Paleorthids

Key to subgroups
FBBA. Paleorthids which have both:

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

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to noncarbonate clay, as follows:

a. In the upper 40 cm of the soil, if the upper
boundary of the petrocalcic horizon is 40 cm
or more below the soil surface,

(1) 0.60 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.15 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.64-(0.038 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
land 13; or

b. In the upper 18 cm of the soil, if the
upper boundary of the petrocalcic horizon is
between 18 and 40 cm from the soil surface,
(1) 0.72 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or
(2) 0.18 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or
(3) 0.77-(0.046 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between

land 13.
Borollic Paleorthids

FBBB. Other Paleorthids that have, in one or more
horizons within 100 cm of the soil surface, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:
1. A chroma of 0, or a hue of 2.5Y or yellower and
a chroma of 1; or

2. Redox concentrations and 50 percent or more
chroma of 2 or less; or

3. Fifty percent or more chroma of 2 or less, and a
higher exchangeable sodium percentage (or
sodium adsorption ratio) in more than half the


386

2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a, In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Haplustolls

HFGL., Other Haplustolls which have:

1. A mollic epipedon 50 cm or more thick with a
texture finer than loamy fine sand; and

2. An irregular decrease in organic-carbon content
from a depth of 25 cm below the mineral soil
surface to a depth of 125 cm, or to a lithic or
paralithic contact if shallower; and

3. A slope of less than 25 percent.
Cumulic Haplustolls

HFGM, Other Haplustolls that have a mollic epipedon
50 cm or more thick with a texture finer than loamy fine
sand,

Pachic Haplustolls

HFGN. Other Haplustolls that have anthraquic
conditions.
Anthraquic Haplustolls

HFGO, Other Haplustolls that have:

1. In one or more horizons within 100 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. Either 0.3 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

3. A slope of less than 25 percent.
Fluvaquentic Haplustolls

HFGP. Other Haplustolls that have, in one or more
horizons within 100 cm of the mineral soil surface,
redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or
artificial drainage).

Aquic Haplustolls


7

percentages of the fine-earth fraction in the two
parts of the control section.

15. Clayey over loamy-skeletal if there is an
absolute difference of 25 percent or more between
clay percentages of the fine-earth fraction in the
two parts of the control section.

16. Clayey over sandy or sandy-skeletal.

17. Clayey-skeletal over sandy or sandy-skeletal.
18. Coarse-loamy over clayey.

19, Coarse-loamy over fragmental.

20. Coarse-loamy over sandy or sandy-skeletal if
the coarse-loamy material contains less than 50
percent fine or coarser sand

21. Coarse-silty over clayey.
22. Coarse-silty over sandy or sandy-skeletal.

23. Fine-loamy over clayey if there is an absolute
difference of 25 percent or more between clay
percentages of the fine-earth fraction in the two
parts of the control section

24. Fine-loamy over fragmental.
25, Fine-loamy over sandy or sandy-skeletal.

26. Fine-silty over clayey if there is an absolute
difference of 25 percent or more between clay
percentages of the fine-earth fraction in the two
parts of the control section.

27. Fine-silty over fragmental.
28. Fine-silty over sandy or sandy-skeletal.
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 contains less than 50 percent fine
or coarser sand.

36. Loamy over pumiceous or cindery.

37, Loamy-skeletal over clayey if there is an
absolute difference of 25 percent or more between
clay percentages of the fine-earth fraction in the
two parts of the control section.

38. Loamy-skeletal over fragmental if the volume
of the fine-earth fraction is 35 percent or more
(absolute) greater in the loamy-skeletal part than
in the fragmental part.


258

KEFD. Other Udorthents that have, in one or more
horizons within 100 cm of the mineral soil surface,
redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or
artificial drainage).
Aquic Udorthents

KEFE. Other Udorthents that are saturated with water,
in one or more layers within 150 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Udorthents

KEFF. Other Udorthents that have 50 percent or more
(by volume) wormholes, worm casts, and filled animal
burrows between either the Ap horizon or a depth of 25
cm from the mineral soil surface, whichever is deeper,
and either a depth of 100 cm or a lithic, paralithic, or
petroferric contact, whichever is shallower,

Vermic Udorthents
KEFG. Other Udorthents.
Typic Udorthents
Ustorthents.
Key to subgroups

KEEA. Ustorthents that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Ustorthents

KEEB. Other Ustorthents which have one or both of the
following:

1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Ustorthents

KEEC. Other Ustorthents that have anthraquic
conditions.
Anthraquic Ustorthents

KEED. Other Ustorthents that have, in one or more
horizons within 100 cm of the mineral soil surface,
redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or
artificial drainage).

Aquic Ustorthents


457

percent or more either of the argillic or kandic horizon if
less than 100 cm thick, or of its upper 100 cm.
Kanhaplaquults, p. 460

GAF. Other Aquults which:

1, Do not have a lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface;
and

2. Within 150 cm of the mineral soil surface,
either:

a. Do not have a clay decrease with
increasing depth of 20 percent or more
(relative) from the maximum clay content;
or

b. Have 5 percent or more (by volume)
skeletans on faces of peds in the layer that
has a 20 percent lower clay content and,
below that layer, a clay increase of 3 percent
or more (absolute) in the fine-earth fraction.
Paleaquults, p. 461

GAG. Other Aquults that have an umbric or a mollic
epipedon.
Umbraquults, p. 463

GAH, Other Aquults that have episaturation.
Epiaquults, p. 458

GAL. Other Aquults,
Endoaquults, p. 458

Albaquults

Key to subgroups

GACA. Albaquults which have one or both of the

following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Albaquults

GACB, Other Albaquults that have 50 percent or more
chroma of 3 or more in one or more horizons between
either the A or Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and a depth of
75 cm,

4rc

Aeric Albaquults


122

a depth of 50 cm below the soil surface is higher
than 8°C.
Aridic Kandiustalfs

ICDH. Other Kandiustalfs which, if neither irrigated nor
fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for 135
cumulative days or less per year when the
temperature at a depth of 50 cm below the soil
surface is higher than 5°C; or
2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is dry
in some or all parts for less than 120 cumulative
days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8°C.
Udic Kandiustalfs

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

Rhodic Kandiustalfs

ICDJ. Other Kandiustalfs.
Typic Kandiustalfs

Kanhaplustalfs

Key to subgroups
ICEA. Kanhaplustalfs that have a lithic contact within

50 cm of the mineral soil surface.
Lithic Kanhaplustalfs

ICEB. Other Kanhaplustalfs that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Kanhaplustalfs
ICEC. Other Kanhaplustalfs which, if neither irrigated
nor fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
cout of 10 years, is dry in some part for six tenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years,
remains moist in some or all parts for less than 90


418

DDCB. Other Eutroperox that have a petroferric contact
within 125 cm of the mineral soil surface,
Petroferric Eutroperox

DDCC. Other Eutroperox that have, within 125 cm of
the mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Aquic Lithic Eutroperox
DDCD. Other Eutroperox that have a lithic contact
within 125 cm of the mineral soil surface.
Lithic Eutroperox

DDCE. Other Eutroperox that have, in one or more
horizons within 125 cm of the mineral soil surface,
both:

1. Five percent or more (by volume) plinthite; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Plinthaquic Eutroperox
DDCF. Other Eutroperox that have 5 percent or more
(by volume) plinthite in one or more horizons within
125 cm of the mineral soil surface.
Plinthic Eutroperox

DDCG. Other Eutroperox that have, in one or more
horizons within 125 cm of the mineral soil surface,
redox depletions with a color value, moist, of 4 or more
and a chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage).

Aquic Eutroperox
DDCH. Other Eutroperox that have both:

1. A clay content of 40 percent or more in the fine-
earth fraction between the soil surface and a depth
* of 18 cm, after mixing; and
2. A kandic horizon that has its upper boundary
within 150 cm of the mineral soil surface.
Kandiudalfic Eutroperox

DDCI. Other Eutroperox which have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. An oxic horizon that has its lower boundary
within 125 cm of the mineral soil surface.
Umbreptic Eutroperox


2

contains more organic matter. It may have formed in an
argillic, a cambic, or an oxic horizon. If peds are
present, the dark colors are most pronounced on
surfaces of peds.

In the field, a sombric horizon is easily mistaken for a
buried A horizon. It can be distinguished from some
buried epipedons by lateral tracing. In thin sections, the
organic matter of a sombric horizon appears more
concentrated on peds and in pores rather than uniformly
dispersed through the matrix.

Spodic horizon

The spodic horizon is an illuvial layer that is 2.5 cm or
more thick, is not part of an Ap horizon, and contains 85
percent or more spodic materials (defined below).

Spodic materials contain illuvial active amorphous
materials composed of organic matter and aluminum,
with or without iron. The term “active” is used here to
describe materials that have a high pH-dependent
charge, a large surface area, and high water retention. In
uncultivated soils the spodic horizon normally lies
below an albic horizon; less commonly, it is either
under an ochric epipedon that does not meet the color
requirements of an albic horizon, or in or under an
umbric epipedon. In some soils the spodic horizon is at
the surface of the mineral soil directly below a thinO
horizon. In cultivated soils it generally occurs directly
below the Ap horizon.

Sulfuric horizon

The sulfuric (L. sulfur) horizon is 15 cm or more thick
and is composed of either mineral or organic soil
material that has a pH value of 3.5 or less (1:1 by
weight in water, or in a minimum of water to permit
measurement) and shows evidence that the low pH
value is caused by sulfuric acid. The evidence is one or
more of the following:

1. Jarosite concentrations, or

2, Directly underlying sulfidic materials (defined
below), or

3. 0,05 percent or more water-soluble sulfate.

A sulfuric horizon forms as a result of drainage, most
commonly artificial, and oxidation of sulfide-rich
mineral or organic soil materials. Such a horizon is
highly toxic to most plants. It may also form in places
where sulfidic materials have been exposed as a result
of surface mining, road construction, dredging, or other
earth-moving operations.


422
1, Five percent or more (by volume) plinthite; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).

Plinthaquic Kandiperox

DDDF. Other Kandiperox that have 5 percent or more
(by volume) plinthite in one or more horizons within
125 cm of the mineral soil surface.

Plinthic Kandiperox

DDDG. Other Kandiperox that have, in one or more
horizons within 125 cm of the mineral soil surface,
redox depletions with a color value, moist, of 4 or more
and a chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage),

Aquic Kandiperox

DDDH. Other Kandiperox that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm: or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Kandiperox

DDDI. Other Kandiperox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 2.5YR or redder
and color value, moist, of 3 or less between 25
and 125 cm from the mineral soil surface.

Humic Rhodic Kandiperox

DDDJ. Other Kandiperox that have both:

1, 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 7.5YR or yellower
and color value, moist, of 6 or more between 25
and 125 cm from the mineral soil surface.

Humic Xanthic Kandiperox

DDDK. Other Kandiperox that have 16 kg/m? or more
organic carbon between the mineral soil surface and a
depth of 100 cm.

Humic Kandiperox

DDDL. Other Kandiperox that have 50 percent or more
hue of 2.5YR or redder and color value, moist, of 3 or
less between 25 and 125 cm from the mineral soil
surface.

Rhodic Kandiperox

DDDM. Other Kandiperox that have 50 percent or more
hue of 7.5YR or yellower and color value, moist, of 6 or


7
Argiborolls

Key to subgroups
HEDA. Argiborolls that have a lithic contact within 50

em of the mineral soil surface.
Lithie Argiborolls

HEDB. Other Argiborolls that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
em or more below the mineral soil surface.

Arenic Argiborolls
HEDC. Other Argiborolls which have:

1. An argillic horizon that has a clay increase with
depth of 20 percent or more (absolute, in the fine-
earth fraction) within its upper 7.5 cm; and

2. A color value, dry, of 5 or more either in the
upper 18 cm of the mollic epipedon, after mixing,
or in an Ap horizon 18 cm or more thick; and

3. A moisture contro] section which, in 6 or more
out of 10 years, is dry in some part for six tenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the
soil surface is higher than 5°C,
Abruptic Aridie Argiborolls
HEDD. Other Argiborolls which have both:

1, An argillic horizon that has a clay increase with
depth of 20 percent or more (absolute, in the fine-
earth fraction) within its upper 7.5 cm; and

2. Either a chroma of 1 or less (crushed and

smoothed sample) in the upper 18 cm of the

mollic epipedon, after mixing, or in an Ap horizon

18 cm or more thick, or a moisture control section

that is moist in some or all of its parts throughout

the year in 6 or more out of 10 years.

Abruptic Udic Argiborolls

HEDE. Other Argiborolls which have an argillic horizon
that has a clay increase with depth of 20 percent or more
(absolute, in the fine-earth fraction) within its upper 7.5
cm.

Abruptic Argiborolls
HEDF. Other Argiborolls which have both:
1. One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or


153

surface, or of the top of an organic layer with
andic soil properties, whichever is shallower; and
2. More than 6.0 percent organic carbon and
colors of a mollic epipedon throughout a layer 50
cm or more thick within 60 cm either of the
mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower.

Hydric Pachic Durudands

CGBD. Other Durudands that have, between 25 and
100 cm either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of
a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that
have a color value, moist, 1 unit or more higher and an
organic-carbon content 1 percent or more (absolute)
lower.

Thaptic Durudands

CGBE. Other Durudands. A
Typic Durudands N

Fulvudands

Key to subgroups
CGDA. Fulvudands that have both:

1. A lithic contact within 50 cm either of the
mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower; and
2. Undried, a 1500-kPa water retention of 70
percent or more throughout a layer 35 cm or more
thick within 100 cm either of the mineral soil
surface, or of the top of an organic layer with
andic soil properties, whichever is shallower.
Hydric Lithic Fulvudands

CGDB. Other Fulvudands that have a lithic contact
within 50 cm either of the mineral soil surface, or of the
top of an organic layer with andic soil properties,
whichever is shallower.

Lithic Fulvudands

CGDC. Other Fulvudands that have more than 2.0
emol(+)/kg Al+ (by 1N KC)) in the fine-earth fraction
of one or more horizons with a total thickness of 10 cm
or more, between 25 and 50 cm either from the mineral
soil surface, or from the top of an organic layer with
andic soil properties, whichever is shallower.

Alic Fulvudands

CGDD. Other Fulvudands that have, in one or more
horizons between 50 and 100 cm either from the
mineral soil surface, or from the top of an organic layer


148

either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Vitric Haplocryands
CBFF. Other Haplocryands that have, between 25 and
100 cm either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of
a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that
have a color value, moist, 1 unit or more higher and an
organic-carbon content | percent or more (absolute)
lower.

Thaptic Haplocryands

CBEG. Other Haplocryands that have a xeric moisture
regime.

Xeric Haplocryands
CBFH. Other Haplocryands.

Typic Haplocryands
Hydrocryands
Key to subgroups

CBDA. Hydrocryands that have a lithic contact within
50 cm either of the mineral soil surface, or of the top of
an organic layer with andic soil properties, whichever is
shallower.

Lithic Hydrocryands

CBDB, Other Hydrocryands that have a placic horizon
within 100 cm either of the mineral soil surface, or of
the top of an organic layer with andic soil properties,
whichever is shallower.

Placic Hydrocryands

CBDC. Other Hydrocryands that have, in one or more
horizons between 50 and 100 cm either from the
mineral soil surface, or from the top of an organic layer
with andic soil properties, whichever is shallower, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:

1. Two percent or more redox concentrations; or

2. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
redox depletions on faces of peds, or in the matrix
if peds are absent; or

3. Enough active ferrous iron to give a positive
reaction to a.,c'-dipyridyl at a time when the soil

is not being irrigated.
Aquic Hydrocryands

CBDD. Other Hydrocryands that have, between 25 and
100 cm either from the mineral soil surface, or from the


Keys to Soil Taxonomy

by
Soil Survey Staff

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

SMSS Technical Monograph No. 19
Fifth Edition, 1992

Pocahontas Press, Inc.
Blacksburg, Virginia -


18
2. One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm ora lithic or paralithic
contact, whichever is shallower.

Udertic Haplustalfs

ICHC. Other Haplustalfs which have one or both of the
following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.
Vertic Haplustalfs

ICHD. Other Haplustalfs that have both:

1. In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. A sandy particle size throughout a layer

extending from the mineral soil surface to the top

of an argillic horizon at a depth of 50 to 100 cm.
Aquic Arenic Haplustalfs

ICHE, Other Haplustalfs that have both:

1. In one or more horizons within 75 cm of the

‘mineral soil surface, redox depletions with a

chroma of 2 or less, and also aquic conditions for

some time in most years (or artificial drainage);

and

2. An argillic horizon that has a base saturation

(by sum of cations) of less than 75 percent

throughout.

Aquultic Haplustalfs

ICHF. Other Haplustalfs that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic


469

a, Do not have a clay decrease with
increasing depth of 20 percent or more
(relative) from the maximum clay content;
or

b. Have 5 percent or more (by volume)
skeletans on faces of peds in the layer that
has a 20 percent lower clay content and,
below that layer, a clay increase of 3 percent
or more (absolute) in the fine-earth fraction.
Kandiudults, p. 472

GCD., Other Udults that have a CEC of 16 cmol(+)/kg
clay or less (by IN NH,OAc pH 7) and an ECEC of 12
cmol(+)/kg clay or less (sum of bases extracted with IN
NH,OAc pH 7, plus 1N-KCl-extractable Al) in 50
percent or more either of the argillic or kandic horizon if
less than 100 cm thick, or of its upper 100 cm.
Kanhapludults, p. 475

GCE. Other Udults which:

1. Do not have a lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface;
and

2. Within 150 cm of the mineral soil surface,
either:

a. Do not have a clay decrease with
increasing depth of 20 percent or more
(relative) from the maximum clay content;
or

b. Have 5 percent or more (by volume)
skeletans on faces of peds in the layer that
has a 20 percent lower clay content and,
below that layer, a clay increase of 3 percent
or more (absolute) in the fine-earth fraction.
Paleudults, p. 477

GCF. Other Udults which have both:

1. An epipedon that has a color value, moist, of 3
or less throughout; and

2. An argillic horizon that has a color value, dry,

of 4 or less, and a color value, moist, that is no

more than 1 unit lower than the value, dry.
Rhodudults, p. 481

GCG. Other Udults.
Hapludults, p. 471



6

Soil depth classes

The following two soil depth modifiers are used for
families in all lithic subgroups of Histosols, except in
the suborder of Folists:

Shallow.—Indicates a lithic contact between 18 and 50
cm from the soil surface.

Micro.—Indicates a lithic contact at a depth of less than
18 cm from the soil surface.

SERIES DIFFERENTIAE WITHIN A FAMILY

Control sections for the soil series are very similar to
those for the family, but they differ in a few important
respects. The particle-size and mineralogy control
sections for families end at the upper boundary of a
fragipan, duripan, or petrocalcic horizon because these
horizons contain few roots, and in contrast to the control
sections for the series, those for the family do not take
into account the thickness of such horizons, or a lithic or
paralithic contact between 50 and 100 cm from the
mineral soil surface. The function of the series is
pragmatic, and differences within a family that affect
the use of a soil should be considered in classifying soil
series Separations of soils at the series level can be
based on differences in particle size, texture,
mineralogy, amount of organic matter, structure, etc.
that have not been recognized as family differentiae.

Primary attention at the series level is given to the
nature of the soil within the control section, especially
to genetic horizons, provided that they are well
expressed and not thin. If the genetic horizons are thin
or not well expressed, attention is centered on a
corresponding part of the regolith. Differences in soil or
regolith which are outside the control section and have
not been recognized as differentiae in categories higher
than the series, but which are relevant to potential uses
of certain soils, are considered as a basis for phase
distinctions.

Control section for the differentiation of series
Whether or not well-expressed genetic horizons are
present, the part of a soil to be considered in
differentiating series within a family of mineral soils is
as follows:

Mineral soils with permafrost —The series control
section for soils that have permafrost within 150 cm of
the soil surface extends from the soil surface to the
shallowest of the following:

1. A lithic or petroferric contact; or

2 A depth of 100 cm if depth to permafrost is less than
75 om, or


379

days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8°C.
Udic Argiustolls

HFEP, Other Argiustolls which have a brittle horizon
within 100 cm of the mineral soil surface that is 15 cm
or more thick and contains either some opal coatings or
20 percent or more (by volume) durinodes,

Duric Argiustolls
HFEQ. Other Argiustolls.

Typic Argiustolls
Calclustolis
Key to subgroups

HEDA. Calciustolls which have a salic horizon that has
its upper boundary within 75 cm of the mineral soil
surface.

Salorthidic Calciustolls

HFDB. Other Calciustolls that have a petrocalcic
horizon and a lithic contact within 50 cm of the mineral
soil surface.

Lithic Petrocalcic Calciustolls

HFDC. Other Calciustolls that have a lithic contact
within $0 cm of the mineral soil surface.
Lithic Calciustolls

HFDD. Other Calciustolls which have both:
1, One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
om of the mineral soil surface; or

b.A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower; and

2, If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some or all parts for six tenths or more of
the cumulative days per year when the soil
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10



234

KB. Other Entisols which have, in one or more layers
between 25 and 100 cm from the mineral soil surface, 3
percent or more (by volume) fragments of diagnostic
horizons that are not arranged in any discemible order.
Arents, p. 241

KC. Other Entisols that have less than 35 percent (by
volume) rock fragments and a texture of loamy fine sand
or coarser, in all layers! between either an Ap horizon or
a depth of 25 cm from the mineral soil surface,
whichever is deeper, and either a depth of 100 cm ora
lithic, paralithic, or petroferric contact, whichever is
shallower.

Psamments, p. 262

KD. Other Entisols which do not have a lithic or
paralithic contact within 25 cm of the mineral soil
surface, and have:

1. A slope of less than 25 percent; and

2. Either 0.2 percent or more organic carbon? at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

3, A mean annual soil temperature above 0°C,

Fluvents, p. 242
KE. Other Entisols.

Orthents, p. 251
AQUENTS
Key to great groups

KAA. Aquents that have sulfidic materials within 50 cm
of the mineral soil surface.
Sulfaquents, p. 240

KAB. Other Aquents that have both:

1. Ann value of more than 0.7, and 8 percent or
more clay in the. fine-earth fraction of all horizons
between 20 and 50 cm from the mineral soil
surface; and
2, A mean annual soil temperature above 0°C.
Hydraquents, p. 240
KAC, Other Aquents that have a cryic soil temperature
regime.
Cryaquents, p. 235

| Lametlae that are either less than 1 em thick or too few to meet the
sequirements for an atgillic horizon may have a texture of sandy loarn,
2 The carbon should be of Holocene age, not fossil carbon from transported.

fragments of bedrock or from buried Pleistocene deposits, The mean
residence time of the carbon should be less than 11,000 years B.P.


181
Vitritorrands

Key to subgroups

BCAA. Vitritorrands that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Vitritorrands

CCAB. Other Vitritorrands which have a petrocalcic
horizon that has its upper boundary within 100 cm of
the mineral soil surface.

Petrocalcic Vitritorrands

CCAC. Other Vitritorrands which have a horizon 15 cm
or more thick, with 20 percent or more (by volume)
cemented soil material that does not slake in water after
air-drying, that has its upper boundary within 100 cm of
the mineral soil surface.

Duric Vitritorrands

CCAD. Other Vitritorrands that have, in one or more
horizons between 50 and 100 cm from the mineral soil
surface, aquic conditions for some time in most years
(or artificial drainage) and one or more of the following:

1, Two percent or more redox concentrations; or

2. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
redox depletions on faces of peds, or in the matrix
if peds are absent; or

3. Enough active ferrous iron to give a positive
reaction to a.,a'-dipyridyl at a time when the soil
is not being irrigated.
Aquic Vitritorrands
CCAE. Other Vitritorrands which have a calcic horizon
that has its upper boundary within 125 om of the
mineral soil surface.

Caleic Vitritorrands
CCAF. Other Vitritorrands.

Typic Vitritorrands
UDANDS
Key to great groups

CGA. Udands that have, in half or more of each pedon,
a placic horizon within 100 cm either of the mineral soil
surface, or of the top of an organic layer with andic soil
properties, whichever is shallower.

Placudands, p. 166

CGB. Other Udands that have, in 75 percent or more of
each pedon, a cemented layer which does not slake in
water after air-drying and which has its upper boundary
within 100 cm either of the mineral soil surface, or of


7

2. No sulfidic materials within 50 cm of the
mineral soil surface; and both:

a. In one or more horizons between 20 and
50 cm below the mineral soil surface, either
an n value of 0.7 or less, or less than 8
percent clay in the fine-earth fraction; and

b. One or both of the following:

K. Other soils.

(i) A histic, a mollic, a plaggen, or an
umbric epipedon, or

(2) In 50 percent or more of the layers
between the mineral soil surface and a
depth of 50 cm, an exchangeable
sodium percentage of 15 or more (or a
sodium adsorption ratio of 13 or
more), which decreases with
increasing depth below 50 cm, and
also ground water within 100 cm of
the mineral soil surface at some time
during the year when the soil is not
frozen in any part.

Inceptisols, p. 289

Entisols, p. 233


Ustipsamments

Key to subgroups

KCEA. Ustipsamments that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Ustipsamments

KCEB, Other Ustipsamments that have, in one or more
horizons within 100 cm of the mineral soil surface,
distinct or prominent redox concentrations, and also
aquic conditions for some time in most years (or
artificial drainage).

Aquic Ustipsamments

KCEC, Other Ustipsamments that are saturated with
water, in one or more layers within 100 cm of the
mineral soil surface, for 1 month or more per year in 6
or more out of 10 years.

Oxyaquic Ustipsamments

KCED. Other Ustipsamments which have lamellae
within 200 cm of the mineral soil surface that meet all
the requirements for an argillic horizon except
thickness? or clay content.

Argic Ustipsamments

KCEE. Other Ustipsamments.
Typic Ustipsamments

Xeropsamments

Key to subgroups
KCFA. Xeropsamments that have a lithic contact within

50 cm of the mineral soil surface.
Lithic Xeropsamments

KCEB. Other Xeropsamments that have both:

1. In one or more horizons within 100 cm of the
mineral soil surface, distinct or prominent redox
concentrations, and also aquic conditions for some
time in most years (or artificial drainage); and
2. A horizon within 100 cm of the mineral soil
surface that is 15 cm or more thick and either
contains 20 percent or more (by volume)
durinodes or is brittle and has firm consistence
when moist.

Aquic Durorthidic Xeropsamments

KCFC. Other Xeropsamments that have, in one or more
horizons within 100 cm of the mineral soil surface,
distinct or prominent redox concentrations, and also
aquic conditions for some time in most years (or
artificial drainage).

Aquic Xeropsamments

8 See footnote 7.


12

or more (absolute) higher than that of the eluvial
horizon.

3. The thickness of the argillic horizon is one tenth or
more the total thickness of all overlying horizons (in a
soil that is not truncated and has no lithologic discon-
tinuity between the eluvial horizon and the underlying
argillic horizon), and one of the following:

a. 7.5 cm or more if the horizon is loamy or
clayey; or

b. 15 cm or more if the horizon is sand or loamy
sand; or

c, If the horizon is composed entirely of lamellae,
15 cm or more combined thickness of lamellae
that are 1 cm or more thick.

4. In structureless soils, the argillic horizon has oriented
clay lining some pores and bridging the sand grains.

5. If peds are present, the argillic horizon has one of the
following:

a. Either clay films on some vertical and hori-
zontal surfaces of peds and in the fine pores, or
oriented clay in 1 percent or more of the cross
section; or

b. A broken or irregular upper boundary and some
clay films in the lowest part of the horizon; or

¢. If the eluvial horizon has 40 percent or more
clay, and if the argillic horizon is clayey and the
clay is kaolinitic, some clay films on peds and in
pores within the lower part of the argillic horizon
if it has blocky or prismatic structure; or

d. No clay films if the argillic horizon is clayey
with 2:1 lattice clays, and if either the overlying
horizon has uncoated grains of sand or silt and the
argillic horizon shows evidence of pressure caused
by swelling (e.g., occasional slickensides or wavy
horizon boundaries), or if the ratio of fine clay to
total clay in the argillic horizon is one third or
more higher than in the overlying or underlying
horizon, or if the fine-clay content in the argillic
horizon is 8 percent or more (absolute) higher
than in the eluvial horizon.

Calcic horizon

The calcic horizon is a horizon in which calcium
carbonate, or calcium and magnesium carbonate, has
accumulated. It may occur within the C horizon or .
within various other horizons such as a mollic epipedon,
an argillic or a natric horizon, or a duripan.

The calcic horizon is 15 cm or more thick and meets one
of the following requirements:


229

thickness of the horizons between the soil surface
and 50 cm depth than in the saturated zone; or

4. Enough active ferrous iron to give a positive
reaction to a.,a'-dipyridyl at a time when the soil
is not being irrigated.
Aquic Paleorthids
FBBC. Other Paleorthids which have both:

1. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime;
and

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to noncarbonate clay, as follows:

a. In the upper 40 cm of the soil, if the upper
boundary of the petrocalcic horizon is 40 cm.
or more below the soil surface,

(1) 0.60 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.15 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.64-(0.038 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
land 13; or

b. In the upper 18 cm of the soil, if the
upper boundary of the petrocalcic horizon is
between 18 and 40 cm from the soil surface,

(1) 0.72 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.18 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or
(3) 0.77-(0.046 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
1 and 13.

Xerollic Paleorthids

FBBD. Other Paleorthids which have both:

1, An aridic moisture regime that borders on an
ustic regime; and

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to noncarbonate clay, as follows:


465

GBFF. Other Haplohumults that have a xeric moisture
regime.

Xeric Haplohumults
GBFG. Other Haplohumults.

Typic Haplohumults
Kandihumults
Key to subgroups

GBCA. Kandihumults that have both:

1. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm? or less, measured
at 33 kPa water retention, and aluminum plus 1/2
iron percentages (by ammonium oxalate) totaling
more than 1.0; and
2. In one or more horizons within 75 cm of the
‘mineral soil surface, redox concentrations, a color
value, moist, of 4 or more, and a hue which is
10YR or yellower, but which becomes redder with
increasing depth within 100 cm of the mineral soil
surface.

Andic Ombroaquic Kandihumults

GBCB. Other Kandihumults that have both:

1. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm} or less, measured
at 33 kPa water retention, and aluminum plus 1/2
iron percentages (by ammonium oxalate) totaling
more than 1.0; and

2. An ustic moisture regime.
Ustandic Kandihumults

GBCC. Other Kandihumults that have, throughout one
or more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm} or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Kandihumults

GBCD. Other Kandihumults that have, in one or more
subhorizons within the upper 25 cm of the argillic or
kandic horizon, redox depletions with a color value,
moist, of 4 or more and a chroma of 2 or less,
accompanied by redox concentrations, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Kandihumults

arc


274

ABCK. Other Borofibrists that have one or more layers,
with a total thickness of 12.5 cm or more, of the
subsurface and bottom tiers consisting of sapric
materials.

Sapric Borofibrists
ABCL. Other Borofibnists.

Typic Borofibrists
Cryofibrists
Key to subgroups

ABBA. Cryofibrists that have a lithic contact within the
control section.

Lithic Cryofibrists
ABBB. Other Cryofibrists that have a mean annual soil
temperature of 0°C or lower.
Pergelic Cryofibrists

ABBC. Other Cryofibrists which have a mineral layer
30 cm or more thick that has its upper boundary within
the control section below the surface tier.

Terric Cryofibrists

ABBD. Other Cryofibrists that have, within organic
materials, cither one mineral layer 5 cm or more thick,
or two or more mineral layers of any thickness, in the
control section below the surface tier.

Fluvaquentic Cryofibrists

ABBE. Other Cryofibrists that have three fourths or
more of the fiber volume in the surface tier derived from

Sphagnum.
Sphagnic Cryofibrists

ABBF. Other Cryofibrists.
Typic Cryofibrists

Luvifibrists

Luvifibrists 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
which have a horizon within the control section that is 2
cm or more thick and contains one half or more (by
volume) 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 are normally acid and that they
have been cultivated for a long time.


409
Natrixerolls

Key to subgroups

HDBA. Natrixerolls which have one or both of the
following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Natrixerolls

HDBB. Other Natrixerolls that have both:

1, In one or more horizons within 75 cm of the
‘mineral soi] surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2, A horizon 15 cm or more thick within 100 cm
of the mineral soil surface that either contains 20
percent or more (by volume) durinodes or is
brittle and has firm consistence when moist.
Aquic Duric Natrixerolls

HDBC. Other Natrixerolls that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Natrixerolls
HDBD. Other Natrixerolls that have an aridic moisture
regime.

Aridic Natrixerolls
HDBE. Other Natrixerolls which have a horizon within
100 cm of the mineral soil surface that is 15 cm or more
thick and either contains 20 percent or more (by

volume) durinodes or is brittle and has firm consistence
when moist.

Duric Natrixerolls
HODBF. Other Natrixerolls,

Typic Natrixerolls
Palexerolls
Key to subgroups

HDCA. Palexerolls that have a natric horizon.
Natric Palexerolls


287

ADFE, Other Medisaprists that have one or more limnic
layers with a total thickness of 5 cm or more within the
control section.

Limnic Medisaprists

ADFF. Other Medisaprists that have, within organic
materials, either one mineral layer 5 cm or more thick,
or two or more mineral layers of any thickness, in the
control section below the surface tier.

Fluvaquentic Medisaprists

ADFG. Other Medisaprists that have one or more
layers, with a total thickness of 12.5 cm or more, of the
subsurface and bottom tiers consisting of fibric
materials,

Fibric Medisaprists

ADFH. Other Medisaprists that have one or more
layers, with a total thickness of 25 cm or more, of the
subsurface and bottom tiers consisting of hemic
materials.

Hemic Medisaprists
ADFI. Other Medisaprists.

Typic Medisaprists
Sulfisaprists
Key to subgroups

ADBA. Sulfisaprists which have a mineral layer 30 cm
or more thick that has its upper boundary within the

control section below the surface tier.

Terric Sulfisaprists
ADBB, Other Sulfisaprists.

Typic Sulfisaprists
Sulfosaprists
Key to subgroups
ADAA. All Sulfosaprists (provisionally).

Typic Sulfosaprists
Troposaprists
Key to subgroups

ADEA. Troposaprists that have a lithic contact within
the control section.
Lithic Troposaprists

ADEB. Other Troposaprists which have both:

1. One or more layers, with a total thickness of
12.5 cm or more, of the subsurface and bottom
tiers consisting of fibric materials; and

o-r


196

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

2. A frigid or colder soil temperature regime, and

an aridic moisture regime that borders on an ustic

regime,

Borollic Natrargids

FACE. Other Natrargids that have, in one or more
horizons within 100 cm of the soil surface, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:

1. A chroma of 0, or a hue of 2.5Y or yellower and
a chroma of 1; or

2. Redox concentrations and 50 percent or more
chroma df 2 or less; or
3. Enough active ferrous iron to give a positive
reaction to 0.,a'-dipyridyl at a time when the soil
is not being irrigated,
Aquic Natrargids
FACG. Other Natrargids which have:

1. A horizon within 100 cm of the soil surface that
is 15 cm or more thick and either contains 20
percent or more (by volume) durinodes or is
brittle and has firm consistence when moist; and

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of

sand to clay, as follows:
a, In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,
(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or
(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or
(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or
b. In the upper 18 cm of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and


307
JDHK. Other Dystrochrepts which have both:

1. Either 0.2 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 tan to a depth of 125 em, or to
a lithic or paralithic contact if shallower; and
2. A slope of less than 25 percent.
Fluventic Dystrochrepts
JDHL. Other Dystrochrepts that have an Ap horizon
with a color value, moist, of 3 or less and a color value,
dry, of 5 or less (crushed and smoothed sample), or
materials between the soil surface and a depth of 18 cm
which have these color values after mixing.
Umbric Dystrochrepts
JDHM, Other Dystrochrepts that have both:

1. An argillic horizon in less than half of each
pedon; and
2. A base saturation (by sum of cations) of 35
percent or more either at a depth of 125 cm from
the top of the argillic horizon, or directly above a
lithic or paralithic contact if shallower.
Ruptic-Alfic Dystrochrepts
JDHN. Other Dystrochrepts that have an argillic horizon
in less than half of each pedon.
Ruptic-Ultic Dystrochrepts
JDHO. Other Dystrochrepts.
Typic Dystrochrepts

Eutrochrepts

Key to subgroups

IDGA. Eutrochrepts that have both:
1. A lithic contact within 50 cm of the mineral soil
surface; and
2. An argillic horizon in less than half of each
pedon.

Lithic Ruptic-Alfic Eutrochrepts

IDGB. Other Eutrochrepts that have a lithic contact
within 50 cm of the mineral soil surface.
Lithic Eutrochrepts

JDGC. Other Eutrochrepts which have one or both of
the following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or


127

ICFL. Other Paleustalfs which have both:

1. If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for six tenths or more of the
cumulative days per year when the soil
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or
b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, remains moist in some or all parts for
less than 90 consecutive days per year when
the temperature at a depth of $0 cm below
the soil surface is higher than 8°C; and
2. A calcic horizon, either within 100 cm of the
mineral soil surface if the weighted average
particle-size class of the upper 50 cm of the
argillic horizon is sandy, or within 60 cm if it is
loamy, or within 50 cm if it is clayey, and
carbonates in all horizons above the calcic
horizon.
Calciorthidic Paleustalfs

ICFM. Other Paleustalfs which, if neither irrigated nor
fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for six tenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years,
remains moist in some or all parts for less than 90
consecutive days per year when the temperature at
a depth of 50 cm below the soil surface is higher
than 8°C,

Aridic Paleustalfs

ICEN. Other Paleustalfs that have a CEC of less than 24

cmol(+) per kg clay (by IN NH,OAc pH 7) in 50

percent or more either of the argillic horizon if less than

100 cm thick, or of its upper 100 cm.

Kandic Paleustalfs

ICFO. Other Paleustalfs which have, throughout the

argillic horizon, a hue of 2.5YR or redder, a color value,

moist, of 3 or less, and a color value, dry, that is no
more than one unit higher than the value, moist.

Rhodic Paleustalfs

wep


298

JAHE. Other Humaquepts that have either 0.2 percent
or more organic carbon at a depth of 125 cm below the
mineral soil surface, or an irregular decrease in organic-
carbon content from a depth of 25 cm to a depth of 125
cm, or to a lithic or paralithic contact if shallower.
Fluvaquentic Humaquepts
JAHF, Other Humaquepts that have a hue of SY or
redder and a chroma of 3 or more in more than 40
percent of the matrix of one or more subhorizons
between 15 and 75 cm from the mineral soil surface.

Aeric Humaquepts
JAHG. Other Humaquepts.

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

Histic Placaquepts

JABB, Other Placaquepts which have, throughout one or
more horizons with a total thickness of 18 cm or more
within 7S cm of the mineral soil surface, one or more of
the following:

1. A fine-earth fraction with both a bulk density of
1.0 g/cm’ or less, measured at 33 kPa water
retention, and aluminum plus 1/2 iron percentages
(by ammonium oxalate) totaling more than 1.0; or
2. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

3. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling

0.40 or more.
Aquandic Placaquepts
JABC. Other Placaquepts that do not, within 100 cm of
the mineral soil surface, have a continuous placic
horizon in each pedon.
Haplic Placaquepts
JABD, Other Placaquepts.
Typic Placaquepts


473

3. In one or more layers either within 75 cm of the
mineral soil surface or, if the chroma throughout
the upper 75 cm results from uncoated sand
grains, within the upper 12.5 cm of the argillic or
kandic horizon, redox depletions with a color
value, moist, of 4 or more and a chroma of 2 or
less, accompanied by redox concentrations, and
also aquic conditions for some time in most years
(or artificial drainage).

Arenic Plinthaquic Kandiudults

GCCB. Other Kandiudults that have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic horizon at a depth of 50 to 100 cm;
and

2. In one or more layers either within 75 cm of the
mineral soil surface or, if the chroma throughout
the upper 75 cm results from uncoated sand
grains, within the upper 12.5 om of the argillic or
kandic horizon, redox depletions with a color
value, moist, of 4 or more and a chroma of 2 or
less, accompanied by redox concentrations, and
also aquic conditions for some time in most years
(or artificial drainage).

Aquic Arenic Kandiudults

GCCC. Other Kandiudults that have both:

1, A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic or a kandic horizon at a depth of 50
to 100 cm; and

2, Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface.

Arenic Plinthic Kandiudults

GCCD. Other Kandiudults that have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic or a kandic horizon at a depth of 50
to 100 cm; and

2. Throughout the argillic or kandic horizon, a hue
of 2.5YR or redder, a color value, moist, of 3 or
less, and a color value, dry, that is no more than
one unit higher than the value, moist.

Arenic Rhodic Kandiudults

GCCE. Other Kandiudults that have a sandy particle
size throughout a layer extending from the mineral soil
‘surface to the top of an argillic or a kandic horizon at a
depth of 50 to 100 cm.

Arenic Kandiudults
GCCF. Other Kandiudults that have both:


133

its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and cither a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Haploxeralfs

IDGE. Other Haploxeralfs which have both:

1, In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
an

2. Throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or more of the following:

a. A fine-earth fraction with both a bulk
density of 1.0 g/cm? or less, measured at 33
kPa water retention, and aluminum plus 1/2
iron percentages (by ammonium oxalate)
totaling more than 1.0; or

'b. More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or
c. A fine-earth fraction containing 30
percent or more particles 0.02 to 2.0 mm in
diameter, and either:
(1) In the 0.02-to-2.0-mm fraction,
more than 30 percent volcanic glass;
or

(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more,
Aquandic Haploxeralfs

IDGF, Other Haploxeralfs that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm} or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1,0.

Andic Haploxeralfs

IDGG. Other Haploxeralfs that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:
1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66


357

its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Haploborolls

HEGF. Other Haploborolls that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm} or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0,

Andic Haploborolls

HEGG. Other Haploborolls that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:
1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like

fragments; or
2. A fine-earth fraction containing 30 percent or
more particles 0,02 to 2.0 mm in diameter, and
either:
a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b, In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more,

Vitrandic Haploborolls

HEGH. Other Haploborolls which have:

1. A mollic epipedon 40 cm or more thick, of
which less than 50 percent has a sandy particle
size, and no paralithic contact or sandy contrasting
layer between 40 and 50 cm from the mineral soil
surface; and

2. An irregular decrease in organic-carbon content
from a depth of 25 cm below the mineral soil
surface to a depth of 125 cm, or to a lithic or
paralithic contact if shallower; and

3. A slope of less than 25 percent and a concave
shape; and

4. Either a chroma of 1 or less (crushed and
smoothed sample) in the upper 18 cm of the
mollic epipedon, after mixing, or in an Ap horizon
18 cm or more thick, or a moisture control section



262

KEE, Other Orthents that have an ustic moisture
regime.
Ustorthents, p. 258

KEF, Other Orthents.
Udorthents, p. 257

Cryorthents

Key to subgroups

KEAA. Cryorthents that have a lithic contact within 50
cm of the mineral soil surface.

Lithic Cryorthents
KEAB. Other Cryorthents that have a mean annual soil
temperature of 0°C or lower.
Pergelic Cryorthents

KEAC., Other Cryorthents that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1, More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0,02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Cryorthents

KEAD. Other Cryorthents that have, in one or more
horizons within 50 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).
Aquic Cryorthents

KEAE, Other Cryorthents that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Cryorthents


188

of an argillic horizon at a depth of 50 cm or more;
and

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a, In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 cm of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

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

Arenic Ustollic Haplargids

FAEM. Other Haplargids which have:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic horizon at a depth of 50 cm or more;
and

2. A moisture control section that is dry in all its
parts for less than three fourths of the cumulative
days per year in 6 or more out of 10 years when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and

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

on an ustic regime,
Arenic Ustalfic Haplargids

FAEN. Other Haplargids that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
cm or more,

Arenic Haplargids


331

percentages (by ammonium oxalate) totaling
0.40 or more.
Vitrandic Fragiumbrepts

JEAC. Other Fragiumbrepts that have, in one or more-
horizons within 50 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial

drainage).
Aquic Fragiumbrepts
JEAD. Other Fragiumbrepts.
Typic Fragiumbrepts
Haplumbrepts
Key to subgroups

JEDA. Haplumbrepts that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Haplumbrepts

JEDB. Other Haplumbrepts that have both:

1. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm! or less, measured
at 33 kPa water retention, and aluminum plus 1/2
iron percentages (by ammonium oxalate) totaling
more than 1.0; and

2. In one or more horizons within 50 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage).
Aquandic Haplumbrepts

JEDC. Other Haplumbrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more i
within 75 cm of the mineral soil surface, a fine-earth N
fraction with both a bulk density of 1.0 g/cm? or less, Cc
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Haplumbrepts

JEDD. Other Haplumbrepts that have, throughout one
or more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:


S17

apparent illuviation of iron, than overlying and
underlying horizons;

(5) Alteration which forms silicate clay or
liberates oxides, or both, and which forms a
granular, blocky, or prismatic structure if volume
changes accompany changes in moisture content,
or

(6) Brittleness.

All the different kinds of B horizons are, or were
originally, subsurface horizons. Included as B horizons,
where contiguous to other genetic horizons, are layers of
illuvial concentration of carbonates, gypsum, or silica
which are the result of pedogenic processes (and may or
may not be cemented), and brittle layers that show other
evidence of alteration, such as prismatic structure or
illuvial accumulation of clay.

Examples of layers that are not B horizons are: layers in
which clay films either coat rock fragments or cover
finely stratified unconsolidated sediments, regardless of
whether the films were formed in place or by
illuviation; layers into which carbonates have been
illuviated but 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 the properties of O, A, E, or B
horizons. Most are mineral layers. The material of C
layers may be either like or unlike the material from
which the solum has presumably formed. The C horizon
may have been modified, even if there is no evidence of
pedogenesis.

Included as C layers are sediment, saprolite,
unconsolidated bedrock, and other geologic materials
which are commonly uncemented and characterized by
low or moderate excavation difficulty, Some soils form
in material that is already highly weathered, and if such
material does not meet the requirements for A, E, or B
horizons, it is designated C. Changes not considered
pedogenic are those not related to overlying horizons.
Layers that contain accumulations of silica, carbonates,
gypsum, or more soluble salts are included in C
horizons, even if indurated. However, if an indurated
layer is obviously affected by pedogenic processes, it is
considered a B horizon.

R layers: Hard Bedrock

Granite, basalt, quartzite, and indurated limestone or
sandstone are examples of bedrock designated R.

R layers are cemented, and excavation difficulty
exceeds moderate. 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


462

2. Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface.

Arenic Plinthic Paleaquults

GAFC. Other Paleaquults which:
1. Do not have an ochric epipedon; and

2. Have a sandy particle size throughout a layer

extending from the mineral soil surface to the top

of an argillic horizon at a depth of 50 to 100 cm.
Arenic Umbric Paleaquults

GAFD. Other Paleaquults that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
to 100 cm.

Arenic Paleaquults

GAFE. Other Paleaquults that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 100
cm or more.

Grossarenic Paleaquults

GAFF. Other Paleaquults that have 5 percent or more
(by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface.

Plinthic Paleaquults

GAFG. Other Paleaquults that have 50 percent or more
chroma of 3 or more in one or more horizons between
either the A or Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and a depth of
75cm.

Aeric Paleaquults

GAFH. Other Paleaquults that do not have an ochric
epipedon.
Umbric Paleaquults
GAFT. Other Paleaquults.
Typic Paleaquults

Plinthaquults

Key to subgroups

GAAA. Plinthaquults that have a CEC (by IN NH,OAc
PH 7) of less than 24 cmol(+)/kg clay! in 50 percent or
more (by volume) of the argillic horizon if less than 100
em thick, or of its upper 100 cm.

Kandic Plinthaquults

1 Some soils with properties that approach those of an Oxisol do not
disperse well. Ifthe ratio of (percent water retained at 1500 kPa tension
‘minus percent organic carbon) to the percentage of measured clay is 0.6 or
‘more, then the percentage of clay is considered to equal either (1) the
measured percentage of clay, or (2) three times (percent water retained at
1500 kPa tension minus percent organic carbon), whichever value is higher,
but no more than 100,


Chapter 8

Aridisols
KEY TO SUBORDERS
FA. Aridisols that have an argillic or a natric horizon.
Argids, p. 177

FB. Other Aridisols.

Orthids, p. 205
ARGIDS
Key to great groups

FAA. Argids which have a duripan that has its upper
boundary within 100 cm of the soil surface, and a natric
horizon.
Nadurargids, p. 191
FAB, Other Argids which have a duripan that has its
upper boundary within 100 cm of the soil surface.
Durargids, p. 178

FAC. Other Argids which have a natric horizon, but do
not have a petrocalcic horizon that has its upper
boundary within 100 cm of the soil surface.

Natrargids, p. 193

FAD. Other Argids which do not have a lithic or
paralithic contact within 50 cm of the soil surface, and
have either:

1. A petrocalcic horizon that has its upper
boundary within 100 cm of the soil surface; or

2. An argillic horizon that has 35 percent or more
clay in the fine-earth fraction of some part, and
either
a. A clay increase of 15 percent or more
(absolute) within a vertical distance of 2.5
cm either within the argillic horizon or at its
upper boundary; or
b. If there is an Ap horizon directly above
the argillic horizon, a clay increase of 10
percent or more (absolute) at the upper
boundary of the argillic horizon.
Paleargids, p. 200

FAE. Other Argids.
Haplargids, p. 182


443

BABH. Other Alaquods which have, within 200 cm of
the mineral soil surface, an argillic or a kandic horizon
that has a base saturation of 35 percent or more (by sum
of cations) in some part.

Alfic Alaquods

BABI. Other Alaquods that have an argillic or a kandic
horizon within 200 cm of the mineral soil surface.

Ultic Alaquods
BABI. Other Alaquods that have an ochric epipedon.

Aeric Alaquods
BABK. Other Alaquods.

Typic Alaquods
Cryaquods
Key to subgroups

BAAA. Cryaquods that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Cryaquods

BAAB, Other Cryaquods that have a mean annual soil

temperature of 0°C or less.
Pergelic Cryaquods

BAAC. Other Cryaquods that have a placic horizon.
within 100 cm of the mineral soil surface in 50 percent
or more of each pedon,

Placic Cryaquods

BAAD, Other Cryaquods which have, in 90 percent or
more of each pedon, a cemented soil layer that does not
slake in water after air-drying and has its upper
boundary within 100 cm of the mineral soil surface.
Duric Cryaquods

BAAE. Other Cryaquods which have andic soil
properties throughout horizons that have a total
thickness of 25 cm or more within 75 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Andic Cryaquods

BAAF, Other Cryaquods that do not have a spodic
horizon 10 cm or more thick in 50 percent or more of
each pedon.

Entic Cryaquods
BAAG. Other Cryaquods.
Typic Cryaquods
Duraquods
sub;

BAEA. Duraquods that have a histic epipedon.
Histic Duraquods

OuUnM


72

between the soil surface and a depth of 50
cm; or

b. Mineral soil layers which, if present, have
a total thickness of 10 cm or less, and
organic soil materials that constitute two
thirds or more of the total thickness of the
soil to a lithic or paralithic contact; or

c, Organic soil materials with an upper
boundary within 40 cm of the soil surface
which are saturated with water for 6 months
or more per year in most years (or
artificially drained), and which have a total
thickness of either:

(1) 60 cm or more if three fourths or
more of their volume consists of moss
fibers, or if their bulk density, moist,
is less than 0.1 g/cm; or
(2) 40 cm or more if they consist
either of sapric or hemic materials, or
of fibric materials with less than three
fourths (by volume) moss fibers and a
bulk density, moist, of 0.1 g/m? or
more,

Histosols, p. 271

B. Other soils which do not have a plaggen epipedon or
an argillic or a kandic horizon above a spodic horizon,
and have one or more of the following:

1. A spodic horizon, an albic horizon in 50 percent
or more of each pedon, and a cryic or pergelic soil
temperature regime; or
2. An Ap horizon containing 85 percent or more
spodic materials; or
3. A spodic horizon with all the following
characteristics:
a. One or more of the following:
(1) A thickness of 10 cm or more; or
(2) An overlying Ap horizon; or
(3) Cementation in 50 percent or more
of each pedon; or
(4) A coarse-loamy, loamy-skeletal, or
finer particle size, and a frigid
temperature regime in the soil; or
(5) A cryic or pergelic temperature
regime in the soil; and
b. An upper boundary within the following
depths from the mineral soil surface: either
(1) Less than 50 cm; or


256

3. A thermic, mesic, or frigid soil temperature
regime, and a torric moisture regime that borders
on a xeric regime.

Durorthidic Xeric Torriorthents

KEBL. Other Torriorthents which have a horizon within
100 cm of the soil surface that is 15 cm or more thick
and either contains 20 percent or more (by volume)
durinodes, or is brittle and has firm consistence when
moist.

Durorthidic Torriorthents

KEBM. Other Torriorthents which have both:

1, A moisture control section which, in 6 or more
out of 10 years, is dry in all its parts for less than
three fourths of the cumulative days per year when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and

2. A hyperthermic, thermic, mesic, frigid, or an
iso soil temperature regime, and a torric moisture
regime that borders on an ustic regime.

Ustic Torriorthents

KEBN. Other Torriorthents which have both:

1. A moisture control section which, in 6 or more
out of 10 years, is dry in all its parts for less than
three fourths of the cumulative days per year when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and

2. A thermic, mesic, or frigid soil temperature
regime, and a torric moisture regime that borders

on a xeric regime.

Xeric Torriorthents
KEBO. Other Torriorthents.

Typic Torriorthents
Troporthents
Key to subgroups
KEDA. Troporthents that have a lithic contact within 50
cm of the mineral soil surface.

Lithic Troporthents

KEDB. Other Troporthents that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm? or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling

more than 1.0,
Andic Troporthents

KEDC. Other Troporthents that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:


326

2. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm? or less, measured
at 33 kPa water retention, and aluminum plus 1/2
iron percentages (by ammonium oxalate) totaling
more than 1.0,

Ustandic Humitropepts

JCAE. Other Humitropepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm: or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0,

Andic Humitropepts

JCAF. Other Humitropepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
‘more particles 0.02 to 2.0 mm in diameter, and
either:

a, In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0,40 or more.

Vitrandic Humitropepts

JCAG. Other Humitropepts that have, in one or more
horizons within 100 cm of the mineral soil surface,
redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or
artificial drainage).
Aquic Humitropepts

JCAH. Other Humitropepts that are saturated with
water, in one or more layers within 100 cm of the
mineral soil surface, for 1 month or more per year in 6
or more out of 10 years.

Oxyaquic Humitropepts

JCAL. Other Humitropepts which have both:

1. An organic-carbon content that decreases
irregularly with increasing depth to the lower
boundary of the cambic horizon; and


47

cm of the argillic or kandic horizon, redox depletions
with a chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage),

Aquic Fragiudults

GCBE. Other Fragiudults that have 5 percent or more
(by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface.

Plinthic Fragiudults

GCBF. Other Fragiudults that have either:

1. Above the fragipan, no argillic or kandic
horizon that has clay films on both vertical and
horizontal surfaces of any structural aggregates; or

2. Between the argillic or kandic horizon and the

fragipan, one or more horizons with 50 percent or

more chroma of 3 or less and with a clay content 3

percent or more (absolute, in the fine-earth

fraction) lower than in both the argillic or kandic

horizon and the fragipan.

Glossic Fragiudults

GCBG. Other Fragiudults which have either an Ap
horizon, or an A horizon 15 cm or more thick, that has a

color value, moist, of 3 or less and a color value, dry, of
5 or less (crushed and smoothed sample).

Humic Fragiudults
GCBH. Other Fragiudults.
Typic Fragiudults
Hapludults
Key to subgroups

GCGA. Hapludults which have both:

1. A lithic contact within 50 cm of the mineral soil
surface; and
2. In each pedon, a discontinuous argillic horizon
that is interrupted by ledges of bedrock.
Ruptic-Lithic-Entic Hapludults
GCGB. Other Hapludults that have a lithic contact
within 50 cm of the mineral soil surface.
Lithic Hapludults

GCGC. Other Hapludults which have one or both of the
following:
1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped U
aggregates in a layer 15 cm or more thick that has L
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a


378
HFEC. Other Argiustolls that have both:
1. One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
em of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower; and

2. If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some or all parts for six tenths or more of
the cumulative days per year when the soil
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or
b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, remains moist in some or all parts for
less than 90 consecutive days per year when
the temperature at a depth of 50 cm below
the soil surface is higher than 8°C,
Torrertic Argiustolls

HFED. Other Argiustolls which have both:
1. One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 om or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower; and

2. If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for four tenths or less of the
cumulative days per year when the



343

its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Endoaquolls

HBGC. Other Endoaquolls that have a histic epipedon.
Histic Endoaquolls

HBGD. Other Endoaquolls which have a buried
Histosol that has its upper boundary within 100 cmi of
the mineral soil surface.

Thapto-Histic Endoaquolls

HBGE. Other Endoaquolls that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or more of
the following:

1, A fine-earth fraction with both a bulk density of
1,0 g/cm} or less, measured at 33 kPa water

Tetention, and aluminum plus 1/2 iron percentages
(by ammonium oxalate) totaling more than 1.0; or

2. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

3, A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b, In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Aquandic Endoaquolls

HBGF. Other Endoaquolls which have a horizon 15 em
or more thick within 100 cm of the mineral soil surface
that either contains 20 percent or more (by volume)
durinodes or is brittle and has firm consistence when
moist.

Duric Endoaquolls

HBGG. Other Endoaquolls that have a mollic epipedon
60 cm or more thick.
Cumulic Endoaquolls

HBGH. Other Endoaquolls which have both:

1, Either 0.3 percent or more organic carbon in all
horizons within 125 cm of the mineral soil
surface, or an irregular decrease in organic-carbon
content from a depth of 25 cm to a depth of 125


533

- 235,237
- 234,242
- 271,278

Frigid soil temperature regime
Fulvicryands .
Fulvudands

Gelicryands .... . 146,147

Genetic soil horizons

H

Halaquepts 290,296
Haplaquox 414,415
Haplargids 177,182
Haploborolls . 346,356
Haplocryands 146,147
Haplocryerts 499

locryods 446
Haplohumods 449

- 416,419
450,452

Haplotorrerts . 100,501
Haplotorrox 423,424
Haploxeralfs .. 130,132
Haploxerands woe 174
Haploxererts $N,513
Haploxerolls . 395,403



2
(2) Redox concentrations of iron; or

(3) Two times or more the amount of iron
(by dithionite citrate) contained in the tilled
surface layer.

Coefficient of linear extensibility (COLE)

The coefficient of linear extensibility (COLE) is the
ratio of the difference between moist length and dry
length of a clod, to its dry length. It is (Lm - La)/Ld,
where Li is the length at 33 kPa tension and La is the
length when dry. COLE can be calculated from the
differences in bulk density of the clod when moist and
when dry. An estimate of COLE can be calculated in the
field by measuring the distance between two pins in a
clod of undisturbed soil at field capacity and again after
the clod has dried, COLE does not apply if the
shrinkage is irreversible.

Durinodes

Durinodes (L. durus, hard, nodus, knot) are weakly
cemented to indurated nodules. The cement is SiO,
presumably opal and microcrystalline forms of silica. It
breaks down in hot concentrated KOH after treatment
with HC! to remove carbonates, but does not break
down with concentrated HCI alone. Dry durinodes do
not slake appreciably in water, but prolonged soaking
can result in spalling of very thin platelets and in some
slaking. Durinodes are firm or very firm; they are brittle
when wet, both before and after treatment with acid;
and they are disconnected and have a diameter of 1 cm
or more. Most durinodes are roughly concentric when
viewed in cross section, and concentric stringers of opal
may be visible under a hand lens.

Interfingering of albic materials

The term interfingering of albic materials means albic
materials that penetrate 5 cm or more into an underlying
argillic or natric horizon along vertical and, to a lesser
degree, horizontal faces of peds. There need not be a
continuous overlying albic horizon. The albic materials
constitute less than 15 percent of the layer which they
Penetrate, but they form continuous skeletans (ped
coatings of clean silt or sand defined by Brewer, 1964)

1 mm or more thick on the vertical ped faces, which
means a total width of 2 mm or more between abutting
peds, Because quartz is such a common constituent of
silt and sand, these skeletans are usually light gray
when moist and nearly white when dry, but their color is
determined in large part by the color of the sand or silt
fraction.

Interfingering of albic materials is recognized if albic
materials:

1, Penetrate 5 cm or more into an underlying argillic or
natric horizon; and


408

2. A slope of less than 25 percent.
Fluventic Haploxerolls

HDFY. Other Haploxerolls that have a mollic epipedon
which has granular structure and which contains, below
any Ap horizon, 50 percent or more (by volume)
wormholes, worm casts, or filled animal burrows.
Vermic Haploxerolls

HDEZ. Other Haploxerolls that have a calcic horizon or
soft powdery lime, either within the following depths or
above a lithic or paralithic contact if shallower, if the
particle-size control section is

1, Sandy: within 150 cm of the mineral soil
surface; or

2. Loamy: within 110 cm of the mineral soil
surface; or

3. Clayey: within 90 cm of the mineral soil
surface.
Calcic Haploxerolls

HDFZa, Other Haploxerolls which:

1. Do not have a cambic horizon and do not, in the
lower part of the mollic epipedon, meet the
requirements for a cambic horizon except color;
and

2. Have a base saturation (by sum of cations) of
75 percent or less in one or more horizons
between either an Ap horizon or a depth of 25 cm
from the mineral soil surface, whichever is
deeper, and either a depth of 75 cm or a lithic or
paralithic contact, whichever is shallower.

Entic Ultic Haploxerolls

HDFZb. Other Haploxerolls that have a base saturation
(by sum of cations) of 75 percent or less in one or more
horizons between either an Ap horizon or a depth of 25
cm from the mineral soil surface, whichever is deeper,
and either a depth of 75 cm or a lithic or paralithic
contact, whichever is shallower.

Ultic Haploxerolls

HDFZe. Other Haploxerolls that either do not have a
cambic horizon and do not, in the lower part of the
mollic epipedon, meet the requirements for a cambic
horizon except color, or have carbonates throughout
either the cambic horizon or the lower part of the mollic
epipedon.

Entic Haploxerolls
HDFZd. Other Haploxerolls.

Typic Haploxerolls


464

NH,OAc pH 7, plus 1N-KCl-extractable Al) in 50

percent or more either of the argillic or kandic horizon if

less than 100 em thick, or of its upper 100 cm.
Kanhaplohumults, p. 466

GBE. Other Humults which:

1, Do not have a lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface;
and

2. Within 150 cm of the mineral soil surface,
either:
a. Do not have a clay decrease with
increasing depth of 20 percent or more
(relative) from the maximum clay content;
or

b. Have 5 percent or more (by volume)
skeletans on faces of peds in the layer that
has a 20 percent lower clay content and,
below that layer, a clay increase of 3 percent
or more (absolute) in the fine-earth fraction.
Palehumults, p. 467

GBF, Other Humults.
Haplohumults, p. 464

Haptohumults

Key to subgroups

GBFA. Haplohumults that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Haplohumults

GBFB. Other Haplohumults that have, in one or more
subhorizons within the upper 25 cm of the argillic
horizon, redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, accompanied by
redox concentrations, and also aquic conditions for some
time in most years (or artificial drainage).

Aquic Haplohumults

GBFC. Other Haplohumults that have, throughout one
or more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-carth
fraction with both a bulk density of 1.0 g/cm} or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0,

Andic Haplohumults

GBFD. Other Haplohumults that have 5 percent or more
(by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface.

Plinthic Haplohumults

GBFE. Other Haplohumults that have an ustic moisture
regime.
Ustic Haplohumults


223
FBCC. Other Durorthids which have:

1. An aridic moisture regime that borders on a
xeric regime; and

2. A moisture control section that is dry in all its
parts for less than three fourths of the cumulative
days per year in 6 or more out of 10 years when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and

3. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or both of the following:

a. More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or

b. A fine-earth fraction containing 30

percent or more particles 0.02 to 2.0 mm in
diameter, and either:

(1) In the 0.02-to-2.0-mm fraction,

more than 30 percent volcanic glass;
or

(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more.
Vitrixerandic Durorthids

FBCD. Other Durorthids which have both:

1. A moisture control section that is dry in all its
parts for less than three fourths of the cumulative
days per year in 6 or more out of 10 years when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and

2, Throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or both of the following:

a. More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or
b. A fine-earth fraction containing 30
percent or more particles 0.02 to 2.0 mm in
diameter, and either:
(1) In the 0.02-to-2.0-mm fraction,
more than 30 percent volcanic glass;
or

—-DpPp


102

between the soil surface and a depth of 18 cm which
have these color values after mixing.
Mollic Fragiudalfs

IEFC. Other Fragiudalfs that have both:

1, Directly above the fragipan, a layer 5 cm or
more thick which either:

a. Has, on faces of primary peds, clay
depletions of clean silt and sand that
constitute } percent or more (by volume) of
the layer; or

b. Is an eluvial horizon (E) and has 3 or
more percent (absolute) less clay in the fine-
earth fraction than both the overlying and
underlying horizons; and
2, In one or more horizons within 40 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage).
Glossaquic Fragindalfs

IEFD. Other Fragiudalfs which:

1, Do not, above the fragipan, have an argillic
horizon with clay films on both vertical and
horizontal faces of any peds; and

2. Have, in one or more horizons within 40 cm of
the mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage).
Aqueptic Fragiudalfs

TEFE, Other Fragiudalfs that have both:

1. In one or more horizons within 40 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. 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
IEFF. Other Fragiudalfs that have, in one or more
horizons within 40 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).
Aquic Fragiudalfs
TEFG, Other Fragiudalfs that are saturated with water,
in one or more layers above the fragipan, for 1 month or
more per year in 6 or more out of 10 years.
Oxyaquic Fragiudalfs


6

those regions are so fragmentary 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 6 or more out of 10
years, the soil moisture control section is not dry in any
part for as long as 90 cumulative days per year. If the
mean annual soil temperature is lower than 22°C and if
the mean winter and summer soil temperatures at
a depth of 50 cm from the soil surface differ by 5°C or
more, the soil moisture control section, in 6 or more out
of 10 years, is dry in all parts for less than 45
consecutive days in the 4 months following the summer
solstice. In addition, the udic moisture regime requires,
except for short periods, a three-phase system, solid-
liquid-gas, in part or all of the soil moisture control
section when the soil temperature is above 5°C.

The udic moisture regime is common to the soils of
humid climates which have well-distributed rainfall, or
which have enough rain in summer so 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.

In climates where precipitation exceeds evapo-
transpiration in all months of most years, the moisture
tension rarely goes up to 100 kPa in the soil moisture
control section, although there are occasional brief
periods when some stored moisture is used. The water
moves through the soil in all months when it is not
frozen. Such an extremely wet moisture regime is called
perudic (L. per, throughout in time; L. udus, humid). In
the names of most taxa, the formative element ud is
used to indicate either a udic or a perudic regime; the
formative element per is used in selected taxa.

Ustic moisture regime.—The ustic (L. ustus, burnt,
implying dryness) moisture regime is intermediate
between the aridic and the udic regime. Its concept is
one of moisture that is limited but is present at a time
when conditions are suitable for plant growth. The
concept of the ustic moisture regime is not applied to
soils that have cryic or pergelic soil temperature regimes
(defined below).

If the mean annual soil temperature is 22°C or higher or
if the mean summer and winter soil temperatures differ
by less than 5°C at a depth of 50 cm below the soil
surface, the soil moisture control section in the ustic
moisture regime, in 6 or more out of 10 years, is dry in
some or all parts for 90 or more cumulative days per
year. But the moisture control section is moist in some
part either for more than 180 cumulative days per year,
or for 90 or more consecutive days.

If the mean annual soil temperature is lower than 22°C
and if the mean summer and winter soil temperatures



250

more and either a chroma of 0 or a hue bluer than
10Y, and also aquic conditions for some time in
most years (or artificial drainage); and

3, Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or more of the following:

a. A fine-earth fraction with both a bulk
density of 1.0 g/cm? or less, measured at 33
kPa water retention, and aluminum plus 1/2
iron percentages (by ammonium oxalate)
totaling more than 1.0; or

b. More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or

c. A fine-earth fraction containing 30

percent or more particles 0.02 to 2.0 mm in
diameter, and either:

(1) In the 0.02-to-2.0-mm fraction,
more than 30 percent volcanic glass;
or

(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-carth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more.
Aquandic Xerofluvents

KDBC. Other Xerofluvents that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm? or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Xerofluvents

KDBD, Other Xerofluvents that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:
1, More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:
"a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron


312

1. If neither irrigated nor fallowed to store
moisture, one of the following:

a, A frigid soil temperature regime, and a
moisture control section which, in 6 or more
out of 10 years, is dry in all parts for four
tenths or more of the cumulative days per
year when the soil temperature at a depth of
50 cm below the soil surface is higher than
5°C; or

b. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for six tenths or more of the
cumulative days per year when the soil
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or
c. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, is moist in some or all parts for less
than 180 cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 8°C; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or

bv. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower.

Torrertic Ustochrepts

JDED. Other Ustochrepts which have one or both of the

following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped.
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Ustochrepts

JDEE. Other Ustochrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more


246

volume) durinodes or is brittle and has firm consistence
when moist.
Durorthidic Torrifluvents

KDDI. Other Torrifluvents which have both:

1, A moisture control section which, in 6 or more
out of 10 years, is dry in all its parts for less than
three fourths of the cumulative days per year when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and

2. A torric moisture regime that borders on an
ustic regime.
Ustic Torrifluvents

KDDJ. Other Torrifluvents which have both:

1. A moisture control section which, in 6 or more
out of 10 years, is dry in all its parts for less than
three fourths of the cumulative days per year when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and
2. A thermic, mesic, or frigid soil temperature
regime, and a tortic moisture regime that borders
on a xeric regime.

Xeric Torrifluvents

KDDK. Other Torrifluvents that have an anthropic
epipedon,

Anthropic Torrifluvents

KDDL. Other Torrifluvents.

Typic Torrifluvents
Tropofluvents
Key to subgroups
KDEA. All Tropofluvents (provisionally).

Typic Tropofluvents
Udifluvents
Key to subgroups

KDFA, Udifluvents that have, throughout one or more
horizons with a total thickness of 18 cm or more within
75 om of the mineral soil surface, a fine-carth fraction
with both a bulk density of 1.0 g/cm: or less, measured
at 33 kPa water retention, and aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling more than
1.0.

Andie Udifluvents

KDFB, Other Udifluvents that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:


163

25 and 50 cm either from the mineral soil surface,
or from the top of an organic layer with andic soil
properties, whichever is shallower; and

2. More than 6.0 percent organic carbon and
colors of a mollic epipedon throughout a layer 50
m or more thick within 60 cm either of the
mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower.

Alic Pachic Melanudands

CGCE, Other Melanudands that have both:

1, More than 2.0 cmol(+)/kg Al* (by IN KCI) in
the fine-earth fraction of one or more horizons
with a total thickness of 10 cm or more, between
25 and 50 cm either from the mineral soil surface,
or from the top of an organic layer with andic soil
properties, whichever is shallower; and

2. Between 40 and 100 cm either from the mineral
soil surface, or from the top of an organic layer
with andic soil properties, whichever is shallower,
a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic
epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more
that have a color value, moist, 1 unit or more
higher and an organic-carbon content 1 percent or
more (absolute) lower.

Alic Thaptic Melanudands

CGCF, Other Melanudands that have more than 2.0
emol(+)/kg Al? (by 1N KCl) in the fine-earth fraction
of one or more horizons with a total thickness of 10 om
or more, between 25 and 50 cm either from the mineral
soil surface, or from the top of an organic layer with
andic soil properties, whichever is shallower.

Alic Melanudands

CGCG, Other Melanudands that have, in one or more
horizons between 50 and 100 cm either from the
mineral soil surface, or from the top of an organic layer
with andic soil properties, whichever is shallower, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:

1. Two percent or more redox concentrations; or

2. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
redox depletions on faces of peds, or in n the matrix
if peds are absent; or

3. Enough active ferrous iron to give a positive
reaction to o.,c'-dipyridyl at a time when the soil
is not being irrigated.

Aquic Melanudands

CGCH. Other Melanudands that have both:



354

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling

0.40 or more.
Vitrandic Cryoborolls

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

Duric Cryoborolls

HEBM. Other Cryoborolls which have both:

1. An albic horizon directly below the mollic
epipedon; and
2. An argillic horizon that has a clay increase with
depth of 20 percent or more (absolute, in the fine-
earth fraction) within its upper 7.5 cm.
Abruptic Cryoborolls
HEBN. Other Cryoborolls which have an argillic
horizon, and either:
1. Above the argillic horizon, an albic horizon, or
a horizon that has color values too high for a
mollic epipedon and a chroma too high for an
albic horizon; or
2. A glossic horizon, or interfingering of albic
materials into the upper part of the argillic
horizon, or skeletans of clean silt and sand
covering 50 percent or more of the faces of peds in
the upper 5 cm of the argillic horizon.
Boralfic Cryoborolls
HEBO. Other Cryoborolls which have:
1. A mollic epipedon 40 cm or more thick with a
texture finer than loamy fine sand; and
2. An irregular decrease in organic-carbon content
from a depth of 25 cm below the mineral soil
surface to a depth of 125 cm, or to a lithic or
paralithic contact if shallower; and

3. A slope of less than 25 percent.
Cumulic Cryoborolls

HEBP. Other Cryoborolls which have both:

1. A mollic epipedon 40 cm or more thick with a

texture finer than loamy fine sand; and

2. A calcic horizon either within or directly below

the mollic epipedon, but no argillic horizon in the

lower part of the mollic epipedon.

Calcic Pachic Cryoborolls

HEBQ. Other Cryoborolls that have both:

1, An argillic horizon; and


300

JAGC, Other Tropaquepts which have one or both of
the following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Tropaquepts

JAGD. Other Tropaquepts that have a histic epipedon.

Histic Tropaquepts
JAGE. Other Tropaquepts which have, throughout one
or more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or more of
the following:

1. A fine-earth fraction with both a bulk density of
1.0 g/cm? or less, measured at 33 kPa water

retention, and aluminum plus 1/2 iron percentages
(by ammonium oxalate) totaling more than 1.0; or

2. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
3. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:
a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0,02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling

0.40 or more.
Aquandic Tropaquepts

JAGF. Other Tropaquepts that have 5 percent or more
(by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface.

Plinthic Tropaquepts

JAGG. Other Tropaquepts that have, in 50 percent or
more of the matrix of one or more horizons between
either the Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and a'depth of
75 cm, colors as follows:

1. A hue of 2.5Y or redder, a color value, moist, of
6 or more, and a chroma of 3 or more; or


508

EECH. Other Gypsiusterts that have, in one or more
horizons within 30 cm of the mineral soil surface, 50
percent or more colors as follows:

1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. A chroma of 3 or more.

Chromic Gypsiusterts
EECL. Other Gypsiusterts.
Typic Gypsiusterts
Haplusterts
Key to subgroups

EEEA. Haplusterts that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Haplusterts

EEEB. Other Haplusterts that have, throughout a layer
15 cm or more thick within 100 cm of the mineral soil
surface, an electrical conductivity of 15 dS/m or more
(1:1 soil:water) for 6 or more months per year in 6 or
more out of 10 years.

Halic Haplusterts

EEEC, Other Haplusterts that have, in one or more
horizons within 100 cm of the mineral soil surface, an
exchangeable sodium percentage of 15 or more (or a
sodium adsorption ratio of 13 or more) for 6 or more
months per year in 6 or more out of 10 years.

Sodic Haplusterts

EEED. Other Haplusterts which have a petrocalcic
horizon that has its upper boundary within 100 cm of
the mineral soil surface.

Petrocalcic Haplusterts

EEEE. Other Haplusterts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
are 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 210
or more cumulative days per year.

Aridic Haplusterts

EEEF. Other Haplusterts which have both:

1. A lithic or paralithic contact within 100 cm of
the mineral soil surface; and

2. If not irrigated during the year, cracks in 6 or
more out of 10 years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50
cm of the mineral soil surface, for less than 150
cumulative days per year.

Leptic Udic Haplusterts


62
Isomesic.— 8° to 15°C.
Isothermic.— 15° to 22°C.
Isohyperthermic.— 22°C or higher.
Other characteristics

Several other soil characteristics besides those
mentioned above are considered in particular taxa for
grouping series into families. These characteristics
include depth of soil, consistence, coatings on sands,
and permanent cracks.

Depth of soil

Distinctions according to soil depth are made in some
great groups and in arenic, grossarenic, and lithic
subgroups. But at the family level some other soils
should also be grouped according to depth, e.g., soils
which have a shallow paralithic contact with weakly
consolidated rock, such as clay shale, that is too
compact for penetration by roots. One soil-depth class
name, shallow, is used to characterize certain soil
families that have one of the following depths (from the
mineral soil surface):

Shallow.—Either:

1, Less than $0 cm to the upper boundary of a duripan
or of a petrocalcic or petrogypsic horizon, or to a lithic,
paralithic, or petroferric contact. Used for families in all
great groups of Alfisols, Andisols, Aridisols, Entisols,
Inceptisols, Mollisols, Spodosols, and Ultisols, except
in the family names of lithic subgroups of these orders,
where it would be redundant. Or:

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

Consistence

In this taxonomy, some cemented horizons, e.g., a
duripan, serve as differentiae in categories above the
family, while others, such as a cemented spodic horizon
(ortstein), do not. But no single family should include
soils both with and without a continuous, shallow,
cemented horizon. In Spodosols, in particular, a
cemented spodic horizon has to be used as a family
differentia. The following two soil consistence classes
are defined for Spodosol families:

Ortstein.—All or part of the spodic horizon, when
moist, is at least weakly cemented 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 one half or more of
each pedon.

