the soils are used as cropland or hayland.
Ustic Haplocryolls.—These soils are like Typic
Haplocryolls, but they have an ustic moisture regime. They are
considered to be transitional to Ustolls. Ustic Haplocryolls
commonly are used as rangeland or are in forests with widely
spaced trees. They are of small extent in the United States.
Vertic Haplocryolls.—These soils have a clayey particlesize
class in a significant part, have expanding clays, and in
normal years have deep cracks. The thickness of the mollic
epipedon, the distribution of organic carbon in the epipedon,
and the presence of redoximorphic features or other evidence of
wetness are not definitive of this subgroup. These soils are of
very small extent in the mountains of the Western United
States.
Xeric Haplocryolls.—These soils are like Typic Haplocryolls,
but they have a xeric moisture regime. They are considered to be
transitional to Xerolls. Xeric Haplocryolls commonly are in
forests with widely spaced trees. They are of small extent in the
United States.
Natricryolls
These are the Cryolls that have a natric horizon but do not
have a duripan. The soils are rare in the United States and
probably elsewhere. Few series have been established in the
United States for this group, and subgroups have not been
Mollisols 583
developed. Because these soils are of such limited extent and
have a small range of properties, few subgroups seem to be
needed.
Definition
Natricryolls are the Cryolls that have a natric horizon but do
not have a duripan with an upper boundary within 100 cm of
the mineral soil surface.
Key to Subgroups
IDBA. All Natricryolls.
Typic Natricryolls
Palecryolls
These are the Cryolls that have an argillic horizon with an
upper boundary more than 60 cm below the surface. Most of
the Palecryolls in the United States are in the mountains of the
Western States. In other countries at high latitudes, Palecryolls
also developed on plains.
Palecryolls have cool or short summers. In the United
States, the vegetation at the time of settlement was either forest
or grass. Many of the soils had grasses and scattered conifer
trees. Most of the soils are used as rangeland or forest. Some
are cultivated and used for small grain or hay.
Definition
Palecryolls are the Cryolls that:
1. Have an argillic horizon that has its upper boundary 60 cm
or more below the mineral soil surface and have a texture of
loamy very fine sand or finer in some horizon above the argillic
horizon;
2. Do not have a natric horizon; and
3. Do not have a duripan that has its upper boundary
within 100 cm of the mineral soil surface.
Key to Subgroups
IDCA. Palecryolls that have, in one or more horizons within
100 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Palecryolls
IDCB. Other Palecryolls that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Palecryolls
IDCC. Other Palecryolls that have an argillic horizon that,
with increasing depth, has a clay increase of 20 percent or
more (absolute, in the fine-earth fraction) within its upper
7.5 cm.
Abruptic Palecryolls
IDCD. Other Palecryolls that have a mollic epipedon that is
40 cm or more thick and has a texture finer than loamy fine
sand.
Pachic Palecryolls
IDCE. Other Palecryolls that have an ustic moisture regime.
Ustic Palecryolls
IDCF. Other Palecryolls that have a xeric moisture regime.
Xeric Palecryolls
IDCG. Other Palecryolls.
Typic Palecryolls
Definition of Typic Palecryolls
Typic Palecryolls are the Palecryolls that:
1. Do not have an argillic horizon that has an increase in clay
content of 20 percent (absolute) or more within a vertical
distance of 7.5 cm below its upper boundary;
2. Do not have, in any horizon within 100 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
3. In normal years are not saturated with water in any layer
within 100 cm of the mineral soil surface for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
4. Have a mollic epipedon that is less than 40 cm thick; and
5. Have a udic moisture regime.
Description of Subgroups
Typic Palecryolls.—The central concept or Typic subgroup
of Palecryolls is fixed on freely drained soils that have a udic
moisture regime and have a mollic epipedon less than 40 cm
thick. These soils do not have an abrupt boundary to the
argillic horizon.
Redox concentrations and shallow ground water are
properties of Aquolls and are the basis for defining the Aquic
subgroup. A thick mollic epipedon is the basis for defining the
Pachic subgroup. The vegetation on Typic Palecryolls is either
forest or grass and shrubs. Most of these soils are used as
forest, grazing land, or wildlife habitat.
Abruptic Palecryolls.—These soils have an abrupt textural
change at the top of the argillic horizon, and most also have an
albic horizon. The vegetation is either forest or grass and
shrubs. Most of these soils are used as forest, grazing land, or
wildlife habitat.
Aquic Palecryolls.—Ground water fluctuates at some depth
584 Soil Taxonomy
in these soils, and redox concentrations are in the horizons that
are saturated part of the time. These soils are not known to
occur in the United States.
Oxyaquic Palecryolls.—These soils are like Typic
Palecryolls, but they are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years. These soils are not
known to occur in the United States.
Pachic Palecryolls.—These soils are like Typic Palecryolls,
but they have a thick mollic epipedon. The argillic horizon
generally is in the lower part of the mollic epipedon. Slopes of
the Pachic Palecryolls in the United States range from gentle to
steep. The soils are moderately extensive in the mountains of
the Western States. The vegetation is either forest or grass and
shrubs. Most of these soils are used as forest, grazing land, or
wildlife habitat.
Ustic Palecryolls.—These soils are like Typic Palecryolls,
but they have an ustic moisture regime. They are considered to
be transitional to Ustolls. Ustic Palecryolls are not known to
occur in the United States.
Xeric Palecryolls.—These soils are like Typic Palecryolls,
but they have a xeric moisture regime. They are considered to
be transitional to Xerolls. Xeric Palecryolls are not known to
occur in the United States.
Rendolls
These are the Mollisols that are of humid regions and that
formed in highly calcareous parent materials, such as
limestone, chalk, drift composed mainly of limestone, or shell
bars. These soils have a mollic epipedon that rests on the
calcareous parent materials or on a cambic horizon that is rich
in carbonates. A few of the soils are so rich in finely divided
lime that the mollic epipedon has a color lighter than normal
but is nevertheless rich in dark colored humus and is within
the limits of a mollic epipedon. Rendolls have a cryic soil
temperature regime or a udic moisture regime, or both.
These soils are not extensive in the United States, but they
are extensive in some parts of the world. They formed under
forest vegetation or under grass and shrubs.
Definition
Rendolls are the Mollisols that:
1. Have a mollic epipedon that is less than 50 cm thick;
2. Have a CaCO3
equivalent of 40 percent or more on the
basis of the whole soil, including coarse fragments as much as
7.5 cm in size in or directly below the mollic epipedon;
3. Do not have an argillic or calcic horizon;
4. Have a udic moisture regime or a cryic temperature regime,
or both; and
5. Do not have both aquic conditions and the colors defined
for Aquolls.
Key to Great Groups
ICA. Rendolls that have a cryic soil temperature regime.
Cryrendolls, p. 584
ICB. Other Rendolls.
Haprendolls, p. 585
Cryrendolls
These are the Rendolls that have a cryic soil temperature
regime. The Cryrendolls in the United States are rare and
occur only in the mountains of the Western States. The
vegetation is mostly grass and shrubs. Some of the soils have
widely spaced coniferous trees.
Definition
Cryrendolls are the Rendolls that have a cryic soil
temperature regime.
Key to Subgroups
ICAA. Cryrendolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Cryrendolls
ICAB. Other Cryrendolls.
Typic Cryrendolls
Definition of Typic Cryrendolls
Typic Cryrendolls are the Rendolls that do not have a lithic
contact within 50 cm of the mineral soil surface.
Description of Subgroups
Typic Cryrendolls.—These soils are more than 50 cm deep
to any lithic contact. Most of the soils have a high content of
small limestone fragments. Typic Cryrendolls are of small
extent. They are in the mountains of Nevada and Wyoming.
The vegetation is mostly grass and shrubs. Some of the soils
have widely spaced coniferous trees. Most of the soils are used
as rangeland or wildlife habitat.
Lithic Cryrendolls.—These soils have a shallow lithic
contact, but they are otherwise like Typic Cryrendolls. The
lithic contact is with limestone. Most Lithic Cryrendolls have a
high content of small limestone fragments. They are of small
extent and are in the mountains of the Western United States.
The vegetation is mostly grass and shrubs. Some of the soils
Mollisols 585
have widely spaced coniferous trees. Most of the soils are used
as rangeland or wildlife habitat.
Haprendolls
These are the Rendolls that have a udic moisture regime and
a soil temperature regime warmer than cryic. Haprendolls are
rare in the United States.
Definition
Haprendolls are the Rendolls that have a udic moisture
regime and a soil temperature regime warmer than cryic.
Key to Subgroups
ICBA. Haprendolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Haprendolls
ICBB. Other Haprendolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Haprendolls
ICBC. Other Haprendolls that have a cambic horizon.
Inceptic Haprendolls
ICBD. Other Haprendolls that have a color value, dry, of 6 or
more either in the upper 18 cm of the mollic epipedon, after
mixing, or in an Ap horizon 18 cm or more thick.
Entic Haprendolls
ICBE. Other Haprendolls.
Typic Haprendolls
Definition of Typic Haprendolls
Typic Haprendolls are the Rendolls that:
1. Do not have a cambic horizon;
2. Do not have a lithic contact within 50 cm of the mineral
soil surface;
3. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that are 5
mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
and
4. Have a dry color value of 5 or less in the upper 18 cm,
after mixing, or in any Ap horizon that is thicker than 18 cm.
Description of Subgroups
Typic Haprendolls.—The central concept or Typic
subgroup of Haprendolls in fixed on freely drained soils that
have a dark mollic epipedon when dry, do not have a cambic
horizon, and do not have a lithic contact within a depth of 50
cm.
A cambic horizon in all or part of each pedon is an extra
horizon that indicates development toward Inceptisols. A high
dry color value in the mollic epipedon suggests weak
development of that horizon and is the basis for defining the
Entic subgroup. A shallow lithic contact is the basis for
defining the Lithic subgroup. Slickensides, wedge-shaped
aggregates, a high linear extensibility, and wide cracks are
properties of Vertisols and are the basis for defining the
intergrades toward soils of that order.
Typic Haprendolls are of small extent. They are in the
humid parts of the United States. They occur from Puerto Rico
to Michigan. The native vegetation is mostly trees and shrubs.
Some of the soils support shrubs and widely spaced trees. Most
of the soils are used as forest, pasture, or wildlife habitat.
Entic Haprendolls.—These soils formed in chalk or marl
and have a color value, dry, of 6 or more, mainly because finely
divided lime is abundant and acts as a white pigment. The soils
do not have a high shrink-swell potential, a cambic horizon, or
a lithic contact within 50 cm of the mineral soil surface. They
are not known to occur in the United States, but they are
extensive in some parts of the world.
Inceptic Haprendolls.—These soils have a cambic horizon
in at least some part of each pedon and generally in the major
part or all of the pedon. The soils are of small extent in the
humid parts of the United States. They occur from Puerto Rico
to Michigan. The native vegetation is mostly trees and shrubs.
Some of the soils support shrubs and widely spaced trees. Most
of the soils are used as cropland, forest, pasture, or wildlife
habitat.
Lithic Haprendolls.—These soils have a shallow lithic
contact but are otherwise like Typic Haprendolls. The
underlying rock is limestone, and there are many small
fragments of the limestone in most of these soils. Lithic
586 Soil Taxonomy
Haprendolls are in the humid parts of the United States. They
occur from Florida to Michigan. The native vegetation is mostly
trees and shrubs. Some of the soils support shrubs and widely
spaced trees. Most of the soils are used as forest, pasture, or
wildlife habitat or for urban development.
Vertic Haprendolls.—These soils have slickensides, wedgeshaped
aggregates, a high linear extensibility, or wide cracks.
They are not known to occur in the United States. The subgroup
is provided for use if needed elsewhere.
Udolls
Udolls are the more or less freely drained Mollisols of humid
climates. In addition to the mollic epipedon, these soils may
have a cambic, calcic, natric, or argillic horizon. They formed
mainly in late-Pleistocene or Holocene deposits or on surfaces
of comparable ages. In the United States, their vegetation at the
time of settlement was dominantly a tall grass prairie, but some
of the soils on Pleistocene surfaces appear to have supported at
some time a boreal forest that was supplanted by grasses
several thousand years ago.
Udolls formed in sediments and on surfaces of varying ages
from Holocene to mid Pleistocene or earlier. The Udolls that
have a thermic or warmer temperature regime, in particular,
may have formed during two or more glacial and interglacial
stages.
Most of the Udolls are in the eastern part of the Great Plains
or are east of the Great Plains. The soils are most extensive in
Illinois, Iowa, and adjacent states. Their temperature regime is
frigid or warmer, and their moisture regime is udic. Where
slopes are not too steep, nearly all of these soils are cultivated.
Maize (corn) and soybeans are the major crops.
Definition
Udolls are the Mollisols that:
1. Have a udic moisture regime;
2. Do not have both an albic horizon and, within 100 cm of
the mineral soil surface, any subhorizon of the albic horizon
and/or of the argillic or natric horizon that has redox
concentrations in the form of masses or concretions, or both,
and also aquic conditions;
3. Do not have both aquic conditions and the colors defined
for Aquolls;
4. Do not have a calcareous horizon that lies directly under
the mollic epipedon at a depth of less than 50 cm and that has
a CaCO3
equivalent of more than 40 percent, including coarse
fragments smaller than 7.5 cm, unless the soil also has an
argillic or calcic horizon or a mollic epipedon 50 cm or more
thick; and
5. Do not have a cryic soil temperature regime.
Key to Great Groups
IGA. Udolls that have a natric horizon.
Natrudolls, p. 597
IGB. Other Udolls that:
1. Have a calcic or petrocalcic horizon that has its upper
boundary within 100 cm of the mineral soil surface; and
2. Do not have an argillic horizon above the calcic or
petrocalcic horizon; and
3. In all parts above the calcic or petrocalcic horizon, after
the materials between the soil surface and a depth of 18 cm
have been mixed, either are calcareous or have a texture of
loamy fine sand or coarser.
Calciudolls, p. 592
IGC. Other Udolls that have one or more of the following:
1. A petrocalcic horizon that has its upper boundary
within 150 cm of the mineral soil surface; or
2. All of the following:
a. No densic, lithic, or paralithic contact within 150 cm
of the mineral soil surface; and
b. Within 150 cm of the mineral soil surface, a clay
decrease, with increasing depth, of less than 20 percent
(relative) from the maximum clay content (noncarbonate
clay); and
c. An argillic horizon with one or more of the
following:
(1) In 50 percent or more of the matrix of one or
more subhorizons in its lower half, hue of 7.5YR or
redder and chroma of 5 or more; or
(2) In 50 percent or more of the matrix of horizons
that total more than one-half the total thickness, hue
of 2.5YR or redder, a value, moist, of 3 or less, and a
value, dry, of 4 or less; or
(3) Many redox concentrations with hue of 5YR or
redder or chroma of 6 or more, or both, in one or more
subhorizons; or
3. A frigid temperature regime; and both
a. An argillic horizon that has its upper boundary 60
cm or more below the mineral soil surface; and
b. A texture finer than loamy fine sand in all horizons
above the argillic horizon.
Paleudolls, p. 599
IGD. Other Udolls that have an argillic horizon.
Argiudolls, p. 587
Mollisols 587
IGE. Other Udolls that have a mollic epipedon that:
1. Either below an Ap horizon or below a depth of 18 cm
from the mineral soil surface, contains 50 percent or more
(by volume) wormholes, wormcasts, or filled animal
burrows; and
2. Either rests on a lithic contact or has a transition zone
to the underlying horizon in which 25 percent or more of
the soil volume consists of discrete wormholes, wormcasts,
or animal burrows filled with material from the mollic
epipedon and from the underlying horizon.
Vermudolls, p. 601
IGF. Other Udolls.
Hapludolls, p. 593
Argiudolls
These are the Udolls that have a relatively thin argillic
horizon or one in which the percentage of clay decreases
rapidly with increasing depth. The mollic epipedon commonly
is black to very dark brown, and the argillic horizon is mostly
brownish. Many of these soils are noncalcareous to a
considerable depth below the argillic horizon. Some of the soils
have a Bk horizon in which secondary carbonates are
concentrated.
Argiudolls formed mostly in late-Wisconsinan deposits or
on surfaces of that age. Many or most of these soils during the
Pleistocene supported boreal forests that were replaced by tall
grass prairies during the Holocene. Argiudolls are extensive
soils in Iowa, Illinois, and adjacent states.
Definition
Argiudolls are the Udolls that:
1. Do not have a natric horizon;
2. Do not have a calcic horizon that has its upper boundary
within 100 cm of the mineral soil surface unless there is an
argillic horizon above the calcic horizon;
3. Do not have a petrocalcic horizon with its upper boundary
within 150 cm of the mineral soil surface; and
4. Have an argillic horizon and a clay distribution in which
the clay content decreases by 20 percent or more from the
maximum clay content within 150 cm of the surface if:
a. Hue is redder than 10YR and chroma of more than 4 is
dominant in the matrix in at least the lower part of the
argillic horizon; or
b. There are many coarse redox concentrations that have
hue redder than 7.5YR or chroma of more than 5.
KeytoSubgroups
IGDA. Argiudolls that have a lithic contact within 50 cm of the
mineral soil surface.
Lithic Argiudolls
IGDB. Other Argiudolls that have both:
1. Aquic conditions for some time in normal years (or
artificial drainage) either:
a. Within 40 cm of the mineral soil surface, in horizons
that also have redoximorphic features; or
b. Directly below the mollic epipedon, in one or more
horizons with a total thickness of 15 cm or more that
have one or more of the following:
(1) A color value, moist, of 4 or more and redox
depletions with chroma of 2 or less; or
(2) Hue of 10YR or redder and chroma of 2 or less;
or
(3) Hue of 2.5Y or yellower and chroma of 3 or less;
and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Aquertic Argiudolls
IGDC. Other Argiudolls that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. In normal years saturation with water in one or more
588 Soil Taxonomy
layers within 100 cm of the mineral soil surface for either or
both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days.
Oxyaquic Vertic Argiudolls
IGDD. Other Argiudolls that have:
1. A texture finer than loamy fine sand and either:
a. A frigid temperature regime and a mollic epipedon
40 cm or more thick; or
b. A mollic epipedon 50 cm or more thick; and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Pachic Vertic Argiudolls
IGDE. Other Argiudolls that have:
1. Above the argillic horizon, an albic horizon or a
horizon that has color values too high for a mollic epipedon
and chroma too high for an albic horizon; or
2. A glossic horizon, or interfingering of albic materials
into the upper part of the argillic horizon, or skeletans of
clean silt and sand covering 50 percent or more of the faces
of peds in the upper 5 cm of the argillic horizon; and
3. Either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Alfic Vertic Argiudolls
IGDF. Other Argiudolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Argiudolls
IGDG. Other Argiudolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Argiudolls
IGDH. Other Argiudolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Argiudolls
IGDI. Other Argiudolls that have aquic conditions for some
time in normal years (or artificial drainage) either:
1. Within 40 cm of the mineral soil surface, in horizons
that also have redoximorphic features; or
2. Directly below the mollic epipedon, in one or more
horizons with a total thickness of 15 cm or more that have
one or more of the following:
a. A color value, moist, of 4 or more and redox
depletions with chroma of 2 or less; or
b. Hue of 10YR or redder and chroma of 2 or less; or
c. Hue of 2.5Y or yellower and chroma of 3 or less.
Aquic Argiudolls
IGDJ. Other Argiudolls that have a texture finer than loamy
fine sand and either:
Mollisols 589
1. A frigid temperature regime and a mollic epipedon 40 cm
or more thick; or
2. A mollic epipedon 50 cm or more thick.
Pachic Argiudolls
IGDK. Other Argiudolls that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Argiudolls
IGDL. Other Argiudolls that have an argillic horizon that:
1. Consists entirely of lamellae; or
2. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
3. Consists of one or more subhorizons that are more
than 20 cm thick, each with an overlying eluvial horizon,
and above these horizons there are either:
a. Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
horizon); or
b. A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon.
Lamellic Argiudolls
IGDM. Other Argiudolls that have a sandy particle-size class
throughout the upper 75 cm of the argillic horizon or
throughout the entire argillic horizon if it is less than 75 cm
thick.
Psammentic Argiudolls
IGDN. Other Argiudolls that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 cm or more.
Arenic Argiudolls
IGDO. Other Argiudolls that have an argillic horizon that,
with increasing depth, has a clay increase of 20 percent or
more (absolute, in the fine-earth fraction) within its upper
7.5 cm.
Abruptic Argiudolls
IGDP. Other Argiudolls that have:
1. Above the argillic horizon, an albic horizon or a
horizon that has color values too high for a mollic epipedon
and chroma too high for an albic horizon; or
2. A glossic horizon, or interfingering of albic materials into
the upper part of the argillic horizon, or skeletans of clean silt
and sand covering 50 percent or more of the faces of peds in
the upper 5 cm of the argillic horizon.
Alfic Argiudolls
IGDQ. Other Argiudolls that have an apparent CEC of less
than 24 cmol(+)/kg clay (by 1N NH4
OAc pH 7) in 50 percent
or more either of the argillic horizon if less than 100 cm thick
or of its upper 100 cm.
Oxic Argiudolls
IGDR. Other Argiudolls that have a calcic horizon within
100 cm of the mineral soil surface.
Calcic Argiudolls
IGDS. Other Argiudolls.
Typic Argiudolls
Definition of Typic Argiudolls
Typic Argiudolls are the Argiudolls that:
1. Do not have aquic conditions for some time in normal
years either:
a. Within 40 cm of the mineral soil surface, in horizons
that also have redoximorphic features; or
b. Directly below the mollic epipedon, in horizons with a
total thickness of 15 cm or more that have one or more of
the following:
(1) A color value, moist, of 4 or more and redox
depletions with chroma of 2 or less; or
(2) Hue of 10YR or redder and chroma of 2 or less; or
(3) Hue of 2.5Y or yellower and chroma of 3 or less;
2. In normal years are not saturated with water in any layer
within 100 cm of the mineral soil surface for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
3. Do not have a lithic contact within 50 cm of the mineral
soil surface;
4. Have an argillic horizon that is finer than the sandy
particle-size class in some part of the upper 75 cm if the
argillic horizon is more than 75 cm thick or in any part if the
argillic horizon is less than 75 cm thick;
5. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
590 Soil Taxonomy
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
6. Have an apparent CEC (by 1N NH4
OAc pH 7) of 24 or
more in 50 percent or more of the argillic horizon or in 50
percent or more of the upper 100 cm of the argillic horizon if
the argillic horizon is thicker than 100 cm;
7. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
8. Do not have a calcic horizon within 100 cm of the soil
surface;
9. Do not have a texture finer than loamy fine sand and
either:
a. A mollic epipedon 50 cm or more thick; or
b. A mollic epipedon 40 cm or more thick and a frigid
temperature regime;
10. Have an argillic horizon that meets none of the following:
a. Consists entirely of lamellae; or
b. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
c. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
(1) Two or more lamellae with a combined thickness
of 5 cm or more (that may or may not be part of the argillic
horizon); or
(2) A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon;
11. Do not have an argillic horizon that, with increasing
depth, has a clay increase of 20 percent or more (absolute, in
the fine-earth fraction) within its upper 7.5 cm;
12. Do not have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of an argillic horizon at a depth of 50 cm or more; and
13. Do not have:
a. Above the argillic horizon, an albic horizon or a
horizon that has color values too high for a mollic epipedon
and chroma too high for an albic horizon; and
b. A glossic horizon, or interfingering of albic materials
into the upper part of the argillic horizon, or skeletans of
clean silt and sand covering 50 percent or more of the faces
of peds in the upper 5 cm of the argillic horizon.
Description of Subgroups
Typic Argiudolls.—The central concept or Typic subgroup
of Argiudolls is fixed on soils that show little evidence of
wetness within a depth of 40 cm or more, that do not have a
shallow lithic contact, that have a loamy or clayey particle-size
class in at least the argillic horizon, and that do not have
slickensides, wedge-shaped aggregates, a high linear
extensibility, or wide cracks in normal years.
Shallow ground water and redoximorphic features are
properties of Aquolls and are the basis for defining the Aquic
and Oxyaquic subgroups. A shallow lithic contact is the basis
for defining the Lithic subgroup. An argillic horizon that has a
sandy particle-size class or consists either entirely or partly of
thin lamellae is weakly developed and is the basis for defining
Psammentic and Lamellic subgroups. Slickensides, wedgeshaped
aggregates, a high linear extensibility, and wide cracks
that are evident in normal years are characteristics of Vertisols
and are the basis for defining the Vertic subgroup. An albic or
glossic horizon or another horizon that has color values too
high for a mollic epipedon and chroma too high for an albic
horizon above the argillic horizon, interfingering of albic
materials into the upper part of the argillic horizon, and
skeletans of clean silt and sand covering 50 percent or more of
the faces of peds in the upper 5 cm of the argillic horizon are
considered characteristics of Alfisols and are the basis for
defining the Alfic subgroup.
Typic Argiudolls are of large extent in the United States.
They are mostly on the eastern Great Plains but occur
throughout much of the country. Most of these soils supported
tall grasses, and most are now used as cropland.
Mollisols 591
Abruptic Argiudolls.—These soils have an abrupt textural
change at the top of the argillic horizon. They show no
evidence of the development of an albic horizon. They are of
very small extent in the United States and occur mostly in
Minnesota. These soils supported chiefly tall grasses. They
commonly are used as cropland.
Alfic Argiudolls.—These soils have an albic or glossic
horizon or another horizon that has color values too high for a
mollic epipedon and chroma too high for an albic horizon
above the argillic horizon, have interfingering of albic
materials into the upper part of the argillic horizon, or have
skeletans of clean silt and sand covering 50 percent or more of
the faces of peds in the upper 5 cm of the argillic horizon.
These soils are of very small extent in the United States and
occur mostly in Minnesota. They supported mostly tall grasses.
They commonly are used as cropland.
Alfic Vertic Argiudolls.—These soils have a clayey
particle-size class in a significant part, have expanding clays,
and in some years have deep cracks. They also have an albic or
glossic horizon or another horizon that has color values too
high for a mollic epipedon and chroma too high for an albic
horizon above the argillic horizon, have interfingering of albic
materials into the upper part of the argillic horizon, or have
skeletans of clean silt and sand covering 50 percent or more of
the faces of peds in the upper 5 cm of the argillic horizon.
These soils are of very small extent in the United States and
occur mostly in North Dakota. They supported mostly tall
grasses. They commonly are used as cropland.
Andic and Vitrandic Argiudolls.—These soils have a
surface mantle or layer in the upper 75 cm that has both a low
bulk density and a high content of weakly crystalline minerals
or that consists of slightly or moderately weathered pyroclastic
materials. These soils are not known to occur in the United
States.
Aquertic Argiudolls.—These soils have lower chroma than
Typic Argiudolls and commonly have faint redoximorphic
features and either shallow ground water at some time during
the year or artificial drainage. They also have a clayey particlesize
class in a significant part, have expanding clays, and in
some years have deep cracks. These soils are of moderate
extent in the United States and occur mostly on the northern
Great Plains. They supported mostly tall grasses and commonly
are used as cropland.
Aquic Argiudolls.—These soils have lower chroma than
Typic Argiudolls and commonly have faint redoximorphic
features and either shallow ground water at some time during
the year or artificial drainage. They are extensive soils in the
glaciated regions of the northern Great Plains of the United
States. They commonly occur in areas between Aquolls and
Typic Argiudolls. Slopes generally are nearly level. Most Aquic
Argiudolls have been artificially drained. They supported
chiefly tall grasses and commonly are used as cropland.
Arenic Argiudolls.—These soils have a sandy or sandyskeletal
particle-size class throughout a layer extending from
the mineral soil surface to the top of the argillic horizon at a
depth of 50 cm or more. The argillic horizon most commonly is at
a depth of 75 to 100 cm. These soils formed in Pleistocene
deposits. They are of very small extent in the United States and
occur mostly in North Dakota and Minnesota. They supported
chiefly tall grasses and commonly are used as cropland.
Calcic Argiudolls.—These soils have a calcic horizon
within 100 cm of the soil surface. They are not known to occur
in the United States. They were established for use in
Argentina.
Lamellic Argiudolls.—These soils are like Typic
Argiudolls in defined properties, but they have an argillic
horizon that consists entirely or partially of lamellae. Most
Lamellic Argiudolls have a sandy particle-size class, and the
upper boundary of the argillic horizon or the upper lamella
may be below a depth of 60 cm. The upper several lamellae are
commonly broken or discontinuous horizontally. These soils
are not known to occur in the United States.
Lithic Argiudolls.—These soils have a shallow lithic
contact but are otherwise like Typic Argiudolls. Slopes are
commonly moderate to steep. Lithic Argiudolls are of small
extent in the United States. They are mostly on the eastern
Great Plains. Most of the soils supported tall grasses and some
widely spaced trees. Most are now used as cropland or pasture.
Oxic Argiudolls.—These soils have a low cation-exchange
capacity in half or more of the argillic horizon (if this horizon
is less than 100 cm thick) or of its upper 100 cm. They are
mostly in areas of warm and humid climates and are not
known to occur in the United States.
Oxyaquic Argiudolls.—These soils are like Typic
Argiudolls, but they are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years. They are moderately
extensive soils in the glaciated regions of the northern Great
Plains of the United States. They commonly are in areas
between the Aquic and Typic subgroups of Argiudolls. Slopes
generally are gentle. Oxyaquic Argiudolls supported mostly tall
grasses and commonly are used as cropland.
Oxyaquic Vertic Argiudolls.—These soils have a clayey
particle-size class in a significant part, have expanding clays,
and in some years have deep cracks. They are saturated with
water within 100 cm of the mineral soil surface for 20 or more
consecutive days or 30 or more cumulative days in normal
years. They are of small extent on the Great Plains of the
United States. Slopes generally are gentle. These soils
supported mostly tall grasses and commonly are used as
cropland.
Pachic Argiudolls.—These soils are like Typic Argiudolls,
but they have a thick mollic epipedon. The argillic horizon
generally starts in the lower part of the mollic epipedon. Slopes
of the Pachic Argiudolls in the United States range from gentle
to steep. The soils are of small extent on the Great Plains of the
United States. Most of the soils are used as cropland.
Pachic Vertic Argiudolls.—These soils have a clayey
592 Soil Taxonomy
particle-size class in a significant part, have expanding clays,
and in some years have deep cracks. They also have a thick
mollic epipedon. The argillic horizon generally starts in the lower
part of the mollic epipedon. These soils are of very small extent
in the United States and occur mostly in North Dakota. They
supported chiefly tall grasses and commonly are used as
cropland.
Psammentic Argiudolls.—These soils formed mostly in
sandy Pleistocene deposits, either dunes or glacial outwash.
The argillic horizon most commonly is 75 to 100 cm below the
soil surface. These soils are of very small extent in the United
States. They supported mostly tall grasses and commonly are
used as cropland.
Vertic Argiudolls.—These soils have a clayey particle-size
class in a significant part, have expanding clays, and in some
years have deep cracks. They are of small extent in the United
States. They occur throughout the Great Plains. They supported
mostly tall grasses and commonly are used as cropland.
Calciudolls
These are the Udolls with a calcic or petrocalcic horizon that
has its upper boundary within 100 cm of the soil surface.
Calciudolls do not have an argillic horizon above the calcic or
petrocalcic horizon. They are calcareous in all subhorizons
overlying the calcic horizon after the upper 18 cm has been
mixed, unless the texture is coarser than loamy very fine sand
or very fine sand. These soils are of small extent on the
northern Great Plains of the United States. They are important
in Argentina.
Definition
Calciudolls are the Udolls that:
1. Have a calcic or petrocalcic horizon that has its upper
boundary within 100 cm of the soil surface;
2. Are calcareous in all parts of all horizons above the calcic
horizon after the upper 18 cm has been mixed, unless the
texture is coarser than loamy very fine sand or very fine sand;
3. Do not have an argillic horizon above the calcic or
petrocalcic horizon; and
4. Do not have a natric horizon.
Key to Subgroups
IGBA. Calciudolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Calciudolls
IGBB. Other Calciudolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick that
has its upper boundary within 125 cm of the mineral soil
surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Calciudolls
IGBC. Other Calciudolls that have, in one or more horizons
within 100 cm of the mineral soil surface, redox depletions
with chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Calciudolls
IGBD. Other Calciudolls that have a slope of less than 25
percent; and either:
1. An organic-carbon content of 0.3 percent or more at a
depth of 125 cm below the mineral soil surface; or
2. An irregular decrease in organic-carbon content from a
depth of 25 cm to a depth of 125 cm or to a lithic or paralithic
contact if shallower.
Fluventic Calciudolls
IGBE. Other Calciudolls.
Typic Calciudolls
Definition of Typic Calciudolls
Typic Calciudolls are the Udolls that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface; and
2. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
and
3. Do not have, in any horizon within 100 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions; and
4. Do not have a slope of less than 25 percent and either of
the following:
a. An organic-carbon content of 0.3 percent or more at a
depth of 125 cm below the mineral soil surface; or
b. An irregular decrease in organic-carbon content from a
Mollisols 593
depth of 25 cm to a depth of 125 cm or to a lithic or paralithic
contact if shallower.
Description of Subgroups
Typic Calciudolls.—The central concept or Typic subgroup
of Calciudolls is fixed on deep soils that show little evidence of
wetness within a depth of 40 cm or more and are calcareous
throughout.
Shallow ground water and redoximorphic features are
properties of Aquolls and are the basis for defining the Aquic
subgroup. A shallow lithic contact is the basis for defining the
Lithic subgroup. Slickensides, wedge-shaped aggregates, a
high linear extensibility, and wide cracks that are evident in
normal years are characteristics of Vertisols and are the basis
for defining the Vertic subgroup.
Typic Calciudolls are of small extent on the northern Great
Plains of the United States. Most of these soils supported tall
grasses and are used as cropland.
Aquic Calciudolls.—These soils have ground water at a
moderate depth in the calcic horizon at some time during the
year, and they have redox depletions with low chroma. The
epipedon also commonly has low chroma. These soils are of
small extent on the northern Great Plains of the United States.
They generally are nearly level and formed in late-Wisconsinan
drift. Nearly all of these soils supported tall grasses and are
used as cropland.
Fluventic Calciudolls.—These soils are freely drained and
formed in alluvium deposited recently enough for the content
of organic carbon to decrease irregularly with increasing depth
or to remain relatively high in the deep layers. The soils are
subject to overflow, primarily when snow melts. Most of these
soils are cultivated if they occur in areas suitable in size and
shape. Fluventic Calciudolls are of very small extent in the
United States. Most are used as cropland.
Lithic Calciudolls.—These soils have a lithic contact
within 50 cm of the mineral soil surface. They are otherwise
similar to Typic Calciudolls. Lithic Calciudolls are not known
to occur in the United States.
Vertic Calciudolls.—These soils are like Typic Calciudolls,
but they have a clayey particle-size class in a significant part,
have expanding clays, and in normal years have deep cracks.
Vertic Calciudolls are not known to occur in the United States.
Hapludolls
These are the Udolls that generally have a cambic horizon
below a mollic epipedon. There may be a Bk horizon below the
cambic horizon, and a few of the soils have enough secondary
carbonates for a calcic horizon.
Hapludolls formed mostly in Holocene or late-Pleistocene
deposits or on surfaces of that age. Slopes generally are gentle,
and most of the soils are cultivated. Hapludolls are extensive
soils in Iowa, Minnesota, and adjacent states.
Definition
Hapludolls are the Udolls that:
1. Do not have an argillic or natric horizon;
2. Do not have a calcic horizon that has its upper boundary
within 100 cm of the mineral soil surface if all parts above the
calcic horizon, after the materials between the soil surface and
a depth of 18 cm have been mixed, either are calcareous or
have a texture of loamy fine sand or coarser; and
3. Have less than 50 percent (by volume) wormholes,
wormcasts, and filled animal burrows in the mollic epipedon
below any plow layer if the epipedon rests on a densic, lithic,
or paralithic contact or have a transition between the mollic
epipedon and the underlying horizon in which less than 25
percent (by volume) consists of wormholes, wormcasts, and
filled animal burrows.
Key to Subgroups
IGFA. Hapludolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Hapludolls
IGFB. Other Hapludolls that have both:
1. Aquic conditions for some time in normal years (or
artificial drainage) either:
a. Within 40 cm of the mineral soil surface, in horizons
that also have redoximorphic features; or
b. Directly below the mollic epipedon, in one or more
horizons with a total thickness of 15 cm or more that
have one or more of the following:
(1) A color value, moist, of 4 or more and redox
depletions with chroma of 2 or less; or
(2) Hue of 10YR or redder and chroma of 2 or less;
or
(3) Hue of 2.5Y or yellower and chroma of 3 or less;
and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Aquertic Hapludolls
594 Soil Taxonomy
IGFC. Other Hapludolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Hapludolls
IGFD. Other Hapludolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and aluminum plus 1
/2 iron percentages (by
ammonium oxalate) totaling more than 1.0.
Andic Hapludolls
IGFE. Other Hapludolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Hapludolls
IGFF. Other Hapludolls that have:
1. Either:
a. A frigid soil temperature regime and a mollic
epipedon 40 cm or more thick, of which less than 50
percent has a sandy or sandy-skeletal particle-size class,
and there is no densic or paralithic contact and no sandy
or sandy-skeletal particle-size class at a depth between 40
and 50 cm from the mineral soil surface; or
b. A mollic epipedon 60 cm or more thick, of which 50
percent or more of the thickness has a texture finer than
loamy fine sand; and
2. Either 0.3 percent or more organic carbon at a depth
of 125 cm below the mineral soil surface or an irregular
decrease in organic-carbon content from a depth of 25 cm to a
depth of 125 cm or to a densic, lithic, or paralithic contact if
shallower; and
3. A slope of 25 percent or less; and
4. In one or more horizons within 100 cm of the mineral soil
surface, redox depletions with chroma of 2 or less and also
aquic conditions for some time in normal years (or artificial
drainage).
Aquic Cumulic Hapludolls
IGFG. Other Hapludolls that have:
1. Either:
a. A frigid soil temperature regime and a mollic
epipedon 40 cm or more thick, of which less than 50
percent has a sandy or sandy-skeletal particle-size class,
and there is no densic or paralithic contact and no sandy
or sandy-skeletal particle-size class at a depth between 40
and 50 cm from the mineral soil surface; or
b. A mollic epipedon 60 cm or more thick, of which 50
percent or more of the thickness has a texture finer than
loamy fine sand; and
2. Either 0.3 percent or more organic carbon at a depth
of 125 cm below the mineral soil surface or an irregular
decrease in organic-carbon content from a depth of 25 cm to
a depth of 125 cm or to a densic, lithic, or paralithic contact
if shallower; and
3. A slope of 25 percent or less.
Cumulic Hapludolls
IGFH. Other Hapludolls that have both:
1. Aquic conditions for some time in normal years (or
artificial drainage) either:
a. Within 40 cm of the mineral soil surface, in horizons
that also have redoximorphic features; or
b. Directly below the mollic epipedon, in one or more
horizons with a total thickness of 15 cm or more that
have one or more of the following:
(1) A color value, moist, of 4 or more and redox
depletions with chroma of 2 or less; or
(2) Hue of 10YR or redder and chroma of 2 or less;
or
(3) Hue of 2.5Y or yellower and chroma of 3 or less;
and
2. A slope of less than 25 percent; and either
a. An organic-carbon content of 0.3 percent or more at
a depth of 125 cm below the mineral soil surface; or
Mollisols 595
b. An irregular decrease in organic-carbon content from
a depth of 25 cm to a depth of 125 cm or to a densic, lithic,
or paralithic contact if shallower.
Fluvaquentic Hapludolls
IGFI. Other Hapludolls that have aquic conditions for some
time in normal years (or artificial drainage) either:
1. Within 40 cm of the mineral soil surface, in horizons
that also have redoximorphic features; or
2. Directly below the mollic epipedon, in one or more
horizons with a total thickness of 15 cm or more that have
one or more of the following:
a. A color value, moist, of 4 or more and redox
depletions with chroma of 2 or less; or
b. Hue of 10YR or redder and chroma of 2 or less; or
c. Hue of 2.5Y or yellower and chroma of 3 or less.
Aquic Hapludolls
IGFJ. Other Hapludolls that have a texture finer than loamy
fine sand and either:
1. A frigid temperature regime and a mollic epipedon 40
cm or more thick; or
2. A mollic epipedon 50 cm or more thick.
Pachic Hapludolls
IGFK. Other Hapludolls that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Hapludolls
IGFL. Other Hapludolls that have a slope of less than 25
percent; and either
1. An organic-carbon content of 0.3 percent or more at a
depth of 125 cm below the mineral soil surface; or
2. An irregular decrease in organic-carbon content from a
depth of 25 cm to a depth of 125 cm or to a densic, lithic, or
paralithic contact if shallower.
Fluventic Hapludolls
IGFM. Other Hapludolls that have both:
1. A mollic epipedon 60 cm or more thick that has a
texture finer than loamy fine sand and contains 50 percent
or more (by volume) wormholes, wormcasts, or filled
animal burrows either below an Ap horizon or below a
depth of 18 cm from the mineral soil surface; and
2. Either do not have a cambic horizon and do not, in the
lower part of the mollic epipedon, meet all of the requirements
for a cambic horizon, except for the color requirements, or
have carbonates throughout either the cambic horizon or the
lower part of the mollic epipedon.
Vermic Hapludolls
IGFN. Other Hapludolls that have a calcic horizon within
100 cm of the mineral soil surface.
Calcic Hapludolls
IGFO. Other Hapludolls that either:
1. Do not have a cambic horizon and do not, in any part of
the mollic epipedon below 25 cm from the mineral soil
surface, meet all of the requirements for a cambic horizon,
except for the color requirements; or
2. Have free carbonates throughout the cambic horizon or
in all parts of the mollic epipedon below a depth of 25 cm
from the mineral soil surface.
Entic Hapludolls
IGFP. Other Hapludolls.
Typic Hapludolls
Definition of Typic Hapludolls
Typic Hapludolls are the Hapludolls that:
1. Do not have aquic conditions for some time in normal
years either:
a. Within 40 cm of the mineral soil surface, in horizons
that also have redoximorphic features; or
b. Directly below the mollic epipedon, in horizons with a
total thickness of 15 cm or more that have one or more of
the following:
(1) A color value, moist, of 4 or more and redox
depletions with chroma of 2 or less; or
(2) Hue of 10YR or redder and chroma of 2 or less; or
(3) Hue of 2.5Y or yellower and chroma of 3 or less;
2. In normal years are not saturated with water in any layer
within 100 cm of the mineral soil surface for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
3. Have a mollic epipedon that is less than 60 cm thick or has
a texture of loamy fine sand or coarser if it is 60 cm or more
thick;
4. Have a cambic horizon or, in the lower part of the mollic
epipedon, meet all of the requirements for a cambic horizon,
except for the color requirments, and either the cambic horizon
or the lower part of the epipedon is free of carbonates in some
part;
596 Soil Taxonomy
5. Either have a regular decrease in organic-carbon content
with increasing depth and, unless a densic, lithic, or paralithic
contact is at some depth between 50 and 125 cm below the soil
surface, have an organic-carbon content of 0.3 percent or less
at a depth within 125 cm of the surface or have a slope of 25
percent or more;
6. Do not have a lithic contact within 50 cm of the mineral
soil surface;
7. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
8. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
9. Do not have a calcic horizon within 100 cm of the soil
surface; and
10. Do not have a texture finer than loamy fine sand and
either:
a. A mollic epipedon 50 cm or more thick; or
b. A mollic epipedon 40 cm or more thick and a frigid
temperature regime.
Description of Subgroups
Typic Hapludolls.—The central concept or Typic subgroup
of Hapludolls is fixed on soils in which there is little evidence
of wetness within a depth of 40 cm or more, in which there is a
thin or moderately thick mollic epipedon, and in which a
cambic horizon is free of carbonates in some part or the lower
part of the mollic epipedon is free of carbonates and resembles
a cambic horizon. These soils do not have a shallow lithic
contact; do not have slickensides, wedge-shaped aggregates, a
high linear extensibility, or wide cracks in normal years; and
show evidence of only a small amount of animal activity.
Low chroma and redoximorphic features are properties of
Aquolls and are the basis for defining Aquic and combination
Aquic subgroups of Hapludolls. An irregular decrease in
organic-carbon content with increasing depth and a relatively
high organic-carbon content in the deep layers indicate recent
alluvium and are the basis for defining the Fluventic subgroup
or, if the soils also are saturated with water at some period, the
Fluvaquentic subgroup. An overthickened epipedon and a
relatively high content of organic carbon in the deep layers
indicate slow accumulation of materials at the surface and, in
part, are the basis for defining the Cumulic subgroup. The
absence of a cambic horizon or the presence of carbonates
throughout the cambic horizon suggests weak weathering and
is the basis for defining the Entic subgroup. A shallow lithic
contact is the basis for defining the Lithic subgroup. Intensive
animal activity is a property of Vermudolls and is the basis for
defining the Vermic subgroup. Slickensides, wedge-shaped
aggregates, a high linear extensibility, and wide cracks that are
evident in normal years are characteristics of Vertisols and are
the basis for defining the Vertic subgroup.
Typic Hapludolls are of large extent in the United States.
They are mostly in Iowa, in Minnesota, and throughout the
eastern Great Plains. Some Typic Hapludolls occur throughout
much of the country. Most supported tall grasses, and most are
now used as cropland.
Andic and Vitrandic Hapludolls.—These soils have a
surface mantle or layer in the upper 75 cm that has both a low
bulk density and a high content of weakly crystalline minerals
or that consists of slightly or moderately weathered pyroclastic
materials. These soils are of very small extent in Oregon in the
United States.
Aquertic Hapludolls.—These soils have lower chroma than
Typic Hapludolls and commonly have faint redoximorphic
features and either shallow ground water at some time during
the year or artificial drainage. They also have a clayey particlesize
class in a significant part, have expanding clays, and in
some years have deep cracks. These soils are of small extent in
the United States and occur mostly in Minnesota and Iowa.
They supported mostly tall grasses and commonly are used as
cropland.
Aquic Hapludolls.—These soils have lower chroma than
Typic Hapludolls, commonly have faint redoximorphic
features, and either have shallow ground water at some time
during the year or have been artificially drained. These are
extensive soils in the glaciated regions of the northern Great
Plains of the United States. They commonly are in areas
Mollisols 597
between Aquolls and Typic Hapludolls. Slopes generally are
nearly level, and most of the soils have been artificially
drained. Aquic Hapludolls supported mostly tall grasses and
commonly are used as cropland.
Aquic Cumulic Hapludolls.—These soils have an
overthickened mollic epipedon. They also have lower chroma
than Typic Hapludolls, commonly have faint redoximorphic
features, and either have shallow ground water at some time
during the year or have been artificially drained. They are at
the base of slopes or on flood plains, where they receive fresh
sediments at a rate slow enough for the material to become
incorporated into the mollic epipedon. Some of the soils are
calcareous throughout their thickness. Aquic Cumulic
Hapludolls are of small extent and are mostly in Iowa. Slopes
are gentle and are mostly plane or concave. These soils
supported mostly tall grasses and commonly are used as
cropland.
Calcic Hapludolls.—These soils are similar to Typic
Hapludolls but have a calcic horizon within 100 cm of the soil
surface. They are of small extent, mostly in Minnesota, in the
United States. They supported mostly tall grasses and
commonly are used as cropland.
Cumulic Hapludolls.—These soils have an overthickened
mollic epipedon. They are at the base of slopes or on flood
plains, where they receive fresh sediments at a rate slow
enough for the material to become incorporated into the mollic
epipedon. These soils are permitted, but not required, to have a
cambic horizon. They may be calcareous throughout their
thickness. Slopes are gentle and are mostly plane or concave.
These soils are of large extent and are widely distributed in the
United States. Many of the soils supported tall grasses, but
some supported trees and shrubs. Most are used as cropland.
Entic Hapludolls.—These soils either do not have a cambic
horizon or are calcareous in the lower part of the mollic
epipedon or throughout any cambic horizon. Most of the soils
are sandy and show relatively weak horizon development.
Slopes are moderate to strong and are convex. These soils are
of small extent, mostly in Iowa and Minnesota, in the United
States. They supported mostly tall grasses and commonly are
used as cropland.
Fluvaquentic Hapludolls.—These soils have lower chroma
than Typic Hapludolls, have faint redoximorphic features, and
either have shallow ground water at some time during the year
or have been artificially drained. They are on flood plains and
formed in recent alluvium in which there are buried A horizons
or in which the content of organic carbon is relatively high in
deep layers. These soils are of moderate extent and are widely
distributed in the United States. Slopes are gentle and are
mostly plane or concave. Many of the soils supported tall
grasses, but some supported trees and shrubs. Most are used as
cropland.
Fluventic Hapludolls.—These soils are freely drained and
are on flood plains. They formed in recent alluvium in which
there are buried A horizons or in which the content of organic
carbon is relatively high in deep layers. Many of the soils do not
have a cambic horizon. The soils are otherwise like Typic
Hapludolls. Fluventic Hapludolls are of moderate extent and
are widely distributed in the United States. Slopes are gentle
and are mostly plane or concave. Many of the soils supported
tall grasses, but some supported trees and shrubs. Most are
used as cropland.
Lithic Hapludolls.—These soils have a shallow lithic
contact. The mollic epipedon commonly extends to the rock.
Some of the soils have impeded drainage because of shallow,
impermeable rock. Lithic Hapludolls are of moderate extent
and are widely distributed in the United States. Slopes are
gentle to very steep. Many of the soils supported grasses, but
some supported trees and shrubs. Most are used as rangeland
or wildlife habitat.
Oxyaquic Hapludolls.—These soils are like Typic
Hapludolls, but they are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years. They are of small
extent but are widely distributed in the United States. They
commonly are in areas between the Aquic and Typic subgroups
of Hapludolls. Slopes generally are gentle. Oxyaquic
Hapludolls supported mostly tall grasses and commonly are
used as cropland.
Pachic Hapludolls.—These soils are like Typic Hapludolls,
but they have a thick mollic epipedon. Slopes range from
gentle to moderately steep. Pachic Hapludolls are of small
extent, mostly on the northern Great Plains of the United
States. They supported mostly tall grasses and commonly are
used as cropland.
Vermic Hapludolls.—These soils show strong evidence of
intensive animal activity, mainly of earthworms and their
predators. The soils are thought to be developing toward
Vermudolls. They do not occur in significant areas in the
United States.
Vertic Hapludolls.—These soils have a clayey particle-size
class in a significant part, have expanding clays, and in some
years have deep cracks. They are of small extent in the United
States and are widely distributed. They supported mostly tall
grasses and commonly are used as cropland.
Natrudolls
These are the Udolls that have a natric horizon. Below
the natric horizon, there is normally one horizon or more
in which carbonates, sulfates, or other soluble salts have
accumulated. Most Natrudolls are in small areas. The soils
are most common in Argentina and on the northern Great
Plains of the United States, where many of the parent
materials contain salts. Most areas of these soils are small
and are nearly level or concave.
Definition
Natrudolls are the Udolls that have a natric horizon.
598 Soil Taxonomy
KeytoSubgroups
IGAA. Natrudolls that have a petrocalcic horizon that has its
upper boundary within 100 cm of the mineral soil surface.
Petrocalcic Natrudolls
IGAB. Other Natrudolls that have both:
1. Visible crystals of gypsum and/or more soluble salts
within 40 cm of the mineral soil surface; and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Leptic Vertic Natrudolls
IGAC. Other Natrudolls that have:
1. A glossic horizon or interfingering of albic materials
into the natric horizon; and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Glossic Vertic Natrudolls
IGAD. Other Natrudolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Natrudolls
IGAE. Other Natrudolls that have visible crystals of gypsum
and/or more soluble salts within 40 cm of the mineral soil
surface.
Leptic Natrudolls
IGAF. Other Natrudolls that have a glossic horizon or
interfingering of albic materials into the natric horizon.
Glossic Natrudolls
IGAG. Other Natrudolls that have a calcic horizon within
100 cm of the mineral soil surface.
Calcic Natrudolls
IGAH. Other Natrudolls.
Typic Natrudolls
Definition of Typic Natrudolls
Typic Natrudolls are the Natrudolls that:
1. Do not have a calcic or petrocalcic horizon that has its
upper boundary within 100 cm of the mineral soil surface;
2. Do not have visible crystals or nests of gypsum or more
soluble salts within 40 cm of the mineral soil surface;
3. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
and
4. Do not have a glossic horizon or interfingering of albic
materials into the natric horizon.
Description of Subgroups
Typic Natrudolls.—The central concept or Typic subgroup
of Natrudolls is fixed on soils that do not have a calcic or
petrocalcic horizon that has its upper boundary within 100 cm
of the mineral soil surface. These soils do not have a glossic
horizon or an albic horizon that interfingers into the natric
horizon. An albic horizon commonly is above the natric
horizon. If there is no albic horizon, there generally are some
skeletans and the color of the lower part of the mollic epipedon
approaches that of an albic horizon.
Visible crystals of gypsum and/or more soluble salts within
40 cm of the mineral soil surface adversely affect the use of
these soils and are the basis for defining the Leptic subgroup.
An albic horizon that has an irregular lower boundary or thick
skeletans on the peds in the upper part of the natric horizon are
Mollisols 599
considered evidence of partial destruction of the natric horizon
and are the basis for defining Glossic and combination Glossic
subgroups.
Typic Natrudolls are of small extent in the United States.
They are mostly on the northern Great Plains of the United
States. They supported mostly salt-tolerant grasses and shrubs.
Slopes are commonly gentle, and many of the soils are
cultivated. Some of the soils are used as rangeland or hayland.
Calcic Natrudolls.—These soils are similar to Typic
Natrudolls but have a calcic horizon within 100 cm of the soil
surface. They are of small extent in the United States and are
important in Argentina. They supported mostly grasses and are
used mostly as cropland.
Glossic Natrudolls.—These soils show evidence of
destruction of the natric horizon. Commonly, they have more
exchangeable magnesium and less sodium than Typic
Natrudolls, at least in the upper part of the natric horizon.
Some Glossic Natrudolls receive more moisture, either as
precipitation or as runoff, than the soils of the Typic subgroup.
Glossic Natrudolls are mostly on the northern Great Plains of
the United States. Most of the Glossic Natrudolls in the United
States are nearly level and are used as cropland.
Glossic Vertic Natrudolls.—These soils have both a high
shrink-swell potential and a glossic horizon or interfingering
of albic materials into the natric horizon. The soils do not have
a petrocalcic horizon within 100 cm or soluble salts, including
gypsum, within 40 cm of the soil surface. These soils occur in
the Dakotas and are used for small grain or alfalfa.
Leptic Natrudolls.—These soils have visible evidence of
salts at least as soluble as gypsum within 40 cm of the soil
surface. They have thinner sola than those of the Typic
subgroup, and the close proximity of the soluble salts to the
surface restricts plant growth. Leptic Natrudolls are moderately
extensive on the northern Great Plains of the United States.
They are on gentle slopes and are used primarily as rangeland.
Leptic Vertic Natrudolls.—These soils have a clayey
particle-size class in a significant part, have expanding clays,
and in normal years have deep cracks. They also have visible
evidence of salts at least as soluble as gypsum within 40 cm of
the soil surface. They have thinner sola than those of the Vertic
subgroup, and the close proximity of the soluble salts to the
surface restricts plant growth. Leptic Vertic Natrudolls are of
small extent in the United States. They are recognized only in
South Dakota. They supported mostly grasses and shrubs. Most
of the soils are used as rangeland.
Petrocalcic Natrudolls.—These soils are similar to Typic
Natrudolls but have a petrocalcic horizon within 100 cm of the
soil surface. They are not known to occur in the United States
but are important in Argentina. They supported mostly grasses
and are used mostly as cropland.
Vertic Natrudolls.—These soils are like Typic Natrudolls,
but they have a clayey particle-size class in a significant part,
have expanding clays, and in normal years have deep cracks.
They are of small extent in the United States. They are
recognized only in South Dakota. They supported mostly
grasses and shrubs. Most of the soils are used as cropland or
rangeland.
Paleudolls
These are the Udolls that have a thick or deep argillic horizon.
Most of the soils have a reddish hue and a content of clay that
decreases slowly with increasing depth. Paleudolls are mainly on
surfaces older than Wisconsinan and are thought to have
formed during at least one glacial stage and one interglacial
stage. These soils are mostly on the southern Great Plains and in
the mountains of the Western United States. They are extensive
only locally. Slopes are gentle to steep.
Definition
Paleudolls are the Udolls that:
1. Do not have a natric horizon; and
2. Have a petrocalcic horizon and do not have an argillic
horizon above the petrocalcic horizon; and
a. In all parts above the petrocalcic horizon, after the
materials between the soil surface and a depth of 18 cm
have been mixed, either are calcareous; or
b. Have a texture of loamy fine sand or coarser; or
3. Have an argillic horizon and a clay distribution in
which the clay content does not decrease by as much as 20
percent from the maximum clay content within 150 cm of
the soil surface, do not have a densic, lithic, or paralithic
contact within that depth, and also have one or both of the
following:
a. Hue of 7.5YR or redder and chroma of 5 or more
dominant in the matrix in some part of the lower half of the
argillic horizon; or
b. Many coarse redox concentrations that have hue redder
than 7.5YR or chroma higher than 5; or
4. Have a frigid temperature regime and both an argillic
horizon that has its upper boundary 60 cm or more below the
mineral soil surface and a texture finer than loamy fine sand in
all horizons above the argillic horizon.
Key to Subgroups
IGCA. Paleudolls that have one or both of the following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
600 Soil Taxonomy
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Paleudolls
IGCB. Other Paleudolls that have a petrocalcic horizon
within 150 cm of the mineral soil surface.
Petrocalcic Paleudolls
IGCC. Other Paleudolls that have, in one or more
subhorizons within the upper 50 cm of the argillic horizon,
redox depletions with chroma of 2 or less and also aquic
conditions for some time in normal years (or artificial
drainage).
Aquic Paleudolls
IGCD. Other Paleudolls that have a texture finer than loamy
fine sand and a mollic epipedon 50 cm or more thick.
Pachic Paleudolls
IGCE. Other Paleudolls that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Paleudolls
IGCF. Other Paleudolls that:
1. Have a calcic horizon that has its upper boundary
within 100 cm of the mineral soil surface; and
2. In all parts above the calcic horizon, after the materials
between the soil surface and a depth of 18 cm have been
mixed, either are calcareous or have a texture of loamy fine
sand or coarser.
Calcic Paleudolls
IGCG. Other Paleudolls.
Typic Paleudolls
Definition of Typic Paleudolls
Typic Paleudolls are the Paleudolls that:
1. Do not have, in any subhorizon within the upper 50 cm of
the argillic horizon, redox depletions with chroma of 2 or less
and also aquic conditions;
2. In normal years are not saturated with water in any layer
within 100 cm of the mineral soil surface for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
3. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that are 5
mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
4. Do not have a petrocalcic horizon within 150 cm of the
mineral soil surface;
5. Do not have a calcic horizon within 100 cm of the soil
surface; and
6. Do not have a texture finer than loamy fine sand and a
mollic epipedon 50 cm or more thick.
Description of Subgroups
Typic Paleudolls.—The central concept or Typic subgroup
of Paleudolls is fixed on soils that show little evidence of
wetness within a depth of 100 cm, that have a mollic epipedon
less than 50 cm thick, and that do not have slickensides,
wedge-shaped aggregates, a high linear extensibility, or wide
cracks in normal years. These soils do not have a petrocalcic
horizon or a shallow calcic horizon.
Shallow ground water and redoximorphic features are
properties of Aquolls and are the basis for defining the Aquic
and Oxyaquic subgroups. Slickensides, wedge-shaped
aggregates, a high linear extensibility, and wide cracks that are
evident in normal years are characteristics of Vertisols and are
the basis for defining the Vertic subgroup.
Typic Paleudolls are of small extent in the United States.
They are mostly on the southern Great Plains but also are in
the mountains in the western part of the United States. Most of
these soils supported tall grasses. Many of the soils on plains
are now used as cropland. The soils in the mountains are used
mostly as rangeland or wildlife habitat.
Aquic Paleudolls.—These soils have redox depletions with
low chroma in the upper part of the argillic horizon (within the
upper 50 cm), and, at some time during the year, ground water
stands in the redox-depleted horizon unless the soils have been
artificially drained. The soils are otherwise like Typic
Paleudolls. Aquic Paleudolls are of small extent in the United
States. They occur on the southern Great Plains of the United
States. Most of these soils supported tall grasses. Many have
gentle slopes and are used as cropland.
Calcic Paleudolls.—These soils are like Typic Paleudolls,
but they have a calcic horizon within 100 cm of the soil
surface. They are not known to occur in the United States.
They were established for use in other countries.
Oxyaquic Paleudolls.—These soils are like Typic
Paleudolls, but they are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years. Oxyaquic Paleudolls
Mollisols 601
are not known to occur in the United States. They were
established for use in other countries.
Pachic Paleudolls.—These soils are like Typic Paleudolls,
but they have a thick mollic epipedon. The argillic horizon
generally starts in the lower part of the mollic epipedon. Slopes
of the Pachic Paleudolls in the United States range from gentle
to steep. The soils are of small extent, mostly in the mountains
of the Western United States. Many of the soils supported
grasses and shrubs, but some supported trees. Most are used as
rangeland, but some are used as grazeable woodland.
Petrocalcic Paleudolls.—These soils have a petrocalcic
horizon within 150 cm, commonly within 100 cm, of the
mineral soil surface. They are not known to occur in the United
States. They were established for use in other countries.
Vertic Paleudolls.—These soils have a clayey particle-size
class in a significant part, have expanding clays, and in some
years have deep cracks. They are of very small extent in the
United States. They supported mostly tall grasses and
commonly are used as cropland.
Vermudolls
Vermudolls are the Udolls that have been intensively mixed
by earthworms or other burrowing animals and their predators.
The most common horizon sequence is the mollic epipedon
consisting of many wormcasts overlying soil material
containing many worm channels filled with dark material from
the mollic epipedon. These soils are not known to occur in
significant areas of the United States, but they are important in
other countries.
Definition
Vermudolls are the Udolls that:
1. Have a mollic epipedon below any Ap horizon, or below a
depth of 18 cm from the mineral soil surface, that has 50
percent or more (by volume) wormholes, wormcasts, or filled
animal burrows and that either rests on a densic, lithic, or
paralithic contact or has a transition to the underlying horizon
in which 25 percent or more of the material consists of discrete
wormholes, wormcasts, or animal burrows filled with material
from the mollic epipedon and the underlying horizon;
2. Do not have an argillic or natric horizon; and
3. Do not have a calcic horizon that has its upper boundary
within 100 cm of the mineral soil surface if all parts above the
calcic horizon, after the materials between the soil surface and
a depth of 18 cm have been mixed, either are calcareous or
have a texture of loamy fine sand or coarser.
Key to Subgroups
IGEA. Vermudolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Vermudolls
IGEB. Other Vermudolls that have a mollic epipedon less than
75 cm thick.
Haplic Vermudolls
IGEC. Other Vermudolls.
Typic Vermudolls
Definition of Typic Vermudolls
Typic Vermudolls are the Vermudolls that:
1. Have a mollic epipedon that is 75 cm or more thick;
2. Do not have a lithic contact within 50 cm of the mineral soil
surface.
Description of Subgroups
Typic Vermudolls.—The central concept or Typic subgroup
of Vermudolls is fixed on soils that are deep to a lithic contact
and have a mollic epipedon 75 cm or more thick. These soils
are not known to occur in the United States.
Haplic Vermudolls.—These soils have a mollic epipedon
less than 75 cm thick. They are otherwise like Typic
Vermudolls. Haplic Vermudolls are of very small extent in the
United States. They are known to occur only in South Dakota
and Minnesota. These soils supported tall grasses. Most of the
soils are now used as cropland.
Lithic Vermudolls.—These soils have a lithic contact at a
depth of 50 cm or less from the mineral soil surface. They are
not known to occur in the United States.
Ustolls
Ustolls are the more or less freely drained Mollisols of
subhumid to semiarid climates. Rainfall occurs mainly during
a growing season, often in heavy showers, but is erratic.
Drought is frequent and may be severe. During a drought, soil
blowing becomes a problem. Without irrigation, the low supply
of moisture usually limits crop yields. Ustolls are extensive
soils on the western Great Plains in the United States.
In addition to the mollic epipedon, most Ustolls have a Bk
horizon that has identifiable secondary carbonates or have a
calcic horizon, but a few of the soils that formed in
noncalcareous materials do not have secondary lime. Ustolls
may also have a cambic, argillic, kandic, petrocalcic, or natric
horizon. If there is a natric horizon, there may be an albic
horizon overlying it, or if there is a cambic or argillic horizon,
there may be a duripan below it. The presence or absence of
these horizons is used, in part, as the basis for defining the
great groups of Ustolls.
Most of the Ustolls on the Great Plains in the United States
had a grass vegetation when the country was settled. Some of
the Ustolls in the mountains of the Western States supported
forest vegetation. The Aridic subgroups supported mostly short
grasses, and the others supported mixtures of short and tall
grasses.
602 Soil Taxonomy
Ustolls formed in sediments and on surfaces of varying ages
from Holocene to mid Pleistocene or earlier. Those that have a
thermic or warmer temperature regime, in particular, may have
formed during two or more glacial and interglacial stages.
The temperature regimes of Ustolls are warmer than cryic.
The moisture regimes are dominantly ustic, but a few of the
soils that are marginal to Aridisols have an aridic (torric)
regime.
Definition
Ustolls are the Mollisols that:
1. Have an ustic moisture regime or an aridic moisture regime
that borders on ustic;
2. Have a temperature regime warmer than cryic;
3. Do not have both an albic horizon and, within 100 cm of the
mineral soil surface, any subhorizon of the albic horizon and/or
of the argillic or natric horizon that has redox concentrations in
the form of masses or concretions, or both, and also aquic
conditions; and
4. Do not have both aquic conditions and the colors defined
for Aquolls.
Key to Great Groups
IFA. Ustolls that have a duripan that has its upper boundary
within 100 cm of the mineral soil surface.
Durustolls, p. 612
IFB. Other Ustolls that have a natric horizon.
Natrustolls, p. 622
IFC. Other Ustolls that:
1. Have either a calcic or gypsic horizon that has its upper
boundary within 100 cm of the mineral soil surface or a
petrocalcic horizon that has its upper boundary within 150
cm of the mineral soil surface; and
2. Do not have an argillic horizon above the calcic, gypsic,
or petrocalcic horizon; and
3. In all parts above the calcic, gypsic, or petrocalcic
horizon, after the materials between the soil surface and a
depth of 18 cm have been mixed, either are calcareous or
have a texture of loamy fine sand or coarser.
Calciustolls, p. 608
IFD. Other Ustolls that have either:
1. A petrocalcic horizon that has its upper boundary
within 150 cm of the mineral soil surface; or
2. An argillic horizon that has one or both of the
following:
a. With increasing depth, no clay decrease of 20 percent
or more (relative) from the maximum clay content
(noncarbonate clay) within 150 cm of the mineral soil
surface (and there is no densic, lithic, or paralithic contact
within that depth); and either
(1) Hue of 7.5YR or redder and chroma of 5 or more in
the matrix; or
(2) Common redox concentrations with hue
of 7.5YR or redder or chroma of 6 or more, or
both; or
b. 35 percent or more clay in its upper part and a clay
increase either of 20 percent or more (absolute) within a
vertical distance of 7.5 cm or of 15 percent or more
(absolute) within a vertical distance of 2.5 cm, in the
fine-earth fraction (and there is no densic, lithic, or
paralithic contact within 50 cm of the mineral soil
surface).
Paleustolls, p. 625
IFE. Other Ustolls that have an argillic horizon.
Argiustolls, p. 602
IFF. Other Ustolls that have a mollic epipedon that:
1. Either below an Ap horizon or below a depth of 18 cm
from the mineral soil surface, contains 50 percent or more
(by volume) wormholes, wormcasts, or filled animal
burrows; and
2. Either rests on a lithic contact or has a transition zone
to the underlying horizon in which 25 percent or more of
the soil volume consists of discrete wormholes, wormcasts,
or animal burrows filled with material from the mollic
epipedon and from the underlying horizon.
Vermustolls, p. 629
IFG. Other Ustolls.
Haplustolls, p. 613
Argiustolls
These are the Ustolls that have an argillic horizon in or
below the mollic epipedon. They do not have a natric or
petrocalcic horizon that has its upper boundary within 150 cm
of the mineral soil surface or a duripan that has its upper
boundary within 100 cm of the mineral soil surface. Most of
these soils have an argillic horizon that, with increasing depth,
has a clay decrease of 20 percent or more (relative) from the
maximum clay content within 150 cm of the mineral soil surface.
Some of the soils have a densic, lithic, or paralithic contact
within 150 cm, and some have no hues of 7.5YR or redder or
have chroma of 4 or less.
Most Argiustolls have a Bk or calcic horizon below the
argillic horizon, and some have a Bz or By horizon below the
Mollisols 603
Bk horizon. Argiustolls formed mostly in late-Pleistocene
deposits or on surfaces of comparable age. They occur in
relatively stable positions. Slopes generally are moderate to
nearly level, and most of the soils are cultivated. Argiustolls
are extensive soils on the western Great Plains and also occur
in the mountains and valleys of the Western United States.
Definition
Argiustolls are the Ustolls that:
1. Have an argillic horizon that has both:
a. A vertical clay distribution in which the clay content
decreases by more than 20 percent from the maximum clay
content (noncarbonate clay) within a depth of less than 150
cm from the soil surface if:
(1) Hue in the matrix is redder than 10YR, and chroma
is higher than 4; or
(2) There are common redox concentrations that have
hue of 7.5YR or redder or chroma higher than 5; and
b. Less than 35 percent clay in the upper part or an
increase of less than 20 percent clay (absolute) within a
vertical distance of 7.5 cm or an increase of less than 15
percent clay (absolute) within a vertical distance of 2.5 cm
at the upper boundary, or there is a densic, lithic, or
paralithic contact within 50 cm of the mineral soil surface;
2. Do not have a duripan that has its upper boundary
within 100 cm of the soil surface;
3. Do not have a petrocalcic horizon that has its upper
boundary within 150 cm of the mineral soil surface;
4. Do not have a natric horizon; and
5. Do not have calcic or gypsic horizon that has its upper
boundary within 100 cm of the soil surface unless there is an
argillic horizon above the calcic or gypsic horizon or some part
of the soil above the calcic or gypsic horizon either is
noncalcareous or has a texture finer than loamy fine sand after
the materials between the soil surface and a depth of 18 cm
have been mixed.
Key to Subgroups
IFEA. Argiustolls that have both:
1. A lithic contact within 50 cm of the mineral soil
surface; and
2. When neither irrigated nor fallowed to store moisture,
have one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some or all parts for six-tenths or more of the cumulative
days per year when the soil temperature at a depth of 50
cm below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some or all parts for six-tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface
is higher than 5 o
C.
Aridic Lithic Argiustolls
IFEB. Other Argiustolls that have both:
1. A lithic contact within 50 cm of the mineral soil
surface; and
2. Above the argillic horizon, either an albic horizon or a
horizon that has color values too high for a mollic epipedon
and chroma too high for an albic horizon.
Alfic Lithic Argiustolls
IFEC. Other Argiustolls that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Argiustolls
IFED. Other Argiustolls that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. When neither irrigated nor fallowed to store moisture,
have one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
604 Soil Taxonomy
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some or all parts for six-tenths or more of the cumulative
days per year when the soil temperature at a depth of 50
cm below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some or all parts for six-tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface
is higher than 5 o
C.
Torrertic Argiustolls
IFEE. Other Argiustolls that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. When neither irrigated nor fallowed to store moisture,
either:
a. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for four-tenths or less of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
b. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for fewer than
120 cumulative days per year when the soil temperature
at a depth of 50 cm below the soil surface is higher than
8 o
C.
Udertic Argiustolls
IFEF. Other Argiustolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick that
has its upper boundary within 125 cm of the mineral soil
surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Argiustolls
IFEG. Other Argiustolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Argiustolls
IFEH. Other Argiustolls that have both:
1. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some or all parts for six-tenths or more of the cumulative
days per year when the soil temperature at a depth of 50
cm below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some or all parts for six-tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface
is higher than 5 o
C; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface,
one or both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
Mollisols 605
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitritorrandic Argiustolls
IFEI. Other Argiustolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Argiustolls
IFEJ. Other Argiustolls that have a texture finer than loamy
fine sand and either:
1. A frigid temperature regime and a mollic epipedon 40
cm or more thick; or
2. A mollic epipedon 50 cm or more thick.
Pachic Argiustolls
IFEK. Other Argiustolls that have, in one or more horizons
within 100 cm of the mineral soil surface, redox depletions
with chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Argiustolls
IFEL. Other Argiustolls that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Argiustolls
IFEM. Other Argiustolls that have either:
1. Above the argillic horizon, an albic horizon or a
horizon that has color values too high for a mollic epipedon
and chroma too high for an albic horizon; or
2. A glossic horizon, or interfingering of albic materials
into the upper part of the argillic horizon, or skeletans of
clean silt and sand covering 50 percent or more of the faces
of peds in the upper 5 cm of the argillic horizon.
Alfic Argiustolls
IFEN. Other Argiustolls that have both:
1. A calcic horizon with its upper boundary within 100 cm
of the mineral soil surface; and
2. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
5 o
C.
Calcidic Argiustolls
IFEO. Other Argiustolls that, when neither irrigated nor
fallowed to store moisture, have one of the following:
1. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for four-tenths
or more of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
or all parts for six-tenths or more of the cumulative days per
year when the soil temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C; or
3. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
a. Is moist in some or all parts for fewer than 90
606 Soil Taxonomy
consecutive days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
b. Is dry in some or all parts for six-tenths or more of the
cumulative days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than
5 o
C.
Aridic Argiustolls
IFEP. Other Argiustolls that, when neither irrigated nor
fallowed to store moisture, have either:
1. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for four-tenths or less of the cumulative days per year
when the soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
2. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for fewer than 120
cumulative days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C.
Udic Argiustolls
IFEQ. Other Argiustolls that have a brittle horizon that is
within 100 cm of the mineral soil surface, is 15 cm or more
thick, and has either some opal coatings or 20 percent or more
(by volume) durinodes.
Duric Argiustolls
IFER. Other Argiustolls.
Typic Argiustolls
Definition of Typic Argiustolls
Typic Argiustolls are the Argiustolls that:
1. Do not have, in any horizon within 100 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
2. In normal years are not saturated with water in any layer
within 100 cm of the mineral soil surface for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
3. Do not have a brittle horizon that is 15 cm or more thick,
is within 100 cm of the soil surface, and has some opal
coatings or 20 percent or more (by volume) durinodes;
4. Do not have a lithic contact within 50 cm of the mineral
soil surface;
5. Do not have either:
a. An albic horizon or another horizon above the argillic
horizon that has a color value too high for a mollic epipedon
and chroma too high for an albic horizon; or
b. A glossic horizon, or interfingering of albic materials in
the upper part of the argillic horizon, or skeletans of clean
silt and sand covering more than half the faces of peds in
the upper 5 cm or more of the argillic horizon;
6. Do not have a texture finer than loamy fine sand and
either:
a. A mollic epipedon 50 cm or more thick; or
b. A mollic epipedon 40 cm or more thick and a frigid
temperature regime;
7. When neither irrigated nor fallowed to store moisture,
have one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for less than
four-tenths of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
or all parts for more than four-tenths but less than six-tenths
of the cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than 5 o
C;
or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is moist in some or all parts for 90 or more
consecutive days per year or is dry for less than six-tenths of
the cumulative days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C
and is dry for more than 120 cumulative days per year when
the soil temperature at a depth of 50 cm below the soil
surface is higher than 8 o
C;
8. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
9. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
Mollisols 607
of 1.0 g/cm3
or less, measured at 33 kPa water retention, and
acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than 35
percent of the whole soil and cinders, pumice, and pumicelike
fragments making up more than 66 percent of these
fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more; and
10. Do not have a calcic horizon with its upper boundary
within 100 cm of the soil surface.
Description of Subgroups
Typic Argiustolls.—The central concept or Typic subgroup
of Argiustolls is fixed on deep, freely drained soils that have
some available moisture during most of the growing season
and do not have a calcic horizon, an albic horizon, a glossic
horizon, interfingering of albic materials, or a horizon that has
color values too high for a mollic epipedon above the argillic
horizon. These soils do not have slickensides, wedge-shaped
aggregates, a high linear extensibility, or wide cracks in
normal years.
Shallow ground water or artificial drainage and redox
depletions with low chroma are properties shared with Aquolls
and are the basis for defining Aquic and Oxyaquic subgroups.
A shallow lithic contact is the basis for defining Lithic and
combination Lithic subgroups. An albic horizon above the
argillic horizon is characteristic of Alfisols and is the basis for
defining the Alfic subgroup. A thick mollic epipedon is the
basis for defining the Pachic subgroup. Argiustolls that are
moist for longer periods of time than is described for the Typic
subgroup are assigned to the Udic subgroup, and those that are
dry for longer periods are assigned to the Aridic subgroup.
Slickensides, wedge-shaped aggregates, a high linear
extensibility, and wide cracks that are evident in normal years
are characteristics of Vertisols and are the basis for defining the
Vertic subgroup.
Typic Argiustolls are of large extent in the United States.
They are mostly on the Great Plains but also are in the
mountains in the western part of the United States. Most of
these soils supported grasses and shrubs. Some of the soils,
mostly those in the mountains, supported trees or grass and
widely spaced trees. Many of the soils on plains are now used
as cropland. The soils in the mountains are used mostly as
rangeland or wildlife habitat.
Alfic Argiustolls.—These soils have an albic horizon or an
eluvial horizon that is too light in color for a mollic epipedon
above the argillic horizon, or they have a glossic horizon,
interfingering of albic materials, or skeletans of clean silt and
sand covering more than half the faces of peds in the upper 5
cm or more of the argillic horizon. The vegetation on these
soils commonly is grass and scattered conifer trees. The soils
are of small extent, mostly in the mountains of Colorado. They
are used mostly as rangeland or wildlife habitat.
Alfic Lithic Argiustolls.—These soils have a lithic contact
within 50 cm of the soil surface and have an albic horizon or
an eluvial horizon that is too light in color for a mollic
epipedon above the argillic horizon, or they have a glossic
horizon, interfingering of albic materials, or skeletans of clean
silt and sand covering more than half the faces of peds in the
upper 5 cm or more of the argillic horizon.
These soils are of very small extent and are known to occur
only in Texas in the United States. They are used as rangeland.
Andic and Vitrandic Argiustolls.—These soils have a
surface mantle or layer in the upper 75 cm that has both a low
bulk density and a high content of weakly crystalline minerals
or that consists of slightly or moderately weathered pyroclastic
materials. These soils are of very small extent in the mountains
of the Western United States. The vegetation is mostly forest or
grass and widely spaced trees. Most of these soils are used as
forest, rangeland, or wildlife habitat.
Aquic Argiustolls.—These soils have redox depletions with
low chroma and either have shallow ground water at some time
of the year or are artificially drained. The color value and
chroma of these soils commonly are lower than those of Typic
Argiustolls. Aquic Argiustolls developed mostly in nearly level
upland areas that commonly are concave. They are of small
extent in the United States. Most of the soils are used as
cropland.
Aridic Argiustolls.—These soils are drier than Typic
Argiustolls, and they do not have a calcic horizon. It is
common but is not required that the color value and chroma
are higher and the depth to carbonates is less than in Typic
Argiustolls. A Bz horizon and a Bk horizon are more common
than in soils of the Typic subgroup. Aridic Argiustolls
generally receive less precipitation than the soils of the Typic
subgroup, or they lose more water through runoff. A few Aridic
Argiustolls that are associated with Aridisols may receive
runoff from other soils.
Aridic Argiustolls are extensive and widely distributed in
the Western United States. The largest extent is on the western
part of the Great Plains. Slopes range from nearly level to
steep. In the United States, many Aridic Argiustolls that have
suitable slopes are used as cropland. Winter wheat and grain
sorghum are common crops. If the temperature regime is frigid
or mesic, many of the soils are fallowed in alternate years to
store moisture. Some of the soils are irrigated, and many of the
more sloping soils are used as rangeland.
Aridic Lithic Argiustolls.—These soils have a lithic
contact within 50 cm of the mineral soil surface and a soil
608 Soil Taxonomy
moisture regime that borders on aridic. They occur on the
western Great Plains of the United States and are used mainly
as rangeland.
Calcidic Argiustolls.—These soils are drier than Typic
Argiustolls and have a calcic horizon with its upper boundary
within 100 cm of the soil surface. Calcidic Argiustolls do not
have a high shrink-swell potential or a lithic contact within 50
cm of the soil surface. They also do not have an albic horizon
above the argillic horizon, a mollic epipedon 50 cm or more
thick, saturation within 100 cm of the soil surface, or a
significant amount of volcanic glass. These soils occur in the
southwestern part of the United States and are used mostly for
grazing by livestock.
Duric Argiustolls.—These soils have a brittle horizon that
is within 100 cm of the mineral soil surface, is 15 cm or more
thick, and has either some opal coatings or 20 percent or more
durinodes. They are otherwise like Typic Argiustolls in their
defined properties and in most other properties. Duric
Argiustolls are not known to occur in the United States.
Lithic Argiustolls.—These soils have a shallow lithic
contact. They may have identifiable secondary carbonates
above the rock, but this feature is not common in the United
States. These soils are of large extent, mostly in the mountains
of the Western United States. They have moderate to very steep
slopes. The vegetation commonly is grass and shrubs, but some
of the soils support forest vegetation. Lithic Argiustolls are
used mostly as rangeland or forest.
Oxyaquic Argiustolls.—These soils are like Typic
Argiustolls, but they are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years. They are of very
small extent in the United States.
Pachic Argiustolls.—These soils have a thick mollic
epipedon that commonly includes at least part of the argillic
horizon. Some of these soils receive extra water as runoff from
other soils. Pachic Argiustolls are extensive in the United
States. They are widely distributed on the Great Plains and in
the mountains of the Western United States. Slopes are nearly
level to steep. Many of these soils supported grasses and
shrubs, but some supported trees. Most of the soils on plains
are used as cropland. Most of the soils in the mountains are
used as rangeland, but some are used as grazeable woodland.
Torrertic Argiustolls.—These soils have a clayey particlesize
class in a significant part, have expanding clays, and in
normal years have deep cracks. They are drier than Vertic
Argiustolls. Torrertic Argiustolls are of small extent in the
United States and occur on the western Great Plains. The
natural vegetation was mostly grasses and shrubs. Slopes
generally are gentle, and many are concave. Most of these soils
are used as cropland, but some are used as rangeland.
Udertic Argiustolls.—These soils have a clayey particlesize
class in a significant part, have expanding clays, and in
many years have deep cracks. They are more moist than Vertic
Argiustolls because they either receive more precipitation or
receive runoff from other soils. Udertic Argiustolls are of small
extent in the United States and occur on the southern Great
Plains. The natural vegetation was mostly grasses. Slopes
generally are gentle, and many are concave. Most of these soils
are used as cropland, but some are used as rangeland.
Udic Argiustolls.—These soils are more moist than Typic
Argiustolls because they either receive more precipitation or
receive runoff from other soils. Most of the Udic Argiustolls in
the United States are in areas between Typic Argiustolls and
Udolls. Udic Argiustolls are extensive soils in the southeastern
part of the Great Plains. The natural vegetation was mostly
grasses and shrubs. Slopes generally are gentle. Most of these
soils are used as cropland.
Vertic Argiustolls.—These soils have a clayey particle-size
class in a significant part, have expanding clays, and in normal
years have deep cracks. They formed mostly in material
weathered from smectite-rich shale or in material weathered
from limestone. They are associated on the landscape with
Usterts and with other Ustolls. Vertic Argiustolls occur
throughout the Great Plains in the United States and are
moderately extensive soils. The natural vegetation was mostly
grasses. Slopes generally are gentle, and most of these soils are
used as cropland.
Vitritorrandic Argiustolls.—These soils have significant
amounts of cinders, pumice, and pumicelike fragments or glass
and have a soil moisture regime that borders on aridic. They do
not have a lithic contact within 50 cm of the soil surface or a
high shrink-swell potential. These soils are not known to occur
in the United States.
Calciustolls
These are the Ustolls that have a gypsic, calcic, or petrocalcic
horizon and that are calcareous in all overlying horizons. These
soils do not have a duripan or an argillic or natric horizon above
the calcic, gypsic, or petrocalcic horizon. Either the parent
materials had more carbonates than the limited rainfall could
remove from the upper horizons, or there is a continuing external
source of carbonates in dust or water.
Calciustolls formed mostly in Pleistocene sediments or in
older materials on surfaces of comparable age. In the United
States, their vegetation was dominantly grass before the soils
were cultivated. Calciustolls are most extensive on the Great
Plains in the United States, but some are in the intermountain
valleys of the Western States.
Definition
Calciustolls are the Ustolls that:
1. Have a calcic or gypsic horizon that has its upper boundary
within 100 cm of the soil surface or a petrocalcic horizon that
has its upper boundary within 150 cm of the soil surface and
are calcareous in all parts of all horizons above the calcic,
petrocalcic, or gypsic horizon after the upper 18 cm has been
Mollisols 609
mixed, unless the texture is coarser than loamy very fine sand or
very fine sand;
2. Do not have an argillic horizon above the calcic, gypsic, or
petrocalcic horizon;
3. Do not have a duripan that has its upper boundary
within 100 cm of the mineral soil surface; and
4. Do not have a natric horizon.
Key to Subgroups
IFCA. Calciustolls that have a salic horizon that has its upper
boundary within 75 cm of the mineral soil surface.
Salidic Calciustolls
IFCB. Other Calciustolls that have a petrocalcic horizon and
a lithic contact within 50 cm of the mineral soil surface.
Lithic Petrocalcic Calciustolls
IFCC. Other Calciustolls that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Calciustolls
IFCD. Other Calciustolls that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some or all parts for six-tenths or more of the cumulative
days per year when the soil temperature at a depth of 50
cm below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some or all parts for six-tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface
is higher than 5 o
C.
Torrertic Calciustolls
IFCE. Other Calciustolls that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. When neither irrigated nor fallowed to store moisture,
either:
a. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for four-tenths or less of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
b. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for fewer than
120 cumulative days per year when the soil temperature
at a depth of 50 cm below the soil surface is higher than
8 o
C.
Udertic Calciustolls
IFCF. Other Calciustolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Calciustolls
IFCG. Other Calciustolls that have a petrocalcic horizon that
610 Soil Taxonomy
has its upper boundary within 100 cm of the mineral soil
surface.
Petrocalcic Calciustolls
IFCH. Other Calciustolls that have a gypsic horizon with its
upper boundary within 100 cm of the mineral soil surface.
Gypsic Calciustolls
IFCI. Other Calciustolls that have a texture finer than loamy
fine sand and either:
1. A frigid temperature regime and a mollic epipedon 40
cm or more thick; or
2. A mollic epipedon 50 cm or more thick.
Pachic Calciustolls
IFCJ. Other Calciustolls that have, in one or more horizons
within 75 cm of the mineral soil surface, redox concentrations
and also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Calciustolls
IFCK. Other Calciustolls that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Calciustolls
IFCL. Other Calciustolls that, when neither irrigated nor
fallowed to store moisture, have one of the following:
1. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for four-tenths
or more of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
or all parts for six-tenths or more of the cumulative days per
year when the soil temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C; or
3. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
a. Is moist in some or all parts for fewer than 90
consecutive days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
b. Is dry in some or all parts for six-tenths or more of
the cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
5o
C.
Aridic Calciustolls
IFCM. Other Calciustolls that, when neither irrigated nor
fallowed to store moisture, have either:
1. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
or all parts for four-tenths or less of the consecutive days per
year when the soil temperature at a depth of 50 cm below
the soil surface is higher than 5 o
C; or
2. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for fewer than 120
cumulative days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C.
Udic Calciustolls
IFCN. Other Calciustolls.
Typic Calciustolls
Definition of Typic Calciustolls
Typic Calciustolls are the Calciustolls that:
1. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox concentrations and also aquic conditions;
2. In normal years are not saturated with water in any layer
within 100 cm of the mineral soil surface for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
3. Do not have a lithic contact within 50 cm of the soil
surface;
4. Do not have a texture finer than loamy fine sand and
either:
a. A mollic epipedon 50 cm or more thick; or
b. A mollic epipedon 40 cm or more thick and a frigid
temperature regime;
5. Do not have a petrocalcic horizon that has its upper
boundary within 100 cm of the mineral soil surface;
6. Do not have a salic horizon that has its upper boundary
within 75 cm of the mineral soil surface;
7. When neither irrigated nor fallowed to store moisture,
have one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for less than
Mollisols 611
four-tenths of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
or all parts for more than four-tenths but less than six-tenths
of the cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than 5 o
C;
or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is moist in some or all parts for 90 or more
consecutive days per year or is dry for less than six-tenths of
the cumulative days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C
and is dry for more than 120 cumulative days per year when
the soil temperature at a depth of 50 cm below the soil
surface is higher than 8 o
C;
8. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
and
9. Do not have a gypsic horizon with its upper boundary
within 100 cm of the mineral soil surface.
Description of Subgroups
Typic Calciustolls.—The central concept or Typic subgroup
of Calciustolls is fixed on soils that do not have a fluctuating
ground water table in their deep layers accompanied by
redoximorphic features, that have an ustic moisture regime,
that have a mollic epipedon of moderate thickness, that have a
calcic horizon rather than a petrocalcic horizon, and that do
not have slickensides, wedge-shaped aggregates, a high linear
extensibility, or wide cracks in normal years.
Redox concentrations and a ground water table that
fluctuates within 100 cm of the mineral soil surface are
properties shared with Aquolls and are the basis for defining
Aquic and Oxyaquic subgroups. A shallow lithic contact is the
basis for defining Lithic and combination Lithic subgroups. A
thick mollic epipedon is the basis for defining the Pachic
subgroup. A petrocalcic horizon indicates development that is
more intensive than normal and is the basis for defining the
Petrocalcic subgroup. Slickensides, wedge-shaped aggregates, a
high linear extensibility, and wide cracks that are evident in
normal years are characteristics of Vertisols and are the basis for
defining the Vertic subgroup.
Typic Calciustolls are of moderately large extent in the United
States. They are widely distributed. The largest extent is on the
Great Plains from Montana to Texas. The soils also are on
tropical islands and in some valleys in the mountains of the
Western United States. Most Typic Calciustolls supported
grasses and shrubs. Most of the soils on plains are now used as
cropland. The soils in the mountains are used mostly as
rangeland or wildlife habitat.
Aquic Calciustolls.—These soils have redox depletions
with low chroma and either have shallow ground water at some
time of the year or are artificially drained. The color value and
chroma of these soils commonly are lower than those of Typic
Calciustolls. Aquic Calciustolls developed mostly in nearly
level upland areas that commonly are concave. These soils are
of small extent in the United States. Most are used as cropland.
Aridic Calciustolls.—These soils are drier than Typic
Calciustolls. They generally receive less precipitation than the
soils in the Typic subgroup, or they lose more water through
runoff. A few of the soils that are associated with Aridisols
may receive runoff from other soils. Aridic Calciustolls are
moderately extensive and widely distributed in the Western
United States. The largest extent is on the western part of the
Great Plains. Slopes range from nearly level to steep. In the
United States, many of the soils that have suitable slopes are
used as cropland. If the temperature regime is frigid or mesic,
many of the soils are fallowed in alternate years to store
moisture. Some of the soils are irrigated, and most of the more
sloping soils are used as rangeland.
Gypsic Calciustolls.—These soils have a gypsic horizon.
They do not have a high shrink-swell potential, a salic or
petrocalcic horizon, or a lithic contact within 50 cm of the
mineral soil surface. These soils are not extensive but occur in
southeastern New Mexico and western Texas. They are used as
rangeland.
Lithic Calciustolls.—These soils have a shallow lithic
contact but are otherwise like Typic Calciustolls in defined
characteristics. Lithic Calciustolls soils are of small extent,
mostly in the Western United States. They have moderate to
very steep slopes. The vegetation is mostly grass and shrubs,
but a few of the soils support forest vegetation. The soils are
used mostly as rangeland or forest.
Lithic Petrocalcic Calciustolls.—These soils have a
petrocalcic horizon overlying hard bedrock within a depth of
50 cm. Typically, the fractures in the underlying bedrock are
filled with cemented secondary carbonates. Most of these soils
are drier than Typic Calciustolls. Slopes are gentle. Lithic
Petrocalcic Calciustolls formed on surfaces older than the
Pleistocene. These soils are extensive locally in Texas. They
are used almost exclusively as rangeland.
Oxyaquic Calciustolls.—These soils are like Typic
Calciustolls, but they are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
612 Soil Taxonomy
or more cumulative days in normal years. These soils are of very
small extent in the United States.
Pachic Calciustolls.—These soils have a thick mollic
epipedon. Most of the soils are nearly level or concave. Many
are on terraces or very broad, flat upland ridges. Pachic
Calciustolls are of small extent on the Great Plains in the
United States. Nearly all of them are used as cropland and are
summer fallowed.
Petrocalcic Calciustolls.—These soils have a petrocalcic
horizon but are otherwise like Typic Calciustolls in defined
properties. In most Petrocalcic Calciustolls, depth to the
petrocalcic horizon is less than 50 cm. Some of the soils that
have a petrocalcic horizon below a depth of 50 cm are
underlain by hard bedrock. Petrocalcic Calciustolls are
extensive on the Great Plains of the United States. The largest
extent is in Texas. Most of the soils are used as rangeland.
Salidic Calciustolls.—These soils have a salic horizon in
the upper part of the profile. They are not known to occur in
the United States.
Torrertic Calciustolls.—These soils have a clayey particlesize
class in a significant part, have expanding clays, and in
normal years have deep cracks. They are drier than Vertic
Calciustolls. Torrertic Calciustolls are of very small extent in
the United States.
Udertic Calciustolls.—These soils have a clayey particlesize
class in a significant part, have expanding clays, and in
normal years have deep cracks. They are more moist than
Vertic Calciustolls because they generally receive more
precipitation. Udertic Calciustolls are of very small extent.
Udic Calciustolls.—These soils are more moist than Typic
Calciustolls because they generally receive more precipitation.
The Udic Calciustolls in the United States are in areas between
Typic Calciustolls and Udolls. Udic Calciustolls are of small
extent and are extensive only in Texas. The natural vegetation
is mostly grasses and shrubs. Slopes generally are gentle. Most
of these soils are used as cropland.
Vertic Calciustolls.—These soils have a clayey particle-size
class in a significant part, have expanding clays, and in normal
years have deep cracks. They formed mostly in material
weathered from smectite-rich shale or in material weathered
from limestone. They are associated on the landscape with
Usterts and with other Ustolls. Vertic Calciustolls occur mostly
in Texas on the Great Plains and are of small extent. The
natural vegetation was mostly grasses. Slopes are mainly
gentle, and most of the soils are used as cropland.
Durustolls
These are Ustolls that have a duripan with its upper
boundary within 100 cm of the soil surface. These soils formed
in the vicinity of cinders and ash falls. Their parent materials
are mainly siliceous tuffs, volcanic ash, cinders, and basic
volcanic rocks. In the United States, the natural vegetation is
mostly grasses and shrubs. These soils are of small extent.
They formed in late-Pleistocene deposits. They are on alluvial
fans and terraces, on nearly level to rolling cinder fans and
plains, and on hilly to very steep cinder cones. They may be
common on the leeward sides of volcanic islands in the Lesser
Antilles.
Definition
Durustolls are the Ustolls that have a duripan that has an
upper boundary within 100 cm of the mineral soil surface.
Key to Subgroups
IFAA. Durustolls that have a natric horizon above the
duripan.
Natric Durustolls
IFAB. Other Durustolls that:
1. Do not have an argillic horizon above the duripan; and
2. Have an aridic moisture regime that borders on ustic.
Haploduridic Durustolls
IFAC. Other Durustolls that have an aridic moisture regime
that borders on ustic.
Argiduridic Durustolls
IFAD. Other Durustolls that do not have an argillic horizon
above the duripan.
Entic Durustolls
IFAE. Other Durustolls that have a duripan that is strongly
cemented or less cemented in all subhorizons.
Haplic Durustolls
IFAF. Other Durustolls.
Typic Durustolls
Definition of Typic Durustolls
Typic Durustolls are the Durustolls that:
1. Have an argillic horizon above the duripan;
2. Have a duripan that is massive and platy and that has half
or more of its upper boundary coated or indurated with opal
and silica, with or without sesquioxides, or that is indurated in
some subhorizon below its upper boundary;
3. Do not have a natric horizon above the duripan; and
4. Do not have an aridic moisture regime.
Description of Subgroups
Typic Durustolls.—The central concept or Typic subgroup
of Durustolls is fixed on soils that have an argillic horizon
above a strongly developed duripan and that have an ustic
moisture regime. An aridic moisture regime is drier than that
of the Typic subgroup and, if the soils also have an argillic
Mollisols 613
horizon, is the basis for defining intergrades to Argids. Soils
that do not have an argillic horizon and that have a moisture
regime drier than that of the Typic subgroup are assigned to the
Haploduridic subgroup.
The Typic subgroup is not the most extensive subgroup, but
it furnishes the best basis for the definition of subgroups. Typic
Durustolls are not known to occur in the United States.
Argiduridic Durustolls.—These soils have an aridic
moisture regime that borders on ustic, but they are otherwise
like Typic Durustolls in their defined properties. The
Argiduridic Durustolls in the United States generally are nearly
level to strongly sloping. They are not extensive in the United
States, but they are moderately extensive locally in Arizona.
The natural vegetation is mostly grasses and shrubs. Most of
the soils are used as rangeland. Some used as wildlife habitat
or recreational areas.
Entic Durustolls.—These soils do not have an argillic
horizon and have an ustic moisture regime. They are not
known to occur in the United States.
Haplic Durustolls.—These soils have an ustic moisture
regime and have a duripan that is strongly cemented or less
cemented in all subhorizons. They do not have an argillic
horizon. These soils are not known to occur in the United
States.
Haploduridic Durustolls.—These soils have an aridic
moisture regime that borders on ustic and do not have an
argillic horizon. In the United States, they are nearly level to
moderately sloping. These soils are of small extent in the
United States, but they are important locally in Arizona. The
natural vegetation is mostly grasses and shrubs, and most of
the soils are used as rangeland.
Natric Durustolls.—These soils have a natric horizon.
They occur on the western Great Plains and are used as
rangeland.
Haplustolls
Most of these soils have a cambic horizon below the mollic
epipedon, and most have a horizon in which carbonates or
soluble salts have accumulated. A few have a calcic horizon. A
few that formed in noncalcareous sediments do not have a
horizon of carbonate accumulation. These are the Ustolls that
do not have a duripan or a natric, petrocalcic, or argillic
horizon. They do not have a calcic or gypsic horizon unless
part of the soil above the calcic or gypsic horizon either is
noncalcareous or has a texture coarser than loamy fine sand
after the materials between the soil surface and a depth of 18
cm have been mixed.
Haplustolls formed mainly in late-Pleistocene or Holocene
deposits or on surfaces of comparable age. Their vegetation has
been dominantly grasses and forbs. They are extensive soils on
the Great Plains of North America, in Eastern Europe, and on
the Pampas in South America. Where slopes are suitable, most
of the soils are used for grain and feed crops.
Definition
Haplustolls are the Ustolls that:
1. Do not have an argillic or natric horizon;
2. Do not have a duripan that has its upper boundary
within 100 cm of the mineral soil surface;
3. Do not have a calcic or gypsic horizon that has its upper
boundary within 100 cm of the mineral soil surface unless
some part of some horizon overlying the calcic or gypsic
horizon is free of carbonates after the surface soil to a depth of
18 cm has been mixed or the texture to this depth is loamy very
fine sand or finer;
4. Have a transition layer between the mollic epipedon and
the underlying horizon that is less than 25 percent (by volume)
wormholes, wormcasts, or filled animal burrows; and
5. Do not have a petrocalcic horizon that has its upper
boundary within 150 cm of the soil surface.
Key to Subgroups
IFGA. Haplustolls that have a salic horizon that has its upper
boundary within 75 cm of the mineral soil surface.
Salidic Haplustolls
IFGB. Other Haplustolls that have, in part of each pedon, a
lithic contact within 50 cm of the mineral soil surface.
Ruptic-Lithic Haplustolls
IFGC. Other Haplustolls that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Haplustolls
IFGD. Other Haplustolls that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
614 Soil Taxonomy
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some or all parts for six-tenths or more of the cumulative
days per year when the soil temperature at a depth of 50
cm below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some or all parts for six-tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface
is higher than 5 o
C.
Torrertic Haplustolls
IFGE. Other Haplustolls that have all of the following:
1. A mollic epipedon 50 cm or more thick with a texture
finer than loamy fine sand; and
a and b. (Deleted text)
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
3. When neither irrigated nor fallowed to store moisture,
either:
a. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for four-tenths or less of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
b. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for fewer than
120 cumulative days per year when the soil temperature
at a depth of 50 cm below the soil surface is higher than 8
o
C.
Pachic Udertic Haplustolls
IFGF. Other Haplustolls that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. When neither irrigated nor fallowed to store moisture,
either:
a. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for four-tenths or less of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
b. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for fewer than
120 cumulative days per year when the soil temperature
at a depth of 50 cm below the soil surface is higher than
8 o
C.
Udertic Haplustolls
IFGG. Other Haplustolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Haplustolls
IFGH. Other Haplustolls that have both:
1. When neither irrigated nor fallowed to store moisture,
one of the following:
Mollisols 615
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years remains moist in some or all parts for fewer
than 90 consecutive days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 8 o
C; and
2. An apparent CEC (by 1N NH4
OAc pH 7) of less
than 24 cmol(+)/kg clay in 50 percent or more of the
soil volume between a depth of 25 cm from the mineral
soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact if shallower. (If the ratio of
[percent water retained at 1500 kPa tension minus percent
organic carbon] to the percentage of measured clay is 0.6 or
more, then the percentage of clay is considered to equal
either the measured percentage of clay or three times
[percent water retained at 1500 kPa tension minus percent
organic carbon], whichever value is higher, but no more
than 100.)
Torroxic Haplustolls
IFGI. Other Haplustolls that have an apparent CEC (by
1N NH4
OAc pH 7) of less than 24 cmol(+)/kg clay in 50
percent or more of the soil volume between a depth of 25
cm from the mineral soil surface and either a depth of 100
cm or a densic, lithic, or paralithic contact if shallower. (If
the ratio of [percent water retained at 1500 kPa tension
minus percent organic carbon] to the percentage of measured
clay is 0.6 or more, then the percentage of clay is considered
to equal either the measured percentage of clay or three times
[percent water retained at 1500 kPa tension minus percent
organic carbon], whichever value is higher, but no more than
100.)
Oxic Haplustolls
IFGJ. Other Haplustolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Haplustolls
IFGK. Other Haplustolls that have both:
1. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some or all parts for six-tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface
is higher than 5 o
C; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface,
one or both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitritorrandic Haplustolls
IFGL. Other Haplustolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
616 Soil Taxonomy
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Haplustolls
IFGM. Other Haplustolls that have:
1. Either:
a. A frigid soil temperature regime and a mollic
epipedon 40 cm or more thick, of which less than 50
percent has a sandy or sandy-skeletal particle-size class,
and there is no densic or paralithic contact and no sandy
or sandy-skeletal particle-size class at a depth between 40
and 50 cm from the mineral soil surface; or
b. A mollic epipedon that is 50 cm or more thick and
has a texture finer than loamy fine sand; and
2. An irregular decrease in organic-carbon content from a
depth of 25 cm below the mineral soil surface to a depth of
125 cm or to a densic, lithic, or paralithic contact if
shallower; and
3. A slope of less than 25 percent; and
4. In one or more horizons within 100 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Cumulic Haplustolls
IFGN. Other Haplustolls that have:
1. Either:
a. A frigid soil temperature regime and a mollic
epipedon 40 cm or more thick, of which less than 50
percent has a sandy or sandy-skeletal particle-size class,
and there is no densic or paralithic contact and no sandy
or sandy-skeletal particle-size class at a depth between 40
and 50 cm from the mineral soil surface; or
b. A mollic epipedon that is 50 cm or more thick and
has a texture finer than loamy fine sand; and
2. An irregular decrease in organic-carbon content from a
depth of 25 cm below the mineral soil surface to a depth of
125 cm or to a densic, lithic, or paralithic contact if
shallower; and
3. A slope of less than 25 percent.
Cumulic Haplustolls
IFGO. Other Haplustolls that have anthraquic conditions.
Anthraquic Haplustolls
IFGP. Other Haplustolls that have both:
1. In one or more horizons within 100 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. A slope of less than 25 percent; and either
a. An organic-carbon content of 0.3 percent or more at
a depth of 125 cm below the mineral soil surface; or
b. An irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm or to a
densic, lithic, or paralithic contact if shallower.
Fluvaquentic Haplustolls
IFGQ. Other Haplustolls that have a texture finer than loamy
fine sand and either:
1. A frigid temperature regime and a mollic epipedon 40
cm or more thick; or
2. A mollic epipedon 50 cm or more thick.
Pachic Haplustolls
IFGR. Other Haplustolls that have, in one or more horizons
within 100 cm of the mineral soil surface, redox depletions
with chroma of 2 or less and also aquic conditions for some
time in most years (or artificial drainage).
Aquic Haplustolls
IFGS. Other Haplustolls that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Haplustolls
IFGT. Other Haplustolls that have both:
1. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
Mollisols 617
consecutive days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some or all parts for six-tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface
is higher than 5 o
C; and
2. A slope of less than 25 percent; and either
a. An organic-carbon content of 0.3 percent or more at
a depth of 125 cm below the mineral soil surface; or
b. An irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm or to a
densic, lithic, or paralithic contact if shallower.
Torrifluventic Haplustolls
IFGU. Other Haplustolls that:
1. When neither irrigated nor fallowed to store moisture,
have one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some or all parts for six-tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface
is higher than 5 o
C; and
2. Either:
a. Do not have a cambic horizon and do not, in any part
of the mollic epipedon below 25 cm from the mineral soil
surface, meet all of the requirements for a cambic
horizon except color; or
b. Have free carbonates throughout the cambic horizon
or in all parts of the mollic epipedon below a depth of 25
cm from the mineral soil surface.
Torriorthentic Haplustolls
IFGV. Other Haplustolls that, when neither irrigated nor
fallowed to store moisture, have one of the following:
1. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for four-tenths
or more of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for six-tenths or more of the cumulative days per year
when the soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
3. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
a. Is moist in some or all parts for fewer than 90
consecutive days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
b. Is dry in some or all parts for six-tenths or more of
the cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
5 o
C.
Aridic Haplustolls
IFGW. Other Haplustolls that have a slope of less than 25
percent; and either
1. An organic-carbon content of 0.3 percent or more at a
depth of 125 cm below the mineral soil surface; or
2. An irregular decrease in organic-carbon content from a
depth of 25 cm to a depth of 125 cm or to a densic, lithic, or
paralithic contact if shallower.
Fluventic Haplustolls
IFGX. Other Haplustolls that have a brittle horizon that is
within 100 cm of the mineral soil surface, is 15 cm or more
thick, and has either some opal coatings or 20 percent or more
(by volume) durinodes.
Duric Haplustolls
IFGY. Other Haplustolls that:
1. When neither irrigated nor fallowed to store moisture,
have either:
a. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for four-tenths or less of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
b. A hyperthermic, isomesic, or warmer iso soil
618 Soil Taxonomy
temperature regime and a moisture control section that in
normal years is dry in some or all parts for fewer than
120 days per year when the soil temperature at a depth of
50 cm below the soil surface is higher than 8 o
C; and
2. Either do not have a cambic horizon and do not, in the
lower part of the mollic epipedon, meet the requirements for
a cambic horizon, except for the color requirements, or have
carbonates throughout either the cambic horizon or the
lower part of the mollic epipedon.
Udorthentic Haplustolls
IFGZ. Other Haplustolls that, when neither irrigated nor
fallowed to store moisture, have either:
1. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for four-tenths or less of the cumulative days per year
when the soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
2. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for fewer than 120
days per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 8 o
C.
Udic Haplustolls
IFGZa. Other Haplustolls that either:
1. Do not have a cambic horizon and do not, in any part of
the mollic epipedon below 25 cm from the mineral soil
surface, meet all of the requirements for a cambic horizon
except color; or
2. Have free carbonates throughout the cambic horizon or
in all parts of the mollic epipedon below a depth of 25 cm
from the mineral soil surface.
Entic Haplustolls
IFGZb. Other Haplustolls.
Typic Haplustolls
Definition of Typic Haplustolls
Typic Haplustolls are the Haplustolls that:
1. Do not have, in any horizon within 100 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
2. In normal years are not saturated with water in any layer
within 100 cm of the mineral soil surface for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
3. Do not have anthraquic conditions;
4. Do not have a texture finer than loamy fine sand and
either:
a. A mollic epipedon 50 cm or more thick; or
b. A mollic epipedon 40 cm or more thick and a frigid
temperature regime;
5. Do not have a brittle horizon that is 15 cm or more thick,
is within 100 cm of the mineral soil surface, and has some opal
coatings or some durinodes (less than 20 percent, by volume);
6. Have a cambic horizon or in the lower part of the mollic
epipedon, meet the requirements for a cambic horizon, except
for the color and organic-carbon content requirements, and
either the cambic horizon or the lower part of the mollic
epipedon is free of carbonates in some part;
7. Have a regular decrease in organic-carbon content with
increasing depth to a level of 0.3 percent or less within 125 cm
of the mineral soil surface unless a densic, lithic, or paralithic
contact occurs at a shallower depth or the slope is 25 percent or
more;
8. Do not have a lithic contact within 50 cm of the mineral
soil surface in any part of each pedon;
9. Do not have a salic horizon that has its upper boundary
within 75 cm of the mineral soil surface;
10. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in most years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
11. When neither irrigated nor fallowed to store moisture,
have one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for less than
four-tenths of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
or all parts for more than four-tenths but less than six-tenths
of the cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than 5 o
C;
or
c. A hyperthermic, isomesic, or warmer iso soil
Mollisols 619
temperature regime and a moisture control section that in
normal years is moist in some or all parts for 90 or more
consecutive days per year or is dry for less than six-tenths of
the cumulative days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C
and is dry for more than 120 cumulative days per year when
the soil temperature at a depth of 50 cm below the soil
surface is higher than 8 o
C;
12. Have an apparent CEC (by 1N NH4
OAc pH 7) of 24 or
more cmol(+)/kg clay in the major part of the soil below a
depth of 25 cm but above 100 cm or a densic, lithic, or
paralithic contact if one is shallower than 100 cm; and
13. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Description of Subgroups
Typic Haplustolls.—The central concept or Typic subgroup
of Haplustolls is fixed on moderately deep or deeper, freely
drained soils that have a mollic epipedon less than 50 cm thick
and either have a cambic horizon or resemble a cambic horizon
in the lower part of the epipedon. These soils do not have
slickensides, wedge-shaped aggregates, a high linear
extensibility, or wide cracks in most years. They generally are
on uplands.
Ground water in the deep layers, redox depletions with low
chroma, and a salic horizon are the basis for defining Aquic
and Salidic subgroups. A thick mollic epipedon in soils that
receive little sediment is the basis for defining the Pachic
subgroup. A moisture regime that borders on udic characterizes
the Udic subgroup. If a cambic horizon is absent and the lower
part of the epipedon does not resemble a cambic horizon, that
feature is considered evidence of weak horizon development
and is the basis for defining the Entic subgroup. A thick
epipedon that shows evidence of accumulation of materials on
the surface is the basis for defining Cumulic and combination
Cumulic subgroups. An irregular decrease in organic-carbon
content with increasing depth or a relatively high content of
organic carbon in the deep layers is a property of Fluvents and
is the basis for defining the Fluventic subgroup or, if ground
water is present and there are redox depletions with low
chroma, the Fluvaquentic subgroup. A clayey texture,
slickensides, wedge-shaped aggregates, a high linear
extensibility, and cracks in normal years are properties shared
with Vertisols and are the basis for defining the Vertic
subgroup.
Typic Haplustolls are of large extent in the United States.
They are mostly on the Great Plains but also are in the
mountains in the western part of the United States and on some
tropical islands. Most of these soils supported grasses and
shrubs. Some of the soils, mostly those in the mountains or on
islands, supported trees or grass and widely spaced trees. Most
of the soils on plains are now used as cropland. The soils in the
mountains are used mostly as rangeland or wildlife habitat.
Andic and Vitrandic Haplustolls.—These soils have a
surface mantle or layer in the upper 75 cm that has both a low
bulk density and a high content of weakly crystalline minerals
or that consists of slightly or moderately weathered pyroclastic
materials. These soils are of very small extent in the mountains
of the Western United States. The vegetation is mostly forest or
grass and widely spaced trees. Most of these soils are used as
forest, rangeland, or wildlife habitat.
Anthraquic Haplustolls.—These soils are like Typic
Haplustolls, but they have been irrigated for the production of
paddy rice for many years and have developed anthraquic
conditions. They are permitted, but not required, to have redox
depletions with chroma of 2 or less in layers that also have
aquic conditions in normal years. They are not extensive and
are not known to occur in the United States. They have level or
nearly level slopes.
Aquic Cumulic Haplustolls.—These soils have a thick
mollic epipedon. They are on flood plains or in concave areas
where fresh sediments have accumulated slowly enough to
have become incorporated in the mollic epipedon. The soils
have ground water and redox depletions with low chroma in
their deep layers. They have ground water when streams are at
high water levels or when they overflow. These soils are of very
small extent in the United States. The natural vegetation is
mostly grass, and some of the soils support widely spaced trees.
Most of the soils are used as cropland or hayland, except for
areas that are very small, that have an irregular shape, or that
are subject to frequent flooding.
Aquic Haplustolls.—These soils have ground water and
redox depletions with low chroma in their deep layers. Most of
the soils are in positions where they receive runoff in addition
to the water that falls on the surface. Slopes are gentle or
concave. The epipedon commonly has a low color value or
chroma, or both. The depth to secondary carbonates may be
greater than normal, and the soils are not required to have a
620 Soil Taxonomy
cambic horizon if the particle-size class is sandy. Some of the
soils are salty. Aquic Haplustolls are mainly in depressions or on
flood plains. They are of small extent in the United States. The
vegetation is mostly grass, and some of the soils support widely
spaced trees. Most of the soils are used as cropland, hayland,
rangeland, or wildlife habitat.
Aridic Haplustolls.—These soils receive less moisture or
lose more water through runoff than Typic Haplustolls, but they
are otherwise like the Typic Haplustolls in defined properties.
A few Aridic Haplustolls that are associated with Aridisols
receive runoff from other soils. Other things being equal, the
depth to carbonates and the organic-carbon content are less in
these soils than in soils of the Typic subgroup. Aridic
Haplustolls are extensive and widely distributed in the Western
United States. The largest extent is in the western part of the
Great Plains. Slopes range from nearly level to steep. In the
United States, many of the soils that have suitable slopes are
used as cropland. Winter wheat and grain sorghum are
common crops. If the temperature regime is frigid or mesic,
many of the soils are fallowed in alternate years to store
moisture. Some of the soils are irrigated, and many of the more
sloping soils are used as rangeland.
Cumulic Haplustolls.—These soils have a thick mollic
epipedon and are on flood plains and alluvial fans where fresh
sediments have accumulated slowly enough to have become
incorporated in the mollic epipedon. The mollic epipedon may
be very thick, or there may be a series of thin buried epipedons.
Consequently, there may not be either a cambic horizon or an
accumulation of secondary carbonates in the soils. These soils
are moderately extensive on the Great Plains and in the
intermountain areas of the southwestern part of the United
States. The natural vegetation is mostly grass and widely
spaced trees. Some of these soils are used as cropland or
hayland, except for areas that are very small, that have an
irregular shape, or are subject to frequent flooding. Other areas
are used for grazing by livestock.
Duric Haplustolls.—These soils have a brittle horizon that
is within 100 cm of the mineral soil surface, is 15 cm or more
thick, and has either some opal coatings or 20 percent or more
durinodes. They are otherwise like Typic Haplustolls in their
defined properties and in most other properties. Duric
Haplustolls are inextensive on the western Great Plains of the
United States.
Entic Haplustolls.—These soils do not have a cambic
horizon, and either the epipedon is mostly calcareous or the
lower part of the epipedon has a coarser texture than is
required for a cambic horizon. Many of the soils have an
epipedon that is calcareous throughout its thickness. Others
have a shallow densic or paralithic contact, and the epipedon
extends to the contact. Entic Haplustolls formed mostly in lateHolocene
sediments or are on surfaces of similar age. These
soils are moderately extensive on the Great Plains of the United
States. Slopes are gentle to very steep. The natural vegetation is
mostly grass, and some of the soils support widely spaced trees.
Most of the soils are used as rangeland. If slopes are suitable,
some of the soils are used as cropland.
Fluvaquentic Haplustolls.—These soils formed in relatively
recent sediments and have ground water and redox depletions
with low chroma. Either the organic-carbon content decreases
irregularly with increasing depth, or it is relatively high in the
deep layers. Most of these soils are in low positions on flood
plains. They have ground water when streams are at high water
levels or when they overflow. These soils are of small extent in
the United States. The natural vegetation is mostly grass, and
some of the soils support widely spaced trees. Most of the soils
are used as cropland or hayland, except for areas that are very
small, that have an irregular shape, or that are subject to
frequent flooding.
Fluventic Haplustolls.—These soils formed mostly in
recent alluvium. The epipedon is between 25 and 50 cm thick,
and either the content of organic carbon decreases irregularly
with increasing depth or it is high in the deep layers. These
soils commonly are calcareous throughout their depth, and they
have few or no identifiable secondary carbonates or do not have
a cambic horizon. The natural vegetation is mostly grass, and
some of the soils support widely spaced trees. Slopes of the
Fluventic Haplustolls in the United States are gentle. Most of
the soils are used as cropland or hayland, except for areas that
are very small, that have an irregular shape, or that are subject
to frequent flooding.
Lithic Haplustolls.—These soils have a shallow lithic
contact. Commonly, the mollic epipedon extends to the rock,
and the soils have neither a cambic horizon nor a horizon that
contains identifiable secondary carbonates. These soils are of
large extent, mostly in the mountains of the Western United
States. They have moderate to very steep slopes. The vegetation
is mostly grass and shrubs, but some of the soils support forest
vegetation. The soils are used mostly as rangeland or forest.
Oxic Haplustolls.—These soils have a CEC that is too low
and epipedons that may be too thick or an organic-carbon
content that is too high at a depth of 125 cm to qualify as Typic
Haplustolls. Slopes range from gentle to steep. Oxic
Haplustolls are of moderate extent at the lower elevations in
Hawaii. Sugarcane is the dominant crop.
Oxyaquic Haplustolls.—These soils are like Typic
Haplustolls, but they are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years. The soils are of
small extent, mostly on the northern Great Plains in the United
States. The natural vegetation is mostly grass and some shrubs.
Most of the soils are used as cropland or hayland.
Pachic Haplustolls.—These soils have a thick mollic
epipedon. Some of the soils receive runoff but little sediment
from the higher adjacent soils. Pachic Haplustolls are extensive
in the United States. They are widely distributed on the Great
Plains and in the mountains of the Western United States.
Slopes are nearly level to steep. Many of these soils supported
grasses and shrubs, but some supported trees. Most of the soils
Mollisols 621
on plains are used as cropland. Most of the soils in the
mountains are used as rangeland, but some are used as
grazeable woodland.
Pachic Udertic Haplustolls.—These soils have a thick
mollic epipedon, a moisture regime that borders on udic, and a
high shrink-swell potential. They receive runoff and are used
for corn, oats, soybeans, or alfalfa. These soils occur in South
Dakota and Iowa.
Ruptic-Lithic Haplustolls.—These soils have a lithic
contact within 50 cm of the surface in part of each pedon, but
the lithic contact is deeper than 50 cm in the rest of the pedon.
In the deeper parts, there is a cambic horizon and the soils
have the other defined properties of Typic Haplustolls. RupticLithic
Haplustolls are of very small extent, mostly in the
mountains of the Western United States. They have moderate
to very steep slopes. The vegetation is mostly grass and shrubs,
but some of the soils support forest vegetation.
Salidic Haplustolls.—These soils have a shallow salic
horizon. Depth to the ground water fluctuates. In the United
States, the soils are known to occur only on flood plains in arid
parts of the intermountain valleys of the Western States. These
soils are used as rangeland.
Torrertic Haplustolls.—These soils have a clayey particlesize
class in a significant part, have expanding clays, and in
normal years have deep cracks. They are drier than Vertic
Haplustolls. Torrertic Haplustolls are of small extent in the
United States and occur mostly on the western Great Plains.
Slopes of the Torrertic Haplustolls in the United States are
gentle or moderate. The natural vegetation was mostly grasses
and shrubs. Most of the soils are used as cropland, but some
are used as rangeland.
Torrifluventic Haplustolls.—These soils are drier than
Typic Haplustolls and formed in alluvium recent enough for
the content of organic carbon to decrease irregularly with
increasing depth or to remain high in the deep layers. The
mollic epipedon is between 25 and 50 cm thick. These soils are
on flood plains or low terraces. Most of them receive some
additional water from flooding. Many are calcareous
throughout and are associated on the landscape with
Torrifluvents. Torrifluventic Haplustolls are of small extent,
mostly on the western Great Plains of the United States. Slopes
generally are nearly level. The natural vegetation is mostly
grass, and some of the soils support widely spaced trees. Most
of the soils are used as cropland or hayland, except for areas
that are very small, that have an irregular shape, or that are
subject to frequent flooding. Some of the soils are used as
rangeland.
Torriorthentic Haplustolls.—These soils are drier than
Typic Haplustolls, and the epipedon is mostly calcareous or the
lower part of the epipedon has a coarser texture than is
required for a cambic horizon. Many of the soils have an
epipedon that is calcareous throughout its thickness. Others
have a shallow densic or paralithic contact, and the epipedon
extends to the contact. Torriorthentic Haplustolls formed mostly
in late-Holocene sediments or are on surfaces of similar age.
These soils are moderately extensive in the United States. They
are mostly on the western Great Plains, but some are in the
mountains of the Western United States. Slopes are gentle to
very steep. The natural vegetation is mostly grass, and some of
the soils support widely spaced trees. Most of the soils are used
as rangeland. If slopes are suitable, some of the soils are used as
cropland.
Torroxic Haplustolls.—These soils have a CEC that is too
low to qualify as Typic Haplustolls and are drier than Typic
Haplustolls. In addition, they may have epipedons too thick or
an organic-carbon content too high at a depth of 125 cm, and
they basically have few or no carbonates. Slopes are gentle or
moderate. The soils are of moderate extent at the lower
elevations in Hawaii. They are used mostly as cropland.
Pineapple and irrigated sugarcane are the principal crops.
Many areas are used as grazing land.
Udertic Haplustolls.—These soils have a clayey particlesize
class in a significant part, have expanding clays, and in
many years have deep cracks. They are more moist than Vertic
Haplustolls because they either receive more precipitation or
receive runoff from other soils. Most of the Udertic Haplustolls
in the United States are on the Great Plains. The natural
vegetation was mostly grasses. Slopes generally are gentle, and
many are concave. Most of the soils are used as cropland, but
some are used as rangeland.
Udic Haplustolls.—These soils are more moist than Typic
Haplustolls because they either receive more precipitation or
receive runoff from other soils. Most of the Udic Haplustolls in
the United States are in areas between Typic Haplustolls and
Udolls. Udic Haplustolls are moderately extensive soils, mostly
in the southeastern part of the Great Plains. The natural
vegetation was mostly grasses and shrubs. Slopes generally are
gentle. Most of the soils are used as cropland.
Udorthentic Haplustolls.—These soils are more moist than
Typic Haplustolls because they either receive more
precipitation or receive runoff from other soils. They do not
have a cambic horizon, and either the epipedon is mostly
calcareous or the lower part of the epipedon has a coarser
texture than is required for a cambic horizon. Some of the soils
have a shallow densic or paralithic contact, and the epipedon
extends to the contact. Udorthentic Haplustolls formed mostly
in late-Holocene sediments or are on surfaces of similar age.
These soils are of small extent on the Great Plains of the
United States. Slopes are gentle to very steep. The natural
vegetation is mostly grass. Most of the soils are used as
rangeland. If slopes are suitable, some of the soils are used as
cropland.
Vertic Haplustolls.—These soils have a clayey particle-size
class in a significant part, have expanding clays, and in many
years have deep cracks. They are otherwise similar to Typic
Haplustolls. Most of the Vertic Haplustolls in the United States
622 Soil Taxonomy
are on the Great Plains. The natural vegetation was mostly
grasses. Slopes generally are gentle. Most of the soils are used
as cropland, but some are used as rangeland.
Vitritorrandic Haplustolls.—These soils have significant
amounts of cinders, pumice, and pumicelike fragments or glass
and have a soil moisture regime that borders on aridic. They do
not have a salic horizon within 75 cm of the soil surface, a
lithic contact within 50 cm of the soil surface, a low CEC, or a
high shrink-swell potential. These soils are not known to occur
in the United States.
Natrustolls
These are the Ustolls that have a natric horizon. The most
common horizon sequence is either a natric horizon in the
lower part of the mollic epipedon or a thin albic horizon over a
columnar natric horizon in which there may or may not be
skeletans on the upper few centimeters of the columns. Below
the natric horizon, there generally is a Bk or Bz horizon. Most
of the areas of these soils are small and are nearly level or
concave. The soils formed mostly in late-Pleistocene sediments.
Definition
Natrustolls are the Ustolls that:
1. Have a natric horizon; and
2. Do not have a duripan that has its upper boundary
within 100 cm of the mineral soil surface.
Key to Subgroups
IFBA. Natrustolls that have all of the following:
1. Visible crystals of gypsum and/or more soluble salts
within 40 cm of the mineral soil surface; and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower;
3. When neither irrigated nor fallowed to store moisture,
have one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some or all parts for six-tenths or more of the cumulative
days per year when the soil temperature at a depth of 50
cm below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some or all parts for six-tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface
is higher than 5 o
C.
Leptic Torrertic Natrustolls
IFBB. Other Natrustolls that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. When neither irrigated nor fallowed to store moisture,
have one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some or all parts for six-tenths or more of the cumulative
days per year when the soil temperature at a depth of 50
cm below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
8 o
C; and
Mollisols 623
(2) Is dry in some or all parts for six-tenths or more of
the cumulative days per year when the soil temperature
at a depth of 50 cm below the soil surface is higher than
5o
C.
Torrertic Natrustolls
IFBC. Other Natrustolls that have both of the following:
1. Visible crystals of gypsum and/or more soluble salts
within 40 cm of the mineral soil surface; and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Leptic Vertic Natrustolls
IFBD. Other Natrustolls that have both:
1. A glossic horizon or interfingering of albic materials
into a natric horizon; and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Glossic Vertic Natrustolls
IFBE. Other Natrustolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact, whichever is shallower.
Vertic Natrustolls
IFBF. Other Natrustolls that have both:
1. Visible crystals of gypsum or of more soluble salts, or
both, within 40 cm of the mineral soil surface; and
2. When neither irrigated nor fallowed to store moisture,
have one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for fourtenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some or all parts for six-tenths or more of the cumulative
days per year when the soil temperature at a depth of 50
cm below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some or all parts for six-tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface
is higher than 5 o
C.
Aridic Leptic Natrustolls
IFBG. Other Natrustolls that have visible crystals of gypsum
or of more soluble salts, or both, within 40 cm of the mineral
soil surface.
Leptic Natrustolls
IFBH. Other Natrustolls that have, in one or more horizons at
a depth between 50 and 100 cm from the mineral soil surface,
aquic conditions for some time in normal years (or artificial
drainage) and one of the following:
1. 50 percent or more chroma of 1 or less and hue of 2.5Y
or yellower; or
2. 50 percent or more chroma of 2 or less and redox
concentrations; or
3. 50 percent or more chroma of 2 or less and also a
higher exchangeable sodium percentage (or sodium
624 Soil Taxonomy
adsorption ratio) between the mineral soil surface and a depth
of 25 cm than in the underlying horizon.
Aquic Natrustolls
IFBI. Other Natrustolls that, when neither irrigated nor
fallowed to store moisture, have one of the following:
1. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for four-tenths
or more of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for six-tenths or more of the cumulative days per year
when the soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
3. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
a. Is moist in some or all parts for fewer than 90
consecutive days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
b. Is dry in some or all parts for six-tenths or more of
the cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
5 o
C.
Aridic Natrustolls
IFBJ. Other Natrustolls that have a horizon, 15 cm or more
thick within 100 cm of the mineral soil surface, that either has
20 percent or more (by volume) durinodes or is brittle and has
a firm rupture-resistance class when moist.
Duric Natrustolls
IFBK. Other Natrustolls that have a glossic horizon or
interfingering of albic materials into a natric horizon.
Glossic Natrustolls
IFBL. Other Natrustolls.
Typic Natrustolls
Definition of Typic Natrustolls
Typic Natrustolls are the Natrustolls that:
1. Do not have, in any horizon at a depth between 50 and 100
cm from the mineral soil surface, aquic conditions and any of
the following:
a. 50 percent or more chroma of 1 or less throughout and
hue of 2.5Y or yellower in some part; or
b. 50 percent or more chroma of 2 or less and redox
concentrations; or
c. 50 percent or more chroma of 2 or less and also a higher
exchangeable sodium percentage (or sodium adsorption ratio)
between the mineral soil surface and a depth of 25 cm than in
the underlying horizon;
2. Do not have a horizon, 15 cm or more thick within 100 cm of
the mineral soil surface, that either has 20 percent or more (by
volume) durinodes or is brittle and has a firm rupture-resistance
class when moist;
3. Do not have a glossic horizon or interfingering of albic
materials into a natric horizon;
4. When neither irrigated nor fallowed to store moisture,
have one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for less than
four-tenths of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
or all parts for more than four-tenths but less than six-tenths
of the cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than 5 o
C;
or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is moist in some or all parts for 90 or more
consecutive days per year or is dry for less than six-tenths of
the cumulative days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C
and is dry for more than 120 cumulative days per year when
the soil temperature at a depth of 50 cm below the soil
surface is higher than 8 o
C;
5. Do not have visible crystals of gypsum or of more soluble
salts, or both, within 40 cm of the mineral soil surface; and
6. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm
or a densic, lithic, or paralithic contact, whichever is
shallower.
Mollisols 625
Description of Subgroups
Typic Natrustolls.—The central concept or Typic subgroup
of Natrustolls is fixed on soils that do not have slickensides,
wedge-shaped aggregates, a high linear extensibility, or wide
cracks in normal years. These soils do not have low chroma
and do not have redox concentrations accompanied by ground
water within 100 cm of the surface. They show little or no
evidence of destruction of the natric horizon and have no
visible crystals of gypsum or of more soluble salts, or both,
within 40 cm of the mineral soil surface. Some of these soils
are saturated with water above the natric horizon.
A glossic horizon and interfingering of albic materials in
the upper part of the natric horizon are considered evidence of
destruction of the natric horizon and are the basis for defining
the Glossic subgroup.
Typic Natrustolls are of small extent in the United States.
They are mostly on the northern Great Plains of the United
States. They supported mostly salt-tolerant grasses and shrubs.
