231

2, Have a mineral layer 30 cm or more thick that has
its upper boundary in the control section below the

surface tier.
Hemic Terrie Tropofibrists
ABDD. Other Tropofibrists that:

1, Have 12.5 cm or more of the thickness of the
subsurface and bottom tiers consisting of sapric
materials; and

2, Have a mineral layer 30 cm or more thick that has
its upper boundary in the control section below the

surface tier.
Sapric Terric Tropofibrists

ABDE. Other Tropofibrists that have a mineral layer 30
mor more thick that has its upper boundary in the
control section below the surface tier.

Terrie Tropofiteists

ABDF. Other Tropofibrists that have limnic layer(s) that
are 5 cm or more thick within the control section.

Limnic Tropofibrists

ABDG. Other Tropofibrists that have a mineral layer
between 5 and 30 cm thick or two or more thin,
continuous mineral layers, within organic materials,
in the control section below the surface tier.
Fluvaquentic Tropofibrists

ABDH. Other Tropofibrists that have 26 cm or more of the
thickness of the subsurface and bottom tiers consisting of

hemic materials.
Hemic Tropofibrists

ABDI. Other Tropofibrists that have 12.5 cm or more of
the thickness of the subsurface and bottom tiers
consisting of sapric materials.

Sapric Tropofibrists
ABDJ. Other Tropofibrists.

‘Typic Tropofibrists
FOLISTS
Key to great groups
AAA. Folists that have a eryic or colder temperature
regime.

Cryofolists, p. 232

AAB. Other Folists that have an isomesic or warmer
temperature regime.
‘Tropofolists, p. 232
AAC. Other Folists that have a frigid temperature
regime.
Borofolista, p. 232


by mottles of higher chroma that are due to
segregation of iron; and

b. Saturation with water in the mottled zone at some
time of year when the soil temperature in that zone
is 5°C or higher, or there is artificial drainage; and

2. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic or kandic horizon that is 60 to 100 cm

below the soil surface.
Aquic Arenic Kandiudults

GCCC. Other Kandiudults that:

1, Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic or kandic horizon that is 50 to 100 cm
below the soil surface; an:

2, Have 5 percent or more plinthite (by volume) in one
or more subhorizons within 150 cm of the soil surface.
Arenie Plinthic Kandiudults

GCCD. Other Kandiudults that:

1. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic or kandic horizon that is 50 to 100. cm
below the soil surface; and

2. Have, throughout the argillic or kandic horizon,
colors with a hue of 2.5YR or redder, a value, moist, of
3 or less, and a value, dry, that is 1 unit or less higher

than the value, moist.
Arenic Rhodic Kandiudults

GCCE, Other Kandiudults that have a layer, starting at
the mineral soil surface, that has a sandy particle-size
class and extends to the top of an argillic or kandic
horizon that is 60 to 100 cm below the soil surface.

Arenic Kandiudults

GCCF. Other Kandiudults that:

1. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic or kandic horizon that is more than
100 cm below the soil surface; and

2. Have 5 percent or more plinthite (by volume) in one
or more subhorizons within 150 cm of the soil surface.
Grossarenic Plinthic Kandiudults

GCCG. Other Kandiudults that have a layer, starting at
the mineral soil surface, that has a sandy particle-size
class and extends to the top of an argillic or kandic
horizon that is more than 100 cm below the soil surface.
Grossarenic Kandiudults

GCCH. Other Kandiudults that:

1, Have an ECEC (sum of bases plus IN KCl-
extractable Al) of 1.5 cmol(+) or less per kg clay in one


b. Less than 100 cm to a lithic or paralithic or a
petroferric contact, Used in families of Oxisols.

Slope or shape of soil

Soils of aquic great groups normally have level or
concave surfaces. They are mainly in places where
ground water saturates the soil during some period of the
year. A few, however, are on the sides of slopes where
water cannot stand and are kept wet by more or leas
continuous precipitation and by seepage of water from
higher areas. In a very few, the hydrostatic pressure
keeps the soi] wet. No consistent internal morphological
clues have yet been found that distinguish these sloping
aquic soils if the dissolved oxygen content is low, but their
recognition in the field from the position of the soil in the
landscape is generally easy. In aquic great groups,
particularly in Aquolls, Aquox, and Aquults, use the
shape of the soil as a family differentia. For Aquolls and
Aquults use classes of level and sloping as these classes
are defined in the Soil Survey Manual. For Aquox use
sloping in the names of families if slope is more than 8
percent. It may be necessary to use slope classes as
family differentiae in other orders, but they should not be
used in families of Aquods or Albaqualfs. Level is
assumed in families of aquic soils if no slope modifier is
used in the family name.

Consistence

Some cemented horizons, for example, a duripan, are
differentiae in the classification in categories above the
family. Others such as a cemented spodic horizon
(ortstein) are not, but no single family should include
soils that have a continuous, shallow, cemented horizon
and soils that do not. In Spodosols, in particular, a
cemented spodic horizon needs to be used as a family
differentia. The following classes of consistence are
defined for Spodosols.

Ortstein..-All or part of the spodic horizon is at least
weakly cemented, when moist, into a massive horizon
that is present in more than half of each pedon.

Noncemented.--The spodic horizon, when moist, is not
cemented into a massive horizon in as much as half of
each pedon.

Cementation of a amall volume into shot or concretions
does not constitute cementation to form a massive
horizon. The name of a family of noncemented Spodosols
normally does not have a modifier to imply lack of
cementation. The name of a family of cemented
Spodosols contains the modifier “ortstein.”

A cemented calcic or gypsic horizon is not identified in
the family name. Many calcic and some gypsic horizons


260

percent organic carbon at 126 em below the soil surface;
an

2. Have slopes of 25 percent or less.
Fh

ventic Ustochrepts

JDDH. Other Ustochrepts that when neither irrigated nor
fallowed to store moisture:

1, If the soil temperature regime is mesic or thermic,
are dry sixth-tenths or more of the time in half or more
years in some part of the moisture control section (not
necessarily the same part) during a period when the
soil temperature, at a depth of 50 cm, exceeds 5°C; or

2. If the soil temperature regime is hyperthermic or
isomesic or warmer, are moist in some or all parts of
the soil moisture control section for less than 90
consecutive days during a period when the soil
temperature at a depth of 50 cm is higher than 8°C.
Aridic Ustochrepts

JDDI. Other Ustochrepts that when neither irrigated nor
fallowed to store moisture:

1. If the soil temperature regime is mesic or thermic,
are dry for four-tenths or less of the cumulative days in
some part of the moisture control section when the soil
temperature at a depth of 50 cm exceeds 5°C; or

2. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or less
during a period when the soil temperature at a depth of
50 cm exceeds 8°C.

‘Udie Ustochrepts
JDDJ, Other Ustochrepts.

‘Typic Ustochrepts
Xerochrepts
Key to subgroups

JDEA. Xerochrepts that have a lithic contact within 50 cm.
of the soil surface in some part but less than half of each

pedon.
RupticLithic Xerochrepts
JDEB. Other Xerochrepts that:

1, Have base saturation (by NH,OAc) of less than 60

percent in all parts of the soil between depths of 25 and
15 cm below the soil surface; and


122

1, Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2, The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
oxtractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vitrandic Fragixeralfs

IDCC. Other Fragixeralfs that have an Ap horizon that
has a color value, moist, of 3 or less and a color value, dry,
of 5 or less when crushed and smoothed, or the soil to a
depth of 18 cm, after mixing, has those colors.

Mollie Fragixeralfs

IDCD. Other Fragixeralfe that have mottles that have
chroma of 2 or less in the upper 25 em of the argillic
horizon, or have mottles that have chroma of 2 or less
within 40 cm of the surface, and the horizons that have
mottles of low chroma are saturated with water at some
time of the year when the soil temperature is 5°C or higher
in those horizons. Mottles are not the same as skeletans

that may also have low chroma,
Aquic Fragixeralfs

IDCE. Other Fragixeralfs that do not have an argillic
horizon above the fregipan that has clay skins on at least
some vertical and horizontal faces of primary or
secondary peda, or both.

Ochreptic Fragixeralfs
IDCF. Other Fragixeralfs.
‘Typic Fragixeralfs
Haploxeralfs
Key to subgroups

IDGA. Haploxeralfs that:

1. Have a lithic contact within 50 cm of the soil surface;
and

2. Have an A horizon that throughout its upper 10 cm has
a color value, moist, of 3 or less and contains 0.7
percent or more organic carbon, or have an Ap horizon
that has a color value, moist, of 3 or less and contains

0.7 percent or more organic carbon.
Lithic Mollic Haploxaralfs


421

Arabic numerals used for this purpose always follow all
letters. Within « C, for example, successive layers could
be Cl, C2, C3, etc.; or if the lower part is gleyed and the
upper part is not, the designations could be C1-C2-Cgl-
Cg2 or C-Cgl-Cg2-R.

These conventions apply whatever the purpose of
subdivision. In many soils, horizons that would be
identified by one unique set of letters are subdivided on
the basis of evident morphological features, such as
structure, color, or texture. These divisions are
numbered consecutively. The numbering starts with 1
at whatever level in the profile any element of the letter
symbol changes. Thus Bt1-Bt2-Btk1-Btk2 is used, not
Bt1-Bt2-Btk3-Btk4. The numbering of vertical
subdivisions within a horizon is not interrupted at a
discontinuity (indicated by a numerical prefix) if the
same letter combination is used in both materials: Bs1-
Bs2- 2Bs3-2Be4 is used, not Bs1-Bs2-2Bs1-2Bs2.

Sometimes, thick layers are subdivided during
sampling for laboratory analyses even though
differences in morphology are not evident in the field.
These layers need to be identified, and this is done
simply by numbering each subdivision consecutively
within a layer having a unique symbol, starting at the
top. For example, four layers of a Bt horizon sampled by
10-cm increments would be designated Bt1, Bt2, Bt3, and
Bu.

DISCONTINUITIES

In mineral soils Arabic numerals are used as prefixes to
indicate discontinuities. Wherever needed, they are
used preceding A,E,B,C, and R, These prefixes are
distinct from Arabic numerals used as suffixes to denote
vertical subdivisions.

A discontinuity is a significant change in particle-size
distribution or mineralogy that indicates a difference in
the material from which the horizons formed and/or a
significant difference in age, unless that difference in
age is indicated by the suffix b. Symbols to identify
discontinuities are used only when they will contribute
substantially to the reader's understanding of
relationships among horizons. Stratification common
to soils formed in alluvium is not designated as
discontinuities unless particle size distribution differs
markedly (strongly contrasting particle-size class as
defined in Soil Taxonomy) from layer to layer even
though genetic horizons have formed in the contrasting
layers.

Where a soil has formed entirely in one kind of
material, a prefix is omitted from the symbol; the whole
profile is material 1. Similarly, the uppermost material
in a profile having 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
though a layer below material 2 is similar to material 1,
it is designated "3" in the sequence. The numbers
indicate change in the material, not the type of


24

a. The less than 2.0 mm fraction has acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more, and there is at
least 30 percent volcanic glass in the 0.02 - 2.0 mm
fraction, or

b. The less than 2.0 mm fraction has acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-extractable
iron of 2.0 percent or more, and there is at least 5 percent
volcanic glass in the 0.02 - 2.0 mm fraction, or

c. The less than 2.0 mm fraction has acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-extractable
iron of between 0.40 percent and 2.0 percent, and there is
enough volcanic glass in the 0.02 - 2.0 mm fraction that
the percentage of glass, when plotted against the
percentage of acid-oxalate-extractable aluminum plus 1/2
acid-oxalate-extractable iron, gives a point within the
shaded area of Figure 1.

30 q
25 Andic Soil
Properties
x
<
2
&
€
E
o
Y 16
a
2
3 |_|
=
B 10
ca
5 | . 4
5
0
) 0.4 1.0 16 20
Acid~oxalate—extractable aluminum

+ 1/2 acid~oxalate—extractable iron (%) in the
legs than 2.0 mm fraction

Figure 1 — Soils that plot in the shaded area have Andic soil
properties if the less than 2.0 mm fraction has phosphate retention
of more than 25 percent and the 0.02 to 2.0 mm fraction is at least
30 percent of the less than 2.0 mm fraction.


349
Kandiudox

Key to subgroups

DEDA. Kandiudox that have mottles of 4 or more value
moist and 2 or less chroma within a depth of 125 cm of the
soil surface and a petroferric contact within 125 cm of the

soil surface.

DEDB. Other Kandiudax that have a petroferric contact
within 125 cm of the soil surface.
Petroferric Kandiudox

DEDC, Other Kandiudox that have mottles of 4 or more
value moist and 2 or less chroma within a depth of 125 cm
of the soil surface and a lithic contact within 125 cm of the

soil surface.
Aquic Lithic Kandiudox

DEDD. Other Kandiudox that have a lithic contact within
a depth of 125 cm of the soil surface.
Lithic Kandiud

DEDE. Other Kandiudox that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the
soil surface and mottles of 4 or more value moist and 2 or
less chroma within a depth of 125 cm of the soil surface.
Plinthaquic Kandiudox

DEDF. Other Kandiudox that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the
soil surface.

Plinthic Kandindox

DEDG, Other Kandiudox that have mottles of 4 or more
value moist and 2 or less chroma within a depth of 125 cm

of the soil surface.
Aquic Kandiudox

DEDH. Other Kandiudox that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g em’ or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic Kandiudox

DEDI. Other Kandiudox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and a color hue of 2.5YR or redder with
moist values of less than 4 in most of the 25 to 125 cm depth

from the soil surface.

Humic Rhodie Kandiud:
DEDJ. Other Kandiudox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and color hue of 7.5YR or yellower with
moist values of 6 or more in most of the 25 to 125 em depth

from the soil surface.
Humic Xanthic Kandiudox


184
2. Dominant chromas, moist, of 2 or Jess on faces of
peds, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or

8. Sufficient active ferrous iron to give a positive
reaction to a,a'-dipyridy] at some time of the year when

not being irrigated.

Aquic Ustivitrands
BEAC, Other Ustivitrands that have, between 25 and 100
cm, a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the
underlying layer.

Thaptic Ustivitrands

BEAD. Other Ustivitrands that have a calcic horizon with
its upper boundary within 125 em of the mineral soil
surface,

Calcic Ustivitrands

BEAE. Other Ustivitrands that have a mollic epipedon.
Mollic Ustivitrands
BEAF, Other Ustivitrands that have an umbric epipedon.
Umbric Ustivitrands

BEAG. Other Ustivitrands.
‘Typic Ustivitrands

XERANDS

Key to great groups
BDA. Xerands that have 1500 kPa water retention of less
than 15 percent on air-dried samples and less than 30
percent on undried samples, throughout a thickness of 35
¢m or more within 60 cm of the mineral soil surface.

P. 156

BDB. Other Xerands that have a melanic epipedon.
Melanoxerands, p. 156

BDC. Other Xerands.
Haploxerands, p. 154

Haploxerands

Key to subgroups
BDCA. Haploxerands that have a lithic contact within 50
cm of the soil surface.

Lithic Haploxerands

BDCB, Other Haploxerands that have, in some
subhorizon between 50 and 100 cm:

1, Two percent or more redox segregations; or


149
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the

underlying layer.
Thaptic Melanudands

BGOR. Other Melanudands that have an argillic or
kandic horizon with its upper boundary within 125 em of
the mineral soil surface or of the upper boundary of an
organic layer with andic soil properties, whichever is
shallower.

Ultic Melanudands
BGCS, Other Melanudands.

‘Typic Melanudands
Placudands
Key to subgroups
BGAA. Placudands that have a lithic contact within 50 cm
of the soil surface.

Lithic Placudands

BGAB. Other Placudands that have, in some subhorizon
between 50 and 100 em of the mineral soil surface or of the
upper boundary of an organic layer with andic soil
properties, whichever is shallower:

1, Two percent or more redox segregations; or

2, Dominant chromas, moist, of 2 or leas on faces of
peds, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or

3. Sufficient active ferrous iron to give a positive
reaction to a,a'-dipyridyl at some time of the year when

not being irrigated.
Aquic Placudands

BGAC. Other Placudands that have extractable bases plus
1N KCl-extractable Al** of less than 2.0 cmol(+) kg’ fine
earth in some subhorizon 30 em or more thick between 25
and 100 em, and have, undried, 1500 kPa water retention
of 70 percent or more throughout a continuous thickness of
35 cm or more within the upper 100 cm of the mineral soil
surface or of the upper boundary of an organic layer with
andic soil properties, whichever is shallower.

Acrudoxie Hydric

BGAD. Other Placudands that have extractable bases plus
1N KCl-extractable Al* of less than 2.0 cmol(+) kg" fine
earth in some subhorizon 30 cm or more thick between 25
and 100 cm of the mineral soil surface or of the upper
boundary of an organic layer with andic soil properties,
whichever is shallower.

BGAE. Other Placudands that hay
more than 25.0 cmol(+) kg” fine e
subhorizon 15 cm or more thick between 25 and 75 cm, and
have less than 30 percent, undried, 1500 kPa water
retention in some subhorizon that meets the requirements
for andic soil properties and that is at least 25 cm thick



KEYS TO SOIL TAXONOMY
BY
SOIL SURVEY STAFF
Agency for International Development

United States Department of Agriculture
Soil Management Support Services

SMSS Technical Monograph No. 19

Virginia Polytechnic Institute
and State University


118

2. If the soil temperature regime is hyperthermic,
isomesic, or warmer, are moist in most years in some
or all parts of the moisture control section for less than
90 consecutive days during a period when the soil
temperature at a depth of 50 cm exceeds 8°C.

Aridic Paleustalfs

ICFM. Other Paleustalfs that have a CEC of less than 24
emol(+) per kg clay (by IN NH«OAc pH 7) in the major
part of the argillic horizon, or the major part of the upper
100 cm of the argillic horizon if thicker than 100 cm.
Kandic Paleustalfs

ICEN, Other Paleustalfs that have, throughout the argillic
or kandic horizon, a hue of 2.5YR or redder, and have a
value, moist, of 3 or less and have a value, dry, that is no
more than one unit higher than the value, moist.

Rhodic Paleustalfs

ICFO. Other Paleustalfs that have an argillic horizon that
has base saturation (by sum of cations) of less than 75
percent throughout,

Ultic Paleustalfs

ICFP, Other Paleustalfs that, when neither irrigated nor
fallowed to store moisture:

1. If the soil temperature regime is mesic or thermic,
are dry for less than four-tenths of the cumulative days
in some part of the moisture control section when the
soil temperature at a depth of 50 cm exceeds 5°C; or

2. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or less
during a period when the soil temperature at a depth of
50 cm exceeds 8°C.

Udic Paleustalfs

ICFQ, Other Paleustalfe.
Typic Paleustalfs

Plinthustalfs

Plinthustalfs are the Ustalfs that have plinthite that forms
a continuous phase or that constitutes more than half the
matrix of some subhorizon of the argillic horizon within
125 cm of the soil surface. There are no soil series in the
United States that are presently classified in this great
group, but the group is provided for other parts of the world.
Subgroups have not been developed.


67

Chapter 4

Identification of the Taxonomic
Class of a Soil

KEY TO SOIL ORDERS

In this key and the other keys that follow, the diagnostic
horizons and the properties mentioned do not include the
properties of buried soils except their organic carbon if of
Holocene age, andic soil properties, and base saturation.
Properties of buried soils are considered in the categories
of subgroups, families, and series but not in those of order,
suborder, and great group. The meaning of the term
"buried soil" is given in chapter 1,

A. Soils that either

1. Have organic soil materials that extend from the
surface to one of the following:

a, A depth within 10 cm or less of a lithic or paralithic
contact, provided the thickness of the organic soil
materials is more than twice that of the mineral soil
above the contact; or

b. Any depth if the organic soi] material rests on
fragmental material (gravel, stones, cobbles) and
the interstices are filled with organic materials, or
rests on a lithic or paralithic contact; or

2. Have organic materials that have an upper boundary
within 40 cm of the surface, and

a, Have one of the following thicknesses:

(1) 60 cm or more if three-fourths or more of the
volume is moss fibers or the moist bulk density is
less than 0.1 g per cubic centimeter (6.25 Ibs per cubic
foot); or

(2) 40 cm or more if

(a) The organic soil material is saturated with
water for long periods (more than 6 months) or is
artificially drained; and *

(b) The organic material consists of sapric or
hemic materials or consists of fibric materials
that are less than three-fourths moas fibers by
volume and have a moist bulk density of 0.1 or
more; and

b. Have organic soil materials that


GBCF. Other Kandihumults that have 6 percent or more
plinthite (by volume) in one or more subhorizons within

150 cm of the soil surface.
Plinthic Kandihumults
GBCG. Other Kandihumults that have an ustic soil
moisture regime.
Ustic Kandihumults

GBCH. Other Kandihumults that have a xeric soil
moisture regime.

Xeric Kandihumults
GBCI. Other Kandihumults that have an anthropic
epipedon.

Anthropic Kandihunzults

GBCJ. Other Kandihumults.

‘Typic Kandihumults
Kanhaplohumults
Key to subgroups

GBDA. Kanhaplchumults that have a lithic contact
within 50 cm of the mineral soil surface,
Lit

thie Kanhaplohumults
GBDB, Other Kanhaplohumults that

1. Have, throughout a cumulative thickness of 18 cm or
more and within a depth of 75 cm, bulk density of the
less than 2.0 mm fraction, measured at 33 kPa water
retention, of 1.0 g cm or less and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of more than 1,0 percent; and

2, Have an ustic soi] moisture regime.
Ustandic

Kanhaplohumults

GBDC. Other Kanhaplohumults that have, throughout a
cumulative thickness of 18 em or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic Kanha;

GBDD. Other Kanhaplohumults that have the following
combination of characteristics in the upper 26 cm or
more of the argillic or kandic horizon:

1. Mottles that have a color value, moist, of 4 or more
and chroma, moist, of 2 or less accompanied by
mottles of higher chroma that are due to segregation of
iron; and

2. Saturation with water in the mottled zone at some
time of the year when the soil temperature in that zone
is 5°C or higher or there is artificial drainage.


296
Tropohemists

Key to subgroups

ACFA. Tropohemists that have a layer of water within
the control section below the surface tier.
Hydric Tropohemists

ACFB. Other Tropohemists that have a lithic contact
within the control section.

Lithic Tropohemists
ACFC. Other Tropahemists that:

1, Have 25 cm or more of the subsurface and bottom
ticrs consisting of fibric materials; and

2, Have a mineral layer 30 cm or more thick that has
its upper boundary in the control section below the

surface tier.
Fibric Terric Tropohemists
ACFD. Other Tropohemists that:

1, Have 25 cm or more of the subsurface and bottom
tiers consisting of sapric materials; and

2. Have a mineral layer 30 cm or more thick that has
its upper boundary in the control section below the

surface tier.
Sapric Terric Tropohemists

ACFE, Other Tropohemists that have a mineral layer 30
cm or more thick that has its upper boundary in the
control section below the surface tier.

Terric Tropohemists

ACFF, Other Tropohemists that have limnic layer(s) 5
em or more thick within the control section.

ACFG. Other Tropohemists that have a mineral layer
between & and 30 cm thick or two or more thin,
continuous mineral layers, within organic materials,
in the control section below the surface tier.
Fluvaquentie

ACFH. Other Tropohemists that have 25 cm or more of
the subsurface and bottom tiers consisting of fibric

materials.
Fibric Tropohemista

ACFI. Other Tropohemists that have 25 cm or more of the
subsurface and bottom tiers consisting of sapric

materials.
Sapric Tropohemists

ACFJ. Other Tropohemists.
Typic Tropohemists


162
the fine earth throughout at least 60 cm of the upper 75 cm,
and have less than 30 percent, undried, 1500 kPa water
retention in some subhorizon that meets the requirements
for andic goil properties and that is at least 25 cm thick
within 100 cm of the mineral soil surface.
Dystric Vitric Haplustands

BFBD. Other Haplustands that have less than 30 percent,
undried, 1500 kPa water retention in some subhorizon
that meets the requirements for andic soil properties and
that is at least 25 cm thick within 100 cm of the mineral
soi] surface or of the upper boundary of an organic layer
with andic soil properties, whichever is shallower.

Vitric Haplustands

BFBE. Other Haplustands that have both more than 6.0

percent organic carbon and colors of the mollic epipedon

throughout at least 50 cm of the upper 60 cm, excluding any

overlying layers that do not have andic soil properties.
Pachic

BFBF, Other Haplustands that have, between 25 and 100
cm, a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the

underlying layer.
‘Thaptic Haplustands

BFBG. Other Haplustands that have a calcic horizon with
its upper boundary within 125 cm of the mineral soil

surface.
Calcic Haplustands

BFBH. Other Hapluatands that have extractable bases plus

IN KCl-extractable Al of leas than 15.0 emol(+) kg’ in the

fine earth throughout at least 60 cm of the upper 75 cm.
Dystrie Haplustands

BFBI. Other Haplustands that have an oxic horizon with
its upper boundary within 125 cm of the mineral soil

surface.
Oxic Haplustands

BFBJ. Other Haplustands that have an argillic or kandic
horizon with its upper boundary within 125 cm of the

mineral soil surface.
Alfic Haplustands

BFBK. Other Haplustands that have a mollic epipedon.
Mollic Haplustands

BFBL. Other Haplustands that have an umbric epipedon.
Umbric Haplustands

BFBM. Other Haplustands.
‘Typic Haplustands


78

IAFC, Other Glossaqualfs that have in more than 40
percent of the matrix’ in one or more subhorizons between
the A or Ap horizon and a depth of 75 cm one of the
following:

1. If mottled, the value, moist, is 4 or more and the
chroma, moist, is 3 or more; or

2. If not mottled, the chroma, moist, is 2 or more.
Aeric Glossaqualfy

IAFD. Other Gloasaqualfs that have an Ap horizon that
has a color value, moist, of 3 or less, and a color value,
dry, of 5 or less after the soil has been crushed and
smoothed; or the soil to a depth of 18 cm, after mixing, has

these colors.

Mollic Glossaqualfs
IAFE, Other Glossaqualfs.

Typic Glossaqualfy
Kandiaqualfs
‘Key to suberoups

IAEA. Kandiaqualfs that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic or kandic horizon that
is 50 to 100 cm below the soil surface.

Arenic Kandiaqualfs

IAEB. Other Kandiaqualfa that have a layer, starting at
the mineral soil surface, that has a sandy particle-size
class and extends to the top of an argillic or kandic
horizon that is more than 100 cm below the soil surface.
Grossarenic Kandiaqualfy

IAEC, Other Kandiaqualfs that have a horizon within 150
em of the soil surface that has 5 percent or more plinthite

by volume.
Plinthic Kandiaqualfs
IAED. Other Kandiaqualfs that:
1. 2. Hoare i moore then 40 perment ofthe matrix i one or

between the A or Ap horizon and a
depth of 75 em one or more ofthe following:

a. If mottled and the mean annual soil temperature
is lower than 15°C, chroma, moist, of 3 or more; or

3 rf the hue is 7.5%R o£ redder and if pede are present, ped exteriors

in the argillic norison shoald have dominant chroma, moist, of 1 or les
‘and ped interiors should have mottlea thet Mave chroma, aoist, of 2 or
less; Af pods are absent, the chroma, woist, should be 1 oF lene

Ammediately below any surface horizon that has color velua, soist, of 3
oF lesa,


270
JEC. Other Umbrepta that have a xeric moisture regime,

Xerumbrepte, p. 273
JED. Other Umbrepts.

Haplumbrepts, p. 271
Cryumbrepts
Key tosubgroups

JEBA. Cryumbrepts that have a lithic contact within 50 em
of the surface in only part of each pedon.
Roaic rithte Cryum
JEBB. Other Cryumbrepts thet:
1. Have a lithic contact within 50 cm of the surface; and
2, Have an umbric epipedon that is discontinuous in
each pedon.
Lithie Ruptic-Entic Cryum
JEBC. Other Cryumbrepts that have a lithic contact within
50 cm of the surface.
Lithic Cryumbrepts
JEBD. Other Cryumbrepts that have a mean annual soil
temperature of 0°C or lower.
Pexgelic Cryumbrepts

JEBE, Other Cryumbrepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm* or less
and acid-oxelate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic

JEBF. Other Cryumbrepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least & percent voleanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

‘Vitrandic Cryumbrepte

JEBG. Other Cryumbrepts that have mottles that have
chroma of 2 or less within 75 cm of the soil surface, and
the mottled horizon is saturated with water at some time of


1, Texture that is very fine sand, loamy very fine sand, or
finer in the fine-earth (less than 2.0 mm) fraction; and

2, Soil structure or absence of rock structure in at least
half the volume; and

3. Minerals that consist of (a) enough amorphous or 2:1
lattice clay to give a cation-exchange capacity (by
NH,4OAc) of more than 16 emol(+) per kg clay or (b) 10
percent or more weatherable minerals; and

4. Evidence of alteration in one of the following forms:

a, Have an aquic moisture regime or artificial
drainage and, beginning at a depth of less than 50 cm,
colors with a hue no bluer than 10Y if the hue changes
on exposure to air, and dominant chroma on faces of
peds if peds are present or in the matrix if peds are
absent as follows:

(1) If there is mottling, the chroma is 2 or less; or

(2) If there is no mottling and the value is less than 4,
the chroma is less than 1; if the value is 4 or more, the
chroma is 1 or less; and

(3) One or more of the following properties:

(a) A regular decrease in the amount of organic
carbon with depth and a content of less than 0.2
percent organic carbon at a depth of 125 cm below
the surface or immediately above a sandy-skeletal
substratum that is at a depth of less than 125 cm; or

(b) Cracks that open and close in most years and
are 1 em or more wide at a depth 50 cm below the
surface; or

(c) Permafrost at some depth; or

(d) A histic epipedon consisting of mineral soil
materials or a mollic or umbric epipedon; or

b. Do not have an aquic moisture regime or artificial
drainage and colors as defined in “a.” and have one or
more of the following properties:

(1) Stronger chroma, redder hue, or higher clay
content than the underlying horizon; or

(2) Evidences of removal of carbonates,
Particularly, the cambic horizon has less carbonate
than the underlying k horizon. If all coarse
fragments in the k horizon are completely coated
with lime, some in the cambic horizon are partly free
of coatings. If coarse fragments in the k horizon are


232
Borofolists

Key to subgroups

AACA. Borofolists that have a lithic contact within 100
cm of the surface.

Lithic Borofolists
AACB. Other Borofolists.

Typic Borofolists
Cryofolists
Key to subgroups

AAAA. Cryofolists that have a lithic contact within 100
cm of the surface.

Lithic Cryofolista
AAAB. Other Cryofolists.

‘Typic Cryofolists
Tropofolists
Key to subgroups

AABA. Tropofolists that have a lithic contact within 100
cm of the surface.

Lithic Tropofolists
AABB. Other Tropofolists.

‘Typic Tropofolists
HEMISTS
Key to great groups

ACA. Hemists that have a sulfuric horizon that has its
upper boundary within 50 cm of the surface.
p. 235

ACB. Other Hemists that have sulfidic materials within
100 cm of the surface.
Sulfthemists, p. 235

ACC, Other Hemists that have a horizon 2 cm or more
thick in which half or more of the volume is humilluvic

materials.
Lavihemiste, p. 234

ACD. Hemists that are frozen in some layers within the
control section about 2 months after the summer solstice
in most years or that are never frozen below a depth of 5
cm in most years but have a mean annual soil

temperature lower than 8°C.
Cryohemista, p. 234

ACE. Other Hemists that have a mean annual soil
temperature lower than 8°C,
Borohemists, p. 233


275

Chapter 11
Mollisols
KEY TO SUBORDERS

HA. Mollisols that have all the following:

1, An albic horizon that lies immediately below the
mollic epipedon or that separates horizons that together
meet all the requirements of a mollic epipedon; and

2. An argillic or a natric horizon; and

3, Chroma of 2 or less in the albic horizon or
characteristics associated with wetness in the albic,
argillic, or natric horizon, namely mottles or iron-
manganese concretions larger than 2 mm or both.
Albolls, p. 277

HB. Other Mollisols that either have an aquic moisture
regime or are artificially drained, and that have one or
more of the following characteristics associated with
wotness:

1. A histic epipedon overlying the mollic epipedon; or

2. An SAR of 13 or more (or sodium saturation of 15
percent or more) in the upper part of the mollic epipedon
and decreasing SAR (or sodium saturation) with
increasing depth below 50 cm; or

3, One of the following combinations of colors, moist:

a, If the lower part of the mollic epipedon' has chroma
of Lor less, there are either

(1) Distinct or prominent mottles in the lower part
of the mollic epipedon; or

(2) A color value, moist, of 4 or more immediately
below the mollic epipedon, or within 75 cm of the
surface if a calcic horizon intervenes, and one of
the following:

(a) If the hue is 10YR or redder and there are
mottlea, chroma is less than 1 or less on ped
surfaces or in the matrix; if there are no mottles,
chroma is less than 1; or

(b) If the hue is nearest 2.5Y and there are
distinct or prominent mottles, chroma is 2 or
Jess on ped surfaces or in the matrix; if there are
no mottles, chroma is 1 or less; or

(c) If the nearest hue is BY or yellower and there
are distinct or prominent mottles, chroma is 3 or

n
Ifthe malhe epapedon extends toa lithic contact within 90 em of the murface, tht
requirement for motiles ia waived.


horizons of Soil Taxonomy. Designations of genetic
horizons express a qualitative judgment about the kind
of changes that are believed to have taken place.
Diagnostic horizons are quantitatively defined features
used to differentiate between taxa. The diagnostic
horizons may encompass several genetic horizons, and
changes implied by genetic horizon designations may
not be large enough to justify recognizing different
diagnostic criteria.

MASTER HORIZONS AND LAYERS

The capital letters O, A, E, B, C, and R represent the
master horizons and layers of soils. The capital 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: Layers dominated by organic
material. Some are saturated with water for long
periods or were once saturated but are now artificially
drained; others have never been saturated.

Some O layers consist of undecomposed or partially
decomposed litter, such as leaves, needles, twigs,
moss, and lichens, that has been deposited on the
surface; they may be on top of either mineral or
organic soils, Other O layers are organic materials
that were deposited under saturated conditions and
that were decomposed to varying stages. The mineral
fraction of such material is only a small percentage of
the volume of the material and generally is much less
than half of the weight. Some soils consist entirely of
material designated as O horizons or layers.

An O layer may be on the surface of a mineral soil or
at any depth beneath the surface if it is buried. A
horizon formed by illuviation of organic material into
a mineral subsoil is not an O horizon, though some
horizons formed in this manner contain much
organic matter.

Ahorizons: Mineral horizons that formed at the surface
or below an O horizon, that exhibit obliteration of all or
much of the original rock structure! and show one or
more of the following:

(1) are characterized by an accumulation of humified
organic matter intimately mixed with the mineral
fraction and are not dominated by properties
characteristic of E or B horizons ‘defi med below) or

(2) have properties resulting from cultivation,
pasturing, or similar kinds of disturbance.

1

Rock structure fine stratification in or weakly ated
‘sediment or peudomorphe of weathered minerals retaining their positions relative to exch
thet and to wnweathare! minerals in saprolite from consolidated rock.



208

paralithic contact is deeper than 50 cm but shallower
than 100 cm; and

3, More than 35 percent clay in horizons that total more
than 50 cm in thickness.
Vertic Cryoborelis

HEBJ, Other Cryoborolls that have, throu;
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cmTM or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic

HEBK. Other Cryoborolls that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a, More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vitrandic Cryoborolls

HEBL. Other Cryoborolls that have a duripan that has its
upper boundary within 100 em of the soil surface.

HEBM. Other Cryoborolls that have an albic horizon
in iately below the mollic epipedon and have an

argillic horizon.
Boralfio Cryoborolls

HEBN. Other Cryoborolls that:

1, Have a mollic epipedon that is 40 cm or more thick
and that has texture finer than loamy fine sand; and

2. Have an irregular decrease in organic carbon
content with increasing depth or have an organic
carbon content of more than 0.3 percent at a depth of 125
cm below the surface; and

3, Have a slope of 25 percent or less.
‘Cumulic Cryoborells

HEBO, Other Cryoborolls that:
1, Have a calcie horizon within or immediately below

the mollic epipedon and do not have an argillic horizon
in the lower part of the mollic epipedon; and


198

Jong in some patt, and that extend upward to the
surface or to the base of an Ap horizon; and

2, The cracks are not open permanently; and

3. A coefficient of linear extensibility (COLE) of 0.09
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 100 em of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 100 em; and

4. More than 35 percent clay in horizons that total more
than 60 cm in thickness.
Vertic Fluvaquents
KADC. Other Fluvaquents that:

1, Have a buried Histosol or a buried histic epipedon
that has its upper boundary within 100 cm of the soil
surface; and

2. Have a difference of less than 5°C between the mean
summer and mean winter soil temperatures at a depth
of 60 cm or at a lithic or paralithic contact, whichever

is shallower.
Thapto-Histic Tropic Fluvaquents

KADD. Other Fluvaquents that have a buried Histosol or
a buried histic epipedon that has its upper boundary
within 100 cm of the soil surface.

Thapto-Histic Fluvaquents

KADE. Other Fluvaquents that have, throughout a
cumulative thickness of 18 cm or more and within a
depth of 76 cm, one or more of the following:

1, Bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 gcmTM or
less and acid-oxalate-extractable aluminum plus /2
acid-oxalate-extractable iron of more than 1.0 percent;
or

2. Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or

3. The 0,02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or
b. At least 5 percent voleanic glass and acid-
oxalate-extractable sluminum plus 1/2 acid-
oxalate-extractable fron of 0.40 percent or more.
Aquandic
KADF. Other Fluvaquents that:

1. Have in more than 40 percent of the matrix in one or
more subhorizons between the Ap horizon or a depth of


308
2, Have the following combination of characteristics:

a. Cracks at some period in most years that are lem.
or more wide at a depth of 50 cm, that are at least 30
cm long in some part, and that extend upward to the
surface or to the base of an Ap horizon; and

b, A coefficient of linear extensibility (COLE) of 0.07
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more
in the upper 125 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 125 cm; and

c. More than 36 percent clay in horizons that total
more than 50 cm in thickness; and

3. The cracks are open less than 135 days in most
years.
Udertic Calciustolls

HFDF. Other Calciustolls that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm
Jong in some part, and that extend upward to the surface
or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.07 or
more in a horizon or horizons at least 50 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 125 cm of the soil or in the whole soil if'a lithic or
paralithic contact is deeper than 50 cm but shallower
than 125 cm; and

3. More than 36 percent clay in horizons that total more
than 60 cm in thickness.
Vertic Calciustolls

HDG. Other Calciustolis that have a petrocalcic horizon
that has its upper boundary within 100 cm of the surface.
Petrocalcic Caleiustolls

HFDH. Other Calciustolls that have a mollic epipedon
that is 60 cm or more thick and its texture is finer than

loamy fine sand.
Pachic Calciustolls

HFDI. Other Calciustolls that have mottles within 75 cm
of the surface that are due to segregation of iron or
manganese and are continuously saturated with water
for 90 days or longer within 100 em of the surface unless

artificially drained.
Aquic Calciustolls

HFDJ. Other Calciustolls that, when neither irrigated nor
fallowed to store moisture:

1. If the soil temperature regime is mesic or thermic,
are dry in some or all parts of the moisture control
section six-tenths or more of the time in half or more
years during a period when the soil temperature at a
depth of 50 cm exceeds 5°C; or


127

less and contains 0.7 percent or more organic carbon, or

have an Ap horizon that has a color value, moist, of 3 or

less and contains 0.7 percent or more organic carbon.
Mollic Palexeralfs

IDFM. Other Palexeralfs.
Typic Palexeralfs

Plinthoxeralfs

Plinthoxeralfs are the Xeralfs that have plinthite that
forms a continuous phase or that constitutes more than
half the matrix of some subhorizon within 150 cm of the
soil surface. Few of these soils are in the United States,
but the soils are moderately extensive in some parts of the
world, Subgroups have not been developed.

Rhodoxeralfs
Koy to subgroups

The list of subgroups that follows is incomplete because
the soils are of such limited extent in the United States.

IDEA, Rhodoxeralfs that have a lithic contact within 50
em of the soil surface.
Lithic Rhodoxeralfs

IDEB. Other Rhodoxeralfs that have a petrocalcic horizon
whose upper boundary is within 150 cm of the soil surface.
Petrocalcic Rhodoxeralfs

IDEC. Other Rhodoxeralfs that have a calcic horizon
whose upper boundary is within 150 cm of the soil surface.
Calcic.

IDED, Other Rhodoxeralfs that have an argillic horizon
that is 15 cm or less thick or is discontinuous in each

pedon.
Ochreptic Rhodoxeralfs

IDEE, Other Rhodoxeralfs.
Typic Rhodoxeralfs


299
a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-

extractable aluminum plus 1/2 acid-oxalate-

extractable iron of 0.40 percent or more.

Vitrandic Argiudolls

HGBF. Other Argiudolls that have mottles within 40 cm of
the surface and, unless artificially drained, the mottled
horizon is saturated with water at some period of the year
when the soil temperature in the mottled horizon is above
5°C, or have a horizon 15 cm or more thick immediately
below the mollie epipedon that:

1. Has a hue of 10¥R or redder and chroma of 2 or less,
or has mottles that have chroma of 2 or less and value of
4 or more and, unless artificially drained, the mottled
horizon is saturated with water at some period of the
year when the soil temperature in the mottled horizon is
above 5°C; or

2. Has a hue of 2.5Y or yellower and chroma of 3 or less.
Aquic Argiudolls

HGBG. Other Argiudolls that have CEC (by IN NH,OAc
pH 7) of less than 2% in the major part of the argillic
horizon, or the major part of the upper 100 cm of the
argillic horizon if the argillic horizon is thicker than 100
cm.

Oxic Argiudolis

HGBH. Other Argiudolls.

‘Typic Argiudolls
Hapludolls
Key to subgroups
HGDA. Hapludolls that have a lithic contact within 50 cm
of the surface.

Lithie Haphudoll

HGDB. Other Hapludolls that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1emor
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the surface
or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.09 or
more in a horizon or horizons at least 60 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 100 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 100 cm; and

3, More than 35 percent clay in horizons that total more
than 50 cm in thickness.
Vertic Hapludolls

HGDC. Other Hapludolls that have, throughout a
cumulative thickness of 18 cm or more and within a depth


184
BADD. Other Vitraquands that have, between 25 and 100
cm, a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the
underlying layer.

‘Thaptic Vitraquands

BADE, Other Vitraquands.

Typic Vitraquands
CRYANDS
Key to great groupe
BBA. Cryands that have a mean annual soil
temperature of 0°C or lower.

Gelieryands, p. 135

BBB. Other Cryands that have a melanic epipedon.
Melanceryands, p. 137

BBC. Other Cryands that have an epipedon meeting the
depth, thickness and organic carbon requirements of a
melanic epipedon and having color value and chroma,

moist, of 3 or less.
Fulvicryands, p, 134

BBD. Other Cryands that have a 1500 kPa water
retention of undried samples of 100 percent or more on
the weighted average throughout a thickness of 35 cm or
more within 100 cm of the mineral soil surface or of the
upper boundary of an organic layer with andic soil
properties, whichever is shallower.

Hydrocryands, p. 136

BBE. Other Cryands that have 1500 kPa water retention
of less than 15 percent on air-dried samples and less
than 30 percent on undried samples, throughout a
thickness of 35 cm or more within 60 cm of the mineral
soil surface or upper boundary of an organic layer with
andic soil properties, whichever is shallower.

Vitricryands, p, 137
BBF. Other Cryands.

Haplocryands, p. 135
Fulvicryands
‘Key to subgroups

BBCA. Fulvicryands that have a lithic contact within 50
em of the soi) surface.
Lithic Fulvieryands

BBCB. Other Fulvicryands that have less than 30
percent, undried, 1500 kPa water retention in some
subhorizon that meets the requirements for andic soil
properties and that is at least 25 cm thick within 100 cm of
the mineral] soil surface or of the upper boundary of an


359
CABG, Other Cryaquods,
‘Typic Cryaquods
Duraquods

‘Duraquods are the Aquods that have a duripan in the
albic horizon and have a temperature regime warmer
than that of Cryaquods.

Fragiaquods
Keyto.subgroups
CAAA. Fragiaquods that have a cryic or colder
temperature regime.
Cryic Fragiaquods
CAAB. Other Fragiaquods that have a histic epipedon.
Histic Fragiaquods

CAAC. Other Fragiaquods that have 5 percent or more by
Yolume of iron-cemented nodules 2.5 to 30 em in
diameter

the spodic horizon.

CAAD. Other Fragiaquods that have a surface horizon
more than 80 em thick that meets all requirements of a
plaggen epipedon except thickness.

Plaggeptic Fragiaquods

CAA, Other Fragiaquods that have an intermittent
upper black subhorizon of the spodic horizon that has a
ratio of free iron (elemental) to carbon that is less than
0.2; or if plowed and the Ap horizon reste directly on the
spodie horizon, have tongues of such a subhorizon.
Humic Fragiaquods

CAAF. Other Fragiaquods that have an argillic or
kandic horizon.

Alfic Fragiaquods
CAAG. Other Fragiaquods.

‘Typic Fragiaquods
Haplaquods
‘Key to subgroups
CAFA. Haplaquods tha that have a lithic contact within 50
cm of the mineral soil surface.

Lithic Haplaquods
CAFB. Diner Haplaquods that have a placic horizon in or
below the spodic horizon.

Placic Haplaquods

CAFC. Other Haplaquods that have a histic epipedon.

CAFD, Other Haplaquods that


254
a, More than 80 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-

extractable aluminum plus 1/2 acid-oxalate-

extractable iron of 0.40 percent or more.
Vitrandic

Dystrochrepts
JDGF. Other Dystrochrepts that:

1. Have mottles that have chroma of 2 or less within 60
cm of the soil surface, and the mottled horizon is
saturated with water at a time when its temperature is
5°C or higher, or the soil has artificial drainage; and

2. Have a content of organic carbon‘ that decreases
irregularly with depth, or are 125 em or more deep to a
lithic or a paralithic contact and have more than 0.2
percent organic carbon at 125 em below the soil surface;
and

3. Have slopes of 25 percent or less.
Fluvaquentic Dystrochrepta

JDGG, Other Dystrochrepts that have mottles that have
chroma of 2 or less within 60 cm of the soil surface, and
the mottled horizon is saturated with water at a time when
its temperature is 6°C or higher, or the soil has artificial

drainage.
Aquic Dystrochrepts
JDGH. Other Dystrochrepts that:

1. Have a content of organic carbon® that decreases
irregularly with depth, or are 125 cm or more deep to a
lithic or a paralithic contact and have more than 0.2
peree nt organic carbon at 125 cm below the soil surface;
ant

2, Have slopes of 25 percent or less; and

3, Have an Ap horizon that has a color value, moist, of 3
or less or a color value, dry, of 8 or less, crushed and
smoothed, or the upper soil to a depth of 18 cm, after
mixing, has these colors.

Fluventic Umbric Dystrochrepts
JDGI. Other Dystrochrepts that:

1. Have a content of organic carbon® that decreases
irregularly with depth, or are 125 cm or more deep to a
lithic or a paralithic contact and have more than 0.2
percent organic carbon at 126 cm below the soil surface;
ani

2, Have slopes of 25 percent or leas.

Fluventic Dystrochrepts

4 7mm carbon should be of Halocene age Ite net the intert to include fomsil carbon froan
bedrock,
S ye carbon should be of Holocene age- Its not tha intent to include fossil carbon free
bedrock.
Site carbon should be of Holocene aga. Tt 19 not the intent to include fomil carbon trem
bedrock.


190

3. Both a dominant chroma of 2 or less and a greater
SAR (or percentage of exchangeable sodium) in more
than half the thickness of the horizons between the
surface and 50 cm depth than in the saturated zone,

FBCC, Other Durorthids that:

1. Are dry in all parts of the moisture control section
for three-fourths or less of the time that the soil
temperature at a depth of 60 cm is 5°C or higher, and
have an aridic moisture regime that borders on a xeric
regime; and

2. Have, throughout a cumulative thickness of 18 cm or
more and within a depth of 75 cm, one or more of the
following:

a. Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders,
pumice, and pumice-like fragments make up more
than 66 percent of these fragments; or

‘b. The 0,02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2,0 mm fraction and
contains either:

(1) More than 20 percent volcanic glass; or

(2) At least & percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Vitrixerandic Durorthids

FBCD, Other Durorthids that:

1. Are dry in all parts of the moisture control section
for three-fourths or less of the time that the soil
temperature at a depth of 50 cm is 5°C or higher; and

2. Have, throughout a cumulative thickness of 18 cm or
more and within a depth of 75 cm, one or more of the
following:

a. Fragments coarser than 2.0 mm constitute more
than 36 percent of the whole soil and cinders,
pumice, and pumice-like fragments make up more
than 66 percent of these fragments; or

b. The 0,02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and
contains either:

(1) More than 30 percent volcanic glass; or
(2) At least 5 percent voleanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of 0.40 percent or more.
Vitrustandic Durorthids

FBCE, Other Durorthids that have the following
combination of characteristics:


392
Palexerolls

Key to subgrouns

HDCA. Palexerolls that have a natric horizon.
Natric Palexerolls

HDCB. Other Palexerolls that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the surface
or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.05 or
more in a horizon or horizons at least 60 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 150 cm of the soil or in the whole soil if a lithic or a
paralithic contact is deeper than 50 cm but shallower
than 150 cm; and

3. More than 35 percent clay in horizons that have a
total thickness of more than 50 cm.
Vertic Palexerolls

HDCC. Other Palexerolls that have a mollic epipedon that
is 50 cm or more thick, and its texture is finer than loamy

fine sand.
Pachic Palexerolls
HDCD. Other Palexerolls that have mottles that have
chroma of 2 or leas within 75 cm of the soil surface.
Aquic
HDCE. Other Palexervlls that:
1, Have an aridic moisture regime; and

2. Have a petrocalcic horizon that has its upper
boundary within 150 cm of the soil surface.
Aridic Petrocaleic

Palexerolls
HODCF. Other Palexerolls that have an aridic moisture
regime.
Aridic Palexerolls

HODCG. Other Palexerolls that have a petrocalcic horizon
that has its upper boundary within 150 cm of the soil

surface.
Petrocalcic Palexerolls

HDCH. Other Palexerolls that have base saturation of 75
percent or less in some part of the argillic horizon or in
the upper 50 cm of the argillic horizon, whichever is

thinner,
Ultic Palexerolls

HDCL. Other Palexerolls that have an argillic horizon
that either does not have a clayey particle-size class in the
upper part, or has an increase in clay content of less than
20 percent clay (absolute) within a vertical distance of 7.5


179

1, A frigid temperature regime and an aridic
moisture regime that borders on an ustic regime; and

2, A weighted average percentage of organic carbon in
the upper 40 cm that is 0.6 percent or more if the
weighted average ratio of sand to clay in the soil above
that depth is 1.0 or less, or is 0.15 percent or more if the
ratio is 13 or more, or is intermediate between 0.6
percent and one-seventh percent if the ratio of sand to
clay is between 1.0 and 13; and a weighted average
percentage of organic carbon in the soil to a depth of 18
cm that is one-fifth or more higher than the values just
stated if there is a paralithic contact at a depth of less
than 40 cm but more than 18 cm.

Borollic Calciorthids

FBEC. Other Calciorthids that have the following
combination of characteristics:

1. Have a lithic contact within 50 cm of the surface;
and

2. Have a weighted average percentage of organic
carbon in the upper 40 cm that is 0.6 percent or more if
the weighted average ratio of sand to clay in the soil
above that depth is 1.0 or less, or is 0.15 percent or more
if the ratio is 13 or more, or is intermediate between 0.6
percent and one-seventh percent if the ratio of sand to
clay is between 1.0 and 13; and a weighted average
percentage of organic carbon in the soil to a depth of 18
cm that is one-fifth or more higher than the values just
stated if there is a lithic or paralithic contact at a depth
of less than 40 cm but more than 18 cm; and

3. Have a mean annual soil temperature lower than
22°C, mean summer and mean winter soil
temperatures at a depth of 50 cm that differ by 5°C or
more, and an aridic moisture regime that borders on a

xeric regime.
Lithic Xervllic Calciorthids

FBED. Other Calciorthids that have the following
combination of characteristics:

1. Have a lithic contact within 50 cm of the surface;
and

2, Have a weighted average percentage of organic
carbon in the upper 40 cm that is 0.6 percent or more if
the weighted average ratio of sand to clay in the soil
above that depth is 1.0 or less, or ia 0.15 percent or more
if the ratio is 13 or more, or is intermediate between 0.6
percent and one-seventh percent if the ratio of sand to
clay is between 1.0 and 13; and a weighted average
percentage of organic carbon in the soil to a depth of 18
cm that is one-fifth or more higher than the values just
stated if there is a lithic or paralithic contact at a depth
of Jess than 40 cm but more than 18 cm; and

8. Have an aridic moisture regime that borders on an
ustic regime.
Lithic Ustollic Calciorthids


73

Chapter 5
Alfisols

KEY TO SUBORDERS

TA. Alfisols that have an aquic moisture regime or are
artificially drained and that have characteristics
associated with wetness, namely, mottles, or iron-
manganese concretions more than 2 mm in diameter, or
chroma of 2 or less immediately below any Ap horizon or
below any dark A horizon in which the moist color value
is 3 or less after the material is rubbed, and one of the
following:

1. Dominant chroma of 2 or less’ in coatings on the
surface of peda and mottles within peds of the argillic or
kandic horizon, or a dominant chroma of 2 or less in
the matrix of the argillic or kandic horizon and mottles
of higher chroma; or
2. If there are no mottles in the argillic or kandic
horizon, a dominant chroma of 1 or less,

Aqualfs, p. 74

1B. Other Alfisols that have

1. A frigid temperature regime but do not have a xeric
moisture regime; or

2. A cryic temperature regime,
Boralfs, p. 84

IC. Other Alfisols that have one of the following:
1. An ustic moisture regime; or

2. An epipedon that is both massive and hard or very
hard when dry, and a moisture regime that is aridic but

marginal to ustic.
Ustalfa, p. 106

ID. Other Alfisols that have one of the following:

1. A xeric moisture regime; or 7

1f the hue 18 redder than 10YR because of red parent materials that
ton, the requirement for low
sre regiae 49 hypartheraic,
Leotheruio, or ischypertheraic, chroma up to ¢ is tentatively pernitied
Af the hue ts 2.S¥ oF $Y and if not] @ietinot or prominent. Such
toils are too fev in the United states to permit tasting these Limits.



288

2. The 0,02 to 2.0 mm fraction constitutes at least 30
Poroent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-

extractable aluminum plus 1/2 acid-oxalate-

extractable iron of 0.40 percent or more.
Vitrandic Fragiochrepts

JDAC. Other Fragiochrepts that have distinct or
prominent mottles in the upper 30cm of the soil.

Aquic Fragiochrepts
SDAD. Other Fragiochrepts that do not have an ochric
epipedon.

Umbric Fragiochrepts

JDAE. Other Fragiochrepts.

‘Typic Fragiochrepts
Ustochrepts
Key to subgroups

JDDA. Ustochrepts that have a lithic contact within 50 cm

of the surface,

Lithtc Ustochrepts
JDDB. Other Ustochrepts that:

1, When neither irrigated nor fallowed to store
moisture:

a. If the soil temperature regime is mesic or thermic,
are dry for four-tenths or less of the cumulative days
in some part of the moisture control section when the

soil temperature at a depth of 50 cm exceeds 5°C; or

b. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or
Jess during a period when the soil temperature at a
depth of 50 cm exceeds 8°C; and

2, Have the following combination of characteristics:

a. Cracks at some period in most years that are 1 cm

or more wide at a depth of 50 cm and that are at least

30 cm long in some part and that extend upward to the
soil surface or the base of an Ap horizon; and

b. A coefficient of linear extensibility (COLE) of 0.07
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more
in the upper 125 cm of the soil or in the whole eoil if a
lithic or paralithic contact is deeper than 80 cm but
shallower than 125 cm; and

¢. More than 35 percent clay in horizons that total
more than 50 cm in thickness.
‘Udertic Ustochrepts


327

1, Cracks at some period in most years that are 1 cm or
more wide at a depth of 60 cm, thet are at least 30 cm
long in some part, and that extend upward to the soil
surface or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.05 or
more in a horizon or horizons at least 60 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 150 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 150 cm; and

3. More than 35 percent clay in horizons that have a
total thickness of more than 50 cm.
Vertic Haploxerolls

HDFE. Other Haploxerolls that:
1, Have an aridic moisture regime; and

2, Have, throughout a cumulative thickness of 18 cm or
more and within a depth of 75 cm, one or more of the
following:

a. Fragments coarser than 2.0 mm constitute more
than 36 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66

percent of these fragments; or

b. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

(1) More than 80 pereent voleanic glass; or

(2) At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Vitritorrandie Haploxerolls

HDFF. Other Haploxerolls that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more than
36 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or
b. At least 5 percent volcanic glass and acid-
oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of 0.40 percent or more.
Vitrandic Haploxerolls
HDFG. Other Haploxerolls that:

1, Have a mollic epipedon that is 50 cm or more thick
and its texture is finer than loamy fine sand; and


378

Paleaquults

Key to subgroups
GAFA. Paleaquults that:

1. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic horizon that is 50 to 100 cm below the
soil surface; and

2. Have 5 percent or more plinthite (by volume) in one
or more subhorizons within 150 em of the soil surface.
Arenic Plinthic Paleaquults

GAFB. Other Paleaquults that:

1. Have a layer, starting at the mineral soil surface,

that has a sandy particle-size class and extends to the
top of an argillic horizon that is 50 to 100 cm below the
soil surface; and

2. Do not have an ochric epipedon.
‘Arenic Umbric Paleaquults

GAFC. Other Paleaquults that have a layer, starting at
the mineral soil surface, that has a sandy particle-size
class and extends to the top of an argillic horizon that is
50 to 100 cm below the soil surface.

Arenic Paleaquults

GAFD. Other Paleaquults that have a layer, starting at
the mineral soil surface, that has a sandy particle-size
class and extends to the top of an argillic horizon that is
more than 100 cm below the soil surface.

Grossarenic Paleaquults
GAFE. Other Paleaquults that have 5 percent or more
plinthite (by volume) in one or more subhorizons within

150 em of the soil surface.
Plinthic Paleaquults

GAFF. Other Pal wults that have a subhorizon that has
dominant chroma of 3 or more within 75 cm of the soil

surface.

Aeric Paleaquults
GAFG, Other Paleaquults that do not have an ochric
epipedon.

Umbric Paleaquults

GAFH. Other Paleaquults.

Typic Paleaquults
Plinthaquults
Key to subgroups

GAAA. Plinthaquults that have a CEC of less than 24
cmol(+) per kg of clay (by IN NH,OAc pH 7) in the major
part of the argillic or kandic horizon, or the major part of


348
DEBB. Other Acrudox that have a petroferric contact
surface,

within 125 cm of the soil
Petroferric Acrudox

DEBC. Other Acrudox that have mottles of 4 or more value
moist and 2 or less chroma within a depth of 125 cm of the
soil surface and a lithic contact within 125 cm of the soil
surface.

Aquic Lithic Acrudox
DEBD. Other Acrudox that have a lithic contact within a
depth of 126 cm of the soil surface.
Lithic Acrudox

DEBE. Other Acrudox that have mottles of 4 or more value
moist and 2 or less chroma within a depth of 126 cm of the
soil surface and have a delta pH (KCI pH - 1:1 water pH)
with a 0 or net positive charge in some layer 18 cm or more
thick within a depth of 125 cm of the soi] surface.

Aquic Anionic Acrudox

DEBF. Other Acrudox that have a delta pH (KCI pH - 1:1
water pH) with a 0 or net positive charge in some layer 18
cm or more thick within a depth of 125 cm of the soil

surface.
Anionic Acrudox

DEBG, Other Acrudox that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the

soil surface.
Plinthie Acrudox

DEBH. Other Acrudox that have mottles of 4 or more value
moist and 2 or less chroma within a depth of 125 cm of the

soil surface.
Aquic Acrudox

DEBI. Other Acrudox that have more than 35 percent base
saturation (NH,OAc) in all parts within a depth of 125 cm
of the soil surface.

Eutric Acrudox
DEBJ. Other Acrudox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of

surface litter, and a color hue of 2.5YR or redder with
moist values of leas than 4 in most of the 25 to 125 cm depth

from the soil surface.

Humic Rhodic Acrudox
DEBK, Other Acrudox that have 16 kg or more organic
carbon per square meter to a depth of 100 em, exclusive of
surface litter, and colar hue of 7.5YR or yellower with
moist values of 6 or more in most of the 25 to 125 cm depth
from the soil surface.

Humic Xanthic Acrudox

DEBL. Other Acrudox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of

surface litter.
Humic Acrudox


a

Aquic moisture regime.--The aquic (L. aqua, water)
moisture regime implies a reducing regime that is
virtually free of dissolved oxygen because the soil is
saturated by ground water or by water of the capillary
fringe. An aquic regime must be a reducing one. Some
soil horizons, at times, are saturated with water while
dissolved oxygen is present, either because the water is
moving or because the environment is unfavorable for
micro-organisms; for example, if the temperature is less
than 1°C such a regime is not considered aquic.

For differentiation in the highest categories of soils that
have an aquic regime, the whole soil must be saturated.
In the subgroups, only the lower horizons are saturated.
The soil is considered to be saturated if water stands in an
unlined borehole at such a shallow depth that the capillary
fringe (see footnote 8) reaches the soil surface except in
noncapillary pores. The water in the borehole is stagnant
and remains colored if a dye is placed in the water. Ina
sandy soil, the thickness of the capillary fringe may be
only 10 to 15cm. In a loamy or clayey soil that does not
shrink or swell appreciably, the thickness may be 30 cm
or more, depending on the size distribution of the pores.

‘The duration of the period that the soil must be saturated to
have an aquic regime is not known. 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 micro-organisms, roots and soil fauna, it
is also implicit in the s concept that the soil temperature is
above biologic zero (5°C) at some time while the soil or the
horizon is saturated,

Very commonly, the level of ground water fluctuates with
the seasons. The level is highest in the rainy season, or
in fall, winter, or spring if cold weather virtually stops
evapotranspiration. There are soils, however, in which
the ground water is always at or very close to the surface,
A tidal marsh and a closed, landlocked depression fed by
perennial streams are examples. The moisture regime
in these soils is called "peraquic.” Although the term is
not used as a formative element for names of taxa, it is
used in their descriptions as an aid in understanding
genesis.

Aridic and torric (L. aridus, dry, and L. torridus,” hot
and dry) moisture regimes,—These terms are used for the
same moisture regime but in different categories of the
taxonomy.

In the aridic (torric) moisture regime, the moisture
control section in most years is

° rorridus tn not the ideal root, but a better one could not he found.
Although soils may not be hot throughout the year, soils that have a
torrie moisture regine are hot and dry in summer.


412

SI Units Conversion Table

CEC and ECEC:
1 meq/100 g soil = 1 cmol(+) per kg soil

Conductivity:
1 mmho/em = 148 per m

Pressure:
15-bar water = 1500 kPa water retention
‘V3-bar water = 33 kPa water retention


AD. Other Histosols.
Saprists, p.237

FIBRISTS

Key to great groups

ABA. Fibrists that have a surface mantle that is three-
fourths or more fibric Sphagnum spp. and that either is
90 cm or more thick, or extends 10 cm or more below
permafrost, or rests on a lithie or paralithic contact,
fragmental materials, or mineral soil materials.

p-229

ABB. Other Fibrists that are frozen in most years in
some layer within the control section about 2 months
after the summer solstice or that are never frozen in
most years below a depth of 5 cm but have a mean annual
soil temperature that is lower than 8°C.

Cryofibrists, p. 227
ABC. Other Fibrists that have a mean annual soil
temperature lower than 8°C,

Borofibrista, p. 226

ABD. Other Fibrists that have a difference of less than
5°C between mean summer and mean winter soil

temperatures at a depth of 30 cm.
‘Tropofibrists, p. 230
ABE. Other Fibrists that do not have a horizon 2 cm or

more thick consisting of half or more humilluvic

materials,
Medifibrists, p. 228

ABF. Other Fibrists.
Luvifibrists, p. 228

Borofibrists
Key to subgroups
ABCA. Borofibrists that have a layer of water within the
control section below the surface tier.
Hydric Borofibrists
ABCB. Other Borofibrists that have a lithic contact
within the control section.
Lithic Borofibrists
ABCC, Other Borofibrists that:
1. Have three-fourths or more of the fibers (by volume)
derived from Sphagnum in the surface tier or more of
the control section; and

2. Have a mineral layer 30 cm or more thick that has
its upper boundary in the control section below the

surface tier.
Sphagnic Terric Borofibrists


102

IEGG. Other Kandiudalfs that have 5 percent or more
plinthite by volume in one or more subhorizons within 150
cm of the soil surface.

Plinthic Kandiudalfs

TEGH. Other Kandiudalfs that have throughout the
argillic or kandic horizon a hue of 2.5YR or redder and
have a value, moist, of 3 or less and have a value, dry, that
is no more than one unit higher than the value, moist,
Rhodic Kandiudalfs

TEGI. Other Kandiudalfs that have an Ap horizon that has
acolor value, moist, of 3 or less and a color value, dry, of 5
or less after the soil has been crushed, or the upper soil,
after mixing to a depth of 18 cm, has these color values.

Mollic Kandiudalfs
TEGJ. Other Kandiudalfs.

Typic Kandiudalfs
Kanhapludalfs
Key to subgroups

TEHA, Kanhapludalfs that have a lithic contact within 50
cm of the soi) surface.
Lithic Kanhapludalfs

IEHB. Other Kanhapludalfs that have mottles that have
chroma of 2 or less within 75 cm of the soil surface, and
the mottled horizons are saturated with water at some time
when the soil temperature at that depth is 6°C or higher or

the soil has artificial drainage.
. Aquic Kanhapludalfs

TEHC. Other Kanhapludalfa that have throughout the
argillic or kandic horizon a hue of 2.5YR or redder and
have a value, moist, of 3 or lesa and have a value, dry, that
is no more than one unit higher than the value, moist.

Rhodic Kanhapludalfs
TEHD. Other Kanhapludalfs.
‘Typic Kanhapludalfs
Natrudalfs
Key to subgroups

IEBA. Natrudalfa that have the following combination of
characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 60 cm, that are at least 30 cm
long in some part and that extend to the surface or to the
base of an Ap horizon; and


38

It should be noted that this is a restricted meaning of
weatherable minerals. Calcite, for example, is readily
soluble in a humid environment. If it is dissolved, it
leaves no trace or residue. Soils that have been intensely
and deeply weathered in a humid environment of the past
are, in some places, preserved today in an arid
environment. Calcite could reappear in one of these soils
if it were brought in as dust. The intent is to include, in
the context of the meaning of weatherable minerals for
this purpose, only those minerals that are unstable in a
humid climate relative to other minerals, such as quartz
and 1:1 lattice clays, and that are more resistant to
weathering than calcite.

LITERATURE CITED

Brewer, R. 1964, Fabric and mineral analysis of soil.
John Wiley and Sons, Inc., New York, London, Sydney.
470p.

Pons, L.J. and LS. 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. 128 p.


2. The 0.02 to 2.0 mm fraction constitutes at least 30
pereent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent voleanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vitrandic Cryochrepts

JDCE. Other Cryochrepts that have mottles that have
chroma of 2 or less within 75 om of the soil surface, and
the mottled horizon is saturated with water at some period
when its temperature is 5°C or more, or the soil has

artificial drainage.
Aquic Cryochrepts

JDCF. Other Cryochrepts that have lamellae within 75 cm
of the soil surface that meet all requirements for an
argillic horizon except thickness.

Alfic Cryochrepts

JDCG. Other Cryochrepts that have base saturation (by
NH,OAo) that is less than 60 percent in all subhorizons

within 75 cm of the surface.

Dystric Cryochrepts
JDCH. Other Cryochrepts.
Typic Cryochrepts
Durochrepts
Key to subgroups

JIDBA. Durochrepts that have, throughout a cumulative
thickness of 18 cm or more and within a depth of 75 cm,
bulk density of the less than 2.0 mm fraction, measured at
33 kPa water retention, of 1.0 g cm*or less and acid-
oxalate-extractable aluminum plus 1/2 acid-oxalate-
extractable iron of more than 1.0 percent.

Andic Durochrepts
JDBB. Other Durochrepts that have distinct or prominent
mottles within the upper 30 cm.

Aquic Durochrepts.

JDBC. Other Durochrepts that do not have a xeric moisture
regime.
Ustic Durochrepts

JDBD. Other Durochrepts that:

1. Do not have a platy or massive indurated duripan;
and

2. Have base saturation (by NH, OAc) of less than 60
¢ throughout the soil between depths of 25 and 75

percent
cm below the soil surface.
Dystric Entic Durochrepts


313

b, The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the lees than 2.0 mm fraction and contains
either:

(1) More than 30 percent volcanic glass; or

(2) At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Vitritorrandic

HFGL. Other Haplustolls that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2, The 0.02 to 2.0 mm fraction constitutes at Jeast 30
Percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b, At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vitrandic Haplustolls

HFGM. Other Haplustolls that:

1. Have a mollic epipedon that is 50 cm or more thick
and its texture is finer than loamy fine sand; and

2. Have an irregular decrease in organic-carbon
content with increasing depth or have more than 0.3
percent at a depth of 125 cm of the surface; and

3. Have a slope of 26 percent or less.
Cumulic Haplustolls

HFGN, Other Haplustolls that have a mollic epipedon that
is 50 cm or more thick and its texture is finer than loamy

fine sand.
Pachic Haplustolls
HFGO. Other Haplustolls that:

1, Have mottles that have chroma of 2 or less within 100
cm of the surface if artificially drained or, if
undrained, are continuously saturated with water
within 100 cm of the soil surface for 90 days or more in
most years; and

2, Have an irregular decrease in organic-carbon
content with increasing depth or have more than 0.3
percent at a depth of 125 cm of the surface; and

38. Have a slope of less than 25 percent.
Fluvaquentic Haplustolls


248

b. At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Aquandic

JAHD. Other Humaguepts that:
1, Have an epipedon that is 60 cm or more thick; and

2. Have a content of organic carbon that decreases
irregularly with depth, or are 125 cm or more deep to a
lithic or a paralithic contact and have more than 0.2
percent organic carbon at 125 em below the aoil

surface.
Cunmlic Humaquepts

JAHE. Other Humaquepts that have a content of organic
carbon that decreases irregularly with depth, or are 125
cm or more deep to a lithic or a paralithic contact and
have more than 0.2 percent organic carbon at 125 cm

below the soil surface.
Flavaquentic Humaquepts

JAHF. Other Humaquepts that have chroma of 3 or more,
moist, and hue of SY or redder in more than 40 percent of
the matrix in one or more subhorizons between depths of

15 and 75 cm.

Aeric Humaquepts
JAHG. Other Humaquepts.

‘Typic Humaquepts
Placaquepts
Key to subgroups
JABA. Placaquepts that have a histic epipedon.

Histic Placaquepts

JABB. Other Placaquepts that have, throughout a
cumulative thickness of 18 cm or more and within a
depth of 75 cm, one or more of the following:

1. Bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g om or
less and acid-oxalate-extractable aluminum plus 1/2
acid-oxalate-extractable iron of more than 1.0 percent;
or

2. Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or

3. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-
oxalate-extractable aluminum plus 1/2 acid-


4. A coefficient of linear extensibility (COLE) of 0.05
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 150 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 150 cm; and

5. More than 35 percent clay in horizons that total more
than 50 cm in thickness.
Borollic Vertic Haplargids
FAEG. Other Haplargids that have:

1. A frigid or colder temperature regime and an aridic
moisture regime that borders on an ustic regime; and

2. A weighted average percentage of organic carbon in
the upper 40 cm that is 0.6 percent or more if the
weighted average ratio of sand to clay in the soil above
that depth is 1.0 or less, or is one-seventh percent or
more if the ratio is 13 or more, or is intermediate
between 0.6 percent and one-seventh percent if the
ratio of sand to clay is between 1.0 and 13; anda
weighted average percentage of o1 ic carbon in the
soil to a depth of 18 cm that is one~! or more higher
than the values just stated if there is a paralithic
contact at a depth of less than 40 cm but more than 18

cm,
Borollic Haplargids

FAEH. Other Haplargids that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30cm
long in some part, and that extend upward to the
surface, to the base of an Ap horizon, or to the top of the
argillic horizon, and the cracka close for 60
consecutive days or more during the 120 days
following the winter solstice in more than 7 out of 10
years; and

2. A coefficient of linear extensibility (COLE) of 0.05
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 150 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 150 em; and

3. More than 35 percent clay in horizons that total more
than 50 cm in thickness; and.

4, A thermic, mesic, or frigid soil temperature
regime.
Xerertic Haplargids

FAEL, Other Haplargids that have the following
combination of characteristics:

1, Cracks at eome period in most years that are 1cm or
more wide at a depth of 50 cm, that are at least 30cm
Jong in some part, and that extend upward to the
surface, to the base of an Ap horizon, or to the top of the


DCDJ. Other Kandiustox that have 16 kg or more organic
carbon per square meter to a depth of 100 em, exclusive of

surface litter.
Humic Kandiustox

DCDK, Other Kandiustox that have a color hue of 2.5YR or
redder with moist values of less than 4 in most of the 25 to
125 cm depth from the soil surface.

Rhodic Kandiustox

DCDL. Other Kandiustox that have a color hue of 7.5YR or
yellower with moist values of 6 or more in most of the 25 to
125 cm depth from the soil surface.

Xanthic Kandiustox.

DCDM. Other Kandiustox.
‘Typic Kandiustox

Sombriustox

Key to subgroups

DCAA. Sombriustox that have a petroferric contact within
a depth of 125 cm of the soil surface.
Petroferric Sombriustox

DCAB. Other Sombriustox that have a lithic contact
within a depth of 125 cm of the soil surface.
Lithic Sombriustox

DCAC. Other Sombriustox that have 16 kg or more
organic carbon per square meter to a depth of 100 cm,

exclusive of surface litter.
Humic Sombriustox

DCAD. Other Sombriustox.
‘Typic Sombriustox


301

8, Have a slope of leas than 25 percent.
Fluvaquentic Hapludolls

HGDG. Other Hapludolls that have mottles within 40 cm
of the surface and, unless artificially drained, the
mottled horizon is saturated with water at some period of
the year when the soil temperature in the mottled horizon
is above 5°C, or have a horizon 15 cm or more thick
immediately below the mollic epipedon that:

1. Has a hue of 10YR or redder and chroma of 2 or less,
or has mottles that have chroma of 2 or less and value of
4 or more and, unless artificially drained, the mottled
horizon is saturated with water at some period of the
year when the soil temperature in the mottled horizon is
above 5°C; or

2. Has a hue of 2.5Y or yellower and chroma of 3 or less.
Aquic Hapludolls

HGDH, Other Hapludolls that:

1. Have an irregular decrease in organic carbon
content with increasing depth or have an organic
carbon content of more than 0.3 percent at a depth of 125
em below the surface; and

2. Have a slope of less than 25 percent.
Fluventic Hapludolls

HGDI. Other Hapludolls that:

1. Have a mollic epipedon 60 cm or more thick with a
texture finer than loamy fine sand; and

2. Do not have a cambic horizon, and the lower part of
the mollic epipedon does not meet the requirements of a
cambic horizon except for color; or either the cambic
horizon or the lower part of the epipedon have
carbonates throughout; and

8, The mollic epipedon, below any Ap horizon, has 50
percent or more by volume of wo! les, wormcasts, or

filled animal burrows.
Vermic Hapludolls

HGDJ. Other Hapludolls that do not have a cambic
horizon, and the lower part of the mollic epipedon does not
meet the requirements of a cambic horizon except for
color; or either the cambic horizon or the lower part of the
epipedon have carbonates throughout.

Entie Hapludolls
HGDK. Other Hapludolls.

‘Typic Hapludolls
Paleudolls
Key to subgroups

HGAA. Paleudolls that have mottles that have chroma of 2
or less in the upper 50 cm of the argillic horizon, and the
mottled horizon is saturated with water at some period


TABLE 1 - KEY TO MINERALOGY CLASSES
(except for Oxisols - see Table 2)

CLASSES APPLIED TO SOILS OF ANY PARTICLE-
SIZE CLASS

Carbonatic

Definition: More than 40% by weight carbonates
(expressed as CaCOs) plus gypsum, and the carbonates
are more than 65% of the sum of carbonates and gypsum.

Determinant size fraction: Whole soil, particles less than
2.0 mm in diameter or whole soil less than 20 mm,
whichever has highest percentage of carbonates plus

gypsum.

Ferritic

Definition: More than 40 % by weight iron oxide
extractable by citrate-dithionite, reported as Fez Os (or
28% reported as Fe).

Determinant size fraction: Whole soil, particles less than
2.0 mm in diameter.

Gibbsitic
Definition: More than 40% by weight hydrated aluminum
oxides, reported as gibbsite and bohemite.

Determinant size fraction: Whole soil, particles less than
2.0 mm in diameter.

Oxidie
Definition: Less than 90% quartz; less than 40% any other
single mineral listed subsequently; and the ratio, percent
extrgctable iron oxide plus percent gibbsite to percent
clay’’ is 0.20 or more. That is,
extractable FeOa/oct,) + gibbsite (pet,) 20.2
clay (pet.)

Determinant size fraction: For quartz and other
minerals, fraction 0.02 to 2.0 mm in diameter; for ratio of
iron oxide and gibbsite to clay, whole soil less than 2.0
mm.

Definition: More than 40% by weight serpentine minerals
(antigorite, chrysotile, fibrolite, and talc).

Determinant size fraction: Whole soil, particles less than
2.0 mm in diameter.

" percentage of clay or percentage of 1500 kPa water retention tines
2.3, whichever 1s greater, provided the ratio of 1500 kPa water
Fetention to olay is 0-6 or more in half oF nore of the control section.


268
JCAF, Other Humitropepts that:

1. Have a content of organic carbon that decreases
irregularly with depth to the base of the cambic horizon;

and

2. Have slopes of 25 percent or less.
Fluventic Humitropepts
JCAG. Other Humitropepts that:

1, Have an ustic moisture regime; and

2. Have a CEC (by NH,OAc pH 7) of less than 24

emol(+) per kg clay’ in the major part of the soil below

a depth of 25 cm but above 100 em or a lithic or paralithic

contact if one is shallower than 100 cm.

Ustoxic Humitropepts

JCAH. Other Humitropepts that have a CEC (by NH,OAc
pH 7) of less than 24 cmol(+) per kg clay" in the major
part of the soil below a depth of 25 cm but above 100 cm or a
lithic or paralithic contact if one is shallower than 100
cm.

Oxic Humitropepts
JCAL Other Humitropepts that have an ustic soil moisture
regime.
Ustic Humitropepts
JCAJ, Other Humitropepts.
‘Typic Humitropepts

Sombritropepts

These soils are the dark, humus-rich Tropepts of
perhumid, cool, hilly or mountainous regions. They have
a sombric horizon in or below a cambic horizon. Most of
them have an umbric epipedon, a perudic soil moisture
regime, and an isomesic temperature regime. They are
not known to occur in the United States and their
classification has not been developed.

Ustropepts
Key to subgroups
ICCA. Ustropepts that have a lithic contact within 50 cm of
the soil surface.
Lithic Ustropepts

3
‘Same cambic horisons that have properties that approach those ofan eric horison donot

aperve well, Ifthe ratia af the percentage of water retained at terminn ef 1500 KPa to the

percentage of day is 0.6 o more, the par of clay we determined by the

higher value of (1) the measured parcantage of clay or (2.8 tines the percentage of water

retained at tension of 1600 kPa.

“

‘Sane cambie horisons that beve propertion that approach thove ofan exic bariaan do nat
inperve well, Ifthe ratio ofthe percentage of water retained at tension of 1500 kPa te the
percentage of lay in 06 or more, the of day ia detereninved by the
higher value of (1) the measured perventage of clay or (2) 2.8 times the percentage of water
retained at tansion of 1500 kPa,



204
Cryofluvents

Key to subgroups

KDAA. Cryofluvents that have, throughout a cumulative
thickness of 18 em or more and within a depth of 75 cm,
bulk density of the less than 2.0 mm fraction, measured
at 33 kPa water retention, of 1.0 g cm or less and acid-
oxalate-extractable aluminum plus 1/2 acid-oxalate-
extractable iron of more than 1.0 percent.

Andic Cryofluvents
KDAB. Other Cryofluvents that have, throughout a
cumulative thickness of 18 cm or more and within a
depth of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Vitrandic

KDAC. Other Cryofluvents that have mottles that have
chroma of 2 or less within 50 cm of the soil surface.

‘Aquic Cryofluvents

KDAD. Other Cryofluvents that have an Ap horizon that

has a color value, moist, of 3 or less and a color value,

dry, of 5 or less when crushed and smoothed, or the A

horizon is 15 em or more thick and has these colors.
Mollic

KDAE. Other Cryofluvents.
‘Typic Cryofiuvents
Torrifluvents
Key to subgroups
KDDA. Torrifluvents that:
1. Have all three of the following characteristics:
a. Cracke at some period in most years that are 1 cm
or more wide at a depth of 50 em, that are at least 30
cm long in some part, and that extend upward to the
soil surface or to the base of an Ap horizon; and
b. A coefficient of linear extensibility (COLE) of
0.05 or more in a horizon or horizons at least 50 cm

thick, and a potential linear extensibility of 6 cm or
more in the upper 150 cm of the soil or in the whole


304

lithic or paralithic contact is deeper than 60 cm but
shallower than 125 cm; and

c. More than 35 percent clay in horizons that total
more than 50 cm in thickness; and

2. The cracks are open 6 months or more in most years.
Torrertic

HFED. Other Argiustolls that:

1, When neither irrigated nor fallowed to store
moisture:

a. If the soil temperature regime is mesic or thermic,
are dry in some or all parts of the moisture control
section for four-tenths or less of the cumulative days
when the soil temperature at a depth of 50 cm exceeds
5°C; or

b. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or
less during a period when the soil temperature at a
depth of 50 cm exceeds 8°C; and

2, Have the following combination of characteristics:

a, Cracks at some period in most years that are 1cm
or more wide at a depth of 50 cm, that are at least 30
em long in some part, and that extend upward to the
surface or to the base of an Ap horizon; and

b. A coefficient of linear extensibility (COLE) of 0.07
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more
in the upper 125 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 125 cm; and

c. More than 35 percent clay in horizons that total
more than 50 cm in thickness; and

3. The cracks are open less than 135 days in most
years.
Udartic Argiustolls

HFEE, Other Argiustolls that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the surface
or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.07 or
more in a horizon or horizons at least 50 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 125 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 126 cm; and


148
kPa water retention in some subhorizon that meets the
requirements for andic soil properties and that is at least
25 cm thick within 100 cm of the mineral soil surface or
of the upper boundary of an organic layer with andic soil
properties, whichever is shallower.
Pachic Vitric Melanudands

BGCK. Other Melanudands that have a sum of bases of
more than 25.0 cmol(+) kg’ fine earth throughout some
subhorizon 15 cm or more thick between 25 and 75 cm,
and have less than 30 percent, undried, 1500 kPa water
retention in some subhorizon that meets the
requirements for andic soil properties and that is at least
25 em thick within 100 cm of the mineral soil surface or
of the upper boundary of an organic layer with andic soil
properties, whichever is shallower.

Eutric Vitric Melanudands

BGCL. Other Hapludands that have less than 30 percent,

undried, 1500 kPa water retention in some subhorizon

that meets the requirements for andic soil properties and

that is at least 25 cm thick within 100 cm of the mineral

soil surface or of the upper boundary of an organic layer

with andic soil properties, whichever is shallower.
Vitric

BGCM. Other Melanudands that have, undried, 1500
kPa water retention of 70 percent or more throughout a
continuous thickness of 35 cm or more within the upper
100 cm, and have both more than 6.0 percent organic
carbon and colors of the mollic epipedon throughout at
least 50 cm of the upper 60 cm, excluding any overlying
layers that do not have andic soil properties.

Hydric Pachic Melanudands

BGON. Other Melanudands that have both more than 6.0

percent organic carbon and colors of the mollic epipedon
Ehroughout at least 60 cm of the upper 60 cm, excluding
any overlying layers that do not have andic soil
properties.

Pachic Melanudands

BGCO. Other Melanudands that have a sum of bases of
more than 25.0 cmol(+) kg” fine earth throughout some
subhorizon 15 cm or more thick between 25 and 75 cm, and
have, undried, 1500 kPa water retention of 70 percent or
more throughout a continuous thickness of 35 cm or more
within the upper 100 cm of the mineral soil surface or of
the upper boundary of an organic layer with andic soil
properties, whichever is shallower.

Eutric Hydric Melanudands

BGCP, Other Melanudands that have, undried, 1500 kPa
water retention of 70 percent or more throughout a
continuous thickness of 35 cm or more within the upper
100 cm of the mineral soil surface or of the upper boundary
of an organic layer with andic soil properties, whichever

is shallower.
Hydric Melanudands

BGCQ. Other Melanudands that have, between 40 and 100
cm, a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm


34

90 consecutive days when the soil temperature at a depth of
50 cm is continuously higher than 8°C. In addition, the
mean annual soil temperature is lower than 22°C, and
mean summer and mean winter soil temperatures differ
by 5°C or more at a depth of 50 cm or at a lithic or paralithic
contact, whichever is shallower.

Soil temperature regimes
Classes of soi] temperature regimes

The following soil temperature regimes are used in
defining classes at various categoric levels in the
taxonomy,

Pergelic (L. per, throughout in time and space, and L.
gelare, to freeze; connoting permanent frost).—Soils with
a pergelic temperature regime have a mean annual
temperature lower than 0°C. These are soils that have
permafrost if they are moist, or dry frost if excess water is
not present. It seems likely that the moist and the dry
pergelic regimes should be defined separately, but at
present we have only fragmentary data on the dry soils of
very high latitudes.

Cryic (Gr, kryos, coldness; connoting very cold soils).
In this regime soils have a mean annual temperature
higher than 0°C (32°F) but lower than 8°C (47°F),

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) at a depth of 50 em or at a 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) There is no O horizon, lower than 15°C (59°F); or
(2) There is an O horizon, lower than 8°C (47°F);

b. If the soil is saturated with water during some part of
the summer, and

(1) There is no O horizon, lower than 13°C (55°F); or

(2) There is an O horizon or a histic epipedon, lower
than 6°C (42°F).

2. In organic soils, either

a. The soil is frozen in some layer within the control
section in most years about 2 months after the summer
solstice; that is, the soil is very cold in winter but
warms up slightly in summer; or


68
TABLE 2 - KEY TO MINERALOGY CLASSES OF
OXISOLS

Does the mineralogy control section have:

1, More than 40 percent iron oxide (more than 28 percent
Fe) by citrate-dithionite in the less than 2.0 mm
fractions?

2. More than 40 percent gibbsite in the less than 2.0 mm
fractions?

3, 18-40 percent iron oxide (12.6- 28 percent Fe) by citrate-
dithionite in the less than 2.0 mm fractions?

4. 18-40 percent gibbsite in the less than 2,0 mm fractions?

5. More than 50 percent by weight kaolinite in the leas
than 0.002 mm fraction?

6. More than 60 percent by weight halloysite in the less
than 0.002 mm fraction?
None of the above---Mixed

1 with or without 2, 4, 5, 6-—Ferritie

2 with or without 3, 5, 6---Gibbsitic

3 with or without 5, 6—Ferruginous

4 with or without 5, 6---Allitic.

Sand 4 with or without 5, 6--Sesquic
§---Kaolinitic

6---Halloysitic


191

1. Have a duripan that is not indurated in any
subhorizon; and

2. Have a duripan whose upper boundary is 18 cm or
deeper, and have a weighted average content of
organic carbon in the upper soil to a depth of 40 cm that
is 0.6 or more if the weighted average ratio of sand to
noncarbonate clay above that depth is 1.0 or less, or is
0.15 percent or more if the ratio is 13 or more, or is
intermediate if the ratio of sand to clay is between 1.0
and 13; and

3. Have a mean annual soil temperature lower than

22°C, mean summer and mean winter soil

temperatures at a depth of 50 cm that differ by 5°C or

more, and have an aridic moisture regime that

borders on a xeric regime.

Haploxerollic Durorthids

FBCF. Other Durorthids that have the following
combination of characteristics:

1, Have a duripan that is not indurated in any
subhorizon; and

2. Have a duripan whose upper boundary is 18 cm or
deeper, and have a weighted average content of
organic carbon in the upper soil to a depth of 40 cm that
is 0.6 or more if the weighted average ratio of sand to
noncarbonate clay above that depth is 1.0 or less, or is
0.15 percent or more if the ratio is 13 or more, or is
intermediate if the ratio of sand to clay is between 1.0
and 13; and

3. Have an aridic moisture regime that borders on an
ustic regime.
Haplustollic Durorthids

FBCG, Other Durorthids that have the following
combination of characteristics:

1. Have a duripan whose upper boundary is 18 cm or
deeper, and have a weighted average content of
organic carbon in the upper soil to a depth of 40 cm that.
is 0.6 or more if the weighted average ratio of sand to
noncarbonate clay above that depth is 1.0 or less, or is
0.15 percent or more if the ratio is 13 or more, or is
intermediate if the ratio of sand to clay is between 1.0
and 13; and

2. Have a mean annual soil temperature lower than
22°C, mean summer and mean winter soil
temperatures at a depth of 50 em that differ by 5°C or
more, and have an aridic moisture regime that

borders on a xeric regime.
Xerollic Durorthids
FBCH. Other Durorthids that are dry in all parts of the
moisture control section for three-fourths or less of the
time that the soil temperature at a depth of 50 cm is 5°C or
higher, and have an aridic moisture regime that borders

on a xeric regime.
Xerochreptic Durorthids


300

of 75 em, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm’ or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andie Hapludolls
HGDD. Other Hapludolls that have, throughout a

cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a, More than 80 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vitrandic Hapludolls

HGDE. Other Hapludolls that:

1, Have a mollic epipedon 60 cm or more thick with a
texture finer than loamy fine sand; and

2. Have an irregular decrease in organic carbon
content with increasing depth, or have an organic
carbon content of more than 0.3 percent at a depth of 125
cm below the surface and no lithic or paralithic contact
within a depth of 125 em; and

3. Have a slope of 25 percent or less.
‘Cumulic Hapludolls

HGDF. Other Hapludolis that:

1. Have mottles within 40 cm of the surface and, unless
artificially drained, the mottled horizon is saturated
with water at some period of the year when the soil
temperature in the mottled horizon is above 5°C, or have
a horizon 15 cm or more thick immediately below the
mollic epipedon that:

a. Has a hue of 10YR or redder and chroma of 2 or
less, or has mottles that have chroma of 2 or less and
value of 4 or more and, unless artificially drained,
the mottled horizon is saturated with water at some
period of the year when the soil temperature in the
mottled horizon is above 5°C; or

b. Has a hue of 2.5Y or yellower and chroma of 3 or
less; and

2. Have an irregular decrease in organic carbon
content with increasing depth or have an organic
carbon content of more than 0.3 percent at a depth of 125
cm below the surface; and


422

material. Where two or more consecutive horizons
formed in one kind of material, the same prefix number
is applied to all of the horizon designations in that
material: Ap-E-Bt1-2Bt2-2Bt3-2BC. The number of
suffixes designating subdivisions of the Bt horizon
continue in consecutive order across the discontinuity.