‘Cementation of a small volume within the spodic
horizon into concretions does not constitute cementation
to form a massive horizon. While the name of a family


266
3. A thermic, mesic, or frigid soil temperature
regime, and a torric moisture regime that borders
on a xeric regime.
Durorthidic Xeric Torripsamments
KCBC. Other Torripsamments which have a horizon
within 100 cm of the soil surface that is 15 cm or more
thick and either contains 20 percent or more (by
volume) durinodes or is brittle and has firm consistence
when moist.
Durorthidic Torripsamments

KCBD. Other Torripsamments which have both:

1, A moisture control section which, in 6 or more
out of 10 years, is dry in all its parts for less than
three fourths of the cumulative days per year when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and
2. A torric moisture regime that borders on an
ustic regime.

Ustic Torripsamments

KCBE. Other Torripsamments which have both:

1. A moisture control section which, in 6 or more
out of 10 years, is dry in all its parts for less than
three fourths of the cumulative days per year when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and

2. 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

KCDA. Tropopsamments that have a lithic contact
within 50 cm of the mineral soil surface.
Lithic Tropopsamments

KCDB. Tropopsamments that have, in one or more
horizons within 100 cm of the mineral soil surface,
redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or
artificial drainage).

Aquic Tropopsamments
KCDC, Other Tropopsamments that are saturated with
water, in one or more layers within 100 cm of the
mineral soil surface, for 1 month or more per year in 6

or more out of 10 years,
Oxyaquic Tropopsamments


202

layer 15 cm or more thick that has its upper
boundary within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more
between the soil surface and either a depth of 100
cm ora lithic or paralithic contact, whichever is
shallower.

Vertic Paleargids

FADD. Other Paleargids which have:

1. A petrocalcic horizon that has its upper
boundary within 100 cm of the soil surface; and

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if the upper
boundary of the petrocalcic horizon is 40 cm
or more below the soil surface,
(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 cm of the soil, if the
upper boundary of the petrocalcic horizon is
between 18 and 40 cm from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between |
and 13; and

3. A mean annual soil temperature lower than
22°C, a difference of S°C or more between mean.
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Petrocalcic Xerollic Paleargids

FADE. Other Paleargids which have:
1, A petrocalcic horizon that has its upper
boundary within 100 cm of the soil surface; and

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if the upper
boundary of the petrocalcic horizon is 40 cm
or more below the soil surface,


445

BAFE. Other Epiaquods that have an argillic or a
kandic horizon within 200 cm of the mineral soil
surface.

Ultic Epiaquods
BAFF. Other Epiaquods that have an umbric epipedon,
Umbric Epiaquods
BAFG. Other Epiaquods.
Typic Epiaquods
Fragiaquods
Key to subgroups
BACA. Fragiaquods that have a histic epipedon,
Histic Fragiaquods

BACB. Other Fragiaquods which have a surface horizon
30 cm or more thick that meets all the requirements for
a plaggen epipedon except thickness,

Plaggeptic Fragiaquods
BACC. Other Fragiaquods which have, within 200 cm
of the mineral soil surface, an argillic or a kandic
horizon.

Argic Fragiaquods
BACD. Other Fragiaquods.

Typic Fragiaquods
Placaquods
Key to subgroups

BADA. Placaquods which have andic soil properties
throughout horizons that have a total thickness of 25 cm
or more within 75 cm either of the mineral soil surface,
or of the top of an organic layer with andic soil
properties, whichever is shallower.

Andic Placaquods
BADB. Other Placaquods.

Typic Placaquods
CRYODS
Key to great groups

BBA. Cryods that have a placic horizon within 100 cm
of the mineral soil surface in 50 percent or more of each
pedon.

ovum

Placocryods, p. 448
BBB. Other Cryods which have, in 90 percent or more
of each pedon, a cemented soil layer that does not slake
in water after air-drying and has its upper boundary
within 100 cm of the mineral soil surface.
Duricryods, p. 446


Durochrepts

Key to subgroups
JDCA. Durochrepts which have both:

1. In one or more horizons within 30 cm of the
mineral soil surface, distinct or prominent redox
concentrations, and also aquic conditions for some
time in most years (or artificial drainage); and

2. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or more of the following:

a, A fine-earth fraction with both a bulk

density of 1.0 g/cm} or less, measured at 33

kPa water retention, and aluminum plus 1/2

iron percentages (by ammonium oxalate)

totaling more than 1.0; or

b. More than 35 percent (by volume)
coarser than 2.0 mm, of which

more than 66 percent are cinders, pumice,

and pumice-like fragments; or

c. A fine-earth fraction containing 30

percent or more particles 0.02 to2.0mmin .

diameter, and either:

(1) In the 0.02-to-2.0-mm fraction,
more than 30 percent volcanic glass;

or

(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more.
Aquandic Durochrepts

JDCB. Other Durochrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm? or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Durochrepts

JDCC. Other Durochrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more

within 75 cm of the mineral soil surface, one or both of
the following:
1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
2. A fine-earth fraction containing 30 percent or

more particles 0.02 to 2.0 mm in diameter, and
either:

az


484

GDBB. Other Kandiustults that have, in one or more
layers within 75 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and a
chroma of 2 or less, accompanied by redox
concentrations, and also aquic conditions for some time
in most years (or artificial drainage).

Aquic Kandiustults

GDBC. Other Kandiustults that have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic or a kandic horizon at a depth of 50
to 100 cm; and

2. Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface.

Arenic Plinthie Kandiustults

GDBD. Other Kandiustults that have a sandy particle
size throughout a layer extending from the mineral soil
surface to the top of an argillic or a kandic horizon at a
depth of 50 to 100 cm.

Arenic Kandiustults

GDBE. Other Kandiustults which have both:

1. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm or less, measured
at 33 kPa water retention, and aluminum plus 1/2
iron percentages (by ammonium oxalate) totaling
more than 1.0; and

2. If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section that
is dry in some part for 135 or less of the
cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or
b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section that is dry in some or all
parts for less than 120 cumulative days per
year when the temperature at a depth of 50
cm below the soil surface is higher than
BC.

Udandic Kandiustults


147
CBCC. Other Fulvicryands.

Typic Fulvicryands
Gelicryands
Key to subgroups
CBAA. All Gelicryands.

Typic Gelicryands
Haplocryands
Key to subgroups

CBFA. Haplocryands that have a lithic contact within
50 cm either of the mineral soil surface, or of the top of
an organic layer with andic soil properties, whichever is
shallower.

Lithic Haplocryands

CBEB. Other Haplocryands that have more than 2.0
emol(+)/kg A+ (by 1N KCl) in the fine-earth fraction
of one or more horizons with a total thickness of 10 cm
or more, between 25 and 50 cm either from the mineral
soil surface, or from the top of an organic layer with
andic soil properties, whichever is shallower.

Alic Haplocryands

CBEC. Other Haplocryands that have, in some
subhorizon between 50 and 100 cm either from the
mineral soil surface, or from the top of an organic layer
with andic soil properties, whichever is shallower, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:

1. Two percent or more redox concentrations; or

2. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
redox depletions on faces of peds, or in the matrix
if peds are absent; or

3, Enough active ferrous iron to give a positive
reaction to a,c:'-dipyridyl at a time when the soil
is not being irrigated,

Aquic Haplocryands

CBFD. Other Haplocryands that have extractable bases
plus IN-KCl-extractable AJ>* totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more
horizons with a total thickness of 30 cm or more,
between 25 and 100 cm either from the mineral soil
surface, or from the top of an organic layer with andic
soil properties, whichever is shallower.

Acrudoxic Haplocryands

CBFE. Other Haplocryands which have, undried, a
1500-kPa water retention of less than 30 percent
throughout one or more layers with andic soil properties
that have a total thickness of 25 cm more within 100 cm


32
Plinthite
Plinthite (Gr. plinthos, brick) is an iron-rich, humus-
poor mixture of clay with quartz and other dilutents. It
commonly occurs as dark red redox concentrations
which usually form platy, polygonal, or reticulate
patterns. Plinthite changes irreversibly to an ironstone
hardpan or to irregular aggregates on exposure to
repeated wetting and drying, especially if it is also
exposed to heat from the sun. The lower boundary of a
zone in which plinthite occurs is usually diffuse or
gradual, but it may be abrupt at a lithologic
discontinuity.

Generally, plinthite forms in a horizon that is saturated
with water for some time during the year. Initially, iron
is normally segregated in the form of soft, more or less
clayey, red or dark red redox concentrations. These
redox concentrations, however, are not considered
plinthite unless there has been enough segregation of
iron to permit their irreversible hardening on exposure.
to repeated wetting and drying. Plinthite in the soil is
usually 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 can then be dispersed in large part by shaking in
water with a dispersing agent.

In a moist soil, plinthite is soft enough so that it can be
cut with a spade. After irreversible hardening, it is no
longer considered plinthite but is called ironstone.
Indurated ironstone materials can be broken or shattered
with a spade but cannot be dispersed by shaking in
water with a dispersing agent

Sequum and bisequum

The sequence of an eluvial horizon and the underlying B
horizon, if one is present, is called a sequum. For
example, an albic horizon and a spodic horizon directly
below it, or a mollic epipedon and an underlying cambic
horizon, or an argillic horizon and a k horizon directly
below it, constitute a sequum. If two sequa are present
in vertical sequence in a single soil, that sequence is
called a bisequum.

Slickensides

Slickensides are polished and grooved surfaces that are
produced by one soil mass sliding past another. Some
slickensides occur at the lower boundary of a slip
surface where a mass of soil moves downward on a
relatively steep slope. Slickensides are very common in
swelling clays that undergo marked changes in moisture
content.


65

1, Saturation with water for more than 6 months per
year (or artificial drainage);

2. Two percent or more (by weight) iron concretions
with lateral dimensions ranging from less than 5 mm to
more than 100 mm, containing 10 percent or more (by
weight) free iron oxide (7 percent or more Fe) and 1
percent or more (by weight) organic matter, and

3. A reddish brown, dark reddish brown, or similar
color which changes little on drying.

If ferrihumic is used as a modifier in the technical name
of a Histosol family, no other mineralogy modifier is
used for that family because the presence of iron is
considered to be by far its most important mineralogical
characteristic.

Modifiers applied only to terric subgroups. —In
families within terric subgroups of Histosols, the same
mineralogy modifiers that are used for mineral soils are
applied to those mineral parts of the soil for which a
particle-size modifier has been used, unless the
mineralogy is ferrihumi:

Modifiers applied to limnic subgroups —If limnic
materials with a thickness of 5 cm or more are present
in the contro! section of Histosol families, and if they do
not have ferrihumic mineralogy, the following family
modifiers are used:

Coprogenous. The limnic materials consist of
coprogenous earth.

Diatomaceous. The limnic materials consist of
diatomaceous earth.

Marly. The limnic materials consist of marl.

Reaction classes

The following two modifiers indicating reaction are
used in families of all subgroups of Histosols:

Euic.—The pH value of undried samples is 4.5 or more
(in 0.01 M CaCl,) in one or more layers of organic soil
materials within the control section.

Dysic —The pH value of undried samples is less than
4,5 (in 0.01 M CaCl.) in all layers of organic soil
materials within the control section.

Soil temperature classes

The soil temperature classes of Histosol families have
the same names and definitions as those used for
families of mineral soils The modifier frigid, however,
would be redundant in the family names of boric and
cryic great groups and is therefore omitted. No
temperature modifier is used for families of pergelic
subgroups.


189
FAEO. Other Haplargids which have:

1. A horizon within 100 cm of the soil surface that
is 15 cm or more thick and either contains 20
percent or more (by volume) durinodes or is
brittle and has firm consistence when moist; and

2, A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 om of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
Tatio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b, In the upper 18 cm of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

3. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, 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 soil surface that is 15 cm or more thick and
either contains 20 percent or more (by volume)
durinodes or is brittle and has firm consistence when
moist.
Duric Haplargids
FAEQ. Other Haplargids which have both:
1. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,

(1) 0.60 or more, with a sand/clay
Tatio of 1.0 or less; or



Plinthaquepts

Plinthaquepts occur mainly in tropical regions. They
have one or more horizons within 125 cm of the mineral
soil surface in which plinthite either forms a continuous
phase or constitutes one half or more of the volume.
These are soils in which the groundwater table
fluctuates considerably during the year, between a level
at or near the soil surface during the rainy season and a
much lower level during the dry season. Most of the
soils have developed in relatively recent alluvial
deposits, probably of late-Pleistocene or Holocene age,
and contain appreciable amounts of weatherable
minerals, Plinthaquepts are not known to occur in the
United States, but the great group is provided because
these soils are thought to be extensive in parts of the
Amazon Basin.

Sulfaquepts

Key to subgroups

JAAA. Sulfaquepts that have a salic horizon within 75
cm of the mineral soil surface.
Salorthidic Sulfaquepts

JAAB. Other Sulfaquepts that have both:
1. An value of more than 0.7; and

2. Eight percent or more clay in the fine-earth
fraction of all horizons between 20 and 50 cm
from the mineral soil surface.

Hydraquentic Sulfaquepts
JAAC. Other Sulfaquepts.
Typic Sulfaquepts
Tropaquepts
Key to subgroups

JAGA. Tropaquepts which have, within 150 cm of the
mineral soil surface, one or more of the following:

1, A sulfuric horizon; or
2. A horizon 15 cm or more thick that has all the
characteristics of a sulfuric horizon, except that it
has a pH value between 3.5 and 4.0; or
3. Sulfidic materials.
Sulfic Tropaquepts
JAGB. Other Tropaquepts that have a lithic contact

within 50 cm of the mineral soil surface.
Lithic Tropaquepts


419

DDCJ, Other Eutroperox which have an oxic horizon
that has its lower boundary within 125 cm of the
mineral soil surface,

Inceptic Eutroperox

DDCK. Other Eutroperox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 2.5YR or redder
and color value, moist, of 3 or less between 25
and 125 cm from the mineral soil surface.

Humic Rhodic Eutroperox

DDCL, Other Eutroperox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 om; and

2. Fifty percent or more hue of 7.5YR or yellower
and color value, moist, of 6 or more between 25
and 125 cm from the mineral soil surface.

Humic Xanthic Eutroperox

DDCM. Other Eutroperox that have 16 kg/m? or more
organic carbon between the mineral soil surface and a
depth of 100 cm.

Humic Eutroperox

DDCN,. Other Eutroperox that have 50 percent or more
hue of 2.5YR or redder and color value, moist, of 3 or
less between 25 and 125 cm from the mineral soil
surface.

Rhodic Eutroperox

DDCO, Other Eutroperox that have 50 percent or more
hue of 7.5YR or yellower and color value, moist, of 6 or
more between 25 and 125 cm from the mineral soil
surface.

Xanthic Eutroperox
DDCP. Other Eutroperox.
Typic Eutroperox
Haploperox
Key to subgroups

DDEA. Haploperox that have, within 125 cm of the
mineral soil surface, both:

1. A petroferric contact; and

2, Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Aquic Petroferric Haploperox
DDEB. Other Haploperox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Haploperox

—-x<O


195

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b, In the upper 18 cm of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
tatio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and
3. A frigid or colder soil temperature regime, and
an aridic moisture regime that borders on an ustic
Tegime.

—-zT>

Borollic Glossic Natrargids
FACE. Other Natrargids which have both:

1. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a, In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
tatio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 cm of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or


309

1, Have, in one or more horizons within 60 cm of
the mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. Do not, in each pedon, have carbonates in all
horizons within 100 cm of the mineral soil
surface.

Aquic Dystric Eutrochrepts

JDGI. Other Eutrochrepts that have, in one or more
horizons within 60 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Eutrochrepts

IDGJ, Other Eutrochrepts that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Eutrochrepts

JDGK. Other Eutrochrepts which:

1. Do not, in each pedon, have carbonates in all
horizons within 100 cm of the mineral soil
surface; and

2. Have either 0.2 percent or more organic carbon
at a depth of 125 cm below the mineral soil
surface, or an irregular decrease in organic-carbon
content from a depth of 25 cm to a depth of 125
cm, or to a lithic or paralithic contact if shallower;
and

3. Have a slope of less than 25 percent.
Dystric Fluventic Eutrochrepts

JDGL. Other Eutrochrepts which have both:

1, Either 0.2 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

2. A slope of less than 25 percent.
Fluventic Eutrochrepts

JDGM. Other Eutrochrepts that have a sandy particle
size in all horizons within 50 cm of the mineral soil
surface.

Arenic Eutrochrepts

JDGN. Other Eutrochrepts that do not, in each pedon,
have carbonates in all horizons within 100 cm of the
mineral soil surface,

Dystric Eutrochrepts

JDGO. Other Eutrochrepts that have 40 percent or more
carbonates, including coarse fragments up to 75 mm in


103

IEFH. Other Fragiudalfs that have, directly above the
fragipan, a layer 5 cm or more thick which either:

1. Has, on faces of primary peds, clay depletions
of clean silt and sand that constitute 1 percent or
more (by volume) of the layer, or

2. Is an eluvial horizon (E) and has 3 or more
percent (absolute) less clay in the fine-earth
fraction than both the overlying and underlying
horizons.

Glossic Fragiudalfs

IEFI. Other Fragiudalfs that do not, above the fragipan,
have an argillic horizon with clay films on both vertical

and horizontal faces of any peds.
Ochreptic Fragiudalfs
TEFJ. Other Fragiudalfs.
Typic Fragiudalfs
A
Fraglossudalfs |

Key to subgroups
IEDA. Fraglossudalfs that have, in one or more
subhorizons within the upper 25 cm of the argillic
horizon, redox depletions with a chroma of 2 or less,
and also aquic conditions for some time in most years
(or artificial drainage),

Aquic Fraglossudalfs
IEDB. Other Fraglossudalfs that are saturated with
water, in one or more layers above the fragipan, for 1
month or mote per year in 6 or more out of 10 years,

Oxyaquic Fraglossudalfs
IEDC. Other Fraglossudalfs,
Typic Fraglossudalfs
Glossudalfs
Key to subgroups

IEEA. Glossudalfs which have a brittle matrix in 25
percent or more of a horizon 10 cm or more thick that
has its upper boundary within 125 cm of the mineral
soil surface,

Fragic Glossudalfs

TEEB. Other Glossudalfs which have both:

1, In one or more subhorizons within the upper 25
cm of the argillic horizon, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or more of the following:


51
XERERTS

Key to great groups

ECA. Xererts which have a duripan that has its upper
boundary within 100 cm of the mineral soil surface.
Durixererts, p. 512

ECB. Other Xererts which have a calcic or petrocalcic
horizon that has its upper boundary within 100 cm of
the mineral soil surface.

Calcixererts, p. 511

ECC. Other Xererts.
Haploxererts, p. 513

Calcixererts

Key to subgroups
ECBA. Calcixererts that have a lithic contact within $0

om of the mineral soil surface.
Lithic Calcixererts

ECBB. Other Calcixererts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
remain 5 mm or more wide, through a thickness of 25
cm or more within 50 cm of the mineral soil surface, for
180 or more consecutive days.

Aridic Calcixererts

ECBC. Other Calcixererts which have a petrocalcic
horizon that has its upper boundary within 100 cm of
the mineral soil surface.

Petrocalcic Calcixererts

ECBD. Other Calcixererts that have a lithic or paralithic
contact within 100 cm of the mineral soil surface.
Leptic Calcixererts

ECBE. Other Calcixererts which have a layer 25 cm or
more thick that contains less than 27 percent clay in its
fine-earth fraction and has its upper boundary within
100 cm of the mineral soil surface.

Entic Calcixererts
ECBF. Other Calcixererts that have, in one or more
horizons within 30 cm of the mineral soil surface, 50
percent or more colors as follows:

1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or

3. A chroma of 3 or more.
Chromic Calcixererts

ECBG. Other Calcixererts.
Typic Calcixererts

mm<


1668

2. Undried, a 1500-kPa water retention of 70
percent or more throughout a layer 35 cm or more
thick within 100 cm either of the mineral soil
surface, or of the top of an organic layer with
andic soil properties, whichever is shallower.

N Eutric Hydric Melanudands

CGCQ. Other Melanudands that have, undried, a 1500-
kPa water retention of 70 percent or more throughout a
Jayer 35 cm or more thick within 100 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Hydric Melanudands

CGCR. Other Melanudands that have, between 40 and
100 cm either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of
a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that
have a color value, moist, 1 unit or more higher and an
organic-carbon content | percent or more (absolute)
lower.

Thaptic Melanudands

CGCS. Other Melanudands which have an argillic or a
kandic horizon that has both:

1. An upper boundary within 125 cm either of the
mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower; and

2. A base saturation (by sum of cations) of less
than 35 percent throughout its upper 50 cm.

Ultic Melanudands
CGCT. Other Melanudands.

Typic Melanudands
Placudands
Key to subgroups

CGAA. Placudands that have a lithic contact within 50
cm either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Lithic Placudands

CGAB. Other Placudands that have, in one or more
horizons between 50 and 100 cm either from the
mineral soil surface, or from the top of an organic layer
with andic soil properties, whichever is shallower, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:

1, Two percent or more redox concentrations; or


125

b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, is dry in some or all parts for less
than 120 cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 8°C; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or
b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower.

Udertic Paleustalfs

ICFB. Other Paleustalfs which have one or both of the

following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a

thickness of 30 cm or more for some time in most

years, and slickensides or wedge-shaped

aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2A

linear extensibility of 6.0 cm or more

between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Paleustalfs

ICFC. Other Paleustalfs which have an argillic horizon
that has a texture of loamy fine sand or coarser, or is
discontinuous horizontally, or is discontinuous vertically
within its upper 20 cm.

Psammentic Paleustalfs

ICFD. Other Paleustalfs that have a sandy particle size

throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 100
cm or more.

Grossarenic Paleustalfs

ICFE. Other Paleustalfs that have both:

1. In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);

and


251

percentages (by ammonium oxalate) totaling
0.40 or more.
Vitrandic Xerofluvents

KDBE. Other Xerofluvents that have either:

1. In one or more horizons within 50 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage); or

2. In one or more horizons within 150 cm of the
mineral soil surface, a color value, moist, of 4 or
more and either a chroma of 0 or a hue of SGY,
5G, 5BG, or 5B; and also aquic conditions for
some time in most years (or artificial drainage).
Aquic Xerofluvents

KDBF. Other Xerofluvents that are saturated with
water, in one or more layers within 150 cm of the
mineral soil surface, for 1 month or more per year in 6
or more out of 10 years.

Oxyaquic Xerofluvents

KDBG. Other Xerofluvents which have a horizon within
100 cm of the mineral soil surface that is 15 cm or more
thick and either contains 20 percent or more (by
volume) durinodes or is brittle and has firm consistence
when moist.

Durorthidic Xerofluvents

KDBH. Other Xerofluvents which have an Ap horizon,

or an A horizon 15 cm or more thick, that has a color E

value, moist, of 3 or less and a color value, dry, of $ or N

less (crushed and smoothed sample). T
Mollic Xerofluvents

KDBI, Other Xerofluvents.
Typic Xerofluvents

ORTHENTS

Key to great groups

KEA. Orthents that have a cryic or pergelic soil
temperature regime.
Cryorthents, p. 252
KEB. Other Orthents that have a torric moisture regime.
Torriorthents, p. 253

KEC. Other Orthents that have a xeric moisture regime.
Xerorthents, p. 260

KED. Other Orthents that have a udic moisture regime,
and a difference of less than 5°C between mean summer
and mean winter soil temperatures at a depth of 50. cm
from the soil surface.

Troporthents, p. 256


42
LITERATURE CITED

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

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 pp.


86

c. Two or more if there are no redox
concentrations.
Udollic Epiaqualfs
IAIG. Other Epiaqualfs that have, in one or more
horizons between the A or Ap horizon and a depth of 75
cm below the mineral soil surface, colors as follows:
either
1. A hue of 7.5YR or redder in 50 percent or more
of the matrix; and
a. If peds are present, a chroma of 2 or more
on 50 percent or more of ped exteriors, or no
redox depletions with a chroma of 2 or less
in ped interiors; or
b. If peds are absent, a chroma of 2 or more
in 50 percent or more of the matrix; or

2. In 50 percent or more of the matrix, a hue of
10YR or yellower and either

a. Both a color value, moist, and chroma of
3 or more; or

b. A chroma of 2 or more if there are no
redox concentrations.
Aeric Epiaqualfs

IAIH. Other Epiaqualfs which have a mollic epipedon,
or an Ap horizon that meets all the requirements for a
mollic epipedon except thickness, or materials between.
the soil surface and a depth of 18 cm that meet these
requirements after mixing.

Mollic Epiaqualfs
IAIL Other Epiaqualfs which have an Ap horizon that
meets all the requirements for an umbric epipedon
except thickness, or materials between the soil surface
and a depth of 18 cm that meet these requirements after
mixing.

Umbric Epiaqualfs
IAW. Other Epiaqualfs.
Typic Epiaqualfs
Fragiaqualfs
Key to subgroups

IADA. Fragiaqualfs that have, between the A or Ap
horizon and a fragipan, a horizon with 50 percent or
more chroma of 3 or more if the hue is 10YR or redder,
or of 4 or more if the hue is 2.5Y or yellower.

Aeric Fragiaqualfs

IADB. Other Fragiaqualfs that have 5 percent or more
(by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface.

Plinthic Fragiaqualfs


6

b. 8 percent or more if the mineral fraction
contains no clay; or

c. 8 + (clay percentage divided by 7.5) percent or
more if the mineral fraction contains less than 60
percent clay.
Most histic epipedons consist of organic soil material as
defined below. Item 2 provides for histic epipedons that
are Ap horizons consisting of mineral soil material.

Melanie epipedon (Gr. melas, melan-, black)

The melanic epipedon is a thick black horizon at or near
the soil surface which contains high concentrations of
organic carbon, usually associated with short-range-
order minerals or aluminum-humus complexes. The
intense black color is attributed to the accumulation of
organic matter from which “Type A” humic acids are
extracted. This organic matter is thought to result from
large amounts of root residues supplied by a gramineous
vegetation, and can be distinguished from organic
matter formed-under forest vegetation by the melanic
index (Honna et al., 1988).2

The suite of secondary minerals is usually dominated by
allophane, and the soil material has a low bulk density
and a high anion adsorption capacity.

The melanic epipedon has both of the following:

1, An upper boundary at, or within 30 cm of, either the
mineral soil surface or the upper boundary of an organic
layer with andic soil properties (defined below),
whichever is shallower, and

2. In layers with a cumulative thickness of 30 cm or
more within a total thickness of 40 cm, all of the
following:
a. Andic soil properties throughout; and
b. A color value, moist, and chroma (Munsell
designations) of 2 or less throughout, and a
melanic index of 1.70 or less throughout; and
c. Six percent or more organic carbon as a

weighted average, and 4 percent or more organic
carbon in all layers.

Mollic epipedon (L. mollis, soft)

The mollic epipedon consists of mineral soil material
and is at the soil surface, unless it underlies either a
recent deposit that is less than 50 em thick and has fine
stratification if not plowed, or a thin layer of organic
soil material. If the surface layer of organic material is

2 Honna, T., S. Yamamoto, and K. Matsui. 1988, A simple procedure to
detennine Melanic Index. See ICOMAND Circular Letter No. 10, pp. 76-
T.


324

within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or

more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Eutropepts

JCDF. Other Eutropepts that have:

1, In one or more horizons within 100 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. Either 0.2 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

3. A slope of less than 25 percent.
Fluvaquentic Eutropepts

JCDG. Other Eutropepts that have, in one or more
horizons within 100 cm of the mineral soil surface,
redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or
artificial drainage).

Aquic Eutropepts

JCDH. Other Eutropepts that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years,

Oxyaquic Eutropepts
JCDI. Other Eutropepts which have both:

1. Either 0.2 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

2. A slope of less than 25 percent.
Fluventic Eutropepts


430

2. Fifty percent or more hue of 2.5YR or redder
and color value, moist, of 3 or less between 25
and 125 cm from the mineral soil surface.

Humic Rhodic Hapludox

DEEK. Other Hapludox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 7.5YR or yellower
and color value, moist, of 6 or more between 25
and 125 cm from the mineral soil surface,

Humic Xanthic Hapludox

DEEL. Other Hapludox that have 16 kg/m? or more
organic carbon between the mineral soil surface and a
depth of 100 cm.

Humic Hapludox

DEEM. Other Hapludox that have 50 percent or more
hue of 2.5YR or redder and color value, moist, of 3 or
less between 25 and 125 cm from the mineral soil
surface.

Rhodic Hapludox

DEEN. Other Hapludox that have 50 percent or more
hue of 7.5YR or yellower and color value, moist, of 6 or
more between 25 and 125 cm from the mineral soil
surface.

Xanthic Hapludox
DEEO. Other Hapludox.
Typic Hapludox
Kandiudox
Key to subgroups

DEDA. Kandiudox that have, within 125 cm of the
mineral soil surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).

Aquic Petroferric Kandiudox

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

DEDC. Other Kandiudox that have, within 125 cm of
the mineral soil surface, both:

1. A lithic contact; and


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264

a, In 25 percent or more of each pedon,
cementation by organic matter and
aluminum, with or without iron; or

b. Aluminum plus 1/2 iron percentages (by
ammonium oxalate) totaling 0.25 or more,
and half that amount or less in an overlying
horizon; or
c. An ODOE value of 0.12 or more, and a
value half as high or lower in an overlying
horizon.

Aquodic Quartzipsamments

KCCC. Other Quartzipsamments that have, in one or
more horizons within 100 cm of the mineral soil
surface, redox depletions with a chroma of 2 or less, and
also aquic conditions for some time in most years (or
artificial drainage).
Aquic Quartzipsamments

KCCD. Other Quartzipsamments that are saturated with
water, in one or more layers within 100 cm of the
mineral soil surface, for 1 month or more per year in 6
or more out of 10 years.

Oxyaquic Quartzipsamments

KCCE. Other Quartzipsamments which have both:
1. An ustic moisture regime; and
2. A clay fraction with a CEC equal to that of the
clay of an oxic horizon, and enough clay to coat 75

percent or more of the sand-grain surfaces.
Ustoxic Quartzipsamments

KCCF. Other Quartzipsamments which have both:
1. A udic moisture regime; and
2. A clay fraction with a CEC equal to that of the
clay of an oxic horizon, and enough clay to coat 75

percent or more of the sand-grain surfaces.
Udoxic Quartzipsamments

KCCG. Other Quartzipsamments that have 5 percent or
more (by volume) plinthite in one or more horizons
within 100 cm of the mineral soil surface.

Plinthic Quartzipsamments

KCCH. Other Quartzipsamments which have both:

1, Lamellae within 200 cm of the mineral soil
surface that meet all the requirements for an
argillic horizon except thickness’ or clay content;
and

2. An ustic moisture regime.
Argic Ustic Quartzipsamments

5 The clay content of very thin lamellae cannot be estimated with precision.
‘The lamellae in soils of argic subgroups are generally about 0.5 to 1 cm
thick, but their total thickness is less than the 15 em required for an argllic
horizon.


149

top of an organic layer with andic soil properties,
whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of
amollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that
have a color value, moist, 1 unit or more higher and an
organic-carbon content | percent or more (absolute)

lower.
Thaptic Hydrocryands
CBDE. Other Hydrocryands.
Typic Hydrocryands
Melanocryands
Key to subgroups

CBBA. Melanocryands that have a lithic contact within
50 cm either of the mineral soil surface, or of the top of
an organic layer with andic soil properties, whichever is
shallower.

Lithic Melanocryands

CBBB, Other Melanocryands that have more than 2.0
emol(+)/kg Al5+ (by 1N KCl) in the fine-earth fraction
of one or more horizons with a total thickness of 10 om
or more, between 25 and 50 om either from the mineral
soil surface, or from the top of an organic layer with
andic soil properties, whichever is shallower.

Alic Melanocryands

CBBC. Other Melanocryands which have, undried, a
1500-kPa water retention of less than 30 percent
throughout one or more layers with andic soil properties
that have a total thickness of 25 cm more within 100 cm
either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Vitric Melanocryands
CBBD. Other Melanocryands.

Typic Melanocryands
Vitricryands
Key to subgroups

CBEA. Vitricryands that have a lithic contact within 50
cm either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Lithic Vitricryands

CBEB. Other Vitricryands that have, in one or more
horizons between 50 and 100 cm either from the
mineral soil surface, or from the top of an organic layer
with andic soil properties, whichever is shallower, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:



Cryosaprists

Key to subgroups
ADCA. Cryosaprists that have a lithic contact within the
control section.

Lithic Cryosaprists
ADCB. Other Cryosaprists that have a mean annual soil
temperature of 0°C or lower.

Pergelic Cryosaprists

ADCC. Other Cryosaprists which have a mineral layer
30 cm or more thick that has its upper boundary within
the control section below the surface tier.

Terric Cryosaprists

ADCD. Other Cryosaprists that have, within organic
materials, either one mineral layer 5 cm or more thick,
or two or more mineral layers of any thickness, in the
control section below the surface tier.

Flovaquentic Cryosaprists

ADCE. Other Cryosaprists.
Typic Cryosaprists

Medisaprists

Key to subgroups

ADDA. Medisaprists that have a lithic contact within
the control section.
Lithie Medisaprists

ADFB, Other Medisaprists which have both:

1. One or more layers, with a total thickness of
12.5 cm or more, of the subsurface and bottom
tiers consisting of fibric materials; and

2. A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Fibric Terric Medisaprists

ADFC. Other Medisaprists which have both:

1. One or more layers, with a total thickness of 25
cm or more, of the subsurface and bottom tiers
consisting of hemic materials; and

2. A mineral layer 30 cm or more thick that has its
upper botindary within the control section below

the surface tier.
Hemic Terric Medisaprists

ADFD. Other Medisaprists which have a mineral layer
30 cm or more thick that has its upper boundary within
the contro! section below the surface tier.

Terric Medisaprists


30

Mesic.—The mean annual soil temperature is 8°C or
higher but lower than 15°C, and the difference between
mean summer and mean winter soil temperatures is
more than 5°C either at a depth of 50 cm from the soil
surface or at a lithic or paralithic contact, whichever is
shallower.

Thermic.—-The mean annual soil temperature is 15°C
or higher but lower than 22°C, and the difference
between mean summer and mean winter soil
temperatures is more than 5°C either at a depth of 50
cm from the soil surface or at a lithic or paralithic
contact, whichever is shallower.

Hyperthermic.—The mean annual soil temperature is
22°C or higher, and the difference between mean.
summer and mean winter soil temperatures is more than
5°C either at a depth of 50 cm from the soil surface or at
a lithic or paralithic contact, whichever is shallower.

If the name of a soil temperature regime has the prefix
iso, the mean summer and mean winter soil
temperatures for June, July, and August and for
December, January, and February differ by less than
5°C at a depth of 50 cm or ata lithic or paralithic
contact, whichever is shallower.

Isofrigid —The mean annual soil temperature is lower
than 8°C,

Isomesic.—The mean annual soil temperature is 8°C or
higher but lower than 15°C.

Isothermic.—The mean annual soil temperature is
15°C or higher but lower than 22°C.

Isohyperthermic.—The mean annual soil temperature
is 22°C or higher.

Spodic materials

Spodic materials have formed in an illuvial horizon that
normally underlies a histic, an ochric, or an umbric
epipedon or an albic horizon. In most undisturbed areas
spodic materials underlie an albic horizon. They may
occur within an umbric epipedon or Ap horizon.

A horizon consisting of spodic materials normally has
an optical-density-of-oxalate-extract (ODOE) value of
0.25 or more, and that value must be at least two times
as high as the ODOE value for an overlying eluvial
horizon, This increase in ODOE value indicates an
accumulation of translocated organic materials in an
illuvial horizon. Soils with spodic materials show
evidence that organic materials and aluminum, with or
without iron, have been moved from an eluvial to an
illuvial horizon. The morphological, chemical, and
physical properties of spodic materials are as follows.


402

percentages (by ammonium oxalate) totaling
0.40 or more,
Vitrandic Durixerolls

HDAD. Other Durixerolls that have, in one or more
horizons above the duripan, redox depletions with a
chroma of 2 or less, and also aquic conditions for some
time in most years (or artificial drainage).
Aquic Durixerolls
HDAE. Other Durixerolls which have both:
1. An aridic moisture regime; and
2. An argillic horizon that has a clay increase with
depth either of 20 percent or more (absolute)
within its upper 7.5 cm, or of 15 percent or more
(absolute) within its upper 2.5 cm, in the fine-
earth fraction.
Abruptic Aridic Durixerolls

HDAF. Other Durixerolls that:

1. Do not have an argillic horizon above the
duripan; and
2. Have an aridic moisture regime.
Orthidic Durixerolls
HDAG. Other Durixerolls that have an aridic moisture
regime.
Aridic Durixerolls
HDAH. Other Durixerolls which have an argillic
horizon that has a clay increase with depth either of 20
percent or more (absolute) within its upper 7.5 cm, or of
15 percent or more (absolute) within its upper 2.5 cm,
in the fine-earth fraction.
Abruptic Durixerolls

HDAL Other Durixerolls which:

1. Have a duripan that is not indurated in any
subhorizon; and
2. Do not have an argillic horizon above the
duripan,
Entic Durixerolls
HDAJ. Other Durixerolls that do not have an argillic
horizon above the duripan.

Haplic Durixerolls
HDAK. Other Durixerolls which have a duripan that is
not indurated in any subhorizon.
Argic Durixerolis

HDAL. Other Durixerolls.
Typic Durixerolls


406

3. A slope of less than 25 percent.
Flavaquentic Haploxerolls

HDFM. Other Haploxerolls that have both:

1. In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and
2. A horizon 15 cm or more thick within 100 cm
of the mineral soil surface that either contains 20
percent or more (by volume) durinodes or is
brittle and has firm consistence when moist.
Aquic Duric Haploxerolls

HDEN. Other Haploxerolls that have both:

1, In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. A base saturation (by sum of cations) of 75
percent or less in one or more horizons between
either an Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and
either a depth of 75 cm or a lithic or paralithic
contact, whichever is shallower.

Aquultic Haploxerolls

HDFO. Other Haploxerolls that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).
Aquic Haploxerolls

HDFP. Other Haploxerolls that are saturated with
water, in one or more layers within 100 cm of the
mineral soil surface, for 1 month or more per year in 6
or more out of 10 years.

Oxyaquic Haploxerolls

HDFQ. Other Haploxerolls which have:
1. An aridic moisture regime; and
2. Either 0.3 percent or more organic carbon in all
horizons within 125 cm of the mineral soil
surface, or an irregular decrease in organic-carbon
content from a depth of 25 cm to a depth of 125
cm, or to a lithic or paralithic contact if shallower;
and

3. A slope of less than 25 percent.
Torrifluventic Haploxerolls

HDFR. Other Haploxerolls which have both:
1, An aridic moisture regime; and


423

more between 25 and 125 cm from the mineral soil
surface.

Xanthic Kandiperox
DDDN. Other Kandiperox.
Typic Kandiperox
Sombriperox
Key to subgroups

DDAA. Sombriperox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Sombriperox

DDAB. Other Sombriperox that have a lithic contact
within 125 cm of the mineral soil surface.
Lithic Sombriperox

DDAC. Other Sombriperox that have 16 kg/m? or more
organic carbon between the mineral soil surface and a
depth of 100 cm.

Humic Sombriperox
DDAD. Other Sombriperox.
Typic Sombriperox
TORROX
Key to great groups

DBA. Torrox that have, in one or more subhorizons of
the oxic horizon within 150 cm of the mineral soil
surface, an ECEC of less than 1.50 cmol(+)/kg clay and
a pH value (in 1N KCl) of 5.0 or more.
Acrotorrox, p. 423

DBB. Other Torrox that have a base saturation (by
NH,OAc) of 35 percent or more in all horizons within
125 cm of the mineral soil surface.

Eutrotorrox, p. 424

DBC. Other Torrox.
Haplotorrox, p. 424

Acrotorrox

Key to subgroups
DBAA. Acrotorrox that have a petroferric contact within

125 em of the mineral soil surface.
Petroferric Acrotorrox

DBAB. Other Acrotorrox that have a lithic contact
within 125 cm of the mineral soil surface.
Lithic Acrotorrox

DBAC. Other Acrotorrox.
Typic Acrotorrox


160

with more than 3.0 percent organic carbon and colors of
a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that
have a color value, moist, 1 unit or more higher and an
organic-carbon content 1 percent or more (absolute)
lower.

Thaptic Hapludands

CGFQ. Other Hapludands that have a sum of
extractable bases of more than 25.0 cmol(+)/kg in the
fine-earth fraction throughout one or more horizons with
a total thickness of 15 cm or more between 25 and 75
em either from the mineral soil surface, or from the top
of an organic layer with andic soil properties, whichever
is shallower.

Eutric Hapludands

CGFR. Other Hapludands which have an oxic horizon.
that has its upper boundary within 125 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.

Oxic Hapludands

CGFS. Other Hapludands which have an argillic or a
kandic horizon that has both:

1, An upper boundary within 125 cm either of the
mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower; and

2. A base saturation (by sum of cations) of less
than 35 percent throughout its upper 50 cm.
Ultic Hapludands

CGEFT. Other Hapludands which have an argillic or a
kandic horizon that has its upper boundary within 125
cm either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Alfic Hapludands
CGFU, Other Hapludands.

Typic Hapludands
Hydrudands
Key to subgroups

CGEA. Hydrudands that have a lithic contact within 50
cm either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Lithic Hydrudands

CGEB. Other Hydrudands that have, in one or more
horizons between 50 and 100 cm either from the
mineral soil surface, or from the top of an organic layer
with andic soil properties, whichever is shallower, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:


Chapter 5

Identification of the Taxonomic
Class of a Soil

All the keys in Soil Taxonomy are designed in such a
way that their user can determine the correct
classification of a soil by going through the key
systematically, starting at the beginning and eliminating
one by one any classes which include criteria that do not
fit the soil in question. The soil belongs into the first
class listed for which it meets all the criteria.

In classifying a specific soil to the subgroup level, the
user of Soil Taxonomy begins by checking through the
Key to soil orders to determine the name of the first
order which, according to the criteria listed, includes the
soil in question. The next step is to go systematically
through the Key to suborders of that particular order to
identify the right suborder for the soil, i.e., the first in
the list for which it meets all the criteria, The same
procedure is used to find the soil’s great group class in
the Key to great groups of the identified suborder.
Likewise, going through the Key to subgroups of that
great group, the user selects as the correct subgroup
name for the classified soil the name of the first taxon
for which it meets all the criteria.

KEY TO SOIL ORDERS

In this key and the other keys that follow, the diagnostic
horizons and the properties mentioned do not include
those below any lithic, paralithic, or petroferric contact,
nor the properties of buried soils except their organic
carbon if of Holocene age, andic soil properties, and
base saturation. Other properties of buried soils are
considered in the categories of subgroup, family, 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 which:

1, Do not have andic soil properties in 60 percent
or more of the thickness between the soil surface
and either a depth of 60 cm, or a lithic or
paralithic contact or duripan if shallower; and

2. Have one or more of the following:

a. Organic soil materials that overlie
fragmental materials and/or fill their
interstices, and either a lithic or paralithic
contact directly below the fragmental
materials, or a thickness of organic plus
fragmental materials totaling 40 cm or more


81

IAGB. Other Albaqualfs which have one or both of the
following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or weds
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Albaqualfs

IAGC. Other Albaqualfs that have both:

1. A chroma of 3 or more in 40 percent or more of
the matrix between the lower boundary of the A
or Ap horizon and a depth of 75 cm from the
mineral soil surface; and
2. An Ap horizon with a color value, moist, of 3 or
less and a color value, dry, of 5 or less (crushed
and smoothed sample), or materials between the
soil surface and a depth of 18 cm which have
these color values after mixing.

Udollic Albaqualfs

IAGD. Other Albaqualfs that have a chroma of 3 or
more in 40 percent or more of the matrix between the
lower boundary of the A or Ap horizon and a depth of
75 cm from the mineral soil surface.

Aeric Albaqualfs

AGE. Other Albaqualfs which have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or more of
the following:
1. A fine-earth fraction with both a bulk density of
1.0 g/cm: or less, measured at 33 kPa water
retention, and aluminum plus 1/2 iron percentages
(by ammonium oxalate) totaling more than 1.0; or
2. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
3 Or
3. A fine-earth fraction containing 30 percent or

more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0,02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron



Keys
to
Soil Taxonomy

by the
Soil Survey Staff

Agency for International Development
United States Department of
Agriculture

Soil Conservation Service

Soil Management Support Services

SMSS Technical Monograph No. 19
Fifth Edition, 1992

Pocahontas Press, Inc.
Blacksburg, Virginia


107
TEKG. Other Hapludalfs which have both:

1, Redox depletions with a chroma of 2 or less in
layers that also have aquic conditions in most
years (or artificial drainage) either:

a. Within the upper 25 cm of the argillic
horizon if its upper boundary is within 50
cm of the mineral soil surface, or

b. Within 75 cm of the mineral soil surface
if the upper boundary of the argillic horizon
is 50 cm or more below the mineral soil
surface; and

2. An argillic horizon that either has a texture of

loamy fine sand or coarser or is discontinuous

vertically within its upper 20 cm.
Psammaquentic Hapludalfs

TEKH. Other Hapludalfs which have an argillic horizon

that either has a texture of loamy fine sand or coarser or

is discontinuous vertically within its upper 20 cm. L
Psammentic Hapludalfs F

IEKI. Other Hapludalfs that have both:

1, In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. A sandy particle size throughout a layer

extending from the mineral soil surface to the top

of an argillic horizon at a depth of 50 cm or more.
Aquic Arenic Hapludalfs

TEKJ. Other Hapludalfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
cm or more,

Arenic Hapludalfs
TEKK. Other Hapludalfs that have anthraquic
conditions.
Anthraquic Hapludalfs

TEKL. Other Hapludalfs which have:
1. An abrupt textural change; and

2. Redox depletions with a chroma of 2 or less in
layers that also have aquic conditions in most
years (or artificial drainage) either:

a, Within the upper 25 cm of the argillic
horizon if its upper boundary is within 50
cm of the mineral soil surface, or

b. Within 75 cm of the mineral soil surface
if the upper boundary of the argillic horizon
is 50 cm or more below the mineral soil
surface; and


181

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 cm of the soil, if the
upper boundary of the duripan is at a depth
of 18 to 40 cm from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and
3, A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soi) temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Haploxerollic Durargids

FABH. Other Durargids which do not have a platy or
massive duripan that is indurated in any subhorizon.
Haplic Durargids

FABI. Other Durargids that have:
1. A duripan at a depth of 18 cm or more; and
2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:
a. In the upper 40 cm of the soil, if the upper
boundary of the duripan is 40 cm or more
below the soil surface,
(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or
(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or
(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or
b, In the upper 18 cm of the soil, if the
upper boundary of the duripan is at a depth
of 18 to 40 cm from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or


429

DEEB. Other Hapludox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Hapludox

DEEC, Other Hapludox that have, within 125 cm of the
mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).

Aquic Lithic Hapludox

DEED, Other Hapludox that have a lithic contact within
125 em of the mineral soil surface.
Lithic Hapludox

DEEE. Other Hapludox that have, in one or more
horizons within 125 cm of the mineral soil surface,
both:

1, Five percent or more (by volume) plinthite; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).

Plinthaquic Hapludox

DEEF. Other Hapludox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125
cm of the mineral soil surface.

Plinthic Hapludox

DEEG. Other Hapludox that have, in one or more
horizons within 125 cm of the mineral soil surface,
redox depletions with a color value, moist, of 4 or more
and a chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage).

Aquic Hapludox

DEEH. Other Hapludox which have an oxic horizon that
has its lower boundary within 125 cm of the mineral
soil surface.

Inceptic Hapludox

DEEI. Other Hapludox that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm? or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Hapludox

DEEJ. Other Hapludox that have both:

1, 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and


130

(absolute) in the fine-earth fraction;
and

D. In the matrix of its lowest subhorizon, one
or both of the following:

(1) A hue of 7.5YR or redder and a
chroma of 5 or more; or

(2) Common or many coarse redox
concentrations with a hue of 7,5YR or
redder or a chroma of 6 or more, or
both; or
3. No lithic or paralithic contact within 50 cm of
the mineral soil surface, and an argillic horizon
which has both:

a. A clayey particle size throughout one or
more subhorizons in its upper part; and
b. At its upper boundary, a clay increase
either of 20 percent or more (absolute)
within a vertical distance of 7.5 cm, or of 15
‘percent or more (absolute) within a vertical
distance of 2.5 cm, in the fine-earth fraction.
Palexeralfs, p. 135
IDG. Other Xeralfs.
Haploxeralfs, p. 132

Durixeralfs

Key to subgroups
IDAA. Durixeralfs that have a natric horizon.
Natric Durixeralfs

IDAB. Other Durixeralfs which have, above the
duripan, one or both of the following:
1. Cracks that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped.
aggregates in a layer 15 cm or more thick; or
2. A linear extensibility of 6.0 cm or more.
Vertic Durixeralfs
IDAC. Other Durixeralfs that have, in one or more
subhorizons within the argillic horizon, redox depletions
with a chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage),
Aquic Durixeraifs

IDAD. Other Durixeralfs which have both:
1. An argillic horizon that has both:

a. A clayey particle size throughout some
subhorizon 7.5 cm or more thick; and

b. At its upper boundary or within some
part, a clay increase either of 20 percent or


158

cm either from the mineral soil surface, or from
the top of an organic layer with andic soil
properties, whichever is shallower; and

2. Undried, a 1500-kPa water retention of 70
percent or more throughout a layer 35 cm or more
thick within 100 cm either of the mineral soil
surface, or of the top of an organic layer with
andic soil properties, whichever is shallower.
Acrudoxic Hydric Hapludands

CGFI. Other Hapludands that have, between 25 and 100
cm either from the mineral soil surface, or from the top
of an organic layer with andic soil properties, whichever
is shallower, both:

1. Extractable bases plus 1N-KCl-extractable Al3+
totaling less than 2.0 cmol(+)/kg in the fine-earth
fraction of one or more horizons with a total
thickness of 30 cm or more; and

2. A layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic
epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more
that have a color value, moist, 1 unit or more
higher and an organic-carbon content | percent or
more (absolute) lower.

Acrudoxic Thaptic Hapludands

CGFJ. Other Hapludands that have both:

1. Extractable bases plus IN-KCl-extractable Al+
totaling less than 2.0 cmol(+)/kg in the fine-earth
fraction of one or more horizons with a total
thickness of 30 cm or more, between 25 and 100
om either from the mineral soil surface, or from
the top of an organic layer with andic soil
properties, whichever is shallower; and

2. An argillic or a kandic horizon that has both:

a. An upper boundary within 125 cm either
of the mineral soil surface, or of the top of
an organic layer with andic soil properties,
whichever is shallower; and

b. A base saturation (by sum of cations) of
less than 35 percent throughout its upper 50
om.

Acrudoxic Ultic Hapludands

CGFK. Other Hapludands that have extractable bases
plus 1N-KCl-extractable Al totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more
horizons with a total thickness of 30 cm or more,
between 25 and 100 cm either from the mineral soil
surface, or from the top of an organic layer with andic
soil properties, whichever is shallower.

Acrudoxic Hapludands


Keys to Soil Taxonomy, Fifth Edition

Prepared by Pocahontas Press
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Citation:
Soil Survey Staff. 1992. Keys to Soil Taxonomy, 5th edition,

SMSS technical monograph No. 19, Blacksburg, Virginia:
Pocahontas Press, Inc. 556 pages.

Fifth Edition, 1992
ISBN  0-936015-39-X. LC 92-28188


190

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0,64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 em of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0,77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

2. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Xerollic Haplargids

FAER. Other Haplargids which have both:

1. A moisture control section that is dry in all its
parts for less than three fourths of the cumulative
days per year in 6 or more out of 10 years when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and
2. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Xeralfic Haplargids

FAES. Other Haplargids which have both:

1. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or

» more, with a sand/clay ratio between 1
and 13; or


210

(2) 0.15 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.64-(0.038 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
land 13; or

b. In the upper 18 cm of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.18 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.77-(0.046 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
land 13; and

3. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Durixerollic Calclorthids

FBEI. Other Calciorthids which have a horizon within
100 cm of the soil surface that is 15 cm or more thick
and either contains 20 percent or more (by volume)
durinodes or is brittle and has firm consistence when
moist.

Duric Calciorthids

FBEJ. Other Calciorthids which have both:

1. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to noncarbonate clay, as follows:

a. In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,
(1) 0.60 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or
(2) 0.15 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or
(3) 0.64-(0.038 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
1 and 13; or


Chapter 13

Oxisols:

KEY TO SUBORDERS

DA, Oxisols that have aquic conditions for some time in
most years (or artificial drainage) in one or more
horizons within 50 cm of the mineral soil surface, and
one or more of the following:

1, A histic epipedon; or
2. An epipedon with a color value, moist, of 3 or

less, and directly below it, a horizon with a
chroma of 2 or less; or

3. Distinct or prominent redox concentrations
within 50 cm of the mineral soil surface, an
epipedon, and directly below it, a horizon with
one or both of the following:

a. Fifty percent or more hue of 2.5Y or
yellower; or
b. A chroma of 3 or less; or

4, Within 50 cm of the mineral soil surface,

enough active ferrous iron to give a positive
reaction to a.,a'-dipyridyl at a time when the soil

is not being irrigated.
Aquox, p. 414
DB. Other Oxisols that have an aridic moisture regime.
Torrox, p. 423
DC. Other Oxisols that have an ustic moisture regime,
Ustox, p. 432
DD. Other Oxisols that have a perudic moisture regime.
Perox, p. 415
DE. Other Oxisols.
Udox, p. 424

1 This chapter on Oxisols was rewritten in 1987 following the
recommendations of the Intemational Committee on the Classification of
‘Oxisols (COMOX), chaired by Hari Eswaran from 1978 to 1981 and then
by S.W. Buol until completion of the task in 1987,

-xO


369

(1) A color value, moist, of 4 or more
and redox depletions with a chroma of
2 or less; or

(2) A hue of 10YR or redder and a
chroma of 2 or less; or

(3) A hue of 2.5Y or yellower and a
chroma of 3 or less; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower.

Aquertic Hapludolls

HGEC. Other Hapludolls which have one or both of the
following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and cither a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower,

Vertic Hapludolls

HGED. Other Hapludolls that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm? or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Hapludolls

HGEE. Other Hapludolls that have, throughout one or
more horizons with a total thickness of 18 om or more
within 75 cm of the mineral soil surface, one or both of
the following:

1, More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

ieee


492

EE. Other Vertisols which, if not irrigated during the
year, have cracks in 6 or more out of 10 years that are 5
mm or more wide, through a thickness of 25 cm or more
within 50 cm of the mineral soil surface, for 90 or more
cumulative days per year.

Usterts, p. 504
EF. Other Vertisols.

Uderts, p. 502
AQUERTS
Key to great groups

EAA. Aquerts which have a salic horizon that has its
upper boundary within 100 cm of the mineral soil
surface.

Salaquerts, p. 498
EAB. Other Aquerts which have a duripan that has its
upper boundary within 100 cm of the mineral soil
surface.
Duraquerts, p. 493

EAC. Other Aquerts that have a natric horizon.
Natraquerts, p. 498

EAD. Other Aquerts which have a calcic horizon that
has its upper boundary within 100 cm of the mineral

soil surface.
Calciaquerts, p. 492
EAE. Other Aquerts that have, throughout one or more

horizons with a total thickness of 25 cm or more within
50 cm of the mineral soil surface, both:

1. An electrical conductivity of the saturation
extract of less than 4.0 dS/m at 25°C; and
2, A pH value of 4,5 or less in 0.01 M CaCl, (5.0
‘or less in 1:1 water).
Dystraquerts, p. 494
EAF. Other Aquerts that have episaturation.
Epiaquerts, p. 496

EAG. Other Aquerts.
Endoaquerts, p. 495

Calclaquerts

Key to subgroups

EADA. Calciaquerts that have, in one or more horizons

between either an Ap horizon or a depth of 25 cm from

the mineral soil surface, whichever is deeper, and either

a depth of 75 cm or the upper boundary of a duripan if
shallower, 50 percent or more colors as follows:


108

3, A base saturation (by sum of cations) of less
than 60 percent at a depth of 125 cm from the top
of the argillic horizon, or at a depth of 180 cm
from the mineral soil surface, or directly above a
lithic or paralithic contact, whichever is
shallowest.

Albaquultic Hapludalfs

TEKM. Other Hapludalfs which have both:
1. An abrupt textural change; and

2. Redox depletions with a chroma of 2 or less in
layers that also have aquic conditions in most
years (or artificial drainage) either:
a, Within the upper 25 cm of the argillic
horizon if its upper boundary is within 50
em of the mineral soil surface, or

b. Within 75 cm of the mineral soil surface
if the upper boundary of the argillic horizon
is 50 cm or more below the mineral soil
surface.

Albaquic Hapludalfs

TEKN. Other Hapludalfs which have both:

1. Interfingering of albic materials, and albic
materials surrounding some peds, in the upper
part of the argillic horizon; and
2. Redox depletions with a chroma of 2 or less in
layers that also have aquic conditions in most
years (or artificial drainage) either:
a. Within the upper 25 cm of the argillic
horizon if its upper boundary is within 50
cm of the mineral soil surface, or
b. Within 75 cm of the mineral soil surface
if the upper boundary of the argillic horizon
is 50 cm or more below the mineral soil

Glossaquic Hapludalfs
IEKO. Other Hap)udalfs which have both:

1. Redox depletions with a chroma of 2 or less in
layers that also have aquic conditions in most
years (or artificial drainage) either:
a. Within the upper 25 cm of the argillic
horizon if its upper boundary is within 50
em of the mineral soil surface, or
b. Within 75 cm of the mineral soil surface
if the upper boundary of the argillic horizon
is 50 cm or more below the mineral soil
surface; and
2. A base saturation (by sum of cations) of less
than 60 percent at a depth of 125 om from the top
of the argillic horizon, or at a depth of 180 cm


489
XERULTS

Key to great groups
GEA. Xenults which:

1, Do not have a lithic or paralithic contact within
150 cm of the mineral soil surface; and

2. Within 150 cm of the mineral soil surface,
either:

a. Do not have a clay decrease with
increasing depth of 20 percent or more
(relative) from the maximum clay content;
or

b. Have 5 percent or more (by volume)
skeletans on faces of peds, or 5 percent or
more (by volume) plinthite, or both, in the
layer that has a 20 percent lower clay
content and, below that layer, a clay
increase of 3 percent or more (absolute) in
the fine-carth fraction.

Palexerults, p.490

GEB. Other Xerults.
Haploxerults, p. 489

Haploxerults

Key to subgroups
GEBA. Haploxerults which have both:

1, A lithic contact within 50 cm of the mineral soil
surface; and

2. In each pedon, a discontinuous argillic horizon
that is interrupted by ledges of bedrock.
Lithic Ruptic-Xerochreptic Haploxerults

GEBB, Other Haploxerults that have a lithic contact
within 50 cm of the mineral soil surface.
Lithic Haploxerults

GEBC. Other Haploxerults that have, in one or more
subhorizons within the upper 25 cm of the argillic
horizon, redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, accompanied by
redox concentrations, and also aquic conditions for some
time in most years (or artificial drainage).
Aquic Haploxerults

GEBD. Other Haploxerults that have a texture of loamy
fine sand or coarser throughout the argillic horizon, or
lamellae within its upper 25 cm.

Psammentic Haploxerults

GEBE. Other Haploxerults that have a sandy particle
size throughout a layer extending from the mineral soil

are


27

the degree of reduction existing in a soil are difficult to
obtain. In the context of Soil Taxonomy, however, only
a degree of reduction that results in reduced Fe is
considered, because it produces the visible
redoximorphic features that are identified in the keys. A
simple field test is available to determine if reduced
iron ions are present. A freshly broken surface of a iN
field-wet soil sample is treated with a,a'-dipyridyl"! in
neutral, 1-normal ammonium-acetate solution, The
appearance of a strong red color on the freshly broken.
surface indicates the presence of reduced iron ions. Use
of a,a'-dipyridyl in a 10-percent acetic-acid solution is
not recommended because the acid is likely to change
soil conditions, for example by dissolving CaCO.

The duration of reduction required for creating aquic
conditions is not specified.

3, Redoximorphic features associated with wetness
Tesult from the reduction and oxidation of iron and
manganese compounds in the soil after saturation with
water and desaturation, respectively. The reduced iron
and manganese ions are mobile and may be transported
by water as it moves through the soil. Certain redox
patterns occur as a function of the patterns in which the
ion-carrying water moves through the soil, and of the
location of aerated zones in the soil. Redox patterns are
also affected by the fact that manganese is reduced more
rapidly than iron, while iron oxidizes more rapidly upon
aeration, Characteristic color patterns are created by
these processes. The reduced iron and manganese ions
may be removed from a soil if vertical or lateral fluxes
of water occur, in which case there is no iron or
manganese precipitation in that soil. Wherever the iron
and manganese is oxidized and precipitated, it forms
either soft masses or hard concretions or nodules.
Movement of iron and manganese as a result of redox
processes in a soil may result in redoximorphic features
that are defined as follows:

a. Redox concentrations.These are zones of
apparent accumulation of Fe-Mn oxides,
including:
(1) Nodules and concretions, i.e., firm,
itegularly shaped bodies with diffuse

11 A positive to the a,o'-<dipyridy! field test for ferrous iron

. ry
absent; this may only mean thatthe level of fre iron in the sol is below the
seit oft to hat to i i nin pata tne

vem 1981. Field test for ferrous iron and ferric-organic
(oa exchange sites or in water-soluble forms) in soils, Australian Jounal of
‘Soil Research 19; 175-180.


212

2. An aridic moisture regime that borders on an
ustic regime.
Ustollic Calciorthids
FBEL, Other Calciorthids which have both:

1. A moisture control section that is dry in all its
parts for less than three fourths of the cumulative
days per year in 6 or more out of 10 years when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and
2. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Xerochreptic Calciorthids

FBEM. Other Calciorthids which have both:

1. A moisture control section that is dry in all its

parts for less than three fourths of the cumulative

days per year in 6 or more out of 10 years when

the soil temperature at a depth of 50 cm from the -

soil surface is 5°C or higher; and

2. An aridic moisture regime that borders on an

ustic regime.

Ustochreptic Calciorthids

FBEN. Other Calciorthids which have reddish peds
below the calcic horizon that either are weakly
calcareous or noncalcareous but are coated with lime.

Argie Calciorthids
FBEO. Other Calciorthids.

Typic Calclorthids
Camborthids
Key to subgroups

FBFA. Camborthids which have:

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

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

3. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 om of the soil, if the lithic
contact is between 40 and 50 cm below the
soil surface,
(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or


Kandiaqualfs
to 1S.

TABA. Kandiaqualfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
to 100 cm.

Arenic Kandiaqualfs

IAEB, Other Kandiaqualfs that have a sandy particle
size throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 100
¢m or more,

Grossarenic Kandiaqualfs

TAEC. Other Kandiaqualfs that have 5 percent or more
(by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface.

Plinthic Kandiaqualfs

TAED. Other Kandiaqualfs that have both:

1. An Ap horizon with a color value, moist, of 3 or
less and a color value, dry, of 5 or less (crushed
and smoothed sample), or materials between the
soil surface and a depth of 18 cm which have
these color values after mixing; and

2. In one or more horizons between the A or Ap
horizon and a depth of 75 cm below the mineral
soil surface, one of the following colors:

a, A hue of 7,5YR or redder in 50 percent or
more of the matrix, and

(4) If peds are present, either a chroma
of 2 or more on 50 percent or more of
ped exteriors, or no redox depletions
with a chroma of 2 or less in ped
interiors; or

(2) If peds are absent, a chroma of 2 or
more in 50 percent or more of the
matrix; or

b. In 50 percent or more of the matrix, a hue
of 10YR or yellower and either

(1) Both a color value, moist, and
chroma of 3 or more; or

(2) A chroma of 2 or more if there are
no redox concentrations.
Aeric Umbric Kandiaqualfs

IAEE. Other Kandiaqualfs that have, in one or more
horizons between the A or Ap horizon and a depth of 75
cm below the mineral soil surface, one of the following
colors:

1. A hue of 7.5YR or redder in 50 percent or more
of the matrix, and


385

fraction with both a bulk density of 1.0 g/cm or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0,

Andic Haplustolls

HFGJ, Other Haplustolls which have both:

1. If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for six tenths or more of the
cumulative days per year when the soil
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, remains moist in some or all parts for
less than 90 consecutive days per year when
the temperature at a depth of 50 cm below
the soil surface is higher than 8°C; and

2, Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or both of the following:

a, More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or

b. A fine-earth fraction containing 30
percent or more particles 0.02 to 2.0 mm in
diameter, and either:

(1) In the 0,02-to-2.0-mm fraction,
tore than 30 percent volcanic glass;
or

(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more.
Vitritorrandic Haplustolls

HFGK, Other Haplustolls that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or


Salitorrerts

Key to subgroups

EDAA. Salitorrerts that have, in one or more horizons
within 100 cm of the soil surface, aquic conditions for
some time in most years (or artificial drainage) and
either:

1. Redoximorphic features; or

2. Enough active ferrous iron to give a positive
reaction to a,a'-dipyridy] at a time when the soil
is not being irrigated.
Aquic Salitorrerts
EDAB. Other Salitorrerts that have a lithic or paralithic
contact, or the upper boundary of a duripan or
petrocalcic horizon, within 100 cm of the soil surface.
Leptic Salitorrerts
EDAC. Other Salitorrerts which have a layer 25 cm or
more thick that contains less than 27 percent clay in its
fine-earth fraction and has its upper boundary within
100 cm of the soil surface.
Entic Salitorrerts

EDAD. Other Salitorrerts that have, in one or more
horizons within 30 cm of the soil surface, 50 percent or
more colors as follows:

1, A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3, A chroma of 3 or more.

Chromic Salitorrerts
EDAE, Other Salitorrerts.
Typic Salitorrerts
UDERTS
Key to great groups

EFA. Uderts that have, throughout one or more horizons
with a total thickness of 25 cm or more within 50 cm of
the mineral soil surface, both:

1. An electrical conductivity of the saturation
extract of less than 4.0 dS/m at 25°C; and

2. ApH value of 4.5 or less in 0.01 M CaCl, (5.0
or less in 1:1 water).
Dystruderts, p.503

EFB, Other Uderts.
Hapluderts, p. 503


198

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 cm of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between |
and 13; and

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

Haplustollic Natrargids

FACK. Other Natrargids which have:

1. An exchangeable sodium percentage of less
than 15 (or a sodium adsorption ratio of less than
13) in 50 percent or more of the natric horizon;
and

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:
a. In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,
(1) 0.60 or more, with a sand/clay
tatio of 1.0 or less; or
(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or
(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

D. In the upper 18 cm of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,


$20

it in a reduced state. Most of the affected layers
have a chroma of 2 or less, and many have redox
concentrations. The low chroma can represent
either the color of reduced iron or the color of
‘uncoated sand and silt particles from which iron
has been removed. The symbol g is not used for
materials of low chroma that have no history of
wetness, such as some shales or E horizons. If g is
used with B, pedogenic change in addition to
gleying is implied. If no other pedogenic change
besides gleying has taken place, the horizon is
designated Cg.

h Illuvial accumulation of organic matter

This symbol is used with B to indicate the
accumulation of illuvial, amorphous, dispersible
organic-matter-sesquioxide complexes if the
sesquioxide component is dominated by aluminum
but is present only in very small quantities. The
organo-sesquioxide material coats sand and silt
particles. In some horizons, these coatings have
coalesced, filled pores, and cemented the horizon.
The symbol h is also used in combination with s
as “Bhs” if the amount of sesquioxide component
is significant but the color value and chroma,
moist, of the horizon is 3 or less.

i Slightly decomposed organic material
This symbol is used with O to indicate the least

decomposed of the organic materials. Its rubbed.
fiber content is 40 percent or more (by volume).

k Accumulation of carbonates

This symbol indicates an accumulation of
alkaline-earth carbonates, commonly calcium
carbonate.

m_ Cementation or induration

This symbol indicates continuous or nearly
continuous cementation. It is used only for
horizons that are more than 90 percent cemented,
although they may be fractured. The cemented
layer is physically root-restrictive. The
cementing agent (or the two
dominant cementing agents) may be indicated by
using defined letter suffixes, singly or in pairs.
The horizon suffix km indicates cementation by
carbonates; qm: cementation by silica, sm:
cementation by iron; ym: cementation by gypsum;
kqm: cementation by lime and silica; and zm:
cementation by salts more soluble than gypsum.
n Accumulation of sodium

This symbol indicates an accumulation of
exchangeable sodium.


83

percentages (by ammonium oxalate)
totaling 0.40 or more.
Aquandic Endoaqualfs

IAJB. Other Endoaqualfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
to 100 cm.

Arenic Endoaqualfs

IAJC. Other Endoaqualfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 100
em or more.

Grossarenic Endoaqualfs

TAJD. Other Endoaqualfs that have, in one or more
horizons between the A or Ap horizon and a depth of 75
cm below the mineral soil surface, one of the following

colors:

1, A hue of 7.5YR or redder in 50 percent or more.
of the matrix; and

a, If peds are present, a chroma of 2 or more
on 50 percent or more of ped exteriors, or no
redox depletions with a chroma of 2 or less
in ped interiors; or

b. If peds are absent, a chroma of 2 or more
in 50 percent or more of the matrix; or

2. In 50 percent or more of the matrix, a hue of
10YR or yellower and either

a. Both a color value, moist, and chroma of
3 or more; or

'b. A chroma of 2 or more if there are no
redox concentrations,
Aeric Endoaqualfs

IAJE, Other Endoaqualfs which have a mollic epipedon,
or an Ap horizon that meets all the requirements for a
mollic epipedon except thickness, or materials between
the soil surface and a depth of 18 cm that meet these
requirements after mixing.

Mollic Endoaqualfs

IAJF. Other Endoaqualfs which have an Ap horizon that
Meets all the requirements for an umbric epipedon
except thickness, or materials between the soil surface
and a depth of 18 cm that meet these requirements after
mixing.

Umbric Endoaqualfs

TAJG. Other Endoaqualfs.

Typic Endoaqualfs


536

Mesic soil temperature regime
Micro soil depth class
Mineral soil material ..

Modifiers that replace names of
Particle-size classes 52

Mollic epipedon ..
MOLLISOLS .

Noncemented class


9

and its organic-carbon content depend on the materials
used for bedding.

A plaggen epipedon can be identified by several means.
Commonly it contains artifacts, such as bits of brick and
pottery, throughout its depth. There may be chunks of
diverse materials, such as black sand and light gray
sand, as large as the size held by a spade. The plaggen
epipedon normally shows spade marks throughout its
depth and also remnants of thin stratified beds of sand
that were probably produced on the soil surface by
beating rains and were later buried by spading,

Umbric epipedon (L. wmbra, shade, hence dark)
Requirements for an umbric epipedon with regard to
color, organic-carbon and phosphorus content,
consistence, structure, n value, and thickness are the
same as those for the mollic epipedon. The umbric
epipedon includes those thick, dark-colored surface
horizons that have a base saturation of less than 50
percent (by NH,OAc). It should be noted that the
restriction against an epipedon that is hard, very hard,
or harder and massive 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
show evidence of a gradual addition of materials during
cultivation, whereas the umbric epipedon does not have
the artifacts, spade marks, and raised surfaces that are
characteristic of the plaggen epipedon.

DIAGNOSTIC SUBSURFACE HORIZONS

The horizons discussed in this section form below the
surface of the soil, although in some areas they form
directly below a layer of leaf litter. They may be
exposed at the surface by truncation of the soil. Some of
these horizons are generally regarded as B horizons,
some are considered B horizons by many but not all
pedologists, while others are generally regarded as parts
of the A horizon,

Agric horizon

The agric horizon (L. ager, field) is an illuvial horizon
which has formed under cultivation and contains
significant amounts of illuvial silt, clay, and humus.
After a soil has been cultivated for a long time, changes
in the horizon directly below the plow layer become
apparent and cannot be ignored in classifying the soil.
The large pores in the plow layer and the absence of
vegetation immediately after plowing permit a turbulent
flow of muddy water to the base of the plow layer. Here
the water can enter wormholes or fine cracks between
peds, and the suspended materials are deposited as the
water is withdrawn into capillary pores. The worm


204

a. 0.60 or more, with a sand/clay ratio of 1.0
or less; or

b. 0.15 or more, with a sand/clay ratio of 13
or more; or

¢. 0.64-(0.038 x sand/clay ratio), or more,
with a sand/clay ratio between | and 13; and

2. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Xerollic Paleargids
FADJ. Other Paleargids which have both:

1. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, between the soil surface and a depth
of 40 cm as follows:

a. 0.60 or more, with a sand/clay ratio of 1.0
or less; or

b. 0.15 or more, with a sand/clay ratio of 13
or mote; or

¢. 0.64-(0.038 x sand/clay ratio), or more,
with a sand/clay ratio between 1 and 13; and

2. An aridic moisture regime that borders on an
ustic regime.
Ustollic Paleargids
FADK. Other Paleargids which have both:

1. A moisture control section that is dry in all its
parts for less than three fourths of the cumulative
days per year in 6 or more out of 10 years when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and
2. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Xeralfic Paleargids

FADL. Other Paleargids which have both:

1. A moisture control section that is dry in all its
parts for less than three fourths of the cumulative
days per year in 6 or more out of 10 years when.
the soil temperature at a depth of 50 cm from the
soil surface 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


52

fodifi E particles

There are two situations in which particle-size class
names are not used. In one, the name is redundant.
Psamments and Psammaquents are sandy by definition,
$0 no particle-size modifier is used in the family names
of those soils.

In the second situation particle-size analysis is difficult
to apply, which is the case with soil materials that are
derived from volcanic ejecta and/or have a high content
of sequioxides and organic matter. Normal particle-size
classes do not characterize these components
adequately, 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 those parts of soils that have andic soil
properties or a high amount of volcanic glass, as is the
case with Andisols and many andic and vitrandic
subgroups of other soil orders. In addition, most Cryods
and Cryaquods and a few other Spodosols that are not
identified in andic subgroups have andic soil properties
in some horizons within the particle-size control section,
and particle-size class names are not used for these
horizons.4

The following is a list of modifiers used as substitutes
for particle-size class names, together with the criteria
for each. These criteria combine particle-size and
mineralogical properties and take the place of both.

1. Substitutes for the fragmental particle-size class:

These classes have a fine-earth component of less than
10 percent of the total volume.

Pumiceous - In the whole soil, more than 60 percent (by
weight) volcanic ash, cinders, lapilli, pumice and

3 Definitions of the geologic terms used in the substitute particle-size
classes are generally the same as in: Bates, RL, and J.A. Jackson, (Eds).
1980, Glossery of Geology. 2nd ed. American Geological Institute, Falls
‘Cluch, VA. 751 pp. However, different definitions are used here for the
following terms:
Cinders. Uncemented, juvenile, vine, vesicular pyroclastic
mail, ot ten 2 run inet non nerin, ihn
fe gaily including vesicles) of more than 1.0 and
jem an 20 gm
Lanilli: Nonvesicular or slightly vesicular pyroclastcs, 2.0 to 76 mm
inateast one dimension, with an apparent speife gravity of 20 or
‘more g/em3,
Phmice-tike: Vesicular pyroclastic matenals other than pumice that
ave an apparent specific gravity (inching veseles) of estan 1.0
plan,

4 Particle-size class names are applied, although with reservations, to spodic
horizons that do not have andic soil properties but contain significant
‘amounts of organic matter. Somewhat different classes probably should be
used for most families of Spodosols, because some series that otherwise
seem reasonably homogeneous are split atthe family level by the particle-
size classes. But altematives have not yet been sufficiently tested,


329

JEC. Other Umbrepts that have a xeric moisture regime.
Xerumbrepts, p. 333

JED. Other Umbrepts.
Haplumbrepts, p. 331

Cryumbrepts

Key to subgroups
JEBA. Cryumbrepts that have a lithic contact within 50
em of the mineral soil surface in less than half of each
pedon.
Ruptic-Lithie Cryumbrepts
JEBB. Other Cryumbrepts which have both:
1. A lithic contact within 50 cm of the mineral soil
surface; and
2. An umbric epipedon that is discontinuous in
each pedon.
Lithic Ruptic-Entic Cryumbrepts

JEBC, Other Cryumbrepts that have a lithic contact
within 50 cm of the mineral soil surface.