Slopes generally are gentle, and many of these soils are
cultivated. Some of the soils are used as rangeland or hayland.
Aquic Natrustolls.—These soils have redox depletions with
low chroma in the upper part of the natric horizon and, at some
time during the year, have ground water in the redox-depleted
horizon unless the soils are artificially drained. The soils are of
very small extent on the Great Plains of the United States.
Most of the soils supported grasses. The soils have gentle
slopes and are used mostly as cropland.
Aridic Leptic Natrustolls.—These soils are drier than
those in the Typic subgroup because they receive less
precipitation or lose more water through runoff. They do not
have a glossic horizon or interfingering of albic materials into
the natric horizon and do not have a high shrink-swell
potential. They are of small extent on the Great Plains of the
United States. Many of the soils supported grasses. The soils
have gentle slopes and are used mostly as rangeland.
Aridic Natrustolls.—These soils are drier than those in the
Typic subgroup because they receive less precipitation or lose
more water through runoff. They are otherwise like Typic
Natrustolls in defined properties. Aridic Natrustolls do not
have gypsum or more soluble salts close to the surface. They
are of small extent on the Great Plains of the United States.
Many of the soils supported grasses. The soils have gentle
slopes and are used mostly as cropland or rangeland.
Duric Natrustolls.—These soils have a horizon, 15 cm or
more thick within 100 cm of the mineral soil surface, that has
20 percent or more (by volume) durinodes or is brittle and has
a firm rupture-resistance class when moist. They are otherwise
like Typic Natrustolls in their defined properties. Duric
Natrustolls are not known to occur in the United States.
Glossic Natrustolls.—These soils show evidence of
destruction of the natric horizon in the form of a glossic
horizon or interfingering of albic materials into the natric
horizon. Commonly, they have more exchangeable magnesium
and less sodium than Typic Natrustolls, at least in the upper
part of the natric horizon. Some Glossic Natrustolls receive more
moisture, either as precipitation or as runoff, than the soils of the
Typic subgroup. Glossic Natrustolls are mostly on the northern
Great Plains of the United States and supported grasses. In the
United States, most of the soils are nearly level and are used as
cropland.
Glossic Vertic Natrustolls.—These soils have a high
shrink-swell potential and either a glossic horizon or
interfingering of albic materials into a natric horizon. These
soils occur in the Dakotas and are used for small grain.
Leptic Natrustolls.—These soils have visible crystals of
gypsum or salts at least as soluble as gypsum within 40 cm of
the soil surface, and their moisture regime does not border on
aridic. Otherwise, these soils are similar to those of the Typic
subgroup. They are of small extent on the northern Great
Plains of the United States. They supported mostly grasses. In
the United States, most of the soils are nearly level and are
used as rangeland.
Leptic Torrertic Natrustolls.—These soils have gypsum or
soluble salts close to the surface, a high shrink-swell potential,
and a soil moisture regime that borders on aridic. They are
inextensive on the western Great Plains and are used as
rangeland.
Leptic Vertic Natrustolls.—These soils have a clayey
particle-size class in a significant part, have expanding clays,
and in normal years have deep cracks. They also have visible
evidence of salts at least as soluble as gypsum within 40 cm of
the soil surface. They have thinner sola than those of the Vertic
subgroup, and the close proximity of the soluble salts to the
surface restricts plant growth. Leptic Vertic Natrustolls are of
very small extent in the United States. They are recognized
only in North Dakota. They supported mostly grasses and
shrubs. Most of the soils are used as rangeland.
Torrertic Natrustolls.—These soils have a clayey particlesize
class in a significant part, have expanding clays, and in
normal years have deep cracks. They are drier than the soils in
the Vertic subgroup because they receive less precipitation or
lose more water through runoff. Torrertic Natrustolls are of
very small extent in the United States. They are recognized
only in North Dakota. They supported mostly grasses and
shrubs. Most of the soils are used as cropland or rangeland.
Vertic Natrustolls.—These soils are like Typic Natrustolls,
but they have a clayey particle-size class in a significant part,
have expanding clays, and in normal years have deep cracks.
They are of small extent on the Great Plains of the United
States. They supported mostly grasses and shrubs. Most of the
soils are used as cropland or rangeland.
Paleustolls
These are the Ustolls on old stable surfaces. They may
commonly have a thick, reddish argillic horizon, or, more
commonly, a clayey argillic horizon that has an abrupt upper
boundary, or they may have a petrocalcic horizon. They
626 Soil Taxonomy
commonly have been partly or completely calcified during the
Holocene, and a Bk or calcic horizon is common in the argillic
horizon. The Paleustolls in the United States are mainly in the
central and southern parts of the Great Plains. At the time of
settlement, they had mostly grass vegetation. Their history
during the Pleistocene has had little study. The petrocalcic
horizon, where it occurs, may be complex, suggesting a
number of alternating cycles of humidity and aridity and slow
accretion of dust and sediment from the arid regions to the
west.
Definition
Paleustolls are the Ustolls that:
1. Have a petrocalcic horizon that has its upper boundary
within 150 cm of the soil surface and either have an argillic
horizon or are noncalcareous in some subhorizon above the
petrocalcic horizon after the surface soil to a depth of 18 cm
has been mixed or have an argillic horizon that has either or
both:
a. A vertical clay distribution in which the clay content
does not decrease by as much as 20 percent from the
maximum clay content (noncarbonate clay) within 150 cm
of the soil surface (and there is no densic, lithic, or
paralithic contact within that depth); and one or both of the
following:
(1) Hue redder than 10YR and chroma greater than 4
in the matrix of at least the lower part; or
(2) Common redox concentrations that have hue
of 7.5YR or redder or chroma greater than 5; or
b. 35 percent or more clay in the upper part and an
increase of at least 20 percent clay (absolute) within a
vertical distance of 7.5 cm or of 15 percent clay (absolute)
within 2.5 cm at the upper boundary and no densic, lithic,
or paralithic contact within 50 cm of the mineral soil
surface;
2. Do not have a duripan that has its upper boundary
within 100 cm of the soil surface; and
3. Do not have a natric horizon.
Key to Subgroups
IFDA. Paleustolls that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. When neither irrigated nor fallowed to store moisture,
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for less
than four-tenths of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some or all parts for six-tenths or more of the cumulative
days per year when the soil temperature at a depth of 50
cm below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some or all parts for six-tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface
is higher than 5 o
C.
Torrertic Paleustolls
IFDB. Other Paleustolls that have both:
1. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower; and
2. When neither irrigated nor fallowed to store moisture,
either:
a. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for four-tenths or less of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
b. A hyperthermic, isomesic, or warmer iso soil
Mollisols 627
temperature regime and a moisture control section that in
normal years is dry in some or all parts for fewer than
120 cumulative days per year when the soil temperature
at a depth of 50 cm below the soil surface is higher than
8 o
C.
Udertic Paleustolls
IFDC. Other Paleustolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Vertic Paleustolls
IFDD. Other Paleustolls that have a texture finer than loamy
fine sand and a mollic epipedon 50 cm or more thick.
Pachic Paleustolls
IFDE. Other Paleustolls that have, in one or more horizons
within 100 cm of the mineral soil surface, redox depletions
with chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Paleustolls
IFDF. Other Paleustolls that have a petrocalcic horizon
within 150 cm of the mineral soil surface.
Petrocalcic Paleustolls
IFDG. Other Paleustolls that:
1. Have a calcic horizon within one of the following
particle-size class (by weighted average in the particle-size
control section) and depth combinations:
a. Sandy or sandy-skeletal and within 100 cm of the
mineral soil surface; or
b. Clayey, clayey-skeletal, fine, or very-fine and within
50 cm of the mineral soil surface; or
c. Any other class and within 60 cm of the mineral soil
surface; and
2. When neither irrigated nor fallowed to store moisture,
have one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for less
than four-tenths of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil surface
is higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for six-tenths or more of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
8 o
C; and
(2) Is dry in some or all parts for six-tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface
is higher than 5 o
C.
Calcidic Paleustolls
IFDH. Other Paleustolls that, when neither irrigated nor
fallowed to store moisture, have one of the following:
1. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for less than
four-tenths of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for six-tenths or more of the cumulative days per year
when the soil temperature at a depth of 50 cm below the soil
surface is higher than 5 o
C; or
3. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
a. Is moist in some or all parts for fewer than 90
consecutive days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
b. Is dry in some or all parts for six-tenths or more of
the cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than
5 o
C.
Aridic Paleustolls
IFDI. Other Paleustolls that, when neither irrigated nor
fallowed to store moisture, have either:
1. A mesic or thermic soil temperature regime and a moisture
control section that in normal years is dry in some part for
628 Soil Taxonomy
four-tenths or less of the cumulative days per year when the
soil temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A hyperthermic, isomesic, or warmer iso soil temperature
regime and a moisture control section that in normal years is
dry in some or all parts for fewer than 120 cumulative days
per year when the soil temperature at a depth of 50 cm below
the soil surface is higher than 8 o
C.
Udic Paleustolls
IFDJ. Other Paleustolls have a calcic horizon within one of
the following particle-size class (by weighted average in the
particle-size control section) and depth combinations:
1. Sandy or sandy-skeletal and within 100 cm of the
mineral soil surface; or
2. Clayey, clayey-skeletal, fine, or very-fine and within 50
cm of the mineral soil surface; or
3. Any other class and within 60 cm of the mineral soil
surface.
Calcic Paleustolls
IFDK. Other Paleustolls that are calcareous throughout after
the surface soil has been mixed to a depth of 18 cm.
Entic Paleustolls
IFDL. Other Paleustolls.
Typic Paleustolls
Definition of Typic Paleustolls
Typic Paleustolls are the Paleustolls that:
1. Are not calcareous throughout after the surface soil has
been mixed to a depth of 18 cm;
2. Do not have, in any horizon within 100 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
3. Do not have a texture finer than loamy fine sand and a
mollic epipedon 50 cm or more thick;
4. Do not have a petrocalcic horizon within 150 cm of the
mineral soil surface;
5. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
6. When neither irrigated nor fallowed to store moisture, have
one of the following:
a. A frigid temperature regime and a moisture control
section that in normal years is dry in all parts for less than
four-tenths of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
b. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
or all parts for more than four-tenths but less than six-tenths
of the cumulative days per year when the soil temperature at
a depth of 50 cm below the soil surface is higher than 5 o
C;
or
c. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is moist in some or all parts for 90 or more
consecutive days per year or is dry for less than six-tenths of
the cumulative days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C
and is dry for more than 120 cumulative days per year when
the soil temperature at a depth of 50 cm below the soil
surface is higher than 8 o
C; and
7. Do not have a calcic horizon with its upper boundary
within 100 cm of the soil surface.
Description of Subgroups
Typic Paleustolls.—The central concept or Typic subgroup
of Paleustolls is fixed on deep, freely drained soils that are
noncalcareous in some part, have a mollic epipedon less than
50 cm thick, and do not have slickensides, wedge-shaped
aggregates, a high linear extensibility, or wide cracks. These
soils do not have a petrocalcic horizon and commonly have an
abrupt increase in content of clay near the top of the argillic
horizon.
A calcic horizon is a property of Calcic great groups and is
the basis for defining intergrades to Calcids and Calciustolls.
Redox depletions with low chroma and ground water are
properties of Aquolls and are the basis for defining the Aquic
subgroup. A thick mollic epipedon is the basis for defining the
Pachic subgroup. A petrocalcic horizon is considered evidence
of more than normal development. Its presence in a soil that
has an ustic moisture regime is the basis for defining the
Petrocalcic subgroup.
A moisture regime that borders on udic is the basis for
defining the Udic subgroup. A clayey texture, slickensides,
wedge-shaped aggregates, a high linear extensibility, and
cracks in normal years are properties shared with Vertisols and
are the basis for defining the Vertic subgroup. An ustic
moisture regime that approaches aridic or a moisture regime
that is aridic is the basis for defining the Aridic subgroup.
Typic Paleustolls are of small extent in the United States.
They are on the Great Plains and in mountain valleys in the
Mollisols 629
western part of the United States. Most of these soils supported
grasses and shrubs and are used as cropland or rangeland.
Aquic Paleustolls.—These soils have ground water within
100 cm of the surface for extended periods and have redox
depletions with low chroma in the saturated zone. Slopes are
gentle. These soils are of very small extent in the United
States.
Aridic Paleustolls.—These soils are drier than those in the
Typic subgroup but are otherwise like Typic Paleustolls in
defined properties. As a group, however, they have less organic
carbon than the soils of the Typic subgroup. Aridic Paleustolls
are moderately extensive in the southwestern part of the Great
Plains in the United States. Slopes are gentle. Most of the soils
supported grasses and shrubs. Many are used as cropland and
commonly are irrigated.
Calcic Paleustolls.—These soils have a calcic horizon in
the argillic horizon. Nearly all are reddish and have a thick,
calcified argillic horizon. They are developing toward
Calciustolls, but the argillic horizon can still be identified.
Calcic Paleustolls are of very small extent in the United States.
Calcidic Paleustolls.—These soils have a calcic horizon in
or below the argillic horizon and are drier than Typic
Paleustolls. Nearly all Calcidic Paleustolls are reddish and
have a thick, calcified argillic horizon. They occur only on the
southern Great Plains and in intermountain areas in the
Western United States, where they are moderately extensive.
Most of these soils supported grasses and shrubs. Many are
used as cropland, but some are used as rangeland.
Entic Paleustolls.—These soils are calcareous throughout
after the surface soil to a depth of 18 cm has been mixed and
do not have a calcic horizon. They are not known to occur in
the United States.
Pachic Paleustolls.—These soils are like Typic Paleustolls,
but they have a thick mollic epipedon. The argillic horizon
generally starts in the lower part of the mollic epipedon. Slopes
of the Pachic Paleustolls in the United States are mostly gentle.
The soils are of small extent, mostly in Texas on the southern
Great Plains of the United States. Most of the soils supported
grasses and shrubs and are used as cropland.
Petrocalcic Paleustolls.—These soils are like Typic
Paleustolls, but they have a petrocalcic horizon within 150 cm
of the surface. They may be calcareous throughout. In the
United States, they are moderately extensive on the southern
Great Plains and in the Southwestern States. These soils
supported grasses and shrubs. Slopes are gentle. Most of the
soils are used for grazing. Some are used as irrigated cropland
if water is available.
Torrertic Paleustolls.—These soils have a clayey particlesize
class in a significant part, have expanding clays, and in
normal years have deep cracks. They are drier than Vertic
Paleustolls. Torrertic Paleustolls are of small extent in the
United States and occur mostly on the southwestern Great
Plains. Slopes of the Torrertic Paleustolls in the United States
are gentle or moderate. The natural vegetation was mostly
grasses and shrubs. Most of the soils are used as cropland,
mostly irrigated, but some are used as rangeland.
Udertic Paleustolls.—These soils have a clayey particlesize
class in a significant part, have expanding clays, and in
normal years have deep cracks. They are more moist than
Vertic Paleustolls. They have more precipitation than Typic
Paleustolls. Udertic Paleustolls are moderately extensive soils
in the eastern part of the southern Great Plains. The natural
vegetation was mostly grasses and shrubs. Slopes are gentle,
and nearly all of the soils are used as cropland.
Udic Paleustolls.—These soils are more moist than Typic
Paleustolls and generally have carbonates at a greater depth.
Slopes of the Udic Paleustolls in the United States are mostly
gentle. The soils are of moderate extent, mostly on the southern
Great Plains of the United States. Most of the soils supported
grasses and shrubs and are used as cropland.
Vertic Paleustolls.—These soils have a clayey particle-size
class in a significant part, have expanding clays, and in normal
years have deep cracks. They may have a mollic epipedon that
is more than 50 cm thick. These soils are of small extent in the
United States and commonly occur on gentle slopes on the
Great Plains. The natural vegetation was mostly grasses and
shrubs. Most of the soils are used as cropland, but some are
used as rangeland.
Vermustolls
These are the Ustolls that have been intensively and
repeatedly mixed by animals, mainly by earthworms and their
predators. The most common horizon sequence is a mollic
epipedon that consists mostly of wormcasts and rests on parent
materials that contain many worm channels filled with dark
materials from the epipedon. There may be a horizon in which
carbonates have precipitated, but mixing by animals may have
destroyed such a horizon or prevented its formation. These
soils are not known to occur in North America, but they are
extensive in Eastern Europe.
Definition
Vermustolls are the Ustolls that:
1. Have a mollic epipedon that:
a. Either below an Ap horizon or below a depth of 18 cm
from the mineral soil surface, contains 50 percent or more
(by volume) wormholes, wormcasts, or filled animal
burrows; and
b. Either rests on a lithic contact or has a transition zone
to the underlying horizon in which 25 percent or more of
the soil volume consists of discrete wormholes, wormcasts,
or animal burrows filled with material from the mollic
epipedon and from the underlying horizon;
2. Do not have a duripan that has its upper boundary
within 100 cm of the mineral soil surface;
630 Soil Taxonomy
3. Do not have an argillic or natric horizon; and
4. Do not meet both of the following:
a. Have a calcic or gypsic horizon that has its upper
boundary within 100 cm of the soil surface or a petrocalcic
horizon that has its upper boundary within 150 cm of the
mineral soil surface; and
b. In all parts above the calcic, gypsic, or petrocalcic
horizon, after the materials between the soil surface and a
depth of 18 cm have been mixed, either are calcareous or
have a texture of loamy fine sand or coarser.
Key to Subgroups
IFFA. Vermustolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Vermustolls
IFFB. Other Vermustolls that have, in one or more horizons
within 100 cm of the mineral soil surface, redox depletions
with chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Vermustolls
IFFC. Other Vermustolls that have a mollic epipedon 75 cm
or more thick.
Pachic Vermustolls
IFFD. Other Vermustolls that have a mollic epipedon less
than 50 cm thick.
Entic Vermustolls
IFFE. Other Vermustolls.
Typic Vermustolls
Definition of Typic Vermustolls
Typic Vermustolls are the Vermustolls that:
1. Have a mollic epipedon that is 50 cm to 75 cm thick;
2. Do not have a lithic contact within 50 cm of the mineral
soil surface; and
3. Do not have, in any horizon within 100 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions.
Description of Subgroups
Typic Vermustolls.—The central concept or Typic subgroup
of Vermustolls is fixed on soils that are deep to a lithic contact
and have a mollic epipedon 50 to 75 cm or more thick. These
soils are not known to occur in the United States.
Aquic Vermustolls.—These soils have aquic conditions and
redox depletions with chroma of 2 or less within 100 cm of the
soil surface. They do not have a lithic contact within 50 cm of
the soil surface. They are rare and are not known to occur in the
United States.
Entic Vermustolls.—These soils have a mollic epipedon
less than 50 cm thick. They are otherwise like Typic
Vermustolls. Entic Vermustolls are not known to occur in the
United States.
Lithic Vermustolls.—These soils have a lithic contact at a
depth of 50 cm or less from the mineral soil surface. They are
not known to occur in the United States.
Pachic Vermustolls.—These soils have a mollic epipedon
more than 75 cm thick. They are otherwise like Typic
Vermustolls. Pachic Vermustolls are not known to occur in the
United States.
Xerolls
These soils are Mollisols of regions that have Mediterranean
climates. As their name implies, they generally have a xeric
moisture regime. Some Xerolls that are marginal to Aridisols,
however, have an aridic moisture regime. Xerolls are dry for
extended periods in summer, but moisture moves through most
of the soils in winter and is stored throughout the part of the
soils above the deep layers or above bedrock in normal years.
Soft, white winter wheat is the most common crop on the
Xerolls in the United States where there is no irrigation and
the temperature regime is mesic. Where the temperature
regime is frigid, the soils are used for spring wheat or for
grazing. With irrigation, many crops are grown, especially
where the temperature regime is thermic or mesic. The soils
that have steep slopes mainly support natural vegetation of
native annual or perennial grasses and of shrubs or trees. These
soils are used mainly for grazing in spring or late in fall. The
native perennial grasses remain dormant during the dry
summers, and the annual grasses grow mainly in spring but
sometimes also in fall if rains occur before the temperature
drops too low.
Characteristically, Xerolls have a relatively thick mollic
epipedon, a cambic or argillic horizon, and an accumulation of
carbonates in the lower part of the B horizon and are neutral in
most horizons.
The Xerolls in the United States formed mainly in latePleistocene
loess that varies in thickness and that overlies
bedrock on nearly level to steep older surfaces. Tertiary lake
sediments, older crystalline rocks, and alluvium are common
parent materials in some areas. The vegetation at the time of
settlement in the areas that have a mesic or frigid temperature
regime was dominantly bunchgrass and shrubs with
wheatgrass (Agropyron), fescue (Festuca), and bluegrass (Poa)
species in association with sagebrush (Artemisia), bitterbrush
(Purshia), and rabbitbrush (Chrysothamnus) species and some
scattered juniper (Juniperus) and pine (Pinus) species. In the
Willamette Valley of Oregon, the vegetation was a savanna of
perennial grasses, oaks, and Douglas-fir. In the areas in
Mollisols 631
California that have thermic temperature regimes, the vegetation
was a savanna of annual grasses and oak species.
Xerolls are not extensive soils in the world, but they are
extensive in parts of Turkey and of northern Africa near the
Mediterranean Sea, in some of the southern republics of the
former USSR, and in Washington, Oregon, Idaho, Utah,
Nevada, and California in the United States. The temperature
regimes are mostly mesic or frigid, but some are thermic.
Definition
Xerolls are the Mollisols that:
1. Have a mean annual soil temperature lower than 22 o
C and
mean summer and mean winter soil temperatures at a depth of
50 cm that differ by 5 o
C or more;
2. Do not have both an albic horizon and, within 100 cm of
the mineral soil surface, any subhorizon of the albic horizon
and/or of the argillic or natric horizon that has redox
concentrations in the form of masses or concretions, or both,
and also aquic conditions;
3. Do not have both aquic conditions and the colors defined
for Aquolls;
4. Have a xeric moisture regime or have a moisture regime
that is aridic bordering on xeric; and
5. Do not have a cryic temperature regime.
Key to Great Groups
IEA. Xerolls that have a duripan within 100 cm of the
mineral soil surface.
Durixerolls,p.639
IEB. Other Xerolls that have a natric horizon.
Natrixerolls,p.650
IEC. Other Xerolls that have either:
1. A petrocalcic horizon that has its upper boundary
within 150 cm of the mineral soil surface; or
2. An argillic horizon that has one or both of the
following:
a. With increasing depth, no clay decrease of 20
percent or more (relative) from the maximum clay
content (noncarbonate clay) within 150 cm of the mineral
soil surface (and there is no densic, lithic, or paralithic
contact within that depth); and either
(1) Hue of 7.5YR or redder and chroma of 5 or more
in the matrix; or
(2) Common redox concentrations with hue
of 7.5YR or redder or chroma of 6 or more, or both;
or
b. A clayey or clayey-skeletal particle-size class in its
upper part and, at its upper boundary, a clay increase
either of 20 percent or more (absolute) within a vertical
distance of 7.5 cm or of 15 percent or more (absolute)
within a vertical distance of 2.5 cm, in the fine-earth
fraction (and there is no densic, lithic, or paralithic
contact within 50 cm of the mineral soil surface).
Palexerolls,p.652
IED. Other Xerolls that:
1. Have a calcic or gypsic horizon that has its upper
boundary within 150 cm of the mineral soil surface; and
2. In all parts above the calcic or gypsic horizon, after the
surface soil has been mixed to a depth of 18 cm, either are
calcareous or have a texture of loamy fine sand or coarser.
Calcixerolls,p.637
IEE. Other Xerolls that have an argillic horizon.
Argixerolls, p. 631
IEF. Other Xerolls.
Haploxerolls, p. 642
Argixerolls
These are the Xerolls that have a relatively thin argillic
horizon or one in which the percentage of clay decreases
rapidly with increasing depth. Generally, the mollic epipedon
is very dark brown and the argillic horizon is dark brown. Most
of these soils have a Bk or calcic horizon below or in the lower
part of the argillic horizon. Argixerolls formed mostly in midPleistocene
or earlier deposits or on surfaces of Tertiary age.
Slopes range from nearly level to very steep. The natural
vegetation is mostly grasses and shrubs, but some of the soils
support coniferous forest vegetation with a grass and shrub
understory and some have an open forest or savanna.
Definition
Argixerolls are the Xerolls that:
1. Do not have a natric horizon;
2. Have an argillic horizon that has:
a. A vertical clay distribution in which the content of clay
decreases by more than 20 percent from the maximum clay
content (noncarbonate clay) within a depth of less than 150
cm from the soil surface if:
(1) Hue is redder than 10YR and chroma is greater
than 4 in the matrix; or
632 Soil Taxonomy
(2) There are common redox concentrations that have
hue of 7.5YR or redder or chroma greater than 5; and
b. Less than 35 percent clay in the upper part or an increase
of less than 20 percent clay (absolute) within a vertical
distance of 7.5 cm or of 15 percent clay (absolute) within 2.5
cm at the upper boundary, or there is a densic, lithic, or
paralithic contact within 50 cm of the soil surface;
3. Do not have a duripan that has its upper boundary
within 100 cm of the soil surface;
4. Do not have a petrocalcic horizon that has its upper
boundary within 150 cm of the soil surface; and
5. Do not have a calcic or gypsic horizon that has its upper
boundary within 150 cm of the mineral soil surface unless
some part of some horizon overlying the calcic or gypsic
horizon is free of carbonates or has a texture that is coarser
than loamy very fine sand after the upper 18 cm has been
mixed.
Key to Subgroups
IEEA. Argixerolls that have both:
1. A lithic contact within 50 cm of the mineral soil
surface; and
2. A base saturation (by sum of cations) of 75 percent or
less in one or more horizons between either the mineral soil
surface or an Ap horizon, whichever is deeper, and the lithic
contact.
Lithic Ultic Argixerolls
IEEB. Other Argixerolls that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Argixerolls
IEEC. Other Argixerolls that have both:
1. An aridic moisture regime; and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Torrertic Argixerolls
IEED. Other Argixerolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Argixerolls
IEEE. Other Argixerolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Argixerolls
IEEF. Other Argixerolls that have both:
1. An aridic moisture regime; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface,
one or both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitritorrandic Argixerolls
IEEG. Other Argixerolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
Mollisols 633
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is equal
to 30 or more.
Vitrandic Argixerolls
IEEH. Other Argixerolls that have both:
1. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. A base saturation (by sum of cations) of 75 percent
or less in one or more horizons between either an Ap
horizon or a depth of 25 cm from the mineral soil
surface, whichever is deeper, and either a depth of 75
cm or a densic, lithic, or paralithic contact, whichever
is shallower.
Aquultic Argixerolls
IEEI. Other Argixerolls that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Argixerolls
IEEJ. Other Argixerolls that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Argixerolls
IEEK. Other Argixerolls that have either:
1. Above the argillic horizon, an albic horizon or a
horizon that has color values too high for a mollic epipedon
and chroma too high for an albic horizon; or
2. A glossic horizon, or interfingering of albic materials
into the upper part of the argillic horizon, or skeletans of
clean silt and sand covering 50 percent or more of the faces
of peds in the upper 5 cm of the argillic horizon.
Alfic Argixerolls
IEEL. Other Argixerolls that have both:
1. A calcic horizon or identifiable secondary carbonates
within one of the following particle-size class (by weighted
average in the particle-size control section) and depth
combinations:
a. Sandy or sandy-skeletal and within 150 cm of the
mineral soil surface; or
b. Clayey, clayey-skeletal, fine, or very-fine and within 90
cm of the mineral soil surface; or
c. Any other class and within 110 cm of the mineral soil
surface; and
2. A mollic epipedon that is 50 cm or more thick and has a
texture finer than loamy fine sand.
Calcic Pachic Argixerolls
IEEM. Other Argixerolls that have both:
1. A mollic epipedon that is 50 cm or more thick and has
a texture finer than loamy fine sand; and
2. A base saturation (by sum of cations) of 75 percent or
less in one or more horizons between either an Ap horizon
or a depth of 25 cm from the mineral soil surface, whichever
is deeper, and either a depth of 75 cm or a densic, lithic, or
paralithic contact, whichever is shallower.
Pachic Ultic Argixerolls
IEEN. Other Argixerolls that have a mollic epipedon that is
50 cm or more thick and has a texture finer than loamy fine
sand.
Pachic Argixerolls
IEEO. Other Argixerolls that have both:
1. An aridic moisture regime; and
2. A horizon within 100 cm of the mineral soil surface
that is 15 cm or more thick and either has 20 percent or
more (by volume) durinodes or is brittle and has a firm
rupture-resistance class when moist.
Argiduridic Argixerolls
IEEP. Other Argixerolls that have a horizon within 100 cm of
the mineral soil surface that is 15 cm or more thick and either
has 20 percent or more (by volume) durinodes or is brittle and
has a firm rupture-resistance class when moist.
Duric Argixerolls
IEEQ. Other Argixerolls that have both:
1. An aridic moisture regime; and
2. A calcic horizon or identifiable secondary carbonates
within one of the following particle-size class (by weighted
average in the particle-size control section) and depth
combinations:
a. Sandy or sandy-skeletal and within 150 cm of the
mineral soil surface; or
634 Soil Taxonomy
b. Clayey, clayey-skeletal, fine, or very-fine and within 90
cm of the mineral soil surface; or
c. Any other class and within 110 cm of the mineral soil
surface.
Calciargidic Argixerolls
IEER. Other Argixerolls that have an aridic moisture
regime.
Aridic Argixerolls
IEES. Other Argixerolls that have a calcic horizon or
identifiable secondary carbonates within one of the following
particle-size class (by weighted average in the particle-size
control section) and depth combinations:
1. Sandy or sandy-skeletal and within 150 cm of the
mineral soil surface; or
2. Clayey, clayey-skeletal, fine, or very-fine and within 90
cm of the mineral soil surface; or
3. Any other class and within 110 cm of the mineral soil
surface.
Calcic Argixerolls
IEET. Other Argixerolls that have a base saturation (by sum
of cations) of 75 percent or less in one or more horizons
between either an Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and either a depth of
75 cm or a densic, lithic, or paralithic contact, whichever is
shallower.
Ultic Argixerolls
IEEU. Other Argixerolls.
Typic Argixerolls
Definition of Typic Argixerolls
Typic Argixerolls are the Argixerolls that:
1. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
2. In normal years are not saturated with water in any layer
within 100 cm of the mineral soil surface for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
3. Do not have either:
a. An albic horizon or another horizon above the argillic
horizon that has a color value too high for a mollic epipedon
and chroma too high for an albic horizon; or
b. A glossic horizon, or interfingering of albic materials in
the upper part of the argillic horizon, or skeletans of clean
silt and sand covering more than half the faces of peds in the
upper 5 cm or more of the argillic horizon;
4. Do not have a calcic horizon or identifiable secondary
carbonates within one of the following particle-size class (by
weighted average in the particle-size control section) and depth
combinations:
a. Sandy or sandy-skeletal and within 150 cm of the
mineral soil surface; or
b. Clayey, clayey-skeletal, fine, or very-fine and within 90
cm of the mineral soil surface; or
c. Any other class and within 110 cm of the mineral soil
surface;
5. Do not have a horizon within 100 cm of the mineral soil
surface that is more than 15 cm thick and that either has at
least 20 percent durinodes or is brittle and has a firm ruptureresistance
class when moist;
6. Do not have a lithic contact within 50 cm of the soil
surface;
7. Have a xeric moisture regime;
8. Have a mollic epipedon that is less than 50 cm thick or has
a texture of loamy fine sand or coarser if it is 50 cm or more
thick;
9. Have a base saturation (by sum of cations) of more than 75
percent in all horizons between either an Ap horizon or a depth
of 25 cm from the mineral soil surface, whichever is deeper,
and either a depth of 75 cm or a densic, lithic, or paralithic
contact, whichever is shallower;
10. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
and
11. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. A bulk density, in the fraction less than 2.0 mm in size,
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and acid-oxalate-extractable aluminum plus 1
/2 acid-oxalateextractable
iron of more than 1.0 percent; or
b. Fragments coarser than 2.0 mm constituting more than
Mollisols 635
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Description of Subgroups
Typic Argixerolls.—The central concept or Typic subgroup
of Argixerolls is fixed on deep soils that have a mollic
epipedon less than 50 cm thick and do not have redox
depletions and aquic conditions within 75 cm of the mineral
soil surface. These soils do not have an albic horizon above the
argillic horizon, nor do they have a glossic horizon or
interfingering of albic materials into the upper part of the
argillic horizon. They are deep to secondary carbonates, but
they have a high base saturation. They do not have
slickensides, wedge-shaped aggregates, a high linear
extensibility, or wide cracks in normal years. These soils do not
have, within a depth of 100 cm, a horizon that is more than 15
cm thick and that has 20 percent or more durinodes or is brittle
and has a firm rupture-resistance class when moist. They are
dry in summer, but they receive and store enough water in
winter and early spring to provide moisture for spring and
early summer crops.
Shallow ground water or artificial drainage and redox
depletions with low chroma are properties of Aquolls and are
the basis for defining the Aquic subgroup. An albic horizon
above the argillic horizon is characteristic of Alfisols and is the
basis for defining the Alfic subgroup. A calcic horizon or
identifiable secondary carbonates at a moderate depth indicate
an intergrade to Calcixerolls and Calcids and are the basis for
defining Calcic and combination Calcic subgroups. A brittle
horizon and the presence of durinodes indicate an intergrade to
Durixerolls and Durids and are the basis for defining the Duric
subgroup. A shallow lithic contact is the basis for defining
Lithic and combination Lithic subgroups. An aridic moisture
regime is a property of Aridisols and is the basis for defining
the Aridic subgroup. A thick mollic epipedon is the basis for
defining Pachic and combination Pachic subgroups. Low base
saturation is a property of Ultisols and is the basis for defining
Ultic and combination Ultic subgroups. Slickensides, wedgeshaped
aggregates, a high linear extensibility, and cracks that
are evident in normal years are properties of Vertisols and are
the basis for defining the Vertic subgroup.
The Typic subgroup is the most extensive subgroup of
Argixerolls and is extensive in parts of the Western United
States. The natural vegetation is mostly grasses and shrubs, but
some of the soils support trees. The soils that have gentle
slopes commonly are used as cropland, some of which is
irrigated. The soils that have moderate slopes are used for dryfarmed
crops. The steep soils are used as rangeland or grazeable
forest.
Alfic Argixerolls.—These soils have an albic or glossic
horizon or another horizon that has color values too high for a
mollic epipedon and chroma too high for an albic horizon
above the argillic horizon, have interfingering of albic
materials into the upper part of the argillic horizon, or have
skeletans of clean silt and sand covering 50 percent or more of
the faces of peds in the upper 5 cm of the argillic horizon.
These soils are of small extent in the United States and occur
mostly in Idaho and Utah. Some supported grasses and shrubs,
and some supported forest vegetation. Slopes range from nearly
level to very steep. The soils that have gentle to moderately
steep slopes are used mostly as cropland. Other soils, mostly
those that have very steep slopes, are used as forest or
rangeland.
Andic and Vitrandic Argixerolls.—These soils have a
surface mantle or layer in the upper 75 cm that has both a low
bulk density and a high content of weakly crystalline minerals
or that consists of slightly or moderately weathered pyroclastic
materials. These soils are of large extent, mostly in the
mountains of Washington, Oregon, and Idaho in the Western
United States. The vegetation either is mostly grass and shrubs
and some widely spaced trees or is coniferous forest. Slopes
range from nearly level to very steep. Many of the less sloping
soils are used as cropland. Most of the other soils are used as
rangeland, forest, or wildlife habitat.
Aquic Argixerolls.—These soils have redox depletions with
low chroma and either have moderately deep ground water at
some time of the year or have artificial drainage. They are
gently sloping or nearly level. They are of small extent in the
United States. The natural vegetation is mostly grass and
shrubs. Most of the soils are used as cropland, but some are
used as rangeland or pasture.
Aquultic Argixerolls.—These soils have redox depletions
with low chroma and either have moderately deep ground
water at some time of the year or have artificial drainage, and
they have a lower base saturation than that in the soils of the
Typic subgroup. Aquultic Argixerolls are rare in the United
States. They are on gently sloping or nearly level, broad valley
terraces. Most of the soils are used as cropland. Truck crops
and orchard crops are commonly grown under irrigation.
Argiduridic Argixerolls.—These soils have an aridic
moisture regime that borders on xeric, and they have a
subhorizon within 100 cm of the surface that does not meet the
requirements for a duripan but is more than 15 cm thick and
either has 20 percent or more (by volume) durinodes or is
brittle when wet and has a firm rupture-resistance class when
moist. These soils are of small extent in the United States. The
636 Soil Taxonomy
natural vegetation is mostly grass and shrubs. The soils
generally have gentle or moderate slopes and are used mostly as
rangeland. Some of the less sloping soils are used as cropland.
Some of the cropland is irrigated.
Aridic Argixerolls.—These soils have an aridic moisture
regime but are otherwise like Typic Argixerolls in their defined
properties. It is common but not required that the color value of
these soils is higher and the content of organic carbon is less
than in soils of the Typic subgroup. Slopes of the Aridic
Argixerolls in the United States are nearly level to very steep.
The soils generally receive less precipitation or lose more water
through runoff and evapotranspiration than the soils of the
Typic subgroup. Aridic Argixerolls are extensive in parts of the
Western United States. The natural vegetation is mostly grass
and shrubs. Most of the soils are used as rangeland or pasture.
Some of the less sloping soils are used as cropland. Some of the
cropland is irrigated.
Calciargidic Argixerolls.—These soils have an aridic
moisture regime that borders on xeric and have a calcic
horizon or identifiable secondary carbonates at a moderate
depth. The Calciargidic Argixerolls in the United States have
nearly level to steep slopes. They are extensive in parts of the
Western United States. The natural vegetation is mostly grass
and shrubs. Most of the soils are used as rangeland or pasture.
Some of the less sloping soils are used as cropland. Some of the
cropland is irrigated.
Calcic Argixerolls.—These soils have a calcic horizon or
identifiable secondary carbonates at a moderate depth but are
otherwise like Typic Argixerolls in their defined properties.
Slopes are nearly level to very steep. Calcic Argixerolls are
extensive in parts of the Western United States. The natural
vegetation is mostly grass and shrubs. Most of the soils are
used as rangeland or pasture. Many of the less sloping soils are
used as cropland. A small amount of the cropland is irrigated.
Calcic Pachic Argixerolls.—These soils have a calcic
horizon or identifiable secondary carbonates at a moderate
depth and have a mollic epipedon that is thicker than the one
in the Typic subgroup. Slopes are nearly level to steep. The
natural vegetation is mostly grass and shrubs. Most of the soils
are used as rangeland or pasture. Many of the less sloping soils
are used as cropland. A small amount of the cropland is
irrigated.
Duric Argixerolls.—These soils have a subhorizon within
100 cm of the surface that does not meet the requirements for a
duripan but is more than 15 cm thick and either has 20 percent
or more (by volume) durinodes or is brittle and has a firm
rupture-resistance class when moist. The soils are rare in the
United States. They are nearly level or sloping and are used as
irrigated cropland or as rangeland.
Lithic Argixerolls.—These soils have a shallow lithic
contact and are permitted, but not required, to have a calcic
horizon or free carbonates beneath the surface layer. They are
extensive in the Western United States. Slopes range from
nearly level to very steep. The natural vegetation is mostly
grass and shrubs. Most of the soils are used as rangeland, as
watersheds, or as habitat for wildlife.
Lithic Ultic Argixerolls.—These soils have a shallow lithic
contact and have less than 75 percent base saturation above the
lithic contact. They are of small extent in the Western United
States. Slopes range from gentle to very steep. The natural
vegetation is mostly a coniferous forest with widely spaced
trees and a grass and shrub understory. Some of the soils
support mostly grasses and shrubs. Most of the soils are used as
grazeable woodland or as rangeland, but some are used as
watersheds or as wildlife habitat.
Oxyaquic Argixerolls.—These soils are like Typic
Argixerolls, but they are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years. Oxyaquic
Argixerolls are of very small extent in the United States.
Pachic Argixerolls.—These soils have a thick mollic
epipedon that commonly includes part of the argillic horizon.
They are extensive soils in parts of the Western United States.
Slopes are nearly level to very steep. The natural vegetation is
mostly grass and shrubs. Some of the soils supported forest
vegetation or oak savanna. Many of the less sloping soils are
used as cropland. The rest of the soils are used mostly as
rangeland or pasture.
Pachic Ultic Argixerolls.—These soils have a thick mollic
epipedon that commonly includes part of the argillic horizon.
They have a base saturation of 75 percent or less in one or
more horizons between either an Ap horizon or a depth of 25
cm from the mineral soil surface, whichever is deeper, and a
depth of 75 cm. These soils are extensive in parts of the
Western United States. Slopes are nearly level to very steep.
The natural vegetation either is mostly a coniferous forest with
a grass and shrub understory or is mostly grasses and shrubs.
Some of the soils supported an open forest or savanna. Many of
the less sloping soils are used as cropland. The rest of the soils
are used mostly as rangeland, pasture, or grazeable forest.
Torrertic Argixerolls.—These soils have a clayey particlesize
class in a significant part, have expanding clays, and in
normal years have deep cracks. They are drier than Vertic
Argixerolls. Torrertic Argixerolls are of small extent in the
United States and occur mostly in Idaho.
Ultic Argixerolls.—These soils have a base saturation of 75
percent or less in one or more horizons between either an Ap
horizon or a depth of 25 cm from the mineral soil surface,
whichever is deeper, and a depth of 75 cm, but they otherwise
are like Typic Argixerolls in their defined properties. Ultic
Argixerolls are extensive in parts of the Western United States.
Slopes range from nearly level to very steep. The natural
vegetation either is mostly a coniferous forest with a grass and
shrub understory or is mostly grasses and shrubs. Some of the
soils supported an open forest or savanna. Many of the less
sloping soils are used as cropland. The rest of the soils are used
mostly as rangeland, pasture, or grazeable forest.
Vertic Argixerolls.—These soils have a clayey particle-size
Mollisols 637
class in a significant part, have expanding clays, and in normal
years have deep cracks. They are of small extent in the United
States. They formed mostly in fine textured lake sediments.
They are associated on the landscape with Xererts and other
Xerolls. The natural vegetation is mostly grass and shrubs.
Most Vertic Argixerolls are nearly level or gently sloping. They
are used mostly as cropland. Some of the cropland is irrigated.
Vitritorrandic Argixerolls.—These soils have an aridic
moisture regime that borders on xeric and have a surface
mantle or layer in the upper 75 cm that consists of slightly or
moderately weathered pyroclastic materials. They are of small
extent, mostly in Nevada and Washington in the Western
United States. The vegetation is mostly grass and shrubs.
Slopes range from nearly level to steep. Most of the soils are
used as rangeland or wildlife habitat. Many of the less sloping
soils are used as cropland.
Calcixerolls
These are the Xerolls that have a calcic or gypsic horizon and
that are calcareous in all overlying horizons. Either the parent
materials had more carbonates than the water from the rainfall
could remove from the upper horizons, or there is a continuing
external source of carbonates in dust or water.
Calcixerolls formed mostly in late-Pleistocene sediments or
older materials on surfaces of comparable age. In the United
States, their native vegetation was mostly grass and shrubs.
These soils are most extensive in the Great Basin of the
Western United States. Slopes range from nearly level to very
steep.
Definition
Calcixerolls are the Xerolls that:
1. Have a calcic or gypsic horizon that has its upper boundary
within 150 cm of the soil surface;
2. Are calcareous in all parts of all horizons above the calcic
or gypsic horizon after the upper 18 cm has been mixed, unless
the texture is coarser than loamy very fine sand or very fine
sand;
3. Do not have a natric horizon;
4. Do not have a duripan within 100 cm of the mineral soil
surface;
5. Do not have a petrocalcic horizon that has its upper
boundary within 150 cm of the soil surface; and
6. Do not have argillic horizon that has one or both of the
following:
a. With increasing depth, no clay decrease of 20 percent or
more (relative) from the maximum clay content
(noncarbonate clay) within 150 cm of the mineral soil
surface (and there is no densic, lithic, or paralithic contact
within that depth); and either
(1) Hue of 7.5YR or redder and chroma of 5 or more in the
matrix;or
(2) Common redox concentrations with hue of 7.5YR or
redder or chroma of 6 or more, or both; or
b. A clayey or clayey-skeletal particle-size class in its upper
part and, at its upper boundary, a clay increase either of 20
percent or more (absolute) within a vertical distance of 7.5 cm
or of 15 percent or more (absolute) within a vertical distance
of 2.5 cm, in the fine-earth fraction (and there is no densic,
lithic, or paralithic contact within 50 cm of the mineral soil
surface).
KeytoSubgroups
IEDA. Calcixerolls that have a lithic contact within 50 cm of the
mineral soil surface.
Lithic Calcixerolls
IEDB. Other Calcixerolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Calcixerolls
IEDC. Other Calcixerolls that have, in one or more horizons
within 75 cm of the mineral soil surface, redox concentrations
and also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Calcixerolls
IEDD. Other Calcixerolls that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Calcixerolls
IEDE. Other Calcixerolls that have a mollic epipedon that is
50 cm or more thick and has a texture finer than loamy fine
sand.
Pachic Calcixerolls
IEDF. Other Calcixerolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
638 Soil Taxonomy
1. More than 35 percent (by volume) fragments coarser than
2.0 mm, of which more than 66 percent is cinders, pumice, and
pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is equal to 30 or more.
Vitrandic Calcixerolls
IEDG. Other Calcixerolls that have an aridic moisture
regime.
Aridic Calcixerolls
IEDH. Other Calcixerolls that have a mollic epipedon that
has, below any Ap horizon, 50 percent or more (by volume)
wormholes, wormcasts, or filled animal burrows.
Vermic Calcixerolls
IEDI. Other Calcixerolls.
Typic Calcixerolls
Definition of Typic Calcixerolls
Typic Calcixerolls are the Calcixerolls that:
1. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox concentrations and also aquic conditions;
2. In normal years are not saturated with water in any layer
within 100 cm of the mineral soil surface for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
3. Have a mollic epipedon that is less than 50 cm thick or has
a texture of loamy fine sand or coarser if it is 50 cm or more
thick;
4. Have a xeric moisture regime;
5. Do not have a lithic contact within 50 cm of the soil
surface;
6. Do not have a mollic epipedon that, below any Ap horizon,
has 50 percent or more (by volume) wormholes, wormcasts, or
filled animal burrows;
7. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
and
8. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, one or both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is equal to 30 or more.
Description of Subgroups
Typic Calcixerolls.—The central concept or Typic subgroup
of Calcixerolls is fixed on deep soils that have a moderately
thick mollic epipedon and have a xeric moisture regime. These
soils do not have a fluctuating ground water table accompanied
by redox concentrations. They do not have slickensides, wedgeshaped
aggregates, a high linear extensibility, or wide cracks in
normal years. They are dry in summer, but they receive and
store enough water in winter and early spring to provide some
moisture for spring and early summer crops.
Redox concentrations and a ground water table that
fluctuates within 75 cm of the mineral soil surface are
properties shared with Aquolls and are the basis for defining
the Aquic subgroup. An aridic moisture regime is drier than
that of Typic Calcixerolls and is the basis for defining the
Aridic subgroup. A shallow lithic contact is the basis for
defining the Lithic subgroup. A thick mollic epipedon is the
basis for defining the Pachic subgroup. Soils that have been
intensively and repeatedly mixed by animals, mainly by
earthworms and their predators, are classified in the Vermic
subgroup. Slickensides, wedge-shaped aggregates, a high
linear extensibility, and cracks that are evident in normal years
are properties of Vertisols and are the basis for defining the
Vertic subgroup.
The Typic subgroup is the most extensive subgroup of
Calcixerolls. Typic Calcixerolls are moderately extensive in the
Western United States. They are nearly level to very steep. The
natural vegetation is mostly grass and shrubs, but some of the
soils support widely spaced juniper and pine species. Many of
the nearly level and gently sloping soils are used as cropland,
much of which is irrigated. Most of the steeper soils are used as
rangeland.
Aquic Calcixerolls.—These soils have moderately deep
ground water at times or artificial drainage and have redox
concentrations. They are of small extent in the Western United
States. The natural vegetation is mostly grass and shrubs. The
soils generally are nearly level and are used mostly as
cropland, hayland, or pasture, much of which is irrigated.
Some of the soils are used as rangeland.
Mollisols 639
Aridic Calcixerolls.—These soils have an aridic moisture
regime that borders on xeric but otherwise are like Typic
Calcixerolls in their defined properties. Commonly, the calcic
horizon is closer to the surface than that in the soils of the
Typic subgroup and the mollic epipedon has less organic
carbon. Aridic Calcixerolls are nearly as extensive as the soils
of the Typic subgroup and are moderately extensive in the
Western United States. Slopes are nearly level to very steep.
The natural vegetation is mostly grass and shrubs, but some of
the soils support widely spaced juniper species. Many of the
nearly level and gently sloping soils are used as cropland, most
of which is irrigated. Most of the steeper soils are used as
rangeland.
Lithic Calcixerolls.—These soils have a lithic contact within
50 cm of the surface and have a xeric moisture regime or one that
is aridic but borders on xeric. They are of small extent in parts of
Nevada, Utah, and southern Idaho in the United States. The
natural vegetation is mostly grass and shrubs, but some of the
soils support widely spaced juniper species. Lithic Calcixerolls
have nearly level to very steep slopes. They are used mostly as
rangeland.
Oxyaquic Calcixerolls.—These soils have ground water
within 100 cm of the mineral soil surface at times during the
year. They are of very small extent in the Western United
States. The natural vegetation is mostly grass and shrubs. The
soils generally are nearly level and are used mostly as
cropland, hayland, or pasture, much of which is irrigated.
Some of the soils are used as rangeland.
Pachic Calcixerolls.—These soils have a mollic epipedon
that is 50 cm or more thick. Otherwise, they are similar to the
soils of the Typic subgroup. Pachic Calcixerolls are of small
extent in the Western United States. The natural vegetation is
mostly grass and shrubs. Many of these soils have nearly level
or gentle slopes, but some range to very steep. The nearly level
and gently sloping soils are used mostly as cropland, hayland,
or pasture, much of which is irrigated. The more sloping soils
are used mostly as rangeland.
Vermic Calcixerolls.—These soils have been intensively
and repeatedly mixed by animals, mainly earthworms and their
predators. The most common horizon sequence is a mollic
epipedon overlying parent material that has many worm
channels filled with dark material from the epipedon. These
soils are not known to occur in the United States. The subgroup
is provided for use elsewhere.
Vertic Calcixerolls.—These soils have a clayey particle-size
class in a significant part, have expanding clays, and in normal
years have deep cracks. They are of very small extent in the
United States. The natural vegetation is mostly grass and
shrubs. These soils generally are nearly level or gently sloping.
They are used as cropland or rangeland. Some of the cropland
is irrigated.
Vitrandic Calcixerolls.—These soils have significant
amounts of cinders, pumice, and pumicelike fragments or
glass. They do not have a lithic contact within 50 cm of the soil
surface, a high shrink-swell potential, or saturation within 100
cm of the soil surface. These soils are not known to occur in the
United States.
Durixerolls
These are the Xerolls that have a duripan that has its upper
boundary within 100 cm of the soil surface. They formed
mainly in Pleistocene sediments. Some of the materials near
the surface of many of these soils are younger than the duripan.
The parent materials commonly were derived, at least partially,
from basic volcanic rocks, siliceous tuffs, pumice, or volcanic
ash. The natural vegetation on the Durixerolls in the United
States was grass and shrubs. These soils occur in the Western
United States, but they are not extensive. They generally are
gently sloping or moderately sloping.
Definition
Durixerolls are the Xerolls that have a duripan within 100
cm of the mineral soil surface.
Key to Subgroups
IEAA. Durixerolls that have, above the duripan, one or both
of the following:
1. Cracks that are 5 mm or more wide through a thickness
of 30 cm or more for some time in normal years, and
slickensides or wedge-shaped aggregates in a layer 15 cm or
more thick; or
2. A linear extensibility of 6.0 cm or more.
Vertic Durixerolls
IEAB. Other Durixerolls that have both:
1. An aridic moisture regime; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface,
one or both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitritorrandic Durixerolls
640 Soil Taxonomy
IEAC. Other Durixerolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm of
the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser than
2.0 mm, of which more than 66 percent is cinders, pumice, and
pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Durixerolls
IEAD. Other Durixerolls that have, in one or more horizons
above the duripan, redox depletions with chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Durixerolls
IEAE. Other Durixerolls that have:
1. An aridic moisture regime; and
2. An argillic horizon that, with increasing depth, has a
clay increase either of 20 percent or more (absolute) within
a vertical distance of 7.5 cm or of 15 percent or more
(absolute) within a vertical distance of 2.5 cm; and
3. A duripan that is neither very strongly cemented nor
indurated in any subhorizon.
Paleargidic Durixerolls
IEAF. Other Durixerolls that have both:
1. An aridic moisture regime; and
2. An argillic horizon that, with increasing depth, has a
clay increase either of 20 percent or more (absolute) within
a vertical distance of 7.5 cm or of 15 percent or more
(absolute) within a vertical distance of 2.5 cm.
Abruptic Argiduridic Durixerolls
IEAG. Other Durixerolls that:
1. Have an aridic moisture regime; and
2. Do not have an argillic horizon above the duripan; and
3. Have a duripan that is neither very strongly cemented
nor indurated in any subhorizon.
Cambidic Durixerolls
IEAH. Other Durixerolls that:
1. Have an aridic moisture regime; and
2. Do not have an argillic horizon above the duripan.
HaploduridicDurixerolls
IEAI. Other Durixerolls that have:
1. An aridic moisture regime; and
2. A duripan that is neither very strongly cemented nor
indurated in any subhorizon.
Argidic Durixerolls
IEAJ. Other Durixerolls that have an aridic moisture regime.
Argiduridic Durixerolls
IEAK. Other Durixerolls that have both:
1. An argillic horizon that, with increasing depth, has a
clay increase either of 20 percent or more (absolute) within
a vertical distance of 7.5 cm or of 15 percent or more
(absolute) within a vertical distance of 2.5 cm; and
2. A duripan that is neither very strongly cemented nor
indurated in any subhorizon.
Haplic Palexerollic Durixerolls
IEAL. Other Durixerolls that have an argillic horizon that,
with increasing depth, has a clay increase either of 20 percent
or more (absolute) within a vertical distance of 7.5 cm or of 15
percent or more (absolute) within a vertical distance of 2.5 cm.
Palexerollic Durixerolls
IEAM. Other Durixerolls that:
1. Have a duripan that is neither very strongly cemented
nor indurated in any subhorizon; and
2. Do not have an argillic horizon above the duripan.
Haplic Haploxerollic Durixerolls
IEAN. Other Durixerolls that do not have an argillic horizon
above the duripan.
Haploxerollic Durixerolls
IEAO. Other Durixerolls that have a duripan that is neither
very strongly cemented nor indurated in any subhorizon.
Haplic Durixerolls
IEAP. Other Durixerolls.
Typic Durixerolls
Definition of Typic Durixerolls
Typic Durixerolls are the Durixerolls that:
1. Have an argillic horizon above the duripan, but the argillic
horizon does not have, with increasing depth, a clay increase
either of 20 percent or more (absolute) within a vertical
distance of 7.5 cm or of 15 percent or more (absolute) within a
vertical distance of 2.5 cm;
Mollisols 641
2. Have a duripan that is either very strongly cemented or
indurated in some subhorizon;
3. Have a xeric moisture regime;
4. Do not have, in any horizon above the duripan, redox
depletions with chroma of 2 or less and also aquic conditions;
5. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, one or both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter, of which 5 percent or
more is volcanic glass, and [(Al plus 1
/2 Fe, percent
extracted by ammonium oxalate) times 60] plus the volcanic
glass (percent) is equal to 30 or more; and
6. Do not have either:
a. Cracks that are 5 mm or more wide, throughout a layer
30 cm or more thick either within 125 cm of the mineral
soil surface or above a duripan if shallower, for some time in
normal years, and slickensides or wedge-shaped aggregates
in a layer 15 cm or more thick that has its upper boundary
within 125 cm of the mineral soil surface or above a duripan
if shallower; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact or a duripan, whichever
is shallower.
Description of Subgroups
Typic Durixerolls.—The central concept or Typic subgroup
of Durixerolls is fixed on freely drained soils that have an
argillic horizon above a very strongly cemented or indurated
duripan. These soils have a relatively gradual increase in
content of clay at the upper boundary of the argillic horizon
and have a xeric moisture regime.
An abrupt increase in content of clay at the upper boundary
of the argillic horizon is a characteristic of soils in which an
argillic horizon has apparently formed after the duripan
developed. This feature is the basis for defining Palexerollic
and combination Palexerollic subgroups and, if the soil also
has an aridic moisture regime, the Abruptic Argiduridic and
Paleargidic subgroups. A weakly developed duripan is
considered less-than-normal development, and its presence is
the basis for defining the intergrades to classes of soils that do
not have a duripan. An aridic moisture regime is drier than
that of the Typic subgroup and is the basis for defining
intergrades to Aridisols. Soils that do not have an argillic
horizon and that have only weak development of the duripan
are classified in Haplic and combination Haplic subgroups.
Soils that do not have an argillic horizon above a strongly
developed duripan are classified in the Haploxerollic subgroup.
Typic Durixerolls are moderately extensive in the Western
United States. These soils generally are nearly level to
moderately sloping. The natural vegetation is mostly grass and
shrubs, but some of the soils support widely spaced juniper and
pine species. Many of the nearly level and gently sloping soils
are used as cropland, some of which is irrigated. Most of the
steeper soils are used as rangeland.
Abruptic Argiduridic Durixerolls.—These soils have an
argillic horizon in which the increase in content of clay is 20
percent (absolute) or more within a vertical distance of 7.5 cm
or is 15 percent (absolute) or more within a vertical distance of
2.5 cm at the upper boundary, have an aridic moisture regime
that borders on xeric, but are otherwise like Typic Durixerolls
in their defined properties. Abruptic Argiduridic Durixerolls
are of small extent in the Western United States. They
generally are nearly level or gently sloping. The natural
vegetation is mostly grass and shrubs, but some of the soils
support widely spaced juniper species. Many of the nearly level
and gently sloping soils are used as cropland, most of which is
irrigated. Most of the steeper soils are used as rangeland or
wildlife habitat.
Aquic Durixerolls.—These soils have redox depletions with
low chroma and either have moderately deep ground water at
some time of the year or have artificial drainage. They are not
known to occur in the United States.
Argidic Durixerolls.—These soils have an argillic horizon
in which the increase in content of clay is less than 20 percent
(absolute) within a vertical distance of 7.5 cm or is less than 15
percent (absolute) within a vertical distance of 2.5 cm at the
upper boundary, have an aridic moisture regime that borders on
xeric, but are otherwise like Typic Durixerolls in their defined
properties. Argidic Durixerolls are of small extent in the
United States. The natural vegetation is mostly grass and
shrubs, but some of the soils support widely spaced juniper and
pine species. Many of the nearly level and gently sloping soils
are used as cropland, most of which is irrigated. Most of the
steeper soils are used as rangeland or wildlife habitat.
Argiduridic Durixerolls.—These soils have an argillic
horizon in which the increase in content of clay is less than 20
percent (absolute) within a vertical distance of 7.5 cm or is less
than 15 percent (absolute) within a vertical distance of 2.5 cm
at the upper boundary. The soils also have an aridic moisture
regime that borders on xeric. These soils are of moderately
small extent in the United States. The natural vegetation is
mostly grass and shrubs, but some of the soils support widely
spaced juniper species. Many of the nearly level and gently
sloping soils are used as cropland, most of which is irrigated.
Most of the steeper soils are used as rangeland or wildlife
habitat.
Cambidic Durixerolls.—These soils have an aridic
moisture regime that borders on xeric and have a duripan that
is less developed than that in the Typic subgroup. The soils
642 Soil Taxonomy
commonly have a cambic horizon but do not have an argillic
horizon above the duripan. They are rare in the United States.
They are nearly level to very steep. The natural vegetation is
mostly grass and shrubs. Many of the nearly level and gently
sloping soils are used as cropland, most of which is irrigated.
Most of the steeper soils are used as rangeland or wildlife
habitat.
Haplic Durixerolls.—These soils have an argillic horizon,
but their duripan is weakly developed. The duripan is less
developed than that of the Typic subgroup. These soils are of
small extent in the United States. They generally are nearly
level to moderately steep. The natural vegetation is mostly
grass and shrubs. Many of the nearly level and gently sloping
soils are used as cropland, some of which is irrigated. Most of
the steeper soils are used as rangeland or wildlife habitat.
Haplic Haploxerollic Durixerolls.—These soils do not
have an argillic horizon and have a weakly developed duripan.
They commonly have a cambic horizon above the duripan.
These soils are rare in the United States. They are nearly level
to very steep. The natural vegetation is mostly grass and
shrubs. Many of the nearly level and gently sloping soils are
used as cropland. Most of the steeper soils are used as
rangeland or wildlife habitat.
Haplic Palexerollic Durixerolls.—These soils have an
argillic horizon in which the increase in content of clay is 20
percent (absolute) or more within a vertical distance of 7.5 cm
or is 15 percent (absolute) or more within a vertical distance of
2.5 cm at the upper boundary. The soils also have a weakly
developed duripan. They are not known to occur in the United
States.
Haploduridic Durixerolls.—These soils do not have an
argillic horizon and have an aridic moisture regime that
borders on xeric, but they are otherwise like Typic Durixerolls
in their defined properties. Haploduridic Durixerolls commonly
have a cambic horizon above the duripan. They are of small
extent in the United States. They are nearly level to steep. The
natural vegetation is mostly grass and shrubs. Many of the
nearly level and gently sloping soils are used as cropland, most
of which is irrigated. Most of the steeper soils are used as
rangeland or wildlife habitat.
Haploxerollic Durixerolls.—These soils do not have an
argillic horizon above the duripan. They commonly have a
cambic horizon above the duripan. They are of small extent in
the United States. They are nearly level to very steep. The
natural vegetation is mostly grass and shrubs, but some of the
soils support widely spaced juniper and pine species. Some of
the nearly level and gently sloping soils are used as cropland.
Most of the steeper soils are used as rangeland or wildlife
habitat.
Paleargidic Durixerolls.—These soils have an argillic
horizon in which the increase in content of clay is 20 percent
(absolute) or more within a vertical distance of 7.5 cm or is 15
percent (absolute) or more within a vertical distance of 2.5 cm
at the upper boundary. The soils also have an aridic moisture
regime that borders on xeric and have a weakly developed
duripan. They are of small extent in the Western United States.
They generally are nearly level or gently sloping. The natural
vegetation is mostly grass and shrubs, but some of the soils
support widely spaced pine and juniper species. Most of the
soils are used as rangeland or wildlife habitat.
Palexerollic Durixerolls.—These soils have an argillic
horizon in which the increase in content of clay is 20 percent
(absolute) or more within a vertical distance of 7.5 cm or is 15
percent (absolute) or more within a vertical distance of 2.5 cm
at the upper boundary. The soils also have a weakly developed
duripan. They are of small extent in the Western United States.
They generally are nearly level or gently sloping. The natural
vegetation is mostly grass and shrubs. Many of the nearly level
and gently sloping soils are used as cropland, some of which is
irrigated. Most of the steeper soils are used as rangeland or
wildlife habitat.
Vertic Durixerolls.—These soils have a clayey particle-size
class in a significant part, have expanding clays, and in normal
years have deep cracks. They are of very small extent in the
Western United States. The natural vegetation is mostly grass
and shrubs. These soils generally are nearly level or gently
sloping. They are used mostly as rangeland.
Vitrandic Durixerolls.—These soils have a surface mantle
or layer in the upper 75 cm that consists of slightly or
moderately weathered pyroclastic materials. They are of small
extent, mostly in Washington and Idaho in the Western United
States. The vegetation is mostly grass and shrubs, but some of
the soils support widely spaced coniferous trees. Slopes range
from nearly level to steep. Most of the less sloping soils are
used as dry cropland. Most of the steep soils are used as
rangeland or wildlife habitat.
Vitritorrandic Durixerolls.—These soils have a surface
mantle or layer in the upper 75 cm that consists of slightly or
moderately weathered pyroclastic materials. They also have an
aridic soil moisture regime that borders on xeric. These soils
are of moderate extent, mostly in Washington and Oregon in
the Western United States. The vegetation is mostly grass and
shrubs, and some of the soils in Oregon have widely spaced
juniper trees. Slopes range from nearly level to moderately
steep. Most of the soils are used as cropland, but some are used
as rangeland or wildlife habitat.
Haploxerolls
These are the more or less freely drained Xerolls that are
characterized by little development in the subsoil. Commonly,
they have a cambic horizon below the mollic epipedon. Some
have only unaltered recent parent materials below the mollic
epipedon. Many have horizons in which secondary carbonates
have accumulated. A few have a calcic horizon, but at least
parts of the surface horizons are free of carbonates.
Mollisols 643
Haploxerolls formed mainly in late-Pleistocene deposits or on
surfaces of comparable age, but some formed on older surfaces.
Parent materials of late-Wisconsinan loess mixed with some
volcanic ash, glacial outwash or till, and alluvium from mixed
sources are common. The natural vegetation is mostly grasses
and shrubs, but some of the soils support a coniferous forest
with a grass and shrub understory and some support an open
forest or savanna. Slopes range from nearly level to very steep.
Definition
Haploxerolls are the Xerolls that:
1. Do not have a duripan that has its upper boundary
within 100 cm of the mineral soil surface;
2. Do not have a petrocalcic horizon that has its upper
boundary within 150 cm of the mineral soil surface;
3. Do not have a calcic or gypsic horizon that has its upper
boundary within 150 cm of the mineral soil surface unless
some part of some horizon overlying the calcic or gypsic
horizon is free of carbonates after the surface soil to a depth of
18 cm has been mixed and the texture is loamy very fine sand,
very fine sand, or finer; and
4. Do not have an argillic or natric horizon.
Key to Subgroups
IEFA. Haploxerolls that have both:
1. A lithic contact within 50 cm of the mineral soil
surface; and
2. A base saturation (by sum of cations) of 75 percent or
less in one or more horizons between either the mineral soil
surface or an Ap horizon, whichever is deeper, and the lithic
contact.
Lithic Ultic Haploxerolls
IEFB. Other Haploxerolls that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Haploxerolls
IEFC. Other Haploxerolls that have both:
1. An aridic moisture regime; and
2. One or both of the following:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is
shallower.
Torrertic Haploxerolls
IEFD. Other Haploxerolls that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that are 5
mm or more wide through a thickness of 30 cm or more for
some time in normal years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has its upper
boundary within 125 cm of the mineral soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Haploxerolls
IEFE. Other Haploxerolls that have both:
1. An aridic moisture regime; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface,
one or both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitritorrandic Haploxerolls
IEFF. Other Haploxerolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Haploxerolls
644 Soil Taxonomy
IEFG. Other Haploxerolls that have:
1. A mollic epipedon that is 50 cm or more thick and has a
texture finer than loamy fine sand; and
2. An irregular decrease in organic-carbon content from a
depth of 25 cm below the mineral soil surface to a depth of
125 cm or to a densic, lithic, or paralithic contact if shallower;
and
3. A slope of less than 25 percent; and
4. In one or more horizons within 75 cm of the mineral soil
surface, redox depletions with chroma of 2 or less and also
aquic conditions for some time in normal years (or artificial
drainage).
Aquic Cumulic Haploxerolls
IEFH. Other Haploxerolls that have:
1. A mollic epipedon that is 50 cm or more thick and has
a texture finer than loamy fine sand; and
2. An irregular decrease in organic-carbon content from a
depth of 25 cm below the mineral soil surface to a depth of
125 cm or to a densic, lithic, or paralithic contact if
shallower; and
3. A slope of less than 25 percent; and
4. A base saturation (by sum of cations) of 75 percent or
less in one or more horizons between either an Ap horizon
or a depth of 25 cm from the mineral soil surface, whichever
is deeper, and either a depth of 75 cm or a densic, lithic, or
paralithic contact, whichever is shallower.
Cumulic Ultic Haploxerolls
IEFI. Other Haploxerolls that have:
1. A mollic epipedon that is 50 cm or more thick and has
a texture finer than loamy fine sand; and
2. An irregular decrease in organic-carbon content from a
depth of 25 cm below the mineral soil surface to a depth of
125 cm or to a densic, lithic, or paralithic contact if
shallower; and
3. A slope of less than 25 percent.
Cumulic Haploxerolls
IEFJ. Other Haploxerolls that have both:
1. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. A slope of less than 25 percent; and either
a. An organic-carbon content of 0.3 percent or more in
all horizons within 125 cm of the mineral soil surface; or
b. An irregular decrease in organic-carbon content from
a depth of 25 cm to a depth of 125 cm or to a densic, lithic,
or paralithic contact if shallower.
FluvaquenticHaploxerolls
IEFK. Other Haploxerolls that have both:
1. In one or more horizons within 75 cm of the mineral soil
surface, redox depletions with chroma of 2 or less and also
aquic conditions for some time in normal years (or artificial
drainage); and
2. A horizon, 15 cm or more thick within 100 cm of the
mineral soil surface, that either has 20 percent or more (by
volume) durinodes or is brittle and has a firm ruptureresistance
class when moist.
Aquic Duric Haploxerolls
IEFL. Other Haploxerolls that have both:
1. In one or more horizons within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and
also aquic conditions for some time in normal years (or
artificial drainage); and
2. A base saturation (by sum of cations) of 75 percent or
less in one or more horizons between either an Ap horizon
or a depth of 25 cm from the mineral soil surface, whichever
is deeper, and either a depth of 75 cm or a densic, lithic, or
paralithic contact, whichever is shallower.
Aquultic Haploxerolls
IEFM. Other Haploxerolls that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Haploxerolls
IEFN. Other Haploxerolls that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Haploxerolls
IEFO. Other Haploxerolls that have both:
1. A mollic epipedon that is 50 cm or more thick and has
a texture finer than loamy fine sand; and
2. A calcic horizon or identifiable secondary carbonates
within one of the following particle-size class (by weighted
average in the particle-size control section) and depth
combinations:
a. Sandy or sandy-skeletal and within 150 cm of the
mineral soil surface; or
Mollisols 645
b. Clayey, clayey-skeletal, fine, or very-fine and within 90
cm of the mineral soil surface; or
c. Any other class and within 110 cm of the mineral soil
surface.
Calcic Pachic Haploxerolls
IEFP. Other Haploxerolls that have both:
1. A mollic epipedon that is 50 cm or more thick and has
a texture finer than loamy fine sand; and
2. A base saturation (by sum of cations) of 75 percent or
less in one or more horizons between either an Ap horizon
or a depth of 25 cm from the mineral soil surface, whichever
is deeper, and either a depth of 75 cm or a densic, lithic, or
paralithic contact, whichever is shallower.
Pachic Ultic Haploxerolls
IEFQ. Other Haploxerolls that have a mollic epipedon that is
50 cm or more thick and has a texture finer than loamy fine
sand.
Pachic Haploxerolls
IEFR. Other Haploxerolls that have:
1. An aridic moisture regime; and
2. A slope of less than 25 percent; and either
a. An organic-carbon content of 0.3 percent or more in
all horizons within 125 cm of the mineral soil surface; or
b. An irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm or to a
densic, lithic, or paralithic contact if shallower.
Torrifluventic Haploxerolls
IEFS. Other Haploxerolls that have both:
1. An aridic moisture regime; and
2. A horizon within 100 cm of the mineral soil surface
that is 15 cm or more thick and either has 20 percent or
more (by volume) durinodes or is brittle and has a firm
rupture-resistance class when moist.
Duridic Haploxerolls
IEFT. Other Haploxerolls that have both:
1. An aridic moisture regime; and
2. A calcic horizon or identifiable secondary carbonates
within one of the following particle-size class (by weighted
average in the particle-size control section) and depth
combinations:
a. Sandy or sandy-skeletal and within 150 cm of the
mineral soil surface; or
b. Clayey, clayey-skeletal, fine, or very-fine and within 90
cm of the mineral soil surface; or
c. Any other class and within 110 cm of the mineral soil
surface.
Calcidic Haploxerolls
IEFU. Other Haploxerolls that have both:
1. An aridic moisture regime; and
2. A sandy particle-size class in all horizons within 100
cm of the mineral soil surface.
Torripsammentic Haploxerolls
IEFV. Other Haploxerolls that:
1. Have an aridic moisture regime; and
2. Either:
a. Do not have a cambic horizon and do not, in any part
of the mollic epipedon below 25 cm from the mineral soil
surface, meet all of the requirements for a cambic
horizon except color; or
b. Have free carbonates throughout the cambic horizon
or in all parts of the mollic epipedon below a depth of 25
cm from the mineral soil surface.
Torriorthentic Haploxerolls
IEFW. Other Haploxerolls that have an aridic moisture
regime.
Aridic Haploxerolls
IEFX. Other Haploxerolls that have a horizon within 100 cm
of the mineral soil surface that is 15 cm or more thick and
either has 20 percent or more (by volume) durinodes or is
brittle and has a firm rupture-resistance class when moist.
Duric Haploxerolls
IEFY. Other Haploxerolls that have a sandy particle-size
class in all horizons within 100 cm of the mineral soil surface.
Psammentic Haploxerolls
IEFZ. Other Haploxerolls that have a slope of less than 25
percent; and either
1. An organic-carbon content of 0.3 percent or more in all
horizons within 125 cm of the mineral soil surface; or
2. An irregular decrease in organic-carbon content from a
depth of 25 cm to a depth of 125 cm or to a densic, lithic, or
paralithic contact if shallower.
Fluventic Haploxerolls
IEFZa. Other Haploxerolls that have a mollic epipedon that has
granular structure and that has, below any Ap horizon, 50
646 Soil Taxonomy
percent or more (by volume) wormholes, wormcasts, or filled
animal burrows.
Vermic Haploxerolls
IEFZb. Other Haploxerolls that have a calcic horizon or
identifiable secondary carbonates within one of the following
particle-size class (by weighted average in the particle-size
control section) and depth combinations:
1. Sandy or sandy-skeletal and within 150 cm of the
mineral soil surface; or
2. Clayey, clayey-skeletal, fine, or very-fine and within 90
cm of the mineral soil surface; or
3. Any other class and within 110 cm of the mineral soil
surface.
Calcic Haploxerolls
IEFZc. Other Haploxerolls that:
1. Do not have a cambic horizon and do not, in the lower
part of the mollic epipedon, meet all of the requirements for
a cambic horizon except color; and
2. Have a base saturation (by sum of cations) of 75 percent
or less in one or more horizons between either an Ap
horizon or a depth of 25 cm from the mineral soil surface,
whichever is deeper, and either a depth of 75 cm or a densic,
lithic, or paralithic contact, whichever is shallower.
Entic Ultic Haploxerolls
IEFZd. Other Haploxerolls that have a base saturation (by
sum of cations) of 75 percent or less in one or more horizons
between either an Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and either a depth of
75 cm or a densic, lithic, or paralithic contact, whichever is
shallower.
Ultic Haploxerolls
IEFZe. Other Haploxerolls that either:
1. Do not have a cambic horizon and do not, in any part of
the mollic epipedon below 25 cm from the mineral soil
surface, meet all of the requirements for a cambic horizon
except color; or
2. Have free carbonates throughout the cambic horizon or
in all parts of the mollic epipedon below a depth of 25 cm
from the mineral soil surface.
Entic Haploxerolls
IEFZf. Other Haploxerolls.
Typic Haploxerolls
Definition of Typic Haploxerolls
Typic Haploxerolls are the Haploxerolls that:
1. Do not have, in any horizon within 75 cm of the mineral soil
surface, redox depletions with chroma of 2 or less and also aquic
conditions;
2. In normal years are not saturated with water in any layer
within 100 cm of the mineral soil surface for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
3. Do not have a calcic horizon or identifiable secondary
carbonates within one of the following particle-size class (by
weighted average in the particle-size control section) and depth
combinations:
a. Sandy or sandy-skeletal and within 150 cm of the
mineral soil surface; or
b. Clayey, clayey-skeletal, fine, or very-fine and within 90
cm of the mineral soil surface; or
c. Any other class and within 110 cm of the mineral soil
surface;
4. Have a mollic epipedon that is less than 50 cm thick or has
a texture of loamy fine sand or coarser if it is 50 cm or more
thick;
5. Do not have a horizon within 100 cm of the mineral soil
surface that is more than 15 cm thick and that either has at
least 20 percent durinodes or is brittle and has a firm ruptureresistance
class when moist;
6. Have a cambic horizon or, in the lower part of the
epipedon, meet all of the requirements for a cambic horizon,
except for the color requirments, and either the cambic horizon
or the lower part of the epipedon is free of carbonates in some
part;
7. Either have a regular decrease in organic-carbon content
with increasing depth and, unless a densic, lithic, or paralithic
contact is at some depth between 50 cm and 125 cm below the
soil surface, have an organic-carbon content of 0.3 percent or
less at a depth within 125 cm of the mineral soil surface or
have a slope of 25 percent or more;
8. Do not have a lithic contact within 50 cm of the soil
surface;
9. Have a base saturation (by sum of cations) of more than 75
percent in all horizons between either an Ap horizon or a depth
of 25 cm from the mineral soil surface, whichever is deeper,
and either a depth of 75 cm or a densic, lithic, or paralithic
contact, whichever is shallower;
10. Do not have a mollic epipedon that has granular structure
and that, below any Ap horizon, has 50 percent or more (by
volume) wormholes, wormcasts, or filled animal burrows;
11. Do not have either:
Mollisols 647
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
12. Have a xeric moisture regime;
13. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, one or more of the
following:
a. Fragments coarser than 2.0 mm constituting more than
35 percent of the whole soil and cinders, pumice, and
pumicelike fragments making up more than 66 percent of
these fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more; and
14. Do not have a sandy particle-size class throughout all
horizons within 100 cm of the mineral soil surface.
Description of Subgroups
Typic Haploxerolls.—The central concept or Typic
subgroup of Haploxerolls is fixed on freely drained soils that
have a xeric moisture regime and do not have aquic conditions
within 75 cm of the mineral soil surface. These soils have a
high base saturation, a moderately thick mollic epipedon, and a
regular decrease in organic-carbon content with increasing
depth. They do not have an accumulation of carbonates at a
shallow depth, and they do not show evidence of cementation
in the upper meter. They do not have slickensides, wedgeshaped
aggregates, a high linear extensibility, or wide cracks in
normal years. Their cambic horizon is not calcareous in some
part, or the lower part of the mollic epipedon meets the
requirements for a cambic horizon and is not calcareous in
some part.
Shallow ground water or artificial drainage and redox
depletions with low chroma are properties of Aquolls and are
the basis for defining the Aquic and Oxyaquic subgroups. A
calcic horizon or identifiable secondary carbonates at a shallow
depth indicate an intergrade to Calcixerolls and are the basis
for defining Calcic and combination Calcic subgroups. A thick
mollic epipedon is the basis for defining Cumulic and Pachic
subgroups. The absence of both a cambic horizon and, in the
lower part of the epipedon, the properties of a cambic horizon,
except for color, or the presence of free carbonates throughout
these horizons is considered evidence of weak horizon
development and is the basis for defining Entic and
combination Entic subgroups. An irregular decrease in organiccarbon
content with increasing depth and a relatively high
content of organic carbon in the deep layers are properties of
Fluvents and, in part, are the basis for defining the Fluventic
subgroup or, if the soil is saturated with water at some period,
the Fluvaquentic subgroup. A shallow lithic contact is the basis
for defining Lithic and combination Lithic subgroups. Low
base saturation is a property of Ultisols and is the basis for
defining the Ultic subgroup. Soils that have been intensively
and repeatedly mixed by animals, mainly by earthworms and
their predators, are classified in the Vermic subgroup. A clayey
texture, slickensides, wedge-shaped aggregates, a high linear
extensibility, and cracks are properties of Vertisols and are the
basis for defining the Vertic subgroup. An aridic moisture
regime is the basis for defining Aridic and Torric subgroups.
The Typic subgroup is one of the most extensive of the
subgroups of Haploxerolls and is extensive in parts of the
Western United States. Typic Haploxerolls are nearly level to
very steep. The native vegetation is dominantly grasses and
shrubs, but some of the soils support widely spaced trees,
mostly pine, oak, and juniper trees. Most of the soils that have
nearly level to moderate slopes are used as cropland, and some
of the nearly level and gently sloping cropland is irrigated.
Some of the soils, mostly those on the steeper slopes, are used
as rangeland.
Aquic Cumulic Haploxerolls.—These soils have redox
depletions with low chroma and either have moderately deep
ground water at some time of the year or are artificially
drained. They also have a thick mollic epipedon. These soils
developed in nearly level areas where they receive more
moisture than the amount that falls on the surface. The native
vegetation is dominantly grasses and shrubs, but some of the
soils support trees, mostly willow and cottonwood. The soils
are of very small extent in the Western United States. They are
used mostly as hayland or pasture, some of which is irrigated.
Aquic Duric Haploxerolls.—These soils have redox
depletions with low chroma and either have shallow ground
water at some time of the year or are artificially drained. Also,
they have a subhorizon within 100 cm of the mineral soil
surface that does not meet the requirements for a duripan but is
more than 15 cm thick and either has 20 percent or more (by
volume) durinodes in a matrix that is not brittle when wet or is
brittle when wet and has a firm rupture-resistance class when
moist. The native vegetation is dominantly grasses and shrubs.
These soils are rare in the United States.
Aquic Haploxerolls.—These soils have redox depletions
with low chroma and either have moderately deep ground
water at some time of the year or are artificially drained. They
are not required to have a cambic horizon, and secondary
carbonates, if present, may be shallower than those in the Typic
648 Soil Taxonomy
subgroup. Aquic Haploxerolls developed in nearly level areas
where they receive more moisture than the amount that falls on
the surface. The native vegetation is dominantly grasses and
shrubs, but some of the soils support trees, mostly pine, willow,
and cottonwood. The soils are of small extent in the Western
United States. They are used mostly as cropland or pasture,
some of which is irrigated.
Aquultic Haploxerolls.—These soils have redox depletions
with low chroma and either have shallow ground water at some
time of the year or are artificially drained. Also, they have a
base saturation of 75 percent or less in one or more horizons
between an Ap horizon or a depth of 25 cm from the mineral
soil surface, whichever is deeper, and a depth of 75 cm. They
are not required to have a cambic horizon. They are nearly
level or gently sloping. The native vegetation is mostly trees.
These soils are of small extent in the Western United States.
The steeper soils are used mainly as forest, and most of the
gently sloping soils have been cleared and are used as
cropland.
Aridic Haploxerolls.—These soils receive less moisture
than Typic Haploxerolls and have an aridic moisture regime.
Aridic Haploxerolls are extensive in the Western United States.
Slopes are nearly level to very steep. The native vegetation is
dominantly grasses and shrubs, and a few of the soils support
widely spaced trees, mostly juniper species. Most of the soils
that have nearly level or gentle slopes are used as cropland,
most of which is irrigated. Some of the soils, mostly the steeper
ones and those with many rock fragments, are used as
rangeland.
Calcic Haploxerolls.—These soils have a calcic horizon or
identifiable secondary carbonates at a moderate depth but are
otherwise like Typic Haploxerolls in their defined properties.
Calcic Haploxerolls are extensive in the Western United States.
Slopes range from nearly level to very steep. The native
vegetation is dominantly grasses and shrubs. Many of the
gently sloping soils are used as cropland, some of which is
irrigated. The steeper soils and the soils with many rock
fragments are used as rangeland.
Calcic Pachic Haploxerolls.—These soils have a calcic
horizon or identifiable secondary carbonates at a moderate
depth and have a mollic epipedon thicker than that of Typic
Haploxerolls. Calcic Pachic Haploxerolls are of moderate
extent in the Western United States. The native vegetation is
dominantly grasses and shrubs, and a few of the soils support
widely spaced trees, mostly oak, juniper, and pine species. The
soils have nearly level to very steep slopes. Many of the nearly
level to moderately sloping soils are used as cropland, some of
which is irrigated. The soils on the steeper slopes are used as
rangeland.
Calcidic Haploxerolls.—These soils have an aridic
moisture regime that borders on xeric. They also have a calcic
horizon or identifiable secondary carbonates at a shallow or
moderate depth. They are permitted, but not required, to have a
cambic horizon. These soils are extensive in parts of the
Western United States. The native vegetation is dominantly
grasses and shrubs, but some of the soils support trees, mostly
juniper and pine species. The soils have nearly level to very
steep slopes. Many of the less sloping soils are used as
cropland, much of which is irrigated. The soils on the steeper
slopes and those with many rock fragments are used as
rangeland or wildlife habitat.
Cumulic Haploxerolls.—These soils have a thick mollic
epipedon. They are on flood plains or in low areas on stream
terraces, or they are in concave areas where fresh sediments
accumulate slowly enough to become part of the mollic
epipedon. The organic-carbon content decreases irregularly
with increasing depth. These soils are permitted, but not
required, to have a cambic horizon or accumulations of
secondary carbonates at a shallow depth. They are moderately
extensive in parts of the Western United States. The native
vegetation is dominantly grasses and shrubs, but some of the
soils support trees, mostly willow and cottonwood. Most of the
soils are nearly level or gently sloping. Many of the larger
areas are used as cropland, much of which is irrigated. The
smaller areas and those dissected by stream channels are used
as rangeland, forest, or wildlife habitat.
Cumulic Ultic Haploxerolls.—These soils have a thick
mollic epipedon and have a base saturation of 75 percent or
less in one or more horizons between either an Ap horizon or a
depth of 25 cm from the mineral soil surface, whichever is
deeper, and a depth of 75 cm. The organic-carbon content
decreases irregularly with increasing depth. These soils are
permitted, but not required, to have a cambic horizon. They are
of small extent in the United States. The native vegetation is
mostly mixed forest. These soils are nearly level or gently
sloping. Most of the larger areas are used as cropland. The
smaller areas and those dissected by stream channels are used
as pasture, forest, or wildlife habitat.
Duric Haploxerolls.—These soils have a subhorizon within
100 cm of the mineral soil surface that does not meet the
requirements for a duripan but is more than 15 cm thick and
either has 20 percent or more (by volume) durinodes or is
brittle when wet and has a firm or very firm rupture-resistance
class when moist. The soils are otherwise like Typic
Haploxerolls. Duric Haploxerolls are not known to occur in the
United States.
Duridic Haploxerolls.—These soils have an aridic moisture
regime that borders on xeric and have a subhorizon within 100
cm of the mineral soil surface that does not meet the
requirements for a duripan but is more than 15 cm thick and
either has 20 percent or more (by volume) durinodes or is
brittle when wet and has a firm or very firm rupture-resistance
class when moist. These soils are not known to occur in the
United States.
Entic Haploxerolls.—These soils do not have a cambic
horizon, and either the epipedon is calcareous or the lower part
of the epipedon is too sandy to be a cambic horizon. Some of
these soils are very shallow to a paralithic or densic contact
Mollisols 649
and have only thin soil horizons. Entic Haploxerolls are of small
extent in the Western United States. The native vegetation is
dominantly grasses and shrubs, and a few of the soils support
widely spaced trees, mostly oak, juniper, or pine species. Slopes
range from nearly level to very steep. The soils are used mostly
as rangeland or wildlife habitat, but some of the soils with nearly
level to moderate slopes are used as cropland, most of which is
irrigated.
Entic Ultic Haploxerolls.—These soils do not have a
cambic horizon, and their base saturation is 75 percent or less
in one or more horizons between an Ap horizon or a depth of
25 cm from the mineral soil surface, whichever is deeper, and a
depth of 75 cm. These soils are of small extent in the United
States. The native vegetation is forest on some of the soils and
grasses and shrubs on others. Slopes range from nearly level to
very steep. The soils are used mostly as forest, rangeland, or
wildlife habitat. Some of the soils with nearly level to moderate
slopes are used as cropland, most of which is irrigated.
Fluvaquentic Haploxerolls.—These soils have redox
depletions with low chroma and either have shallow ground
water at some time of the year or are artificially drained. Their
organic-carbon content either decreases irregularly with
increasing depth or remains relatively high as depth increases.
The soils are not required to have a cambic horizon. They
developed on nearly level flood plains where they receive more
moisture than the amount that falls on the surface. The native
vegetation is dominantly grasses and shrubs, but some of the
soils support trees, mostly willow and cottonwood.
Fluvaquentic Haploxerolls are of small extent in the Western
United States. They are used mostly as cropland, hayland, or
pasture, some of which is irrigated. Some small areas and areas
that are dissected by stream channels or are subject to frequent
flooding are used as pasture, rangeland, or wildlife habitat.
Fluventic Haploxerolls.—These soils have an organiccarbon
content that decreases irregularly with increasing depth
or remains high as depth increases. They are permitted, but not
required, to have a cambic horizon or to have secondary
carbonates at a depth shallower than in soils of the Typic
subgroup. Fluventic Haploxerolls are on nearly level flood
plains, formed mainly in loamy alluvium, and commonly are
stratified as a result of frequent flooding. They are of small
extent in the Western United States. They generally are nearly
level. The native vegetation is dominantly grasses and shrubs,
but some of the soils support trees, mostly pine, oak, and
cottonwood. The soils are used mostly as cropland, hayland, or
pasture, much of which is irrigated. Some small areas and
areas that are dissected by stream channels or are subject to
frequent flooding are used as pasture, rangeland, or wildlife
habitat.
Lithic Haploxerolls.—These soils have a shallow lithic
contact. The mollic epipedon commonly extends to bedrock. In
some of the soils, a cambic horizon intervenes. Lithic
Haploxerolls are extensive in the Western United States. The
native vegetation is dominantly grasses and shrubs, and some
of the soils support widely spaced trees, mostly pine, juniper,
and oak. Slopes are nearly level to very steep. Most of the soils
are used as rangeland or grazeable forest.
Lithic Ultic Haploxerolls.—These soils have a shallow lithic
contact, and their base saturation is 75 percent or less in some
part of the soils above the lithic contact. These soils are
moderately extensive in the United States. The native
vegetation is forest on some of the soils and grasses and shrubs
on others. Slopes range from nearly level to very steep. Most of
the soils are used as grazeable forest or rangeland.
Oxyaquic Haploxerolls.—These soils are like Typic
Haploxerolls, but they are saturated with water within 100 cm
of the mineral soil surface for 20 or more consecutive days or
30 or more cumulative days in normal years. These soils are of
small extent in the United States. Slopes are nearly level or
gently sloping. The native vegetation is dominantly grasses and
shrubs, but some of the soils support trees, mostly willow and
cottonwood. The soils are used mostly as cropland, hayland, or
pasture, much of which is irrigated. Some of the soils are used
as pasture, rangeland, or wildlife habitat.
Pachic Haploxerolls.—These soils are similar to Typic
Haploxerolls, but they have a thicker mollic epipedon. They are
extensive in parts of the Western United States. Slopes are
nearly level to very steep. The native vegetation is dominantly
grasses and shrubs, but some of the soils support widely spaced
trees, mostly oak or juniper. Many of the less sloping soils are
used as cropland, some of which is irrigated. The steeper soils
and those with many rock fragments are used as rangeland or
wildlife habitat.
Pachic Ultic Haploxerolls.—These soils have a mollic
epipedon that is thicker than that in soils of the Typic
subgroup, and they have a base saturation of 75 percent or less
in one or more horizons between an Ap horizon or a depth of
25 cm from the mineral soil surface, whichever is deeper, and a
depth of 75 cm. Pachic Ultic Haploxerolls are moderately
extensive in the Western United States. They range from nearly
level to very steep. The native vegetation is grasses and shrubs
on some of the soils and forest on others. Many of the less
sloping soils are used as cropland, some of which is irrigated.
The steeper soils and those with many rock fragments are used
mainly as rangeland, forest, or wildlife habitat.
Psammentic Haploxerolls.—These soils have a sandy
particle-size class. Because they are sandy, they do not have a
cambic horizon. They are of small extent in the United States.
The native vegetation is dominantly grasses and shrubs, and a
few of the soils support widely spaced trees, mostly oak,
juniper, and pine species. Slopes generally are moderate or
gentle, and most of the soils are used as rangeland. Some
nearly level or gently sloping soils are used as irrigated
cropland, hayland, or pasture.
Torrertic Haploxerolls.—These soils have a clayey particlesize
class in a significant part, have expanding clays, and in
650 Soil Taxonomy
normal years have deep cracks. They also have an aridic
moisture regime that borders on xeric. They are not known to
occur in the United States.
Torrifluventic Haploxerolls.—These soils have an aridic
moisture regime that borders on xeric and formed in alluvium that
is recent enough for the content of organic carbon to decrease
irregularly with increasing depth or to remain high as depth
increases. These soils are of small extent in the Western United
States. The native vegetation is dominantly grasses and shrubs,
but some of the soils support widely spaced trees. Most of the
larger areas are used as irrigated cropland or pasture. Some of
the smaller areas and those dissected by stream channels are
used as rangeland or wildlife habitat.
Torriorthentic Haploxerolls.—These soils have an aridic
moisture regime that borders on xeric and do not have a
cambic horizon. They are of small extent in the Western United
States. The native vegetation is dominantly grasses and shrubs,
and a few of the soils support widely spaced trees, mostly
juniper and pine species. Slopes are nearly level to very steep.
Most of the soils are used as rangeland or grazeable forest.
Torripsammentic Haploxerolls.—These soils have a sandy
particle-size class and have an aridic moisture regime that
borders on xeric. Because they are sandy, they do not have a
cambic horizon. They are of small extent in the Western United
States. The native vegetation is dominantly grasses and shrubs,
but some of the soils support trees, mostly juniper and pine
species. Slopes are nearly level to very steep. Most of the soils
are used as rangeland or grazeable forest. Some that are nearly
level or gently sloping are used as irrigated cropland.
Ultic Haploxerolls.—These soils have a lower degree of
base saturation than Typic Haploxerolls. Many Ultic
Haploxerolls receive more precipitation than the Typic
Haploxerolls. The native vegetation is grasses and shrubs on
some of the soils and forest on others. Some of the soils support
widely spaced trees, mostly oak or juniper. Ultic Haploxerolls
are extensive in the Western United States. Many of the less
sloping soils are used as cropland. The steeper soils and those
with many rock fragments are used mainly as rangeland,
forest, or wildlife habitat.
Vermic Haploxerolls.—These soils have a mollic epipedon
that has granular structure. The most common horizon
sequence is a mollic epipedon consisting of many wormcasts
overlying a horizon containing many worm channels filled
with dark soil from the mollic epipedon. These soils have not
been identified in the United States. The subgroup is provided
for use elsewhere.
Vertic Haploxerolls.—These soils have a clayey particlesize
class in a significant part, have expanding clays, and in
normal years have deep cracks. The native vegetation is mostly
grasses and forbs on most of the soils but is forest or widely
spaced trees on others. Vertic Haploxerolls are of small extent
in the Western United States. Many of the less sloping soils are
used as cropland, some of which is irrigated. The steeper soils
are used mostly as rangeland, forest, or wildlife habitat.
Vitrandic Haploxerolls.—These soils have a surface
mantle or layer in the upper 75 cm that consists of slightly or
moderately weathered pyroclastic materials. They are of large
extent, mostly in Washington, Oregon, and Idaho in the
Western United States. The vegetation is either mostly grass
and shrubs or coniferous forest. Some of the soils support
widely spaced trees. Slopes range from nearly level to very
steep. Many of the less sloping soils are used as cropland.
Most of the others are used as rangeland, forest, or wildlife
habitat.
Vitritorrandic Haploxerolls.—These soils have an aridic
moisture regime that borders on xeric and have a surface
mantle or layer in the upper 75 cm that consists of slightly or
moderately weathered pyroclastic materials. These soils are
moderately extensive, mostly in Oregon, Nevada, and
Washington in the Western United States. The vegetation is
mostly grass and shrubs, but some of the soils support trees,
mostly juniper species. Slopes range from nearly level to very
steep. Many of the less sloping soils are used as cropland,
much of which is irrigated. The steeper soils and those with
many rock fragments are used mainly as rangeland or wildlife
habitat.
Natrixerolls
These are the Xerolls that have a natric horizon and do not
have a duripan. The natric horizon commonly has either
prismatic or columnar structure, and there is a Bk horizon in
or below the natric horizon. Some of the soils have a thin albic
horizon above the natric horizon. The areas of Natrixerolls are
mostly small. These soils formed mostly in mixed sediments of
late-Pleistocene age, commonly in depressions, in basins, or on
low terraces.
Definition
Natrixerolls are the Xerolls that:
1. Have a natric horizon; and
2. Do not have a duripan that has its upper boundary within
100 cm of the mineral soil surface.
Key to Subgroups
IEBA. Natrixerolls that have one or both of the following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Natrixerolls
Mollisols 651
IEBB. Other Natrixerolls that have both:
1. In one or more horizons within 75 cm of the mineral soil
surface, redox depletions with chroma of 2 or less and also
aquic conditions for some time in normal years (or artificial
drainage); and
2. A horizon, 15 cm or more thick within 100 cm of the
mineral soil surface, that either has 20 percent or more (by
volume) durinodes or is brittle and has a firm ruptureresistance
class when moist.
Aquic Duric Natrixerolls
IEBC. Other Natrixerolls that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Natrixerolls
IEBD. Other Natrixerolls that have an aridic moisture
regime.
Aridic Natrixerolls
IEBE. Other Natrixerolls that have a horizon within 100 cm
of the mineral soil surface that is 15 cm or more thick and
either has 20 percent or more (by volume) durinodes or is
brittle and has a firm rupture-resistance class when moist.
Duric Natrixerolls
IEBF. Other Natrixerolls.
Typic Natrixerolls
Definition of Typic Natrixerolls
Typic Natrixerolls are the Natrixerolls that:
1. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
2. Do not have a horizon within 100 cm of the mineral soil
surface that is more than 15 cm thick and that either has at
least 20 percent durinodes or is brittle and has a firm ruptureresistance
class when moist;
3. Have a xeric moisture regime; and
4. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Description of Subgroups
Typic Natrixerolls.—The central concept or Typic
subgroup of Natrixerolls is fixed on soils that have a xeric
moisture regime, that do not have redox depletions with low
chroma in the upper 75 cm accompanied by ground water at a
shallow depth, and do not have slickensides, wedge-shaped
aggregates, a high linear extensibility, and wide cracks in
normal years.
Shallow ground water or artificial drainage and redox
depletions with low chroma are properties of Aquolls and are
the basis for defining the Aquic subgroup. A brittle horizon
and the presence of durinodes indicate an intergrade to
Durixerolls and are the basis for defining Duric and
combination Duric subgroups. An aridic moisture regime is
used, in part, as the basis for defining the Aridic subgroup. A
clayey texture, slickensides, wedge-shaped aggregates, a high
linear extensibility, and cracks are properties of Vertisols and
are the basis for defining the Vertic subgroup.
The Typic subgroup is the most extensive subgroup of
Natrixerolls, but it is of small extent in the Western United
States. The native vegetation is mostly grasses and shrubs.
Slopes generally are gentle but range from nearly level to steep.
Most of the less sloping soils are used as irrigated cropland or
pasture, and the other soils are used mainly as rangeland or
wildlife habitat.
Aquic Duric Natrixerolls.—These soils have redox
depletions with low chroma and either are saturated with water
at some time of the year or have artificial drainage. In addition,
they have a subhorizon within 100 cm of the surface that does
not meet the requirements for a duripan but is more than 15 cm
thick and either has 20 percent or more (by volume) durinodes
or is brittle when wet and has a firm rupture-resistance class
when moist. These soils are not known to occur in the United
States.
Aquic Natrixerolls.—These soils have redox depletions
with low chroma and either are saturated with water at some
time of the year or have artificial drainage. They developed
mostly on nearly level valley or marine terraces. They are of
very small extent in the Western United States. The native
vegetation is mostly grasses and shrubs. Most of the soils are
used as irrigated cropland or pasture, and the others are used
mainly as rangeland or wildlife habitat.
Aridic Natrixerolls.—These soils are like Typic
Natrixerolls, but they receive less moisture. They are not
known to occur in the United States.
Duric Natrixerolls.—These soils have a subhorizon within
100 cm of the surface that does not meet the requirements for a
duripan but is more than 15 cm thick and either has 20 percent
or more (by volume) durinodes or is brittle when wet and has a
firm rupture-resistance class when moist. These soils are not
known to occur in the United States.
Vertic Natrixerolls.—These soils have a clayey particle-size
class in a significant part, have expanding clays, and in normal
years have deep cracks. They occur in California
652 Soil Taxonomy
and in other Western States. They commonly are used as
rangeland.
Palexerolls
These are the Xerolls that formed on old surfaces, commonly
on basalt plains of Miocene or Pliocene age that later, during or
after the late Pleistocene, received a thin covering of loess or of
mixed loess and ash. Slopes range
from nearly level to very steep. The soils commonly have a
thick, dark brown or reddish brown, clayey argillic horizon
that has an abrupt upper boundary, or they have a petrocalcic
horizon. A calcic or Bk horizon is common in the lower part
of the argillic horizon or below it. The native vegetation was
mainly bunchgrasses and some shrubs. Some of the soils
supported a coniferous forest with an understory of grasses and
shrubs or supported an open forest or savanna. Palexerolls
occur in parts of the Western United States, but they are not
extensive.
Definition
Palexerolls are the Xerolls that:
1. Have a petrocalcic horizon that has its upper boundary
within 150 cm of the soil surface or have an argillic horizon
that has one or both of the following characteristics:
a. A vertical clay distribution in which the clay content
does not decrease by as much as 20 percent from the
maximum clay content within a vertical distance of 150 cm
below the soil surface and one or more of the following:
(1) Hue redder than 10YR and chroma greater than 4
dominant in the matrix of at least the lower part of the
argillic horizon; or
(2) Common redox concentrations that have hue
of 7.5YR or redder or chroma greater than 5, or both;
or
b. 35 percent or more clay and an increase of at least 20
percent clay (absolute) within a vertical distance of 7.5 cm
or of 15 percent clay (absolute) within a distance of 2.5 cm
at the upper boundary (and there is no densic, lithic, or
paralithic contact within 50 cm of the mineral soil surface);
2. Do not have a natric horizon; and
3. Do not have a duripan that has its upper boundary
within 100 cm of the soil surface.
Key to Subgroups
IECA. Palexerolls that have one or both of the following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Palexerolls
IECB. Other Palexerolls that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:
1. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
2. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Palexerolls
IECC. Other Palexerolls that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Palexerolls
IECD. Other Palexerolls that have a mollic epipedon that is
50 cm or more thick and has a texture finer than loamy fine
sand.
Pachic Palexerolls
IECE. Other Palexerolls that have both:
1. An aridic moisture regime; and
2. A petrocalcic horizon that has its upper boundary
within 150 cm of the mineral soil surface.
Petrocalcidic Palexerolls
IECF. Other Palexerolls that have a horizon, 15 cm or more
thick within 100 cm of the mineral soil surface, that either has
20 percent or more (by volume) durinodes or is brittle and has
a firm rupture-resistance class when moist.
Duric Palexerolls
IECG. Other Palexerolls that have an aridic moisture regime.
Aridic Palexerolls
Mollisols 653
IECH. Other Palexerolls that have a petrocalcic horizon that
has its upper boundary within 150 cm of the mineral soil
surface.
Petrocalcic Palexerolls
IECI. Other Palexerolls that have a base saturation of 75
percent or less in one or more subhorizons either within the
argillic horizon if more than 50 cm thick or within its upper 50
cm.
Ultic Palexerolls
IECJ. Other Palexerolls that have an argillic horizon that has
either:
1. Less than 35 percent clay in the upper part; or
2. At its upper boundary, a clay increase that is both less
than 20 percent (absolute) within a vertical distance of 7.5
cm and less than 15 percent (absolute) within a vertical
distance of 2.5 cm, in the fine-earth fraction.
Haplic Palexerolls
IECK. Other Palexerolls.
Typic Palexerolls
Definition of Typic Palexerolls
Typic Palexerolls are the Palexerolls that:
1. Have an argillic horizon that has 35 percent or more clay
in the upper part and an increase in clay content of 20 percent
(absolute) or more within a vertical distance of 7.5 cm or of 15
percent (absolute) or more within a distance of 2.5 cm at the
upper boundary;
2. Do not have, in any horizon within 75 cm of the mineral
soil surface, redox depletions with chroma of 2 or less and also
aquic conditions;
3. Do not have a petrocalcic horizon that has its upper
boundary within 150 cm of the soil surface;
4. Have a mollic epipedon that is less than 50 cm thick or has
a texture of loamy fine sand or coarser if it is more than 50 cm
thick;
5. Have a base saturation of more than 75 percent throughout
the argillic horizon or in the upper 50 cm of the argillic
horizon, whichever is thinner;
6. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact, whichever is shallower;
7. Do not have a horizon, 15 cm or more thick within 100 cm of
the mineral soil surface, that either has 20 percent or more (by
volume) durinodes or is brittle and has a firm rupture-resistance
class when moist;
8. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, one or both of the following:
a. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
b. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more; and
9. Have a xeric moisture regime.
Description of Subgroups
Typic Palexerolls.—The central concept or Typic subgroup
of Palexerolls is fixed on deep, freely drained soils that have a
clayey argillic horizon that has an abrupt upper boundary.
These soils have a moderately thick mollic epipedon, a high
base saturation, and a xeric moisture regime. They do not have
a petrocalcic horizon that has its upper boundary within 150
cm of the soil surface.
A petrocalcic horizon is the basis for defining the
Petrocalcic subgroup. A thick mollic epipedon is the basis for
defining the Pachic subgroup. A base saturation that is less
than normal is the basis for defining the Ultic subgroup.
The Typic subgroup is the most extensive subgroup of
Palexerolls. It is moderately extensive in parts of the Western
United States. The native vegetation is dominantly grasses and
shrubs. Some of the soils support widely spaced trees, mostly
oak and juniper species. Most of the soils are used as
rangeland. Some that have nearly level to moderate slopes are
used as cropland, and some of the nearly level and gently
sloping cropland is irrigated. Most of the soils on the steeper
slopes are used as rangeland.
Aquic Palexerolls.—These soils have redox depletions with
low chroma and either have shallow ground water at some time
of the year or are artificially drained. They developed in nearly
level or gently sloping areas where they receive more moisture
than the amount that falls on the surface. The native vegetation
is dominantly grasses and shrubs, but some of the soils support
trees, mostly oak species. The soils are of very small extent in
the Western United States. They are used mostly as cropland or
pasture, some of which is irrigated.
654
Aridic Palexerolls.—These soils have an aridic moisture
regime that borders on xeric, but they otherwise are like Typic
Palexerolls in their defined properties. They are of small extent
in the Western United States. Slopes are nearly level to very
steep. The native vegetation is dominantly grasses and shrubs,
and a few of the soils support widely spaced trees, mostly
juniper species. Most of the soils are used as rangeland. A few
that have nearly level or gentle slopes are used as irrigated
cropland or pasture.
Duric Palexerolls.—These soils have a horizon, 15 cm or
more thick within 100 cm of the mineral soil surface, that
either has 20 percent or more (by volume) durinodes or is
brittle and has a firm rupture-resistance class when moist. The
soils do not have a high shrink-swell potential; significant
amounts of volcanic ash, cinders, or glass near the surface; a
thick mollic epipedon; a petrocalcic horizon; or aquic
conditions within 75 cm of the mineral soil surface. These soils
occur in Oregon and are used for grazing by livestock.
Haplic Palexerolls.—These soils are similar to Typic
Palexerolls, but they do not have a clayey argillic horizon that
has an abrupt upper boundary. They are not known to occur in
the United States.
Pachic Palexerolls.—These soils have a thick mollic
epipedon. They are of small extent in the Western United
States. Slopes range from nearly level to very steep. The native
vegetation is grasses and shrubs on most of the soils, but some
of the soils support coniferous forest or savanna with widely
spaced trees, mostly juniper. Most of the soils are used as
rangeland. Some are used as grazeable woodland, and a few
that have nearly level or gentle slopes are used as cropland or
pasture, some of which is irrigated.
Petrocalcic Palexerolls.—These soils have a petrocalcic
horizon that generally has its upper boundary within 150 cm of
the soil surface. The argillic horizon that overlies the calcic
horizon commonly is calcareous in the lower part. These soils
are of small extent in the Western United States. The native
vegetation is dominantly a sparse forest of juniper and pine
trees interspersed with grasses and shrubs. Slopes are nearly
level to steep. Most of the soils are used as rangeland. Some are
used as grazeable woodland, and a few that have nearly level or
gentle slopes are used as irrigated cropland or pasture.
Petrocalcidic Palexerolls.—These soils have an aridic
moisture regime that borders on xeric and have a petrocalcic
horizon. The petrocalcic horizon commonly is shallower than
75 cm and, in some of the soils, it is less than 50 cm below the
surface. Petrocalcidic Palexerolls are of small extent in the
Western United States. The native vegetation is dominantly a
sparse forest of juniper and pine trees interspersed with grasses
and shrubs. Slopes are nearly level to steep. Most of the soils
are used as rangeland. Some are used as grazeable woodland,
and a few that have nearly level or gentle slopes are used as
irrigated cropland or pasture.
Ultic Palexerolls.—These soils have a lower degree of base
saturation than Typic Palexerolls. Many Ultic Palexerolls
receive more precipitation than the Typic Palexerolls. The
native vegetation is forest on some Ultic Palexerolls and
grasses and shrubs on others. Some of the soils support widely
spaced trees, mostly oak or juniper. The soils are of small
extent in the Western United States. Slopes are nearly level to
very steep. Some of the soils in the less sloping areas are used
as cropland. The steeper soils and those with many rock
fragments are used mainly as forest, rangeland, or wildlife
habitat.
Vertic Palexerolls.—These soils have a clayey particle-size
class in a significant part, have expanding clays, and in normal
years have deep cracks. The native vegetation is mostly
grasses, shrubs, and forbs. These soils are of small extent in the
Western United States. Most of the soils are used as rangeland.
Some of the less sloping soils are used as cropland or pasture,
some of which is irrigated.
Vitrandic Palexerolls.—These soils have significant
amounts of vocanic ash, cinders, or glass in one or more layers
18 cm or more thick within 75 cm of the mineral soil surface.
They do not have a high shrink-swell potential. These soils
occur in Oregon. They are used for timber production or for
grazing by livestock.
655
Oxisols are weathered soils that are low in fertility. They
are most common on the gentle slopes of geologically
old surfaces in tropical and subtropical regions. Their profiles
are distinctive because of a lack of obvious horizons. Their
surface horizons are normally somewhat darker than the
subsoil, but the transition of subsoil features is gradual.
Oxisols consist mainly of quartz, kaolinite, oxides, and
organic matter. Both the structure and “feel” of Oxisols are
deceptive. Upon first examination, they appear structureless
and have the feel of a loamy texture. While some are loamy or
even coarser textured, many have a fine or very-fine particlesize
class, but the clay is aggregated in a strong grade of fine
and very fine granular structure. To obtain a true “feel” of the
texture, a wet sample must be worked for several minutes in
the hands to break down the aggregates. The strong granular
structure apparently causes most Oxisols to have a much more
rapid permeability than would be predicted, given the particlesize
class. Although compaction and reduction in permeability
can be caused by cultivation, the soils are extremely resistant to
compaction and are so free draining that cultivation can take
place soon after rain without puddling.
Oxisols occur in every soil moisture regime from aridic to
perudic and aquic. The natural vegetation ranges from tropical
rain forests to desert savannas. The lack of a unifying climatic
factor throughout their geographic distribution indicates that
climatic changes have taken place since these soils formed or
that highly weathered parent material has been transported to
areas with a dry climate. As part of the definition, the soils are
limited to a very low cation-exchange capacity and very few
weatherable minerals. They occur over many kinds of geologic
bedrock. Close examination, commonly to a great depth,
however, shows evidence that the material in which the soils
formed has been transported. Where the material clearly is not
transported, formation is most common in mafic rock.
Although many Oxisols are extremely infertile, some have
small but adequate supplies of nutrients and are immediately
productive when cultivated. The reserves of plant nutrients
even in the most fertile Oxisols are not great, and, to sustain
high yields, fertilizer and lime are needed after only a few
years of cultivation. In most of the Oxisols, fertilizers are
needed for the first crop unless the soils are fertile enough for
one or two crops because of the ash derived from burning the
natural vegetation. Phosphorus generally is the most restricted
plant nutrient, mainly because of the tendency of the clay- and
oxide-rich surface horizon to fix large amounts of fertilizer
phosphorus in an unavailable form. Once this tendency to fix
the phosphate has been overcome by an initial application,
however, there is no further fixation problem and annual
fertilizer rates are no higher than those for other soils. Because
of the initial expense of fertilization, Oxisols are cultivated
extensively only where modern agronomic techniques are
sustainable by an infrastructure of agribusiness. Under
primitive, shifting cultivation, the soils are used only if they
naturally support a large biomass, which can yield a large
volume of ash upon burning.
Road building and other engineering practices are relatively
easy in most Oxisols because of the physical stability of the
clay. There is little silt in most Oxisols; thus, the soils hold
little water that is available to plants. The content of organic
matter is commonly much higher than is indicated by the soil
color, which may result from red staining of the associated iron
oxides. The organic matter is very stable, infertile humus and
is slow to decompose in many of these soils.
The most extensive areas of Oxisols are on the interior
plateaus of South America, the lower portion of the Amazon
basin, significant portions of the central African basin, and
important areas in Asia, Australia, and several tropical and
subtropical islands. Oxisols are of small extent in the United
States, and many of the taxa are not known to occur in the
country. Because many of the taxa occur only outside the
United States, less is known about the vegetation, extent, and
use of these taxa. The descriptions of many of the subgroups in
this chapter are necessarily brief.
Definition of Oxisols and Limits Between
Oxisols and Soils of Other Orders
Oxisols are mineral soils that:
1. Meet one of these two requirements:
a. Have, within 150 cm of the mineral soil surface, the
upper boundary of an oxic horizon and no kandic horizon;
or
b. Have 40 percent or more (by weight) clay in the fineCHAPTER
17
Oxisols1
1
This chapter was rewritten in 1987 following recommendations of the International
Committee on the Classification of Oxisols (ICOMOX), chaired by Hari Eswaran from 1978 to
1981 and then by S.W. Buol until completion of the task in 1987.
656 Soil Taxonomy
earth fraction between the mineral soil surface and a depth
of 18 cm, after mixing, and a kandic horizon that meets the
weatherable mineral requirements of an oxic horizon and
that has its upper boundary within 150 cm of the mineral
soil surface; and
2. Do not have either of the following:
a. Permafrost within 100 cm of the soil surface; or
b. Gelic materials within 100 cm of the soil surface and
permafrost within 200 cm of the soil surface; and
3. Do not have, above the oxic or kandic horizon, one or
more of the following:
a. A spodic horizon and an albic horizon in 50 percent or
more of each pedon and a cryic or pergelic soil temperature
regime; or
b. An Ap horizon containing 85 percent or more spodic
materials; or
c. A spodic horizon with all of the following
characteristics:
(1) One or more of the following:
(a) A thickness of 10 cm or more; or
(b) An overlying Ap horizon; or
(c) Cementation in 50 percent or more of each
pedon; or
(d) A coarse-loamy, loamy-skeletal, or finer particlesize
class and a frigid temperature regime; or
(e) A cryic or pergelic temperature regime; and
(2) An upper boundary within the following depths
from the mineral soil surface: either
(a) Less than 50 cm; or
(b) Any depth above the kandic or oxic horizon if
the soil has a sandy particle-size class in at least some
part between the mineral soil surface and the spodic
horizon; and
(3) A lower boundary as follows:
(a) Either at a depth of 25 cm or more below the
mineral soil surface, or at the top of a duripan or
fragipan, or at a densic, lithic, paralithic, or
petroferric contact, whichever is shallowest; or
(b) At any depth,
1) If the spodic horizon has a coarse-loamy,
loamy-skeletal, or finer particle-size class and the
soil has a frigid temperature regime; or
2) If the soil has a cryic or pergelic temperature
regime; and
4. Do not have andic soil properties in 60 percent or more of
the thickness between either the mineral soil surface or the top
of an organic layer with andic soil properties, whichever is
shallower, and either a depth of 60 cm from the shallower of
the above or a densic, lithic, or paralithic contact, a duripan, or
a petrocalcic horizon if shallower than 60 cm.
Limits Between Oxisols and the Other Soil Orders
The definition of Oxisols must provide criteria that separate
Oxisols from soils of all other orders. The aggregate of these
criteria defines the limits of Oxisols in relation to all other
known kinds of soil.
1. Unlike Alfisols, Aridisols, Entisols, Inceptisols, Mollisols,
Ultisols, and Vertisols, Oxisols must have one of the following
characteristics:
a. An oxic horizon and no kandic horizon within 150 cm
of the mineral soil surface; or
b. A kandic horizon that meets the weatherable mineral
requirements of an oxic horizon that has its upper boundary
within 150 cm of the mineral soil surface; and 40 percent or
more (by weight) clay in the fine-earth fraction between the
mineral soil surface and a depth of 18 cm after mixing.
2. Unlike Andisols, Oxisols must not have andic soil
properties in 60 percent or more of the thickness between
either the mineral soil surface or the top of an organic layer
with andic soil properties, whichever is shallower, and either a
depth of 60 cm from the shallower of the above or a densic,
lithic, or paralithic contact, a duripan, or a petrocalcic horizon
if shallower than 60 cm.
3. Unlike Gelisols, Oxisols do not have:
a. Permafrost within 100 cm of the soil surface; or
b. Gelic materials within 100 cm of the soil surface and
permafrost within 200 cm of the soil surface.
4. Unlike Histosols, Oxisols do not have organic soil
materials that meet one or more of the following:
a. Overlie cindery, fragmental, or pumiceous materials
and/or fill their interstices and directly below these
materials have a densic, lithic, or paralithic contact; or
b. When added with the underlying cindery, fragmental, or
pumiceous materials, total 40 cm or more between the soil
surface and a depth of 50 cm; or
c. Constitute two-thirds or more of the total thickness of
the soil to a densic, lithic, or paralithic contact and have no
mineral horizons or have mineral horizons with a total
thickness of 10 cm or less; or
d. Are saturated with water for 30 days or more in normal
years (or are artificially drained), have an upper boundary
Oxisols 657
within 40 cm of the soil surface, and have a total thickness
of either:
(1) 60 cm or more if three-fourths or more of their volume
consists of moss fibers or if their bulk density, moist, is
less than 0.1 g/cm3
; or
(2) 40 cm or more if they consist either of sapric or hemic
materials, or of fibric materials with less than three-fourths
(by volume) moss fibers and a bulk density, moist, of 0.1 g/
cm3
or more.
5. Unlike Spodosols, Oxisols must not have an Ap horizon
consisting of spodic materials or a spodic horizon above a
kandic horizon and must not have one or more of the
following:
a. An albic horizon in 50 percent or more of each pedon
and a cryic soil temperature regime; or
b. A spodic horizon with all of the following
characteristics:
(1) One or more of the following:
(a) A thickness of 10 cm or more; or
(b) An overlying Ap horizon; or
(c) Cementation in 50 percent or more of each
pedon; or
(d) A coarse-loamy, loamy-skeletal, or finer particlesize
class and a frigid temperature regime; or
(e) A cryic temperature regime; and
(2) An upper boundary within the following depths
from the mineral soil surface: either
(a) Less than 50 cm; or
(b) Less than 200 cm if the soil has a sandy particlesize
class between the mineral soil surface and the
spodic horizon; and
(3) A lower boundary as follows:
(a) Either at a depth of 25 cm or more below the
mineral soil surface, or at the top of a duripan or
fragipan, or at a densic, lithic, paralithic, or
petroferric contact, whichever is shallowest; or
(b) At any depth if the spodic horizon has a coarseloamy,
loamy-skeletal, or finer particle-size class and
the soil has a frigid temperature regime, or if the soil
has a cryic temperature regime.
Representative Pedon and Data
Following is a description of a representative Oxisol. Data
for the pedon identified in this description are given in the
table “Characterization Data for an Oxisol.”
Classification: Fine, kaolinitic, isohyperthermic Aeric Haplaquox
Site identification number: 85P0741
Location: Brazil; main road to CPAC/EMBRAPA, 3 km from
Br-41 (1.4 km after headquarters), approximately 300 m to
the right
Latitude: 15 degrees 35 minutes 30 seconds S.
Longitude: 47 degrees 43 minutes 10 seconds W.
Slope: 5 percent
Elevation: 950 m above m.s.l.
Soil moisture regime: Aquic
Drainage class: Poorly drained
Diagnostic horizons: An ochric epipedon from a depth of
0 to 30 cm and an oxic horizon from a depth of 30 to
180 cm
In the following pedon description, colors are for moist soil
unless otherwise indicated.
Ap—0 to 18 cm; dark gray (10YR 4/1) clay, dark gray (10YR
4/1) dry; common fine redox concentrations; moderate fine
and medium granular structure; hard, firm, sticky and
plastic; common fine roots; many very fine and fine
tubular pores; yellowish red (5YR 5/8) oxides along roots;
clear smooth boundary.
A—18 to 30 cm; dark gray (10YR 4/1) clay, gray (10YR 5/1)
dry; common fine prominent redox concentrations; weak
fine granular structure parting to weak fine subangular
blocky; very hard, very firm, sticky and plastic; common
fine roots; common very fine and fine tubular pores; abrupt
wavy boundary.
BAg—30 to 38 cm; pale yellow (5Y 8/3) clay, light gray
(10YR 7/1) dry; common fine prominent redox
concentrations; weak fine and medium subangular blocky
structure; slightly hard, firm, sticky and plastic; few roots;
clear wavy boundary.
Bg1—38 to 70 cm; pale yellow (5Y 8/3) clay, white (10YR
8/1) dry; common fine prominent redox concentrations;
weak fine and medium subangular blocky structure;
slightly hard, friable, sticky and plastic; few roots; gradual
wavy boundary.
Bg2—70 to 110 cm; white (5Y 8/2) clay, white (10YR 8/1)
dry; few fine and medium prominent redox concentrations;
weak fine and medium subangular blocky structure; hard,
firm, sticky and plastic; clear wavy boundary.
BCg—110 to 180 cm; pinkish white (5YR 8/2) clay, white
(10YR 8/2) dry; common medium and coarse prominent
redox concentrations; moderate medium and thick platy
structure parting to weak fine and medium angular and
subangular blocky; hard, firm, sticky and plastic; gradual
wavy boundary.
Cg—180 to 220 cm; pale yellow (5Y 7/4 and 2.5Y 7/4) clay;
white (5Y 8/1) to reddish yellow (7.5YR 6/8) redox
depletions and concentrations; wet soil compacted by
auger.
658 Soil Taxonomy
Characterization Data for an Oxisol
SITE IDENTIFICATION NO.: 85P0741
CLASSIFICATION: FINE, KAOLINITIC, ISOHYPERTHERMIC AERIC HAPLAQUOX
GENERAL METHODS: 1B1A, 2A1, 2B
-1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-
-----------------------------------------------------------------------------------------------------------------------------------
(- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)
CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT
SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF
NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE
<- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL
85P3892 0- 18 Ap 53.9 21.1 25.0 40.5 10.1 11.0 6.9 11.3 6.3 0.4 0.1 -- -- -- 18 --
85P3893 18- 30 A 53.8 20.4 25.8 40.9 9.4 11.0 6.3 12.2 6.9 0.4 -- -- -- -- 19 --
85P3894 30- 38 BAg 56.9 19.6 23.5 43.0 9.6 10.0 6.4 10.8 5.8 0.5 -- -- -- -- 17 --
85P3895 38- 70 Bg1 60.0 20.3 19.7 45.0 9.5 10.8 5.7 8.9 4.5 0.3 0.3 -- -- -- 14 --
85P3896 70-110 Bg2 59.7 20.6 19.7 42.0 10.5 10.1 5.7 9.2 4.5 0.3 -- TR -- -- 14 --
85P3897 110-180 BCg 60.7 20.4 18.9 40.6 10.3 10.1 5.5 8.8 4.3 0.3 -- TR TR -- 13 --
-----------------------------------------------------------------------------------------------------------------------------------
ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD
C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE
DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL
(cm) 6A1c 6B3a 6S3 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A3a 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1
Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm
0- 18 2.12 0.139 0.7 0.3 -- 0.19 0.39 41 18 1.28 1.35 0.018 27.4 25.1 18.2 0.05
18- 30 1.59 0.098 0.3 0.2 -- 0.17 0.40 41 19 1.25 1.41 0.041 32.8 30.2 17.8 0.11
30- 38 1.00 0.084 0.1 0.2 -- 0.12 0.38 41 19 1.23 1.35 0.032 31.4 28.4 18.3 0.08
38- 70 0.48 0.028 0.1 0.1 -- 0.11 0.39 45 20 1.09 1.20 0.033 33.9 29.7 19.7 0.07
70-110 0.26 0.027 0.2 0.1 -- 0.11 0.43 47 21 1.16 1.26 0.028 33.2 29.5 21.0 0.04
110-180 0.18 0.013 0.4 0.1 -- 0.09 0.43 48 18 1.24 1.32 0.021 30.1 28.2 22.1 0.03
-----------------------------------------------------------------------------------------------------------------------------------
(- NH4OAc EXTRACTABLE BASES -) ACID- EXTR (- - - -CEC - - -) Al -BASE SAT- CO3 AS RES. (- - - - - PH - - - - -)
Ca Mg Na K SUM ITY Al SUM NH4- BASES SAT SUM NH4 CaCO3 ohms KC1 NaF CaCl2 H2O
DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc + Al OAc <2mm /cm IN .01M
(cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 6G9a 5A3a 5A8b 5A3b 5G1 5C3 5C1 6E1g 8E1 8C1g 8C1d 8C1f 8C1f
<- - - - - - - - - - - -meq / 100 g - - - - - - - - - - -> <- - - - -Pct - - - -> 1:2 1:1
0- 18 0.2 0.4 TR -- 0.6 14.5 2.3 15.1 10.4 2.9 79 4 6 3.7 9.1 3.9 4.1
18- 30 -- 0.1 TR -- 0.1 12.8 2.9 12.9 9.1 3.0 97 1 1 3.7 9.4 3.9 4.3
30- 38 -- TR TR -- TR 10.6 2.8 10.6 7.1 2.8 100 TR TR 3.8 4.0 4.4
38- 70 -- -- TR -- TR 9.2 1.8 9.2 6.3 1.8 100 TR TR 3.9 9.9 4.2 5.0
70-110 -- -- TR -- TR 8.1 1.9 8.1 6.5 1.9 100 TR TR 4.0 4.2 5.1
110-180 -- -- TR -- TR 7.1 1.6 7.1 5.4 1.6 100 TR TR 4.0 9.8 4.3 5.3
-----------------------------------------------------------------------------------------------------------------------------------
ACID OXALATE EXTRACTION PHOSPHOUS KCl TOTAL (- -WATER CONTENT- - )(- - - - WATER DISPERSIBLE - - - - ) MIN AGGRT
OPT Fe Si Al CIT- Mn C 0.06 1- 2- 15 <- - PIPETTE - - >< - HYDROMETER - > SOIL STABL
DEN RET ACID BAR BAR BAR BAR CLAY SILT SAND CLAY SILT SAND CONT <5mm
SAMPLE HZ 8J 6C9a 6V2 6G12 6S4 6S5 6D3 6A2d 4B1c 4B1a 4B1a 4B2b <- - - 3A1c - - -><- - - SML - - -> 8F1 4G1
NO. NO <- P c t o f < 2 m m -><- p p m ->< - - - - - - - - - - P e r c e n t o f < 2 m m - - - - - - - - - - >< Pct>
85P3892 1 0.13 0.42 0.02 0.38 1.94 21.0
85P3893 2 0.08 0.19 0.01 0.38 1.45 21.7
85P3894 3 0.05 0.11 0.39 0.87 21.5
85P3895 4 0.04 0.05 0.08 0.39 0.46 23.2
85P3896 5 0.02 0.02 0.08 0.32 0.24 25.8
85P3897 6 0.02 0.03 0.09 0.28 0.16 25.8
-----------------------------------------------------------------------------------------------------------------------------------
< - - - - - - - - - - - - - - - - - - - - - - CLAY MINERALOGY (<.002mm) - - - - - - - - - - - - - - - - - - - - - - ->
FRAC- < - - - - - X-RAY - - - - - ->< - - - THERMAL - - - ->< - - - - - - - ELEMENTAL - - - - - - - ->< - -> EGME INTERSAMPLE
TION < >< - DTA - ->< - TGA - -> SiO2 Al2O3 Fe2O3 MgO CaO K2O Na2O < > RETN PRETA<
- - - - - 7A2i - - - - - ->< - 7A6 - >< - 7A4b - >< - - - - - - - - - 7C3 - - - - - - - - ->< > 7D2 TION
NUMBER <- - >< - - - - Peak size - - - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - -><mg/g>< - ->
85P3892 TCLY KK 5 GI 2 VR 2 KK70 GI 4 2.3 0.1
85P3896 TCLY KK 5 GI 2 VR 2 KK80 GI 5 1.1
85P3897 TCLY KK 5 GI 2 VR 2 GE 1 KK76 GI 5 1.3
-----------------------------------------------------------------------------------------------------------------------------------
SAND - SILT MINERALOGY (2.0-0.002mm)
SAMPLE FRACTION OPTICAL GRAIN COUNT PERCENT
NUMBER < - - - - - - - -- - - - - - - - - TOTAL RESISTANT - - 7B1a - - - - - - - - ->
85P3896 VFS 100 QZ88 PO12 OPtr MItr
-----------------------------------------------------------------------------------------------------------------------------------
The chemical data are based on the fraction less than 2 mm in size.
Fraction interpretation: TCLY, total clay, <0.002 mm; VFS, very fine sand, 0.05-0.10 mm.
Mineral interpretation: KK, kaolinite; GI, gibbsite; VR, vermiculite; QZ, quartz; PO, plant opal; OP, opaques; MI, mica;
GE, goethite.
Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.
Pedon mineralogy based on clay: Kaolinitic.
Family mineralogy: Kaolinitic.
Oxisols 659
Key to Suborders
EA. Oxisols that have aquic conditions for some time in normal
years (or artificial drainage) in one or more horizons within 50 cm
of the mineral soil surface and have one or more of the
following:
1. A histic epipedon; or
2. An epipedon with a color value, moist, of 3 or less
and, directly below it, a horizon with chroma of 2 or less;
or
3. Distinct or prominent redox concentrations within 50
cm of the mineral soil surface, an epipedon, and, directly
below it, a horizon with one or both of the following:
a. 50 percent or more hue of 2.5Y or yellower; or
b. Chroma of 3 or less; or
4. Within 50 cm of the mineral soil surface, enough active
ferrous iron to give a positive reaction to alpha,alphadipyridyl
at a time when the soil is not being irrigated.
Aquox, p. 659
EB. Other Oxisols that have an aridic moisture regime.
Torrox,p.671
EC. Other Oxisols that have an ustic or xeric moisture
regime.
Ustox, p. 683
ED. Other Oxisols that have a perudic moisture regime.
Perox,p.662
EE. OtherOxisols.
Udox,p.673
Aquox
These are wet Oxisols in shallow depressions and in
seepage areas at the base of slopes. Because the water table
may fluctuate seasonally in the soils, there is a tendency to
accumulate iron in the form of secondary nodules, concretions,
and plinthite. Most areas of these soils are small.
