United States
Department of Agriculture
Keys to
Soil Taxonomy
Twelfth Edition, 2014
Keys to Soil Taxonomy
By Soil Survey Staff
United States Department of Agriculture
Natural Resources Conservation Service
Twelfth Edition, 2014
	
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ii
Cover Images (clockwise from top left)
A soil profile from the Laguardia series located in Soundview Park, Bronx, New York
City, USA. The soil formed in a thick deposit of human-transported material that contains a
high content of cohesive, persistent artifacts such as brick, concrete, and metal. It has an
anthropic epipedon and an artifactic human-altered and human-transported material family
class, and classifies as an Anthropic Udorthent. This profile was shown on the field tour for
the 2009 SUITMA Conference, New York City. (SUITMA, or Soils of Urban, Industrial,
Transportation, and Mining Areas, is a working group of the International Union of Soil
Sciences, or IUSS.) Photo by Richard K. Shaw, Soil Scientist, Natural Resources
Conservation Service, Somerset, New Jersey.
Seasonally flooded cropland of rice and vegetable paddies located in Dhulikhel, Nepal. The
soils on these paddies have anthric saturation and will qualify in Anthraquic subroups. The
paddies display anthropogenic microfeatures, namely, the hillslope terraces which were
contoured to the slope of the land. Deposits of human-transported material are thicker on the
front portion of each terrace and thinner on the back portions. Photo by John M. Galbraith,
Associate Professor of Soil Science, Virginia Polytechnic Institute and State University,
Blacksburg, Virginia, USA.
A soil profile of an Anthroportic Udorthent in a dredgic human-altered and humantransported
material family class, located near Stony Creek, Virginia, USA. This soil has an
irregular decrease in carbon with depth which is unrelated to natural processes such as alluvial
deposition. It has two distinct deposits of human-transported material. The upper deposit was
moved by bulldozers and contains mechanically detached and re-oriented pieces of diagnostic
horizons. Separating the two deposits is a dark-colored horizon with a high content of wood
ash and charcoal. The lower deposit consists of dredged spoil material with a high content of
sand and large red bodies of clay. Photo by W. Lee Daniels, Professor of Environmental
Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA.
A soil profile of an Anthroportic Udorthent in a dredgic human-altered and humantransported
material family class, near Stony Creek, Virginia, USA. This soil formed in two
deposits of human-transported material. The upper deposit was moved by machinery and
contains mechanically detached and re-oriented pieces of diagnostic horizons in humantransported
material; the lower deposit was hydraulically dredged. Photo by John M.
Galbraith, Associate Professor of Soil Science, Virginia Polytechnic Institute and State
University, Blacksburg, Virginia, USA.
A soil profile of an Anhydritic Aquisalid from the United Arab Emirates (UAE). This soil
formed in alluvium on a coastal sabkha. Capillary rise of ground water, which has a high
content of soluble salts and contains calcium sulfate, aids the accumulation of mobile minerals
in the soil. An anhydritic horizon and a salic horizon occur together in the zone between the
soil surface and a depth of about 60 centimeters. Photo by Shabbir A. Shahid, Soil Correlator/
Lead Soil Taxonomist, International Center for Biosaline Agriculture, Dubai, UAE.
A soil profile of an Anthrodensic Udorthent in a spolic human-altered and humantransported
material family class, near Stony Creek, Virginia, USA. This soil formed in
deposits of human-transported material which were compacted by machinery. A densic
contact occurs at a depth of 8 cm along with an irregular decrease in organic matter
content with mechanically detached and re-oriented pieces of diagnostic horizons. Photo by
John M. Galbraith, Associate Professor of Soil Science, Virginia Polytechnic Institute and
State University, Blacksburg, Virginia, USA.
iii
	v
Table of Contents
Foreword....................................................................................................................................vii
Chapter   1:	 The Soils That We Classify....................................................................................1
Chapter   2:	 Differentiae for Mineral Soils and Organic Soils...................................................3
Chapter   3:	 Horizons and Characteristics Diagnostic for the Higher Categories......................7
Chapter   4:	 Identification of the Taxonomic Class of a Soil...................................................37
Chapter   5:	 Alfisols.................................................................................................................43
Chapter   6:	 Andisols................................................................................................................87
Chapter   7:	 Aridisols.............................................................................................................107
Chapter   8:	 Entisols...............................................................................................................135
Chapter   9:	 Gelisols...............................................................................................................157
Chapter 10:	 Histosols.............................................................................................................167
Chapter 11:	 Inceptisols...........................................................................................................173
Chapter 12:	 Mollisols.............................................................................................................211
Chapter 13:	 Oxisols................................................................................................................257
Chapter 14:	 Spodosols...........................................................................................................273
Chapter 15:	 Ultisols...............................................................................................................283
Chapter 16:	 Vertisols..............................................................................................................305
Chapter 17:	 Family and Series Differentiae and Names........................................................317
Chapter 18:	 Designations for Horizons and Layers...............................................................335
Appendix..................................................................................................................................343
Index........................................................................................................................................353
	vii
Foreword
This publication, Keys to Soil Taxonomy, Twelfth Edition, 2014, coincides with the 20th
World Congress of Soil Science, to be held on Jeju Island, Korea in June 2014. The Keys
to Soil Taxonomy serves two purposes. It provides the taxonomic keys necessary for the
classification of soils in a form that can be used easily in the field. It also acquaints users of
soil taxonomy with recent changes in the classification system. The twelfth edition of the
Keys to Soil Taxonomy incorporates all changes approved since the publication in 1999 of
the second edition of Soil Taxonomy: A Basic System of Soil Classification for Making and
Interpreting Soil Surveys.
The authors of the Keys to Soil Taxonomy are identified as the “Soil Survey Staff.” This
term is meant to include all of the soil classifiers in the National Cooperative Soil Survey
program and in the international community who have made significant contributions to the
improvement of the taxonomic system. The authors plan to continue issuing updated editions
of the Keys to Soil Taxonomy as changes warrant new editions.
One change in this edition is recognizing the occurrence of anhydrite (CaSO4
) in soils
with the addition of a new diagnostic horizon, a new mineralogy class, and new Anhydritic
subgroups for use in soil survey. These are significant improvements to soil taxonomy
which resulted from international collaboration with soil scientists of the United Arab
Emirates, where the soils with anhydrite were discovered. Pedologists in Argentina have
also contributed to this edition with amendments to improve classification of the Mollisols
of the Pampean region and to recognize the abrupt textural change in more soils having this
important genetic characteristic.
Another major change is the incorporation of many of the final recommendations of
the International Committee on Anthropogenic Soils (ICOMANTH). This international
committee began in 1995 under the chairmanship of Dr. Ray Bryant and has continued
under Dr. John Galbraith of Virginia Polytechnic Institute and State University. Some of
the recommendations of ICOMANTH broadly expand the use of geomorphic positions as
taxonomic criteria for soils which occur on artificial (i.e., anthropogenic) landforms and
microfeatures. One of the attributes of soil taxonomy states that the differentiae selected
for classification are soil properties. Characteristics of a site, such as geomorphic position,
are not used as criteria for classifying natural, undisturbed soils. Geomorphic position had
previously been used only in the required characteristics of the plaggen epipedon; now,
its appropriateness for classifying other human-altered and human-transported soils is
being tested. In addition, the definition of the anthropic epipedon has been expanded and
simplified, two major materials have been defined, higher taxa have been consolidated at
the subgroup category under seven defined extragrades, and a new family category class has
been introduced to convey information on the safety and origin of human-altered and humantransported
material. Dr. Galbraith’s diligent efforts chairing ICOMANTH have yielded
amendments which have improved the morphologic description and taxonomic classification
of human-altered and human-transported soils as well as the recognition of anthropogenic
earth-surface features.
Since it was first published 39 years ago, Soil Taxonomy: A Basic System of Soil
Classification for Making and Interpreting Soil Surveys has been used to support soil survey
efforts in many countries around the world. It has been translated into several languages.
Soil scientists from many nations have contributed significantly to the development of soil
taxonomy. The Natural Resources Conservation Service (NRCS) Soil Science Division
viii	
encourages the further use of soil taxonomy internationally and anticipates future
collaborations with the international soil science community in order to continually improve
this classification system. I hope that continuing communication and collaboration will result
in a truly universal soil classification system.
David W. Smith
Soil Science Division Director
Natural Resources Conservation Service
	1
S
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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, in deep water, or on the barren ice of
glaciers. In this sense, soil has a thickness that is determined by
the rooting depth of plants.
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
(Soil Survey Staff, 1999). This definition is expanded from the
previous version of Soil Taxonomy (Soil Survey Staff, 1975) 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
either 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 about 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
the practicality of soil survey, 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) and noncemented
bedrocks (some densic materials, defined later) have been
described below the lower boundary of soil and used to
differentiate soil series (series control section, defined in chapter
17). This is permissible even though the paralithic materials
below a paralithic contact are not considered soil in the true
sense. In areas where soil has thin, pedogenically 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 limit of 200 cm.
Soil, as defined in this text, does not need to have discernible
genetic horizons, although the presence or absence of genetic
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
or in cracks of exposed bedrock (i.e., rock outcrop), but trees
and rock outcrop are regarded as nonsoil.
Soil has many temporal properties that fluctuate hourly,
daily, and seasonally. It may be alternately cold, warm, dry,
or moist. Biological activity is slowed or stopped if the soil
becomes too cold or too dry. The soil receives additions of
fresh, undecomposed 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,
The Soils That We Classify
CHAPTER 1
2	
soil fauna, temperature, and moisture status 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 a sequence of genetic horizons in a pedon
that is covered with a surface mantle of new soil material
(defined below) that is 50 cm or more thick, a plaggen epipedon
(defined in chapter 3), or a layer of human-transported material
(defined in chapter 3) that is 50 cm or more thick. The rules for
the taxonomic classification of pedons that include a buried soil
are given in chapter 4.
Surface Mantle of New Soil Material
A surface mantle of new soil material is a layer of naturally
deposited mineral material that 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 in chapter 3.
However, there remains a layer 7.5 cm or more thick that
fails the requirements for all diagnostic horizons, as defined
later, overlying a genetic horizon sequence that can be clearly
identified as 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. A surface mantle of new soil material
that does not have the required thickness specified for buried
soils can be used to establish a phase of a soil series, or even
another soil series, if the mantle affects use and management of
the soil.
Literature Cited
Soil Survey Staff. 1975. Soil Taxonomy: A Basic System of
Soil Classification for Making and Interpreting Soil Surveys.
Soil Conservation Service. U.S. Department of Agriculture
Handbook 436.
Soil Survey Staff. 1999. Soil Taxonomy: A Basic System of
Soil Classification for Making and Interpreting Soil Surveys.
2nd edition. Natural Resources Conservation Service. U.S.
Department of Agriculture Handbook 436.
	3
D
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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 fineearth
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 shortrange-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 and Histels.
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 3.
In the determination of whether a soil is organic or mineral,
the thickness of horizons is measured from the soil surface
(defined below) whether that is a horizon composed of mineral*
Mineral soils include all soils except the suborder Histels and the order Histosols.
Differentiae for Mineral Soils*
and Organic Soils
CHAPTER 2
4	 Keys to Soil Taxonomy
soil material or one composed of organic soil material. This
determination is different for buried soils as defined in chapter
1. Thus, any horizon at the surface, designated with capital letter
O, is considered an organic horizon if it meets the requirements
of organic soil material, and its thickness is added to that of
any other organic horizons to determine the total thickness of
organic soil material. Plant materials at the soil surface must
be at least slightly decomposed to be considered part of an
O horizon. Undecomposed plant litter is excluded from the
concept of O horizons.
Soil Surface
The term “soil surface” is based on the upper limit of soil.
The upper limit of soil is the boundary between soil and either
air, shallow water, live plants, or plant materials that have not
begun to decompose. The soil surface is a horizon composed of
either mineral soil material or organic soil material.
Mineral Soil Surface
The term “mineral soil surface” is the datum or horizontal
plane used for measurements of depth or thickness in mineral
soils (defined below). The mineral soil surface has two forms.
It is either a soil surface composed of mineral soil material
or it is the boundary between a horizon composed of organic
soil material and a horizon composed of mineral soil material.
The upper boundary of the first horizon, encountered at
or below the soil surface that is composed of mineral soil
material, is considered the mineral soil surface. For example,
a upland mineral soil with an 5-cm-thick Oi horizon within a
horizon sequence of Oi-A-E-Bt-C has two surfaces for depth
measurements. There is a soil surface at the boundary between
either air or undecomposed plant material and the Oi horizon
(at a depth of 0 cm). There is also a mineral soil surface at the
boundary between the Oi and A horizons (at a depth of 5 cm).
Definition of Mineral Soils
Mineral soils are soils that have either:
1.  Mineral soil materials that meet one or more of the
following:
a.  Overlie cindery, fragmental, or pumiceous materials
and/or have voids†
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 threefourths
(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 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 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-
† 
Materials that meet the definition of the cindery, fragmental, or pumiceous substitute
for particle-size class but have more than 10 percent, by volume, voids that are filled with
organic soil materials are considered to be organic soil materials.
Differentiae for Mineral Soils and Organic Soils	 5
D
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F
fourths (by volume) moss fibers and a bulk density, moist,
of 0.1 g/cm3
or more; or
e.  Are 80 percent or more of the 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 or Histel) 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.
	 7
D
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A
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 horizons and characteristics defined below are not in
a key format. The “required characteristics” for horizons or
features, however, are arranged as a key. 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. The exclusions are stated in the
horizon definitions.
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 (5 mm or less thick) 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 commonly
forms in deposits of tephra and can receive fresh deposits of
volcanic ash. Therefore, this horizon is permitted to have layers
within and above the epipedon that are not part of the melanic
epipedon.
A recent alluvial or eolian deposit that retains fine
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 forms in human-altered or humantransported
material (defined below). These epipedons
form in soils which occur on anthropogenic landforms and
microfeatures or which are higher than the adjacent soils by as
much as or more than the thickness of the anthropic epipedon.
They may also occur in excavated areas. Most anthropic
epipedons contain artifacts other than those associated with
agricultural practices (e.g., quicklime) and litter discarded by
humans (e.g., aluminum cans). Anthropic epipedons may have
an elevated phosphorus content from human additions of food
debris (e.g., bones), compost, or manure, although a precise
value is not required. Although anthropic epipedons formed
at the soil surface, they may now be buried. Most anthropic
epipedons occur in soils of gardens, middens (Hester et al.,
1975), and urban areas, and most also meet the definition of
another diagnostic mineral epipedon or subsurface horizon.
Required Characteristics
The anthropic epipedon consists of mineral soil material that
shows evidence of the purposeful alteration of soil properties or
of earth-surface features by human activity. The field evidence
Horizons and Characteristics Diagnostic for the Higher Categories
CHAPTER 3
8	 Keys to Soil Taxonomy
of alteration is significant and excludes agricultural practices
such as shallow plowing or addition of amendments, such as
lime or fertilizer.
The anthropic epipedon includes eluvial horizons that are at
or near the soil surface, and it extends to the base of horizons
that meet all the criteria shown below or it extends to the top of
the first underlying diagnostic illuvial horizon (defined below
as an argillic, kandic, natric, or spodic horizon). The anthropic
epipedon meets all of the following:
1.  When dry, has structural units with a diameter of 30 cm or
less; and
2.  Has rock structure, including fine stratifications (5 mm or
less thick), in less than one-half of the volume of all parts; and
3.  Formed in human-altered or human-transported material
(defined below) on an anthropogenic landform or microfeature
(defined below); and either:
a.  Directly overlies mine or dredged spoil material which
has rock structure, a root-limiting layer, or a lithologic
discontinuity with horizons that are not derived from humanaltered
or human-transported material (defined below); or
b. Has one or more of the following throughout:
(1)  Artifacts, other than agricultural amendments
(e.g., quicklime) and litter discarded by humans (e.g.,
aluminum cans); or
(2)  Midden material (i.e., eating and cooking waste and
associated charred products); or
(3)  Anthraquic conditions; and
4.  Has a minimum thickness that is either:
a.  The entire thickness of the soil above a root-limiting
layer (defined in chapter 17) if one occurs within 25 cm of
the soil surface; or
b.  25 cm; and
5.  Has an n value (defined below) of less than 0.7.
Folistic Epipedon
Required Characteristics
The folistic epipedon is 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 g/cm3
; 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 2). Item 2 provides for a folistic epipedon
that is an Ap horizon consisting of mineral soil material.
Histic Epipedon
Required Characteristics
The histic epipedon is a layer (one or more horizons) that is
characterized by saturation (for 30 days or more, cumulative)
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 g/cm3
; 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 2). 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
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
Horizons and Characteristics Diagnostic for the Higher Categories	 9
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* 
The concept of dominant color is defined in the Soil Survey Manual (Soil Survey
Division Staff, 1993).
b.  A color value of 2.5 or less, moist, and chroma of 2 or
less throughout; and
c.  A melanic index (defined in the appendix) of 1.70 or less
throughout; and
d.  6 percent or more organic carbon as a weighted average
and 4 percent or more organic carbon in all layers.
Mollic Epipedon
Required Characteristics
The mollic epipedon consists of mineral soil material and,
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, a petrocalcic horizon, or a duripan (all defined below)
is less than 18 cm, 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 stratifications (5 mm or less
thick), in less than one-half of the volume of all parts; and
3.  One of the following:
a.  Both of the following:
(1)  Dominant color* with a value of 3 or less, moist,
and of 5 or less, dry; and
(2)  Dominant color with chroma of 3 or less, moist; 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 of 5 or
less, moist; and
4.  A base saturation (by NH4
OAc) of 50 percent or more
throughout; and
5.  An organic-carbon content of:
a.  2.5 percent or more if the epipedon has a color value of 4
or 5, moist; or
b.  0.6 percent (absolute) more than that of the C horizon (if
one occurs) if the mollic epipedon has a color value less than
1 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 the epipedon does not meet the
qualifications in 5-a or 5-b above; and
6.  The minimum thickness of the epipedon is as follows:
a.  25 cm if:
(1)  The texture class of the epipedon is loamy fine sand
or coarser throughout; or
(2)  There are no underlying diagnostic horizons
(defined below) and the organic-carbon content of the
underlying materials decreases irregularly with increasing
depth; or
(3)  Any of the following, if present, are 75 cm or more
below the mineral soil surface:
(a)  The upper boundary of the shallowest of any
identifiable secondary carbonates or a calcic horizon,
petrocalcic horizon, duripan, or fragipan (defined
below); and/or
(b)  The lower boundary of the deepest of an argillic,
cambic, natric, oxic, or spodic horizon; or
b.  10 cm if the epipedon has a texture class finer than
loamy fine sand (when mixed) and it is directly above a
densic, lithic, or paralithic contact, a petrocalcic horizon, or a
duripan; or
c.  18 to 25 cm and the thickness is one-third or more of the
total thickness between the mineral soil surface and:
(1)  The upper boundary of the shallowest of any
identifiable secondary carbonates or a calcic horizon,
petrocalcic horizon, duripan, or fragipan; and/or
(2)  The lower boundary of the deepest of an argillic,
cambic, natric, oxic, or spodic horizon; or
d.  18 cm if none of the above conditions apply; 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 below the soil surface is 5 o
C or
higher, if the soil is not irrigated; and
8. The n value (defined below) is less than 0.7.
Ochric Epipedon
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. Many ochric epipedons
have either a 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 umbric epipedon (and has less
than 15 percent calcium carbonate equivalent in the fine-earth
fraction). Ochric epipedons also include horizons of organic
10	 Keys to Soil Taxonomy
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.
Plaggen Epipedon
The plaggen epipedon is a thick, human-made mineral
surface layer that has been produced by long-continued
manuring. A plaggen epipedon can be identified by several
means. Commonly, it contains artifacts, such as brick and
potsherds, throughout its thickness. There may be earthy
fragments (i.e., clods) 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 at least in its
lower part. It may also contain remnants of thin stratified beds
of sand that were probably produced on the soil surface by
beating rains and were later buried. A map unit delineation of
soils with plaggen epipedons would tend to occur on straightsided
anthropogenic landforms that are higher than adjacent
land surfaces by as much as or more than the thickness of the
plaggen epipedon.
Required Characteristics
The plaggen epipedon consists of mineral soil material and
meets all of the following:
1.  It occurs in soils on locally raised landforms and contains
one or both of the following:
a.  Artifacts, other than agricultural amendments (e.g.,
quicklime) and litter discarded by humans (e.g., aluminum
cans); or
b.  Spade marks below a depth of 30 cm; and
2.  It has colors with a value of 4 or less, moist, 5 or less, dry,
and chroma of 2 or less; and
3.  It has an organic-carbon content of 0.6 percent or more; and
4.  It has a thickness of 50 cm or more of human-transported
material (defined below); and
5.  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 below the soil surface is 5 o
C or
higher, if the soil is not irrigated.
Umbric Epipedon
Required Characteristics
The umbric epipedon consists of mineral soil material and,
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, a petrocalcic horizon, or a duripan (all defined below)
is less than 18 cm, 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 stratifications (5 mm or less
thick), in less than one-half of the volume of all parts; and
3.  Both of the following:
a.  Dominant color* with a value of 3 or less, moist, and of
5 or less, dry; and
b.  Dominant color with chroma of 3 or less, moist; and
4.  A base saturation (by NH4
OAc) of less than 50 percent in
some or all parts; and
5.  An organic-carbon content of:
a.  0.6 percent (absolute) more than that of the C horizon
(if one occurs) if the umbric epipedon has a color value less
than 1 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 the epipedon does not meet the
qualifications in 5-a above; and
6.  The minimum thickness of the epipedon is as follows:
a.  25 cm if:
(1)  The texture class of the epipedon is loamy fine sand
or coarser throughout; or
(2)  There are no underlying diagnostic horizons
(defined below) and the organic-carbon content of the
underlying materials decreases irregularly with increasing
depth; or
(3)  Any of the following, if present, are 75 cm or more
below the mineral soil surface:
(a)  The upper boundary of the shallowest of any
identifiable secondary carbonates or a calcic horizon,
petrocalcic horizon, duripan, or fragipan (defined
below); and/or
Horizons and Characteristics Diagnostic for the Higher Categories	 11
D
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(b)  The lower boundary of the deepest of an argillic,
cambic, natric, oxic, or spodic horizon; or
b.  10 cm if the epipedon has a texture class finer than
loamy fine sand (when mixed) and it is directly above a
densic, lithic, or paralithic contact, a petrocalcic horizon, or a
duripan; or
c.  18 to 25 cm and the thickness is one-third or more of the
total thickness between the mineral soil surface and:
(1)  The upper boundary of the shallowest of any
identifiable secondary carbonates or a calcic horizon,
petrocalcic horizon, duripan, or fragipan; and/or
(2)  The lower boundary of the deepest of an argillic,
cambic, natric, oxic, or spodic horizon; or
d.  18 cm if none of the above conditions apply; 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 below the soil surface 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 locally raised landforms that are characteristics 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 are composed of mineral soil material.
They may be exposed at the surface by truncation of the soil.
Some of these horizons are designated as B horizons by many,
but not all, pedologists and others are generally designated as
parts of A or E horizons.
Agric Horizon
The agric horizon is an illuvial horizon that has formed under
cultivation and contains significant amounts of illuvial silt, clay,
and humus.
Required Characteristics
The agric horizon is directly below an Ap horizon and has a
thickness of 10 cm or more, and either:
1.  5 percent or more (by volume) wormholes, including
coatings that are 2 mm or more thick and have a color value of
4 or less, moist, and chroma of 2 or less; or
2.  5 percent or more (by volume) lamellae that have a
thickness of 5 mm or more and have a color value of 4 or less,
moist, and chroma of 2 or less.
Albic Horizon
The albic horizon is an eluvial horizon, 1 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.
Anhydritic Horizon
The anhydritic horizon is a horizon in which anhydrite
has accumulated through neoformation or transformation to a
significant extent. It typically occurs as a subsurface horizon. It
commonly occurs in conjunction with a salic horizon (defined
below).
Required Characteristics
The anhydritic horizon meets all of the following
requirements:
1.  Is 15 cm or more thick; and
2.  Is 5 percent or more (by weight) anhydrite; and
3.  Has hue of 5Y, chroma (moist and dry) of 1 or 2, and value
of 7 or 8; and
4.  Has a product of thickness, in cm, multiplied by the
anhydrite content (percent by weight) of 150 or more (thus, a
horizon 30 cm thick that is 5 percent anhydrite qualifies as an
anhydritic horizon); and
5.  Has anhydrite as the predominant calcium sulfate mineral
with gypsum either absent or present only in minor amounts.
Argillic Horizon
An argillic horizon is normally a subsurface horizon with a
significantly higher percentage of phyllosilicate clay than the
overlying soil material. 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.
Required Characteristics
1.  All argillic horizons must meet both of the following
requirements:
12	 Keys to Soil Taxonomy
† 
Particle-size classes are used in this required characteristic as a convenient proxy for
many possible combinations of USDA texture class and texture modifier and do not imply
that the soil meeting this option for the diagnostic horizon also meets the particle-size class
criteria in the family classification.
a.  One of the following:
(1)  If the argillic horizon meets the particle-size class
criteria for coarse-loamy, fine-loamy, coarse-silty, finesilty,
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; or
(2)  If the argillic horizon meets the sandy or sandyskeletal
particle-size criteria, 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.
Required Characteristics
The calcic horizon:
1.  Is 15 cm or more thick; and
2. Has one or more of the following:
a.  15 percent or more (by weight, fine-earth fraction)
CaCO3
equivalent, and its CaCO3
equivalent is 5 percent or
more (absolute) higher than that of an underlying horizon; or
b.  15 percent or more (by weight, fine-earth fraction)
CaCO3
equivalent and 5 percent or more (by volume)
identifiable secondary carbonates; or
c.  5 percent or more (by weight, fine-earth fraction)
calcium carbonate equivalent and:
(1)  Has less than 18 percent clay in the fine-earth
fraction; and
(2)  Meets the criteria for a sandy, sandy-skeletal, coarseloamy,
or loamy-skeletal particle-size class†
(defined in
chapter 17); and
(3)  Has 5 percent or more (by volume) identifiable
secondary carbonates or a calcium carbonate equivalent
(by weight, fine-earth fraction) that is 5 percent or more
(absolute) higher than that of an underlying horizon; and
3.  Is not cemented or indurated in any part by carbonates, with
or without other cementing agents, or is cemented in some part
and the cemented part satisfies one of the following:
a.  It is characterized by so much lateral discontinuity that
roots can penetrate through noncemented zones or along
vertical fractures with a horizontal spacing of less than 10
cm; or
b.  The cemented layer is less than 1 cm thick and consists
of a laminar cap underlain by a lithic or paralithic contact; or
c.  The cemented layer is less than 10 cm thick.
Cambic Horizon
A cambic horizon is the result of physical alterations,
chemical transformations, or removals or of a combination of
two or more of these processes.
Required Characteristics
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:
Horizons and Characteristics Diagnostic for the Higher Categories	 13
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1.  Has a texture class 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,
including fine stratifications (5 mm or less thick), 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 neutral colors with no
hue (N) and zero chroma; 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, including fine
stratifications (5 mm or less thick), in more than one-half 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, salic, spodic, or
sulfuric horizon; and
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 is a silica-cemented subsurface horizon with or
without auxiliary cementing agents. It can occur in conjunction
with a petrocalcic horizon.
Required Characteristics
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
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 layer 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; and
6.  The layer is not effervescent (in dilute HCl).
Glossic Horizon
The glossic (Gr. glossa, tongue) horizon develops as a result
of the degradation of an argillic, kandic, or natric horizon from
which clay and free iron oxides are removed.
Required Characteristics
The glossic horizon is 5 cm or more thick and consists of:
1.  An eluvial part (albic materials, defined below), which
constitutes 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 a horizon in which gypsum has
accumulated or been transformed to a significant extent. It
14	 Keys to Soil Taxonomy
typically occurs as a subsurface horizon, but it may occur at the
surface in some soils.
Required Characteristics
A gypsic horizon meets all of the following requirements:
1.  Is 15 cm or more thick; and
2.  Is not cemented by gypsum, with or without other
cementing agents; is cemented and the cemented parts are
less than 5 mm thick; or is cemented but, because of lateral
discontinuity, roots can penetrate along vertical fractures with a
horizontal spacing of less than 10 cm; and
3.  Is 5 percent or more (by weight) gypsum and has 1 percent
or more (by volume) visible secondary gypsum that has either
accumulated or been transformed; and
4.  Has a product of thickness, in cm, multiplied by the
gypsum content (percent by weight) 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 any cementation is as described in 2 above.
Kandic Horizon
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 is increasing with depth within a vertical distance of
15 cm and is either:
(1)  4 percent or more (absolute) higher than that in the
overlying 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
overlying 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
overlying 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 upper 100 cm has a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse
sand, loamy sand, or loamy fine sand throughout; or
(2)  Within 100 cm from the mineral soil surface if the
clay content in the fine-earth fraction of the overlying
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 class 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
A natric horizon is an illuvial horizon that is normally
present in the subsurface and has a significantly higher
percentage of silicate clay than the overlying horizons. It shows
evidence of clay illuviation that has been accelerated by the
dispersive properties of sodium.
Required Characteristics
The natric horizon:
1.  Meets one of the following thickness requirements:
a.  If the horizon meets the particle-size class criteria
for 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 onetenth
as thick as the sum of the thickness of all overlying
horizons, whichever is greater; or
b.  If the horizon meets sandy or sandy-skeletal particle-size
class criteria, it must be at least 15 cm thick; or
Horizons and Characteristics Diagnostic for the Higher Categories	 15
D
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c.  If the 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
2.  Has evidence of clay illuviation in at least one of the
following forms:
a.  Oriented clay bridging the sand grains; or
b.  Clay films lining pores; or
c.  Clay films on both vertical and horizontal surfaces of
peds; or
d.  Thin sections with oriented clay bodies that are more
than 1 percent of the section; or
e.  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
3.  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 horizon, 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 illuvial 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 illuvial 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 illuvial horizon must contain
at least 8 percent (absolute) more clay (42 percent versus 50
percent, for example); and
4. Has either:
a.  Columnar or prismatic structure in some part (generally
the upper part), which may part to blocky structure; 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
5. Has 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 extractable acidity (at pH 8.2) in one or more
horizons within 40 cm of its upper boundary and 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
Required Characteristics
Ortstein has all of the following:
1.  Consists of spodic materials (defined below); and
2.  Is in a layer that is 50 percent or more cemented; and
3.  Is 25 mm or more thick.
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.
Oxic Horizon
Required Characteristics
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 class of sandy loam or finer in the fine-earth
fraction; and
3.  Less than 10 percent weatherable minerals in the 0.05 to 0.2
mm 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.  Within a vertical distance of 15 cm or more from the upper
boundary (i.e, diffuse), 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 overlying 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 overlying 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 overlying 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
16	 Keys to Soil Taxonomy
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.)
Petrocalcic Horizon
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.
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 a horizon in which visible
secondary gypsum has accumulated or has been transformed.
The horizon is cemented (i.e., extremely weakly cemented
through indurated cementation classes), and the cementation is
both laterally continuous and root limiting, even when the soil is
moist. The horizon typically occurs as a subsurface horizon, but
it may occur at the surface in some soils.
Required Characteristics
A petrogypsic horizon meets all of the following
requirements:
1.  Is cemented or indurated by gypsum, with or without other
cementing agents; and
2.  Because of lateral continuity, can be penetrated by roots
only along vertical fractures with a horizontal spacing of 10 cm
or more; and
3.  Is 5 mm or more thick; and
4.  Is 40 percent or more (by weight) gypsum.
Placic Horizon
The placic (Gr. base of plax, flat stone; meaning a thin
cemented pan) horizon is a thin, black to dark reddish pan
that is cemented by iron (or iron and manganese) and organic
matter.
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 (defined below), 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.
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 (F. sombre, dark) horizon 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
Horizons and Characteristics Diagnostic for the Higher Categories	 17
D
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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).
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 in a layer 2.5 cm or more thick that is not part of any
Ap horizon.
Diagnostic Soil Characteristics for Mineral
Soils
Diagnostic soil characteristics are features of the soil that
are used in various places in the keys or in the definitions of
diagnostic horizons.
Abrupt Textural Change
An abrupt textural change is a specific kind of change
that may occur between an epipedon composed of mineral
soil material or an eluvial horizon and an underlying argillic,
glossic, kandic, or natric horizon. It is characterized by a
considerable increase in clay content within a very short vertical
distance in the zone of contact.
In soils that have an abrupt textural change, there normally
is no transitional horizon between a mineral epipedon or
an eluvial horizon and an argillic, glossic, kandic, or natric
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) into parts of an argillic,
kandic, or natric 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.
Required Characteristics
An abrupt textural change meets both of the following
requirements:
1.  The noncarbonate clay content in the fine-earth fraction of
the argillic, glossic, kandic, or natric horizon is at least 8 percent
(by weight); and
2.  The noncarbonate clay content in the fine-earth fraction of
the argillic, glossic, kandic, or natric horizon must either:
a.  Double within a vertical distance of 7.5 cm or less if
the clay content, in the fine-earth fraction of the epipedon
composed of mineral soil material or the eluvial horizon, is
less than 20 percent (e.g., an increase from 4 to 8 percent); or
b.  Increase by 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
horizon is 2 times or more the amount contained in the
overlying epipedon composed of mineral soil material or the
eluvial horizon.
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 of 3, moist, and 6 or more, dry; or
b.  A color value of 4 or more, moist, and 5 or more, dry; or
2.  Chroma of 3 or less; and either
a.  A color value of 6 or more, moist; or
b.  A color value of 7 or more, dry; 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.
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 commonly form during weathering of
tephra or other parent materials containing a significant content
of volcanic glass. Soils that are in cool, humid climates and
have abundant organic carbon, however, may develop andic soil
properties without the influence of volcanic glass. A suite of
18	 Keys to Soil Taxonomy
glass and glass-coated minerals rich in silica is termed volcanic
glass in this taxonomy. These minerals are relatively soluble
and undergo fairly rapid transformation when the soils are
moist. Andic soil properties represent a stage in transition where
weathering and transformation of primary alumino-silicates
(e.g., volcanic glass) have proceeded only to the point of the
formation of short-range-order materials, such as allophane,
imogolite, and ferrihydrite, or of metal-humus complexes. The
concept of andic soil properties includes moderately weathered
soil material, rich in short-range-order materials or metalhumus
complexes, or both, with or without volcanic glass
(required characteristic 2) and weakly weathered soil, less rich
in short-range-order materials with volcanic glass (required
characteristic 3).
Relative amounts of allophane, imogolite, ferrihydrite, or
metal-humus complexes in the colloidal fraction are inferred
from laboratory analyses of aluminum, iron, and silica extracted
by ammonium oxalate, and from phosphate retention. Soil
scientists may use smeariness or pH in 1N sodium fluoride
(NaF) as field indicators of andic soil properties. Volcanic
glass content is the percent volcanic glass (by grain count) in
the coarse silt and sand (0.02 to 2.0 mm) fraction. Most soil
materials with andic soil properties consist of mineral soil
materials, but some are organic soil materials with less than 25
percent organic carbon.
Required Characteristics
Soil materials with andic soil properties must have a fineearth
fraction that meets the following requirements:
1.  Less than 25 percent organic carbon (by weight) and one or
both of the following:
2.  All of the following:
a.  Bulk density, measured at 33 kPa water retention, of
0.90 g/cm3
or less; and
b.  Phosphate retention of 85 percent or more; and
c.  Al plus ½ Fe content (by ammonium oxalate) equal to
2.0 percent or more; or
3.  All of the following:
a.  30 percent or more of the fine-earth fraction is 0.02 to
2.0 mm in size; and
b.  Phosphate retention of 25 percent or more; and
c.  Al plus ½ Fe content (by ammonium oxalate) equal to
0.4 percent or more; and
d.  Volcanic glass content of 5 percent or more; and
e.  [(Al plus ½ Fe content, percent) times (15.625)] +
[volcanic glass content, percent] = 36.25 or more.
The shaded area in figure 1 illustrates criteria 3c, 3d, and 3e.
Anhydrous Conditions
Anhydrous (Gr. anydros, waterless) conditions refer to
the moisture condition of soils in very cold deserts and other
areas with permafrost (often dry permafrost). These soils
typically have low precipitation (usually less than 50 mm
water equivalent per year) and a moisture content of less than 3
percent by weight. Anhydrous soil conditions are similar to the
aridic (torric) soil moisture regimes (defined below), except that
the soil temperature at 50 cm is less than 5 o
C throughout the
year in the soil layers with these conditions.
Required Characteristics
Soils with anhydrous conditions have a mean annual soil
temperature of 0 o
C or colder. The layer from 10 to 70 cm
below the soil surface has a soil temperature of less than 5o
C
throughout the year and this layer:
1.  Includes no ice-impregnated permafrost; and
2.  Is dry (water held at 1500 kPa or more) in one-half or more
of the soil for one-half or more of the time the layer has a soil
temperature above 0 o
C; or
Figure 1.—Soils that are plotted in the shaded area meet the andic
soil properties criteria c, d, and e under item 3 of the required
characteristics. To qualify as soils with andic properties, the soils
must also meet the listed requirements for organic-carbon content,
phosphate retention, and particle-size distribution.
Horizons and Characteristics Diagnostic for the Higher Categories	 19
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3.  Has a rupture-resistance class of loose to slightly hard
throughout when the soil temperature is 0 o
C or colder, except
where a cemented pedogenic horizon occurs.
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 or concretions 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
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. Some 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.
Free Carbonates
The term “free carbonates” is used in the definitions of a
number of taxa, is used as a criterion for the isotic mineralogy
class, and is mentioned in the discussion of chemical analyses
in the appendix. It refers to soil carbonates that are uncoated
or unbound and that effervesce visibly or audibly when treated
with cold, dilute HCl. The term “free carbonates” is nearly
synonymous with the term “calcareous.” Soils that have free
carbonates generally have calcium carbonate as a common
mineral, although sodium and magnesium carbonates are also
included in this concept. Soils or horizons with free carbonates
may have inherited the carbonate compounds from parent
materials without any translocation or transformation processes
acting on them. There is no implication of pedogenesis in the
concept of free carbonates, as there is in identifiable secondary
carbonates (defined below), although most forms of secondary
carbonates are freely effervescent.
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 calcareous loess or limestone residuum.
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
20	 Keys to Soil Taxonomy
argillic, kandic, or natric horizon along vertical and, to a lesser
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, kandic,
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
Lamellae (lamella, if singular) are illuvial horizons less than
7.5 cm thick. 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.
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 rock 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 class 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 fine-earth
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 fineearth
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. Linear extensibility is a criterion for most
Vertic subgroups in this taxonomy and is calculated as summed
products from the mineral soil surface to a depth of 100 cm or
to a root-limiting layer (defined in chapter 17).
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 (Soil Survey Division Staff, 1993) and chapter 18 of
this document.
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 example, 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 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
Horizons and Characteristics Diagnostic for the Higher Categories	 21
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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).
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 palm of a 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); and if no soil
material flows through the fingers during full compression,
the sample has an n value less than 0.7 (nonfluid manner of
failure class).
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.
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 level-bedded or
tilted, and may contain only a small percentage of Fe2
O3
. In the
Tropics, the ironstone is generally more or less vesicular.
22	 Keys to Soil Taxonomy
Plinthite
Plinthite (Gr. plinthos, brick) is an iron-rich, humus-poor
mixture of clay with quartz and other minerals. 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 seep 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 occurs as discrete bodies
larger than 2 mm that can be separated from the matrix. A moist
aggregate of plinthite will withstand moderate rolling between
thumb and forefinger and is less than strongly cemented. Moist
or air-dried plinthite will not slake when submerged in water
even with gentle agitation. 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.
Individual aggregates of plinthite in a continuous phase are
interconnected, and the spacing of cracks or zones that roots can
enter is 10 cm or more.
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. Examples are quartz, zircon, tourmaline,
beryl, anatase, rutile, iron oxides and oxyhydroxides, 1:1
dioctahedral phyllosilicates (kandites), gibbsite, and hydroxyaluminum
interlayered 2:1 minerals (Burt and Soil Survey
Staff, 2014).
Slickensides
Slickensides are polished and grooved surfaces and generally
have dimensions exceeding 5 cm. They are produced when one
soil mass slides past another. Some slickensides occur at the
lower boundary of a slip surface where 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:
Horizons and Characteristics Diagnostic for the Higher Categories	 23
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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,
and 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)  Al plus 1
/2 Fe 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.
Volcanic Glass
Volcanic glass is defined herein as optically isotropic
translucent glass or pumice of any color. It includes glass,
pumice, glass-coated crystalline minerals, glass aggregates, and
glassy materials.
Volcanic glass is typically a dominant component in
relatively unweathered tephra. Weathering and mineral
transformation of volcanic glass can produce short-range-order
minerals, such as allophane, imogolite, and ferrihydrite.
Volcanic glass content is the percent (by grain count) of
glass, glass-coated mineral grains, glass aggregates, and glassy
materials in the 0.02 to 2.0 mm fraction. Typically, the content
is determined for one particle-size fraction (i.e., coarse silt, very
fine sand, or fine sand) and used as an estimate of glass content
in the 0.02 to 2.0 mm fraction.
Volcanic glass content is a criterion in classification of andic
soil properties, subgroups with the formative element “vitr(i),”
families with “ashy” substitutes for particle-size class, and the
glassy mineralogy class.
Weatherable Minerals
Several references are made to weatherable minerals in
this taxonomy. Obviously, the stability (i.e., ability to remain
unaltered) 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. Examples of the minerals that are included in
the meaning of weatherable minerals are all 2:1 phyllosilicates,
chlorite, sepiolite, palygorskite, allophane, 1:1 trioctahedral
phyllosilicates (serpentines), feldspars, feldspathoids,
ferromagnesian minerals, volcanic glass, zeolites, dolomite, and
apatite in the 0.02 to 2.0 mm fraction.
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. Calcite, carbonate
aggregates, anhydrite, gypsum, and halite are not considered
weatherable minerals because they are mobile in the soil.
Mobile minerals appear to be recharged in some otherwise
strongly weathered soils.
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.
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
24	 Keys to Soil Taxonomy
Figure 2.—Value and chroma of pyrophosphate solution of fibric and
sapric soil materials.
2.  Show evidence of the cellular structure of the plants from
which they are derived; and
3.  Either are 20 mm 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 20 mm 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
wood fragments (comparable to rock fragments in mineral
soils). Wood fragments may be in the soil or on the soil
surface.
Fibric Soil Materials
Fibric soil materials are organic soil materials that either:
1.  Contain three-fourths or more (by volume) fibers after
rubbing, excluding wood fragments (defined above); 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 (fig. 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 (Gr. hemi, half; implying intermediate decomposition)
soil materials 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.
Sapric Soil Materials
Sapric (Gr. sapros, rotten) soil materials 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 the following characteristics:
1.  The fiber content, after rubbing, is less than one-sixth
(by volume), excluding wood fragments (defined above);
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 (fig. 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.
Kinds of Limnic Materials
The presence or absence of limnic deposits is taken into
account in the higher categories of Histosols but not Histels.
Horizons and Characteristics Diagnostic for the Higher Categories	 25
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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.
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 of 4 or less, moist; 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 white chromatographic or filter paper that has a color
value of 7 or more and chroma of 2 or less (fig. 2) or
has a cation-exchange capacity of less than 240 cmol(+)
per kg organic matter (measured by loss on ignition),
or both.
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
(measured by loss on ignition), or both.
Marl
A layer of marl is a limnic layer that:
1.  Has a color value of 5 or more, moist; 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.
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
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 layers,
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 layers
to a depth of 60 cm either contain three-fourths or more fibers
derived from Sphagnum, Hypnum, or other mosses or have
a bulk density of less than 0.1 g/cm3
. 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 g/cm3
. 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,
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.
26	 Keys to Soil Taxonomy
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 g/cm3
). If the fibric moss extends to a depth of 60
cm and is the dominant material within this depth (three-fourths
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
that are diagnostic for both mineral and organic soils.
Aquic Conditions
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 or the prevention
of surface or ground water from reaching the soils by dams,
levees, surface pumps, or other means. In these soils water
table levels and/or their duration are changed significantly in
connection with specific types of land use. Upon removal of the
drainage practices, aquic conditions would return. 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 wellsealed
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 condition that occurs 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 of 4 or more,
moist, and chroma of 2 or less in macropores; or
(b)  Redox concentrations of iron and/or manganese;
or
(c)  2 times or more the amount of iron (extractable
by dithionite-citrate) than is 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.
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
Horizons and Characteristics Diagnostic for the Higher Categories	 27
D
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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, 1N ammonium acetate
solution. The appearance of a strong red color on the freshly
broken surface indicates the presence of reduced iron ions
(i.e., Fe2+
). 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. For soils with very low levels of iron, the use
of a field test such as Indicator of Reduction in Soils (IRIS)
tubes painted with ferric iron may be warranted in order to
document reducing conditions. Use of alpha,alpha-dipyridyl in
a 10 percent solution of aceticacid 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 FeMn
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.
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 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.
Densic Contact
A densic (L. densus, thick) contact 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.
28	 Keys to Soil Taxonomy
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. 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. 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
Gelisols composed mainly of organic soil materials, the lithic
contact is diagnostic at the subgroup level if it is within 50
cm of the soil surface in Folistels or within 100 cm of the soil
surface in Fibristels, Hemistels, and Sapristels. In Histosols
the lithic contact must be at the lower boundary of the control
section to be recognized at the subgroup level.
Paralithic Contact
A paralithic (lithic-like) 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.
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 ruptureresistance
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.
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 impregnated 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
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
Horizons and Characteristics Diagnostic for the Higher Categories	 29
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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.
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:
1.  Annual precipitation that is plus or minus one standard
deviation of the long-term (30 years or more) mean annual
precipitation; and
2.  Mean monthly precipitation that is plus or minus one
standard deviation of the long-term monthly precipitation for 8
of the 12 months.
For the most part, normal years can be calculated from the
mean annual precipitation; however, when catastrophic events
occur during a year, 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 (Soil
Survey Staff, 1975). When precipitation data are evaluated to
determine if the criterion for the presence of aquic conditions,
or number of days that the moisture control section is moist, or
number of days that some part of the soil is saturated has been
met, it is permissible to include data from periods with below
normal rainfall. Similarly, when precipitation data are evaluated
to determine if the criterion for the number of days that the
moisture control section is dry has been met, it is permissible
to include data from periods with above normal rainfall. It is
assumed that if the criteria are met during these periods, they
will also be met during normal years.
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) 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.
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 of 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 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.
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 or fallowing. These
cultural practices affect the soil moisture conditions as long as
they are continued.
Aquic soil moisture regime.—The aquic (L. aqua, water)
soil 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 soil 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
30	 Keys to Soil Taxonomy
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 soil moisture
regime.
Aridic and torric (L. aridus, dry, and L. torridus, hot
and dry) soil moisture regimes.—These terms are used for
the same moisture regime but in different categories of the
taxonomy.
In the aridic (torric) soil 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 below
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 below the soil
surface is above 8 o
C.
Soils that have an aridic (torric) soil 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 soil moisture regime, and
soluble salts accumulate in the soils if there is a source.
The limits set for soil temperature exclude from these soil
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 soil moisture regime.—The udic (L. udus, humid)
soil 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 below 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
soil moisture regime requires, except for short periods, a threephase
system, solid-liquid-gas, in part or all of the soil moisture
control section when the soil temperature is above 5 o
C.
The udic soil 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 when it is not frozen.
Such an extremely wet soil 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.
Ustic soil moisture regime.—The ustic (L. ustus, burnt;
implying dryness) soil 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 soil
moisture regime is not applied to soils that have permafrost
(defined above).
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 soil 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
if the mean summer and winter soil temperatures differ by
6 o
C or more at a depth of 50 cm below the soil surface, the
soil moisture control section in areas of the ustic soil 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.
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 soil 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 soil moisture regime.—The xeric (Gr. xeros, dry)
soil 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 soil
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 winter solstice. Also, in normal years, the moisture
control section is moist in some part for more than half of the
Horizons and Characteristics Diagnostic for the Higher Categories	 31
D
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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 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
below the soil surface or at a densic, lithic, or paralithic contact
if shallower.
Soil Temperature Regimes
Classes of Soil Temperature Regimes
Following is a description of the soil temperature regimes
used in defining classes at various categorical levels in this
taxonomy.
Gelic (L. gelare, to freeze).— Soils in this temperature
regime have a mean annual soil temperature at or below 0 o
C
(in Gelic suborders and Gelic great groups) or 1 o
C or lower (in
Gelisols) either at a depth of 50 cm below the soil surface or at
a densic, lithic, or paralithic contact, whichever is shallower.
Cryic (Gr. kryos, coldness; indicating very cold
soils).—Soils in this temperature regime have a mean annual
temperature between 0 and 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 below 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: between 0 and 15 o
C; or
(2)  If there is an O horizon: between 0 and 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: between 0 and 13 o
C; or
(2)  If there is an O horizon or a histic epipedon:
between 0 and 6 o
C.
2.  In organic soils the mean annual soil temperature is
between 0 and 6 o
C.
Cryic soils that have an aquic soil moisture regime
commonly are churned by frost.
Isofrigid soils can also have a cryic soil temperature
regime. A few with organic materials in the upper part are
exceptions.
The concepts of the soil temperature regimes described
below are used in defining classes of soils in the lower
categories of soil taxonomy (i.e., family and soil series).
Frigid.—A soil with a frigid soil temperature regime is
warmer in summer than a soil with a cryic regime, but its mean
annual temperature is between 0 and 8 o
C and the difference
between mean summer (June, July, and August) and mean
winter (December, January, and February) soil temperatures is
6 o
C or more either at a depth of 50 cm below 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 6 o
C or more either at a
depth of 50 cm below 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 6 o
C or more
either at a depth of 50 cm below 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 6 o
C or more either at a depth of 50
cm below 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
(elemental S or most commonly sulfide minerals, such as
pyrite or iron monosulfides). They are mineral or organic soil
materials that have a pH value of more than 3.5 and that become
significantly more acid when oxidized. 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 hydroxysulfate mineral
jarosite may segregate, forming the yellow redoximorphic
concentrations that commonly characterize a sulfuric horizon.
32	 Keys to Soil Taxonomy
The transition from sulfidic materials to a sulfuric horizon
normally requires only a few months 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.
Required Characteristics
Sulfidic materials have one or both of the following:
1.  A pH value (1:1 in water) of more than 3.5, and, when the
materials are incubated at room temperature as a layer 1 cm
thick under moist aerobic conditions (repeatedly moistened
and dried on a weekly basis), the pH decreases by 0.5 or more
units to a value of 4.0 or less (1:1 by weight in water or in a
minimum of water to permit measurement) within 16 weeks or
longer until the pH reaches a nearly constant value if the pH is
still dropping after 16 weeks; or
2.  A pH value (1:1 in water) of more than 3.5 and 0.75 percent
or more S (dry mass), mostly in the form of sulfides, and less
than three times as much calcium carbonate equivalent as S.
Sulfuric Horizon
Brackish water sediments frequently contain pyrite or other
iron sulfide minerals (or, rarely, elemental sulfur), which form
sulfuric acid upon the oxidation of the sulfur forms they contain
and/or upon the oxidation and hydrolysis of the iron in the
iron sulfides. Pyrite is an iron sulfide mineral that forms as a
result of the microbial decomposition of organic matter under
anaerobic conditions. Pyrite forms after iron oxide and sulfate
from sea water (or other sources) become reduced to ferrous
iron and sulfide, respectively, and then combine to form a very
insoluble compound (see description of the sulfidization process
given by Fanning and Fanning, 1989, or Fanning et al., 2002).
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 (and
the hydrolysis of the ferric iron produced) are iron oxides (and
under sufficiently acidic and oxidizing conditions, jarosite
and/or schwertmannite) and sulfuric acid. The jarosite has
a straw-yellow color and frequently lines pores in the soil.
Jarosite concentrations are among the indicators of a sulfuric
horizon, but jarosite is not present in all sulfuric horizons.
The low pH and high amount of soluble sulfates, and/or
underlying sulfidic materials, are other 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 (L. sulfur) horizon forms as a result of drainage
(most commonly artificial drainage) and oxidation of sulfiderich
mineral 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 and, if sufficiently acid at
the soil surface, may prevent plant growth or limit it to certain
plant species, such as Phragmites australis, that can tolerate the
acidity under certain conditions.
Required Characteristics
The sulfuric horizon is 15 cm or more thick and is composed
of either mineral or organic soil material that has a pH value
(1:1 by weight in water or in a minimum of water to permit
measurement) of 3.5 or less or less than 4.0 if sulfide or other
S-bearing minerals that produce sulfuric acid upon their
oxidation are present. The horizon shows evidence that the low
pH value is caused by sulfuric acid.
The evidence is one or both of the following:
1.  The horizon has:
a.  Concentrations of jarosite, schwertmannite, or other iron
and/or aluminum sulfates or hydroxysulfate minerals; or
b.  0.05 percent or more water-soluble sulfate; or
2.  The layer directly underlying the horizon consists of
sulfidic materials (defined above).
Characteristics Diagnostic for
Human-Altered and HumanTransported
Soils
Following are descriptions of the characteristics that are
diagnostic for human-altered and human-transported soils. The
diagnostic surface and subsurface horizons that may be present
in these soils are defined above.
Anthropogenic Landforms and
Microfeatures
Anthropogenic Landforms
Anthropogenic landforms are discrete, artificial landforms
that are mappable at common survey scales, such as 1:10,000
to 1:24,000. For more information on these terms, see Part 629
of the National Soil Survey Handbook (U.S. Department of
Agriculture).
Constructional Anthropogenic Landforms
Constructional anthropogenic landforms include the
following:
1.   Artificial islands
2.   Artificial levees
3.   Burial mounds
4.   Dumps
5.   Dredge-deposit shoals
6.   Dredge spoil banks
7.   Filled marshland
8.   Earthworks
9.   Fill
10.  Filled pits
Horizons and Characteristics Diagnostic for the Higher Categories	 33
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11.  Filled enclosures
12.  Irrigationally raised land
13.  Raised land
14.  Landfills
15.  Locally raised landforms
16.  Middens
17.  Mounds
18.  Railroad beds
19.  Reclaimed land
20.  Rice paddies
21.  Road beds
22.  Sanitary landfills
23.  Spoil banks
24.  Spoil piles
Destructional Anthropogenic Landforms
Destructional anthropogenic landforms include the
following:
1.   Beveled cuts
2.   Borrow pits
3.   Canals
4.   Cuts (i.e., road or railroad)
5.   Cutbanks
6.   Dredged channels
7.   Earthworks
8.   Floodways
9.   Gravel pits
10.  Leveled land
11.  Log landings
12.  Openpit mines
13. Quarries
14.  Rice paddies
15.  Sand pits
16.  Scalped area
17.  Sewage lagoons
18.  Surface mines
Anthropogenic Microfeatures
Anthropogenic microfeatures are discrete, artificial features
formed on or near the earth’s surface (and which may now
be buried) typically too small to delineate at common survey
scales, such as larger than 1:10,000. For more information on
these terms, see Part 629 of the National Soil Survey Handbook
(U.S. Department of Agriculture).
Constructional Anthropogenic Microfeatures
Constructional anthropogenic microfeatures include the
following:
1.   Breakwater (i.e., groins or jetties)
2.   Burial mounds
3.   Conservation terraces
4.   Dikes
5.   Double-bedding mounds
6.   Dumps
7.   Embankments
8.   Fills
9.   Hillslope terraces
10. Interfurrows
11.  Middens
12.  Revetments (i.e., seawalls)
13.  Rice paddies
14.  Spoil banks
15.  Spoil piles
Destructional Anthropogenic Microfeatures
Destructional anthropogenic microfeatures include the
following:
1.   Cutbanks
2.   Ditches
3.   Furrows
4.   Hillslope terraces
5.   Impact craters
6.   Skid trails
7.   Scalped areas
Artifacts
Artifacts (L. arte, by skill, and factum, to do or make) are
materials created, modified, or transported from their source
by humans usually for a practical purpose in habitation,
manufacturing, excavation, agriculture, or construction
activities. Examples of discrete (> 2mm) artifacts are bitumen
(asphalt), brick, cardboard, carpet, cloth, coal combustion
by-products, concrete, glass, metal, paper, plastic, rubber,
and both treated and untreated wood products. Mechanically
abraded rocks (e.g., rocks with metal scrape marks or gouges),
rocks worn smooth or shaped by physical action (e.g., grinding
stones), or physically broken and shaped rocks and debitage
are artifacts (e.g., stone tool flakes). Examples of nonpersistent
artifacts repeatedly added to soil to improve agricultural
production include biosolids, aglime, quicklime, and synthetic
inorganic fertilizers. Humans have also added midden
material to the soil to increase agricultural productivity, but
these additions (e.g., bones, shells, and cooking waste and
associated charred by-products) have persisted to produce
long-term (hundreds to thousands of years) changes in soil
properties (e.g., Terra Preta de Indio soils). Artifacts also
include litter discarded by humans (e.g., aluminum cans) that
appears to serve no apparent purpose or function for alteration
of soil.