Tf an R layer is below a soil that formed in residuum and
the material of the R layer is judged to be like that from
which the material of the soil weathered, the Arabic
number prefix is not used. If the R layer would not
produce material like that in the solum, the number
prefix is used, as in A-Bt-C-2R or A-Bt-2R. If part of the
solum formed in residuum, "R" is given the appropriate
prefix: Ap-Bt1-2Bt2-2Bt3-2C1-2C2-2R.

Buried horizons (designated "b") are special problems.
A buried horizon is obviously not in the same deposit as
horizons in the overlying deposit. Some buried horizons,
however, formed in material lithologically like that of
the overlying deposit. A prefix is not used to distinguish
material of such buried horizons. If the material in
which a horizon of a buried soil formed is lithologically
unlike that of the overlying material, the discontinuity
is designated by number prefixes and the symbol for a
buried horizon is used as well: Ap-Bt1-Bt2-BC-C-2ABb-
2Btb1-2Btb2-2C.

In organic soils, discontinuities between different kinds
of layers are not identified. In most cases the

differences are shown by the letter suffix designations,
if the different layers are organic, or by the master
symbol if the different layers are mineral.

USE OF THE PRIME

Identical letter and numeral designations may be
appropriate for two or more horizons separated by at least
one horizon or layer of a different kind in the same
pedon, The sequence A-E-Bt-E-Btx-C is an example:
the soil has two E horizons. To make communication
easier, the prime is used with the master horizon symbol
of the lower of two horizons having identical
designations: A-E-Bt-E'-Btx-C, The prime is applied to
the capital letter designation, and any lower case
symbols follow it: B’t. The prime is not used unless all
designations of two different layers are identical.
Rarely, three layers have identical symbols; a double
prime can be used: E".

The same principle applies in designating layers of
organic soils. The prime is used only to distinguish two
or more horizona that have identical symbols: Oi-C-O'i-
C’ or Oi-C-Oe-C’. The prime is added to the lower C
layer to differentiate it from the upper.


197

KAE. Other Aquents that have a difference of less than
5°C between the mean summer and mean winter soil

tomperatures at a depth of 50 cm.
‘Tropaquents, p. 202

KAF. Other Aquents that have a sandy particle-size
class in all subhorizons between the Ap horizon or a
depth of 25 cm, whichever is deeper, and 100 cm or a lithic
or paralithic contact, whichever is shallower, and that
have mean summer and mean winter soil temperatures
at a depth of 50 cm that differ by 5°C or more.

p.201
KAG. Other Aquents.
Haplaquents, p. 200
Cryaquents
Key ta subgroups

KACA. Cryaquents that have, throughout a cumulative
thickness of 18 cm or more and within a depth of 75 cm,
one or more of the following:

1. Bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm’? or
Joss and acid-oxalate-extractable aluminum plus 1/2
acid-oxalate-extractable iron of more than 1.0 percent;
or

2, Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or

3, The 0.02 to 2.0 mm fraction constitutes at least 30
ereent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or
b. At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of 0.40 percent or more.

‘Cryaquents
KACB. Other Cryaquents.
Typic Cryaquents
Fluvaquents
Key to subgroups

KADA. Fluvaquents that have sulfidic materials within
100 cm of the mineral] soil surface.
Sulfic Fluvaquents

KADB. Other Fluvaquents that have the following
combination of characteristics:

1, Cracks at some period in most years that are 1 cm or
more wide at a depth of 60 cm, that are at least 30 cm


310

2. If the soil temperature regime is hyperthermic or
isomesic, or warmer, are moist in some or all parts of
the moisture control section for less than 90 consecutive
days during a period when the soil temperature at a
depth of 50 cm exceeds 8°C; and

3. Have an aridic moisture regime that borders on
ustic,
Aridic Durustolls

HFAD. Other Durustolls that do not have an argillic
horizon above the duripan.
Entic Durustolls

HFAE. Other Durustolls that have a duripan that is not
massive or platy or that has less than half of its upper
boundary coated or indurated with opal and silica with or
without sesquioxides and that is not indurated in some
subhorizon below its upper boundary.

Haplic Durustolls
HFAF. Other Durustolls.
‘Typic Durustolls
Haplustolls
Key to subgroups

HFGA. Haplustolls that have a salic horizon that has its
upper boundary within 75 cm of the surface.
Salorthidic Haplustolis
HFGB. Other Haplustolls that:
1. Have a lithic contact within 50 cm of the surface; and
2, Have a cambic horizon in some part but less than
half of each pedon.
Lithic Ruptic-Entic Haplustolls
HFGC, Other Haplustolls that have a lithic contact within
50 cm of the surface in a part of each pedon.
Ruptic-Lithic Haplustolls
HFGD. Other Haplustolls that have a lithic contact within
50 cm of the surface.
Lithic Haplustolls
HFGE. Other Haplustolls that:
1. Have the following combination of characteristics:
a. Cracks at some period in most years that are 1cm
or more wide at a depth of 50 cm, that are at least 30
cm long in some part, and that extend upward to the
surface or to the base of an Ap horizon; and
b. A coefficient of linear extensibility (COLE) of 0.07
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more
in the upper 125 cm of the soil or in the whole soil if e

lithic or paralithic contact is deeper than 50 cm but
shallower than 125 cm; and


103

2, A coefficient of linear extensibility (COLE) of 0.09 or
more in a horizon or horizons at least 50 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 100 cm of the soil, or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 100 cm; and

3. More than 35 percent clay in horizons that total more
than 50 cm in thickness.
Vertic Natrudalfs

IEBB. Other Natrudalfs that have tonguing or
interfingering of albic materials more than 2.5 cm into
the natric horizon.

Glossic Natrudalfs

IEBC. Other Natrudalfs that have an Ap horizon that has a
color value, moist, of 2 or less, or the soil to a depth of 18
cm, after mixing, has that color value.

Mollic Natrudalfs

IEBD. Other Natrudalfs that do not have mottles that have
chroma of 2 or less within 26 cm of the upper boundary of
the natric horizon.

Aeric Natrudalfs
TEBE. Other Natrudalfs.

Typic Natrudalfs
Paleudalfs
Key to subgroups

IEIA. Paleudalfs that have the following combination of
characteristics:

1, Cracks at some period in most years that are 1em or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part and that extend upward to the surface
or to the base of an Ap horizon; and

2, A coefficient of linear extensibility (COLE) of 0.09 or
more in a horizon or horizons at least 50 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 100 cm of the soil, or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 100 cm; and

3, More than 36 percent clay in horizons that total more
than 60 cm in thickness.
Vertic Paleudalfs

IEIB. Other Paleudalfs that:
1, Have mottles that have chroma of 2 or less within 75

cm of the soil surface, and the mottled horizons are
saturated with water at some time when the soil


168
in a nonbrittle matrix or is brittle and has firm

consistence when moist.
Duric Haplargids
FAEQ. Other Haplargids that have:

1. A weighted average percentage of organic carbon in
the upper 40 cm that is 0.6 percent or more if the
weighted average ratio of sand to clay in the soil above
that depth is 1.0 or leas, or is one-seventh percent or
more if the ratio is 13 or more, or is intermediate
between 0.6 percent and one-seventh percent if the
ratio of sand to clay is between 1.0 and 13; anda
weighted average percentage of organic carbon in the
soil to a depth of 18 cm that is one-fifth or more higher
than the values just stated if there ig a paralithic
contact at a depth of less than 40 em but more than 18
em; ani

2. A mean annual soil temperature lower than 22°C,
mean summer and mean winter soil temperatures at
a depth of 50 cm that differ by 5°C or more, and an
aridic moisture regime that borders on a xeric

regime.
Xerollic Haplargids
FAER. Other Haplargids that are:

1. Dry in all parts of the moisture control section three-
fourths or less of the time (cumulative) that the soil
temperature is 5°C or higher at a depth of 50 cm; and

2, Have a mean annual soi] temperature lower than
22°C, mean summer and mean winter soil
temperatures at a depth of 50 cm that differ by 6°C or
more, and an aridic moisture regime that borders on a

xeric regime.
Xeralfic Haplargids
FAES. Other Haplargids that have:

1. A weighted average percentage of organic carbon in
the upper 40 cm that is 0.6 percent or more if the
weighted average ratio of sand to clay in the soil above
that depth is 1.0 or Jess, or is one-seventh percent or
more if the ratio is 13 or more, or is intermediate
between 0.6 percent and one-seventh percent if the
ratio of sand to clay is between 1,0 and 13; anda
weighted average percentage of organic carbon in the
soil to a depth of 18 cm that is one-fifth or more higher
than the values just stated if there is a paralithic
contact at a depth of leas than 40 em but more than 18
om; an

2, A mean annual soil temperature of 8°C or higher
and an aridic moisture regime that borders on an

ustic regime.
Ustollic Haplargids
FAET. Other Haplargids that are:
1. Dry in all parts of the moisture control section three-

fourths or less of the time (cumulative) that the soil
temperature is 5°C or higher at a depth of 50 cm; and


126
IDGO. Other Haploxeralfs.
‘Typic Haploxeralfa

Natrixeralfs

Key to subgroups:

IDBA. Natrixeralfe that have mottles that have chroma of
2 or less within 75 cm of the soil surface and there is
ground water in the mottled horizon at some time when
the temperature of that horizon is 5°C or higher.

Aquic Natrixeralfs
IDBB. Other Natrixeralfs.

Typic Natrixeralfs
Palexeralfs
Key to subgroups

IDFA. Palexeralfs that have the following combination of
characteristics:

1, Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm
Jong in some part and that extend upward to the surface
or to the base of an Ap horizon if the soil is not irrigated;
and

2. A coefficient of linear extensibility (COLE) of 0.05 or
more in a horizon or horizons at least 50 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 150 em of the soil or in the whole sojl if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 150 cm, and

3, More than 86 perent clay in horizons that total more
than 50 cm in thickness.
Vertic Palexeralfs

IDFB. Other Palexeralfe that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 gcmTM or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic Palexeralfs

IDFC. Other Palexeralfs that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or


253
JDBE. Other Durochrepts that do nat have a platy or

massive indurated duripan,
Entic Durochrepts

JDBF. Other Durochrepts that have base saturation (by

NH,OAc) of less than 60 percent throughout the soil

between depths of 25 and 75 cm below the soi] surface.
Dystric:

SDBG. Other Durochrepts.
‘Typic Durochrepts

Dystrochrepts
Key to subgroups

JDGA. Dystrochrepts that:

1. Have a lithic contact within 60 cm of the soil surface;
and

2, Have an argillic horizon in less than half of each
pedon, and the base saturation (by sum of cations) in the
subhorizon just above the lithic contact is 35 percent or

more.
JDGB. Other Dystrochrepts that;

1. Have a lithic contact within 50 cm of the soil surface;
and

2. Have an argillic horizon in less than half of each
pedon and have base saturation (by sum of cations) in
the subhorizon just above the lithic contact that is less

than 35 percent.
Lithic Ruptic-Ultic Dystrochrepts
JDGC. Other Dystrochrepts that have a lithic contact
within 50 cm of the soil surface.
Lithic Dystrochrepts

JDGD. Other Dystrochrepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm” or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

SDGE. Other Dystrochrepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2, The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:


44
Subsurface tier

The subsurface tier is 60 em (24 in.) thick unless the
control section ends at a lithic or paralithic contact or at
water within this depth or unless the soil is frozen at too
shallow a depth. In any of these situations the subsurface
tior extends from the base of the surface tier to the base of
the control section. It includes any unconsolidated
mineral layers that may be present within those depths.

Bottom tier

The bottom tier is 40 cm (16 in.) thick unless the control
section stops within the maximum span.

The control section is terminated at a shallower depth by
water or by a lithic or a paralithic contact, or at a depth 25
cm (10 in.) below a layer that is frozen 2 months after the
summer solstice.


pumice-like fragments make up more than 66 percent
of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At Jeast § percent volcanic glass and acid-oxalate-
extractable aluminum plus V/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vitrandie Cryoboralfs

IBDE. Other Cryoboralfs that have mottles that have
chroma of 2 or less within 75 cm of the surface, or the soils
are continuously saturated with water for 3 months or
Jonger within 100 cm of the surface where undrained.
Aquic Cryoboralfs

IBDF, Other Cryoboralfs that have an argillic horizon

that has a texture that is loamy fine sand or coarser or is

discontinuous vertically in the upper 15 cm (in lamellae).
Psammentic

IBDG, Other Cryoboralfs that have an Ap horizon that has
acolor value, moist, of 3 or less, or the upper soil has a
moist color value of 3 or less after mixing to a depth of 15
cm. :
‘Mollie Cryoboralfs

IBDH. Other Cryoboralfs that have albic materials
tonguing in an argillic horizon.

Glossic Cryoboralfs

IBDI. Other Cryoboralfs.
Typic Cryoboralfs

Eutroboralfs
Key to subgroups
IBEA. Eutroboralfs that have a lithic contact within 50 cm.
of the surface.

Lithic Eutroboralis

IBEB. Other Eutroboralfs that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 gem TM or less
and acid-oxalate-extractable iron of more than 1.0

percent.
Andic Eutroboralfs

IBEC. Other Eutroboralfs that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:


7

(2) If there are no underlying diagnostic horizons
and the organic-carbon content of the underlying
materials decreases irregularly with increasing
depth (as in recent alluvium that is not finely
stratified); or

e, In other soils, the epipedon must be 18 cm (7 in.) or
more thick if none of the conditions that are listed in 6,
¢, and d exist.

6. The epipedon has less than 250 parts per million (ppm)
of P20s soluble in 1 percent citric acid, or it either has
increasing amounts of P2Os soluble in citric acid below
the opipedon or the amounts of P20s soluble in citric acid
decrease or increase irregularly with depth below the
cpipedon, or there are phosphate nodules within the
epipedon. This restriction is made to eliminate plow
layers of very old arable soils and kitchen middens that
have acquired, under use, the properties of the mollic
epipedon, but to include the epipedon of a soil developed in
highly phosphatic parent material.

7. If the soil is not irrigated, some part of the epipedon is
moist 3 months or more of the year (cumulative) in more
than 7 out of 10 years at times when the soil temperature at
a depth of 50 cm is 5°C or higher.

8. The n value (defined later in this chapter) is less than
0.7, Although many soils that have a mollic epipedon are
very poorly drained, a mollic epipedon does not, have the
very high water content of sediments that have been
continuously under water since deposition.

Ochric epipedon (Gr. ochros, pale)

An ochric epipedon is one that is too high in value or
chroma, is too dry, has too little organic matter, has ann
value too high, or is too thin to be mollic, umbric,
anthropic, plaggen or histic, or it is both hard and

massive when dry. An epipedon is ochric if the Munsell
color value after rubbing is 6 or higher when dry or 4 or
higher when moist, if the chroma is 4 or more’, or ifthe A
or Ap horizon that has both low value and low chroma is
too thin to be a mollic or an umbric epipedon. Epipedons
that have a color value after rubbing of 5 or less, dry, and 3
or less, moist, are also ochric provided they are no darker
than the 1C horizon and do not have as much as 0.6 percent
more organic carbon than the 1C horizon. The ochric
epipedon includes eluvial horizons that are at or near the
surface (the E horizon and an albic horizon, which is
defined later) and extends to the first underlying
diagnostic illuvial horizon (defined later as an argillic,

2 the chroma iz permitted to range up to but not to include 4.0 soils
Uhat have @ hyperthermic or taohypertheraic teaperature regine, The
color when moist i¢ that of a specinen that is moist enough that an
additional drop of water produess no change in the color. the color
whan dry $e that of a apecinan dry enough that continued drying produase
fo further change.


926

(2) At least 6 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Vitritorrandic

HDAB. Other Durixerolls that have, throughout a
cumulative thickness of 18 em or more and within a depth
of 75 em, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more than
86 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2, The 0.02 to 2.0 mm fraction constitutes at least 30
Perce nt of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 6 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vitrandic Durixerolls

HDAC. Other Durixerolls that have mottles that have
chroma of 2 or less above the duripan.
Aquic Durixerolls

HDAD. Other Durixervlls that:
1, Have an argillic horizon that has an increase in
clay content of 20 percent (absolute) or more within a
vertical distance of 7.5 cm or an increase of 15 percent
or more (absolute) within a distance of 2.5 cm at the
upper boundary; and

2, Have an aridic moisture regime.
ic Avidic Durixerolis

HDAE. Other Durixerolls that:

1. Do not have an argillic horizon above the duripan;
and

2, Have an aridic moisture regime.

Orthidic Durixerolls
HDAF. Other Durixerolls that have an aridic moiature
regime.
Aridic Durixerolls

HDAG, Other Durixervlls that have an argillic horizon
that has an increase in clay content of 20 percent
(absolute) or more within a vertical distance of 7.5 cm or
an increase of 16 percent or more (absolute) within a
distance of 2.5 cm at the upper boundary.

Abruptie Durixerolls

HDAH, Other Durixerolls that:
1. Do not have a duripan that is massive, platy, or

prismatic and that has half or more of its upper
boundary indurated or coated with opal or opal and


TABLE OF CONTENTS
Chapter 1: The Soil That We Classify and Horizons
and Properties Diagnostic fo for r the he Higher Categori
Mineral Soils.

Chapter 2: Horizons and Properties Diagnostic

for the Higher Categories: Organic Soils. ............. E-)
Chapter 3: Family Differentiae..............s.0esseeseeees 5
Table 1. Key to Mineralogy Classes..............060065 8

Table 2. Key to Mineralogy Classes of

Chapter 4: Identification of the

Taxonomic Class of a Soil
Chapter 5: AMsols........6...ccscseseeeeseeesesseseeesseees B
Chapter 6: Andisols............-.:.scceseeeeereseeeeesereree 129
Chapter 7: Aridisols .........c.csccseesessseeeeeneeeeseteres 1
Chapter 8: Entisols .........--..ssscceeessseeesscceeessenes 195
Chapter 9: Histosols ...........0.cccseessesseeseeeeausererer 25
Chapter 10: Inceptisols .........s:ccssscesceesseeteseeneeens poe
Chapter 11: Mollisols ..........c:ccsescescseeseseeeesceseaes 275
Chapter 12: Oxisols ...........-:seseeeeeeestnteeeeeeteeeenee 335
Chapter 18: Spodosols ..........-.:6s:eccssereeeeeeeeeretnee 357
Chapter 14: Ultisols .............:ccsseeeeserensenterevenees p
Chapter 15; Vertisols...... OT
SI Units Conversion Table ............:::::sceereeeetteee a2
Designations for Horizons

and Layers + A3

Textural Triangle . . Inside back cover


ICDC. Other Eutropepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm’ or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

JICDD, Other Eutropepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vi

fitrandic Eutropepts
JCDE. Other Eutropepts that:

1. Have a content of organic carbon'! that decreases
irregularly with depth, or are 125 cm or more deep to a
lithic or a paralithic contact and have more than 0.2
porcont organic carbon at 125 em below the sll surface;
an

2, Have slopes of 25 percent or less; and

3. Have mottles that have chroma of 2 or less within 100
cm of the soil surface, and the mottled horizon is
saturated with water at some time during the year, or
there is artificial drainage.

Fhwoaquentic Eutropepts

JCDF, Other Eutropepts that have mottles that have
chroma of 2 or less within 100 cm of the soil surface, and
the mottled horizon is saturated with water at some time
during the year, or there is artificial drainage.

JCDG. Other Eutropepts that:

1. Have a content of organic carbon’? that decreases
irregularly with depth, or are 125 cm or more deep toa
lithic or a paralithic contact and have more than 0.2
percent organic carbon at 125 em below the soil surface;
an

u
‘Tha carbon shauld bn of Holocene age. It ia not the intent to mnchade foes carbon from

bedrock.

12 ye carbon should be of Halecane age, It ia not the intent to include fowl carbon from

bedrock.


150
within 100 cm of the mineral aoil surface or of the upper
boundary of an organic layer with andic eoil properties,

whichever is shallower.
Eutric Vitric Placudands

BGAF. Other Placudands that have less than 30 percent,
undried, 1500 kPa water retention in some subhorizon
that meets the requirements for andic soil properties and
that is at least 25 om thick within 100 cm of the mineral
soil surface or of the upper boundary of an organic layer
with andic soil properties, whichever is shallower.

Vitric Placudands

BGAG. Other Placudands that have, undried, 1500 kPa
water retention of 70 percent or more throughout a
continuous thickness of 35 cm or more within the upper
100 cm, and have both more than 6 percent organic carbon
and colors of the mollic epipedon throughout at least 50cm
of the upper 60 cm, excluding any overlying layers that do
not have andic soil properties.

Hydric Pachic Placudands

BGAH. Other Placudands that have both more than 6.0

percent organic carbon and colors of the mollic epipedon

throughout at least 50 cm of the upper 60 cm, excluding any

overlying layers that do not have andic soil properties.
Pachic

BGAI, Other Placudands that have, undried, 1500 kPa
water retention of 70 percent or more throughout a
continuous thickness of 35 cm or more within the upper
100 cm of the mineral soil surface or of the upper boundary
of an organic layer with andic soil properties, whichever

is shallower.
Hydric Placudands

BGAJ, Other Placudands that have, between 25 and 100
em, a layer 10 em or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the

underlying layer.
‘Thaptic Placudands

BGAK, Other Placudands that have a sum of bases of
more than 25.0 cmol(+) kg fine earth throughout some
subhorizon 15 cm or more thick between 25 and 75 cm of
the mineral soil surface or of the upper boundary of an
organic layer with andic soil properties, whichever is

shallower.

Eutric Placudands
BGAL. Other Placudands.

Typic Placudands
USTANDS
Key to great groups

BFA. Ustands that have a duripan with its upper boundary
within 100 em of the mineral soil surface.
Durustands, p. 151


287

2, Have an albic horizon immediately below the mollic
epipedon; and

8, Have a lithic contact within a depth of 50 cm of the
surface.
Boralfic Lithic Cryoborolls

HEBB. Other Cryoborolls that have an argillic horizon

that is continuous throughout each pedon, and have a

lithic contact within a depth of 50 cm of the surface.
Argic Lithic

HEBC, Other Cryoborolls that have a lithic contact within
a depth of 60 cm of the surface and have a mollic epipedon
that is discontinuous in each pedon.

Lithic RupticEntic Cryoborolls

HEBD. Other Cryoborolls that have a lithic contact within
a depth of 50 cm of the surface and have an argillic
horizon that is intermittent in each pedon,

Lithic Ruy

iptic-Argic Cryoborolls
HEBE. Other Cryoborolls that have a lithic contact within
a depth of 50 cm of the surface.
Lithic Cryoborolls

HEBF. Other Cryoborolls that have a mean annual soil

temperature of 0°C or less.
Pergelic Cryoborolls

HEBG. Other Cryoborolls that have an argillic horizon
and an SAR of 13 or more (or 15 percent or more
saturation with exchangeable sodium) in the major part

of the argillic horizon.
Natric Cryoborolls

HEBH, Other Cryoborolls that have an argillic horizon
and the following combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30cm
long in some part, and that extend upward to the surface
or ta the base of an Ap horizon; and

2. A potential linear extensibility of 6 cm or more in the
upper 100 cm of the soil or the whole soil if ‘a lithic or
paralithic contact is deeper than 50 cm but shallower
than 100 cm; and

3, More than 35 percent clay in horizons that total more
than 60 cm in thickness.
Argic Vertic Cryoborolls

HEBIL. Other Cryoborolls that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1. cm or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the surface
or to the base of an Ap horizon; and

2. A potential linear extensibility of 6 cm or more in the
upper 100 cm of the soil or the whole soil if a lithic or


ay

1. The fiber content after rubbing is three-fourths’ or more
of the soil volume, excluding coarse fragments and
mineral layers; or

2. The fiber content after rubbing is two-fifths or more of
the soil volume, excluding coarse fragments and
mineral layers, and the material yields a sodium
pyrophosphate extract color on white chromatographic
paper that has value and chroma of 7/1, 7/2, 8/1, 8/2, or &/3
(Munsell designations).

Hemic coil materials

Hemic soil materials (Gr. hemi, half; implying
intermediate decomposition) are intermediate in degree
of decomposition between the less decomposed fibric and
the more decomposed sapric materials. They have
morphological features that give intermediate values for
fiber content, bulk density, and water content. They are
partly altered both physically and biochemically.

Sapric soil materials (Gr. sapros, rotten)

These are the most highly decomposed of the organic
materials, They normally have the smallest amount of
plant fiber, the highest bulk density, and the lowest water
content on a dry-weight basis at saturation. They 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 the others.

Sapric materials have the following characteristics:

1. The fiber content after rubbing is less than one-sixth of
the soil volume, excluding coarse fragments and
mineral layers; and

2. The sodium pyrophosphate extract color on
chromatographic paper is below or to the right of a line
drawn to exclude blocks 5/1, 6/2, and 7/3.

Humilluvic materials

Iuvial humus accumulates in the lower parts of some
organic soils if they are acid and have been drained and
cultivated. The illuvial humus has a younger CTM* age
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 illuvial humus
should constitute at least half the volume of a layer at least
2 cm thick.

" ractions are used rather than percentages to avoid inplying = higher
degree of accuracy than is warranted.


405
GEBH. Other Haploxerults.
‘Typic Haploxerults
Palexerults ‘
Palexerults are the Xerults that
1. Have both the following characteristics:

a. An argillic horizon that in its upper 60 cm has
Jess than 10 percent weatherable minerals in the 20-
to 200-micron fraction; and

b. Aclay distribution such that the percentage of
clay does not decrease from its maximum amount
by more than 20 percent within 150 cm of the soil
surface, or the layer in which the percentage of clay
js less than the maximum has skeletans on ped
faces or has 5 percent or more plinthite by volume;
and

2. Have a color value, moist, of 4 or more in some part
of the epipedon or have an argillic horizon that has a
color value, dry, of 5 or more in some subhorizon or a
color value, moist, of 4 or more; and

8. Do not have plinthite that forms a continuous phase
or constitutes more than half the matrix in any
subhorizon within 125 cm of the soil surface; and

4. Do not have a fragipan.

LITERATURE CITED

Sys, C, 1969. The soils of central Africa in the American
Classification - 7th Approximation. African Soils.
XIV:25-44.


410

with color value of 3 or leas, moist, and 6 or less, dry, is
less than 30 cm thick in half or more of each pedon.
‘Udorthentic:

EDBB. Other Pellusterts that have cracks that remain
open for 150 or less cumulative days during each year, or
have a mean annual soil temperature that is less than

18°C.
Udic Pelhustests

EDBC, Other Pellusterts that have a color value, moist, of
4 or more or a value, dry, of 6 or more in the surface
horizon, or the horizon with color value of 3 or less,

moist, and 5 or less, dry, is less than 30 cm thick in half

or more of each pedon.
Entic Pellusterts

EDBD. Other Pellusterts that have within 100 cm of the
soil surface prismatic or blocky structure accompanied
by clay skins on ped faces that have a color value lower
than that in the matrix.

Paleustollic Pellusterts
EDBE. Other Pellusterts.
‘Typic Pallusterts
XERERTS
Key to great groups

, moist, of 2
the upper 30
cm in more than half of each pedon.

p4l0
EAB. Other Xererts,

p4il
Chromoxererts
Key to subgroups

EAAA. Chromoxererts that have distinct or prominent
mottlea (these terms refer to contrast, not size) within 50
cm of the soil surface in more than half of each pedon.

EAAB. Other Chromoxererts that have a color value,
moist, of 4 or more or a value, dry, of 6 or more in the
surface horizon, or the horizon with color value of 3 or
less, moist, and 5 or less, dry, is less than 30 cm thick in

half or more of each pedon.
Entic Chromoxererts

EAAC. Other Chromoxererts that have, within 100 cm of
the soil surface, prismatic or blocky structure
accompanied by clay skins on ped faces that have a color
value lower than that in the matrix.

Chromoxererts


162

weighted average ratio of sand to clay in the upper soil
to that depth is 1.0 or lesa, or is one-seventh percent or
more if the ratio is 13 or more, or is intermediate
between 0.6 percent and one-seventh pervent ifthe
ratio of sand to clay in the upper soil is more than 1.0
but less than 13; and the weighted average percentage
of organic carbon in the upper soil to a depth of 18 cm is
one-fifth or more higher than the values just stated if a
duripan is present at a depth of less than 40 cm but
more than 18 em; and

3. A mean annual soil temperature lower than 22°C,
mean auromer and mean winter soil temperatures at
a depth of 60 cm that differ by 5°C or more, and an
aridic moisture regime that borders on a xeric

regime.
Haploxerollic Durargids

FAAG. Other Durargids that do not have a platy or
massive duripan that is indurated in some subhorizon.
Haplic Durargids

FAAH. Other Durargids that have the following
combination of characteristics:

1. A duripan at a depth of 18 emor more; and

2, The weighted average percentage of organic carbon
in the upper soil to a depth of 40 cm is 0.6 or more if the
weighted average ratio of sand to clay in the upper soil
to that depth is 1.0 or less, or is one-seventh percent or
more if the ratio is 13 or more, or is intermediate
‘between 0.6 percent and one-seventh percent if the
ratio of sand to clay in the upper soil is more than 1.0
but less than 13; and the weighted average percentage
of organic carbon in the upper soil to a depth of 18 cm is
one-fifth or more higher than the values just stated if a
duripan is present at a depth of less than 40 cm but
more than 18 cm; and

3, A mean annual soil temperature lower than 22°C,
mean summer and mean winter soil temperatures at
a depth of 50 cm that differ by 5°C or more, and an
aridic moisture regime that borders on a xeric

regime.
Xerollic Durargids
FAAI. Other Durargids that are dry in all parts of the
moisture control section three-fourths of the time
(cumulative) or less that the soil temperature at a depth of
50 cm is 5°C or higher.
Ustalfic Durargids

FAAJ. Other Durargids.
Typic Durargids


72

6, In half or more of the upper 50 cm, an SAR of 13” or
more (or sodium saturation that is 15 percent or more)
that decreases with depth below 50 cm and, within a
depth of 100 cm, have ground water at some period
during the year when the soil is not frozen in any part.
Inceptisols, p. 241

K, Other soils.
Entisols, p. 195

2 he percentage of sactameain medium (EAT) 6 woud in the definition

mearured by the normal method if the conductivity (EC) of the saturation
extract is leas than 20 43 per m at 25°C. If the conductivity ts 20
ahos or nore and SAR in more then 10, SAK ie daterained on a sample
that has been leached with distilled water unti} EC of the leachate
decreases to about A nahos per centimeter but not to lene then 4. ESP
Of 15 or more is replaced by SAR of 13 or more if TC in large ancugh to
Fequire 4 correction for soluble salts in calculating ESP. If IC is low



e1

3. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a, More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-

extractable iron of 0.40 percent or more.
Aquandic Ochraqualfs

TAIB. Other Ochraqualfa that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic horizon that is 50 to 100

cm below the soil surface.
Arenic Ochraqualfs

IAIC. Other Ochraqualfs that have a layer, starting at the
mineral soi! surface, that has a sandy particle-size class
and extends to the top of an argillic horizon that is more
than 100 cm below the soil surface.

Grossarenic Ochraqualfs

IAID. Other Ochraqualfs that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm and at least 30 cm long in
some part and that extend upward to the surface or to the
base of an Ap or an albic horizon; and

2, A coefficient of linear extensibility (COLE) of 0.09 or
more in a horizon or horizons at least 50 cm thick, and
a potential linear extensibility of 6 cm or more in the
‘upper eoil to a depth of 100 cm or in the whole soil if a
lithic, paralithic, or petroferric contact is deeper than 50
cm but not deeper than 100 cm; and

3. More than 36 percent clay in horizons that have total
thickness of more than 60 cm.

Vertic Ochraqualfs
IAIE. Other Ochraqualfs that:
1. Have in more than 40 percent of the matrix’ in one or
more subhorizons between the A or Ap horizon and a
depth of 75 cm one or more of the following:

a. If mottled and the mean annual soil temperature
is lower than 15°C, chroma, moist, of 3 or more; or

“Uf the hue ia 7.5%M oF redder and if pads are present, pad exteriors

in the azgillic horizon should have dominant chroaa, moist, of 1 of lest
and ped interiors ehould have mcttles that have chraea, moist, of 2 oF
less: LF pede are absent, the chroma, moist, should be 1 or les
ineediately below any surface horixon that has oolor value, aciat, of 3
of less.



KEYS
SOIL TAXONOMY

by

SOIL SURVEY STAFF

Agency for International Development.
United States Department of Agriculture
Soil Management Support Services

WATIONAG
wee
ee

% 7
D> s
ONSEmvanion

SMSS Technical Monograph No, 19
Fourth Edition, 1990

Virginia Polytechnic Institute
and State University


107

ICE. Other Ustalfs that have a CEC of 16 cmol(+) or less
per kg clay (by 1N NH4OAc pH 7) and an ECEC of 12
cmol(+) or less per kg clay (sum of bases extracted with
1N NH,OAc pH 7 plus 1N KCl-extractable Al) in the
major part of the argillic or kandic horizon, or the major
part of the upper 100 cm of the argillic or kandic horizon if
these horizons are thicker than 100 cm.

Kanhaplustalfs, p. 113

ICF. Other Ustalfs that either

1. Have a petrocalcic horizon that has its upper boundary
within 150 cm of the soil surface; or

2. Do not have a lithic or paralithic contact within 150 cm
of the surface; and the argillic horizon

a. Has a clay distribution such that the percentage of
clay does not decrease by as much as 20 percent of the
maximum within a depth of 150 cm from the soil
surface, or the layer in which the clay percentage
decreases by more than 20 percent has at least 5
percent of the volume consisting of skeletans on
faces of peds and there is at least 3 percent (absolute)
increase in clay below the layer; and

b. Has one or more of the following:

(1) Hues redder than 10YR and chroma of more
than 4 in the matrix of at least the lower part of the
horizon; or

(2) Hues of 7.5YR or redder and value, moist, that
is less than 4 and value, dry, that is less than 5
throughout the major part of the horizon; or

(8) Common coarse mottles that have hue of 7.5YR
or redder or chroma of more than 5 in the lower
part of the horizon; or

8. Do not have a lithic or paralithic contact within 50 cm
of the surface, and have an argillic horizon in which
the upper part has a clayey particle-size class and there
is an increase of at least 20 percent clay (absolute)
within a vertical distance of 7.5 cm, or of at least 15
percent clay (absolute) within a vertical distance of 2.5
cm at the upper boundary.

Paleustalfy, p.115

ICG. Other Ustalfs that have an argillic horizon that has
throughout its thickness a hue redder than 5YR, a color
value, moist, of 3 or less, and a color value, dry, no more
than one unit higher than the value, moist.

Rhodustalfs, p, 119

ICH. Other Ustalfs.
Haplustalfs, p. 108


183

if the ratio is 18 or more, or is intermediate between 0.6
percent and one-seventh percent if the ratio of sand to
clay is between 1.0 and 13; and a weighted average
pereentage of organic carbon in the soil to a depth of 18
cm that is one-fifth or more higher than the values just
stated if there is a lithic or paralithic contact at a depth
of less than 40 cm but more than 18 em; and

4. Have a mean annual soil temperature lower than
22°C, mean summer and mean winter soil
temperatures at a depth of 50 cm that differ by 5°C or
more, and an aridic moisture regime that borders on a

xeric regime.
Durixerollic Lithic Camborthids

FBFC. Other Camborthids that have the following
combination of characteristics:

1. Have a lithic contact within 50 em of the surface;
and

2, Have a weighted average percentage of organic
carbon in the upper 40 cm that is 0.6 percent or more if
the weighted average ratio of sand to clay in the soil
above that depth is 1,0 or less, or is 0.15 percent or more
if the ratio is 13 or more, or is intermediate between 0.6
percent and one-seventh percent if the ratio of sand to
clay is between 1.0 and 13; and a weighted average
percentage of organic carbon in the soil to a depth of 18
cm that is one-fifth or more higher than the values just
stated if there is a lithic or paralithic contact at a depth
of leas than 40 cm but more than 18 cm; and

3. Have a mean annual soil temperature lower than
summer and mean winter soil
res at a depth of 50 cm that differ by 5°C or
more, and an aridic moisture regime that borders on a
xeric regime.
Lithic Xerollic Camborthids
FBFD. Other Camborthids that have a lithic contact

within 50 cm of the surface.
Lithic Camborthids

FBFE. Other Camborthids that have an SAR of more
than 45, or 40 percent or more saturation with sodium,
throughout the cambic horizon, and the saturated.
hydraulic conductivity is slow or very slow.

Natric

FBFF. Other Camborthids that have the following
combination of characteristics:

1, Have a frigid or colder temperature regime; and

2. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the soil
surface or to the base of an Ap horizon, and the cracks
are not closed for as many as 60 consecutive days of
the 120 days following the winter solstice in 3 or more
years out of 10; and


131
BAAD. Other Cryaquands that have, between 25 and 100
cm, a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the
underlying layer.

‘Thaptic Cryaquands
BAAE. Other Cryaquands.
Typic Cryaquands
Duraquands
Key to subgroups

BACA, Duraquands that have a histic epipedon.
Histie

BACB. Other Duraquands that have extractable bases plus
IN KCl-extractable Al** of less than 2.0 cmol(+) kg” fine
earth in some subhorizon 30 cm or more thick between 25

and 100 cm. .
Acraquoxic Duraquands

BACC. Other Duraquands that have, between 25 and 100
cm, a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the
underlying layer.

Thaptic Duraquands
BACD. Other Duraquands.
Typic Duraquands
Haplaquands
Key to subgroups

BAFA. Haplaquands that have a lithic contact within 50
cm of the soil surface.
Lithic Haplaquands

BAFB. Other Haplaquands that have a petroferric
contact within 100 cm of the soil surface.
Haplaquands

BAFC, Other Haplaquands that have a horizon with its
upper boundary within 100 cm of the mineral soil surface
or upper boundary of an organic layer with andic soil
properties, whichever is shallower, which is more than
15 cm thick and contains 20 percent or more (by volume)
cemented soil material that does not slake in water after

air drying.
Duric Haplaquands
BAFD. Other Haplaquands that have a histic epipedon.
Histic Haplaquands


160

1. Dominant chroma of 1 or less throughout the
horizons and hue as yellow or yellower than 2.5Y in

some part; or

2. Dominant chroma of 2 or less and mottles that are
not due to segregated lime; or

3. Both a dominant chroma of 2 or less and a greater
SAR (or percentage of. exchangeable sodium) in more
than half the thickness of the horizon between the
surface and 50 cm depth than in the saturated zone.
Aquic Durargids

FAAB. Other Durargids that have the following
combination of characteristics:

1. A duripan at a depth 18 cm or more; and

2. The weighted average percentage of organic carbon
in the upper soil to a depth of 40 cm is 0.6 or more if the
weighted average ratio of sand to clay in the upper soil
to that depth is 1.0 or less, or is one-seventh percent or
more if the ratio is 13 or more, or is intermediate
between 0.6 percent and one-seventh percent if the
ratio of sand to clay in the upper soil is more than 1.0
but less than 13; and the weighted average percentage
of organic carbon in the upper soil to a depth of 18 cm is
one-fifth or more higher than the values just stated if'a
duripan is present at a depth of less than 40 cm but
more than 18 cm; and

3. A mean annual soil temperature lower than 22°C,
mean summer and mean winter soil temperatures at
a depth of 50 cm that differ by 5°C or more, and an
aridic moisture regime that borders on a xeric
regime; and

4. An argillic horizon that has 35 percent or more clay
in some part and also has either:

a. An increase of 15 percent or more clay (absolute)
within a vertical distance of 2.5 cm at the upper
boundary of the argillic horizon; or

b. An increase of 10 percent or more clay (absolute)
if cultivated and the lower boundary of the Ap
horizon is the upper boundary of the argillic

horizon.
Abruptic Xerollic Durargids

FAAC. Other Durargids that have an argillic horizon
that has 85 percent or more clay in some part, and also
have either:

1, An increase of 15 percent or more clay (absolute)
within a vertical distance of 2.5 cm at the upper
boundary of the argillic horizon; or

2. An increase of 10 percent or more clay (absolute) if
cultivated and the lower boundary of the Ap horizon is
the upper boundary of the argillic horizon.

‘Abruptic


FOREWORD

This publication, Keys to Soil Taxonomy, serves two
purposes. It provides the taxonomic keys required for the
classification of a soil in a form that can be used easily in
the field, and it serves as a means of providing an up-to-
date version of Soil Taxonomy that includes all revisions
to the keys that have been approved. It replaces the keys in
Soil Taxonomy, but it does not replace Agriculture
Handbook 436, which contains descriptive material,
laboratory data, and chapters on other subjects related to
Soil Taxonomy. This is the third update of the Keys to Soil
Taxonomy, which was originally printed in 1983, and we
plan to continue reprinting the keys about every two years.
Agriculture Handbook 436 will be revised and reissued in
the future, after most of the current ongoing International
Soil Classification Committees (ICOMs) have completed
their mandates, but probably not before about 1995.

This publication incorporates all amendments approved to
date and published in National Soil Taxonomy Handbook
(NSTH) Issues 1 through 13. It includes the
recommendations of the International Committee on Low
Activity Clays (NSTH Issue # 8), the International
Committee on Oxisols (NSTH Issue # 11), and the
International Committee on Andisols (NSTH Issue # 13).
This edition of the Keys to Soil Taxonomy contains a
revised format to the Keys to Subgroups which is also
published in NSTH Issue # 13.

The keys reproduced here were extracted from a
computerized copy of Soil Taxonomy which is maintained
in complete, up-to-date form.

RICHARD W. ARNOLD
Director, Soil Survey Division
Soil Conservation Service

1990


192

FBCI. Other Durorthids that have the following
combination of characteristics:

1, Have a duripan whose upper boundary is 18 cm or
deeper, and have a weighted average content of
organic carbon in the upper soil to a depth of 40 cm that
is 0.6 or more if the weighted average ratio of sand to
noncarbonate clay above that depth is 1.0 or less, or is
0.15 percent or more if the ratio is 13 or more, or is.
intermediate if the ratio of sand to clay is between 1.0
and 13; and

2. Have an aridic moisture regime that borders on an
ustic regime.
Ustollic Durorthids
FBCJ. Other Durorthids that are dry in all parts of the
moisture control section for three-fourths or less of the
fame thet the nol temperature atx dap of 50 xn ia °C or
hi; a
‘Ustochreptic Durorthide

FBCK, Other Durorthids that have a duripan that is not
indurated in any subhorizon.

Entic Durorthids
FBCL. Other Durorthids.

‘Typic Durorthids
Gypsiorthids
‘Key to subgroups

FBDA. Gypsiorthids that have a petrogypsic horizon
whose upper boundary is within 100 cm of the soil

surface,
Petrogypeic Gypeiorthids

FBDB. Other Gypsiorthids that have a gypsic horizon in
which the product of the percentage of gypsum and the
thickness in centimeters above a depth of 150 cm is less
than 3,000, and have a calcic horizon above the gypsic

horizon.
Calcic Gypsiorthids
FBDC. Other Gypsiorthide that have a gypsic horizon in

which the product of the percentage of gypsum and the
thickness in centimeters above a depth of 150 cm is less

than 3,000. Cambic
FBDD. Other Gypsiorthids. ype
Paleorthids

‘Key to subgroups

FBBA. Paleorthids that:

1. Have a petrocalcic horizon whose upper boundary is
18 cm or deeper, and have a weighted average content
of organic carbon in the upper soil to a depth of 40 cm


212

Jong in some part, and that extend upward to the soil
surface or the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.05
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 150 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 150 cm; and

3. More than 35 percent clay in horizons that total more
than 50 cm in thickness,
Vertic Torriorthents

KEBD. Other Torriorthents that:

1. Have a lithic contact within 50 cm of the surface;
and

2. Are dry in all parts of the moisture control section
less than three-fourths of the time (cumulative) that the
soil temperature at a depth of 50 cm is 5°C or higher
and they either (1) have a hyperthermic or an iso soil
temperature regime or (2) have a thermic, mesic or
frigid soil temperature regime and have an aridic
moisture regime that borders on an ustic regime.
Lithie Ustic Torriorthents

KEBE, Other Torriorthents that:

1. Have a lithic contact within 50 cm of the surface;
and

2. Are dry in all parts of the moisture control section
less than three-fourths of the time (cumulative) that the
soil temperature at a depth of 60 em is 5°C or higher
and they have a thermic, mesic, or frigid soil
temperature regime and an aridic moisture regime
that borders on a xeric regime.

Lithic Xeric Torriorthents

KEBF. Other Torriorthents that have a lithic contact
within 50 cm of the surface.
Lithic Torriorthents

KEBG. Other Torriorthents that have, throughout a
cumulative thickness of 18 cm or more and within a
depth of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a, More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-
oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Vitrandic Torriorthents


416

throughout the transition zone. In the other, parts that are
characteristic of an overlying or paderlying horizon are
enclosed by parts that are characteristic of the other
horizon, Special conventions are used to designate these
kinds of horizons.

Horizons dominated by properties of one master et horizon
but having subordinate properties of another. Tw

capital letter symbols are used, as AB, EB, BE, BC. The
master horizon symbol that is given first designates the
kind of horizon whose properties dominate the
transitional horizon, An AB horizon, for example, has
characteristics of both an overlying A horizon and an
underlying B horizon, but is more like the A than like

In some cases, a horizon can be designated as
transitional even if one of the master horizons to which it
is apparently transitional is not present. A BE horizon
may be recognized in a truncated soil if its properties are
similar to those of a BE horizon in a soil in 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
material.

Horizons in which distinct parts have recognizable
Properties of the two kinds of master horizons indicated
by the capital letters. The two capital letters are
separated by a virgule (/), as E/B, B/E, B/C. Most of the
individual parts of one of the components are
surrounded by the other.

The designation may be used even though horizons
similar to one or both of the components are not present,
if the separate components can be recognized in the
transitional horizon. The first symbol is that of the
horizon that makes up the greater volume.

SUBORDINATE DISTINCTIONS WITHIN MASTER
HORIZONS AND LAYERS

Lower case letters are used as suffixes to designate
specific kinds of master horizons and layers. The word
“accumulation” is used in many of the definitions in the
sense that the horizon must have more of the material in
question than is presumed to have been present in the
Parent material. The symbols and their meanings are
as follows:

a Highly decomposed organic material

‘This symbol is used with "0" to indicate the most
highly decomposed of the organic materials. The
mubbed fiber content is less than about 17 percent of the
volume.

b Buried genetic horizon

This symbol is used in mineral soils to indicate
identifiable buried horizons with major genetic
features that were formed before burial. Genetic
horizons may or may not have formed in the

overlying material, which may be either like or


371

or more in some part or has a mean annual soil
temperature lower than 8°C.

Alfic Haplorthods
CDEI. Other Haplorthods that have an argillic or kandic
horizon below the spodic horizon.

Ultic Haplorthods

CDE4J. Other Haplorthods that:

1. Have a black intermittent upper subhorizon that has
a ratio of free iron (elemental) to carbon that is less
than 0.2; or

2, Have 6 pervent or more organic carbon in the upper
10 em of the spodic horizon,
Humic Haplorthods

CDEK. Other Haplorthods that have a spodic horizon that
does not have any of the following:

1. A continuous horizon at least 2.5 cm thick that is
very firm or extremely firm when moist (ortstein);
nor

2. A texture of very fine sand or finer, and a thickness
of more than 10 cm and a weighted average of at least
1.2 percent organic carbon in the upper 10 em; nor

3. A coarse-loamy, loamy-skeletal, sandy-skeletal, or
sandy particle-size class and color value and chroma,
moist, of 3 or less in at least the upper 7.5 cm of the

spodic horizon.
Entic Haplorthods

CDEL. Other Haplorthods.
Typic Haplorthods

Placorthods

‘These are the orthods that have a placic horizon in the
spodic horizon. They are not known to occur in the
United States, and they are thought to be rare elsewhere
in the world. Subgroups have not been defined.

Troporthods

These are the Orthods that have an isomesic or warmer
iso temperature regime. They are not known to occur in.
the United States, but the group is provided for use
elsewhere. Subgroups have not been defined.


108

Durustalfs

Durustalfs are the Ustalfs that have a duripan whose
upper boundary is within 100 cm of the surface. They are
not known to occur in the United States, and subgroups
have not been developed. They are provided for use in
other countries,

Haplustalfs

Key to subgroups

ICHA, Haplustalfs that have a lithic contact within 50 cm
of the soil surface.
Lithic Haplustalfs

ICHB. Other Haplustalfs that:

1, When neither irrigated nor fallowed to store
moisture:

a. If the soil temperature regime is mesic or thermic,
are dry for four-tenths or less of the cumulative days
in some part of the moisture control section when the

soil temperature at a depth of 50 cm exceeds 5°C; or

b. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or
less during a period when the soil temperature at a
depth of 50 cm exceeds 8°C; and

2. Have the following combination of characteristics:

a. Cracks at some period in most years that are Lem
or more wide at a depth of 50 cm, that are at least 30
cm long in some part, and that extend to the surface
or to the base of an Ap horizon if the soil is not
irrigated; and

b, A coefficient of linear extensibility (COLE) of 0.07
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more
in the upper 125 cm of the soil or in the whole soil if a
lithic or paralithie contact is deeper than 50 em but
shallower than 125 cm; and

c. More than 35 percent clay in horizons that total

more than 50 cm in thickness,
Udertic Haplustalfs

ICHC. Other Haplustalfs that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30cm


29
Soft powdery lime

Soft powdery lime is a phrase that is used in the
definitions of a number of taxa. It refers to translocated
authigenic lime, soft enough to be cut readily with a
fingernail, that was precipitated in place from the soil
solution rather than inherited from a soil parent material
such as a calcareous loess or till, It should be present in
a significant enough accumulation to constitute ak
horizon.

To be identifiable, soft powdery lime must have some
relation to the soil structure or fabric. It may disrupt the
fabric to form spheroidal aggregates, or white eyes, that
are soft and powdery when dry. Or the lime may be
present as soft coatings in pores or on structural faces. If
present as coatings, it covers a significant part of the
surface. Commonly, it coats the whole surface to a
thickness of 1 to 5 mm or more. But only part of a surface
may be coated if little lime is present in the soil. The
coatings should be thick enough to be visible when moist
and should cover a continuous area large enough to be
more than filaments. The pseudomycelia commonly
seen in a dry calcareous horizon do not come within the
meaning of soft powdery lime, Pseudomycelia are soft
powdery filaments on structural faces, commonly
branching, but they may come and go with the seasons
and may be only lime that was precipitated in a single
season by the withdrawal of stored soil moisture rather
than a k horizon.

Soft coatings on hard lime concretions are also excluded
from the meaning of soft powdery lime. These may be
thin or thick, and they may be the result of either current
accumulation or removal of lime. That is, the concretion
may be growing or may be undergoing dissolution, and
either process can produce a soft coating.

Soil moisture regimes

The soil moisture regime, as the term is used here, refers
to the presence or absence either of ground water or of
water held at a tension less than 1500 kPa in the soil or in
specific horizons by periods of the year. Water held at a
tension of 1600 kPa or more is not available to keep most
mesophytic plants alive. The availability of water also is
affected by dissolved salts. A soil may be saturated with
water that is too salty to be available to most plants, but it
would seem better to call such a soil salty rather than dry.
Consequently, we consider a horizon to be dry when the
moisture tension is 1500 kPa or more. If water is held at a
tension of less than 1500 kPa but more than zero, we
consider the horizon to be moist. A soil may be
continuously moist in some or all horizons throughout the
year or for some part of the year. It may be moist in
winter and dry in summer or the reverse. In the northern
hemisphere, summer refers to the months of June, July,


214
Troporthents

Kev to subgroups
KEDA. Troporthents that have a lithic contact within 50
cm of the soil surface.

Lithic Troporthents

KEDB. Other Troporthents that have, throughout a
cumulative thickness of 18 em or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 83 kPa water retention, of 1.0 g em” or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic

KEDC. Other Troporthents that have, throughout a
cumulative thickness of 18 cm or more and within a
depth of 75 em, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of 0.40 percent or more.
Vitrandic

KEDD, Other Troporthents.

Typic Troporthents
Udorthents
Key to subgroups
KEEA. Udorthents that have a lithic contact within 50 cm
of the surface.
Lithic Udorthents

KEEB. Other Udorthents that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 gem’ or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic Udorthents

KEEC, Other Udorthents that have, throughout a
cumulative thickness of 18 cm or more and within a
depth of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or


has mottles that have chroma of 2 or less within a depth
of 76 cm below the soil surface.
Aquic Eutroborslfs

IBEG, Other Eutroboralfs that have an argillic horizon

that has a texture that is loamy fine sand or coarser or is

discontinuous vertically in the upper 15 cm (in lamellae),
Peammentic Eutroboralfs

IBEH. Other Eutroboralfs that have a layer, atarting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic horizon that is more
than 50 cm below the soil surface.

Arenic Eutroboralfs

IBEI. Other Eutroboralfs that have an Ap horizon that has
a color value, moist, of 3 or less and a color value, dry, of &
or less (crushed and amoothed), or the soil, after mixing to
a depth of 18 cm, has these colors.

Mollic Eutroboralfs

IBEJ. Other Eutroboralfs that have tongues of albic
materials in the argillic horizon (interfingering is
permitted).

Glossic Eutroboralfs
IBEK. Other Eutroboralfs.
‘Typic Eutroboralfs
Fragiboralfs
Key to subgroups

IBBA. Fragiboralfs that have, throughout a cumulative
thickness of 18 cm or more and within a depth of 75 cm,
bulk density of the less than 2.0 fraction, measured at
33 kPa water retention, of 1.0 g cm” or less and acid-
oxalate-extractable aluminum plus 1/2 acid-oxalate-
extractable iron of more than 1.0 percent.

Andic Fragiboralfs

IBBB. Other Fragiboralfs that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more than
85 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2, The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a, More than 30 percent volcanic glass; or


2, Saturation with water in the mottled zone at some
time of year when the soil temperature in that zone is
5°C or higher, or artificial drainage.

Aquic Hapludults

GCGH. Other Hapludults that have an Ap horizon that
has a color value, moist, of 3 or less and has a value, dry,
of 5 or less when crushed and smoothed; or the A horizon
is 15 cm or thicker and its color value, moist, is 3 or less,
Humic Hapludults

GCGI. Other Hapludults that have an argillic horizon 25
cm or less thick.

Ochreptic Hapludults
GCGVJ. Other Hapludults.
‘Typic Hapludults
Kandiudults
Key to subgroups

GCCA. Kandiudults that:

1, Have the following combination of characteristics
in the upper 75 cm of the soil if the chroma in all or part
of the upper 75 cm is not controlled by uncoated sand
grains; or if the chroma throughout the upper 75 cm is
controlled by uncoated sand grains, have the

following combination of characteristics throughout
the upper 12.5 cm of the argillic or kandic horizon:

a. Mottles that have a color value, moist, of 4 or more
and chroma, moist, of 2 or less accompanied by
mottles of higher chroma that are due to segregation
of iron; and

»b. Saturation with water in the mottled zone at some
time of year when the soil temperature in that zone
is 5°C or higher, or there is artificial drainage; and

2. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic or kandic horizon that is 50 to 100 cm
below the soil surface; and

3. Have 5 percent or more plinthite (by volume) in one
or more subhorizons within 150 cm of the soil surface.
nic Pli

GCCB,. Other Kandiudults that:

1, Have the following combination of characteristics
in the upper 75 cm of the soil if the chroma in all or part
of the upper 75 cm is not controlled by uncoated sand
grains; or if the chroma throughout the upper 75 cm is.
controlled by uncoated sand grains, have the
following combination of characteristics throughout
the upper 12.5 cm of the argillic or kandic horizon:

a, Mottles that have a color value, moist, of 4 or
more and chroma, moist, of 2 or less accompanied


200
KADI. Other Fluvaquents that:

1, Have an Ap horizon that has a color value, moist, of
3 or less and a color value, dry, of 5 or less when
crushed and smoothed, or the A horizon is 15 cm or
more thick and has these colors; and

2. Have base saturation (by NH,OAc) of less than 50

percent in some horizon and it does not increase to 50
percent or more within a depth of 100 cm below the soil

surface.
Humaqueptic Fluvaquents
KADJ. Other Fluvaquents that:

1, Have an Ap horizon that has @ color value, moist, of
8 or less and a color value, dry, of 5 or less when
crushed and smoothed, or the A horizon is 15 cm or
more thick and has these colors; and

2, Have base saturation (by NH,OAc) of 50 percent or

more throughout the soil or it increases to 50 percent or
more within a depth of 100 cm below the soil surface.

Fluvaquents
KADK. Other Fluvaquents,
Typic Fluvaquents
Haplaquents
Key to subgroups

KAGA. Haplaquents that have sulfidic materials within
100 cm of the mineral soil surface.
Sulfic Haplaquents

KAGB. Other Haplaquents that have a lithic contact
within 50 em of the eoil surface.
Lithic Haplaquente

KAGC. Other Haplaquents that have in more than 40
percent of the matrix in one or more subhorizons between
the Ap horizon or a depth of 25 cm, whichever is deeper,
and 75 cm one or more of the following:

1, If mottled and

a, If the hue is 2.5Y or redder® and the value, moist,
is more than 5, the chroma, moist, is 3 or more; or

b. If the hue is 2.5Y or redder and the value, moist, is
5 or less, the chroma, moist, is 2 or more; or

c, If the hue is yellower than 2.5Y, the chroma,
moist, is 3 or more; or

‘moist, of 2 of less) if peda
are absent, the chrowa, own iamediacely below any
Mingece norston eMe has lve, eoists of 3 oF tate.



IAIG. Other Ochraqualfs that have in more than 40
percent of the matrix’ in one or more subhorizons between
the A or Ap horizon and a depth of 75 cm one or more of the
following:

1, If mottled and the mean annual soil temperature is
lower than 15°C, chroma, moist, of 8 or more; or

2. If mottled and the mean annual soil temperature is
15°C or more:

a, If the hue is 2.5Y or redder and the value, moist, is
more than 5, the chroma is 3 or more; or

b. If the hue is 2.5Y or redder and the value, moist, is
5 or less, the chroma, moist, is 2 or more; or

¢. If the hue is yellower than 2.5Y, the chroma, moist,
is 8 or more; or

3. If not mottled, the chroma, moist, is 2 or more.
Aeric Ochraqualfs

IAIH, Other Ochraqualfs that have an Ap horizon that
meets all the requirements of a mollic epipedon except
thickness; or the upper soil to a depth of 18 cm, after
mixing, meets these requirements.

Mollic Ochraquelf

IATL, Other Ochraqualfs that have an Ap horizon that
meets all the requirements of an umbric epipedon except
thickness; or the upper soil to a depth of 18 cm, after
mixing, meets these requirements.

Umbric Ochraqualfz

YAW. Other Ochraqualfs.
‘Typic Ochraqualfs
Plinthaqualfs

Plinthaqualfs are the Aqualfs that have plinthite that
forms a continuous phase or that constitutes half or more
of the matrix of some subhorizon of the argillic horizon
within 150 cm of the soil surface.

Umbraqualfs
Key to subgroups

IAHA. Umbraqualfs that have, throughout a cumulative
thickness of 18 cm or more and within a depth of 75 cm,
one or more of the following:

© af the hoe 1s 7.5YR oF redder and if pods are present, ped exteriors
4n the axgilic nozizon should have dominant chroma, molat, of 1 or less
and pad interiors should have mottles that have chroma, moist, of 2 or
ese) if peds are absent, the chroma, moist, should be 1 oF

Immediately below any surface horizon that has color velue, moist, of 3
or lesa,



WW

overlie a B horizon or any other soil horizon except, in
some places, a buried soil.

An albic horizon, therefore, is defined as a surface or a
lower horizon that has such thin or discontinuous
coatings on the sand or silt particles that the hue and
chroma of the horizon are determined chiefly by the color
of the sand and silt particles.

The color value, moist, of an albic horizon is 4 or more, or
the value, dry, ie 5 or more, or both. Ifthe value, dry, is 7
or more, or the value, moist, is 6 or more, the chroma is 3
or less either dry or moist. If the value, dry, is 5 or 6, or the
value, moist, is 4 or 5, the chroma is closer to 2 than to 3
cither dry or moist. If parent materials have a hue of 5YR
or redder, a chroma, moist, of 3 is permitted in the albic
horizon if the chroma is due to the color of uncoated silt or
sand grains. Under an albic horizon there is usually a B
horizon that is an argillic or a spodic horizon, but in some
few sandy soils the underlying horizon is too weakly
developed to meet the levels of accumulation required for
those horizons,

Argillic horizon

An argillic horizon is an illuvial horizon in which layer-
lattice silicate clays have accumulated by illuviation to a
significant extent. The process of illuviation, of course,
does not preclude concurrent formation of clay in the
illuvial horizon, If the horizon is illuvial, it must have
formed below the surface of the mineral soil though later
it may have been exposed at the surface by erosion.

In summary, we can say that an argillic horizon is one
that contains illuvial layer-lattice clays. This horizon
forms below an eluvial horizon, but it may be at the

surface if a oil has been partially truncated. It hes the
following properties that can be used for identification:

1. If an eluvial horizon remains and if there is no
lithologic discontinuity between it and the argillic
horizon, the argillic horizon contains more total clay and
more fine clay than the eluvial horizon, as follows. The
increases in clay are reached within a vertical distance
of 30 cm or less.

a. If any part of the eluvial horizon has leas than 15
percent total clay in the fine-earth fraction (less than
2.0 mm), the argillic horizon must contain at least 3
percent more clay (13 percent versus 10 percent, for
example). The ratio of fine clay to total clay normally
is greater in the argillic horizon than in the overlying
eluvial horizons or the underlying horizon by about
one-third or more.

b. If the eluvial horizon has more than 15 percent and
Jess than 40 percent total clay in the fine-earth fraction,


KDDD. Other Torrifluvents that have, throughout a
cumulative thickness of 18 cm or more and within a
depth of 75 cm, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least § percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Vitrandic Torrifluvents

KDDE. Other Torrifluvents that:

1, Have a horizon within 100 cm of the surface that is
more than 15 cm thick and either contains as much as
20 percent durinodes or is brittle and has firm
consistence when moist; and

2. Are dry in all parts of the moisture control section
for less than three-fourths of the time (cumulative) that
the soil temperature at a depth of 50 cm is 5°C or more
and they have a thermic, mesic, or frigid soil
temperature regime and a torric moisture regime that
borders on a xeric regime.

Durorthidic Xeric Torrifluvents

KDDD. Other Torrifluvents that have a horizon within
100 cm of the surface that is more than 15 cm thick that
cither contains as much as 20 percent durinodes or is
brittle and has firm consistence when moist.
Durorthidic Torriffuvents

KDDE. Other Torrifluvents that are dry in all parts of
the moisture control section for less than three-fourths of
the time (cumulative) that the soil temperature at a depth
of 50 cm is 5°C or more and they have a torric moisture
regime that borders on an ustic regime.

Ustic Torriflavents

KDDF. Other Torrifluvents that are dry in all parts of
the moisture control section for less than three-fourths of
the time (cumulative) that the soil temperature at a depth
of 50 cm is 5°C or more and they have a thermic, mesic, or
frigid soil temperature regime and a torric moisture
regime that borders on a xeric regime.

Xeric Torrifluvents

KDDG. Other Torriffuvents that have an anthropic
epipedon.
Anthropic Torrifluvents

KDDH. Other Torrifluvents.
Typic Torriflavents


29. Hydrous over clayey-skeletal.

30. Hydrous over clayey.

31. Hydrous over fragmental.

32, Hydrous over loamy-skeletal.

33. Hydrous over loamy.

34, Hydrous over sandy or sandy-skeletal.

35. Loamy over sandy or sandy-skeletal if the loamy
material has less than 60 percent fine or coarser sand.
36. Loamy-skeletal over clayey if there is an absolute
difference of more than 25 percent in the percentage of
clay in the fine-earth fraction.

37. Loamy-skeletal over fragmental.

38. Loamy-skeletal over sandy.

39. Medial over ashy.

40. Medial over clayey-skeletal.

41. Medial over clayey.

42. Medial over fragmental.

43. Medial over hydrous.

44, Medial over loamy-skeletal.

45. Medial over loamy.

46. Medial over pumiceous or cindery.

47, Medial over sandy or sandy-skeletal,

48. Pumiceous or ashy-pumiceous over loamy,

49, Pumiceous or ashy-pumiceous over medial-
skeletal.

50. Pumiceous or ashy-pumiceous over medial.

51. Pumiceous or ashy-pumiceous over sandy or sandy-
skeletal.

52. Sandy over clayey.

53. Sandy over loamy if the loamy material has less
than 50 percent fine or coarser sand.

64. Sandy-skeletal over loamy if the loamy material
has less than 50 percent fine or coarser sand.

The intent in setting up classes of strongly contrasting
particle sizes is to identify changes in pore-size
distribution that seriously affect movement and retention
of water and that have not been identified in higher
categories. The list given is intended for use in grouping
the eoil series of the United States into families. It is not
intended as a complete list. For example, fine sand over
coarse sand is common in the Udipsamments of western
Europe but is not known to be important in the United
States.

Choice of 7 or 11 particle-size classes

Only the seven particle-size classes are used in lithic,
arenic, and grossarenic subgroups and in shallow
families.

In families of Ultisola not included in the preceding item,
subclasses of loamy particle-size classes are used but not.
subclasses of the clayey classes.

Contrasting families are recognized if substitute terms
are used to characterize the materials in a part of the


330

HDFR. Other Haploxerolls that:
1. Have an aridic moisture regime; and
2. Have a calcic horizon or soft, powdery secondary
lime within a depth of 160 cm if the weighted average
particle-size class between a depth of 25 and 100 cm, or
between a depth of 25 cm and a lithic or paralithic
contact that is shallower than 100 cm, is sandy; within
110 em if the average particle-size class is loamy; or
within 90 cm if it is clayey.

HDFS. Other Haploxerolls that:
1. Have an aridic moisture regime; and

2. Have a sandy particle-size class in all subhorizons
to a depth of 100 cm or more.
Torripasmmentic Haploxerolls

HDFT. Other Haploxerolls that:

1. Have an aridic moisture regime; and

2. Do not have a cambic horizon, and the lower part of
the mollic epipedon does not meet the requirements of a
cambic horizon except for color, or either the cambic
horizon or the lower part of the epipedon has carbonates
throughout.

‘Torriorthentic Haploxerolls
HDFU. Other Haploxerolls that. have an aridic moisture
regime.
Aridic Haploxerolls

HDFV. Other Haploxerolls that have a horizon within 100
em of the surface that is more than 16 cm thick and either
contains at least 20 percent durinodes or is brittle and has

firm consistence when moist.
Doric Haploxerolls
HDFW. Other Haploxerolls that:

1. Have an irregular decrease in organic carbon
content with increasing depth, or have an organic
carbon content of more than 0.3 percent throughout to a
depth of 125 em of the surface; and

2. Have a slope of leas than 25 percent.
‘Fluventie Haploxerolls

HDFX. Other Haploxerolls that have a mollic epipedon
that has granular structure and that, below any Ap
horizon, has 50 percent or more by volume or wormholes,
wormeasts, or filled animal burrows.

Vermic Haploxerolls
HDFY., Other Haploxerolls that have a calcic horizon or
soft, powdery secondary lime within a depth of 150 cm if
the weighted average particle-size class between a depth of
25 and 100 cm, or between a depth of 25 cm anda lithicor
paralithic contact that ia shallower than 100 cm, is sandy;


172

1. A horizon within 100 cm of the surface that is more
than 15 cm thick and that either contains 20 percent or
more durinodes in a nonbrittle matrix or is brittle and
has firm consistence when moist; and

2. A weighted average percentage of organic carbon in
the upper soil to a depth of 40 cm that is 0.6 or more ifthe
weighted average of sand to clay to that depth is 1.0 or
less, or is one-seventh percent or more if the ratio is 13
or more, or is intermediate between 0.6 and one-
seventh percent if the ratio is between 1.0 and 13; and a
weighted average percentage of organic carbon in the
surface soil to a depth of 18 cm that is one-fifth or more
higher than the values just stated if there is a
paralithic contact that is shallower than 40 cm but
deeper than 18 em; and

3. A mean annual soil temperature lower than 22°C,
mean summer and mean winter soil temperatures at
a depth of 50 cm that differ by 5°C or more, and an
aridic moisture regime that borders on a xeric

regime.
Durixerollic Natrargids

FACG, Other Natrargids that have a horizon within 100
cm of the surface that is more than 15 em thick and that
cither contains 20 percent or more durinodes in a

nonbrittle matrix or is brittle and has firm consistence

when moist.
Duric Natrargids

FACH. Other Natrargids that have the following
combination of characteristics:

1, More than 10 percent of the ped surfaces deeper than
2.5 em below the upper boundary of the natric horizon
covered by skeletans; and

2. A weighted average percentage of organic carbon in
the upper soil to a depth of 40 cm that is 0.6 or more if the
weighted average of sand to clay to that depth is 1.0 or
less, or is one-seventh it or more if the ratio is 13
or more, or is inte: liate between 0.6 and one-
seventh percent if the ratio is between 1.0 and 13; and a
weighted average percentage of organic carbon in the
surface soil to a depth of 18 cm that is one-fifth or more
higher than the values just stated if there is a
paralithic contact that is shallower than 40 cm but
deeper than 18 em; and

8. An aridic moisture regime that borders on ustic.
Glossic Ustollic Natrargids

FACI. Other Natrargids that have the following
combination of characteristics:

1. An SAR of less than 13 or less than 15 percent
saturation with sodium throughout the major part of
the natric horizon; and

2. A weighted average percentage of organic carbon in
the upper goil ta a depth of 40 cm that is 0.6 or more if the
weighted average of sand to clay to that depth is 1.0 or
Jess, or is one-seventh percent or more if the ratio is 13


290

2. Have an albic horizon immediately below the mollic
epipedon; and

3. Have an increase in clay content of 20 percent

(absolute) or more within a vertical distance of 7.5 cm

below the upper boundary of the argillic horizon.
Abruptic

HEBW, Other Cryoborolls that have an argillic horizon
that is continuous throughout each pedon.
‘Argic Cryoborolls

HEBX. Other Cryoborolls that have a calcic horizon
within or immediately below the mollic epipedon.
Caleie

HEBY. Other Cryoborolls that have an albic horizon
immediately below the mollic epipedon.

Albic Cryoborolls
HEBZ, Other Cryoborolls.

‘Typic Cryoborolls
Haploborolls
Key to subgroups

HEGA. Haploborolls that have a salic horizon that has its
upper boundary within a depth of 75 cm below the surface.
Salorthidic Haploborolls

HEGB. Other Haploborolls that have a lithic contact
within a depth of 50 cm in part of each pedon.
Ruptic-Lithic Haplobarells

HEGC. Other Haploborolls that have a lithic contact
within a depth of 50 cm of the surface.
Lithic Haploborolle

HEGD. Other Haploborolls that:

1. Have a chroma, moist, after rubbing of 1 or leas in the
upper part of the mollic epipedon after it has been mixed
to a depth of 18 cm or in any Ap horizon that is more
than 18 cm thick, or the soil is not dry in all parts of the
moisture control section at some time in most years;
and

2. Have the following combination of characteristics:

a. Cracks at some period in most years that are 1 cm

or more wide at a depth of 50 cm and that are at least

30 cm long in some part and that extend upward to the
surface or to the base of an Ap horizon; and

b. Potential linear extensibility of 6 cm or more in
the upper 100 cm of the soil or in the whole soil ifa
lithic or paralithic contact is deeper than 50 cm but
shallower than 100 cm; and

c. More than 35 percent clay in horizons that total
more than 50 cm in thickness.
‘Udertic Haploborolls

eal


IEFF, Other Fragiudalfs that have mottles that have
chroma of 2 or less in the upper 25 cm of the argillic
horizon or have mottles that have chroma of 2 or less
within 40 em of the surface, and the horizons that have
mottles of low chroma are saturated with water at some
time of year when the soil temperature is 5°C or higher in

those horizons.
Aquie Fragiudalfs

IEFG, Other Fragiudalfs that have, immediately above
the fragipan, thick skeletans of clean sand and silt on
primary ped faces, or have an eluvial horizon (E’) that
has thick skeletans and as much as 3 percent (absolute)
less clay than both the overlying and underlying
horizons.

Glossic Fragiudalfs

IEFH. Other Fragiudalfs that do not have an argillic
horizon above the fragipan that has clay skins on at least
some vertical and horizontal faces of primary or
secondary peds.

Ochreptic Fragiudalfs
IEFI. Other Fragiudalfs.

Typic Fragiudalfs
Fraglossudalfs
Key to subgroups

IEEA. Fraglossudalfs that have mottles that have chroma
of 2 or less in the upper 25 cm of the argillic horizon, and
the mottled horizons are saturated with water at some
season when the soil temperature is 5°C or higher.

Aquic Fraglossudalfs
IEEB. Other Fraglossudalfs.
‘Typic Fraglossudalfs
Glossudalfs
Key to subgroups

IEDA. Glossudalfs that have a brittle matrix in one-
fourth or more of some subhorizon that is at least 10cm
thick and that has an upper boundary within 125 em of the
surface.

Fragic Glossudalfs

IEDB. Other Glossudalfs that have mottles that have
chroma of 2 or less in the upper 25 cm of the argillic
horizon, and the mottled horizons are saturated with
water at some season when their temperature is 5°C or
higher.

Aquic Glossudalfs


298

underlying horizon in which 25 percent or more of the
material is discrete wormholes, wormcasts, or filled

animal burrows that contain material from the mollic
epipedon and from the underlying horizon.

p.302

HGD. Other Udolls.

Hapludolls, p. 299
Argiudolls
Key to subgroups
HGBA, Argiudolls that have a lithic contact within 50 cm
of the surface.

Lithic Argiudolls

HGBB, Other Argiudolls that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the surface
or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.09 or
more in a horizon or horizons at least 50 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 100 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 100 cm; and

3, More than 35 percent clay in horizons that total more
than 60 cm in thickness.
Vertic Argiudolls

HGBC. Other Argiudolls that have texture that is loamy
fine sand or coarser in the argillic horizon, or the argillic
horizon consists entirely of lamellae with a combined

thickness of 15 em or more.
Peammentic Argiudolls

HGBD. Other Argiudolls that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 76 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm* or leas
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic

HGBE. Other Argiudolls that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:


186

b, Dominant chroma of 2 or less and mottles that are
due to segregation of iron or manganese; or

¢, Both a dominant chroma of 2 or less and a greater
SAR (or percentage of exchangeable Na) in more
than half the thickness of the horizons between the
surface and a depth of 50 cm than in the saturated
zone; and

2. Have a horizon within 100 cm of the surface that is
more than 15 cm thick and either contains 20 percent
or more durinodes or is brittle and has firm

consistence when moist.
Aquic Duric Camborthids

FBFL, Other Camborthids that are saturated with water
for 90 consecutive days or more within 100 cm of the
surface in most years or have any of the following
characteristics within 100 cm of the soil surface if the
soil of that zone is saturated with water at some period in
most years or the soil is artificially drained:

1, Dominant chroma of 1 or less throughout and hue of
2.5Y or yellower in some part; or

2. Dominant chroma of 2 or less and mottles that are
due to segregation of iron or manganese; or

3. Both a dominant chroma of 2 or less and a greater
SAR (or percentage of exchangeable Na) in more than
half the thickness of the horizons between the surface
and a depth of 50 cm than in the ay vote zone.

FBFM. Other Camborthids that:

1. Are dry in all parts of the moisture control section
for three-fourths or less of the time (cumulative) that
the soil temperature is 5°C or more at a depth of 50 cm
unless the soil is irrigated, and have an aridic
moisture regime that borders on a xeric moisture
regime; and

2. Have, throughout a cumulative thickness of 18 cm or
more and within a depth of 75 cm, one or more of the
following:

a. Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders,
pumice, and pumice-like fragments make up more
than 66 percent of these fragments; or

/b. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and
contains either:

()) More than 30 percent volcanic glass; or
(2) At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of 0.40 percent or more.
Vitrixerandic Camborthids


257

2. Have a content of organic carbon that decreases
irregularly with depth, or are 125 cm or more deep to a
lithic or a paralithic contact and have more than 0.2
percent organic carbon at 125 cm below the soil surface;
and

8. Have slopes of 26 percent or less.
Dystric Fluventic Eutrochrepts

JDFJ. Other Eutrochrepts that:

1, Have a content of organic carbon that decreases
irregularly with depth, or are 125 cm or more deep to a
lithic or a paralithic contact and have more than 0.2
percent organic carbon at 125 cm below the soil surface;
and

2. Have slopes of 25 percent or less.
Fluventic Eutrochrepts

IDFK, Other Eutrochrepts that have a sandy particle-size
class from the soil surface to a depth of 50 cm or more.

JDFL. Other Eutrochrepts that do not have carbonates
within a depth of 100 cm in all parts of each pedon.
Dystric’

JDFM. Other Eutrochrepts that have 40 percent or more
carbonates, including the coarse fragments up to 75 mm
in diameter, in and below the cambic horizon but above a
lithic or paralithic contact and above a depth of 100 cm.
Rendollic Eutrochrepts

JDEN, Other Eutrochrepts that have an argillic horizon
in some part but in less than half of each pedon.
Ruptic-Alfic Eutrochrepts

JDFO. Other Eutrochrepts.
‘Typic Eutrochrepts

Fragiochrepts
Key to subgroups

JDAA. Fragiochrepts that have, throughout a cumulative
thickness of 18 em or more and within a depth of 75 cm,
bulk density of the less than 2.0 mm fraction, measured at
33 kPa water retention, of 1.0 g cm’ or less and acid-
oxalate-extractable aluminum plus 1/2 acid-oxalate-
extractable iron of more than 1.0 percent.

Andic Fragiochrepts

JDAB. Other Fragiochrepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more than
86 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or


264

thick, and a potential linear extensibility of 6 cm or
more in the upper 100 cm or 125 cm, respectively, of the
soil or in the whole soil if a lithic or paralithic contact is
deeper than 50 cm but shallower than 100 cm or 125 cm;
and

3. More than 35 percent clay in horizons thet total more
than 50 cm in thickness.
‘Vertic Dystropepts

JCED. Other Dystropepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 7 cra, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g em or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

JCEE. Other Dystropepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 pereent
of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a, More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vitrandic Dystropepts
ICEF. Other Dystropepts that have mottles that have
chroma of 2 or less within 100 cm of the soil surface, and
the mottled horizon is saturated with water at some time of
year, or the soil has artificial drainage.

Aquic Dystropepts

JCEG, Other Dystropepts that:

1. Have a content of organic carbon® that decreases
irregularly with depth, or are 125 cm or more deep to a
lithic or a paralithic contact and have more than 0.2
percent organic carbon at 125 cm below the soil surface;
and

2. Have slopes of 25 percent or less.
Fhuventic Dystropepts

a
‘The carban should be of Holocone age. It ia nat the intent to include foes! earbon frm
bedrock.


71
aridic moisture regime that borders on a xeric

regime.
Lithic Xerollic Natrargids

FACB. Other Natrargids that have a lithic contact
within 50 cm of the soil surface.
Lithic Natrargids

FACC. Other Natrargids that have the following
combination of characteristics:

1. More than 10 percent of the ped surfaces deeper than
2.5 cm below the upper boundary of the natric horizon
covered by skeletans; and

2. A weighted average percentage of organic carbon in
‘the upper soil to a depth of 40 cm that is 0.6 or more if the
weighted average of sand to clay to that depth is 1.0 or
less, or is one-seventh percent or more if the ratio is 13
or more, or is intermediate between 0.6 percent and
one-seventh percent if the ratio is between 1.0 and 13;
and a weighted average percentage of organic carbon
in the surface soil to a depth of 18 cm that is one-fifth or
more higher than the values just stated ifthere is a
paralithic contact that is shallower than 40 cm but
doeper than 18 cm; and

3. A frigid or colder temperature regime and an aridic
moisture regime bordering on ustic.
Borollic Glossie Natrargids

FACD. Other Natrargids that have:

1. A weighted average percentage of organic carbon in
the upper soil to a depth of 40 cm that is 0.6 or more if the
weighted average of sand to clay to that depth is 1.0 or
less, or is one-seventh percent or more if the ratio is 13
or more, or is intermediate between 0.6 and one-
seventh percent if the ratio is between 1.0 and 13; and a
weighted average percentage of organic carbon in the
surface soil to a depth of 18 cm that is one-fifth or more
higher than the values just stated if there is a
paralithic contact that is shallower than 40 cm but
deeper than 18 cm; and

2. A frigid or colder temperature regime and an aridic
moisture regime bordering on ustic.
Borollic Natrargids
FACE. Other Natrargids that are saturated with water in
some horizon within 100 cm of the surface at some time
and have either of the following characteristics in the
horizon or horizons that are saturated:

1. Dominant chroma of 1 or leas throughout and hue of
2.8Y or yellower in some part; or

2. Both a dominant chroma of 2 or less and mottles that
are not due to segregated lime,
Aquie Natrargids

FACF, Other Natrargids that have the following
combination of characteristics:


401
during a period when the soil temperature at a depth of
50 cm exceeds 8°C.
Udie Kandiustults

GDBJ. Other Kandiustults that have, throughout the
argillic or kandic horizon, colors with a hue of 2.5YR or
redder, a value, moist, of 3 or less, and a value, dry, that
is one unit or less higher than the value, moist.

GDBK. Other Kandiustults.
Typic Kandiustults

Kanhaplustults

Key to subgroups

GDCA. Kanhaplustults that have a lithic contact within
50 cm of the mineral soil surface.

Lithic Kanhaplustults
GDCB. Other Kanhaplustults that have an ECEC (sum of

bases plus KCl-extractable Al) of 1.5 emol(+) or lesa per
kg clay in one or more subhorizons within a depth of 150

em below the soil surface.
Acrustoxic Kanhaplustults

GDCC. Other Kanhaplustults that have the following
combination of characteristics in the upper 75 cm of the
soil if the chroma in all or part of the upper 75 cm is not
controlled by uncoated sand grains; or if the chroma
throughout the upper 75 cm is controlled by uncoated sand
grains, have the following combination of
characteristics throughout the upper 12.5 em of the
argillic or kandic horizon:

1, Mottles that have a color value, moist, of 4 or more
and chroma. moist, of 2 or less accompanied by
mottles of higher chroma that are due to segregation of
iron; and

2. Saturation with water in the mottled zone at some
time of year when the soil temperature in that zone is
5°C or higher or there is artificial drainage.

Aquic Kanhaplustults

GDCD. Other Kanhaplustults that have a layer, starting
at the mineral soil surface, that has a sandy particle-size
class and extends to the top of an argillic or kandic
horizon that is 60 to 100 cm below the soil surface.

Arenic

GDCE. Other Kanhaplustults that:

1. Have, throughout a cumulative thickness of 18 cm or
more and within a depth of 75 cm, bulk density of the
Jess than 2.0 mm fraction, measured at 33 kPa water
retention, of 1.0 g cm’ or less and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of more than 1.0 percent; and

2, When neither irrigated nor fallowed to store
moisture:


243
2, Have a mean annual soil temperature that is 0°C or
lower.
Histic Pergelic Cryaquepts
JAEC. Other Cryaquepts that:

1. Have a histic epipedon that is discontinuous in each
pedon; and

2. Have a mean annual soil temperature that is 0°C or
lower.
Pergelic Ruptic-Histic Cryaquepts
JAED, Other Cryaquepts that:
1. Have an umbric epipedon; and
2. Have a mean annual soil temperature that is 0°C or
lower.
Humic Pergelic Cryaquepis
JAEE. Other Cryaquepts that have a mean annual soil
tomperature that is 0°C or lower.
Pergelic Cryaquepts
JAEF. Other Cryaquepts that have a histic epipedon.
Histic

JAEG. Other Cryaquepts that have, throughout a
cumulative thickness of 18 cm or more and within a
depth of 75 cm, one or more of the following:

1, Bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cmTM or
less and acid-oxalate-extractable aluminum plus 1/2
acid-oxalate-extractable iron of more than 1.0 percent;
or

2. Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or

3. The 0.02 to 2.0 mm fraction constitutes at least 30
Poroent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or
b. At least 5 percent volcanic glass and acid-
oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of 0.40 percent or more.
Aquandic
JAEH. Other Cryaquepts that:
1, Have chroma of 8 or more in more than 40 percent of
the mass of one or more horizons between depths of 15
and 50 cm; and

2. Have an umbric epipedon.
Aeric Humic Cryaquepts


926

sesquioxides or that is indurated in some subhorizon
below its upper boundary; and

2. Do not have an argillic horizon above the duripan.
Entic Durixerolls

HDAI. Other Durixerolls that do not have an argillic
horizon above the duripan.
Haplic Durixerolls

HDAJ. Other Durixerolls that do not have a duripan that
is massive, platy, or prismatic and that has half or more
of its upper boundary indurated or coated with opal or opal
and sesquioxides or that is indurated in some subhorizon
below its upper boundary.

Argic Durixerolls
HDAK. Other Durixerolls.

Typic Durixerolls
Haploxerolls
Key to subgroups

HDFA. Haploxerolls that:

1, Have a lithic contact within 50 cm of the soil surface;
and

2. Have base saturation (by sum of cations) of 75 percent
or less in some part of the soil above the lithic contact.
Lithic Ultic Haploxerolls

HDFB. Other Haploxerolls that have a lithic contact
within 50 em of the soil surface.
Lithic Haploxerolls
HODFC, Other Haploxerolls that:
1, Have an aridic moisture regime; and
2. Have the following combination of characteristics:

a. Cracks at some period in most years that are cm
or more wide at a depth of 60 cm, that are at least 30
cm long in some part, and that extend upward to the
soi] surface or to the base of an Ap horizon; and

b. A coefficient of linear extensibility (COLE) of 0.05
or more in a horizon or horizons at least 60 cm thick,
and a potential linear extensibility of 6 cm or more
in the upper 160 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 150 cm; and

c. More than 35 percent clay in horizons that have a
total thickness of more than 50 cm.
Torrertic Haploxerolls

HDFD. Other Haploxerolls that have the following
combination of characteristics:


74

2. An epipedon that is both massive and hard or very
hard when dry, and a moisture regime that is aridic but
marginal to xeric.

Xeralfa, p.119
IE. Other Alfisols that have a udic moisture regime.
Udalfs, p. 91
AQUALFS
Key to great groups

IAA. Aqualfs that have plinthite that forms a continuous
phase or constitutes half or more of the matrix within
some subhorizon between 30 and 150cm below the surface

of the soil.
Plinthaqualfs, p. 83
IAB. Other Aqualfs that have a natric horizon and do not

have a duripan.
Natraqualfe, p. 80

IAC. Other Aqualfs that have a duripan.
Duraqualfe, p. 77

IAD. Other Aqualfs that have a fragipan.
Fragiaqualfs, p. 7

TAE. Other Aqualfs that have a CEC of 16 cmol(+) or less
per kg clay (by IN NH4OAc pH 7) and an ECEC of 12
cmol(+) or less per kg clay (sum of bases extracted with
1N NH,OAc pH 7 plus IN KCl-extractable Al) in the
major part of the argillic or kandic horizon, or the major
part of the upper 100 cm of the argillic or kandic horizon if
these horizons are thicker than 100 cm.

Kandiaqualfa, p.78
IAF, Other Aqualfs that have an albic horizon tonguing
into an argillic horizon.

Glossaqualfa, p. 77
IAG. Other Aqualfs that have an abrupt textural change
between an ochric epipedon or an albic horizon and an

argillic horizon and have slow or very slow hydraulic
conductivity in the argillic horizon.
Albaqualfe, p. 75

JAH. Other Aqualfs that have an umbric epipedon.
Umbraqualfs, p. 83

? gydraulic conductivity is defined as the rate of internal water
novanent vader a unit potential gradient. In this text the tera refers
To vertical saturated hydraulic conduccivity. slow and very slow rates
[efor to 4 to 10 and last than 4 cm vater per day, respectively,


230
ADDC. Other Medisaprists that:

1, Have 25 cm or more of the subsurface and bottom
tiers consisting of hemic materials; and

2. Have a mineral layer 30 cm or more thick that has
its upper boundary in the control section below the

surface tier,
Hemic Terric Medisaprists

ADDD. Other Medisaprists that have a mineral layer 30
cm or more thick that has its upper boundary in the
control section below the surface tier.

Terric Medisaprists
ADDE. Other Medisaprists that have limnic layer(s)
that are 6 cm or more thick within the control section.
ADDF. Other Medisaprists that have a mineral layer
between 5 and 30 cm thick or two or more thin,
continuous mineral layers, within organic materials,
in the control section below the surface tier.
ADDG. Other Medisaprists that have 12.5 om or more of
the subsurface and bottom tiers consisting of fibric

materials.
Fibric Medisaprists

ADDH. Other Medisaprists that have 25 cm or more of
the subsurface and bottom tiers consisting of hemic

materials.