Definition
Aquox are the Oxisols that have aquic conditions for some
time in normal years (or artificial drainage) in one or more
horizons within 50 cm of the mineral soil surface and have one
or more of the following:
1. A histic epipedon; or
2. An epipedon directly above a horizon with 50 percent or
more hue of 2.5Y or yellower or chroma of 3 or less and
distinct or prominent redox concentrations within 50 cm of the
mineral soil surface; or
3. An epipedon with a color value, moist, of 3 or less directly
above a horizon with chroma of 2 or less; or
4. Within 50 cm of the mineral soil surface, enough active
ferrous iron to give a positive reaction to alpha,alpha-dipyridyl
at a time when the soil is not being irrigated.
Key to Great Groups
EAA. Aquox that have, in one or more subhorizons of an
oxic or kandic horizon within 150 cm of the mineral soil
surface, an apparent ECEC of less than 1.50 cmol(+) per kg
clay and a pH value (in 1N KCl) of 5.0 or more.
Acraquox, p. 659
EAB. Other Aquox that have plinthite forming a continuous
phase within 125 cm of the mineral soil surface.
Plinthaquox, p. 661
EAC. Other Aquox that have a base saturation (by NH4
OAc)
of 35 percent or more in all horizons within 125 cm of the
mineral soil surface.
Eutraquox, p. 660
EAD. Other Aquox.
Haplaquox, p. 661
Acraquox
This great group is provided for those Aquox with extremely
low cation-exchange capacities. Few examples have been made
available for study.
Definition
Acraquox are the Aquox that have an apparent ECEC of less
than 1.50 cmol(+) per kg clay and a pH value (1N KCl) of 5.0 or
more in some part of an oxic or kandic horizon within 150 cm of
the mineral soil surface.
KeytoSubgroups
EAAA. Acraquox that have 5 percent or more (by volume)
plinthite in one or more horizons within 125 cm of the mineral
soil surface.
Plinthic Acraquox
EAAB. Other Acraquox that have, directly below an
epipedon, a horizon 10 cm or more thick that has 50 percent or
more chroma of 3 or more.
Aeric Acraquox
EAAC. Other Acraquox.
Typic Acraquox
660 Soil Taxonomy
DefinitionofTypicAcraquox
Typic Acraquox are the Acraquox that:
1. Do not have, within 125 cm of the mineral soil surface, a
horizon that has more than 5 percent plinthite (by volume);
and
2. Do not have, directly below an epipedon, a horizon 10
cm or more thick that has 50 percent or more chroma of 3 or
more.
Description of Subgroups
Typic Acraquox.—The central concept or Typic subgroup
of Acraquox is fixed on soils that have dominantly low chroma
in a layer 10 cm or more thick that is directly below an
epipedon. These soils also have less than 5 percent plinthite in
all horizons within a depth of 125 cm. They are not known to
occur in the United States.
Aeric Acraquox.—These soils are like Typic Acraquox, but
they have chroma dominantly of 3 or more in a layer 10 cm or
more thick that is directly below an epipedon. Aeric Acraquox
are considered intergrades between Acraquox and Acrudox or
Acroperox. They are not known to occur in the United States.
Plinthic Acraquox.—These soils have 5 percent or more
(by volume) plinthite in one or more horizons within 125 cm of
the mineral soil surface. The soils are not known to occur in
the United States.
Eutraquox
These Aquox have a base saturation (pH 7) of more than 35
percent in all horizons to a depth of 125 cm. They do not have
plinthite that forms a continuous phase within 125 cm of the
mineral soil surface and do not have both a very low apparent
ECEC and a pH value (1N KCl) of 5.0 or more in some part of
the oxic or kandic horizon.
Definition
Eutraquox are the Aquox that:
1. Have more than 35 percent base saturation (by NH4
OAc)
in all parts within 125 cm of the mineral soil surface;
2. Do not have plinthite that forms a continuous phase
within 125 cm of the mineral soil surface; and
3. Do not have an apparent ECEC of less than 1.50 cmol(+)
per kg clay and a pH value (1N KCl) of 5.0 or more in some
part of an oxic or kandic horizon within 150 cm of the mineral
soil surface.
Key to Subgroups
EACA. Eutraquox that have a histic epipedon.
Histic Eutraquox
EACB. Other Eutraquox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface.
Plinthic Eutraquox
EACC. Other Eutraquox that have, directly below an
epipedon, a horizon 10 cm or more thick that has 50 percent or
more chroma of 3 or more.
Aeric Eutraquox
EACD. Other Eutraquox that have 16 kg/m2
or more organic
carbon between the mineral soil surface and a depth of 100 cm.
Humic Eutraquox
EACE. Other Eutraquox.
Typic Eutraquox
DefinitionofTypicEutraquox
Typic Eutraquox are the Eutraquox that:
1. Do not have a histic epipedon;
2. Do not have, within 125 cm of the mineral soil surface, a
horizon that has more than 5 percent plinthite (by volume);
3. Do not have, directly below an epipedon, a horizon 10 cm
or more thick that has 50 percent or more chroma of 3 or more;
and
4. Have less than 16 kg of organic carbon per m2
to a depth
of 100 cm, exclusive of surface litter.
Description of Subgroups
Typic Eutraquox.—The central concept or Typic subgroup
of Acraquox is fixed on soils that do not have a histic epipedon
and have dominantly low chroma in a layer 10 cm or more
thick that is directly below an epipedon. These soils also have
less than 16 kg/m2
organic carbon to a depth of 100 cm and
less than 5 percent plinthite in all horizons within a depth of
125 cm. They are not known to occur in the United States.
Aeric Eutraquox.—These soils have chroma dominantly of
3 or more in a layer 10 cm or more thick that is directly below
an epipedon. Aeric Eutraquox are considered intergrades
between Eutraquox and Eutrudox or Eutroperox. They are not
known to occur in the United States.
Histic Eutraquox.—These soils have a histic epipedon.
They commonly are wet much of the year and are among the
wettest of the soils in this great group. Histic Eutraquox are not
known to occur in the United States.
Humic Eutraquox.—These soils are like Typic Eutraquox,
but they have 16 kg or more organic carbon per m2
within 100
cm of the mineral soil surface. These soils are not known to
occur in the United States.
Plinthic Eutraquox.—These soils have 5 percent or more
(by volume) plinthite in one or more horizons within 125 cm of
the mineral soil surface. They are not known to occur in the
United States.
Oxisols 661
Haplaquox
These are the Aquox that have low base status in one or
more subhorizons of the oxic or kandic horizon. They do not
have plinthite that forms a continuous phase within 125 cm of
the mineral soil surface and do not have both a very low
apparent ECEC and a pH value (1N KCl) of 5.0 or more in
some part of the oxic or kandic horizon.
Definition
Haplaquox are the Aquox that:
1. Have 35 percent or less base saturation (by NH4
OAc) in
some or all parts within 125 cm of the mineral soil surface;
2. Do not have plinthite that forms a continuous phase
within 125 cm of the mineral soil surface; and
3. Do not have an apparent ECEC of less than 1.50 cmol(+)
per kg clay and a pH value (1N KCl) of 5.0 or more in some
part of an oxic or kandic horizon within 150 cm of the mineral
soil surface.
Key to Subgroups
EADA. Haplaquox that have a histic epipedon.
Histic Haplaquox
EADB. Other Haplaquox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface.
Plinthic Haplaquox
EADC. Other Haplaquox that have, directly below an
epipedon, a horizon 10 cm or more thick that has 50 percent or
more chroma of 3 or more.
Aeric Haplaquox
EADD. Other Haplaquox that have 16 kg/m2
or more organic
carbon between the mineral soil surface and a depth of 100 cm.
Humic Haplaquox
EADE. Other Haplaquox.
Typic Haplaquox
Definition of Typic Haplaquox
Typic Haplaquox are the Haplaquox that:
1. Do not have a histic epipedon;
2. Do not have, within 125 cm of the mineral soil surface, a
horizon that has more than 5 percent plinthite (by volume);
3. Do not have, directly below an epipedon, a horizon 10 cm
or more thick that has 50 percent or more chroma of 3 or more;
and
4. Have less than 16 kg of organic carbon per m2
to a depth
of 1 m, exclusive of surface litter.
Description of Subgroups
Typic Haplaquox.—The central concept or Typic subgroup of
Haplaquox is fixed on soils that do not have a histic epipedon
and have dominantly low chroma in a layer 10 cm or more thick
that is directly below an epipedon. These soils also have less
than 16 kg/m2
organic carbon to a depth of 100 cm and less than
5 percent plinthite in all horizons within a depth of 125 cm. They
are not known to occur in the United States.
Aeric Haplaquox.—These soils have chroma dominantly of
3 or more in a layer 10 cm or more thick that is directly below
an epipedon. Aeric Haplaquox are considered intergrades
between Haplaquox and Hapludox or Haploperox. They are not
known to occur in the United States.
Histic Haplaquox.—These soils have a histic epipedon.
They commonly are wet much of the year and are among the
wettest of the soils in this great group. Histic Haplaquox are
not known to occur in the United States.
Humic Haplaquox.—These soils are like Typic Haplaquox,
but they have 16 kg or more organic carbon per m2
within 100
cm of the mineral soil surface. They are of very small extent in
Puerto Rico and generally are forested.
Plinthic Haplaquox.—These soils have 5 percent or more
(by volume) plinthite in one or more horizons within 125 cm of
the mineral soil surface. They are not known to occur in the
United States.
Plinthaquox
This great group is provided for pedons of Aquox that have
continuous plinthite within 125 cm of the mineral soil surface
and an apparent ECEC of more than 1.50 cmol(+) per kg clay
or a pH value (1N KCl) of 5.0 or more in some part of an oxic
or kandic horizon within 150 cm of the mineral soil surface.
Only small areas of Plinthaquox have been observed, and no
data have been made available for study.
Definition
Plinthaquox are the Aquox that:
1. Have plinthite that forms a continuous phase within 125
cm of the mineral soil surface; and
2. Do not have an apparent ECEC of less than 1.50 cmol(+)
per kg clay and a pH value (1N KCl) of 5.0 or more in some
part of an oxic or kandic horizon within 150 cm of the mineral
soil surface.
Key to Subgroups
EABA. Plintaquox that have, directly below an epipedon, a
horizon 10 cm or more thick that has 50 percent or more
chroma of 3 or more.
Aeric Plinthaquox
EABB. Other Plinthaquox.
Typic Plinthaquox
662 Soil Taxonomy
DefinitionofTypicPlinthaquox
Typic Plinthaquox are the Plinthaquox that, directly below an
epipedon, do not have a horizon 10 cm or more thick that has 50
percent or more chroma of 3 or more.
Description of Subgroups
Typic Plinthaquox.—The central concept or Typic
subgroup of Haplaquox is fixed on soils that have dominantly
low chroma in a layer 10 cm or more thick that is directly below
an epipedon. These soils are not known to occur in the United
States.
Aeric Plinthaquox.—These soils have chroma dominantly
of 3 or more in a layer 10 cm or more thick that is directly
below an epipedon. They are not known to occur in the United
States.
Perox
Perox are well drained Oxisols with a perudic soil moisture
regime. Clearing and burning are difficult because of
atmospheric wetness. Curing many seed crops and storing
produce also are difficult. There are no large areas of the
perudic soil moisture regime, but areas of this regime appear
distinctive enough to show and identify on some small-scale
soil maps.
Definition
Perox are the Oxisols that have a perudic soil moisture
regime.
Key to Great Groups
EDA. Perox that have a sombric horizon within 150 cm of
the mineral soil surface.
Sombriperox,p.671
EDB. Other Perox that have, in one or more subhorizons of
an oxic or kandic horizon within 150 cm of the mineral soil
surface, an apparent ECEC of less than 1.50 cmol(+) per kg
clay and a pH value (1N KCl) of 5.0 or more.
Acroperox, p. 662
EDC. Other Perox that have a base saturation (by NH4
OAc)
of 35 percent or more in all horizons within 125 cm of the
mineral soil surface.
Eutroperox, p. 664
EDD. Other Perox that have a kandic horizon that has its
upper boundary within 150 cm of the mineral soil surface.
Kandiperox, p. 668
EDE. OtherPerox.
Haploperox, p. 666
Acroperox
These are the Perox that do not have a sombric horizon within
150 cm of the mineral soil surface and have, in all subhorizons of
an oxic or kandic horizon within 150 cm of the mineral soil
surface, a very low effective cation-exchange value and a pH
value (1N KCl) of 5.0 or more.
Definition
Acroperox are the Perox that:
1. Have an apparent ECEC of less than 1.50 cmol(+) per kg
clay and a pH value (1N KCl) of 5.0 or more in some part of an
oxic or kandic horizon within 150 cm of the mineral soil surface;
and
2. Do not have a sombric horizon within 150 cm of the mineral
soil surface.
KeytoSubgroups
EDBA. Acroperox that have, within 125 cm of the mineral soil
surface, both:
1. A petroferric contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Petroferric Acroperox
EDBB. Other Acroperox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Acroperox
EDBC. Other Acroperox that have, within 125 cm of the
mineral soil surface, both:
1. A lithic contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Lithic Acroperox
EDBD. Other Acroperox that have a lithic contact within 125
cm of the mineral soil surface.
Lithic Acroperox
EDBE. Other Acroperox that have a delta pH (KCl pH minus
1:1 water pH) with a 0 or net positive charge in a layer 18 cm
or more thick within 125 cm of the mineral soil surface.
Anionic Acroperox
EDBF. Other Acroperox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface.
Plinthic Acroperox
Oxisols 663
EDBG. Other Acroperox that have, in one or more horizons
within 125 cm of the mineral soil surface, redox depletions with a
color value, moist, of 4 or more and chroma of 2 or less and also
aquic conditions for some time in normal years (or artificial
drainage).
Aquic Acroperox
EDBH. Other Acroperox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. In all horizons at a depth between 25 and 125 cm from
the mineral soil surface, more than 50 percent colors that
have both of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less.
Humic Rhodic Acroperox
EDBI. Other Acroperox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. 50 percent or more hue of 7.5YR or yellower and a
color value, moist, of 6 or more at a depth between 25 and
125 cm from the mineral soil surface.
Humic Xanthic Acroperox
EDBJ. Other Acroperox that have 16 kg/m2
or more organic
carbon between the mineral soil surface and a depth of 100 cm.
Humic Acroperox
EDBK. Other Acroperox that have, in all horizons at a depth
between 25 and 125 cm from the mineral soil surface, more
than 50 percent colors that have both of the following:
1. Hue of 2.5YR or redder; and
2. A value, moist, of 3 or less.
Rhodic Acroperox
EDBL. Other Acroperox that have 50 percent or more hue of
7.5YR or yellower and a color value, moist, of 6 or more at a
depth between 25 and 125 cm from the mineral soil surface.
Xanthic Acroperox
EDBM. Other Acroperox.
Typic Acroperox
Definition of Typic Acroperox
Typic Acroperox are the Acroperox that:
1. Have neither a petroferric nor a lithic contact within 125
cm of the mineral soil surface;
2. Have a delta pH (KCl pH minus 1:1 water pH) with a net
negative charge in all parts within 125 cm of the mineral soil
surface;
3. Do not have, within 125 cm of the mineral soil surface, a
horizon that has more than 5 percent plinthite (by volume);
4. Do not have, in any horizon within 125 cm of the mineral
soil surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less and also aquic conditions;
5. Have less than 16 kg of organic carbon per m2
to a depth
of 1 m, exclusive of surface litter; and
6. Have, in some horizon at a depth between 25 and 125 cm
from the mineral soil surface, 50 percent or less colors that
have both of the following:
a. Hue of 2.5YR or redder and a color value, moist, of 3 or
less; and
b. Hue of 7.5YR or yellower and a color value, moist, of 6
or more.
Description of Subgroups
Typic Acroperox.—The central concept or Typic subgroup
of Acroperox is fixed on soils that do not have a petroferric
contact, a lithic contact, or redox depletions with a color value,
moist, of 4 or more and chroma of 2 or less within 125 cm of
the mineral soil surface and also do not have aquic conditions
for some time in normal years. These soils have less than 16
kg/m2
organic carbon to a depth of 100 cm and less than 5
percent plinthite in all horizons within a depth of 125 cm.
Their colors are reddish, but the soils do not have very dark
reddish colors throughout the layers between depths of 25 and
125 cm. These soils are not known to occur in the United
States.
Anionic Acroperox.—These soils have a delta pH (KCl pH
minus 1:1 water pH) with a 0 or net positive charge in a layer
18 cm or more thick within 125 cm of the mineral soil surface.
The soils are of very small extent and are known to occur only
in Hawaii in the United States.
Aquic Acroperox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). Aquic Acroperox are considered
intergrades between Acroperox and Acraquox. They are not
known to occur in the United States.
Aquic Lithic Acroperox.—These soils have, within 125 cm
of the mineral soil surface, both a lithic contact and redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). The soils are not known to occur
in the United States.
Aquic Petroferric Acroperox.—These soils have, within 125
cm of the mineral soil surface, both a petroferric contact and
redox depletions with a color value, moist, of 4 or more and
664 Soil Taxonomy
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage). The soils are not known to
occur in the United States.
Humic Acroperox.—These soils are like Typic Acroperox,
but they have 16 kg or more organic carbon per m2
within 100
cm of the mineral soil surface. They are not known to occur in
the United States.
Humic Rhodic Acroperox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, more than 50 percent colors that have hue of
2.5YR or redder and a value, moist, of 3 or less. They also
have 16 kg or more organic carbon per m2
within 100 cm of the
mineral soil surface. These soils are not known to occur in the
United States.
Humic Xanthic Acroperox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, more than 50 percent colors that have hue of
7.5YR or yellower and value, moist, of 6 or more. They also
have 16 kg or more organic carbon per m2
within 100 cm of the
mineral soil surface. These soils are not known to occur in the
United States.
Lithic Acroperox.—These soils have a lithic contact within
125 cm of the mineral soil surface. They are not known to
occur in the United States.
Petroferric Acroperox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
Plinthic Acroperox.—These soils have 5 percent or more
(by volume) plinthite in one or more horizons within 125 cm of
the mineral soil surface. They are not known to occur in the
United States.
Rhodic Acroperox.—These soils are like Typic Acroperox,
but they have, in all horizons at a depth between 25 and 125
cm from the mineral soil surface, more than 50 percent colors
that have hue of 2.5YR or redder and a value, moist, of 3 or
less. The soils are not known to occur in the United States.
Xanthic Acroperox.—These soils are like Typic Acroperox,
but they have hue of 7.5YR or yellower and a color value,
moist, of 6 or more in all horizons at a depth between 25 and
125 cm from the mineral soil surface. The soils are not known
to occur in the United States.
Eutroperox
These are the Perox that have a base saturation (by NH4
OAc)
of 35 percent or more in all horizons within 125 cm of the mineral
soil surface. They do not have a sombric horizon within 150 cm
of the mineral soil surface and have, in all subhorizons of an oxic
or kandic horizon within 150 cm of the mineral soil surface, an
apparent ECEC of 1.50 or more cmol(+) per kg clay or a pH value
(1N KCl) of less than 5.0.
Definition
Eutroperox are the Perox that:
1. Have more than 35 percent base saturation (by NH4
OAc) in
all parts within 125 cm of the mineral soil surface;
2. Do not have a sombric horizon within 150 cm of the mineral
soil surface; and
3. Do not have an apparent ECEC of less than 1.50 cmol(+)
per kg clay and a pH value (1N KCl) of 5.0 or more in some part
of an oxic or kandic horizon within 150 cm of the mineral soil
surface.
KeytoSubgroups
EDCA. Eutroperox that have, within 125 cm of the mineral soil
surface, both:
1. A petroferric contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Petroferric Eutroperox
EDCB. Other Eutroperox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Eutroperox
EDCC. Other Eutroperox that have, within 125 cm of the
mineral soil surface, both:
1. A lithic contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Lithic Eutroperox
EDCD. Other Eutroperox that have a lithic contact within
125 cm of the mineral soil surface.
Lithic Eutroperox
EDCE. Other Eutroperox that have, in one or more horizons
within 125 cm of the mineral soil surface, both:
1. 5 percent or more (by volume) plinthite; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Plinthaquic Eutroperox
EDCF. Other Eutroperox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface.
Plinthic Eutroperox
EDCG. Other Eutroperox that have, in one or more horizons
within 125 cm of the mineral soil surface, redox depletions
with a color value, moist, of 4 or more and chroma of 2 or less
Oxisols 665
and also aquic conditions for some time in normal years (or
artificial drainage).
AquicEutroperox
EDCH. Other Eutroperox that have a kandic horizon that has
its upper boundary within 150 cm of the mineral soil surface.
Kandiudalfic Eutroperox
EDCI. Other Eutroperox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. An oxic horizon that has its lower boundary within 125
cm of the mineral soil surface.
Humic Inceptic Eutroperox
EDCJ. Other Eutroperox that have an oxic horizon that has
its lower boundary within 125 cm of the mineral soil surface.
Inceptic Eutroperox
EDCK. Other Eutroperox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. In all horizons at a depth between 25 and 125 cm from
the mineral soil surface, more than 50 percent colors that
have both of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less.
Humic Rhodic Eutroperox
EDCL. Other Eutroperox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. 50 percent or more hue of 7.5YR or yellower and a
color value, moist, of 6 or more at a depth between 25 and
125 cm from the mineral soil surface.
Humic Xanthic Eutroperox
EDCM. Other Eutroperox that have 16 kg/m2
or more
organic carbon between the mineral soil surface and a depth of
100 cm.
Humic Eutroperox
EDCN. Other Eutroperox that have, in all horizons at a
depth between 25 and 125 cm from the mineral soil surface,
more than 50 percent colors that have both of the following:
1. Hue of 2.5YR or redder; and
2. A value, moist, of 3 or less.
Rhodic Eutroperox
EDCO. Other Eutroperox that have 50 percent or more hue of
7.5YR or yellower and a color value, moist, of 6 or more at a
depth between 25 and 125 cm from the mineral soil surface.
Xanthic Eutroperox
EDCP. Other Eutroperox.
Typic Eutroperox
Definition of Typic Eutroperox
Typic Eutroperox are the Eutroperox that:
1. Have neither a petroferric nor a lithic contact within 125
cm of the mineral soil surface;
2. Do not have, within 125 cm of the mineral soil surface, a
horizon that has more than 5 percent plinthite (by volume);
3. Do not have, in any horizon within 125 cm of the mineral
soil surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less and also aquic conditions;
4. Do not have a kandic horizon with its upper boundary
within 150 cm of the mineral soil surface;
5. Have an oxic horizon with a lower boundary 125 cm or
more from the mineral soil surface;
6. Have less than 16 kg of organic carbon per m2
to a depth
of 1 m, exclusive of surface litter; and
7. Have, in some horizon at a depth between 25 and 125 cm
from the mineral soil surface, 50 percent or less colors that
have both of the following:
a. Hue of 2.5YR or redder and a color value, moist, of 3 or
less; and
b. Hue of 7.5YR or yellower and a color value, moist, of 6
or more.
Description of Subgroups
Typic Eutroperox.—The central concept or Typic subgroup
of Eutroperox is fixed on soils that have a thick oxic horizon.
These soils do not have a petroferric contact, a lithic contact, or
redox depletions with a color value, moist, of 4 or more and
chroma of 2 or less within 125 cm of the mineral soil surface
and also do not have aquic conditions for some time in normal
years. The soils have less than 16 kg/m2
organic carbon to a
depth of 100 cm and less than 5 percent plinthite in all
horizons within a depth of 125 cm. Their colors are reddish,
but the soils do not have very dark reddish colors throughout
the layers between depths of 25 and 125 cm. These soils are not
known to occur in the United States.
Aquic Eutroperox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
666 Soil Taxonomy
years (or artificial drainage). Aquic Eutroperox are considered
intergrades between Eutroperox and Eutraquox. They are not
known to occur in the United States.
Aquic Lithic Eutroperox.—These soils have, within 125
cm of the mineral soil surface, both a lithic contact and redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). The soils are not known to occur
in the United States.
Aquic Petroferric Eutroperox.—These soils have, within
125 cm of the mineral soil surface, both a petroferric contact
and redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage). The soils are not
known to occur in the United States.
Humic Eutroperox.—These soils are like Typic
Eutroperox, but they have 16 kg or more organic carbon per m2
within 100 cm of the mineral soil surface. They are not known
to occur in the United States.
Humic Inceptic Eutroperox.—These soils have an oxic
horizon that has its lower boundary within 125 cm of the
mineral soil surface. They also have 16 kg or more organic
carbon per m2
within 100 cm of the mineral soil surface. These
soils are not known to occur in the United States.
Humic Rhodic Eutroperox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, more than 50 percent colors that have hue of
2.5YR or redder and a value, moist, of 3 or less. They also
have 16 kg or more organic carbon per m2
within 100 cm of the
mineral soil surface. These soils are not known to occur in the
United States.
Humic Xanthic Eutroperox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, colors that have hue of 7.5YR or yellower and
value, moist, of 6 or more. They also have 16 kg or more
organic carbon per m2
within 100 cm of the mineral soil
surface. These soils are not known to occur in the United
States.
Inceptic Eutroperox.—These soils have an oxic horizon
that has its lower boundary within 125 cm of the mineral soil
surface. They are not known to occur in the United States.
Kandiudalfic Eutroperox.—These soils have a kandic
horizon that has its upper boundary within 125 cm of the
mineral soil surface. They are not known to occur in the United
States.
Lithic Eutroperox.—These soils have a lithic contact
within 125 cm of the mineral soil surface. They are not known
to occur in the United States.
Petroferric Eutroperox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
Plinthaquic Eutroperox.—These soils have, within 125 cm of
the mineral soil surface, redox depletions with a color value,
moist, of 4 or more and chroma of 2 or less and also aquic
conditions for some time in normal years (or artificial
drainage). They have 5 percent or more (by volume) plinthite
in one or more horizons within 125 cm of the mineral soil
surface. These soils are not known to occur in the United
States.
Plinthic Eutroperox.—These soils have 5 percent or more
(by volume) plinthite in one or more horizons within 125 cm of
the mineral soil surface. They are not known to occur in the
United States.
Rhodic Eutroperox.—These soils are like Typic
Eutroperox, but they have, in all horizons at a depth between
25 and 125 cm from the mineral soil surface, more than 50
percent colors that have hue of 2.5YR or redder and a value,
moist, of 3 or less. These soils are not known to occur in the
United States.
Xanthic Eutroperox.—These soils are like Typic Eutroperox,
but they have hue of 7.5YR or yellower and a color value, moist,
of 6 or more in all horizons at a depth between 25 and 125 cm
from the mineral soil surface. The soils are not known to occur in
the United States.
Haploperox
These are the Perox that have, in all subhorizons of an oxic
horizon within 150 cm of the mineral soil surface, an apparent
ECEC of 1.50 or more cmol(+) per kg clay or a pH value (1N
KCl) of less than 5.0. They also have a base saturation (by
NH4
OAc) of less than 35 percent in some horizon within 125
cm of the mineral soil surface and do not have a kandic or
sombric horizon that has its upper boundary within 150 cm of
the mineral soil surface. The subsoil has granular structure,
and the epipedons may be either dark or light colored.
Definition
Haploperox are the Perox that:
1. Have 35 percent or less base saturation (by NH4
OAc) in
some or all parts within 125 cm of the mineral soil surface;
2. Do not have a sombric horizon within 150 cm of the
mineral soil surface;
3. Do not have an apparent ECEC of less than 1.50 cmol(+)
per kg clay and a pH value (1N KCl) of 5.0 or more in some
part of an oxic horizon within 150 cm of the mineral soil
surface; and
4. Do not have a kandic horizon that has its upper boundary
within 150 cm of the mineral soil surface.
Key to Subgroups
EDEA. Haploperox that have, within 125 cm of the mineral
soil surface, both:
1. A petroferric contact; and
2. Redox depletions with a color value, moist, of 4 or more
Oxisols 667
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
AquicPetroferricHaploperox
EDEB. Other Haploperox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Haploperox
EDEC. Other Haploperox that have, within 125 cm of the
mineral soil surface, both:
1. A lithic contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Lithic Haploperox
EDED. Other Haploperox that have a lithic contact within
125 cm of the mineral soil surface.
Lithic Haploperox
EDEE. Other Haploperox that have, in one or more horizons
within 125 cm of the mineral soil surface, both:
1. 5 percent or more (by volume) plinthite; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Plinthaquic Haploperox
EDEF. Other Haploperox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface.
Plinthic Haploperox
EDEG. Other Haploperox that have, in one or more horizons
within 125 cm of the mineral soil surface, redox depletions
with a color value, moist, of 4 or more and chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Haploperox
EDEH. Other Haploperox that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Haploperox
EDEI. Other Haploperox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. In all horizons at a depth between 25 and 125 cm from the
mineral soil surface, more than 50 percent colors that have
both of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less.
Humic Rhodic Haploperox
EDEJ. Other Haploperox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. 50 percent or more hue of 7.5YR or yellower and a
color value, moist, of 6 or more at a depth between 25 and
125 cm from the mineral soil surface.
Humic Xanthic Haploperox
EDEK. Other Haploperox that have 16 kg/m2
or more
organic carbon between the mineral soil surface and a depth of
100 cm.
Humic Haploperox
EDEL. Other Haploperox that have, in all horizons at a
depth between 25 and 125 cm from the mineral soil surface,
more than 50 percent colors that have both of the following:
1. Hue of 2.5YR or redder; and
2. A value, moist, of 3 or less.
Rhodic Haploperox
EDEM. Other Haploperox that have 50 percent or more hue
of 7.5YR or yellower and a color value, moist, of 6 or more at a
depth between 25 and 125 cm from the mineral soil surface.
Xanthic Haploperox
EDEN. Other Haploperox.
Typic Haploperox
Definition of Typic Haploperox
Typic Haploperox are the Haploperox that:
1. Have neither a petroferric nor a lithic contact within 125
cm of the mineral soil surface;
2. Do not have, within 125 cm of the mineral soil surface, a
horizon that has more than 5 percent plinthite (by volume);
3. Do not have, in any horizon within 125 cm of the mineral
soil surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less and also aquic conditions;
4. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, a bulk density, in the
fraction less than 2.0 mm in size, of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and acid-oxalate-
668 Soil Taxonomy
extractable aluminum plus 1
/2 acid-oxalate-extractable iron of
more than 1.0 percent;
5. Have less than 16 kg of organic carbon per m2
to a depth
of 1 m, exclusive of surface litter; and
6. Have, in some horizon at a depth between 25 and 125 cm
from the mineral soil surface, 50 percent or less colors that
have both of the following:
a. Hue of 2.5YR or redder and a color value, moist, of 3 or
less; and
b. Hue of 7.5YR or yellower and a color value, moist, of 6
or more.
Description of Subgroups
Typic Haploperox.—The central concept or Typic subgroup
of Haploperox is fixed on soils that do not have a petroferric
contact, a lithic contact, or redox depletions with a color value,
moist, of 4 or more and chroma of 2 or less within 125 cm of
the mineral soil surface and also do not have aquic conditions
for some time in normal years. These soils have less than 16
kg/m2
organic carbon to a depth of 100 cm and have less than 5
percent plinthite in all horizons within a depth of 125 cm.
Their colors are reddish, but the soils do not have very dark
reddish colors throughout the layers between depths of 25 and
125 cm. They do not have a surface mantle or layer in the
upper 75 cm with both a low bulk density and a high content of
weakly crystalline minerals. These soils are not known to occur
in the United States.
Andic Haploperox.—These soils have a surface mantle or
layer in the upper 75 cm with both a low bulk density and a
high content of weakly crystalline minerals. The soils are not
known to occur in the United States.
Aquic Haploperox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). Aquic Haploperox are considered
intergrades between Haploperox and Haplaquox. They are not
known to occur in the United States.
Aquic Lithic Haploperox.—These soils have, within 125
cm of the mineral soil surface, both a lithic contact and redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). The soils are not known to occur
in the United States.
Aquic Petroferric Haploperox.—These soils have, within
125 cm of the mineral soil surface, both a petroferric contact
and redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage). These soils are not
known to occur in the United States.
Humic Haploperox.—These soils are like Typic
Haploperox, but they have 16 kg or more organic carbon per m2
within 100 cm of the mineral soil surface. They are not known to
occur in the United States.
Humic Rhodic Haploperox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, more than 50 percent colors that have hue of
2.5YR or redder and a value, moist, of 3 or less. They also have
16 kg or more organic carbon per m2
within 100 cm of the mineral
soil surface. These soils are not known to occur in the United
States.
Humic Xanthic Haploperox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, colors that have hue of 7.5YR or yellower and
value, moist, of 6 or more. They also have 16 kg or more
organic carbon per m2
within 100 cm of the mineral soil
surface. These soils are not known to occur in the United
States.
Lithic Haploperox.—These soils have a lithic contact
within 125 cm of the mineral soil surface. They are not known
to occur in the United States.
Petroferric Haploperox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
Plinthaquic Haploperox.—These soils have, in one or
more horizons within 125 cm of the mineral soil surface, 5
percent or more (by volume) plinthite, redox depletions with a
color value, moist, of 4 or more and chroma of 2 or less, and
aquic conditions for some time in normal years (or artificial
drainage). The soils are not known to occur in the United
States.
Plinthic Haploperox.—These soils have 5 percent or more
(by volume) plinthite in one or more horizons within 125 cm of
the mineral soil surface. They are not known to occur in the
United States.
Rhodic Haploperox.—These soils are like Typic
Haploperox, but they have, in all horizons at a depth between
25 and 125 cm from the mineral soil surface, more than 50
percent colors that have hue of 2.5YR or redder and a value,
moist, of 3 or less. The soils are not known to occur in the
United States.
Xanthic Haploperox.—These soils are like Typic Haploperox,
but they have hue of 7.5YR or yellower and a color value, moist,
of 6 or more in all horizons at a depth between 25 and 125 cm
from the mineral soil surface. These soils are not known to occur
in the United States.
Kandiperox
These are the clayey Perox that have a kandic horizon that
has its upper boundary within 150 cm of the mineral soil
surface. They do not have a sombric horizon within 150 cm of
the mineral soil surface, but they have, in all subhorizons of a
kandic horizon within 150 cm of the mineral soil surface, an
Oxisols 669
apparent ECEC of 1.50 or more cmol(+) per kg clay or a pH
value (1N KCl) of less than 5.0. They also have a base
saturation (by NH4
OAc) of less than 35 percent in some
horizon within 125 cm of the mineral soil surface. The subsoil
has granular structure, and the epipedons may be either dark
or light colored.
Definition
Kandiperox are the Perox that:
1. Have the upper boundary of a kandic horizon within 150 cm
of the mineral soil surface;
2. Have 35 percent or less base saturation (by NH4
OAc) in
some or all parts within 125 cm of the mineral soil surface;
3. Do not have a sombric horizon within 150 cm of the
mineral soil surface; and
4. Do not have an apparent ECEC of less than 1.50 cmol(+)
per kg clay and a pH value (1N KCl) of 5.0 or more in some
part of a kandic horizon within 150 cm of the mineral soil
surface.
Key to Subgroups
EDDA. Kandiperox that have, within 125 cm of the mineral
soil surface, both:
1. A petroferric contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Petroferric Kandiperox
EDDB. Other Kandiperox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Kandiperox
EDDC. Other Kandiperox that have, within 125 cm of the
mineral soil surface, both:
1. A lithic contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Lithic Kandiperox
EDDD. Other Kandiperox that have a lithic contact within
125 cm of the mineral soil surface.
Lithic Kandiperox
EDDE. Other Kandiperox that have, in one or more horizons
within 125 cm of the mineral soil surface, both:
1. 5 percent or more (by volume) plinthite; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
PlinthaquicKandiperox
EDDF. Other Kandiperox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface.
Plinthic Kandiperox
EDDG. Other Kandiperox that have, in one or more horizons
within 125 cm of the mineral soil surface, redox depletions
with a color value, moist, of 4 or more and chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Kandiperox
EDDH. Other Kandiperox that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Kandiperox
EDDI. Other Kandiperox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. In all horizons at a depth between 25 and 125 cm from
the mineral soil surface, more than 50 percent colors that
have both of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less.
Humic Rhodic Kandiperox
EDDJ. Other Kandiperox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. 50 percent or more hue of 7.5YR or yellower and a
color value, moist, of 6 or more at a depth between 25 and
125 cm from the mineral soil surface.
Humic Xanthic Kandiperox
EDDK. Other Kandiperox that have 16 kg/m2
or more
organic carbon between the mineral soil surface and a depth of
100 cm.
Humic Kandiperox
EDDL. Other Kandiperox that have, in all horizons at a
depth between 25 and 125 cm from the mineral soil surface,
more than 50 percent colors that have both of the following:
1. Hue of 2.5YR or redder; and
670 Soil Taxonomy
2. A value, moist, of 3 or less.
RhodicKandiperox
EDDM. Other Kandiperox that have 50 percent or more hue of
7.5YR or yellower and a color value, moist, of 6 or more at a
depth between 25 and 125 cm from the mineral soil surface.
Xanthic Kandiperox
EDDN. Other Kandiperox.
Typic Kandiperox
Definition of Typic Kandiperox
Typic Kandiperox are the Kandiperox that:
1. Have neither a petroferric nor a lithic contact within 125
cm of the mineral soil surface;
2. Do not have, within 125 cm of the mineral soil surface, a
horizon that has more than 5 percent plinthite (by volume);
3. Do not have, in any horizon within 125 cm of the mineral
soil surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less and also aquic conditions;
4. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, a bulk density, in the
fraction less than 2.0 mm in size, of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and acid-oxalateextractable
aluminum plus 1
/2 acid-oxalate-extractable iron of
more than 1.0 percent;
5. Have less than 16 kg of organic carbon per m2
to a depth
of 1 m, exclusive of surface litter; and
6. Have, in some horizon at a depth between 25 and 125 cm
from the mineral soil surface, 50 percent or less colors that
have both of the following:
a. Hue of 2.5YR or redder and a color value, moist, of 3 or
less; and
b. Hue of 7.5YR or yellower and a color value, moist, of 6
or more.
Description of Subgroups
Typic Kandiperox.—The central concept or Typic
subgroup of Kandiperox is fixed on soils that do not have a
petroferric contact, a lithic contact, or redox depletions with a
color value, moist, of 4 or more and chroma of 2 or less within
125 cm of the mineral soil surface and also do not have aquic
conditions for some time in normal years. These soils have less
than 16 kg/m2
organic carbon to a depth of 100 cm and less
than 5 percent plinthite in all horizons within a depth of 125
cm. Their colors are reddish, but the soils do not have very
dark reddish colors throughout the layers between depths of 25
and 125 cm. They do not have a surface mantle or layer in the
upper 75 cm with both a low bulk density and a high content of
weakly crystalline minerals. These soils are not known to occur
in the United States.
Andic Kandiperox.—These soils have a surface mantle or
layer in the upper 75 cm with both a low bulk density and a
high content of weakly crystalline minerals. The soils are not
known to occur in the United States.
Aquic Kandiperox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). Aquic Kandiperox are considered
intergrades between Kandiperox and Aquox. They are not
known to occur in the United States.
Aquic Lithic Kandiperox.—These soils have, within 125
cm of the mineral soil surface, both a lithic contact and redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). The soils are not known to occur
in the United States.
Aquic Petroferric Kandiperox.—These soils have, within
125 cm of the mineral soil surface, both a petroferric contact
and redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage). The soils are not
known to occur in the United States.
Humic Kandiperox.—These soils are like Typic
Kandiperox, but they have 16 kg or more organic carbon per
m2
within 100 cm of the mineral soil surface. They are not
known to occur in the United States.
Humic Rhodic Kandiperox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, more than 50 percent colors that have hue of
2.5YR or redder and a value, moist, of 3 or less. They also
have 16 kg or more organic carbon per m2
within 100 cm of the
mineral soil surface. These soils are not known to occur in the
United States.
Humic Xanthic Kandiperox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, colors that have hue of 7.5YR or yellower and
value, moist, of 6 or more. They also have 16 kg or more
organic carbon per m2
within 100 cm of the mineral soil
surface. These soils are not known to occur in the United
States.
Lithic Kandiperox.—These soils have a lithic contact
within 125 cm of the mineral soil surface. They are not known
to occur in the United States.
Petroferric Kandiperox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
Plinthaquic Kandiperox.—These soils have, in one or
more horizons within 125 cm of the mineral soil surface, 5
percent or more (by volume) plinthite, redox depletions with a
color value, moist, of 4 or more and chroma of 2 or less, and
Oxisols 671
aquic conditions for some time in normal years (or artificial
drainage). The soils are not known to occur in the United
States.
Plinthic Kandiperox.—These soils have 5 percent or more
(by volume) plinthite in one or more horizons within 125 cm of
the mineral soil surface. They are not known to occur in the
United States.
Rhodic Kandiperox.—These soils are like Typic
Kandiperox, but they have, in all horizons at a depth between
25 and 125 cm from the mineral soil surface, more than 50
percent colors that have hue of 2.5YR or redder and a value,
moist, of 3 or less. The soils are not known to occur in the
United States.
Xanthic Kandiperox.—These soils are like Typic Kandiperox,
but they have hue of 7.5YR or yellower and a color value, moist,
of 6 or more in all horizons at a depth between 25 and 125 cm
from the mineral soil surface. The soils are not known to occur in
the United States.
Sombriperox
These are the Perox that have a sombric horizon. They are not
known to occur in the United States at this time but are expected
to occur in other parts of the world.
Definition
Sombriperox are the Perox that have a sombric horizon within
150 cm of the mineral soil surface.
KeytoSubgroups
EDAA. Sombriperox that have a petroferric contact within 125
cm of the mineral soil surface.
Petroferric Sombriperox
EDAB. Other Sombriperox that have a lithic contact within
125 cm of the mineral soil surface.
Lithic Sombriperox
EDAC. Other Sombriperox that have 16 kg/m2
or more
organic carbon between the mineral soil surface and a depth of
100 cm.
Humic Sombriperox
EDAD. Other Sombriperox.
Typic Sombriperox
Definition of Typic Sombriperox
Typic Sombriperox are the Sombriperox that:
1. Have neither a petroferric nor a lithic contact within 125
cm of the mineral soil surface; and
2. Have less than 16 kg of organic carbon per m2
to a depth
of 1 m, exclusive of surface litter.
Description of Subgroups
Typic Sombriperox.—The central concept or Typic
subgroup of Sombriperox is fixed on soils that do not have
a petroferric or lithic contact within 125 cm of the mineral
soil surface. These soils also have less than 16 kg/m2
organic
carbon to a depth of 100 cm. They are not known to occur in
the United States.
Humic Sombriperox.—These soils are like Typic
Sombriperox, but they have 16 kg or more organic carbon per
m2
within 100 cm of the mineral soil surface. They are not
known to occur in the United States.
Lithic Sombriperox.—These soils have a lithic contact
within 125 cm of the mineral soil surface. They are not known
to occur in the United States.
Petroferric Sombriperox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
Torrox
These are Oxisols of arid regions. They have an aridic
moisture regime, and many of them have a higher base
saturation than other Oxisols. Torrox are excellent soils for a
variety of crops if irrigation water and fertilizer are applied.
These soils are known to occur only Hawaii in the United
States and perhaps in some areas in Australia.
Definition
Torrox are the Oxisols that have an aridic (torric) moisture
regime.
Key to Great Groups
EBA. Torrox that have, in one or more subhorizons of an
oxic or kandic horizon within 150 cm of the mineral soil
surface, an apparent ECEC of less than 1.50 cmol(+) per kg
clay and a pH value (1N KCl) of 5.0 or more.
Acrotorrox, p. 671
EBB. Other Torrox that have a base saturation (by NH4
OAc)
of 35 percent or more in all horizons within 125 cm of the
mineral soil surface.
Eutrotorrox, p. 672
EBC. OtherTorrox.
Haplotorrox, p. 672
Acrotorrox
These are the Torrox that have, in all subhorizons of an oxic
or kandic horizon within 150 cm of the mineral soil surface, a
very low effective cation-exchange value and a pH value (1N
KCl) of 5.0 or more.
672 Soil Taxonomy
Definition
Acrotorrox are the Torrox that have an apparent ECEC of less
than 1.50 cmol(+) per kg clay and a pH value (1N KCl) of 5.0 or
more in some part of an oxic or kandic horizon within 150 cm of
the mineral soil surface.
KeytoSubgroups
EBAA. Acrotorrox that have a petroferric contact within 125
cm of the mineral soil surface.
Petroferric Acrotorrox
EBAB. Other Acrotorrox that have a lithic contact within
125 cm of the mineral soil surface.
Lithic Acrotorrox
EBAC. Other Acrotorrox.
Typic Acrotorrox
Definition of Typic Acrotorrox
Typic Acrotorrox are the Acrotorrox that have neither a
petroferric nor a lithic contact within 125 cm of the mineral
soil surface.
Description of Subgroups
Typic Acrotorrox.—The central concept or Typic subgroup
of Acrotorrox is fixed on soils that do not have a petroferric or
lithic contact within 125 cm of the mineral soil surface. These
soils are not known to occur in the United States.
Lithic Acrotorrox.—These soils have a lithic contact
within 125 cm of the mineral soil surface. They are not known
to occur in the United States.
Petroferric Acrotorrox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
Eutrotorrox
These are the Torrox that have more than 35 percent base
saturation (by NH4
OAc) in all parts within 125 cm of the
mineral soil surface. They also have, in some subhorizon of an
oxic or kandic horizon within 150 cm of the mineral soil
surface, an effective cation-exchange value higher than very
low or a pH value (1N KCl) of less than 5.0. These soils occur
mainly in Hawaii, where they are used for irrigated crops.
Definition
Eutrotorrox are the Torrox that:
1. Have more than 35 percent base saturation (by NH4
OAc)
in all parts within 125 cm of the mineral soil surface; and
2. Do not have an apparent ECEC of less than 1.50 cmol(+)
per kg clay and a pH value (1N KCl) of 5.0 or more in some
part of an oxic or kandic horizon within 150 cm of the mineral
soil surface.
KeytoSubgroups
EBBA. Eutrotorrox that have a petroferric contact within 125
cm of the mineral soil surface.
Petroferric Eutrotorrox
EBBB. Other Eutrotorrox that have a lithic contact within
125 cm of the mineral soil surface.
Lithic Eutrotorrox
EBBC. Other Eutrotorrox.
Typic Eutrotorrox
Definition of Typic Eutrotorrox
Typic Eutrotorrox are the Eutrotorrox that have neither a
petroferric nor a lithic contact within 125 cm of the mineral
soil surface.
Description of Subgroups
Typic Eutrotorrox.—The central concept or Typic
subgroup of Eutrotorrox is fixed on soils that do not have a
petroferric or lithic contact within 125 cm of the mineral soil
surface. These soils are not known to occur in the United
States.
Lithic Eutrotorrox.—These soils have a lithic contact
within 125 cm of the mineral soil surface. They are not known
to occur in the United States.
Petroferric Eutrotorrox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
Haplotorrox
These are the Torrox that have 35 percent or less base
saturation (by NH4
OAc) in some part within 125 cm of the
mineral soil surface. They also have, in some subhorizon of an
oxic or kandic horizon within 150 cm of the mineral soil
surface, an effective cation-exchange value higher than very
low or a pH value (1N KCl) of less than 5.0.
Definition
Haplotorrox are the Torrox that:
1. Have 35 percent or less base saturation (by NH4
OAc) in
some or all parts within 125 cm of the mineral soil surface;
and
2. Do not have an apparent ECEC of less than 1.50 cmol(+)
per kg clay and a pH value (1N KCl) of 5.0 or more in some
part of an oxic or kandic horizon within 150 cm of the mineral
soil surface.
Key to Subgroups
EBCA. Haplotorrox that have a petroferric contact within
125 cm of the mineral soil surface.
Petroferric Haplotorrox
Oxisols 673
EBCB. Other Haplotorrox that have a lithic contact within 125
cm of the mineral soil surface.
Lithic Haplotorrox
EBCC. Other Haplotorrox.
Typic Haplotorrox
DefinitionofTypicHaplotorrox
Typic Haplotorrox are the Haplotorrox that have neither a
petroferric nor a lithic contact within 125 cm of the mineral
soil surface.
Description of Subgroups
Typic Haplotorrox.—The central concept or Typic
subgroup of Haplotorrox is fixed on soils that do not have a
petroferric or lithic contact within 125 cm of the mineral soil
surface. These soils are not known to occur in the United
States.
Lithic Haplotorrox.—These soils have a lithic contact
within 125 cm of the mineral soil surface. They are not known
to occur in the United States.
Petroferric Haplotorrox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
Udox
Udox are well drained Oxisols with a udic soil moisture
regime. They are moist because of natural rainfall in normal
years and are dry in some parts for less than 90 days, a period
that is short enough for rain-fed crops to be grown
continuously in normal years. There are fewer than 90 days
during which crops are not planted. In local terms there are 1
to 3 months that considered “dry” in normal years. Udox are an
extensive suborder, occurring mostly in South America and in
parts of Africa and Asia.
Definition
Udox are the Oxisols that have a udic moisture regime.
Key to Great Groups
EEA. Udox that have a sombric horizon within 150 cm of the
mineral soil surface.
Sombriudox, p. 682
EEB. Other Udox that have, in one or more subhorizons of
an oxic or kandic horizon within 150 cm of the mineral soil
surface, an apparent ECEC of less than 1.50 cmol(+) per kg
clay and a pH value (1N KCl) of 5.0 or more.
Acrudox, p. 673
EEC. Other Udox that have a base saturation (by NH4
OAc) of
35 percent or more in all horizons within 125 cm of the mineral
soil surface.
Eutrudox, p. 675
EED. Other Udox that have a kandic horizon that has its upper
boundary within 150 cm of the mineral soil surface.
Kandiudox, p. 680
EEE. OtherUdox.
Hapludox, p. 678
Acrudox
These are Udox that have very low CEC values in the
subsoil and that do not have a sombric horizon within 150 cm of
the mineral soil surface. Frequent but small applications of
fertilizer and lime are required. Because the CEC is low, the
amount of exchangeable aluminum in the subsoil is low. This
deficiency can be corrected by leaching basic cations from lime
and fertilizer.
Definition
Acrudox are the Udox that:
1. Have an apparent ECEC of less than 1.50 cmol(+) per kg
clay and a pH value (1N KCl) of 5.0 or more in some part of an
oxic or kandic horizon within 150 cm of the mineral soil surface;
and
2. Do not have a sombric horizon within 150 cm of the mineral
soil surface.
KeytoSubgroups
EEBA. Acrudox that have, within 125 cm of the mineral soil
surface, both:
1. A petroferric contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Petroferric Acrudox
EEBB. Other Acrudox that have a petroferric contact within
125 cm of the mineral soil surface.
Petroferric Acrudox
EEBC. Other Acrudox that have, within 125 cm of the
mineral soil surface, both:
1. A lithic contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Lithic Acrudox
674 Soil Taxonomy
EEBD. Other Acrudox that have a lithic contact within 125 cm
of the mineral soil surface.
LithicAcrudox
EEBE. Other Acrudox that have, within 125 cm of the
mineral soil surface, both:
1. A delta pH (KCl pH minus 1:1 water pH) with a 0 or
net positive charge in a layer 18 cm or more thick; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Anionic Aquic Acrudox
EEBF. Other Acrudox that have a delta pH (KCl pH minus
1:1 water pH) with a 0 or net positive charge in a layer 18 cm
or more thick within 125 cm of the mineral soil surface.
Anionic Acrudox
EEBG. Other Acrudox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface.
Plinthic Acrudox
EEBH. Other Acrudox that have, in one or more horizons
within 125 cm of the mineral soil surface, redox depletions
with a color value, moist, of 4 or more and chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Acrudox
EEBI. Other Acrudox that have a base saturation (by
NH4
OAc) of 35 percent or more in all horizons within 125 cm
of the mineral soil surface.
Eutric Acrudox
EEBJ. Other Acrudox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. In all horizons at a depth between 25 and 125 cm from
the mineral soil surface, more than 50 percent colors that
have both of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less.
Humic Rhodic Acrudox
EEBK. Other Acrudox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. 50 percent or more hue of 7.5YR or yellower and a
color value, moist, of 6 or more at a depth between 25 and 125
cm from the mineral soil surface.
HumicXanthicAcrudox
EEBL. Other Acrudox that have 16 kg/m2
or more organic
carbon between the mineral soil surface and a depth of 100 cm.
Humic Acrudox
EEBM. Other Acrudox that have, in all horizons at a depth
between 25 and 125 cm from the mineral soil surface, more
than 50 percent colors that have both of the following:
1. Hue of 2.5YR or redder; and
2. A value, moist, of 3 or less.
Rhodic Acrudox
EEBN. Other Acrudox that have 50 percent or more hue
of 7.5YR or yellower and a color value, moist, of 6 or more
at a depth between 25 and 125 cm from the mineral soil
surface.
Xanthic Acrudox
EEBO. Other Acrudox.
Typic Acrudox
Definition of Typic Acrudox
Typic Acrudox are the Acrudox that:
1. Have neither a petroferric nor a lithic contact within 125
cm of the mineral soil surface;
2. Have a delta pH (KCl pH minus 1:1 water pH) with a net
negative charge in all parts within 125 cm of the mineral soil
surface;
3. Do not have, within 125 cm of the mineral soil surface, a
horizon that has more than 5 percent plinthite (by volume);
4. Do not have, in any horizon within 125 cm of the mineral
soil surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less and also aquic conditions;
5. Have 35 percent or less base saturation (by NH4
OAc) in
some subhorizon within 125 cm of the mineral soil surface;
6. Have less than 16 kg of organic carbon per m2
to a depth
of 1 m, exclusive of surface litter; and
7. Have, in some horizon at a depth between 25 and 125 cm
from the mineral soil surface, 50 percent or less colors that
have both of the following:
a. Hue of 2.5YR or redder and a color value, moist, of 3 or
less; and
b. Hue of 7.5YR or yellower and a color value, moist, of 6
or more.
Oxisols 675
Description of Subgroups
Typic Acrudox.—The central concept or Typic subgroup of
Acrudox is fixed on soils that do not have a petroferric contact,
a lithic contact, or redox depletions with a color value, moist, of 4
or more and chroma of 2 or less within 125 cm of the mineral soil
surface and also do not have aquic conditions for some time in
normal years. These soils have less than 16 kg/m2
organic
carbon to a depth of 100 cm and have less than 5 percent
plinthite in all horizons within a depth of 125 cm. Their colors are
reddish, but the soils do not have very dark reddish colors
throughout the layers between depths of 25 and 125 cm. These
soils are of small extent in Hawaii.
Anionic Acrudox.—These soils have a delta pH (KCl pH
minus 1:1 water pH) with a 0 or net positive charge in a layer
18 cm or more thick within 125 cm of the mineral soil surface.
They are of small extent and are known to occur only in
Hawaii and Puerto Rico in the United States.
Anionic Aquic Acrudox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). They have a delta pH (KCl pH
minus 1:1 water pH) with a 0 or net positive charge in a layer
18 cm or more thick within 125 cm of the mineral soil surface.
These soils are not known to occur in the United States.
Aquic Acrudox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). Aquic Acrudox are considered
intergrades between Acrudox and Acraquox. They are not
known to occur in the United States.
Aquic Lithic Acrudox.—These soils have, within 125 cm
of the mineral soil surface, both a lithic contact and redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). The soils are not known to occur
in the United States.
Aquic Petroferric Acrudox.—These soils have, within 125
cm of the mineral soil surface, both a petroferric contact and
redox depletions with a color value, moist, of 4 or more and
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage). The soils are not known
to occur in the United States.
Eutric Acrudox.—These soils have a base saturation (by
NH4
OAc) of 35 percent or more in all horizons within 125 cm
of the mineral soil surface. The soils are not known to occur in
the United States.
Humic Acrudox.—These soils are like Typic Acrudox, but
they have 16 kg or more organic carbon per m2
within 100 cm
of the mineral soil surface. They are not known to occur in the
United States.
Humic Rhodic Acrudox.—These soils have, in all horizons at
a depth between 25 and 125 cm from the mineral soil surface,
more than 50 percent colors that have hue of 2.5YR or redder
and a value, moist, of 3 or less. They also have 16 kg or more
organic carbon per m2
within 100 cm of the mineral soil surface.
These soils are not known to occur in the United
States.
Humic Xanthic Acrudox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, colors that have hue of 7.5YR or yellower and
value, moist, of 6 or more. They also have 16 kg or more
organic carbon per m2
within 100 cm of the mineral soil
surface. These soils are not known to occur in the United
States.
Lithic Acrudox.—These soils have a lithic contact within 125
cm of the mineral soil surface. They are not known to occur in
the United States.
Petroferric Acrudox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
Plinthic Acrudox.—These soils have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface. They are of small extent in Hawaii.
Rhodic Acrudox.—These soils are like Typic Acrudox, but
they have, in all horizons at a depth between 25 and 125 cm
from the mineral soil surface, more than 50 percent colors that
have hue of 2.5YR or redder and a value, moist, of 3 or less.
The soils are not known to occur in the United States.
Xanthic Acrudox.—These soils are like Typic Acrudox, but
they have hue of 7.5YR or yellower and a color value, moist, of
6 or more in all horizons at a depth between 25 and 125 cm
from the mineral soil surface. The soils are not known to occur
in the United States.
Eutrudox
These are the Udox with high base saturation throughout the
profile. They do not have a sombric horizon within 150 cm of the
mineral soil surface. They have, in all subhorizons of an oxic or
kandic horizon within 150 cm of the mineral soil surface, an
apparent ECEC of 1.50 cmol(+) per kg clay or more or a pH value
(1N KCl) of less than 5.0. These soils are highly valued by
shifting cultivators and are most common in areas near basic
geologic rock.
Definition
Eutrudox are the Udox that:
1. Have more than 35 percent base saturation (by NH4
OAc) in
all parts within 125 cm of the mineral soil surface;
2. Do not have a sombric horizon within 150 cm of the mineral
soil surface; and
3. Do not have an apparent ECEC of less than 1.50 cmol(+)
per kg clay and a pH value (1N KCl) of 5.0 or more in some part
of an oxic or kandic horizon within 150 cm of the mineral soil
surface.
676 Soil Taxonomy
KeytoSubgroups
EECA. Eutrudox that have, within 125 cm of the mineral soil
surface, both:
1. A petroferric contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Petroferric Eutrudox
EECB. Other Eutrudox that have a petroferric contact within
125 cm of the mineral soil surface.
Petroferric Eutrudox
EECC. Other Eutrudox that have, within 125 cm of the
mineral soil surface, both:
1. A lithic contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Lithic Eutrudox
EECD. Other Eutrudox that have a lithic contact within 125
cm of the mineral soil surface.
Lithic Eutrudox
EECE. Other Eutrudox that have, in one or more horizons
within 125 cm of the mineral soil surface, both:
1. 5 percent or more (by volume) plinthite; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Plinthaquic Eutrudox
EECF. Other Eutrudox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface.
Plinthic Eutrudox
EECG. Other Eutrudox that have, in one or more horizons
within 125 cm of the mineral soil surface, redox depletions
with a color value, moist, of 4 or more and chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Eutrudox
EECH. Other Eutrudox that have a kandic horizon that has
its upper boundary within 150 cm of the mineral soil surface.
Kandiudalfic Eutrudox
EECI. Other Eutrudox that have both:
1. 16 kg/m2
or more organic carbon between the mineral soil
surface and a depth of 100 cm; and
2. An oxic horizon that has its lower boundary within 125
cm of the mineral soil surface.
HumicIncepticEutrudox
EECJ. Other Eutrudox that have an oxic horizon that has its
lower boundary within 125 cm of the mineral soil surface.
Inceptic Eutrudox
EECK. Other Eutrudox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. In all horizons at a depth between 25 and 125 cm from
the mineral soil surface, more than 50 percent colors that
have both of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less.
Humic Rhodic Eutrudox
EECL. Other Eutrudox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. 50 percent or more hue of 7.5YR or yellower and a
color value, moist, of 6 or more at a depth between 25 and
125 cm from the mineral soil surface.
Humic Xanthic Eutrudox
EECM. Other Eutrudox that have 16 kg/m2
or more organic
carbon between the mineral soil surface and a depth of 100 cm.
Humic Eutrudox
EECN. Other Eutrudox that have, in all horizons at a depth
between 25 and 125 cm from the mineral soil surface, more
than 50 percent colors that have both of the following:
1. Hue of 2.5YR or redder; and
2. A value, moist, of 3 or less.
Rhodic Eutrudox
EECO. Other Eutrudox that have 50 percent or more hue of
7.5YR or yellower and a color value, moist, of 6 or more at a
depth between 25 and 125 cm from the mineral soil surface.
Xanthic Eutrudox
EECP. Other Eutrudox.
Typic Eutrudox
Definition of Typic Eutrudox
Typic Eutrudox are the Eutrudox that:
Oxisols 677
1. Have neither a petroferric nor a lithic contact within 125 cm
of the mineral soil surface;
2. Do not have, within 125 cm of the mineral soil surface, a
horizon that has more than 5 percent plinthite (by volume);
3. Do not have, in any horizon within 125 cm of the mineral soil
surface, redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions;
4. Do not have a kandic horizon with its upper boundary
within 150 cm of the mineral soil surface;
5. Have an oxic horizon with a lower boundary 125 cm or
more from the mineral soil surface;
6. Have less than 16 kg of organic carbon per m2
to a depth
of 1 m, exclusive of surface litter; and
7. Have, in some horizon at a depth between 25 and 125 cm
from the mineral soil surface, 50 percent or less colors that
have both of the following:
a. Hue of 2.5YR or redder and a color value, moist, of 3 or
less; and
b. Hue of 7.5YR or yellower and a color value, moist, of 6
or more.
Description of Subgroups
Typic Eutrudox.—The central concept or Typic subgroup
of Eutrudox is fixed on soils that have a thick oxic horizon.
These soils do not have a petroferric contact, a lithic contact, or
redox depletions with a color value, moist, of 4 or more and
chroma of 2 or less within 125 cm of the mineral soil surface
and also do not have aquic conditions for some time in normal
years. They have less than 16 kg/m2
organic carbon to a depth
of 100 cm and have less than 5 percent plinthite in all horizons
within a depth of 125 cm. Their colors are reddish, but the
soils do not have very dark reddish colors throughout the layers
between depths of 25 and 125 cm. These soils are of small
extent in Hawaii.
Aquic Eutrudox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). Aquic Eutrudox are considered
intergrades between Eutrudox and Eutraquox. They are not
known to occur in the United States.
Aquic Lithic Eutrudox.—These soils have, within 125 cm
of the mineral soil surface, both a lithic contact and redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). The soils are not known to occur
in the United States.
Aquic Petroferric Eutrudox.—These soils have, within
125 cm of the mineral soil surface, both a petroferric contact
and redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some time
in normal years (or artificial drainage). The soils are not known
to occur in the United States.
Humic Eutrudox.—These soils are like Typic Eutrudox, but
they have 16 kg or more organic carbon per m2
within 100 cm
of the mineral soil surface. They are not known to occur in the
United States.
Humic Inceptic Eutrudox.—These soils have an oxic
horizon that has its lower boundary within 125 cm of the
mineral soil surface. They also have 16 kg or more organic
carbon per m2
within 100 cm of the mineral soil surface. These
soils are not known to occur in the United States.
Humic Rhodic Eutrudox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, more than 50 percent colors that have hue of
2.5YR or redder and a value, moist, of 3 or less. They also
have 16 kg or more organic carbon per m2
within 100 cm of the
mineral soil surface. These soils are not known to occur in the
United States.
Humic Xanthic Eutrudox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, colors that have hue of 7.5YR or yellower and
value, moist, of 6 or more. They also have 16 kg or more
organic carbon per m2
within 100 cm of the mineral soil
surface. These soils are not known to occur in the United
States.
Inceptic Eutrudox.—These soils have an oxic horizon that
has its lower boundary within 125 cm of the mineral soil
surface. They are of small extent in Hawaii.
Kandiudalfic Eutrudox.—These soils have a kandic
horizon that has its upper boundary within 125 cm of the
mineral soil surface. They are not known to occur in the United
States.
Lithic Eutrudox.—These soils have a lithic contact within
125 cm of the mineral soil surface. They are of very small
extent, mostly in Puerto Rico.
Petroferric Eutrudox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
Plinthaquic Eutrudox.—These soils have, within 125 cm
of the mineral soil surface, redox depletions with a color value,
moist, of 4 or more and chroma of 2 or less and also aquic
conditions for some time in normal years (or artificial
drainage). They have 5 percent or more (by volume) plinthite
in one or more horizons within 125 cm of the mineral soil
surface. These soils are not known to occur in the United
States.
Plinthic Eutrudox.—These soils have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface. The soils are not known to occur in the
United States.
Rhodic Eutrudox.—These soils are like Typic Eutrudox, but
they have, in all horizons at a depth between 25 and 125 cm from
the mineral soil surface, more than 50 percent colors that have
678 Soil Taxonomy
hue of 2.5YR or redder and a value, moist, of 3 or less. The soils
are not known to occur in the United States.
Xanthic Eutrudox.—These soils are like Typic Eutrudox, but
they have hue of 7.5YR or yellower and a color value, moist, of 6
or more in all horizons at a depth between 25 and 125 cm from
the mineral soil surface. The soils are not known to occur in the
United States.
Hapludox
These are the Udox that do not have a sombric horizon
within 150 cm of the mineral soil surface and have, in all
subhorizons of an oxic horizon within 150 cm of the mineral
soil surface, an apparent ECEC of 1.50 or more cmol(+) per kg
clay or a pH value (1N KCl) of less than 5.0. They also have a
base saturation (by NH4
OAc) of less than 35 percent in some
horizon within 125 cm of the mineral soil surface and do not
have a kandic horizon that has its upper boundary within 150
cm of the mineral soil surface. The subsoil has granular
structure, and the epipedons may be either dark or light
colored. Hapludox commonly are acid, and the subsoil ranges
from dark red to pale yellow. These soils are common in the
uplands of Africa, the central part of Indonesia, and many
other areas.
Definition
Hapludox are the Udox that:
1. Have 35 percent or less base saturation (by NH4
OAc) in
some or all parts within 125 cm of the mineral soil surface;
2. Do not have a sombric horizon within 150 cm of the
mineral soil surface;
3. Do not have an apparent ECEC of less than 1.50 cmol(+)
per kg clay and a pH value (1N KCl) of 5.0 or more in some
part of an oxic horizon within 150 cm of the mineral soil
surface; and
4. Do not have the upper boundary of a kandic horizon
within 150 cm of the mineral soil surface.
Key to Subgroups
EEEA. Hapludox that have, within 125 cm of the mineral
soil surface, both:
1. A petroferric contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Petroferric Hapludox
EEEB. Other Hapludox that have a petroferric contact within
125 cm of the mineral soil surface.
Petroferric Hapludox
EEEC. Other Hapludox that have, within 125 cm of the mineral
soil surface, both:
1. A lithic contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
AquicLithicHapludox
EEED. Other Hapludox that have a lithic contact within 125
cm of the mineral soil surface.
Lithic Hapludox
EEEE. Other Hapludox that have, in one or more horizons
within 125 cm of the mineral soil surface, both:
1. 5 percent or more (by volume) plinthite; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Plinthaquic Hapludox
EEEF. Other Hapludox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface.
Plinthic Hapludox
EEEG. Other Hapludox that have, in one or more horizons
within 125 cm of the mineral soil surface, redox depletions
with a color value, moist, of 4 or more and chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Hapludox
EEEH. Other Hapludox that have an oxic horizon that has its
lower boundary within 125 cm of the mineral soil surface.
Inceptic Hapludox
EEEI. Other Hapludox that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Hapludox
EEEJ. Other Hapludox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. In all horizons at a depth between 25 and 125 cm from
the mineral soil surface, more than 50 percent colors that
have both of the following:
Oxisols 679
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less.
Humic Rhodic Hapludox
EEEK. Other Hapludox that have both:
1. 16 kg/m2
or more organic carbon between the mineral soil
surface and a depth of 100 cm; and
2. 50 percent or more hue of 7.5YR or yellower and a color
value, moist, of 6 or more at a depth between 25 and 125 cm
from the mineral soil surface.
Humic Xanthic Hapludox
EEEL. Other Hapludox that have 16 kg/m2
or more organic
carbon between the mineral soil surface and a depth of 100 cm.
Humic Hapludox
EEEM. Other Hapludox that have, in all horizons at a depth
between 25 and 125 cm from the mineral soil surface, more
than 50 percent colors that have both of the following:
1. Hue of 2.5YR or redder; and
2. A value, moist, of 3 or less.
Rhodic Hapludox
EEEN. Other Hapludox that have 50 percent or more hue of
7.5YR or yellower and a color value, moist, of 6 or more at a
depth between 25 and 125 cm from the mineral soil surface.
Xanthic Hapludox
EEEO. Other Hapludox.
Typic Hapludox
Definition of Typic Hapludox
Typic Hapludox are the Hapludox that:
1. Have neither a petroferric nor a lithic contact within 125
cm of the mineral soil surface;
2. Do not have, in any horizon within 125 cm of the mineral
soil surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less and also aquic conditions;
3. Have an oxic horizon with a lower boundary 125 cm or
more from the mineral soil surface;
4. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, a bulk density, in the
fraction less than 2.0 mm in size, of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and acid-oxalateextractable
aluminum plus 1
/2 acid-oxalate-extractable iron of
more than 1.0 percent;
5. Have less than 16 kg of organic carbon per m2
to a depth
of 1 m, exclusive of surface litter; and
6. Have, in some horizon at a depth between 25 and 125 cm
from the mineral soil surface, less than 50 percent colors that
have both of the following:
a. Hue of 2.5YR or redder and a color value, moist, of 3 or
less; and
b. Hue of 7.5YR or yellower and a color value, moist, of 6 or
more.
Description of Subgroups
Typic Hapludox.—The central concept or Typic subgroup of
Hapludox is fixed on soils that do not have a petroferric contact,
a lithic contact, or redox depletions with a color value, moist, of 4
or more and chroma of 2 or less within 125 cm of the mineral soil
surface and also do not have aquic conditions for some time in
normal years. These soils have less than 16 kg/m2
organic
carbon to a depth of 100 cm and have less than 5 percent
plinthite in all horizons within a depth of 125 cm. Their colors are
reddish, but the soils do not have very dark reddish colors
throughout the layers between depths of 25 and 125 cm. They
do not have a surface mantle or layer in the upper 75 cm with
both a low bulk density and a high content of weakly crystalline
minerals. These soils are of small extent, mostly in Puerto Rico
and Hawaii.
Andic Hapludox.—These soils have a surface mantle or
layer in the upper 75 cm with both a low bulk density and a
high content of weakly crystalline minerals. The soils are not
known to occur in the United States.
Aquic Hapludox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). Aquic Hapludox are considered
intergrades between Hapludox and Haplaquox. They are not
known to occur in the United States.
Aquic Lithic Hapludox.—These soils have, within 125 cm
of the mineral soil surface, both a lithic contact and redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). The soils are not known to occur
in the United States.
Aquic Petroferric Hapludox.—These soils have, within
125 cm of the mineral soil surface, both a petroferric contact
and redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage). The soils are not
known to occur in the United States.
Humic Hapludox.—These soils are like Typic Hapludox,
but they have 16 kg or more organic carbon per m2
within 100
cm of the mineral soil surface. They are of very small extent,
mostly in Puerto Rico.
Humic Rhodic Hapludox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, more than 50 percent colors that have hue of
2.5YR or redder and a value, moist, of 3 or less. They also
680 Soil Taxonomy
have 16 kg or more organic carbon per m2
within 100 cm of the
mineral soil surface. They are not known to occur in the United
States.
Humic Xanthic Hapludox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, more than 50 percent colors that have hue of
7.5YR or yellower and value, moist, of 6 or more. They also
have 16 kg or more organic carbon per m2
within 100 cm of the
mineral soil surface. These soils are not known to occur in the
United States.
Inceptic Hapludox.—These soils have an oxic horizon that
has its lower boundary within 125 cm of the mineral soil
surface. They are of small extent, mostly in Puerto Rico and
Hawaii.
Lithic Hapludox.—These soils have a lithic contact within
125 cm of the mineral soil surface. They are of very small
extent, mostly in Puerto Rico.
Petroferric Hapludox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
Plinthaquic Hapludox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, 5 percent
or more (by volume) plinthite, redox depletions with a color
value, moist, of 4 or more and chroma of 2 or less, and aquic
conditions for some time in normal years (or artificial
drainage). The soils are not known to occur in the United
States.
Plinthic Hapludox.—These soils have 5 percent or more
(by volume) plinthite in one or more horizons within 125 cm of
the mineral soil surface. The soils are not known to occur in
the United States.
Rhodic Hapludox.—These soils are like Typic Hapludox,
but they have, in all horizons at a depth between 25 and 125
cm from the mineral soil surface, more than 50 percent colors
that have hue of 2.5YR or redder and a value, moist, of 3 or
less. The soils are of very small extent, mostly in Puerto Rico.
Xanthic Hapludox.—These soils are like Typic Hapludox, but
they have hue of 7.5YR or yellower and a color value, moist, of 6
or more in all horizons at a depth between 25 and 125 cm from
the mineral soil surface. The soils are not known to occur in the
United States.
Kandiudox
These are the clayey Udox that have a kandic horizon that
has its upper boundary within 150 cm of the mineral soil
surface. They do not have a sombric horizon within 150 cm of
the mineral soil surface, but they have, in all subhorizons of a
kandic horizon within 150 cm of the mineral soil surface, an
apparent ECEC of 1.50 or more cmol(+) per kg clay or a pH
value (1N KCl) of less than 5.0. They also have a base
saturation (by NH4
OAc) of less than 35 percent in some
horizon within 125 cm of the mineral soil surface. The subsoil
has a moderate grade of blocky structure in most pedons. The
epipedons are either dark or light colored.
Definition
Kandiudox are the Udox that:
1. Have the upper boundary of a kandic horizon within 150 cm
of the mineral soil surface;
2. Have 35 percent or less base saturation (by NH4
OAc) in
some or all parts within 125 cm of the mineral soil surface;
3. Do not have a sombric horizon within 150 cm of the
mineral soil surface; and
4. Do not have an apparent ECEC of less than 1.50 cmol(+)
per kg clay and a pH value (1N KCl) of 5.0 or more in some
part of a kandic horizon within 150 cm of the mineral soil
surface.
Key to Subgroups
EEDA. Kandiudox that have, within 125 cm of the mineral
soil surface, both:
1. A petroferric contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Petroferric Kandiudox
EEDB. Other Kandiudox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Kandiudox
EEDC. Other Kandiudox that have, within 125 cm of the
mineral soil surface, both:
1. A lithic contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Lithic Kandiudox
EEDD. Other Kandiudox that have a lithic contact within
125 cm of the mineral soil surface.
Lithic Kandiudox
EEDE. Other Kandiudox that have, in one or more horizons
within 125 cm of the mineral soil surface, both:
1. 5 percent or more (by volume) plinthite; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Plinthaquic Kandiudox
Oxisols 681
EEDF. Other Kandiudox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface.
PlinthicKandiudox
EEDG. Other Kandiudox that have, in one or more horizons
within 125 cm of the mineral soil surface, redox depletions
with a color value, moist, of 4 or more and chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Kandiudox
EEDH. Other Kandiudox that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Kandiudox
EEDI. Other Kandiudox that have both:
1. 16 kg/m2
or more organic carbon between the mineral soil
surface and a depth of 100 cm; and
2. In all horizons at a depth between 25 and 125 cm from the
mineral soil surface, more than 50 percent colors that have
both of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less.
Humic Rhodic Kandiudox
EEDJ. Other Kandiudox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. 50 percent or more hue of 7.5YR or yellower and a
color value, moist, of 6 or more at a depth between 25 and
125 cm from the mineral soil surface.
Humic Xanthic Kandiudox
EEDK. Other Kandiudox that have 16 kg/m2
or more organic
carbon between the mineral soil surface and a depth of 100 cm.
Humic Kandiudox
EEDL. Other Kandiudox that have, in all horizons at a depth
between 25 and 125 cm from the mineral soil surface, more
than 50 percent colors that have both of the following:
1. Hue of 2.5YR or redder; and
2. A value, moist, of 3 or less.
Rhodic Kandiudox
EEDM. Other Kandiudox that have 50 percent or more hue
of 7.5YR or yellower and a color value, moist, of 6 or more
at a depth between 25 and 125 cm from the mineral soil
surface.
XanthicKandiudox
EEDN. OtherKandiudox.
Typic Kandiudox
DefinitionofTypicKandiudox
Typic Kandiudox are the Kandiudox that:
1. Have neither a petroferric nor a lithic contact within 125 cm
of the mineral soil surface;
2. Do not have, within 125 cm of the mineral soil surface, a
horizon that has more than 5 percent plinthite (by volume);
3. Do not have, in any horizon within 125 cm of the mineral
soil surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less and also aquic conditions;
4. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, a bulk density, in the
fraction less than 2.0 mm in size, of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and acid-oxalateextractable
aluminum plus 1
/2 acid-oxalate-extractable iron of
more than 1.0 percent;
5. Have less than 16 kg of organic carbon per m2
to a depth
of 1 m, exclusive of surface litter; and
6. Have, in some horizon at a depth between 25 and 125 cm
from the mineral soil surface, less than 50 percent colors that
have both of the following:
a. Hue of 2.5YR or redder and a color value, moist, of 3 or
less; and
b. Hue of 7.5YR or yellower and a color value, moist, of 6
or more.
Description of Subgroups
Typic Kandiudox.—The central concept or Typic subgroup
of Kandiudox is fixed on soils that do not have a petroferric
contact, a lithic contact, or redox depletions with a color value,
moist, of 4 or more and chroma of 2 or less within 125 cm of
the mineral soil surface and also do not have aquic conditions
for some time in normal years. These soils have less than 16
kg/m2
organic carbon to a depth of 100 cm and have less than 5
percent plinthite in all horizons within a depth of 125 cm.
Their colors are reddish, but the soils do not have very dark
reddish colors throughout the layers between depths of 25 and
125 cm. They do not have a surface mantle or layer in the
upper 75 cm with both a low bulk density and a high content of
weakly crystalline minerals. These soils are of small extent,
mostly in Puerto Rico.
Andic Kandiudox.—These soils have a surface mantle or
layer in the upper 75 cm with both a low bulk density and a
682 Soil Taxonomy
high content of weakly crystalline minerals. The soils are not
known to occur in the United States.
Aquic Kandiudox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and chroma of
2 or less and also aquic conditions for some time in normal years
(or artificial drainage). Aquic Kandiudox are considered
intergrades between Kandiudox and Aquox. They are not known
to occur in the United States.
Aquic Lithic Kandiudox.—These soils have, within 125
cm of the mineral soil surface, both a lithic contact and redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). The soils are not known to occur
in the United States.
Aquic Petroferric Kandiudox.—These soils have, within
125 cm of the mineral soil surface, both a petroferric contact
and redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage). The soils are not
known to occur in the United States.
Humic Kandiudox.—These soils are like Typic Kandiudox,
but they have 16 kg or more organic carbon per m2
within 100
cm of the mineral soil surface. They are not known to occur in
the United States.
Humic Rhodic Kandiudox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, more than 50 percent colors that have hue of
2.5YR or redder and a value, moist, of 3 or less. They also
have 16 kg or more organic carbon per m2
within 100 cm of the
mineral soil surface. These soils are not known to occur in the
United States.
Humic Xanthic Kandiudox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, more than 50 percent colors that have hue of
7.5YR or yellower and value, moist, of 6 or more. They also
have 16 kg or more organic carbon per m2
within 100 cm of the
mineral soil surface. These soils are not known to occur in the
United States.
Lithic Kandiudox.—These soils have a lithic contact
within 125 cm of the mineral soil surface. They are not known
to occur in the United States.
Petroferric Kandiudox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
Plinthaquic Kandiudox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, 5 percent
or more (by volume) plinthite, redox depletions with a color
value, moist, of 4 or more and chroma of 2 or less, and aquic
conditions for some time in normal years (or artificial
drainage). The soils are not known to occur in the United
States.
Plinthic Kandiudox.—These soils have 5 percent or more
(by volume) plinthite in one or more horizons within 125 cm of
the mineral soil surface. The soils are not known to occur in the
United States.
Rhodic Kandiudox.—These soils are like Typic
Kandiudox, but they have, in all horizons at a depth between
25 and 125 cm from the mineral soil surface, more than 50
percent colors that have hue of 2.5YR or redder and a value,
moist, of 3 or less. The soils are not known to occur in the
United States.
Xanthic Kandiudox.—These soils are like Typic Kandiudox,
but they have hue of 7.5YR or yellower and a color value, moist,
of 6 or more in all horizons at a depth between 25 and 125 cm
from the mineral soil surface. The soils are not known to occur in
the United States.
Sombriudox
These are the Udox that have a sombric horizon. These soils
are poorly understood. They have an increase in content of
organic carbon in the subsoil. The only known pedons are near
the Rift Valley in Africa.
Definition
Sombriudox are the Udox that have a sombric horizon
within 150 cm of the mineral soil surface.
Key to Subgroups
EEAA. Sombriudox that have a petroferric contact within
125 cm of the mineral soil surface.
Petroferric Sombriudox
EEAB. Other Sombriudox that have a lithic contact within
125 cm of the mineral soil surface.
Lithic Sombriudox
EEAC. Other Sombriudox that have 16 kg/m2
or more
organic carbon between the mineral soil surface and a depth of
100 cm.
Humic Sombriudox
EEAD. Other Sombriudox.
Typic Sombriudox
Definition of Typic Sombriudox
Typic Sombriudox are the Sombriudox that:
1. Have neither a petroferric nor a lithic contact within 125
cm of the mineral soil surface; and
2. Have less than 16 kg of organic carbon per m2
to a depth
of 1 m, exclusive of surface litter.
Description of Subgroups
Typic Sombriudox.—The central concept or Typic
subgroup of Sombriudox is fixed on soils that do not have a
petroferric or lithic contact within 125 cm of the mineral soil
Oxisols 683
surface. These soils have less than 16 kg/m2
organic carbon to a
depth of 100 cm. They are not known to occur in the United
States.
Humic Sombriudox.—These soils are like Typic
Sombriudox, but they have 16 kg or more organic carbon per
m2
within 100 cm of the mineral soil surface. They are not known
to occur in the United States.
Lithic Sombriudox.—These soils have a lithic contact
within 125 cm of the mineral soil surface. They are not known
to occur in the United States.
Petroferric Sombriudox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
Ustox
These are the Oxisols that have an ustic moisture regime.
Because of natural rainfall, they are moist in normal years for
at least 90 days (a period that usually is long enough for one
rain-fed crop) but not for more than 270 days. Crops are not
grown continuously because there is inadequate moisture for at
least 90 days in normal years. Ustox may be the most extensive
suborder, occurring over a large portion of the interior of South
America and in extensive areas of Africa. A few Ustox are in
areas of the xeric soil moisture regime, for example, in
Australia. The range of natural rainfall within the Ustox
provides that two crops can be grown on some Ustox but only
one crop can be grown on others unless supplemental irrigation
is available.
Definition
Ustox are the Oxisols that have an ustic moisture regime.
Key to Great Groups
ECA. Ustox that have a sombric horizon within 150 cm of
the mineral soil surface.
Sombriustox, p. 692
ECB. Other Ustox that have, in one or more subhorizons of
an oxic or kandic horizon within 150 cm of the mineral soil
surface, an apparent ECEC of less than 1.50 cmol(+) per kg
clay and a pH value (1N KCl) of 5.0 or more.
Acrustox, p. 683
ECC. Other Ustox that have a base saturation (by NH4
OAc)
of 35 percent or more in all horizons within 125 cm of the
mineral soil surface.
Eutrustox, p. 685
ECD. Other Ustox that have a kandic horizon that has its
upper boundary within 150 cm of the mineral soil surface.
Kandiustox, p. 690
ECE. OtherUstox.
Haplustox, p. 688
Acrustox
These are the Ustox with very low cation-exchange values.
They do not have a sombric horizon within 150 cm of the
mineral soil surface. They can easily have their chemical
environment altered by applications of fertilizer and lime.
Because of a low buffering capacity, small but frequent
applications of fertilizer and lime are desirable. A low content
of exchangeable aluminum in the subsoil can be corrected by
leaching basic cations from lime and fertilizer.
Definition
Acrustox are the Ustox that:
1. Have an apparent ECEC of less than 1.50 cmol(+) per kg
clay and a pH value (1N KCl) of 5.0 or more in some part of an
oxic or kandic horizon within 150 cm of the mineral soil
surface; and
2. Do not have a sombric horizon within 150 cm of the
mineral soil surface.
Key to Subgroups
ECBA. Acrustox that have, within 125 cm of the mineral soil
surface, both:
1. A petroferric contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Petroferric Acrustox
ECBB. Other Acrustox that have a petroferric contact within
125 cm of the mineral soil surface.
Petroferric Acrustox
ECBC. Other Acrustox that have, within 125 cm of the
mineral soil surface, both:
1. A lithic contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Lithic Acrustox
ECBD. Other Acrustox that have a lithic contact within 125
cm of the mineral soil surface.
Lithic Acrustox
ECBE. Other Acrustox that have, within 125 cm of the
mineral soil surface, both:
684 Soil Taxonomy
1. A delta pH (KCl pH minus 1:1 water pH) with a 0 or net
positive charge in a layer 18 cm or more thick; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Anionic Aquic Acrustox
ECBF. Other Acrustox that have a delta pH (KCl pH minus
1:1 water pH) with a 0 or net positive charge in a layer 18 cm
or more thick within 125 cm of the mineral soil surface.
Anionic Acrustox
ECBG. Other Acrustox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface.
Plinthic Acrustox
ECBH. Other Acrustox that have, in one or more horizons
within 125 cm of the mineral soil surface, redox depletions
with a color value, moist, of 4 or more and chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Acrustox
ECBI. Other Acrustox that have a base saturation (by
NH4
OAc) of 35 percent or more in all horizons within 125 cm
of the mineral soil surface.
Eutric Acrustox
ECBJ. Other Acrustox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. In all horizons at a depth between 25 and 125 cm from
the mineral soil surface, more than 50 percent colors that
have both of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less.
Humic Rhodic Acrustox
ECBK. Other Acrustox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. 50 percent or more hue of 7.5YR or yellower and a
color value, moist, of 6 or more at a depth between 25 and
125 cm from the mineral soil surface.
Humic Xanthic Acrustox
ECBL. Other Acrustox that have 16 kg/m2
or more organic
carbon between the mineral soil surface and a depth of 100 cm.
Humic Acrustox
ECBM. Other Acrustox that have, in all horizons at a depth
between 25 and 125 cm from the mineral soil surface, more
than 50 percent colors that have both of the following:
1. Hue of 2.5YR or redder; and
2. A value, moist, of 3 or less.
Rhodic Acrustox
ECBN. Other Acrustox that have 50 percent or more hue of
7.5YR or yellower and a color value, moist, of 6 or more at a
depth between 25 and 125 cm from the mineral soil surface.
Xanthic Acrustox
ECBO. Other Acrustox.
Typic Acrustox
Definition of Typic Acrustox
Typic Acrustox are the Acrustox that:
1. Have neither a petroferric nor a lithic contact within 125
cm of the mineral soil surface;
2. Have a delta pH (KCl pH minus 1:1 water pH) with a net
negative charge in all parts within 125 cm of the mineral soil
surface;
3. Do not have, within 125 cm of the mineral soil surface, a
horizon that has more than 5 percent plinthite (by volume);
4. Do not have, in any horizon within 125 cm of the mineral
soil surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less and also aquic conditions;
5. Have 35 percent or less base saturation (by NH4
OAc) in
some subhorizon within 125 cm of the mineral soil surface;
6. Have less than 16 kg of organic carbon per m2
to a depth
of 1 m, exclusive of surface litter; and
7. Have, in some horizon at a depth between 25 and 125 cm
from the mineral soil surface, 50 percent or less colors that
have both of the following:
a. Hue of 2.5YR or redder and a color value, moist, of 3 or
less; and
b. Hue of 7.5YR or yellower and a color value, moist, of 6
or more.
Description of Subgroups
Typic Acrustox.—The central concept or Typic subgroup of
Acrustox is fixed on soils that do not have a petroferric contact,
a lithic contact, or redox depletions with a color value, moist,
of 4 or more and chroma of 2 or less within 125 cm of the
mineral soil surface and also do not have aquic conditions for
some time in normal years. These soils have less than 16 kg/m2
organic carbon to a depth of 100 cm and have less than 5
percent plinthite in all horizons within a depth of 125 cm.
Oxisols 685
Their colors are reddish, but the soils do not have very dark
reddish colors throughout the layers between depths of 25 and
125 cm. These soils are not known to occur in the United
States.
Anionic Acrustox.—These soils have a delta pH (KCl pH
minus 1:1 water pH) with a 0 or net positive charge in a layer
18 cm or more thick within 125 cm of the mineral soil surface.
They are of very small extent and are known to occur only in
Hawaii in the United States.
Anionic Aquic Acrustox.—These soils have, in one or
more horizons within 125 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). They have a delta pH (KCl pH
minus 1:1 water pH) with a 0 or net positive charge in a layer
18 cm or more thick within 125 cm of the mineral soil surface.
These soils are not known to occur in the United States.
Aquic Acrustox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). Aquic Acrustox are considered
intergrades between Acrustox and Acraquox. They are not
known to occur in the United States.
Aquic Lithic Acrustox.—These soils have, within 125 cm
of the mineral soil surface, both a lithic contact and redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). The soils are not known to occur
in the United States.
Aquic Petroferric Acrustox.—These soils have, within 125
cm of the mineral soil surface, both a petroferric contact and
redox depletions with a color value, moist, of 4 or more and
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage). The soils are not known
to occur in the United States.
Eutric Acrustox.—These soils have a base saturation (by
NH4
OAc) of 35 percent or more in all horizons within 125 cm
of the mineral soil surface. The soils are not known to occur in
the United States
Humic Acrustox.—These soils are like Typic Acrustox, but
they have 16 kg or more organic carbon per m2
within 100 cm
of the mineral soil surface. They are not known to occur in the
United States.
Humic Rhodic Acrustox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, more than 50 percent colors that have hue of
2.5YR or redder and a value, moist, of 3 or less. They also
have 16 kg or more organic carbon per m2
within 100 cm of the
mineral soil surface. These soils are not known to occur in the
United States.
Humic Xanthic Acrustox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, more than 50 percent colors that have hue of
7.5YR or yellower and value, moist, of 6 or more. They also have
16 kg or more organic carbon per m2
within 100 cm of the mineral
soil surface. These soils are not known to occur in the United
States.
Lithic Acrustox.—These soils have a lithic contact within
125 cm of the mineral soil surface. They are not known to
occur in the United States.
Petroferric Acrustox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
Plinthic Acrustox.—These soils have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface. The soils are not known to occur in the
United States.
Rhodic Acrustox.—These soils are like Typic Acrustox, but
they have, in all horizons at a depth between 25 and 125 cm
from the mineral soil surface, more than 50 percent colors that
have hue of 2.5YR or redder and a value, moist, of 3 or less.
The soils are not known to occur in the United States.
Xanthic Acrustox.—These soils are like Typic Acrustox, but
they have hue of 7.5YR or yellower and a color value, moist, of 6
or more in all horizons at a depth between 25 and 125 cm from
the mineral soil surface. The soils are not known to occur in the
United States.
Eutrustox
These are the Ustox with high base saturation throughout the
profile. They do not have a sombric horizon within 150 cm of the
mineral soil surface. They have, in all subhorizons of an oxic or
kandic horizon within 150 cm of the mineral soil surface, an
apparent ECEC of 1.50 cmol(+) per kg clay or more or a pH value
(1N KCl) of less than 5.0. These soils are well known by local
farmers because of their relatively high natural fertility.
Commonly, they supported natural forests while the surrounding
areas of like rainfall but low base status supported savannas.
Currently, forest vegetation is rare because the forests have
been completely cut by native farmers. Why these Ustox have
high saturation throughout their profile is not known, but they
tend to occur over or near basic rocks, such as limestone and
basalt.
Definition
Eutrustox are the Ustox that:
1. Have more than 35 percent base saturation (by NH4
OAc) in
all parts within 125 cm of the mineral soil surface;
2. Do not have a sombric horizon within 150 cm of the mineral
soil surface; and
3. Do not have an apparent ECEC of less than 1.50 cmol(+)
per kg clay and a pH value (1N KCl) of 5.0 or more in some part
of an oxic or kandic horizon within 150 cm of the mineral soil
surface.
686 Soil Taxonomy
KeytoSubgroups
ECCA. Eutrustox that have, within 125 cm of the mineral soil
surface, both:
1. A petroferric contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Petroferric Eutrustox
ECCB. Other Eutrustox that have a petroferric contact within
125 cm of the mineral soil surface.
Petroferric Eutrustox
ECCC. Other Eutrustox that have, within 125 cm of the
mineral soil surface, both:
1. A lithic contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Lithic Eutrustox
ECCD. Other Eutrustox that have a lithic contact within 125
cm of the mineral soil surface.
Lithic Eutrustox
ECCE. Other Eutrustox that have, in one or more horizons
within 125 cm of the mineral soil surface, both:
1. 5 percent or more (by volume) plinthite; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Plinthaquic Eutrustox
ECCF. Other Eutrustox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface.
Plinthic Eutrustox
ECCG. Other Eutrustox that have, in one or more horizons
within 125 cm of the mineral soil surface, redox depletions
with a color value, moist, of 4 or more and chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Eutrustox
ECCH. Other Eutrustox that have a kandic horizon that has
its upper boundary within 150 cm of the mineral soil surface.
Kandiustalfic Eutrustox
ECCI. Other Eutrustox that have both:
1. 16 kg/m2
or more organic carbon between the mineral soil
surface and a depth of 100 cm; and
2. An oxic horizon that has its lower boundary within 125
cm of the mineral soil surface.
Humic Inceptic Eutrustox
ECCJ. Other Eutrustox that have an oxic horizon that has its
lower boundary within 125 cm of the mineral soil surface.
Inceptic Eutrustox
ECCK. Other Eutrustox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. In all horizons at a depth between 25 and 125 cm from
the mineral soil surface, more than 50 percent colors that
have both of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less.
Humic Rhodic Eutrustox
ECCL. Other Eutrustox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. 50 percent or more hue of 7.5YR or yellower and a
color value, moist, of 6 or more at a depth between 25 and
125 cm from the mineral soil surface.
Humic Xanthic Eutrustox
ECCM. Other Eutrustox that have 16 kg/m2
or more organic
carbon between the mineral soil surface and a depth of 100 cm.
Humic Eutrustox
ECCN. Other Eutrustox that have, in all horizons at a depth
between 25 and 125 cm from the mineral soil surface, more
than 50 percent colors that have both of the following:
1. Hue of 2.5YR or redder; and
2. A value, moist, of 3 or less.
Rhodic Eutrustox
ECCO. Other Eutrustox that have 50 percent or more hue of
7.5YR or yellower and a color value, moist, of 6 or more at a
depth between 25 and 125 cm from the mineral soil surface.
Xanthic Eutrustox
ECCP. Other Eutrustox.
Typic Eutrustox
Definition of Typic Eutrustox
Typic Eutrustox are the Eutrustox that:
Oxisols 687
1. Have neither a petroferric nor a lithic contact within 125 cm
of the mineral soil surface;
2. Do not have, within 125 cm of the mineral soil surface, a
horizon that has more than 5 percent plinthite (by volume);
3. Do not have, in any horizon within 125 cm of the mineral
soil surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less and also aquic conditions;
4. Do not have a kandic horizon with its upper boundary
within 150 cm of the mineral soil surface;
5. Have an oxic horizon with a lower boundary 125 cm or
more from the mineral soil surface;
6. Have less than 16 kg of organic carbon per m2
to a depth
of 1 m, exclusive of surface litter; and
7. Have, in some horizon at a depth between 25 and 125 cm
from the mineral soil surface, 50 percent or less colors that
have both of the following:
a. Hue of 2.5YR or redder and a color value, moist, of 3 or
less; and
b. Hue of 7.5YR or yellower and a color value, moist, of 6
or more.
Description of Subgroups
Typic Eutrustox.—The central concept or Typic subgroup
of Eutrustox is fixed on soils that have a thick oxic horizon.
These soils do not have a petroferric contact, a lithic contact, or
redox depletions with a color value, moist, of 4 or more and
chroma of 2 or less within 125 cm of the mineral soil surface
and also do not have aquic conditions for some time in normal
years. The soils have less than 16 kg/m2
organic carbon to a
depth of 100 cm and have less than 5 percent plinthite in all
horizons within a depth of 125 cm. Their colors are reddish,
but the soils do not have very dark reddish colors throughout
the layers between depths of 25 and 125 cm. These soils are not
known to occur in the United States.
Aquic Eutrustox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). Aquic Eutrustox are considered
intergrades between Eutrustox and Eutraquox. They are not
known to occur in the United States.
Aquic Lithic Eutrustox.—These soils have, within 125 cm
of the mineral soil surface, both a lithic contact and redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). The soils are not known to occur
in the United States.
Aquic Petroferric Eutrustox.—These soils have, within
125 cm of the mineral soil surface, both a petroferric contact
and redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some time
in normal years (or artificial drainage). The soils are not known
to occur in the United States.
Humic Eutrustox.—These soils are like Typic Eutrustox,
but they have 16 kg or more organic carbon per m2
within 100
cm of the mineral soil surface. They are not known to occur in
the United States.
Humic Inceptic Eutrustox.—These soils have an oxic
horizon that has its lower boundary within 125 cm of the
mineral soil surface. They also have 16 kg or more organic
carbon per m2
within 100 cm of the mineral soil surface. These
soils are not known to occur in the United States.
Humic Rhodic Eutrustox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, more than 50 percent colors that have hue of
2.5YR or redder and a value, moist, of 3 or less. They also
have 16 kg or more organic carbon per m2
within 100 cm of the
mineral soil surface. These soils are not known to occur in the
United States.
Humic Xanthic Eutrustox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, colors that have hue of 7.5YR or yellower and
value, moist, of 6 or more. They also have 16 kg or more
organic carbon per m2
within 100 cm of the mineral soil
surface. These soils are not known to occur in the United
States.
Inceptic Eutrustox.—These soils have an oxic horizon that
has its lower boundary within 125 cm of the mineral soil
surface. They are of very small extent, mostly in Hawaii and
Guam.
Kandiustalfic Eutrustox.—These soils have a kandic
horizon that has its upper boundary within 125 cm of the
mineral soil surface. They are not known to occur in the United
States.
Lithic Eutrustox.—These soils have a lithic contact within
125 cm of the mineral soil surface. They are of small extent,
mostly in Puerto Rico and Hawaii.
Petroferric Eutrustox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
Plinthaquic Eutrustox.—These soils have, within 125 cm
of the mineral soil surface, redox depletions with a color value,
moist, of 4 or more and chroma of 2 or less and also aquic
conditions for some time in normal years (or artificial
drainage). They have 5 percent or more (by volume) plinthite
in one or more horizons within 125 cm of the mineral soil
surface. These soils are not known to occur in the United
States.
Plinthic Eutrustox.—These soils have 5 percent or more
(by volume) plinthite in one or more horizons within 125 cm of
the mineral soil surface. The soils are not known to occur in
the United States.
Rhodic Eutrustox.—These soils are like Typic Eutrustox,
but they have, in all horizons at a depth between 25 and 125
688 Soil Taxonomy
cm from the mineral soil surface, more than 50 percent colors
that have hue of 2.5YR or redder and a value, moist, of 3 or
less. The soils are of small extent, mostly in Hawaii.
Xanthic Eutrustox.—These soils are like Typic Eutrustox, but
they have hue of 7.5YR or yellower and a color value, moist, of 6
or more in all horizons at a depth between 25 and 125 cm from
the mineral soil surface. The soils are not known to occur in the
United States.
Haplustox
These are the Ustox that do not have a sombric horizon
within 150 cm of the mineral soil surface but that have, in all
subhorizons of an oxic horizon within 150 cm of the mineral
soil surface, an apparent ECEC of 1.50 or more cmol(+) per kg
clay or a pH value (1N KCl) of less than 5.0. They have a base
saturation (by NH4
OAc) of less than 35 percent in some
horizon within 125 cm of the mineral soil surface and do not
have a kandic horizon that has its upper boundary within 150
cm of the mineral soil surface. The subsoil has granular
structure, and the epipedons may be either dark or light
colored. Haplustox are dark red to yellow and all intervening
colors in the subsoil. They occur in vast areas in central South
America and Africa.
Definition
Haplustox are the Ustox that:
1. Have 35 percent or less base saturation (by NH4
OAc) in
some or all parts within 125 cm of the mineral soil surface;
2. Do not have a sombric horizon within 150 cm of the
mineral soil surface;
3. Do not have an apparent ECEC of less than 1.50 cmol(+)
per kg clay and a pH value (1N KCl) of 5.0 or more in some
part of an oxic horizon within 150 cm of the mineral soil
surface; and
4. Do not have the upper boundary of an oxic horizon
within 150 cm of the mineral soil surface.
Key to Subgroups
ECEA. Haplustox that have, within 125 cm of the mineral
soil surface, both:
1. A petroferric contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Petroferric Haplustox
ECEB. Other Haplustox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Haplustox
ECEC. Other Haplustox that have, within 125 cm of the mineral
soil surface, both:
1. A lithic contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Lithic Haplustox
ECED. Other Haplustox that have a lithic contact within 125
cm of the mineral soil surface.
Lithic Haplustox
ECEE. Other Haplustox that have, in one or more horizons
within 125 cm of the mineral soil surface, both:
1. 5 percent or more (by volume) plinthite; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Plinthaquic Haplustox
ECEF. Other Haplustox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface.
Plinthic Haplustox
ECEG. Other Haplustox that have, within 125 cm of the
mineral soil surface, both:
1. The lower boundary of the oxic horizon; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aqueptic Haplustox
ECEH. Other Haplustox that have, in one or more horizons
within 125 cm of the mineral soil surface, redox depletions
with a color value, moist, of 4 or more and chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Haplustox
ECEI. Other Haplustox that are saturated with water in one
or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Haplustox
ECEJ. Other Haplustox that have an oxic horizon that has its
lower boundary within 125 cm of the mineral soil surface.
Inceptic Haplustox
Oxisols 689
ECEK. Other Haplustox that have both:
1. 16 kg/m2
or more organic carbon between the mineral soil
surface and a depth of 100 cm; and
2. In all horizons at a depth between 25 and 125 cm from the
mineral soil surface, more than 50 percent colors that have
both of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less.
Humic Rhodic Haplustox
ECEL. Other Haplustox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. 50 percent or more hue of 7.5YR or yellower and a
color value, moist, of 6 or more at a depth between 25 and
125 cm from the mineral soil surface.
Humic Xanthic Haplustox
ECEM. Other Haplustox that have 16 kg/m2
or more organic
carbon between the mineral soil surface and a depth of 100 cm.
Humic Haplustox
ECEN. Other Haplustox that have, in all horizons at a depth
between 25 and 125 cm from the mineral soil surface, more
than 50 percent colors that have both of the following:
1. Hue of 2.5YR or redder; and
2. A value, moist, of 3 or less.
Rhodic Haplustox
ECEO. Other Haplustox that have 50 percent or more hue of
7.5YR or yellower and a color value, moist, of 6 or more at a
depth between 25 and 125 cm from the mineral soil surface.
Xanthic Haplustox
ECEP. Other Haplustox.
Typic Haplustox
Definition of Typic Haplustox
Typic Haplustox are the Haplustox that:
1. Have neither a petroferric nor a lithic contact within 125
cm of the mineral soil surface;
2. Do not have, within 125 cm of the mineral soil surface, a
horizon that has more than 5 percent plinthite (by volume);
3. Do not have, in any horizon within 125 cm of the mineral
soil surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less and also aquic conditions;
4. Are not saturated with water in any layer within 100 cm of
the mineral soil surface in normal years for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
5. Have an oxic horizon with a lower boundary 125 cm or more
from the mineral soil surface;
6. Do not have mottles with a color value, moist, of 4 or more
and chroma of 2 or less within 25 cm of the mineral soil
surface; and
7. Have, in some horizon at a depth between 25 and 125 cm
from the mineral soil surface, 50 percent or less colors that
have both of the following:
a. Hue of 2.5YR or redder and a color value, moist, of 3 or
less; and
b. Hue of 7.5YR or yellower and a color value, moist, of 6
or more.
Description of Subgroups
Typic Haplustox.—The central concept or Typic subgroup
of Haplustox is fixed on soils that do not have a petroferric
contact, a lithic contact, or redox depletions with a color value,
moist, of 4 or more and chroma of 2 or less within 125 cm of
the mineral soil surface and also do not have aquic conditions
for some time in normal years. These soils have less than 16
kg/m2
organic carbon to a depth of 100 cm and have less than 5
percent plinthite in all horizons within a depth of 125 cm.
Their colors are reddish, but the soils do not have very dark
reddish colors throughout the layers between depths of 25 and
125 cm. These soils are not known to occur in the United
States.
Aqueptic Haplustox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). They have an oxic horizon that
has its lower boundary within 125 cm of the mineral soil
surface. Aqueptic Haplustox are considered intergrades
between Haplustox and Aquepts. They are not known to occur
in the United States.
Aquic Haplustox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). Aquic Haplustox are considered
intergrades between Haplustox and Haplaquox. They are not
known to occur in the United States.
Aquic Lithic Haplustox.—These soils have, within 125 cm
of the mineral soil surface, both a lithic contact and redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). The soils are not known to occur
in the United States.
Aquic Petroferric Haplustox.—These soils have, within
690 Soil Taxonomy
125 cm of the mineral soil surface, both a petroferric contact and
redox depletions with a color value, moist, of 4 or more and
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage). The soils are not known to
occur in the United States.
Humic Haplustox.—These soils are like Typic Haplustox,
but they have 16 kg or more organic carbon per m2
within 100
cm of the mineral soil surface. They are not known to occur in
the United States.
Humic Rhodic Haplustox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, more than 50 percent colors that have hue of
2.5YR or redder and a value, moist, of 3 or less. They also
have 16 kg or more organic carbon per m2
within 100 cm of the
mineral soil surface. These soils are not known to occur in the
United States.
Humic Xanthic Haplustox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, more than 50 percent colors that have hue of
7.5YR or yellower and value, moist, of 6 or more. They also
have 16 kg or more organic carbon per m2
within 100 cm of the
mineral soil surface. These soils are not known to occur in the
United States.
Inceptic Haplustox.—These soils have an oxic horizon that
has its lower boundary within 125 cm of the mineral soil
surface. They are not known to occur in the United States.
Lithic Haplustox.—These soils have a lithic contact within
125 cm of the mineral soil surface. They are not known to
occur in the United States.
Oxyaquic Haplustox.—These soils are saturated with water
within 100 cm of the mineral soil surface for 20 or more
consecutive days or 30 or more cumulative days in normal
years. They are not known to occur in the United States.
Petroferric Haplustox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
Plinthaquic Haplustox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, 5 percent
or more (by volume) plinthite, redox depletions with a color
value, moist, of 4 or more and chroma of 2 or less, and aquic
conditions for some time in normal years (or artificial
drainage). The soils are not known to occur in the United
States.
Plinthic Haplustox.—These soils have 5 percent or more
(by volume) plinthite in one or more horizons within 125 cm of
the mineral soil surface. The soils are not known to occur in
the United States.
Rhodic Haplustox.—These soils are like Typic Haplustox,
but they have, in all horizons at a depth between 25 and 125
cm from the mineral soil surface, more than 50 percent colors
that have hue of 2.5YR or redder and a value, moist, of 3 or
less. The soils are of very small extent, mostly in Puerto Rico.
Xanthic Haplustox.—These soils are like Typic Haplustox,
but they have hue of 7.5YR or yellower and a color value,
moist, of 6 or more in all horizons at a depth between 25 and 125
cm from the mineral soil surface. The soils are not known to
occur in the United States.
Kandiustox
These are the clayey Ustox that have a kandic horizon that
has its upper boundary within 150 cm of the mineral soil
surface. They do not have a sombric horizon within 150 cm of
the mineral soil surface, but they have, in all subhorizons of a
kandic horizon within 150 cm of the mineral soil surface, an
apparent ECEC of 1.50 or more cmol(+) per kg clay or a pH
value (1N KCl) of less than 5.0. They also have a base
saturation (by NH4
OAc) of less than 35 percent in some
horizon within 125 cm of the mineral soil surface. The subsoil
has a moderate grade of blocky structure in most pedons. The
epipedons are either dark or light colored. The subsoil shows
evidence of translocated clay only in a few areas. In some
pedons it tends to have a weak or moderate grade of blocky
structure. In most of the soils, however, there is a strong
secondary structure that is fine granular.
Definition
Kandiustox are the Ustox that:
1. Have the upper boundary of a kandic horizon within 150
cm of the mineral soil surface;
2. Have 35 percent or less base saturation (by NH4
OAc)
in some or all parts within 125 cm of the mineral soil
surface;
3. Do not have a sombric horizon within 150 cm of the
mineral soil surface; and
4. Do not have an apparent ECEC of less than 1.50 cmol(+)
per kg clay and a pH value (1N KCl) of 5.0 or more in some
part of a kandic horizon within 150 cm of the mineral soil
surface.
Key to Subgroups
ECDA. Kandiustox that have, within 125 cm of the mineral
soil surface, both:
1. A petroferric contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Petroferric Kandiustox
ECDB. Other Kandiustox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Kandiustox
ECDC. Other Kandiustox that have, within 125 cm of the
mineral soil surface, both:
Oxisols 691
1. A lithic contact; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Lithic Kandiustox
ECDD. Other Kandiustox that have a lithic contact within
125 cm of the mineral soil surface.
Lithic Kandiustox
ECDE. Other Kandiustox that have, in one or more horizons
within 125 cm of the mineral soil surface, both:
1. 5 percent or more (by volume) plinthite; and
2. Redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Plinthaquic Kandiustox
ECDF. Other Kandiustox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface.
Plinthic Kandiustox
ECDG. Other Kandiustox that have, in one or more horizons
within 125 cm of the mineral soil surface, redox depletions
with a color value, moist, of 4 or more and chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Kandiustox
ECDH. Other Kandiustox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. In all horizons at a depth between 25 and 125 cm from
the mineral soil surface, more than 50 percent colors that
have both of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less.
Humic Rhodic Kandiustox
ECDI. Other Kandiustox that have both:
1. 16 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm; and
2. 50 percent or more hue of 7.5YR or yellower and a
color value, moist, of 6 or more at a depth between 25 and
125 cm from the mineral soil surface.
Humic Xanthic Kandiustox
ECDJ. Other Kandiustox that have 16 kg/m2
or more
organic carbon between the mineral soil surface and a depth of
100cm.
Humic Kandiustox
ECDK. Other Kandiustox that have, in all horizons at a
depth between 25 and 125 cm from the mineral soil surface,
more than 50 percent colors that have both of the following:
1. Hue of 2.5YR or redder; and
2. A value, moist, of 3 or less.
Rhodic Kandiustox
ECDL. Other Kandiustox that have 50 percent or more hue
of 7.5YR or yellower and a color value, moist, of 6 or more at a
depth between 25 and 125 cm from the mineral soil surface.
Xanthic Kandiustox
ECDM. Other Kandiustox.
Typic Kandiustox
Definition of Typic Kandiustox
Typic Kandiustox are the Kandiustox that:
1. Have neither a petroferric nor a lithic contact within 125
cm of the mineral soil surface;
2. Do not have, within 125 cm of the mineral soil surface, a
horizon that has more than 5 percent plinthite (by volume);
3. Do not have, in any horizon within 125 cm of the mineral
soil surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less and also aquic conditions;
4. Have less than 16 kg of organic carbon per m2
to a depth
of 1 m, exclusive of surface litter; and
5. Have, in some horizon at a depth between 25 and 125 cm
from the mineral soil surface, 50 percent or less colors that
have both of the following:
a. Hue of 2.5YR or redder and a color value, moist, of 3 or
less; and
b. Hue of 7.5YR or yellower and a color value, moist, of 6
or more.
Description of Subgroups
Typic Kandiustox.—The central concept or Typic subgroup
of Kandiustox is fixed on soils that do not have a petroferric
contact, a lithic contact, or redox depletions with a color value,
moist, of 4 or more and chroma of 2 or less within 125 cm of
the mineral soil surface and also do not have aquic conditions
for some time in normal years. These soils have less than 16
kg/m2
organic carbon to a depth of 100 cm and have less than 5
percent plinthite in all horizons within a depth of 125 cm.
Their colors are reddish, but the soils do not have very dark
reddish colors throughout the layers between depths of 25 and
692 Soil Taxonomy
125 cm. These soils are not known to occur in the United
States.
Aquic Kandiustox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). Aquic Kandiustox are considered
intergrades between Kandiustox and Aquox. They are not
known to occur in the United States.
Aquic Lithic Kandiustox.—These soils have, within 125
cm of the mineral soil surface, both a lithic contact and redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage). The soils are not known to occur
in the United States.
Aquic Petroferric Kandiustox.—These soils have, within
125 cm of the mineral soil surface, both a petroferric contact
and redox depletions with a color value, moist, of 4 or more
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage). The soils are not
known to occur in the United States.
Humic Kandiustox.—These soils are like Typic
Kandiustox, but they have 16 kg or more organic carbon per m2
within 100 cm of the mineral soil surface. They are not known
to occur in the United States.
Humic Rhodic Kandiustox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, more than 50 percent colors that have hue of
2.5YR or redder and a value, moist, of 3 or less. They also
have 16 kg or more organic carbon per m2
within 100 cm of the
mineral soil surface. These soils are not known to occur in the
United States.
Humic Xanthic Kandiustox.—These soils have, in all
horizons at a depth between 25 and 125 cm from the mineral
soil surface, more than 50 percent colors that have hue of
7.5YR or yellower and value, moist, of 6 or more. They also
have 16 kg or more organic carbon per m2
within 100 cm of the
mineral soil surface. These soils are not known to occur in the
United States.
Lithic Kandiustox.—These soils have a lithic contact
within 125 cm of the mineral soil surface. They are not known
to occur in the United States.
Petroferric Kandiustox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
Plinthaquic Kandiustox.—These soils have, in one or more
horizons within 125 cm of the mineral soil surface, 5 percent
or more (by volume) plinthite, redox depletions with a color
value, moist, of 4 or more and chroma of 2 or less, and aquic
conditions for some time in normal years (or artificial
drainage). The soils are not known to occur in the United
States.
Plinthic Kandiustox.—These soils have 5 percent or more
(by volume) plinthite in one or more horizons within 125 cm of
the mineral soil surface. The soils are not known to occur in the
United States.
Rhodic Kandiustox.—These soils are like Typic
Kandiustox, but they have, in all horizons at a depth between
25 and 125 cm from the mineral soil surface, more than 50
percent colors that have hue of 2.5YR or redder and a value,
moist, of 3 or less. The soils are not known to occur in the
United States.
Xanthic Kandiustox.—These soils are like Typic Kandiustox,
but they have hue of 7.5YR or yellower and a color value, moist,
of 6 or more in all horizons at a depth between 25 and 125 cm
from the mineral soil surface. The soils are not known to occur in
the United States.
Sombriustox
These are the Ustox that have a sombric horizon. They are
poorly understood. They have an increase in content of organic
carbon in the subsoil. Commonly, this layer has andic soil
properties or some properties of spodic materials. The only
known pedons are near the Rift Valley in Africa.
Definition
Sombriustox are the Ustox that have a sombric horizon
within 150 cm of the mineral soil surface.
Key to Subgroups
ECAA. Sombriustox that have a petroferric contact within
125 cm of the mineral soil surface.
Petroferric Sombriustox
ECAB. Other Sombriustox that have a lithic contact within
125 cm of the mineral soil surface.
Lithic Sombriustox
ECAC. Other Sombriustox that have 16 kg/m2
or more
organic carbon between the mineral soil surface and a depth of
100 cm.
Humic Sombriustox
ECAD. Other Sombriustox.
Typic Sombriustox
Definition of Typic Sombriustox
Typic Sombriustox are the Sombriustox that:
1. Have neither a petroferric nor a lithic contact within 125
cm of the mineral soil surface; and
2. Have less than 16 kg of organic carbon per m2
to a depth
of 1 m, exclusive of surface litter.
Oxisols 693
Description of Subgroups
Typic Sombriustox.—The central concept or Typic
subgroup of Sombriustox is fixed on soils that do not have a
petroferric or lithic contact within 125 cm of the mineral soil
surface. These soils have less than 16 kg/m2
organic carbon to a
depth of 100 cm. They are not known to occur in the United
States.
Humic Sombriustox.—These soils are like Typic
Sombriustox, but they have 16 kg or more organic carbon per m2
within 100 cm of the mineral soil surface. They are not known to
occur in the United States.
Lithic Sombriustox.—These soils have a lithic contact
within 125 cm of the mineral soil surface. They are not known to
occur in the United States.
Petroferric Sombriustox.—These soils have a petroferric
contact within 125 cm of the mineral soil surface. They are not
known to occur in the United States.
695
The feature that is common to most Spodosols is the
presence of a spodic horizon, in which amorphous
mixtures of organic matter and aluminum, with or without
iron, have accumulated. The spodic horizon may be destroyed
by cultivation, yet spodic materials may still be present. In
undisturbed soils there commonly is an overlying eluvial
horizon, generally with a gray or light gray color similar to
that of uncoated quartz. In some Spodosols this horizon is too
thin to be preserved after cultivation, while in others it is very
thick. Below the spodic horizon, there may be a fragipan or
another sequum that has an argillic horizon. A few Spodosols
have a placic horizon either on or within a spodic horizon or
on a fragipan. Some Spodosols have layers thicker than a
placic horizon that are cemented by spodic materials and
organic matter (ortstein).
Most Spodosols have few clay-sized phyllosilicates. The
particle-size class is mostly sandy, sandy-skeletal, coarseloamy,
loamy-skeletal, or coarse-silty. In a few of the soils, it is
fine-loamy.
Spodosols are most extensive in areas of cool, humid or
perhumid climates. They also formed, however, in hot, humid
tropical regions and in warm, humid regions, where they occur
mostly in areas of quartz-rich sands that have a fluctuating
level of ground water. In many of the latter soils, the silt and
sand fractions contain very few weatherable minerals and the
albic horizons tend to be thick. Soils with an albic horizon 200
cm or more thick, however, are excluded from Spodosols and
are grouped with Entisols. Some of the very deep spodic
horizons may be buried, but it seems likely that others have
formed at great depths because the overlying soil materials
have very little iron and aluminum that could precipitate the
organic carbon. In some areas the source of aluminum may be
the ground water. Exclusion of a soil from Spodosols if the
albic horizon is very thick is largely pragmatic. The chemical
and physical properties of many Spodosols and Andisols are
very similar. The definition of spodic materials, however, is
based on the concept of organic matter and aluminum, with or
without iron, accumulating by illuviation.
The Spodosols in the United States occur mainly in areas of
late-Pleistocene or Holocene deposits. They are common in
Alaska, in the higher mountains of the West, in the Great
Lakes States, in the Northeast, and along the Atlantic coast of
both the United States and Canada. They also occur in
Northern Europe and northwestern Asia as well as New
Zealand and southern Australia. Most are covered with
coniferous or, less commonly, hardwood forests if they are not
cultivated or grazed. In tropical areas the vegetation may be
rain forest, palms, or a savanna that probably is anthropic.
The moisture regime of Spodosols is mostly udic, but a few
of the soils have a xeric regime. Some have aquic conditions.
Spodosols may have any soil temperature regime.
Spodosols are naturally infertile, but they can be highly
responsive to good management. Under cultivation, the spodic
horizon may be biologically destroyed, particularly if lime and
nitrogen are applied.
Definition of Spososols and Limits Between
Spodosols and Soils of Other Orders
Spodosols are mineral soils that do not have a plaggen
epipedon or an argillic or kandic horizon above a spodic
horizon and have one or more of the following:
1. A spodic horizon, an albic horizon in 50 percent or more
of each pedon, and a cryic soil temperature regime; or
2. An Ap horizon containing 85 percent or more spodic
materials; or
3. A spodic horizon that has all of the following properties:
a. One or more of the following:
(1) A thickness of 10 cm or more; or
(2) An overlying Ap horizon; or
(3) Cementation in 50 percent or more of each pedon;
or
(4) A coarse-loamy, loamy-skeletal, or finer particlesize
class and a frigid temperature regime; or
(5) A cryic temperature regime; and
b. An upper boundary within the following depths from
the mineral soil surface: either
(1) Less than 50 cm; or
(2) Less than 200 cm if the soil has a sandy or sandyCHAPTER
18
Spodosols1
1
This chapter was rewritten in 1992 following recommendations of the International
Committee on the Classification of Spodosols (ICOMOD), chaired initially by F. Ted Miller,
then by Robert V. Rourke (since 1986).
696 Soil Taxonomy
skeletal particle-size class between the mineral soil
surface and the spodic horizon; and
c. A lower boundary as follows:
(1) Either at a depth of 25 cm or more below the
mineral soil surface, at the top of a duripan or fragipan,
or at a densic, lithic, paralithic, or petroferric contact,
whichever is shallowest; or
(2) At any depth,
(a) If the spodic horizon has a coarse-loamy, loamyskeletal,
or finer particle-size class and the soil has a
frigid temperature regime; or
(b) If the soil has a cryic temperature regime; and
d. Either:
(1) A directly overlying albic horizon in 50 percent or
more of each pedon; or
(2) No andic soil properties in 60 percent or more of
the thickness either:
(a) Within 60 cm either of the mineral soil surface
or of the top of an organic layer with andic soil
properties, whichever is shallower, if there is no
densic, lithic, or paralithic contact, duripan, or
petrocalcic horizon within that depth; or
(b) Between either the mineral soil surface
or the top of an organic layer with andic soil
properties, whichever is shallower, and a densic,
lithic, or paralithic contact, a duripan, or a petrocalcic
horizon.
Limits Between Spodosols and the Other Soil
Orders
The definition of Spodosols must provide criteria that
separate Spodosols from all other soil orders. These criteria
define the limits of Spodosols in relation to all other known
kinds of soil.
1. Unlike Alfisols and Ultisols, Spodosols do not have an
argillic or kandic horizon above a spodic horizon.
2. Unlike Andisols, Aridisols, Entisols, Inceptisols,
Oxisols, Mollisols, and Vertisols, Spodosols have a spodic
horizon or an Ap horizon with 85 percent or more spodic
materials.
4. Unlike Gelisols, Spodosols do not have permafrost
within 100 cm of the soil surface or both permafrost within
200 cm of the soil surface and gelic materials within 100
cm of the soil surface.
5. Unlike Histosols, Spodosols must meet the definition of
mineral soils.
Representative Pedon and Data
Following is a description of a representative Spodosol. Data
for the pedon identified in this description are given in the table
“Characterization Data for a Spodosol.”
Classification: Coarse-loamy, isotic Typic Haplocryod
Site identification number: 95P0037
Location: Kuopio County, Finland; about 20 m east-southeast
of a gravel road; close to the village of Haapapuro
Finnish coordinates: X—6974.300 & Y—3522.920
Quadrangle name: Finnish Quad 4 Kainuu, Yleiskartta
Generalkarta
Latitude: 62 degrees 52 minutes 17 seconds N.
Longitude: 27 degrees 27 minutes 1 seconds E.
Slope: 7 percent
Aspect: 100 degrees
Horizontal shape: Plane
Vertical shape: Plane
Microrelief: Kind—mound; elevation—40 cm; pattern—
reticulate (net)
Elevation: 120 m
Landscape: Plateaus
Landform: Till plain
Parent material: Basal till
Annual precipitation: 510 mm
Average annual air temperature: 3 o
C
Average annual soil temperature: 5 o
C
Weather station name: Kuopio, Finland
Boulders and stones: Covering 2 percent of the surface
Natural drainage class: Well drained
Permeability class: Moderate
Land use: Mixed coniferous and hardwood forest (not grazed)
Plant association: Taiga forest
Soil moisture regime: Udic
Soil temperature regime: Cryic
Particle-size control section: 33 to 108 cm
Diagnostic horizons: An albic horizon from a depth of 8 to 25
cm and a spodic horizon at a depth of 25 to 48 cm
Described by: D.L. Newton, S.E. Lee, Dr. M. Raisanen, and
H.R. Mount
In the following pedon description, colors are for moist soil
unless otherwise indicated.
Oi—0 to 3 cm; dark reddish brown (5YR 3/2) fibric material;
weak very fine granular structure; very friable, nonsticky
and nonplastic; many fine and medium roots throughout;
many fine to coarse interstitial pores; 80 percent fiber
unrubbed, 75 percent rubbed; 5 percent subangular gravel;
extremely acid; abrupt smooth boundary.
Oe—3 to 8 cm; black (5YR 2/1) extremely cobbly hemic material;
weak very fine granular structure; very friable, nonsticky
and nonplastic; many fine and medium roots throughout;
many fine and medium interstitial pores; 60 percent fiber
unrubbed, 20 percent rubbed; 10 percent subangular gravel,
Spodosols 697
Characterization Data for a Spodosol
SITE IDENTIFICATION NO.: 95P0037
CLASSIFICATION: COARSE-LOAMY, ISOTIC TYPIC HAPLOCRYOD
GENERAL METHODS: 1B1A, 2A1, 2B
-1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-
-----------------------------------------------------------------------------------------------------------------------------------
(- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)
CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT
SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF
NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE
<- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL
95P 312 0- 3 Oi -- -- -- --
95P 313 3- 8 Oe -- -- -- 81
95P 314 8- 25 E 1.8 19.9 78.3 10.3 9.6 12.7 25.1 23.0 13.1 4.4 4 8 2 70 83
95P 315 25- 48 Bs 3.3 24.5 72.2 14.2 10.3 12.8 20.6 17.1 13.5 8.2 9 16 4 71 45
95P 316 48- 64 BC 1.9 34.7 63.4 21.6 13.1 11.5 18.1 16.6 11.4 5.8 8 14 5 65 27
95P 317 64-100 C 1.9 32.6 65.5 20.4 12.2 12.7 20.5 15.6 10.3 6.4 6 15 1 63 22
-----------------------------------------------------------------------------------------------------------------------------------
ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD
C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE
DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL
(cm) 6A1c 6B4a 6S3b 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A5 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1
Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm
0- 3 52.5 1.679 82.8
3- 8 50.9 1.279 83.3
8- 25 0.76 0.073 0.1 TR -- 2.56 1.33 2.4
25- 48 2.32 0.204 1.6 0.9 -- 4.39 4.48 8.6
48- 64 0.33 0.031 0.5 0.2 -- 1.58 2.53 2.5
64-100 0.12 0.015 0.3 0.1 -- 0.95 1.21 1.3
-----------------------------------------------------------------------------------------------------------------------------------
(- NH4OAc EXTRACTABLE BASES -) ACID- EXTR (- - - -CEC - - -) Al -BASE SAT- CO3 AS RES. COND.(- - - -PH - - -)
Ca Mg Na K SUM ITY Al SUM NH4- BASES SAT SUM NH4 CaCO3 ohms mmhos NaF CaCl2 H2O
DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc + Al OAc <2mm /cm /cm .01M
(cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 6G9d 5A3a 5A8c 5A3b 5G1 5C3 5C1 6E1g 8E1 8I 8C1d 8C1f 8C1f
<- - - - - - - - - - - -meq / 100 g - - - - - - - - - - -> <- - - - -Pct - - - -> 1:2 1:1
0- 3 25.4 7.7 0.3 5.2 38.6 73.7 112.3 84.4 34 46 6.1 3.8 4.3
3- 8 5.9 4.7 0.3 2.5 13.4 99.3 112.7 101.2 12 13 6.0 2.7 3.3
8- 25 0.2 0.2 0.1 0.1 0.6 3.8 1.5 4.4 4.6 2.1 71 14 13 7.1 3.4 3.9
25- 48 0.5 0.2 0.1 0.1 0.9 20.9 1.6 21.8 14.5 2.5 64 4 6 10.9 4.4 4.5
48- 64 0.1 0.1 TR -- 0.2 4.0 0.1 4.2 3.0 0.3 33 5 7 10.3 5.0 4.9
64-100 0.1 0.1 TR TR 0.2 2.0 TR 2.2 1.8 9 11 9.9 4.9 5.3
-----------------------------------------------------------------------------------------------------------------------------------
ACID OXALATE EXTRACTION PHOSPHORUS KCl TOTAL (- -WATER CONTENT- - )(- - - - WATER DISPERSIBLE - - - - ) MIN AGGRT
OPT Fe Si Al CIT- Mn C 0.06 1- 2- 15 <- - PIPETTE - - >< - HYDROMETER - > SOIL STABL
DEN RET ACID BAR BAR BAR BAR CLAY SILT SAND CLAY SILT SAND CONT <5mm
SAMPLE HZ 8J 6C9a 6V2b 6G12b 6S4b 6S5 6D3b 6A2e 4B1c 4B1a 4B1a 4B2b <- - - 3A1c - - -><- - - SML - - -> 8F1 4G1
NO. NO <- P c t o f < 2 m m -><- p p m ->< - - - - - - - - - - P e r c e n t o f < 2 m m - - - - - - - - - - >< Pct>
95P 312 1 47.75 152.8 13
95P 313 2 0.06 0.13 0.02 0.11 45.15 84.6 13
95P 314 3 0.05 0.11 0.01 0.04 TR 1.40 4.3 2.4
95P 315 4 0.34 0.93 0.42 1.51 TR 3.77 13.9 14.8
95P 316 5 0.03 0.29 0.18 0.53 -- 0.43 5.7 4.8
95P 317 6 0.02 0.17 0.07 0.21 -- 0.16 4.1 2.3
-----------------------------------------------------------------------------------------------------------------------------------
< - - - - - - - - - - - - - - - - - - - - SAND - SILT MINERALOGY (2.0-0.002mm) - - - - - - - - - - - - - - - - - - - - >
FRAC- < - - - - - X-RAY - - ->< - - - THERMAL - - - ->< - - - - - - - OPTICAL - - - - - - - - >< >INTERSAMPLE
TION < >< - DTA - ->< - TGA - ->TOT RE< - - - - - GRAIN COUNT - - - - - ->< >PRETA<
- - - - 7A2i - - - - >< - 7A3c - >< - 7A4c - >< - - - - - - - - 7B1a - - - - - - - - ->< > TION
NUMBER < - ->< - - - Peak Size - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - - - - - - - ->< - ->
95P 314 FS 46 QZ45 FP23 FK18 BT 4 HN 4 PR 3
95P 314 FS MS 3 GN 1 OPtr TMtr CAtr
95P 315 FS 56 QZ51 BT17 FK12 PR 7 FP 5 FE 3
95P 315 FS HN 2 GN 1 MS 1 OP 1 RAtr MZtr
95P 315 FS TMtr
95P 316 FS 54 QZ49 FK24 BT12 FP 6 PR 4 CD 3
95P 316 FS HN 1 OP 1 FE 1 MStr TMtr GNtr
95P 317 FS 62 QZ57 FK23 BT 8 PR 4 FP 3 HN 2
95P 317 FS CD 2 TM 1 OP 1 GN 1 MStr
-----------------------------------------------------------------------------------------------------------------------------------
The chemical data are based on the fraction less than 2 mm in size.
Fraction interpretation: FS, fine sand, 0.1-0.25 mm.