Human-Altered Material
Human-altered material is parent material for soil that
has undergone anthroturbation (soil mixing or disturbance)
by humans. It occurs in soils that have either been used for
gardening, been deeply mixed in place, excavated and replaced,
or compacted in place for the artificial ponding of water.
34	 Keys to Soil Taxonomy
‡
Surfaces that formed by shearing intersect irregularly in diverging and converging
directions.
Human-altered material may be composed of either organic or
mineral soil material. It may contain artifacts (e.g., shells or
bones) used as agricultural amendments, but the majority of the
material has no evidence that it was transported from outside of
the pedon.
Human-altered material occurs in soils which are disturbed
for various reasons. For example, human-altered material
occurs in agricultural soils which are deeply-plowed or ripped
to disrupt a root-limiting layer (defined in chapter 17) or other
physical restriction. Gravesites in cemeteries contain humanaltered
material as well as artifacts. Densic contacts form at the
top of wet, slowly permeable (i.e., puddled) layers when they
are compacted by humans and destroy structure and impede
water percolation. Subsequent artificial ponding in such humanaltered
material results in anthric saturation (defined above) for
the purpose of growing crops like rice in paddy soils.
Diagnostic horizons formed by significant illuviation (e.g.,
argillic or petrocalcic horizons) have not been documented
as occurring in human-altered material. However, laterally
tracing an illuvial horizon or diagnostic characteristic to find
a discontinuity where the horizon or characteristic is abruptly
absent can be used to identify human-altered material. The
lateral discontinuity typically extends along linear boundaries.
When the lateral discontinuity occurs at the edge of an
anthropogenic landform or microfeature (defined above), it
confirms the destructional origin of the landform or feature
and identifies the human-altered material produced through
excavation. It is often the preponderance of evidence (best
professional judgment) along with published or historical
evidence and onsite observations that allows the most consistent
identification of excavated human-altered material.
Required Characteristics
Human-altered material meets both of the following:
1.  It occurs in one of the following:
a.  A field tilled with a subsoiler to a depth of 50 cm or
more to break up an impermeable or root-restrictive layer; or
b.  A destructional (excavated) anthropogenic landform or
microfeature (e.g., borrow pit); or
c.  A field ponded for agriculture (e.g., rice paddy); and
2.  It does not meet the requirements of human-transported
material (defined below) and has evidence of purposeful
alteration by humans which results in one of the following:
a.  3 percent or more (by volume) mechanically detached
and re-oriented pieces of diagnostic horizons or
characteristics in a horizon or layer 7.5 cm or more thick; or
b.  50 percent or more (by volume) divergent-shaped
structures (from L. divergent, to veer)‡ 
in a horizon or layer
7.5 cm or more thick formed from traffic or mechanical
pressure exceeding the shear strength of moist loamy or
clayey soil material; or
c.  Excavated and replaced soil material overlying either
bones or artifacts arranged in ceremonial position or human
body parts prepared to prevent decay; or
d.  Mechanically-abraded rock fragments; or
e.  Excavated and replaced soil material unconformably
overlying features (e.g., scrape marks) that indicate
excavation by mechanical tools in some part of the pedon; or
f.  An abrupt lateral discontinuity of subsurface horizons
and characteristics at the edge of a refilled or unfilled
destructional (excavated) anthropogenic landform or
microfeature; or
g.  Anthraquic conditions in a horizon or layer 7.5 cm or
more thick; or
h.  A densic contact or thick platy structure in at least 50
percent of a pedon accompanied by additional evidence
(e.g., scrape marks) that it was formed by human-induced
mechanical compaction.
Human-Transported Material
Human-transported material is parent material for soil that
has been moved horizontally onto a pedon from a source area
outside of that pedon by purposeful human activity, usually with
the aid of machinery or hand tools. This material often contains
a lithologic discontinuity or a buried horizon just below an
individual deposit. In some cases it is not possible to distinguish
between human-transported material and parent material from
mass movement processes (e.g., landslides) without intensive
onsite examination and analysis.
Human-transported material may be composed of either
organic or mineral soil material and may contain detached
pieces of diagnostic horizons which are derived from excavated
soils. It may also contain artifacts (e.g., asphalt) that are
not used as agricultural amendments (e.g., biosolids) or are
litter discarded by humans (e.g., aluminum cans). Humantransported
material has evidence that it did not originate
from the same pedon which it overlies. In some soils,
irregular distribution with depth or in proximity away from an
anthropogenic landform, feature, or constructed object (e.g., a
road or building) of modern products (e.g., radioactive fallout,
deicers, or lead-based paint) may mark separate depositions
of human-transported materials or mark the boundary with
in situ soil material below or beside the human-transported
material. In other soils, a discontinuity exists between the
human-transported material and the parent material (e.g., a
2C horizon) or root-limiting layer (e.g., a 2R layer) beneath it.
Multiple forms of evidence may be required to identify humantransported
material where combinations of human actions and
natural processes interact. Examples of these combinations
include human-transported material deposited by dredging
Horizons and Characteristics Diagnostic for the Higher Categories	 35
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§ 
A void created when soil materials with a high content of rock fragments are
transported and deposited without packing or sorting. The result is a trio of rock fragments
stacked in a manner than prevents fine earth from filling the void.
adjacent to active beaches, human- or water-deposited litter
on flood plains and beneath water bodies, and deposits from
natural geologic events (e.g., airfall volcanic ash) mantling
anthropogenic landforms and microfeatures. Therefore, it is
often the preponderance of evidence, including published
or historical evidence and onsite observations, that allows
identification of human-transported material.
Required Characteristics
Human-transported material meets both of the following:
1.  It occurs either:
a.  On a constructional anthropogenic landform or
microfeature (e.g., artificial levees); or
b.  Within the boundaries of a destructional (excavated)
anthropogenic landform or microfeature (e.g., borrow pit);
and
2.  It has evidence of purposeful transportation by humans and
an origin outside of the pedon by at least one of the following:
a.  A layer of soil material 7.5 cm or more thick which
unconformably overlies material that has no evidence of
originating outside of the pedon (e.g., an in situ, laterally
continuous kandic horizon); or
b.  Artifacts other than agricultural amendments (e.g.,
quicklime) and litter discarded by humans (e.g., aluminum
cans); or
c.  Mechanically detached pieces of diagnostic horizons
or characteristics or saprolite (isovolumetric, weathered,
uncemented pseudomorphs of weathered bedrock) that do
not correspond with the underlying material. The pieces
often have random orientation relative to each other and the
soil surface and contrast abruptly in texture, mineralogy, or
color with the surrounding material; or
d.  Soil material that contains mechanically abraded rock or
pararock fragments; or
e.  Mechanically fractured rock or pararock fragments with
splintered or sharp edges that do not correspond with the
fragments in the underlying soil material (i.e., fractures that
cut through rather than between individual minerals); or
f.  Mechanical scrape marks at some part of the boundary
between materials that do not correspond with each other; or
g.  Soil material 7.5 cm or more thick that overlies a
manufactured layer contact; or
h.  Bridging voids§
between rock fragments in a horizon
or layer 7.5 cm or more thick in mine spoil with at least 35
percent (by volume) rock fragments; or
i.  An irregular distribution pattern of modern anthropogenic
particulate artifacts (e.g., radioactive fallout or immobile
pollutants) or discrete artifacts that are unrelated to the
deposition or transportation processes of natural parent
materials such as eolian material, alluvium, or colluvium.
The irregular distribution occurs above or across the contact
between soil materials that do not correspond with each
other or laterally with distance away from a source (e.g.,
the amount of lead-based paint decreases away from a
building).
Manufactured Layer
A manufactured layer is an artificial, root-limiting layer
beneath the soil surface consisting of nearly continuous, humanmanufactured
materials whose purpose is to form an impervious
barrier. The materials used to make the layer impervious include
geotextile liners, asphalt, concrete, rubber, and plastic. The
presence of manufactured layers can be used to differentiate soil
series.
Manufactured Layer Contact
A manufactured (L. humanus, of or belonging to man, and
L. factum, to do or make) layer contact is an abrupt contact
between soil and a manufactured layer (defined above). It has
no cracks, or the spacing of cracks that roots can enter is 10 cm
or more.
Subgroups for Human-Altered and HumanTransported
Soils
The following subgroup adjectives recognize distinct groups
of human-altered and human-transported soils. Soils using
these adjectives are considered extragrades since they do not
represent an intergrade to any other named taxon (Soil Survey
Staff, 1999). They are listed in order of interpretive significance
as a guide, but the significance and order may change slightly
depending on the great group in which they are recognized.
They are not used in combination with each other even though
some soils may have properties of several subgroups. These
adjectives may be combined alphabetically with adjectives
connoting other soil properties, such as high organic matter
content (e.g., Anthropic Humic) or the presence of sulfidic
materials (e.g., Anthroportic Sulfic), to form the names for
additional extragrade subgroups. Additional adjectives for
other properties will generally increase the importance of
the subgroup and result in higher placement within a key to
subgroups.
1.  Anthraquic (modified from Gr. anthropos, human, and L.
aqua, water). Soils that have anthraquic conditions (i.e., anthric
saturation). These soils are extensive in flooded rice paddies.
36	
2.  Anthrodensic (modified from Gr. anthropos, human, and
L. densus, marked by compactness). Soils that have a densic
contact due to mechanical compaction (e.g., a compacted mine
spoil) in more than 90 percent of the pedon (measured laterally)
within 100 cm of the mineral soil surface.
3.  Anthropic (modified from Gr. anthropos, human). Soils
that have an anthropic epipedon based on the presence of
artifacts or midden material.
4.  Plaggic (modified from Ger. plaggen, sod). Soils that have
a plaggen epipedon.
5.  Haploplaggic (Gr. haplous, simple, and Ger. plaggen, sod).
Soils that have a surface horizon 25 cm to less than 50 cm thick
that meets all of the requirements for a plaggen epipedon except
thickness.
6.  Anthroportic (modified from Gr. anthropos, human, and L.
portāre, to carry). Soils that formed in 50 cm or more of humantransported
material. This adjective is used primarily for soils
that formed in human-transported material of dredged or mine
spoil areas as well as for soils of urban areas and transportation
corridors.
7.  Anthraltic (modified from Gr. anthropos, human, and L.
alterāre, to change). Soils that formed in 50 cm or more of
human-altered material. This adjective is used primarily for
human-altered material where ripping or deep plowing has
fractured and displaced diagnostic subsurface horizons that
were root-limiting (e.g., duripans) and in excavated areas (e.g.,
borrow pits).
Literature Cited
Brewer, R. 1976. Fabric and Mineral Analysis of Soils. 2nd
edition. John Wiley and Sons, New York.
Burt, R. and Soil Survey Staff. 2014. Soil Survey Laboratory
Methods Manual. Soil Survey Investigations Report 42,
Version 5.0. U.S. Department of Agriculture, Natural Resources
Conservation Service, National Soil Survey Center.
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.
Fanning, D.S., and M.C.B. Fanning. 1989. Soil: Morphology,
Genesis, and Classification. John Wiley and Sons, New York.
Fanning, D.S., M.C. Rabenhorst, S.N. Burch, K.R. Islam,
and S.A. Tangren. 2002. Sulfides and Sulfates. In J.B. Dixon
and D.G. Schulze (eds.), Soil Mineralogy with Environmental
Applications, pp. 229-260. Soil Sci. Soc. Am., Madison, WI.
Hester, T.R., R.F. Heizer, and J.A. Graham. 1975. Field
Methods in Archaeology. Mayfield Publishing, Palo Alto, CA.
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.
Soil Survey Division Staff. 1993. Soil Survey Manual.
Soil Conservation Service. U.S. Department of Agriculture
Handbook 18.
Soil Survey Staff. 1975. Soil Taxonomy: A Basic System of
Soil Classification for Making and Interpreting Soil Surveys.
Soil Conservation Service. U.S. Department of Agriculture
Handbook 436.
Soil Survey Staff. 1999. Soil Taxonomy: A Basic System of
Soil Classification for Making and Interpreting Soil Surveys.
Soil Conservation Service. 2nd edition. Natural Resources
Conservation Service. U.S. Department of Agriculture
Handbook 436.
U.S. Department of Agriculture, Natural Resources
Conservation Service. National Soil Survey Handbook, title
430-VI. Part 629: Glossary of Landform and Geologic Terms.
(Available online.)
	 37
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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 user is familiar with the definitions of soil
and buried soils (defined in chapter 1), mineral and organic
soil material (defined in chapter 2), and the diagnostic horizons
and characteristics (defined in chapter 3). Users should also be
familiar with the meanings of the terms used for describing soils
given in the Soil Survey Manual (Soil Survey Division Staff,
1993) and the Field Book for Describing and Sampling Soils
(Schoeneberger et al., 2012). Chapter 18 of this publication
is an excerpt from the Soil Survey Manual that contains the
symbolic designations for genetic soil horizons and layers.
Although not a part of soil taxonomy, the designations are
reproduced in this publication for convenience. The appendix of
this publication contains general descriptions of the laboratory
methods for physical, chemical, organic, and mineralogical
properties and where they are used as criteria in soil taxonomy.
The index at the back of this publication indicates the pages on
which definitions of terms are given.
Conventional rules should be used to round numerical
values. Numerical values are rounded to the same number
of digits as used in the taxonomic criteria. For example, soil
taxonomy requires using percentages for clay content in whole
numbers (integers) when applying taxonomic criteria such as
the required characteristics of the argillic horizon and the key to
particle-size classes (defined in chapter 17). However, primary
characterization data supplied from soil laboratories often report
clay content, by weight, in tenths of a percent (one decimal
place). When measured data are applied in classifying the soil,
one must first note the level of precision used as a class limit
and then round the measured data to the same level of precision.
The conventional rules for rounding numbers in soil taxonomy
are as follows:
• If the digit immediately to the right of the last significant
figure is more than 5, round up to the next higher digit. For
example, 34.8 rounds to 35 (round up because the digit to be
dropped is more than halfway between 34 and 35).
• If the digit immediately to the right of the last significant
figure is less than 5, round down to the next lower digit. For
example, 34.4 rounds to 34 (round down because the digit to
be dropped is less than halfway between 34 and 35).
• If the digit immediately to the right of the last significant
figure is equal to 5, round to the adjacent even number, either
up or down. Some examples are 17.5 rounds to 18 (round up
because the result is an even number) and 34.5 rounds to 34
(round down because the result is an even number).
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 17 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 using 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 are given in chapter 17.
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
Identification of the Taxonomic Class of a Soil
CHAPTER 4
38	 Keys to Soil Taxonomy
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 and family criteria.
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. Although most other diagnostic
soil characteristics of the buried soil are not considered, organic
carbon if of Holocene age, andic soil properties, base saturation,
and all properties used to determine family and series placement
are considered.
If diagnostic horizons or characteristics are criteria that must
be “within” a specified depth measured from the soil surface,
then the upper boundary of the first subhorizon meeting the
requirements for the diagnostic horizon or characteristic must
be within the specified depth.
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. 157
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 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 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. 167
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 or gelic 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 texture class that is finer than coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or
loamy fine sand in the fine-earth fraction and a frigid
temperature regime in the soil; or
(5)  A cryic or gelic 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 texture class of
coarse sand, sand, fine sand, loamy coarse sand, loamy
sand, or loamy fine sand, in the fine-earth fraction, in
some horizon between the mineral soil surface and the
spodic horizon; and
* 
Materials that meet the definition of the cindery, fragmental, or pumiceous substitute
for particle-size class 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 	 39
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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 texture class that is
finer than coarse sand, sand, fine sand, loamy coarse
sand, loamy sand, or loamy fine sand in the fineearth
fraction and the soil has a frigid temperature
regime; or
(b)  If the soil has a cryic or gelic 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.
Spodosols, p. 273
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. 87
E.  Other soils that have either:
1.  An oxic horizon within 150 cm of the mineral soil
surface and no kandic horizon 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. 257
F.  Other soils that have:
1.  A layer 25 cm or more thick, within 100 cm of the
mineral soil surface, that has either slickensides or wedgeshaped
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. Cracks†
that open and close periodically.
Vertisols, p. 305
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 within 100 cm of the
soil surface: a cambic horizon with a lower depth of
25 cm or more; a cryic soil temperature regime and a
cambic horizon; an anhydritic, 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 within 150 cm of the mineral soil
surface.
Aridisols, p. 107
† 
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.
40	 Keys to Soil Taxonomy
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 texture class of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand in the fine-earth fraction 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:
(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. 283
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. 211
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. 43
K.  Other soils that have either:
1.  One or more of the following:
a.  A cambic horizon that is within 100 cm of the mineral
soil surface and has a 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 within a depth of 100 cm of the
mineral soil surface; or
c.  A fragipan or an oxic, sombric, or spodic horizon
within 200 cm of the mineral soil surface; or
d.  A sulfuric horizon within 150 cm of the mineral soil
surface; or
e.  A cryic or gelic soil 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 more of the following:
(1)  A folistic, histic, mollic, plaggen, or umbric
epipedon; or
(2)  A salic horizon; or
(3)  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
Identification of the Taxonomic Class of a Soil 	 41
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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. 173
L.  Other soils.
Entisols, p. 135
Literature Cited
Schoeneberger, P.J., D.A. Wysocki, E.C. Benham, and Soil
Survey Staff. 2012. Field Book for Describing and Sampling
Soils, Version 3.0. Natural Resources Conservation Service,
National Soil Survey Center.
Soil Survey Division Staff. 1993. Soil Survey Manual.
Soil Conservation Service. U.S. Department of Agriculture
Handbook 18.
	43
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Key to Suborders
JA.  Alfisols 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 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; 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. 43
JB.  Other Alfisols that have a cryic or isofrigid soil
temperature regime.
Cryalfs, p. 52
JC.  Other Alfisols that have an ustic soil moisture regime.
Ustalfs, p. 67
JD.  Other Alfisols that have a xeric soil moisture regime.
Xeralfs, p. 79
JE.  Other Alfisols.
Udalfs, p. 56
Aqualfs
Key to Great Groups
JAA.  Aqualfs that have a cryic soil temperature regime.
Cryaqualfs, p. 45
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. 51
JAC.  Other Aqualfs that have a duripan.
Duraqualfs, p. 45
JAD.  Other Aqualfs that have a natric horizon.
Natraqualfs, p. 51
JAE.  Other Aqualfs that have a fragipan within 100 cm of the
mineral soil surface.
Fragiaqualfs, p. 49
JAF.  Other Aqualfs that have a kandic horizon.
Kandiaqualfs, p. 50
JAG.  Other 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.
Vermaqualfs, p. 52
JAH.  Other Aqualfs that have an abrupt textural change
between the ochric epipedon or albic horizon and the argillic
horizon and have a saturated hydraulic conductivity of 0.4
cm/hr (1.0 µm/sec) or slower (moderately low or lower Ksat
class) in the argillic horizon.
Albaqualfs, p. 44
JAI.  Other Aqualfs that have a glossic horizon.
Glossaqualfs, p. 49
JAJ.  Other Aqualfs that have episaturation.
Epiaqualfs, p. 47
JAK.  Other Aqualfs.
Endoaqualfs, p. 45
Alfisols
CHAPTER 5
44	 Keys to Soil Taxonomy
Albaqualfs
Key to Subgroups
JAHA.  Albaqualfs that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 peds 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 peds 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 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 wedgeshaped
peds 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, or the upper 18 cm of the mineral
soil meets all of the requirements for a mollic epipedon,
except for thickness, 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) particles 2.0 mm or
larger in diameter, 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, or the
upper 18 cm of the mineral soil meets all of the requirements
for a mollic epipedon, except for thickness, after mixing.
Mollic Albaqualfs
Alfisols	 45
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JAHI.  Other Albaqualfs that have an umbric epipedon, or the
upper 18 cm of the mineral soil meets all of the requirements
for an umbric epipedon, except for thickness, after mixing.
Umbric Albaqualfs
JAHJ.  Other Albaqualfs.
Typic Albaqualfs
Cryaqualfs
Key to Subgroups
JAAA.  All Cryaqualfs (provisionally).
Typic Cryaqualfs
Duraqualfs
Key to Subgroups
JACA.  All Duraqualfs (provisionally).
Typic Duraqualfs
Endoaqualfs
Key to Subgroups
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) particles 2.0 mm or
larger in diameter, 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 peds 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 wedgeshaped
peds 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 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 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:
46	 Keys to Soil Taxonomy
(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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 Endoaqualfs
JAKH.  Other Endoaqualfs that have both:
1.  A mollic epipedon, or the upper 18 cm of the mineral
soil meets all of the requirements for a mollic epipedon,
except for thickness, 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, or the upper 18 cm of the mineral
soil meets all of the requirements for an umbric epipedon,
except for thickness, 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, or the
upper 18 cm of the mineral soil meets all of the requirements
for a mollic epipedon, except for thickness, after mixing.
Mollic Endoaqualfs
JAKL.  Other Endoaqualfs that have an umbric epipedon,
or the upper 18 cm of the mineral soil meets all of the
Alfisols	 47
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requirements for an umbric epipedon, except for thickness, after
mixing.
Umbric Endoaqualfs
JAKM.  Other Endoaqualfs.
Typic Endoaqualfs
Epiaqualfs
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 peds 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 peds 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.
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 peds 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
48	 Keys to Soil Taxonomy
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 wedgeshaped
peds 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) particles 2.0 mm or
larger in diameter, 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 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 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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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
JAJI.  Other Epiaqualfs that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 both:
1.  An umbric epipedon, or the upper 18 cm of the mineral
soil meets all of the requirements for an umbric epipedon,
except for thickness, 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
Alfisols	 49
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(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, or the upper 18 cm of the mineral
soil meets all of the requirements for a mollic epipedon,
except for thickness, 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, or the
upper 18 cm of the mineral soil meets all of the requirements
for a mollic epipedon, except for thickness, after mixing.
Mollic Epiaqualfs
JAJN.  Other Epiaqualfs that have an umbric epipedon, or the
upper 18 cm of the mineral soil meets all of the requirements
for an umbric epipedon, except for thickness, after mixing.
Umbric Epiaqualfs
JAJO.  Other Epiaqualfs.
Typic Epiaqualfs
Fragiaqualfs
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 a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 18 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 18 cm after mixing.
Humic Fragiaqualfs
JAEE.  Other Fragiaqualfs.
Typic Fragiaqualfs
Glossaqualfs
Key to Subgroups
JAIA.  Glossaqualfs that have a histic epipedon.
Histic Glossaqualfs
50	 Keys to Soil Taxonomy
JAIB.  Other Glossaqualfs that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 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 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, or the
upper 18 cm of the mineral soil meets the requirements for a
mollic epipedon after mixing.
Mollic Glossaqualfs
JAIG.  Other Glossaqualfs.
Typic Glossaqualfs
Kandiaqualfs
Key to Subgroups
JAFA.  Kandiaqualfs that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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.  A color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 18 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 18 cm 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:
Alfisols	 51
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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,
or the upper 18 cm of the mineral soil meets the color
requirements for an umbric epipedon after mixing.
Umbric Kandiaqualfs
JAFG.  Other Kandiaqualfs.
Typic Kandiaqualfs
Natraqualfs
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 wedgeshaped
peds 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
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, or the
upper 18 cm of the mineral soil meets the color requirements for
a mollic epipedon after mixing.
Mollic Natraqualfs
JADG.  Other Natraqualfs.
Typic Natraqualfs
Plinthaqualfs
Key to Subgroups
JABA.  All Plinthaqualfs (provisionally).
Typic Plinthaqualfs
52	 Keys to Soil Taxonomy
Vermaqualfs
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
JAGB.  Other Vermaqualfs.
Typic Vermaqualfs
Cryalfs
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 class 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. 55
JBB.  Other Cryalfs that have a glossic horizon.
Glossocryalfs, p. 52
JBC.  Other Cryalfs.
Haplocryalfs, p. 53
Glossocryalfs
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 wedgeshaped
peds 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) particles 2.0 mm or
larger in diameter, 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
Alfisols	 53
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2.  In 60 percent or more of the volume of a layer 15 cm or
more thick.
Fragic Glossocryalfs
JBBH.  Other Glossocryalfs that have all of the following:
1.  A xeric soil moisture regime; and
2.  A color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 18 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 18 cm after mixing; and
3.  A base saturation (by NH4
OAc) of 50 percent or more
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 both:
1.  A xeric soil moisture regime; and
2.  A color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 18 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 18 cm after mixing.
Umbric Xeric Glossocryalfs
JBBJ.  Other Glossocryalfs that meet all of the following:
1.  Are dry in some part of the moisture control section for
45 or more days (cumulative) in normal years; and
2.  Have a color value, moist, of 3 or less and a color value,
dry, of 5 or less (crushed and smoothed sample) either
throughout the upper 18 cm of the mineral soil (unmixed) or
between the mineral soil surface and a depth of 18 cm after
mixing; and
3.  Have a base saturation (by NH4
OAc) of 50 percent or
more 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 soil 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 have both:
1.  A color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 18 cm of the mineral soil (unmixed) or between
the mineral soil surface and a depth of 18 cm after mixing;
and
2.  A base saturation (by NH4
OAc) of 50 percent or more
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 a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 18 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 18 cm after mixing.
Umbric Glossocryalfs
JBBO.  Other Glossocryalfs that have a base saturation (by
NH4
OAc) of 50 percent or more 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
Haplocryalfs
Key to Subgroups
JBCA.  Haplocryalfs that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Haplocryalfs
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 wedgeshaped
peds 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
54	 Keys to Soil Taxonomy
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) particles 2.0 mm or
larger in diameter, 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
meets one of the following:
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:
1.  Have an argillic, kandic, or natric horizon that is 35 cm
or less thick; and
2.  Do not have a densic, lithic, or paralithic contact within
100 cm of the mineral soil surface.
Inceptic Haplocryalfs
JBCJ.  Other Haplocryalfs that have all of the following:
1.  A xeric soil moisture regime; and
2.  A color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 18 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 18 cm after mixing; and
3.  A base saturation (by NH4
OAc) of 50 percent ormore
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 both:
1.  A xeric soil moisture regime; and
2.  A color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 18 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 18 cm after mixing.
Umbric Xeric Haplocryalfs
JBCL.  Other Haplocryalfs that meet all of the following:
1.  Are dry in some part of the moisture control section for
45 or more days (cumulative) in normal years; and
2.  Have a color value, moist, of 3 or less and a color value,
dry, of 5 or less (crushed and smoothed sample) either
throughout the upper 18 cm of the mineral soil (unmixed) or
between the mineral soil surface and a depth of 18 cm after
mixing; and
3.  Have a base saturation (by NH4
OAc) of 50 percent or
more 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 soil moisture
regime.
Xeric Haplocryalfs
Alfisols	 55
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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 have both:
1.  A color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 18 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 18 cm after mixing; and
2.  A base saturation (by NH4
OAc) of 50 percent ormore
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 a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 18 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 18 cm after mixing.
Umbric Haplocryalfs
JBCQ.  Other Haplocryalfs that have a base saturation (by
NH4
OAc) of 50 percent ormore 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
Palecryalfs
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) particles 2.0 mm or
larger in diameter, 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 soil 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 have both:
1.  A color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 18 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 18 cm after mixing; and
2.  A base saturation (by NH4
OAc) of 50 percent ormore
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 a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 18 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 18 cm after mixing.
Umbric Palecryalfs
JBAI.  Other Palecryalfs.
Typic Palecryalfs
56	 Keys to Soil Taxonomy
Udalfs
Key to Great Groups
JEA.  Udalfs that have a natric horizon.
Natrudalfs, p. 64
JEB.  Other Udalfs that have both:
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. 57
JEC.  Other Udalfs that have both:
1.  A glossic horizon; and
2.  A fragipan within 100 cm of the mineral soil surface.
Fraglossudalfs, p. 57
JED.  Other Udalfs that have a fragipan within 100 cm of the
mineral soil surface.
Fragiudalfs, p. 57
JEE.  Other Udalfs that meet all of the following:
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 is 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. 63
JEF.  Other Udalfs that have a kandic horizon.
Kanhapludalfs, p. 64
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 is 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 soil 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 class 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. 65
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. 67
Alfisols	 57
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JEI.  Other Udalfs that have a glossic horizon.
Glossudalfs, p. 58
JEJ.  Other Udalfs.
Hapludalfs, p. 59
Ferrudalfs
Key to Subgroups
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
Fragiudalfs
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) particles 2.0 mm or
larger in diameter, 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
JEDE.  Other Fragiudalfs.
Typic Fragiudalfs
Fraglossudalfs
Key to Subgroups
JECA.  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, 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) particles 2.0 mm or
larger in diameter, 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
58	 Keys to Soil Taxonomy
JECE.  Other Fraglossudalfs.
Typic Fraglossudalfs
Glossudalfs
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 peds 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 peds 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 wedgeshaped
peds 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
b.  More than 35 percent (by volume) particles 2.0 mm
or larger in diameter, 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) particles 2.0 mm or
Alfisols	 59
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larger in diameter, 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:
1.  In one or more subhorizons within 75 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); and
2.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand throughout a layer extending from the mineral soil
surface to the top of the argillic horizon at a depth of 50 cm
or more below the mineral soil surface.
Aquic Arenic Glossudalfs
JEII.  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
JEIJ.  Other Glossudalfs 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 a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand throughout a layer extending from the mineral soil
surface to the top of the argillic horizon at a depth of 50 cm
or more below the mineral soil surface.
Arenic Oxyaquic Glossudalfs
JEIK.  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
JEIL.  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
JEIM.  Other Glossudalfs that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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
JEIN.  Other Glossudalfs that have a glossic horizon less than
50 cm in total thickness.
Haplic Glossudalfs
JEIO.  Other Glossudalfs.
Typic Glossudalfs
Hapludalfs
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:
60	 Keys to 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 peds 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 peds 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 peds 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 peds 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 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
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for some time in normal years and slickensides or wedgeshaped
peds 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) particles 2.0 mm or
larger in diameter, 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:
1.  In one or more horizons within 75 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); and
2.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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:
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 a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand throughout a layer extending from the mineral soil
surface to the top of the argillic horizon at a depth of 50 cm
or more below the mineral soil surface.
Arenic Oxyaquic Hapludalfs
JEJM.  Other Hapludalfs that have anthraquic conditions.
Anthraquic Hapludalfs
JEJN.  Other Hapludalfs that have all of the following:
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:
62	 Keys to Soil Taxonomy
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.  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
JEJO.  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
JEJP.  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
JEJQ.  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
JEJR.  Other Hapludalfs that have both:
1.  A color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 18 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 18 cm 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
JEJS.  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
JEJT.  Other Hapludalfs that have both:
1.  A mollic epipedon, or the upper 18 cm of the mineral
soil meets the color requirements for a mollic epipedon after
mixing; and
2.  Saturation with water in 1 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.
Mollic Oxyaquic Hapludalfs
JEJU.  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:
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1.  20 or more consecutive days; or
2.  30 or more cumulative days.
Oxyaquic Hapludalfs
JEJV.  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
JEJW.  Other Hapludalfs that have an argillic horizon that
meets one of the following:
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
JEJX.  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
JEJY.  Other Hapludalfs that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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
JEJZ.  Other Hapludalfs that have interfingering of albic
materials in one or more subhorizons of the argillic horizon.
Glossic Hapludalfs
JEJZa.  Other Hapludalfs that:
1.  Have an argillic horizon that is 35 cm or less thick; and
2.  Do not have a densic, lithic, or paralithic contact within
100 cm of the mineral soil surface.
Inceptic Hapludalfs
JEJZb.  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
JEJZc.  Other Hapludalfs that have a mollic epipedon, or the
upper 18 cm of the mineral soil meets all the color requirements
for a mollic epipedon after mixing.
Mollic Hapludalfs
JEJZd.  Other Hapludalfs.
Typic Hapludalfs
Kandiudalfs
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:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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
64	 Keys to Soil Taxonomy
2.  Have 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:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  Have 5 percent or more (by volume) plinthite in one or
more horizons within 150 cm of the mineral soil surface.
Grossarenic Plinthic Kandiudalfs
JEEF.  Other Kandiudalfs that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 75 cm of the kandic horizon or throughout the entire
kandic horizon if 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.  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, or the
upper 18 cm of the mineral soil meets the color requirements for
a mollic epipedon after mixing.
Mollic Kandiudalfs
JEEK.  Other Kandiudalfs.
Typic Kandiudalfs
Kanhapludalfs
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 50 cm of the kandic horizon or throughout the entire
kandic horizon if 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.  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
Natrudalfs
Key to Subgroups
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 peds 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
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JEAB.  Other Natrudalfs that have both:
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
Paleudalfs
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 wedgeshaped
peds 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
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) particles 2.0 mm or
larger in diameter, 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 anthraquic conditions.
Anthraquic Paleudalfs
JEGE.  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
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.  5 percent or more (by volume) plinthite in one or more
horizons within 150 cm of the mineral soil surface.
Plinthaquic 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
66	 Keys to Soil Taxonomy
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
JEGH.  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
JEGI.  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
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
JEGL.  Other Paleudalfs that:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  Have 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:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  Have 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
meets one of the following:
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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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
Alfisols	 67
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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 75 cm of the argillic horizon or throughout the entire
argillic horizon if 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.  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, or the
upper 18 cm of the mineral soil meets the color requirements for
a mollic epipedon after mixing.
Mollic Paleudalfs
JEGV.  Other Paleudalfs.
Typic Paleudalfs
Rhodudalfs
Key to Subgroups
JEHA.  All Rhodudalfs (provisionally).
Typic Rhodudalfs
Ustalfs
Key to Great Groups
JCA.  Ustalfs that have a duripan within 100 cm of the mineral
soil surface.
Durustalfs, p. 68
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. 79
JCC.  Other Ustalfs that have a natric horizon.
Natrustalfs, p. 73
JCD.  Other Ustalfs that meet all of the following:
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 is 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. 71
JCE.  Other Ustalfs that have a kandic horizon.
Kanhaplustalfs, p. 73
JCF.  Other Ustalfs that have one or more of the following:
1.  A petrocalcic horizon 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 is
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
35 percent or more noncarbonate clay throughout one or
68	 Keys to Soil Taxonomy
more subhorizons in its upper part, and one or both of the
following:
a.  At its upper boundary, a clay increase of 20 percent or
more (absolute, in the fine-earth fraction) within a vertical
distance of 7.5 cm or of 15 percent or more (absolute, in
the fine-earth fraction) within a vertical distance of 2.5
cm; or
b.  An abrupt textural change between the eluvial
horizon and the upper boundary of the argillic horizon.
Paleustalfs, p. 76
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. 79
JCH.  Other Ustalfs.
Haplustalfs, p. 68
Durustalfs
Key to Subgroups
JCAA.  All Durustalfs (provisionally).
Typic Durustalfs
Haplustalfs
Key to Subgroups
JCHA.  Haplustalfs that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Haplustalfs
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 peds 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 peds 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 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 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 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
Alfisols	 69
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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 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 peds 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 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 less 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
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 peds 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 Haplustalfs
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 wedgeshaped
peds 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:
1.  In one or more horizons within 75 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); and
2.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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) particles 2.0 mm or
larger in diameter, 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
70	 Keys to Soil Taxonomy
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
meets one of the following:
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:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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,
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
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 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 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.
Arenic Aridic Haplustalfs
JCHO.  Other Haplustalfs that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 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 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.
Calcidic Haplustalfs
JCHQ.  Other Haplustalfs 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 soil
Alfisols	 71
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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 soil 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:
1.  Have an argillic horizon that is 35 cm or less thick; and
2.  Do not have a 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 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 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
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 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 dry in some or all parts for less 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.
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 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 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 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
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 soil temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C.
Udic Haplustalfs
JCHX.  Other Haplustalfs.
Typic Haplustalfs
Kandiustalfs
Key to Subgroups
JCDA.  Kandiustalfs that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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:
1.  In one or more horizons within 75 cm of the mineral
soil surface, have redox depletions with chroma of 2 or less
72	 Keys to Soil Taxonomy
and also aquic conditions for some time in normal years (or
artificial drainage); and
2.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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
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:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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,
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 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 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.
Arenic Aridic Kandiustalfs
JCDF.  Other Kandiustalfs that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 soil 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 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 less 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 Kandiustalfs
JCDI.  Other Kandiustalfs that have, in all subhorizons in
the upper 75 cm of the kandic horizon or throughout the entire
kandic horizon if 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.  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
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Kanhaplustalfs
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 soil 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 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 less 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 Kanhaplustalfs
JCEE.  Other Kanhaplustalfs that have, in all subhorizons in
the upper 50 cm of the kandic horizon or throughout the entire
kandic horizon if 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.  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
Natrustalfs
Key to Subgroups
JCCA.  Natrustalfs that have a salic horizon 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 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 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 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 peds in a layer 15 cm or more thick that
74	 Keys to Soil Taxonomy
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 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 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 peds 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 peds 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 Natrustalfs
JCCE.  Other Natrustalfs that have both of the following:
1.  Visible crystals of gypsum or 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 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 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
Alfisols	 75
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for some time in normal years and slickensides or wedgeshaped
peds 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:
1.  In one or more horizons within 75 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); and
2.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 within
150 cm of the mineral soil surface.
Petrocalcic Natrustalfs
JCCK.  Other Natrustalfs that have visible crystals of gypsum
or 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 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 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 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.
Haplargidic Natrustalfs
JCCM.  Other Natrustalfs 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 soil temperature at a depth of 50 cm below the soil
surface is higher than 5 °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 °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 soil temperature at
a depth of 50 cm below the soil surface is higher than
8 °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 °C; and
2.  A glossic horizon or interfingering of albic materials into
the natric horizon.
Aridic Glossic Natrustalfs
76	 Keys to Soil Taxonomy
JCCN.  Other Natrustalfs 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 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 soil 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
JCCO.  Other Natrustalfs that have a mollic epipedon, or the
upper 18 cm of the mineral soil meets the color requirements for
a mollic epipedon after mixing.
Mollic Natrustalfs
JCCP.  Other Natrustalfs.
Typic Natrustalfs
Paleustalfs
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 peds 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 peds 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 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 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 less 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
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 peds 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
Alfisols	 77
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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 wedgeshaped
peds 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:
1.  In one or more horizons within 75 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); and
2.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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
meets one of the following:
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
JCFJ.  Other Paleustalfs that:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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,
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
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
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 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.
Arenic Aridic Paleustalfs
JCFK.  Other Paleustalfs that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
78	 Keys to Soil Taxonomy
loamy sand, or loamy fine sand 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 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 soil 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
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 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; 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 free
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 soil 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 soil 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 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 75 cm of the argillic horizon or throughout the entire
argillic horizon if 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.  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 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
Alfisols	 79
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normal years is dry in some or all parts for less 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 Paleustalfs
JCFU.  Other Paleustalfs.
Typic Paleustalfs
Plinthustalfs
Key to Subgroups
JCBA.  All Plinthustalfs (provisionally).
Typic Plinthustalfs
Rhodustalfs
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
either of the argillic horizon if less than 100 cm thick or of its
upper 100 cm.
Kanhaplic Rhodustalfs
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 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 less 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 Rhodustalfs
JCGD.  Other Rhodustalfs.
Typic Rhodustalfs
Xeralfs
Key to Great Groups
JDA.  Xeralfs that have a duripan within 100 cm of the mineral
soil surface.
Durixeralfs, p. 80
JDB.  Other Xeralfs that have a natric horizon.
Natrixeralfs, p. 83
JDC.  Other Xeralfs that have a fragipan within 100 cm of the
mineral soil surface.
Fragixeralfs, p. 80
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. 84
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. 85
JDF.  Other Xeralfs that have one or more of the following:
1.  A petrocalcic horizon 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 is
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 35 percent or more noncarbonate clay throughout one or
more subhorizons in its upper part, and one or both of the
following:
a.  A clay increase of 20 percent or more (absolute, in the
fine-earth fraction) within a vertical distance of 7.5 cm or
of 15 percent or more (absolute, in the fine-earth fraction)
80	 Keys to Soil Taxonomy
within a vertical distance of 2.5 cm, either within the
argillic or kandic horizon or at its upper boundary; or
b.  An abrupt textural change between the eluvial
horizon and the upper boundary of the argillic or kandic
horizon.
Palexeralfs, p. 83
JDG.  Other Xeralfs.
Haploxeralfs, p. 81
Durixeralfs
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 peds 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 35 percent or more
noncarbonate clay throughout one or more subhorizons
totaling 7.5 cm or more thick, and one or both of the
following:
a.  A clay increase of 20 percent or more (absolute, in the
fine-earth fraction) within a vertical distance of 7.5 cm or
of 15 percent or more (absolute, in the fine-earth fraction)
within a vertical distance of 2.5 cm, either within the
argillic horizon or at its upper boundary; or
b.  An abrupt textural change between the eluvial horizon
and the upper boundary of the argillic horizon; 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
35 percent or more noncarbonate clay throughout one or more
subhorizons totaling 7.5 cm or more thick, and one or both of
the following:
1.  A clay increase of 20 percent or more (absolute, in the
fine-earth fraction) within a vertical distance of 7.5 cm or
of 15 percent or more (absolute, in the fine-earth fraction)
within a vertical distance of 2.5 cm, either within the argillic
horizon or at its upper boundary; or
2.  An abrupt textural change between the eluvial horizon
and the upper boundary of the argillic horizon.
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
Fragixeralfs
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) particles 2.0 mm or
larger in diameter, 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 Fragixeralfs
JDCC.  Other Fragixeralfs that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 18 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 18 cm after mixing.
Mollic Fragixeralfs
Alfisols	 81
A
L
F
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
Haploxeralfs
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 more
for some time in normal years and slickensides or wedgeshaped
peds 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) particles 2.0 mm
or larger in diameter, 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) particles 2.0 mm or
larger in diameter, 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
82	 Keys to Soil Taxonomy
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:
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
meets one of the following:
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 within
100 cm of the mineral soil surface.
Calcic Haploxeralfs
JDGQ.  Other Haploxeralfs that:
1.  Have an argillic or kandic horizon that is 35 cm or less
thick; and
2.  Do not have a 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
the upper 10 cm of the mineral soil (unmixed) or throughout the
upper 18 cm of the mineral soil after mixing.
Mollic Haploxeralfs
JDGT.  Other Haploxeralfs.
Typic Haploxeralfs
Alfisols	 83
A
L
F
Natrixeralfs
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 wedgeshaped
peds 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
Palexeralfs
Key to Subgroups
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 wedgeshaped
peds 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) particles 2.0 mm
or larger in diameter, 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) particles 2.0 mm or
larger in diameter, 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
84	 Keys to Soil Taxonomy
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
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
within 150 cm of the mineral soil surface.
Petrocalcic Palexeralfs
JDFH.  Other Palexeralfs that have an argillic horizon that
meets one of the following:
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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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, 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, in the fine-earth fraction) within a
vertical distance of 7.5 cm and of less than 15 percent
(absolute, in the fine-earth fraction) 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
the upper 10 cm of the mineral soil (unmixed) or throughout the
upper 18 cm of the mineral soil after mixing.
Mollic Palexeralfs
JDFR.  Other Palexeralfs.
Typic Palexeralfs
Plinthoxeralfs
Key to Subgroups
JDDA.  All Plinthoxeralfs (provisionally).
Typic Plinthoxeralfs
Alfisols	 85
A
L
F
Rhodoxeralfs
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 peds 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
JDEC.  Other Rhodoxeralfs that have a petrocalcic horizon
within 150 cm of the mineral soil surface.
Petrocalcic Rhodoxeralfs
JDED.  Other Rhodoxeralfs that have a calcic horizon 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 35 cm thick or is discontinuous
horizontally in each pedon.
Inceptic Rhodoxeralfs
JDEF.  Other Rhodoxeralfs.
Typic Rhodoxeralfs
	 87
A
N
D
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. 87
DB.  Other Andisols that have a gelic soil temperature regime.
Gelands, p. 94
DC.  Other Andisols that have a cryic soil temperature regime.
Cryands, p. 90
DD.  Other Andisols that have an aridic soil moisture regime.
Torrands, p. 94
DE.  Other Andisols that have a xeric soil moisture regime.
Xerands, p. 105
DF.  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 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 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. 103
DG.  Other Andisols that have an ustic soil moisture regime.
Ustands, p. 102
DH.  Other Andisols.
Udands, p. 95
Aquands
Key to Great Groups
DAA.  Aquands that have a gelic soil temperature regime.
Gelaquands, p. 89
DAB.  Other Aquands that have a cryic soil temperature
regime.
Cryaquands, p. 88
DAC.  Other Aquands that have, in half or more of each
pedon, a placic horizon within 100 cm of the mineral soil
surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Placaquands, p. 90
DAD.  Other Aquands that have, in 75 percent or more of
each pedon, a cemented horizon within 100 cm of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Duraquands, p. 88
DAE.  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 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 the mineral soil surface or the top of an organic
Andisols
CHAPTER 6
88	 Keys to Soil Taxonomy
layer with andic soil properties, whichever is shallower, and
a densic, lithic, or paralithic contact.
Vitraquands, p. 90
DAF.  Other Aquands that have a melanic epipedon.
Melanaquands, p. 89
DAG.  Other Aquands that have episaturation.
Epiaquands, p. 89
DAH.  Other Aquands.
Endoaquands, p. 88
Cryaquands
Key to Subgroups
DABA.  Cryaquands 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 Cryaquands
DABB.  Other Cryaquands that have a histic epipedon.
Histic Cryaquands
DABC.  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
DABD.  Other Cryaquands.
Typic Cryaquands
Duraquands
Key to Subgroups
DADA.  Duraquands that have a histic epipedon.
Histic Duraquands
DADB.  Other Duraquands that have a sum of 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
DADC.  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
DADD.  Other Duraquands.
Typic Duraquands
Endoaquands
Key to Subgroups
DAHA.  Endoaquands 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 Endoaquands
DAHB.  Other Endoaquands that have a horizon 15 cm or
more thick that has 20 percent or more (by volume) cemented
soil material within 100 cm of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Duric Endoaquands
DAHC.  Other Endoaquands that have a histic epipedon.
Histic Endoaquands
DAHD.  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.
Alic Endoaquands
DAHE.  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 of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Hydric Endoaquands
DAHF.  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
Andisols	 89
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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
DAHG.  Other Endoaquands.
Typic Endoaquands
Epiaquands
Key to Subgroups
DAGA.  Epiaquands that have a horizon 15 cm or more thick
that has 20 percent or more (by volume) cemented soil material
within 100 cm of the mineral soil surface or of the top of an
organic layer with andic soil properties, whichever is shallower.
Duric Epiaquands
DAGB.  Other Epiaquands that have a histic epipedon.
Histic Epiaquands
DAGC.  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.
Alic Epiaquands
DAGD.  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 of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Hydric Epiaquands
DAGE.  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
DAGF.  Other Epiaquands.
Typic Epiaquands
Gelaquands
Key to Subgroups
DAAA.  Gelaquands that have a histic epipedon.
Histic Gelaquands
DAAB.  Other Gelaquands that have gelic materials within
200 cm of the mineral soil surface.
Turbic Gelaquands
DAAC.  Other Gelaquands 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 Gelaquands
DAAD.  Other Gelaquands.
Typic Gelaquands
Melanaquands
Key to Subgroups
DAFA.  Melanaquands 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 Melanaquands
DAFB.  Other Melanaquands that have a sum of 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
DAFC.  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 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 of the mineral soil surface or of the top of
an organic layer with andic soil properties, whichever is
shallower.
Hydric Pachic Melanaquands
DAFD.  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 of the mineral
90	 Keys to Soil Taxonomy
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Hydric Melanaquands
DAFE.  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 of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Pachic Melanaquands
DAFF.  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
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 Melanaquands
DAFG.  Other Melanaquands.
Typic Melanaquands
Placaquands
Key to Subgroups
DACA.  Placaquands 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 Placaquands
DACB.  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 within 100 cm of
the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower.
Duric Histic Placaquands
DACC.  Other Placaquands that have a horizon 15 cm or more
thick that has 20 percent or more (by volume) cemented soil
material within 100 cm of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Duric Placaquands
DACD.  Other Placaquands that have a histic epipedon.
Histic Placaquands
DACE.  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
DACF.  Other Placaquands.
Typic Placaquands
Vitraquands
Key to Subgroups
DAEA.  Vitraquands 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 Vitraquands
DAEB.  Other Vitraquands that have a horizon 15 cm or more
thick that has 20 percent or more (by volume) cemented soil
material within 100 cm of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Duric Vitraquands
DAEC.  Other Vitraquands that have a histic epipedon.
Histic Vitraquands
DAED.  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.
Thaptic Vitraquands
DAEE.  Other Vitraquands.
Typic Vitraquands
Cryands
Key to Great Groups
DCA.  Cryands that have, in 75 percent or more of each pedon,
a cemented horizon within 100 cm of the mineral soil surface
or of the top of an organic layer with andic soil properties,
whichever is shallower.
Duricryands, p. 91
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DCB.  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 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. 93
DCC.  Other Cryands that have a melanic epipedon.
Melanocryands, p. 93
DCD.  Other Cryands that have a layer that meets the depth,
thickness, and organic-carbon requirements for a melanic
epipedon.
Fulvicryands, p. 91
DCE.  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 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 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. 93
DCF.  Other Cryands.
Haplocryands, p. 92
Duricryands
Key to Subgroups
DCAA.  Duricryands 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 Duricryands
DCAB.  Other Duricryands 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 properties, whichever is shallower; and
2.  Saturation with water in one or more layers above the
cemented horizon in normal years for either or both:
a.  20 or more consecutive days; or
b.  30 or more cumulative days.
Eutric Oxyaquic Duricryands
DCAC.  Other Duricryands that are saturated with water in one
or more layers above the cemented horizon in normal years for
either or both:
1.  20 or more consecutive days; or
2.  30 or more cumulative days.
Oxyaquic Duricryands
DCAD.  Other Duricryands 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 properties, whichever is
shallower.
Eutric Duricryands
DCAE.  Other Duricryands.
Typic Duricryands
Fulvicryands
Key to Subgroups
DCDA.  Fulvicryands 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 Fulvicryands
DCDB.  Fulvicryands that have a folistic epipedon.
Folistic Fulvicryands
DCDC.  Other Fulvicryands that have both:
92	 Keys to Soil Taxonomy
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 properties, whichever is shallower; and
2.  Throughout a layer 50 cm or more thick within 60 cm of
the mineral soil surface or of the top of an organic layer with
andic 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 Fulvicryands
DCDD.  Other Fulvicryands 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 properties, whichever is
shallower.
Eutric Fulvicryands
DCDE.  Other Fulvicryands that have, throughout a layer 50
cm or more thick within 60 cm 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 Fulvicryands
DCDF.  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 of the mineral soil surface or of
the top of an organic layer with andic soil properties, whichever
is shallower.
Vitric Fulvicryands
DCDG.  Other Fulvicryands.
Typic Fulvicryands
Haplocryands
Key to Subgroups
DCFA.  Haplocryands 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 Haplocryands
DCFB.  Other Haplocryands that have a folistic epipedon.
Folistic Haplocryands
DCFC.  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
DCFD.  Other Haplocryands that are saturated with water
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 Haplocryands
DCFE.  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
DCFF.  Other Haplocryands that have an albic horizon
overlying a cambic horizon in 50 percent or more of each pedon
or have a spodic horizon in 50 percent or more of each pedon.
Spodic Haplocryands
DCFG.  Other Haplocryands that have a sum of 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
DCFH.  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
Andisols	 93
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of 25 cm or more within 100 cm of the mineral soil surface or of
the top of an organic layer with andic soil properties, whichever
is shallower.
Vitric Haplocryands
DCFI.  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
DCFJ.  Other Haplocryands that have a xeric soil moisture
regime.
Xeric Haplocryands
DCFK.  Other Haplocryands.
Typic Haplocryands
Hydrocryands
Key to Subgroups
DCBA.  Hydrocryands 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 Hydrocryands
DCBB.  Other Hydrocryands that have a placic horizon
within 100 cm of the mineral soil surface or of the top of an
organic layer with andic soil properties, whichever is shallower.
Placic Hydrocryands
DCBC.  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
DCBD.  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
DCBE.  Other Hydrocryands.
Typic Hydrocryands
Melanocryands
Key to Subgroups
DCCA.  Melanocryands that have a lithic contact within 50 cm
of the mineral soil surface or of the top of an organic layer that
has andic soil properties, whichever is shallower.
Lithic Melanocryands
DCCB.  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 of the mineral soil surface or of
the top of an organic layer with andic soil properties, whichever
is shallower.
Vitric Melanocryands
DCCC.  Other Melanocryands.
Typic Melanocryands
Vitricryands
Key to Subgroups
DCEA.  Vitricryands that have a lithic contact within 50 cm of
the mineral soil surface or of the top of an organic layer that has
andic soil properties, whichever is shallower.
Lithic Vitricryands
DCEB.  Other Vitricryands that have a folistic epipedon.
Folistic Vitricryands
DCEC.  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
94	 Keys to 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
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
DCED.  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
DCEE.  Other Vitricryands that have an albic horizon
overlying a cambic horizon in 50 percent or more of each pedon
or have a spodic horizon in 50 percent or more of each pedon.
Spodic Vitricryands
DCEF.  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
DCEG.  Other Vitricryands that have a xeric soil moisture
regime and a mollic or umbric epipedon.
Humic Xeric Vitricryands
DCEH.  Other Vitricryands that have a xeric soil moisture
regime.
Xeric Vitricryands
DCEI.  Other Vitricryands that have both:
1.  An argillic or kandic horizon 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 the upper 50 cm or throughout the entire
argillic or kandic horizon if it is less than 50 cm thick.
Ultic Vitricryands
DCEJ.  Other Vitricryands that have an argillic or kandic
horizon within 125 cm of the mineral soil surface or of the top
of an organic layer with andic soil properties, whichever is
shallower.
Alfic Vitricryands
DCEK.  Other Vitricryands that have a mollic or umbric
epipedon.
Humic Vitricryands
DCEL.  Other Vitricryands.
Typic Vitricryands
Gelands
Key to Great Groups
DBA.  All Gelands are considered Vitrigelands.
Vitrigelands, p. 94
Key to Subgroups
DBAA.  Vitrigelands that have a mollic or umbric epipedon.
Humic Vitrigelands
DBAB.  Other Vitrigelands that have gelic materials within
200 cm of the mineral soil surface.
Turbic Vitrigelands
DBAC.  Other Vitrigelands.
Typic Vitrigelands
Torrands
Key to Great Groups
DDA.  Torrands that have, in 75 percent or more of each
pedon, a cemented horizon within 100 cm of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Duritorrands, p. 95
DDB.  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 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 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. 95
DDC.  Other Torrands.
Haplotorrands, p. 95
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Duritorrands
Key to Subgroups
DDAA.  Duritorrands that have a petrocalcic horizon within
100 cm of the mineral soil surface.
Petrocalcic Duritorrands
DDAB.  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 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 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
DDAC.  Other Duritorrands.
Typic Duritorrands
Haplotorrands
Key to Subgroups
DDCA.  Haplotorrands that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Haplotorrands
DDCB.  Other Haplotorrands that have a horizon 15 cm or
more thick that has 20 percent or more (by volume) cemented
soil material within 100 cm of the mineral soil surface.
Duric Haplotorrands
DDCC.  Other Haplotorrands that have a calcic horizon within
125 cm of the mineral soil surface.
Calcic Haplotorrands
DDCD.  Other Haplotorrands.
Typic Haplotorrands
Vitritorrands
Key to Subgroups
DDBA.  Vitritorrands that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Vitritorrands
DDBB.  Other Vitritorrands that have a horizon 15 cm or more
thick that has 20 percent or more (by volume) cemented soil
material within 100 cm of the mineral soil surface.
Duric Vitritorrands
DDBC.  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
DDBD.  Other Vitritorrands that have a calcic horizon within
125 cm of the mineral soil surface.
Calcic Vitritorrands
DDBE.  Other Vitritorrands.