Lithic Cryumbrepts
JEBD. Other Cryumbrepts that have a mean annual soil
temperature of 0°C or lower,
Pergelic Cryumbrepts

JEBE. Other Cryumbrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm? or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Cryumbrepts

JEBF. Other Cryumbrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66

percent are cinders, pumice, and pumice-like
fragments; or
2. A fine-earth fraction containing 30 percent or

more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

oz-


170
Haplustands

Key to subgroups

CFBA. Haplustands that have a lithic contact within 50
cm either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Lithic Haplustands

CFBB. Other Haplustands that have, in one or more
horizons between 50 and 100 cm either from the
mineral soil surface, or from the top of an organic layer
with andic soil properties, whichever is shallower, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:

1. Two percent or more redox concentrations; or

2. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
redox depletions on faces of peds, or in the matrix
if peds are absent; or

3. Enough active ferrous iron to give a positive
reaction to a.,a'-dipyridyl at a time when the soil
is not being irrigated.
Aquic Haplustands
CFBC. Other Haplustands that have both:

1. Extractable bases plus 1N-KCl-extractable A+
totaling less than 15.0 cmol(+)/kg in the fine-earth
fraction throughout one or more horizons with a
total thickness of 60 cm or more within 75 cm
either of the mineral soil surface, or of the top of
an organic layer with andic soil properties,
whichever is shallower; and

2. Undried, a 1500-kPa water retention of less
than 30 percent throughout one or more layers
with andic soil properties that have a total
thickness of 25 cm more within 100 cm either of
the mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower.

Dystric Vitric Haplustands

CFBD. Other Haplustands which have, undried, a 1500-
kPa water retention of less than 30 percent throughout
one or more layers with andic soil properties that have a
total thickness of 25 cm more within 100 cm either of
the mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Vitric Haplustands


493
1. A hue of 2.5Y or redder and either:

a. A color value, moist, of 6 or more and a
chroma of 3 or more; or

b. A color value, moist, of 5 or less and a
chroma of 2 or more; or

2. A hue of SY and a chroma of 3 or more; or
3, A chroma of 2 or more, and no redox

concentrations.
Aeric Calciaquerts
EADB. Other Calciaquerts.
Typic Calciaquerts
Duraquerts
Key to subgroups

EABA. Duraquerts which, if not irrigated during the
year, have cracks in 6 or more out of 10 years that are 5
mm or more wide, through a thickness of 25 cm or more
within 50 cm of the mineral soil surface, for 210 or
more cumulative days per year,

Aridic Duraquerts

EABB. Other Duraquerts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
are 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 90 or
more cumulative days per year.

Ustic Duraquerts

EABC. Other Duraquerts that have, in one or more
horizons between either an Ap horizon or a depth of 25
cm from the mineral soil surface, whichever is deeper,
and cither a depth of 75 cm or the upper boundary of the
duripan if shallower, 50 percent or more colors as
follows:

1. A hue of 2.5Y or redder and either:

a. A color value, moist, of 6 or more and a
chroma of 3 or more; or

b. A color value, moist, of 5 or less and a
chroma of 2 or more; or

2. A hue of SY and a chroma of 3 or more; or

3. A chroma of 2 or more, and no redox
concentrations.
Aeric Duraquerts

EABD. Other Duraquerts that have, in one or more
Vv
R

horizons within 30 cm of the mineral soil surface, one
or both of the following in more than half of each
pedon:


515

Designations for Horizons
and Layers

Genetic soil horizons are not the equivalent of the
diagnostic horizons of Soil Taxonomy. While
designations of genetic horizons express a qualitative
judgment about the kinds of changes that are believed to
have taken place in a soil, diagnostic horizons are
quantitatively defined features which are used to
differentiate between taxa. A diagnostic horizon may
encompass several genetic horizons, and changes
implied by genetic horizon designations may not be
large enough to justify recognizing different diagnostic
horizons. Genetic horizons are designated as follows.

MASTER HORIZONS AND LAYERS

The capital letters O, A, E, B, C, and R represent the
master horizons and layers of soils. These 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 consist of organic material that was deposited
under saturated conditions and has decomposed to
varying stages. The mineral fraction of such material
constitutes only a small percentage of its volume and
generally much less than half of its weight. Some soils
consist entirely of materials designated as O horizons or
layers.

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

A horizons: Mineral horizons which have formed at the
surface or below an O horizon; they exhibit obliteration
of all or much of the original rock structure! and show
one or both of the following: (1) an accumulation of
humified organic matter intimately mixed with the

1 Rock structure includes fine stratification in unconsolidated soi! materials
2s well s peeudomorphs of weathered minerals that retain their positions
relative to each other and to unweathered minerals in saprolite,


463

GAAB. Other Plinthaquults.
Typic Plinthaquults

Umbraquults

Key to subgroups

GAGA. Umbraquults that have 5 percent or more (by
volume) plinthite in one or more horizons within 150

om of the mineral soil surface.
Plinthic Umbraquults
GAGB. Other Umbraquults.
Typic Umbraquults
HUMULTS
Key to great groups

GBA. Humults that have a sombric horizon within 100
cm of the mineral soil surface.
Sombrihumults, p. 468

GBB. Other Humults that have one or more horizons
within 150 cm of the mineral soil surface in which
plinthite either forms a continuous phase or constitutes
one half or more of the volume.

Plinthohumults, p. 468

GBC. Other Humults which:

1. Do not have a lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface;
and

2. Have a CEC of 16 cmol(+)/kg clay or less (by
IN NH,OAc pH 7) and an ECEC of 12 cmol(+)/kg
clay or less (sum of bases extracted with 1N
'NH,OAc pH 7, plus 1N-KCl-extractable Al) in 50
percent or more either of the argillic or kandic
horizon if less than 100 cm thick, or of its upper
100 cm; and

3. Within 150 cm of the mineral soil surface,
either:

a, Do not have a clay decrease with depth of
20 percent or more (relative) from the
maximum clay content; or

b, Have 5 percent or more (by volume)
skeletans on faces of peds in the layer that
has a 20 percent lower clay content and,
below that layer, a clay increase of 3 percent
or more (absolute) in the fine-earth fraction.
Kandihumults, p. 465

GBD. Other Humults that have a CEC of 16 cmol(+)/kg
clay or less (by IN NH,OAc pH 7) and an ECEC of 12
cmol(+)/kg clay or less (sum of bases extracted with IN



Chapter 11

Inceptisols

KEY TO SUBORDERS
JA. Inceptisols which have:

1. Aquic conditions for some time in most years
(or artificial drainage) in a layer between 40 and
50 cm from the mineral soil surface, and one or
more of the following:

a, A histic epipedon; or

b. A sulfuric horizon that has its upper
boundary within 50 cm of the mineral soil
surface; or

¢. A mollic, an ochric, or an umbric
epipedon that is underlain directly, or within
50 cm of the mineral soil surface, by a
horizon that has, on faces of peds or in the
matrix if peds are absent, 50 percent or
more chroma of either:

(1) Two or less if there are redox
concentrations; or

(2) One or less; or

2. An exchangeable sodium percentage (ESP) of
15 or more (or a sodium adsorption ratio, SAR, of
13 or more) in half or more of the soil volume
within 50 cm of the mineral soil surface, and a
decrease in ESP (or SAR) values with increasing
depth below 50 cm, and ground water within 100
em of the mineral soil surface for some time
during the year; or

3. Within 50 cm of the mineral soil surface,
enough active ferrous iron to give a positive
reaction to c.,ct'-dipyridy] at a time when the soil
is not being irrigated.

Aquepts, p. 290

JB. Other Inceptisols that have a plaggen epipedon.
Plaggepts, p. 320

JC. Other Inceptisols that have an isomesic or a warmer
iso temperature regime.
Tropepts, p. 320

JD, Other Inceptisols that have either:
1, An ochric epipedon; or

2. A mesic or warmer soil temperature regime and.
an umbric or a mollic epipedon less than 25 cm
thick.

Ochrepts, p. 301


is 50 cm or more below the mineral soil
surface.
Glossaquic Eutroboralfs

IBEG. Other Eutroboralfs that have redox depletions
with a chroma of 2 or less in layers that also have aquic
conditions in most years (or artificial drainage) either:

1, Within the upper 25 cm of the argillic horizon
if its upper boundary is within 50 cm of the
mineral soil surface; or

2. Within 75 cm of the mineral soil surface if the
upper boundary of the argillic horizon is 50 em or
more below the mineral soil surface.

Aquic Eutroboralfs

IBEH. Other Eutroboralfs that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Eutroboralfs

IBEI. Other Eutroboralfs which have an argillic horizon
that either has a texture of loamy fine sand or coarser,
or is discontinuous vertically in its upper 15 cm (in
lamellae).

ar D>

Psammentic Eutroboralfs

IBEJ. Other Eutroboralfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
cm or more.

Arenic Eutroboralfs

IBEK. Other Eutroboralfs that have an Ap horizon with
acolor value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample), or materials
between the soil surface and a depth of 18 cm which
have these color values after mixing.

Mollic Eutroboralfs
IBEL. Other Eutroboralfs that have a glossic horizon.
Glossic Eutroboralfs
IBEM. Other Eutroboralfs.
Typic Eutroboralfs
Fragiboralfs
Key to subgroups

IBBA. Fragiboralfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction
with both a bulk density of 1.0 g/cm or less, measured
at 33 kPa water retention, and aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling more than
1.0.

Andic Fragiboralfs


297

JACE. Other Halaquepts.
Typic Halaquepts

Humaquepts

Key to subgroups

JAHA. Humaquepts that have an a value either of 0.7 or
more in one or more layers between 20 and 50 cm from
the mineral soil surface, or of 0.9 or more in one or
more layers between 50 and 80 cm.

Hydraquentic Humaquepts

JAHB. Other Humaquepts which have a histic
epipedon.

Histic Humaquepts
JAHC. Other Humaquepts which have, throughout one
or more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or more of
the following:

1. A fine-earth fraction with both a bulk density of
1.0 g/cm? or less, measured at 33 kPa water

retention, and aluminum plus 1/2 iron percentages
(by ammonium oxalate) totaling more than 1.0; or

2. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

3. A fine-earth fraction containing 30 percent or
‘more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2,0-mm fraction, more than
30 percent volcanic glass; or
b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
Percentages (by ammonium oxalate) totaling
0.40 or more,

Aquandic Humaquepts

JAHD. Other Humaquepts which have both:
1. An epipedon 60 cm or more thick; and

2. Either 0.2 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower.

Cumulic Humaquepts


184

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between |
and 13; or

b, In the upper 18 cm of the soil, if the lithic
contact is between 18 and 40 cm from the
soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

3. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Lithic Xerollic Haplargids

FAED, Other Haplargids which have:

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

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if the lithic
contact is between 40 and 50 cm from the
soil surface,
(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or
(2) 0.15 or more, with a sand/elay
ratio of 13 or more; or
(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or
b. In the upper 18 cm of the soil, if the lithic
contact is between 18 and 40 cm from the
soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or


255

KEBG. Other Torriorthents that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the soil surface, one or both of the
following:

1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a, In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b, In the 0.02-to-2,0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Torriorthents

KEBH. Other Torriorthents that have both:

1. In one or more horizons within 100 cm of the
soil surface, redox depletions with a chroma of 2
or less, and also aquic conditions for some time in
most years (or artificial drainage); and

2. A horizon within 100 cm of the soil surface that

is 15 cm or more thick and either contains 20

percent or more (by volume) durinodes or is

brittle and has firm consistence when moist.
Aquic Durorthidic Torriorthents

KEBI. Other Torriorthents that have, in one or more
horizons within 100 cm of the soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).
Aquic Torriorthents

KEBJ. Other Torriorthents that are saturated with
water, in one or more layers within 150 cm of the soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Torriorthents

KEBK. Other Torriorthents which have:

1, A horizon within 100 cm of the soil surface that
is 15 cm or more thick and either contains 20
percent or more (by volume) durinodes or is
brittle and has firm consistence when moist; and

2. A moisture control section which, in 6 or more
out of 10 years, is dry in all its parts for less than
three fourths of the cumulative days per year when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and



262

KECH. Other Xerorthents which have a horizon within
100 cm of the mineral soil surface that is 15 cm or more
thick and either contains 20 percent or more (by
volume) durinodes or is brittle and has firm consistence
when moist.

Durorthidic Xerorthents

KECI. Other Xerorthents that have a base saturation (by
NH,OAc) of less than 60 percent in all horizons
‘between 25 and 75 cm from the mineral soil surface.

Dystric Xerorthents
KECJ. Other Xerorthents.
Typic Xerorthents
PSAMMENTS
Key to great groups

KCA. Psamments that have a cryic or pergelic soil
temperature regime.
Cryopsamments, p. 262
KCB. Other Psamments that have a toric moisture
regime.
Torripsamments, p. 265
KCC. Other Psamments that have, within the particle-
size control section, more than 90 percent silica and
other extremely durable minerals in the 0.02-to-2,0-mm
fraction.
Quartzipsamments, p. 263
KCD. Other Psamments that have a udic moisture
regime, and a difference of less than 5°C between mean.
summer and mean winter soil temperatures at a depth of
50 cm from the soil surface.
Tropopsamments, p. 266
KCE. Other Psamments that have an ustic moisture
regime.
Ustipsamments, p. 268
KCF. Other Psamments that have a xeric moisture
regime.
Xeropsamments, p. 268
KCG. Other Psamments.
Udipsamments, p. 267

Cryopsamments

Key to subgroups
KCAA. Cryopsamments that have a lithic contact within

50 cm of the mineral soil surface.
Lithic Cryopsamments


169
USTANDS

Key to great groups

CFA. Ustands which have a duripan that has its upper
boundary within 100 cm either of the mineral soil
surface, or of the top of an organic layer with andic soil
properties, whichever is shallower.

Durustands, p. 169

CFB. Other Ustands.
Haplustands, p. 170

Durustands

Key to subgroups

CFAA. Durustands that have, in one or more horizons
‘between 50 and 100 cm either from the mineral soil
surface, or from the top of an organic layer with andic
soil properties, whichever is shallower, aquic conditions
for some time in most years (or artificial drainage) and
one or more of the following:

1. Two percent or more redox concentrations; or

2. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
redox depletions on faces of peds, or in the matrix
if peds are absent; or

3. Enough active ferrous iron to give a positive
reaction to ,a''-dipyridy| at a time when the soil
is not being irrigated.

Aquic Durustands

CFAB, Other Durustands that have, between 25 and

100 cm either from the mineral soil surface, or from the

top of an organic layer with andic soil properties,

whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of

a mollic epipedon throughout, underlying one or more

horizons with a total thickness of 10 cm or more that

have a color value, moist,-1 unit or more higher and an
organic-carbon content | percent or more (absolute)
lower.

Thaptic Durustands

CFAC. Other Durustands that have an umbric epipedon.
Humic Durustands

CFAD. Other Durustands.
Typic Durustands


398
a, Sandy: within 150 cm of the mineral soil
surface; or
b. Loamy: within 110 cm of the mineral soil
surface; or
¢. Clayey: within 90 cm of the mineral soil
surface; and

2. A mollic epipedon 50 cm or more thick with a
texture finer than loamy fine sand.
Calcic Pachic Argixerolls

HDEJ. Other Argixerolls that have both:

1. A mollic epipedon 50 cm or more thick with a
texture finer than loamy fine sand; and

2. A base saturation (by sum of cations) of 75
percent or less in one or more horizons between
either an Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and
either a depth of 75 cm ora lithic or paralithic
contact, whichever is shallower.
Pachic Ultic Argixerolls
HDEK. Other Argixerolls that have a mollic epipedon
50 cm or more thick with a texture finer than loamy fine
sand.
Pachic Argixerolls

HDEL. Other Argixerolls that have both:

1. In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and
2. A base saturation (by sum of cations) of 75
percent or less in one or more horizons between.
either an Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and
either a depth of 75 cm or a lithic or paralithic
contact, whichever is shallower.
Aquultic Argixerolls
HDEM. Other Argixerolls that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).
Aquic Argixerolls
HDEN. Other Argixerolls that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of

10 years.
Oxyaquic Argixerolls
HDEO. Other Argixerolls which have both:
1. An aridic moisture regime; and


241
KAAB. Other Sulfaquents which have both:

1, Sulfidic materials that have their upper
boundary 30 cm or more below the mineral soil
surface; and

2. An n value of 0.7 or less in one or more
horizons between 20 and 50 cm from the mineral
soil surface.

Haplic Sulfaquents
KAAC, Other Sulfaquents.
Typic Sulfaquents
ARENTS
Key to great groups

KBA. Arents that have an ustic moisture regime.
Ustarents, p. 242

KBB. Other Arents that have a xeric moisture regime,
Xerarents, p. 242

KBC. Other Arents that have a torric moisture regime.
Torriarents, p. 241

KBD. Other Arents.
Udarents, p. 241

Torriarents

Torriarents are the Arents that have a torric soil
moisture regime.

Udarents

Key to subgroups

KBDA. Udarents that have fragments of an argillic
horizon with a base saturation (by sum of cations) of 35
percent or more within 100 cm of the mineral soi)
surface.

Alfie Udarents

KBDB. Other Udarents that have fragments of an
argillic horizon within 100 cm of the mineral soil
surface.

Ultic Udarents

KBDC. Other Udarents that have fragments of a mollic
epipedon within 100 cm of the mineral soil surface.
Mollic Udarents

KBDD, Other Udarents,
Udarents

4zm


452

features, and also aquic conditions for some time in
most years (or artificial drainage).

Aquic Fragiorthods
BDCB. Other Fragiorthods that are saturated with
water, in one or more layers within 100 cm of the
mineral soil surface, for 1 month or more per year in 6

or more out of 10 years.
Oxyaquic Fragiorthods

BDCC. Other Fragiorthods which have a surface
horizon 30 cm or more thick that meets all the
requirements for a plaggen epipedon except thickness,

Plaggeptic Fragiorthods
BDCD. Other Fragiorthods which have, within 200 cm
of the mineral soil surface, an argillic or a kandic
horizon that has a base saturation of 35 percent or more
(by sum of cations) in some part.

Alfic Fragiorthods

BDCE. Other Fragiorthods that have an argillic or a
kandic horizon within 200 cm of the mineral soil
surface.

Ultic Fragiorthods

BDCF. Other Fragiorthods which have a spodic horizon
that does not have any of the following:

1. A texture of very fine sand or finer, a thickness
of more than 10 cm, and a weighted average of
1.2 percent or more organic carbon in the upper
10 cm; nor

2. A coarse-loamy or loamy-skeletal particle size,
and a color value, moist, and chroma of 3 or less
(crushed and smoothed sample) in the upper

7.5 cm; nor

3. A sandy-skeletal or sandy particle size, and a

color value, moist, and chroma of 3 or less
(crushed and smoothed sample) in the upper

2.5 cm.
Entic Fragiorthods
BDCG. Other Fragiorthods.
Typic Fragiorthods
Haplorthods
Key to subgroups

BDEA. Haplorthods which have both:
1. A lithic contact within 50 cm of the mineral soil
susface; and .
2. A spodic horizon that does not have any of the
following:
a. A texture of very fine sand or finer, a
thickness of more than 10 cm, and a


325

ICDJ. Other Eutropepts.
Typic Eutropepts

Humitropepts
Key to subgroups

JCAA, Humitropepts that have a lithic contact within 50
om of the mineral soil surface.
Lithic Humitropepts

ICAB. Other Humitropepts which have both:
1. One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower; and

2. In one or more horizons within 100 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage).
Aquertic Humitropepts

JCAC. Other Humitropepts which have one or both of
the following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm ora lithic or paralithic contact,
whichever is shallower.

Vertic Humitropepts

JCAD. Other Humitropepts that have both:
1, An ustic moisture regime; and


73

(2) Less than 200 cm if the soil has a
sandy particle size between the
mineral soil surface and the spodic
horizon; and

c. A lower boundary as follows:

(1) Either at a depth of 25 cm or more
below the mineral soil surface, or at
the top of a duripan or fragipan, or at a
lithic, paralithic, or petroferric contact,
whichever is shallowest; or
(2) At any depth,
(a) If the spodic horizon has a
coarse-loamy, loamy-skeletal, or
finer particle size, and the soil
has a frigid temperature regime,
or
(b) If the soil has a cryic or
pergelic temperature regime;
and

d. Either:
(1) A directly overlying albic horizon
in 50 percent or more of each pedon,
or
(2) No andic soil properties in 60
percent or more of the thickness
either:
(@) Within 60 om either of the
mineral soil surface, or of the
top of an organic layer with
andic soil properties, whichever
is shallower, if there is no lithic
or paralithic contact, duripan, or
petrocalcic horizon within that
depth; or
(b) Between either the mineral
soil surface, or the top of an
organic layer with andic soil
properties, whichever is
shallower, and a lithic or
paralithic contact, duripan, or
petrocalcic horizon.
Spodosols, p. 441
C. Other soils that have andic soil properties in 60
percent or more of the thickness either:

1. Within 60 om either of the mineral soil surface,
or of the top of an organic layer with andic soil
properties, whichever is shallower, if there is no
lithic or paralithic contact, duripan, or petrocalcic
horizon within that depth; or


237

depth of 75 cm, colors in 50 percent or more of the
matrix as follows:

1. A hue of 2.5Y or redder, a color value, moist, of
6 or more, and a chroma of 3 or more; or

2. A hue of 2.5Y or redder, a color value, moist, of
5 or less, and a chroma of 2 or more; or

3. A hue of SY and a chroma of 3 or more; or

4. A chroma of 2 or more if there are no redox

concentrations.
Aeric Epiaquents

KAFB, Other Epiaquents which have both:

1, An Ap horizon, or an A horizon 15 cm or more
thick, that has a color value, moist, of 3 or less
and a color value, dry, of 5 or less (crushed and
smoothed sample); and

2. A base saturation (by NH,OAc) of less than 50
percent at a depth of 100 cm from the mineral soil
surface.

Humaqueptic Epiaquents

KAFC. Other Epiaquents which have either an Ap
horizon, or an A horizon 15 cm or more thick, that has a
color value, moist, of 3 or less and a color value, dry, of
5 or less (crushed and smoothed sample).

Mollic Epiaquents
KAFD. Other Epiaquents.

Typic Epiaquents
Fluvaquents
Key to subgroups

KAEA. Fluvaquents which have, within 100 cm of the
mineral soil surface, one or both of the following:

1. Sulfidic materials; or

2. A horizon 15 cm or more thick that has all the
characteristics of a sulfuric horizon, except that it
has a pH value between 3.5 and 4.0,

Sulfic Fluvaquents

KAEB. Other Fluvaquents which have one or both of

the following:
1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a


217

cm or a lithic or paralithic contact, whichever is
shallower.
Vertic Camborthids

FBFK. Other Camborthids which have both:

1. A horizon within 100 cm of the soil surface that
is 15 cm or more thick and either contains 20
percent or more (by volume) durinodes or is
brittle and has firm consistence when moist; and

2. In one or more horizons within 100 cm of the
soil surface, aquic conditions for some time in
most years (or artificial drainage) and one or more
of the following:

a. A chroma of 0, or a hue of 2.5Y or
yellower and a chroma of 1; or

'b. Redox concentrations and 50 percent or
more chroma of 2 or less; or

c. Fifty percent or more chroma of 2 or less
and, in horizons with a total thickness of 25
cm or more within 50 cm of the soil surface,
a higher exchangeable sodium percentage
(or sodium adsorption ratio) than in the zone
with aquic conditions; or
d. Enough active ferrous iron to give a
positive reaction to a,a'-dipyridyl at a time
when the soil is not being irrigated.

Aquic Duric Camborthids

FBFL. Other Camborthids that have, in one or more
horizons within 100 cm of the soil surface, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:

1. A chroma of 0, or a hue of 2.5Y or yellower and
a chroma of 1; or

2. Redox concentrations and 50 percent or more
chroma of 2 or less; or

3. Fifty percent or more chroma of 2 or less, and a
higher exchangeable sodium percentage (or
sodium adsorption ratio) in more than half the
thickness of the horizons between the soil surface
and a depth of 50 om than in the saturated zone;
or

4. Enough active ferrous iron to give a positive
reaction to a,a'-dipyridyl at a time when the soil
is not being irrigated.
Aquic Camborthids
FBFM. Other Camborthids which have:

1. A moisture control section that is dry in all its
parts for less than three fourths of the cumulative
days per year in 6 or more out of 10 years when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and

-D>


516

mineral fraction and not dominated by properties
characteristic of E or B horizons (defined below), or (2)
properties resulting from cultivation, pasturing, or
similar kinds of disturbance.

If a surface horizon has properties of both A and E
horizons but the feature emphasized is an accumulation
of humified organic matter, it is designated 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 small
amounts of organic matter; it has a morphology distinct
from the C layer, although the mineral fraction is
unaltered or only slightly altered by weathering. Such a
horizon is designated A because it is at the surface;
however, recent alluvial or eolian deposits that retain
fine stratification are not considered to be A horizons
unless cultivated.

E horizons: Mineral horizons in which the main feature
is loss of silicate clay, iron, or aluminum, or some
combination of these, leaving a concentration of sand
and silt particles. These horizons exhibit obliteration of
all or much of the original rock structure?,

An E horizon is most commonly differentiated from an
underlying B horizon in the same sequum by a color of
higher value or lower chroma or both, by coarser
texture, or by a combination of these properties. In some
soils the color of the E horizon is that of the sand and
silt particles, but in many soils coatings of iron oxides
or other compounds mask the color of the primary
particles. An E horizon is most commonly differentiated
from an overlying A horizon by its lighter color, It
generally contains less organic matter than the A
horizon. An E horizon is commonly near the surface
below an O or A horizon and above a B horizon, but the
symbol E can be used for eluvial horizons which are
within or between parts of the B horizon, or which
extend to depths greater than normal observation if the
horizon is pedogenic.

B horizons: Horizons which have formed below an A, E,
or O horizon; they are dominated by the obliteration of
all or much of the original rock structure and show one
or more of the following:

(1) Muvial concentration of silicate clay, iron,
aluminum, humus, carbonates, gypsum, or silica,
alone or in combination;

(2) Evidence of removal of carbonates;
(3) Residual concentration of sesquioxides,

(4) Coatings of sesquioxides that make the
horizon conspicuously lower in color value,
higher in chroma, or redder in hue, without

2 See footnote 1.


33

Soft powdery lime

Soft powdery lime is a term 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 has

been precipitated in place from the soil solution rather M
than inherited from a soil parent material such as a '
calcareous loess or till. It should be present in a N

significant enough accumulation to constitute a k
horizon.

Soft powdery lime may either disrupt the soil structure
or fabric to form spheroidal aggregates (white eyes) that
are soft and powdery when dry; or it may be present as
soft coatings in pores or on structural faces. If present as
coatings, it covers a significant part of the surfaces.
Commonly, it coats all of them to a thickness between 1
and more than 5 mm; but if little lime is present in the
soil, the surfaces may be only partially coated. The
coatings should be thick enough to be visible when
moist and should cover a continuous area larger 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 that are
commonly branching, on structural faces. They may
come and go with the seasons and may be lime that has
been precipitated in a single season by the withdrawal
of stored soil moisture, rather than a & horizon.

Soft coatings on hard lime concretions are also excluded
from the meaning of soft powdery lime. These may be
thin or thick and may be the result of either current
accumulation or removal of lime, i.e., the concretion
may be either growing or undergoing dissolution, and
either process can produce a soft coating.

Soil moisture regimes

‘The term soil moisture regime refers to the presence or
absence either of ground water or of water held at a
tension of less than 1500 kPa, in the soil or in specific
horizons, by periods of the year. Water held at a tension
of 1500 kPa or more is not available to keep most
mesophytic plants alive. The availability of water is also
affected by dissolved salts. But if a soil 1s saturated with
water that is too salty to be available to most plants, we
call such a soil salty rather than dry. Consequently, a
horizon is considered dry when the moisture tension is
1500 kPa or more, and is considered moist if water 1s
held at a tension of less than 1500 kPa but more than
zero, A soil may be continuously moist in some or all
horizons either throughout the year or for some part of
the year. It may be either moist in winter and dry in
summer, or the reverse. In the northern hemisphere,
summer refers to the months of June, July, and August,
and winter means December, January, and February.


b. A fine-earth fraction containing 30
percent or more particles 0.02 to 2.0 mm in
diameter, and either:
(1) In the 0.02-to-2.0-mm fraction,
more than 30 percent volcanic glass;
or

(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more.
Vitrixerandic Durargids
FABF. Other Durargids which have both:

1. A moisture control section that is dry in all its
parts for less than three fourths of the cumulative
days per year in 6 or more out of 10 years when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and

2. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or both of the following:

a. More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or

b. A fine-earth fraction containing 30
percent or more particles 0.02 to 2.0 mm in
diameter, and either:

(1) In the 0.02-to-2.0-mm fraction,
more than 30 percent volcanic glass;
or
(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more.
Ustivitrandic Durargids

FABG. Other Durargids which have:

1. A duripan 18 cm or more below the soil surface
that is either not platy or massive, or not indurated
in any subhorizon; and

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if the upper
boundary of the duripan is 40 cm or more
below the soil surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or


219
FBFO. Other Camborthids which have:

1, A horizon within 100 cm of the soil surface that
is 15 cm or more thick and either contains 20
percent or more (by volume) durinodes or is
brittle and has firm consistence when moist; and

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b, In the upper 18 cm of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

3. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean.
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Durixerollic Camborthids

FBFP. Other Camborthids which have a horizon within
100 cm of the soil surface that is 15 cm or more thick
and either contains 20 percent or more (by volume)
durinodes or is brittle and has firm consistence when
moist.

Duric Camborthids

FBFQ. Other Camborthids which have either 0.2
percent or more organic carbon at a depth of 125 cm
below the mineral soil surface, or an irregular decrease
in organic-carbon content from a depth of 25 cm either
to a depth of 125 cm, or to a lithic or paralithic contact
if shallower.

Fluventic Camborthids

FBFR. Other Camborthids that have both:
1, An anthropic epipedon; and

—-Dp


45

detected and the color of the pyrophosphate extract is to
the left or above this line, the possibility that the
material is limnic must be considered.

Humilluvic mate
Humilluvic material, i.e., illuvial humus, accumulates in
the lower parts of some organic soils if they are acid and
have been drained and cultivated. The humilluvic
material has a younger C!4 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
humilluvic material must constitute one half or more (by
volume) of a layer 2 cm or more thick.

Limnic materials

The presence or absence of limnic deposits is taken into
account in the higher categories of organic soils
(Histosols, see below), while the nature of such deposits
is considered in the lower categories. Limnic materials
include both organic and inorganic materials that were
either (1) deposited in water by precipitation or through
the action of aquatic organisms, such as algae or
diatoms, or (2) derived from underwater and floating
aquatic plants and subsequently modified by aquatic
animals. They include coprogenous earth (sedimentary
peat), diatomaceous earth, and marl.

Coprogenous earth

A coprogenous-earth (sedimentary peat) layer is a
limnic layer which;

1. Contains many fecal pellets with diameters between a
few hundredths and a few tenths of a millimeter; and

2. Has a color value, moist, of 4 or less; and

3. Either forms a slightly viscous water suspension and
is slightly plastic but not sticky, or shrinks upon drying
to form clods that are difficult to rewet and often tend to
crack along horizontal planes; and

4. Normally contains almost no visible fragments of
plants; and

5, Either yields a saturated sodium-pyrophosphate
extract on white chromatographic or filter paper that has
a higher color value and lower chroma than 10 YR 7/3
(Munsell designations), or has a cation-exchange
capacity of less than 240 cmol(+) per kg organic matter
(measured by loss on ignition), or both.

Diatom:

A diatomaceous-earth layer is a limnic layer which.

1. If not previously dried, has a matrix color value of 3,
4, or 5, which changes irreversibly on drying as the

fom ke)


116

(relative) from the maximum clay content;
or

b. Have 5 percent or more (by volume)
skeletans on faces of peds in the layer that
has a 20 percent lower clay content and,
below that layer, a clay increase of 3 percent
‘or more (absolute) in the fine-earth fraction.
Kandiustalfs, p. 120

ICE. Other Ustalfs that have a CEC of 16 cmol(+)/kg
clay or less (by IN NH,OAc pH 7) and an ECEC of 12
cmol(+)/kg clay or less (sum of bases extracted with IN
NH,OAc pH 7, plus 1N-KCl-extractable Al) in 50
percent or more either of the argillic or kandic horizon if
less than 100 cm thick, or of its upper 100 cm.
Kanhaplustalfs, p. 122

ICF. Other Ustalfs which have one or more of the
following:
1. A petrocalcic horizon that has its upper
boundary within 150 cm of the mineral soil
surface; or

2. No lithic or paralithic contact within 150 cm of
the mineral soil surface, and an argillic horizon
which has both:

a, Within 150 cm of the mineral soil surface,
either

(1) No clay decrease with increasing
depth of 20 percent or more (relative)
from the maximum clay content; or

(2) Five percent or more (by volume)
skeletans on faces of peds in the layer
that has a 26 percent lower clay
content and, below that layer, a clay
increase of 3 percent or more.
(absolute) in the fine-earth fraction;
and

b. One or more of the following:

(1) In the matrix of its lowest
subhorizon, a hue of 7.5YR or redder
and a chroma of 5 or more; or

(2) In 50 percent or more of its matrix,
a hue of 7.5YR or redder, a color
value, moist, or 3 or less, and a color
value, dry, of 4 or less; or

(3) In the matrix of its lowest
subhorizon, common or many coarse
redox concentrations with a hue of
7.5YR or redder or a chroma of 6 or
more, or both; or


51

Loamy.!—In the fine-earth fraction, a texture of loamy
very fine sand, very fine sand, or finer, including less
than 35 percent (by weight) clay; in the whole soil, less
than 35 percent (by volume) rock fragments.

Coarse-loamy. In the fraction less than 75 mm in
diameter, 15 percent or more (by weight) particles with
diameters of 0.1 to 75 mm (fine sand or coarser,
including rock fragments up to 7.5 cm in diameter); in
the fine-earth fraction, less than 18 percent (by weight)
clay.

Fine-loamy, In the fraction less than 75 mm in diameter,
15 percent or more (by weight) particles with diameters
of 0,1 to 75 mm (fine sand or coarser, including rock
fragments up to 7.5 cm in diameter); in the fine-earth
fraction, 18 to 35 percent (by weight) clay (Vertisols are
excluded).

Coarse-silty In the fraction less than 75 mm in
diameter, less than 15 percent (by weight) particles with
diameters of 0.1 to 75 mm (fine sand or coarser,
including rock fragments up to 7.5 em in diameter); in
the fine-earth fraction, less than 18 percent (by weight)
clay.

Fine-silty. In the fraction less than 75 mm in diameter,
less than 15 percent (by weight) particles with
diameters of 0.1 to 75 mm (fine sand or coarser,
including rock fragments up to 7.5 cm in diameter); in
the fine-earth fraction, 18 to 35 percent (by weight) clay
(Vertisols are excluded).

Clayey.2— In the fine-earth fraction, 35 percent or more
(by weight) clay: in the whole soil, less than 35 percent
(by volume) rock fragments.

Fine. 35 to 60 percent (by weight) clay (30 to 60 percent
in Vertisols) in the fine-earth fraction.

Very fine. 60 percent or more (by weight) clay in the
fine-earth fraction.

1 If the ratio of (percent water retained at 1500 kPa tension minus percent.
organic carbon) to the percentage of measured clay is 0.6 or more in half or
more of the control section, then the percentage of clay is considered to be
2.5 times (percent water retained at 1500 kPa tension minus percent organic
carbon), but no more than 100. Carbonates of clay size are not considered to
‘be clay but are treated as silt in all particle-size classes

2 See preceding footnote.


203

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b, In the upper 18 cm of the soil, if the
upper boundary of the petrocalcic horizon is
between 18 and 40 cm from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

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 which have:

1. A petrocalcic horizon that has its upper
boundary within 100 om of the soil surface; and

2. A moisture control section that is dry in all its
parts for less than three fourths of the cumulative
days per year in 6 or more out of 10 years when
the soil temperature at a depth of 50cm from the
soil surface is 5°C or higher; and

3. 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 which have a petrocalcic
horizon that has its upper boundary within 100 cm of
the soil surface.

Petrocaicic Paleargids

FADH. Other Paleargids which have a horizon within
100 cm of the soil surface that is 15 cm or more thick
and either contains 20 percent or more (by volume)
durinodes or is brittle and has firm consistence when
moist.

Duric Paleargids
FADL. Other Paleargids which have both:

1. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, between the soil surface and a depth
of 40 cm as follows:

—-DpP


137

2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0,02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Palexeralfs

IDFE. Other Palexeralfs that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Palexeralfs
IDFF. Other Palexeralfs which have a petrocalcic |

horizon that has its upper boundary within 150 cm of
the mineral soil surface.
Petrocalcic Palexeralfs

IDFG. Other Palexeralfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
m or more.

Arenic Palexeralfs

IDFH. Other Palexeralfs that have an exchangeable
sodium percentage of 15 or more (or 4 sodium
adsorption ratio of 13 or more) in one or more horizons
within 100 cm of the mineral soil surface.

Natric Palexeralfs

IDFI. Other Palexeralfs that have a calcic horizon within
150 cm of the mineral soil surface.
Calcic Palexeralfs

IDFA. Other Palexeralfs that have 5 percent or more (by
volume) plinthite in one or more horizons within 150
cm of the mineral soil surface.

Plinthic Palexeralfs

IDFK. Other Palexeralfs which have an argillic horizon
that has a base saturation (by sum of cations) of less
than 75 percent throughout.

Ultic Palexeralfs

IDFL. Other Palexeralfs with an argillic horizon that has
neither:

1. A clayey particle size throughout any
subhorizon in its upper part; nor


313

within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm! or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Ustochrepts

JDEF-. Other Ustochrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1, More than 35 percent (by volume) fragments
coarser than 2,0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:
a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling

0.40 or more.
Vitrandic Ustochrepts
JDEG. Other Ustochrepts that have anthraquic
conditions,
Anthraquic Ustochrepts

JDEH. Other Ustochrepts that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Ustochrepts

JDEI. Other Ustochrepts which have:

1. Either 0,2 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

2. A slope of less than 25 percent; and

3. If neither irrigated nor fallowed to store
moisture, one of the following:

a2-

a. A frigid soil temperature regime, and a
moisture control section which, in 6 or more
out of 10 years, is dry in all parts for four
tenths or more of the cumulative days per
year when the soil temperature at a depth of
50 on below the soil surface is higher than
S°C; or


46

result of the irreversible shrinkage of organic-matter
coatings on diatoms (identifiable by microscopic, 440X,
examination of dry samples); and

2. Either yields a saturated sodium-pyrophosphate
extract on white chromatographic or filter paper that has
a higher color value and lower chroma than 10 YR 7/3
(Munsell designations), or has a cation-exchange
capacity of less than 240 cmol(+) per kg organic matter
(by loss on ignition), or both.

Marl

A maz! layer is a limnic layer which:

1. Has a color value, moist, of 5 or more; and

2. Reacts with dilute HCI to evolve CO;.

Marl usually does not change its color irreversibly on
drying because a layer of marl contains too little organic
matter, even before it has been shrunk by drying, to coat
the carbonate particles.

THICKNESS OF ORGANIC SOIL
MATERIALS (CONTROL SECTION OF
HISTOSOLS)

For practical reasons an arbitrary control section has
been established for the classification of organic soils
(Histosols). Depending on the kinds of soil materials
that are present in the surface layer, the control section
has a thickness of either 130 cm or 160 cm from the soil
surface, if there is no lithic or paralithic contact, thick
layer of water, or permafrost within the respective limit.
The thicker contro! section is used if the surface soil
layer to a depth of 60 cm either contains three fourths or
more fibers derived from Sphagnum, Hypnum, or other
mosses, or has a bulk density of less than 0.1 g/em?.
Layers of water, which may be between a few
centimeters and many meters thick in these soils, are
considered to be the lower boundary of the control
section only if the water extends below a depth of 130
or 160 cm, respectively. A lithic or paralithic contact, if
shallower than 130 or 160 cm, constitutes the lower
boundary of the control section; or the lower boundary
of the control section is 25 cm below the upper limit of
permafrost 2 months after the summer solstice. An
unconsolidated mineral substratum shallower than those
limits does not change the lower boundary of the control
section.

The control section of Histosols is divided somewhat
arbitrarily into three tiers: surface, subsurface, and
bottom tiers.

Surface tier

The surface tier of a Histosol extends from the soil
surface to a depth of 60 cm if either (1) the materials


403
Haploxerolls

Key to subgroups
HODFA. Haploxerolls that have both:

1. A lithic contact within 50 cm of the mineral soil
surface; and

2. A base saturation (by sum of cations) of 75
percent or less in one or more horizons between.
either the mineral soil surface or an Ap horizon,
whichever is deeper, and the lithic contact.

Lithic Ultic Haploxerolls

HDEB. Other Haploxerolls that have a lithic contact
within 50 cm of the mineral soil surface.
Lithic Haploxerolls

HDFC. Other Haploxerolls which have both:
1, An aridic moisture regime; and
2. One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
om of the mineral soil surface; or

». A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower.

Torrertic Haploxerolls

HDFD, Other Haploxerolls which have one or both of
the following:

1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has M
its upper boundary within 125 om of the mineral J
soil surface; or \

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Haploxerolls

HDFE. Other Haploxerolls that have both:
1. An aridic moisture regime; and
2. Throughout one or more horizons with a total

thickness of 18 cm or more within 75 om of the
mineral soil surface, one or both of the following:


214

summer and mean winter soil temperatures at a

depth of 50 cm from the soil surface, and an aridic

moisture regime that borders on a xeric regime.
Durixerollic Lithic Camborthids

FBFC. Other Camborthids which have:

1, A lithic contact within 50 cm of the soil
surface; and

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if the lithic
contact is between 40 and 50 cm below the
soil surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 cm of the soil, if the lithic
contact is between 18 and 40 cm from the
soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

3. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at 2
depth of 50 cm from the soil surface, 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 soil surface.
Lithic Camborthids

FBFE. Other Camborthids that have an exchangeable
sodium percentage of 40 or more (or a sodium
adsorption ratio of 45 or more) throughout the cambic
horizon, and a low or very low saturated hydraulic
conductivity.

Natric Camborthids
FBFF. Other Camborthids which have:

1. A frigid or colder temperature regime; and


302

JDDB. Other Cryochrepts that have a mean annual soil
temperature of 0°C or lower.
Pergelic Cryochrepts

JDDC. Other Cryochrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm? or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0,

Andic Cryochrepts
JDDD. Other Cryochrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0,02 to 2.0 mm in diameter, and
either:

a. In the 0,02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Cryochrepts
JDDE. Other Cryochrepts that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage),

Aquic Cryochrepts

JDDF. Other Cryochrepts that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of

10 years.
Oxyaquic Cryochrepts
JDDG. Other Cryochrepts which have lamellae within
75 cm of the mineral soil surface that meet all the
requirements for an argillic horizon except thickness,
Alfic Cryochrepts
JDDH. Other Cryochrepts that have a base saturation
(by NH,OAc) of less than 60 percent in all horizons
within 75 cm of the mineral soil surface.
Dystric Cryochrepts
JDDI. Other Cryochrepts.
Typic Cryochrepts


208

3. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Lithic Xerollic Calciorthids

FBED. Other Calciorthids which have:

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

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to noncarbonate clay, as follows:

a. In the upper 40 cm of the soil, if the lithic
contact is between 40 and 50 cm below the
soil surface,

(1) 0.60 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.15 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.64-(0.038 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
1 and 13; or

b. In the upper 18 cm of the soil, if the lithic
contact is between 18 and 40 cm from the
soil surface,

(1) 0.72 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.18 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.77-(0.046 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
1 and 13; and

3. An aridic moisture regime that borders on an.
ustic regime.
Lithic Ustollic Calciorthids
FBEE. Other Calciorthids that have a lithic contact
within 50 cm of the soil surface.
Lithic Calciorthids

FBEF. Other Calciorthids which have both:

1. A horizon within 100 cm of the soil surface that
is 15 cm or more thick and either contains 20
percent or more (by volume) durinodes or is
brittle and has firm consistence when moist; and


336

intervenes, a color value, moist, of 4
or more and one of the following:

(a) Fifty percent or more chroma
of 1 on faces of peds or in the
matrix, a hue of 10YR or redder,
and redox concentrations; or

(b) Fifty percent or more chroma
of 2 or less on faces of peds or in
the matrix, a hue of 2.5Y, and
redox concentrations; or

(c) Fifty percent or more chroma
of 1 on faces of peds or in the
matrix, and a hue of 2.5Y or
yellower; or

(d) Fifty percent or more chroma
of 3 or less on faces of peds or in
the matrix, a hue of SY, and
redox concentrations; or

(©) Fifty percent or more chroma
of 0 on faces of peds or in the
matrix; or

(f) A hue of SGY, 5G, 5BG, or
5B; or

(g) Any color if it results from
uncoated sand grains; or

b. A chroma of 2 in the lower part of the
mollic epipedon, and either

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

(2) Directly below the mollic
epipedon, one of the following matrix
colors:

(a) A color value, moist, of 4, a
chroma of 2, and some redox
depletions with a color value,
moist, of 4 or more and a
chroma of 1 or less; or

(b) A color value, moist, of 5 or
more, a chroma of 2 or less, and
redox concentrations; or

(c) A color value, moist, of 4
and a chroma of 1 or less; or

5. Between 40 and 50 cm from the mineral soil
surface, enough active ferrous iron to give a
positive reaction to a,a'-dipyridyl at a time when
the soil is not being irrigated.

Aquolls, p. 339


215

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, between the soil surface and a depth
of 40 cm as follows:

a. 0.60 or more, with a sand/clay ratio of 1.0
or less; or

b. 0.15 or more, with a sand/clay ratio of 13
‘or more; or

¢. 0.64-(0.038 x sand/clay ratio), or more,
with a sand/clay ratio between 1 and 13; and

3. One or both of the following:

a. Cracks within 125 cm of the soil surface
that are 5 mm or more wide through a
thickness of 30 cm or more for some time in
most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the soil surface; or

b. A linear extensibility of 6.0 cm or more
between the soil surface and either a depth
of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Borollic Vertic Camborthids

FBFG. Other Camborthids which have both:

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

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between |
and 13; or

b, In the upper 18 cm of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

A
R
|



440

DCDJ. Other Kandiustox that have 16 kg/m? or more
organic carbon between the mineral soil surface and a
depth of 100 cm.

Humic Kandiustox

DCDK. Other Kandiustox that have 50 percent or more
hue of 2.5YR or redder and color value, moist, of 3 or
less between 25 and 125 cm from the mineral soil
surface.

Rhodic Kandiustox

DCDL. Other Kandiustox that have 50 percent or more
hue of 7.5YR or yellower and color value, moist, of 6 or
more between 25 and 125 cm from the mineral soil
surface.

Xanthic Kandiustox
DCDM., Other Kandiustox.
Typic Kandiustox
Sombriustox
Key to subgroups

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

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

DCAC. Other Sombriustox that have 16 kg/m? or more
organic carbon between the mineral soil surface and a
depth of 100 cm.

Humic Sombriustox

DCAD. Other Sombriustox.
Typic Sombriustox


76
H. Other soils that have both of the following:
1, Either

a. A mollic epipedon; or

b. Both a surface horizon which meets all
the requirements for a mollic epipedon
except thickness after the soil has been
mixed to a depth of 18 cm, and a subhorizon
more than 7.5 cm thick, within the upper
part of an argillic, a kandic, or a natric
horizon, that meets the color, organic-carbon
content, base saturation, and structure
requirements of a mollic epipedon but is
separated from the surface horizon by an
albic horizon; and
2. A base saturation of 50 percent or more (by
NH,OAc) in all horizons either between the upper
boundary of any argillic, kandic, or natric horizon
and a depth of 125 cm below that boundary, or
‘between the mineral soil surface and a depth of
180 cm, or between the mineral soil surface and a
lithic or paralithic contact, whichever depth is
shallowest.
Moliisols, p. 335

I, Other soils which have either:
1. An argillic, a kandic, or a natric horizon; or
2. A fragipan that has clay films 1 mm or more

thick in some part. ‘AMfsols, p. 79
, P.

J. Other soils which have either:
1. One or more of the following:

a, A cambic horizon; or
b, Aquic conditions within 50 cm of the
mineral soil surface for some time in most
years (or artificial drainage), and
permafrost; or
¢. Within 100 cm of the mineral soil surface,
the upper boundary of one or more of the

following: a calcic, petrocalcic, gypsic,
petrogypsic, or placic horizon or a duripan;
or

d. Either a fragipan or an oxic horizon that
has its upper boundary within 200 cm of the
mineral soil surface; or

¢. A sulfuric horizon that has its upper
boundary within 150 cm of the mineral soil
surface; or


355

2. A mollic epipedon 40 cm or more thick with a
texture finer than loamy fine sand.
Argic Pachic Cryoborolls

HEBR. Other Cryoborolls that have a mollic epipedon
40 cm or more thick with a texture finer than loamy fine
sand.

Pachic Cryoborolls
HEBS. Other Cryoborolls that have both:
1. An argillic horizon; and

2. In one or more horizons within 100 cm of the
mineral soil surface, distinct or prominent redox.
concentrations, and also aquic conditions for some
time in most years (or artificial drainage).
Argiaquic Cryoborolls
HEBT. Other Cryoborolls that have:

1. Either 0.3 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

2. In one or more horizons within 100 cm of the
mineral soil surface, distinct or prominent redox
concentrations, and also aquic conditions for some
time in most years (or artificial drainage); and

3. A slope of less than 25 percent.
Fluvaquentic Cryoborolls

HEBU. Other Cryoborolls that have, in one or more
horizons within 100 cm of the mineral soil surface,
distinct or prominent redox concentrations, and also
aquic conditions for some time in most years (or
artificial drainage),

Aquic Cryoborolls
HEBV. Other Cryoborolls that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of

10 years.
Oxyaquic Cryoborolls
HEBW. Other Cryoborolls which have both:

1. Either 0.3 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

2. A slope of less than 25 percent.
Fluventic Cryoborolls

HEBX. Other Cryoborolls that have an argillic horizon.
Argic Cryoborolls


305

2. An argillic horizon in less than half of each
pedon.
Lithic Ruptic-Ultic Dystrochrepts

JDHC. Other Dystrochrepts that have a lithic contact
within 50 cm of the mineral soil surface.
Lithic Dystrochrepts

JDHD, Other Dystrochrepts which have both:

1, In one or more horizons within 60 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or more of the following:

a. A fine-earth fraction with both a bulk
density of 1.0 g/cm? or less, measured at 33
kPa water retention, and aluminum plus 1/2
iron percentages (by ammonium oxalate)
totaling more than 1.0; or

b. More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or

c, A fine-earth fraction containing 30
percent or more particles 0.02 to 2.0 mm in
diameter, and either:

(1) In the 0.02-to-2.0-mm fraction,
more than 30 percent volcanic glass;
or

(2) In the 0.02-to-2.0-mm fraction, 5

percent or more volcanic glass, and in

the fine-earth fraction, aluminum plus |

1/2 iron percentages (by ammonium.

oxalate) totaling 0.40 or more. c
Aquandic Dystrochrepts

JDHE. Other Dystrochrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-carth
fraction with both a bulk density of 1.0 g/cm} or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Dystrochrepts

JDHF, Other Dystrochrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1, More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66


87

IADC. Other Fragiaqualfs that have an Ap horizon with
a color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample), or materials
between the soil surface and a depth of 18 cm which
have these color values after mixing.

Umbric Fragiaqualfs
TADD. Other Fragiaqualfs.
Typic Fragiaqualfs
Glossaqualfs
Key to subgroups

TAFA. Glossaqualfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
em to 100 cm.

Arenic Glossaqualfs

TAFB, Other Glossaqualfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 100
cm or more,

ry
L

Grossarenic Glossaqualfs

IAFC, Other Glossaqualfs that have, in one or more
horizons between the A or Ap horizon and a depth of 75
cm below the mineral soil surface, one of the following
colors:

1, A hue of 7.5YR or redder in 50 percent or more
of the matrix, and

a, If peds are present, either a chroma of 2
or more on 50 percent or more of ped
exteriors, or no redox depletions with a
chroma of 2 or leks in ped interiors; or

». If peds are absent, a chroma of 2 or more
in 50 percent or more of the matrix; or

2, In 50 percent or more of the matrix, a hue of
10YR or yellower and either

a. Both a color value, moist, and chroma of
3 or more; or

b. A chroma of 2 or more if there are no
redox concentrations.
Aeric Glossaqualfs

IAFD. Other Glossaqualfs that have an Ap horizon with
a color value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample), or materials
between the soil surface and a depth of 18 cm which
have these color values after mixing.

Mollic Glossaqualfs

TAFE. Other Glossaqualfs.
Typic Glossaqualfs


40
Definition of spodic materials
Spodic materials are mineral soil materials that do not
have all the properties of an argillic or a kandic horizon,
are dominated by illuvial active amorphous materials

composed of organic matter and aluminum, with or
without iron, and have both.

1. A pH value in water (1:1) of 5.9 or less and an
organic-carbon content of 0.6 percent or more; and

2. One or more of the following:

a Anoverlying albic horizon which extends
horizontally through 50 percent or more of each
pedon, and have, directly under the albic horizon,
colors, moist (crushed and smoothed sample), as
follows:

(1) A hue of 5YR or redder, or

(2) A hue of 7.5YR, color value of 5 or less,
and chroma of 4 or less; or

(3) A hue of 10YR or neutral and a color
value and chroma of 2 or less; or

(4) A color of LOYR 3/1; or

b. One of the colors listed above or a hue of
7.5YR, color value, moist, of 5 or tess, and
chroma of 5 or 6 (crushed and smoothed sample),
and one or more of the following morphologic or
chemical properties:

(1) Cementation by organic matter and
aluminum, with or without iron, in 50
percent or more of each pedon, and very
firm or firmer consistence in the cemented
part; or

(2) Ten percent or more cracked coatings on
sand grains; or

(3) Aluminum plus 1/2 iron percentages (by
ammonium oxalate) totaling 0.50 or

more, and half that amount or less in an
overlying umbric (or subhorizon of an
umbric) epipedon, or an ochric epipedon or
albic horizon; or

(4) An optical-density-of-oxalate-extract
(ODOE) value of 0.25 or more, and a value
half as high or lower in an overlying umbric
(or subhorizon of an umbric) epipedon, or an
ochric epipedon or albic horizon

Sulfidic materials

Sulfidic materials contain oxidizable sulfur compounds,
and are mineral or organic soil materials with a pH
value of more than 3.5 which, if incubated as a layer 1
em thick under moist aerobic conditions (field capacity)
at room temperature, show a drop in pH of 0.5 or more


128

ICFP. Other Paleustalfs that have an argillic horizon
with a base saturation (by sum of cations) of less than
75 percent throughout.
Uitic Paleustalfs
ICFQ. Other Paleustalfs which, if neither irrigated nor
fallowed to store moisture, have either:
1. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for four tenths
or less of the cumulative days per year when the
temperature at a depth of 50 cm below the soil
surface is higher than 5°C; or

2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is dry
in some or all parts for less than 120 cumulative
days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8°C.
Udic Paleustalfs

ICFR, Other Paleustalfs.
Typic Paleustalfs

Plinthustalfs

Plinthustalfs are the Ustalfs that have one or more
horizons within 150 cm of the mineral soil surface in
which plinthite either forms a continuous phase or
constitutes one half or more of the volume. 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.

Rhodustalfs

Key to subgroups
ICGA. Rhodustalfs that have a lithic contact within 50
cm of the mineral soil surface.

Lithic Rhodustalfs

ICGB. Other Rhodustalfs that have a CEC of less than
24 cmol(+) per kg clay (by IN NH,OAc pH 7) in 50
percent or more either of the argillic horizon if less than
100 cm thick, or of its upper 100 cm.

Kanhaplic Rhodustalfs

ICGC. Other Rhodustalfs which, if neither irrigated nor
fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime,
and a moisture contro! section which, in 6 or more
out of 10 years, is dry in some part for four tenths
or less of the cumulative days per year when the


405
HDFH. Other Haploxerolls which have:

1. A mollic epipedon 50 cm or more thick with a
texture finer than loamy fine sand; and

2. An irregular decrease in organic-carbon content
from a depth of 25 cm below the mineral soil
surface to a depth of 125 cm, or to a lithic or
paralithic contact if shallower; and

3. A slope of less than 25 percent.
Cumulic Haploxerolls

HDFI. Other Haploxerolls that have both:

1, A mollic epipedon 50 cm or more thick with a
texture finer than loamy fine sand; and

2. A calcic horizon or soft powdery lime, either
within the following depths or above a lithic or
paralithic contact if shallower, if the particle-size
control section is

a. Sandy: within 150 cm of the mineral soil
surface; or

b. Loamy: within 110 cm of the mineral soil
surface; or

c. Clayey: within 90 cm of the mineral soil
surface.
Calcic Pachic Haploxerolls

HDFJ. Other Haploxerolls that have both:

1. A mollic epipedon 50 cm or more thick with a
texture finer than loamy fine sand; and

2. A base saturation (by sum of cations) of 75
percent or less in one or more horizons between
either an Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and
either a depth of 75 cm or a lithic or paralithic
contact, whichever is shallower.

Pachic Ultic Haploxerolls

HDFK. Other Haploxerolls that have a mollic epipedon M
50 cm or more thick with a texture finer than loamy fine fe)
sand.

L

Pachic Haploxerolls
HODFL. Other Haploxerolls that have:

1. In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. Either 0.3 percent or more organic carbon in all
horizons within 125 cm of the mineral soil
surface, or an irregular decrease in organic-carbon
content from a depth of 25 cm to a depth of 125
om, or to a lithic or paralithic contact if shallower;
and


112,

IEHC. Other Kanhapludalfs that are saturated with
water, in one or more layers within 100 cm of the
mineral soil surface, for | month or more per year in 6
or more out of 10 years."

Oxyaquic Kanhapludalfs

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

Rhodic Kanhapludalfs
TEHE. Other Kanhapludalfs.
Typic Kanhapludalfs
Natrudalfs
Key to subgroups

IEBA. Natrudalfs which have one or both of the
following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.
Vertic Natrudalfs

IEBB, Other Natrudalfs that have either a glossic
horizon, or interfingering of albic materials into the
natric horizon.

Glossic Natrudalfs
TEBC. Other Natrudalfs that have an Ap horizon with a
color value, moist, of 2 or less (crushed and smoothed
sample), or materials between the soil surface and a
depth of 18 cm which have that color value after

Mollic Natrudalfs
IEBD, Other Natrudalfs.

Typic Natrudalfs
Paleudalfs
Key to subgroups

IEIA. Paleudalfs which have one or both of the
following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a


272

2. In the organic parts of the surface and
subsurface tiers if there is a continuous mineral
layer 40 cm or more thick that has its upper

boundary within the subsurface tier,
Heniists, p. 279
AD. Other Histosols.
Saprists, p. 284
FIBRISTS
Key to great groups

ABA. Fibrists that have a surface mantle in which fibric
Sphagnum constitutes three fourths or more of the
volume and which is either 90 cm or more thick, or
extends 10 cm or more below the upper boundary of
frozen‘ soil materials, or rests on a lithic or paralithic
contact, fragmental materials, or mineral soil materials.
Sphagnofibrists, p. 276

ABB. Other Fibrists which, in most years, either:

1. Are frozen in one or more layers within the
control section 2 months after the summer
solstice; or
2. Never freeze below a depth of 5 cm from the
soil surface but have a mean annual soil
temperature lower than 8°C.

Cryofibrists, p. 274

ABC. Other Fibrists that have a mean annual soil

temperature lower than 8°C,
Borofibrists, p. 272

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 from the soil surface.
Tropofibrists, p. 277

ABE. Other Fibrists that have a horizon 2 om or more
thick in which humilluvic materials constitute one half
or more of the volume.

Luvifibrists, p. 274

ABF. Other Fibrists.
Medifibrists, p. 275

Borofibrists

Key to subgroups

ABCA. Borofibrists that have a layer of water within
the control section below the surface tier.
Hydric Borofibrists

4 Frozen 2 months after the summer solstice,


1241

ICDC. Other Kandiustalfs that have 5 percent or more
(by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface.

Plinthic Kandiustalfs

ICDD. Other Kandiustalfs that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Kandiustalfs
ICDE. Other Kandiustalfs which have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic horizon at a depth of 50 to 100 cm;
and

2. If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for six tenths or more of the
cumulative days per year when the soil
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or
b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, remains moist in some or all parts for
less than 90 consecutive days per year when
the temperature at a depth of 50 cm below
the soil surface is higher than 8°C.

Arenic Aridic Kandiustalfs

ICDF. Other Kandiustalfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50

to 100 cm,
Arenic Kandiustalfs

ICDG. Other Kandiustalfs which, if neither irrigated nor
fallowed to store moisture, have either:

1, A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for six tenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years,
remains moist in some or all parts for less than 90
consecutive days per year when the temperature at



209

2. In one or more horizons within 100 cm of the
soil surface, aquic conditions for some time in
most years (or artificial drainage) and one or more
of the following:

a. A chroma of 0, or a hue of 2.5Y or
yellower and a chroma of 1; or

b. Redox concentrations and 50 percent or
more chroma of 2 or less; or

¢. Fifty percent or more chroma of 2 or less
and, in horizons with a total thickness of 25
cm or more within 50 cm of the soil surface,
a higher exchangeable sodium percentage
(or sodium adsorption ratio) than in the zone
with aquic conditions; or
d. Enough active ferrous iron to give a
positive reaction to a,a'-dipyridyl at a time
when the soil is not being irrigated.

Aquic Durie Calciorthids

FBEG. Other Calciorthids that have, in one or more
horizons within 100 cm of the soil surface, aquic
conditions for some time in most years (or artificial
drainage), and one or more of the following:

1. A chroma of 0, or a hue of 2.5Y or yellower and
achroma of 1; or

2. Redox concentrations and 50 percent or more
chroma of 2 or less; or

3. Fifty percent or more chroma of 2 or less and,

in horizons with a total thickness of 25 cm or

more within 50 cm of the soil surface, a higher

exchangeable sodium percentage (or sodium

adsorption ratio) than in the zone with aquic

conditions; or

4. Enough active ferrous iron to give a positive

reaction to «.,a'-dipyridy] at a time when the soil

is not being irrigated.

Aquic Calciorthids

FBEH,. Other Calciorthids which have:

1. A horizon within 100 cm of the soil surface that
is 15 cm or more thick and either contains 20
percent or more (by volume) durinodes or is
brittle and has firm consistence when moist; and

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to noncarbonate clay, as follows:

a. In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,

(1) 0.60 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

-u>


126

2. A sandy particle size throughout a layer

extending from the mineral soil surface to the top

of an argillic horizon at a depth of 50 to 100 cm.
Aquic Arenic Paleustalfs

ICFF. Other Paleustalfs that have 5 percent or more (by
volume) plinthite in one or more horizons within 150
cm of the mineral soil surface.

Plinthic Paleustaifs

ICFG. Other Paleustalfs that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Paleustalfs

ICFH. Other Paleustalfs that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

‘Oxyaquie Paleustalfs

ICFI. Other Paleustalfs which have a petrocalcic horizon
that has its upper boundary within 150 cm of the
mineral soil surface.

Petrocalcic Paleustalfs

ICFJ. Other Paleustalfs which have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic horizon at a depth of 50 to 100 cm;
and

2. If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for six tenths or more of the
cumulative days per year when the soil
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or
b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, remains moist in some or all parts for
less than 90 consecutive days per year when.
the temperature at a depth of 50 cm below
the soil surface is higher than 8°C.

Arenic Aridic Paleustalfs

ICFK. Other Paleustalfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
to 100 cm.

Arenic Paleustalfs


482

b. Have 5 percent or more (by volume)
skeletans on faces of peds in the layer that
has a 20 percent lower clay content and,
below that layer, a clay increase of 3 percent
or more (absolute) in the fine-earth fraction.
Kandiustults, p. 483

GDC. Other Ustults that have a CEC of 16 cmol(+)/kg
clay or less (by IN NH,OAc pH 7) and an ECEC of 12
emol(+)/kg clay or less (sum of bases extracted with IN
NH,OAc pH 7, plus IN-KCl-extractable Al) in 50
percent or more either of the argillic or kandic horizon if
less than 100 cm thick, or of its upper 100 cm.
Kanhaplustults, p. 486

GDD. Other Ustults which:

1. Do not have a lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface;
and

2. Within 150 cm of the mineral soil surface,
either:

a. Do not have a clay decrease with
increasing depth of 20 percent or more
(relative) from the maximum clay content;
or

b. Have 5 percent or more (by volume)
skeletans on faces of peds in the layer that
has a 20 percent lower clay content and,
below that layer, a clay increase of 3 percent
or more (absolute) in the fine-earth fraction.
Paleustults, p. 488

GDE. Other Ustults which have both:

1. An epipedon that has a color value, moist, of 3
or less throughout; and

2. An argillic horizon that has a color value, dry,

of 4 or less, and a color value, moist, that is no

more than 1 unit lower than the value, dry.
Rhodustults, p. 488

GDF. Other Ustults.
Haplustults, p. 482

Haplustults

Key to subgroups

GDFA. Haplustults that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Haplustults

GDEB, Other Haplustults that have a petroferric contact
within 100 cm of the mineral soil surface.
Petroferric Haplustults

GDFC. Other Haplustults that have, in one or more
layers both within the upper 12.5 cm of the argillic


Chapter 9

Entisols

KEY TO SUBORDERS

KA. Entisols that have one or more of the following:

1. Aquic conditions and sulfidic materials within
50 cm of the mineral soil surface; or
2, Permanent saturation with water, and a reduced
matrix in all horizons below a depth of 25 cm
from the mineral soil surface; or
3. In a layer between 40 and 50 cm from the
mineral soil surface, aquic conditions for some
time in most years (or artificial drainage) and one
or more of the following:
a. A texture finer than loamy fine sand and,
in 50 percent or more of the matrix, one or
more of the following:

(1) A chroma of 0; or

(2) A chroma of I or less and a color
value, moist, of 4 or more; or
(3) A chroma of 2 or less, and redox
concentrations; or
b. A texture of loamy fine sand or coarser
and, in 50 percent or more of the matrix,
one or more of the following:
(1) A chroma of 0; or
(2) A hue of 10YR or redder, a color
value, moist, of 4 or more, and a
chroma of 1; or
(3) A hue of 10YR or redder, a
chroma of 2 or less, and redox
concentrations; or
(4) A hue of 2.5Y or yellower, a
chroma of 3 or less, and distinct or
prominent redox concentrations; or
(5) A hue of 2.5Y or yellower and a
chroma of 1; or
(© A hue of SGY, 5G, 5BG, or 5B; or
(7) Any color if it results from.
uncoated sand grains; or
c. Enough active ferrous iron to give a
Positive reaction to a.,a'-dipyridyl at a time
when the soil is not being irrigated.
Aquents, p, 234

4zm


801
Gypsitorrerts

Key to subgroups

EDBA. Gypsitorrerts that have, in one or more horizons
within 30 cm of the soil surface, 50 percent or more
colors as follows:

1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. A chroma of 3 or more.

Chromic Gypsitorrerts
EDBB, Other Gypsitorrerts,
Typic Gypsitorrerts
Haplotorrerts
Key to subgroups

EDDA. Haplotorrerts that have, throughout a layer 15
em or more thick within 100 cm of the soil surface, an
electrical conductivity of 15 dS/m or more (1:1
soil:water) for 6 or more months per year in 6 or more
out of 10 years.

Halic Haplotorrerts

EDDB, Other Haplotorrerts that have, in one or more
horizons within 100 cm of the soil surface, an
exchangeable sodium percentage of 15 or more (or a
sodium adsorption ratio of 13 or more) for 6 or more
months per year in 6 or more out of 10 years,

Sodic Haplotorrerts

EDDC. Other Haplotorrerts that have a lithic or
paralithic contact, or the upper boundary of a duripan,
within 100 cm of the soil surface.

Leptic Haplotorrerts

EDDD. Other Haplotorrerts which have a layer 25 cm or
more thick that contains less than 27 percent clay in its
fine-earth fraction and has its upper boundary within
100 cm of the soil surface.

Entic Haplotorrerts

EDDE. Other Haplotorrerts that have, in one or more
horizons within 30 cm of the soil surface, 50 percent or
more colors as follows:

1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or

3. A chroma of 3 or more.
Chromic Haplotorrerts

EDDF. Other Haplotorrerts.
Typic Haplotorrerts


221

2. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Xerollic Camborthids

FBFT. Other Camborthids which have both:

1. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,
(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or
(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or
(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between |
and 13; or
b, In the upper 18 cm of the soil, if there is a

paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

2. An aridic moisture regime that borders on an
ustic regime.

-upP

Ustollic Camborthids
FBFU. Other Camborthids which have both:

1. A moisture control section that is dry in all its
parts for less than three fourths of the cumulative
days per year in 6 or more out of 10 years when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and

2. An aridic moisture regime that borders on a
xeric regime,
Xerochreptic Camborthids

FBFV. Other Camborthids which have both:

1. A moisture control section that is dry in all its
parts for less than three fourths of the cumulative
days per year in 6 or more out of 10 years when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and


503
Dystruderts

Key to subgroups
EFAA. Dystruderts that have more than 2.0 cmol(+)/kg
Al (by IN KCl) in the fine-carth fraction throughout a
layer 10 cm or more thick with an upper boundary
between 25 and 50 cm from the mineral soil surface.
Alic Dystruderts
EFAB. Other Dystruderts that have, in one or more
horizons within 100 cm of the mineral soil surface,
aquic conditions for some time in most years (or
artificial drainage) and either:
1, Redoximorphic features; or
2. Enough active ferrous iron to give a positive
reaction to a.,a:'-dipyridyl at a time when the soil
is not being irrigated.
Aquic Dystruderts
EFAC. Other Dystruderts that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.
Oxyaquic Dystruderts

EFAD. Other Dystruderts that have a lithic or paralithic
contact within 100 cm of the mineral soil surface.

Leptic Dystruderts
EFAE. Other Dystruderts which have a layer 25 cm or
more thick that contains less than 27 percent clay in its
fine-earth fraction and has its upper boundary within
100 cm of the mineral soil surface.

Entic Dystruderts

EFAF. Other Dystruderts that have, in one or more
horizons within 30 cm of the mineral soil surface, 50
percent or more colors as follows:

1. A color value, moist, of 4 or more; or
2, A color value, dry, of 6 or more; or
3. A chroma of 3 or more.

Chromic Dystruderts
EFAG. Other Dystruderts.
Typic Dystruderts
Hapluderts
Key to subgroups

EFBA. Hapluderts that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Hapluderts

EFBB, Other Hapluderts that have, in one or more
horizons within 100 cm of the mineral soil surface,

am<


180
1. Two percent or more redox concentrations; or

2. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
redox depletions on faces of peds, or in the matrix
if peds are absent; or

3. Enough active ferrous iron to give a positive
reaction to o,a'-dipyridyl at a time when the soil
is not being irrigated.

Aquic Vitricryands

CBEC. Other Vitricryands that have, between 25 and
100 cm either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of
amollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 em or more that
have a color value, moist, 1 unit or more higher and an
organic-carbon content | percent or more (absolute)
lower.

Thaptic Vitricryands

CBED. Other Vitricryands that have a xeric moisture
regime and a mollic or an umbric epipedon.
Humic Xeric Vitricryands

CBEE. Other Vitricryands that have a xeric moisture
regime.

Xeric Vitricryands
CBEF. Other Vitricryands which have an argillic or a
kandic horizon that has its upper boundary within 125
om either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Alfic Vitricryands

CBEG. Other Vitricryands that have a mollic or an
umbric epipedon.

Humic Vitricryands
CBEH. Other Vitricryands.
Typic Vitricryands
TORRANDS
Key to great groups

CCA. All Torrands.
Vitritorrands, p. 151


154

with andic soil properties, whichever is shallower, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:

1. Two percent or more redox concentrations; or

2. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
redox depletions on faces of peds, or in the matrix
if peds are absent; or

3. Enough active ferrous iron to give a positive
reaction to a.,0"-dipyridyl at a time when the soil
is not being irrigated.

Aquic Fulvudands

CGDE. Other Fulvudands that have both:

1. Extractable bases plus 1N-KCl-extractable Al>*
totaling less than 2.0 cmol(+)/kg in the fine-earth
fraction of one or more horizons with a total
thickness of 30 cm or more, between 25 and 100
cm either from the mineral soil surface, or from
the top of an organic layer with andic soil
properties, whichever is shallower; and

2. Undried, a 1500-kPa water retention of 70
percent or more throughout a layer 35 cm or more
thick within 100 cm either of the mineral soil
surface, or of the top of an organic layer with
andic soil properties, whichever is shallower.
Acrudoxic Hydric Fulvudands

CGDF. Other Fulyudands which have both:

1. Extractable bases plus 1N-KC]-extractable AB+
totaling less than 2.0 cmol(+)/kg in the fine-earth
fraction of one or more horizons with a total
thickness of 30 cm or more, between 25 and 100
cm either from the mineral soil surface, or from
the top of an organic layer with andic soil
properties, whichever is shallower; and
2. An argillic or a kandic horizon that has both:
a, An upper boundary within 125 cm either
of the mineral soil surface, or of the top of
an organic layer with andic soil properties,
whichever is shallower; and
b. A base saturation (by sum of cations) of
less than 35 percent throughout its upper 50

om.
Acrudoxic Ultic Fulvudands

CGDG. Other Fulvudands that have extractable bases
plus 1N-KCl-extractable Al>* totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more
horizons with a total thickness of 30 cm or more,
between 25 and 100 cm either from the mineral soil
surface, or from the top of an organic layer with andic
soil properties, whichever is shallower.

Acrudoxic Fulvadands


337
HC. Other Mollisols which:

1, Have a mollic epipedon less than 50 cm thick;
and

2. Do not have an argillic or a calcic horizon; and

3. Have, either within or directly below the mollic
epipedon, mineral soil materials less than 7.5 cm
in diameter that have a CaCO, equivalent of 40
percent or more; and

4. Have either a udic moisture regime or a cryic
soil temperature regime.
Rendolls, p. 363
HD. Other Mollisols that have either a xeric moisture
regime or an aridic moisture regime bordering on a
xeric regime, but do not have a cryic soil temperature
regime.
Xerolls, p. 394
HE. Other Mollisols that have a frigid, cryic, or pergelic
soil temperature regime.
Borolls, p. 346
HF. Other Mollisols that have either an ustic moisture
regime, or an aridic moisture regime that borders on an
ustic regime.

Ustolls, p. 373
HG. Other Mollisols.

Udolls, p. 364
ALBOLLS
Key to great groups

HAA. Albolls that have a natric horizon.
Natralbolls, p. 339

HAB. Other Albolls.
Argialbolls, p. 337

Argialbolls

Key to subgroups
HABA. Argialbolls which have both:
1, One or both of the following:

a, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
em of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either



447

BBDB. Other Haplocryods that have a mean annual soil
temperature of 0°C or less.
Pergelic Haplocryods

BBDC. Other Haplocryods which have both:

1. In one or more horizons within 75 cm of the
mineral soil surface, redoximorphic features, and
also aquic conditions for some time in most years
(or artificial drainage); and
2, Andic soil properties throughout horizons that
have a total thickness of 25 cm or more within 75
cm either of the mineral soil surface, or of the top
of an organic layer with andic soil properties,
whichever is shallower.

Aquandic Haplocryods

BBDD. Other Haplocryods which have andic soil
properties throughout horizons that have a total
thickness of 25 cm or more within 75 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.

Andic Haplocryods
BBDE. Other Haplocryods that have, in one or more
horizons within 75 cm of the mineral soil surface,
tedoximorphic features, and also aquic conditions for
some time in most years (or artificial drainage).

Aquic Haplocryods
BBDF. Other Haplocryods that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of

10 years.
Oxyaquic Haplocryods

BBDG. Other Haplocryods that have 1.1 percent or less
organic carbon in the upper 10 cm of the spodic horizon.

Entic Haplocryods
BBDH. Other Haplocryods.

Typic Haplocryods
Humicryods
Key to subgroups
BBCA. Humicryods that have a lithic contact within 50
em of the mineral soil surface.

Lithic Humicryods

BBCB. Other Humicryods that have a mean annual soil
temperature of 0°C or less.
Pergelle Humicryods
BBCC. Other Humicryods which have both:
1. In one or more horizons within 75 cm of the
mineral soil surface, redoximorphic features, and
also aquic conditions for some time in most years
(or artificial drainage); and

Ovum


525

is lithologically unlike the overlying material, the
discontinuity is indicated by a number prefix, and the
symbol for the buried horizon is used in addition, e.g.:
Ap-Btl-Bt2-BC-C-2ABb-2Btb]-2Btb2-2C,

In organic soils, discontinuities between different kinds
of layers are not identified. In most cases such
differences are identified either by letter-suffix
designations if the different layers are organic, or by the
master symbol if the different layers are mineral.

USE OF THE PRIME

Ifa pedon contains two or more horizons of the same
kind which are separated by one or more horizons of a
different kind, identical letter and number symbols can
be used for those horizons that have the same
characteristics. For example, the sequence A-E-Bt-E-
Btx-C identifies a soil that has two E horizons. To
emphasize this characteristic, the prime (the symbol ') is
added after the master-horizon symbol of the lower of
the two horizons that have identical designations, e.g.:
A-E-Bt-E'-Btx-C. The prime, when appropriate, is
applied to the capital-letter horizon designation, and any
lower-case letter symbols follow it: B't. It is used only
when the letter designations of the two layers in
question are completely identical. In the rare cases when
three layers have identical letter symbols, a double
prime can be used for the lowest of these layers: E".