Mineral interpretation: QZ, quartz; FP, plagioclase feldspar; FK, potassium feldspar; BT, biotite; HN, hornblende; PR, pyroxene;
MS, muscovite; GN, garnet; OP, opaques; TM, tourmaline; CA, calcite; FE, iron oxides; RA, resistant aggregate; MZ, monazite;
CD, chalcedony.
Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.
698 Soil Taxonomy
60 percent subangular cobbles, and 10 percent subangular
stones; extremely acid; abrupt smooth boundary.
E—8 to 25 cm; gray (10YR 5/1) extremely cobbly loamy sand,
light gray (10YR 7/1) dry; weak fine granular structure;
very friable, nonsticky and nonplastic; common fine and
medium roots throughout; many fine to coarse interstitial
pores; estimated bulk density of 1.5 g cm-3
; 10 percent
subangular gravel, 60 percent subangular cobbles, and 10
percent subangular stones; very strongly acid; abrupt
smooth boundary.
Bs—25 to 48 cm; dark brown (7.5YR 3/4) very cobbly fine
sandy loam; weak fine granular structure; very friable,
moderately smeary, nonsticky and nonplastic; common
fine and medium roots throughout; many fine interstitial
pores; estimated bulk density of 1.2 g cm-3
; 20 percent
subangular gravel and 15 percent subangular cobbles;
strongly acid; gradual smooth boundary.
BC—48 to 64 cm; light olive brown (2.5Y 5/4) gravelly fine
sandy loam; weak fine granular structure; very friable,
nonsticky and nonplastic; few fine roots throughout; many
fine interstitial pores; estimated bulk density of 1.5 g cm-3
;
15 percent subangular gravel; moderately acid; gradual
smooth boundary.
C—64 to 100 cm; 60 percent olive (5Y 5/3) and 40 percent
olive gray (5Y 5/2) gravelly sandy loam; friable, nonsticky
and nonplastic; few very fine interstitial pores; estimated
bulk density of 1.5 g cm-3
; 15 percent subangular gravel;
slightly acid.
Key to Suborders
CA. Spodosols that have aquic conditions for some time in
normal years (or artificial drainage) in one or more horizons
within 50 cm of the mineral soil surface and have one or both
of the following:
1. A histic epipedon; or
2. Within 50 cm of the mineral soil surface,
redoximorphic features in an albic or a spodic horizon.
Aquods, p. 698
CB. Other Spodosols that have a cryic soil temperature
regime.
Cryods, p. 705
CC. Other Spodosols that have 6.0 percent or more organic
carbon in a layer 10 cm or more thick within the spodic
horizon.
Humods, p. 709
CD. Other Spodosols.
Orthods, p. 712
Aquods
Aquods are the Spodosols of wet regions. They are
characterized either by a shallow fluctuating water table or an
extremely humid climate. If the soil temperature regime is
mesic, isomesic, or warmer, most of the soils have a nearly
white albic horizon thick enough to persist under cultivation
or, in the wettest Aquods, a black surface horizon resting on a
dark reddish brown spodic horizon that is virtually free of iron.
Other Aquods have a placic horizon or a duripan or are
cemented by an amorphous mixture of sesquioxides and
organic matter.
The Aquods that do not have a placic horizon normally
have a transitional horizon between the albic horizon and the
spodic horizon, a feature virtually unique to these soils.
Aquods formed mainly in sandy materials of Pleistocene
age. They may have any temperature regime. Water-loving
plants of a very wide variety, ranging from sphagnum in cold
areas to palms in the tropics, grow on these soils. In the United
States, relatively few Aquods are cultivated, except in New
Jersey and Florida.
Definition
Aquods are the Spodosols that have aquic conditions for
some time in normal years (or artificial drainage) in one or
more horizons within 50 cm of the mineral soil surface and
have one or both of the following:
1. A histic epipedon; or
2. Within 50 cm of the mineral soil surface, redoximorphic
features in an albic or spodic horizon.
Key to Great Groups
CAA. Aquods that have a cryic soil temperature regime.
Cryaquods, p. 700
CAB. Other Aquods that have less than 0.10 percent iron (by
ammonium oxalate) in 75 percent or more of the spodic
horizon.
Alaquods, p. 699
CAC. Other Aquods that have a fragipan with its upper
boundary within 100 cm of the mineral soil surface.
Fragiaquods, p. 704
CAD. Other Aquods that have a placic horizon within 100
cm of the mineral soil surface in 50 percent or more of each
pedon.
Placaquods, p. 704
CAE. Other Aquods that have, in 90 percent or more of each
Spodosols 699
pedon, a cemented soil layer that has its upper boundary within
100 cm of the mineral soil surface.
Duraquods, p. 701
CAF. Other Aquods that have episaturation.
Epiaquods, p. 703
CAG. Other Aquods.
Endoaquods, p. 702
Alaquods
These soils occur primarily in the southeastern part of the
United States. Their water table generally fluctuates and in the
process reduces iron and moves it out of the soils. The spodic
horizon consists mostly of an accumulation of organic matter
and aluminum and commonly has few or no redoximorphic
features. The albic horizon in the drier Alaquods is normally
thick. The wettest Alaquods have no albic horizon but
generally have uncoated sand grains above the spodic horizon.
Alaquods normally have a sandy particle-size class. Because of
their high humus content, however, some of them feel and
behave like loamy soils.
Definition
Alaquods are the Aquods that:
1. Have less than 0.10 percent iron (by ammonium oxalate)
in 75 percent or more of the spodic horizon; and
2. Do not have a cryic soil temperature regime.
Key to Subgroups
CABA. Alaquods that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Alaquods
CABB. Other Alaquods that have, in 90 percent or more of
each pedon, a cemented soil layer that does not slake in water
after air drying and has its upper boundary within 100 cm of
the mineral soil surface.
Duric Alaquods
CABC. Other Alaquods that have a histic epipedon.
Histic Alaquods
CABD. Other Alaquods that have both:
1. Within 200 cm of the mineral soil surface, an argillic or
kandic horizon that has a base saturation of 35 percent or
more (by sum of cations) in some part; and
2. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
a spodic horizon at a depth of 75 to 125 cm.
Alfic Arenic Alaquods
CABE. Other Alaquods that have both:
1. An argillic or kandic horizon within 200 cm of the mineral
soil surface; and
2. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
a spodic horizon at a depth of 75 to 125 cm.
Arenic Ultic Alaquods
CABF. Other Alaquods that have both:
1. An umbric epipedon; and
2. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
a spodic horizon at a depth of 75 cm or more.
Arenic Umbric Alaquods
CABG. Other Alaquods that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of a spodic horizon at a depth of
75 to 125 cm.
Arenic Alaquods
CABH. Other Alaquods that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of a spodic horizon at a depth of
125 cm or more.
Grossarenic Alaquods
CABI. Other Alaquods that have, within 200 cm of the
mineral soil surface, an argillic or kandic horizon that has a
base saturation of 35 percent or more (by sum of cations) in
some part.
Alfic Alaquods
CABJ. Other Alaquods that have an argillic or kandic
horizon within 200 cm of the mineral soil surface.
Ultic Alaquods
CABK. Other Alaquods that have an ochric epipedon.
Aeric Alaquods
CABL. Other Alaquods.
Typic Alaquods
Definition of Typic Alaquods
Typic Alaquods are the Alaquods that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Do not have, in 90 percent or more of each pedon, any
cemented soil layer that does not slake in water after air drying
and has its upper boundary within 100 cm of the mineral soil
surface;
700 Soil Taxonomy
3. Do not have a histic or ochric epipedon;
4. Do not have an argillic or kandic horizon; and
5. Do not have a sandy particle-size class throughout a layer
extending from the mineral soil surface to the top of a spodic
horizon at a depth of 75 cm or more.
Description of Subgroups
Typic Alaquods.—The Typic subgroup of Alaquods is
centered on soils that have an umbric epipedon but do not have
a lithic contact within 50 cm of the soil surface, an argillic or
kandic horizon within 200 cm, a histic or ochric epipedon, a
cemented layer, or a sandy or sandy-skeletal particle-size class
from the soil surface to the top of a spodic horizon at a depth of
75 cm or more. Typic Alaquods commonly are saturated for
shorter periods than the Histic subgroups and for longer
periods than the Aeric subgroups. They occur in the
southeastern part of the United States as well as along the
Atlantic coast as far north as New Jersey. Typic Alaquods are
used as woodland, as grazing land, or for cultivated crops,
when water is controlled.
Aeric Alaquods.—These are the Alaquods that have an
ochric epipedon. The presence of the ochric epipedon is
indicative of Alaquods that are saturated for shorter periods
than the Typic subgroup. These soils do not have a lithic
contact within 50 cm of the soil surface, an argillic or kandic
horizon within 200 cm, a histic epipedon, a cemented layer, or
a sandy or sandy-skeletal particle-size class from the soil
surface to the top of a spodic horizon at a depth of 75 cm or
more. Commonly, the soils are forested. They occur along the
Atlantic coast from Florida to Virginia.
Alfic Alaquods.—These are the Alaquods that have an
argillic or kandic horizon with a base saturation of 35 percent
or more in some part. These soils do not have a lithic contact
within 50 cm of the soil surface, a histic epipedon, a cemented
soil layer, or a sandy or sandy-skeletal particle-size class from
the surface to the top of a spodic horizon at a depth of 75 cm or
more. The soils are mostly in wooded areas in Florida. Some
have been planted to pine or citrus trees.
Alfic Arenic Alaquods.—These are the Alaquods that have
a thick sandy E horizon above the spodic horizon and an
argillic or kandic horizon with a base saturation of at least 35
percent in at least some part. These soils most commonly occur
in Florida and are used as grazing land or for citrus.
Arenic Alaquods.—These are the Alaquods that have a
sandy E horizon 75 to 125 cm above the spodic horizon. These
soils do not have an argillic or kandic horizon, a lithic contact
within 50 cm of the soil surface, a cemented layer, or a histic
epipedon. They occur in Florida and North Carolina and are
used as woodland, as grazing land, or for citrus production.
Arenic Ultic Alaquods.—These are the Alaquods that have
an argillic or kandic horizon and sandy E horizons 75 to 125
cm thick above the spodic horizon. These soils do not have a
lithic contact within 50 cm of the soil surface, a cemented layer,
or a histic epipedon. They occur in Florida and commonly have
been planted to pine trees.
Arenic Umbric Alaquods.—These soils have an umbric
epipedon and sandy E horizons at least 75 cm thick above the
spodic horizon. These soils do not have a lithic contact within
50 cm of the soil surface, a cemented layer, a histic epipedon,
or an argillic or kandic horizon. They occur in Florida.
Duric Alaquods.—These are the Alaquods that have a
cemented soil layer but do not have a lithic contact within 50
cm of the soil surface. The cemented soil layer commonly is
ortstein, but it could also be cemented by silica. These soils are
rare in the United States.
Grossarenic Alaquods.—These are the Alaquods that have
sandy E horizons 125 cm or more thick above the spodic
horizon. These soils do not have an argillic or kandic horizon,
a histic epipedon, a cemented layer, or a lithic contact within
50 cm of the soil surface. They occur in Florida and the
Carolinas and commonly are used for pulp production.
Histic Alaquods.—These are the Alaquods that have a
histic epipedon. Typically, these soils are saturated close to the
surface. They do not have a lithic contact within 50 cm of the
soil surface or a cemented layer. They occur in Florida and are
used as woodland.
Lithic Alaquods.—These are the Alaquods that have a
lithic contact within 50 cm of the soil surface. These soils are
rare in the world.
Ultic Alaquods.—These are the Alaquods that have an
argillic or kandic horizon that has less than 35 percent base
saturation in all parts. These soils do not have a lithic contact
within 50 cm of the soil surface, a cemented layer, a histic
epipedon, or thick sandy E horizons above the spodic horizon.
They occur in Florida, the Carolinas, and Georgia. Some of
these soils have been planted to pine, and some are used as
grazing land or for the production of truck crops.
Cryaquods
These Aquods occur in areas of cold climates, mainly at high
latitudes. Because they are both cold and wet, Cryaquods have
been given low priority for study. Most are covered with
coniferous forest or tundra vegetation. Aquic conditions persist
during much of the growing season. In the United States, these
soils occur in Alaska.
Definition
Cryaquods are the Aquods that have a cryic soil temperature
regime.
Key to Subgroups
CAAA. Cryaquods that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Cryaquods
Spodosols 701
CAAB. Other Cryaquods that have a placic horizon within 100
cm of the mineral soil surface in 50 percent or more of each
pedon.
Placic Cryaquods
CAAC. Other Cryaquods that have, in 90 percent or more of
each pedon, a cemented soil layer that does not slake in water
after air drying and has its upper boundary within 100 cm of
the mineral soil surface.
Duric Cryaquods
CAAD. Other Cryaquods that have andic soil properties
throughout horizons that have a total thickness of 25 cm or
more within 75 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Andic Cryaquods
CAAE. Other Cryaquods that have a spodic horizon less than
10 cm thick in 50 percent or more of each pedon.
Entic Cryaquods
CAAF. Other Cryaquods.
Typic Cryaquods
Definition of Typic Cryaquods
Typic Cryaquods are the Cryaquods that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Do not have andic soil properties throughout horizons that
have a total thickness of 25 cm or more within 75 cm either of
the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower;
3. Do not have, in 50 percent or more of each pedon, a placic
horizon within 100 cm of the mineral soil surface;
4. Do not have, in 90 percent or more of each pedon, a
cemented soil layer that does not slake in water after air drying
and has its upper boundary within 100 cm of the mineral soil
surface; and
5. Have a spodic horizon 10 cm or more thick in 50 percent
or more of each pedon.
Description of Subgroups
Typic Cryaquods.—The Typic subgroup of Cryaquods is
centered on soils that have a spodic horizon 10 cm or more
thick. Typic Cryaquods do not have a lithic contact within 50
cm of the soil surface, a placic horizon, a cemented soil layer,
or andic soil properties in a layer 25 cm or more thick within
75 cm of the soil surface.
Andic Cryaquods.—These are the Cryaquods that have
andic soil properties throughout horizons with a total thickness
of 25 cm or more within 75 cm of the soil surface. These soils
do not have a lithic contact within 50 cm of the soil surface, a
placic horizon, or a cemented soil layer.
Duric Cryaquods.—These are the Cryaquods that have a
cemented soil layer. The cemented layer commonly is ortstein,
but in some soils the cementing agents are not well understood.
These soils do not have a lithic contact within 50 cm of the soil
surface or a placic horizon.
Entic Cryaquods.—These are the Cryaquods that have a
spodic horizon that is less than 10 cm thick. These soils do not
have a lithic contact within 50 cm of the soil surface, a placic
horizon, a cemented layer, or andic soil properties in one-third
or more of the upper 75 cm.
Lithic Cryaquods.—These are the Cryaquods that have a
lithic contact within 50 cm of the mineral soil surface. These
soils are relatively rare in the world. They commonly are
forested.
Placic Cryaquods.—These are the Cryaquods that have a
placic horizon. The placic horizon commonly is convoluted.
These soils do not have a lithic contact within 50 cm of the soil
surface.
Duraquods
These Aquods have a cemented soil layer that in many areas
is a combination of iron and/or aluminum and organic matter.
In some of these soils, silica also is a cementing agent.
Duraquods are seasonally saturated above the cemented soil
layer but not necessarily below it. In the United States, these
soils occur mostly in the Northwest and in Michigan. They also
are known to occur in New Zealand, under kauri pine. The
cemented soil layer in Duraquods severely restricts plant
rooting. Currently, few of these soils are recognized.
Definition
Duraquods are the Aquods that:
1. Have, in 90 percent or more of each pedon, a cemented soil
layer that does not slake in water after air drying and has its
upper boundary within 100 cm of the mineral soil surface;
2. Have 0.10 percent or more iron (by ammonium oxalate)
in 75 percent or more of the spodic horizon;
3. Do not have a cryic temperature regime;
4. Do not have a fragipan with its upper boundary within 100
cm of the mineral soil surface; and
5. Do not have a placic horizon within 100 cm of the mineral
soil surface in 50 percent or more of each pedon.
Key to Subgroups
CAEA. Duraquods that have a histic epipedon.
Histic Duraquods
CAEB. Other Duraquods that have andic soil properties
throughout horizons that have a total thickness of 25 cm or
702 Soil Taxonomy
more within 75 cm either of the mineral soil surface or of the top
of an organic layer with andic soil properties, whichever is
shallower.
Andic Duraquods
CAEC. Other Duraquods.
Typic Duraquods
DefinitionofTypicDuraquods
Typic Duraquods are the Duraquods that:
1. Do not have a histic epipedon; and
2. Do not have andic soil properties throughout horizons that
have a total thickness of 25 cm or more within 75 cm either of
the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower.
Description of Subgroups
Typic Duraquods.—The Typic subgroup of Duraquods is
centered on soils that do not have a histic epipedon and do not
have andic soil properties in one-third or more of the upper 75
cm. Typic Duraquods are the most common subgroup of
Duraquods and occur on the west coast, in New England, and
in Indiana and Michigan in the United States.
Andic Duraquods.—These soils have a cemented layer that
commonly is ortstein but is not limited to ortstein. These soils
do not have a histic epipedon. They occur in the State of
Washington.
Histic Duraquods.—These soils have a histic epipedon.
They are rare in the world.
Endoaquods
These Aquods do not have a perched water table. They have
a considerable accumulation of iron in addition to aluminum
and organic carbon in the spodic horizon. The spodic horizon
has few to many redoximorphic features and commonly is
brown to dark reddish brown. Most Endoaquods have an albic
horizon. Some of the wettest do not have an albic horizon but
normally have uncoated sand grains above the spodic horizon.
Definition
Endoaquods are the Aquods that:
1. Have endosaturation;
2. Have 0.10 percent or more iron (by ammonium oxalate)
in 75 percent or more of the spodic horizon;
3. Do not have a cryic temperature regime;
4. Do not have a fragipan with its upper boundary within 100
cm of the mineral soil surface;
5. Do not have a placic horizon within 100 cm of the mineral
soil surface in 50 percent or more of each pedon; and
6. Do not have, in 90 percent or more of each pedon, a
cemented soil layer that does not slake in water after air drying
and has its upper boundary within 100 cm of the mineral soil
surface.
Key to Subgroups
CAGA. Endoaquods that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Endoaquods
CAGB. Other Endoaquods that have a histic epipedon.
Histic Endoaquods
CAGC. Other Endoaquods that have andic soil properties
throughout horizons that have a total thickness of 25 cm or
more within 75 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Andic Endoaquods
CAGD. Other Endoaquods that have an argillic or kandic
horizon within 200 cm of the mineral soil surface.
Argic Endoaquods
CAGE. Other Endoaquods that have an umbric epipedon.
Umbric Endoaquods
CAGF. Other Endoaquods.
Typic Endoaquods
Definition of Typic Endoaquods
Typic Endoaquods are the Endoaquods that:
1. Do not have a histic or umbric epipedon;
2. Do not have andic soil properties throughout horizons that
have a total thickness of 25 cm or more within 75 cm either of
the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower;
3. Do not have an argillic or kandic horizon underlying the
spodic horizon; and
4. Do not have a lithic contact within 50 cm of the mineral
soil surface.
Description of Subgroups
Typic Endoaquods.—The Typic subgroup of Endoaquods is
centered on soils that have an ochric epipedon. These soils do
not have a lithic contact within 50 cm of the soil surface, an
argillic or kandic horizon, or andic soil properties in a layer 25
cm or more thick within 75 cm of the soil surface. The soils
occur in both the western and northeastern parts of the United
States and in Michigan, Wisconsin, and Indiana.
Andic Endoaquods.—These are the Endoaquods that have
andic soil properties throughout horizons totaling 25 cm or
Spodosols 703
more thick from the soil surface to a depth of 75 cm. These soils
do not have a histic epipedon or a lithic contact within 50 cm of
the soil surface.
Argic Endoaquods.—These are the Endoaquods that have
an argillic or kandic horizon below the spodic horizon. These
soils do not have a lithic contact within 50 cm of the soil
surface, a histic epipedon, or andic soil properties in a layer 25
cm or more thick from the soil surface to a depth of 75 cm. The
soils occur in Michigan and Wisconsin.
Histic Endoaquods.—These are the Endoaquods that have
a histic epipedon. Commonly, these soils are saturated
throughout most of the year. They do not have a lithic contact
within 50 cm of the soil surface.
Lithic Endoaquods.—These are the Endoaquods that have
a lithic contact within 50 cm of the soil surface. These soils are
rare in the world.
Umbric Endoaquods.—These are the Endoaquods that have
an umbric epipedon. These soils do not have a lithic contact
within 50 cm of the soil surface, a histic epipedon, an argillic or
kandic horizon, or andic soil properties in a layer 25 cm or more
thick from the soil surface to a depth of 75 cm. The soils occur in
North Carolina and Florida.
Epiaquods
These Aquods have a perched water table above one or more
relatively impermeable layers. Epiaquods normally have a
considerable accumulation of iron in addition to aluminum and
organic matter. The relatively impermeable layers commonly
are argillic horizons or dense till.
Definition
Epiaquods are the Aquods that:
1. Have episaturation;
2. Have 0.10 percent or more iron (by ammonium oxalate)
in 75 percent or more of the spodic horizon;
3. Do not have a cryic temperature regime;
4. Do not have a fragipan with its upper boundary within 100
cm of the mineral soil surface;
5. Do not have a placic horizon within 100 cm of the
mineral soil surface in 50 percent or more of each pedon;
and
6. Do not have, in 90 percent or more of each pedon, a
cemented soil layer that does not slake in water after air drying
and has its upper boundary within 100 cm of the mineral soil
surface.
Key to Subgroups
CAFA. Epiaquods that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Epiaquods
CAFB. Other Epiaquods that have a histic epipedon.
Histic Epiaquods
CAFC. Other Epiaquods that have andic soil properties
throughout horizons that have a total thickness of 25 cm or
more within 75 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Andic Epiaquods
CAFD. Other Epiaquods that have, within 200 cm of the
mineral soil surface, an argillic or kandic horizon that has a
base saturation of 35 percent or more (by sum of cations) in
some part.
Alfic Epiaquods
CAFE. Other Epiaquods that have an argillic or kandic
horizon within 200 cm of the mineral soil surface.
Ultic Epiaquods
CAFF. Other Epiaquods that have an umbric epipedon.
Umbric Epiaquods
CAFG. Other Epiaquods.
Typic Epiaquods
Definition of Typic Epiaquods
Typic Epiaquods are the Epiaquods that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Do not have a histic or umbric epipedon;
3. Do not have andic soil properties throughout horizons that
have a total thickness of 25 cm or more within 75 cm either of
the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower; and
4. Do not have an argillic or kandic horizon underlying the
spodic horizon.
Description of Subgroups
Typic Epiaquods.—The Typic subgroup of Epiaquods is
centered on soils that have an ochric epipedon. These soils do
not have an argillic or kandic horizon, a lithic contact within
50 cm of the soil surface, or andic soil properties in a layer 25
cm or more thick from the surface to a depth of 75 cm. These
soils occur in the northeastern part of the United States and in
Michigan and Wisconsin.
Alfic Epiaquods.—These soils have an argillic or kandic
horizon that has a base saturation of 35 percent or more in at
least some part. They do not have a lithic contact within 50 cm
of the soil surface or andic soil properties in a layer 25 cm or
more thick within 75 cm of the soil surface. These soils occur
in Michigan, Minnesota, and Wisconsin.
704 Soil Taxonomy
Andic Epiaquods.—These soils have andic soil properties in a
layer 25 cm or more thick within 75 cm of the soil surface. They
do not have a lithic contact within 50 cm of the soil surface or a
histic epipedon.
Histic Epiaquods.—These soils have a histic epipedon.
They tend to be saturated during most of the growing season.
They do not have a lithic contact within 50 cm of the soil
surface. These soils occur in Michigan.
Lithic Epiaquods.—These soils have a lithic contact within
50 cm of the soil surface. They are rare in the world.
Ultic Epiaquods.—These soils have an argillic horizon that
has a base saturation of less than 35 percent in all parts. They
do not have a lithic contact within a depth of 50 cm, a histic
epipedon, or andic soil properties in a layer 25 cm or more
thick within 75 cm of the soil surface. These soils occur in
Michigan, Minnesota, and Wisconsin.
Umbric Epiaquods.—These are the Epiaquods that have an
umbric horizon. These soils do not have a lithic contact within
50 cm of the soil surface, a histic epipedon, an argillic or
kandic horizon, or andic soil properties in a layer 25 cm or
more thick within 75 cm of the soil surface.
Fragiaquods
These are the Aquods that have a fragipan below the spodic
horizon, normally at a depth of 40 to 75 cm below the mineral
soil surface. Plant roots are shallow, and the soil clinging to the
roots of falling trees has in many areas developed a microrelief
of 20 to 50 cm. The soil temperature regime is normally frigid.
These soils are nearly level, but few of them are cultivated,
except for those used for the production of hay. Most of the
soils are forested. Fragiaquods are not extensive in the United
States.
Definition
Fragiaquods are the Aquods that:
1. Have a fragipan with its upper boundary within 100 cm of
the mineral soil surface;
2. Have 0.10 percent or more iron (by ammonium oxalate)
in 75 percent or more of the spodic horizon; and
3. Do not have a cryic temperature regime.
Key to Subgroups
CACA. Fragiaquods that have a histic epipedon.
Histic Fragiaquods
CACB. Other Fragiaquods that have a surface horizon 30 cm
or more thick that meets all of the requirements for a plaggen
epipedon except thickness.
Plagganthreptic Fragiaquods
CACC. Other Fragiaquods that have an argillic or kandic
horizon within 200 cm of the mineral soil surface.
Argic Fragiaquods
CACD. Other Fragiaquods.
Typic Fragiaquods
DefinitionofTypicFragiaquods
Typic Fragiaquods are the Fragiaquods that:
1. Do not have a histic epipedon;
2. Do not have a surface horizon more than 30 cm thick that
meets all of the requirements for a plaggen epipedon except
thickness; and
3. Do not have, within 200 cm of the mineral soil surface, an
argillic or kandic horizon that has a base saturation of 35
percent or more (by sum of cations) in any part.
Description of Subgroups
Typic Fragiaquods.—The Typic subgroup of Fragiaquods
is centered on soils that do not have a histic epipedon, an
argillic or kandic horizon, or a surface horizon 30 cm or more
thick that meets all of the requirements for a plaggen epipedon
except thickness. These soils generally support forest
vegetation, but some have been cleared and are used as pasture.
Typic Fragiaquods occur in Michigan, New York, and
Vermont.
Argic Fragiaquods.—These soils have an argillic or kandic
horizon. Commonly, the argillic or kandic horizon is within
the fragipan. These soils do not have a histic epipedon or a
surface horizon 30 cm or more thick that meets all of the
requirements for a plaggen epipedon except thickness. They
are known to occur in Michigan.
Histic Fragiaquods.—These soils have a histic epipedon.
Commonly, they are saturated throughout most of the growing
season. They are rare in the world.
Plagganthreptic Fragiaquods.—These are the Fragiaquods
that have a surface horizon 30 cm or more thick that has all of
the properties of a plaggen epipedon except thickness. These
soils are rare in the world, but they do occur in Europe.
Placaquods
These are the Aquods that have an involute placic horizon.
The horizons above the placic horizon have low-contrast
mottles that are probably caused by organic matter. Placaquods
are known to occur only in areas of perhumid oceanic climates.
Many have, or used to have, sphagnum and heath vegetation.
Definition
Placaquods are the Aquods that:
Spodosols 705
1. Have a placic horizon within 100 cm of the mineral soil
surface in 50 percent or more of each pedon;
2. Have 0.10 percent or more iron (by ammonium oxalate)
in 75 percent or more of the spodic horizon;
3. Do not have a cryic temperature regime; and
4. Do not have a fragipan with its upper boundary within 100
cm of the mineral soil surface.
Key to Subgroups
CADA. Placaquods that have andic soil properties
throughout horizons that have a total thickness of 25 cm or
more within 75 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Andic Placaquods
CADB. Other Placaquods.
Typic Placaquods
Definition of Typic Placaquods
Typic Placaquods are the Placaquods that do not have andic
soil properties throughout horizons that have a total thickness
of 25 cm or more within 75 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Description of Subgroups
Typic Placaquods.—The Typic subgroup of Placaquods
is centered on soils that do not have andic soil properties
in a layer 25 cm or more thick within 75 cm of the soil
surface. These soils occur in Great Britain and in Western
Europe.
Andic Placaquods.—These are the Placaquods that have
andic soil properties in a layer 25 cm or more thick within 75
cm of the surface. These soils are rare in the world.
Cryods
Cryods are the Spodosols of high latitudes and/or high
elevations. In the United States, they occur mostly in southeast
Alaska and in the mountains of Washington and Oregon. Some
of these soils are in the mountains of New York and northern
New England. Many Cryods formed in volcanic ash or glacial
drift, and some formed in residuum or colluvium on mountain
slopes. Cryods commonly have an O horizon over a very thin
or intermittent albic horizon, which overlies a well-developed
spodic horizon. Some of the soils have a placic horizon,
ortstein, or another cemented soil layer within 100 cm of the
mineral soil surface. In many Cryods the content of organic
carbon in the upper part of the spodic horizon is relatively
high. The vegetation is mostly a coniferous forest or alpine
tundra.
Definition
Cryods are the Spodosols that:
1. Have a cryic temperature regime; and
2. Do not have both aquic conditions within 50 cm of the
mineral soil surface and either of the following:
a. A histic epipedon; or
b. Within 50 cm of the mineral soil surface,
redoximorphic features in an albic or spodic horizon.
Key to Great Groups
CBA. Cryods that have a placic horizon within 100 cm of the
mineral soil surface in 50 percent or more of each pedon.
Placocryods, p. 709
CBB. Other Cryods that have, in 90 percent or more of each
pedon, a cemented soil layer that does not slake in water after
air drying and has its upper boundary within 100 cm of the
mineral soil surface.
Duricryods, p. 705
CBC. Other Cryods that have 6.0 percent or more organic
carbon throughout a layer 10 cm or more thick within the
spodic horizon.
Humicryods, p. 708
CBD. Other Cryods.
Haplocryods, p. 706
Duricryods
These are the Cryods that have, either within or below the
spodic horizon, a cemented horizon that is considered ortstein
if it is more than 2.5 cm thick and part of the spodic horizon.
In the United States, these soils are known to occur in the State
of Washington. They probably also occur in other cold regions
of the world.
Definition
Duricryods are the Cryods that:
1. Have, in 90 percent or more of each pedon, a cemented soil
layer that does not slake in water after air drying and has its
upper boundary within 100 cm of the mineral soil surface; and
2. Do not have a placic horizon within 100 cm of the mineral
soil surface in 50 percent or more of each pedon.
Key to Subgroups
CBBA. Duricryods that have both:
1. Redoximorphic features in one or more horizons
within 75 cm of the mineral soil surface and also aquic
706 Soil Taxonomy
conditions for some time in normal years (or artificial
drainage); and
2. Andic soil properties throughout horizons that have a
total thickness of 25 cm or more within 75 cm either of the
mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower.
Aquandic Duricryods
CBBB. Other Duricryods that have andic soil properties
throughout horizons that have a total thickness of 25 cm or
more within 75 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Andic Duricryods
CBBC. Other Duricryods that have redoximorphic features in
one or more horizons within 75 cm of the mineral soil surface
and also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Duricryods
CBBD. Other Duricryods that are saturated with water in one
or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Duricryods
CBBE. Other Duricryods that have 6.0 percent or more
organic carbon throughout a layer 10 cm or more thick within
the spodic horizon.
Humic Duricryods
CBBF. Other Duricryods.
Typic Duricryods
Definition of Typic Duricryods
Typic Duricryods are the Duricryods that:
1. Do not have andic soil properties throughout horizons that
have a total thickness of 25 cm or more within 75 cm either of
the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower;
2. Do not have 6.0 percent or more organic carbon
throughout a layer 10 cm or more thick within the spodic
horizon;
3. Do not have redoximorphic features in one or more
horizons within 75 cm of the mineral soil surface and also
aquic conditions for some time in normal years; and
4. Are not saturated with water in any layer within 100 cm of
the mineral soil surface in normal years for either or both 20 or
more consecutive days or 30 or more cumulative days.
Description of Subgroups
Typic Duricryods.—The Typic subgroup of Duricryods is
centered on soils that are not saturated with water within 100
cm of the soil surface and soils that do not have andic soil
properties in a layer 25 cm or more thick within 75 cm of the
soil surface. These soils also do not have thick Bh or Bhs
horizons. They are wooded and occur in Alaska.
Andic Duricryods.—These are the Duricryods that are
intergrades to the Andisols. They have andic soil properties in
a layer 25 cm or more thick within 75 cm of the soil surface.
They do not have aquic conditions and redox features within
75 cm of the soil surface. They are wooded and occur in the
State of Washington.
Aquandic Duricryods.—These are the Duricryods that
have andic soil properties in a layer 25 cm or more thick
within 75 cm of the soil surface and have aquic conditions
accompanied by redoximorphic features within 75 cm of the
soil surface. These soils are rare in the world.
Aquic Duricryods.—These are the Duricryods that have
aquic conditions accompanied by redoximorphic features
within 75 cm of the soil surface. These soils do not have andic
soil properties in a layer 25 cm or more thick within 75 cm of
the soil surface. They are rare in the world.
Humic Duricryods.—These are the Duricryods that have
a thick Bh or Bhs horizon. These soils are not saturated
within 100 cm of the soil surface and do not have andic soil
properties in a layer 25 cm or more thick within 75 cm of the
soil surface.
Oxyaquic Duricryods.—These are the Duricryods that are
saturated within 100 cm of the soil surface for 20 or more
consecutive days or 30 or more cumulative days in normal
years. Commonly, these soils are saturated by snowmelt during
the spring. They do not have either redoximorphic features
within 75 cm of the soil surface or andic soil properties in a
layer 25 cm or more thick within 75 cm of the soil surface.
Haplocryods
These are the Cryods of high latitudes or high elevations that
do not have a fragipan, a placic horizon, or other cemented soil
layers and do not have a very high content of organic matter in
the spodic horizon. The horizons are mostly thin but may be
strongly contrasting. The base of the spodic horizon is generally
less than 50 cm below the mineral soil surface. Some
Haplocryods have permafrost at varying depths below the
spodic horizon. Others have, below the spodic horizon, another
sequum with an argillic or kandic horizon. In the United
States, these soils occur mostly in Alaska and in the higher
mountains of the West and Northeast.
Definition
Haplocryods are the Cryods that:
1. Do not have 6.0 percent or more organic carbon
Spodosols 707
throughout a layer 10 cm or more thick within the spodic
horizon;
2. Do not have, in 50 percent or more of each pedon, a placic
horizon within 100 cm of the mineral soil surface; and
3. Do not have, in 90 percent or more of each pedon, a
cemented soil layer that does not slake in water after air drying
and has its upper boundary within 100 cm of the mineral soil
surface.
Key to Subgroups
CBDA. Haplocryods that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Haplocryods
CBDB. Other Haplocryods that have both:
1. Redoximorphic features in one or more horizons
within 75 cm of the mineral soil surface and also aquic
conditions for some time in normal years (or artificial
drainage); and
2. Andic soil properties throughout horizons that have a
total thickness of 25 cm or more within 75 cm either of the
mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower.
Aquandic Haplocryods
CBDC. Other Haplocryods that have andic soil properties
throughout horizons that have a total thickness of 25 cm or
more within 75 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Andic Haplocryods
CBDD. Other Haplocryods that have redoximorphic features
in one or more horizons within 75 cm of the mineral soil
surface and also aquic conditions for some time in normal
years (or artificial drainage).
Aquic Haplocryods
CBDE. Other Haplocryods that are saturated with water in
one or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Haplocryods
CBDF. Other Haplocryods that have 1.1 percent or less
organic carbon in the upper 10 cm of the spodic horizon.
Entic Haplocryods
CBDG. Other Haplocryods.
Typic Haplocryods
DefinitionofTypicHaplocryods
Typic Haplocryods are the Haplocryods that:
1. Do not have a lithic contact within 50 cm of the mineral soil
surface;
2. Do not have andic soil properties throughout horizons that
have a total thickness of 25 cm or more within 75 cm either of
the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower;
3. Do not have redoximorphic features in one or more
horizons within 75 cm of the mineral soil surface and also
aquic conditions for some time in normal years;
4. Are not saturated with water in any layer within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years; and
5. Have 1.2 percent or more organic carbon in the upper 10
cm of the spodic horizon.
Description of Subgroups
Typic Haplocryods.—The Typic subgroup of Haplocryods
is centered on soils that have more than 1.1 percent organic
carbon in the upper 10 cm of the spodic horizon. These soils do
not have a lithic contact within 50 cm of the soil surface, andic
soil properties in a layer 25 cm or more thick within 75 cm of
the soil surface, or a saturated layer within 100 cm of the soil
surface. They commonly are forested, and some are used for
timber production. A few have been cleared and are used for
hay. Typic Haplocryods occur in Oregon and Alaska.
Andic Haplocryods.—These are the Haplocryods that have
andic soil properties in a layer 25 cm or more thick within 75
cm of the soil surface. These soils do not have a lithic contact
within 50 cm of the soil surface and do not have aquic
conditions and redoximorphic features within 75 cm of the soil
surface. They occur in Washington and Alaska, where they are
used for timber production and wildlife habitat. A few areas
have been cleared for crop production.
Aquandic Haplocryods.—These are the Haplocryods that
have both andic soil properties in a layer 25 cm or more thick
within 75 cm of the soil surface and aquic conditions and
redoximorphic features within 75 cm of the soil surface. These
soils do not have a lithic contact within 50 cm of the soil
surface. They are rare in the world.
Aquic Haplocryods.—These are the Haplocryods that have
aquic conditions and redoximorphic features within 75 cm of
the soil surface. These soils do not have andic soil properties in
a layer 25 cm or more thick within 75 cm of the soil surface or
a lithic contact within 50 cm of the soil surface. The soils
support forest vegetation and occur in New Hampshire, Maine,
and New York.
Entic Haplocryods.—These are the Haplocryods that have
1.1 percent or less organic carbon in the upper 10 cm of the
spodic horizon. These soils do not have a lithic contact within
708 Soil Taxonomy
50 cm of the soil surface, andic soil properties in a layer 25 cm or
more thick within 75 cm of the soil surface, or a saturated layer
within 100 cm of the soil surface. The soils occur in Alaska and
commonly are forested.
Lithic Haplocryods.—These are the Haplocryods that have
a lithic contact within 50 cm of the soil surface. These soils
occur under forest vegetation in Washington and in an alpine
environment in Alaska.
Oxyaquic Haplocryods.—These are the Haplocryods that are
saturated with water within 100 cm of the soil surface for 20 or
more consecutive days or 30 or more cumulative days
in normal years. These soils do not have redoximorphic
features within 75 cm of the soil surface or andic soil
properties in a layer 25 cm or more thick within 75 cm of
the soil surface.
Humicryods
Humicryods are the Cryods of high latitudes or high
elevations. In the United States, they occur mostly in southeast
Alaska and in the mountains of Washington and Oregon. Some
are in the higher mountains of the Northeast. Humicryods
commonly have a thick O horizon over a very thin or
intermittent albic horizon, which overlies a dark colored spodic
horizon. They have a high content of organic carbon in the
upper part of the spodic horizon. The vegetation commonly is a
coniferous forest or alpine tundra.
Definition
Humicryods are the Cryods that:
1. Have 6.0 percent or more organic carbon throughout a
layer 10 cm or more thick within the spodic horizon;
2. Do not have, in 50 percent or more of each pedon, a placic
horizon within 100 cm of the mineral soil surface; and
3. Do not have, in 90 percent or more of each pedon, a
cemented soil layer that does not slake in water after air drying
and has its upper boundary within 100 cm of the mineral soil
surface.
Key to Subgroups
CBCA. Humicryods that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Humicryods
CBCB. Other Humicryods that have both:
1. Redoximorphic features in one or more horizons
within 75 cm of the mineral soil surface and also aquic
conditions for some time in normal years (or artificial
drainage); and
2. Andic soil properties throughout horizons that have a
total thickness of 25 cm or more within 75 cm either of the
mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower.
Aquandic Humicryods
CBCC. Other Humicryods that have andic soil properties
throughout horizons that have a total thickness of 25 cm or
more within 75 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Andic Humicryods
CBCD. Other Humicryods that have redoximorphic features
in one or more horizons within 75 cm of the mineral soil
surface and also aquic conditions for some time in normal
years (or artificial drainage).
Aquic Humicryods
CBCE. Other Humicryods that are saturated with water in
one or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Humicryods
CBCF. Other Humicryods.
Typic Humicryods
Definition of Typic Humicryods
Typic Humicryods are the Humicryods that:
1. Are not saturated with water in any layer within 100 cm of
the mineral soil surface in normal years for either or both 20 or
more consecutive days or 30 or more cumulative days;
2. Do not have redoximorphic features in one or more
horizons within 75 cm of the mineral soil surface and also
aquic conditions for some time in normal years;
3. Do not have a lithic contact within 50 cm of the mineral
soil surface; and
4. Do not have andic soil properties throughout horizons that
have a total thickness of 25 cm or more within 75 cm either of
the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower.
Description of Subgroups
Typic Humicryods.—The Typic subgroup of Humicryods is
centered on soils that do not have a lithic contact within 50 cm
of the soil surface, saturation with water within 100 cm of the
soil surface, or andic soil properties in a layer 25 cm or more
thick within 75 cm of the soil surface. These soils commonly
are forested and are used for timber production and wildlife
habitat. They occur in the northeastern part of the United
States and in Oregon and Alaska.
Spodosols 709
Andic Humicryods.—These are the Humicryods that have
andic soil properties in a layer 25 cm or more thick within 75
cm of the soil surface. These soils do not have a lithic contact
within 50 cm of the soil surface or aquic conditions and
redoximorphic features within 75 cm of the soil surface. They
occur in the States of Alaska and Washington. In Alaska the
soils occur under alpine tundra, and in Washington they are
under forest vegetation.
Aquandic Humicryods.—These are the Humicryods that
have andic soil properties in a layer 25 cm or more thick
within 75 cm of the soil surface and have aquic conditions and
redoximorphic features within 75 cm of the soil surface. These
soils do not have a lithic contact within 50 cm of the soil
surface. They occur in the State of Washington. They are used
for woodland and wildlife habitat.
Aquic Humicryods.—These are the Humicryods that have
aquic conditions and redoximorphic features within 75 cm of
the soil surface. These soils do not have a lithic contact within
50 cm of the soil surface or andic soil properties in a layer 25
cm or more thick within 75 cm of the soil surface. The soils
occur in the Northeastern United States and support forest
vegetation.
Lithic Humicryods.—These are the Humicryods that have
a lithic contact within 50 cm of the soil surface. These soils
occur in Alaska, Maine, Vermont, New Hampshire, and New
York and are used for wildlife habitat and woodland.
Oxyaquic Humicryods.—These are the Humicryods that are
saturated with water for 20 or more consecutive days or 30 or
more cumulative days in normal years. These soils do not have a
lithic contact within 50 cm of the soil surface or andic soil
properties in a layer 25 cm or more thick within 75 cm of the soil
surface. The soils formed under forest vegetation in Maine, New
Hampshire, New York, and Vermont.
Placocryods
These Cryods have a placic horizon, normally within the
spodic horizon. In the United States, they are known to occur
only in Alaska. They are thought to be rare elsewhere in the
world.
Definition
Placocryods are the Cryods that have a placic horizon
within 100 cm of the mineral soil surface in 50 percent or more
of each pedon.
Key to Subgroups
CBAA. Placocryods that have andic soil properties
throughout horizons that have a total thickness of 25 cm or
more within 75 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Andic Placocryods
CBAB. Other Placocryods that have 6.0 percent or more
organic carbon in a layer 10 cm or more thick within the
spodic horizon.
Humic Placocryods
CBAC. Other Placocryods.
Typic Placocryods
Definition of Typic Placocryods
Typic Placocryods are the Placocryods that:
1. Do not have andic soil properties throughout horizons that
have a total thickness of 25 cm or more within 75 cm either of
the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower; and
2. Do not have 6.0 percent or more organic carbon in a
layer 10 cm or more thick within the spodic horizon.
Description of Subgroups
Typic Placocryods.—The Typic subgroup of Placocryods is
centered on soils that do not have andic soil properties in a
layer 25 cm or more thick within 75 cm of the soil surface or
6.0 percent or more organic carbon in a layer 10 cm or more
thick within the spodic horizon. These soils are rare in the
world.
Andic Placocryods.—These are the Placocryods that
have andic soil properties in a layer 25 cm or more thick
within 75 cm of the soil surface. These soils are rare in the
world.
Humic Placocryods.—These are the Placocryods that have
6.0 percent or more organic carbon in a layer 10 cm or more
thick within the spodic horizon. These soils do not have andic
soil properties in a layer 25 cm or more thick within 75 cm of
the soil surface.
Humods
Humods are the relatively freely drained Spodosols that
have a large accumulation of organic carbon in the spodic
horizon. Undisturbed Humods may have either a thin,
intermittent or a distinct, continuous albic horizon over a
spodic horizon, which in its upper part is nearly black and
has reddish hue. The hue normally becomes yellower with
increasing depth.
Humods formed predominantly in Pleistocene or Holocene
deposits. In the United States, they developed mainly under a
coniferous forest. In Western Europe they are common in areas
of sandy materials where heather (Calluna vulgaris) is, or used
to be, a dominant plant. In tropical regions most Humods have
supported a rain forest.
Humods are not extensive in the United States. They are
known to occur in Maine and in the Pacific Northwest, mostly
in small areas, and may occur in the Southeast.
710 Soil Taxonomy
Definition
Humods are the Spodosols that:
1. Have 6.0 percent or more organic carbon in a layer 10 cm or
more thick within the spodic horizon;
2. Do not have a cryic temperature regime; and
3. Do not have both aquic conditions within 50 cm of the
mineral soil surface and either of the following:
a. A histic epipedon; or
b. Within 50 cm of the mineral soil surface,
redoximorphic features in an albic or spodic horizon.
Key to Great Groups
CCA. Humods that have a placic horizon within 100 cm of
the mineral soil surface in 50 percent or more of each pedon.
Placohumods, p. 711
CCB. Other Humods that have, in 90 percent or more of each
pedon, a cemented soil layer that does not slake in water after
air drying and has its upper boundary within 100 cm of the
mineral soil surface.
Durihumods, p. 710
CCC. Other Humods that have a fragipan with its upper
boundary within 100 cm of the mineral soil surface.
Fragihumods, p. 710
CCD. Other Humods.
Haplohumods, p. 710
Durihumods
These are the Humods with a layer that is cemented,
commonly with sesquioxides and organic matter but in some
areas also with silica. These soils are not common in the
United States but occur in some areas in the Pacific Northwest
and the Southeast.
Definition
Durihumods are the Humods that:
1. Have, in 90 percent or more of each pedon, a cemented soil
layer that does not slake in water after air drying and has its
upper boundary within 100 cm of the mineral soil surface; and
2. Do not have, in 50 percent or more of each pedon, a placic
horizon within 100 cm of the mineral soil surface.
Key to Subgroups
CCBA. Durihumods that have andic soil properties
throughout horizons that have a total thickness of 25 cm or
more within 75 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Andic Durihumods
CCBB. Other Durihumods.
Typic Durihumods
DefinitionofTypicDurihumods
Typic Durihumods are the Durihumods that do not have
andic soil properties throughout horizons that have a total
thickness of 25 cm or more within 75 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Description of Subgroups
Typic Durihumods.—The Typic subgroup of Durihumods
is centered on soils that do not have andic soil properties in a
layer 25 cm or more thick within 75 cm of the soil surface.
These soils are rare in the world.
Andic Durihumods.—These are the Durihumods that have
andic soil properties in a layer 25 cm or more thick within 75
cm of the soil surface. These soils are rare in the United States.
Fragihumods
These Humods have a fragipan below the spodic horizon and
do not have a placic horizon. They are not known to occur in the
United States, and a classification of subgroups has not been
developed.
Definition
Fragihumods are the Humods that:
1. Have a fragipan with its upper boundary within 100 cm of
the mineral soil surface;
2. Do not have, in 50 percent or more of each pedon, a placic
horizon within 100 cm of the mineral soil surface; and
3. Do not have, in 90 percent or more of each pedon, a
cemented soil layer that does not slake in water after air drying
and has its upper boundary within 100 cm of the mineral soil
surface.
Key to Subgroups
CCCA. All Fragihumods (provisionally).
TypicFragihumods
Haplohumods
Haplohumods are the Humods commonly in cool to warm,
moist coastal regions, although some are in inland areas at
higher elevations. These soils occur in the Northeast and the
Pacific Northwest; in the Southeastern United States,
particularly in areas of sandy deposits; and in Western Europe,
where most of them at some time supported heather (Calluna
Spodosols 711
vulgaris). If undisturbed, these soils generally have an umbric
epipedon and an albic horizon overlying a spodic horizon with
reddish hue and a black upper subhorizon rich in organic
carbon. Some of the soils, however, have an ochric epipedon.
Definition
Haplohumods are the Humods that:
1. Do not have a fragipan with its upper boundary within 100
cm of the mineral soil surface;
2. Do not have, in 50 percent or more of each pedon, a placic
horizon within 100 cm of the mineral soil surface; and
3. Do not have, in 90 percent or more of each pedon, a
cemented soil layer that does not slake in water after air drying
and has its upper boundary within 100 cm of the mineral soil
surface.
Key to Subgroups
CCDA. Haplohumods that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Haplohumods
CCDB. Other Haplohumods that have andic soil properties
throughout horizons that have a total thickness of 25 cm or
more within 75 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Andic Haplohumods
CCDC. Other Haplohumods that have a surface horizon 30
cm or more thick that meets all of the requirements for a
plaggen epipedon except thickness.
Plagganthreptic Haplohumods
CCDD. Other Haplohumods.
Typic Haplohumods
Definition of Typic Haplohumods
Typic Haplohumods are the Haplohumods that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Do not have andic soil properties throughout horizons that
have a total thickness of 25 cm or more within 75 cm either of
the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower; and
3. Do not have a surface horizon more than 30 cm thick that
meets all of the requirements for a plaggen epipedon except
thickness.
Description of Subgroups
Typic Haplohumods.—The Typic subgroup of
Haplohumods is centered on soils that do not have a lithic
contact within 50 cm of the soil surface, andic soil properties in a
layer 25 cm or more thick within 75 cm of the soil surface, or a
surface horizon 30 cm or more thick that meets all of the
requirements for a plaggen epipedon except thickness.
Andic Haplohumods.—These soils have andic soil
properties in a layer 25 cm or more thick within 75 cm of the
soil surface. They do not have a lithic contact within 50 cm of
the soil surface.
Lithic Haplohumods.—These soils have a lithic contact
within 50 cm of the soil surface.
Plagganthreptic Haplohumods.—These soils have a surface
horizon 30 cm or more thick that has all of the attributes of a
plaggen epipedon except thickness. They do not have a lithic
contact within 50 cm of the soil surface or andic soil properties
in a layer 25 cm or more thick within 75 cm of the soil surface.
They occur in Europe.
Placohumods
These are the Humods that have a placic horizon within the
spodic horizon. They are probably rare in the world but are
known to occur in eastern Canada and in parts of Western
Europe, where their vegetation is, or used to be, heather.
Definition
Placohumods are the Humods that have a placic horizon
within 100 cm of the mineral soil surface in 50 percent or more
of each pedon.
Key to Subgroups
CCAA. Placohumods that have andic soil properties
throughout horizons that have a total thickness of 25 cm or
more within 75 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Andic Placohumods
CCAB. Other Placohumods.
Typic Placohumods
Definition of Typic Placohumods
Typic Placohumods are the Placohumods that do not have
andic soil properties throughout horizons that have a total
thickness of 25 cm or more within 75 cm either of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Description of Subgroups
Typic Placohumods.—The Typic subgroup of Placohumods
is centered on soils that do not have andic soil properties in a
layer 25 cm or more thick within 75 cm of the soil surface.
These soils are rare in the world.
Andic Placohumods.—These are the Placohumods that
have andic soil properties in a layer 25 cm or more thick
712 Soil Taxonomy
within 75 cm of the soil surface. These soils are rare in the
world.
Orthods
Orthods are the relatively freely drained Spodosols that have
a horizon of accumulation containing aluminum, or aluminum
and iron, and organic carbon. These are the most common
Spodosols in the northern parts of Europe and in the United
States. They formed predominantly in coarse, acid Pleistocene
or Holocene deposits under a mostly coniferous forest
vegetation. If undisturbed, Orthods normally have an O
horizon, an albic horizon, and a spodic horizon and may have
a fragipan. Some of these soils, however, have been mixed by
the roots of falling trees or by animals and have a very thin
albic horizon or no albic horizon. In cultivated areas the albic
horizon is very commonly mixed with part of the spodic
horizon. In the United States, the moisture regime of Orthods
is predominantly udic, but a few have a xeric regime. The soil
temperature regimes range from frigid to hyperthermic.
Orthods are extensive in the southeastern part of the United
States, the Northeast, the Great Lakes States, and the
mountains of the West.
Definition
Orthods are the Spodosols that:
1. Do not have 6.0 percent or more organic carbon in a
layer 10 cm or more thick within the spodic horizon;
2. Do not have a cryic temperature regime; and
3. Do not have both aquic conditions within 50 cm of the
mineral soil surface and either of the following:
a. A histic epipedon; or
b. Within 50 cm of the mineral soil surface,
redoximorphic features in an albic or spodic horizon.
Key to Great Groups
CDA. Orthods that have, in 50 percent or more of each
pedon, a placic horizon within 100 cm of the mineral soil
surface.
Placorthods, p. 720
CDB. Other Orthods that have, in 90 percent or more of each
pedon, a cemented soil layer that does not slake in water after
air drying and has its upper boundary within 100 cm of the
mineral soil surface.
Durorthods, p. 714
CDC. Other Orthods that have a fragipan with its upper
boundary within 100 cm of the mineral soil surface.
Fragiorthods, p. 714
CDD. Other Orthods that have less than 0.10 percent iron (by
ammonium oxalate) in 75 percent or more of the spodic
horizon.
Alorthods, p. 712
CDE. Other Orthods.
Haplorthods, p. 716
Alorthods
These are the Orthods that have accumulations of aluminum
that are relatively high compared to the accumulations of iron.
These soils formed predominantly in sandy deposits. The soils
have low accumulations of iron either because of intensive
leaching or because of parent materials that are low in iron.
Alorthods normally have a thick albic horizon and an ochric
epipedon. They are more common in areas of warm climates
than in cool environments. In the United States, they occur
mainly in the Southeast.
Definition
Alorthods are the Orthods that:
1. Have less than 0.10 percent iron (by ammonium oxalate)
in 75 percent or more of the spodic horizon;
2. Do not have, in 50 percent or more of each pedon, a placic
horizon within 100 cm of the mineral soil surface;
3. Do not have a fragipan with its upper boundary within 100
cm of the mineral soil surface; and
4. Do not have, in 90 percent or more of each pedon, a
cemented soil layer that does not slake in water after air drying
and has its upper boundary within 100 cm of the mineral soil
surface.
Key to Subgroups
CDDA. Alorthods that are saturated with water in one or
more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Alorthods
CDDB. Other Alorthods that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
a spodic horizon at a depth of 75 to 125 cm; and
2. An argillic or kandic horizon below the spodic horizon.
Arenic Ultic Alorthods
CDDC. Other Alorthods that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
Spodosols 713
mineral soil surface to the top of a spodic horizon at a depth of
75 to 125 cm.
Arenic Alorthods
CDDD. Other Alorthods that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
a spodic horizon at a depth of 125 cm or more; and
2. In 10 percent or more of each pedon, less than 3.0
percent organic carbon in the upper 2 cm of the spodic
horizon.
Entic Grossarenic Alorthods
CDDE. Other Alorthods that have, in 10 percent or more of
each pedon, less than 3.0 percent organic carbon in the upper 2
cm of the spodic horizon.
Entic Alorthods
CDDF. Other Alorthods that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of a spodic horizon at a depth of
125 cm or more.
Grossarenic Alorthods
CDDG. Other Alorthods that have a surface horizon 30 cm
or more thick that meets all of the requirements for a plaggen
epipedon except thickness.
Plagganthreptic Alorthods
CDDH. Other Alorthods that have, within 200 cm of the
mineral soil surface, an argillic or kandic horizon that has a
base saturation of 35 percent or more (by sum of cations) in
some part.
Alfic Alorthods
CDDI. Other Alorthods that have an argillic or kandic
horizon within 200 cm of the mineral soil surface.
Ultic Alorthods
CDDJ. Other Alorthods.
Typic Alorthods
Definition of Typic Alorthods
Typic Alorthods are the Alorthods that:
1. Are not saturated with water in any layer within 100 cm of
the mineral soil surface in normal years for either or both 20 or
more consecutive days or 30 or more cumulative days;
2. Do not have a sandy particle-size class throughout a layer
extending from the mineral soil surface to the top of a spodic
horizon at a depth of 75 cm;
3. Do not have an argillic or kandic horizon;
4. Do not have a surface horizon 30 cm or more thick that
meets all of the requirements for a plaggen epipedon except
thickness;
5. Do not have an argillic or kandic horizon within 200 cm of
the mineral soil surface; and
6. Have, in 10 percent or more of each pedon, 3.0 percent or
more organic carbon in the upper 2 cm of the spodic horizon.
Description of Subgroups
Typic Alorthods.—The Typic subgroup of Alorthods is
centered on soils that are not saturated with water for 20 or
more consecutive days or 30 or more cumulative days in
normal years and do not have an argillic or kandic horizon, a
sandy or sandy-skeletal particle-size class from the mineral soil
surface to the top of a spodic horizon at a depth of 75 to 125
cm, less than 3.0 percent organic carbon in the upper 2 cm of
the spodic horizon, or a surface horizon 30 cm or more thick
that has all of the attributes of a plaggen epipedon except
thickness. These soils have not been recognized in the United
States.
Alfic Alorthods.—These are the Alorthods that have an
argillic or kandic horizon with 35 percent or more base
saturation in at least some part. These soils are not saturated
with water for 20 or more consecutive days or 30 or more
cumulative days in normal years and do not have a sandy or
sandy-skeletal particle-size class from the mineral soil surface
to the top of a spodic horizon at a depth of 75 cm or more, less
than 3.0 percent organic carbon in the upper 2 cm of the spodic
horizon, or a surface horizon 30 cm or more thick that has all
of the attributes of a plaggen epipedon except thickness. Alfic
Alorthods are rare in the world.
Arenic Alorthods.—These are the Alorthods that have a
sandy or sandy-skeletal particle-size class from the mineral soil
surface to the top of a spodic horizon at a depth of 75 to 125
cm. These soils do not have an argillic or kandic horizon and
are not saturated with water for 20 or more consecutive days or
30 or more cumulative days in normal years. They occur in
Florida. They generally support woodland vegetation, but some
have been cleared for community development.
Arenic Ultic Alorthods.—These are the Alorthods that
have a sandy or sandy-skeletal particle-size class from the
mineral soil surface to the top of a spodic horizon at a depth of
75 to 125 cm and have an argillic or kandic horizon. These
soils are not saturated with water for 20 or more consecutive
days or 30 or more cumulative days in normal years. They
occur in Europe.
Entic Alorthods.—These are the Alorthods that have less
than 3.0 percent organic carbon in the upper 2 cm of the spodic
horizon. These soils are not saturated with water for 20 or
more consecutive days or 30 or more cumulative days in
normal years and do not have an argillic or kandic horizon or a
sandy or sandy-skeletal particle-size class from the mineral soil
surface to the top of a spodic horizon at a depth of 75 to 125
714 Soil Taxonomy
cm. The soils occur in Puerto Rico and Florida. Among the
uses of these soils are native pasture and coconut production.
Entic Grossarenic Alorthods.—These are the Alorthods that
have a sandy or sandy-skeletal particle-size class from the
mineral soil surface to the top of a spodic horizon at a depth of
125 cm or more and have less than 3.0 percent organic carbon
in the upper 2 cm of the spodic horizon. These soils are not
saturated with water for 20 or more consecutive days or 30 or
more cumulative days in normal years and do not have an
argillic or kandic horizon. They are common in the
southeastern part of the United States. Most do or did support
hardwood vegetation, but some have been cleared for crop
production.
Grossarenic Alorthods.—These are the Alorthods that
have a sandy or sandy-skeletal particle-size class from the
mineral soil surface to the top of a spodic horizon at a depth of
125 cm or more and have 3.0 percent or more organic carbon
in the upper 2 cm of the spodic horizon. These soils do not
have an argillic or kandic horizon and are not saturated with
water for 20 or more consecutive days or 30 or more
cumulative days in normal years. They are rare in the world.
Oxyaquic Alorthods.—These are the Alorthods that are
saturated with water for 20 or more consecutive days or 30 or
more cumulative days in normal years. These soils occur in
many States in the southeastern part of the United States. They
have a variety of uses, including tame pasture, woodland, and
the production of citrus and other crops.
Plagganthreptic Alorthods.—These are the Alorthods that
have a surface horizon 30 cm or more thick that meets all of
the requirements for a plaggen epipedon except thickness.
These soils are not saturated with water for 20 or more
consecutive days or 30 or more cumulative days in normal
years and do not have an argillic or kandic horizon, a sandy or
sandy-skeletal particle-size class from the mineral soil surface
to the top of a spodic horizon at a depth of 75 cm or more, or
less than 3.0 percent organic carbon in the upper 2 cm of the
spodic horizon. The soils are rare but are known to occur in
Europe.
Ultic Alorthods.—These are the Alorthods that have an
argillic or kandic horizon with a base saturation of less than 35
percent in all parts. These soils are not saturated with water for
20 or more consecutive days or 30 or more cumulative days in
normal years and do not have a sandy or sandy-skeletal
particle-size class from the mineral soil surface to the top of a
spodic horizon at a depth of 75 cm or more or less than 3.0
percent organic carbon in the upper 2 cm of the spodic horizon.
The soils are rare in the United States.
Durorthods
These are the Orthods that have a cemented soil layer.
These soils formed in sandy and loamy deposits. The cemented
soil layer commonly is composed of spodic materials and in
many areas is within 50 cm of the mineral soil surface. The
cementing agents commonly are combinations of iron, aluminum,
and organic matter, but silica may be an important cementing
agent in some of these soils.
Definition
Durorthods are the Orthods that:
1. Have, in 90 percent or more of each pedon, a cemented soil
layer that does not slake in water after air drying and has its
upper boundary within 100 cm of the mineral soil surface; and
2. Do not have, in 50 percent or more of each pedon, a placic
horizon within 100 cm of the mineral soil surface.
Key to Subgroups
CDBA. Durorthods that have andic soil properties
throughout horizons that have a total thickness of 25 cm or
more within 75 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Andic Durorthods
CDBB. Other Durorthods.
Typic Durorthods
Definition of Typic Durorthods
Typic Durorthods are the Durorthods that do not have andic
soil properties throughout horizons that have a total thickness
of 25 cm or more within 75 cm either of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Description of Subgroups
Typic Durorthods.—The Typic subgroup of Durorthods is
centered on soils without andic soil properties in a layer 25 cm
or more thick within 75 cm of the soil surface. The cemented
layer in these soils commonly is ortstein. The soils occur in
Michigan and New York. Most are forested, but some areas
have been cleared and are used for hay and pasture.
Andic Durorthods.—These are the Durorthods that have
andic soil properties in a layer 25 cm or more thick in the
upper 75 cm. These soils occur in the State of Washington and
support forest vegetation.
Fragiorthods
Fragiorthods are the Orthods that have a fragipan below the
spodic horizon. They formed mainly in loamy deposits, but
some formed in sandy deposits containing a considerable
amount of fine and very fine sand. The fragipan may be thick,
or it may have formed in the eluvial (E´) horizon of a lower
sequum that overlies an argillic horizon. Generally, a lighter
colored eluvial horizon has developed above the fragipan,
presumably because of the lateral movement of ground water.
Trees growing on Fragiorthods are normally shallow rooted
Spodosols 715
and are sometimes blown down. When the trees are blown
down, there is a mixing of soil horizons above the fragipan. As
a consequence, many of these soils have a weakly expressed
albic horizon or no albic horizon or have a thin, intermittent
albic horizon below part of the spodic horizon. A distinct
microrelief is a normal feature, unless the soils have been
smoothed by cultivation. In the United States, the soil
temperature regimes of Fragiorthods are mostly frigid, but
some are mesic bordering on frigid.
Definition
Fragiorthods are the Orthods that:
1. Have a fragipan with its upper boundary within 100 cm of
the mineral soil surface;
2. Do not have, in 50 percent or more of each pedon, a placic
horizon within 100 cm of the mineral soil surface; and
3. Do not have, in 90 percent or more of each pedon, a
cemented soil layer that does not slake in water after air drying
and has its upper boundary within 100 cm of the mineral soil
surface.
Key to Subgroups
CDCA. Fragiorthods that have redoximorphic features in one
or more horizons within 75 cm of the mineral soil surface and
also aquic conditions for some time in normal years (or
artificial drainage).
Aquic Fragiorthods
CDCB. Other Fragiorthods that:
1. Are saturated with water in one or more layers
within 100 cm of the mineral soil surface in normal
years for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days; and
2. Have, within 200 cm of the mineral soil surface, an
argillic or kandic horizon that has a base saturation of 35
percent or more (by sum of cations) in some part.
Alfic Oxyaquic Fragiorthods
CDCC. Other Fragiorthods that are saturated with water in
one or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Fragiorthods
CDCD. Other Fragiorthods that have a surface horizon 30
cm or more thick that meets all of the requirements for a
plaggen epipedon except thickness.
Plagganthreptic Fragiorthods
CDCE. Other Fragiorthods that have, within 200 cm of the
mineral soil surface, an argillic or kandic horizon that has a
base saturation of 35 percent or more (by sum of cations) in
some part.
Alfic Fragiorthods
CDCF. Other Fragiorthods that have an argillic or kandic
horizon within 200 cm of the mineral soil surface.
Ultic Fragiorthods
CDCG. Other Fragiorthods that have a spodic horizon that
has one of the following:
1. A texture of very fine sand, loamy very fine sand, or
finer; and
a. A thickness of 10 cm or less; and
b. A weighted average of less than 1.2 percent organic
carbon; and
c. Within the upper 7.5 cm, either or both a moist color
value or chroma of 4 or more (crushed and smoothed
sample); or
2. A texture of loamy fine sand, fine sand, or coarser and
either or both a moist color value or chroma of 4 or more
(crushed and smoothed sample) in the upper 2.5 cm.
Entic Fragiorthods
CDCH. Other Fragiorthods.
Typic Fragiorthods
Definition of Typic Fragiorthods
Typic Fragiorthods are the Fragiorthods that:
1. Do not have redoximorphic features in any horizon
within 75 cm of the mineral soil surface and also aquic
conditions;
2. Are not saturated with water in any layer within 100
cm of the mineral soil surface in normal years for either or
both 20 or more consecutive days or 30 or more cumulative
days;
3. Do not have a surface horizon 30 cm or more thick that
meets all of the requirements for a plaggen epipedon except
thickness;
4. Do not have an argillic or kandic horizon within 200 cm of
the mineral soil surface; and
5. Have a spodic horizon with one or more of the following:
a. A texture of very fine sand, loamy very fine sand, or
finer; and
(1) A thickness of more than 10 cm; or
(2) A weighted average of 1.2 percent or more organic
carbon in the upper 10 cm; or
716 Soil Taxonomy
(3) Within the upper 7.5 cm, either or both a moist color
value or chroma of 3 or less (crushed and smoothed
sample); or
b. A texture of loamy fine sand, fine sand, or coarser and a
color value, moist, and chroma of 3 or less (crushed and
smoothed sample) in the upper 2.5 cm.
Description of Subgroups
Typic Fragiorthods.—The Typic subgroup of Fragiorthods
is centered on properties that are not evident. Typic
Fragiorthods are not saturated within 100 cm of the soil surface
and do not have an argillic or kandic horizon, a surface
horizon 30 cm or more thick that has all of the attributes of a
plaggen epipedon except thickness, or a moist value and
chroma of 4 or more. These soils are forested and occur in
Michigan, New York, and Pennsylvania.
Alfic Fragiorthods.—These are the Fragiorthods that have
an argillic horizon that has a base saturation of 35 percent or
more in at least some part. These soils are not saturated for
extended periods within 100 cm of the soil surface. They do
not have a surface layer 30 cm or more thick that has all of the
attributes of a plaggen epipedon except thickness. They are
wooded and occur in Wisconsin and Michigan.
Alfic Oxyaquic Fragiorthods.—These are the Fragiorthods
that have an argillic horizon with a base saturation of 35
percent or more in some part and are saturated with water for
extended periods within 100 cm of the soil surface. These soils
do not have redoximorphic features within 75 cm of the soil
surface. They occur in Michigan and Wisconsin. They
commonly are wooded, but some have been cleared and are
used for small grain or hay.
Aquic Fragiorthods.—These are the Fragiorthods that have
aquic conditions and redoximorphic features within 75 cm of
the soil surface. These soils commonly occur in New York and
Pennsylvania. They generally support forest vegetation, but
some areas have been cleared for crop production.
Entic Fragiorthods.—These are the Fragiorthods that have
a value and chroma, moist, of 4 or more. These soils are not
saturated for extended periods within 100 cm of the surface, do
not have an argillic or kandic horizon, and do not have a
surface horizon 30 cm or more thick that meets all of the
requirements for a plaggen epipedon except thickness. The
soils support forest vegetation and occur in New York, New
Hampshire, and Vermont.
Oxyaquic Fragiorthods.—These are the Fragiorthods that
are saturated for extended periods within 100 cm of the soil
surface. These soils do not have redoximorphic features within
75 cm of the soil surface or an argillic or kandic horizon with a
base saturation of 35 percent or more in at least some part.
Oxyaquic Fragiorthods occur in Wisconsin and Michigan and
support northern hardwoods.
Plagganthreptic Fragiorthods.—These are the
Fragiorthods that have a surface layer 30 cm or more thick that
has all of the properties of a plaggen epipedon except thickness.
These soils do not have an argillic or kandic horizon with a base
saturation of 35 percent or more in at least some part and are not
saturated with water for extended periods within 100 cm of the
soil surface. The soils are rare. They occur in small areas of
Europe.
Ultic Fragiorthods.—These are the Fragiorthods that have
an argillic or kandic horizon with a base saturation of less than
35 percent in all parts. These soils are not saturated with water
for extended periods within 100 cm of the soil surface and do
not have a surface horizon 30 cm or more thick that meets all
of the requirements for a plaggen epipedon except thickness.
The soils are rare in the world.
Haplorthods
These are the relatively freely drained Orthods that either
have an albic horizon and a spodic horizon or, under
cultivation, commonly have only a spodic horizon below an Ap
horizon. The spodic horizon may rest on a lower sequum with
an argillic or kandic horizon, on relatively unaltered
unconsolidated materials, or on rock. The soil temperature
regime is frigid or warmer, and the moisture regime is
predominantly udic. Most Haplorthods have, or used to have,
forest vegetation, mainly conifers but also hardwoods in some
areas. A majority of these soils formed in sandy deposits or in
materials weathered from sandstone or quartzite.
Definition
Haplorthods are the Orthods that:
1. Do not have less than 0.10 percent iron (by ammonium
oxalate) in 75 percent or more of the spodic horizon;
2. Do not have, in 50 percent or more of each pedon, a placic
horizon within 100 cm of the mineral soil surface;
3. Do not have a fragipan with its upper boundary within 100
cm of the mineral soil surface; and
4. Do not have, in 90 percent or more of each pedon, a
cemented soil layer that does not slake in water after air drying
and has its upper boundary within 100 cm of the mineral soil
surface.
Key to Subgroups
CDEA. Haplorthods that have a lithic contact within 50 cm
of the mineral soil surface; and either
1. A spodic horizon with a texture of very fine sand,
loamy very fine sand, or finer; and
a. A thickness of 10 cm or less; and
Spodosols 717
b. A weighted average of less than 1.2 percent organic
carbon; and
c. Within the upper 7.5 cm, either or both a moist color
value or chroma of 4 or more (crushed and smoothed
sample); or
2. A spodic horizon with a texture of loamy fine sand, fine
sand, or coarser and either or both a moist color value or
chroma of 4 or more (crushed and smoothed sample) in the
upper 2.5 cm.
Entic Lithic Haplorthods
CDEB. Other Haplorthods that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Haplorthods
CDEC. Other Haplorthods that have both:
1. Fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm
of the mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm
or more thick; and
2. Redoximorphic features in one or more horizons
within 75 cm of the mineral soil surface and also aquic
conditions for some time in normal years (or artificial
drainage).
Fragiaquic Haplorthods
CDED. Other Haplorthods that have both:
1. Redoximorphic features in one or more horizons
within 75 cm of the mineral soil surface and also aquic
conditions for some time in normal years (or artificial
drainage); and
2. Within 200 cm of the mineral soil surface, an argillic or
kandic horizon that has a base saturation of 35 percent or
more (by sum of cations) in some part.
Aqualfic Haplorthods
CDEE. Other Haplorthods that have redoximorphic features
in one or more horizons within 75 cm of the mineral soil
surface and also aquic conditions for some time in normal
years (or artificial drainage); and either
1. A spodic horizon with a texture of very fine sand,
loamy very fine sand, or finer; and
a. A thickness of 10 cm or less; and
b. A weighted average of less than 1.2 percent organic
carbon; and
c. Within the upper 7.5 cm, either or both a moist color
value or chroma of 4 or more (crushed and smoothed
sample); or
2. A spodic horizon with a texture of loamy fine sand, fine
sand, or coarser and either or both a moist color value or
chroma of 4 or more (crushed and smoothed sample) in the
upper 2.5 cm.
Aquentic Haplorthods
CDEF. Other Haplorthods that have redoximorphic features
in one or more horizons within 75 cm of the mineral soil
surface and also aquic conditions for some time in normal
years (or artificial drainage).
Aquic Haplorthods
CDEG. Other Haplorthods that have:
1. Within 200 cm of the mineral soil surface, an argillic or
kandic horizon that has a base saturation of 35 percent or
more (by sum of cations) in some part; and
2. Saturation with water in one or more layers within 100
cm of the mineral soil surface in normal years for either or
both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days.
Alfic Oxyaquic Haplorthods
CDEH. Other Haplorthods that have:
1. Within 200 cm of the mineral soil surface, an argillic or
kandic horizon; and
2. Saturation with water in one or more layers within 100
cm of the mineral soil surface in normal years for either or
both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days.
Oxyaquic Ultic Haplorthods
CDEI. Other Haplorthods that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Haplorthods
CDEJ. Other Haplorthods that, below the spodic horizon but
not below an argillic horizon, have lamellae (two or more)
within 200 cm of the mineral soil surface.
Lamellic Haplorthods
CDEK. Other Haplorthods that are saturated with water in one
718 Soil Taxonomy
or more layers within 100 cm of the mineral soil surface in normal
years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Haplorthods
CDEL. Other Haplorthods that have andic soil properties
throughout horizons that have a total thickness of 25 cm or
more within 75 cm either of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Andic Haplorthods
CDEM. Other Haplorthods that have, within 200 cm of the
mineral soil surface, an argillic or kandic horizon that has a
base saturation of 35 percent or more (by sum of cations) in
some part.
Alfic Haplorthods
CDEN. Other Haplorthods that have an argillic or kandic
horizon within 200 cm of the mineral soil surface.
Ultic Haplorthods
CDEO. Other Haplorthods that have a spodic horizon that
has one of the following:
1. A texture of very fine sand, loamy very fine sand, or
finer; and
a. A thickness of 10 cm or less; and
b. A weighted average of less than 1.2 percent organic
carbon; and
c. Within the upper 7.5 cm, either or both a moist color
value or chroma of 4 or more (crushed and smoothed
sample); or
2. A texture of loamy fine sand, fine sand, or coarser and
either or both a moist color value or chroma of 4 or more
(crushed and smoothed sample) in the upper 2.5 cm.
Entic Haplorthods
CDEP. Other Haplorthods.
Typic Haplorthods
Definition of Typic Haplorthods
Typic Haplorthods are the Haplorthods that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Do not have redoximorphic features in any horizon
within 75 cm of the mineral soil surface and also aquic
conditions;
3. Are not saturated with water in any layer within 100 cm of
the mineral soil surface in normal years for either or both 20 or
more consecutive days or 30 or more cumulative days;
4. Do not have an argillic or kandic horizon within 200 cm of
the mineral soil surface;
5. Do not have andic soil properties throughout horizons that
have a total thickness of 25 cm or more within 75 cm either of
the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower;
6. Have a spodic horizon with one or more of the following:
a. A texture of very fine sand, loamy very fine sand, or
finer; and
(1) A thickness of more than 10 cm; or
(2) A weighted average of 1.2 percent or more organic
carbon in the upper 10 cm; or
(3) Within the upper 7.5 cm, either or both a moist
color value or chroma of 3 or less (crushed and smoothed
sample); or
b. A texture of loamy fine sand, fine sand, or coarser and a
color value, moist, and chroma of 3 or less (crushed and
smoothed sample) in the upper 2.5 cm;
7. Do not have lamellae (two or more) within 200 cm of the
soil surface; and
8. Have fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Description of Subgroups
Typic Haplorthods.—The Typic subgroup of Haplorthods
is centered on soils that do not have an argillic or kandic
horizon, a lithic contact within 50 cm of the mineral soil
surface, saturation with water for extended periods within 100
cm of the mineral soil surface, andic soil properties in a layer
25 cm or more thick within 75 cm of the soil surface, fragic
properties, lamellae, or both a chroma and value, moist, of 4 or
more. These soils occur in the northeastern and northwestern
parts of the United States as well as Michigan, Wisconsin,
Minnesota, West Virginia, and Maryland. They generally
support forest vegetation, but some have been cleared for
pasture or crop production. The most common crops are small
grain, corn for silage, and in Maine potatoes.
Alfic Haplorthods.—These are the Haplorthods that have
an argillic or kandic horizon that has a base saturation of 35
Spodosols 719
percent or more in at least some part. These soils do not have a
lithic contact within 50 cm of the soil surface, saturation with
water for extended periods within 100 cm of the mineral soil
surface, fragic properties, lamellae, or andic soil properties in a
layer 25 cm or more thick within 75 cm of the soil surface. The
soils occur in Michigan, Wisconsin, and New York. They
generally are forested, but some of the less sloping areas are
used for small grain or hay.
Alfic Oxyaquic Haplorthods.—These are the Haplorthods
that have an argillic or kandic horizon with a base saturation of
35 percent or more in at least some part and are saturated with
water for extended periods within 100 cm of the mineral soil
surface. These soils do not have aquic conditions and
redoximorphic features within 75 cm of the mineral soil
surface or a lithic contact within 50 cm of the soil surface.
They occur in Wisconsin and Michigan. Most of the soils are
forested, but some have been cleared and are used for small
grain or hay.
Andic Haplorthods.—These are the Haplorthods that have
andic soil properties in a layer 25 cm or more thick within 75
cm of the soil surface. These soils do not have a lithic contact
within 50 cm of the soil surface, fragic soil properties,
saturation with water for extended periods within 100 cm of
the soil surface, or lamellae. They occur in Washington and are
wooded.
Aqualfic Haplorthods.—These are the Haplorthods that
have an argillic or kandic horizon with a base saturation of 35
percent or more in at least some part and aquic conditions and
redoximorphic features within 75 cm of the mineral soil
surface. These soils do not have a lithic contact within 50 cm
of the soil surface or fragic soil properties. They occur in
Washington, Michigan, and Wisconsin. Most of the soils are
forested, but some have been cleared for crop production.
Aquentic Haplorthods.—These are the Haplorthods that
have aquic conditions and redoximorphic features within 75
cm of the soil surface and have a value and chroma, moist, of 4
or more. These soils do not have an argillic or kandic horizon,
fragic soil properties, or a lithic contact within 50 cm of the
mineral soil surface. They occur in Oregon, Washington,
Minnesota, Michigan, Wisconsin, and New York. They formed
under forest vegetation. Some areas have been cleared and are
used for hay or pasture.
Aquic Haplorthods.—These are the Haplorthods that have
aquic conditions and redoximorphic features within 75 cm of
the mineral soil surface. These soils do not have a lithic contact
within 50 cm of the soil surface, an argillic or kandic horizon,
fragic soil properties, or a value and chroma, moist, of 4 or
more. They occur in New England and the Lake States. Most
are forested.
Entic Haplorthods.—These are the Haplorthods that have
both a value and chroma, moist, of 4 or more. These soils do
not have an argillic or kandic horizon, a lithic contact within
50 cm of the mineral soil surface, saturation with water for
extended periods within 100 cm of the mineral soil surface,
andic soil properties in a layer 25 cm or more thick within 75
cm of the soil surface, fragic properties, or lamellae. The soils
occur in the Pacific Northwest, in the Northeast, and in
Michigan, Wisconsin, Virginia, Pennsylvania, Maryland, and
West Virginia. Commonly, these soils are wooded, but some
have been cleared and are used for hay, corn, oats, potatoes, or
fruit crops.
Entic Lithic Haplorthods.—These are the Haplorthods that
have both a value and chroma, moist, of 4 or more and have a
lithic contact within 50 cm of the mineral soil surface. These
soils are wooded and occur in Wisconsin.
Fragiaquic Haplorthods.—These are the Haplorthods that
have aquic conditions and redoximorphic features within 75
cm of the mineral soil surface and have fragic properties or a
fragipan between depths of 100 and 200 cm. These soils do not
have a lithic contact within 50 cm of the mineral soil surface.
They are rare in the world.
Fragic Haplorthods.—These are the Haplorthods that have
fragic properties or a fragipan between depths of 100 and 200
cm. These soils do not have a lithic contact within 50 cm of the
soil surface and are not saturated with water for extended
periods within 100 cm of the mineral soil surface. They are
rare in the world.
Lamellic Haplorthods.—These are the Haplorthods that
have lamellae. These soils do not have a lithic contact within
50 cm of the soil surface, saturation with water for extended
periods within 100 cm of the mineral soil surface, or fragic
properties. They occur in Michigan. In some areas they are
forested. In other areas they have been cleared and are used for
small grain, hay, or potatoes.
Lithic Haplorthods.—These are the Haplorthods that have
a lithic contact within 50 cm of the soil surface but do not have
both a value and chroma, moist, of 4 or more. These soils occur
in the Northeast as well as Michigan. Most support forest
vegetation, but some areas have been cleared and are used for
hay or pasture.
Oxyaquic Haplorthods.—These are the Haplorthods that
are saturated with water within 100 cm of the mineral soil
surface for 20 or more consecutive days or 30 cumulative days
in normal years. These soils do not have a lithic contact within
50 cm of the mineral soil surface, aquic conditions and
redoximorphic features within 75 cm of the mineral soil
surface, fragic properties, or lamellae. The soils occur in
Washington, Michigan, Wisconsin, and the northeastern part
of the United States. In most areas these soils are wooded, but
some areas have been cleared and are used for hay and pasture.
Oxyaquic Ultic Haplorthods.—These are the Haplorthods
that have an argillic or kandic horizon with a base saturation of
less than 35 percent in all parts and in normal years are
saturated with water for 20 or more consecutive days or 30 or
720
more cumulative days within 100 cm of the mineral soil
surface. These soils do not have a lithic contact within 50 cm
of the soil surface or aquic conditions and redoximorphic
features within 75 cm of the mineral soil surface. Oxyaquic
Ultic Haplorthods occur in Wisconsin. They generally are
wooded, but some have been cleared and are used for corn,
hay, or pasture.
Ultic Haplorthods.—These are the Haplorthods that have an
argillic horizon that has a base saturation of less than 35 percent
in all parts. These soils do not have a lithic contact within 50 cm
of the mineral soil surface, fragic soil properties, lamellae, or
andic soil properties in a layer 25 cm or more thick within 75 cm
of the soil surface and are not saturated with water for extended
periods within 100 cm of the mineral soil surface. The soils are
rare in the world.
Placorthods
These are the Orthods that have a placic horizon within 100
cm of the mineral soil surface. These soils are not known to
occur in the continental United States and are thought to be
rare elsewhere in the world.
Definition
Placorthods are the Orthods that have a placic horizon
within 100 cm of the mineral soil surface in 50 percent or more
of each pedon.
Key to Subgroups
CDAA. All Placorthods (provisionally).
Typic Placorthods
721
Ultisols are soils that have an argillic or kandic horizon
with low base saturation. They may have any soil
temperature regime and any soil moisture regime except aridic.
There is more precipitation than evapotranspiration at some
season, and some water moves through the soils and into a
moist or wet substratum. The release of bases by weathering
usually is equal to or less than the removal by leaching, and
most of the bases commonly are held in the vegetation and the
upper few centimeters of the soils. Base saturation in most
Ultisols decreases with increasing depth because the vegetation
has concentrated the bases at a shallow depth. Cultivation,
therefore, is a shifting cultivation unless soil amendments are
applied.
Ultisols are most extensive in warm, humid climates that
have a seasonal deficit of precipitation. They are mainly on
Pleistocene or older surfaces. They formed in a very wide
variety of parent materials, but very few have many primary
minerals that contain bases other than some micas. Some of the
few that have a supply of bases are intensively cultivated.
Kaolin, gibbsite, and aluminum-interlayered clays are common
in the clay fraction. Smectites also may be present if they are in
the parent materials. Extractable aluminum normally is high
except in the Paleudults and other pale-groups. A calciumdeficient
argillic horizon is common in the Ultisols in the
United States.
Most of the Ultisols in the United States had a vegetation of
coniferous or hardwood forests at the time of settlement.
Savannas are present in other parts of the world, but they may
be anthropic.
Definition of Ultisols and Limits Between
Ultisols and Soils of Other Orders
Ultisols are the mineral soils that:
1. Have either:
a. An argillic or kandic horizon, but no fragipan, and a
base saturation (by sum of cations) of less than 35 percent at
one of the following depths:
(1) If the epipedon has a sandy or sandy-skeletal
particle-size class throughout, either:
(a) 125 cm below the upper boundary of the argillic
or kandic horizon (but no deeper than 200 cm below
the mineral soil surface) or 180 cm below the mineral
soil surface, whichever is deeper; or
(b) At a densic, lithic, paralithic, or petroferric
contact if shallower; or
(2) The shallowest of the following depths:
(a) 125 cm below the upper boundary of the argillic
or kandic horizon; or
(b) 180 cm below the mineral soil surface; or
(c) At a densic, lithic, paralithic, or petroferric
contact; or
b. A fragipan and both of the following:
(1) Either an argillic or kandic horizon above, within,
or below it or clay films 1 mm or more thick in one or
more of its subhorizons; and
(2) A base saturation (by sum of cations) of less than 35
percent at the shallowest of the following depths:
(a) 75 cm below the upper boundary of the fragipan;
or
(b) 200 cm below the mineral soil surface; or
(c) At a densic, lithic, paralithic, or petroferric
contact;
2. Do not have either of the following:
a. Permafrost within 100 cm of the soil surface; or
b. Gelic materials within 100 cm of the soil surface and
permafrost within 200 cm of the soil surface;
3. Do not have andic soil properties in 60 percent or more of
the thickness between either the mineral soil surface or the top
of an organic layer with andic soil properties, whichever is
shallower, and either a depth of 60 cm from the shallower of
the above or a densic, lithic, or paralithic contact, a duripan, or
a petrocalcic horizon if shallower than 60 cm;
4. Do not have an Ap horizon containing 85 percent or more
spodic materials;
5. Have an argillic or kandic horizon above any spodic
horizon that has either of the following:
a. An overlying albic horizon in 50 percent or more of
CHAPTER 19
Ultisols
722 Soil Taxonomy
each pedon and a cryic soil temperature regime; or
b. All of the following characteristics:
(1) One or more of the following:
(a) A thickness of 10 cm or more; or
(b) An overlying Ap horizon; or
(c) Cementation in 50 percent or more of each
pedon; or
(d) A coarse-loamy, loamy-skeletal, or finer particlesize
class and a frigid soil temperature regime; or
(e) A cryic soil temperature regime; and
(2) An upper boundary within the following depths
from the mineral soil surface: either
(a) Less than 50 cm; or
(b) Less than 200 cm if the soil has a sandy particlesize
class in at least some part between the mineral
soil surface and the spodic horizon; and
(3) A lower boundary as follows:
(a) Either at a depth of 25 cm or more below the
mineral soil surface, or at the top of a duripan or
fragipan, or at a densic, lithic, paralithic, or
petroferric contact, whichever is shallowest; or
(b) At any depth,
1) If the spodic horizon has a coarse-loamy,
loamy-skeletal, or finer particle-size class and the
soil has a frigid temperature regime; or
2) If the soil has a cryic temperature regime;
6. Do not have an oxic horizon that has its upper boundary
within 150 cm of the mineral soil surface unless there is a
kandic horizon above the oxic horizon;
7. Have less than 40 percent (by weight) clay in the fine-earth
fraction between the mineral soil surface and a depth of 18 cm
(after mixing) if the kandic horizon has the weatherablemineral
properties of an oxic horizon and has its upper
boundary within 150 cm of the mineral soil surface;
8. Do not have all of the following:
a. A layer 25 cm or more thick, with an upper boundary
within 100 cm of the mineral soil surface, that has either
slickensides close enough to intersect or wedge-shaped
aggregates that have their long axes tilted 10 to 60 degrees
from the horizontal; and
b. A weighted average of 30 percent or more clay in the
fine-earth fraction either between the mineral soil surface
and a depth of 18 cm or in an Ap horizon, whichever is
thicker, and 30 percent or more clay in the fine-earth
fraction of all horizons between a depth of 18 cm and either
a depth of 50 cm or a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon if shallower; and
c. Cracks that open and close periodically;
9. Do not have an aridic moisture regime; and
10. Do not have a salic horizon and meet all of the following
criteria:
a. Are not saturated with water in one or more layers
within 100 cm of the soil surface for 1 month or more in
normal years; and
b. Do not have a moisture control section that is dry in at
least some part in normal years; and
c. Have a sulfuric horizon that has its upper boundary
within 150 cm of the mineral soil surface.
Limits Between Ultisols and the Other Soil Orders
The definition of Ultisols must provide criteria that separate
Ultisols from soils of all other orders. The aggregate of these
criteria defines the limits of Ultisols in relation to all other
known kinds of soil.
1. Unlike Alfisols, Ultisols must have one of the following
characteristics:
a. No fragipan and a base saturation (by sum of cations) of
less than 35 percent at one of the following depths:
(1) If there is an epipedon that has a sandy or sandyskeletal
particle-size class throughout, either:
(a) 125 cm below the upper boundary of the argillic
horizon (but no deeper than 200 cm below the mineral
soil surface) or 180 cm below the mineral soil surface,
whichever is deeper; or
(b) At a densic, lithic, paralithic, or petroferric
contact if shallower; or
(2) If the epipedon does not have a sandy or sandyskeletal
particle-size class throughout, the shallowest of
the following depths:
(a) 125 cm below the upper boundary of the argillic
or kandic horizon; or
(b) 180 cm below the mineral soil surface; or
(c) At a densic, lithic, paralithic, or petroferric
contact; or
b. A fragipan and a base saturation (by sum of cations) of
less than 35 percent at the shallowest of the following
depths:
(1) 75 cm below the upper boundary of the fragipan; or
Ultisols 723
(2) 200 cm below the mineral soil surface; or
(3) At a densic, lithic, paralithic, or petroferric
contact.
2. Unlike Andisols, Ultisols must not have andic soil
properties in 60 percent or more of the thickness between
either the mineral soil surface or the top of an organic layer
with andic soil properties, whichever is shallower, and either a
depth of 60 cm from the shallower of the above or a densic,
lithic, or paralithic contact, a duripan, or a petrocalcic horizon
if shallower than 60 cm.
3. Unlike Aridisols, Ultisols must not:
a. Have an aridic soil moisture regime; and
b. Have a salic horizon and meet all of the following
criteria:
(1) Are not saturated with water in one or more layers
within 100 cm of the soil surface for 1 month or more in
normal years; and
(2) Do not have a moisture control section that is dry in
at least some part in normal years; and
(3) Have a sulfuric horizon that has its upper boundary
within 150 cm of the mineral soil surface.
4. Unlike Entisols and Inceptisols, Ultisols must have one of
the following:
a. An argillic or kandic horizon; or
b. A fragipan that meets all of the requirements for an
argillic or kandic horizon or that has clay films more than
1 mm thick in some part.
5. Unlike Gelisols, Ultisols do not have:
a. Permafrost within 100 cm of the soil surface; or
b. Gelic materials within 100 cm of the soil surface and
permafrost within 200 cm of the soil surface.
6. Unlike Histosols, Ultisols do not have organic soil
materials that meet one or more of the following:
a. Overlie cindery, fragmental, or pumiceous materials
and/or fill their interstices1
and directly below these
materials have either a densic, lithic, or paralithic contact;
or
b. When added with the underlying cindery, fragmental, or
pumiceous materials, total 40 cm or more between the soil
surface and a depth of 50 cm; or
c. Constitute two-thirds or more of the total thickness of
the soil to a densic, lithic, or paralithic contact and have no
mineral horizons or have mineral horizons with a total
thickness of 10 cm or less; or
d. Are saturated with water for 30 days or more in normal
years (or are artificially drained), have an upper boundary
within 40 cm of the soil surface, and have a total thickness
of either:
(1) 60 cm or more if three-fourths or more of their
volume consists of moss fibers or if their bulk density,
moist, is less than 0.1 g/cm3
; or
(2) 40 cm or more if they consist either of sapric or
hemic materials, or of fibric materials with less than
three-fourths (by volume) moss fibers and a bulk density,
moist, of 0.1 g/cm3
or more.
7. Unlike Mollisols, Ultisols must have one of the following:
a. An argillic or kandic horizon, but no fragipan, and a
base saturation (by sum of cations) of less than 35 percent at
one of the following depths:
(1) If there is an epipedon that has a sandy or sandyskeletal
particle-size class throughout, either:
(a) 125 cm below the upper boundary of the argillic
horizon (but no deeper than 200 cm below the mineral
soil surface) or 180 cm below the mineral soil surface,
whichever is deeper; or
(b) At a densic, lithic, paralithic, or petroferric
contact if shallower; or
(2) If the epipedon does not have a sandy or sandyskeletal
particle-size class throughout, the shallowest of
the following depths:
(a) 125 cm below the upper boundary of the argillic
or kandic horizon; or
(b) 180 cm below the mineral soil surface; or
(c) At a densic, lithic, paralithic, or petroferric
contact; or
b. A fragipan and a base saturation (by sum of cations) of
less than 35 percent at the shallowest of the following
depths:
(1) 75 cm below the upper boundary of the fragipan;
or
(2) 200 cm below the mineral soil surface; or
(3) At a densic, lithic, paralithic, or petroferric contact.
8. Unlike Oxisols, Ultisols must not have either:
a. An oxic horizon that has its upper boundary within 150
cm of the mineral soil surface; or
b. 40 percent or more (by weight) clay in the fine-earth
fraction between the mineral soil surface and a depth of 18
1
Materials that meet the definition of cindery, fragmental, or pumiceous but have more
than 10 percent (by volume) voids that are filled with organic soil materials are considered to
be organic soil materials.
724 Soil Taxonomy
cm (after mixing) and a kandic horizon that has less than 10
percent weatherable minerals and has its upper boundary
within 150 cm of the mineral soil surface.
9. Unlike Spodosols, Ultisols must not have an Ap horizon
consisting of spodic materials or a spodic horizon above the
argillic, kandic, or natric horizon and must not have have one
or more of the following:
a. An albic horizon in 50 percent or more of each pedon
and a cryic soil temperature regime; or
b. A spodic horizon with all of the following
characteristics:
(1) One or more of the following:
(a) A thickness of 10 cm or more; or
(b) An overlying Ap horizon; or
(c) Cementation in 50 percent or more of each
pedon; or
(d) A coarse-loamy, loamy-skeletal, or finer particlesize
class and a frigid soil temperature regime; or
(e) A cryic soil temperature regime; and
(2) An upper boundary within the following depths
from the mineral soil surface: either
(a) Less than 50 cm; or
(b) Less than 200 cm if the soil has a sandy particlesize
class between the mineral soil surface and the
spodic horizon; and
(3) A lower boundary as follows:
(a) Either at a depth of 25 cm or more below the
mineral soil surface, or at the top of a duripan or
fragipan, or at a densic, lithic, paralithic, or
petroferric contact, whichever is shallowest; or
(b) At any depth if the spodic horizon has a coarseloamy,
loamy-skeletal, or finer particle-size class and
the soil has a frigid temperature regime or if the soil
has a cryic temperature regime.
10. Unlike Vertisols, Ultisols must not have all of the
following:
a. A layer 25 cm or more thick, with an upper boundary
within 100 cm of the mineral soil surface, that has either
slickensides close enough to intersect or wedge-shaped
aggregates that have their long axes tilted 10 to 60 degrees
from the horizontal; and
b. A weighted average of 30 percent or more clay in the
fine-earth fraction either between the mineral soil surface
and a depth of 18 cm or in an Ap horizon, whichever is
thicker, and 30 percent or more clay in the fine-earth
fraction of all horizons between a depth of 18 cm and either
a depth of 50 cm or a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon if shallower; and
c. Cracks that open and close periodically.
Representative Pedon and Data
Following is a description of a representative Ultisol. Data for
the pedon identified in this description are given in the table
“Characterization Data for an Ultisol.”
Classification: Fine, kaolinitic, thermic Typic Kandiudult
Site identification number: 82P0398
Location: Autauga County, Alabama; SW1
/4SW1
/4SW1
/4 sec.
33, T. 18 N., R. 16 E.
Latitude: 32 degrees 29 minutes 19 seconds N.
Longitude: 86 degrees 28 minutes 10 seconds W.
Slope: 1 percent
Elevation: 122 m
Landform: Terrace
Parent material: Fluvial or marine sediments
Soil moisture regime: Udic
Permeability class: Moderate
Drainage class: Well drained
Water table: None observed within a depth of 9 m
Land use: Forest land (not grazed)
Vegetation: Native hardwoods and pine
Particle-size control section: 12 to 62 cm
Diagnostic features: An ochric epipedon from a depth of 0 to
12 cm, a kandic from a depth of 12 to more than 200 cm,
and an argillic horizon from a depth of 12 to more than
200 cm
Described by: Brown and Stubbs
In the following pedon description, colors are for moist soil
unless otherwise indicated. Texture terms are for field textures.
Ap—0 to 12 cm; dark yellowish brown (10YR 4/4) fine sandy
loam; weak medium subangular blocky structure; very
friable; many fine and medium roots; common organic
coatings; few wormcasts; abundant active fire ant cavities;
strongly acid; clear smooth boundary.
Bt1—12 to 40 cm; red (2.5YR 4/6) clay loam; moderate
medium subangular blocky structure; friable; common fine
and medium roots; many tubular pores (abandoned root
channels); few distinct clay films on faces of peds;
common active fire ant cavities; very strongly acid; clear
wavy boundary.
Bt2—40 to 86 cm; red (2.5YR 4/6) clay loam; moderate
medium subangular blocky structure; firm; common
distinct clay films on faces of peds; very strongly acid;
clear wavy boundary.
Bt3—86 to 140 cm; red (2.5YR 4/6) clay loam; common
medium prominent yellowish brown (10YR 5/4) redox
depletions; weak medium and coarse prismatic structure
Ultisols 725
Characterization Data for an Ultisol
SITE IDENTIFICATION NO.: 82P0398
CLASSIFICATION: FINE, KAOLINITIC, THERMIC TYPIC KANDIUDULT
GENERAL METHODS: 1B1A, 2A1, 2B
-1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-
-----------------------------------------------------------------------------------------------------------------------------------
(- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)
CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT
SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF
NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE
<- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL
82P2043 0- 12 Ap 12.3 15.3 72.4 9.9 8.6 6.7 12.2 33.6 22.5 3.4 0.7 1 1 -- 61 2
82P2044 12- 40 Bt1 35.0 18.4 46.6 26.5 13.4 5.0 7.6 21.4 14.8 2.3 0.5 TR TR -- 39 TR
82P2045 40- 86 Bt2 35.3 17.7 47.0 27.6 12.2 5.5 7.6 21.2 14.8 2.4 1.0 TR TR -- 39 TR
82P2046 86-140 Bt3 40.9 12.3 46.8 29.6 8.5 3.8 7.0 21.3 15.3 2.4 0.8 TR TR -- 40 TR
82P2047 140-280 Bt4 44.6 9.3 46.1 28.0 5.3 4.0 6.9 20.7 15.2 2.4 0.9 TR TR -- 39 TR
-----------------------------------------------------------------------------------------------------------------------------------
ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD
C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE
DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL
(cm) 6A1c 6B3a 6S3 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A3a 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1
Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm
0- 12 1.25 0.057 0.3 0.1 TR 0.34 0.36 1.46 1.50 0.009 9.6 4.4 0.08
12- 40 0.51 0.037 1.3 0.2 -- 0.16 0.34 1.55 1.60 0.011 15.1 11.8 0.05
40- 86 0.32 0.019 1.4 0.2 -- 0.15 0.36 1.51 1.58 0.015 18.1 12.7 0.08
86-140 0.20 1.7 TR -- 0.14 0.34 1.75 1.80 0.009 16.0 14.0 0.04
140-280 0.19 1.8 0.2 -- 0.12 0.33 1.72 1.75 0.006 17.2 14.8 0.04
-----------------------------------------------------------------------------------------------------------------------------------
(- NH4OAc EXTRACTABLE BASES -) ACID- EXTR (- - - -CEC - - -) Al -BASE SAT- CO3 AS RES. COND.(- - - -PH - - -)
Ca Mg Na K SUM ITY Al SUM NH4- BASES SAT SUM NH4 CaCO3 ohms mmhos KCl CaCl2 H2O
DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc + Al OAc <2mm /cm /cm IN .01M
(cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 6G9a 5A3a 5A8b 5A3b 5G1 5C3 5C1 6E1g 8E1 8I 8C1g 8C1f 8C1f
<- - - - - - - - - - - -meq / 100 g - - - - - - - - - - -> <- - - - -Pct - - - -> 1:2 1:1
0- 12 1.3 0.4 -- 0.1 1.8 4.5 0.4 6.3 4.2 2.2 18 29 43 4.1 4.9 5.1
12- 40 1.5 0.7 0.2 0.1 2.5 6.1 1.0 8.6 5.7 3.5 29 29 44 3.9 4.7 5.0
40- 86 0.9 0.8 0.2 0.1 2.0 6.4 1.4 8.4 5.3 3.4 41 24 38 3.8 4.7 5.0
86-140 0.1 0.3 0.1 0.1 0.6 7.0 2.7 7.6 5.6 3.3 82 8 11 3.7 4.6 5.0
140-280 0.2 0.3 0.2 0.1 0.8 13.0 2.9 13.8 5.3 3.7 78 6 15 3.7 4.5 4.9
-----------------------------------------------------------------------------------------------------------------------------------
< - - - - - - - - - - - - - - - - - - - - - - - CLAY MINERALOGY (<.002mm) - - - - - - - - - - - - - - - - - - - - - - >
FRAC- < - - - - - X-RAY - - - - - ->< - - - THERMAL - - - ->< - - - - - - - ELEMENTAL - - - - - - - ->< - -> EGME INTERSAMPLE
TION < >< - DTA - ->< - TGA - -> SiO2 Al2O3 Fe2O3 MgO CaO K2O Na2O < > RETN PRETA<
- - - - - 7A2i - - - - - ->< - 7A6 - >< - 7A4b - >< - - - - - - - - - 7C3 - - - - - - - - ->< > 7D2 TION
NUMBER <- - >< - - - - Peak size - - - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - -><mg/g>< - ->
82P2044 TCLY KK 4 VR 3 MI 1 GI 1 KK49 GI 4 8.7 0.5
82P2047 TCLY KK 5 VR 3 GI 1 GE 1 KK61 GI 1 8.6 0.4
-----------------------------------------------------------------------------------------------------------------------------------
< - - - - - - - - - - - - - - - - - - SAND - SILT MINERALOGY (2.0-0.002mm)- - - - - >
< -- - - - - - - - - -- OPTICAL - - - - - - - - - - - - - - - - - - - - - - - - - - >
SAMPLE FRACTION TOTAL RESISTANT < - - - - - - - - - - -GRAIN COUNT - - - - - -- - - - - - ->
82P2044 VFS 99 QZ98 OP 1 TMtr ZRtr BTtr FKtr MStr EPtr
82P2047 VFS 99 QZ96 KK 3 MStr BTtr OPtr HNtr ZRtr TMtr
-----------------------------------------------------------------------------------------------------------------------------------
The chemical data are based on the fraction less than 2 mm in size.
parting to moderate medium subangular blocky; very firm;
few tubular pores (abandoned root channels); many
distinct clay films on faces of peds; few highly weathered
quartz pebbles less than 3 cm in diameter; very strongly
acid; gradual wavy boundary.
Bt4—140 to 280 cm; red (2.5YR 4/6) clay; common medium
prominent light brownish gray (10YR 6/2) and common
medium prominent brownish yellow (10YR 6/6) redox
depletions; weak medium and coarse prismatic structure
parting to weak medium subangular blocky; very firm;
726 Soil Taxonomy
common tubular pores (abandoned root channels); common
faint clay films on faces of peds; few black stains on faces
of peds; strongly acid; gradual wavy boundary.
Bt5—280 to 430 cm; yellowish red (5YR 4/6) clay; common
medium prominent gray (10YR 6/1) and common medium
prominent red (2.5YR 4/6) redox depletions and
concentrations; weak medium and coarse prismatic
structure parting to moderate medium subangular blocky;
very firm; few faint clay films on faces of peds; 5 percent
rounded quartzite gravel; very strongly acid; clear wavy
boundary.
2C1—430 to 530 cm; stratified yellow (10YR 8/6), red (2.5YR
5/6), and gray (N 6/0) loamy sand; firm; few mica flakes;
very strongly acid; abrupt wavy boundary.
3C2—530 to 900 cm; stratified red (2.5YR 5/6) and yellowish
brown (10YR 5/6) very gravelly sandy loam; very firm; 60
percent rounded quartzite gravel; few highly weathered,
gray and light gray pebbles; very strongly acid.
Key to Suborders
HA. Ultisols that have aquic conditions for some time in
normal years (or artificial drainage) in one or more horizons
within 50 cm of the mineral soil surface and one or both of the
following:
1. Redoximorphic features in all layers between either the
lower boundary of an Ap horizon or a depth of 25 cm from
the mineral soil surface, whichever is deeper, and a depth of
40 cm and one of the following within the upper 12.5 cm of
the argillic or kandic horizon:
a. Redox concentrations and 50 percent or more redox
depletions with chroma of 2 or less either on faces of
peds or in the matrix; or
b. 50 percent or more redox depletions with chroma of
1 or less either on faces of peds or in the matrix; or
c. Distinct or prominent redox concentrations and 50
percent or more hue of 2.5Y or 5Y in the matrix and also
a thermic, isothermic, or warmer soil temperature
regime; or
2. Within 50 cm of the mineral soil surface, enough active
ferrous iron to give a positive reaction to alpha,alphadipyridyl
at a time when the soil is not being irrigated.
Aquults, p. 726
HB. Other Ultisols that have one or both of the following:
1. 0.9 percent (by weighted average) or more organic
carbon in the upper 15 cm of the argillic or kandic horizon;
or
2. 12 kg/m2
or more organic carbon between the mineral
soil surface and a depth of 100 cm.
Humults, p. 738
HC. Other Ultisols that have a udic moisture regime.
Udults, p. 747
HD. Other Ultisols that have an ustic moisture regime.
Ustults, p. 767
HE. Other Ultisols.
Xerults, p. 778
Aquults
These are the Ultisols in wet areas where ground water is
very close to the surface during part of each year, usually in
winter and spring in middle latitudes, and is deep at another
time. These soils are mostly grayish or olive in the subsoil and
formed mainly in alluvium and marine deposits that are of
Pleistocene age or older.
Aquults are extensive on the coastal plains in the United
States, particularly along the Atlantic Ocean and the Gulf of
Mexico. Their slopes are gentle. Most of the soils had and
many still have a forest vegetation.
Aquults have an ochric or umbric epipedon and an argillic
or kandic horizon. Some have a fragipan, and others have
plinthite in or below the argillic or kandic horizon.
Definition
Aquults are the Ultisols that have aquic conditions for some
time in normal years (or artificial drainage) in one or more
horizons within 50 cm of the mineral soil surface and one or
both of the following:
1. Redoximorphic features in all layers between either the
lower boundary of an Ap horizon or a depth of 25 cm below the
mineral soil surface, whichever is deeper, and a depth of 40 cm
or more and one of the following within the upper 12.5 cm of
the argillic or kandic horizon:
a. Redox concentrations and 50 percent or more redox
depletions with chroma of 2 or less either on faces of peds or
in the matrix; or
b. 50 percent or more redox depletions with chroma of 1
or less either on faces of peds or in the matrix; or
c. Distinct or prominent redox concentrations and 50
percent or more hue of 2.5Y or 5Y in the matrix and also a
thermic, isothermic, or warmer soil temperature regime; or
2. Within 50 cm of the mineral soil surface, enough active
ferrous iron to give a positive reaction to alpha,alpha-dipyridyl
at a time when the soil is not being irrigated.
Key to Great Groups
HAA. Aquults that have one or more horizons within 150
cm of the mineral soil surface in which plinthite either forms
Ultisols 727
a continuous phase or constitutes one-half or more of the
volume.
Plinthaquults, p. 737
HAB. Other Aquults that have a fragipan with an upper
boundary within 100 cm of the mineral soil surface.
Fragiaquults, p. 731
HAC. Other Aquults that have an abrupt textural change
between the ochric epipedon or albic horizon and the argillic or
kandic horizon and have 0.4 cm/hr or slower (low or very low)
saturated hydraulic conductivity in the argillic or kandic
horizon.
Albaquults, p. 727
HAD. Other Aquults that:
1. Do not have a densic, lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface; and
2. Have a kandic horizon; and
3. Within 150 cm of the mineral soil surface, either:
a. With increasing depth, do not have a clay decrease of
20 percent or more (relative) from the maximum clay
content; or
b. Have 5 percent or more (by volume) clay depletions
on faces of peds in the layer that has a 20 percent lower
clay content and, below that layer, a clay increase of 3
percent or more (absolute) in the fine-earth fraction.
Kandiaquults, p. 732
HAE. Other Aquults that have a kandic horizon.
Kanhaplaquults, p. 734
HAF. Other Aquults that:
1. Do not have a densic, lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface; and
2. Within 150 cm of the mineral soil surface, either:
a. With increasing depth, do not have a clay decrease of
20 percent or more (relative) from the maximum clay
content; or
b. Have 5 percent or more (by volume) clay depletions
on faces of peds in the layer that has a 20 percent lower
clay content and, below that layer, a clay increase of 3
percent or more (absolute) in the fine-earth fraction.
Paleaquults, p. 735
HAG. Other Aquults that have an umbric or mollic epipedon.
Umbraquults, p. 738
HAH. Other Aquults that have episaturation.
Epiaquults, p. 729
HAI. Other Aquults.
Endoaquults, p. 728
Albaquults
These are the Aquults that have a marked increase in
percentage of clay at an abrupt boundary at the top of the
argillic or kandic horizon. The argillic or kandic horizon
generally is clayey and has low or very low hydraulic
conductivity. In normal years water is perched for a while
above the argillic or kandic horizon when the soils are
rewetting and later saturates the whole soil. Slopes are nearly
level, and draining the soils is difficult. In the Southeastern
United States, these soils formed mostly in acid, latePleistocene
sediments and are on low marine or stream
terraces. Most of them have a season when the upper horizons
are dry. Some of the Albaquults in the United States have been
cleared for grazing or cropping, but many are still in forests.
Definition
Albaquults are the Aquults that:
1. Have an abrupt textural change between the ochric
epipedon or the albic horizon and the argillic or kandic horizon
and have saturated hydraulic conductivity in the argillic
horizon of 0.4 cm/hr or slower;
2. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface; and
3. Do not have plinthite that forms a continuous phase or
constitutes half or more of the matrix of any subhorizon within
150 cm of the mineral soil surface.
Key to Subgroups
HACA. Albaquults that have one or both of the following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Albaquults
HACB. Other Albaquults that have a kandic horizon.
Kandic Albaquults
HACC. Other Albaquults that have 50 percent or more
chroma of 3 or more in one or more horizons between either
the A or Ap horizon or a depth of 25 cm from the mineral soil
surface, whichever is deeper, and a depth of 75 cm.
Aeric Albaquults
728 Soil Taxonomy
HACD. Other Albaquults.
Typic Albaquults
Definition of Typic Albaquults
Typic Albaquults are the Albaquults that:
1. Have more than 50 percent chroma of 2 or less in all
horizons between either the A or Ap horizon or a depth of 25
cm from the mineral soil surface, whichever is deeper, and a
depth of 75 cm; and
2. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
and
3. Do not have a kandic horizon.
Description of Subgroups
Typic Albaquults.—These are the Albaquults that have 50
percent or more chroma of 2 or less in all horizons between
either the A or Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and a depth of 75
cm. These soils do not have slickensides, wedge-shaped
aggregates, a high linear extensibility, or wide cracks. Soils
that have slickensides, wedge-shaped aggregates, a high linear
extensibility, or wide cracks are assigned to the Vertic subgroup
because these properties are shared with Vertisols.
Typic Albaquults are nearly level and are difficult to drain.
Some are cultivated, but many are used as pasture or are in
forests. The soils occur mostly on the coastal plain of the
Southeastern United States and are of moderately small extent.
Aeric Albaquults.—Chroma in these soils is 3 or more in
more than 50 percent of some horizon between the bottom of
the A or Ap horizon and a depth of 75 cm. The period of
saturation with water in these soils is shorter than the one
characteristic of Typic Albaquults. Aeric Albaquults are of very
small extent in the United States and occur mostly in
California. They generally are either cultivated or used as
pasture.
Kandic Albaquults.—These soils are like Typic
Albaquults, but they have a kandic horizon. Kandic Albaquults
are not known to occur in the United States. The subgroup is
provided for use in other parts of the world.
Vertic Albaquults.—These soils are like Typic Albaquults,
but they are high in expanding clays and have cracks 5 mm or
more wide, slickensides, wedge-shaped aggregates, or a linear
extensibility of 6.0 cm or more between the mineral soil surface
and either a depth of 100 cm or a densic, lithic, or paralithic
contact, whichever is shallower. The soils are considered
intergrades between Albaquults and Aquerts. Vertic Albaquults
are not known to occur in the United States. The subgroup is
provided for use in other parts of the world.
Endoaquults
Endoaquults are the Aquults that have endoaquic saturation
and do not have a mollic or umbric epipedon. The ground
water fluctuates from a level near the soil surface to below the
argillic horizon and is sometimes below a depth of 200 cm.
These soils have an epipedon that rests on an argillic horizon
without an abrupt textural change if the argillic horizon has
moderately low or lower saturated hydraulic conductivity. They
do not have a kandic horizon. They have no fragipan or
horizon in which plinthite either forms a continuous phase or
constitutes one-half or more of the volume within 150 cm of
the mineral soil surface.
Before cultivation, most Endoaquults supported either
deciduous broadleaf or coniferous forest plants. Generally, the
soils are nearly level.
Definition
Endoaquults are the Aquults that:
1. Have endosaturation;
2. Do not have a kandic horizon;
3. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface;
4. Do not have an abrupt textural change at the upper
boundary of the argillic horizon if the hydraulic conductivity of
that horizon is 0.4 cm/hr or slower;
5. Do not have plinthite that either forms a continuous phase
or constitutes more than half the matrix (by volume) in any
horizon within 150 cm of the mineral soil surface;
6. Do not have a mollic or umbric epipedon; and
7. Have, with increasing depth within 150 cm of the mineral
soil surface, a decrease of 20 percent or more (relative) from
the maximum clay content and either less than 5 percent (by
volume) clay depletions on faces of peds in the layer that has
the 20 percent lower clay content or, below that layer, no clay
increase or an increase of less than 3 percent (absolute).
Key to Subgroups
HAIA. Endoaquults that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 to 100 cm.
Arenic Endoaquults
HAIB. Other Endoaquults that have a sandy or sandy-skeletal
Ultisols 729
particle-size class throughout a layer extending from the mineral
soil surface to the top of an argillic horizon at a depth of 100 cm
or more.
Grossarenic Endoaquults
HAIC. Other Endoaquults that have 50 percent or more
chroma of 3 or more in one or more horizons between either
the A or Ap horizon or a depth of 25 cm from the mineral soil
surface, whichever is deeper, and a depth of 75 cm.
Aeric Endoaquults
HAID. Other Endoaquults.
Typic Endoaquults
Definition of Typic Endoaquults
Typic Endoaquults are the Endoaquults that:
1. Do not have a sandy particle-size class throughout a layer
extending from the mineral soil surface to the top of an argillic
horizon at a depth of 50 cm or more; and
2. Have more than 50 percent chroma of 2 or less in all
horizons between either the A or Ap horizon or a depth of 25
cm from the mineral soil surface, whichever is deeper, and a
depth of 75 cm.
Description of Subgroups
Typic Endoaquults.—These are the Endoaquults that have
50 percent or more chroma of 2 or less in all horizons between
either the A or Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and a depth of 75
cm. These soils do not have a sandy particle-size class
throughout a layer extending from the mineral soil surface to
the top of the argillic horizon if the argillic horizon is at a
depth of 50 cm or more. Slopes generally are nearly level. The
natural vegetation consisted of forest plants. Some of the soils
are cultivated, but many are used as pasture or are in forests.
The soils occur mostly on the coastal plain of the Southeastern
United States and are of moderate extent.
Aeric Endoaquults.—Chroma in these soils is 3 or more in
more than 50 percent of some horizon between the bottom of
the A or Ap horizon and a depth of 75 cm. The period of
saturation with water in these soils is shorter than the one
characteristic of Typic Endoaquults. Aeric Endoaquults are of
small extent and occur mostly on the coastal plain of the
Southeastern United States. The natural vegetation consisted of
forest plants. Most of these soils are nearly level. Some have
been cleared and artificially drained and are used as cropland
or pasture, and some are used as forest.
Arenic Endoaquults.—These soils have a sandy layer,
starting at the mineral soil surface, that is between 50 and 100
cm thick. Many of the soils developed in somewhat sandier
materials and have less clay in the argillic horizon than the
Typic Endoaquults. Arenic Endoaquults are mainly on the
coastal plain of the Southeastern United States. They are of
small extent. The natural vegetation consisted of forest plants.
Most of these soils are nearly level. Most are used as forest, but
some have been cleared and artificially drained and are used as
cropland or pasture.
Grossarenic Endoaquults.—These soils have a sandy layer,
starting at the mineral soil surface, that is between 100 and 200
cm thick in the major part of the pedon, but they are otherwise
similar to Typic Endoaquults in defined properties. Grossarenic
Endoaquults are not known to occur in the United States. The
subgroup is provided for use in other parts of the world.
Epiaquults
Epiaquults are the Aquults that have epiaquic saturation and
do not have a mollic or umbric epipedon. Water is perched on a
less permeable layer, commonly an argillic horizon. These soils
have an epipedon that rests on an argillic horizon without an
abrupt textural change if the argillic horizon has moderately
low or lower saturated hydraulic conductivity. They do not
have a kandic horizon. They do not have a fragipan or a
horizon in which plinthite either forms a continuous phase or
constitutes one-half or more of the volume within 150 cm of
the mineral soil surface.
Before cultivation, most Epiaquults supported either
deciduous broadleaf or coniferous forest plants. Slopes
generally are nearly level.
Definition
Epiaquults are the Aquults that:
1. Do not have a kandic horizon;
2. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface;
3. Do not have an abrupt textural change at the upper
boundary of the argillic horizon if the hydraulic conductivity of
that horizon is low;
4. Do not have plinthite that either forms a continuous phase
or constitutes more than half the matrix (by volume) in any
horizon within 150 cm of the mineral soil surface;
5. Do not have a mollic or umbric epipedon;
6. Have, with increasing depth within 150 cm of the mineral
soil surface, a decrease of 20 percent or more (relative) from
the maximum clay content and either less than 5 percent (by
volume) clay depletions on faces of peds in the layer that has
the 20 percent lower clay content or, below that layer, no clay
increase or an increase of less than 3 percent (absolute); and
7. Have episaturation.
Key to Subgroups
HAHA. Epiaquults that have one or both of the following:
1. Cracks within 125 cm of the mineral soil surface that are 5
730 Soil Taxonomy
mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Epiaquults
HAHB. Other Epiaquults that have:
1. Fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm
of the mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm
or more thick; and
2. 50 percent or more chroma of 3 or more in one or more
horizons between either the A or Ap horizon or a depth of
25 cm from the mineral soil surface, whichever is deeper,
and a depth of 75 cm.
Aeric Fragic Epiaquults
HAHC. Other Epiaquults that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 to 100 cm.
Arenic Epiaquults
HAHD. Other Epiaquults that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 100 cm or more.
Grossarenic Epiaquults
HAHE. Other Epiaquults that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Epiaquults
HAHF. Other Epiaquults that have 50 percent or more
chroma of 3 or more in one or more horizons between either
the A or Ap horizon or a depth of 25 cm from the mineral soil
surface, whichever is deeper, and a depth of 75 cm.
Aeric Epiaquults
HAHG. Other Epiaquults.
Typic Epiaquults
DefinitionofTypicEpiaquults
Typic Epiaquults are the Epiaquults that:
1. Do not have a sandy particle-size class throughout a layer
extending from the mineral soil surface to the top of an argillic
horizon at a depth of 50 cm or more;
2. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
3. Have more than 50 percent chroma of 2 or less in all
horizons between either the A or Ap horizon or a depth of 25
cm from the mineral soil surface, whichever is deeper, and a
depth of 75 cm; and
4. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick.
Description of Subgroups
Typic Epiaquults.—These are the Epiaquults that have 50
percent or more chroma of 2 or less in all horizons between
either the A or Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and a depth of 75
cm. These soils do not have slickensides, wedge-shaped
aggregates, a high linear extensibility, or wide cracks. They do
not have a sandy particle-size class throughout a layer
extending from the mineral soil surface to the top of the
argillic horizon if the argillic horizon is at a depth of 50 cm or
more. Soils that have slickensides, wedge-shaped aggregates, a
high linear extensibility, or wide cracks are assigned to the
Vertic subgroup because these properties are shared with
Vertisols.
Typic Epiaquults generally are nearly level. They occur
mostly in the Eastern United States and are of very small
extent. The natural vegetation consisted of forest plants. The
soils commonly are underlain by slowly permeable materials
and are difficult to drain. Some are used as cropland, but many
are used as pasture or forest.
Aeric Epiaquults.—Chroma in these soils is 3 or more in
more than 50 percent of some horizon between the bottom of
the A or Ap horizon and a depth of 75 cm. The period of
saturation with water in these soils is shorter than the one
Ultisols 731
characteristic of Typic Epiaquults. Aeric Epiaquults range from
nearly level to moderately steep. The natural vegetation
consisted of forest plants. These soils are of small extent in the
Eastern United States. Some are underlain by slowly permeable
materials and are difficult to drain. Some are used as cropland,
but many are used as pasture or forest.
Aeric Fragic Epiaquults.—Chroma in these soils is 3 or
more in more than 50 percent of some horizon between the
bottom of the A or Ap horizon and a depth of 75 cm. These
soils have fragic soil properties in 30 percent or more of the
volume of a layer 15 cm or more thick that has its upper
boundary within 100 cm of the mineral soil surface or in 60
percent or more of the volume of a layer 15 cm or more thick.
The soils are not known to occur in the United States. The
subgroup is provided for use in other parts of the world.
Arenic Epiaquults.—These soils have a sandy layer,
starting at the mineral soil surface, that is between 50 and 100
cm thick. They are otherwise like Typic Epiaquults in most
other defined properties. Arenic Epiaquults are not known to
occur in the United States. The subgroup is provided for use in
other parts of the world.
Fragic Epiaquults.—These soils have fragic soil properties
in 30 percent or more of the volume of a layer 15 cm or more
thick that has its upper boundary within 100 cm of the mineral
soil surface or in 60 percent or more of the volume of a layer
15 cm or more thick. These soils are not known to occur in the
United States. The subgroup is provided for use in other parts
of the world.
Grossarenic Epiaquults.—These soils have a sandy layer,
starting at the mineral soil surface, that is between 100 and 200
cm thick in the major part of the pedon. They are not known to
occur in the United States. The subgroup is provided for use in
other parts of the world.
Vertic Epiaquults.—These soils are similar to Typic
Epiaquults, but they are high in expanding clays and have
cracks 5 mm or more wide, slickensides, wedge-shaped
aggregates, or a linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
The soils are considered intergrades between Epiaquults and
Aquerts. Vertic Epiaquults are of very small extent in the
United States. The subgroup is provided for use in other parts
of the world.
Fragiaquults
These are the Aquults that have a fragipan with an upper
boundary within 100 cm of the mineral soil surface. Plinthite
does not form a continuous phase or constitute one-half or
more of the volume of any layer with an upper boundary within
150 cm of the mineral soil surface. Normally, the fragipan lies
below the argillic or kandic horizon. In a few of the soils,
however, it may be in the lower part of the argillic or kandic
horizon. The fragipan in some Fragiaquults is virtually
identical to the one in Alfisols, Inceptisols, and Spodosols. In
some Fragiaquults, however, there is one aberrant feature—a
small amount of plinthite. At this stage of knowledge, it is not
certain that the fragipan that has plinthite is the same as the
others. The behavior, however, is the same. For pragmatic
reasons, the pan that has plinthite currently is considered to be
a fragipan if its upper boundary is within 100 cm of the
mineral soil surface.
Definition
Fragiaquults are the Aquults that:
1. Have a fragipan with an upper boundary within 100 cm of
the mineral soil surface; and
2. Do not have plinthite that forms a continuous phase or
constitutes more than half the matrix of any subhorizon within
150 cm of the mineral soil surface.
Key to Subgroups
HABA. Fragiaquults that have 50 percent or more chroma of
3 or more in one or more horizons between either the A or Ap
horizon or a depth of 25 cm from the mineral soil surface,
whichever is deeper, and the fragipan.
Aeric Fragiaquults
HABB. Other Fragiaquults that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Fragiaquults
HABC. Other Fragiaquults that have a mollic or umbric
epipedon.
Umbric Fragiaquults
HABD. Other Fragiaquults.
Typic Fragiaquults
Definition of Typic Fragiaquults
Typic Fragiaquults are the Fragiaquults that:
1. Do not have a mollic or umbric epipedon;
2. Have 50 percent or more chroma of 2 or less in all
horizons between the A or Ap horizon and the fragipan; and
3. Have less than 5 percent (by volume) plinthite in all
subhorizons within 150 cm of the mineral soil surface.
Description of Subgroups
Typic Fragiaquults.—The central concept or Typic
subgroup of Fragiaquults is fixed on soils that have an ochric
epipedon and are gray and mottled in all horizons between the
bottom of the A or Ap horizon and the top of the fragipan.
These soils have little or no plinthite in the fragipan.
The presence of plinthite is considered abnormal and is used
to define the Plinthic subgroup. Chroma of 3 or more in some
732 Soil Taxonomy
subhorizon above the fragipan suggests somewhat better
drainage than that in Typic Fragiaquults and defines the Aeric
subgroup.
Typic Fragiaquults generally are nearly level or gently
sloping. They occur mostly in the Eastern United States and
are of very small extent. The natural vegetation consisted of
forest plants. The fragipan commonly is slowly permeable. As
a result, these soils are difficult to drain. Some of the soils are
used as cropland, but many are used as pasture or forest.
Aeric Fragiaquults.—These soils have dominant chroma of
3 or more in some horizon between the bottom of the A or Ap
horizon and the top of the fragipan. They generally are
somewhat better drained than soils of the Typic subgroup.
Aeric Fragiaquults range from nearly level to moderately
sloping. The natural vegetation consisted of forest plants.
These soils are of very small extent in the Eastern United
States. The fragipan commonly is slowly permeable. As a
result, the soils are difficult to drain. Some of the soils are used
as cropland, but many are used as pasture or forest.
Plinthic Fragiaquults.—These soils have plinthite that
constitutes between 5 and 50 percent of the matrix in the
fragipan. These soils are not known to occur in the United
States. The subgroup is provided for use in other parts of the
world.
Umbric Fragiaquults.—These soils have a mollic or
umbric epipedon. They are not known to occur in the United
States. The subgroup is provided for use in other parts of the
world.
Kandiaquults
Kandiaquults are the Aquults that have a kandic horizon and
a clay distribution in which the percentage of clay does not
decrease from its maximum amount by as much as 20 percent
within a depth of 150 cm from the mineral soil surface, or the
layer in which the clay percentage decreases has at least 5
percent of the volume consisting of clay depletions on faces of
peds and there is at least a 3 percent (absolute) increase in clay
content below this layer. These soils have an epipedon that
rests on a kandic horizon without an abrupt textural change if
the kandic horizon has moderately low or lower saturated
hydraulic conductivity. They do not have a fragipan or a
horizon in which plinthite either forms a continuous phase or
constitutes one-half or more of the volume within 150 cm of
the mineral soil surface. Kandiaquults are not known to occur
in the United States. The great group is provided for use in
other parts of the world.
Definition
Kandiaquults are the Aquults that:
1. Have a kandic horizon;
2. Do not have a densic, lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface;
3. Have a clay distribution in which the percentage of clay
does not decrease from its maximum amount by as much as 20
percent within a depth of 150 cm from the mineral soil surface,
or the layer in which the clay percentage decreases by more
than 20 percent has at least 5 percent of the volume consisting
of clay depletions on faces of peds and there is at least a 3
percent (absolute) increase in clay content below this layer;
4. Do not have plinthite that forms a continuous phase or
constitutes more than half the volume of some subhorizon
within 150 cm of the mineral soil surface;
5. Do not have a fragipan that has its upper boundary
within 100 cm of the mineral soil surface; and
6. Do not have both an abrupt textural change between the
epipedon or the albic horizon and the kandic horizon and a
saturated hydraulic conductivity of 0.4 cm/hr or slower in the
kandic horizon.
Key to Subgroups
HADA. Kandiaquults that have an ECEC of 1.5 cmol(+)/kg
clay or less (sum of bases extracted with 1N NH4
OAc pH 7,
plus 1N KCl-extractable Al) in one or more horizons within
150 cm of the mineral soil surface.
Acraquoxic Kandiaquults
HADB. Other Kandiaquults that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
a kandic horizon at a depth of 50 to 100 cm; and
2. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Arenic Plinthic Kandiaquults
HADC. Other Kandiaquults that:
1. Have a mollic or umbric epipedon; and
2. Have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface
to the top of a kandic horizon at a depth of 50 to 100 cm.
Arenic Umbric Kandiaquults
HADD. Other Kandiaquults that have a sandy or sandyskeletal
particle-size class throughout a layer extending from
the mineral soil surface to the top of a kandic horizon at a
depth of 50 to 100 cm.
Arenic Kandiaquults
HADE. Other Kandiaquults that have a sandy or sandyskeletal
particle-size class throughout a layer extending from
the mineral soil surface to the top of a kandic horizon at a
depth of 100 cm or more.