Typic Vitritorrands
Udands
Key to Great Groups
DHA.  Udands that have, in half or more of each pedon, a
placic horizon within 100 cm of the mineral soil surface or of
the top of an organic layer with andic soil properties, whichever
is shallower.
Placudands, p. 102
DHB.  Other Udands that have, in 75 percent or more of
each pedon, a cemented horizon within 100 cm of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Durudands, p. 96
DHC.  Other Udands that have a melanic epipedon.
Melanudands, p. 100
DHD.  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 the
mineral soil surface or the top of an organic layer with andic
96	 Keys to Soil Taxonomy
soil properties, whichever is shallower, and a densic, lithic,
or paralithic contact, a duripan, or a petrocalcic horizon.
Hydrudands, p. 99
DHE.  Other Udands that have a layer that meets the depth,
thickness, and organic-carbon requirements for a melanic
epipedon.
Fulvudands, p. 96
DHF.  Other Udands.
Hapludands, p. 97
Durudands
Key to Subgroups
DHBA.  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 alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquic Durudands
DHBB.  Other Durudands 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 properties, whichever is
shallower.
Eutric Durudands
DHBC.  Other Durudands that have a sum of 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
DHBD.  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
DHBE.  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 of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Pachic Durudands
DHBF.  Other Durudands.
Typic Durudands
Fulvudands
Key to Subgroups
DHEA.  Fulvudands that have both:
1.  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; 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
DHEB.  Other Fulvudands 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 Fulvudands
DHEC.  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
DHED.  Other Fulvudands that are saturated with water 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 Fulvudands
DHEE.  Other Fulvudands that have, on undried samples, a
1500 kPa water retention of 70 percent or more throughout
Andisols	 97
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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.
Hydric Fulvudands
DHEF.  Other Fulvudands that have a sum of 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
DHEG.  Other Fulvudands that have both:
1.  An argillic or kandic horizon 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 the upper 50 cm of the argillic or kandic
horizon.
Ultic Fulvudands
DHEH.  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 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
DHEI.  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
DHEJ.  Other Fulvudands that have, throughout a layer 50 cm
or more thick within 60 cm 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
DHEK.  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
DHEL.  Other Fulvudands.
Typic Fulvudands
Hapludands
Key to Subgroups
DHFA.  Hapludands 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 Hapludands
DHFB.  Other Hapludands that have anthraquic conditions.
Anthraquic Hapludands
DHFC.  Other Hapludands that have both:
1.  A horizon 15 cm or more thick that has 20 percent or
more (by volume) cemented soil material within 100 cm 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
DHFD.  Other Hapludands that have a horizon 15 cm or more
98	 Keys to Soil Taxonomy
thick that has 20 percent or more (by volume) cemented soil
material within 100 cm of the mineral soil surface or of the
top of an organic layer with andic soil properties, whichever is
shallower.
Duric Hapludands
DHFE.  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
DHFF.  Other Hapludands that are saturated with water 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 Hapludands
DHFG.  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
DHFH.  Other Hapludands that have both:
1.  A sum of extractable bases (by NH4
OAc) 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; 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 of the mineral soil surface or of the top of
an organic layer with andic soil properties, whichever is
shallower.
Acrudoxic Hydric Hapludands
DHFI.  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.  A sum of extractable bases (by NH4
OAc) 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; 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
DHFJ.  Other Hapludands that have both:
1.  A sum of extractable bases (by NH4
OAc) 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; and
2.  An argillic or kandic horizon that has both:
a.  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
b.  A base saturation (by sum of cations) of less than 35
percent throughout its upper 50 cm.
Acrudoxic Ultic Hapludands
DHFK.  Other Hapludands that have a sum of 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
DHFL.  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 of the mineral soil surface or of
the top of an organic layer with andic soil properties, whichever
is shallower.
Vitric Hapludands
DHFM.  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
Andisols	 99
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within 100 cm 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
DHFN.  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 of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Hydric Hapludands
DHFO.  Other Hapludands that have both:
1.  A sum of extractable bases (by NH4
OAc) 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 more
that have a color value, moist, 1 unit or more higher and an
organic-carbon content 1 percent or more (absolute) lower.
Eutric Thaptic Hapludands
DHFP.  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
DHFQ.  Other Hapludands that have a sum of extractable
bases (by NH4
OAc) 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
DHFR.  Other Hapludands that have an oxic horizon within
125 cm of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Oxic Hapludands
DHFS.  Other Hapludands that have both:
1.  An argillic or kandic horizon 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 the upper 50 cm of the argillic or kandic
horizon.
Ultic Hapludands
DHFT.  Other Hapludands that have an argillic or kandic
horizon within 125 cm of the mineral soil surface or of the top
of an organic layer with andic soil properties, whichever is
shallower.
Alfic Hapludands
DHFU.  Other Hapludands.
Typic Hapludands
Hydrudands
Key to Subgroups
DHDA.  Hydrudands 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 Hydrudands
DHDB.  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
DHDC.  Other Hydrudands that have, at a depth between 25
100	 Keys to Soil Taxonomy
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.  A sum of extractable bases (by NH4
OAc) 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; 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
DHDD.  Other Hydrudands that have a sum of 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
DHDE.  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
DHDF.  Other Hydrudands that have a sum of extractable
bases (by NH4
OAc) 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 Hydrudands
DHDG.  Other Hydrudands that have both:
1.  An argillic or kandic horizon 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 the upper 50 cm of the argillic or kandic
horizon.
Ultic Hydrudands
DHDH.  Other Hydrudands.
Typic Hydrudands
Melanudands
Key to Subgroups
DHCA.  Melanudands that have a lithic contact within 50 cm
of the mineral soil surface or of the top of an organic layer that
has andic soil properties, whichever is shallower.
Lithic Melanudands
DHCB.  Other Melanudands that have anthraquic conditions.
Anthraquic Melanudands
DHCC.  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
DHCD.  Other Melanudands that have both:
1.  A sum of extractable bases (by NH4
OAc) 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; 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 of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Acrudoxic Vitric Melanudands
DHCE.  Other Melanudands that have both:
1.  A sum of 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
Andisols	 101
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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 of the mineral soil surface or of the top of
an organic layer with andic soil properties, whichever is
shallower.
Acrudoxic Hydric Melanudands
DHCF.  Other Melanudands that have a sum of 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
DHCG.  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 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 of the mineral soil surface or of the top of
an organic layer with andic soil properties, whichever is
shallower.
Pachic Vitric Melanudands
DHCH.  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 of the mineral soil surface or of
the top of an organic layer with andic soil properties, whichever
is shallower.
Vitric Melanudands
DHCI.  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 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 of the mineral soil surface or of the top of
an organic layer with andic soil properties, whichever is
shallower.
Hydric Pachic Melanudands
DHCJ.  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 of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Pachic Melanudands
DHCK.  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 of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Hydric Melanudands
DHCL.  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
DHCM.  Other Melanudands that have both:
1.  An argillic or kandic horizon 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 the upper 50 cm of the argillic or kandic
horizon.
Ultic Melanudands
DHCN.  Other Melanudands that have a sum of extractable
bases (by NH4
OAc) of more than 25.0 cmol(+)/kg in the fineearth
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
DHCO.  Other Melanudands.
Typic Melanudands
102	 Keys to Soil Taxonomy
Placudands
Key to Subgroups
DHAA.  Placudands that have a lithic contact within 50 cm of
the mineral soil surface or of the top of an organic layer that has
andic soil properties, whichever is shallower.
Lithic Placudands
DHAB.  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
DHAC.  Other Placudands that have a sum of 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
DHAD.  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 of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Hydric Placudands
DHAE.  Other Placudands.
Typic Placudands
Ustands
Key to Great Groups
DGA.  Ustands that have, in 75 percent or more of each
pedon, a cemented horizon within 100 cm of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Durustands, p. 102
DGB.  Other Ustands.
Haplustands, p. 102
Durustands
Key to Subgroups
DGAA.  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
DGAB.  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
DGAC.  Other Durustands that have a melanic, mollic, or
umbric epipedon.
Humic Durustands
DGAD.  Other Durustands.
Typic Durustands
Haplustands
Key to Subgroups
DGBA.  Haplustands 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 Haplustands
DGBB.  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
Andisols	 103
A
N
D
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
DGBC.  Other Haplustands that have both:
1.  A sum of 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 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 of the mineral soil surface or of the top of
an organic layer with andic soil properties, whichever is
shallower.
Dystric Vitric Haplustands
DGBD.  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 of the mineral soil surface or of
the top of an organic layer with andic soil properties, whichever
is shallower.
Vitric Haplustands
DGBE.  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 of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Pachic Haplustands
DGBF.  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
DGBG.  Other Haplustands that have a calcic horizon within
125 cm of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Calcic Haplustands
DGBH.  Other Haplustands that have a sum of 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
DGBI.  Other Haplustands that have an oxic horizon within
125 cm of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.
Oxic Haplustands
DGBJ.  Other Haplustands that have both:
1.  An argillic or kandic horizon 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 the upper 50 cm or throughout the entire
argillic or kandic horizon if it is less than 50 cm thick.
Ultic Haplustands
DGBK.  Other Haplustands that have an argillic or kandic
horizon within 125 cm of the mineral soil surface or of the top
of an organic layer with andic soil properties, whichever is
shallower.
Alfic Haplustands
DGBL.  Other Haplustands that have a melanic, mollic, or
umbric epipedon.
Humic Haplustands
DGBM.  Other Haplustands.
Typic Haplustands
Vitrands
Key to Great Groups
DFA.  Vitrands that have an ustic soil moisture regime.
Ustivitrands, p. 104
104	 Keys to Soil Taxonomy
DFB.  Other Vitrands.
Udivitrands, p. 104
Udivitrands
Key to Subgroups
DFBA.  Udivitrands 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 Udivitrands
DFBB.  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
DFBC.  Other Udivitrands that are saturated with water 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 Udivitrands
DFBD.  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
DFBE.  Other Udivitrands that have both:
1.  An argillic or kandic horizon 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 the upper 50 cm of the argillic or kandic
horizon.
Ultic Udivitrands
DFBF.  Other Udivitrands that have an argillic or kandic
horizon within 125 cm of the mineral soil surface or of the top
of an organic layer with andic soil properties, whichever is
shallower.
Alfic Udivitrands
DFBG.  Other Udivitrands that have a melanic, mollic, or
umbric epipedon.
Humic Udivitrands
DFBH.  Other Udivitrands.
Typic Udivitrands
Ustivitrands
Key to Subgroups
DFAA.  Ustivitrands 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 Ustivitrands
DFAB.  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
DFAC.  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
DFAD.  Other Ustivitrands that have a calcic horizon within
Andisols	 105
A
N
D
125 cm of the soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower.
Calcic Ustivitrands
DFAE.  Other Ustivitrands that have a melanic, mollic, or
umbric epipedon.
Humic Ustivitrands
DFAF.  Other Ustivitrands.
Typic Ustivitrands
Xerands
Key to Great Groups
DEA.  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 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 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. 106
DEB.  Other Xerands that have a melanic epipedon.
Melanoxerands, p. 106
DEC.  Other Xerands.
Haploxerands, p. 105
Haploxerands
Key to Subgroups
DECA.  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
DECB.  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
DECC.  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
DECD.  Other Haploxerands that have a calcic horizon within
125 cm of the mineral soil surface.
Calcic Haploxerands
DECE.  Other Haploxerands that have both:
1.  An argillic or kandic horizon 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 the upper 50 cm of the argillic or kandic
horizon.
Ultic Haploxerands
DECF.  Other Haploxerands that have both:
1.  A mollic or umbric epipedon; and
2.  An argillic or kandic horizon 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
DECG.  Other Haploxerands that have an argillic or kandic
horizon 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
DECH.  Other Haploxerands that have a mollic or umbric
epipedon.
Humic Haploxerands
DECI.  Other Haploxerands.
Typic Haploxerands
106	
Melanoxerands
Key to Subgroups
DEBA.  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 of the mineral
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
Pachic Melanoxerands
DEBB.  Other Melanoxerands.
Typic Melanoxerands
Vitrixerands
Key to Subgroups
DEAA.  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
DEAB.  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
DEAC.  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
DEAD.  Other Vitrixerands that have both:
1.  A melanic, mollic, or umbric epipedon; and
2.  An argillic or kandic horizon 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
DEAE.  Other Vitrixerands that have both:
1.  An argillic or kandic horizon 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 the upper 50 cm or throughout the entire
argillic or kandic horizon if it is less than 50 cm thick.
Ultic Vitrixerands
DEAF.  Other Vitrixerands that have an argillic or kandic
horizon 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
DEAG.  Other Vitrixerands that have a melanic, mollic, or
umbric epipedon.
Humic Vitrixerands
DEAH.  Other Vitrixerands.
Typic Vitrixerands
	 107
A
R
I
Key to Suborders
GA.  Aridisols that have a cryic soil temperature regime.
Cryids, p. 122
GB.  Other Aridisols that have a salic horizon within 100 cm
of the soil surface.
Salids, p. 132
GC.  Other Aridisols that have a duripan within 100 cm of the
soil surface.
Durids, p. 126
GD.  Other Aridisols that have a gypsic or petrogypsic
horizon within 100 cm of the soil surface and do not have a
petrocalcic horizon overlying these horizons.
Gypsids, p. 129
GE.  Other Aridisols that have an argillic or natric horizon
and do not have a petrocalcic horizon within 100 cm of the soil
surface.
Argids, p. 107
GF.  Other Aridisols that have a calcic or petrocalcic horizon
within 100 cm of the soil surface.
Calcids, p. 116
GG.  Other Aridisols.
Cambids, p. 118
Argids
Key to Great Groups
GEA.  Argids that have a duripan or a petrocalcic or
petrogypsic horizon within 150 cm of the soil surface.
Petroargids, p. 115
GEB.  Other Argids that have a natric horizon.
Natrargids, p. 112
GEC.  Other Argids that do not have a densic, lithic, or
paralithic contact within 50 cm of the soil surface and have
either:
1.  An argillic horizon that has 35 percent or more
noncarbonate clay throughout one or more subhorizons in its
upper part, and one or both of the following:
a.  A clay increase of 15 percent or more (absolute, in
the fine-earth fraction) within a vertical distance of 2.5 cm
either within the argillic horizon or at its upper boundary;
or
b.  An abrupt textural change between the eluvial
horizon and the upper boundary of the argillic horizon; 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. 114
GED.  Other Argids that have a gypsic horizon within 150 cm
of the soil surface.
Gypsiargids, p. 109
GEE.  Other Argids that have a calcic horizon within 150 cm
of the soil surface.
Calciargids, p. 107
GEF.  Other Argids.
Haplargids, p. 110
Calciargids
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
Aridisols
CHAPTER 7
108	 Keys to Soil Taxonomy
for some time in normal years and slickensides or wedgeshaped
peds 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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher 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 wedgeshaped
peds 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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher 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 peds
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:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  Have a moisture control section that, in normal years,
is dry in all parts for less than three-fourths of the time
(cumulative) when the soil temperature at a depth of 50 cm
below the soil surface is 5 o
C or higher and a soil moisture
regime that borders on ustic.
Arenic Ustic Calciargids
GEEG.  Other Calciargids that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 both:
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and 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 ruptureresistance
class when moist.
Durinodic Calciargids
GEEJ.  Other Calciargids that have both:
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Petronodic Xeric Calciargids
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GEEK.  Other Calciargids that have both:
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on ustic.
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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) particles 2.0 mm or
larger in diameter, 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, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Calciargids
GEEP.  Other Calciargids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Calciargids
GEEQ.  Other Calciargids.
Typic Calciargids
Gypsiargids
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 ruptureresistance
class when moist.
Durinodic Gypsiargids
GEDC.  Other Gypsiargids that have both:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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
110	 Keys to 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 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) particles 2.0 mm or
larger in diameter, 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, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Gypsiargids
GEDF.  Other Gypsiargids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Gypsiargids
GEDG.  Other Gypsiargids.
Typic Gypsiargids
Haplargids
Key to Subgroups
GEFA.  Haplargids that have both:
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 both:
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 parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Lithic Xeric Haplargids
GEFC.  Other Haplargids that have both:
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 parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher 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 wedgeshaped
peds 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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher 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 peds 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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
Aridisols	 111
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soil surface is 5 o
C or higher 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
or more wide through a thickness of 30 cm or more for some
time in normal years and slickensides or wedge-shaped peds
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:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  Have a moisture control section that, in normal years,
is dry in all parts for less than three-fourths of the time
(cumulative) when the soil temperature at a depth of 50 cm
below the soil surface is 5 o
C or higher and a soil moisture
regime that borders on ustic.
Arenic Ustic Haplargids
GEFJ.  Other Haplargids that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 both:
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher 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 ruptureresistance
class when moist.
Durinodic Haplargids
GEFM.  Other Haplargids that have both:
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and 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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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
112	 Keys to Soil Taxonomy
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) particles 2.0 mm or
larger in diameter, 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, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Haplargids
GEFR.  Other Haplargids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Haplargids
GEFS.  Other Haplargids.
Typic Haplargids
Natrargids
Key to Subgroups
GEBA.  Natrargids that have both:
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 parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Lithic Xeric Natrargids
GEBB.  Other Natrargids that have both:
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 parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher 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:
1.  In normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric; and
2. Have 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 most years and slickensides or wedgeshaped
peds 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.
Xerertic Natrargids
GEBE.  Other Natrargids that:
1.  In normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic; and
2. Have 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 most years and slickensides or wedgeshaped
peds 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.
Ustertic Natrargids
GEBF.  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 peds
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
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GEBG.  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
GEBH.  Other Natrargids that have both:
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Durinodic Xeric Natrargids
GEBI.  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 ruptureresistance
class when moist.
Durinodic Natrargids
GEBJ.  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
GEBK.  Other Natrargids that have both:
1.  Skeletans covering 10 percent or more of the surfaces of
peds at a depth of 2.5 cm or more below the upper boundary
of the natric horizon; and
2.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on ustic.
Glossic Ustic Natrargids
GEBL.  Other Natrargids that have both:
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on ustic.
Haplic Ustic Natrargids
GEBM.  Other Natrargids that have both:
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Haploxeralfic Natrargids
GEBN.  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
GEBO.  Other Natrargids that have both:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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
GEBP.  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) particles 2.0 mm or
larger in diameter, 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
114	 Keys to Soil Taxonomy
by ammonium oxalate) times 60] plus the volcanic glass
(percent) is 30 or more.
Vitrandic Natrargids
GEBQ.  Other Natrargids that, in normal years, 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 below the soil surface is 5o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Natrargids
GEBR.  Other Natrargids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Natrargids
GEBS.  Other Natrargids that have skeletans covering 10
percent or more of the surfaces of peds at a depth of 2.5 cm or
more below the upper boundary of the natric horizon.
Glossic Natrargids
GEBT.  Other Natrargids.
Typic Natrargids
Paleargids
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 peds
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:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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 a moisture control section that, in normal years,
is dry in all parts for less than three-fourths of the time
(cumulative) when the soil temperature at a depth of 50 cm
below the soil surface is 5 o
C or higher and a soil moisture
regime that borders on ustic.
Arenic Ustic Paleargids
GECD.  Other Paleargids that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 within 150
cm of the soil surface.
Calcic Paleargids
GECF.  Other Paleargids that have both:
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher 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 ruptureresistance
class when moist.
Durinodic Paleargids
GECH.  Other Paleargids that have both:
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on ustic.
Petronodic Ustic Paleargids
Aridisols	 115
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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:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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) particles 2.0 mm or
larger in diameter, 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, in normal years, 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 below the surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Paleargids
GECM.  Other Paleargids that, in normal years, 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 below the surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Paleargids
GECN.  Other Paleargids.
Typic Paleargids
Petroargids
Key to Subgroups
GEAA.  Petroargids that have both:
1.  A petrogypsic horizon within 150 cm of the soil surface;
and
2.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
surface is 5 o
C or higher and a soil moisture regime that
borders on ustic.
Petrogypsic Ustic Petroargids
GEAB.  Other Petroargids that have a petrogypsic horizon
within 150 cm of the soil surface.
Petrogypsic Petroargids
GEAC.  Other Petroargids that have both:
1.  A duripan within 150 cm of the soil surface; and
2.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Duric Xeric Petroargids
GEAD.  Other Petroargids that have a duripan within 150 cm
of the soil surface.
Duric Petroargids
GEAE.  Other Petroargids that have a natric horizon.
Natric Petroargids
GEAF.  Other Petroargids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Petroargids
GEAG.  Other Petroargids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Petroargids
GEAH.  Other Petroargids.
Typic Petroargids
116	 Keys to Soil Taxonomy
Calcids
Key to Great Groups
GFA.  Calcids that have a petrocalcic horizon within 100 cm of
the soil surface.
Petrocalcids, p. 118
GFB.  Other Calcids.
Haplocalcids, p. 116
Haplocalcids
Key to Subgroups
GFBA.  Haplocalcids that have both:
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 parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Lithic Xeric Haplocalcids
GFBB.  Other Haplocalcids that have both:
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 parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher 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 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 peds
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,
that contain 20 percent or more (by volume) durinodes or are
brittle and have at least a firm rupture-resistance class when
moist.
Aquic Durinodic Haplocalcids
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 both:
1.  A duripan within 150 cm of the soil surface; and
2.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Duric Xeric Haplocalcids
GFBH.  Other Haplocalcids that have a duripan within 150 cm
of the soil surface.
Duric Haplocalcids
GFBI.  Other Haplocalcids that have both:
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher 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
Aridisols	 117
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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 Haplocalcids
GFBK.  Other Haplocalcids that have both:
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Petronodic Xeric Haplocalcids
GFBL.  Other Haplocalcids that have both:
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and 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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Sodic Xeric Haplocalcids
GFBO.  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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and 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
GFBQ.  Other Haplocalcids that have both:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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) particles 2.0 mm or
larger in diameter, 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, in normal years, are dry in all
parts of the moisture control section for less than three-fourths
118	 Keys to Soil Taxonomy
of the time (cumulative) when the soil temperature at a depth of
50 cm below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Haplocalcids
GFBT.  Other Haplocalcids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Haplocalcids
GFBU.  Other Haplocalcids.
Typic Haplocalcids
Petrocalcids
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
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:
1.  An argillic horizon within 100 cm of the soil surface;
and
2.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Xeralfic Petrocalcids
GFAD.  Other Petrocalcids that have both:
1.  An argillic horizon within 100 cm of the soil surface;
and
2.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on ustic.
Ustalfic Petrocalcids
GFAE.  Other Petrocalcids that have an argillic horizon within
100 cm of the soil surface.
Argic Petrocalcids
GFAF.  Other Petrocalcids that have both:
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, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Petrocalcids
GFAI.  Other Petrocalcids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Petrocalcids
GFAJ.  Other Petrocalcids.
Typic Petrocalcids
Cambids
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. 119
GGB.  Other Cambids that have a duripan or a petrocalcic or
petrogypsic horizon within 150 cm of the soil surface.
Petrocambids, p. 122
GGC.  Other Cambids.
Haplocambids, p. 119
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Aquicambids
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 have both:
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and 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 ruptureresistance
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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) particles 2.0 mm or
larger in diameter, 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 meet both of the following:
1.  Have a total thickness of less than 50 cm of humantransported
material in the surface horizons; and
2.  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.
Fluventic Aquicambids
GGAH.  Other Aquicambids that, in normal years, are dry
in all parts of the moisture control section for less than threefourths
of the time (cumulative) when the soil temperature at a
depth of 50 cm below the soil surface is 5 o
C or higher and have
a soil moisture regime that borders on xeric.
Xeric Aquicambids
GGAI.  Other Aquicambids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Aquicambids
GGAJ.  Other Aquicambids.
Typic Aquicambids
Haplocambids
Key to Subgroups
GGCA.  Haplocambids that have both:
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 parts for less than three-fourths of the time (cumulative)
120	 Keys to Soil Taxonomy
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Lithic Xeric Haplocambids
GGCB.  Other Haplocambids that have both:
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 parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on ustic.
Lithic Ustic Haplocambids
GGCC.  Other Haplocambids that have a lithic contact within
50 cm of the soil surface.
Lithic Haplocambids
GGCD.  Other Haplocambids 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 wedgeshaped
peds 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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Xerertic Haplocambids
GGCE.  Other Haplocambids 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 wedgeshaped
peds 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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on ustic.
Ustertic Haplocambids
GGCF.  Other Haplocambids 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 peds
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
GGCG.  Other Haplocambids that have both:
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Durinodic Xeric Haplocambids
GGCH.  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)
durinodes or are brittle and have at least a firm ruptureresistance
class when moist.
Durinodic Haplocambids
GGCI.  Other Haplocambids that have both:
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Petronodic Xeric Haplocambids
GGCJ.  Other Haplocambids that have both:
1.  One or more horizons, within 100 cm of the soil
surface and with a combined thickness of 15 cm or more,
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that contain 20 percent or more (by volume) nodules or
concretions; and
2.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on ustic.
Petronodic Ustic Haplocambids
GGCK.  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
GGCL.  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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Sodic Xeric Haplocambids
GGCM.  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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on ustic.
Sodic Ustic Haplocambids
GGCN.  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
GGCO.  Other Haplocambids that have both:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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
GGCP.  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) particles 2.0 mm or
larger in diameter, 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
GGCQ.  Other Haplocambids that meet all of the following:
1.  Have a total thickness of less than 50 cm of humantransported
material in the surface horizons; and
2.  In normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric; and
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.
Xerofluventic Haplocambids
GGCR.  Other Haplocambids that meet all of the following:
1.  Have a total thickness of less than 50 cm of humantransported
material in the surface horizons; and
2.  In normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic; and
3.  Have an irregular decrease in organic-carbon content
122	 Keys to 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.
Ustifluventic Haplocambids
GGCS.  Other Haplocambids that meet both of the following:
1.  Have a total thickness of less than 50 cm of humantransported
material in the surface horizons; and
2.  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.
Fluventic Haplocambids
GGCT.  Other Haplocambids that have an anthropic epipedon.
Anthropic Haplocambids
GGCU.  Other Haplocambids that, in normal years, are dry
in all parts of the moisture control section for less than threefourths
of the time (cumulative) when the soil temperature at a
depth of 50 cm below the soil surface is 5 o
C or higher and have
a soil moisture regime that borders on xeric.
Xeric Haplocambids
GGCV.  Other Haplocambids that, in normal years, are dry
in all parts of the moisture control section for less than threefourths
of the time (cumulative) when the soil temperature at a
depth of 50 cm below the soil surface is 5 o
C or higher and have
a soil moisture regime that borders on ustic.
Ustic Haplocambids
GGCW.  Other Haplocambids.
Typic Haplocambids
Petrocambids
Key to Subgroups
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.
Sodic Petrocambids
GGBB.  Other Petrocambids that have both:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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) particles 2.0 mm or
larger in diameter, 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, in normal years, are dry
in all parts of the moisture control section for less than threefourths
of the time (cumulative) when the soil temperature at a
depth of 50 cm below the soil surface is 5 o
C or higher and have
a soil moisture regime that borders on xeric.
Xeric Petrocambids
GGBE.  Other Petrocambids that, in normal years, are dry
in all parts of the moisture control section for less than threefourths
of the time (cumulative) when the soil temperature at a
depth of 50 cm below the soil surface is 5 o
C or higher and have
a soil moisture regime that borders on ustic.
Ustic Petrocambids
GGBF.  Other Petrocambids.
Typic Petrocambids
Cryids
Key to Great Groups
GAA.  Cryids that have a salic horizon within 100 cm of the
soil surface.
Salicryids, p. 126
GAB.  Other Cryids that have a duripan, petrocalcic horizon,
or petrogypsic horizon within 100 cm of the soil surface.
Petrocryids, p. 125
Aridisols	 123
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GAC.  Other Cryids that have a gypsic horizon within 100 cm
of the soil surface.
Gypsicryids, p. 124
GAD.  Other Cryids that have an argillic or natric horizon.
Argicryids, p. 123
GAE.  Other Cryids that have a calcic horizon within 100 cm
of the soil surface.
Calcicryids, p. 123
GAF.  Other Cryids.
Haplocryids, p. 124
Argicryids
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
peds 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 within 100
cm of the soil surface.
Natric Argicryids
GADD.  Other Argicryids that have both:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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) particles 2.0 mm or
larger in diameter, 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, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Argicryids
GADG.  Other Argicryids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Argicryids
GADH.  Other Argicryids.
Typic Argicryids
Calcicryids
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
124	 Keys to Soil Taxonomy
or larger in diameter, 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
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) particles 2.0 mm or
larger in diameter, 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, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Calcicryids
GAEE.  Other Calcicryids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Calcicryids
GAEF.  Other Calcicryids.
Typic Calcicryids
Gypsicryids
Key to Subgroups
GACA.  Gypsicryids that have a calcic horizon.
Calcic Gypsicryids
GACB.  Other Gypsicryids that have both:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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) particles 2.0 mm or
larger in diameter, 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
Haplocryids
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
wedge-shaped peds 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
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GAFC.  Other Haplocryids that have both:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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) particles 2.0 mm or
larger in diameter, 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, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Haplocryids
GAFF.  Other Haplocryids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Haplocryids
GAFG.  Other Haplocryids.
Typic Haplocryids
Petrocryids
Key to Subgroups
GABA.  Petrocryids that have both:
1.  A duripan that is strongly cemented or less cemented
in all subhorizons within 100 cm of the soil surface;
and
2.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Xereptic Petrocryids
GABB.  Other Petrocryids that have both:
1.  A duripan within 100 cm of the soil surface; and
2.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher and a soil moisture regime that
borders on xeric.
Duric Xeric Petrocryids
GABC.  Other Petrocryids that have a duripan within 100 cm
of the soil surface.
Duric Petrocryids
GABD.  Other Petrocryids that have a petrogypsic horizon
within 100 cm of the soil surface.
Petrogypsic Petrocryids
GABE.  Other Petrocryids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Petrocryids
GABF.  Other Petrocryids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Petrocryids
GABG.  Other Petrocryids.
Typic Petrocryids
126	 Keys to Soil Taxonomy
Salicryids
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
Durids
Key to Great Groups
GCA.  Durids that have a natric horizon above the duripan.
Natridurids, p. 128
GCB.  Other Durids that have an argillic horizon above the
duripan.
Argidurids, p. 126
GCC.  Other Durids.
Haplodurids, p. 127
Argidurids
Key to Subgroups
GCBA.  Argidurids that have 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 peds in a layer 15 cm or more
thick that is 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 both:
1.  An argillic horizon that has 35 percent or more
noncarbonate clay throughout one or more subhorizons and
one or more of the following:
a.  A clay increase of 15 percent or more (absolute, in
the fine-earth fraction) 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,
in the fine-earth fraction) at the upper boundary of the
argillic horizon; or
c.  An abrupt textural change between the eluvial horizon
and the upper boundary of the argillic horizon; and
2.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher 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 noncarbonate clay throughout one or more
subhorizons and one or more of the following:
1.  A clay increase of 15 percent or more (absolute, in the
fine-earth fraction) within a vertical distance of 2.5 cm either
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, in
the fine-earth fraction) at the upper boundary of the argillic
horizon; or
3.  An abrupt textural change between the eluvial horizon
and the upper boundary of the argillic horizon.
Abruptic Argidurids
GCBE.  Other Argidurids that have both:
1.  A duripan that is strongly cemented or less cemented in
all subhorizons; and
2.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher 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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
Aridisols	 127
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soil surface 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) particles 2.0 mm
or larger in diameter, 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) particles 2.0 mm or
larger in diameter, 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, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Argidurids
GCBJ.  Other Argidurids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Argidurids
GCBK.  Other Argidurids.
Typic Argidurids
Haplodurids
Key to Subgroups
GCCA.  Haplodurids 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.
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 both:
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 both:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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 Haplodurids
128	 Keys to Soil Taxonomy
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) particles 2.0 mm or
larger in diameter, 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, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Haplodurids
GCCI.  Other Haplodurids.
Typic Haplodurids
Natridurids
Key to Subgroups
GCAA.  Natridurids that have 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 peds in a layer 15 cm or more
thick that is 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.
Aquic Natrargidic Natridurids
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 both:
1.  A duripan that is strongly cemented or less cemented in
all subhorizons; and
2.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher 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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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:
Aridisols	 129
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1.  More than 35 percent (by volume) particles 2.0 mm or
larger in diameter, 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, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Natridurids
GCAI.  Other Natridurids.
Typic Natridurids
Gypsids
Key to Great Groups
GDA.  Gypsids that have a petrogypsic or petrocalcic horizon
within 100 cm of the soil surface.
Petrogypsids, p. 132
GDB.  Other Gypsids that have a natric horizon within 100 cm
of the soil surface.
Natrigypsids, p. 131
GDC.  Other Gypsids that have an argillic horizon within 100
cm of the soil surface.
Argigypsids, p. 129
GDD.  Other Gypsids that have a calcic horizon within 100 cm
of the soil surface.
Calcigypsids, p. 130
GDE.  Other Gypsids.
Haplogypsids, p. 130
Argigypsids
Key to Subgroups
GDCA.  Argigypsids that have a lithic contact within 50 cm of
the soil surface.
Lithic Argigypsids
GDCB.  Other Argigypsids 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 peds
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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) particles 2.0 mm or
larger in diameter, 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
130	 Keys to Soil Taxonomy
GDCG.  Other Argigypsids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Argigypsids
GDCH.  Other Argigypsids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Argigypsids
GDCI.  Other Argigypsids.
Typic Argigypsids
Calcigypsids
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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) particles 2.0 mm or
larger in diameter, 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, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Calcigypsids
GDDF.  Other Calcigypsids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Calcigypsids
GDDG.  Other Calcigypsids.
Typic Calcigypsids
Haplogypsids
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 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
Aridisols	 131
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GDEE.  Other Haplogypsids that have both:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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) particles 2.0 mm or
larger in diameter, 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, in normal years, are dry
in all parts of the moisture control section for less than threefourths
of the time (cumulative) when the soil temperature at a
depth of 50 cm below the soil surface is 5 o
C or higher and have
a soil moisture regime that borders on xeric.
Xeric Haplogypsids
GDEH.  Other Haplogypsids that, in normal years, are dry
in all parts of the moisture control section for less than threefourths
of the time (cumulative) when the soil temperature at a
depth of 50 cm below the soil surface is 5 o
C or higher and have
a soil moisture regime that borders on ustic.
Ustic Haplogypsids
GDEI.  Other Haplogypsids.
Typic Haplogypsids
Natrigypsids
Key to Subgroups
GDBA.  Natrigypsids that have a lithic contact within 50 cm
of the soil surface.
Lithic Natrigypsids
GDBB.  Other Natrigypsids 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 peds
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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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) particles 2.0 mm or
132	 Keys to Soil Taxonomy
larger in diameter, 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 Natrigypsids
GDBF.  Other Natrigypsids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Natrigypsids
GDBG.  Other Natrigypsids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Natrigypsids
GDBH.  Other Natrigypsids.
Typic Natrigypsids
Petrogypsids
Key to Subgroups
GDAA.  Petrogypsids that have a petrocalcic horizon 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, in normal years, is dry in
all parts for less than three-fourths of the time (cumulative)
when the soil temperature at a depth of 50 cm below the
soil surface 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) particles 2.0 mm
or larger in diameter, 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) particles 2.0 mm or
larger in diameter, 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, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on xeric.
Xeric Petrogypsids
GDAF.  Other Petrogypsids that, in normal years, 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 below the soil surface is 5 o
C or higher and have a soil
moisture regime that borders on ustic.
Ustic Petrogypsids
GDAG.  Other Petrogypsids.
Typic Petrogypsids
Salids
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. 132
GBB.  Other Salids.
Haplosalids, p. 133
Aquisalids
Key to Subgroups
GBAA.  Aquisalids that have an anhydritic horizon within 100
cm of the soil surface.
Anhydritic Aquisalids
Aridisols	 133
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GBAB.  Other Aquisalids that have a gypsic or petrogypsic
horizon within 100 cm of the soil surface.
Gypsic Aquisalids
GBAC.  Other Aquisalids that have a calcic or petrocalcic
horizon within 100 cm of the soil surface.
Calcic Aquisalids
GBAD.  Other Aquisalids.
Typic Aquisalids
Haplosalids
Key to Subgroups
GBBA.  Haplosalids that have a duripan within 100 cm of the
soil surface.
Duric Haplosalids
GBBB.  Other Haplosalids that have a petrogypsic horizon
within 100 cm of the soil surface.
Petrogypsic Haplosalids
GBBC.  Other Haplosalids that have an anhydritic horizon
within 100 cm of the soil surface.
Anhydritic Haplosalids
GBBD.  Other Haplosalids that have a gypsic horizon within
100 cm of the soil surface.
Gypsic Haplosalids
GBBE.  Other Haplosalids that have a calcic horizon within
100 cm of the soil surface.
Calcic Haplosalids
GBBF.  Other Haplosalids.
Typic Haplosalids
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Key to Suborders
LA.  Entisols that have a positive water potential at the soil
surface for more than 21 hours of each day in all years.
Wassents, p. 154
LB.  Other 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 class finer than loamy fine sand and, in
50 percent or more of the matrix, one or more of the
following:
(1)  Neutral colors with no hue (N) and zero chroma;
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 class of loamy fine sand or coarser and,
in 50 percent or more of the matrix, one or more of the
following:
(1)  Neutral colors with no hue (N) and zero chroma;
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. 136
LC.  Other Entisols that have less than 35 percent (by volume)
rock fragments and a texture class of loamy fine sand or coarser
in all layers (sandy loam lamellae are permitted) within the
particle-size control section.
Psamments, p. 150
LD.  Other Entisols that do not have a densic, lithic, or
paralithic contact within 25 cm of the mineral soil surface, a
total thickness of 50 cm or more of human-transported material
in the surface horizons, or a surface mantle of new soil material
50 cm or more thick that is not derived from alluvial deposition,
and they:
1.  Do not occur on an anthropogenic landform or
microfeature; and
2.  Have a slope of less than 25 percent; and
3. Have one or both of the following:
a.  An organic-carbon content (Holocene age) of 0.2
percent or more at a depth of 125 cm below the mineral
soil surface; 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; and
4.  Have a soil temperature regime:
a.  That is warmer than cryic; or
b.  That is gelic or cryic and the soil has:
(1)  No gelic materials; 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. 139
Entisols
CHAPTER 8
136	 Keys to Soil Taxonomy
LE.  Other Entisols.
Orthents, p. 145
Aquents
Key to Great Groups
LBA.  Aquents that have sulfidic materials within 50 cm of the
mineral soil surface.
Sulfaquents, p. 139
LBB.  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. 138
LBC.  Other Aquents that have a gelic soil temperature regime.
Gelaquents, p. 138
LBD.  Other Aquents that have a cryic soil temperature
regime.
Cryaquents, p. 136
LBE.  Other Aquents that have less than 35 percent (by
volume) rock fragments and a texture class of loamy fine sand
or coarser in all layers (sandy loam lamellae are permitted)
within the particle-size control section.
Psammaquents, p. 138
LBF.  Other Aquents that do not have a total thickness of
50 cm or more of human-transported material in the surface
horizons or a surface mantle of new soil material 50 cm or more
thick that is not derived from alluvial deposition, and they:
1  Do not occur on an anthropogenic landform or
microfeature; and
2.  Have a slope of less than 25 percent; and
3. Have 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 0.2 percent
or more; 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.
Fluvaquents, p. 137
LBG.  Other Aquents that have episaturation.
Epiaquents, p. 137
LBH.  Other Aquents.
Endoaquents, p. 136
Cryaquents
Key to Subgroups
LBDA.  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) particles 2.0 mm or
larger in diameter, 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
LBDB.  Other Cryaquents.
Typic Cryaquents
Endoaquents
Key to Subgroups
LBHA.  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 and does not have sulfide or other
sulfur-bearing minerals.
Sulfic Endoaquents
LBHB.  Other Endoaquents that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Endoaquents
LBHC.  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.
Sodic Endoaquents
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LBHD.  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
LBHE.  Other Endoaquents that have both:
1.  A color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 15 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 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.
Humaqueptic Endoaquents
LBHF.  Other Endoaquents that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 15 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 15 cm after mixing.
Mollic Endoaquents
LBHG.  Other Endoaquents.
Typic Endoaquents
Epiaquents
Key to Subgroups
LBGA.  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
LBGB.  Other Epiaquents that have both:
1.  A color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 15 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 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.
Humaqueptic Epiaquents
LBGC.  Other Epiaquents that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 15 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 15 cm after mixing.
Mollic Epiaquents
LBGD.  Other Epiaquents.
Typic Epiaquents
Fluvaquents
Key to Subgroups
LBFA.  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 and does not have sulfide or other
sulfur-bearing minerals.
Sulfic Fluvaquents
LBFB.  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 wedgeshaped
peds 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
LBFC.  Other Fluvaquents that have a buried layer of organic
soil materials, 20 cm or more thick, within 100 cm of the
mineral soil surface.
Thapto-Histic Fluvaquents
LBFD.  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:
138	 Keys to Soil Taxonomy
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) particles 2.0 mm or
larger in diameter, 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
LBFE.  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
LBFF.  Other Fluvaquents that have both:
1.  A color value, moist, of 3 or less and a color value,
dry, of 5 or less (crushed and smoothed sample) either
throughout the upper 15 cm of the mineral soil (unmixed) or
between the mineral soil surface and a depth of 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.
Humaqueptic Fluvaquents
LBFG.  Other Fluvaquents that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 15 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 15 cm after mixing.
Mollic Fluvaquents
LBFH.  Other Fluvaquents.
Typic Fluvaquents
Gelaquents
Key to Subgroups
LBCA.  All Gelaquents.
Typic Gelaquents
Hydraquents
Key to Subgroups
LBBA.  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 and does not have sulfide or other
sulfur-bearing minerals.
Sulfic Hydraquents
LBBB.  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
LBBC.  Other Hydraquents that have a buried layer of organic
soil materials, 20 cm or more thick, within 100 cm of the
mineral soil surface.
Thapto-Histic Hydraquents
LBBD.  Other Hydraquents.
Typic Hydraquents
Psammaquents
Key to Subgroups
LBEA.  Psammaquents that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Psammaquents
LBEB.  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
LBEC.  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:
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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 Psammaquents
LBED.  Other Psammaquents that have both:
1.  A color value, moist, of 3 or less and a color value,
dry, of 5 or less (crushed and smoothed sample) either
throughout the upper 15 cm of the mineral soil (unmixed) or
between the mineral soil surface and a depth of 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.
Humaqueptic Psammaquents
LBEE.  Other Psammaquents that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 15 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 15 cm after mixing.
Mollic Psammaquents
LBEF.  Other Psammaquents.
Typic Psammaquents
Sulfaquents
Key to Subgroups
LBAA.  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
LBAB.  Other Sulfaquents that have a histic epipedon.
Histic Sulfaquents
LBAC.  Other Sulfaquents that have a buried layer of organic
soil materials, 20 cm or more thick, within 100 cm of the
mineral soil surface.
Thapto-Histic Sulfaquents
LBAD.  Other Sulfaquents.
Typic Sulfaquents
Fluvents
Key to Great Groups
LDA.  Fluvents that that have a gelic soil temperature regime.
Gelifluvents, p. 140
LDB.  Other Fluvents that have a cryic soil temperature
regime.
Cryofluvents, p. 139
LDC.  Other Fluvents that have a xeric soil moisture regime.
Xerofluvents, p. 144
LDD.  Other Fluvents that have an ustic soil moisture regime.
Ustifluvents, p. 142
LDE.  Other Fluvents that have an aridic (or torric) soil
moisture regime.
Torrifluvents, p. 140
LDF.  Other Fluvents.
Udifluvents, p. 141
Cryofluvents
Key to Subgroups
LDBA.  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
LDBB.  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) particles 2.0 mm or
larger in diameter, 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
LDBC.  Other Cryofluvents that have, in one or more horizons
within 50 cm of the mineral soil surface, redox depletions with
140	 Keys to Soil Taxonomy
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Cryofluvents
LDBD.  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
LDBE.  Other Cryofluvents that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 15 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 15 cm after mixing.
Mollic Cryofluvents
LDBF.  Other Cryofluvents.
Typic Cryofluvents
Gelifluvents
Key to Subgroups
LDAA.  Gelifluvents that have, in one or more horizons within
100 cm of the mineral soil surface, both redox depletions with
chroma of 2 or less and aquic conditions for some time in
normal years (or artificial drainage).
Aquic Gelifluvents
LDAB.  Other Gelifluvents.
Typic Gelifluvents
Torrifluvents
Key to Subgroups
LDEA.  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 peds 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 parts for less than three-fourths of the cumulative days per
year when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher; and
3.  An aridic (or torric) soil moisture regime that borders on
ustic.
Ustertic Torrifluvents
LDEB.  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
peds 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
LDEC.  Other Torrifluvents that have:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the cumulative days per
year when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher; and
2.  A thermic, mesic, or frigid soil temperature regime and
an aridic (or torric) soil 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) particles 2.0 mm
or larger in diameter, 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
LDED.  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) particles 2.0 mm or
larger in diameter, 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
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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
LDEE.  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
LDEF.  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
LDEG.  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 at least a firm
rupture-resistance class when moist; and
2.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the cumulative days per
year when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher; and
3.  A thermic, mesic, or frigid soil temperature regime and
an aridic (or torric) soil moisture regime that borders on
xeric.
Duric Xeric Torrifluvents
LDEH.  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 at least a firm rupture-resistance class when
moist.
Duric Torrifluvents
LDEI.  Other Torrifluvents that have both:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the cumulative days per
year when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher; and
2.  An aridic (or torric) soil moisture regime that borders on
ustic.
Ustic Torrifluvents
LDEJ.  Other Torrifluvents that have both:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the cumulative days per
year when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher; and
2.  A thermic, mesic, or frigid soil temperature regime and
an aridic (or torric) soil moisture regime that borders on
xeric.
Xeric Torrifluvents
LDEK.  Other Torrifluvents that have an anthropic epipedon.
Anthropic Torrifluvents
LDEL.  Other Torrifluvents.
Typic Torrifluvents
Udifluvents
Key to Subgroups
LDFA.  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 peds 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:
(1)  Neutral colors with no hue (N) and zero chroma;
or
(2)  Hue of 5GY, 5G, 5BG, or 5B and also aquic
conditions for some time in normal years (or artificial
drainage).
Aquertic Udifluvents
LDFB.  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-
142	 Keys to Soil Taxonomy
shaped peds 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
LDFC.  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
LDFD.  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) particles 2.0 mm or
larger in diameter, 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
LDFE.  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:
a.  Neutral colors with no hue (N) and zero chroma; or
b.  Hue of 5GY, 5G, 5BG, or 5B and also aquic
conditions for some time in normal years (or artificial
drainage).
Aquic Udifluvents
LDFF.  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
LDFG.  Other Udifluvents that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 15 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 15 cm after mixing.
Mollic Udifluvents
LDFH.  Other Udifluvents.
Typic Udifluvents
Ustifluvents
Key to Subgroups
LDDA.  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 peds 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:
(1)  Neutral colors with no hue (N) and zero chroma;
or
(2)  Hue of 5GY, 5G, 5BG, or 5B and also aquic
conditions for some time in normal years (or artificial
drainage).
Aquertic Ustifluvents
LDDB.  Other Ustifluvents that have both of the following:
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 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
Entisols	 143
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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, is moist in some or all parts for less 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.  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 peds 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
LDDC.  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 peds 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
LDDD.  Other Ustifluvents that have anthraquic conditions.
Anthraquic Ustifluvents
LDDE.  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:
a.  Neutral colors with no hue (N) and zero chroma; or
b.  Hue of 5GY, 5G, 5BG, or 5B and also aquic
conditions for some time in normal years (or artificial
drainage).
Aquic Ustifluvents
LDDF.  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
LDDG.  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 soil temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C.
Aridic Ustifluvents
LDDH.  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 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 dry in some or all parts for less 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 Ustifluvents
LDDI.  Other Ustifluvents that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 15 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 15 cm after mixing.
Mollic Ustifluvents
144	 Keys to Soil Taxonomy
LDDJ.  Other Ustifluvents.
Typic Ustifluvents
Xerofluvents
Key to Subgroups
LDCA.  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 wedgeshaped
peds 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
LDCB.  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:
a.  Neutral colors with no hue (N) and zero chroma; or
b.  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) particles 2.0 mm
or larger in diameter, 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
LDCC.  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
LDCD.  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) particles 2.0 mm or
larger in diameter, 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
LDCE.  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:
a.  Neutral colors with no hue (N) and zero chroma; or
b.  Hue of 5GY, 5G, 5BG, or 5B; or
c.  Aquic conditions for some time in normal years.
Aquic Xerofluvents
LDCF.  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
LDCG.  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
LDCH.  Other Xerofluvents that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 15 cm of the
Entisols	 145
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mineral soil (unmixed) or between the mineral soil surface and
a depth of 15 cm after mixing.
Mollic Xerofluvents
LDCI.  Other Xerofluvents.
Typic Xerofluvents
Orthents
Key to Great Groups
LEA.  Orthents that have a gelic soil temperature regime.
Gelorthents, p. 145
LEB.  Other Orthents that have a cryic soil temperature
regime.
Cryorthents, p. 145
LEC.  Other Orthents that have an aridic (or torric) soil
moisture regime.
Torriorthents, p. 145
LED.  Other Orthents that have a xeric soil moisture regime.
Xerorthents, p. 149
LEE.  Other Orthents that have an ustic soil moisture regime.
Ustorthents, p. 147
LEF.  Other Orthents.
Udorthents, p. 147
Cryorthents
Key to Subgroups
LEBA.  Cryorthents that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Cryorthents
LEBB.  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) particles 2.0 mm or
larger in diameter, 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
LEBC.  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
LEBD.  Other Cryorthents 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 Cryorthents
LEBE.  Other Cryorthents that have lamellae within 200 cm of
the mineral soil surface.
Lamellic Cryorthents
LEBF.  Other Cryorthents.
Typic Cryorthents
Gelorthents
Key to Subgroups
LEAA.  Gelorthents that have, in one or more horizons within
100 cm of the mineral soil surface, both redox depletions with
chroma of 2 or less and aquic conditions for some time in
normal years (or artificial drainage).
Aquic Gelorthents
LEAB.  Other Gelorthents 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 Gelorthents
LEAC.  Other Gelorthents.
Typic Gelorthents
Torriorthents
Key to Subgroups
LECA.  Torriorthents that have all of the following:
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 parts for less than three-fourths of the cumulative days per
year when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher; and
3.  A hyperthermic, thermic, mesic, frigid, or iso soil
146	 Keys to Soil Taxonomy
temperature regime and an aridic (or torric) soil moisture
regime that borders on ustic.
Lithic Ustic Torriorthents
LECB.  Other Torriorthents that have all of the following:
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 parts for less than three-fourths of the cumulative days per
year when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher; and
3.  A thermic, mesic, or frigid soil temperature regime and
an aridic (or torric) soil moisture regime that borders on
xeric.
Lithic Xeric Torriorthents
LECC.  Other Torriorthents that have a lithic contact within 50
cm of the soil surface.
Lithic Torriorthents
LECD.  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 wedgeshaped
peds 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 parts for less than three-fourths of the cumulative days per
year when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher; and
3.  A thermic, mesic, or frigid soil temperature regime and
an aridic (or torric) soil moisture regime that borders on
xeric.
Xerertic Torriorthents
LECE.  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 wedgeshaped
peds 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 parts for less than three-fourths of the cumulative days per
year when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher; and
3.  An aridic (or torric) soil moisture regime that borders on
ustic.
Ustertic Torriorthents
LECF.  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 peds
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
LECG.  Other Torriorthents that have 50 cm or more of
human-altered material.
Anthraltic Torriorthents
LECH.  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) particles 2.0 mm or
larger in diameter, 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
LECI.  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
LECJ.  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
Entisols	 147
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LECK.  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
at least a firm rupture-resistance class when moist.
Duric Torriorthents
LECL.  Other Torriorthents that have both:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the cumulative days per
year when the soil temperature at a depth of 50 cm below 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) soil moisture
regime that borders on ustic.
Ustic Torriorthents
LECM.  Other Torriorthents that have both:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the cumulative days per
year when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher; and
2.  A thermic, mesic, or frigid soil temperature regime and
an aridic (or torric) soil moisture regime that borders on
xeric.
Xeric Torriorthents
LECN.  Other Torriorthents.
Typic Torriorthents
Udorthents
Key to Subgroups
LEFA.  Udorthents that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Udorthents
LEFB.  Other Udorthents that have both of the following:
1.  A densic contact due to mechanical compaction in more
than 90 percent of the pedon (measured laterally) within 100
cm of the soil surface; and
2.  An exchangeable sodium percentage of 15 or more (or a
sodium adsorption ratio of 13 or more) in a horizon at least
25 cm thick within 100 cm of the soil surface.
Anthrodensic Sodic Udorthents
LEFC.  Other Udorthents that have a densic contact due to
mechanical compaction in more than 90 percent of the pedon
(measured laterally) within 100 cm of the soil surface.
Anthrodensic Udorthents
LEFD.  Other Udorthents that have 50 cm or more of humantransported
material.
Anthroportic Udorthents
LEFE.  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) particles 2.0 mm or
larger in diameter, 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 Udorthents
LEFF.  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
LEFG.  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
LEFH.  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
LEFI.  Other Udorthents.
Typic Udorthents
Ustorthents
Key to Subgroups
LEEA.  Ustorthents that have both:
1.  A lithic contact within 50 cm of the mineral soil surface;
and
148	 Keys to Soil Taxonomy
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 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, is moist in some or all parts for less 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.
Aridic Lithic Ustorthents
LEEB.  Other Ustorthents that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Ustorthents
LEEC.  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 peds 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 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 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, is moist in some or all parts for less 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.
Torrertic Ustorthents
LEED.  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 peds 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
LEEE.  Other Ustorthents that have anthraquic conditions.
Anthraquic Ustorthents
LEEF.  Other Ustorthents that have a densic contact due to
mechanical compaction in more than 90 percent of the pedon
(measured laterally) within 100 cm of the soil surface.
Anthrodensic Ustorthents
LEEG.  Other Ustorthents that have 50 cm or more of humantransported
material.
Anthroportic Ustorthents
LEEH.  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
LEEI.  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
LEEJ.  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 at least a firm rupture-resistance class when moist.
Durinodic Ustorthents
LEEK.  Other Ustorthents that have both:
1.  When neither irrigated nor fallowed to store moisture,
one of the following:
Entisols	 149
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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 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, is moist in some or all parts for less 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.  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) particles 2.0 mm
or larger in diameter, 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
LEEL.  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) particles 2.0 mm or
larger in diameter, 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
LEEM.  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 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.
Aridic Ustorthents
LEEN.  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 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 dry in some or all parts for less 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 Ustorthents
LEEO.  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
LEEP.  Other Ustorthents.
Typic Ustorthents
Xerorthents
Key to Subgroups
LEDA.  Xerorthents that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Xerorthents
150	 Keys to Soil Taxonomy
LEDB.  Other Xerorthents that have both of the following:
1.  50 cm or more of human-altered material; and
2.  An exchangeable sodium percentage of 15 or more (or a
sodium adsorption ratio of 13 or more) in a horizon at least
25 cm thick within 100 cm of the soil surface.
Anthraltic Sodic Xerorthents
LEDC.  Other Xerorthents that have 50 cm or more of humanaltered
material.
Anthraltic Xerorthents
LEDD.  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) particles 2.0 mm or
larger in diameter, 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
LEDE.  Other Xerorthents 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 Xerorthents
LEDF.  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
LEDG.  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 at least a firm rupture-resistance class when moist.
Durinodic Xerorthents
LEDH.  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 or in the
horizon directly above a root-limiting layer (defined in chapter
17) that is at a shallower depth.
Dystric Xerorthents
LEDI.  Other Xerorthents.
Typic Xerorthents
Psamments
Key to Great Groups
LCA.  Psamments that have a cryic soil temperature regime.
Cryopsamments, p. 150
LCB.  Other Psamments that have an aridic (or torric) soil
moisture regime.
Torripsamments, p. 152
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. 151
LCD.  Other Psamments that have an ustic soil moisture
regime.
Ustipsamments, p. 153
LCE.  Other Psamments that have a xeric soil moisture regime.
Xeropsamments, p. 153
LCF.  Other Psamments.