Hemic Medisapri
ADDI. Other Medisaprists.

Typic Medisaprists

Troposaprists
Key to subgroups
ADCA. Troposaprists that have a lithic contact within the
control section.

Lithic Troposaprists

ADCB. Other Troposaprists that:

1. Have 12.5 cm or more of the subsurface and bottom
tiers consisting of fibric materials; and

2. Have a mineral layer 30 cm or more thick that has
its upper boundary in the control section below the

surface tier.
Fibric Terrie Troposaprists
ADCC. Other Troposaprists that:

1, Have 25 cm or more of the subsurface and bottom
tiers consisting of hemic materials; and


219
within 100 cm of the soil surface for 60 or more days,
cumulative, in most years.
Aquic Quartzipsamments
KCCE. Other Quartzipsamments that:
1. Have an ustic moisture regime; and
2. Have a clay fraction that has a CEC equal to that of
the clay of an oxic horizon and have enough clay to
coat at least 75 percent of the surfaces of the sand
grains.
Ustoxic Quarizipaamments
KCCF. Other Quartzipsamments that
1. Have a udic moisture regime; and
2, Have a clay fraction that has a CEC equal to that of
the clay of an oxic horizon and have enough clay to
coat at least 75 percent of the surfaces of the sand
grains,
Orthoxic Quartzipsamments

KCCG. Other Quartzipsamments that have 6 percent or
more plinthite in one or more subhorizons above a depth

of 100 cm,
Plinthic Quartzipsamments

KCCH. Other Quartzipsamments that have an ustic
moisture regime.

Ustic Quartzipsamments
KCCI. Other Quartzipsamments that have a xeric
moisture regime.

Xeric Quartzipeamments
KCOJ. Other Quartzipsamments that have an albic
horizon!? at the surface or immediately under an A or an

Ap horizon that is underlain by another horizon that has
a color value more than one unit darker or chroma of 6 or

more,

Spodic Quartzipeamments
KCCK. Other Quartzipsamments.

Typic Quartzipsamments
Torripsamments
Key to subgroups

KCBA. Torripsamments that have a lithic contact within
50 cm of the soil surface.

Lithic Torripgamments
KCBB. Other Torripsamments that:

1. Have a horizon within 100 cm of the surface that is
more than 15 cm thick and either contains 20 percent

a
The albic norizon mist be thick enough to be preserved after the soil
to « depth of 18 cm is mixed,


96

b. The soil is not frozen in most yeara below a depth of 5
cm; that is, the soil is cold throughout the year but,
because of marine influence, does not freeze in most
years,

Cryie soils that have an aquic moisture regime
commonly are churned by frost.

Most isofrigid soils with a mean annual soil temperature
above 0°C have a eryic temperature regime. A few with
organic materials in the upper part are exceptions.
Throughout this text all isofrigid soils without permafrost
are considered to have a cryic temperature regime.

Frigid.--The frigid regime and some of the others that
follow are used chiefly in defining classes of soils in the
low categories. In the frigid regime the soil is warmer in
summer than in the cryic regime, but its mean annual
temperature is lower than 8°C (47°F), and the difference
between mean winter and mean summer soil
temperature is more than §°C (9°F) at a depth of 50 cm or at
a lithic or paralithic contact, whichever is shallower.

Mesic.--The mean annual soil temperature is 8°C or
higher but lower than 15°C (69°F) and the difference
between mean summer and mean winter soil
temperature is more than 5°C at a depth of 50 cm or at a
lithic or paralithic contact, whichever is shallower.

‘Thermic.--The mean annual soil temperature is 15°C
(59°F) or higher but lower than 22°C (72°F), and the
difference between mean summer and mean winter soil
temperature is more than 5°C at a depth of 50 cmor at a
lithic or paralithic contact, whichever is shallower.

Hyperthermic.--The mean annual soil temperature is
22°C (72°F) or higher, and the difference between mean
summer and mean winter soil temperature is more than
8°C at a depth of 50 cmor at a lithic or paralithic contact,
whichever is shallower.

Ifthe name of a soil temperature regime has the prefix iso,
the mean summer and winter soil temperature for June,
July, and August and for December, January, and
February differ by less than 5°C at a depth of 60 cmor at a
lithic or paralithic contact, whichever is shallower.

Isofrigid.-The mean annual soil temperature is lower
than 8'C (47°F).

Isomesic.--The mean annual soil temperature is 8°C or
higher but lower than 15°C (59°F).

Isothermic.--The mean annual soil temperature is 15°C
or higher but lower than 22°C (72°F).


182

temperature lower than 22°C, mean summer and mean
winter soil temperatures at a depth of 60 cm that differ by
5°C or more, and an aridic moisture regime that borders

on a xeric regime.
Xerochreptic Calciorthids

FBEM. Other Calciorthids that are dry in all parts of the
moisture control section three-fourths or less of the time
(cumulative) that the soil temperature is 5°C or higher at
a depth of 50 cm and have an aridic moisture regime that

borders on an ustic regime.
‘Ustochreptic Calciorthids

FBEN, Other Calciorthids that have reddish peda below

the calcic horizon that are weakly calcareous or

noncalcareous but that are thickly coated with lime.
Argic Calciorthids

FBEO. Other Calciorthids.
Typic Calciorthids

Camborthids

Key to subgroups

FBFA. Camborthids that have the following combination
of characteristics:

1. Have a frigid or colder temperature regime and an
aridic moisture regime that borders on an ustic
regime; and

2. Have @ lithic contact within 60 cm of the surface;
an

3, Have a weighted average percentage of organic
carbon in the upper 40 cm that is 0.6 percent or more if
the weighted average ratio of sand to clay in the soil
above that depth is 1.0 or less, or is 0.15 percent or more
if the ratio is 13 or more, or is intermediate between 0.6
percent and one-seventh percent if the ratio of sand to
clay is between 1.0 and 13; and a weighted average
percentage of organic carbon in the soil to a depth of 18
cm that is one-fifth or more higher than the values just
stated if there is a lithic or paralithic contact at a depth
of less than 40 cm but more than 18 cm.

Boroliic Lithie Camborthids

FBFB. Other Camborthids that have the following
combination of characteristics:

1. Have a horizon within 100 cm of the surface that is
more than 15 cm thick and either contains 20 percent
or more durinodes or is brittle and hs
consistence when moist; and

2. Have a lithic contact within 60 cm of the surface;
and

3, Have a weighted average percentage of organic
carbon in the upper 40 cm that is 0.6 percent or more if
the weighted average ratio of sand to clay in the soil
above that depth is 1.0 or leas, or is 0.15 percent or more


221

KCDB, Other Udipaamments that have mottles that have
chroma of 2 or less above a depth of 100 cm.
Aquie Udipsamments

KCDC, Other Udipsamments that have an albic horizon
that is thick enough to be preserved after the soil has been
mixed to a depth of 18 cm and is underlain by a horizon
that has a color value one unit or more darker and that
meets all requirements for a spodic horizon except the

index of accumulation.
Spodic Udipsamments

KCDD. Other Udipsamments that have lamellae within
150 cm of the soil surface that meet all requirements for
an argillic horizon except thickness!2, and either have
base saturation of 35 percent or more at a depth of 125 cm
below the uppermost lamella or have a frigid
temperature regime.

Alfic Udipsamments

KCDE, Other Udipsamments that have lamellae within
150 cm of the soil surface that meet all requirements for
an argillic horizon except thickness.!3

Ultic Udipsamments

KCDF. Other Udipsamments that have a surface horizon

between 25 and 60 cm thick that meets all requirements

for a plaggen epipedon except thickness.
Plaggeptic Udipsamments

KCDG. Other Udipsamments.

‘Typic Udipsamments
Ustipsamments
Key to subgroups
KCGA, Ustipsamments that have a lithic contact within
50 cm of the surface.

Lithic Ustipsamments

KCGB. Other Ustipsamments that have distinct or
prominent mottles above a depth of 100 cm or are
saturated with water within 100 cm of the surface during
some time of year in most years.

Aquie Ustipeamments

KCGC. Other Ustipsamments that have lamellae within
150 cm of the soil surface that meet all requirements for
an argillic horizon except thickness!“ and base

2

‘the olay content cannot be estimated with precision in lamellae that
are vary thin. The lamellae in soils of alfic subgroups generally are
about 0.5 to 1 an thick, but their total thickness is lese than the 15
gp required for an argiiiie horizon.

‘The clay content cannot be aatinated with precision in lamellae that
are very thin. Tha lamellae in soils of alfic subgroups generally are
‘about 0.5 to 1 on thick, but thedy total thickness is lees than the 15
gq Fequired for an argiilie horizon.

‘The clay content cannot be
are very thin. The lamellae
about 0,5 to 1 am thick, but their total thickness is lees than the 15
on required for an argiilic horizon.



47

Fine-loamy. By weight, 15 percent or more of the particles
are fine sand (diameter 0.25-0.1 mm) or coarser,
including fragments up to 7.5 cm in diameter; 18 through
34 percent clay in the fine-earth fraction (less than 30
percent in Vertisols).

Coarse-silty, By weight, less than 15 percent of the
particles are fine sand (diameter 0,25-0.1 mm) or
coarser, including fragments up to 7.5 cm in diameter;
less than 18 percent clay in the fine-earth fraction.

Fine-silty. By weight, less than 15 percent of the particles
are fine sand (diameter 0.25-0.1 mm) or coarser,
including fragments up to 7.5 cm in diameter; 18 through
34 percent clay in the fine-earth fraction (less than 30
percent in Vertisols).

Clayey.”- The fine earth contains 35 percent or more clay
by weight, and rock fragments are less than 35 percent by
volume.

Fine. A clayey particle-size class that has 36 through 59
percent clay in the fine-earth fraction (30 through 59
percent in Vertisols).

Very-fine. A clayey particle-size class that has 60 percent
or more clay in the fine-earth fraction.

Modifiers that repl f particle-size classes?

There are three situations in which particle-size class
names are not used. In one, the name is redundant.
Psamments and Psammaquents, by definition, are
sandy, and no particle-size class name is needed or used
in the family name.

In the second situation, soil materials derived from
volcanic ejecta, particle-size analysis is difficult to apply
because the soil material commonly consists of
aggregates containing volcanic glass and allophane.

7 if the ratio of 1500 kPa water retention to clay Le 0
half or nore of the control section,
considered to be 2.5 tines the percentege of 1500 kPa
Carkonates of clay size are not considered to be clay but are treated as
gilt in all particle-sise classes.

> the definition of the geologic terms used in the mubstitute particle-
in0 classes are the sane as those in! Bates, B.l,7 Jackson, J.A.
(kds.). 1980. Gleasary of Geclogy (Second Edition). American
Geological Institute. alls Church, VA. 751 p., with the following
exceptions:

Cinders! Uncmented Juvenile viteic vesicular pyroclastic material,
nore than 2.0 mm in at least one dinansion, with an spparent specific
gravity (including vesicles) of more than 1-0 and lose than 2.0.

Aapillt: Non or slightly vesicular pyroclasticg, 2.0 to 76 mm in at
want one dimension, with an apparent specific gravity of 2.0 or
mort

Pumtoa-Like: Vesteular pyroclastic materials other than puntos but
having an apparent upeciftc gravity (including vesicles) of leas than
1.05


116

paralithic contact is deeper than 50 cm but shallower
than 125 cm; and

3. More than 35 percent clay in horizons that total more
than 50 cm in thickness.
Vertic Paleustalfs

ICFC. Other Paleustalfs that have an argillic horizon that
is discontinuous horizontally, or is discontinuous
vertically in the upper 20 cm of its thickness, or has a
texture that is loamy fine sand or coarser.

Psammentic Paleustalfs

ICFD. Other Paleustalfs that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic horizon that is more
than 100 cm below the soil surface.

Grossarenic Paleustalfs

ICFE. Other Paleustalfs that:

1, Have mottles that have chroma of 2 or less within 75
om of the soil surface and the mottled horizon is
saturated with water at some time of the year when the
temperature of the horizon is 5°C or higher; and

2. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic horizon that is 50 to 100 cm below the
soil surface,

Aquic Arenic Paleustalfs

ICFF. Other Paleustalfe that have 5 percent or more
plinthite by volume in one or more subhorizons within 150

cm of the soil surface.
Plinthic Paleustalfs

ICFG. Other Paleustalfs that have mottles that have
chroma of 2 or less within 76 cm of the soil surface, and
the mottled horizon is saturated with water at some time of
the year when the temperature of the horizon is 5°C or

higher.
Aquic Paleustalfs

ICFH. Other Paleustalfs that have a petrocalcic horizon
that has its upper boundary within 150 cm of the soil

surface.
Petrocalcic Paleustalfs
ICFI. Other Paleustalfs that:
1. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the

top of an argillic horizon that is 50 to 100 cm below the
soil surface; and


52

section or the horizons. If there are strongly contrasting
particle-size classes, both particle-size classes are
named. Thus, if the weighted average of the upper part of
the control section is loamy fine sand and the lower part
is clay, the family differentia is sandy over clayey. If
there are more than two contrasting particle-size classes
within the control section, the classes differing most in
median particle size are named. Sandy includes fine
sand as well as coarser sands. Substitute names for
particle-size class names are applied only if the
materials extend at least. 10 cm into the upper part of the
control section.

The following particle-size classes are strongly
contrasting if the transition between them is less than
12.5 cm thick:

1, Ashy over loamy-skeletal.

2. Ashy over loamy.

3. Ashy over medial-skeletal.

4, Ashy over medial.

5. Ashy over pumiceous or cindery if there is an
absolute difference of 20 percent or more in volume of
rock fragments.

6. Ashy over sandy or sandy-skeletal.

7. Cindery over loamy.

8, Cindery over medial-skeletal.

9, Cindery over medial.

10. Clayey over fine-silty if there is an absolute
difference of more than 25 percent in the percentage of
clay.

12. Clayey over fragmental.

13. Clayey over loamy if there is an absolute difference
of more than 28 percent in the percentage of clay.

14. Clayey over loamy-skeletal if there is an absolute
difference of more than 25 percent in the percentage of
clay in the fine-earth fraction.

18. Clayey over sandy or sandy-skeletal.

16. Clayey-ekeletal over sandy.

17. Coarse-loamy over clayey.

18. Coarse-loamy over fragmental.

19. Coarse-loamy over sandy or sandy-skeletal if the
coarse-loamy material has less than 50 percent fine or
coarser sand.

20. Coarse-silty over clayey.

21. Coarse-silty over sandy or sandy-skeletal.

22, Fine-loamy over clayey if there is an absolute
difference of more than 25 percent in the percentage of
clay.

23. Fine-loamy over fragmental.

24. Fine-loamy over pumiceous or cindery.

25. Fine-loamy over sandy or sandy-skeletal.

26. Fine-silty over clayey if there is an absolute
difference of more than 25 percent in the percentage of
clay.

27. Fine-silty over fragmental.

28. Fine-silty over sandy or sandy-skeletal.


205

soil if @ lithic or paralithic contact is deeper than 50
cm but shallower than 150 em; and

c. More than 35 percent clay in horizons that total
more than 50 cm in thickness within the upper 100
cm; ant

2. Unless the soils are irrigated, the cracks remain
open in most years from 175 to 240 days, cumulative,
and are not closed for as many as 60 consecutive days
during the 120 days following the winter solstice in 3
or more years out of 10 if the soil temperature regime is

thermic, mesic, or frigid.
Ustertic Torrifluvents

KDDB. Other Torrifluvents that have ail three of the
following characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the soil
surface or to the base of an Ap horizon; and

2, A coefficient of linear extensibility (COLE) of 0.05
or more in 4 horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 150 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 150 cm; and

3. More than 35 percent clay in horizons that total more
than 50 cm in thickness within the upper 100 cm.
Vertic Torrifluvents

KDDC, Other Torrifluvents that:

1. Are dry in all parts of the moisture control section
for less than three-fourths of the time (cumulative) that
the soil temperature at a depth of 50 cm is 5°C or more
and they have a thermic, mesic, or frigid soil
temperature regime and a torric moisture regime that
borders on a xeric regime; and

2. Have, throughout a cumulative thickness of 18 cm or
more and within a depth of 76 cm, one or more of the
following:

a. Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders,
pumice, and pumice-like fragments make up more
than 66 percent of these fragmenta; or

b. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and
contains either:

(1) More than 30 percent volcanic glass; or

(2) At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Vitrixerandic Torrifiuvents


138
BBEE. Other Vitricryands that have a spodic horizon,
and an associated eluvial horizon with its upper

boundary within 125 cm of the mineral soil surface or of
the upper boundary of an organic layer with andic soil

properties, whichever is shallower.
Spodic Vitricryands

BBEF. Other Vitricryands that have an argillic or
kandic horizon with its upper boundary within 125 em of
the mineral soil surface or of the upper boundary of an
organic layer with andic soil properties, whichever is

shallower.
Alfic Vitricryands

BBEG. Other Vitricryands.

Typic Vitricryands
TORRANDS
Key to great groupe
BCA. All Torrands are regarded as Vitritorrands.

Vitritorrands, p. 138
Vitritorrands
Key to subgroups

BCAA. Vitritorrands that have a lithic contact within 50
em of the soil surface,
Lithic Vitritorrands

BCAB, Other Vitritorrands that have a petrocalcic
horizon with its upper boundary within 100 cm of the

mineral soi] surface.
Petrocalcic Vitritorrands

BCAC, Other Vitritorrands that have a horizon with its
upper boundary within 100 cm of a mineral soil surface
which is more than 15 cm thick and contains 20 percent
or more (by volume) cemented soil material that does not
slake in water after air drying.

Durie Vitritorrands

BCAD. Other Vitritorrands that have, in some
subhorizon between 50 and 100 cm:
1, Two percent or more redox segregations; or
2. Dominant chromas, moist, of 2 or less on faces of
peds, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or
3. Sufficient active ferrous iron to give a positive
reaction to a,a’-dipyridyl at some time of the year.
Aquic Vitritorrands

BCAE. Other Vitritorrands that have a calcic horizon
with its upper boundary within 125 cm of the mineral soil

surface.
Calcic Vitritorrands


314

HGP, Other Haplustolls that have mottles that have
chroma of 2 or leas within 100 cm of the surface if
artificially drained or, if undrained, are continuously
saturated with water within 100 cm of the soil surface for

90 days or more in most years.
Aquic Haplustolls
HFGQ. Other Haplustolls that:

1. When neither irrigated nor fallowed to store
moisture:

a. If the soil temperature regime is mesic or thermic,
are dry six-tenths or more of the time in half or more
years in some part of the moisture control section (not.
necessarily the same ) during a period when the
soil temperature at a depth of 50 cm exceeds §°C; or

b. If the soil temperature regime is hyperthermic or
isomesic, or warmer, are moist in some or all parts
of the moisture control section for less than 90
consecutive days during a period when the soil
temperature at a depth of 50 cm exceeds 8°C; and

2, Have an irregular decrease in organic-carbon.
content with increasing depth or have more than 0.3
percent at a depth of 125 cm of the surface; and

8. Have a slope of less than 25 percent.
Torrifluventic Haplustolls

HFGR. Other Haplustolls that:

1, When neither irrigated nor fallowed to store
moisture:

a. If the soil temperature regime is mesic or thermic,
are dry six-tenths or more of the time in half or more
years in some part of the moisture contro) section (not
necessarily the same part) during a period when the
soil temperature at a of 50 cm exceeds 5°C; or

b. If the soil temperature regime is hyperthermic or
isomesic, or warmer, are moist in some or all parts
of the moisture control section for less than 90
consecutive days during a period when the soil
temperature at a depth of 50 cm exceeds 8°C; and

2. Do not have a cambic horizon, and the lower part of
the mollic epipedon does not mect the requirements of a
cambic horizon except for color and for organic-carbon
content, or either the cambic horizon or the lower part of
the mollic epipedon has carbonates throughout.
Torriorthentic

HFGS. Other Haplustolls that when neither irrigated nor
fallowed to store moisture:

1, If the soil temperature regime is mesic or thermic,
are dry six-tenths or more of the time in half or more
years in some part of the moisture control section (not
necessarily the same part) during a period when the

soll temperature ata depth of 50 cm exceeds 5°C; or


46

These components are not adequately described by
normal particle-size classes, especially as they often
cannot be readily dispersed and the results of dispersion
are variable. Consequently, normal particle-size class
names are not used for that part of the soi) that has andic
soil properties or that is high in volcanic glass, as is the
situation with Andisols by definition. In families of
Andisols and in most andic and vitrandic subgroups of
other soil orders the following substitutes for particle-size
class names are used for the part of the soil that does not
disperse,

In the third situation, the content of allophane and

organic matter is also high and particle size has only
limited relation to the physical and chemical properties of
the soils. This seems to be normal in soils that have both a
cryic temperature regime and a spodic horizon.
Therefore, particle-size class names are not used for the
spodic horizons of most Cryaquods, Cryohumods,
Cryorthods, or Cryic Placohumods and for some other
Spodosols .

The following terms are substituted for the particle-size
class names in the taxa that have been listed unless the
particle-size modifier is redundant, They reflect
combination of particle size and mineralogy, and they
take the place of both.

A. Substitutes for the fragmental class:

These classes have inanfficient fine earth to fill 10
percent of interstices coarser than 1 mm,

Pumiceous - More than 60 percent by weight of the whole
soil is composed, of volcanic ash, cinders, lapilli, pumice
and pumice-like fragments more than 1 mm in
diameter; pumice or pumice-like fragments form two-
thirds or more by volume of the fraction coarser then 2.0
mm.

Cindery - More than 60 percent by weight of the whole soil
is composed of volcanic ash, cinders, lapilli, pumice and
pumice-like fragments more than 1 mm in diameter;
pumice or pumice-like fragments form less than two-
thirds by volume of the fraction coarser than 2.0 mm.

B. Substitutes for the non-fragmental classes:

* particle-site clase anes are applied to other spodic herisens but
with reservations. Somavhat different olesses probably should be Used
for most fai liee oF Spodosole, but data are too few to perait the
testing of alternatives, Some series that vould othervise be reasonably
honogensous are split at the family level by the particle-size clasees.
These soils have appreciable but not very large anounte of organic
fatter in the spodic horizon.

S punica-like: Veatoular pyroclastic materials other than puntos but
having an apparent specific gravity (including vesicles) of less than
1.0 g/ece



407

Chapter 15
Vertisols
KEY TO SUBORDERS

EA. Vertisols that have a thermic, mesic, or frigid soil
temperature regime and, unless irrigated, have cracks
that open and close once each year and remain open for
60 consecutive days or more in the 90 days following the
summer solstice in more than 7 out of 10 years but that
are closed for 60 consecutive days or more during the 90
days following the winter solstice.
Xererts, p. 410

EB. Other Vertisols that, unless irrigated, have in most
years cracks that either remain open throughout the year
or are closed for less than 60 consecutive days at a period
when the soil temperature at a depth of 50 cm is
continuously higher than 8°C.

Torrerts, p.407

EC, Other Vertisols that have cracks that open and close
one or more times during the year in most years but do
not remain open for as many as 90 cumulative days in
most years.

Uderts, p. 408
ED. Other Vertisols.

Usterts, p. 409
TORRERTS
Key to subgroups

EBAA. Torrerts that:

1, Have a surface horizon 30 cm or more thick with a
color value of 3 or less, moist, in half or more of each
pedon; and

2, Have prismatic or blocky structure accompanied by
clay skins on ped faces that have a color value lower
than that in the matrix within 100 cm of the soil

surface.
Paleustollic Torrerts

EBAB. Other Torrerts that have a surface horizon 30 cm
or more thick with a color value of 3 or less, moist, in
half or more of each pedon.

Mollic Torrerts

EBAC. Other Torrerts that have prismatic or blocky
structure accompanied by clay skins on ped faces that
have a color value lower than that in the matrix within

100 cm of the soil surface.
Argidic Torrerts

EBAD. Other Torrerts.
‘Typic Torrerts


216

KEFE. Other Ustorthents that have 50 percent or more (by
volume) wormholes, wormcasts, and filled animal
burrows between the bottom of the Ap horizon or a depth of
25 cm, whichever is deeper, and a depth of 100 cm or a
lithic or paralithic ar petroferric contact, whichever is

shallower.
‘Vermic Ustorthents
KEFF. Other Ustorthents.
Typic Ustorthents
Xerorthents
Key to subgroups

KECA. Xerorthents that have a lithic contact within 50
cm of the soil surface.
Lithic Xerarthents

KECB. Other Xerorthents that have, throughout a
cumulative thickness of 18 cm or more and within a
depth of 75 cm, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more
than 36 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains

either:
a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Vitrandic.

KECC, Other Xerorthents that:

1. Are saturated with water within 150 cm of the
surface at any time of year in most years; and

2. Have a horizon within 100 cm of the surface that is
more than 16 cm thick and either contains 20 percent
or more durinodes or is brittle and has firm

consistence when moist.
‘Aquic Durorthidic Xerorthents

KECD. Other Xerorthents that are saturated with water
within 150 cm of the surface at any time of year in most

years.
Aquic Xerorthents

KECE. Other Xerorthents that have a horizon within 100
em of the surface that is more than 15 cm thick and either
contains 20 percent or more durinodes or is brittle and
has firm consistence when moist.

Durorthidic Xerorthents


303
there is no lithic or paralithic contact within 60 cm of

the surface of the soil.
Paleustolls, p. 317

HFD. Other Ustolls that do not have an argillic horizon
above a calcic, gypsic, or petrocalcic horizon, and that
have a calcic or gypsic horizon that has its upper boundary
within 100 cm of the soil surface or that have a petrocalcic
horizon that has its upper boundary within 150 cm of the
surface, and that are calcareous in all overlying
subhorizons after the upper soil to a depth of 18 cm has been
mixed, unless the texture is coarser than loamy very fine

sand or very fine sand.
Caleiustolls, p. 307

HFE, Other Ustolla that have an argillic horizon,
Argiustolls, p. 303

HFF, Other Ustolls that have a mollic epipedon below any
Ap horizon that is 50 percent or more by volume
wormholes and wormeasts or filled animal burrows, and
that either rests on a lithic contact or has a transition to the
underlying horizon in which 25 percent or more of the
material is discrete wormcasts or animal burrows filled
with material from the mollic epipedon and the
underlying horizon.

Vermustolls, p. 319
HFG. Other Ustolls.

Haplustolls, p. 310
Argiustolls
Key to subgroups

HFEA. Argiustolls that:

1, Have an albic horizon or other eluvial horizon above
the argillic horizon that has a color value too high for a
mollic epipedon and chroma too high for an albic
horizon; and

2, Have a lithic contact within 50 cm of the surface.
Alfie Lithic

HFEB, Other Argiustolls that have a lithic contact within
50 cm of the surface.
Lithic Argiustolls
HFEC. Other Argiustolls that:
1, Have the following combination of characteristics:

a, Cracks at some period in most years that are Lem
or more wide at a depth of 50 cm, that are at least 30
cm long in some part, and that extend upward to the
surface or to the base of an Ap horizon; and

b. A coefficient of linear extensibility (COLE) of 0.07
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more
in the upper 125 cm of the soil or in the whole soil if a


210

KEC. Other Orthents that have a xeric moisture regime.
p 216

KED. Other Orthents that have a udic moisture regime
and mean summer and mean winter soil temperatures
at a depth of 50 cm that differ by less than 5°C.

‘Troporthents, p. 214
KEE, Other Orthents that have a udic moisture regime.
p24
KEF, Other Orthents.
Ustorthents, p. 215
Cryorthents
Key to subgroups

KEAA, Cryorthents that have a lithic contact within 50
cm of the soil surface.
Lithic Cryorthents
KEAB. Other Cryorthents that have a mean annual soil
temperature that is 0°C or lower.
Pergelic Cryorthents

KEAC. Other Cryorthents that have, throughout a
cumulative thickness of 18 cm or more and within a
depth of 75 cm, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more
than 36 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
perpent of the less than 2.0 mm fraction and contains
either:

a, More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Vitrandic

KEAD. Other Cryorthents that have mottles that have
chroma of 2 or leas within 50 cm of the soi] surface.

KEAE. Other Cryorthents that have lamellae within 150
cm of the soil surface that meet all requirements for an
argillic horizon except thickness.

Alfic Cryorthants

KEAF. Other Cryorthents.
Typic Cryorthents

8

‘The clay content cannot be estimated with precision in lapellae that
are very thin. The lmmellae in soila of alfic aubgroups ganezally are
bout 0.5 te 1 om thiok, but their total thickness ie less than the 15
qm required for an argillic horiton.


338
DDBB. Other Acroperox that have a petroferric contact
within 125 cm of the soil surface.
Petroferric Acroperox
DDBC, Other Acroperox that have mottles of 4 or more

value moist and 2 or less chroma within a depth of 125 cm
of the soil surface and a lithic contact within 125 cm of the

soil surface.
Aquic Lithic Acroperox

DDBD. Other Acroperox that have a lithic contact within a
depth of 125 cm of the soil surface.
Lithic Acroperox

DDBE. Other Acroperox that have a delta pH (KCI pH - 1:1
water pH) with a 0 or net positive charge in some layer 18
cm or more thick within a depth of 125 cm of the soil

surface,
Anionic Acroperox

DDBF. Other Acroperox that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the

soil surface.
Plinthic Acroperox

DDBG. Other Acroperox that have mottles of 4 or more
value moist and 2 or less chroma within a depth of 125 cm

of the soil surface.
Aquic Acroperox

DDBH. Other Acroperox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and a color hue of 2.5YR or redder with
moist values of leas than 4 in most of the 25 to 125 cm depth

from the soil surface.
Humic Rhodic Acroperox

DDBI. Other Acroperox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and color hue of 7.5YR or yellower with
moist values of 6 or more in most of the 25 to 125 cm depth

from the soil surface.
Humic Xanthic Acroperox

DDBJ, Other Acroperox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of

surface litter.
Humic Acroperox

DDBK. Other Acroperox that have a color hue of 2.5YR or
redder with moist values of less than 4 in most of the 25 to

125 cm depth from the soil surface.
Rhodic Acroperox

DDBL. Other Acroperox that have a color hue of 7.5YR or
yellower with moist values of 6 or more in moat of the 25 to

125 cm depth from the soil surface.
‘Xanthic Acroperox

DDBM. Other Acroperox.
‘Typic Acroperox


217

KECF. Other Xerorthents that have base saturation (by
NH, Ac) of less than 60 percent in all parte of the soil

between depths of 25 and 75 em below the soil surface.
Dystric

KEDG. Other Xerorthents.

‘Typic Xerorthents
PSAMMENTS
Key to great groups

KCA. Psamments that have a cryic or pergelic soil
temperature regime.

Cryopsamments, p. 217
KCB. Other Psamments that have a torric moisture
regime.
Torripaamments, p. 219

KCC. Other Psamments that have, in the particle size

control section, more than 90 percent silica

minerals (quartz, chalcedony or opal) or other

extremely durable minerals in the 0.02 to 2.0 mm

fraction that are resistant to weathering.
Quartzipsamments, p, 218

KCD, Other Psamments that have a udic moisture
regime and mean summer and mean winter soil
temperatures at a depth of 50 cm that differ by 5°C or
more.

Udipsamments, p, 220
KCE. Other Psamments that have a udic moisture
regime.

‘Tropopsamments, p, 220

KCF, Other Psamments that have a xeric moisture
regime.

Xeropsammenta, p, 222
KCG. Other Psamments.

Ustipeamments, p, 221
Cryopsamments
Key ta subgroups

KCAA. Cryopsamments that have a lithic contact within
50 cm of the soil surface.
Lithic Cryopeamments

KCAB. Other Cryopsamments that have a mean annual
soil temperature that is 0°C or lower.
Pergelic Cryopeamments

KCAC. Other Cryopsamments that have mottles that
have chroma of 2 or less within 50 em of the soil surface.
Aquic

KCAD. Other Cryopsamments that have an albic horizon
that is 5 cm or more thick and underlain by a horizon
that has a color value one unit or more darker and that


77

Duraqualfs

Duraqualfs are the Aqualfs that have a duripan below the
argillic horizon. They are not known to occur in the
United States. The group has been proposed for other
countries, but definitions of subgroups have not been
suggested,

Fragiaqualfs
Key to subgroups

IADA. Fragiaqualfs that have a mottled horizon between
the A or Ap horizon and a fragipan that has dominant
chroma more than 2 if the hue is 10YR or redder or more
than 3 if the hue is 2.5Y or yellower.

Aeric Fragiaqualfs

TADB. Other Fragiaqualfs that have 5 percent or more
plinthite (by volume) in one or more subhorizons within

150 cm of the surface.
Plinthic Fragiaqualfs

TADC. Other Fragiaqualfs that have an Ap horizon that
has a color value, moist, of 3 or less and a color value, dry,
of 5 or less after the soil has been crushed and smoothed;
or the upper soil to a depth of 18 cm, after mixing, has these

color values.
Umbric Fragiaqualfs
IADD. Other Fragiaqualfs,
Typic Fragiaqualfe
Glossaqualfs
Kev to subgroups

IAFA. Glossaqualfs that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic horizon that is 60 to 100

om below the soil surface.
Arenic Glossaqualfs

IAFB. Other Glossaqualfs that have a layer, starting at
the mineral soil surface, that has a sandy particle-size
class and extends to the top of an argillic horizon that is
more than 100 cm below the soil surface.

Grossarenic Gloesaqualfs


357

Chapter 18
Spodosols

KEY TO SUBORDERS

CA. Spodosols that either have an aquic moisture
regime! or are artificially drained and have
characteristics associated with wetness, namely one or
more of the following:

1. A histie epipedon; or

2, Mottling in an albic horizon or in the upper part of
the spodic horizon; or

3. A duripan in the albic horizon; or

4. If free iron and manganese are absent or if the color
value, moist, is less than 4 in the upper part of the
spodic horizon, either

a. Have any color if there are no coatings of iron
oxides on the individual grains of silt and sand in
or immediately below the spodic horizon wherever
the value, moist, is 4 or more; or

b, Have fine or medium mottles of iron or
manganese in the materials immediately below the
spodic horizon; or

5. A placic horizon that rests on a fragipan or on a

spodic horizon or on an albic horizon that is underlain

by a apodic horizon but is not in  spodic horizon.
Aquods, p. 357

CB. Other Spodosols that have a spodic horizon in which
the ratio of free iron (by dithionite-citrate) to carbon (both
elemental) is 6 or more in all subhorizons,

Ferrods, p. 363

CC. Other Spodosols that have a spodic horizon in which
some subhorizon that is present in more than half of each
pedon has a ratio of free iron to carbon of leas than 0.2.

Humods, p. 363
CD. Other Spodosols.

Orthods, p. 367
AQUODS
Key to great groups

CAA. Aquods that have a fragipan below the spodic
horizon but do not have a placic horizon above the

fragipan.
Fragiaquods, p. 359

1
Ifa placie horizon, duripan, or fragipan is present, tbe wil need not be saturated below
‘Uaat horisen.


308
a, More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vitrandic Argivstolls

HFEI. Other Argiustolls that have an albic horizon or
other eluvial horizon above the argillic horizon that has a
color value too high for a mollic epipedon and chroma too
high for an albic horizon, and the mean annual soil

temperature is lower than 10°C.
Boralfic Argiustolls

HFEJ. Other Argiustolls that have an albic horizon or
other eluvial horizon above the argillic horizon that has a
color value too high for a mollic epipedon and chroma too
high for an albic horizon, and the mean annual soil

temperature is 10°C or more.
Ustalfic Argiustolls

HFEK, Other Argiustolls that have a mollic epipedon 50
cm or more thick with a texture finer than loamy fine

sand.
Pachic Argiustolls

HFEL. Other Argiustolls that have mottles that have
chroma of 2 or lesa within 100 em of the soil surface and
are continuously saturated with water within 100 cm of the
soil surface for 3 months or more in most years unless

artificially drained,
Aquic Argiustolls

HFEM. Other Argiustolls that, when neither irrigated
nor fallowed to store moisture:

1, If the soil temperature regime is mesic or thermic,
are dry six-tenths or more of the time in some or all
parts of the moisture control section (not necessarily the
same part) in half or more years during the period

when the soil temperature at a depth of 50 cm is higher
than 5°C; or

2. If the soil temperature regime is hyperthermic, or
isomesic, or warmer, are moist in some or all parts of
the moisture control section for less than 90 consecutive
days during a period when the soil temperature at a
depth of 50 cm is higher than 8°C.

Aridic Argiustolls

HFEN. Other Argiustolls that, when neither irrigated nor
fallowed to store moisture:

1. If the soil temperature regime is mesic or thermic,
are dry for four-tenths or less of the cumulative days in
some part of the moisture control section when the soil
temperature at a depth of 50 cm exceeds 5°C; or

2. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or less
during a period when the soil temperature at a depth of

60 cm exceeds 8°C.
Udic Argiustolls


87

1. Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil, and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a, More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vitrandic Eutroboralfs

IBED. Other Eutroboralfs that:

1, Have an argillic horizon that has mottles that have
chroma of 2 or Jess within a depth of 75 cm below the soil
surface ; and

2. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of the argillic horizon that is more than 50 cm below
the soil surface,

Aquic Arenic Eutroboralfs

IBEE. Other Eutroboralfs that:
1. Have an argillic horizon that either

a. Has its upper boundary at less than 50 cm below the
soil surface and has mottles that have chroma of 2 or
less in the upper 25 cm if the mottled layer is
saturated with water at some time when the soil
temperature is 5°C or higher; or

b. Has an upper boundary at 50 cm or more, and the
soil has mottles that have chroma of 2 or less within a
depth of 75 cm below the soil surface; and

2. Have tongues of albic materials in the argillic
horizon (interfingering is permitted).
Glossaquic Eutroboralis

IBEF, Other Eutroboralfs that have an argillic horizon
that either:

1. Has its upper boundary at less than 60 cm below the
soil surface, and has mottles that have chroma of 2 or
less in the upper 25 cm if the mottled layer is saturated
with water at some time when the soil temperature is
5°C or higher; or

2. Has an upper boundary at 50 cm or more, and the soil


42
Limni ‘al

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.

Conrogenous earth

A coprogenous earth (sedimentary peat) layer is a limnic
layer that

1. Contains many fecal pellets a few hundredths to a few
tenths of a millimeter in diameter; and

2, Has a color value, moist, of less than 5; and

3. Either forms a slightly viscous water suspension and is
slightly plastic but not sticky, or shrinks upon drying to
form clods that are difficult to rewet and that often tend to
crack along horizontal planes; and

4, Is normally, but not necessarily, nearly devoid of
fragments of plants that can be recognized with the eye;
and

5. Yields a saturated sodium pyrophosphate extract on
white filter paper that has higher color value and lower
chroma than 10 YR 7/3, or the cation-exchange capacity is
Jess than 240 cmol(+) per kg of organic matter (measured
by loss on ignition), or both.

Diatomaceous earth
A diatomaceous earth layer is a limnic layer that

1. Has a matrix color value of 3 through 5 if not previously
dried, and the value changes irreversibly on drying. The
color change resulta from irreversible shrinkage of
organic matter coatings on diatoms, which can be
identified by microscopic (440X) examination of dry
samples; and

2. Yields a color higher in value and lower in chroma
than 10 YR 7/3 on white filter paper that is inserted into a
paste made of the material in a saturated sodium
pyrophosphate solution, or the cation-exchange capacity is
less than 240 cmol(+) per kg of organic matter (by loss on
ignition), or both.

Marl
A marl layer is a limnie layer that


129

Chapter 6

Andisols’

KEY TO SUBORDERS

BA. Andisols that have a histic epipedon or experienced
periods of saturation and reduction, as evidenced by one
or more of the following within 50 cm of the mineral soil
surface or of the upper boundary of an organic layer with
andic soj] properties, whichever is shallower, unless
irrigated and evidence occurs above a depth of 40 cm and
not ws

1, Two percent or more redox segregations?; or

2, Dominant chromas, moist, of 2 or less on faces of
peds, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or

3. Sufficient active ferrous i iron to give a positive
reaction to a,a'-dipyridyl® at some time of the year
irrigated.

when not being i

Aquands, p. 130
BB. Other Andisols that have a cryic or pergelic soil
temperature regime.

Cryands, p 134

BC. Other Andisols that have an aridic moisture
regime,

Torrands, p.138

BD. Other Andisols that have a xeric moisture regime.
p.154

BE. Other Andisols that have 1500 kPa water retention of
Jess than 16 percent on air-dried samples and less than

30 percent on undried samples, throughout a thickness of
85 cm or more within 60 cm of the mineral soil surface or

International Committe on the Classification of Andisole (ICOHAND) ,
ghatred by Wats Leamy, wow Zeatand soit Bureau.

precipitation in the form of axides,

A Ponisi svarhion to the dipyeidyl fiend eat for faowe tron
(childs 1981") aay be used to confize the ext
conditions, and 18 especially useful in aicval
saturation, normal norpholegical indicators 0!
etther absent of obscured (aa by the dark col
melanic great groups). A negative reaction, however, dows not imply
that reducing conditions are neceaserily, or always, absent; this may
merely mean that the level of free iron in the soll ix below the
senritavity Limit of the teat or that the soil is in an oxidited phase
Ae the tine of testing.

Childs, C.M, 1961: Field teat for ferrous izen and farrie-oryanic
complexes (an exchange sites or in water-soluble forms) in soils,
‘Australian Journal of foil Research 191 175-1



409

USTERTS

Key to great groups

EDA. Usterts that have a chroma, moist, of 2 or more in
some part of the matrix of the upper 30 cm in more than
half of each pedon.

Chromusterts, p. 409
EDB. Other Usterts,
Pellusterts, p.409
Chromusterts
Key to subgroups

EDAA. Chromusterts that

1. Have cracks that remain open from 90 to 150
cumulative days in most years and have a mean
annual soil temperature that is less than 15°C; and

2. Have a color value, moist, of 4 or more or a value,
dry, of 6 or more in the surface horizon, or the horizon
with color value of 3 or less, moist, and 5 or less, dry, is
less than 30 cm thick in half or more of each pedon.
Udorthentic Chromusterts

EDAB. Other Chromusterts that have cracks that remain
open from 90 to 150 cumulative days in most years, and
have a mean annual soil temperature that is less than

" Udie Chromusterts

EDAC. Other Chromusterts that have, within 100 cm of
the soil surface, prismatic or blocky structure
accompanied by clay skins on ped faces that have a color
value lower than that in the matrix.

Paleustollic Chromusterts

EDAD. Other Chromusterts that have a color value,
moist, of 4 or more or a value, dry, of 6 or more in the
surface horizon, or the horizon with color value of 3 or
less, moist, and § or less, dry, is less than 30 cm thick in
half or more of each pedon.

Entic Chromusterts
EDAE. Other Chromusterts.

‘Typic Chromusterts
Pellusterts
Key to suberoups

EDBA. Pellusterts that

1, Have cracks that remain open for 150 or less
cumulative days during each year or have a mean
annual soil temperature that is less than 15°C; and

2. Have a color value, moist, of 4 or more or a value,
dry, of 6 or more in the surface horizon, or the horizon


192

2. When neither irrigated nor fallowed to store
moisture:

a. If the soil temperature regime is mesic or thermic,
are moist six-tenths or less of the time in half or more
years in some part of the moisture control section (not
necessarily the same part) when the soil temperature
at a depth of 50 cm exceeds 5°C; or

b. If the soil temperature regime is hyperthermic,
isomesic, or warmer, are moist in most years in
some or all parts of the moisture control section for
legs than 180 days during a period when the soil
temperature at a depth of 50 em exceeds 8°C.

Arenic Aridic Kandiustalfs

ICDF. Other Kandiustalfs that have a layer, starting at
the mineral soil surface, that has a sandy particle-size
class and extends to the top of en argillic or kandic
horizon that is 60 to 100 em below the soil surface.

Arenic Kandiustalfs

ICDG. Other Kandiustalfs that, when neither irrigated
nor fallowed to store moisture:

1, If the soil temperature regime is mesic or thermic,
are moist six-tenths or less of the time in half or more
years in some part of the moisture control section (not
necessarily the same part) when the soil temperature at
a depth of 50 cm exceeds 5°C; or

2. If the soil temperature regime is hyperthermic,
isomesic, or Warmer, are moist in most years in some
or all parts of the moisture control section for less than
180 days during a period when the soil temperature at a
depth of 50 cm exceeds 8°C.

Aridic Kandiustalfs

ICDH. Other Kandiustalfs that, when neither irrigated
nor fallowed to store moisture:

1. If the soil temperature regime is mesic or thermic,
are dry for 186 or less cumulative days in some part of
the moisture control section when the soil temperature
at a depth of 50 cm exceeds 6°C; or

2. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or less
during a period when the soil temperature at a depth of
50 cm exceeds 8°C.

Udic Kandiustalfs

ICDI. Other Kandiustalfs that have, throughout the
argillic or kandic horizon, a hue of 2.5YR or redder, and
have a value, moist, of 3 or less and have a value, dry, that


273
JEDG. Other Haplumbrepts that:

1. Have an umbric or a mollic epipedon that is 50 cm or
more thick; a:
2, Have a content of organic carbon’ that decreases
irregularly with depth; and
8. Have slopes of 25 percent or less.
Cumulic Haplumbrepts:
JEDH. Other Haplumbrepts that have an umbric or a
mollic epipedon that is 50 cm or more thick.
Pachic Haphmmbrepts
JEDI. Other Haplumbrepts that have mottles that have
chroma of 2 or leas within 60 cm of the soil surface, and

the mottled horizon is saturated with water at some time of
the year when its temperature is more than 5°C, or there is

artificial drainage.
Aquic Haplumbrepts:
JEDJ. Other Haplumbrepts that:

1, Have a content of organic carbon!’ that decreases
irregularly with depth; and

2. Have slopes of 25 percent or less.

Fiuventic Haplombrepts
EDK Other Haplumbrepts that do not have a cambic
jorizon,
Entic Haplumbrepts
JEDL, Other Haplumbrepts.
‘Typic Haphmbrepts
Xerumbrepts
Key to subgroups
JECA. Xerumbrepts that have a lithic contact within 50 cm
of the soil surface.
Lithic Xerumbrepts

JECB, Other Xerumbrepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 83 kPa water retention, of 1.0 g cm’ or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andie’

JECC. Other Xerumbrepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

16
‘The carton should be of Hoteoene age. Jt te not the intent to include foal! eazbon from

Ww
‘The carton should be of Holocene age. It is not the intent to include fail carbon from
bedrock.


121

1. Have an argillic horizon that:

a. Has 35 percent or more clay in some subhorizon at
least 7.5 cm thick; and

b, Has an increase in clay content that ia 15 percent
or more (absolute) within a vertical distance of 2.5
cm, or is 20 percent or more (absolute) within a
vertical distance of 7.5 cm, at the upper boundary or
within some part; and

2. Have a duripan that is not both massive, platy, or
prismatic and more than half of its upper boundary
indurated and coated with opal or with opal and
sesquioxides, or indurated in some subhorizon below

the upper boundary.
Abruptic Haplic Durixeralfs

IDAD. Other Durixeralfs that have an argillic horizon
that:

1. Has 36 percent or more clay in some subhorizon at
least 7.5 cm thick; and

2. Has an increase in clay content that is 15 percent or
more (absolute) within a vertical distance of 2.5 cm, or
is 20 percent or more (absolute) within a vertical
distance of 7.5 cm, at the upper boundary or within some

part.
Abruptic Durixeralfs

IDAE. Other Durixeralfs that have a duripan that is not
both massive, platy, or prismatic and more than half of its
upper boundary indurated and coated with opal or with
opal and sesquioxides, or indurated in some subhorizon.
below the upper boundary.

Haplic Durixeralfs
IDAF, Other Durixeralfs.

Typic Durixeralfs
Fragixeralfs
Key to subgroups

IDCA. Fragixeralfs that have, throughout a cumulative
thickness of 18 cm or more and within a depth of 75 cm,
bulk density of the less than 2.0 mm fraction, measured at
38 kPa water retention, of 1.0 g em” or less and acid-
oxalate-extractable aluminum plus 1/2 acid-oxalate-
extractable iron of more than 1.0 percent.

Andic Fragixeralfs

IDCB. Other Fragixeralfs that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:


ait
Torriorthents

Key to subgroups
KEBA. Torriorthents that:
1. Have the following combination of characteristics:

a, Cracks at some period in most years that are lcm
or more wide at a depth of 50 cm, that are at least 30
em long in some part, and that extend upward to the
soil surface or the base of an Ap horizon; and

b. A coefficient of linear extensibility (COLE) of
0.05 or more in a horizon or horizons at least 50 cm
thick, and a potential linear extensibility of 6 cm or
more in the upper 150 em of the soil or in the whole
soil if a lithic or paralithic contact is deeper than 50
cm but shallower than 150 em; and

c. More than 35 percent clay in horizons that total
more than 50 cm in thickness; and

2. Unless irrigated, they have cracks that remain open
from 176 to 240 days, cumulative, and are not closed
for as many as 60 consecutive days during the 120
days following the winter solstice in 3 or more years
out of 10 if the soil temperature regime is thermic,

mesic, or frigid.
Ustertic Torriorthents
KEBB. Other Torriorthents that:
1. Have the following combination of characteristics:

a. Cracks at some period in most years that are 1 cm
or more wide at a depth of 50 cm, that are at least 30
cm long in some part, and that extend upward to the
soil surface or the base of an Ap horizon; and

b. A coefficient of linear extensibility (COLE) of
0.05 or more in a horizon or horizons at least 60 cm
thick, and a potential linear extensibility of 6 cm or
more in the upper 150 cm of the soil or in the whole
soil if a lithic or paralithic contact is deeper than 50
em but shallower than 150 cm; and

c. More than 36 percent clay in horizons that total
more than 50 cm in thickness; and

2, Have a thermic, mesic, or frigid soil temperature
regime and have cracks that are closed for 60
consecutive days or more during the 120 days
following the winter solstice in more than 7 years out

of 10,
Xerertic Torriorthents

KEBC. Other Torriorthents that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1cmor
more wide at a depth of 50 cm, that are at least 30 cm


126

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a, More than 30 percent volcanic glass; or

b. At least 6 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vitrandic Palexeralfs

IDFD. Other Palexeralfs that have mottles that have
chroma of 2 or less within 75 cm of the soil surface, and
the mottled horizon is saturated with water at some time of
the year when its temperature is 6°C or higher or there is
artificial drainage.

Aquic Palexeralfs

IDFE. Other Palexeralfa that have a petrocalcic horizon
whose upper boundary is within 150 cm of the soil surface.
Petrocalcic Palexeralfs

IDFF. Other Palexeralfs that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic horizon that is more
than 50 cm below the soil surface.

Arenic Palexeralts

IDFG, Other Palexeralfa that have 15 percent or more
saturation with sodium in one or more subhorizons
within 100 cm of the soil surface.

Natric Palexeralfs

IDFH. Other Palexeralfs that have a calcic horizon
within 150 cm of the soil surface.
Caleic Palexeralfs

IDFI. Other Palexeralfs that have 5 percent or more
plinthite (by volume) in one or more subhorizons within
150 cm of the soil surface.

Plinthic Palexeralfs

IDFJ. Other Palexeralfs that have an argillic horizon that
has less than 75 percent base saturation (by sum of
cations) throughout.

Ultic Palexeralfs

IDFK. Other Palexeralfs that have an argillic horizon in
which the upper part does not have a clayey particle-size
class, or there is an increase of less than 20 percent clay
(absolute) within a vertical distance of 7.5 cm or less than
15 percent clay (absolute) within 2.6 cm at the upper

boundary.
Haplic Palexeralfs

IDFL. Other Palexeralfs that have an A horizon that,
throughout its upper 10 cm, has a color value, moist, of 3 or


2, Have a mineral layer 30 cm or more thick that has
its upper boundary in the control section below the

surface tier.
Fibric Terric Medihemists
ACGD, Other Medihemists that:

1, Have 25 cm or more of the subsurface and bottom
tiers consisting of sapric materials; and

2, Have a mineral layer 30 cm or more thick that has
its upper boundary in the control section below the

surface tier,
Sapric Terric Medihamists

ACGE. Other Medihemists that have a mineral layer 30
cm or more thick that has its upper boundary in the
control section below the surface tier.

Terric Medihemists

ACGF, Other Medihemists that have limnic layer(s) 5
cm or more thick within the control section.
Limnic Medihemi

ACGG, Other Medihemists that have a mineral layer

between 5 and 30 cm thick or two or more thin,

continuous mineral layers, within organic materials,

in the control section below the surface tier.
Fluvaquentic Medihemists

ACGH. Other Medihemists that have 25 cm or more of the
subsurface and bottom tiers consisting of fibric

materials.
Fibric Medihemists

ACGI, Other Medihemists that have 25 cm or more of the
subsurface and bottom tiers consisting of sapric

materials.

Sapric Medihemists
ACGJ, Other Medihemists.

‘Typic Medihemists
Sulfihemists
Key to subgroups

ACBA. Sulfihemists that have a mineral layer 30 cm or
more thick that has its upper boundary in the control

section below the surface tier.

Terric Sulfihemists
ACBB, Other Sulfihemists.

Typic Sulfihemists
Sulfohemists
Kay to subgroups

ACAA. All Sulfohemists (provisionally).
Typic


223

180 cm of the soil surface that meet all requirements for
an argillic horizon except thickness.”

Ultic Xeropeamments
KCEG. Other Xeropsamments that have base saturation
(by NH, OAc) of less than 60 percent throughout the soil
between depths of 25 and 75 cm below the soil surface.

KCFH. Other Xeropsamments.

‘Typic Xeropaamments

”
‘the clay content cannot be estinated with precision in Lanellas that

are vary thin, The lamellae in soils of alfi generally are

about 0.5 to i om thick, but thet i

on required for an argiliie horizon.



BFB. Other Ustands.
Haplustands, p. 151

Durustands

Key to subgroups

BFAA. Durustands that have, in some subhorizon
between 50 and 100 cm:

1. Two percent or more redox segregations; or
2. Dominant chromas, moist, of 2 or less on faces of
peds, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or

3, Sufficient active ferrous iron to give a positive
reaction to a, ~dipyridyl at some time of the year when

not being irrigated.
Aquic Durustands
BFAB. Other Durustands that have, between 25 and 100
cm, a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the
underlying layer.
Thaptic Darustands

BFAC. Other Durustands that have a mollic epipedon.
Mollic Pecvetands
BFAD. Other Durustands that have an umbric epipedon.
Umbric Durustands
BFAE, Other Durvatands.
‘Typic Durustands
Haplustands
Key to subgroups
BFBA, Haplustands that have a lithic contact within 50
cm of the soil surface,
Lithic Haplustands

BFBB. Other Haplustands that have, in some subhorizon
between 50 and 100 cm:

1. Two percent or more redox segregations; or

2. Dominant chromas, moist, of 2 or less on faces of
peda, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or

3. Sufficient active ferrous iron to give a positive
reaction to a,a'-dipyridyl at some time of the year when

not being irrigated.
Aquic Haplustands

BFBC, Other Haplustands that have extractable bases plus
1N KCl-extractable Al** of less than 15.0 cmol(+) kg in


186
2. Dominant chromas, moist, of 2 or less on faces of
peds, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or

3. Sufficient active ferrous iron to give a positive
reaction to a,a'-dipyridyl at some time of the year when

not being irrigated.
Aquic Haploxerands

BDCC, Other Haploxerands that have an argillic or
kandic horizon with its upper boundary within 125 cm of
the mineral soil surface, and base saturation (by sum of
cations) of less than 35 percent throughout the upper 50 cm
of that horizon, and have leas than 30 percent, undried,
1500 kPa water retention in some subhorizon that meets
the requirements for andic soil properties and that is at
least 25 cm thick within 100 cm of the mineral soil

surface.
Ultic Vitric Haploxerands

BDCD. Other Haploxerands that have less than 30
percent, undried, 1600 kPa water retention in some
subhorizon that meets the requirements for andic soil
properties and that is at least 25 em thick within 100 em of

the mineral soil surface.
Vitric Haploxerands

BDCE. Other Haploxerands that have, between 25 and 100
~em, a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the

underlying layer,
Thaptic Haploxerands

BDCF, Other Haploxerands that have a calcic horizon
with its upper boundary within 125 cm of the mineral soil

surface.
Calcic Haploxerands

BDCG. Other Haploxerands that have an argillic or

kandic horizon with its upper boundary within 126 cm of

the mineral soi] surface or of the upper boundary of an

organic layer with andic soil properties, whichever is

shallower, and base saturation (by sum of cations) of lesa

than 36 percent throughout the upper 50 cm of that horizon,
Ultic

BDCH. Other Haploxerands that have
1. A mollic epipedon; and
2. An argillic or kandic horizon with its upper
boundary within 125 cm of the mineral soil surface.
Argixerollic Haploxerands

BDCL. Other Haploxerands that have an argillic or
kandie horizon with its upper boundary within 125 cm of

the mineral soil surface.
Alfic Haploxerands
BDCJ. Other Haploxerands that have a mollic epipedon.
Mollie Haploxerands


339
Eutroperox
‘Key to subgroups
DDCA, Eutroperox that have mattles of 4 or more value

moist and 2 or less chroma within a depth of 125 cm of the
soil surface and a petroferric contact within 125 cm of the

soil surface.
Aquic Petroferric Eutroperox
DDCB. Other Eutroperox that have a petroferric contact
within 126 cm of the soil surface.
Petroferric Eutroperox

DDCC, Other Eutroperox that have mottles of 4 or more
value moist and 2 or less chroma within a depth of 125 cm
of the soil surface and a lithic contact within 125 cm of the

soil surface.
Agquic Lithic Eutroperox

DDCD, Other Eutroperox that have a lithic contact within
a depth of 125 cm of the soil surface,
‘Lithic Eutroperox

DDCE. Other Eutroperox that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the
soil surface and mottles of 4 or more value moist and 2 or
Jess chroma within a depth of 125 cm of the soil surface.
Plinthaquic:

DDCF. Other Eutroperox that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the

soil surface.
Piinthic Eutroperox

DDCG. Other Eutroperox that have mottles of 4 or more
value moist and 2 or less chroma within a depth of 125 cm

of the soil surface.
Aquic Eutroperox

DDCH. Other Eutroperox that have more than 40 percent
clay in the surface 18 cm after mixing, and have the upper
boundary of 2 kandic horizon within a depth or 150 cm of

the soil surface.
Kandindalfic Eutroperox

DDCI. Other Eutroperox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and have the lower boundary of the oxic
horizon within a depth of 125 cm of the soil surface.
‘Umbreptic Eutroperox

DDCJ. Other Eutroperox that have the lower boundary of
the oxic horizon within a depth of 125 cm of the soil

surface,
Inceptic Eutroperax

DDCK. Other Eutroperox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and a color hue of 2.5YR or redder with

moist values of less than 4 in most of the 25 to 125 cm depth

from the soil surface.
Humic Rhodic Eutroperox


KEYS TO SOIL TAXONOMY
Prepared by Crop and Soil Environmental Sciences

Department
Virginia Polytechnic Institute
and State University
Blacksburg, Virginia

For
THE SOIL MANAGEMENT SUPPORT SERVICES

Soil Management Support Services is a program of
international technical assistance in soil survey,
classification, interpretation, and use and management of
soils in the intertropical countries of the Agency for
International Development implemented by the Soil
Conservation Service of the United States Department of
Agriculture under PASA No. AG/DSB-1129-5-79.

This publication was produced under a cooperative
agreement between the Soil Management Support Services
(SMSS) and Virginia Tech's University Relations and
Crop and Soil Environmental Sciences department s from
fanding by the Agency for International Development
(A.LD.).

The contents of this publication were provided by the Soil
Conservation Service (SCS). Staff of Virginia Tech's
Publication Unit prepared the camera-ready manscript
from text-files provided by SCS.

To obtain additional copies in developing countries:

Ask your AID country mission or write to:
SMSS Program Leader

Soil Conservation Service

U. S. Department of Agriculture

P. O. Box 2890

Washington, DC 20013

To obtain additional copies in the USA and developed
countries write to:

International Soils

Department of Crop and Soil Environmental Sciences
Virginia Tech

Blacksburg, Virginia 24061-0404

U.S. and developed countries’ requests should include a
check for $12.00 in US dollars per copy made out to the Crop
and Soil Environmental Sciences Department, Virginia
Tech.

Citation:
Soil Survey Staff. 1990. Keys to Soil Taxonomy, fourth
edition. SMSS technical monograph no. 6. Blacksburg,
Virginia.
Fourth Edition
1990
ISBN 0-929900-01-4


251
OCHREPTS

Key to great groups

JDA. Ochrepts that have a fragipan.
Fragiochrepta, p. 257
IDB. Other Ochrepts that have a duripan whose upper
boundary is within 100 cm of the soil surface.
Durochrepts, p. 252
JDC. Other Ochrepts that have a cryic or pergelic
temperature regime.
Cryochrepts, p. 251

JDD. Other Ochrepts that have an ustic moisture regime.
Ustochrepts, p. 258

JDE. Other Ochrepts that have a xeric moisture regime.
Xerochrepts, p. 260

JDF. Other Ochrepts that have one or both of the following:

1. Carbonates in the cambic horizon or in the C horizon
but within the soil; or

2, Base saturation (by NH,OAc) that is 60 percent or

more in some subhorizon between depths of 25 and 75
em below the soil surface.

Eutrochrepts, p. 255

JDG. Other Ochrepts.
Dystrochrepts, p. 253

Cryochrepts
Key to subgroups
JDCA. Cryochrepts that have a lithic contact within 50 cm
of the soil surface.

Lithie Cryochrepts

SDCB. Other Cryochrepts that have a mean annual soil
temperature of 0°C or lower.
Pergelic Cryochrepts

JDCC. Other Cryochrepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cmTM or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic Cryochrepts

JDCD, Other Cryochrepts that have, throughout
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or


256

JDGJ. Other Dystrochrepts that have an Ap horizon that
has a color value, moist, of 3 or less or a color value, dry,
of 6 or less, crushed and smoothed, or the upper soil to a
depth of 18 cm, after mixing, has these colors.
Umbric Dystrochrepts

JDGK. Other Dystrochrepts that have an argillic horizon

in less than half of each pedon, and the base saturation (by

sum of cations) at a depth of 125 cm below the upper

boundary of the argillic horizon or in the subhorizon just

above a lithic or paralithic contact is 35 percent or more.
Ruptic-Alfic

JDGL. Other Dystrochrepts that have an argillic horizon
in less than half of each pedon, and the base saturation (by
sum of cations) at a depth of 125 cm below the upper
boundary of the argillic horizon or in the subhorizon just
above a lithic or paralithic contact is less than 35 percent.
i Dystrochrepts

RuptioUltic
JDGM. Other Dystrochrepts.
‘Typic Dystrochrepts
Eutrochrepts
Key to subgroups
JDFA. Eutrochrepts that:

1. Have a lithic contact within 50 cm of the soil surface;
and

2. Have an argillic horizon in some part but in less
than half of each pedon.
Lithic Ruptic-Alfic Eutrochrepts
JDFB. Other Eutrochrepts that have a lithic contact within
50 cm of the soil surface.
Lithic Eutrochrepts

JDFC. Other Eutrochrepts that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm
Jong in some part, and that extend to the soil surface or
to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.09 or
more in a horizon or horizons at least 50 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 100 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 100 cm; and

8, More than 35 percent clay in horizons that total more
than 50 cm in thickness.
Vertic Eutrochrepts
JDFD. Other Eutrochrepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth

of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm or less


280

HBAC. Other Cryaquolls that have a buried Histosol that
has its upper boundary within a depth of 100 cm.

‘Thapto-Histic Crysquolls
HBAD. Other Cryaquolls that have, throughout a

cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1. Bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm’ or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent; or

2, Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

3. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a, More than 30 percent voleanic glass; or
b. At least 5 percent voleanic glass and acid-oxalate-

extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.
Cryaquolls

HBAE. Other Cryaquolls that have an argillic horizon.
Argic Cryaquells
HBAF, Other Cryaquolls thet have a calcic horizon
within or immediately below the mollic epipedon.
Calcie

HBAG. Other Cryaquolls that have a mollic epipedon that
is 50 cm or more thick.

Cumulic Cryaquolls
HBAH. Other Cryaquolls.
Typic Cryaquolls
Duraquolls
Key to subgroups
HBBA. Duraquolls that have a natric horizon.
‘Natrie Duraquolls

HBBB. Other Duraquolls that have an argillic horizon.

HBBC. Other Duraquolls.

Typic Duraquolls
Haplaquolls
Key to subgroups
HBFA. Haplaquolls that have a lithic contact within a
depth of 50 em of the surface.

Lithic Haplaquolls


145
legs than 35 percent throughout the upper 50 cm of that

horizon.
Ultic Hapludands

BGFS. Other Hapludands that have an argillic or
kandic horizon with its upper boundary within 125 cm of
the mineral soil surface or of the upper boundary of an
organic layer with andic soil properties, whichever is

shallower.
Alfic Hapludands
BGFT. Other Hapludands. .
Typic Hapludands
Hydrudands
Key to subgroups

BGEA. Hydrudands that have a lithic contact within 50
cm of the soil surface.
Lithie Hydrudands

BGEB. Other Hydrudands that have, in some subhorizon
between 50 and 100 cm of the mineral soil surface or of
the upper boundary of an organic layer with andic soil
properties, whichever is shallower:

1. Two percent or more redox segregations; or

2. Dominant chromas, moist, of 2 or less on faces of
peds, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or

8, Sufficient active ferrous iron to give a positive
reaction to a,a'-dipyridy] at some time of the year

when not being irrigated.
Aquic Hydrudands

BGEC. Other Hapludands that have extractable bases plus
1N KCl-extractable Al®* of less than 2.0 cmol(+) kg” fine
earth in some subhorizon 30 cm or more thick between 25
and 100 cm, and have, between 25 and 100 cm, a layer 10
em or more thick with more than 3.0 percent organic
carbon and colors of a mollic epipedon throughout,
occurring below a horizon or horizons, 10 cm or more
thick, with color value 1 unit or more higher and organic
carbon content 1 percent or more lower than the

underlying layer.
Acrudoxic Thaptic Hydrudands

BGED. Other Hydrudands that have extractable bases
plus IN KCl-extractable Al* of less than 2.0 emol(+) kg?
fine earth in some subhorizon 30 em or more thick

between 25 and 100 cm.
Acrudoxic Hydrudands

BGEE. Other Hydrudands that have, between 25 and 100
cm, a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and


105

TEIG, Other Paleudalfs that:

1. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic horizon that is more than 100 cm below
the soil surface; and

2. Have 5 percent or more plinthite (by volume) in one
or more subhorizons within 150 cm of the soil surface.
Grossarenic Plinthic Paleudalfs

IEIH. Other Paleudalfs that have an argillic horizon that
is discontinuous horizontally, or is discontinuous
vertically in the upper 20 cm of its thickness, or has a
texture that is loamy fine sand or coarser.

Psammentic Paleudalfs

IEIL Other Paleudalfs that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic horizon that is 50 to 100
cm below the soil surface.

Arenic Paleudalfs

IEJJ, Other Paleudalfs that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic horizon that is more
than 100 cm below the soil surface.

Grossarenic Paleudalfs

IEKK. Other Paleudalfs that have 5 percent or more
pliathite (by volume) in one or more subhorizons within
150 cm of the surface.

Plinthic Paleudalfs

TEIL. Other Paleudalfs that either:

1. Have subhorizons in the upper part of the argillic
horizon that have skeletans that

a. Have moist chroma of 2 or less; and

b. Occupy 5 percent or more of the volume of the
subhorizon; or

2, Have albic materials that constitute as much as 5
percent of some subhorizon of the argillic horizon.
Glossic Paleudalfs

IEIM. Other Psleudalfs that have throughout the argillic
or kandic horizon a hue of 2.5YR or redder, and have a

value, moist, of 3 or less and have a value, dry, that is no
more than one unit higher than the value, moist.
lic Paleudalfs

TEIN. Other Paleudalfs that have an Ap horizon that has a
color value, moist, of 3 or less and a color value, dry, no


964
CCB. Other Humods that have an isomesic or warmer

iso temperature regime.
‘Tropohumods, p. 366

CCC, Other Humods that have a fragipan below the
spodic horizon,

Fragihumods, p, 364
CCD. Other Humods that have a cryic temperature
regime.

Cryohumods, p. 364

CCE, Other Humods.

Haplohumods, p. 365
Cryohumods
Key to subgroups

CCDA. Cryohumods that have a lithic contact within 50
cm of the mineral soil surface.

Lithic Cryohumods
CCDB, Other Cryohumods that have a mean annual soil

temperature of 0°C or lower.
Pergelic Cryohumods

CCDC. Other Cryohumods that have, throughout a
cumulative thickness of 18 em or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

CCDD. Other Cryohumods that have an intermittent
placic horizon in the spodic horizon.
Placic Cryohumods

CCDE. Other Cryohumods that have an argillic or
kandic horizon below the spodic horizon.
Alfic Cryohumods

CCDF. Other Cryohumods that have less than 6 percent
organic carbon (weighted average) in the matrix of the
upper 30 cm of the spodic horizon or, if the spodic horizon
is leas than 30 cm thick, in the 30 cm directly below the

top of the spodic horizon.
Haplic Cryohumods

CCDG, Other Cryohumods.
‘Typic Cryohumods

Fragihumods

‘These are the Humods that have a fragipan below the
spodic horizon and do not have a placic horizon. They
are not known to occur in the United States, and the
classification of subgroups has not been developed,


2. Saturation with water in the mottled zone at some
time of year when the soil temperature in that zone is
5°C or higher or there is artificial drainage.

Aguic ts

GCDH, Other Kanhapludults that have 5 percent or more
plinthite (by volume) in one or more subhorizons within

150 cm of the soil surface.
Plinthic Kanhapludults

GCDI, Other Kanhapludults that have, in the upper 75 cm
of the soil, a hue of 10YR or yellower in one or more
subhorizons that have a color value, moist, of 4 or more
and mottles with chroma of 3 or more and the hue
becomes redder with depth within 100 cm of the soil

surface.
Epiaquic Kanhapludults

GCDJ, Other Kenhapludults that have, throughout the
argillic or kandic horizon, colors with a hue of 2.5YR or
redder, a value, moist, of 3 or less, and a value, dry, that
is one unit or less higher than the value, moist.

Rhodic Kanhaphudults

GCDK. Other Kanhapludults.
‘Typic Kanhapludults

Paleudults

Key to subgroups

GCEA. Paleudults that have a horizon that is above the
argillic horizon whose lower boundary is deeper than 18
cm and that meets all requirements for a spodic horizon
except that the horizon is intermittent.

Spodic Paleudults

GCEB. Other Paleudults that:

1. Have texture that is loamy fine sand or coarser in
all parts of the argillic horizon, or the argillic horizon
has lamellae in some or all parts of the upper 100 cm;
and

2. Have the following combination of characteriatics
in the upper 75 cm of the soil if the chroma in all or part
of the upper 75 cm is not controlled by uncoated sand
grains; or if the chroma throughout the upper 75 cm is
controlled by uncoated sand grains, have the
following combination of characteristics throughout
the upper 12.5 cm of the argillic horizon:

a. Mottles that have a color value, moist, of 4 or more
and chroma, moist, of 2 or less and mottles of higher
chroma that are due to segregation of iron; and

b. Saturation with water in the mottled zone at some

time of year when the soil temperature in that zone

is 5°C or higher, or there is artificial drainage.
Peammaquentic

GCEC. Other Paleudults that have texture that is loamy
fine sand or coarser in all parts of the argillic horizon,


204

than 18 cm thick, or the soil is moist in some or all parts
of the moisture control section at all times in most
years; and

2, Do not have a cambic horizon, and the lower part of
the mollic epipedon does not meet the requirements of a
cambic horizon except for color.

‘Uderthentic Haploborolis

HEGS. Other Haploborvlls that have a chroma, moist,
after rubbing of 1 or less in the upper part of the mollic
epipedon after it has been mixed to a depth of 18 cm, or in
any Ap horizon that is more than 18 cm thick, or the soil is
moist in some or all parts of the moisture control section

at all times in moat years.
Udic Haploborolis

HEGT. Other Haploborolls that do not have a cambic
horizon, and the lower part of the mollic epipedon does not
meet the requirements of a cambic horizon except for
color.

Entic Haploborolls
HEGU. Other Haploborolls.

‘Typic Haploborolls
Natriborolls
Key to subgroups

HECA. Natriborolls that have visible crystals or nests of
gypsum or more soluble salts within 40 cm of the surface

of the soil.
Leptic Natriborells
HECB. Other Natriborolls that have both of the following:

1. Acolor value, dry, of 5 in the upper 18 cm of the mollic
epipedon, after mixing, or in any Ap horizon that is
more than 18 em; and

2. A moisture control section that is dry in some part
six-tenths or more of the time that the soil temperature
at a depth of 50 cm is above 5°C in most years.

Aridic Natriborolls

HECC, Other Natriborolls that:

1. Have tonguing or interfingering of an albic horizon
more than 2.5 em into the natric horizon; and

2, Have a chroma, moist, after rubbing, of 1 or less in
the upper part of the mollic epipedon to a depth of 18 cm,
after mixing, or in any Ap horizon that is more than 18

em thick.
Glossic Udic Natriboroils

HECD. Other Natriborolls that have a chroma, moist,
after rubbing, of 1 or less in the upper part of the mollic
epipedon to a depth of 18 cm, after mixing, or in any Ap
horizon that is more than 18 cm thick.

Udie Natriborells


367
Hapludults

Key to subgroups
GCGA. Hapludults that:

1. Have a lithic contact within 50 cm of the surface of
the mineral soil; and

2. Have a discontinuous argillic horizon in each
pedon that is interrupted by ledges of bedrock.

GCGB. Other Hapludults that have a lithic contact within
80 cm of the surface of the mineral soil.
Lithic Hapludults

GCGC. Other Hapludults that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1. cm or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the soil
surface, to the base of an Ap horizon, or to a depth
within 25 em of the soil surface; and

2. A coefficient of linear extensibility (COLE) of 0.09
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 100 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 100 cm; and

3, More than 36 percent clay in horizons that total more
than 50 em in thickness,
Vertic Hapludults

GCGD. Other Hapludults that have s texture that is
loamy fine sand or coarser throughout the argillic
horizon or have an argillic horizon that has lamellae

within the upper 25 cm.
Psammentic Hapludults

GCGE. Other Hapludults that have a layer, starting at
the mineral soil surface, that has a sandy particle-size
class and extends to the top of an argillic horizon that is
50 to 100 cm below the soil surface.

Arenie Hapludults

GCGF. Other Hapludults that have a layer, starting at
the mineral soi) surface, that has a sandy particle-size
class and extends to the top of an argillic horizon that is
more than 100 cm below the soil surface.

Grossarenic Hapludults
GCGG. Other Hapludults that have the following

combination of characteristics in the upper 60 cm of the
argillic horizon:

1, Mottles that have a color value, moist, of 4 or more
and chroma, moist, of 2 or less, and also mottles of
higher chroma that are due to segregation of iron; and


ome em apt

cee

mee

2, Have a mollic epipedon that is 40 cm or more thick
and that has texture finer than loamy fine sand.
Calcic Pachic

HEBP. Other Cryoborolls that:
1, Have an argillic horizon; and

2, Have a mollic epipedon that is 40 cm or more thick
and that has texture finer than loamy fine sand.
‘Argic Pachic Cryoborolls

HEBQ. Other Cryoborolls that have a mollic epipedon that
is 40 cm or more thick and that has texture finer than

loamy fine sand.
Pachic Cryoborolls
HEBR. Other Cryoborolls that:
1. Have an argillic horizon; and

2, Have distinct or prominent mottles that are due to
segregation of iron or manganese within 100 em of the
surface if artificially drained and, if undrained, are
continuously saturated with water within a depth of 100

om for 90 days or longer.
Argiaquic Cryoborolls
HEBS. Other Cryoborolls that:

1. Have an irregular decrease in organic carbon
content with increasing depth or have an organic
carbon content of more than 0.3 percent at a depth of 125.
cm of the surface; and

2. Have distinct or prominent mottles that are due to
segregation of iron or manganese within 100 cm of the
surface and, if undrained, are continuously saturated
with water within a depth of 100 cm for 90 days or
longer; and

3. Have a slope of less than 25 percent.
Fiovaquentic Cryoborolls
HEBT. Other Cryoborvlls that have distinct or prominent
mottles that are due to segregation of iron or manganese

within 100 cm of the surface and, if undrained, are
continuously saturated with water within a depth of 100

cm for 90 days or longer.
Aqui Cryoborolls
HEBU. Other Cryoborvlls that:
1, Have an irregular decrease in organic carbon
content with increasing depth or have an organic
carbon content of more than 0.3 percent at a depth of 125
cm below the surface; and

2. Have a slope of less than 25 percent.
Fluventic Cryoborolis

HEBV. Other Cryoborolls that:
1, Have an argillic horizon; and


65
Kaolinitie
Definition: More than half kaolinite, tabular halloysite’
dickite, and nacrite by weight, amaller amounts of other

1:1 or non-expanding 2:1 layer minerals or gibbsite, and
less than 10% montmorillonite.

Determinant size fraction: Less than 0.002 mm.
Montmorillonitic
Definition: More than half montmorillonite and

nontronite by weight or a mixture that has more
montmorillonite than any other one clay mineral,

Determinant size fraction: Less than 0.002 mm.

‘ion: More than half illite (hydrous mica) by
weight and commonly more than 4% K20.

Determinant size fraction: Less than 0.002 mm.

Vermiculitic
Definition: More than half vermiculite by weight or more
vermiculite than any other one clay mineral.

Determinant size fraction: Less than 0.002 mm.
Chloritic

Definition: More than half chlorite by weight or more
chlorite than any other clay mineral.

Determinant size fraction: Less than 0.002 mm.

Mixed 2
Definition: Other soils“.

Determinant size fraction: Less than 0.002 mm.

18 seplolitic, defined
septolite, attapzigite,

taining more than half by weight of
nd palygorakite, @hould be named 1f found.



61

1. If there are no strongly contrasting particle-size
classes, as defined later, and there is no root-limiting
layer between the top of the argillic, kandic, or natric
horizon and a depth of 100 cm, particle-size modifiers
or substitutes are used to describe the whole argillic,
kandic, or natric horizon if it is less than 50 em thick®
or the upper 50 cm of the argillic, kandic, or natric
horizon if it is more than 50 cm thick.

2. If there are horizons or layers of strongly contrasting
particle-size classes, as defined later, within or below
the argillic, kandic, or natric horizon and within a
depth of 100 cm, particle-size modifiers or substitutes
are used to describe material from the top of the argillic,
kandic, or natric horizon to a depth of 100 cm or to a root
limiting layer, whichever is shallower.

3, If there is a root-limiting layer below an argillic,
kandic, or natric horizon, particle-size modifiers or
substitutes are used to describe material from the top of
the argillic, kandic, or natric horizon, excluding any
part incorporated in an Ap horizon, to the top of the root-
limiting layer, or are used to describe the upper 50 cm of
the argillic, kandic, or natric horizon, whichever of
these is less.

E. In other soils in the orders Alfisols and Ultisols and in
great groups of Aridisols and Mollisols that have an
argillic, kandic, or natric horizon that has its upper
boundary at a depth of more than 100 cm and that are not
in a grossarenic subgroup, particle-size modifiers or
substitutes are applied to describe material from a depth of
25 em to a depth of 100 cm below the mineral surface.

F, In other soils in which the lower boundary of the

argillic or natric horizon is shallower than 25 cm, that is,
they have a & horizon in which there is soft powdery lime,
or have a calcic or other named diagnostic horizon that
has its upper boundary within 25 om of the surface, or have
rock structure dominant within that depth, particle-size
classes are used to describe material from the top of the
argillic horizon or the base of an Ap horizon, whichever is
shallower, to a root-limiting layer or to a depth of 100 cm,
whichever is shallowest.

Strongt . icle-size cl

In applying names of particle-size classes, the weighted
average particle-size class of the control section or of the
horizon listed is named unless there are strongly
contrasting particle-size classes within the control

§ the upper boundary of the argillic or kandic horizon ia not always

obvious. If properties of an argillic horison are present but the upper
boundary is gradual, use the depth at which the percentage of clay
‘exceeds that of a higher lying horison by the appropriate anount after
fitting te a mooth curve. If the boundary 1¢ irregular or broken, as

in MB or BEA horizons, use the depth at which half or nore of the
volume has the fabric of an argillic horizon.


279

HBEC, Other Argiaquolls that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the surface
of the soil or to the base of the Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.09 or
more in a horizon or horizons at least 50 cm thick, and
@ potential linear extensibility of 6 cm or more in the
soil to a depth of 100 cm or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 100 cm; and

3, More than 35 percent clay in horizons that total more
than 50 cm in thickness.
Vertic Argiaquolls

HBED. Other Argiaquolls that have an argillic horizon
that has an increase in clay content of 20 percent
(absolute) or more within & vertical distance of 7.5 em
below the upper boundary.

Abruptic Argiaquolls
HBEE. Other Argiaquolls.
Typic Argiaquolls
Calciaquolls
Key to subgroups

HBDA. Calciaquolls that have a petrocalcic horizon that
has its upper boundary within 100 cm of the surface.
Petrocaleic Calei

HBDB. Other Calciaquoils that have color that has
dominant chroma of 3 or more in the matrix or on the ped
surfaces in one or more subhorizons within 75 cm of the
surface or have one of the following colors immediately
below the mollic epipedon:

1. If the hue is 2.5Y or yellower and there are distinct or
prominent mottles, the chroma, moist, is 3 or more; if
there are no mottles, the chroma, moist, is 2 or more; or

2. If the hue is 10YR or redder the chroma, moist, is 2 or
more.

Aeric Calciaquolls
HBDC. Other Calciaquolls.

Typic Caleiaquolls
Cryaquolls
Key to subgrouns
HBAA. Cryaquolls that have a mean annual soil
temperature of 0°C or lower.

Pergelic Cryaquolls

HBAB. Other Cryaquolls that have a histic epipedon.
Histic Cryaquolls


174
FACM. Other Natrargids that have:

1. A weighted average percentage of organic carbon in
the upper soil to a depth of 40 cm that is 0.6 or more if the
weighted average of sand to clay to that depth is 1.0 or
less, or is one-seventh percent or more if the ratio is 13
or more, or is intermediate between 0.6 and one-
seventh percent if the ratio is between 1.0 and 13; and a
weighted average percentage of organic carbon in the
surface soil to a depth of 18 cm that is one-fifth or more
higher than the values just stated if there is a

paralithic contact that is shallower than 40 cm but
deeper than 18 cm; and

2. A mean annual soil temperature of 8°C or higher
and an aridic moisture regime that borders on an

ustic regime.
Ustollic Natrargids
FACN. Other Natrargids that have more than 10 percent

of the ped surfaces deeper than 2.5 cm below the upper
boundary of the natric horizon covered by skeletans.

Glossic Natrargids
FACO. Other Natrargids.
‘Typic Natrargids
Paleargids
Key to subgroups

FADA. Paleargids that have the following combination
of characteristics:

1. A weighted average percentage of organic carbon in
the upper soil to a depth of 40 cm of 0.6 percent or more
if the weighted average ratio of sand to clay above this
depth is 1.0 or less, or one-seventh percent or less if the
ratio is 13 or more, or an intermediate percentage of
organic carbon if the ratio of sand to clay is between
1.0 and 18; and a weighted average percentage of
organic carbon in the surface soil to a depth of 18 cm
that is one-fifth or more higher than the values just
stated if there is a petrocalcic horizon whose upper
boundary is shallower than 40 cm but deeper than 18
cm; an

2. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the soil
surface, to the base of an Ap horizon, or to the top of the
argillic horizon, and the cracks are not closed for as
many as 60 consecutive days of the 120 days following
the winter solstice in 3 or more years out of 10; and

3. A coefficient of linear extensibility (COLE) of 0.05
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 150 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 150 cm; and


396
GCEL. Other Paleudults that:

1, Have at least one subhorizon in the argillic horizon
and within 125 em of the soil surface that has all the
properties of a fragipan except that it is brittle in 40 to
60 percent of the volume; and

2. Haye the following combination of characteristics
in the upper 75 cm of the soil if the chroma in all or part
of the upper 75 cm is not controlled by uncoated sand
grains; or if the chroma throughout the upper 75 cm ie
controlled by uncoated sand grains, have the
following combination of characteristics throughout
the upper 12.5 em of the argillic horizon:

a, Mattles that have a color value, moist, of 4 or more
and chroma, moist, of 2 or less and mottles of higher
chroma that are due to segregation of iron; and

b, Saturation with water in the mottled zone at some
time of year when the soil temperature in that zone
is 5°C or higher, or artificial drainage.

i Paleudults

GCEM. Other Paleudults that have the following
combination of characteristics in the upper 75 cm of the
soil if the chroma in all or part of the upper 75 cm is not
controlled by uncoated sand grains; or if the chroma
throughout the upper 75 cm is controlled by uncoated sand
grains, have the following combination of
characteristics throughout the upper 12.5 cm of the
argillic horizon:

1. Mottles that have a color value, moist, of 4 or more
and chroma, moist, of 2 or less and mottles of higher
chroma that are due to segregation of iron; and

2, Saturation with water in the mottled zone at some
time of year when the soil temperature in that zone is
5°C or higher, or artificial drainage.

Aquic Paleudults

GCEN, Other Paleudults that have 5 percent or more
plinthite (by volume) in one or more subhorizons within

150 cm of the soil surface.
Plinthic Paleudults

GCEO, Other Paleudults that have at least one
subhorizon in the argillic horizon and within 125 cm of
the soil surface that has all the properties of a fragipan
except that it is brittle in 40 to 60 percent of the volume.

GCEP, Other Paleudults that have, throughout the upper
100 cm of the argillic horizon, a color value, moist, of 3 or
less and a color value, dry, 1 unit or less higher than the
value, moist, and do not have mottles with chroma of 8 or

more.
Rhodic Paleudults

GCEQ. Other Paleudults,
Typic Paleudults


100

within that depth at some time when the soil
temperature is 5°C or higher; or

b. If the upper boundary of the argillic horizon is
deeper than 50 cm, has mottles that have chroma of 2
or less within a depth of 75 cm below the soil surface;
and

2. Have an Ap horizon that has a color value, moist, of 3
or less or a color value, dry, of 5 or less (crushed and
smoothed), or the upper soil to a depth of 18 cm, after

mixing, has these colors,
Aquollic Hapludalfs

IEKO. Other Hapludalfs that have an argillic horizon
that either:

1. If its upper boundary is less than 50 cm below the soil
surface, has mottles that have chroma of 2 or less in the
upper 25 em, and it is saturated with water within that
depth at some time when the soil temperature is 5°C or
higher; or

2. If the upper boundary of the argillic horizon is deeper
than 50 cm, has mottles that have chroma of 2 or less
within a depth of 75 cm below the soil surface.

Aquic Hapludalfs

IEKP. Other Hapludalfs that have albic materials that
constitute 5 percent or more of the volume of one or more
subhorizons of the argillic horizon, and the mean annual
soil temperature is 10°C or higher.

Glossic Hapludalfs

TEKQ. Other Hapludalfs that have interfingering of albic
materials and albic materials surrounding some peds in
the upper part of the argillic horizon, and the mean
annual soil temperature is lower than 10°C.

Glossoboric Hapludalfs

IEKR. Other Hapludalfs that have base saturation (by
sum of cations) of less than 60 percent at a depth 125 cm
below the top of the argillic horizon, or 180 cm below the
soil surface, or immediately above a lithic or paralithic
contact, whichever is least.

‘Ultic Hapludalfs

TEKS. Other Hapludalfs that have an Ap horizon that has
acolor value, moist, of 3 or less and has a color value, dry,
of 6 or less (crushed and smoothed), or the upper soil to a
depth of 18 cm, after mixing, has these colors.

Mollic Haphudalfs

TEKT. Other Hapludalfs.
‘Typic Hapludalfs


261
2. Have a lithic contact within 50 cm of the soil surface.
Dystric Lithie Xerochrepts

JDEC. Other Xerochrepts that:

1. Have a lithic contact within 50 cm of the soil surface;
and

2. Have an intermittent cambic horizon.
re ‘ se Xeroch
JDED. Other Xerochrepts that have a lithic contact within
50 cm of the soil surface.
LithieXerock

JDEE. Other Xerochrepts that have a petrocalcic horizon
within a depth of 100 cm of the soil surface.
Petrocaleic Xerochrepts

JDEF. Other Xerochrepts that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, thet are at least 30 cm
Jong in some part, and that extend upward to the soil
surface or to the base of an Ap horizon; and

2, A coefficient of linear extensibility (COLE) of 0.05 or
more in a horizon or horizons at least 50 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 150 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 160 cm; and

3, More than 36 percent clay in horizons that total more
than 50 cm in thickness.
Vertic Xerochrepts

JDEG. Other Xerochrepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 gcm* or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

‘Andic:

JDEH. Other Xerochrepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more than
36 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2, The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b, At least 5 percent volcanic glass and acid-oxalate-


25
Coefficient of linear extensibility, COLE

This coefficient is the ratio of the difference between the
moist length and the dry length of a clod to its dry length.
It is (Lm - LdVLd, where Lm is the length at 33 kPa
tension and Ld is the length when dry. It can be
calculated from the difference in bulk density of the clod
when moist and when dry. COLE can be estimated from
shrinkage of a sample that has been packed at field
capacity into a mold and then dried.

Durinodes

Durinodes (L. durus, hard; nodus, knot) are weakly
cemented to indurated nodules. The cement is SiO2,
presumably opal and microcrystalline forms of silica. It
breaks down in hot concentrated KOH after treatment
with HCl to remove carbonates but does 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 and some slaking. The
durinodes are firm or very firm; they are brittle when
wet, both before and after treatment with acid; and they
are disconnected and range upward in size from a
diameter of about 1 cm. Most durinodes are roughly
concentric when viewed in cross section, and concentric
stringers of opal may be visible under a hand lens.