Grossarenic Kandiaquults
Ultisols 733
HADF. Other Kandiaquults that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Kandiaquults
HADG. Other Kandiaquults that have 50 percent or more
chroma of 3 or more in one or more horizons between either
the A or Ap horizon or a depth of 25 cm from the mineral soil
surface, whichever is deeper, and a depth of 75 cm.
Aeric Kandiaquults
HADH. Other Kandiaquults that have a mollic or umbric
epipedon.
Umbric Kandiaquults
HADI. Other Kandiaquults.
Typic Kandiaquults
Definition of Typic Kandiaquults
Typic Kandiaquults are the Kandiaquults that:
1. Do not have a subhorizon that has dominant chroma of 3
or more within 75 cm of the mineral soil surface;
2. Do not have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of an argillic horizon at a depth of 50 cm or more;
3. Have less than 5 percent (by volume) plinthite in all
subhorizons within 150 cm of the mineral soil surface;
4. Do not have a mollic or umbric epipedon; and
5. Have an ECEC (sum of bases plus 1N KCl-extractable Al)
of more than 1.5 cmol(+)/kg clay in all subhorizons to a depth
of 150 cm below the mineral soil surface.
Description of Subgroups
Typic Kandiaquults.—The central concept or Typic
subgroup of Kandiaquults is fixed on soils that (1) have
dominantly low chroma between the A or Ap horizon and a
depth of 75 cm or more from the mineral soil surface, (2) do
not have a mollic or umbric epipedon, (3) do not have a thick
epipedon with a sandy or sandy-skeletal particle-size class
throughout, (4) have less than 5 percent (by volume) plinthite
in all subhorizons within 150 cm of the mineral soil surface,
and (5) have an ECEC (sum of bases plus 1N KCl-extractable
Al) of more than 1.5 cmol(+)/kg clay in all subhorizons to a
depth of 150 cm below the mineral soil surface.
A chroma higher than that of Typic Kandiaquults is
characteristic of soils that are saturated for shorter periods and
serves to define intergrades to freely drained soils. Color
values, moist, of 2 or 3 in a plow layer indicate a higher-thannormal
content of organic matter and form the basis for
defining intergrades to other great groups. A thick layer of
sand or loamy sand, starting at the mineral soil surface, is the
basis for defining the Arenic and Grossarenic subgroups.
Typic Kandiaquults are not known to occur in the United
States. The subgroup is provided for use in other parts of the
world.
Acraquoxic Kandiaquults.—These soils have an ECEC of
1.5 cmol(+)/kg clay or less (sum of bases extracted with 1N
NH4
OAc pH 7, plus 1N KCl-extractable Al) in one or more
horizons within 150 cm of the mineral soil surface. Recycling
of plant nutrients from decaying vegetation is critical for plant
growth on the soils. These soils are not known to occur in the
United States. The subgroup is provided for use in other parts
of the world.
Aeric Kandiaquults.—Below the A or Ap horizon, these
soils have chroma that is too high for the Typic subgroup, but
they are otherwise like Typic Kandiaquults in their defined
properties and in many other properties. Aeric Kandiaquults
are not known to occur in the United States. The subgroup is
provided for use in other parts of the world.
Arenic Kandiaquults.—These soils have a sandy or sandyskeletal
particle-size class throughout a layer extending from
the mineral soil surface to the top of a kandic horizon at a
depth of 50 to 100 cm below the mineral soil surface. These
soils are not known to occur in the United States.
Arenic Plinthic Kandiaquults.—These soils have a sandy
or sandy-skeletal particle-size class throughout a layer
extending from the mineral soil surface to the top of a kandic
horizon at a depth of 50 to 100 cm below the mineral soil
surface. They also have 5 percent or more (by volume) plinthite
in one or more horizons within 150 cm of the mineral soil
surface. These soils are not known to occur in the United
States. The subgroup is provided for use in other parts of the
world.
Arenic Umbric Kandiaquults.—These soils have a sandy
or sandy-skeletal particle-size class throughout a layer
extending from the mineral soil surface to the top of a kandic
horizon at a depth of 50 to 100 cm below the mineral soil
surface. They also have an umbric or mollic epipedon. These
soils are not known to occur in the United States. The subgroup
is provided for use in other parts of the world.
Grossarenic Kandiaquults.—These soils have a sandy or
sandy-skeletal particle-size class throughout a layer extending
from the mineral soil surface to the top of a kandic horizon at a
depth of 100 cm or more below the mineral soil surface. They
are not known to occur in the United States. The subgroup is
provided for use in other parts of the world.
Plinthic Kandiaquults.—These soils have 5 percent or
more (by volume) plinthite in one or more horizons within 150
cm of the mineral soil surface. They are not known to occur in
the United States. The subgroup is provided for use in other
parts of the world.
Umbric Kandiaquults.—These soils are like Typic
Kandiaquults, but they have an umbric or mollic epipedon.
734 Soil Taxonomy
They are not known to occur in the United States. The
subgroup is provided for use in other parts of the world.
Kanhaplaquults
Kanhaplaquults are the Aquults that have a kandic horizon
and a clay distribution in which the percentage of clay
decreases from its maximum amount by as much as 20 percent
within a depth of 150 cm from the mineral soil surface, and the
layer in which the clay percentage decreases has less than 5
percent of the volume consisting of clay depletions on faces of
peds or there is an increase in clay content of less than 3
percent (absolute) below this layer. These soils have an
epipedon that rests on a kandic horizon without an abrupt
textural change if the kandic horizon has moderately low or
lower saturated hydraulic conductivity. They do not have a
fragipan or a horizon in which plinthite either forms a
continuous phase or constitutes one-half or more of the volume
within 150 cm of the mineral soil surface. Kanhaplaquults are
not known to occur in the United States. The great group is
provided for use in other parts of the world.
Definition
Kanhaplaquults are the Aquults that:
1. Have a kandic horizon;
2. Have a clay distribution in which the percentage of clay
decreases from its maximum amount by 20 percent or more
within a depth of 150 cm from the mineral soil surface, and the
layer in which the percentage of clay is less than the maximum
has less than 5 percent of the volume consisting of clay
depletions on faces of peds or there is an increase in clay
content of less than 3 percent (absolute) below this layer;
3. Do not have plinthite that forms a continuous phase or
constitutes more than half the volume of some subhorizon
within 150 cm of the mineral soil surface;
4. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface; and
5. Do not have both an abrupt textural change between the
epipedon or the albic horizon and the kandic horizon and
saturated hydraulic conductivity of 0.4 cm/hr or slower in the
kandic horizon.
Key to Subgroups
HAEA. Kanhaplaquults that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or more of the following:
1. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
2. More than 35 percent (by volume) fragments coarser than
2.0 mm, of which more than 66 percent is cinders, pumice, and
pumicelike fragments; or
3. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
a. In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
b. [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Kanhaplaquults
HAEB. Other Kanhaplaquults that have 5 percent or more
(by volume) plinthite in one or more horizons within 150 cm of
the mineral soil surface.
Plinthic Kanhaplaquults
HAEC. Other Kanhaplaquults that:
1. Have a mollic or umbric epipedon; and
2. Have 50 percent or more chroma of 3 or more in one or
more horizons between either the A or Ap horizon or a
depth of 25 cm from the mineral soil surface, whichever is
deeper, and a depth of 75 cm.
Aeric Umbric Kanhaplaquults
HAED. Other Kanhaplaquults that have 50 percent or more
chroma of 3 or more in one or more horizons between either
the A or Ap horizon or a depth of 25 cm from the mineral soil
surface, whichever is deeper, and a depth of 75 cm.
Aeric Kanhaplaquults
HAEE. Other Kanhaplaquults that have a mollic or umbric
epipedon.
Umbric Kanhaplaquults
HAEF. Other Kanhaplaquults.
Typic Kanhaplaquults
Definition of Typic Kanhaplaquults
Typic Kanhaplaquults are the Kanhaplaquults that:
1. Do not have a mollic or umbric epipedon;
2. Do not have a subhorizon that has dominant chroma of 3
or more within 75 cm of the mineral soil surface;
3. Have less than 5 percent (by volume) plinthite in all
subhorizons within 150 cm of the mineral soil surface; and
4. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, any of the following:
a. A fine-earth fraction with both a bulk density of 1.0
Ultisols 735
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Description of Subgroups
Typic Kanhaplaquults.—The central concept or Typic
subgroup of Kanhaplaquults is fixed on soils that (1) have
dominantly low chroma between the A or Ap horizon and a
depth of 75 cm or more from the mineral soil surface, (2) do
not have a mollic or umbric epipedon, (3) have less than 5
percent (by volume) plinthite in all subhorizons within 150 cm
of the mineral soil surface, and (4) do not have a surface
mantle or layer in the upper 75 cm that has both a low bulk
density and a high content of weakly crystalline minerals or
that consists of slightly or moderately weathered pyroclastic
materials.
A chroma higher than that of Typic Kanhaplaquults is
characteristic of soils that are saturated for shorter periods and
serves to define intergrades to freely drained soils. A mollic or
umbric epipedon is the basis for defining the Umbric subgroup.
Typic Kanhaplaquults are not known to occur in the United
States. The subgroup is provided for use in other parts of the
world.
Aeric Kanhaplaquults.—Below the A or Ap horizon, these
soils have chroma that is too high for the Typic subgroup, but
they are otherwise like Typic Kanhaplaquults in their defined
properties and in many other properties. Aeric Kanhaplaquults
are not known to occur in the United States. The subgroup is
provided for use in other parts of the world.
Aeric Umbric Kanhaplaquults.—These soils have an
umbric or mollic epipedon. Below the A or Ap horizon, they
have chroma that is too high for the Typic subgroup. They are
otherwise like Typic Kanhaplaquults in their defined properties
and in many other properties. Aeric Umbric Kanhaplaquults
are not known to occur in the United States. The subgroup is
provided for use in other parts of the world.
Aquandic Kanhaplaquults.—These soils are influenced by
volcanic ejecta. When weathered, they have high P-retention,
low bulk density, and high porosity. They are not known to
occur in the United States.
Plinthic Kanhaplaquults.—These soils have 5 to 50
percent (by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface. They are not known to occur
in the United States. The subgroup is provided for use in other
parts of the world.
Umbric Kanhaplaquults.—These soils have an umbric or
mollic epipedon. They are otherwise like Typic Kanhaplaquults
in their defined properties and in most other properties. These
soils are not known to occur in the United States. The subgroup
is provided for use in other parts of the world.
Paleaquults
These are the Aquults that have a clay distribution in which
the percentage of clay does not decrease from its maximum
amount by as much as 20 percent within a depth of 150 cm
from the mineral soil surface, or the layer in which the clay
percentage decreases has at least 5 percent of the volume
consisting of clay depletions on faces of peds and there is at
least a 3 percent increase in clay content below this layer.
These soils have an epipedon that rests on an argillic horizon
without an abrupt textural change if the argillic horizon has
moderately low or lower saturated hydraulic conductivity. They
do not have a fragipan or a horizon in which plinthite either
forms a continuous phase or constitutes one-half or more of the
volume within 150 cm of the mineral soil surface.
Paleaquults formed mostly on mid-Pleistocene or older land
surfaces, on high marine or river terraces or old deltas. They
are of large extent in the Southeastern United States. The
natural vegetation consisted of forest plants, mostly watertolerant
conifers or hardwood trees.
Definition
Paleaquults are the Aquults that:
1. Have a clay distribution in which the percentage of clay
does not decrease from its maximum by as much as 20 percent
within a depth of 150 cm from the mineral soil surface, or the
layer in which the clay percentage decreases by more than 20
percent has at least 5 percent of the volume consisting of clay
depletions on faces of peds and there is at least a 3 percent
(absolute) increase in clay content below this layer;
2. Do not have a densic, lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface;
3. Do not have a kandic horizon;
4. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface;
5. Do not have plinthite that forms a continuous phase or
constitutes more than half the matrix in any subhorizon within
150 cm of the mineral soil surface; and
6. Do not have both an abrupt textural change between the
epipedon or the albic horizon and the argillic horizon and
saturated hydraulic conductivity of 0.4 cm/hr or slower in the
argillic horizon.
736 Soil Taxonomy
KeytoSubgroups
HAFA. Paleaquults that have one or both of the following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Paleaquults
HAFB. Other Paleaquults that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
an argillic horizon at a depth of 50 to 100 cm; and
2. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Arenic Plinthic Paleaquults
HAFC. Other Paleaquults that:
1. Have a mollic or umbric epipedon; and
2. Have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface
to the top of an argillic horizon at a depth of 50 to 100 cm.
Arenic Umbric Paleaquults
HAFD. Other Paleaquults that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 to 100 cm.
Arenic Paleaquults
HAFE. Other Paleaquults that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 100 cm or more.
Grossarenic Paleaquults
HAFF. Other Paleaquults that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Paleaquults
HAFG. Other Paleaquults that have 50 percent or more
chroma of 3 or more in one or more horizons between either
the A or Ap horizon or a depth of 25 cm from the mineral soil
surface, whichever is deeper, and a depth of 75 cm.
Aeric Paleaquults
HAFH. Other Paleaquults that have a mollic or umbric
epipedon.
Umbric Paleaquults
HAFI. Other Paleaquults.
Typic Paleaquults
Definition of Typic Paleaquults
Typic Paleaquults are the Paleaquults that:
1. Do not have, between either the bottom of the A or Ap
horizon or a depth of 25 cm from the mineral soil surface,
whichever is deeper, and a depth of 75 cm from the mineral
soil surface, a horizon that has dominant chroma of 3 or more;
2. Do not have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of an argillic horizon at a depth of 50 cm or more;
3. Have less than 5 percent (by volume) plinthite in all
horizons within 150 cm of the mineral soil surface;
4. Do not have a mollic or umbric epipedon; and
5. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Description of Subgroups
Typic Paleaquults.—The central concept or Typic subgroup
of Paleaquults is fixed on soils that have grayish colors in the
matrix below the A or Ap horizon, do not have plinthite, have
a texture finer than loamy fine sand within 50 cm of the
mineral soil surface, and have an ochric epipedon.
Chroma in some subhorizon too high for Typic Paleaquults
is a characteristic used to define the Aeric subgroup, an
intergrade to Paleudults. A thick sandy layer, starting at the
mineral soil surface, defines Arenic and Grossarenic
subgroups. A small amount of plinthite suggests intergrades to
Plinthaquults. An umbric or mollic epipedon is used to define
the Umbric subgroup.
Typic Paleaquults generally are nearly level. They occur
mostly on the coastal plain of the Southeastern United States
and are of moderate extent. The natural vegetation consisted of
forest plants. Most of these soils are used as forest, but some
have been cleared and are used as cropland or pasture.
Aeric Paleaquults.—These soils have a subhorizon,
generally near the surface, that has chroma of 3 or more and
Ultisols 737
normally have a seasonal high water table that is deeper than
that in Typic Paleaquults or has more oxygen. Aeric
Paleaquults commonly are nearly level or gently sloping. The
natural vegetation consisted of forest plants. These soils occur
mostly on the coastal plain of the Southeastern United States
and are of moderate extent. Many of the soils have been cleared
and are used as cropland, but some are used as pasture or
forest.
Arenic Paleaquults.—These soils have a sandy layer,
starting at the mineral soil surface, that is between 50 and 100
cm thick and are permitted to have brownish colors in the
matrix below the A or Ap horizon, but they are otherwise like
Typic Paleaquults in defined properties. Most Arenic
Paleaquults developed in somewhat sandier materials and have
less clay in the argillic horizon than the soils in the Typic
subgroup. The natural vegetation consisted of forest plants.
The Arenic Paleaquults in the United States are mainly on the
coastal plains in Georgia, Alabama, and Florida. They are
moderately extensive. Most of these soils are used as forest, but
some have been cleared and are used as cropland or pasture.
Arenic Plinthic Paleaquults.—These soils have a sandy
layer, starting at the mineral soil surface, that is between 50
and 100 cm thick and have 5 to 50 percent plinthite at a depth
of less than 150 cm. The horizons that have plinthite are
mostly firm and less permeable than the overlying horizons.
The Arenic Plinthic Paleaquults in the United States are mostly
in Florida and Georgia. They are of small extent. Most of these
soils are used as forest, but some have been cleared and are
used as cropland or pasture.
Arenic Umbric Paleaquults.—These soils have an umbric
or mollic epipedon, and their particle-size class is sandy or
sandy-skeletal to a depth between 50 and 100 cm, although the
epipedon is not necessarily that thick. These soils formed in
somewhat sandier parent materials and in some areas are
wetter than Typic Paleaquults. Arenic Umbric Paleaquults are
of very small extent in the Southeastern United States. Most of
these soils are used as forest, but some have been cleared and
are used as cropland or pasture.
Grossarenic Paleaquults.—These soils have a sandy layer,
starting at the mineral soil surface, that is between 100 and 200
cm thick in the major part of the pedon and are permitted to
have brownish colors in the matrix below the A or Ap horizon,
but they are otherwise similar to Typic Paleaquults in defined
properties. The parent materials commonly are more sandy
than those of the soils in the Typic subgroup. Grossarenic
Paleaquults are of small extent in the Southeastern United
States. Most of these soils are used as forest, but some have
been cleared and are used as cropland or pasture.
Plinthic Paleaquults.—These soils have 5 to 50 percent (by
volume) plinthite in some horizon within 150 cm of the
mineral soil surface. They are of small extent in the Southern
United States. These soils are used as forest or have been
cleared and are used as cropland or pasture.
Umbric Paleaquults.—These soils have an umbric or
mollic epipedon but are otherwise like Typic Paleaquults in
defined properties. Many Umbric Paleaquults are the wettest of
the Paleaquults and are ponded in winter. Umbric Paleaquults are
of small extent in the Southeastern United States. Most of these
soils are used as forest, but some have been cleared and are
used as cropland or pasture.
Vertic Paleaquults.—These soils are high in expanding clays
and have cracks 5 mm or more wide, slickensides, wedge-shaped
aggregates, or a linear extensibility of 6.0 cm or more between
the mineral soil surface and either a depth of 100 cm or a densic,
lithic, or paralithic contact, whichever is shallower. These soils
are intergrades between Paleaquults and Aquerts. They are not
known to occur in the United States. The subgroup is provided
for use in other parts of the world.
Plinthaquults
These are the Aquults that have plinthite that either forms a
continuous phase or constitutes more than half the matrix of
some subhorizon within 125 cm of the mineral soil surface.
These soils are mostly in intertropical areas. They make up a
small area in Puerto Rico.
Definition
Plinthaquults are the Aquults that have plinthite that forms
a continuous phase or constitutes more than half the matrix of
some subhorizon within 125 cm of the mineral soil surface.
Key to Subgroups
HAAA. Plinthaquults that have a kandic horizon or a CEC
(by 1N NH4
OAc pH 7) of less than 24 cmol(+)/kg clay in 50
percent or more (by volume) of the argillic horizon if less than
100 cm thick or of its upper 100 cm.
Kandic Plinthaquults
HAAB. Other Plinthaquults.
Typic Plinthaquults
Definition of Typic Plinthaquults
Typic Plinthaquults are the Plinthaquults that have a CEC
of 24 cmol(+) or more per kg clay (by 1N NH4
OAc pH 7) in the
major part of the argillic horizon or the major part of the upper
100 cm of the argillic horizon if it is thicker than 100 cm.
Description of Subgroups
Typic Plinthaquults.—Typic Plinthaquults are the
Plinthaquults that have a CEC of 24 cmol(+) or more per kg
clay (by 1N NH4
OAc pH 7) in 50 percent or more of the
argillic horizon or of the upper 100 cm of the argillic horizon if
it is thicker than 100 cm. These soils are not known to occur in
the United States. The subgroup is provided for use in other
parts of the world.
Kandic Plinthaquults.—These are the Plinthaquults that
have a kandic horizon or have a CEC of less than 24 cmol(+)
738 Soil Taxonomy
per kg clay (by 1N NH4
OAc pH 7) in 50 percent or more of the
argillic horizon or of the upper 100 cm of the argillic horizon if it
is thicker than 100 cm. These soils are of very small extent. They
are known to occur only in Puerto Rico.
Umbraquults
These are the Aquults that commonly have an umbric
epipedon. These soils do not have a horizon within 150 cm of
the mineral soil surface in which plinthite either forms a
continuous phase or constitutes one-half or more of the volume.
They do not have a fragipan with an upper boundary within
100 cm of the mineral soil surface or a kandic horizon. They
do not have both an abrupt textural change between an albic
horizon and the argillic horizon and low or very low saturated
hydraulic conductivity in the argillic horizon. They have,
within 150 cm of the mineral soil surface, either a densic,
lithic, paralithic, or petroferric contact, or they have, with
increasing depth, a clay decrease of 20 percent or more
(relative) from the maximum clay content and less than 5
percent (by volume) skeletans on faces of peds in the layer that
has the 20 percent lower clay content or, below that layer, no
clay increase of 3 percent or more (absolute) in the fine-earth
fraction.
Umbraquults are among the wettest of the Aquults, and
their argillic horizon is not so strongly developed as that in
most of the other Aquults. The natural vegetation consisted
mostly of water-tolerant trees and herbs.
Definition
Umbraquults are the Aquults that:
1. Have an umbric or mollic epipedon;
2. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface;
3. Do not have plinthite that forms a continuous phase or
constitutes more than half of the matrix of any subhorizon
within 150 cm of the mineral soil surface;
4. Have a clay distribution in which the percentage of clay
decreases from its maximum by 20 percent or more within a
depth of 150 cm below the mineral soil surface, and the layer
in which the percentage of clay is less than the maximum has
less than 5 percent of the volume consisting of clay depletions
on faces of peds or there is an increase in clay content of less
than 3 percent (absolute) below this layer;
5. Do not have an abrupt textural change at the upper
boundary of the argillic horizon if the hydraulic conductivity of
that horizon is 0.4 cm/hr or slower; and
6. Do not have a kandic horizon.
KeytoSubgroups
HAGA. Umbraquults that have 5 to 50 percent (by volume)
plinthite in one or more horizons within 150 cm of the mineral
soil surface.
Plinthic Umbraquults
HAGB. Other Umbraquults.
Typic Umbraquults
Definition of Typic Umbraquults
Typic Umbraquults are the Umbraquults that have less than
5 percent (by volume) plinthite in all subhorizons within 150
cm of the mineral soil surface.
Description of Subgroups
Typic Umbraquults.—These soils are the Umbraquults that
do not have plinthite that constitutes 5 percent or more of the
matrix of any subhorizon within 150 cm of the soil surface.
They are moderately extensive on the low coastal plains along
the Atlantic Ocean. Some of the soils have been drained and
cleared and are used as cropland or pasture, but many are used
as forest.
Plinthic Umbraquults.—These soils have plinthite that
constitutes 5 percent or more of the matrix of a horizon within
150 cm of the soil surface. This subgroup is not known to occur
in the United States. It is provided for use in other parts of the
world.
Humults
Humults are the more or less freely drained, humus-rich
Ultisols of mid or low latitudes. At mid latitudes they are
mostly dark colored, but at low latitudes the content of humus
is not necessarily reflected by the color. These soils are mainly
in mountainous areas that have high rainfall but also have a
moisture deficit during some season. Most of the Humults in
the United States formed in a basic country rock on surfaces
that are late Pleistocene or older. Slopes commonly are strong.
If the soils are cultivated, the argillic or kandic horizon may be
at the surface. To keep the eroded and uneroded soils together
in the classification, the definition of the suborder is written in
terms of the carbon content of the whole soil or of the argillic
or kandic horizon. The natural vegetation consisted mostly of
coniferous forest plants at mid latitudes and rain forest plants
at low latitudes.
Definition
Humults are the Ultisols that do not have both aquic
conditions and the colors defined for Aquults and that meet
either or both of the following:
Ultisols 739
1. Have 0.9 percent or more organic carbon in the upper 15 cm
of the argillic or kandic horizon; or
2. Have 12 kg or more organic carbon in a unit volume
of 1 m2
to a depth of 100 cm, exclusive of any O horizon.
Key to Great Groups
HBA. Humults that have a sombric horizon within 100 cm of
the mineral soil surface.
Sombrihumults, p. 747
HBB. Other Humults that have one or more horizons within
150 cm of the mineral soil surface in which plinthite either
forms a continuous phase or constitutes one-half or more of the
volume.
Plinthohumults, p. 747
HBC. Other Humults that:
1. Do not have a densic, lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface; and
2. Have a kandic horizon; and
3. Within 150 cm of the mineral soil surface, either:
a. With increasing depth, do not have a clay decrease of
20 percent or more (relative) from the maximum clay
content; or
b. Have 5 percent or more (by volume) clay depletions
on faces of peds in the layer that has a 20 percent lower
clay content and, below that layer, a clay increase of 3
percent or more (absolute) in the fine-earth fraction.
Kandihumults, p. 741
HBD. Other Humults that have a kandic horizon.
Kanhaplohumults, p. 743
HBE. Other Humults that:
1. Do not have a densic, lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface; and
2. Within 150 cm of the mineral soil surface, either:
a. With increasing depth, do not have a clay decrease of
20 percent or more (relative) from the maximum clay
content; or
b. Have 5 percent or more (by volume) clay depletions
on faces of peds in the layer that has a 20 percent lower
clay content and, below that layer, a clay increase of 3
percent or more (absolute) in the fine-earth fraction.
Palehumults, p. 745
HBF. Other Humults.
Haplohumults, p. 739
Haplohumults
These are the Humults that have an argillic horizon and
have one of the following: (1) a densic, lithic, paralithic, or
petroferric contact within 150 cm of the mineral soil surface or
(2) with increasing depth, a clay decrease of 20 percent or
more (relative) from the maximum clay content and less than 5
percent (by volume) clay depletions on faces of peds in any
layer that has a 20 percent lower clay content or, below that
layer, the fine-earth fraction has a clay increase of less than 3
percent. Many of these soils have a thin argillic horizon. The
Haplohumults in the United States are mainly in mountains
close to the Pacific Ocean and have gentle to very steep slopes.
Most of the soils had and still have a coniferous forest
vegetation. Their content of organic carbon, in kilograms per
hectare, commonly is high relative to that of most other kinds
of soil. Some of the soils have an umbric epipedon, but many
have a color value and chroma higher than the value and
chroma of mollic or umbric epipedons.
Definition
Haplohumults are the Humults that:
1. Do not have a fragipan or kandic horizon;
2. Have a clay distribution in which, with increasing depth,
the percentage of clay decreases from its maximum amount
by more than 20 percent within 150 cm of the mineral soil
surface, and the layer in which the percentage of clay is less
than the maximum has less than 5 percent of the volume
consisting of skeletans on faces of peds or there is an increase
in clay content of less than 3 percent (absolute) below this
layer;
3. Do not have a sombric horizon within 100 cm of the mineral
soil surface; and
4. Do not have plinthite that forms a continuous phase or
constitutes more than half the volume of some subhorizon
within 150 cm of the mineral soil surface.
Key to Subgroups
HBFA. Haplohumults that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Haplohumults
HBFB. Other Haplohumults that have both:
1. In one or more subhorizons within the upper 25 cm of
the argillic horizon, redox depletions with a color value,
moist, of 4 or more and chroma of 2 or less, accompanied by
redox concentrations, and also aquic conditions for some
time in normal years (or artificial drainage); and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface, a
fine-earth fraction with both a bulk density of 1.0 g/cm3
or
740 Soil Taxonomy
less, measured at 33 kPa water retention, and Al plus 1
/2 Fe
percentages (by ammonium oxalate) totaling more than 1.0.
AquandicHaplohumults
HBFC. Other Haplohumults that have, in one or more
subhorizons within the upper 25 cm of the argillic horizon,
redox depletions with a color value, moist, of 4 or more and
chroma of 2 or less, accompanied by redox concentrations and
by aquic conditions for some time in normal years (or artificial
drainage).
Aquic Haplohumults
HBFD. Other Haplohumults that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm3
or less, measured at 33 kPa
water retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Haplohumults
HBFE. Other Haplohumults that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Haplohumults
HBFF. Other Haplohumults that in normal years are
saturated with water in one or more layers within 100 cm of
the mineral soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Haplohumults
HBFG. Other Haplohumults that have an ustic moisture
regime.
Ustic Haplohumults
HBFH. Other Haplohumults that have a xeric moisture
regime.
Xeric Haplohumults
HBFI. Other Haplohumults.
Typic Haplohumults
Definition of Typic Haplohumults
Typic Haplohumults are the Haplohumults that:
1. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, a bulk density, in the
fraction less than 2.0 mm in size, of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and acid-oxalateextractable
aluminum plus 1
/2 acid-oxalate-extractable iron of
more than 1.0 percent;
2. Have a udic moisture regime;
3. In normal years are not saturated with water in one or more
layers within 100 cm of the mineral soil surface for either or
both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
4. Do not have a lithic contact within 50 cm of the mineral soil
surface; and
5. Have less than 5 percent (by volume) plinthite in all
subhorizons within 150 cm of the mineral soil surface.
Description of Subgroups
Typic Haplohumults.—The central concept or Typic
subgroup of Haplohumults is fixed on relatively freely drained
soils that have a udic moisture regime.
Both the precipitation and the humidity are high. Redox
depletions with low chroma and a fluctuating level of ground
water are properties shared with Aquults and define the Aquic
subgroup. An appreciable amount of plinthite is considered
abnormal and is used to define the Plinthic subgroup. Ustic and
xeric moisture regimes are considered abnormal but are highly
significant to soil-plant relationships and define the Ustic and
Xeric subgroups, respectively. A shallow lithic contact is the
basis for definition of the Lithic subgroup. Soils that have a
thin mantle or layer in the upper 75 cm that has both a low
bulk density and a high content of weakly crystalline minerals
are excluded because they are considered to be intergrades to
Andisols.
Typic Haplohumults are gently sloping to very steep. They
are moderately extensive in the Western United States. They
are mostly in western Oregon, Puerto Rico, California, and
Hawaii. Most of the soils are used as forest. Where slopes are
suitable, some of the soils have been cleared and are used as
cropland or pasture.
Andic Haplohumults.—These soils have a surface mantle
that has a low bulk density and a high content of weakly
crystalline minerals in at least some part of the upper 75 cm.
The soils are rare in the United States and occur only in the
western part of the State of Washington. The natural vegetation
consisted of coniferous forest plants. Slopes range from gentle
to very steep. These soils are used as forest.
Aquandic Haplohumults.—These soils have a surface
mantle that has a low bulk density and a high content of
weakly crystalline minerals in at least some part of the upper
75 cm. They have redox depletions with low chroma, and the
level of ground water fluctuates in the horizons with
redoximorphic depletions or the soils are artificially drained.
These soils occur in the Pacific Northwest.
Aquic Haplohumults.—These soils have redox depletions
with low chroma, and the level of ground water fluctuates in
the horizons with redoximorphic depletions or the soils are
artificially drained. These soils developed in sediments derived
largely from basic rocks. They are of small extent, mostly in
Ultisols 741
Oregon, in the United States. The natural vegetation consisted
of coniferous forest plants. Slopes generally are nearly level or
gently sloping. Many of the soils have been cleared and are
used as hayland, pasture, or cropland.
Lithic Haplohumults.—These soils have a shallow lithic
contact and an argillic horizon that commonly is thin. They are
not known to occur in the United States. The subgroup is
provided for use in other parts of the world.
Oxyaquic Haplohumults.—These soils are saturated with
water for 20 consecutive days and/or 30 cumulative days within
100 cm of the mineral soil surface during normal years. They
may or may not have redoximorphic features. If they occur, the
redoximorphic features are either weakly expressed or lower in
the profile than is defined for the Aquic subgroup. Oxyaquic
Haplohumults occur in Oregon and are used for timber
production or pasture.
Plinthic Haplohumults.—These soils have a subhorizon
with 5 to 50 percent (by volume) plinthite within 150 cm of the
mineral soil surface. They are rare in the United States and are
known to occur only on marine terraces along the northern
California coast. The natural vegetation consisted of coniferous
forest plants. Slopes generally are nearly level to moderately
steep. Most of these soils are used as forest, but some are used
as sites for homes.
Ustic Haplohumults.—These soils have an ustic soil
moisture regime. They occur in Hawaii and along the coast of
California, where the soil temperature regime is isomesic,
isothermic, or isohyperthermic. The natural vegetation
consisted of forest plants. Slopes generally are nearly level to
moderately steep. Most of these soils are used as pasture, but
some are used as cropland or homesites.
Xeric Haplohumults.—These soils have a xeric moisture
regime but are otherwise like Typic Haplohumults in defined
properties. Most Xeric Haplohumults have an ochric epipedon
despite the high content of organic carbon. The color of the
epipedon is dark, but the chroma is too high for an umbric
epipedon. Xeric Haplohumults are moderately extensive and
occur mostly in California and Oregon. In the United States,
slopes are nearly level to very steep. Most of these soils are
used as forest, but some are used as cropland, pasture, or
homesites.
Kandihumults
Kandihumults are the Humults that have a kandic horizon and
a clay distribution in which the percentage of clay does not
decrease from its maximum amount by as much as 20 percent
within a depth of 150 cm from the mineral soil surface, or the
layer in which the clay percentage decreases has at least 5
percent of the volume consisting of skeletans on faces of peds
and there is at least a 3 percent (absolute) increase in clay
content below this layer. These soils do not have a sombric
horizon. They have no horizon in which plinthite either forms
a continuous phase or constitutes one-half or more of the
volume within 150 cm of the mineral soil surface. Kandihumults
are of small extent in California and Hawaii.
Definition
Kandihumults are the Humults that:
1. Have a kandic horizon;
2. Do not have a densic, lithic, paralithic, or petroferric contact
within 150 cm of the mineral soil surface;
3. Have a clay distribution in which the percentage of clay
does not decrease from its maximum amount by as much as 20
percent within a depth of 150 cm from the mineral soil surface,
or the layer in which the clay percentage decreases by more
than 20 percent has at least 5 percent of the volume consisting
of clay depletions on faces of peds and there is at least a 3
percent (absolute) increase in clay content below this layer;
4. Do not have a sombric horizon within 150 cm of the
mineral soil surface; and
5. Do not have plinthite that forms a continuous phase or that
constitutes more than 50 percent of the volume of some
subhorizon within 150 cm of the mineral soil surface.
Key to Subgroups
HBCA. Kandihumults that meet all of the following:
1. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface,
have a fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; and
2. In one or more horizons within 75 cm of the mineral
soil surface, have redox concentrations, a color value, moist,
of 4 or more, and hue that is 10YR or yellower and becomes
redder with increasing depth within 100 cm of the mineral
soil surface; and
3. In normal years are saturated with water in one or more
layers within 100 cm of the mineral soil surface for either or
both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days.
Andic Ombroaquic Kandihumults
HBCB. Other Kandihumults that have both:
1. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface, a
fine-earth fraction with both a bulk density of 1.0 g/cm3
or
less, measured at 33 kPa water retention, and Al plus 1
/2 Fe
percentages (by ammonium oxalate) totaling more than 1.0;
and
742 Soil Taxonomy
2. An ustic moisture regime.
Ustandic Kandihumults
HBCC. Other Kandihumults that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm3
or less, measured at 33 kPa
water retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Kandihumults
HBCD. Other Kandihumults that have, in one or more
subhorizons within the upper 25 cm of the kandic horizon,
redox depletions with a color value, moist, of 4 or more and
chroma of 2 or less, accompanied by redox concentrations and
by aquic conditions for some time in normal years (or artificial
drainage).
Aquic Kandihumults
HBCE. Other Kandihumults that:
1. Have, in one or more horizons within 75 cm of the
mineral soil surface, redox concentrations, a color value,
moist, of 4 or more, and hue that is 10YR or yellower and
becomes redder with increasing depth within 100 cm of the
mineral soil surface; and
2. In normal years are saturated with water in one or more
layers within 100 cm of the mineral soil surface for either or
both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days.
Ombroaquic Kandihumults
HBCF. Other Kandihumults that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Kandihumults
HBCG. Other Kandihumults that have an ustic moisture
regime.
Ustic Kandihumults
HBCH. Other Kandihumults that have a xeric moisture
regime.
Xeric Kandihumults
HBCI. Other Kandihumults that have an anthropic epipedon.
Anthropic Kandihumults
HBCJ. Other Kandihumults.
Typic Kandihumults
DefinitionofTypicKandihumults
Typic Kandihumults are the Kandihumults that:
1. Do not have, in any subhorizon within the upper 25 cm of
the kandic horizon, redox depletions with a color value, moist,
of 4 or more and chroma of 2 or less, accompanied by redox
concentrations and by aquic conditions;
2. Have a udic moisture regime;
3. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, a bulk density, in the
fraction less than 2.0 mm in size, of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and acid-oxalateextractable
aluminum plus 1
/2 acid-oxalate-extractable iron of
more than 1.0 percent;
4. Have less than 5 percent (by volume) plinthite in all
subhorizons within 150 cm of the mineral soil surface;
5. Do not have, in one or more horizons within 75 cm of the
mineral soil surface, redox concentrations, a color value, moist,
of 4 or more, and hue that is 10YR or yellower and becomes
redder with increasing depth within 100 cm of the mineral soil
surface; and
6. Do not have an anthropic epipedon.
Description of Subgroups
Typic Kandihumults.—The central concept or Typic
subgroup of Kandihumults is fixed on freely drained soils that
do not have an anthropic epipedon and have a udic moisture
regime. These soils also have less than 5 percent plinthite in all
horizons to a depth of 150 cm or more below the mineral soil
surface. Soils that have redox depletions with low chroma near
the surface in one or more horizons that also have aquic
conditions for some time in normal years (or artificial
drainage) are excluded from Typic Kandihumults because these
properties are shared with Aquults.
Soils that have a mantle or layer in the upper 75 cm that has
both a low bulk density and a high content of weakly
crystalline minerals are excluded from the Typic subgroup
because they are considered to be intergrades to Andisols. A
soil moisture regime that is ustic or xeric is considered
abnormal and defines the Ustic and Xeric subgroups,
respectively.
Typic Kandihumults are of small extent in the United States
and are known to occur only in California. The natural
vegetation consisted of coniferous forest plants. Slopes range
from gentle to steep. These soils are used mostly as forest.
Where slopes are suitable, some of the soils have been cleared
and are used as cropland or pasture.
Andic Kandihumults.—These soils have a mantle or layer
in the upper 75 cm that has both a low bulk density and a high
Ultisols 743
content of weakly crystalline minerals. They are not known to
occur in the United States. They are defined for use in other
parts of the world.
Andic Ombroaquic Kandihumults.—These soils have, in
one or more horizons within 75 cm of the mineral soil surface,
redox concentrations, a color value, moist, of 4 or more, and
hue that is 10YR or yellower and becomes redder with
increasing depth within 100 cm of the mineral soil surface.
They also have a mantle or layer in the upper 75 cm that has
both a low bulk density and a high content of weakly
crystalline minerals. These soils are not known to occur in the
United States. They are defined for use in other parts of the
world.
Anthropic Kandihumults.—These soils are similar to
Typic Kandihumults, but they have been used as cropland for
long periods and have an anthropic epipedon. They are not
known to occur in the United States. They are defined for use
in other parts of the world.
Aquic Kandihumults.—These soils are like Typic
Kandihumults, but they have redox depletions with low
chroma within 75 cm of the mineral soil surface. The redox
depletions are caused by periods of wetness. The soils are in
nearly level to sloping areas. They are not known to occur in
the United States. They are defined for use in other parts of
the world.
Ombroaquic Kandihumults.—These soils have, in one or
more horizons within 75 cm of the mineral soil surface, redox
concentrations, a color value, moist, of 4 or more, and hue that
is 10YR or yellower and becomes redder with increasing depth
within 100 cm of the mineral soil surface. The soils are not
known to occur in the United States. They are defined for use
in other parts of the world.
Plinthic Kandihumults.—These soils are similar to Typic
Kandihumults, but they have 5 to 50 percent (by volume)
plinthite in one or more horizons within 150 cm of the
mineral soil surface. The soils are not known to occur in the
United States. They are defined for use in other parts of the
world.
Ustandic Kandihumults.—These soils have an ustic
moisture regime and a mantle or layer in the upper 75 cm
that has both a low bulk density and a high content of weakly
crystalline minerals. They are not known to occur in the
United States. They are defined for use in other parts of the
world.
Ustic Kandihumults.—These soils are like Typic
Kandihumults, but they have an ustic moisture regime. They
are intergrades between Kandihumults and Kandiustults. Ustic
Kandihumults are not known to occur in the United States.
They are defined for use in other parts of the world.
Xeric Kandihumults.—These soils are like Typic
Kandihumults, but they have a xeric moisture regime. They are
intergrades between Kandihumults and Xerults. Xeric
Kandihumults are not known to occur in the United States.
They are defined for use in other parts of the world.
Kanhaplohumults
Kanhaplohumults are the Humults that have a kandic horizon
and have a clay distribution in which the percentage of clay
decreases from its maximum amount by as much as 20 percent
within a depth of 150 cm from the mineral soil surface, and the
layer in which the clay percentage decreases has less than 5
percent of the volume consisting of skeletans on faces of peds
or there is an increase in clay content of less than 3 percent
(absolute) below this layer. These soils do not have a sombric
horizon within 100 cm of the mineral soil surface. They have no
horizon in which plinthite either forms a continuous phase or
constitutes one-half or more of the volume within 150 cm of the
mineral soil surface. Kanhaplohumults are of very small extent
and are known to occur only in California and Hawaii in the
United States.
Definition
Kanhaplohumults are the Humults that:
1. Have a kandic horizon;
2. Have a clay distribution in which the percentage of clay
decreases from its maximum amount by 20 percent or more
within a depth of 150 cm from the mineral soil surface, and the
layer in which the percentage of clay is less than the maximum
has less than 5 percent of the volume consisting of skeletans on
faces of peds or there is an increase in clay content of less than
3 percent (absolute) below this layer;
3. Do not have a sombric horizon within 150 cm of the
mineral soil surface; and
4. Do not have plinthite that forms a continuous phase or that
constitutes more than 50 percent of the volume of some
subhorizon within 150 cm of the mineral soil surface.
Key to Subgroups
HBDA. Kanhaplohumults that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Kanhaplohumults
HBDB. Other Kanhaplohumults that have both:
1. An ustic moisture regime; and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface, a
fine-earth fraction with both a bulk density of 1.0 g/cm3
or
less, measured at 33 kPa water retention, and Al plus 1
/2 Fe
percentages (by ammonium oxalate) totaling more than 1.0.
Ustandic Kanhaplohumults
HBDC. Other Kanhaplohumults that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm3
or less, measured at 33 kPa
744 Soil Taxonomy
water retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Kanhaplohumults
HBDD. Other Kanhaplohumults that have, in one or more
subhorizons within the upper 25 cm of the kandic horizon,
redox depletions with a color value, moist, of 4 or more and
chroma of 2 or less, accompanied by redox concentrations and
by aquic conditions for some time in normal years (or artificial
drainage).
Aquic Kanhaplohumults
HBDE. Other Kanhaplohumults that:
1. Have, in one or more horizons within 75 cm of the
mineral soil surface, redox concentrations, a color value,
moist, of 4 or more, and hue that is 10YR or yellower and
becomes redder with increasing depth within 100 cm of the
mineral soil surface; and
2. In normal years are saturated with water in one or more
layers within 100 cm of the mineral soil surface for either or
both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days.
Ombroaquic Kanhaplohumults
HBDF. Other Kanhaplohumults that have an ustic moisture
regime.
Ustic Kanhaplohumults
HBDG. Other Kanhaplohumults that have a xeric moisture
regime.
Xeric Kanhaplohumults
HBDH. Other Kanhaplohumults that have an anthropic
epipedon.
Anthropic Kanhaplohumults
HBDI. Other Kanhaplohumults.
Typic Kanhaplohumults
Definition of Typic Kanhaplohumults
Typic Kanhaplohumults are the Kanhaplohumults that:
1. Do not have, in any subhorizon within the upper 25 cm of
the argillic or kandic horizon, redox depletions with a color
value, moist, of 4 or more and chroma of 2 or less,
accompanied by redox concentrations and by aquic conditions;
2. Do not have a lithic contact within 50 cm of the mineral
soil surface;
3. Have a udic moisture regime;
4. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, a bulk density, in the
fraction less than 2.0 mm in size, of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and acid-oxalateextractable
aluminum plus 1
/2 acid-oxalate-extractable iron of
more than 1.0 percent;
5. Have, within 75 cm of the mineral soil surface, hue
of 7.5YR or redder in all horizons with a color value, moist,
of 4 or more if there are redox concentrations or if the hue
becomes redder with increasing depth within 100 cm of the
mineral soil surface; and
6. Do not have an anthropic epipedon.
Description of Subgroups
Typic Kanhaplohumults.—The central concept or Typic
subgroup of Kanhaplohumults is fixed on moderately deep or
deeper, freely drained soils that do not have an anthropic
epipedon and that have a udic moisture regime. Soils that have
redox depletions with low chroma near the surface in one or
more horizons that also have aquic conditions for some time in
normal years (or artificial drainage) are excluded from the
Typic subgroup because these properties are shared with
Aquults.
Soils that have a mantle or layer in the upper 75 cm that has
both a low bulk density and a high content of weakly
crystalline minerals are excluded from the Typic subgroup
because they are considered to be intergrades to Andisols. A
soil moisture regime that is ustic or xeric is considered
abnormal and defines the Ustic and Xeric subgroups,
respectively.
Typic Kanhaplohumults are of very small extent in the
United States and are known to occur only in California and
Hawaii. The natural vegetation consisted of forest plants.
Slopes range from nearly level to sloping. These soils are used
mostly as forest, cropland, or pasture.
Andic Kanhaplohumults.—These soils have a mantle or
layer in the upper 75 cm that has both a low bulk density and a
high content of weakly crystalline minerals. They are not
known to occur in the United States. They are defined for use
in other parts of the world.
Anthropic Kanhaplohumults.—These soils are similar to
Typic Kanhaplohumults, but they have been used as cropland
for long periods and have an anthropic epipedon. They are not
known to occur in the United States. They are defined for use
in other parts of the world.
Aquic Kanhaplohumults.—These soils are similar to Typic
Kanhaplohumults, but they have redox depletions with low
chroma within 75 cm of the mineral soil surface. The redox
depletions are caused by periods of wetness. The soils are in
nearly level to sloping areas. They are not known to occur in
the United States. They are defined for use in other parts of the
world.
Lithic Kanhaplohumults.—These soils have a lithic
contact within 50 cm of the mineral soil surface. They are not
Ultisols 745
known to occur in the United States. They are defined for use in
other parts of the world.
Ombroaquic Kanhaplohumults.—These soils have, in one
or more horizons within 75 cm of the mineral soil surface,
redox concentrations, a color value, moist, of 4 or more, and
hue that is 10YR or yellower and becomes redder with
increasing depth within 100 cm of the mineral soil surface.
They are not known to occur in the United States. They are
defined for use in other parts of the world.
Ustandic Kanhaplohumults.—These soils have an ustic
moisture regime and a mantle or layer in the upper 75 cm that
has both a low bulk density and a high content of weakly
crystalline minerals. They are not known to occur in the United
States. They are defined for use in other parts of the world.
Ustic Kanhaplohumults.—These soils are like Typic
Kanhaplohumults, but they have an ustic moisture regime.
They are intergrades between Kanhaplohumults and
Kanhaplustults. They are not known to occur in the United
States. The subgroup is defined for use in other parts of the
world.
Xeric Kanhaplohumults.—These soils are like Typic
Kanhaplohumults, but they have a xeric moisture regime. They
are intergrades between Kanhaplohumults and Xerults. Xeric
Kanhaplohumults are not known to occur in the United States.
The subgroup is defined for use in other parts of the world.
Palehumults
These are the Humults that are on old stable surfaces and
that have a clay distribution in which the percentage of clay
does not decrease from its maximum amount by as much as 20
percent within a depth of 150 cm from the mineral soil surface,
or the layer in which the clay percentage decreases has at least
5 percent of the volume consisting of clay depletions on faces
of peds and there is at least a 3 percent increase in clay content
below this layer. These soils have an argillic horizon. They do
not have plinthite that forms a continuous phase or that
constitutes more than half the volume of any subhorizon within
125 cm of the mineral soil surface. These soils are moderately
extensive. They are mostly in California, western Oregon and
Washington, and Hawaii. Like other Humults in the United
States, they formed mostly in material weathered from basic
rocks or in alluvium derived from basic rocks. Most
Palehumults have had a forest vegetation, and many still have
a forest vegetation.
Definition
Palehumults are the Humults that:
1. Do not have a kandic horizon;
2. Have a clay distribution in which the percentage of clay
does not decrease from its maximum amount by 20 percent or
more within a depth of 150 cm from the mineral soil surface,
or the layer in which the clay percentage decreases by more
than 20 percent has at least 5 percent of the volume consisting
of clay depletions on faces of peds and there is at least a 3
percent (absolute) increase in clay content below this layer;
3. Do not have a sombric horizon within 100 cm of the
mineral soil surface; and
4. Do not have plinthite that forms a continuous phase or that
constitutes more than half the volume of any subhorizon within
125 cm of the mineral soil surface.
Key to Subgroups
HBEA. Palehumults that have both:
1. In one or more subhorizons within the upper 25 cm of
the argillic horizon, redox depletions with a color value,
moist, of 4 or more and chroma of 2 or less, accompanied by
redox concentrations, and also aquic conditions for some
time in normal years (or artificial drainage); and
2. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral
soil surface, a fine-earth fraction with both a bulk density
of 1.0 g/cm3
or less, measured at 33 kPa water retention,
and Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling more than 1.0.
Aquandic Palehumults
HBEB. Other Palehumults that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Palehumults
HBEC. Other Palehumults that have, in one or more
subhorizons within the upper 25 cm of the argillic horizon,
redox depletions with a color value, moist, of 4 or more and
chroma of 2 or less, accompanied by redox concentrations and
by aquic conditions for some time in normal years (or artificial
drainage).
Aquic Palehumults
HBED. Other Palehumults that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Palehumults
HBEE. Other Palehumults that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Palehumults
746 Soil Taxonomy
HBEF. Other Palehumults that have an ustic moisture
regime.
Ustic Palehumults
HBEG. Other Palehumults that have a xeric moisture regime.
Xeric Palehumults
HBEH. Other Palehumults.
Typic Palehumults
Definition of Typic Palehumults
Typic Palehumults are the Palehumults that:
1. In normal years are not saturated with water in one or
more layers within 100 cm of the mineral soil surface for either
or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
2. Have a udic moisture regime;
3. Have less than 5 percent (by volume) plinthite in all
subhorizons within 150 cm of the mineral soil surface; and
4. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, a bulk density, in the
fraction less than 2.0 mm in size, of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and acid-oxalateextractable
aluminum plus 1
/2 acid-oxalate-extractable iron of
more than 1.0 percent.
Description of Subgroups
Typic Palehumults.—The central concept or Typic
subgroup of Palehumults is fixed on freely drained soils that
have a udic moisture regime. These soils typically have an
ochric epipedon and albic and argillic horizons. Redox
depletions with low chroma and a fluctuating level of ground
water are properties shared with Aquults and define the Aquic
subgroup. An appreciable amount of plinthite is considered
abnormal and is used to define the Plinthic subgroup. Ustic and
xeric moisture regimes are considered abnormal but are highly
significant to soil-plant relationships and define Ustic and
Xeric subgroups, respectively. Soils that have a mantle or layer
in the upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals are excluded from the
Typic subgroup because they are considered to be intergrades to
Andisols.
Typic Palehumults are moderately extensive in the United
States. They are mostly in western Oregon and Washington, in
Hawaii, and in Puerto Rico. The natural vegetation consisted
mostly of coniferous forest plants in Oregon and Washington
and tropical broadleaf forest plants in Hawaii and Puerto Rico.
Slopes range from nearly level to very steep. These soils are
used mostly as forest. Where slopes are suitable, some of the
soils have been cleared and are used as pasture, cropland, or
homesites.
Andic Palehumults.—These soils have a surface mantle or
layer in the upper 75 cm that has both a low bulk density and a
high content of weakly crystalline minerals in at least some
part of the upper 75 cm. The soils are of very small extent in
California. The natural vegetation consisted mostly of grasses
and shrubs. Slopes range from nearly level to moderately
sloping. These soils are used mostly as pasture or cropland.
Aquandic Palehumults.—These soils have a surface mantle
or layer in the upper 75 cm that has both a low bulk density
and a high content of weakly crystalline minerals in at least
some part of the upper 75 cm. They have redox depletions with
low chroma, and the level of ground water fluctuates in the
iron-depleted horizons or the soils are artificially drained.
These soils occur in the Pacific Northwest.
Aquic Palehumults.—These soils have redox depletions
with low chroma, and the level of ground water fluctuates in
the redox-depleted horizons or the soils are artificially drained.
In the United States, these soils are of very small extent and
occur in western Oregon. The natural vegetation consisted
mostly of coniferous forest plants. Slopes range from nearly
level to steep. These soils are used mostly as forest. Some of
the less sloping soils have been cleared and are used as pasture.
Oxyaquic Palehumults.—These soils are saturated with
water for 20 or more consecutive days and/or 30 or more
cumulative days during normal years. They may or may not
have redoximorphic features. If present, the redoximorphic
features are either weakly expressed or lower in the profile than
is required for the Aquic subgroup. Oxyaquic Palehumults
occur in the Pacific Northwest and are used as pasture or
woodland.
Plinthic Palehumults.—These soils have 5 to 50 percent
(by volume) plinthite in some horizon within 150 cm of the
mineral soil surface but otherwise are similar to the soils in the
Typic subgroup. Plinthic Palehumults are of very small extent.
They are known to occur in Puerto Rico. The natural
vegetation consisted of tropical trees and shrubs. These soils
are used mostly as pasture or cropland.
Ustic Palehumults.—These soils have an ustic moisture
regime. They are of very small extent in the United States.
They are known to occur in Hawaii. They are used mostly as
pasture or cropland.
Xeric Palehumults.—These soils have a xeric moisture
regime but are otherwise like Typic Palehumults in defined
properties. They are moderately extensive in the United States.
They occur in the Sierra Nevada and Coast Ranges of
California and the Coast Range and western Cascade
Mountains of Oregon and Washington. They also occur in the
Willamette Valley and Puget lowlands of Oregon and
Washington, respectively. The natural vegetation consisted
mostly of coniferous forest plants. Slopes range from nearly
level to very steep. These soils are used mostly as forest. Where
Ultisols 747
slopes are suitable, some of the soils have been cleared and are
used as pasture, cropland, or homesites.
Plinthohumults
Plinthohumults are the Humults that do not have a sombric
horizon within 100 cm of the mineral soil surface and have
plinthite that forms a continuous phase in, or constitutes more
than half the volume of, one or more horizons within 150 cm
of the mineral soil surface. These soils are not known to occur
in the United States. The great group has been provided for use
in other countries.
Key to Subgroups
HBBA. All Plinthohumults.
TypicPlinthohumults
Sombrihumults
These Humults have a sombric horizon that has its upper
boundary within 100 cm of the mineral soil surface. They are
not known to occur in the United States. The great group is
provided for use elsewhere.
Key to Subgroups
HBAA. All Sombrihumults.
TypicSombrihumults
Udults
These are the more or less freely drained, humus-poor
Ultisols that have a udic moisture regime. They are in humid
climates, and most receive well distributed rainfall. Most have
light colored upper horizons, commonly a grayish horizon that
rests on a yellowish brown to reddish argillic or kandic
horizon. A few that developed from basic rocks have a dark
brown or reddish brown surface horizon that rests on a dark
red or dusky red argillic or kandic horizon. Some have a
fragipan or plinthite, or both, in or below the argillic or kandic
horizon.
Udults developed in sediments and on surfaces that range
from late Pleistocene to Pliocene or possibly older. Many are
cultivated, either with the use of soil amendments or in a
system in which they are cropped for a very few years and then
are returned to forest to allow the trees to regather in their
tissues the small supply of nutrients. Most of these soils have
or had a forest vegetation, but some have a savanna that
probably is anthropic.
Definition
Udults are the Ultisols that:
1. Do not have both aquic conditions and the colors defined
for Aquults;
2. Have less than 0.9 percent, by weighted average, organic
carbon in the upper 15 cm of the argillic or kandic horizon and
have less than 12 kg organic carbon in a unit volume of 1 m2
to
a depth of 100 cm, exclusive of any O horizon; and
3. Have a udic moisture regime.
Key to Great Groups
HCA. Udults that have one or more horizons within 150 cm
of the mineral soil surface in which plinthite either forms a
continuous phase or constitutes one-half or more of the volume.
Plinthudults, p. 766
HCB. Other Udults that have a fragipan with an upper
boundary within 100 cm of the mineral soil surface.
Fragiudults, p. 748
HCC. Other Udults that:
1. Do not have a densic, lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface; and
2. Have a kandic horizon; and
3. Within 150 cm of the mineral soil surface, either:
a. With increasing depth, do not have a clay decrease of
20 percent or more (relative) from the maximum clay
content; or
b. Have 5 percent or more (by volume) clay depletions
on faces of peds in the layer that has a 20 percent lower
clay content and, below that layer, a clay increase of 3
percent or more (absolute) in the fine-earth fraction.
Kandiudults, p. 754
HCD. Other Udults that have a kandic horizon.
Kanhapludults, p. 758
HCE. Other Udults that:
1. Do not have a densic, lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface; and
2. Within 150 cm of the mineral soil surface, either:
a. With increasing depth, do not have a clay decrease of
20 percent or more (relative) from the maximum clay
content; or
b. Have 5 percent or more (by volume) clay depletions
on faces of peds in the layer that has a 20 percent lower
clay content and, below that layer, a clay increase of 3
percent or more (absolute) in the fine-earth fraction.
Paleudults, p. 761
748 Soil Taxonomy
HCF. Other Udults that have both:
1. An epipedon that has a color value, moist, of 3 or less
throughout; and
2. In all subhorizons in the upper 100 cm of the argillic
horizon or throughout the entire argillic horizon if it is less
than 100 cm thick, more than 50 percent colors that have all
of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less; and
c. A dry value no more than 1 unit higher than the
moist value.
Rhodudults, p. 766
HCG. Other Udults.
Hapludults, p. 750
Fragiudults
These are the Udults that have a fragipan with an upper
boundary within 100 cm of the mineral soil surface. They have
no horizon within 150 cm of the mineral soil surface in which
plinthite either forms a continuous phase or constitutes onehalf
or more of the volume. These soils formed mainly in
loamy alluvium or in residuum. The fragipan commonly has an
upper boundary about 50 to 75 cm below the mineral soil
surface. Perched ground water is above the pan at some period
during the year, and many of the soils have thick, gray clay
depletions near the top of the fragipan and in vertical seams
between structural units.
The Fragiudults in the United States are principally on
gentle slopes throughout the Southeastern States. The
temperature regime is mesic or thermic. The vegetation on the
Fragiudults in the United States has been a forest either of
conifers or of broadleaf deciduous trees.
Definition
Fragiudults are the Udults that:
1. Have a fragipan with an upper boundary within 100 cm of
the mineral soil surface; and
2. Do not have one or more horizons within 150 cm of the
mineral soil surface in which plinthite either forms a
continuous phase or constitutes one-half or more of the volume.
Key to Subgroups
HCBA. Fragiudults that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic or kandic horizon
at a depth of 50 to 100 cm.
Arenic Fragiudults
HCBB. Other Fragiudults that have both of the following:
1. In one or more horizons within 40 cm of the mineral soil
surface, redox depletions with chroma of 2 or less and also
aquic conditions for some time in normal years (or artificial
drainage); and
2. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Plinthaquic Fragiudults
HCBC. Other Fragiudults that meet both of the following:
1. Meet one or more of the following:
a. Have a glossic horizon above the fragipan; or
b. Do not have, above the fragipan, an argillic or
kandic horizon that has clay films on both vertical and
horizontal surfaces of any structural aggregates; or
c. Between the argillic or kandic horizon and the
fragipan, have one or more horizons with 50 percent or
more chroma of 3 or less and with a clay content 3
percent or more (absolute, in the fine-earth fraction)
lower than that in both the argillic or kandic horizon and
the fragipan; and
2. In one or more horizons within 40 cm of the mineral
soil surface, have redox depletions with chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage).
Glossaquic Fragiudults
HCBD. Other Fragiudults that have, in one or more
subhorizons above the fragipan and within the upper 25 cm of
the argillic or kandic horizon, redox depletions with chroma of
2 or less and also aquic conditions for some time in normal
years (or artificial drainage).
Aquic Fragiudults
HCBE. Other Fragiudults that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Fragiudults
HCBF. Other Fragiudults that meet one or more of the
following:
1. Have a glossic horizon above the fragipan; or
2. Do not have, above the fragipan, an argillic or kandic
horizon that has clay films on both vertical and horizontal
surfaces of any structural aggregates; or
3. Between the argillic or kandic horizon and the fragipan,
have one or more horizons with 50 percent or more chroma
of 3 or less and with a clay content 3 percent or more
(absolute, in the fine-earth fraction) lower than that in both
the argillic or kandic horizon and the fragipan.
Glossic Fragiudults
Ultisols 749
HCBG. Other Fragiudults that have a color value, moist, of 3 or
less and a color value, dry, of 5 or less (crushed and smoothed
sample) in either:
1. An Ap horizon that is 18 cm or more thick; or
2. The surface layer after mixing of the upper 18 cm.
Humic Fragiudults
HCBH. Other Fragiudults.
Typic Fragiudults
Definition of Typic Fragiudults
Typic Fragiudults are the Fragiudults that:
1. Above the fragipan, have an argillic or kandic horizon that
has some clay films on both vertical and horizontal surfaces of
some structural aggregates;
2. Do not have a glossic horizon above the fragipan;
3. Between the argillic or kandic horizon and the fragipan,
do not have an intervening horizon (one or more) that has
dominant chroma of 3 or less and that has as much as 3
percent less clay (absolute) than both the overlying argillic or
kandic horizon and the underlying fragipan;
4. Do not have, in any subhorizon above the fragipan and
within the upper 25 cm of the argillic or kandic horizon, redox
depletions with chroma of 2 or less and also aquic conditions;
5. Do not have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of an argillic or kandic horizon at a depth of 50 to 100
cm;
6. Have less than 5 percent (by volume) plinthite in all
horizons within 150 cm of the mineral soil surface; and
7. Have a color value, moist, of 4 or more or a value, dry, of 6
or more, when crushed and smoothed, in any Ap horizon 18
cm or more thick and in any surface layer after mixing of the
upper 18 cm.
Description of Subgroups
Typic Fragiudults.—The central concept or Typic subgroup
of Fragiudults is fixed on soils that have an argillic or kandic
horizon that is underlain by a fragipan without an intervening
eluvial horizon. These soils do not have redox depletions with
low chroma in the upper 25 cm of the argillic horizon or above
the fragipan if the part of the argillic or kandic horizon above
the fragipan is less than 25 cm thick. The soils have less than 5
percent plinthite within 150 cm of the mineral soil surface. The
surface layer has a color value of 4 or more, moist, and 6 or
more, dry, after mixing of the upper 18 cm.
Typic Fragiudults are more extensive than the soils of the
other subgroups. Their characteristics provide the best basis for
defining other subgroups. Since no Fragiudult is freely drained,
redox depletions with low chroma and ground water at some time
of the year must be present at a shallower depth in Aquic
Fragiudults than in many other kinds of Aquic subgroups.
A perched water table at the top of the fragipan tends to
reduce and remove free iron oxides and accelerate the
eluviation of clay and thus to produce a glossic horizon or a
second eluvial horizon, an E´. If the marks of this process are
distinct, the part of the B horizon above the fragipan is a
cambic horizon and the clay films in the fragipan tend to be
thick. This combination of horizons defines the glossic
intergrades. A thick sandy (sand or loamy sand) layer, starting
at the mineral soil surface, is considered abnormal and defines
the Arenic subgroup. Plinthite in Fragiudults suggests
polygenesis and defines the Plinthic subgroup.
Typic Fragiudults are of large extent in the Southeastern
United States. The natural vegetation consisted of forest plants.
Slopes range from nearly level to moderately steep. These soils
are used mostly as forest. Where slopes are suitable, some of
the soils have been cleared and are used as pasture, cropland,
or homesites.
Aquic Fragiudults.—These soils have redox depletions
with low chroma at a shallow depth and have aquic conditions
in the iron-depleted horizon at some time of the year unless the
soils have been artificially drained. The soils are otherwise
similar to Typic Fragiudults in defined properties and also in
most accessory properties. Most Aquic Fragiudults have a
mesic soil temperature regime. Aquic Fragiudults are
moderately extensive in the Eastern United States. They
generally are nearly level to moderately sloping. The natural
vegetation consisted of forest plants. Many of these soils are
used as forest. Some have been cleared and are used as pasture,
cropland, or homesites.
Arenic Fragiudults.—These soils have a sandy layer,
starting at the mineral soil surface, that is between 50 and 100
cm thick. They are not known to occur in the United States.
The subgroup is provided for use in other parts of the world.
Glossaquic Fragiudults.—These soils have redox
depletions with low chroma at a shallow depth and also have
aquic conditions in the iron-depleted horizon at some time of
the year or have been artificially drained. They meet one or
more of the following: (1) have a glossic horizon, (2) do not
have an argillic or kandic horizon above the fragipan, or (3)
have an eluvial horizon at the top of the fragipan. These soils
are of small extent in the Eastern United States. They generally
are nearly level or gently sloping. The natural vegetation
consisted of forest plants. The soils are used mostly as forest.
Some areas have been cleared and are used as cropland or
pasture.
Glossic Fragiudults.—These soils meet one or more of the
following: (1) have a glossic horizon, (2) do not have an
argillic or kandic horizon above the fragipan, or (3) have an
eluvial horizon at the top of the fragipan. The soils are
otherwise like Typic Fragiudults in defined properties and in
other properties. Glossic Fragiudults are moderately extensive
750 Soil Taxonomy
in the areas adjoining the lower Mississippi River Valley. They
generally are nearly level to strongly sloping. The natural
vegetation consisted of forest plants. Many of the soils have
been cleared and are used as cropland, but large areas are used
as forest.
Humic Fragiudults.—These soils have dark colored surface
layers. They are not sandy from the mineral soil surface to a
depth of 50 cm or more and do not have aquic conditions close
to the surface. They do not have plinthite or a glossic horizon.
Most of these soils are forested.
Plinthaquic Fragiudults.—These soils have plinthite in the
fragipan, have redox depletions with low chroma at a shallow
depth, and have either a fluctuating water table in the irondepleted
zone or artificial drainage. These soils are not known
to occur in the United States. The subgroup is provided for use
in other parts of the world.
Plinthic Fragiudults.—These soils have 5 to 50 percent
plinthite in some layer within 150 cm of the mineral soil
surface. They are of small extent in the United States and occur
only on coastal plain in the South. They generally are nearly
level or gently sloping. The natural vegetation consisted of
forest plants. Many of the soils have been cleared and are used
as cropland, but large areas are used as forest.
Hapludults
These are the Udults that do not have a fragipan and that
have less than 50 percent plinthite in all horizons within 150
cm of the mineral soil surface. These soils have one of the
following: (1) a densic, lithic, paralithic, or petroferric contact
within 150 cm of the mineral soil surface or (2) with
increasing depth, a clay decrease of 20 percent or more
(relative) from the maximum clay content and less than 5
percent (by volume) clay depletions on faces of peds in any
layer that has a 20 percent lower clay content or, below that
layer, the fine-earth fraction has a clay increase of less than 3
percent. Many of the soils have a thin argillic horizon. The
color of the argillic horizon is not both dark and reddish
throughout the upper 100 cm. Most of the soils formed in areas
of acid rocks or sediments on surfaces that are at least of
Pleistocene age. Where the soils are not cultivated, the
vegetation consists almost exclusively of forest plants, either
hardwood trees or conifers.
Hapludults are extensive in the Southeastern United States,
in the Middle Atlantic States, and on the coastal plain along
the Gulf of Mexico in the Southern States east of the
Mississippi River. Slopes generally are gently sloping to steep,
but a few of the soils on the lowest part of the coastal plain are
nearly level.
Definition
Hapludults are the Udults that:
1. Do not have a kandic horizon;
2. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface;
3. Do not have plinthite that forms a continuous phase or
constitutes more than half the matrix in any subhorizon within
150 cm of the mineral soil surface;
4. Have a color:
a. With hue of 5YR or yellower; or
b. With a value, moist, of 4 or more in some part of the
epipedon or a value of 5 or more, dry, or of 4 or more,
moist, in some subhorizon of an argillic horizon; and
5. Have a clay distribution in which, with increasing depth,
the percentage of clay decreases from its maximum amount by
more than 20 percent within 150 cm of the mineral soil
surface, and the layer in which the percentage of clay is less
than the maximum has less than 5 percent of the volume
consisting of skeletans on faces of peds or there is an increase
in clay content of less than 3 percent (absolute) below this
layer.
Key to Subgroups
HCGA. Hapludults that have either or both:
1. In each pedon, a discontinuous lithic contact within 50
cm of the mineral soil surface; and
2. In each pedon, a discontinuous argillic horizon that is
interrupted by ledges of bedrock.
Lithic-Ruptic-Entic Hapludults
HCGB. Other Hapludults that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Hapludults
HCGC. Other Hapludults that have one or both of the
following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Hapludults
HCGD. Other Hapludults that have both:
1. Fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm
of the mineral soil surface; or
Ultisols 751
b. In 60 percent or more of the volume of a layer 15 cm or
more thick; and
2. In one or more layers within 75 cm of the mineral soil
surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less, accompanied by redox
concentrations, and also aquic conditions for some time in
normal years (or artificial drainage).
Fragiaquic Hapludults
HCGE. Other Hapludults that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
an argillic horizon at a depth of 50 to 100 cm; and
2. In one or more subhorizons within the upper 60 cm
of the argillic horizon, redox depletions with a color
value, moist, of 4 or more and chroma of 2 or less,
accompanied by redox concentrations, and also aquic
conditions for some time in normal years (or artificial
drainage).
Aquic Arenic Hapludults
HCGF. Other Hapludults that have, in one or more
subhorizons within the upper 60 cm of the argillic horizon,
redox depletions with a color value, moist, of 4 or more and
chroma of 2 or less, accompanied by redox concentrations and
by aquic conditions for some time in normal years (or artificial
drainage).
Aquic Hapludults
HCGG. Other Hapludults that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Hapludults
HCGH. Other Hapludults that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Hapludults
HCGI. Other Hapludults that have an argillic horizon that:
1. Consists entirely of lamellae; or
2. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
3. Consists of one or more subhorizons that are more
than 20 cm thick, each with an overlying eluvial horizon,
and above these horizons there are either:
a. Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
horizon); or
b. A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon.
Lamellic Hapludults
HCGJ. Other Hapludults that have a sandy particle-size class
throughout the upper 75 cm of the argillic horizon or
throughout the entire argillic horizon if it is less than 75 cm
thick.
Psammentic Hapludults
HCGK. Other Hapludults that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 to 100 cm.
Arenic Hapludults
HCGL. Other Hapludults that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 100 cm or more.
Grossarenic Hapludults
HCGM. Other Hapludults that have:
1. No densic, lithic, or paralithic contact within 50 cm of
the mineral soil surface; and
2. An argillic horizon 25 cm or less thick.
Inceptic Hapludults
HCGN. Other Hapludults that have a color value, moist, of 3
or less and a color value, dry, of 5 or less (crushed and
smoothed sample) in either:
1. An Ap horizon that is 18 cm or more thick; or
2. The surface layer after mixing of the upper 18 cm.
Humic Hapludults
HCGO. Other Hapludults.
Typic Hapludults
Definition of Typic Hapludults
Typic Hapludults are the Hapludults that:
1. Do not have, in any subhorizon within the upper 60 cm of
the argillic horizon, redox depletions with a color value, moist,
752 Soil Taxonomy
of 4 or more and chroma of 2 or less, accompanied by redox
concentrations and by aquic conditions;
2. In normal years are not saturated with water in any layer
within 100 cm of the mineral soil surface for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
3. Do not have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of an argillic horizon at a depth of 50 cm or more;
4. Have an argillic horizon more than 25 cm thick;
5. Have a color value, moist, of 4 or more or a value, dry, of 6
or more, when crushed and smoothed, in any Ap horizon 18
cm or more thick and in any surface layer after mixing of the
upper 18 cm;
6. Do not have a lithic contact within 50 cm of the mineral
soil surface in some or all parts of each pedon;
7. Have an argillic horizon that is finer than the sandy
particle-size class in some part of the upper 75 cm if the
argillic horizon is more than 75 cm thick or in any part if the
argillic horizon is less than 75 cm thick;
8. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
9. Have an argillic horizon that meets none of the following:
a. Consists entirely of lamellae; or
b. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
c. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
(1) Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
horizon); or
(2) A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon; and
10. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick.
Description of Subgroups
Typic Hapludults.—The central concept or Typic subgroup
of Hapludults is fixed on freely drained soils that are
moderately deep or deeper to hard rock, have an ochric
epipedon that is not both thick and sandy (not sand or loamy
sand), have a loamy or clayey particle-size class in the argillic
horizon, but do not have deep cracks in normal years. Ground
water at a moderate depth, redox depletions with low chroma
at a shallow depth, and a fluctuating level of ground water in
the iron-depleted zone are properties shared with Aquults and
define the Oxyaquic and Aquic subgroups.
A thick sandy layer, starting at the mineral soil surface,
defines Arenic and Grossarenic subgroups. A shallow lithic
contact defines the Lithic subgroup. A dark colored, relatively
thick ochric epipedon or an umbric epipedon is considered
abnormal and indicates an intergrade to Humults. A very thin
argillic horizon also is considered abnormal and is used to
define the Inceptic subgroup. A sandy particle-size class and
lamellae in the argillic horizon indicate development that is
weaker than normal and define the Psammentic and Lamellic
subgroups. A clayey particle-size class, deep cracks, and a high
COLE are properties shared with Vertisols and define the
Vertic subgroup.
Typic Hapludults are of very large extent in the Eastern and
Southeastern United States. The natural vegetation consisted of
forest plants. Slopes range from nearly level to steep. Where
slopes are suitable, many of these soils are used as cropland.
Many of the soils, particularly those that are steep, are used as
forest. Some are used as pasture or homesites.
Aquic Arenic Hapludults.—These soils have a layer,
starting at the mineral soil surface, that has a sandy or sandyskeletal
particle-size class and is 50 to 100 cm thick. They are
artificially drained or have ground water that fluctuates in
depth, and the horizons that are or were saturated have redox
depletions with low chroma. The ground water may be more
than 60 cm below the top of the argillic horizon if artificial
drainage has been provided. Most of these soils are in the
sandy parts of the coastal plain in the Eastern and Southeastern
United States. The natural vegetation consisted of forest plants.
Aquic Arenic Hapludults are of small extent. Many of these
soils are used as cropland or forest. Some are used as pasture or
homesites.
Aquic Hapludults.—These soils are artificially drained or
have ground water that fluctuates in depth, and the horizons
that are or were saturated have redox depletions with low
Ultisols 753
chroma. The ground water may be more than 60 cm below the
top of the argillic horizon if artificial drainage has been
provided. The level of ground water is high in winter and early
spring. These soils are of large extent in the Eastern and
Southeastern United States. The natural vegetation consisted of
forest plants. Slopes are nearly level to moderately sloping.
Many of these soils are used as cropland or forest. Some are
used as pasture or homesites.
Arenic Hapludults.—These soils have a layer, starting at
the mineral soil surface, that has a sandy or sandy-skeletal
particle-size class and is between 50 and 100 cm thick. Most of
these soils are in the sandy parts of the coastal plain in the
Eastern and Southeastern United States. The natural vegetation
consisted of forest plants. Arenic Hapludults are of moderate
extent. Many of these soils are used as cropland, and many are
used as forest. Some are used as pasture or homesites.
Fragiaquic Hapludults.—These soils are similar to Typic
Hapludults, but they have redox depletions with low chroma
and also aquic conditions at a shallow depth for some time in
normal years. They have fragic soil properties in 30 percent or
more of the volume of a layer 15 cm or more thick that has its
upper boundary within 100 cm of the mineral soil surface or in
60 percent or more of the volume of a layer 15 cm or more
thick anywhere in the soils. These soils are not extensive in the
United States.
Fragic Hapludults.—These soils are similar to Typic
Hapludults, but they have fragic soil properties in 30 percent or
more of the volume of a layer 15 cm or more thick that has its
upper boundary within 100 cm of the mineral soil surface or in
60 percent or more of the volume of a layer 15 cm or more
thick anywhere in the soils. These soils are not extensive in the
United States.
Grossarenic Hapludults.—These soils have a layer,
starting at the mineral soil surface, that has a sandy or sandyskeletal
particle-size class and is more than 100 cm thick.
These soils are not known to occur in the United States. The
subgroup is provided for use in other parts of the world.
Humic Hapludults.—These soils have a dark colored
surface layer. Some have an umbric epipedon or, if heavily
limed, a mollic epipedon. Humic Hapludults are mainly in the
mountains in the Southeastern United States. They are of
moderate extent. The natural vegetation consisted of forest
plants. Slopes range from nearly level to very steep. Many of
these soils are used as cropland or forest. Some are used as
pasture.
Inceptic Hapludults.—These soils have a thin argillic
horizon. Some of the soils are moderately deep to a lithic,
densic, or paralithic contact. Some have a thin argillic horizon
over sandy materials. In the United States, Inceptic Hapludults
are moderately extensive in the Piedmont and on the coastal
plain of the Middle Atlantic and Southern States. The natural
vegetation consisted of forest plants. Slopes range from nearly
level to very steep. Most of the soils are used as forest,
cropland, or pasture.
Lamellic Hapludults.—These soils are like Typic
Hapludults, but they have an argillic horizon that consists
entirely of lamellae or is a combination of two or more
lamellae and one or more subhorizons with a thickness of 7.5
to 20 cm, each layer with an overlying eluvial horizon. In some
of the soils, the argillic horizon consists of one or more
subhorizons that are more than 20 cm thick, each with an
overlying eluvial horizon, and above these horizons there are
either two or more lamellae with a combined thickness of 5 cm
or more or a combination of lamellae and one or more parts of
the argillic horizon 7.5 to 20 cm thick, each with an overlying
eluvial horizon. These soils are not known to occur in the
United States. The subgroup is provided for use in other parts
of the world.
Lithic Hapludults.—These soils have a continuous shallow
lithic contact and an argillic horizon that is continuous
throughout each pedon. These soils are of small extent, mostly
in the Eastern United States. The natural vegetation consisted
of forest plants. Slopes range from nearly level to very steep.
The soils are used mainly as forest.
Lithic-Ruptic-Entic Hapludults.—These soils have either
a discontinuous argillic horizon in each pedon or a shallow
lithic contact only in part of each pedon, or both. Where the
lithic contact is shallow, the argillic horizon commonly is thin.
Where the lithic contact is very shallow, there is no argillic
horizon. In some of these soils, depth to the lithic contact
varies greatly within a pedon and an argillic horizon is only in
the deepest parts of the pedon. Lithic-Ruptic-Entic Hapludults
are not known to occur in the United States. The subgroup is
provided for use in other parts of the world.
Oxyaquic Hapludults.—These soils are like Typic
Hapludults, but they are saturated with water within 100 cm of
the mineral soil surface for 20 or more consecutive days or 30
or more cumulative days in normal years. In addition, they are
permitted to have a dark colored Ap horizon or a dark colored
A horizon after the upper 18 cm has been mixed. These soils
are of small extent in the United States. Slopes are gentle to
steep. The natural vegetation consisted of forest plants. Most of
these soils are used as forest. Some have been cleared and are
used as cropland or pasture.
Psammentic Hapludults.—These soils have a sandy or
sandy-skeletal particle-size class throughout the upper 75 cm of
the argillic horizon or throughout the entire argillic horizon if
it is less than 75 cm thick. They are of small extent in the
United States. They are considered intergrades between
Udipsamments and Hapludults. Slopes generally are nearly
level to moderately steep. The natural vegetation consisted of
forest plants. About half of these soils have been cleared and
are used as cropland or pasture, and about half are used as
forest.
Vertic Hapludults.—These soils have deep cracks and
appreciable amounts of swelling clays. The swelling clays and
low saturated hydraulic conductivity seem to be the most
important properties of the soils of this subgroup. Most of these
754 Soil Taxonomy
soils formed in clayey parent materials. Vertic Hapludults are of
small extent. The natural vegetation consisted of forest plants.
Slopes are gentle to moderately steep. Most of the soils are used
as forest, but some, mostly the less sloping ones, have been
cleared and are used as cropland or pasture.
Kandiudults
Kandiudults are the Udults that are very deep and have a
kandic horizon and a clay distribution in which the percentage
of clay does not decrease from its maximum amount by as
much as 20 percent within a depth of 150 cm from the mineral
soil surface, or the layer in which the clay percentage decreases
has at least 5 percent of the volume consisting of skeletans on
faces of peds and there is at least a 3 percent (absolute)
increase in clay content below this layer. These soils do not
have a fragipan or a horizon in which plinthite either forms a
continuous phase or constitutes one-half or more of the volume
within 150 cm of the mineral soil surface. Kandiudults are of
moderate extent in the Southeastern United States.
Definition
Kandiudults are the Udults that:
1. Have a kandic horizon;
2. Do not have a densic, lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface;
3. Have a clay distribution in which the percentage of clay
does not decrease from its maximum amount by as much as 20
percent within a depth of 150 cm from the mineral soil surface,
or the layer in which the clay percentage decreases by more
than 20 percent has at least 5 percent of the volume consisting
of skeletans on faces of peds and there is at least a 3 percent
(absolute) increase in clay content below this layer;
4. Do not have plinthite that forms a continuous phase or
constitutes more than half the volume in some subhorizon
within 150 cm of the mineral soil surface; and
5. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface.
Key to Subgroups
HCCA. Kandiudults that have:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
a kandic horizon at a depth of 50 to 100 cm; and
2. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface; and
3. In one or more layers either within 75 cm of the
mineral soil surface or, if the chroma throughout the upper
75 cm results from uncoated sand grains, within the upper
12.5 cm of the kandic horizon, redox depletions with a color
value, moist, of 4 or more and chroma of 2 or less,
accompanied by redox concentrations, and also aquic
conditions for some time in normal years (or artificial
drainage).
Arenic Plinthaquic Kandiudults
HCCB. Other Kandiudults that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
a kandic horizon at a depth of 50 to 100 cm; and
2. In one or more layers either within 75 cm of the
mineral soil surface or, if the chroma throughout the upper
75 cm results from uncoated sand grains, within the upper
12.5 cm of the kandic horizon, redox depletions with a color
value, moist, of 4 or more and chroma of 2 or less,
accompanied by redox concentrations, and also aquic
conditions for some time in normal years (or artificial
drainage).
Aquic Arenic Kandiudults
HCCC. Other Kandiudults that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
a kandic horizon at a depth of 50 to 100 cm; and
2. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Arenic Plinthic Kandiudults
HCCD. Other Kandiudults that have both:
1. A sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface
to the top of a kandic horizon at a depth of 50 to 100 cm;
and
2. In all subhorizons in the upper 75 cm of the kandic
horizon or throughout the entire kandic horizon if it is less
than 75 cm thick, more than 50 percent colors that have all
of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less; and
c. A dry value no more than 1 unit higher than the
moist value.
Arenic Rhodic Kandiudults
HCCE. Other Kandiudults that have a sandy or sandyskeletal
particle-size class throughout a layer extending from
the mineral soil surface to the top of a kandic horizon at a
depth of 50 to 100 cm.
Arenic Kandiudults
HCCF. Other Kandiudults that have both:
Ultisols 755
1. A sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface
to the top of a kandic horizon at a depth of 100 cm or more;
and
2. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Grossarenic Plinthic Kandiudults
HCCG. Other Kandiudults that have a sandy or sandyskeletal
particle-size class throughout a layer extending from
the mineral soil surface to the top of a kandic horizon at a
depth of 100 cm or more.
Grossarenic Kandiudults
HCCH. Other Kandiudults that have both:
1. An ECEC of 1.5 cmol(+)/kg clay or less (sum of bases
extracted with 1N NH4
OAc pH 7, plus 1N KCl-extractable
Al) in one or more horizons within 150 cm of the mineral
soil surface; and
2. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Acrudoxic Plinthic Kandiudults
HCCI. Other Kandiudults that have an ECEC of 1.5
cmol(+)/kg clay or less (sum of bases extracted with 1N
NH4
OAc pH 7, plus 1N KCl-extractable Al) in one or more
horizons within 150 cm of the mineral soil surface.
Acrudoxic Kandiudults
HCCJ. Other Kandiudults that have both:
1. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface; and
2. In one or more layers within 75 cm of the mineral soil
surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less, accompanied by redox
concentrations, and also aquic conditions for some time in
normal years (or artificial drainage).
Plinthaquic Kandiudults
HCCK. Other Kandiudults that have both:
1. In one or more layers within 75 cm of the mineral soil
surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less, accompanied by redox
concentrations, and also aquic conditions for some time in
normal years (or artificial drainage); and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface,
one or more of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Kandiudults
HCCL. Other Kandiudults that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Kandiudults
HCCM. Other Kandiudults that have, in one or more layers
within 75 cm of the mineral soil surface, redox depletions with
a color value, moist, of 4 or more and chroma of 2 or less,
accompanied by redox concentrations and by aquic conditions
for some time in normal years (or artificial drainage).
Aquic Kandiudults
HCCN. Other Kandiudults that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Kandiudults
HCCO. Other Kandiudults that:
1. Have, in one or more horizons within 75 cm of the
mineral soil surface, redox concentrations, a color value,
moist, of 4 or more, and hue that is 10YR or yellower and
becomes redder with increasing depth within 100 cm of the
mineral soil surface; and
2. In normal years are saturated with water in one or more
layers within 100 cm of the mineral soil surface for either or
both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days.
Ombroaquic Kandiudults
HCCP. Other Kandiudults that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
756 Soil Taxonomy
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Kandiudults
HCCQ. Other Kandiudults that have a sombric horizon
within 150 cm of the mineral soil surface.
Sombric Kandiudults
HCCR. Other Kandiudults that have, in all subhorizons in
the upper 75 cm of the kandic horizon or throughout the entire
kandic horizon if it is less than 75 cm thick, more than 50
percent colors that have all of the following:
1. Hue of 2.5YR or redder; and
2. A value, moist, of 3 or less; and
3. A dry value no more than 1 unit higher than the moist
value.
Rhodic Kandiudults
HCCS. Other Kandiudults.
Typic Kandiudults
Definition of Typic Kandiudults
Typic Kandiudults are the Kandiudults that:
1. Do not, in any layer either within 75 cm of the mineral
soil surface or, if the chroma throughout the upper 75 cm
results from uncoated sand grains, within the upper 12.5
cm of the kandic horizon, have redox depletions with a
color value, moist, of 4 or more and chroma of 2 or less,
accompanied by redox concentrations and by aquic conditions;
2. In normal years are not saturated with water in any
layer within 100 cm of the mineral soil surface for either or
both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
3. Have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of a kandic horizon at a depth of 50 cm or more;
4. Have less than 5 percent (by volume) plinthite in all
subhorizons within 150 cm of the mineral soil surface;
5. In all parts of the upper 75 cm of the kandic horizon,
have 50 percent or less colors that have all of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less; and
c. A dry value no more than 1 unit higher than the moist
value;
6. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, any of the following:
a. A fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al
plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0; or
b. More than 35 percent (by volume) fragments coarser
than 2.0 mm, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
c. A fine-earth fraction containing 30 percent or more
particles 0.02 to 2.0 mm in diameter; and
(1) In the 0.02 to 2.0 mm fraction, 5 percent or more
volcanic glass; and
(2) [(Al plus 1
/2 Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more;
7. Have, within 75 cm of the mineral soil surface, hue
of 7.5YR or redder in all horizons with a color value, moist,
of 4 or more if there are redox concentrations or if the hue
becomes redder with increasing depth within 100 cm of the
mineral soil surface;
8. Have an ECEC (sum of bases plus 1N KCl-extractable Al)
of more than 1.5 cmol(+)/kg clay in all subhorizons to a depth
of 150 cm below the mineral soil surface; and
9. Do not have a sombric horizon within 150 cm of the
mineral soil surface.
Description of Subgroups
Typic Kandiudults.—The central concept or Typic
subgroup of Kandiudults is fixed on freely drained soils that do
not have a sombric horizon and are very deep. The epipedon is
not both thick and sandy (not sand or loamy sand). These soils
have less than 5 percent plinthite and have a low, but not
extremely low, cation-exchange capacity. They do not have a
surface mantle or layer in the upper 75 cm that has both a low
bulk density and a high content of weakly crystalline minerals.
Ground water at a moderate depth, redox depletions with
low chroma at a shallow depth, and a fluctuating level of
ground water in the iron-depleted zone are properties shared
with Aquults and define the Oxyaquic and Aquic subgroups. A
thick sandy layer, starting at the mineral soil surface, defines
Arenic and Grossarenic subgroups.
Typic Kandiudults are of small extent in the Southeastern
United States. The natural vegetation consisted of forest plants.
Slopes range from nearly level to steep. Where slopes are
suitable, many of these soils are used as cropland. Where
slopes are steep, the soils are used as forest. Some of the soils
are used as pasture or homesites.
Acrudoxic Kandiudults.—These soils have an extremely
low cation-exchange capacity. Recycling of plant nutrients
from decaying vegetation is critical for plant growth on these
soils. The soils are not known to occur in the United States.
The subgroup is provided for use in other parts of the world.
Ultisols 757
Acrudoxic Plinthic Kandiudults.—These soils have an
extremely low cation-exchange capacity and have 5 to 50
percent (by volume) plinthite in some subhorizon within 150
cm of the surface. Recycling of plant nutrients from decaying
vegetation is critical for plant growth on these soils. The soils
are not known to occur in the United States. The subgroup is
provided for use in other parts of the world.
Andic Kandiudults.—These soils have a surface mantle or
layer in the upper 75 cm that has both a low bulk density and a
high content of weakly crystalline minerals in at least some
part of the upper 75 cm. The soils are not known to occur in
the United States. The subgroup is provided for use in other
parts of the world.
Aquandic Kandiudults.—These soils have a surface mantle
or layer in the upper 75 cm that has both a low bulk density
and a high content of weakly crystalline minerals in at least
some part of the upper 75 cm. They also have ground water
that fluctuates in depth or are artificially drained, and the
horizons that are or were saturated have redox depletions with
low chroma. These soils are not known to occur in the United
States. The subgroup is provided for use in other parts of the
world.
Aquic Arenic Kandiudults.—These soils have a layer,
starting at the mineral soil surface, that has a sandy or sandyskeletal
particle-size class and is 50 to 100 cm thick. They
have ground water that fluctuates in depth or are artificially
drained, and the horizons that are or were saturated have redox
depletions with low chroma. These soils are not known to
occur in the United States. The subgroup is provided for use in
other parts of the world.
Aquic Kandiudults.—These soils have ground water that
fluctuates in depth or are artificially drained, and the horizons
that are or were saturated have redox depletions with low
chroma. These soils are not known to occur in the United
States. The subgroup is provided for use in other parts of the
world.
Arenic Kandiudults.—These soils have a layer, starting at
the mineral soil surface, that has a sandy or sandy-skeletal
particle-size class and is between 50 and 100 cm thick. Most of
the soils are in the sandy parts of the coastal plain in the
Southeastern United States. The natural vegetation consisted of
mixed forest plants. Arenic Kandiudults are of small extent in
the United States. Many of these soils are used as cropland or
forest, but some are used as pasture or homesites.
Arenic Plinthaquic Kandiudults.—These soils have a
layer, starting at the mineral soil surface, that has a sandy or
sandy-skeletal particle-size class and is between 50 and 100 cm
thick. They have, in one or more horizons within 75 cm of the
mineral soil surface, redox depletions with chroma of 2 or less
and also aquic conditions for some time in normal years (or
artificial drainage). In addition, the soils have 5 to 50 percent
(by volume) plinthite in one or more horizons within 150 cm of
the mineral soil surface. These soils are not known to occur in
the United States. The subgroup is provided for use in other
parts of the world.
Arenic Plinthic Kandiudults.—These soils have a layer,
starting at the mineral soil surface, that has a sandy or sandyskeletal
particle-size class and is between 50 and 100 cm thick.
They also have 5 to 50 percent (by volume) plinthite in one or
more horizons within 150 cm of the mineral soil surface. These
soils are of very small extent in the United States.
Arenic Rhodic Kandiudults.—These soils have a layer,
starting at the mineral soil surface, that has a sandy or sandyskeletal
particle-size class and is between 50 and 100 cm thick.
They also have, in the epipedon and the upper part of the
kandic horizon, hue of 2.5YR or redder, a value, moist, of 3 or
less, and a dry color value no more than 1 unit higher than the
moist value. These soils are not known to occur in the United
States. The subgroup is provided for use in other parts of the
world.
Grossarenic Kandiudults.—These soils have a sandy or
sandy-skeletal particle-size class throughout a layer extending
from the mineral soil surface to the top of a kandic horizon at a
depth of 100 cm or more below the mineral soil surface. These
soils are of small extent in the United States.
Grossarenic Plinthic Kandiudults.—These soils have 5
percent or more plinthite (by volume) in some subhorizon
within 150 cm of the surface. In addition, they have a sandy or
sandy-skeletal particle-size class throughout a layer extending
from the mineral soil surface to the top of a kandic horizon at a
depth of 100 cm or more below the mineral soil surface. These
soils are not known to occur in the United States. The subgroup
is provided for use in other parts of the world.
Ombroaquic Kandiudults.—These soils have, in one or
more horizons within 75 cm of the mineral soil surface, redox
concentrations, a color value, moist, of 4 or more, and hue that
is 10YR or yellower and becomes redder with increasing depth
within 100 cm of the mineral soil surface. The soils are not
known to occur in the United States. They are defined for use
in other parts of the world.
Oxyaquic Kandiudults.—These soils are saturated with
water within 100 cm of the mineral soil surface for 20 or more
consecutive days or 30 or more cumulative days in normal
years. The soils are not known to occur in the United States.
The subgroup is provided for use in other parts of the world.
Plinthaquic Kandiudults.—These soils have, in one or
more horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage). They
have 5 to 50 percent (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface. Plinthaquic
Kandiudults are intergrades between Plinthaquults and
Kandiudults. They are not known to occur in the United States.
They are defined for use in other parts of the world.
Plinthic Kandiudults.—These soils have 5 to 50 percent (by
volume) plinthite in some subhorizon within 150 cm of the
758 Soil Taxonomy
surface. They are not known to occur in the United States. They
are defined for use in other parts of the world.
Rhodic Kandiudults.—These soils are like Typic
Kandiudults, but the upper part of their kandic horizon has hue
of 2.5YR or redder, a color value, moist, of 3 or less, and a dry
value no more than 1 unit higher than the moist value. Rhodic
Kandiudults are of small extent in the United States. The
natural vegetation consisted of forest plants. Slopes range from
nearly level to moderately steep. Many of these soils are used
as cropland. Some, particularly the most sloping ones, are used
as forest. Some are used as pasture or homesites.
Sombric Kandiudults.—These soils are like Typic
Kandiudults, but they have a sombric horizon. They are not
known to occur in the United States. They are defined for use
in other parts of the world.
Kanhapludults
Kanhapludults are the Udults that have a kandic horizon.
They do not have a fragipan with an upper boundary within
100 cm of the mineral soil surface or plinthite that forms a
continuous phase or constitutes more than half the volume in
some subhorizon within 150 cm of the soil surface. The soils
are less than 150 cm deep, or the kandic horizon has a clay
distribution in which the content of clay decreases from its
maximum amount by 20 percent or more within a depth of 150
cm from the soil surface, and the layer in which the percentage
of clay is less than the maximum has less than 5 percent of the
volume consisting of skeletans on faces of peds or there is an
increase in clay content of less than 3 percent (absolute) below
this layer. Most of these soils have a thermic or warmer soil
temperature regime. The natural vegetation consisted of forest
plants. Many of the soils have been cleared and are used as
cropland or pasture.
Definition
Kanhapludults are the Udults that:
1. Have a kandic horizon;
2. Have a clay distribution in which the percentage of clay
decreases from its maximum amount by 20 percent or more
within a depth of 150 cm from the soil surface, and the layer in
which the percentage of clay is less than the maximum has less
than 5 percent of the volume consisting of skeletans on faces of
peds or there is an increase in clay content of less than 3
percent (absolute) below this layer;
3. Do not have plinthite that forms a continuous phase or
constitutes more than half the volume in some subhorizon
within 150 cm of the soil surface; and
4. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface.
KeytoSubgroups
HCDA. Kanhapludults that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Kanhapludults
HCDB. Other Kanhapludults that have both:
1. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface; and
2. In one or more layers within 75 cm of the mineral soil
surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less, accompanied by redox
concentrations, and also aquic conditions for some time in
normal years (or artificial drainage).
Plinthaquic Kanhapludults
HCDC. Other Kanhapludults that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
a kandic horizon at a depth of 50 to 100 cm; and
2. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Arenic Plinthic Kanhapludults
HCDD. Other Kanhapludults that have a sandy or sandyskeletal
particle-size class throughout a layer extending from
the mineral soil surface to the top of a kandic horizon at a
depth of 50 to 100 cm.
Arenic Kanhapludults
HCDE. Other Kanhapludults that have an ECEC of 1.5
cmol(+)/kg clay or less (sum of bases extracted with 1N
NH4
OAc pH 7, plus 1N KCl-extractable Al) in one or more
horizons within 150 cm of the mineral soil surface.
Acrudoxic Kanhapludults
HCDF. Other Kanhapludults that have both:
1. Fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm
of the mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm
or more thick; and
2. In one or more layers within 75 cm of the mineral soil
surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less, accompanied by redox
concentrations, and also aquic conditions for some time in
normal years (or artificial drainage).
Fragiaquic Kanhapludults
Ultisols 759
HCDG. Other Kanhapludults that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm3
or less, measured at 33 kPa
water retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Kanhapludults
HCDH. Other Kanhapludults that have, in one or more layers
within 75 cm of the mineral soil surface, redox depletions with
a color value, moist, of 4 or more and chroma of 2 or less,
accompanied by redox concentrations and by aquic conditions
for some time in normal years (or artificial drainage).
Aquic Kanhapludults
HCDI. Other Kanhapludults that:
1. Have, in one or more horizons within 75 cm of the
mineral soil surface, redox concentrations, a color value,
moist, of 4 or more, and hue that is 10YR or yellower and
becomes redder with increasing depth within 100 cm of the
mineral soil surface; and
2. In normal years are saturated with water in one or more
layers within 100 cm of the mineral soil surface for either or
both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days.
Ombroaquic Kanhapludults
HCDJ. Other Kanhapludults that in normal years are
saturated with water in one or more layers within 100 cm of
the mineral soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Kanhapludults
HCDK. Other Kanhapludults that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Kanhapludults
HCDL. Other Kanhapludults that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Kanhapludults
HCDM. Other Kanhapludults that have, in all subhorizons in
the upper 50 cm of the kandic horizon or throughout the entire
kandic horizon if it is less than 50 cm thick, more than 50 percent
colors that have all of the following:
1. Hue of 2.5YR or redder; and
2. A value, moist, of 3 or less; and
3. A dry value no more than 1 unit higher than the moist
value.
Rhodic Kanhapludults
HCDN. Other Kanhapludults.
Typic Kanhapludults
Definition of Typic Kanhapludults
Typic Kanhapludults are the Kanhapludults that:
1. Do not, in any layer either within 75 cm of the mineral soil
surface or, if the chroma throughout the upper 75 cm results
from uncoated sand grains, within the upper 12.5 cm of the
kandic horizon, have redox depletions with a color value,
moist, of 4 or more and chroma of 2 or less, accompanied by
redox concentrations and by aquic conditions;
2. In normal years are not saturated with water in one or
more layers within 100 cm of the mineral soil surface for either
or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days;
3. Do not have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of a kandic horizon at a depth of 50 to 100 cm;
4. Have less than 5 percent (by volume) plinthite in all
subhorizons within 150 cm of the soil surface;
5. Do not have a lithic contact within 50 cm of the soil
surface;
6. Have, within 75 cm of the mineral soil surface, hue
of 7.5YR or redder in all horizons with a color value, moist,
of 4 or more if there are redox concentrations or if the hue
becomes redder with increasing depth within 100 cm of the
mineral soil surface;
7. In all parts of the upper 50 cm of the kandic horizon,
have 50 percent or less colors that have all of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less; and
c. A dry value no more than 1 unit higher than the moist
value;
8. Do not have, throughout a cumulative thickness of 18
cm or more and within a depth of 75 cm, a bulk density, in
the fraction less than 2.0 mm in size, of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and acid-oxalate-
760 Soil Taxonomy
extractable aluminum plus 1
/2 acid-oxalate-extractable iron of
more than 1.0 percent;
9. Have an ECEC (sum of bases plus 1N KCl-extractable Al) of
more than 1.5 cmol(+)/kg clay in all subhorizons to a depth of
150 cm below the soil surface; and
10. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick.
Description of Subgroups
Typic Kanhapludults.—The central concept or Typic
subgroup of Kanhapludults is fixed on freely drained soils that
are more than 50 cm deep to a lithic contact. The epipedon is
not both thick and sandy (not sand or loamy sand). These soils
have less than 5 percent plinthite and have a low, but not
extremely low, cation-exchange capacity. They do not have a
surface mantle or layer in the upper 75 cm that has both a low
bulk density and a high content of weakly crystalline minerals.
Soils that have, in the upper part of the kandic horizon, 50
percent or more colors with hue of 2.5YR or redder, a value,
dry, of 3 or less, and moist and dry color values that differ from
each other by 1 unit or less than 1 unit are excluded from Typic
Kanhapludults because these properties are shared with
Rhodudults. Ground water at a moderate depth, redox
depletions with low chroma at a shallow depth, and a
fluctuating level of ground water in the redox-depleted zone
are properties shared with Aquults and define the Oxyaquic
and Aquic subgroups. A thick sandy layer, starting at the
mineral soil surface, defines the Arenic subgroup.
Typic Kanhapludults are of small extent in the Southeastern
United States. The natural vegetation consisted of forest plants.
Slopes range from nearly level to steep. Where slopes are
suitable, many of the soils are used as cropland. The steeper
soils are used as forest. Some of the soils are used as pasture or
homesites.
Acrudoxic Kanhapludults.—These soils have an extremely
low cation-exchange capacity. Recycling of plant nutrients
from decaying vegetation is critical for plant growth on these
soils. The soils are not known to occur in the United States.
The subgroup is provided for use in other parts of the world.
Andic Kanhapludults.—These soils have a surface mantle
or layer in the upper 75 cm that has both a low bulk density
and a high content of weakly crystalline minerals in at least
some part of the upper 75 cm. The soils are not known to occur
in the United States. The subgroup is provided for use in other
parts of the world.
Aquic Kandhapludults.—These soils have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage). The soils
are of very small extent in the United States.
Arenic Kanhapludults.—These soils have a layer, starting
at the mineral soil surface, that has a sandy or sandy-skeletal
particle-size class and is between 50 and 100 cm thick. They
are of very small extent in the United States. They are on the
coastal plain in the Southeastern United States. The natural
vegetation consisted of mixed forest plants. These soils are
used mostly as cropland or forest.
Arenic Plinthic Kanhapludults.—These soils have a layer,
starting at the mineral soil surface, that has a sandy or sandyskeletal
particle-size class and is between 50 and 100 cm thick.
They also have 5 to 50 percent (by volume) plinthite in one or
more horizons within 150 cm of the mineral soil surface. These
soils are not known to occur in the United States. The subgroup
is provided for use in other parts of the world.
Fragiaquic Kanhapludults.—These soils have redox
depletions with low chroma and also aquic conditions at a
shallow depth for some time in normal years. They have fragic
soil properties in 30 percent or more of the volume of a layer
15 cm or more thick that has its upper boundary within 100 cm
of the mineral soil surface or in 60 percent or more of the
volume of a layer 15 cm or more thick anywhere in the soils.
These soils are not extensive in the United States.
Fragic Kanhapludults.—These soils have fragic soil
properties in 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm of the
mineral soil surface or in 60 percent or more of the volume of a
layer 15 cm or more thick anywhere in the soils. These soils
are not extensive in the United States.
Lithic Kanhapludults.—These soils have a lithic contact
within 50 cm of the mineral soil surface. In addition, they are
permitted to have any color, saturation, or redox feature
allowed in Kanhapludults. Lithic Kanhapludults are not known
to occur in the United States. The subgroup is provided for use
in other parts of the world.
Ombroaquic Kanhapludults.—These soils have, in one or
more horizons within 75 cm of the mineral soil surface, redox
concentrations, a color value, moist, of 4 or more, and hue that
is 10YR or yellower and becomes redder with increasing depth
within 100 cm of the mineral soil surface. The soils are not
known to occur in the United States. They are defined for use
in other parts of the world.
Oxyaquic Kanhapludults.—These soils are saturated with
water within 100 cm of the mineral soil surface for 20 or more
consecutive days or 30 or more cumulative days in normal
years. In addition, the soils are permitted, but not required, to
have a kandic horizon that has 50 percent or more colors with
hue of 2.5YR or redder, a value, dry, of 3 or less, and moist and
dry color values that differ from each other by 1 unit or less
than 1 unit. These soils are considered intergrades to Aquults.
They are of very small extent in the United States.
Plinthaquic Kanhapludults.—These soils have, in one or
more horizons within 75 cm of the mineral soil surface, redox
Ultisols 761
depletions with chroma of 2 or less and also aquic conditions for
some time in normal years (or artificial drainage). They have 5 to
50 percent (by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface. They are intergrades between
Plinthaquults and Kanhapludults. They are not known to occur
in the United States. The subgroup is defined for use in other
parts of the world.
Plinthic Kanhapludults.—These soils have 5 to 50 percent
(by volume) plinthite in some subhorizon within 150 cm of the
surface. They are not known to occur in the United States. The
subgroup is defined for use in other parts of the world.
Rhodic Kanhapludults.—These soils are like Typic
Kanhapludults, but the upper part of their kandic horizon has
hue of 2.5YR or redder, a color value, moist, of 3 or less, and a
dry value no more than 1 unit higher than the moist value.
Rhodic Kanhapludults are of small extent in the United States.
The natural vegetation consisted of forest plants. Slopes range
from nearly level to moderately steep. These soils are used
mostly as cropland or forest, but some are used as pasture or
homesites.
Paleudults
These are the very deep, more or less freely drained Udults
on very old stable land surfaces. These soils do not have a
kandic horizon. Many have a thick argillic horizon. The soils
have a clay distribution in which the percentage of clay does
not decrease from its maximum amount by as much as 20
percent within a depth of 150 cm from the mineral soil surface,
or the layer in which the clay percentage decreases has at least
5 percent of the volume consisting of clay depletions on faces
of peds and there is at least a 3 percent (absolute) increase in
clay content below this layer. These soils do not have a
fragipan or a horizon in which plinthite either forms a
continuous phase or constitutes one-half or more of the volume
within 150 cm of the mineral soil surface.
Paleudults are extensive in the Southeastern United States
and in the Middle Atlantic States. Slopes generally are gently
sloping to steep, but a few of the soils on coastal plains are
nearly level. The natural vegetation consisted of forest plants,
mostly hardwoods or mixed conifers and hardwoods. Many of
these soils have been cleared and are used as cropland or
pasture.
Definition
Paleudults are the Udults that:
1. Do not have a densic, lithic, or paralithic contact
within 150 cm of the soil surface;
2. Have a clay distribution in which the percentage of clay
does not decrease from its maximum amount by more than 20
percent within 150 cm of the soil surface, or the layer in which
the percentage of clay decreases by more than 20 percent has at
least 5 percent of the volume consisting of skeletans on faces of
peds and there is at least a 3 percent (absolute) increase in clay
content below this layer;
3. Do not have a kandic horizon;
4. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface; and
5. Do not have plinthite that forms a continuous phase or
constitutes more than half the matrix in any subhorizon within
150 cm of the soil surface.
Key to Subgroups
HCEA. Paleudults that have one or both of the following:
1. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower.
Vertic Paleudults
HCEB. Other Paleudults that have a horizon 5 cm or more
thick, either below an Ap horizon or at a depth of 18 cm or
more from the mineral soil surface, whichever is deeper, that
has one or more of the following:
1. In 25 percent or more of each pedon, cementation by
organic matter and aluminum, with or without iron; or
2. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
3. An ODOE value of 0.12 or more, and a value half as
high or lower in an overlying horizon.
Spodic Paleudults
HCEC. Other Paleudults that have:
1. In one or more layers either within 75 cm of the
mineral soil surface or, if the chroma throughout the upper
75 cm results from uncoated sand grains, within the upper
12.5 cm of the argillic horizon, redox depletions with a
color value, moist, of 4 or more and chroma of 2 or less,
accompanied by redox concentrations, and also aquic
conditions for some time in normal years (or artificial
drainage); and
2. A sandy or sandy-skeletal particle-size class throughout
762 Soil Taxonomy
a layer extending from the mineral soil surface to the top of an
argillic horizon at a depth of 50 cm or more; and
3. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Arenic Plinthaquic Paleudults
HCED. Other Paleudults that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
an argillic horizon that is 50 cm or more below the mineral
soil surface; and
2. In one or more layers either within 75 cm of the
mineral soil surface or, if the chroma throughout the upper
75 cm results from uncoated sand grains, within the upper
12.5 cm of the argillic horizon, redox depletions with a
color value, moist, of 4 or more and chroma of 2 or less,
accompanied by redox concentrations, and also aquic
conditions for some time in normal years (or artificial
drainage).
Aquic Arenic Paleudults
HCEE. Other Paleudults that have both:
1. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface; and
2. In one or more layers either within 75 cm of the
mineral soil surface or, if the chroma throughout the upper
75 cm results from uncoated sand grains, within the upper
12.5 cm of the argillic horizon, redox depletions with a
color value, moist, of 4 or more and chroma of 2 or less,
accompanied by redox concentrations, and also aquic
conditions for some time in normal years (or artificial
drainage).
Plinthaquic Paleudults
HCEF. Other Paleudults that have both:
1. Fragic soil properties:
a. In 30 percent or more of the volume of a layer 15 cm
or more thick that has its upper boundary within 100 cm
of the mineral soil surface; or
b. In 60 percent or more of the volume of a layer 15 cm
or more thick; and
2. In one or more layers within 75 cm of the mineral soil
surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less, accompanied by redox
concentrations, and also aquic conditions for some time in
normal years (or artificial drainage).
Fragiaquic Paleudults
HCEG. Other Paleudults that have, in one or more layers
within 75 cm of the mineral soil surface, redox depletions with a
color value, moist, of 4 or more and chroma of 2 or less,
accompanied by redox concentrations and by aquic conditions
for some time in normal years (or artificial drainage).
Aquic Paleudults
HCEH. Other Paleudults that have anthraquic conditions.
Anthraquic Paleudults
HCEI. Other Paleludults that in normal years are saturated
with water in one or more layers within 100 cm of the mineral
soil surface for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Paleudults
HCEJ. Other Paleudults that have an argillic horizon that:
1. Consists entirely of lamellae; or
2. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
3. Consists of one or more subhorizons that are more
than 20 cm thick, each with an overlying eluvial horizon,
and above these horizons there are either:
a. Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
horizon); or
b. A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon.
Lamellic Paleudults
HCEK. Other Paleudults that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
an argillic horizon at a depth of 50 to 100 cm; and
2. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Arenic Plinthic Paleudults
HCEL. Other Paleudults that have a sandy particle-size class
throughout the upper 75 cm of the argillic horizon or
throughout the entire argillic horizon if it is less than 75 cm
thick.
Psammentic Paleudults
HCEM. Other Paleudults that have both:
1. A sandy or sandy-skeletal particle-size class throughout
Ultisols 763
a layer extending from the mineral soil surface to the top of an
argillic horizon at a depth of 100 cm or more; and
2. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Grossarenic Plinthic Paleudults
HCEN. Other Paleudults that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Paleudults
HCEO. Other Paleudults that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
an argillic horizon at a depth of 50 to 100 cm; and
2. In all subhorizons in the upper 75 cm of the argillic
horizon or throughout the entire argillic horizon if it is less
than 75 cm thick, more than 50 percent colors that have all
of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less; and
c. A dry value no more than 1 unit higher than the
moist value.
Arenic Rhodic Paleudults
HCEP. Other Paleudults that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 to 100 cm.
Arenic Paleudults
HCEQ. Other Paleudults that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 100 cm or more.
Grossarenic Paleudults
HCER. Other Paleudults that have fragic soil properties:
1. In 30 percent or more of the volume of a layer 15 cm or
more thick that has its upper boundary within 100 cm of the
mineral soil surface; or
2. In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Paleudults
HCES. Other Paleudults that have, in all subhorizons in the
upper 75 cm of the argillic horizon or throughout the entire
argillic horizon if it is less than 75 cm thick, more than 50
percent colors that have all of the following:
1. Hue of 2.5YR or redder; and
2. A value, moist, of 3 or less; and
3. A dry value no more than 1 unit higher than the moist
value.
Rhodic Paleudults
HCET. Other Paleudults.
Typic Paleudults
Definition of Typic Paleudults
Typic Paleudults are the Paleudults that:
1. Do not, in any layer either within 75 cm of the mineral soil
surface or, if the chroma throughout the upper 75 cm results
from uncoated sand grains, within the upper 12.5 cm of the
argillic horizon, have redox depletions with a color value,
moist, of 4 or more and chroma of 2 or less, accompanied by
redox concentrations and by aquic conditions;
2. Do not have anthraquic conditions;
3. Do not have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of an argillic horizon at a depth of 50 cm or more;
4. Have less than 5 percent (by volume) plinthite in all
subhorizons within 150 cm of the soil surface;
5. In all parts of the upper 75 cm of the argillic horizon,
have 50 percent or less colors that have all of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less; and
c. A dry value no more than 1 unit higher than the moist
value;
6. Have an argillic horizon that is finer than the sandy
particle-size class in some part of the upper 75 cm if the
argillic horizon is more than 75 cm thick or in any part if the
argillic horizon is less than 75 cm thick;
7. Do not have a horizon 5 cm or more thick, either below an
Ap horizon or at a depth of 18 cm or more from the mineral
soil surface, whichever is deeper, that has one or more of the
following:
a. In 25 percent or more of each pedon, cementation
by organic matter and aluminum, with or without iron;
or
b. Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling 0.25 or more, and half that amount or less in an
overlying horizon; or
c. An ODOE value of 0.12 or more, and a value half as
high or lower in an overlying horizon;
8. Have fragic soil properties:
a. In less than 30 percent of the volume of all layers 15 cm
764 Soil Taxonomy
or more thick that have an upper boundary within 100 cm of
the mineral soil surface; and
b. In less than 60 percent of the volume of all layers 15 cm
or more thick;
9. Do not have either:
a. Cracks within 125 cm of the mineral soil surface that
are 5 mm or more wide through a thickness of 30 cm or
more for some time in normal years, and slickensides or
wedge-shaped aggregates in a layer 15 cm or more thick
that has its upper boundary within 125 cm of the mineral
soil surface; or
b. A linear extensibility of 6.0 cm or more between the
mineral soil surface and either a depth of 100 cm or a
densic, lithic, or paralithic contact, whichever is shallower;
10. Have an argillic horizon that meets none of the following:
a. Consists entirely of lamellae; or
b. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
c. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
(1) Two or more lamellae with a combined thickness
of 5 cm or more (that may or may not be part of the
argillic horizon); or
(2) A combination of lamellae (that may or may not be
part of the argillic horizon) and one or more parts of the
argillic horizon 7.5 to 20 cm thick, each with an
overlying eluvial horizon; and
11. In normal years are not saturated with water in any layer
within 100 cm of the mineral soil surface for either or both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days.
Description of Subgroups
Typic Paleudults.—The central concept or Typic subgroup
of Paleudults is fixed on freely drained soils that have an
epipedon that is not both sandy and thick, that have little or no
plinthite, and that have an argillic horizon that is loamy or
clayey and is not composed of thin lamellae.
A fluctuating ground water table at a moderately shallow
depth, with or without redox depletions with low chroma, is a
property shared with Aquults and is used as the basis for
defining Aquic and Oxyaquic subgroups. A thick sandy layer,
starting at the mineral soil surface, is considered abnormal and
is used to define Arenic and Grossarenic subgroups. An
appreciable amount of plinthite also is considered abnormal
and is used to define the Plinthic subgroup. A dark red argillic
horizon is a property shared with Rhodudults and is used to
define the Rhodic subgroup. A sandy argillic horizon is used to
define the Psammentic subgroup. An argillic horizon composed
partly or wholly of lamellae is used to define the Lamellic
subgroup.
Typic Paleudults are of large extent in the Eastern and
Southeastern United States. The natural vegetation consisted of
forest plants. Slopes range from nearly level to steep. Where
slopes are suitable, many of the soils are used as cropland. The
steeper soils are used as forest. Some of the soils are used as
pasture or homesites.
Anthraquic Paleudults.—These soils have anthraquic
conditions. Nearly all of them have been used for rice in
irrigated paddies for long periods of time. Anthraquic
Paleudults are not known to occur in the United States. The
subgroup is provided for use in other parts of the world.
Aquic Arenic Paleudults.—These soils have a layer,
starting at the mineral soil surface, that is 50 cm or more thick
and has a sandy or sandy-skeletal particle-size class
throughout. They also have ground water that fluctuates in
depth or are artificially drained, and the zone in which the
water stands or formerly stood has redox depletions with low
chroma within 75 cm of the soil surface or in the upper 12.5
cm of the argillic horizon. Commonly, the argillic horizon has
more sand and less clay than the argillic horizon in the Typic
subgroup. The Aquic Arenic Paleudults in the United States
are mostly in areas of sandy deposits on the coastal plain in the
Southeastern States. The natural vegetation consisted of forest
plants. The soils are of small extent. They are nearly level or
gently sloping. Most are used as cropland or forest.
Aquic Paleudults.—These soils have, within 75 cm of the
soil surface, ground water that fluctuates in depth or are
artificially drained, and the zone in which water stands or
formerly stood has redox depletions with low chroma. These
soils are extensive on the coastal plains in the Southern United
States. The natural vegetation consisted of forest plants. These
soils generally are nearly level or gently sloping. Many are
used as cropland, and many are used as forest. Some are used
as pasture or homesites.
Arenic Paleudults.—These soils have a layer, starting at
the mineral soil surface, that is between 50 and 100 cm thick
and has a sandy or sandy-skeletal particle-size class, that is, the
texture is sand or loamy sand. The soils are otherwise like
Typic Paleudults in defined properties, but the argillic horizon
tends to have more sand and less clay than the one in the Typic
subgroup. In the United States, Arenic Paleudults occur on the
coastal plain from Maryland to Texas. The natural vegetation
consisted of forest plants. The soils are of moderate extent.
Slopes generally are nearly level to strongly sloping. Most of
the soils are used as cropland or forest, but some are used as
pasture.
Arenic Plinthaquic Paleudults.—These soils have a layer,
starting at the mineral soil surface, that is 50 cm or more thick
Ultisols 765
and has a sandy or sandy-skeletal particle-size class, that is, the
texture of the fine-earth fraction is sand or loamy sand. The
soils also have a small or moderate amount of plinthite in the
argillic horizon, and the ground water fluctuates at some depth
within the epipedon but is sometimes above the argillic
horizon. The subhorizons that have plinthite normally restrict
the movement of water, and the soils may have a perched water
table for short periods. These soils occur on the coastal plains
in the Southern United States. The natural vegetation consisted
of forest plants. These soils are of small extent. They are nearly
level or gently sloping. Most are used as cropland or forest.
Some are used as pasture.
Arenic Plinthic Paleudults.—These soils have some
plinthite in the argillic horizon and have a layer, starting at the
mineral soil surface, that is between 50 and 100 cm thick and
has a sandy or sandy-skeletal particle-size class, that is, the
texture of the fine-earth fraction is sand or loamy sand. The
soils are otherwise like Typic Paleudults in defined properties,
but they differ from the Typic subgroup in several respects. The
argillic horizon commonly has more sand and less clay than
the one in the Typic subgroup, the subhorizons that have
plinthite normally slow the movement of water, and the soils
may have a perched water table for short periods. The natural
vegetation consisted of forest plants. These soils are of small
extent in the United States. They are mostly on the coastal
plains in the Southern States. They are nearly level or gently
sloping. Most are used as cropland or forest. Some are used as
pasture.
Arenic Rhodic Paleudults.—These soils have a low color
value and are mostly dark red throughout the upper part of the
argillic horizon. The epipedon also is normally dark colored,
and there is a layer, starting at the mineral soil surface and
extending to a depth of 50 to 100 cm, that has a sandy or
sandy-skeletal particle-size class. The dark color is caused
chiefly by the large amount of free iron oxides rather than by
organic matter. These soils are not known to occur in the
United States. They are defined for use in other parts of the
world.
Fragiaquic Paleudults.—These soils have, within 75 cm of
the soil surface, ground water that fluctuates in depth or are
artificially drained, and the zone in which water stands or
formerly stood has redox depletions with low chroma. The soils
also have a large amount of soil aggregates with fragic soil
properties in a layer 15 cm or more thick. The amount of
plinthite in any subhorizon within a depth of 150 cm is
restricted to less than 5 percent. These soils are moderately
extensive in the Southern United States. They are nearly level
or gently sloping. Most are used as cropland or forest. Some
are used as pasture.
Fragic Paleudults.—These soils have a large amount of soil
aggregates with fragic soil properties in a layer 15 cm or more
thick. The amount of plinthite in any subhorizon is restricted to
less than 5 percent in any subhorizon within a depth of 150
cm. These soils are of small extent in the Southeastern United
States. Most of the soils are used as forest or cropland. Some
are used as pasture.
Grossarenic Paleudults.—These soils have a layer, starting
at the mineral soil surface, that has a sandy or sandy-skeletal
particle-size class (a texture of sand or loamy sand in the fineearth
fraction) and that is between 100 and 200 cm thick. The
argillic horizon tends to have appreciably more sand and less
clay than the one in the soils of the Typic subgroup.
Grossarenic Paleudults are moderately extensive on the coastal
plains in the Southern United States. The natural vegetation
consisted of forest plants. Slopes range from nearly level to
moderately steep. These soils are used mostly as cropland or
forest. Some are used as pasture or homesites.
Grossarenic Plinthic Paleudults.—These soils have a
layer, starting at the mineral soil surface, that has a sandy or
sandy-skeletal particle-size class (a texture of sand or loamy
sand in the fine-earth fraction) and that is between 100 and
200 cm thick. These soils have 5 to 50 percent plinthite in
some horizon within 150 cm of the soil surface. The argillic
horizon has appreciably more sand and less clay than the one
in Typic Paleudults. Grossarenic Plinthic Paleudults are of
small extent in the Southeastern United States. The natural
vegetation consisted of forest plants. These soils generally are
nearly level or gently sloping. They are used mostly as forest or
cropland.
Lamellic Paleudults.—These soils are similar to Typic
Paleudults, but they have an argillic horizon that consists
entirely of lamellae or is a combination of two or more
lamellae and one or more subhorizons with a thickness of 7.5
to 20 cm, each layer with an overlying eluvial horizon. In some
of the soils, the argillic horizon consists of one or more
subhorizons that are more than 20 cm thick, each with an
overlying eluvial horizon, and above these horizons there are
either two or more lamellae with a combined thickness of 5 cm
or more or a combination of lamellae and one or more parts of
the argillic horizon 7.5 to 20 cm thick, each with an overlying
eluvial horizon. These soils are of small extent in the
Southeastern United States. The natural vegetation consisted of
forest plants. These soils generally are nearly level or gently
sloping. They are used mostly as forest or cropland. Some are
used as pasture or homesites.
Oxyaquic Paleudults.—These soils are saturated with
water within 100 cm of the mineral soil surface for 20 or more
consecutive days and/or 30 or more cumulative days during
normal years. The soils are in scattered areas throughout the
Southeastern United States. Many were forested but have been
cleared and are used for crop production.
Plinthaquic Paleudults.—These soils have 5 to 50 percent
plinthite in some horizon within 150 cm of the soil surface.
Ground water in the soils fluctuates in depth, or there is
artificial drainage. The subhorizon in which water stands or
formerly stood has redox depletions with low chroma, or the
soil color is a result of the color of the uncoated sand grains.
The argillic horizon, especially the subhorizons that have
766 Soil Taxonomy
plinthite, tends to slow the movement of water, and there may
be ground water perched above these subhorizons for short
periods. These soils are of very small extent in the Southeastern
United States. The natural vegetation consisted of forest plants.
Slopes generally are nearly level or gently sloping. These soils
are used mostly as forest or cropland.
Plinthic Paleudults.—These soils have 5 to 50 percent
plinthite in some horizon within 150 cm of the soil surface.
The argillic horizon, especially the subhorizons that have
plinthite, tends to slow the movement of water. These soils
formed on the coastal plain in the Southeastern United States.
They are of moderate extent. The natural vegetation consisted
of forest plants. Slopes generally are nearly level to strongly
sloping. Plinthic Paleudults are used mostly as cropland or
forest. Some are used as pasture.
Psammentic Paleudults.—These soils have an argillic
horizon that has a sandy or sandy-skeletal particle-size class
throughout or throughout the upper 75 cm if it is more than 75
cm thick. The sand fraction of the Psammentic Paleudults in
the United States is dominantly quartz. The upper part of the
epipedon commonly is an albic horizon. These soils are of
small extent and occur only on the coastal plains of the
Southern States. The natural vegetation consisted of forest
plants. Slopes generally are nearly level to strongly sloping.
These soils are used mostly as forest or cropland. Some are
used as pasture or homesites.
Rhodic Paleudults.—These soils have a low color value
and are mostly dark red throughout the upper part of the
argillic horizon. The epipedon also is normally dark colored.
The dark color is mainly the result of a large amount of free
iron oxides rather than the content of organic matter, but
organic matter tends to be more abundant in these soils than in
Typic Paleudults. Most Rhodic Paleudults formed in basic
parent materials and tend to have more total phosphorus than
the soils of the Typic subgroup. Rhodic Paleudults are of small
extent in the Southeastern United States. The natural
vegetation consisted of forest plants. Slopes generally are
nearly level to moderately steep. Most of these soils are used as
cropland if slopes are gentle. Some of the soils, mainly the
most sloping ones, are used as forest or pasture.
Spodic Paleudults.—In these soils, the upper part of the B
horizon has a weak accumulation of amorphous materials and
the lower part is an argillic horizon. In the Spodic Paleudults
in the United States, the horizons above the argillic horizon
have a texture of sand or loamy sand. These soils are of very
small extent in the Southeastern United States. The natural
vegetation consisted of forest plants. The soils are nearly level
or gently sloping. They are used mostly as cropland or forest.
Vertic Paleudults.—These soils are high in expanding
clays and have cracks 5 mm or more wide, slickensides,
wedge-shaped aggregates, or a linear extensibility of 6.0 cm or
more between the mineral soil surface and either a depth of 100
cm or a densic, lithic, or paralithic contact, whichever is
shallower. The soils are considered intergrades between
Paleudults and Uderts. They are not known to occur in the
United States. The subgroup is provided for use in other parts
of the world.
Plinthudults
These are the more or less freely drained Udults that have a
large amount of plinthite in the argillic or kandic horizon.
They are mainly in intertropical regions and in some areas are
extensive. They are not known to occur in the United States.
The great group is provided for use in other parts of the world.
Definition
Plinthudults are the Udults that have plinthite that either
forms a continuous phase in, or constitutes more than half the
matrix of, one or more horizons within 150 cm of the mineral
soil surface.
Key to Subgroups
HCAA. All Plinthudults.
TypicPlinthudults
Rhodudults
These are the freely drained Udults that are of mid or low
latitudes and have a dark colored epipedon and an argillic
horizon with dark reddish colors throughout the upper part.
These soils do not have a fragipan, and they have less than 50
percent plinthite in all horizons within 150 cm of the mineral
soil surface. They have one of the following: (1) a densic,
lithic, paralithic, or petroferric contact within 150 cm of the
mineral soil surface or (2) with increasing depth, a clay
decrease of 20 percent or more (relative) from the maximum
clay content and less than 5 percent (by volume) skeletans on
faces of peds in any layer that has a 20 percent lower clay
content or, below that layer, the fine-earth fraction has a clay
increase of less than 3 percent. Many of the soils have a thin
argillic horizon. Rhodudults formed under forest vegetation
and commonly from basic rocks or sediments. As a
consequence, they tend to have more total phosphorus than
most other Udults. They also tend to be less erosive.
Rhodudults range from nearly level to very steep. Most of
these soils formed in sediments or on surfaces of the latter half
of the Pleistocene (Illinoian or Wisconsinan). Where slopes are
suitable, most of the soils are used as cropland. In many of the
soils, the plow layer includes material that was part of the
argillic horizon.
Definition
Rhodudults are the Udults that:
1. Have an epipedon that has a color value, moist, of 3 or less
throughout;
2. In all subhorizons in the upper 100 cm of the argillic
Ultisols 767
horizon or throughout the entire argillic horizon if it is less than
100 cm thick, have more than 50 percent colors with all of the
following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less; and
c. A dry value no more than 1 unit higher than the moist
value;
3. Do not have a kandic horizon;
4. Do not have a fragipan with an upper boundary within 100
cm of the mineral soil surface;
5. Do not have plinthite that forms a continuous phase or
constitutes more than half the matrix in any subhorizon within
150 cm of the mineral soil surface; and
6. Have a clay distribution in which, with increasing depth,
the percentage of clay decreases from its maximum amount by
more than 20 percent within a depth of 150 cm below the soil
surface, and the layer in which the percentage of clay is less
than the maximum has less than 5 percent of the volume
consisting of skeletans on faces of peds or there is an increase
in clay content of less than 3 percent (absolute) below this
layer.
Key to Subgroups
HCFA. Rhodudults that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Rhodudults
HCFB. Other Rhodudults that have a sandy particle-size class
throughout the upper 75 cm of the argillic horizon or
throughout the entire argillic horizon if it is less than 75 cm
thick.
Psammentic Rhodudults
HCFC. Other Rhodudults.
Typic Rhodudults
Definition of Typic Rhodudults
Typic Rhodudults are the Rhodudults that:
1. Have an argillic horizon that is finer than the sandy
particle-size class in some part of the upper 75 cm if the
argillic horizon is more than 75 cm thick or in any part if the
argillic horizon is less than 75 cm thick; and
2. Do not have a lithic contact within 50 cm of the soil
surface.
Description of Subgroups
Typic Rhodudults.—The central concept or Typic subgroup
of Rhodudults is fixed on well drained soils that are moderately
deep to very deep. The only features that cause exclusions from
the Typic subgroup are those that have been used as
conventions throughout this taxonomy. The absence of an
Aquic subgroup probably reflects the nature of the underlying
rock, which seems to preclude the presence of shallow ground
water. These soils formed mostly from basic rocks and
sediments.
Typic Rhodudults are of moderate extent in the Southeastern
United States. The natural vegetation consisted of forest plants.
Slopes are nearly level to very steep. Most of these soils are
used as cropland if slopes are gentle. Some of the soils, mainly
the most sloping ones, are used as forest or pasture.
Lithic Rhodudults.—These soils have a lithic contact
within 50 cm of the mineral soil surface. They are not known
to occur in the United States. The subgroup is provided for use
in other parts of the world.