Udipsamments, p. 152
Cryopsamments
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
Entisols	 151
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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
Quartzipsamments
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 soil moisture regime; and
2.  Have a clay fraction with a CEC of 16 cmol(+) or less
per kg clay (by 1N 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
LCCF.  Other Quartzipsamments that meet all of the
following:
1.  Have a udic soil moisture regime; and
2.  Have a clay fraction with a CEC of 16 cmol(+) or less
per kg clay (by 1N 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 soil 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 soil
moisture regime.
Ustic Quartzipsamments
LCCK.  Other Quartzipsamments that have a xeric soil
moisture regime.
Xeric Quartzipsamments
152	 Keys to Soil Taxonomy
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
Torripsamments
Key to Subgroups
LCBA.  Torripsamments that have a lithic contact within 50
cm of the soil surface.
Lithic Torripsamments
LCBB.  Other Torripsamments 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 Torripsamments
LCBC.  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
LCBD.  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 at least a firm rupture-resistance class when moist.
Haploduridic Torripsamments
LCBE.  Other Torripsamments that have both:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the cumulative days per
year when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher; and
2.  An aridic (or torric) soil moisture regime that borders on
ustic.
Ustic Torripsamments
LCBF.  Other Torripsamments that have both:
1.  A moisture control section that, in normal years, is dry in
all parts for less than three-fourths of the cumulative days per
year when the soil temperature at a depth of 50 cm below the
soil surface is 5 o
C or higher; and
2.  A thermic, mesic, or frigid soil temperature regime and
an aridic (or torric) soil moisture regime that borders on
xeric.
Xeric Torripsamments
LCBG.  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
LCBH.  Other Torripsamments.
Typic Torripsamments
Udipsamments
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:
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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.
Haploplaggic Udipsamments
LCFG.  Other Udipsamments.
Typic Udipsamments
Ustipsamments
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
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 soil 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
Xeropsamments
Key to Subgroups
LCEA.  Xeropsamments that 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 at least 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
154	 Keys to Soil Taxonomy
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
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 at least 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 or in the
horizon directly above a root-limiting layer (defined in chapter
17) that is at a shallower depth.
Dystric Xeropsamments
LCEI.  Other Xeropsamments.
Typic Xeropsamments
Wassents
Key to Great Groups
LAA.  Wassents that have, in all horizons within 100 cm of the
mineral soil surface, an electrical conductivity of less than 0.2
dS/m in a 1:5 (soil:water), by volume, supernatant (not extract).
Frasiwassents, p. 154
LAB.  Other Wassents that have less than 35 percent (by
volume) rock fragments and a texture class of loamy fine sand
or coarser in all layers within the particle-size control section.
Psammowassents, p. 155
LAC.  Other Wassents that have a horizon or horizons with
a combined thickness of at least 15 cm within 50 cm of the
mineral soil surface that contain sulfidic materials.
Sulfiwassents, p. 156
LAD.  Other Wassents 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.
Hydrowassents, p. 155
LAE.  Other Wassents that have a total thickness of less than
50 cm of human-transported material in the surface horizons
and one or both of the following:
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.
Fluviwassents, p. 154
LAF.  Other Wassents.
Haplowassents, p. 155
Fluviwassents
Key to Subgroups
LAEA.  Fluviwassents that have a horizon or horizons with
a combined thickness of at least 15 cm within 100 cm of the
mineral soil surface that contain sulfidic materials.
Sulfic Fluviwassents
LAEB.  Other Fluviwassents that have a lithic contact within
100 cm of the mineral soil surface.
Lithic Fluviwassents
LAEC.  Other Fluviwassents that have a buried layer of
organic soil materials, 20 cm or more thick, within 100 cm of
the mineral soil surface.
Thapto-Histic Fluviwassents
LAED.  Other Fluviwassents that have chroma of 3 or more
in 40 percent or more of the matrix of one or more horizons
between a depth of 15 and 100 cm from the soil surface.
Aeric Fluviwassents
LAEE.  Other Fluviwassents.
Typic Fluviwassents
Frasiwassents
Key to Subgroups
LAAA.  Frasiwassents that have, in all horizons at a depth
between 20 and 50 cm below the mineral soil surface, both an
Entisols	 155
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n value of more than 0.7 and 8 percent or more clay in the fineearth
fraction.
Hydric Frasiwassents
LAAB.  Other Frasiwassents that have a lithic contact within
100 cm of the mineral soil surface.
Lithic Frasiwassents
LAAC.  Other Frasiwassents that have less than 35 percent (by
volume) rock fragments and a texture class of loamy fine sand
or coarser in all layers within the particle-size control section.
Psammentic Frasiwassents
LAAD.  Other Frasiwassents that have a buried layer of
organic soil materials, 20 cm or more thick, within 100 cm of
the mineral soil surface.
Thapto-Histic Frasiwassents
LAAE.  Other Frasiwassents that have a total thickness of
less than 50 cm of human-transported material in the surface
horizons and one or both of the following:
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 Frasiwassents
LAAF.  Other Frasiwassents that have chroma of 3 or more
in 40 percent or more of the matrix of one or more horizons
between a depth of 15 and 100 cm from the soil surface.
Aeric Frasiwassents
LAAG.  Other Frasiwassents.
Typic Frasiwassents
Haplowassents
Key to Subgroups
LAFA.  Haplowassents that have a horizon or horizons with
a combined thickness of at least 15 cm within 100 cm of the
mineral soil surface that contain sulfidic materials.
Sulfic Haplowassents
LAFB.  Other Haplowassents that have a lithic contact within
100 cm of the mineral soil surface.
Lithic Haplowassents
LAFC.  Other Haplowassents that have chroma of 3 or
more in 40 percent or more of the matrix of one or more
horizons between a depth of 15 and 100 cm from the soil
surface.
Aeric Haplowassents
LAFD.  Other Haplowassents.
Typic Haplowassents
Hydrowassents
Key to Subgroups
LADA.  Hydrowassents that have a horizon or horizons with
a combined thickness of at least 15 cm within 100 cm of the
mineral soil surface that contain sulfidic materials.
Sulfic Hydrowassents
LADB.  Other Hydrowassents that have, in all horizons at a
depth between 20 and 100 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.
Grossic Hydrowassents
LADC.  Other Hydrowassents that have a lithic contact within
100 cm of the mineral soil surface.
Lithic Hydrowassents
LADD.  Other Hydrowassents that have a buried layer of
organic soil materials, 20 cm or more thick, within 100 cm of
the mineral soil surface.
Thapto-Histic Hydrowassents
LADE.  Other Hydrowassents.
Typic Hydrowassents
Psammowassents
Key to Subgroups
LABA.  Psammowassents that have a horizon or horizons with
a combined thickness of at least 15 cm within 100 cm of the
mineral soil surface that contain sulfidic materials.
Sulfic Psammowassents
LABB.  Other Psammowassents that have a lithic contact
within 100 cm of the mineral soil surface.
Lithic Psammowassents
LABC. Other Psammowassents that have a total thickness of
less than 50 cm of human-transported material in the surface
horizons and one or both of the following:
1.  At a depth of 125 cm below the mineral soil surface,
an organic-carbon content (Holocene age) of 0.2 percent or
156	
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 Psammowassents
LABD.  Other Psammowassents that have chroma of 3 or
more in 40 percent or more of the matrix of one or more
horizons between a depth of 15 and 100 cm from the soil
surface.
Aeric Psammowassents
LABE. Other Psammowassents.
Typic Psammowassents
Sulfiwassents
Key to Subgroups
LACA.  Sulfiwassents that have a lithic contact within 100 cm
of the mineral soil surface.
Lithic Sulfiwassents
LACB.  Other Sulfiwassents 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 Sulfiwassents
LACC.  Other Sulfiwassents that have a buried layer of
organic soil materials, 20 cm or more thick, within 100 cm of
the mineral soil surface.
Thapto-Histic Sulfiwassents
LACD.  Other Sulfiwassents that have a total thickness of
less than 50 cm of human-transported material in the surface
horizons and one or both of the following:
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 Sulfiwassents
LACE.  Other Sulfiwassents that have chroma of 3 or more
in 40 percent or more of the matrix of one or more horizons
between a depth of 15 and 100 cm from the soil surface.
Aeric Sulfiwassents
LACF.  Other Sulfiwassents.
Typic Sulfiwassents
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Gelisols
CHAPTER 9
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.  Comprise 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 shallower.
Histels, p. 157
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. 162
AC.  Other Gelisols.
Orthels, p. 158
Histels
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. 158
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 within 100 cm of the soil surface; and
2.  Less than three-fourths (by volume) Sphagnum fibers in
the organic soil material to a depth of 50 cm or to a densic,
lithic, or paralithic contact, whichever is shallower.
Glacistels, p. 158
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
shallower.
Fibristels, p. 157
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
shallower.
Hemistels, p. 158
AAE.  Other Histels.
Sapristels, p. 158
Fibristels
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 layer of mineral soil
material 30 cm or more thick within 100 cm of the soil surface.
Terric Fibristels
AACC.  Other Fibristels that meet both of the following:
1.  Have a total thickness of less than 50 cm of humantransported
material in the surface horizons; and
2.  Have, within the organic soil materials, either one layer
of mineral soil material 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 (by
volume) of the fibric soil materials are derived from Sphagnum
to a depth of 50 cm or to a densic, lithic, or paralithic contact,
whichever is shallower.
Sphagnic Fibristels
AACE.  Other Fibristels.
Typic Fibristels
158	 Keys to Soil Taxonomy
Folistels
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 within 100 cm
of the soil surface.
Glacic Folistels
AAAC.  Other Folistels.
Typic Folistels
Glacistels
Key to Subgroups
AABA.  Glacistels that have more thickness of hemic soil
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
soil materials than any other kind of organic soil material in the
upper 50 cm.
Sapric Glacistels
AABC.  Other Glacistels.
Typic Glacistels
Hemistels
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 layer of mineral soil
material 30 cm or more thick within 100 cm of the soil surface.
Terric Hemistels
AADC.  Other Hemistels that meet both of the following:
1.  Have a total thickness of less than 50 cm of humantransported
material in the surface horizons; and
2.  Have, within the organic soil materials, either one layer
of mineral soil material 5 cm or more thick or two or more
layers of any thickness within 100 cm of the soil surface.
Fluvaquentic Hemistels
AADD.  Other Hemistels.
Typic Hemistels
Sapristels
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 layer of mineral soil
material 30 cm or more thick within 100 cm of the soil surface.
Terric Sapristels
AAEC.  Other Sapristels that meet both of the following:
1.  Have a total thickness of less than 50 cm of humantransported
material in the surface horizons; and
2.  Have, within the organic soil materials, either one layer
of mineral soil material 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
Orthels
Key to Great Groups
ACA.  Orthels that have a histic epipedon.
Historthels, p. 160
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. 159
ACC.  Other Orthels that have anhydrous conditions.
Anhyorthels, p. 159
ACD.  Other Orthels that have a mollic epipedon.
Mollorthels, p. 161
ACE.  Other Orthels that have an umbric epipedon.
Umbrorthels, p. 162
ACF.  Other Orthels that have an argillic horizon within 100
cm of the mineral soil surface.
Argiorthels, p. 160
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 a texture class of loamy fine sand
or coarser in all layers within the particle-size control section.
Psammorthels, p. 162
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ACH.  Other Orthels.
Haplorthels, p. 160
Anhyorthels
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 within 100
cm of the mineral soil surface.
Glacic Anhyorthels
ACCC.  Other Anhyorthels that have a petrogypsic horizon
within 100 cm of the mineral soil surface.
Petrogypsic Anhyorthels
ACCD.  Other Anhyorthels that have a gypsic horizon within
100 cm of the mineral soil surface.
Gypsic Anhyorthels
ACCE.  Other Anhyorthels that have both of the following:
1.  A horizon 15 cm or more thick that has a nitrate
concentration of 118 mmol(-)/L or more in a 1:5 soil:water
extract; and
2.  The product of horizon thickness (in cm) times nitrate
concentration [in mmol(-)/L] is 3,500 or more.
Nitric Anhyorthels
ACCF.  Other Anhyorthels that have a salic horizon within 100
cm of the mineral soil surface.
Salic Anhyorthels
ACCG.  Other Anhyorthels that have a calcic horizon within
100 cm of the mineral soil surface.
Calcic Anhyorthels
ACCH.  Other Anhyorthels.
Typic Anhyorthels
Aquorthels
Key to Subgroups
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 within 100
cm of the mineral soil surface.
Glacic Aquorthels
ACBC.  Other Aquorthels that have a sulfuric horizon or
sulfidic materials 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) particles 2.0 mm or
larger in diameter, 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 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 class of loamy fine sand
or coarser in all layers within the particle-size control section.
Psammentic Aquorthels
ACBI.  Other Aquorthels that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  One or both of the following:
a.  At a depth of 125 cm below the mineral soil surface,
160	 Keys to Soil Taxonomy
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 Aquorthels
ACBJ.  Other Aquorthels.
Typic Aquorthels
Argiorthels
Key to Subgroups
ACFA.  Argiorthels that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Argiorthels
ACFB.  Other Argiorthels that have a glacic layer 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
Haplorthels
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 within 100
cm of the mineral soil surface.
Glacic Haplorthels
ACHC.  Other Haplorthels that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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
4.  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 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 Haplorthels
ACHD.  Other Haplorthels that have a folistic epipedon.
Folistic Haplorthels
ACHE.  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
ACHF.  Other Haplorthels that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Haplorthels
ACHG.  Other Haplorthels.
Typic Haplorthels
Historthels
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 within 100
cm of the soil surface.
Glacic Historthels
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ACAC.  Other Historthels that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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
4.  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 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 Historthels
ACAD.  Other Historthels that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Historthels
ACAE.  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
ACAF.  Other Historthels.
Typic Historthels
Mollorthels
Key to Subgroups
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 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 wedgeshaped
peds 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 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) particles 2.0 mm or
larger in diameter, 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 a folistic epipedon.
Folistic Mollorthels
ACDG.  Other Mollorthels that have both:
1.  A mollic epipedon that is 40 cm or more thick with a
texture class finer than loamy fine sand; and
2.  A slope of less than 25 percent.
Cumulic Mollorthels
ACDH.  Other Mollorthels that have, in one or more horizons
within 100 cm of the mineral soil surface, distinct or prominent
162	 Keys to Soil Taxonomy
redox concentrations and also aquic conditions for some time
during normal years (or artificial drainage).
Aquic Mollorthels
ACDI.  Other Mollorthels.
Typic Mollorthels
Psammorthels
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 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
Umbrorthels
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 within 100
cm of the mineral soil surface.
Glacic Umbrorthels
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 wedgeshaped
peds 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 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) particles 2.0 mm or
larger in diameter, 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 a folistic epipedon.
Folistic Umbrorthels
ACEG.  Other Umbrorthels that have both:
1.  An umbric epipedon that is 40 cm or more thick with a
texture class finer than loamy fine sand; and
2.  A slope of less than 25 percent.
Cumulic Umbrorthels
ACEH.  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
ACEI.  Other Umbrorthels.
Typic Umbrorthels
Turbels
Key to Great Groups
ABA.  Turbels that have, in 30 percent or more of the pedon,
more than 40 percent, by volume, organic soil materials from
Gelisols	 163
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the soil surface to a depth of 50 cm which meet the saturation
requirement for a histic epipedon.
Histoturbels, p. 164
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. 163
ABC.  Other Turbels that have anhydrous conditions.
Anhyturbels, p. 163
ABD.  Other Turbels that have a mollic epipedon.
Molliturbels, p. 164
ABE.  Other Turbels that have an umbric epipedon.
Umbriturbels, p. 165
ABF.  Other Turbels that have less than 35 percent (by
volume) rock fragments and a texture class of loamy fine sand
or coarser in all layers within the particle-size control section.
Psammoturbels, p. 164
ABG.  Other Turbels.
Haploturbels, p. 163
Anhyturbels
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 within 100
cm of the mineral soil surface.
Glacic Anhyturbels
ABCC.  Other Anhyturbels that have a petrogypsic horizon
within 100 cm of the mineral soil surface.
Petrogypsic Anhyturbels
ABCD.  Other Anhyturbels that have a gypsic horizon within
100 cm of the mineral soil surface.
Gypsic Anhyturbels
ABCE.  Other Anhyturbels that have both of the following:
1.  A horizon 15 cm or more thick that has a nitrate
concentration of 118 mmol(-)/L or more in a 1:5 soil:water
extract; and
2.  The product of horizon thickness (in cm) times nitrate
concentration [in mmol(-)/L] is 3,500 or more.
Nitric Anhyturbels
ABCF.  Other Anhyturbels that have a salic horizon within 100
cm of the mineral soil surface.
Salic Anhyturbels
ABCG.  Other Anhyturbels that have a calcic horizon within
100 cm of the mineral soil surface.
Calcic Anhyturbels
ABCH.  Other Anhyturbels.
Typic Anhyturbels
Aquiturbels
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 within 100
cm of the mineral soil surface.
Glacic Aquiturbels
ABBC.  Other Aquiturbels that have a sulfuric horizon or
sulfidic materials within 100 cm of the mineral soil surface.
Sulfuric Aquiturbels
ABBD.  Other Aquiturbels 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 Aquiturbels
ABBE.  Other Aquiturbels that have less than 35 percent (by
volume) rock fragments and a texture class of loamy fine sand
or coarser in all layers within the particle-size control section.
Psammentic Aquiturbels
ABBF.  Other Aquiturbels.
Typic Aquiturbels
Haploturbels
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 within 100
cm of the mineral soil surface.
Glacic Haploturbels
164	 Keys to Soil Taxonomy
ABGC.  Other Haploturbels that have a folistic epipedon.
Folistic Haploturbels
ABGD.  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
ABGE.  Other Haploturbels.
Typic Haploturbels
Histoturbels
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 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
Molliturbels
Key to Subgroups
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 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 wedgeshaped
peds 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 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) particles 2.0 mm or
larger in diameter, 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 a folistic epipedon.
Folistic Molliturbels
ABDG.  Other Molliturbels that have both:
1.  A mollic epipedon that is 40 cm or more thick with a
texture class finer than loamy fine sand; and
2.  A slope of less than 25 percent.
Cumulic Molliturbels
ABDH.  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
ABDI.  Other Molliturbels.
Typic Molliturbels
Psammoturbels
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 within
100 cm of the mineral soil surface.
Glacic Psammoturbels
Gelisols	 165
G
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L
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
Umbriturbels
Key to Subgroups
ABEA.  Umbriturbels that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Umbriturbels
ABEB.  Other Umbriturbels that have a glacic layer 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 wedgeshaped
peds 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 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) particles 2.0 mm or
larger in diameter, 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 a folistic epipedon.
Folistic Umbriturbels
ABEG.  Other Umbriturbels that have both:
1.  An umbric epipedon that is 40 cm or more thick with a
texture class finer than loamy fine sand; and
2.  A slope of less than 25 percent.
Cumulic Umbriturbels
ABEH.  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).
Aquic Umbriturbels
ABEI.  Other Umbriturbels.
Typic Umbriturbels
	 167
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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. 168
BB.  Other Histosols that have a positive water potential at the
soil surface for more than 21 hours of each day in all years.
Wassists, p. 171
BC.  Other Histosols that:
1.  Have more thickness of fibric 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 layer of mineral soil material 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 and there is a continuous
layer of mineral soil material 40 cm or more thick that has
its upper boundary within the subsurface tier; and
2.  Do not have a sulfuric horizon within 50 cm of the soil
surface; and
3.  Do not have sulfidic materials within 100 cm of the soil
surface.
Fibrists, p. 167
BD.  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 layer of mineral soil material 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 and there is a continuous layer
of mineral soil material 40 cm or more thick that has its
upper boundary within the subsurface tier.
Saprists, p. 170
BE.  Other Histosols.
Hemists, p. 169
Fibrists
Key to Great Groups
BCA.  Fibrists that have a cryic soil temperature regime.
Cryofibrists, p. 167
BCB.  Other Fibrists in which Sphagnum fibers constitute
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,
fragmental materials, or other mineral soil materials if at a depth
of less than 90 cm.
Sphagnofibrists, p. 168
BCC.  Other Fibrists.
Haplofibrists, p. 168
Cryofibrists
Key to Subgroups
BCAA.  Cryofibrists that have a layer of water within the
control section, below the surface tier.
Hydric Cryofibrists
BCAB.  Other Cryofibrists that have a lithic contact at the
lower boundary of the control section.
Lithic Cryofibrists
BCAC.  Other Cryofibrists that have a layer of mineral soil
material 30 cm or more thick that has its upper boundary within
the control section, below the surface tier.
Terric Cryofibrists
BCAD.  Other Cryofibrists that meet both of the following:
1.  Have a total thickness of less than 50 cm of humantransported
material in the surface horizons; and
2.  Have, within the organic soil materials, either one layer
of mineral soil material 5 cm or more thick or two or more
Histosols
CHAPTER 10
168	 Keys to Soil Taxonomy
layers of mineral soil material of any thickness in the control
section, below the surface tier.
Fluvaquentic Cryofibrists
BCAE.  Other Cryofibrists in which three-fourths or more
of the fiber volume in the surface tier is derived from
Sphagnum.
Sphagnic Cryofibrists
BCAF.  Other Cryofibrists.
Typic Cryofibrists
Haplofibrists
Key to Subgroups
BCCA.  Haplofibrists that have a layer of water within the
control section, below the surface tier.
Hydric Haplofibrists
BCCB.  Other Haplofibrists that have a lithic contact at the
lower boundary of the control section.
Lithic Haplofibrists
BCCC.  Other Haplofibrists that have one or more limnic
layers with a total thickness of 5 cm or more within the control
section.
Limnic Haplofibrists
BCCD.  Other Haplofibrists that have a layer of mineral soil
material 30 cm or more thick that has its upper boundary within
the control section, below the surface tier.
Terric Haplofibrists
BCCE.  Other Haplofibrists that meet both of the following:
1.  Have a total thickness of less than 50 cm of humantransported
material in the surface horizons; and
2.  Have, within the organic soil materials, either one layer
of mineral soil material 5 cm or more thick or two or more
layers of mineral soil material of any thickness in the control
section, below the surface tier.
Fluvaquentic Haplofibrists
BCCF.  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
BCCG.  Other Haplofibrists.
Typic Haplofibrists
Sphagnofibrists
Key to Subgroups
BCBA.  Sphagnofibrists that have a layer of water within the
control section, below the surface tier.
Hydric Sphagnofibrists
BCBB.  Other Sphagnofibrists that have a lithic contact at the
lower boundary of the control section.
Lithic Sphagnofibrists
BCBC.  Other Sphagnofibrists that have one or more limnic
layers with a total thickness of 5 cm or more within the control
section.
Limnic Sphagnofibrists
BCBD.  Other Sphagnofibrists that have a layer of mineral soil
material 30 cm or more thick that has its upper boundary within
the control section, below the surface tier.
Terric Sphagnofibrists
BCBE.  Other Sphagnofibrists that meet both of the following:
1.  Have a total thickness of less than 50 cm of humantransported
material in the surface horizons; and
2.  Have, within the organic soil materials, either one layer
of mineral soil material 5 cm or more thick or two or more
layers of mineral soil material of any thickness in the control
section, below the surface tier.
Fluvaquentic Sphagnofibrists
BCBF.  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
BCBG.  Other Sphagnofibrists.
Typic Sphagnofibrists
Folists
Key to Great Groups
BAA.  Folists that have a cryic soil temperature regime.
Cryofolists, p. 169
BAB.  Other Folists that have an aridic (or torric) soil moisture
regime.
Torrifolists, p. 169
BAC.  Other Folists that have an ustic or xeric soil moisture
regime.
Ustifolists, p. 169
Histosols	 169
H
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BAD.  Other Folists.
Udifolists, p. 169
Cryofolists
Key to Subgroups
BAAA.  Cryofolists that have a lithic contact within 50 cm of
the soil surface.
Lithic Cryofolists
BAAB.  Other Cryofolists.
Typic Cryofolists
Torrifolists
Key to Subgroups
BABA.  Torrifolists that have a lithic contact within 50 cm of
the soil surface.
Lithic Torrifolists
BABB.  Other Torrifolists.
Typic Torrifolists
Udifolists
Key to Subgroups
BADA.  Udifolists that have a lithic contact within 50 cm of
the soil surface.
Lithic Udifolists
BADB.  Other Udifolists.
Typic Udifolists
Ustifolists
Key to Subgroups
BACA.  Ustifolists that have a lithic contact within 50 cm of
the soil surface.
Lithic Ustifolists
BACB.  Other Ustifolists.
Typic Ustifolists
Hemists
Key to Great Groups
BEA.  Hemists that have a sulfuric horizon within 50 cm of the
soil surface.
Sulfohemists, p. 170
BEB.  Other Hemists that have sulfidic materials within 100
cm of the soil surface.
Sulfihemists, p. 170
BEC.  Other Hemists that have a horizon 2 cm or more thick
in which humilluvic material constitutes one-half or more of the
volume.
Luvihemists, p. 170
BED.  Other Hemists that have a cryic soil temperature
regime.
Cryohemists, p. 169
BEE.  Other Hemists.
Haplohemists, p. 169
Cryohemists
Key to Subgroups
BEDA.  Cryohemists that have a layer of water within the
control section, below the surface tier.
Hydric Cryohemists
BEDB.  Other Cryohemists that have a lithic contact at the
lower boundary of the control section.
Lithic Cryohemists
BEDC.  Other Cryohemists that have a layer of mineral soil
material 30 cm or more thick that has its upper boundary within
the control section, below the surface tier.
Terric Cryohemists
BEDD.  Other Cryohemists that meet both of the following:
1.  Have a total thickness of less than 50 cm of humantransported
material in the surface horizons; and
2.  Have, within the organic soil materials, either one layer
of mineral soil material 5 cm or more thick or two or more
layers of mineral soil material of any thickness in the control
section, below the surface tier.
Fluvaquentic Cryohemists
BEDE.  Other Cryohemists.
Typic Cryohemists
Haplohemists
Key to Subgroups
BEEA.  Haplohemists that have a layer of water within the
control section, below the surface tier.
Hydric Haplohemists
170	 Keys to Soil Taxonomy
BEEB.  Other Haplohemists that have a lithic contact at the
lower boundary of the control section.
Lithic Haplohemists
BEEC.  Other Haplohemists that have one or more limnic
layers with a total thickness of 5 cm or more within the control
section.
Limnic Haplohemists
BEED.  Other Haplohemists that have a layer of mineral soil
material 30 cm or more thick that has its upper boundary within
the control section, below the surface tier.
Terric Haplohemists
BEEE.  Other Haplohemists that meet both of the following:
1.  Have a total thickness of less than 50 cm of humantransported
material in the surface horizons; and
2.  Have, within the organic soil materials, either one layer
of mineral soil material 5 cm or more thick or two or more
layers of mineral soil material of any thickness in the control
section, below the surface tier.
Fluvaquentic Haplohemists
BEEF.  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
BEEG.  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
BEEH.  Other Haplohemists.
Typic Haplohemists
Luvihemists
Key to Subgroups
BECA.  All Luvihemists (provisionally).
Typic Luvihemists
Sulfihemists
Key to Subgroups
BEBA.  Sulfihemists that have a layer of mineral soil material
30 cm or more thick that has its upper boundary within the
control section, below the surface tier.
Terric Sulfihemists
BEBB.  Other Sulfihemists.
Typic Sulfihemists
Sulfohemists
Key to Subgroups
BEAA.  All Sulfohemists (provisionally).
Typic Sulfohemists
Saprists
Key to Great Groups
BDA.  Saprists that have a sulfuric horizon within 50 cm of the
soil surface.
Sulfosaprists, p. 171
BDB.  Other Saprists that have sulfidic materials within 100
cm of the soil surface.
Sulfisaprists, p. 171
BDC.  Other Saprists that have a cryic soil temperature regime.
Cryosaprists, p. 170
BDD.  Other Saprists.
Haplosaprists, p. 171
Cryosaprists
Key to Subgroups
BDCA.  Cryosaprists that have a lithic contact at the lower
boundary of the control section.
Lithic Cryosaprists
BDCB.  Other Cryosaprists that have one or more limnic
layers with a total thickness of 5 cm or more within the control
section.
Limnic Cryosaprists
BDCC.  Other Cryosaprists that have a layer of mineral soil
material 30 cm or more thick that has its upper boundary within
the control section, below the surface tier.
Terric Cryosaprists
BDCD.  Other Cryosaprists that meet both of the following:
1.  Have a total thickness of less than 50 cm of humantransported
material in the surface horizons; and
2.  Have, within the organic soil materials, either one layer
of mineral soil material 5 cm or more thick or two or more
layers of mineral soil material of any thickness in the control
section, below the surface tier.
Fluvaquentic Cryosaprists
BDCE.  Other Cryosaprists.
Typic Cryosaprists
Histosols	 171
H
I
S
Haplosaprists
Key to Subgroups
BDDA.  Haplosaprists that have a lithic contact at the lower
boundary of the control section.
Lithic Haplosaprists
BDDB.  Other Haplosaprists that have one or more limnic
layers with a total thickness of 5 cm or more within the control
section.
Limnic Haplosaprists
BDDC.  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 layer of mineral soil material 30 cm or more thick that
has its upper boundary within the control section, below the
surface tier.
Halic Terric Haplosaprists
BDDD.  Other Haplosaprists that have, throughout a layer
30 cm or more 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.
Halic Haplosaprists
BDDE.  Other Haplosaprists that have a layer of mineral soil
material 30 cm or more thick that has its upper boundary within
the control section, below the surface tier.
Terric Haplosaprists
BDDF.  Other Haplosaprists that meet both of the following:
1.  Have a total thickness of less than 50 cm of humantransported
material in the surface horizons; and
2.  Have, within the organic soil materials, either one layer
of mineral soil material 5 cm or more thick or two or more
layers of mineral soil material of any thickness in the control
section, below the surface tier.
Fluvaquentic Haplosaprists
BDDG.  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.
Hemic Haplosaprists
BDDH.  Other Haplosaprists.
Typic Haplosaprists
Sulfisaprists
Key to Subgroups
BDBA.  Sulfisaprists that have a layer of mineral soil material
30 cm or more thick that has its upper boundary within the
control section, below the surface tier.
Terric Sulfisaprists
BDBB.  Other Sulfisaprists.
Typic Sulfisaprists
Sulfosaprists
Key to Subgroups
BDAA.  All Sulfosaprists (provisionally).
Typic Sulfosaprists
Wassists
Key to Great Groups
BBA.  Wassists that have, in all horizons within 100 cm of the
soil surface, an electrical conductivity of less than 0.2 dS/m in a
1:5 (soil:water), by volume, supernatant (not extract).
Frasiwassists, p. 171
BBB.  Other Wassists that have a horizon or horizons, with a
combined thickness of at least 15 cm within 50 cm of the soil
surface, that contain sulfidic materials.
Sulfiwassists, p. 172
BBC.  Other Wassists.
Haplowassists, p. 172
Frasiwassists
Key to Subgroups
BBAA.  Frasiwassists that:
1.  Have more thickness of fibric 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 layer of mineral soil material 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 and there is a
continuous layer of mineral soil material 40 cm or more
thick that has its upper boundary within the subsurface
tier; and
172	
2.  Do not have sulfidic materials within 100 cm of the soil
surface.
Fibric Frasiwassists
BBAB.  Other Frasiwassists 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 layer of mineral soil material 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 and there is a continuous layer
of mineral soil material 40 cm or more thick that has its
upper boundary within the subsurface tier.
Sapric Frasiwassists
BBAC.  Other Frasiwassists.
Typic Frasiwassists
Haplowassists
Key to Subgroups
BBCA.  Haplowassists that have a horizon or horizons, with a
combined thickness of 15 cm within 100 cm of the soil surface,
that contain sulfidic materials.
Sulfic Haplowassists
BBCB.  Other Haplowassists that have more thickness of
fibric 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 layer of mineral soil material 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 and there is a continuous layer
of mineral soil material 40 cm or more thick that has its
upper boundary within the subsurface tier.
Fibric Haplowassists
BBCC.  Other Haplowassists 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 layer of mineral soil material 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 and there is a continuous layer
of mineral soil material 40 cm or more thick that has its
upper boundary within the subsurface tier.
Sapric Haplowassists
BBCD.  Other Haplowassists.
Typic Haplowassists
Sulfiwassists
Key to Subgroups
BBBA.  Sulfiwassists that have more thickness of fibric 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 layer of mineral soil material 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 and there is a continuous layer
of mineral soil material 40 cm or more thick that has its
upper boundary within the subsurface tier.
Fibric Sulfiwassists
BBBB.  Other Sulfiwassists 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 layer of mineral soil material 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 and there is a continuous layer
of mineral soil material 40 cm or more thick that has its
upper boundary within the subsurface tier.
Sapric Sulfiwassists
BBBC.  Other Sulfiwassists.
Typic Sulfiwassists
	 173
I
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C
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 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. 173
KB.  Other Inceptisols that have a gelic soil temperature regime.
Gelepts, p. 185
KC.  Other Inceptisols that have a cryic soil temperature
regime.
Cryepts, p. 180
KD.  Other Inceptisols that have an ustic soil moisture regime.
Ustepts, p. 195
KE.  Other Inceptisols that have a xeric soil moisture regime.
Xerepts, p. 203
KF.  Other Inceptisols.
Udepts, p. 187
Aquepts
Key to Great Groups
KAA.  Aquepts that have a sulfuric horizon within 50 cm of
the mineral soil surface.
Sulfaquepts, p. 179
KAB.  Other Aquepts that have, within 100 cm of the mineral
soil surface, one or more horizons in which plinthite or a
cemented diagnostic horizon either forms a continuous phase or
constitutes one-half or more of the volume.
Petraquepts, p. 179
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. 178
KAD.  Other Aquepts that have a fragipan within 100 cm of
the mineral soil surface.
Fragiaquepts, p. 177
KAE.  Other Aquepts that have a gelic soil temperature
regime.
Gelaquepts, p. 177
KAF.  Other Aquepts that have a cryic soil temperature regime.
Cryaquepts, p. 174
KAG.  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. 179
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174	 Keys to Soil Taxonomy
KAH.  Other Aquepts that have a histic, melanic, mollic, or
umbric epipedon.
Humaquepts, p. 178
KAI.  Other Aquepts that have episaturation.
Epiaquepts, p. 176
KAJ.  Other Aquepts.
Endoaquepts, p. 175
Cryaquepts
Key to Subgroups
KAFA.  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
value between 3.5 and 4.0 and does not have sulfide or other
sulfur-bearing minerals; or
3.  Sulfidic materials.
Sulfic Cryaquepts
KAFB.  Other Cryaquepts that have both a histic epipedon and
a lithic contact within 50 cm of the mineral soil surface.
Histic Lithic Cryaquepts
KAFC.  Other Cryaquepts that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Cryaquepts
KAFD.  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 wedgeshaped
peds 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
KAFE.  Other Cryaquepts that have a histic epipedon.
Histic Cryaquepts
KAFF.  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) particles 2.0 mm or
larger in diameter, 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
KAFG.  Other Cryaquepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Cryaquepts
KAFH.  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
KAFI.  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
KAFJ.  Other Cryaquepts that have a mollic or umbric
epipedon.
Humic Cryaquepts
KAFK.  Other Cryaquepts.
Typic Cryaquepts
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Endoaquepts
Key to Subgroups
KAJA.  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
value between 3.5 and 4.0 and does not have sulfide or other
sulfur-bearing minerals; or
3.  Sulfidic materials.
Sulfic Endoaquepts
KAJB.  Other Endoaquepts that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Endoaquepts
KAJC.  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 wedgeshaped
peds 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
KAJD.  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) particles 2.0 mm or
larger in diameter, 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
KAJE.  Other Endoaquepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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
4.  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 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 Endoaquepts
KAJF.  Other Endoaquepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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
176	 Keys to Soil Taxonomy
a densic, lithic, or paralithic contact, whichever is
shallower.
Fluvaquentic Endoaquepts
KAJG.  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
KAJH.  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
KAJI.  Other Endoaquepts that have both:
1.  A color value, moist, of 3 or less and a color value,
dry, of 5 or less (crushed and smoothed sample) either
throughout the upper 15 cm of the mineral soil (unmixed) or
between the mineral soil surface and a depth of 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
KAJJ.  Other Endoaquepts that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 15 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 15 cm after mixing.
Mollic Endoaquepts
KAJK.  Other Endoaquepts.
Typic Endoaquepts
Epiaquepts
Key to Subgroups
KAIA.  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 wedgeshaped
peds 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
KAIB.  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) particles 2.0 mm or
larger in diameter, 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
KAIC.  Other Epiaquepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Epiaquepts
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KAID.  Other Epiaquepts that have fragic soil properties
either:
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
KAIE.  Other Epiaquepts 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 Epiaquepts
KAIF.  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 sample) either throughout
the upper 15 cm of the mineral soil (unmixed) or between
the mineral soil surface and a depth of 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
KAIG.  Other Epiaquepts that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 15 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 15 cm after mixing.
Mollic Epiaquepts
KAIH.  Other Epiaquepts.
Typic Epiaquepts
Fragiaquepts
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
Gelaquepts
Key to Subgroups
KAEA.  Gelaquepts that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Gelaquepts
KAEB.  Other Gelaquepts that have a histic epipedon.
Histic Gelaquepts
KAEC.  Other Gelaquepts 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) particles 2.0 mm or
larger in diameter, 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 Gelaquepts
178	 Keys to Soil Taxonomy
KAED.  Other Gelaquepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Gelaquepts
KAEE.  Other Gelaquepts that have a mollic or umbric
epipedon.
Humic Gelaquepts
KAEF.  Other Gelaquepts that have gelic materials within 200
cm of the mineral soil surface.
Turbic Gelaquepts
KAEG.  Other Gelaquepts.
Typic Gelaquepts
Halaquepts
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 wedgeshaped
peds 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) particles 2.0 mm or
larger in diameter, 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 one or more horizons,
with a combined thickness of 15 cm or more, that contain 20
percent or more (by volume) cemented soil material and are
within 100 cm 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
Humaquepts
Key to Subgroups
KAHA.  Humaquepts 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.
Hydraquentic Humaquepts
KAHB.  Other Humaquepts that have a histic epipedon.
Histic Humaquepts
KAHC.  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) particles 2.0 mm or
larger in diameter, of which more than 66 percent is cinders,
pumice, and pumicelike fragments; or
Inceptisols	 179
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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
KAHD.  Other Humaquepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  An umbric or mollic epipedon that is 60 cm or more
thick; and
4.  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 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.
Cumulic Humaquepts
KAHE.  Other Humaquepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Humaquepts
KAHF.  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
KAHG.  Other Humaquepts.
Typic Humaquepts
Petraquepts
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
Sulfaquepts
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 8 or more 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
Vermaquepts
Key to Subgroups
KAGA.  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
180	 Keys to Soil Taxonomy
KAGB.  Other Vermaquepts.
Typic Vermaquepts
Cryepts
Key to Great Groups
KCA.  Cryepts that have an umbric or mollic epipedon.
Humicryepts, p. 184
KCB.  Other Cryepts that have a calcic or petrocalcic horizon
within 100 cm of the mineral soil surface.
Calcicryepts, p. 180
KCC.  Other Cryepts that meet both of the following:
1.  Do not have free carbonates within 200 cm of the
mineral soil surface; and
2.  Have a base saturation (by NH4
OAc) of less than 50
percent, either:
a.  In one-half or more of the thickness between 25
and 75 cm below the mineral soil surface and there is
no placic horizon, duripan, fragipan, or densic, lithic, or
paralithic contact within 50 cm of the mineral soil surface;
or
b.  In a layer, 10 cm or more thick, directly above a
placic horizon, duripan, fragipan, or densic, lithic, or
paralithic contact within 50 cm of the mineral soil surface.
Dystrocryepts, p. 180
KCD.  Other Cryepts.
Haplocryepts, p. 182
Calcicryepts
Key to Subgroups
KCBA.  Calcicryepts that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Calcicryepts
KCBB.  Other Calcicryepts 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 Calcicryepts
KCBC.  Other Calcicryepts that have a xeric soil moisture
regime.
Xeric Calcicryepts
KCBD.  Other Calcicryepts that are dry in some part of the
moisture control section for 45 or more days (cumulative) in
normal years.
Ustic Calcicryepts
KCBE.  Other Calcicryepts.
Typic Calcicryepts
Dystrocryepts
Key to Subgroups
KCCA.  Dystrocryepts that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Dystrocryepts
KCCB.  Other Dystrocryepts 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 ½ Fe (by ammonium oxalate) of 1.0 percent or more;
or
b.  More than 35 percent (by volume) particles 2.0 mm
or larger in diameter, 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 ½ Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Dystrocryepts
KCCC.  Other Dystrocryepts that have both:
1.  A xeric soil 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 ½ Fe
(by ammonium oxalate) of 1.0 percent or more.
Haploxerandic Dystrocryepts
KCCD.  Other Dystrocryepts that have both:
1.  A xeric soil moisture regime; and
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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) particles 2.0 mm
or larger in diameter, 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 ½ Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrixerandic Dystrocryepts
KCCE.  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 ½ Fe (by ammonium oxalate) of 1.0
percent or more.
Andic Dystrocryepts
KCCF.  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) particles 2.0 mm or
larger in diameter, 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 ½ Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Dystrocryepts
KCCG.  Other Dystrocryepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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
4.  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 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 Dystrocryepts
KCCH.  Other Dystrocryepts that have a folistic epipedon.
Folistic Dystrocryepts
KCCI.  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
KCCJ.  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
KCCK.  Other Dystrocryepts that have lamellae (two or more)
within 200 cm of the mineral soil surface.
Lamellic Dystrocryepts
KCCL.  Other Dystrocryepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Dystrocryepts
KCCM.  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
182	 Keys to Soil Taxonomy
2.  Al plus ½ Fe (by ammonium oxalate) of 0.25 percent 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
KCCN.  Other Dystrocryepts that have a xeric soil moisture
regime.
Xeric Dystrocryepts
KCCO.  Other Dystrocryepts that are dry in some part of the
moisture control section for 45 or more days (cumulative) in
normal years.
Ustic Dystrocryepts
KCCP.  Other Dystrocryepts that have a base saturation
(by NH4
OAc) of 50 percent or more in one or more horizons
between 25 and 50 cm from the mineral soil surface.
Eutric Dystrocryepts
KCCQ.  Other Dystrocryepts.
Typic Dystrocryepts
Haplocryepts
Key to Subgroups
KCDA.  Haplocryepts that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Haplocryepts
KCDB.  Other Haplocryepts 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 ½ Fe (by ammonium oxalate) of 1.0 percent or more;
or
b.  More than 35 percent (by volume) particles 2.0 mm
or larger in diameter, 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 ½ Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Haplocryepts
KCDC.  Other Haplocryepts that have both:
1.  A xeric soil 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 ½ Fe
(by ammonium oxalate) of 1.0 percent or more.
Haploxerandic Haplocryepts
KCDD.  Other Haplocryepts that have both:
1.  A xeric soil 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) particles 2.0 mm
or larger in diameter, 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 ½ Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrixerandic Haplocryepts
KCDE.  Other Haplocryepts that have both:
1.  A moisture control section that is dry in some part for 45
or more days (cumulative) in normal years; 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 ½ Fe
(by ammonium oxalate) of 1.0 percent or more.
Haplustandic Haplocryepts
KCDF.  Other Haplocryepts that have both:
1.  A moisture control section that is dry in some part for 45
or more days (cumulative) in normal years; 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:
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a.  More than 35 percent (by volume) particles 2.0 mm
or larger in diameter, 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 ½ Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Ustivitrandic Haplocryepts
KCDG.  Other Haplocryepts 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 ½ Fe (by ammonium oxalate) of 1.0 percent or
more.
Andic Haplocryepts
KCDH.  Other Haplocryepts 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) particles 2.0 mm or
larger in diameter, 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 ½ Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Haplocryepts
KCDI.  Other Haplocryepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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
4.  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 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 Haplocryepts
KCDJ.  Other Haplocryepts 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 Haplocryepts
KCDK.  Other Haplocryepts 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 Haplocryepts
KCDL.  Other Haplocryepts that have lamellae (two or more)
within 200 cm of the mineral soil surface.
Lamellic Haplocryepts
KCDM.  Other Haplocryepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Haplocryepts
KCDN.  Other Haplocryepts that have identifiable secondary
carbonates within 100 cm of the mineral soil surface.
Calcic Haplocryepts
KCDO.  Other Haplocryepts that have a xeric soil moisture
regime.
Xeric Haplocryepts
KCDP.  Other Haplocryepts that are dry in some part of the
184	 Keys to Soil Taxonomy
moisture control section for 45 or more days (cumulative) in
normal years.
Ustic Haplocryepts
KCDQ.  Other Haplocryepts.
Typic Haplocryepts
Humicryepts
Key to Subgroups
KCAA.  Humicryepts that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Humicryepts
KCAB.  Other Humicryepts 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 ½ Fe (by ammonium oxalate) of 1.0 percent or more;
or
b.  More than 35 percent (by volume) particles 2.0 mm
or larger in diameter, 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 ½ Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Aquandic Humicryepts
KCAC.  Other Humicryepts that have both:
1.  A xeric soil 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 ½ Fe
(by ammonium oxalate) of 1.0 percent or more.
Haploxerandic Humicryepts
KCAD.  Other Humicryepts that have both:
1.  A xeric soil 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) particles 2.0 mm
or larger in diameter, 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 ½ Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrixerandic Humicryepts
KCAE.  Other Humicryepts 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 ½ Fe (by ammonium oxalate) of 1.0 percent or
more.
Andic Humicryepts
KCAF.  Other Humicryepts 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) particles 2.0 mm or
larger in diameter, 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 ½ Fe, percent extracted by ammonium
oxalate) times 60] plus the volcanic glass (percent) is
equal to 30 or more.
Vitrandic Humicryepts
KCAG.  Other Humicryepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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
4.  One or both of the following:
a.  At a depth of 125 cm below the mineral soil surface,
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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 Humicryepts
KCAH.  Other Humicryepts 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 Humicryepts
KCAI.  Other Humicryepts 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 Humicryepts
KCAJ.  Other Humicryepts that have lamellae (two or more)
within 200 cm of the mineral soil surface.
Lamellic Humicryepts
KCAK.  Other Humicryepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Humicryepts
KCAL.  Other Humicryepts 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 ½ Fe (by ammonium oxalate) of 0.25 percent 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 Humicryepts
KCAM.  Other Humicryepts that have a xeric soil moisture
regime.
Xeric Humicryepts
KCAN.  Other Humicryepts that have a base saturation (by
NH4
OAc) of 50 percent or more, either:
1.  In one-half or more of the total thickness between 25
and 75 cm from the mineral soil surface; or
2.  In some part of the 10 cm thickness directly above a
densic, lithic, or paralithic contact that occurs less than 50
cm below the mineral soil surface.
Eutric Humicryepts
KCAO.  Other Humicryepts.
Typic Humicryepts
Gelepts
Key to Great Groups
KBA.  Gelepts that have an umbric or mollic epipedon.
Humigelepts, p. 186
KBB.  Other Gelepts that have a base saturation (by NH4
OAc)
of less than 50 percent, either:
1.  In one or more horizons totaling 25 cm or more in
thickness within 50 cm below the mineral soil surface and
there is no placic horizon, duripan, fragipan, or densic, lithic,
or paralithic contact within 50 cm of the mineral soil surface;
or
2.  In one-half or more of the thickness between the mineral
soil surface and the top of a placic horizon, duripan, fragipan,
or densic, lithic, or paralithic contact occurring within 50 cm
of the mineral soil surface.
Dystrogelepts, p. 185
KBC.  Other Gelepts.
Haplogelepts, p. 186
Dystrogelepts
Key to Subgroups
KBBA.  Dystrogelepts that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Dystrogelepts
KBBB.  Other Dystrogelepts that have, throughout one or
more horizons with a total thickness of 18 cm or more within
186	 Keys to Soil Taxonomy
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 Dystrogelepts
KBBC.  Other Dystrogelepts 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 Dystrogelepts
KBBD.  Other Dystrogelepts that do not have irregular or
broken horizon boundaries, and have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Dystrogelepts
KBBE.  Other Dystrogelepts that have gelic materials within
200 cm of the mineral soil surface.
Turbic Dystrogelepts
KBBF.  Other Dystrogelepts.
Typic Dystrogelepts
Haplogelepts
Key to Subgroups
KBCA.  Haplogelepts that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Haplogelepts
KBCB.  Other Haplogelepts 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 Haplogelepts
KBCC.  Other Haplogelepts 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 Haplogelepts
KBCD.  Other Haplogelepts that do not have irregular or
broken horizon boundaries, and have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Haplogelepts
KBCE.  Other Haplogelepts that have gelic materials within
200 cm of the mineral soil surface.
Turbic Haplogelepts
KBCF.  Other Haplogelepts.
Typic Haplogelepts
Humigelepts
Key to Subgroups
KBAA.  Humigelepts that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Humigelepts
KBAB.  Other Humigelepts 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 ½ Fe (by ammonium oxalate) of 1.0 percent or
more.
Andic Humigelepts
KBAC.  Other Humigelepts 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 Humigelepts
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KBAD.  Other Humigelepts 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 Humigelepts
KBAE.  Other Humigelepts that do not have irregular or
broken horizon boundaries, and have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Humigelepts
KBAF.  Other Humigelepts that have gelic materials within
200 cm of the mineral soil surface.
Turbic Humigelepts
KBAG.  Other Humigelepts that have a base saturation (by
NH4
OAc) of 50 percent or more, either:
1.  In one-half or more of the total thickness between 25
and 75 cm from the mineral soil surface; or
2.  In some part of the 10 cm thickness directly above a
densic, lithic, or paralithic contact that occurs less than 50
cm below the mineral soil surface.
Eutric Humigelepts
KBAH.  Other Humigelepts.
Typic Humigelepts
Udepts
Key to Great Groups
KFA.  Udepts that have a sulfuric horizon within 50 cm of the
mineral soil surface.
Sulfudepts, p. 195
KFB.  Other Udepts that have a duripan or another cemented
horizon within 100 cm of the mineral soil surface.
Durudepts, p. 187
KFC.  Other Udepts that have a fragipan within 100 cm of the
mineral soil surface.
Fragiudepts, p. 193
KFD.  Other Udepts that have an umbric or mollic epipedon.
Humudepts, p. 193
KFE.  Other Udepts that have one or both of the following:
1.  Free carbonates throughout; 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 or directly above a root-limiting
layer (defined in chapter 17) that is at a shallower depth.
Eutrudepts, p. 190
KFF.  Other Udepts.
Dystrudepts, p. 188
Durudepts
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) particles 2.0 mm
or larger in diameter, 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
188	 Keys to Soil Taxonomy
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
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 Durudepts
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) particles 2.0 mm or
larger in diameter, 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
Dystrudepts
Key to Subgroups
KFFA.  Dystrudepts 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 a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 18 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 18 cm after mixing.
Humic Lithic Dystrudepts
KFFB.  Other Dystrudepts that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Dystrudepts
KFFC.  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 wedgeshaped
peds 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
KFFD.  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) particles 2.0 mm
or larger in diameter, 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
KFFE.  Other Dystrudepts that have both:
1.  In 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.  Saturation with water 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.
Andic Oxyaquic Dystrudepts
KFFF.  Other Dystrudepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm
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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
KFFG.  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) particles 2.0 mm or
larger in diameter, 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
KFFH.  Other Dystrudepts that have both:
1.  Fragic soil properties either:
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
KFFI.  Other Dystrudepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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
4.  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 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 Dystrudepts
KFFJ.  Other Dystrudepts that have both:
1.  A color value, moist, of 3 or less and a color value,
dry, of 5 or less (crushed and smoothed sample) either
throughout the upper 18 cm of the mineral soil (unmixed) or
between the mineral soil surface and a depth of 18 cm after
mixing; 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
KFFK.  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
KFFL.  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
KFFM.  Other Dystrudepts that have fragic soil properties
either:
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
KFFN.  Other Dystrudepts that have lamellae (two or more)
within 200 cm of the mineral soil surface.
Lamellic Dystrudepts
KFFO.  Other Dystrudepts that have both:
1.  A color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 18 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 18 cm after mixing; and
190	 Keys to Soil Taxonomy
2.  A sandy particle-size class in all subhorizons throughout
the particle-size control section.
Humic Psammentic Dystrudepts
KFFP.  Other Dystrudepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  A color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 18 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 18 cm after mixing; and
4.  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 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
KFFQ.  Other Dystrudepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Dystrudepts
KFFR.  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
KFFS.  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
KFFT.  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
KFFU.  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
KFFV.  Other Dystrudepts that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 18 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 18 cm after mixing.
Humic Dystrudepts
KFFW.  Other Dystrudepts.
Typic Dystrudepts
Eutrudepts
Key to Subgroups
KFEA.  Eutrudepts that have both:
1.  A color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
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the upper 18 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 18 cm after mixing; and
2.  A lithic contact within 50 cm of the mineral soil surface.
Humic Lithic Eutrudepts
KFEB.  Other Eutrudepts that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Eutrudepts
KFEC.  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 peds 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
KFED.  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 peds 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
KFEE.  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
KFEF.  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) particles 2.0 mm or
larger in diameter, 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
KFEG.  Other Eutrudepts that have anthraquic conditions.
Anthraquic Eutrudepts
KFEH.  Other Eutrudepts that have both:
1.  Fragic soil properties either:
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
KFEI.  Other Eutrudepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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
4.  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 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
192	 Keys to Soil Taxonomy
KFEJ.  Other Eutrudepts that meet both of the following:
1.  In one or more horizons within 60 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); and
2.  Do not have free carbonates throughout any horizon
within 100 cm of the mineral soil surface.
Aquic Dystric Eutrudepts
KFEK.  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
KFEL.  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
KFEM.  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
KFEN.  Other Eutrudepts that have lamellae (two or more)
within 200 cm of the mineral soil surface.
Lamellic Eutrudepts
KFEO.  Other Eutrudepts that have do not have free
carbonates throughout any horizon within 100 cm of the mineral
soil surface, and have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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.
Dystric Fluventic Eutrudepts
KFEP.  Other Eutrudepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Eutrudepts
KFEQ.  Other Eutrudepts that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand in all horizons within 50 cm of
the mineral soil surface.
Arenic Eutrudepts
KFER.  Other Eutrudepts that do not have free carbonates
throughout any horizon within 100 cm of the mineral soil
surface.
Dystric Eutrudepts
KFES.  Other Eutrudepts that have a CaCO3
equivalent of 40
percent or more, including fragments 2 to 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
KFET.  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
KFEU.  Other Eutrudepts that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 18 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 18 cm after mixing.
Humic Eutrudepts
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KFEV.  Other Eutrudepts.
Typic Eutrudepts
Fragiudepts
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) particles 2.0 mm or
larger in diameter, 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 Fragiudepts
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 one or both of the
following:
1.  An umbric or mollic epipedon; or
2.  A color value, moist, of 3 or less and a color value,
dry, of 5 or less (crushed and smoothed sample) either
throughout the upper 18 cm of the mineral soil (unmixed) or
between the mineral soil surface and a depth of 18 cm after
mixing.
Humic Fragiudepts
KFCE.  Other Fragiudepts.
Typic Fragiudepts
Humudepts
Key to Subgroups
KFDA.  Humudepts that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Humudepts
KFDB.  Other Humudepts 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 wedgeshaped
peds 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 Humudepts
KFDC.  Other Humudepts 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) particles 2.0 mm
or larger in diameter, 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 Humudepts
KFDD.  Other Humudepts that have both:
1.  In 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
194	 Keys to Soil Taxonomy
percentages (by ammonium oxalate) totaling more than 1.0;
and
2.  Saturation with water 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.
Andic Oxyaquic Humudepts
KFDE.  Other Humudepts 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 Humudepts
KFDF.  Other Humudepts 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) particles 2.0 mm or
larger in diameter, 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 Humudepts
KFDG.  Other Humudepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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
4.  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 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 Humudepts
KFDH.  Other Humudepts 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 Humudepts
KFDI.  Other Humudepts 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 Humudepts
KFDJ.  Other Humudepts that have a sandy particle-size class
in all subhorizons throughout the particle-size control section.
Psammentic Humudepts
KFDK.  Other Humudepts 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 Humudepts
KFDL.  Other Humudepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  An umbric or mollic epipedon that is 50 cm or more
thick; and
4.  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 0.2 percent
or more and no densic, lithic, or paralithic contact within
that depth; or
b.  An irregular decrease in organic-carbon content
Inceptisols	 195
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C
(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 Humudepts
KFDM.  Other Humudepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Humudepts
KFDN.  Other Humudepts that have an umbric or mollic
epipedon that is 50 cm or more thick.