Gilgai

Gilgai is the microrelief that is typical of clayey soils that
have a high coefficient of expansion with changes in
moisture content and that also have distinct seasonal
changes in moisture content. The microrelief consists of
either a succession of enclosed microbasins and
microknolls in nearly level areas, or of microvalleys
and microridges that run up and down the slope. The
height of the microridges commonly ranges from a few
centimeters to 1 m. Rarely does the height approach 2 m.

Lithic contact

A lithic contact is a boundary between soil and coherent
underlying material. Except in Ruptic-Lithic subgroups
the underlying material must be continuous within the
limits of a pedon except for cracks produced in place
without significant displacement of the pieces. Cracks
should be few, and their average horizontal spacing
should be 10 cm or more, The underlying material must
be sufficiently coherent when moist to make hand
digging with a spade impractical, although it may be
chipped or scraped with a spade. If it is a single mineral,
it must have a hardness by Mohs scale of 3 or more. If it is
not a single mineral, chunks of gravel size that can be
broken out must not disperse during shaking for 15 hours
in water or in sodium hexametaphosphate solution. The
underlying material considered here does not include


ABAB. Other Sphagnofibrists that have a layer of water
within the control section beneath the surface tier.

ABAC. Other Sphagnofibrists that have a lithic contact
within the control section.
Lithic Sphagnofibrists

ABAD. Other Sphagnofibrists that are frozen within the
control section about 2 months after the summer solstice
or aro frozen below a depth of § cm in most years and

have a mean annual goil ternperature lower than 8°C but

higher than 0°C,
Cryic Sphagnofibrists

ABAE. Other Sphagnofibrists that have a mineral layer
30 em or more thick that has its upper boundary in the
control section below the surface tier.

Terric Sphagnofibrists

ABAF. Other Sphagnofibrists that have limnic layer(s)
that are 5 cm or more thick within the control section.
Limnic Sphagnofiheists

ABAG, Other Sphagnofibrists that have a mineral layer
between 5 and 30 cm thick or two or more thin,
continuous mineral layers, within organic materials,
in the control section below the surface tier.

ABAH, Other Sphagnofibrists that have 25 cm or more of
the subsurface and bottom tiers consisting of hemic

materials.
Hemic Sphagnofibrists

ABAI. Other Sphagnofibrists that have 12.5 cm or more
of the subsurface and bottom tiers consisting of sapric

materials,

Sapric Sphagnofibrists
ABAJ. Other Sphagnofibrists.

‘Typic Sphagnofibrists
Tropofibrists
Key to subgroups

ABDA. Tropofibrists that have a layer of water within
the control section below the surface tier.
Hydric Tropofibrists

ABDB. Other Tropofibrists that have a lithic contact
within the control section.
Lithic Tropofibrists
ABDC. Other Tropofibrists that:
1, Have 25 cm or more of the thickness of the

subsurface and bottom tiers consisting of hemic
materials; and


298

continuous mineral layers, within organic materials,
in the control section below the surface tier.
Flw Borosaprists

ADBG, Other Borosaprists that have 12.5 cm or more of
the subsurface and bottom tiers consisting of fibric
materials,

Fibric Borosaprists

ADBH. Other Borosaprists that have 25 cm or more of the
subsurface and bottom tiers consisting of hemic

materials.
Hemic Borosaprists

ADBI. Other Borosaprists.

‘Typic Boroeaprists
Cryosaprists
Key to subgroups
ADAA. Cryosaprists that have a lithic contact within the
control section.

Lithic Cryosaprists

ADAB. Other Cryosaprists that have a mean annual soil
temperature of 0°C or lower.
Pergelic Cryosaprists

ADAC. Other Cryosaprists that have a mineral layer 30
cm or more thick that has its upper boundary in the
control section below the surface tier.

Terric Cryosaprists

ADAD., Other Cryosaprists that have a mineral layer
between 5 and 30 cm thick or two or more thin,
continuous mineral layers, within organic materials,
in the control section below the surface tier.
Fluvaquentic

ADAE. Other Cryosaprists.

‘Typic Cryosaprists
Medisaprists
Key to subgroups
ADDA. Medisaprists that have a lithic contact within the
control section.

Lithic Medisaprists

ADDB. Other Medisaprists that:

1. Have 12.5 em or more of the subsurface and bottom.
tiers consisting of fibric materials; and

2. Have a mineral layer 30 cm or more thick that has
its upper boundary in the contro} section below the

surface tier.
Fibric Terric Medisaprists


21

water hangs or moves laterally at a lithologic
discontinuity.

Salic horizon

A salic horizon is a horizon 15 cm or more thick that
contains a secondary enrichment of salts more soluble in
cold water than gypsum. It contains at least 2 percent salt,
and the product of its thickness in centimeters and salt
percentage by weight is 60 or more. Thus, a horizon 20 cm
thick would need to contain 3 percent salt to qualify as a
salic horizon and a horizon 30 cm thick would need 2
percent.

Sombric horizon

The sombric horizon is a subsurface horizon of mineral
soils 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 of a spodic horizon relative to clay, and it does
not have the high base saturation of a natric horizon, The
sombric horizon does not underlie an albic horizon.

Sombric horizons are thought to be restricted to the cool
moist soils of the high plateaus and mountains in tropical
or subtropical regions. Because of the annual leaching,
base saturation is low, less than 50 percent by NH,OAc.

The sombric horizon has lower color value or chroma, or
both, than the overlying horizon and commonly, but not
necessarily, contains more organic matter than the
overlying horizon. It may have formed in an argillic, a
cambic, or, possibly, an oxic horizon. If peds are present,
the dark colors are most pronounced on ped surfaces.

A sombric horizon is easily confused in the field with a
buried A horizon. It can be distinguished from some
buried epipedons by lateral tracing. In thin sections, the
organic matter of a sombric horizon appears more
concentrated on peds and in pores than uniformly
dispersed through the matrix.

Spodic horizon

A spodic horizon is normally a subsurface horizon that
underlies an O, A, Ap, or E horizon. It may, however,
meet the definition of an umbric epipedon. A spodic
horizon has the morphological or the chemical and
physical characteristics that are listed next, and its hue
and chroma remain constant with increasing depth or the
subhorizon that has the reddest hue or the highest chroma
is near the top of the horizon. The color changes within 50


104

temperature at that depth is 5°C or higher or the soil has
artificial drainage; and

2, Have 5 percent or more plinthite (by volume) in one
or more subhorizons within 150 em of the soil surface.

Plinthaquic Paleudalfs
IKIC. Other Paleudalfs that:

1. Have mottles that have chroma of 2 or less within 75
cm of the soil surface, and the mottled horizons are
saturated with water at some time when the soil
temperature at that depth is 5°C or higher or the soil has
artificial drainage; and

2, Have subhorizons in the upper part of the argillic
horizon that have skeletans that

a. Have moist chroma of 2 or less; and
b. Occupy 5 percent or more of the volume of the
subhorizon.
Glogssaquic Paleudalfs
IEID. Other Paleudalfs that:

1, Have mottles that have chroma of 2 or less within 75
om of the soil surface, and the mottled horizons are
saturated with water at some time when the soil
temperature at that depth is 5°C or higher or the soil has
artificial drainage; and

2. Have an increase of 15 percent clay or more
(absolute) within a vertical distance of 2.5 cm at the
upper boundary of the argillic horizon.

Albequic Paleudalfs

IEIE. Other Paleudalfs that have mottles that have
chroma of 2 or leas within 75 em of the soil surface, and
the mottled horizons are saturated with water at some time
when the soil temperature at that depth is §°C or higher or
the soil has artificial drainage.

Aquic Paleudalfs

IEIF. Other Paleudalfs that:

1, Have a layer, starting at the mineral soil surface,

that has a sandy particle-size class and extends to the
top of an argillic horizon that is 50 to 100 cm below the
soil surface; and

2, Have 5 percent or more plinthite (by volume) in one
or more subhorizons within 150 cm of the soil surface.
Arenic Plinthic Paleudalfs


358

CAB, Other Aquods that do not have a placic horizon but
have a cryic temperature regime.
Cryaquods, p. 358

CAC. Other Aquods that have a strongly cemented or
indurated albic horizon that does not slake in water
when a dry fragment is immersed.

Duraquods, p. 359

CAD, Other Aquods that have a placic horizon that rests
on a spodic horizon or on a fragipan or on an albic
horizon that rests on a spodic horizon.

Placaquods, p. 361

CAE. Other Aquods that have a mean annual soil
temperature of 8°C or higher and mean summer and
mean winter soil temperatures at a depth of 50 cm that

differ by less than 5°C.
‘Tropaquods, p. 362
CAF. Other Aquods that have in more than 50 percent of

each pedon a spodic horizon in which some subhorizon
has a ratio of free iron (by dithionite-citrate) to carbon

(both elemental) that is less than 0.2.

Haplaquods, p. 359
CAG. Other Aquods.

Sideraquods, p. 361
Cryaquods
Bey to subgroups
CABA. Cryaquods that have a lithic contact within 50 cm
of the surface of the mineral soil,

Lithic Cryaquods

CABB. Other Cryaquods that:

1. Have a mean annual soil temperature of 0°C or less;
and

2. Have a ratio of free iron to carbon (elemental) of 0.2
or more throughout.
Pergelic Sideric Cryaquods
CABC. Other Cryaquods that have a mean annual soil
temperature of 0°C or less,
Pergelic Cryaquods

CABD. Other Cryaquods that have a ratio of free iron to
carbon (elemental) of 0.2 or more throughout.

Cryaquods
CABE. Other Cryaquods that have an argillic or kandic
horizon.
Alfic Cryaquods

CABF. Other Cryaquods that do not have a continuous
spodic horizon that is 10 cm or more thick or that is very

firm when moist.
Entic Cryaquods


418

but is present only in very small quantities. The
organosesquioxide material coats sand and silt
particle. Tn some horizons, coatings have coalesced,
ores, and cemented the horizon. The symbol
+ 7 also used in combination with "s" as "Bhs" if
the amount of sesquioxide component is significant
but value and chroma of the horizon are approximately
3 or less.

i Slightly decomposed organic material

This symbol is used with "0" to indicate the least
decomposed of the organic materials. Rubbed fiber
content is more than about 40 percent of the volume.
Usually occurs in soils not saturated for prolonged
periods.

k Accumulation of carbonates

‘This symbol is used to indicate accumulation of
alkaline earth carbonates, commonly calcium
carbonate.

m Cementation or induration

This symbol is used to indicate continuous or nearly
continuous cementation. Symbol is used only for
horizons that are more than 90 percent cemented,
though they may be fractured, ‘The layer is root
restrictive and roots do not enter except along fracture
planes. The single predominant or codominant
cementing agent may be indicated using defined
letter suffixes singly or in pairs. If the horizon is
cemented by carbonates, "km" is used; by silica,
"qm"; by iron, "am"; by gypsum, “ym”; by both lime
and silica, "kqm"; by salts more soluble than
gypsum, "zm",

n_ Accumulation of sodium

This symbol is used to indicate accumulation of
exchangeable sodium.

0 Residual accumulation of sesquioxides

This symbol is used to indicate residual accumulation
of sesquioxides, It differs from the use of symbol "s"
which indicates illuvial accumulation of organic
matter and sesquioxide complexes.

p Tillage or other disturbance

This symbol is used to indicate disturbance of the
surface layer by mechanical means, pasturing, or
similar uses. A disturbed organic horizon is
designated Op. A disturbed mineral horizon, even
though clearly once a E, B, or C horizon, is designated
Ap.

q Accumulation of silica

This symbol is used to indicate accumulation of
secondary silica, If silica cements the layer and


163
Haplargids
Key to subgroups

FAEA. Haplargids that have the following combination
of characteristics:

1. A frigid or colder temperature regime and an aridic
moisture regime that borders on an ustic regime; and

2. A lithic contact within 60 cm of the surface; and

3. A weighted average percentage of organic carbon in
the upper 40 cm that is 0.6 percent or more if the
weighted average ratio of sand to clay in the soil above
that depth is 1.0 or less, or is one-seventh percent or
more if the ratio is 13 or more, or is intermediate
between 0.6 percent and one-seventh percent if the
ratio of sand to clay is between 1.0 and 13; anda
weighted average percentage of organic carbon in the
soil to a depth of 18 cm that is one-fifth or more higher
than the values just stated if there is a lithic or
paralithic contact at a depth of less than 40 cm but more

than 18cm.
Borollic Lithic Haplargids

FAEB. Other Haplargids that have the following
combination of characteristics:

1, A lithic contact within 50 cm of the surface; and

2. A weighted average percentage of organic carbon in
the upper 40 cm that is 0.6 percent or more if the
weighted average ratio of sand to clay in the soil above
that depth is 1.0 or less, or is one-seventh percent or
more if the ratio is 13 or more, or is intermediate
between 0.6 percent and one-seventh percent if the
ratio of sand to clay is between 1,0 and 13; anda
weighted average percentage of organic carbon in the
toil to a depth of 18-em that is one-ith or more higher
than the values just stated if there is a lithic or
paralithic contact at a depth of less than 40 cm but more
than 18 cm; and

3, An argillic horizon that is not continuous
throughout the area of each pedon; and

4. A mean annual soi] temperature lower than 22°C,
mean summer and mean winter soil temperatures at
a depth of 50 em that differ by 5°C or more, and an
aridic moisture regime that borders on a xeric

regime.
Lithic Ruptic-Entic Xerollic Haplargids

FAEC. Other Haplargids that have the following
combination of characteristics:

1.A lithic contact within 50 cm of the surface; and

2. A weighted average percentage of organic carbon in
the upper 40 cm that is 0.6 percent or more if the
weighted average ratio of sand to clay in the soil above
that depth is 1.0 or less, or is one-seventh percent or


ait

c. More than 36 percent clay in horizons that total
more than 50 cm in thickness; and

2. The cracks are open more than 6 months in most
years.
Torrertic Haplustolls
HFGF. Other Haplustolis that:

1, When neither irrigated nor fallowed to store
moisture:

a. If the soil temperature regime is mesic or thermic,
are dry for four-tenths or less of the cumulative days
in some part of the moisture control section when the

soil temperature at a depth of 60 cm exceeds 5°C; or

b. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or
less during a period when the soil temperature at a
depth of 50 cm exceeds 8°C; and

2, Have the following combination of characteristics:

a, Cracks at some period in most years that are 1cm
or more wide at a depth of 50 cm, that are at least 30
em long in some part, and that extend upward to the
surface or to the base of an Ap horizon; and

b. A coefficient of linear extensibility (COLE) of 0.07
or more in a horizon or horizons at least 60 cm thick,
and a potential linear extensibility of 6 cm or more
in the upper 125 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 125 cm; and

¢c, More than 35 percent clay in horizons that total
more than 80 cm in thickness; and

8. The cracks are open less than 185 days in most
years.
Udertic Haplustolls

HFGG, Other Haplustolls that have the following
combination of characteristics:

1, Cracks at some period in most years that are 1. cm or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the surface
or to the base of an Ap horizon; amd

2, A coefficient of linear extensibility (COLE) of 0.07 or
more in a horizon or horizons at least 60 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 125 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 125 cm; and

3. More than 35 percent clay in horizons that total more
than 60 cm in thickness.
Vertic Haplustolls


379

the upper 100 cm of the argillic or kandic horizon if these
horizons are thicker than 100 cm.

Kandic Plinthaquults
GAAB. Other Plinthaquults.
‘Typic Plinthaquults
Umbraquults
Key to subgroups

GAHA. Umbraquults that have 5 percent or more
plinthite (by volume) in one or more subhorizons within
150 cm of the soil surface.

Plinthie Umbraquults
GAHB. Other Umbraquults. Typle Umbraquolts
HUMULTS
Key to great groups

GBA, Humults that have a sombric horizon within 100
em of the soil surface.
Sombrihumults, p. 384

GBB. Other Humults that have plinthite that forms a
continuous phase or constitutes more than 60 percent of
the volume of some subhorizon within 150 cm of the soil

surface.
Fiinthohumults, p. 384
GBC. Other Humults that

1, Have a CEC of 16 cmol(+) or less per kg clay (by 1N
NH, 0Ac pH 7) and an ECEC of 12 cmol(+) or less per
kg clay (sum of bases extracted with IN NH,OAc pH 7
plus 1N KCl-extractable Al) in the major part of the
argillic or kandic horizon, or the major part of the
upper 100 cm of the argillic or kandic horizon if these
horizons are thicker than 100 cm; and

2, Do not have a lithic, lithic, or petroferric contact
within 150 cm of the soil surface; and

3, Have a clay distribution such that the percentage of
clay does not decrease from its maximum amount by
as much as 20 percent within a depth of 150 cm from the
soil surface, or the layer in which the clay percentage
decreases by more than 20 percent has at least 6 percent
of the volume consisting of skeletans on faces of peda
and there is at least 3 percent (absolute) increase in

clay below the layer.
Kandihumults, p. 381

GBD. Other Humults that have a CEC of 16 cmol(+) or
less per kg clay (by IN NH, OAc pH 7) and an ECEC of 12
cmol(+) or less per kg clay (sum of bases extracted with
IN NH, OAc pH 7 plus IN KCl-extractable Al) in the
major part of the argillic or kandic horizon, or the major


166

argillic horizon, and the cracks remain open from 175
to 240 days, cumulative, in most years; and

2. A coefficient of linear extensibility (COLE) of 0.05
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 150 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 em but
shallower than 150 cm; and

3, More than 36 percent clay in horizons that total more
than 50 cm in thickness,
Ustertic Haplargids

FAEJ. Other Haplargids that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 80 cm
long in some part, and that extend upward to the
surface, to the base of an Ap horizon, or to the top of the
argillic horizon; and

2. A coefficient of linear extensibility (COLE) of 0.05
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 150 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 150 cm; and

8, More than 36 percent clay in horizons that total more
than 50 cm in thickness,
Vertic Haplargids

FAEK. Other Haplargids that are saturated with water
for 90 consecutive days or more within 100 cm of the
surface in most years or have any of the following
characteristics within a depth of 100 cm below the surface
if there is ground water within this depth at some time in
most years:

1. Dominant chroma of 1 or less throughout and a hue
2.8Y or yellower in some part; or

2, Dominant chroma of 2 or less and mottles that are
not due to segregated lime; or

3. Both a dominant chroma of 2 or less and a greater
SAR (or percentage of exchangeable Na) in more than
half the thickness of the horizons between the surface
and 50 cm depth than in the saturated zone.

Aquic Haplargids

FAEL, Other Haplargids that have the following
combination of characteristics:

1. A texture that is loamy fine sand or coarser in all
subhorizons above a depth of 50 em; and

2. A weighted average percentage of organic carbon in
the upper 40 cm that is 0.6 percent or more if the
weighted average ratio of sand to clay in the soil above
that depth is 1.0 or lesa, or is one-seventh percent or
more if the ratio is 13 or more, or is intermediate


170

4. A mean annual soil temperature lower than 22°C,
mean summer and mean winter soil temperatures at
a depth of 50 cm that differ by 5°C or more, and an
aridic moisture regime that borders on a xeric

regime.
Haploxerollic Nadurargids

FABD. Other Nadurargids that do not have a platy or
massive duripan that is indurated in some subhorizon.

plie Nadurargids
FABE. Other Nadurargids that have:

1. A duripan 18 cm or deeper; and

2. A weighted average percentage of organic carbon in
the upper soil to a depth of 40 cm that is 0.6 or more if the
weighted average ratio of sand to clay to that depth is
1.0 or less, or that is one-seventh percent or more if the
ratio of sand to clay is 13 or more, or is intermediate
between 0.6 percent and one-seventh percent if the
ratio of sand to clay is between 1.0 and 13; anda
weighted average percentage of organic carbon in the
surface soil to a depth of 18 cm that ia one-fifth or more
higher than the values just stated if there is a duripan
that is shallower than 40 cm but deeper than 18 cm; and

3. A mean annual soil temperature lower than 22°C,
mean summer and mean winter soil temperatures at
a depth of 50 cm that differ by 5°C or more, and an
aridic moisture regime that borders on a xeric

regime.
Xerollic Nadurargids
FABF. Other Nadurargids.
‘Typic Nadurargids
Natrargide
Key to subgroups

FACA. Natrargids that have the following combination
of characteristics:

1.A lithic contact within 50 cm of the soil surface; and

2. A weighted average percentage of organic carbon in
the upper soil to a depth of 40 cm that is 0.6 or more if the
weighted average of sand to clay to that depth is 1.0 or
less, or is one-seventh percent or more if the ratio is 13
or more, or is intermediate between 0.6 percent and
one-seventh percent if the ratio is between 1.0 and 13;
and a weighted average percentage of organic carbon
in the surface soil to a depth of 18 cm that is one-fifth or
more higher than the values just stated if there is a
lithic or paralithic contact that is shallower than 40 cm
but deeper than 18 cm; and

3. A mean annual soil temperature lower than 22°C,
mean summer and mean winter soil temperatures at
a depth of 60 cm that differ by 5°C or more, and an


a3

Ustic moisture regime.—The ustic (L. ustus, burnt,
implying dryness) moisture regime is intermediate
between the aridic and the udic regime. The concept is
one of limited moisture, but the moisture is present at a
time when conditions are suitable for plant growth. The
ustic moisture regime is not applied to soils that have
eryic or pergelic temperature regimes, which are defined
later.

If the mean annual soil temperature is 22°C or higher or if
the mean summer and winter soi] temperatures differ by
less than 5°C at a depth of 50 cm, the soil moisture control
section in the ustic moisture regime is dry in some or all
parts for 90 or more cumulative days in most years. But
the moisture control section is moist in some part for more
than 180 cumulative days, or it is continuously moist in
some part for at least 90 consecutive days.

Ifthe mean annual soil temperature is lower than 22°C
and if the mean summer and winter soil temperatures
differ by 5°C or more at a depth of 50 cm, the soil moisture
control section in the ustic regime ia dry in some or all
parts for 90 or more cumulative days in most years, But it
is not dry in all parts for more than half the time that the
soil temperature is higher than 5°C at a depth of 60 cm (the
aridic and torric regimes). Also, it is not dry in all parts
for as long as 45 consecutive days in the 4 months that
follow the summer solstice in 6 or more years out of 10 if
the moisture control section is moist in all parts for 45 or
more consecutive days in the 4 months that follow the
winter solstice in 6 or more years out of 10 (xeric regime).

In tropical and subtropical regions that have either one or
two dry seasons, summer and winter have little

meaning. In those regions, the ustic regime is that
typified in a monsoon climate that has 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 they have a
dormant period while the soil is dry.

Xeric moisture regime.--The xeric moisture regime (Gr.
xeros, dry) is that typified in Mediterranean climates,
where winters are moist and cool and summers are warm
and dry. The moisture, coming in winter when potential
evapotrangpiration is at a minimum, is particularly
effective for leaching. In a xeric moisture regime, the
soil moisture control section is dry in all parts for 45 or
more consecutive days within the 4 months that follow the
suminer solstice in 6 or more years out of 10. It is moist in
all parts for 45 or more consecutive days within the 4
months that follow the winter solstice in 6 or more years
out of 10. The moisture control section is moist in some
part more than half the time, cumulative, that the soil
temperature at a depth of 50 cm is higher than 5°C, or in 6
or more years out of 10 it is moist in some part for at least


176

3. A mean annual soil temperature lower than 22°C,
mean summer and mean winter soil temperatures at
a depth of 60 cm that differ by 5°C or more, and an
aridic moisture regime that borders on a xeric

regime.
Petrocalcic Xerollic Paleargids

FADE, Other Paleargids that have the following
combination of characteristics:

1. A petrocalcic horizon whose upper boundary is
within 100 em of the soil surface; and

2. A weighted average percentage of organic carbon in
the upper soil to a depth of 40 cm of 0.6 percent or more
if the weighted average ratio of sand to clay above this
depth is 1.0 or Jess, or one-seventh percent or less if the
ratio is 13 or more, or an intermediate percentage of
organic carbon if the ratio of sand to clay is between
1.0 and 13; and a weighted average percentage of
organic carbon in the surface soil to a depth of 18 cm
that is one-fifth or more higher than the values just
stated if there is a petrocalcic horizon whose upper
boundary is challower than 40 cm but deeper than 18
cm; an

3. A mean annual soil temperature that is 8°C or
higher and an aridic moisture regime that borders on

an ustic regime.
Petrocalcic Ustollic Paleargids
FADF. Other Paleargids that:

1, Have a petrocalcic horizon whose upper boundary is
within 100 cm of the soil surface; and

2. Are dry in all parts of the moisture control section
three-fourths or less of the time (cumulative) that the
soll temperature at a depth of 50 cm is 5°C or higher;
an

3, Have a mean annual soil temperature that is 8°C or
higher and an aridic moisture regime that borders on

an ustic regime.
Petrocalcic Ustalfic Paleargids

FADG. Other Paleargids that have a petrocalcic horizon
whose upper boundary is within 100 cm of the soil

surface.
Petrocalcic Paleargids

FADH. Other Paleargids that have a horizon within 100
cm of the surface that is more than 16 cm thick and either
contains 20 percent or more durinodes or is brittle and
has firm consistence when moist.

Duric Paleargids

FADI. Other Paleargids that have:

1, A weighted average percentage of organic carbon in
the upper soil to a depth of 40 cm of 0.6 percent or more
if the weighted average ratio of sand to clay above this
depth is 1.0 or less, or one-seventh percent or Jess if the
ratio is 13 or more, or an intermediate percentage of


278

a. More than 30 percent volcanic glass; or

b. At least 6 percent volcanic glass and acid-oxalate-

extractable aluminum plus 1/2 acid-oxalate-

extractable iron of 0.40 percent or more.
Aquandic

c Argialbolls
HABE, Other Argialbolls.

Typic Argialbolis
Natralbolls
‘Key to subgroups
HAAA. All Natralbolls (provisionally).

‘Typic Natralbolls
AQUOLLS
Key to great groups
HBA. Aquolls that have a cryic or pergelic temperature
regime.

Cryaquolls, p.279

HBB. Other Aquolls that have a duripan that has its upper
boundary within 100 cm of the surface.
Duraquolls, p. 280

HBC, Other Aquolls that have a natric horizon.
Natraquolls, p. 282

HBD, Other Aquolls that have a calcic or gypsic horizon
that has its upper boundary within 40 cm of the surface
and do not have an argillic horizon unless it is a buried

horizon.
Calciaquolls, p. 279
HBE, Other Aquolls that have an argillic horizon.
Argiaquolls, p. 278
HBF. Other Aquolls.
Haplaquolls, p. 280
Argiaquolls
Key to subgroups

HBEA. Argiaquolls that have a layer starting at the
mineral soil surface that has a sandy particle-size class
throughout and extends to the upper boundary of the
argillic horizon and the upper boundary of the argillic
horizon is between 50 and 100 cm below the soil surface.
Arenic Argiaquolls

HBEB. Other Argiaquolls that have a layer starting at the
mineral soil surface that has a sandy particle-size class
throughout and extends to the upper boundary of the
argillic horizon and the upper boundary of the argillic
horizon is more than 100 cm below the soil surface,

Grossarenic Argiaquolls


984

GBEG, Other Palehumults.
Typic Palehumults

Plinthohumults

These are the Humults that have plinthite that forms a
continuous phase or that constitutes more than half the
volume of some subhorizon within 125 cm of the soil
surface. They are not known to occur in the United
States, but the great group has been proposed for other
countries (Sys 1969). Subgroups have not been developed.

Sombrihumults

These are the Humults that have a sombric horizon
whose upper boundary is within 100 cm of the soil
surface. They are not known to occur in the United
States, but the great group is provided for use elsewhere.
Humoxic and orthoxic subgroups have been proposed
(Sys 1969) for the soils that have low CEC, that is, less
than 24 cmol(+) per kg clay. The humoxic subgroup is
proposed for soils that have an isothermic or cooler
temperature regime and the orthoxic subgroup for soils
that have an isohyperthermic temperature regime.

UDULTS

Key to great groups

GCA, Udults that have plinthite that forms a continuous
phase or constitutes more than half the volume in some
subhorizon within 150 cm of the soil surface.

‘, p.397

GCB, Other Udults that have a fragipan in or below the
argillic or kandic horizon.

Fragiudults, p, 385
GCC. Other Udults that

1, Have a CEC of 16 emol(+) or less per kg clay (by IN
NH,OAc pH 7) and an ECEC of 12 cmol(+) or less per
kg clay (sum of bases extracted with IN NH,OAc pH 7
plus 1N KCl-extractable Al) in the major part of the
argillic or kandic horizon, or the major part of the
upper 100 cm of the argillic or kandic horizon if these
horizons are thicker than 100 em; and

2, Do not have a lithic, paralithic, or ferric contact
within 150 cm of the soil surface; ai

3, Have a clay distribution such that the percentage of
clay does not decrease from its maximum amount by
as much as 20 percent within a depth of 150 cm from the
soil surface, or the layer in which the clay percentage
decreases by more than 20 percent has at least 5 percent
of the volume consisting of skeletans on faces of peds
and there is at least 3 percent (absolute) increase in

clay below the layer.
Kandiudults, p. 388


374

GAB. Other Aquults that have a fragipan and, if there is
5 percent or more by volume of plinthite in some
subhorizon, the upper boundary of the fragipan is within
100 cm of the surface of the soil.

Fragiaquults, p. 375

GAC. Other Aquults that have an abrupt textural change
between the ochric epipedon or the albic horizon and the
argillic or kandic horizon, and have slow hydraulic
conductivity in the argillic or kandic horizon.
Albaquults, p. 375

GAD. Other Aquults that

1, Have a CEC of 16 cmol(+) or leas per kg clay (by IN
NH,OAc pH 7) and an ECEC of 12 cmol(+) or less per
kg clay (sum of bases extracted with IN NH,OAc pH 7
plus 1N KClextractable Al) in the major part of the
argillic or kandic horizon, or the major part of the
upper 100 cm of the argillic or kandic horizon if these
horizons are thicker than 100 em; and

2. Do not have a lithic, paralithic, or petroferric contact
within 150 cm of the soil surface; and

3. Have a clay distribution such that the percentage of
clay does not decrease from its maximum by as much
as 20 percent within a depth of 150 cm from the soil
surface, or the layer in which the clay percentage
decreases by more than 20 percent has at least 5 percent
of the volume consisting of skeletans on faces of peds
and there is at least 3 percent (absolute) increasé in

clay below the layer.
Kandiaquults, p. 376

GAE, Other Aquults that have a CEC of 16 cmol(+) or less
per kg clay (by IN NH, OAc pH 7) and an ECEC of 12
cmol(+) or less per kg clay (sum of bases extracted with
1NNH,0Ac pH 7 plus 1N KCl-extractable Al) in the
major part of the argillic or kandic horizon, or the major
part of the upper 100 cm of the argillic or kandic horizon
if these horizons are thicker than 100 cm.
Kanhaplaquults, p. 377

GAF. Other Aquults that do not have a lithic, paralithic,
or petroferric contact within 150 cm of the soil surface
and have a clay distribution such that the percent of
clay does not decrease from its maximum amount by as
much as 20 percent within a depth of 150 cm from the soil
surface, or the layer in which the clay percentage

by more than 20 percent has at least 5 percent of
the volume consisting of skeletans on faces of peds and
there is at least 3 percent (absolute) increase in clay

below the layer.
Paleaquults, p. 378

GAG. Other Aquults that have an ochric epipedon.
Ochraquults, p. 377

GAH. Other Aquults that have an umbric or a mollic
epipedon,
Umbraquults, p. 379


233

ACF. Other Hemists that have a difference of less than
65°C between mean summer and mean winter soil

temperatures at a depth of 30 cm.
‘Tropahamistas, p. 236
ACG. Other Hemists.
Medihemists, p. 234
Borohemists
‘Key to subgroups

ACEA. Borchemists that have a layer of water within the
control section below the surface tier.
Hydric Borohemists
ACEB, Other Borohemists that have a lithic contact
within the control section.
Lithic Borohemists
ACEC. Other Borohemists that:

1, Have 2 em or more of the subsurface and bottom
tiers consisting of fibric materials; and

2, Have a mineral layer 30 cm or more thick that has
its upper boundary in the control section below the

surface tier.
Fibric Terric Borohemists
ACED. Other Borohemists that:

1. Have 25 cm or more of the subsurface and bottom
tiers consisting of sapric materials; and

2, Have a mineral layer 30 cm or more thick that has
its upper boundary in the control section below the

surface tier.
Sapric Terric Borohemists

ACEE. Other Borohemists that have a mineral layer 30
cm or more thick that has its upper boundary in the
control section below the surface tier.

Terric Borohemists

ACEF. Other Borohemists that have limnic layer(s) 5 cm
or more thick within the control section.

Limnic Borohemists
ACEG. Other Borohemists that have a mineral layer
‘between 5 and 30 cm thick or two or more thin,

continuous mineral layers, within organic materials,
in the control section below the surface tier.

ACEH. Other Borohemists that have 25 cm or more of the
subsurface and bottom tiers consisting of fibric
materials.

Fibric Borohemists
ACEL Other Borohemists that have 25 cm or more of the


4

is no more than one unit higher than the value, moist.
Rhodic Kanhaplustalfs

ICEF. Other Kanhaplustalfs.
Typic Kanhaplustalfs

Natrustalfs
Key to subgroups

ICCA. Natrustalfs that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the tap of a natric horizon that is more than
100 cm below the soil surface.

Grossarenic Natrustalfs

ICCB, Other Natrustalfs that:

1. Have mottles that have chroma of 2 or less within 75
cm of the soil surface and there is ground water in the
mottled horizon at some time of year when the soil
temperature is °C or higher; and

2. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic horizon that is 50 to 100 cm below the
soil surface.

Aquic Arenic Natrustalfs

ICCC. Other Natrustalfs that have mottles that have
chroma of 2 or less within 75 cm of the soil surface and
there is ground water in the mottled horizon at some time
of year when the soil temperature is 5°C or higher.

Aquic Natrustalfs

ICCD, Other Natrustalfs that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic horizon that is 50 to 100
cm below the soil surface.

Arenic Natrustalfs

ICCE. Other Natrustalfs that have a petrocalcic horizon
that has its upper boundary within 150 cm of the surface.
Petrocalcic Natrustalfs

ICCF. Other Natrustalfs that have a salic horizon that has
its upper boundary within 75 cm of the soil surface.
Salorthidic Natrustalfs

ICCG. Other Natrustalfs that have an Ap horizon that has

acolor value, moist, of 3 or less, or the soil, after mixing to

a depth of 18 cm, has a color value, moist, of 3 or less.
Mollic Natrustalfs


380

part of the upper 100 cm of the argillic or kandic horizon
if these horizons are thicker than 100 cm.
p. 382

GBE, Other Humults that have a clay distribution such
that the percentage of clay does not decrease from its
maximum amount by 20 percent or more within a depth
of 150 cm from the soil surface, or the layer in which the
clay percentage decreases by more than 20 percent has at
least 5 percent of the volume consisting of skeletans on
faces of peds and there is at least 3 percent (absolute)
increase in clay below the layer.

Palehumults, p. 383
GBF. Other Humults.
Haplohumutts, p. 380
Haplohumults
‘Key to subgroups

GBEA, Haplohumults that have a lithic contact within 50
em of the mineral soil surface.
Lithic Haplohumults

GBEB. Other Haplohumults that have the following
combination of characteristics in the upper 25 cm or
more of the argillic horizon:

1. Mottles that have a color value, moist, of 4 or more
and chroma, moist, of 2 or less accompanied by
mottles of higher chroma that are due to segregation of
iron; and

2. Saturation with water in the mottled zone at some
time of year when the soil temperature in that zone is
5°C or more or they are artificially drained.

Aquic

GBEC, Other Haplohumults that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm” or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic Hap

GBED, Other Haplohumults that have 5 percent or more
plinthite (by volume) in one or more subhorizons within
150 cm of the soil surface.
Plinthie Haplohummulta

GBEE, Other Haplohumults that have an ustic soil
moisture regime.

Ustic Haplohumults
GBEF. Other Haplohumults that have a xeric soil
moisture regime.

Xeric Haplohumults

GBEG. Other Haplohumults,
Typic Haplobumults


267
2, Have slopes of 25 percent or less.

Fluventic Eutropepts
JCDH. Other Eutropepts.
‘Typic Entropepts
Humitropepts
Key to subgroups

JCAA. Humitropepts that have a lithic contact within 50
cm of the soil surface.

Lithie Humi
JCAB, Other Humitropepts that:

1. Have, throughout a cumulative thickness of 18 cm or
more and within e depth of 75 cm, bulk density of the
less than 2.0 mm fraction, measured at 33 kPa water
retention, of 1.0 g em’ or less and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of more than 1.0 percent; and

2, Have an ustic moisture regime.

Ustandic Humitropepts

JCAC. Other Humitropepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic Humitropepts
JCAD. Other Humitropepts that have, throughout a

cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2, The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.
‘Vitranddic Humi
JCAE. Other Humitropepts that have mottles that have

chroma of 2 or less within 100 cm of the soil surface, and
the mottled horizon is saturated with water at some time of

year, or there is artificial drainage.
Aquic Humitropepts


195

Chapter 8
Entisols
KEY TO SUBORDERS

KA. Entisols that

1. Have sulfidic materials within 50 cm of the
mineral soil surface; or

2. Are permanently saturated with water and have in
all horizons below 25 cm

a. Dominant hue that is neutral or bluer than 10Y;
and

b. Colors that change on exposure to the air; or

3. Are saturated with water at some time of year or are
artificially drained and have, within 50 cm of the
surface, dominant color (moist) in the matrix as
follows:

a. In horizons that have texture finer than loamy
fine sand in some or all subhorizons, or that have
more than 36 percent (by volume) of rock fragments
in some subhorizon:

(1) If there is mottling, chroma is 2 or less; or

(2) If there is no mottling and the value is less
than 4, chroma is less than 1; if the value is 4 or
more, chroma is 1 or less; or

b. In horizons that have texture of loamy fine sand
or coarser in all subhorizons:

(1) If the hue is as red or redder than 10YR and
there is mottling, chroma is 2 or less; if there is no
mottling and the value is less than 4, chroma is
Jess than 1; or if the value is 4 or more, chroma is
1or less; or

(2) If the hue is between 10YR and 10Y and there is
distinct or prominent mottling, chroma is 8 or
less; if there is no mottling, chroma is 1 or less; or

(8) Hue is bluer than 1OY; or

(4) Any color if the color is due to uncoated grains

of sand.

Aquents, p, 196

KB. Other Entisols that have 3 percent or more, by
volume, fragments of diagnostic horizons in one or
more subhorizons between 25 and 100 cm below the soil
surface, and the fragments are not arranged in

discernible order.
Arents, p. 202


349
Sombriperox

Key to subgroups

DDAA. Sombriperox that have a petroferric contact within
a depth of 125 cm of the soil surface,
Petrofeeric Sombriperox

DDAB. Other Sombriperox that have a lithic contact
within a depth of 125 cm of the soil surface.
‘Lithic Sombriperox.

DDAC. Other Sombriperox that have 16 kg or more
organic carbon per square meter to a depth of 100 cm,
exclusive of surface litter.

Humic Sombriperox
DDAD, Other Sombriperox.
‘Typic Sombriperox
TORROX
Key to great groups

DBA. Torrox that have both an apparent ECEC of less than
1.60 emol(+) per kg clay and a pH value (IN KCl) of 5.0 or
more in some part of the oxic horizon within a depth of 150

cm of the soil surface.
Acrotorrox, p. 343

DBB, Other Torrox that have more than 35 percent base
saturation (NH,OAc) in all parts within a depth of 125 cm
of the soil surface.

Eutrotorrox, p. 343
DBC, Other Torrox.
Haplotorrax, p. 344
Acrotorrox
Key to subgroups
DBAA. Acrotorrox that have a petroferric contact within a
depth of 125 em of the soil surface.
Petroferric Acrotorrox
DBAB. Other Acrotorrox that have a lithic contact within
a depth of 125 cm of the soil surface.
Lithic Acrotorrox
DBAC, Other Acrotorrox.
‘Typic Acrotorrox
Eutrotorrox
Key to subgroups
DBBA. Eutrotorrox that have a petroferric contact within a
depth of 125 cm of the soil surface,

Petroferric Eutrotorrox


265
JCEH. Other Dystropepts that:
1. Have an ustic moisture regime; and

2. Have a CEC (by IN NH,OAc pH 7) of less than 24
cmol(+) per kg clay® in the major part of the soil below a
depth of 25 cm but above 100 cm or a lithic or paralithic
contact if one is shallower than 100 cm.

‘Ustaxic Dystropepts

JCEI. Other Dystropepts that have a CEC (by IN NH,OAc
pH 7) of less than 24 cmol(+) per kg clay” in the major
part of the soil below a depth of 25 cm but above 100 cmora
lithic or paralithic contact if one is shallower than 100
em.

Oxic Dystzopepts
JCEJ, Other Dystropepts that have an ustic moisture
regime.

Ustic Dystropepts
JCEK. Other Dystropepts.

Typic Dystropepts

Eutropepts
Kev to subgroups
ICDA. Eutropepts that have a lithic contact within 50 cm of
the soil surface.

Lithic Eutropepts

JCDB. Other Eutropepts that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30cm
long in some part and that extend upward to the soil
surface or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.09 or
more in a horizon or horizons at least 50 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 100 cm of the soil, or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 100 cm; and

8, More than 35 percent clay in horizons that total more
than 50 cm in thickness,
Vertic Eutropepts

°
‘Some cambie herisana that have properties that approach these ofan eae herizan do net
dupersn wall Ifthe ratio ofthe percentage of water retained at tensian of 1800 kPa to the
of menwured clay ia 06 or mare, tha percentage of clay ia determined ty the
|igher value of (1) tha measured parvontage of clay oe (2) 2.5 times the percentage of water
‘tana eon 1600 Pa,
X

‘Some camble horizons that have properties that approach those of an ane horiam de not
iapervo well, Ifthe ratio ofthe percentage of water Petsined at tenaian of 1800 kPa to the
perountage of mossured clay ix 0.6 or more, the percentage of clay in determined by the
hugher value of (1) the measured pereentage of clay or (2) 2.5 timan the porvantage of water
‘retained at tension of 1600 kPa.


259

JDDC. Other Ustochrepts that have the following
combination of characteristics:

1, Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm and that are at least 30cm
long in some part and that extend upward to the soil
surface or the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.07 or
more in a horizon or horizons at least 60 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 125 em of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 125 cm; and

3. More than 35 percent clay in horizons that total more
than 50 cm in thickness.
‘Vertic Ustochrepts

SDDD. Other Ustochrepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the leas than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andie

JDDE. Other Ustochrepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a, More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vitrandic Ustochrepts

JDDF. Other Ustochrepts that have mottles that have
chroma of 2 or less within 75 cm of the soil surface, and
the mottled horizon is saturated with water at some period
when its temperature is 5°C or more, or the soil has

artificial drainage.
Aguic Ustochrepts
JDDG. Other Ustochrepts that:
1, Have a content of organic carbon’ that decreases

irregularly with depth, or are 125 em or more deep to a
lithic or a paralithic contact and have more than 0.2

1
‘The carbon should be of Holocene age. Tt is not the antent te inchude foal carbon fm
bedrock.


274

1. Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-

extractable iron of 0.40 percent or more.
Vitrandic Xerumbrepts
JECD, Other Xerumbrepts that have an umbric or mollic
epipedon that is 50 cm or more thick.
Pachic Xerumbrepts

JECE. Other Xerumbrepts that have mottles that have
chroma of 2 or less within 75 cm of the soil surface, and

the mottled horizon is saturated with water at some time of
the year when its temperature is more than °C, or there is”

artificial drainage.
Aquic Xerumbrepts
JECF, Other Xerumbrepts that:

1. Have a content of organic carbon that decreases
irregularly with depth; and

2. Have slopes of 25 percent or less.

Fluventic Xerumbrepts
JECG, Other Xerumbrepts that do not have a cambic
horizon.
Entic Xerumbrepts

JECH. Other Xerumbrepts.
‘Typic Xerumbrepts


2e7
ABCD. Other Borofibrists that:

1, Have 25 cm or more of the subsurface and bottom
tiers consisting of hemic materials; and

2, Have a mineral layer 30 cm or more thick that has
its upper boundary in the control section below the

surface tier.
Hemic Terric Borofibrists
ABCE. Other Borofibrists that:

1, Have 12.5 cm or more of the subsurface and bottom
tiers consisting of sapric materials; and

2, Have a mineral layer 30 em or more thick that has
its upper boundary in the control section below the

surface tier.
Sapric Terric Borofibrists

ABCF. Other Borofibrists that have a mineral layer 30
cm or more thick that has its upper boundary in the
control section below the surface tier.

Texric Borofibrists

ABCG. Other Borofibrists that have limnic layer(s)
within the control section 5 cm or more thick.
Limnic Borofibrists

ABCH. Other Borofibrists that have a mineral layer
between 5 and 30 cm thick or two or more thin,
continuous mineral layers, within organic materials,
in the control section below the surface tier.
Fluvaquentic Borofibrists

ABCI, Other Borofibrists that have three-fourths or more
of the fibers (by volume) derived from Sphagnum in the
surface tier or more of the control section,

Sphagnic Borofibrists

ABCJ. Other Borofibrists that have 25 cm or more of the
subsurface and bottom tiers consisting of hemic

materials.
Hemic Borofibrists

ABCK. Other Borofibrists that have 12.5 cm or more of
the subsurface and bottom tiers consisting of sapric

materials.

Sapric Borofibrists
ABCL. Other Borofibrists.

Typic Borofibrists
Cryofibrists
Key to subgroups

ABBA. Cryofibrists that have a lithic contact within the
control section,
Lithic Cryofibrists


136
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the

underlying layer.
‘Thaptic Haplocryands
BBFG. Other Haplocryands that have a xeric soil

moisture regime.
Xeric Haplocryands

BBFH. Other Haplocryands that have a spodic horizon,
and an associated eluvial horizon with its upper
boundary within 125 cm of the mineral soil surface or of
the upper boundary of an organic layer with andic soil
properties, whichever ia shallower.

‘Spodic Haplocryands
BBFYI. Other Haplocryands.

Typic Haplocryands
Hydrocryands
Key to subgroups

BBDA. Hydrocryands that have a lithic contact within 50
em of the soil surface.
Lithic Hydrocryands

BBDB. Other Hydrocryands that have a placic horizon
within 100 cm of the soil surface.

Placic Hydrocryands
BBDC. Other Hydrocryands that have, in some
subhorizon between 50 and 100 cm of the mineral soil

surface or of the upper boundary of an organic layer with
andic soil properties, whichever is shallower:

1. Two percent or more redox segregations; or

2, Dominant chromas, moist, of 2 or less on faces of
peds, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or

3. Sufficient active ferrous iron to give a positive
reaction to a,a'-dipyridyl at some time of the year

when not being irrigated.
Aquic Hydroeryands

BBDD. Other Hydroeryands that have, between 25 and
100 cm, a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the

underlying layer.
‘Thaptic Hydrocryands

BBDE, Other Hydrocryands.
‘Typic Hydrocryands


178
ORTHIDS

Key to great groups

FBA. Orthids that have a salic horizon whose upper
boundary is within 75 cm of the soil surface, and are
saturated with water within a depth of 100 cm for 1 month
or more in most years or have artificial drainage, and
do not have a duripan that has an upper boundary within
100 cm of the soil surface.

Salorthids, p, 194

FBB. Other Orthids that have a petrocalcic horizon whose
upper boundary is within 100 cm of the soil surface and
which is not overlain by a duripan.

Paleorthids, p.192

FBC. Other Orthids that have a duripan whose upper
boundary is within 100 em of the soil surface.
Bp. 189

FBD. Other Orthids that have a gypsic or petrogypsic
horizon whose upper boundary is within 100 em of the soil

surface.
Gypsiorthids, p. 192

FBE. Other Orthids that have a calcic horizon whose
upper boundary is within 100 cm of the surface, and that
are calcareous in all parts above the calcic horizon after
the upper soil, to a depth of 18 cm, is mixed unless the
texture is as coarse or coarser than loamy fine sand.
Calciorthids, p. 178

FBF. Other Orthids (that have a cambic horizon).
Camborthids, p. 182

Calciorthids

Key to subgroups

FBEA, Calciorthids that have the following combination
of characteristics:

1. Have a frigid temperature regime and an aridic
moisture regime that borders on an ustic regime; and

2. Have a lithic contact within 50 cm of the surface;
and

3. Have a weighted average percentage of organic
carbon in the upper 40 cm that is 0.6 percent or more if
the weighted average ratio of sand to clay in the soil
above that depth is 1.0 or less, or is 0.15 percent or more
if the ratio is 13 or more, or is intermediate between 0.6
percent and one-seventh pervent if the ratio of sand to
clay is between 1.0 and 13; and a weighted average
percentage of organic carbon in the soil to a depth of 18
cm that is one-fifth or more higher than the values just
stated if there is a lithic or paralithic contact at a depth
of less than 40 cm but more than 18 cm.

Borollic Lithic Calciorthids

FBEB. Other Calciorthids that have:


2901

HEGE. Other Haploborolls that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm and that are at least 30 cm
long in some part and that extend upward to the surface
or to the base of an Ap horizon; and

2. Potential linear extensibility of 6 cm or more in the
‘upper 100 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 100 cm; and

3. More than 36 percent clay in horizons that total more
than 50 cm in thickness.
Vertic Haploborolis

HEGF. Other Haploborolls that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm” or less
and acid-oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of more than 1.0 percent.
Andic Haploborolls

HEGG. Other Haploborolls that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more than
85 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-

extractable iron of 0.40 percent or more.
Vitrandic Haploborolls

HEGH. Other Haploborolls that:

1. Have a mollic epipedon 40 cm or more thick, and the
epipedon does not have a sandy particle-size class in
the major part, and there is no paralithic contact or a
sandy contrasting layer between deptha of 40 and 50
cm, an

2. Have an irregular decrease in organic carbon
content with increasing depth, or have an organic
carbon content of more than 0.3 percent at a depth of 125
cm below the surface; and

3. Have a slope of less than 25 percent and a concave
shape; and

4, Have a chroma, moist, after rubbing of 1 or leas in the
upper part of the mollic epipedon after it has been mixed
to a depth of 18 cm, or in any Ap horizon that is more


942
of the soil surface and a lithic contact within 125 cm of the

soil surface.
Aquic Lithic Kandiperox

DDDD. Other Kandiperox that have a lithic contact within
a depth of 126 cm of the soil surface.
Lithie Kandiperox

DDDE. Other Kandiperox that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the
soil surface and mottles of 4 or more value moist and 2 or
less chroma within a depth of 125 cm of the soil surface.
Plinthaquic

DDDF-. Other Kandiperox that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the

soil surface.
Plinthic Kandiperox

DDDG. Other Kandi, that have mottles of 4 or more
value moist and 2 or leas chroma within a depth of 125 em

of the soil surface.
Aquic Kandiperox

DDDH. Other Kandiperox that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm or Jess
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic

DDDI. Other Kandiperox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and a color hue of 2.5YR or redder with

moist values of leas than 4 in most of the 25 to 125 cm depth

from the soil surface.
Humic Rhodic Kandiperox

DDD4J. Other Kandiperox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and color hue of 7.5YR or yellower with
moist values of 6 or more in most of the 25 to 125 cm depth

from the soil surface.
Humic Xanthic Kandiperox

DDDK. Other Kandiperox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of

surface litter.
Humic Kandiperox

DDDL. Other Kandiperox that have a color hue of 2.5YR
or redder with moist values of Jess than 4 in most of the 25
to 125 cm depth from the soil surface.

Rhodic Kandiperox
DDDM. Other Kandiperox that have a color hue of 7.5YR
or yellower with moist values of 6 or more in most of the 25
to 125 cm depth from the soil surface.

Xanthie Kandiperox

DDDN. Other Kandiperox.
‘Typic Kandiperax


363

1. 5 percent or more by volume of iron-cemented
nodules, 2.5 to 30 cm in diameter, throughout the spodic
horizon; or

2. Have in less than 50 percent of each pedon a spodic
horizon in which some subhorizon has a ratio of free
iron (by dithionite-citrate) to carbon (both elemental)

of less than 0.2.
Sideric Tropaquods

CAEH, Other Tropaquods that have an argillic or
kandic horizon underlying the spodic horizon.

CAEI. Other Tropaquods that have a spodic horizon that
has a weighted average of less than 0.6 percent organic
carbon in the matrix of the upper 30 cm of the spodic
horizon, and the upper subhorizon of the spodic horizon
either

1. Has less than 2.3 percent organic carbon in the
upper 2 cm; or

2. The Horizon with 2.3 percent or more organic carbon
is present in 90 percent or leas of each pedon.
Entic’

CAEJ. Other Tropaquods that have an ochric epipedon,
and the surface layer would not meet the requirements
for an umbric epipedan if plowed to a depth of 25 cm.

CAEK. Other Tropaquods.
‘Typic Tropaquods

FERRODS
This suborder is provisional. Ferrods are not known to
occur in the United States, but the suborder ia provided for

use elsewhere. The classification has not been
developed.

Ferrods are the Spodosols that.
1, Have a spodic horizon that has in all subhorizons a

ratio of percentage of free iron (by dithionite-citrate) to
Pereantage of carbon (both elemental) of 6 or more;
an

2. Do not have an aquic moisture regime or artificial
drainage or do not have the characteristics associated
with wetness as defined for Aquods.

HUMODS
Key to grent groups
CCA. Humods that have a placic horizon in the spodic
horizon.
Placohumods, p. 366


87

temperature at a depth of 50 cm or at a lithic or paralithic
contact, whichever is shallower, the classes, defined in
terms of the mean annual soil temperature, are as.
follows:

Isofrigid.--Below 8°C (47°F).
Isomesic.~From 8° to 15°C (47° to 59°F ),
Isothermic.~From 15° to 22°C (59° to 72°F).
Isohyperthermic.--22°C (72°F) or higher.

The appropriate limit between isofrigid and isomesic
cannot be tested in the United States and probably will
need to be revised.

Other characteristics

Several soil characteristics other than those already
mentioned are needed in particular taxa to provide
reasonable groupings of series into families. Some of
these seem to be logical family criteria. Others probably
should have been used in higher categories, but the lack of
information about them makes it much safer to use them
as family differentiae at this time. These characteristics
include depth of soil, consistence, moisture equivalent,
slope of soil, and permanent cracks.

Depth of soil

Classes of shallow and deep soils may be needed at the
family level in all the orders of mineral soils. Some
distinctions in depth are made in great groups and in
arenic, paralithic, and lithic subgroups, but some other
soils should also be grouped in families according to
depth, Some soils have a paralithic contact over soft rock
such as clay shale that is too compact for penetration by
roots, The soil depth classes follow:

Micro.--Less than 18 cm through diagnostic horizons.

Used in cryic great groups but not in pergelic subgroups or
in Entisols.

Shallow..-Two depths are considered shallow:

a, Less than 50 cm to the upper boundary of a duripan or
petrocalcic horizon or to a lithic, paralithic or
petroferric contact. Used in lithic and petroferric
subgroups of Oxisols and all great groups of Alfisols,
Aridisols, Entisols, Inceptisols, Mollisols, Spodosols,
and Ultisols, except pergelic subgroups of the cryic
great groups and lithic subgroups. It is emphasized that
the adjective “shallow” is not used in the family name
of lithic subgroups of orders, other than Oxisols,
because it would be redundant.


Wt

some part of the moisture control section when the soil
temperature at a depth of 50 cm exceeds 5°C; or

2, If the soil temperature regime is hyperthermic,
isomesic, or warmer, the goila are dry in some or all
parts of the moisture control section for 90 days or less
during a period when the soil temperature at a depth of
50 cm exceeds 8°C.

Udic Haplustalfs
ICHN. Other Haplustalfs,
‘Typic Haplustalfs
Kandiustalfs
Kev to subgroups

ICDA. Kandiustalfs that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic or kandic horizon that
is more than 100 cm below the soil surface.

Grossarenic Kandiustalfs

ICDB. Other Kandiustalfs that:

1, Have mottles that have chroma of 2 or less within 75
cm of the soil surface, and the mottled horizon is
saturated with water at some time of the year when the
soil temperature at that depth is 6°C or higher or the soil
has artificial drainage; and

2. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic or kandic horizon that is 50 to 100 cm
below the soil surface.

Aquic Arenic Kandiustalfs

ICDC. Other Kandiustalfs that have 5 percent or more
plinthite by volume in one or more subhorizons within 150

cm of the soil surface,
Plinthic Kandiustalfs

ICDD. Other Kandiustalfs that have mottles that have
chroma of 2 or less within 75 cm of the soil surface, and
the mottled horizon is saturated with water at some time of
the year when the soil temperature at that depth is 5°C or
higher or the soil has artificial drainage.

Aquic Kandiustalfs

ICDE. Other Kandiustalfs that:

1. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic or kandic horizon that is 50 to 100 cm
below the soi] surface; and


75

IAI. Other Aqualfs.
Ochraqualfs, p. 80

Albaqualfs

Key to subgroups

IAGA. Albaqualfs that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic horizon that is more
than 50 cm below the soil surface.

Arenic Albaqualfs

IAGB. Other Albaqualfs that:
1, Have the following combination of characteristics:

a. Cracks at some period in most years that are Lem
or more wide at a depth of 50 cm and at least 30 cm
long in some part and that extend upward to the
surface or to the base of an Ap or an albic horizon;
and

b. A coefficient of linear extensibility (COLE) of 0.09
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 em or more
in the soil to a depth of 100 cm or in the whole soil if
the depth to a lithic or paralithic contact is more than
50 cm but less than 100 cm; and

¢. More than 35 percent clay in horizons that have a
total thickness of more than 50 cm; and

2, Have a surface horizon that, after the soil to a depth of
18 cm has been mixed, has 30 percent or more clay and
is discontinuous throughout each pedon,

Ruptic-Vertic Albaqualfs

TAGC. Other Albaqualfs that have the following
combination of characteristics:

1, Cracks at some period in most years that are 1 cm or

more wide at a depth of 50 cm and at least 30 cm long in
some part and that extend upward to the surface or to the
base of an Ap or an albic horizon; and

2. A coefficient of linear extensibility (COLE) of 0.09 or
more in a horizon or horizons at least 50 cm thick, and
potential linear extensibility of 6 cm or more in the
soil to a depth of 100 cm or in the whole soil if the depth to
a lithic or paralithic contact is more than 50 cm but leas
than 100 cm; and

3. More than 365 percent clay in horizons that have a
total thickness of more than 50 em.

Vertic Albaqualfs
IAGD, Other Albaqualfs that:


316

2. If the soil temperature regime is hyperthermic or
isomesic, or warmer, are moist in some or all parts of
the moisture control section for leas than 90 consecutive
days during a period when the soil temperature at a
depth of 50 em exceeds 8°C.

Aridic Haplustolls

HEFGT. Other Haplustolls that:

1. Have an irregular decrease in organic-carbon
content with increasing depth or have more than 0.3
percent at a depth of 125 cm of the surface; and

2, Have a slope of less than 25 percent.
Fluventic Haplustolls

HFGU. Other Haplustolls that have a brittle horizon 15 cm
or more thick within 100 cm of the surface that contains
some opal coatings or 20 percent or more by volume

durinodes.
Duric Haplustolls
HFGV. Other Haplustolls that:

1, When neither irrigated nor fallowed to store
moisture:

If the soil temperature regime is mesic or thermic,
are dry for four-tenths or less of the cumulative days
in some part of the moisture control section when the
soil temperature at a depth of 50 cm exceeds 5°C; or

b. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or
less during a period when the soil temperature at a
depth of 50 cm exceeds 8°C; and

2. Do not have a cambic horizon, and the lower part of
the mollic epipedon does not meet the requirements of a
cambic horizon except for color; or the cambic horizon
and any part of the mollic epipedon below a depth of 25
cm has carbonates throughout.

Udorthentic Haplustolls

HFGW. Other Haplustolls that when neither irrigated
nor fallowed to store moisture:

1. If the soil temperature regime is mesic or thermic,
are dry for four-tenths or less of the cumulative days in
some part of the moisture control section when the soil
temperature at a depth of 50 cm exceeds 5°C; or

2, If the soil temperature regime is hyperthermic,
igzomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or less
during a period when the soil temperature at a depth of

50 cm exceeds 8°C.
Udie Haplustolls

HFGX. Other Haplustolls that do not have a cambic
horizon, and the lower part of the mollic epipedon does not
meet the requirements of a cambic horizon except for color
and for organic-carbon content, or either the cambic


27
Paralithic contact

A paralithic (lithiclike) contact is a boundary between
soil and continuous coherent underlying material. It
differs from a lithic contact in that the underlying
material, if a single mineral, has a hardness by Mohs
scale of less than 3. If the underlying material is not a
single mineral, chunks of gravel size that can be broken
out disperse more or less completely during 16 hours of
end-over-end shaking in water or in sodium
hexametaphosphate solution and, when moist, the
material can be dug with difficulty with a spade. The
material underlying a peralithic contact is normally a
partly consolidated sedimentary rock such as sandstone,
siltstone, marl, or shale, and its bulk density or
consolidation is such that roots cannot enter. There may
be cracks in the rock, but the horizontal spacing between
cracks should be 10 cm or more.

Permafrost

Permafrost is a layer in which the temperature is
perennially at or below 0°C, whether the consistence is
very hard or loose. Dry permafrost has loose consistence.

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 absent
or is present only in traces. The indurated layer must be
continuous within the limits of a pedon but may be
fractured if the average lateral distance between
fractures is 10 cm or more. The indurated layer is
distinguished from a placic horizon and from an
indurated spodic horizon (ortstein) because it contains
little or no organic matter. Organic matter is present in
both the other horizons.

Several features can aid in making the distinction
between a lithic and a petroferric contact, First, a
petroferric contact is roughly horizontal. Second, the
amount of iron in the material immediately below a
petroferric contact is high. The content of Fe203 normally
ranges upward from 30 percent. Third, the ironstone
sheets below a petroferric contact are thin. Their
thickness ranges from a few centimeters to a very few
meters, Sandstone, on the other hand, may be thin or very
thick, may be level bedded or tilted, and may have only a
smal] percentage of Fe20s. In the tropics the ironstone
commonly is more or less vesicular.

Plinthite

Plinthite (Gr. plinthos, brick) is an iron-rich, humus-
poor mixture of clay with quartz and other dilutents. It


344
DBBB. Other Eutrotorrox that have a lithic contact within

a depth of 125 cm of the soil surface.

‘Lithic Butrotorrox
DBBC. Other Eutrotorrox.

Typic Eutrotorrox
Haplotorrox
Key to subgroups
DBCA. Haplotorrox that have a petroferric contact within
a depth of 125 cm of the soil surface.

Petroferric Haplotorrox

DBCB. Other Haplotorrox that have a lithic contact within
a depth of 125 cm of the soil surface.

Lithic Haplotorrox
DBCC. Other Haplotorrox.

Typic Haplotorrox
uDOoXx
Key to great groups

DEA. Udox that have a sombric horizon within a depth of
150 cm of the soil surface.
Sombriudax, p. 350

DEB. Other Udox that have both an apparent ECEC of less
than 1.50 cmol(+) per kg clay and a pH value (1N KCl) of
5.0 or more in some part of the oxic or kandic horizon
within a depth of 150 cm of the soil surface.

Acrudox, p. 244

DEC. Other Udox that have more than 35 percent base
saturation (NH,OAc) in all parts within a depth of 125 cm

of the soil surface.
Eutrudan, p. 46
DED. Other Udox that have more than 40 percent clay in

the surface 18 cm after mixing, and have the upper
boundary of a kandic horizon within a depth of 160 cm of

the surface.
Kandiudox, p. 349
DEE. Other Udox.
Hapludox, p. 347
Acrudox
‘Key to subgroups

DEBA. Acrudox that have mottles of 4 or more value moist
and 2 or leas chroma within a depth of 125 cm of the soil
surface and a petroferric contact within 125 cm of the soil

surface.
Aquic Petroferric Acrudox


93

value, moist of less than 3.5, and a color value, dry, no
more than 1 unit higher than the value, moist.
Rhodudalfs, p. 106

IEK. Other Udalfs.
Hapludalfs, p. 96

Agrudalfs

Agrudalfs are the Udalfs that have an agric horizon.
Some but not all have an anthropic epipedon. They have
been in farms for many hundreds of years and have
received heavy applications of animal manure and other
amendments. They are not known to occur in the United
States. It seems probable that only the typic and anthropic
subgroups are needed. The Agrudalfs of wegtern Europe
have been farmed for more than 1,000 years, and the
early farmers selected only the best soils for cultivation.
All of them are well drained, and they seem quite similar
in most properties. The Typic Agrudalfs do not have an
anthropic epipedon.

Ferrudalfs
Koy to subgroups

IECA. Ferrudalfs that have mottles that have chroma of 2
or less within the upper 60 cm, and the horizons that have
mottles of low chroma are saturated with water at some
time of year or the soi) has artificial drainage. The
mottles should be distinguished from skeletans that may
also have low chroma.

Aquic Ferrudalfs
TECB. Other Ferrudalfs.

‘Typic Ferrudalfs
Fragiudalfs
Key to subgroups

IEFA. Fragiudalfs that:

1. Do not have an argillic horizon above the fragipan
that has clay skins on at least some vertical and
horizontal faces of primary or secondary peds, or both;
and

2. Have, immediately above the fragipan, thick
skeletans of clean sand and silt on primary ped faces
or have an eluvial horizon (E) that has thick skeletans
and ag much aa 3 percent (absolute) leas clay than both
the overlying and underlying horizons; and

© personal contunication from R, Tavernier,


DCCG. Other Eutrustox that have mottles of 4 or more
value moist and 2 or less chroma within a depth of 125 cm

of the soil surface.
Aquic Eutrustox

DCCH. Other Eutrustox that have more than 40 percent
clay in the surface 18 cm after mixing, and have the upper
boundary of a kandic horizon within a depth or 150 cm of

the soil surface.
Kandiustalfic Eutrustox

DCCL. Other Eutrustox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and have the lower boundary of the oxic
horizon within a depth of 125 cm of the soil surface.
Umbreptic Eutrustox
DCCJ. Other Eutrustox that have the lower boundary of the
oxic horizon within a depth of 126 cm of the soil surface.
Inceptic Eutrustox

DCOK. Other Eutrustox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and a color hue of 2.5YR or redder with

moist values of less than 4 in most of the 25 to 125 cm depth

from the soil surface.

Humie Rhodic Eutrustax
DCCL. Other Eutrustox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and color hue of 7.5YR or yellower with
moist values of 6 or more in most of the 25 to 125 em depth
from the soil surface.

Humic Xanthic Butrustox

DCCM. Other Eutrustox that have 16 kg or more organic
carbon per square meter to a depth of 100 om, exclusive of

surface litter.
Humic Eutrustox

DCCN. Other Eutrustox that have a color hue of 2.5YR or
redder with moist values of less than 4 in most of the 25 to

125 cm depth from the soil surface.
Rhodic Eutrustox

DCCO. Other Eutrustox that have a color hue of 7.5YR or
yellower with moist values of 6 or more in most of the 25 to

126 cm depth from the soil surface.
Xanthic Eutrustox
DCCP. Other Eutrustox.
Typic Eutrustox
Haplustox
Key to subgroups

DCEA. Haplustox that have mottles of 4 or more value
moist and 2 or less chroma within a depth of 125 cm of the
soil surface and a petroferric contact within 125 cm of the

soil surface.
Aquic Petroferric Haplustox


natric, or spodic horizon). If the underlying horizon is a
B horizon of alteration (defined later as a cambic or oxic
horizon) and there is no surface horizon that is
appreciably darkened by humus, the most convenient
lower limit of the ochric epipedon is the base of the plow
layer or an equivalent depth in a soil that has not been
plowed. Actually, the same subhorizon in an unplowed
soil may be both a part of the epipedon and a part of the
cambic horizon. The epipedon and the subsurface
diagnostic horizons are not mutually exclusive. The
ochric epipedon does not have rock structure. It does not
include fresh sediments that are finely stratified.

Melanic epipedon (Gr. melas-anos, black)

The melanic epipedon is a thick black horizon occurring
at or near the surface, containing high concentrations of
organic carbon, usually associated with short-range-
order minerals or aluminum-humus complexes. The
intense black color is ascribed in Japan to the
accumulation of organic matter from which "Type A”
humic acids are extracted. This organic matter is
thought to result from the supply of large amounts of root
residues from a graminaceous vegetation, and can be
distinguished from organic matter formed, under forest
by the melanic index (Honna et al., 1988).

The melanic epipedon meets the following requirements:

1, It has an upper boundary at or within 30 cm of the
mineral soil surface or upper boundary of an organic
layer that meets andic soil properties, defined later,
whichever is shallower; and

2. It has, in a cumulative thickness of 30 cm or more
within a total thickness of 40 cm:

a, Moist Munsell value and chroma of 2 or less
throughout and a melanic index of 1.70 or less
throughout, and

b. Six percent or more organic carbon as a weighted
average, and no less than 4 percent organic carbon in
any subhorizon; and

3. It has andic soil properties in all parts that meet 1 and 2
above.

Plaggen epipedon (Gee. plaggen, sod)

The plaggen epipedon is a manmade surface layer 50 cm
(20 in.) or more thick that has been produced by long-
continued manuring.

3 gonna, T+) Yamamoto, 5.1 Mateut, K. 1988. A ataple procedure to
determine Helanic Index. Sew ICOMAND Cirovlar latter No. 10, p. 26-77.


76

1. Have chroma of 3 or more in more than 40 percent of
the mass between the bottom of the A or the Ap horizon
and a depth of 75 cm; and

2. Have an Ap horizon that has a color value, moist, of 3
or less and a color value, dry, of 5 or less after the soil

has been crushed and smoothed, or have, after the soil to
a depth of 18 cm has been mixed, an upper layer that has.

these colors,
Udollic Albaqualfs

TAGE. Other Albaqualfs that have chroma of 3 or more in
more than 40 percent of the mass between the bottom of the
Aor the Ap horizon and a depth of 75 cm.

Aeric Albaqualfs
TAGF. Other Albaqualfs that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following: ©

1, Bulk density of the leas than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 gcm~ or
less, and acid-oxalate-extractable aluminum plus 1/2
acid-oxalate-extractable iron of more than 1.0 percent;
or

2, Fragments coarser than 2.0 mm constitute more than
36 percent of the whole soil, and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

3. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the les than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Aquandic Albaqualfs

IAGG. Other Albaqualfe that have an Ap horizon that has
a color value, moist, of 3 or less and a color value, dry, of 5
or leas after the soil has been crushed and smoothed, or
have, after the soil to a depth of 18 cm has been mixed, an

upper layer that has these colors.
Mollie Albaqualfs

IAGH. Other Albaqualfs that have a horizon within a
dopth of 100 cm from the surface that is brittle, is 15 cm or
more thick, and contains some opal coatings or 20 percent

or more durinodes,
Durorthidic Albaqualfs

IAGI, Other Albaqualfs.
Typic Albaqualfs


62

b. If mottled and the mean annual soil temperature is
18°C or more:

(1) If the hue is 2.5Y or redder and the value, moist,
is more than 5, the chroma is 3 or more; or

(2) If the hue is 2.5Y or redder and the value, moist,
is 5 or less, the chroma, moist, is 2 or more; or

(8) If the hue is yellower than 2.5Y, the chroma,
moist is 3 or more; or

¢. If not mottled, the chroma, moist, is 2 or more; and
2. Have an Ap horizon that meets all the requirements
of an umbrie epipedon except thickness; or the upper
soil to a depth of 18 cm, after mixing, meets these

requirements,
Aeric Umbric Ochraqualfs

IAIF. Other Ochraqualfs that:

1. Have in more than 40 percent of the matrix” in one or
more subhorizons between the A or Ap horizon and a
depth of 75 cm one or more of the following:

a. If mottled and the mean annual soil temperature
is lower than 15°C, chroma, moist, of 3 or more; or

b. If mottled and the mean annual soil temperature is
18°C or more:

(1) If the hue is 2.5Y or redder and the value, moist,
is more than 6, the chroma is 3 or more; or

(2) If the hue is 2.5Y or redder and the value, moist,
is 5 or less, the chroma, moist, is 2 or more; or

(3) If the hue is yellower than 2.5Y, the chroma,
moist, is 3 or more; or

¢. If not mottled, the chroma, moist, is 2 or more; and
2, Have an Ap horizon that meets all the requirements
of a mollic epipedon except thickness; or the upper soil
to a depth of 18 cm, after mixing, meets these

requirements,
Udollic Ochraqualfs

5 if tne hue Se 7.5YR or redder and if peds are present, ped exteriors

Anaediately below any surface horizon that haz color value, potat, of 3
oF lesa,


229

2. Have a mineral layer 30 cm or more thick that has
its upper boundary in the control section below the

surface tier.
Hemic Terric Medifibrists
ABEE. Other Medifibrists that:

1, Have 12.5 cm or more of the subsurface and bottom
tiers consisting of sapric materials; and

2, Have a mineral layer 30 cm or more thick that has
its upper boundary in the control section below the

surface tier.
Sapric Tarric Medifibrists

ABEF. Other Medifibrists that have a mineral layer 30
cm or more thick that has its upper boundary in the
control section below the surface tier.

Terrie Medifibrists

ABEG. Other Medifibrists that have limnic layer(s) that
are 5 cm or more thick within the control section.
Limnic Medifibrists

ABEH. Other Medifibrists that have a mineral layer
between 5 and 30 cm thick or two or more thin,
continuous mineral layers, within organic materials,
in the control section below the surface tier.
Fluvaquentic Medifibrists

ABEI. Other Medifibrists that have three-fourths or more
of the fiber volume in the surface tier or more of the
control section derived from Sphagnum.

Sphagnic Medifibrists

ABEJ. Other Medifibrists that have 25 cm or more of the
subsurface and bottom tiers consisting of hemic

materials,
Hemic Medifibriste

ABEK, Other Medifibrists that have 12.5 cm or more of
the subsurface and bottom tiers consisting of sapric

materials.

Sapric Medifibrists
ABEL. Other Medifibrists.

‘Typic Medifibrists
Sphagnofibrists
Key tasnbgroups

ABAA. Sphagnofibriate that:

1. Have a mean annual soil temperature of 0°C or less;
and

2. Are frozen within the control section about 2 months
after the summer solstice or are frozen below a depth of 5

cm in most years.
Pergelic Sphagnofibrists


347

surface litter, and have the lower boundary of the oxic
horizon within a depth of 125 cm of the soil surface.
Umbeeptic

DECJ. Other Eutrudox that have the lower boundary of the
oxic horizon within a depth of 125 cm of the soil surface.
Inveptic’

DECK. Other Eutrudox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and a color hue of 2.5YR or redder with
moist values of less than 4 in most of the 25 to 125 cm depth
from the soil surface.

Humic Rhodic Eutrudox

DECL. Other Eutrudox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and color hue of 7.5YR or yellower with

moist values of 6 or more in most of the 25 to 125 cm depth

from the soil surface.
Humic Xanthic Eutrudox

DECM. Other Eutrudox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of

surface litter.
Humic Eutrudox

DECN. Other Eutrudox that have a color hue of 2.5YR or
redder with moist values of less than 4 in most of the 25 to
126 cm depth from the soil surface.

Rhodic Eutrudox

DECO. Other Eutrudox that have a color hue of 7.5YR or
yellower with moist values of 6 or more in most of the 25 to
125 cm depth from the soil surface.

Xanthic Eutrudox
DECP. Other Eutrudox.
Typic Eutrudox
Hapludox
Key to subgroups

DEEA. Hapludox that have mottles of 4 or more value
moist and 2 or less chroma within a depth of 125 cm of the
soil surface and a petroferric contact within 125 cm of the

soil surface.
Agquic Petroferric Hapludox
DEEB. Other Hapludox that have a petroferric contact
within 125 cm of the soil surface.
Petroferrie Haphudox

DEEC. Other Haphudox that have mottles of 4 or more
value moist and 2 or less chroma within a depth of 125 cm
of the soil surface and a lithic contact within 125 cm of the
soil surface.

Aquic Lithic Hapludox

DEED. Other Hapludox that have a lithic contact within a
depth of 125 cm of the soil surface.
Lithic Haphadox


920
HFFF, Other Vermustolls.

Typic Vermustolls
XEROLLS
Key to great groups
HDA. Xerolls that have a duripan within 100 cm of the soil
surface.

Durixerolls, p. 324

HDB. Other Xerolla that have a natric horizon but do not
have a petrocalcic horizon that has its upper boundary
within 150 cm of the soil surface.

Natrixerolls, p. 331

HDC. Other Xerolls that have a petrocalcic horizon that
its upper boundary within 150 cm of the soil surface or
ta argillic horizon that has either or both

1, A vertical clay distribution such that the clay content
does not decrease by as much as 20 percent of the
maximum clay content within 150 em of the soil
surface, and also one or more of

a, A hue redder than 10YR and chroma higher than 4
in the matrix; or

b. Common coarse mottles that have a hue of 7.5¥R or
redder or chroma higher than 5, or both; or

2. A particle-size class in the upper part that is clayey
and an increase in clay content of at least 20 percent
clay (absolute) within a vertical distance of 7.5 cm or
an increase of 15 percent clay (absolute) within a
distance of 2.5 cm at the upper boundary and no lithic or
paralithic contact within 60 cm of the soil surface.
Palexerolls, p. 332

HDD. Other Xervlls that have a calcic or gypsic horizon
that has its upper boundary within 150 em of the soil
surface and that are calcareous in all parts of all horizons
above the calcic or horizon after the upper soil to a
depth of 18 cm has mixed unless the texture is coarser
than loamy very fine sand or very fine sand.

Calcixerolls, p.223
HDE. Other Xerolls that have an argillic horizon.
Argixerolls, p. 320
HDF. Other Xerolle.
Haploxerolls, p. 326
Argixerolls
Key to subgroups

HDEA. Argixerolls that have a lithic contact within 50 cm
of the soil surface and have base saturation (by sum of
cations) of 75 percent or less in some part of the soil above

the lithic contact,
Lithic Ultic Argixerolls


4

The histic epipedon, therefore, can be defined as a layer
(one horizon or more) at or near the surface that is
saturated with water for 30 consecutive days or more at
some time in most years, or is artificially drained, and
that meets one of the following requirements:

1, The surface horizon consists of organic soil material
that either

a. Is 76 percent or more, by volume, sphagnum fibers or
has a bulk density, when moist, of less than 0.1 and is
Jess than 60 cm (24 in.) but more than 20 cm thick; or

b, Is less than 40 cm but more than 20 cm thick and
meets one of the following requirements with respect to
organic-carbon content and thicknet

(1) Has 18 percent or more organic carbon if the
mineral fraction is 60 percent or more clay; or

(2) Has 12 percent or more organic carbon if the
mineral fraction has no clay; or

(3) Has an intermediate proportional content of
organic carbon if part but less than 60 percent of the
mineral fraction is clay.

2. The plow layer is 25 cm or more thick and has 8 percent
or more organic carbon if it has no clay, or 16 percent or
more organic carbon if 60 percent or more of the mineral
fraction is clay, or an intermediate proportional content
of organic carbon if part but less than 60 percent of the
mineral fraction is clay.

3, A layer of organic material that has enough organic
carbon and is thick enough to satisfy one of the
requirements under item 1 lies beneath a surface layer of
mineral materials that is less than 40 cm (16 in.) thick.
In such a soil, the histic epipedon has been buried but the
mineral materials at the surface are too thin to be
considered diagnostic in the classification.

4. A surface layer of organic material less than 25 cm
thick that has enough organic carbon to satisfy the
minimum requirements under item 2 after the soil has
‘been mixed to a depth of 25 cm.

Mollic epipedon (L, mollis, soft)

The mollic epipedon is defined in terms of its morphology
rather than its genesis. It consists of mineral soil
material. It is a surface horizon or horizons unless (a) it
underlies a recent deposit that is less than 50 cm thick and
that has fine stratifications if not plowed or (b) it
underlies a thin layer of organic material in a wet soil
(see histic epipedon). If the layer of organic material is


321
HDEB. Other Argixerolls that have a lithic contact within

50 cm of the soi] surface.
Lithic Argixerolls

HDEC. Other Argixerolls that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more Wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the surface
or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0,05 or
more in a horizon or horizons at least §0 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 150 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 150 cm; and

3. More than 35 percent clay in horizons that have a
total thickness of more than 50 cm.

Vertic Argixerolls

HDED, Other Argixerolls that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1,0 gcm* or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic Argixerolls

HDEE. Other Argixerolls that:
1 Have an aridic moisture regime; and

2, Have, throughout a cumulative thickness of 18 cm or
more and within a depth of 75 cm, one or more of the
following:

a. Fragments coarser than 2.0 mm constitute more
than 36 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or

b. The 0,02 to 2.0 mm fraction constitutes at least 30
perce! re nt of the less than 2.0 mm fraction and contains
either:

(1) More than 30 percent volcanic glass; or

(2) At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Vitritorrandic.

HDEF. Other Argixerolls that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or


110

2, When neither irrigated nor fallowed to store
moisture:

a, If the soil temperature regime is mesic or thermic,
are dry six-tenths or less of the time in half or more
years in some part of the moisture control section (not
necessarily the same part) during a period when the
soil temperature at a depth of 60 cm exceeds 5°C; or

b. If the soil temperature regime is hyperthermic, or
isomesic or a warmer iso-temperature regime, the
soils are moist in most years in some or all parts of
the moisture control section for less than 90
consecutive days during a period when the soil
temperature at a depth of 50 cm exceeds 8°C.

Arenic Aridic Haplustalfs

ICHI. Other Haplustalfs that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic horizon that is more

than 50 cm below the soil surface.
Arenie Haplustalfs

ICHJ, Other Haplustalfs that, when neither irrigated nor
fallowed to store moisture:

1, If the soil temperature regime is mesic or thermic,
are dry six-tenths or less of the time in half or more
years in some part of the moisture control section (not
necessarily the same part) during a period when the
soil temperature at a depth of 60 cm exceeds 5°C; or

2. If the soil temperature regime is hyperthermic, or
isomesic or a warmer iso-temperature regime, the soils
are moist in most years in some or all parts of the
moisture control section for less than 90 consecutive
days during a period when the soil temperature at a

depth of 50 cm exceeds 8°C.
Aridic Haplustalfs

ICHK. Other Haplustalfs that have CEC of less than 24
cmol(+) per kg clay (by IN NH4OAc pH 7) in the major
part of the argillic horizon or in the major part of the upper
100 em if the argillic harizon is more than 100 cm thick.

Kanhaplic Haplustalfs

ICHL. Other Haplustalfs that have an argillic horizon
that has base saturation (by sum of cations) of less than 75

percent throughout.
Ultic Haplustalfs

ICHM. Other Haplustalfs that, when neither irrigated nor
fallowed to store moisture:

1. If the soil temperature regime is mesic or thermic,
are dry for four-tenths or less of the cumulative days in


346

DEBM. Other Acrudox that have a color hue of 2.5YR or
redder with moist values of less than 4 in most of the 25 to
125 cm depth from the soil surface.

Rhodie Acrudox

DEBN. Other Acrudox thet have a color hue of 7.5YR or
yellower with moist vatues of 6 or more in most of the 25 to
125 cm depth from the soil surface.

Xanthic Acrudox
DEBO. Other Acrudox.
‘Typic Acrudox
Eutrudox
Key to subgroups

DECA. Eutrudox that have mottles of 4 or more value
moist and 2 or less chroma within a depth of 125 cm of the
soil surface and a petroferric contact within 125 cm of the

soil surface.
Aquic Petroferric Eutrudox

DECB. Other Eutrudox that have a petroferric contact
within 125 cm of the soil surface.
Petroferric Eutrudox

DECC. Other Eutrudox that have mottles of 4 or more
value moist and 2 or less chroma within a depth of 125 cm
of the soil surface and a lithic contact within 125 cm of the

soil surface.
Aquie Lithic Extrudox

DECD. Other Eutrudox that have a lithic contact within a
depth of 125 cm of the soil surface.
Lithic Eutrudox

DECE. Other Eutrudox that have more than 5

plinthite in some horizon within a depth of 125 em of the

soil surface and mottles of 4 or more value moist and 2 or

less chroma within a depth of 125 cm of the soil surface.
vlinthe ead

DECF. Other Eutrudox that have more than 5 percent
plinthite in some horizon within a depth of 125 em of the
soil surface.

Plinthic Eutrudox

DECG. Other Eutrudox that have mottles of 4 or more
value moist and 2 or less chroma within a depth of 125 em

of the soil surface.
Aguie Buteudox
DECH. Other Eutrudox that have more than 40 percent
clay in the surface 18 cm after mixing, and have the upper
boundary of a kandic horizon within a depth or 150 cm of
the soi] surface.
Kandiudelfic Eutudox

DECI. Other Eutrudox that have 16 kg or more organic
carbon per square meter to a depth of 100 em, exclusive of


GDD. Other Ustults that have a clay distribution such
that the percentage of clay does not decrease from its
maximum amount by as much as 20 percent of that
maximum within 150 em of the soil surface, or the layer
in which the clay percentage decreases by more than 20
percent has at least 5 percent of the volume consisting of
skeletans on faces of peds and there is at least 3 percent
(absolute) increase in clay below the layer,

p.403

GDE, Other Ustults that have:

1. An epipedon that has a color value, moist, of 3 or less
in all parts; and

2. An argillic horizon that has a color value, dry, of
less than 5 and not more than 1 unit higher than the
value, moist,

Rhodustults, p. 408
GDF. Other Ustults.

Haplustults, p. 398
Haplustults
Key to subgroups

GDFA. Haplustults that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Haplustults

GDFB, Other Haplustults that have a petroferric contact
within 100 cm of the soil surface.
Petroferric Haplustults

GDFC. Other Haplustults that have the following
combination of characteristics in the upper 76 cm of the
soil and in the upper 12.6 cm of the argillic horizon:

1, Mottles that have a color value, moist, of 4 or more
and chroma, moist, of 2 or less and mottles of higher
chroma that are due to segregation of iron; and

2. Saturation with water in the mottled zone at some
time of year when the soil temperature in that zone is
5°C or higher, or there is artificial drainage.
Aquic Haplustalts
GDFD. Other Haplustults that have a layer, starting at
the mineral soil surface, that has a sandy particle-size
class and extends to the top of an argillic horizon that is
50 to 100 cm below the soil surface.
Arenic Haplustults

GDFE. Other Haphustults that have, in the upper 75 cm of
the soil, a hue of 10YR or yellower in one or more
subhorizons that have a color value, moist, of 4 or more
and mottles with chroma of 3 or more and the hue
becomes redder with depth within 100 cm of the soil

surface.
Epiaquic Haplustults


80

Natraqualfs

Key to subgroups
TABA. Natraqualfs that

1. Have tonguing or interfingering of albic materials
more than 2.5 cm into the natric horizon; and

2. Have, in all horizons within 40 cm of the soil surface,
less than 16 percent saturation with sodium and less
magnesium and sodium than calcium and extractable
acidity.

Albic Gloasic Natraqualfs

IABB. Other Natraqualfe that have less than 15 percent
saturation with sodium, and have less magnesium and
sodium than calcium and extractable acidity, throughout
the upper 15 cm of the natric horizon or in all horizons
within 40 cm of the soil surface, whichever is deeper.
Albic Natraqualfs

IABC. Other Natraqualfs that have tonguing or
interfingering of albic materials more than 2.5 cm into

the natric horizon.
Glossic Natraqualfs

IABD. Other Natraqualfs that have an Ap horizon that has
a color value, moist, of 3 or leas and a color value, dry, of 5
or less after the soil has been crushed and smoothed; or the
soil to a depth of 18 cm, after mixing, has these colors.

Mollic Natraqualfs
IABE. Other Natraqualfs.

‘Typic Natraqualfs
Ochraqualfe
Key to subgroups

IAIA. Ochraqualf that have, throughout a cumulative
thickness of 18 cm or more and within a depth of 76 cm,
one or more of the following:

1. Bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 gem” or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1,0 percent; or

2, Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or


FBFU. Other Camborthids that are dry in all parts of the
moisture control section for three-fourths or less of the
time (cumulative) that the soil temperature is 5°C or more
at a depth of 50 cm unless the soil is irrigated, and have
an aridic moisture regime that borders on a xeric

moisture regime.
Xerochreptic Camborthids

FBFV, Other Camborthids that are dry in all parts of the
moisture control section for three-fourths or less of the
time (cumulative) that the soil temperature is 5°C or more
at a depth of 50 cm unless the soil is irrigated, and have
an aridic moisture regime that borders on an ustic
moisture regime and a hyperthermic, thermic, or mesic
soil temperature regime.

Ustochneptic Camborthids
FBFW. Other Camborthids.
‘Typic Camborthids
Durorthids
Key to subgroups

FBCA. Durorthids that have the following combination
of characteristics:

1, Are saturated with water for 90 consecutive days or
more in most years within 100 cm of the surface, or
have one or more subhorizons within 100 cm of the soil
surface with any of the following characteristics if the
horizon is saturated with water at some period in most.
years, or the soil is artificially drained:

a, Dominant chroma of 1 or less throughout and hue
of 2.5Y or yellower in some part; or

b. Dominant chroma of 2 or less accompanied by
mottles that are not due to segregated lime; or

¢. Both a dominant chroma of 2 or less and a greater
SAR (or percentage of exchangeable sodium) in
more than half the thickneas of the horizons between
the surface and 50 em depth than in the saturated
zone; an

2. Have a duripan that is not indurated in any
subhorizon.
Aquentic Durorthids

FBCB. Other Durorthids that are saturated with water for

90 consecutive days or more in most years within 100 cm

of the surface, or have one or more subhorizons within

100 cm of the soil surface with any of the following

characteristics if the horizon is saturated with water at

gome period in most years, or the soil is artificially
ained:

1. Dominant chroma of 1 or less throughout and hue of
2.5Y or yellower in some part; or

2. Dominant chroma of 2 or less accompanied by
mottles that are not due to segregated lime; or


108

more than 1 unit higher than the value, moist, or the soil,
after mixing to a depth of 18 cm, has these color values,
Mollic Paleudalfs

TEIO. Other Paleudalfs.
Typic Paleudalts

Rhodudalfs

Rhodudalfs are dark red Udalfs of midlatitudes that have
a thinner solum than the Paleudalfs. The definition is
parallel to that of other Rhodic great groups. Their parent
materials are basic. These soils are rare in the United
States. Definitions of subgroups have not been developed.