The same principle applies in designating layers of
organic soils. The prime is used only to distinguish two
or more horizons that have identical symbols; e.g., Oi-
C-O'%i-C' when the soil has two identical Oi layers, or
Oi-C-Oe-C' when the two C layers are of the same kind.


Keys to Soil Taxonomy, Fifth Edition, 1992

Published by Pocahontas Press, Inc., Blacksburg, Virginia,
USA.

Printed and bound in the United States of America by
BookMasters, Inc., Ashland, Ohio, U.S.A.

© 1992 The content of this book is not copyrighted, but
Pocahontas Press reserves all rights to the particular format in
which that content appears in this book. These pages may not
be reproduced in any form or by any electronic or mechanical
means including information storage and retrieval systems
without permission in writing from the publisher.

ISBN 0-936015-39-X LC 92-28188

First Printing 1992


249

1. A frigid soil temperature regime, and a
moisture control section which, in 6 or more out of
10 years, is dry in some or all parts for less than
105 cumulative days per year when the soil
temperature at a depth of 50 cm below the soil
surface is higher than 5°C; or

2. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for less than
four tenths of the cumulative days per year when
the temperature at a depth of 50 cm below the soil
surface is higher than $°C; or

3. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is dry
in some or all parts for less than 120 cumulative
days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8°C.
Udiec Ustifluvents

KDCG. Other Ustifluvents which have an Ap horizon,
or an A horizon 15 cm or more thick, that has a color
value, moist, of 3 or less and a color value, dry, of 5 or

less (crushed and smoothed sample).

Mollic Ustifluvents
KDCH. Other Ustifluvents.

Typic Ustifluvents
Xerofiluvents
Key to subgroups

KDBA. Xerofluvents which have one or both of the
following:

1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either 2
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Xerofluvents

KDBB. Other Xerofluvents which have:

1. In one or more horizons within 50 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage); or
2. In one or more horizons within 150 cm of the
mineral soil surface, a color value, moist, of 4 or

4zZm


253

KEAF. Other Cryorthents which have lamellae within
150 cm of the mineral soil surface that meet all the
requirements for an argillic horizon except thickness.4

Alfic Cryorthents
KEAG. Other Cryorthents,
Typic Cryorthents
Torriorthents
Key to subgroups
KEBA. Torriorthents which have:

1. One or both of the following:

a. Cracks within 125 cm of the soil surface
that are 5 mm or more wide through a
thickness of 30 cm or more for some time in
most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the soil surface; or

b. A linear extensibility of 6.0 cm or more
between the soil surface and either a depth
of 100 cm or a lithic or paralithic contact,
whichever is shallower; and

2. A moisture control section which, in 6 or more
out of 10 years, is dry in all its parts for less than
three fourths of the cumulative days per year when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and
3. A hyperthermic, thermic, mesic, frigid, or an
iso soil temperature regime, and a torric moisture
regime that borders on an ustic regime.

Ustertic Torriorthents

KEBB. Other Torriorthents which have:
1. One or both of the following:

a. Cracks within 125 cm of the soil surface
that are 5 mm or more wide through a
thickness of 30 cm or more for some time in
most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the soil surface; or

b. A linear extensibility of 6.0 cm or more
between the soil surface and either a depth
of 100 cm or a lithic or paralithic contact,
whichever is shallower; and

4 The clay content of very thin lamellae cannot be estimated with precision.
‘The lamellae in soils of alfic subgroups are generally about 0.5 to lcm
thick, but their total thickness is less than the 15 om required for an argillic
horizon,


279
Cryofolists

Key to subgroups

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

Lithic Cryofolists
AAAB. Other Cryofolists.

Typic Cryofolists
Medifolists
Key to subgroups

AADA. Medifolists that have a lithic contact within 100
cm of the soil surface.

Lithic Medifolists
AADB, Other Medifolists.

Typic Medifolists
Tropofolists
Key to subgroups

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

Lithic Tropofolists
AABB. Other Tropofolists,

Typic Tropofolists
HEMISTS
Key to great groups

ACA. Hemists which have a sulfuric horizon that has its
upper boundary within 50 cm of the soil surface,
Sulfohemists, p. 283

ACB. Other Hemists that have sulfidic materials within
100 cm of the soil surface.
Sulfihemists, p. 283

ACC. Other Hemists that have a horizon 2 cm or more
thick in which humilluvic materials constitute one half
or more of the volume.

Luvihemists, p. 281

ACD. Other Hemists which, in most years, either:

1. Are frozen in one or more layers within the
control section 2 months after the summer
solstice; or


144

2. More than 6.0 percent organic carbon and
colors of a mollic epipedon throughout a layer 50
cm or more thick within 60 cm either of the
mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower.

Hydric Pachic Melanaquands

CAED. Other Melanaquands that have, undried, a 1500-
kPa water retention of 70 percent or more throughout a
layer 35 cm or more thick within 100 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.

Hydric Melanaquands
CAEE. Other Melanaquands that have, between 40 and
100 cm either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of
a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that
have a color value, moist, ] unit or more higher and an
organic-carbon content | percent or more (absolute)
lower.

Thaptic Melanaquands
CAEE. Other Melanaquands.
Typic Melanaquands
Placaquands
Key to subgroups

CABA. Placaquands that have a lithic contact within 50
cm either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Lithic Placaquands

CABB. Other Placaquands which have both:
1, A histic epipedon; and

2. A horizon 15 cm or more thick, with 20 percent
or more (by volume) cemented soil material that
does not slake in water after air-drying, that has
its upper boundary within 100 cm either of the
mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower.

Duric Histic Placaquands


105

and also aquic conditions for some time in most years
(or artificial drainage).
Aquic Glossudalfs
IEEF. Other Glossudalfs that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.
Oxyaquic Glossudalfs
IEEG. Other Glossudalfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
cm or more.
Arenic Glossudalfs

IEEH. Other Glossudalfs that do not have a glossic
horizon 50 cm or more thick.

Haplic Glossudalfs
IEEL. Other Glossudalfs.

Typic Glossudalfs
Hapludalfs
Key to subgroups

IEKA. Hapludalfs that have both:

1. A lithic contact within 50 cm of the mineral soil
surface; and

2. In one or more subhorizons within the upper 25
em of the argillic horizon, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage).
Aquic Lithic Hapludalfs

IEKB. Other Hapludalfs that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Hapludalfs

IEKC. Other Hapludalfs which have both:
1. One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower; and

2. Redox depletions with a chroma of 2 or less in
layers that also have aquic conditions in most
years (or artificial drainage) either:


362

2. A mean summer soil temperature either at a
depth of 50 cm below the soil surface or at a lithic
or paralithic contact, whichever is shallower, of
less than 15°C if there is no O horizon, or of less
than 8°C if there is an O horizon.

Abruptic Cryic Paleborolls

HEAC. Other Paleborolls which have an argillic horizon
that has a clay increase with depth of 20 percent or more
(absolute, in the fine-earth fraction) within its upper 7.5
cm.

Abruptic Paleborolls

HEAD. Other Paleborolls which have one or both of the

following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6,0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Paleborolls

HEAE. Other Paleborolls that have a mean summer soil
temperature either at a depth of 50 cm below the soil
surface or at a lithic or paralithic contact, whichever is
shallower, of less than 15°C if there is no O horizon, or
of less than 8°C if there is an O horizon.

Cryic Paleborolls

HEAF. Other Paleborolls that have a mollic epipedon
50 cm or more thick.
Pachic Paleborolls

HEAG. Other Paleborolls that have, in one or more
horizons within 100 cm of the mineral soil surface,
redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or
artificial drainage).

Aquic Paleborolis
HEAH. Other Paleborolls that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years,

Oxyaquic Paleborolls

HEAI. Other Paleborolls.

Typic Paleborolls


390

HEBB. Other Natrustolls that have visible crystals of
gypsum or of more soluble salts, or both, within 40 cm
of the mineral soil surface.

Leptic Natrustoils

HFBC. Other Natrustolls that have, in one or more
horizons between 50 and 100 cm ftom the mineral soil
surface, aquic conditions for some time in most years
(or artificial drainage) and one of the following:

1. Fifty percent or more chroma of | or less, and a
hue of 2.5Y or yellower; or

2. Fifty percent or more chroma of 2 or less, and
redox concentrations; or

3. Fifty percent or more chroma of 2 or less; and
also a higher exchangeable sodium percentage (or
sodium adsorption ratio) between the mineral soil
surface and a depth of 25 cm than in the
underlying horizon.

Aquic Natrustolls

HEBD. Other Natrustolls which have, if neither
irrigated nor fallowed to store moisture, either:

1. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for six tenths
or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years,
remains moist in some or all parts for less than 90
consecutive days per year when the temperature at
a depth of 50 cm below the soil surface is higher
than 8°C,

Aridic Natrustolls

HFBE. Other Natrustolls which have a brittle horizon
within 100 cm of the mineral soil surface that is 15 cm
or more thick and contains either some opal coatings or
20 percent or more (by volume) durinodes.

Duric Natrustolls

HFBF. Other Natrustolls that have a glossic horizon, or
interfingering of albic materials into a natric horizon.
Glossic Natrustolls

HFBG. Other Natrustolls.
Typic Natrustolls


293
Endoaquepts

Key to subgroups
JAJA. Endoaquepts which have, within 150 cm of the
mineral soil surface, one or more of the following:

1. A sulfuric horizon; or

2. A horizon 15 cm or more thick that has all the
characteristics of a sulfuric horizon, except that it
has a pH value between 3.5 and 4.0; or

3. Sulfidic materials.
Sulfic Endoaquepts

JAJB. Other Endoaquepts that have a lithic contact
within 50 cm of the mineral soil surface.
Lithic Endoaquepts

JAJC. Other Endoaquepts which have one or both of the

following:
1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Endoaquepts

JAJD. Other Endoaquepts that have, throughout one or

more horizons with a total thickness of 18 cm or more

within 75 cm of the mineral soil surface, one or more of

the following: ;
1. A fine-earth fraction with both a bulk density of N
1.0 g/cm? or less, measured at 33 kPa water Cc
retention, and aluminum plus 1/2 iron percentages
(by ammonium oxalate) totaling more than 1.0; or

2. More than 35 percent (by volume) fragments
coarser than 2,0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

3. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or


384

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Haplustolls

HFGG. Other Haplustolls which have both:

1. If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for six tenths or more of the
cumulative days per year when the soil
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, remains moist in some or all parts for
less than 90 consecutive days per year when
the temperature at a depth of 50 cm below
the soil surface is higher than 8°C; and

2. A CEC (by 1N NH,OAc pH 7) of less than 24
emol(+)/kg clay? in 50 percent or more of the soil
volume between a depth of 25 cm from the
mineral soil surface and either a depth of 100 cm,
ora lithic or paralithic contact if shallower.
Torroxic Haplustolls

HFGH. Other Haplustolls that have a CEC (by IN
NH,OAc pH 7) of less than 24 cmol(+)/kg clay? in 50
percent or more of the soil volume between a depth of
25 cm from the mineral soil surface and either a depth
of 100 cm, or a lithic or paralithic contact if shallower.
Oxic Haplustolls

HFGI. Other Haplustolls that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth

2 Some soils with properties that approach those of an oxic horizon do not
disperse well. If the ratio of (percent water retained at 1500 kPa tension
minus percent organic carbon) to the percentage of measured clay is 0.6 or
more, then the percentage of clay is considered to equal either (1) the
measured percentage of clay, or (2) three times (percent water retained at
1500 kPa tension minus percent organic carbon), whichever value is higher,
but no more than 100.

3 See footnote 2.


288

2. A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Fibric Terric Troposaprists

ADEC. Other Troposaprists which have both:

1. One or more layers, with a total thickness of 25
cm or more, of the subsurface and bottom tiers
consisting of hemic materials; and

2. A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Hemic Terrie Troposaprists

ADED., Other Troposaprists which have a mineral layer
30 cm or more thick that has its upper boundary within
the control section below the surface tier.

Terric Troposaprists

ADEE. Other Troposaprists that have one or more
limnic layers with a total thickness of 5 cm or more
within the control section.

Limnic Troposaprists

ADEF. Other Troposaprists that have, within organic
materials, either one mineral layer 5 cm or more thick,
or two or more mineral layers of any thickness, in the
control section below the surface tier.

Fluvaquentic Troposaprists

ADEG. Other Troposaprists that have one or more
layers, with a total thickness of 12.5 cm or more, of the
subsurface and bottom tiers consisting of fibric
materials.

Fibric Troposaprists

ADEH. Other Troposaprists that have one or more
layers, with a total thickness of 25 cm or more, of the
subsurface and bottom tiers consisting of hemic
materials.

Hemic Troposaprists

ADEI. Other Troposaprists.
Typic Troposaprists


64
FAMILY DIFFERENTIAE FOR HISTOSOLS

Most of the differentiae which are used to distinguish
families of Histosols (organic soils) have already been
defined, either because they are used as differentiae in
mineral soils as well as Histosols, or because their
definitions are used for the classification of some
Histosols in categories higher than the family. In the
following, differentiae not previously mentioned are
defined and the classes in which they are used are
enumerated,

The order in which family modifiers, if appropriate for a
particular family, are placed in the technical family
names of Histosols, is as follows:

Particle size

Mineralogy, including nature of limnic deposits

Reaction

Soil temperature regime

Soil depth

Particle-size classes
Particle-size modifiers are used only in family names of
terric subgroups of Histosols. The following terms are
used:

Fragmental

Loamy-skeletal or clayey-skeletal

Sandy or sandy-skeletal

Loamy

Clayey
The meanings of these terms are the same as those
defined for particle-size classes of mineral soils. The
proper term is selected to describe the weighted average
particle size of either the upper 30 cm of the mineral

layer or of that part of the mineral layer that is within
the control section, whichever is thicker.

Mineralogy classes

Three different kinds of mineralogy classes are
recognized for families in certain great groups and
subgroups of Histosols:

Ferrihumic.—Used for families of Histosols, i.e.,
Fibrists, Hemists, and Saprists, except Sphagnofibrists
and sphagnic subgroups of other great groups.
Ferrihumic soil material, i.e., bog iron, is an authigenic
(formed in place) deposit consisting of hydrated iron
oxide mixed with organic matter, either dispersed and
soft or cemented into large aggregates, in a mineral or
organic layer that has all the following characteristics:


434

DCBF. Other Acrustox that have a delta pH (KCI pH
minus |:1 water pH) with a 0 or net positive charge in a
layer 18 cm or more thick within 125 cm of the mineral
soil surface.

Anionic Acrustox

DCBG. Other Acrustox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125
cm of the mineral soil surface.

Plinthic Acrustox

DCBH. Other Acrustox that have, in one or more
horizons within 125 cm of the mineral soil surface,
redox depletions with a color value, moist, of 4 or more
and a chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage).

Aquic Acrustox

DCBI. Other Acrustox that have a base saturation (by
‘NH,OAc) of 35 percent or more in all horizons within
125 cm of the mineral soil surface.

Eutric Acrustox

DCBJ. Other Acrustox that have both:

1, 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 2.5YR or redder
and color value, moist, of 3 or less between 25
and 125 cm from the mineral soil surface.

Humic Rhodic Acrustox

DCBK. Other Acrustox that have both:

1, 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 7.5YR or yellower
and color value, moist, of 6 or more between 25
and 125 cm from the mineral soil surface.

Humic Xanthic Acrustox

DCBL, Other Acrustox that have 16 kg/m? or more
organic carbon between the mineral soil surface and a
depth of 100 cm.

Humic Acrustox

DCBM. Other Acrustox that have 50 percent or more
hue of 2.5YR or redder and color value, moist, of 3 or
less between 25 and 125 cm from the mineral soil
surface,

Rhodic Acrustox

DCBN. Other Acrustox that have 50 percent or more
hue of 7.5YR or yellower and color value, moist, of 6 or
‘more between 25 and 125 cm from the mineral soil
surface.

Xanthic Acrustox

DCBO. Other Acrustox.
Typic Acrustox


480

2, In one or more layers within 75 cm of the
mineral soil surface, redox depletions with a color
value, moist, of 4 or more and a chroma of 2 or
less, accompanied by redox concentrations, and
also aquic conditions for some time in most years
(or artificial drainage).

Plinthaquic Paleudults

GCEM. Other Paleudults that have both:

1. Within 125 cm of the mineral soil surface, one
or more subhorizons in the argillic horizon with
all the properties of a fragipan, except that only 40
to 60 percent of the volume is brittle; and
2. In one or more layers within 75 cm of the
mineral soil surface, redox depletions with a color
value, moist, of 4 or more and a chroma of 2 or
less, accompanied by redox concentrations, and
also aquic conditions for some time in most years
(or artificial drainage).
Fragiaquic Paleudults
GCEN. Other Paleudults that have anthraquic
conditions.
Anthraquic Paleudults

GCEO. Other Paleudults that have, in one or more
layers within 75 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and a
chroma of 2 or less, accompanied by redox
concentrations, and also aquic conditions for some time
in most years (or artificial drainage).

Aquic Paleudults

GCEP. Other Paleudults that have 5 percent or more (by
volume) plinthite in one or more horizons within 150
cm of the mineral soil surface.

Plinthic Paleudults

GCEQ. Other Paleudults that have, within 125 cm of
the mineral soil surface, one or more subhorizons in the
argillic horizon with all the properties of a fragipan,
‘except that only 40 to 60 percent of the volume is
brittle.

Fragic Paleudults

GCER. Other Paleudults which have, throughout the
upper 100 cm of the argillic horizon:
1. Acolor value, moist, of 3 or less and a color
value, dry, that is no more than 1 unit higher than
the value, moist; and
2. No redox concentrations with a chroma of 3 or

more,
Rhodic Paleudults

GCES, Other Paleudults.
Typic Paleudults


436

2. A kandic horizon that has its upper boundary
within 150 cm of the mineral soil surface.
Kandiustalfic Eutrustox

DCCI. Other Eutrustox which have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. An oxic horizon that has its lower boundary
within 125 cm of the mineral soil surface.
Umbreptic Eutrustox

DCCJ. Other Eutrustox which have an oxic horizon that
has its lower boundary within 125 cm of the mineral
soil surface.

Inceptic Eutrustox

DCCK. Other Eutrustox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 2.5YR or redder
and color value, moist, of 3 or less between 25
and 125 cm from the mineral soil surface.

Humic Rhodic Eutrustox

DCCL. Other Eutrustox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 7.5YR or yellower
and color value, moist, of 6 or more between 25
and 125 cm from the mineral soil surface.

Humic Xanthic Eutrustox

DCCM. Other Eutrustox that have 16 kg/m? or more
organic carbon between the mineral soil surface and a
depth of 100 cm.

Humic Eutrustox

DCCN. Other Eutrustox that have 50 percent or more
hue of 2.5YR or redder and color value, moist, of 3 or
less between 25 and 125 cm from the mineral soil
surface.

Rhodic Eutrustox

DCCO, Other Eutrustox that have 50 percent or more
hue of 7.5YR or yellower and color value, moist, of 6 or
more between 25 and 125 cm from the mineral soil
surface,

Xanthic Eutrustox

DCCP. Other Eutrustox.
Typic Eutrustox

Haplustox

Key to subgroups

DCEA. Haplustox that have, within 125 cm of the
mineral soil surface, both:


50

classes for this taxonomy, the very fine sand has been
allowed to “float.” It is included with the sand if the
texture (fine-earth fraction) of a soil is sand, loamy fine
sand, or coarser. But it is treated as silt if the texture is
very fine sand, loamy very fine sand, sandy loam, silt
loam, or finer.

No single set of particle-size classes seems adequate to
serve as family differentiae for all the different kinds of
soils. So this taxonomy is providing a choice of either 7
or 11 particle-size classes, of which the second set
replaces the /oamy class of the first set with 4 and the
clayey class with 2 more narrowly defined classes (see
below). This permits relatively fine distinctions between
families of soils for which particle size is important,
while providing broader groupings for soils in which
particle sizes are difficult to measure precisely, or for
which narrowly defined particle-size classes would
produce undesirable separations. Thus the term clayey
is used for some soil families to indicate a clay content
of 35 percent or more in specific horizons, while in
other families the more narrowly defined terms fine and
very fine indicate that these horizons have clay contents
either of 35 to 60 percent, or of 60 percent or more, in
their fine-earth fraction. The term fine earth refers to
particles smaller than 2.0 mm in diameter. The term
rock fragments means particles 2.0 mm or more in
diameter and includes all particles with horizontal
dimensions smaller than the size of a pedon. It is not the
same as the term coarse fragments, which excludes
stones and boulders with diameters of 25 cm or more.

Definition of classes

Fragmental.—90 percent or more (by volume) rock
fragments and voids; less than 10 percent (by volume)
particles less than 2.0 mm in diameter.

Sandy-skeletal —35 percent or more (by volume) rock
fragments; 10 percent or more (by volume) particles less
than 2.0 mm in diameter (fine-earth fraction) with a
texture of sand or loamy sand, including less than 50
percent (by weight) very fine sand.

Loamy-skeletal —35 percent or more (by volume) rock
fragments; 10 percent or more (by volume) particles less
than 2.0 mm in diameter (fine-earth fraction) with a
texture of loamy very fine sand, very fine sand, or finer,
including less than 35 percent (by weight) clay.

Clayey-skeletal —35 percent or more (by volume) rock
fragments, 10 percent or more (by volume) particles less
than 2.0 mm in diameter (fine-earth fraction), including
35 percent or more (by weight) clay

Sandy.—In the fine-earth fraction, a texture of sand or
loamy sand, including less than 50 percent (by weight)
very fine sand; in the whole soil, less than 35 percent
(by volume) rock fragments.


541

W-X-Y-Z

XERERTS
Xeric moisture regime ..



470
Fragiudults

Key to subgroups

GCBA. Fragiudults that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
to 100 cm.

Arenic Fragiudults

GCBB. Other Fragiudults which have:
1. Either of the following:

a. Above the fragipan, no argillic or kandic
horizon that has clay films on both vertical
and horizontal surfaces of any structural
aggregates; or

b. Between the argillic or kandic horizon
and the fragipan, one or more horizons with
50 percent or more chroma of 3 or less and
with a clay content 3 percent or more
(absolute, in the fine-earth fraction) lower
than in both the argillic or kandic horizon
and the fragipan; and

2. In one or more horizons within 40-cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

3. Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface.

Plinthaquic Fragiudults

GCBC. Other Fragiudults that have both:
1. Either of the following:

a. Above the fragipan, no argillic or kandic
horizon that has clay films on both vertical
and horizontal surfaces of any structural
aggregates; or

b. Between the argillic or kandic horizon
and the fragipan, one or more horizons with
50 percent or more chroma of 3 or less and
with a clay content 3 percent or more
(absolute, in the fine-earth fraction) lower
than in both the argillic or kandic horizon
and the fragipan; and

2. In one or more horizons within 40 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage).
Glossaquic Fragiudults

GCBD. Other Fragiudults that have, in one or more
subhorizons above the fragipan and within the upper 25


AQUULTS

Key to great groups

GAA. Aquults that have one or more horizons within
150 cm of the mineral soil surface in which plinthite
either forms a continuous phase or constitutes one half
or more of the volume.

Plinthaquults, p. 462

GAB. Other Aquults which have a fragipan that has its
upper boundary either:

1, Within 200 cm of the mineral soil surface if no
horizon contains 5 percent or more (by volume)
plinthite; or
2. Within 100 cm of the mineral soil surface if
there is 5 percent or more (by volume) plinthite in
‘one or more horizons of the soil.

Fragiaquults, p. 459

GAC. Other Aquults that have an abrupt textural change
between the ochric epipedon or albic horizon and the
argillic or kandic horizon, and have low hydraulic
conductivity in the argillic or kandic horizon.

Albaquults, p. 457
GAD. Other Aquults which:

1. Do not have a lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface;
and

2. Have a CEC of 16 cmol(+)/kg clay or Jess (by
IN NH,OAc pH 7) and an ECEC of 12 cmol(+)/kg
clay or less (sum of bases extracted with 1N
‘NH,OAc pH 7, plus IN-KCl-extractable Al) in 50
percent or more either of the argillic or kandic
horizon if less than 100 om thick, or of its upper
100 cm; and

3, Within 150 cm of the mineral soil surface,
either:

a. Do not have a clay decrease with
increasing depth of 20 percent or more
(relative) from the maximum clay content;
or

b. Have 5 percent or more (by volume)
skeletans on faces of peds in the layer that
has a 20 percent lower clay content and,
below that layer, a clay increase of 3 percent
or more (absolute) in the fine-earth fraction.
Kandiaquults, p. 459

GAE. Other Aquults that have a CEC of 16 cmol(+y/kg
clay or less (by IN NH,OAc pH 7) and an ECEC of 12
cmol(+)/kg clay or less (sum of bases extracted with IN
NH,OAc pH 7, plus 1N-KCl-extractable Al) in 50


518

equipment. The bedrock may contain cracks, but these
are generally too few and too small to allow roots to
penetrate, The cracks may be coated or filled with clay
or other material,

Transitional and combination horizons

Horizons dor ies of one master hori:
Horizons domiuated by oiupertict of ane sae Two
capital-letter symbols are used for such transitional
horizons, e.g., AB, EB, BE, or BC. The first of these
symbols indicates that the properties of the horizon so
designated dominate the transitional horizon. An AB
horizon, for example, has characteristics of both an
overlying A horizon and an underlying B horizon, but it
is more like the A than like the B.

In some cases, a horizon can be designated as
transitional even if one of the master horizons to which
it presumably forms a transition is not present. A BE
horizon may be recognized in a truncated soil if its
properties are similar to those of a BE horizon in a soil
from which the overlying E horizon has not been
removed by erosion. A BC horizon may be recognized
even if no underlying C horizon is present; it is
transitional to assumed parent materials.

properties of the two kinds of master horizons indicated
by the capital letters: The two capital letters
designating such combination horizons are separated by
a virgule (/), e.g., E/B, B/E, or B/C, Most of the
individual parts of one horizon component are
surrounded by the other.

The designation may be used even when horizons
similar to one or both of the components are not present,
provided that the separate components can be
recognized in the combination horizon. The first symbol
is that of the horizon with the greater volume.

Single sets of horizon designators do not cover all
situations; therefore, some improvising has to be done.
For example, Alfic Udipsamments have lamellae that
are separated from each other by eluvial layers. Because
it is generally not practical to describe each lamella and
eluvial layer as a separate horizon, the horizons can be
combined but the components described separately. One
horizon then contains several lamellae and eluvial layers
and can be designated an “E and Bt” horizon. The
complete horizon sequence for this soil could be: Ap-
Bw-E and Btl-E and Bt2-C.

SUBORDINATE DISTINCTIONS WITHIN
MASTER HORIZONS AND LAYERS

Lower-case letters are used as suffixes to designate
specific kinds of master horizons and layers, The term


278

ABDEF. Other Tropofibrists that have one or more limnic
layers with a total thickness of 5 cm or more within the
control section.

Limnic Tropofibrists

ABDG. Other Tropofibrists that have, within organic
materials, either one mineral layer 5 cm or more thick,
or two or more mineral layers of any thickness, in the
control section below the surface tier.

Fluvaquentic Tropofibrists

ABDH. Other Tropofibrists that have one or more
layers, with a total thickness of 25 cm or more, of the
subsurface and bottom tiers consisting of hemic
materials,

Hemic Tropofibrists

ABDI. Other Tropofibrists that have one or more layers,
with a total thickness of 12.5 cm or more, of the
subsurface and bottom tiers consisting of sapric
materials.

Sapric Tropofibrists
ABDI. Other Tropofibrists.

Typic Tropofibrists
FOLISTS
Key to great groups

AAA. Folists that have a cryic or colder soil temperature
regime.

Cryofolists, p. 279
AAB. Other Folists that have an isomesic or warmer
soil temperature regime.

Tropofolists, p. 279

AAC. Other Folists that have a frigid soil temperature
regime.

Borofolists, p. 278

AAD, Other Folists.
Medifolists, p. 279

Borofolists

Key to subgroups
AACA. Borofolists that have a lithic contact within 100
om of the soil surface,

Lithic Borofolists

AACB. Other Borofolists.
Typic Borofolists


172
VITRANDS

Key to great groups

CEA. Vitrands that have an ustic moisture regime.
Ustivitrands, p. 173

CEB. Other Vitrands.
Udivitrands, p. 172

Udivitrands

Key to subgroups

CEBA, Udivitrands that have a lithic contact within 50
em either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Lithic Udivitrands
CEBB. Other Udivitrands that have, in one or more
horizons between 50 and 100 cm either from the
mineral soil surface, or from the top of an organic layer
with andic soil properties, whichever is shallower, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:

1. Two percent or more redox concentrations; or

2. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
redox depletions on faces of peds, or in the matrix
if peds are absent; or

3. Enough active ferrous iron to give a positive
reaction to a0. -dipyrigyl at a time when the soil

is not being irrigated.
Aquic Udivitrands

CEBC. Other Udivitrands that have, between 25 and
100 cm either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of
a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that
have a color value, moist, 1 unit or more higher and an
organic-carbon content 1 percent or more (absolute)
lower.
Thaptic Udivitrands

CEBD. Other Udivitrands which have both:

1, An argillic or a kandic horizon that has its

upper boundary within 125 cm of the mineral soil

surface, or of the upper boundary of an organic

layer with andic soil properties, whichever is

shallower; and


393

2. Have, if neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for six tenths or more of the
cumulative days per year when the soil
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or
b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, remains moist in some or all parts for
less than 90 consecutive days per year when
the temperature at a depth of 50 cm below
the soil surface is higher than 8°C.
Calciorthidic Paleustolls

HFCH. Other Paleustolls which have, if neither
irrigated nor fallowed to store moisture, either:

1. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for six tenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years,
remains moist in some or all parts for less than 90
consecutive days per year when the temperature at
a depth of 50 cm below the soil surface is higher
than 8°C.

Aridic Paleustolls

HFCI. Other Paleustolls which have, if neither irrigated
nor fallowed to store moisture, either:

1. A mesic or thermic soil temperature regime,
and @ moisture control section which, in 6 or more
out of 10 years, is dry in some part for four tenths
or less of the cumulative days per year when the
temperature at a depth of 50 cm below the soil
surface is higher than 5°C; or

2, A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is dry
in some or all parts for less than 120 cumulative
days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8°C.
Udic Paleustolis

HFCJ. Other Paleustolls which are calcareous
throughout after the soil has been mixed to a depth of
18 cm, and have a calcic horizon within the following
depths if the particle-size control section is


100

IEH. Other Udalfs that have a CEC of 16 cmol(+)/kg
clay or less (by IN NH,OAc pH 7) and an ECEC of 12
emol(+)/kg clay or less (sum of bases extracted with IN
NH,OAc pH 7, plus 1N-KCl-extractable Al) in 50
percent or more either of the argillic or kandic horizon if
less than 100 cm thick, or of its upper 100 cm.
Kanbapludalfs, p. 111

TEL. Other Udalfs which:

1. Do not have a lithic or paralithic contact within
150 cm of the mineral soil surface; and

2. Within 150 cm of the mineral soil surface,
either
a, Do not have a clay decrease with depth of
20 percent or more (relative) from the
maximum clay content; or

b. Have 5 percent or more (by volume)
skeletans on faces of peds in the layer that
has a 20 percent lower clay content and,
below that layer, a clay increase of 3 percent
or more (absolute) in the fine-earth fraction;
and

3. Have one or more of the following in the
argillic horizon:
a. In the matrix of its lowest subhorizon, a
hue redder than 10YR and 50 percent or
more chroma of 5 or more; or

b. In 50 percent or more of its matrix, a hue
of 2.SYR or redder, a color value, moist, of

3 or less, and a color value, dry, of 4 or less;
or

¢, In one or more subhorizons, many coarse

redox concentrations with a hue redder than

7.5YR or a chroma of 6 or more, or both.
Paleudalfs, p. 112

IEJ. Other Udalfs which have throughout the argillic
horizon a hue of 2.5YR or redder, a color value, moist,
of 3 or less, and a color value, dry, no more than 1 unit
higher than the value, moist.

Rhodudalfs, p. 115

TEK. Other Udalfs.
Hapludalfs, p. 105

Agrudalfs

Agrudalfs are the Udalfs that have an agric horizon;
some of them have an anthropic epipedon. These soils
have been farmed 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 for this great group.


259

KEEE, Other Ustorthents that are saturated with water,
in one or more layers within 150 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Ustorthents

KEEF. Other Ustorthents which have a horizon within
100 cm of the mineral soil surface that is 15 cm or more
thick and either contains 20 percent or more (by
volume) durinodes or is brittle and has firm consistence
when moist.

Durorthidic Ustorthents

KEEG. Other Ustorthents which, if neither irrigated nor
fallowed to store moisture, have one of the following:

1. A frigid soil temperature regime, and a
moisture control section which, in 6 or more out of
10 years, is dry in all parts for four tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil
surface is higher than 5°C; or

2. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for six tenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

3. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is
moist in some or all parts for less than 180
cumulative days per year when the temperature at
a depth of 50 cm below the soil surface is higher
than 8°C.

Aridic Ustorthents

KEEH. Other Ustorthents which, if neither irrigated nor
fallowed to store moisture, have one of the following:

1. A frigid soil temperature regime, and a
moisture control section which, in 6 or more out of
10 years, is dry in some or all parts for less than
105 cumulative days per year when the soil
temperature at a depth of 50 cm below the soil
surface is higher than 5°C; or

2. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for less than
four tenths of the cumulative days per year when
the temperature at a depth of $0 cm below the soil
surface is higher than 5°C; or

3. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is dry
in some or all parts for less than 120 cumulative

4zm


23

OTHER DIAGNOSTIC SOIL.
CHARACTERISTICS

Abrupt textural change

An abrupt textural change is a specific kind of change
that may occur between an ochric epipedon or albic
horizon and an argillic horizon. It is characterized by a
considerable increase in clay content within a very short
vertical distance in the zone of contact. If the clay
content of the fine-earth fraction of the ochric epipedon
or albic horizon is less than 20 percent, it doubles
within a vertical distance of 7.5 cm or less. If the clay
content of the fine-earth fraction of the ochric epipedon
or albic horizon is 20 percent or more, there is an
increase of 20 percent or more (absolute) within a
vertical distance of 7.5 cm or less (¢.g., an increase from
22 to 42 percent), and the clay content in some part of
the argillic horizon is two times or more the amount
contained in the overlying horizon.

Normally there is no transitional horizon between an
ochric epipedon or albic horizon and an argillic horizon,
or it is too thin to be sampled. Some soils, however,
have a glossic horizon or interfingering of albic
materials (defined below) in parts of the argillic
horizon. The upper boundary of such a horizon is
irregular or even discontinuous. Sampling this mixture
as a single horizon might create the impression of a
relatively thick transitional horizon, whereas the
thickness of the actual transition at the contact may be
no more than 1 mm.

Albic materials

Albic (L. albus, white) materials are soil materials with
a color that is largely determined by the color of primary
sand and silt particles, rather than by the color of their
coatings. The definition implies that clay and/or free
iron oxides have been removed from the materials, or
the oxides have been segregated to such an extent that
the color of the materials is largely determined by the
color of the primary particles.

Albic materials have one of the following colors:
1. A chroma of 2 or less, and either:

a. A color value, moist, of 3 or more, and a color
value, dry, of 6 or more; or

b, A color value, moist, of 4 or more, and a color
value, dry, of 5 or more; or

2. A chroma of 3 or less, and
a. A color value, moist, of 6 or more; or
b. A color value, dry, of 7 or more; or


27

b. In the upper 18 cm of the soil, if the
upper boundary of the duripan is between 18
and 40 cm from the soil surface,

(1) 0.72 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.18 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.77-(0.046 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
1 and 13.

Ustollic Durorthids

FBCJ. Other Durorthids which have a moisture control
section that is dry in all its parts for less than three
fourths of the cumulative days per year in 6 or more out
of 10 years when the soil temperature at a depth of 50
em from the soil surface is 5°C or higher.

Ustochreptic Durorthids

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

Entice Durorthids
FBCL. Other Durorthids.

Typic Durorthids
Gypsiorthids
Key to subgroups

FBDA. Gypsiorthids which have a petrogypsic horizon
that has its upper boundary within 100 cm of the soil
surface.

Petrogypsic Gypsiorthids

FBDB. Other Gypsiorthids that have both:
1. A calcie horizon above the gypsic horizon; and

2. A gypsic horizon for which the product of its
gypsum percentage multiplied by its thickness in
centimeters, above a depth of 150 cm from the soil
surface, is less than 3,000,
Calcic Gypsiorthids
FBDC. Other Gypsiorthids that have a gypsic horizon
for which the product of its gypsum percentage
multiplied by its thickness in centimeters, above a depth
of 150 cm from the soil surface, is less than 3,000.
‘Cambic Gypsiorthids

FBDD. Other Gypsiorthids.
Typic Gypsiorthids



Endoaquents

Key to subgroups
KAGA. Endoaquents which have, within 100 cm of the
mineral soil surface, one or both of the following:

1. Sulfidic materials; or

2. A horizon 15 cm or more thick that has all the
characteristics of a sulfuric horizon, except that it
has a pH value between 3.5 and 4.0.

Sulfic Endoaquents

KAGB. Other Endoaquents that have a lithic contact
within 50 cm of the mineral soil surface.
Lithic Endoaquents

KAGC. Other Endoaquents that have, in one or more
horizons between either the Ap horizon or a depth of 25
em from the mineral soil surface, whichever is deeper,
and a depth of 75 cm, colors in 50 percent or more of
the matrix as follows:

1. A hue of 2.5Y or redder, a color value, moist, of
6 or more, and a chroma of 3 or more; or

2. A hue of 2.5Y or redder, a color value, moist, of
5 or less, and a chroma of 2 or more; or

3. A hue of SY and a chroma of 3 or more; or

4. A hue of SY or redder and a chroma of 2 or
more if there are no redox concentrations.
Aeric Endoaquents

KAGD. Other Endoaquents which have both:

1. An Ap horizon, or an A horizon 15 cm or more
thick, that has a color value, moist, of 3 or less
and a color value, dry, of 5 or less (crushed and
smoothed sample); and

2. A base saturation (by NH,OAc) of less than 50
percent at a depth of 100 cm from the mineral soil
surface.
Humaqueptic Endoaquents
KAGE. Other Endoaquents which have either an Ap
horizon, or an A horizon 15 cm or more thick, that has a

color value, moist, of 3 or less and a color value, dry, of
5 or less (crushed and smoothed sample).

Mollic Endoaquents
KAGF. Other Endoaquents.

Typic Endoaquents
Epiaquents
Key to subgroups

KAFA. Epiaquents that have, in one or more horizons
between either the Ap horizon or a depth of 25 om from
the mineral soil surface, whichever is deeper, and a


19
1. Either

a. Columns, or less commonly, prisms in some
(usually the upper) part, which may break to
blocks; or

b. Rarely, blocky structure, and tongues of an
eluvial horizon which contain uncoated silt or
sand grains and extend more than 2.5 cm into the
horizon; and

2. Either

a. An exchangeable sodium percentage (ESP) of

15 percent or more (or a sodium adsorption ratio,
SAR, of 13 or more) in one or more subhorizons

within 40 om of its upper boundary; or

b. More exchangeable magnesium plus sodium
than calcium plus exchange acidity (at pH 8.2) in
‘one or more subhorizons within 40 cm of its upper
boundary, if the ESP is 15 or more (or the SAR is
13 or more) in one or more horizons within 200
em of the mineral soil surface.

Oxic horizon

The oxic horizon is a mineral subsurface horizon of
sandy loam or a finer particle size with low cation
exchange capacity and low weatherable-mineral content.
Its upper boundary is either 18 cm below the mineral
soil surface or at the lower boundary of an Ap horizon,
whichever is deeper, or at a greater depth where
mineralogical and charge characteristics meet the
requirements for the oxic horizon. Any increase in clay
content at the upper boundary must be diffuse. The
lower boundary of the oxic horizon is also defined by its
mineralogical and charge requirements and may, in
addition, be defined by the presence of saprolite with
rock structure.

The oxic horizon does not have andic soil properties
(defined below), and has all the following
characteristics:

1. A thickness of 30 cm or more; and

2. A particle size of sandy loam or finer in the fine-earth
fraction; and

3. Less than 10 percent weatherable minerals in the 50-
to-200-micron fraction; and

4, Rock structure in less than 5 percent of its volume, or
sesquioxide coatings on lithorelicts containing
weatherable minerals; and

5. A diffuse upper particle-size boundary, i.e., within a
vertical distance of 15 cm, a clay increase with depth of:

a. Less than 4 percent (absolute) in its fine-earth
fraction if that of the surface horizon contains less
than 20 percent clay; or


104

a. A fine-earth fraction with both a bulk
density of 1.0 g/cm} or less, measured at 33
kPa water retention, and aluminum plus 1/2
iron percentages (by ammonium oxalate)
totaling more than 1.0; or

b. More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or

c. A fine-earth fraction containing 30
percent or more particles 0.02 to 2.0 mm in
diameter, and either:

(1) In the 0.02-to-2.0-mm fraction,
more than 30 percent volcanic glass;
or

(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more.
Aquandic Glossudalfs

TEEC. Other Glossudalfs that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm: or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0,

Andic Glossudalfs

TEED. Other Glossudalfs that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Glossudalfs

IEEE. Other Glossudalfs that have, in one or more
subhorizons within the upper 25 cm of the argillic
horizon, redox depletions with a chroma of 2 or less,


356

HEBY, Other Cryoborolls that have a calcic horizon
either within or directly below the mollic epipedon.
Calcic Cryoborolls

HEBZ. Other Cryoborolls that have an albic horizon
directly below the mollic epipedon.

Albic Cryoborolls
HEBZa. Other Cryoborolls.

Typic Cryoborolls
Haploborolis
Key to subgroups

HEGA. Haploborolls which have a salic horizon that has
its upper boundary within 75 cm of the mineral soil
surface.

Salorthidic Haploborolls

HEGB, Other Haploborolls that have, in part but not all
of each pedon, a lithic contact within 50 cm of the
mineral soil surface.

Ruptic-Lithic Haploborolls

HEGC. Other Haploborolls that have a lithic contact
within 50 cm of the mineral soil surface.
Lithic Haploborolls

HEGD, Other Haploborolls which have both:

1. Either a chroma of | or less (crushed and
smoothed sample) in the upper 18 cm of the
mollic epipedon, after mixing, or in an Ap horizon
18 cm or more thick, or a moisture control section
that is not dry in all its parts throughout the year
in 6 or more out or of 10 years; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower.

Udertic Haploborolls

HEGE. Other Haploborolls which have one or both of
the following:

1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has


415

DACD. Other Eutraquox that have 16 kg/m? or more
organic carbon between the mineral soil surface and a
depth of 100 cm.

Humic Eutraquox
DACE, Other Eutraquox.
Typic Eutraquox
Haplaquox
Key to subgroups
DADA. Haplaquox that have a histic epipedon.
Histic Haplaquox

DADB. Other Haplaquox that have 5 percent or more
(by volume) plinthite in one or more horizons within
125 cm of the mineral soil surface.

Plinthic Haplaquox

DADC. Other Haplaquox which have, directly below an
epipedon, a horizon 10 cm or more thick that has 50
percent or more chroma of 3 or more.

Aeric Haplaquox

DADD. Other Haplaquox that have 16 kg/m? or more
organic carbon between the mineral soil surface and a
depth of 100 cm.

Humic Haplaquox
DADE. Other Haplaquox.
Typie Haplaquox
Plinthaquox
Key to subgroups

DABA. Plinthaquox which have, directly below an
epipedon, a horizon 10 cm or more thick that has 50
percent or more chroma of 3 or more.

Aeric Plinthaquox
DABB. Other Plinthaquox.

Typic Plinthaquox
PEROX
Key to great groups

DDA. Perox that have a sombric horizon within 150 cm
of the mineral soil surface.
Sombriperox, p. 423

DDB. Other Perox that have, in one or more
subhorizons of the oxic or kandic horizon within 150 cm
of the mineral soil surface, an ECEC of less than 1.50
emol(+)/kg clay and a pH value (in 1N KCl) of 5.0 or
more.

Acroperox, p. 416


432

DEDK. Other Kandiudox that have 16 kg/m? or more
organic carbon between the mineral soil surface and a
depth of 100 cm.

Humic Kandiudox

DEDL. Other Kandiudox that have 50 percent or more
hue of 2.5YR or redder and color value, moist, of 3 or
Jess between 25 and 125 cm from the mineral soil
surface.

Rhodic Kandiudox

DEDM. Other Kandiudox that have 50 percent or more
hue of 7.5YR or yellower and color value, moist, of 6 or
more between 25 and 125 cm from the mineral soil
surface.

Xanthic Kandiudox
DEDN. Other Kandiudox.
Typic Kandiudox
Sombriudox
Key to subgroups

DEAA. Sombriudox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Sombriudox

DEAB, Other Sombriudox that have a lithic contact
within 125 cm of the mineral soil surface.
Lithic Sombriudox

DEAC. Other Sombriudox that have 16 kg/m? or more
organic carbon between the mineral soil surface and a
depth of 100 cm.

Humic Sombriudox
DEAD. Other Sombriudox.
Typic Sombriudox
USTOX
Key to great groups

DCA. Ustox that have a sombric horizon within 150 em
of the mineral soil surface,
Sombriustox, p. 440

DCB. Other Ustox that have, in one or more
subhorizons of the oxic or kandic horizon within 150 cm
of the mineral soil surface, an ECEC of less than 1.50
cmol(+)/kg clay and a pH value (in 1N KCl) of 5.0 or
more,

Acrustox, p. 433

DCC, Other Ustox that have a base saturation (by
NH,OAc) of 35 percent or more in all horizons within
125 cm of the mineral soil surface.

Eutrustox, p. 435


161
1. Two percent or more redox concentrations; or

2. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
redox depletions on faces of peds, or in the matrix
if peds are absent; or

3. Enough active ferrous iron to give a positive

reaction to «,a'-dipyridyl at a time when the soil

is not being irrigated.

Aquic Hydrudands

CGEC. Other Hydrudands which have, between 25 and
100 cm either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, both:

1. Extractable bases plus 1N-KCl-extractable AB*
totaling less than 2.0 cmol(+)/kg in the fine-earth
fraction of one or more horizons with a total
thickness of 30 cm or more; and

2. A layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic
epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more
that have a color value, moist, 1 unit or more
higher and an organic-carbon content 1 percent or
more (absolute) lower.

Acrudoxic Thaptic Hydrudands

CGED., Other Hydrudands that have extractable bases
plus 1N-KCl-extractable Al?* totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more
horizons with a total thickness of 30 cm or more,
between 25 and 100 cm either from the mineral soil
surface, or from the top of an organic layer with andic
soil properties, whichever is shallower.

Acrudoxic Hydrudands

CGEE. Other Hydrudands that have, between 25 and
100 cm either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of
a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that
have a color value, moist, 1 unit or more higher and an
organic-carbon content | percent or more (absolute)
lower,

Thaptic Hydrudands

CGEF. Other Hydrudands that have a sum of
extractable bases of more than 25.0 cmol(+)/kg in the
fine-earth fraction throughout one or more horizons with
a total thickness of 15 cm or more between 25 and 75
cm either from the mineral soil surface, or from the top
of an organic layer with andic soil properties, whichever
is shallower.

Eutric Hydrudands


30

diameter, in all horizons between the top of the cambic

horizon and either a depth of 100 cm from the mineral

soil surface, or a lithic or paralithic contact if shallower.
Rendollic Eutrochrepts

JDGP. Other Eutrochrepts that have an argillic horizon
in less than half of each pedon.
Ruptic-Alfic Eutrochrepts

JDGQ. Other Eutrochrepts.
Typic Eutrochrepts

Fragiochrepts

Key to subgroups

JDBA. Fragiochrepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction
with both a bulk density of 1.0 g/cm? or less, measured
at 33 kPa water retention, and aluminum plus 1/2 iron
erventages (by ammonium oxalate) totaling more than

0.

Andic Fragiochrepts

JDBB. Other Fragiochrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:
1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
2. A fine-carth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:
a. In the 0.02-to-2,0-mm fraction, more than
30 percent volcanic glass; or
b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling

0.40 or more.
Vitrandic Fragiochrepts

JDBC. Other Fragiochrepts that have, in one or more
horizons within 30 cm of the mineral soil surface,
distinct or prominent redox concentrations, and also
aquic conditions for some time in most years (or

artificial drainage),
Aquic Fragiochrepts

JDBD. Other Fragiochrepts that do not have an ochric
epipedon.
Umbric Fragiochrepts
JDBE. Other Fragiochrepts.
Typic Fragiochrepts


376

temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or
b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, is dry in some or all parts for less
than 120 cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 8°C.

Udertic Argiustolls

HFEE. Other Argiustolls which have one or both of the

following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Argiustolls

HFEF. Other Argiustolls that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm? or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Argiustolls

HFEG. Other Argiustolls which have both:

1. If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some or all parts for six tenths or more of
the cumulative days per year when the soil
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or
b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, remains moist in some or all parts for
less than 90 consecutive days per year when
the temperature at a depth of 50 cm below
the soil surface is higher than 8°C; and

2. Throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the

mineral soil surface, one or both of the following:


164

1. Extractable bases plus 1N-KCl-extractable A+
totaling less than 2.0 emol(+)/kg in the fine-earth
fraction of one or more horizons with a total
thickness of 30 cm or more, between 25 and 100
cm either from the mineral soil surface, or from
the top of an organic layer with andic soil
properties, whichever is shallower; and
2. Undried, a 1500-kPa water retention of less
than 30 percent throughout one or more layers
with andic soil properties that have a total
thickness of 25 cm more within 100 cm either of
the mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower.

Acrudoxic Vitric Melanudands

CGCI. Other Melanudands that have both:

1. Extractable bases plus 1N-KCl-extractable Al+
totaling less than 2.0 cmol(+)/kg in the fine-earth
fraction of one or more horizons with a total
thickness of 30 cm or more, between 25 and 100
cm either from the mineral soil surface, or from
the top of an organic layer with andic soil
properties, whichever is shallower; and

2. Undried, a 1500-kPa water retention of 70
percent or more throughout a layer 35 cm or more
thick within 100 cm either of the mineral soil
surface, or of the top of an organic layer with
andic soil properties, whichever is shallower.
Acrudoxic Hydric Melanudands

CGCJ. Other Melanudands that have extractable bases
plus 1N-KCl-extractable AP* totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more
horizons with a total thickness of 30 cm or more,
between 25 and 100 cm either from the mineral soil
surface, or from the top of an organic layer with andic
soil properties, whichever is shallower.

Acrudoxic Melanudands

CGCK. Other Melanudands that have both:

1. More than 6.0 percent organic carbon and
colors of a mollic epipedon throughout a layer 50
om or more thick within 60 cm either of the
mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower; and

2. Undried, a 1500-kPa water retention of less
than 30 percent throughout one or more layers
with andic soil properties that have a total
thickness of 25 cm more within 100 cm either of
the mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower.

Pachic Vitric Melanudands


168

CGAF, Other Placudands which have, undried, a 1500-
kPa water retention of less than 30 percent throughout
one or more layers with andic soil properties that have a
total thickness of 25 cm more within 100 cm either of
the mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Vitric Placudands

CGAG. Other Placudands that have both:

1. Undried, a 1500-kPa water retention of 70
percent or more throughout a layer 35 cm or more
thick within 100 cm either of the mineral soil
surface, or of the top of an organic layer with
andic soil properties, whichever is shallower; and

2. More than 6.0 percent organic carbon and
colors of a mollic epipedon throughout a layer 50
em or more thick within 60 cm either of the
mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower.

Hydric Pachic Placudands

CGAH. Other Placudands that have more than 6.0
percent organic carbon and colors of a mollic epipedon
throughout a layer 50 cm or more thick within 60 cm
either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Pachic Placudands

CGAL. Other Placudands that have, undried, a 1500-kPa
water retention of 70 percent or more throughout a layer
35 cm or more thick within 100 cm either of the mineral
soil surface, or of the top of an organic layer with andic
soil properties, whichever is shallower.

Hydric Placudands

CGAJ. Other Placudands that have, between 25 and 100
cm either from the mineral soil surface, or from the top
of an organic layer with andic soil properties, whichever
is shallower, a layer 10 cm or more thick with more
than 3.0 percent organic carbon and colors of a mollic
epipedon throughout, underlying one or more horizons
with a total thickness of 10 cm or more that have a color
value, moist, ] unit or more higher and an organic-
carbon content 1 percent or more (absolute) lower.
Thaptic Placudands

CGAK. Other Placudands that have a sum of extractable
bases of more than 25.0 cmol(+)/kg in the fine-earth
fraction throughout one or more horizons with a total
thickness of 15 cm or more between 25 and 75 cm
either from the mineral soil surface, or from the top of
an organic layer with andic soil properties, whichever is
shallower.

Eutric Placudands

CGAL. Other Placudands.
Typic Placudands


438

surface, for 1 month or more per year in 6 or more out of
10 years.
Oxyaquic Haplustox

DCEJ. Other Haplustox which have an oxic horizon that
has its lower boundary within 125 cm of the mineral
soil surface.

Inceptic Haplustox

DCEK. Other Haplustox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 2.5YR or redder
and color value, moist, of 3 or less between 25
and 125 cm from the mineral soil surface,

Humic Rhodic Haplustox

DCEL. Other Haplustox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 7.5YR or yellower
and color value, moist, of 6 or more between 25
and 125 cm from the mineral soil surface.

Humic Xanthic Haplustox

DCEM. Other Haplustox that have 16 kg/m? or more
organic carbon between the mineral soil surface and-a-

depth of 100 cm,
Humic Haplustox

DCEN. Other Haplustox that have 50 percent or more
hue of 2.5YR or redder and color value, moist, of 3 or
less between 25 and 125 cm from the mineral soil
surface.

Rhodic Haplustox
DCEO. Other Haplustox that have 50 percent or more
hue of 7.5YR or yellower and color value, moist, of 6 or
more between 25 and 125 cm from the mineral soil
surface.

Xanthic Haplustox
DCEP. Other Haplustox.
Typic Haplustox
Kandiustox
Key to subgroups

DCDA. Kandiustox that have, within 125 cm of the
mineral soil surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage),

Aquic Petroferric Kandiustox


M

between the fingers with difficulty, the n value is
between 0.7 and 1.0; if the soil flows easily between the
fingers, the n value is 1 or more.

Paralithic contact

A paralithic (lithiclike) contact is a boundary between
soil and a 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 does not
consist of a single mineral, chunks of gravel size that
can be broken out disperse more or less completely
during 15 hours of shaking in water or in a sodium
hexametaphosphate solution and, when moist, the
material can be dug with difficulty with a spade.
Normally the material underlying a paralithic contact is
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 their horizontal spacing is
10 cm or more.

Permafrost

Permafrost is a layer in which the temperature is
perennially at or below 0°C, whether its 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 either
absent or present only in traces. The indurated layer
must be continuous within the limits of each pedon, but
may be fractured if the average lateral distance between
fractures is 10 cm or more. The fact that this ironstone
layer contains little or no organic matter distinguishes it
from a placic horizon and from an indurated spodic
horizon (ortstein, see below), both of which contain
organic matter.

Several features can aid in making the distinction
between a lithic and a petroferric contact. First, a
petroferric contact is roughly horizontal. Second, the
material directly below a petroferric contact contains a
high amount of iron (normally 30 percent or more
Fe,0,). Third, the ironstone sheets below a petroferric
contact are thin; their thickness ranges from a few
centimeters to very few meters, Sandstone, on the other
hand, may be thin or very thick, may be level-bedded or
tilted, and may contain only a small percentage of
Fe,0;. In the tropics, the ironstone is generally more or
less vesicular,



Chapter 16

Vertisols*

KEY TO SUBORDERS

EA. Vertisols which have, in one or more horizons
between 40 and 50 cm from the mineral soil surface,
aquic conditions for some time in most years (or
artificial drainage) and one or both of the following:
1. In more than half of each pedon, either on faces
of peds or in the matrix if peds are absent, 50
percent or more chroma of either

a. Two or less if redox concentrations are
present; or
b. One or less; or
2. Enough active ferrous iron to give a positive
reaction to a,,a'-dipyridyl at a time when the soil
is not being irrigated.
Aquerts, p. 492
EB. Other Vertisols that have a cryic soil temperature
regime.
Cryerts, p. 499
EC. Other Vertisols which, in 6 or more out of 10 years,
have both:

1, A thermic, mesic, or frigid soil temperature
regime; and
2. If not irrigated during the year, cracks that
remain both:
a. Five mm or more wide, through a
thickness of 25 cm or more within 50 cm of
the mineral soil surface, for 60 or more
consecutive days during the 90 days
following the summer solstice; and

b. Closed for 60 or more consecutive days
during the 90 days following the winter
solstice.

Xererts, p. 511

ED. Other Vertisols which, if not irrigated during the
year, have cracks in 6 or more out of 10 years that
remain closed for less than 60 consecutive days during a
period when the soil temperature at a depth of 50 cm
from the soil surface is higher than 8°C.

Torrerts, p. 500

1 This chapter on Vertisols was rewritten in 1992 following the
recommendations of the Intemational Committee on the Classification of
Vertisols (ICOMERT), chaired by Juan Comerma,

Vv
E


174

CEAD., Other Ustivitrands which have a calcic horizon
that has its upper boundary within 125 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Calcic Ustivitrands

CEAE, Other Ustivitrands that have an umbric
epipedon.

Humic Ustivitrands
CEAF. Other Ustivitrands.
Typic Ustivitrands
XERANDS
Key to great groups

CDA. Xerands that have a 1500-kPa water retention of
less than 15 percent on air-dried samples and of less
than 30 percent on undried samples, throughout one or
more horizons with a total thickness of 35 cm or more
within 60 cm either of the mineral soil surface, or of the
top of an organic layer with andic soil properties,
whichever is shallower.

Vitrixerands, p. 176

CDB. Other Xerands that have a melanic epipedon.
Melanoxerands, p. 175

CDC. Other Xerands.
Haploxerands, p. 174

Haploxerands

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

Lithic Haploxerands

CDCB, Other Haploxerands that have, in one or more
horizons between 50 and 100 cm either from the
mineral soil surface, or from the top of an organic layer
with andic soil properties, whichever is shallower, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:

1. Two percent or more redox concentrations; or

2. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
redox depletions on faces of peds, or in the matrix
if peds are absent; or

3, Enough active ferrous iron to give a positive
reaction to a,a'-dipyridyl at a time when the soil
is not being irrigated.

Aquic Haploxerands


a7

ABAG. Other Sphagnofibrists that have, within organic
materials, either one mineral layer 5 cm or more thick,
or two or more mineral layers of any thickness, in the
control section below the surface tier.

Fluvaquentic Sphagnofibrists

ABAH. Other Sphagnofibrists that have one or more
layers, with a total thickness of 25 cm or more, of the
subsurface and bottom tiers consisting of hemic
materials.

Hemic Sphagnofibrists

ABAI. Other Sphagnofibrists that have one or more
layers, with a total thickness of 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 which have both:

1. One or more layers, with a total thickness of 25
cm or more, of the subsurface and bottom tiers
consisting of hemic materials; and

2, A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Hemic Terric Tropofibrists

ABDD. Other Tropofibrists which have both:

1, One or more layers, with a total thickness of
12.5 cm or more, of the subsurface and bottom
tiers consisting of sapric materials; and
2. A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Sapric Terric Tropofibrists

ABDE. Other Tropofibrists which have a mineral layer
30 cm or more thick that has its upper boundary within
the control section below the surface tier.

Terric Tropofibrists


381

HFDG. Other Calciustolls which have a petrocalcic
horizon that has its upper boundary within 100 cm of
the mineral soil surface.

Petrocalcic Calciustolls

HFDH. Other Calciustolls that have a mollic epipedon
40 cm or more thick with a texture finer than loamy fine
sand.

Pachic Calciustolls

HFDI. Other Calciustolls that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
concentrations, and also aquic conditions for some time
in most years (or artificial drainage).
Aquic Calciustolls

HFDJ. Other Calciustolls that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Calciustolls

HEDK. Other Calciustolls which have, if neither
irrigated nor fallowed to store moisture, either:

1. A mesic or thermic soil temperature regime,
and a moisture contro! section which, in 6 or more
out of 10 years, is dry in some or all parts for six
tenths or more of the cumulative days per year
when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5°C; or

2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years,
remains moist in some or all parts for less than 90
consecutive days per year when the temperature at
a depth of 50 cm below the soil surface is higher
than 8°C,

Aridic Calciustolls

HFDL. Other Calciustolls which have, if neither
irrigated nor fallowed to store moisture, either:

1. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some or all parts for four
tenths or less of the cumulative days per year
when the temperature at a depth of 50 cm below
the soil surface is higher than 5°C; or

2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is dry
in some or all parts for less than 120 cumulative
days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8°C.
Udic Calciustolls

HFDM. Other Calciustolls.
Typic Calciustolls

ros


amt

1, Within 40 cm of the mineral soil surface, in
horizons that also have redoximorphic features; or

2. Directly below the mollic epipedon, in one or
more horizons with a total thickness of 15 cm or
more that have one or more of the following:

a. A color value, moist, of 4 or more and
redox depletions with a chroma of 2 or less;
or

b. A hue of 10YR or redder and a chroma of
2 or less; or

c. A hue of 2.5Y or yellower and a chroma
of 3 or less.
Aquic Hapludolls

HGEI. Other Hapludolls that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Hapludolis

HGEJ. Other Hapludolls which have both:

1. Either 0.3 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

2. A slope of less than 25 percent.
Fluventic Hapludolls

HGEK. Other Hapludolls which have both:

1, A mollic epipedon 60 cm or more thick that has
a texture finer than loamy fine sand and contains
50 percent or more (by volume) wormholes, worm
casts, or filled animal burrows, either below an
Ap horizon or below a depth of 18 cm from the
mineral soil surface; and

2. Either do not have a cambic horizon and do not,
in the lower part of the mollic epipedon, meet the
requirements for a cambic horizon except color, or
have carbonates throughout either the cambic
horizon or the lower part of the mollic epipedon.
Vermic Hapludolis

HGEL. Other Hapludolls that have a calcic horizon
within 100 cm of the mineral soil surface.
Calcic Hapludolls

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

Entic Hapludolls


230

a. In the upper 40 cm of the soil, if the upper
boundary of the petrocalcic horizon is 40 cm
or more below the soil surface,

(1) 0.60 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.15 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.64-(0.038 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
1 and 13; or

b. In the upper 18 cm of the soil, if the
upper boundary of the petrocalcic horizon is
between 18 and 40 cm from the soil surface,

(1) 0.72 or more, with a
.sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.18 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.77-{0,046 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
1 and 13.

Ustollic Paleorthids

FBBE. Other Paleorthids which have both:

1. A moisture control section that is dry in all its
parts for less than three fourths of the cumulative
days per year in 6 or more out of 10 years when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and

2. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime,
Xerochreptic Paleorthids

FBBF. Other Paleorthids which have both:

1. A moisture control section that is dry in all its
parts for less than three fourths of the cumulative
days per year in 6 or more out of 10 years when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and
2, A mesic, thermic, or hyperthermic soil
temperature regime, and an aridic moisture
regime that borders on an ustic regime.
Ustochreptic Paleorthids


497

sodium adsorption ratio of 13 or more) for 6 or more
months per year in 6 or more out of 10 years.
Sodic Epiaquerts

EAFC. Other Epiaquerts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
are 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 210
or more cumulative days per year.

Aridic Epiaquerts
EAFD. Other Epiaquerts which have a thermic, mesic,
or frigid soil temperature regime and which, if not
irrigated during the year, have cracks in 6 or more out of
10 years that remain both:

1. Five mm or more wide, through a thickness of
25 om or more within 50 cm of the mineral soil
surface, for 60 or more consecutive days during
the 90 days following the summer solstice; and

2. Closed for 60 or more consecutive days during
the 90 days following the winter solstice.
Xeric Epiaquerts

EAFE. Other Epiaquerts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
are 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 90 or
more cumulative days per year.

Ustic Epiaquerts
EAFF. Other Epiaquerts that have, in one or more
horizons between either an Ap horizon or a depth of 25
cm from the mineral soil surface, whichever is deeper,
and a depth of 75 cm, 50 percent or more colors as
follows:

1. A hue of 2.5Y or redder and either:

a. A color value, moist, of 6 or more and a
chroma of 3 or more; or

b. A color value, moist, of 5 or less and a
chroma of 2 or more; or

2. A hue of SY and a chroma of 3 or more; or

3. A chroma of 2 or more, and no redox
concentrations.
Aeric Epiaquerts

EAFG. Other Epiaquerts that have a lithic or paralithic
contact within 100 cm of the mineral soil surface.

Leptic Epiaquerts
EAFH. Other Epiaquerts which have a layer 25 cm or
more thick that contains less than 27 percent clay in its
fine-earth fraction and has its upper boundary within
100 cm of the mineral soil surface.

Entic Epiaquerts

EAFI. Other Epiaquerts that have, in one or more
horizons within 30 cm of the mineral soil surface, one

mm<


514
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or

3. A chroma of 3 or more.
Chromic Haploxererts
ECCJ. Other Haploxererts.
Typic Haploxererts


453

weighted average of 1.2 percent or more
organic carbon in the upper 10 cm; nor

b. A coarse-loamy or loamy-skeletal particle
size, and a color value, moist, and chroma of
3 or less (crushed and smoothed sample) in
the upper 7.5 cm; nor

c. A sandy-skeletal or sandy particle size,
and a color value, moist, and chroma of 3 or
less (crushed and smoothed sample) in the
upper 2.5 cm.

Entic Lithic Haplorthods

BDEB. Other Haplorthods that have a lithic contact
within 50 cm of the mineral soil surface.
Lithic Haplorthods

BDEC. Other Haplorthods which have both:

1, In one or more horizons within 75 cm of the
mineral soil surface, redoximorphic features, and
also aquic conditions for some time in most years
(or artificial drainage); and
2. Within 200 cm of the mineral soil surface, an
argillic or a kandic horizon that has a base
saturation of 35 percent or more (by sum of
cations) in some part.

Aqualfic Haplorthods

BDED. Other Haplorthods which have both:

1, In one or more horizons within 75 cm of the
mineral soil surface, redoximorphic features, and
also aquic conditions for some time in most years
(or artificial drainage); and

2. A spodic horizon that does not have any of the
following:

a, A texture of very fine sand or finer, a
thickness of more than 10 cm, anda
weighted average of 1.2 percent or more
organic carbon in the upper 10 cm; nor

b. A coarse-loamy or loamy-skeletal particle
size, and a color value, moist, and chroma of
3 or less (crushed and smoothed sample) in
the upper 7.5 cm; nor

c. A sandy-skeletal or sandy particle size,
and a color value, moist, and chroma of 3 or
less (crushed and smoothed sample) in the
upper 2.5 cm.

Aquentic Haplorthods

BDEE. Other Haplorthods that have, in one or more
horizons within 75 cm of the mineral soil surface,
redoximorphic features, and also aquic conditions for
some time in most years (or artificial drainage).

Aquic Haplorthods

Oo


114

TEIG. Other Paleudalfs that are saturated with water, in
one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Paleudalfs

IEIH. Other Paleudalfs that have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic horizon at a depth of 50 to 100 cm;
and

2. Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface.

Arenic Plinthic Paleudalfs

TEI. Other Paleudalfs that have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic horizon at a depth of 100 cm or
more; and

2, Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface.
Grossarenic Plinthic Paleudalfs
TEM. Other Paleudalfs which have an argillic horizon
that has a texture of loamy fine sand or coarser, or is
discontinuous horizontally, or is discontinuous vertically
within its upper 20 cm.
Psammentic Paleudalfs
TEIK, Other Paleudalfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
to 100 cm.
Arenic Paleudalfs

IEIL. Other Paleudalfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 100
cm or more.

Grossarenic Paleudalfs

IEIM. Other Paleudalfs that have 5 percent or more (by
volume) plinthite in one or more horizons within 150
cm of the mineral soil surface.

Plinthic Paleudalfs

TEIN. Other Paleudalfs that have either:

1. In the upper part of the argillic horizon, one or
more subhorizons that have 5 percent or more (by
volume) skeletans with a chroma of 2 or less; or

2. Five percent or more (by volume) albic
materials in some subhorizon of the argillic
horizon.

Glossic Paleudalfs


377

a. More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or

b. A fine-earth fraction containing 30
percent or more particles 0.02 to 2.0 mm in
diameter, and either:

(1) In the 0.02-to-2.0-mm fraction,
more than 30 percent volcanic glass;
or

(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0,40 or more.
Vitritorrandic Argiustolls

HFEH. Other Argiustolls that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soi] surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
2. A fine-earth fraction containing 30 percent or
more particles 0,02 to 2.0 mm in diameter, and
either:
a. In the 0,02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Argiustolls

HFEL. Other Argiustolls which have a mean annual soil
temperature lower than 10°C, and either:

1. Above the argillic horizon, an albic horizon, or
a horizon that has color values too high for a
mollic epipedon and a chroma too high for an
albic horizon; or
2. A glossic horizon, or interfingering of albic
materials into the upper part of the argillic
horizon, or skeletans of clean silt and sand
covering 50 percent or more of the faces of peds in
the upper 5 cm of the argillic horizon.

Boralfic Argiustolls

HFEJ. Other Argiustolls which have either:

1. Above the argillic horizon, an albic horizon, or
a horizon that has color values too high for a



444

BAEB, Other Duraquods which have andic soil
properties throughout horizons that have a total
thickness of 25 om or more within 75 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.

Andic Duraquods
BAEC. Other Duraquods.
Typic Duraquods
Endoaquods
Key to subgroups
BAGA. Endoaquods that have a histic epipedon.
Histic Endoaquods

BAGB, Other Endoaquods which have andic soil
properties throughout horizons that have a total
thickness of 25 cm or more within 75 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Andic Endoaquods

BAGC. Other Endoaquods that have an argillic or a
kandic horizon within 200 cm of the mineral soil
surface.

Argic Endoaquods

BAGD. Other Endoaquods that have an umbric
epipedon.

Umbric Endoaquods
BAGE, Other Endoaquods.
Typic Endoaquods
Epiaquods
Key to subgroups
BAFA, Epiaquods that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Epiaquods
BAFB. Other Epiaquods that have a histic epipedon.
Histic Epiaquods

BAFC. Other Epiaquods which have andic soil
properties throughout horizons that have a total
thickness of 25 cm or more within 75 cm cither of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Andic Epiaquods

BAFD. Other Epiaquods which have, within 200 cm of
the mineral soil surface, an argillic or a kandic horizon
that has a base saturation of 35 percent or more (by sum
of cations) in some part.

Alfic Epiaquods


INDEX



265

KCCL Other Quartzipsamments which have lamellae
within 200 cm of the mineral soil surface that meet all
the requirements for an argillic horizon except
thickness or clay content.

Argic Quartzipsamments

KCCI. Other Quartzipsamments that have an ustic
moisture regime.
Ustic Quartzipsamments
KCCK. Other Quartzipsamments that have a xeric
moisture regime,
Xeric Quartzipsamments
KCCL. Other Quartzipsamments which have a horizon
5 cm or more thick, either below an Ap horizon or at a
depth of 18 cm or more from the mineral soil surface,
whichever is deeper, that has one or more of the
following:
1, In 25 percent or more of each pedon,
cementation by organic matter and aluminum,
with or without iron; or
2, Aluminum plus 1/2 iron percentages (by
ammonium oxalate) totaling 0.25 or more, and
half that amount or less in an overlying horizon;
or

3. An ODOE value of 0.12 or more, and a value
half as high or lower in an overlying horizon.

Spodic Quartzipsamments -
KCCM,. Other Quartzipsamments. F
Typic Quartzipsamments T
Torripsamments
Key to subgroups

KCBA. Torripsamments that have a lithic contact within
50 cm of the soil surface.
Lithic Torripsamments

KCBB. Other Torripsamments which have:

1. A horizon within 100 cm of the soil surface that
is 15 cm or more thick and either contains 20
percent or more (by volume) durinodes or is
brittle and has firm consistence when moist; and

2. A moisture control section which, in 6 or more
out of 10 years, is dry in all its parts for less than
three fourths of the cumulative days per year when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and

6 See foomote 5.


193

depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Haploxerollic Nadurargids

FAAE. Other Nadurargids which have a duripan that is
not indurated in any subhorizon.
Haplic Nadurargids

FAAF. Other Nadurargids which have:

1. A duripan 18 cm or more below the soil
surface; and

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if the upper
boundary of the duripan is 40 cm or more
below the soil surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 cm of the soil, if the
upper boundary of the duripan is between 18
and 40 cm from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

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

Xerollic Nadurargids
FAAG. Other Nadurargids.
Typic Nadurargids
Natrargids
Key to subgroups

FACA. Natrargids which have:

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


499
CRYERTS

Key to great groups

EBA. Cryerts that have 10 kg/m? or more organic carbon
between the mineral soil surface and a depth of 50 cm.
Humicryerts, p. 499

EBB. Other Cryerts.
Haplocryerts, p. 499

Haplocryerts

Key to subgroups

EBBA. Haplocryerts that have, in one or more horizons
within 100 cm of the mineral soil surface, an
exchangeable sodium percentage of 15 or more (or a
sodium adsorption ratio of 13 or mote) for 6 or more
months per year in 6 or more out of 10 years.

Sodic Haplocryerts

EBBB. Other Haplocryerts that have, in one or more.
horizons within 30 cm of the mineral soil surface, 50
percent or more colors as follows:

1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. A chroma of 3 or more.

Chromic Haplocryerts
EBBC. Other Haplocryerts.
Typic Haplocryerts
Humicryerts
Key to subgroups

EBAA. Humicryerts that have, in one or more horizons
within 100 cm of the mineral soil surface, an
exchangeable sodium percentage of 15 or more (or a
sodium adsorption ratio of 13 or more) for 6 or more
months per year in 6 or more out of 10 years.

Sodic Humicryerts

EBAB. Other Humicryerts.
Typic Humicryerts



ut
3. A hue of 2.5Y or yellower and a chroma of 2 or
more if there are no distinct or prominent redox
concentrations.

Aeric Calciaquolls
HBDC. Other Calciaquolls.

Typic Calciaquolls
Cryaquolis
Key to subgroups

HBAA. Cryaquolls that have a mean annual soil
temperature of 0°C or lower.
Pergelic Cryaquolls

HBAB, Other Cryaquolls which have one or both of the
following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped.
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,

whichever is shallower.
Vertic Cryaquolls
HBAC. Other Cryaquolls that have a histic epipedon.
Histic Cryaquolls

HBAD. Other Cryaquolls which have a buried Histosol
that has its upper boundary within 100 cm of the
mineral soil surface.

Thapto-Histic Cryaquolls

HBAE. Other Cryaquolls which have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or more of
the following:

1. A fine-earth fraction with both a bulk density of
1.0 g/cm} or less, measured at 33 kPa water

retention, and aluminum plus 1/2 iron percentages
(by ammonium oxalate) totaling more than 1.0; or

2. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

3. A fine-earth fraction containing 30 percent or

more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or


263

KCAB, Other Cryopsamments that have a mean annual
soil temperature of 0°C or lower.
Pergelic Cryopsamments

KCAC. Other Cryopsamments that have, in one or more
horizons within 50 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Cryopsamments

KCAD. Other Cryopsamments that are saturated with
water, in one or more layers within 100 cm of the
mineral soil surface, for 1 month or more per year in 6
or more out of 10 years.

Oxyaquic Cryopsamments

KCAE. Other Cryopsamments which have a horizon 5
cm or more thick that has one or more of the following:

1. In 25 percent or more of each pedon,
cementation by organic matter and aluminum,
with or without iron; or

2. Aluminum plus 1/2 iron percentages (by
ammonium oxalate) totaling 0.25 or more, and
half that amount or less in an overlying horizon;
or

3, An ODOE value of 0.12 or more, and a value
half as high or lower in an overlying horizon.
Spodic Cryopsamments
KCAF. Other Cryopsamments which have lamellae
within 200 cm of the mineral soil surface that meet all
the requirements for an argillic horizon except
thickness.

Argic Cryopsamments

KCAG. Other Cryopsamments.
Typic Cryopsamments

Quartzipsamments

Key to subgroups

KCCA. Quartzipsamments that have a lithic contact
within 50 cm of the mineral soil surface.
Lithic Quartzipsamments

KCCB. Other Quartzipsamments which have both:

1, In one or more horizons within 100 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. A horizon 5 cm or more thick, either below an
Ap horizon or at a depth of 18 cm or more from
the mineral soil surface, whichever is deeper, that
has one or more of the following:


257

1, More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or

more particles 0.02 to 2.0 mm in diameter, and
either:

a, In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling

0.40 or more.
Vitrandic Troporthents
KEDD. Other Troporthents.
Typic Troporthents
Udorthents
Key to subgroups
KEFA. Udorthents that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Udorthents

KEFB, Other Udorthents that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm} or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

4zm

Andic Udorthents

KEFC. Other Udorthents that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-carth fraction containing 30 percent or
mere particles 0,02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b, In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Udorthents


273

ABCB, Other Borofibrists that have a lithic contact
within the control section.
Lithic Borofibrists

ABCC. Other Borofibrists which have both:

1, Three fourths or more of the fiber volume in the
surface tier derived from Sphagnum; and

2. A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Sphagnic Terric Borofibrists

ABCD, Other Borofibrists which have both:

1, One or more layers, with a total thickness of 25
cm or more, of the subsurface and bottom tiers
consisting of hemic materials; and

2. A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Hemic Terric Borofibrists

ABCE. Other Borofibrists which have both;

1, One or more layers, with a total thickness of
12,5 cm or more, of the subsurface and bottom
tiers consisting of sapric materials; and

2. A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Sapric Terric Borofibrists

ABCF, Other Borofibrists which have a mineral layer
30 cm or more thick that has its upper boundary within
the control section below the surface tier.