Pachic Humudepts
KFDO.  Other Humudepts that have a base saturation (by
NH4
OAc) of 60 percent or more either:
1.  In one-half or more of the total thickness between 25
and 75 cm from the mineral soil surface; or
2.  In some part of the 10 cm thickness directly above a
densic, lithic, or paralithic contact that occurs less than 50
cm below the mineral soil surface.
Eutric Humudepts
KFDP.  Other Humudepts that do not have a cambic horizon
and do not, in any part of the umbric or mollic epipedon, meet
the requirements for a cambic horizon, except for the color
requirements.
Entic Humudepts
KFDQ.  Other Humudepts.
Typic Humudepts
Sulfudepts
Key to Subgroups
KFAA.  All Sulfudepts (provisionally).
Typic Sulfudepts
Ustepts
Key to Great Groups
KDA.  Ustepts that have a duripan within 100 cm of the
mineral soil surface.
Durustepts, p. 197
KDB.  Other Ustepts that have both:
1.  A calcic horizon within 100 cm of the mineral soil
surface or a petrocalcic horizon within 150 cm of the mineral
soil surface; and
2.  Either free carbonates or a texture class 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. 195
KDC.  Other Ustepts that have an umbric or mollic epipedon
Humustepts, p. 202
KDD.  Other Ustepts that meet 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. 197
KDE.  Other Ustepts.
Haplustepts, p. 198
Calciustepts
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 peds in a layer 15 cm or more thick that
has its upper boundary within 125 cm of the mineral soil
surface; or
196	 Keys to Soil Taxonomy
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 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 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 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 peds 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 Calciustepts
KDBE.  Other Calciustepts that have a petrocalcic horizon
within 100 cm of the mineral soil surface.
Petrocalcic Calciustepts
KDBF.  Other Calciustepts that have a gypsic horizon 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 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 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
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 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 Calciustepts
KDBJ.  Other Calciustepts.
Typic Calciustepts
Inceptisols	 197
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C
Durustepts
Key to Subgroups
KDAA.  All Durustepts (provisionally).
Typic Durustepts
Dystrustepts
Key to Subgroups
KDDA.  Dystrustepts that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Dystrustepts
KDDB.  Other Dystrustepts 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 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 5o
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; 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 peds 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 Dystrustepts
KDDC.  Other Dystrustepts 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 wedgeshaped
peds 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 Dystrustepts
KDDD.  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
KDDE.  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) particles 2.0 mm or
larger in diameter, 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
KDDF.  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
KDDG.  Other Dystrustepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
198	 Keys to Soil Taxonomy
3.  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 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 Dystrustepts
KDDH.  Other Dystrustepts 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 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 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 Dystrustepts
KDDI.  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
KDDJ.  Other Dystrustepts that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 18 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 18 cm after mixing.
Humic Dystrustepts
KDDK.  Other Dystrustepts.
Typic Dystrustepts
Haplustepts
Key to Subgroups
KDEA.  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 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 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.
Aridic Lithic Haplustepts
KDEB.  Other Haplustepts that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Haplustepts
KDEC.  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
Inceptisols	 199
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C
control section that in normal years is dry in some or all
parts for fewer 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
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 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 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;
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 peds 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 Haplustepts
KDED.  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 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; 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 peds 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
KDEE.  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 wedgeshaped
peds 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
KDEF.  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
KDEG.  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) particles 2.0 mm or
larger in diameter, 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
200	 Keys to Soil Taxonomy
KDEH.  Other Haplustepts that have anthraquic conditions.
Anthraquic Haplustepts
KDEI.  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
KDEJ.  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
KDEK.  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
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
KDEL.  Other Haplustepts that have lamellae (two or more)
within 200 cm of the mineral soil surface.
Lamellic Haplustepts
KDEM.  Other Haplustepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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; and
4.  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 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
KDEN.  Other Haplustepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 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
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 soil temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C;
and
4.  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 0.2 percent
Inceptisols	 201
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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
KDEO.  Other Haplustepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Haplustepts
KDEP.  Other Haplustepts that have a gypsic horizon within
100 cm of the mineral soil surface.
Gypsic Haplustepts
KDEQ.  Other Haplustepts that have both:
1.  A calcic horizon 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 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.
Haplocalcidic Haplustepts
KDER.  Other Haplustepts that have both:
1.  A calcic horizon 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 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 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
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 soil temperature at a
depth of 50 cm below the soil surface is higher than 8 o
C.
Calcic Udic Haplustepts
KDES.  Other Haplustepts that have a calcic horizon within
100 cm of the mineral soil surface.
Calcic Haplustepts
KDET.  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 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:
202	 Keys to Soil Taxonomy
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 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 Haplustepts
KDEU.  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
KDEV.  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 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 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 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 Haplustepts
KDEW.  Other Haplustepts.
Typic Haplustepts
Humustepts
Key to Subgroups
KDCA.  Humustepts that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Humustepts
KDCB.  Other Humustepts 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 Humustepts
KDCC.  Other Humustepts 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) particles 2.0 mm or
larger in diameter, 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 Humustepts
KDCD.  Other Humustepts 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 Humustepts
KDCE.  Other Humustepts 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 Humustepts
KDCF.  Other Humustepts 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 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
Inceptisols	 203
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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 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 Humustepts
KDCG.  Other Humustepts.
Typic Humustepts
Xerepts
Key to Great Groups
KEA.  Xerepts that have a duripan within 100 cm of the
mineral soil surface.
Durixerepts, p. 204
KEB.  Other Xerepts that have a fragipan within 100 cm of the
mineral soil surface.
Fragixerepts, p. 206
KEC.  Other Xerepts that have an umbric or mollic epipedon.
Humixerepts, p. 208
KED.  Other Xerepts that have both:
1.  A calcic horizon within 100 cm of the mineral soil
surface or a petrocalcic horizon within 150 cm of the mineral
soil surface; and
2.  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.
Calcixerepts, p. 203
KEE.  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. 204
KEF.  Other Xerepts.
Haploxerepts, p. 206
Calcixerepts
Key to Subgroups
KEDA.  Calcixerepts that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Calcixerepts
KEDB.  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 wedgeshaped
peds 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
KEDC.  Other Calcixerepts that have a petrocalcic horizon
within 100 cm of the mineral soil surface.
Petrocalcic Calcixerepts
KEDD.  Other Calcixerepts that have an exchangeable 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
KEDE.  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) particles 2.0 mm or
larger in diameter, 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
KEDF.  Other Calcixerepts that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
204	 Keys to Soil Taxonomy
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Calcixerepts
KEDG.  Other Calcixerepts.
Typic Calcixerepts
Durixerepts
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) particles 2.0 mm
or larger in diameter, 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 Durixerepts
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
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 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) particles 2.0 mm or
larger in diameter, 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
Dystroxerepts
Key to Subgroups
KEEA.  Dystroxerepts 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 a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 18 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 18 cm after mixing.
Humic Lithic Dystroxerepts
KEEB.  Other Dystroxerepts that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Dystroxerepts
KEEC.  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:
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
Inceptisols	 205
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b.  More than 35 percent (by volume) particles 2.0 mm
or larger in diameter, 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
KEED.  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
KEEE.  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) particles 2.0 mm or
larger in diameter, 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
KEEF.  Other Dystroxerepts that have both:
1.  Fragic soil properties either:
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
KEEG.  Other Dystroxerepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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
4.  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 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
KEEH.  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
KEEI.  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
KEEJ.  Other Dystroxerepts that have fragic soil properties
either:
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
KEEK.  Other Dystroxerepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  A color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 18 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 18 cm after mixing; and
4.  One or both of the following:
206	 Keys to Soil Taxonomy
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 Dystroxerepts
KEEL.  Other Dystroxerepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Dystroxerepts
KEEM.  Other Dystroxerepts that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 18 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 18 cm after mixing.
Humic Dystroxerepts
KEEN.  Other Dystroxerepts.
Typic Dystroxerepts
Fragixerepts
Key to Subgroups
KEBA.  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
KEBB.  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) particles 2.0 mm or
larger in diameter, 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
KEBC.  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
KEBD.  Other Fragixerepts that have one or both of the
following:
1.  An umbric or mollic epipedon; or
2.  A color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 18 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 18 cm after mixing.
Humic Fragixerepts
KEBE.  Other Fragixerepts.
Typic Fragixerepts
Haploxerepts
Key to Subgroups
KEFA.  Haploxerepts 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 a color value, dry,
of 5 or less (crushed and smoothed sample) either throughout
the upper 18 cm of the mineral soil (unmixed) or between the
mineral soil surface and a depth of 18 cm after mixing.
Humic Lithic Haploxerepts
KEFB.  Other Haploxerepts that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Haploxerepts
KEFC.  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
Inceptisols	 207
I
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for some time in normal years and slickensides or wedgeshaped
peds 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
KEFD.  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) particles 2.0 mm
or larger in diameter, 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 Haploxerepts
KEFE.  Other Haploxerepts that have both:
1.  In 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.  Saturation with water 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.
Andic Oxyaquic Haploxerepts
KEFF.  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
KEFG.  Other Haploxerepts that have both:
1.  Saturation with water 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.  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.  More than 35 percent (by volume) particles 2.0 mm
or larger in diameter, 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.
Oxyaquic Vitrandic Haploxerepts
KEFH.  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) particles 2.0 mm or
larger in diameter, 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
KEFI.  Other Haploxerepts that have a gypsic horizon within
100 cm of the mineral soil surface.
Gypsic Haploxerepts
KEFJ.  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
208	 Keys to Soil Taxonomy
KEFK.  Other Haploxerepts that have lamellae (two or more)
within 200 cm of the mineral soil surface.
Lamellic Haploxerepts
KEFL.  Other Haploxerepts that have fragic soil properties
either:
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
KEFM.  Other Haploxerepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Haploxerepts
KEFN.  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
KEFO.  Other Haploxerepts that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 18 cm of the
mineral soil (unmixed) or between the mineral soil surface and
a depth of 18 cm after mixing.
Humic Haploxerepts
KEFP.  Other Haploxerepts.
Typic Haploxerepts
Humixerepts
Key to Subgroups
KECA.  Humixerepts that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Humixerepts
KECB.  Other Humixerepts 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) particles 2.0 mm
or larger in diameter, 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 Humixerepts
KECC.  Other Humixerepts 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 Humixerepts
KECD.  Other Humixerepts 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) particles 2.0 mm or
larger in diameter, 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
Inceptisols	 209
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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 Humixerepts
KECE.  Other Humixerepts 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 Humixerepts
KECF.  Other Humixerepts 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 Humixerepts
KECG.  Other Humixerepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  An umbric or mollic epipedon that is 50 cm or more
thick; and
4.  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 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.
Cumulic Humixerepts
KECH.  Other Humixerepts that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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 Humixerepts
KECI.  Other Humixerepts that have an umbric or mollic
epipedon that is 50 cm or more thick.
Pachic Humixerepts
KECJ.  Other Humixerepts that do not have a cambic horizon
and do not, in any part of the umbric or mollic epipedon, meet
the requirements for a cambic horizon, except for the color
requirements.
Entic Humixerepts
KECK.  Other Humixerepts.
Typic Humixerepts
	211
Key to Suborders
IA.  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 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); and
4.  A soil temperature regime that is warmer than cryic.
Albolls, p. 212
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 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;*
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 neutral colors with no
hue (N) and zero chroma 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
* 
If the mollic epipedon extends to a lithic contact within 30 cm of the mineral soil
surface, the requirement for redoximorphic features is waived.
M
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Mollisols
CHAPTER 12
212	 Keys to Soil Taxonomy
to alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquolls, p. 213
IC.  Other Mollisols that:
1.  Have a mollic epipedon that is 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 75 mm in diameter
that have a CaCO3
equivalent of 40 percent or more; and
4.  Have either or both:
a.   A udic soil moisture regime; or
b.  A cryic soil temperature regime.
Rendolls, p. 221
ID.  Other Mollisols that have a gelic soil temperature regime.
Gelolls, p. 221
IE.  Other Mollisols that have a cryic soil temperature regime.
Cryolls, p. 217
IF.  Other Mollisols that have either a xeric soil moisture
regime or an aridic soil moisture regime that borders on xeric.
Xerolls, p. 246
IG.  Other Mollisols that have either an ustic soil moisture
regime or an aridic soil moisture regime that borders on ustic.
Ustolls, p. 230
IH.  Other Mollisols.
Udolls, p. 222
Albolls
Key to Great Groups
IAA.  Albolls that have a natric horizon.
Natralbolls, p. 213
IAB.  Other Albolls.
Argialbolls, p. 212
Argialbolls
Key to Subgroups
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 peds 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 wedgeshaped
peds 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 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
Mollisols	 213
2.  More than 35 percent (by volume) particles 2.0 mm or
larger in diameter, 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
Natralbolls
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
Aquolls
Key to Great Groups
IBA.  Aquolls that have a cryic soil temperature regime.
Cryaquolls, p. 214
IBB.  Other Aquolls that have a duripan within 100 cm of the
mineral soil surface.
Duraquolls, p. 214
IBC.  Other Aquolls that have a natric horizon.
Natraquolls, p. 217
IBD.  Other Aquolls that have a calcic or gypsic horizon within
40 cm of the mineral soil surface but do not have an argillic
horizon unless it is a buried horizon.
Calciaquolls, p. 213
IBE.  Other Aquolls that have an argillic horizon.
Argiaquolls, p. 213
IBF.   Other Aquolls that have episaturation.
Epiaquolls, p. 216
IBG.  Other Aquolls.
Endoaquolls, p. 214
Argiaquolls
Key to Subgroups
IBEA.  Argiaquolls that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 wedgeshaped
peds 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 one or both of the
following:
1.  An argillic horizon that has a clay increase of 20 percent
or more (absolute, in the fine-earth fraction) within a vertical
distance of 7.5 cm, either within the horizon or at its upper
boundary; or
2.  An abrupt textural change between the eluvial horizon
and the upper boundary of the argillic horizon.
Abruptic Argiaquolls
IBEE.  Other Argiaquolls.
Typic Argiaquolls
Calciaquolls
Key to Subgroups
IBDA.  Calciaquolls that have a petrocalcic horizon within 100
cm of the mineral soil surface.
Petrocalcic Calciaquolls
M
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214	 Keys to Soil Taxonomy
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
Cryaquolls
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 wedgeshaped
peds 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) particles 2.0 mm or
larger in diameter, 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
IBAG.  Other Cryaquolls that have a mollic epipedon that is
50 cm or more thick.
Cumulic Cryaquolls
IBAH.  Other Cryaquolls.
Typic Cryaquolls
Duraquolls
Key to Subgroups
IBBA.  Duraquolls that have a natric horizon.
Natric Duraquolls
IBBB.  Other Duraquolls that have 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 peds in a layer 15 cm or more
thick that is 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 Duraquolls
IBBC.  Other Duraquolls that have an argillic horizon.
Argic Duraquolls
IBBD.  Other Duraquolls.
Typic Duraquolls
Endoaquolls
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 of the following:
1.  A mollic epipedon that is 60 cm or more thick; and
Mollisols	 215
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 peds 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.
Cumulic Vertic Endoaquolls
IBGC.  Other Endoaquolls that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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
4.  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 peds 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.
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 wedgeshaped
peds 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) particles 2.0 mm or
larger in diameter, 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 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
at least a firm rupture-resistance class when moist.
Duric Endoaquolls
IBGI.  Other Endoaquolls that have a mollic epipedon that is
60 cm or more thick.
Cumulic Endoaquolls
IBGJ.  Other Endoaquolls that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  One or both of the following:
a.  An organic-carbon content (Holocene age) of 0.3
percent or more in all horizons within 125 cm of the
mineral soil surface; or
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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 Endoaquolls
IBGK.  Other Endoaquolls.
Typic Endoaquolls
Epiaquolls
Key to Subgroups
IBFA.  Epiaquolls that have both of the following:
1.  A mollic epipedon that is 60 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 peds 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.
Cumulic Vertic Epiaquolls
IBFB.  Other Epiaquolls that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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
4.  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 peds 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.
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 wedgeshaped
peds 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) particles 2.0 mm or
larger in diameter, 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
at least a firm rupture-resistance class when moist.
Duric Epiaquolls
Mollisols	 217
IBFH.  Other Epiaquolls that have a mollic epipedon that is 60
cm or more thick.
Cumulic Epiaquolls
IBFI.  Other Epiaquolls that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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 Epiaquolls
IBFJ.  Other Epiaquolls.
Typic Epiaquolls
Natraquolls
Key to Subgroups
IBCA.  Natraquolls that have a petrocalcic horizon within 100
cm of the mineral soil surface.
Petrocalcic Natraquolls
IBCB.  Other 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 peds 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
IBCC.  Other Natraquolls that have a glossic horizon or
interfingering of albic materials into the natric horizon.
Glossic Natraquolls
IBCD.  Other Natraquolls.
Typic Natraquolls
Cryolls
Key to Great Groups
IEA.  Cryolls that have a duripan within 100 cm of the mineral
soil surface.
Duricryolls, p. 219
IEB.  Other Cryolls that have a natric horizon.
Natricryolls, p. 220
IEC.  Other Cryolls that have both of the following:
1.  An argillic horizon that has its upper boundary 60 cm or
more below the mineral soil surface; and
2.  A texture class finer than loamy fine sand in all horizons
above the argillic horizon.
Palecryolls, p. 220
IED.  Other Cryolls that have an argillic horizon.
Argicryolls, p. 217
IEE.  Other Cryolls that have both of the following:
1.  A calcic or petrocalcic horizon 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 free carbonates or a texture class of
loamy fine sand or coarser.
Calcicryolls, p. 218
IEF.  Other Cryolls.
Haplocryolls, p. 219
Argicryolls
Key to Subgroups
IEDA.  Argicryolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Argicryolls
IEDB.  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 wedgeshaped
peds 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
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218	 Keys to Soil Taxonomy
IEDC.  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
IEDD.  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) particles 2.0 mm or
larger in diameter, 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
IEDE.  Other Argicryolls that have one or both of the
following:
1.  An argillic horizon that has a clay increase of 20 percent
or more (absolute, in the fine-earth fraction) within a vertical
distance of 7.5 cm, either within the horizon or at its upper
boundary; or
2.  An abrupt textural change between the eluvial horizon
and the upper boundary of the argillic horizon.
Abruptic Argicryolls
IEDF.  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
IEDG.  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
IEDH.  Other Argicryolls that have both of the following:
1.  A mollic epipedon that is 40 cm or more thick and has a
texture class finer than loamy fine sand; and
2.  A calcic horizon within 100 cm of the mineral soil
surface.
Calcic Pachic Argicryolls
IEDI.  Other Argicryolls that have a mollic epipedon that is 40
cm or more thick and has a texture class finer than loamy fine
sand.
Pachic Argicryolls
IEDJ.  Other Argicryolls that have a calcic horizon within 100
cm of the mineral soil surface.
Calcic Argicryolls
IEDK.  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
IEDL.  Other Argicryolls that have an ustic soil moisture
regime.
Ustic Argicryolls
IEDM.  Other Argicryolls that have a xeric soil moisture
regime.
Xeric Argicryolls
IEDN.  Other Argicryolls.
Typic Argicryolls
Calcicryolls
Key to Subgroups
IEEA.  Calcicryolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Calcicryolls
IEEB.  Other Calcicryolls 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) particles 2.0 mm or
larger in diameter, 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
Mollisols	 219
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 Calcicryolls
IEEC.  Other Calcicryolls that have a petrocalcic horizon
within 100 cm of the mineral soil surface.
Petrocalcic Calcicryolls
IEED.  Other Calcicryolls that have a mollic epipedon that is
40 cm or more thick and has a texture class finer than loamy
fine sand.
Pachic Calcicryolls
IEEE.  Other Calcicryolls that have an ustic soil moisture
regime.
Ustic Calcicryolls
IEEF.  Other Calcicryolls that have a xeric soil moisture
regime.
Xeric Calcicryolls
IEEG.  Other Calcicryolls.
Typic Calcicryolls
Duricryolls
Key to Subgroups
IEAA.  Duricryolls that have an argillic horizon.
Argic Duricryolls
IEAB.  Other Duricryolls that have a calcic horizon above the
duripan.
Calcic Duricryolls
IEAC.  Other Duricryolls.
Typic Duricryolls
Haplocryolls
Key to Subgroups
IEFA.  Haplocryolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Haplocryolls
IEFB.  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 more
for some time in normal years and slickensides or wedgeshaped
peds 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
IEFC.  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
IEFD.  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) particles 2.0 mm or
larger in diameter, 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
IEFE.  Other Haplocryolls that have all of the following:
1.  A mollic epipedon that is 40 cm or more thick and has a
texture class finer than loamy fine sand; and
2.  A slope of less than 25 percent; and
3.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
4.  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
5.  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
IEFF.  Other Haplocryolls that have all of the following:
1.  A mollic epipedon that is 40 cm or more thick and has a
texture class finer than loamy fine sand; and
2.  A slope of less than 25 percent; and
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3.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
4.  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 Haplocryolls
IEFG.  Other Haplocryolls that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3. One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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
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).
Fluvaquentic Haplocryolls
IEFH.  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
IEFI.  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
IEFJ.  Other Haplocryolls that have both of the following:
1.  A mollic epipedon that is 40 cm or more thick and has a
texture class finer than loamy fine sand; and
2.  A calcic horizon within 100 cm of the mineral soil
surface.
Calcic Pachic Haplocryolls
IEFK.  Other Haplocryolls that have a mollic epipedon that
is 40 cm or more thick and has a texture class finer than loamy
fine sand.
Pachic Haplocryolls
IEFL.  Other Haplocryolls that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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 Haplocryolls
IEFM.  Other Haplocryolls that have a calcic horizon within
100 cm of the mineral soil surface.
Calcic Haplocryolls
IEFN.  Other Haplocryolls that have an ustic soil moisture
regime.
Ustic Haplocryolls
IEFO.  Other Haplocryolls that have a xeric soil moisture
regime.
Xeric Haplocryolls
IEFP.  Other Haplocryolls.
Typic Haplocryolls
Natricryolls
Key to Subgroups
IEBA.  All Natricryolls.
Typic Natricryolls
Palecryolls
Key to Subgroups
IECA.  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
IECB.  Other Palecryolls that in normal years are saturated
Mollisols	 221
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
IECC.  Other Palecryolls that have one or both of the
following:
1.  An argillic horizon that has a clay increase of 20 percent
or more (absolute, in the fine-earth fraction) within a vertical
distance of 7.5 cm, either within the horizon or at its upper
boundary; or
2.  An abrupt textural change between the eluvial horizon
and the upper boundary of the argillic horizon.
Abruptic Palecryolls
IECD.  Other Palecryolls that have a mollic epipedon that is 40
cm or more thick and has a texture class finer than loamy fine
sand.
Pachic Palecryolls
IECE.  Other Palecryolls that have an ustic soil moisture
regime.
Ustic Palecryolls
IECF.  Other Palecryolls that have a xeric soil moisture
regime.
Xeric Palecryolls
IECG.  Other Palecryolls.
Typic Palecryolls
Gelolls
Key to Great Groups
IDA.  All Gelolls.
Haplogelolls, p. 221
Haplogelolls
Key to Subgroups
IDAA.  Haplogelolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Haplogelolls
IDAB.  Other Haplogelolls 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 Haplogelolls
IDAC.  Other Haplogelolls 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 Haplogelolls
IDAD.  Other Haplogelolls 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 Haplogelolls
IDAE.  Other Haplogelolls that have gelic materials within
200 cm of the mineral soil surface.
Turbic Haplogelolls
IDAF.  Other Haplogelolls that have both of the following:
1.  A mollic epipedon that is 40 cm or more thick and has a
texture class finer than loamy fine sand; and
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.
Cumulic Haplogelolls
IDAG.  Other Haplogelolls.
Typic Haplogelolls
Rendolls
Key to Great Groups
ICA.  Rendolls that have a cryic soil temperature regime.
Cryrendolls, p. 221
ICB.  Other Rendolls.
Haprendolls, p. 222
Cryrendolls
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
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Haprendolls
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 wedgeshaped
peds 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 that is 18 cm or more thick.
Entic Haprendolls
ICBE.  Other Haprendolls.
Typic Haprendolls
Udolls
Key to Great Groups
IHA.  Udolls that have a natric horizon.
Natrudolls, p. 228
IHB.  Other Udolls that:
1.  Have a calcic or petrocalcic horizon within 100 cm of
the mineral soil surface; and
2.  Do not have an argillic horizon above the calcic or
petrocalcic horizon; and
3.  Have free carbonates 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.
Calciudolls, p. 225
IHC.  Other Udolls that have one or both of the following:
1.  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 noncarbonate clay content;
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
2.  A frigid soil temperature regime and both of the
following:
a.  An argillic horizon that has its upper boundary 60 cm
or more below the mineral soil surface; and
b.  A texture class finer than loamy fine sand in all
horizons above the argillic horizon.
Paleudolls, p. 229
IHD.  Other Udolls that have an argillic horizon.
Argiudolls, p. 222
IHE.  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. 230
IHF.  Other Udolls.
Hapludolls, p. 226
Argiudolls
Key to Subgroups
IHDA.  Argiudolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Argiudolls
Mollisols	 223
IHDB.  Other Argiudolls that have a petrocalcic horizon within
100 cm of the mineral soil surface.
Petrocalcic Argiudolls
IHDC.  Other Argiudolls that have both of the following:
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.  Within 75 cm of the mineral soil surface, 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 peds 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
IHDD.  Other Argiudolls that have both of the following:
1.  In normal years saturation 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; 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 peds 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 Argiudolls
IHDE.  Other Argiudolls that have both of the following:
1.  A mollic epipedon that has a texture class finer than
loamy fine sand and that is either:
a.  40 cm or more thick in a frigid soil temperature
regime; or
b.  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 peds 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
IHDF.  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.  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 peds 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
IHDG.  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
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for some time in normal years and slickensides or wedgeshaped
peds 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
IHDH.  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
IHDI.  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) particles 2.0 mm or
larger in diameter, 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
IHDJ.  Other Argiudolls that have both of the following:
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.  Within 75 cm of the mineral soil surface, 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 mollic epipedon that has a texture class finer than
loamy fine sand and that is either:
a.  40 cm or more thick in a frigid soil temperature
regime; or
b.  50 cm or more thick.
Aquic Pachic Argiudolls
IHDK.  Other Argiudolls that have a mollic epipedon that has a
texture class finer than loamy fine sand and that is either:
1.  40 cm or more thick in a frigid soil temperature regime;
or
2.  50 cm or more thick.
Pachic Argiudolls
IHDL.  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.  Within 75 cm of the mineral soil surface, 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
IHDM.  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
IHDN.  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
Mollisols	 225
argillic horizon 7.5 to 20 cm thick, each with an overlying
eluvial horizon.
Lamellic Argiudolls
IHDO.  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
IHDP.  Other Argiudolls that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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
IHDQ.  Other Argiudolls that have one or both of the
following:
1.  An argillic horizon that has a clay increase of 20 percent
or more (absolute, in the fine-earth fraction) within a vertical
distance of 7.5 cm, either within the horizon or at its upper
boundary; or
2.  An abrupt textural change between the eluvial horizon
and the upper boundary of the argillic horizon.
Abruptic Argiudolls
IHDR.  Other Argiudolls 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 Argiudolls
IHDS.  Other Argiudolls 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.
Oxic Argiudolls
IHDT.  Other Argiudolls that have a calcic horizon within 100
cm of the mineral soil surface.
Calcic Argiudolls
IHDU.  Other Argiudolls.
Typic Argiudolls
Calciudolls
Key to Subgroups
IHBA.  Calciudolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Calciudolls
IHBB.  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 wedgeshaped
peds 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
IHBC.  Other Calciudolls that have both of the following:
1.  An anthropic epipedon; and
2.  A petrocalcic horizon that formed in human-transported
material within 100 cm of the mineral soil surface.
Anthropic Petrocalcic Calciudolls
IHBD.  Other Calciudolls 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 Calciudolls
IHBE.  Other Calciudolls that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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 Calciudolls
IHBF.  Other Calciudolls.
Typic Calciudolls
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Hapludolls
Key to Subgroups
IHFA.  Hapludolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Hapludolls
IHFB.  Other Hapludolls that have a petrocalcic horizon within
100 cm of the mineral soil surface.
Petrocalcic Hapludolls
IHFC.  Other Hapludolls that have both of the following:
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.  Within 75 cm of the mineral soil surface, 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 peds 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
IHFD.  Other Hapludolls that have both of the following:
1.  A mollic epipedon that has a texture class finer than
loamy fine sand and that is either:
a.  40 cm or more thick in a frigid soil temperature
regime; or
b.  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 peds 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 Hapludolls
IHFE.  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 wedgeshaped
peds 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
IHFF.  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 Al + 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0.
Andic Hapludolls
IHFG.  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) particles 2.0 mm or
larger in diameter, 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
IHFH.  Other Hapludolls that have all of the following:
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
Mollisols	 227
2.  Either:
a.  A frigid soil temperature regime and a mollic
epipedon that is 40 cm or more thick, of which less than
50 percent meets sandy or sandy-skeletal particle-size
class criteria, 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 60 cm or more thick, of
which 50 percent or more of the thickness has a texture
class finer than loamy fine sand; and
3.  A slope of less than 25 percent; and
4.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
5.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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.
Aquic Cumulic Hapludolls
IHFI.  Other Hapludolls that have all of the following:
1.  Either:
a.  A frigid soil temperature regime and a mollic
epipedon that is 40 cm or more thick, of which less than
50 percent meets sandy or sandy-skeletal particle-size
class criteria, 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 60 cm or more thick, of
which 50 percent or more of the thickness has a texture
class finer than loamy fine sand; and
2.  A slope of less than 25 percent; and
3.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
4.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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 Hapludolls
IHFJ.  Other Hapludolls that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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.  Within 75 cm of the mineral soil surface, 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
4.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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 Hapludolls
IHFK.  Other Hapludolls that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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 Hapludolls
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IHFL.  Other Hapludolls that have both of the following:
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.  Within 75 cm of the mineral soil surface, 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 mollic epipedon that has a texture class finer than
loamy fine sand and that is either:
a.  40 cm or more thick in a frigid soil temperature
regime; or
b.  50 cm or more thick.
Aquic Pachic Hapludolls
IHFM.  Other Hapludolls that have a mollic epipedon that has
a texture class finer than loamy fine sand and that is either:
1.  40 cm or more thick in a frigid soil temperature regime;
or
2.  50 cm or more thick.
Pachic Hapludolls
IHFN.  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.  Within 75 cm of the mineral soil surface, 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
IHFO.  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
IHFP.  Other Hapludolls that have both:
1.  A mollic epipedon that is 60 cm or more thick that has
a texture class 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 the requirements for
a cambic horizon, except for the color requirements, or have
free carbonates throughout either the cambic horizon or the
lower part of the mollic epipedon.
Vermic Hapludolls
IHFQ.  Other Hapludolls that have a calcic horizon within 100
cm of the mineral soil surface.
Calcic Hapludolls
IHFR.  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 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
IHFS.  Other Hapludolls.
Typic Hapludolls
Natrudolls
Key to Subgroups
IHAA.  Natrudolls that have a petrocalcic horizon within 100
cm of the mineral soil surface.
Petrocalcic Natrudolls
IHAB.  Other Natrudolls 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 peds in a layer 15 cm or more thick that
Mollisols	 229
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
IHAC.  Other Natrudolls that have both of the following:
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 peds 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
IHAD.  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 wedgeshaped
peds 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
IHAE.  Other Natrudolls that have visible crystals of gypsum
and/or more soluble salts within 40 cm of the mineral soil
surface.
Leptic Natrudolls
IHAF.  Other Natrudolls that have one or both of the
following:
1.  A natric horizon that has a clay increase of 20 percent or
more (absolute, in the fine-earth fraction) within a vertical
distance of 7.5 cm, either within the horizon or at its upper
boundary; or
2.  An abrupt textural change between the eluvial horizon
and the upper boundary of the natric horizon.
Abruptic Natrudolls
IHAG.  Other Natrudolls that have a glossic horizon or
interfingering of albic materials into the natric horizon.
Glossic Natrudolls
IHAH.  Other Natrudolls that have a calcic horizon within 100
cm of the mineral soil surface.
Calcic Natrudolls
IHAI.  Other Natrudolls.
Typic Natrudolls
Paleudolls
Key to Subgroups
IHCA.  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 peds 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 Paleudolls
IHCB.  Other Paleudolls that have both of the following:
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.  Within 75 cm of the mineral soil surface, 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 mollic epipedon that has a texture class finer than
loamy fine sand and that is either:
a.  40 cm or more thick in a frigid soil temperature
regime; or
b.  50 cm or more thick.
Aquic Pachic Paleudolls
M
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230	 Keys to Soil Taxonomy
IHCC.  Other Paleudolls that have a mollic epipedon that has
a texture class finer than loamy fine sand and that is 50 cm or
more thick.
Pachic Paleudolls
IHCD.  Other Paleudolls that have, in one or more subhorizons
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 Paleudolls
IHCE.  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
IHCF.  Other Paleudolls that have both of the following:
1.  A calcic horizon 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 free carbonates or a texture class of loamy fine
sand or coarser.
Calcic Paleudolls
IHCG.  Other Paleudolls.
Typic Paleudolls
Vermudolls
Key to Subgroups
IHEA.  Vermudolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Vermudolls
IHEB.  Other Vermudolls that have a mollic epipedon that is
less than 75 cm thick.
Haplic Vermudolls
IHEC.  Other Vermudolls.
Typic Vermudolls
Ustolls
Key to Great Groups
IGA.  Ustolls that have a duripan within 100 cm of the mineral
soil surface.
Durustolls, p. 236
IGB.  Other Ustolls that have a natric horizon.
Natrustolls, p. 242
IGC.  Other Ustolls that:
1.  Have either a calcic or gypsic horizon within 100 cm of
the mineral soil surface or a petrocalcic horizon 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, have either free carbonates
or a texture class of loamy fine sand or coarser.
Calciustolls, p. 234
IGD.  Other Ustolls that have either:
1.  A petrocalcic horizon 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 noncarbonate clay
content 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 noncarbonate clay throughout one
or more subhorizons in its upper part, and one or both of
the following:
(1)  A clay increase of 20 percent or more (absolute,
in the fine-earth fraction) within a vertical distance
of 7.5 cm or of 15 percent or more (absolute, in the
fine-earth fraction) within a vertical distance of 2.5
cm, either within the argillic horizon or at its upper
boundary (and there is no densic, lithic, or paralithic
contact within 50 cm of the mineral soil surface); or
(2)  An abrupt textural change between the eluvial
horizon and the upper boundary of the argillic horizon
(and there is no densic, lithic, or paralithic contact
within 50 cm of the mineral soil surface).
Paleustolls, p. 244
IGE.  Other Ustolls that have an argillic horizon.
Argiustolls, p. 231
IGF.  Other Ustolls that have a mollic epipedon that:
Mollisols	 231
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. 246
IGG.  Other Ustolls.
Haplustolls, p. 236
Argiustolls
Key to Subgroups
IGEA.  Argiustolls that have both of the following:
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 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 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
IGEB.  Other Argiustolls that have both of the following:
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
IGEC.  Other Argiustolls that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Argiustolls
IGED.  Other Argiustolls that have both of the following:
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.  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 peds 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 Argiustolls
IGEE.  Other Argiustolls that have both of the following:
1.  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 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 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
M
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232	 Keys to Soil Taxonomy
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 peds 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 Argiustolls
IGEF.  Other Argiustolls that have all of the following:
1.  A mollic epipedon that has a texture class finer than
loamy fine sand and that is either:
a.  40 cm or more thick in a frigid soil temperature
regime; or
b.  50 cm or more thick; 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;
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 peds 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 Udertic Argiustolls
IGEG.  Other Argiustolls that have both of the following:
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 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;
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 peds 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 Argiustolls
IGEH.  Other Argiustolls that have both of the following:
1.  A mollic epipedon that has a texture class finer than
loamy fine sand and that is either:
a.  40 cm or more thick in a frigid soil temperature
regime; or
b.  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 peds 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 Argiustolls
IGEI.  Other Argiustolls that have one or both of the
following:
1.  Cracks within 125 cm of the mineral soil surface that are
Mollisols	 233
5 mm or more wide through a thickness of 30 cm or more
for some time in normal years and slickensides or wedgeshaped
peds 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
IGEJ.  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
IGEK.  Other Argiustolls that have both of the following:
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 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) particles 2.0 mm
or larger in diameter, 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 Argiustolls
IGEL.  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) particles 2.0 mm or
larger in diameter, 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
IGEM.  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
IGEN.  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
IGEO.  Other Argiustolls that have a mollic epipedon that has
a texture class finer than loamy fine sand and that is either:
1.  40 cm or more thick in a frigid soil temperature regime;
or
2.  50 cm or more thick.
Pachic Argiustolls
IGEP.  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
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234	 Keys to Soil Taxonomy
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
IGEQ.  Other Argiustolls that have both of the following:
1.  A calcic horizon 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 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 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
IGER.  Other Argiustolls 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 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
5 o
C.
Aridic Argiustolls
IGES.  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
IGET.  Other Argiustolls that have a horizon, 15 cm or more
thick within 100 cm of the mineral soil surface, that either is
brittle and has some opal coats or has 20 percent or more (by
volume) durinodes.
Duric Argiustolls
IGEU.  Other Argiustolls.
Typic Argiustolls
Calciustolls
Key to Subgroups
IGCA.  Calciustolls that have a salic horizon within 75 cm of
the mineral soil surface.
Salidic Calciustolls
IGCB.  Other Calciustolls that have a petrocalcic horizon and a
lithic contact within 50 cm of the mineral soil surface.
Lithic Petrocalcic Calciustolls
IGCC.  Other Calciustolls that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Calciustolls
IGCD.  Other Calciustolls that have both of the following:
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
Mollisols	 235
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 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.  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 peds 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 Calciustolls
IGCE.  Other Calciustolls that have both of the following:
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 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;
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 peds 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 Calciustolls
IGCF.  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 peds 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
IGCG.  Other Calciustolls that have a petrocalcic horizon
within 100 cm of the mineral soil surface.
Petrocalcic Calciustolls
IGCH.  Other Calciustolls that have a gypsic horizon within
100 cm of the mineral soil surface.
Gypsic Calciustolls
IGCI.  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
IGCJ.  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
IGCK.  Other Calciustolls that have a mollic epipedon that has
a texture class finer than loamy fine sand and that is either:
1.  40 cm or more thick in a frigid soil temperature regime;
or
2.  50 cm or more thick.
Pachic Calciustolls
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236	 Keys to Soil Taxonomy
IGCL.  Other Calciustolls 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 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
5 o
C.
Aridic Calciustolls
IGCM.  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
IGCN.  Other Calciustolls.
Typic Calciustolls
Durustolls
Key to Subgroups
IGAA.  Durustolls that have a natric horizon above the
duripan.
Natric Durustolls
IGAB.  Other Durustolls that:
1.  Do not have an argillic horizon above the duripan; and
2.  Have an aridic soil moisture regime that borders on
ustic.
Haploduridic Durustolls
IGAC.  Other Durustolls that have an aridic soil moisture
regime that borders on ustic.
Argiduridic Durustolls
IGAD.  Other Durustolls that do not have an argillic horizon
above the duripan.
Entic Durustolls
IGAE.  Other Durustolls that have a duripan that is strongly
cemented or less cemented in all subhorizons.
Haplic Durustolls
IGAF.  Other Durustolls.
Typic Durustolls
Haplustolls
Key to Subgroups
IGGA.  Haplustolls that have a salic horizon within 75 cm of
the mineral soil surface.
Salidic Haplustolls
IGGB.  Other Haplustolls that have, in part of each pedon, a
lithic contact within 50 cm of the mineral soil surface.
Ruptic-Lithic Haplustolls
IGGC.  Other Haplustolls that have both of the following:
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 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
Mollisols	 237
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 lithic contact within 50 cm of the mineral soil surface.
Aridic Lithic Haplustolls
IGGD.  Other Haplustolls that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Haplustolls
IGGE.  Other Haplustolls that have both of the following:
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.  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 peds 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 Haplustolls
IGGF.  Other Haplustolls that have both of the following:
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 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.  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 peds 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 Haplustolls
IGGG.  Other Haplustolls that have all of the following:
1.  A mollic epipedon that has a texture class finer than
loamy fine sand and that is either:
a.  40 cm or more thick in a frigid soil temperature
regime; or
b.  50 cm or more thick; 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;
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 peds 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
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238	 Keys to Soil Taxonomy
or a densic, lithic, or paralithic contact, whichever is
shallower.
Pachic Udertic Haplustolls
IGGH.  Other Haplustolls that have both of the following:
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 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;
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 peds 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 Haplustolls
IGGI.  Other Haplustolls that have both of the following:
1.  A mollic epipedon that has a texture class finer than
loamy fine sand and that is either:
a.  40 cm or more thick in a frigid soil temperature
regime; or
b.  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 peds 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 Haplustolls
IGGJ.  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 wedgeshaped
peds 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
IGGK.  Other Haplustolls that have both of the following:
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 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 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, whichever is 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
IGGL.  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, whichever is 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
Mollisols	 239
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
IGGM.  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
IGGN.  Other Haplustolls that have both of the following:
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 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) particles 2.0 mm
or larger in diameter, 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
IGGO.  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) particles 2.0 mm or
larger in diameter, 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 Haplustolls
IGGP.  Other Haplustolls that have all of the following:
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.  Either:
a.  A frigid soil temperature regime and a mollic
epipedon that is 40 cm or more thick, of which less than
50 percent meets sandy or sandy-skeletal particle-size
class criteria, 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 class finer than loamy fine sand; and
3.  A slope of less than 25 percent; and
4.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
5.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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.
Aquic Cumulic Haplustolls
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240	 Keys to Soil Taxonomy
IGGQ.  Other Haplustolls that have all of the following:
1.  Either:
a.  A frigid soil temperature regime and a mollic
epipedon that is 40 cm or more thick, of which less than
50 percent meets sandy or sandy-skeletal particle-size
class criteria, 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 class finer than loamy fine sand; and
2.  A slope of less than 25 percent; and
3.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
4.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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 Haplustolls
IGGR.  Other Haplustolls that have anthraquic conditions.
Anthraquic Haplustolls
IGGS.  Other Haplustolls that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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
4.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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 Haplustolls
IGGT.  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
IGGU.  Other Haplustolls that have a mollic epipedon that has
a texture class finer than loamy fine sand and that is either:
1.  40 cm or more thick in a frigid soil temperature regime;
or
2.  50 cm or more thick.
Pachic Haplustolls
IGGV.  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
IGGW.  Other Haplustolls that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  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 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
Mollisols	 241
4.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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 Haplustolls
IGGX.  Other Haplustolls that:
1.  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 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 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.  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 the requirements for a cambic horizon,
except for the color requirements; 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
IGGY.  Other Haplustolls 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 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
5 o
C.
Aridic Haplustolls
IGGZ.  Other Haplustolls that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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 Haplustolls
IGGZa.  Other Haplustolls that have a horizon, 15 cm or more
thick within 100 cm of the mineral soil surface, that either is
brittle and has some opal coats or has 20 percent or more (by
volume) durinodes.
Duric Haplustolls
IGGZb.  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
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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
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
free carbonates throughout either the cambic horizon or the
lower part of the mollic epipedon.
Udorthentic Haplustolls
IGGZc.  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
IGGZd. 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 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 Haplustolls
IGGZe.  Other Haplustolls.
Typic Haplustolls
Natrustolls
Key to Subgroups
IGBA.  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.  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 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
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 peds 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 Natrustolls
IGBB.  Other Natrustolls that have both of the following:
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 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
Mollisols	 243
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.  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 peds 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 Natrustolls
IGBC.  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 peds 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
IGBD.  Other Natrustolls that have both of the following:
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 peds 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
IGBE.  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 wedgeshaped
peds 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
IGBF.  Other Natrustolls that have both of the following:
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 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.  Visible crystals of gypsum and/or more soluble salts
within 40 cm of the mineral soil surface.
Aridic Leptic Natrustolls
IGBG.  Other Natrustolls that have visible crystals of gypsum
and/or more soluble salts within 40 cm of the mineral soil
surface.
Leptic Natrustolls
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244	 Keys to Soil Taxonomy
IGBH.  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 adsorption
ratio) between the mineral soil surface and a depth of 25 cm
than in the underlying horizon.
Aquic Natrustolls
IGBI.  Other Natrustolls 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 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
5 o
C.
Aridic Natrustolls
IGBJ.  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
at least a firm rupture-resistance class when moist.
Duric Natrustolls
IGBK.  Other Natrustolls that have a glossic horizon or
interfingering of albic materials into a natric horizon.
Glossic Natrustolls
IGBL.  Other Natrustolls.
Typic Natrustolls
Paleustolls
Key to Subgroups
IGDA.  Paleustolls that have both of the following:
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 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.  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 peds 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 Paleustolls
IGDB.  Other Paleustolls that have both of the following:
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 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	 245
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;
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 peds 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 Paleustolls
IGDC.  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 wedgeshaped
peds 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
IGDD.  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
IGDE.  Other Paleustolls that have a mollic epipedon that has
a texture class finer than loamy fine sand and that is 50 cm or
more thick.
Pachic Paleustolls
IGDF.  Other Paleustolls that have a petrocalcic horizon within
150 cm of the mineral soil surface.
Petrocalcic Paleustolls
IGDG.  Other Paleustolls that have both of the following:
1.  A calcic horizon within one of the following particlesize
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,
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 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.
Calcidic Paleustolls
IGDH.  Other Paleustolls 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 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
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246	 Keys to Soil Taxonomy
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
IGDI.  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 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
IGDJ.  Other Paleustolls that 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
IGDK.  Other Paleustolls that have free carbonates throughout
after the surface horizons have been mixed to a depth of 18 cm.
Entic Paleustolls
IGDL.  Other Paleustolls.
Typic Paleustolls
Vermustolls
Key to Subgroups
IGFA.  Vermustolls that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Vermustolls
IGFB.  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
IGFC.  Other Vermustolls that have a mollic epipedon that is
75 cm or more thick.
Pachic Vermustolls
IGFD.  Other Vermustolls that have a mollic epipedon that is
less than 50 cm thick.
Entic Vermustolls
IGFE.  Other Vermustolls.
Typic Vermustolls
Xerolls
Key to Great Groups
IFA.  Xerolls that have a duripan within 100 cm of the mineral
soil surface.
Durixerolls, p. 249
IFB.  Other Xerolls that have a natric horizon.
Natrixerolls, p. 255
IFC.  Other Xerolls that have either:
1.  A petrocalcic horizon 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 noncarbonate clay
content 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 noncarbonate clay throughout one
or more subhorizons in its upper part, and one or both of
the following:
(1)  A clay increase of 20 percent or more (absolute,
in the fine-earth fraction) within a vertical distance
of 7.5 cm or of 15 percent or more (absolute, in the
fine-earth fraction) within a vertical distance of 2.5
cm, either within the argillic horizon or at its upper
boundary (and there is no densic, lithic, or paralithic
contact within 50 cm of the mineral soil surface); or
(2)  An abrupt textural change between the eluvial
horizon and the upper boundary of the argillic horizon
(and there is no densic, lithic, or paralithic contact
within 50 cm of the mineral soil surface).
Palexerolls, p. 255
Mollisols	 247
IFD.  Other Xerolls that have both of the following:
1.  A calcic or gypsic horizon 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 free
carbonates or a texture class of loamy fine sand or coarser.
Calcixerolls, p. 249
IFE.  Other Xerolls that have an argillic horizon.
Argixerolls, p. 247
IFF.  Other Xerolls.
Haploxerolls, p. 251
Argixerolls
Key to Subgroups
IFEA.  Argixerolls that have both of the following:
1.  An aridic soil moisture regime; and
2.  A lithic contact within 50 cm of the mineral soil surface.
Aridic Lithic Argixerolls
IFEB.  Other Argixerolls that have both of the following:
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
IFEC.  Other Argixerolls that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Argixerolls
IFED.  Other Argixerolls that have both of the following:
1.  An aridic soil 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 peds 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
IFEE.  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 peds 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
IFEF.  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
IFEG.  Other Argixerolls that have both of the following:
1.  An aridic soil 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) particles 2.0 mm
or larger in diameter, 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
IFEH.  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) particles 2.0 mm or
larger in diameter, 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
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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
IFEI.  Other Argixerolls that have both of the following:
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
IFEJ.  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
IFEK.  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
IFEL.  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
IFEM.  Other Argixerolls that have both of the following:
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 class finer than loamy fine sand.
Calcic Pachic Argixerolls
IFEN.  Other Argixerolls that have both of the following:
1.  A mollic epipedon that is 50 cm or more thick and has a
texture class 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
IFEO.  Other Argixerolls that have a mollic epipedon that is 50
cm or more thick and has a texture class finer than loamy fine
sand.
Pachic Argixerolls
IFEP.  Other Argixerolls that have both of the following:
1.  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 at least a firm ruptureresistance
class when moist; and
2.  An aridic soil moisture regime.
Argiduridic Argixerolls
IFEQ.  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 at least a firm rupture-resistance class when moist.
Duric Argixerolls
IFER.  Other Argixerolls that have both of the following:
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.  An aridic soil moisture regime.
Calciargidic Argixerolls
Mollisols	 249
IFES.  Other Argixerolls that have an aridic soil moisture
regime.
Aridic Argixerolls
IFET.  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
IFEU.  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
IFEV.  Other Argixerolls.
Typic Argixerolls
Calcixerolls
Key to Subgroups
IFDA.  Calcixerolls that have both of the following:
1.  An aridic soil moisture regime; and
2.  A lithic contact within 50 cm of the mineral soil surface.
Aridic Lithic Calcixerolls
IFDB.  Other Calcixerolls that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Calcixerolls
IFDC.  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 wedgeshaped
peds 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
IFDD.  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
IFDE.  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
IFDF.  Other Calcixerolls that have a mollic epipedon that is
50 cm or more thick and has a texture class finer than loamy
fine sand.
Pachic Calcixerolls
IFDG.  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:
1.  More than 35 percent (by volume) particles 2.0 mm or
larger in diameter, 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
IFDH.  Other Calcixerolls that have an aridic soil moisture
regime.
Aridic Calcixerolls
IFDI.  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
IFDJ.  Other Calcixerolls.
Typic Calcixerolls
Durixerolls
Key to Subgroups
IFAA.  Durixerolls that have 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
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slickensides or wedge-shaped peds in a layer 15 cm or more
thick that is 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 Durixerolls
IFAB.  Other Durixerolls that have both of the following:
1.  An aridic soil 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) particles 2.0 mm
or larger in diameter, 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
IFAC.  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) particles 2.0 mm or
larger in diameter, 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
IFAD.  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
IFAE.  Other Durixerolls that have all of the following:
1.  An aridic soil moisture regime; and
2.  One or both of the following:
a.  An argillic horizon that has a clay increase of 20
percent or more (absolute, in the fine-earth fraction)
within a vertical distance of 7.5 cm or of 15 percent or
more (absolute, in the fine-earth fraction) within a vertical
distance of 2.5 cm, either within the horizon or at its
upper boundary; or
b.  An abrupt textural change between the eluvial
horizon and the upper boundary of the argillic horizon;
and
3.  A duripan that is neither very strongly cemented nor
indurated in any subhorizon.
Paleargidic Durixerolls
IFAF.  Other Durixerolls that have both of the following:
1.  An aridic soil moisture regime; and
2.  One or both of the following:
a.  An argillic horizon that has a clay increase of 20
percent or more (absolute, in the fine-earth fraction)
within a vertical distance of 7.5 cm or of 15 percent or
more (absolute, in the fine-earth fraction) within a vertical
distance of 2.5 cm, either within the horizon or at its
upper boundary; or
b.  An abrupt textural change between the eluvial
horizon and the upper boundary of the argillic horizon.
Abruptic Argiduridic Durixerolls
IFAG.  Other Durixerolls that:
1.  Have an aridic soil 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
IFAH.  Other Durixerolls that:
1.  Have an aridic soil moisture regime; and
2.  Do not have an argillic horizon above the duripan.
Haploduridic Durixerolls
IFAI.  Other Durixerolls that have both of the following:
1.  An aridic soil moisture regime; and
2.  A duripan that is neither very strongly cemented nor
indurated in any subhorizon.
Argidic Durixerolls
IFAJ.  Other Durixerolls that have an aridic soil moisture
regime.
Argiduridic Durixerolls
Mollisols	 251
IFAK.  Other Durixerolls that have both of the following:
1.  A duripan that is neither very strongly cemented nor
indurated in any subhorizon; and
2.  One or both of the following:
a.  An argillic horizon that has a clay increase of 20
percent or more (absolute, in the fine-earth fraction)
within a vertical distance of 7.5 cm or of 15 percent or
more (absolute, in the fine-earth fraction) within a vertical
distance of 2.5 cm, either within the horizon or at its
upper boundary; or
b.  An abrupt textural change between the eluvial
horizon and the upper boundary of the argillic horizon.
Haplic Palexerollic Durixerolls
IFAL.  Other Durixerolls that have one or both of the
following:
1.  An argillic horizon that has a clay increase of 20 percent
or more (absolute, in the fine-earth fraction) within a vertical
distance of 7.5 cm or of 15 percent or more (absolute, in
the fine-earth fraction) within a vertical distance of 2.5 cm,
either within the horizon or at its upper boundary; or
2.  An abrupt textural change between the eluvial horizon
and the upper boundary of the argillic horizon.
Palexerollic Durixerolls
IFAM.  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
IFAN.  Other Durixerolls that do not have an argillic horizon
above the duripan.
Haploxerollic Durixerolls
IFAO.  Other Durixerolls that have a duripan that is neither
very strongly cemented nor indurated in any subhorizon.
Haplic Durixerolls
IFAP.  Other Durixerolls.
Typic Durixerolls
Haploxerolls
Key to Subgroups
IFFA.  Haploxerolls that have both of the following:
1.  An aridic soil moisture regime; and
2.  A lithic contact within 50 cm of the mineral soil surface.
Aridic Lithic Haploxerolls
IFFB.  Other Haploxerolls that have both of the following:
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
IFFC.  Other Haploxerolls that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Haploxerolls
IFFD.  Other Haploxerolls that have both of the following:
1.  An aridic soil 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 peds 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
IFFE.  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 wedgeshaped
peds 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
IFFF.  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, 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 Haploxerolls
IFFG.  Other Haploxerolls that have both of the following:
1.  An aridic soil moisture regime; and
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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) particles 2.0 mm
or larger in diameter, 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
IFFH.  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) particles 2.0 mm or
larger in diameter, 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
IFFI.  Other Haploxerolls that have all of the following:
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 mollic epipedon that is 50 cm or more thick and has a
texture class finer than loamy fine sand; and
3.  A slope of less than 25 percent; and
4.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
5.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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.
Aquic Cumulic Haploxerolls
IFFJ.  Other Haploxerolls that have all of the following:
1.  A mollic epipedon that is 50 cm or more thick and has a
texture class finer than loamy fine sand; and
2.  A slope of less than 25 percent; and
3.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
4.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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
5.  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
IFFK.  Other Haploxerolls that have all of the following:
1.  A mollic epipedon that is 50 cm or more thick and has a
texture class finer than loamy fine sand; and
2.  A slope of less than 25 percent; and
3.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
4.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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 Haploxerolls
IFFL.  Other Haploxerolls that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
Mollisols	 253
3.  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
4.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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 Haploxerolls
IFFM.  Other Haploxerolls that have both of the following:
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 at least a firm ruptureresistance
class when moist.
Aquic Duric Haploxerolls
IFFN.  Other Haploxerolls that have both of the following:
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
IFFO.  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
IFFP.  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
IFFQ.  Other Haploxerolls that have both of the following:
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 class finer than loamy fine sand.
Calcic Pachic Haploxerolls
IFFR.  Other Haploxerolls that have both of the following:
1.  A mollic epipedon that is 50 cm or more thick and has a
texture class 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
IFFS.  Other Haploxerolls that have a mollic epipedon that is
50 cm or more thick and has a texture class finer than loamy
fine sand.
Pachic Haploxerolls
IFFT.  Other Haploxerolls that have all of the following:
1.  An aridic soil moisture regime; and
2.  A slope of less than 25 percent; and
3.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
4.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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 Haploxerolls
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IFFU.  Other Haploxerolls that have both of the following:
1.  An aridic soil 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 at least a firm ruptureresistance
class when moist.