USTALFS
Key to great groupe
ICA. Ustalfs that have a duripan that has its upper
boundary within 100 em of the surface.

Durustalfs, p. 108

ICB. Other Ustalfs that have plinthite that forms a
continuous phase or constitutes more than half the matrix
within some subhorizon of the argillic horizon within 150

cm of the surface.
Plinthustalfs, p.118

ICC. Other Ustalfs that have a natric horizon,
Natrustalit, p, 114

ICD. Other Ustalfs that

1. Have a CEC of 16 cmol(+) or less per kg clay (by 1N
NH,OAc pH 7) and an ECEC of 12 emol(+) or less per kg
clay (sum of bases extracted with 1N NH4OAc pH 7 plus
1N KCl-extractable Al) in the major part of the argillic
or kandic horizon, or the major part of the upper 100 cm
of the argillic or kandic horizon if these horizons are
thicker than 100 cm; and

2. Do not have a lithic, paralithic or petroferric contact
within 150 cm of the soil surface; and

8, Have a clay distribution such that the percentage of
clay does not decrease from its maximum amount by as
much as 20 percent within a depth of 150 cm from the
soil surface, or the layer in which the clay percentage
decreases by more than 20 percent has at least 5 percent
of the volume consisting of skeletans on faces of peds
and there is at least 3 percent (absolute) increase in
clay below the layer.

Kandiustalfs, p.111


1
(absolute) within a vertical distance of 7.5 cm from its
upper boundary,
Abruptic Paleboralfs

IBAE. Other Paleboralfs that have an Ap horizon that has
a color value, moist, of 3 or leas and a color value, dry, of 5
or less when crushed and smoothed, or the soil to a depth of
18 cm has these colors after mixing.

Moliic Paleboralfs

IBAF. Other Paleboralfs.
‘Typic Paleboralfs

UDALFS

Key to great groups

TEA. Udalfs that have an agric horizon,
Agrudalfs, p. 93

IEB, Other Udalfs that have a natric horizon.
Natrudalfs, p. 102

TEC, Other Udalfe that

1. Do not have a continuous albic horizon above the
argillie horizon; and

2. Have a broken upper boundary of the argillic
horizon; and

3, Have discrete nodules in the argillic horizon that
range from 2.5 to 30 cm in diameter; exteriors of
nodules are enriched and weakly cemented or
indurated with iron and have redder hue or stronger
chroma than interiors of nodules.

Ferrudalfs, p. 93

TED. Other Udalfs that have tongues of albic materials in
the argillie horizon and do not have a fragipan.
Glossudalfs, p. 95

IEE, Other Udalfs that have tongues of albic materials in
the argillic horizon and have a fragipan.
Fraglossudalfs, p. 95

IEF. Other Udalfs that have a fragipan.
Fragiudalfy, p98

IEG. Other Udalfs that

1, Have a CEC of 16 cmol(+) or less per kg clay (by 1N
NH,OAc pH 7) and an 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 the major part of the argillic
or kandic horizon, or the major part of the upper 100 cm


181

clay is between 1.0 and 13; and a weighted average
percentage of organic carbon in the soil to a depth of 18
cm that is one-fifth or more higher than the values just
stated if there is a paralithic contact at a depth of less
than 40 cm but more than 18 cm; and

8. Have a mean annual soil temperature lower than
22°C, mean summer and mean winter soil
temperatures at a depth of 50 cm that differ by 5°C or
more, and an aridic moisture regime that borders on a

xeric regime. ie Cal

FBEI. Other Calciorthids that have a horizon within 100
em of the surface that is more than 16 cm thick and either
contains 20 percent or more durinodes or is brittle and
has firm consistence when moist.

Duric Calciorthids

FBEJ. Other Calciorthids that have the following
combination of characteristics:

1, Have a weighted average percentage of organic
carbon in the upper 40 cm that is 0.6 percent or more if
the weighted average ratio of sand to clay in the soil
above that depth is 1.0 or less, or is 0.15 percent or more
ifthe ratio is 18 or more, or is intermediate between 0.6
percent and one-seventh percent if the ratio of sand to
clay is between 1.0 and 13; and a weighted average
percentage of organic carbon in the soil to a depth of 18
cm that is one-fifth or more higher than the values just
stated if there is a paralithic contact at a depth of less
than 40 cm but more than 18 cm; and

2, Have a mean annual soil temperature lower than
22°C, mean summer and mean winter soil
temperatures at a depth of 60 cm that differ by 6°C or
more, and an aridic moisture regime that borders on a

xeric regime.
Xerollic Calciorthids

FBEK. Other Calciorthids that have the following
combination of characteristics:

1. Have a weighted average percentage of organic
carbon in the upper 40 cm that is 0.6 percent or more if
the weighted average ratio of sand to clay in the soil
above that depth is 1.0 or less, or is 0.15 percent or more
if the ratio is 13 or more, or is intermediate between 0.6
percent and one-seventh percent if the ratio of sand to
clay is between 1.0 and 13; and a weighted average
percentage of organic carbon in the soil to a depth of 18
cm that is one-fifth or more higher than the values just
stated if there is a paralithic contact at a depth of less
than 40 cm but more than 18 cm; and

2, Have an aridic moisture regime that borders on an
ustic regime.
Ustollic Calciorthids
FBEL. Other Calciorthids that are dry in all parta of the
moisture control section three-fourths or less of the time

(cumulative) that the soil temperature is 5°C or higher at
a depth of 50 cm, and have a mean annual soil


184

3. A coefficient of linear extensibility (COLE) of 0.05
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 150 cm of the soil or in the whole soil ifa
lithic or paralithic contact is deeper than 50 cm but
shallower than 150 cm; and

4, More than && percent clay in horizons that total more
than 50 cm in thickness; and

5. Have a weighted average percentage of organic
carbon in the upper 40 cm that is 0.6 percent or more if
the weighted average ratio of sand to clay in the soil
above that depth is 1.0 or less, or is 0,15 percent or more
if the ratio is 13 or more, or is intermediate between 0.6
percent and one-seventh percent if the ratio of sand to
clay is between 1.0 and 13.

Borollic Vertic Camborthids

FBFG, Other Camborthids that have the following
combination of characteristics:

1. Have a frigid or colder temperature regime and an
aridic moisture regime that borders on an ustic
regime; and

2. Have a weighted average percentage of organic
carbon in the upper 40 cm that is 0.6 percent or more if
the weighted average ratio of sand to clay in the soil
above that depth is 1.0 or less, or is 0.15 percent or more
if the ratio is 13 or more, or is intermediate between 0.6
percent and one-seventh percent if the ratio of sand to
clay is between 1.0 and 13; and a weighted average
percentage of organic carbon in the soil to a depth of 18
cm that is one-fifth or more higher than the values just
stated if there is a paralithic contact at a depth of less
than 40 cm but more than 18 em.

Borollic Camborthids

FBFH. Other Camborthids that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm.
long in some part, and that extend upward to the soil
surface or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.05
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 150 cm of the soil or in the whole soil ifa
lithic or paralithic contact is deeper than 50 cm but
shallower than 150 cm; and

3, More than 36 percent clay in horizons that total more
than 50 cm in thickness; and

4. Have a thermic, mesic, or frigid soil temperature
regime and have cracks that are closed for 60
consecutive days or more during the 120 days
following the winter solstice in more than 7 years out

of 10.
Xerertic Camborthids


are weakly cemented and some are indurated. The
recognition of a petrocalcic or petrogypsic horizon is
expected to meet most, if not all, the needs for recognition
of cementation in those horizons. Taxa of these cemented
soils are not named in the family category.

Classes of coatings (on sands)

Despite the emphasis given to particle-size classes in the
taxonomy, variability remains in the sandy particle-size
class, which takes in sands and loamy sands. Some
sands are very clean, almost completely free of silt and
clay. Others are mixed with appreciable amounts of finer
grains. A moisture equivalent of 2 percent makes a
reasonable division of the sands at the family level. Two
classes of Quartzipsamments are defined in terms of
their moisture equivalent.

Coated.--The moisture equivalent is 2 percent or more.

Uncoated.--The moisture equivalent is less than 2
percent. The moisture retained at tension of 50 kPa may
be substituted for the moisture equivalent. Or, if moisture
tension data are not available, the silt plus clay is 5
percent or less,

Classes of permanent cracks

Hydraquents consolidate” after drainage and become
Fluvaquents. In the process, they form polyhedrons,
roughly 12 to 50 cm in diameter, depending on the n-value
and particle size, The polyhedrons are separated by
cracks that range in width from 2 mm to more than 1m.
The polyhedrons may shrink and swell with changes in
moisture content of the soil, but the cracks are permanent
and can persist for some hundreds of years even though
the soils are cultivated. The cracks permit rapid
movement of water through the soil either vertically or
laterally. Yet the soils may have the same particle size,
mineralogy, and other family properties as soils that are
not cracked or that have cracks that open and close with
the seasons. The soils that have permanent cracks are so
rare in the United States that only a provisional
definition of their characteristics can be presented.

The modifier “cracked” is used only to designate
families of Fluvaquents. It means that there are
continuous, permanent, lateral and vertical cracks, at
least 2 mm wide, spaced at average lateral intervals of 50
cm or less, If this modifier is not in the family name,
permanent cracks are assumed to be absent.

7 the process 1s dagignated by & Dutch word that means "co cipenTM
because tha change resanbles the change in consistence of chease as
water ia removed,


55

It is recognized that it is normally impossible to be certain
of the percentages of the various kinds of clay minerals.
Quantitative methods of identification are still subject to
change. Although much progress has been made in the
past few decades, an element of judgment enters into the
estimation, All the evidence does not need to come from
X-ray, surface, and DTA determinations. Other physical
and chemical properties suggest the mineralogy of many
clayey soils. Changes in volume, cation-exchange
capacity, and the consistence are useful in estimating the
nature of clay.

The description of clay mineralogy in naming families
of clayey soils is based on the weighted average of the
control section.

Calcareous and reaction classes

The presence or absence of carbonates and the reaction
are treated together because they are so intimately

related. A calcareous horizon cannot be strongly acid.
Calcareous classes are applied to the section between a
depth of 25 and 50 cm or between a depth of 25 cm and a
lithic or paralithic contact that is below a depth of 25 but not
50 em, or to some part of the soil above a lithic or paralithic
contact that is shallower than 25cm. Two classes,
calcareous and noncalcareous, are used in selected taxa.
The definitions follow.

Calcareous.--The fine-earth fraction effervesces in all
parts with cold dilute HCl.

Noncalcareous,--The fine-earth fraction does not
effervesce in all parts with cold dilute HCl. The term
noncaleareous is not used as a part of a family name.

It should be noted that a soil that contains dolomite is
calcareous and that effervescence of dolomite, when
treated with cold dilute HCl, is slow.

Reaction classes are applied to the control section that is
defined for particle-size classes, Three classes (acid,
nonacid, and allic) are used in selected taxa. The
definitions follow.

Acid.-The pH is less than 5.0 in 0.01 M CaCl (2:1)
throughout the control section (about 5.5 in H20, 1:1).

Nonacid.~The pH is 5.0 or more in 0.01 M CaClg (2:1) in
at least some part of the control section. The term nonacid
is not used in the family name of calcareous soils.

Allic.--There is more than 2 cmol(+) of KCl-extractable
Al per kg soil (leas than 2.0 mm fraction) in some 30 cm
layer in the control section.


7

Sixth, texture of the fine-earth fraction of a fragipan is
finer than fine sand, and the percentage of clay is
generally loss than 35; in most soils appreciably less.
‘The texture normally is loamy, that is, silt loam, loam, or
sandy loam.

Seventh, an air-dry fragment about the size of a fist
slakes or fractures when placed in water.

Gypsic horizon

The gypsic horizon is a noncemented or weakly cemented
horizon of enrichment with secondary sulfates that is 15
cm or more thick, has at least 5 percent more gypsum than
the C horizon or the underlying stratum, and in which the
product of the thickness in centimeters and the percentage
of gypsum is 150 or more, Thus, a horizon 30 cm thick that
has § percent gypsum qualifies if gypsum is absent in the
underlying horizon. A layer 30 cm thick that has 6
percent gypsum qualifies if the gypsum content of the
underlying horizon is not more than 1 percent.
Cementation is weak enough that a dry fragment slakes
in water.

The percentage of gypsum can be calculated by
multiplying the milliequivalents of gypsum per 100 g soil
by the milliequivalent weight of gypsum, which is 0.086.
4

Kandic horizon
The kandic horizon:

1. Is a vertically continuous subsurface horizon and has,
starting at the point where the clay increase requirements
are met, a CEC of 16 cmol(+) or less per kg clay (by IN
NH4OAc pH 7) and an ECEC of 12 cmol(+) or less per kg
clay (sum of bases extracted with IN NH4OAc pH 7 plus
1N KCl-extractable Al) in at least the major part of the
horizon.

2, Has a thickness of at least 30 cm, or if lithic,
paralithic, or petroferric contact occurs within 50 cm of the
soil surface, then the thickness of the kandic horizon is at
least 60 percent of the vertical distance between 18 cm and
the contact but at least 15 cm thick.

8, Has a texture of loamy very fine sand or finer.

4, 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 if there is no lithic, paralithic, or
petroferric contact within 50 cm,

me kandic horton, and the Aandi and kanhapli great groups in
chapters, represent the work of the International Committee on
Fieation of Low Activity Clays (ICOMAC), chaired by F/A.



297

SAPRISTS

Key to great groups

ADA. Sapriste that are frozen in some layer within the
control section about 2 months after the summer solstice
or that are never frozen below a depth of 5 cm but have a
mean annual soil temperature lower than 8°C.

Cryosaprists, p. 238
ADB. Other Saprists that have a mean annual soil
temperature lower than 8°C,

Borosaprists, p. 237

ADC. Other Saprists that have less than 6°C difference
between mean summer and mean winter soil

temperatures at a depth of 30 cm.
‘Troposaprists, p. 239

ADD. Other Saprists that do not have a horizon of
humilluvic materials 2 cm or more thick.

p. 238
Borosaprists
Key to subgroups
ADBA. Borosaprists that have a lithic contact within the
control section,
Lithic Borosaprists

ADBB. Other Borosaprists that:

1. Have 12.5 cm or more of the subsurface and bottom
tiers consisting of fibric materials; and

2, Have a mineral layer 30 cm or more thick that has
its upper boundary in the control section below the

surface tier.
Fibric Terric Borosaprists
ADBC. Other Borosaprists that:

1, Have 25 cm or more of the subsurface and bottom
tiers consisting of hemic materials; and

2, Have a mineral layer 30 cm or more thick that has
its upper boundary in the control section below the

surface tier.
Hemic Tesric Borosaprists

ADBD. Other Borosaprists that have a mineral layer 30
cm or more thick that has its upper boundary in the
control section below the surface tier.

Terric Borosaprists

ADBE. Other Borosaprists that have limnic layer(s) that
are 6 cm or more thick within the control section.

ADBF. Other Borosaprists that have a mineral layer
between 5 and 30 cm thick or two or more thin,


46

distinctions in soils if the particle size is important and
broader groupings if the particle size is not susceptible to
precise measurement or if the use of narrowly defined
classes produces undesirable groupings. Thus in some
families the term “clayey” indicates that there is 35
percent or more clay in defined horizons, but in other
families the term "fine" indicates that the clay fraction
constitutes 35 through 59 percent of the fine earth of the
horizons, and the term "very-fine” indicates 60 percent or
more clay. The term "rock fragments” refers to particles
2.0 mm in diameter or larger and includes all sizes that
have horizontal dimensions less than the size of a pedon.
It is not the same as coarse fragments, which excludes
stones and boulders larger than about 25 cm. The term
“fine earth" refers to particles smaller than 2.0 mm in
diameter.

Definition of cl

Fragmental.--Stones, cobbles, gravel, and very coarse
sand particles; too little fine earth to fill some of the
interstices larger than 1 mm in diameter.

Sandy-skeletal.-Rock fragments 2.0 mm in diameter or
larger make up 35 percent or more by volume; enough
earth to fill interstices larger than 1 mm; the fraction
finer than 2.0 mm is sandy as defined for the sandy
particle-size class.

Loamy-skeletal.Rock fragments make up 35 percent or
more by volume; enough fine earth to fill interstices
larger than 1 mm; the fraction finer than 2.0 mm is
loamy as defined for the loamy particle-size class.

Clayey-skeletal.Rock fragments make up 35 percent or
more by volume; enough fine earth to fill interstices
larger than 1 mm; the fraction finer than 2.0 mm is
clayey as defined for the clayey particle-size class.

Sandy.—The texture of the fine earth is sand or loamy
sand that contains less than 50 percent very fine sand;
rock fragments make up less than 35 percent by volume.

Loamy....The texture of the fine earth is loamy very fine
sand, very fine sand, or finer, but the amount of clay is
less than 35 percent; rock fragments are less than 35
percent by volume.

Coarse-loamy. By weight, 15 percent or more of the
particles are fine sand (diameter 0.25-0.1 mm) or
coarser, including fragments up to 7.5 em in diameter;
less than 18 percent clay in the fine-earth fraction.

} ke ene atio of 1500 kPa water retention to clay 1s 0.6 of nore in
half or nore of the contre section, the percentage of clay is
‘considered to be 2,5 tines the percentage of 1500 kPa water retention,
Garbonates of clay site are not considered to be clay but are treated as
silt in all particle-size classes.


271

the year when ita temperature is 5°C or more, or there is
artificial drainage,

Aquic Cryumbrepts
JEBH. Other Cryumbrepts that do not have a cambic
horizon.

Entic Cryombrepts
JEBL Other Cryumbrepts.

Typic Cryumbrepts
Fragiumbrepts
Key to subgroups

The definitions that follow are incomplete because there
are few of these soils in the United States.

JEAA. Fragiumbrepts that have, throughout a cumulative
thickness of 18 cm or more and within a depth of 75 cm,
bulk density of the less than 2.0 mm fraction, measured at
33 kPa water retention, of 1.0 g em’ or less and acid-
oxalate-extractable aluminum plus 1/2 acid-oxalate-
extractable iron of more than 1.0 percent.
Andie Fragiumbrepts
JEAB. Other Fragiumbrepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:
1. Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or
2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:
a. More than 30 percent volcanic glass; or
b. At least & percent volcanic glass and acid-oxalate-

extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.
Vitrandic:

JEAC. Other Fragiumbrepts that have mottles that have
chroma of 2 or less within 50 cm of the soil surface.

JEAD. Other Fragiumbrepts.
Typic Fragiumbrepts
Haplumbrepts
Key to.subgroups
JEDA. Haplumbrepts that have a lithic contact within 50
cm of the soil surface.
Lithic Haplumbrepts


318

years in some part of the moisture control section (not
necessarily the same part) during a period when the
soil temperature at a depth of 50 cm exceeds 5°C; or

2. If the soil temperature regime is hyperthermic or
isomesic, or warmer, are moist in some or all parts of
the moisture control section for lesa than 90 consecutive
days during a period when the aoil temperature at a
depth of 50 cm exceeds 8°C.
Aridic Paleustolls
HFCI. Other Paleustolls that, when neither irrigated nor
fallowed to store moisture:
1. If the soil temperature regime is mesic or thermic,
are dry for four-tenths or less of the cumulative days in
some part of the moisture control section when the soil
temperature at a depth of 60 cm exceeds 5°C; or
2. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or less
during a period when the soil temperature at a depth of
50 cm exceeds 8°C.
Udie Paleustolls
HFCJ. Other Paleustolls that are calcareous throughout
after the upper soil to a depth of 18 cm has been mixed and
have a calcic horizon within a depth of 100 em if the
particle-size class of the upper 50 cm of the argillic
horizon is sandy, 60 cm if it is loamy, and 50 cm if it is
clayey.
Calcic Paleustolls
HFCK. Other Paleustolls that are calcareous throughout

after the upper soil to a depth of 18 cm has been mixed.
Entic Paleustolis

HFCL. Other Paleustolls.
Typic Paleustolla

Vermustolls
Key to subgroups
HFFA, Vermustolls that have a lithic contact within 50
cm of the surface.

Lithic Vermustolls
HFFB. Other, Vermustolls that have a mollic epipedon
that is 75 cm or more thick.

Pachic Vermustolls

HFFC. Other Vermustolls that have mottles that have
chroma of 2 or less within 100 cm of the surface.

Aguic Vermustolls

HFFD. Other Vermustolls that have a cambic horizon.
Haplic Vermustalls

HFFE. Other Vermustolls that have a mollic epipedon
Jess than 50 cm thick.
Entic Vermustolls


Jess than two-thirds by volume of the rock fragments; fine
earth is hydrous.

Control section f& icle-size cl hei
substitutes .

Names of particle-size classes or their substitutes as
defined are applied to specific horizons or to the materials
between given limits of depth that are defined in terms of
either the distance below the surface of the mineral soil or
the upper boundary of a specified horizon or root-limiting
layer. The vertical section so defined is called the control
section. Root-limiting layers include fragipans,
duripans, continuous ortstein, petrocalcic and petrogypsic
horizons, and lithic, paralithic, and petroferric contacts.
Definitions of the control section for determination of the
particle-size classes are arranged as a key.

A. Particle-size modifiers or substitutes are used to
describe material from the surface to @ root-limiting
layer if any of these come within a depth of 36 cm (14 in.)
or less; or to a depth of 36 cm if the soil temperature is 0°C
or lower within this depth about 2 months after the
summer solstice.

B. In Andisols particle-size modifiers or substitutes are
used to describe material from the mineral soil surface or
upper boundary of an organic layer that meets andic soil
properties, whichever is shallower, to 100 cm or to a lithic,
paralithic, or petroferric contact, to a duripan, or to a
petrocaleic or placic horizon if the depth to any of these is
less than 100 em; or to a depth 25 cm below the level at
which the soil temperature is 0°C about 2 months after the
summer solstice; whichever is shallower.

C. In great groups of Spodosols, Alfisols, and Ultisols that
have a spodic horizon or a fragipan in or above an
argillic or kandie horizon; in Oxiaols; and in other soils
that do not have an argillic, kandic, or natric horizon:

1. Particle-size modifiers or substitutes are used to
describe material from the base of the Ap horizon or
from a depth of 25 cm, whichever is greater, to a root-
limiting layer if the depth is less than 100 cm; or toa
depth 25 cm below the level at which the soil temperature
is 0°C about 2 months after the summer solstice;
whichever is shallower.

2. Otherwise, particle-size modifiers or substitutes are
used to describe material from a depth of 25 cm toa
depth of 100 cm.

D. In other soils of the orders Alfisols and Ultisols and in
great groups of Aridisols and Mollisols that have an
argillic or kandic horizon that has (a) a lower boundary
deeper than 25 cm (see E) and (b) an upper boundary
shallower than 100 cm, or the soil is in a grossarenic
subgroup:


JDEP. Other Xerochrepts.
‘Typic Xerochrepts

PLAGGEPTS
Plaggepts are the soils that have a plaggen epipedon.
TROPEPTS

Key to great groups

JCA. Tropepts that have base saturation of less than 50
percent (by NH,OAc) in some subhorizon between depths
of 25 and 100 em and have 12 kg or more organic carbon,
exclusive of surface litter, per square meter in the soil to a
depth of 100 cm, or to a lithic, paralithic, or petroferric
contact if one is shallower than 100 cm, and do not have a

sombric horizon.
Humitropepts, p. 267

JCB, Other Tropepts that have a sombric horizon.
Sombritropepte, p. 268

JCC. Other Tropepts that have an ustic moisture regime
and have base saturation (by NH,OAc) of 50 percent or
more in all subhorizons between depths of 25 and 100 cm,
or between 26 cm and a lithic, paralithic or petroferric
contact if one is shallower than 100 cm.

‘Ustropepts, p. 268

JCD. Other Tropepts that have base saturation (by
NH,OAc) of 50 percent or more in all subhorizons between
depths of 25 and 100 cm, or between 25 cm and a lithic or
paralithic contact if one is shallower than 100 cm.

‘Eutropepts, p. 265
JCE. Other Tropepts.
Dystropepts, p. 263
Dystropepts
Key to subgroups

JCEA. Dystropepts that have a lithic contact within 50 cm
of the soil surface.

Lithic Dystropepts
JCEB. Other Dystropepts that have a petroferric contact
within 50 cm of the soil surface.
Petroferric Dystropepts

JCEC. Other Dystropepts that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 em or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the soil
surface or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.09 or
more if the soil moisture regime is udic, or 0.07 or more
if it is ustic, in a horizon or horizons at least 50 cm


79

b. If mottled and the mean annual soil temperature is
15°C or more:

(2) If the hue is 2.5Y or redder and the value, moist,
is more than 5, the chroma, moist, is 3 or more; or

(2) If the hue is 2.5Y or redder and the value, moist,
is 5 or less, the chroma, moist, is 2 or more; or

(8) If the hue is yellower than 2.6Y, the chroma,
moist, is 3 or more; or

c. If not mottled, the chroma, moist, is 2or more; and

2. Have an Ap horizon that has a color value, moist, of 3
or leas and a color value, dry, of 5 or less after the soil
has been crushed; or the upper soil to a depth of 18 cm,
after mixing, has these color values.

Aeric Umbric Kandiaqualfs

IAEE, Other Kandiaqualfs that have in more than 40
percent of the matrix in one or more subhorizons between.
the A or Ap horizon and a depth of 75 cm one or more of the
following:

1, If mottled and the mean annual soil temperature is
lower than 15°C, chroma, moist, of 3 or more; or

2. If mottled and the mean annual aoil temperature is
15°C or more:

a. If the hue is 2.5Y or redder and the value, moist, is
more than 5, the chroma, moist, ie 3 or more; or

b. If the hue is 2.5Y or redder and the value, moist, is
5 or less, the chroma, moist, is 2 or more; or

¢, If the hue is yellower than 2.5Y, the chroma, moist,
is 3 or more; or

3, Ifnot mottled, the chroma, moist, is 2 or more.
Aeric Kandiaqualfs

IAFF, Other Kandiaqualfs that have an Ap horizon that
has a color value, moist, of 3 or leas and a color value, dry,
of 6 or less after the soil has been crushed; or the upper soil
to a depth of 18 cm, after mixing, has these color values.
Umbric Kandiaqualfs

IAEG. Other Kandiaqualfs.
Typic Kandiaqualfs


305
3. More than 36 percent clay in horizons that total more
than 50 cm in thickness.
Vertic Argiustolis

HFEF, Other Argiustolls that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm” or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent. .

HFEG, Other Argiustolls that:

1. When neither irrigated nor fallowed to store
moisture:

a. If the soil temperature regime is mesic or thermic,
are dry six-tenths or more of the time in some or all
parts of the moisture control section (not necessarily
the same part) in half or more years during the
riod when the soil temperature at a depth of 50 cm is
‘igher than 5°C; or

b, If the soil temperature regime is hyperthermic, or
isomesic, or warmer, are moist in some or all parts
of the moisture control section for less than 90
consecutive days during a period when the soil
temperature at a depth of 50 cm is higher than 8°C;
and

2. Have, throughout a cumulative thickness of 18 cm or
more and within a depth of 75 cm, one or more of the
following:

a. Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or

b. The 0.02 to 2.0 mm fraction constitutes at least 30
Penvent of the less than 2.0 mm fraction and contains
either:

(1) More than 30 percent volcanic glass; or

(2) At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Vitritorrandic Argiustolls

HFEH. Other Argiustolls that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2, The 0.02 to 2.0 mm fraction constitutes at least 30
pore ne nt of the less than 2.0 mm fraction and contains
either:


318

HFCC, Other Paleustolls that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 60 cm, that are at least 30cm
long in some part, and that extend upward to the surface
or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.07 or
more in a horigon or horizons at least 50 cm thick, and
@ potential linear extensibility of 6 cm or more in the
upper 125 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 125 cm; and

3. More than 35 percent clay in horizons that have total
thickness of more than 50 cm.
Vertic Paleustolls

HEFCD. Other Paloustolls that have a mollic epipedon that
is 50 cm or more thick and its texture is finer than loamy

fine sand.
Pachic Paleustolls
HFCE. Other Paleustolls that have a petrocalcic horizon
within 150 em of the surface.
Petrocalcic Paleustolls

HFCF, Other Paleustolis that have mottles that have
chroma of 2 or leas within 100 cm of the surface if
artificially drained or, if undrained in most years, are
continuously saturated with water in the mottled horizon

for 90 days or more.
Aquic Paleustalls
HFCG. Other Paleustolls that:

1, Are calcareous throughout after the upper soil to. a
depth of 18 cm has been mixed and have a calcic
horizon within a depth of 100 cm ifthe

class of the upper 50 cm of the argillic horizon is “aandy,
60 cm if loamy, and 50 cm if clayey; and

2. When neither irrigated nor fallowed to store
moisture:

a, If the soi) temperature regime is mesic or thermic,
are dry aix-tenths or more of the time in half or more
years in some part of the moisture control section (not
necessarily the same ;) during a period when the
soil temperature at a of 50 cm exceeds 5°C; or

b. If the soil temperature regime is hyperthermic or
isomesic, or warmer, are moist in some or all parts
of the moisture control section for less than 90
consecutive days during a period when the soil
temperature at a depth of 50 cm exceeds 8°C.
Calciorthidic Paleustolls

HFCH. Other Paleustolls that, when neither irrigated nor
fallowed to store moisture:

1. If the soil temperature regime is mesic or thermic,
are dry six-tenths or more of the time in half or more


142
BGDM. Other Fulvodands that have, between 40 and 100
cm, a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the

underlying layer.
Thaptic Fulvudands

BGDN. Other Fulvudands that have a sum of bases of
more than 25.0 cmol(+) kg" fine earth throughout some
subhorizon 15 cm or more thick between 26 and 75 cm of
the mineral soil surface or of the upper boundary of an
organic layer with andic soil properties, whichever is

shallower.

Eutric Fulvudands
BGDO. Other Fulvudands.

Typic Fulvudands
Hapludands
Key to subgroups

BGFA, Hapludands that have a lithic contact within 50
cm of the soil surface.
Lithic Hapludands

BGFB. Other Hapludands that have a petroferric contact,
within 100 em of the soil surface.
Petroferric Hapludands

BGFC, Other Hapludands that have a horizon with its
upper boundary within 100 cm of the mineral soil surface
or of the upper boundary of an organic layer with andic
soil properties, whichever is shallower, which is more
than 15 em thick and contains 20 percent or more (by
volume) cemented soi] material that does not slake in
water after air drying, and have, in some subhorizon
between 50 and 100 cm:

1, Two percent or more redox segregations; or

2. Dominant chromas, moist, of 2 or less on faces of
peds, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or

3. Sufficient active ferrous iron to give a positive
reaction to a,a'-dipyridyl at some time of the year

when not being irrigated.
Aquic Durie Hapludands

BGFD. Other Hapludands that have a horizon with its
upper boundary within 100 cm of the mineral soil surface
or of the upper boundary of an organic layer with andic
soil properties, whichever is shallower, which is more
than 15 cm thick and contains 20 percent or more (by
volume) cemented soil material that does not slake in

fter aii a
water al air drying.


195
organic layer with andic soil properties, whichever is
shallower.

Vitric Fulvicryands
BBCC. Other Fulvicryands,

Typic Fulvicryands
Gelicryands
Key to subgroups

BBAA. All Gelicryands are regarded as Typic.
Typic

Haplocryands

Key to subgroups
BBFA. Haplocryands that have a lithic contact within 50

om of the soil surface.
Lithie Haplocryands

BBFB. Other Haplocryands that have IN KCl-
extractable Al** of more than 2.0 cmol(+) kg” fine earth
throughout a layer 10 cm or more thick between 25 and 50

cm.
Alic Haplocryands

BBFC. Other Haplocryands that have, in some
subhorizon between 50 and 100 cm of the mineral soil
surface or upper boundary of an organic layer with
andic soil properties, whichever is shallower:

1. Two percent or more redox segregations; or

2. Dominant chromas, moist, of 2 or Jess on faces of
peds, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or

8. Sufficient active ferrous iron to give a positive
reaction to a,a'-dipyridyl at some time of the year

when not being irrigated.
Aquic Haplocryands

BBFD. Other Haplocryands that have extractable bases
plus 1N KCl-extractable Al®* of leas than 2.0 cmol(+) kg?
fine earth in some subhorizon 30 cm or more thick.

between 25 and 100 cm.
Acrudoxic Haplocryands

BBFE. Other Haplocryands that have less than 30
percent, undried, 1500 kPa water retention in some
subhorizon that meets the requirements for andic soil
properties and that is at least 25 cm thick within 100 cm of
the mineral soi] surface or of the upper boundary of an
organic layer with andic soil properties, whichever is

shallower.
Vitric Haplocryands

BBFF. Other Haplocryands that have, between 25 and 100
cm, a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm


12

the ratio of clay in the argillic horizon to that in the
eluvial horizon must be 1.2 or more. The ratio of fine
clay to total clay in the argillic horizon is normally
greater than in the eluvial horizon by about one-third or

more.

c. If the eluvial horizon has more than 40 percent total
clay in the fine-earth fraction, the argillic horizon
must contain at least 8 percent more clay or, if the total
clay content exceeds 60 percent, 8 percent more fine
clay (50 percent versus 42 percent, for example).

2, An argillic horizon should be at least one-tenth as thick
as the sum of the thickness of all overlying horizons, or it
should be 15 cm or more thick if the eluvial and illuvial
horizons together are more than 150 em thick. If the
argillic horizon is sand or loamy sand, it should be at
least 15 cm thick. If it is composed entirely of lamellae,
lamellae 1 cm or more thick should have a combined
thickness of at least 15m. If the argillic horizon is
loamy or clayey, it should be at least 7.5 cm thick.

3. In structureless soils, the argillic horizon has oriented
clay bridging the sand grains and also in some pores.

4. If peds are present, an argillic horizon should meet one
of the following requirements:

a. Have clay skins on some of both the vertical and
horizontal ped surfaces and in the fine pores or have
oriented clay in 1 percent or more of the cross section;
or

b. Meet requirements 1 and 2 and also have a broken or
irregular upper boundary and some clay skins in the
lowest part of the horizon; or

¢. If the horizon is clayey, if the clay is kaolinitic, and
if the surface horizon has more than 40 percent clay,
have some clay skins on peds and in pores in the lower
part of the horizon that has blocky or prismatic
structure; or

d. If the illuvial horizon is clayey with 2-to-1 lattice
clays, an argillic horizon does not need to have clay
skins if there are uncoated grains of sand aor silt in the
overlying horizon and evidences of pressure caused by
swelling, or if the ratio of fine to total clay in the
horizon is greater by at least one-third than the ratio in
the overlying or the underlying horizon, or if it has.
more than 8 percent more fine clay. The evidences of
pressure may be occasional slickensides or wavy
horizon boundaries in the illuvial horizon.

6. Ifa soil has a lithologic discontinuity between the
eluvial horizon and the argillic horizon or if only a plow
layer overlies the argillic horizon, the argillic horizon


1, Have a content of organic carbon that decreases
irregularly with increasing depth; or

2. Have more than 0.3 percent carbon in all
subhorizons within 125 em of the soil surface.
Fiuvaquentic

Haplaquolls
HBFI. Other Haplaquolls.

Typic Haplaquolls
Natraquolls
Key to subgroups
HBCA, All Natraquolls (provisional),

Typic Natraquolls
BOROLLS
Key to great groups

HEA. Borolls that have an argillic horizon that has its
upper boundary deeper than 60 cm below the mineral soil
surface’, and that have texture finer than loamy fine sand
in all subhorizons above the argillic horizon.

p. 295

HEB. Other Borolls that have a cryic or pergelic
temperature regime.
Cryoborolls, p. 286

HEC. Other Borolls that have a natric horizon but do not
have a cambic horizon that is above the natric horizon and
separated from it by an albic horizon,

Natriborolls, p. 204

HED. Other Borolls that have an argillic horizon but do

not have a cambic horizon that is above the argillic

horizon and separated from it by an albic horizon.
Argiborolls, p. 283

HEE. Other Borolls that have a mollic epipedon that,
below any Ap horizon, is 60 percent or more by volume
wormholes, wormeasts, or filled animal burrows and that
cither rests on a lithic contact or has a transition to the
underlying horizon in which 25 percent or more of the
material is discrete wormholes, wormcasts, or animal
burrows filled with material from the mollic epipedon

and the underlying horizon,
Vermiborolls, p. 296

HEF. Other Borolls that have a calcic or petrocalci
horizon whose upper boundary is within 100 em of the soil
surface and that are calcareous in all parts of all horizons
above the caleic or petrocalcic horizon, after the upper soil
to a depth of 18 cm has been mixed, unless the texture is
coarser than loamy very fine sand.

Caleiborolls, p. 286

2

therein a nurface mantle thet haw G0 pervent ar more vtric voleanie ext, cinders, ar
time vitric pyroclastic materials, the depth to the englliehorinon is measured from the
‘base of thin mantle rather than from the minaral sol wurface,


402

a. If the soil temperature regime is mesic or
thermic, are dry for 135 cumulative days or less in
some part of the moisture control section when the

soil temperature at a depth of 50 cm exceeds 5°C; or

b. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or al
parts of the moisture control section for 90 days or
less during @ period when the soil temperature at a
depth of 50 em exceeds 8°C.
Udandic Kanhaplustults
GDCF. Other Kanhaplustults that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 76 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.
Andic Kanhaphastalts
GDCG. Other Kanhaplustults that have 5 percent or more
plinthite (by volume) in one or more subhorizons within

150 cm of the soil surface.
Plinthic Kanhaplustults

GDCH. Other Kanhaplustults that have, in the upper 75
em of the soil, a hue of LOYR or yellower in one or more
subhorizons that have a color value, moist, of 4 or more
and mottles with chroma of 3 or more and the hue
becomes redder with depth within 100 cm of the soil

surface,
Epiaquic Kanhaplustults

GDCI. Other Kanhaplustults that when neither irrigated
nor fallowed to store moisture:

1. If the soil temperature regime is mesic or thermic,

are moist six-tenths or less of the time in half or more
years in some part of the moisture control section (not
necessarily the same part) when the soil temperature
at a depth of 50 cm exceeds 5°C; or .

2. If the soil temperature regime is hyperthermic,

isomesic, or Warmer, are moist in most years in some
or all parts of the moisture control section for less than
180 days during a period when the soil temperature at a

depth of 50 cm exceeds 8°C.
Aridic Kanhaplustults

GDCJ. Other Kanhaplustults that when neither irrigated
nor fallowed to store moisture:

1. If the soil temperature regime is mesic or
thermic, are dry for 135 cumulative days or less in
some part of the moisture control section when the
soil temperature at a depth of 50 cm exceeds 5°C; or

2. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or
less during a period when the soil temperature at a

depth of §0 cm exceeds 8°C.
‘Udic Kanhaplustults


137
Melanocryands

Key to subgroups:
BBBA. Melanocryands that have a lithic contact within
50 cm of the soil surface.

Lithic Melanocryands

BBBB. Other Melanocryands that have IN KCI-
extractable Al** of more than 2.0 cmol(+) kg? fine earth
throughout a layer 10 cm or more thick between 25 and 50

cm.
Alic Melanocryands

BBBC. Other Melanocryands that have less than 30
percent, undried, 1500 kPa water retention in some
subhorizon that meets the requirements for andic soil
properties and that is at least 25 cm thick within 100 cm of
the mineral soil surface or of the upper boundary of an
organic layer with andic eoil properties, whichever is

shallower.

Vitric Melanocryands
BBBD. Other Melanocryands.

‘Typic Melanceryands
Vitricryands
Key to subgroups

BBEA. Vitricryands that have a lithic contact within 50
em of the soil surface,
Lithic Vitricryands

BBEB. Other Vitricryands that have, in some subhorizon
between 50 and 100 cm of the mineral soil surface or of
the upper boundary of an organic layer with andic soil
properties, whichever is shallower:

1, Two percent or more redox segregations; or

2. Dominant chromas, moist, of 2 or less on faces of
peds, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or

8, Sufficient active ferrous iron to give a positive
reaction to a,a'-dipyridyl at some time of the year

when not being irrigated.
“Aquic Vitricryands
BBEC. Other Vitricryands that have, between 25 and 100
em, a layer 10 cm or more thick with more than 3.0
pereent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 em

or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the

underlying layer.
‘Thaptic Vitri 1
BBED. Other Vitricryands that have a xeric moisture
regime.
Xeric Vitricryands


64

particle-size control section. If the substitute terms are
used only for the upper part then only the seven particle-
size classes are used. For example, we might use cindery
over loamy but not cindery over fine-loamy.

Only two particle-size classes are used to separate
families in Vertisols, fine if there is less than 60 percent
clay and very-fine if there is 60 percent or more clay in
the weighted average of the control section.

Mineralogy classes
‘The control section

Mincralogy classes are based on the approximate
mineralogical composition of selected size fractions of
the same segment of the soil (control section) that is used
for application of particle-size classes.

Pe ing mineralogy modifi

Contrasting mineralogy modifiers are not recognized
except where substitutes for particle-size class modifiers
have been used. In identifying and naming the
contrasting mineralogy modifiers in families of those
soils, the seven particle-size classes are used to describe
the lower part of the section. For example, a pair of
contrasting layers is named as medial over loamy,
mixed, not medial over coarse-loamy, mixed.

If there are layers of contrasting particle size in the
control section, the mineralogy class of the upper part of
the control section is definitive of the family mineralogy.
For example, if there is fine-loamy material of mixed
mineralogy over sandy material that is siliceous, the
proper modifiers to describe the family are fine-loamy
over sandy, mixed, not fine-loamy, mixed, over sandy,
siliceous.

Key to mineralogy classes

All mineral soils, except Oxisols, are placed in the first
mineralogy class of the key (Table 1) that accommodates
them although they may appear also to meet the
requirements of other mineralogy classes. The correct
mineralogy class for Oxisols is determined by using the
key in Table 2. These are keys, not complete definitions.
Substitute terms connoting both particle size and
mineralogy are based on combined texture, consistence,
and mineralogy classes and are used to indicate
important variations in Andisols, in many intergrades
to Andisols, and in many eryic great groups and cryic
subgroups of Spodosols. Mineralogy classes are not
named in Calciaquolls because the effect of the carbonates
overshadows other differences in mineralogy, and they
are not named in Quartzipsamments, which, by
definition, are siliceous,


Chapter 1

The Soil That We Classify and Horizons

and Properties Diagnostic for the Higher
Categories: Mineral Soils

THE SOIL THAT WE CLASSIFY

Soil, as used in this text, is the collection of natural bodies
on the earth's surface, in places modified or even made by
man of earthy materials, containing living matter and
supporting or capable of supporting plants out-of-doors.
Its upper limit is air or shallow water. At its margins it
grades to deep water or to barren areas of rock or ice. Its
lower limit to the not-soil beneath is perhaps the most
difficult to define. Soil includes the horizons near the
surface that differ from the underlying rock material as
a result of interactions, through time, of climate, living
organisms, parent materials, and relief, In the few
places where it contains thin cemented horizons that are
impermeable to roots, soil is as deep as the deepest
horizon. More commonly soil grades at its lower margin
to hard rock or to earthy materials virtually devoid of
roots, animals, or marks of other biologic activity. The
lower limit of soil, therefore, is normally the lower limit
of biologic activity, which generally coincides with the
common rooting depth of native perennial plants, If
cither biological activity or current pedogenic processes
extend to depths greater than 200 cm, the lower limit of the
soil that we classify is arbitrarily set at 200 cm. Yet in
defining mapping units for detailed soil surveys, lower
layers that influence the movement and content of water
and air in the soil of the root zone must also be considered.

BURIED SOILS

A soil is considered to be a buried soil if there is a surface
mantle of new material that is 50 cm or more thick or if
there is a surface mantle between 30 and 50 cm thick and
the thickness of the mantle is at least half that of the
named diagnostic horizons that are preserved in the
buried soil. A mantle that is less than 30 cm thick is not
considered in the taxonomy but, if important to the use of
the soil, is considered in establishing a phase. The soil
that we classify in places where a mantle is present,
therefore, has its upper boundary at the surface or less
than 50 cm below the surface, depending on the thickness
of its horizons.

A surface mantle of new material as defined here is
largely unaltered. It is usually finely stratified and
overlies a horizon sequence that can be clearly identified
as the solum of a buried soil in at least part of the pedon, as
defined in the following chapter. The recognition of a


GDFF, Other Haplustults that have 5 percent or more
pliathite (by volume) in one or more subhorizons within

160 em of the soil surface.
Plinthic Haplustults

GDFG. Other Haplustults that have CEC of less than 24
cmol(+) per kg clay (by IN NH, Ode pH 7) in the major
part of the argillic horizon, or the major part of the upper
100 cm of the argillic horizon if the argillic horizon is
thicker than 100 em.

Kanhaplic Haplustults
GDFH. Other Haplustults.
‘Typic Haplustults
Kandiustults
Key to subgroups

GDBA, Kandiustults that have an ECEC (eum of bases
plus KCl-extractable Al) of 1.5 cmol(+) or less per kg
clay in one or more subhorizons within a depth of 150 cm

below the soil surface.
Acrustoxic Kandiustults

GDBB, Other Kandiustults that have the following
combination of characteristics in the upper 75 em of the
soil if the chroma in all or part of the upper 75 cm is not
controlled by uncoated sand grains; or if the chroma
throughout the upper 76 cm is controlled by uncoated sand
grains, have the following combination of
characteristics throughout the upper 12.5 cm of the
argillic or kandic horizon:

1. Mottles that have a color value, moist, of 4 or more
and chroma, moist, of 2 or less accompanied by
maottles of higher chroma that are due to segregation of
iron; and

2. Saturation with water in the mottled zone at some
time of year when the soil temperature in that zone is
5°C or higher or there is artificial drainage.

Aquic Kandiustults

GDBC. Other Kandiustults that:

1, Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic or kandic horizon that is 60 to 100 cm
below the soil surface; and

2. Have 6 percent or more plinthite (by volume) in one
or more subhorizons within 150 cm of the soil surface.
Arenic Plinthic Kandiustults

GDBD. Other Kandiustults that have a layer, starting at
the mineral soil surface, that has a sandy particle-size
class and extends to the top of an argillic or kandic
horizon that is 50 to 100 cm below the soil surface.

Arenic Kandiustults


176

4. More than 36 percent clay in horizons that total more
than 50 cm in thickness; and

5. A rigid or colder soil emperature regime.

FADB. Other Paleargids that have:

1. A weighted average percentage of organic carbon in
the upper sail to a depth of 40 cm of 0.6 percent or more
if the weighted average ratio of sand to clay above this
depth is 1.0 or less, or one-seventh percent or less if the
ratio is 13 or more, or an intermediate percentage of
organic carbon if the ratio of sand to clay is between
1.0 and 13; and a weighted average percentage of

organic carbon in the surface soil to a depth of 18 cm
thet is one-fifth or more higher than the values just
stated if there is a petrocalcic horizon whose upper
Doundary is shallower than 40 cm but deeper than 18
om; and

2. A frigid or colder soil temperature regime and an
aridic moisture regime that on an ustic
regime.

Borollic Paleargids

FADC. Other Paleargids that have the following
combination of characteristics:

1, Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the soil
surface, to the base of an Ap horizon, or to the top of the
argillic horizon; and

2. A coefficient of linear extensibility (COLE) of 0.05
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 150 cm of the soil or in the whole soil ifa
lithic or paralithic contact is deeper than 50 cm but
shallower than 150 cm; and

3. More than 35 percent clay in horizons that total more
than 50 cm in thickness.
‘Vertic Paloargids

FADD. Other Paleargids that have the following
combination of characteristica:

1. A petrocalcic horizon whose upper boundary is.
within 100 cm of the soil surface; and

2. A weighted average percentage of organic carbon in
the upper soil to a depth of 40 cm of 0.6 percent or more
if the weighted average ratio of sand to clay above this
depth is 1.0 or less, or one-seventh percent or less if the
ratio is 13 or more, or an intermediate percentage of
organic carbon if the ratio of sand to clay is between
1.0 and 13; and a weighted average percentage of
organic carbon in the surface soil to a depth of 18 cm
that is one-fifth or more higher than the values just
stated if there is a petrocalcic horizon whose upper
boundary is shallower than 40 cm but deeper than 18
cm; and


25 em, whichever is deeper, and a depth of 75 cm, one or
more of the following:

a. If mottled and

(1) Ifthe hue ia 2.8Y or redder! and the value,
moist, is more than 5, the chroma, moist, is 3 or
more; or

(2) If the hue is 2.5Y or redder and the value,
moist, is 5 or less, the chroma, moist, is 2 or more;
or

(8) If the hue is yellower than 2.5Y, the chroma,
moist, is 3 or more; or

b. The chroma, moist, is 2 or more and there are no
mottles; and

2. Have a difference of less than 5°C between the mean
summer and mean winter soil temperatures at a depth
of 50 cm or at a lithic or paralithic contact, whichever

is shallower.
Aaric Tropic Fluvaquents

KADG. Other Fluvaquents that have in more than 40
percent of the matrix in one or more subhorizons between
the Ap horizon or a depth of 25 cm, whichever is

and a depth of 75 cm, one or more of the following:

1. If mottled and

a. If the hue is 2.5Y or redder® and the value, moist,
is more than 5, the chroma, moist, is 3 or more; or

b. If the hue is 2.5Y or redder and the value, moist, is
5 or less, the chroma, moist, is 2 or more; or

¢. If the hue is yellower than 2.5Y, the chroma,
moist, is 3 or more; or

2. The chroma, moi:
mottles.

2 or more and there are no

Aeric Fluvaquents

KADH. Other Fluvaquents that have a difference of less
than 5°C between the mean summer and mean winter
soil temperatures at a depth of 50 cm or at a lithic or
paralithic contact, whichever is shallower.

Tropic Fluvaquents

hue of the matrix ie 7.SYR or redder and if peda are preent,
fore have dominant chroma, soist, of 1 os less, and ped

ve ott les that have chroma, wotst, of 2 or leas) if peds
are absent, the chroma, poist, i# 1 or less immediately below any
aurface horizon that has value, moist, of 2 or lees.

3
If the hue of the matrix in 7.51 oF redder and if pede

ped have dominant chroma, moist, of 1 or

sett ies that have chroma, moist, af 2

‘the chroma, moist, ia 1 or less innediately helo any

Strvace hetizon that has value, nolets of 3 er ines



222
saturation of 35 percent or more at a depth of 125 cm below
the uppermost lamella.

Alfic Ustipsamments
KCGD. Other Ustipsamments that have lamellae within

150 cm of the soi] surface that meet all requirements for
an argillic horizon except thickness.!5

Ultic Ustipsamments
KCGE. Other Ustipsamments.

Typic Ustipsamments
Xeropsamments
Key to subgroups

KCFA. Xeropsamments that have a lithic contact within
50 em of the soil surface.

Lithic Xeropsamments
KCFB, Other Xeropsamments that:

1. Have distinct or prominent mottles above a depth of
100 cm or are saturated with water within 100 cm of the

surface during some time of year in most years; and

2. Have a horizon within 100 cm of the surface that is
more than 15 cm thick and either contains 20 percent
or more durinodes in a nonbrittle matrix or is brittle
and has firm consistence when moist.

Aquic Durorthidic

‘Xeropeamments

KCFC. Other Xeropsamments that have distinct or
prominent mottles above a depth of 100 cm or are
saturated with water within 100 cm of the surface during
some time of year in most years.

Aquie Xeropeamments
KCFD. Other Xeropsamments that have a horizon within
100 cm of the surface that is more than 15 cm thick and
either contains 20 percent or more durinodes or is brittle
and has firm consistence when moist.

Xeropsammeants

KCFE, Other Xeropsamments that have lamellae within
150 cm of the soi] surface that meet all requirements for
an argillic horizon except thickness” and have base
saturation of 35 percent or more at a depth of 125 cm below

the uppermost lamella.
Alfic Xeropeamments
KCFF, Other Xeropsamments that have lamellae within

fod with precision in leneliae that
14 of alfic subgroups generally are
eal thickness ia less than che 15
fg Fetvized for an argiilte horizon.

‘The clay content cannot be estimated with precision in lamellae that
are very chin, The lanellee in soils of alfie aubgroups generally are
‘about 0.8 to 1 cx thick, bur their total thickness is less than the 1S
om required for aa argillie horizon.


164

more if the ratio is 13 or more, or is intermediate
between 0.6 percent and one-seventh percent if the
ratio of sand to clay is between 1.0 and 13; anda
weighted average percentage of organic carbon in the
soil to a depth of 18 cm that is one-fifth or more higher
than the values just stated if there is a lithic or
paralithic contact at a depth of less than 40 cm but more
than 18 cm; and

3. A mean annual soil temperature lower than 22°C,
mean summer and mean winter soil temperatures at
a depth of 50 cm that differ by 5°C or more, and an
aridic moisture regime that borders on a xeric

regime.
Lithic Xerollic Haplargid

PAED. Other Haplargids that have the following
combination of characteristics:

1. A lithic contact within 50 em of the surface; and

2. A weighted average percentage of organic carbon in
the upper 40 cm that is 0.6 percent or more if the
weighted average ratio of sand to clay in the soil above
that depth is 1.0 or less, or is one-seventh percent or
more if the ratio is 13 or more, or is intermediate
between 0.6 percent and one-seventh percent if the
ratio of sand to clay is between 1.0 and 18; anda
weighted average percentage of organic carbon in the
soil to a depth of 18 cm that is one-fifth or more higher
than the values just stated if there is a lithic or
paralithic contact at a depth of less than 40 cm but more
than 18 cm; and

3. A mean annual soil temperature of 8°C or higher
and an aridic moisture regime that borders on an.

ustic regime.
Lithic Ustollic Haplargids
AEE. Other Haplargids that have a lithic contact
within 50 cm of the surface.
Lithic Haplargids

PAEF, Other Haplargids that have the following
combination of characteristics:

1. A frigid or colder temperature regime; and

2. A weighted average percentage of organic carbon in
the upper 40 cm that is 0.6 pervent or more if the
weighted average ratio of sand to clay in the soil above
that depth is 1.0 or less, or is one-seventh percent or
more if the ratio is 13 or more, or is intermediate
between 0.6 percent and one-seventh percent if the
ratio of sand to clay is between 1.0 and 13; and

3. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the
surface, to the base of an Ap horizon, or to the top of the
argillic horizon, and the cracks are not closed for as
many as 60 consecutive days of the 120 days following
the winter solstice in 3 or more years out of 10; and


n

a. If there is an argillic, kandic or natric horizon,
from its upper boundary to a depth of 125 cm below that
boundary, or to a depth 180 cm below the soil surface
or to a lithic or paralithic contact, whichever is least;
or

b. If there is no argillic, kandic, or natric horizon, in
all subhorizons to a depth 180 cm below the soil
surface or to a lithic or paralithic contact, whichever
is least.

Mollisols, p. 275

I. Other soils that either

1. Have an argillic, kandie or natric horizon but no
fragipan; or

2, Have a fragipan that

a, Is in or underlies an argillic or kandic horizon;
or

b. Meets all requirements of an argillic or kandic
horizon; or

c. Has clay skins more than 1 mm thick in some
part.
Alfisols, p.73

J. Other soils that have no sulfidic material within 50 cm
of the mineral soil surface; and have between 20 and 50
em below the mineral soil surface an n value of 0.7 or less
in one or more subhorizons or less than 8 percent clay in
one or more subhorizons; and have one or more of the
following:

1. An umbric, mollic, histic (either mineral or
organic) or plaggen epipedon; or

2. A cambic horizon or both an aquic moisture regime
and permafrost; or

8, Within 100 cm of the surface, a calcic, petrocalcic,
gypsic, petrogypsic, or placic horizon or a duripan; or

4. A fragipan or an oxic horizon with its upper
boundary between a depth of 160 and 200 cm; or

5. A sulfuric horizon whose upper boundary is within 50
em of the soil surface; or


26

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 soil surface of Oxisols and within 50
cm of the soil surface of all other mineral soils.

Mottles that have chroma of 2 or less

It refers to colors in a horizon in which parts have chroma
of 2 or less, moist, and value, moist, of 4 or more, whether
or not that part is dominant in volume or whether or not it
is a continuous phase surrounding spots of higher
chroma, If either the minor or major part of a horizon has
chroma of 1 to 2 and value, moist, of 4 or more and there
are spots of higher chroma, the part that has the lower
chroma is included in the meaning of "mottles that have
chroma of 2 or less.” The part is excluded from the
meaning if all the horizon has chroma of 2 or less or if no
part of the horizon has chroma as low as 2.

The phrase also means that the horizon that has such
mottles is saturated with water at some period of the year
or the soil is artificially drained. It is also implicit in the
meaning that the temperature of the horizon is above the
biologic zero, which is about 5°C (41°F), during at least a
part of the time that the horizon is saturated.

nvalue

The n value (Pons and Zonneveld 1966) refers to the
relation between the percentage of water under field
conditions and the percentages of inorganic clay and of
humus, The n valve is helpful in predicting whether the
soil may be grazed by livestock or will support other loads,
and the degree of subsidence that would occur after
drainage. The n value can be calculated for mineral soil
materials that are not thixotropic by the formula:

n=(A-0.2RML + 3H)

Ais 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 (organic carbon x 1.724).

Few data are available in the United States for
calculations of the n value, but the critical n value of 0.7
can be approximated closely in the field by a simple test of
squeezing the soil in the hand. If the soil flows with
difficulty between the fingers, the 7 value is between 0.7
and 1.0. If the soil flows easily between the fingers, the n
value is 1 or more.


8, Have, at some time in most years unless irrigated or
cultivated, open cracks at a depth of 50 cm that are at
least 1 em wide and extend upward to the surface or to
the base of the plow layer or surface crust; and

4. Have one or more of the following:
a. Gilgai; or

b. At some depth between 25 and 100 cm, slickensides
close enough to intersect; or

c. At some depth between 25 and 100 cm, wedge-

shaped natural structural aggregates that have their

long axes tilted 10 to 60° from the horizontal.
Vertisols, p. 407

F. Other soils that have an ochric or anthropic epipedon
and either:

1, Do not have an argillic or a natric horizon but

a, Are saturated with water within 100 cm of the
surface for 1 month or more in some years and have
a salic horizon whose upper boundary is within 75 cm
of the surface; or

b. Have one or more of the following horizons whose
upper boundary is within 100 cm of the soil surface: a
petrocalcic, calcic, gypsic, petrogypsic, or cambic
horizon or a duripan; and have an aridic moisture
regime; or

2. Have an argillic or a natric horizon and have

a. An aridic moisture regime; and

b. An epipedon that is not both massive and herd or
very hard when dry.

Aridisols, p. 159

G. Other soils that have a mesic, isomesic, or warmer
temperature regime, do not have tongues of albic
materials in the argillic horizon that have vertical
dimensions of as much as 50 cm if there are more than 10
percent weatherable minerals in the 20- to 200-micron
fraction, but have one of the following combinations of
characteristics: either

joke are open, the oracks may be largely filled
with granvler aaterials from the surface. But they are considered to be
‘open in the sense that the polyhedrone are separated.


146
organic carbon content 1 percent or more lower than the

underlying layer.
Thaptic Hydrudands

BGEF. Other Hydrudands that have a sum of bases of
more than 25.0 cmoK +) kg" fine earth throughout some
subhorizon 15 cm or more thick between 25 and 75 cm of
the mineral soi] surface or of the upper boundary of an
organic layer with andic soil properties, whichever is

shallower.
Eutric Hydrudands

BGEG. Other Hydrudands that have an argillic or
kandic horizon with its upper boundary within 125 cm of
the mineral soil surface or of the upper boundary of an
organic layer with andic soil properties, whichever is

shallower.

Ultic Hydrudands
BGEH. Other Hydrudands.

Typic Hydrudands
Melanudands
Key to subgroups

BGCA. Melanudands that have a lithic contact within 50
cm of the soil surface.
Lithic Melanudands

BGCB. Other Melanudands that have IN KCl-
extractable Al** of more than 2.0 cmol(+) kg" fine earth
throughout a layer 10 cm or more thick between 25 and 50
cm, and have, in some subhorizon between 50 and 100 cm
of the mineral soil surface or of the upper boundary of an
organic layer with andic soil properties, whichever is
shallower:

1, Two percent or more redox segregations; or

2, Dominant chromas, moist, of 2 or less on faces of
peds, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or

8, Sufficient active ferrous iron to give a positive
reaction to a,a'-dipyridyl at some time of the year

when not being irrigated.
Alic Aquic Melanudands

BGCC. Other Melanudands that have 1N KCl-
extractable Al* of more than 2.0 cmol(+) kg fine earth
throughout a layer 10 cm or more thick between 25 and 50
cm, and have both more than 6.0 percent organic carbon
and colors of the mollic epipedon throughout at least 50
cm of the upper 60 cm, excluding any overlying layers
that do not have andic soil properties.

Alic Pachic Melanudands

BGCD. Other Melanudands that have 1N KCl-
extractable Al®* of more than 2.0 cmol(+) kg”! fine earth
throughout a layer 10 em or more thick between 25 and 50
cm, and have, between 40 and 100 cm, a layer 10 cm or
more thick with more than 3.0 percent organic carbon


62
Soil temperature classes

Names and definitions of classes follow the rules given
for soil temperature classes of mineral soils, Frigid,
however, is redundant in boric and cryic great groups
and is not used. No temperature modifier is used in
pergelic subgroups.

Soil depth classea

Soil depth modifiers are used in all lithic subgroups of
Histosols except in the suborder of Folists. It is assumed
that lithic Folists have a shallow lithic contact. Other
lithic Histosols have a lithic contact within the control
section but it may be as much as 160 cm deep.

Shallow families.--Used in lithic subgroups to indicate a
lithic contact between a depth of 18cm and 50 cm,

Micro families.--Used to indicate a lithic contact
shallower than 18 cm without regard to soil temperature.
(In mineral soils, micro families are restricted to cryic
great groups.)

LITERATURE CITED
Soil Survey Staff. 1951. Soil survey manual. U.S, Dept.

Agr. Handb. 18. U.S. Govt. Printing Office,
Washington, DC.


Chapter 12
Oxisols"
KEY TO SUBORDERS

DA. Oxisols that are either saturated with water within 30
cm of the mineral soil surface 30 days per year in most
years or artificially drained, and have one or more of the
following:

1. A histic epipedon; or
2. If faintly mottled or not mottled within 50 cm of the

soil surface, an epipedon that has a moist color value of
3 or leas and chroma of 2 or less immediately below the

epipedon; or
3. If there are distinct or prominent mottles within 50
em of the soil surface, a chroma of 3 or less or a hue of
2.8Y or yellower in 50 percent or more of the horizon
immediately below the epipedon.
Aquox, p. 335
DB. Other Oxisols that have an aridic soil moiature
regime.
Torrox, p. 343
DC. Other Oxisols that have an ustic soil moisture
Tegime,
Ustox, p. 350

DD. Other Oxisols that have a perudic soil moisture
regime.

Perox, p. 337
DE. Other Oxisols.
Udox, p. 344
AQUOX
Key to great groups

DAA. Aquox that have an apparent ECEC of less than 1.50
emol(+) per kg clay and a pH value (IN KCI) of 5.0 or
more in some part of the oxic horizon within a depth of 150
cm of the soil surface.

Acraquox, p. 336

DAB. Other Aquox that have plinthite forming a
continuous phase within a depth of 125 em of the soil

surface,
Plinthaquox, p. 337

1

‘This chapter on Oxisole was rewritten in 1987 flowing the recommendatioas of tbe
International Coramittoe on the Clansification af Oxieals (GOMON, chaired by H.
‘Eewaren from 1078 to 1983 and then by 8. Bool until ita completian in 1987,


19

SAR is 13 or more (or ESP is 15 or more) in some
horizon within 200 cm of the surface.

Oxic horizon

The oxic horizon is intended to characterize a mineral
subsurface horizon of sandy loam or finer particle size
with low cation exchange capacity and low weatherable
mineral content. The upper boundary of the oxic horizon
is at 18 cm below the soil surface or the base of the Ap
horizon, whichever is deeper, or at a deeper depth where
the mineralogical and charge characteristics meet the
requirements of the oxic horizon.

In summary, the oxic horizon is a subsurface horizon
that:

1.Is at least 30 cm thick; and

2. Has a particle size of sandy loam or finer in the fine
earth fraction; and

3. Has a fine-earth fraction (less than 2.0 mm) that has
an apparent ECEC (NH4OAc bases plus IN KCI-
extractable Al) equal to or less than 12 cmol(+) per kg clay
and an apparent CEC pH 7 (NH4OAc CEC) equal to or less
than 16 cmol(+) per kg clay (measured clay or 3 x 1500
kPa water retention, whichever is greater but less than
100); and

4. Does not have as much as 10 percent weatherable
mincrals in the 50-200 micron fraction; and

8. Has a diffuse upper particle-size boundary (i.e., less
than 1.2 times clay content increase within a vertical
distance of 15 cm if the surface horizon contains 20-40
percent clay; less than 4 percent absolute clay content
increase if the surface contains 20 percent or less clay;
Jese than 8 percent absolute if the surface contains 40
percent or more clay); and

6. Does not have andic soil properties; and

7. Has less than 5 percent by volume that shows rock
structure unless the lithorelicts containing weatherable
minerals are coated with sesquioxides,

Petrocalcic horizon

The petrocalcic horizon is a continuous, cemented or
indurated calcic horizon that is cemented by calcium
carbonate or in some places by calcium and some
magnesium carbonate. Accessory silica may be present.
The petrocalcic horizon is continuously cemented
throughout the pedon to the degree that dry fragments do
not slake in water. It cannot be penetrated by spade or
auger when dry. It is massive or platy, very hard or


304
or the argillic horizon has lamellae in some or all parts
of the upper 100 cm.

Peammentic Paleudults

GCED. Other Paleudults that:

1. Have the following combination of characteristics
in the upper 75 em of the soil if the chroma in all or part
of the upper 75 cm is not controlled by uncoated sand
grains; or if the chroma throughout the upper 75 cm is
controlled by uncoated sand grains, have the
following combination of characteristica throughout
the upper 12.5 cm of the argillic horizon:

a. Mottles that have a color value, moist, of 4 or more
and chroma, moist, of 2 or less accompanied by
mottles of higher chroma that are due to segregation
of iron; and

b, Saturation with water in the mottled zone at some
time of year when the soil temperature in that zone
is 5°C or higher, or there is artificial drainage; and

2. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic horizon that is 50 to 100 cm below the
soil surface; and

3. Have 5 percent or more plinthite (by volume) in one
or more subhorizons within 150 cm of the soil surface.
Arenic Plinthaquic Paleudults

GCEE. Other Paleudults that:

1. Have the following combination of characteristics
in the upper 75 cm of the soil if the chroma in all or part
of the upper 75 cm is not controlled by uncoated sand
grains; or if the chroma throughout the upper 75 cm is
controlled by uncoated sand grains, have the
following combination of characteristics throughout
the upper 12.5 em of the argillic horizon:

a. Mottles that have a color value, moist, of 4 or more
and chroma, moist, of 2 or less and mottles of higher
chroma that are due to segregation of iron; and

b, Saturation with water in the mottled zone at ome
time of year when the soil temperature in that zone
is 6°C or higher, or there is artificial drainage; and

2. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillie horizon that is 50 to 100 em below the

soil surface.
Aquic Arenic Paleudults

GCEF, Other Paleudults that:

1. Have a layer, starting at the mineral soil surface,

that has a sandy particle-size class and extends to the
top of an argillic horizon that is 50 to 100 em below the
soi] surface; and


Isohyperthermic.--The mean annual soil temperature is
22°C or higher.

Sulfidic materials

Sulfidic materials are waterlogged mineral or organic
soil materials that contain 0.75 percent or more sulfur
(dry weight), mostly in the form of sulfides, and that have
less than three times as much carbonate (CaCO3
equivalent) as sulfur. Sulfidic materials accumulate in
a soil that is permanently saturated, generally with
brackish water. The sulfates in the water are biologically
reduced to sulfides as the soil materials accumulate.
Sulfidic materials are most common in coastal marshes
near the mouths of rivers that carry noncalcareous
sediments, but they may occur in fresh-water marshes if
there is sulfur in the water. If the soil is drained, the
sulfides oxidize and form sulfuric acid. The pH, which
normally is near neutrality before drainage, may drop
below 2. The acid reacts with the soil to form iron and
aluminum sulfates. The iron sulfate, jarosite,
segregates and forms the bright-yellow mottles that
characterize a sulfuric horizon. The transition from
sulfidic materials to a sulfuric horizon normally
requires a very few yeara. A sample of sulfidic
matcrials, if air dried slowly in shade for about 2 months
with occasional remoistening, becomes extremely acid.
For quick identification in the field, a sample can be
oxidized by boiling in concentrated H2O2 and measuring
the drop in pH.”

Tonguing and interfingering
i lbic ri

Tongues of albic materials consist of penetrations of
bleached material that has the color of an albic horizon in
an argillic or a natric horizon, along ped surfaces if peds
are present. No continuous albic horizon need be present
above the tongues, The penetrations have a vertical
dimension of more than 5 cm in any argillic or natric
horizon. Their horizontal dimension is 5 mm or more in
a fine-textured argillic or natric horizon (clay, silty clay,
or sandy clay), 10 mm or more in a moderately fine
textured argillic or natric horizon (clay loam, sandy clay
loam, or silty clay loam), and 15 mm or more in a
medium or coarser textured argillic or natric horizon
(silt loam, loam, very fine sandy loam, or coarser). The
penetrations must occupy more than 15 percent of the
matrix of some part of the argillic or natric horizon before
they are considered tongues.

burns and 1s dangeroun. Gloves



157
BDAF. Other Vitrixerands that have an argillic or
kandic horizon with ite upper boundary within 125 em of
the mineral soi) surface.
Alfic Vitrixerands

BDAG. Other Vitrixerands that have a mollic epipedon.
Mollic Vitrixerands

BDAH, Other Vitrixerands that have an umbric
epipedon,
Umbric Vitrixerands

BDAI. Other Vitrixerands.
Typic Vitrixerands


246

3. More than 36 percent clay in horizons that total more
than 50 cm in thickness.
‘Vertic Haplaquepts

JAID. Other Haplaquepts that have, throughout a

cumulative thickness of 18 cm or more and within a
depth of 75 cm, one or more of the following:

1. Bulk density of the leas than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 gcm* or
less and acid-oxalate-extractable aluminum plus 1/2
acid-oxalate-extractable iron of more than 1.0 percent;
or

2, Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or

3. The 0.02 to 2.0 mm fraction constitutes at least 30

percent of the lesa than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-
oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of 0.40 percent or more.
Aquandic Haplaquepts
JAIE. Other Haplaquepts that have in more than 40
percent of the matrix in one or more subhorizons between.

the A or Ap horizon and a depth of 75 cm, one or more of
the following:

1. If mottled and the mean annual soil temperature is
lower than 15°C, moist chroma of 3 or more; or

2. If mottled and the mean annual soil temperature is
15°C or higher:

a. Ifthe hue is 2.5Y or redder’ and the value, moist,
is more than 5, the chroma, moist, is 3 or more; or

b. If the hue is 2.5Y or redder and the value, moist, is
5 or less, the chroma, moist, is 2 or more; or

c. If the hue is 6Y or yellower, the chroma, moist, is 3
or more; or

3. The chroma, moist, is 2 or more if mottles are not
present,
Acric Haplaquepts

If the hue ia 7.5¥R oF redder in the matrix and if peds are present,
‘should have doainant chroma, moist, of 2 ar less and
the ped interiors should have nottles that have chrome, moiat, of 2 or
lene; if there are no peda, the chroma, moist, should be 1 or less
Anmediately below any surface horizon that hes a value, noiet, of lase
than 5.



Acid and nonacid classes are used only in names of
families of Entisols and Aquepts; they are not used in
sandy, sandy-skeletal, and fragmental families of these
taxa, nor are they used in Sulfaquepts and Fragiaquepts,
or in families that have carbonatic or gypsic mineralogy.
The allic class is used only in names of families of
Oxisols.

Calcareous classes are used if appropriate in the same
taxa as reaction classes and, in addition, are used in
families of Aquolls except for Calciaquolls and for
Aquolls that have an argillic horizon. Caleareous and
reaction classes are not used in soils that have carbonatic
or gypsic mineralogy. A soil that is calcareous is never
acid, Calcareous therefore implies nonacid, and both
names are not used because nonacid would be redundant.
Similarly, noncaleareous would be redundant in acid
families, and it is not used as part of the family name. If
calcareous is used in a family name, calcareous is
considered to be a subclass of mineralogy. It follows the
mineralogy class name and is shown in parenthesis, for
example: fine-loamy, mixed (calcareous), mesic Typic
Haplaquolls.

Soil temperature classes

Soil temperature classes, as named and defined here, are
used as family differentise in all orders. The names are
used as family modifiers unless the name of a higher
taxon carries the same limitation. Thus, frigid is
implied in all boric suborders and cryic great groups, and
is redundant if used in the name of a family.

The Celsius (centigrade) scale is the standard.
Approximate Fahrenheit equivalents are indicated
parenthetically. It is assumed that the temperature is that
of a soil that is not being irrigated.

For soils in which the difference is 5°C (9°F) or more
between mean summer (June, July, and August in the
northern hemisphere) and mean winter (December,
January, and February in the northern hemisphere) soil
temperature at a depth of 50 cm or at a lithic or paralithic
contact, whichever is shallower, the classes, defined in
terms of the mean annual soil temperature, are as
follows:

Frigid.--Below 8°C (47°F).

Mesic.~From 8° to 15°C (47° to 59°F).
Thermic.-From 15° to 22°C (59°t 0 72°F).
Hyperthermic.~22°C (72°F) or higher.

For soils in which the difference is less than 5°C (9°F)
between mean summer and mean winter soil


245

acid-oxalate-extractable iron of more than 1.0 percent;
or

2. Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soi] and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or

3. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 80 percent volcanic glass; or
b. At least 5 percent volcanic glass and acid-
oxelate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of 0.40 percent or more.
; septs
JACC. Other Halaquepts that have chroma of 3 or more
in more than 40 percent of the matrix in one or more
subhorizons between depths of 15 and 76 cm.
Aeric Halaquepts
JACD. Other Halaquepts that have a mollic epipedon.
‘Mollie Halaquepts
JACE. Other Halaquepts.
‘Typic Halaquepts
Haplaquepts
Key to subgroups
JAIA. Haplaquepts that have one or both of the following:
1. Jarosite mottles and a pH between 3.5 and 4.0 (1:1

water, air dried slowly in shade) in some subhorizon
within 50 cm of the soil surface; or

2. Jarosite mottles and a pH of less than 4.0 (1:1 water,
air dried slowly in shade) in some subhorizon between

depths of 50 and 150 cm.
Sulfic Haplaquepts
JAIB. Other Haplaquepts that have a lithic contact within
50 cm of the soil surface.
Lithic Haplaquepts

JAIC. Other Haplaquepts that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm
Jong in some part, and that extend upward to the soil
surface or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.09
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 100 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 100 cm; and


22

cm from the top of the horizon.’ If the soil temperature
regime is frigid or warmer, some part of the spodic
horizon must meet one or more of the following
requirements below a depth of 12.5 cm or below any Ap
horizon that is present. If the soil temperature regime is
cryic or pergelic, there is no requirement for depth. In
addition, the spodic horizon must meet one or more of the
following requirements:

1, Have a subhorizon more than 2.5 cm thick that is
continuously cemented by some combination of organic
matter with iron or aluminum or with both; or

2. Have a particle-size class that is sandy or coarse-
loamy, and sand grains are covered with cracked
coatings or there are distinct dark pellets of coarse-silt
size or larger, or both; or

3. Have one or more subhorizons in which

a. If there is 0.1 percent or more extractable iron, the
ratio of iron plus aluminum (elemental) extractable by
pyrophosphate at pH 10 to percentage of clay is 0.2 or
more (percentage of pyrophosphate-extractable Fe + Al
at pH 10/clay percentage of 0.2 or more) or if there is
less than 0.1 percent extractable iron, the ratio of
aluminum plus carbon extractable by pyrophosphate at
pH 10 to percentage clay is 0.2 or more; and

b. The sum of pyrophosphate-extractable iron plus
aluminum is half or more of the extractable sum of
dithionite-citrate extractable iron plus aluminum
(percentage of pyrophosphate-extractable Fe +
AVpercentage of dithionite-citrate extractable Fe + Al
of 0.5 or more); and

c. The combined index of accumulation of amorphous
material must be 65 or more. The index for each
subhorizon is calculated by subtracting half of the clay
percentage from CEC at pH 8.2 and multiplying the
remainder by the thickness of the subhorizon in
centimeters. The results for all subhorizons are then
added and the total must be 65 or more.

Sulfuric horizon

The sulfuric (L. sulfur) horizon is composed either of
mineral or organic soil materia] that has both a pH less
than 3.5 (1:1 in water) and jarosite mottles (the color of
fresh straw that has a hue of 2.5Y or yellower and chroma
of 6 or more).

A sulfuric horizon forms as a result of artificial drainage
and oxidation of sulfide-rich mineral or organic

© y chin black horizon that has color value of 2 or less may overlie
this horton. :


144

soil surface or of the upper boundary of an organic layer

with andic soil properties, whichever is shallower.
Vitric Hapludands

BGFL, Other Hapludands that have, undried, 1500 kPa
water retention of 70 percent or more throughout a
continuous thickness of 35 cm or more within the upper
100 cm, and have, between 25 and 100 cm, a layer 10 cm
or more thick with more than 3.0 percent organic carbon
and colors of a mollic epipedon throughout, occurring
below a horizon or horizons, 10 cm or more thick, with
color value 1 unit or more higher and organic carbon
content 1 percent or more lower than the underlying

layer.
Hydric Thaptic Hapludands

BGEM. Other Hapludands that have, undried, 1500 kPa
water retention of 70 percent or more throughout a
continuous thickness of 85 cm or more within the upper

100 cm.
Hydric Hapludands

BHFN, Other Hapludands that have a sum of bases of
more than 25.0 cmoi(+) kg"! fine earth throughout some
subhorizon 15 cm or more thick between 25 and 75 cm of
the mineral soil surface or of the upper boundary of an
organic layer with andic soil properties, whichever is
shallower, and have, between 25 and 100 cm, a layer 10
em or more thick with more than 3.0 percent organic
carbon and colors of a mollic epipedon throughout,
occurring below a horizon or horizons, 10 cm or more
thick, with color value 1 unit or more higher and organic
carbon content 1 percent or more lower than the

underlying layer.
Eutric Thaptic Haphulands

BGFO, Other Hapludands that have, between 25 and 100
cm, a layer 10 em or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the

underlying layer.
‘Thaptic Hapludands

BGFP. Other Hapludands that have a sum of bases of
more than 25.0 cmol(+) kg’? fine earth throughout some
subhorizon 15 cm or more thick between 25 and 75 cm of
the mineral soil surface or of the upper boundary of an
organic layer with andic soil properties, whichever is

shallower.
Eutric Hapludands

BGFQ. Other Hapludands that have an oxic horizon with
its upper boundary within 125 cm of the mineral soil
surface or of the upper boundary of an organic layer with
andic aoil properties, whichever is shallower.

Oxic

BGFR. Other Hapludands that have an argillic or
kandic horizon with its upper boundary within 125 cm of
the mineral soil surface or of the upper boundary of an
organic layer with andic soil properties, whichever is
shallower, and base saturation (by sum of cations) of


. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vitrandic Fragiboralfs

IBBC. Other Fragiboralfs that have mottles that have
chroma of 2 or less in the upper 25 em of the argillic
horizon, and are saturated with water at some time within
that depth when the soil temperature at a depth of 50 cm is

5°C or more.
. Aquic Fragiboralfs
IBBD, Other Fragiboralfs.
Typic Fragiboralfs
Glossoboralfs
Key to subgroups

IBFA. Glossoboralfs that have a lithic contact within 60
cm of the soil surface.
Lithic Glossoboralfs

IBFB. Other Glossoboralfs that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2,0 mm fraction,
measured at 33 kPa water retention, of 1.0 gem’ or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic Glossoboralfs

IBFC. Other Glossoboralfs that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more than.
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 5 peroent voleanic glass and acid-oxalate-

extractable aluminum plus 1/2 acid-oxalate-

extractable iron of 0.40 percent or more.
Vitrandic Glossoboralfs

IBFD. Other Glossoboralfs that have mottles that have
chroma of 2 or less in the upper 25 cm of the argillic
horizon if the mottled horizons are saturated with water at
a time when the soil temperature is 5°C or higher,

Aquic Glossoboralfs


322

2. The 0.02 to 2.0 mm fraction constitutes at least 30
Percent of the less than 2.0 mm fraction and contains
either:

a, More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vitrandic Argixerolls

HDEG. Other Argixerolls that have an albic horizon
above the argillic horizon and the mean annual soil

temperature is lower than 10°C.
Boralfic Argixerolls
HDEH. Other Argixerolis that:

1. Have a calcic horizon or soft, powdery secondary
lime within a depth of 160 cm if the weighted average
class of the upper 50 cm of the argillic
andy, 110 cm if it is loamy, and 90 cm if it is
ve a lithic contact that is shallower than

2. Have a mollic epipedon that is 50 cm or more thick
with a texture finer than loamy fine sand.
‘alcic Pachic Argixerolls

HDEI. Other Argixerolls that:

1. Have a mollic epipedon that is 50 cm or more thick
with a texture finer than loamy fine sand; and

2. Have base saturation (by sum of cations) of 75 percent
or leas in some part in the upper 75 cm or above a lithic
or paralithic contact, whichever is shallower.

Pachic Ultic Argixerolls

HDEJ. Other Argixerolls that have a mollic epipedon that
is 50 cm or more thick with a texture finer than loamy

fine sand.
Pachic Argixerolls
HDEK. Other Argixerolls that:

1. Have mottles that have chroma of 2 or less within 75
em of the surface and are continuously saturated with
water within 100 cm of the soil surface for 90 days or
more in most years, unless artificially drained; and

2. Have base saturation (by sum of cations) of 75 percent

or less in some part in the upper 75 cm or above a lithic

or paralithic contact, whichever is shallower.
Aquultic Argixerolls

HDEL, Other Argixerolls that have mottles that have
chroma of 2 or less within 75 cm of the surface and are
continuously saturated with water within 100 cm of the
soil surface for 90 days or more in most years, unless
artificially drained.

Aquic Argixerolls

HDEM. Other Argixerolls that:


285

pumice-like fragments make up more than 66 percent
of these fragments; or

2, The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glaas and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

fitrandic Argiborolls
HEDJ, Other Argiborolls that:

1, Have a mollic epipedon that is 40 cm or more thick,
and its texture is finer than loamy fine sand; and

2. Have a chroma (rubbed), moist, of 1 or less in the
upper 18 cm of the mollic epipedon after mixing, or in
any Ap horizon that is more than 18 cm thick, or the soil
is moist in some or all parts of the moisture control
section at all times in most years.

Pachic Udie Argiborolls

HEDK. Other Argiborolls that have a mollic epipedon that
ia 40 cm or more thick, and its texture is finer than loamy

fine sand.
Pachic Argiborolls
HEDL, Other Argiborolls that have both:

1. Acolor value, dry, of 5 in the upper 18 cm of the mollic
epipedon, after mixing, or in any Ap horizon that is
more than 18 em thick; and

2. A moisture control section that is dry in some part
six-tenths or more of the time that the soil temperature
at a depth of 60 cm is above 5°C in most years.

Aridie Argiborolls

HEDM. Other Argiborolls that have mottles that have
chroma of 2 or less within 100 cm of the surface and, if
undrained, are continuously saturated with water for as
long as 90 days within 100 cm of the gurface.

Aquic Argiborolls

HEDN, Other Argiborolls that:

1, Have tonguing or interfingering of albic materials
in the upper part of the argillic horizon, or skeletans of
clean silt and sand covering more than half the ped
faces in the upper 5 cm or more of the argillic horizon;
an

2. Have a chroma (rubbed), moist, of 1 or less in the
upper 18 cm of the mollic epipedon after mixing, or in
week p horizon that ie tore thon 18 cea nk eel
is moist in some or all parts of the moisture control
section at all times in most years.

Boralfic Udie Argiborolls


173

or more, or is intermediate between 0.6 and one-
seventh percent if the ratio is between 1.0 and 13; and
weighted average percentage of organic carbon in the
surface soil to a depth of 18 cm that is one-fifth or more
higher than the values just stated if there is a
paralithic contact that is shallower than 40 cm but
deeper than 18 cm; and

3, A mean annual soil temperature of 8°C or higher
and an aridic moisture regime that borders on ustic.

Haplustollic Natrargids

FACJ. Other Natrargids that have the following
combination of characteristics:

1. An SAR of less than 13 or less than 15 percent
saturation with sodium throughout the major part of
the natric horizon; and

2. A weighted average percentage of organic carbon in
the upper soil to a depth of 40 em that is 0.6 or more ifthe
weighted average of sand to clay to that depth is 1.0 or
less, or is one-seventh percent or more if the ratio is 13
or more, or is intermediate between 0.6 and one-
seventh percent if the ratio is between 1.0 and 13; and a
weighted average percentage of organic carbon in the
surface soil to a depth of 18 cm that is one-fifth or more
higher than the values just stated if there is a
paralithic contact that is shallower than 40 cm but
deeper than 18 cm; and

3. A mean annual soil temperature lower than 22°C,
mean summer and mean winter soil temperatures at,
a depth of 50 cm that differ by 5°C or more, and an
aridic moisture regime that borders on xeric.
Haploxerollic Natrargids

FACK. Other Natrargids that have an SAR of less than
13 or less than 16 percent saturation with sodium
throughout the major part of the natric horizon.

Haplic Natrargids

FACL. Other Natrargids that have:

1, A weighted average percentage of organic carbon in
the upper soil to a depth of 40 cm that is 0.6 or more ifthe
weighted average of sand to clay to that depth is 1.0 or
less, or is one-seventh percent or more if the ratio is 13
or more, or is intermediate between 0.6 and one-
seventh percent if the ratio is between 1.0 and 13; and a
weighted average percentage of organic carbon in the
surface soil to a depth of 18 cm that is one-fifth or more
higher than the values just stated if there is a
paralithic contact that is shallower than 40 cm but
deeper than 18 em; and

2. A mean annual soil temperature lower than 22°C,
mean summer and mean winter soil temperatures at
a depth of 50 cm that differ by 5°C or more, and an
aridic moisture regime that borders on xeric,
Xerollic Natrargids


43

1. Has a color value, moist, of 5 or more; and
2. Reacts with dilute HC] to evolve CO2.

Marl usually does not change color irreversibly on
drying. A layer of marl contains too little organic matter
to coat the carbonate, even before it has been shrunk by
drying.

THICKNESS OF ORGANIC MATERIALS (CONTROL
SECTION)

For practical reasons an arbitrary control section has
been established for taxonomy of Histosols. It is either 130
(61 in.) or 160 cm (63 in.) thick, depending on the kind
of material, provided that no lithic or paralithic contact,
thick layer of water, or frozen soil occurs within those
limits. The thicker control section is used if the surface
layer to a depth of 60 cm (24 in.) has three-fourths or more
fibers derived from Sphagnum or from Hypnum or other
mosses or has a bulk density less than 0.1. Layers of
water may be thin or thick, from a few centimeters to
many meters. Water is taken as the base of the control
section only if the water extends below a depth of 120 cm or
160 cm, depending on the kind of material above it. A
lithic or a paralithic contact shallower than 130 cm (51
in.) or 160 cm (63 in.), depending on the kind of material
above it, is taken as the base of the control section, or the
base is placed 25 cm (10 in.) below the depth at which the
soil is frozen about 2 months after the summer solstice.
An unconsolidated mineral substratum shallower than
those limits does not change the base of the control section.

The control section has been divided somewhat
arbitrarily into three tiers, the surface, subsurface, and
bottom tiers.

Surface tier

The surface tier is the upper 60 cm (24 in.) if (1) the
material is fibric and three-fourths or more of the fiber
volume is derived from Sphagnum or mosses, or (2) the
material haa a bulk density less than 0.1; otherwise, the
surface tier is the top 30 cm (12 in.) exclusive of loose
surface litter or living mosses.

A surface mineral layer less than 40 cm (16 in.) thick is
present on some organic soils as a result of flooding,
additions by men to increase soil strength or reduce frost
hazard, voleanic eruptions, or other causes. If present, it
is considered a part of the surface tier, even though it may
be more than 30 cm thick, and the depth then is measured
from the top of the mineral layer.


84

1. Bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 gcm' or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent; or

2. Fragments coarser than 2.0 mm constitute more than
85 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragmenta; or

3. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent voleanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Aquandic Umbraqualfs

IAHB. Other Umbraqualfe that have a layer, starting at
the mineral soil surface, that has a sandy particle-size
class and extends to the top of an argillic horizon that is 50

to 100 cm below the soil surface.
Arenic Umbraqualfs

IAHC, Other Umbraqualfs that have a layer, starting at
the mineral soil surface, that has a sandy particle-size
class and extends to the top of an argillic horizon that is
more than 100 em below the soil surface.

Grossarenic Umbraqualfs

IAHD, Other Umbraqualfs that have, in the umbric
epipedon and in horizons above the argillic horizon, soft
discrete nodules 2.5 to 30 cm in diameter that constitute
more than 5 percent of the volume, that are cemented by
iron, and that lie above and in an irregular or broken
upper boundary of the argillic horizon.

Ferrudalfic Umbraqualfs
IAHE. Other Umbraqualfa.
‘Typic Umbraqualls
BORALFS
Key to great groups

TBA. Boralfs that have an argillic horizon with its upper
boundary deeper than 60 cm below the mineral surface,”
that have texture finer than loamy fine sand in some
subhorizon above the argillic horizon, and that have

Tif toere ia « worface mantle that hae mora then 60 percent vitric voleanse ash, cinders, oF
other vitrie pyroclastic materials, the depth to tha argillie horison is meamured from the
base of thia mente rather then frum the warfase the mineral vi.