Terric Borofibrists

ABCG. Other Borofibrists that have one or more limnic
layers with a total thickness of 5 cm or more within the
control section.

Limnic Borofibrists

ABCH. Other Borofibrists that have, within organic
materials, either one mineral layer 5 cm or more thick,
or two or more mineral layers of any thickness, in the
control section below the surface tier.

Fluvaquentic Borofibrists

ABCI. Other Borofibrists that have three fourths or
more of the fiber volume in the surface tier derived from
Sphagnum.

Sphagnic Borofibrists
ABC]. Other Borofibrists that have one or more layers,
with a total thickness of 25 cm or more, of the
subsurface and bottom tiers consisting of hemic
materials.

Hemic Borofibrists


224

(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more.
Ustivitrandic Durorthids

FBCE. Other Durorthids which have:

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

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to noncarbonate clay, as follows:

a. In the upper 40 cm of the soil, if the upper
boundary of the duripan is 40 cm or more
below the soil surface,

(1) 0.60 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.15 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.64-(0.038 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
land 13; or

b. In the upper 18 cm of the soil, if the

upper boundary of the duripan is between 18
and 40 cm from the soil surface,

(1) 0.72 or more, with a

sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.18 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.77-(0.046 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
1 and 13; and

3. A mean annual soil temperature lower than
22°C, a difference of S°C or more between mean.
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Haploxerollic Durorthids

FBCF. Other Durorthids which have:

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

2. An aridic moisture regime that borders on an
ustic regime; and


476
GCDB. Other Kanhapludults that have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic or a kandic horizon at a depth of 50
to 100 cm; and

2. Five percent or more (by volume) plinthite in
‘one or more horizons within 150 cm of the
mineral soil surface.

Arenic Plinthic Kanhapludults

GCDC. Other Kanhapludults that have a sandy particle
size throughout a layer extending from the mineral soil
surface to the top of an argillic or a kandic horizon at a
depth of 50 to 100 cm.

Arenic Kanhapludults

GCDD. Other Kanhapludults that have an ECEC of 1.5
cmol(+)/kg clay or less (sum of bases extracted with 1N
NH,OAc pH 7, plus 1N-KCl-extractable Al) in one or
more horizons within 150 cm of the mineral soil
surface,

Acrudoxic Kanhapludults

GCDE. Other Kanhapludults that have both:

1. Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface; and

2. In one or more layers within 75 cm of the
mineral soil surface, redox depletions with a color
value, moist, of 4 or more and a chroma of 2 or
less, accompanied by redox concentrations, and
also aquic conditions for some time in most years
(or artificial drainage).

Plinthaquic Kanhapludults

GCDF. Other Kanhapludults that have, throughout one
or more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm? or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Kanhapludults

GCDG., Other Kanhapludults that have, in one or more
layers within 75 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and a
chroma of 2 or less, accompanied by redox.
concentrations, and also aquic conditions for some time
in most years (or artificial drainage).
Aquic Kanhapluduits

GCDH. Other Kanhapludults that have 5 percent or
more (by volume) plinthite in one or more horizons
within 150 cm of the mineral soil surface.

Plinthic Kanhapludults


135

its upper 75 cm or above a lithic or paralithic contact,
whichever is shallower.
Ultic Haploxeralfs

IDGO. Other Haploxeralfs that have a color value,
moist, of 3 or less and 0.7 percent or more organic

carbon, either throughout an Ap horizon or throughout
the upper 10 cm of an A horizon.

Molllc Haploxeralfs
IDGP. Other Haploxeralfs.

Typic Haploxeralfs
Natrixeralfs
Key to subgroups

IDBA. Natrixeralfs which have one or both of the

following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Natrixeralfs

IDBB. Other Natrixeralfs that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Natrixeralfs.
IDBC. Other Natrixeralfs.

Typic Natrixeralfs
Palexeralfs
Key to subgroups
IDFA. Palexeralfs which have one or both of the
following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or


479

also aquic conditions for some time in most years
(or artificial drainage).
Aquic Arenic Paleudults

GCEG. Other Paleudults that have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic horizon at a depth of 50 to 100 cm;
and

2. Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface.
Arenic Plinthic Paleudults
GCEH. Other Paleudults which have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic horizon at a depth of 50 to 100 cm;
and

2, Throughout the upper 100 cm of the argillic
horizon,

a. A color value, moist, of 3 or less and a
color value, dry, that is no more than 1 unit
higher than the value, moist; and

b. No redox concentrations with a chroma of
3 or more,
Arenic Rhodic Paleudults

GCEI. Other Paleudults that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
to 100 cm.

Arenic Paleudults

GCEJ. Other Paleudults that have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic horizon at a depth of 100 cm or
more; and

2. Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface.

Grossarenic Plinthic Paleudults

GCEK. Other Paleudults that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 100
cm or more.

Grossarenic Paleudults

GCEL. Other Paleudults that have both:

1. Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface; and

4rc


176
Vitrixerands

Key to subgroups

CDAA. Vitrixerands that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Vitrixerands

CDAB. Other Vitrixerands that have, in one or more
horizons between 50 and 100 cm either from the
mineral soil surface, or from the top of an organic layer
with andic soil properties, whichever is shallower, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:

1, Two percent or more redox concentrations; or

2. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
redox depletions on faces of peds, or in the matrix
if peds are absent; or
3, Enough active ferrous iron to give a positive
reaction to a,a’'-dipyridyl at a time when the soil
is not being irrigated.
Aquic Vitrixerands
CDAC. Other Vitrixerands that have, between 25 and
100 cm from the mineral soil surface, a layer 10 cm or
more thick with more than 3.0 percent organic carbon
and colors of a mollic epipedon throughout, underlying
‘one or more horizons with a total thickness of 10 cm or
more that have a color value, moist, 1 unit or more
higher and an organic-carbon content 1 percent or more
(absolute) lower.
Thaptic Vitrixerands

CDAD. Other Vitrixerands which have both:

1, A melanic, a mollic, or an umbric epipedon;
and

2. An argillic or a kandic horizon that has its
upper boundary within 125 cm of the mineral soil
surface, or of the top of an organic layer with
andic soil properties, whichever is shallower.
Alfic Humic Vitrixerands

CDAE, Other Vitrixerands which have an argillic or a
kandic horizon that has its upper boundary within 125

cm of the mineral soil surface.
Alfic Vitrixerands
CDAF. Other Vitrixerands that have a melanic, 2
mollic, or an umbric epipedon.
Humic Vitrixerands

CDAG. Other Vitrixerands.
Typic Vitrixerands


JE. Other Inceptisols.
‘Umbrepts, p. 328

AQUEPTS

Key to great groups

JAA. Aquepts which have a sulfuric horizon that has its
upper boundary within 50 cm of the mineral soil
surface.

Sulfaquepts, p. 299

JAB. Other Aquepts that have, in half or more of each
pedon, a placic horizon within 100 cm of the mineral

soil surface.
Placaquepts, p. 298

JAC. Other Aquepts that have, in one or more horizons
with a total thickness of 25 cm or more within 50 cm of
the mineral soil surface, either an exchangeable sodium
percentage (ESP) of 15 or more (or a sodium adsorption
ratio, SAR, of 13 or more), and a decrease in ESP (or
SAR) values with increasing depth below 50 cm.
Halaquepts, p. 296

JAD. Other Aquepts that have a fragipan.
Fragiaquepts, p. 295
JAE, Other Aquepts that have a eryic or pergelic soit

temperature regime.
Cryaquepts, p. 291

JAF. Other Aquepts that have one or more horizons
within 125 cm of the mineral soil surface in which
plinthite either forms a continuous phase or constitutes
one half or more of the volume.
Plinthaquepts, p. 299
JAG. Other Aquepts that have a difference of less than
5°C between mean summer and mean winter soil
temperatures either at a depth of 50 cm from the soil
surface, or at a lithic or paralithic contact, whichever is
shallower.
Tropaquepts, p. 299
JAH. Other Aquepts that have a histic, a mollic, or an
umbric epipedon.
Humaquepts, p. 297
JAI. Other Aquepts that have episaturation.
Epiaquepts, p. 294

JAJ. Other Aquepts.
Endoaquepts, p. 293


Argiaquolls
Key to subgroups
HBEA. Argiaquolls that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
cm to 100 cm.
Arenic Argiaquolls

HBEB. Other Argiaquolls that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 100
cm or more.

Grossarenic Argiaquolls

HBEC. Other Argiaquolls which have one or both of the
following:
1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.
Vertic Argiaquolls

HBED. Other Argiaquolls which have an argillic
horizon that has a clay increase with depth of 20 percent
or more (absolute, in the fine-earth fraction) within its
‘upper 7.5 cm, .

Abruptic Argiaquolls
HBEE. Other Argiaquolls.
Typic Argiaquolls
Calciaquolls
Key to subgroups

HBDA. Calciaquolls which have a petrocalcic horizon
that has its upper boundary within 100 cm of the
mineral soil surface.
Petrocalcic Calciaquolis

HBDB. Other Calciaquolls that have 50 percent or more
chroma of 3 or more on faces of peds or in the matrix of
‘one or more horizons within 75 cm of the mineral soil
surface, or have, directly below the mollic epipedon,
colors as follows:

1. A hue of 2.5Y or yellower and a chroma of 3 or

more; or

2. A hue of 10YR or redder and a chroma of 2 or

more; or


361

HECB. Other Natriborolls that have visible crystals of
gypsum anW/or more soluble salts within 40 cm of the
mineral soil surface.

Leptic Natriborolls

HECC. Other Natriborolls which have both:

1. A color value, dry, of 5 or more either in the
upper 18 cm of the mollic epipedon, after mixing,
or in an Ap horizon 18 cm or more thick; and

2. A moisture control section which, in 6 or more
out of 10 years, is dry in some part for six tenths
or more of the cumulative days when the soil
temperature at a depth of 50 cm below the soil
surface is higher than 5°C.

Aridic Natriborolls

HECD. Other Natriborolls that have both:

1. A glossic horizon, or interfingering of albic
materials into the natric horizon; and

2. A chroma of 1 or less (crushed and smoothed
sample) either in the upper 18 cm of the mollic
epipedon, after mixing, or in an Ap horizon 18 cm
or more thick,

Glossic Udic Natriborolls

HECE, Other Natriborolls that have a chroma of 1 or
less (crushed and smoothed sample) either in the upper
18 cm of the mollic epipedon, after mixing, or in an Ap
horizon 18 cm or more thick,

Udic Natriborolis

HECF. Other Natriborolls that have a glossic horizon, or
interfingering of albic materials into the natric horizon.

HEAA. Paleborolls that have both:

Glossic Natriborolls
HECG. Other Natriborolls.
Typic Natriborolls
Paleborolls
Key to subgroups

ros

1, A mollic epipedon 50 cm or more thick; and

2. A mean summer soil temperature either at a
depth of 50 cm below the soil surface or at a lithic
or paralithic contact, whichever is shallower, of
less than 15°C if there is no O horizon, or of less
than 8°C if there is an O horizon.

Cryic Pachic Paleborolls

HEAB. Other Paleborolls which have both:

1. An argillic horizon that has a clay increase with
depth of 20 percent or more (absolute, in the fine-
earth fraction) within its upper 7.5 cm; and


56

control section, the name for the thicker part is used for
that soil family.

If, however, the particle-size control section consists of
two parts with strongly contrasting particle-size or
substitute classes (listed below) and if the transition
zone between them is less than 12.5 om thick, both class
names are used. For example, if the weighted average
particle size of the control section’s upper part is loamy
fine sand and that of the lower part is clay, with a
transition zone of less than 12.5 cm, the family particle-
size class of that soil is sandy over clayey. If the
particle-size control section includes more than one pair
of the strongly contrasting classes listed below, then the
pair of adjacent classes that contrast most strongly is
used in classifying the soil family; however, substitute
class names are used only if the soil materials to which
they apply extend 10 cm or more into the upper part of
the particle-size control section.

The following particle-size or substitute classes are
considered strongly contrasting if the transition zone
between the two parts of the particle-size control section
is less than 12.5 cm thick:

1. Ashy over clayey.

2. Ashy over loamy-skeletal,

3. Ashy over loamy,

4, Ashy over medial-skeletal.

5. Ashy over medial if the water content at 1500
kPa tension in dried samples of the fine-earth
fraction is 10 percent or less for the ashy materials
and 15 percent or more for the medial materials.
6, Ashy over pumiceous or cindery if there is an
absolute difference of 20 percent or more between
volumes of rock fragments in the two parts of the
control section.

7. Ashy over sandy or sandy-skeletal,

8. Ashy-skeletal over fragmental or cindery if the
volume of the fine-earth fraction is 35 percent or
more (absolute) greater in the ashy-skeletal part
than in the fragmental or cindery part.

9. Cindery over loamy.

10. Cindery over medial-skeletal.

11, Cindery over medial.

12. Clayey over fine-silty if there is an absolute
difference of 25 percent or more between clay
percentages of the fine-earth fraction in the two
parts of the control section.

13, Clayey over fragmental,

14. Clayey over loamy if there is an absolute
difference of 25 percent or more between clay


ant
IEGE. Other Kandiudalfs that have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic horizon at a depth of 100 cm or

more;

2. Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface.

Grossarenic Plinthic Kandiudalfs

TEGF. Other Kandiudalfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
to 100 cm.

Arenic Kandiudalfs

IEGG. Other Kandiudalfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 100
cm or more.

Grossarenic Kandiudalfs

TEGH. Other Kandiudalfs that have 5 percent or more
(by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface,

Plinthic Kandiudalfs

IEGI. Other Kandiudalfs that have, throughout the
argillic or kandic horizon, a hue of 2.5YR or redder, a
color value, moist, of 3 or less, and a color value, dry,
that is no more than one unit higher than the value,
moist. .
Rhodic Kandiudalfs
TEGJ. Other Kandiudalfs that have an Ap horizon with a
color value, moist, of 3 or less and a color value, dry, of
5 or less (crushed and smoothed sample), or materials
between the soil surface and a depth of 18 cm which

have these color values after mixing.

Mollic Kandiudalfs
IEGK. Other Kandiudalfs.

Typic Kandiudalfs
Kanhapludalfs
Key to subgroups

TEHA. Kanhapludalfs that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Kanhapludalfs

TEHB. Other Kanhapludalfs that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Kanhapludalfs


427

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).

Aquic Petroferric Eutrudox

DECB. Other Eutrudox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Eutrudox

DECC. Other Eutrudox that have, within 125 cm of the
mineral soil surface, both:

1, A lithic contact; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).

Aquic Lithic Eutrudox

DECD. Other Eutrudox that have a lithic contact within
125 cm of the mineral soil surface.
Lithic Eutrudox

DECE. Other Eutrudox that have, in one or more
horizons within 125 cm of the mineral soil surface,
both:

1. Five percent or more (by volume) plinthite; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).

Plinthaquic Eutrudox

DECF. Other Eutrudox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125
cm of the mineral soil surface.

Plinthic Eutrudox

DECG. Other Eutrudox that have, in one or more
horizons within 125 cm of the mineral soil surface,
redox depletions with a color yalue, moist, of 4 or more
and a chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage).

Aquic Eutrudox

DECH. Other Eutrudox that have both;

1. A clay content of 40 percent or more in the fine-
earth fraction between the soil surface and a depth
of 18 cm, after mixing; and

2. A kandic horizon that has its upper boundary
within 150 cm of the mineral soil surface.
Kandiudalfic Eutrudox

DECI. Other Eutrudox which have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

10)
x
I



14

2, Between either the mineral soil surface, or the
top of an organic layer with andic soil properties,
whichever is shallower, and a lithic or paralithic
contact, duripan, or petrocalcic horizon.
Andisols, p. 139
D. Other soils which have either:

1. An oxic horizon that has its upper boundary
within 150 cm of the mineral soil surface, and no
kandic horizon that has its upper boundary within
that depth; or

2. 40 percent or more (by weight) clay in the fine-
earth fraction between the mineral soil surface
and a depth of 18 cm (after mixing), and a kandic
horizon that has the weatherable-mineral
properties of an oxic horizon and has its upper
boundary within 100 cm of the mineral soil
surface.

Oxisols, p. 413

E. Other soils which have:

1. A layer 25 om or more thick, with an upper
boundary within 100 cm of the mineral soil
surface, that has either slickensides close enough
to intersect or wedge-shaped aggregates which
have their long axes tilted 10 to 60 degrees from
the horizontal; and

2. A weighted average of 30 percent or more clay
in the fine-earth fraction either between the
mineral soil surface and a depth of 18 cm or in an
Ap horizon, whichever is thicker, and 30 percent
or more clay in the fine-earth fraction of all
horizons between a depth of 18 cm and either a
depth of 50 cm, or a lithic or paralithic contact,
duripan, or petrocalcic horizon if shallower; and

3. Cracks! that open and close periodically.
Vertisols, p. 491

F. Other soils that have an ochric or anthropic epipedon,
and either:

1. Do not have an argillic, a natric, or a sulfuric
horizon, but have either:

a. Saturation with water within 100 cm of
the mineral soil surface for 1 month or more
per year in some years, and a salic horizon
that has its upper boundary within 75 cm of
the mineral soil surface; or

1 A crack is a separation between gross polyhedrons. If the surface horizon.
is strongly self-mulching, ic.,a mass of loose granules, o ifthe soil is
cultivated while cracks are open, the cracks may be largely filled with
‘granular materials from the surface; but they are open in the sense that the
polyhedrons are separated. A crack is regarded as open if it controls the
jnfiltration and percolation of water in a dry clayey soil.


314

b. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for six tenths or more of the
cumulative days per year when the soil
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or
c. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, is moist in some or all parts for less
than 180 cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 8°C.
Torrifluventic Ustochrepts
JDEJ. Other Ustochrepts which have:

1. Either 0.2 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

2. A slope of less than 25 percent; and

3. If neither irrigated nor fallowed to store
moisture, one of the following:

a. A frigid soil temperature regime, and a
moisture control section which, in 6 or more
out of 10 years, is dry in some or all parts
for less than 105 cumulative days per year
when the soil temperature at a depth of 50
cm below the soil surface is higher than
5°C; or
b. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for less than four tenths of the
cumulative days per year when the

at a depth of 50 cm below the
soil surface is higher than 5°C; or
c. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, is dry in some or all parts for less
than 120 cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 8°C.

Udifluventic Ustochrepts
IDEK. Other Ustochrepts which have both:

1. Either 0.2 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and


Figure 1
“ x
28 Andlic Soil
Properties

=
s
3 20
€
€
3
; 15
g
§
3
£
3 10
Go

5

C)

° 04 1.0 15 20
xalate—extractable aluminum
+ 1/2 Sg alate ee iron (%) in the
less 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.

Aquic conditions?

Soils with aquic (L. aqua, water) conditions are those
which currently experience continuous or periodic
saturation and reduction. The presence of these

conditions is indicated by redoximorphic features

(defined below) and can be verified, except in

artificially drained soils,° by measuring saturation and
reduction.

° The terin aquic conditions was introduced, and other changes were made
Soil Taxonomy, in 1992 as a result of recommendations
submitted to SCS by the Intemational Committee on Aquic Moisture
Regime (ICOMAQ), which was established in 1982 and chaired initially by
Frank Moonnann, then by Johan Bouma (since 1985),
10 Actificral drainage is defined here as removal of free water from souls (by
surface mounding, ditches, of subsurface tiles) to the extent that watertable
Jevels are changed significantly in connection with specific types of land
use. In the keys, artificially drained souls are included with soils that have
aquic conditions


342

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling

0.40 or more,
Aquandic Cryaquolls
HBAF, Other Cryaquolls that have an argillic horizon.
Argic Cryaquolls

HBAG. Other Cryaquolls that have a calcic horizon
either within or directly below the mollic epipedon.
Calcic Cryaquolls

HBAH. Other Cryaquolls that have a mollic epipedon
50 cm or more thick.

Cumulic Cryaquolls
HBAI. Other Cryaquolls.
Typic Cryaquolls
Duraquolis
Key to subgroups
HBBA. Duraquolls that have a natric horizon.
Natric Duraquolls

HBBB. Other Duraquolls which have, above the
duripan, one or both of the following:

1. Cracks that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick; or

2. A linear extensibility of 6.0 cm or more,

Vertic Duraquolls
HBBC. Other Duraquolls that have an argillic horizon.

Argic Duraquolls
HBBD. Other Duraquolls.

Typic Duraquolls
Endoaquolls
‘Key to subgroups

HBGA. Endoaquolls that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Endoaquolls

HBGB. Other Endoaquolls which have one or both of
the following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has


93

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more,

Vitrandic Cryoboralfs

IBDF. Other Cryoboralfs that have, in one or more
horizons within 75.cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Cryoboralfs

IBDG, Other Cryoboralfs that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Cryoboralfs
IBDH. Other Cryoboralfs which have an argillic horizon A
that either has a texture of loamy fine sand or coarser,
or is discontinuous vertically in its upper 15 cm (in
lamellae).

>

Psammentic Cryoboralfs
IBDI. Other Cryoboralfs that have a color value, moist,
of 3 or less (crushed and smoothed sample) either in an
Ap horizon, or between the soil surface and a depth of
15 cm, after mixing.

Mollic Cryoboralfs
IBDJ. Other Cryoboralfs that have a glossic horizon.
Glossic Cryoboralfs
IBDK. Other Cryoboralfs.
Typic Cryoboralfs
Eutroboralfs
Key to subgroups

IBEA. Eutroboralfs that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Eutroboralfs

IBEB, Other Eutroboralfs which have one or both of the
following:

1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2, A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a


351

section that is moist in some or all of its parts
throughout the year in 6 or more out of 10 years.

Udic Argiborolls
HEDS. Other Argiborolls that have an albic horizon
directly below the mollic epipedon.
Albollic Argiborolls
HEDT. Other Argiborolls.
Typic Argiborolls
Calciborolls
Key to subgroups
HEFA. Calciborolls that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Calciborolls

HEFB. Other Calciborolls which have a petrocalcic
horizon that has its upper boundary within 100 cm of
the mineral soil surface.

Petrocalcic Calciborolls

HEFC. Other Calciborolls which have both:

1. A color value, dry, of 5 or more either in the
upper 18 cm of the mollic epipedon, after mixing,
or in an Ap horizon 18 cm or more thick; and

2. A moisture control section which, in 6 or more
out of 10 years, is dry in some part for six tenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the
soil surface is higher than 5°C.
Aridic Calciborolls
HEFD. Other Calciborolls that have, in one or more
horizons within 100 cm of the mineral soil surface,
distinct or prominent redox concentrations, and also
aquic conditions for some time in most years (or
artificial drainage).
Aquic Calciborolls
HEFE. Other Calciborolls that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Calclborolls

HEFF. Other Calciborolls that have a udic moisture
regime.
Udie Calciborolls
HEFG. Other Calciborolls.
Typic Calciborolls


6

so thick that the soil is recognized as a Histosol (defined
below), the mollic epipedon is considered to be buried.

The mollic epipedon has the following properties:

1. Soil structure is strong enough so that one half or
more of the horizon is not both hard, very hard, or
harder and massive when dry. Very coarse prisms, with
a diameter of 30 cm or more, are included in the
meaning of massive if there is no secondary structure «
within the prisms.

2. Unless the fine-earth fraction has 15 percent or more
calcium carbonate equivalent, crushed and smoothed
samples have a Munsell color value of 3 or less when
moist and of $ or less when dry, and a chroma of 3 or
less; normally the color value is at least 1 Munsell unit
lower or the chroma at least 2 units lower (both moist
and dry) than that of the 1C horizon if 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 shale can also 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 should have a
lower color 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(s) 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
(ie, a lithic or paralithic contact, defined below).

The mollic epipedon has dark color and low chroma in
50 percent or more of its matrix. If its structure is fine
granular or fine blocky, the sample when broken may
show only the color of the coatings of peds. The color of
the matrix in such situations can be determined only by
crushing or briefly rubbing the sample. Prolonged
rubbing should be avoided because it may cause
darkening of a sample if soft iron-manganese
concretions are present, crushing should be just
sufficient to mix the coatings with the matrix. The color
value when dry should be determined after the crushed
sample has been smoothed to eliminate shadows.

If the fine-earth fraction has 15 to 40 percent calcium
carbonate equivalent, the limit for the color value, dry,
is waived. If it has 40 percent or more calcium
carbonate equivatent, the limit for the color value, dry,
is waived and the color value, moist, is 5 or less. These

3 The color when moist is that of a specimen moist enough so that an.
additional drop of water produces no change in its color. The color when
dry is that ofa specimen dry enough so that continued drying produces no
further change


75

b, An aridic soil moisture regime and,
within 100 cm of the mineral soil surface,
the upper boundary of one or more of the
following: a calcic, petrocalcic, gypsic,
petrogypsic, or cambic horizon or a duripan;
or

2. Have an argillic or a natric horizon, and both:
a. An aridic moisture regime; and
b. An epipedon that is not both hard, very

hard, or harder and massive when dry.
Aridisols, p. 177

G, Other soils that have either:

1. An argillic or a kandic horizon, but no fragipan,
and a base saturation (by sum of cations) of less
than 35 percent at one of the following depths:

a. If the epipedon has a sandy or sandy-

skeletal particle size throughout, either:
(1) 125 cm below the upper boundary
of the argillic horizon (but no deeper
than 200 cm below the mineral soil
surface), or 180 cm below the mineral
soil surface, whichever is deeper; or
(2) Ata lithic, paralithic, or
petroferric contact if shallower; or

b. The shallowest of the following depths:

(1) 125 cm below the upper boundary
of the argillic or kandic horizon; or

(2) 180 cm below the mineral soil
surface; or

(3) Ata lithic, paralithic, or
petroferric contact; or

2, A fragipan and both of the following:

a, Either an argillic or a kandic horizon
above, within, or below it, or clay films
1 mm or more thick in one or more of its
subhorizons; and
b. A base saturation (by sum of cations) of
less than 35 percent at the shallowest of the
following depths:
(1) 75 cm below the upper boundary
of the fragipan; or
(2) 200 cm below the mineral soil
surface; or
(3) Ata lithic, paralithic, or
petroferric contact.
Ultisols, p. 455

<mx


82
percentages (by ammonium oxalate) totaling

0.40 or more.
Aquandic Albaqualfs

IAGF. Other Albaqualfs that have an Ap horizon with a
color value, moist, of 3 or less and a color value, dry, of
5 or less (crushed and smoothed sample), or materials
between the soil surface and a depth of 18 cm which
have these color values after mixing.

Mollic Albaqualfs

IAGG. Other Albaqualfs which have, within 100 cm of
the mineral soil surface, the upper boundary of a brittle
horizon 15 cm or more thick that contains either some
opal coatings or 20 percent or more (by volume)

durinodes.
Durorthidic Albaqualfs

IAGH. Other Albaqualfs.
Typic Albaqualfs

Duraquaifs

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.

Endoaqualfs

Key to subgroups

IAJA. Endoaqualfs which have, throughout one or more

horizons with a total thickness of 18 cm or more within

75 om of the mineral soil surface, one or more of the

following:
1. A fine-earth fraction with both a bulk density of
1.0 g/cm? or less, measured at 33 kPa water
retention, and aluminum plus 1/2 iron percentages
(by ammonium oxalate) totaling more than 1.0; or
2. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
3. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron


228

b. In the upper 18 cm of the soil, if the

upper boundary of the duripan is between 18
and 40 cm from the soil surface,

(1) 0.72 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.18 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.77-(0.046 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
land 13; and

2. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Xerollic Durorthids

FBCH. Other Durorthids which have both:

1. An aridic moisture regime that borders on a

xeric regime; and

2. A moisture control section that is dry in all its

parts for less than three fourths of the cumulative

days per year in 6 or more out of 10 years when

the soil temperature at a depth of 50 cm from the

soil surface is S°C or higher.

Xerochreptic Durorthids

FBCI. Other Durorthids which have both:

1. An aridic moisture regime that borders on an
ustic regime; and

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to noncarbonate clay, as follows:

a. In the upper 40 cm of the soil, if the upper
boundary of the duripan is 40 cm or more
below the soil surface,

(1) 0.60 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.15 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.64-(0.038 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
1 and 13; or


345

percentages (by ammonium oxalate) totaling
0.40 or more.
Aquandic Epiaquolls

HBFE. Other Epiaquolls which have a horizon 15 cm or
more thick within 100 cm of the mineral soil surface
that either contains 20 percent or more (by volume)
durinodes or is brittle and has firm consistence when
moist.
Duric Epiaquolls

HBFF. Other Epiaquolls that have a mollic epipedon 60
om or more thick.

Cumulic Epiaquolls

HBFG. Other Epiaquolls which have:

1. Either 0.3 percent or more organic carbon in all
horizons within 125 cm of the mineral soil
surface, or an irregular decrease in organic-carbon.
content from a depth of 25 cm to a depth of 125
cm, or to a lithic or paralithic contact if shallower;
and

2, A slope of less than 25 percent.

Fluvaquentic Epiaquolls
HBFH. Other Epiaquolls.
Typic Epiaquolls
Natraquolls
Key to subgroups

HBCA. Natraquolls which have one or both of the
following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Natraquolls

HBCB. Other Natraquolls (provisionally).
Typic Natraquolls

ros


319

b, In the 0,02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more,

Vitrandic Xerochrepts

JDFJ. Other Xerochrepts that have a gypsic horizon
within 100 cm of the mineral soil surface,
Gypsic Xerochrepts

JDFK. Other Xerochrepts that have both:

1. In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. A base saturation (by NH,OAc) of less than 60
percent in all horizons between 25 and 75 cm
from the mineral soil surface.

Aquic Dystric Xerochrepts

IDFL, Other Xerochrepts that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Xerochrepts
JDFM. Other Xerochrepts which have:

1. A base saturation (by NH,OAc) of less than 60
percent in all horizons between 25 and 75 cm
from the mineral soil surface; and

2. Either 0.2 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

3, A slope of less than 25 percent,
Dystric Fluventic Xerochrepts

IDFN. Other Xerochrepts which have both:

1, Either 0.2 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

2. A slope of less than 25 percent,
Fluventic Xerochrepts

JDFO, Other Xerochrepts that have a base saturation

(by NH,OAc) of less than 60 percent in all horizons

between 25 and 75 cm from the mineral soil surface.
Dystric Xerochrepts

JDFP. Other Xerochrepts that have a calcic horizon or
soft powdery lime, either within the following depths or


2

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
each pedon. The recognition of a surface mantle should
not be based only on studiés of associated soils.


483

horizon and within 75 cm of the mineral soil surface,
redox depletions with a color value, moist, of 4 or more
and a chroma of 2 or less, accompanied by redox
concentrations, and also aquic conditions for some time
in most years (or artificial drainage).

Aquic Haplustults

GDFD. Other Haplustults that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
to 100 cm.

Arenic Haplustults

GDFE. Other Haplustults that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
concentrations, a color value, moist, of 4 or more, and a
hue which is 10YR or yellower, but which becomes
redder with increasing depth within 100 cm of the
mineral soil surface.

Ombroaquic Haplustults

GDFF. Other Haplustults that have 5 percent or more
(by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface,

Plinthic Haplustults

GDFG. Other Haplustults that have a CEC (by IN
NH,OAc pH 7) of less than 24 cmol(+)/kg clay? in 50
percent or more of the argillic horizon if less than 100
om thick, or of its upper 100 cm.

Kanhaplic Haplustults
GDFH. Other Haplustults.
Typic Haplustults
Kandiustults
Key to subgroups

GDBA. Kandiustults that have an ECEC of 1.5
cemol(+)/kg clay or less (sum of bases extracted with IN
NH,OAc pH 7, plus 1N-KCl-extractable Al) in one or
mote horizons within 150 cm of the mineral soil
surface.

Acrustoxic Kandiustults

2 Some soils with properties that approach those of an Oxisol do not tl
disperse well. If the ratio of (percent water retained at 1500 kPa tension
‘minus percent organic carbon) to the percentage of measured clay is 0.6 oF T
more, then the percentage of clay is considered to equal either (1) the

measured percentage of clay, or (2) three times (percent water retained at

1500 kPa tension minus percent organic carbon), whichever value is higher,

but no more than 100.


461

1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.
Aquandic Kanhaplaquults

GAEB. Other Kanhaplaquults that have 5 percent or
more (by volume) plinthite in one or more horizons
within 150 cm of the mineral soil surface.

Plinthic Kanhaplaquults

GAEC. Other Kanhaplaquults which:
1, Do not have an ochric epipedon; and

2. Have 50 percent or more chroma of 3 or more
in one or more horizons between either the A or
Ap horizon or a depth of 25 cm from the mineral
soil surface, whichever is deeper, and a depth of
75 cm.

Aeric Umbric Kanhaplaquults

GAED. Other Kanhaplaquults that have 50 percent or
more chroma of 3 or more in one or more horizons
between either the A or Ap horizon or a depth of 25 cm
from the mineral soil surface, whichever is deeper, and
a depth of 75 cm.

Aeric Kanhaplaquults

GAEE. Other Kanhaplaquults that do not have an ochric
epipedon.

Umbric Kanhaplaquults
GAEF. Other Kanhaplaquults.
Typic Kanhaplaquults
Paleaquults
Key to subgroups

GAFA. Paleaquults which have one or both of the
following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm ora lithic or paralithic contact,
whichever is shallower.
Vertic Paleaquults

GAFB. Other Paleaquults that have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic horizon at a depth of 50 to 100 cm;
and

arc


GBEG. Other Palehumults.
Typic Palebumults

Plinthohumults

Plinthohumults are the Humults which have plinthite
that forms a continuous phase in, or constitutes more
than half the volume of, one or more horizons within
150 cm of the mineral soil surface, 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 Humults have a sombric horizon that has its
‘upper boundary within 100 cm of the mineral soil
surface. They are not known to occur in the United
States, but the great group is provided for use
elsewhere. Humoxic and orthoxic subgroups have been
proposed (Sys, 1969) for the soils that have a low CEC
(ic,, less than 24 cmol(+)/kg clay). The humoxic
subgroup is proposed for soils with an isothermic or
cooler soil temperature regime, and the orthoxic
subgroup for soils with an isohyperthermic soil
temperature regime.

UDULTS

Key to great groups

GCA, Udults that have one or more horizons within 150
cm of the mineral soil surface in which plinthite either
forms a continuous phase or constitutes one half or more
of the volume,

Plinthudults, p, 481

GCB. Other Udults that have a fragipan within or below
the argillic or kandic horizon.
Fragiudults, p. 470

GCC. Other Udults which:

1. Do not have a lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface;
and

2. Have a CEC of 16 cmol(+)/kg clay or less (by
IN NH,OAc pH 7) and an ECEC of 12 cmol(+)/kg
clay or less (sum of bases extracted with IN
NH,OAc pH 7, plus IN-KCl-extractable Al) in 50
percent or more either of the argillic or kandic
horizon if less than 100 cm thick, or of its upper
100 cm; and

3. Within 150 cm of the mineral soil surface,
either:


485

GDBF, Other Kandiustults that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Kandiustults

GDBG. Other Kandiustults that have $ percent or more
(by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface.

Plinthic Kandiustults

GDBH. Other Kandiustults which, if neither irrigated
nor fallowed to store moisture, have either:

1. A thermic, mesic, or colder soil temperature
regime, and a moisture control section which, in 6
or more out of 10 years, is dry in some part for
more than four tenths of the cumulative days per
year when the soi] temperature at a depth of 50
cm below the soil surface is higher than 5°C; or

2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is
moist in some or all parts for less than 180
cumulative days per year when the temperature at
a depth of 50 cm below the soil surface is higher
than 8°C.

Aridic Kandiustults

GDBI. Other Kandiustults which, if neither irrigated nor
fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for 135
cumulative days or less per year when the
temperature at a depth of 50 cm below the soil
surface is higher than 5°C; or

2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is dry
in some or all parts for less than 120 cumulative
days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8°C.
‘Udic Kandiustults

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

Rhodic Kandiustults

GDBK. Other Kandiustults.
Typic Kandiustults

U


320

above a lithic or paralithic contact if shallower, if the
particle-size control section is

1, Sandy: within 150 cm of the mineral soil

surface; or
2. Loamy: within 110 cm of the mineral soil
surface; or
3. Clayey: within 90 cm of the mineral soil
surface,

Calcixerollic Xerochrepts

JIDFQ. Other Xerochrepts.
Typic Xerochrepts

PLAGGEPTS

Plaggepts are the soils that have a plaggen epipedon.
Because Plaggepts are not known to occur in the United
States, their classification has not been developed
beyond the idea that they should be grouped into a
single suborder.

TROPEPTS

Key to great groups
JCA. Tropepts which:

1. Have a base saturation of less than 50 percent
(by NH,OAc) in one or more horizons between 25
and 100 cm from the mineral soil surface; and

2. Have 12 kg/m? or more organic carbon between
the mineral soil surface and either a depth of 100
cm or a lithic, paralithic, or petroferric contact,
whichever is shallower; and

3. Do not have a sombric horizon.
Humitropepts, p. 325

JCB. Other Tropepts that have a sombric horizon.
Sombritropepts, p. 327

JCC. Other Tropepts that have both:
1. An ustic moisture regime; and

2. A base saturation (by NH,OAc) of 50 percent or
more in all horizons between a depth of 25 cm
from the mineral soil surface and either a depth of
100 cm, or a lithic, paralithic, or petroferric
contact if shallower,

Ustropepts, p. 327

ICD. Other Tropepts that have a base saturation (by
NH,OAc) of 50 percent or more in all horizons between
a depth of 25 cm from the mineral soil surface and


110

2. A mean annual soil temperature lower than
10°C.
Glossoboric Hapludalfs

IEKU. Other Hapludalfs that have a base saturation (by
sum of cations) of less than 60 percent at a depth of 125
em below the top of the argillic horizon, or at a depth of
180 cm below the mineral soil surface, or directly above
a lithic or paralithic contact, whichever is shallowest.
Ultic Hapludalfs

IEKV. Other Hapludalfs that have an Ap horizon with 4
color value, moist, of 3 or less and a color value, dry, of
5 or less (crushed and smoothed sample), or materials
between the soil surface and a depth of 18 cm which
have these color values after mixing.

Mollic Hapludalfs
IEKW, Other Hapludalfs.
Typic Hapludalfs
Kandiudalfs
Key to subgroups
JEGA. Kandiudalfs that have both:

1. In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface.

Plinthaquic Kandiudalfs

IEGB, Other Kandiudalfs that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage),
Aquic Kandiudalfs

IEGC. Other Kandiudalfs that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Kandiudalfs

IEGD. Other Kandiudalfs that have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic horizon at a depth of 50 cm to 100
om; and
2. Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface.

Arenic Plinthic Kandiudalfs


344

em, or to a lithic or paralithic contact if shallower;
and

2. A slope of less than 25 percent.
Fluvaquentic Endoaquolls

HBGI. Other Endoaquolls,
Typic Endoaquolls

Epiaquolls
Key to subgroups

HBFA. Epiaquolls that have one or both of the

following:
1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Epiaquolls

HBFB. Other Epiaquolls that have a histic epipedon.
Histic Epiaquolls

HBEFC. Other Epiaquolls which have a buried Histosol
that has its upper boundary within 100 cm of the
mineral soil surface.

Thapto-Histic Epiaquolls

HBFD. Other Epiaquolls that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or more of
the following:
1. A fine-earth fraction with both a bulk density of
1.0 g/cm} or less, measured at 33 kPa water
retention, and aluminum plus 1/2 iron percentages
(by ammonium oxalate) totaling more than 1.0; or

2. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
3. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either
a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or
b. In the 0,02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron


477

GCDI. Other Kanhapludults that have, in one or more
horizons within 75 cm of the mineral soil surface, redox.
concentrations, a color value, moist, of 4 or more, and a
hue which is 10YR or yellower, but which becomes
redder with increasing depth within 100 cm of the
mineral soil surface.

Ombroaquic Kanhapludults

GCDJ. Other Kanhapludults that are saturated with
water, in one or more layers within 100 cm of the
mineral soil surface, for 1 month or more per year in 6
or more out of 10 years.

Oxyaquic Kanhapludults

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

Rhodic Kanhapludults
GCDL. Other Kanhapludults.
Typic Kanhapludults
Paleudults
Key to subgroups

GCEA. Paleudults which have one or both of the
following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Paleudults

GCEB. Other Paleudults which have a horizon 5 cm or

more thick, either below an Ap horizon or at a depth of
18 cm or more from the mineral soil surface, whichever
is deeper, that has one or more of the following:

1, In 25 percent or more of each pedon,
cementation by organic matter and aluminum,
with or without iron; or

2. Aluminum plus 1/2 iron percentages (by
ammonium oxalate) totaling 0.25 or more, and
half that amount or less in an overlying horizon;
or



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 of 1.5
cmol(+)/kg clay or less (sum of bases extracted with IN
NH,OAc pH 7, plus IN-KCl-extractable Al) in one or
more horizons within 150 cm of the mineral soil
surface.

Acrustoxic Kanhaplustults

GDCC. Other Kanhaplustults that have, in one or more
layers within 75 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and a
chroma of 2 or less, accompanied by redox.
concentrations, and also aquic conditions for some time
in most years (or artificial drainage).

Aquic Kanhaplustults

GDCD. Other Kanhaplustults that have a sandy particle
size throughout a layer extending from the mineral soil
surface to the top of an argillic or a kandic horizon at a
depth of 50 to 100 cm.

Arenic Kanhaplustults

GDCE. Other Kanhaplustults which have both:

1, Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm} or less, measured
at 33 kPa water retention, and aluminum plus 1/2
iron percentages (by ammonium oxalate) totaling
more than 1.0; and

2, If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for 135 cumulative days or less
per year when the temperature at a depth of
50 cm below the soil surface is higher than
5°C; or

b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, is dry in some or all parts for less
than 120 cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 8°C.

Udandic Kanhaplustults

GDCF. Other Kanhaplustults that have, throughout one
or more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth


396
HDC. Other Xerolls which have either:

1, A petrocalcic horizon that has its upper

boundary within 150 cm of the mineral soil

surface; or

2. An argillic horizon that has one or both of the

following:
a, No clay decrease with increasing depth of
20 percent or more (relative) from the
maximum clay content within 150 cm of the
mineral soil surface (and there is no lithic or
paralithic contact within that depth), and
either:

(1) A hue of 7.5YR or redder and a
chroma of 5 or more in the matrix; or

(2) Common coarse redox
concentrations with a hue of 7.5YR or
redder or a chroma of 6 or more, or
both; or

b. A clayey particle size in its upper part,
and at its upper boundary, a clay increase of
either 20 percent or more (absolute) within
a vertical distance of 7.5 cm, or of 15
percent or more (absolute) within a vertical
distance of 2.5 cm, in the fine-earth fraction
(and there is no lithic or paralithic contact
within 50 cm of the mineral soil surface).
Palexerolls, p. 409

HDD. Other Xerolls which:

1. Have a calcic or gypsic horizon that has its
upper boundary within 150 cm of the mineral soil
surface; and

2. In all parts above the calcic or gypsic horizon,
after the soil has been mixed to a depth of 18 cm,
are either calcareous or have a texture of loamy
fine sand or coarser.

Calcixerolls, p. 400

HDE. Other Xerolls that have an argillic horizon,
Argixerolls, p. 395

HDF. Other Xerolls.
Haploxerolls, p. 403

Argixerolls
Key to subgroups
HDEA. Argixerolls that have both:

1, A lithic contact within 50 cm of the mineral soil
surface; and

2. A base saturation (by sum of cations) of 75
percent or less in one or more horizons between


IE. Other Alfisols.
Udalfs, p. 99

AQUALFS

Key to great groups

TAA. Aqualfs that have one or more horizons between
30 and 150 cm from the mineral soil surface in which
plinthite either forms a continuous phase or constitutes
one half or more of the volume.

Plinthaqualfs, p. 90

TAB. Other Aqualfs that have a duripan,
Duraqualfs, p. 82

IAC. Other Aqualfs that have a natric horizon.
Natraqualfs, p. 89

JAD. Other Aqualfs that have a fragipan.
Fragiaqualfs, p. 86

TAE. Other Aqualfs that have a CEC of 16 cmol(+)/kg
clay or less (by IN NH,OAc pH 7) and an ECEC of 12
cmol(+)/kg clay or less (sum of bases extracted with IN
NH,OAc pH 7, plus 1N-KCl-extractable Al) in 50
percent or more either of the argillic or kandic horizon if
less than 100 cm thick, or of its upper 100 cm.
Kandiaqualfs, p. 88

IAF. Other Aqualfs that have a glossic horizon.
Glossaqualfs, p, 87
IAG. Other Aqualfs that have an abrupt textural change
between the ochric epipedon or albic horizon and the
argillic horizon, and have a low or very low saturated
hydraulic conductivity in the argillic horizon.
Albaqualfs, p. 80
TAH. Other Aqualfs that have an umbric epipedon.
Umbraqualfs, p. 90

TAI. Other Aqualfs that have episaturation.

Epiaqualfs, p. 84
IAJ. Other Aqualfs.
Endoaqualfs, p. 82
Albaqualfs
Key to subgroups

IAGA, Albaqualfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
cm or more.

Arenic Albaqualfs


187
1. One or both of the following:

a. Cracks within 125 cm of the soil surface
that are 5 mm or more wide through a
thickness of 30 cm or more for some time in
most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
om of the soil surface; or

b. A linear extensibility of 6.0 cm or more
between the soil surface and either a depth
of 100 cm or a lithic or paralithic contact,
whichever is shallower; and

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

Ustertic Haplargids

FAEJ. Other Haplargids which have one or both of the
following:

1. Cracks within 125 cm of the soil surface that
are 5 mm or more wide through a thickness of 30
cm or more for some time in most years, and
slickensides or wedge-shaped aggregates in a
layer 15 cm or more thick that has its upper
boundary within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more
between the soil surface and either a depth of 100
cm ora lithic or paralithic contact, whichever is
shallower.

Vertic Haplargids

FAEK. Other Haplargids that have, in one or more
horizons within 100 cm of the soil surface, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:

1. A chroma of 0, or a hue of 2.5Y or yellower and
a chroma of 1; or

2. Redox concentrations and 50 percent or more
chroma of 2 or less; or

3. Fifty percent or more chroma of 2 or less and,
in horizons with a total thickness of 25 cm or
more within 50 cm of the soil surface, a higher
exchangeable sodium percentage (or sodium
adsorption ratio) than in the zone with aquic
conditions; or

4, Enough active ferrous iron to give a positive
reaction to «,c'-dipyridyl at a time when the soil
is not being irrigated.

Aquic Haplargids

FAEL. Other Haplargids which have:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top


437
1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4
‘or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Aquic Petroferric Haplustox
DCEB. Other Haplustox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Haplustox

DCEC. Other Haplustox that have, within 125 cm of the
mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Aquic Lithic Haplustox
DCED. Other Haplustox that have a lithic contact
within 125 cm of the mineral soil surface.
Lithic Haplustox

DCEE. Other Haplustox that have, in one or more
horizons within 125 cm of the mineral soil surface,
both:

1. Five percent or more (by volume) plinthite; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).

Plinthaquic Haplustox

DCEF. Other Haplustox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125
cm of the mineral soil surface.

Plinthic Haplustox

DCEG. Other Haplustox that have, within 125 cm of the
mineral soil surface, both:

1. The lower boundary of the oxic horizon; and

2, Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).

Aqueptic Haplustox

DCEH. Other Haplustox that have, in one or more
horizons within 125 cm of the mineral soil surface,
redox depletions with a color value, moist, of 4 or more
and a chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage).

Aquic Haplustox

DCEI. Other Haplustox that are saturated with water, in
one or more layers within 100 cm of the mineral soil


108

a. Within the upper 25 cm of the argillic
horizon if its upper boundary is within 50
cm of the mineral soil surface, or

b. Within 75 cm of the mineral soil surface
if the upper boundary of the argillic horizon
is 50 cm or more below the mineral soil
surface,

Aquertic Hapludalfs

IEKD. Other Hapludalfs which have one or both of the

following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Hapludalfs

IEKE. Other Hapludalfs that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm? or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0,

Andic Hapludalfs

IEKF, Other Hapludalfs that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2,0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:
a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or
b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus }/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.
Vitrandic Hapludalfs


1

surface to the top of an argillic horizon at a depth of 50
to 100. cm.
Arenic Umbraqualfs

IAHC. Other Umbraqualfs that have a sandy particle
size throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 100
cm or more.

Grossarenic Umbraqualfs

IAHD. Other Umbraqualfs that have, in one or more
horizons above the argillic horizon, 5 percent or more
(by volume) discrete nodules 2.5 to 30 cm in diameter
that are cemented by iron.

Ferrudalfic Umbraqualfs
TAHE. Other Umbraqualfs.
Typic Umbraqualfs
BORALFS
Key to great groups

IBA. Boralfs which have all of the following:

1. An argillic horizon that has its upper boundary

60 cm or more below the mineral surface; and

2. A texture finer than loamy fine sand in one or

more horizons above the argillic horizon; and

3. Either a glossic horizon, or interfingering of

albic materials into the argillic horizon.
Paleboralfs, p. 97

IBB. Other Boralfs that have a fragipan.
Fragiboralfs, p. 95

IBC. Other Boralfs that have a natric horizon.
Natriboralfs, p. 97

IBD. Other Boralfs that have a cryic soil temperature
regime.

Cryoboralfs, p. 92
IBE. Other Boralfs that have both:

1. A base saturation (by sum of cations) of 60

percent or more in all subhorizons of the argillic

horizon; and

2. A moisture control section that is dry in one or

more horizons for some time in most years.
Eutroboralfs, p. 93

IBF. Other Boralfs.
Glossoboralfs, p. 96



179

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

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

4, An argillic horizon that has 35 percent or more
clay in the fine-earth fraction of some part, and
either

a. A clay increase of 15 percent or more

(absolute) within a vertical distance of 2.5

cm either within the argillic horizon or at its

upper boundary; or

b. If there is an Ap horizon directly above

the argillic horizon, a clay increase of 10

percent or more (absolute) at the upper

boundary of the argillic horizon.

Abruptic Xerollic Durargids

FABD. Other Durargids which have an argillic horizon
that has 35 percent or more clay in the fine-earth
fraction of some part, and either

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

2. If there is an Ap horizon directly above the
argillic horizon, a clay increase of 10 percent or
more (absolute) at the upper boundary of the
argillic horizon.
Abruptic Durargids
FABE. Other Durargids that have both:

1. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime;
and

2. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or both of the following:

a. More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or

-DP>


182

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

3. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean.
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Xerollic Durargids

FABJ. Other Durargids which have a moisture control
section that is dry in all its parts for less than three
fourths of the cumulative days per year in 6 or more out
of 10 years when the soil temperature at a depth of 50
cm from the soil surface is 5°C or higher.

Ustalfic Durargids
FABK. Other Durargids.
Typic Durargids
Haplargids
Key to subgroups
FAEA. Haplargids which have:

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

2. A lithic contact within 50 cm of the soil
surface; and

3. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if the lithic
contact is between 40 and 50 cm from the
soil surface,
(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or
(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or
(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or
b, In the upper 18 cm of the soil, if the lithic
contact is between 18 and 40 cm from the
soil surface,
(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; ar

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or


58

39. Loamy-skeletal over sandy or sandy-skeletal if
the loamy material has less than 50 percent fine or
coarser sand.

40. Medial over ashy if the water content at 1500
kPa tension in dried samples of the fine-earth
fraction is 15 percent or more for the medial

materials and 10 percent or less for the ashy
materials.

41. Medial over clayey-skeletal.

42. Medial over clayey.

43. Medial over fragmental.

44. Medial over hydrous.

45. Medial over loamy-skeletal.

46, Medial over loamy.

47, Medial over pumiceous or cindery.

48. Medial over sandy or sandy-skeletal.

49. Pumiceous or ashy-pumiceous over loamy.

50. Pumiceous or ashy-pumiceous over medial-
skeletal.

51. Pumiceous or ashy-pumiceous over medial,

52. Pumiceous or ashy-pumiceous over sandy or
sandy-skeletal.

53. Sandy over clayey.

54. Sandy over loamy if the loamy material
contains less than 50 percent fine or coarser sand.

55. Sandy-skeletal over loamy if the loamy
material contains less than 50 percent fine or
coarser sand.

‘The purpose in setting up classes of strongly contrasting
particle sizes has been to identify changes in pore-size
distribution which are not identified in higher soil
categories and which seriously affect the movement and
retention of water. The above list has been compiled for
use in grouping the soil series of the United States into
families, and is not intended as a complete list. For
example, “fine sand over coarse sand” is a pair of
strongly contrasting particle-size classes common among
Udipsamments in western Europe, but not included here
because it is much less common in the United States.

1 particle-size classes
Only seven particle-size class names are used for
families of shallow soils and those in lithic, arenic, and
grossarenic subgroups.

With families of Ultisols not included in the preceding
item, subclasses of the loamy particle-size class, but not
those of the clayey class, are used.


54

tension of 100 percent or more on undried samples; less
than 35 Percent (by volume) rock fragments.

- 35 percent or more (by volume)
rock fragments, of which two thirds or more (by
volume) are pumice or pumice-like fragments, a hydrous
fine-earth fraction.

Hydrous-skeletal - 35 percent or more (by volume) rock
fragments, of which less than two thirds (by volume) are
pumice or pumice-like fragments; a hydrous fine-earth
fraction.

substitutes

The particle-size and substitute class names listed above
are applied to certain horizons, or to the soil materials
within specific depth limits, which have been
designated as the particle-size control section. The
lower boundary of the control section may be at a
specified depth (in centimeters) from the mineral soil
surface, or at the upper boundary of a root-limiting
layer, i.e., a duripan, a fragipan, a petrocalcic,
petrogypsic, or placic horizon, or continuous ortstein; or
at a lithic, paralithic, or petroferric contact. The
following list of particle-size control sections for
particular kinds of soils is arranged as a key.6 The
control sections are as follows:

1, For soils that have, within 36 cm of the mineral soil
surface,

a. A root-limiting layer: Between the mineral soil
surface and the root-limiting layer,

b. A soil temperature of 0°C or lower, 2 months
after the summer solstice: Between the mineral
soil surface and a depth of 36 cm.

2. For Andisols: Between either the mineral soil surface
or the upper boundary of an organic layer with andic
soil properties, whichever is shallower, and the
shallowest of the following: (a) a depth of 100 cm, or
(b) a root-limiting layer or contact, or (c) a depth of 25
cm below the level to which the soil is frozen 2 months
after the summer solstice.

3. For those great groups of Alfisols, Spodosols, and
Ultisols that have a fragipan or spodic horizon in or
above an argillic or a kandic horizon; for Oxisols; and
for other soils that do not have an argillic, kandic, or
natric horizon; Between the lower boundary of an Ap
horizon or a depth of 25 cm from the mineral soil
surface, whichever is deeper, and the shallowest of the

6 This key, like the others in Soil Taxonomy, 1s designed in such a way that
the reader makes the correct classification by gomg through the key
systematically, starting atthe beginning and elimnatang one by one any
classes which include criteria that do not fit the soi! in question ‘The soil
‘belongs into the first class listed for which it meets the criteria


15

or in alternating acid and alkali, are present in some
pores and on some structural faces; or some durinodes
are present, and

3. If soaked in acid, cementation is destroyed in less
than half of any laminar capping that may be present or
in any other continuous or imbricated subhorizon,
cementation in such layers is, however, 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 (L. fragilis, brittle; meaning brittle pan) is a
loamy or, uncommonly, a sandy subsurface horizon
which may underlie an albic, argillic, cambic, or spodic
horizon. It has a very low organic-matter content, a
higher bulk density than the overlying horizons, and
hard or very hard consistence when dry (is seemingly
cemented). When moist, a fragipan has moderate or
weak brittleness (i.¢., tendency for a ped or clod to
Tupture suddenly rather than undergo slow deformation
when pressure is applied). A dry fragment slakes or
fractures when placed in water. A fragipan typically has
redoximorphic features, is slowly or very slowly
permeable to water, and has few or many bleached,
roughly vertical planes which are faces of coarse or very
coarse polyhedrons or prisms.

There is no known laboratory procedure for identifying
asample from a fragipan, and because no single unique
property of fragipans exists, a combination of clues must
be used for field identification of such a pan, as follows:

1. A fragipan lies below, although not necessarily
directly below, an eluvial horizon, unless the soil has
been truncated. In a truncated soil the fragipan can be
traced up slope to where an eluvial horizon has been
preserved,

2. If there is an argillic or a cambic horizon above the
fragipan, an E' horizon commonly intervenes between.
the fragipan and the overlying horizon. This E' horizon
is marked by uncoated grains of sand and silt and seems
associated with water which either stands above the pan
or moves laterally along its surface.

3. If the fragipan is not saturated for long periods of
time, some or all pedons normally have bleached
vertical streaks 10 cm or more apart which form a
roughly polygonal pattern on a horizontal plane and
which are bounded by strong brown or reddish brown
streaks where iron and manganese have accumulated.
This polygonal color pattern may be absent if the pan is
saturated for long periods or if its texture is sandy.

4. If the moisture content of the fragipan is near the
wilting point, the matrix between its streaks is very


235

KAD. Other Aquents that have a sandy particle size in
all horizons between either the Ap horizon or a depth of
25 cm from the mineral soil surface, whichever is
deeper, and a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower.

Psammaquents, p. 240

KAE. Other Aquents that have either 0.2 percent or
more organic carbon} at a depth of 125 cm below the
mineral] soil surface, or an irregular decrease in organic-
carbon content from a depth of 25 cm to a depth of 125
cm, or to a lithic or paralithic contact if shallower.
Fluvaquents, p. 237

KAF, Other Aquents that have episaturation.
Epiaquents, p. 236

KAG. Other Aquents.
Endoaquents, p. 236

Cryaquents

Key to subgroups

KACA. Cryaquents which have, throughout one or more
horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, one or more of the
following:

1. A fine-earth fraction with both a bulk density of
1.0 g/cm} or less, measured at 33 kPa water

retention, and aluminum plus 1/2 iron percentages
(by ammonium oxalate) totaling more than 1.0; or

2. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

3. A fine-earth fraction containing 30 percent or

more particles 0,02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

4zZm

Aquandic Cryaquents

KACB. Other Cryaquents.
Typic Cryaquents

3 See footnote 2.


44

2. Show evidence of the cellular structure of the plants
from which they are derived, and

3. Are either 2 om or less in their smallest dimension, or
are decomposed enough so they can be crushed and
shredded with the fingers.

Pieces of wood which are larger than 2 cm in cross
section and which are so undecomposed that they cannot
be crushed and shredded with the fingers, such as large
branches, logs, and stumps, are not considered to be
fibers but coarse fragments (comparable to gravel,
stones, and boulders in mineral soils).

Fibric soil materials (L. fibra, fiber)

Fibric soil materials are organic soil materials which
either:

1, Contain three fourths? or more (by volume) fibers
after rubbing, excluding coarse fragments; or

2. Contain two fifths or more (by volume) fibers after
rubbing, excluding coarse fragments; and yield color
values and chromas of 7/1, 7/2, 8/1, 8/2, or 8/3
(Munsell designations) on white chromatographic or
filter paper that is inserted into a paste made of the soil
‘materials in a saturated sodium pyrophosphate solution.

Hemic soil materials (Gr. hemi, half, implying
intermediate decomposition)

Hemic soil materials are intermediate in their degree of
decomposition between the less decomposed fibric and
more decomposed sapric materials. Their morphological
features give intermediate values for fiber content, bulk
density, and water content. They are partly altered both
physically and biochemically.

Sapric soil materials (Gr. sapros, rotten)

These are the most highly decomposed of the three
kinds of organic soil materials. They have the smallest
amount of plant fiber, the highest bulk density, and the
lowest water content on a dry-weight basis at saturation.
Sapric soil materials are commonly very dark gray to
black. They are relatively stable, i.e., they change very
little physically and chemically with time in comparison
to other organic soil materials.

Sapric materials have the following characteristics:
1. Their fiber content, after rubbing, is less than one
sixth (by volume), excluding coarse fragments; and

2. Their sodium-pyrophosphate-extract color on white
chromatographic or filter paper is below or to the right
of a line drawn to exclude blocks 5/1, 6/2, and 7/3
(Munsell designations). If few or no fibers can be

2 Fractions are used rather than percentages to avoid implying a higher
degree of accuracy than is justified.


269

KCFD, Other Xeropsamments that are saturated with
water, in one or more layers within 100 cm of the
mineral soil surface, for 1 month or more per year in 6
or more out of 10 years.

Orxyaquic Xeropsamments

KCFE. Other Xeropsamments which have a horizon
within 100 cm of the mineral soil surface that is 15 cm
or more thick and either contains 20 percent or more (by
volume) durinodes or is brittle and has firm consistence
when moist.

Durorthidic Xeropsamments

KCFF. Other Xeropsamments which have lamellae
within 200 cm of the mineral soil surface that meet all
the requirements for an argillic horizon except
thickness? or clay content.

Argic Xeropsamments

KCFG. Other Xeropsamments that have a base
saturation (by NH,OAc) of less than 60 percent in all
horizons between 25 and 75 cm from the mineral soil
surface.

Dystric Xeropsamments

KCFH. Other Xeropsamments.
Typic Xeropsamments

9 See foomote 7.


504

aquic conditions for some time in most years (or
artificial drainage) and either:

1. Redoximorphic features; or

2. Enough active ferrous iron to give a positive

reaction to a.,a'-dipyridyl at a time when the soil

is not being irrigated.

Aquic Hapluderts

EFBC. Other Hapluderts that are saturated with water,

in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of

10 years.
Oxyaquic Hapluderts
EFBD. Other Hapluderts that have a lithic or paralithic
contact within 100 cm of the mineral soil surface.
Leptic Hapluderts
EFBE. Other Hapluderts which have a layer 25 cm or
more thick that contains less than 27 percent clay in its
fine-earth fraction and has its upper boundary within
100 cm of the mineral soil surface.
Entic Hapluderts

EFBF. Other Hapluderts that have, in one or more
horizons within 30 cm of the mineral soil surface, 50
percent or more colors as follows:

1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. A chroma of 3 or more.

Chromic Hapluderts
EFBG. Other Hapluderts,
Typic Hapladerts
USTERTS
Key to great groups

EEA. Usterts that have, throughout one or more
horizons with a total thickness of 25 cm or more within
50 cm of the mineral soil surface, both:

1. An electrical conductivity of the saturation
extract of less than 4.0 dS/m at 25°C; and

2. A pH value of 4.5 or less in 0.01 M CaCl, (5.0
or less in 1:1 water).
Dystrusterts, p. 506

EEB, Other Usterts which have a salic horizon that has
its upper boundary within 100 cm of the mineral soil
surface.

Salusterts, p. 510


318
JDFG. Other Xerochrepts which have both:

1, In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or more of the following:

a. A fine-earth fraction with both a bulk
density of 1.0 g/cm} or less, measured at 33
kPa water retention, and aluminum plus 1/2
iron percentages (by ammonium oxalate)
totaling more than 1.0; or

b. More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or

c. A fine-earth fraction containing 30
percent or more particles 0.02 to 2.0 mm in
diameter, and either:

(1) In the 0.02-to-2.0-mm fraction,
more than 30 percent volcanic glass;
or

(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more.
Aquandic Xerochrepts

IDGH. Other Xerochrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-carth
fraction with both a bulk density of 1.0 g/cm} or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Xerochrepts

JDFL Other Xerochrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:
1, More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
2. A fine-carth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or


Chapter 4

Family and Series Differentiae

FAMILY DIFFERENTIAE FOR MINERAL
SOILS

To distinguish families of mineral soils within a
subgroup, the following differentiae are used. They are
listed and defined in the same sequence in which the
descriptive adjectives relating to each differentia appear
in the family names.

Particle-size classes
Mineralogy classes

Calcareous and reaction classes
Soil temperature classes

Soil depth classes

Soil consistence classes
Classes of coatings

Classes of cracks

Particle-size classes

The term particle size is used to characterize the grain-
size composition of a whole soil, while the term fexture
is used in describing its fine-earth fraction, which
consists of particles with a diameter of less than 2.0
mm.

The particle-size classes of this taxonomy represent a
compromise between conventional divisions in
pedologic and in engineering classifications.
Engineering classifications have set the limit between
sand and silt at a diameter of 74 microns, while
pedologic classifications have put it at either 50 or 20
microns, Engineering classifications have been based on
grain-size percentages by weight in the soil fraction less
than 74 mm in diameter, while textural classes in
pedologic classifications have been based on
percentages by weight in the fraction less than 2.0 mm
in diameter. In engineering classifications, the very-fine-
sand separate (diameter between 0.05 mm and 0.1 mm)
has been subdivided by the 74-micron limit. In defining
the particle-size classes for this taxonomy, a similar
division has been made, but in a different way. A fine
sand or loamy fine sand normally contains an
appreciable amount of very fine sand, but the very-fine-
sand fraction is mostly coarser than 74 microns. A silty
sediment such as loess may also contain an appreciable
amount of very fine sand, most of which, however, is
finer than 74 microns. So in designing the particle-size


421

2. Fifty percent or more hue of 7.5YR or yellower
and color value, moist, of 6 or more between 25
and 125 cm from the mineral soil surface.

Humic Xanthic Haploperox

DDEK. Other Haploperox that have 16 kg/m? or more
organic carbon between the mineral soil surface and a
depth of 100 cm.

Humic Haploperox

DDEL, Other Haploperox that have 50 percent or more
hue of 2.5YR or redder and color value, moist, of 3 or
less between 25 and 125 cm from the mineral soil
surface.

Rhodic Haploperox

DDEM. Other Haploperox that have 50 percent or more
hue of 7.5YR or yellower and color value, moist, of 6 or
more between 25 and 125 cm from the mineral soil
surface.

Xanthic Haploperox
DDEN, Other Haploperox.
Typic Haploperox
Kandiperox
Key to subgroups

DDDA. Kandiperox that have, within 125 cm of the
mineral soil surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Aquic Petroferric Kandiperox
DDDB. Other Kandiperox that have a petroferric

contact within 125 cm of the mineral soil surface.
Petroferric Kandiperox

DDDC. Other Kandiperox that have, within 125 cm of
the mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage),

Aquic Lithic Kandiperox

DDDD. Other Kandiperox that have a lithic contact
within 125 cm of the mineral soil surface.
Lithic Kandiperox

DDDE. Other Kandiperox that have, in one or more
horizons within 125 cm of the mineral soil surface,
both:



261

KECC. Other Xerorthents that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm} or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Xerorthents

KECD. Other Xerorthents that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:
1, More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Xerorthents

KECE. Other Xerorthents that have both:

1. In one or more horizons within 100 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. A horizon within 100 cm of the mineral soil
surface that is 15 cm or more thick and either
contains 20 percent or more (by volume)
durinodes or is brittle and has firm consistence
when moist.

Aquic Durorthidic Xerorthents

KECF. Other Xerorthents that have, in one or more
horizons within 100 cm of the mineral soil surface,
redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or
artificial drainage).
Aquic Xerorthents

KECG. Other Xerorthents that are saturated with water,
in one or more layers within 150 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Xerorthents


Chapter 6
Alfisols

KEY TO SUBORDERS

IA. Alfisols that have, in one or more horizons within
50 cm of the mineral soil surface, aquic conditions for
some time in most years (or artificial drainage), and
have one or both of the following:

1, Redoximorphic features in all layers between
either the lower boundary of an Ap horizon or a
depth of 25 cm below the mineral soil surface,
whichever is deeper, and a depth of 40 cm; and
one of the following within the upper 12.5 cm of
the argillic, natric, or kandic horizon:

a, Fifty percent or more redox depletions

with a chroma of 2 or less on faces of peds,
and redox concentrations within peds; or

b. Redox concentrations and 50 percent or
more redox depletions with a chroma or 2 or
less in the matrix; or

c, Fifty percent or more redox depletions
with a chroma of 1 or less on faces of peds
or in the matrix, or both; or

2. In the horizons that have aquic conditions,
‘enough active ferrous iron to give a positive
reaction to o.,a'-dipyridy] at a time when the soil
is not being irrigated.
Aquaifs, p. 80
IB, Other Alfisols that have either:
1. A frigid temperature regime, but not a xeric
moisture regime; or
2. A cryic temperature regime.
Boralfs, p. 91
IC. Other Alfisols that have either:
1. An ustic moisture regime; or

2. An epipedon that is both hard, very hard, or

harder and massive when dry, and an aridic

moisture regime that borders on an ustic regime.
Ustalfs, p. 115

ID. Other Alfisols that have either:
1. A xeric moisture regime; or

2, An epipedon that is both hard, very hard, or

harder and massive when dry, and an aridic

moisture regime that borders on a xeric regime.
Xeralfs, p. 129

mr>


304

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Durochrepts

JDCD. Other Durochrepts that have, in one or more
horizons within 30 cm of the mineral soil surface,
distinct or prominent redox concentrations, and also
aquic conditions for some time in most years (or

artificial drainage).
Aquic Durechrepts
JDCE. Other Durochrepts that do not have a xeric
moisture regime.
Ustic Durochrepts

JDCF. Other Durochrepts which have both:

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

2, A base saturation (by NH,OAc) of less than 60
percent in all horizons between 25 and 75 cm
from the mineral soil surface.

Dystric Entic Durochrepts

JDCG. Other Durochrepts which have a duripan that is
not indurated in any subhorizon,
Entic Durochrepts

JDCH. Other Durochrepts that have a base saturation
(by NH,OAc) of less than 60 percent in all horizons
between 25 and 75 cm from the mineral soil surface.

Dystric Durochrepts
JDCI, Other Durochrepts.
Typic Durochrepts
Dystrochrepts
Key to subgroups

JDHA. Dystrochrepts that have:
1. A lithic contact within 50 cm of the mineral soil
surface; and .
2. An argillic horizon in less than half of each
pedon; and
3. A base saturation (by sum of cations) of 35
percent or more in the horizon directly above the
lithic contact,

Lithic Ruptic-Alfic Dystrochrepts

JDHB. Other Dystrochrepts that have both:

1, A lithic contact within 50 cm of the mineral soil
surface; and


509
EEEG. Other Haplusterts which have both:

1. A layer 25 cm or more thick that contains less
than 27 percent clay in its fine-earth fraction and
has its upper boundary within 100 cm of the
mineral soil surface; and
2. If not irrigated during the year, cracks in 6 or
more out of 10 years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50
cm of the mineral soil surface, for less than 150
cumulative days per year.

Entic Udic Haplusterts

EEEH. Other Haplusterts which have both:

1. In one or more horizons within 30 cm of the
mineral soil surface, 50 percent or more colors as
follows:

a. A color value, moist, of 4 or more; or
b. A color value, dry, of 6 or more; or
c. A chroma of 3 or more; and

2, If not irrigated during the year, cracks in 6 or
more out of 10 years that are 5 mm or more wide,
through a thickness of 25 cm or more within 50
cm of the mineral soil surface, for less than 150
cumulative days per year,

Chromic Udic Haplusterts

EEEI. Other Haplusterts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
are 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for less
than 150 cumulative days per year.

Udic Haplusterts

EEEJ. Other Haplusterts that have a lithic or paralithic
contact, or the upper boundary of a duripan, within 100
cm of the mineral soil surface.

Leptic Haplusterts
EEEK. Other Haplusterts which have a layer 25 cm or
more thick that contains less than 27 percent clay in its
fine-earth fraction and has its upper boundary within
100 cm of the mineral soil surface.

Entic Haplusterts

EEEL. Other Haplusterts that have, in one or more
horizons within 30 cm of the mineral soil surface, 50
percent or more colors as follows:

1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or

3. A chroma of 3 or more.
Chromic Haplusterts

EEEM. Other Haplusterts.
Typic Haplusterts

am<


317

3. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is dry
in some or all parts for less than 120 cumulative
days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8°C.

Udic Ustochrepts
JDER. Other Ustochrepts.
Typic Ustochrepts
Xerochrepts
Key to subgroups

IDFA. Xerochrepts that have a lithic contact within 50
cm of the mineral soil surface in less than half of each
pedon.

Ruptic-Lithic Xerochrepts
IDFB. Other Xerochrepts that have both:

1. A lithic contact within 50 cm of the soil
surface; and
2. A base saturation (by NH,OAc) of less than 60
percent in all horizons between 25 cm from the
mineral soil surface and the lithic contact.

Dystric Lithic Xerochrepts

JDFC. Other Xerochrepts that have both:

1. A lithic contact within 50 cm of the mineral soil
surface; and

2. A discontinuous cambic horizon in each pedon.
Lithic Ruptic-Xerorthentic Xerochrepts

JDFD, Other Xerochrepts that have a lithic contact
within 50 cm of the mineral soil surface.
Lithic Xerochrepts

JDFE. Other Xerochrepts that have a petrocalcic horizon
within 100 cm of the mineral soil surface.
Pe‘rocalcic Xerochrepts

JDFF. Other Xerochrepts which have one or both of the

following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Xerochrepts


41

whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of
a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that
have acolor value, moist, 1 unit or more higher and an
organic-carbon content I percent or more (absolute)
lower.

Thaptic Cryaquands
CAAE, Other Cryaquands.
Typic Cryaquands
Duraquands
Key to subgroups
CACA. Duraquands that have a histic epipedon.
Histic Duraquands

CACB. Other Duraquands that have extractable bases
plus IN-KCl-extractable Al totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more
horizons with a total thickness of 30 cm or more,
between 25 and 100 cm either from the mineral soi]
surface, or from the top of an organic layer with andic
soil properties, whichever is shallower.

Acraquoxic Duraquands

CACC. Other Duraquands that have, between 25 and
100 cm either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of
a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that
have a color value, moist, 1 unit or more higher and an
organic-carbon content | percent or more (absolute)
lower.

Thaptic Duraquands
CACD. Other Duraquands.
Typic Duraquands
Endoaquands
Key. to subgroups

CAGA. Endoaquands that have a lithic contact within
50 cm either of the mineral soil surface, or of the top of
an organic layer with andic soil properties, whichever is
shallower.
Lithic Endoaquands

CAGB. Other Endoaquands that have a petroferric
contact within 100 cm either of the mineral soil surface,
or of the top of an organic layer with andic soil
properties, whichever is shallower.

Petroferric Endoaquands


134

percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0,02 to 2.0 mm in diameter, and
either:
a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0,40 or more.

Vitrandic Haploxeralfs

IDGH. Other Haploxeralfs which have both:

1, In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. An argillic horizon that has a base saturation
(by sum of cations) of less than 75 percent in one
or more subhorizons within its upper 75 cm or
above a lithic or paralithic contact, whichever is
shallower.

Aquultic Haploxeralfs

IDGI. Other Haploxeralfs that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Haploxeralfs

IDGJ. Other Haploxeralfs that have an exchangeable
sodium percentage of 15 or more (or a sodium.
adsorption ratio of 13 or more) in one or more
subhorizons of the argillic horizon.

Natric Haploxeralfs

IDGK. Other Haploxeralfs which have an argillic
horizon that is either discontinuous vertically within its
upper 20 cm, or has a sandy particle size.

Psammentic Haploxeralfs

IDGL. Other Haploxeralfs that have 5 percent or more
(by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface.

Plinthic Haploxeralfs

IDGM. Other Haploxeralfs which have a calcic horizon
that has its upper boundary within 100 cm of the
mineral soil surface.

Calcic Haploxeralfs
IDGN. Other Haploxeralfs which have an argillic

horizon that has a base saturation (by sum of cations) of
less than 75 percent in one or more subhorizons within


10

channels, root channels, and surfaces of peds in the
horizon underlying the plow layer become coated with a
dark-colored mixture of organic matter, silt, and clay.
The accumulations on the sides of wormholes become
thick and can eventually fill them. If worms are scarce,
the accumulations may take the form of lamellae that
range in thickness from a few millimeters to about 1 cm.
The lamellae and the coatings on the sides of
wormholes always have a lower color value and chroma.
than the soil matrix.

The agric horizon can have somewhat different forms in
different climates if there are differences in soil fauna.
In a humid temperate climate where soils have a udic
moisture regime and a mesic soil temperature regime
(defined below), earthworms can become abundant. If
there are earthworm holes which, including their
coatings, constitute $ percent or more (by volume) of the
horizon and if the coatings are 2 mm or more thick and
have a color value, moist, of 4 or less and a chroma of 2
or less, the horizon is an agric horizon. After long
cultivation, the content of organic matter in the agric
horizon is not likely to be high, but the carbon-nitrogen
ratio is low (usually less than 8). The pH value of the
agric horizon is close to neutral (6 to 6.5).