Duridic Haploxerolls
IFFV.  Other Haploxerolls that have both of the following:
1.  An aridic soil 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
IFFW.  Other Haploxerolls that have both of the following:
1.  An aridic soil moisture regime; and
2.  A sandy particle-size class in all horizons within 100 cm
of the mineral soil surface.
Torripsammentic Haploxerolls
IFFX.  Other Haploxerolls that:
1.  Have an aridic soil 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 the requirements for a cambic horizon,
except for the color requirements; 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
IFFY.  Other Haploxerolls that have an aridic soil moisture
regime.
Aridic Haploxerolls
IFFZ.  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 at least a firm rupture-resistance class when moist.
Duric Haploxerolls
IFFZa.  Other Haploxerolls that have a sandy particle-size
class in all horizons within 100 cm of the mineral soil surface.
Psammentic Haploxerolls
IFFZb.  Other Haploxerolls that have all of the following:
1.  A slope of less than 25 percent; and
2.  A total thickness of less than 50 cm of humantransported
material in the surface horizons; and
3.  One or both of the following:
a.  An organic-carbon content (Holocene age) 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
(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 Haploxerolls
IFFZc.  Other Haploxerolls that have a mollic epipedon that
has granular structure and that has, below any Ap horizon, 50
percent or more (by volume) wormholes, wormcasts, or filled
animal burrows.
Vermic Haploxerolls
IFFZd.  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
IFFZe.  Other Haploxerolls that:
1.  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; 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
Mollisols	 255
is deeper, and either a depth of 75 cm or a densic, lithic, or
paralithic contact, whichever is shallower.
Entic Ultic Haploxerolls
IFFZf.  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
IFFZg.  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 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 Haploxerolls
IFFZh.  Other Haploxerolls.
Typic Haploxerolls
Natrixerolls
Key to Subgroups
IFBA.  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 peds 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
IFBB.  Other Natrixerolls that have both of the following:
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 at least a firm ruptureresistance
class when moist.
Aquic Duric Natrixerolls
IFBC.  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
IFBD.  Other Natrixerolls that have an aridic soil moisture
regime.
Aridic Natrixerolls
IFBE.  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 at least a firm rupture-resistance class when moist.
Duric Natrixerolls
IFBF.  Other Natrixerolls.
Typic Natrixerolls
Palexerolls
Key to Subgroups
IFCA.  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 peds 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
IFCB.  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) particles 2.0 mm or
larger in diameter, 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
IFCC.  Other Palexerolls that have, in one or more horizons
within 75 cm of the mineral soil surface, redox depletions with
M
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chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).
Aquic Palexerolls
IFCD.  Other Palexerolls that have a mollic epipedon that is 50
cm or more thick and has a texture class finer than loamy fine
sand.
Pachic Palexerolls
IFCE.  Other Palexerolls that have both of the following:
1.  A petrocalcic horizon within 150 cm of the mineral soil
surface; and
2.  An aridic soil moisture regime.
Petrocalcidic Palexerolls
IFCF.  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
at least a firm rupture-resistance class when moist.
Duric Palexerolls
IFCG.  Other Palexerolls that have an aridic soil moisture
regime.
Aridic Palexerolls
IFCH.  Other Palexerolls that have a petrocalcic horizon within
150 cm of the mineral soil surface.
Petrocalcic Palexerolls
IFCI.  Other Palexerolls that have a base saturation (by sum of
cations) 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
IFCJ.  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
IFCK.  Other Palexerolls.
Typic Palexerolls
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Oxisols
CHAPTER 13
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. 257
EB.  Other Oxisols that have an aridic soil moisture regime.
Torrox, p. 262
EC.  Other Oxisols that have an ustic or xeric soil moisture
regime.
Ustox, p. 267
ED.  Other Oxisols that have a perudic soil moisture regime.
Perox, p. 258
EE.  Other Oxisols.
Udox, p. 263
Aquox
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 (1N KCl) of 5.0 or more.
Acraquox, p. 257
EAB.  Other Aquox that have plinthite forming a continuous
phase within 125 cm of the mineral soil surface.
Plinthaquox, p. 258
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. 257
EAD.  Other Aquox.
Haplaquox, p. 258
Acraquox
Key to Subgroups
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
Eutraquox
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
258	 Keys to Soil Taxonomy
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
Haplaquox
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
Plinthaquox
Key to Subgroups
EABA.  Plinthaquox 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
Perox
Key to Great Groups
EDA.  Perox that have a sombric horizon within 150 cm of the
mineral soil surface.
Sombriperox, p. 262
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. 258
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. 259
EDD.  Other Perox that have a kandic horizon within 150 cm
of the mineral soil surface.
Kandiperox, p. 261
EDE.  Other Perox.
Haploperox, p. 260
Acroperox
Key to Subgroups
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
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
Oxisols	 259
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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
Eutroperox
Key to Subgroups
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 and
also aquic conditions for some time in normal years (or artificial
drainage).
Aquic Eutroperox
EDCH.  Other Eutroperox that have a kandic horizon 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
260	 Keys to Soil Taxonomy
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
Haploperox
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
and chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).
Aquic Petroferric Haploperox
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
Oxisols	 261
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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
Kandiperox
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).
Plinthaquic Kandiperox
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
262	 Keys to Soil Taxonomy
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
2.  A value, moist, of 3 or less.
Rhodic Kandiperox
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
Sombriperox
Key to Subgroups
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
Torrox
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. 262
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. 262
EBC.  Other Torrox.
Haplotorrox, p. 262
Acrotorrox
Key to Subgroups
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
Eutrotorrox
Key to Subgroups
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
Haplotorrox
Key to Subgroups
EBCA.  Haplotorrox that have a petroferric contact within 125
cm of the mineral soil surface.
Petroferric Haplotorrox
EBCB.  Other Haplotorrox that have a lithic contact within
125 cm of the mineral soil surface.
Lithic Haplotorrox
EBCC.  Other Haplotorrox.
Typic Haplotorrox
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Udox
Key to Great Groups
EEA.  Udox that have a sombric horizon within 150 cm of the
mineral soil surface.
Sombriudox, p. 267
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. 263
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. 264
EED.  Other Udox that have a kandic horizon within 150 cm
of the mineral soil surface.
Kandiudox, p. 266
EEE.  Other Udox.
Hapludox, p. 265
Acrudox
Key to Subgroups
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
EEBD.  Other Acrudox that have a lithic contact within 125
cm of the mineral soil surface.
Lithic Acrudox
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.
Humic Xanthic Acrudox
264	 Keys to Soil Taxonomy
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
Eutrudox
Key to Subgroups
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 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.
Humic Inceptic Eutrudox
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
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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
Hapludox
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).
Aquic Lithic Hapludox
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:
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
266	 Keys to Soil Taxonomy
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
Kandiudox
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
EEDF.  Other Kandiudox hat have 5 percent or more (by
volume) plinthite in one or more horizons within 125 cm of the
mineral soil surface.
Plinthic Kandiudox
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
Oxisols	 267
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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 Kandiudox
EEDN.  Other Kandiudox.
Typic Kandiudox
Sombriudox
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
Ustox
Key to Great Groups
ECA.  Ustox that have a sombric horizon within 150 cm of the
mineral soil surface.
Sombriustox, p. 271
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. 267
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. 268
ECD.  Other Ustox that have a kandic horizon within 150 cm
of the mineral soil surface.
Kandiustox, p. 270
ECE.  Other Ustox.
Haplustox, p. 269
Acrustox
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:
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
268	 Keys to Soil Taxonomy
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
Eutrustox
Key to Subgroups
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 within
150 cm of the mineral soil surface.
Kandiustalfic Eutrustox
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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
Haplustox
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
270	 Keys to Soil Taxonomy
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
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
Kandiustox
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:
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
Oxisols	 271
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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 100
cm.
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
Sombriustox
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
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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. 273
CB.  Other Spodosols that have a gelic soil temperature
regime.
Gelods, p. 277
CC.  Other Spodosols that have a cryic soil temperature
regime.
Cryods, p. 275
CD.  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. 277
CE.  Other Spodosols.
Orthods, p. 278
Aquods
Key to Great Groups
CAA.  Aquods that have a cryic soil temperature regime.
Cryaquods, p. 274
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. 273
CAC.  Other Aquods that have a fragipan within 100 cm of the
mineral soil surface.
Fragiaquods, p. 275
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. 275
CAE.  Other Aquods that have, in 90 percent or more of each
pedon, a cemented horizon within 100 cm of the mineral soil
surface.
Duraquods, p. 274
CAF.  Other Aquods that have episaturation.
Epiaquods, p. 275
CAG.  Other Aquods.
Endoaquods, p. 274
Alaquods
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 horizon within 100 cm of the mineral
soil surface.
Duric Alaquods
CABC.  Other Alaquods that have a histic epipedon.
Histic Alaquods
CABD.  Other Alaquods that:
1.  Within 200 cm of the mineral soil surface, have an
argillic or kandic horizon that has a base saturation (by sum
of cations) of 35 percent or more in some part; and
2.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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:
1.  Have an argillic or kandic horizon within 200 cm of the
mineral soil surface; and
2.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand throughout a layer extending from the mineral soil
Spodosols
CHAPTER 14
274	 Keys to Soil Taxonomy
surface to the top of a spodic horizon at a depth of 75 to 125
cm.
Arenic Ultic Alaquods
CABF.  Other Alaquods that:
1.  Have an umbric epipedon; and
2.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 (by sum of cations) of 35 percent or more 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
Cryaquods
Key to Subgroups
CAAA.  Cryaquods that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Cryaquods
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 horizon 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
Duraquods
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
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
Endoaquods
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
Spodosols	 275
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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
Epiaquods
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 (by sum of cations) of 35 percent or more 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
Fragiaquods
Key to Subgroups
CACA.  Fragiaquods that have a histic epipedon.
Histic Fragiaquods
CACB.  Other Fragiaquods that have a surface horizon
between 25 and 50 cm thick that meets all of the requirements
for a plaggen epipedon except thickness.
Haploplaggic 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
Placaquods
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
Cryods
Key to Great Groups
CCA.  Cryods that have a placic horizon within 100 cm of the
mineral soil surface in 50 percent or more of each pedon.
Placocryods, p. 277
CCB.  Other Cryods that have, in 90 percent or more of each
pedon, a cemented horizon within 100 cm of the mineral soil
surface.
Duricryods, p. 275
CCC.  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. 276
CCD.  Other Cryods.
Haplocryods, p. 276
Duricryods
Key to Subgroups
CCBA.  Duricryods 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 Duricryods
276	 Keys to Soil Taxonomy
CCBB.  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
CCBC.  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
CCBD.  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
CCBE.  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
CCBF.  Other Duricryods.
Typic Duricryods
Haplocryods
Key to Subgroups
CCDA.  Haplocryods that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Haplocryods
CCDB.  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
CCDC.  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
CCDD.  Other Haplocryods that have a folistic epipedon.
Folistic Haplocryods
CCDE.  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
CCDF.  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
CCDG.  Other Haplocryods that have 1.1 percent or less
organic carbon in the upper 10 cm of the spodic horizon.
Entic Haplocryods
CCDH.  Other Haplocryods.
Typic Haplocryods
Humicryods
Key to Subgroups
CCCA.  Humicryods that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Humicryods
CCCB.  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
CCCC.  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
CCCD.  Other Humicryods that have a folistic epipedon.
Folistic Humicryods
CCCE.  Other Humicryods that have redoximorphic features
Spodosols	 277
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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
CCCF.  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
CCCG.  Other Humicryods.
Typic Humicryods
Placocryods
Key to Subgroups
CCAA.  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
CCAB.  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
CCAC.  Other Placocryods.
Typic Placocryods
Gelods
Key to Great Groups
CBA.  Gelods that have 6.0 percent or more organic carbon
throughout a layer 10 cm or more thick within the spodic
horizon.
Humigelods, p. 277
CBB.  Other Gelods.
Haplogelods, p. 277
Haplogelods
Key to Subgroups
CBBA.  Haplogelods that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Haplogelods
CBBB.  Other Haplogelods 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 Haplogelods
CBBC.  Other Haplogelods 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 Haplogelods
CBBD.  Other Haplogelods that have gelic materials within
200 cm of the mineral soil surface.
Turbic Haplogelods
CBBE.  Other Haplogelods.
Typic Haplogelods
Humigelods
Key to Subgroups
CBAA.  Humigelods that have a lithic contact within 50 cm of
the mineral soil surface.
Lithic Humigelods
CBAB.  Other Humigelods 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 Humigelods
CBAC.  Other Humigelods 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 Humigelods
CBAD.  Other Humigelods that have gelic materials within
200 cm of the mineral soil surface.
Turbic Humigelods
CBAE.  Other Humigelods.
Typic Humigelods
Humods
Key to Great Groups
CDA.  Humods that have a placic horizon within 100 cm
of the mineral soil surface in 50 percent or more of each
pedon.
Placohumods, p. 278
278	 Keys to Soil Taxonomy
CDB.  Other Humods that have, in 90 percent or more of each
pedon, a cemented horizon within 100 cm of the mineral soil
surface.
Durihumods, p. 278
CDC.  Other Humods that have a fragipan within 100 cm of
the mineral soil surface.
Fragihumods, p. 278
CDD.  Other Humods.
Haplohumods, p. 278
Durihumods
Key to Subgroups
CDBA.  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
CDBB.  Other Durihumods.
Typic Durihumods
Fragihumods
Key to Subgroups
CDCA.  All Fragihumods (provisionally).
Typic Fragihumods
Haplohumods
Key to Subgroups
CDDA.  Haplohumods that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Haplohumods
CDDB.  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
CDDC.  Other Haplohumods that have a surface horizon
between 25 and 50 cm thick that meets all of the requirements
for a plaggen epipedon except thickness.
Haploplaggic Haplohumods
CDDD.  Other Haplohumods.
Typic Haplohumods
Placohumods
Key to Subgroups
CDAA.  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
CDAB.  Other Placohumods.
Typic Placohumods
Orthods
Key to Great Groups
CEA.  Orthods that have, in 50 percent or more of each pedon,
a placic horizon within 100 cm of the mineral soil surface.
Placorthods, p. 281
CEB.  Other Orthods that have, in 90 percent or more of each
pedon, a cemented horizon within 100 cm of the mineral soil
surface.
Durorthods, p. 279
CEC.  Other Orthods that have a fragipan within 100 cm of the
mineral soil surface.
Fragiorthods, p. 279
CED.  Other Orthods that have less than 0.10 percent iron
(by ammonium oxalate) in 75 percent or more of the spodic
horizon.
Alorthods, p. 278
CEE.  Other Orthods.
Haplorthods, p. 280
Alorthods
Key to Subgroups
CEDA.  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
CEDB.  Other Alorthods that:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand throughout a layer extending from the mineral soil
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surface to the top of a spodic horizon at a depth of 75 to 125
cm; and
2.  Have an argillic or kandic horizon below the spodic
horizon.
Arenic Ultic Alorthods
CEDC.  Other Alorthods that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 Alorthods
CEDD.  Other Alorthods that:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  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 Grossarenic Alorthods
CEDE.  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
CEDF.  Other Alorthods that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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
CEDG.  Other Alorthods that have a surface horizon between
25 and 50 cm thick that meets all of the requirements for a
plaggen epipedon except thickness.
Haploplaggic Alorthods
CEDH.  Other Alorthods that have, within 200 cm of the
mineral soil surface, an argillic or kandic horizon that has a base
saturation (by sum of cations) of 35 percent or more in some
part.
Alfic Alorthods
CEDI.  Other Alorthods that have an argillic or kandic horizon
within 200 cm of the mineral soil surface.
Ultic Alorthods
CEDJ.  Other Alorthods.
Typic Alorthods
Durorthods
Key to Subgroups
CEBA.  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
CEBB.  Other Durorthods.
Typic Durorthods
Fragiorthods
Key to Subgroups
CECA.  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
CECB.  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 (by sum
of cations) of 35 percent or more in some part.
Alfic Oxyaquic Fragiorthods
CECC.  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
CECD.  Other Fragiorthods that have a surface horizon
between 25 and 50 cm thick that meets all of the requirements
for a plaggen epipedon except thickness.
Haploplaggic Fragiorthods
CECE.  Other Fragiorthods that have, within 200 cm of the
mineral soil surface, an argillic or kandic horizon that has a base
saturation (by sum of cations) of 35 percent or more in some
part.
Alfic Fragiorthods
280	 Keys to Soil Taxonomy
CECF.  Other Fragiorthods that have an argillic or kandic
horizon within 200 cm of the mineral soil surface.
Ultic Fragiorthods
CECG.  Other Fragiorthods that have a spodic horizon that has
one of the following:
1.  A texture class of very fine sand, loamy very fine sand,
or finer and all of the following:
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 class 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
CECH.  Other Fragiorthods.
Typic Fragiorthods
Haplorthods
Key to Subgroups
CEEA.  Haplorthods that have a lithic contact within 50 cm of
the mineral soil surface and either:
1.  A spodic horizon with a texture class of very fine sand,
loamy very fine sand, or finer and all of the following:
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 class 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
CEEB.  Other Haplorthods that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Haplorthods
CEEC.  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
CEED.  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 (by sum of cations)
of 35 percent or more in some part.
Aqualfic Haplorthods
CEEE.  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 class of very fine sand,
loamy very fine sand, or finer and all of the following:
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 class 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
CEEF.  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
CEEG.  Other Haplorthods that have:
1.  Within 200 cm of the mineral soil surface, an argillic or
kandic horizon that has a base saturation (by sum of cations)
of 35 percent or more 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:
Spodosols	 281
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a.  20 or more consecutive days; or
b.  30 or more cumulative days.
Alfic Oxyaquic Haplorthods
CEEH.  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
CEEI.  Other Haplorthods that have fragic soil properties
either:
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
CEEJ.  Other Haplorthods that have both:
1.  Saturation with water in 1 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.  Below the spodic horizon but not below an argillic
horizon, lamellae (two or more) within 200 cm of the
mineral soil surface.
Lamellic Oxyaquic Haplorthods
CEEK.  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
CEEL.  Other Haplorthods 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 Haplorthods
CEEM.  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
CEEN.  Other Haplorthods that have, within 200 cm of the
mineral soil surface, an argillic or kandic horizon that has a base
saturation (by sum of cations) of 35 percent or more in some
part.
Alfic Haplorthods
CEEO.  Other Haplorthods that have an argillic or kandic
horizon within 200 cm of the mineral soil surface.
Ultic Haplorthods
CEEP.  Other Haplorthods that have a spodic horizon that has
one of the following:
1.  A texture class of very fine sand, loamy very fine sand,
or finer and all of the following:
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 class 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
CEEQ.  Other Haplorthods.
Typic Haplorthods
Placorthods
Key to Subgroups
CEAA.  All Placorthods (provisionally).
Typic Placorthods
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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. 283
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. 287
HC.  Other Ultisols that have a udic soil moisture regime.
Udults, p. 290
HD.  Other Ultisols that have an ustic soil moisture regime.
Ustults, p. 298
HE.  Other Ultisols.
Xerults, p. 302
Aquults
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 a
continuous phase or constitutes one-half or more of the volume.
Plinthaquults, p. 287
HAB.  Other Aquults that have a fragipan within 100 cm of the
mineral soil surface.
Fragiaquults, p. 285
HAC.  Other Aquults that have an abrupt textural change
between the ochric epipedon or albic horizon and the argillic or
kandic horizon and have a saturated hydraulic conductivity of
0.4 cm/hr (1.0 µm/sec) or slower (moderately low or lower Ksat
class) in the argillic or kandic horizon.
Albaquults, p. 284
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. 285
HAE.  Other Aquults that have a kandic horizon.
Kanhaplaquults, p. 286
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:
Ultisols
CHAPTER 15
284	 Keys to Soil Taxonomy
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. 286
HAG.  Other Aquults that have an umbric or mollic epipedon.
Umbraquults, p. 287
HAH.  Other Aquults that have episaturation.
Epiaquults, p. 284
HAI.  Other Aquults.
Endoaquults, p. 284
Albaquults
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 wedgeshaped
peds 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
HACD.  Other Albaquults.
Typic Albaquults
Endoaquults
Key to Subgroups
HAIA.  Endoaquults that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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
Epiaquults
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 mm or more wide through a thickness of 30 cm or
more for some time in normal years and slickensides or
wedge-shaped peds 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 both of the following:
1.  Fragic soil properties either:
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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
Ultisols	 285
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loamy sand, or loamy fine sand 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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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
either:
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
Fragiaquults
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
Kandiaquults
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:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  Have 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 texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  Have a mollic or umbric epipedon.
Arenic Umbric Kandiaquults
HADD.  Other Kandiaquults that have a texture class (fineearth
fraction) of coarse sand, sand, fine sand, loamy coarse
sand, loamy sand, or loamy fine sand 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 texture class (fineearth
fraction) of coarse sand, sand, fine sand, loamy coarse
sand, loamy sand, or loamy fine sand 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
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
286	 Keys to Soil Taxonomy
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
Kanhaplaquults
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) particles 2.0 mm or
larger in diameter, 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 have both of the following:
1.  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; and
2.  A mollic or umbric epipedon.
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
Paleaquults
Key to Subgroups
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 wedgeshaped
peds 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:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  Have 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 texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  Have a mollic or umbric epipedon.
Arenic Umbric Paleaquults
HAFD.  Other Paleaquults that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand throughout a layer extending
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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
Plinthaquults
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
Umbraquults
Key to Subgroups
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
Humults
Key to Great Groups
HBA.  Humults that have a sombric horizon within 100 cm of
the mineral soil surface.
Sombrihumults, p. 290
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. 290
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) 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.
Kandihumults, p. 288
HBD.  Other Humults that have a kandic horizon.
Kanhaplohumults, p. 289
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) 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.
Palehumults, p. 289
HBF.  Other Humults.
Haplohumults, p. 287
Haplohumults
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 of the following:
1.  In one or more subhorizons within the upper 25 cm of
the argillic horizon, redox depletions with a color value,
288	 Keys to Soil Taxonomy
moist, of 4 or more and chroma of 2 or less, accompanied
by both redox concentrations and 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 Haplohumults
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 both redox concentrations
and 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 soil moisture
regime.
Ustic Haplohumults
HBFH.  Other Haplohumults that have a xeric soil moisture
regime.
Xeric Haplohumults
HBFI.  Other Haplohumults.
Typic Haplohumults
Kandihumults
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 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,
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.  An ustic soil 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 both redox concentrations
and aquic conditions for some time in normal years (or artificial
drainage).
Aquic Kandihumults
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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 soil moisture
regime.
Ustic Kandihumults
HBCH.  Other Kandihumults that have a xeric soil moisture
regime.
Xeric Kandihumults
HBCI.  Other Kandihumults that have an anthropic epipedon.
Anthropic Kandihumults
HBCJ.  Other Kandihumults.
Typic Kandihumults
Kanhaplohumults
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 of the
following:
1.  An ustic soil 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 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 both redox concentrations
and 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 soil
moisture regime.
Ustic Kanhaplohumults
HBDG.  Other Kanhaplohumults that have a xeric soil
moisture regime.
Xeric Kanhaplohumults
HBDH.  Other Kanhaplohumults that have an anthropic
epipedon.
Anthropic Kanhaplohumults
HBDI.  Other Kanhaplohumults.
Typic Kanhaplohumults
Palehumults
Key to Subgroups
HBEA.  Palehumults that have both of the following:
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 both redox concentrations and aquic conditions for some
time in normal years (or artificial drainage); and
290	 Keys to Soil Taxonomy
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 both redox concentrations
and 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
HBEF.  Other Palehumults that have an ustic soil moisture
regime.
Ustic Palehumults
HBEG.  Other Palehumults that have a xeric soil moisture
regime.
Xeric Palehumults
HBEH.  Other Palehumults.
Typic Palehumults
Plinthohumults
Key to Subgroups
HBBA.  All Plinthohumults.
Typic Plinthohumults
Sombrihumults
Key to Subgroups
HBAA.  All Sombrihumults.
Typic Sombrihumults
Udults
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. 298
HCB.  Other Udults that have a fragipan within 100 cm of the
mineral soil surface.
Fragiudults, p. 291
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) 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.
Kandiudults, p. 293
HCD.  Other Udults that have a kandic horizon.
Kanhapludults, p. 295
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) 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.
Paleudults, p. 296
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HCF.  Other Udults that have both of the following:
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. 298
HCG.  Other Udults.
Hapludults, p. 291
Fragiudults
Key to Subgroups
HCBA.  Fragiudults that have a texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 have both:
1.  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 peds; 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, 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 peds; 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
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
Hapludults
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
292	 Keys to Soil Taxonomy
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 wedgeshaped
peds 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 of the following:
1.  Fragic soil properties either:
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 both redox
concentrations and aquic conditions for some time in normal
years (or artificial drainage).
Fragiaquic Hapludults
HCGE.  Other Hapludults that:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  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 both redox concentrations and 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 both redox concentrations and aquic conditions
for some time in normal years (or artificial drainage).
Aquic Hapludults
HCGG.  Other Hapludults that have fragic soil properties
either:
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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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
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HCGM.  Other Hapludults that:
1.  Do not have a densic, lithic, or paralithic contact within
50 cm of the mineral soil surface; and
2.  Have an argillic horizon that is 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
Kandiudults
Key to Subgroups
HCCA.  Kandiudults that have all of the following:
1.  A texture class (fine-earth fraction) of coarse sand, sand,
fine sand, loamy coarse sand, loamy sand, or loamy fine sand
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 both redox concentrations and aquic conditions for some
time in normal years (or artificial drainage).
Arenic Plinthaquic Kandiudults
HCCB.  Other Kandiudults that:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  Have, 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 both redox concentrations and
aquic conditions for some time in normal years (or artificial
drainage).
Aquic Arenic Kandiudults
HCCC.  Other Kandiudults that:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  Have 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:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  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:
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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  Have 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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand throughout a layer extending
294	 Keys to Soil Taxonomy
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 of the following:
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 of the following:
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 both redox
concentrations and aquic conditions for some time in normal
years (or artificial drainage).
Plinthaquic Kandiudults
HCCK.  Other Kandiudults that have both of the following:
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 both redox
concentrations and 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) particles 2.0 mm
or larger in diameter, 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 both redox concentrations and 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:
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
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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
Kanhapludults
Key to Subgroups
HCDA.  Kanhapludults that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Kanhapludults
HCDB.  Other Kanhapludults that have both of the following:
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 both redox
concentrations and aquic conditions for some time in normal
years (or artificial drainage).
Plinthaquic Kanhapludults
HCDC.  Other Kanhapludults that:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  Have 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 texture class (fineearth
fraction) of coarse sand, sand, fine sand, loamy coarse
sand, loamy sand, or loamy fine sand 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 of the following:
1.  Fragic soil properties either:
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 both redox
concentrations and aquic conditions for some time in normal
years (or artificial drainage).
Fragiaquic Kanhapludults
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 both redox concentrations and 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
296	 Keys to Soil Taxonomy
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
either:
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
Paleudults
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 wedgeshaped
peds 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 all of the following:
1.  A texture class (fine-earth fraction) of coarse sand, sand,
fine sand, loamy coarse sand, loamy sand, or loamy fine sand
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.  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 argillic horizon, redox depletions with a color value,
moist, of 4 or more and chroma of 2 or less, accompanied
by both redox concentrations and aquic conditions for some
time in normal years (or artificial drainage).
Arenic Plinthaquic Paleudults
HCED.  Other Paleudults that:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  Have, 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 both redox concentrations and
aquic conditions for some time in normal years (or artificial
drainage).
Aquic Arenic Paleudults
HCEE.  Other Paleudults that have anthraquic conditions.
Anthraquic Paleudults
HCEF.  Other Paleudults that have both of the following:
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
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by both redox concentrations and aquic conditions for some
time in normal years (or artificial drainage).
Plinthaquic Paleudults
HCEG.  Other Paleudults that have both of the following:
1.  Fragic soil properties either:
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 both redox
concentrations and aquic conditions for some time in normal
years (or artificial drainage).
Fragiaquic Paleudults
HCEH.  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 both redox concentrations and aquic conditions
for some time in normal years (or artificial drainage).
Aquic Paleudults
HCEI.  Other Paleudults 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:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  Have 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:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  Have 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:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  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:
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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand throughout a layer extending
298	 Keys to Soil Taxonomy
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 texture class (fine-earth
fraction) of coarse sand, sand, fine sand, loamy coarse sand,
loamy sand, or loamy fine sand 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
either:
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
Plinthudults
Key to Subgroups
HCAA.  All Plinthudults.
Typic Plinthudults
Rhodudults
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
Ustults
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. 302
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. 299
HDC.  Other Ustults that have a kandic horizon.
Kanhaplustults, p. 300
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. 301
HDE.  Other Ustults that have both of the following:
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:
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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. 302
HDF.  Other Ustults.
Haplustults, p. 299
Haplustults
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 a color
value, moist, of 4 or more and chroma of 2 or less, accompanied
by both redox concentrations and aquic conditions for some
time in normal years (or artificial drainage).
Aquic Haplustults
HDFD.  Other Haplustults that have a texture class (fineearth
fraction) of coarse sand, sand, fine sand, loamy coarse
sand, loamy sand, or loamy fine sand 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
Kandiustults
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 both redox concentrations and aquic conditions
for some time in normal years (or artificial drainage).
Aquic Kandiustults
HDBC.  Other Kandiustults that:
1.  Have a texture class (fine-earth fraction) of coarse sand,
sand, fine sand, loamy coarse sand, loamy sand, or loamy
fine sand 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.  Have 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 texture class (fineearth
fraction) of coarse sand, sand, fine sand, loamy coarse
sand, loamy sand, or loamy fine sand 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 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,
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
300	 Keys to Soil Taxonomy
2.  When neither irrigated nor fallowed to store moisture,
either:
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 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
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.
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 soil 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 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 Kandiustults
HDBJ.  Other Kandiustults 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 Kandiustults
HDBK.  Other Kandiustults.
Typic Kandiustults
Kanhaplustults
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 both redox concentrations and aquic conditions
for some time in normal years (or artificial drainage).
Aquic Kanhaplustults
HDCD.  Other Kanhaplustults that have a texture class
(fine-earth fraction) of coarse sand, sand, fine sand, loamy
coarse sand, loamy sand, or loamy fine sand 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 of the following:
Ultisols	 301
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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 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.
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 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 soil 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 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 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.
Rhodic Kanhaplustults
HDCL.  Other Kanhaplustults.
Typic Kanhaplustults
Paleustults
Key to Subgroups
HDDA.  All Paleustults.
Typic Paleustults
302	 Keys to Soil Taxonomy
Plinthustults
Key to Subgroups
HDAA.  Plinthustults that have either:
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
Rhodustults
Key to Subgroups
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
Xerults
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. 303
HEB.  Other Xerults.
Haploxerults, p. 302
Haploxerults
Key to Subgroups
HEBA.  Haploxerults that have both of the following:
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 both redox
concentrations and 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:
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 of the argillic or kandic horizon 7.5 to 20 cm thick,
each with an overlying eluvial horizon.
Lamellic Haploxerults
Ultisols	 303
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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 texture class (fineearth
fraction) of coarse sand, sand, fine sand, loamy coarse
sand, loamy sand, or loamy fine sand 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 texture class (fineearth
fraction) of coarse sand, sand, fine sand, loamy coarse
sand, loamy sand, or loamy fine sand 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
Palexerults
Key to Subgroups
HEAA.  Palexerults that have both of the following:
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 both redox concentrations and 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 both redox
concentrations and 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 retention,
and Al plus 1
/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0.
Andic Palexerults
HEAD.  Other Palexerults.
Typic Palexerults
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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 to give a positive reaction
to alpha,alpha-dipyridyl at a time when the soil is not being
irrigated.
Aquerts, p. 305
FB.  Other Vertisols that have a cryic soil temperature regime.
Cryerts, p. 309
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
b.  Closed for 60 or more consecutive days during the 90
days following the winter solstice.
Xererts, p. 315
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. 309
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. 311
FF.  Other Vertisols.
Uderts, p. 310
Aquerts
Key to Great Groups
FAA.  Aquerts that have within 100 cm of the mineral soil
surface either:
1.  A sulfuric horizon; or
2.  Sulfidic materials.
Sulfaquerts, p. 309
FAB.  Other Aquerts that have a salic horizon within 100 cm
of the mineral soil surface.
Salaquerts, p. 308
FAC.  Other Aquerts that have a duripan within 100 cm of the
mineral soil surface.
Duraquerts, p. 306
FAD.  Other Aquerts that have a natric horizon within 100 cm
of the mineral soil surface.
Natraquerts, p. 308
FAE.  Other Aquerts that have a calcic horizon within 100 cm
of the mineral soil surface.
Calciaquerts, p. 306
FAF.  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. 306
FAG.  Other Aquerts that have episaturation.
Epiaquerts, p. 307
FAH.  Other Aquerts.
Endoaquerts, p. 307
Vertisols
CHAPTER 16
306	 Keys to Soil Taxonomy
Calciaquerts
Key to Subgroups
FAEA.  Calciaquerts 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 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
FAEB.  Other Calciaquerts.
Typic Calciaquerts
Duraquerts
Key to Subgroups
FACA.  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
FACB.  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
FACC.  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
FACD.  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
FACE.  Other Duraquerts 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 Duraquerts
FACF.  Other Duraquerts.
Typic Duraquerts
Dystraquerts
Key to Subgroups
FAFA.  Dystraquerts that have, in one or more horizons within
100 cm of the mineral soil surface, jarosite concentrations and a
pH value of 4.0 or less (1:1 water, air-dried slowly in shade).
Sulfaqueptic Dystraquerts
FAFB.  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
FAFC.  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
FAFD.  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
Vertisols	 307
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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
FAFE.  Other Dystraquerts that have a densic, lithic, or
paralithic contact within 100 cm of the mineral soil surface.
Leptic Dystraquerts
FAFF.  Other Dystraquerts that have a layer, 25 cm or more
thick within 100 cm of the mineral soil surface, that contains
less than 27 percent clay in its fine-earth fraction.
Entic Dystraquerts
FAFG.  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
FAFH.  Other Dystraquerts.
Typic Dystraquerts
Endoaquerts
Key to Subgroups
FAHA.  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
FAHB.  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
FAHC.  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
FAHD.  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
FAHE.  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
FAHF.  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
FAHG.  Other Endoaquerts that have a densic, lithic, or
paralithic contact within 100 cm of the mineral soil surface.
Leptic Endoaquerts
FAHH.  Other Endoaquerts that have a layer, 25 cm or more
thick within 100 cm of the mineral soil surface, that contains
less than 27 percent clay in its fine-earth fraction.
Entic Endoaquerts
FAHI.  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
FAHJ.  Other Endoaquerts.
Typic Endoaquerts
Epiaquerts
Key to Subgroups
FAGA.  Epiaquerts that have, throughout a layer 15 cm
or more thick within 100 cm of the mineral soil surface, an
308	 Keys to Soil Taxonomy
electrical conductivity of 15 dS/m or more (saturated paste) for
6 or more months in normal years.
Halic Epiaquerts
FAGB.  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
FAGC.  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
FAGD.  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
FAGE.  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
FAGF.  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
FAGG.  Other Epiaquerts that have a densic, lithic, or
paralithic contact within 100 cm of the mineral soil surface.
Leptic Epiaquerts
FAGH.  Other Epiaquerts that have a layer, 25 cm or more
thick within 100 cm of the mineral soil surface, that contains
less than 27 percent clay in its fine-earth fraction.
Entic Epiaquerts
FAGI.  Other Epiaquerts 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 Epiaquerts
FAGJ.  Other Epiaquerts.
Typic Epiaquerts
Natraquerts
Key to Subgroups
FADA.  All Natraquerts.
Typic Natraquerts
Salaquerts
Key to Subgroups
FABA.  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
FABB.  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
FABC.  Other Salaquerts that have a densic, lithic, or paralithic
contact within 100 cm of the mineral soil surface.
Leptic Salaquerts
FABD.  Other Salaquerts that have a layer, 25 cm or more
thick within 100 cm of the mineral soil surface, that contains
less than 27 percent clay in its fine-earth fraction.
Entic Salaquerts
FABE.  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
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2.  A color value, dry, of 6 or more; or
3.  Chroma of 3 or more.
Chromic Salaquerts
FABF.  Other Salaquerts.
Typic Salaquerts
Sulfaquerts
Key to Subgroups
FAAA.  Sulfaquerts that have a salic horizon within 75 cm of
the mineral soil surface.
Salic Sulfaquerts
FAAB.  Other Sulfaquerts that do not have a sulfuric horizon
within 100 cm of the mineral soil surface.
Sulfic Sulfaquerts
FAAC.  Other Sulfaquerts.
Typic Sulfaquerts
Cryerts
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. 309
FBB.  Other Cryerts.
Haplocryerts, p. 309
Haplocryerts
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
Humicryerts
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
Torrerts
Key to Great Groups
FDA.  Torrerts that have a salic horizon within 100 cm of the
soil surface.
Salitorrerts, p. 310
FDB.  Other Torrerts that have a gypsic horizon within 100 cm
of the soil surface.
Gypsitorrerts, p. 310
FDC.  Other Torrerts that have a calcic or petrocalcic horizon
within 100 cm of the soil surface.
Calcitorrerts, p. 309
FDD.  Other Torrerts.
Haplotorrerts, p. 310
Calcitorrerts
Key to Subgroups
FDCA.  Calcitorrerts that have a petrocalcic horizon within
100 cm of the soil surface.
Petrocalcic Calcitorrerts
FDCB.  Other Calcitorrerts that have a densic, lithic, or
paralithic contact or a duripan within 100 cm of the soil surface.
Leptic Calcitorrerts
FDCC.  Other Calcitorrerts that have a layer, 25 cm or more
thick within 100 cm of the soil surface, that contains less than
27 percent clay in its fine-earth fraction.
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
310	 Keys to Soil Taxonomy
2.  A color value, dry, of 6 or more; or
3.  Chroma of 3 or more.
Chromic Calcitorrerts
FDCE.  Other Calcitorrerts.
Typic Calcitorrerts
Gypsitorrerts
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
Haplotorrerts
Key to Subgroups
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 a duripan within 100 cm of the soil
surface.
Leptic Haplotorrerts
FDDD.  Other Haplotorrerts that have a layer, 25 cm or more
thick within 100 cm of the soil surface, that contains less than
27 percent clay in its fine-earth fraction.
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
Salitorrerts
Key to Subgroups
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 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, a duripan, or a petrocalcic horizon within 100
cm of the soil surface.
Leptic Salitorrerts
FDAC.  Other Salitorrerts that have a layer, 25 cm or more
thick within 100 cm of the soil surface, that contains less than
27 percent clay in its fine-earth fraction.
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
Uderts
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:
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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. 311
FFB.  Other Uderts.
Hapluderts, p. 311
Dystruderts
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 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 within 100 cm of the mineral soil surface, that contains
less than 27 percent clay in its fine-earth fraction.
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
Hapluderts
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 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 either or both:
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 within 100 cm of the mineral soil surface, that contains
less than 27 percent clay in its fine-earth fraction.
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
Usterts
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:
312	 Keys to Soil Taxonomy
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. 312
FEB.  Other Usterts that have a salic horizon within 100 cm of
the mineral soil surface.
Salusterts, p. 314
FEC.  Other Usterts that have a gypsic horizon within 100 cm
of the mineral soil surface.
Gypsiusterts, p. 313
FED.  Other Usterts that have a calcic or petrocalcic horizon
within 100 cm of the mineral soil surface.
Calciusterts, p. 312
FEE.  Other Usterts.
Haplusterts, p. 313
Calciusterts
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
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 a duripan within 100 cm of the mineral soil
surface.
Leptic Calciusterts
FEDH.  Other Calciusterts that have a layer, 25 cm or more
thick within 100 cm of the mineral soil surface, that contains
less than 27 percent clay in its fine-earth fraction.
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
Dystrusterts
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
2.  Enough active ferrous iron 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
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FEAE.  Other Dystrusterts that have a densic, lithic, or
paralithic contact or a duripan within 100 cm of the mineral soil
surface.
Leptic Dystrusterts
FEAF.  Other Dystrusterts that have a layer, 25 cm or more
thick within 100 cm of the mineral soil surface, that contains
less than 27 percent clay in its fine-earth fraction.
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
Gypsiusterts
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, a duripan, or a petrocalcic horizon within 100
cm of the mineral soil surface.
Leptic Gypsiusterts
FECG.  Other Gypsiusterts that have a layer, 25 cm or more
thick within 100 cm of the mineral soil surface, that contains
less than 27 percent clay in its fine-earth fraction.
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
Haplusterts
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
within 150 cm of the mineral soil surface.
Petrocalcic Haplusterts
FEEE.  Other Haplusterts that have a gypsic horizon within
150 cm of the mineral soil surface.
Gypsic Haplusterts
FEEF.  Other Haplusterts that have a calcic horizon within 150
cm of the mineral soil surface.
Calcic Haplusterts
314	 Keys to Soil Taxonomy
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
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 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.
Leptic Udic Haplusterts
FEEJ.  Other Haplusterts that have both:
1.  A layer, 25 cm or more thick within 100 cm of the
mineral soil surface, that contains less than 27 percent clay in
its fine-earth fraction; 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 a duripan within 100 cm of the mineral soil
surface.
Leptic Haplusterts
FEEN.  Other Haplusterts that have a layer, 25 cm or more
thick within 100 cm of the mineral soil surface, that contains
less than 27 percent clay in its fine-earth fraction.
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
Salusterts
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 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,
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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, a duripan, or a petrocalcic horizon within 100 cm of the
mineral soil surface.
Leptic Salusterts
FEBF.  Other Salusterts that have a layer, 25 cm or more thick
within 100 cm of the mineral soil surface, that contains less than
27 percent clay in its fine-earth fraction.
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
Xererts
Key to Great Groups
FCA.  Xererts that have a duripan within 100 cm of the
mineral soil surface.
Durixererts, p. 315
FCB.  Other Xererts that have a calcic or petrocalcic horizon
within 100 cm of the mineral soil surface.
Calcixererts, p. 315
FCC.  Other Xererts.
Haploxererts, p. 316
Calcixererts
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
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 within 100 cm of the mineral soil surface, that contains
less than 27 percent clay in its fine-earth fraction.
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
Durixererts
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 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,
316	
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
Haploxererts
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 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 within 100 cm of the mineral soil surface, that contains
less than 27 percent clay in its fine-earth fraction.
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
	 317
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Families and series serve purposes that are largely pragmatic;
the series name is abstract, and the technical family name is
descriptive. In this chapter 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.
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 differentiae are used to
form the family name. The class names are listed and defined in
the same sequence (shown below) in which they appear in the
family names.
Particle-size classes and their substitutes
Human-altered and human-transported material classes
Mineralogy classes
Cation-exchange activity classes
Calcareous and reaction classes
Soil temperature classes
Soil depth classes
Rupture-resistance classes
Classes of coatings on sands
Classes of permanent 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,
cinders, rock fragments, or gypsum.
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 pedological classifications have set it at either 20, 50, or
63 microns. The USDA and this taxonomy use a diameter of
50 microns to set the limit between sand and silt. Engineering
classifications have been based on grain-size percentages,
by weight, in the soil fraction less than 75 mm (3 inches) in
diameter, while texture 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 class 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 fraction if the texture class
(fine-earth fraction) of a soil is fine sand, loamy fine sand, or
coarser. It is treated as silt, however, if the texture class 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 10
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 mm in diameter. Rock fragments are particles 2 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 mm or
more in diameter that are in a rupture-resistance class that is
less cemented than the strongly cemented class are referred to
as pararock fragments. Pararock fragments, like rock fragments,
include all particles between 2 mm and a horizontal dimension
smaller than the size of a pedon. Most pararock fragments
Family and Series Differentiae and Names
CHAPTER 17
318	 Keys to Soil Taxonomy
are broken into particles less than 2 mm 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 assignment of particle-size classes.
However, cinders, lapilli, pumice, and pumicelike fragments
are treated as general fragments in the pumiceous and cindery
substitute classes (defined below), regardless of their ruptureresistance
class. Rock fragments and pararock fragments may
be of either geologic or pedogenic origin. Artifacts (defined
in chapter 3) are of human origin. Artifacts 2 mm or larger in
diameter which are both cohesive and persistent* (e.g., brick)
are treated as rock fragments for the assignment of particle-size
classes.
Substitutes for particle-size classes are used for soils
that have andic soil properties or a high content of volcanic
glass, pumice, cinders, rock fragments, or gypsum. These
materials cannot be readily dispersed and have variable results
of dispersion. The substitute classes dominated by rock and
pararock fragments have too little fine-earth material for valid
data, and soil properties are dominated by the fragments.
Consequently, normal particle-size classes do not adequately
characterize these soils. Substitutes for particle-size class names
are used for those parts of soils that have andic soil properties
or a high content of volcanic glass, pumice, or cinders, as is the
case with Andisols and many Andic and Vitrandic subgroups
of other soil orders. The “gypseous” substitutes for particlesize
class are used for mineral soils (e.g., Aridisols) that have
a high content of gypsum. 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 nor a substitute for a particle-size
class is used for Psamments, Psammaquents, Psammowassents,
Psammoturbels, Psammorthels, and Psammentic subgroups that
meet sandy particle-size class criteria. These taxa, by definition,
meet sandy particle-size class criteria (i.e., have a texture class
of sand or loamy sand), so the sandy particle-size class is
considered redundant in the family name. The ashy substitute
class, however, is used, if appropriate in these taxa (e.g., high
content of volcanic glass).
Particle-size classes are applied, although with reservations,
to the control sections of soils with 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 is used for 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
a modifier 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 particlesize
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 and 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 control
section for particle-size classes and their substitutes. 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
* 
Artifact cohesion is the relative ability of an artifact to remain intact after significant
disturbance and is based on whether the artifact can be easily broken into <2 mm diameter
pieces either by hand or with a mortar and pestle. Cohesive artifacts cannot easily be
broken. Artifact persistence is the relative ability of artifacts to withstand weathering and
decay over time. Persistent artifacts remain intact for a decade or more. Part 618 of the
National Soil Survey Handbook (available online) contains more information on the data
elements used for describing artifacts.
Family and Series Differentiae and Names	 319
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may coincide with the upper boundary of a root-limiting layer
(defined below).
Root-Limiting Layers
The concept of root-limiting layers as used in this taxonomy
defines the base of the soil horizons considered for most (but
not all) differentiae at the family level. The properties of soil
materials above the base and within the control section are
used for assignment of classes, such as particle-size classes and
their substitutes. One notable exception to the concept of rootlimiting
layers is in assignment of soil depth classes (defined
below) to soils with fragipans. Unless otherwise indicated, the
following are considered root-limiting layers in this chapter:
a duripan; a fragipan; petrocalcic, petrogypsic, and placic
horizons; continuous ortstein (i.e., 90 percent or more cemented
and has lateral continuity); and densic, lithic, manufactured
layer, paralithic, and petroferric contacts.
Key to the Control Section for Particle-Size Classes and
Their Substitutes in Mineral Soils
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 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.
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 items 1 through 4 below. For other soils, go to section 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 section 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 either in a Lamellic subgroup or that 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 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 soil 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 rootlimiting
layer.
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
320	 Keys to Soil Taxonomy
contrasting classes, the weighted average soil materials within
the particle-size 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
pumicelike†
fragments and, in the fraction 2 mm or larger
in diameter, 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 2 mm or larger in diameter,
less than two-thirds (by volume) pumice and/or pumicelike
fragments.
Cindery
or
3.  Other 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 portion of
the control section (if the control section is not in one of the
strongly contrasting particle-size classes listed below), or in
a portion of the control section that qualifies as a part 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 30 percent
or more of the fine-earth fraction in the 0.02 to 2.0 mm
fraction, and have a volcanic glass content (by grain
count) of 30 percent or more in the 0.02 to 2.0 mm
fraction; 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.  They have a fine-earth fraction that has andic soil
properties and that has a water content at 1500 kPa tension
of less than 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.  They 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
† 
Pumicelike—vesicular pyroclastic materials other than pumice that have an apparent
specific gravity (including vesicles) of less than 1.0 g/cm3
.
Family and Series Differentiae and Names	 321
F
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c.  Have less than 35 percent (by volume) rock
fragments.
Hydrous
or
4.  They have, in the fraction less than 20 mm in diameter,
40 percent of more (by weight) gypsum and one of the
following:
a.  A total of 35 percent or more (by volume) rock
fragments.
Gypseous-skeletal
or
b.  Less than 35 percent (by volume) rock fragments and
50 percent or more (by weight) particles with diameters of
0.1 to 2.0 mm.
Coarse-gypseous
or
c.  Less than 35 percent (by volume) rock fragments.
Fine-gypseous
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, then
the percentage of clay is estimated by the following formula:
Clay % = 2.5(% water retained at 1500 kPa tension - % organic
carbon). See appendix for more information.
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 a total content of rock fragments, plus any
artifacts 2 mm or larger in diameter which are both cohesive
and persistent, of 35 percent or more (by volume) and a
texture class of coarse sand, sand, fine sand, loamy coarse
sand, loamy sand, or loamy fine sand in the fine-earth
fraction.
Sandy-skeletal
or
2.  Have a total content of rock fragments, plus any
artifacts 2 mm or larger in diameter which are both cohesive
and persistent, of 35 percent or more (by volume) and less
than 35 percent (by weight) clay.
Loamy-skeletal
or
3.  Have a total content of rock fragments, plus any artifacts
2 mm or larger in diameter which are both cohesive and
persistent, of 35 percent or more (by volume).
Clayey-skeletal
or
4.  Have a texture class of coarse sand, sand, fine sand,
loamy coarse sand, loamy sand, or loamy fine sand in the
fine-earth fraction.
Sandy
or
5.  Have a texture class 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 a part in a strongly
contrasting particle-size class (listed below).
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 gravel and
artifacts 2 to 75 mm in diameter which are both cohesive and
persistent) 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 gravel and
artifacts 2 to 75 mm in diameter which are both cohesive and
persistent) and, in the fine-earth fraction, 18 to less than 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 gravel and
artifacts 2 to 75 mm in diameter which are both cohesive and
persistent) and, in the fine-earth fraction, less than 18 percent
(by weight) clay.
Coarse-silty
or
322	 Keys to Soil Taxonomy
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 gravel and
artifacts 2 to 75 mm in diameter which are both cohesive and
persistent) and, in the fine-earth fraction, 18 to less than 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 a part 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 (by weight) 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 particle-size or substitute classes listed below are
considered strongly contrasting if both parts are 12.5 cm or
more thick (including the thickness of these parts not entirely
within 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
name is used as the family class if part of the control section
meets the criteria for either class. The following classes are
listed alphabetically and are not presented in a key format.
  1.  Ashy over clayey
  2.  Ashy over clayey-skeletal
  3.  Ashy over loamy
  4.  Ashy over loamy-skeletal
  5.  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 part and 15 percent or more for the
medial part)
  6.  Ashy over medial-skeletal
  7.  Ashy over pumiceous or cindery
  8.  Ashy over sandy or sandy-skeletal
  9.  Ashy-skeletal over clayey
10.  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)
11.  Ashy-skeletal over loamy-skeletal
12.  Ashy-skeletal over sandy or sandy-skeletal
13.  Cindery over loamy
14.  Cindery over medial
15.  Cindery over medial-skeletal
16.  Clayey over coarse-gypseous
17.  Clayey over fine-gypseous (if there is an absolute
difference of 15 percent or more gypsum between the two
parts of the control section)
18.  Clayey over fragmental
19.  Clayey over gypseous-skeletal
20.  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)
21.  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)
22.  Clayey over sandy or sandy-skeletal
23.  Clayey-skeletal over sandy or sandy-skeletal
24.  Coarse-loamy over clayey
25.  Coarse-loamy over fragmental
26.  Coarse-loamy over sandy or sandy-skeletal (if the coarseloamy
material contains less than 50 percent, by weight,
fine sand or coarser sand)
27.  Coarse-silty over clayey
28.  Coarse-silty over sandy or sandy-skeletal
29.  Fine-loamy 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)
30.  Fine-loamy over fragmental
31.  Fine-loamy over sandy or sandy-skeletal
32.  Fine-silty over clayey (if there is an absolute difference
Family and Series Differentiae and Names	 323
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of 25 percent or more between clay percentages of
the fine-earth fraction in the two parts of the control
section)
33.  Fine-silty over fragmental
34.  Fine-silty over sandy or sandy-skeletal
35.  Hydrous over clayey
36.  Hydrous over clayey-skeletal
37.  Hydrous over fragmental
38.  Hydrous over loamy
39.  Hydrous over loamy-skeletal
40.  Hydrous over sandy or sandy-skeletal
41.  Loamy over ashy or ashy-pumiceous
42.  Loamy over coarse-gypseous (if there is an absolute
difference of 15 percent or more gypsum between the two
parts of the control section)
43.  Loamy over fine-gypseous (if there is an absolute
difference of 15 percent or more gypsum between the two
parts of the control section)
44.  Loamy over pumiceous or cindery
45.  Loamy over sandy or sandy-skeletal (if the loamy material
contains less than 50 percent, by weight, fine sand or
coarser sand)
46.  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)
47.  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)
48.  Loamy-skeletal over fragmental (if the volume of the fineearth
fraction is 35 percent or more [absolute] greater in
the loamy-skeletal part than in the fragmental part)
49.  Loamy-skeletal over gypseous-skeletal (if there is an
absolute difference of 15 percent or more gypsum between
the two parts of the control section)
50.  Loamy-skeletal over sandy or sandy-skeletal (if the loamy
material contains less than 50 percent, by weight, fine
sand or coarser sand)
51.  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 part and 10 percent or less for the
ashy part)
52.  Medial over ashy-pumiceous or ashy-skeletal (if the water
content at 1500 kPa tension in dried samples of the fineearth
fraction is 15 percent or more for the medial part and
10 percent or less for the ashy part)
53.  Medial over clayey
54.  Medial over clayey-skeletal
55.  Medial over fragmental
56.  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 part)
57.  Medial over loamy
58.  Medial over loamy-skeletal
59.  Medial over pumiceous or cindery
60.  Medial over sandy or sandy-skeletal
61.  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 in the fragmental
or cindery part)
62.  Medial-skeletal over loamy-skeletal
63.  Medial-skeletal over sandy or sandy-skeletal
64.  Pumiceous or ashy-pumiceous over loamy
65.  Pumiceous or ashy-pumiceous over loamy-skeletal
66.  Pumiceous or ashy-pumiceous over medial
67.  Pumiceous or ashy-pumiceous over medial-skeletal
68.  Pumiceous or ashy-pumiceous over sandy or sandy-
skeletal
69.  Sandy over clayey
70.  Sandy over loamy (if the loamy material contains less than
50 percent, by weight, fine sand or coarser sand)
71.  Sandy-skeletal over loamy (if the loamy material contains
less than 50 percent, by weight, fine sand or coarser sand)
Human-Altered and Human-Transported
Material Classes
Human-altered and human-transported material classes are
intended to provide useful information on the behavior and
interpretations for use of soils which formed in human-altered
or human-transported material (defined in chapter 3).
Use of Human-Altered and Human-Transported Material
Classes
Human-altered and human-transported material classes are
only used in taxa of mineral soils where one of the following
occurs: (1) human-altered or human-transported material
extends from the soil surface to a depth of 50 cm or to a
324	 Keys to Soil Taxonomy
root-limiting layer, whichever is shallower; or (2) the soil
classifies in an Anthraltic, Anthraquic, Anthrodensic, Anthropic,
Anthroportic, Haploplaggic, or Plaggic extragrade subgroup
(defined in chapter 3). In other taxa, the class is omitted from
the family name and the parent material is identified at the soil
series level.
Examples of soils that use human-altered and humantransported
material classes and formed in human-transported
material are a fine, methanogenic, mixed, active, nonacid,
thermic Anthrodensic Ustorthent, which was compacted during
construction of a sanitary landfill, and a fine-loamy, spolic,
mixed, active, calcareous, mesic Anthroportic Udorthent, which
resulted from reclamation of a surface coal mine. An example
of a soil using a human-altered and human-transported material
class, which formed in human-altered material as a result of
mechanical displacement of a preexisting natric horizon, is
a fine, araric, smectitic, calcareous, thermic Anthraltic Sodic
Xerorthent.
Key to the Control Section for Human-Altered and HumanTransported
Material Classes
The control section for the human-altered and humantransported
material classes is from the soil surface to one of the
following depths, whichever is shallower:
A.  200 cm; or
B.  The lower boundary of the deepest horizon formed in
human-altered or human-transported material; or
C.  A lithic or paralithic contact.
Key to Human-Altered and Human-Transported Material
Classes
The following key to human-altered and human-transported
material classes is designed to make important distinctions in
the order of most importance to human health and safety.