256

and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

SDFE. Other Eutrochrepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more than
85 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2, The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a, More than 30 percent volcanic glass; or

b. At least 5 nt volcanic glass and acid-oxelate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more,

Vitrandic Eutrochrepts

JDFF. Other Eutrochrepts that:

1, Have mottles that have chroma of 2 or less within 60
cm of the soil surface, and the mottled horizon is
saturated with water at some period when its
temperature is 5°C or more, or the soil has artificial
drainage; and

2. Have a content of organic carbon that decreases
irregularly with depth, or are 125 cm or more deep to a
lithic or a paralithic contact and have more than 0.2
Pereent organic carbon at 125 cm below the soil surface;
an

3. Have slopes of 25 percent or less.
Fiavaquentic Eutrochrepts
JDFG. Other Eutrochrepts that:

1, Have mottles that have chroma of 2 or less within 60
em of the soi] surface, and the mottled horizon is
saturated with water at some period when its
temperature is 5°C or more, or the soil has artificial
drainage; and

2. Do not have carbonates within a depth of 100 cm in all
parts of each pedon.
Aquic Dystric Eutrochrepts
SDFH. Other Eutrochrepts that have mottles that have
chroma of 2 or less within 60 cm of the soil surface, and
the mottled horizon is saturated with water at some period,
when its temperature is 5°C or more, or the soil has
artificial drainage.
Aquic Eutrochrepts
JDFI. Other Eutrochrepts that:

1, Do not have carbonates within a depth of 100 cm in all
parts of each pedon; and


323

1. Have a horizon within 100 cm of the surface that is
more than 15 cm thick and either contains at least 20
percent durinodes or is brittle and has firm consistence
when moist; and

2. Have an aridic moisture regime.
Durargidic Argixerolls
HDEN. Other Argixerolls that have a horizon within 100
cm of the surface that is more than 15 em thick and either
contains at least 20 percent durinodes or is brittle and has
firm consistence when moist.
Duric Argixerolls

HDEO. Other Argixerolls that:
1, Have an aridic moisture regime; and

2. Have a calcic horizon or soft, powdery secondary
lime within a depth of 150 em if the weighted average
class of the upper 50 em of the argillic
horizon is sandy, 110 cm if it is loamy, and 90 om if it is
clayey, or above a lithic contact that is shallower than
depths.

Aridic Calcic Argixerolls
HDEP. Other Argixerolls that have an aridic moisture
regime.

HDEQ. Other Argixerolls that have a calcic horizon or
soft, powdery secondary lime within a depth of 150 em if
the weighted average particle-size class of the upper 50 cm
of the illic horizon is sandy, 110 cm if it is loamy, and
90 cm if it is clayey, or above a lithic contact that is
shallower than these depths.

Calcic Argixerolls
HDER. Other Argixerolls that have base saturation (by
sum of cations) of 75 percent or less in some part in the

upper 75 em or above a lithic or paralithic contact,
whichever is shallower.
Ultic Argixerolls

HDES. Other Acgirarlle that have an albic horizon
above the argillic

Albic Argixerolls
HDET. Other Argixerolls.

Typic Argixerolls
Calcixerolls
Key te subgroups
HDDA. Calcixerolls that have a lithic contact within 50
cm of the soil surface.

Lithie Calcixerolls

HDDB. Other Calcixerolls that have the following
combination of characteristics:

1, Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30cm


286

HEDO. Other Argiborolls that have tonguing or
interfingering of albic materials in the upper part of the
argillic horizon, or skeletans of clean silt and sand
covering more than half the ped faces in the upper 5 cm or
more of the argillic horizon.

Boralfic Argiborolls

HEDP. Other Argiborolls that have a chroma (rubbed),
moist, of 1 or less in the upper 18 cm of the mollic epipedon
after mixing, or in any Ap horizon that is more than 18
em thick, or the soil is moist in some or all parts of the
moisture control section at all times in most years,

‘Udie Argiborolls
HEDQ. Other Argiborolls that have an albic horizon that
lies immediately below the mollic epipedon.

HEDR. Other Argiborolls.

Typic Argiborolis
Calciborolls
Key to subgroups
HEFA, Calciborolls that have a lithic contact within a
depth of 50 cm of the surface.
Lithic Calciborolls

HEFB. Other Calciborolls that have a petrocalcic horizon
that has its upper boundary within 100 cm of the surface.
Petrocalcic Calciborolls

HEFC. Other Calciborolls that have both the following:

1. A color value, dry, of 5 in the upper 18 cm of the mollic
epipedon after mixing, or in any Ap horizon that is
more than 18 cm thick; and

2. A moisture control section that is dry in some part
six-tenths or more of the time in most years that the soil
temperature at a depth of 50 cm is above 5°C.

Aridic Calciborolls

HEFD. Other Calciborolls that have distinct or prominent
mottles that are due to segregation of iron or manganese
within 100 cm of the surface and, if undrained, are
continuously saturated with water for as long as 90 days
within 100 cm of the surface.

Aquic Calciborolls
HEFE. Other Calciborolls.

‘Typic Caleiborolls
Cryoborolls
Key to subgroups

HEBA. Cryoborolls that have the following combination
of characteristics:

1, Have an argillic horizon; and


77

organic carbon if the ratio of sand to clay ia between
1.0 and 13; and a weighted average percentage of
organic carbon in the surface soil to a depth of 18 cm
that is one-fifth or more higher than the values just
stated if there is a petrocalcic horizon whose upper
boundary is shallower than 40 cm but deeper than 18
cm; and

2. A mean annual soil temperature lower than 22°C,
mean summer and mean winter soil temperatures at
a depth of 50 cm that differ by 5°C or more, and an
aridic moisture regime that borders on a xeric

regime.
Xerollic Paleargids
FADJ. Other Paleargids that have:

1. A weighted average percentage of organic carbon in
the upper soil to a depth of 40 cm of 0.6 percent or more
if the weighted average ratio of sand to clay above this
depth is 1.0 or less, or one-seventh percent or less if the
ratio is 13 or more, or an intermediate percentage of
organic carbon if the ratio of sand to clay is between
1.0 and 13; and a weighted average percentage of
organic carbon in the surface soil to a depth of 18 cm
that is one-fifth or more higher than the values just
stated if there is a petrocalcic horizon whose upper
boundary is shallower than 40 cm but deeper than 18
cm; and

2. An aridic moisture regime that borders on an ustic
regime.
Ustollic Paleargids
FADK, Other Paleargids that:

1. Are dry in all parts of the moisture contro] section
three-fourths or less of the time (cumulative) that the
soil temperature at a depth of §0 cm is 5°C or higher;
and

2. Have a mean annual soil temperature lower than
22°C, mean summer and mean winter soi)
temperatures at a depth of 50 cm that differ by 6°C or
more; and an aridic moisture regime that borders on a

xeric regime.
Xeralfic Paleargids
FADLE, Other Paleargids that:
1, Are dry in all parts of the moisture control section
three-fourths or lesa of the time (cumulative) that the
soil temperature at a depth of 50 cm is 5°C or higher;

and

2, A mean annual soil temperature that is 8°C or
higher and an aridic moisture regime that borders on

‘an ustic regime.
Ustalfic Paleargids

FADM. Other Paleargids.
‘Typic Paleargids


213
KEBH, Other Torriorthents that:

1, Are saturated with water within 150 cm of the
surface at any time of year in most years; and

2, Have a horizon within 100 cm of the surface that is
more than 15 em thick and either contains 20 percent
or more durinodes or ia brittle and has firm
consistence when moist.

‘Aquic Durorthidic Torriorthents

KEBI. Other Torriorthents that are saturated with water
within 150 cm of the surface at any time of year in most

years.
Aquic Torriorthents
KEBJ. Other Torriorthents that:

1, Have a horizon within 100 cm of the surface that is
more than 15 cm thick and either contains 20 percent
or more durinodes or is brittle and has firm
consistence when moist; and

2. Are dry in all parts of the moisture control section

leas than three-fourths of the time (cumulative) that the

soil temperature at a depth of 50 cm is 5°C or higher

and they have a thermic, mesic, or frigid soil

temperature regime and have a torric moisture

regime that borders on a xeric regime.
Durorthidic Xeric Torriorthents

KEBK. Other Torriorthents that have a horizon within
100 cm of the surface that is more than 15 cm thick and
either contains 20 percent or more durinodes or is brittle
and has firm consistence when moist.

Torriorthents

KEBL. Other Torriorthents that are dry in all parts of the
moisture control section less than three-fourths of the
time (cumulative) that the soil tem) re at a depth of
50 cm is 5°C or higher and they either (1) have a

per or an iso soil temperature regime or (2)
have a thermic, mesic, or a frigid soil temperature
regime and have an aridic moisture regime that borders

on an ustic regime.
‘Ustic Torriorthents

KEBM. Other Torriorthents that are dry in all parts of
the aoe ce tat hea than three-fourths ofthe
ime (cumulative) that the soil temperature at a depth of
50 cm is 5°C or higher and they have a thermic, mesic, or
frigid soil temperature regime and a torric moisture
regime that borders on a xeric regime.
Xeric Torriorthents

KEBN. Other Torriorthents.
Typic Torriorthents


365
Haplohumods

Key to subgroups
CCEA. Haplohumods that have a lithic contact within 50
cm of the soil surface.

Lithic Haplohumods
CCEB. Other Haplohumods that:

1, Have a layer starting at the mineral soil surface
that has a sandy particle-size class throu; it and
extends to at least the upper boundary of the spodic
horizon, and the upper boundary of the spodic horizon
is between 75 and 125 cm below the soil surface; and

2. Have an argillic or kandic horizon below the spodic
horizon.
Arenic Ultic Haplohumods

CCEC. Other Haplohumods that have a layer starting at
the mineral soil surface that has a sandy particle-size
class throughout and extends to at least the upper
boundary of the spodic horizon, and the upper boundary
of the spodic horizon is between 75 and 125 cm below the

soil surface.
Arenic Haplohumods
CCED. Other Haplohumods that:

1. Have a layer starting at the mineral soil surface
that has a sandy particle-size class throughout and
extends to at least the upper boundary of the spodic
horizon, and the upper boundary of the spodic horizon
is between 125 and 200 cm below the soil surface; and

2, Have both:

a. A spodic horizon that has a weighted average of
less than 0.6 percent organic carbon in the matrix of
the upper 30 cm of the spodic horizon or below any Ap
horizon; and

b. Any black upper subhorizon of the spodic horizon
that has 3 percent or more organic carbon in the
upper 2 cm is present in 90 percent or less of the area

of each pedon.
Grossarenic Entic Haplohumods

CCEE. Other Haplohumods that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the leas than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent,

Andic

CCEF. Other Haplohumods that have the following
combination of characteristics:

1. A spodic horizon that has a weighted average of less
than 0.6 percent organic carbon in the matrix of the


203
Udarents

Key to subgroups
KBDA. Udarents that have fragments of an argillic
horizon that has base saturation (by sum of cations) that

is 85 percent or more within the upper 100 cm of the soil.
Alfic Udarents

KBDB. Other Udarents that have fragments of an
argillic horizon within the upper 100 cm of the soil.

KBDC. Other Udarents that have fragments of a mollic
cpipedon within the upper 100 cm of the soil.
‘Mollic Udarents

KBDC. Other Udarents.
Udarents

Ustarents

Ustarents are the Arents that have an ustic soil moisture
regime.

Xerarents

‘Key to subgroups
KBBA. Xerarents that have fragments of an argillic
horizon that has base saturation (by sum of cations) that

is 35 percent or more within the upper 100 cm of the soil.
Alfic Xerarents

KBBB. Other Xerarents,
Xerarents

FLUVENTS
Key to great groups
KDA. Fluvents that have a cryic soil temperature
regime.
Cryoftuventa, p. 204

KDB. Other Fluvents that have a xeric moisture regime.
‘Xerofluvents, p. 208

KDC. Other Fluvents that have an ustic moisture
regime.
Ustifluvents, p. 208

KDD. Other Fluvents that have a torric moisture regime.
Torrifluvents, p. 204

KDE. Other Fluvents that have an isomesic, isothermic,
or isohyperthermic temperature regime.
‘Tropofluvents, p. 207

KDF. Other Fluvents.
Udifluvents, p. 207


367
ORTHODS
Key to great groups
CDA. Orthods that have a placic horizon in the spodic
horizon.
Placorthods, p. 371
CDB. Other Orthods that have a fragipan below the spodic
horizon.
Fragiorthods, p. 368
CDC. Other Orthods that have a cryic or pergelic
temperature regime.
Cryorthods, p. 367

CDD, Other Orthods that have an isomesic or warmer iso
temperature regime.

‘Troparthods, p. 371
CDE. Other Orthods.

Haplorthods, p. 369
Cryorthods
Key to subgroups

CDCA. Cryorthods that:

1. Have more than 6 percent organic carbon in the
upper 10 cm of the spodic horizon; and

2. Have a lithic contact within 50 em of the soil
surface.
CDCB. Other Cryorthods that have a lithic contact within
50 em of the soil surface.
Lithic Cryorthods
CDCC. Other Cryorthods that have a mean annual soil
temperature of 0°C or less.
Pergelic Cryorthods
CDCD. Other Cryorthods that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 gcm* or less

and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

‘Andic Cryorthods

CDCE. Other Cryorthods that have an argillic or kandic
horizon below the spodic horizon.

Baralfic Cryorthods

CDCE. Other Cryorthods that do not have a cemented or

indurated spodic horizon and have less than 1.2 percent

organic carbon in the upper 10 cm of the spodic horizon.
Entic Cryorthods


61

iron in some places is present in large cemented
aggregates. In others it may be mostly dispersed and soft.
The colors normally are shades of dark reddish brown,
commonly mixed with black, and the colors change little
on drying. The content of iron oxide ranges from 10
percent to more than 20 percent.

Ferrihumic material either is saturated with water for
long periods (more than 6 months) or is in an artificially
drained soil. The content of free iron oxide should exceed
10 percent (7 percent Fe), but the horizon may be either
organic or mineral provided there is at least 1 percent
organic matter, The materials should have more than 2
percent (by weight) concretions of iron, which may range
in size from fine (less than 5 mm) to 1 m or more in the
largest lateral dimension. Colors should be dark reddish
brown or reddish brown, or should be close to those colors.
‘The presence of ferrihumic material within the control
section is one of the family differentiae.

If ferrihumic is used as a modifier in the technical
family name, no other mineralogy modifier is used
because the presence of the iron is considered to be, by far,
the most important characteristic.

Modifiers applied only to terric subgroups.-The
mineralogy modifiers used for mineral soils are applied
to the mineral parts of the soil for which a particle-size
modifier has been used if the mineralogy is not
ferrihumic.

Modifiers applied to limnic subgroups.—If limnic
materials are present in the control section, if they are 5
cm or more thick, and if the materials do not have
ferrihumic mineralogy, the following modifiers are
used,
Coprogenous. Limnic materials that consist of
coprogenous earth are present.

Diatomaceous. Limnic materials that consist of
diatomaceous earth are present.

Marly. Limnic materials that consist of marl are
present.

Reaction classes

Modifiers to indicate reaction are used in all subgroups,
The meanings follow.

Euic.--The pH of undried samples is 4.5 or more (0.01 M
CaCl,) in at least some part of the organic materials in the
control section.

Dysic.-The pH is less than 4.5 (in 0.01 M CaCl) in all
parts of the organic materials in the control section.


277

HE, Other Mollisols that have a frigid, cryic, or pergelic
temperature regime.
Borolls, p. 282

HF, Other Mollisols that have an ustic or an aridic
moisture regime that borders on ustic.

Ustolls, p. 302
HG. Other Mollisols.

Udolls, p. 297
ALBOLLS
Key to great groups

HAA. Albolls that have a natric horizon,
Natralbolls, p. 278

HAB. Other Albolls.
Argialbolls, p. 277

Argialbolls
Key to subgroups
HABA. Argialbolls that:

1, Do not have an abrupt textural change from the albic
to the argillic horizon; and

2, When not irrigated, are dry in all parts of the
moisture control section for as long as 45 consecutive
days during the 120 days following the summer solstice
in more than 6 out of 10 years.
Argiaquic Xeric Argialbolls
HABB. Other Argialbolls that do not have an abrupt

textural change from the albic to the argillic horizon.
Argiaquic Argialbolls

HABC. Other Argialbolls that, when not irrigated, are
dry in all parts of the moisture control section for as long
as 45 consecutive days during the 120 days following the
summer solstice in more than 6 out of 10 years.

Xeric Argialbolls

HABD. Other Argialbolls that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1. Bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g em’ or less
and acid-oxalate-extractable aluminum plus /2 acid-
oxalate-extractable iron of more than 1.0 percent; or

2. Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

3, The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:


86
albic materials tonguing or interfingering in the

argillic horizon.
Paleboralfs, p.90

IBB. Other Boralfs that have a fragipan.
Fragiboralfs, p. 88

IBC, Other Boralfs that have a natric horizon.
Natriboralfs, p. 90

IBD. Other Boralfe that have a eryic temperature regime.
Cryoboralfs, p. 85

IBE. Other Boralfs that have base saturation (by sum of
cations) of 60 percent or more in all subhorizons of the
argillic horizon and are dry in some horizon at some

time im most years.
Eutroboralfa, p. 86

IBF. Other Boralfs that either are never dry in any
horizon in most years or have base saturation (by sum of
cations) of less than 60 percent in some subhorizon of the

argillic horizon.
Glossoboralfs, p. 89
Cryoboralfs

Key to subgroups
IBDA. Cryoboralfs that:

1. Have a lithic contact within 50 cm of the surface; and

2. Have an Ap horizon that has a color value, moist, of 3
or less, or the upper soil, to a depth of 15 cm after
mixing, has a moist color value of 3 or less,

Lithic Mollic Cryoboralfs
IBDB. Other Cryoboralfs that have a lithic contact within
50 cm of the surface.
Lithic Cryoboralfs

IBDC, Other Cryoboralfs that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm” or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic Cryoboralfs

IBDD, Other Cryoboralfs that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and


292

than 18 cm thick, or the soil is moist in some or all parts
of the moisture contro) section at all times in most

years.
Cumulic Udie Haploborolls
HEGI. Other Haploborolls that:

1. Have a mollic epipedon 40 cm or more thick, and the
epipedon does not have a sandy particle-size class in
the major part, and there is no paralithic contact or a
sandy contrasting layer between depths of 40 and 50
cm; and

2, Have an irregular decrease in organic carbon
content with increasing depth, or have an organic
carbon content of more than 0,3 percent at a depth of 125
cm below the surface; and

3. Have a slope of less than 25 percent and a concave
shape.
Cumulic Haploborells
HEGJ, Other Haploborolls that:

1. Have a mollic epipedon 40 cm or more thick, and the
epipedon does not have a sandy particle-size class in
the major part, and there is no paralithic contact or a
sandy: contrasting layer between depths of 40 and 50
em; an

2. Have a chroma, moist, after rubbing of 1 or less in the
upper part of the mollic epipedon after it has been mixed
to a depth of 18, cm or in any Ap horizon that is more
than 18 cm thick, or the soil is moist in some or all parts
of the moisture control section at all times in most

years,
Pachic Udic Haploborolls

HEGK. Other Haploborolls that have a mollic epipedon 40
cm or more thick, and the epipedon does not have a sandy
particle-size class in the major part, and there is no
paralithic contact or a sandy contrasting layer between

depths of 40 and 50 em.
Pachic Haploborolls
HEGL, Other Haploborolls that:

1. Have an irregular decrease in organic carbon
content with increasing depth, or have an organic
carbon content of more than 0.3 percent at a depth of 126
cm below the aurface; and

2. Have mottles that have chroma of 2 or less within 100
em of the surface and, if undrained, are continuously
saturated with water in the mottled horizon for 90 days
or more in most years; and

3. Have a slope of less than 25 percent.
Fluvaquentic Haploborolls

HEGM. Other Haploborolls that have mottles that have
chroma of 2 or less within 100 cm of the surface and, if

i

oat Parle tai


324

long in some part, and that extend upward to the surface
or to the base of an Ap horizon; and

2. A coefficient of near extensibility (COLE) of 0.05 or
more in a horizon or horizons at least 50 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 160 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 150 cm; and

3. More than 35 percent clay in horizons that have a
total thickness of more than 50 cm.
Vertic Calcixerolls

HDDC. Other Calcixerolls that have a mollic epipedon
that is 50 cm or more thick and its texture is finer than
loamy fine sand.

Pachic Caleixerolls

HDDD. Other Calcixerolls that have mottles within 75 cm
of the surface that are due to segregation of iron or
manganese, and the soils are continuously saturated with
water within 100 cm of the soil surface for 90 days or more
in most years, unless artificially drained.

Aquic Caleixerolls
HDDE. Other Calcixerolla that have an aridie moisture
regime.

Aridic Caleixerolls

HDDF. Other Calcixerolls that have a mollic epipedon
that below any Ap horizon has 50 percent or more by
volume wormholes, wormcasts, or filled animal

burrows.
Vermic Caleixerolls
HDDG. Other Calcizerolls.
Typic Calcixerolls
Durixerolls
Key to subgroups

HDAA. Durixerolls that:
1. Have an aridic moisture regime; and

2. Have, throughout a cumulative thickness of 18 em or
more and within a depth of 75 cm, one or more of the
following:

a. Fragments coarser than 2.0 mm constitute more
than 35 pereent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or
b. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

(1) More than 30 percent volcanic glass; or


a61

CAFJ. Other Haplaquods that have 5 percent or more by
volume of iron-cemented nodules 2.5 to 30 em in
diameter throughout the spodic horizon.

Sideric Haplaquods
CAFK. Other Haplaquods that have an argillic or
kandic horizon underlying the spodic horizon and have
either base saturation of 35 percent or more (by sum of
cations) in some part of the argillic or kandic horizon or
have a mean annual soil temperature lower than 8°C.

Alfic Ha)

CAFL, Other Haplaquods that have an argillic or
kandic horizon underlying the spodic horizon.

Ultic Haplaquods
CAFM. Other Haplaquods that:

1, Have an ochric epipedon, and the surface layer
would not meet the requirements for an umbric
epipedon if it were plowed to a depth of 25 cm; and

2, Have a spodic horizon that has a weighted average
of less than 0.6 percent organic carbon in the matrix of
the upper 80 cm of the spodic horizon, and the upper
subhorizon of the spodic horizon either

a. Has less than 2.3 percent organic carbon in the
‘upper 2 cm; or

b. The subhorizon with 2.3 percent or more organic
carbon is present in 90 percent or less of each pedon.
Entic Haplaquods

CAFN. Other Haplaquods that do not have an umbric
epipedon or one that would meet the requirements for an
umbric epipedon if it were plowed to a depth of 25 to 30 cm.

‘Acric Haplaquods
CAFO. Other Haplaquods.

Typie Haplaquods
Placaquods
Key to subgroups
CADA. All Placaquods (provisional).

‘Typic Placaquods
Sideraquods
Key to subgroups

CAGA. Sideraquods that have a histic epipedon.
Histic Si

CAGB. Other Sideraquods that have an argillic or
kandic horizon and have base saturation of 35 pereent or
more (by sum of cations) in some part of the argillic or

kandic horizon or have a mean annual soil temperature

lower than 8°C.
Alfic Sideraquods


120

IDE. Other Xeralfs that have an argillic horizon that, in
all parts, has a color hue redder than 5YR and a value,
moist, 3 or less and a value, dry, no more than one unit
higher than the value, moist.

Rhodoxeralfs, p. 127

IDF. Other Xeralfs that have either:

1, A petrocalcic horizon whose upper boundary is within
150 cm of the soil surface; or

2. Do not have a lithic or paralithic contact within 150
em of the soil surface; and the argillic horizon

a. Has a vertical clay distribution such that the
percentage of clay does not decrease from the
maximum by as much as 20 percent throughout a
depth of 150 cm from the soil surface, or the horizon in
which the clay decreases either has greater than 5
percent plinthite by volume or has skeletans or other
evidences of clay eluviation; and

b. Has one or both of the following:

(1) A hue redder than 10YR and chroma, moist or
dry, of more than 4 in the matrix of at least the
lower part of the argillic horizon; or

(2) Common coarse mottles that have a hue of
7.5YR or redder or chroma, moist or dry, greater
than 5, or both, in at least the lower part of the
argillic horizon; or

3. Have an argillic horizon that has a clayey particle-
size class in the upper part and an increase of at least 20
percent clay (absolute) within a vertical distance of 7.5
cm or of at least 16 percent clay (absolute) within a
vertical distance of 2.8 cm at the upper boundary; and
there is no lithic or paralithic contact within 50 cm of
the surface of the soil.

Palexeralfs, p. 125
IDG. Other Xeralfs.
Haploxeralfs, p. 122
Durixeralfs
Key to subgroups
IDAA. Durixeralfs that have a natrie horizon.
Natric Durixeralfs

IDAB. Other Durixeralfs that have mottles in the argillic
horizon that have chroma of 2 or less.
Aquic Durixeralfs

IDAC, Other Durixeralfs that:


196

KC. Other Entisols that have below the Ap horizon or
below a depth of 26 cm, whichever is deeper, less than 35
percent (by volume) of rock fragments and that have
texture of loamy fine sand or coarser in all subhorizons*
either to a depth of 100 cm or to a lithic, paralithic, or
petroferric contact, whichever is shallower.
‘Psammenta, p. 217

KD. Other Entisols that do not have a lithic or paralithic
contact within 26 cm of the soil surface and that have
slopes of leas than 25 percent and organic-carbon content
that decreases irregularly with depth or remains above a
level of 0.2 percent to a depth of 125 cm, and the mean
annual soil temperature is higher than 0°C, (Strata of
sand or loamy sand may have less organic carbon if
finer sediments at a depth of 125 cm or below have 0.2
percent organic carbon or more).

Fivventa, p. 203
KE. Other Entisols.

Orthents, p. 209
AQUENTS
Key to great groups

KAA, Aquents that have sulfidic materials within 50 cm
of the mineral soil surface.
Sulfaquents, p. 202

KAB, Other Aquents that have ann value of more than
0.7 and that have at least 8 percent clay in all
subhorizons between a depth of 20 and 50 cm and that
have a mean annual soil temperature higher than 0°C.
Hydraquents, p. 201

KAC. Other Aquents that have a cryic but not a pergelic?
soil temperature regime.
(Cryaquents, p. 197

KAD. Other Aquents that have an organic-carbon
content? that decreases irregularly with depth or that
remains above 0.2 percent to a depth of 125 cm; and that
have texture finer than loamy fine sand in some or all
subhorizons between the Ap horizon or a depth of 25 cm,
whichever is deeper, and 100 em or a lithic or paralithic
contact, whichever is shallower. Thin strata of sand
may have less organic carbon if the finer sediments at a
depth of 125 cm or below have 0.2 percent organic carbon.

or more.
Fluvaquents, p, 197

a
Lanellas that are less than 1 om thick ar that are too fav to mest the

requiresente for an argillic horiton are permitted to have texture of

gandy loam. See the definition of an argillic horizon (Ch. 1).

2

Soils that othervise could be Aquente are grouped with Aquepte if
Ehere Ls permafrost.
3

‘The carbon should be of Bolocene age. It ia not the intent to include
fossil carbon from transported frequents of bedrock or from Duriad
Flalstocane deporite, ‘The mean residence tine of the carbon should be
ete than 11,000 yours BAP,


395

2, Have 6 percent or more plinthite (by volume) in one
or more subhorizons within 160 cm of the soil surface.
Arenic Plintbic Paleudults

GCEG. Other Paleudults that:

1, Have a layer, atarting at the mineral soil surface,

that has a sandy particle-size class and extends to the
top of an argillic horizon that is 60 to 100 cm below the
soil surface; and

2. Have an argillic horizon that has a color value,
moist, of 3 or less and do not have mottles of 3 or more
within 100 cm of the top of the argillic horizon, and
have a color value, dry, 1 unit or less higher than the
value, moist, throughaut the soil within that depth.
Arenic Rhodic Paleudults

GCEH. Other Paleudults that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic horizon that is 50 to
100 cm below the soil surface.

Arenic Paleudults

GCEI. Other Paleudults that:

1. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic horizon that is more 100 cm below the
soil surface; and

2. Have 5 percent or more plinthite (by volume) in one
or more subhorizons within 150 cm of the soil surface.
Grossarenic Palendults

GCEJ. Other Paleudults that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic horizon that is more
than 100 cm below the soil surface,

Grossarenic Paleudults

GCEK. Other Paleudults that:

1. Have 6 percent or more plinthite (by volume) in one
or more subhorizons within 160 cm of the soil surface;
and

2. Have the following combination of characteristics
in the upper 75 cm of the soil if the chroma in all or part
of the upper 75 cm ia not controlled by uncoated sand
grain; or if the chroma throughout the upper 75 cm is
controlled by uncoated sand grains, have the
following combination of characteristics throughout
the upper 12.5 cm of the argillic horizon:

a. Mottles that have a color value, moist, of 4 or more
and chroma, moist, of 2 or leas and mottles of higher
chroma that are due to segregation of iron; and

)b, Saturation with water in the mottled zone at some

time of year when the soil temperature in that zone

is 5°C or higher, or they are artificially drained.
Plinthaquic Paleudults


123
IDGB. Other Haploxeralfs that:

1. Have a lithic contact within 50 cm of the soil surface;
and

2. Have an argillic horizon that is discontinuous
horizontally throughout the area of each pedon.
Lithic Ruptic-Xerochreptic Haploxeralfs

IDGC. Other Haploxeralfs that have a lithic contact
within 50 cm of the soil surface.
Lithic Haploxeralfs

IDGD. Other Haploxeralfs that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 60 cm, that are at least 30 cm
Jong in some part, and that extend upward to the surface
or to the base of an Ap horizon if the soil is not irrigated;
and

2. A coefficient of linear extensibility (COLE) of 0.05 or
more in a horizon or horizons at least 50 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 150 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 150 em; and

3. More than 36 percent clay in horizons that total more
than 60 cm in thickness.
Vertic Haploxeralfs

IDGE. Other Haploxeralfs that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm frgetion,
measured at 33 kPa water retention, of 1.0 g cm” or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic Haploxeralfs

IDGF, Other Haploxeralfs that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more than
85 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or


983

GBDE. Other Kanhaplohumults that have, in the upper 75
em of the soil, a hue of 10YR or yellower in one or more
subhorizons that have a color value, moist, of 4 or more
and mottles with chroma of 3 or more and the hue
‘becomes redder with depth within 100 cm of the soil

surface.
Epiequic Kanhaplohumults

GBDF. Other Kanhaplohumults that have an ustic soil
moisture regime.

‘Ustic Kanhaplohumults
GBDG. Other Kanhaplohumults that have a xeric soil
moisture regime.

Xeric Kanhaplohumults
GBDH. Other Kanhaplohumults that have an anthropic

in.

opipedo Anthropic Kanhaplohumults
GBDI. Other Kanhaplohumults.

‘Typic Kanhaplohumults
Palehumults
Key to subgroups

GBEA. Other Palchumults that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cmTM or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic Palehumults

GBEB. Palchumults that have the following combination
of characteristics in the upper 25 cm or more of the
argillic horizon:

1. Mottles that have a color value, moist, of 4 or more,
and chroma, moist, of 2 of less accompanied by mottles
of higher chroma that are due to segregation of iron;
and

2. Saturation with water in the mottled zone at some
time of year when the soil temperature in that zone is
5°C or more or there is artificial drainage.

Aquie Palehumults

GBEC. Other Palchumults that have 5 pereent or more
plinthite (by volume) in one or more subhorizons within
150 cm of the soil surface.

Plinthic Palehumults
GBED. Other Palehumults that have an ustic moisture
regime.
Ustic Palehumults

GBEP. Other Palehumults that have a xeric moisture
regime.
Xeric Palehumults


404

has skeletans on ped faces or has 5 percent or more
plinthite by volume.

Palexerults, p. 405
GEB, Other Xerults.
Haploxerults, p. 404
Haploxerults
Key to subgroups

GEBA. Haploxerults that:

1. Have a lithic contact within 60 cm of the mineral
soil surface; and

2. Have a discontinuous argillic horizon in each
pedon that ia interrupted by ledges of bedrock.
RupticLithic-Xerochreptic

GEBB. Other Haploxerulte that have a lithic contact
within 50 cm of the mineral soil surface.

Lithic Haploxerults

GEBC. Other Haploxerults thet have the following
combination of characteristics in the upper 25 cm or
more of the argillic horizon:

1. Mottles that have a color value, moist, or 4 or more
and chroma, moist, of 2 or less and also mottles of
higher chroma that are due to segregation of iron; and

2. Saturation with water in the mottled zone at some
time of year when the soil temperature in that zone is
58°C or higher, or the soil is artificially drained.

Aquic Haploxerults

GEBD. Other Haploxerults that have texture that is
loamy fine sand or coarser in all parts of the argillic
horizon, or have an argillic horizon that has lamellae in

the upper 25 cm.
Psammentic Haploxerults

GEBE, Other Haploxerults that have a layer, starting at
the mineral soi] surface, that has a sandy particle-size
class and extends to the top of an argillic horizon that is
50 to 100 cm below the soil surface.

Arenic Haploxerults

GEBF, Other Haploxerults that have a layer, starting at
the mineral soi] surface, that has a sandy particle-size
class and extends to the top of an lic horizon that is
more than 100 cm below the soil surface.

Haploxerults

GEBG. Other Haploxerults that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the leas than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm” or leas
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic Haploxerults


30

and August, and winter means December, January, and
February. A soil or a horizon is considered to be saturated
with water when water stands in an unlined borehole
close enough to the soil surface orto the horizon in
question that the capillary fringe? reaches the surface or
the top of the horizon.

Soil 1 sesti

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 (1 in.) of
water within 24 hours. The lower boundary is the depth to
which a dry soil will be moistened by 7.5 cm (3 in.) of
water within 48 hours. These depths are exclusive of 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 lithic, petroferric,
or paralithic contact or to a petrocalcic horizon or a
duripan, the upper boundary of the rock or of the cemented
horizon is the lower boundary of the soil moisture control
section. If 2.5 cm of water moistens the soil to one of these
contacts or horizons, the soil moisture control section is
the lithic contact itself, the paralithic contact, or the upper
boundary of the cemented horizon. The control section of
the latter soil is moist if the upper boundary of the rock or
the cemented horizon has a thin film of water. If the upper
boundary is dry, the control section is dry.

As a rough guide to the limits, the soil moisture control
section lies approximately between 10 and 30 cm (4 and 12
in.) if the particle-size class is fine-loamy, coarse-silty,
fine-silty, or clayey. The control section extends
approximately from a depth of 20 em to a depth of 60 cm( 8
to 24 in.) if the particle-size class is coarse-loamy, and
from 30 to 90 cm (12 to 36 in.) if the particle-size class is
sandy,

Classes of soil moisture regimes

The moisture regimes are defined in terms of the ground-
water level and in terms of the presence or absence of
water held at a tension less than 1500 kPa in the moisture
control section by periods of the year. It is assumed in the
definitions that the soil supports whatever vegetation it is
capable of supporting. In other words, it is in crops, grass,
or native vegetation; it is not being fallowed to increase
the amount of stored moisture, nor is it being irrigated by
man. These cultural practices affect the soil moisture
condition as long as they are continued.

" qha capillary fringe 18 the zone just sbove the water table (sere
gauge pressure) Chat remains aleost saturated (Soil Sei. Soc. Amer,
Gloasary, 1965, p. 332).


386

3. Have 6 percent or more plinthite (by volume) in one
or more subhorizons within 150 cm of the soil surface.
Plinthaquic

GCBC. Other Fragiudults that:
1. Meet either of the following:

a. Do not have an argillic or kandic horizon above
the fragipan that has some clay skins on both
vertical and horizontal surfaces of some structural
aggregates; or

b, Have an intervening horizon (one or more)
between the argillic or kandic horizon and the
fragipan that has dominant chroma of 8 or less and
that has as much as 3 percent less clay (absolute)
than both the overlying argillic or kandie horizon
and the underlying fragipan; and

2. Have mottles that have chroma of 2 or less within 40

em of the soil surface.
Glossaquic Fragindults

GCBD. Other Fragiudults that have mottles that have

chroma of 2 or less above the top of the fragipan and

within the upper 26 cm of the argillic or kandic horizon.
‘Aquic

GCBE. Other Fragiudults that have 5 percent or more
plinthite (by volume) in one or more subhorizons within

150 cm of the soil surface.
Plinthic Fragiudults

GCBF. Other Fragiudults that meet either of the
following:

1. Do not have an argillic or kandic horizon above the
fragipan that has some clay skins on both vertical and
horizontal surfaces of some structural aggregates; or

2, Have an intervening horizon (one or more) between
the argillic or kandic horizon and the fragipan that
has dominant chroma of 3 or less and that has as much
as 3 percent less clay (absolute) than both the overlying
argillic or kandic horizon and the underlying

fragipan.
Glossic Fragiudults

GCBG. Other Fragiudults that have an Ap horizon that
has a color value, moist, of 3 or less and has a value, dry,
of 5 or less when crushed and smoothed (smoothed with a
knife to eliminate shadows), or the A horizon is 15 cm or
more thick and its color value, moist, is 3 or less.

GCBH. Other Fragiudults.
‘Typle Fragivdolts


997

DADC. Other Haplaquox that have mottles with chroma of
more than 2 in 50 percent or more of the horizon
immediately below the epipedon,

Aerie Haplaquox

DADD. Other Haplaquox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of

the surface litter.
Humic Haplaquox
DADE. Other Haplaquox.
Typic Haplaquox
Plinthaquox
Key to subgroups

DABA. Plinthaquox that have mottles with chroma of
more than 2 in 50 percent or more of the horizon

immediately below the epipedon.

Aeric Plinthaquox
DABB. Other Plinthaquox.

‘Typic Plinthaquox
PEROX
Key to great groups
DDA. Perox that have a sombric horizon within 150 cm of
the soil surface.

Sombriperox, p. 343

DDB. Other Perox that have both an apparent ECEC of less
than 1.60 cmol(+) per kg clay and a pH value (IN KC}) of
5,0 or more in some part of the oxic or kandic horizon
within a depth of 150 cm of the soil surface.

Acroperox, p. 337

DDC. Other Perox that have more than 36 percent base
saturation (NH,OAc) in all parts within a depth of 125 cm

of the soil surface.
‘Butroperus, p. 339

DDD. Other Perox that have more than 40 percent clay in
the surface 18 cm after mixing, and have the upper
boundary of a kandic horizon within a depth of 150 cm of
the soil surface,

Kandiperox, p. 341
DDE. Other Perox.

Haploperox, p. 340
Acroperox
Key to subgroups

DDBA. Acroperox that have mottles of 4 or more value
moist and 2 or less chroma within a depth of 125 cm of the
soi] surface and a petroferric contact within 125 cm of the

soil surface.
Aquie Petroferric Acroperax


156
BDCK. Other Haploxerands that have an umbric

epipedon.
Umbric Haploxerands
BDCL. Other Haploxerands.
Typic Haploxerands
Melanoxerands
Key to subgroups

BDBA. Melanoxerands that have both more than 6.0
percent organic carbon and colors of the mollic epipedon
throughout at least 50 em of the upper 60 cm, excluding any
overlying layers that do not have andic soil properties.
Pachic Melanoxerands

BDBB. Other Melanoxerands.
‘Typic Melanoxerands

Vitrixerands

Key to subgroups
BDAA, Vitrixerands that have a lithic contact within 50
cm of the soil surface.

Lithic Vitrixerands

BDAB. Other Vitrixerands that have, in some subhorizon
between 50 and 100 cm:

1, Two percent or more redox segregations; or

2, Dominant chromas, moist, of 2 or less on faces of
peds, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or

3, Sufficient active ferrous iron to give a positive
reaction to a,a'-dipyridyl at some time of the year when

not being irrigated. Vitek

BDAC. Other Vitrixerands that have, between 25 and 100
cm, a layer 10 em or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the

underlying layer.
‘Thaptic Vitrixerands
BDAD. Other Vitrixerands that have a spodic horizon,
and an associated eluvial horizon with its upper boundary
within 125 cm of the mineral soil surface.
Spodic Vitrixerands
BDAE. Other Vitrixerands that have

1. A mollic epipedon; and

2, An argillic or kandic horizon with its upper
boundary within 125 cm of the mineral soil surface.
Argixerollic Vitrixerands


377
Kanhaplaquults

Key to subgroups

GABA. Kanhaplaquults that have, throughout a

cumulative thickness of 18 cm or more and within a depth

of 75 cm, bulk density of the less than 2.0 mm fraction,

measured at 33 kPa water retention, of 1.0 g em* or leas

and acid-oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of more than 1.0 percent.
Aquandic

GAEB. Other Kanhaplaquults that have 5 percent or
more plinthite (by volume) in one or more subhorizons
within 150 cm of the soil surface.

Plinthic Kanhaplaquults
GAEC. Other Kanhaplaquults that:

1. Have a subhorizon that has dominant chroma of 3 or
more within 75 cm of the soil surface; and

2, Have a mollic or histic epipedon.
‘Aerio Umbric Kanhaplaquults

GAED. Other Kanhaplaquults that have a subhorizon
that has dominant chroma of 3 or more within 75 cm of

the soil surface.

Aeric Kanhaplaquults
GAKE. Other Kanhaplaquults that have a mollic or
histic epipedon.

Umbric Kanhaplaquults

GAEF. Other Kanhaplaquults.

Typic Kanhaplaquults
Ochraquults
Key te subgroups

GAGA. Ochraquults that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic horizon that is 50 to

100 cm below the soil surface.
Arenic Ochraquults

GAGB. Other Ochraquults that have a layer, starting at
the mineral soil surface, that has a sandy particle-size
class and extends to the top of an argillic horizon that is
more than 100 cm below the soil surface.

Grossarenic Ochraquults

GAGC. Other Ochraquults that have dominant chroma
of 3 or more in one or more subhorizons between the A or

Ap horizon and a depth of 76 cm.
Aeric Ochraquults

GAGD. Other Ochraquults.
‘Typic Ochraquults


180
FBEE. Other Calciorthide that have a lithic contact

within 50 cm of the surface.
Lithic Calciorthids

FBEF. Other Calciorthids that have the following
combination of characteristics:

1, Are saturated with water for 90 consecutive days or
more in most years within 100 cm of the surface or
have any of the following characteristics within a
depth of 100 cm below the surface if the soil above that
depth is saturated with water at some period in most
years or the soil is artificially drained:

a. Dominant chroma of 1 or less throughout and hue
of 2.5Y or yellower in some part; or

b. Dominant chroma of 2 or less and mottles that are
not due to segregated lime; or

c. Both a dominant chroma of 2 or less and a greater
SAR (or percentage of exchangeable Na) in more
than half the thickness of the horizons between the
surface and 50 cm than in the saturated zone; and

2, Have a horizon within 100 cm of the surface that is
more than 15 cm thick and either contains 20 percent
or more durinodes or is brittle and has firm

consistence when moist.

FBEG. Other Calciorthids that are saturated with water
for 90 consecutive days or more in most years within 100
em of the surface or have any of the following
characteristics within a depth of 100 cm below the surface
if the soil above that depth is saturated with water at eome
period in most years or the soil is artificially drained:

1, Dominant chroma of 1 or Jess throughout and hue of
2.5Y or yellower in some part; or .

2. Dominant chroma of 2 or less and mottles that are
not due to segregated lime; or

8. Both a dominant chroma of 2 or less and a greater
SAR (or percentage of exchangeable Na) in more than
half the thickness of the horizons between the surface

and 50 cm than in the saturated zone.
Aquic Calciorthids

FBEH. Other Calciorthids that have the following
combination of characteristics:

1, Have a horizon within 100 cm of the surface that is
more than 15 cm thick and either contains 20 percent
or more durinodes or is brittle and has firm
consistence when moist; and

2. Have a weighted average percentage of organic
carbon in the upper 40 cm that is 0.6 percent or more if
the weighted average ratio of sand to clay in the soil
above that depth is 1.0 or less, or is 0.15 percent or more
if the ratio is 13 or more, or is intermediate between 0.6
percent and one-seventh percent if the ratio of sand to


3, Base saturation is 50 percent or more by the NH,OAc
method,

4. The organic-carbon content is 2.5 percent or more in
the upper 18 cm if the color requirement is waived because
of finely divided lime. Otherwise, the organic-carbon
content is at least 0.6 percent (1 percent organic matter)
throughout the thickness of soil specified in item 5.

The mollic epipedon consists of mineral rather than
organic soil material. Its organic-carbon content,
therefore, has an upper as well as a lower limit. The
upper limit of organic carbon in a mollic epipedon is the
same as that of mineral soil material; in part it is the
lower limit for the histic epipedon, defined later in this
chapter. Because an organic horizon can form above a
mollic epipedon in a wet soil, the mollic epipedon is not
necessarily the surface horizon but is the uppermost
horizon composed of mineral soil material.

5. The thickness is one of the following after mixing the
upper 18 cm of soil or the whole soil if the depth to rock,
petrocalcic horizon, or duripan is less than 18 cm:

a. Ten om or more if the epipedon is underlain directly
by a lithic contact; 10 cm or more in soils of shallow
families in which the epipedon is underlain directly by
a paralithic contact, a petrocalcic horizon, or a duripan,
all defined later in this chapter; or

b. In other soils the epipedon must be more than 25 cm
thick if its texture if finer than loamy fine sand and

(1) The upper boundary of pedogenic lime that is
present as filaments, soft coatings, or soft nodules is
deeper than 75 cm; and

(2) The base of any argillic, natric, spodic, cambic,
or oxic horizon is deeper than 75 cm; and

(3) The upper boundary of any petrocalcic horizon,
fragipan, or duripan is deeper than 75 cm; or

c. In other soils that have a loamy or clayey epipedon,
the thickness of the epipedon must be 18 cm or more and
it must be more than one-third of the depth from the top
of the epipedon to the shallowest of one of the features
listed in (b) if that is less than 75 cm; or

@ In other soils the epipedon must be more than 25 cm
thick if either

(1) The texture of the epipedon is as coarse as or
coarser than loamy fine sand throughout its
thickness; or


417

unlike the assumed parent material of the buried soil.
The symbol is not used in organic soils or to separate
an organic layer from a mineral layer.

¢ Concretions or nodules

This symbol is used to indicate a significant
accumulation of concretions or of nodules.
Cementation is required, The cementing agent is not
specified except it cannot be silica. This symbol is not
used if concretions or nodules are dolomite or calcite
or more soluble salts, but it is used if the nodules or
concretions enriched in minerals that contain
iron, aluminum, manganese, or titanium. Their
consistence is specified in the horizon description.

d Dense unconsolidated sediments or materials

This symbol is used to indicate naturally occurring or
manmade, unconsolidated sediments or materials
with high bulk density, such as dense basal till, plow

ns and other mechanically compacted zones, The
fayer is root restrictive and roote do not enter except
along fracture planes.

© Organic material of intermediate decomposition

This symbol is used with “O" to indicate organic
materials of intermediate decomposition, Rubbed
fiber content is 17 to 40 percent of the volume. Usually
occurs in soils saturated for prolonged periods;
however, can occur in soils not saturated for prolonged
periods.

{ Frozen soil

This symbol is used to indicate that the horizon or
layer contains permanent ice, Symbol is not used for
seasonally frozen-layers or for "dry permafrost”
(material that is colder than 0°C but does not contain
ice),

Strong gleying

This symbol is used to indicate either that iron has
been reduced and removed during soil formation or
that saturation with stagnant water has preserved a
reduced state. Most of the affected layera have low
chroma and many are mottled. The low chroma can
be the color of reduced iron or the color of uncoated
sand and silt particles from which iron has been
removed. Symbol "g” is not used for soil materials of
low chroma, such as some shales or E horizons, unless
they have a history of wetness, If "g” is used with "B,”
pedogenic change in addition to gleying is implied. If
no other Pedogenic change in addition to gleying has
taken place, the horizon is designated Cg.

cy

h  Mluvial accumulation of organic matter

‘This symbol is used with "B" to indicate the
accumulation of illuvial, amorphous, dispersible
organic matter-sesquioxide complexes if the
sesquioxide component is dominated by aluminum


366

upper 30 cm of the spodic horizon or below any Ap
horizon; and

2. Any black upper subhorizon of the spodic horizon
that has 3 percent or more organic carbon in the upper 2
cm is present in 90 percent or less of the area of each

pedon.
Entic Haplohumods
CCEG., Other Haplohumods that have a layer starting at
the mineral soil surface that has a sandy particle-size
class throughout and extends to at least the upper

boundary of the spodic horizon, and the upper boundary
of the spodic horizon is between 125 and 200 cm below the

soil surface.
Grossarenic Haplohumods

CCEH. Other Haplohumods that have 5 percent or more
by volume of iron-cemented nodules, 2.5 to 30 cm in
diameter, throughout the spodic horizon.

Ferrudalfic Haplohumods

CCEI. Other Haplohumods that have a surface horizon
more than 30 cm thick that meets all the requirements

for a plaggen epipedon except thickness.
Plaggeptic Haplohumods

CCEJ, Other Haplohumods that have an argillic or
kandic horizon below the spodic horizon.

‘Ultic Haplohumods

CCEK. Other Haplohumods that have less than 3 percent.
organic carbon in the upper 2 cm of the spodic horizon, or
any black upper subhorizon of the spodic horizon that has
3 percent or more organic carbon in the upper 2 cm is
present in leas than 90 percent of the area of each pedon.

CCEL, Other Haplohumods that have a xeric moisture

regime.

Xeric Haplohumods
CCEM. Other Haplohumods.

Typic Haplohumods
Placohumods
Key to subgroups

CCAA. Placohumods that have a cryic or colder
temperature regime.
Cryic Placohumods

CCAB. Other Placohumods.
Typic Placohumods

Tropohumods

‘Tropohumods are the Humods that have an isomesic or a
warmer iso temperature regime.


207
‘Tropofluvents

Tropofluvents are the Fluvents that

1, Have an isomesic or warmer iso temperature
regime; and

2. Have a udic moisture regime.

Only one series of Tropofluvents has been recognized in
the United States, and subgroups have not been defined.
It is suggested that the definition of the typic subgroup
should parallel that of Typic Udifluvents in the great
group that is defined next.

Udifluvents

Key to subgroups

KDFA. Udifluvents that have, throughout a cumulative
thickness of 18 em or more and within a depth of 75 cm,
bulk density of the less than 2.0 mm fraction, measured
at 33 kPa water retention, of 1.0 g cm” or less and acid-
oxalate-extractable aluminum plus 1/2 acid-oxalate-
extractable iron of more than 1.0 percent,

Andie Udifluvents

KDFB. Other Udifluvents that have, throughout a
cumulative thickness of 18 cm or more and within a
depth of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more
than 36 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
porcent of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
Percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Vitrandic Udifluvents

KDFC. Other Udifluvents that have mottles within 50 cm
of the surface that have chroma of 2 or less or, at a depth
between 50 and 100 cm, have one or more horizons that
are saturated with water at some period or that are
artificially drained and have chroma less than 1 or hue
bluer than 10Y and value, moist, of 4 or more.

‘Aquic Udifluvents

KDFD. Other Udifluvents that have an Ap horizon that
has a color value, moist, of 3 or less and a color value,
dry, of 5 or less when crushed and smoothed, or the A
horizon is 15 cm or more thick and has these colors.
Mollic Udifluvents

KDFE. Other Udifluvents.
‘Typic Udifluvents


139
BCAP, Other Vitritorrands.

UDANDS

Key to great groups

BGA. Udands that have a placic horizon within 100 cm of
the mineral soil surface or of the upper boundary of an
organic layer with andic soil properties, whichever is
shallower, in half or more of each pedon.

Placudands, p. 149

BGB, Other Udands that have a cemented layer in 75
percent or more of each pedon which does not slake in
water after air drying, with its upper boundary within
100 cm of the mineral soil surface or of the upper
boundary of an organic layer with andie soil properties,

whichever is shallower.
Durudands, p. 139

BGC, Other Udands that have a melanic epipedon.
Melanudands, p. 146

Typic Vitritorrands

BGD. Other Udands that have an epipedon meeting the
depth, thickness and organic carbon requirements of a
melanic epipedon and having color value and chroma,

moist, of 3 or less.
Fulvudands, p. 140

BGE. Other Udands that have a 1500 kPa water retention
of undried samples of 100 percent or more on the
weighted average throughout a thickness of 35 cm or
more within 100 cm of the mineral soil surface or of the
upper boundary of an organic layer with andic soil
properties, whichever is shallower.

Hydrudands, p. 145
BGF. Other Udands,

Hapludands, p. 142
Durudands
Key to subgroups

BGBA. Durudands that have, in some subhorizon
‘between 50 and 100 cm:

1, Two percent or more redox segregations; or

2, Dominant chromas, moist, of 2 or less on faces of
peds, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or

3. Sufficient active ferrous iron to give a positive
reaction to a,a'-dipyridy! at some time of the year
when not being irrigated.

Aquic Durudands

BGBB, Other Durudands that have extractable bases plus
1N KC1 extractable Al** of less than 2.0 cmol(+) kg’ fine
earth in some subhorizon 30 cm or more thick between 25

and 100 cm.
Acrudoxic Durudands


378

Albaquults

Key to subgroups
GACA. Albaquults that:

1, Have one or more of the following characteristics in
more than 40 percent of the matrix between the Ap
horizon and a depth of 75 em:

a Dominant chroma, moist, of 3 or more if mottles of
higher chroma are present; or

b. Chroma, moist, of 2 or more if mottles are absent;
or

c. Dominant hue of 10YR or redder if distinct or
prominent mottles are present and there is also a
thermic, isothermic, or warmer soil temperature
regime; or

2. Have an ochric epipedon that has higher chroma or
redder hue, or both, than the underlying argillic or
kandic horizon.

Aerie Albaquults
GACB. Other Albaquults.

Typic Albaquults
Fragiaquults
Key to subgroups

GABA. Fragiaquults that:

1. Either do not have mottles or have dominant chroma
of 8 or more in some subhorizon between the A or Ap
horizon and the fragipan; and

2. Have 6 percent or more plinthite (by volume) in one
or more subhorizons within 150 of the soil surface.
Plinthudic. i

GABB. Other Fragiaquults that either do not have
mottles or have dominant chroma of 3 or more in some
subhorizon between the A or Ap horizon and the

fragipan.
Acric Fragiaquults
GABC, Other Fragiaquults that have 5 percent or more

plinthite (by volume) in one or more subhorizons within
150 em of the soil surface.

Plinthic Fragiaquults
GABD. Other Fragiaquults that do not have an ochric
epipedon.

Umbric Fragiaquults

GABE. Other Fragiaquults.


HECE. Other Natriborolls that have tonguing or
interfingering of an albic horizon more than 2.5 cm into
the natric horizon.

Gloasic Natriborolls
HECF. Other Natriborolls.
‘Typic Natriborolls
Paleborolls
Key to subgroups
HEAA. Paleborolls that:

1, Have a mean summer soil temperature at a depth of
50 cm or at a lithic or paralithic contact, whichever is
shallower, of less than 15°C if there is no O horizon or
less than 8°C if there is an O horizon; and

2, Have a mollic epipedon that is 50 cm or more thick.
Cryic Pachic Paleborolls

HEAB. Other Paleborolls that:

1, Have an argillic horizon that has an increase in
clay content of 20 percent (absolute) or more within a
vertical distance of 7.5 cm below its upper boundary;
and

2. Have a mean summer soil temperature at a depth of
50 cm or-at a lithic or paralithic contact, whichever is
shallower, of less than 15°C if there is no O horizon or

Jess than 8°C if there is an O horizon,
Abruptic Cryic Paleborolls

HEAC. Other Paleborolls that have an argillic horizon
that has an increase in clay content of 20 percent
(absolute) or more within a vertical distance of 7.5 cm

below its upper boundary.
Abruptic Paleboralls

HEAD. Other Paleborolis that have a mean summer soil

temperature at a depth of 60 cm or at a lithic or paralithic

contact, whichever is shallower, of less than 16°C if there

is no O horizon or less than 8°C if there is an O horizon.
Cryic

HEAE. Other Paleborvlls that have a mollic epipedon that
is 60 cm or more thick.

Pachie Paleborvlls
HEAF. Other Paleborolls that have mottles that have
chroma of 2 or less within 100 cm of the surface and, if

undrained, are continuously saturated with water in the
mottled horizon for as long as 90 days in most years.
Aquic Pale!

HEAG. Other Paleborolls.
‘Typic Paleborolls


370

the color is due to uncoated sand grains, have a water
table within 100 cm of the soil surface for 60 days or
more, cumulative, in most years; or

2, Have chroma of 2 or less if mottled, or chroma less
than 2 if not mottled, that is dominant in the matrix
within 15 cm below the bage of the spodic horizon and.
within 100 cm of the surface of the soil; and

8, Have an argillic or kandic horizon below the spodic
horizon, and the argillic or kandic horizon either has
base saturation of 35 percent or more in some part or
has a mean annual soil temperature lower than 8°C,

CDEF, Other Haplorthods that:

1, Have distinct or prominent mottles of approximate
spherical shape in the spodic horizon and the
variability in color is not associated with differences
in consistence in such a manner that the redder or
darker parts are extremely firm or very firm, and, if
the color is due to unco; sand grains, have a water
table within 100 cm of the soil surface for 60 days or
more, cumulative, in most years; and

2. Have a spodic horizon that does not have any of the
following:

a. A continuous horizon at least 2.5 cm thick that is
very firm or extremely firm when moist (ortstein);
nor

b. A texture of very fine sand or finer, and a
thickness of more than 10 cm and a weighted
average of at least 1.2 percent organic carbon in the
upper 10 cm; nor

c. A coarse-loamy, loamy-skeletal, sandy-skeletal,
or sandy particle-size class and color value and
chroma, moist, of 3 or less in at least the upper 7.5

em of the spodic horizon.
Aquentic Haplorthods
CDEG. Other Haplorthods that:

1. Have distinct or prominent mottles of approximate
spherical shape in the spodic horizon and the
variability in color is not associated with differences
in consistence in such a manner that the redder or
darker parts are extremely firm or very firm, and, if
the color is due to uncoated sand grains, have a water
table within 100 cm of the soil surface for 60 days or
more, cumulative, in most years; or

2. Have chroma of 2 or less if mottled, or chroma less
than 2 if not mottled, that is dominant in the matrix
within 15 cm below the base of the spodic horizon and
within 100 cm of the surface of the soil.

Aquic Haplorthods

CDEH. Other Haplorthods that have an argillic or
kandic horizon below the spodic horizon, and the argillic
or kandic horizon either has base saturation of 35 percent


147
and colors of a mollic epipedon throughout, occurring
below a horizon or horizons, 10 cm or more thick, with
color value 1 unit or more higher and organic carbon
content 1 percent or more lower than the underlying

layer,
Alic Thaptic Melanudands

BGCE. Other Melanudands that have 1N KCI-
extractable Al** of more than 2.0 cmol(+) kg” fine earth
throughout a layer 10 cm or more thick between 25 and 50

cm.
Alic Melanudands

BGCF. Other Melanudands that have, in some
subhorizon between 50 and 100 cm of the mineral soil
surface or of the upper boundary of an organic layer with
andic soil properties, whichever is shallower:

1. Two percent or more redox segregations; or

2, Dominant chromas, moist, of 2 or less on faces of
peds, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or

3, Sufficient active ferrous iron to give a positive
reaction to a,a'-dipyridyl at some time of the year

when not being irrigated.
Aquic Melanudands

BGCG. Other Melanudands that have extractable bases
plus IN KCl extractable Al®* of less than 2.0 cmol(+) kg!
fine earth in some subhorizon 30 cm or more thick
between 25 and 100 cm, and have less than 30 percent,
undried, 1600 kPa water retention in some subhorizon
that meets the requirements for andic sail properties and
that is at least 25 cm thick within 100 cm of the mineral
soil surface or of the upper boundary of an organic layer
with andic soil properties, whichever is shallower.
Acrudoxic Vitric

BGCH. Other Melanudands that have extractable bases
plus 1N KCl-extractable Al? of less than 2.0 cmol(+) kg?
fine earth in some subhorizon 30 cm or more thick
between 25 and 100 cm, and have, undried, 1500 kPa water
retention of 70 percent or more throughout a continuous
thickness of 35 cm or more within the upper 100 em of the
mineral soil surface or of the upper boundary of an
organic layer with andic soil properties, whichever is

shallower.
Acrudoxic Hydric Melanudands

BGCI. Other Melanudands that have extractable bases
plus 1N KCl-extractable Al* of less than 2.0 cmol(+) kg?
fine earth in some subhorizon 30 cm or more thick
between 25 and 100 cm of the mineral soil surface or of the
upper boundary of an organic layer with andic soil
properties, whichever is shallower.

Acrudoxic Melanudands

BGCJ, Other Melanudands that have both more than 6.0
percent organic carbon and colors of the mollic epipedon
throughout at least 50 cm of the upper 60 cm, excluding
any overlying layers that do not have andic soil
properties, and have less than 30 percent, undried, 1500



247
JAIF. Other Haplaquepts that:

1. Have an Ap horizon that has a color value, moist, of
3 or less and a value, dry, of 5 or less when crushed
and smoothed, or have an A horizon that is 15 em or
more thick if its color value, moist, is 3 or leas; and

2, Have base saturation (by NH,OAo) of leas than 50
percent in some horizon and it does not increase with
depth to a value of 50 percent or more.

‘Humic Haplaquepts

JAIG. Other Haplaquepts that:

1. Have an Ap horizon that has a color value, moist, of
3 or less and a value, dry, of 6 or less when crushed
and amoothed, or have an A horizon that ie 16 cm or
more thick if its color value, moist, is 3 or less; and

2, Have base saturation (by NH,OAc) of 50 percent or

more throughout or it increases with depth to a value of
50 percent or more.

Mollic Haplaquepts
JAIH. Other Haplaquepts.

Typic Haplaquepts
Humaquepts
Key to subgroups

JAHA. Humaquepts that have an n value of 0.9 or more

between depths of 50 and 80 cm, or of more than 0.7 in one

or more layers between depths of 20 and 50 cm.
Hydraquentic Humaquepts

JAHB. Other Humaquepts that have a histic epipedon
whose upper boundary is at or near the soil surface.
Histic

JAHC, Other Humaquepts that have, throughout
cumulative thickness of 18 em or more and within a
depth of 75 em, one or more of the following:

1. Bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 gcmTM or
less and acid-oxalate-extractable aluminum plus 1/2
acid-oxalate-extractable iron of more than 1.0 percent;
or

2. Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or

3. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent voleanic glass; or


ant

EAAD. Other Chromoxererts,
Typic Chromoxererts

Pelloxererts
Key to subgroups

EABA. Pelloxererts that have in one or more
subhorizone within a depth of 100 cm a chroma, either
dry or moist, of 2 or more, or have between 30 cm and 100
cm neither distinct or prominent mottles, nor
coneretions that are due to segregated iron or

manganese.
Chromic Pelloxererts

EABB, Other Pelloxererts that have a color value, moist,
of 4 or more or a value, dry, of 6 or more in the surface
horizon, or the horizon with color value of 3 or less,
moist, and 6 or less, dry, is less than 30 cm thick in half

or more of each pedon,
Entic Pelloxererts

EABC. Other Pelloxererts.
Typic Pelloxererts


316

horizon or the lower part of the mollic epipedon has
carbonates throughout,

Entic Haplustolis
HFGY. Other Haplustolls.

‘Typic Haptustolls
Natrustolls
Key to subgroups

HFBA. Natrustolls that have visible crystals or nests of
gypsum or more soluble salts within 40 cm of the surface.
Leptic Natrustalls

HFBB, Other Natrustolls that have one or more of the
following characteristics within 100 em of the surface:

1. Dominant chroma of 1 or less throughout and hue as
yellow or yellower than 2.5 Y in some part; or

2. Dominant chroma of 2 or less and mottles that are not
due to segregated lime; or

3. Dominant chroma of 2 or less and a decrease in the
percentage of exchangeable sodium from the upper 25-
centimeter layer to the underlying layer.

Aquic Natrustolls

HFBC. Other Natrustolls that, when neither irrigated not
fallowed to store moisture:

1, If the soil temperature ig mesic or thermic,
are dry six-tenthe or more of the time in half or more
years in some part of the moisture control section (not
necessarily the same part) during a period when the
soil temperature at a depth of 50 cm exceeds 5°C; or

2, If the soil temperature regime is hyperthermic, or
isomesic or warmer, are moist in some or all parts of
the moisture control section for less than 90 consecutive
days during a period when the soil temperature at a

depth of 50 cm exceeds 8°C.
Aridic Natrustolls

HFBD. Other Natrustolls that have a brittle horizon 15 em.
or more thick that is within 100 cm of the surface and that
contains some opal coatings or 20 percent or more by

volume durinos
Duric Natrustolis

HFBE. Other Natrustolls that have tonguing or
interfingering of an albic horizon more than 2.5 cm into

a natric horizon.
Gloasic Natrustolls

HFBF. Other Natrustolls.
Typic Natrustolls


400
GDBE. Other Kandiustulte that:

1. Have, throughout a cumulative thickness of 18 cm or
more and within a depth of 75 cm, bulk density of the
less than 2.0 mm fraction, measured at 33 kPa water
retention, of 1.0 g em’ or less and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of more than 1.0 percent; and

2, When neither irrigated nor fallowed to store
moisture:

a. If the soil temperature regime is mesic or
thermic, are dry for 135 cumulative days or less in
some part of the moisture control section when the
soil temperature at a depth of 50 cm exceeds 5°C; or

b. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or
less during a period when the soil temperature at a

depth of 50 cm exceeds 8°C.
Udandic Kandiustults

GDBF. Other Kandiustults that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cmTM or leas
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

GDBG. Other Kandiustults that have 5 percent or more
plinthite (by volume) in one or more subhorizons within

150 cm of the soi) surface.
Plinthic Kandiustults

GDBH. Other Kandiustults that when neither irrigated
nor fallowed to store moisture have either:

1, If the soil temperature regime is mesic or thermic,

are moist six-tenths or less of the time in half or more
years in some part of the moisture control section (not
necessarily the same part) when the soil temperature
at a depth of 50 cm exceeds 5°C; or

2. If the soil temperature regime ia hyperthermic,
isomesic, or warmer, are moist in most years in some
or all parts of the moisture control section for less than
180 days during a period when the soil temperature at a

depth of 50 cm exceeds 8°C.
Aridic Kandiustults

GDBI. Other Kandiustults that when neither irrigated
nor fallowed to store moisture have either:

1. If the soil temperature regime is mesic or thermic,
are dry for 135 cumulative days or less in some part of
the moisture control section when the soil temperature
at a depth of 50 cm exceeds 5°C; or

2. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or less


153
VITRANDS

Key to great groups
BEA. Vitrands that have an ustic soil moisture regime.
Us p. 163
BEB. Other Vitrands,
Udivitrands, p. 153
Udivitrands
‘Key to subgroups
BEBA. Udivitrands that have a lithic contact within 50 cm
of the soil surface.
Lithic Udivitrands

BEBB, Other Udivitrands that have, in some subhorizon
between 50 and 100 cm:

1, Two percent or more redox segregations; or

2. Dominant chromas, moist, of 2 or less on faces of
peds, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or

3, Sufficient active ferrous iron to give a positive
reaction to a,a'-dipyridy] at some time of the year when

not being irrigated.
Aquie Udivitrands

BEBC. Other Udivitrands that have, between 25 and 100
em, a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the

underlying layer,
Thaptic Udivitrands

BEBD. Other Udivitrands that have a spodic horizon, and
an associated eluvial horizon with its upper boundary
within 125 cm of the mineral soil surface or of the upper
boundary of an organic layer with andic soil properties,
whichever is shallower.

Spodie Udivitrands
BEBE. Other Udivitrands.

Typic Udivitrands
Ustivitrands
Key to aubgroups.

BEAA. Ustivitrands that have a lithic contact within 50
em of the soil surface,
Lithic Ustivitrands

BEAB. Other Ustivitrands that have, in some subhorizon
between 50 and 100 cm:

1, Two percent or more redox segregations; or


329

2, Have an irregular decrease in organic carbon
content with increasing depth, or have an organic
carbon content of more than 0.3 percent throughout to a
depth of 125 em of the surface; and

3. Have a slope of less than 25 percent.
Fluvaquentic Haploxerolls

HDFM. Other Haploxerolls that:

1, Have mottles that have chroma of 2 or less within 75
cm of the surface, and the soils are continuously
saturated with water within 100 cm of the soil surface
for 90 days or more in most years, unless artificially
drained; and

2. Have a horizon within 100 cm of the surface that is
more than 15 cm thick and either contains at least 20
percent durinodes or is brittle and has firm consistence

when moist.
Aquic Duric Haploxerolls
HDFN. Other Haploxerolls that:

1, Have mottles that have chroma of 2 or less within 75
cm of the surface, and the soils are continuously
saturated with water within 100 cm of the soil surface
for 90 days or more in most years, unless artificially
drained; and

2, Have base saturation (by sum of cations) of 75 percent

or less in some part within a depth of 75 cm from the soil
surface or above a lithic or paralithic contact,

whichever is shallower.
Aquultic Haploxerolls
HDFO. Other Haploxerolls that have mottles that have
chroma of 2 or less within 75 cm of the surface, and the

soils are continuously saturated with water within 100 cm
of the soil surface for 90 days or more in most years,

unless artificially drained.
Aquic Haploxerolls
HDFP. Other Haploxerolls that:
1. Have an aridic moisture regime; and
2. Have an irregular decrease in organic carbon
content with increasing depth, or have an organic
carbon content of more than 0.3 percent throughout to a
depth of 125 cm of the surface; and
3. Have a slope of less than 25 percent.
Torcift io Hapl 1
HDFQ. Other Haploxerolls that:
1, Have an aridic moisture regime; and
2. Have a horizon within 100 cm of the surface that is
more than 16 cm thick and either contains at least 20
percent durinodes or is brittle and has firm consistence

when moist.
Aridic Duric Haploxerolls


a1

of 75 em, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm” or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 poroents

GCCM. Other Kandiudults that have the following
combination of characteristics in the upper 75 cm of the
soil if the chroma in all or part of the upper 75 cm is not
controlled by uncoated sand grains; or if the chroma
throughout the upper 75 cm is controlled by uncoated sand
grains, have the following combination of
characteristics throughout the upper 12.5 cm of the
argillic or kandic horizon:

1. Mottles that have a color value, moist, of 4 or more
and chroma, moist, of 2 or less accompanied by
mottles of higher chroma that are due to segregation of
iron; an

2. Saturation with water in the mottled zone at some
time of year when the soil temperature in that zone is
5°C or higher, or there is artificial drainage.

Aquic Kandiudults

GCCN. Other Kandiudults that have 5 percent or more
plinthite (by volume) in one or more subhorizons within

150 cm of the soil surface.

Plinthic Kandiudults
GCCO. Other Kandiudults that have, in the upper 75 cm
of the soil, a hue of 10YR or yellower in one or more
subhorizons that have a color value, moist, of 4 or more
and mottles with chroma of 3 or more and the hue
becomes redder with depth within 100 cm of the soil
surface.

Epiaquic Kandiudults
GCCP, Other Kandiudults that have @ sombric horizon
within 150 cm of the aoil surface.

Sombric Kandiudults
GCCQ, Other Kandiudults that have, throughout the
argillic or kandic horizon, colors with a hue of 2.5YR or
redder, a value, moist, of 3 or less, and a value, dry, that
is 1 unit or less higher than the value, moist.

Rhodic Kandindults

GCCR, Other Kandiudults,
‘Typic Kandiudults

Kanhapludults
Key to subgroups
GCDA. Kanhapludults that have a lithic contact within
50 cm of the soil surface.

Lithic Kanhapludults
GCDB. Other Kanhapludults that:

1, Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the


45

Chapter3.
Family Differentiae
MINERAL SOILS

The differentiae used to distinguish families of mineral
soils within a subgroup are listed next in the order in
which the descriptive terms appear in the family name
and in which the terms are defined in this chapter.

Particle-size classes
Mineralogy classes

Caleareous and reaction classes
Soil temperature classes

Soil depth classes

Soil slopes classes

Soil consistence classes
Classes of coatings (on sand)
Classes of cracks

Particle-size classes

Particle size refers to grain-size distribution of the whole
soil and is not the same as texture, which refers to the
fine-earth fraction. The fine-earth fraction consists of
the particles that have a diameter of less than 2.0 mm.
Particle-size classes are a kind of compromise between
engineering and pedologic classifications. The limit
between sand and silt is a diameter of 74 microns in the
engineering classification and of either 50 or 20 microns
in pedologic classifications. The engineering
classifications are based on percentages by weight in the
fraction less than 74 mm in diameter, and textural
classes are based on percentages by weight in the fraction
less than 2.0 mm in diameter.

The very fine sand separate (diameter between 0.05 mm
and 0.1 mm) is split in engineering classifications. In
defining particle-size classes, much the same split is
made but in a different manner. A fine sand or loamy
fine sand normally has an appreciable content of very
fine sand, but the very fine sand fraction is mostly
coarser than 74 microns. A silty sediment, euch as loess,
may also have an appreciable component of very fine
sand, but most of the very fine sand is finer than 74
microns. So, in particle-size classes, the very fine sand
is allowed to “float.” It is treated as sand if the texture is
fine sand, loamy fine sand, or a coarser class. It is
treated as silt if the texture is very fine sand, loamy very
fine sand, sandy loam, silt loam, or a finer class.

No single set of particle-size classes seems appropriate as
family differentiae for all kinds of soils. The classes
that follow provide for a choice of either 7 or 11 particle-
size classes. This choice permits relatively fine


249
oxalate-extractable iron of 0.40 percent or more.
Aquandic

JABC, Other Placaquepts that do not have a continuous
placic horizon within 100 cm of the soil surface

throughout each pedon.
° " Haplic Placaquepts

JABD, Other Placaquepts.
Typic Placaquepts

Plinthaquepts

These are mainly Aquepts of intertropical regions.
They have plinthite that forms a continuous phase or
occupies more than half the matrix of some subhorizon
deeper than 30 cm but within 125 cm of the soil surface.
‘These are soils in which the ground-water leve)
fluctuates appreciably during the year. Water is at or
near the surince during the rainy season but drops
during a dry season. Most of‘these soils are in relatively
recent alluvium, probably of late- Pleistocene or
Holocene age. Weatherable minerals are present in
appreciable amounts. These soils are not known to occur
in the United States, but the great group is provided
because the soils are thought to be extensive in parts of the
Amazon basin.

Sulfaquepts

Key to subgroups

JAAA, All Sulfaquepts (provisional).
Typic Sulfaquepts

Tropaquepts
Key to subgroups

JAGA. Tropaquepts that have one or both of the
following:

1, Jarosite mottles and a pH between 3.6 and 4,0 (1:1
water, air dried slowly in shade) in some subhorizon
within 50 cm of the soil surface; or

2. Jarosite mottles and a pH of less than 4.0 (1:1 water,
air dried slowly in shade) in some subhorizon between
depths of 50 and 150 cm.

Sulfic Tropaquepts
JAGB. Other Tropaquepts that have a lithic contact
within 50 cm of the soil surface.

Lithic Tropaquepts

JAGC. Other Tropaquepts that have the following
combination of characteristics:

1. Cracks at some time in most years that are 1 em or
more wide at a depth of 50 cm, that are at least 30cm
Jong in some part, and that extend upward to the soil
surface or to the base of an Ap horizon; and


200

KDBB. Other Xerofluvents that have, throughout a
cumulative thickness of 18 cm or more and within a
depth of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soi) and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or

2. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b, At least 5 percent volcanic glass and acid-
oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0. 40 0 percent or more.
‘itrandic Xerofluvents

KDBC. Other Xerofluvents that:

1. Are saturated with water within 150 cm of the
surface during any period in most years; and

2, Have a horizon within 100 cm of the surface that is
more than 15 cm thick and either contains 20 percent
or more durinodes or is brittle and has firm
consistence when moist.

Aquic Durorthidic Xerofluvents

KDBD. Other Xerofluvents that are saturated with water
within 150 cm of the surface during any period in most

years,
Aquic Xerofluvents

KDBE, Other Xerofluvents that have a horizon within 100
cm of the surface that is more than 15 cm thick and either
contains 20 percent or more durinodes or is brittle and

has firm consistence when moist.
Xerofluvents

KDBF, Other Xerofluvents that have an Ap horizon that
has a color value, moist, of 3 or less and a color value,
dry, of 5 or less when crushed and smoothed, or the A
horizon is 16 cm or more thick and has these colors.

Mollic Xerofluvents
KDBG. Other Xerofluvents.
‘Typic Xeroffuvents
ORTHENTS
Key to great groups
KEA. Orthents that have a cryic or pergelic temperature
regime.
Cryorthents, p. 210

KEB. Other Orthents that have a torric moisture regime.
Torriorthents, p. 211


228
ABBB. Other Cryofibrists that have a mean annual soil

temperature of 0°C or lower.
Pergelic Cryofibrists

ABBC. Other Cryofibrists that have a mineral layer 30
mor more thick that has its upper boundary in the
control section below the surface tier.
Terric Cryofibrists

ABBD, Other Cryofibrists that have a mineral layer
between 5 and 30 cm thick or two or more thin,
continuous mineral layers, within organic materials,
in the control section below the surface tier.

Fluvaquentic Cryofibrists

ABBE. Other Cryofibrists that have three-fourths or more
of their fiber volume derived from Sphagnum spp. in the
surface tier or more of the control section.
Sphagnic Cryofitrists
ABBF. Other Cryofibrists.
‘Typie Cryofibrists

Luvifibrists

Lavifibrists are not known to occur in the United States,
but the great group is provided tentatively for use in other
countries if needed. These soils are the Fibrists that
have a horizon within the control section that is 2.cm or
more thick consisting of half or more humilluvic
materials, Because these soils cannot be studied in the
United States, a precise definition is not attempted here.
It should be noted, however, that the soils normally are
acid and that they have been cultivated for a long time.

Medifibrists

Key to subgroups
ABEA. Medifibrists that have a layer of water within the
control section below the surface tier.
Hydric Medifibrists
ABEB. Other Medifibrists that have a lithic contact
within the control section.
Lithic Medifibrists
ABEC. Other Medifibrists that:
1, Have three-fourths or more of the fibers (by volume)
derived from Sphagnum in the surface tier or more of
the control section; and

2. Have a mineral layer 30 em or more thick thet has
its upper boundary in the control section below the

surface tier.
Sphagnic Terric Medifibrists
ABED. Other Medifibrists that:

1. Have 25 cm or more of the subsurface and bottom
tiers consisting of hemic materials; and


5

thick enough that the soil is organic, the mineral soil is
considered to be buried.

The mollic epipedon has the following properties:

1. Soil structure is strong enough that the major part of the
horizon is not both massive and hard or very hard when
dry. Very coarse prisms, more than 30 cm in diameter,
are included in the meaning of massive if there is no
secondary structure within the prisms.

2. Unless there is more than 40 percent finely divided
lime, both broken and crushed samples have Munsell
color value of 3 or darker when moist and 6 or darker
when dry, and chroma of 3 or less when moist; the color
value normally is at least 1 Munsell unit darker or the
chroma is at least 2 units less (both moist and dry) than
that of the 1C horizon if a 1C horizon is present. If only a
2C horizon or an R layer is present, the comparison
should be made with the horizon that overlies the 2C,
Some parent materials such as loess, cinders, alluvium,
or carbonaceous shales also can have dark color and low
chroma. Soils formed in such materials may accumulate
appreciable amounts of organic matter but have no visible
darkening in the epipedon. In this situation, the
requirement that the mollic epipedon have lower value or
chroma than the 1C horizon, or than the next underlying
horizon if there is no 1C, is waived if (a) the surface
horizon (horizons) meets all other requirements for a
mollic epipedon and, in addition, has at least 0.6 percent
more organic carbon than the 1C or the 2C horizon or if (b)
the epipedon extends to rock (either a lithic or paralithic
contact as defined later).

‘The mollic epipedon is expected to have dark color and
low chroma throughout the major part of its matrix, If the
structure is fine granular or fine blocky, the color when
broken may be only the color of the coatings. The color of
the matrix in such situations can be determined only by
crushing or briefly rubbing the sample. Prolonged
rubbing should be avoided because it may cause
darkening of a sample if soft iron-manganese
concretions are present; crushing should be only enough
to break and mix the coatings. The color value when dry
should be determined after the crushed sample has been
smoothed to eliminate shadows,

If there is more than 40 percent finely divided lime, the
limits of color value, dry, are waived; the color value,
moist, then should be 5 or less. This waiver is necessary
because finely divided lime acts as a white pigment.

} mye chrom in peraitted to range up to but not to include 4.0 soils
‘that avo @ hypertherale or isohyperthermic temperature regioe. the
color when molat is that of » specinen that ia moist enough chat an
Additional drop of water produces no change in the color. The color
when dry i that of @ specimen dry enough that continued dxying produces
‘no further change.


242

JE. Other Inceptisols.
Umbrepta, p. 269

AQUEPTS

Key to great groups

JAA. Aquepts that have a sulfuric horizon whose upper
boundary is within 50 cm of the mineral soil surface.
p. 249

JAB, Other Aquepts that have a placic horizon within 100
om of the mineral soil surface in half or more of each

pedon.
Placaquepts, p. 248

JAC. Other Aquepts that have an SAR of 13 or more (or
have sodium saturation that is 15 percent or more) in
half or more of the upper 60 cm of soil that decreases with

depth below 50 cm.
Halaquepts, p. 244

JAD. Other Aquepts that have a fragipan.
p. 244

JAE. Other Aquepts that have a cryic or pergelic soil
temperature regime.
Cryaquepts, p. 242

JAF. Other Aquepts that have plinthite that forms a
continuous phase or constitutes more than half the
matrix within some subhorizon in the upper 125 cm of the

soil.
Plinthaquepts, p. 249

JAG. Other Aquepts that have a difference of less than
5°C between the mean summer and mean winter soil
temperatures at a depth of 50 cm or at a lithic or paralithic
contact, whichever is shallower.

‘Tropaquepts, p. 249
JAH. Other Aquepts that have an umbric, a mollic, or a
histic epipedon.

Humaquepts, p. 247
JAL Other Aquepts.

Haplaquepts, p. 245
Cryaquepts
Key to subgroups

JAEA. Cryaquepts that have a histic epipedon and have a
lithic contact within 50 cm of the soil surface.
se ee

JAEB. Other Cryaquepts that:

1. Have a histic epipedon that is continuous in each
pedon; ai


39

Chapter2

Horizons and Properties Diagnostic for the
Higher Categories: Organic Soils

ORGANIC SOLL MATERIALS

Organic soil materials and organic soils:

1. Are saturated with water for long periods or are
artificially drained and, excluding live roots, (a) have 18
percent or more organic carbon if the mineral fraction is
60 percent or more clay, (b) have 12 percent or more
organic carbon if the mineral fraction has no clay, or (c)
have a proportional content of organic carbon between 12
and 18 percent if the clay content of the mineral fraction
is between zero and 60 percent; or

2, Are never saturated with water for more than a few
days and have 20 percent or more organic carbon.

DEFINITION OF ORGANIC SOILS
Organic soils (Histosols) are soils that

1, Have organic soil materials that extend from the
surface to one of the following:

a. A depth within 10 cm or less of a lithic or paralithic
contact, provided the thickness of the organic soil
materials is more than twice that of the mineral soil
above the contact; or

b. Any depth if the organic soil material rests on
fragmental material (gravel, stones, cobbles) and the
interstices are filled with organic materials, or rests
on a lithic or paralithic contact; or

2, Have organic materials that have an upper boundary
within 40 cm of the surface and

a. Have one of the following thicknesses:

(1) 60 cm or more if three-fourths or more of the
volume is moss fibers or the moist bulk density is
Jess than 0.1 g per cubic centimeter (6.25 Ibs per cubic
foot); or

(2) 40 cm or more if
(a) The organic soil material is saturated with

water for long periods (more than 6 months) or is
artificially drained; and


928

2. Have an irregular decrease in organic carbon
content with increasing depth, or have an organic
carbon content of more than 0.3 percent throughout to a
depth of 126 cm of the surface; and

8, Have a slope of 28 percent or less; and

4, Have base saturation (by sum of cations) of 76 percent
or less in some part within a depth of 75 cm from the soil
surface or above a lithic or paralithic contact,

whichever is shallower.
Cumulic Ultic Haploxerolls
HDFH. Other Haploxerolls that:

1. Have a mollic epipedon that is 50 em or mote thick
and ite texture is finer than loamy fine sand; and

2, Have an irregular decrease in organic carbon
content with increasing depth, or have an organic
carbon content of more than 0.3 percent throughout to a
depth of 125 cm of the surface; and

3. Have a slope of 25 percent or less.
Cumulic Haploxeralls

HODFI. Other Haploxerolls that:

1, Have a caleic horizon or soft, powdery secondary
lime within a depth of 150 om if the weighted average
particle-size class between a depth of 25 and 100 cm, or
between a depth of 26 cm and a lithic or paralithie
contact that js shallower than 100 cm, is sandy; within
110 cm if the average particle-size class is loamy; or
within 90 cm if it is clayey; and

2. Have a mollic epipedon that is 50 cm or more thick
and its texture is finer than loamy fine sand.
Caleic Pachic Haploxerolls
HDFJ. Other Haploxerolls that:

1. Have a mollic epipedon that is 60 em or more thick
and its texture is finer than loamy fine sand; and

2. Have base saturation (by sum of cations) of 75 percent
or less in some part within a depth of 75 cm from the soil
surface or above a lithic or paralithic contact,

whichever is shallower.
Pachic Ultic Haploxerolls

HODFK. Other Haploxerolls that have a mollic epipedon
that is 50 cm or more thick and its texture is finer than

loamy fine sand.
Pachic Haploxerolls
HDFL. Other Haploxerolls that:

1. Have mottles that have chroma of 2 or less within 75
cm of the surface, and the soils are continuously
saturated with water within 100 cm of the soil surface
for 90 days or more in most years, unless artificially
drained; and


119

Rhodustalfs

Key to subgroups

Because these soils are rare in the United States, the
classification that follows probably is incomplete, and it
is provisional.

ICGA. Rhodustalfs that have a lithic contact within 50 cm
of the soil surface.
Lithic Rhodustalfs

ICGB. Other Rhodustalfs that have a CEC of less than 24
cmol(+) per kg clay (by IN NH4OAc pH 7) in the major
part of the argillic horizon, or the major part of the upper
100 em of the argillic horizon if the argillic horizon is

thicker than 100 cm.
Kanhaplic Rhodustalfs

ICGC. Other Rhodustalfs that, when neither irrigated nor
fallowed to store moisture:

1. If the soil temperature regime is mesic or thermic,
are dry for four-tenths or less of the cumulative days in
some part of the moisture control section when the soil
temperature at a depth of 50 cm exceeds 5°C; or

2. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or less
during a period when the soil temperature at a depth of
50 cm exceeds 8°C.

Udie Rhodustalfs
IOGD. Other Rhodustalfs.

‘Typle Rhodustals
XERALFS
Key to great groups

IDA. Xeralfs that have a duripan whose upper boundary is
within 100 cm of the soil surface but below an argillic or a

natric horizon.
Durixeralfs, p. 120

IDB. Other Xeralfs that have a natric horizon.
Natrixeralfs, p, 125

IDC. Other Xeralfs that have a fragipan.

Fragixeralfs, p.121
IDD. Other Xeralfs that have plinthite that forms a
continuous phase in, or constitutes more than half the
matrix of, some subhorizon of the argillic horizon within

160 cm of the soil surface.
Plinthoxeralfy, p. 127


215

2, The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more,
Vitrandic

KEED. Other Udorthents that are saturated with water
for as long as 1 month within 150 cm of the surface.
Aquic

KEEE. Other Udorthents that have 50 percent or more by
volume of wormholes, wormcasts, and filled animal
‘burrows between the bottom of the Ap horizon or a depth of
25 cm, whichever is deeper, and a depth of 100 cm or a
lithic or paralithic or petroferric contact, whichever is

shallower.
Vermic Udorthents
KEEF. Other Udorthents.
Typic Udorthents
Ustorthents
Key to subgroups

KEFA. Other Ustorthents that have a lithic contact
within 50 cm of the surface.
Lithic Ustorthents

KEFB. Ustorthents that have the following combination
of characteristics:

1, Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the soil
surface or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.07
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 em or more in
the upper 125 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 126 em; and

3. More than 36 percent clay in horizons that total more
than 50 cm in thickness.
Vertic Ustorthents

KEFC, Other Ustorthents that are saturated with water
within 150 cm of the surface for as long as 1 month in

most years.
Aquic Ustorthents

KEFD, Other Ustorthents that have a horizon within 100
cm of the surface that is more than 15 cm thick and either
contains 20 percent or more durinodes or is brittle and
has firm consistence when moist.

Durorthidic Ustorthents


5. Has more total clay than the overlying coarser textured
surface horizon and the increased clay content is reached
within a vertical distance of 15 cm or less as follows:

a. If the surface horizon as defined above has less than
20 percent total clay, the kandic horizon begins where

some subhorizon contains at least 4 percent more clay

absolute than the overlying horizon.

b. If the surface horizon as defined above has 20 to 40
percent total clay the kandic horizon begins where
some subhorizon has at least 1.2 times more clay than
the overlying horizon.

¢. If the surface horizon as defined above has more than
40 percent total clay, the kandic horizon begins where
some subhorizon has at least 8 percent more clay
absolute than the overlying horizon.