Psammentic Rhodudults.—These soils have a sandy or
sandy-skeletal particle-size class throughout the argillic
horizon or throughout the upper 75 cm of the argillic horizon if
it is more than 75 cm thick. The soils are not known to occur
in the United States. The subgroup is provided for use in other
parts of the world.
Ustults
These are the more or less freely drained Ultisols that have an
ustic soil moisture regime and a relatively low content of organic
carbon. They occur in regions where rainfall is moderately low to
high but evapotranspiration exceeds precipitation. Some Ustults
have a single dry season each year, as in areas of a monsoon
climate, and others have alternating moist and dry periods
throughout the growing season. Ustults can have any soil
temperature regime but generally have one that is isomesic,
thermic,orwarmer.
Most Ustults have an ochric epipedon that rests on an
argillic or kandic horizon, which may or may not contain
plinthite. A petroferric contact is common in some parts of the
world.
The vegetation commonly consists of forest or savanna
plants. These soils are of small extent in the United States.
Definition
Ustults are the Ultisols that:
1. Do not have both aquic conditions and the colors defined
for Aquults;
2. Have an ustic moisture regime;
3. Have less than 0.9 percent (by weighted average) organic
carbon in the upper 15 cm of the argillic or kandic horizon,
exclusive of any Ap horizon; and
4. Have less than 12 kg organic carbon in a unit volume
768 Soil Taxonomy
of 1 m2
to a depth of 100 cm below the base of any O horizon or
the mineral soil surface.
Key to Great Groups
HDA. Ustults that have one or more horizons within 150 cm of
the mineral soil surface in which plinthite either forms a
continuous phase or constitutes one-half or more of the volume.
Plinthustults, p. 776
HDB. Other Ustults that:
1. Do not have a densic, lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface; and
2. Have a kandic horizon; and
3. Within 150 cm of the mineral soil surface, either:
a. With increasing depth, do not have a clay decrease of
20 percent or more (relative) from the maximum clay
content; or
b. Have 5 percent or more (by volume) skeletans on
faces of peds in the layer that has a 20 percent lower clay
content and, below that layer, a clay increase of 3 percent
or more (absolute) in the fine-earth fraction.
Kandiustults, p. 770
HDC. Other Ustults that have a kandic horizon.
Kanhaplustults, p. 773
HDD. Other Ustults that:
1. Do not have a densic, lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface; and
2. Within 150 cm of the mineral soil surface, either:
a. With increasing depth, do not have a clay decrease of
20 percent or more (relative) from the maximum clay
content; or
b. Have 5 percent or more (by volume) skeletans on
faces of peds in the layer that has a 20 percent lower clay
content and, below that layer, a clay increase of 3 percent
or more (absolute) in the fine-earth fraction.
Paleustults, p. 776
HDE. Other Ustults that have both:
1. An epipedon that has a color value, moist, of 3 or less
throughout; and
2. In all subhorizons in the upper 100 cm of the argillic
horizon or throughout the entire argillic horizon if it is less
than 100 cm thick, more than 50 percent colors that have all
of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less; and
c. A dry value no more than 1 unit higher than the moist
value.
Rhodustults, p. 777
HDF. Other Ustults.
Haplustults, p. 768
Haplustults
These are the Ustults that have a thin or moderately thick
zone of maximum clay content in the argillic horizon and are
very deep to any horizon that is one-half or more plinthite.
They are not both dark colored in the epipedon and dark red
throughout the argillic horizon. Slopes range from gentle to
very steep. Many of these soils are in tropical climates and are
farmed by means of shifting cultivation.
Haplustults are of small extent in the United States. They
are mainly in Texas, California, and Puerto Rico. They are
extensive in some parts of the world.
Definition
Haplustults are the Ustults that:
1. Do not have a kandic horizon;
2. Do not have plinthite that forms a continuous phase or
constitutes more than half the matrix in any subhorizon within
150 cm of the mineral soil surface;
3. Have a color value of 4 or more, moist, in some part of the
epipedon or have an argillic horizon that has a color with hue
less red than 2.5YR and a value of 5 or more, dry, or of 4 or
more, moist, in some subhorizon; and
4. Have a clay distribution in which, with increasing depth,
the percentage of clay decreases from its maximum amount by
more than 20 percent within 150 cm of the mineral soil
surface, and the layer in which the percentage of clay is less
than the maximum has less than 5 percent of the volume
consisting of skeletans on faces of peds or there is an increase
in clay content of less than 3 percent (absolute) below this
layer.
Key to Subgroups
HDFA. Haplustults that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Haplustults
HDFB. Other Haplustults that have a petroferric contact
within 100 cm of the mineral soil surface.
Petroferric Haplustults
HDFC. Other Haplustults that have, in one or more layers
both within the upper 12.5 cm of the argillic horizon and
within 75 cm of the mineral soil surface, redox depletions with
Ultisols 769
a color value, moist, of 4 or more and chroma of 2 or less,
accompanied by redox concentrations and by aquic conditions
for some time in normal years (or artificial drainage).
Aquic Haplustults
HDFD. Other Haplustults that have a sandy or sandy-skeletal
particle-size class throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth
of 50 cm or more below the mineral soil surface.
Arenic Haplustults
HDFE. Other Haplustults that:
1. Have, in one or more horizons within 75 cm of the
mineral soil surface, redox concentrations, a color value,
moist, of 4 or more, and hue that is 10YR or yellower and
becomes redder with increasing depth within 100 cm of the
mineral soil surface; and
2. In normal years are saturated with water in one or more
layers within 100 cm of the mineral soil surface for either or
both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days.
Ombroaquic Haplustults
HDFF. Other Haplustults that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Haplustults
HDFG. Other Haplustults that have a CEC (by 1N NH4
OAc
pH 7) of less than 24 cmol(+)/kg clay in 50 percent or more of
the entire argillic horizon if less than 100 cm thick or of its
upper 100 cm.
Kanhaplic Haplustults
HDFH. Other Haplustults.
Typic Haplustults
Definition of Typic Haplustults
Typic Haplustults are the Haplustults that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Do not have a petroferric contact within 100 cm of the
mineral soil surface;
3. Do not have, in any layer within the upper 12.5 cm of the
argillic horizon and within 75 cm of the mineral soil surface,
redox depletions with a color value, moist, of 4 or more and
chroma of 2 or less, accompanied by redox concentrations and
by aquic conditions;
4. Have, within 75 cm of the mineral soil surface, hue
of 7.5YR or redder in all horizons with a color value, moist,
of 4 or more if there are redox concentrations or if the hue
becomes redder with increasing depth within 100 cm of the
mineral soil surface;
5. Have less than 5 percent (by volume) plinthite in all
subhorizons within 150 cm of the mineral soil surface;
6. Have a CEC of 24 cmol(+) or more per kg clay (by 1N
NH4
OAc pH 7) in the major part of the argillic horizon or in
the major part of the upper 100 cm of the argillic horizon if
this horizon is thicker than 100 cm; and
7. Do not have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of an argillic horizon at a depth of 50 to 100 cm.
Description of Subgroups
Typic Haplustults.—The central concept or Typic subgroup
of Haplustults is fixed on freely drained soils that are deep or
moderately deep to hard rock or to a petroferric contact, do not
have a thick epipedon of sand or loamy sand, have little or no
plinthite, and have clay that is at least semiactive.
Redox depletions with low chroma at a moderately shallow
depth accompanied by seasonal ground water in the irondepleted
zone are properties shared with Aquults and define
the Aquic subgroup. A yellowish brown or olive brown color in
the upper part of the soils along with reddish redox
concentrations and a redder hue at some depth are associated
with wetness at the surface and define the Ombroaquic
subgroup. A thick sandy layer, starting at the mineral soil
surface, defines the Arenic subgroup. Clay that has low activity
suggests strong weathering, a property of Kanhaplustults, and
defines the Kanhaplic subgroup. Plinthite is considered
abnormal, and its presence is used to define the Plinthic
subgroup. A petroferric contact also is considered abnormal
and defines the Petroferric subgroup.
Typic Haplustults are of small extent in the United States.
They are mostly in Texas, California, Puerto Rico, and the
Virgin Islands. The natural vegetation consisted mostly of
coniferous forest plants in California, broadleaf forest or
savanna plants in Texas, and tropical forest plants in Puerto
Rico and the Virgin Islands. Slopes range from nearly level to
very steep. Some of these soils are used as forest. Where slopes
are suitable, many of the soils have been cleared and are used
as pasture, cropland, or homesites.
Aquic Haplustults.—These soils have ground water in the
upper part of the argillic horizon at some time of the year or
are artificially drained, and they have redox depletions with
low chroma in the horizons that are or were saturated. They are
not known to occur in the United States. The subgroup is
provided for use in other parts of the world.
Arenic Haplustults.—These soils have a thick layer of sand
or loamy sand, starting at the mineral soil surfac. The argillic
horizon normally has more sand and less clay than the one in
770 Soil Taxonomy
Typic Haplustults. Arenic Haplustults are rare in the United
States and are known to occur only in Texas.
Kanhaplic Haplustults.—These soils have a strongly
weathered clay fraction that has a moderately low or low CEC.
They are otherwise like Typic Haplustults in defined properties,
but they tend to have less extractable aluminum and a higher
pH. Kanhaplic Haplustults are not known to occur in the
United States or in Puerto Rico. The subgroup is provided for
use in other parts of the world.
Lithic Haplustults.—These soils have a shallow lithic
contact. They are not known to occur in the United States or in
Puerto Rico. The subgroup is provided for use in other parts of
the world.
Ombroaquic Haplustults.—These soils have yellowish
brown or olive brown colors in the upper horizons, commonly
on the faces of peds only, and have redder redox concentrations
inside the peds. The hue becomes redder with increasing depth.
These soils are not known to occur in the United States or in
Puerto Rico. The subgroup is provided for use in other parts of
the world.
Petroferric Haplustults.—These soils have a petroferric
contact within 100 cm of the mineral soil surface but are
otherwise similar to Typic Haplustults in defined properties.
They are not known to occur in the United States or in Puerto
Rico. The subgroup is provided for use in other parts of the
world.
Plinthic Haplustults.—These soils have a moderate or small
amount of plinthite in or below the argillic horizon but are
otherwise like Typic Haplustults in defined properties. They
probably have or have had a fluctuating level of ground water,
which is or was absent or is present for shorter periods in the
soils of the Typic subgroup. Plinthic Haplustults are not known
to occur in the United States. The subgroup is provided for use
in other parts of the world.
Kandiustults
Kandiustults are the Ustults that have a kandic horizon.
These soils have a clay distribution in which the percentage of
clay does not decrease from its maximum amount by as much
as 20 percent within a depth of 150 cm from the mineral soil
surface, or the layer in which the clay percentage decreases by
more than 20 percent has at least 5 percent of the volume
consisting of clay depletions on faces of peds and there is at
least a 3 percent (absolute) increase in clay content below this
layer. The soils do not have plinthite that forms a continuous
phase or constitutes more than half the volume in some
subhorizon within 150 cm of the soil surface. Most of the soils
have a thermic or warmer soil temperature regime. The natural
vegetation consisted of forest or savanna plants. Many of the
soils have been cleared and are used as cropland or pasture.
Definition
Kandiustults are the Ustults that:
1. Have a kandic horizon;
2. Do not have a densic, lithic, paralithic, or petroferric contact
within 150 cm of the mineral soil surface;
3. Have a clay distribution in which the percentage of clay
does not decrease from its maximum amount by as much as 20
percent within a depth of 150 cm from the mineral soil surface,
or the layer in which the clay percentage decreases by more
than 20 percent has at least 5 percent of the volume consisting
of clay depletions on faces of peds and there is at least a 3
percent (absolute) increase in clay content below this layer; and
4. Do not have plinthite that forms a continuous phase or
constitutes more than half the volume of some subhorizon
within 150 cm of the mineral soil surface.
Key to Subgroups
HDBA. Kandiustults that have an ECEC of 1.5 cmol(+)/kg
clay or less (sum of bases extracted with 1N NH4
OAc pH 7,
plus 1N KCl-extractable Al) in one or more horizons within
150 cm of the mineral soil surface.
Acrustoxic Kandiustults
HDBB. Other Kandiustults that have, in one or more layers
within 75 cm of the mineral soil surface, redox depletions with
a color value, moist, of 4 or more and chroma of 2 or less,
accompanied by redox concentrations and by aquic conditions
for some time in normal years (or artificial drainage).
Aquic Kandiustults
HDBC. Other Kandiustults that have both:
1. A sandy or sandy-skeletal particle-size class throughout
a layer extending from the mineral soil surface to the top of
a kandic horizon at a depth of 50 cm or more; and
2. 5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Arenic Plinthic Kandiustults
HDBD. Other Kandiustults that have a sandy or sandyskeletal
particle-size class throughout a layer extending from
the mineral soil surface to the top of a kandic horizon at a
depth of 50 cm or more.
Arenic Kandiustults
HDBE. Other Kandiustults that have both:
1. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface, a
fine-earth fraction with both a bulk density of 1.0 g/cm3
or
less, measured at 33 kPa water retention, and Al plus 1
/2 Fe
percentages (by ammonium oxalate) totaling more than 1.0;
and
2. When neither irrigated nor fallowed to store moisture,
either:
Ultisols 771
a. A mesic or thermic soil temperature regime and a
moisture control section that is dry in some part for 135
or fewer of the cumulative days per year when the
temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
b. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that is
dry in some or all parts for fewer than 120 cumulative
days per year when the temperature at a depth of 50 cm
below the soil surface is higher than 8 o
C.
Udandic Kandiustults
HDBF. Other Kandiustults that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Kandiustults
HDBG. Other Kandiustults that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Kandiustults
HDBH. Other Kandiustults that, when neither irrigated nor
fallowed to store moisture, have either:
1. A thermic, mesic, or colder soil temperature regime and
a moisture control section that in normal years is dry in
some part for more than four-tenths of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
2. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
a. Is moist in some or all parts for fewer than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
b. Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 5 o
C.
Aridic Kandiustults
HDBI. Other Kandiustults that, when neither irrigated nor
fallowed to store moisture, have either:
1. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for 135 or fewer of the cumulative days per year when
the temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A hyperthermic, isomesic, or warmer iso soil temperature
regime and a moisture control section that in normal years is
dry in some or all parts for fewer than 120 cumulative days
per year when the temperature at a depth of 50 cm below the
soil surface is higher than 8 o
C.
Udic Kandiustults
HDBJ. Other Kandiustults that have, in all subhorizons in
the upper 50 cm of the kandic horizon or throughout the entire
kandic horizon if it is less than 75 cm thick, more than 50
percent colors that have all of the following:
1. Hue of 2.5YR or redder; and
2. A value, moist, of 3 or less; and
3. A dry value no more than 1 unit higher than the moist
value.
Rhodic Kandiustults
HDBK. Other Kandiustults.
Typic Kandiustults
Definition of Typic Kandiustults
Typic Kandiustults are the Kandiustults that:
1. Do not have, in any layer within 75 cm of the mineral soil
surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less, accompanied by redox
concentrations and by aquic conditions;
2. Have less than 5 percent (by volume) plinthite in all
subhorizons within 150 cm of the mineral soil surface;
3. Do not have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of a kandic horizon at a depth of 50 to 100 cm;
4. In all parts of the upper 75 cm of the kandic horizon,
have 50 percent or less colors that have all of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less; and
c. A dry value no more than 1 unit higher than the moist
value;
5. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, a bulk density, in the
fraction less than 2.0 mm in size, of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and acid-oxalateextractable
aluminum plus 1
/2 acid-oxalate-extractable iron of
more than 1.0 percent;
6. When neither irrigated nor fallowed to store moisture:
a. If the soil temperature regime is thermic, mesic, or colder,
are moist in some part of the moisture control section (not
necessarily the same part) for more than
772 Soil Taxonomy
six-tenths of the time in normal years when the soil
temperature at a depth of 50 cm exceeds 5 o
C; or
b. If the soil temperature regime is hyperthermic,
isomesic, or warmer, have a moisture control section that in
normal years:
(1) Is moist in some or all parts for 90 or more
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
or
(2) Is dry in some part for less than six-tenths of the
cumulative days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 5 o
C;
7. When neither irrigated nor fallowed to store moisture:
a. If the soil temperature regime is mesic or thermic, are
dry in some part of the moisture control section for more
than 135 cumulative days per year when the soil
temperature at a depth of 50 cm exceeds 5 o
C; or
b. If the soil temperature regime is hyperthermic,
isomesic, or warmer, are dry in some or all parts of the
moisture control section for 120 or more cumulative days
per year during a period when the soil temperature at a
depth of 50 cm exceeds 8 o
C; and
8. Have an ECEC (sum of bases plus 1N KCl-extractable Al)
of more than 1.5 cmol(+)/kg clay in all subhorizons to a depth
of 150 cm below the mineral soil surface.
Description of Subgroups
Typic Kandiustults.—The central concept or Typic
subgroup of Kandiustults is fixed on freely drained, very deep
soils that have an ustic moisture regime that is approaching
neither the udic nor the aridic regime. The epipedon is not both
thick and sandy (not sand or loamy sand). These soils have less
than 5 percent plinthite and have a low, but not extremely low,
cation-exchange capacity. They do not have a surface mantle or
layer in the upper 75 cm that has both a low bulk density and a
high content of weakly crystalline minerals.
Ground water at a moderate depth, redox depletions with
low chroma at a shallow depth, and a fluctuating level of
ground water in the redox-depleted zone are properties shared
with Aquults and define the Aquic subgroup. A thick sandy
layer, starting at the mineral soil surface, defines the Arenic
subgroup.
Typic Kandiustults are not known to occur in the United
States. The subgroup is provided for use in other parts of the
world.
Acrustoxic Kandiustults.—These soils have an extremely
low cation-exchange capacity. Recycling of plant nutrients
from decaying vegetation is critical for plant growth on these
soils. The soils are not known to occur in the United States.
The subgroup is provided for use in other parts of the world.
Andic Kandiustults.—These soils have a surface mantle or
layer in the upper 75 cm that has both a low bulk density and a
high content of weakly crystalline minerals in at least some
part of the upper 75 cm. The soils are not known to occur in
the United States. The subgroup is provided for use in other
parts of the world.
Aquic Kandiustults.—These soils have ground water that
fluctuates in depth or are artificially drained, and the horizons
that are or were saturated have redox depletions with low
chroma. These soils are not known to occur in the United
States. The subgroup is provided for use in other parts of the
world.
Arenic Kandiustults.—These soils have a layer, starting at
the mineral soil surface, that has a sandy or sandy-skeletal
particle-size class and is 50 cm or more thick. They are not
known to occur in the United States. The subgroup is provided
for use in other parts of the world.
Arenic Plinthic Kandiustults.—These soils have a layer,
starting at the mineral soil surface, that has a sandy or sandyskeletal
particle-size class and is between 50 and 100 cm thick.
They also have 5 to 50 percent (by volume) plinthite in one or
more horizons within 150 cm of the mineral soil surface. These
soils are of very small extent in the United States.
Aridic Kandiustults.—These soils are drier than Typic
Kandiustults. They are intergrades between Argids and
Kandiustults. Aridic Kandiustults are not known to occur in
the United States. They are defined for use in other parts of the
world.
Plinthic Kandiustults.—These soils have 5 to 50 percent
(by volume) plinthite in some subhorizon within 150 cm of the
surface. They are not known to occur in the United States.
They are defined for use in other parts of the world.
Rhodic Kandiustults.—These soils are like Typic
Kandiustults, but the upper part of their kandic horizon has
hue of 2.5YR or redder, a color value, moist, of 3 or less, and a
dry value no more than 1 unit higher than the moist value.
Rhodic Kandiustults are not known to occur in the United
States. They are defined for use in other parts of the world.
Udandic Kandiustults.—These soils have a surface mantle
or layer in the upper 75 cm that has both a low bulk density
and a high content of weakly crystalline minerals in at least
some part of the upper 75 cm. They are dry in some part of the
moisture control section for less than four-tenths of the
cumulative days per year when the soil temperature at a depth
of 50 cm exceeds 5 o
C if the soil temperature regime is mesic
or thermic and are dry in some or all parts of the moisture
control section for fewer than 90 days during a period when the
soil temperature at a depth of 50 cm exceeds 8o
C if the soil
temperature regime is hyperthermic, isomesic, or warmer.
These soils are intergrades between Kandiustults and Udands.
They are not known to occur in the United States. They are
defined for use in other parts of the world.
Udic Kandiustults.—These soils are like Typic Kandiustults,
but they are dry in some part of the moisture control section for
Ultisols 773
less than four-tenths of the cumulative days per year when the
soil temperature at a depth of 50 cm exceeds 5 o
C if the soil
temperature regime is mesic or thermic and are dry in some or all
parts of the moisture control section for fewer than 90 days
during a period when the soil temperature at a depth of 50 cm
exceeds 8o
C if the soil temperature regime is hyperthermic,
isomesic, or warmer. These soils are intergrades between
Kandiustults and Kandiudults. They are not known to occur in
the United States. They are defined for use in other parts of the
world.
Kanhaplustults
These are the Ustults that have a kandic horizon and are
very deep to any horizon that is one-half or more plinthite.
They have a clay distribution in which the percentage of clay
decreases from its maximum amount by 20 percent or more
within a depth of 150 cm from the mineral soil surface, and the
layer in which the percentage of clay is less than the maximum
has less than 5 percent of the volume consisting of clay
depletions on faces of peds or there is an increase in clay
content of less than 3 percent (absolute) below this layer. These
soils have a thin or moderately thick zone of maximum clay
content. Slopes range from gentle to very steep. Many of the
soils are in tropical climates and are farmed by means of shifting
cultivation.
Kanhaplustults are not known to occur in the United States.
They are defined for use in other parts of the world.
Definition
Kanhaplustults are the Ustults that:
1. Have a kandic horizon;
2. Have a clay distribution in which the percentage of clay
decreases from its maximum amount by 20 percent or more
within a depth of 150 cm from the mineral soil surface, and the
layer in which the percentage of clay is less than the maximum
has less than 5 percent of the volume consisting of skeletans on
faces of peds or there is an increase in clay content of less than
3 percent (absolute) below this layer; and
3. Do not have plinthite that forms a continuous phase or
constitutes more than half the volume of some subhorizon
within 150 cm of the mineral soil surface.
Key to Subgroups
HDCA. Kanhaplustults that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Kanhaplustults
HDCB. Other Kanhaplustults that have an ECEC of 1.5
cmol(+)/kg clay or less (sum of bases extracted with 1N
NH4
OAc pH 7, plus 1N KCl-extractable Al) in one or more
horizons within 150 cm of the mineral soil surface.
Acrustoxic Kanhaplustults
HDCC. Other Kanhaplustults that have, in one or more
layers within 75 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and chroma
of 2 or less, accompanied by redox concentrations and by
aquic conditions for some time in normal years (or artificial
drainage).
AquicKanhaplustults
HDCD. Other Kanhaplustults that have a sandy or sandyskeletal
particle-size class throughout a layer extending from
the mineral soil surface to the top of a kandic horizon at a
depth of 50 to 100 cm.
Arenic Kanhaplustults
HDCE. Other Kanhaplustults that have both:
1. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface, a
fine-earth fraction with both a bulk density of 1.0 g/cm3
or
less, measured at 33 kPa water retention, and Al plus 1
/2 Fe
percentages (by ammonium oxalate) totaling more than 1.0;
and
2. When neither irrigated nor fallowed to store moisture,
either:
a. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in
some part for 135 or fewer of the cumulative days per
year when the temperature at a depth of 50 cm below the
soil surface is higher than 5 o
C; or
b. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for fewer than
120 cumulative days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C.
Udandic Kanhaplustults
HDCF. Other Kanhaplustults that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm3
or less, measured at 33 kPa
water retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Kanhaplustults
HDCG. Other Kanhaplustults that have 5 percent or more (by
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.
Plinthic Kanhaplustults
HDCH. Other Kanhaplustults that:
1. Have, in one or more horizons within 75 cm of the mineral
soil surface, redox concentrations, a color value, moist, of 4 or
more, and hue that is 10YR or yellower and becomes redder
774 Soil Taxonomy
with increasing depth within 100 cm of the mineral soil
surface; and
2. In normal years are saturated with water in one or more
layers within 100 cm of the mineral soil surface for either or
both:
a. 20 or more consecutive days; or
b. 30 or more cumulative days.
Ombroaquic Kanhaplustults
HDCI. Other Kanhaplustults that, when neither irrigated nor
fallowed to store moisture, have either:
1. A thermic, mesic, or colder soil temperature regime and
a moisture control section that in normal years is dry in
some part for more than four-tenths of the cumulative days
per year when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5 o
C; or
2. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years:
a. Is moist in some or all parts for fewer than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
b. Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature
at a depth of 50 cm below the soil surface is higher than
5 o
C.
Aridic Kanhaplustults
HDCJ. Other Kanhaplustults that, when neither irrigated nor
fallowed to store moisture, have either:
1. A mesic or thermic soil temperature regime and a
moisture control section that in normal years is dry in some
part for 135 or fewer of the cumulative days per year when
the temperature at a depth of 50 cm below the soil surface is
higher than 5 o
C; or
2. A hyperthermic, isomesic, or warmer iso soil
temperature regime and a moisture control section that in
normal years is dry in some or all parts for fewer than 120
cumulative days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8 o
C.
Udic Kanhaplustults
HDCK. Other Kanhaplustults that have, in all subhorizons in
the upper 50 cm of the kandic horizon or throughout the entire
kandic horizon if it is less than 50 cm thick, more than 50
percent colors that have all of the following:
1. Hue of 2.5YR or redder; and
2. A value, moist, of 3 or less; and
3. A dry value no more than 1 unit higher than the moist
value.
RhodicKanhaplustults
HDCL. Other Kanhaplustults.
Typic Kanhaplustults
Definition of Typic Kanhaplustults
Typic Kanhaplustults are the Kanhaplustults that:
1. Do not have a lithic contact within 50 cm of the mineral
soil surface;
2. Do not have, in any layer within 75 cm of the mineral soil
surface, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less, accompanied by redox
concentrations and by aquic conditions;
3. Have, within 75 cm of the mineral soil surface, hue
of 7.5YR or redder in all horizons with a color value, moist,
of 4 or more if there are redox concentrations or if the hue
becomes redder with increasing depth within 100 cm of the
mineral soil surface;
4. Have less than 5 percent (by volume) plinthite in all
subhorizons within 150 cm of the mineral soil surface;
5. Do not have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of a kandic horizon at a depth of 50 to 100 cm;
6. In all parts of the upper 50 cm of the kandic horizon,
have 50 percent or less colors that have all of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less; and
c. A dry value no more than 1 unit higher than the moist
value;
7. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, a bulk density, in the
fraction less than 2.0 mm in size, of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and acid-oxalateextractable
aluminum plus 1
/2 acid-oxalate-extractable iron of
more than 1.0 percent;
8. Have an ECEC (sum of bases plus 1N KCl-extractable Al)
of more than 1.5 cmol(+)/kg clay in all subhorizons to a depth
of 150 cm below the mineral soil surface;
9. When neither irrigated nor fallowed to store moisture:
a. If the soil temperature regime is thermic, mesic, or
colder, are moist in some part of the moisture control
section (not necessarily the same part) for more than sixtenths
of the time in normal years when the soil temperature
at a depth of 50 cm exceeds 5 o
C; or
b. If the soil temperature regime is hyperthermic,
Ultisols 775
isomesic, or warmer, in normal years are moist in some or all
parts of the moisture control section for 180 or more days
during a period when the soil temperature at a depth of 50 cm
exceeds 8 o
C; and
10. When neither irrigated nor fallowed to store moisture:
a. If the soil temperature regime is mesic or thermic, are dry
in some part of the moisture control section for more than 135
cumulative days per year when the soil temperature at a
depth of 50 cm exceeds 5 o
C; or
b. If the soil temperature regime is hyperthermic,
isomesic, or warmer, in normal years the moisture control
section:
(1) Is moist in some or all parts for fewer than 90
consecutive days per year when the temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
(2) Is dry in some part for six-tenths or more of the
cumulative days per year when the soil temperature at a
depth of 50 cm below the soil surface is higher than 5 o
C.
Description of Subgroups
Typic Kanhaplustults.—The central concept or Typic
subgroup of Kanhaplustults is fixed on freely drained soils that
have an ustic moisture regime that is approaching neither the
udic nor the aridic regime. These soils are more than 50 cm
deep to a lithic contact. The epipedon is not both thick and
sandy (not sand or loamy sand). The soils have less than 5
percent plinthite and have a low, but not extremely low, cationexchange
capacity. They do not have a surface mantle or layer
in the upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals.
Soils that have, in the upper part of the kandic horizon, 50
percent or more colors with hue of 2.5YR or redder, a value,
dry, of 3 or less, and moist and dry color values that differ from
each other by 1 unit or less than 1 unit are excluded from Typic
Kanhaplustults because these properties are shared with
Rhodustults. Ground water at a moderate depth, redox
depletions with low chroma at a shallow depth, and a
fluctuating level of ground water in the redox-depleted zone
are properties shared with Aquults and define the Oxyaquic
and Aquic subgroups. A thick sandy layer, starting at the
mineral soil surface, defines the Arenic subgroup.
Typic Kanhaplustults are not known to occur in the United
States. They are defined for use in other parts of the world.
Acrudoxic Kanhaplustults.—These soils have an
extremely low cation-exchange capacity. Recycling of plant
nutrients from decaying vegetation is critical for plant growth
on these soils. The soils are not known to occur in the United
States. The subgroup is provided for use in other parts of the
world.
Andic Kanhaplustults.—These soils have a surface mantle
or layer in the upper 75 cm that has both a low bulk density and
a high content of weakly crystalline minerals in at least some
part of the upper 75 cm. The soils are not known to occur in the
United States. The subgroup is provided for use in other parts
of the world.
Aquic Kanhaplustults.—These soils have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with chroma of 2 or less and also aquic conditions
for some time in normal years (or artificial drainage). The soils
are not known to occur in the United States. The subgroup is
provided for use in other parts of the world.
Arenic Kanhaplustults.—These soils have a layer, starting
at the mineral soil surface, that has a sandy or sandy-skeletal
particle-size class and is between 50 and 100 cm thick. They
are not known to occur in the United States. The subgroup is
provided for use in other parts of the world.
Aridic Kanhaplustults.—These soils are drier than Typic
Kanhaplustults. They are intergrades between Argids and
Kanhaplustults. Aridic Kanhaplustults are not known to occur
in the United States. They are defined for use in other parts of
the world.
Lithic Kanhaplustults.—These soils have a lithic contact
within 50 cm of the mineral soil surface. In addition, they are
permitted to have any color, saturation, or redox feature
allowed in Kanhaplustults. Lithic Kanhaplustults are not
known to occur in the United States. The subgroup is provided
for use in other parts of the world.
Ombroaquic Kanhaplustults.—These soils have, in one or
more horizons within 75 cm of the mineral soil surface, redox
concentrations, a color value, moist, of 4 or more, and hue that
is 10YR or yellower and becomes redder with increasing depth
within 100 cm of the mineral soil surface. The soils are not
known to occur in the United States. They are defined for use
in other parts of the world.
Plinthic Kanhaplustults.—These soils have 5 to 50 percent
(by volume) plinthite in some subhorizon within 150 cm of the
surface. They are not known to occur in the United States.
They are defined for use in other parts of the world.
Rhodic Kanhaplustults.—These soils are like Typic
Kanhaplustults, but the upper part of their kandic horizon has
hue of 2.5YR or redder, a color value, moist, of 3 or less, and a
dry value no more than 1 unit higher than the moist value.
Rhodic Kanhaplustults are not known to occur in the United
States. They are defined for use in other parts of the world.
Udandic Kanhaplustults.—These soils have a moisture
regime that borders on udic and have a surface mantle or layer
in the upper 75 cm that has both a low bulk density and a high
content of weakly crystalline minerals in at least some part of
the upper 75 cm. These soils are not known to occur in the
United States. They are defined for use in other parts of the
world.
Udic Kanhaplustults.—These soils are like Typic
Kanhaplustults, but they are dry in some part of the moisture
control section for less than four-tenths of the cumulative days
776 Soil Taxonomy
per year when the soil temperature at a depth of 50 cm exceeds
5 o
C if the soil temperature regime is mesic or thermic and are dry
in some or all parts of the moisture control section for fewer than
90 days during a period when the soil temperature at a depth of
50 cm exceeds 8o
C if the soil temperature regime is hyperthermic,
isomesic, or warmer. The soils are intergrades between
Kanhaplustults and Kanhapludults. Udic Kanhaplustults are not
known to occur in the United States. They are defined for use in
other parts of the world.
Paleustults
These are the more or less freely drained Ustults that have an
argillic horizon. They have a clay distribution in which the
percentage of clay does not decrease from its maximum amount
by as much as 20 percent within a depth of 150 cm from the
mineral soil surface, or the layer in which the clay percentage
decreases has at least 5 percent of the volume consisting of
skeletans on faces of peds and there is at least a 3 percent
(absolute) increase in clay content below this layer. These soils
have no horizon in which plinthite either forms a continuous
phase or constitutes one-half or more of the volume within 150
cm of the mineral soil surface. Many of the soils have a thick
argillic horizon. Commonly, there are small or moderate
amounts of plinthite at some depth in the soils. Paleustults are
on old stable surfaces that have gentle slopes. They are very
rare in the United States and are known to occur only in
California. The great group is provided for use elsewhere.
Definition
Paleustults are the Ustults that:
1. Within 150 cm of the mineral soil surface, either:
a. With increasing depth, do not have a clay decrease of 20
percent or more (relative) from the maximum clay content;
or
b. Have 5 percent or more (by volume) skeletans on faces
of peds in the layer that has a 20 percent lower clay content
and, below that layer, a clay increase of 3 percent or more
(absolute) in the fine-earth fraction; and
2. Do not have any horizon within 150 cm of the mineral soil
surface in which plinthite either forms a continuous phase or
constitutes one-half or more of the volume; and
3. Do not have a kandic horizon.
Key to Subgroups
HDDA. All Paleustults.
Typic Paleustults
Plinthustults
These are the more or less freely drained Ustults that have a
large amount of plinthite. Slopes are mostly gentle or
moderate. These soils are not known to occur in the United
States or in Puerto Rico. The great group is provided for use
elsewhere.
Definition
Plinthustults are the Ustults that have one or more horizons
within 150 cm of the mineral soil surface in which plinthite
either forms a continuous phase or constitutes one-half or more
of the volume.
Key to Subgroups
HDAA. Plinthustults that have:
1. A densic, lithic, paralithic, or petroferric contact
within 150 cm of the mineral soil surface; or
2. Within 150 cm of the mineral soil surface, both:
a. With increasing depth, a clay decrease of 20 percent
or more (relative) from the maximum clay content; and
b. Less than 5 percent (by volume) skeletans on faces of
peds in the layer that has a 20 percent lower clay content
or, below that layer, a clay increase of less than 3 percent
(absolute) in the fine-earth fraction.
Haplic Plinthustults
HDAB. Other Plinthustults.
Typic Plinthustults
Definition of Typic Plinthustults
Typic Plinthustults are the Plinthustults that:
1. Do not have a densic, lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface; and
2. Have a clay distribution in which the percentage of clay
does not decrease from its maximum amount by as much as 20
percent within a depth of 150 cm from the mineral soil surface,
or the layer in which the clay percentage decreases by more
than 20 percent has at least 5 percent of the volume consisting
of skeletans on faces of peds and there is at least a 3 percent
(absolute) increase in clay content below this layer.
Description of Subgroups
Typic Plinthustults.—These are the very deep Plinthustults
that have a clay distribution in which the percentage of clay
does not decrease from its maximum amount by as much as 20
percent within a depth of 150 cm from the mineral soil surface,
or the layer in which the clay percentage decreases by more
than 20 percent has at least 5 percent of the volume consisting
of skeletans on faces of peds and there is at least a 3 percent
(absolute) increase in clay content below this layer. These soils
are not known to occur in the United States. They are defined
for use in other parts of the world.
Haplic Plinthustults.—These are the Plinthustults that are
moderately deep or that have a clay distribution in which the
Ultisols 777
percentage of clay decreases from its maximum amount by 20
percent or more within a depth of 150 cm from the mineral soil
surface, and the layer in which the clay percentage decreases
by more than 20 percent has less than 5 percent of the volume
consisting of skeletans on faces of peds or there is an increase
in clay content of less than 3 percent (absolute) below this
layer. These soils are not known to occur in the United States.
They are defined for use in other parts of the world.
Rhodustults
These are the Ustults that have a dark colored epipedon and
a dark red or dusky red argillic horizon. They are moderately
deep or have a clay distribution in which the percentage of clay
decreases from its maximum amount by 20 percent or more
within a depth of 150 cm from the mineral soil surface, and the
layer in which the clay percentage decreases by more than 20
percent has less than 5 percent of the volume consisting of
skeletans on faces of peds or there is an increase in clay content
of less than 3 percent (absolute) below this layer. These soils
formed mainly in material weathered from basic rocks. As a
consequence, they tend to have more total phosphorus than
most other Ustults.
Rhodustults have gentle to steep slopes. Most of the soils
formed in alluvium or on slopes of the later half of the
Pleistocene, either Illinoian or Wisconsinan.
Rhodustults are rare in the United States and are known to
occur only on the Pacific Trust Islands.
Definition
Rhodustults are the Ustults that:
1. Have an epipedon that has a color value, moist, of 3 or less
throughout;
2. In all subhorizons in the upper 100 cm of the argillic
horizon or throughout the entire argillic horizon if it is less
than 100 cm thick, have more than 50 percent colors with all
of the following:
a. Hue of 2.5YR or redder; and
b. A value, moist, of 3 or less; and
c. A dry value no more than 1 unit higher than the moist
value;
3. Do not have plinthite that forms a continuous phase or
constitutes more than half the matrix in any subhorizon in the
upper 150 cm;
4. Have a clay distribution in which, with increasing depth,
the percentage of clay decreases from its maximum amount by
more than 20 percent within 150 cm of the mineral soil
surface, and the layer in which the percentage of clay is less
than the maximum has less than 5 percent of the volume
consisting of skeletans on faces of peds or there is an increase
in clay content of less than 3 percent (absolute) below this layer;
and
5. Do not have a kandic horizon.
KeytoSubgroups
HDEA. Rhodustults that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Rhodustults
HDEB. Other Rhodustults that have a sandy particle-size
class throughout the upper 75 cm of the argillic horizon or
throughout the entire argillic horizon if it is less than 75 cm
thick.
Psammentic Rhodustults
HDEC. Other Rhodustults.
Typic Rhodustults
Definition of Typic Rhodustults
Typic Rhodustults are the Rhodustults that:
1. Have an argillic horizon that is finer than the sandy
particle-size class in some part of the upper 75 cm if the
argillic horizon is more than 75 cm thick or in any part if the
argillic horizon is less than 75 cm thick;
2. Do not have a lithic contact within 50 cm of the mineral
soil surface.
Description of Subgroups
Typic Rhodustults.—The central concept or Typic
subgroup of Rhodustults is fixed on well drained soils that are
moderately deep to very deep. These soils do not have a lithic
contact within 50 cm of the mineral soil surface. The argillic
horizon is finer than the sandy or sandy-skeletal particle-size
class. The absence of an Aquic subgroup probably reflects the
nature of the underlying rock, which seems to preclude the
presence of shallow ground water. These soils formed mostly
from basic rocks and sediments.
Typic Rhodustults are of small extent on the Pacific
Trust Islands of the United States. The natural vegetation
consisted of savanna plants. Slopes are nearly level to very
steep. Most of these soils are used as cropland if slopes are
gentle.
Lithic Rhodustults.—These soils have a lithic contact
within 50 cm of the mineral soil surface. They are not known
to occur in the United States. The subgroup is provided for use
in other parts of the world.
Psammentic Rhodustults.—These soils have a sandy or
sandy-skeletal particle-size class throughout the entire argillic
horizon or throughout the upper 75 cm of the argillic horizon if
this horizon is more than 75 cm thick. Psammentic
Rhodustults are not known to occur in the United States. The
subgroup is provided for use in other parts of the world.
778 Soil Taxonomy
Xerults
These are more or less freely drained Ultisols of
Mediterranean climates. These soils have a xeric moisture
regime and a moderate or small amount of organic matter. They
generally have an ochric or umbric epipedon that rests on a
brownish to reddish argillic or kandic horizon. They are not
extensive in the United States, except locally in California and
Oregon. They are gently sloping to very steep. Most of the
Xerults in the United States are in the mountains. The natural
vegetation consisted mostly of coniferous forest plants.
Definition
Xerults are the Ultisols that:
1. Have a xeric soil moisture regime;
2. Have less than 0.9 percent organic carbon in the upper 15
cm of the argillic horizon, exclusive of any Ap horizon;
3. Have less than 12 kg organic carbon in a unit volume
of 1 m2
to a depth of 100 cm below the base of any O horizon
or the mineral soil surface; and
4. Do not have both aquic conditions and the colors defined
for Aquults.
Key to Great Groups
HEA. Xerults that:
1. Do not have a densic, lithic, or paralithic contact
within 150 cm of the mineral soil surface; and
2. Within 150 cm of the mineral soil surface, either:
a. With increasing depth, do not have a clay decrease of
20 percent or more (relative) from the maximum clay
content; or
b. Have 5 percent or more (by volume) skeletans on
faces of peds or 5 percent or more (by volume) plinthite,
or both, in the layer that has a 20 percent lower clay
content and, below that layer, a clay increase of 3 percent
or more (absolute) in the fine-earth fraction.
Palexerults, p. 780
HEB. Other Xerults.
Haploxerults, p. 778
Haploxerults
These are the Xerults that have a clay distribution in which
the percentage of clay decreases from its maximum amount by
as much as 20 percent within a depth of 150 cm from the
mineral soil surface, and the layer in which the clay percentage
decreases has less than 5 percent of the volume consisting of
skeletans on faces of peds or there is an increase in clay content
of less than 3 percent (absolute) below this layer. These soils
typically have an ochric epipedon that rests on a brownish or
reddish argillic or kandic horizon. In the United States, they
occur mostly in the Sierra Nevada and Cascade Mountains and
support coniferous forest plants. The soils are moderately
extensive in those mountains but are rare elsewhere in the
United States.
Definition
Haploxerults are the Xerults that:
1. Have a densic, lithic, or paralithic contact within 150 cm
of the mineral soil surface; or
2. Within 150 cm of the mineral soil surface, have:
a. With increasing depth, a clay decrease of 20 percent or
more (relative) from the maximum clay content; and
b. Less than 5 percent (by volume) skeletans on faces of
peds in the layer that has a 20 percent lower clay content or,
below that layer, no clay increase of 3 percent or more
(absolute) in the fine-earth fraction.
Key to Subgroups
HEBA. Haploxerults that have both:
1. A lithic contact within 50 cm of the mineral soil
surface; and
2. In each pedon, a discontinuous argillic or kandic
horizon that is interrupted by ledges of bedrock.
Lithic Ruptic-Inceptic Haploxerults
HEBB. Other Haploxerults that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Haploxerults
HEBC. Other Haploxerults that have, in one or more
subhorizons within the upper 25 cm of the argillic or kandic
horizon, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less, accompanied by redox
concentrations and by aquic conditions for some time in
normal years (or artificial drainage).
Aquic Haploxerults
HEBD. Other Haploxerults that have, throughout one or
more horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm3
or less, measured at 33 kPa
water retention, and Al plus 1
/2 Fe percentages (by ammonium
oxalate) totaling more than 1.0.
Andic Haploxerults
HEBE. Other Haploxerults that have an argillic or kandic
horizon that:
Ultisols 779
1. Consists entirely of lamellae; or
2. Is a combination of two or more lamellae and one or more
subhorizons with a thickness of 7.5 to 20 cm, each layer with
an overlying eluvial horizon; or
3. Consists of one or more subhorizons that are more
than 20 cm thick, each with an overlying eluvial horizon,
and above these horizons there are either:
a. Two or more lamellae with a combined thickness of
5 cm or more (that may or may not be part of the argillic
or kandic horizon); or
b. A combination of lamellae (that may or may not be
part of the argillic or kandic horizon) and one or more
parts o the argillic or kandic horizon 7.5 to 20 cm thick,
each with an overlying eluvial horizon.
Lamellic Haploxerults
HEBF. Other Haploxerults that have a sandy particle-size
class throughout the upper 75 cm of the argillic or kandic
horizon or throughout the entire horizon if it is less than 75 cm
thick.
Psammentic Haploxerults
HEBG. Other Haploxerults that have a sandy or sandyskeletal
particle-size class throughout a layer extending from
the mineral soil surface to the top of an argillic or kandic
horizon at a depth of 50 to 100 cm.
Arenic Haploxerults
HEBH. Other Haploxerults that have a sandy or sandyskeletal
particle-size class throughout a layer extending from
the mineral soil surface to the top of an argillic or kandic
horizon at a depth of 100 cm or more.
Grossarenic Haploxerults
HEBI. Other Haploxerults.
Typic Haploxerults
Definition of Typic Haploxerults
Typic Haploxerults are the Haploxerults that:
1. Do not have, in any subhorizon within the upper 25 cm of
the argillic horizon, redox depletions with a color value, moist,
of 4 or more and chroma of 2 or less, accompanied by redox
concentrations and by aquic conditions;
2. Do not have a lithic contact within 50 cm of the mineral
soil surface;
3. Have an argillic or kandic horizon that is finer than the
sandy particle-size class in some part of the upper 75 cm if the
argillic or kandic horizon is more than 75 cm thick or in any
part if the argillic or kandic horizon is less than 75 cm thick;
4. Do not have, throughout a cumulative thickness of 18 cm
or more and within a depth of 75 cm, a bulk density, in the
fraction less than 2.0 mm in size, of 1.0 g/cm3
or less,
measured at 33 kPa water retention, and acid-oxalateextractable
aluminum plus 1
/2 acid-oxalate-extractable iron of
more than 1.0 percent;
5. Do not have a sandy or sandy-skeletal particle-size class
throughout a layer extending from the mineral soil surface to
the top of an argillic or kandic horizon at a depth of 50 to 100
cm; and
6. Have an argillic or kandic horizon that meets none of the
following:
a. Consists entirely of lamellae; or
b. Is a combination of two or more lamellae and one or
more subhorizons with a thickness of 7.5 to 20 cm, each
layer with an overlying eluvial horizon; or
c. Consists of one or more subhorizons that are more than
20 cm thick, each with an overlying eluvial horizon, and
above these horizons there are either:
(1) Two or more lamellae with a combined thickness
of 5 cm or more (that may or may not be part of the
argillic or kandic horizon); or
(2) A combination of lamellae (that may or may not be
part of the argillic or kandic horizon) and one or more
parts of the argillic or kandic horizon 7.5 to 20 cm thick,
each with an overlying eluvial horizon.
Description of Subgroups
Typic Haploxerults.—The central concept or Typic
subgroup of Haploxerults is fixed on freely drained soils that
are deep or moderately deep to hard rock, have an epipedon
that is not both thick and sandy (not sand or loamy sand), have
a continuous argillic or kandic horizon throughout the pedon,
and do not have a surface mantle that is influenced by
pyroclastic materials. Most of the Haploxerults in the United
States are Typic Haploxerults. Typic Haploxerults occur mostly
in the Sierra Nevada and Cascade Mountains in California and
Oregon. The natural vegetation consists mostly of coniferous
forest plants, but in some areas it consists of savanna plants or
is dominated by shrubs. These soils are of moderate extent.
Most are used as forest. Where slopes are suitable, some of the
soils have been cleared and are used as cropland, pasture, or
homesites.
Andic Haploxerults.—These soils have a surface mantle or
layer in the upper 75 cm that has both a low bulk density and a
high content of weakly crystalline minerals in at least some
part of the upper 75 cm. The soils are not known to occur in
the United States. They are defined for use in other parts of the
world.
Aquic Haploxerults.—These soils have redox depletions
with low chroma and also aquic conditions at a shallow depth
for some time in normal years. The soils are not known to
780 Soil Taxonomy
occur in the United States. They are defined for use in other
parts of the world.
Arenic Haploxerults.—These soils have a layer, starting at
the mineral soil surface, that has a sandy or sandy-skeletal
particle-size class and is between 50 and 100 cm thick. The
soils are not known to occur in the United States. They are
defined for use in other parts of the world.
Grossarenic Haploxerults.—These soils have a layer,
starting at the mineral soil surface and extending to the top of
the argillic or kandic horizon, that has a sandy or sandyskeletal
particle-size class and is more than 100 cm thick. The
soils are not known to occur in the United States. The subgroup
is provided for use in other parts of the world.
Lamellic Haploxerults.—These soils have an argillic or
kandic horizon that consists entirely of lamellae or is a
combination of two or more lamellae and one or more
subhorizons with a thickness of 7.5 to 20 cm, each layer with
an overlying eluvial horizon. In some of the soils, the argillic
or kandic horizon consists of one or more subhorizons that are
more than 20 cm thick, each with an overlying eluvial horizon,
and above these horizons there are either two or more lamellae
with a combined thickness of 5 cm or more or a combination of
lamellae and one or more parts of the argillic or kandic horizon
7.5 to 20 cm thick, each with an overlying eluvial horizon.
Lamellic Haploxerults are not known to occur in the United
States. The subgroup is provided for use in other parts of the
world.
Lithic Haploxerults.—These soils are like Typic
Haploxerults, but they have a lithic contact within 50 cm of the
mineral soil surface. They are not known to occur in the United
States. The subgroup is provided for use in other parts of the
world.
Lithic Ruptic-Inceptic Haploxerults.—These soils have a
lithic contact within 50 cm of the mineral soil surface and an
intermittent argillic or kandic horizon. They characteristically
have an irregular or wavy boundary at the lithic contact. The
argillic or kandic horizon typically does not occur in the parts
of the pedon that have a very shallow lithic contact. These soils
are not known to occur in the United States. The subgroup is
provided for use in other parts of the world.
Psammentic Haploxerults.—These soils have an argillic or
kandic horizon that has a sandy or sandy-skeletal particle-size
class throughout or throughout the upper 75 cm if the horizon
is more than 75 cm thick. The soils are not known to occur in
the United States. The subgroup is provided for use in other
parts of the world.
Palexerults
These are the Xerults that have a clay distribution in which
the percentage of clay does not decrease from its maximum
amount by as much as 20 percent within a depth of 150 cm
from the mineral soil surface, or the layer in which the clay
percentage decreases has at least 5 percent of the volume
consisting of skeletans on faces of peds and there is at least a 3
percent increase in clay content below this layer. These soils
are mainly on old stable or metastable surfaces in the Cascade
and coastal mountains of Oregon and California. Slopes are
gentle to very steep. The soils are probably rare in the world,
but they may be extensive locally in areas of humid
Mediterranean climates.
Definition
Palexerults are the Xerults that:
1. Do not have a densic, lithic, or paralithic contact
within 150 cm of the mineral soil surface; and
2. Within 150 cm of the mineral soil surface, either:
a. With increasing depth, do not have a clay decrease of 20
percent or more (relative) from the maximum clay content;
or
b. Have 5 percent or more (by volume) skeletans on faces
of peds in the layer that has a 20 percent lower clay content
and, below that layer, a clay increase of 3 percent or more
(absolute) in the fine-earth fraction.
Key to Subgroups
HEAA. Palexerults that have both:
1. In one or more subhorizons within the upper 25 cm of
the argillic or kandic horizon, redox depletions with a color
value, moist, of 4 or more and chroma of 2 or less,
accompanied by redox concentrations, and also aquic
conditions for some time in normal years (or artificial
drainage); and
2. Throughout one or more horizons with a total thickness
of 18 cm or more within 75 cm of the mineral soil surface,
a fine-earth fraction with both a bulk density of 1.0 g/cm3
or less, measured at 33 kPa water retention, and Al plus
1
/2 Fe percentages (by ammonium oxalate) totaling more
than 1.0.
Aquandic Palexerults
HEAB. Other Palexerults that have, in one or more
subhorizons within the upper 25 cm of the argillic or kandic
horizon, redox depletions with a color value, moist, of 4 or
more and chroma of 2 or less, accompanied by redox
concentrations and by aquic conditions for some time in
normal years (or artificial drainage).
Aquic Palexerults
HEAC. Other Palexerults that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a
bulk density of 1.0 g/cm3
or less, measured at 33 kPa water
Ultisols 781
retention, and Al plus 1
/2 Fe percentages (by ammonium oxalate)
totaling more than 1.0.
Andic Palexerults
HEAD. Other Palexerults.
Typic Palexerults
Definition of Typic Palexerults
Typic Palexerults are the Palexerults that:
1. Do not have, in one or more subhorizons within the
upper 25 cm of the argillic or kandic horizon, redox depletions
with a color value, moist, of 4 or more and chroma of 2 or less,
accompanied by redox concentrations and by aquic conditions
for some time in normal years;
2. Do not have, throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the mineral soil
surface, a fine-earth fraction with both a bulk density of 1.0
g/cm3
or less, measured at 33 kPa water retention, and Al plus
1
/2 Fe percentages (by ammonium oxalate) totaling more than
1.0.
Description of Subgroups
Typic Palexerults.—The central concept or Typic subgroup
of Palexerults is fixed on well drained soils that are not
significantly influenced by volcanic ash. These soils are on old
landscapes, and in some areas the clay mineralogy is
influenced by kaolinite. The soils occur in the Pacific
Northwest and are used for timber production.
Andic Palexerults.—These are the well drained Palexerults
that are significantly influenced by volcanic ash. When
weathered, the volcanic ash influences P-retention, porosity,
and other soil properties. These soils occur in the Pacific
Northwest and are used for timber production.
Aquandic Palexerults.—These soils have aquic conditions
in the upper 25 cm of the argillic or kandic horizon and are
significantly influenced by volcanic ash. The soils occur in the
Pacific Northwest and are used for timber production.
Aquic Palexerults.—These soils have aquic conditions in
the upper 25 cm of the argillic or kandic horizon but are not
significantly influenced by volcanic ash. The soils occur in the
Pacific Northwest and are used for timber production.
783
The central concept of Vertisols is that of clayey soils that
have deep, wide cracks for some time during the year
and have slickensides within 100 cm of the mineral soil
surface. They shrink when dry and swell when moistened.
Vertisols make up a relatively homogeneous order because of
the amounts and kinds of clay common to them; however, their
microvariability within a pedon is great. Before the advent of
modern classification systems, these soils were already well
known for their characteristic color, the cracks they produce
during the dry season, and the difficulty of their engineering
properties.
In many countries where Vertisols are extensive, they are
known by local names, such as cracking clays (Australia),
Adobe (Philippines), Shachiang (China), Black Cotton soils
(India), Smolnitza (Bulgaria, Rumania), Tirs (Morocco),
Makande (Malawi), Vleigrond (South Africa), and Sonsosuite
(Nicaragua). In addition, numerous coined terms have been
used to identify the soils. Examples are Margalite soils
(Indonesia), Densinegra soils (Angola), and Grumusols
(United States).
These soils generally are sticky in the wet season and hard
in the dry season, so they require special cultivation practices
regardless of whether modern equipment or traditional
implements, such as a hoe or bullock-drawn plow, are used.
Because their unique properties restrict engineering uses, the
soils are well known among engineers. The movement of these
soils can tilt trees; throw fenceposts, telephone poles, and
power poles out of line; and break pipelines, highway
pavements, and the masonry foundations of buildings.
Vertisols are mapped in many countries. The largest areas
are in Australia (80,000,000 ha), India (73,000,000 ha), the
Sudan (50,000,000 ha), and the United States (18,000,000 ha).
The soil moisture regime is ustic in about 65 percent of the
areas where the Vertisols occur, aridic in 18 percent of the
areas, udic in 13 percent, and xeric in 4 percent. The defined
moisture regimes, however, have little significance in areas of
these soils because, when rainfall occurs, the water commonly
runs into the cracks, so that the soils are remoistened from both
above and below. Because of the difficulty in defining soil
moisture regimes in Vertisols, the duration that cracks open
CHAPTER 20
Vertisols1
and close are used to differentiate the various soil moisture
regimes. Vertisols are known to occur in all soil temperature
regimes that are cryic and warmer.
The shrink-swell phenomenon, which is responsible for the
genesis and behavior of Vertisols, is a complex, dynamic, but
incompletely understood set of processes. Expressions of this
phenomenon are linear and normal gilgai, cyclic horizons,
surface cracking upon desiccation, and the formation of
slickensides. Of these properties, cracks when the soils are dry
and slickensides are the unifying morphogenetic markers in all
Vertisols. Although the process of shrinking and swelling is
important in Vertisols, it does not preclude the formation of
diagnostic horizons and features. For example, Vertisols can
have calcic, gypsic, or salic horizons. Taxa have been
developed to accommodate these diagnostic horizons and
features.
Internal movement affects the thickness of soil horizons,
which can vary widely within a pedon. A black A horizon, for
example, may be only a few centimeters thick or even absent
on microknolls but is more than 100 cm thick in
microdepressions. The organic-matter content and the depth to
carbonates or to a Bk horizon can be equally variable.
Shrink-swell processes in soils are related to the total
content of clay, the content of fine clay, and mineralogy.
Vertisols generally have a high clay content (50 to 70 percent)
and a relatively large proportion of fine clay in the clay
fraction. The clays in Vertisols consist predominantly of 2:1and
2:2-layer clay minerals, but some have considerable
amounts of other clay minerals. Apart from the amounts and
types of clay, a number of other factors determine the
morphological features of Vertisols. Prior soil moisture content,
for example, is a very important factor in the shrink-swell
process; vertic features are best expressed where the soil has
undergone maximum change from a wet to a dry state. The
moisture change by itself, however, is insufficient to induce all
the vertic properties. To produce movement along the
slickensides, there must be a confining pressure, which is
provided by the thickness of the soil material above the
slickensides. The shrink-swell potential of the clays may be
reduced by an admixture of organic matter, carbonates, or other
particles. The coefficient of linear extensibility (COLE)
normally ranges from 0.07 to 0.2.
Intergrades to Vertisols are recognized in several of the
1
This chapter was rewritten in 1992 following the recommendations of the International
Committee on the Classification of Vertisols (ICOMERT), chaired by Dr. Juan Comerma.
784 Soil Taxonomy
other soil orders. There are basically two kinds of intergrades,
although both are considered in the same subgroup. One
consists of soils that show evidence of swelling and shrinking
as a result of changes from a wet to a dry state but that do not
meet the minimum requirements for Vertisols. The intergrades
of the other kind show little or no evidence of actual soil
movement, but they have potential for soil movement because
of the relatively high COLE. These intergrades, however, do
not become dry enough or moist enough for soil movement to
occur, except in years with unusually low or abnormally high
precipitation.
Vertisols generally have gentle slopes, although a few are
strongly sloping. The natural vegetation is predominantly
grass, savanna, open forest, or desert shrub.
Most Vertisols are well suited to mechanized farming if
there is plenty of rainfall or irrigation water and if suitable
management practices are followed. Large areas of Vertisols in
the world are not farmed, however, because their cultivation
would require too much energy, especially where traditional,
low-input methods are used. This constraint is a major limiting
land-use characteristic of Vertisols.
Irrigation of Usterts, Xererts, and Torrerts presents special
problems because of very slow permeability. Bypass flow
through open cracks is common. Because the permeability of
these soils is so slow, irrigation may result in waterlogging and
a buildup of salinity unless adequate artificial drainage is
provided. A drainage system designed for Alfisols or Ultisols
may be totally inadequate for Vertisols.
Definition of Vertisols and Limits Between
Vertisols and Soils of Other Orders
Vertisols are mineral soils that have all of the following:
1. A layer 25 cm or more thick, with an upper boundary
within 100 cm of the mineral soil surface, that has either
slickensides close enough to intersect or wedge-shaped
structural units that have their long axes tilted 10 to 60 degrees
from the horizontal; and
2. A weighted average of 30 percent or more clay in the fineearth
fraction either between the mineral soil surface and a
depth of 18 cm or in an Ap horizon, whichever is thicker, and
30 percent or more clay in the fine-earth fraction of all
horizons between a depth of 18 cm and either a depth of 50 cm
or a densic, lithic, or paralithic contact, a duripan, or a
petrocalcic horizon if shallower; and
3. Cracks2
that open and close periodically.
Limits Between Vertisols and Soils of Other
Orders
The definition of Vertisols must provide criteria that separate
Vertisols from all other soil orders. The aggregate of these
criteria defines the limits of Vertisols in relation to the other
known kinds of soil.
1. Unlike Gelisols, Vertisols do not have permafrost
within 100 cm of the soil surface or both permafrost within
200 cm of the soil surface and gelic materials within 100 cm
of the soil surface.
2. Unlike Andisols, Vertisols do not have andic soil
properties in 60 percent or more of the thickness between
either the mineral soil surface or the top of an organic layer
with andic soil properties, whichever is shallower, and a depth
of 60 cm or a densic, lithic, or paralithic contact, a duripan, or
a petrocalcic horizon, whichever is shallowest.
3. Unlike Spodosols, Vertisols do not have a spodic horizon
or an Ap horizon consisting of spodic materials.
4. Unlike Oxisols, Vertisols do not have, within 150 cm of
the mineral soil surface, an oxic horizon or a kandic horizon
that meets the weatherable-mineral requirements for an oxic
horizon and also 40 percent or more clay in the surface 18 cm
after mixing.
5. Unlike Alfisols, Ultisols, Inceptisols, Aridisols, and
Entisols, Vertisols have the following properties:
a. A layer 25 cm or more thick, with an upper boundary
within 100 cm of the mineral soil surface, that has either
slickensides close enough to intersect or wedge-shaped
structural units that have their long axes tilted 10 to 60
degrees from the horizontal; and
b. A weighted average of 30 percent or more clay in the
fine-earth fraction either between the mineral soil surface
and a depth of 18 cm or in an Ap horizon, whichever is
thicker, and 30 percent or more clay in the fine-earth
fraction of all horizons between a depth of 18 cm and either
a depth of 50 cm or a densic, lithic, or paralithic contact, a
duripan, or a petrocalcic horizon if shallower; and
c. Cracks that open and close periodically.
Representative Pedon and Data
Following is a description of a representative Vertisol. Data
for the pedon identified in this description are given in the
table “Characterization Data for a Vertisol.”
Classification: Fine, smectitic, isohyperthermic Typic Haplustert
Site identification number: 90P0616
Location: Icrasat Prod. Agriculture Field #Bw1, India
Latitude: 16 degrees 00 minutes 00 seconds N.
2
A crack is a separation between gross polyhedrons. If the surface horizon is strongly selfmulching,
i.e., a mass of loose granules, or if the soil is cultivated while cracks are open, the
cracks may be largely filled with granular materials from the surface, but they are open in the
sense that the polyhedrons are separated. A crack is regarded as open if it controls the
infiltration and percolation of water in a dry, clayey soil.
Vertisols 785
Longitude: 78 degrees 00 minutes 00 seconds E.
Landscape: Plains
Landform: Playa
Microrelief: 20 to 50 cm, linear
Slope: 1 percent, plane, northeast facing
Annual precipitation: 760 mm
Weather station: Icrasat
Soil moisture regime: Ustic
Permeability class: Moderately slow
Drainage class: Well drained
Depth to water table: More than 200 cm
Land use: Cropland
Vegetation: Sorghum, pigeon pea
Hazard of erosion or deposition: Slight
Runoff: None
Parent material: Alluvium derived from igneous material
Described by: R.J. Engel
In the following pedon description, colors are for moist soil
unless otherwise indicated.
Ap—0 to 15 cm; dusky red (2.5YR 3/2), crushed, clay;
moderate medium subangular blocky structure parting to
moderate very fine and fine subangular blocky; very firm,
very sticky and very plastic; many very fine and fine roots
throughout; many very fine and fine vesicular and tubular
pores; neutral (pH 7.2); 5 percent igneous pebbles; abrupt
smooth boundary.
AB—15 to 30 cm; very dark gray (10YR 3/1), crushed, clay;
moderate fine and medium subangular blocky structure;
very firm, very sticky and very plastic; common very fine
and fine roots throughout; many very fine and fine
vesicular and tubular pores; neutral (pH 7.0); 2 percent
igneous pebbles; clear wavy boundary.
Bss1—30 to 53 cm; very dark gray (10YR 3/1), crushed, clay;
strong fine angular blocky structure parting to strong fine
subangular blocky; very firm, very sticky and very plastic;
common very fine and fine roots between peds; common
very fine and fine tubular pores; few discontinuous distinct
intersecting slickensides on horizontal faces of peds;
neutral (pH 7.0); 1 percent igneous pebbles; clear wavy
boundary.
Bss2—53 to 89 cm; very dark gray (10YR 3/1), crushed,
clay; strong fine angular blocky structure; very firm, very
sticky and very plastic; few very fine and fine roots
between peds; common very fine and fine tubular pores;
common continuous distinct intersecting slickensides on
horizontal faces of peds; neutral (pH 7.0); gradual wavy
boundary.
Bss3—89 to 122 cm; very dark grayish brown (2.5Y 3/2),
crushed, clay; strong fine and medium angular blocky
structure; very firm, very sticky and very plastic; few very
fine and fine roots between peds; common very fine and
fine tubular pores; common continuous distinct
intersecting slickensides on horizontal faces of peds;
neutral (pH 7.0); gradual wavy boundary.
Bssck1—122 to 155 cm; dark grayish brown (2.5Y 4/2), crushed,
clay; strong medium and coarse angular blocky structure;
very firm, very sticky and very plastic; few very fine and
fine roots between peds; common continuous distinct
intersecting slickensides on horizontal faces of peds;
common irregular carbonate concretions and common
medium and coarse rounded dark concretions; moderately
alkaline (pH 8.0); gradual wavy boundary.
Bssck2—155 to 193 cm; dark grayish brown (2.5Y 4/2),
crushed, clay; strong medium and coarse angular blocky
structure; very firm, very sticky and very plastic; few very
fine and fine roots between peds; common continuous
distinct intersecting slickensides on horizontal faces of
peds; common irregular carbonate concretions and
common medium and coarse rounded dark concretions;
moderately alkaline (pH 8.0); clear smooth boundary.
Bck—193 to 234 cm; olive brown (2.5Y 4/4), crushed, clay;
moderate medium and coarse angular blocky structure;
very firm, very sticky and very plastic; many irregular
carbonate concretions and common medium and coarse
rounded dark concretions; moderately alkaline (pH 8.2).
Key to Suborders
FA. Vertisols that have, in one or more horizons within 50 cm
of the mineral soil surface, aquic conditions for some time in
normal years (or artificial drainage) and one or both of the
following:
1. In more than half of each pedon, either on faces of peds
or in the matrix if peds are absent, 50 percent or more
chroma of either:
a. 2 or less if redox concentrations are present; or
b. 1 or less; or
2. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated.
Aquerts, p. 787
FB. Other Vertisols that have a cryic soil temperature regime.
Cryerts, p. 796
FC. Other Vertisols that in normal years have both:
1. A thermic, mesic, or frigid soil temperature regime; and
2. If not irrigated during the year, cracks that remain both:
a. 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 60 or
more consecutive days during the 90 days following the
summer solstice; and
786 Soil Taxonomy
Characterization Data for a Vertisol
SITE IDENTIFICATION NO.: 90P0616
CLASSIFICATION: FINE, SMECTITIC, ISOHYPERTHERMIC TYPIC HAPLUSTERT
GENERAL METHODS: 1B1A, 2A1, 2B
-1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-
-----------------------------------------------------------------------------------------------------------------------------------
(- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)
CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT
SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF
NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE
<- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL
90P3653 0- 14 Ap 49.0 26.3 24.7 8.0 20.4 5.9 4.8 8.9 5.7 3.1 2.2 6 4 1 29 11
90P3654 14- 29 AB 51.3 28.3 20.4 8.4 20.7 7.6 2.5 7.4 5.2 2.7 2.6 6 3 -- 25 9
90P3655 29- 54 Bss1 53.5 25.3 21.2 9.9 20.5 4.8 3.9 5.7 4.2 3.1 4.3 4 3 -- 23 7
90P3656 54- 89 Bss2 56.6 26.9 16.5 13.8 21.8 5.1 4.0 5.0 3.3 2.4 1.8 3 2 -- 17 5
90P3657 89-121 Bss3 61.2 25.9 12.9 18.2 21.6 4.3 2.9 3.5 2.3 2.2 2.0 1 2 -- 13 3
90P3658 121-155 Bssck1 61.0 27.4 11.6 24.1 21.6 5.8 2.5 4.1 2.5 1.4 1.1 2 2 -- 13 4
90P3659 155-193 Bssck2 60.7 24.5 14.8 27.0 1.3 21.0 3.5 3.1 4.0 2.9 2.4 2.4 5 7 -- 22 12
90P3660 193-234 Bck 58.3 24.3 17.4 27.0 1.3 21.0 3.3 3.3 4.4 3.1 2.8 3.8 5 24 -- 39 29
-----------------------------------------------------------------------------------------------------------------------------------
ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD
C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE
DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL
(cm) 6A1c 6B3a 6S3 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A3a 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1
Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm
0- 14 0.63 1.10 0.38 1.28 1.66 0.085 31.3 18.7 0.15
14- 29 0.42 1.06 0.39 1.27 1.68 0.092 32.7 19.9 0.16
29- 54 0.39 1.04 0.39 1.31 1.79 0.105 33.1 21.1 0.15
54- 89 0.35 1.02 0.42 1.24 1.91 0.151 38.7 23.5 0.18
89-121 0.19 0.92 0.42 1.25 1.91 0.149 37.5 25.4 0.15
121-155 0.11 0.93 0.42 1.19 1.96 0.176 39.7 25.6 0.16
155-193 0.08 0.89 0.41 1.08 1.85 0.181 48.1 24.9 0.24
193-234 0.04 0.86 0.42 1.25 1.89 0.118 36.5 24.2 0.13
-----------------------------------------------------------------------------------------------------------------------------------
(- NH4OAc EXTRACTABLE BASES -) ACID- (- -CEC- -) EXCH SAR BASE CO3 AS RES. CaSO4 AS (- - - -PH - - -)
Ca Mg Na K SUM ITY SUM NH4- Na SATURATION CaCO3 ohms GYPSUM SAT CaCl2 H2O
DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc SUM NH4OAc <2mm /cm <2mm <20mm PASTE .01M
(cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 5A3a 5A8b 5D2 5E 5C3 5C1 6E1g 8E1 6F1a 6F4 8C1b 8C1f 8C1f
<- - - - - - - - - -meq / 100 g - - - - - - - - - -> Pct <- -Pct- > Pct <- -Pct -> 1:2 1:1
0- 14 9.2 0.1 0.8 0.8 54.0 TR TR 100 1 7.7 7.2 7.6
14- 29 10.0 -- 0.7 54.6 -- 100 100 4 7.4 8.1
29- 54 13.1 0.1 0.9 1.0 55.9 TR 100 3 7.5 7.9
54- 89 18.2 0.4 0.8 57.5 1 100 100 2 7.6 8.3
89-121 21.2 1.1 0.8 56.4 2 2 100 100 3 1700 7.7 7.7 8.3
121-155 22.7 2.2 0.8 56.5 4 100 100 3 7.7 8.4
155-193 22.8 3.3 0.8 54.3 6 100 100 5 7.8 8.3
193-234 21.6 4.7 0.7 50.4 9 8 100 100 7 8.0 7.8 8.5
-----------------------------------------------------------------------------------------------------------------------------------
(- - - - - - - - - - -WATER EXTRACTED FROM SATURATED PASTE- - - - - - - - - - - - - )PRED.
TOTAL ELEC. ELEC.
Ca Mg Na K CO3 HCO3 F Cl SO4 NO2 NO3 H2O SALTS COND. COND.
DEPTH EST. 8A3a 8I
(cm) 6N1b 6O1b 6P1b 6Q1b 6I1b 6J1b 6U1a 6K1c 6L1c 6W1a 6M1c 8A 8D5 mmhos mmhos
< - - - - - - - - - - - - - -meq / liter - - - - - - - - - - - -> <- -Pct- -> /cm /cm
0- 14 4.2 1.1 0.1 0.1 -- 4.5 0.1 0.2 0.7 -- -- 72.9 TR 0.49 0.29
14- 29 0.19
29- 54 0.17
54- 89 0.20
89-121 1.3 0.8 1.8 TR -- 2.3 0.2 0.1 1.3 0.1 -- 91.3 TR 0.39 0.27
121-155 0.02
155-193 0.01
193-234 0.3 0.2 4.2 TR -- 2.6 0.6 0.2 0.9 0.1 0.4 98.4 TR 0.48 0.44
-----------------------------------------------------------------------------------------------------------------------------------
< - - - - - - - - - - - - - - - - - - - - - - - CLAY MINERALOGY (<.002mm) - - - - - - - - - - - - - - - - - - - - - - >
FRAC- < - - - - - X-RAY - - - - - ->< - - - THERMAL - - - ->< - - - - - - - ELEMENTAL - - - - - - - ->< - -> EGME INTERSAMPLE
TION < >< - DTA - ->< - TGA - -> SiO2 Al2O3 Fe2O3 MgO CaO K2O Na2O < > RETN PRETA<
- - - - - 7A2i - - - - - ->< - 7A6 - >< - 7A4b - >< - - - - - - - - - 7C3 - - - - - - - - ->< > 7D2 TION
NUMBER <- - >< - - - - Peak size - - - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - -><mg/g>< - ->
90P3655 TCLY MT 4 KK 2 MI 2 QZ 1 19.0 9.7 1.0
90P3657 TCLY MT 4 KK 3 MI 2 QZ 1 20.0 9.9 1.2
90P3659 TCLY MT 4 KK 2 MI 2 QZ 1 19.0 9.7 1.3
-----------------------------------------------------------------------------------------------------------------------------------
The chemical data are based on the fraction less than 2 mm in size.
Fraction interpretation: TCLY, total clay, <0.002 mm.
Mineral interpretation: MT, montmorillonite; KK, kaolinite; MI, mica; QZ, quartz.
Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.
Pedon mineralogy based on clay: Smectitic.
Family mineralogy: Smectitic.
Vertisols 787
b. Closed for 60 or more consecutive days during the 90
days following the winter solstice.
Xererts, p. 813
FD. Other Vertisols that, if not irrigated during the year, have
cracks in normal years that remain closed for less than 60
consecutive days during a period when the soil temperature at a
depth of 50 cm from the soil surface is higher than 8 o
C.
Torrerts, p. 797
FE. Other Vertisols that, if not irrigated during the year, have
cracks in normal years that are 5 mm or more wide, through a
thickness of 25 cm or more within 50 cm of the mineral soil
surface, for 90 or more cumulative days per year.
Usterts, p. 804
FF. Other Vertisols.
Uderts, p. 801
Aquerts
Aquerts are the wet Vertisols. They have aquic conditions at
or near the surface for extended periods during the year, but
they also are dry for periods long enough in normal years for
cracks to open. These soils are typically in low areas, such as
glacial lake plains, flood plains, stream terraces, and
depressions. Previously, there were no provisions for wet
Vertisols in soil taxonomy, and these soils were assigned to the
Vertic subgroups of Aquolls, Aqualfs, and Aquepts.
Definition
Aquerts are the Vertisols that have, in one or more horizons
within 50 cm of the mineral soil surface, aquic conditions for
some time in normal years (or artificial drainage) and one or
both of the following:
1. In more than half of each pedon, either on faces of peds or
in the matrix if peds are absent, 50 percent or more chroma of
either:
a. 2 or less if redox concentrations are present; or
b. 1 or less; or
2. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is not
being irrigated.
Key to Great Groups
FAA. Aquerts that have a salic horizon that has its upper
boundary within 100 cm of the mineral soil surface.
Salaquerts, p. 795
FAB. Other Aquerts that have a duripan that has its upper
boundary within 100 cm of the mineral soil surface.
Duraquerts, p. 788
FAC. Other Aquerts that have a natric horizon or have an
exchangeable sodium percentage of 15 percent or more (or a
sodium adsorption ratio of 13 or more) within 100 cm of the
mineral soil surface.
Natraquerts, p. 795
FAD. Other Aquerts that have a calcic horizon that has its
upper boundary within 100 cm of the mineral soil surface.
Calciaquerts, p. 787
FAE. Other Aquerts that have, throughout one or more
horizons with a total thickness of 25 cm or more within 50 cm
of the mineral soil surface, both:
1. An electrical conductivity in the saturation extract of less
than 4.0 dS/m at 25 o
C; and
2. A pH value of 4.5 or less in 0.01 M CaCl2
(5.0 or less in 1:1
water).
Dystraquerts, p. 789
FAF. Other Aquerts that have episaturation.
Epiaquerts, p. 793
FAG. Other Aquerts.
Endoaquerts, p. 791
Calciaquerts
Calciaquerts are the Aquerts that have a calcic horizon. In
addition, they commonly have a mollic epipedon. In the United
States, these soils occur on the northern Great Plains. They are
used mostly for crops. Before 1992, most of these soils were
classified as Calciaquolls.
Definition of Subgroups
Calciaquerts are the Aquerts that:
1. Have a calcic horizon that has its upper boundary
within 100 cm of the mineral soil surface;
2. Do not have a salic horizon or a duripan that has its upper
boundary within 100 cm of the mineral soil surface; and
3. Do not have a natric horizon or an exchangeable sodium
percentage of 15 percent or more (or a sodium adsorption ratio
of 13 or more) within 100 cm of the mineral soil surface.
Key to Subgroups
FADA. Calciaquerts that have, in one or more horizons
between either an Ap horizon or a depth of 25 cm from the
788 Soil Taxonomy
mineral soil surface, whichever is deeper, and either a depth of 75
cm or the upper boundary of a duripan if shallower, 50 percent or
more colors as follows:
1. Hue of 2.5Y or redder and either:
a. A color value, moist, of 6 or more and chroma of 3 or
more; or
b. A color value, moist, of 5 or less and chroma of 2 or
more; or
2. Hue of 5Y and chroma of 3 or more; or
3. Chroma of 2 or more and no redox concentrations.
Aeric Calciaquerts
FADB. Other Calciaquerts.
Typic Calciaquerts
Definition of Typic Calciaquerts
Typic Calciaquerts are the Calciaquerts that, in more than
half of each pedon, do not have a horizon, between either an
Ap horizon or a depth of 25 cm from the mineral soil surface,
whichever is deeper, and either a depth of 75 cm or the upper
boundary of a duripan if shallower, that has any of the
following:
1. Hue of 2.5Y or redder and either:
a. A color value, moist, of 6 or more and chroma of 3 or
more; or
b. A color value, moist, of 5 or less and chroma of 2 or
more; or
2. Hue of 5Y or yellower and chroma of 3 or more; or
3. Chroma of 2 or more and no redox concentrations.
Description of Subgroups
Typic Calciaquerts.—The Typic subgroup of Calciaquerts
is centered on poorly drained or very poorly drained soils that
have dominantly gleyed colors close to the surface. These soils
occur in Minnesota, Montana, South Dakota, and North
Dakota and are used for small grain or sugar beets.
Aeric Calciaquerts.—These are the Calciaquerts with
dominantly bright colored layers toward the soil surface. These
soils do not have aquic conditions that persist for long periods.
They occur in Minnesota and are used for small grain, sugar
beets, or sunflowers.
Duraquerts
Duraquerts are the Aquerts that have a duripan. These soils
commonly are derived from volcanic materials. In the United
States, all of these soils have aquic conditions for part of the
year and either have a xeric moisture regime or border a xeric
moisture regime. Several subgroups are provided for use in other
parts of the world.
Definition
Duraquerts are the Aquerts that:
1. Do not have a salic horizon that has its upper boundary
within 100 cm of the mineral soil surface; and
2. Have a duripan that has its upper boundary within 100 cm
of the mineral soil surface.
Key to Subgroups
FABA. Duraquerts that, if not irrigated during the year, have
cracks in normal years that are 5 mm or more wide, through a
thickness of 25 cm or more within 50 cm of the mineral soil
surface, for 210 or more cumulative days per year.
Aridic Duraquerts
FABB. Other Duraquerts that have a thermic, mesic, or frigid
soil temperature regime and that, if not irrigated during the
year, have cracks in normal years that remain both:
1. 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 60 or
more consecutive days during the 90 days following the
summer solstice; and
2. Closed for 60 or more consecutive days during the 90
days following the winter solstice.
Xeric Duraquerts
FABC. Other Duraquerts that, if not irrigated during the
year, have cracks in normal years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50 cm of the
mineral soil surface, for 90 or more cumulative days per year.
Ustic Duraquerts
FABD. Other Duraquerts that have, in one or more horizons
between either an Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and either a depth of
75 cm or the upper boundary of the duripan if shallower, 50
percent or more colors as follows:
1. Hue of 2.5Y or redder and either:
a. A color value, moist, of 6 or more and chroma of 3
or more; or
b. A color value, moist, of 5 or less and chroma of 2 or
more; or
2. Hue of 5Y and chroma of 3 or more; or
3. Chroma of 2 or more and no redox concentrations.
Aeric Duraquerts
FABE. Other Duraquerts that have, in one or more horizons
Vertisols 789
within 30 cm of the mineral soil surface, one or both of the
following in more than half of each pedon:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more.
Chromic Duraquerts
FABF. Other Duraquerts.
Typic Duraquerts
Definition of Typic Duraquerts
Typic Duraquerts are the Duraquerts that:
1. If not irrigated during the year, do not have cracks in
normal years that are 5 mm or more wide, through a thickness
of 25 cm or more within 50 cm of the mineral soil surface, for
90 or more cumulative days per year;
2. Do not have, in more than half of each pedon, a horizon,
between either an Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and either a depth of
75 cm or the upper boundary of the duripan if shallower, that
has any of the following:
a. Hue of 2.5Y or redder and either:
(1) A color value, moist, of 6 or more and chroma of 3
or more; or
(2) A color value, moist, of 5 or less and chroma of 2 or
more; or
b. Hue of 5Y or yellower and chroma of 3 or more; or
c. Chroma of 2 or more and no redox concentrations;
3. Have, in all horizons within 30 cm of the mineral soil
surface, one or both of the following in more than half of each
pedon:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less; and
4. Do not have both a thermic, mesic, or frigid soil
temperature regime and, if not irrigated during the year, cracks
in normal years that remain both:
a. 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 60 or
more consecutive days during the 90 days following the
summer solstice; and
b. Closed for 60 or more consecutive days during the 90
days following the winter solstice.
Description of Subgroups
Typic Duraquerts.—The Typic subgroup of Duraquerts is
centered on poorly drained or very poorly drained soils with
dark colored surface layers. These soils do not have a moisture
regime that borders on xeric, aridic, or ustic. They are not known
to occur in the United States.
Aeric Duraquerts.—These are the Duraquerts that
commonly are considered to be somewhat poorly drained.
Bright colors toward the surface indicate that aquic conditions
do not persist for long periods. These soils do not have a
moisture regime that borders on aridic, ustic, or xeric.
Aridic Duraquerts.—These are the Duraquerts that have
aquic conditions for short periods during the year and are dry
for most of the year. These soils require cracks to be open 210
cumulative days during normal years.
Chromic Duraquerts.—These are the Duraquerts that have
light colored surface layers. They are dominantly gleyed below
the surface layers and do not have a moisture regime that
borders on aridic, ustic, or xeric.
Ustic Duraquerts.—These are the Duraquerts that have a
moisture regime that borders on ustic. These soils have aquic
conditions for part of the year but have moisture deficits for
much of the growing season.
Xeric Duraquerts.—These are the Duraquerts that have
aquic conditions for at least a part of the winter but are dry
during the summer. These soils occur in California. They are
used for pasture or irrigated crops, including rice.
Dystraquerts
Dystraquerts are the Aquerts that have dominantly low pH
values and low electrical conductivity in the upper 50 cm.
These soils commonly occur in low areas, such as flood plains
and terraces, but a few occur on uplands. The soils are
extensive in the Southern United States. Many of them are
cropped, but some are forested.
Definition
Dystraquerts are the Aquerts that:
1. Have, throughout one or more horizons with a total
thickness of 25 cm or more within 50 cm of the mineral soil
surface, both:
a. An electrical conductivity in the saturation extract of
less than 4.0 dS/m at 25 o
C; and
b. A pH value of 4.5 or less in 0.01 M CaCl2
(5.0 or less in
1:1 water);
2. Do not have a calcic or salic horizon or a duripan that has
its upper boundary within 100 cm of the mineral soil surface;
and
3. Do not have a natric horizon or an exchangeable sodium
percentage of 15 percent or more (or a sodium adsorption ratio
of 13 or more) within 100 cm of the mineral soil surface.
Key to Subgroups
FAEA. Dystraquerts that have, in one or more horizons
within 100 cm of the mineral soil surface, jarosite concentrations
790 Soil Taxonomy
and a pH value of 4.0 or less (1:1 water, air-dried slowly in
shade).
Sulfaqueptic Dystraquerts
FAEB. Other Dystraquerts that, if not irrigated during the
year, have cracks in normal years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50 cm of the
mineral soil surface, for 210 or more cumulative days per year.
Aridic Dystraquerts
FAEC. Other Dystraquerts that, if not irrigated during the
year, have cracks in normal years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50 cm of the
mineral soil surface, for 90 or more cumulative days per year.
Ustic Dystraquerts
FAED. Other Dystraquerts that have, in one or more horizons
between either an Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and a depth of 75
cm, 50 percent or more colors as follows:
1. Hue of 2.5Y or redder and either:
a. A color value, moist, of 6 or more and chroma of 3
or more; or
b. A color value, moist, of 5 or less and chroma of 2 or
more; or
2. Hue of 5Y and chroma of 3 or more; or
3. Chroma of 2 or more and no redox concentrations.
Aeric Dystraquerts
FAEE. Other Dystraquerts that have a densic, lithic, or
paralithic contact within 100 cm of the mineral soil surface.
Leptic Dystraquerts
FAEF. Other Dystraquerts that have a layer 25 cm or more
thick that contains less than 27 percent clay in its fine-earth
fraction and has its upper boundary within 100 cm of the
mineral soil surface.
Entic Dystraquerts
FAEG. Other Dystraquerts that have, in one or more horizons
within 30 cm of the mineral soil surface, one or both of the
following in more than half of each pedon:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more.
Chromic Dystraquerts
FAEH. Other Dystraquerts.
Typic Dystraquerts
Definition of Typic Dystraquerts
Typic Dystraquerts are the Dystraquerts that:
1. Do not have, in any horizon within 100 cm of the mineral soil
surface, both jarosite concentrations and a pH value of 4.0 or
less (1:1 water, air-dried slowly in shade);
2. If not irrigated during the year, do not have cracks in normal
years that are 5 mm or more wide, through a thickness of 25 cm
or more within 50 cm of the mineral soil surface, for 90 or more
cumulative days per year;
3. Do not have, in any horizon between either an Ap horizon or
a depth of 25 cm from the mineral soil surface, whichever is
deeper, and a depth of 75 cm, any of the following in more
than half of each pedon:
a. Hue of 2.5Y or redder and either:
(1) A color value, moist, of 6 or more and chroma of 3
or more; or
(2) A color value, moist, of 5 or less and chroma of 2 or
more; or
b. Hue of 5Y or yellower and chroma of 3 or more; or
c. Chroma of 2 or more and no redox concentrations;
4. Do not have a densic, lithic, or paralithic contact
within 100 cm of the mineral soil surface;
5. Do not have a layer 25 cm or more thick that contains less
than 27 percent clay in its fine-earth fraction and has its upper
boundary within 100 cm of the mineral soil surface; and
6. Have, in all horizons within 30 cm of the mineral soil
surface, one or both of the following in more than half of each
pedon:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less.
Description of Subgroups
Typic Dystraquerts.—The Typic subgroup of Dystraquerts
is centered on poorly drained or very poorly drained, deep or
very deep, clayey soils with dark colored surface layers. These
soils do not have concentrations of jarosite or a soil moisture
regime that borders on aridic or ustic.
Aeric Dystraquerts.—These are the Dystraquerts that are
not dominated by gleyed colors from a depth of 25 to 75 cm.
Most of these soils are considered somewhat poorly drained.
Aeric Dystraquerts do not have concentrations of jarosite or a
soil moisture regime that borders on ustic or aridic. They occur
in Texas and are used as woodland.
Aridic Dystraquerts.—These are the Dystraquerts that
have aquic conditions for a short period during the year and
are dry the remainder of the year. These soils do not have
concentrations of jarosite.
Chromic Dystraquerts.—These are the deep or very deep,
clayey, poorly drained or very poorly drained Dystraquerts that
have light colored surface layers. These soils do not have
Vertisols 791
concentrations of jarosite or a soil moisture regime that borders
on aridic or ustic. They occur in many of the Southern States of
the United States. Most of these soils have been cleared for
crop production. Some are wooded.
Entic Dystraquerts.—These are the deep or very deep,
poorly drained or very poorly drained Dystraquerts that have
less than 27 percent clay in a layer 25 cm or more thick within
100 cm of the soil surface. These soils do not have
concentrations of jarosite or a soil moisture regime that borders
on aridic or ustic.
Leptic Dystraquerts.—These are the poorly drained or
very poorly drained Dystraquerts that are less than 100 cm to a
lithic, densic, or paralithic contact. These soils do not have
concentrations of jarosite or a soil moisture regime that borders
on ustic or aridic.
Sulfaqueptic Dystraquerts.—These are the Dystraquerts
that have concentrations of jarosite. They commonly occur in
coastal areas. They have not been recognized in the United
States.
Ustic Dystraquerts.—These are the Dystraquerts that have a
soil moisture regime that borders on ustic. These soils do not
have concentrations of jarosite. They occur in Texas and are
wooded.
Endoaquerts
Endoaquerts are the Aquerts that do not have a soil layer
that perches water. These soils commonly are wet from the
bottom to the top. They occur in the Far Western States, on the
northern Great Plains, and in the Southern States. Before 1992,
most were considered Haplaquepts.
Definition
Endoaquerts are the Aquerts that:
1. Do not have a salic or calcic horizon or a duripan that has
its upper boundary within 100 cm of the mineral soil surface;
2. Do not have both of the following:
a. An electrical conductivity in the saturation extract of
less than 4.0 dS/m at 25 o
C; and
b. A pH value of 4.5 or less in 0.01 M CaCl2
(5.0 or less in
1:1 water) in more than 50 percent of the soil volume
between the mineral soil surface and a depth of 50 cm in
each pedon;
3. Have endosaturation; and
4. Do not have a natric horizon or an exchangeable sodium
percentage of 15 percent or more (or a sodium adsorption ratio
of 13 or more) within 100 cm of the mineral soil surface.
Key to Subgroups
FAGA. Endoaquerts that have, throughout a layer 15 cm or
more thick within 100 cm of the mineral soil surface, an
electrical conductivity of 15 dS/m or more (saturated paste) for 6
or more months in normal years.
Halic Endoaquerts
FAGB. Other Endoaquerts that have, in one or more horizons
within 100 cm of the mineral soil surface, an exchangeable
sodium percentage of 15 or more (or a sodium adsorption ratio
of 13 or more) for 6 or more months in normal years.
Sodic Endoaquerts
FAGC. Other Endoaquerts that, if not irrigated during the
year, have cracks in normal years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50 cm of the
mineral soil surface, for 210 or more cumulative days per year.
Aridic Endoaquerts
FAGD. Other Endoaquerts that have a thermic, mesic, or
frigid soil temperature regime and that, if not irrigated during
the year, have cracks in normal years that remain both:
1. 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 60 or
more consecutive days during the 90 days following the
summer solstice; and
2. Closed for 60 or more consecutive days during the 90
days following the winter solstice.
Xeric Endoaquerts
FAGE. Other Endoaquerts that, if not irrigated during the
year, have cracks in normal years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50 cm of the
mineral soil surface, for 90 or more cumulative days per year.
Ustic Endoaquerts
FAGF. Other Endoaquerts that have, in one or more horizons
between either an Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and a depth of 75
cm, 50 percent or more colors as follows:
1. Hue of 2.5Y or redder and either:
a. A color value, moist, of 6 or more and chroma of 3
or more; or
b. A color value, moist, of 5 or less and chroma of 2 or
more; or
2. Hue of 5Y and chroma of 3 or more; or
3. Chroma of 2 or more and no redox concentrations.
Aeric Endoaquerts
FAGG. Other Endoaquerts that have a densic, lithic, or
paralithic contact within 100 cm of the mineral soil surface.
Leptic Endoaquerts
FAGH. Other Endoaquerts that have a layer 25 cm or more
792 Soil Taxonomy
thick that contains less than 27 percent clay in its fine-earth
fraction and has its upper boundary within 100 cm of the
mineral soil surface.
Entic Endoaquerts
FAGI. Other Endoaquerts that have, in one or more horizons
within 30 cm of the mineral soil surface, one or both of the
following in more than half of each pedon:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more.
Chromic Endoaquerts
FAGJ. Other Endoaquerts.
Typic Endoaquerts
Definition of Typic Endoaquerts
Typic Endoaquerts are the Endoaquerts that:
1. Do not have both a thermic, mesic, or frigid soil
temperature regime and, if not irrigated during the year, cracks
in normal years that remain both:
a. 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 60 or
more consecutive days during the 90 days following the
summer solstice; and
b. Closed for 60 or more consecutive days during the 90
days following the winter solstice;
2. If not irrigated during the year, do not have cracks in
normal years that are 5 mm or more wide, through a thickness
of 25 cm or more within 50 cm of the mineral soil surface, for
90 or more cumulative days per year;
3. Do not have, in any horizon between either an Ap horizon
or a depth of 25 cm from the mineral soil surface, whichever is
deeper, and a depth of 75 cm, any of the following in more
than half of each pedon:
a. Hue of 2.5Y or redder and either:
(1) A color value, moist, of 6 or more and chroma of 3
or more; or
(2) A color value, moist, of 5 or less and chroma of 2 or
more; or
b. Hue of 5Y or yellower and chroma of 3 or more; or
c. Chroma of 2 or more and no redox concentrations;
4. Do not have a densic, lithic, or paralithic contact
within 100 cm of the mineral soil surface;
5. Do not have a layer 25 cm or more thick that contains less
than 27 percent clay in its fine-earth fraction and has its upper
boundary within 100 cm of the mineral soil surface;
6. Have, throughout all layers 15 cm or more thick
within 100 cm of the mineral soil surface, an electrical
conductivity of less than 15 dS/m (saturated paste) for 6 or
more months in normal years;
7. Have, in all horizons within 100 cm of the mineral soil
surface, an exchangeable sodium percentage of less than 15 (or
a sodium adsorption ratio of less than 13) for 6 or more months
in normal years; and
8. Have, in all horizons within 30 cm of the mineral soil
surface, one or both of the following in more than half of each
pedon:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less.
Description of Subgroups
Typic Endoaquerts.—The Typic subgroup of Endoaquerts
is centered on deep or very deep, poorly drained or very poorly
drained, clayey soils with dark colored surface layers. These
soils do not have significant amounts of salts or sodium and do
not have a soil moisture regime that borders on aridic, xeric, or
ustic. They occur in North Dakota, South Dakota, and
Minnesota and are used for hay and pasture or for small grain,
when drained.
Aeric Endoaquerts.—These are the Endoaquerts that are
not dominantly gleyed from a depth of 25 to 75 cm. Most of
these soils are considered somewhat poorly drained. Aeric
Endoaquerts do not have significant amounts of salts or sodium
or a soil moisture regime that borders on aridic, xeric, or ustic.
They occur in Texas and are used mostly as native pasture.
Aridic Endoaquerts.—These are the Endoaquerts that have
aquic conditions for short periods and are dry for most of the
year. These soils do not have significant amounts of salts or
sodium. They occur in California and are used as irrigated
pasture.
Chromic Endoaquerts.—These are the deep or very deep,
poorly drained or very poorly drained, clayey Endoaquerts that
have light colored surface layers. These soils do not have
significant amounts of sodium or salts or a soil moisture
regime that borders on xeric, aridic, or ustic. Chromic
Endoaquerts occur in the Dakotas, Montana, Texas, and
Arkansas. They are used mostly as pasture, but some are used
for hay.
Entic Endoaquerts.—These are the deep or very deep,
poorly drained or very poorly drained Endoaquerts that have a
layer 25 cm or more thick with less than 27 percent clay. These
soils do not have significant amounts of sodium or salts or a
soil moisture regime that borders on ustic, aridic, or xeric.
They are not known to occur in the United States.
Halic Endoaquerts.—These are the Endoaquerts that have
significant amounts of salts. They are not known to occur in
the United States.
Leptic Endoaquerts.—These are the poorly drained or very
poorly drained Endoaquerts that have a lithic, paralithic, or
Vertisols 793
densic contact within 100 cm of the soil surface. These soils do
not have significant amounts of sodium or salts or a moisture
regime that borders on ustic, aridic, or xeric. They are rare in
the world.
Sodic Endoaquerts.—These are the Endoaquerts that have
significant amounts of sodium, but not salts. They occur in
California and are used mostly as irrigated cropland or pasture.
Ustic Endoaquerts.—These are the Endoaquerts that have
a moisture regime that borders on xeric or aridic. They do not
have significant amounts of salts or sodium.
Xeric Endoaquerts.—These are the Endoaquerts that have a
soil moisture regime that borders on xeric. They do not have
significant amounts of sodium or salts. These soils occur in
Oregon, Washington, and California. They are used for
pasture, rangeland, or irrigated crops.
Epiaquerts
Epiaquerts are the Aquerts that have one or more soil layers
that perch water. Commonly, these layers are close to the
surface. These soils occur on a variety of landforms, including
flood plains, glacial lake planes, and depressions. In the United
States, they occur in a number of Western States, on the
northern Great Plains, and in the South. They also occur in
Puerto Rico.
Definition
Epiaquerts are the Aquerts that:
1. Do not have a calcic or salic horizon or a duripan that has
its upper boundary within 100 cm of the mineral soil surface;
2. Do not have both:
a. An electrical conductivity in the saturation extract of
less than 4.0 dS/m at 25 o
C; and
b. A pH value of 4.5 or less in 0.01 M CaCl2
(5.0 or less in
saturated paste) in more than 50 percent of the soil volume
between the mineral soil surface and a depth of 50 cm in
each pedon;
3. Have episaturation; and
4. Do not have a natric horizon or an exchangeable sodium
percentage of 15 percent or more (or a sodium adsorption ratio
of 13 or more) within 100 cm of the mineral soil surface.
Key to Subgroups
FAFA. Epiaquerts that have, throughout a layer 15 cm or
more thick within 100 cm of the mineral soil surface, an
electrical conductivity of 15 dS/m or more (saturated paste) for
6 or more months in normal years.
Halic Epiaquerts
FAFB. Other Epiaquerts that have, in one or more horizons
within 100 cm of the mineral soil surface, an exchangeable
sodium percentage of 15 or more (or a sodium adsorption ratio of
13 or more) for 6 or more months in normal years.
Sodic Epiaquerts
FAFC. Other Epiaquerts that, if not irrigated during the year,
have cracks in normal years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50 cm of the
mineral soil surface, for 210 or more cumulative days per year.
Aridic Epiaquerts
FAFD. Other Epiaquerts that have a thermic, mesic, or frigid
soil temperature regime and that, if not irrigated during the
year, have cracks in normal years that remain both:
1. 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 60 or
more consecutive days during the 90 days following the
summer solstice; and
2. Closed for 60 or more consecutive days during the 90
days following the winter solstice.
Xeric Epiaquerts
FAFE. Other Epiaquerts that, if not irrigated during the year,
have cracks in normal years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50 cm of the
mineral soil surface, for 90 or more cumulative days per year.
Ustic Epiaquerts
FAFF. Other Epiaquerts that have, in one or more horizons
between either an Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and a depth of 75
cm, 50 percent or more colors as follows:
1. Hue of 2.5Y or redder and either:
a. A color value, moist, of 6 or more and chroma of 3
or more; or
b. A color value, moist, of 5 or less and chroma of 2 or
more; or
2. Hue of 5Y and chroma of 3 or more; or
3. Chroma of 2 or more and no redox concentrations.
Aeric Epiaquerts
FAFG. Other Epiaquerts that have a densic, lithic, or
paralithic contact within 100 cm of the mineral soil surface.
Leptic Epiaquerts
FAFH. Other Epiaquerts that have a layer 25 cm or more
thick that contains less than 27 percent clay in its fine-earth
fraction and has its upper boundary within 100 cm of the
mineral soil surface.
Entic Epiaquerts
FAFI. Other Epiaquerts that have, in one or more horizons
794 Soil Taxonomy
within 30 cm of the mineral soil surface, one or both of the
following in more than half of each pedon:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more.
Chromic Epiaquerts
FAFJ. Other Epiaquerts.
Typic Epiaquerts
Definition of Typic Epiaquerts
Typic Epiaquerts are the Epiaquerts that:
1. Do not have both a thermic, mesic, or frigid soil
temperature regime and, if not irrigated during the year, cracks
in normal years that remain both:
a. 5 mm or more wide, throughout a layer 25 cm or more
thick within 50 cm of the mineral soil surface, for 60 or
more consecutive days during the 90 days following the
summer solstice; and
b. Closed for 60 or more consecutive days during the 90
days following the winter solstice;
2. Do not have, in any horizon between either an Ap horizon
or a depth of 25 cm from the mineral soil surface, whichever is
deeper, and a depth of 75 cm, any of the following in more
than half of each pedon:
a. Hue of 2.5Y or redder and either:
(1) A color value, moist, of 6 or more and chroma of 3
or more; or
(2) A color value, moist, of 5 or less and chroma of 2 or
more; or
b. Hue of 5Y or yellower and chroma of 3 or more; or
c. Chroma of 2 or more and no redox concentrations;
3. Do not have a densic, lithic, or paralithic contact
within 100 cm of the mineral soil surface;
4. Do not have a layer 25 cm or more thick that contains less
than 27 percent clay in its fine-earth fraction and has its upper
boundary within 100 cm of the mineral soil surface;
5. Have, if not irrigated during the year, cracks in normal
years that are 5 mm or more wide, through a thickness of 25
cm or more within 50 cm of the mineral soil surface, for 90 to
210 or more cumulative days per year;
6. Have, throughout all layers 15 cm or more thick
within 100 cm of the mineral soil surface, an electrical
conductivity of less than 15 dS/m (saturated paste) for 6
or more months in normal years;
7. Have, in all horizons within 100 cm of the mineral soil
surface, an exchangeable sodium percentage of less than 15
(or a sodium adsorption ratio of less than 13) for 6 or more
months in normal years; and
8. Have, in all horizons within 30 cm of the mineral soil
surface, one or both of the following in more than half of each
pedon:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less.
Description of Subgroups
Typic Epiaquerts.—The Typic subgroup of Epiaquerts is
centered on deep or very deep, poorly drained or very poorly
drained, clayey soils with dark colored surface layers. These
soils do not have significant amounts of salts or sodium and do
not have a soil moisture regime that borders on aridic, xeric, or
ustic. They occur in North Dakota, South Dakota, Minnesota,
Montana, Missouri, Arkansas, Louisiana, and Mississippi.
They are used for hay and pasture or as cropland, when
drained.
Aeric Epiaquerts.—These are the Epiaquerts that are not
dominantly gleyed from a depth of 25 to 75 cm. Many of these
soils are considered somewhat poorly drained. Aeric
Epiaquerts do not have significant amounts of salts or sodium
or a soil moisture regime that borders on aridic, xeric, or ustic.
They occur in Texas, Louisiana, Oklahoma, Alabama,
Mississippi, and Missouri. These soils are mostly cropped, but
some are wooded.
Aridic Epiaquerts.—These are the Epiaquerts that have
aquic conditions for short periods and are dry for most of the
year. These soils do not have significant amounts of salts or
sodium.
Chromic Epiaquerts.—These are the deep or very deep,
poorly drained or very poorly drained, clayey Epiaquerts that
have light colored surface layers. These soils do not have
significant amounts of sodium or salts or a soil moisture
regime that borders on xeric, aridic, or ustic. They occur in
Arkansas. They are used mostly as pasture, but some are used
for hay or other crops.
Entic Epiaquerts.—These are the deep or very deep, poorly
drained or very poorly drained Epiaquerts that have a layer 25
cm or more thick with less than 27 percent clay. These soils do
not have significant amounts of sodium or salts or a soil
moisture regime that borders on ustic, aridic, or xeric. They are
not known to occur in the United States.
Halic Epiaquerts.—These are the Epiaquerts that have
significant amounts of salts. They are not known to occur in
the United States.
Leptic Epiaquerts.—These are the poorly drained or very
poorly drained Epiaquerts that have a lithic, paralithic, or
densic contact within 100 cm of the soil surface. These soils do
not have significant amounts of sodium or salts or a moisture
regime that borders on ustic, aridic, or xeric.
Sodic Epiaquerts.—These are the Epiaquerts that have
significant amounts of sodium, but not salts. They occur in
Vertisols 795
California, Montana, and Puerto Rico. They are used mostly as
irrigated cropland, as wildlife habitat, or as pasture. In Puerto
Rico they are used for sugarcane.
Ustic Epiaquerts.—These are the Epiaquerts that have a
moisture regime that borders on ustic. These soils do not have
significant amounts of salts or sodium. They occur in Texas
and Oklahoma and are used as rangeland.
Xeric Epiaquerts.—These are the Epiaquerts that have a soil
moisture regime that borders on xeric. These soils do not have
significant amounts of sodium or salts. They occur in Oregon,
Nevada, Idaho, and California. They are used for pasture,
rangeland, or irrigated crops. In some areas they are used for rice
production.
Natraquerts
Natraquerts are the Aquerts with significant amounts of
sodium. In many areas these soils occur on flood plains or
glacial lake plains. The high sodium content limits their use as
cropland. Most of the soils are used as rangeland, pasture, or
hayland. Most Natraquerts in the United States formed in
alluvium or lacustrine deposits derived dominantly from
sedimentary rocks. Natraquerts occur in the Dakotas, Montana,
Iowa, Nebraska, and Texas.
Definition
Natraquerts are the Aquerts that:
1. Do not have a salic horizon or a duripan that has its upper
boundary within 100 cm of the mineral soil surface; and
2. Have a natric horizon or an exchangeable sodium
percentage of 15 percent or more (or a sodium adsorption ratio
of 13 or more) within 100 cm of the mineral soil surface.
Key to Subgroups
FACA. All Natraquerts.
TypicNatraquerts
Salaquerts
Salaquerts are the Aquerts with significant amounts of salts.
These soils are not known to occur in the United States.
Definition
Salaquerts are the Aquerts that have a salic horizon that
has an upper boundary within 100 cm of the mineral soil
surface.
Key to Subgroups
FAAA. Salaquerts that, if not irrigated during the year, have
cracks in normal years that are 5 mm or more wide, through a
thickness of 25 cm or more within 50 cm of the mineral soil
surface, for 210 or more cumulative days per year.
Aridic Salaquerts
FAAB. Other Salaquerts that, if not irrigated during the year,
have cracks in normal years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50 cm of the
mineral soil surface, for 90 or more cumulative days per year.
Ustic Salaquerts
FAAC. Other Salaquerts that have a densic, lithic, or
paralithic contact within 100 cm of the mineral soil surface.
Leptic Salaquerts
FAAD. Other Salaquerts that have a layer 25 cm or more
thick that contains less than 27 percent clay in its fine-earth
fraction and has its upper boundary within 100 cm of the
mineral soil surface.
Entic Salaquerts
FAAE. Other Salaquerts that have, in one or more horizons
within 30 cm of the mineral soil surface, 50 percent or more
colors as follows:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. Chroma of 3 or more.
Chromic Salaquerts
FAAF. Other Salaquerts.
Typic Salaquerts
Definition of Typic Salaquerts
Typic Salaquerts are the Salaquerts that:
1. If not irrigated during the year, do not have cracks in
normal years that are 5 mm or more wide, through a thickness
of 25 cm or more within 50 cm of the mineral soil surface, for
90 or more cumulative days per year;
2. Do not have a densic, lithic, or paralithic contact
within 100 cm of the mineral soil surface;
3. Do not have a layer 25 cm or more thick that contains less
than 27 percent clay in its fine-earth fraction and has its upper
boundary within 100 cm of the mineral soil surface; and
4. Have, in all horizons within 30 cm of the mineral soil
surface, 50 percent or more colors as follows:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less; or
c. Chroma of 2 or less.
Description of Subgroups
Typic Salaquerts.—The Typic subgroup of Salaquerts is
centered on deep or very deep, clayey soils with dark colored
surface layers. These soils do not have a soil moisture regime
that borders on ustic or aridic.
796 Soil Taxonomy
Aridic Salaquerts.—These are the Salaquerts that have
aquic conditions for short periods during the year and are dry
for most of the year.
Chromic Salaquerts.—These are the deep or very deep,
clayey Salaquerts that have light colored surface layers. These
soils do not a soil moisture regime that borders on aridic or
ustic.
Entic Salaquerts.—These are the deep or very deep
Salaquerts that have a layer 25 cm or more thick with less than
27 percent clay. These soils do not have a moisture regime that
borders on ustic or aridic.
Leptic Salaquerts.—These are the Salaquerts that have a
lithic, paralithic, or densic contact within 100 cm of the soil
surface. These soils do not have a moisture regime that borders
on aridic or ustic.
Ustic Salaquerts.—These are the Salaquerts that have aquic
conditions for part of the year but also are dry for significant
periods during a normal year.
Cryerts
Cryerts are the Vertisols that have a cryic temperature
regime. Previously, the definition of Vertisols limited their
extent to warmer climates. Fine textured soils in cold
temperature regimes periodically shrink and swell, forming the
diagnostic characteristics of Vertisols. Cracks commonly open
once a year, late in the summer. Cryerts occur on the cold
prairies of Canada, where they commonly are derived from
lacustrine deposits. They also occur in the Rocky Mountains
of the United States.
Definition
Cryerts are the Vertisols that:
1. Have a cryic soil temperature regime; and
2. Do not have, in any horizon within 50 cm of the mineral soil
surface, aquic conditions and any of the following:
a. In more than half of each pedon, either on faces of peds
or in the matrix if peds are absent, 50 percent or more
chroma of either:
(1) 2 or less if redox concentrations are present; or
(2) 1 or less if redox concentrations are absent; or
b. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated.
Key to Great Groups
FBA. Cryerts that have 10 kg/m2
or more organic carbon
between the mineral soil surface and a depth of 50 cm.
Humicryerts, p. 797
FBB. Other Cryerts.
Haplocryerts, p. 796
Haplocryerts
Haplocryerts are the Cryerts without significant
accumulations of organic carbon. These soils occur in the
Rocky Mountains of the United States. They are of limited
extent.
Definition
Haplocryerts are the Cryerts that have less than 10 kg/m2
organic carbon between the mineral soil surface and a depth of
50 cm.
Key to Subgroups
FBBA. Haplocryerts that have, in one or more horizons
within 100 cm of the mineral soil surface, an exchangeable
sodium percentage of 15 or more (or a sodium adsorption ratio
of 13 or more) for 6 or more months in normal years.
Sodic Haplocryerts
FBBB. Other Haplocryerts that have, in one or more horizons
within 30 cm of the mineral soil surface, 50 percent or more
colors as follows:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. Chroma of 3 or more.
Chromic Haplocryerts
FBBC. Other Haplocryerts.
Typic Haplocryerts
Definition of Typic Haplocryerts
Typic Haplocryerts are the Haplocryerts that have:
1. In all horizons within 100 cm of the mineral soil surface,
an exchangeable sodium percentage of less than 15 (or a
sodium adsorption ratio of less than 13) for 6 or more months
in normal years; and
2. In all horizons within 30 cm of the mineral soil surface, 50
percent or more colors as follows:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less; or
c. Chroma of 2 or less.
Description of Subgroups
Typic Haplocryerts.—The Typic subgroup of Haplocryerts
is centered on soils that have dark colored surface horizons and
do not have significant amounts of sodium. These soils are rare
in the world.
Vertisols 797
Chromic Haplocryerts.—These are the Haplocryerts that
have light colored surface horizons but do not have significant
amounts of sodium. These soils are rare in the world.
Sodic Haplocryerts.—These are the Haplocryerts that have
significant amounts of sodium. These soils are rare in the
world.
Humicryerts
Humicryerts are the Cryerts that have rather high amounts
of organic carbon. These soils formed under a variety of
vegetative types. They occur in the Rocky Mountains of the
United States.
Definition
Humicryerts are the Cryerts that have 10 kg/m2
or more
organic carbon between the mineral soil surface and a depth of
50 cm.
Key to Subgroups
FBAA. Humicryerts that have, in one or more horizons
within 100 cm of the mineral soil surface, an exchangeable
sodium percentage of 15 or more (or a sodium adsorption ratio
of 13 or more) for 6 or more months in normal years.
Sodic Humicryerts
FBAB. Other Humicryerts.
Typic Humicryerts
Definition of Typic Humicryerts
Typic Humicryerts are the Humicryerts that have, in all
horizons within 100 cm of the mineral soil surface, an
exchangeable sodium percentage of less than 15 (or a sodium
adsorption ratio of less than 13) for 6 or more months in
normal years.
Description of Subgroups
Typic Humicryerts.—The Typic subgroup of Humicryerts
is centered on soils that do not have significant amounts of
sodium. These soils occur in Idaho and are used as wildlife
habitat.
Sodic Humicryerts.—These are the Humicryerts that have
significant amounts of sodium. These soils are rare in the
world.
Torrerts
Torrerts are the Vertisols of arid climates. Their cracks
commonly stay open for most of the year but may close for at
least a few days in most years. The cracks are closed for less
than 60 days during the growing season. Many of these soils
dot the landscape in closed depressions that may be ponded
from time to time by runoff from the higher areas. Some
Torrerts are more continuous and commonly are underlain by
parent materials that tend to weather to smectictic clays, such as
basalt.
Torrerts are subdivided by the presence or absence of
accumulations of salts, which are important to the use and
management of the soils. Salitorrerts, Gypsitorrerts, and
Calcitorrerts have a salic, gypsic, and calcic horizon,
respectively. Haplotorrerts do not have significant
accumulations of salts.
The Torrerts in the United States occur mostly in the
Southwest, although a few are in Hawaii. Most commonly, they
are used as rangeland.
Definition
Torrerts are the Vertisols that:
1. If not irrigated during the year, have cracks in normal years
that remain closed for less than 60 consecutive days during a
period when the soil temperature at a depth of 50 cm from the
soil surface is continuously higher than 8 o
C;
2. Do not have a cryic soil temperature regime;
3. Do not have, in any horizon within 50 cm of the mineral soil
surface, aquic conditions and any of the following:
a. In more than half of each pedon, either on faces of peds
or in the matrix if peds are absent, 50 percent or more
chroma of either:
(1) 2 or less if redox concentrations are present; or
(2) 1 or less if redox concentrations are absent; or
b. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated; and
4. In normal years do not have both:
a. A thermic, mesic, or frigid soil temperature regime; and
b. If not irrigated during the year, cracks that remain both:
(1) 5 mm or more wide, throughout a layer 25 cm or
more thick within 50 cm of the soil surface, for 60 or
more consecutive days during the 90 days following the
summer solstice; and
(2) Closed for 60 or more consecutive days during the
90 days following the winter solstice.
Key to Great Groups
FDA. Torrerts that have a salic horizon that has its upper
boundary within 100 cm of the soil surface.
Salitorrerts, p. 800
798 Soil Taxonomy
FDB. Other Torrerts that have a gypsic horizon that has its
upper boundary within 100 cm of the soil surface.
Gypsitorrerts, p. 798
FDC. Other Torrerts that have a calcic or petrocalcic horizon
that has its upper boundary within 100 cm of the soil surface.
Calcitorrerts, p. 798
FDD. Other Torrerts.
Haplotorrerts, p. 799
Calcitorrerts
Calcitorrerts are the Torrerts that have a calcic or petrocalcic
horizon. These soils are not extensive among the Torrerts. They
are used mostly for grazing by livestock. Some are used for
irrigated alfalfa. Calcitorrerts occur in Arizona and other areas of
the Southwestern United States.
Definition
Calcitorrerts are the Torrerts that:
1. Have a calcic or petrocalcic horizon that has its upper
boundary within 100 cm of the soil surface; and
2. Do not have a gypsic or salic horizon that has its upper
boundary within 100 cm of the soil surface.
Key to Subgroups
FDCA. Calcitorrerts that have a petrocalcic horizon that has
its upper boundary within 100 cm of the soil surface.
Petrocalcic Calcitorrerts
FDCB. Other Calcitorrerts that have a densic, lithic, or
paralithic contact, or the upper boundary of a duripan, within
100 cm of the soil surface.
Leptic Calcitorrerts
FDCC. Other Calcitorrerts that have a layer 25 cm or more
thick that contains less than 27 percent clay in its fine-earth
fraction and has its upper boundary within 100 cm of the soil
surface.
Entic Calcitorrerts
FDCD. Other Calcitorrerts that have, in one or more
horizons within 30 cm of the soil surface, 50 percent or more
colors as follows:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. Chroma of 3 or more.
Chromic Calcitorrerts
FDCE. Other Calcitorrerts.
Typic Calcitorrerts
Definition of Typic Calcitorrerts
Typic Calcitorrerts are the Calcitorrerts that:
1. Do not have a petrocalcic horizon that has its upper
boundary within 100 cm of the soil surface;
2. Do not have a densic, lithic, or paralithic contact, or
the upper boundary of a duripan, within 100 cm of the soil
surface;
3. Do not have a layer 25 cm or more thick that contains less
than 27 percent clay in its fine-earth fraction and has its upper
boundary within 100 cm of the mineral soil surface; and
4. Have, in all horizons within 30 cm of the mineral soil
surface, 50 percent or more colors as follows:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less; or
c. Chroma of 2 or less.
Description of Subgroups
Typic Calcitorrerts.—The Typic subgroup of Calcitorrerts
is centered on deep or very deep soils that have a clay loam or
finer texture in all layers within 100 cm of the soil surface and
that have relatively dark surface layers. These soils do not have
a petrocalcic horizon. They occur in Arizona and are used for
grazing by livestock.
Chromic Calcitorrerts.—These are the deep or very deep
Calcitorrerts that have a color value, moist, of 4 or more; a dry
value of 6 or more; or chroma of 3 or more. These soils have a
clay loam or finer texture in all layers from the soil surface to a
depth of 100 cm and do not have a petrocalcic horizon.
Entic Calcitorrerts.—These are the deep or very deep
Calcitorrerts that have a layer 25 cm or more thick within 100
cm of the soil surface that contains less than 27 percent clay.
These soils do not have a petrocalcic horizon.
Leptic Calcitorrerts.—These are the Calcitorrerts that are
moderately deep or shallower to a densic, paralithic, or lithic
contact or a duripan. These soils do not have a petrocalcic
horizon.
Petrocalcic Calcitorrerts.—These are the Calcitorrerts that
have a petrocalcic horizon. They occur in Arizona and are used
for grazing by livestock.
Gypsitorrerts
Gypsitorrerts are the Torrerts that have a gypsic horizon that
has its upper boundary within 100 cm of the soil surface. These
soils occur in arid areas of the world where the parent
materials are high in content of gypsum. A high shrink-swell
potential and gypsum content in these soils limit many
building activities unless measures that counteract the
shrinking and swelling and the dissolution of gypsum are
applied. These soils occur in the Southwestern United States.
Vertisols 799
Definition
Gypsitorrerts are the Torrerts that:
1. Have a gypsic horizon that has its upper boundary
within 100 cm of the soil surface; and
2. Do not have a salic horizon that has its upper boundary
within 100 cm of the soil surface.
Key to Subgroups
FDBA. Gypsitorrerts that have, in one or more horizons
within 30 cm of the soil surface, 50 percent or more colors as
follows:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. Chroma of 3 or more.
Chromic Gypsitorrerts
FDBB. Other Gypsitorrerts.
Typic Gypsitorrerts
Definition of Typic Gypsitorrerts
Typic Gypsitorrerts are the Gypsitorrerts that have, in all
horizons within 30 cm of the soil surface, 50 percent or more
colors as follows:
1. A color value, moist, of 3 or less; or
2. A color value, dry, of 5 or less; or
3. Chroma of 2 or less.
Description of Subgroups
Typic Gypsitorrerts.—The Typic subgroup of Gypsitorrerts
is centered on soils that have surface layers with a color value,
moist, of 3 or less; a value, dry, of 5 or less; and chroma of 2 or
less. These soils are relatively rare, but they occur in Arizona.
They are used for grazing by livestock.
Chromic Gypsitorrerts.—These are the Gypsitorrerts that
have a color value, moist, of 4 or more; a color value, dry, of 6
or more; or chroma of 3 or more. These soils occur in New
Mexico and are used for grazing by livestock.
Haplotorrerts
Haplotorrerts are the Torrerts that do not have a salic, gypsic,
or calcic horizon. This is the most extensive great group of
Torrerts. These soils occur in many of the Western States and in
Texas and Hawaii. They are used as urban land, cropland, or
rangeland.
Definition
Haplotorrerts are the Torrerts that do not have a calcic,
gypsic, petrocalcic, or salic horizon that has its upper boundary
within 100 cm of the soil surface.
KeytoSubgroups
FDDA. Haplotorrerts that have, throughout a layer 15 cm or
more thick within 100 cm of the soil surface, an electrical
conductivity of 15 dS/m or more (saturated paste) for 6 or more
months in normal years.
Halic Haplotorrerts
FDDB. Other Haplotorrerts that have, in one or more
horizons within 100 cm of the soil surface, an exchangeable
sodium percentage of 15 or more (or a sodium adsorption ratio
of 13 or more) for 6 or more months in normal years.
Sodic Haplotorrerts
FDDC. Other Haplotorrerts that have a densic, lithic, or
paralithic contact, or the upper boundary of a duripan, within
100 cm of the soil surface.
Leptic Haplotorrerts
FDDD. Other Haplotorrerts that have a layer 25 cm or more
thick that contains less than 27 percent clay in its fine-earth
fraction and has its upper boundary within 100 cm of the soil
surface.
Entic Haplotorrerts
FDDE. Other Haplotorrerts that have, in one or more
horizons within 30 cm of the soil surface, 50 percent or more
colors as follows:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. Chroma of 3 or more.
Chromic Haplotorrerts
FDDF. Other Haplotorrerts.
Typic Haplotorrerts
Definition of Typic Haplotorrerts
Typic Haplotorrerts are the Haplotorrerts that:
1. Do not have a densic, lithic, or paralithic contact, or the
upper boundary of a duripan, within 100 cm of the soil
surface;
2. Do not have a layer 25 cm or more thick that contains less
than 27 percent clay in its fine-earth fraction and has its upper
boundary within 100 cm of the soil surface;
3. Have, in all layers 15 cm or more thick within 100 cm of
the soil surface, an electrical conductivity of less than 15 dS/m
(saturated paste) for 6 or more months in normal years;
4. Have, in all horizons within 100 cm of the soil surface, an
exchangeable sodium percentage of less than 15 (or a sodium
adsorption ratio of less than 13) for 6 or more months in
normal years; and
800 Soil Taxonomy
5. Have, in all horizons within 30 cm of the soil surface, 50
percent or more colors as follows:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less; or
c. Chroma of 2 or less.
Description of Subgroups
Typic Haplotorrerts.—The Typic subgroup of Haplotorrerts
is centered on soils that are deep or very deep, that have a clay
loam or finer texture in all horizons between the soil surface and
a depth of 100 cm, that have relatively dark colored surface
horizons, and that do not have significant amounts of salts or
sodium. In Texas, New Mexico, and Arizona, these soils are used
for rangeland or irrigated crops. In Hawaii the soils are used for
irrigated sugarcane.
Chromic Haplotorrerts.—These are the deep or very deep
Haplotorrerts that have a color value, moist, of 4 or more; a
color value, dry, of 6 or more; or chroma of 3 or more. These
soils do not have significant amounts of salts or sodium. They
occur in Idaho, California, Colorado, New Mexico, and Texas.
Most commonly, they are used for grazing.
Entic Haplotorrerts.—These are the deep or very deep
Haplotorrerts that have a layer 25 cm or more thick within 100
cm of the soil surface that has 27 percent or less clay. These
soils do not have significant amounts of salts or sodium. They
occur in New Mexico and are used as urban land, rangeland, or
irrigated cropland.
Halic Haplotorrerts.—These are the Haplotorrerts that
have a significant accumulation of salts. They occur in Texas
and New Mexico and are used for grazing by livestock.
Leptic Haplotorrerts.—These are the Haplotorrerts that
have a lithic, paralithic, or densic contact or a duripan within
100 cm of the soil surface. These soils do not have significant
amounts of salts or sodium. They are known to occur in New
Mexico and Hawaii, where they are used as rangeland and
pasture, respectively.
Sodic Haplotorrerts.—These are the Haplotorrerts that
have a significant accumulation of sodium and do not have
significant amounts of salts. These soils occur in Nevada,
California, and Texas. They are used for rangeland or irrigated
crops.
Salitorrerts
Salitorrerts are the Torrerts that have a salic horizon. In some
of these soils, salts accumulate because of a periodic water
table. In others, scant precipitation and the impermeable nature
of the soils facilitate the accumulation of salts. Salitorrerts have
not been recognized in the United States.
Definition
Salitorrerts are the Torrerts that have a salic horizon that has
its upper boundary within 100 cm of the soil surface.
KeytoSubgroups
FDAA. Salitorrerts that have, in one or more horizons within
100 cm of the soil surface, aquic conditions for some time in
normal years (or artificial drainage) and either:
1. Redoximorphic features; or
2. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated.
Aquic Salitorrerts
FDAB. Other Salitorrerts that have a densic, lithic, or
paralithic contact, or the upper boundary of a duripan or
petrocalcic horizon, within 100 cm of the soil surface.
Leptic Salitorrerts
FDAC. Other Salitorrerts that have a layer 25 cm or more
thick that contains less than 27 percent clay in its fine-earth
fraction and has its upper boundary within 100 cm of the soil
surface.
Entic Salitorrerts
FDAD. Other Salitorrerts that have, in one or more horizons
within 30 cm of the soil surface, 50 percent or more colors as
follows:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. Chroma of 3 or more.
Chromic Salitorrerts
FDAE. Other Salitorrerts.
Typic Salitorrerts
Definition of Typic Salitorrerts
Typic Salitorrerts are the Salitorrerts that:
1. Do not have, in any horizon within 100 cm of the soil
surface, aquic conditions and either:
a. Redoximorphic features; or
b. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated;
2. Do not have a densic, lithic, or paralithic contact, or the
upper boundary of a duripan or petrocalcic horizon, within 100
cm of the soil surface;
3. Do not have a layer 25 cm or more thick that contains less
than 27 percent clay in its fine-earth fraction and has its upper
boundary within 100 cm of the soil surface; and
4. Have, in all horizons within 30 cm of the soil surface, 50
percent or more colors as follows:
Vertisols 801
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less; or
c. Chroma of 2 or less.
Description of Subgroups
Typic Salitorrerts.—The Typic subgroup of Salitorrerts is
centered on deep or very deep soils that have a clay loam or
finer texture from the soil surface to a depth of 100 cm. These
soils do not have aquic conditions within 100 cm of the soil
surface, and they have relatively dark colored surface layers.
Aquic Salitorrerts.—These are the Salitorrerts that have
aquic conditions within 100 cm of the soil surface for some
time in normal years. The aquic conditions commonly are of
very short duration.
Chromic Salitorrerts.—These are the deep or very deep
Salitorrerts that have a color value, moist, of 4 or more; a color
value, dry, of 6 or more; or chroma of 3 or more. These soils
have a clay loam or finer texture from the soil surface to a
depth of 100 cm.
Entic Salitorrerts.—These are the deep or very deep
Salitorrerts that have a layer 25 cm or more thick that has 27
percent or less clay within 100 cm of the soil surface. These
soils do not have aquic conditions within 100 cm of the soil
surface.
Leptic Salitorrerts.—These are the Salitorrerts that are
moderately deep or shallower to a lithic, paralithic, or densic
contact or a duripan or petrocalcic horizon. These soils do not
have aquic conditions within 100 cm of the soil surface.
Uderts
Uderts are the Vertisols of humid areas. These soils have
cracks that open and close, depending upon the amount of
precipitation. In some years the cracks may not open
completely.
The Uderts in the United States occur on gentle slopes and
are derived dominantly from marine shales, marls, and
alluvium. At one time many of these soils supported grass,
although some support a hardwood or pine forest.
Definition
Uderts are the Vertisols that:
1. Do not have a cryic soil temperature regime;
2. Do not have, in any horizon within 50 cm of the mineral
soil surface, aquic conditions and any of the following:
a. In more than half of each pedon, either on faces of peds
or in the matrix if peds are absent, 50 percent or more
chroma of either:
(1) 2 or less if redox concentrations are present; or
(2) 1 or less if redox concentrations are absent; or
b. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated;
3. In normal years do not have both:
a. A thermic, mesic, or frigid soil temperature regime;
and
b. If not irrigated during the year, cracks that remain both:
(1) 5 mm or more wide, throughout a layer 25 cm or
more thick within 50 cm of the mineral soil surface, for
60 or more consecutive days during the 90 days following
the summer solstice; and
(2) Closed for 60 or more consecutive days during the
90 days following the winter solstice;
4. If not irrigated during the year, do not have cracks in
normal years that remain closed for less than 60 consecutive
days during a period when the soil temperature at a depth of 50
cm from the soil surface is continuously higher than 8 o
C; and
5. If not irrigated during the year, do not have cracks in
normal years that are 5 mm or more wide, through a thickness
of 25 cm or more within 50 cm of the mineral soil surface, for
90 or more cumulative days.
Key to Great Groups
FFA. Uderts that have, throughout one or more horizons with
a total thickness of 25 cm or more within 50 cm of the mineral
soil surface, both:
1. An electrical conductivity in the saturation extract of
less than 4.0 dS/m at 25 o
C; and
2. A pH value of 4.5 or less in 0.01 M CaCl2
(5.0 or less in
saturated paste).
Dystruderts, p. 801
FFB. Other Uderts.
Hapluderts, p. 803
Dystruderts
Dystruderts are the acid Uderts. These soils are derived
dominantly from acid, fine textured materials and occur on
alluvial plains, deltas, interfluves, and side slopes. Commonly,
they are underlain by sediments high in bases. Some of these
soils have diagnostic horizons, including argillic, calcic, and
gypsic horizons.
In the United States, these soils occur in Texas and in the
Southeastern States from Arkansas to Florida. They are used as
cropland, pasture, or woodland.
802 Soil Taxonomy
Definition
Dystruderts are the Uderts that have, throughout one or more
horizons with a total thickness of 25 cm or more within 50 cm of
the mineral soil surface, both:
1. An electrical conductivity in the saturation extract of less
than 4.0 dS/m at 25 o
C; and
2. A pH value of 4.5 or less in 0.01 M CaCl2
(5.0 or less in
saturated paste).
Key to Subgroups
FFAA. Dystruderts that have, in one or more horizons within
100 cm of the mineral soil surface, aquic conditions for some
time in normal years (or artificial drainage) and either:
1. Redoximorphic features; or
2. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated.
Aquic Dystruderts
FFAB. Other Dystruderts that are saturated with water in one
or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Dystruderts
FFAC. Other Dystruderts that have a densic, lithic, or
paralithic contact within 100 cm of the mineral soil surface.
Leptic Dystruderts
FFAD. Other Dystruderts that have a layer 25 cm or more
thick that contains less than 27 percent clay in its fine-earth
fraction and has its upper boundary within 100 cm of the
mineral soil surface.