A.  Mineral soils that have, in some part of the human-altered
and human-transported material control section, one of the
following:
1.  The detectible evolution (>1.6 ppb) of methanethiol (i.e.,
methyl mercaptan) odor from the decomposition of nonpersistent
artifacts (e.g., garbage, wood-mill pulp, sewage treatment
plant by-products) or evidence of the collection and/or
burning of methane gas.
Methanogenic
or
2.  A horizon or layer 7.5 cm or more thick, with more than
35 percent (by volume) artifacts of asphalt (bitumen) that are
2 mm in diameter or larger.
Asphaltic
or
3.  A horizon or layer 7.5 cm or more thick, with more than
35 percent (by volume) artifacts of concrete that are 2 mm in
diameter or larger.
Concretic
or
4.  A horizon or layer 7.5 cm or more thick, with more than
40 percent (by weight) artifacts of synthetic gypsum products
such as flue gas desulfurization gypsum, phosphogypsum,
or fluorogypsum (e.g., drywall or plaster) in the fine-earth
fraction.
Gypsifactic
or
5.  A horizon or layer 7.5 cm or more thick, with more than
35 percent (by volume) artifacts of coal combustion by-products
(e.g., bottom ash or coal slag) that are 2 mm in diameter
or larger.
Combustic
or
6.  A horizon or layer 7.5 cm or more thick, with more than
15 percent (by grain count in the 0.02 to 0.25 mm fraction)
artifacts of light-weight, coal combustion by-products (e.g.,
fly ash scrubbed from emission stacks).
Ashifactic
or
7.  A horizon or layer 7.5 cm or more thick, with more than
5 percent (by grain count in the 0.02 to 0.25 mm fraction)
artifacts of pyrolysis (e.g., fuel coke or biochar).
Pyrocarbonic
or
8.  A horizon or layer 50 cm or more thick, with 35 percent
or more (by volume) artifacts which are both cohesive and
persistent and are 2 mm in diameter or larger.
Artifactic
or
9.  A horizon or layer 50 cm or more thick, with 15 percent
or more (by volume) artifacts which are both cohesive and
persistent and are 2 mm in diameter or larger.
Pauciartifactic
or
10.  A horizon or layer 50 cm or more thick, with finely
stratified (5 cm or less thick) human-transported material
that was water-deposited (e.g., sediment from dredging or
irrigation).
Dredgic
or
Family and Series Differentiae and Names	 325
F
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11.  A horizon or layer 50 cm or more thick of humantransported
material.
Spolic
or
12.  A horizon or layer 7.5 cm or more thick, with 3 percent
or more (by volume) mechanically detached and re-oriented
pieces of diagnostic horizons or characteristics.
Araric
or
B.  All other soils: No human-altered or human-transported
material classes are used.
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. A mineralogy class is assigned to all
mineral soils, except for Quartzipsamments.
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,
mineralogy classes are used for both of the named parts of
particle-size classes or substitute classes, unless they are the
same. The same mineralogy class name cannot be used for
both parts of the control section (e.g., “mixed over mixed”).
Examples of soils that require assignment of two different
mineralogy classes are a clayey over sandy or sandy-skeletal,
smectitic over mixed, thermic Vertic Haplustept and an ashyskeletal
over loamy-skeletal, glassy over mixed (if the ashyskeletal
part has 30 percent or more volcanic glass), superactive
Vitrandic Argicryoll. Examples of soils that are not assigned
two mineralogy classes are an ashy over clayey, mixed (if both
the ashy part with andic soil properties and the clayey part
without andic soil properties are mixed), superactive, mesic
Typic Vitraquand and a fine-loamy over sandy or sandy-skeletal,
mixed (if both the fine-loamy and sandy or sandy-skeletal parts
are mixed), active, frigid Pachic Argiudoll.
A.  Oxisols and “kandi” and “kanhap” great groups of Alfisols
and Ultisols that in the mineralogy control section have:
1.  More than 40 percent (by weight) iron oxide as Fe2
O3
(more than 28 percent Fe), extractable by dithionite-citrate,
in the fine-earth fraction.
Ferritic
or
2.  More than 40 percent (by weight) gibbsite in the fineearth
fraction.
Gibbsitic
or
3. Both:
a.  18 to 40 percent (by weight) iron oxide as Fe2
O3
(12.6
to 28 percent Fe), extractable by dithionite-citrate, in the
fine-earth fraction; and
b.  18 to 40 percent (by weight) gibbsite in the fine-earth
fraction.
Sesquic
or 
4.  18 to 40 percent (by weight) iron oxide as Fe2
O3
(12.6 to
28 percent Fe), extractable by dithionite-citrate, in the fineearth
fraction.
Ferruginous
or 
5.  18 to 40 percent (by weight) gibbsite in the fine-earth
fraction.
Allitic
or
6.  More than 50 percent (by weight) kaolinite plus
halloysite, dickite, nacrite, and other 1:1 or nonexpanding
2:1 layer minerals and gibbsite and less than 10 percent (by
weight) smectite minerals (montmorillonite, beidellite, and
nontronite) in the fraction less than 0.002 mm in diameter,
and more kaolinite than halloysite.
Kaolinitic
or
7.  More than 50 percent (by weight) halloysite plus
kaolinite and allophane and less than 10 percent (by
weight) smectite minerals (montmorillonite, beidellite, and
nontronite) in the fraction less than 0.002 mm in diameter.
Halloysitic
or
326	 Keys to Soil Taxonomy
8.  All other soils in section A.
Mixed
or
B.  Other soils with horizons in the mineralogy control section
that have a substitute class that replaces the particle-size class,
other than fragmental, and that have:
1.  40 percent or more (by weight) gypsum either in the
fine-earth fraction or in the fraction less than 20 mm in
diameter, whichever has a higher percentage of gypsum.
Hypergypsic
or
2. Both:
a.  A sum of 8 times the Si (percent by weight extracted
by ammonium oxalate from the fine-earth fraction) plus
2 times the Fe (percent by weight extracted by
ammonium oxalate from the fine-earth fraction) of 5 or
more; and
b.  The product of 8 times the Si is more than the product
of 2 times the Fe.
Amorphic
or
3.  A sum of 8 times the Si (percent by weight extracted by
ammonium oxalate from the fine-earth fraction) plus 2 times
the Fe (percent by weight extracted by ammonium oxalate
from the fine-earth fraction) of 5 or more.
Ferrihydritic
or
4.  30 percent or more (by grain count) volcanic glass in the
0.02 to 2.0 mm fraction.
Glassy
or
5.  All other soils in section B.
Mixed
or
C.  Other mineral soils and soils in Terric subgroups of
Histosols and Histels that have horizons or layers in the
mineralogy control section composed of mineral soil material
that has:
1.  Any particle-size class and 15 percent or more (by
weight) anhydrite, either in the fine-earth fraction or in the
fraction less than 20 mm in diameter, whichever has a higher
percentage of anhydrite.
Anhydritic
or
2.  Any particle-size class and 15 percent or more (by
weight) gypsum, either in the fine-earth fraction or in the
fraction less than 20 mm in diameter, whichever has a higher
percentage of gypsum.
Gypsic
or
3.  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 diameter, whichever has a higher percentage of
carbonates plus gypsum.
Carbonatic
or
4.  Any particle-size class, except for fragmental, and more
than 40 percent (by weight) iron oxide as Fe2
O3
(more than
28 percent Fe) extractable by dithionite-citrate, in the fineearth
fraction.
Ferritic
or
5.  Any particle-size class, except for fragmental, and more
than 40 percent (by weight) gibbsite and boehmite in the
fine-earth fraction.
Gibbsitic
or
6.  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 Mg-rich
amphiboles, in the fine-earth fraction.
Magnesic
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 soils and soils in Terric subgroups of
Histosols and Histels that have a clayey, clayey-skeletal, fine,
or very-fine particle-size class and have horizons or layers
composed of mineral soil material that:
1.  In the fine-earth fraction, have a total percent (by
weight) iron oxide as Fe2
O3
(percent Fe extractable by
dithionite-citrate times 1.43) plus the percent (by weight)
gibbsite of more than 10.
Parasesquic
or
2.  In the fraction less than 0.002 mm in diameter:
Family and Series Differentiae and Names	 327
F
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a.  Have more than 50 percent (by weight) halloysite
plus kaolinite and allophane and more halloysite than any
other single kind of clay mineral.
Halloysitic
or
b.  Have more than 50 percent (by weight) kaolinite plus
halloysite, dickite, nacrite, and other 1:1 or nonexpanding
2:1 layer minerals and gibbsite and less than 10 percent
(by weight) smectite minerals (montmorillonite,
beidellite, and nontronite).
Kaolinitic
or
c.  Have more smectite minerals (montmorillonite,
beidellite, and nontronite), by weight, than any other
single kind of clay mineral.
Smectitic
or
d.  Have more than 50 percent (by weight) illite (hydrous
mica) and commonly more than 4 percent K2
O.
Illitic
or
e.  Have more vermiculite than any other single kind of
clay mineral.
Vermiculitic
or
f.  In more than one-half of the thickness, have all of the
following:
(1)  No free carbonates; and
(2)  A sodium fluoride pH (NaF pH) of 8.4 or more;
and
(3)  A ratio of 1500 kPa water to measured clay of 0.6
or more.
Isotic
or
g.  All other soils in section D.
Mixed
or
E.  All other soils (except for Quartzipsamments) that
have horizons or layers composed of mineral soil material that
has:
1.  More than 45 percent (by grain count) mica and stable
mica pseudomorphs in the 0.02 to 0.25 mm fraction.
Micaceous
or
2.  A total percent (by weight) iron oxide as Fe2
O3
(percent
Fe extractable by dithionite-citrate times 1.43) plus the
percent (by weight) gibbsite of more than 10 in the fine-earth
fraction.
Parasesquic
or
3.  In more than one-half of the thickness, all of the
following:
a.  No free carbonates; and
b.  A sodium fluoride pH (NaF pH) of 8.4 or more; 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 or grain count) silica
minerals (quartz, chalcedony, or opal) and other resistant
minerals in the 0.02 to 2.0 mm fraction.
Siliceous
or
5.  All other soil properties.
Mixed
Cation-Exchange Activity Classes
The cation-exchange activity classes help in making
interpretations about the nutrient-holding capacity of soils
and their suites of colloids. The cation-exchange capacity 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, calculated by weighted
average in the control section. In the following classes “clay”
excludes clay-size carbonates. Percent carbonate clay must be
subtracted from percent total clay before calculating the CEC
to clay ratio. 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
in a part of contrasting families), then the percentage of clay
is estimated by the following formula: Clay % = 2.5(% water
retained at 1500 kPa tension - % organic carbon). See appendix
for more information.
Use of the Cation-Exchange Activity Classes
The cation-exchange activity classes are used for soils
classified in the mixed or 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 nor to Oxisols or “kandi” and “kanhap”
328	 Keys to Soil Taxonomy
great groups and subgroups of Alfisols and Ultisols because
assigning classes to organic soils or taxa defined by low-activity
clay would be misleading or redundant information. Cationexchange
activity classes are not assigned to Psamments,
“psamm” great groups of Entisols and Gelisols, Psammentic
subgroups, or other soils with sandy or sandy-skeletal particlesize
classes or the fragmental substitute class because the low
clay content causes cation-exchange activity classes to be less
useful and less reliable. Soils with other substitutes for particlesize
class (e.g., ashy) or with mineralogy classes such as
smectitic also are not assigned cation-exchange activity classes,
since such soils have a high cation-exchange capacity (CEC)
and/or the clay mineralogy dictates soil properties.
For soils with strongly contrasting particle-size classes,
where both named parts of the control section use a cationexchange
activity class, the class associated with the particlesize
class that has the most clay is named. For example, in a
pedon with a classification of fine-loamy over clayey, mixed,
active, calcareous, thermic Typic Udorthent, the cationexchange
activity class “active” is associated with the clayey,
lower part of the control section. For other soils with strongly
contrasting particle-size classes, where one named part of the
control section uses a cation-exchange activity class and one
named part does not, the class is associated with the part which
requires usage. For example, in a pedon with a classification of
coarse-loamy over sandy or sandy-skeletal, mixed, superactive,
calcareous, mesic Oxyaquic Ustifluvent, the cation-exchange
activity class “superactive” is associated with the coarse-loamy,
upper part of the control section.
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.
Key to Cation-Exchange Activity Classes
A.  Soils that are not Histosols, Histels, Oxisols, or
Psamments, that are not in “psamm” great groups of Entisols
or Gelisols, that are not in Psammentic subgroups, that are not
in “kandi” or “kanhap” great groups or subgroups of Alfisols or
Ultisols, that do not have a sandy or sandy-skeletal particle-size
class or any substitute for a particle-size class throughout the
entire control section, and that have:
1.  A mixed or siliceous mineralogy class; and
2.  A ratio of cation-exchange capacity (by 1N NH4
OAc
pH 7) to percent clay (by weight) of:
a.  0.60 or more.
Superactive
or
b.  0.40 to 0.60.
Active
or
c.  0.24 to 0.40.
Semiactive
or
d.  Less than 0.24.
Subactive
or
B.  All other soils: No cation-exchange activity classes are
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 below, 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 taxon.
Use of the Calcareous Class
The calcareous class is used in the names of the families of
Entisols, Gelisols, Aquands, Aquepts, Aquolls, and all Gelic
suborders and Gelic great groups, but it is not used for any of
the following:
1.  Calciaquolls, Natraquolls, and Argiaquolls
2.  Cryaquolls and Duraquolls that have an argillic or natric
horizon
3.  Duraquands and Placaquands
4.  Sulfaquepts, Fragiaquepts, and Petraquepts
5.  The Psamments, Psammaquents, Psammowassents,
Psammoturbels, Psammorthels, and Psammentic subgroups that
have no particle-size class
6.  Sandy, sandy-skeletal, cindery, pumiceous, or fragmental
families
7.  Families with anhydritic, carbonatic, gypsic, or hypergypsic
mineralogy
8. Histels
Use of the Acid and Nonacid Reaction Classes
The acid and nonacid classes are used in the names of the
families of Entisols, Gelisols, Aquands, Aquepts, and all Gelic
suborders and Gelic great groups, but they are not used for any
of the following:
1.  Duraquands and Placaquands
2.  Sulfaquepts, Fragiaquepts, and Petraquepts
3.  The Psamments, Psammaquents, Psammowassents,
Psammoturbels, Psammorthels, and Psammentic subgroups that
have no particle-size class
Family and Series Differentiae and Names	 329
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4.  Sandy, sandy-skeletal, cindery, pumiceous, or fragmental
families
5.  Families with anhydritic, carbonatic, gypsic, or hypergypsic
mineralogy
6.  Histels
Use of the Allic Class
The allic class is used only in the families of Oxisols.
Control Section for Calcareous and Reaction Classes
The control section for the calcareous class is one of the
following:
1.  All Gelisols (except for Histels) and all Gelic suborders
and Gelic great groups: The layer from the mineral soil surface
to a depth of 25 cm or to a root-limiting layer, whichever is
shallower.
2.  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-limiting layer.
3.  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.
4.  All other listed soils: Between a depth of 25 and 50 cm
below the mineral soil surface.
The control section for the acid and nonacid classes is one of
the following:
1.  All Gelisols (except for Histels) and all Gelic suborders
and Gelic great groups: The layer from the mineral soil surface
to a depth of 25 cm or to a root-limiting layer, whichever is
shallower.
2.  All other listed soils: The same control section depths as
those for particle-size classes.
The control section for the allic class 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 is either at a depth
of 50 cm below the soil surface or at the upper boundary of 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 and Gelic suborders and great groups 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
330	 Keys to Soil Taxonomy
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 (72 o
F).
Isothermic
or
4. 22 o
C (72 o
F) or higher.
Isohyperthermic
Soil Depth Classes
Soil depth classes are used in all families of mineral soils
and Histels that have a root-limiting layer at a specified
depth from the mineral soil surface, except for those families
in Lithic subgroups (defined below) and those with a fragipan.
The root-limiting layers included in soil depth classes are
duripans; petrocalcic, petrogypsic, and placic horizons;
continuous ortstein (i.e., is 90 percent or more cemented and
has lateral continuity); and densic, lithic, manufactured
layer, paralithic, and petroferric contacts. Soil depth classes
for Histosols are given later in this chapter. One soil depth
class name, “shallow,” is used to characterize certain soil
families that have one of the depths indicated in the following
key.
Key to Soil Depth Classes for Mineral Soils and Histels
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.  Other mineral soils and Folistels 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.  Other Histels that are less than 50 cm deep to a rootlimiting
layer.
Shallow
or
D.  All other Histels and 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.
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 plus 2 times the weighted average clay 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 on Sands
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 on Sands
A.  Quartzipsamments that have a sum of the weighted average
silt (by weight) plus 2 times the weighted average clay (by
weight) of more than 5.
Coated
or
Family and Series Differentiae and Names	 331
F
A
M
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
depending on the season. 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 Organic Soils
Most of the differentiae that are used to distinguish families
of organic soils (Histosols and Histels) have already been
defined, either because they are used as differentiae in mineral
soils as well as organic soils or because their definitions are
used for the classification of some Histosols and Histels in
categories above 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 class names, if appropriate for a
particular soil, are placed in the 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 six classes defined below are more generalized than
those used for mineral soils.
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 3), whichever is thicker.
Key to Particle-Size Classes of Organic Soils
A.  Terric subgroups of Histosols and Histels that 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 class of coarse sand, sand, fine sand, loamy
coarse sand, loamy sand, or loamy fine sand in the fine-earth
fraction.
Sandy or sandy-skeletal
or
3.  Less than 35 percent (by weight) clay in the fine-earth
fraction and a total content of rock fragments plus any
artifacts 2 mm or larger in diameter which are both cohesive
and persistent of 35 percent or more (by volume).
Loamy-skeletal
or
4.  A total content of rock fragments plus any artifacts 2 mm
or larger in diameter which are both cohesive and persistent
of 35 percent or more (by volume).
Clayey-skeletal
or
5.  A clay content of 35 percent or more (by weight) in the
fine-earth fraction.
Clayey
or
332	 Keys to Soil Taxonomy
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 3. 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 Soil Material and 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); and
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) extractable by dithionite-citrate
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 Folists,
Sphagnofibrists, or 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 3) 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
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
Family and Series Differentiae and Names	 333
F
A
M
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
or to a pumiceous, cindery, or fragmental substitute class. The
root-limiting layers included in soil depth classes of Histosols
are duripans; petrocalcic, petrogypsic, and placic horizons;
continuous ortstein (i.e., is 90 percent or more cemented and
has lateral continuity); and densic, lithic, manufactured layer,
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 for Histosols
A.  Histosols that are less than 18 cm deep to a root-limiting
layer or to a pumiceous, cindery, or fragmental substitute class.
Micro
or
B.  Other Histosols, excluding Folists, that have a root-limiting
layer or a pumiceous, cindery, or fragmental 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 certain diagnostic subsurface
horizons, such as a duripan, fragipan, or petrocalcic horizon,
because these horizons have few roots. The thickness of such
root-limiting horizons is taken into account in differentiating
concepts of competing soil series, when they occur within
the series control section. In contrast, the thickness of such
horizons is not used in the control sections for the family. The
series control section includes materials starting at the soil
surface and extends into the first 25 cm of densic materials,
a manufactured layer, or paralithic materials, if the densic,
manufactured layer, or paralithic contacts, respectively, are less
than 125 cm below the mineral soil surface. In contrast, the
properties of materials below any densic, lithic, manufactured
layer, paralithic, or petroferric contact are not used for
classification in the categories above the series (i.e., order
through family). The properties of horizons and layers below
the particle-size control section, a depth between 100 and 150
cm (or to 200 cm if in a diagnostic horizon) from the mineral
soil surface, also are considered in the series category of this
taxonomy.
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, manufactured layer, 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, manufactured
layer, or paralithic contact or 150 cm below the soil surface,
334	
whichever is shallower, if there is a densic, manufactured
layer, or paralithic contact within 150 cm; or
3.  A depth of 150 cm if the base 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, manufactured layer, 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.
	335
H
O
R
This chapter describes soil layers and genetic soil horizons.
The genetic horizons are not the equivalent of the diagnostic
horizons of Soil Taxonomy. While designations of genetic
horizons express a qualitative judgment about the kinds
of changes that are believed to have taken place in a soil,
diagnostic horizons are quantitatively defined features that are
used to differentiate between taxa. A diagnostic horizon may
encompass several genetic horizons, and the changes implied by
genetic horizon designations may not be large enough to justify
recognition of different diagnostic horizons.
Master Horizons and Layers
The capital letters O, L, A, E, B, C, R, M, and W represent
the master horizons and layers of soils. These letters are the
base symbols to which other characters are added to complete
the designations. Most horizons and layers are given a single
capital-letter symbol; some require two.
O horizons or layers: Horizons or layers dominated by
organic soil materials. Some are saturated with water for long
periods or were once saturated but are now artificially drained;
others have never been saturated.
Some O horizons or layers consist of slightly decomposed to
highly decomposed litter, such as leaves, needles, twigs, moss,
and lichens, that has been deposited on the surface of either
mineral or organic soils. Other O horizons or layers consist of
organic materials that were deposited under saturated conditions
and have decomposed to varying stages. The mineral fraction
of such material constitutes only a small percentage of the
volume of the material and generally much less than half of its
weight. Some soils consist entirely of materials designated as O
horizons or layers.
An O horizon or layer may be at the surface of a mineral
soil, or it may be at any depth below the surface if it is buried. A
horizon formed by illuviation of organic material into a mineral
subsoil is not an O horizon, although some horizons that have
formed in this manner contain considerable amounts of organic
matter. Horizons or layers composed of limnic materials are not
designated as O horizons.
L horizons or layers: Limnic horizons or layers include
both organic and mineral limnic materials that were either (1)
deposited in water by precipitation or through the actions of
aquatic organisms, such as algae and diatoms, or (2) derived
from underwater and floating aquatic plants and subsequently
modified by aquatic animals.
L horizons or layers include coprogenous earth (sedimentary
peat), diatomaceous earth, and marl. They are used only
in Histosols. They have only the following subordinate
distinctions: co, di, or ma. They do not have the subordinate
distinctions of the other master horizons and layers.
A horizons: Mineral horizons that have formed at the soil
surface or below an O horizon. They exhibit obliteration of all
or much of any original rock structure*
and show one or more of
the following:
1.  An accumulation of humified organic matter closely
mixed with the mineral fraction and not dominated by
properties characteristic of E or B horizons (defined below);
2.  Properties resulting from cultivation, pasturing, or
similar kinds of disturbance; or
3.  A morphology that is distinct from the underlying E, B,
or C horizon, resulting from processes related to the surface.
If a surface horizon has properties of both A and E horizons
but the feature emphasized is an accumulation of humified
organic matter, it is designated as an A horizon. In some areas,
such as regions with warm, arid climates, the undisturbed
surface horizon is less dark than the adjacent underlying
horizon and contains only small amounts of organic matter.
It has a morphology distinct from the C horizon, although the
mineral fraction is unaltered or only slightly altered by the
weathering of minerals considered to be weatherable (defined in
chapter 3). Such a horizon is designated as an A horizon because
it is at the soil surface. Recent alluvial or eolian deposits that
retain most of the original rock structure are not considered to
have A horizons unless they are cultivated.
E horizons: Mineral horizons in which the main feature
is the eluvial loss of silicate clay, iron, aluminum, or some
combination of these, leaving a concentration of sand and silt
particles. These horizons exhibit obliteration of all or much of
the original rock structure.
An E horizon is most commonly differentiated from an
underlying B horizon in the same sequum by a color of higher
value or lower chroma, or both, by coarser texture, or by a
combination of these properties. In some soils the color of the
E horizon is that of the sand and silt particles, but in many
* 
Rock structure includes fine stratification (5 mm or less thick) 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.
Designations for Horizons and Layers
CHAPTER 18
336	 Keys to Soil Taxonomy
soils coatings of iron oxides or other compounds mask the
color of the primary particles. An E horizon is most commonly
differentiated from an overlying A horizon by its lighter color.
It generally contains less organic matter than the A horizon.
An E horizon is commonly near the soil surface, below an O
or A horizon and above a B horizon. However, the symbol E
can be used for eluvial horizons that are at the soil surface, that
are within or between parts of the B horizon, or that extend to
depths greater than those of normal observation, if the horizons
have resulted from pedogenic processes.
B horizons: Mineral horizons that have formed below an A,
E, or O horizon. They exhibit obliteration of all or much of the
original rock structure and show one or more of the following
as evidence of pedogenesis:
1.  Illuvial concentration of silicate clay, iron, aluminum,
humus, sesquioxides, carbonates, anhydrite, gypsum, salts
more soluble than gypsum, or silica, alone or in combination;
2.  Evidence of the removal, addition, or transformation of
carbonates, anhydrite, and/or gypsum;
3.  Residual concentration of oxides, sesquioxides, and
silicate clay, alone or in combination;
4.  Coatings of sesquioxides that make the horizon color
conspicuously lower in value, higher in chroma, or redder
in hue, than overlying and underlying horizons, without
apparent illuviation of iron;
5.  Alteration that forms silicate clay or liberates oxides, or
both, and that forms pedogenic structure if volume changes
accompany changes in moisture content;
6.  Brittleness; or
7.  Strong gleying when accompanied by other evidence of
pedogenic change.
All of the different kinds of B horizons are, or were
originally, subsurface horizons. Examples of B horizons are
horizons (which may or may not be cemented) with illuvial
concentrations of carbonates, gypsum, anhydrite, or silica that
are the result of pedogenic processes and are contiguous to other
genetic horizons and brittle horizons that show other evidence
of alteration, such as prismatic structure or illuvial accumulation
of clay.
Examples of layers that are not B horizons are layers in
which clay films either coat rock fragments or cover finely
stratified unconsolidated sediments, regardless of whether the
films were formed in place or by illuviation; layers into which
carbonates have been illuviated but that are not contiguous to an
overlying genetic horizon; and layers with strong gleying but no
other pedogenic changes.
C horizons or layers: Mineral horizons or layers, excluding
strongly cemented and harder bedrock, that are little affected
by pedogenic processes and lack the properties of O, A, E, B, or
L horizons. The material of C horizons or layers may be either
like or unlike the material from which the solum has presumably
formed. The C horizon may have been modified, even if there is
no evidence of pedogenesis.
Included as C layers (typically designated Cr) are sediment,
saprolite, bedrock, and other geologic materials that are
moderately cemented or less cemented. The excavation
difficulty in these materials commonly is low or moderate.
Some soils form in material that is already highly weathered,
and if such material does not meet the requirements for A,
E, or B horizons, it is designated by the letter C. Changes
that are not considered pedogenic are those not related to the
overlying horizons. Some layers that have accumulations of
silica, carbonates, gypsum, or more soluble salts are included
in C horizons, even if cemented. However, if a cemented layer
formed through pedogenic processes, versus geologic processes
(e.g., lithification), it is considered a B horizon.
R layers: Strongly cemented to indurated bedrock.
Granite, basalt, quartzite, limestone, and sandstone are
examples of bedrock that commonly are cemented enough to be
designated by the letter R. The excavation difficulty commonly
exceeds high. The R layer is sufficiently coherent when moist to
make hand-digging with a spade impractical, although the layer
may be chipped or scraped. Some R layers can be ripped with
heavy power equipment. The bedrock may have fractures, but
these are generally too few or too widely spaced to allow root
penetration. The fractures may be coated or filled with clay or
other material.
M layers: Root-limiting layers beneath the soil surface
consisting of nearly continuous, horizontally oriented, humanmanufactured
materials.
Examples of materials designated by the letter M include
geotextile liners, asphalt, concrete, rubber, and plastic, if they
are present as continuous, horizontal layers.
W layers: Water.
This symbol indicates water layers within or beneath the
soil. The water layer is designated as Wf if it is permanently
frozen and as W if it is not permanently frozen. The W (or Wf)
designation is not used for shallow water, ice, or snow above
the soil surface.
Transitional and Combination Horizons
Horizons dominated by properties of one master horizon
but having subordinate properties of another.—Two capitalletter
symbols are used for such transitional horizons, e.g., AB,
EB, BE, or BC. The first of these symbols indicates that the
properties of the horizon so designated dominate the transitional
horizon. An AB horizon, for example, has characteristics of
both an overlying A horizon and an underlying B horizon, but it
is more like the A horizon than the B horizon.
In some cases a horizon can be designated as transitional
even if one of the master horizons to which it presumably forms
a transition is not present. A BE horizon may be recognized
in a truncated soil if its properties are similar to those of a BE
Designations for Horizons and Layers 	 337
H
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horizon in a soil from which the overlying E horizon has not
been removed by erosion. A BC horizon may be recognized
even if no underlying C horizon is present; it is transitional to
assumed parent materials.
Horizons with two distinct parts that have recognizable
properties of the two kinds of master horizons indicated by
the capital letters.—The two capital letters designating such
combination horizons are separated by a virgule (/), e.g.,
E/B, B/E, or B/C. Most of the individual parts of one horizon
component are surrounded by the other. The designation
may be used even when horizons similar to one or both of
the components are not present, provided that the separate
components can be recognized in the combination horizon. The
first symbol is that of the horizon with the greater volume.
Single sets of horizon designators do not cover all situations;
therefore, some improvising is needed. For example, Lamellic
Udipsamments have lamellae that are separated from each
other by eluvial layers. Because it is generally not practical to
describe each lamella and eluvial layer as a separate horizon,
the horizons can be combined but the components are described
separately. One horizon then has several lamellae and eluvial
layers and can be designated as an “E and Bt” horizon. The
complete horizon sequence for these soils could be: Ap-Bw-E
and Bt1-E and Bt2-C.
Suffix Symbols
Lowercase letters are used as suffixes to designate specific
subordinate distinctions within master horizons and layers. The
term “accumulation” is used in many of the definitions of such
suffixes to indicate that these horizons must contain more of the
material in question than is presumed to have been present in
the parent material. The use of a suffix symbol is not restricted
only to those horizons that meet certain criteria for diagnostic
horizons and other criteria as defined in Soil Taxonomy. If
there is any evidence of accumulation, the appropriate suffix
(or suffixes) should be assigned. The suffix symbols and their
meanings are as follows:
a  Highly decomposed organic material
This symbol is used with O horizons to indicate the
most highly decomposed organic materials, which have
a fiber content of less than 17 percent (by volume) after
rubbing.
b  Buried genetic horizon
This symbol is used to indicate identifiable buried
horizons with major genetic features that were developed
before burial. Genetic horizons may or may not have
formed in the overlying material, which may be either
like or unlike the assumed parent material of the buried
horizon. This symbol is not used to separate horizons
composed of organic soil material, that are forming at
the soil surface, from underlying horizons composed of
mineral soil material. It may be used for organic soils, but
only if they are buried by mineral soil materials.
c  Concretions or nodules
This symbol indicates a significant accumulation
of concretions or nodules. Cementation is required.
The cementing agent commonly is iron, aluminum,
manganese, or titanium. It cannot be silica, dolomite,
calcite, gypsum, anhydrite, or soluble salts.
co  Coprogenous earth
This symbol, used only with L horizons, indicates a
limnic layer of coprogenous earth (sedimentary peat).
d  Physical root restriction
This symbol indicates noncemented, root-restricting
layers in naturally occurring or human-made sediments
or materials. Examples of natural layers are dense till and
some noncemented shales and siltstones. Examples of
human-made dense layers are plowpans and mechanically
compacted zones in human-transported material.
di  Diatomaceous earth
This symbol, used only with L horizons, indicates a
limnic layer of diatomaceous earth.
e  Organic material of intermediate decomposition
This symbol is used with O horizons to indicate
organic materials of intermediate decomposition. The
fiber content of these materials is 17 to less than 40
percent (by volume) after rubbing.
f  Frozen soil or water
This symbol indicates that a horizon or layer contains
permanent ice. The symbol is not used for seasonally
frozen layers or for dry permafrost.
ff  Dry permafrost
This symbol indicates a horizon or layer that is
continually colder than 0o
C and does not contain enough
ice to be cemented by ice. This suffix is not used for
horizons or layers that have a temperature warmer than
0o
C at some time of the year.
g  Strong gleying
This symbol indicates either that iron has been reduced
and removed during soil formation or that saturation with
stagnant water has preserved it in a reduced state. Most
of the affected layers have chroma of 2 or less, and many
have redox concentrations. The low chroma can represent
either the color of reduced iron or the color of uncoated
sand and silt particles from which iron has been removed.
The symbol g is not used for materials of low chroma
338	 Keys to Soil Taxonomy
that have no history of wetness, such as some shales
or E horizons. If the symbol is used with B horizons,
pedogenic change (e.g., soil structure) in addition to
gleying is implied. If no other pedogenic change besides
gleying has taken place, the horizon is designated Cg.
h  Illuvial accumulation of organic matter
This symbol is used with B horizons to indicate
the accumulation of illuvial, amorphous, dispersible
complexes of organic matter and sesquioxides. The
sesquioxide component is dominated by aluminum and
is present only in very small quantities. The organosesquioxide
material coats sand and silt particles. In some
horizons these coatings have coalesced, filled pores,
and cemented the horizon. The symbol h is also used
in combination with s (e.g., Bhs) if the amount of the
sesquioxide component is significant but the value and
chroma, moist, of the horizon are 3 or less.
i  Slightly decomposed organic material
This symbol is used with O horizons to indicate the
least decomposed of the organic materials. The fiber
content of these materials is 40 percent or more (by
volume) after rubbing.
j  Accumulation of jarosite
Jarosite is a potassium (ferric) iron hydroxy sulfate
mineral, KFe3
(SO4
)2
(OH)6
, that is commonly an alteration
product of pyrite that has been exposed to an oxidizing
environment. Jarosite has hue of 2.5Y or yellower and
normally has chroma of 6 or more, although chroma as
low as 3 or 4 has been reported. It forms in preference to
iron (hydr)oxides in active acid sulfate soils at pH of 3.5
or less and can be stable in post-active acid sulfate soils
for long periods of time at higher pH.
jj  Evidence of cryoturbation
Evidence of cryoturbation includes irregular and
broken horizon boundaries, sorted rock fragments, and
organic soil materials occurring as bodies and broken
layers within and/or between mineral soil layers. The
organic bodies and layers are most commonly at the
contact between the active layer and the permafrost.
k  Accumulation of secondary carbonates
This symbol indicates an accumulation of visible
pedogenic calcium carbonate (less than 50 percent, by
volume). Carbonate accumulations occur as carbonate
filaments, coatings, masses, nodules, disseminated
carbonate, or other forms.
kk  Engulfment of horizon by secondary carbonates
This symbol indicates major accumulations of
pedogenic calcium carbonate. The suffix kk is used when
the soil fabric is plugged with fine grained pedogenic
carbonate (50 percent or more, by volume) that occurs as
an essentially continuous medium. The suffix corresponds
to stage III of the carbonate morphogenetic stages (Gile et
al., 1966) or a higher stage.
m  Pedogenic cementation
This symbol indicates continuous or nearly continuous
pedogenic cementation. It is used only for horizons that
are 90 percent or more cemented, although they may
be fractured. The cemented layer is physically rootrestrictive.
The predominant cementing agent (or the two
dominant ones) may be indicated by adding defined letter
suffixes, singly or in pairs. The horizon suffix kkm (and
less commonly km) indicates cementation by carbonates;
qm, cementation by silica; sm, cementation by iron; yym,
cementation by gypsum; kqm, cementation by carbonates
and silica; and zm, cementation by salts more soluble than
gypsum. The symbol m is not used for permanently frozen
layers impregnated by ice.
ma  Marl
This symbol, used only with L horizons, indicates a
limnic layer of marl.
n  Accumulation of sodium
This symbol indicates an accumulation of
exchangeable sodium.
o  Residual accumulation of sesquioxides
This symbol indicates a residual accumulation of
sesquioxides.
p  Tillage or other disturbance
This symbol indicates a disturbance of a horizon by
mechanical means, pasturing, or similar uses. A disturbed
organic horizon is designated Op. A disturbed mineral
horizon is designated Ap even though it is clearly a
former E, B, or C horizon.
q  Accumulation of silica
This symbol indicates an accumulation of secondary
silica.
r  Weathered or soft bedrock
This symbol is used with C to indicate layers of
bedrock that are moderately cemented or less cemented.
Examples are weathered igneous rock and partly
consolidated sandstone, siltstone, or shale. The excavation
difficulty is low to high.
s  Illuvial accumulation of sesquioxides and organic matter
This symbol is used with B horizons to indicate
an accumulation of illuvial, amorphous, dispersible
Designations for Horizons and Layers 	 339
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complexes of organic matter and sesquioxides if both the
organic matter and sesquioxide components are significant
and if either the value or chroma, moist, of the horizon is
4 or more. The symbol is also used in combination with
h (e.g., Bhs) if both the organic matter and sesquioxide
components are significant and if the value and chroma,
moist, are 3 or less.
se  Presence of sulfides
This symbol indicates the presence of sulfides in
mineral or organic horizons. Horizons with sulfides
typically have dark colors (e.g., value ≤ 4, chroma ≤ 2).
These horizons typically form in soils associated with
coastal environments that are permanently saturated
or submerged (i.e., tidal marshes or estuaries). Soil
materials which have sulfidization actively occurring
emanate hydrogen sulfide gas, which is detectable by its
odor (Fanning and Fanning, 1989; Fanning et al., 2002).
Sulfides may also occur in upland environments that
have a source of sulfur. Soils in such environments are
often of geologic origin and may not produce a hydrogen
sulfide odor. Examples include soils formed in parent
materials derived from coal deposits, such as lignite, or
soils formed in coastal plain deposits, such as glauconite,
that have not been oxidized because of thick layers of
overburden.
ss  Presence of slickensides
This symbol indicates the presence of pedogenic
slickensides. Slickensides result directly from the swelling
of clay minerals and shear failure, commonly at angles
of 20 to 60 degrees above horizontal. They are indicators
that other vertic characteristics, such as wedge-shaped
peds and surface cracks, may be present.
t  Accumulation of silicate clay
This symbol indicates an accumulation of silicate clay
that either has formed within a horizon and subsequently
has been translocated within the horizon or has been
moved into the horizon by illuviation, or both. At least
some part of the horizon should show evidence of clay
accumulation either as coatings on surfaces of peds or in
pores, as lamellae, or as bridges between mineral grains.
u  Presence of human-manufactured materials (artifacts)
This symbol indicates the presence of objects
or materials that have been created or modified by
humans, usually for a practical purpose in habitation,
manufacturing, excavation, or construction activities.
Examples of artifacts are bitumen (asphalt), boiler
slag, bottom ash, brick, cardboard, carpet, cloth, coal
combustion by-products, concrete (detached pieces),
debitage (i.e., stone tool flakes), fly ash, glass, metal,
paper, plasterboard, plastic, potsherd, rubber, treated
wood, and untreated wood products.
v  Plinthite
This symbol indicates the presence of iron-rich,
humus-poor, reddish material that is firm or very firm
when moist and is less than strongly cemented. The
material hardens irreversibly when exposed to the
atmosphere and to repeated wetting and drying.
w  Development of color or structure
This symbol is used only with B horizons to indicate
the development of color or structure, or both, with little
or no apparent illuvial accumulation of material. It should
not be used to indicate a transitional horizon.
x  Fragipan character
This symbol indicates a genetically developed layer
that has a combination of firmness and brittleness and
commonly a higher bulk density than the adjacent layers.
Some part of the layer is physically root-restrictive.
y  Accumulation of gypsum
This symbol indicates an accumulation of gypsum.
The suffix y is used when the horizon fabric is dominated
by soil particles or minerals other than gypsum. Gypsum
is present in amounts that do not significantly obscure or
disrupt other features of the horizon. In unique but rare
soils, this symbol may be used to connote the presence of
anhydrite.
yy  Dominance of horizon by gypsum
This symbol indicates a horizon that is dominated
by the presence of gypsum. The gypsum content may
be due to an accumulation of secondary gypsum, the
transformation of primary gypsum inherited from parent
material, or other processes. The suffix yy is used when
the horizon fabric has such an abundance of gypsum
(generally 50 percent or more, by volume) that pedogenic
and/or lithologic features are obscured or disrupted
by growth of gypsum crystals. Colors associated with
horizons that have suffix yy typically are highly whitened
(e.g., value of 7 through 9.5 and chroma of 4 or less). In
unique but rare soils, this symbol may be used to connote
the presence of anhydrite.
z  Accumulation of salts more soluble than gypsum
This symbol indicates an accumulation of salts that are
more soluble than gypsum.
Conventions for Using Letter Suffixes
Many master horizons and layers that are symbolized by a
single capital letter have one or more lowercase letter suffixes.
The following rules apply:
1.  Letter suffixes directly follow the capital letter of the
master horizon or layer, or the prime symbol, if used.
340	 Keys to Soil Taxonomy
2.  More than three suffixes are rarely used.
3.  If more than one suffix is needed, the following letters, if
used, are written first: a, d, e, h, i, r, s, t, and w. Except in the
Bhs horizon or Crt†
layer designations, none of these letters
are used in combination for a single horizon.
4.  If more than one suffix is needed and the horizon is not
buried, the following symbols, if used, are written last: c, f,
g, m, v, and x. Examples are Bjc and Bkkm. If any of these
suffixes are used together in the same horizon, symbols
c and g are written last (e.g., Btvg), with one exception.
For horizons using symbol f together with any of the other
symbols in this rule, symbol f (frozen soil or water) is written
last, e.g., Cdgf.
5.  If a genetic horizon is buried, the suffix b is written last,
e.g., Oab.
6.  Suffix symbols h, s, and w are not used with g, k, kk, n,
o, q, y, yy, or z.
7.  If the above rules do not apply to certain suffixes, such
as k, kk, q, y, or yy, the suffixes may be listed together
in order of assumed dominance or listed alphabetically if
dominance is not a concern.
A B horizon that has a significant accumulation of clay and
also shows evidence of a development of color or structure,
or both, is designated Bt (suffix symbol t has precedence
over symbols w, s, and h). A B horizon that is gleyed or has
accumulations of carbonates, sodium, silica, gypsum, or
salts more soluble than gypsum or residual accumulations of
sesquioxides carries the appropriate symbol: g, k, kk, n, q, y,
yy, z, or o. If illuvial clay also is present, t precedes the other
symbol, e.g., Bto.
Vertical Subdivision
Commonly, a horizon or layer identified by a single letter or
a combination of letters has to be subdivided. For this purpose,
numbers are added to the letters of the horizon designation.
These numbers follow all the letters. Within a sequence of C
horizons, for example, successive horizons may be designated
C1, C2, C3, etc. If the lower horizons are strongly gleyed
and the upper horizons are not strongly gleyed, they may be
designated C1-C2-Cg1-Cg2 or C-Cg1-Cg2-R.
These conventions apply whatever the purpose of the
subdivision. In many soils a horizon that could be identified
by a single set of letters is subdivided because of the need
to recognize differences in morphological features, such as
structure, color, or texture. These divisions are numbered
consecutively, but the numbering starts again with 1 wherever
in the profile any letter of the horizon symbol changes, e.g.,
Bt1-Bt2-Btk1-Btk2 (not Bt1-Bt2-Btk3-Btk4). The numbering
of vertical subdivisions within consecutive horizons is not
interrupted at a discontinuity (indicated by a numerical prefix)
if the same letter combination is used in both materials, e.g.,
Bs1-Bs2-2Bs3-2Bs4 (not Bs1-Bs2-2Bs1-2Bs2).
During sampling for laboratory analyses, thick soil
horizons are sometimes subdivided even though differences
in morphology are not evident in the field. These subdivisions
are identified by numbers that follow the respective horizon
designations. For example, four subdivisions of a Bt horizon
sampled by 10-cm increments are designated Bt1, Bt2, Bt3,
and Bt4. If the horizon has already been subdivided because
of differences in morphological features, the set of numbers
that identifies the additional sampling subdivisions follows the
first number. For example, three subdivisions of a Bt2 horizon
sampled by 10-cm increments are designated Bt21, Bt22, and
Bt23. The descriptions for each of these sampling subdivisions
can be the same, and a statement indicating that the horizon has
been subdivided only for sampling purposes can be added.
Discontinuities
Numbers are used as prefixes to horizon designations
(preceding the capital letters A, E, B, C, and R) to indicate
discontinuities in mineral soils. These prefixes are distinct
from the numbers that are used as suffixes denoting vertical
subdivisions.
A discontinuity that can be identified by a number prefix is
a significant change in particle-size distribution or mineralogy
that indicates a difference in the parent material from which
the horizons have formed and/or a significant difference in
age, unless that difference in age is indicated by the suffix
b. Symbols that identify discontinuities are used only when
they can contribute substantially to an understanding of the
relationships among horizons. The stratification common
to soils that formed in alluvium is not designated as a
discontinuity, unless particle-size distribution differs markedly
from layer to layer (i.e., particle-size classes are strongly
contrasting), even though genetic horizons may have formed in
the contrasting layers.
Where a soil has formed entirely in one kind of material,
the whole profile is understood to be material 1 and the number
prefix is omitted from the symbol. Similarly, the uppermost
material in a profile consisting of two or more contrasting
materials is understood to be material 1, but the number is
omitted. Numbering starts with the second layer of contrasting
material, which is designated 2. Underlying contrasting layers
are numbered consecutively. Even when the material of a layer
below material 2 is similar to material 1, it is designated 3 in
the sequence; the numbers indicate a change in materials, not
types of material. Where two or more consecutive horizons have
formed in the same kind of material, the same prefix number
indicating the discontinuity is applied to all the designations
of horizons in that material, e.g., Ap-E-Bt1-2Bt2-2Bt3-2BC.
† 
Indicates weathered bedrock or saprolite in which clay films are present.
Designations for Horizons and Layers 	 341
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The suffix numbers designating vertical subdivisions of the Bt
horizon continue in consecutive order across the discontinuity.
However, vertical subdivisions do not continue across lithologic
discontinuities if the horizons are not consecutive or contiguous
to each other. If other horizons intervene, another vertical
numbering sequence begins for the lower horizons, e.g., A-C1-
C2-2Bw1-2Bw2-2C1-2C2.
If an R layer is present below a soil that has formed in
residuum and if the material of the R layer is judged to be like
the material from which the soil has developed, the number
prefix is not used. The prefix is used, however, if it is thought
that the R layer would produce material unlike that in the solum,
e.g., A-Bt-C-2R or A-Bt-2R. If part of the solum has formed in
residuum, the symbol R is given the appropriate prefix, e.g.,
Ap-Bt1-2Bt2-2Bt3-2C1-2C2-2R.
A buried genetic horizon (designated by the letter b) presents
special problems. It is obviously not in the same deposit as
the overlying horizons. Some buried horizons, however, have
formed in material that is lithologically like the overlying
deposit. A prefix is not used to distinguish material of such a
buried horizon. If the material in which a horizon of a buried
soil has formed is lithologically unlike the overlying material,
the discontinuity is indicated by a number prefix and the symbol
for the buried horizon also is used, e.g., Ap-Bt1-Bt2-BC-C-
2ABb-2Btb1-2Btb2-2C.
Discontinuities between different kinds of layers in organic
soils are not identified. In most cases such differences are
identified either by letter-suffix designations if the different
layers are organic materials (e.g., Oe vs. Oa) or by the master
horizon symbol if the different layers are mineral or limnic
materials (e.g., Oa vs. Ldi).
Use of the Prime Symbol
If two or more horizons with identical number prefixes and
letter combinations are separated by one or more horizons with
a different horizon designation in a pedon, identical letter and
number symbols can be used for those horizons that have the
same characteristics. For example, the sequence A-E-Bt-EBtx-C
identifies a soil that has two E horizons. To emphasize
this characteristic, the prime symbol (´) is added after the
master-horizon symbol of the lower of the two horizons that
have identical designations, e.g., A-E-Bt-E´-Btx-C. The prime
symbol, where appropriate, is placed after the capital-letter
horizon designation and before the lowercase suffix letter
symbols that follow it, e.g., B´t.
The prime symbol is not used unless all letters and number
prefixes are completely identical. The sequence A-Bt1-Bt2-
2E-2Bt1-2Bt2 is an example. It has two Bt master horizons
of different lithologies; thus, the Bt horizons are not identical
and the prime symbol is not needed. The prime symbol is
used for soils with lithologic discontinuities when horizons
have identical designations, e.g., A-C-2Bw-2Bc-2B´w-3Bc. In
this example, the soil has two identical 2Bw horizons but two
different Bc horizons (a 2Bc and a 3Bc), so the prime symbol is
used only with the lower 2Bw horizon (2B´w). In the rare cases
where three layers have identical letter symbols, double prime
symbols can be used for the lowest of these horizons, e.g., E´´.
Vertical subdivisions of horizons or layers (number suffixes)
are not taken into account when the prime symbol is assigned.
The sequence A-E-Bt-E´-B´t1-B´t2-B´t3-C is an example.
These same principles apply in designating layers of organic
soils. The prime symbol is used only to distinguish two or more
horizons that have identical symbols, e.g., Oi-C-O´i-C´ (when
the soil has two identical Oi and C layers) and Oi-C-Oe-C´
(when the soil has two identical C layers). The prime symbol is
added to the lower layers to differentiate them from the upper.
Use of the Caret Symbol
The caret symbol (^) is used as a prefix to master horizon
designations to indicate mineral or organic horizons formed
in human-transported material. This material has been moved
horizontally onto a pedon from a source area outside of that
pedon by purposeful human activity, usually with the aid of
machinery or hand tools. All horizons and layers formed in
human-transported material are indicated by a caret prefix (e.g.,
^A-^C-Ab-Btb). When they can contribute substantially to
an understanding of the relationship of the horizons or layers,
number prefixes may be used before the caret symbol to indicate
the presence of discontinuities within the human-transported
material (e.g., ^Au-^Bwu-^BCu-2^Cu1-2^Cu2) or between the
human-transported material and underlying horizons formed in
other parent materials (e.g., ^A-^C1-2^C2-3Bwb).
Sample Horizon and Layer Sequences
The following examples illustrate some common horizon and
layer sequences of important soils (subgroup taxa) and the use
of numbers to identify vertical subdivisions and discontinuities.
Transitional horizons, combination horizons, and the use of the
prime and caret symbols are also illustrated. The examples were
selected from soil descriptions on file and modified to reflect
present conventions.
Mineral soils
Typic Hapludoll: A1-A2-Bw-BC-C
Typic Haplustoll: Ap-A-Bw-Bk-Bky1-Bky2-C
Cumulic Haploxeroll: Ap-A-Ab-C-2C-3C
Typic Argialboll: Ap-A-E-Bt1-Bt2-BC-C
Typic Argiaquoll: A-AB-BA-Btg-BCg-Cg
Alfic Udivitrand: Oi-A-Bw1-Bw2-2E/Bt-2Bt/E1-2Bt/E2-
2Btx1-2Btx2
Entic Haplorthod: Oi-Oa-E-Bs1-Bs2-BC-C
Typic Haplorthod: Ap-E-Bhs-Bs-BC-C1-C2
Typic Fragiudalf: Oi-A-E-BE-Bt1-Bt2-B/E-Btx1-Btx2-C
Typic Haploxeralf: A1-A2-BAt-2Bt1-2Bt2-2Bt3-2BC-2C
Glossic Hapludalf: Ap-E-B/E-Bt1-Bt2-C
Typic Paleudult: A-E-Bt1-Bt2-B/E-B’t1-B’t2-B’t3
Typic Hapludult: Oi-A1-A2-BA-Bt1-Bt2-BC-C
Arenic Plinthic Paleudult: Ap-E-Bt-Btc-Btv1-Btv2-BC-C
342	
Xeric Haplodurid: A-Bw-Bkq-2Bkqm
Vertic Natrigypsid: A-Btn-Btkn-Bky-2By-2BCy-2Cr
Typic Calciargid: A-Bt-Btk1-Btk2-C
Typic Dystrudept: Ap-Bw1-Bw2-C-R
Typic Fragiudept: Ap-Bw-E-Bx1-Bx2-C
Typic Endoaquept: Ap-AB-Bg1-Bg2-BCg-Cg
Typic Haplustert: Ap-A-Bss-BCss-C
Typic Hapludox: Ap-A/B-Bo1-Bo2-Bo3-Bo4-Bo5
Typic Udifluvent: Ap-C-Ab-C’
Anthrodensic Ustorthent: ^Ap-^C/B-^Cd-2C
Anthroportic Udorthent: ^Ap-^Cu-Ab-Btb-C
Typic Aquiturbel: Oi-OA-Bjjg-Cjjg-Cjjgf
Organic soils
Typic Haplosaprist: Oap-Oa1-Oa2-Oa3-C
Typic Sphagnofibrist: Oi1-Oi2-Oi3-Oe
Limnic Haplofibrist: Oi-Lco-O’i1-O’i2-L’co-Oe-C
Lithic Cryofolist: Oi-Oa-R
Typic Hemistel: Oi-Oe-Oef
Literature Cited
Fanning, D.S., and M.C.B. Fanning. 1989. Soil: Morphology,
Genesis, and Classification. John Wiley and Sons, New York.
Fanning, D.S., M.C. Rabenhorst, S.N. Burch, K.R.
Islam, and S.A. Tangren. 2002. Sulfides and Sulfates. In
J.B. Dixon and D.G. Schulze (eds.), Soil Mineralogy with
Environmental Applications, pp. 229-260. Soil Sci. Soc. Am.,
Madison, WI.
Gile, L.H., F.F. Peterson, and R.B. Grossman. 1966.
Morphological and Genetic Sequences of Carbonate
Accumulation in Desert Soils. Soil Sci. 101:347–360.
	343
Laboratory Methods for Soil
Taxonomy
The standard laboratory methods upon which the operational
definitions of the second edition of Soil Taxonomy (Soil
Survey Staff, 1999) are based are described in the Soil Survey
Laboratory Methods Manual (Burt and Soil Survey Staff,
2014). The Charles E. Kellogg Soil Survey Laboratory (KSSL)
of the National Soil Survey Center in Lincoln, Nebraska
is where many of the standard methods were developed
and are routinely performed to support the characterization
and classification of soils. Laboratory data for the National
Cooperative Soil Survey (NCSS) program is available from
KSSL and cooperators’ laboratories in the online NCSS soil
characterization database.
The Soil Survey Laboratory Methods Manual documents
methodology and serves as a reference for the laboratory
analyst. The Soil Survey Laboratory Information Manual (Soil
Survey Staff, 2011) is a companion manual that provides brief
summaries of the KSSL methods as well as detailed discussion
of the use and application of the resulting data. The Soil Survey
Field and Laboratory Methods Manual (Soil Survey Staff,
2009) is a how-to reference for the scientist in a soil survey
office setting.
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. Soil taxonomy has many class
limits, at all categorical levels, that are based on chemical
or physical properties determined in the laboratory. One can
question the rationale for a given class limit, but that is not the
purpose of this appendix. This appendix is designed to show
what procedures are used for measuring 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 “clay”
as used in the criteria for particle-size classes. There is no
one definition of clay that works well for all soils. Hence, a
process for testing the validity of a pipette 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 gravimetric water content measurement at 1500 kPa
tension and on percent organic carbon. See the section below
titled “Other Information Useful in Classifying Soils,” for more
information.
Data Elements Used in Classifying Soils
Detailed explanations of laboratory methods are given in
the Soil Survey Laboratory Methods Manual (Burt and Soil
Survey Staff, 2014). Each method is listed by code on the data
sheet at the beginning of the chapters describing soil orders
in the second edition of Soil Taxonomy. On the data sheets
presented with each order, the method code (e.g., 3A1 for
Particles <2mm) 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 measurement reported on the data sheets in the
second edition of Soil Taxonomy and some units used as criteria
in the Keys to Soil Taxonomy are not SI (international system
of units) units. The following are conversions to SI units of
measurement:
1 meq/100 g = 1 cmol(+)/kg
1 meq/liter = 1 mmol (±)/L
1 mmho/cm = 1 dS/m
15 bar = 1500 kPa
1
/3 bar = 33 kPa
1
/10 bar = 10 kPa
1 percent = 10 g kg-1
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 both texture and
particle-size classes. Texture class 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 diameter and the fraction equal to or more than 2
mm.
Physical Analyses
Bulk density is obtained typically by equilibration of Sarancoated
natural fabric clods at designated pressure differentials.