Natric horizon

The natric horizon (NL. natrium, sodium; implying
presence of sodium) is a special kind of argillic horizon.
It has, in addition to the properties of the argillic horizon:

1. Either

a. Prisms or, more commonly, columns in some part,
usually the upper part, that may or may not break to
blocks; or

b. Rarely, blocky structure and tongues of an eluvial
horizon, in which there are uncoated silt or sand
grains, extending more than 2.5 cm into the horizon;
and

x

Either

a. Tho SAR’ is 18 or more ( or 15 percent or more
saturation with exchangeable sodium) in some
subhorizon within 40 em of the upper boundary; or

b. More exchangeable magnesium plus sodium than
calcium plus exchange acidity (at pH 8.2) in some
subhorizon within 40 cm of the upper boundary if the

5 the percentage of exchangeable sodium (ESP) is used in the definition
of the natric horizon and in 2 muaber of the taxa, Since thin text was
written, the U.S. Salinity Laboratory (personal communication from c. A.
Bower) has revised ita definition of sodic (alkal1) soils and the method
for measuring the sodium adsorption ratio (SAR) ax follows: SAR 1s

neasured by the normal method if the conductivity (Ic) of the saturation
extract 1s lesa than 20 45 per m at 25°C. If the conductivity $8 20 d5
or sore and SAR is more than 10, 3AR 4s determined on a sample that has

been leached with distilled water until ZC of the leachate decreases to
about 4 di per meter but not to leas than 4. ESP of 15 ox wore ix

Girernined directly fon the replaced cation,


948

DEEE. Other Haphudox that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the
soil surface and mottles of 4 or more value moist and 2 or
less chroma within a depth of 125 cm of the soil surface.
Plinthaquic Hapludox

DEEF, Other Hapludox that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the

soil surface.
Plinthic Hapludox

DEEG. Other Hapludox that have mottles of 4 or more
value moist and 2 or less chroma within a depth of 125 cm

of the soil surface.
Aquic Hapludox

DEEH. Other Hapludox that have the lower boundary of
the oxic horizon within a depth or 125 cm of the soil

surface,
Inceptic Haphudox

DEEI. Other Hapludox that have, throughout a cumulative
thickness of 18 cm or more and within a depth of 75 cm,
bulk density of the leas than 2.0 mm fraction, measured at
33 kPa water retention, of 1.0 g cm or less and acid-
oxalate-extractable aluminum plus 1/2 acid-oxalate-
extractable iron of more than 1.0 percent.

Andic Hapludox

DEEJ. Other Hapludox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and a color hue of 2.5YR or redder with
moist values of less than 4 in most of the 25 to 125 cm depth

from the soil surface,
Humic Rhodic Hapludox

DEEK. Other Hapludox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and color hue of 7.5YR or yellower with

moist values of 6 or more in most of the 25 to 125 cm depth

from the soil surface.
Humic Xanthic Hapludox

DEEL. Other Hapludox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of

surface litter.
Humic Hapludox

DEEM. Other Hapludox that have a color hue of 2.5YR or
redder with moist values of less than 4 in most of the 25 to

125 em depth from the soil surface.
Rhodic Haphudox

DEEN. Other Hapludox that have a color hue of 7.5YR or
yellower with moist values of 6 or more in most of the 25 to
125 cm depth from the soil surface.

Xanthic Haphidox

DEEO. Other Hapludox.
Typic Haphudox


13

needs to have clay skins in only some part, either in some
fine pores or, if peds exist, on some vertical and
horizontal ped surfaces. Either thin sections should show
that some part of the horizon has about 1 percent or more of
oriented clay bodies, or the ratio of fine clay to total clay
should be greater than in the overlying or the underlying
horizon.

Calcic horizon

‘The calcic horizon is a horizon of accumulation of
calcium carbonate or of calcium and magnesium
carbonate. The accumulation may be in the C horizon, but
it may also be in a variety of other horizons such as a
mollic epipedon, an argillic or a natric horizon, or a
duripan.

The calcic horizon has two forms. In one, the underlying
materials have less carbonate than the calcic horizon.
This form of calcic horizon includes horizons of
secondary carbonate enrichment that are 15 cm (6 in.) or
more thick, have a carbonate content equivalent to 15
percent or more CaCO, and have a CaCOg equivalent at
least 5 percent greater than the C horizon. In the other
form, the calcic horizon is 15 cm or more thick, has a
CaCOs equivalent of 15 percent or more, and contains 5
percent or more, by volume, of identifiable secondary
carbonates as pendants on pebbles, as concretions, or as
soft powdery forms. If this calcic horizon rests on
limestone, marl, or other very highly calcareous
materials (40 percent or more CaCO, equivalent), the

percentage of carbonates need not decrease with depth.

If the particle-size class is sandy, sandy-skeletal, coarse-
loamy, or loamy-skeletal with less than 18 percent clay,
the 15 percent requirement for CaCOg equivalent is
waived. But to qualify as a calcic horizon, the horizon
must have at least 5 percent (by volume) more soft
powdery secondary CaCO; than an underlying horizon,
and the calcic horizon must be at least 16 cm thick.

If a horizon enriched with secondary carbonate is
indurated or cemented to the degree that dry fragments do
not slake in water, it is considered to be a petrocalcic
horizon, which is discussed later. Air-dry fragments of a
ealcic horizon will slake in water. Pendants below rocks
and concretions normally do not slake, but these are not
connected, and the soil material between the concretions
will slake,

Cambic horizon

In summary, the cambic horizon is an altered horizon
that does not have the dark color, organic-matter content,
and structure that are definitive of a histic, a mollic, or an
umbric epipedon, and it has


403

GDCK. Other Kanhaplustults that have, throughout the
argillic or kandic horizon, colors with a hue of 2.5YR or
redder, a value, moist, of 3 or less, and a value, dry, that
is one unit or less higher than the value, moist.

Rhodic

GDCL. Other Kanhaplustults,
Typic Kanhaplustults

Paleustults

Paleustults are the Ustults that

1. Have a clay distribution such that the percentage of
clay does not decrease from its maximum amount by
more than 20 percent of that maximum within 150 cm
of the soil surface, or the layer in which the clay
percentage decreases by more than 20 percent has at
Jeast 5 percent of the volume consisting of skeletans on
faces of peds and there is at least 3 percent (absolute)
increase in clay below the layer.

2. Do not have plinthite that forms a continuous phase

or constitutes more than half the matrix in any

subhorizon within 150 cm of the soil surface; and

3. Do not have a fragipan or kandic horizon,
Plinthustults

Plinthustults are the Ustults that have plinthite that
forms a continuous phase or constitutes more than half
the matrix within some subhorizon in the upper 150 cm of
the soil.

Rhodustults

Key to subgroups
GDEA. Rhodustults that have a lithic contact within 50
em of the soil surface.

Lithic Rhodustults

GDEB. Other Rhodustults that have texture that is loamy
fine sand or coarser in all parts of the argillic horizon.
Psammentic

GDEC, Other Rhodustults.
‘Typic Rhodustults

XERULTS

Key to great groups

GEA. Xerults that have an argillic horizon that has less
than 10 percent weatherable minerals in the 20- to 200-
micron fraction in its upper 50 cm and have a clay
distribution such that the percentage of clay does not
decrease from its maximum amount by more than 20
percent within 150 cm of the soil surface, or the layer in
which the percentage of clay is less than the maximum


surface mantle should not be based solely on studies of
associated soils.

MINERAL SOIL MATERIAL
Mineral soil material either

1, Is never saturated with water for more than a few days
and has less than 20 percent organic carbon by weight; or

2, Is saturated with water for long periods or has been
artificially drained, and has

a. Less than 18 percent organic carbon by weight if 60
percent or more of the mineral fraction is clay; or

b. Less than 12 percent organic carbon by weight if the
mineral fraction has no clay; or

c. A proportional content of organic carbon between 12
and 18 percent if the clay content of the mineral
fraction is between zero and 60 percent.

Soil material that has more organic carbon than the
amounts just given is considered to be organic material.

DEFINITION OF MINERAL SOILS

Mineral soils, in this taxonomy, are soils that meet one of
the following requirements:

1. Mineral soil material less than 2.0 mm in diameter
(the fine-earth fraction) makes up more than half the
thickness of the upper 80 cm (31 in.); or

2. The depth to bedrock is less than 40 cm and the layer or
layers of mineral soil directly above the rock either are 10
cm or more thick or have half or more of the thickness of
the overlying organic soil material; or

3. The depth to bedrock is 40 cm or more, the mineral soil
material immediately above the bedrock is 10 cm or more
thick, and either

a. Organic soil material is less than 40 cm thick and is
decomposed (consisting of hemic or sapric materials as
defined later) or has a bulk density of 0.1 or more; or

b. Organic soil material is less than 60 cm thick and
either is undecomposed sphagnum or moss fibers or has
a bulk density that is less than 0,1.

DIAGNOSTIC SURFACE HORIZONS; THE EPIPEDON
Seven diagnostic horizons that form at the surface are

defined. Any horizon, however, may be at the surface of a
truncated soil. A horizon that forms at the surface is


192
BAFE. Other Haplaquands that have IN KCl-extractable
Al** of more than 2.0 cmol(+) kg" fine earth throughout «
layer 10 cm or more thick between 25 and 50 em

BAFF, Other Haplaquands that have, undried,1500 kPa

water of 70 percent or more throughout a continuous

thickness of 35 cm or more within the upper 100 cm.
Hydric Hay

BAFG, Other Haplaquands that have, between 25 and 100
cm, a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the
underlying layer.

‘Thaptic Haplaquands
BAFH. Other Haplaquands,
Typic Haplaquands
Melanaquands
‘Key to subgroups

BAEA. Mel: ands that have a lithic contact within
50 cm of the soil surface. :
Lithic Melanaquands

BAEB. Other Melanaquands that have extractable bases
plus 1N KCl-extractable Al* of less than 2.0 cmol(+) kg?
fine earth in some subhorizon 30 cm or more thick

between 25 and 100 cm.
Acraquoxic Melanaquands

BAEC. Other Melanaquands that have, undried, 1500
kPa water retention of 70 percent or more throughout a
continuous thickness of 35 cm or more within the upper
100 cm, and have both more than 6.0 percent organic
carbon and colors of a mollic epipedon throughout at
Jeast 50 cm of the upper 60 cm, excluding any overlying
layers that do not have andic soil properties.

Hydric Pachic Melanaquands

BAED. Other Melanaquands that have, undried, 1500
kPa water retention of 70 percent or more throughout a
continuous thickness of 35 cm or more within the upper

100 cm,
Hydric Melanaquands

BAEE, Other Melanaquands that have, between 40 and
100 cm, a layer 10 em or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the

underlying layer.
Thaptic Melanaquands

BAEF, Other Melanaquands,
‘Typic Melanaquands


DAC, Other Aquox that have more than 35 percent base
saturation (NH,OAc) in all parts within a depth of 125 cm
of the soil surface.

Eutragquox, p. 336
DAD. Other Aquox.

Haplaquox, p. 336
Acraquox
Key to subgroups

DAAA. Acraquox that have more than 5 percent plinthite
in some horizon within a depth of 125 cm of the soil

surface.
Plinthic Acraquox

DAAB. Other Acraquox that have motties with chroma of
more than 2 in 60 pereent or more of the horizon

immediately below the epipedon.

Aesic Acraquox
DAAC. Other Acraquox.

‘Typic Acraquox
Eutraquox
Key to subgroups

DACA. Eutraquox that have a histic epipedon.
Histic:
DACB, Other Butraquox that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the
soil surface.
Plinthic Eutrequex

DACC. Other Eutraquox that have mottles with chroma of
more than 2 in 50 percent or more of the horizon
immediately below the epipedon.

Aeric Eatraquox

DACD. Other Eutraquox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of

surface litter,
Humic Eutraquox
DACE. Other Eutraquox.
‘Typic Eutrequox
Haplaquox
Key to subgroups

DADA. Haplaquox that have a histic epipedon.
Histic

DADB. Other Hapiaquox that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the

soil surface.
Plinthic Haplaquox


2968
Vermiborolls

Key to subgroups
HEEA. Vermiborolls that have a lithic contact within a
depth of 50 cm of the surface.

Lithic Vermiborolls

HEEB. Other Vermiborolls that have both of the
following:

1. A color value, dry, of 5 in the upper 18 cm of the mollic
epipedon, after mixing, or in any Ap horizon that is
more than 18 cm thick; and

2. A moisture control section that is dry in some part
six-tenths or more of the time that the soil temperature
at a depth of 50 cm is above 5°C in most years.

Aridic Vermiborolls

HEEC. Other Vermiboralls that:
1. Have a mollic epipedon less than 75 cm thick; and

2, Have a chroma, moist, after rubbing, of 1 or less in
the upper part of the mollic epipedon to a depth of 18 cm,
after mixing, or in any Ap horizon that is more than 18

em thick.
Hapludic Vermiborolls

HEED. Other Vermiborolls that have a chroma, moist,
after rubbing, of 1 or less in the upper part of the mollic
epipedon to a depth of 18 cm, after mixing, or in any Ap
horizon that is more than 18 cm thick.

Udie Vermiborolls

HEEE. Other Vermiborolls that have a mollic epipedon
less than 75 cm thick.

Haplic Vermiborolls
HEEF. Other Vermiborolls.

Typic Vermiborolls
RENDOLLS
Key to subgroups

HCAA. Rendolls that:

1, Have a soil temperature regime that is cryic or
pergelic; and

2, Have a lithic contact within a depth of 60 cm of the
surface.
Cryic Lithic Rendolls
HCAB. Other Rendolls that have a lithic contact within a
depth of 50 em of the surface.
Lithic Rendolls

HCAC. Other Rendolls that have a soil temperature
ime that is cryic or pergelic.
regi eryic or pergel


109

long in some part, and that extend to the eurface or to the
base of an Ap horizon if the soil is not irrigated; and

2. A coefficient of linear extensibility (COLE) of 0.07 or
more in a horizon or horizons at leat 50 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 125 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 125 cm; and.

3. More than 35 percent clay in horizons that total more
than 50 cm in thickness.
Vertic Haplustalfs

ICHD. Other Haplustalfs that:

1. Have mottles that have chroma of 2 or less within 75
em of the soil surface, and the mottled horizon is
saturated with water at some time during the year or the
soil has artificial drainage; and

2, Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic horizon that is more than 50 cm below

the soil surface.
Aquic Arenic Haplustalfs
ICHE. Other Haplustalfe that:

1 Have mottles that have chroma of 2 or less within 75
cm of the soil surface, and the mottled horizon is
saturated with water at some time during the year or the
soil has artificial drainage; and

2, Have an argillic horizon that has base saturation (by
sum of cations) of less than 75 percent throughout.
Aquultic Haplustalfs

ICHF. Other Haplustalfs that have mottles that have
chroma of 2 or less within 75 cm of the soil surface, and
the mottled horizon is saturated with water at some time
during the year or the soil has artificial drainage.

Aquic Haplustalfs

ICHG. Other Haplustalfs that have an argillic horizon
that is discontinuous horizontally, or is discontinuous
vertically in the upper 20 cm of its thickness, or has a
texture that is loamy fine sand or coarser.

Peammentic Haplustalfs

ICHH. Other Haplustalfs that:

1. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic horizon that is more than 50 cm below
the soil surface; and


(1) Do not have a mineral layer as much as 40 cm
thick either at the surface or whose upper boundary is
within a depth of 40 cm from the surface; and

(2) Do not have mineral layers, taken cumulatively,
as thick as 40 cm within the upper 80 cm; and

c. Do not have andic soil properties in layers 35 cm or
more thick within a depth of 60 cm from the surface.
Histosols, p. 225

B. Other soils that have andic soil properties throughout
subhorizons, whether buried or not, which have a
cumulative thickness of 35 cm or more within 60 cm of the
mineral soil surface or upper boundary of an organic
layer that meets andic soil properties, whichever is
shallower.

Andisols, p. 129

C. Other soils that do not have a plaggen epipedon but that
have either:

1. A spodic horizon whose upper boundary is within 200
om of the surface; or

2. A placic horizon that meets all the requirements of a
spodic horizon except thickness and index of
accumulation and rests on a fragipan, on a spodic
horizon, or on an albic horizon that rests on a fragipan.

Spodosols, p. 357
D. Other soils that have either:

1. An oxic horizon with its upper boundary within 150
em of the soil surface, and do not have a clay content
increase necessary to define the upper boundary of a
kandic horizon within a depth of 150 cm of the soil
surface, or

2. 40 percent or more clay in the surface 18 em, after
mixing, and, with its upper boundary within 160 cm of
the soil surface, either an oxic horizon, or a kandic
horizon that meets the weatherable mineral
requirements of an oxic horizon.

Oxisols, p. 335
E. Other soils that

1. Do not have a lithic or paralithic contact, petrocalcic
horizon, or duripan within 50 cm of the surface; and

2, After the soil to a depth of 18 cm has been mixed, as by
plowing, have 30 percent or more clay in all
subhorizons to a depth of 50 cm or more; and


208
Ustifluvents

Key to subgroups

KDCA. Ustifluvents that have the following combination
of characteristics:

1. Cracks at some period in most years, when the soil
is not irrigated, that are 1 cm or more wide at a depth of
50 em, that aro at least 30 cm long in some part, and
that extend upward to the soil surface or to the base of
an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.07
or more in @ horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 125 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 60 cm but
shallower than 125 cm; and

8, More than 35 percent clay in horizons that total more
than 60 cm in 5
Vertic Ustifluvents

KDCB, Other Ustifluvents that have mottles within 50 cm
of the surface that have chroma of 2 or leas or have, at 4
depth within 150 cm of the surface, a horizon that is
saturated with water at some period or is artificially
drained and that has chroma less than 1 or a hue bluer

than 10Y.
‘Aquic Ustiflavents

KDCC, Other Ustifluvents that have an Ap horizon that
has a color value, moist, of 3 or less and a color value,
dry, of 6 or lesa when crushed and smoothed, or the A
horizon is 15 em or more thick and has these colors.

Mollic Ustifluvents
KDCD, Other Ustifluvents.

‘Typie Ustifluvents
Xerofluvents
Key to subgroups

KDBA. Xerofluvents that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30cm
long in some part, and that extend upward to the soil
surface or to the base of an Ap horizon; and

2, A coefficient of linear extensibility (COLE) of 0.05
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 150 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 150 cm; and

3. More than 35 percent clay in horizons that total more
than 50 cm in thickness.
Vertic Xeroftuvents


23

materials. Such a horizon is highly toxic to plants and
virtually free of living roots.

OTHER DIAGNOSTIC SOIL CHARACTERISTICS
Abrupt textural change

An abrupt textural change is a change from an ochric
epipedon or an albic horizon to an argillic horizon. There
is, in the zone of contact, a very appreciable increase in
clay content within a very short distance in depth, Ifthe
clay content of the ochric epipedon or the albic horizon is
Jess than 20 percent, the clay content should double within
a distance in depth of 7.5 cm or less, If the clay content
exceeds 20 percent, the increase in clay content should be
at least 20 percent of the fine-earth fraction, for example,
from 22 percent to 42 percent, within a distance of 7.5 cm
in depth, and the clay content in some part of the argillic
horizon should be at least double that of the horizon above.
A transitional horizon normally is not present or is too
thin to be sampled. In some soils, however, there may be
tonguing or interfingering of albic materials, which are
defined later, in parts of the argillic horizon. The
horizon boundary in such a soil is irregular or even
discontinuous. The sampling of such a mixture as a
single horizon might create the impression of a relatively
thick transitional horizon, even though the thickness of
the actual transition at the contact may be only 1 mm or
80.

Andic soil properties

To have andic soil properties, the soil material must have
less than 25 percent organic carbon and meet one or both
of the following two requirements:

1. Either

a, Acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron is 2.0 percent or more in the
less than 2.0 mm fraction, and

b. Bulk density of the less than 2.0 mm fraction,

measured at 33 kPa water retention, is 0.90 g em” or
less, and

¢. Phosphate retention’ of the less than 2.0 mm fraction
is 85 percent or more; or

2. The less than 2.0 mm fraction has phosphate retention
of more than 25 percent and the 0.02 - 2.0 mm fraction is at
least 30 percent of the less than 2.0 mm fraction; and
meets one of the following three requirements:

7 iakenore, L.C.7 Searle, P.L.s Daly, B.X. 1987. Methods for chanical
apalyain of soils. NZ Soil Bureau Sodentifie Report #0. p. 44-45.


368

CDCF, Other Cryorthods that have more than 6 percent
organic carbon in the upper 10 cm of the spodic horizon.
Humic Cryorthods

CDCG. Other Cryorthods.
‘Typic Cryorthods

Fragiorthods
Key to subgroups
CDBA. Fragiorthods that have a eryic or pergelic
temperature regime.

Cryic Fragiorthods
CDBB. Other Fragiorthods that:

1, Have distinct or prominent mottles in the spodic
horizon; and

2, Have a spodic horizon that does not have any of the
following:

a. A continuous horizon that is at least 2.5 cm thick
and is very firm or extremely firm when moist
(ortstein); nor

b. A texture of very fine sand or finer, and a
thickness of more than 10 cm and at least 1.2 percent
organic carbon (weighted average) in the upper 10
cm; nor

c. A coarse-loamy, loamy-skeletal, sandy-skeletal,

or sandy particle-size class and color value and

chroma of 3 or less in at least the upper 7.5 cm.
Aquentic

CDBC. Other Fragiorthods that have distinct or
prominent mottles in the spodic horizon.
Aquic Fragiorthods

CDBD. Other Fragiorthods that have a surface horizon
more than 30 cm thick that meets all the requirements

for a plaggen epipedon except thickness,
Plaggeptic Fragiorthods

CDBE. Other Fragiorthods that have an argillic or
kandic horizon below the spodic horizon and have base
saturation of 35 percent or more in some part of the
argillic or kandic horizon or have a mean annual soil

temperature of less than 8°C.
Alfic Fragiorthods

CDBF. Other Fragiorthods that have an argillic or
kandic horizon below the spodic horizon.

Ultic Fragiorthods

CDBG. Other Fragiorthods that have a spodic horizon
that does not have any of the following:

1. A continuous horizon that is at least 2.5 cm thick
and is very firm or extremely firm when moist
(ortstein); nor


143,
BGFE. Other Hapludands that have 1N KCl-extractable
Al** of more than 2.0 cmol(+) kg" fine earth throughout a
layer 10 cm or more thick between 25 and 50 cm.
Alic Hapludands

BGFF. Other Hapludands that have, in some subhorizon
between 50 and 100 cm of the mineral soil surface or of
the upper boundary of an organic layer with andic soil
properties, whichever is shallower:

1. Two percent or more redox segregations; or

2. Dominant chromas, moist, of 2 or less on faces or
peds, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or less; or

3. Sufficient active ferrous iron to give a positive
reaction to a,a'-dipyridyl at some time of the year

when not being irrigated.
Aquic Hapludands

BGFG. Other Hapludands that have extractable bases plus
1N KCl-extractable Al of less than 2.0 cmol(+) kg’ fine
earth in some subhorizon 30 cm or more thick between 25
and 100 cm, and have, undried, 1500 kPa water retention
of 70 percent or more throughout a continuous thickness of
35 cm or more within the upper 100 cm.
Acrudoxic Hydric Hapludands

BGFH. Other Hapludands that have extractable bases
plus 1N KCl-extractable Al* of less than 2.0 cmol(+) kg?
fine earth in some subhorizon 30 cm or more thick
between 25 and 100 cm, and have, between 25 and 100m, a
layer 10 cm or more thick with more than 3.0 percent
organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the

underlying layer.
Acrudoxic Thaptic Hapludands

BGFI. Other Hapludands that have extractable bases plus
1N KCl-extractable Al** of less than 2.0 cmol(+) kg” fine
earth in some subhorizon 30 cm or more thick between 25
and 100 cm, and have an argillic or kandic horizon with
its upper boundary within 125 cm of the mineral soil
surface or of the upper boundary of an organic layer with
andic soil properties, whichever is shallower, and base
saturation (by sum of cations) of less than 35 percent
throughout the upper 60 cm of that horizon.

Acrudoxic Ultic Hapludands

BGFJ. Other Hapludands that have extractable bases plus
1N KCl-extractable Al®* of less than 2.0 cmol(+) kg? fine
earth in some subhorizon 30 cm or more thick between 25

and 100 cm.
Acrudoxic Hapludands

BGFK. Other Hapludands that have less than 30 percent,
undried, 1500 kPa water retention in some subhorizon
that meets the requirements for andic soil properties and
that is at least 25 cm thick within 100 cm of the mineral


2at

Chapter 10
Inceptisols
KEY TO SUBORDERS

JA, Inceptisols that

1, Have an aquic moisture regime or are artificially
drained and have one or more of the following:

a. A histic epipedon; or

b. A sulfuric horizon that has its upper boundary
within 50 cm of the mineral soil surface; or

c. An umbric or mollic epipedon that is underlain
immediately or at a depth of leas than 50 cm below
the soil surface by a horizon that has dominant
colors, moist, on ped faces, or in the matrix if peds
are absent, as follows:

()) If there is mottling, chroma is 2 or less;! or
(2) If there is no mottling, chroma is 1 or less; or

d. An ochric epipedon that is underlain at a depth of
less than 50 cm below the mineral soil surface by a
cambic horizon or a fragipan, either or both of which
have dominant color, moist, on ped faces, or in the
matrix if peds are absent as follows:

(2) If there is mottling, chroma is 2 or less;7or

(2) If there is no mottling, chroma is 1 or less; or
2, Have an SAR of 13 or more (or sodium saturation
that is 15 percent or more) in half or more of the soil to
a depth of 50 cm that decreases with depth below 50 cm,
and ground water within 100 cm of the surface at some
time of the year.

Aquepts, p. 242

JB, Other Inceptisols that have a plaggen epipedon.
Plaggepts, p. 263

JC. Other Inceptisols that have an isomesic or warmer
iso temperature regime.
‘Tropepts, p. 263

JD. Other Inceptisols that have an ochric epipedon; or
that have an umbric or mollic epipedon thet is leas than
25 cm thick and have also a mesic or warmer soil

temperature regime.
Ochrepts, p. 251

1
If the hue {a redder than 10YR because of red parant materials that
rennin red after oltrate-dithionite extraction, the requirement for low

ghee ta waived,

If the hue is redder than 10YR because of red parent saterials that
rewain red after oitrate-dithionite extraction, the requiresent fer low
chrome 46 waived.


373

Chapter 14
Ultisols
KEY TO SUBORDERS

GA. Ultisols, either saturated with water at some time of
year or artificially drained, that have characteristics
associated with wetness, namely, mottles, iron-
manganese concretions more than 2 mm in diameter, or
chroma, moist, of 2 or less immediately below any Ap or
Ahorizon that has a value, moist, of 3 or less when
rubbed; and also one or more of the following:

1. Dominant chroma, moist, of 2 or less in coatings on
the surface of peds and mottles within the peds, or
dominant chroma of 2 or less in the matrix of the
argillic or kandic horizon and mottles of higher
chroma (if the hue is redder than 10YR because of
parent materials that remain red after citrate-
dithionite extraction, the requirement for low chroma
is waived); or

2. Chroma, moist, of 1 or less on surfaces of peds or in
the matrix of the argillic or kandic horizon; or

3. Dominant hue of 2.5Y or 6Y in the matrix of the
argillic or kandic horizon and distinct or prominent
mottles and also a thermic or isothermic or warmer

soil temperature regime.
Aquults, p. 373
GB. Other Ultisols that have either or both of the
following characteristics:

1. Have 0.9 percent or more organic carbon in the
upper 16 cm of the argillic or kandic horizon; or

2, Have 12 kg or more orgenie carbon inthe soil por
square meter to a depth of 100 em below the top of
mineral soil surface, exclusive of any O horizon that
may be present.

Hurts, p. 379

GC. Other Ultisols that have a udic moisture regime.
Udults, p. 334

GD. Other Ultisols that have an ustic moisture regime.
Ustulte, p. 397

GE. Other Ultisols that have a xeric moisture regime.
p.403
AQUULTS

Key to great groupe

GAA. Aquults that have plinthite that forms a continuous
phase or constitutes more than half the matrix of some

subhorizon within 150 cm of the soil surface.
‘ Plinthaquults, p. 378.


376

Kandiaquults

Key to subgroups

GADA. Kandiaquults that have an ECEC (sum of bases
plus IN KCl-extractable Al) of 1.5 emol(+) or less per kg
clay in one or more subhorizons to a depth of 150 em

below the soil surface.
Acric Kandiaquults
GADB. Other Kandiaquults that:

1, Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic or kandic horizon that is 50 to 100 cm
below the soil surface; and

2, Have 5 percent or more plinthite (by volume) in one
or more subhorizons within 150 cm of the soil surface.
Arenic Plinthic Kandiaquults
GADC. Other Kandiaquults that:
1, Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the

top of an argillic or kandic horizon that is 50 to 100 cm
below the soil surface; and

2. Do not have an ochrie epipedon.
Arenic Umbric Kandiaquults
GADD. Other Kandiaquults that have a layer, starting at
the mineral soil surface, that has a sandy particle-size
class and extends to the top of an argillic or kandic

horizon that is 50 to 100 cm below the soil surface.
Arenic Kandiaqaults

GADE. Other Kandiaquults that have a layer, starting at
the mineral soil surface, that has a sandy particle-size
class and extends to the top of an argillic or kandic
horizon that is more than 100 cm below the soil surface.
Grossarenie Kandi

GADF. Other Kandiaquults that have 5 percent or more
plinthite (by volume) in one or more subhorizons within

150 cm of the soil surface.
Plinthic Kandiaquul

GADG. Other Kandiaquults that have a subhorizon that
has dominant chroma of 3 or more within 75 cm of the

soil surface.
Aeric Kandiaquolts
GADH. Other Kandiaquults that do not have an ochric
epipedon.
Umbric Kandiaquults

GADI. Other Kandiaquults.
Typic Kandiaquults


The color of a plaggen epipedon and its organic-carbon
content depend on sources of the materials used for
bedding.

The plaggen epipedon can be identified by several
means. Commonly it contains artifacts, such as bits of
brick and pottery, throughout its depth. Chunks of diverse
materials, such as black sand and light gray sand, as
large as the size held by a spade may be present. The
plaggen epipedon normally shows spade marks
throughout its depth and also remnants of thin stratified
beds of sand that probably were produced on the surface by
beating rains and later were buried by spading.

‘Umbric epipedon (L. umbra, shade, hence dark)

Requirements of the umbric epipedon are comparable to
those of the mollic epipedon in color, organic-carbon and
phosphorus content, consistence, structure, n value, and
thickness, The umbric epipedon includes those thick,
dark-colored surface horizons that have base saturation
of less than 50 percent (by NH,OAc). It should be noted
that the restriction against a hard or very hard and
massive epipedon when dry is applied only to those
epipedons that become dry. If the epipedon is always
moist, there is no restriction on its consistence or
structure when dry, It should also be noted that some
plaggen epipedons meet all these requirements but also
have evidences of slow addition of materials under
cultivation. The umbric epipedon does not have the
artifacts, spade marks, and raised surfaces that are
evidences of slow additions in the plaggen epipedon.

DIAGNOSTIC SUBSURFACE HORIZONS

The horizons discussed in this section form below the
surface of the soil, although in some places they form
immediately below a layer of leaf litter. They may be
exposed at the surface by truncation of the soil. Some of
these horizons are generally considered to be B horizons;
some are considered B horizons by many but not all
pedologists; others are generally considered to be parts of
the A horizon.

Agric horizon

The agric horizon (L. ager, field) is an illuvial horizon
formed under cultivation that contains significant
amounts of illuvial silt, clay, and humus. After long-
continued cultivation, changes in the horizon
immediately below the plow layer become apparent and
cannot be ignored in classifying the soil. The large pores
in the plow layer and the absence of vegetation
immediately after plowing permit turbulent flow of
muddy water to the base of the plow layer. Here the water
can enter wormholes or fine cracks between peds, and the
suspended materials are deposited as the water is


141
percent or more throughout a continuous thickness of 35

cm or more within the upper 100 em.
Acrudoxic Hydric Fulvudands

BGDF, Other Fulvudands that have extractable bases plus
IN KCl-extractable Al* of less than 2.0 cmol(+) kg’ fine
earth in some subhorizon 30 cm or more thick between 25
and 100 cm, and have an argillic or kandic horizon with
its upper boundary within 125 cm of the mineral soil
surface or of the upper boundary of an organic layer with
andic soil properties, whichever is shallower, and base
saturation (by sum of cations) of less than 36 percent
throughout the upper 50 cm of that horizon.

Acrudoxic Ultic Fulvudands

BGDG. Other Fulvudands that have extractable bases plus
IN KCl-extractable Al of leas than 2.0 cmol(+) kg" fine
earth in some subhorizon 30 cm or more thick between 25

and 100 cm.
Acrudoxic Fulvudands

BGDH. Other Fulvudands that have, undried, 1600 kPa
water retention of 70 percent or more throughout a
continuous thickness of 35 cm or more within the upper
100 cm, and have both more than 6.0 percent organic
carbon and colors of the mollic epipedon throughout at
least 50 cm of the upper 60 cm, excluding any overlying
jayers that do not have andic soil properties.

Hydric Pachic Fulvudands

BGDI. Other Fulvudands that have a sum of bases of
more than 25.0 cmol(+) kg’ fine earth throughout some
subborizon 15 cm or more thick between 25 and 75 cm,
and have both more than 6.0 mnt organic carbon and
colors of the mollic epipedon throughout at least 50 cm of
the upper 60 cm, excluding any overlying layers that do
not have andic soil properties.

Eutric Pachic Fulvudands

BGDJ. Other Fulvudands that have both more than 6.0
percent organic carbon and colors of the mollic epipedon
throughout at least 50 cm of the upper 60 cm, excluding
any overlying layers that do not have andic soil

properties.
Pachie Fulvudands

BGDK. Other Fulvudands that have, undried, 1500 kPa
water retention of 70 percent or more throughout a
continuous thickness of 35 cm or more within the upper
100 cm, and have, between 25 and 100 cm, a layer 10 cm
‘or more thick with more than 3.0 percent organic carbon
and colors of a mollic epipedon throughout, occurri
below a horizon or horizons, 10 cm or more thick, wit
color value 1 unit or more higher and organic carbon
content 1 percent or more lower than the underlying

layer.

Hydric Thaptic Fulvudands
BGDL. Other Fulvudands that have, undried, 1500 kPa
water retention of 70 percent or more throughout a
continuous thickness of 85 cm or more within the upper

100 cm.
Hydric Fulvudands


362
CAGC. Other Sideraquods that have an argillic or
kandic horizon.
Ultic Sideraquods

CAGD. Other Sideraquods that have a spodic horizon that
either:

1. Is not very firm or firmer in any subhorizon when
moist; or

2. Is 10 em or Jess thick or contains less than 1.2
percent organic carbon in the upper 10 cm.

Entic Sideraquods
CAGE, Other Sideraquods.

Typic Sideraquods
Tropaquods
Key to subgroups

CAEA. Tropaquods that:
1. Have a histic epipedon; and

2. Have a lithic contact within 50 cm of the surface.
Histic Lithic

CAEB. Other Tropaquods that have a lithic contact
within 60 cm of the surface.
Lithic Tropaquods

CAEC. Other Tropaquods that have a histic epipedon.
Histic

CAED. Other Tropaquods that
1. Have an umbric epipedon; and

2. Have a layer starting at the mineral soil surface
that has a sandy particle-size class throughout and
extends to at least the upper boundary of the spodic
horizon, and the upper boundary of the spodic horizon
is deeper than 75 cm below the soil surface.

Arenic Umbrie Tropaquods

CAEE. Other Tropaquods that have a layer starting at the
mineral soil surface that has a sandy particle-size class
throughout and extends to at least the upper boundary of
the spodic horizon, and the upper boundary of the spodic
horizon is between 75 and 125 cm below the soil surface.
‘Aeric Arenic Tropaquods

CAEF. Other Tropaquods that have a layer starting at the
mineral soil surface that has a sandy particle-size class
throughout and extends to at least the upper boundary of
the spodic horizon, and the upper boundary of the spodic
horizon is between 125 and 200 cm below the soil surface.
‘Aeric Grossarenic Tropaquods

CAEG. Other Tropaquods that have either


gat

DDEG. Other Haploperox that have mottles of 4 or more
value moist and 2 or less chroma within a depth of 125 cm

of the soil surface.
Aquic Haploperox

DDEH. Other Haploperox that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

‘Andic Haploperox

DDEI. Other Haploperox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and a color hue of 2.5YR or redder with

moist values of less than 4 in most of the 25 to 125 cm depth

from the soil surface.
Humic Rhodiec Haploparox

DDEJ. Other Haploperox that have 16 kg or more organic
carbon per square meter to a depth of 100 em, exclusive of
surface litter, and color hue of 7.5YR or yellower with

moist values of 6 or more in most of the 25 to 125 em depth

from the soil surface.
Humic Xanthic Haploperox

DDEK. Other Haploperox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of

surface litter.
Humic Haploperox:

DDEL. Other Haploperox that have a color hue of 2.5YR or
redder with moist values of less than 4 in most of the 25 to
125 cm depth from the soil surface.

Rhodic Haploperox

DDEM. Other Haploperox that have a color hue of 7.5YR
or yellower with moist values of 6 or more in most of the 25
to 126 cm depth from the soil surface.

‘Xanthic Haploperox
DDEN. Other Haploperox.
‘Typic Haploperox
Kandiperox
Key to subgroups

DDDA. Kandiperox that have mottles of 4 or more value
moist and 2 or less chroma within a depth of 125 cm of the
soil surface and a petroferric contact within 126 cm of the

soil surface.
Aquic Petroferric Kandiperox

DDDB. Other Kandiperox that have a petroferric contact
within 125 cm of the soil surface.

Petroferric Kandiperox
DDDC. Other Kandiperox that have mottles of 4 or more
value moist and 2 or less chroma within a depth of 125 cm


340

pp. Other Eutroperox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of

surface litter, and color hue of 7.5YR or yellower with

moist values of 6 or more in most of the 25 to 125 cm depth

from the soil surface.
Humic Xanthic Eutroperox

DDCM. Other Eutroperox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of

surface litter.
Humic Eutroperox
DDCN. Other Eutroperox that have a color hue of 2.5YR or

redder with moist values of less than 4 in most of the 25 to
125 cm depth from the soil surface.
Rhodic Eutroperox

DDCO, Other Eutroperox that have a color hue of 7.5YR or
yellower with moist values of 6 or more in most of the 25 to

125 cm depth from the soil surface.
Xanthic Eutroperox
DDOP. Other Eutroperox.
‘Typic Eatroperox
Haploperox
Key to subgroups

DDEA. Haploperox that have mottles of 4 or more value
moist and 2 or less chroma within a depth of 125 cm of the
soil surface and a petroferric contact within 125 cm of the

soil surface.
Aquic Petroferric Haploperox

DDEB. Other Haploperox that have a petroferric contact
within 125 cm of the soil surface.

Petroferric Haploperox

DDEC. Other Haploperox that have mottles of 4 or more
value moist and 2 or leas chroma within a depth of 125 cm
of the soil surface and a lithic contact within 125 cm of the

soil surface,
Aquic Lithic Haploperox

DDED. Other Haploperox that have a lithic contact within
a depth of 125 em of the soil surfs
Lithic Haploperox

DDEE. Other Hay that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the
soil surface and mottles of 4 or more value moist and 2 or
Jess chroma within a depth of 126 cm of the soil surface.
Plinthaquic Haploperox

DDEF. Other Haploperox that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the

soil surface.
Plinthic Haploperox


DCBK. Other Acrustox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and color hue of 7.5¥R or yellower with
moist values of 6 or more in most of the 25 to 125 cm depth

from the soil surface.
Humic Xanthic Acrustox

DCBL. Other Acrustox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter.

Humic Acrustox

DCBM. Other Acrustox that have a color hue of 2.5YR or
redder with moist values of less than 4 in most of the 25 to
125 cm depth from the soil surface.

Rhodic Acrustox

DCBN, Other Acrustox that have a color hue of 7.5YR or
yelloweér with moist values of 6 or more in most of the 25 to

125 em depth from the soil surface.
Xanthic Acrustox
DCBO. Other Acrustox.
Typic Acrustox
Eutrustox
Key to subgroups

DCCA. Eutrustox that have mottles of 4 or more value
moist and 2 or less chroma within a depth of 125 cm of the
soil surface and a petroferric contact within 125 cm of the

soil surface.
Aquic Petroferric Eutrustox

DCCB. Other Eutrustox that have a petroferric contact
within 125 cm of the soil surface.
Petroferric Butrustox

DCCC. Other Eutrustox that have mottles of 4 or more
value moist and 2 or less chroma within a depth of 125 cm
of the soil surface and a lithic contact within 125 cm of the

soil surface.
Aquic Lithic Eutrustox

DCCD. Other Eutrustox that have a lithic contact within a
depth of 125 cm of the soil surface.
Lithic Evtrustox

DCCE. Other Eutrustox that have more than 5 pervent
plinthite in some horizon within a depth of 125 cm of the
soil surface and mottles of 4 or more value moist and 2 or
less chroma within a depth of 125 cm of the soil surface.
Plinthaquic Eutrustox

DCCF. Other Eutrustox that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the

soil surface.
Piinthic Eutrustax


185

FBFTI. Other Camborthid: have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the soil
surface or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.05
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 150 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 150 cm; and

3, More than 36 percent clay in horizons that total more
than 50 em in thickness; and

4. In most years, unless irrigated, have cracks that
remain open for 175 to 240 days, cumulative, and the
cracks are not closed for as many as 60 consecutive
days during the 120 days following the winter solstice
in 3 or more years out of 10 if the soil temperature
regime is thermic, mesic, or frigid.

Ustertic Camborthids

FBFJ. Other Camborthids that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm.
long in some part, and that extend upward to the soil
surface or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.05
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 150 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 60 em but
shallower than 150 cm; and

3. More than 35 percent clay in horizons that total more
than 60 cm in thickness; and

4. Unless the soils are irrigated, the cracks remain
open in most years for more than 240 days,
cumulative, and are not closed in most years for as
many as 60 consecutive days at any season.

fextic Camborthids

FBFK. Other Camborthids that have the following
combination of characteristics:

1. Are saturated with water for 90 consecutive days or
more within 100 cm of the surface in most years or
have any of the following characteristics within 100
em of the soil surface if the soil of that zone is saturated
with water at some period in most years or the soil is
artificially drained:

a. Dominant chroma of 1 or leas throughout and hue
of 2.5Y or yellower in some part; or


931
within 110 cm if the average particle-size class is loamy;

or within 90 cm if it is clayey.
Calcic Haploxerclls
HDFZ. Other Haploxerolla that:

1. Do not have a cambic horizon, and the lower part of
the epipedon does not meet the requirements of a cambic
horizon except for color; and

2. Have base saturation (by sum of cations) of 75 percent
or less i some part within a depth of 75 cm from the soil
surface or above a lithic or paralithic contact,

whichever is shallower.
Entic Ultic Haploxerolls

HDFZa. Other Haploxerolls that have base saturation (by
sum of cations) of 75 percent or leas in some part within a
depth of 75 cm from the soil surface or above a lithic or

paralithic contact, whichever is shallower:

itic Haploxerolls

HDFZb, Other Haploxerolls that do not have a cambic
horizon, and the lower part of the epipedon does not meet
the requirements of a cambic horizon except for color, or
either the cambic horizon or the lower part of the epipedon
has carbonates throughout,

Entic Haploxerolls
HDFZc. Other Haploxerolis.

‘Typic Haploxerolls
Natrixerolls
Key to subgroups

HDBA, Natrixerolls that:

1, Have mottles that have chroma of 2 or less within 75
em of the soil surface; and

2. Have a horizon within 100 cm of the surface that ia
more than 16 cm thick and either contains at least 20
percent durinodes or is brittle and has firm consistence
when moist.

Aquic Duric Natrixerolls

HODBB. Other Natrixerolls that have mottles that have
chroma of 2 or less within 75 cm of the soil surface.

Aquic Natrixerolls
HDBC. Other Natrixerolls that have an aridic moisture
regime.
Aridic Natrixerolls

HDBD. Other Natrixerolls that have a horizon within 100
cm of the surface that is more than 15 cm thick and either
contains at least 20 percent durinodes or is brittle and has

firm consistence when moist.
Duric Natrixerolls

HODBE. Other Natrixerolls.
Typic Natrixerolls


GCD. Other Udults that have a CEC of 16 cmol(+) or less
per kg clay (by IN NH,OAc pH 7) and an ECEC of 12
emol(+) or less per kg clay (sum of bases extracted with
IN NH, OAc pH 7 plus 1N KCl-extractable Al) in the
major part of the argillic or kandic horizon, or the major
part of the upper 100 cm of the argillic or kandic horizon
if these horizons are thicker than 100 cm.
Kanhapludults, p. 391

GCE. Other Udults that do not have a lithic or paralithic
contact within 150 cm of the mineral soil surface and
that have a clay distribution such that the percentage of
clay does not decrease from its maximum amount by
more than 20 percent within 150 cm of the soil surface, or
the layer in which the clay percentage decreases by more
than 20 percent has at least 5 percent of the volume
consisting of skeletans on faces of peds and there is at
least 3 percent (absolute) increase in clay below the

layer.
Paloudults, p. 393
GCF. Other Udults that have

1. An epipedon that has a color value, moist, of 3 or less
in all parts; and

2, An argillic horizon that has a color value, dry, of
less than 5 and not more than 1 unit higher than the

value, moist.
Rhodudults, p. 397
GCG. Other Udults.
Hapludults, p. 387
Fragiudults
Key to subgroups

GCBA. Fragiudults that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and oxtends to the top of an argillic horizon that is 50 to

100 cm below the soil surface.
Arenic Fragiudults
GCBB. Other Fragiudults that:
1. Meet either of the following:

a. Do not have an argillic or kandic horizon above
the fragipan that has some clay skins on both
vertical and horizontal surfaces of some structural
aggregates; or

b. Have an intervening horizon (one or more)
between the argillic or kandic horizon and the
fragipan that has dominant chroma of 3 or less and
that has as much as 3 percent less clay (absolute)
than both the overlying argillic or kandic horizon
and the underlying fragipan; and

2. Have mottles that have chroma of 2 or less within 40
cm of the soil surface; and


28

commonly occurs as dark red mottles, which usually are
in 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 exposed also to heat from the
sun. The lower boundary of a zone in which plinthite
occurs usually is diffuse or gradual, but it may be abrupt
at a ithologic discontinuity.

Generally, plinthite forms in a horizon that is saturated
with water at some season. The original segregation of
the iron normally is in the form of soft, more or less
clayey, red or dark red mottles. The mottles are not
considered plinthite unless there has been enough
segregation of iron to permit irreversible hardening on
exposure to wetting and drying. Plinthite in the soil
usually is firm or very firm when the soil moisture
content is near field capacity and hard when the moisture
content is below the wilting point. Plinthite does not
harden irreversibly as a result of a single cycle of drying
and rewetting, After a single drying, it will remoisten,
and then it can be dispersed in large part by shaking in
water with a dispersing agent.

In a moist soil, plinthite is soft enough that it can be cut
with a spade. After irreversible hardening, it is no
longer considered plinthite but ia called ironstone,
Indurated ironstone materials can be broken or shattered
with a spade but cannot be dispersed by shaking in water
with a dispersing agent,

Potential linear extensibility

This characteristic is the sum of the products, for each
horizon, of the thickness of the horizon in centimeters and
the COLE of the horizon.

Sequum: number and kind

A sequence of an eluvial horizon and its subjacent B
horizon, if one is present, is called a sequum. An albic
horizon and a spodic horizon immediately underlying it,
for example, constitute a sequum. Similarly, a mollic
epipedon over a cambic horizon or an argillic horizon
over a k horizon also constitute a sequum. Two sequa
may be present in vertical sequence in a single soil, and
that sequence is called a bisequum.

Slickensides

Slickensides are polished and grooved surfaces that are
produced by one mass sliding past another. Some of them
occur at the base of a slip surface where a mass of soil
moves downward on a relatively steep slope.
Slickensides are very common in swelling clays in
which there are marked changes in moisture content.


167

between 0.6 percent and one-seventh percent if the
ratio of sand to clay is between 1.0 and 13; and a
weighted average percentage of organic carbon in the
soil to a depth of 18 cm that is one-fifth or more higher
than the values just stated if there is a paralithic
contact at a depth of lesa than 40 em but more than 18
cm; an

3, A mean annual soil temperature of 8°C or higher
and an aridic moisture regime that borders on an

ustic regime.
Arenie Ustollic Haplargids

FAEM. Other Haplargids that have the following
combination of characteristics:

1. A texture that is loamy fine sand or coarser in al]
subhorizons above a depth of 50 cm; and

2, Dry in all parts of the moisture control section three-
fourths or less of the time (cumulative) that the soil
temperature is 5°C or higher at a depth of 0 cm; and

3, A mean annual soil temperature of 8°C or higher
and an aridic moisture regime that borders on an

uatic regime.
Arenic Ustalfic Haplargids

FAEN. Other Haplargids that have a texture that is
loamy fine sand or coarser in all subhorizons above a

depth of 50 cm.
Arenic Haplargids

FAEO. Other Haplargids that have the following
combination of characteristics:

1, A horizon within 100 cm of the surface that is more
than 15 cm thick and that either contains 20 percent or
more (by volume) durinodes in a nonbrittle matrix or
is brittle and has firm consistence when moist; and

2. A weighted average percentage of organic carbon in
the upper 40 cm that is 0.6 percent or more if the
weighted average ratio of sand to clay in the soi] above
that depth is 1.0 or leas, or is one-seventh percent or
more if the ratio is 13 or more, or is intermediate
between 0.6 percent and one-seventh percent if the
ratio of sand to clay is between 1.0 and 13; anda
weighted average percentage of organic carbon in the
soi) to a depth of 18 cm that is one-fifth or more higher
than the values just stated if there is a paralithic
contact at a depth of less than 40 cm but more than 18
cm; ant

3. A mean annual soil temperature lower than 22°C,
mean summer and mean winter soil temperatures at
a depth of 60 cm that differ by 5°C or more, and an
aridic moisture regime that borders on a xeric

regime.
Durixerollic Haplargids
FAEP. Other Haplargids that have a horizon within 100

em of the surface that is more than 15 cm thick and that
either contains 20 percent or more (by volume) durinodes


278

less on ped surfaces or in the matrix; if there are
no mottles, chroma is 1 or less; or

(d) The hue is bluer than 10Y or the color is
neutral; or .

(e) The color results from uncoated mineral
grains; or

b. If the lower part of the mollic epipedon has chroma
of more than 1 but not more than 2, there are either

(1) Distinct or prominent mottles in the lower
mollic epipedon; or

(2) Base colors immediately below the mollic
epipedon that have one or more of the following
properties:
(a) Value of 4 and chroma of 2 and also some
mottles that have value of 4 or more and chroma
Jess than 2; or

(b) Value of 5 or more and chroma of 2 or leas
and also mottles that have higher chroma; or

(c) Value of 4 and chroma less than 2; or

4. A caleic or petrocalcic horizon that has its upper
boundary within 40 cm of the surface.
Aquolls, p. 278

HC. Other Mollisols that have all the following
characteristics:

1, Have a mollic epipedon that is not more than 50 cm
thick; and

2. Do not have an argillic horizon; and
3. Do not have a calcic horizon; and
4, The soi) materials in or immediately below any
mollic epipedon, including coarse fragments less than
7.5 cm in diameter, have a CaCO, equivalent of 40
percent or more; and
5. Have a udic moisture regime or a cryic temperature
regime,

Rendolls, p. 296

HD. Other Mollieols that have a xeric moisture regime or
an aridic moisture regime bordering on xeric but do not
have a cryic temperature regime.

Xerolls, p. 320


167
FBEN. Other Camborthids that:

1. Are dry in all parts of the moisture control section
for three-fourths or less of the time (cumulative) that
the soil temperature is 5°C or more at a depth of 60cm
‘unless the soil is irrigated, and have an aridic
moisture regime that borders on an ustic moisture
regime and a hyperthermic, thermic, or mesic soil
temperature regime; and

2. Have, throughout a cumulative thickness of 18 em or
more and within a depth of 75 cm, one or more of the
following:

a, Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders,
pumice, and pumice-like fragments make up more
than 66 percent of these fragments; or

b. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and
contains either:

(1) More than 30 percent voleanic glass; or

(2) At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Vitrustandic Camborthids

FBFO. Other Camborthids that have the following
combination of characteristics:

1, Have a horizon within 100 cm of the surface that is
more than 15 cm thick and either contains 20 percent
or more durinodes or is brittle and has firm
consistence when moist; and

2, Have a weighted average percentage of organic
carbon in the upper 40 cm that is 0.6 percent or more if
the weighted average ratio of sand to clay in the soil
above that depth is 1.0 or less, or is 0.15 percent or more
if the ratio is 13 or more, or is intermediate between 0.6
percent and one-seventh percent if the ratio of sand to
clay is between 1.0 and 13; and a weighted average
percentage of organic carbon in the soil to a depth of 18
cm that is one-fifth or more higher than the values just
stated if there is a paralithic contact at a depth of less
than 40 cm but more than 18 em; and

3. Have a mean annual soil temperature lower than
22°C, mean summer and mean winter soil
temperatures at a depth of 50 cm that differ by 5°C or
more, and an aridic moisture regime that borders on a

xeric regime.
Durixerollic Camborthids

FBFP. Other Camborthida that have a horizon within 100
cm of the surface that is more than 16 cm thick and either
contains 20 percent or more durinodes or ia brittle and
has firm consistence when moist.

Duric Camborthids


351

Haplustox, p. 353

DCBA. Acrustox that have mottles of 4 or more value
moist and 2 or less chroma within a depth of 125 cm of the
soil surface and a petroferric contact within 125 cm of the

soil surface.
Aquic Petroferrie Acrustox

DCBB. Other Acrustox that have a petroferric contact
within 125 cm of the soil surface.
Petroferric Acrustox

DCBC. Other Acrustox that have mottles of 4 or more value
moist and 2 or less chroma within a depth of 125 cm of the
soil surface and a lithic contact within 125 cm of the soil

surface.

DCBD. Other Acrustox that have a lithic contact within a
depth of 125 cm of the soil surface.
Lithic Acrustox

DCBE. Other Acrustox that have mottles of 4 or more value
moist and 2 or less chroma within a depth of 125 cm of the
soil surface and have a delta pH (KCl pH - 1:1 water pH)
with a 0 or net positive charge in some layer 18 cm or more
thick within a depth of 125 cm of the aoil surface.

DCBF. Other Acrustox that have a delta pH (KCI pH - 1:1
water pH) with a 0 or net positive charge in some layer 18
cm or more thick within a depth of 125 cm of the soil
surface.

Anionic Acrustox
DCBG. Other Acrustox that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the
soil surface.

Plinthie Acrustox

DCBH. Other Acrustox that have mottles of 4 or more
value moist and 2 or less chroma within a depth of 125 cm

of the soil surface.
Agquic Acrustox

DCBI. Other Acrustox that have more than 35 percent base
saturation (NH,OAc) in all parts within a depth of 125 cm
of the soil surface.

Eutric Acrustox

DCBJ. Other Acrustox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and a color hue of 2.5YR or redder with

moist values of Jess than 4 in most of the 25 to 125 cm depth

from the soil surface.
Humic Rhodic Acrustax


272
JEDB. Other Haplumbrepts that:

1, Have, throughout a cumulative thickness of 18 cm or
more and within a depth of 75 cm, bulk density of the
Jess than 2.0 mm fraction, measured at 33 kPa water
retention, of 1.0 g cm’? or less and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of more than 1.0 percent; and

2, Have mottles that have chroma of 2 or less within 50
cm of the soil surface, and the mottled horizon is
saturated with water at some time of the year when its
temperature is more than 5°C, or there is artificial

drainage.
Aquandic Haplumbrepts

JEDC, Other Haplumbrepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm* or less
and acid-oxelate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of more than 1.0 percent.
Andic

JEDD. Other Haplumbrepts that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2. The 0.02 to 2,0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a, More than 30 percent volcanic glass; or

b, At least 5 percent volcanic glass and acid-oxalate-

extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.
Vitrandic

JEDE. Other Haplumbrepts that:
1. Do not have a cambic horizon; and
2, Have sandy particle-size class from the mineral soil
surface to a depth of 100 cm or more, and have in the 0.02
to 2.0 mm fraction more than 90 percent silica

minerals (quartz, chalcedony or opal) or other
extremely durable minerals that are resistant to

weathering.
Quartzipeammentic Haplumbrepts

JEDF. Other Haplumbrepts that have a sandy particle-
size class from the mineral soil surface to a depth of 100

cm or more.
Psammentic Haplumbrepts


ais

Ifa surface horizon has properties of both A and E
horizons but the feature emphasized is an
accumulation of humified organic matter, it is
designated an A horizon. In some places, as in warm
arid climates, the undisturbed surface horizon is less
dark than the adjacent underlying horizon and
contains only smal} amounts of organic matter. It
has a morphology distinct from the C layer, though the
mineral fraction is unaltered or only slightly altered
by weathering. Such a horizon is designated A
because it is at the surface. However, recent alluvial
or colian deposits that retain fine stratification are not
considered to be an A horizon unless cultivated.

E horizons: Mineral horizons in which the main feature
is loss of silicate clay, iron, aluminum, or some
combination of these, leaving a concentration of sand
and silt particles and exhibiting obliteration of all or
much of the original rock structure?.

An E horizon is usually, but not necessarily, lighter in
color than an underlying B horizon. In some soils the
color is that of the sand and silt particles, but in many
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 and it generally has less
organic matter than the A horizon. An E horizon is
most commonly differentiated from an underlying B
horizon in the same sequum by color of higher value or
lower chroma or both, by coarser texture, or by a
combination of these properties. An E horizon is
commonly near the surface below an O or A horizon
and above a B horizon, but the symbol E can be used for
eluvial horizons within or between parts of the B
horizon or that extend to depths greater than normal
observation if the horizon has resulted from soil
genesis.

B horizons: Horizons that formed below an A, E, or O
horizon and that are dominated by ¢ obliteration of all or
much of the original rock structure and show one or
more of the following:

(1) illuvial concentration of silicate clay, iron,
aluminum, humus, carbonates, gypsum, or silica,
alone or in combination;

(2) evidence of removal of carbonates;

(8) residual concentration of sesquioxides;

(4) coatings of sesquioxides that make the horizon
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 granular, blocky, or

2
Rock structure inctodes fine stratification in unconsolidated sediment or perudamorpha
f weathered minnrale retaining their postions relative to each other and to unweathered
minerals in asprohte from consotidated rocks,
2
Rock structure ineludes fine stratification in unconsolidated ealimant or peeudomarpha
of weathared minerals retaining their positions relative to each other and to unwenthbered
‘minerals in oxprolite from consolidated rocks,


ICCB, Other Ustropepts that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30cm
long in some part, and that extend upward to the soil
surface or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.07 or
more in a horizon or horizons at least 60 com thick, and
a potential linear extensibility of 6 cm or more in the
upper 125 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 125 em; and

3. More than 38 percent clay in horizons that total more
than 50 em in thickness.
Vertic Ustropepts

ICCC. Other Ustropepts that have mottles that have
chroma of 2 or less within 100 cm of the soil surface, and
the mottled horizon is saturated with water at some time of
the year, or there is artificial drainage.
Aquic Ustropepts
ICCD. Other Ustropepts that have a CEC (by NH,OAc pH 7)
of less than 24 cmol(+) per kg clay! in the major part of
the soil below a depth of 25 em but above 100 cmor a lithic
or paralithic contact if one is shallower than 100 cm.
Oxic Ustropepts
ICCE. Other Ustropepts that:
1, Have a content of organic carbon that decreases
irregularly with depth, or are 125 cm or more deep to a
lithic or a paralithic contact and have more than 0.2

percent organic carbon at 125 cm below the soil surface;
and

2. Have slopes of 25 percent or less.

Fluventic Ustropepts
JCCF, Other Ustropepts.
Typic Ustropepts
UMBREPTS
Key to great groupe
JEA. Umbrepts that have a fragipan.
Fragiumbrepts, p. 271

JEB. Other Umbrepts that have a cryic or pergelic
temperature regime.
Cryumbrepts, p. 270

6
‘Some cambic horisona that have properties thet approach those of an oxic honson de net
iaperse weil. Ifthe ratio ofthe percentage of water retained at tenmion of 1500 kPs to the
oti clay ia 06 cr mere, the of lay by the
Iugher value of (1) the measured percentage of clay or (2) 2.6 times the percentage of water
‘tained at tansian of 1600 kPa,



97

and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic Hapludalfs

IEKE, Other Hapludalfs that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2, The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the Jess than 2.0 mm fraction and contains
either:

a, More than 30 percent volcanic glass; or

b, At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus V/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vitrandic Hapludalfs

TEKF. Other Hapludalfs that:
1, Have an argillic horizon that

a, If its upper boundary is less than 50 cm below the
soil surface, has mottles that have chroma of 2 or less
in the upper 25 cm, and it is saturated with water
within that depth at some time when the soil
temperature is 5°C or higher; or

b, If the upper boundary of the argillic horizon is
deeper than 50 cm, has mottles that have chroma of 2
or less within a depth of 75 cm below the soil surface;
and

2. Have an argillic horizon that is discontinuous
horizontally, or is discontinuous vertically in the upper
20 cm of its thickness, or has a texture that is loamy fine

sand or coarser.
Psammaquentic Hapludalfs

IEKG. Other Hapludalfs that have an argillic horizon
that is discontinuous horizontally, or is discontinuous
vertically in the upper 20 cm of its thickness, or has a
texture that is loamy fine sand or coarser.

Peammentic Hapludalfs

IEKH. Other Hapludalfs that:
1. Have an argillic horizon that

a. If its upper boundary is less than 50 cm below the
soil surface, has mottles that have chroma of 2 or less


140

BGBC. Other Durudands that have, undried, 1500 kPa
water retention of 70 percent or more throughout a
continuous thickness of 35 cm or more within the upper
100 cm, and have both more than 6.0 percent organic
carbon and colors of a mollic epipedon throughout at
least 50 cm of the upper 60 cm, excluding any overlying
layers that do not have andic soil properties.

Hydrrie Pachic Durudands

BGBD. Other Durudands that have, between 25 and 100
em, a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm.
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the
underlying layer.

‘Thaptic Durudands
BGBE. Other Durudands.
Typic Durudands
Fulvudands
Key to subgroups

BGDA. Fulvodands that have, undried, 1500 kPa water
retention of 70 percent or more throughout 4 continuous
thickness of 35 cm or more, and have a lithic contact
within 50 cm of the soil surface.

Hydric Lithic Fulvudands

BGDB. Other Fulvudands that have a lithic contact
within 50 cm of the soil surface.
Lithie Fulvudands

BGDC. Other Fulvudands that have 1N KCl-extractable
Al** of more than 2.0 emol(+) kg’ fine earth throughout a
layer 10 cm or more thick between 25 and 50 cm.

Alic Fulvadands
BGDD. Other Fulvudands that have, in some subhorizon
between 60 and 100 cm of the mineral soil surface or of

the upper boundary of an organic layer with andic soil
properties, whichever is shallower:

1, Two percent or more redox segregations; or

2. Dominant chromas, moist, of 2 or less on faces of
ped, or in the matrix if peds are absent, other than in
any horizon that has color values, moist, of 3 or leas; or

3. Sufficient active ferrous iron to give a positive
reaction to a,a'-dipyridyl at some time of the year
when not being irrigated.

Aquic Fulvudands

BGDE. Other Fulvudands that have extractable bases plus
1N KCl-extractable Al** of less than 2.0 cmol(+) kg? fine
earth in some subhorizon 30 cm or more thick between 25
and 100 cm, and have, undried, kPa water retention of 70


undrained, are continuously saturated with water in the
mottled horizon for 90 days or more in most years.
Aquic

HEGN. Other Haploborolls that:
1. Have both of the following:

a. Acolor value, dry, of 6 in the upper 18 cm of the
mollic epipedon, after mixing, or in any Ap horizon
that is more than 18 cm thick; and

'b. A moisture control section that is dry in some part
six-tenths or more of the time that the soil
temperature at a depth of 50 cm is above 5°C in most
years; and

2. Have an irregular decrease in organic carbon
content with increasing depth, or have an organic
carbon content of more than 0.3 percent at a depth of 125
em below the surface; and

8. Have a slope of less than 25 percent.
Torrifluventic Haploborolls

HEGO. Other Haploborolls that have the following
combination of characteristics:

1. Acolor value, dry, of 6 in the upper 18 cm of the mollic
epipedon, after mixing, or in any Ap horizon that is
more than 18 cm thick; and

2. A moisture control section that ia dry in some part
six-tenths or more of the time that the soil temperature
at a depth of 60 cm is above 5°C in most years; and

8. Do not have a cambic horizon, and the lower part of
the mollic epipedon does not meet the requirements of a
cambic horizon except for color,

Torriorthentic Haploborolls

HEGP. Other Haploborolls that have both of the following:

1. Acolor value, dry, of 5 in the upper 18 cm of the mollic
epipedon, after mixing, or in any Ap horizon that is
more than 18 cm thick; and

2, A moisture control section that is dry in some part

six-tenths or more of the time that the soil temperature

at a depth of §0 cm is above 5°C in most years.

Aridic Haploborolis

HEGQ. Other Haploborolls that have an irregular
decrease in organic carbon content with increasing
depth, or have an organic carbon content of more than 0.3
percent at a depth of 125 cm below the surface; and have a

slope of leas than 25 percent.
Fluventic Haploborolls
HEGR. Other Haploborolls that:
1, Have a chroma, moist, after rubbing of 1 or less in the

upper part of the mollic epipedon after it has been mixed
to a depth of 18 cm, or in any Ap horizon that is more


90

IBFE, Other Glossoboralfs that have an argillic horizon

that has a texture that is loamy fine sand or coarser or is

discontinuous vertically in the upper 15 cm (in lamellae).
Psammentic Glossoboralfe

IBFF. Other Glossoboralfs that do not have tongues of
albic materials in the argillic horizon.
Eutric Glossoboralfs

IBFG. Other Glossoboralfe.
Typic Glossoboralfs

Natriboralfs

Natriboralfs are the Boralfs that have a natric horizon.
‘They are rare in the United States, and subgroups have
not been developed.

Paleboralfs

Key to subgroups

IBAA, Paleboralfs that have, throughout a cumulative
thickness of 18 cm or more and within a depth of 75 cm,
bulk density of the less than 2.0 mm fraction, measured at
33 kPa water retention, of 1.0 gem” or less and acid-
oxalate-extractable aluminum plus 1/2 acid-oxalate-

extractable iron of more than 1.0 percent.
Andic Paleboralfs

IBAB. Other Paleboralfs that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1. Fragments coarser than 2.0 mm constitute more than
35 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

2. The 0,02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vitrandic Paleboralfs

IBAC. Other Paleboralfs that have mottles that have
chroma of 2 or less within 100 cm of the surface.
Aquic Paleboralfs

IBAD. Other Paleboralfs that have an argillic horizon
that has an increase in clay content of 20 percent or more


317
Paleustolls

Key to subgroups
HFCA. Paleustolls that:
1. Have the following combination of characteristics:

a. Cracks at some period in most years that are 1 cm
or more wide at a depth of 50 cm, that are at least 30
cm long in some part, and that extend upward to the
surface or to the base of an Ap horizon; and

b. A coefficient of linear extensibility (COLE) of 0.07
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more
in the upper 125 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 125 cm; and

c. More than 36 percent clay in horizons that have
total thickness of more than 50 cm; and

2, The cracks are open for more than 180 days,
cumulative, in most years.
Torrertic Paleustolls

HFCB. Other Paleustolls that:

1 When neither irrigated nor fallowed to store
moisture:

a. If the soil temperature regime is mesic or thermic,
are dry for four-tenths or less of the cumulative days
in some part of the moisture control section when the
soil temperature at a depth of 50 cm exceeds 5°C; or

b. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or
Jess during o period when the soil temperature at a
depth of 60 cm exceeds 8°C; and

2, Have the following combination of characteristics:

a. Cracks at some period in most years that are 1 em
or more wide at a depth of 50 cm, that are at least 30
em long in some part, and that extend upward to the
surface or to the base of an Ap horizon; and

b. A coefficient of linear extensibility (COLE) of 0.07
or more in a horizon or horizons at least 50 cm thick,
and a potential] linear extensibility of 6 cm or more
in the upper 125 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 125 cm; and

c, More than 36 percent clay in horizons that have
total thickness of more than 50 cm; and

3. The cracks are open less than 135 days, cumulative,
in most years.
Udertic Paleustolls


220

or more durisodes or is brittle and has firm
consistence when moist; and

2, Are dry in all parts of the moisture control section
for less than three-fourths of the time (cumulative) that
the soil temperature at a depth of 50 cm is 5°C or

and have a thermic, mesic, or frigid soil temperature
regime and a torric moisture regime that borders on

xeric.
Durorthidic Xeric Torripeamments

KCBC. Other Torripaamments that have a horizon
within 100 cm of the surface that is more than 16 cm thick
and either contains 20 percent or more durinodes or is
brittle and has firm consistence when moist.
Durorthidic Torripsamments

KCBD. Other Torripsamments that are dry in all parts
of the moisture control section less than three-fourths of
the time (cumulative) that the soil temperature at a depth
of 50 cm is 6°C or higher and have a torric moisture
regime that borders on an ustic regime.

jstic Torripsamments

KCBE. Other Torripaamments that are dry in all parts of
the moisture control section less than three-fourths of the
time (cumulative) that the soil temperature at a depth of
50 cm is 5°C or higher and have a thermic, mesic, or
frigid soil temperature regime and a torric moisture
regime that borders on a xeric regime. -

‘Xeric Torripsamments

KCBF. Other Torripsamments.
‘Typic Torripsamments

Tropopsamments
Key to subgroups
KCEA. Tropopsamments that have a lithic contact
within 50 cm of the soil surface.

Lithic Tropopsamments
KCEB. Tropopsamments that have mottles above a depth
of 100 cm that have chroma of 2 or less, or if the color is
due to uncoated sand grains, have a ground-water table

within 100 cm of the soil surface for 60 or more
cumulative days in most years.

Aquic Tropopaamments
_ KCEC. Other Tropopsamments.
Typic Tropopsamments
Udipsamments
Key to subgroups

KCDA. Udipsamments that have a lithic contact within a
depth of 50 cm.
Lithic Udipeamments


194

or is 0.15 percent or more if the ratio is 13 or more, or is
intermediate if the ratio of sand to clay is between 1.0
and 13; and have a weighted average percentage of
organic carbon in the surface soil to a depth of 18 cm
that is one-fifth or more higher than the values just
stated if there is a petrocalcic horizon that is shallower
than 40 cm but deeper than 18 cm; and

2, Have an aridic moisture regime that borders on an
ustic regime.
Ustollic Paleorthids
FBBE. Other Paleorthids that:

1, Are dry in all parts of the moisture control section
for three-fourths or less of the time (cumulative) that
the soil temperature is °C or higher at a depth of 50 em;
and

2. Have a mean annual soil temperature lower than
22°C, mean summer and mean winter soil
temperatures at a depth of 50 cm that differ by 5°C or
more, and have an aridic moisture regime that

borders on a xeric regime.
Xerochreptic Paleorthids
FBBP, Other Paleorthids that:

1, Are dry in all parts of the moisture control section
for three-fourths or less of the time (cumulative) that
the soil temperature is 5°C or higher at a depth of 50 cm;
and

2. Have a mesic, thermic, or hyperthermic soil
temperature regime and an aridic moisture regime

that borders on an ustic regime.
Paleorthide
FBBG, Other Paleorthids.
‘Typic Paleorthids
Salorthids
Key to subgroups

FBAA. Salorthids that have a weighted average content
of organic carbon in the upper soil to a depth of 40 cm that
is 0.6 percent or more if the weighted average ratio of
sand to noncarbonate clay to this depth is 1,0 or less, or is
0.15 percent or more if the ratio is 13 or more, or is
intermediate if the ratio of sand to clay is between 1.0

and 13.
Aquollic Salorthids

FBAB. Other Salorthids.
Typic Salorthids


355

DCEN, Other Haplustox that have a color hue of 7.5YR or
yellower with moist values of 6 or more in most of the 25 to
125 cm depth from the soil surface.

Xanthic Haplustox
DCEO. Other Haplustox.
Typic Haplustox
Kandiustox
Key to subgroups

DCDA. Kandiustox that have mottles of 4 or more value
moist and 2 or less chroma within a depth of 125 cm of the
soil surface and a petroferric contact within 125 cm of the

soil surface,
Aquic Petroferric Kandiustox

DCDB. Other Kandiustox that have a petroferric contact
within 125 cm of the soil surface.

Petroferric Kandiustox
DCDC. Other Kandiustox that have mottles of 4 or more

value moist and 2 or less chroma within a depth of 125 cm
of the soil surface and a lithic contact within 125 cm of the

soil surface.
Aquic Lithic Kandiustox

DCDD. Other Kandiustox that have a lithic contact within
a depth of 125 cm of the soil surface.
Lithic Kandiustox

DCDE. Other Kandiustox that have more than 5 percent
pliathite in some horizon within a depth of 125 cm of the
soil surface and mottles of 4 or more value moist and 2 or
less chroma within a depth of 125 cm of the soil surface.
Kandiustox

DCDF. Other Kandiustox that have more than 5 percent
Plinthite in some horizon within a depth of 125 cm of the

soil surface.
Plinthic Kandiustox

DCDG. Other Kandiustox that have mottles of 4 or more
value moist and 2 or less chroma within a depth of 125 em

of the soil surface.
Aquic Kandiustox

DCDH. Other Kandiustox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and a color hue of 2.5YR or redder with
moist values of less than 4 in most of the 25 to 125 cm depth

from the soil surface.

Humic Rhodic Kandiustox
DCDI. Other Kandiustox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and color hue of 7.5YR or yellower with
moist values of 6 or more in most of the 25 to 125 cm depth

from the soil surface.
Humnic Xanthic Kandiustox


withdrawn into capillary pores. The worm channels, root
channels, or ped surfaces become coated with a dark-
colored mixture of organic matter, silt, and clay. The
accumulation on the sides of wormholes becomes thick
and eventually can fill them. If worms are scarce, the
accumulation may take the form of thick lamellae that
may range in thickness from a few millimeters to about 1
cm. The coatings on the sides of wormholes and lamellae
always have lower color value and chroma than the soil
matrix.

The agric horizon has somewhat different forms in
different climates if there are differences in soil fauna.
In a humid temperate climate, where soils have what is
later defined as a udic moisture regime and a mesic
temperature regime, earthworms can become abundant.
If there are earthworm holes that, with their coatings,
constitute 5 percent or more of the volume and if the
coatings are 2 mm or more thick and have color value of 4
or less and chroma of 2 or less, moist, the horizon is
considered an agric horizon. After long-continued
cultivation, tho content of organic matter is not likely to
be high, but the carbon-nitrogen ratio in the agric horizon
is low, usually less than 8. The pH of the agric horizon is
close to neutrality, 6 to 6.5.

In a Mediterranean climate, where soils have what is
later defined as a xeric soil moisture regime, earthworms
are less common and the illuvial materials accumulate
as lamellae directly below the Ap horizon. If the lamellae
are 5 mm or more thick, have color value of 4 or less,
moist, and chroma of 2 or less, and constitute 5 percent or
more by volume of a horizon thet is 10 cm or more thick,
the horizon is considered an agric horizon.

Albic horizon

The albic (L. albus, white) horizon is one from which clay
and free iron oxides have been removed or in which the
oxides have been segregated to the extent that the color of
the horizon is determined by the color of the primary sand
and silt particles rather than by the coatings on these
particles. An albic horizon may be at the surface of the
mineral soil; it may lie just above an argillic or a spodic
horizon; it may lie between a spodic horizon and either a
fragipan or an argillic horizon; or it may lie between an
argillic horizon and a fragipan or between a cambic
horizon and an argillic horizon, natric horizon, or
fragipan. It is usually underlain by a spodic, natric, or
argillic horizon, a fragipan, or a relatively impervious
layer that can produce a perched water table and either
stagnant or moving water.

Deep deposits of pure white sand can be formed by wind or
wave action. Although these deposits have the apparent
morphology of an albic horizon, they are in fact a parent
material. The white sand in such a deposit does not


IEDC. Other Glossudalifs that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic horizon that is more
than 50 cm below the soil surface.

Arenic Glossudalfs

IEDD. Other Glossudalfs that do not have tongues of albic
materials that extend through at least the upper 50 cm of
the argillic horizon.

Haplic Glossudalfs
IEDE. Other Glossudalfs.
Typic Glossudalfs
Hapludalfs
Key to subgroups

IEKA. Hapludalfs that:

1. Have mottles with chroma of 2 or less in the upper 25
cm of the argillic horizon, or throughout the argillic
horizon if the argillic horizon is thinner than 25 cm,
and are saturated with water within that depth at some
time when the soil temperature is 5°C or higher; and

2. Have a lithic contact within 50 cm of the soil surface.
‘Aquic Lithic Hapludalfs

IEKB. Other Hapludalfs that have a lithic contact within
50 cm of the soil surface.
Lithic Hapludalfs

IEKC. Other Hapludalfs that have the following
combinations of characteristics:

1. Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm and at least 30 cm long in
some part and that extend to the surface or to the base of
‘an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.09 or
more in a horizon or horizons at least 50 cm thick, and
a potential linear extensibility of 6 em or more in the
upper 100 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 100 cm; and

3. More than 36 percent clay in horizons that total more
than 50 cm in thickness within the control section.
Vertic Hapludelfs

IEKD, Other Haphidalfs that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g em’ or less


369

2. A texture of very fine sand or finer, and a thickness
of more than 10 cm and at least 1.2 percent organic
carbon (weighted average) in the upper 10 cm; nor

3. A coarse-loamy, loamy-skeletal, sandy-skeletal, or
sandy particle-size class and color value and chroma
of 3 or less in at least the upper 7.5 cm.

Entic Fragiorthods
CDBH. Other Fragiorthods.

‘Typic Fragiorthods
Haplorthods
Key to subgroups

CDEA. Haplorthode that:

1. Have a spodic horizon that does not have any of the
following:

a. A continuous horizon at least 2.5 cm thick that is
very firm or extremely firm when moist (ortstein);
nor

b. A texture of very fine sand or finer, and a
thickness of more than 10 cm and a weighted
average of at least 1.2 percent organic carbon in the
‘upper 10 cm; nor

c. A coarse-loamy, loamy-skeletal, sandy-skeletal,
or sandy particle-size class and color value and
chroma, moist, of 3 or less in at least the upper 7.5
em of the spodic horizon; and

2. Have a lithic contact within 50 cm of the surface.
Entic Lithic Haplorthods

CDEB. Other Haplorthods that have a lithic contact
within 60 cm of the surface.
Lithic Haplorthods

CDEC. Other Haplorthods that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm® or leas
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic Haplorthods

CDED, Other Haplorthods that have a horizon 15 cm or
more thick below the spodic horizon and within 100 cm of
the surface that has a brittle matrix when wet or contains

some durinodes.
Duric Haplorthods
CDEE. Other Haplorthods that:

1. Have distinct or prominent mottles of approximate
spherical shape in the spodic horizon and the
variability in color is not associated with differences
in consistence in such a manner that the redder or
darker parts are extremely firm or very firm, and, if


168

FBFQ,. Other Camborthids that have a content of organic
carbon that decreases irregularly with depth below a
dopth of 25 em or, unless a lithic or paralithic contact
occurs at a shallower depth, has a level of 0.2 percent or
more at a depth 125 cm below the surface.

Fluventic Camborthids

FBFR. Other Camborthids that:
1. Have an anthropic epipedon; and

2. Have a weighted average percentage of organic
carbon in the upper 40 cm that is 0.6 percent or more if
the weighted average ratio of sand to clay in the soil
above that depth is 1.0 or less, or is 0.15 percent or more
if the ratio is 13 or more, or is intermediate between 0.6
percent and one-seventh percent if the ratio of sand to
clay is between 1.0 and 13; and a weighted average
percentage of organic carbon in the soil to a depth of 18
cm that is one-fifth or more higher than the values just
stated if there is @ paralithic contact at a depth of less
than 40 cm but more than 18 em.

‘Camborthids

FBFS. Other Camborthids that:

1. Have a weighted average percentage of organic
carbon in the upper 40 em that is 0.6 percent or more if
the weighted average ratio of sand to clay in the soil
above that depth is 1.0 or less, or is 0.15 percent or more
ifthe ratio is 13 or more, or is intermediate between 0.6
percent and one-seventh percent if the ratio of sand to
clay is between 1.0 and 13; and a weighted average
percentage of organic carbon in the soil to a depth of 18
‘cm that is one-fifth or more higher than the values just
stated if there is @ paralithic contact at a depth of less
than 40 cm but more than 18 cm; and

2. Have a mean annual soil temperature lower than
22°C, mean summer and mean winter soil
temperatures at a depth of 50 cm that differ by 5°C or
more, and an aridic moisture regime that borders on a

xeric regime.
Xerollic Camborthids
FBFT. Other Camborthids that:

1, Have a weighted average percentage of organic
carbon in the upper 40 cm that is 0.6 percent or more if
the weighted average ratio of sand to clay in the soil
above that depth is 1.0 or less, or is 0.15 percent or more
if the ratio is 13 or more, or is intermediate between 0.6
percent and one-seventh percent if the ratio of sand to
clay is between 1.0 and 13; and a weighted average
percentage of organic carbon in the soi} to a depth of 18
cm that is one-fifth or more higher than the values just
stated if there is a paralithic contact at a depth of less
than 40 cm but more than 18 cm; and

2, Have an aridic moisture regime that borders on an
ustic regime.
Ustollic Camborthids


101

Kandiudalfs

Key to subgroups
IEGA, Kandiudalfs that:

1. Have mottles that have chroma of 2 or less within 75
cm of the soil surface, and the mottled horizon is
saturated with water at some time when the soi]
temperature at that depth is 5°C or higher or the soil has
artificial drainage; and

2. Have 5 percent or more plinthite by volume in one or
more subhorizons within 150 cm of the soil surface.

Kandindalfs

IEGB, Other Kandiudalfs that have mottles that have
chroma of 2 or less within 75 cm of the soil surface, and
the mottled horizon is saturated with water at some time
when the soil temperature at that depth is 5°C or higher or
the soil has artificial drainage.

Aquic Kandiudalfs

IEGC, Other Kandiudalfs that:

1. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic or kandic horizon that is 50 to 100 cm
below the soil surface; and

2, Have & percent or more plinthite by volume in one or
more subhorizons within 150 cm of the soil surface.
Arenic Plinthic Kandiudalfs

TEGD, Other Kandiudalfs that:

1. Have a layer, starting at the mineral soil surface,

that has a sandy particle-size class and extends to the
top of an argillic or kandic horizon that is more than
100 cm below the soil surface; and

2. Have 5 percent or more plinthite by volume in one or
more subhorizons within 150 cm of the soil surface.
Grossarenic Plinthic Kandiudalfs

IEGE. Other Kandiudalfs that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic or kandic horizon that
is 50 to 100 cm below the soil surface.

Arenic Kandiudalfs

IEGF. Other Kandiudalfs that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic or kandic horizon that
is more than 100 cm below the soil surface,

Groasarenic Kandiudalfs


225
Chapter 9
Histosols

KEY TO SUBORDERS

AA. Histosols that are never saturated with water for
more than a few days following heavy rains; and

1, Have a lithic or paralithic contact less than 100 cm

from the surface or have fragmenta] materials in

which the interstices are filled or partly filled with

grgenio materials in half or more of each pedon, or
th;

2, Less than three-fourths of the thickness of organic
materials consists of Sphagnum fibers.
Folists, p. 231

AB. Other Histosols that

1. Are dominantly’ fibric in the subsurface tier if that
tier is wholly organic except for a thin mineral layer
or layers, or the organic parts of the surface and
subsurface tiera are dominantly fibric if a continuous
mineral layer 40 cm or more thick begins within the
depth limit of the subsurface tier; or

2. Have a surface mantle that has three-fourths or
more of its volume consisting of fibers derived from
Sphagnum and that rests on a lithic or paralithic
contact, fragmenta] materials, or mineral soil, or on
frozen? materials within the limita in depth of the
surface or subaurface tier; and

3, Do not have a sulfuric horizon whose upper
boundary is within 50 cm of the surface and do not
have sulfidic materials within 100 cm of the surface.

Fibrista, p. 226

AC. Other Histosols that

1. Are dominantly hemic in the subsurface tier if that
tier is wholly organic except for a thin mineral layer
or layers; or are dominantly hemic in the organic part
of the surface and subsurface tiers if a continuous
mineral layer 40 cm or more thick begina within the
depth limits of the subsurface tier; or

2, Have a sulfuric horizon whose upper boundary is
within 60 cm of the surface or have sulfidic materials
within 100 cm of the surface,

Hamicts, p. 232

1
Dominant, in this context, means the most abundant. If only two kinds
of organic pateriale are present, the fibric materials occupy half or
more of the volume. If there are both heeic and sapric materials ae
well aa fibric, the fibric materials may oocupy less than half of the
yoliwe boe have acre volue than either the hands or sapric materials.

Froven 2 onthe after the auaner solstice.


a12
HFGH. Other Haplustolls that:

1. When neither irrigated nor fallowed to store
moisture:

a. If the soil temperature regime is mesic or thermic,
are dry six-tenths or more of the time in half or more
years in some part of the moisture control section (not
necessarily the same part) during a period when the
soil temperature at a depth of 50 cm exceeds 5°C; or

b. If the soil temperature regime is hyperthermic or
isomesic, or warmer, are moist in some or all parts
of the moisture control section for less than 90
consecutive days during a period when the soil
temperature at a depth of 50 cm exceeds 8°C; and

2. Have CEC (by IN NH, OAc pH 7) of less than 24
cemol(+) per kg clay in the major part of the soil below a
depth of 25 cm but above 100 cm or a lithic or paralithic
contact if one is shallower than 100 cm.

Torroxic Haplustolls

HFGI. Other Haplustolls that have CEC (by IN NH,OAc
pH 7) of less than 24 cmol(+) per kg clay in the major part
of the soil below a depth of 25 cm but above 100 cm or
lithic or paralithic contact if one is shallower than 100

cm.
Oxic Hapluatolis

HFGJ. Other Haplustolls that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm or less
and acid-oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of more than 1.0 percent,
‘Andie Haplustolls

HFGK. Other Haplustolls that:

1. When neither irrigated nor fallowed to store
moisture:

a. If the soil temperature regime is mesic or thermic,
are dry six-tenths or more of the time in half or more
years in some part of the moisture control section (not
necessarily the same part) during a period when the
soil temperature at a depth of 50 cm exceeds 5°C; or

b. If the soil temperature regime is hyperthermic or
isomesic, or warmer, are moist in some or all parts
of the moisture control section for less than 90
consecutive days during a period when the soil
temperature at a depth of 50 cm exceeds 8°C; and

2. Have, throughout a cumulative thickness of 18 cm or
more and within a depth of 75 cm, one or more of the
following:

a. Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or


302

when its temperature is more than 5°C, or the soil has
artificial drainage.

Aquic Paleudolls
HGAB. Other Paleudolls.

Typic Paleudolls
Vermudolls
Key te subgroups

HGCA. Vermudolls that have a lithic contact within 50
cm of the surface,
Lithic Vermndolls

HGCB. Other Vermudolls that have a cambic horizon.
Haplic Vermudolls

HGCC. Other Vermudolls that have a mollic epipedon that
is less than 75 em thick.

Entic Vermudolls
HGCD. Other Vermudalls,

Typic Vermudolls
USTOLLS
Key to great groups
HFA. Ustolls that have a duripan with its upper boundary
within 100 cm of the soil surface.

Durustolls, p. 309

HFB. Other Ustolls that have a natric horizon.

Natrustolls, p. 316

HFC. Other Ustolls that have a petrocalcic horizon that
has its upper boundary within 150 cm of the soil surface,
and that have an argillic horizon or are noncalcareous in
some subhorizon above the petrocalcic horizon after the
surface soil to a depth of 18 cm has been mixed, or that

have an argillic horizon that has one or both of the
following:

1. A vertical clay distribution such that the clay content
does not decrease by as much as 20 percent of the
maximum clay content within 150 cm of the soil
surface and the soil does not have a lithic or paralithic
contact within that depth, and the argillic horizon has
one or both of these:

a. A hue redder than 1OYR and chroma higher than 4
in the matrix; or

b. Common coarse mottles that have a hue of 7.5YR or
redder or chroma higher than 5; or

2. A particle-size class in the upper part that is clayey,
and an increase of at least 20 percent clay (absolute)
within a vertical distance of 7.5 cm or of 15 percent clay
(absolute) within 2.5 cm at the upper boundary, and


Sulfaquents

Key to subgroups

KAAA, Sulfaquents that have sulfidic materials at a
depth of 30 cm or more and ann value of less than 1.

Haplic Sulfaquents
KAAB. Other Sulfaquents.
Typic Sulfaquents
Tropaquents

‘The definition of the great group of Tropaquents that
follows cannot be tested in the United States and is
provisional.

Tropaquents are the Aquents that

1. Have an isomesic or warmor iso temperature
regime; and

2, Have an n value of 0.7 or less or have less than 8
Peteent clay in some subhorizon between 20 and 50 cm;
an

3. Have an organic-carbon content” that decreases
regularly with depth below 25 cm and reaches a level
of 0.2 percent or less within a depth of 125 cm.

Subgroups have not been defined.
ARENTS
Key to great groupe
KBA. Arents that have an ustic soil] moisture regime.
p. 203
KBB, Other Arents that have a xeric soil moisture
regime.
Xerarents, p. 203
KBC, Other Arents that have a torric soil moisture
regime.
Torriarents, p. 202
KBD, Other Arents.
‘Udarents, p. 203
Torriarents
Torriarents are the Arents that have a torric soil
moisture regime.
7
‘The carhon should be of Holocene age. It ie not the intent to include

forsil carbon from transported fraguenta of bedrock or from buried
Pleistocene deposite. ‘The mean residence tine of tha carbon should be
Less than 11,000 years B.P.


981
Kandihumults

Definiti
Key to subgroups
GBCA. Kandihumults that:

1. Have, throughout a cumulative thickness of 18 cm or
more and within a depth of 75 cm, bulk density of the
Jess than 2,0 mm fraction, measured at 33 kPa water
retention, of 1.0 g cm’ or less and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of more than 1.0 percent; and

2. Have, in the upper 75 cm of the soil, a hue of 10YR or
yellower in one or more subhorizons that have a color
value, moist, of 4 or more and mottles with chroma of 3
or more and the hue becomes redder with depth within
100 cm of the soil surface.