In a Mediterranean climate where soils have a xeric soil
moisture regime (defined below), earthworms are less
common and the illuvial materials accumulate as
lamellae directly below the Ap horizon. If these
lamellae are 5 mm or more thick, have a color value,
moist, of 4 or less and a chroma of 2 or less, and
constitute 5 percent or more (by volume) of a horizon 10
em or more thick, this horizon is an agric horizon.

Albic horizon

The albic (L. albus, white) horizon is an eluvial horizon
1.0 cm or more thick which contains 85 percent or more
(by volume) albic materials (defined below). It usually
occurs below an A horizon but may be at the mineral
soil surface. Under the albic horizon there is usually an
argillic, cambic, kandic, natric, or spodic horizon or a
fragipan (defined below). The albic horizon may lie
between a spodic horizon and either a fragipan or an
argillic horizon; or it may be between an argillic or a
kandic horizon and a fragipan. It may lie between a
mollic epipedon and an argillic or natric horizon, or
between a cambic horizon and an argillic, kandic, or
natric horizon or a fragipan. The albic horizon may
separate horizons which, if together, would meet the
requirements for a mollic epipedon. It may separate
lamellae that together meet the requirements for an
argillic horizon; these lamellae are not considered to be
part of the albic horizon.

In some soils the horizon underlying the albic horizon is
too sandy or too weakly developed to have the levels of
accumulation required for an argillic, a kandic, a natric,


281

or two or more mineral layers of any thickness, in the
control section below the surface tier.
Fluvaquentic Borohemists

ACEH. Other Borohemists that have one or more layers,
with a total thickness of 25 cm or more, of the
subsurface and bottom tiers consisting of fibric
materials,

Fibric Borohemists

ACEI, Other Borohemists that have one or more layers,
with a total thickness of 12.5 cm or more, of the
subsurface and bottom tiers consisting of sapric
materials,

Sapric Borohemists
ACEJ. Other Borohemists,

Typic Borohemists
Cryohemists
Key to subgroups

ACDA. Cryohemists that have a lithic contact within the
control section.

Lithic Cryohemists

ACDB. Other Cryohemists that have a mean annual soil
temperature of 0°C or lower.

Pergelic Cryohemists

ACDC. Other Cryohemists which have a mineral layer
30 cm or more thick that has its upper boundary within
the control section below the surface tier.

Terric Cryohemists

ACDD. Other Crychemists that have, within organic
materials, either one mineral layer 5 cm or more thick,
or two or more mineral layers of any thickness, in the
control section below the surface tier.

Fluvaquentic Cryohemists

ACDE. Other Cryohemists.
Typic Cryohemists

Luvihemists

Luvihemists are not known to occur in the United
States, but the great group is provided tentatively for
use in other countries if needed. These are the Hemists
which have, within the control section, a horizon 2 cm
or more thick in which humilluvic materials constitute
one half or more of the volume. Because Luvihemists
cannot be studied in the United States, a precise
definition of these soils is not attempted here. It should
be noted, however, that they are normally acid and have
been cultivated for a long time.


399

2. A horizon within 100 cm of the mineral soil

surface that is 15 cm or more thick and either

contains 20 percent or more (by volume)

durinodes or is brittle and has firm consistence

when moist.

Durargidic Argixerolls

HDEP. Other Argixerolls that have a horizon within 100
cm of the mineral soil surface that is 15 cm or more
thick and either contains 20 percent or more (by
volume) durinodes or is brittle and has firm consistence

when moist.
Duric Argixeroils

HDEQ. Other Argixerolls that have both:
1, An aridic moisture regime; and
2. A calcic horizon or soft powdery lime, either
within the following depths or above a lithic or

paralithic contact if shallower, if the particle-size
control section is

a. Sandy: within 150 cm of the mineral soil
surface; or

b. Loamy: within 110 cm of the mineral soil
surface; or

c. Clayey: within 90 cm of the mineral soil

surface.
Aridic Calcic Argixerolls

HDER. Other Argixerolls that have an aridic moisture
regime.

Aridic Argixerolls
HDES, Other Argixerolls that have a calcic horizon or
soft powdery lime, either within the following depths or
above a lithic or paralithic contact if shallower, if the
particle-size control section is

1. Sandy: within 150 cm of the mineral soil
surface; or
2. Loamy: within 110 cm of the mineral soil
surface; or

3. Clayey: within 90 cm of the mineral soil
surface.

Calcic Argixerolls

HDET. Other Argixerolls that have a base saturation (by
sum of cations) of 75 percent or less in one or more
horizons between either an Ap horizon or a depth of 25
cm from the mineral soil surface, whichever is deeper,
and either a depth of 75 cm or a lithic or paralithic
contact, whichever is shallower.

Ultic Argixerolls
HDEU. Other Argixerolls that have an albic horizon
above the argillic horizon.

Albic Argixerolls


136

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Palexeralfs

IDFB. Other Palexeralfs which have both:

1. In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or more of the following:

a, A fine-earth fraction with both a bulk
density of 1.0 g/cm? or less, measured at 33
kPa water retention, and aluminum plus 1/2
iron percentages (by ammonium oxalate)
totaling more than 1.0; or

b. More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or

cc. A fine-earth fraction containing 30
percent or more particles 0.02 to 2,0 mm in
diameter, and either:

(1) In the 0.02-to-2.0-mm fraction,
more than 30 percent volcanic glass;
or

(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more.
Aquandic Palexeralfs

IDFC. Other Palexeralfs that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm: or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Palexeralfs

IDFD. Other Palexeralfs that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:
1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or


53

pumice-like’ fragments with diameters of more than 1
mm; in the fraction coarser than 2.0 mm, two thirds or
more (by volume) pumice or pumice-like fragments,

Cindery - In the whole soil, more than 60 percent (by
weight) volcanic ash, cinders, lapilli, pumice and
pumice-like fragments with diameters of more than }
mm; in the fraction coarser than 2.0 mm, less than two
thirds (by volume) pumice and pumice-like fragments.

2. Substitutes for the non-fragmental particle-size
classes:

These classes have a fine-earth component of 10 percent
or more of the total volume,

Ashy - Less than 35 percent (by volume) rock
fragments; a fine-earth fraction which contains 30
percent or more (by weight) particles between 0.02 and
2.0 mm in diameter and which has either:

a. Andic soil properties, and a water content at
1500 kPa tension of less than 30 percent on
‘undried samples and less than 12 percent on dried
samples; or

b. No andic soil properties, and a total of 30
percent or more of the 0.02-to-2.0-mm fraction (by
grain count) consisting of volcanic glass, glass
aggregates, glass-coated grains, and other vitric
volcaniclastics.

Ashy-pumiceous - 35 percent or more (by volume) rock
fragments, of which two thirds or more (by volume) are
pumice or pumice-like fragments; an ashy fine-earth
fraction.

Ashy-skeletal . 35 percent or more (by volume) rock
fragments, of which less than two-thirds (by volume)
are pumice and pumice-like fragments; an ashy fine-
earth fraction.

Medial - A fine-earth fraction which has andic soil
properties, and which has a water content at 1500 kPa
tension of 12 percent on air-dried samples and of 30 to
100 percent on undried samples; less than 35 percent
(by volume) rock fragments.

Medial-pumiceous - 35 percent or more (by volume)
rock fragments, of which two thirds or more (by
volume) are pumice or pumice-like fragments; a medial
fine-earth fraction.

Medial-skeletal - 35 percent or more (by volume) rock
fragments, of which less than two thirds (by volume) are
pumice or pumice-like fragments; a medial fine-earth
fraction.

Hydrous - A fine-earth fraction which has andic soil
Properties, and which has a water content at 1500 kPa

5 See footnote 3.


TABLE OF CONTENTS

Foreword
Chapter 1: The Soil That We C!
and Buried Soils ..

Chapter 2: Horizons and Properties Diagnostic for the
Higher Categories: Mineral Soils ed

Chapter 3: Horizons and Properties Diagnosti for the
Higher Categories: Organic Soils. 3
Chapter 4: Family and Series Differentiae..
Table 1. Key to Mineralogy Classes... a
Table 2. Key to Mineralogy Classes of Oxisols..70

Chapter 5: Identification of the Taxonomic Class
of a Soil.......

Chapter 10: Histosols..
Chapter 11: Inceptisols.
Chapter 12: Mollisols..
Chapter 13: Oxisols
Chapter 14: Spodosols.....
Chapter 15: Ultisols
Chapter 16: Vertisols ..
Designations for Horizons and Layers...
SI Unit Conversion Table...
Textural Triangle (Figure 2
Index...



396

either the mineral soil surface or an Ap horizon,
whichever is deeper, and the lithic contact.
Lithic Ultic Argixerolls

HDEB. Other Argixerolls that have a lithic contact
within 50 cm of the mineral soil surface.
Lithic Argixerolls

HDEC. Other Argixerolls which have both:
1. An aridic moisture regime; and
2. One or both of the following:

a, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm ora lithic or paralithic
contact, whichever is shallower.

Torrertic Argixerolls

HDED. Other Argixerolls which have one or both of the

following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Argixerolls

HDEE. Other Argixerolls that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm? or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0,

Andic Argixerolls

HDEF. Other Argixerolls that have both:
1. An aridic moisture regime; and
2. Throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or both of the following:

a, More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which


478

3. An ODOE value of 0.12 or more, and a value
half as high or lower in an overlying horizon.
Spodic Paleudults

GCEC. Other Paleudults that have both:

1, A texture of loamy fine sand or coarser
throughout the argillic horizon, or lamellae within
its upper 100 cm; and

2. In one or more layers either within 75 cm of the
mineral soil surface or, if the chroma throughout
the upper 75 cm results from uncoated sand
grains, within the upper 12.5 cm of the argillic or
kandic horizon, redox depletions with a color
value, moist, of 4 or more and a chroma of 2 or
less, accompanied by redox concentrations, and
also aquic conditions for some time in most years
(or artificial drainage).

Psammaquentic Paleudults

GCED., Other Paleudults that have a texture of loamy
fine sand or coarser throughout the argillic horizon, or
lamellae within its upper 100 cm.

Psammentic Paleudults

GCEE. Other Paleudults that have:

1. In one or more layers either within 75 cm of the
mineral soil surface or, if the chroma throughout
the upper 75 cm results from uncoated sand
grains, within the upper 12.5 cm of the argillic or
kandic horizon, redox depletions with a color
value, moist, of 4 or more and a chroma of 2 or
less, accompanied by redox concentrations, and
also aquic conditions for some time in most years
(or artificial drainage); and

2. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic horizon at a depth of 50 to 100 cm;
and

3. Five percent or more (by volume) plinthite in
‘one or more horizons within 150 cm of the
mineral soil surface.

Arenic Plinthaquic Paleudults

GCEF, Other Paleudults that have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic horizon at a depth of 50 to 100 cm;
and

2. In one or more layers either within 75 cm of the
mineral soil surface or, if the chroma throughout
the upper 75 cm results from uncoated sand
grains, within the upper 12,5 cm of the argillic or
kandic horizon, redox depletions with a color
value, moist, of 4 or more and a chroma of 2 or
less, accompanied by redox concentrations, and


173

2. A base saturation (by sum of cations) of less
than 35 percent throughout the upper 50 cm of the
argillic or kandic horizon.
Ultic Udivitrands
CEBE. Other Udivitrands which have an argillic or a
kandic horizon that has its upper boundary within
125 cm of the mineral soil surface, or of the upper
boundary of an organic layer with andic soil properties,
whichever is shallower.
Alfic Udivitrands

CEBF. Other Udivitrands that have a melanic, a mollic,
or an umbric epipedon.

Humic Udivitrands
CEBG. Other Udivitrands.
Typic Udivitrands
Ustivitrands
Key to subgroups

CEAA. Ustivitrands that have a lithic contact within 50
em either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Lithic Ustivitrands
CEAB. Other Ustivitrands that have, in one or more
horizons between 50 and 100 cm either from the
mineral soil surface, or from the top of an organic layer
with andic soil properties, whichever is shallower, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:

1. Two percent or more redox concentrations; or

2. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
redox depletions on faces of peds, or in the matrix
if peds are absent; or
3. Enough active ferrous iron to give a positive
reaction to c.,c''-dipyridy] at a time when the soil
is not being irrigated.
Aquic Ustivitrands
CEAC. Other Ustivitrands that have, between 25 and
100 cm either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of
a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that
have a color value, moist, 1 unit or more higher and an
Organic-carbon content | percent or more (absolute)
lower.
Thaptic Ustivitrands


624
DISCONTINUITIES

In mineral soils, Arabic numerals are used as prefixes to
horizon designations (preceding A, B, B, C, and R) to
indicate discontinuities. These prefixes are distinct from
the Arabic numerals that are used as suffixes to denote
vertical subdivisions,

A discontinuity which can be identified by a number
prefix is a significant change in particle-size distribution
or mineralogy that indicates a difference in the material
from which the horizons have formed, and/or a
significant difference in age, unless that difference in
age is indicated by the suffix b. Symbols to identify
discontinuities are used only when they can contribute
substantially to an understanding of the relationships
among horizons. Stratification common to soils formed
in alluvium is not designated as a discontinuity, unless
particle-size distribution differs markedly from layer to
layer (i.¢., particle-size classes are strongly contrasting),
even though genetic horizons may have formed in the
contrasting layers.

Where a soil has formed entirely in one kind of
material, the whole profile is understood to be material
1 and the number prefix is omitted from the symbol.
Similarly, the uppermost material in a profile consisting
of two or more contrasting materials is understood to be
material 1, but the number is omitted. Numbering starts
with the second layer of contrasting material, which is
designated 2. Underlying contrasting layers are
numbered consecutively. Even when the material of a
layer below material 2 is similar to material 1, it is
designated 3 in the sequence; the numbers indicate a
change in materials, not types of material. Where two or
more consecutive horizons have formed in the same
kind of material, the same prefix number is applied to
all the designations of horizons in that material: Ap-E-
Btl-2Bt2-2Bt3-2BC. The suffix numbers designating
subdivisions of the Bt horizon continue in consecutive
order across the discontinuity.

If an R layer is present below a soil that has formed in
residuum, and if the material of the R layer is judged to
be like the material from which the soil has developed,
the Arabic-number prefix is not used. But the prefix is
used if it is thought that the R layer would produce
material unlike that in the solum, e.g.: A-Bt-C-2R, or A-
Bt-2R. If part of the solum has formed in residuum, the
symbol R is given the appropriate prefix: Ap-Btl-2Bt2-
2Bt3-2C1-2C2-2R.

A buried horizon (designated b) presents special
problems, It is obviously not in the same deposit as the
overlying horizons, Some buried horizons, however,
have formed in material which is lithologically like the
overlying deposit. A prefix is not used to distinguish
material of such a buried horizon. If, however, the
material in which a horizon of a buried soil has formed


197

3. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Durixerollic Natrargids

FACH. Other Natrargids which have a horizon within
100 cm of the soil surface that is 15 cm or more thick
and either contains 20 percent or more (by volume)
durinodes or is brittle and has firm consistence when
moist.

Duric Natrargids
FACL. Other Natrargids which have:

1. Skeletans on 10 percent or more of the faces of
peds that are 2.5 cm or more below the upper
boundary of the natric horizon; and

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a, In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 cm of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between |
and 13; and
3. An aridic moisture regime that borders on an.
ustic regime.
Glossic Ustollic Natrargids
FACJ. Other Natrargids which have:

1, An exchangeable sodium percentage of less
than 15 (or a sodium adsorption ratio of less than
13) in 50 percent or more of the natric horizon;
and

-DpP


220

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 cm of the soil, if there is a

paralithic contact between 18 and 40 cm.
from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13,

Anthropic Camborthids

FBFS. Other Camborthids which have both:

1. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:
a. In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,
(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or
(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or
(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or
b. In the upper 18 om of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and


162

CGEG. Other Hydrudands which have an argillic or a
kandic horizon that has both:

1. An upper boundary within 125 cm either of the
mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower; and

2. A base saturation (by sum of cations) of less
than 35 percent throughout its upper 50 cm.

Ultic Hydrudands
CGEH. Other Hydrudands.

Typic Hydrudands
Melanudands
Key to subgroups

CGCA. Melanudands that have a lithic contact within
50 cm either of the mineral soil surface, or of the top of
an organic layer with andic soil properties, whichever is
shallower.

Lithic Melanudands

CGCB. Other Melanudands that have anthraquic
conditions.

Anthraquic Melanudands
CGCC. Other Melanudands that have both:

1. More than 2.0 cmol(+)/kg Al* (by IN KCI) in
the fine-earth fraction of one or more horizons
with a total thickness of 10 cm or more, between
25 and 50 cm either from the mineral soil surface,
or from the top of an organic layer with andic soil
properties, whichever is shallower; and

2. In one or more horizons between 50 and 100 cm
either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, aquic conditions for some
time in most years (or artificial drainage) and one
or more of the following:

a. Two percent or more redox

concentrations; or

b. A color value, moist, of 4 or more, and 50

percent or more chroma of 2 or less either in

redox depletions on faces of peds, or in the

matrix if peds are absent; or

c. Enough active ferrous iron to give a

positive reaction to o.,c'-dipyridyl at a time

when the soil is not being irrigated.

Alice Aquic Melanudands
CGCD. Other Melanudands that have both:

1. More than 2.0 cmol(+)/kg AP* (by IN KCI) in
the fine-earth fraction of one or more horizons
with a total thickness of 10 cm or more, between


70

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 dithionite citrate) in the fine-earth
fraction?

2, More than 40 percent gibbsite in the fine-earth
fraction?

3. 18 to 40 percent iron oxide (12.6 to 28 percent
Fe) (by dithionite citrate) in the fine-earth
fraction?

4. 18 to 40 percent gibbsite in the fine-earth
fraction?

5. More than 50 percent (by weight) kaolinite in
the fine-earth fraction?

6. More than 50 percent (by weight) halloysite in
the fine-earth fraction?

If none of the above—Mixed
1 with or without 2, 4, 5, 6—Ferritic
2 with or without 3, 5, 6—Gibbsitic
3 with or without 5, 6—-Ferruginous
4 with or without 5, 6—Allitic
3 and 4 with or without 5, 6—Sesquic
5—Kaolinitic
6—Halloysitic


24

c. A chroma that is controlled by the color of
uncoated grains of silt or sand, a hue of SYR or
redder, and color values listed in 1.a or 1.b above.

Relatively unaltered layers of light-colored sand,
volcanic ash, or other materials deposited by wind or
water are not considered albic materials, although they
may have the same color and apparent morphology.
These deposits are parent materials which have not had
clay and/or free iron removed and do not overlie an
illuvial horizon or other soil horizon except a buried
soil. Light-colored krotovina or filled root channels
should only be considered albic materials if they have
no fine stratifications or lamellae, if any sealing along
krotovina walls has been destroyed, and if these
intrusions have, after deposition, been leached of free
iron oxides and/or clay.

Andi soil properties

To be recognized as having andic soil properties, soil
materials must contain less than 25 percent (by weight)
organic carbon and meet one or both of the following
requirements:

1, In the fine-earth fraction, all of the following:

a. Aluminum plus 1/2 iron percentages (by
ammonium oxalate) totaling 2.0 percent or more,
and

b. A bulk density, measured at 33 kPa water
retention, of 0.90 g/cm? or less, and

c. A phosphate retention® of 85 percent or more; or

2. In the fine-earth fraction, a phosphate retention of 25
percent or more, 30 percent or more particles of 0.02 to
2.0 mm, and one of the following:

a. Aluminum plus 1/2 iron percentages (by
ammonium oxalate) totaling 0.40 or more and, in
the 0.02-to-2.0-mm fraction, 30 percent or more
volcanic glass; or

b. Aluminum plus 1/2 iron percentages (by
ammonium oxalate) totaling 2.0 or more and, in
the 0,02-to-2.0-mm fraction, 5 percent or more
volcanic glass; or

c. Aluminum plus 1/2 iron percentages (by
ammonium oxalate) totaling between 0.40 and 2.0
and, in the 0.02-to-2.0-mm fraction, enough
volcanic glass so that the glass percentage, when
plotted against the value obtained by adding
aluminum plus 1/2 iron percentages in the fine-
earth fraction, falls within the shaded area of
Figure 1.

8 Blakemore, L.C., P-L. Searle, and BK Daly. 1987. Methods for chemical
analysis of soils. NZ Soil Bureau Scientific Report 80. pp 44-45.


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

A. MINERALOGY CLASSES OF SOIL FAMILIES
IN ANY PARTICLE-SIZE CLASS

Carbonatic: More than 40 percent (by weight)
carbonates (expressed as CaCO) plus gypsum, with
carbonates constituting more than 65 percent of the total
weight of carbonates plus gypsum, either in the fine-
earth fraction or in the less-than-20-mm fraction,
whichever has a higher percentage of carbonates plus
gypsum.

Ferritic: More than 40 percent (by weight) iron oxide
(extractable by dithionite citrate), reported as Fe,O, (or
28 percent reported as Fe), in the fine-earth fraction.
Gibbsitic: More than 40 percent (by weight) hydrated
aluminum oxides, reported as gibbsite and bohemite, in
the fine-earth fraction.

Oxidic: In the 0.02-to-2.0-mm fraction, less than 90
percent quartz and less than 40 percent of any other
single kind of mineral listed below; in the fine-earth
fraction, a ratio of extractable-iron-oxide plus gibbsite
percentages to the clay percentage? that is 0.20 or more:

extractable Fe2 Os (pet.) + gibbsite (pet.)
clay (pet.)

Serpentinitic: More than 40 percent (by weight)
serpentine minerals (antigorite, chrysotile, fibrolite, and
talc) in the fine-earth fraction.

Gypsic: More than 40 percent (by weight) carbonates
(expressed as CaCO;) plus gypsum, with gypsum
constituting more than 35 percent of the total weight of
carbonates plus gypsum, either in the fine-earth fraction
or in the less-than-20-mm fraction, whichever has a
higher percentage of carbonates plus gypsum.
Glauconitic: More than 40 percent (by weight)
glauconite in the fine-earth fraction.

202

| This key, like the others in Soil Taxonomy, is designed in such a way that
through

belongs into the fist class listed for which it meets the criteria. In the case
of Table 1, the user should first go through all the items in section A and, if
the soil in question does not meet the criteria for any class listed there,
proceed either to section B or to section C, depending on the particle-size
class of the soil.

2 Ifthe ratio of (percent water retained at 1500 kPa tension minus percent
organic carbon) to the percentage of measured clay is 0.6 or more in half or
‘mire of the control section, then the percentage of clay is considered to be
2.5 times (percent water retained at 1500 kPs tension minus percent organic
carbon), but no more than 100.


145

CABC. Other Placaquands which have a horizon 15 cm
or more thick, with 20 percent or more (by volume)
cemented soil material that does not slake in water after
air-drying, that has its upper boundary within 100 cm
either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Duric Placaquands

CABD. Other Placaquands that have a histic epipedon.
Histic Placaquands

CABE, Other Placaquands that have, between 25 and
100 om either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of
a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that
have a color value, moist, 1 unit or more higher and an
organic-carbon content 1 percent or more (absolute)
lower.

Thaptic Placaquands
CABF. Other Placaquands, N
Typic Placaquands D

Vitraquands

Key to subgroups

CADA. Vitraquands that have a lithic contact within 50
cm either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Lithic Vitraquands

CADB. Other Vitraquands which have a horizon 15 cm
or more thick, with 20 percent or more (by volume)
cemented soil material that does not slake in water after
air-drying, that has its upper boundary within 100 cm
either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Duric Vitraquands

CADC. Other Vitraquands that have a histic epipedon.
Histic Vitraquands

CADD. Other Vitraquands that have, between 25 and
100 cm either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of
a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that
have a color value, moist, 1 unit or more higher and an
organic-carbon content 1 percent or more (absolute)
lower.

Thaptic Vitraquands


498

or both of the following in more than half of each
pedon:
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more.
Chromic Epiaquerts
EAFJ. Other Epiaquerts.
Typic Epiaquerts

Natraquerts

Key to subgroups

EACA. All Natraquerts.
Typic Natraquerts

Salaquerts

Key to subgroups

BAAA. Salaquerts which, if not irrigated during the
year, have cracks in 6 or more out of 10 years that are 5
mm or more wide, through a thickness of 25 cm or more
within 50 cm of the mineral soil surface, for 210 or
more cumulative days per year.

Aridic Salaquerts
EAAB. Other Salaquerts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
are 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 90 or
more cumulative days per year.

Ustic Salaquerts

EAAC. Other Salaquerts that have a lithic or paralithic
contact within 100 cm of the mineral soil surface.

Leptic Salaquerts
EAAD. Other Salaquerts which have a layer 25 cm or
more thick that contains less than 27 percent clay in its
fine-earth fraction and has its upper boundary within
100 cm of the mineral soil surface.

Entic Salaquerts

EAAE. Other Salaquerts that have, in one or more
horizons within 30 cm of the mineral soil surface, 50
percent or more colors as follows:

1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or

3. A chroma of 3 or more.
Chromic Salaquerts

EAAF. Other Salaquerts.
Typic Salaquerts


61

The terms acid and nonacid are used only in names of
certain families of Entisols and Aquepts; they are not
used in sandy, sandy-skeletal, cindery, pumiceous, and
fragmental families of these taxa, or in Sulfaquepts and
Fragiaquepts, or in families with a carbonatic or gypsic
mineralogy. The term allic is used only in names of
Oxisol families.

Calcareous classes, if appropriate, are applied to the
same taxa as reaction classes and are also used in family
names of Aquolls, except Calciaquolls and Aquolls with
an argillic horizon. Calcareous and reaction class names
are not used in soil families that have a carbonatic or
gypsic mineralogy. Because calcareous implies
nonacid, the term nonacid is omitted as redundant if a
soil family is termed calcareous. Ifa soil is both
nonacid and noncalcareous, only the class name nonacid
is used (noncalcareous is never used in a family name).
The term calcareous, when used as a family modifier, is
considered a subclass of mineralogy and is added to the
mineralogy class name in parentheses, e.g.: fine-loamy,
mixed (calcareous), mesic Typic Haplaquolls.

Soil temperature classes

Soil temperature classes, as named and defined here,
are used as family differentiae in all orders. The names
are used as family modifiers unless the criteria for a
higher taxon carry the same limitation. Thus frigid is
implied in all boric suborders and cryic great groups,
and would be redundant if used in the names of families
within these classes of soils.

The Celsius (centigrade) scale is the standard. It is
assumed that the temperature is that of a soil that is not
For soil families that have a difference of 5°C or more
between mean summer (June, July, and August in the
northern hemisphere) and mean winter (December,
January, and February in the northern hemisphere) soil
temperatures, either at a depth of 50 cm from the soil
surface or at a lithic or paralithic contact, whichever is
shallower, the soil temperature classes, defined in terms
of the mean annual soil temperature, are as follows:

Frigid. — Lower than 8°C.
Mesic.— 8° to 15°C.
Thermic.— 15° to 22°C.
Hyperthermic— 22°C or higher.

For soil families that have a difference of less than 5°C
between mean summer and mean winter soil
temperatures, either at a depth of 50 cm from the soil
surface or at a lithic or paralithic contact, whichever is
shallower, the soil temperature classes, defined in terms
of the mean annual soil temperature, are as follows:

Isofrigid — Lower than 8°C.


506

fine-earth fraction and has its upper boundary within
100 cm of the mineral soil surface.
Entic Calciusterts

EEDI. Other Calciusterts that have, in one or more
horizons within 30 cm of the mineral soil surface, 50
percent or more colors as follows:

1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. A chroma of 3 or more.

Chromic Caleiusterts
BEDJ. Other Calciusterts.
Typic Calciusterts
Dystrusterts
Key to subgroups

EEAA. Dystrusterts that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Dystrusterts

EEAB. Other Dystrusterts that have, in one or more
horizons within 100 cm of the mineral soil surface,
aquic conditions for some time in most years (or
artificial drainage) and either:

1. Redoximorphic features; or

2. Enough active ferrous iron to give a positive
reaction to a.,a'-dipyridyl at a time when the soil
is not being irrigated.
Aquic Dystrusterts
EEAC. Other Dystrusterts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
are 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 210
or more cumulative days per year.
Aridic Dystrusterts

EFEAD, Other Dystrusterts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
are 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for less
than 150 cumulative days.

Udic Dystrusterts

EEAE. Other Dystrusterts that have a lithic or paralithic
contact, or the upper boundary of a duripan, within 100
cm of the mineral soil surface.

Leptic Dystrusterts

EEAF, Other Dystrusterts which have a layer 25 cm or
more thick that contains less than 27 percent clay in its
fine-carth fraction and has its upper boundary within
100 cm of the mineral soil surface.

Entic Dystrusterts


333

JEDM. Other Haplumbrepts.
Typic Haplumbrepts

Xerumbrepts

Key to subgroups

JECA. Xerumbrepts that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Xerumbrepts

JECB. Other Xerumbrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-carth
fraction with both a bulk density of 1.0 g/cm? or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Xerumbrepts

JECC. Other Xerumbrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2,0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0,02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Xerumbrepts

JECD. Other Xerumbrepts that have an umbric or a
mollic epipedon that is 50 cm or more thick.
Pachic Xerumbrepts

JECE. Other Xerumbrepts that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Xerumbrepts


7
Argillic horizons consisting of lamellae and intervening
albic materials are not within the concept of the glossic
horizon.

Gypsic horizon

The gypsic horizon is a horizon of enrichment with
secondary sulfates that is 15 cm or more thick and has
the following properties:

1, It is noncemented (an air-dried fragment slakes in
water); and

2. Its gypsum content is 5 percent or more (absolute)
higher than that of an underlying 1C horizon; and

3. The product of its thickness in centimeters multiplied
by its gypsum percentage is 150 or more.

Thus, a horizon 30 cm thick that has 5 percent gypsum
qualifies as a gypsic horizon if gypsum is absent in an
underlying 1C horizon. A layer 30 cm thick that has 6
percent gypsum qualifies if the gypsum content of the
underlying horizon is no more than 1 percent, The
gypsum percentage can be calculated by multiplying the
milliequivalents of gypsum per 100 g soil by the
milliequivalent weight of CaSO,-2H,0, which is 0.086.

Kandic horizon’
The kandic horizon:
1. Is a vertically continuous subsurface horizon that
underlies a coarser-textured surface horizon. The
minimum thickness of the surface horizon is 18 cm after
mixing, or 5 cm if the textural transition to the kandic
horizon is abrupt and there is no lithic, paralithic, or
petroferric contact (defined below) within 50 cm of the
mineral soil surface.
2. Has its upper boundary:
a. At the point where the clay percentage in the
fine-earth fraction, increasing with depth within a
vertical distance of 15 cm or less, is either
(1) 4 percent or more (absolute) higher than
in the surface horizon if that horizon has
less than 20 percent total clay in the fine-
earth fraction; or
(2) 20 percent or more (relative) higher than
in the surface horizon if that horizon has 20
to 40 percent total clay in the fine-earth
fraction; or
(3) 8 percent or more (absolute) higher than
in the surface horizon if that horizon has

‘5 The kandic horizon and the kandi and kanhapli great groups of soils
represent the work of the Intemational Committee on the Classification of
Low Activity Clays (ICOMLAC), chaired by Dr, Frank R. Moorman.



301
Paleustolls

Key to subgroups
HECA. Paleustolls which have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower; and

2. If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some or all parts for six tenths or more of
the cumulative days per year when the soil
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, remains moist in some or all parts for
less than 90 consecutive days per year when
‘the temperature at a depth of 50 cm below
the soil surface is higher than 8°C.
Torrertic Paleustolls

HFCB. Other Paleustolls which have both:
1. One or both of the following:

a, Cracks within 125 cm of the mineral soil M
surface that are 5 mm or more wide through ie)
a thickness of 30 cm or more for some time L

in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm ora lithic or paralithic
contact, whichever is shallower; and

2, If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section


34

The intent in defining the soil moisture control section
is to facilitate estimation of soil moisture regimes from
climatic data. The upper boundary of this control section
is the depth to which a dry (tension of more than 1500
kPa, but not air-dry) soil will be moistened by 2.5 cm of
water within 24 hours. The lower boundary is the depth
to which a dry soil will be moistened by 7.5 cm of water
within 48 hours, These depths do not include the depth
of moistening along any cracks or animal burrows that
are open to the surface.

If 7.5 cm of water moistens the soil to a lithic,
paralithic, or petroferric contact or to a petrocalcic
horizon or a duripan, the upper boundary of the rock or
of the cemented horizon constitutes the lower boundary
of the soil moisture control section. If a soil is
moistened to one of these contacts or horizons by 2.5 cm
of water, the soil moisture control section is the lithic
contact itself, the paralithic contact, or the upper
boundary of the cemented horizon. The control section
of such a soil is considered moist if the upper boundary
of the rock or the cemented horizon has a thin film of
water. If that upper boundary is dry, the control section
is considered dry.

The moisture control section of a soil extends
approximately: (1) from 10 to 30 cm below the soil
surface if the particle-size class of the soil is fine-loamy,
coarse-silty, fine-silty, or clayey; (2) from 20 cm to 60
cm if the particle-size class is coarse-loamy; and (3)
from 30 to 90 om if the particle-size class is sandy. If
the soil contains coarse fragments that do not absorb
and release water, the limits of the moisture control
section are deeper. In addition to the particle-size class,
the limits of the soil moisture control section are also
affected by differences in soil structure or pore-size
distribution, or by other factors that influence movement
and retention of water in the soil.

iE i) re

The soil moisture regimes are defined in terms of the
groundwater level, and in terms of the seasonal
presence or absence of water held at a tension of less
than 1500 kPa in the moisture control section. It is
assumed in the definitions that the soil supports
whatever vegetation it is capable of supporting, i.e., it
may be in crops, grass, or native vegetation, but it is not
being irrigated, nor fallowed to increase the amount of
stored moisture. These cultural practices affect the soil
moisture conditions as long as they are continued,

Aquic moisture regime.—The aquic (L. agua, water)
moisture regime signifies a reducing regime in a soil
that is virtually free of dissolved oxygen because it is
saturated by ground water or by water of the capillary
fringe. Some soils at times are saturated with water
while dissolved oxygen is present, either because the


186

CGDL. Other Fulvudands that have, undried, a 1500-
kPa water retention of 70 percent or more throughout a
layer 35 cm or more thick within 100 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Hydric Fulvudands

CGDM. Other Fulvudands that have, between 40 and
100 cm either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of
a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that
have a color value, moist, 1 unit or more higher and an
organic-carbon content 1 percent or more (absolute)
lower.

Thaptic Fulvudands

CGDN. Other Fulvudands that have a sum of
extractable bases of more than 25.0 cmol(+)/kg in the
fine-earth fraction throughout one or more horizons with
a total thickness of 15 cm or more between 25 and 75
cm either from the mineral soil surface, or from the top
of an organic layer with andic soil properties, whichever
is shallower.

Eutric Fulvudands
CGDO. Other Fulvudands.

Typic Fulvudands
Hapludands
Key to subgroups

CGFA, Hapludands that have a lithic contact within 50
cm either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Lithic Hapludands

CGFB, Other Hapludands that have a petroferric contact
within 100 cm either of the mineral soil surface, or of
the top of an organic layer with andic soil properties,
whichever is shallower.

Petroferric Hapludands

CGFC. Other Hapludands that have anthraquic
conditions.
Anthraquic Hapludands

CGFD. Other Hapludands which have both:

1. A horizon 15 cm or more thick, with 20 percent
or more (by volume) cemented soil material that
does not slake in water after air-drying, that has
its upper boundary within 100 cm either of the
mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower; and


244

a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower; and

2. A moisture control section which, in 6 or more
out of 10 years, is dry in all its parts for less than
three fourths of the cumulative days per year when.
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and

3. A hyperthermic, thermic, mesic, frigid, or an
iso soil temperature regime, and a torric moisture
regime that borders on an ustic regime.

Ustertic Torrifluvents

KDDB. Other Torrifluvents which have one or both of
the following:

1, Cracks within 125 cm of the soil surface that
are 5 mm or more wide through a thickness of 30
cm or more for some time in most years, and
slickensides or wedge-shaped aggregates in a
layer 15 cm or more thick that has its upper
boundary within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more
between the soil surface and either a depth of 100
om or a lithic or paralithic contact, whichever is
shallower.

Vertic Torrifluvents

KDDC. Other Torrifluvents which have:

1. A moisture control section which, in 6 or more
out of 10 years, is dry in all its parts for less than
three fourths of the cumulative days per year when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and

2. A thermic, mesic, or frigid soil temperature
regime, and a torric moisture regime that borders
on a xeric regime; and

3. Throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or both of the following:

a. More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or

b.A fine-earth fraction containing 30
percent or more particles 0.02 to 2.0 mm in
diameter, and either:
(1) In the 0,02-to-2.0-mm fraction,
more than 30 percent volcanic glass;
or

(2) In the 0,02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus


55

following: (a) a depth of 100 om, or (b) a root-limiting
layer or contact, or (c) a depth of 25 cm below the level
to which the soil is frozen 2 months after the summer
solstice.

4. For those Alfisols, Ultisols, and great groups of
Aridisols and Mollisols which have an argillic, a kandic,
or a natric horizon that has its upper boundary within
100 cm of the mineral soil surface and its lower
boundary at a depth of 25 cm or more, or which are in a
grossarenic subgroup, one of the following:

a. If there are no horizons or layers of strongly
contrasting particle sizes (defined below), and
there is no root-limiting layer or contact at a depth
of less than 50 cm from the top of the argillic,
kandic, or natric horizon: Either the whole argillic,
kandic, or natric horizon if less than 50 cm thick,
or its upper 50 cm; or

b. If there are horizons or layers of strongly
contrasting particle sizes within or below the
argillic, kandic, or natric horizon and within 100
om of the mineral soil surface: Between the upper
boundary of the argillic, kandic, or natric horizon
and either a depth of 100 cm from the mineral soil
surface or a root-limiting layer or contact,
whichever is shallower; or

c. If there is a root-limiting layer or contact
directly below the argillic, kandic, or natric
horizon: Between the upper boundary of the
argillic, kandic, or natric horizon and either the
root-limiting layer or contact, or a depth of 50 cm
from the top of the argillic, kandic, or natric
horizon, whichever is shallower.
5, For those Alfisols, Ultisols, and great groups of
Aridisols and Mollisols which have an argillic, a kandic,
or a natric horizon that has its upper boundary at a depth
of 100 cm or more from the mineral surface, and which
are not in a grossarenic subgroup: Between the lower
boundary of an Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and a depth of
100. cm.

6. For other soils which have an argillic or a natric
horizon that has its lower boundary at a depth of less
than 25 cm from the mineral soil surface: Between the
upper boundary of the argillic or natric horizon and
cither a depth of 100 cm or a root-limiting layer or
contact, whichever is shallower.

In general, the weighted average particle size of the
whole control section determines what particle-size or
substitute class name is used for a soil family. Ifa
particle-size class name applies for one part and a
substitute class name for the remaining part of the



243,

within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0,40 or more,

Vitrandic Cryofluvents

KDAC. Other Cryofluvents that have, in one or more
horizons within 50 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Cryofluvents

KDAD. Other Cryofluvents that are saturated with

water, in one or more layers within 100 cm of the

mineral soil surface, for 1 month or more per year in 6

or more out of 10 years. E
Oxyaquic Cryofluvents N

KDAE., Other Cryofluvents which have an Ap horizon,
or an A horizon 15 cm or more thick, that has a color
value, moist, of 3 or less and a color value, dry, of 5 or

less (crushed and smoothed sample).

Mollie Cryofluvents
KDAF, Other Cryofluvents.

Typic Cryofluvents
Torrifluvents
Key to subgroups

KDDA. Torrifluvents which have:
1. One or both of the following:

a, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge~
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
om of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either


2

b. Less than 20 percent (relative) in its fine-earth
fraction if that of the surface horizon contains 20
to 40 percent clay; or

c. Less than 8 percent (absolute) in its fine-earth
fraction if that of the surface horizon contains 40
percent or more clay), and

6. ACEC 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).

Petrocalcic horizon

The petrocalcic horizon is indurated or cemented
throughout each pedon by calcium carbonate or, less
commonly, by calcium and magnesium carbonate, with
or without accessory silica, to such a degree that dry
fragments do not slake in water. If soaked in acid,
cementation of the petrocalcic horizon is destroyed in
half or more of its lateral extent in each pedon. The
horizon is massive or platy, very hard, extremely hard,
or harder (cannot be penetrated by spade or auger) when
dry, and very firm, extremely firm, or firmer when
moist. Its noncapillary pores are filled, and it is a barrier
to roots. Its hydraulic conductivity is moderately low to
very low. A laminar capping commonly is present but is
not required.

The petrocalcic horizon is typically 10 em or more thick.
A minimum thickness of 2.5 cm is required if it is
laminar and rests on bedrock, and if the product of its
thickness in centimeters multiplied by its percentage of
CaCO, equivalent is 200 or more.

Petrogypsic horizon

The petrogypsic horizon 1s a horizon 10 cm or more
thick which is so strongly cemented with gypsum that
dry fragments do not slake in water and roots cannot
enter. Its gypsum content commonly is far greater than
the minimum requirements for a gypsic horizon, usually
60 percent or more. Petrogypsic horizons are restricted
to arid climates and to parent materials that are rich in
gypsum. They are rare in the United States but are
common in parts of Africa and Asia.

Placic horizon

The placic horizon (Gr. plax, plak-, flat stone; meaning
a thin cemented pan) is a thin, black to dark reddish pan
that is cemented either by iron, or iron and manganese,
or an iron-organic-matter complex. It is generally
between 2 and 10 mm thick, but may be as thin as 1 mm.
or, in spots, up to 40 mm thick. It is often associated

7 The percentage of clay is either measured by the pipette method, or
estimated to be 3 times (percent water retained at 1500 kPa tension minus
ppereent organic carbon), whichever value is higher, but no more than 100.


143

CAFC, Other Epiaquands that have a histic epipedon.
Histic Epiaquands

CAFD. Other Epiaquands that have more than 2.0
emol(+)/kg Al (by 1N KCI) in the fine-earth fraction
of one or more horizons with a total thickness of 10 cm
or more, between 25 and 50 cm either from the mineral
soil surface, or from the top of an organic layer with
andic soil properties, whichever is shallower.

Alic Epiaquands

CAFE. Other Epiaquands that have, undried, a 1500-
kPa water retention of 70 percent or more throughout a
layer 35 cm or more thick within 100 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Hydric Epiaquands

CAFF, Other Epiaquands that have, between 25 and
100 cm either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of
a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that
have a color value, moist, 1 unit or more higher and an
organic-carbon content 1 percent or more (absolute)
lower.

Thaptic Epiaquands
CAKG. Other Epiaquands.
Typic Epiaquands
Melanaquands
Key to subgroups

CAEA. Melanaquands that have a lithic contact within
50 cm either of the mineral soil surface, or of the top of
an organic layer with andic soil properties, whichever is
shallower.

Lithic Melanaquands

CAEB. Other Melanaquands that have extractable bases
plus 1N-KCl-extractable Al* totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more
horizons with a total thickness of 30 cm or more,
between 25 and 100 cm either from the mineral soil
surface, or from the top of an organic layer with andic
soil properties, whichever is shallower.
Acraquoxic Melanaquands

CAEC. Other Melanaquands that have both:

1. Undried, a 1500-kPa water retention of 70

percent or more throughout a layer 35 cm or more

thick within 100 cm either of the mineral soil

surface, or of the top of an organic layer with

andic soil properties, whichever is shallower; and



89

a. If peds are present, either a chroma of 2
or more on 50 percent or more of ped
exteriors, or no redox depletions with a
chroma of 2 or less in ped interiors; or
b. If peds are absent, a chroma of 2 or more
in 50 percent or more of the matrix; or
2. In 50 percent or more of the matrix, a hue of
10YR or yellower and either

a. Both a color value, moist, and chroma of
3 or more; or

b. A chroma of 2 or more if there are no
redox concentrations.
Aeric Kandiaqualfs

IAEF. Other Kandiaqualfs that have an Ap horizon with
acolor value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample), or materials

between the soil surface and a depth of 18 cm which
have these color values after mixing.
Umbric Kandiaqualfs

Typic Kandiaqualfs
Natraqualfs
Key to subgroups
TACA. Natraqualfs which have one or both of the
following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped.
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Natraqualfs

TACB. Other Natraqualfs that have both:
1. A glossic horizon, or interfingering of albic
materials into the natric horizon; and
2. In all horizons within 40 cm of the mineral soil
surface, an exchangeable sodium percentage of
less than 15 percent, and less magnesium and
sodium than calcium and extractable acidity.

Albic Glossic Natraqualfs

IACC. Other Natraqualfs that have an exchangeable
sodium percentage of less than 15 percent, and less
magnesium and sodium than calcium and extractable


488

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

Rhodic Kanhaplustults
GDCL. Other Kanhaplustults.

Typic Kanhaplustults

Paleustults

Paleustults are the Ustults which:
1, Within 150 cm of the mineral soil surface, either:

a. Do not have a clay decrease with increasing
depth of 20 percent or more (relative) from the
maximum clay content; or

b. Have 5 percent or more (by volume) skeletans
‘on faces of peds in the layer that has a 20 percent
lower clay content and, below that layer, a clay
increase of 3 percent or more (absolute) in the
fine-earth fraction; and
2. Do not have any horizon within 150 cm of the
mineral soi] surface in which plinthite either forms a
continuous phase or constitutes one half or more of the
volume; and

3. Do not have a fragipan or kandic horizon.

Plinthustults

Plinthustults are the Ustults that have one or more
horizons within 150 cm of the mineral soil surface in
which plinthite either forms a continuous phase or
constitutes one half or more of the volume.

Rhodustults

Key to subgroups
GDEA. Rhodustults that have a lithic contact within 50

cm of the mineral soil surface.
Lithic Rhodustults

GDEB. Other Rhodustults that have a texture of loamy
fine sand or coarser throughout the argillic horizon,
Psammentic Rhodustults

GDEC. Other Rhodustults,
Typic Rhodustults


321

either a depth of 100 cm, or a lithic, paralithic, or
petroferric contact if shallower,
Eutropepts, p. 323

ICE. Other Tropepts.
Dystropepts, p. 321

Dystropepts

Key to subgroups

JCEA, Dystropepts that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Dystropepts

ICEB. Other Dystropepts that have a petroferric contact
within 50 cm of the mineral soil surface.
Petroferric Dystropepts

ICEC. Other Dystropepts which have one or both of the
following:

1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Dystropepts

JCED. Other Dystropepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm} or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0,
Andic Dystropepts

JCEE. Other Dystropepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments

coarser than 2.0 mm, of which more than 66

percent are cinders, pumice, and pumice-like

fragments; or

2. A fine-earth fraction containing 30 percent or

more particles 0,02 to 2.0 mm in diameter, and

either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

oz-


284

ACFG. Other Tropohemists that have, within organic
materials, either one mineral layer 5 cm or more thick,
or two or more mineral layers of any thickness, in the
contro] section below the surface tier.

Fluvaquentic Tropohemists

ACFH. Other Tropohemists that have one or more
layers, with a total thickness of 25 cm or more, of the
subsurface and bottom tiers consisting of fibric
materials.

Fibric Tropohemists

ACFI. Other Tropohemists that have one or more layers,
with a total thickness of 12.5 cm or more, of the
subsurface and bottom tiers consisting of sapric
materials.

Sapric Tropohemists
ACFJ. Other Tropohemists.
Typic Tropohemists
SAPRISTS
Key to great groups

ADA. Saprists which have a sulfuric horizon that has its
upper boundary within 50 cm of the soil surface.
Sulfosaprists, p. 287

ADB. Other Saprists that have sulfidic materials within
100 cm of the soil surface.
Sulfisaprists, p. 287

ADC. Other Saprists which, in most years, either:

1, Are frozen in one or more layers within the

control section 2 months after the summer

solstice; or

2, Never freeze below a depth of 5 cm from the

soil surface but have a mean annual soil

temperature lower than 8°C.

Cryosaprists, p. 286

ADD. Other Saprists that have a mean annual soil

temperature lower than 8°C.

Borosaprists, p. 285
ADE. Other Saprists that have less than 5°C difference
between mean summer and mean winter soil
temperatures at a depth of 30 cm from the soil surface.

Troposaprists, p. 287

ADE, Other Saprists.

Medisaprists, p. 286


474

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic or a kandic horizon at a depth of 100
cm or more; and

2. Five percent or more (by volume) plinthite in
‘one or more horizons within 150 cm of the
mineral soil surface.

Grossarenic Plinthic Kandiudults

GCCG. Other Kandiudults that have a sandy particle
size throughout a layer extending from the mineral soil
surface to the top of an argillic or a kandic horizon at a
depth of 100 cm or more.

Grossarenic Kandiudults

GCCH. Other Kandiudults that have both:

1, An BCEC of 1.5 cmol(+)/kg clay or less (sum of
bases extracted with IN NH,O<Ac pH 7, plus IN-
KCl-extractable Al) in one or more horizons
within 150 cm of the mineral soil surface; and
2. Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface.

Acrudoxic Plinthic Kandiudults

GCCI, Other Kandiudults that have an ECEC of 1.5
cmol(+)/kg clay or less (sum of bases extracted with IN
'NH,OAc pH 7, plus 1N-KCl-extractable Al) in one or
more horizons within 150 cm of the mineral soil
surface.

Acrudoxic Kandiudults

GCCJ. Other Kandiudults that have both:

1. Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface; and

2. In one or more layers within 75 cm of the
mineral soil surface, redox depletions with a color
value, moist, of 4 or more and a chroma of 2 or
less, accompanied by redox concentrations, and
also aquic conditions for some time in most years
(or artificial drainage).

Plinthaquic Kandiudults

GCCK. Other Kandiudults that have both:

1. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm? or less, measured
at 33 kPa water retention, and aluminum plus 1/2
iron percentages (by ammonium oxalate) totaling
more than 1.0; and

2. In one or more layers within 75 cm of the
mineral soil surface, redox depletions with a color
value, moist, of 4 or more and a chroma of 2 or
less, accompanied by redox concentrations, and


431

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage),
Aquic Lithic Kandiudox
DEDD. Other Kandiudox that have a lithic contact
within 125 cm of the mineral soil surface.
Lithic Kandiudox

DEDE. Other Kandiudox that have, in one or more
horizons within 125 cm of the mineral soil surface,
both:

1, Five percent or more (by volume) plinthite; and

2, Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Plinthaquic Kandiudox
DEDF, Other Kandiudox that have 5 percent or more
(by volume) plinthite in one or more horizons within
125 cm of the mineral soil surface.
Plinthic Kandiudox

DEDG. Other Kandiudox that have, in one or more
horizons within 125 cm of the mineral soil surface,
redox depletions with a color value, moist, of 4 or more
and a chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage).

Aquic Kandiudox

DEDH. Other Kandiudox that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm? or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Kandiudox

DEDI. Other Kandiudox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 om; and

2. Fifty percent or more hue of 2.5YR or redder
and color value, moist, of 3 or less between 25
and 125 cm from the mineral soil surface.

Humic Rhodic Kandiudox

DEDJ. Other Kandiudox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 7.5YR or yellower
and color value, moist, of 6 or more between 25
and 125 cm from the mineral soil surface.

Humic Xanthic Kandiudox


428

2. An oxic horizon that has its lower boundary
within 125 cm of the mineral soil surface.
Umbreptic Eutrudox

DECJ. Other Eutrudox which have an oxic horizon that
has its lower boundary within 125 cm of the mineral
soil surface.

Inceptic Eutrudox

DECK. Other Eutrudox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 2.5YR or redder
and color value, moist, of 3 or less between 25
and 125 cm from the mineral soil surface.

Humic Rhodic Eutrudox

DECL. Other Eutrudox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 7.5YR or yellower
and color value, moist, of 6 or more between 25
and 125 cm from the mineral soil surface.

Humic Xanthic Eutrudox

DECM. Other Eutrudox that have 16 kg/m? or more
organic carbon between the mineral’soil surface and a
depth of 100 cm.

Humic Eutrudox

DECN. Other Eutrudox that have 50 percent or more
hue of 2.5YR or redder and color value, moist, of 3 or
less between 25 and 125 cm from the mineral soil
surface,

Rhodic Eutrudox

DECO. Other Eutrudox that have 50 percent or more
hue of 7.5YR or yellower and color value, moist, of 6 or
more between 25 and 125 cm from the mineral soil
surface.

Xanthic Eutrudox
DECP. Other Eutrudox.
Typic Eutrudox
Hapludox
Key to subgroups

DEEA. Hapludox that have, within 125 cm of the
mineral soil surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage),

Aquic Petroferric Hapludox


439

DCDB. Other Kandiustox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Kandiustox

DCDC. Other Kandiustox that have, within 125 cm of
the mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Aquic Lithic Kandiustox
DCDD. Other Kandiustox that have a lithic contact
within 125 cm of the mineral soil surface.
Lithic Kandiustox

DCDE. Other Kandiustox that have, in one or more
horizons within 125 cm of the mineral soil surface,
both:

1. Five percent or more (by volume) plinthite; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Plinthaquic Kandiustox
DCDF. Other Kandiustox that have 5 percent or more
(by volume) plinthite in one or more horizons within
125 om of the mineral soil surface.
Plinthic Kandiustox

DCDG. Other Kandiustox that have, in one or more
horizons within 125 cm of the mineral soil surface,
redox depletions with a color value, moist, of 4 or more
and a chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage).

Aquic Kandiustox
DCDH. Other Kandiustox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2, Fifty percent or more hue of 2.5YR or redder

and color value, moist, of 3 or less between 25 re)

and 125 em from the mineral soil surface. x
Humic Rhodic Kandiustox |

DCDI. Other Kandiustox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 7.5YR or yellower
and color value, moist, of 6 or more between 25
and 125 cm from the mineral soil surface.

Humic Xanthic Kandiustox


471

CFBE. Other Haplustands that have more than 6.0
percent organic carbon and colors of a mollic epipedon
throughout a layer 50 cm or more thick within 60 cm
either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Pachic Haplustands

CFBF. Other Haplustands that have, between 25 and
100 cm either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of
a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that
have a color value, moist, 1 unit or more higher and an
organic-carbon content | percent or more (absolute)
lower,

Thaptic Haplustands

CFBG. Other Haplustands which have a calcic horizon
that has its upper boundary within 125 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Calcic Haplustands

CFBH. Other Haplustands that have extractable bases
plus 1N-KCl-extractable Al** totaling less than 15.0
cmol(+)/kg in the fine-earth fraction throughout one or
more horizons with a total thickness of 60 cm or more
within 75 cm either of the mineral soil surface, or of the
top of an organic layer with andic soil properties,
whichever is shallower.

Dystric Haplustands

CFBI. Other Haplustands which have an oxic horizon
that has its upper boundary within 125 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Oxic Haplustands
CFBJ. Other Haplustands which have an argillic or a
kandic horizon that has its upper boundary within 125
em either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.
Alfic Haplustands
CFBK. Other Haplustands that have an umbric
epipedon.
Humic Haplustands
CFBL. Other Haplustands.
Typic Haplustands


a

units to a pH value of 4.0 or less (1:1 by weight in
water, or in a minimum of water to permit
measurement) within 8 weeks.

Sulfidic materials accumulate as a soil or sediment
which is permanently saturated, generally with brackish
water. The sulfates in the water are biologically reduced
to sulfides as the materials accumulate. Sulfidic
materials most commonly accumulate in coastal marshes
near the mouths of rivers that carry noncalcareous
sediments, but they may occur in fresh-water marshes if
there is sulfur in the water. Upland sulfidic materials
may have accumulated in a similar manner in the
geologic past.

Ifa soil containing sulfidic materials is drained, or if
sulfidic materials are otherwise exposed to aerobic
conditions, the sulfides oxidize and form sulfuric acid.
The pH value, which normally is near neutrality before
drainage or exposure, may drop below 3. The acid may
induce formation of iron and aluminum sulfates. The
iron sulfate, jarosite, may segregate to form the yellow
mottles that commonly characterize a sulfuric horizon.
The transition from sulfidic materials to a sulfuric
horizon normally requires very few years and may occur
within a few weeks. A sample of sulfidic materials, if
air-dried slowly in shade for about 2 months with
occasional remoistening, becomes extremely acid,

M
N

Weatherable minerals

Several references are made to weatherable minerals in
the text of this and subsequent chapters. Obviously, the
stability of a mineral in a soil is a partial function of the
soil moisture regime. Where weatherable minerals are
referred to in the definitions of diagnostic horizons and
of various taxa in this taxonomy, a humid climate, either
present or past, is always assumed, Minerals that are
included in the meaning of weatherable minerals are as
follows:

1. Clay minerals: All 2.1 lattice clays except one which
is currently considered to be an aluminum-interlayered
chlorite. Sepiolite, talc, and glauconite are also included
in this group of weatherable clay minerals, although
they are not everywhere of clay size.

2. Silt- and sand-size minerals (0.02 to 0.2 mm in
diameter). Feldspars, feldspathoids, ferromagnesian
minerals, glass, micas, zeolites, and apatite.

Obviously, this is a restricted meaning of the term
weatherable minerals. The intent is to include, in the
definitions of diagnostic horizons and various taxa, only
those weatherable minerals which are unstable in a
humid climate compared to other minerals, such as
quartz and 1:1 lattice clays, but which are more resistant
to weathering than calcite.


Epiaqualfs

Key to subgroups

IAIA. Epiaqualfs which have one or both of the
following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Epiaqualfs

TAIB. Other Epiaqualfs which have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or more of
the following:

1. A fine-earth fraction with both a bulk density of
1.0 g/om} or less, measured at 33 kPa water

retention, and aluminum plus 1/2 iron percentages
(by ammonium oxalate) totaling more than 1.0; or

2. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

3. A fine-earth fraction containing 30 percent or
‘more particles 0.02 to 2.0 mm in diameter, and
either:

a, In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b, In the 0,02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling

0.40 or more.
Aquandic Epiaqualfs

IAIC. Other Epiaqualfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
to 100 cm.

Arenic Epiaqualfs

IAID. Other Epiaqualfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 100
cm or more,

Grossarenic Epiaqualfs


Surface
horizons
tier...

T
Table 1.—Key to mineralogy classes ...
Table 2.—Key to mineralogy classes (Oxisols)

Temperature classes—
See Soil temperature classes
Textural

change, abrupt ..

ic perature regime
Tiers (diagnostic horizons of Histosols)
bottom tier ...

surface tier
TORRANDS...



254

2. A moisture control section which, in 6 or more
out of 10 years, is dry in all its parts for less than
three fourths of the cumulative days per year when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and
3. A thermic, mesic, or frigid soil temperature
regime, and a torric moisture regime that borders
on a xeric regime,

Xerertic Torriorthents

KEBC. Other Torriorthents which have one or both of
the following:

1. Cracks within 125 cm of the soil surface that
are 5 mm or more wide through a thickness of 30
cm or more for some time in most years, and
slickensides or wedge-shaped aggregates in a
layer 15 cm or more thick that has its upper
boundary within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more
between the soil surface and either a depth of 100
cm ora lithic or paralithic contact, whichever is
shallower.

Vertic Torriorthents

KEBD. Other Torriorthents which have:

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

2. A moisture control section which, in 6 or more
out of 10 years, is dry in all its parts for less than
three fourths of the cumulative days per year when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and
3. A hyperthermic, thermic, mesic, frigid, or an
iso soil temperature regime, and a torric moisture
regime that borders on an ustic regime.

Lithic Ustic Torriorthents

KEBE. Other Torriorthents which have:

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

2. A moisture control section which, in 6 or more
out of 10 years, is dry in all its parts for less than
three fourths of the cumulative days per year when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and

3. A thermic, mesic, or frigid soil temperature
regime, and a torric moisture regime that borders

on a xeric regime.
Lithic Xeric Torriorthents

KEBF, Other Torriorthents that have a lithic contact
within 50 cm of the soil surface.
Lithic Torriorthents


322

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Dystropepts

JCEF. Other Dystropepts that have, in one or more
horizons within 100 cm of the mineral soil surface,
redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or
artificial drainage).

Aquic Dystropepts

ICEG. Other Dystropepts that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for | month or more per year in 6 or more out of
10 years,

Oxyaquic Dystropepts

JCEH. Other Dystropepts which have both:

1, Either 0.2 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

2. A slope of less than 25 percent.
Fluventic Dystropepts

JCEI. Other Dystropepts that have both:
1. An ustic moisture regime; and

2. ACEC (by IN NH,OAc pH 7) of less than 24
emol(+)/kg clay! in 50 percent or more of the soil
volume between a depth of 25 cm from the
mineral soil surface and either a depth of 100 cm,
or a lithic or paralithic contact if shallower.
Ustoxic Dystropepts

JCEJ. Other Dystropepts that have a CEC (by 1N
NH,OAc pH 7) of less than 24 cmol(+)/kg clay? in 50
percent or more of the soil volume between a depth of
25 cm from the mineral soil surface and either a depth
of 100 cm, or a lithic or paralithic contact if shallower.
Oxic Dystropepts

IJCEK. Other Dystropepts that have an ustic moisture

regime,
Ustic Dystropepts

1 Some cambic horizons with properties that approach those of an oxic
horizon do not disperse well. Ifthe ratio of (percent water retained at 1500
kPa tension minus percent organic carbon) to the percentage of measured
clay in the fine-earth fraction is 0.6 or more, then the percentage of clay is
‘considered to equal either (1) the measured percentage of clay, or (2) three
times (percent water retained at 1500 kPa tension minus percent organic
carbon), whichever value is higher, but no more than 100.

2 See footnote 1.


Borosaprists

Key to subgroups
ADDA. Borosaprists that have a lithic contact within

the control section.
Lithic Borosaprists

ADDB. Other Borosaprists which have both:

1. One or more layers, with a total thickness of
12.5 cm or more, of the subsurface and bottom
tiers consisting of fibric materials; and

2, A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Fibric Terric Borosaprists

ADDC. Other Borosaprists which have both:

1, One or more layers, with a total thickness of 25
cm or more, of the subsurface and bottom tiers
consisting of hemic materials; and

2. A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Hemic Terric Borosaprists

ADDD. Other Borosaprists which have a mineral layer
30 cm or more thick that has its upper boundary within
the control section below the surface tier.

Terric Borosaprists

ADDE. Other Borosaprists that have one or more limnic
layers with a total thickness of 5 cm or more within the
control section.

Limnic Borosaprists

ADDF. Other Borosaprists that have, within organic
materials, either one mineral layer 5 cm or more thick,
or two or more mineral layers of any thickness, in the
control section below the surface tier.

Fluvaquentic Borosaprists

ADDG. Other Borosaprists that have one or more
layers, with a total thickness of 12.5 cm or more, of the
subsurface and bottom tiers consisting of fibric
materials.

Fibric Borosaprists

ADDH. Other Borosaprists that have one or more
layers, with a total thickness of 25 cm or more, of the
subsurface and bottom tiers consisting of hemic
materials,

Hemic Borosaprists

ADDI. Other Borosaprists.
Typic Borosaprists


446

BBC. Other Cryods that have 6 percent or more organic
carbon throughout a layer 10 cm or more thick within.
the spodic horizon,

Humicryods, p. 447
BBD. Other Cryods,

Haplocryods, p. 446

Duricryods

Key to subgroups
BBBA. Duricryods which have both:

1, In one or more horizons within 75 om of the
mineral soil surface, redoximorphic features, and
also aquic conditions for some time in most years
(or artificial drainage); and

2. Andic soil properties throughout horizons that
have a total thickness of 25 cm or more within 75
cm either of the mineral soil surface, or of the top
of an organic layer with andic soil properties,

whichever is shallower.
Aquandic Duricryods

BBBB. Other Duricryods which have andic soil
properties throughout horizons that have a total
thickness of 25 cm or more within 75 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Andic Duricryods

BBBC. Other Duricryods that have, in one or more
horizons within 75 cm of the mineral soil surface,
redoximorphic features, and also aquic conditions for
some time in most years (or artificial drainage),

Aquic Duricryods

BBBD. Other Duricryods that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Duricryods

BBBE. Other Duricryods that have 6 percent or more
organic carbon throughout a layer 10 cm or more thick
within the spodic horizon.

Humic Duricryods
BBBF. Other Duricryods.
Typic Duricryods
Haplocryods
Key to subgroups

BBDA. Haplocryods that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Haplocryods


175

CDCC. Other Haploxerands that have, between 25 and
100 cm from the mineral soil surface, a layer 10 cm or
more thick with more than 3.0 percent organic carbon
and colors of a mollic epipedon throughout, underlying
one or more horizons with a total thickness of 10 cm or
more that have a color value, moist, | unit or more
higher and an organic-carbon content | percent or more
(absolute) lower.

Thaptic Haptoxerands

CDCD. Other Haploxerands which have a calcic horizon
that has its upper boundary within 125 cm of the
mineral soil surface.

Calcic Haploxerands

CDCE. Other Haploxerands which have an argillic or a
kandic horizon that has both:

1. An upper boundary within 125 cm of the
mineral soil surface, and
2. A base saturation (by sum of cations) of less

than 35 percent throughout its upper 50 cm.
Ultic Haploxerands
CDCF. Other Haploxerands which have both:
1. A mollic or an umbric epipedon; and
2. An argillic or a kandic horizon that has its
upper boundary within 125 cm of the mineral soil
surface, or of the top of an organic layer with
andic soil properties, whichever is shallower.
Alfic Humic Haploxerands
CDCG. Other Haploxerands which have an argillic or a
kandic horizon that has its upper boundary within 125
cm of the mineral soil surface. :
Alfic Haploxerands

CDCH. Other Haploxerands that have a molli¢ or an
umbric epipedon.

Humic Haploxerands
CDCI. Other Haploxerands.
Typic Haploxerands
Melanoxerands
Key to subgroups

CDBA. Melanoxerands that have more than 6.0 percent
organic carbon and colors of a mollic epipedon
throughout a layer 50 cm or more thick within 60 cm.
either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Pachic Melanoxerands

CDBB. Other Melanoxerands.
Typic Melanoxerands

ozD>p


24

b. In the upper 18 cm of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.18 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.77-(0.046 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
1 and 13; and

2. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Xerollic Calciorthids

FBEK. Other Calciorthids which have both:

1. A weighted average percentage of organic

carbon, relative to the weighted average ratio of

sand to noncarbonate clay, as follows: A
R
|

a. In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,

(1) 0.60 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.15 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.64-(0.038 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
1 and 13; or

b. In the upper 18 om of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.18 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.77-(0.046 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
J and 13; and


Vermiborolls

Key to subgroups

HEEA. Vermiborolls that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Vermiborolls

HEEB. Other Vermiborolls which have both:

1. Acolor value, dry, of 5 either in the upper 18
em of the mollic epipedon, after mixing, or in an
Ap horizon 18 cm or more thick; and

2. A moisture control section which, in 6 or more
out of 10 years, is dry in some part for six tenths.
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the
soil surface is higher than 5°C. .

Aridic Vermiborolls

HEEC. Other Vermiborolls that have both:
1. A mollic epipedon less than 75 em thick; and

2. A chroma of 1 or less (crushed and smoothed
sample) either in the upper 18 cm of the mollic
epipedon, after mixing, or in an Ap horizon 18 cm
or more thick.

Hapludic Vermiborolls

HEED. Other Vermiborolls that have a chroma of 1 or
less (crushed and smoothed sample) either in the upper
18 cm of the mollic epipedon, after mixing, or in an Ap
horizon 18 cm or more thick.

Udic Vermiborolls

HEEE. Other Vermiborolls that have a mollic epipedon
Jess than 75 cm thick.

Haplic Vermiborolls
HEEF. Other Vermiborolls.

Typic Vermiborolls
RENDOLLS
Key to subgroups

HCAA. Rendolls that have both;
1. A cryic or pergelic soil temperature regime; and

2, A lithic contact within 50 cm of the mineral soil
surface.
Cryic Lithic Rendolls
HCAB. Other Rendolls that have a lithic contact within

50 cm of the mineral soil surface.
Lithic Rendolls

HCAC, Other Rendolls that have a cryic or pergelic soil
temperature regime.

Cryic Rendolls

TOs


201
2. A frigid or colder soil temperature regime; and
3. One or both of the following:

a. Cracks within 125 cm of the soil surface
that are 5 mm or more wide through a
thickness of 30 cm or more for some time in
most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the soil surface; or

b. A linear extensibility of 6.0 cm or more
between the soil surface and either a depth
of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Borollic Vertic Paleargids

FADB. Other Paleargids which have both:

1. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if there is
no petrocalcic horizon within 40 cm of the
soil surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between |
and 13; or

b. In the upper 18 cm of the soil, if there is a
petrocalcic horizon with an upper boundary
between 18 and 40 cm from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/elay ratio), or
more, with a sand/clay ratio between }
and 13; and

2. A frigid or colder soil temperature regime, and
an aridic moisture regime that borders on an ustic
regime.

Borollic Paleargids

FADC. Other Paleargids which have one or both of the
following:

1. Cracks within 125 om of the soil surface that
are 5 mm or more wide through a thickness of 30
cm or more for some time in most years, and
slickensides or wedge-shaped aggregates in a


365

(2) In one or more of its subhorizons,
many coarse redox concentrations with
a hue of SYR or redder or a chroma of
6 or more, or both.

Paleudolls, p. 372

HGB. Other Udolls which:

1. Have a calcic horizon that has its upper
boundary within 100 cm of the mineral soil
surface; and

2. Do not have an argillic horizon above the calcic
horizon; and
3. In all parts above the calcic or petrocalcic
horizon, after the materials between the soil
surface and a depth of 18 cm have been mixed,
are either calcareous or have a texture of loamy
fine sand or coarser.

Calciudolls, p. 368

HGC. Other Udolls that have an argillic horizon.
Argiudolls, p. 365

HGD. Other Udolls that have a mollic epipedon which:

1. Either below an Ap horizon or below a depth of
18 cm from the mineral soil surface, contains 50
percent or more (by volume) wormholes, worm
casts, or filled animal burrows; and

2. Either rests on a lithic contact, or has a
transition zone to the underlying horizon in which
25 percent or more of the soil volume consists of
discrete wormholes, worm casts, or animal
burrows filled with material from the mollic
epipedon and from the underlying horizon.
Vermudolls, p. 373

HGE. Other Udolls,
Hapludolls, p, 368

Argiudolls

Key to subgroups
HGCA, Argiudolls that have a lithic contact within 50
cm of the mineral soil surface.

Lithic Argiudolls

HGCB. Other Argiudolls which have both:

1. Aquic conditions for some time in most years
(or artificial drainage), either:

a, Within 40 cm of the mineral soil surface,
in horizons that also have redoximorphic
features; or

b. Directly below the mollic epipedon, in
one or more horizons with a total thickness

roe


60

they are not mentioned in families of Quartzipsamments.
because these soils are siliceous by definition.

Obviously, it is normally impossible to be certain what
percentages of the different kinds of clay minerals are
present in a soil, Quantitative methods of identification
are still subject to change, and although much progress
has been made in the past few decades, an element of
judgement still enters into the estimation. However, one
does not have to depend exclusively on X-ray, surface,
and DTA determinations. Other physical and chemical
properties, e.g., changes in volume, cation-exchange
capacity, and consistence, can suggest the mineralogy of
many clayey soils,

The clay mineralogy descriptions for clayey soils are
based on the weighted average percentages of the
control section’s fine-earth fraction.

Calcareous and reaction classes

In the following, presence or absence of carbonates in
mineral soils and reaction classes are treated together
because they are so intimately related; ¢.g., a calcareous
horizon cannot be strongly acid. Two classes identifying
the presence or absence of carbonates, calcareous and
noncalcareous, are defined for selected taxa. Their
control section is one of the following: (1) between 25
and 50 cm from the mineral soil surface, or (2) between
a depth of 25 cm from the mineral soil surface and a
lithic or paralithic contact at a depth between 25 and 50
om, or (3) a layer directly above a lithic or paralithic
contact that is less than 25 cm below the mineral soil
surface. Definitions of the two classes are as follows:

Calcareous.—The fine-earth fraction effervesces in all
parts with cold dilute HCI.

Noncalcareous.——The fine-earth fraction does not
effervesce in all parts with cold dilute HCI. The term
noncalcareous is not used as part of the family name.

It should be noted that a soil containing dolomite is
calcareous, and that effervescence of dolomite, when
treated with cold dilute HCl, is slow.

‘The control section for reaction classes is the same as
for particle-size classes. Three classes, acid, nonacid,
and allic, are defined for use in selected taxa, as
follows:

Acid.—The pH is less than 5,0 in 0.01 M CaCl, (2:1)
throughout the control section (about 5.5 in H,O, 1:1).

Nonacid.—The pH is 5.0 or more in 0.01 M CaCl, (2:1)
in some or all layers of the control section. The term
nonacid is not used in the family name of calcareous
soils.

Alltic.—A layer 30 cm or more thick within the control
section contains more than 2 cmol(+) of KCl-extractable
Al per kg soil in the less-than-2.0-mm fraction.


276

ABFJ. Other Medifibrists that have one or more layers,
with a total thickness of 25 cm or more, of the
subsurface and bottom tiers consisting of hemic
materials.

Hemic Medifibrists

ABFK. Other Medifibrists that have one or more layers,
with a total thickness of 12.5 cm or more, of the
subsurface and bottom tiers consisting of sapric
materials.

Sapric Medifibrists
ABFL. Other Medifibrists.

Typic Medifibrists
Sphagnofibrists
Key to subgroups

ABAA. Sphagnofibrists which:

1, Have a mean annual soil temperature of 0°C or
less; and

2. In most years, are either frozen in one or more
layers within the control section 2 months after
the summer solstice, or freeze to a depth of 5 cm
or more below the soil surface.

Pergelic Sphagnofibrists

ABAB, Other Sphagnofibrists that have a layer of water
within the control section below the surface tier.
Hydric Sphagnofibrists

ABAC. Other Sphagnofibrists that have a lithic contact
within the control section.
Lithic Sphagnofibrists

ABAD. Other Sphagnofibrists which:

1, Have a mean annual soil temperature between
0°C and 8°C; and
2. In most years, are either frozen in one or more
layers within the control section 2 months after
the summer solstice, or freeze to a depth of 5S cm
or more below the soil surface.

Cryic Sphagnofibrists

ABAE. Other Sphagnofibrists which have a mineral
layer 30 cm or more thick that has its upper boundary
within the control section below the surface tier.

Terric Sphagnofibrists

ABAF. Other Sphagnofibrists that have one or more
limnic layers with a total thickness of 5 cm or more
within the control section,

Limnic Sphagnofibrists


487

fraction with both a bulk density of 1.0 g/cm} or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Kanhaplustults

GDCG. Other Kanhaplustults that have 5 percent or
more (by volume) plinthite in one or more horizons
within 150 cm of the mineral soil surface.

Plinthic Kanhaplustults

GDCH. Other Kanhaplustults that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
concentrations, a color value, moist, of 4 or more, anda
hue which is 10YR or yellower, but which becomes
redder with increasing depth within 100 cm of the
mineral soil surface.

Ombroaquic Kanhaplustults
GDCI. Other Kanhaplustults which, if neither irrigated
nor fallowed to store moisture, have either:

1. A thermic, mesic, or colder soil temperature
regime, and a moisture control section which, in 6
or more out of 10 years, is dry in some part for
more than four tenths of the cumulative days per
year when the soil temperature at a depth of 50
em below the soil surface is higher than 5°C; or

2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is
moist in some or all parts for less than 180
cumulative days per year when the temperature at
a depth of 30 cm below the soil surface is higher
than 8°C,

Aridic Kanhaplustults

GDCJ. Other Kanhaplustults which, if neither irrigated
nor fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for 135
cumulative days or less per year when the
temperature at a depth of 50 cm below the soil
surface is higher than 5°C; or
2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is dry
in some or all parts for less than 120 cumulative
days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8°C.
Udic Kanhaplustults



85
IAIE. Other Epiaqualfs which have:

1, An Ap horizon that meets all the requirements
for an umbric epipedon except thickness, or
materials between the soil surface and a depth of
18 cm that meet these requirements after mixing;
and

2. In one or more horizons between the A or Ap
horizon and a depth of 75 cm below the mineral
soil surface, one of the following colors:

a. A hue of 7.5YR or redder in 50 percent or
more of the matrix; and

(1) If peds are present, a chroma of 2
or more on 50 percent or more of ped
exteriors, or no redox depletions with
a chroma of 2 or less in ped interiors;

or

(2) If peds are absent, a chroma of 2 or Jal
more in 50 percent or mote of the L
matrix; or F

b. In 50 percent or more of the matrix, a hue
of 10YR or yellower and either

(1) Both a color value, moist, and
chroma of 3 or more; or

(2) A chroma of 2 or more if there are
no redox concentrations.
Aeric Umbric Epiaqualfs

IAIF. Other Epiaqualfs which have both:

1. A mollic epipedon, or an Ap horizon that meets
all the requirements for a mollic epipedon except
thickness, or materials between the soil surface
and a depth of 18 cm that meet these requirements
after mixing; and

2. In 50 percent or more of the matrix in one or
more horizons between the A or Ap horizon and a
depth of 75 cm from the mineral soil surface,
chromas as follows:

a. Three or more if the mean annual soil
temperature is lower than 15°C; or
b. If the mean annual soil temperature is
15°C or higher:

(1) Three or more if the hue is 2.5Y or

redder and the color value, moist, is 6
or more; or

(2) Two or more if the hue is 2.5Y or
redder and the color value, moist, is 5
or less; or

(3) Three or more if the hue is
yellower than 2.5Y; or


201
Cryaquepts

Key to subgroups

JAEA, Cryaquepts which have, within 150 cm of the
mineral soil surface, one or more of the following:

1. A sulfuric horizon; or

2. A horizon 15 cm or more thick that has all the
characteristics of a sulfuric horizon, except that it
has a pH value between 3.5 and 4.0; or

3. Sulfidic materials,
Sulfic Cryaquepts

JAEB. Other Cryaquepts that have both a histic
epipedon and a lithic contact within 50 om of the
mineral soil surface.