Entic Dystruderts
FFAE. Other Dystruderts that have, in one or more horizons
within 30 cm of the mineral soil surface, 50 percent or more
colors as follows:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. Chroma of 3 or more.
Chromic Dystruderts
FFAF. Other Dystruderts.
Typic Dystruderts
Definition of Typic Dystruderts
Typic Dystruderts are the Dystruderts that:
1. Do not have, in any horizon within 100 cm of the mineral soil
surface, aquic conditions and either:
a. Redoximorphic features; or
b. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated;
2. Do not have a densic, lithic, or paralithic contact
within 100 cm of the mineral soil surface;
3. Do not have a layer 25 cm or more thick that contains less
than 27 percent clay in its fine-earth fraction and has its upper
boundary within 100 cm of the mineral soil surface;
4. Are not saturated with water in any layer within 100 cm of
the mineral soil surface in normal years for:
a. 20 or more consecutive days; or
b. 30 or more cumulative days; and
5. Have, in all horizons within 30 cm of the mineral soil
surface, 50 percent or more colors as follows:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less; or
c. Chroma of 2 or less.
Description of Subgroups
Typic Dystruderts.—The Typic subgroup of Dystruderts is
centered on deep or very deep, dark colored soils that are not
saturated within 100 cm of the soil surface for extended
periods. These soils do not have a layer as much as 25 cm thick
with less than 27 percent clay from the soil surface to a depth
of 100 cm.
Aquic Dystruderts.—These are the Dystruderts that have
aquic conditions and redoximorphic features within 100 cm of
the mineral soil surface. These soils do not have high amounts
of aluminum. In the United States, they commonly formed in
thick sediments of acid clays over more alkaline clays. These
soils occur in Mississippi, Alabama, Arkansas, and Louisiana
and are used as cropland, pasture, or woodland.
Chromic Dystruderts.—These are the deep or very deep
Dystruderts that have light colored layers within 30 cm of the
mineral soil surface. These soils are not saturated for extended
periods within 100 cm of the mineral soil surface. They do not
have layers with less than 27 percent clay within 100 cm of the
mineral soil surface. The soils are extensive in the
Southeastern United States and commonly are wooded.
Entic Dystruderts.—These are the deep or very deep
Dystruderts that have a layer 25 cm or more thick that contains
less than 27 percent clay and has its upper boundary within
100 cm of the mineral soil surface. These soils are not
saturated within 100 cm of the mineral soil surface for
significant periods.
Leptic Dystruderts.—These are the shallow or moderately
Vertisols 803
deep Dystruderts. They are not saturated within a depth of 100
cm for significant periods. They are not known to occur in the
United States.
Oxyaquic Dystruderts.—These are the Dystruderts that are
saturated for significant periods within 100 cm of the mineral
soil surface but do not have redoximorphic features. These soils
occur in Texas and Louisiana.
Hapluderts
Hapluderts are the Uderts with pH values that are dominantly
above 5.0 in the upper 50 cm. These soils typically have high
base saturation, and some have diagnostic horizons, including
argillic horizons. Hapluderts occur on uplands and in lower
areas. They formed in a variety of fine textured parent material,
including alluvium.
In the United States, these soils commonly occur in the
Southeast but also occur on the northern Great Plains and in
the Pacific Northwest.
Definition
Hapluderts are the Uderts that do not have both:
1. An electrical conductivity in the saturation extract of less
than 4.0 dS/m at 25 o
C; and
2. A pH value of 4.5 or less in 0.01 M CaCl2
(5.0 or less in
saturated paste) in more than 50 percent of the soil volume
between the mineral soil surface and a depth of 50 cm in each
pedon.
Key to Subgroups
FFBA. Hapluderts that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Hapluderts
FFBB. Other Hapluderts that have, in one or more horizons
within 100 cm of the mineral soil surface, aquic conditions
for some time in normal years (or artificial drainage) and
either:
1. Redoximorphic features; or
2. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated.
Aquic Hapluderts
FFBC. Other Hapluderts that are saturated with water in one
or more layers within 100 cm of the mineral soil surface in
normal years for:
1. 20 or more consecutive days; or
2. 30 or more cumulative days.
Oxyaquic Hapluderts
FFBD. Other Hapluderts that have a densic, lithic, or paralithic
contact within 100 cm of the mineral soil surface.
Leptic Hapluderts
FFBE. Other Hapluderts that have a layer 25 cm or more
thick that contains less than 27 percent clay in its fine-earth
fraction and has its upper boundary within 100 cm of the
mineral soil surface.
Entic Hapluderts
FFBF. Other Hapluderts that have, in one or more horizons
within 30 cm of the mineral soil surface, 50 percent or more
colors as follows:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. Chroma of 3 or more.
Chromic Hapluderts
FFBG. Other Hapluderts.
Typic Hapluderts
Definition of Typic Hapluderts
Typic Hapluderts are the Hapluderts that:
1. Do not have a densic, lithic, or paralithic contact
within 100 cm of the mineral soil surface;
2. Do not have, in any horizon within 100 cm of the mineral
soil surface, aquic conditions and either:
a. Redoximorphic features; or
b. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated;
3. Do not have a layer 25 cm or more thick that contains less
than 27 percent clay in its fine-earth fraction and has its upper
boundary within 100 cm of the mineral soil surface;
4. Are not saturated with water in any layer within 100 cm of
the mineral soil surface in normal years for:
a. 20 or more consecutive days; or
b. 30 or more cumulative days; and
5. Have, in all horizons within 30 cm of the mineral soil
surface, 50 percent or more colors as follows:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less; or
c. Chroma of 2 or less.
Description of Subgroups
Typic Hapluderts.—The Typic subgroup of Hapluderts is
centered on deep or very deep soils that are not saturated for
804 Soil Taxonomy
significant periods within 100 cm of the mineral soil surface.
These soils have rather dark colored surface layers and a clay
loam or finer texture throughout. They occur in Texas,
Alabama, Oklahoma, and Arkansas and on the northern Great
Plains. They are used as cropland, pasture, or rangeland.
Aquic Hapluderts.—These are the Hapluderts that have
aquic conditions and redoximorphic features within 100 cm of
the mineral soil surface. They do not have a lithic contact
within 50 cm of the mineral soil surface. These soils occur in
Alabama, Texas, Oklahoma, Kansas, Louisiana, and Puerto
Rico. They are used as cropland, woodland, or pasture.
Chromic Hapluderts.—These are the deep or very deep
Hapluderts that have light colored surface layers. These soils
are not saturated for extended periods within 100 cm of the
mineral soil surface. They have a clay loam or finer texture
from the mineral soil surface to a depth of 100 cm. These soils
are common in the South, in the Southeast, and on the
northern Great Plains. They are used as cropland, pasture, or
woodland.
Entic Hapluderts.—These are the deep or very deep
Hapluderts that have a layer 25 cm or more thick that contains
less than 27 percent clay within 100 cm of the mineral soil
surface. These soils are not saturated for extended periods
within 100 cm of the mineral soil surface. They are
uncommon. They occur in Texas and are used as pasture or
cropland.
Leptic Hapluderts.—These are the Hapluderts that have a
densic, lithic, or paralithic contact within 100 cm of the
mineral soil surface but do not have a lithic contact within 50
cm of the mineral soil surface. These soils are not saturated for
extended periods within 100 cm of the mineral soil surface.
They occur in Alabama and Louisiana and are used as
cropland, pasture, or hayland.
Lithic Hapluderts.—These are the Hapluderts that have a
lithic contact within 50 cm of the mineral soil surface. They
are not common and have not been recognized in the United
States.
Oxyaquic Hapluderts.—These are the Hapluderts that are
saturated with water for extended periods within 100 cm of the
mineral soil surface but do not have redoximorphic features.
They also do not have a lithic contact within 50 cm of the
mineral soil surface. They are extensive and occur in the
South, the Southeast, and the Pacific Northwest. They are used
mostly as cropland or pasture.
Usterts
These are the Vertisols in temperate areas that do not receive
high amounts of rainfall during the summer, in areas of
monsoonal climate, and in tropical and subtropical areas that
have two rainy and two dry seasons. Cracks open and close
once or twice during the year. Usterts are extensive in Texas,
on the Great Plains, in Australia, in Africa south of the Sahara,
and in India. Many of these soils formed in gently sloping
areas of fine textured marine deposits or alluvium. Some are
derived from basic igneous rocks. If irrigated, Usterts are used
intensively, but large areas are used for grazing because of a
lack of machinery to till the soils.
Definition
Usterts are the Vertisols that:
1. Do not have a cryic soil temperature regime;
2. Do not have, in any horizon within 50 cm of the mineral soil
surface, aquic conditions and any of the following:
a. In more than half of each pedon, either on faces of peds
or in the matrix if peds are absent, 50 percent or more
chroma of either:
(1) 2 or less if redox concentrations are present; or
(2) 1 or less if redox concentrations are absent; or
b. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated;
3. In normal years do not have both:
a. A thermic, mesic, or frigid soil temperature regime; and
b. If not irrigated during the year, cracks that remain both:
(1) 5 mm or more wide, throughout a layer 25 cm or
more thick within 50 cm of the mineral soil surface, for
60 or more consecutive days during the 90 days following
the summer solstice; and
(2) Closed for 60 or more consecutive days during the
90 days following the winter solstice;
4. If not irrigated during the year, do not have cracks in
normal years that remain closed for less than 60 consecutive
days during a period when the soil temperature at a depth of 50
cm from the soil surface is continuously higher than 8 o
C; and
5. If not irrigated during the year, have cracks in normal
years that are 5 mm or more wide, through a thickness of 25
cm or more within 50 cm of the mineral soil surface, for 90 or
more cumulative days per year.
Key to Great Groups
FEA. Usterts that have, throughout one or more horizons
with a total thickness of 25 cm or more within 50 cm of the
mineral soil surface, both:
1. An electrical conductivity in the saturation extract of
less than 4.0 dS/m at 25 o
C; and
2. A pH value of 4.5 or less in 0.01 M CaCl2
(5.0 or less in
saturated paste).
Dystrusterts, p. 806
Vertisols 805
FEB. Other Usterts that have a salic horizon that has its upper
boundary within 100 cm of the mineral soil surface.
Salusterts, p. 811
FEC. Other Usterts that have a gypsic horizon that has its
upper boundary within 100 cm of the mineral soil surface.
Gypsiusterts, p. 808
FED. Other Usterts that have a calcic or petrocalcic horizon
that has its upper boundary within 100 cm of the mineral soil
surface.
Calciusterts, p. 805
FEE. Other Usterts.
Haplusterts, p. 809
Calciusterts
Calciusterts are the Usterts that have a calcic or petrocalcic
horizon. These soils commonly are derived from parent
materials rich in carbonates, such as marine deposits or even
eolian material. Previously, it was thought that diagnostic
horizons could not form in Vertisols because of self-churning.
These earlier concepts were not accurate. Some Calciusterts
have mollic epipedons. Although Calciusterts have limited
acreage in the United States, they are significant in other parts
of the world.
Definition
Calciusterts are the Usterts that:
1. Have a calcic or petrocalcic horizon that has its upper
boundary within 100 cm of the mineral soil surface;
2. Do not have both:
a. An electrical conductivity in the saturation extract of
less than 4.0 dS/m at 25 o
C; and
b. A pH value of 4.5 or less in 0.01 M CaCl2
(5.0 or less in
saturated paste) in more than 50 percent of the soil volume
between the mineral soil surface and a depth of 50 cm in
each pedon; and
3. Do not have a gypsic or salic horizon that has its upper
boundary within 100 cm of the mineral soil surface.
Key to Subgroups
FEDA. Calciusterts that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Calciusterts
FEDB. Other Calciusterts that have, throughout a layer 15
cm or more thick within 100 cm of the mineral soil surface, an
electrical conductivity of 15 dS/m or more (saturated paste) for
6 or more months in normal years.
Halic Calciusterts
FEDC. Other Calciusterts that have, in one or more horizons
within 100 cm of the mineral soil surface, an exchangeable
sodium percentage of 15 or more (or a sodium adsorption ratio
of 13 or more) for 6 or more months in normal years.
Sodic Calciusterts
FEDD. Other Calciusterts that have a petrocalcic horizon
that has its upper boundary within 100 cm of the mineral soil
surface.
Petrocalcic Calciusterts
FEDE. Other Calciusterts that, if not irrigated during the
year, have cracks in normal years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50 cm of the
mineral soil surface, for 210 or more cumulative days per year.
Aridic Calciusterts
FEDF. Other Calciusterts that, if not irrigated during the
year, have cracks in normal years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50 cm of the
mineral soil surface, for less than 150 cumulative days per
year.
Udic Calciusterts
FEDG. Other Calciusterts that have a densic, lithic, or
paralithic contact, or the upper boundary of a duripan, within
100 cm of the mineral soil surface.
Leptic Calciusterts
FEDH. Other Calciusterts that have a layer 25 cm or more
thick that contains less than 27 percent clay in its fine-earth
fraction and has its upper boundary within 100 cm of the
mineral soil surface.
Entic Calciusterts
FEDI. Other Calciusterts that have, in one or more horizons
within 30 cm of the mineral soil surface, 50 percent or more
colors as follows:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. Chroma of 3 or more.
Chromic Calciusterts
FEDJ. Other Calciusterts.
Typic Calciusterts
Definition of Typic Calciusterts
Typic Calciusterts are the Calciusterts that:
1. Do not have a densic, lithic, or paralithic contact, or the
upper boundary of a duripan or petrocalcic horizon, within 100
cm of the mineral soil surface;
2. Do not have a layer 25 cm or more thick that contains less
806 Soil Taxonomy
than 27 percent clay in its fine-earth fraction and has its upper
boundary within 100 cm of the mineral soil surface;
3. If not irrigated during the year, have cracks in normal
years that are 5 mm or more wide, through a thickness of 25
cm or more within 50 cm of the mineral soil surface, for 150 to
210 cumulative days per year;
4. Have, throughout all layers 15 cm or more thick
within 100 cm of the mineral soil surface, an electrical
conductivity of less than 15 dS/m (saturated paste) for 6
or more months in normal years;
5. Have, in all horizons within 100 cm of the mineral soil
surface, an exchangeable sodium percentage of less than 15 (or
a sodium adsorption ratio of less than 13) for 6 or more months
in normal years; and
6. Have, in all horizons within 30 cm of the mineral soil
surface, 50 percent or more colors as follows:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less; or
c. Chroma of 2 or less.
Description of Subgroups
Typic Calciusterts.—The Typic subgroup of Calciusterts is
centered on deep or very deep soils that do not have significant
amounts of salts or sodium. In addition, these soils do not have
a petrocalcic horizon, soil moisture regimes that border on
aridic or udic, a layer with less than 27 percent clay, or light
colored surface layers. These soils are rare in the United States
but occur in Puerto Rico, where they are used for pasture or
sugarcane.
Aridic Calciusterts.—These are the Calciusterts that have
a soil moisture regime that borders on aridic. These soils do
not have a lithic contact within 50 cm of the soil surface, a
petrocalcic horizon, or significant amounts of salts or sodium.
They are of small extent in the Southwestern United States and
are used as rangeland.
Chromic Calciusterts.—These are the deep or very deep
Calciusterts that have light colored surface layers but do not
have significant amounts of salts or sodium. These soils do not
have a petrocalcic horizon, soil moisture regimes that border
on aridic or udic, or a layer with less than 27 percent clay. The
soils are rare in the United States.
Entic Calciusterts.—These are the deep or very deep
Calciusterts that have a layer with less than 27 percent clay but
do not have significant amounts of salts or sodium. These soils
do not have a petrocalcic horizon or soil moisture regimes that
border on aridic or udic. The soils are rare in the United States.
Halic Calciusterts.—These are the Calciusterts that have a
significant accumulation of salts. These soils do not have a
lithic contact within 50 cm of the soil surface. They are not
known to occur in the United States.
Leptic Calciusterts.—These are the Calciusterts that have
a lithic, paralithic, or densic contact within 100 cm of the soil
surface but do not have a lithic contact within 50 cm of the soil
surface. These soils do not have significant amounts of salts or
sodium, a moisture regime that borders on udic or aridic, or a
petrocalcic horizon. The soils are rare in the United States.
Lithic Calciusterts.—These are the Calciusterts that have a
lithic contact within 50 cm of the soil surface. They are not
known to occur in the United States.
Petrocalcic Calciusterts.—These are the Calciusterts that
have a petrocalcic horizon. They do not have a lithic contact
within 50 cm of the soil surface or significant amounts of salts
or sodium. These soils occur in Texas and are used as
rangeland or pasture.
Sodic Calciusterts.—These are the Calciusterts that have
significant amounts of sodium, but not salts. They do not have
a lithic contact within 50 cm of the soil surface. These soils are
rare in the United States and are used as rangeland.
Udic Calciusterts.—These are the Calciusterts that have a
soil moisture regime that borders on udic. They do not have a
petrocalcic horizon, a lithic contact within 50 cm of the soil
surface, or significant amounts of salts or sodium. These soils
occur in Texas. They commonly are used as rangeland, but
some are used for cultivated crops.
Dystrusterts
Dystrusterts are the Usterts that have a dominant pH value of
5.0 or less and an electrical conductivity of less than 4.0
dS/m within 50 cm of the soil surface. These soils commonly
formed in acid clays and are underlain by more alkaline parent
materials. They commonly are derived from marine sediments.
They are not known to occur in the United States but were
established to accommodate other countries.
Definition
Dystrusterts are the Usterts that have, throughout one or
more horizons with a total thickness of 25 cm or more within
50 cm of the mineral soil surface, both:
1. An electrical conductivity in the saturation extract of less
than 4.0 dS/m at 25 o
C; and
2. A pH value of 4.5 or less in 0.01 M CaCl2
(5.0 or less in
saturated paste).
Key to Subgroups
FEAA. Dystrusterts that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Dystrusterts
FEAB. Other Dystrusterts that have, in one or more horizons
within 100 cm of the mineral soil surface, aquic conditions
for some time in normal years (or artificial drainage) and
either:
1. Redoximorphic features; or
Vertisols 807
2. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated.
Aquic Dystrusterts
FEAC. Other Dystrusterts that, if not irrigated during the
year, have cracks in normal years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50 cm of the
mineral soil surface, for 210 or more cumulative days per
year.
Aridic Dystrusterts
FEAD. Other Dystrusterts that, if not irrigated during the
year, have cracks in normal years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50 cm of the
mineral soil surface, for less than 150 cumulative days.
Udic Dystrusterts
FEAE. Other Dystrusterts that have a densic, lithic, or
paralithic contact, or the upper boundary of a duripan, within
100 cm of the mineral soil surface.
Leptic Dystrusterts
FEAF. Other Dystrusterts that have a layer 25 cm or more
thick that contains less than 27 percent clay in its fine-earth
fraction and has its upper boundary within 100 cm of the
mineral soil surface.
Entic Dystrusterts
FEAG. Other Dystrusterts that have, in one or more horizons
within 30 cm of the mineral soil surface, 50 percent or more
colors as follows:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. Chroma of 3 or more.
Chromic Dystrusterts
FEAH. Other Dystrusterts.
Typic Dystrusterts
Definition of Typic Dystrusterts
Typic Dystrusterts are the Dystrusterts that:
1. Do not have a densic, lithic, or paralithic contact, or the
upper boundary of a duripan, within 100 cm of the mineral soil
surface;
2. Do not have, in any horizon within 100 cm of the mineral
soil surface, aquic conditions and either:
a. Redoximorphic features; or
b. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated;
3. Do not have a layer 25 cm or more thick that contains less
than 27 percent clay in its fine-earth fraction and has its upper
boundary within 100 cm of the mineral soil surface;
4. If not irrigated during the year, have cracks in normal
years that are 5 mm or more wide, through a thickness of 25
cm or more within 50 cm of the mineral soil surface, for 150 to
210 cumulative days per year; and
5. Have, in all horizons within 30 cm of the mineral soil
surface, 50 percent or more colors as follows:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less; or
c. Chroma of 2 or less.
Description of Subgroups
Typic Dystrusterts.—The Typic subgroup of Dystrusterts is
centered on deep or very deep soils that do not have a soil
moisture regime that borders on udic or aridic. These soils do
not have aquic conditions for significant periods within 100 cm
of the soil surface. In addition, they do not have a layer with
less than 27 percent clay or light colored surface layers.
Aquic Dystrusterts.—These are the Dystrusterts that have
aquic conditions for extended periods within 100 cm of the soil
surface. These soils do not have a lithic contact within 50 cm
of the soil surface.
Aridic Dystrusterts.—These are the Dystrusterts that have
a soil moisture regime that borders on aridic. They do not have
a lithic contact within 50 cm of the soil surface or aquic
conditions for extended periods within 100 cm of the soil
surface.
Chromic Dystrusterts.—These are the deep or very deep
Dystrusterts that have light colored surface layers but do not
have a lithic contact within 50 cm of the soil surface or aquic
conditions for extended periods within 100 cm of the soil
surface. These soils do not have soil moisture regimes that
border on aridic or udic or a layer with less than 27 percent
clay.
Entic Dystrusterts.—These are the deep or very deep
Dystrusterts that have a layer with less than 27 percent clay but
do not have a lithic contact within 50 cm of the soil surface.
These soils do not have soil moisture regimes that border on
aridic or udic or aquic conditions for extended periods within
100 cm of the soil surface.
Leptic Dystrusterts.—These are the Dystrusterts that have
a lithic, paralithic, or densic contact within 100 cm of the soil
surface but do not have a lithic contact within 50 cm of the soil
surface. These soils do not have a moisture regime that borders
on udic or aridic or aquic conditions for extended periods
within 100 cm of the soil surface.
Lithic Dystrusterts.—These are the Dystrusterts that have
a lithic contact within 50 cm of the soil surface.
Udic Dystrusterts.—These are the Dystrusterts that have a
soil moisture regime that borders on udic. They do not have a
808 Soil Taxonomy
lithic contact within 50 cm of the soil surface or aquic
conditions for extended periods within 100 cm of the soil
surface.
Gypsiusterts
These are the Usterts that have a gypsic horizon. They are
derived from parent materials rich in gypsum. Even in areas of
an ustic moisture regime, the gypsum is not leached because of
the very slow permeability associated with these soils. Some of
the soils occur on the edges of depressions where gypsum is
deposited at the capillary fringe. Gypsiusterts are rare in the
United States, but they occur in Texas, where they are used as
rangeland or pasture.
Definition
Gypsiusterts are the Usterts that:
1. Have a gypsic horizon that has its upper boundary
within 100 cm of the mineral soil surface;
2. Do not have both:
a. An electrical conductivity in the saturation extract of
less than 4.0 dS/m at 25 o
C; and
b. A pH value of 4.5 or less in 0.01 M CaCl2
(5.0 or less in
saturated paste) in more than 50 percent of the soil volume
between the mineral soil surface and a depth of 50 cm in
each pedon; and
3. Do not have a salic horizon that has its upper boundary
within 100 cm of the mineral soil surface.
Key to Subgroups
FECA. Gypsiusterts that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Gypsiusterts
FECB. Other Gypsiusterts that have, throughout a layer 15
cm or more thick within 100 cm of the mineral soil surface, an
electrical conductivity of 15 dS/m or more (saturated paste) for
6 or more months in normal years.
Halic Gypsiusterts
FECC. Other Gypsiusterts that have, in one or more horizons
within 100 cm of the mineral soil surface, an exchangeable
sodium percentage of 15 or more (or a sodium adsorption ratio
of 13 or more) for 6 or more months in normal years.
Sodic Gypsiusterts
FECD. Other Gypsiusterts that, if not irrigated during the
year, have cracks in normal years that are 5 mm or more
wide, through a thickness of 25 cm or more within 50 cm of
the mineral soil surface, for 210 or more cumulative days per
year.
Aridic Gypsiusterts
FECE. Other Gypsiusterts that, if not irrigated during the
year, have cracks in normal years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50 cm of the
mineral soil surface, for less than 150 cumulative days per
year.
Udic Gypsiusterts
FECF. Other Gypsiusterts that have a densic, lithic, or
paralithic contact, or the upper boundary of a duripan or
petrocalcic horizon, within 100 cm of the mineral soil
surface.
Leptic Gypsiusterts
FECG. Other Gypsiusterts that have a layer 25 cm or more
thick that contains less than 27 percent clay in its fine-earth
fraction and has its upper boundary within 100 cm of the
mineral soil surface.
Entic Gypsiusterts
FECH. Other Gypsiusterts that have, in one or more horizons
within 30 cm of the mineral soil surface, 50 percent or more
colors as follows:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. Chroma of 3 or more.
Chromic Gypsiusterts
FECI. Other Gypsiusterts.
Typic Gypsiusterts
Definition of Typic Gypsiusterts
Typic Gypsiusterts are the Gypsiusterts that:
1. Do not have a densic, lithic, or paralithic contact, or the
upper boundary of a duripan or petrocalcic horizon, within 100
cm of the mineral soil surface;
2. Do not have a layer 25 cm or more thick that contains less
than 27 percent clay in its fine-earth fraction and has its upper
boundary within 100 cm of the mineral soil surface;
3. Have, throughout all layers 15 cm or more thick
within 100 cm of the mineral soil surface, an electrical
conductivity of less than 15 dS/m (saturated paste) for 6
or more months in normal years;
4. Have, in all horizons within 100 cm of the mineral soil
surface, an exchangeable sodium percentage of less than 15 (or
a sodium adsorption ratio of less than 13) for 6 or more months
in normal years;
5. If not irrigated during the year, have cracks in normal
years that are 5 mm or more wide, through a thickness of 25
cm or more within 50 cm of the mineral soil surface, for 150 to
210 cumulative days per year; and
Vertisols 809
6. Have, in all horizons within 30 cm of the mineral soil surface,
50 percent or more colors as follows:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less; or
c. Chroma of 2 or less.
Description of Subgroups
Typic Gypsiusterts.—The Typic subgroup of Gypsiusterts
is centered on deep or very deep soils that do not have
significant amounts of salts or sodium. In addition, these soils
do not have soil moisture regimes that border on aridic or udic, a
layer with less than 27 percent clay, or light colored surface
layers.
Aridic Gypsiusterts.—These are the Gypsiusterts that have
a soil moisture regime that borders on aridic. They do not have
a lithic contact within 50 cm of the soil surface or significant
amounts of salts or sodium.
Chromic Gypsiusterts.—These are the deep or very deep
Gypsiusterts that have light colored surface layers but do not
have significant amounts of salts or sodium. These soils do not
have soil moisture regimes that border on aridic or udic or a
layer with less than 27 percent clay.
Entic Gypsiusterts.—These are the deep or very deep
Gypsiusterts that have a layer with less than 27 percent clay
but do not have significant amounts of salts or sodium. These
soils do not have a soil moisture regime that borders on aridic
or udic.
Halic Gypsiusterts.—These are the Gypsiusterts that have
a significant accumulation of salts. These soils do not have a
lithic contact within 50 cm of the soil surface.
Leptic Gypsiusterts.—These are the Gypsiusterts that have
a lithic, paralithic, or densic contact within 100 cm of the soil
surface but do not have a lithic contact within 50 cm of the soil
surface. These soils do not have significant amounts of salts or
sodium or a moisture regime that borders on udic or aridic.
Lithic Gypsiusterts.—These are the Gypsiusterts that have
a lithic contact within 50 cm of the soil surface.
Sodic Gypsiusterts.—These are the Gypsiusterts that have
significant amounts of sodium, but not salts. These soils do not
have a lithic contact within 50 cm of the soil surface. They
occur in Texas and are used as rangeland or pasture.
Udic Gypsiusterts.—These are the Gypsiusterts that have a
soil moisture regime that borders on udic. They do not have a
lithic contact within 50 cm of the soil surface or significant
amounts of salts or sodium.
Haplusterts
Haplusterts are the most common of the Usterts. They are
derived from a variety of parent materials, including
sedimentary rocks, alluvium, marl, and basic igneous rocks.
Slopes range from nearly level to strongly sloping.
Haplusterts occur in many Western and Southwestern States,
on the northern Great Plains, and in Puerto Rico and
the Virgin Islands. They are used as rangeland, cropland, or
pasture.
Definition
Haplusterts are the Usterts that:
1. Do not have both:
a. An electrical conductivity in the saturation extract of less
than 4.0 dS/m at 25 o
C; and
b. A pH value of 4.5 or less in 0.01 M CaCl2
(5.0 or less in
saturated paste) in more than 50 percent of the soil volume
between the mineral soil surface and a depth of 50 cm in
each pedon; and
2. Do not have a calcic, gypsic, petrocalcic, or salic horizon
that has its upper boundary within 100 cm of the mineral soil
surface.
Key to Subgroups
FEEA. Haplusterts that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Haplusterts
FEEB. Other Haplusterts that have, throughout a layer 15 cm
or more thick within 100 cm of the mineral soil surface, an
electrical conductivity of 15 dS/m or more (saturated paste) for
6 or more months in normal years.
Halic Haplusterts
FEEC. Other Haplusterts that have, in one or more horizons
within 100 cm of the mineral soil surface, an exchangeable
sodium percentage of 15 or more (or a sodium adsorption ratio
of 13 or more) for 6 or more months in normal years.
Sodic Haplusterts
FEED. Other Haplusterts that have a petrocalcic horizon that
has its upper boundary within 150 cm of the mineral soil
surface.
Petrocalcic Haplusterts
FEEE. Other Haplusterts that have a gypsic horizon that has
its upper boundary within 150 cm of the mineral soil surface.
Gypsic Haplusterts
FEEF. Other Haplusterts that have a calcic horizon that has
its upper boundary within 150 cm of the mineral soil surface.
Calcic Haplusterts
FEEG. Other Haplusterts that have both:
1. A densic, lithic, or paralithic contact within 100 cm of
the mineral soil surface; and
2. If not irrigated during the year, cracks in normal years
810 Soil Taxonomy
that are 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 210 or more
cumulative days per year.
Aridic Leptic Haplusterts
FEEH. Other Haplusterts that, if not irrigated during the
year, have cracks in normal years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50 cm of the
mineral soil surface, for 210 or more cumulative days per year.
Aridic Haplusterts
FEEI. Other Haplusterts that have both:
1. A densic, lithic, or paralithic contact within 100 cm of
the mineral soil surface; and
2. If not irrigated during the year, cracks in 6 or more out
of 10 years that are 5 mm or more wide, through a thickness
of 25 cm or more within 50 cm of the mineral soil surface,
for less than 150 cumulative days per year.
Leptic Udic Haplusterts
FEEJ. Other Haplusterts that have both:
1. A layer 25 cm or more thick that contains less than 27
percent clay in its fine-earth fraction and has its upper
boundary within 100 cm of the mineral soil surface; and
2. If not irrigated during the year, cracks in normal years
that are 5 mm or more wide, through a thickness of 25 cm
or more within 50 cm of the mineral soil surface, for less
than 150 cumulative days per year.
Entic Udic Haplusterts
FEEK. Other Haplusterts that have both:
1. In one or more horizons within 30 cm of the mineral
soil surface, 50 percent or more colors as follows:
a. A color value, moist, of 4 or more; or
b. A color value, dry, of 6 or more; or
c. Chroma of 3 or more; and
2. If not irrigated during the year, cracks in normal years
that are 5 mm or more wide, through a thickness of 25 cm
or more within 50 cm of the mineral soil surface, for less
than 150 cumulative days per year.
Chromic Udic Haplusterts
FEEL. Other Haplusterts that, if not irrigated during the year,
have cracks in normal years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50 cm of the
mineral soil surface, for less than 150 cumulative days per
year.
Udic Haplusterts
FEEM. Other Haplusterts that have a densic, lithic, or
paralithic contact, or the upper boundary of a duripan, within
100 cm of the mineral soil surface.
Leptic Haplusterts
FEEN. Other Haplusterts that have a layer 25 cm or more
thick that contains less than 27 percent clay in its fine-earth
fraction and has its upper boundary within 100 cm of the
mineral soil surface.
Entic Haplusterts
FEEO. Other Haplusterts that have, in one or more horizons
within 30 cm of the mineral soil surface, 50 percent or more
colors as follows:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. Chroma of 3 or more.
Chromic Haplusterts
FEEP. Other Haplusterts.
Typic Haplusterts
Definition of Typic Haplusterts
Typic Haplusterts are the Haplusterts that:
1. Do not have a densic, lithic, or paralithic contact, or the
upper boundary of a duripan or petrocalcic horizon, within 100
cm of the mineral soil surface;
2. Do not have a layer 25 cm or more thick that contains less
than 27 percent clay in its fine-earth fraction and has its upper
boundary within 100 cm of the mineral soil surface;
3. Have, throughout all layers 15 cm or more thick
within 100 cm of the mineral soil surface, an electrical
conductivity of less than 15 dS/m or more (saturated paste)
for 6 or more months in normal years;
4. Have, in all horizons within 100 cm of the mineral soil
surface, an exchangeable sodium percentage of less than 15 (or
a sodium adsorption ratio of less than 13) for 6 or more months
in normal years;
5. If not irrigated during the year, have cracks in normal
years that are 5 mm or more wide, through a thickness of 25
cm or more within 50 cm of the mineral soil surface, for 150 to
210 cumulative days per year;
6. Have, in all horizons within 30 cm of the mineral soil
surface, 50 percent or more colors as follows:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less; or
c. Chroma of 2 or less; and
7. Do not have a calcic or gypsic horizon with an upper
boundary within 150 cm of the mineral soil surface.
Vertisols 811
Description of Subgroups
Typic Haplusterts.—The Typic subgroup of Haplusterts is
centered on deep or very deep soils that do not have significant
amounts of salts or sodium. In addition, these soils do not have
a petrocalcic horizon, soil moisture regimes that border on
aridic or udic, a calcic or gypsic horizon within a depth of 150
cm, a layer with less than 27 percent clay, or light colored
surface layers. In the United States, these soils occur in Texas,
New Mexico, Oklahoma, South Dakota, Hawaii, and Puerto
Rico. They are used for crop production as well as rangeland.
Aridic Haplusterts.—These are the Haplusterts that have a
soil moisture regime that borders on aridic. They do not have a
lithic contact within 50 cm of the soil surface, a petrocalcic
horizon, or significant amounts of salts or sodium. These soils
occur in South Dakota, Montana, Colorado, Nebraska, Texas,
and Wyoming. They commonly are used as rangeland.
Aridic Leptic Haplusterts.—These are the Haplusterts that
have a soil moisture regime that borders on aridic and that
have a lithic, paralithic, or densic contact within 100 cm of the
soil surface but do not have a lithic contact within 50 cm of the
soil surface. These soils do not have a petrocalcic horizon or
significant amounts of salts or sodium. They occur on the
northern Great Plains and in the Southwestern United States
and commonly are used as rangeland.
Calcic Haplusterts.—These are the Haplusterts that have a
calcic horizon with its upper boundary within 150 cm of the
soil surface. They do not have significant accumulations of
salts or sodium. These soils occur in India and the United
States. Most are used as cropland.
Chromic Haplusterts.—These are the deep or very deep
Haplusterts that have light colored surface layers but do not
have significant amounts of salts or sodium. These soils do not
have a petrocalcic horizon, soil moisture regimes that border
on aridic or udic, or a layer with less than 27 percent clay.
They occur in New Mexico and Texas and are used mostly as
rangeland.
Chromic Udic Haplusterts.—These are the deep or very
deep Haplusterts that have light colored surface layers and a
moisture regime that borders on udic but do not have
significant amounts of salts or sodium. These soils do not have
a petrocalcic horizon or a layer with less than 27 percent clay.
They occur in Colorado, Texas, Montana, North Dakota,
Wyoming, and Oklahoma. They are used as rangeland or
cropland.
Entic Haplusterts.—These are the deep or very deep
Haplusterts that have a layer with less than 27 percent clay but
do not have significant amounts of salts or sodium. These soils
do not have a petrocalcic horizon or soil moisture regimes that
border on aridic or udic. They are rare in the United States.
Entic Udic Haplusterts.—These are the deep or very deep
Haplusterts that have a layer with less than 27 percent clay and
a moisture regime that borders on udic but do not have
significant amounts of salts or sodium. These soils do not have
a petrocalcic horizon. They occur in Texas, where they are used
as rangeland, and in Puerto Rico, where they are used for
sugarcane.
Gypsic Haplusterts.—These are the Haplusterts that have a
gypsic horizon with its upper boundary within 150 cm of the
soil surface. They do not have significant accumulations of
salts or sodium. These soils occur in India and the United
States. Many are used as cropland. Some of the soils in India
are mined for gypsum.
Halic Haplusterts.—These are the Haplusterts that have a
significant accumulation of salts. These soils do not have a
lithic contact within 50 cm of the soil surface. They are not
known to occur in the United States.
Leptic Haplusterts.—These are the Haplusterts that have a
lithic, paralithic, or densic contact within 100 cm of the soil
surface but do not have a lithic contact within 50 cm of the soil
surface. These soils do not have significant amounts of salts or
sodium, a moisture regime that borders on udic or aridic, or a
petrocalcic horizon. They occur in South Dakota and Nebraska
and are used as rangeland or cropland.
Leptic Udic Haplusterts.—These are the Haplusterts that
have a lithic, paralithic, or densic contact within 100 cm of the
soil surface and a moisture regime that borders on udic but do
not have a lithic contact within 50 cm of the soil surface. These
soils do not have significant amounts of salts or sodium or a
petrocalcic horizon. They occur in the Southwestern United
States and on the northern Great Plains. They are used as
cropland, rangeland, or pasture.
Lithic Haplusterts.—These are the Haplusterts that have a
lithic contact within 50 cm of the soil surface. They are rare in
the United States.
Petrocalcic Haplusterts.—These are the Haplusterts that
have a petrocalcic horizon. They do not have a lithic contact
within 50 cm of the soil surface or significant amounts of salts
or sodium. These soils are not known to occur in the United
States.
Sodic Haplusterts.—These are the Haplusterts that have
significant amounts of sodium, but not salts. They do not have
a lithic contact within 50 cm of the soil surface. These soils
occur in Montana, Utah, Puerto Rico, Texas, South Dakota, the
Virgin Islands, and the Channel Islands off the coast of
southern California. Most of the soils are used as rangeland,
but some are used as cropland.
Udic Haplusterts.—These are the Haplusterts that have a soil
moisture regime that borders on udic. They do not have a
petrocalcic horizon, a lithic contact within 50 cm of the soil
surface, or significant amounts of salts or sodium. These soils
occur in the Southwestern United States and on the northern
Great Plains. They commonly are used as rangeland, but some
are used for cultivated crops.
Salusterts
These are the Usterts that have a salic horizon. Many of
these soils are derived from salty marine deposits. Salts are
812 Soil Taxonomy
difficult to leach in Salusterts, and few areas are used as
cropland. These soils are not known to occur in the United
States.
Definition
Salusterts are the Usterts that:
1. Have a salic horizon that has its upper boundary
within 100 cm of the mineral soil surface; and
2. Do not have both:
a. An electrical conductivity in the saturation extract of
less than 4.0 dS/m at 25 o
C; and
b. A pH value of 4.5 or less in 0.01 M CaCl2
(5.0 or less in
saturated paste) in more than 50 percent of the soil volume
between the mineral soil surface and a depth of 50 cm in
each pedon.
Key to Subgroups
FEBA. Salusterts that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Salusterts
FEBB. Other Salusterts that have, in one or more horizons
within 100 cm of the mineral soil surface, an exchangeable
sodium percentage of 15 or more (or a sodium adsorption ratio
of 13 or more) for 6 or more months in normal years.
Sodic Salusterts
FEBC. Other Salusterts that have, in one or more horizons
within 100 cm of the mineral soil surface, aquic conditions for
some time in normal years (or artificial drainage) and either:
1. Redoximorphic features; or
2. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated.
Aquic Salusterts
FEBD. Other Salusterts that, if not irrigated during the
year, have cracks in normal years that are 5 mm or more
wide, through a thickness of 25 cm or more within 50 cm of
the mineral soil surface, for 210 or more cumulative days per
year.
Aridic Salusterts
FEBE. Other Salusterts that have a densic, lithic, or
paralithic contact, or the upper boundary of a duripan or
petrocalcic horizon, within 100 cm of the mineral soil surface.
Leptic Salusterts
FEBF. Other Salusterts that have a layer 25 cm or more thick
that contains less than 27 percent clay in its fine-earth fraction
and has its upper boundary within 100 cm of the mineral soil
surface.
Entic Salusterts
FEBG. Other Salusterts that have, in one or more horizons
within 30 cm of the mineral soil surface, 50 percent or more
colors as follows:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. Chroma of 3 or more.
Chromic Salusterts
FEBH. Other Salusterts.
Typic Salusterts
Definition of Typic Salusterts
Typic Salusterts are the Salusterts that:
1. Do not have a densic, lithic, or paralithic contact, or the
upper boundary of a duripan or petrocalcic horizon, within 100
cm of the mineral soil surface;
2. Do not have, in any horizon within 100 cm of the mineral
soil surface, aquic conditions and either:
a. Redoximorphic features; or
b. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated;
3. If not irrigated during the year, do not have cracks in
normal years that are 5 mm or more wide, through a thickness
of 25 cm or more within 50 cm of the mineral soil surface, for
210 or more cumulative days per year;
4. Do not have a layer 25 cm or more thick that contains less
than 27 percent clay in its fine-earth fraction and has its upper
boundary within 100 cm of the mineral soil surface;
5. Have, in all horizons within 100 cm of the mineral soil
surface, an exchangeable sodium percentage of less than 15 (or
a sodium adsorption ratio of less than 13) for 6 or more months
in normal years; and
6. Have, in all horizons within 30 cm of the mineral soil
surface, 50 percent or more colors as follows:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less; or
c. Chroma of 2 or less.
Description of Subgroups
Typic Salusterts.—The Typic subgroup of Salusterts is
centered on deep or very deep soils that do not have significant
Vertisols 813
amounts of sodium. In addition, these soils do not have a soil
moisture regime that borders on aridic, aquic conditions within
100 cm of the soil surface, a layer with less than 27 percent
clay, or light colored surface layers.
Aquic Salusterts.—These are the Salusterts that have aquic
conditions within 100 cm of the soil surface. These soils do not
have a lithic contact within 50 cm of the soil surface or
significant amounts of sodium.
Aridic Salusterts.—These are the Salusterts that have a soil
moisture regime that borders on aridic. They do not have a
lithic contact within 50 cm of the soil surface, aquic conditions
within 100 cm of the soil surface, or significant amounts of
sodium.
Chromic Salusterts.—These are the deep or very deep
Salusterts that have light colored surface layers but do not have
significant amounts of sodium. These soils do not have a soil
moisture regime that borders on aridic, a layer with less than
27 percent clay, or aquic conditions within 100 cm of the soil
surface.
Entic Salusterts.—These are the deep or very deep
Salusterts that have a layer with less than 27 percent clay but
do not have significant amounts of sodium. These soils do not
have a soil moisture regime that borders on aridic or aquic
conditions within 100 cm of the soil surface.
Leptic Salusterts.—These are the Salusterts that have a
lithic, paralithic, or densic contact within 100 cm of the soil
surface but do not have a lithic contact within 50 cm of the soil
surface. These soils do not have significant amounts of sodium,
a moisture regime that borders on aridic, or aquic conditions
within 100 cm of the soil surface.
Lithic Salusterts.—These are the Salusterts that have a
lithic contact within 50 cm of the soil surface.
Sodic Salusterts.—These are the Salusterts that have
significant amounts of sodium. These soils do not have a lithic
contact within 50 cm of the soil surface.
Xererts
Xererts are the Vertisols of Mediterranean climates, which are
typified by cool, wet winters and warm, dry summers. These
soils have cracks that regularly close and open each year.
Because the soils dry every summer and remoisten in the
winter, damage to structures and roads is very significant. If
not irrigated, these soils are used for small grain or grazing. In
the United States, most of the soils supported grasses before
they were cultivated.
Definition
Xererts are the Vertisols that:
1. Do not have a cryic soil temperature regime;
2. Do not have, in any horizon within 50 cm of the mineral soil
surface, aquic conditions and any of the following:
a. In more than half of each pedon, either on faces of peds
or in the matrix if peds are absent, 50 percent or more
chroma of either:
(1) 2 or less if redox concentrations are present; or
(2) 1 or less if redox concentrations are absent; or
b. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated; and
3. In normal years, have both:
a. A thermic, mesic, or frigid soil temperature regime; and
b. If not irrigated during the year, cracks that remain both:
(1) 5 mm or more wide, throughout a layer 25 cm or
more thick within 50 cm of the mineral soil surface, for
60 or more consecutive days during the 90 days following
the summer solstice; and
(2) Closed for 60 or more consecutive days during the
90 days following the winter solstice.
Key to Great Groups
FCA. Xererts that have a duripan that has its upper boundary
within 100 cm of the mineral soil surface.
Durixererts, p. 814
FCB. Other Xererts that have a calcic or petrocalcic horizon
that has its upper boundary within 100 cm of the mineral soil
surface.
Calcixererts,p.813
FCC. Other Xererts.
Haploxererts, p. 816
Calcixererts
Calcixererts are the Xererts that have a calcic or petrocalcic
horizon. Many of these soils formed in fine textured
sedimentary rocks. In the United States, some of the soils are
used for irrigated crops. The others are used as rangeland,
pasture, or nonirrigated cropland.
Definition
Calcixererts are the Xererts that:
1. Have a calcic or petrocalcic horizon with an upper
boundary within 100 cm of the mineral soil surface; and
814 Soil Taxonomy
2. Do not have a duripan with an upper boundary within 100
cm of the mineral soil surface.
Key to Subgroups
FCBA. Calcixererts that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Calcixererts
FCBB. Other Calcixererts that have a petrocalcic horizon
that has its upper boundary within 100 cm of the mineral soil
surface.
Petrocalcic Calcixererts
FCBC. Other Calcixererts that, if not irrigated during the
year, have cracks in normal years that remain 5 mm or more
wide, through a thickness of 25 cm or more within 50 cm of
the mineral soil surface, for 180 or more consecutive days.
Aridic Calcixererts
FCBD. Other Calcixererts that have a densic, lithic, or
paralithic contact within 100 cm of the mineral soil surface.
Leptic Calcixererts
FCBE. Other Calcixererts that have a layer 25 cm or more
thick that contains less than 27 percent clay in its fine-earth
fraction and has its upper boundary within 100 cm of the
mineral soil surface.
Entic Calcixererts
FCBF. Other Calcixererts that have, in one or more horizons
within 30 cm of the mineral soil surface, 50 percent or more
colors as follows:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. Chroma of 3 or more.
Chromic Calcixererts
FCBG. Other Calcixererts.
Typic Calcixererts
Definition of Typic Calcixererts
Typic Calcixererts are the Calcixererts that:
1. Do not that have a densic, lithic, or paralithic contact
within 100 cm of the mineral soil surface;
2. If not irrigated during the year, do not have cracks in
normal years that remain 5 mm or more wide, through a
thickness of 25 cm or more within 50 cm of the mineral soil
surface, for 180 or more consecutive days;
3. Do not have a petrocalcic horizon that has its upper
boundary within 100 cm of the mineral soil surface;
4. Do not have a layer 25 cm or more thick that contains less
than 27 percent clay in its fine-earth fraction and has its
upper boundary within 100 cm of the mineral soil surface;
and
5. Have, in all horizons within 30 cm of the mineral soil surface,
50 percent or more colors as follows:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less; or
c. Chroma of 2 or less.
Description of Subgroups
Typic Calcixererts.—The Typic subgroup of the Calcixererts
is centered on deep or very deep soils that do not have a
petrocalcic horizon or a soil moisture regime that borders on
aridic. These soils tend to have dark colored surface layers and a
clay loam or finer texture throughout.
Aridic Calcixererts.—These are the Calcixererts that have
a soil moisture regime that borders on aridic and do not have a
lithic contact within 50 cm of the soil surface. These soils are
used for irrigated crops or rangeland.
Chromic Calcixererts.—These are the deep or very deep
Calcixererts that have light colored surface layers. These soils
do not have a petrocalcic horizon or a soil moisture regime that
borders on aridic. They typically have a clay loam or finer
texture throughout. These soils occur in Idaho and are used as
rangeland or for irrigated or nonirrigated crops.
Entic Calcixererts.—These are the deep or very deep
Calcixererts that have a layer 25 cm or more thick that
contains less than 27 percent clay. These soils do not have a
petrocalcic horizon or a soil moisture regime that borders on
aridic. They occur in California and Idaho and are used as
rangeland or for irrigated or nonirrigated crops.
Leptic Calcixererts.—These are the Calcixererts that have
a densic, lithic, or paralithic contact within 100 cm of the soil
surface but do not have a lithic contact within 50 cm of the soil
surface. They do not have a petrocalcic horizon or a soil
moisture regime that borders on aridic. These soils occur in
California and are used for pasture and hay.
Lithic Calcixererts.—These are the Calcixererts that have
a lithic contact within 50 cm of the soil surface. These soils are
not extensive in the world and are not known to occur in the
United States.
Petrocalcic Calcixererts.—These are the Calcixererts that
have a petrocalcic horizon. They do not have a lithic contact
within 50 cm of the soil surface or a soil moisture regime that
borders on aridic. These soils occur in California and are used
for pasture, rangeland, or irrigated or nonirrigated crops.
Durixererts
Durixererts are the Xererts that have a duripan. Most of
these soils are derived from basic igneous rocks, but some
formed in mixed alluvium. The Durixererts in the United States
Vertisols 815
occur in California and Idaho and are used for crop production
or rangeland.
Definition
Durixererts are the Xererts that have a duripan that has its
upper boundary within 100 cm of the mineral soil surface.
Key to Subgroups
FCAA. Durixererts that have, throughout a layer 15 cm or
more thick above the duripan, an electrical conductivity of 15
dS/m or more (saturated paste) for 6 or more months in normal
years.
Halic Durixererts
FCAB. Other Durixererts that have, in one or more horizons
above the duripan, an exchangeable sodium percentage of 15 or
more (or a sodium adsorption ratio of 13 or more) for 6 or
more months in normal years.
Sodic Durixererts
FCAC. Other Durixererts that have, in one or more horizons
above the duripan, aquic conditions for some time in normal
years (or artificial drainage) and either:
1. Redoximorphic features; or
2. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated.
Aquic Durixererts
FCAD. Other Durixererts that, if not irrigated during the
year, have cracks in normal years that remain 5 mm or more
wide, through a thickness of 25 cm or more above the duripan,
for 180 or more consecutive days.
Aridic Durixererts
FCAE. Other Durixererts that, if not irrigated during the
year, have cracks in normal years that remain 5 mm or more
wide, through a thickness of 25 cm or more above the duripan,
for less than 90 consecutive days.
Udic Durixererts
FCAF. Other Durixererts that have a duripan that is not
indurated in any subhorizon.
Haplic Durixererts
FCAG. Other Durixererts that have, in one or more horizons
within 30 cm of the mineral soil surface, 50 percent or more
colors as follows:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. Chroma of 3 or more.
Chromic Durixererts
FCAH. Other Durixererts.
Typic Durixererts
Definition of Typic Durixererts
Typic Durixererts are the Durixererts that:
1. Do not have, in any horizon above the duripan, aquic
conditions and either:
a. Redoximorphic features; or
b. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated;
2. Have, throughout all layers 15 cm or more thick above the
duripan, an electrical conductivity of less than 15 dS/m
(saturated paste) for 6 or more months in normal years;
3. Have, in all horizons above the duripan, an exchangeable
sodium percentage of less than 15 (or a sodium adsorption
ratio of less than 13) for 6 or more months in normal years;
4. If not irrigated during the year, have cracks in normal
years that remain 5 mm or more wide, throughout a layer 25
cm or more thick above the duripan, for 90 to 180 consecutive
days;
5. Have a duripan that is either platy or massive and also is
indurated in some subhorizon; and
6. Have, in all horizons within 30 cm of the mineral soil
surface, 50 percent or more colors as follows:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less; or
c. Chroma of 2 or less.
Description of Subgroups
Typic Durixererts.—The Typic subgroup of Durixererts is
centered on soils that have dark colored surface layers and a
duripan that is indurated in at least some part. These soils do
not have significant amounts of salts and sodium. In addition,
they do not have aquic conditions within 100 cm of the soil
surface or a soil moisture regime that borders on aridic or udic.
Aquic Durixererts.—These are the Durixererts that have
aquic conditions within 100 cm of the soil surface for extended
periods. These soils do not have significant amounts of salts
and sodium. They occur in California and are used for crop
production, pasture, or rangeland.
Aridic Durixererts.—These are the Durixererts that have a
soil moisture regime that borders on aridic. They do not have
significant amounts of salts or sodium or aquic conditions for
significant periods within 100 cm of the soil surface. These
soils occur in California and are used mostly for irrigated
crops.
Chromic Durixererts.—These are the Durixererts that have
light colored surface layers and a duripan that is indurated in
816 Soil Taxonomy
at least some part. These soils do not have significant amounts
of salts and sodium, a moisture regime that borders on aridic or
udic, or aquic conditions for extended periods within 100 cm of
the soil surface. They occur in Idaho and California and are
used as rangeland.
Halic Durixererts.—These are the Durixererts that have
significant amounts of salts. They are not known to occur in
the United States.
Haplic Durixererts.—These are the Durixererts that have a
duripan that is not indurated in any part. These soils do not
have significant amounts of salts and sodium, a moisture
regime that borders on aridic or udic, or aquic conditions for
significant periods within 100 cm of the soil surface. They
occur in California and are used for crop production or
rangeland.
Sodic Durixererts.—These are the Durixererts that have
significant amounts of sodium, but not salts. These soils are
not known to occur in the United States.
Udic Durixererts.—These are the Durixererts that have
a soil moisture regime that borders on udic. These soils do
not have significant amounts of salts or sodium or aquic
conditions for extended periods within 100 cm of the soil
surface.
Haploxererts
Haploxererts are the Xererts that do not have a calcic or
petrocalcic horizon or a duripan. These are the most common
of the Xererts. They formed in a variety of parent materials,
including volcanic and sedimentary rocks, lacustrine deposits,
and alluvium. In many areas these soils are used for grazing by
livestock. In some areas they are used for citrus, small grain,
truck crops, or rice.
Definition
Haploxererts are the Xererts that do not have a duripan or a
calcic or petrocalcic horizon that has its upper boundary within
100 cm of the mineral soil surface.
Key to Subgroups
FCCA. Haploxererts that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Haploxererts
FCCB. Other Haploxererts that have, throughout a layer 15
cm or more thick within 100 cm of the mineral soil surface, an
electrical conductivity of 15 dS/m or more (saturated paste) for
6 or more months in normal years.
Halic Haploxererts
FCCC. Other Haploxererts that have, in one or more
horizons within 100 cm of the mineral soil surface, an
exchangeable sodium percentage of 15 or more (or a sodium
adsorption ratio of 13 or more) for 6 or more months in normal
years.
Sodic Haploxererts
FCCD. Other Haploxererts that, if not irrigated during the
year, have cracks in normal years that remain 5 mm or more
wide, through a thickness of 25 cm or more within 50 cm of
the mineral soil surface, for 180 or more consecutive days.
Aridic Haploxererts
FCCE. Other Haploxererts that have, in one or more
horizons within 100 cm of the mineral soil surface, aquic
conditions for some time in normal years (or artificial
drainage) and either:
1. Redoximorphic features; or
2. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated.
Aquic Haploxererts
FCCF. Other Haploxererts that, if not irrigated during the
year, have cracks in normal years that remain 5 mm or more
wide, through a thickness of 25 cm or more within 50 cm of
the mineral soil surface, for less than 90 consecutive days.
Udic Haploxererts
FCCG. Other Haploxererts that have a densic, lithic, or
paralithic contact within 100 cm of the mineral soil surface.
Leptic Haploxererts
FCCH. Other Haploxererts that have a layer 25 cm or more
thick that contains less than 27 percent clay in its fine-earth
fraction and has its upper boundary within 100 cm of the
mineral soil surface.
Entic Haploxererts
FCCI. Other Haploxererts that have, in one or more horizons
within 30 cm of the mineral soil surface, 50 percent or more
colors as follows:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. Chroma of 3 or more.
Chromic Haploxererts
FCCJ. Other Haploxererts.
Typic Haploxererts
Definition of Typic Haploxererts
Typic Haploxererts are the Haploxererts that:
1. Do not have a densic, lithic, or paralithic contact
within 100 cm of the mineral soil surface;
Vertisols 817
2. Do not have, in any horizon within 100 cm of the mineral soil
surface, aquic conditions and either:
a. Redoximorphic features; or
b. Enough active ferrous iron (Fe2+
) to give a positive
reaction to alpha,alpha-dipyridyl at a time when the soil is
not being irrigated;
3. Do not have a layer 25 cm or more thick that contains less
than 27 percent clay in its fine-earth fraction and has its upper
boundary within 100 cm of the mineral soil surface;
4. Have, throughout all layers 15 cm or more thick
within 100 cm of the mineral soil surface, an electrical
conductivity of less than 15 dS/m (saturated paste) for 6
or more months in normal years;
5. Have, in all horizons within 100 cm of the mineral soil
surface, an exchangeable sodium percentage of less than 15 (or
a sodium adsorption ratio of less than 13) for 6 or more months
in normal years;
6. If not irrigated during the year, have cracks in normal
years that remain 5 mm or more wide, through a thickness of
25 cm or more within 50 cm of the mineral soil surface, for 90
or more but less than 180 consecutive days; and
7. Have, in all horizons within 30 cm of the mineral soil
surface, 50 percent or more colors as follows:
a. A color value, moist, of 3 or less; or
b. A color value, dry, of 5 or less; or
c. Chroma of 2 or less.
Description of Subgroups
Typic Haploxererts.—The Typic subgroup of Haploxererts
is centered on deep or very deep, clayey soils with dark colored
surface layers. These soils do not have significant amounts of
sodium or salts, a soil moisture regime that borders on aridic or
udic, or aquic conditions within 100 cm of the soil surface for
extended periods. They occur in Oregon, Idaho, and California
and are used for rangeland, pasture, or dryland or irrigated
crops.
Aquic Haploxererts.—These are the Haploxererts that have
aquic conditions within 100 cm of the soil surface for extended
periods. These soils do not have significant amounts of salts or
sodium or a lithic contact within 50 cm of the soil surface.
They occur in Oregon and California and are used for pasture
or irrigated crops, including rice.
Aridic Haploxererts.—These are the Haploxererts that
have a soil moisture regime that borders on aridic. They do not
have a lithic contact within 50 cm of the soil surface or
significant amounts of sodium and salts. These soils occur in
Nevada and California, including the Channel Islands off the
coast of southern California. The soils are used for rangeland
or crop production. In some areas they are irrigated and
planted to citrus.
Chromic Haploxererts.—These are the deep or very deep,
clayey Haploxererts with light colored surface layers. These
soils do not have significant amounts of sodium or salts, a soil
moisture regime that borders on udic or aridic, or aquic
conditions for significant periods within 100 cm of the soil
surface. They occur in California, Idaho, and Oregon. They
generally are used as rangeland, but the more nearly level areas
are used for irrigated or nonirrigated crops.
Entic Haploxererts.—These are the deep or very deep
Haploxererts that have a layer 25 cm or more thick with less
than 27 percent clay. These soils do not have significant
amounts of salts or sodium, a moisture regime that borders on
aridic or udic, or aquic conditions for extended periods within
100 cm of the soil surface. They occur in Oregon and are used
as rangeland.
Halic Haploxererts.—These are the Haploxererts that have
significant amounts of salts. These soils do not have a lithic
contact within 50 cm of the soil surface. They occur in
California, including the Channel Islands off the coast of
southern California. They are used for rangeland or irrigated
crops.
Leptic Haploxererts.—These are the Haploxererts that
have a densic, lithic, or paralithic contact within 100 cm of the
soil surface but do not have a lithic contact within 50 cm of the
soil surface. These soils do not have significant amounts of
sodium or salts, a soil moisture regime that borders on udic or
aridic, or aquic conditions for extended periods within 100 cm
of the soil surface. They occur in Nevada, California, Oregon,
and Idaho. They are used mostly as rangeland, but small areas
are used for irrigated crops.
Lithic Haploxererts.—These are the Haploxererts that
have a lithic contact within 50 cm of the soil surface. They are
not known to occur in the United States.
Sodic Haploxererts.—These are the Haploxererts that have
significant amounts of sodium, but not salts. These soils do not
have a lithic contact within 50 cm of the soil surface. They
occur in California. Some of the soils are used for crops,
including rice.
Udic Haploxererts.—These are the Haploxererts that have
a soil moisture regime that borders on udic. These soils do not
have significant amounts of sodium or salts, a lithic contact
within 50 cm of the soil surface, or aquic conditions for
significant periods within 100 cm of the soil surface. They
occur in Oregon, where they are used for nonirrigated or
irrigated crops, including orchards.
819
As was noted in chapter 6, families and series serve
purposes that are largely pragmatic, the series name is
abstract, and the technical family name is descriptive. In the
paragraphs that follow, the descriptive terms used in the names
of families are defined, the control sections to which the terms
apply are given, and the criteria, including the taxa in which
they are used, are indicated. An example of a family is given to
show how the family name is derived, and the differences
between two series in that family are pointed out as examples
of series differentiae.
Family Differentiae for Mineral Soils and
Mineral Layers of Some Organic Soils
The following differentiae are used to distinguish families of
mineral soils and the mineral layers of some organic soils
within a subgroup. The class names of these components are
used to form the family name. The components are listed and
defined in the same sequence in which the components appear
in the family names.
Particle-size classes
Mineralogy classes
Cation-exchange activity classes
Calcareous and reaction classes
Soil temperature classes
Soil depth classes
Rupture-resistance classes
Classes of coatings
Classes of cracks
Particle-Size Classes and Their Substitutes
Definition of Particle-Size Classes and Their Substitutes for
Mineral Soils
The first part of the family name is the name of either a
particle-size class or a substitute for a particle-size class. The
term particle-size class is used to characterize the grain-size
composition of the whole soil, including both the fine earth and
the rock and pararock fragments up to the size of a pedon, but
it excludes organic matter and salts more soluble than gypsum.
Substitutes for particle-size classes are used for soils that have
andic soil properties or a high content of volcanic glass,
pumice, or cinders.
The particle-size classes of this taxonomy represent a
compromise between conventional divisions in pedologic and
engineering classifications. Engineering classifications have
set the limit between sand and silt at a diameter of 74 microns,
while pedologic classifications have set it at either 50 or 20
microns. Engineering classifications have been based on grainsize
percentages, by weight, in the soil fraction less than 74
mm in diameter, while textural classes in pedologic
classifications have been based on percentages, by weight, in
the fraction less than 2.0 mm in diameter. In engineering
classifications, the separate very fine sand (diameter between
50 and 100 microns or 0.05 and 0.1 mm) has been subdivided
at 74 microns. In defining the particle-size classes for this
taxonomy, a similar division has been made, but in a different
way. Soil materials that have a texture of fine sand or loamy
fine sand normally have an appreciable amount of very fine
sand, most of which is coarser than 74 microns. A silty
sediment, such as loess, may also contain an appreciable
amount of very fine sand, most of which is finer than 74
microns. Thus, in the design of particle-size classes for this
taxonomy, the very fine sand has been allowed to “float.” It is
included with the sand if the texture (fine-earth fraction) of a
soil is sand, loamy fine sand, or coarser. It is treated as silt,
however, if the texture is very fine sand, loamy very fine sand,
sandy loam, silt loam, or finer.
No single set of particle-size classes seems adequate to serve
as family differentiae for all of the different kinds of soil. Thus,
this taxonomy provides 2 generalized and 11 more narrowly
defined classes, which permit relatively fine distinctions
between families of soils for which particle size is important,
while providing broader groupings for soils in which narrowly
defined particle-size classes would produce undesirable
separations. Thus, the term “clayey” is used for some soil
families to indicate a clay content of 35 percent (30 percent in
Vertisols) or more in specific horizons, while in other families
the more narrowly defined terms “fine” and “very-fine”
indicate that these horizons have a clay content either of 35 (30
percent in Vertisols) to 60 percent or of 60 percent or more in
their fine-earth fraction. Fine earth refers to particles smaller
than 2.0 mm in diameter. Rock fragments are particles 2.0 mm
or more in diameter that are strongly cemented or more
resistant to rupture and include all particles with horizontal
dimensions smaller than the size of a pedon. Cemented
fragments 2.0 mm or more in diameter that are in a ruptureresistance
class that is less cemented than the strongly
CHAPTER 21
Family and Series Differentiae and Names
820 Soil Taxonomy
cemented class are referred to as pararock fragments. Pararock
fragments, like rock fragments, include all particles between
2.0 mm and a horizontal dimension smaller than the size of a
pedon. Most pararock fragments are broken into fragments 2.0
mm or less in diameter during the preparation of samples for
particle-size analysis in the laboratory. Therefore, pararock
fragments are generally included with the fine earth in the
particle-size classes, although cinders, pumice, and pumicelike
fragments are treated as fragments in the substitutes for
classes, regardless of their rupture-resistance class.
Substitutes for particle-size classes are used for soils that
have andic soil properties or a high content of volcanic glass,
pumice, or cinders. These materials cannot be readily
dispersed, and the results of dispersion vary. Consequently,
normal particle-size classes do not adequately characterize
these components. Substitutes for particle-size class names are
used for those parts of soils that have andic soil properties or a
high amount of volcanic glass, pumice, or cinders, as is the
case with Andisols and many Andic and Vitrandic subgroups
of other soil orders. Some Spodosols, whether identified in
Andic subgroups or not, have andic soil properties in some
horizons within the particle-size control section, and particlesize
substitute class names are used for these horizons.
Neither a particle-size class name nor a substitute for a
particle-size class name is used for Psamments,
Psammaquents, and Psammentic subgroups that are in a sandy
particle-size class. These taxa have, by definition, either a
sandy particle-size class or an ashy substitute class. The sandy
particle-size class is considered redundant in the family name.
The ashy substitute class, however, is named, if appropriate in
these taxa.
Particle-size class names are applied, although with
reservations, to spodic horizons and other horizons that do not
have andic soil properties but contain significant amounts of
allophane, imogolite, ferrihydrite, or aluminum-humus
complexes. The isotic mineralogy class (defined below) is
helpful in identifying these particle-size classes.
In general, the weighted average particle-size class of the
whole particle-size control section (defined below) determines
what particle-size class name is used as a component of the
family name.
Strongly Contrasting Particle-Size Classes
If the particle-size control section consists of two parts with
strongly contrasting particle-size or substitute classes (listed
below), if both parts are 12.5 cm or more thick (including parts
not in the control section), and if the transition zone between
them is less than 12.5 cm thick, both class names are used. For
example, the family particle-size class is sandy over clayey if
all of the following criteria are met: the soil meets criterion D
(listed below) under the control section for particle-size classes
or their substitutes; any Ap horizon is less than 30 cm thick;
the weighted average particle-size class of the upper 30 cm of
the soil is sandy; the weighted average of the lower part is
clayey; and the transition zone is less than 12.5 cm thick. If a
substitute name applies to one or more parts of the particle-size
control section and the parts are not strongly contrasting
classes, the name of the thickest part (cumulative) is used as
the soil family name.
Aniso Class
If the particle-size control section includes more than one
pair of the strongly contrasting classes, listed below, then the
soil is assigned to an aniso class named for the pair of adjacent
classes that contrast most strongly. The aniso class is
considered part of the particle-size class name and is set off by
commas after the particle-size name. An example is a sandy
over clayey, aniso, mixed, active, mesic Aridic Haplustoll.
Generalized Particle-Size Classes
Two generalized particle-size classes, loamy and clayey, are
used for shallow classes (defined below) and for soils in
Arenic, Grossarenic, and Lithic subgroups. The clayey class is
used for all strongly contrasting particle-size classes with more
than 35 percent clay (30 percent in Vertisols). The loamy
particle-size class is used for contrasting classes, where
appropriate, to characterize the lower part of the particle-size
control section. The generalized classes, where appropriate, are
also used for all strongly contrasting particle-size classes that
include a substitute class. For example, loamy over pumiceous
or cindery (not fine-loamy over pumiceous or cindery) is used.
Six generalized classes, defined later in this chapter, are
used for Terric subgroups of Histosols and Histels.
Control Section for Particle-Size Classes or Their
Substitutes in Mineral Soils
The particle-size and substitute class names listed below are
applied to certain horizons, or to the soil materials within
specific depth limits, that have been designated as the particlesize
control section. The lower boundary of the control section
may be at a specified depth (in centimeters) below the mineral
soil surface or below the upper boundary of an organic layer
with andic soil properties, or it may be at the upper boundary
of a root-limiting layer. Unless otherwise indicated, the
following are considered root-limiting layers in this chapter: a
duripan; a fragipan; petrocalcic, petrogypsic, and placic
horizons; continuous ortstein; and densic, lithic, paralithic,
and petroferric contacts. The following list of particle-size
control sections for particular kinds of mineral soils is
arranged as a key. This key, like other keys in this taxonomy, is
designed in such a way that the reader makes the correct
classification by going through the key systematically, starting
at the beginning and eliminating one by one all classes that
include criteria that do not fit the soil in question. The soil
belongs to the first class for which it meets all of the criteria
listed. The upper boundary of an argillic, natric, or kandic
horizon is used in the following key. This boundary is not
always obvious. If one of these horizons is present but the
Family and Series Differentiae and Names 821
upper boundary is irregular or broken, as in an A/B or B/A
horizon, the depth at which half or more of the volume has the
fabric of an argillic, natric, or kandic horizon should be
considered the upper boundary.
Key to the Control Section for Particle-Size Classes or Their
Substitutes in Mineral Soils
A. For mineral soils that have a root-limiting layer (listed
above) within 36 cm of the mineral soil surface or below the
upper boundary of organic soil materials with andic soil
properties, whichever is shallower: From the mineral soil
surface or the upper boundary of the organic soil materials with
andic soil properties, whichever is shallower, to the rootlimiting
layer; or
B. For Andisols: Between either the mineral soil surface or
the upper boundary of an organic layer with andic soil
properties, whichever is shallower, and the shallower of the
following: (a) a depth 100 cm below the starting point or (b) a
root-limiting layer; or
C. For those Alfisols, Ultisols, and great groups of Aridisols
and Mollisols, excluding soils in Lamellic subgroups, that have
an argillic, kandic, or natric horizon that has its upper
boundary within 100 cm of the mineral soil surface and its
lower boundary at a depth of 25 cm or more below the mineral
soil surface or that are in a Grossarenic or Arenic subgroup,
use 1 through 4 below. For other soils, go to D below.
1. Strongly contrasting particle-size classes (defined and
listed later) within or below the argillic, kandic, or natric
horizon and within 100 cm of the mineral soil surface: The
upper 50 cm of the argillic, kandic, or natric horizon or to a
depth of 100 cm, whichever is deeper, but not below the
upper boundary of a root-limiting layer; or
2. All parts of the argillic, kandic, or natric horizon in or
below a fragipan: Between a depth of 25 cm from the
mineral soil surface and the top of the fragipan; or
3. A fragipan at a depth of less than 50 cm below the top
of the argillic, kandic, or natric horizon: Between the upper
boundary of the argillic, kandic, or natric horizon and the
top the fragipan; or
4. Other soils that meet C above: Either the whole argillic,
kandic, or natric horizon if 50 cm or less thick or the upper
50 cm of the horizon if more than 50 cm thick.
D. For those Alfisols, Ultisols, and great groups of Aridisols
and Mollisols that are in a Lamellic subgroup or have an
argillic, kandic, or natric horizon that has its upper boundary
at a depth of 100 cm or more from the mineral surface and that
are not in a Grossarenic or Arenic subgroup: Between the
lower boundary of an Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and 100 cm below
the mineral soil surface or a root-limiting layer, whichever is
shallower; or
E. For other soils that have an argillic or natric horizon that has
its lower boundary at a depth of less than 25 cm from the mineral
surface: Between the upper boundary of the argillic
or natric horizon and a depth of 100 cm below the mineral
soil surface or a root-limiting layer, whichever is shallower;
or
F. All other mineral soils: Between the lower boundary of an
Ap horizon or a depth of 25 cm below the mineral soil surface,
whichever is deeper, and the shallower of the following: (a) a
depth of 100 cm below the mineral soil surface or (b) a root-
limitinglayer.
Key to the Particle-Size and Substitute Classes of Mineral
Soils
This key, like other keys in this taxonomy, is designed in such
a way that the reader makes the correct classification by going
through the key systematically, starting at the beginning and
eliminating one by one all classes that include criteria that do
not fit the soil or layer in question. The class or substitute name
for each layer within the control section must be determined
from the key. If any two layers meet the criteria for strongly
contrasting particle-size classes (listed below), the soil is named
for that strongly contrasting class. If more than one pair meets
the criteria for strongly contrasting classes, the soil is also in an
aniso class named for the pair of adjacent classes that contrast
most strongly. If the soil has none of the strongly contrasting
classes, the weighted average soil materials within the particlesize
control section generally determine the class. Exceptions are
soils that are not strongly contrasting and that have a substitute
class name for one or more parts of the control section. In these
soils the class or substitute name of the thickest (cumulative)
part within the control section is used to determine the family
name.
A. Mineral soils that have, in the thickest part of the control
section (if the control section is not in one of the strongly
contrasting particle-size classes listed below), or in a part of the
control section that qualifies as an element in one of the
strongly contrasting particle-size classes listed below, or
throughout the control section, a fine-earth component
(including associated medium and finer pores) of less than 10
percent of the total volume and that meet one of the following
sets of substitute class criteria:
1. Have, in the whole soil, more than 60 percent (by
weight) volcanic ash, cinders, lapilli, pumice, and
pumicelike1
fragments and, in the fraction coarser than
1
Pumicelike—vesicular pyroclastic materials other than pumice that have an apparent
specific gravity (including vesicles) of less than 1.0 g/cm3
.
822 Soil Taxonomy
2.0 mm, two-thirds or more (by volume) pumice and/or
pumicelike fragments.
Pumiceous
or
2. Have, in the whole soil, more than 60 percent (by
weight) volcanic ash, cinders, lapilli, pumice, and
pumicelike fragments and, in the fraction coarser than 2.0
mm, less than two-thirds (by volume) pumice and
pumicelike fragments.
Cindery
or
3. Other mineral soils that have a fine-earth component of
less than 10 percent (including associated medium and finer
pores) of the total volume.
Fragmental
or
B. Other mineral soils that have a fine-earth component of 10
percent or more (including associated medium and finer pores)
of the total volume and meet, in the thickest part of the control
section (if the control section is not in one of the strongly
contrasting particle-size classes listed below), or in a part of
the control section that qualifies as an element in one of the
strongly contrasting particle-size classes listed below, or
throughout the control section, one of the following sets of
substitute class criteria:
1. They:
a. Have andic soil properties and have a water
content at 1500 kPa tension of less than 30 percent on
undried samples and less than 12 percent on dried
samples; or
b. Do not have andic soil properties, have a total of 30
percent or more of the fine-earth fraction in the 0.02 to
2.0 mm fraction, and have (by grain count) 30 percent or
more of that fraction consisting of volcanic glass, glass
aggregates, glass-coated grains, and other vitric
volcaniclastics; and
c. Have one of the following;
(1) A total of 35 percent or more (by volume) rock
and pararock fragments, of which two-thirds or more
(by volume) is pumice or pumicelike fragments.
Ashy-pumiceous
or
(2) 35 percent or more (by volume) rock fragments.
Ashy-skeletal
or
(3) Less than 35 percent (by volume) rock
fragments.
Ashy
or
2. Have a fine-earth fraction that has andic soil properties
and that has a water content at 1500 kPa tension of 12
percent or more on air-dried samples or of 30 to 100 percent
on undried samples; and
a. Have a total of 35 percent or more (by volume) rock
and pararock fragments, of which two-thirds or more (by
volume) is pumice or pumicelike fragments.
Medial-pumiceous
or
b. Have 35 percent or more (by volume) rock
fragments.
Medial-skeletal
or
c. Have less than 35 percent (by volume) rock
fragments.
Medial
or
3. Have a fine-earth fraction that has andic soil properties
and that has a water content at 1500 kPa tension of 100
percent or more on undried samples; and
a. Have a total of 35 percent or more (by volume) rock
and pararock fragments, of which two-thirds or more (by
volume) is pumice or pumicelike fragments.
Hydrous-pumiceous
or
b. Have 35 percent or more (by volume) rock
fragments.
Hydrous-skeletal
or
c. Have less than 35 percent (by volume) rock
fragments.
Hydrous
or
Note: In the following classes, “clay” excludes clay-size
carbonates. Carbonates of clay size are treated as silt. If the
ratio of percent water retained at 1500 kPa tension to the
percentage of measured clay is 0.25 or less or 0.6 or more in
half or more of the particle-size control section or part of the
particle-size control section in strongly contrasting classes,
Family and Series Differentiae and Names 823
then the percentage of clay is estimated by the following
formula: Clay % = 2.5(% water retained at 1500 kPa tension - %
organic carbon).
C. Other mineral soils that, in the thickest part of the control
section (if part of the control section has a substitute for
particle-size class and is not in one of the strongly contrasting
particle-size classes listed below), or in a part of the control
section that qualifies as an element in one of the strongly
contrasting particle-size classes listed below, or throughout the
control section, meet one of the following sets of particle-size
class criteria:
1. Have 35 percent or more (by volume) rock fragments
and a fine-earth fraction with a texture of sand or loamy
sand, including less than 50 percent (by weight) very fine
sand.
Sandy-skeletal
or
2. Have 35 percent or more (by volume) rock fragments
and less than 35 percent (by weight) clay.
Loamy-skeletal
or
3. Have 35 percent or more (by volume) rock fragments.
Clayey-skeletal
or
4. Have a texture of sand or loamy sand, including less
than 50 percent (by weight) very fine sand in the fine-earth
fraction.
Sandy
or
5. Have a texture of loamy very fine sand, very fine sand,
or finer, including less than 35 percent (by weight) clay in
the fine-earth fraction (excluding Vertisols), and are in a
shallow family (defined below) or in a Lithic, Arenic, or
Grossarenic subgroup, or the layer is an element in a
strongly contrasting particle-size class (listed below) and the
layer is the lower element or the other element is a
substitute for particle-size class.
Loamy
or
6. Have, in the fraction less than 75 mm in diameter, 15
percent or more (by weight) particles with diameters of 0.1
to 75 mm (fine sand or coarser, including rock fragments up
to 7.5 cm in diameter) and, in the fine-earth fraction, less
than 18 percent (by weight) clay.
Coarse-loamy
or
7. Have, in the fraction less than 75 mm in diameter, 15
percent or more (by weight) particles with diameters of 0.1 to
75 mm (fine sand or coarser, including rock fragments up to
7.5 cm in diameter) and 18 to 35 percent (by weight) clay
(Vertisols are excluded).
Fine-loamy
or
8. Have, in the fraction less than 75 mm in diameter, less
than 15 percent (by weight) particles with diameters of 0.1
to 75 mm (fine sand or coarser, including rock fragments up
to 7.5 cm in diameter) and, in the fine-earth fraction, less
than 18 percent (by weight) clay.
Coarse-silty
or
9. Have, in the fraction less than 75 mm in diameter, less
than 15 percent (by weight) particles with diameters of 0.1
to 75 mm (fine sand or coarser, including rock fragments up
to 7.5 cm in diameter) and, in the fine-earth fraction, 18 to
35 percent (by weight) clay (Vertisols are excluded).
Fine-silty
or
10. Have 35 percent or more (by weight) clay (more
than 30 percent in Vertisols) and are in a shallow family
(defined below) or in a Lithic, Arenic, or Grossarenic
subgroup, or the layer is an element in a strongly
contrasting particle-size class (listed below).
Clayey
or
11. Have (by weighted average) less than 60 percent (by
weight) clay in the fine-earth fraction.
Fine
or
12. Have 60 percent or more clay.
Very-fine
Strongly Contrasting Particle-Size Classes
The purpose of strongly contrasting particle-size classes is
to identify changes in pore-size distribution or composition that
are not identified in higher soil categories and that seriously
affect the movement and retention of water and/or nutrients.
The following particle-size or substitute classes are
considered strongly contrasting if both parts are 12.5 cm or
more thick (including parts not in the particle-size control
section; however, substitute class names are used only if the
soil materials to which they apply extend 10 cm or more into
the upper part of the particle-size control section) and if the
transition zone between the two parts of the particle-size
control section is less than 12.5 cm thick.
Some classes, such as sandy and sandy-skeletal, have been
combined in the following list. In those cases the combined
824 Soil Taxonomy
name is used as the family class if part of the control section
meets the criteria for either class.
1. Ashy over clayey
2. Ashy over clayey-skeletal
3. Ashy over loamy-skeletal
4. Ashy over loamy
5. Ashy over medial-skeletal
6. Ashy over medial (if the water content at 1500 kPa tension in
dried samples of the fine-earth fraction is 10 percent or less for
the ashy materials and 15 percent or more for the medial
materials)
7. Ashy over pumiceous or cindery
8. Ashy over sandy or sandy-skeletal
9. Ashy-skeletal over fragmental or cindery (if the volume of
the fine-earth fraction is 35 percent or more [absolute] greater
in the ashy-skeletal part than in the fragmental or cindery part)
10. Cindery over loamy
11. Cindery over medial-skeletal
12. Cindery over medial
13. Clayey over fine-silty (if there is an absolute difference of
25 percent or more between clay percentages of the fine-earth
fraction in the two parts of the control section)
14. Clayey over fragmental
15. Clayey over loamy (if there is an absolute difference of 25
percent or more between clay percentages of the fine-earth
fraction in the two parts of the control section)
16. Clayey over loamy-skeletal (if there is an absolute
difference of 25 percent or more between clay percentages of
the fine-earth fraction in the two parts of the control section)
17. Clayey over sandy or sandy-skeletal
18. Clayey-skeletal over sandy or sandy-skeletal
19. Coarse-loamy over clayey
20. Coarse-loamy over fragmental
21. Coarse-loamy over sandy or sandy-skeletal (if the coarseloamy
material contains less than 50 percent fine sand or
coarser sand)
22. Coarse-silty over clayey
23. Coarse-silty over sandy or sandy-skeletal
24. Fine-loamy over clayey (if there is an absolute difference
of 25 percent or more between clay percentages of the fineearth
fraction in the two parts of the control section)
25. Fine-loamy over fragmental
26. Fine-loamy over sandy or sandy-skeletal
27. Fine-silty over clayey (if there is an absolute difference of
25 percent or more between clay percentages of the fine-earth
fraction in the two parts of the control section)
28. Fine-silty over fragmental
29. Fine-silty over sandy or sandy-skeletal
30. Hydrous over clayey-skeletal
31. Hydrous over clayey
32. Hydrous over fragmental
33. Hydrous over loamy-skeletal
34. Hydrous over loamy
35. Hydrous over sandy or sandy-skeletal
36. Loamy over sandy or sandy-skeletal (if the loamy
material contains less than 50 percent fine sand or coarser
sand)
37. Loamy over pumiceous or cindery
38. Loamy-skeletal over cindery (if the volume of the fineearth
fraction is 35 percent or more [absolute] greater in the
loamy-skeletal part than in the cindery part)
39. Loamy-skeletal over clayey (if there is an absolute
difference of 25 percent or more between clay percentages of
the fine-earth fraction in the two parts of the control section)
40. Loamy-skeletal over fragmental (if the volume of the
fine-earth fraction is 35 percent or more [absolute] greater in
the loamy-skeletal part than in the fragmental part)
41. Loamy-skeletal over sandy or sandy-skeletal (if the loamy
material has less than 50 percent fine sand or coarser sand)
42. Medial over ashy (if the water content at 1500 kPa
tension in dried samples of the fine-earth fraction is 15 percent
or more for the medial materials and 10 percent or less for the
ashy materials)
43. Medial over ashy-pumiceous or ashy-skeletal (if the water
content at 1500 kPa tension in dried samples of the fine-earth
fraction is 15 percent or more for the medial materials and 10
percent or less for the ashy part)
44. Medial over clayey-skeletal
45. Medial over clayey
46. Medial over fragmental
47. Medial over hydrous (if the water content at 1500 kPa
tension in undried samples of the fine-earth fraction is 75
percent or less for the medial materials)
Family and Series Differentiae and Names 825
48. Medial over loamy-skeletal
49. Medial over loamy
50. Medial over pumiceous or cindery
51. Medial over sandy or sandy-skeletal
52. Medial-skeletal over fragmental or cindery (if the volume
of the fine-earth fraction is 35 percent or more [absolute]
greater in the medial-skeletal part than the fragmental or cindery
part)
53. Pumiceous or ashy-pumiceous over loamy
54. Pumiceous or ashy-pumiceous over medial-skeletal
55. Pumiceous or ashy-pumiceous over medial
56. Pumiceous or ashy-pumiceous over sandy or sandy-
skeletal
57. Sandy over clayey
58. Sandy over loamy (if the loamy material contains less
than 50 percent fine sand or coarser sand)
59. Sandy-skeletal over loamy (if the loamy material contains
less than 50 percent fine sand or coarser sand)
Mineralogy Classes
The mineralogy of soils is known to be useful in making
predictions about soil behavior and responses to management.
Some mineralogy classes occur or are important only in certain
taxa or particle-size classes, and others are important in all
particle-size classes. The following key to mineralogy classes is
designed to make those distinctions.
Control Section for Mineralogy Classes
The control section for mineralogy classes is the same as
that defined for the particle-size classes and their substitutes.
Key to Mineralogy Classes
This key, like other keys in this taxonomy, is designed in
such a way that the reader makes the correct classification by
going through the key systematically, starting at the beginning
and eliminating one by one any classes that include criteria
that do not fit the soil in question. The soil belongs to the first
class for which it meets all of the required criteria. The user
should first check the criteria in section A and, if the soil in
question does not meet the criteria listed there, proceed on to
sections B, C, D, and E, until the soil meets the criteria listed.
All criteria are based on a weighted average.
For soils with strongly contrasting particle-size classes, the
mineralogy for both named particle-size classes or substitutes
are given, unless they are the same. Examples are an ashy over
clayey, mixed (if both the ashy and clayey parts are mixed),
superactive, mesic Typic Vitraquand and a clayey over sandy
or sandy-skeletal, smectitic over mixed, thermic Vertic
Haplustept.
A. Oxisols and “kandi” and “kanhap” great groups of
Alfisols and Ultisols that in the mineralogy control section
have:
1. More than 40 percent iron oxide (more than 28 percent
Fe), by dithionite citrate, in the fine-earth fraction.
Ferritic
or
2. More than 40 percent gibbsite in the fine-earth fraction.
Gibbsitic
or
3. Both:
a. 18 to 40 percent iron oxide (12.6 to 28 percent Fe),
by dithionite citrate, in the fine-earth fraction; and
b. 18 to 40 percent gibbsite in the fine-earth fraction.
Sesquic
or
4. 18 to 40 percent iron oxide (12.6 to 28 percent Fe), by
dithionite citrate, in the fine-earth fraction.
Ferruginous
or
5. 18 to 40 percent gibbsite in the fine-earth fraction.
Allitic
or
6. More than 50 percent (by weight) kaolinite plus
halloysite, dickite, nacrite, and other 1:1 and nonexpanding
2:1 layer minerals and gibbsite in the fraction less than
0.002 in size and more kaolinite than halloysite.
Kaolinitic
or
7. More than 50 percent (by weight) halloysite plus
kaolinite and allophane in the fraction less than 0.002 in
size.
Halloysitic
or
8. All other properties.
Mixed
or
B. Other soil layers or horizons, in the mineralogy control
826 Soil Taxonomy
section, that have a substitute class that replaces the particlesize
class, other than fragmental, and that:
1. Have a sum of 8 times the Si (percent by weight extracted
by acid oxalate) plus 2 times the Fe (percent by weight
extracted by acid oxalate) of 5 or more, and 8 times the Si is
more than 2 times the Fe.
Amorphic
or
2. Other soils that have a sum of 8 times the Si (percent
by weight extracted by acid oxalate) plus 2 times the Fe
(percent by weight extracted by acid oxalate) of 5 or
more.
Ferrihydritic
or
3. Other soils that have 30 percent or more (by grain
count) volcanic glass in the 0.02 to 2.0 mm fraction.
Glassy
or
4. All other soils that have a substitute class.
Mixed
or
C. Other mineral soil layers or horizons, in the mineralogy
control section, in all other mineral soil orders and in Terric
subgroups of Histosols and Histels that have:
1. Any particle-size class and more than 40 percent (by
weight) carbonates (expressed as CaCO3
) plus gypsum, with
gypsum constituting more than 35 percent of the total
weight of carbonates plus gypsum, either in the fine-earth
fraction or in the fraction less than 20 mm in size,
whichever has a higher percentage of carbonates plus
gypsum.
Gypsic
or
2. Any particle-size class and more than 40 percent (by
weight) carbonates (expressed as CaCO3
) plus gypsum,
either in the fine-earth fraction or in the fraction less than
20 mm in size, whichever has a higher percentage of
carbonates plus gypsum.
Carbonatic
or
3. Any particle-size class, except for fragmental, and more
than 40 percent (by weight) iron oxide (extractable by
dithionite citrate), reported as Fe2
O3
(or 28 percent reported
as Fe), in the fine-earth fraction.
Ferritic
or
4. Any particle-size class, except for fragmental, and more
than 40 percent (by weight) hydrated aluminum oxides,
reported as gibbsite and bohemite, in the fine-earth
fraction.
Gibbsitic
or
5. Any particle-size class, except for fragmental, and more
than 40 percent (by weight) magnesium-silicate minerals,
such as the serpentine minerals (antigorite, chrysotile, and
lizardite) plus talc, olivines, Mg-rich pyroxenes, and Mgrich
amphiboles, in the fine-earth fraction.
Magnesic
or
6. Any particle-size class, except for fragmental, and a total
iron oxide, by weight (Fe extracted by citrate-dithionite times
1.43 is used to determine the iron oxide), plus percent (by
weight) gibbsite of more than 10 percent in the fine-earth
fraction.
Parasesquic
or
7. Any particle-size class, except for fragmental, and more
than 20 percent (by weight) glauconitic pellets in the fineearth
fraction.
Glauconitic
or
D. Other mineral soil layers or horizons, in the mineralogy
control section, of soils in all other mineral orders and in
Terric subgroups of Histosols and Histels, in a clayey, clayeyskeletal,
fine or very-fine particle-size class, that in the fraction
less than 0.002 mm in size:
1. Have more than one-half (by weight) halloysite plus
kaolinite and allophane and more halloysite than any other
single mineral.
Halloysitic
or
2. Have more than one-half (by weight) kaolinite plus
halloysite, dickite, and nacrite, and other 1:1 or
nonexpanding 2:1 layer minerals or gibbsite, and less than
10 percent (by weight) smectite.
Kaolinitic
or
3. Have more smectite (montmorillonite, beidellite, and
nontronite), by weight, than any other single kind of clay
mineral.
Smectitic
or
Family and Series Differentiae and Names 827
4. Have more than one-half (by weight) illite (hydrous mica)
and commonly more than 4 percent K2
O.
Illitic
or
5. Have more vermiculite than any other single kind of clay
mineral.
Vermiculitic
or
6. In more than one-half of the thickness, meet all of the
following:
a. Have no free carbonates; and
b. The pH of a suspension of 1 g soil in 50 ml 1 M NaF
is more than 8.4 after 2 minutes; and
c. The ratio of 1500 kPa water to measured clay is 0.6
or more.
Isotic
or
7. All other soils in this category.
Mixed
or
E. All other mineral soil layers or horizons (except for those
in Quartzipsamments), in the mineralogy control section, that
have:
1. More than 40 percent (by weight) (80 percent by grain
count) mica and stable mica pseudomorphs in the 0.02 to
2.0 mm fraction.
Micaceous
or
2. More than 25 percent (by weight) (65 percent by grain
count) mica and stable mica pseudomorphs in the 0.02 to
2.0 mm fraction.
Paramicaceous
or
3. In more than one-half of the thickness, all of the
following:
a. No free carbonates; and
b. The pH of a suspension of 1 g soil in 50 ml 1 M NaF
is more than 8.4 after 2 minutes; and
c. A ratio of 1500 kPa water to measured clay of 0.6 or
more.
Isotic
or
4. More than 90 percent (by weight) silica minerals
(quartz, chalcedony, or opal) and other extremely durable
minerals that are resistant to weathering, in the 0.02 to 2.0 mm
fraction.
Siliceous
or
5. All other properties.
Mixed
Cation-Exchange Activity Classes
The cation-exchange activity classes help in making
interpretations of mineral assemblages and of the nutrientholding
capacity of soils in mixed and siliceous mineralogy
classes of clayey, clayey-skeletal, coarse-loamy, coarse-silty,
fine, fine-loamy, fine-silty, loamy, loamy-skeletal, and very-fine
particle-size classes. Cation-exchange activity classes are not
assigned to Histosols and Histels, and they are not assigned to
Oxisols and “kandi” and “kanhap” great groups and
subgroups of Alfisols and Ultisols because assigning such
classes to them would be redundant. Cation-exchange activity
classes are not assigned to the sandy, sandy-skeletal, or
fragmental particle-size class because the low clay content
causes cation-exchange activity classes to be less useful and
less reliable.
The cation-exchange capacity (CEC) is determined by
NH4
OAc at pH 7 on the fine-earth fraction. The CEC of the
organic matter, sand, silt, and clay is included in the
determination. The criteria for the classes use ratios of CEC to
the percent, by weight, of silicate clay, both by weighted
average in the control section. In the following classes “clay”
excludes clay-size carbonates. If the ratio of percent water
retained at 1500 kPa tension to the percentage of measured
clay is 0.25 or less or 0.6 or more in half or more of the
particle-size control section (or part in contrasting families),
then the percentage of clay is estimated by the following
formula: Clay % = 2.5(% water retained at 1500 kPa tension %
organic carbon).
Control Section for Cation-Exchange Activity Classes
The control section for cation-exchange activity classes is
the same as that used to determine the particle-size and
mineralogy classes. For soils with strongly contrasting particlesize
classes, where both named parts of the control section use
a cation-exchange activity class, the class associated with the
particle-size class that has the most clay is named. For
example, in a pedon with a classification of loamy over clayey,
mixed, active, calcareous, thermic Typic Udorthent, the cationexchange
activity class “active” is associated with the clayey
part of the control section.
Key to Cation-Exchange Activity Classes
A. Soils that are not Histosols, Histels, or Oxisols, that are
not in “kandi” or “kanhap” great groups or subgroups of
Alfisols and Ultisols, that are in either a mixed or siliceous
828 Soil Taxonomy
mineralogy class, that are not in a fragmental, sandy, or sandyskeletal
particle-size class or any substitute for a particle-size
class, and that have a ratio of cation-exchange capacity (by
NH4
OAc at pH 7) to clay (percent by weight) of:
1. 0.60ormore.
Superactive
2. 0.40 to 0.60.
Active
3. 0.24 to 0.40.
Semiactive
4. Less than 0.24.
Subactive
or
B. All other soils: No cation-exchange activity classes used.
Calcareous and Reaction Classes of Mineral Soils
The presence or absence of carbonates, soil reaction, and the
presence of high concentrations of aluminum in mineral soils
are treated together because they are so intimately related.
There are four classes—calcareous, acid, nonacid, and allic.
These are defined later in the key to calcareous and reaction
classes. The classes are not used in all taxa, nor is more than
one used in the same taxa.
Use of the Calcareous and Reaction Classes
The calcareous, acid, and nonacid classes are used in the
names of the families of Entisols, Aquands, and Aquepts,
except they are not used in any of the following:
1. Duraquands and Placaquands
2. Sulfaquepts, Fragiaquepts, and Petraquepts
3. Sandy, sandy-skeletal, cindery, pumiceous, or fragmental
families
4. Families with carbonatic or gypsic mineralogy
The calcareous class, in addition to those listed above, is
used in the names of the families of Aquolls, except it is not
used with any of the following:
1. Calciaquolls, Natraquolls, and Argiaquolls
2. Cryaquolls and Duraquolls that have an argillic horizon
3. Families with carbonatic or gypsic mineralogy
The allic class is used only in families of Oxisols.
Control Section for Calcareous and Reaction Classes
The control section for the calcareous class is one of the
following:
1. Soils with a root-limiting layer that is 25 cm or less below the
mineral soil surface: A 2.5-cm-thick layer directly above the root-
limitinglayer.
2. Soils with a root-limiting layer that is 26 to 50 cm below the
mineral soil surface: The layer between a depth of 25 cm below
the mineral soil surface and the root-limiting layer.
3. All other listed soils: Between a depth of 25 and 50 cm below
the mineral soil surface.
The control section for the acid, nonacid, and allic classes is
the same as that for particle-size classes.
Key to Calcareous and Reaction Classes
A. Oxisols that have a layer, 30 cm or more thick within the
control section, that contains more than 2 cmol(+) of KClextractable
Al per kg soil in the fine-earth fraction.
Allic
B. Other listed soils that, in the fine-earth fraction, effervesce
(in cold dilute HCl) in all parts of the control section.
Calcareous
C. Other listed soils with a pH of less than 5.0 in 0.01 M
CaCl2
(1:2) (about pH 5.5 in H2
O, 1:1) throughout the control
section.
Acid
D. Other listed soils with a pH of 5.0 or more in 0.01 M
CaCl2
(1:2) in some or all layers in the control section.
Nonacid
It should be noted that a soil containing dolomite is
calcareous and that effervescence of dolomite, when treated
with cold dilute HCl, is slow.
The calcareous, acid, nonacid, and allic classes are listed in
the family name, when appropriate, following the mineralogy
and cation-exchange activity classes.
Soil Temperature Classes
Soil temperature classes, as named and defined here, are used
as part of the family name in both mineral and organic soils.
Temperature class names are used as part of the family name
unless the criteria for a higher taxon carry the same limitation.
Thus, frigid is implied in all cryic suborders, great groups, and
subgroups and would be redundant if used in the names of
families within these classes.
The Celsius (centigrade) scale is the standard. It is assumed
that the temperature is that of a soil that is not being irrigated.
Control Section for Soil Temperature
The control section for soil temperature either is at a depth
of 50 cm from the soil surface or is at the upper boundary of
Family and Series Differentiae and Names 829
a root-limiting layer, whichever is shallower. The soil
temperature classes, defined in terms of the mean annual
soil temperature and the difference between mean summer
and mean winter temperatures, are determined by the following
key.
Key to Soil Temperature Classes
A. Gelisols that have a mean annual soil temperature as
follows:
1. -10 o
C or lower.
Hypergelic
or
2. -4 o
C to -10 o
C.
Pergelic
or
3. +1 o
C to -4 o
C.
Subgelic
or
B. Other soils that have a difference in soil temperature of
6 o
C or more between mean summer (June, July, and August in
the Northern Hemisphere) and mean winter (December,
January, and February in the Northern Hemisphere) and a
mean annual soil temperature of:
1. Lower than 8 o
C (47 o
F).
Frigid
or
2. 8 o
C (47 o
F) to 15 o
C (59 o
F).
Mesic
or
3. 15 o
C (59 o
F) to 22 o
C (72 o
F).
Thermic
or
4. 22 o
C (72 o
F) or higher.
Hyperthermic
or
C. All other soils that have a mean annual soil temperature
as follows:
1. Lower than 8 o
C (47 o
F).
Isofrigid
or
2. 8 o
C (47 o
F) to 15 o
C (59 o
F).
Isomesic
or
3. 15 o
C (59 o
F) to 22 o
C (72o
F).
Isothermic
or
4. 22 o
C (72 o
F) or higher.
Isohyperthermic
Soil Depth Classes
Soil depth classes are used in all families that have a rootlimiting
layer at a specified depth from the mineral soil
surface, except for those families in Lithic subgroups and those
with a fragipan. The root-limiting layers included in soil depth
classes are duripans; petrocalcic, petrogypsic, and placic
horizons; continuous ortstein (90 percent or more); and densic,
lithic, paralithic, and petroferric contacts. Soil depth classes for
Histosols and Histels are given later in this chapter. One soil
depth class name, “shallow,” is used to characterize certain
mineral soil families that have one of the depths indicated in
the following key.
Key to Soil Depth Classes
A. Oxisols that are less than 100 cm deep (from the mineral
soil surface) to a root-limiting layer and are not in a Lithic
subgroup.
Shallow
or
B. Soils in all other mineral soil orders that are less than 50
cm deep (from the mineral soil surface) to a root-limiting layer
and are not in a Lithic subgroup.
Shallow
or
C. All other mineral soils: No soil depth class used.
Rupture-Resistance Classes
In this taxonomy, some partially cemented soil
materials, such as durinodes, serve as differentiae in
categories above the family, while others, such as partially
cemented spodic materials (ortstein), do not. No single
family, however, should include soils both with and without
partially cemented horizons. In Spodosols, a partially
cemented spodic horizon is used as a family differentia.
The following rupture-resistance class is defined for families
of Spodosols:
A. Spodosols that have an ortstein horizon.
Ortstein
or
B. All other soils: No rupture-resistance class used.
830 Soil Taxonomy
Classes of Coatings (on Sands)
Despite the emphasis given to particle-size classes in this
taxonomy, variability remains in the sandy particle-size class,
which includes sands and loamy sands. Some sands are very
clean, i.e., almost completely free of silt and clay, while others
are mixed with appreciable amounts of finer grains. Clay is
more efficient at coating sand than is silt. A weighted average
silt (by weight) plus 2 times the weighted average clay (by
weight) of more than 5 makes a reasonable division of the
sands at the family level. Two classes of Quartzipsamments are
defined in terms of their content of silt plus 2 times their content
of clay.
Control Section for Classes of Coatings
The control section for classes of coatings is the same as that
for particle-size classes or their substitutes and for mineralogy
classes.
Key to Classes of Coatings
A. Quartzipsamments that have a sum of the weighted average
silt (by weight) plus 2 times the weighted average clay of more
than 5.
Coated
or
B. Other Quartzipsamments.
Uncoated
Classes of Permanent Cracks
Some Hydraquents consolidate or shrink after drainage and
become Fluvaquents or Humaquepts. In the process they can
form polyhedrons roughly 12 to 50 cm in diameter, depending
on their n value and texture. These polyhedrons are separated
by cracks that range in width from 2 mm to more than 1 cm.
The polyhedrons may shrink and swell with changes in the
moisture content of the soils, but the cracks are permanent and
can persist for several hundreds of years, even if the soils are
cultivated. The cracks permit rapid movement of water through
the soils, either vertically or laterally. Such soils may have the
same texture, mineralogy, and other family properties as soils
that do not form cracks or that have cracks that open and close
with the seasons. Soils with permanent cracks are very rare in
the United States.
Control Section for Classes of Permanent Cracks
The control section for classes of permanent cracks is from
the base of any plow layer or 25 cm from the soil surface,
whichever is deeper, to 100 cm below the soil surface.
Key to Classes of Permanent Cracks
A. Fluvaquents or Humaquepts that have, throughout a layer
50 cm or more thick, continuous, permanent, lateral and
vertical cracks 2 mm or more wide, spaced at average lateral
intervals of less than 50 cm.
Cracked
or
B. All other Fluvaquents and Humaquepts: No class of
permanent cracks used.
Family Differentiae for Histosols and
Histels
Most of the differentiae that are used to distinguish families
of Histosols and Histels have already been defined, either
because they are used as differentiae in mineral soils as well as
Histosols and Histels or because their definitions are used for
the classification of some Histosols and Histels in categories
higher than the family. In the following descriptions,
differentiae not previously mentioned are defined and the
classes in which they are used are enumerated.
The order in which family classes, if appropriate for a
particular family, are placed in the technical family names of
Histosols and Histels is as follows:
Particle-size classes
Mineralogy classes, including the nature of limnic deposits in
Histosols
Reaction classes
Soil temperature classes
Soil depth classes (used only in Histosols)
Particle-Size Classes
Particle-size classes are used only for the family names of
Terric subgroups of Histosols and Histels. The classes are
determined from the properties of the mineral soil materials in
the control section through use of the key to particle-size
classes. The classes are more generalized than those for soils in
other orders.
Control Section for Particle-Size Classes
The particle-size control section is the upper 30 cm of the
mineral layer or of that part of the mineral layer that is within
the control section for Histosols and Histels (given in chapter
4), whichever is thicker.
Key to Particle-Size Classes of Histosols and Histels
A. Terric subgroups of Histosols and Histels that
Family and Series Differentiae and Names 831
have (by weighted average) in the particle-size control
section:
1. A fine-earth component of less than 10 percent
(including associated medium and finer pores) of the total
volume.
Fragmental
or
2. A texture (of the fine earth) of sand or loamy sand,
including less than 50 percent (by weight) very fine sand in
the fine-earth fraction.
Sandy or sandy-skeletal
or
3. Less than 35 percent clay in the fine-earth fraction and
a content of rock fragments of 35 percent or more of the
total volume.
Loamy-skeletal
or
4. A content of rock fragments of 35 percent or more of
the total volume.
Clayey-skeletal
or
5. A clay content of 35 percent or more in the fine-earth
fraction.
Clayey
or
6. All other Terric subgroups of Histosols and Histels.
Loamy
or
B. All other Histosols and Histels: No particle-size class
used.
Mineralogy Classes
There are three different kinds of mineralogy classes
recognized for families in certain great groups and subgroups
of Histosols. The first kind is the ferrihumic soil material
defined below. The second is three types of limnic materials—
coprogenous earth, diatomaceous earth, and marl, defined in
chapter 4. The third is mineral layers of Terric subgroups. The
key to mineralogy classes for these mineral layers is the same
as that for mineral soils. Terric subgroups of Histels also have
the same mineralogy classes as those for mineral soils.
Ferrihumic Mineralogy Class
Ferrihumic soil material, i.e., bog iron, is an authigenic
(formed in place) deposit consisting of hydrated iron oxide
mixed with organic matter, either dispersed and soft or cemented
into large aggregates, in a mineral or organic layer that has all of
the following characteristics:
1. Saturation with water for more than 6 months per year (or
artificial drainage);
2. 2 percent or more (by weight) iron concretions having lateral
dimensions ranging from less than 5 to more than 100 mm and
containing 10 percent or more (by weight) free iron oxide (7
percent or more Fe) and 1 percent or more (by weight) organic
matter; and
3. A dark reddish or brownish color that changes little on
drying.
The ferrihumic mineralogy class is used for families of
Fibrists, Hemists, and Saprists, but it is not used for
Sphagnofibrists and Sphagnic subgroups of other great groups.
If the ferrihumic class is used in the family name of a Histosol,
no other mineralogy classes are used in that family because the
presence of iron is considered to be by far the most important
mineralogical characteristic.
Mineralogy Classes Applied Only to Limnic Subgroups
Limnic materials (defined in chapter 4) with a thickness of
5 cm or more are mineralogy class criteria if the soil does not
also have ferrihumic mineralogy. The following family classes
are used: coprogenous, diatomaceous, and marly.
Control Section for the Ferrihumic Mineralogy Class and
Mineralogy Classes Applied to Limnic Subgroups
The control section for the ferrihumic mineralogy class and
the classes applied to Limnic subgroups is the same as the
control section for Histosols.
Mineralogy Classes Applied Only to Terric Subgroups
For Histosols and Histels in Terric subgroups, use the same
key to mineralogy classes as that used for mineral soils unless a
Histosol also has ferrihumic mineralogy.
Control Section for Mineralogy Classes Applied Only to
Terric Subgroups
For Terric subgroups of Histosols and Histels, use the same
control section for mineralogy classes as that used for the
particle-size classes.
Key to Mineralogy Classes
A. Histosols (except for Folists), Sphagnofibrists, and
Sphagnic subgroups of other great groups that have ferrihumic
soil material within the control section for Histosols.
Ferrihumic
or
B. Other Histosols that have, within the control section for
832 Soil Taxonomy
Histosols, limnic materials, 5 cm or more thick, that consist of:
1. Coprogenous earth.
Coprogenous
or
2. Diatomaceous earth.
Diatomaceous
or
3. Marl.
Marly
or
C. Histels and other Histosols in Terric subgroups: Use the
key to mineralogy classes for mineral soils.
or
D. All other Histels and Histosols: No mineralogy class used.
Reaction Classes
Reaction classes are used in all families of Histosols and
Histels. The two classes recognized are defined in the
following key:
A. Histosols and Histels that have a pH value, on undried
samples, of 4.5 or more (in 0.01 M CaCl2
) in one or more
layers of organic soil materials within the control section for
Histosols.
Euic
or
B. All other Histosols and Histels.
Dysic
Soil Temperature Classes
The soil temperature classes of Histosols are determined
through use of the same key and definitions as those used for
mineral soils. Histels have the same temperature classes as
other Gelisols.
Soil Depth Classes
Soil depth classes refer to the depth to a root-limiting layer, a
fragmental particle-size class, or a cindery or pumiceous
substitute class. The root-limiting layers included in soil depth
classes of Histosols are duripans; petrocalcic, petrogypsic, and
placic horizons; continuous ortstein; and densic, lithic,
paralithic, and petroferric contacts. The following key is used
for families in all subgroups of Histosols. The shallow class is
not used in the suborder Folists.
Key to Soil Depth Classes
A. Histosols that are less than 18 cm deep to a root-limiting
layer, to a fragmental particle-size class, or to a cindery or
pumiceous substitute class.
Micro
or
B. Other Histosols, excluding Folists, that have a rootlimiting
layer, a fragmental particle-size class, or a cindery or
pumiceous substitute class at a depth between 18 and 50 cm
from the soil surface.
Shallow
or
C. All other Histosols: No soil depth class used.
Series Differentiae Within a Family
The function of the series is pragmatic, and differences
within a family that affect the use of a soil should be
considered in classifying soil series. The separation of soils at
the series level of this taxonomy can be based on any property
that is used as criteria at higher levels in the system. The
criteria most commonly used include presence of, depth to,
thickness of, and expression of horizons and properties
diagnostic for the higher categories and differences in texture,
mineralogy, soil moisture, soil temperature, and amounts of
organic matter. The limits of the properties used as differentiae
must be more narrowly defined than the limits for the family.
The properties used, however, must be reliably observable or be
inferable from other soil properties or from the setting or
vegetation.
The differentiae used must be within the series control
section. Differences in soil or regolith that are outside the
series control section and that have not been recognized as
series differentiae but are relevant to potential uses of certain
soils are considered as a basis for phase distinctions.
Control Section for the Differentiation of Series
The control section for the soil series is similar to that for
the family, but it differs in a few important respects. The
particle-size and mineralogy control sections for families end
at the upper boundary of a fragipan, duripan, or petrocalcic
horizon because these horizons have few roots. In contrast to
the control section for the series, the thickness of such horizons
is not taken into account in the control sections for the family.
The series control section includes materials starting at the soil
surface and also the first 25 cm below a densic or paralithic
contact if its upper boundary is less than 125 cm below the
mineral soil surface. Properties of horizons and layers below
the particle-size control section, a depth between 100 and 150
Family and Series Differentiae and Names 833
cm (or to 200 cm if in a diagnostic horizon) from the mineral soil
surface, also are considered.
Key to the Control Section for the Differentiation of Series
The part of a soil to be considered in differentiating series
within a family is as follows:
A. Mineral soils that have permafrost within 150 cm of the
soil surface: From the soil surface to the shallowest of the
following:
1. A lithic or petroferric contact; or
2. A depth of 100 cm if the depth to permafrost is less
than 75 cm; or
3. 25 cm below the upper boundary of permafrost if
that boundary is 75 cm or more below the soil surface;
or
4. 25 cm below a densic or paralithic contact; or
5. A depth of 150 cm; or
B. Other mineral soils: From the soil surface to the
shallowest of the following:
1. A lithic or petroferric contact; or
2. A depth of either 25 cm below a densic or paralithic
contact or 150 cm below the soil surface, whichever is
shallower, if there is a densic or paralithic contact within
150 cm; or
3. A depth of 150 cm if the bottom of the deepest
diagnostic horizon is less than 150 cm from the soil surface;
or
4. The lower boundary of the deepest diagnostic horizon
or a depth of 200 cm, whichever is shallower, if the lower
boundary of the deepest diagnostic horizon is 150 cm or
more below the soil surface; or
C. Organic soils (Histosols and Histels): From the soil surface
to the shallowest of the following:
1. A lithic or petroferric contact; or
2. A depth of 25 cm below a densic or paralithic contact;
or
3. A depth of 100 cm if the depth to permafrost is less
than 75 cm; or
4. 25 cm below the upper boundary of permafrost if that
boundary is between a depth of 75 and 125 cm below the
soil surface; or
5. The base of the bottom tier.
Application of Family and Series Differentiae
ApplicationofFamilyDifferentiae
The differentiae of families, like those of the higher
categories, can be more readily understood if they are applied
to real soils. A rather complex family can demonstrate how the
family criteria are determined. The Boistfort and Bunker series
are in the medial over clayey, mixed over parasesquic, mesic
family of Pachic Fulvudands. A pedon (not the typifying
pedon) of the Boistfort series has been sampled and studied in
the laboratory. The discussion that follows shows how the
classes used as components of the family name are selected.
The particle-size class or substitute class is the first
component in the name of a family. Before the class can be
selected, the control section must be known, and before the
control section can be determined, the diagnostic horizons and
properties must be identified. The epipedon of the Boistfort
soils has andic soil properties. It is not dark colored enough for
a melanic epipedon but is dark enough, is thick enough, and
has enough organic carbon for a mollic or umbric epipedon.
The base saturation is less than 6 percent throughout. Thus, the
epipedon is umbric. The 2Bw horizon in the Boistfort soils
does not have the evidence that organic carbon and aluminum
have been moved from an eluvial to an illuvial horizon
required for spodic materials. The soils have the required
thickness of andic soil properties in the required location (item
D in the “Key to Soil Orders” in chapter 8) for the Andisol
order. The control section for particle-size is determined
through use of the criteria in item B (a). The particle-size control
section is from 5 cm (the mineral soil surface) to 105 cm.
The upper part of the particle-size control section, from 5 to
53 cm, in the type location meets the criteria for medial listed
in item B-2-c in the key to particle-size classes and substitutes
for classes. The lower part, from 53 to 105 cm, in the type
location meets the criteria for clayey, item 10 under C. The soil
materials meet the requirements for strongly contrasting
particle-size classes, and the combination “medial over clayey”
is included as number 45 on the list of classes considered as
strongly contrasting.
The control section for mineralogy classes is the same as
that used for the particle-size classes. The mineralogy classes
are given for both named particle-size classes for families with
strongly contrasting particle-size classes, unless the mineralogy
classes are the same for both parts. The mineralogy classes are
determined through use of the key to mineralogy classes.
“Medial” is a substitute class name that replaces the name of
particle-size classes. This family is part of the Andisol soil
order. Thus, it fails item A and meets item B of the key. Based
on the laboratory data, this part of the control section has
834 Soil Taxonomy
mixed mineralogy. The clayey part fails items A and B. This
layer meets the criteria listed in item C. The parasesquic class,
item 6 under C, is the first class in the key for which this layer
meets all of the criteria. The family mineralogy is mixed over
parasesquic.
Cation-exchange activity classes are used only for layers
with both mixed or siliceous mineralogy and a clayey, clayeyskeletal,
coarse-loamy, coarse-silty, fine, fine-loamy, fine-silty,
loamy, loamy-skeletal, or very-fine particle-size class. In this
family, the mixed mineralogy is associated with the medial
substitute for a particle-size class and the parasesquic
mineralogy is associated with the clayey particle-size class.
Therefore, no cation-exchange activity class is used in this
familyname.
Calcareous and reaction classes are not used in families of
Udands.
The mean soil temperatures are estimated from climatic data.
The mean winter soil temperature is about 3 o
C (38 o
F), the mean
summer soil temperature is about 16 o
C (60 o
F), and the mean
annual soil temperature is about 15 o
C (59 o
F). These data are
within the class criteria for mesic temperatures, item 2 under B, in
the key to temperature classes.
The Boistfort and Bunker soils have no root-limiting layers
within 100 cm. They therefore fail items A and B in the key to
soil depth classes but meet criterion C. No soil depth class is
used for soils that meet criterion C.
The keys indicate that families of Andisols do not have
rupture-resistance classes, classes of coatings (on sands), or
classes of permanent cracks.
The classes that are components of the family name are
medial over clayey, mixed over parasesquic, and mesic. The
family name is medial over clayey, mixed over parasesquic,
mesic Pachic Fulvudands.
Application of Series Differentiae
Standard descriptions of the Boistfort and Bunker series are
given at the end of this chapter. If we compare the descriptions
of the typifying pedons of these two series, we note that the
particle-size control section of the Bunker soils averages 15 to 35
percent basalt fragments and that of the Boistfort soils averages
less than 10 percent. This difference is relatively small but
reflects differences in setting and parent materials that affect the
use of the soils. The Boistfort soils formed in material weathered
from basalt in the more stable positions on foothills and
mountains, and the Bunker soils formed in colluvium derived
from basalt on metastable slopes. Both of the soils are used for
the production of lumber. The differences in these soils affect
both tree growth and the construction and maintenance of the
roads needed when the trees are harvested.
The Bunker series allows basalt at a depth of 100 to more
than 150 cm from the mineral soil surface. This range in depth
to a lithic contact could be used as a criterion to divide the
Bunker series into two series, as the lithic contact is within the
control section for the series. Because this depth difference is
difficult to separate in mapping and has little effect on the use
of these soils for the production of lumber, the series is allowed
this wide range in soil depth. Many soil series that are in other
climates or that have more intensive uses are separated on the
basis of having or not having a lithic contact between 100 and
150 cm.
This example shows the nature of series differentiae.
Generally, the series within a given family have several small
differences in the nature or arrangement of horizons, in the
absence of horizons, in the nature of the soil materials in the
series control section, or in soil moisture or soil temperature.
These differences commonly reflect differences in setting,
climate, and/or parent materials that have important effects on
the use of the soils. The differences permit, but do not require,
the separation of soil series within a family. The differentiae
are discussed under the category of series in chapter 6.
A full treatment of series differentiae within families is
beyond the scope of this text. Series differentiae vary among
families, subgroups, great groups, and even orders. The
principle, however, remains the same. The series are
distinguished within a family primarily because of the need to
facilitate quantitative interpretations of soil behavior.
Family and Series Differentiae and Names 835
LOCATION BOISTFORT WA
Established Series
Rev. CJM/RFP/RJE/TLA
08/98
BOISTFORT SERIES
The Boistfort series consists of very deep, well drained soils formed in
material weathered from basalt and a component of volcanic ash in the
upper part. Boistfort soils are on foothills and mountains and have slopes
of 0 to 65 percent. The average annual precipitation is about 2,300 mm,
and the average annual temperature is about 10 degrees C.
TAXONOMIC CLASS: Medial over clayey, mixed over parasesquic,
mesic Pachic Fulvudands
TYPICAL PEDON: Boistfort silt loam - forested. (Colors are for moist
soil unless otherwise stated. All textures are apparent field textures.)
Oi—0 to 5 cm (0 to 2 inches); slightly decomposed twigs, needles, and
moss.
Ac—5 to 28 cm (2 to 11 inches); dark brown (7.5YR 3/2) silt loam, dark
grayish brown (10YR 4/2) dry; weak fine granular structure; soft, very
friable, slightly sticky and slightly plastic, and weakly smeary; many
coarse, medium, and fine roots; many medium tubular pores; 25 percent
weakly cemented shotlike concretions; very strongly acid; clear wavy
boundary. (18 to 30 cm thick)
A—28 to 53 cm (11 to 21 inches); dark brown (7.5YR 3/2) silty clay
loam, dark brown (10YR 4/3) dry; moderate very fine subangular blocky
structure; slightly hard, friable, sticky and plastic, and weakly smeary;
many coarse, medium, and fine roots; many medium tubular pores; few
firm shotlike concretions; very strongly acid; clear wavy boundary. (0 to
25 cm thick)
2Bw1—53 to 99 cm (21 to 39 inches); dark brown (7.5YR 4/4) silty clay,
yellowish brown (10YR 5/6) dry; weak fine subangular blocky structure; hard,
friable, sticky and plastic, and weakly smeary; few fine roots; common medium
tubular and interstitial pores; extremely acid; gradual wavy boundary.
2Bw2—99 to 140 cm (39 to 55 inches); strong brown (7.5YR 5/6) silty clay,
strong brown (10YR 5/8) dry; weak very fine subangular blocky structure; very
hard, friable, sticky and plastic, and weakly smeary; few fine tubular and common
medium interstitial pores; extremely acid; clear wavy boundary. (Combined
thickness of the 2Bw horizon: 50 to 100 cm)
2BC—140 to 157 cm (55 to 62 inches); strong brown (7.5YR 5/6) silty clay,
yellowish brown (10YR 5/6) dry; weak very fine subangular blocky structure;
very hard, friable, sticky and plastic, and weakly smeary; few fine tubular and
common medium interstitial pores; extremely acid.
TYPE LOCATION: Thurston County, Washington; Capitol State Forest, about 5
miles northwest of Littlerock, 540 meters west and 180 meters north of the
southeast corner of sec. 24, T. 17 N., R. 4 W.
RANGE IN CHARACTERISTICS: The thickness of the solum ranges from 100
to more than 150 cm, and the depth to basalt is more than 150 cm. The content of
rock fragments averages less than 10 percent in the particle-size control section.
The upper part of the particle-size control section, 5 to 105 cm, has an estimated
moist bulk density of 0.65 to 0.90 g/cc, a volcanic glass content of 0 to 5
percent, acid-oxalate-extractable aluminum plus one-half iron of 2.0 to
3.0 percent, phosphate retention of 85 to 100 percent, and 15-bar water
retention of 15 to 30 percent for air-dried samples. The content of
organic carbon is less than 4 percent in some part between 50 and 75 cm.
Under forest cover, the mean annual soil temperature is about 10 degrees
C (50 degrees F) and ranges from 8 to 11 degrees C.
The A horizon has value and chroma of 2 or 3 when rubbed and moist and
value and chroma of 2, 3, or 4 when dry. This horizon is moderately acid
to very strongly acid.
Some pedons have AB and BA horizons.
The 2Bw horizon has hue of 5YR or 7.5YR and value and chroma of 4
through 6 moist, 5 through 8 dry. The apparent field texture averages clay
loam, silty clay loam, or silty clay, but in some thin subhorizons it is
gravelly or cobbly silty clay loam, gravelly or cobbly clay loam, or
gravelly or cobbly silty clay. This horizon is moderately acid to extremely
acid.
COMPETING SERIES: These are the Bunker soils. Bunker soils
contain 15 to 35 percent rock fragments in the particle-size control
section.
GEOGRAPHIC SETTING: Boistfort soils are in stable positions on
foothills and mountains. Slopes are mostly less than 30 percent, but they
range from 0 to 65 percent. The soils formed in material weathered from
basalt and a component of volcanic ash in the upper part. Elevations
range from 30 to 540 meters. These soils are in a marine climate with
cool, wet winters and cool, dry summers. The average annual precipitation
ranges from 1,800 to 3,000 mm. The average January temperature is
about 3 degrees C, the average July temperature is about 16 degrees C, and
the average annual temperature is about 10 degrees C. The growing season
(-2 degrees C) is 200 to 240 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing
Bunker soils and the Astoria, Elochoman, Katula, Lates, Lytell, Murnen, and
Zenker soils. Astoria soils are in a fine class and are Udepts. Elochoman, Lytell,
and Zenker soils are in a medial class. In addition, Lytell and Zenker soils average
more than 35 percent pararock fragments, consisting of weathered sandstone or
siltstone, in the particle-size control section. Katula soils are in a medial-skeletal
class and have a lithic contact between 50 and 100 cm. Lates and Murnen soils are
in a medial class and a frigid class.
DRAINAGE , RUNOFF, AND PERMEABILITY: Well drained; very low to
medium runoff; moderate permeability.
USE AND VEGETATION: Forested. The vegetation is mainly Douglas-fir,
western redcedar, and red alder with an understory of western swordfern,
Oregongrape, red huckleberry, and vine maple.
DISTRIBUTION AND EXTENT: Southwestern Washington. The series is of
moderate extent.
SERIES ESTABLISHED: Grays Harbor County (Grays Harbor County Area),
Washington, 1970.
REMARKS: The diagnostic horizons and features recognized in this pedon are an
umbric epipedon from the mineral soil surface (at 5 cm) to 53 cm and a cambic
horizon from 53 to 157 cm. The upper 48 cm of the particle-size control section
has andic soil properties.
ADDITIONAL DATA: Characterization data for this series are available;
NSSL pedon numbers 84P0906 and 40A3303.
National Cooperative Soil Survey
U.S.A.
836
LOCATION BUNKER WA
Established Series
Rev. FG/RFP/RJE/TLA
08/98
BUNKER SERIES
The Bunker series consists of deep, well drained soils formed in colluvium
weathered from basalt and a component of volcanic ash in the upper part. These
soils are on foothills and mountains. Slopes are 1 to 90 percent. The average
annual precipitation is about 2,300 mm, and the average annual temperature is
about 10 degrees C.
TAXONOMIC CLASS: Medial over clayey, mixed over parasesquic, mesic
Pachic Fulvudands
TYPICAL PEDON: Bunker loam - forested. (Colors are for moist soil unless
otherwise stated. All textures are apparent field textures.)
Oi—0 to 3 cm (0 to 1 inch); loose, slightly decomposed Douglas-fir needles, twigs,
and moss.
Oa—3 to 5 cm (1 to 2 inches); decomposed litter; dark red with many white
mycelia.
A—5 to 29 cm (2 to 12 inches); dark reddish brown (5YR 3/3) loam, reddish
brown (5YR 4/3) dry; moderate fine granular structure; slightly hard, friable,
slightly sticky and slightly plastic, and weakly smeary; many roots; 15 percent
angular basalt pebbles; moderately acid (pH 5.9); clear wavy boundary. (25 to 36
cm thick)
BA—29 to 47 cm (12 to 19 inches); dark reddish brown (5YR 3/4) gravelly clay
loam, reddish brown (5YR 4/4) dry; moderate medium and fine subangular blocky
structure; hard, friable, sticky and plastic, and weakly smeary; many roots; 30
percent angular basalt pebbles; few medium and fine shotlike concretions;
moderately acid (pH 5.9); clear irregular boundary. (5 to 25 cm thick)
2Bw1—47 to 88 cm (19 to 35 inches); dark reddish brown (5YR 3/4) gravelly
clay loam, reddish brown (5YR 4/4) dry; moderate medium and fine subangular
blocky structure; hard, firm, sticky and plastic, and weakly smeary; common roots;
many fine pores; 30 percent angular basalt pebbles; moderately acid (pH 5.8);
gradual wavy boundary.
2Bw2—88 to 134 cm (35 to 53 inches); reddish brown (5YR 4/4) clay loam,
reddish brown (5YR 5/4) dry; moderate medium subangular blocky structure;
slightly hard, firm, sticky and plastic, and weakly smeary; many roots; many fine
pores; 10 percent angular basalt pebbles; moderately acid (pH 6.0); clear irregular
boundary. (Combined thickness of the 2Bw horizon: 50 to 90 cm)
2BC—134 to 156 cm (53 to 62 inches); dark brown (7.5YR 3/4) clay loam,
reddish brown (5YR 4/4) dry; weak medium subangular blocky structure; slightly
hard, friable, sticky and plastic, and weakly smeary; few roots; 10 percent angular
basalt pebbles; moderately acid (pH 6.0); clear irregular boundary. (10 to 30 cm
thick)
2R—156 cm (62 inches); fractured basalt.
TYPE LOCATION: Lewis County, Washington; on logging road number
5, Weyerhaeuser Company McDonald Tree Farm; approximately 570
meters south and 570 meters west of the northeast corner of sec. 11, T.
12 N., R. 5 W.
RANGE IN CHARACTERISTICS: The mean annual soil temperature
ranges from 8 to 11 degrees C. The depth to fractured bedrock ranges
from 100 to more than 150 cm from the mineral soil surface. The
content of basalt fragments in the particle-size control section averages
15 to 35 percent. The upper part of the particle-size control section (4 to
104 cm) has an estimated moist bulk density of 0.65 to 0.90 g/cc, a
volcanic glass content of 0 to 5 percent, acid-oxalate-extractable
aluminum plus one-half iron of 2.0 to 3.0 percent, phosphate retention of
85 to 100 percent, and 15-bar water retention of 15 to 30 percent for airdried
samples. The content of organic carbon is less than 4 percent in
some part of the upper 75 cm of the particle-size control section.
Reaction ranges from very strongly acid to moderately acid.
The A horizon has hue of 5YR or 7.5YR, value of 2 or 3 moist, 4 or 5
dry, and chroma of 1 to 3 moist, 3 or 4 dry. It has 0 to 35 percent
pebbles.
The BA horizon has hue of 5YR or 7.5YR, value of 3 or 4 moist, 4 or 5
dry, and chroma of 2 to 4 moist. It has 0 to 35 percent pebbles.
The 2B horizon has hue of 5YR through l0YR, value of 3 or 4 moist, 4 or
5 dry, and chroma of 3 or 4 moist. It ranges from loam to clay loam, silt
loam, or silty clay loam with 10 to 35 percent rock fragments.
COMPETING SERIES: These are the Boistfort soils. Boistfort soils
average 0 to 10 percent basalt fragments in the particle-size control
section.
GEOGRAPHIC SETTING: Bunker soils are on metastable side slopes and
foot slopes at elevations of 30 to 660 meters. Slopes are mostly 30 to 90
percent but range from 1 to 90 percent. These soils formed in colluvium
weathered from basalt and a component of volcanic ash in the upper part.
Winters are cool and moist, and summers are warm and dry. The average
annual temperature is about 10 degrees C, the average January temperature
is about 3 degrees C, and the average July temperature is about 16 degrees
C. The annual precipitation ranges from 1,800 to 3,000 mm. The growing
season (-2 degrees C) is 200 to 240 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Astoria,
Katula, Lytell, Swem, Murnen, Squally, and Zenker soils and the competing
Boistfort soils. Astoria soils are Udepts and are in a fine class. Katula and
Squally soils are in a medial-skeletal class. Lytell and Zenker soils are in a
medial class and average more than 35 percent sandstone or siltstone
pararock fragments in the particle-size control section. Murnen soils are
in a frigid temperature class. Swem soils are in a medial class and have
grayish iron depletions in the particle-size control section.
DRAINAGE, RUNOFF, AND PERMEABILITY: Well drained; very low
to high runoff; moderate permeability.
USE AND VEGETATION: Forested. Bunker soils are used for timber
production, watershed, wildlife habitat, and recreation. The vegetation is mainly
Douglas-fir and western hemlock with an understory of western swordfern,
Oregongrape, red huckleberry, and vine maple.
DISTRIBUTION AND EXTENT: Southwestern Washington. The series is
extensive.
SERIES ESTABLISHED: Wahkiakum County, Washington, 1976.
REMARKS: The diagnostic horizons and features recognized in this pedon are an
umbric epipedon from the mineral soil surface to 29 cm and a cambic horizon from
29 to 156 cm. The upper 43 cm of the particle-size control section has andic soil
properties.
ADDITIONAL DATA: The classification is based on laboratory data taken on the
Boistfort series. These data are available at the National Soil Survey Laboratory,
Lincoln, Nebraska: Pedon numbers 40A3303 and 84P0906.
National Cooperative Soil Survey
U.S.A.
837
This chapter describes the geographic extent and pattern
of the 12 soil orders and 64 suborders recognized in the
current taxonomic system as these taxa occur in the United
States. The geography of the orders and suborders, the nature
of the topography on which they occur, the parent materials,
and the principal uses of the soils are specified. More detailed
descriptions of the soil orders and suborders and the lower
categories of the taxonomic system are given in individual
chapters on the soil orders.