Andic Epiaquic Kandihumults

GBCB. Other Kandihumults that:

1. Have, throughout a cumulative thickness of 18 cm or
more and within a depth of 75 cm, bulk density of the
less than 2.0 mm fraction, measured at 33 kPa water
retention, of 1.0 g cm” or less and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of more than 1.0 percent; and

2, Have an ustic soil moisture regime.
Ustandic Kandihumults

GBCC. Other Kandihumults that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm’ or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent,

Andic Kandibumults

GBCD. Other Kandihumults that have the following
combination of characteristics in the upper 25 cm or
more of the argillic or kandic horizon:

1, Mottles that have a color value, moist, of 4 or more,
and chroma, moist, of 2 or less accompanied by
mottles of higher chroma that are due to segregation of
iron; and

2, Saturation with water in the mottled zone at some
time of year when the soil temperature in that zone is
5°C or more or there is artificial drainage.

Aquic Kandihumults

GBCE. Other Kandihumults that have, in the upper 75 cm
of the soil, a hue of 10YR or yellower in one or more
subhorizons that have a color value, moist, of 4 or more
and mottles with chroma of 3 or more and the hue
becomes redder with depth within 100 cm of the soil

surface.
Epiaquic Kandihumults


that is 0.6 percent or more if the weighted average ratio
of sand to noncarbonate clay to thia depth ie 1.0 or less,
or is 0.15 percent or more if the ratio is 13 or more, or is
intermediate if the ratio of sand to clay is between 1.0
and 13; and have a weighted average percentage of
organic carbon in the eurface soil to a depth of 18 cm
that is one-fifth or more higher than the values just
stated if there is a petrocalcic horizon that is shallower
than 40 cm but deeper than 18 em; and

2. Have a frigid or colder temperature regime and an
aridic moisture regime that borders on an ustic

regime.
Borollic Paleorthids

FBBB. Other Paleorthids that are saturated with water
for 90 consecutive days or more in most years within 100
em below the soil surface, or have one or more
subhorizons with any of the following characteristics
within 100 cm of the surface if the horizon is saturated
with water at some period in most years, or the soil is
artificially drained:

1. Dominant chroma of 1 or less throughout and hue of
2.5Y or yellower in some part; or

2, Dominant chroma of 2 or less and mottles that are
not due to segregated lime; or

8. Both a dominant chroma of 2 or less and a greater
SAR (or percentage of exchangeable Na) in more than
half the thickness of the horizons between the surface
and 50 cm depth than in the saturated zone.

Aquic Paleorthids

FBBC. Other Paleorthids that:

1. Have a petrocalcic horizon whose upper boundary is
18 cm or deeper, and have a weighted average content
of organic carbon in the upper soil to a depth of 40 cm
that is 0.6 percent or more if the weighted average ratio
of sand to noncarbonate clay to thie depth is 1.0 or less,
or is 0,15 percent or more if the ratio is 13 or more, or is
intermediate if the ratio of sand to clay is between 1.0
and 13; and have a weighted average percentage of
organic carbon in the surface soil to a depth of 18 cm
that is one-fifth or more higher than the values just
stated if there is a petrocalcic horizon that is shallower
than 40 cm but deeper than 18 cm; and

2. Have a mean annual soil temperature lower than
22°C, mean summer and mean winter soil
temperatures at a depth of 50 cm that differ by 5°C or
more, and have an aridic moisture regime that

borders on a xeric regime.
Xerollic Paleorthids
FBBD. Other Paleorthids that:

1. Have a petrocalcic horizon whose upper boundary is
18 em or deeper, and have a weighted average content
of organic carbon in the upper soil to a depth of 40 cm
that ie 0.6 percent or more if the weighted average ratio
of sand to noncarbonate clay to this depth is 1.0 or less,


117

2. When not irrigated and when not fallowed to store
moisture:

a. If the soil temperature regime is mesic or thermic,
are dry six-tenths or more of the time in half or more
years in some part of the moisture control section (not
necessarily the same part) during a period when the
soil temperature at. a depth of 50 cm exceeds 5°C; or

b. If the soil temperature regime is hyperthermic,
isomesic, or warmer, are moist in most years in
some or all parts of the moisture control section for
less than 90 consecutive days during a period when
the soil temperature at a depth of 50 cm exceeds 8°C.
Arenic Aridic Paleustalfs

ICFYJ. Other Paleustalfs that have a layer, starting at the
mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic horizon that is 50 to 100
cm below the soil surface.

Arenic Paleustalfs

ICFK. Other Paleustalfs that:

1, When not irrigated and when not fallowed to store
moisture:

a. If the soil temperature regime is mesic or thermic,
are dry six-tenths or more of the time in half or more
years in some part of the moisture control section (not
necessarily the same part) during a period when the
soil temperature at a depth of 50 cm exceeds 5°C; or

b. If the soil temperature regime is hyperthermic,
isomesic, or warmer, are moist in most years in
some or all parts of the moisture control section for
less than 90 consecutive days during a period when
the soil temperature at a depth of 50 cm exceeds 8°C;
and

2. Have a calcic horizon within a depth of 100 cm if the
weighted average particle-size class of the upper 50 cm
of the argillic horizon is sandy, 60 cm if it is loamy, or
60 cm if it is clayey, and they have carbonates in all
subhorizons above the calcic horizon.

Calciorthidic Paleustalfs

ICFL. Other Paleustalfs that, when not irrigated and
when not fallowed to store moisture:

1. If the soil temperature regime is mesic or thermic,
are dry six-tenths or more of the time in half or more
years in some part of the moisture control section (not
necessarily the same part) during a period when the
soil temperature at a depth of 50 cm exceeds 5°C; or


64

Gypsic

Definition: More than 40% by weight of carbonates
(expressed as CaCOs) plus gypsum, and the gypsum is
more than 35% of the sum of carbonates and gypsum.

Determinant size fraction: Whole soil, particles less than
2.0 mm in diameter, or whole soil less than 20 mm,
whichever has higher percentage of carbonates plus
gypsum.

Glauconitic
Definition: More than 40% glauconite by weight.

Determinant size fraction: Whole soil, particles less than
2.0 mm in diameter.

CLASSES APPLIED TO SOILS THAT HAVE A
FRAGMENTAL, SANDY,
SANDY-SKELETAL, LOAMY, OR LOAMY-SKELETAL
PARTICLE SIZE CLASS

Micaceous 9

Definition: More than 40% mica by weight’

Determinant size fraction: 0.02 to 20 mm.

Siliceous 10

Definition: More than 90% by weight "of silica minerals
(quartz, chalcedony, or opal) and other extremely durable
minerals that are resistant to weathering.

Determinant size fraction: 0.02 to 2.0 mm.

Mixed

Definition: All others that have less than 40% of any one
mineral other than quartz or feldspars.

Determinant size fraction: 0.02 to 2.0 mm.

CLASSES APPLIED TO SOILS THAT HAVE A CLAYEY
OR
CLAYEY-SKELETAL PARTICLE-SIZE CLASS
Halloysitic un
Definition: More than half halloysite’ by weight and
smaller amounts of allophane or kaolinite or both.

Determinant size fraction: Less than 0.002 mm.

Percentages by weight are estimated fro grain counts, Usually, a
feactiona of # conventional

cenart of the soil.

watimated from grain counts. Usually, =

° nant site fractions of a convent ional

echanioel analysin in sufficient for placement of the soil.

12 gaiioyatte ae used hare includes only the tubular forms. what has

been called tabular halloysite i= grouped here with Keolinite,



244

JAEL. Other Cryaquepts that have chroma of 3 or more in
more than 40 percent of the mass of one or more horizons

between depths of 15 and 50 cm.

Aerie Cryacuepts
JAEJ. Other Cryaquepts that have an umbric epipedon.

Humic Cryaquepts

JAEK. Other Cryaquepts.

‘Typic Cryaquepts
Fragiaquepts
Key to subgroups

JADA, Fragiaquepts that have in more than 40 percent of
the matrix of one or more subhorizona between the plow
layer and 75 cm or, if there is no plow layer, between a
depth of 15 and 75 cm, moist colors as follows:

1. If there is mottling, chroma of 3 or more; or

2, If there is no mottling, chroma of 2 or more.
Aeric

JADB, Other Fragiaquepts that have a histic, mollic, or

umbric epipedon.
Humic Fragiaquepts
JADC. Other Fragiaquepts.
‘Typic Fragiaquepts
Halaquepts
Key to subgroups

JACA. Halaquepts that have the following combination
of characteristics:

1. Cracks at some period in most years that are 1 em or
more wide at a depth of 50 cm, that are at least 30 cm
Jong in some part, and that extend upward to the soil
surface or to the base of an Ap horizon; and

2, A coefficient of linear extensibility (COLE) of 0.09
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 100 cm of the soil or in the whole soil if a
lithic or paralithie contact is deeper than 50 cm but
shallower than 100 cm; and

3. More than 35 percent clay in horizons that total more
than 50 cm in thickness.
Vertic Halnquepts

JACB. Other Halaquepts that have, throughout
cumulative thickness of 18 em or more and within a
depth of 76 cm, one or more of the following:

1. Bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm”
Jess and acid-oxalate-extractable aluminum lus 1 v2


70

1, Have an argillic or kandic horizon but not a
fragipan and have base saturation (by sum of cations)
of less than 35 percent at the following depths: either

a. If the argillic or kandic horizon has in some part a
hue of 5YR or yellower, or a color value, moist, of 4 or
more, or a color value, dry, that is more than 1 unit
higher than the value, moist, the shallowest of the
following:

(1) 125 em below the upper boundary of the argillic
or kandic horizon; or

(2) 180 cm below the surface of the soil; or

(3) Immediately above a lithic or paralithic
contact; or

b. If the argillic or kandic horizon has some other
color or if the epipedon has a sandy or sandy-skeletal
particle-size class throughout, the deepest of 125 cm
below the upper boundary of the argillic horizon, 180
cm below the surface of the soil, or immediately
above a lithic or a paralithic contact if it is shallower;
or

2. Have a fragipan that

a. Meets all the requirements of an argillic or
kandic horizon or has clay skins more than 1 mm
thick in some part, or underlies an argillic or
kandic horizon; and

b. Has base saturation (by sum of cations) of less
than 35 percent at a depth of 75 cm below the upper
boundary of the fragipan or immediately above a
lithic or paralithic contact, whichever is shallower.
Ultisols, p. 373

H. Other soils that
1. Have either:
a, A mollic epipedon; or

b. A surface horizon that, after the soil to a depth of 18
cm is mixed, meets all requirements of a mollic
epipedon except thickness, and, in addition, an upper
subhorizon more than 7.5 cm thick that is in an
argillic, kandic or a natric horizon, that meets the
requirements of a mollic epipedon with respect to
color, content of organic carbon, base saturation, and
structure but is separated from the surface horizon by
an albic horizon; and, in addition,

2. Have base saturation of 50 percent or more (by
NH4OAc) as follows: either


201
2. The chroma, moist, is 2 or more if there are no
mottles.
Aeric Haplaquents
KAGD. Other Haplaquents that have an Ap horizon that
has a color value, moist, of 3 or less and a color value,

dry, of 5 or less when crushed and smoothed, or the A
horizon is 15 cm or more thick and has these colors.

KAGE. Other Haplaquents.

‘Typic Haplaquents
Hydraquents
Kev to subgroups
KABA. All Hydraquents (provisionally).

Typic Hydraquents
Psammaquents
Key ta. aubgroups

KAFA. Psammaquents that have a lithic contact within
50 cm of the soil surface.
Lithic Paammaquents

KAFB. Other Psammaquents that have an albic horizon
at the surface or immediately under an A or Ap horizon
that, in turn, is underlain by another horizon that has a
color value more than one unit darker or that has

chroma of 6 or more.
Spodic Psammaquents
KAFC. Other Psammaquents that:

1. Have an Ap horizon that has a color value, moist, of
8 or less and a color value, dry, of 5 or less when
crushed and smoothed, or the A horizon is 15 cm or
more thick and has these colors; and

2. Have base saturation (by NH,OAc) of less than 50
percent in more than half the thickness of the

subhorizons within the upper 100 cm.
Homaqueptic Peammaquents
KADD. Other Paammaquents that:

1. Have an Ap horizon that has a color value, moist, of
8 or less and a color value, dry, of or less when
crushed and smoothed, or the A horizon is 15 cm or
more thick and has these colors; and

2. Have base saturation (by NH,OAc) of 50 percent or

more in more than half the thickness of the
subhorizone within the upper 100 cm.

Mollic Pasammaquents

KADE. Other Psammaquents.
Typic Psammaquents


307

HFEO, Other Argiustolls that have a brittle horizon 15 em
or more thick within 100 cm of the soil surface that
contains some opal coatings or 20 percent or more by
volume durinodes.

Durie Argiustolls
HFEP. Oth justolls.
er Argiustolls. ype tole
Calciustolls
Koy to subgroups

HFDA. Calciustolls that have a salic horizon that has its
upper boundary within 75 cm of the surface,
Salorthidic Calciustolls

HFDB. Other Calciustolls that have a petrocalcic horizon
and have a lithic contact within 50 cm of the soil surface.
Lithic Calciustolls

HFDC. Other Calciustolls that have a lithic contact within
50 cm of the soil surface.
Lithic Calciustolls
HFDD. Other Calciustolls that:
1. Have the following combination of characteristics:

a. Cracks at some period in most years that are lcm
or more wide at a depth of 50 cm, that are at least 30
cm long in some pare and that extend upward to the
surface or to the base of an Ap horizon; and

b. A coefficient of linear extensibility (COLE) of 0.07
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more
in the upper 125 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 60 cm but
shallower than 125 cm; and

c. More than 35 percent clay in horizons that total
more than 50 cm in thickness; and

2. The cracks are open 180 days or more, cumulative, in
most years.
Torrertic Calciustolls
HFDE. Other Calciustolls that:

1, When neither irrigated nor fallowed to store
moisture:

a. If the soil temperature regime is mesic or thermic,
are dry for four-tenths or less of the cumulative days
in some part of the moisture control section when the
soil temperature at a depth of 60 cm exceeds 5°C; or

b. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or
Jess during a period when the soil temperature at a
depth of 50 cm exceeds 8°C; and


397
Plinthudults

Plinthudults are the Udults that have plinthite that forms
a continuous phase or constitutes more than half the
matrix of some subhorizon in the upper 150 cm of the soil.

Rhodudults

Key to subgroups
GCFA. Rhodudults that have a lithic contact within 50
cm of the soil surface.
Lithic Rhodudults

GCFB. Other Rhodudults that have texture that is loamy
fine sand or coarser throughout the argillic horizon,
Psammentic

GCFC. Other Rhodudults.
Typic Rhodudults

USTULTS

Key to great groups

GDA. Ustults that have plinthite that forms a continuous
phase or that constitutes more than half the volume of
some subhorizon within 150 cm of the soil surface.

p.403

GDB. Other Ustults that

1. Have a CEC of 16 cmol(+) or less per kg clay (by IN
NH,OAc pH 7) and an ECEC of 12 cmol(+) or less per
kg clay (sum of bases extracted with IN NH,OAc pH 7
plus 1N KCl-extractable Al) in the major part of the
argillic or kandic horizon, or the major part of the
upper 100 cm of the argillic or kandic horizon if these
horizons are thicker than 100 cm; and

2. Do not have a lithic, paralithic, or petroferric contact
within 150 cm of the soil surface; and

3. Have a clay distribution such that the percentage of
clay does not decrease from its maximum amount by
as much as 20 percent within a depth of 150 cm from the
soil surface, or the layer in which the clay percentage
decreases by more than 20 percent has at least 5 percent
of the volume consisting of skeletans on faces of peds
and there is at least 3 percent (absolute) increase in

clay below the layer,
Kandiustults, p. 399

GDC. Other Ustults that have a CEC of 16 cmol(+) or less.
per kg clay (by IN NH, OAc pH 7) and an ECEC of 12
cmol(+) or less per kg clay (sum of bases extracted with
IN NH, OAc pH 7 plus IN KCl-extractable Al) in the
major part of the argillic or kandic horizon, or the major
part of the upper 100 cm of the argillic or kandic horizon
if these horizons are thicker than 100 cm.
Kanhaplustults, p. 401


933

mor of less than 15 percent clay (absolute) within a
distance of 2.5 cm at the upper boundary.
Haplic Palexerolls

HDCJ. Other Palexerolls.
Typic Palexerolls


18

coated only on the under side, those in the cambic
horizon should be free of coatings; or

(8) If carbonates are absent in the parent material
and in the dust that falls on the soil, the required
evidence of alteration is satisfied by the presence of
soil structure and the absence of rock structure; and

5. Properties that do not meet the requirements of an
argillic, kandic, or spodic horizon; and

6. No cementation or induration and no brittle
consistence when moist; and

7, Enough thickness that its base is at least 25 cm (10 in.)
below the soil surface unless the soil temperature regime

is eryic or pergelic,
Duripan

The duripan (L. durus, hard, plus pan; meaning
hardpan) is a subsurface horizon that is cemented by
silica to the degree that fragments from the air-dry
horizon do not slake during prolonged soaking in water
or in HCL. In summary, the duripan is a silica-cemented
subsurface horizon in which

1. Cementation is strong enough that dry fragments from
some subhorizon do not slake in water, even during

prolonged wetting; and

2, Coatings of silica, insoluble in 1N HCI even during
prolonged soaking but soluble in hot concentrated KOH or
in alternating acid and alkali, are present in some pores
and on some structural faces; or some durinodes are
present; and

3. Cementation is not destroyed by soaking in acid in
more than half of any laminar capping that may be
present or in some other continuous or imbricated
subhorizon. Cementation in such layers is completely
destroyed by hot concentrated KOH, either by a single
treatment or by alternating with acid; and

4. If fractured, the average lateral distance between
fracture points is 10 cm or more.

Fragipan

A fragipan (modified from L. fragilis, brittle, and pan;
meaning brittle pan) is a loamy or uncommonly a sandy
subsurface horizon that may but does not necessarily
underlie a cambic, spodic, argillic, or albic horizon. It
has a very low content of organic matter, has high bulk
density relative to the horizons above it, and is seemingly
cemented when dry, having then hard or very hard
consistence. When moist, a fragipan has moderate or


420

horizons designated "x" do not have all the properties
of a fragipan.

y Accumulation of gypsum

This symbol is used to indicate accumulation of
gypsum.

z Accumulation of salts more soluble than gypsum

This symbol is used to indicate accumulation of salts
more soluble than gypsum.

CONVENTIONS FOR USING LETTER SUFFIXES

Many master horizons and layers that are symbolized
by a single capital letter will have one or more lower
case letter suffixes. The following rules apply:

Letter suffixes should imunediately follow the capital
letter.

Seldom are more than three suffixes used.

If a surface horizon is disturbed, only “p” is used,
except where there are surface accumulations of
calcium carbonate, calcium sulfate or more soluble
salts (Calciaquolls, for example).

‘When more than one suffix is needed, the following
letters, if used, are written first: a, d, e, h, i,r, 8, t, and
w. Except for Bhs or Crt* horizons, none of these letters
are used in combination in a single horizon.

If more than one suffix is needed and the horizon is
not buried, these symbols, if used, are written last: c, f,
g, m,v, and x. Some examples: Btc, Bkm, and Bsv.

If a horizon is buried, the suffix "b" is written last.
Suffix "b" is used only for buried mineral soils.

AB horizon that has significant accumulation of clay
and also shows evidence of development of color or
structure, or both, is designated Bt ("t" has precedence
over “w", "s", and “h"). A B horizon that is gleyed or
that has accumulations of carbonates, sodium, silica,
gypsum, salts more soluble than gypsum, or residual
accumulation of sesquioxides carries the appropriate
symbol- 4.) k, n, g y, z, oro. If illuvial clay is also
present, "t” precedes the other symbol: Bto.

Suffixes "h’, “s", and "w" are not used with g, k, n, q,
y, 2, or 0, unless needed for explanatory purposes.

Unless otherwise given, suffixes are listed
alphabetically.

VERTICAL SUBDIVISION

Commonly a horizon or layer designated by a single
combination of letters needs to be subdivided. The

Indicating: x saprolite in which clay fitme are


392

top of an argillic or kandic horizon that is 60 to 100 cm
below the soil surface; and

2, Have 5 percent or more plinthite (by volume) in one
or more subhorizons within 150 cm of the soil surface.
Arenic Plinthic

GCDC. Other Kanhapludults that have a layer, starting
at the mineral soil surface, that has a sandy particle-size
class and extends to the top of an argillic or kandic
horizon that is 50 to 100 cm below the soil surface.

Arenic Kanhapludults
GCDD. Other Kanhapludults that have an ECEC (sum of
bases plus 1N KCl-extractable Al) of 1.5 cmol(+) or less
per kg clay in one or more subhorizons within a depth of

150 cm below the soil surface,
Acrudoxic Kanhapludults
GCDE. Other Kanhapludults that:

1. Have 5 percent or more plinthite (by volume) in one
or more subhorizons within 160 cm of the soil surface;
an

2. Have the following combination of characteristics
in the upper 75 cm of the soil if the chroma in all or part
of the upper 75 em is not controlled by uncoated sand
grains; or if the chroma throughout the upper 75 cm is
controlled by uncoated sand grains, have the
following combination of characteristics throughout
the upper 12.5 cm of the argillic or kandic horizon:

a, Mottles that have a color value, moist, of 4 or more
and chroma, moist, of 2 or less accompanied by
mottles of higher chroma that are due to segregation
of iron; and

b, Saturation with water in the mottled zone at some

time of year when the soil temperature in that zone

is 5°C or higher or there is artificial drainage.
Plinthaquic Kanhay

GCDF. Other Kanhapludults that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm’ or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

Andic Kanhaptudults

GCDG, Other Kanhapludults that have the following
combination of characteristics in the upper 75 cm of the
soil if the chroma in all or part of the upper 75 cm is not
controlled by uncoated sand grains; or if the chroma
throughout the upper 75 cm is controlled by uncoated sand
grains, have the following combination of
characteristics throughout the upper 12.5 cm of the
argillie or kandic horizon:

1. Mottles that have a color value, moist, of 4 or more
and chroma, moist, of 2 or less accompanied by
mottles of higher chroma that are due to segregation of
iron; and


161
FAAD. Other Durargids that have

1. A mean annual soil temperature lower than 22°C,
mean summer and mean winter soil temperatures at
a depth of 50 cm that differ by 6°C or more, and an
aridic moisture regime that borders on a xeric
regime; and

2. Throughout a cumulative thickness of 18 cm or
more and within a depth of 75 cm, one or more of the
following:

a. Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders,
pumice, and pumice-like fragments make up more
than 66 percent of these fragments; or

b. The 0,02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and
contains either:

(i) More than 30 percent volcanic glass; or

(2) At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Vitrixerandic

FAAE. Other Durargids that

1. Are dry in all parts of the moisture control section
three-fourths of the time (cumulative) or less that the
soil temperature at a depth of 50 cm is 5°C or higher;
and

2. Have, throughout a cumulative thickness of 18 cm or
more and within a depth of 75 cm, one or more of the
following:

a, Fragments coarser than 2.0 mm constitute more
than 35 percent of the whole soil and cinders,
pumice, and pumice-like fragments make up more
than 66 percent of these fragments; or

b. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and
contains either:

(1) More than 80 percent volcanic glass; or

(2) At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Vitrustandic

FAAF. Other Durargids that do not have a platy or
massive duripan that is indurated in some subhorizon
and that have the following combination of
characteristics:

1. A duripan at a depth of 18 em or more; and

2, The weighted average percentage of organic carbon
in the upper soil to a depth of 40 cm is 0.6 or more if the


234

subsurface and bottom tiers consisting of sapric
materials.

Sepric Borchemists
ACEJ. Other Borohemists.

Typic Borchemists
Cryohemists
Key to subgroups
ACDA. Cryohemists that have a lithic contact within the
control section.

Lithic Cryohemicts
ACDB. Other Crychemists that have a mean annual soil
temperature of 0°C or lower.

Pergelic Cryohemists

ACDC. Other Cryohemists that have a mineral layer 30
cm or more thick that has its upper boundary in the
control section below the surface tier.

Terric Crychemists

ACDD. Other Crychemists that have a mineral layer

between 5 and 30 cm thick or two or more thin,

continuous mineral layers, within organic materials,

in the control section below the surface tier.
Flovaquentic Cryohamists

ACDE. Other Cryohemists,
Typic Crychemists

Luvihemists

Luvihemists are not known to occur in the United States
but the great group is provided tentatively for use in other
countries if needed. They are the Hemists that have a
horizon that is 2 cm or more thick within the control
section, and half or more of the volume of that horizon
consists of humilluvic materials. Because these soils
cannot be studied in the United States, a precise
definition is not attempted here. It should be noted,
however, that they are normally acid and that they have
been cultivated for a long time.

Medihemists
Key to subgroups
ACGA, Medihemists that have a layer of water within
the control section below the surface tier.

Hydric Medihemists
ACGB. Other Medihemists that have a lithic contact
within the control section.

Lithic Medihemists

ACGC. Other Medihemists that:

1. Have 25 cm or more of the subsurface and bottom
tiers consisting of fibric materials; and


350

DEDK. Other Kandiudox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of

surface litter.
Humic Kandiudox

DEDL. Other Kandiudox that have a color hue of 2.5YR or
redder with moist values of less than 4 in most of the 25 to

125 cm depth from the soil surface.
Rhodie Kandiudox

DEDM. Other Kandiudox that have a color hue of 7.5YR or
yellower with moist values of 6 or more in most of the 25 to
125 cm depth from the soil surface.

Xanthic Kandiudox

DEDN. Other Kandiudox.
Typic Kandiudox
Sombriudox
Key to subgroups
DEAA. Sombriudox that have a petroferric contact within
a depth of 125 cm of the soil surface.
Petroferric Sombriudox
DEAB. Other Sombriudox that have a lithic contact within
a depth of 125 cm of the soil surface.
Lithic Sombriudox

DEAC. Other Sombriudox that have 16 kg or more organic
carbon per square meter to a depth of 100 em, exclusive of

surface litter.
Humic Sombriudox

DEAD. Other Sombriudox.

Typic Sombrindox
USTOX
Key to great groups
DCA. Ustox that have a sombric horizon within 150 em of
the soil surface.

Sombriustox, p. 356

DCB. Other Ustox that have both an apparent ECEC of less
than 1.50 cmol(+) per kg clay and a pH value (1N KCl) of 5
or more in some part of the oxic or kandic horizon within

a depth of 150 cm of the soil surface.

Acrustox, p. 351
DCC. Other Ustox that have more than 35 percent base
saturation (NH,OAc) in all parts within a depth of 125 cm
of the soil surface,

Eutrustox, p. 352,
DCD. Other Ustox that have more than 40 percent clay in
the surface 18 cm after mixing, and have the upper
boundary of a kandic horizon within a depth of 150 cm of

the soil surface.
Kandiustox, p. 355


98

in the upper 25 cm, and it is saturated with water
within that depth at some time when the soil
temperature is 5°C or higher; or

b. If the upper boundary of the argillic horizon is
deeper than 50 cm, has mottles that have chroma of 2
or less within a depth of 75 cm below the soil surface;
and

2. Have a layer, starting at the mineral soil surface,
that has a sandy particle-size class and extends to the
top of an argillic horizon that is more than 50 cm below

the soil surface.
Aquic Arenic Hapludalfs
IEKI. Other Hapludalfs that have a layer, starting at the

mineral soil surface, that has a sandy particle-size class
and extends to the top of an argillic horizon that is more

than 50 em below the soil surface.

Arenic Hapludalfe
IEKJ. Other Hapludalfs that:

1. Have an abrupt textural change and mottles in the
upper 25 cm of the argillic horizon; and

2. Have an argillic horizon that:

a. If its upper boundary is less than 50 cm below the
soil surface, has mottles that have chroma of 2 or less
in the upper 25 cm, and it is saturated with water
within that depth at some time when the soil
temperature is 5°C or higher; or

b. If the upper boundary of the argillic horizon is
deeper than 50 cm, has mottles that have chroma of 2
or less within a depth of 75 cm below the soil surface;
and

3. Have base saturation (by sum of cations) of less than
60 percent at a depth 125 cm below the top of the argillic

horizon, or 180 em below the soil surface, or
immediately above a lithic or paralithic contact,

whichever is least.
Albaquultic Hapludalfs
TEKK. Other Hapludalfs that:

1, Have an abrupt textural change and mottles in the
upper 25 cm of the argillic horizon; and

2, Have an argillic horizon that:
a, If its upper boundary is less than 50 cm below the

soil surface, has mottles that have chroma of 2 or less
in the upper 25 cm, and it is saturated with water


20

extremely hard when dry, and very firm or extremely
firm when moist. Noncapillary pores are filled, and the
petrocalcic horizon is a barrier to roots. Hydraulic
conductivity is moderately slow to very slow. The
horizon is usually much more than 10 cm (4 in.) thick.

A laminar capping commonly is present but is not
required.

If a laminar horizon rests on bedrock, it is considered a
petrocalcic horizon if it is 2.6 cm or more thick and the
product of the thickness in centimeters multiplied by the
percentage of CaCOz equivalent is 200 or more.

Petrogypsic horizon

The petrogypsic horizon is a gypsic horizon that is
strongly enough cemented with gypsum that dry
fragments do not slake in water and that roots cannot
enter. The gypsum content commonly is far greater than
the minimum requirements for the gypsic horizon and
usually exceeds 60 percent. Petrogypsic horizons are
restricted to arid climates and to parent materials that are
rich in gypsum.

Placic horizon

The placic horizon (Gr. base of plax, flat stone; meaning
a thin cemented pan) is a thin, black to dark reddish pan
cemented by iron, by iron and manganese, or by an iron-
organic matter complex. Its thickness ranges generally
from 2 to 10 mm. Rarely, it is as thin mm or as thick
as 20 to 40 mm in spots. It may be, but is not necessarily,
associated with stratification in parent materials. It is in
the solum, roughly parallel to the soil surface, and is
commonly within the upper 50 cm of the mineral soil. It
has & pronounced wavy or even convolute form. It
normally occurs as a single pan, not as multiple sheets
one underlying another, but in places it may be
bifurcated. It is a barrier to water and roots.

An iron-cemented pan is strong brown to dark reddish
brown, A pan cemented by iron and manganese or by
iron-organic matter complexes is black or reddish black.
A single pan may contain two or more layers cemented by
different agents. Iron-organic matter cements
commonly are present in the upper part of the pan.

Identification is seldom difficult. The hard brittle pan
differs so much from the material in which it occurs and
is so close to the surface of the mineral soi] material that it
is obvious unless its thickness is minimal. A few
analyses of placic horizons show that organic carbon is
present in amounts ranging from 1 percent to 10 percent
or more, The presence of organic carbon as well as the
shape and position of the pan distinguish the placic
horizon from the ironstone sheet that may form where


49

These classes have sufficient fine earth to fill 10 percent
or more of the interstices coarser than 1 mm.

Ashy - Rock fragments make up less than 35 percent by
volume and the fine earth is either:

a. Thirty percent or more by weight volcanic glass,
glass aggregates, glass coated grains or other vitric
voleaniclastics; or

b. Thirty percent or more by weight is between 0.02 and
2.0 mm in diameter and 5 percent or more of the 0.02 to
2,0 mm fraction is volcanic glass, glass aggregates,
glass coated grains, or other vitric volcaniclastics, and
the Al, + Feo/2 is 0.4 percent or more, and the water at
1500 kPa is less than 30 percent on undried samples
and less than 12 percent on dried samples of the fine
earth.

Ashy-pumiceous - Rock fragments make up 36 percent or
more by volume; pumice or pumice-like fragments are
two-thirds or more by volume of the rock fragments; fine
earth is ashy.

- Rock fragments make up 35 percent or
more by volume; pumice or pumice-like fragments are
less than two-thirds by volume of the rock fragments; fine
earth is ashy.

Media] - The fine earth has andic soil properties; water at
1500 kPa is 12 percent or more on air-dried samples of the
fine earth, or is 30 percent or more on undried samples,
but is less than 100 percent on undried samples; rock
fragments make up less than 35 percent by volume.

Medial-pumiceous - Rock fragments make up 35 percent

or more by volume; pumice or pumice-like fragments are
two-thirds or more by volume of the rock fragments; fine

earth is medial.

Medial-skeletal- Rock fragments make up 35 percent or
more by volume; pumice or pumice-like fragments are
less than two-thirds by volume of the rock fragments; fine
earth is medial.

Hydvong - The fine earth has andic soil properties; water
at 1600 kPa is 100 percent or more on undried samples of
the fine earth; rock fragments make up leas than 35
percent by volume.

Hydrous-pumiceoug - Rock fragments make up 35 percent
or more by volume; pumice or pumice-like fragments are
two-thirds or more by volume of the rock fragments; fine
earth is hydrous.

Hydrous-skeletal - Rock fragments make up 86 percent or
more by volume; pumice or pumice-like fragments are


96

3. Have an Ap horizon that has a color value, moist, of 3
or less and a color value, dry, of 5 or less when crushed
and smoothed, or the soil, after mixing to a depth of 18

cm, has those colors,
Umbreptic Fragiudalfs

IEF. Other Fragiudalfs that have an Ap horizon that has
acolor value, moist, of 3 or less and a color value, dry, of 5
or less when crushed and smoothed, or the soil, after
mixing to a depth of 18 em, has those colors,

Mollic Fragiudalfs

IEFC. Other Fragiudalfs that:

1, Have, immediately above the fragipan, thick
skeletans of clean sand and silt on primary ped faces,
or have an eluvial horizon (E’) that has thick skeletans
and as much as 3 percent (absolute) less clay than both
the overlying and underlying horizons; and

2. Have mottles that have chroma of 2 or leas in the

upper 25 cm of the argillic horizon or have mottles that

have chroma of 2 or less within 40 cm of the surface,

and the horizons that have mottles of low chroma are

saturated with water at some time of year when the soil

temperature is 5°C or higher in those horizons.
Glossaquic Fragiudalfs

IEFD. Other Fragiudalfs that:

1. Do not have an argillic horizon above the fragipan
that has clay skins on at least some vertical and
horizontal faces of primary or secondary peds, or both;
and

2. Have mottles that have chroma of 2 or less in the

upper 25 em of the argillic horizon or have mottles that

have chroma of 2 or less within 40 cm of the surface,

and the horizons that have mottles of low chroma are

saturated with water at some time of year when the soil

temperature is 8°C or higher in those horizons.
‘Aqueptic Fragiudalfs

IEFE. Other Fragiudalfs that:

1. Have mottles that have chroma of 2 or leas in the
upper 25 cm of the argillic horizon or have mottles that
have chroma of 2 or Jess within 40 cm of the surface,
and the horizons that have mottles of low chroma are
saturated with water at some time of year when the soil
temperature is 5°C or higher in those horizons; and

2. Have, within a vertical distance of 7.5 cm at the top of

the argillic horizon, a clay increase of more than 15

percent (absolute) in the fine-earth fraction.
Albaquic Fragiudalfs


419

cementation is continuous or nearly continuous,
“qm” is used.

1 Weathered or soft bedrock

This symbol is used with "C" to indicate layers of soft
bedrock or saprolite, such as weathered igneous rock,
partly consolidated soft sandstone, siltstone, and
shale. Roots cannot enter except along fracture
planes. The material can be dug with a spade.

8 Illuvial accumulation of sesquioxides and organic
matter

This symbol is used with "B” to indicate the
accumulation of illuvial, amorphous, dispersible
organic matter-sesquioxide complexes if both the
organic matter and sesquioxide components are
significant and the value and chroma of the horizon is
more than 3. The symbol is also used in combination
with "h” as "Bhs" if both the organic matter and
sesquioxide components are significant and the value
and chroma are approximately 3 or less.

ss Presence of slickensides

This symbol is used to indicate the presence of
slickensides. Slickensides result directly from
swelling of clay minerals and shear failure,
commonly at angles of 20 to 60° above horizontal.
They are indicators that other vertic characteristics
such as wedge-shaped peds and surface cracks may be
present.

o

Accumulation of silicate clay

This symbol is used to indicate an accumulation of
silicate clay either by illuviation into the horizon or by
formation and subsequent translocation within the
horizon, or both. The clay can be in the form of
coatings on ped surfaces or in pores, lamellae, or
bridges between mineral grains.

v_ Plinthite

This symbol is used to indicate the presence of iron-
rich, humus-poor, reddish material that is firm or
very firm when moist and that hardens irreversibly
when exposed to the atmosphere and to repeated
and drying. These properties are characteristic of
plinthite.

w. Development of color or structure
This symbol is used with "B" to indicate 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 is used to indicate genetically developed
firmness, brittleness, or high bulk density. These
features are characteristic of fragipans, but some


240

2. Have a mineral layer 30 cm or more thick that has
its upper boundary in the control section below the

surface tier.
Hemic Terric Troposaprists

ADCD. Other Troposaprists that have a mineral layer 30
em or more thick that hes ite upper boundary in the
control section below the surface tier.

Terric Troposaprists

ADCE. Other Troposaprists that have limnic layer(s)
that are 5 cm or more thick within the control section.

‘Troposaprists

ADCF. Other Troposaprists that have a mineral layer
between 5 and 30 em thick or two or more thin,
continuous mineral layers, within organic materials,
in the control section below the surface tier.
Fluvaquentic Troposaprists

ADCG. Other Troposaprists that have 12.5 cm or more of
the subsurface and bottom tiers consisting of fibric

materials,
Fibric Troposaprists

ADCH. Other Troposaprists that have 25 em or more of
the subsurface and bottom tiers consisting of hemic

materials.
Hemic Troposaprists

ADCI. Other Troposaprists.
‘Typic Troposaprists


1, Dry in all parts more than half the time (cumulative)
that the soil temperature at a depth of 50 cm is above 5°C;

and

2. Never moist in some or all parts for as long as 90
consecutive days when the soil temperature at a depth of 50
em is above 8°C.

Soils that have an aridic or a torric moisture regime are
normally in arid climates. A few are in semiarid
climates and either have physical properties that keep
them dry, such as a crusty surface that virtually precludes
infiltration of water, or they are very shallow over
bedrock. There is little or no leaching in these moisture
Tegimes, and soluble salts accumulate in the soil if there
is a source of them.

The limits of soil temperature exclude from these
moisture regimes the very cold and dry regions of
Greenland and adjacent islands. Such fragmentary
data are available on the soils of those regions that no
provision is made for their moisture regimes in this
taxonomy.

Udic moisture regime.-The udic (L. udus, humid)
moisture regime implies that in most years the soil
moisture control section is not dry in any part for as long
as 90 days (cumulative). If the mean annual soil
temperature is lower than 22°C and if the mean winter
and mean summer soil temperatures at a depth of 50 cm
differ by 5°C or more, the soil moisture control section is
not dry in all parts for as long as 45 consecutive days in
the 4 months that follow the summer solstice in 6 or more
years out of 10. In addition, the udic moisture regime
requires, except for short periods, a three-phase system,
solid-liquid-gas, in part, but not necessarily in all, of the
soil when the soil temperature is above 5°C.

The udic moisture regime is common to the soils of humid
climates that have well-distributed rainfall or that have
enough rain in summer that the amount of stored
moisture plus rainfall is approximately equal to or
exceeds the amount of evapotranspiration. Water moves
down through the soil at some time in most years.

If precipitation exceeds evapotranspiration in all months
of most years, there are occasional brief periods when
some stored moisture is used, but the moisture tension
rarely becomes as great as 100 kPa in the soil moisture
control section, The water moves through the soil in all
months that it is not frozen. This extremely wet moisture
regime is called "perudic" (L. per, throughout in time, L.
udus, moist). The formative element ud is used in the
names of most taxa to indicate either a udic or a perudic
regime. The formative element per is used in selected
taxa.


169

2. A mean annual soil temperature of 8°C or higher
and an aridic moisture regime that borders on an

ustic regime.
Ustalfic Haplargids
FAEU. Other Haplargids,
Typic Haplargids
Nadurargids
‘Key to subgroups

FABA. Nadurargids that:

1. Are saturated with water in some horizon within a
depth of 100 cm at some time and have either of the
following characteristics within the horizon or
horizons that are saturated:

a, Dominant chroma of 1 or‘less throughout and hue
of 2.5Y or yellower in some part; or

b. Both a dominant chroma of 2 or less and mottles
that are not due to segregated lime; and

2. Do not have a platy or massive duripan that is
indurated in some subhorizon.
Aquic Haplic Nadurargids
FABB. Other Nadurargids that are saturated with water
in some horizon within a depth of 100 cm at some time
and have either of the following characteristics within
the horizon or horizons that are saturated;

1, Dominant chroma of 1 or less throughout and hue of
2.8Y or yellower in some part; or

2. Both a dominant chroma of 2 or less and mottles that
are not due to segregated lime.
Aquic Nadurargids

FABC. Other Nadurargids that have the following
combination of characteristics:

1, Do not have a duripan that is indurated in some
subhorizon; and

2. A duripan 18 om or deeper; and

3. A weighted average percentage of organic carbon in
the upper soil to a depth of 40 cm that is 0.6 or more if the
weighted average ratio of sand to clay to that depth is
1.0 or Jess, or that is one-seventh percent or more if the
ratio of sand to clay is 13 or more, or is intermediate
between 0.6 percent and one-seventh percent if the
ratio of sand to clay is between 1.0 and 13; anda
weighted average percentage of organic carbon in the
surface soil to a depth of 18 cm that is one-fifth or more
higher than the values just stated if there is a duripan
that is shallower than 40 cm but deeper than 18 cm; and


360

1, Have an umbric epipedon or the surface layer would
meet the requirements for an umibric epipedon if it
were plowodlo's depth of 25 em; and

2. Have a layer starting at the mineral soil surface
that has a sandy particle-size class throughout and
extends to at least the upper boundary of the spodic
horizon, and the upper boundary of the spodic horizon.
is deeper than 75 cm below the soil surface.

Arenic Umbric Haplaquods

CAFE, Other Haplaquods that:

1. Have an argillic or kandic horizon underlying the
spodic horizon and have either base saturation of 35
percent or more (by sum of cations) in some part of the
argillic or kandic horizon or have a mean annual soil
temperature lower than 8°C; and

2. Have a layer starting at the mineral soil surface

that has a sandy particle-size class throughout and

extends to at least the upper boundary of the spodic

horizon, and the upper boundary of the spodic horizon

is between 75 and 125 em below the soil surface,
Alfic Arenic

CAFF. Other Haplaquods that:

1. Have an argillic or kandic horizon underlying the
spodic horizon; and

2. Have a layer starting at the mineral soil surface
that has a sandy particle-size class throughout and
extends to at least the upper boundary of the spodic
horizon, and the upper boundary of the spodic horizon.
is between 75 and 125 cm below the soil surface,
Arenic Ultic Haplaquods

CAFG. Other Haplaquods that have a layer starting at
the mineral soil surface that has a sandy particle-size
class throughout and extends to at least the upper
boundary of the spodic horizon, and the upper boundary
of the spodic horizon is between 75 and 125 cm below the

soil surface.
Arenic Haplaquods

CAFH. Other Haplaquods that have a layer starting at
the mineral soil surface that has a sandy particle-size
class throughout and extends to at least the upper
boundary of the spodie horizon, and the upper boundary
of the spodic horizon is between 125 and 200 cm below the
soil surface.

Grossarenic Haplaquods
CAFL. Other Haplaquods that:

1. Have an argillic or kandic horizon underlying the
spodic horizon; and

2. Have 5 percent or more by volume of iron-cemented
nodules 2.5 to 30 cm in diameter throughout the spodic

horizon.
Ferrudalfic Haplaquods


408
UDERTS

Key to great groups

ECA. Uderts that have a chroma, moist, of 2 or more
dominant in the matrix of some subborizon in the upper
30 cm in more than half of each pedon.

‘(Chromuderts, p. 408
ECB. Other Uderts.
Pelluderts, p. 408
Chromuderts
Key to subgrouns

ECAA. Chromuderts that:

1. Have distinct or prominent mottles within 50 cm of
the soil surface in more than half of each pedon (the
terms refer to contrast, not to size of the mottles); and

2. Have a color value, moist, of 4 or more or a value,
dry, of 6 or more in the surface horizon, or the horizon
with color value of 3 or less, moist, and 5 or less, dry, is
less than 30 cm thick in half or more of each pedon.
Aquentic Chromuderts

ECAB. Other Chromuderts that have distinct or
prominent mottles within 50 cm of the soil surface in
more than half of each Pedon (the terms refer to contrast,

not to size of the
Aquic Chromuderts

ECAC. Other Chromuderts that have a color value, moist,
of 4 or more or a value, dry, of 6 or more in the surface

horizon or the horizon with color value or 3 or less, moist,
and 5 or less, dry, is less than 30 cm thick in half or more

of each pedon.

Entic Chromuderts
ECAD. Other Chromuderts.

Typic Chromuderts
Pelluderts
Key to subgroups

ECBA. Pelluderta that have a color value, moist, of 4 or
more or a value, dry, of 6 or more in the surface horizon,
or the horizon with color value of 3 or less, moist, and 5 or
Jess, dry, is less-than 30 cm thick in half or more of each

pedon.

ECBB. Other Pelluderts.
Typic Pelluderts


133

Placaquands
Key to subgroups
BABA. Placaquands that have a lithic contact within 50
cm of the soi] surface.
Lithic Placaquands

BABB, Other Placaquands that have a histic epipedon,
and have a horizon with its upper boundary within 100
cm of the mineral soil surface or of the upper boundary of
an organic layer with andic soil properties, whichever is
shallower, which is more than 15 cm thick and contains
20 percent or more (by volume) cemented soil material
that does not slake in water after air drying.

Duric Histic Placaquands

BABC, Other Placaquands that have a horizon with its
upper boundary within 100 cm of the mineral soil surface
or of the upper boundary of an organic layer with andic
aoil properties, whichever is shallower, which is more
than 15 cm thick and contains 20 percent or more (by
volume) cemented soil material that does not slake in

water after air drying.
Durie Placaquands
BABD, Other Placaquands that have a histic epipedon.
Histic Placaquands

BABE. Other Placaquands that have, between 25 and 100
cm, a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic epipedon
throughout, occurring below a horizon or horizons, 10 cm
or more thick, with color value 1 unit or more higher and
organic carbon content 1 percent or more lower than the
underlying layer.

Thaptic Placaquands
BABF. Other Placaquands.
‘Typic Placaquands
Vitraquands
Key to subgroups

BADA, Vitraquands that have a lithic contact within 50
em of the soil surface,
Lithic Vitraquands

BADB. Other Vitraquands that have a horizon with its
upper boundary within 100 cm of the mineral soil surface
or of the upper boundary of an organic layer with andic
soil properties, whichever is shallower, which is more
than 16 cm thick and contains 20 percent or more (by
volume) cemented soi] material that does not slake in

water after air drying.
Duric Vitraquands
BADC. Other Vitraquands that have a histic epipedon.
Histic


16

weak brittleness, which is the tendency for a ped or clod to
rupture suddenly when pressure is applied rather than to
undergo slow deformation. A dry fragment slakes or
fractures when placed in water. A fragipan is usually
mottled, is slowly or very slowly permeable to water, and
has few or many bleached, roughly vertical planes that
are faces of coarse or very coarse polyhedrons or prisms.

Identification

There is no known laboratory procedure for identifying a
sample of a fragipan. Identification is primarily a field
problem. A combination of clues must be used because
there is no single unique property of fragipans. First,
position is important. A fragipan lies below an eluvial
horizon unless the soil has been truncated, but it is not
necessarily immediately below. If the soil has been
truncated, the pan can be traced up slope until it lies under
an eluvial horizon.

Second, if there is an argillic or a cambic horizon above a
fragipan, there is commonly an E’ horizon between the
fragipan and the overlying horizon. The E' horizon is
marked by uncoated grains of sand and silt. This
horizon seems related to water that either stands above the
pan or moves laterally along its surface.

Third, if the pan is not saturated for long periods, some or
all pedons normally have bleached vertical streaks that
form a roughly polygonal pattern on a horizontal plane.
The bleached streaks are bounded by strong brown or
reddish brown streaks where iron and manganese have
accumulated. Ifthe pan is saturated for long periods or if
the texture is sandy, the polygonal color pattern may be
absent.

Fourth, if the moisture content is near the wilting point,
the matrix between the streaks is very firm. If it is near
field capacity, the matrix is brittle. The brittle matrix
should constitute 60 percent or more of the volume of some
subhorizon,

Fifth, fine feeder roots are virtually absent in the brittle
parts of a fragipan. If brittleness is so weakly expressed
that fine feeder roots are present throughout the horizon,
the horizon should not be considered a fragipan. It should
be noted, however, that some trees have tap roots that
extend through a well-expreased fragipan, but this is the
exception rather than the rule. It is characteristic of
fragipans that few or many roots may be present in the
bleached vertical streaks and that few or no fine roots are
present in the brittle matrix between the bleached streaks.
The fine roots should not be present at intervals of less
than 10 cm except within bleached vertical streaks, and
the mean horizontal dimensions of the brittle matrix
should be at least 10 cm.


297

HCAD. Other Rendolls that have the following
combination of characteristics:

1, Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the surface
or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0.09 or
more in a horizon or horizons at least 50 cm thick, and
4 potential linear extensibility of 6 cm or more in the
upper 100 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 100 cm; and

8, More than 35 percent clay in horizons that total more
than 50 cm in thickness.
Vertic Rendolls

HCAE. Other Rendolls that have a cambic horizon
throughout the pedon and the mean summer and mean
winter soil temperatures at a depth of 50 cm differ by less

than 5°C.
Eutropeptic Rendolls
HCAF. Other Rendolls that have a cambie horizon
throughout the pedon,
Butrochreptic Rendolls

HCAG. Other Rendolls that have a dry color value of 6 or
more after the surface soil to a depth of 18 cm has been
mixed or of any Ap horizon that is deeper than 18 cm.

HCAH. Other Rendolls.
Typic Rendolls

UDOLLS

Key to great groups

HGA. Udolls that have an argillic horizon and a clay
distribution such that the clay content does not decrease by
as much as 20 percent of the maximum clay content
within 150 cm of the soil surface and there is no lithic or
paralithic contact within that depth, and there is one or
both of the following features:

1, Hue redder than 10YR and chroma greater than 4
dominant in the matrix in at least the lower part of an
argillic horizon; or

2, Many coarse mottles that have hue redder than 7.5YR
or chroma greater than 5.
Paleudolls, p. 301

HGB, Other Udolls that have an argillic horizon.
‘Argiudolls, p. 298

HGC, Other Udolls that have a mollic epipedon that, below
any Ap horizon, is 50 percent or more by volume
wormbholes, wormcasts, or filled animal burrows and that
either rests on a lithic contact or has a transition to an


415

prismatic structure if volume changes accompany
changes in moisture content; or
(6) brittleness.

All kinds of B horizons are subsurface horizons or
wore originally. Included as B horizons where
contiguous to another genetic horizon are layers of
illuvial concentration of carbonates, gypsum, or
silica that are the result of pedogenic processes (these
layers may or may not be cemented) and brittle layers
that have 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 coat rock fragments or are on
finely stratified unconsolidated sediments, whether
the films were formed in place or by illuviation,
layers into which carbonates have been illuviated but
which are not contiguous to an overlying genetic
horizon, and layers with gleying but no other
pedogenic changes.

C horizons or layers: Horizons or layers, excluding
hard bedrock, that are little affected by pedogenic
processes and lack properties of O, A, E, or B horizons.
Most are mineral layers. The material of C layers may
be either like or unlike that from which the solum
presumably formed. AC horizon may have been
modified even if there is no evidence of pedogenesis.

Included as C layers are sediments, saprolite, and
unconsolidated bedrock and other geologic materials
that commonly will slake within 24 hours when air-
dry or drier chunks are placed in water and that, when
moist, can be dug with a spade. Some soils form in
material that is already highly weathered, and such
material that does not meet the requirements of A, E,
or B horizons is designated C, Changes not
considered pedogenic are those not related to
overlying horizons. Layers having accumulations of
silica, carbonates, or gypsum or more soluble salts are
included in C horizons, even if indurated, unless
these layers are obviously affected by pedogenic
processes; then they are a B horizon.

R layers: Hard bedrock.

Granite, basalt, quartzite and indurated limestone or
sandstone are examples of bedrock that are designated
R. Air-dry or drier chunks of an R layer when placed
in water.will not slake within 24 hours. The R layer is
sufficiently coherent when moist to make hand
digging with a spade impractical, although it may be
chipped or scraped, Some R layers can be ripped with
heavy power equipment. The bedrock may contain
cracks, but these are few enough and small enough
that few roots can penetrate. The cracks may be coated
or filled with clay or other material.

Transitional horizons

‘There are two kinds of transitional horizons. In one, the
properties of an underlying or overlying horizon are
superimposed on properties of the other horizon


60
FAMILY DIFFERENTIAE FOR HISTOSOLS

Most of the differentiae used to distinguish families of
Histosols have been defined earlier, either because they
are differentiae in mineral soils as well as in Histosols;
or because their definitions are essential for the
classification of some Histosols in categories higher than
the family. The differentiae that are not defined
elsewhere are defined in this section and the taxa in
which they are used are enumerated.

The order in which family modifiers are placed in the
technical family names of Histosols follows. The
modifiers chosen are those appropriate to the particular
family.

Particle size
Mineralogy, including nature of limnic deposits
Reaction

Soil temperature regime
Soil depth

The differentiae are discussed in the remainder of this
section.

Particle-size classes

Particle-size modifiers are used in family names of
Histosols only in terric subgroups. The terms used
follow,

Fragmental

Loamy-skeletal or clayey-skeletal
Sandy or sandy-skeletal

Loamy

Clayey

The meaning of each of these terms is the same as that
defined for particle-size classes of mineral soils. The
proper term is selected to describe the weighted average
particle size of the upper 30 cm of the mineral layer or that
part of the mineral layer that is within the control section,
whichever is thicker.

Mineralogy classes

Mineralogy classes of Histosols are of three kinds,
according to the nature of the subgroup or great group.

Ferrihumic.--Containing ferrihumic materials within
the control section (applied to Fibrists, Hemists, and
Saprists, except Sphagnofibrista and sphagnic subgroups
of other great groups). Bog iron is present in some
Histosols or in organic soi) materials. It is called
ferrihumic material. It consists of authigenic deposits
(formed in place) of hydrated iron oxides mixed with
varying kinds or amounts of organic materials. The


218
meets all requirements of a spodic horizon except the
index of accumulation.

‘Spodic Cryopeamments
KCAE. Other Cryopsamments that have lamellae within

150 cm of the soil surface that meet all requirements for
an argillic horizon except thickness.

Alfic Cryopsammentsa
KCAF. Other Cryopsamments.

Typic Cryopsamments
Quartzipsamments
Key to subgroups

KCCA. Quartzipsamments that have a lithic contact
within 60 cm of the soil surface.

Lithic Quartzipsamments
KCCB. Other Quartzipsamments that:

1. Have mottles above a depth of 100 cm that have
chroma of 2 or less or, if the color is due to uncoated
sand grains, have the water table within 100 cm of the
soil surface for 60 or more days, cumulative, in most
years; and

2. Have an albic horizon’ at the surface or
immediately under an A or an Ap horizon that is
underlain by another horizon that has a color value
more than one unit darker or chroma of 6 or more; and

3. Have a difference of less than 5°C between the mean
winter and mean summer soil temperatures at a depth

of 50 cm,
‘Tropaquodic Quartzipsamments
KCCC., Other Quartzipsamments that:

1. Have mottles above a depth of 100 cm that have
chroma of 2 or less or, if the color is due to uncoated
sand grains, have a water table within 100 cm of the
soil surface for 60 or more days, cumulative, in most
years; and

2, Have an albic horizon!” at the surface or
immediately under an A or an Ap horizon that is
underlain by another horizon that has a color value
more than one unit darker or chroma of 6 or more.
i a1 it

KCCD. Other Quartzipsamments that have mottles above
a depth of 100 cm that have chroma of 2 or less or, if the
color is due to uncoated sand grains, have the water table

°
‘The albic horiton must ba thick enough to be preserved after the soil

ko adapt of 18 on in mined,
10

‘The albie horison must be thick enough to be preserved after the soil
to a depth of 10 om ie mined.


190
upper boundary of an organic layer with andic soil
properties, whichever is shallower.

Vitrands, p. 153

BF. Other Andisols that have an ustic soil moisture
regime.

Ustands, p.150
BG. Other Andisols.

Udands, p. 139
AQUANDS
Key to great groups

BAA. Aquands that have a cryic or pergelic soil
temperature regime.
Cryaquands, p.130

BAB. Other Aquands that have a placic horizon within
100 cm of the mineral soil surface or upper boundary of
an organic layer with andic soil properties, whichever is
shallower, in half or more of each pedon.

Placaquands, p. 133

BAC, Other Aquands that have a cemented layer in 75
percent or more of each pedon which does not slake in

water after drying, with its upper boundary within 100
cm of the mineral soil surface or upper boundary of an
organic layer with andic soil properties, whichever is

shallower,

Durequands, p, 131
BAD. Other Aquands that have 1500 kPa water retention
of Jess than 15 percent on air-dried samples and leas
than 30 percent on undried samples, throughout a
thickness of 35 cm or more within 60 cm of the mineral
soil surface or upper boundary of an organic layer with
andic soil properties, whichever is shallower.

p. 133

BAE, Other Aquands that have a melanie epipedon.
Melanaquands, p.132

BAF. Other Aquands.
Haplaquands, p. 131

Cryaquands
Key to subgroups
BAAA. Cryaquands that have a lithic contact within 50
cm of the soil surface.

Lithic Cryaquands
BAAB., Other Cryaquands that have a mean annual soil
temperature of 0°C or lower.

Pergelic Cryaquands

BAAC. Other Cryaquands that have a histic epipedon.

Histic Cryaquands


119

is no more than one unit higher than the value, moist.
Rhodie in

ICDJ, Other Kandiustalfa.
‘Typic Kandiustalfs

Kanhaplustalfs

Key to subgroups
ICEA. Kanhaplustalfs that have a lithic contact within 50

em of the soil surface,
Lithic Kanhaplustalfs

ICEB, Other Kanhaplustalfs that have mottles that have
chroma of 2 or less within 75 cm of the soil surface, and
the mottled horizon is saturated with water at some time
when the soil tomperature at that depth is 5°C or higher or

the soil has artificial drainage.
Aquic Kanhaplustalfs

ICEC. Other Kanhaplustalfs that, when neither irrigated
nor fallowed to store moisture:

1. If the soil temperature regime is mesic or thermic,
are moist less than six-tenths of the time in half or
more years in some part of the moisture control section
(not necessarily the same part) when the soil
temperature at a depth of 60 cm exceeds 5°C; or

2. If the soil temperature regime is hyperthermic,

isomesic, or warmer, are moist in most years in some
or all parts of the moisture control section for less than
180 days during a Period w when the soil temperature at a

dopth of 50 cm exceeds 8°C.
Aridic Kanhaplustalfs

ICED. Other Kanhaplustalfs that, when neither irrigated
nor fallowed to store moisture:

1 If the soil temperature regime is mesic or thermic,
are dry for 136 or less cumulative days in some part of
the moisture control section when the soil temperature
at a depth of 50 cm exceeds 5°C; or

2. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or less
during a period y when the soil temperature at a depth of

50 cm exceeds 8°C.
Udic Kanhaplustalfs

ICEE. Other Kanhaplustalfs that have, throughout the
argillic or kandic horizon, a hue of 2.5YR or redder, and
have a value, moist, of 3 or less and have a value, dry, that


262

extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.
Vitrandic:

‘Xerochrepts

JDEL Other Xerochrepts that have a gypsic horizon within
a depth of 100 cm of the soil surface.

Gypsic Xerochrepts

JDEJ. Other Xerochrepts that:

1. Have mottles that have chroma of 2 or less within 75
cm of the soil surface; and

2. Have base saturation (by NH,OAc) of less than 60
percent in all parts of the soil between depths of 25 and
75 cm below the soil surface.

Aquic Dystric Xerochrepts

JDEK. Other Xerochrepts that have mottles that have
chroma of 2 or less within 75 cm of the soil surface.

JDEL. Other Xerochrepts that:

1. Have base saturation (by NH,OAc) of less than 60

percent in all parts of the soil between depths of 25 and
75 cm below the soil surface; and

2. Have a content of organic carbon that decreases
irregularly with depth, or are 125 cm or more deep to a
lithic or a paralithic contact and have more than 0.2
percent organic carbon at 125 cm below the soil surface;
and

3. Have slopes of 25 percent or less.
Dystric Fluventic Xerochrepts

JDEM. Other Xerochrepts that:

1. Have a content of organic carbon that decreases
irregularly with depth, or are 125 cm or more deep to a
lithic or a paralithic contact and have more than 0.2
percent organic carbon at 125 cm below the soil s1
and

2, Have slopes of 26 percent or less.
Fiwventic Xerochrepts
IDEN. Other Xerochrepts that have base saturation (by
NH, 0Ac) of less than 60 percent in all parts of the soil

between depths of 25 and 75 cm below the soil surface.
Dystric Xerochrepts

JDEO. Other Xerochrepts that have a calcic horizon or soft
powdery lime within a depth of 150 cm if the weighted
average particle-size class from depths of 25 to 100 cm is
sandy or to a lithic or paralithic contact if one is

shallower than 100 cm, or within a depth of 110 em ifthe
weighted average particle-size class is loamy, or within a

depth of 90 cm if it is clayey.
Calcixerollic Xerochrepts


954
DCEB. Other Hapiustox that have a petroferric contact
within 125 cm of the soil surface.
Petroferric Haplustox

DCEC. Other Haplustox that have mottles of 4 or more
value moist and 2 or leas chroma within a depth of 125 cm
of the soil surface and a lithic contact within 126 cm of the

soil surface.
Aquie Lithie Haplustox

DCED. Other Haplustox that have a lithic contact within a
depth of 125 cm of the soil surface.
Lithic Haplustox

DCEE. Other Haplustox that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the
soil surface and mottles of 4 or more value moist and 2 or
less chroma within a depth of 125 cm of the soil surface.
Plinthaquic

DCEF. Other Haplustox that have more than 5 percent
plinthite in some horizon within a depth of 125 cm of the

soil surface.
Plinthic Haptustox

DCEG. Other Haplustox that have mottles of 4 or more
value moist and 2 or leas chroma within a depth of 125 cm
of the soil surface and have the lower boundary of the oxic
horizon within a depth or 125 em of the soil surface.
Aqueptic Haphastox

DCEH. Other Haplustox that have mottles of 4 or more
value moist and 2 or leas chroma within a depth of 125 cm

of the soil surface,
Aquic Haplustox

DCEL Other Haplustox that have the lower boundary of the
oxic horizon within a depth or 125 cm of the soil surface.

DCEJ. Other Haplustox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and a color hue of 2.5YR or redder with
moist values of less than 4 in most of the 25 to 126 cm depth

from the soil surface.
Humic Rhodic Haplustox

DCEK. Other Haplustox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of
surface litter, and color hue of 7.5YR or yellower with
moist values of 6 or more in most of the 25 to 125 cm depth
from the soi] surface.

Humic Xanthic Haplustox

DCEL. Other Haplustox that have 16 kg or more organic
carbon per square meter to a depth of 100 cm, exclusive of

surface litter.
Humic Haplustox

DCEM. Other Haplustox that have a color hue of 2.5YR or
redder with moist values of less than 4 in most of the 25 to

125 cm depth from the soil surface.
Rhodie Haphustox


283
HEG. Other Borolls.

Haploborolis, p. 290
Argiborolls
Key to subgroups
HEDA. Argiborolls that have a lithic contact within a
depth of 50 cm of the surface.
Lithic Argiborolls

HEDB. Other Argiborolls that:

1. Have an argillic horizon that has an increase in
clay content of 20 percent (absolute) or more within a
vertical distance of 7.5 cm below the upper boundary;
and

2, Have either or both

a. A color value, dry, of 6 or more in the upper 18 cm
of the mollic epipedon, after mixing, or in any Ap
horizon that is more than 18 cm thick; or

b. A moisture control section that is dry in some part

six-tenths or more of the time in most years that the

soil temperature at a depth of 50 cm is above 5°C.
Abruptic Aridic Argiborolls

HEDC. Other Argiborolls that:

1. Have an argillic horizon that has an increase in
clay content of 20 percent (absolute) or more within a
wertieal distance of 7.5 cm below the upper boundary;
an

2. Have a chroma (rubbed), moist, of 1 or less in the
upper 18 cm of the mollic epipedon after mixing, or in
any Ap horizon that is more than 18 cm thick, or the soil
is moist in some or all parts of the moisture control
section at all times in most years.

Abruptic Udic Argiborolis
HEDD, Other Argiborolls that:

1. Have an lic horizon that has an increase in
clay content of 20 percent (absolute) or more within a
vertical distance of 7.5 cm below the upper boundary;
an

2. Have an albic horizon immediately below the mollic
epipedon; and
3. Have mottles that have chroma of 2 or leas within 100
cm of the surface and, if undrained, are continuously
saturated with water for as long as 90 days within 100
em of the surface.

Albic Argiborolls

HEDE. Other Argiborolls thet have an argillic horizon
that has an increase in clay content of 20 percent


115

ICCH. Other Natrustalfs.

Paleustalfs

Key to subgroups
ICA. Paleustalfs that:

1. When neither irrigated nor fallowed to store
moisture:

a. If the soil temperature regime is mesic or thermic,
are dry for less than four-tenths of the cumulative
days in some part of the moisture control section
hen the soll temperature at « depth of 60 em exceeds
5°C; or

b. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or
Jess during a period when the soil temperature at a
depth of 50 cm exceeds 8°C; and

2. Have the following combination of characteristics:

a. Cracks at some period in most years that are 1 cm
or more wide at a depth of 50 cm, that are at least 30
cm long in some part, and that extend upward to the
surface or to the base of an Ap horizon if the soil is not
irrigated; and

b. A coefficient of linear extensibility (COLE) of 0.07
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more
in the upper 125 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 125 cm; and

c. More than 36 percent clay in horizons that total
more than 60 cm in thickneas.
Udertic Paleustalfs

ICFB. Other Paleustalfs that have the following
combination of characteristics:

1 Cracks at some period in most years that are 1. cm or
more wide at a depth of 50 cm, that are at least 30 cm
long in some part, and that extend upward to the surface
or to the base of an Ap horizon if the soil is not irrigated;
and

2. A coefficient of linear extensibility (COLE) of 0.07 or
more in a horizon or horizons at least 50 cm thick, and
8 potential linear extensibility of 6 cm or more in the
upper 125 cm of the soil or in the whole soil if a lithic or


281

HBFB, Other Haplaquolls that have the following
combination of characteristics:

1, Cracks at some period in most years that are 1 cm or
more wide at a depth of 50 cm, that are at Ieast 30 cm
long in some part, and that extend upward to the surface
or to the base of an Ap horizon; and

2. A coefficient of linear extensibility (COLE) of 0,09 or
more in a horizon or horizons at least 50 cm thick, and
a potential linear extensibility of 6 cm or more in the
upper 100 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 50 cm but shallower
than 100 cm; and

3, More than 36 percent clay in horizons that total more
than 50 cm in thickness.
Vertic Haplaquolls
HBFC. Other Haplaquolls that have a histic epipedon.
Histic Hapla

HBFD. Other Haplaquolls that have a buried Histosol that
has its upper boundary within 100 em of the soil surface.
‘Thapto-Histic Haplaquolls

HBFE. Other Haplaquolls that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1, Bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cmTM or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent; or

2. Fragments coarser than 2.0 mm constitute more than.
36 percent of the whole soil and cinders, pumice, and
pumice-like fragments make up more than 66 percent
of these fragments; or

8, The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2,0 mm fraction and contains
either:

a. More than 30 percent volcanic glass; or

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Aquandic Haplaquolls

HBFF. Other Haplaquolls that have a horizon 15 cm or
more thick that is within 100 cm of the surface and that
contains at least 20 percent (by volume) of durinodes or is
brittle and has firm consistence when moist.

Duric Haplaquolls
HBFG. Other Haplaquolls that have a mollic epipedon
that is 60 em or more thick.
Cumulic Haplaquolls

HBFH. Other Haplaquolls that have slope of less than 25
percent; and


250

2. A coefficient of linear extensibility (COLE) of 0.09
or more in a horizon or horizons at least 50 cm thick,
and a potential linear extensibility of 6 cm or more in
the upper 100 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 100 cm; and

3, More than 35 percent clay in horizons that total more
than 50 cm in thickness.
Vertic Tropaquepts

JAGD. Other Tropaquepts that have a histic epipedon that
has its upper boundary at or near the surface.

Histic Tropaquepts

JAGE. Other Tropaquepts that have, throughout a
cumulative thickness of 18 cm or more and within a
depth of 75 em, one or more of the following:

1, Bulk density of the less than 2.0 mm fraction
measured at 33 kPa water retention, of 1.0 gem or
jess and acid-oxalate-extractable aluminum plus 1/2
acid-oxalate-extractable iron of more than 1.0 percent;
or

2. Fragments coarser than 2.0 mm constitute more
than 365 percent of the whole soil and cinders, pumice,
and pumice-like fragments make up more than 66
percent of these fragments; or

3. The 0.02 to 2.0 mm fraction constitutes at least 30
percent of the less than 2.0 mm fraction and contains
either:

a. More than 30 percent voleanic glass; or

b, At least 5 percent volcanic glass and acid-

oxalate-extractable aluminum plus 1/2 acid-

oxalate-extractable iron of 0.40 percent or more.
Aquandic

JAGF, Other Tropaquepts that have 5 percent or more (by
volume) of plinthite in one or more subhorizons within

150 cm of the soil surface.
Plinthic Tropaquepts

JAGG, Other Tropaquepts that have in more than 40
percent of the matrix in one or more subhorizons between
the A or Ap horizon and a depth of 75 cm one or more of
the following:

1. If mottled and if the hue is 2.5Y or redder and the
value, moist, is more than 5, the chroma, moist, is 3 or
more; if the value, moist, is 5 or less, the chroma,
moist, is 2 or more; or

2. If mottled and if the hue is yellower than 2.5Y, the
chroma, moist, is 3 or more; or

3. The chroma, moist, is 2 or more if not mottled.
Aeric

JAGH. Other Tropaquepts.
Typic Tropaquepts


309

2. If the soil temperature regime is hyperthermic or
isomesic, or warmer, are moist in some or all parts of
the moisture control section for leas than 90 consecutive
days during any period when the soil temperature at a
depth of 60 cm exceeds 8°C.

Aridic Calciustolls

HFODK. Other Calciustolls that, when neither irrigated
nor fallowed to store moisture:

1. If the coil temperature regime is mesic or thermic,
are dry in some or all parts of the moisture control
section for four-tenths or less of the cumulative days
when the soil temperature at a depth of 50 cm exceeds
65°C; or

2. If the soil temperature regime is hyperthermic,
isomesic, or warmer, the soils are dry in some or all
parts of the moisture control section for 90 days or less
during a period when the soil temperature at a depth of
50 cm exceeds 8°C.

Udic Caleiustolls

HFDL. Other Calciustolls.

Typic Calciustolls
Durustolls
Key to subgroups
HFAA. Durustolls that have a natric horizon above the
duripan,

Natric Durustolls

HFAB. Other Durustolla that do not have an argillic
horizon above the duripan and, when neither irrigated
nor fallowed to store moisture:

1, If the soil temperature regime is mesic or thermic,
are dry six-tenths or more of the time in half or more
years in some part of the moisture control section (not
necessarily the same part) during the period when the
soil temperature at a depth of 50 cm exceeds 6°C; or

2. If the soil temperature regime is hyperthermic or
isomesic, or warmer, are moist in some or all parte of
the moisture control section for less than 90 consecutive
days during the period when the soil temperature at a
depth of 50 cm exceeds 8°C; and

8, Have an aridic moisture regime that borders on
ustic.
Orthidic Durustolls

HFAC. Other Durustolls that, when neither irrigated nor
fallowed to store moisture:

1. If the soil temperature regime is mesic or thermic,
are dry six-tenths or more of the time in half or more
years in some part of the moisture control section (not.
necessarily the same :) during a period when the
soil temperature at a of 60 cm exceeds 5°C; or


3

called an epipedon (Gr. epi, over or upon, and pedon,

soil). The epipedon not only has formed at the surface but
it also has been either appreciably darkened by organic
matter or eluviated or, as a minimum, rock structure has
been destroyed. Such a horizon may become covered by
thin deposits of fresh alluvium or by thin eolian deposits
without losing its identity as an epipedon, The depth to
which an epipedon must be buried to be considered part of
a buried soil is defined below. Generally a buried
horizon lies below a depth of 50 cm or more, usually more.

There can be only one epipedon formed in the mineral
surface horizon(s) of a soil. This epipedon may be
overlain by organic materials that may meet the
definition of a histic epipedon (defined later). Otherwise
one soil may contain only one epipedon.

A recent alluvial or eolian deposit that retains fine
stratifications or an Ap horizon that is directly underlain
by material that retains fine stratifications is not
included in the concept of the epipedon because time has
not been sufficient for scil-forming processes to erase
these transient marks of deposition and for diagnostic
and accessory properties to develop.

The epipedon is not a synonym for the A horizon because
it may include part or all of the illuvial B horizon if the
darkening by organic matter extends from the surface
into or through the B horizon. To avoid changes in
classification of a soil as the result of plowing, the
properties of the epipedon, except for structure, should be
determined after the surface soil to a depth of 18 cm has
been mixed or, if the depth to bedrock is less than 18 cm,
after the whole soil down to rock has been mixed.

Anthropic epipedon.

In summary, the anthropic epipedon conforms to all the
requirements of the mollic epipedon except (1) the limits
on acid-soluble PaOs, with or without the base saturation,
or (2) the length of the period during which it has
available moisture. Additional data on anthropic
epipedons from several parts of the world may permit
improvements in this definition.

Histic epipedon (Gr. histos, tissue)

‘The histic epipedon normally is at the surface, although it
may be buried at a shallow depth. It normally is a thin
horizon of peat or muck if the soil has not been plowed. If
the soil has been plowed, the histic epipedon has the very
high content of organic matter that results from mixing
peat with some mineral material. Since peaty deposits
occur in wet places, the histic epipedon either is saturated
with water for 30 consecutive days or more during the
year or has been artificially drained.


of the argillic or kandic horizon if these horizons are
thicker than 100 em; and

2. Do not have a lithic, paralithic, or petroferric contact
within 150 cm of the soil surface; and

8, Have a clay distribution such that the percentage of
clay does not decrease from its maximum amount by as
much as 20 percent within a depth of 150 cm from the
soil surface, or the layer in which the clay percentage
decreases by more than 20 percent has at least 5 percent
of the volume consisting of skeletans on faces of peds
and there is at least 3 percent (absolute) increase in

clay below the layer.
Kandiudalfs, p. 101

IEH, Other Udalfs that have a CEC of 16 cmoK+) or less
per kg clay (by IN NH,OAc pH 7) and an ECEC of 12
cmol(+) or less per kg clay (sum of bases extracted with
1N NH40Ac pH 7 plus 1N KCl-extractable Al) in the
major part of the argillic or kandic horizon, or the major
part of the upper 100 cm of the argillic or kandic horizon if
these horizons are thicker than 100 cm.

Kanhapludalfs, p. 102

IEI. Other Udalfs that

1. Do not have a lithic or paralithic contact within 150
cm of the soil surface; and

2. Have clay distribution such that the percentage of
clay does not decrease by as much as 20 percent of the
maximum within a depth of 150 cm from the soil
surface, or the layer in which the clay percentage
decreases by more than 20 percent has at least 5 percent
of the volume consisting of skeletans on faces of peds
and there js at least 3 percent (absolute) increase in
clay below the layer; and

8, Have one or more of the following in the argillic
horizon:

a. Hue redder than 10YR and chroma more than 4
dominant in the matrix in at least the lower part; or

b. Hue of 2.5YR or redder and value, moist, of leas
than 4 and value, dry, of less than 5 throughout the
major part; or

c. Many coarse mottles that have hue redder than
‘7.5YR or chroma more than 5, or both, in some

subhorizon.
Paleudalfe, p. 103

IEJ. Other Udalfe that have an argillic horizon that has
throughout its thickness a hue redder than 5YR, a color


37

Interfingering of albic materials consists of penetrations
of albic materials into an underlying argillic or natric
horizon along faces of peds, primarily along vertical
faces but to a lesser degree along horizontal faces. No
continuous albic horizon need be present. The
penetrations are not wide enough to constitute tonguing,
but they form continuous skeletans (ped coatings of clean
silt or sand defined by Brewer, 1964) more than 1 mm
thick on the vertical ped faces, which means a total width
of more than 2 mm between abutting peds. Because quartz
is such a common constituent of soils, the skeletans
usually appear to be nearly white when dry and light gray
when moist, but their color is determined in large part by
the color of the sand or silt fraction.

To be recognized as interfingering, all the following
requirements must be met in a horizon that is 6 cm or
more thick:

1. Half or more of the matrix consists of peds of the
argillic or natric horizon; and

2 Albic materials are thicker than 2 mm on vertical
faces between abutting peds but are too thin to be tongues;
and

3, Clay skins are present in the peds, at least in pores.

Albic materials meet the following requirements for
color: If the value, dry, is 7 or more, or the value, moist, is
6 or more, the chroma is 3 or less either dry or moist. Ifthe
value, dry, is 5 or 6 and the value, moist, is 4 or 5, the
chroma is closer to 2 than to 3 either dry or moist.

Weatherable minerals

Several references are made to weatherable minerals in
the text of this chapter and later chapters. Obviously, the
stability of a mineral in a soil is a partial function of the
soil moisture regime. In the context of the references in
the definitions of diagnostic horizons and of various taxa,
a humid climate is always assumed, either present or
past. Minerals that are included in the meaning of
weatherable minerals are:

1. Clay minerals: All 2:1 lattice clays except one that is
currently considered to be an aluminum-interlayered
chlorite. Sepiolite, talc, and glauconite are also included
in the meaning of this group of weatherable clay
minerals, although they are not everywhere of clay size.

2, Silt- and sand-size minerals (0.02 to 0.2 mm in
diameter): Feldspars, feldspathoids, ferromagnesian
minerals, glass, micas, zeolites, and apatite.


or more subhorizons within a depth of 150 em below the
soil surface; and

2. Have 5 percent or more plinthite (by volume) in one
or more subhorizons within 150 m of the soil surface.
Acradoxic Plinthic Kandiudults

GCCI. Other Kandiudults that have an ECEC (sum of
bases plus 1N KCl-extractable Al) of 1.5 cmol(+) or less
per kg clay in one or more subhorizons within a depth of
150 cm below the soil surface.

Acrudoxic Kandindults

GCCJ. Other Kandiudults that:

1. Have the following combination of characteristics
in the upper 75 cm of the soil if the chroma in all or part
of the upper 76 cm is not controlled by uncoated sand
grains; or if the chroma throughout the upper 76 cm is
controlled by uncoated sand grains, have the
following combination of characteristics throughout
the upper 12.8 cm of the argillic or kandic horizon:

a. Mottles that have a color value, moist, of 4 or more
and chroma, moist, of 2 or less accompanied by
mottles of higher chroma that are due to segregation
of iron; and

b. Saturation with water in the mottled zone at some
time of year when the soil temperature in that zone
is 5°C or higher, or there is artificial drainage; and

2, Have § percent or more plinthite (by volume) in one
or more subhorizons within 150 cm of the soil surface.
Plinthaquic Kandiudults

GCCK. Other Kandiudults that:

1, Have, throughout a cumulative thickness of 18 cm or
more and within a depth of 75 cm, bulk density of the
less than 2.0 mm fraction, measured at 33 kPa water
retention, of 1.0 g cm’ or less and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of more than 1.0 percent; and

2. Have the following combination of characteristics
in the upper 75 em of the soil if the chroma in all or part
of the upper 75 em is not controlled by uncoated sand
grains; or if the chroma throughout the upper 75 em ia
controlled by uncoated sand grains, have the
following combination of characteristics throughout
the upper 12.8 cm of the argillic or kandic horizon:

a.Mottles that have a color value, moist, of 4 or more
and chroma, moist, of 2 or less accompanied by
mottles of higher chroma that are due to segregation

of iron; and

b. Saturation with water in the mottled zone at some

time of year when the soil temperature in that zone

is 5°C or higher, or there is artificial drainage.
‘Aquandie

GCCL. Other Kandiudults that have, throughout a
cumulative thickness of 18 cm or more and within a depth


159

Chapter7

Aridisols

KEY TO SUBORDERS
FA, Aridisols that have an argillic or a natric horizon.

Argids, p. 159
FB, Other Aridiaols.

Orthids, p. 178
ARGIDS
Key to great groups

FAA. Argids that have a duripan’ below an argillic
horizon and do not have a natric horizon.

Durargids, p.159
FAB, Other Argids that have a duripan below a natric
horizon,
Nadurargids, p. 169

FAC. Other Argids that have a natric horizon and do not
have a petrocalcic horizon.
Natrargids, p. 170

FAD. Other Argids that do not have a lithic or paralithic
contact within 50 cm of the soil surface, that have a
petrocalcic horizon or that have an argillic horizon that
bas 35 percent or more clay in some part, and that have
either:

1, An increase of 15 percent or more clay (absolute)
within a vertical distance of 2.5 cm at the upper
boundary of the argillic horizon; or

2. An increase of 10 percent or more clay (absolute) if
cultivated and the lower boundary of the Ap horizon is
the upper boundary of the argillic horizon.

Paleargids, p. 174
FAE. Other Argids.

Haplargids, p. 163
Durargids
Key to subgroups

FAAA, Durargids that are saturated with water within
100 cm of the surface for 90 consecutive days or more in
most years, or have any of the following characteristics
within 100 cm of the soil surface if there is ground water
within this depth at some time in most years:

rT
A duripan oF # petrocalcic horizon must have ite upper boundary within
100 em of the surface to be diagnostic in Aridisola,


124

b. At least 5 percent volcanic glass and acid-oxalate-
extractable aluminum plus 1/2 acid-oxalate-
extractable iron of 0.40 percent or more.

Vitrandic Haploxeralfs

IDGG, Other Haploxeralfs that:

1. Have mottles that have chroma of 2 or less within 75
cm of the soil surface and the mottled horizon is
saturated with water at some time when the temperature
of that horizon is 5°C or higher or there is artificial
drainage; and

2. Have an argillic horizon that has base saturation (by
sum of cations) of less than 75 percent in one or more
subhorizons of the upper 75 cm or to a lithic or paralithic
contact, whichever is shallower.

Aquultic Haploxeralfs

IDGH. Other Haploxeralfs that have mottles that have
chroma of 2 or less within 75 em of the soil surface and the
mottled horizon is saturated with water at some time when
the temperature of that horizon is §°C or higher or there is
artificial drainage.

Aquic Haploxerelfs

IDGI. Other Haploxeralfs that have exchangeable sodium
that is 15 percent or more of the CEC (at pH 8.2) in one or
more subhorizons in the argillic horizon,

Natric Haploxeralfs

IDGJ. Other Haploxeralfs that have an argillic horizon
that is discontinuous vertically within the upper 20 cm or
has a sandy particle-size class.

Psammentic Haploxeralfs

IDGK. Other Haploxeralfs that have 5 percent or more
plinthite (by volume) in one or more subhorizons within

150 cm of the soil surface.
Plinthic Haploxeralfs

IDGL, Other Haploxeralfs that have a calcic horizon that
has its upper boundary within the upper 100 cm of soil.
Calcic Haploxeralfs

IDGM. Other Haploxeralfa that have an argillic horizon
that has base saturation (by sum of cations) of less than 75
percent in one or more subhorizons of the upper 75 cm or to
a lithic or paralithie contact, whichever is shallower.
Ultic Haploxeralfs

IDGN. Other Haploxeralfs that have an A horizon that
has throughout its upper 10 cm a color value, moist, of 3 or
less and 0.7 percent or more organic carbon, or have an
Ap horizon that has a color value, moist, of 3 or less and
contains 0.7 percent or more organic carbon.

Mellic Haploxeralfs


204
(absolute) or more within a vertical distance of 7.5 cm

below the upper boundary.
Abruptic Argiborolls
HEDF. Other Argiborolls that:
1, Have the following combination of characteristics:

a. Cracks at some period in most years that are 1 cm
or more wide at a depth of 60 cm, that are at least 30
em long in some part, and that extend upward to the
surface or to the base of an Ap horizon; and

b. A potential linear extensibility of 6 cm or more in
the upper 100 cm of the soil or in the whole soil if a
lithic or paralithic contact is deeper than 50 cm but
shallower than 100 cm; and

¢. More than 35 percent clay in horizons that total
more than 50 cm in thickness; and

. Have both

r<)

a. Acolor value, dry, of & in the upper 18 cm of the
mollic epipedon, after mixing, or in any Ap horizon
that is more than 18 cm thick; and

b. A moisture control section that is dry in some part
six-tenths or more of the time that the aoil
tomperature at a depth of 0 cm is above 5°C in moat

years.
Ustertic Argiborolls

HEDG. Other Argiborolls that have the following
combination of characteristics:

1. Cracks at some period in most years that are 1cm or
more wide at a depth of 50 cm, that. are at least 30 cm
long in some part, and that extend upward to the surface
or to the base of an Ap horizon; and

2. A potential linear extensibility of 6 cm or more in the
upper 100 cm of the soil or in the whole soil if a lithic or
paralithic contact is deeper than 60 cm but shallower
than 100 cm; and

3, More than 35 percent clay in horizons that total more
than 50 cm in thickness.
Vertic Argiborolls

HEDH. Other Argiborolls that have, throughout a
cumulative thickness of 18 em or more and within a depth
of 75 cm, bulk density of the less than 2.0 mm fraction,
measured at 33 kPa water retention, of 1.0 g cm“ or less
and acid-oxalate-extractable aluminum plus 1/2 acid-
oxalate-extractable iron of more than 1.0 percent.

HEDI. Other Argiborolls that have, throughout a
cumulative thickness of 18 cm or more and within a depth
of 75 cm, one or more of the following:

1, Fragments coarser than 2.0 mm constitute more than
36 percent of the whole soil and cinders, pumice, and


within that depth at some time when the soil
temperature is 6°C or higher; or

b. If the upper boundary of the argillic horizon is

deeper than 50 cm, has mottles that have chroma of 2

or less within a depth of 75 cm below the soil surface.
‘Albaquic Hapludalfs

TEKL. Other Hapludalfs that:

1. Have interfingering of albic materials and albic
materials surrounding some peds in the upper part of
the argillic horizon; and

2. Have an argillic horizon that

a. If its upper boundary is less than 50 cm below the
soil surface, has mottles that have chroma of 2 or less
in the upper 25 cm, and it is saturated with water
within that depth at some time when the oil
temperature is 5°C or higher; or

b, If the upper boundary of the argillic horizon is
deeper than 50 cm, has mottles that have chroma of 2
or less within a depth of 75 cm below the soil surface.

Glossaquic Hapludalfs
IEKM. Other Hapludalfs that:
1. Have an argillic horizon that:

a. If its upper boundary is less than 50 cm below the
soil surface, has mottles that have chroma of 2 or less
in the upper 25 cm, and it is saturated with water
within that depth at some time when the soil
temperature is 5°C or higher; or

b. If the upper boundary of the argillic horizon is
deeper than 50 cm, has mottles that have chroma of 2
or less within a depth of 75 cm below the soil surface;
and

2. Have base saturation (by sum of cations) of less than
60 percent at a depth 125 cm below the top of the argillic
horizon, or 180 cm below the soil surface, or
immediately above a lithic or paralithic contact,
whichever is least.
Aquultic Hapludalfs
TEKN. Other Hapludalfs that:

1. Have an argillic horizon that

a. If ite upper boundary is less than 50 cm below the

soil surface, has mottles that have chroma of 2 or less
in the upper 25 cm, and it is aaturated with water


40

(b) The organic material consists of sapric or
hemic materials, or consists of fibric materials
that are less than three-fourths moss fibers by
volume and have a moist bulk density of 0.1 or
more; and

b, Have organic soil materials that

(1) Do not have a mineral layer as much as 40 cm
thick either at the surface or whose upper boundary is
within a depth of 40 cm from the surface; and

(2) Do not have mineral layers, taken cumulatively,
as thick as 40 em within the upper 80 cm; and

8, Do not have andic soil properties in layers 35 cm or
more thick within a depth of 60 cm from the surface.

It is a general rule that a soil is classed as an organic soil
(Histosol) either if more than half of the upper 80 cm (32
in.) of soil is organic or if organic soil material of any
thickness rests on rock or on fragmental material
having interstices filled with organic materials.

KINDS OF ORGANIC SOIL MATERIALS

Three basic kinds of organic soil materials are
distinguished, fibric, hemic, and sapric, according to the
degree of decomposition of the original plant materials.

Fibers

A fiber is a fragment or piece of plant tissue, excluding
live roots, that is large enough to be retained on a 100-
mesh sieve (openings 0.15 mm in diameter) and that
retains recognizable cellular structure of the plant from
which it came. The material is screened after dispersion
in sodium hexametaphosphate. Fragments larger than 2
cm in cross section or in their smallest dimension, to be
called fibers, must be decomposed enough that they can be
crushed and shredded with the fingers. Fragments of
wood that are larger than 2 cm in cross section and that
are 80 undecomposed that they cannot be crushed and
shredded with the fingers are not considered fibers. Such
fragments of undecomposed wood in the form of large
branches, logs, and stumps are considered to be coarse
fragments, comparable to gravel, stones, and boulders in
mineral soils.

Fibric soil materials (L. fibra, fiber)

Fibric soil materials have the following characteristica:


PERCENT SAND

Chart showing the percentages of clay (below 0.002 mm), silt (0.002
to 0.05 mm), and sand (0.05 to 2.0 mm) in the basic soil textural
classes.