Appendix
344	 Keys to Soil Taxonomy
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 tension and when
ovendry. For soils of medium and finer texture, the bulk density
is determined when the sample is at 33 kPa tension and when
ovendry. Bulk density is used as a criterion in the definitions of
mineral and organic soils, the required characteristics for folistic
and histic epipedons, the key to soil orders (i.e., Histosols),
the required characteristics for andic soil properties, and the
intergrade subgroups of Andic (except Kandic), Aquandic, and
Vitrandic (“vitr”). Bulk density measured at 33 kPa tension
is also used to convert other analytical results to a volumetric
basis. For example, the Humults suborder has a critical limit
of 12 kilograms or more of organic carbon per square meter
(kg/m2
) between the mineral soil surface and a depth of 100 cm.
The calculation is described below in the section titled “Other
Information Useful in Classifying Soils.”
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. The COLE is used to compute linear
extensibility (defined below). COLE multiplied by 100 is called
linear extensibility percent (LEP).
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 from the mineral soil surface to a depth of 100
cm or to a root-limiting layer if shallower. Linear extensibility
is used as an alternate criterion in Vertic (“ertic”) subgroups
throughout soil taxonomy.
Particle-size analysis in the laboratory determines the
proportion of the various size particles (separates) in a soil
sample. The values for sand, silt, and clay content as well as
their various size fractions are reported in percent of the <2 mm
material (fine-earth fraction) on a dry weight basis. Material
2 mm or larger in diameter (e.g., rock fragments) are visually
estimated or measured separately (on a volume basis), sieved
out of the sample, and thus are not considered in the analysis
of the sample. Of the material smaller than 2 mm in diameter,
the amount of the five sand fractions is determined by sieving.
The amount of the silt and clay fractions is determined by
a differential rate of settling in water. Either the pipette or
hydrometer method is used for measuring silt and clay contents.
Organic matter and dissolved mineral matter are removed in
the pipette procedure but not in the hydrometer procedure.
The two procedures are generally very similar, but a few
samples, especially those with high organic matter or high
soluble salts, exhibit wide discrepancies. Routinely removing
these substances (and, for some samples, carbonates, iron, and
silica) helps the dispersion process prior to fractioning the soil
separates and measuring them. For samples suspected of having
andic soil properties, the samples are not dried and are analyzed
in a field-moist state. This protocol avoids the irreversible
hardening of colloids into microaggregates that occurs during
drying and which decreases measured clay contents. For
soils high in gypsum (>40 %), the samples are dispersed
using sonication and an aqueous ethanol solution to prevent
dissolution of gypsum prior to particle-size analysis.
Particle-size analysis data is used in the definitions of soil
texture class (Soil Survey Division Staff, 1993). They are used
in soil taxonomy for many criteria based on texture class, clay
content, sand fraction content, and content of coarse silt through
very coarse sand (0.02 to 2 mm). The ratios discussed below
in the section titled “Other Information Useful in Classifying
Soils” are useful internal checks of the validity of particle-size
analyses.
Water content (retention) is the soil water content at a given
soil water tension. In KSSL data, it is computed and reported
as gravimetric water content on a fine-earth (< 2 mm) basis.
Measurements of water content are commonly made at 33
kPa (10 kPa for coarse textured and some moderately coarse
textured soils) and 1500 kPa tension. The water content at 1500
kPa tension is determined by desorption of crushed and sieved
fine-earth (<2 mm) soil material which may be undried (i.e.,
field-moist) or air-dried. Water content at 1500 kPa tension is
used as a criterion in the Vitrands suborder; in the Vitric (“vitr”)
and Hydric (“hydr”) great groups and subgroups of Andisols;
for the ashy, medial, and hydrous substitutes for particle-size
class; and for several strongly contrasting particle-size classes.
Measurement of 1500 kPa water content on undried samples
is particularly important for soils suspected of having andic
soil properties since it is needed for classification in the ashy,
medial, and hydrous substitutes for particle-size class.
Chemical Analyses
Ion Exchange and Extractable Cations
Cation-exchange capacity (CEC) as determined with
ammonium acetate (1N NH4
OAc) at pH 7 (CEC-7), by sum of
cations at pH 8.2 (CEC-8.2), and by bases plus aluminum is
used for different purposes in soil taxonomy. The CEC depends
on the method of analysis as well as the nature of the exchange
complex. CEC by ammonium acetate is measured at pH 7. CEC
by the sum of cations at pH 8.2 is calculated by adding the sum
of bases and the extractable acidity (defined below). CEC by
bases plus aluminum, or effective cation-exchange capacity
(ECEC), is derived by adding the sum of extractable bases
and the 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
KSSL data sheets as cmol(+)/kg-1
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
Appendix 	 345
to all soils. CEC at pH 8.2 is not reported if the soil contains
free carbonates, gypsum, or significant amounts of soluble
salts because bases, such as calcium, are extracted from these
soluble (i.e., mobile) substances. The effective cation-exchange
capacity (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 using other extracting cations will
yield somewhat different results. It is important to know the
procedure, pH, and extracting cation used before CEC data are
evaluated or data from different sources are compared.
If the ratio of CEC-7 or ECEC to percent clay is multiplied
by 100, the product represents the cation-exchange capacity of
just the clay fraction and is expressed in whole numbers which
are cmol(+)/kg clay. The CEC-7 and ECEC of the clay fraction
are used directly in this taxonomy in the required characteristics
of the kandic and oxic horizons. The CEC-7 of the clay fraction
is also used as a criterion in Kandic and Kanhaplic subgroups
of Alfisols and Ultisols, Udoxic and Ustoxic subgroups of
Quartzipsamments, and Oxic subgroups of Inceptisols and
Mollisols. The ECEC of the clay fraction is used as criteria
for Acric (“acr”) great groups of Oxisols and Acric (“acr”)
subgroups of Ultisols.
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 cmol(+)/kg-1
soil. Extractable
acidity data are reported on some data sheets as exchangeable
acidity and on others as exchangeable H+
. Extractable acid is
used to calculate the cation-exchange capacity by the sum of
cations method (CEC-8.2) and is also used as an option in the
required characteristics of the natric horizon.
Extractable aluminum is the amount of aluminum extracted
by 1N KCl. It is considered exchangeable and a measure
of the “active” acidity present in soils with a 1:1 water pH
≤5.5. Extractable aluminum is measured at KSSL by atomic
absorption. Many laboratories measure the aluminum by
titration with a base to the phenolphthalein 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 cmol(+)/kg-1
soil. It is used to calculate
ECEC and in the criteria for Alic and some Eutric subgroups of
Andisols.
Sum of extractable bases is the sum of the basic cations
calcium, magnesium, sodium, and potassium that are extracted
with ammonium acetate buffered at pH 7. The bases are
extracted from the cation-exchange complex by displacement
with ammonium ions. They are equilibrated, filtered in an autoextractor,
and measured by atomic absorption. The individual
cations and the sum of cations are reported as cmol(+)/kg-1
soil.
The term “extractable bases” is used instead of “exchangeable
bases” because soluble salts and some bases from carbonates
can be included in the extract.
Exchangeable magnesium plus sodium and calcium plus
extractable acidity (at pH 8.2) is used as a criterion for the
natric horizon and Albic subgroups of Natraqualfs. The
extractable acidity is measured at pH 8.2, and the magnesium,
sodium, and calcium are extracted at pH 7.0 with ammonium
acetate. See the paragraphs above on extractable acidity and
extractable bases.
Base saturation is reported on the data sheets as the
percentage of the cation-exchange capacity (CEC) occupied
by the four basic cations described above. It is reported in
KSSL data by two methods: sum of cations at pH 8.2 and
ammonium acetate at pH 7. Base saturation by ammonium
acetate is equal to the sum of extractable bases, divided by
the CEC by ammonium acetate (CEC-7), and multiplied by
100. If calcium carbonate or gypsum are present in a sample,
then the extractable calcium may contain calcium from these
minerals and the base saturation is assumed to be 100 percent.
Base saturation by sum of cations is equal to the sum of bases
extracted by ammonium acetate, divided by the CEC by sum
of cations (CEC-8.2), 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 shown on KSSL datasheets
even if carbonates (reported as calcium carbonate) are present.
The base saturation (by CEC-7) is set to 100 percent if
346	 Keys to Soil Taxonomy
significant amounts of carbonates or gypsum are present. Base
saturation by ammonium acetate is used in this taxonomy in the
required characteristics for the mollic and umbric epipedons,
the key to soil orders (Mollisols), and many great groups (e.g.,
Eutrudepts) and subgroups (e.g., Eutric Haplocryalfs) in several
orders. Base saturation by sum of cations is used in the key to
soil orders to identify Ultisols and in several Alfic, Dystric, and
Ultic subgroups of Alfisols, Andisols, Inceptisols, Mollisols, and
Spodosols (e.g., Alfic Fragiorthods).
Soil pH
The pH of soil is measured in water and salt solutions by
several methods. It is measured by a digital pH meter in a
soil-water solution, soil-salt solution, or saturated paste. 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.
The 1:1 water pH is determined in a solution of one part
dry soil mixed with one part water. It is used directly in the
required characteristics for sulfidic materials, Sulfic subgroups
of Entisols and Inceptisols, and the Sulfaqueptic Dystraquerts
subgroup. It is also used in a calculation with 1N KCl pH
(described below).
The 1:2 CaCl2
pH is determined in a solution of one part
soil to two parts 0.01M calcium chloride (CaCl2
). It is used in
mineral soils as a criterion for Dystric (“dystr”) great groups of
Vertisols and in the key to calcareous and reaction classes. It is
used in organic soils (i.e., Histosols and Histels) in the key to
reaction classes.
The 1N KCl pH is measured in a solution of 1N potassium
chloride (KCl) mixed 1:1 with soil. It is used directly as a
criterion for the Acric (“acr”) great groups of Oxisols. It is also
used in a simple calculation with the 1:1 water pH. The “delta
pH” (a term for 1N KCl pH minus 1:1 water pH) is used as a
criterion for the Anionic subgroups of Oxisols.
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
and are more popular in regions with less acidic soils. Readings
in 1N KCl also tend to be uniform and are more popular
in regions with more acidic soils. If KCl is used to extract
exchangeable aluminum, the pH reading (in KCl) shows the pH
at which the aluminum was extracted.
The saturated paste pH is usually compared to the 1:1 water
pH and the 1:2 CaCl2
pH. The usual pH sequence is as follows:
1:1 water pH > 1:2 CaCl2
pH > saturated paste pH. If the
saturated paste pH is > 1:2 CaCl2
pH, the soil is nonsaline. If the
saturated paste pH is ≥ 1:1 water pH, the soil may be sodium
saturated and does not have free carbonates. The saturated paste
pH is used as a criterion for the Dystrusterts and Dystruderts
great groups.
The oxidized pH is used to determine whether known or
suspected sulfidic materials are present and whether they will
oxidize to form a sulfuric horizon. Soil materials that have
a pH value (1:1 water pH) of more than 3.5 are incubated at
room temperature in a 1-cm-thick layer under moist, aerobic
conditions and repeatedly dried and remoistened on a weekly
basis. Sulfidic materials 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 16 weeks or
longer, if the pH is still dropping after 16 weeks, until the pH
reaches a nearly constant value.
The sodium fluoride pH (NaF pH) is measured in a
suspension of 1 gram of soil in 50 ml 1M NaF after stirring for
2 minutes. A NaF pH of 9.4 or more is a strong indicator that
short-range-order minerals dominate the soil exchange complex.
A NaF pH of 8.4 or more is a criterion for the isotic mineralogy
class. It indicates a significant influence of short-range-order
minerals on the exchange complex. Soil materials with free
carbonates also have high NaF pH values. NaF is poisonous
with ingestion and eye contact and moderately hazardous with
skin contact.
Sulfur and Extractable Anions
Nitrate concentration is measured in a 1:5 soil:water extract.
The nitrate content (NO3
)
of the extract is measured by a flowinjection
analyzer. The results are reported in mmol(-)/L-1
and
are used in a simple calculation as criteria for Nitric subgroups
of Gelisols.
Phosphate retention refers to the percent phosphorus retained
by soil after equilibration with 1,000 mg/kg phosphorus solution
for 24 hours. This analyte is also referred to as New Zealand
(NZ) phosphorus retention. Percent phosphate retention is
used in the required characteristics for andic soil properties. It
identifies soils in which phosphorus fixation may be a problem
affecting agronomic uses.
Total sulfur (S) is the content of organic and inorganic forms
of sulfur. KSSL uses a combustion technique for analysis of
total S. It is reported as percent of air-dry, fine-earth material.
Total sulfur is used, along with 1:1 water pH, as a criterion in
the required characteristics for sulfidic materials.
Water-soluble sulfate is used as a criterion for the sulfuric
horizon. The sulfate content (SO4
2)is
measured from a 1:500
soil:water extract using an ion chromatograph. The sulfate
content is initially measured in mg L-1
and later converted to
percent in the soil. It is reported as aqueous-extractable sulfate
to the nearest hundredths of a percent.
Carbonates and Calcium Sulfates
Calcium carbonate equivalent is the amount of carbonates
in the soil as measured by treating the sample with 3N 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 either less than 2 mm or less than 20 mm in
Appendix 	 347
diameter. Calcium carbonate equivalent is used in the required
characteristics for the mollic epipedon and calcic horizon and
as criteria for the Rendolls suborder, the Rendollic Eutrudepts
subgroup, and the carbonatic mineralogy class.
Gypsum content is determined by extraction in water and
precipitation in acetone. The amount of gypsum (CaSO4
•2H2
O)
is reported as a percentage of the total dry weight of the fraction
less than 2 mm in diameter and the fraction less than 20 mm
in diameter. 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. Gypsum
content is used in the required characteristics for gypsic and
petrogypsic horizons and as criteria for the gypseous substitute
classes, several strongly contrasting particle-size classes, and
the hypergypsic, gypsic, and carbonatic mineralogy classes.
Anhydrite content is quantified by the difference in two
analytical procedures. Anhydrite (CaSO4
) and gypsum are
both extracted and measured by a procedure using acetone to
precipitate dissolved calcium sulfate from an aqueous solution.
The acetone procedure commonly used to quantify gypsum also
extracts anhydrite, and for soils with both of these minerals,
the results of the analysis represent the sum of gypsum and
anhydrite in the soil. Gypsum (but not anhydrite) is quantified
by thermal gravimetric analysis, a method that measures the
weight loss of a sample by heating it from 20 to 200ºC at a rate
of 2ºC/min. The weight of water loss between 75 and 115ºC
is used to quantify the gypsum based on a theoretical weigh
loss of 20.9% (Karathanasis and Harris, 1994). Therefore, the
percent anhydrite in a sample can be derived from the difference
between the acetone method (Σgypsum+anhydrite) and thermal
(gypsum) procedure. More details can be found in Wilson et al.
(2013). Anhydrite content is used in the required characteristics
for the anhydritic horizon and as a criterion for the anhydritic
mineralogy class.
Soluble Salts
Electrical conductivity (EC) is the conductivity of electricity
through the water extracted from saturated soil paste. It is
reported as dS/m and is used as a criterion for the salic horizon
and in Halic subgroups of Vertisols.
Electrical conductivity 1:1 is the electrolytic conductivity
of a suspension of 1 part soil to 1 part water. The results are
used to classify some saline organic soils composed of highly
decomposed organic materials into the Halic subgroups of
Haplosaprists. The conductivity is reported as dS/m.
Electrical conductivity 1:5 by volume(EC1:5 vol
) is the
electrolytic conductivity of a diluted, unfiltered supernatant of 1
part soil to 5 parts distilled water as measured by volume. The
EC1:5 vol
is used to indicate the threshold between different taxa
for freshwater and brackish subaqueous soils. It is reported as
dS/m.
Exchangeable sodium percentage (ESP) is reported as a
percentage of the CEC by ammonium acetate at pH 7. Watersoluble
sodium is converted to cmol(+)/kg-1
soil. This value
is subtracted from extractable sodium, divided by the CEC
(by ammonium acetate), and multiplied by 100. An ESP of 15
percent or more is used in this taxonomy as a criterion for the
natric horizon, the Halaquepts great group, Natric subgroups,
and most Sodic subgroups.
Sodium adsorption ratio (SAR) was developed as a measure
of irrigation water quality. This calculated value uses the
soluble calcium, magnesium, and sodium content (reported in
mmol(+) L-1
) determined in water extracted from a saturated
paste and measured by atomic absorption spectrophotometry.
The formula is SAR = Na/[(Ca+Mg)/2]0.5
. An SAR of 13 or
more is used as an alternate criterion to the exchangeable
sodium percentage criterion for the natric horizon, the
Halaquepts great group, Natric subgroups, and most Sodic
subgroups.
Selective Dissolutions
Ammonium 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 of the
fine-earth fraction. 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 (described below) to identify the
sources of iron and aluminum in the soil. Pyrophosphate
extracts iron and aluminum associated with organic materials.
Dithionite-citrate extracts iron from iron oxides and
oxyhydroxides as well as from organic matter. A field test using
potassium hydroxide (KOH) can be used to estimate the amount
of aluminum that is extractable by ammonium oxalate (Soil
Survey Staff, 2009).
The oxalate-extractable aluminum plus one-half iron
contents are used as criteria for andic soil properties and spodic
materials (used for classifying soils in the Andisol and Spodosol
orders) and in the Andic and Spodic subgroups in other orders.
The relative amounts of oxalate-extractable iron and silicon
are used to define the amorphic and ferrihydritic mineralogy
classes.
Optical density of oxalate extract (ODOE) is determined
with a spectrophotometer using a 430 nm wavelength. An
increase in the ODOE value in an illuvial horizon, relative
to an overlying eluvial horizon, indicates an accumulation of
translocated organic materials. The optical density of oxalate
extract is used in the definition of spodic materials as well
as Spodic subgroups of Entisols, Gelisols, Inceptisols, and
Ultisols.
Dithionite-citrate extractable iron is the percentage of iron as
Fe2
O3
removed in a single extraction. It is measured by atomic
absorption and reported as a percentage of the total dry weight.
The iron is primarily from ferric oxides (e.g., hematite and
348	 Keys to Soil Taxonomy
magnetite) and iron oxyhydroxides (e.g., 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. Percent iron oxide extracted by
dithionite-citrate is used to define anthric saturation (anthraquic
conditions), the ferritic, ferruginous, sesquic, and parasesquic
mineralogy classes, and ferrihumic soil material.
Organic Analyses
Color of sodium-pyrophosphate extract is used as a criterion
in the identification of different kinds of organic soil materials
and limnic 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 compared to
the chips of a Munsell soil-color chart.
Fiber content is determined for horizons of organic soil
material on the decomposed plant materials that are less than
20 mm in cross section. The fiber content is reported as percent
by volume before rubbing and after rubbing between the
thumb and fingers. Only the fiber content after rubbing is used
as criteria in soil taxonomy since it partially defines the three
kinds of organic soil materials (fibric, hemic, and sapric) used
to classify organic soils (i.e., Histosols and Histels). The rubbed
fiber content is in the definitions of suffix symbols “a,” “e,”
and “i” which are used with master symbol “O” to designate
horizons in both organic and mineral soils (Soil Survey Division
Staff, 1993).
Melanic index is used in the required characteristics of the
melanic epipedon. The index is related to the ratio of the humic
and fulvic acids in the organic fraction of the soil (Honna et al.,
1988). The index is used to distinguish humified organic matter
thought to result from large amounts of gramineous vegetation
from humified organic matter formed from forest vegetation.
The melanic index is calculated as the absorbance of the
extracting solution at wavelength 450 nm over the absorbance at
wavelength 520 nm.
Organic carbon data in the NCSS soil characterization
database have been determined mostly by wet digestion
(Walkley, 1935). Because of environmental concerns about
waste products, however, that method is no longer used
at KSSL. The method that is currently used at KSSL to
determine organic carbon is a dry combustion procedure that
determines the percent total carbon. Total carbon is the sum of
organic and inorganic carbon. In calcareous horizons the content
of organic carbon is determined by subtracting the amount of
inorganic carbon contributed by carbonates from
the total carbon data (percent organic carbon = percent total
carbon – [% <2 mm CaCO3
x 0.12]). The content of organic
carbon determined by this computation is very close to the
content determined by the wet digestion method. Values for
organic carbon are multiplied by the Van Bemmelen factor
of 1.724 to estimate percent organic matter. Organic-carbon
content is used in many places in soil taxonomy. Some
examples are the definition of mineral soil material, the required
characteristics of diagnostic surface horizons (such as a Histic
epipedon), and criteria for taxa that connote the presence of
horizons high in organic matter (such as the Humults suborder).
Organic matter is determined by measuring the mineral
content of a sample using loss on ignition (LOI). The percent
organic matter is calculated by difference (i.e., 100 – percent
mineral content). The organic matter content measured by LOI
is used with CEC data in criteria which define coprogenous
earth and diatomaceous earth.
Mineral Analyses
Mineralogy of the clay, silt, and sand fractions is needed
for classification in some taxa. X-ray diffraction (XRD) and
thermal and petrographic analyses are classically viewed as
mineralogy techniques, although some mineralogy classes (e.g.,
ferritic, amorphic, gypsic, carbonatic, and isotic) are determined
by chemical and/or physical analyses.
Halloysite, illite, kaolinite, smectite, vermiculite, and other
minerals in the clay fraction (less than 0.002 mm) may be
identified by XRD analysis. Relative peak positions identify
clay minerals, and peak intensities are the basis for semiquantitative
estimates of mineral percent by weight in the clay
fraction. KSSL reports relative peak intensities of clay minerals
from XRD in a five-class system that generally corresponds
to percent by weight of a mineral (class 1 = 0 to 2 percent,
class 2 = 3 to 9 percent, class 3 = 10 to 29 percent, class 4 =
30 to 50 percent, and class 5 = more than 50 percent). There
are multiple potential interferences in the analysis of a clay
sample (Burt and Soil Survey Staff, 2014). Peak intensities may
be attenuated by one or more interferences, and the reported
class may underestimate the actual amount of mineral present.
Thus, these assigned percentages are given for informational
use only and should not be used to quantify minerals in a clay
fraction. Clay minerals are listed in the order of decreasing
quantity on the data sheet. XRD is used to determine smectitic,
vermiculitic, illitic, kaolinitic, or halloysitic mineralogy classes
in Soil Taxonomy. Some family classes require a clay mineral
to be more than one-half (by weight) of the clay fraction,
corresponding to XRD class 5. Other mineralogy classes require
more of the specified mineral than any other single mineral,
corresponding to the clay mineral being listed in the first ordinal
position on the KSSL data sheet.
Kaolinite and gibbsite may be determined by thermal
analysis. Results from this analysis are reported as percent
by weight in the clay fraction and are more quantitative than
the results of XRD for these minerals. Thermal analysis is a
technique in which the dried sample (typically the clay fraction)
is heated in a controlled environment. Certain minerals undergo
Appendix 	 349
decomposition at specific temperature ranges, and the mineral
can be quantified when compared to standard clays. Results may
be used to determine kaolinitic and gibbsitic family mineralogy
classes, complementary to or in lieu of XRD data.
Resistant minerals, weatherable minerals, volcanic glass,
magnesium-silicate minerals, glauconitic pellets, mica, and
stable mica pseudomorphs may be determined by petrographic
analysis. Magnesium-silicate minerals (e.g., serpentine
minerals) and glauconitic pellets are reported as percent by
weight in the fine-earth fraction (less than 2.0 mm). Resistant
minerals, weatherable minerals, and volcanic glass are
determined as percent of total grains counted in the coarse silt
through very coarse sand (0.02 to 2.0 mm) fractions, while
mica and stable mica pseudomorphs are determined in the
0.02 to 0.25 mm fractions (coarse silt, very fine sand, and fine
sand).
Individual mineral grains in a specific particle-size fraction
are mounted on a glass slide, identified, and counted (at least
300 grains) under a polarizing light microscope. Data are
reported as percent of grains counted for a specific size fraction.
This percentage is generally regarded as equivalent to weight
percent for spherical minerals. Alternative techniques are
available for determining weight percent micas and other platy
grains in a soil separate. The usual KSSL protocol is to count
mineral grains in either the coarse silt (0.02-0.05 mm), very
fine sand (0.05-0.10 mm), or fine sand (0.10-0.25 mm) fraction,
whichever one has the highest weight percent based on particlesize
analysis. Mineral or glass content in the analyzed fraction
is assumed to be representative of the content in the whole 0.02
to 2.0 mm or fine-earth fraction. It may be necessary to count
additional fractions to obtain a reliable estimate of volcanic
glass content in soil materials with a non-uniform distribution
of glass in dominant particle-size fractions. If more than
one fraction is counted, the weighted average of the counted
fractions may be calculated to represent glass content in the
0.02 to 2.0 mm fraction. For soils expected to have significant
amounts of glass in dominant fractions of medium, coarse, or
very coarse sand, grain counts are needed.
Two general types of petrographic analysis are conducted at
KSSL: (1) complete mineral grain count, in which all minerals
in the sample are identified and counted, or (2) a glass count,
in which glass, glass aggregates, glass-coated minerals, and
glassy materials are identified and quantified and all other
minerals are counted as “other.” Other isotropic grains, such as
plant opal, sponge spicules, and diatoms, also are identified and
quantified in the glass count grain studies. Glass-coated grains
are crystalline mineral grains in which more than 50 percent
of the grain is coated with glass. Grains coated with glass
are either specifically identified (e.g., glass-coated feldspar)
or are identified with a general category (e.g., glass-coated
grain) depending on the level of certainty. “Glassy materials”
is a general category for grains that have optical properties of
glass but lack definitive characteristics of glass, glass-coated
grains, or glass aggregates. Percent of total resistant minerals
is reported on the KSSL data sheet. (Calcite and more soluble
minerals are included in determinations of the percentage of
resistant minerals reported on the laboratory data sheet but
are not included in the values used in this taxonomy.) Total
percent volcanic glass, weatherable minerals, or other groups of
minerals used in classification may be calculated by summing
the percent of individual minerals included in the group. A
current, complete list of minerals in each category is in the Soil
Survey Laboratory Information Manual (Soil Survey Staff,
2011).
Other Information Useful in Classifying
Soils
Volumetric amounts of organic carbon are used in some
taxonomic criteria (e.g., Humults suborder). 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.
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, natric, or oxic horizons.
The ratio of water content at 1500 kPa tension to clay content
is used to indicate the relevancy of a particle-size analysis.
If the ratio is 0.6 or more and the soil does not have andic
soil properties, incomplete dispersion of the clay is assumed.
For most soils, 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 1500
kPa water to clay 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-sized
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 or anhydrite,
which decrease the ratio to less than 0.3; and (6) clay minerals
within grains of sand and silt, which hold water at 1500 kPa and
thus increase the ratio (which are most common in shale and in
pseudomorphs of primary minerals in saprolite).
The ratio of CEC by ammonium acetate at pH 7 (CEC-7)
to percent total clay can be used to estimate clay mineralogy
and clay dispersion. 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
350	 Keys to Soil Taxonomy
available. As described previously, if the ratio of 1500 kPa
water to clay is 0.25 or less or 0.6 or more, the measured clay
content and the calculated ratio of CEC-7 to percent clay is not
valid. The ratio of CEC-7 to percent clay is used as a criterion in
applying cation-exchange activity classes for certain loamy and
clayey soils which have either mixed or siliceous mineralogy.
It is important to note that the ratio must be recalculated for
soils which contain clay-sized carbonates since carbonate
clay is excluded from the concept of “clay” for taxonomic
classifications. Measured carbonate clay is subtracted from
measured total clay to arrive at a valid number for the silicate
(i.e., noncarbonate) clay fraction, and the ratio is recalculated.
Literature Cited
Burt, R., and Soil Survey Staff. 2014. Soil Survey
Laboratory Methods Manual. Soil Survey Investigations Report
42, Version 5.0. U.S. Department of Agriculture, Natural
Resources Conservation Service, National Soil Survey Center.
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.
Karathanasis, A.D., and W.G. Harris. 1994. Quantitative
Thermal Analysis of Soil Minerals. In J.E. Amonette and L.W.
Zelany (eds.), Quantitative Methods in Soil Mineralogy. SSSA
Misc. Pub., pp. 360-411. Soil Sci. Soc. Am., Madison, WI.
Soil Survey Division Staff. 1993. Soil Survey Manual.
Soil Conservation Service. U.S. Department of Agriculture
Handbook 18.
Soil Survey Staff. 1999. Soil Taxonomy: A Basic System of
Soil Classification for Making and Interpreting Soil Surveys.
2nd edition. Natural Resources Conservation Service. U.S.
Department of Agriculture Handbook 436.
Soil Survey Staff. 2009. Soil Survey Field and Laboratory
Methods Manual. Soil Survey Investigations Report No. 51,
Version 1.0. R. Burt (ed.). U.S. Department of Agriculture,
Natural Resources Conservation Service.
Soil Survey Staff. 2011. Soil Survey Laboratory Information
Manual. Soil Survey Investigations Report No. 45, Version
2.0. R. Burt (ed.). U.S. Department of Agriculture, Natural
Resources Conservation Service. (Available online.)
Walkley, A. 1935. An Examination of Methods for
Determining Organic Carbon and Nitrogen in Soils. J. Agr. Sci.
25:598-609.
Wilson, M.A., S.A. Shahid, M.A. Abdelfattah, J.A.
Kelley, and J.E. Thomas. 2013. Anhydrite Formation on
the Coastal Sabkha of Abu Dhabi, United Arab Emirates.
In Shahid, S.A., F.K. Taha, and M.A. Abdelfattah (eds.),
Advances in Soil Classification, Land Use Planning and Policy
Implications—Innovative Thinking of Resource Inventory for
Sustainable Use and Management of Land Resources, Chapter
8, pp. 123-140. Springer SBM Publishing, The Netherlands.
Appendix 	 351
Percentages of clay (less than 0.002 mm), silt (0.002 to 0.05 mm),
and sand (0.05 to 2.0 mm) in the basic soil texture classes
	353
Index
A
A horizons.  See Horizons and layers.
Abrupt textural change...............................................................17
Acraquox..................................................................................257
Acroperox................................................................................258
Acrotorrox................................................................................262
Acrudox....................................................................................263
Acrustox...................................................................................267
Agric horizon.............................................................................11
Alaquods..................................................................................273
Albaqualfs..................................................................................44
Albaquults................................................................................284
Albic horizon.............................................................................11
Albic materials...........................................................................17
Albolls......................................................................................212
Alfisols.......................................................................................43
Alorthods.................................................................................278
Andic soil properties..................................................................17
Andisols.....................................................................................87
Anhydritic horizon.....................................................................11
Anhydrous conditions................................................................18
Anhyorthels..............................................................................159
Anhyturbels..............................................................................163
Aniso class...............................................................................318
Anthric saturation.  See Aquic conditions.
Anthropic epipedon......................................................................7
Anthropogenic landforms and microfeatures.............................32
Aqualfs.......................................................................................43
Aquands.....................................................................................87
Aquents....................................................................................136
Aquepts....................................................................................173
Aquerts.....................................................................................305
Aquic conditions........................................................................26
Redoximorphic features.........................................................26
Reduced matrix..................................................................27
Redox concentrations.........................................................27
Redox depletions................................................................27
Reduction...............................................................................26
Saturation...............................................................................26
Anthric saturation (anthraquic conditions)........................26
Endosaturation...................................................................26
Episaturation......................................................................26
Aquic moisture regime.  See Soil moisture regimes.
Aquicambids............................................................................119
Aquisalids................................................................................132
Aquiturbels...............................................................................163
Aquods.....................................................................................273
Aquolls.....................................................................................213
Aquorthels................................................................................159
Aquox.......................................................................................257
Aquults.....................................................................................283
Argialbolls................................................................................212
Argiaquolls...............................................................................213
Argicryids................................................................................123
Argicryolls...............................................................................217
Argids.......................................................................................107
Argidurids................................................................................126
Argigypsids..............................................................................129
Argillic horizon..........................................................................11
Argiorthels...............................................................................160
Argiudolls................................................................................222
Argiustolls................................................................................231
Argixerolls...............................................................................247
Aridic moisture regime.  See Soil moisture regimes.
Aridisols...................................................................................107
Artifacts......................................................................................33
Artificial drainage.  See Aquic conditions.
B
B horizons.  See Horizons and layers.
Bottom tier.................................................................................26
Buried soils..................................................................................2
C
C horizons or layers.  See Horizons and layers.
Calcareous and reaction classes of mineral soils.....................328
Calciaquerts..............................................................................306
Calciaquolls..............................................................................213
Calciargids...............................................................................107
Calcic horizon............................................................................12
Calcicryepts..............................................................................180
Calcicryids...............................................................................123
Calcicryolls..............................................................................218
Calcids......................................................................................116
Calcigypsids.............................................................................130
Calcitorrerts..............................................................................309
Calciudolls...............................................................................225
Calciustepts..............................................................................195
354	 Keys to Soil Taxonomy
Calciusterts...............................................................................312
Calciustolls...............................................................................234
Calcixerepts..............................................................................203
Calcixererts..............................................................................315
Calcixerolls..............................................................................249
Cambic horizon..........................................................................12
Cambids...................................................................................118
Caret symbol in horizon designations......................................341
Cation-exchange activity classes for mineral soils..................327
Chemical analyses....................................................................344
Ion exchange and extractable cations..................................344
Soil pH.................................................................................346
Sulfur and extractable anions...............................................346
Carbonates and calcium sulfates..........................................346
Soluble salts.........................................................................347
Selective dissolutions...........................................................347
Coatings (classes) on sands......................................................330
Coefficient of linear extensibility (COLE)................................19
Control section of Histosols and Histels....................................25
Coprogenous earth.  See Limnic materials.
Cryalfs........................................................................................52
Cryands......................................................................................90
Cryaqualfs..................................................................................45
Cryaquands................................................................................88
Cryaquents...............................................................................136
Cryaquepts...............................................................................174
Cryaquods................................................................................274
Cryaquolls................................................................................214
Cryepts.....................................................................................180
Cryerts......................................................................................309
Cryic temperature regime.  See Soil temperature regimes.
Cryids.......................................................................................122
Cryods......................................................................................275
Cryofibrists...............................................................................167
Cryofluvents.............................................................................139
Cryofolists................................................................................169
Cryohemists.............................................................................169
Cryolls......................................................................................217
Cryopsamments........................................................................150
Cryorthents...............................................................................145
Cryosaprists.............................................................................170
Cryoturbation.............................................................................27
Cryrendolls...............................................................................221
D
Densic contact............................................................................27
Densic materials.........................................................................28
Diagnostic subsurface horizons.................................................11
Diagnostic surface horizons.........................................................7
Diatomaceous earth.  See Limnic materials.
Discontinuities in horizon designations...................................340
Duraqualfs..................................................................................45
Duraquands................................................................................88
Duraquerts................................................................................306
Duraquods................................................................................274
Duraquolls................................................................................214
Duricryands................................................................................91
Duricryods................................................................................275
Duricryolls...............................................................................219
Durids.......................................................................................126
Durihumods.............................................................................278
Durinodes...................................................................................19
Duripan......................................................................................13
Duritorrands...............................................................................95
Durixeralfs.................................................................................80
Durixerepts...............................................................................204
Durixererts...............................................................................315
Durixerolls...............................................................................249
Durorthods...............................................................................279
Durudands..................................................................................96
Durudepts.................................................................................187
Durustalfs...................................................................................68
Durustands...............................................................................102
Durustepts................................................................................197
Durustolls.................................................................................236
Dystraquerts.............................................................................306
Dystrocryepts...........................................................................180
Dystrogelepts...........................................................................185
Dystroxerepts...........................................................................204
Dystrudepts..............................................................................188
Dystruderts...............................................................................311
Dystrustepts.............................................................................197
Dystrusterts..............................................................................312
E
E horizons.  See Horizons and layers.
Endoaqualfs................................................................................45
Endoaquands..............................................................................88
Endoaquents.............................................................................136
Endoaquepts.............................................................................175
Endoaquerts..............................................................................307
Endoaquods..............................................................................274
Endoaquolls..............................................................................214
Endoaquults..............................................................................284
Endosaturation.  See Aquic conditions.
Entisols.....................................................................................135
Epiaqualfs..................................................................................47
Epiaquands.................................................................................89
Epiaquents................................................................................137
Epiaquepts................................................................................176
Epiaquerts................................................................................307
Epiaquods.................................................................................275
Epiaquolls................................................................................216
Epiaquults................................................................................284
Epipedon......................................................................................7
Episaturation.  See Aquic conditions.
Index	355
Eutraquox.................................................................................257
Eutroperox................................................................................259
Eutrotorrox...............................................................................262
Eutrudepts................................................................................190
Eutrudox...................................................................................264
Eutrustox..................................................................................268
F
Family differentiae for mineral soils........................................317
Family differentiae for organic soils........................................331
Ferrihumic soil material...........................................................332
Ferrudalfs...................................................................................57
Fibers.  See Organic soil materials.
Fibric soil materials.  See Organic soil materials.
Fibristels...................................................................................157
Fibrists.....................................................................................167
Fluvaquents..............................................................................137
Fluvents....................................................................................139
Fluviwassents...........................................................................154
Folistels....................................................................................158
Folistic epipedon..........................................................................8
Folists.......................................................................................168
Fragiaqualfs................................................................................49
Fragiaquepts.............................................................................177
Fragiaquods..............................................................................275
Fragiaquults..............................................................................285
Fragic soil properties..................................................................19
Fragihumods............................................................................278
Fragiorthods.............................................................................279
Fragipan.....................................................................................13
Fragiudalfs.................................................................................57
Fragiudepts...............................................................................193
Fragiudults...............................................................................291
Fragixeralfs................................................................................80
Fragixerepts..............................................................................206
Fraglossudalfs............................................................................57
Frasiwassents...........................................................................154
Frasiwassists............................................................................171
Free carbonates..........................................................................19
Frigid temperature regime.  See Soil temperature regimes.
Fulvicryands...............................................................................91
Fulvudands.................................................................................96
G
Gelands......................................................................................94
Gelaquands.................................................................................89
Gelaquents................................................................................138
Gelaquepts................................................................................177
Gelepts.....................................................................................185
Gelic materials...........................................................................28
Gelic temperature regime.  See Soil temperature regimes.
Gelifluvents..............................................................................140
Gelisols....................................................................................157
Gelods......................................................................................277
Gelolls......................................................................................221
Gelorthents...............................................................................145
Glacic layer................................................................................28
Glacistels..................................................................................158
Glossaqualfs...............................................................................49
Glossic horizon..........................................................................13
Glossocryalfs..............................................................................52
Glossudalfs.................................................................................58
Gypsiargids..............................................................................109
Gypsic horizon...........................................................................13
Gypsicryids..............................................................................124
Gypsids....................................................................................129
Gypsitorrerts............................................................................310
Gypsiusterts.............................................................................313
H
Halaquepts................................................................................178
Haplaquox................................................................................258
Haplargids................................................................................110
Haplocalcids.............................................................................116
Haplocambids..........................................................................119
Haplocryalfs...............................................................................53
Haplocryands.............................................................................92
Haplocryepts............................................................................182
Haplocryerts.............................................................................309
Haplocryids..............................................................................124
Haplocryods.............................................................................276
Haplocryolls.............................................................................219
Haplodurids..............................................................................127
Haplofibrists.............................................................................168
Haplogelepts............................................................................186
Haplogelods.............................................................................277
Haplogelolls.............................................................................221
Haplogypsids...........................................................................130
Haplohemists............................................................................169
Haplohumods...........................................................................278
Haplohumults...........................................................................287
Haploperox...............................................................................260
Haplorthels...............................................................................160
Haplorthods..............................................................................280
Haplosalids...............................................................................133
Haplosaprists............................................................................171
Haplotorrands.............................................................................95
Haplotorrerts............................................................................310
Haplotorrox..............................................................................262
Haploturbels.............................................................................163
Haplowassents..........................................................................155
Haplowassists...........................................................................172
Haploxeralfs...............................................................................81
Haploxerands...........................................................................105
Haploxerepts............................................................................206
Haploxererts.............................................................................316
Haploxerolls.............................................................................251
Haploxerults.............................................................................302
356	 Keys to Soil Taxonomy
Hapludalfs..................................................................................59
Hapludands................................................................................97
Hapluderts................................................................................311
Hapludolls................................................................................226
Hapludox..................................................................................265
Hapludults................................................................................291
Haplustalfs.................................................................................68
Haplustands..............................................................................102
Haplustepts...............................................................................198
Haplusterts...............................................................................313
Haplustolls...............................................................................236
Haplustox.................................................................................269
Haplustults...............................................................................299
Haprendolls..............................................................................222
Hemic soil materials.  See Organic soil materials.
Hemistels..................................................................................158
Hemists....................................................................................169
Histels......................................................................................157
Histic epipedon............................................................................8
Historthels................................................................................160
Histosols...................................................................................167
Histoturbels..............................................................................164
Horizons and layers..................................................................335
A horizons............................................................................335
B horizons............................................................................336
C horizons or layers.............................................................336
E horizons............................................................................335
L horizons or layers..............................................................335
M layers...............................................................................336
O horizons or layers.............................................................335
R layers................................................................................336
W layers...............................................................................336
Human-altered and human-transported material classes
for mineral soils...................................................................323
Human-altered material.............................................................33
Human-transported material......................................................34
Humaquepts.............................................................................178
Humicryepts.............................................................................184
Humicryerts..............................................................................309
Humicryods..............................................................................276
Humigelepts.............................................................................186
Humigelods..............................................................................277
Humilluvic material...................................................................24
Humixerepts.............................................................................208
Humods....................................................................................277
Humudepts...............................................................................193
Humults....................................................................................287
Humustepts..............................................................................202
Hydraquents.............................................................................138
Hydrocryands.............................................................................93
Hydrowassents.........................................................................155
Hydrudands................................................................................99
Hyperthermic temperature regime.  See Soil temperature
regimes.
I
Identifiable secondary carbonates..............................................19
Inceptisols................................................................................173
Interfingering of albic materials.................................................19
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..............................................................................50
Kandiaquults............................................................................285
Kandic horizon...........................................................................14
Kandihumults...........................................................................288
Kandiperox...............................................................................261
Kandiudalfs................................................................................63
Kandiudox................................................................................266
Kandiudults..............................................................................293
Kandiustalfs...............................................................................71
Kandiustox...............................................................................270
Kandiustults.............................................................................299
Kanhaplaquults........................................................................286
Kanhaplohumults.....................................................................289
Kanhapludalfs............................................................................64
Kanhapludults..........................................................................295
Kanhaplustalfs............................................................................73
Kanhaplustults..........................................................................300
Key to soil orders.......................................................................38
L
L horizons or layers.  See Horizons and layers.
Laboratory methods for soil taxonomy....................................343
Lamellae.....................................................................................20
Limnic materials (kinds)............................................................24
Coprogenous earth.................................................................25
Diatomaceous earth................................................................25
Marl........................................................................................25
Linear extensibility (LE)............................................................20
Lithic contact.............................................................................28
Lithologic discontinuities...........................................................20
Luvihemists..............................................................................170
M
M layers.  See Horizons and layers.
Manufactured layer....................................................................35
Manufactured layer contact........................................................35
Marl.  See Limnic materials.
Melanaquands............................................................................89
Melanic epipedon.........................................................................8
Melanocryands...........................................................................93
Melanoxerands.........................................................................106
Melanudands............................................................................100
Index	 357
Mesic temperature regime.  See Soil temperature regimes.
Mineral analyses......................................................................348
Mineral soil material....................................................................3
Mineral soil surface......................................................................4
Mineral soils.................................................................................4
Mineralogy classes for mineral soils........................................325
Mineralogy classes for organic soils........................................332
Mollic epipedon...........................................................................9
Mollisols..................................................................................211
Molliturbels..............................................................................164
Mollorthels...............................................................................161
N
n value........................................................................................21
Natralbolls................................................................................213
Natraqualfs.................................................................................51
Natraquerts...............................................................................308
Natraquolls...............................................................................217
Natrargids.................................................................................112
Natric horizon............................................................................14
Natricryolls..............................................................................220
Natridurids...............................................................................128
Natrigypsids.............................................................................131
Natrixeralfs................................................................................83
Natrixerolls..............................................................................255
Natrudalfs...................................................................................64
Natrudolls.................................................................................228
Natrustalfs..................................................................................73
Natrustolls................................................................................242
Normal years..............................................................................29
O
O horizons or layers.  See Horizons and layers.
Ochric epipedon...........................................................................9
Organic analyses......................................................................348
Organic soil material....................................................................3
Organic soil materials (kinds) .................................................. 23
Fibers.....................................................................................23
Fibric soil materials................................................................24
Hemic soil materials..............................................................24
Sapric soil materials...............................................................24
Organic soils................................................................................4
Orthels......................................................................................158
Orthents....................................................................................145
Other information useful in classifying soils...........................349
Orthods.....................................................................................278
Ortstein.......................................................................................15
Oxic horizon...............................................................................15
Oxisols.....................................................................................257
P
Paleaquults...............................................................................286
Paleargids.................................................................................114
Palecryalfs..................................................................................55
Palecryolls................................................................................220
Palehumults..............................................................................289
Paleudalfs...................................................................................65
Paleudolls.................................................................................229
Paleudults.................................................................................296
Paleustalfs..................................................................................76
Paleustolls................................................................................244
Paleustults................................................................................301
Palexeralfs..................................................................................83
Palexerolls................................................................................255
Palexerults................................................................................303
Paralithic contact........................................................................28
Paralithic materials.....................................................................28
Pararock fragments..................................................................317
Particle-size classes and their substitutes for mineral soils.....317
Particle-size classes for organic soils.......................................331
Permafrost..................................................................................28
Permanent cracks (classes) in mineral soils.............................331
Peraquic moisture regime.  See Soil moisture regimes.
Perox........................................................................................258
Perudic moisture regime.  See Soil moisture regimes.
Petraquepts...............................................................................179
Petroargids...............................................................................115
Petrocalcic horizon.....................................................................16
Petrocalcids..............................................................................118
Petrocambids............................................................................122
Petrocryids...............................................................................125
Petroferric contact......................................................................21
Petrogypsic horizon...................................................................16
Petrogypsids.............................................................................132
Physical analyses.....................................................................343
Placaquands................................................................................90
Placaquods...............................................................................275
Placic horizon.............................................................................16
Placocryods..............................................................................277
Placohumods............................................................................278
Placorthods...............................................................................281
Placudands...............................................................................102
Plaggen epipedon.......................................................................10
Plinthaqualfs..............................................................................51
Plinthaquox..............................................................................258
Plinthaquults............................................................................287
Plinthite......................................................................................22
Plinthohumults.........................................................................290
Plinthoxeralfs.............................................................................84
Plinthudults..............................................................................298
Plinthustalfs...............................................................................79
Plinthustults.............................................................................302
Prime symbol in horizon designations.....................................341
Psammaquents..........................................................................138
Psamments...............................................................................150
Psammorthels...........................................................................162
358	 Keys to Soil Taxonomy
Psammoturbels.........................................................................164
Psammowassents.....................................................................155
Q
Quartzipsamments....................................................................151
R
R layers.  See Horizons and layers.
Ratio, 1500 kPa water to clay..................................................349
Ratio, CEC to clay...................................................................349
Reaction classes for organic soils............................................332
Redoximorphic features.  See Aquic conditions.
Reduction. See Aquic conditions.
Rendolls...................................................................................221
Resistant minerals......................................................................22
Rhodoxeralfs..............................................................................85
Rhodudalfs.................................................................................67
Rhodudults...............................................................................298
Rhodustalfs................................................................................79
Rhodustults..............................................................................302
Rock fragments........................................................................317
Rock structure..............................................................................7
Root-limiting layers.................................................................319
Rounding....................................................................................37
Rupture-resistance classes for mineral soils............................330
S
Salaquerts.................................................................................308
Salic horizon..............................................................................16
Salicryids..................................................................................126
Salids........................................................................................132
Salitorrerts................................................................................310
Salusterts..................................................................................314
Sample horizon and layer sequences.......................................341
Sapric soil materials.  See Organic soil materials.
Sapristels..................................................................................158
Saprists.....................................................................................170
Saturation. See Aquic conditions.
Series control section...............................................................333
Series differentiae within a family...........................................333
Slickensides................................................................................22
Soil	.............................................................................................1
Soil color, water state criteria....................................................37
Soil depth classes for Histosols................................................333
Soil depth classes for mineral soils and Histels.......................330
Soil moisture regimes................................................................28
Aquic......................................................................................29
Aridic and torric.....................................................................30
Peraquic..................................................................................30
Perudic...................................................................................30
Udic........................................................................................30
Ustic.......................................................................................30
Xeric.......................................................................................30
Soil surface...................................................................................4
Soil temperature classes for mineral soils................................329
Soil temperature classes for organic soils................................333
Soil temperature regimes...........................................................31
Cryic.......................................................................................31
Frigid......................................................................................31
Gelic.......................................................................................31
Hyperthermic.........................................................................31
Isofrigid..................................................................................31
Isohyperthermic.....................................................................31
Isomesic.................................................................................31
Isothermic..............................................................................31
Mesic......................................................................................31
Thermic..................................................................................31
Sombric horizon.........................................................................16
Sombrihumults.........................................................................290
Sombriperox.............................................................................262
Sombriudox..............................................................................267
Sombriustox.............................................................................271
Sphagnofibrists.........................................................................168
Spodic horizon...........................................................................17
Spodic materials.........................................................................22
Spodosols.................................................................................273
Strongly contrasting particle-size classes................................318
Subgroups for human-altered and human-transported soils......35
Subsurface tier...........................................................................25
Suffix symbols in horizon designations...................................337
Conventions for using letter suffixes...................................339
Sulfaquents...............................................................................139
Sulfaquepts...............................................................................179
Sulfaquerts...............................................................................309
Sulfidic materials.......................................................................31
Sulfihemists..............................................................................170
Sulfisaprists..............................................................................171
Sulfiwassents............................................................................156
Sulfiwassists.............................................................................172
Sulfohemists.............................................................................170
Sulfosaprists.............................................................................171
Sulfudepts................................................................................195
Sulfuric horizon.........................................................................32
Surface mantle of new soil material.............................................2
Surface tier.................................................................................25
T
Thermic temperature regime.  See Soil temperature regimes.
Torrands.....................................................................................94
Torrerts.....................................................................................309
Torric moisture regime.  See Soil moisture regimes.
Torrifluvents.............................................................................140
Torrifolists................................................................................169
Torriorthents.............................................................................145
Torripsamments........................................................................152
Torrox.......................................................................................262
Transitional and combination horizons....................................336
Turbels.....................................................................................162
Index	 359
U
Udalfs.........................................................................................56
Udands.......................................................................................95
Udepts......................................................................................187
Uderts.......................................................................................310
Udic moisture regime.  See Soil moisture regimes.
Udifluvents...............................................................................141
Udifolists..................................................................................169
Udipsamments..........................................................................152
Udivitrands...............................................................................104
Udolls.......................................................................................222
Udorthents................................................................................147
Udox.........................................................................................263
Udults.......................................................................................290
Ultisols.....................................................................................283
Umbraquults.............................................................................287
Umbric epipedon........................................................................10
Umbriturbels............................................................................165
Umbrorthels.............................................................................162
Ustalfs........................................................................................67
Ustands.....................................................................................102
Ustepts.....................................................................................195
Usterts......................................................................................311
Ustic moisture regime.  See Soil moisture regimes.
Ustifluvents..............................................................................142
Ustifolists.................................................................................169
Ustipsamments.........................................................................153
Ustivitrands..............................................................................104
Ustolls......................................................................................230
Ustorthents...............................................................................147
Ustox........................................................................................267
Ustults......................................................................................298
V
Vermaqualfs...............................................................................52
Vermaquepts.............................................................................179
Vermudolls...............................................................................230
Vermustolls..............................................................................246
Vertical subdivision in horizon designations...........................340
Vertisols...................................................................................305
Vitrands....................................................................................103
Vitraquands................................................................................90
Vitricryands................................................................................93
Vitrigelands................................................................................94
Vitritorrands...............................................................................95
Vitrixerands..............................................................................106
Volcanic glass.............................................................................23
W
W layers.  See Horizons and layers.
Wassents...................................................................................154
Wassists....................................................................................171
Weatherable minerals.................................................................23
X
Xeralfs........................................................................................79
Xerands....................................................................................105
Xerepts.....................................................................................203
Xererts......................................................................................315
Xeric moisture regime.  See Soil moisture regimes.
Xerofluvents.............................................................................144
Xerolls......................................................................................246
Xeropsamments........................................................................153
Xerorthents...............................................................................149
Xerults......................................................................................302
360	
The Soils That We Classify
Differentiae for Mineral Soils and Organic Soils
Horizons and Characteristics Diagnostic for the Higher Categories
Andisols
Identification of the Taxonomic Class of a Soil
Designations for Horizons and Layers
Family and Series Differentiae and Names
Vertisols
Ultisols
Spodosols
Oxisols
Mollisols
Inceptisols
Histosols
Gelisols
Entisols
Aridisols
Alfisols
S
O
I
D
I
F
D
I
A
I
D
E
A
L
F
A
N
D
A
R
I
E
N
T
G
E
L
H
I
S
I
N
C
M
O
L
O
X
I
S
P
O
U
L
T
V
E
R
F
A
M
H
O
R
	1
Chapter 8, page 147
The subgroup “Anthropic Udorthents” is added with the code
LEFD. Codes for other subgroups are adjusted accordingly.
Delete:
LEFD.  Other Udorthents that have 50 cm or more of humantransported
material.
Anthroportic Udorthents
LEFE.  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) particles 2.0 mm or
larger in diameter, 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 Udorthents
LEFF.  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
LEFG.  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
LEFH.  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
LEFI.  Other Udorthents.
Typic Udorthents
Insert:
LEFD.  Other Udorthents that have an anthropic epipedon.
Anthropic Udorthents
LEFE.  Other Udorthents that have 50 cm or more of humantransported
material.
Anthroportic Udorthents
LEFF.  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) particles 2.0 mm or
larger in diameter, 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 Udorthents
LEFG.  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
LEFH.  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:
Errata for Keys to Soil Taxonomy, 12th edition
2	 Errata for Keys to Soil Taxonomy, 12th edition
1.  20 or more consecutive days; or
2.  30 or more cumulative days.
Oxyaquic Udorthents
LEFI.  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
LEFJ.  Other Udorthents.
Typic Udorthents
Chapter 18, Page 335
The paragraphs describing A horizons are reverted to
the paragraphs from the 11th edition of the “Keys to Soil
Taxonomy.”
Delete:
A horizons: Mineral horizons that have formed at the soil
surface or below an O horizon. They exhibit obliteration of all
or much of any original rock structure*
and show one or more of
the following:
1.  An accumulation of humified organic matter closely
mixed with the mineral fraction and not dominated by
properties characteristic of E or B horizons (defined below);
2.  Properties resulting from cultivation, pasturing, or
similar kinds of disturbance; or
3.  A morphology that is distinct from the underlying E, B,
or C horizon, resulting from processes related to the surface.
If a surface horizon has properties of both A and E horizons
but the feature emphasized is an accumulation of humified
organic matter, it is designated as an A horizon. In some areas,
such as regions with warm, arid climates, the undisturbed
surface horizon is less dark than the adjacent underlying
horizon and contains only small amounts of organic matter.
It has a morphology distinct from the C horizon, although the
mineral fraction is unaltered or only slightly altered by the
weathering of minerals considered to be weatherable (defined in
chapter 3). Such a horizon is designated as an A horizon because
it is at the soil surface. Recent alluvial or eolian deposits that
retain most of the original rock structure are not considered to
have A horizons unless they are cultivated.
Insert:
A horizons: Mineral horizons that have formed at the
surface or below an O horizon. They exhibit obliteration of all
or much of the original rock structure*
and show one or both of
the following: (1) an accumulation of humified organic matter
closely mixed with the mineral fraction and not dominated by
properties characteristic of E or B horizons (defined below) or
(2) properties resulting from cultivation, pasturing, or similar
kinds of disturbance.
If a surface horizon has properties of both A and E horizons
but the feature emphasized is an accumulation of humified
organic matter, it is designated as an A horizon. In some areas,
such as areas of warm, arid climates, the undisturbed surface
horizon is less dark than the adjacent underlying horizon
and contains only small amounts of organic matter. It has a
morphology distinct from the C layer, although the mineral
fraction is unaltered or only slightly altered by weathering.
Such a horizon is designated as an A horizon because it is
at the surface. Recent alluvial or eolian deposits that retain
fine stratification are not considered to be A horizons unless
cultivated.
Issued May 15, 2014