Histic Lithic Cryaquepts
JAEC, Other Cryaquepts that have a lithic contact
within 50 cm of the mineral soil surface,

Lithic Cryaquepts

JAED, Other Cryaquepts which have both:

1. A histic epipedon that is continuous in cach
pedon; and
2. A mean annual soil temperature of 0°C or
lower.
Histic Pergelic Cryaquepts
JAEE, Other Cryaquepts which have both:
1. A histic epipedon that is discontinuous in each
2. A mean annual soil temperature of 0°C or
lower.
Pergelic Ruptic-Histic Cryaquepts
JAEF, Other Cryaquepts which have both:
1. An umbric epipedon; and
2. A mean annual soil temperature of 0°C or

lower.
Humic Pergelic Cryaquepts

JAEG. Other Cryaquepts that have a mean annual soil
temperature of 0°C or lower,
Pergelic Cryaquepts
JAEH, Other Cryaquepts which have one or both of the
following:
1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shi
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or


460
GADB. Other Kandiaquults that have both:

1, A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic or a kandic horizon at a depth of 50
to 100 cm; and

2, Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface.

Arenic Plinthic Kandiaquults

GADC. Other Kandiaquults which:
1. Do not have an ochric epipedon; and

2. Have a sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic or a kandic horizon at a depth of 50
to 100 cm.

Arenic Umbric Kandiaquults

GADD. Other Kandiaquults that have a sandy particle
size throughout a layer extending from the mineral soil
surface to the top of an argillic or a kandic horizon at a
depth of 50 to 100 cm.

Arenic Kandiaquults

GADE. Other Kandiaquults that have a sandy particle
size throughout a layer extending from the mineral soil
surface to the top of an argillic or a kandic horizon at a
depth of 100 cm or more.

Grossarenic Kandiaquults

GADF, Other Kandiaquults that have 5 percent or more
(by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface.

Plinthic Kandiaquults

GADG. Other Kandiaquults that have 50 percent or
more chroma of 3 or more in one or more horizons
between either the A or Ap horizon or a depth of 25 cm
from the mineral soil surface, whichever is deeper, and
a depth of 75 cm.

Aeric Kandiaquults

GADH. Other Kandiaquults that do not have an ochric
epipedon.

Umbric Kandiaquults
GADI. Other Kandiaquults,
Typic Kandiaquults
Kanhaplaquults
Key to subgroups

GAEA. Kanhaplaquults that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-carth
fraction with both a bulk density of 1.0 g/cm? or less,
measured at 33 kPa water retention, and aluminum plus


323
ICEL. Other Dystropepts.

Typic Dystropepts
Eutropepts
Key to subgroups
ICDA. Eutropepts that have a lithic contact within 50
cm of the mineral soil surface.

Lithic Eutropepts

JCDB. Other Eutropepts which have both:
1. One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and cither
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower, and

2. In one or more horizons within 100 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage).
Aquertic Eutropepts
ICDC. Other Eutropepts which have one or both of the
following:

1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 om or a lithic or paralithic contact,
whichever is shallower.

Vertic Eutropepts

JCDD. Other Eutropepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm} or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Eutropepts

JCDE. Other Eutropepts that have, throughout one or
more horizons with a total thickness of 18 cm or more


359

redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or
artificial drainage).

Aquic Haploborolls
HEGN. Other Haploborolls that are saturated with
water, in one or more layers within 100 cm of the
mineral soil surface, for 1 month or more per year in 6

or more out of 10 years.
Oxyaquic Haploborolls
HEGO. Other Haploborolls which have:

1. A color value, dry, of 5 or more either in the

upper 18 cm of the mollic epipedon, after mixing,
or in an Ap horizon 18 cm or more thick; and

2. If not irrigated, a moisture control section
which, in 6 or more out of 10 years, is dry in some
part for six tenths or more of the cumulative days
per year when the soil temperature at a depth of
50 cm below the soil surface is 5°C or higher; and

3. Either 0.3 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

4. A slope of less than 25 percent.
Torrifluventic Haploborolls

HEGP. Other Haploborolls which:

1, Have a color value, dry, of 5 or more either in
the upper 18 cm of the mollic epipedon, after
mixing, or in an Ap horizon 18 cm or more thick;
and

2. If not irrigated, have a moisture control section
which, in 6 or more out of 10 years, is dry in some
part for six tenths or more of the cumulative days
per year when the soil temperature at a depth of
50 cm from the soil surface is 5°C or higher; and
3. Do not have a cambic horizon and do not, in the
lower part of the mollic epipedon, meet the
requirements for a cambic horizon except color.
Torriorthentic Haploborolls

HEGQ. Other Haploborolls which have both:

1. A color value, dry, of 5 or more either in the

upper 18 cm of the mollic epipedon, after mixing,
or in an Ap horizon 18 cm or more thick; and

2. A moisture control section which, in 6 or more
out of 10 years, is dry in some part for six tenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the
soil surface is higher than 5°C.

Aridic Haploborolls



120

remains moist in some or all parts for less than 90
consecutive days per year when the temperature at
a depth of 50 cm below the soil surface is higher
than 8°C.

Aridic Haplustalfs

ICHL. Other Haplustalfs that have a CEC of less than
24 emol(+)/kg clay (by IN NH,OAc pH 7) in 50 percent
or more either of the argillic horizon if less than 100 cm
thick, or of its upper 100 cm.

Kanhaplic Haplustalfs

ICHM. Other Haplustalfs that have an argillic horizon
with a base saturation (by sum of cations) of less than
75 percent throughout.

Ultic Haplustalfs

ICHN. Other Haplustalfs which, if neither irrigated nor
fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for four tenths
or less of the cumulative days per year when the
temperature at a depth of 50 cm below the soil
surface is higher than 5°C; or

2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is dry
in some or all parts for less than 120 cumulative
days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8°C.

Udic Haplustalfs
ICHO. Other Haplustalfs.
Typic Haplustalfs
Kandiustalfs
Key to subgroups

ICDA. Kandiustalfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 100
cm or more.

Grossarenic Kandiustalfs

ICDB. Other Kandiustalfs that have both:

1, In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. A sandy particle size throughout a layer
jing from the mineral soil surface to the top
of an argillic horizon at a depth of 50 to 100 cm.
Aquic Arenic Kandiustalfs


194

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if the lithic
contact is 40 cm or more below the soil

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 cm of the soil, if the lithic
contact is between 18 and 40 cm from the
soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
tatio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

3. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an 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 which have one or both of the
following:

1. Cracks within 125 cm of the soil surface that
are 5 mmm or more wide through a thickness of 30
cm or more for some time in most years, and
slickensides or wedge-shaped aggregates in a
layer 15 ctf or more thick that has its upper
boundary within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more
between the soil surface and either a depth of 100
cm ora lithic or paralithic contact, whichever is
shallower.

Vertic Natrargids

FACD. Other Natrargids which have:

1, Skeletans on 10 percent or more of the faces of
peds that are 2.5 cm or more below the upper
boundary of the natric horizon; and


392

which, in 6 or more out of 10 years, is dry in
some part for four tenths or less of the
cumulative days per year when the
temperature at a depth of 50 om below the
soil surface is higher than 5°C; or

b. A hyperthenmic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, is dry in some or all parts for less
than 120 cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 8°C.

Udertic Paleustolls

HFCC. Other Paleustolls which have one or both of the
following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and cither a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Paleustolls

HFCD., Other Paleustolls that have a mollic epipedon 50
cm or more thick with a texture finer than loamy fine
sand,

Pachic Paleustolls

HFCE. Other Paleustolls that have a petrocalcic horizon
within 150 cm of the mineral soil surface,
Petrocalcic Paleustolls

HFCF. Other Paleustolls that have, in one or more
horizons within 100 cm of the mineral soil surface,
redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or
artificial drainage).

Aquic Paleustolls
HFCG. Other Paleustolls which:

1, Are calcareous throughout after the soil has
been mixed to a depth of 18 cm, and have a calcic
horizon within the following depths if the particle-
size control section is
a, Sandy: within 100 cm of the mineral soil
surface; or
b. Loamy: within 60 cm of the mineral soil
surface; or
¢, Clayey: within 50 cm of the mineral soil
surface; and


481
Plinthudults

Plinthudults are the Udults which have plinthite that
either forms a continuous phase in, or constitutes more
than half the matrix of, one or more horizons within 150
em of the mineral soil surface.

Rhodudults

Key to subgroups
GCFA. Rhodudults that have a lithic contact within 50

cm of the mineral soil surface.
Lithic Rhodudults

GCEB. Other Rhodudults that have a texture of loamy
fine sand or coarser throughout the argillic horizon.

Psammentic Rhodudults
GCFC. Other Rhodudults.
Typic Rhodudults
USTULTS
Key to great groups

GDA. Ustults that have one or more horizons within
150 cm of the mineral soil surface in which plinthite
either forms a continuous phase or constitutes one half
or more of the volume.

Plinthustults, p. 488

GDB. Other Ustults which:

1. Do not have a lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface;
and

2. Have a CEC of 16 cmol(+)/kg clay or less (by
IN NH,OAc pH 7) and an ECEC of 12 emol(+)/kg
clay of less (sum of bases extracted with 1N
NH,OAc pH 7, plus IN-KCl-extractable Al) in 50
percent or mote either of the argillic or kandic
horizon if less than 100 cm thick, or of its upper
100 cm; and

3. Within 150 cm of the mineral soil surface,
either:
a. Do not have a clay decrease with
increasing depth of 20 percent or more
(relative) from the maximum clay content;
or



123

consecutive days per year when the temperature at
a depth of 50 cm below the soil surface is higher
than 8°C.

Aridic Kanhaplustalfs

ICED. Other Kanhaplustalfs which, if neither irrigated
nor fallowed to store moisture, have either:

1, A mesic or thermic soi] temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for 135
curnulative days or less per year when the
temperature at a depth of 50 cm below the soil
surface is higher than 5°C; or
2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is dry
in some or all parts for less than 120 cumulative
days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8°C.
Udic Kanhaplustalfs

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

Rhodic Kanhaplustalfs
ICEF. Other Kanhaplustalfs,
Typic Kanhaplustalfs
Natrustalfs
Key to subgroups

ICCA. Natrustalfs which have one or both of the

following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped.
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Natrustalfs

ICCB. Other Natrustalfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 100
cm or more.

Grossarenic Natrustalfs

ar >


380

years, remains moist in some or all parts for
less than 90 consecutive days per year when
the temperature at a depth of 50 cm below
the soil surface is higher than 8°C.
Torrertic Calciustolls

HFDE. Other Calciustolls which have both:
1, One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates ina layer 15 cm or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or

b, A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower; and

2. If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for four tenths or less of the
cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, is dry in some or all parts for less
than 120 cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 8°C.

Udertic Calciustolis

HFDF. Other Calciustolls which have one or both of the
following:

1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Calciustolls


Durixerolis

Key to subgroups

HDAA. Durixerolls which have, above the duripan, one
or both of the following:

1. Cracks that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick; or

2. A linear extensibility of 6.0 cm or more.
Vertic Durixerolls

HDAB. Other Durixerolls that have both:
1. An aridic moisture regime; and
2. Throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or both of the following:

a. More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or

b. A fine-earth fraction containing 30

percent or more particles 0.02 to 2.0 mm in
diameter, and either:

(1) In the 0.02-to-2.0-mm fraction,
more than 30 percent volcanic glass;
or

(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more.
Vitritorrandic Durixerolls

HDAC. Other Durixerolls that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of M
the following: 0
1, More than 35 percent (by volume) fragments L
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:
a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron



28

boundaries if formed in situ, or with sharp
boundaries after pedoturbation;

(2) Masses, i.e., soft bodies of variable
shapes within the matrix; and

(3) Pore linings, i.e., zones of accumulation
along pores which may be either coatings on.
pore surfaces or impregnations from the
tmatrix adjacent to the pores.

b. Redox depletions —These are zones of low
chroma (2 or less) where either Fe-Mn oxides
alone or both Fe-Mn oxides and clay have been
stripped out, including:
(1) Iron depletions, i.e., zones which contain
low amounts of Fe and Mn oxides but have
a clay content similar to that of the adjacent
matrix (often referred to as albans or
neoalbans); and

(2) Clay depletions, i.e., zones which
contain low amounts of Fe, Mn, and clay
(often referred to as silt coatings or
skeletans).
c. Reduced matrix.—This is a soil matrix which
has a low chroma in situ, but undergoes a change
in hue or chroma within 30 minutes after the soil
material has been exposed to air.
d. In soils that have no visible redoximorphic
features, a positive reaction to an o.,a'-dipyridy]

solution satisfies the requirement for
redoximorphic features.

Field experience indicates that it is not possible to
define a specific set of redoximorphic features that is
uniquely characteristic of all the taxa in one particular
category. Therefore color patterns that are unique to
specific taxa are referenced in the keys.

represent a special kind of aquic

Anthraquic conditions

conditions which occur in soils that are cultivated and
irrigated. Soils with anthraquic conditions must meet
the requirements for aquic conditions and in addition
have both of the following:

a. A tilled surface layer and a directly underlying
slowly permeable layer which have, for three
months or more per year in most years, both
(1) Saturation and reduction; and
(2) A chroma of two or less in the matrix;
and
b. A subsurface horizon with one or more of the
following:
(1) Redox depletions with a color value,
moist, of 4 or more and a chroma of 2 or less
in macropores; or


383

a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower; and

2. If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some or all parts for six tenths or more of
the cumulative days per year when the soil
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, remains moist in some or all parts for
less than 90 consecutive days per year when
the temperature at a depth of 50 cm below
the soil surface is higher than 8°C.
Torrertic Haplustolls

HFGE. Other Haplustolls which have both:
1, One or both of the following:

a, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower; and

2. If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in

some part for four tenths or less of the
cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

b, A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, is dry in some or all parts for less
than 120 cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 8°C.
Udertic Haplustolls
HFGF, Other Haplustolls which have one or both of the
following:



Chapter 12

Mollisols

KEY TO SUBORDERS

HA. Mollisols that have:
1, An argillic or a natric horizon; and

2. An albic horizon with a chroma of 2 or less that
is 2.5 cm or more thick, has its lower boundary 18
cm or more below the mineral soil surface, and
either lies directly below the mollic epipedon or
separates horizons that together meet all the
requirements for a mollic epipedon; and

3. In one or more subhorizons of the albic and/or
the argillic or natric horizon and within 100 cm of
the mineral soil surface, redox concentrations in
the form of masses or concretions or both, and
also aquic conditions for some time in most years
(or artificial drainage).

Albolls, p. 337

HB. Other Mollisols which have aquic conditions for
some time in most years (or artificial drainage) between
40 and 50 cm from the mineral soil surface, and one or
more of the following:
1, A histic epipedon overlying the mollic
epipedon; or
2, An exchangeable sodium percentage (ESP) of
15 or more (or a sodium adsorption ratio, SAR, of
13 or more) in the upper part of the mollic
epipedon, and a decrease in ESP (or SAR) values
with increasing depth below 50 cm from the
mineral soil surface; or

3. A calcic or petrocalcic horizon that has its
upper boundary within 40 cm of the mineral soil
surface; or

4. One of the following colors:

a. A chroma of 1 or less in the lower part of
the mollic epipedon!, and either
(1) Distinct or prominent redox
concentrations in the lower part of the
mollic epipedon; or
(2) Either directly below the mollic

epipedon, or within 75 cm of the
mineral soil surface if a calcic horizon

Te the moltic epipedon extends to a lithic contact within 30 cm of the
mineral soil surface, the requirement for redoximorphic features is waived.


155.
CGDH. Other Fulvudands that have both:

1, Undried, a 1500-kPa water retention of 70
percent or more throughout a layer 35 cm or more
thick within 100 cm either of the mineral soil
surface, or of the top of an organic layer with
andic soil properties, whichever is shallower, and

2. More than 6,0 percent organic carbon and
colors of a mollic epipedon throughout a layer 50
cm or more thick within 60 cm either of the
mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower.

Hydric Pachic Fulvudands

CGDI. Other Fulvudands that have both:

1. A sum of extractable bases of more than 25.0
emol(+)/kg in the fine-earth fraction throughout
‘one or more horizons with a total thickness of 15
em or more between 25 and 75 om either from the
mineral soil surface, or from the top of an organic
layer with andic soil properties, whichever is
shallower; and

2. More than 6.0 percent organic carbon and
colors of a mollic epipedon throughout a layer 50
em or more thick within 60 cm either of the
mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower.

Eutric Pachic Fulvudands

CGDJ. Other Fulvudands that have more than 6.0
percent organic carbon and colors of a mollic epipedon
throughout a layer 50 cm or more thick within 60 cm
either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Pachic Fulvudands

CGDK. Other Fulvudands that have both:

1. Undried, a 1500-kPa water retention of 70
percent or more throughout a layer 35 cm or more
thick within 100 cm either of the mineral soil
surface, or of the top of an organic layer with
andic soil properties, whichever is shallower; and

2. Between 40 and 100 cm either from the mineral
soil surface, or from the top of an organic layer
with andic soil properties, whichever is shallower,
a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic
epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more
that have a color value, moist, | unit or more
higher and an organic-carbon content 1 percent or
more (absolute) lower.

Hydric Thaptic Fulvudands

2>


374

percent or more (absolute) within a vertical
distance of 2.5 cm, in the fine-earth fraction
(and there is no lithic or paralithic contact
within 50 cm of the mineral soil surface).
Paleustolls, p. 391

HFD. Other Ustolls which:

1. Have either a calcic or gypsic horizon that has
its upper boundary within 100 cm of the soil
surface, or a petrocalcic horizon that has its upper
boundary within 150 cm of the mineral soil
surface; and
2. Do not have an argillic horizon above the
calcic, gypsic, or petrocalcic horizon; and
3. In all parts above the calcic, gypsic, or
petrocalcic horizon, after the materials between.
the soil surface and a depth of 18 cm have been
mixed, are either calcareous or have a texture of
loamy fine sand or coarser.

Calciustolls, p. 379

HEE, Other Ustolls that have an argillic horizon.
Argiustolls, p. 374

HFF. Other Ustolls that have a mollic epipedon which:

1. Either below an Ap horizon or below a depth of
18 cm from the mineral soil surface, contains 50
percent or more (by volume) wormholes, worm
casts, or filled animal burrows; and

2. Either rests on a lithic contact, or has a
transition zone to the underlying horizon in which
25 percent or more of the soil volume consists of
discrete wormholes, worm casts, or animal
burrows filled with material from the mollic
epipedon and from the underlying horizon.
Vermustolls, p. 394

HFG. Other Ustolls.
Haplustolls, p. 382

Argiustolls

Key to subgroups
HFEA. Argiustolls which have both:

1. A lithic contact within 50 cm of the mineral soil

surface; and

2, Above the argillic horizon, either an albic

horizon, or a horizon that has color values too high

for a mollic epipedon and a chroma too high for an

albic horizon.

Alfic Lithic Argiustolls

HFEB. Other Argiustolls that have a lithic contact

within 50 cm of the mineral soil surface.
Lithic Argiustolls


178
Durargids

Key to subgroups

FABA,. Durargids which have, above the duripan, one
or both of the following:

1. Cracks that are 5 mm or more wide through a

thickness of 30 cm or more for some time in most

years, and slickensides or wedge-shaped

aggregates in a layer 15 cm or more thick; or

2. A linear extensibility of 6.0 cm or more.

Vertic Durargids

FABB, Other Durargids that have, in one or more
horizons within 100 cm of the soil surface, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:

1, A chroma of 0, or a hue of 2,5Y or yellower and
a chroma of 1; or

2. Redox concentrations and $0 percent or more
chroma of 2 or less; or

3. Fifty percent or more chroma of 2 or less and,
in horizons with a total thickness of 25 cm or
more within 50 cm of the soil surface, a higher
exchangeable sodium percentage (or sodium
adsorption ratio) than in the zone with aquic
conditions; or
4. Enough active ferrous iron to give a positive
reaction to a,c'-dipyridyl at a time when the soil
is not being irrigated.

Aquic Durargids

FABC. Other Durargids which have:

1. A duripan that has its upper boundary 18 cm or
more below the soil surface; and

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:
a. Within 40 om of the soil surface, if the
upper boundary of the duripan is at a depth
of 40 cm or more,
(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or
(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or
(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 cm of the soil, if the

upper boundary of the duripan is at a depth
of 18 to 40 cm,


4
deposition and for diagnostic and accessory properties to
develop.

An epipedon is not the same as an A horizon; it may
include part or all of the illuvial B horizon if the
darkening by organic matter extends from the soil
surface into or through the B horizon. To avoid changes
in the classification of a soil as a result of plowing, the
properties of the epipedon, except for structure, should
be determined after mixing the surface soil to a depth of
18 cm, or the whole soil if its depth to bedrock is less
than 18 cm,

Anthropic epipedon

The anthropic epipedon conforms to all the
requirements for the mollic epipedon (defined below)
except either (1) the limits on acid-soluble P,O,, with or
without the base saturation, or (2) the duration of
available moisture. Additional data on anthropic
epipedons from several parts of the world may permit
future improvements in this definition.

Histic epipedon (Gr. histos, tissue)
The histic epipedon is normally at the soil surface,
although it may be buried. It consists of organic soil
material (peat or muck) if the soil has not been plowed.
If the soil has been plowed, the epipedon normally has a
high content of organic matter that results from mixing
organic soil material with some mineral material. The
histic epipedon either has aquic conditions for some
time in most years or has been artificially drained.
The histic epipedon can thus be defined as a layer (one
or more horizons) that has aquic conditions for some
time in most years (or is artificially drained), and either:
1, Consists of organic soil material which:

a. Is 20 to 60 cm thick and either contains 75

percent or more (by volume) sphagnum fibers or
has a bulk density, moist, of less than 0.1 g/cm};
or

b. Is 20 to 40 cm thick and has an organic-carbon
content (by weight) of:
(1) 18 percent or more if the mineral
fraction contains 60 percent or more clay; or
(2) 12 percent or more if the mineral
fraction contains no clay; or
(3) 12 + (clay percentage multiplied by 0.1)
percent or more if the mineral fraction
contains less than 60 percent clay; or
2. Is an Ap horizon which, when mixed to a depth of 25
cm, has an organic-carbon content (by weight) of:
a. 16 percent or more if the mineral fraction
contains 60 percent or more clay; or


458

GACC. Other Albaquults,
Typic Albaquults

Endoaquults

Key to subgroups

GAIA. Endoaquults that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
to 100 cm.

Arenic Endoaquults

GAIB, Other Endoaquults that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 100
cm or more.

Grossarenic Endoaquults

GAIC. Other Endoaquults that have 50 percent or more
chroma of 3 or more in one or more horizons between
either the A or Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and a depth of
75 cm.

Aeric Endoaquults
GAID. Other Endoaquults.
Typic Endoaquults
Epiaquults
Key to subgroups

GAHA. Epiaquults that have one or both of the
following:
1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.
Vertic Epiaquults

GAHB. Other Epiaquults that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
to 100 cm.

Arenic Epiaquults


ty (LE).
Coefficient oft (COLE).
Lithic contact ...
Litter—See Organic soil material
Loamy particle-size class
Loamy-skeletal particle-size cl
Lower case suffixes (genetic horizons)
conventions for using

Mar! .....
Master horizons and layers (genetic)
Materials

albic ... 23

Melanudands ...


414

AQUOX

Key to great groups

DAA. Aquox that have, in one or more subhorizons of
the oxic horizon within 150 cm of the mineral soil
surface, an ECEC of less than 1.50 cmol(+)/kg clay and
a pH value (in 1N KC)) of 5.0 or more.

Acraquox, p. 414

DAB. Other Aquox that have plinthite forming a
continuous phase within 125 cm of the mineral soil
surface,

Plinthaquox, p. 415

DAC. Other Aquox that have a base saturation (by
NH,OAc) of 35 percent or more in all horizons within
125 cm of the mineral soil surface.

Eutraquox, p. 414

DAD. Other Aquox.
Haplaquox, p. 415

Acraquox

Key to subgroups

DAAA. Acraquox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125
cm of the mineral soil surface.

Plinthic Acraquox

DAAB., Other Acraquox which have, directly below an
epipedon, a horizon 10 cm or more thick that has 50
percent or more chroma of 3 or more.

Aeric Acraquox
DAAC. Other Acraquox.
Typic Acraquox
Eutraquox
Key to subgroups
DACA. Eutraquox that have a histic epipedon.
Histic Eutraquox

DACB. Other Eutraquox that have 5 percent or more
(by volume) plinthite in one or more horizons within
125 cm of the mineral soil surface.

Plinthic Eutraquox

DACC. Other Eutraquox which have, directly below an
epipedon, a horizon 10 cm or more thick that has 50
percent or more chroma of 3 or more.

Aeric Eutraquox


364

HCAD. Other Rendolls which have one or both of the
following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Rendolls

” HCAE. Other Rendolls that have both:
1, A cambic horizon; and

2. A difference of less than 5°C between mean

summer and mean winter soil temperatures at a

depth of 50 cm below the soil surface.
Eutropeptic Rendolls

HCAF. Other Rendolls that have a cambic horizon.
Eutrochreptic Rendolls

HCAG. Other Rendolls that have a color value, dry, of 6
or more either in the upper 18 cm of the mollic
epipedon, after mixing, or in an Ap horizon 18 cm or
more thick,

Entic Rendolls
HCAH. Other Rendolls.

Typic Rendolls
UDOLLS
Key to great groups

HGA. Udolls which have either:
1, A petrocalcic horizon that has its upper
boundary within 150 cm of the mineral soil
surface; or

2. Both:

a. Within 150 cm of the mineral soil surface,
neither a lithic or paralithic contact nor a
clay decrease with increasing depth of 20
percent or more (relative) from the
maximum clay content; and
b. An argillic horizon which has either:
(1) In its lowest subhorizon, a hue of
7.5YR or redder and a chroma of 5 or

more in 50 percent or more of the
matrix; or


205

FADM. Other Paleargids.
Typic Paleargids

ORTHIDS

Key to great groups
FBA. Orthids which:

1. Have a salic horizon that has its upper boundary
within 75 cm of the soil surface; and

2. Are saturated with water within 100 cm of the
soil surface for 1 month or more per year in most
years (or artificially drained); and

3. Do not have a duripan that has its upper
boundary within 100 cm of the soil surface.
Salorthids, p. 231

FBB. Other Orthids which have a petrocalcic horizon
that has its upper boundary within 100 cm of the soil
surface and is not overlain by a duripan.

Paleorthids, p. 228

FBC. Other Orthids which have a duripan that has its
upper boundary within 100 cm of the soil surface.
Durorthids, p. 222

FBD. Other Orthids which have a gypsic or petrogypsic
horizon that has its upper boundary within 100 cm of
the soil surface.

—m>

Gypsiorthids, p. 227
FBE. Other Orthids which:
1. Have a calcic horizon that has its upper
boundary within 100 cm of the soil surface; and

2. In all parts above the calcic horizon, after the
materials between the soil surface and a depth of
18 cm have been mixed, are either calcareous or
have a texture of loamy fine sand or coarser.
Calciorthids, p. 205

FBF. Other Orthids.
Camborthids, p. 212

Calciorthids

Key to subgroups

FBEA. Calciorthids which have:
1. A frigid soil temperature regime, and an aridic
moisture regime that borders on an ustic regime;
and

2. A lithic contact within 50 cm of the soil
surface; and


138

2. At its upper boundary, a clay increase of 20
percent or more (absolute) within a vertical
distance of 7.5 cm, or of 15 percent or more
(absolute) within a vertical distance of 2.5 cm, in
the fine-earth fraction.

Haplic Palexeralfs

IDFM. Other Palexeralfs that have a color value, moist,
of 3 or less and 0.7 percent or more organic carbon,
either throughout an Ap horizon or throughout the upper
10 cm of an A horizon.

Moliic Palexeralfs

IDEN. Other Palexeralfs.
Typic Palexeraifs

Plinthoxeralfs

Plinthoxeralfs are the Xeralfs that have one or more
horizons within 150 cm of the mineral soil surface in
which plinthite either forms a continuous phase or
constitutes one half or more of the volume. There are
few of these soils in the United States, but they are
moderately extensive in other parts of the world.
Subgroups have not been developed.

Rhodoxeralfs

Key to subgroups

IDEA. Rhodoxeralfs that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Rhodoxeralfs

IDEB. Other Rhodoxeralfs which have a petrocalcic
horizon that has its upper boundary within 150 cm of
the mineral soil surface.

Petrocalcic Rhodoxeralfs

IDEC. Other Rhodoxeralfs which have a calcic horizon
that has its upper boundary within 150 cm of the
mineral soil surface.

Calcic Rhodoxeralfs

IDED., Other Rhodoxeralfs which have an argillic
horizon that is either less than 15 cm thick or is
discontinuous horizontally in each pedon.

Ochreptic Rhodoxeralfs

IDEE. Other Rhodoxeralfs.
Typic Rhodoxeralfs


424
Eutrotorrox

Key to subgroups

DBBA. Eutrotorrox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Eutrotorrox

DBBB. Other Eutrotorrox that have a lithic contact
within 125 cm of the mineral soil surface.

Lithic Eutrotorrox
DBBC. Other Eutrotorrox.

Typic Eutrotorrox
Haplotorrox
Key to subgroups

DBCA. Haplotorrox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Haplotorrox

DBCB. Other Haplotorrox that have a lithic contact
within 125 cm of the mineral soil surface.

Lithic Haplotorrox
DBCC. Other Haplotorrox.

Typic Haplotorrox
UDOX
Key to great groups

DEA. Udox that have a sombric horizon within 150 cm
of the mineral soil surface,
Sombriudox, p. 432

DEB. Other Udox that have, in one or more subhorizons
of the oxic or kandic horizon within 150 cm of the
mineral soil surface, an ECEC of less than 1.50
mol(+)/kg clay and a pH value (in 1N KCl) of 5.0 or
more.

Acrudox, p. 425

DEC. Other Udox that have a base saturation (by
NH,OAc) of 35 percent or more in all horizons within
125 cm of the mineral soil surface.

Eutrudox, p. 426

DED, Other Udox that have both:

1. A clay content of 40 percent or more in the fine-
earth fraction between the soil surface and a depth
of 18 cm, after mixing; and

2. A kandic horizon that has its upper boundary
within 150 cm of the mineral soil surface,
Kandiudox, p. 430


372

HGEN. Other Hapludolls.
Typic Hapludolls

Paleudolls

Key to subgroups
HGAA. Paleudolls which have one or both of the
following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Paleudolls

HGAB. Other Paleudolls that have a petrocalcic horizon
within 150 cm of the mineral soil surface.
Petrocalcic Paleudolls

HGAC. Other Paleudolls that have, in one or more
subhorizons within the upper 50 cm of the argillic
horizon, redox depletions with a chroma of 2 or less,
and also aquic conditions for some time in most years
(or artificial drainage).

Aquic Paleudolls

HGAD. Other Paleudolls that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Paleudolls

HGAE. Other Paleudolls which:

1, Have a calcic horizon that has its upper
boundary within 100 cm of the mineral soil
surface; and

2. In all parts above the calcic horizon, after the
materials between the soil surface and a depth of
18 cm have been mixed, are either calcareous or
have a texture of loamy fine sand or coarser.
Calcic Paleudolls

HGAF. Other Paleudolls.
Typic Paleudolls


204

b, In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.
Aquandic Endoaquepts
JAJE. Other Endoaquepts that have, in one or more.
horizons between the A or Ap horizon and a depth of 75
cm below the mineral soil surface, one of the following
colors:
1. A hue of 7.5YR or redder in 50 percent or more
of the matrix, and

a. If peds are present, either a chroma of 2
or more on 50 percent or more of ped
exteriors, or no redox depletions with a
chroma of 2 or less in ped interiors; or

b. If peds are absent, a chroma of 2 or more
in 50 percent or more of the matrix; or

2. In SO percent or more of the matrix, a hue of
10YR or yellower and either

a, Both a color value, moist, and chroma of
3 or more; or
b. A chroma of 2 or more if there are no

redox concentrations,
Aeric Endoaquepts

JASE. Other Endoaquepts which have:

1, An Ap horizon, or an A horizon 15 cm or more

thick, with a color value, moist, of 3 or less and a

color value, dry, of 5 or less (crushed and

smoothed sample); and

2. A base saturation (by NH,OAc) of less than 50

percent that does not increase with depth to 50

percent or more within 100 cm of the mineral soil

surface.

Humic Endoaquepts

JAJG. Other Endoaquepts that have an Ap horizon, or

an A horizon 15 cm or more thick, with a color value,
moist, of 3 or less and a color value, dry, of 5 or less

(crushed and smoothed sample).

Mollic Endoaquepts
JAJH. Other Endoaquepts.

Typic Endoaquepts
Epiaquepts
Key to subgroups

JAIA. Epiaquepts which have one or both of the
following:


454

BDEF. Other Haplorthods that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Haplorthods

BDEG. Other Haplorthods which have andic soil
properties throughout horizons that have a total
thickness of 25 cm or more within 75 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Andic Haplorthods

BDEH. Other Haplorthods which have, within 200 cm
of the mineral soil surface, an argillic or a kandic
horizon that has a base saturation of 35 percent or more
(by sum of cations) in some part.

Alfic Haplorthods

BDEI. Other Haplorthods that have an argillic or a
kandic horizon within 200 cm of the mineral soil
surface.

Ultic Haplorthods

BDEJ. Other Haplorthods which have a spodic horizon
that does not have any of the following:

1. A texture of very fine sand or finer, a thickness
of more than 10 cm, and a weighted average of
1,2 percent or more organic carbon in the upper
10 cm; nor

2. A coarse-loamy or loamy-skeletal particle size,
and a color value, moist, and chroma of 3 or less
(crushed and smoothed sample) in the upper

7.5 0m; nor

3. A sandy-skeletal or sandy particle size, and a
color value, moist, and chroma of 3 or less
(crushed and smoothed sample) in the upper

2.5 cm.
Entic Haplorthods
BDEK. Other Haplorthods.
Typic Haplorthods
Placorthods
Key to subgroups

BDAA. All Placorthods (provisionally).
Typic Placorthods


512
Durixererts

Key to subgroups

ECAA. Durixererts that have, throughout a layer 15 cm
or more thick above the duripan, an electrical
conductivity of 15 dS/m or more (1:1 soil:water) for 6 or
more months per year in 6 or more out of 10 years.
Halic Durixererts

ECAB. Other Durixererts that have, in one or more
horizons above the duripan, an exchangeable sodium
percentage of 15 or more (or a sodium adsorption ratio
of 13 or more) for 6 or more months per year in 6 or
more out of 10 years.

Sodic Durixererts
ECAC. Other Durixererts that have, in one or more
horizons above the duripan, aquic conditions for some
time in most years (or artificial drainage) and either:

1. Redoximorphic features; or

2. Enough active ferrous iron to give a positive
reaction to o.,c:'-dipyridyl at a time when the soil
is not being irrigated.
Aquic Durixererts
ECAD. Other Durixererts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
remain 5 mm or more wide, through a thickness of 25
cm or more above the duripan, for 180 or more
consecutive days.
Aridic Durixererts
ECAE. Other Durixererts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
remain 5 mm or more wide, through a thickness of 25
cm or more above the duripan, for less than 90
consecutive days.
Udic Durixererts
ECAF. Other Durixererts which have a duripan that is
not indurated in any subhorizon.
Haplic Durixererts

ECAG. Other Durixererts that have, in one or more
horizons within 30 cm of the mineral soil surface, 50
percent or more colors as follows:

1, A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or

3. A chroma of 3 or more.
Chromic Durixererts

ECAH. Other Durixererts.
Typic Durixererts


527
SI Unit Conversion Table

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

Conductivity:
Immho/em = 1 dS/m

Pressure:

15-bar water = 1500 kPa water retention
1/3-bar water = 33 kPa water retention

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.


7

within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
2. A fine-carth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:
a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Argiudolls

HGCG. Other Argiudolls which have aquic conditions
for some time in most years (or artificial drainage),
either:

1, Within 40 cm of the mineral soil surface, in
horizons that also have redoximorphic features; or

2. Directly below the mollic epipedon, in one or
more horizons with a total thickness of 15 cm or
more that have one or more of the following:

a. A color value, moist, of 4 or more and
redox depletions with a chroma of 2 or less;
or

b. A hue of 10YR or redder and a chroma of
2 or less; or

c. A hue of 2.5Y or yellower and a chroma
of 3 or less,
Aquic Argiudolls

HGCH. Other Argiudolls that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Argiudolis

HGCI. Other Argiudolls that have a mollic epipedon 50
cm or more thick with a texture finer than loamy fine
sand.

Pachic Argiudolls

IJGCJ. Other Argiudolls that have a CEC of less than 24
emol(+)/kg clay (by IN NH,OAc pH 7) in 50 percent or
more either of the argillic horizon if less than 100 cm
thick, or of its upper 100 cm.

Oxie Argiudolls

HGCK. Other Argiudolls that have a calcic horizon
within 100 cm of the mineral soil surface.
Calcic Argiudolis

r


146,

CADE. Other Vitraquands,
Typic Vitraquands

CRYANDS

Key to great groups

CBA. Cryands that have a mean annual soil temperature
of 0°C or lower.
Gelieryands, p. 147

CBB. Other Cryands that have a melanic epipedon,
Melanocryands, p. 149

CBC. Other Cryands which have an epipedon with a
color value, moist, and chroma of 3 or less that meets
the depth, thickness, and organic-carbon requirements
for a melanic epipedon.

Fulvicryands, p. 146

CBD. Other Cryands that have, undried, a 1500-kPa
water retention of 100 percent or more throughout one
or more layers with a total thickness of 35 cm or more
within 100 cm either of the mineral soil surface, or of
the top of an organic layer with andic soil properties,
whichever is shallower,

Hydrocryands, p. 148

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

Vitricryands, p. 149

CBF. Other Cryands.
Haplocryands, p. 147

Fulvicryands

Key to subgroups

CBCA. Fulvicryands that have a lithic contact within 50
cm either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Lithic Fulvicryands

CBCB. Other Fulvicryands which have, undried, a
1500-kPa water retention of less than 30 percent
throughout one or more layers with andic soil properties
that have a total thickness of 25 cm more within 100 cm
either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Vitric Fulvicryands


450

or more within 75 cm either of the mineral soil surface,
or of the top of an organic layer with andic soil
properties, whichever is shallower.

Andic Placohumods
BCAB. Other Placohumods.

Typic Placohumods
ORTHODS
Key to great groups

BDA. Orthods that have, in 50 percent or more of each
pedon, a placic horizon within 100 cm of the mineral
soil surface.

Placorthods, p. 454

BDB. Other Orthods which have, in 90 percent or more
of each pedon, a cemented soil layer that does not slake
in water after air-drying and has its upper boundary
within 100 cm of the mineral soil surface.

Durorthods, p. 451

BDC. Other Orthods that have a fragipan.
Fragiorthods, p. 451

BDD. Other Orthods that have less than 0.10 percent
iron (by ammonium oxalate) in 75 percent or more of
the spodic horizon.

Alorthods, p. 450

BDE. Other Orthods.
Haplorthods, p. 452

Alorthods

Key to subgroups

BDDA. Alorthods that are saturated with water, in one
or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Alorthods

BDDB. Other Alorthods that have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of the spodic horizon at a depth of 75 to 125 cm;
and

2. An argillic or a kandic horizon below the spodic
horizon.
Arenic Ultic Alorthods

BDDC. Other Alorthods that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of the spodic horizon at a depth of
75 to 125 cm.

Arenic Alorthods


507

EEAG. Other Dystrusterts that have, in one or more
horizons within 30 cm of the mineral soil surface, 50
percent or more colors as follows:

1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or
3. A chroma of 3 or more.

Chromic Dystrusterts

EEAH. Other Dystrusterts.

Typic Dystrusterts
Gypsiusterts
Key to subgroups
EECA. Gypsiusterts that have a lithic contact within 50
om of the mineral soil surface.

Lithic Gypsiusterts

EECB. Other Gypsiusterts that have, throughout a layer
15 cm or more thick within 100 cm of the mineral soil
surface, an electrical conductivity of 15 dS/m or more
(1:1 soil:water) for 6 or more months per year in 6 or
more out of 10 years,

Halic Gypsiusterts

EECC. Other Gypsiusterts that have, in one or more
horizons within 100 cm of the mineral soil surface, an
exchangeable sodium percentage of 15 or more (or a
sodium adsorption ratio of 13 or more) for 6 or more
months per year in 6 or more out of 10 years.

Sodic Gypsiusterts

EECD. Other Gypsiusterts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
are 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 210
or more cumulative days per year.

Aridic Gypsiusterts

EECE. Other Gypsiusterts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
are 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for less
than 150 cumulative days per year.
‘Udic Gypsiusterts

EECF. Other Gypsiusterts that have a lithic or paralithic
contact, or the upper boundary of a duripan or
petrocalcic horizon, within 100 cm of the mineral soil
surface,

Leptic Gypsiusterts

EECG. Other Gypsiusterts which have a layer 25 cm or
more thick that contains less than 27 percent clay in its
fine-earth fraction and has its upper boundary within
100 cm of the mineral soil surface.

Entic Gypsiusterts

mm<


245

1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more.
Vitrixerandic Torrifluvents

KDDD. Other Torrifluvents that have, throughout one
or more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1, More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a, In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more,

Vitrandic Torrifluvents

KDDE. Other Torrifluvents that have, in one or more
horizons within 100 cm of the soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Torrifluvents
KDDF. Other Torrifluvents that are saturated with
water, in one or more layers within 150 cm of the soil
surface, for 1 month or more per year in 6 or more out of
10 years,

Oxyaquic Torrifluvents
KDDG. Other Torrifluvents which have:

1. A horizon within 100 cm of the mineral soil
surface that is 15 cm or more thick and cither
contains 20 percent or more (by volume)
durinodes or is brittle and has firm consistence
when moist; and

2. A moisture control section which, in 6 or more

out of 10 years, is dry in all its parts for less than

three fourths of the cumulative days per year when

the soil temperature at a depth of 50 cm from the

soil surface is 5°C or higher; and

3. A thermic, mesic, or frigid soil temperature

regime, and a torric moisture regime that borders

on a xeric regime,

Durorthidic Xeric Torrifluvents

KDDH. Other Torrifluvents which have a horizon
within 100 cm of the mineral soil surface that is 15 cm
or more thick and either contains 20 percent or more (by


407

2. A horizon within 100 cm of the mineral soil
surface that is 15 cm or more thick and either
contains 20 percent or more (by volume)
durinodes or is brittle and has firm consistence
when moist.
Aridic Duric Haploxerolls
HDFS. Other Haploxerolls that have both:

1, An aridic moisture regime; and
2. A calcic horizon or soft powdery lime, either
within the following depths or above a lithic or
paralithic contact if shallower, if the particle-size
control section is

a, Sandy: within 150 cm of the mineral soil

surface; or

b. Loamy: within 110 cm of the mineral soil

surface; or

c. Clayey: within 90 cm of the mineral soil
surface.

Calciorthidic Haploxerolls
HDFT. Other Haploxerolls that have both:
1. An aridic moisture regime; and
2. A sandy particle size in all horizons within 100
cm of the mineral soil surface.
Torripsammentic Haploxerolls
HDFU. Other Haploxerolls which:
1. Have an aridic moisture regime; and

2. Either do not have a cambic horizon and do not,
in the lower part of the mollic epipedon, meet the
requirements for a cambic horizon except color, or
have carbonates throughout either the cambic
horizon or the lower part of the mollic epipedon.
Torriorthentic Haploxerolls

HDFV. Other Haploxerolls that have an aridic moisture
regime.

Aridic Haploxerolls
HDFW. Other Haploxerolls that have a horizon within
100 cm of the mineral soil surface that is 15 cm or more
thick and either contains 20 percent or more (by
volume) durinodes or is brittle and has firm consistence
when moist.

Duric Haploxerolls

HDFX. Other Haploxerolls which have both:

1. Either 0.3 percent or more organic carbon in all
horizons within 125 cm of the mineral soil
surface, or an irregular decrease in organic-carbon
content from a depth of 25 cm to a depth of 125
cm, or to a lithic or paralithic contact if shallower;
and

rog


DEE. Other Udox.
Hapludox, p. 428

Acrudox

Key to subgroups

DEBA. Acrudox that have, within 125 cm of the
mineral soil surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Aquic Petroferric Acrudox
DEBB. Other Acrudox that have a petroferric contact
within 125 om of the mineral soil surface,
Petroferric Acrudox

DEBC. Other Acrudox that have, within 125 cm of the
mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Aquic Lithic Acrudox
DEBD. Other Acrudox that have a lithic contact within

125 cm of the mineral soil surface.
Lithic Acrudox

DEBE. Other Acrudox that have, within 125 cm of the
mineral soil surface, both:

1. A delta pH (KCI pH minus 1:1 water pH) with
2 0 or net positive charge in a layer 18 cm or more
thick; and
2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Anionic Aquic Acrudox
DEBF. Other Acrudox that have a delta pH (KCI pH
minus 1:1 water pH) with a 0 or net positive charge ina
layer 18 cm or more thick within 125 cm of the mineral
soil surface,
Anionic Acrudox

DEBG. Other Acrudox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125
cm of the mineral soil surface.

Plinthic Acrudox

DEBH. Other Acrudox that have, in one or more
horizons within 125 cm of the mineral soil surface,

(0)


318
2. A slope of less than 25 percent.

Fluventic Ustochrepts
JDEL. Other Ustochrepts which have both:

1. A calcic horizon that has its upper boundary
within 100 cm of the mineral soil surface; and

2. If neither irrigated nor fallowed to store
moisture, one of the following:

a. A frigid soil temperature regime, and a
moisture control section which, in 6 or more
out of 10 years, is dry in all parts for four
tenths or more of the cumulative days per
year when the soil temperature at a depth of
50 cm below the soil surface is higher than
5°C; or

b. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for six tenths or more of the
cumulative days per year when the soil
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

c. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, is moist in some or all parts for less
than 180 cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 8°C,
Calciorthidic Ustochrepts

JDEM. Other Ustochrepts which have both:

1, A calcic horizon that has its upper boundary
within 100 cm of the mineral soil surface; and

2. If neither irrigated nor fallowed to store
moisture, one of the following:

a. A frigid soil temperature regime, and a

moisture control section which, in 6 or more

out of 10 years, is dry in some or all parts
for less than 105 cumulative days per year
when the soil temperature at a depth of 50
cm below the soil surface is higher than
5°C; or

b. A mesic or thermic soil temperature
regime, and a moisture control section

which, in 6 or more out of 10 years, is dry in

some part for less than four tenths of the
cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

c. A hyperthermic, an isomesic, or a warmer

iso soil temperature regime, and a moisture

control section which, in 6 or more out of 10


472

depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.
Vertic Hapludults

GCGD. Other Hapludults that have a texture of loamy
fine sand or coarser throughout the argillic horizon, or
lamellae within its upper 25 cm.

Psammentic Hapludults

GCGE. Other Hapludults that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
to 100 cm.

Arenic Hapludults

GCGF. Other Hapludults that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 100
cm or more.

Grossarenic Hapludults

GCGG. Other Hapludults that have, in one or more
subhorizons within the upper 60 cm of the argillic
horizon, redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, accompanied by
redox concentrations, and also aquic conditions for some
time in most years (or artificial drainage).

Aquic Hapludults

GCGH. Other Hapludults that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Hapludults

GCGI. Other Hapludults which have either an Ap
horizon, or an A horizon 15 cm or more thick, that has a
color value, moist, of 3 or less and a color value, dry, of
5 or less (crushed and smoothed sample).

Humic Hapludults

GCGJ. Other Hapludults that have an argillic horizon
25 cm or less thick.

Ochreptic Hapludults
GCGK. Other Hapludults,
Typic Hapludults
Kandiudults
Key to subgroups

GCCA. Kandiudults that have:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic horizon at a depth of 50 to 100 cm;
and

2. Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface; and


467

accompanied by redox concentrations, and also aquic
conditions for some time in most years (or artificial
drainage).
Aquic Kanhaplohumults
GBDE. Other Kanhaplohumults that have, in one or
more horizons within 75 cm of the mineral soil surface,
redox concentrations, a color value, moist, of 4 or more,
and a hue which is 10YR or yellower, but which
becomes redder with increasing depth within 100 cm of
the mineral soil surface.
Ombroaquic Kanhaplohumults
GBDF. Other Kanhaplohumults that have an ustic
moisture regime.
Ustic Kanhaplohumults
GBDG. Other Kanhaplohumults that have a xeric
moisture regime.
Xeric Kanhaplohumults
GBDH. Other Kanhaplohumults that have an anthropic
epipedon.

Anthropic Kanhaplohumults
GBDI. Other Kanhaplohumults,
Typic Kanhaplohumults
Palehumults
Key to subgroups

GBEA. Palehumults that have, throughout one or more
horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction
with both a bulk density of 1.0 g/cm? or less, measured
at 33 kPa water retention, and aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling more than
1.0.

Andic Palehumults

GBEB. Other Palehumults that have, in one or more
subhorizons within the upper 25 cm of the argillic
horizon, redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, accompanied by
redox concentrations, and also aquic conditions for some
time in most years (or artificial drainage).
Aquic Palehumults
GBEC. Other Palehumults that have 5 percent or more
(by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface.
Plinthic Palehumults
GBED. Other Palehumults that have an ustic moisture
regime.
Ustic Palehumults
GBEF. Other Palehumults that have a xeric moisture
regime.
Xeric Palehumults



397

more than 66 percent are cinders, pumice,
and pumice-like fragments; or

. A fine-earth fraction containing 30
percent or more particles 0.02 to 2.0 mm in
diameter, and either:

(1) In the 0.02-to-2.0-mm fraction,
more than 30 percent volcanic glass;
or

(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more.
Vitritorrandic Argixerolls

HDEG. Other Argixerolls that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Argixerolls

HDEH. Other Argixerolls which have a mean annual
soil temperature lower than 10°C, and either:

1. Above the argillic horizon, an albic horizon, or
a horizon that has color values too high for a
mollic epipedon and a chroma too high for an
albic horizon; or
2. A glossic horizon, or interfingering of albic
materials into the upper part of the argillic
horizon, or skeletans of clean silt and sand
covering 50 percent or more of the faces of peds in
the upper 5 cm of the argillic horizon.

Boralfic Argixerolls

HDEL. Other Argixerolls that have both:

1. A calcic horizon or soft powdery lime, either
within the following depths or above a lithic or
paralithic contact if shallower, if the particle-size
control section is


530

Clayey ees class
Clayey-skeletal Partclesize class...



152
the top of an organic layer with andic soil properties,
whichever is shallower.

Durudands, p. 152

CGC. Other Udands that have a melanic epipedon.
Melanudands, p. 162

CGD. Other Udands which have an epipedon with a
color value, moist, and chroma of 3 or less that meets
the depth, thickness, and organic-carbon requirements
of a melanic epipedon.

Fulvudands, p. 153

CGE. Other Udands that have, undried, a 1500-kPa
water retention of 100 percent or more throughout one
or more layers with a total thickness of 35 cm or more
within 100 cm either of the mineral soil surface, or of
the top of an organic layer with andic soil properties,
whichever is shallower.

Hydrudands, p. 160

CGF. Other Udands.
Hapludands, p. 156

Durudands

Key to subgroups

CGBA. Durudands that have, in one or more horizons
between 50 and 100 cm either from the mineral soil
surface, or from the top of an organic layer with andic
soil properties, whichever is shallower, aquic conditions
for some time in most years (or artificial drainage) and
one or more of the following:

1. Two percent or more redox concentrations; or

2. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
tedox depletions on faces of peds, or in the matrix
if peds are absent; or
3. Enough active ferrous iron to give a positive
reaction to a,a'-dipyridyl at a time when the soil
is not being irrigated.
Aquic Durudands
CGBB. Other Durudands that have extractable bases
plus 1N-KCl-extractable Al*+ totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more
horizons with a total thickness of 30 cm or more,
‘between 25 and 100 cm either from the mineral soil
surface, or from the top of an organic layer with andic
soil properties, whichever is shallower.
Acrudoxic Durudands

GBC. Other Durudands that have both:

1, Undried, a 1500-kPa water retention of 70
percent or more throughout a layer 35 cm or more
thick within 100 cm either of the mineral soil


449

in water after air-drying and has its upper boundary
within 100 cm of the mineral soil surface.
Durihumods, p. 449

BCC. Other Humods that have a fragipan.
Fragihumods, p. 449

BCD. Other Humods.
Haplohumods, p. 449

Durihumods

Key to subgroups

BCBA. Durihumods which have andic soil properties
throughout horizons that have a total thickness of 25 cm
or more within 75 cm either of the mineral soil surface,
or of the top of an organic layer with andic soil
Properties, whichever is shallower.

Andic Durihumods
BCBB. Other Durihumods.
Typic Durihumods
Fragihumods
Key to subgroups
BCCA. All Fragihumods (provisionally).
Typic Fragihumods
Haplohumods
Key to subgroups
BCDA. Haplohumods that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Haplohumods

BCDB. Other Haplohumods which have andic soil
properties throughout horizons that have a total
thickness of 25 cm or more within 75 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Andic Haplohumods

BCDC, Other Haplohumods which have a surface

horizon 30 cm or more thick that meets all the

requirements for a plaggen epipedon except thickness,
Plaggeptic Haplohumods

BCDD. Other Haplohumods.

ovum

Typic Haplohumods

Placohumods

Key to subgroups

BCAA. Placohumods which have andic soil properties
throughout horizons that have a total thickness of 25 cm


328

years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,

whichever is shallower.
Vertic Ustropepts

ICCC. Other Ustropepts that have, in one or more
horizons within 100 cm of the mineral soil surface,
redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or

artificial drainage).
Aquic Ustropepts

ICCD. Other Ustropepts that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Ustropepts
ICCE. Other Ustropepts that have a CEC (by IN
NH,OAc pH 7) of less than 24 cmol(+)/kg clay’ in 50
percent or more of the soil volume between a depth of
25 cm from the mineral soil surface and either a depth
of 100 cm, or a lithic or paralithic contact if shallower.

Oxic Ustropepts

JICCF. Other Ustropepts which have both:

1. Either 0.2 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

2. A slope of less than 25 percent.

Fluventic Ustropepts
JCCG. Other Ustropepts.
Typic Ustropepts
UMBREPTS
Key to great groups

JEA. Umbrepts that have a fragipan.
Fragiumbrepts, p. 330

JEB. Other Umbrepts that have a cryic or pergelic soil
temperature regime.
Cryumbrepts, p. 329

5 See footnote 3.


388

2. Either do not have a cambic horizon and do not,
in the lower part of the mollic epipedon, meet the
requirements for a cambic horizon except color, or
have carbonates throughout either the cambic
horizon or the lower part of the mollic epipedon.
Torriorthentic Haplustolls

HFGT. Other Haplustolls which have, if neither
irrigated nor fallowed to store moisture, either:

1. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for six tenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years,
remains moist in some or all parts for less than 90
consecutive days per year when the temperature at
a depth of 50 cm below the soil surface is higher
than 8°C.

Aridic Haplustolls

HFGU, Other Haplustolls which have both:

1. Either 0.3 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

2. A slope of less than 25 percent.
Fluventic Haplustolls

HFGV. Other Haplustolls which have a brittle horizon
within 100 cm of the mineral soil surface that is 15 cm
or more thick and contains either some opal coatings or
20 percent or more (by volume) durinodes.

Duric Haplustolls

HFGW, Other Haplustolls which:

1. Have, if neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for four tenths or less of the
cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, is dry in some or all parts for less
than 120 days per year when the


Chapter 3

Horizons and Properties Diagnostic
for the Higher Categories: Organic
Soils1

ORGANIC SOIL MATERIAL

Organic soil material either:

1, Is saturated with water for long periods (or artificially
drained) and, excluding live roots, has an organic~
carbon content (by weight) of:

a. 18 percent or more if the mineral fraction
contains 60 percent or more clay; or

b. 12 percent or more if the mineral fraction
contains no clay; or

c. 12 + (clay percentage multiplied by 0.1) percent
or more if the mineral fraction contains less than
60 percent clay; or

2. Is never saturated with water for more than a few
days and contains 20 percent or more (by weight)
organic carbon.

Item 1 in this definition covers materials that have been
called peat and muck. Item 2 is intended to include what
has been called litter or an O horizon.

KINDS OF ORGANIC SOIL MATERIALS

Three different kinds of organic soil materials are
distinguished in this taxonomy, based on the degree of
decomposition of the plant materials from which they
are derived, The three kinds (defined below) are: (1)
fibric, (2) hemic, and (3) sapric. Because of the
importance of fiber content in the definitions of these
materials, fibers are defined before the kinds of organic
soil materials, as follows.

Fibers

Fibers, in the terminology of this taxonomy, are pieces
of plant tissue in organic soil materials (excluding live
roots) which:

1. Are large enough to be retained on a 100-mesh sieve
(openings 0.15 mm in diameter) when the materials are
screened after dispersion in sodium hexametaphosphate;

1 Organic soils are referred to as Histosols in this taxonomy.


Salorthids .. 205,231
Salusterts 504,510
Sandy partic] . 50,69

Sandy-skeletal particle size class ..

Shallow depth of soil
SI unit conversion tab]
Skeletans ...


247

1, More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:
a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Udifluvents
KDFC. Other Udifluvents that have either:

1, In one or more horizons within 50 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage); or

2. In one or more horizons within 100 cm of the
mineral soil surface, a color value, moist, of 4 or
more and either a chroma of 0 or a hue of SGY,
5G, 5BG, or 5B, and also aquic conditions for
some time in most years (or artificial drainage).
Aquic Udifluvents

KDFD. Other Udifluvents that are saturated with water, [aa
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of.
10 years.

Oxyaquic Udifluvents

KDFE. Other Udifluvents which have an Ap horizon, or
an A horizon 15 cm or more thick, that has a color
value, moist, of 3 or less and a color value, dry, of 5 or

less (crushed and smoothed sample).

Mollic Udifluvents
KDFF, Other Udifluvents.

Typic Udifluvents
Ustifluvents
Key to subgroups

KDCA. Ustifluvents which have one or both of the
following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped.
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or


207

sand/noncarbonate-clay ratio between
land 13; or

b. In the upper 18 cm of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.18 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.77-(0.046 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
land 13.

Borollic Calciorthids

FBEC. Other Calciorthids which have:

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

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to noncarbonate clay, as follows:

a. In the upper 40 cm of the soil, if the lithic
contact is between 40 and 50 cm below the
soil surface,

(1) 0.60 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.15 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.64-(0.038 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
1 and 13; or

b, In the upper 18 cm of the soil, if the lithic
contact is between 18 and 40 cm from the
soil surface,

(1) 0.72 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.18 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.77-(0.046 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
land 13; and

—-D>


225

3. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to noncarbonate clay, as follows:

a, In the upper 40 cm of the soil, if the upper
boundary of the duripan is 40 cm or more
below the soil surface,

(1) 0.60 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.15 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.64-(0.038 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
and 13; or

b. In the upper 18 cm of the soil, if the
‘upper boundary of the duripan is between 18
and 40 cm from the soil surface,

(1) 0.72 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.18 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.77-(0.046 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
Vand 13,

Haplustollic Durorthids
FBCG. Other Durorthids which have both:

1. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to noncarbonate clay, as follows:

a. In the upper 40 cm of the soil, if the upper
boundary of the duripan is 40 cm or more
below the soil surface,

(1) 0.60 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.15 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.64-(0.038 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
land 13; or


459

GAHC. Other Epiaquults that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 100
cm or more.

Grossarenic Epiaquults

GAHD. Epiaquults that have 50 percent or more chroma
of 3 or more in one or more horizons between either the
Aor Ap horizon or a depth of 25 cm from the mineral
soil surface, whichever is deeper, and a depth of 75 cm.

Aeric Epiaquults
GAHE. Other Epiaquults.

Typic Epiaquults
Fragiaquults
Key to subgroups

GABA. Fragiaquults that have both:

1. Fifty percent or more chroma of 3 or more in
one or more horizons between either the A or Ap
horizon or a depth of 25 cm from the mineral soil
surface, whichever is deeper, and the fragipan;
and

2. Five percent or more (by volume) plinthite in
‘one or more horizons within 150 cm of the
mineral soil surface,

Plinthudic Fragiaquults

GABB, Other Fragiaquults that have 50 percent or more
chroma of 3 or more in one or more horizons between
either the A or Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and the
fragipan.
Aeric Fragiaquults

GABC. Other Fragiaquults that have 5 percent or more
(by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface,

Plinthic Fragiaquults

GABD., Other Fragiaquults that do not have an ochric
epipedon.

Umbric Fragiaquults
GABE. Other Fragiaquults,
Typic Fragiaquults
Kandiaquults
Key to subgroups

GADA,. Kandiaquults that have an ECEC of 1.5
cmol(+)/kg clay or less (sum of bases extracted with IN
NH,OAc pH 7, plus 1N-KCl-extractable Al) in one or
mote horizons within 150 cm of the mineral soil
surface.

Acraquoxic Kandiaquults



Chapter 2

Horizons and Properties Diagnostic
for the Higher Categories: Mineral
Soils! HW
N

MINERAL SOIL MATERIAL

Mineral soi! material either:

1. Is never saturated with water for more than a few
days and contains less than 20 percent (by weight)
organic carbon; or

2. Is saturated with water for long periods (or artificially
drained) and, excluding live roots, has an organic-
carbon content (by weight) of:

a, Less than 18 percent if the mineral fraction
contains 60 percent or more clay; or

b. Less than 12 percent if the mineral fraction
contains no clay; or

c, Less than 12 + (clay percentage multiplied by
0.1) percent if the mineral fraction contains less
than 60 percent clay.

Soil material that contains more than the above amounts
of organic carbon is considered to be organic soil
material.

DIAGNOSTIC SURFACE HORIZONS; THE
EPIPEDON

Any horizon may be at the surface of a truncated soil.
The following section, however, is concerned with
seven diagnostic horizons that have formed at the soil
surface, A horizon that has developed at the soil surface
is called an epipedon (Gr. epi, over, upon; and pedon,
soil). It is a horizon in which rock structure has been
destroyed and which has either been darkened by
organic matter or eluviated. Such a horizon may become
covered by thin alluvial or 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 above (Chapter 1).

A recent alluvial or eolian deposit that retains fine
stratification, or an Ap horizon directly underlain by
such stratified material, is not included in the concept of
the epipedon because time has not been sufficient for
soil-forming processes to erase these transient marks of

1 Mineral souls include all soil orders in this taxonomy except Histosols.


448

2. Andic soil properties throughout horizons that
have a total thickness of 25 cm or more within 75
cm either of the mineral soil surface, or of the top
of an organic layer with andic soil properties,

whichever is shallower.
Aquandic Humicryods

BBCD. Other Humicryods which have andic soil
properties throughout horizons that have a total
thickness of 25 cm or more within 75 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Andic Humicryods

BBCE. Other Humicryods that have, in one or more
horizons within 75 cm of the mineral soil surface,
redoximorphic features, and also aquic conditions for
some time in most years (or artificial drainage).

Aquic Humicryods

BBCF. Other Humicryods that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of

10 years.
Oxyaquic Humicryods
BBCG. Other Humicryods.
Typic Humicryods
Placocryods
Key to subgroups

BBAA. Placocryods which have andic soil properties
throughout horizons that have a total thickness of 25 cm
or more within 75 cm either of the mineral soil surface,
or of the top of an organic layer with andic soil
properties, whichever is shallower.

Andic Placocryods

BBAB, Other Placocryods that have 6 percent or more
organic carbon in a layer 10 cm or more thick within the

spodic horizon.
Humic Placocryods
BBAC. Other Placocryods.
Typic Placocryods
HUMODS
Key to great groups

BCA. Humods that have a placic horizon within 100 cm
of the mineral soil surface in 50 percent or more of each

pedon.
Placohumods, p. 449

BCB. Other Humods which have, in 90 percent or more
of each pedon, a cemented soil layer that does not slake


240

Hydraquents
Key to subgroups
KABA. All Hydraquents (provisionally).
Typic Hydraquents

Psammaquents
Key to subgroups
KADA. Psammaquents that have a lithic contact within
50 cm of the mineral soil surface.

Lithic Psammaquents

KADB. Other Psammaquents which have a horizon 5
cm or more thick, either below an Ap horizon or at a
depth of 18 cm or more from the mineral soil surface,
whichever is deeper, that has one or more of the
following:
1. In 25 percent or more of each pedon,
cementation by organic matter and aluminum,
with or without iron; or

2. Aluminum plus 1/2 iron percentages (by
ammonium oxalate) totaling 0.25 or more, and
half that amount or less in an overlying horizon;
or

3. An ODOE value of 0.12 or more, and a value
half as high or lower in an overlying horizon.
Spodic Psammaquents

KADC. Other Psammaquents which have both:

1. An Ap horizon, or an A horizon 15 cm or more
thick, that has a color value, moist, of 3 or less
and a color value, dry, of 5 or less (crushed and
smoothed sample); and
2. A base saturation (by NH,OAc) of less than 50
percent in horizons with a total thickness of 50 cm
or more within 100 cm of the mineral soil surface.
Humaqueptic Psammaquents
KADD. Other Psammaquents which have either an Ap
horizon, or an A horizon 15 cm or more thick, that has a
color value, moist, of 3 or less and a color value, dry, of
5 or less (crushed and smoothed sample).

Mollic Psammaquents
KADE. Other Psammaquents.

Typic Psammaquents
Sulfaquents
Key to subgroups

KAAA. Sulfaquents that have a histic epipedon.
Histic Sulfaquents


37

differ by 5°C or more at a depth of 50 cm from the soil
surface, the soil moisture control section in the ustic
regime is dry in some or all parts for 90 or more
cumulative days per year in most years. But it is not dry
in all parts for more than half the cumulative days when
the soil temperature at a depth of 50 cm is higher than
5°C. If the moisture control section, in 6 or more out of
10 years, is moist in all parts for 45 or more consecutive
days in the 4 months following the winter solstice, the
moisture control section is dry in all parts for less than
45 consecutive days in the 4 months following the
summer solstice.

In tropical and subtropical regions that have a monsoon
climate with either one or two dry seasons, summer and
winter seasons have little meaning. In those regions, the
moisture regime is ustic if there is at least one rainy
season of 3 months or more. In temperate regions of
subhumid or semiarid climates, the rainy seasons are
usually spring and summer or spring and fall, but never
winter, Native plants are mostly annuals, or plants that
have a dormant period while the soil is dry.

Xeric moisture regime.—The xeric moisture regime
(Gr. xeros, dry) is the typical moisture regime of
Mediterranean climates, where winters are moist and
cool and summers are warin and dry. The moisture,
coming during the winter when potential evapo-
transpiration is at a minimum, is particularly effective
for leaching. In a xeric moisture regime the soil
moisture control section, in 6 or more out of 10 years, is
dry in all parts for 45 or more consecutive days in the 4
months following the summer solstice, and moist in all
parts for 45 or more consecutive days in the 4 months
following the winter solstice. Also, in 6 or more out of
10 years, the moisture control section is moist in some
Part for more than half the cumulative days per year
when the soil temperature at a depth of 50 cm from the
soil surface is higher than 5°C, and for 90 or more
consecutive days when the soil temperature at a depth of
50 cm is higher than 8°C. The mean annual soil
temperature is lower than 22°C, and mean summer and.
mean winter soil temperatures differ by 5°C or more
cither at a depth of 50 cm from the soil surface, or at a
lithic or paralithic contact if shallower.

Soil temperature regimes
Classes of soil 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; meaning 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 there is no


327

2. A slope of less than 25 percent.
Fluventic Humitropepts

JCAJ. Other Humitropepts that have both:
1. An ustic moisture regime; and

2. A CEC (by IN NH,OAc pH 7) of less than 24
emol(+)/kg clay? in 50 percent or more of the soil
volume between a depth of 25 cm from the
mineral soil surface and either a depth of 100 cm,
or a lithic or paralithic contact if shallower.
Ustoxic Humitropepts

JCAK. Other Humitropepts that have a CEC (by IN
'NH,OAc pH 7) of less than 24 cmol(+)/kg clay* in 50
percent or more of the soil volume between a depth of
25 cm from the mineral soil surface and either a depth
of 100 om, or a lithic or paralithic contact if shallower.
Oxic Humitropepts

JCAL. Other Humitropepts that have an ustic moisture
regime.

Ustic Humitropepts
JCAM, 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 within or below a cambic horizon.
Most of them have an umbric epipedon, a perudic soil
moisture regime, and an isomesic soil 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 mineral soil surface.
Lithic Ustropepts

ICCB. Other Ustropepts which have one or both of the
following:
1. Cracks within 125 cm of the mineral soil

surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most

3 Some cambic horizons with properties that approach those of an oxic
horizon do not disperse well. If the ratio of (percent water retained at 1500
kPa tension minus percent organic carbon) to the percentage of measured
clay in the fine-earth fraction is 0.6 or more, then the percentage of clay is
considered to equal either (1) the measured percentage of clay, or (2) three
times (percent water retained at 1500 kPa tension minus percent organic
carbon), whichever value is higher, but no more than 100,

4 See foomote 3.


19

conditions for some time in most years (or artificial
drainage).
Aquic Haplustalfs

ICHG. Other Haplustalfs that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for | month or more per year in 6 or more out of
10 years.

Oxyaquic Haplustalfs

ICHH, Other Haplustalfs which have an argillic horizon
that has a texture of loamy fine sand or coarser, or is
discontinuous horizontally, or is discontinuous vertically
within its upper 20 cm.

Psammentic Haplustalfs

ICHI. Other Haplustalfs which have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of an argillic horizon at a depth of 50 cm or more;
and

2. If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for six tenths or more of the
cumulative days per year when the soil
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
contro] section which, in 6 or more out of 10
years, remains moist in some or all parts for
less than 90 consecutive days per year when
the temperature at a depth of 50 cm below
the soil surface is higher than 8°C.

Arenic Aridic Haplustalfs

ICHI. Other Haplustalfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
cm or more,

Arenic Haplustalfs

ICHK. Other Haplustalfs which, if neither irrigated nor
fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for six tenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years,



213

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 cm of the soil, if the lithic
contact is between 18 and 40 cm from the
soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13.

Borollic Lithic Camborthids

FBFB. Other Camborthids which have:

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

2. A horizon within 100 cm of the soil surface that
is 15 em or more thick and either contains 20
percent or more (by volume) durinodes or is
brittle and has firm consistence when moist; and

3. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if the lithic
contact is between 40 and 50 cm below the
soil surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 cm of the soil, if the lithic
contact is between 18 and 40 cm from the
soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

4. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean

-D>


475

also aquic conditions for some time in most years
(or artificial drainage).
Aquandic Kandiudults

GCCL. Other Kandiudults that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm} or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0,

Andic Kandiudults

GCCM. Other Kandiudults that have, in one or more
layers within 75 cm of the mineral soil surface, redox
depletions with a color value, moist, of 4 or more and a
chroma of 2 or less, accompanied by redox
concentrations, and also aquic conditions for some time
in most years (or artificial drainage).
Aquic Kandiudults

GCCN. Other Kandiudults that have 5 percent or more
(by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface.

Plinthic Kandiudults

GCCO. Other Kandiudults that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
concentrations, a color value, moist, of 4 or more, and a
hue which is 10YR or yellower, but which becomes
redder with increasing depth within 100 cm of the
mineral soil surface.

Ombroaquic Kandiudults

GCCP. Other Kandiudults that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Kandiudults

GCCQ, Other Kandiudults that have a sombric horizon
within 150 cm of the mineral soil surface.
Sombric Kandiudults

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

Rhodic Kandiudults
GCCS, Other Kandiudults.

Typic Kandiudults

Kanhapludults

Key to subgroups

GCDA. Kanhapludults that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Kanhapludults

arc


510
Salusterts

Key to subgroups

EEBA. Salusterts that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Salusterts

EEBB, Other Salusterts that have, in one or more
horizons within 100 cm of the mineral soil surface, an
exchangeable sodium percentage of 15 or more (or a
sodium adsorption ratio of 13 or more) for 6 or more
months per year in 6 or more out of 10 years.

Sodic Salusterts

EEBC. Other Salusterts that have, in one or more
horizons within 100 cm of the mineral soil surface,
aquie conditions for some time in most years (or
artificial drainage) and either:

1. Redoximorphic features; or

2. Enough active ferrous iron to give a positive

'-dipyridy| at a time when the soil
is not being irrigated.

Aquic Salusterts

EEBD. Other Salusterts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
are 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 210
or more cumulative days per year.

Aridic Salusterts

EEBE. Other Salusterts that have a lithic or paralithic
contact, or the upper boundary of a duripan or
petrocalcic horizon, within 100 cm of the mineral soil
surface.

Leptic Salusterts

EEBF. Other Salusterts which have a layer 25 cm or
more thick that contains less than 27 percent clay in its
fine-earth fraction and has its upper boundary within
100 cm of the mineral soil surface.

Entic Salusterts

EEBG. Other Salusterts that have, in one or more.
horizons within 30 cm of the mineral soil surface, 50
percent or more colors as follows:

1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or

3, A chroma of 3 or more.
Chromic Salusterts

EEBH. Other Salusterts.
Typic Salusterts


442

BAE. Other Aquods which have, in 90 percent or more
of each pedon, a cemented soil layer that does not slake
in water after air-drying and has its upper boundary
within 100 cm of the mineral soil surface.

Duraquods, p. 443

BAF. Other Aquods that have episaturation.
Epiaquods, p. 444

BAG. Other Aquods.
Endoaquods, p. 444

Alaquods

Key to subgroups

BABA. Alaquods that have a lithic contact within 50 cm
of the mineral soil surface.
Lithic Alaquods

BABB. Other Alaquods which have, in 90 percent or
more of each pedon, a cemented soil layer that does not
slake in water after air-drying and has its upper
boundary within 100 cm of the mineral soil surface.
Duric Alaquods

BABC. Other Alaquods that have a histic epipedon,
Histic Alaquods

BABD. Other Alaquods which have both:

1, Within 200 cm of the mineral soil surface, an
argillic or a kandic horizon that has a base
saturation of 35 percent or more (by sum of
cations) in some part; and

2. A sandy particle size throughout a layer

extending from the mineral soil surface to the top

of the spodic horizon at a depth of 75 to 125 cm.
Alfic Arenic Alaquods

BABE. Other Alaquods that have both:

1. An argillic or a kandic horizon within 200 cm
of the mineral soil surface; and

2. A sandy particle size throughout a layer

extending from the mineral soil surface to the top

of the spodic horizon at a depth of 75 to 125 cm.
Arenic Ultic Alaquods

BABF. Other Alaquods that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of the spodic horizon at a depth of
75 to 125 em.

Arenic Alaquods

BABG. Other Alaquods that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of the spodic horizon at a depth of 125
cm or more.

Grossarenic Alaquods


16

firm; if it is near field capacity, the matrix is brittle.
This brittle matrix constitutes 60 percent or more (by
volume) of one or more subhorizons of the fragipan.

5. The brittleness in parts of the fragipan is well enough
expressed so that there are virtually no fine feeder roots
in this brittle matrix, which has mean horizontal
dimensions of 10 cm or more. The surrounding bleached
vertical streaks may contain few to many fine feeder
roots and some tap roots of trees.

6. The fine-earth fraction of a fragipan has a texture
finer than fine sand and generally contains less than 35
percent clay (in most soils considerably less); it is
generally loamy (silt loam, loam, or sandy loam).

7. A fist-sized, air-dried fragment of a fragipan slakes or
fractures when placed in water.

Glossic horizon

The glossic (Gr. glossa, tongue) horizon is 5 cm or more
thick and consists of:

1. An eluvial part, i.e., albic materials (defined below),
which constitute 15 to 85 percent (by volume) of the
glossic horizon; and

2. An illuvial part, i.e., remnants of an argillic, a kandic,
or a natric horizon (defined below).

The glossic horizon develops as a result of the
degradation of an argillic, a kandic, or a natric horizon,
from which clay and free iron oxides are removed. This
process of eluviation gradually progresses from the
exteriors of peds to their interiors. In early stages of the
development, the peds of the remnant argillic, kandic,
or natric horizon still form structural units that extend
throughout the glossic horizon, constituting close to 85
percent of its volume. In later stages, some of these
structural units no longer extend throughout the horizon,
and in the most advanced stages of the degradation
process remnant peds constitute little more than 15
percent (by volume) of the glossic horizon and are
completely surrounded by albic materials. The boundary
between the illuvial and eluvial parts of the glossic
horizon may be either abrupt or clear, and either
irregular or broken.