The maps of the United States at the end of this publication
show the geographic distribution of the soil orders and
suborders in the United States and the territories,
commonwealths, and island nations served by the United States
Department of Agriculture, Natural Resources Conservation
Service. The dominant order map and the dominant suborder
maps are at scales of approximately 1:15,000,000 and
1:52,000,000, respectively, except in Alaska and the Pacific Basin
islands.
The maps provide an illustration of the dominant soil
orders and suborders derived from the State Soil Geographic
Data Base, or STATSGO (USDA, NRCS, 1994, revised 1998;
USDA, NRCS, 1996). The dominant soil orders and
suborders represent the largest land area of each STATSGO
map unit (summed component percentage) for each order
and suborder category. The soil orders and suborders for
the U.S. Virgin Islands and the Pacific Basin islands served
by the Natural Resources Conservation Service were
determined from published soil survey reports and from local
information.
The soil order and suborder concepts for each STATSGO
map unit were revised according to soil series name (118,568
component records for 10,872 map units) through use of the
Soil Classification File (USDA, NRCS, 1997). These data records
were further correlated to make them consistent with the current
concepts of the taxonomic system.
The maps of the United States include 1 map showing the
dominant orders and 12 maps showing the dominant suborders
within each order. The dominant order map has a legend that
includes 12 dominant order categories, 1 category of
codominant orders, and 2 categories for miscellaneous lands,
plus water. The codominant category is used only in Alaska,
where the STATSGO scale is 1:1,000,000. Given this smaller
scale, there is much greater uncertainty associated with this
portion of the map and a multi-taxa unit was chosen.
During the correlation of the STATSGO component records,
the following were included in the rock outcrop category:
badlands, cinder land, lava flows, rock outcrop, rough
mountainous land, and rubble land. Glacier ice fields in
Alaska and continuously snow-covered areas at high elevations
of the mountains in the Western States were included in the
ice/tundra category. In addition, several miscellaneous land
areas were included with the Entisol and Aridisol orders and
suborders. Psamments included dune land, coastal dunes, and
blown-out land. Salids included playas and salt flats. Orthents
included dumps, pits, gullied land, and scoria land. Fluvents
included riverwash and beaches; however, they excluded areas
of riverwash and beaches with permafrost. Arents included
urban land.
Gelisols did not occur in the Alaska STATSGO and Soil
Classification File (USDA, NRCS, Soil Survey Staff, 1997) and
were approximated through use of the pergelic subgroups for
STATSGO components. Additional study and evaluation are
needed to determine the proper placement and extent of these
map units in Alaska.
The 12 dominant suborder maps each have legends that
identify the possible suborders within a given order. The
dominant suborder for each STATSGO map unit is the most
extensive suborder of the dominant order in the map unit. The
Gelisol suborders were approximated through use of local
information that helped to correlate the Alaska STATSGO
component soil series.
The table “Total Area of Soil Orders and Suborders in the
United States” shows the approximate area, in square kilometers,
and the percentages of the soil orders and suborders in the
United States, based on a total area of 9,147,537 square
kilometers. Some suborders are of very small extent or are not
known to occur in the United States. These suborders are not
shown on the map; however, the extent of all STATSGO map
unit components is accounted for in the table.
Alfisols
Alfisols are extensive in the United States. They make up
about 13.9 percent of the surface area. Typically, they have an
ochric epipedon, an argillic horizon, and moderate or high base
saturation. In normal years water is held at less than 1500 kPa
tension in some or all parts of the moisture control section
more than one-half of the time when the soils are warm enough
CHAPTER 22
Soils of the United States
838 Soil Taxonomy
Alfisols ...........................................1,269,283 ................ 13.88
Aqualfs ......................................... 215,497 .................. 2.36
Cryalfs ............................................. 69,129 .................. 0.76
Udalfs ............................................ 622,300 .................. 6.80
Ustalfs ........................................... 281,586 .................. 3.08
Xeralfs ............................................. 80,771 .................. 0.88
Andisols .......................................... 155,812 .................. 1.69
Aquands ........................................... 2,299 .................. 0.03
Cryands ........................................... 87,531 .................. 0.95
Torrands ............................................... 134 ..................<.01
Udands............................................ 17,456 .................. 0.19
Ustands ............................................. 1,149 .................. 0.01
Vitrands ........................................... 17,319 .................. 0.18
Xerands ........................................... 29,924 .................. 0.33
Aridisols .......................................... 760,122 .................. 8.30
Argids ........................................... 322,921 .................. 3.53
Calcids .......................................... 221,716 .................. 2.42
Cambids ........................................ 103,009 .................. 1.12
Cryids ................................................... 562 .................. 0.01
Durids ............................................. 74,371 .................. 0.81
Gypsids ........................................... 14,061 .................. 0.15
Salids............................................... 23,482 .................. 0.26
Entisols ..........................................1,122,383 ................ 12.27
Aquents ........................................ 124,331 .................. 1.36
Arents ............................................. 21,232 .................. 0.23
Fluvents ........................................ 178,579 .................. 1.95
Orthents ........................................ 549,579 .................. 6.01
Psamments .................................... 248,662 .................. 2.72
Gelisols ............................................. 792,945 .................. 8.68
Histels ............................................. 87,440 .................. 0.96
Orthels .......................................... 124,975 .................. 1.37
Turbels .......................................... 580,530 .................. 6.35
Histosols .......................................... 149,555 .................. 1.63
Fibrists ............................................ 22,058 .................. 0.24
Folists ............................................... 8,795 .................. 0.09
Hemists ........................................... 29,159 .................. 0.32
Saprists ........................................... 89,543 .................. 0.98
Inceptisols ....................................... 889,441 .................. 9.71
Anthrepts ................................................ 0 .................. 0
Aquepts ........................................ 123,753 .................. 1.35
Cryepts.......................................... 190,517 .................. 2.08
Udepts .......................................... 348,528 .................. 3.81
Ustepts.......................................... 149,122 .................. 1.62
Xerepts............................................ 77,521 .................. 0.85
Mollisols ........................................ 1,966,457 ................ 21.49
Albolls ............................................ 15,314 .................. 0.17
Aquolls ......................................... 233,749 .................. 2.55
Cryolls ........................................... 136,132 .................. 1.49
Rendolls ............................................ 3,223 .................. 0.03
Udolls ............................................ 356,064 .................. 3.89
Ustolls ........................................... 884,688 .................. 9.67
Xerolls ........................................... 337,287 .................. 3.69
Oxisols ................................................. 1,666 .................. 0.02
Aquox ..................................................... 0 .................. 0
Perox ......................................................15 ..................<.01
Torrox ...................................................... 0 .................. 0
Udox .................................................. 1,048 .................. 0.01
Ustox .................................................... 603 .................. 0.01
Spodosols ........................................ 317,665 .................. 3.47
Aquods ........................................... 55,269 .................. 0.60
Cryods ............................................ 85,873 .................. 0.94
Humods ............................................. 4,612 .................. 0.05
Orthods ......................................... 171,911 .................. 1.88
Ultisols ............................................. 842,259 .................. 9.20
Aquults ........................................... 75,472 .................. 0.82
Humults ........................................... 16,489 .................. 0.18
Udults ........................................... 742,749 .................. 8.12
Ustults ................................................. 823 .................. 0.01
Xerults .............................................. 6,726 .................. 0.07
Vertisols ........................................... 181,482 .................. 1.99
Aquerts ........................................... 55,469 .................. 0.61
Cryerts .................................................... 0 .................. 0
Torrerts............................................ 10,025 .................. 0.11
Uderts ............................................. 30,934 .................. 0.34
Usterts ............................................ 74,120 .................. 0.81
Xererts ............................................ 10,934 .................. 0.12
Water2
............................................... 118,973 .................. 1.30
Rock and ice ..................................... 577,304 .................. 6.35
Rock .............................................. 269,382 .................. 2.94
Rock and ice .................................. 307,922 .................. 3.41
Ice ..................................................... 1,108 .................. 0.01
Unclassified .......................................... 1,082 .................. 0.01
Total surface area........................... 9,147,537 .................. 100
1
Percentage of the surface area of the United States and the territories, commonwealths,
and island nations served by the Natural Resources Conservation Service.
2
Water as represented in State Soil Geographic Data Base (USDA, NRCS, 1994 and
1996).
Total Area of Soil Orders and Suborders in the United States
Order/suborder Square kilometers Percent1
Order/suborder Square kilometers Percent1
Soils of the United States 839
for plants to grow. Some Alfisols also have a fragipan, a duripan,
a kandic horizon, a natric horizon, a petrocalcic horizon, plinthite,
or other features.
Alfisols are divided into five suborders based on soil
moisture or soil temperature. These properties tend to limit the
suborders to specific regions of the country.
Aqualfs, which have aquic conditions, are of moderate
extent in the United States. They make up about 2.4 percent of
the surface area. They occur mostly in association with soils
that have a udic moisture regime. The largest extent is in an
area bordering the southern part of the Mississippi River, in
southern Illinois, and in Indiana and Ohio. Most Aqualfs,
except those that have a frigid or cryic temperature regime,
have some artificial drainage or other water control and are
used as cropland. Corn and soybeans are the most common
crops. Rice also is a common crop on Aqualfs that have a
thermic or warmer temperature regime. Before they were
cultivated, some of the soils were under forest vegetation and
others were under grass. Nearly all Aqualfs are believed to
have supported forest vegetation at some time in the past.
Cryalfs, which have a cryic soil temperature regime, are of
small extent in the United States. They make up about 0.8
percent of the surface area. They occur mostly in association
with Inceptisols and Mollisols at high elevations, mainly in the
Rocky Mountains in the Western United States. Most of the
Cryalfs in the United States are used as forest because of their
short, cool growing season.
Udalfs, which have a udic moisture regime, are of large
extent in the United States. They make up about 6.8 percent of
the surface area. They form a belt extending from Minnesota
through Wisconsin, Michigan, Indiana, and Ohio and ending
in New York State. This belt has mostly Spodosols and
Inceptisols to the north, Mollisols to the west, and Ultisols to
the south and east. Another large area of Udalfs begins in
southern Iowa and extends through Missouri, Illinois, and the
States to the south bordering the Mississippi River. Smaller
areas of Udalfs are associated with the Ultisols in the
Southeastern States. The Alfisols in the Southern States formed
mostly in materials that are younger and/or have more bases
than those of the associated Ultisols. All Udalfs are believed to
have supported forest vegetation at some time during
development. Most of the Udalfs with a mesic or warmer
temperature regime currently support or formerly supported
deciduous forest vegetation, and many with a frigid
temperature regime currently support or formerly supported
mixed coniferous and deciduous trees. Many Udalfs have been
cleared of trees and are used intensively as cropland. As a
result of erosion, some have only an argillic or kandic horizon
below an Ap horizon. Others retain most of their eluvial
horizons above the argillic or kandic horizon.
Ustalfs, which have an ustic soil moisture regime, are of
large extent in the United States. They make up about 3.1
percent of the surface area. They tend to occur in association
with Mollisols on the southern Great Plains, mostly in Texas
and Oklahoma. They also occur in association with Aridisols,
Inceptisols, and Mollisols throughout the Rocky Mountain
States from Montana to Arizona and New Mexico and in
association with Entisols in the Black Hills of South Dakota.
The dry season or seasons are pronounced enough for the trees
to be either deciduous or xerophytic. Many Ustalfs currently
support or formerly supported savanna vegetation, and some
supported grassland vegetation. Most are used as cropland or
grazing land. Some are used as irrigated cropland. Wheat and
sorghum are the most common crops. Cotton also is grown on
the Ustalfs with a thermic or warmer temperature regime.
Xeralfs, which have a xeric soil moisture regime, are of small
extent in the United States. They make up about 0.9 percent of
the surface area. They occur mainly in association with
Mollisols, Inceptisols, and Andisols. They are mostly in
California, but small areas are in Oregon, Washington, Idaho,
and Utah. The natural vegetation was a mixture of annual
grasses, forbs, and woody shrubs on the warmest and driest
Xeralfs and coniferous forest on the coolest and most moist
Xeralfs. Xeralfs are used mostly as cropland, forest, or grazing
land. Small grains, mostly winter wheat, are the most common
crops. A wide variety of crops are grown on irrigated Xeralfs.
Andisols
Andisols are of small extent in the United States. They
make up about 1.7 percent of the surface area. The colloidal
fraction of these soils is dominated by short-range-order
minerals or Al-humus complexes. Many Andisols developed in
volcanic ejecta and/or in volcaniclastic materials. Some of the
soils are dominated by short-range-order minerals that
weathered from nonvolcanic primary alumino-silicates. The
dominant process in the formation of Andisols is the
transformation of minerals. Translocation within the soils and
accumulation of the translocated compounds are normally
minimal. The accumulation of organic matter, complexed with
aluminum, however, is characteristic of some Andisols.
Andisols may have any diagnostic epipedon, provided that the
minimum requirements for the order are met in and/or below the
epipedon. These soils commonly have an ochric or umbric
epipedon and a cambic horizon. Some have buried diagnostic
horizons. Andisols can have any soil moisture regime and any
soil temperature regime, but they cannot have permafrost. They
can occupy any position on the landscape and can occur at any
elevation. One of the outstanding features of Andisols is their
generally high natural productivity. The dominance of physical
properties that favor the growth of most plants and the most
common occurrence of the soils in areas of considerable rainfall
have resulted in volcanic soils that generally are regarded as
highly fertile.
Andisols are divided into seven suborders based on soil
moisture and temperature regimes, soil wetness, and the
amount of water held too tightly for plants to use.
Aquands, which have aquic conditions at or near the soil
840 Soil Taxonomy
surface, are of very small extent in the United States. They make
up less than 0.1 percent of the surface area and do not dominate
any areas on the map. They commonly have dark colored
surface horizons that meet the requirements for a histic, umbric,
or mollic epipedon. They occur mostly in western Washington
and Oregon, in the lower landscape positions and under forest
or grass vegetation. Some of the soils have been drained and are
used as cropland or pasture.
Cryands, which have a cryic temperature regime, are of
moderate extent in the United States. They make up about 1.0
percent of the surface area. They dominate some areas in
Alaska and in the mountains of the Pacific Northwest. Most
of the soils formed under coniferous forest vegetation.
Cryands commonly have a thin O horizon, an ochric or
umbric epipedon, and a cambic horizon. They developed
mostly in late-Pleistocene or Holocene deposits. Most are used
as forest.
Torrands, which have an aridic (or torric) moisture regime
and a temperature regime warmer than cryic, are of very small
extent in the United States. They make up less than 0.1 percent
of the surface area. The extent is too small for the soils to be
shown on the map. A very few areas of these soils are in
western Oregon and in Hawaii. Most of the soils formed under
grassy or shrub vegetation. Commonly, Torrands have an
ochric or mollic epipedon and a cambic horizon. Some have a
duripan or a petrocalcic horizon. The Torrands in the United
States generally developed in late-Pleistocene or Holocene
deposits. They are used as rangeland or as irrigated cropland.
Udands, which have a udic moisture regime, a temperature
regime warmer than cryic, and a relatively high content of
water held too tightly for plants to use, are of small extent in
the United States. They make up about 0.2 percent of the
surface area. They dominate in some areas, mostly in western
Washington and Oregon and in Hawaii. Most of the soils
formed under forest vegetation. Characteristically, Udands
have an ochric or umbric epipedon and a cambic horizon.
Some have a cemented pan. Most developed in late-Pleistocene
or Holocene deposits. Udands are used mostly as forest, but
some have been cleared and are used as cropland or pasture.
Ustands, which have an ustic moisture regime, a
temperature regime warmer than cryic, and a relatively high
content of water held too tightly for plants to use, are of very
small extent in the United States. They make up less than 0.1
percent of the surface area. They are mostly in Hawaii. They
formed mostly under forest or savanna vegetation.
Characteristically, Ustands have an ochric, mollic, or umbric
epipedon and a cambic horizon. Most of the Ustands in the
United States developed in late-Pleistocene or Holocene
deposits. Ustands are used mostly as forest, cropland, or
pasture or for urban development.
Vitrands, which are the more or less well drained, coarse
textured Andisols that have a udic or ustic moisture regime, a
temperature regime warmer than cryic, and a low content of
water held too tightly for plants to use, are of small extent in
the United States. They make up about 0.2 percent of the surface
area. They occur mostly in Idaho, Oregon, and Washington.
Most of the soils formed under coniferous forest vegetation, but
some formed under grass and shrubs. Characteristically, Vitrands
have an ochric or mollic epipedon and a cambic horizon. They
are relatively young soils that developed mostly in Holocene
deposits. They are used mostly as forest, but some are used as
rangeland and some have been cleared and are used as cropland
or pasture.
Xerands, which have a xeric moisture regime and a frigid,
mesic, or thermic temperature regime, are of small extent in
the United States. They make up about 0.3 percent of the
surface area. They are mostly in Washington, California,
Oregon, and Idaho. Most of the Xerands that have a frigid or
mesic temperature regime formed under coniferous forest
vegetation. Some Xerands, mostly those with a thermic
temperature regime, formed under grass and shrub vegetation.
Characteristically, Xerands have an ochric or mollic epipedon
and a cambic horizon. They developed mostly in latePleistocene
or Holocene deposits. They are used mostly as
forest, but some have been cleared and are used as cropland or
pasture.
Aridisols
Aridisols are moderately extensive in the United States. They
make up about 8.3 percent of the surface area. They are in the
Western States. For long periods, they are too dry for
mesophytic plants to grow. During most of the time when they
are warm enough for plants to grow, the soils are dry or salty,
or both. There are no periods as long as 90 consecutive days
when the soils are warm enough for plants to grow and soil
moisture is continuously available for plant growth. The
concept of Aridisols is based on the limited availability of soil
moisture for sustained plant growth. In areas bordering deserts,
the absolute precipitation may be high. Because of runoff or a
very low storage capacity in the soils, or both, however, the
actual soil moisture regime is aridic.
Soil moisture and, to a lesser extent, soil temperature
regimes control processes in these soils. The soil moisture
regime is used, in conjunction with diagnostic horizons, to
define the Aridisol order. The soil moisture regime is the single
most important limitation affecting the use of the soils.
Because of an extreme imbalance between evapotranspiration
and precipitation, many Aridisols in a sense are incipient
evaporites. The dominant process in Aridisols is one of
accumulation and concentration of weathering products. The
redistribution and accumulation of soluble materials in some
layer of the soils are common. The products of this process not
only give special attributes that distinguish the soils but also
limit the use of the soils. Four of the seven suborders are
defined on the basis of the composition and accumulation of
the soluble fraction. Weathering and clay and silica
translocation also occur in Aridisols.
Soils of the United States 841
Aridisols are divided into seven suborders based on
diagnostic horizons and soil temperature regimes.
Argids are the Aridisols that have an argillic or natric horizon,
but not a duripan or a gypsic, petrocalcic, petrogypsic, or salic
horizon, within 100 cm of the soil surface. They are of large
extent in the United States and are the suborder with the largest
extent on the map. They make up about 3.5 percent of the
surface area. They have a temperature regime warmer than cryic.
The presence of an argillic horizon is often attributed to a more
moist paleoclimate, although there is evidence that clay
illuviation has occurred during the Holocene in arid soils,
especially where the soil moisture regime grades toward ustic
or xeric. Most Argids are used as rangeland or wildlife habitat.
Some are used as irrigated cropland.
Calcids are the Aridisols that have a calcic or petrocalcic
horizon and have calcium carbonate in the layers above. They
are of moderate extent in the United States. They make up
about 2.4 percent of the surface area. They have a temperature
regime warmer than cryic. The parent materials are high in
content of carbonates, or carbonates were added as dust, or
both. Precipitation has been insufficient to remove the
carbonates or even move them to great depths. The upper
boundary of the calcic or petrocalcic horizon is normally
within 50 cm of the soil surface. These soils are in the Western
States. Most are used as rangeland or wildlife habitat. Some
are used as irrigated cropland. If the soils are used as cropland,
micronutrient deficiencies are normal.
Cambids are the Aridisols that have a cambic horizon
within 100 cm of the soil surface. They do not have other
diagnostic horizons, such as petrocalcic, gypsic, or calcic
horizons, unless the upper boundary of such horizons is 100
cm or more below the soil surface. The soils are characterized
by the least degree of soil development. They are of moderate
extent in the United States. They make up about 1.1 percent of
the surface area. They are mostly in Washington State. These
soils have a temperature regime warmer than cryic. Most are
used as rangeland or wildlife habitat. Some are used as
irrigated cropland.
Cryids are the Aridisols of cold areas. They have a cryic
temperature regime. The growing season is short. The short
growing season and arid conditions severely limit the use of
these soils. The soils are of very small extent in the United
States. They make up about 0.01 percent of the surface area.
The extent is too small for the soils to be shown on the map.
The soils are at high elevations in mountain valleys and basins
in Idaho. They can have a duripan or an argillic, calcic,
cambic, gypsic, natric, petrocalcic, petrogypsic, or salic
horizon. Most of these soils are used as rangeland or wildlife
habitat.
Durids are the Aridisols that have a duripan, but not a salic
horizon, that has an upper boundary within 100 cm of the soil
surface. Many duripans are within 50 cm of the soil surface.
These soils have a temperature regime warmer than cryic. They
are of small extent in the United States. They make up about
0.8 percent of the surface area. They are in the Western States.
The largest extent is in Nevada and Idaho. These soils occur
dominantly on gentle slopes. Many formed in sediments that
contain pyroclastics. Most of the soils are used as rangeland or
wildlife habitat. A few are used as irrigated cropland.
Gypsids are the Aridisols that have a gypsic or petrogypsic
horizon, but not a duripan or a salic horizon, within 100 cm of
the soil surface. They have a temperature regime warmer than
cryic. They are of small extent in the United States. They make
up about 0.15 percent of the surface area. They are mostly in
the Southwestern States. They are on many segments of the
landscape. Some of the soils have a calcic horizon or related
horizons, which overlie the gypsic horizon. The gypsic horizon
limits many soil uses. A petrogypsic horizon is an even greater
limitation. Most of these soils are used as rangeland or wildlife
habitat.
Salids are the Aridisols that have a salic horizon that has its
upper boundary within 100 cm of the soil surface. They are
commonly in depressions (playas). They are of small extent in
the United States. They make up about 0.26 percent of the
surface area. They are mostly in Utah and Nevada. In a warm,
arid environment, salts commonly accumulate at or near the
surface if there are both a supply of salts in the soils or in water
and a net upward movement of water in the soils. In some
areas salic horizons formed in salty parent materials without
the presence of ground water. Silica can accumulate and form
duripans if the ground water is sufficiently alkaline. As a rule,
Salids are unsuitable for agricultural uses unless they are
leached of salts. Leaching the salts is an expensive
undertaking, particularly if there is no natural outlet for the
drainage water. Most of these soils are used as rangeland or
wildlife habitat.
Entisols
Entisols are extensive in the United States. They make up
about 12 percent of the surface area. Most of the soils have no
diagnostic horizons other than an ochric epipedon. Some have
a cambic horizon with its base at a depth of less than 25 cm
below the mineral soil surface. A few Entisols that have a
sandy or sandy-skeletal particle-size class have a horizon that
would be a cambic horizon were it not for the particle-size
class exclusion, and a very few have an albic horizon. In
coastal marshes some Entisols that have sulfidic materials
within 50 cm of the mineral soil surface have a histic epipedon.
On many landscapes the soil material is too thin or has not
been in place long enough for pedogenic processes to form
diagnostic horizons. Some Entisols have steep, actively eroding
slopes, and others are on flood plains or glacial outwash plains
that receive new deposits of alluvium at frequent intervals.
Some Entisols are old and deep enough to have formed
diagnostic horizons, but they consist mostly of quartz or other
minerals that are resistant to the weathering needed to form
diagnostic horizons. Buried diagnostic horizons are permitted
842 Soil Taxonomy
in Entisols if they meet the definition of “buried soil” in
chapter 1.
Entisols may have any mineral parent material, vegetation,
age, or moisture regime and any temperature regime, but they
cannot have permafrost at a depth of less than 100 cm below
the soil surface. The only features common to all Entisols are
the virtual absence of diagnostic horizons and the mineral
nature of the soils.
Entisols are divided into five suborders based on wetness
and soil characteristics.
Aquents, or the wet Entisols, are of moderate extent in the
United States. They make up about 1.4 percent of the surface
area. They are widely distributed. They dominate some of the
delineations along the southern Atlantic and gulf coasts and on
the flood plains along the Mississippi River and along other
rivers and streams. Some Aquents are forming, mostly in sandy
deposits, in other parts of the country. Aquents can have any
temperature regime, but they cannot have permafrost within
100 cm of the soil surface. Most of the soils are forming in
recent sediments. They support vegetation that tolerates
permanent or periodic wetness. They are used mostly as
pasture, cropland, forest, or wildlife habitat.
Arents are of small extent in the United States. They make
up about 0.2 percent of the surface area. They do not have
diagnostic horizons because they have been deeply mixed by
plowing, spading, or other methods of moving by humans.
They are important soils for irrigated crop production in
California. Small areas also occur throughout the country.
Some are areas where the soil profile was removed and then
replaced after strip-mining. Others are urban areas and resulted
from cuts and fills made to shape or level the soils for
development. Some were modified for use as irrigated
cropland. Arents retain some fragments that can be identified
as parts of a former spodic or argillic horizon, a duripan, or
other feature, but the fragments do not themselves form
diagnostic horizons, are not arranged in any discernible order,
and are mixed with the materials of other horizons. Some of
the soils are the result of deliberate soil modification intended
to break up or remove a duripan or another root-restrictive
layer. Arents are used mostly as cropland, urban land, or
pasture. Some are used as wildlife habitat.
Fluvents are the more or less freely drained Entisols that
formed in recent water-deposited sediments on flood plains,
fans, and deltas along rivers and small streams throughout
the country. They are of moderate extent in the United
States. They make up about 2.0 percent of the surface area.
Some of the largest areas are on the flood plains along the
Mississippi River. The age of the sediments is commonly a
few years or decades to a few hundred years in humid areas.
It may be somewhat more in arid areas. Most Fluvents are
frequently flooded, unless they are protected by dams or
levees. Stratification of the materials is normal. These soils
can have any kind of vegetation and any temperature regime,
but they cannot have permafrost within 100 cm of the soil
surface. They can have any moisture regime but cannot
meet the criteria for Aquents. Most Fluvents are used as
rangeland, forest, pasture, or wildlife habitat. Some are used
as cropland.
Orthents are extensive in the United States. They make up
about 6.0 percent of the surface area. They are mainly in the
Western States. They are commonly on recent erosional
surfaces. The erosion may be geologic or may have been
induced by cultivation, mining, or other factors, but any soil
that existed has been completely removed or so truncated that
the diagnostic horizons are very thin or do not occur. Some of
the soils, mostly those in the Rocky Mountain States, are less
than 25 cm deep to a lithic or paralithic contact. Some of the
soils, mostly those in the Western States, are deep, have an
aridic moisture regime, and are characterized by little horizon
development. A few Orthents are forming in recent volcanic
deposits, loamy or fine textured eolian deposits, solifluction or
glacial deposits, landslide debris, or mudflows. Orthents can
have any kind of vegetation and any temperature regime, but
they cannot have permafrost within 100 cm of the soil surface.
They cannot have aquic conditions, a high water table, and the
colors defined for Aquents. Orthents are used mostly as
rangeland, pasture, or wildlife habitat.
Psamments are moderately extensive in the United States.
They make up about 2.7 percent of the surface area. They occur
throughout the country. Some of the largest areas are in
Nebraska, California, Minnesota, Wisconsin, Michigan,
Arizona, and Florida. These soils are sandy in all layers within
the particle-size control section. Because Psamments store less
water than other deep soils, they have lower yields than most
other soils in humid climates. Because they lose little
precipitation to runoff and store the moisture deeply, they are
among the most productive rangeland soils in some arid and
semiarid climates. Some Psamments are forming in poorly
graded (well sorted) sands on shifting or stabilized sand dunes,
in cover sands, or in sandy parent materials that were sorted in
an earlier geologic cycle. Some are forming in sands that were
sorted by water and are on outwash plains, lake plains, natural
levees, or beaches. Psamments occur under any climate, but
they cannot have permafrost within 100 cm of the soil surface.
They can have any vegetation and are on surfaces of virtually
any age from recent historic to Pliocene or older. The
Psamments on old stable surfaces commonly consist of quartz
sand, which cannot form diagnostic horizons that involve the
accumulation of clays or sesquioxides. Ground water is
typically deeper than 50 cm and commonly is much deeper.
Some Psamments that are nearly bare are subject to soil
blowing and drifting and provide poor support for wheeled
vehicles. Because very gravelly sands do not have these two
qualities, they are excluded from Psamments and are grouped
with Orthents. Psamments are used mostly as rangeland,
pasture, or wildlife habitat.
Soils of the United States 843
Gelisols
Gelisols are moderately extensive in the United States. They
make up about 8.7 percent of the surface area. They are known
to occur only in Alaska. Most of the soils have a layer of gelic
materials that is underlain by permafrost within 100 cm of the
soil surface. Diagnostic horizons may or may not be present.
Permafrost influences pedogenesis through its effect on the
downward movement of the soil solution and on the soilforming
processes. Cryoturbation (frost mixing) is an
important process in many Gelisols and results in irregular or
broken horizons, involutions, organic matter accumulation on
the permafrost table, oriented rock fragments, and silt caps on
rock fragments. Cryoturbation occurs when two freezing fronts,
one from the surface and the other from the permafrost, merge
during freeze-back in autumn. Ice segregation is an important
property of gelic materials and occurs when the soil solution
migrates toward ice, increasing the volume of ice. Volume
changes also occur as the water freezes. In the drier areas
cryoturbation is less pronounced or does not occur, but the soils
still have gelic materials, as manifested by structure that results
from segregated ice. The importance of any diagnostic
horizons is overshadowed by the properties of the gelic
materials and the associated permafrost.
Gelisols are divided into three suborders based on the kind
of soil materials (organic or mineral) and expression of
cryoturbation in the mineral soil materials. The delineation
Gelisols/Inceptisols is a mosaic of Gelisols with a subgelic
temperature class and Cryepts.
Histels are the Gelisols with large amounts of organic
carbon that commonly accumulate under anaerobic conditions,
or the organic matter at least partially fills voids in fragmental,
cindery, or pumiceous materials. Cold temperatures contribute
to the accumulation of organic matter. These soils are of small
extent in the United States. They make up about 0.96 percent
of the surface area. They are in Alaska. The vegetation is
mostly mosses, sedges, and shrubs. The soils are used as
wildlife habitat.
Orthels are the Gelisols that show little or no evidence of
cryoturbation. These soils are of moderate extent in the United
States. They make up about 1.4 percent of the surface area.
They occur throughout the Gelisol area in Alaska. Orthels are
generally drier than Turbels and Histels. The vegetation is
mostly lichens, mosses, sedges, shrubs, black spruce, and white
spruce. The soils are used mostly as wildlife habitat. A small
amount of the acreage is used as cropland or for urban
development.
Turbels are the Gelisols that have one or more horizons
showing cryoturbation in the form of irregular, broken, or
distorted horizon boundaries, involutions, an accumulation of
organic matter on top of the permafrost, ice or sand wedges, or
oriented rock fragments. These soils are of large extent in the
United States. They make up about 6.4 percent of the surface
area. They occur throughout the Gelisol area in Alaska. The
vegetation is mostly mosses, sedges, shrubs, and black spruce.
The soils are used mostly as wildlife habitat. A small amount
of the acreage is used as cropland or for urban development.
The Gelisols in the Gelisols/Inceptisols delineation include
Turbels, Orthels, and Histels in a mosaic with Cryepts. The
Gelisols generally have a subgelic temperature class. The
Cryepts occur on slopes that receive more solar radiation or in
areas where fire or land clearing has changed the thermal
properties of the soils enough to allow the permafrost to thaw
to a depth of 2 meters or more.
Histosols
Histosols are of small extent in the United States. They make
up about 1.6 percent of the surface area. They are forming in
organic soil materials that do not have permafrost within 100 cm
of the soil surface. The general rule is that a soil is classified as a
Histosol if half or more of the upper 80 cm is organic. A soil also
is classified as a Histosol without regard to the thickness of
organic materials if the organic materials rest on rock or fill or
partially fill voids in fragmental, cindery, or pumiceous materials.
If the bulk density is very low (less than 0.1 gram per cubic
centimeter), three-fourths or more of the upper 80 cm must be
organic.
Histosols are divided into four suborders based on soil
wetness and the degree of decomposition of the organic
materials.
Fibrists are the wet, slightly decomposed Histosols. They are
of small extent in the United States. They make up about 0.24
percent of the surface area. The largest extent is in southern
Alaska. More than two-thirds of these soils consists of fiber
that is not destroyed by rubbing between the thumb and
fingers. The botanic origin of much of the materials can be
readily determined. The bulk density generally is less than 0.1
gram per cubic centimeter. These soils commonly are in closed
depressions or on broad flats, such as coastal plains. Many
have ground water near the soil surface nearly all the time. The
level of the ground water fluctuates, but it seldom drops much
below the bottom of the surface tier. Most of the soils support
natural vegetation of widely spaced, small trees, shrubs, forbs,
and grasses and grasslike plants.
Folists are the more or less freely drained Histosols that
consist primarily of O horizons derived from leaf litter, twigs,
and branches resting on bedrock or on fragmental materials in
which the interstices are partly or completely filled with
organic materials. These soils are of very small extent in the
United States. They make up about 0.09 percent of the surface
area. The largest extent is in Hawaii and Alaska. Some Folists
developed in the mountains and the most humid parts of the
conterminous United States. Most of these soils support forest
vegetation. Some of the soils in Hawaii mainly support grass.
A few of the soils in Hawaii are used for specialty crops or for
urban or recreational development.
Hemists are the wet Histosols in which the organic materials
844 Soil Taxonomy
are moderately decomposed. These soils are of small extent in
the United States. They make up about 0.3 percent of the
surface area. The largest extent is in Minnesota and Alaska.
The soils are mainly in closed depressions and on broad flats,
such as coastal plains and outwash plains. The botanic origin
of much of the organic material cannot be readily determined.
The fiber content of the organic material is mostly between
one-sixth and two-thirds after rubbing between the thumb and
fingers. The bulk density commonly is between 0.1 and 0.2
gram per cubic centimeter. Ground water is at or very close to
the surface much of the time unless artificial drainage has been
provided. The level of ground water may fluctuate but seldom
drops much below the bottom of the surface tier. Most Hemists
support natural vegetation and are used as woodland,
rangeland, or wildlife habitat. Some have been cleared and
drained and are used as cropland.
Saprists are the wet Histosols in which the organic materials
are well decomposed. These soils are of moderate extent in the
United States. They make up about 1.0 percent of the surface
area. The largest extent is in Michigan, Florida, Wisconsin,
Minnesota, and Alaska. Small areas are common on the
Atlantic and gulf coasts. The soils are mainly in closed
depressions and on broad flats, such as coastal plains and
outwash plains. The botanic origin of the organic material is
difficult to determine in most of these soils. The fiber content
of the organic material is mostly less than one-sixth after
rubbing between the thumb and fingers. Most of the soils have
a bulk density of more than 0.2 gram per cubic centimeter. The
water table tends to fluctuate within the soils, or the soils were
aerobic during drier periods in the past. Many Saprists support
natural vegetation and are used as woodland, rangeland, or
wildlife habitat. Some of the soils, mostly those with a mesic or
warmer temperature regime, have been cleared and drained
and are used as cropland.
Inceptisols
Inceptisols are soils of cool to very warm, humid and
subhumid regions. They are moderately extensive and widely
distributed in the United States. They make up about 9.7
percent of the surface area. The largest area is one that includes
the southern New England States and the Appalachian
Mountains. Other areas are on the southern Great Plains; in
the Rocky Mountains; in eastern Montana; in the coastal and
Cascade Mountains of California, Oregon, and Washington;
and in northeastern Minnesota.
Inceptisols have many kinds of diagnostic horizons and
epipedons. They cannot have an argillic, kandic, or natric
horizon unless it is buried. Spodic and oxic horizons also are
excluded unless the top of the horizon is deep. Inceptisols can
have an anthropic, histic, mollic, ochric, plaggen, or umbric
epipedon. The most common diagnostic horizons in the
Inceptisols in the United States are an ochric epipedon and a
cambic horizon. An umbric epipedon and a fragipan also are
common. Most Inceptisols do not have sandy texture
throughout. They are largely forming on late- or postPleistocene
surfaces if evapotranspiration normally exceeds
precipitation at some time of the year. If precipitation exceeds
potential evapotranspiration in most months, Inceptisols occur
in areas of old as well as young surfaces or deposits. If the soil
temperature regime is frigid or cryic in these humid regions,
Inceptisols form mainly in the more clayey parent materials
and Spodosols form in the materials that have little clay.
Inceptisols range from very poorly drained to excessively
drained. A cambic horizon is not required if there is an umbric,
histic, or plaggen epipedon or if there is a fragipan or duripan
or a placic, calcic, petrocalcic, gypsic, petrogypsic, salic, or
sulfuric horizon.
Inceptisols may have any moisture regime except aridic and
any temperature regime, but they cannot have permafrost at a
depth of less than 100 cm below the soil surface.
Inceptisols are divided into four suborders based on soil
moisture and temperature regimes, soil wetness, and the kind
of epipedon.
Anthrepts are the more or less freely drained Inceptisols that
have either an anthropic or plaggen epipedon. They can have
almost any temperature regime and almost any vegetation.
These soils are not known to occur in the United States.
Aquepts are the wet Inceptisols. They are of moderate extent
and are widely distributed in the United States. They make up
about 1.4 percent of the surface area. Their natural drainage is
poor or very poor, and, if the soils have not been artificially
drained, ground water is at or near the soil surface at some
time during normal years but typically not in all seasons. The
soils generally have a gray to black surface horizon and a gray
subsurface horizon that has redox concentrations and begins at
a depth of less than 50 cm. Most Aquepts formed in latePleistocene
or younger deposits in depressions, on nearly level
plains, or on flood plains. They can have almost any particlesize
class except fragmental and any temperature regime, but
they cannot have permafrost. Many formed under forest
vegetation, but they can have almost any kind of vegetation.
Most of the soils have a cambic horizon, and some have a
fragipan. Aquepts are used mostly as cropland, pasture, forest,
or wildlife habitat.
Cryepts are the cold Inceptisols of high mountains or high
latitudes. They cannot have permafrost. They are of moderate
extent in the United States. They make up about 2.1 percent of
the surface area. They are mostly in the high mountains of the
West as well as southern Alaska. The vegetation is mostly
conifers or mixed conifers and hardwoods. These soils formed
mostly in loess, drift, or alluvium or in solifluction deposits of
late-Pleistocene or Holocene age. They commonly have a thin
ochric epipedon and a brownish cambic horizon. Some have
bedrock within 100 cm of the surface. Most are used as forest
or wildlife habitat. Some of the soils, mostly those in Alaska,
are used as cropland.
Udepts are mainly the more or less freely drained Inceptisols
Soils of the United States 845
that have a udic or perudic moisture regime. They are of large
extent in the United States. They make up about 3.8 percent of
the surface area. They are most extensive in the Appalachian
Mountains, on the Allegheny Plateau, in northeastern
Minnesota, and in Oregon. They formed on nearly level to
steep surfaces, mostly of late-Pleistocene or Holocene age.
Where the soil moisture regime is perudic, some of the soils
formed in older deposits. Most of the soils currently support or
formerly supported forest vegetation, but some support shrub or
grass vegetation. The vegetation was mostly coniferous forest
in the Northwest and mixed or hardwood forest in the Eastern
States. A few Udepts have been formed from Mollisols through
truncation of the mollic epipedon, mostly under cultivation.
Most Udepts have an ochric or umbric epipedon and a cambic
horizon. Some also have a fragipan, a duripan, or a sulfuric
horizon. Most are used as forest or have been cleared and are
used as cropland or pasture.
Ustepts are the more or less freely drained Inceptisols that
have an ustic moisture regime. They are of moderate extent in
the United States. They make up about 1.6 percent of the
surface area. They are most common on the Great Plains,
mostly in Montana, Texas, and Oklahoma. They receive
dominantly summer precipitation. They formed mostly in
Pleistocene or Holocene deposits or on steep slopes. Many of
these soils are calcareous at a shallow depth and have a Bk or
calcic horizon. A few have formed from Mollisols through
truncation of the mollic epipedon, mostly under cultivation.
Most of the soils have an ochric or umbric epipedon and a
cambic horizon. Some have a duripan. The native vegetation
commonly was grass, but some of the soils supported trees.
Most Ustepts are used as cropland or pasture. Some are used as
rangeland, forest, or wildlife habitat.
Xerepts are mainly the more or less freely drained Inceptisols
that have a xeric moisture regime. They are of small extent in the
United States. They make up about 0.85 percent of the surface
area. They are in the western part of the United States, mostly in
California, Oregon, and Washington. They receive dominantly
winter precipitation and have a frigid, mesic, or thermic
temperature regime. Most Xerepts formed in Pleistocene or
Holocene deposits or on steep slopes. Many are calcareous at a
shallow depth and have a Bk or calcic horizon. Most have an
ochric or umbric epipedon and a cambic horizon. Some have a
duripan, and a few have a fragipan. The native vegetation
commonly was coniferous forest on the soils with a frigid or
mesic temperature regime and shrubs, grasses, and widely
spaced trees on the soils with a thermic temperature regime.
Most Xerepts are used as forest, cropland, or pasture. Some are
used as rangeland or wildlife habitat.
Mollisols
Mollisols are very extensive in the United States. They make
up about 21.5 percent of the surface area. Most are on the
Great Plains and in the Western States. Nearly all Mollisols
have a mollic epipedon. Many also have an argillic or natric
horizon or a calcic horizon. A few have an albic horizon. Some
also have a duripan or a petrocalcic horizon. Most have
supported grass vegetation at some time, although many
apparently have been forested at times. Some of the soils,
mostly those in the mountains, formed in base-rich materials
under forest vegetation. Mollisols may have any of the defined
temperature regimes but do not have permafrost. They can
have any moisture regime, but enough available moisture to
support perennial grasses seems to be essential. Where the
temperature is frigid or warmer and slopes are not too steep,
Mollisols are used mainly as cropland. Generally, grains and
sorghum are grown in the drier regions and maize (corn) and
soybeans in the warmer, humid regions.
Mollisols are divided into seven suborders based on soil
moisture, soil temperature, and diagnostic horizons.
Albolls are the Mollisols that have both an albic horizon
and fluctuating ground water. They are of small extent in the
United States. They make up about 0.2 percent of the surface
area. They are mostly on the Great Plains, in eastern
Washington, and in Oregon and Idaho. Most are saturated with
water at or near the soil surface at some time during winter or
spring in normal years. In summer ground water is commonly
deeper than 200 cm. Below the albic horizon, there is either an
argillic horizon or, less commonly, a natric horizon. Albolls
developed mostly on broad, nearly level to sloping ridges and
back slopes or in closed depressions. Most have a perched
water table. Most formed in late-Pleistocene deposits. Most
supported grass or grass and shrub vegetation. In early stages
of development, some are thought to have supported forest
vegetation that was later succeeded by grass. Most of the soils
have gentle slopes and are used as cropland.
Aquolls are the wet Mollisols that do not have an albic
horizon and that have dominantly low-chroma and highcontrast
redox depletions or concentrations in or below the
epipedon. These soils are of moderate extent in the United
States. They make up about 2.6 percent of the surface area.
They occur in all areas where there are Mollisols, but they are
most extensive in glaciated areas of the Midwestern States,
mainly Iowa, Minnesota, North Dakota, and Indiana. They also
occur in Florida. Commonly, they are in low areas where water
collects and stands, but some are on broad flats or on seepy
hillsides. Most have supported a vegetation of grasses, sedges,
and forbs, but some supported forest vegetation. Aquolls can
have any temperature regime, but they cannot have permafrost.
Most have a mesic or frigid temperature regime, have been
artificially drained, and are used as cropland.
Cryolls are the cool or cold, more or less freely drained
Mollisols. They are of moderate extent in the United States.
They make up about 1.5 percent of the surface area. Most are
in the high mountains of the Western States. Some are in
Alaska. Cryolls have a cryic temperature regime and a udic or
xeric moisture regime. They support forest, grass, or grass and
shrub vegetation. In Alaska forests of spruce, birch, and aspen
846 Soil Taxonomy
trees are common. Cryolls are used mostly as rangeland. Some
are used as forest and some as pasture.
Rendolls are the Mollisols that are of humid regions and
formed in highly calcareous parent materials, such as
limestone, chalk, and drift composed mainly of limestone, or
on shell bars. These soils are of very small extent in the United
States. They make up less than 0.1 percent of the surface area.
They are in Florida, on tropical islands, and in a few areas in
the mountains of the Western States. They formed mostly
under forest vegetation or under grass and shrubs. They have a
mollic epipedon that rests on the calcareous parent materials or
on a cambic horizon that is rich in carbonates. A few of the
soils are so rich in finely divided lime that the mollic epipedon
has a color lighter than normal but is nevertheless rich in darkcolored
humus and is within the limits of a mollic epipedon.
Rendolls have a cryic soil temperature regime or a udic
moisture regime, or both. Most are used as cropland or pasture,
but some are used as rangeland or forest.
Udolls are the more or less freely drained Mollisols of
humid climates. They are of large extent in the United States.
They make up about 3.9 percent of the surface area. They are
in the eastern part of the Great Plains and east of the Great
Plains. They are most extensive in Minnesota, Illinois, Iowa,
and North Dakota. In addition to the mollic epipedon, most of
the soils have a cambic, calcic, natric, or argillic horizon. The
soils formed mainly in late-Pleistocene or Holocene deposits
or on surfaces of comparable age. The vegetation at the time
of settlement was dominantly tall grass prairie. The
temperature regime is frigid or warmer, and the moisture
regime is udic. Where slopes are not too steep, nearly all of
these soils are used as cropland. Some are used as pasture or
rangeland.
Ustolls are the more or less freely drained Mollisols of
subhumid to semiarid climates. They are of large extent in the
United States. They make up about 9.7 percent of the surface
area. They are mostly on the western Great Plains. They also
are common throughout the Rocky Mountain States. In
addition to the mollic epipedon, most Ustolls have a Bk
horizon that has identifiable secondary carbonates or have a
calcic horizon, but a few that formed in noncalcareous
materials do not have secondary lime. Ustolls may also have a
cambic, argillic, kandic, or natric horizon. Most of the Ustolls
on the Great Plains supported grass vegetation when the
country was settled. Some Ustolls, mostly those in the
mountains of the Western States, supported forest vegetation.
On the Great Plains, the most moist Ustolls supported mostly
tall grasses, the drier ones supported mostly short grasses, and
the others supported mixtures of short and tall grasses. Ustolls
have a frigid or warmer temperature regime. They generally
have an ustic moisture regime, but a few that are marginal to
Aridisols have an aridic moisture regime. Rainfall comes
mainly during a growing season, often in heavy showers, but is
erratic. Drought is frequent and may be severe. Without
irrigation, the low supply of moisture usually limits crop yields.
During a drought, soil blowing can be a problem. Most of these
soils are used as cropland or rangeland.
Xerolls are the more or less freely drained Mollisols of
regions that have Mediterranean climates. These soils are of
large extent in the United States. They make up about 3.7
percent of the surface area. They are in the Pacific Northwest,
California, Idaho, Nevada, and western Utah. They generally
have a xeric moisture regime, but some that are marginal to
Aridisols have an aridic moisture regime. Xerolls are dry for
extended periods in summer, but moisture moves through most
of the soils in winter and is stored above the deep layers or
above bedrock in normal years. Characteristically, Xerolls have
a relatively thick mollic epipedon and a cambic or argillic
horizon. Any accumulation of carbonates is in the lower part of
the B horizon. These soils are neutral in most horizons. The
vegetation at the time of settlement was dominantly bunchgrass
and shrubs or trees in the areas that have a mesic or frigid
temperature regime, a savanna of perennial grasses and oak
and Douglas-fir in the Willamette Valley of Oregon, and a
savanna of annual grasses and oak species on the Xerolls in
California that have a thermic temperature regime. Many
irrigated crops are grown on the Xerolls in the United States,
especially where the temperature regime is thermic or mesic.
Most of the soils that have gentle or moderate slopes are used
as cropland. The very steep soils are used mainly as rangeland,
but some are used as forest.
Oxisols
Oxisols are of very small extent in the United States. They
make up less than 0.1 percent of the surface area. They are
only on tropical and subtropical islands. They are most
common on the gentle slopes of geologically old surfaces on
the tropical and subtropical islands. Their profiles are
distinctive because of a lack of obvious horizons. Both the
structure and “feel” of Oxisols are deceptive. Upon first
examination, they appear structureless and have the feel of a
loamy texture. While some are loamy or even coarser textured,
many are in a fine or very-fine particle-size class, but the clay
is aggregated in a strong grade of fine and very fine granular
structure. Oxisols have a very low cation-exchange capacity
and have very few weatherable minerals. Most are infertile.
The natural vegetation ranges from tropical rain forests to
desert savannas.
Oxisols are divided into five suborders based on the
moisture regime and soil wetness.
Aquox are the wet Oxisols. They are rare in the United
States and are known to occur only in Puerto Rico. They are in
shallow depressions and in seepage areas at the base of slopes.
Most areas of these soils are small.
Perox are the well drained Oxisols with a perudic soil
moisture regime. They are rare in the United States and are
known to occur only in Hawaii. Curing many seed crops and
storage of produce are difficult on these soils.
Soils of the United States 847
Torrox are the Oxisols of arid regions. They have an aridic
moisture regime. Many have a higher base saturation than that
in other Oxisols. Torrox are very rare in the United States.
Udox are well drained Oxisols with a udic soil moisture
regime. They are of very small extent in the United States.
They make up less than 0.1 percent of the surface area. They
are known to occur only in Hawaii, Puerto Rico, and Guam.
They have a year-round growing season. They are moist
because of rainfall in normal years and are dry in some parts
for less than 90 days. The dry period is short enough for rainfed
crops to be grown continuously in normal years.
Ustox are the Oxisols that have an ustic moisture regime.
They are of very small extent in the United States. They make
up less than 0.1 percent of the surface area. They are known to
occur only in Hawaii, Puerto Rico, and Guam. Because of
natural rainfall, they are moist for at least 90 but not more than
270 days in normal years, a period that is usually long enough
for one rain-fed crop. Crops are not grown continuously on
these soils because there is inadequate moisture for at least 90
days in normal years.
Spodosols
Spodosols are of small extent in the United States. They make
up about 3.5 percent of the surface area. They have a spodic
horizon or spodic materials, both of which consist of
accumulated amorphous mixtures of organic matter and
aluminum, with or without iron. The moisture regime
generally is udic, but some of the soils have aquic conditions.
Spodosols may have any soil temperature regime, but they
cannot have permafrost. In undisturbed soils there is commonly
an overlying eluvial horizon, generally with a gray or light
gray color similar to that of uncoated quartz. The spodic
horizon may be destroyed by cultivation. Yet, spodic materials
may still be present. Below the spodic horizon, there may be a
fragipan or another sequum that has an argillic horizon. In
some Spodosols spodic materials are cemented by sesquioxides
and organic matter (ortstein) that are thicker than a placic
horizon. Most Spodosols are forming in late-Pleistocene or
Holocene deposits. Most have few clay-sized phyllosilicates
and have a sandy, sandy-skeletal, coarse-loamy, loamy-skeletal,
or coarse-silty particle-size class.
Spodosols are most extensive in areas of cool, humid or
perhumid climates in the Northeastern States, southern Alaska,
the Great Lakes States, and the high mountains of the
Northwestern States. These soils also formed in warm, humid
subtropical and tropical regions, mainly Florida and the
southern Atlantic coast, where they occur mostly in areas of
quartz-rich sands that have a fluctuating level of ground
water. In many of the latter soils, the silt and sand fractions
contain very little iron and very few weatherable minerals and
the albic horizons tend to be thick. The chemical and physical
properties of many Spodosols and Andisols are very similar.
The definition of spodic materials, however, is based on the
concept of organic matter and aluminum, with or without
iron, accumulating through illuviation. Spodosols are
naturally infertile soils, but they can be highly responsive to
good management. Under cultivation, particularly if lime
and nitrogen are applied, the spodic horizon may be
destroyed.
Spodosols are divided into four suborders based on soil
wetness, soil temperature regime, or content of organic matter
in the spodic horizon.
Aquods are the wet Spodosols. They are characterized by a
shallow fluctuating water table. They are of small extent in the
United States. They make up about 0.6 percent of the surface
area. They dominate the Spodosol delineations in Florida and
along the Atlantic coast. They are a component of many of the
delineations in the Northeastern and Great Lakes States.
Aquods formed mainly in materials of Pleistocene age. They
can have any temperature regime, but they cannot have
permafrost. In the warmer areas most of the soils have a nearly
white albic horizon thick enough to persist under cultivation
or, in the wettest Aquods, a black surface horizon resting on a
dark reddish brown spodic horizon that is virtually free of iron.
Some Aquods have ortstein that is cemented by an amorphous
mixture of sesquioxides and organic matter. The vegetation is
water-loving plants, ranging from moss, shrubs, and trees in
cold areas to mixed forests and palms in the warmest areas.
Most Aquods are used as forest or wildlife habitat. Some,
mostly in Florida and New Jersey, have been cleared and are
used as cropland or pasture. Aquods are naturally infertile, but
they can be highly responsive to good management. The spodic
horizon can be destroyed under cultivation, particularly if lime
and nitrogen are applied.
Cryods are the cold Spodosols of high latitudes and/or high
elevations. They are of small extent in the United States. They
make up about 0.9 percent of the surface area. They are mostly
in southern Alaska and in the mountains of Washington and
Oregon. Some are in the high mountains of New York and
northern New England. Most Cryods formed in glacial drift
and some in residuum or colluvium. Those in Alaska,
Washington, and Oregon commonly formed at least partially in
volcanic ash. Cryods commonly have an O horizon over a very
thin or intermittent albic horizon, which overlies a well
developed spodic horizon. Some have ortstein or another
cemented soil layer within 100 cm of the mineral soil surface.
In many Cryods the content of organic carbon in the upper part
of the spodic horizon is relatively high. The vegetation is
mostly coniferous forest. Most Cryods are used as forest or
wildlife habitat.
Humods are the relatively freely drained Spodosols that
have a large accumulation of organic carbon in the spodic
horizon. They are of very small extent in the United States.
They make up less than 0.1 percent of the surface area. They
are mostly in Washington State, but a few are known to occur
on tropical islands and in the Northeastern and Southeastern
States. Humods formed dominantly in Pleistocene or Holocene
848 Soil Taxonomy
sediments. The undisturbed soils may have either a thin,
intermittent or a distinct, continuous albic horizon over a
spodic horizon. The upper part of the spodic horizon
commonly is nearly black and has a reddish hue. The hue
normally becomes less red with increasing depth. Most
Humods formed under coniferous forest vegetation. These
soils are used mainly as forest.
Orthods are the relatively freely drained Spodosols that have
a moderate accumulation of organic carbon in the spodic
horizon. They are of moderate extent in the United States.
They make up about 1.9 percent of the surface area. They occur
in all of the Spodosol delineations, except for those in Alaska.
They are most extensive in the Northeastern United States and
the Great Lakes States. Most Orthods formed in coarse
textured, acid Pleistocene or Holocene deposits under
coniferous forest vegetation. If undisturbed, Orthods normally
have thin O and albic horizons over a spodic horizon. A few
have a fragipan below the spodic horizon. Under cultivation,
the albic horizon is very commonly mixed with part of the
spodic horizon. The Orthods in the United States generally
have a udic moisture regime, but a few have a xeric moisture
regime. The soil temperature regime ranges from frigid to
hyperthermic. Most Orthods are used as forest or have been
cleared and are used as cropland or pasture. Orthods are
naturally infertile, but they can be highly responsive to good
management. The spodic horizon can be destroyed under
cultivation, particularly if lime and nitrogen are applied.
Ultisols
Ultisols are moderately extensive in the United States. They
make up about 9.2 percent of the surface area. Typically, they
have an ochric epipedon and an argillic or kandic horizon that
has few bases and commonly is calcium deficient. The base
saturation in most Ultisols decreases with increasing depth,
probably because the vegetation has added recycled bases at the
surface. Ultisols can have any soil moisture regime except
aridic and any soil temperature regime, but they cannot have
permafrost. Most of the Ultisols in the United States have a
udic moisture regime and a mesic or thermic temperature
regime. Ultisols are extensive in the warm, humid parts of the
country. They formed in a wide variety of parent materials,
mainly on Pleistocene or older surfaces. Most of these soils
supported mixed coniferous and hardwood forest vegetation at
the time of settlement. Some are now used as cropland or
pasture.
Ultisols are divided into five suborders based on the soil
moisture regime, soil wetness, and content of organic carbon in
the upper part of the profile.
Aquults are the Ultisols in wet areas where ground water is
very close to the surface during part of each year, usually in
winter and spring, and is deep at other times. These soils are of
small extent in the United States. They make up about 0.8
percent of the surface area. They are on the coastal plains,
particularly along the Atlantic Ocean and the Gulf of Mexico.
The soils are mostly grayish or olive in the subsoil and formed
mainly in alluvium and marine deposits that are of Pleistocene
age or older. They have an ochric or umbric epipedon and an
argillic or kandic horizon. Some have a fragipan. Slopes are
gentle. Most of the soils formerly supported forest vegetation.
Many still support forest vegetation.
Humults are the more or less freely drained, humus-rich
Ultisols. They are of small extent in the United States. They
make up about 0.2 percent of the surface area. They dominate
most of the Ultisol delineations in Oregon and Washington and
also occur in California and Puerto Rico. They commonly
receive high rainfall but also have a moisture deficit during
some season. Most of the Humults in the United States formed
in material weathered from basic country rock on latePleistocene
or older surfaces. Slopes are commonly steep. If the
soils are cultivated, the argillic or kandic horizon may be near
the surface. Humults generally have a dark colored epipedon.
The vegetation was mostly coniferous forest in the Northwest
and rain forest in the tropics. Most of these soils are used as
forest or have been cleared and are used as cropland or pasture.
Udults are the more or less freely drained, relatively humuspoor
Ultisols that have a udic moisture regime. They are of
large extent in the United States. They make up about 8.1
percent of the surface area. They dominate most of the Ultisol
delineations in the southern and eastern parts of the country.
Most of these soils receive well distributed rainfall. Most have
light colored upper horizons, commonly including a grayish
horizon that rests on a yellowish brown to reddish argillic or
kandic horizon. A few of the Udults that formed in material
weathered from basic rocks have a dark brown or reddish
brown surface horizon that rests on a dark red or dusky red
argillic or kandic horizon. Some Udults have a fragipan or
plinthite, or both, in or below the argillic or kandic horizon.
Udults developed in sediments and on surfaces that range from
late Pleistocene to Pliocene or possibly older. Most of these
soils currently support or formerly supported mixed forest
vegetation. Many have been cleared and are used as cropland,
mostly with the use of soil amendments.
Ustults are the more or less freely drained Ultisols that have
an ustic soil moisture regime and have a relatively low content
of organic carbon. They are of very small extent in the United
States. They make up less than 0.1 percent of the surface area.
They occur in the extreme western part of the Ultisol
delineation in Texas. Some are in California and on tropical
islands. Ustults formed in regions where rainfall is moderately
low to high but where evapotranspiration exceeds precipitation.
Some Ustults, mostly those in California, have a single dry
season each year, and others have alternating moist and dry
periods throughout the growing season. Most Ustults have a
thermic or warmer temperature regime. The vegetation is
commonly forest or savanna. Some of the soils have been
cleared and are used as cropland or pasture.
Xerults are the more or less freely drained Ultisols of
Soils of the United States 849
Mediterranean climates. They are of moderate extent in the
United States. They make up about 0.1 percent of the surface
area. They dominate some Ultisol delineations in California
and Oregon. They have a xeric moisture regime and a
moderate amount of organic matter. Most Xerults have an
ochric or umbric epipedon and a brownish to reddish argillic
horizon. They are generally on gentle to very steep mountain
slopes. The vegetation formerly was and currently is mostly
coniferous forest. Most of these soils are used as forest, but
some have been cleared and are used as cropland or pasture.
Vertisols
Vertisols are of small extent in the United States. They make
up about 2.0 percent of the surface area. They are clayey soils
that have deep, wide cracks for some time during the year and
have slickensides within 100 cm of the mineral soil surface.
They shrink as they dry and swell as they become moist. They
are a relatively homogeneous order because of the kinds and
amounts of clay common to them, but their microvariability
within a pedon is great. Vertisols can have any soil temperature
regime but cannot have permafrost, and they can have any
moisture regime. Although the process of shrinking and
swelling is important in Vertisols, it does not preclude the
formation of diagnostic horizons and features. For example,
Vertisols commonly have a mollic epipedon and a cambic
horizon and can have a calcic, gypsic, or salic horizon. They
generally have gentle slopes, although a few are strongly
sloping. The natural vegetation is predominantly grass,
savanna, open forest, or desert shrub. Most Vertisols are well
suited to mechanized frming if there is plenty of rainfall or
irrigation water. Vertisols are well known among engineers
because their unique properties limit engineering uses.
Vertisols are divided into six suborders based on soil
wetness, soil temperature, and soil moisture. These properties
tend to limit the suborders to specific regions of the country.
Aquerts are of small extent in the United States. They make
up about 0.6 percent of the surface area. They are the wet
Vertisols. They have aquic conditions at or near the soil surface
for extended periods during the year but also are dry enough in
normal years for cracks to open during some periods. These
soils are mostly in Texas, the lower Mississippi River Valley,
and the valley of the Red River of the North. They typically are
nearly level and are in low areas, such as glacial lake plains,
flood plains, stream terraces, and coastal lowlands. The natural
vegetation is predominantly forest, grass, or savanna. These
soils are used mostly as rangeland, cropland, or forest.
Drainage of cropland presents special problems since the
saturated hydraulic conductivity of these soils is very low.
Because the permeability of these soils is so slow, a surface
drainage system commonly is installed in areas used as
cropland or pasture. Rice is grown on some Aquerts that have a
thermic or warmer temperature regime.
Cryerts are not known to occur in the United States. They
are the Vertisols that have a cryic temperature regime. They are
cold, but they periodically shrink and swell, forming the
diagnostic characteristics of Vertisols. Cracks commonly open
once a year, late in summer.
Torrerts are of small extent in the United States. They make
up about 0.1 percent of the surface area. They are in areas too
small to be shown on the map. They are the Vertisols of arid
climates. They are in western Texas and in Arizona and New
Mexico. The cracks in these soils commonly stay open for most
of the year but close for at least part of the winter in normal
years. Many of the soils are in closed depressions that may be
ponded from time to time. Some areas of Torrerts are more
continuous and are commonly underlain by basalt or other
parent materials that tend to weather to smectitic clays.
Torrerts commonly have an ochric epipedon and a cambic,
salic, gypsic, or calcic horizon. The native vegetation is mostly
grasses and forbs. These soils are used mainly as rangeland.
The use of Torrerts as irrigated cropland presents special
problems since the saturated hydraulic conductivity is very low.
Bypass flow through open cracks is common. Because the
permeability of these soils is so slow, irrigation may result in
water-logging and a buildup of salinity unless an adequate
artificial drainage system can be installed.
Uderts are of small extent in the United States. They make
up about 0.3 percent of the surface area. They are the Vertisols
of humid areas. They have cracks that open and close,
depending on the amount of precipitation. In some years the
cracks may not open completely. These soils are mostly in
Texas, in the lower Mississippi River Valley, in the valley of
the Red River of the North, and in Alabama and Mississippi.
They typically are nearly level or gently sloping and are mostly
on coastal plains, flood plains, stream terraces, and glacial lake
plains. Most Uderts occur on gentle slopes and are derived
from marine shales, marl, and alluvium. At one time many of
these soils supported grass and widely spaced trees, although
some supported hardwood forest vegetation. Uderts are used
mostly as pasture, cropland, or forest. Because the saturated
hydraulic conductivity of these soils is very low, a surface
drainage system is commonly used to remove excess water
from cropland. Rice is grown on some Uderts that have a
thermic or warmer temperature regime.
Usterts are of small extent in the United States. They make
up about 0.8 percent of the surface area. They are mostly in
Texas, South Dakota, and Montana. They receive low amounts
of rainfall during the summer, and cracks open and close once
or twice during normal years. A few of these soils are on
tropical and subtropical islands. Many Usterts formed in nearly
level or gently sloping areas of fine textured marine deposits,
shale, or alluvium. Some formed in material weathered from
basic igneous rocks. The native vegetation is mostly grasses
and forbs. Usterts are used mainly as rangeland or cropland.
The use of Usterts as irrigated cropland presents special
problems since the saturated hydraulic conductivity is very low.
Bypass flow through open cracks is common. Because the
850
permeability of these soils is so slow, irrigation may result in
water-logging and a buildup of salinity unless an adequate
artificial drainage system can be installed.
Xererts are of small extent in the United States. They make
up about 0.1 percent of the surface area. They are the Vertisols
of Mediterranean climates, which are typified by cool, wet
winters and warm, dry summers. Xererts are mostly in California,
Oregon, and Idaho. They have cracks that regularly close and
open each year. Because these soils become dry every summer
and moisten in winter, damage to structures and roads is very
significant. Many Xererts are nearly level to sloping. Most
formed in material weathered from basic igneous rocks or shale
or in alluvium. The native vegetation is mostly grasses and
forbs. Xererts are used mainly as rangeland or cropland.
Irrigated rice is grown on some Xererts that have a thermic
temperature regime. Bypass flow through open cracks is a
concern. The use of Xererts as irrigated cropland presents some
special problems. Because the permeability of these soils is so
slow, irrigation may result in water-logging and a buildup of
salinity unless an adequate artificial drainage system can be
installed.
Literature Cited
United States Department of Agriculture, Natural Resources
Conservation Service. 1994 (revised 1998). State Soil Geographic
Data for U.S. States and Territory of Puerto Rico. Soil Surv. Staff.
(Digital general soil maps and attribute tables)
United States Department of Agriculture, Natural Resources
Conservation Service. 1996. Alaska State Geographic Data
Base. Soil Surv. Staff. (Digital general soil maps and attribute
tables)
United States Department of Agriculture, Natural
Resources Conservation Service. March 1997. Soil
Classification File. Soil Surv. Staff. Iowa State Univ. Stat. Lab.,
Ames, Iowa.
851
CHAPTER 23
World Distribution of Orders and Suborders
The only comprehensive and international effort to
develop an assessment of the soil resources of the world
was undertaken in the 1960’s by the Food and Agriculture
Organization of the United Nations (FAO-UNESCO). After
World War II, many Western countries undertook systematic
soil surveys and similar activities were initiated in developing
countries through bilateral programs. FAO also had ongoing
national assessments in some developing countries and to
enable these assessments developed a legend for the eventual
Soil Map of the World at a scale of 1:5,000,000. The maps of
the different regions of the world were published at different
periods during the 1970’s. No information was available for
many countries or regions within these countries. For these
reasons, there is a high degree of variability in the quality of
information from country to country. Despite this variability,
the maps are the only reference base available on a global
scale. In 1992, the maps were digitized by FAO. The digital
copy was used for the world map in this publication.
Soil Taxonomy has been subject to many changes since its
first edition was published in 1975. Though the translation of
the FAO legend to the most recent version of Soil Taxonomy
presents only minor problems, converting the FAO soil map
results in important errors. The conversion was done by
assigning terms in Soil Taxonomy to FAO terms, taking into
consideration the soil moisture and temperature regimes (SMR
and STR). All polygons with the same FAO class term have an
equivalent term in Soil Taxonomy. The errors introduced by
this process are illustrated by the case of the soils in the
western Amazon Basin. On the FAO map, these are shown as
Orthic Ferralsols, which are equivalent to Typic Hapludox in
Soil Taxonomy. A recent soil map of Brazil depicts these soils
as Acrisols, or Ultisols in Soil Taxonomy. Consequently, though
every effort was made to incorporate recent information, in
some cases the process of manipulating rastorized digital data
made it impossible to make the changes.
The map of the world at the end of this publication shows
the distribution of the major soil orders. The table “World
Distribution of Orders and Suborders” provides estimates of
the area of different orders and suborders on a global basis and
also the area of climatic environments, or major eco-regions.
Only the suborders that are extensive enough to be shown on
the world map are listed. Soil patterns are distinct and show
the role of soil moisture and temperature regimes interacting
with parent materials. In Europe, the soil moisture regimes
show a north-south trend and the consequent effect on soil
formation is illustrated by horizontal patterns of the soils. In
North America and particularly in the United States, the soil
moisture regimes show an east-west trend and the soil patterns
reflect this trend. On the eastern seaboard, the soils are Ultisols,
and as one proceeds westward, they give way to Mollisols,
Alfisols, and Aridisols. Finally, in the Rocky Mountains, the
soils are Inceptisols and some Andisols. Farther north in North
America, the soils are dominantly Inceptisols and Spodosols,
which give way to Histosols and Gelisols in the northern tundra
zone.
Gelisols, the most recent soil order introduced into the
system of soil taxonomy, occupy about 8.6 percent of the icefree
land surface. Few detailed soil maps depict these soils, as
previous classification systems did not differentiate the soils
based on permafrost. The lower geographic limit of Gelisols for
this map is defined by a mean annual soil temperature of less
than 0 o
C and by a mean summer soil temperature of less than
10 o
C. The northern part of the Gelisol zone grades to ice.
Organic soils, or Histosols, occupy about 1.2 percent of the
land surface. This percentage does not include the 0.8 percent
of Histels, which are present in the Gelisol region and which
form the largest contiguous extent of organic soils. The next
largest area of organic soils is adjacent to the tundra soils in
the boreal belt. These organic soils are the “Cryo” great groups
of Fibrists, Hemists, and Saprists. Tropical Histosols are
dominantly in Southeast Asia, mainly in Sumatra and
Kalimantan. Many of the tropical Histosols are on coastal
plains and have very low pH because of the presence of acid
sulfate materials. Unlike the temperate and boreal Histosols,
which formed in areas of moss and grassy vegetation, tropical
Histosols are woody and frequently contain large trunks of
undecomposed trees. These woody materials make cultivation
of such soils difficult.
Spodosols are dominantly in the colder regions of the world
where STR is mesic or colder and SMR is udic or perudic.
These boreal Spodosols occupy about 2.7 percent of the land
surface. Podsolization results from release of large quantities of
organic acids in the organic-rich surface soil horizons.
Characteristically, these soils form in sandy materials or in
materials with only small amounts of weatherable minerals that
have the potential to alter and release bases. In the Tropics,
soils with similar morphology are in areas of coastal beach
deposits. The largest contiguous extent of such soils is on the
coastal plains of the Amazon Basin. The soils are described
and classified as Spodosols but frequently are not the result of
852 Soil Taxonomy
Histels ......... 1.01 0.77 0 0 0 0 0 0 1.011 0.77
Turbels ........ 6.33 4.84 0 0 0 0 0 0 6.316 4.83
Orthels......... 3.91 2.99 0 0 0 0 0 0 3.903 2.98
Gelisols ....................................11.26 8.61 0 0 0 0 0 0 11.230 8.59
Fibrists ........ 0.20 0.15 0 0 0 0 0.194 0.15 0 0
Saprists ....... 0.34 0.26 0.317 0.24 0.022 0.02 0 0 0 0
Hemists ....... 0.99 0.76 0 0 0.099 0.08 0.884 0.68 0 0
Histosols .................................. 1.53 1.17 0.317 0.24 0.121 0.09 1.078 0.82 0 0
Aquods ....... 0.17 0.13 0.013 0.01 0.055 0.04 0.099 0.08 0 0
Cryods......... 2.46 1.88 0 0 0 0 2.455 1.88 0 0
Humods ....... 0.06 0.04 0.029 0.02 0.028 0.02 0.000078 0 0 0
Orthods ....... 0.67 0.51 0.018 0.01 0.508 0.39 0.138 0.11 0 0
Spodosols ................................ 3.35 2.56 0.060 0.05 0.592 0.45 2.693 2.06 0 0
Cryands ....... 0.26 0.2 0 0 0 0 0.254 0.19 0 0
Torrands ...... 0.001 0 0.001 0 0 0 0 0 0 0
Xerands ....... 0.032 0.02 0 0 0.032 0.02 0 0 0 0
Vitrands ....... 0.28 0.21 0.202 0.15 0.077 0.06 0.000605 0 0 0
Ustands ....... 0.62 0.05 0.058 0.04 0.003 0 0 0 0 0
Udands ........ 0.28 0.21 0.185 0.14 0.089 0.07 0.001 0 0 0
Andisols .................................. 0.91 0.7 0.448 0.34 0.202 0.16 0.256 0.2 0 0
Aquox ......... 0.32 0.24 0.320 0.24 0 0 0 0 0 0
Torrox .......... 0.031 0.02 0.027 0.02 0.004 0 0 0 0 0
Ustox ........... 3.10 2.37 3.086 2.36 0.009 0.01 0 0 0 0
Perox............ 1.16 0.89 1.010 0.77 0.151 0.12 0 0 0 0
Udox ............ 5.20 3.98 5.166 3.95 0.032 0.02 0 0 0 0
Oxisols ..................................... 9.81 7.5 9.610 7.35 0.197 0.15 0 0 0 0
Order Suborder
World Distribution of Orders and Suborders
Area ice-free land
106
km2
%
Area tropical
106
km2
%
Area temperate
106
km2
%
Area boreal
106
km2
%
Area tundra
106
km2
%
World Distribution of Orders and Suborders 853
Aquerts ....... 0.054 0 0.000763 0 0.004 0 0 0 0 0
Cryerts......... 0.014 0.01 0 0 0 0 0.014 0.01 0 0
Xererts......... 0.098 0.08 0 0 0.098 0.08 0 0 0 0
Torrerts ........ 0.889 0.68 0.238 0.18 0.647 0.5 0 0 0 0
Usterts......... 1.767 1.35 1.169 0.89 0.594 0.45 0.002 0 0 0
Uderts ......... 0.384 0.29 0.086 0.07 0.297 0.23 0 0 0 0
Vertisols ................................... 3.160 2.42 1.494 1.14 1.642 1.26 0.017 0.01 0 0
Cryids .......... 0.943 0.72 0 0 0 0 0.940 0.72 0 0
Salids........... 0.890 0.68 0.052 0.04 0.632 0.48 0.195 0.15 0.000691 0
Gypsids ....... 0.682 0.52 0.228 0.17 0.429 0.33 0.024 0.02 0 0
Argids ......... 5.407 4.13 0.573 0.44 4.035 3.09 0.782 0.6 0 0
Calcids......... 4.872 3.73 0.451 0.34 4.400 3.36 0.013 0.01 0 0
Cambids ...... 2.931 2.24 0.561 0.43 2.063 1.58 0.302 0.23 0 0
Aridisols ..................................15.728 12.02 1.867 1.43 11.560 8.84 2.258 1.73 0.000691 0
Aquults ....... 1.280 0.98 1.042 0.8 0.235 0.18 0.000058 0 0 0
Humults ....... 0.343 0.26 0.277 0.21 0.061 0.05 0.004 0 0 0
Udults ......... 5.539 4.24 2.654 2.03 2.872 2.2 0.009 0.01 0 0
Ustults......... 3.869 2.96 3.630 2.78 0.234 0.18 0.001 0 0 0
Xerults......... 0.018 0.01 0 0 0.0009 0 0.017 0.01 0 0
Ultisols .....................................11.052 8.45 7.605 5.81 3.405 2.6 0.033 0.03 0 0
Albolls......... 0.027 0.02 0 0 0.001 0 0.026 0.02 0 0
Aquolls ....... 0.118 0.09 0.001 0 0.084 0.06 0.031 0.02 0 0
Rendolls ...... 0.265 0.2 0.120 0.09 0.103 0.08 0.040 0.03 0 0
Cryolls ......... 1.163 0.89 0 0 0 0 1.160 0.89 0 0
Xerolls ......... 0.924 0.71 0 0 0.873 0.67 0.050 0.04 0 0
Ustolls ......... 5.244 4.01 0.184 0.14 2.370 1.81 2.682 2.05 0 0
Udolls .......... 1.261 0.96 0.054 0.04 1.058 0.81 0.146 0.11 0 0
Mollisols .................................. 9.005 6.89 0.361 0.28 4.491 3.43 4.139 3.16 0 0
Order Suborder
World Distribution of Orders and Suborders--Continued
Area ice-free land
106
km2
%
Area tropical
106
km2
%
Area temperate
106
km2
%
Area boreal
106
km2
%
Area tundra
106
km2
%
854 Soil Taxonomy
Aqualfs ....... 0.836 0.64 0.407 0.31 0.373 0.29 0.054 0.04 0 0
Cryalfs ......... 2.517 1.92 0 0 0 0 2.509 1.92 0 0
Ustalfs ......... 5.663 4.33 3.773 2.88 1.719 1.31 0.165 0.13 0 0
Xeralfs ......... 0.896 0.69 0 0 0.848 0.65 0.046 0.04 0 0
Udalfs .......... 2.706 2.07 0.616 0.47 1.926 1.47 0.158 0.12 0 0
Alfisols ....................................12.620 9.65 4.797 3.67 4.868 3.72 2.933 2.24 0 0
Aquepts ...... 3.199 2.45 1.498 1.15 1.183 0.9 0.502 0.38 0 0
Cryepts ........ 0.456 0.35 0 0 0 0 0.456 0.35 0 0
Ustepts ........ 4.241 3.24 2.804 2.14 1.372 1.05 0.060 0.05 0 0
Xerepts ........ 0.685 0.52 0 0 0.674 0.52 0.009 0.01 0 0
Udepts......... 4.247 3.25 1.755 1.34 2.153 1.65 0.333 0.26 0 0
Inceptisols ...............................12.829 9.81 6.058 4.63 5.383 4.12 1.362 1.04 0 0
Aquents ...... 0.116 0.09 0.105 0.08 0.010 0.01 0 0 0 0
Psamments .. 4.428 3.39 2.799 2.14 1.625 1.24 0.001 0 0 0
Fluvents ...... 2.860 2.19 1.017 0.78 1.455 1.11 0.368 0.28 0 0
Orthents ......13.733 10.5 2.095 1.6 11.264 8.61 0.363 0.28 0 0
Entisols ....................................21.137 16.16 6.019 4.6 14.355 10.98 0.732 0.56 0 0
Total ..................................130.796 100 39.193 29.97 51.865 39.65 19.327 14.78 20.188 15.43
Ocean ..........364.654
Shifting
sands ......... 5.321 4.07 0.545 0.42 4.680 3.58 0.092 0.07 0 0
Rock ............ 13.076 10 0.007 0.01 0.363 0.28 3.727 2.85 8.956 6.85
Ice................ 14.640
Miscellaneous ..........................397.692
Order Suborder
World Distribution of Orders and Suborders--Continued
Area ice-free land
106
km2
%
Area tropical
106
km2
%
Area temperate
106
km2
%
Area boreal
106
km2
%
Area tundra
106
km2
%
World Distribution of Orders and Suborders 855
the podsolization process that operates in the temperate or
boreal climates. The sandy levee deposits or stranded beach
deposits occur in association with Aquepts and Saprists. The
dissolved organic colloids seep up the sands (capillary effect)
and precipitate at the capillary fringe of the ground water table.
The resulting morphology is that of a spodic horizon.
Andisols dominate the circum-Pacific belt, or the Ring of
Fire. They are frequently associated with current or former
volcanic activity. Depending on the intensity and periodicity of
the volcanic activity, deposits of several ages may characterize
a soil. In the colder and moister parts of the world, Andisols
are characterized by dark mollic-like or umbric-like epipedons.
Buried horizons with similar organic-rich horizons may be
typical. In the Tropics, organic accumulation is not so rapid. In
addition, weathering and mineral alteration lead to the formation
of a clay fraction dominated by halloysite and kaolinite. A
normal toposequence in the Tropics is Andisols on the upper
slopes, in association with Inceptisols, which give way to
Ultisols and Oxisols on the gentler topography. In some
Andisols in which the content of organic matter is low and
short-range-order minerals dominate the colloids, the soils may
have a net positive charge. These Andisols are counterparts of
the suborder Anionic Acrudox in terms of mineral-chemical
composition.
Oxisols are confined to the intertropical regions, which by
definition have an iso STR. Most of the Oxisols occur between
the Tropics of Cancer and Capricorn. The largest extent is in
Brazil, followed by the Congo Basin in Central Africa.
Characteristically, Oxisols formed in preweathered and
transported deposits. Weathering may continue in the
postdepositional phase. Other pedogenic processes are slow
unless there is a fluctuating water table. On the volcanic
islands of the Pacific and in Southeast Asia, basic or ultrabasic
rocks may weather to form Oxisols. Although there is always
the possibility of admixture with alluvial or colluvial products,
these soils are generally thought to have formed directly on the
rocks, unlike the Oxisols of the Amazon or Congo Basins.
Vertisols occupy about 2.4 percent of the land surface and
are about equally distributed in tropical and temperate areas.
They are among the soils in which soil properties are a function
of the mineralogical composition of the clay fraction. For the
smectites to form and persist in the soils, one of the
requirements is that the soil solution have a high pH, which
results in high amounts of bases and soluble silica. Thus, most
of the Vertisols occur in semiarid or arid environments. The
countries with large areas of Vertisols are Sudan, India,
Australia, and the United States. In semiarid southern Africa,
large contiguous areas of Vertisols are in Zambia, Zimbabwe,
and South Africa. In other areas Vertisols occur sporadically in
basins adjoining Andisols.
Although about a third of the land mass of the world is arid,
Aridisols occupy only about 12 percent of the land surface. By
definition, Aridisols must have a diagnostic horizon; the
remaining soils in arid regions are Entisols with associated
unstabilized dunes and rocky land. About 60 percent of the
Aridisols are in the temperate parts of the world. The rest have
tropical and boreal climates. Argids are the most extensive
Aridisols and are frequently in areas where the aridic SMR
borders on the ustic or xeric SMR. Calcids, which occupy about
3.7 percent of the land area, are associated with the Argids.
Translocation and subsurface accumulation of carbonates,
gypsum, and salts require some moisture. Formation of the
horizons diagnostic for these suborders may be a current
process or may have taken place in historic or geologic periods.
Because of the current aridity of the sites where these soils
occur, it is generally assumed that many of the diagnostic
features may have a “paleo” origin.
Ultisols and Alfisols occupy 8.5 and 9.7 percent of the land
surface, respectively. Ultisols are more common in the
intertropical areas, while Alfisols are in the temperate areas.
Also, there is greater proportion of Alfisols than of Ultisols in
the semiarid parts of the world. The dominant feature of both
Ultisols and Alfisols is the presence of an argillic horizon.
Other diagnostic horizons or properties define the subclasses.
A lighter textured surface soil, which makes tillage easy, and a
heavier textured underlying argillic horizon, which enables
greater storage of water and nutrients, favor crop production.
Many of these soils occur on flat to gently undulating
landscapes and have been used by farmers since the beginning
of civilization.
Mollisols, which have a thick, organic-rich surface horizon,
are among the most productive soils in the world. Some of the
world’s record yields have been obtained on these soils.
Mollisols occupy about 6.9 percent of the land mass and are
concentrated in the temperate and boreal regions of the world.
They are important soils in the semiarid parts of the world,
particularly in the regions with a Mediterranean climate. The
cool climate permits a slow accumulation of the humified
organic matter. Because of the excellent quality of the soils and
the very favorable climate, these soils are very productive and
make up the breadbasket of modern times. Large areas of such
soils characterize the Midwest in the United States, the steppes
of the former Soviet Union, the northern part of Argentina, and
part of Uruguay.
Inceptisols and Entisols together occupy about 25 percent of
the land surface. Generally on young surfaces, they occur in
association with rock outcrops and sand dunes. These soils
formed in recent coastal and riverine deposits. They formed in
marine alluvium under brackish water conditions. Entisols are
potential acid sulfate soils, and Inceptisols are actual acid
sulfate soils. When drained, potential acid sulfate soils
(Sulfaquents) are converted to actual acid sulfate soils
(Sulfaquepts). The process results in release of a considerable
amount of sulfuric acid, making these soils and the soils
adjacent to them extremely acid.
Because of different data sets, the map of the world and the
map of the United States in this publication do not always
exactly match.
857
Laboratory Methods for Soil Taxonomy
The standard laboratory methods upon which the
operational definitions of this edition of Soil Taxonomy are
based are described in the Soil Survey Laboratory Methods
Manual (USDA, NRCS, 1996). Copies of standard laboratory
data sheets are included with the typifying pedons in the
chapters on soil orders in this edition of Soil Taxonomy. For
specific information about an analytical procedure, these data
sheets should be checked and reference should be made to the
Soil Survey Laboratory Methods Manual. Much of the
information included in this appendix is derived from “Soil
Survey Laboratory Methods for Characterizing Physical and
Chemical Properties and Mineralology of Soils” (Kimble,
Knox, and Holzhey, 1993). Also, the information is summarized
in the Soil Survey Laboratory Information Manual (USDA,
NRCS,1995).
Pedon characterization data, or any soil survey data, are most
useful when the operations for collecting the data are well
understood. The mental pictures and conceptual definitions
that aid in visualizing properties and processes often differ
from the information supplied by an analysis. Also, results
differ by method, even though two methods may carry the same
name or the same concept. There is uncertainty in comparing
one bit of data with another without knowledge of how both
bits were gathered. Operational definitions, definitions tied to a
specific method, are needed. This soil taxonomy has many
class limits (at all levels) that are based on chemical or
physical properties determined in the laboratory. One can
question a given limit, but that is not the purpose of this
appendix. This appendix is written to show what procedures
are used for given class limits. By using specific class limits,
everyone will come to the same classification if they follow the
same procedures.
This taxonomy is based almost entirely on criteria that are
defined operationally. One example is the definition of particlesize
classes. There is no one definition of clay that works well
for all soils. Hence, an operation for testing the validity of a
clay measurement and a default operation for those situations
where the clay measurement is not valid are defined. The
default method is based on a water content at 1500 kPa and on
content of organic carbon.
Data Elements Used in Classifying Soils
Detailed explanations of laboratory methods are given in the
Soil Survey Laboratory Methods Manual (USDA, NRCS, 1996).
Each method is listed by code on the data sheet at the beginning
of the chapters describing soil orders. On the data sheets
presented with each order, the method code is shown for each
determination made. These data sheets should be consulted for
reference to the Soil Survey Laboratory Methods Manual. This
manual specifies method codes for pedon sampling, sample
handling, site selection, sample collection, and sample
preparation.
The units of measure reported on the data sheets are not SI
units. Following are SI conversions:
1 meq/100 g = 1 cmol(+)/kg
1 mmho/cm = 1 dS/m
15 bar = 1500 kPa
1
/3 bar = 33 kPa
1
/10 bar = 10 kPa
In this taxonomy the terms (1) particle-size analysis (size
separates), (2) texture, and (3) particle-size classes are all used.
Particle-size analysis is needed to determine texture and
particle-size classes. Texture differs from particle-size class in
that texture includes only the fine-earth fraction (less than 2
mm), while particle size includes both the fraction less than 2
mm in size and the fraction equal to or more than 2 mm.
Atterberg limits are determined on the fraction less than 0.4
mm in size. Plasticity index is the difference in water content
between liquid limit and plastic limit. It is the range of water
content over which a soil paste can be deformed without
breaking, but it does not include flow as a liquid under
operationally defined conditions. Liquid limit is the minimum
water content at which the paste begins to flow as a liquid.
Samples that do not deform without breaking at any water
content are reported as NP, nonplastic. Operational definitions
are in the Annual Book of ASTM Standards (ASTM, 1998).
Bulk density is obtained typically by equilibration of Sarancoated
natural fabric clods at designated pressure differentials.
Bulk densities are determined at two or more water contents.
For coarse textured and moderately coarse textured soils, they
are determined when the sample is at 10 kPa suction and when
APPENDIX
858 Soil Taxonomy
ovendry. For soils of medium and finer texture, the bulk densities
are determined when the sample is at 33 kPa suction and when
ovendry.
Bulk density determined at 33 kPa suction is used to convert
other analytical results to a volumetric basis (for example, kg
of organic carbon per m3
).
Coefficient of linear extensibility (COLE) is a derived value.
It is computed from the difference in bulk density between a
moist clod and an ovendry clod. It is based on the shrinkage of
a natural soil clod between a water content of 33 kPa (10 kPa
for sandier soils) and ovendry.
Linear extensibility (LE) of a soil layer is the product of the
thickness, in centimeters, multiplied by the COLE of the layer
in question. The LE of a soil is the sum of these products for
all soil horizons. COLE multiplied by 100 is called linear
extensibility percent (LEP).
Water retention difference (WRD) is computed from water
retentions at 33 kPa (10 kPa for sandier soils) and 1500 kPa
suction. It is converted to cm of water per cm of soil through
use of the bulk density. The 33 or 10 kPa water is determined
by desorption of the natural fabric clods, and the 1500 kPa
water is determined by desorption of crushed soil.
Organic carbon data in the National Soil Survey Laboratory
(NSSL) data base have been determined mostly by wet
digestion (Walkley, 1935). Because of environmental concerns
about waste products, however, that procedure is no longer in
use. The only procedure that is currently used to determine
organic carbon is a dry combustion procedure that determines
the percent of total carbon. The content of organic carbon is
determined by subtracting the amount of carbon contributed by
carbonates from total carbon data. The content of organic
carbon determined by this computation is very close to the
content determined by the wet digestion procedure.
Nitrogen in the NSSL data base is reported as a percentage
of the total dry weight. A soil sample is combusted at high
temperature with oxygen to release NOx, and the N2 is
measured by thermal conductivity detection.
Iron and aluminum extracted by citrate dithionite are
removed in a single extraction. They are measured by atomic
absorption and reported as a percentage of the total dry weight.
The iron is primarily from ferric oxides (hematite, magnetite)
and iron oxyhydroxides (goethite). Aluminum substituted into
these minerals is extracted simultaneously. The dithionite
reduces the ferric iron, and the citrate stabilizes the iron by
chelation. Iron and aluminum bound in organic matter are
extracted if the citrate is a stronger chelator than the organic
molecules. Manganese extracted by this procedure also is
recorded. The iron extracted is commonly related to the clay
distribution within a pedon.
Extractable bases (calcium, magnesium, sodium, and
potassium) are extracted with ammonium acetate buffered at
pH 7. They are equilibrated, filtered in an auto-extractor, and
measured by atomic absorption. They are reported as meq/100
g soil. The bases are extracted from the cation-exchange
complex by displacement with ammonium ions. The term
“extractable bases” is used instead of “exchangeable bases”
because soluble salts and some bases from carbonates can be
included in the extract.
Sum of bases is the sum of the calcium, magnesium,
sodium, and potassium described in the previous paragraph.
Extractable acidity is the acidity released from the soil by a
barium chloride-triethanolamine solution buffered at pH 8.2. It
includes all the acidity generated by replacement of the
hydrogen and aluminum from permanent and pH-dependent
exchange sites. It is reported as meq/100 g soil. Extractable
acidity data are reported on some data sheets as exchangeable
acidity and on others as exchangeable H+
.
Extractable aluminum is exchangeable aluminum extracted
by 1N KCl. It is a major constituent only in strongly acid soils
(pH of less than 5.0). Aluminum will precipitate if the pH rises
above 4.5 to 5.0 during analysis. The extractant KCl usually
affects the soil pH 1 unit or less. Extractable aluminum is
measured at the NSSL by atomic absorption. Many laboratories
measure the aluminum by titration with a base to the
phenopthalein end point. Titration measures exchangeable
acidity as well as extractable aluminum. Soils with a pH below
4.0 or 4.5 are likely to have values determined by atomic
absorption similar to values determined by titration because
very little hydrogen is typically on the exchange complex. If
there is a large percentage of organic matter, however, some
hydrogen may be present. For some soils it is important to
know which procedure was used. Extractable aluminum is
reported as meq/100 g soil.
Aluminum saturation is the amount of KCl-extractable Al
divided by extractable bases (extracted by ammonium acetate)
plus the KCl-extractable Al. It is expressed as percent. A
general rule of thumb is that if there is more than 50 percent
Al saturation, Al problems in the soil are likely. The problems
may not be related to Al toxicity but to a deficiency of calcium
and/or magnesium.
Cation-exchange capacity (CEC) by ammonium acetate (at
pH 7), by sum of cations (at pH 8.2), and by bases plus
aluminum is given on the data sheets in the chapters on soil
orders. The CEC depends on the method of analysis as well as
the nature of the exchange complex. CEC by sum of cations at
pH 8.2 is calculated by adding the sum of bases and the
extractable acidity. CEC by ammonium acetate is measured at
pH 7. CEC by bases plus aluminum, or effective cationexchange
capacity (ECEC), is derived by adding the sum of
bases and KCl-extractable Al. Aluminum extracted by 1N KCl
is negligible if the extractant pH rises toward 5.5. ECEC then
is equal to extractable bases. CEC and ECEC are reported on
the data sheets as meq/100 g soil.
The reported CEC may differ from the CEC of the soil at its
natural pH. The standard methods allow the comparison of one
soil with another even though the pH of the extractant differs
from the pH of the natural soil. Cation-exchange capacity by
ammonium acetate and by sum of cations applies to all soils.
Appendix 859
CEC at pH 8.2 is not reported if the soil contains free carbonates
because bases are extracted from the carbonates. The effective
CEC (ECEC) is reported only for acid soils. ECEC is not reported
for soils having soluble salts, although it can be calculated by
subtracting the soluble components from the extractable
components. ECEC also may be defined as bases plus aluminum
plus hydrogen. That is the more common definition for
agronomic interpretations. This taxonomy specifies bases plus
aluminum.
Generally, the ECEC is less than the CEC at pH 7, which in
turn is less than the CEC at pH 8.2. If the soil is dominated by
positively charged colloids (e.g., iron oxides), however, the
trend is reversed. Most soils have negatively charged colloids,
which cause the CEC to increase with increasing pH. This
difference in CEC is commonly called the pH-dependent or
variable charge. The CEC at the soil pH can be estimated by
plotting the CEC of the soil vs. the pH of the extractant on a
graph and reading the CEC at the soil pH.
CEC measurements at pH levels other than those described
in the paragraphs above and CEC derived by use of other
cations will yield somewhat different results. It is important to
know the procedure, pH, and cation used before evaluating
CEC data or comparing data from different sources.
Base saturation is reported on the data sheets as percent of
the CEC. It is reported as CEC by sum of cations at pH 8.2 and
by ammonium acetate at pH 7. Base saturation by ammonium
acetate is equal to the sum of the bases extracted by ammonium
acetate, divided by the CEC (by ammonium acetate), and
multiplied by 100. If extractable calcium is not reported on the
data sheet because of free carbonates or salts in the sample,
then the base saturation is assumed to be 100 percent.
Base saturation percentage by sum of cations is equal to the
sum of bases extracted by ammonium acetate, divided by the
CEC (by sum of cations), and multiplied by 100. This value is
not reported if either extractable calcium or extractable acidity
is omitted.
Differences between the two methods of determining base
saturation reflect the amount of the pH-dependent CEC. Class
definitions in this taxonomy specify which method is used.
The sum of exchangeable cations is considered equal to the
sum of bases extracted by ammonium acetate unless
carbonates, gypsum, or other salts are present. When these
salts are present, the sum of the bases extracted by ammonium
acetate typically exceeds 100 percent of the CEC. Therefore, a
base saturation of 100 percent is assumed. The amount of
calcium from carbonates is usually much larger than the
amount of magnesium from the carbonates. Extractable
calcium is not shown on the data sheet if more than a trace
(more than 0.4 percent) of carbonates (reported as calcium
carbonate) is present or if calculated base saturation exceeds
110 percent, based on CEC by ammonium acetate at pH 7.
Calcium carbonate equivalent is the amount of carbonates
in the soil as measured by treating the sample with HCl. The
evolved carbon dioxide is measured manometrically. The
amount of carbonate is then calculated as a calcium carbonate
equivalent regardless of the form of carbonates (dolomite,
sodium carbonate, magnesium carbonate, etc.) in the sample.
Calcium carbonate equivalent is reported as a percentage of the
total dry weight of the sample. It can be reported on material
that is less than 2 mm or less than 20 mm in size.
Calcium sulfate as gypsum is determined by extraction in
water and precipitation in acetone. The amount of gypsum is
reported as a percentage of the total dry weight of the fraction
less than 2 mm in size and the fraction less than 20 mm in
size. Drying soils to oven-dryness, the standard base for
reporting the data, removes part of the water of hydration from
the gypsum. Many measured values, particularly water
retention values, must be recalculated to compensate for the
weight of the water of hydration lost during drying.
pH is measured in water and in salts. The pH measured in
water is determined in distilled water typically mixed 1:1 with
dry soil. The pH measured in potassium chloride is determined
in 1N KCl solution mixed 1:1 with soil. The pH measured in
calcium chloride is determined in 0.01M CaCl2
solution mixed
2:1 with soil.
The pH is measured by a pH meter in a soil-water or soilsalt
solution. The extent of the dilution is shown in the heading
on the data sheets. A ratio of 1:1 means one part dry soil and
one part water, by weight.
Measurement of pH in a dilute salt solution is common
because it tends to mask seasonal variations in pH. Readings in
0.01M CaCl2
tend to be uniform regardless of the time of year.
Readings in 1N KCl also tend to be uniform. The former are
more popular in regions with less acid soils. The latter are
more popular in regions with more acid soils. If KCl is used to
extract exchangeable aluminum, the pH reading (in KCl)
shows the pH at which the aluminum was extracted.
The pH may also be measured in 1N sodium fluoride. This
measurement is usually used to identify soils that are
dominated by short-range-order minerals, such as Andisols and
Spodosols. In soils that have a significant component of poorly
ordered minerals, such as the soils in the isotic mineralogy
class, the pH in NaF will be greater than 8.5. Soils with free
carbonates also have high pH values in NaF. Therefore, care
must be taken in interpreting these data.
Water-soluble cations and anions are determined in water
extracted from a saturated paste. The cations include calcium,
magnesium, sodium, and potassium, and the anions include
carbonate, bicarbonate, sulfate, chloride, nitrate, fluoride,
phosphate, silicate, and borate. The cations and anions can be
reported as cmol(+)/l.
Exchangeable sodium percentage (ESP) is reported as a
percentage of the CEC by ammonium acetate at pH 7. Watersoluble
sodium is converted to meq/100 g soil. This value is
subtracted from extractable sodium, divided by the CEC (by
ammonium acetate), and multiplied by 100. An ESP of more
than 15 percent is used in this taxonomy as a criterion for the
natric horizon.
860 Soil Taxonomy
Sodium adsorption ratio (SAR) was developed as a measure
of irrigation water quality. Water-soluble sodium is divided by
water-soluble calcium and magnesium. The formula is SAR =
Na/[(Ca+Mg)/2]0.5
. An SAR of 13 or more is used as an
alternate to the ESP criterion for the natric horizon.
Electrical conductivity (EC) is the conductivity of the water
extracted from saturated paste. The EC is used to determine the
total content of salts. It is reported as mmhos/cm, which is
equal to dS/m.
Total salts is calculated from the electrical conductivity of
the saturation extract. It is reported as a weight percentage of
the total water-soluble salts in the soil.
Phosphate retention (P ret.) refers to the percent phosphorus
retained by soil after equilibration with 1,000 mg/kg
phosphorus solution for 24 hours. This procedure is used in the
classification of andic soil materials. It identifies soils in which
phosphorus fixation may be a problem affecting agronomic
uses.
Acid-oxalate-extractable aluminum, iron, and silicon are
determined by a single extraction made in the dark with 0.2
molar ammonium oxalate at a pH of 3.5. The amount of
aluminum, iron, and silicon is measured by atomic absorption
and reported as a percentage of the total dry weight. These
values are used as criteria in identifying soils in the Andisol
and Spodosol orders and in the andic and spodic subgroups in
other orders. The procedure extracts iron, aluminum, and
silicon from organic matter and from amorphous mineral
material. It is used in conjunction with dithionite-citrate and
pyrophosphate extractions to identify the sources of iron and
aluminum in the soil. Pyrophosphate extracts iron and
aluminum from organic matter. Dithionite citrate extracts iron
from iron oxides and oxyhydroxides as well as from organic
matter.
Sodium-pyrophosphate-extractable iron and aluminum are
determined by a single extraction and measured by atomic
absorption. Results are reported as a percentage of the total dry
weight. This procedure has been used widely to extract iron
and aluminum from organic matter. It successfully removes
much of the organo-metal accumulations in spodic horizons
but extracts little of the inorganically bound iron and
aluminum.
Potassium-hydroxide-extractable aluminum is determined
by atomic absorption spectrophotometry. This procedure has
been used in the past but is not used in this taxonomy. The data
can be used in the field to estimate the amount of acid-oxalateextractable
aluminum.
Melanic index is used in the identification of the melanic
epipedon. The index is a ratio of the humic and fulvic acids
in the organic fraction of the soil (Honna, Yamamoto, and
Matsui, 1988). About 0.50 gram of air-dried soil material that is
less than 2 mm in size is shaken with 25 ml of 0.5 percent NaOH
solution in a 50-ml centrifuge tube for 1 hour at room
temperature. One drop of a flocculating agent is added, and
the mixture is centrifuged at 4,000 rpm for 10 minutes. The
melanic index is the ratio of the absorbance at 450 nm over that
at 520 nm.
Citric-acid-extractable phosphorus (acid-soluble
phosphate) is used to separate the mollic epipedon (less than
1,500 mg/kg P2
O5
) from the anthropic epipedon (equal to or
more than 1,500 mg/kg).
Exchangeable manganese and calcium plus exchangeable
acidity (at pH 8.2) is used as a criterion for the natric horizon.
The exchangeable acidity is measured at pH 8.2, and the
manganese and calcium are extracted at pH 7.0 with
ammonium acetate. See the paragraphs about extractable
acidity and exchangeable bases.
Color of sodium-pyrophosphate extract is used as a criterion
in the separation of different types of organic materials. A
saturated solution is made by adding 1 g of sodium
pyrophosphate to 4 ml of distilled water, and a moist organic
matter sample is added to the solution. The sample is mixed
and allowed to stand overnight, chromatographic paper is
dipped in the solution, and the color of the paper is ascertained
through use of a Munsell color chart.
Water-soluble sulfate is used in the definition of the sulfuric
horizon. The sulfate is determined in the saturation extract and
is reported as one of the anions.
Mineralogy of the clay, silt, and sand fractions is required in
some taxa. The different techniques employed are X-ray
diffraction analysis, thermal analysis, and petrographic
analysis.
X-ray diffraction analysis (XRD) is reported in a five-class
system based mostly on relative peak intensities. It is useful in
determining relative amounts of clay minerals. It is used to
differentiate between the smectitic and vermiculitic mineralogy
classes.
Thermal analysis is reported as weight percent of the clay
fraction. It helps to determine kaolinitic, gibbsitic, and other
mineralogy classes.
Petrographic analysis is reported as percent of grains
counted. Minerals are identified by use of a petrographic
microscope. At least 300 grains of a coarse silt, very fine sand,
or fine sand separate are identified and counted. Weatherable
minerals, resistant minerals, and volcanic glass are identified
by this procedure. A complete list of these is in Appendix XXI
of the Soil Survey Laboratory Methods Manual (USDA, NRCS,
1996).
Other Information Useful in Classifying Soils
Volumetric amounts of organic carbon are used in some
taxonomic criteria. The following calculation is used: (Datum
[percent] times bulk density [at 33 or 10 kPa] times thickness
[cm]) divided by 10. This calculation is normally used for
organic carbon, but it can be used for some other
measurements. Each horizon is calculated separately, and the
product of the calculations can be summed to any desired
depth, commonly 100 cm.
Appendix 861
Ratios that can be developed from the data are useful in
making internal checks of the data, in making managementrelated
interpretations, and in answering taxonomic questions.
Some of the ratios are used as criteria in determining argillic,
kandic, or oxic horizons.
The ratio of 1500 kPa water to clay is used to indicate the
relevancy of the particle-size determination. If the ratio is
greater than 0.6 and the soil does not have andic soil
properties, incomplete dispersion of the clay is assumed and
clay is estimated by the following formula: Clay % = 2.5(%
water retained at 1500 kPa tension - % organic carbon). For a
typical soil with well dispersed clays, the ratio is 0.4. Some
soil-related factors that can cause deviation from the 0.4 value
are: (1) low-activity clays (kaolinites, chlorites, and some
micas), which tend to have a ratio of 0.35 or below; (2) iron
oxides and clay-size carbonates, which tend to decrease the
ratio; (3) organic matter, which increases the ratio because it
increases the water content at 1500 kPa; (4) andic and spodic
materials and materials with an isotic mineralogy class, which
increase the ratio because they do not disperse well; (5) large
amounts of gypsum; and (6) clay minerals within grains of
sand and silt. These clay minerals hold water at 1500 kPa and
thus increase the ratio. They are most common in shale and in
pseudomorphs of primary minerals in saprolite.
The ratio of CEC by ammonium acetate at pH 7 to clay can
be used to estimate clay mineralogy and clay dispersion. If the
ratio is multiplied by 100, the product is cmol(+)/kg clay. The
following ratios are typical for the following classes of clay
mineralogy: less than 0.2, kaolinitic; 0.2-0.3, kaolinitic or
mixed; 0.3-0.5, mixed or illitic; 0.5-0.7, mixed or smectitic;
and more than 0.7, smectitic. These ratios are most valid when
some detailed mineralogy data are available. If the ratio of
1500 kPa water to clay is less than 0.3 or more than 0.6, the
ratio of CEC by ammonium acetate to clay is not valid. Ratios
of 1500 kPa water to clay of 0.6 or more are typical of poorly
dispersed clays, andic and spodic materials, and materials with
an isotic mineralogy class, and ratios of less than 0.3 are
common in some soils that contain large amounts of gypsum.
A ratio of CEC at pH 8.2 to 1500 kPa water of more than
1.5 and more exchange acidity than the sum of bases plus KClextractable
Al imply a soil with a high pH-dependent charge.
Along with bulk density data, they help to distinguish soils that
have andic and spodic materials or soils that have materials
with an isotic mineralogy class from soils with minerals that
are more crystalline.
Literature Cited
American Society for Testing and Materials. 1998. Annual
Book of ASTM Standards. Vol. 4.08, D 4318-95a.
Honna,T., S. Yamamoto, and K. Matsui. 1988. A Simple
Procedure to Determine Melanic Index That Is Useful for
Differentiating Melanic from Fulvic Andisols. Pedol. 32: 69-
78.
Kimble,J.M,E.G.Knox,andC.S.Holzhey.1993.Soil
Survey Laboratory Methods for Characterizing Physical and
Chemical Properties and Mineralology of Soils. In
Applications of Agriculture Analysis in Environmental
Studies, ASTM Spec. Pub. 1162, K.B. Hoddinott and T.A.
O’Shay, eds.
United States Department of Agriculture, Natural Resources
Conservation Service. 1995. Soil Survey Laboratory
Information Manual. Natl. Soil Surv. Cent., Soil Surv. Lab.,
SSIR45.
United States Department of Agriculture, Natural Resources
Conservation Service. 1996. Soil Survey Laboratory Methods
Manual. Natl. Soil Surv. Cent., SSIR 42.
Walkley, A. 1935. An Examination of Methods for
Determining Organic Carbon and Nitrogen in Soils. J. Agr.
Sci. 25: 598-609.
863
Index
A
Abrupt textural change .............................................................79
Acraquox ................................................................................ 659
Acroperox ............................................................................... 662
Acrotorrox ............................................................................... 671
Acrudox .................................................................................. 673
Acrustox ................................................................................. 683
Agric horizon ............................................................................ 28
Alaquods ................................................................................ 699
Albaqualfs .............................................................................. 168
Albaquults .............................................................................. 727
Albic horizon ............................................................................ 29
Albic materials ..........................................................................79
Albolls .................................................................................... 560
Alfisols ................................................................................... 163
Alorthods................................................................................ 712
Andic soil properties ................................................................ 80
Andisols ................................................................................. 271
Anhydrous conditions .............................................................80
Anhyorthels............................................................................ 452
Anhyturbels............................................................................ 463
Aniso class ............................................................................. 820
Anthracambids ....................................................................... 357
Anthrepts................................................................................ 494
Anthropic epipedon.................................................................. 22
Aqualfs ................................................................................... 167
Aquands ................................................................................. 275
Aquents .................................................................................. 393
Aquepts .................................................................................. 494
Aquerts ................................................................................... 787
Aquic conditions ...................................................................... 90
Aquic moisture regime. See Soil moisture regimes.
Aquicambids ........................................................................... 357
Aquisalids ............................................................................... 387
Aquiturbels ............................................................................. 464
Aquods ................................................................................... 698
Aquolls ................................................................................... 563
Aquorthels .............................................................................. 453
Aquox ..................................................................................... 659
Aquults ................................................................................... 726
Arents ..................................................................................... 403
Argialbolls .............................................................................. 560
Argiaquolls ............................................................................. 564
Argicryids ............................................................................... 366
Argicryolls .............................................................................. 575
Argids ..................................................................................... 331
Argidurids ............................................................................... 372
Argigypsids ............................................................................ 379
Argillic horizon .........................................................................29
Argiorthels .............................................................................. 455
Argiudolls ............................................................................... 587
Argiustolls .............................................................................. 602
Argixerolls ............................................................................... 631
Aridic moisture regime. See Soil moisture regimes.
Aridisols ................................................................................. 329
B
Bottom tier ................................................................................90
Buried soils ...............................................................................10
C
Calcareous and reaction classes for mineral soils ................... 828
Calciaquerts ............................................................................ 787
Calciaquolls............................................................................. 565
Calciargids .............................................................................. 333
Calcic horizon............................................................................ 34
Calcicryids .............................................................................. 367
Calcicryolls ............................................................................. 578
Calcids .................................................................................... 351
Calcigypsids ........................................................................... 381
Calcitorrerts............................................................................. 798
Calciudolls .............................................................................. 592
Calciustepts ............................................................................ 531
Calciusterts ............................................................................. 805
Calciustolls ............................................................................. 608
Calcixerepts ............................................................................. 543
Calcixererts .............................................................................. 813
Calcixerolls .............................................................................. 637
Cambic horizon .........................................................................35
Cambids .................................................................................. 357
Cation-exchange activity classes for mineral soils .................. 827
Classification ............................................................................ 15
Coatings (classes) on sands ................................................... 830
Coefficient of linear extensibility (COLE) .................................. 80
Control section of Histosols and Histels .................................. 89
Coprogenous earth. See Organic soil material.
Cryalfs ..................................................................................... 189
864 Soil Taxonomy
Cryands................................................................................... 285
Cryaqualfs ............................................................................... 171
Cryaquands............................................................................. 276
Cryaquents ............................................................................. 394
Cryaquepts ............................................................................. 495
Cryaquods .............................................................................. 700
Cryaquolls ............................................................................... 566
Cryepts ................................................................................... 512
Cryerts .................................................................................... 796
Cryic temperature regime. See Soil temperature
regimes.
Cryids...................................................................................... 365
Cryods .................................................................................... 705
Cryofibrists ............................................................................. 475
Cryofluvents ........................................................................... 407
Cryofolists .............................................................................. 478
Cryohemists ............................................................................ 480
Cryolls ..................................................................................... 575
Cryopsamments ...................................................................... 432
Cryorthents ............................................................................. 420
Cryosaprists ............................................................................ 484
Cryoturbation............................................................................ 92
Cryrendolls ............................................................................. 584
D
Densic contact ..........................................................................92
Densic materials ........................................................................92
Diagnostic subsurface horizons ............................................... 28
Diagnostic surface horizons ..................................................... 21
Diatomaceous earth. See Organic soil material.
Duraqualfs .............................................................................. 171
Duraquands ............................................................................ 277
Duraquerts .............................................................................. 788
Duraquods .............................................................................. 701
Duraquolls .............................................................................. 568
Duricryands ............................................................................ 285
Duricryods .............................................................................. 705
Duricryolls .............................................................................. 579
Durids ..................................................................................... 372
Durihumods ............................................................................ 710
Durinodes ................................................................................. 80
Duripan .....................................................................................38
Duritorrands ............................................................................ 294
Durixeralfs ............................................................................... 254
Durixerepts .............................................................................. 545
Durixererts ............................................................................... 814
Durixerolls ............................................................................... 639
Durorthods ............................................................................. 714
Durudands .............................................................................. 298
Durudepts ............................................................................... 517
Durustalfs ............................................................................... 230
Durustands ............................................................................. 316
Durustepts .............................................................................. 533
Durustolls ............................................................................... 612
Dystraquerts ........................................................................... 789
Dystrocryepts ......................................................................... 512
Dystroxerepts.......................................................................... 546
Dystrudepts ............................................................................ 518
Dystruderts ............................................................................. 801
Dystrustepts ........................................................................... 534
Dystrusterts ............................................................................ 806
E
Endoaqualfs ............................................................................ 171
Endoaquands .......................................................................... 278
Endoaquents ........................................................................... 395
Endoaquepts ........................................................................... 498
Endoaquerts ............................................................................ 791
Endoaquods ............................................................................ 702
Endoaquolls ............................................................................ 569
Endoaquults ............................................................................ 728
Entisols ................................................................................... 389
Epiaqualfs ............................................................................... 175
Epiaquands ............................................................................. 279
Epiaquents .............................................................................. 396
Epiaquepts .............................................................................. 502
Epiaquerts ............................................................................... 793
Epiaquods ............................................................................... 703
Epiaquolls ............................................................................... 571
Epiaquults ............................................................................... 729
Epipedon ................................................................................... 21
Eutraquox ................................................................................ 660
Eutrocryepts ........................................................................... 514
Eutroperox ............................................................................... 664
Eutrotorrox .............................................................................. 672
Eutrudepts .............................................................................. 524
Eutrudox .................................................................................. 675
Eutrustox ................................................................................. 685
Extragrades ............................................................................. 123
F
Families ................................................................................... 123
Family differentiae for Histosols and Histels .......................... 830
Family differentiae for mineral soils......................................... 819
Ferrudalfs ................................................................................ 201
Fibers. See Organic soil material.
Fibric soil materials. See Organic soil material.
Fibristels ................................................................................. 448
Fibrists .................................................................................... 474
Fluvaquents ............................................................................ 397
Fluvents .................................................................................. 406
Folistels................................................................................... 449
Folistic epipedon ...................................................................... 22
Folists ..................................................................................... 478
Fragiaqualfs ............................................................................ 181
Index 865
Fragiaquepts ........................................................................... 504
Fragiaquods ............................................................................ 704
Fragiaquults ............................................................................ 731
Fragic soil properties ................................................................ 81
Fragihumods ........................................................................... 710
Fragiorthods ........................................................................... 714
Fragipan .................................................................................... 39
Fragiudalfs .............................................................................. 202
Fragiudepts ............................................................................. 529
Fragiudults .............................................................................. 748
Fragixeralfs .............................................................................. 256
Fragixerepts............................................................................. 549
Fraglossudalfs ........................................................................ 203
Frigid temperature regime. See Soil temperature
regimes.
Fulvicryands ........................................................................... 286
Fulvudands ............................................................................. 300
G
Gelicmaterials ........................................................................... 92
Gelisols ................................................................................... 445
Glaciclayer ................................................................................92
Glacistels ................................................................................. 450
Glossaqualfs ........................................................................... 182
Glossic horizon .........................................................................41
Glossocryalfs .......................................................................... 189
Glossudalfs ............................................................................. 205
Great groups ........................................................................... 122
Gypsiargids ............................................................................. 337
Gypsic horizon ..........................................................................42
Gypsicryids ............................................................................. 368
Gypsids ................................................................................... 379
Gypsitorrerts ........................................................................... 798
Gypsiusterts............................................................................ 808
H
Halaquepts .............................................................................. 505
Haplanthrepts ......................................................................... 494
Haplaquox ............................................................................... 661
Haplargids ............................................................................... 339
Haplocalcids ........................................................................... 351
Haplocambids ......................................................................... 359
Haplocryalfs............................................................................ 193
Haplocryands.......................................................................... 287
Haplocryerts ........................................................................... 796
Haplocryids............................................................................. 369
Haplocryods ........................................................................... 706
Haplocryolls............................................................................ 579
Haplodurids ............................................................................ 375
Haplofibrists ........................................................................... 476
Haplogypsids.......................................................................... 382
Haplohemists .......................................................................... 481
Haplohumods.......................................................................... 710
Haplohumults.......................................................................... 739
Haploperox .............................................................................. 666
Haplorthels ............................................................................. 456
Haplorthods ............................................................................ 716
Haplosalids ............................................................................. 388
Haplosaprists .......................................................................... 485
Haplotorrands ......................................................................... 295
Haplotorrerts ........................................................................... 799
Haplotorrox ............................................................................. 672
Haploturbels ........................................................................... 465
Haploxeralfs ............................................................................ 258
Haploxerands .......................................................................... 323
Haploxerepts ........................................................................... 551
Haploxererts ............................................................................ 816
Haploxerolls ............................................................................ 642
Haploxerults ............................................................................ 778
Hapludalfs ............................................................................... 208
Hapludands............................................................................. 303
Hapluderts .............................................................................. 803
Hapludolls ............................................................................... 593
Hapludox ................................................................................. 678
Hapludults .............................................................................. 750
Haplustalfs .............................................................................. 230
Haplustands............................................................................ 317
Haplustepts............................................................................. 536
Haplusterts ............................................................................. 809
Haplustolls .............................................................................. 613
Haplustox ................................................................................ 688
Haplustults ............................................................................. 768
Haprendolls............................................................................. 585
Hemic soil materials. See Organic soil material.
Hemistels ................................................................................ 450
Hemists ................................................................................... 480
Histels ..................................................................................... 448
Histic epipedon .........................................................................22
Historthels .............................................................................. 457
Histosols ................................................................................. 473
Histoturbels ............................................................................ 466
Humaquepts............................................................................ 507
Humicryerts............................................................................. 797
Humicryods............................................................................. 708
Humilluvic material. See Organic soil material.
Humods................................................................................... 709
Humults................................................................................... 738
Hydraquents ........................................................................... 400
Hydrocryands ......................................................................... 289
Hydrudands ............................................................................ 308
Hyperthermic temperature regime. See Soil temperature
regimes.
I
Identifiable secondary carbonates ............................................81
866 Soil Taxonomy
Inceptisols .............................................................................. 489
Interfingering of albic materials.................................................81
Intergrades .............................................................................. 122
Isofrigid temperature regime. See Soil temperature
regimes.
Isohyperthermic temperature regime. See Soil temperature
regimes.
Isomesic temperature regime. See Soil temperature
regimes.
Isothermic temperature regime. See Soil temperature
regimes.
K
Kandiaqualfs ........................................................................... 184
Kandiaquults .......................................................................... 732
Kandic horizon ..........................................................................42
Kandihumults.......................................................................... 741
Kandiperox .............................................................................. 668
Kandiudalfs............................................................................. 217
Kandiudox ............................................................................... 680
Kandiudults ............................................................................ 754
Kandiustalfs ............................................................................ 237
Kandiustox .............................................................................. 690
Kandiustults ........................................................................... 770
Kanhaplaquults....................................................................... 734
Kanhaplohumults.................................................................... 743
Kanhapludalfs ......................................................................... 219
Kanhapludults ........................................................................ 758
Kanhaplustalfs ........................................................................ 240
Kanhaplustults ....................................................................... 773
Key to soil orders.................................................................... 160
L
Lamellae ....................................................................................82
Liminc materials. See Organic soil material.
Linear extensibility (LE).............................................................83
Lithic contact ............................................................................ 92
Lithologic discontinuities ......................................................... 83
Luvihemists............................................................................. 483
M
Marl. See Organic soil material.
Melanaquands ........................................................................ 281
Melanic epipedon ..................................................................... 23
Melanocryands ....................................................................... 291
Melanoxerands ....................................................................... 325
Melanudands .......................................................................... 310
Mesic temperature regime. See Soil temperature regimes.
Mineral soil material ..................................................................19
Mineral soils ............................................................................. 20
Mineralogy classes for Histosols and Histels ........................ 831
Mineralogy classes for mineral soils ....................................... 825
Mollic epipedon ........................................................................23
Mollisols ................................................................................. 555
Molliturbels............................................................................. 466
Mollorthels ............................................................................. 457
N
n value ......................................................................................84
Natralbolls ............................................................................... 562
Natraqualfs ............................................................................. 186
Natraquerts ............................................................................. 795
Natraquolls ............................................................................. 574
Natrargids ............................................................................... 343
Natric horizon............................................................................ 44
Natricryolls ............................................................................. 582
Natridurids .............................................................................. 377
Natrigypsids ........................................................................... 384
Natrixeralfs .............................................................................. 263
Natrixerolls .............................................................................. 650
Natrudalfs ............................................................................... 221
Natrudolls ............................................................................... 597
Natrustalfs .............................................................................. 241
Natrustolls .............................................................................. 622
Nomenclature in soil taxonomy ............................................... 125
Names of families ................................................................ 126
Names of great groups ........................................................ 125
Names of orders .................................................................. 125
Names of series ................................................................... 126
Names of subgroups ........................................................... 125
Names of suborders ............................................................ 125
Rules of nomenclature ........................................................ 157
Single formative elements ................................................... 157
Normal years ............................................................................. 94
O
Ochric epipedon ........................................................................25
Orders ..................................................................................... 119
Organic soil material ..................................................................19
Fibers ....................................................................................87
Fibric soil materials ............................................................... 87
Hemic soil materials............................................................... 87
Humilluvicmaterial ................................................................ 88
Limnicmaterials..................................................................... 88
Coprogenous earth ........................................................... 88
Diatomaceous earth .......................................................... 89
Marl................................................................................... 89
Sapric soil materials............................................................... 87
Organic soils ............................................................................. 20
Orthels .................................................................................... 452
Orthents .................................................................................. 420
Orthods ................................................................................... 712
Ortstein .....................................................................................45
Index 867
Oxichorizon .............................................................................. 45
Oxisols .................................................................................... 655
P
Paleaquults ............................................................................. 735
Paleargids................................................................................ 346
Palecryalfs ............................................................................... 198
Palecryolls ............................................................................... 583
Palehumults............................................................................. 745
Paleudalfs................................................................................ 222
Paleudolls................................................................................ 599
Paleudults ............................................................................... 761
Paleustalfs ............................................................................... 246
Paleustolls ............................................................................... 625
Paleustults .............................................................................. 776
Palexeralfs ............................................................................... 264
Palexerolls ............................................................................... 652
Palexerults ............................................................................... 780
Paralithic contact ...................................................................... 92
Paralithic materials ....................................................................92
Particle-size classes for Histosols and Histels ........................ 830
Particle-size classes for mineral soils ...................................... 819
Pedon ........................................................................................ 10
Permafrost ................................................................................. 93
Permanent cracks (classes) in mineral soils............................. 830
Perox ....................................................................................... 662
Petraquepts ............................................................................. 509
Petroargids .............................................................................. 350
Petrocalcic horizon ....................................................................47
Petrocalcids............................................................................. 355
Petrocambids .......................................................................... 364
Petrocryids .............................................................................. 371
Petroferric contact ..................................................................... 85
Petrogypsic horizon .................................................................. 48
Petrogypsids ........................................................................... 386
Placaquands............................................................................ 282
Placaquods ............................................................................. 704
Placic horizon ............................................................................ 48
Placocryods ............................................................................ 709
Placohumods .......................................................................... 711
Placorthods ............................................................................. 720
Placudands ............................................................................. 314
Plagganthrepts ........................................................................ 494
Plaggen epipedon ..................................................................... 26
Plinthaqualfs ........................................................................... 188
Plinthaquox ............................................................................. 661
Plinthaquults ........................................................................... 737
Plinthite .....................................................................................85
Plinthohumults ........................................................................ 747
Plinthoxeralfs .......................................................................... 269
Plinthudults............................................................................. 766
Plinthustalfs ............................................................................ 252
Plinthustults............................................................................ 776
Psammaquents ........................................................................ 401
Psamments .............................................................................. 432
Psammorthels .......................................................................... 459
Psammoturbels ........................................................................ 468
Q
Quartzipsamments ................................................................... 434
R
Reaction classes for Histosols and Histels ............................. 832
Redox concentrations ............................................................... 91
Redox depletions ...................................................................... 91
Redoximorphic features.............................................................91
Reduced matrix ..........................................................................91
Reduction.................................................................................. 90
Rendolls .................................................................................. 584
Resistant minerals ..................................................................... 85
Rhodoxeralfs ........................................................................... 269
Rhodudalfs ............................................................................. 228
Rhodudults ............................................................................. 766
Rhodustalfs............................................................................. 252
Rhodustults ............................................................................ 777
Rupture-resistance classes for mineral soils ........................... 829
S
Salaquerts ............................................................................... 795
Salic horizon.............................................................................. 49
Salicryids ................................................................................ 372
Salids ...................................................................................... 387
Salitorrerts ............................................................................... 800
Salusterts ................................................................................ 811
Sapric soil materials. See Organic soil material.
Sapristels ................................................................................ 451
Saprists ................................................................................... 484
Saturation.................................................................................. 90
Series ...................................................................................... 123
Series control section.............................................................. 832
Series differentiae within a family............................................ 832
Slickensides .............................................................................. 85
Soil ..............................................................................................9
Soil depth classes for Histosols and Histels ........................... 832
Soil depth classes for mineral soils ......................................... 829
Soil moisture control section .................................................... 94
Soil moisture regimes ................................................................ 93
Aquic .................................................................................... 96
Aridic and torric ....................................................................96
Udic....................................................................................... 97
Ustic ......................................................................................98
Xeric ......................................................................................99
Soil temperature classes for Histosols and Histels ................. 832
Soil temperature classes for mineral soils................................ 828
868 Soil Taxonomy
Soil temperature regimes ......................................................... 100
Cryic .................................................................................... 111
Frigid ................................................................................... 112
Hyperthermic ...................................................................... 112
Isofrigid............................................................................... 112
Isohyperthermic .................................................................. 112
Isomesic .............................................................................. 112
Isothermic ........................................................................... 112
Mesic .................................................................................. 112
Thermic ............................................................................... 112
Sombric horizon ........................................................................49
Sombrihumults ........................................................................ 747
Sombriperox ............................................................................ 671
Sombriudox ............................................................................. 682
Sombriustox ............................................................................ 692
Sphagnofibrists....................................................................... 477
Spodic horizon ..........................................................................49
Spodic materials ........................................................................86
Spodosols ............................................................................... 695
Strongly contrasting particle-size classes ............................... 820
Subgroups .............................................................................. 122
Suborders................................................................................ 121
Subsurface tier ..........................................................................89
Sulfaquents ............................................................................. 403
Sulfaquepts ............................................................................. 510
Sulfidic materials ..................................................................... 112
Sulfihemists............................................................................. 483
Sulfisaprists ............................................................................ 486
Sulfohemists ........................................................................... 483
Sulfosaprists ........................................................................... 487
Sulfudepts ............................................................................... 530
Sulfuric horizon ....................................................................... 112
Surface tier ................................................................................89
T
Thermic temperature regime. See Soil temperature
regimes.
Torrands .................................................................................. 294
Torrerts ................................................................................... 797
Torriarents............................................................................... 404
Torric moisture regime. See Soil moisture regimes.
Torrifluvents ........................................................................... 408
Torrifolists ............................................................................... 479
Torriorthents ........................................................................... 421
Torripsamments....................................................................... 436
Torrox ...................................................................................... 671
Turbels .................................................................................... 462
Typic subgroups ..................................................................... 122
U
Udalfs...................................................................................... 200
Udands ................................................................................... 297
Udarents ................................................................................. 404
Udepts .................................................................................... 516
Uderts ..................................................................................... 801
Udic moisture regime. See Soil moisture regimes.
Udifluvents ............................................................................. 411
Udifolists ................................................................................ 479
Udipsamments ........................................................................ 438
Udivitrands ............................................................................. 320
Udolls...................................................................................... 586
Udorthents .............................................................................. 425
Udox ........................................................................................ 673
Udults ..................................................................................... 747
Ultisols .................................................................................... 721
Umbraquults ........................................................................... 738
Umbric epipedon ....................................................................... 26
Umbriturbels ........................................................................... 469
Umbrorthels ............................................................................ 460
Ustalfs ..................................................................................... 228
Ustands................................................................................... 315
Ustarents ................................................................................ 405
Ustepts ................................................................................... 530
Usterts .................................................................................... 804
Ustic moisture regime. See Soil moisture regimes.
Ustifluvents ............................................................................ 414
Ustifolists................................................................................ 479
Ustipsamments ....................................................................... 439
Ustivitrands ............................................................................ 322
Ustolls ..................................................................................... 601
Ustorthents ............................................................................. 426
Ustox ....................................................................................... 683
Ustults .................................................................................... 767
V
Vermaqualfs............................................................................. 188
Vermaquepts ........................................................................... 511
Vermudolls .............................................................................. 601
Vermustolls ............................................................................. 629
Vertisols .................................................................................. 783
Vitrands ................................................................................... 319
Vitraquands ............................................................................. 283
Vitricryands ............................................................................. 292
Vitritorrands ............................................................................ 296
Vitrixerands ............................................................................. 326
W
Weatherable minerals ................................................................ 86
X
Xeralfs ..................................................................................... 253
Xerands................................................................................... 323
Xerarents ................................................................................ 406
Index 869
Xerepts ................................................................................... 542
Xererts .................................................................................... 813
Xeric moisture regime. See Soil moisture regimes.
Xerofluvents ........................................................................... 417
Xerolls ..................................................................................... 630
Xeropsamments ...................................................................... 441
Xerorthents ............................................................................. 430
Xerults .................................................................................... 778
870
The date that changes were posted to the PDF file is indicated at the end of each item on the
this list of corrections.
Page 49, column 2, salic horizon, required characteristics, item 1, line 2: Add “the water
extracted from” after “dS/m in” (5/00).
Page 57, caption for photo 11. Change “Umbrept” to “Xerept” (5/00).
Pages 331-388. Change the first letter of the symbols for all Aridisols from “F” to “G” (5/00).
Page 331, column 2, key to suborders, GE, line 2: Delete “that has its upper boundary within
100 cm of the soil surface” (5/00).
Page 333, column 1, definition of Argids, item 1: Delete “that has its upper boundary within
100 cm of the soil surface” (5/00).
Page 352, column 2, Petronodic Ustic Haplocalcids: Change the symbol FEBL to GFBL
(5/00).
Page 361, column 1, Petronodic Ustic Haplocambids: Change the symbol FEDJ to GGDJ
(5/00).
Page 614, column 1, IFGE (Pachic Udertic Haplustolls), item 1, lines 1 and 2: Change “A
mollic epipedon with a texture finer than loamy fine sand; and either ” to “A mollic epipedon
50 cm or more thick with a texture finer than loamy fine sand; and ” and delete items a and b
(5/00).
Page 825, column 2, and page 826, column 1, key to mineralogy classes, item B, lines 2 and 3:
Change “that replaces the particle-size class and that” to “that replaces the particle-size class,
other than fragmental, and that” (5/00).
Page 828, column 2, key to calcareous and reaction classes, last sentence: Change “following
the mineralogy class” to “following the mineralogy and cation-exchange activity classes”
(5/00).
Soil Taxonomy
Second Edition, 1999
Errata