A glossic horizon usually occurs between an overlying,
albic horizon and an underlying argillic, kandic, or
natric horizon or fragipan. It can lie between an argillic,
cambic, or kandic horizon and a fragipan. In the early
stages of the degradation process described above, a
glossic horizon can be within an argillic, kandic, or
natric horizon, or within a fragipan if the fragipan shows
evidence of the degradation of an argillic horizon. An
albic horizon may be below, or between subhorizons of,
the glossic horizon.


BOROLLS

Key to great groups
HEA. Borolls which have both:

1, An argillic horizon that has its upper
60 cm or more below the mineral soil surface; and

2. A texture finer than loamy fine sand in all
horizons above the argillic horizon.
Paleborolls, p. 361

HEB. Other Borolls that have a cryic or pergelic soil

temperature regime.
Cryoborolls, p. 352

HEC. Other Borolls which 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. 360

HED. Other Borolls which 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.
Argiborolis, p, 347

HEE. Other Borolls that have a mollic epipedon which:

1, Either below an Ap horizon or below a depth of
18 cm from the mineral soil surface, contains 50
percent or more (by volume) wormholes, worm
casts, or filled animal burrows; and

2. Either rests on a lithic contact, or has a
transition zone to the underlying horizon in which
25 percent or more of the soil volume consists of
discrete wormholes, worm casts, or animal
burrows filled with material from the mollic
epipedon and from the underlying horizon.
Vermiborolls, p. 363

HEF, Other Borolls which:

1. Have a calcic or petrocalcic horizon that has its
upper boundary within 100 cm of the mineral soil
surface; and .
2. In all parts above the calcic or petrocalcic
horizon, after the materials between the soil
surface and a depth of 18 cm have been mixed,
are either calcareous or have a texture of loamy
fine sand or coarser.

Calciborolls, p. 351

HEG., Other Borolls.
Haploborolls, p. 356


Ww

or a spodic horizon. Some soils have, directly below the
albic horizon, either a lithic or paralithic contact, or
another relatively impervious layer that produces a
perched water table with stagnant or moving water.

Argillic horizon

An argillic horizon is an illuvial horizon which contains
significant accumulations of illuviated layer-lattice
silicate clays, It must have formed below an eluvial
horizon but may be found at the surface of a partially
truncated soil. The following characteristics are used for
its identification:

1. If there is a lithologic discontinuity between the
overlying cluvial horizon and the argillic horizon or if it
is overlain only by a plow layer, clay films are required
only in some part of the argillic horizon, either in some
fine pores or, if peds are present, on some vertical and
horizontal surfaces of peds. Either some part of the
horizon is shown in thin section to have 1 percent or
more oriented clay bodies, or the ratio of fine clay to
total clay in the argillic horizon is higher than in the
overlying or the underlying horizon.

2. If an eluvial horizon remains and there is no
lithologic discontinuity between it and the underlying
argillic horizon, the argillic horizon contains, within 30
cm of its upper boundary, higher percentages of total
clay and fine clay than the eluvial horizon, as follows:

a. If any part of the overlying eluvial horizon has
less than 15 percent total clay in its fine-earth
fraction, the total clay content in the argillic
horizon is 3 percent or more (absolute) higher
than in the eluvial horizon (e.g., 13 percent versus
10 percent). The ratio of fine clay to total clay in
the argillic horizon is normally one third or more
higher than in the overlying eluvial or in the
underlying horizon.

b. If the overlying eluvial horizon has 15 to 40
percent total clay in its fine-earth fraction, the
total clay content in the argillic horizon is 20
percent or more (relative) higher than in the
eluvial horizon (¢.g., 24 percent versus 20 per-
cent), The ratio of fine clay to total clay in the
argillic horizon is normally one third or more
higher than in the eluvial horizon.

c. If the eluvial horizon has 40 to 60 percent total
clay in the fine-earth fraction, the total clay con-
tent in the argillic horizon is 8 percent or more
(absolute) higher than in the eluvial horizon (e.g.,
50 percent versus 42 percent).

d. If the eluvial horizon has 60 percent or more
total clay in the fine-earth fraction, the fine-clay
content in the argillic horizon should be 8 percent


400
HDEV. Other Argixerolls.

Typic Argixerolls
Calcixerolls
Key to subgroups
HDDA. Calcixerolls that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Calcixerolls

HDDB. Other Calcixerolls which have one or both of
the following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Calcixerolls

HDDC. Other Calcixerolls that have a mollic epipedon
50 cm or more thick with a texture finer than loamy fine
sand.

Pachic Calcixerolls

HDDD. Other Calcixerolls that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
concentrations, and also aquic conditions for some time
in most years (or artificial drainage).

Aquic Calcixerolls
HDDE. Other Calcixerolls that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Calcixerolls

HDDF. Other Calcixerolls that have an aridic moisture
regime.

Aridic Calcixerolls
HDDG. Other Calcixerolls which have a mollic
epipedon that contains, below any Ap horizon, 50
percent or more (by volume) wormholes, worm casts, or

filled animal burrows.
Vermic Calcixerolls

HDDH. Other Calcixerolls.
Typic Calcixerolls


FOREWORD

This publication, Keys to Soil Taxonomy, serves two
purposes. It provides the taxonomic keys necessary for
the classification of soils according to Soil Taxonomy in
a form that can be used easily in the field, and it also
acquaints users of Soil Taxonomy with recent changes
in the classification system. This volume includes all
revisions of the keys that have so far been approved,
replacing the original keys in Soil Taxonomy: A Basic
System of Soil Classification for Making and
Interpreting Soil Surveys (1975), the work on which this
abridged version, first published in 1983, is based. We
plan to continue issuing updated editions of Keys to Soil
Taxonomy approximately every two years. After most of
the current International Soil Classification Committees
(ICOMs) have completed their mandates, Soil

Taxonomy in its entirety is to be revised and
republished.

This publication incorporates all amendments approved
to date and published in National Soil Taxonomy
Handbook (NSTH) Issues 1-16, It includes the
recommendations of the International Committee on
Low Activity Clays (NSTH Issue #8), the International
Committee on Oxisols (NSTH Issue #11), the
International Committee on Andisols (NSTH Issue #13),
the International Committee on Vertisols (NSTH Issue
#16), the International Committee on Aquic Moisture
Regime (NSTH Issue #16), and the International
Committee on Spodosols (NSTH Issue #16). Editorial
changes have been made throughout this edition of Keys
to Soil Taxonomy to make grammatical corrections and
clarify the intent of the criteria.

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

The authors of Keys to Soil Taxonomy are identified as
“Soil Survey Staff.” This term is meant to include all
the soil classifiers in the National Cooperative Soil
Survey program and in the international community who
have made significant contributions to the improvement
of Soil Taxonomy.

RICHARD W. ARNOLD
Director, Soil Survey Division
Soil Conservation Service
1992


134

more (absolute) within a vertical distance of
7.5 om, or of 15 percent or more (absolute)
within a vertical distance of 2.5 cm, in the
fine-earth fraction; and

2. A duripan that is not indurated in any
subhorizon.
Abruptic Haplic Durixeralfs

IDAE. Other Durixeralfs which have an argillic horizon
that has both:

1, A clayey particle size throughout some
subhorizon 7.5 cm or more thick; and

2. At its upper boundary or within some part, a
clay increase either of 20 percent or more.
(absolute) within a vertical distance of 7.5 cm, or
of 15 percent or more (absolute) within a vertical
distance of 2.5 cm, in the fine-earth fraction.
Abruptic Durixeralfs

IDAF, Other Durixeralfs which have a duripan that is
not indurated in any subhorizon.

Haplic Durixeralfs
IDAG. Other Durixeralfs,

Typic Durixeralfs
Fragixeralfs
Key to subgroups

IDCA. Fragixeralfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within.
75 cm of the mineral soil surface, a fine-earth fraction
with both a bulk density of 1.0 g/cm? or less, measured
at 33 kPa water retention, and aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling more than
1.0.

Andic Fragixeralfs

IDCB. Other Fragixeralfs that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1, More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0,02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron


34
JECF. Other Xerumbrepts which have both:

1. An irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

2. A slope of less than 25 percent.
Fluventic Xerumbrepts

JECG. Other Xerumbrepts that do not have a cambic
horizon.

Entic Xerumbrepts

JECH. Other Xerumbrepts.
Typic Xerumbrepts


513
Haploxererts

Key to subgroups
ECCA. Haploxererts that have a lithic contact within 50

em of the mineral soil surface.
Lithic Haploxererts

ECCB. Other Haploxererts that have, throughout a layer
15 cm or more thick within 100 cm of the mineral soil
surface, an electrical conductivity of 15 dS/m or more
(1:1 soil:water) for 6 or more months per year in 6 or
more out of 10 years.

Halic Haploxererts

ECCC. Other Haploxererts that have, in one or more
horizons within 100 cm of the mineral soil surface, an
exchangeable sodium percentage of 15 or more (or a
sodium adsorption ratio of 13 or more) for 6 or more
months per year in 6 or more out of 10 years.

Sodic Haploxererts

ECCD. Other Haploxererts which, if not irrigated
during the year, have cracks in 6 or more out of 10 years
that remain 5 mm or more wide, through a thickness of
25 cm or more within 50 cm of the mineral soil surface,
for 180 or more consecutive days.

Aridic Haploxererts

ECCE. Other Haploxererts that have, in one or more
horizons within 100 cm of the mineral soil surface,
aquic conditions for some time in most years (or
artificial drainage) and either

1. Redoximorphic features; or

2. Enough active ferrous iron to give a positive
reaction to «,a'-dipyridyl at a time when the soil
is not being irrigated.
Aquic Haploxererts
ECCF. Other Haploxererts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
remain 5 mm or more wide, through a thickness of 25
cm or more within 50 cm of the mineral soil surface, for
less than 90 consecutive days,
Udic Haploxererts

ECCG, Other Haploxererts that have a lithic or
paralithic contact within 100 cm of the mineral soil
surface.

Leptic Haploxererts

ECCH. Other Haploxererts which have a layer 25 cm or
more thick that contains less than 27 percent clay in its
fine-earth fraction and has its upper boundary within
100 cm of the mineral soil surface,

Entic Haploxererts

ECCI. Other Haploxererts that have, in one or more
horizons within 30 cm of the mineral soil surface, 50
percent or more colors as follows:



490

surface to the top of an argillic horizon at a depth of 50
to 100 cm.
Arenic Haploxerults

GEBF, Other Haploxerults that have a sandy particle
size throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 100
cm or more.

Grossarenic Haploxerults

GEBG. Other Haploxerults that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm} or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Haploxerults
GEBH, Other Haploxerults.

Typic Haploxerults
Palexerults
Palexerults are the Xerults which:

1. Do not have a lithic or paralithic contact within 150
cm of the mineral soil surface; and

2. Within 150 cm of the mineral soil surface, either:

a. Do not have a clay decrease with increasing
depth of 20 percent or more (relative) from the
maximum clay content; or

b. Have 5 percent or more (by volume) skeletans
‘on faces of peds in the layer that has a 20 percent
lower clay content and, below that layer, a clay
increase of 3 percent or more (absolute) in the
fine-earth fraction.

LITERATURE CITED

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


295

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more

between the mineral soil surface and cither a

depth of 100 cm or a lithic or paralithic contact,

whichever is shallower.

Vertic Epiaquepts

JAIB. Other Epiaquepts that have, in one or more
horizons between the A or Ap horizon and a depth of 75
cm below the mineral soil surface, one of the following
colors:

1. A hue of 7.5YR or redder in 50 percent or more
of the matrix, and

a, If peds are present, either a chroma of 2
or more on 50 percent or more of ped
exteriors, or no redox depletions with a
chroma of 2 or less in ped interiors; or

b, Ifpeds are absent, a chroma of 2 or more
in 50 percent or more of the matrix; or

2. In 50 percent or more of the matrix, a hue of

10YR or yellower and either
a, Both a color value, moist, and chroma of
3 or more; or
b, A chroma of 2 or more if there are no
redox concentrations.
Aeric Epiaquepts
JAIC. Other Epiaquepts.
‘Typic Epiaquepts N
Fragiaquepts
Key to subgroups

JADA. Fragiaquepts that have, in 50 percent or more of
the matrix of one or more horizons, either between the
plow layer and a depth of 75 cm below the mineral soil
-Surface or, if there is no plow layer, between 15 and 75
em depth, a chroma of either

1. Three or more; or

2. Two or more if there are no redox
concentrations.
Aeric Fragiaquepts

JADB. Other Fragiaquepts that have a histic, a mollic,
or an umbric epipedon.
Humic Fragiaquepts


109

from the mineral soil surface, or directly above a
lithic or paralithic contact, whichever is
shallowest.

Aquultic Hapludalfs

IEKP. Other Hapludalfs which have both:

1, An Ap horizon that has a color value, moist, of
3 or less and a color value, dry, of 5 or less
(crushed and smoothed sample), or materials
between the soil surface and a depth of 18 cm
which have these color values after mixing; and

2. Redox depletions with a chroma of 2 or less in
layers that also have aquic conditions in most
years (or artificial drainage) either:

a. Within the upper 25 cm of the argillic
horizon if its upper boundary is within 50
em of the mineral soil surface, or

b. Within 75 cm of the mineral soil surface
if the upper boundary of the argillic horizon
is 50 cm or more below the mineral soil
surface.

Aquollic Hapludalfs

TEKQ. Other Hapludalfs which have redox depletions
with a chroma of 2 or less in layers that also have aquic
conditions in most years (or artificial drainage) either:

1. Within the upper 25 cm of the argillic horizon.
if its upper boundary is within 50 cm of the
mineral soil surface, or
2. Within 75 cm of the mineral soil surface if the
upper boundary of the argillic horizon is 50 cm or
more below the mineral soil surface.

Aquic Hapludalfs

TEKR. Other Hapludalfs that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years,

Oxyaquic Hapludalfs

TEKS. Other Hapludalfs that have both;

1. Five percent or more (by volume) albic
materials in one or more subhorizons of the
argillic horizon; and
2. A mean annual soil temperature of 10°C or
higher.
Glossic Hapludalfs
IEKT. Other Hapludalfs that have both:

1. In the upper part of the argillic horizon,
interfingering of albic materials and albic
materials surrounding some peds; and


67

3. 25 cm below the upper boundary of permafrost if that
boundary is 75 cm or more below the soil surface, or

4, 25 cm below a paralithic contact; or
5. A depth of 150 cm.

Alll other mineral soils.—-The series control section for
all other mineral soils extends from the soil surface to
the shallowest of the following:

1. A lithic or petroferric contact, or

2. A depth of either 25 cm below a paralithic contact or
150 cm below the soil surface, whichever is shallower,
if there is a paralithic contact within 150 cm; or

3. A depth of 150 cm if the bottom of the deepest
diagnostic horizon is less than 150 cm from the soil
surface; or

4. The lower boundary of the deepest diagnostic horizon
or a depth of 200 cm, whichever is shallower, if the
lower boundary of the deepest diagnostic horizon is 150
cm or more below the soil surface.

Organic soils (Histosols) ~The series control section
for Histosols normally consists of the surface,
subsurface, and bottom tiers, with the same exceptions
with respect to the lower boundary of the control section
as defined above for the higher categories of Histosols.

Zon


206

3. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to noncarbonate clay, as follows:

a, In the upper 40 cm of the soil, if the lithic
contact is between 40 and 50 cm below the
soil surface,

(1) 0.60 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.15 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.64-(0.038 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between
1 and 13; or

b. In the upper 18 em of the soil, if the lithic
contact is between 18 and 40 cm from the
soil surface,

(1) 0.72 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or

(2) 0.18 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or

(3) 0.77-(0,046 x sand/noncarbonate-
clay ratio), or more, with a
sand/noncarbonate-clay ratio between

land 13.
Borollic Lithic Calciorthids

FBEB. Other Calciorthids which have both:
1. A frigid soil temperature regime, and an aridic
moisture regime that borders on an ustic regime;
and
2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to noncarbonate clay, as follows:
a, In the upper 40 om of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,
(1) 0.60 or more, with a
sand/noncarbonate-clay ratio of 1.0 or
less; or
(2) 0.15 or more, with a
sand/noncarbonate-clay ratio of 13 or
more; or
(3) 0.64-(0.038 x sand/noncarbonate-
clay ratio), or more, with a


2

with stratification in parent materials. The placic
horizon is in the solum, commonly within 50 cm of the
mineral soil surface, and roughly parallel with it. It has
a pronounced wavy or even convolute form. Normally it
occurs as a single pan rather than as multiple sheets
(one underlying another), but it may be bifurcated. It is
a barmier to water and roots.

If cemented by iron, the pan is strong brown to dark
reddish brown; if cemented by iron and manganese or
by iron-organic-matter complexes, it is black or reddish
black. A single pan may contain two or more layers that
are cemented by different agents; commonly iron-
organic-matter complexes are found in the upper part of
the pan.

Unless its thickness is minimal, identification of a
placic horizon is seldom difficult because the hard,
brittle pan differs so much from the material in which it
occurs and is so close to the mineral soil surface.
Analyses of placic horizons show that they contain
between 1 and more than 10 percent organic carbon.
The presence of organic carbon and the shape and
position of the placic horizon distinguish it from the
ironstone sheets that may form where water hangs, or
moves laterally, at a lithologic discontinuity.

Salic horizon

A salic horizon is a horizon 15 cm or more thick
containing a secondary enrichment of salts which, in
cold water, are more soluble than gypsum. It has a salt
content of 2 percent or more (by weight) throughout,
and the product of its thickness (in centimeters)
multiplied by its salt percentage (by weight) is 60 or
more. Thus, a horizon 20 cm thick must contain 3
percent salt to qualify as a salic horizon, while a horizon
30 cm thick requires 2 percent.

Sombric horizon

The sombric horizon (Sp sombra shade, hence dark) is
a subsurface horizon of mineral soils which has formed
under free drainage. It contains illuvial humus that is
neither associated with aluminum, as is the humus in
the spodic horizon, nor dispersed by sodium, as is
common in the natric horizon. Consequently the sombric
horizon does not have the high cation-exchange capacity
in its clay that characterizes a spodic horizon, and it
does not have the high base saturation of a natric
horizon, It does not underlie an albic horizon.

Sombric horizons are thought to be restricted to the
cool, moist soils of high plateaus and mountains in
tropical or subtropical regions. Because of strong
leaching, their base saturation is low (less than 50
percent by NH,OAc).

The sombric horizon has a lower color value or chroma,
or both, than the overlying horizon and commonly

M
N


of 15 cm or more that have one or more of
the following:

(1) A color value, moist, of 4 or more
and redox depletions with a chroma of
2 or less; or

(2) A hue of 10YR or redder and a
chroma of 2 or less; or

(3) A hue of 2.5Y or yellower anda
chroma of 3 or less; and

2. One or both of the following:

a, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
em of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower.

Aquertic Argiudolls

HGCC. Other Argiudolls which have one or both of the
following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and cither a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Argiudolls

HGCD. Other Argiudolls which have an argillic horizon
that either has a texture of loamy fine sand or coarser, or
consists entirely of lamellae,

Psammentic Argiudolls

HGCE. Other Argiudolls that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm} or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling

more than 1.0,
Andic Argiudolls

HGCF. Other Argiudolls that have, throughout one or
more horizons with a total thickness of 18 cm or more


v Plinthite

This symbol indicates the presence of iron-rich,
humus-poor reddish material that is firm or very
firm when moist and hardens irreversibly when
exposed to the atmosphere and to repeated wetting
and drying.

w Development of color or structure
This symbol is used with B to indicate the
development of color or structure, or both, with
little or no apparent illuvial accumulation of
material. It should not be used to indicate a
transitional horizon,

x Fragipan character
This symbol indicates a genetically developed
layer that has a combination of firmness,
brittleness, very coarse prisms with few to many
bleached vertical faces, and commonly a higher
bulk density than adjacent layers. Some part of the
layer is physically root-restrictive.

y Accumulation of gypsum
This symbol indicates a gypsum accumulation,

z Accumulation of salts more soluble than gypsum

This symbol indicates an accumulation of salts
that are more soluble than gypsum.

CONVENTIONS FOR USING LETTER
SUFFIXES

Many master horizons and layers that are symbolized by
a single capital letter have one or more lower-case letter
suffixes. The following rules apply:

Letter suffixes should immediately follow the
capital letter.

More than three suffixes are rarely used.

If more than one suffix is needed, the following
letters, if used, are written first: a, d, e, h, i, r, s, t,
and w. Except in the Bhs or Crt} horizon
designations, 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, the following symbols, if used, are
written last: o, f, g, m, v, and x. Some examples:
Btc, Bkm, and Bsv.

Ifa horizon is buried, the suffix b is written last. It
is used only for buried mineral soils.

3 indicates weathered bedrock of saprolite in which clay films are present.


142

CAGC. Other Endoaquands which have a horizon 15 cm
or more thick, with 20 percent or more (by volume)
cemented soil material that does not slake in water after
air-drying, that has its upper boundary within 100 cm
either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Duric Endoaquands

CAGD, Other Endoaquands that have a histic epipedon.
Histic Endoaquands

CAGE. Other Endoaquands that have more than 2.0
cmol(+)/kg Al* (by IN KCl) in the fine-earth fraction
of one or more horizons with a total thickness of 10 cm
or more, between 25 and 50 cm either from the mineral
soil surface, or from the top of an organic layer with
andic soil properties, whichever is shallower.

Alic Endoaquands

CAGF. Other Endoaquands that have, undried, a 1500-
kPa water retention of 70 percent or more throughout a
layer 35 cm or more thick within 100 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Hydric Endoaquands

CAGG. Other Endoaquands that have, between 25 and
100 cm either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, a layer 10 cm or more thick
with more than 3.0 percent organic carbon and colors of
a mollic epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more that
have a color value, moist, 1 unit or more higher and an
organic-catbon content 1 percent or more (absolute)
lower.

Thaptic Endoaquands
CAGH. Other Endoaquands.
Typic Endoaquands
Epiaquands
Key to subgroups

CAFA. Other Epiaquands that have a petroferric contact
within 100 cm either of the mineral soil surface, or of
the top of an organic layer with andic soil properties,
whichever is shallower.

Petroferric Epiaquands

CAFB. Other Epiaquands that have a horizon 15 cm or
more thick, with 20 percent or more (by volume)
cemented soil material that does not slake in water after
ait-drying, that has its upper boundary within 100 em
either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Duric Epiaquands


519

accumulation is used in many of the definitions of such
horizons to indicate that these horizons must contain
more of the material in question than is presumed to
have been present in the parent material. The suffix
symbols and their meanings are as follows:

a Highly decomposed organic material
This symbol is used with O to indicate the most
highly decomposed organic materials, which have
a rubbed fiber content of less than 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 developed before burial.
Genetic horizons may or may not have formed in
the overlying material, which may be either like or
unlike the assumed parent material of the buried
soil. This symbol is not used in organic soils or to
separate an organic from a mineral layer.

¢ Concretions or nodules

This symbol indicates a significant accumulation
of concretions or nodules, Cementation is
required, but the cementing agent is not specified,
except that it cannot be silica. This symbol is not
used if the concretions or nodules consist of
dolomite or calcite or more soluble salts, but it is
used if the nodules or concretions are enriched
with minerals that contain iron, aluminum,
Manganese, or titanium.

d Physical root restriction

This symbol indicates root-restricting layers in
naturally occurring or man-made unconsolidated
sediments or materials, such as dense basal till,
plow pans, and other mechanically compacted
zones,

e Organic material of intermediate decomposition
This symbol is used with O to indicate organic
materials of intermediate decomposition. Their
tubbed fiber content is 17 to 40 percent (by
volume).

f Frozen soil

This symbol indicates that a horizon or layer
contains permanent ice. The symbol is not used
for seasonally frozen layers or for so-called dry
permafrost (material that is colder than O°C but
does not contain ice).

& Strong gleying

This symbol indicates either that iron has been
reduced and removed during soil formation, or
that saturation with stagnant water has preserved


239

em, colors in 50 percent or more of the matrix as
follows:

a, A hue of 2.5Y or redder, a color value,
moist, of 6 or more, and a chroma of 3 or
more; or

b. A hue of 2.5Y or redder, a color value,
moist, of 5 or less, and a chroma of 2 or
more; or

c. A bue of SY and a chroma of 3 or more;
or

d. A chroma of 2 or more if there are no
redox concentrations.
Aeric Tropic Fluvaquents

KAKG., Other Fluvaquents that have, in one or more
horizons between either the Ap horizon or a depth of 25
cm from the mineral soil surface, whichever is deeper,
and a depth of 75 cm, colors in 50 percent or more of
the matrix as follows:

1, A hue of 2.5Y or redder, a color value, moist, of
6 or more, and a chroma of 3 or more; or

2. A hue of 2.5Y or redder, a color value, moist, of
5 or less, and a chroma of 2 or more; or

3. A hue of SY and a chroma of 3 or more; or

4. A chroma of 2 or more if there are no redox
concentrations.
Aeric Fluvaquents

KAEH. Other Fluvaquents that have a difference of less
than 5°C between mean summer and mean winter soil
temperatures, either at a depth of 50 cm from the soil
surface or at a lithic or paralithic contact, whichever is
shallower.

Tropic Fluvaquents

KAEL Other Fluvaquents which have both:

1, An Ap horizon, or an A horizon 15 cm or more
thick, that has a color value, moist, of 3 or less
and a color value, dry, of 5 or less (crushed and
smoothed sample); and

2. A base saturation (by NH,OAc) of less than 50
percent at a depth of 100 cm from the mineral soil
surface.

Humaqueptic Fluvaquents

KAEJ. Other Fluvaquents which have an Ap horizon, or
an A horizon 15 cm or more thick, that has a color
value, moist, of 3 or less and a color value, dry, of 5 or
less (crushed and smoothed sample).

Mollic Fluvaquents

KAEK, Other Fluvaquents.
Typic Fluvaquents

42m


Chapter 14

Spodosols'

KEY TO SUBORDERS

BA. Spodosols that have aquic conditions for some time
in most years (or artificial drainage) in one or more
horizons within 50 cm of the mineral soil surface, and
one or both of the following:

1, A histic epipedon; or
2. Within 50 cm of the mineral soil surface,
redoximorphic features in an albic or a spodic
horizon.
Aquods, p. 441
BB. Other Spodosols that have a cryic or pergelic soil
temperature regime.
Cryods, p. 445

BC. Other Spodosols that have 6 percent or more
organic carbon in a layer 10 cm or more thick within the
spodic horizon.

Humods, p. 448
BD. Other Spodosols.

Orthods, p. 450
AQUODS
Key to great groups

BAA. Aquods that have a ctyic or pergelic soil
temperature regime.
Cryaquods, p. 443

BAB. Other Aquods that have less than 0.10 percent
iron (by ammonium oxalate) in 75 percent or more of
the spodic horizon.
Alaquods, p. 442

BAC. Other Aquods that have a fragipan.

Fragiaquods, p. 445
BAD. Other Aquods that have a placic horizon within
100 cm of the mineral soil surface in 50 percent or more

of each pedon.
Placaquods, p. 445

| This chapter on Spodosols was rewritten in 1992 following the
recommendations of the Intemational Committee on the Classification of
Spodosols (ICOMOD), chaired initially by F. Ted Miller, then by Robert V.
Rourke (since 1986).

oun


370

2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:
a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Hapludolls

HGEF. Other Hapludolls which have:

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

2. Either 0.3 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

3. A slope of 25 percent or less.
Cumulic Hapludolls

HGEG. Other Hapludolls that have;

1. Aquic conditions for some time in most years
(or artificial drainage), either:
a, Within 40 cm of the mineral soil surface,

in horizons that also have redoximorphic
features; or

b. Directly below the mollic epipedon, in
‘one or more horizons with a total thickness

of 15 cm or more that have one or more of
the following:

(1) A color value, moist, of 4 or more
and redox depletions with a chroma of
2 or less; or

(2) A hue of 10YR or redder and a
chroma of 2 or less; or

(3) A hue of 2.5Y or yellower and a
chroma of 3 or less; and

2. Either 0.3 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

3. A slope of less than 25 percent.
Fluvaquentic Hapludolis

HGEH. Other Hapludolls which have aquic conditions
for some time in most years (or artificial drainage),
either:


373
Vermudolis

Key to subgroups

HGDA. Vermudolls that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Vermudolls

HGDB. Other Vermudolls that have a cambic horizon.
Haplic Vermudolls

HGDC. Other Vermudolls that have a mollic epipedon
less than 75 em thick.

Entic Vermudolls
HGDD. Other Vermudolls.

Typic Vermudolls
USTOLLS
Key to great groups

HFA, Ustolls which have a duripan that has its upper
boundary within 100 cm of the mineral soil surface.
Durustolls, p. 382

HFB. Other Ustolls that have a natric horizon.
Natrustolls, p. 389

HFC. Other Ustolls which have either:

1, A petrocalcic horizon that has its upper
boundary within 150 cm of the mineral soil
surface, and either an argillic horizon or, after the
materials between the soil surface and a depth of
18 cm have been mixed, one or more
noncalcareous horizons above the petrocalcic
horizon; or
2. An argillic horizon that has one or both of the
following:
a. No clay decrease with increasing depth of
20 percent or more (relative) from the
maximum clay content within 150 cm of the
mineral soil surface (and there is no lithic or
paralithic contact within that depth), and
either:

(1) A hue of 7.5YR or redder and a
chroma of 5 or more in the matrix; or

(2) Common coarse redox
concentrations with a hue of 7.5YR or
redder or a chroma of 6 or more, or
both; or

b. A clayey particle size in its upper part,
and at its upper boundary, a clay increase of
either 20 percent or more (absolute) within
a vertical distance of 7.5 cm, or of 15



7

changes are necessary because finely divided lime acts
as a white pigment.

3. Base saturation is 50 percent or more by the NH,OAc
method.

4. The organic-carbon content is either 0.6 percent or
more throughout the thickness of the mollic epipedon,
or 2.5 percent or more in layers that have a color value,
moist, of 4 or 5 and a fine-earth fraction with a calcium
carbonate equivalent of 40 percent or more,

Since the mollic epipedon consists of mineral soil
material, the upper limit of its organic-carbon content is
the same as that defined above for mineral soil material.

5. After mixing the upper 18 cm of the mineral soil, or
the whole mineral soil if its depth to a lithic or
paralithic contact, petrocalcic horizon, or duripan (all
defined below) is less than 18 cm, the thickness of the
epipedon is as follows:

a. 10 cm or more if the epipedon is directly above
a lithic or paralithic contact, a petrocalcic horizon,
or a duripan; or

b. 25 cm or more if either

(1) The texture of the epipedon is loamy
fine sand or coarser throughout; or

(2) There are no underlying diagnostic
horizons (defined below) and the organic-
carbon content of the underlying materials
decreases irregularly with increasing depth.
(as in recent alluvial deposits); or

cc, 25 cm or more if the epipedon is finer than
loamy fine sand and if all of the following are 75
em or more below the mineral soil surface:

(1) The upper boundary of any pedogenic
lime that is present as filaments, soft
coatings, or soft nodules; and

(2) The lower boundary of any argillic,
cambic, natric, oxic, or spodic horizon
(defined below); and

(3) The upper boundary of any petrocalcic
horizon, duripan, or fragipan; or
d, If the epipedon is loamy or clayey, 18 cm or
more, and one third or more of the total thickness
between the top of the epipedon and the
shallowest of any features listed in (c) that are
less than 75 cm below the mineral soil surface; or

e. 18 cm or more if none of the above conditions
apply.
6. The epipedon has less than 250 parts per million

(ppm) of P.O, soluble in 1 percent citric acid, or it does
not have a regular decrease in the amounts of P,O; with



140

AQUANDS

Key to great groups
CAA. Aquands that have a cryic or pergelic soil
temperature regime.

Cryaquands, p. 140

CAB. Other Aquands that have, in half or more of each
pedon, a placic horizon within 100 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.

Placaquands, p. 144
CAC. Other Aquands that have, in 75 percent or more
of each pedon, a cemented layer which does not slake in
water after air-drying and which has its upper boundary
within 100 cm either of the mineral soil surface, or of
the top of an organic layer with andic soil properties,
whichever is shallower.

Duraquands, p. 141

CAD. Other Aquands that have a 1500-kPa water
retention of less than 15 percent on air-dried samples
and of less than 30 percent on undried samples,
throughout one or more horizons with a total thickness
of 35 cm or more within 60 cm either of the mineral soil
surface, or of the top of an organic layer with andic soil
properties, whichever is shallower.
Vitraquands, p. 145
CAE. Other Aquands that have a melanic epipedon.
Melanaquands, p. 143
CAF. Other Aquands that have episaturation.
Epiaquands, p. 142

CAG. Other Aquands.
Endoaquands, p. 141

Cryaquands

Key to subgroups
CAAA. Cryaquands that have a lithic contact within 50
cm either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.
Lithic Cryaquands

CAAB. Other Cryaquands that have a mean annual soil
temperature of 0°C or lower.

Pergelic Cryaquands

CAAC. Other Cryaquands that have a histic epipedon.

Histic Cryaquands
CAAD. Other Cryaquands that have, between 25 and
100 cm either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,


360
HEGR. Other Haploborolls which have both:

1. Either 0.3 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

2. A slope of less than 25 percent.
Fluventic Haploborolls

HEGS. Other Haploborolls which:

1. Have either a chroma of | or less (crushed and
smoothed sample) in the upper 18 om of the
mollic epipedon, after mixing, or in an Ap horizon
18 cm or more thick, or a moisture control section
that is moist in some or all of its parts throughout
the year in 6 or more out of 10 years; and

2. Do not have a cambic horizon and do not, in the

lower part of the mollic epipedon, meet the

requirements for a cambic horizon except color.
Udorthentic Haploborolis

HEGT. Other Haploborolls that have either a chroma of
1 or less (crushed and smoothed sample) in the upper 18
om of the mollic epipedon, after mixing, or in an Ap
horizon 18 cm or more thick, or a moisture control
section that is moist in some or all of its parts
throughout the year in 6 or more out of 10 years.

Udic Haploborolls
HEGU. Other Haploborolls that do not have a cambic
horizon and do not, in the lower part of the mollic
epipedon, meet the requirements for a cambic horizon
except color.

Entic Haploborolls
HEGV. Other Haploborolls.

Typic Haploborolls
Natriborolis
Key to subgroups

HECA. Natriborolls which have one or both of the
following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.
Vertic Natriborolls


339

3. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than.
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling

0.40 or more.
Aquandic Argialbolls

HABG., Other Argialbolls.

Typic Argialbolls
Natralbolls
Key to subgroups
HAAA. All Natralbolls (provisionally).

‘Typic Natralbolls
AQUOLLS
Key to great groups

HBA. Aquolls that have a cryic or pergelic soil
temperature regime.

Cryaquolls, p. 341
HBB. Other Aquolls which have a duripan that has its
upper boundary within 100 cm of the mineral soil
surface.

Duraquolls, p. 342

HBC. Other Aquolls that have a natric horizon.
Natraquolls, p. 345
HBD. Other Aquolls which have a calcic or gypsic
horizon that has its upper boundary within 40 cm of the
mineral soil surface, but do not have an argillic horizon
unless it is a buried horizon.
Calciaquolls, p. 340

HBE. Other Aquolls that have an argillic horizon,
Argiaquolls, p. 340
HBF. Other Aquolls that have episaturation.
Epiaquolls, p. 344
HBG. Other Aquolls.
Endoaquolls, p. 342

roz


338

a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower; and

2. If not irrigated, a moisture control section
which, in 6 or more out of 10 years, is dry in all
parts for 45 or more consecutive days during the
120 days following the summer solstice.
Xerertie Argialbolls
HABB. Other Argialbolls which have one or both of the
following:
1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,

whichever is shallower.
Vertic Argialbolls

HABC. Other Argialbolls which:

1, Do not have an abrupt textural change from the
albic to the argillic horizon; and
2. If not irrigated, have a moisture control section
which, in 6 or more out of 10 years, is dry in all
parts for 45 or more consecutive days during the
120 days following the summer solstice.
Argiaquic Xeric Argialbolls
HABD. Other Argialbolls that do not have an abrupt
textural change from the albic to the argillic horizon.
Argiaquic Argialbolls
HABE. Other Argialbolls which, if not irrigated, have a
moisture control section which, in 6 or more out of 10
years, is dry in all parts for 45 or more consecutive days
during the 120 days following the summer solstice.
Xeric Argialbolls
HABF, Other Argialbolls which have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or more of
the following:

1. A fine-earth fraction with both a bulk density of
1.0 g/cm? or less, measured at 33 kPa water
retention, and aluminum plus 1/2 iron percentages
(by ammonium oxalate) totaling more than 1.0; or
2. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or


350

2, A moisture control section which, in 6 or more
out of 10 years, is dry in some part for six tenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the
soil surface is higher than 5°C.

Aridic Argiborolls

HEDN. Other Argiborolls that have, in one or more
horizons within 100 cm of the mineral soil surface,
redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or
artificial drainage).

Aquic Argiborolls
HEDO. Other Argiborolls that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of

10 years.
Oxyaquic Argiborolls
HEDP. Other Argiborolls which have both:

1. Either a chroma of 1 or less (crushed and
smoothed sample) in the upper 18 cm of the
mollic epipedon, after mixing, or in an Ap horizon
18 cm or more thick, or a moisture control section
that is moist in some or all of its parts throughout
the year in 6 or more out of 10 years; and

2. Either:

a. Above the argillic horizon, an albic
horizon, or a horizon that has color values
too high for a mollic epipedon and a chroma
too high for an albic horizon; or
b. A glossic horizon, or interfingering of
albic materials into the upper part of the
argillic horizon, or skeletans of clean silt
and sand covering 50 percent or more of the
faces of peds in the upper 5 cm of the
argillic horizon.

Boralfic Udie Argiborolls

HEDQ. Other Argiborolls which have either:

1. Above the argillic horizon, an albic horizon, or
a horizon that has color values too high for a
mollic epipedon and a chroma too high for an
albic horizon; or
2. A glossic horizon, or interfingering of albic
materials into the upper part of the argillic
horizon, or skeletans of clean silt and sand
covering 50 percent or more of the faces of peds in
the upper 5 cm of the argillic horizon.

Boralfic Argiborolls

HEDR. Other Argiborolls that have either a chroma of |
or less (crushed and smoothed sample) in the upper 18
om of the mollic epipedon, after mixing, or in an Ap
horizon 18 cm or more thick, or a moisture control


183

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13.

Borollic Lithic Haplargids

FAEB, Other Haplargids which have:

1, A lithic contact within 50 cm of the soil
surface; and

2. An argillic horizon that is discontinuous
horizontally in each pedon; and

3. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if the lithic
contact is between 40 and 50 cm from the
soil surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 om of the soil, if the lithic
contact is between 18 and 40 cm from the
soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between |
and 13; and

4. A mean annual soi] temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Lithic Ruptic-Entic Xerollic Haplargids

FAEC. Other Haplargids which have:

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

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if the lithic
contact is between 40 and 50 cm from the
soil surface,

—u>


330

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Cryumbrepts

JEBG. Other Cryumbrepts that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).
Aquic Cryumbrepts

JEBH. Other Cryumbrepts that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Cryumbrepts
JEBI. Other Cryumbrepts that do not have a cambic
horizon.

Entic Cryumbrepts
JEBJ. Other Cryumbrepts.
Typic Cryumbrepts
Fragiumbrepts
Key to subgroups

JEAA. Fragiumbrepts that have, throughout one or more
horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction
with both a bulk density of 1.0 g/cm} or less, measured
at 33 kPa water retention, and aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling more than
1.0.

Andic Fragiumbrepts

JEAB. Other Fragiumbrepts that have, throughout one
or more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1, More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66

percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron


Durustolls

Key to subgroups
HFAA. Durustolls that have a natric horizon above the
duripan.
Natric Durustolls
HFAB. Other Durustolls which:
1. Do not have an argillic horizon above the
duripan; and
2. Have an aridic moisture regime that borders on
an ustic regime.
Orthidic Durustolls
HFAC. Other Durustolls that have an aridic moisture
regime that borders on an ustic regime.
Aridic Durustolls
HFAD. Other Durustolls that do not have an argillic
horizon above the duripan.

Entic Durustolls
HFAE. Other Durustolls which have a duripan that is
not indurated in any subhorizon.

Haplic Durustolls

HFAF. Other Durustolls.

Typic Durustolls
Haplustolls
Key to subgroups

HFGA. Haplustolls which have a salic horizon that has
its upper boundary within 75 cm of the mineral soil
surface.

Salorthidic Haplustolls

HFGB. Other Haplustolls that have, in part of each
pedon, a lithic contact within 50 cm of the mineral soil
surface.

Ruptic-Lithic Haplustolls

HEFGC. Other Haplustolls that have a lithic contact
within 50 cm of the mineral soil surface.
Lithic Haplustolls

HFGD. Other Haplustolls which have both:
1. One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either


Chapter 15
Ultisols

KEY TO SUBORDERS

GA. Ultisols that have aquic conditions for some time in
most years (or artificial drainage) in one or more
horizons within 50 cm of the mineral soil surface, and
one or both of the following:

1. Redoximorphic features in all layers between
either the lower boundary of an Ap horizon or a
depth of 25 cm from the mineral soil surface,
whichever is deeper, and a depth of 40 cm; and
one of the following within the upper 12.5 cm of
the argillic or kandic horizon:
a, Redox concentrations, and 50 percent or
more redox depletions with a chroma of 2 or
less either on faces of peds or in the matrix;
or

b, Fifty percent or more redox depletions
with a chroma of | or less either on faces of
peds or in the matrix; or

c, Distinct or prominent redox
concentrations and 50 percent or more hue
of 2.5Y or SY in the matrix, and also a
thermic, isothermic, or warmer soil
temperature regime; or
2. Within 50 cm of the mineral soil surface,
enough active ferrous iron to give a positive
reaction to a.,a'-dipyridyl at a time when the soil
is not being irrigated,
Aquults, p. 456
GB. Other Ultisols that have one or both of the
following:
1. 0.9 percent or more organic carbon in the upper
15 cm of the argillic or kandic horizon; or

2. 12 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm,
Humults, p. 463

GC. Other Ultisols that have a udic moisture regime.
Udults, p. 468

GD. Other Ultisols that have an ustic moisture regime.
Ustults, p. 481

GE. Other Ultisols.
Xerults, p. 489

are


c 3
Elements of;

1. Saturation is characterized by zero or positive
pressure in the soil-water and can generally be
determined by observing free water in an unlined auger
hole. However, problems may arise in clayey soils with
peds, where an unlined auger hole may fill with water
flowing along faces of peds while the soil matrix is and
remains unsaturated (bypass flow). Such free water may
incorrectly suggest the presence of a water table, while
the actual water table occurs at greater depth. Use of
well-sealed piezometers or tensiometers is therefore
recommended for measuring saturation. Problems may,
however, still occur if water runs into piezometer slits
near the bottom of the piezometer hole or if
tensiometers with slowly reacting manometers are used.
The first problem can be overcome by using piezometers
with smaller slits, and the second by using transducer
tensiometry, which reacts faster than manometers. Soils
are considered wet if they have pressure heads greater
than -1 kPa. Only macropores such as cracks between
peds or channels are then filled with air, while the soil
matrix is usually still saturated. Obviously, exact
measurements of the wet state can only be obtained with
tensiometers. For operational purposes, the use of
piezometers is recommended as a standard method.

The duration of saturation required for creating aquic
conditions is variable, depending on the soil
environment, and is not specified.

Three types of saturation are defined:

a. Endosaturation. —The soil is saturated with
water in all layers from the upper boundary of
saturation to a depth of 200 cm or more from the
mineral soil surface.

b. Episaturation.-The soil is saturated with water
in one or more layers within 200 cm of the
mineral soil surface and also has one or more
unsaturated layers, with an upper boundary above
200 om depth, below the saturated layer. The zone
of saturation, i.e., the water table, is perched on
top of a relatively impermeable layer.

c. Anthric saturation. —This variant of
episaturation is associated with controlled
flooding (for such crops as wetland rice and
cranberries), which causes reduction processes in
the saturated, puddled surface soil and oxidation
of reduced and mobilized iron and manganese in
the unsaturated subsoil.

2. The degree of reduction in a soil can be character-
ized by the direct measurement of redox potentials.
Direct measurements should take into account chemical
equilibria as expressed by stability diagrams in standard.
soil textbooks. Reduction and oxidation processes are
also a function of soil pH. Accurate measurements of


165
CGCL, Other Melanudands that have both:

1. A sum of extractable bases of more than 25.0
cmol(+)/kg in the fine-earth fraction throughout
‘one or more horizons with a total thickness of 15
cm or more between 25 and 75 cm either from the
mineral soil surface, or from the top of an organic
layer with andic soil properties, whichever is
shallower; and

2. Undried, a 1500-kPa water retention of less
than 30 percent throughout one or more layers
with andic soil properties that have a total
thickness of 25 cm more within 100 cm either of
the mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower.

Eutric Vitric Melanudands

CGCM. Other Melanudands which have, undried, a
1500-kPa water retention of less than 30 percent
throughout one or more layers with andic soil properties
that have a total thickness of 25 cm more within 100 cm
either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Vitric Melanudands

CGCN. Other Melanudands that have both:

1. Undried, a 1500-kPa water retention of 70
Percent or more throughout a layer 35 cm or more
thick within 100 cm either of the mineral soil
surface, or of the top of an organic layer with
andic soil properties, whichever is shallower; and

2. More than 6.0 percent organic carbon and
colors of a mollic epipedon throughout a layer 50
em or more thick within 60 cm either of the
mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower.

Hydric Pachic Melanudands

CGCO. Other Melanudands that have more than 6.0
Percent organic carbon and colors of a mollic epipedon
throughout a layer 50 cm or more thick within 60 cm
either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Pachic Melanudands

GCP. Other Melanudands that have both:

1. A sum of extractable bases of more than 25.0
cmol(+)/kg in the fine-earth fraction throughout
one or more horizons with a total thickness of 15
¢m or more between 25 and 75 cm either from the
mineral soil surface, or from the top of an organic
layer with andic soil properties, whichever is
shallower; and


495

EAEG. Other Dystraquerts which have a layer 25 cm or
more thick that contains less than 27 percent clay in its
fine-earth fraction and has its upper boundary within
100 cm of the mineral soil surface.

Entic Dystraquerts

EAEH. Other Dystraquerts that have, in one or more
horizons within 30 cm of the mineral soil surface, one
or both of the following in more than half of each

pedon:

1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more,

Chromic Dystraquerts
FAEI. Other Dystraquerts.
Typic Dystraquerts
Endoaquerts
Key to subgroups

EAGA. Endoaquerts that have, throughout a layer 15 cm
or more thick within 100 cm of the mineral soil surface,
an electrical conductivity of 15 dS/m or more (1:1
soil:water) for 6 or more months per year in 6 or more
out of 10 years,

Halic Endoaquerts

EAGB. Other Endoaquerts that have, in one or more
horizons within 100 cm of the mineral soil surface, an
exchangeable sodium percentage of 15 or more (or a
sodium adsorption ratio of 13 or more) for 6 or more
months per year in 6 or more out of 10 years.

Sodic Endoaquerts

EAGC. Other Endoaquerts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
are 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 210
or more cumulative days per year.

Aridic Endoaquerts

EAGD. Other Endoaquerts which have a thermic,
mesic, or frigid soil temperature regime and which, if
not irrigated during the year, have cracks in 6 or more
out of 10 years that remain both:

1, Five mm or more wide, through a thickness of
25 cm or more within 50 cm of the mineral soil
surface, for 60 or more consecutive days during
the 90 days following the summer solstice; and

2. Closed for 60 or more consecutive days during
the 90 days following the winter solstice.
Xeric Endoaquerts

EAGE. Other Endoaquerts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
are 5 mm or more wide, through a thickness of 25 em or

mm<


278
Medifibrists

Key to subgroups

ABFA. Medifibrists that have a layer of water within
the contro} section below the surface tier.
Hydric Medifibrists

ABEFB. Other Medifibrists that have a lithic contact
within the control section.
Lithic Medifibrists

ABFC. Other Medifibrists which have both:

1, Three fourths or more of the fiber volume in the
surface tier derived from Sphagnum; and

2. A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Sphagnic Terric Medifibrists

ABFD. Other Medifibrists which have both:

1, One or more layers, with a total thickness of 25
cm or more, of the subsurface and bottom tiers
consisting of hemic materials; and

2. A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Hemic Terric Medifibrists

ABFE. Other Medifibrists which have both:

1, One or more layers, with a total thickness of
12.5 cm or more, of the subsurface and bottom
tiers consisting of sapric materials; and

2. A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Sapric Terric Medifibrists

ABFF. Other Medifibrists which have a mineral layer
30 cm or more thick that has its upper boundary within.
the control section below the surface tier.

Terric Medifibrists

ABFG. Other Medifibrists that have one or more limnic
layers with a total thickness of 5 cm or more within the
control section.

Limnic Medifibrists

ABFH. Other Medifibrists that have, within organic
materials, either one mineral layer 5 cm or more thick,
or two or more mineral layers of any thickness, in the
control section below the surface tier.

Fluvaquentic Medifibrists

ABFI. Other Medifibrists that have three fourths or
more of the fiber volume in the surface tier derived from
Sphagnum.

Sphagnic Medifibrists


185

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between |
and 13; 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
FAEE. Other Haplargids that have a lithic contact
within 50 cm of the soil surface.
Lithic Haplargids

FAEF, Other Haplargids which have:
1. A frigid or colder soil temperature regime; and

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a, In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 cm of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0,77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

3. One or both of the following:

a, Cracks within 125 cm of the soil surface
that are 5 mm or more wide through a
thickness of 30 cm or more for some time in
most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the soil surface; or

b. A linear extensibility of 6.0 cm or more
between the soil surface and either a depth
of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Borollic Vertic Haplargids

A
R


349

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower. o

Vertic Argiborolls

HEDI. Other Argiborolls that have, throughout one ot
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm} or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Argiborolls

HEDJ. Other Argiborolls that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2,0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:
a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0,02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Argiborolls

HEDK. Other Argiborolls which have both:

1. A mollic epipedon 40 cm or more thick with a
texture finer than loamy fine sand; and

2. Either a chroma of | or less (crushed and
smoothed sample) in the upper 18 cm of the
mollic epipedon, after mixing, or in an Ap horizon
18 cm or more thick, or a moisture control section
that is moist in some or all of its parts throughout
the year in 6 or more out of 10 years.
Pachic Udic Argiborolls
HEDL. Other Argiborolls that have a mollic epipedon
40 cm or more thick with a texture finer than loamy fine
sand.
Pachic Argiborolls

HEDM. Other Argiborolls which have both:

1. A color value, dry, of 5 or more either in the
upper 18 cm of the mollic epipedon, after mixing,
or in an Ap horizon 18 cm or more thick; and


Chapter 10

Histosols

KEY TO SUBORDERS

AA. Histosols which are never saturated with water
except for a few days following heavy rains, and which
have both:

1. A lithic or paralithic contact within 100 cm of
the soil surface, and/or fragmental materials
resting on a lithic or paralithic contact; and

2. Less than three fourths (by volume) Sphagnum
fibers in the organic soil materials,
Folists, p. 278
AB. Other Histosols which either:
1, Are dominantly! fibric either

a. In the subsurface tier if that tier is wholly
organic except for one or more thin mineral
layers; or

b. In the organic parts of the surface and
subsurface tiers if there is a continuous
mineral layer 40 cm or more thick that has
its upper boundary within the subsurface
tier; or

2. Have a surface mantle in which Sphagnum
fibers constitute three fourths or more of the
volume, and which rests on a lithic or paralithic
contact, fragmental materials, mineral soil, or
frozen? materials within the surface or subsurface
tier.

Fibrists, p. 272
AC. Other Histosols that are dominantly? hemic either:

1. In the subsurface tier if that tier is wholly
organic except for one or more thin mineral layers;
or

| Dominant, in this context, means “the most abundant." Ifonly two kinds
of organic materials are present, the fibric materials, if dominant, constitute
half or more of the volume. If there are both hemic and sapric materials as
well as fibric, the fibric materials, if dominant, may constitute less than half
of the volume but have more volume than either the hemic or the sapric
materials.

2 Frozen 2 months after the summer solstice.

3 Dominant, in this context, means the most abundant of the three different
kinds of organic soil materials (fibric, hemie, or sapric).


410

HDCB. Other Palexerolls which have one or both of the
following:
1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.
Vertic Palexerolls

HDCC. Other Palexerolls that have a mollic epipedon
50 cm or more thick with a texture finer than loamy fine
sand.

Pachic Palexerolls

HDCD. Other Palexerolls that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Palexerolls
HDCE. Other Palexerolls which have both:

1. Anaridic moisture regime; and

2. A petrocalcic horizon that has its upper
boundary within 150 cm of the mineral soil
surface.

Aridic Petrocalcic Palexerolls

HDCF. Other Palexerolls that have an aridic moisture
regime.
Aridic Palexerolls
HDCG. Other Palexerolls which have a petrocalcic
horizon that has its upper boundary within 150 cm of
the mineral soil surface.
Petrocalcic Palexerolls

HDCH. Other Palexerolls that have a base saturation of
75 percent or less in one or more subhorizons either
within the argillic horizon if more than 50 cm thick, or
within its upper 50 cm.

Ultic Palexerolls
HDCT. Other Palexerolls which have an argillic horizon
that either:

1, Does not have a clayey particle size in its upper
part; or
2, At its upper boundary, has a clay increase either

of less than 20 percent (absolute) within a vertical
distance of 7.5 cm, or of less than 15 percent


267

KCDD. Other Tropopsamments.
Typic Tropopsamments

Udipsamments

Key to subgroups

KCGA. Udipsamments that have a lithic contact within
50 cm of the mineral soil surface.
Lithic Udipsamments

KCGB. Other Udipsamments that have, in one or more
horizons within 100 cm of the mineral soil surface,
redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or
artificial drainage).

Aquic Udipsamments

KCGC. Other Udipsamments that are saturated with
water, in one or more layers within 100 cm of the
mineral soil surface, for 1 month or more per year in 6
‘or more out of 10 years.

Oxyaquic Udipsamments

KCGD. Other Udipsamments which have a horizon 5
cm or more thick, either below an Ap horizon or at a
depth of 18 cm or more from the mineral soil surface,
whichever is deeper, that has one or more of the
following:

1. In 25 percent or more of each pedon,
cementation by organic matter and aluminum,
with or without iron; or

2. Aluminum plus 1/2 iron percentages (by
ammonium oxalate) totaling 0.25 or more, and
half that amount or less in an overlying horizon;
or

3, An ODOE value of 0.12 or more, and a value
half as high or lower in an overlying horizon.
Spodic Udipsamments

KCGE. Other Udipsamments which have lamellae
within 200 cm of the mineral soil surface that meet all
the requirements for an argillic horizon except
thickness? or clay content.

Argic Udipsamments

KCGF. Other Udipsamments which have a surface

horizon between 25 and 50 cm thick that meets all the

requirements for a plaggen epipedon except thickness.
Plaggeptic Udipsamments

KCGG. Other Udipsamments.
Typic Udipsamments

7 The clay content of very thin lamellae cannot be estimated with precision.
‘The lamelize in soils of argic subgroups are generally about 0.5 to cm
thick, but their total thickness is less than the 15 cm required for an argillic
horizon.

42m


97

1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:
a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Glossoboralfs

IBFD. Other Glossoboralfs that have, in one or more
subhorizons within the upper 25 cm of the argillic
horizon, redox depletions with a chroma of 2 or less,
and also aquic conditions for some time in most years
(or artificial drainage).

Aquic Glossoboralfs

IBFE. Other Glossoboralfs that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.
Oxyaquic Glossoboralfs

IBFF. Other Glossoboralfs which have an argillic
horizon that either has a texture of loamy fine sand or
coarser, or is discontinuous vertically in its upper 15 cm
(in Jamellae).

Psammentic Glossoboralfs

IBFG. Other Glossoboralfs that do not have a glossic
horizon.
Eutric Glossoboralfs
IBFH. Other Glossoboralfs.
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 one or more
horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction
with both a bulk density of 1.0 g/cm} or less, measured
at 33 kPa water retention, and aluminum plus 1/2 iron


Chapter 7

Andisols:

KEY TO SUBORDERS

CA. Andisols that have either:
1. A histic epipedon; or
2. In a layer between 40 and 50 cm either from the
mineral soil surface or from the top of an organic
layer with andic soil properties, whichever is
shallower, aquic conditions for some time in most

years (or artificial drainage) and one or more of
the following:

a, Two percent or more redox
concentrations; or

b. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
redox depletions on faces of peds, or in the
matrix if peds are absent; or

c, Enough active ferrous iron to give a

Positive reaction to a,c'-dipyridyl at a time

when the soil is not being irrigated.
‘Aquands, p. 140

CB. Other Andisols that have a cryic or pergelic soil
temperature regime.
Cryands, p. 146
CC. Other Andisols that have an aridic moisture regime.
Torrands, p. 150

CD. Other Andisols that have a xeric moisture regime.
Xerands, p. 174

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

Vitrands, p. 172

CF. Other Andisols that have an ustic moisture regime.
Ustands, p. 169

CG. Other Andisols.
Udands, p. 151

| This chapter builds on the preliminary Andisol Proposal (1978) by Guy D.
‘Smith (NZ Soil Bureau Record 96) and represents the work of the
Intemational Committee on the Classification of Andisols (ICOMAND),
chaired by Michael L. Leamy, New Zealand Soil Bureau,

z>


292

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,

whichever is shallower.
Vertic Cryaquepts
JAEI. Other Cryaquepts that have a histic epipedon.
Histic Cryaquepts

JAE]. Other Cryaquepts which have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or more of
the following:
1. A fine-earth fraction with both a bulk density of
1.0 g/cm? or less, measured at 33 kPa water
retention, and aluminum plus 1/2 iron percentages
(by ammonium oxalate) totaling more than 1.0; or
2. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
3. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:
a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or
b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron

percentages (by ammonium oxalate) totaling
0.40 or more.

Aquandic Cryaquepts
JAEK. Other Cryaquepts that have both:
1. A chroma of 3 or more in 40 percent or more of

the matrix of one or more horizons between 15
and 50 cm from the mineral soil surface; and

2. An umbric epipedon:
Aeric Humic Cryaquepts
JAEL. Other Cryaquepts that have a chroma of 3 or
more in 40 percent or more of the matrix of one or more
horizons between 15 and 50 cm from the mineral soil
surface.
Aeric Cryaquepts
JAEM. Other Cryaquepts that have an umbric epipedon.
Humic Cryaquepts

JAEN, Other Cryaquepts.
Typic Cryaquepts


acidity, either throughout the upper 15 cm of the natric
horizon, or in all horizons within 40 cm of the mineral
soil surface, whichever is deeper.
. Albic Natraqualfs
IACD. Other Natraqualfs that have a glossic horizon, or
interfingering of albic materials into the natric horizon.
Glossic Natraqualfs

TACE. Other Natraqualfs that have an Ap horizon with a
color value, moist, of 3 or less and a color value, dry, of
5 or less (crushed and smoothed sample), or materials
between the soil surface and a depth of 18 cm which
have these color values after mixing.

Mollic Natraqualfs

IACF. Other Natraqualfs.
Typic Natraqualfs

Plinthaqualfs

Plinthaqualfs are the Aqualfs that have one or more
horizons between 30“and 150 cm from the mineral soil
surface in which plinthite either forms a continuous
phase or constitutes one half or more of the volume.

Umbraqualfs

Key to subgroups

IAHA. Umbraqualfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, one or more of the
following:

1. A fine-earth fraction with both a bulk density of
1.0 g/cm} or less, measured at 33 kPa water

retention, and aluminum plus 1/2 iron percentages
(by ammonium oxalate) totaling more than 1.0; or

2. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
3. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:
a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Aquandic Umbraqualfs

TAHB. Other Umbraqualfs that have a sandy particle
size throughout a layer extending from the mineral soil


534

Hemic soil materials
HEMISTS.....
Histic epipedon
HISTOSOLS (organic soils).

diagnostic horizons and properties
family differentiae
series control section ..
Horizons
diagnostic, mineral soils
subs
surface

diagnostic, organic soils (3 tiers) 46
genetic (designations for) .. 15
combination .. 18
master . 15

subordinate distinctions within
transitional ...
use of letter suffixes for

Isofrigid soil temperature regime ..
Isohyperthermic soil temperature regime
Isomesic soil temperature regime
Isothermic soil temperature regime.


316

years, is dry in some or all parts for less
than 120 cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 8°C.

Calcic Udic Ustochrepts

JDEN. Other Ustochrepts which have a calcic horizon
that has its upper boundary within 100 cm of the
mineral soil surface.

Calcic Ustochrepts

JDEO. Other Ustochrepts which, if neither irrigated nor
fallowed to store moisture, have one of the following:

1, A frigid soil temperature regime, and a
moisture contro} section which, in 6 or more out of
10 years, is dry in all parts for four tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 cm below the soil
surface is higher than 5°C; or

2. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for six tenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

3, A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is
moist in some or all parts for less than 180
cumulative days per year when the temperature at
a depth of 50 cm below the soil surface is higher
than 8°C.

Aridic Ustochrepts

JDEP. Other Ustochrepts that have a base saturation (by
sum of cations) of less than 60 percent in all horizons
between either an Ap horizon or a depth of 25 cm from
the mineral soil surface, whichever is deeper, and either
a depth of 75 cm ora lithic or paralithic contact,
whichever is shallower.

Dystric Ustochrepts

JDEQ, Other Ustochrepts which, if neither irrigated nor
fallowed to store moisture, have one of the following:

1. A frigid soil temperature regime, and a
moisture control section which, in 6 or more out of
10 years, is dry in some or all parts for less than
105 cumulative days per year when the soil
temperature at a depth of 50 cm below the soil
surface is higher than 5°C; or

2. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for less than
four tenths of the cumulative days per year when
the temperature at a depth of 50 cm below the soil
surface is higher than 5°C; or


494
1. A color value, moist, of 4 or more; or
2. A color value, dry, of 6 or more.

Chromic Duraquerts
EABE. Other Duraquerts,
Typic Duraquerts
Dystraquerts
Key to subgroups

EAEA, Dystraquerts that have, in one or more horizons
within 100 cm of the mineral soil surface, jarosite
concentrations and a pH value of 4.0 or less (1:1 water,
air-dried slowly in shade),

Sulfaqueptic Dystraquerts

EAEB. Other Dystraquerts that have more than 2.0
emol(+)/kg Al?+ (by IN KCI) in the fine-earth fraction
throughout a layer 10 cm or more thick with an upper
boundary between 25 and 50 cm from the mineral soil
surface.

Alic Dystraquerts

EAEC. Other Dystraquerts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
are 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 210
or more cumulative days per year.

Aridic Dystraquerts
EAED. Other Dystraquerts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
are 5 mm or more wide, through a thickness of 25 cm or
more within 50 om of the mineral soil surface, for 90 or
more cumulative days per year.

Ustic Dystraquerts

EAEE. Other Dystraquerts that have, in one or more
horizons between either an Ap horizon or a depth of 25
em from the mineral soil surface, whichever is deeper,
and a depth of 75 cm, 50 percent or more colors:as
follows:

1. A hue of 2.5Y or redder and either:

a. A color value, moist, of 6 or more and a
chroma of 3 or more; or

b. A color value, moist, of 5 or less and a
chroma of 2 or more; or

2. A hue of SY and a chroma of 3 or more; or

3. A chroma of 2 or more, and no redox
concentrations.
Aeric Dystraquerts
EAEF, Other Dystraquerts that have a lithic or
paralithic contact within 100 cm of the mineral soil

surface.
Leptic Dystraquerts


218

2. An aridic moisture regime that borders on a
xeric regime; and
3, Throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or both of the following:

a. More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or

b.A fine-earth fraction containing 30
percent or more particles 0,02 to 2.0 mm in
diameter, and either:

(1) In the 0.02-to-2.0-mm fraction,
more than 30 percent volcanic glass;
or

(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more.
Vitrixerandic Camborthids

FBFN, Other Camborthids which have:

1, A moisture control section that is dry in all its
parts for less than three fourths of the cumulative
days per year in 6 or more out of 10 years when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and

2. A hyperthermic, thermic, or mesic soil
temperature regime, and an aridic moisture
regime that borders on an ustic regime; and

3. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or both of the following:

a. More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or

b. A fine-earth fraction containing 30

percent or more particles 0.02 to 2.0 mm in
diameter, and either:

(1) In the 0.02-to-2.0-mm fraction,
more than 30 percent volcanic glass;
or

(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more.
Ustivitrandic Camborthids


192

b. Redox concentrations and 50 percent or
more chroma of 2 or less; or

c. Enough active ferrous iron to give a
positive reaction to o,a'-dipyridy! at a time
when the soil is not being irrigated.

Aquic Haplic Nadurargids

FAAC, Other Nadurargids that have, in one or more
horizons within 100 cm of the soil surface, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:

1, A chroma of 0, or a hue of 2.5Y or yellower and
a chroma of 1; or

2, Redox concentrations and 50 percent or more
chroma of 2 or less; or

3, Enough active ferrous iron to give a positive
reaction to o,0.'-dipyridy] at a time when the soil

is not being irrigated.
Aquic Nadurargids

FAAD. Other Nadurargids which have:

1, A duripan 18 cm or more below the soil surface
that is not indurated in any part; and

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if the upper
boundary of the duripan is 40 cm or more
below the soil surface,

(1) 0.60 or more, with a sand/clay
ratio of }.0 or less; or

(2) 0.15 or more, with a sand/clay
tatio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between I
and 13; or

b. In the upper 18 cm of the soil, if the

upper boundary of the duripan is between 18
and 40 cm from the soil surface,

(1) 0.72 or more, with a sand/clay
tatio of 1.0 or less; or
(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or
(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

3, A mean annual soil temperature lower than

22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a


353

1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 em or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Argic Vertic Cryoborolls

HEBI., Other Cryoborolls which have one or both of the

following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Cryoborolls

HEBJ. Other Cryoborolls that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm} or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Cryoborolls

HEBK. Other Cryoborolls that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and

either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

ros


increasing depth below the epipedon, or there are
phosphate nodules within the epipedon. This restriction
is made to eliminate plow layers of very old arable soils
and kitchen middens which, under use, have acquired
the properties of a mollic epipedon, while including 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 (cumulative) per year in 8 or
more out of 10 years during times when the soil
temperature at a depth of 50 cm is 5°C or higher.

8. The 7 value (defined below) is less than 0.7.
Although many soils that have a mollic epipedon are
very poorly drained, a mollic epipedon does not have the
same very high water content as sediments that have
been continuously under water since deposition.

Ochric epipedon (Gr. ochros, pale)

The ochric epipedon fails to meet the definitions for any
of the other 6 epipedons because it is too thin or too dry,
has too high a color value or chroma, contains too little
organic matter, or has too high an 7 value or melanic
index, or is both hard and massive when dry. Most
ochric epipedons have either a Munsell color value of 4
or more when moist and 6 or more when dry, or a
chroma of 4 or more’, or include an A or Ap horizon
that has both low color values and low chroma but is too
thin to be recognized as a mollic or an umbric epipedon
{and has less than 15 percent calcium carbonate
equivalent in the fine-earth fraction). The ochric
epipedon includes eluvial horizons that are at or near
the soil surface, and it extends to the first underlying
diagnostic illuvial horizon (defined below as an argillic,
a kandic, a natric, or a spodic horizon). If the underlying
horizon is a B horizon of alteration (defined below as a
cambic or oxic horizon) and there is no surface horizon
that is appreciably darkened by humus, the lower limit
of the ochric epipedon is the lower boundary of the plow
layer or an equivalent depth in a soil that has not been
plowed. Actually, the same horizon in an unplowed soil
may be both a part of the epipedon and a part of the
cambic horizon; the ochric epipedon and the subsurface
diagnostic horizons are not mutually exclusive. The
ochric epipedon does not have rock structure and does
not include finely stratified fresh sediments.

Plaggen epipedon (Ger. Plaggen, sod)

The plaggen epipedon is a man-made surface layer 50
cm or more thick that has been produced by long-
continued manuring. The color of a plaggen epipedon

4 The color when moist is that of a specimen moist enough so that an.
‘additional drop of water produces no change in color. The color when dry is
that of a specimen dry enough so that continued drying produces no further
change in cotor.


96

IBBB, Other Fragiboralfs that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Fragiboralfs

IBBC. Other Fragiboralfs that have, in one or more
subhorizons within the upper 25 cm of the argillic
horizon, redox depletions with a chroma of 2 or less,
and also aquic conditions for some time in most years
(or artificia) drainage).

Aquic Fragiboralfs
IBBD. Other Fragiboralfs that are saturated with water,

in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of

10 years,

Oxyaquic Fragiboralfs
IBBE. Other Fragiboralfs.

Typic Fragiboralfs

Glossoboralfs
Key to subgroups
IBFA. Glossoboralfs that have a lithic contact within 50
cm of the mineral soil surface.

Lithic Glossoboralfs

IBFB. Other Glossoboralfs that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm: or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Glossoboralfs

IBFC. Other Glossoboralfs that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:


368

HGCL. Other Argiudolls.
Typic Argiudolls

Calciudolls

Key to subgroups
HGBA. Calciudolls that have a lithic contact within 50

cm of the mineral soil surface.
Lithic Calciudolls

HGBB. Other Calciudolls which have one or both of the
following:

1, Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and cither a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Calciudolls

HGBC. Other Calciudolls that have, in one or more
horizons within 100 cm of the mineral soil surface,
redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or

artificial drainage).

Aquic Caleiudolis
HGBD. Other Calciudolls.

Typic Calciudolls
Hapludolls
Key to subgroups
HGEA. Hapludolls that have a lithic contact within 50
cm of the mineral soil surface.

Lithic Hapludolls

HGEB. Other Hapludolls which have both:

1. Aquic conditions for some time in most years
(or artificial drainage), either:

a. Within 40 cm of the mineral soil surface,
in horizons that also have redoximorphic
features; or

b. Directly below the mollic epipedon, in
one or more horizons with a total thickness
of 15 cm or more that have one or more of
the following:


186.

FAEG. Other Haplargids which have both:

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

2. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a. In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 cm of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13.

Borollic Haplargids

FAEH. Other Haplargids which have both:

1, One or both of the following:

a. Cracks within 125 cm of the soil surface
that are 5 mm or more wide through a
thickness of 30 cm or more for some time in
most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
em of the soil surface; or

b. A linear extensibility of 6.0 cm or more
between the soil surface and either a depth
of 100 cm or a lithic or paralithic contact,
whichever is shallower; and

2. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean.
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Xerertic Haplargids

FAEL. Other Haplargids which have both:


101

The Agrudalfs of western 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

Key to subgroups

JECA. Ferrudalfs that have, in one or more horizons
within 60 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Ferrudalfs
TECB. Other Ferrudalfs.

Typic Ferrudalfs
Fragiudalfs
Key to subgroups
TEFA. Fragiudalfs which:

1. Do not, above the fragipan, have an argillic
horizon with clay films on both vertical and
horizontal faces of any peds; and

2. Have, directly above the fragipan, a layer 5 cm
or more thick which either:

a. Has, on faces of primary peds, clay
depletions of clean silt and sand that
constitute 1 percent or more (by volume) of
the layer; or
b, Is an eluvial horizon (E) and has 3 or
more percent (absolute) less clay in the fine-
earth fraction than both the overlying and
underlying horizons; and
3. Have an Ap horizon with a color value, moist,
of 3 or less and a color value, dry, of 5 or less
(crushed and smoothed sample), or materials

between the soil surface and a depth of 18 cm
which have these color values after mixing; and

4. Have a base saturation (by NH,OAc) of less
than 50 percent in one or more layers of the
epipedon.
Umbreptic Fragiudalfs
IEFB. Other Fragiudalfs that have an Ap horizon with a
color value, moist, of 3 or less and a color value, dry, of
5 or less (crushed and smoothed sample), or materials

| Personal communication from R. Tavernier.


451
BDDD. Other Alorthods that have both:

1. A sandy particle size throughout a layer
extending from the mineral soil surface to the top
of the spodic horizon at a depth of 125 cm or
more; and

2. In 10 percent or more of each pedon, less than 3
percent organic carbon in the upper 2 cm of the
spodic horizon.
Grossarenic Entic Alorthods
BDDE. Other Alorthods that have, in 10 percent or
more of each pedon, less than 3 percent organic carbon
in the upper 2 cm of the spodic horizon.
Entic Alorthods

BDDF. Other Alorthods that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of the spodic horizon at a depth of 125
cm or more.

Grossarenic Alorthods

BDDG. Other Alorthods which have a surface horizon
30 cm or more thick that meets all the requirements for
a plaggen epipedon except thickness.

Plaggeptic Alorthods

BDDH. Other Alorthods which have, within 200 cm of
the mineral soil surface, an argillic or a kandic horizon
that has a base saturation of 35 percent or more (by sum
of cations) in some part.

Alfic Alorthods

BDDI. Other Alorthods that have an argillic or a kandic
horizon within 200 cm of the mineral soil surface.

Ultic Alorthods
BDDJ. Other Alorthods,

Typic Alorthods
Durorthods
Key to subgroups

BDBA. Durorthods which have andic soil properties
throughout horizons that have a total thickness of 25 cm
or more within 75 cm either of the mineral soil surface,
or of the top of an organic layer with andic soil

Properties, whichever is shallower.
Andic Durorthods
BDBB. Other Durorthods. Ay
Typic Durorthods fe
Fragiorthods
Key to subgroups

BDCA. Fragiorthods that have, in one or more horizons
within 75 cm of the mineral soil surface, redoximorphic


222

2. A hyperthermic, thermic, or mesic soil

temperature regime, and an aridic moisture

regime that borders on an ustic regime.
Ustochreptic Camborthids

FBFW, Other Camborthids.
Typic Camborthids

Durorthids

Key to subgroups
FBCA. Durorthids which have both:

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

2. In one or more horizons within 100 cm of the
soil surface, aquic conditions for some time in
most years (or artificial drainage) and one or more
of the following:

a. A chroma of 0, or a hue of 2.5Y or
yellower and a chroma of 1; or

b. Redox concentrations and 50 percent or
more chroma of 2 or less; or

¢. Fifty percent or more chroma of 2 or less,
and a higher exchangeable sodium
percentage (or sodium adsorption ratio) in
more than half the thickness of the horizons
between the soil surface and 50 cm depth
than in the saturated zone; or

d, Enough active ferrous iron to give a

positive reaction to a,a’-dipyridyl at a time

when the soil is not being irrigated.

Aquentic Durorthids

FBCB. Other Durorthids that have, in one or more
horizons within 100 cm of the soil surface, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:

1, A chroma of 0, or a hue of 2.5Y or yellower and
a chroma of 1; or

2. Redox concentrations and 50 percent or more
chroma of 2 or less; or

3. Fifty percent or more chroma of 2 or less, and a
higher exchangeable sodium percentage (or
sodium adsorption ratio) in more than half the
thickness of the horizons between the soil surface
and 50 cm depth than in the saturated zone; or

4, Enough active ferrous iron to give a positive
reaction to a.,a.'-dipyridyl at a time when the soil
is not being irrigated.

Aquic Durorthids


tt
Sulfochrepts

Key to subgroups
JDAA. All Sulfochrepts (provisionally).

Typic Sulfochrepts
Ustochrepts
Key to subgroups
IDEA. Ustochrepts that have a lithic contact within 50
cm of the mineral soil surface.

Lithic Ustochrepts

JDEB. Other Ustochrepts which have both:

1. If neither irrigated nor fallowed to store
moisture, one of the following:

a. A frigid soil temperature regime, and a
moisture control section which, in 6 or more
out of 10 years, is dry in some or all parts
for less than 105 cumulative days per year
when the soil temperature at a depth of 50
cm below the soil surface is higher than
5°C; or

b. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for less than four tenths of the
cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

c. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, is dry in some or all parts for less
than 120 cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 8°C; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or
b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower.
Udertic Ustochrepts
JDEC. Other Ustochrepts which have both:



301

2, A hue of 2,5Y or redder, a color value, moist, of
5 or less, and a chroma of 2 or more; or

3. A hue of SY and a chroma of 3 or more; or
4, A chroma of 2 or more if there are no redox.

concentrations.
Aeric Tropaquepts
JAGH. Other Tropaquepts.
Typic Tropaquepts
OCHREPTS
Key to great groups

IDA. Ochrepts that have a sulfuric horizon within 50 cm
of the mineral soil surface.
Sulfochrepts, p. 311

JDB, Other Ochrepts that have a fragipan.
Fragiochrepts, p. 310
JDC. Other Ochrepts which have a duripan that has its
upper boundary within 100 cm of the mineral soil
surface.
Durochrepts, p. 303

IDD. Other Ochrepts that have a cryic or pergelic soil
temperature regime,

Cryochrepts, p. 301
SDE. Other Ochrepts that have an ustic moisture
regime.

Ustochrepts, p. 311
JDF. Other Ochrepts that have a xeric moisture regime.

Xerochrepts, p. 317
JDG. Other Ochrepts that have one or both of the
following:

1, Carbonates within the soil; or

2. A base saturation (by NH,OAc) of 60 percent or
more in one or more horizons between 25 and 75
cm from the mineral soil surface.
Eutrochrepts, p. 307
JDH. Other Ochrepts.
Dystrochrepts, p. 304

Cryochrepts

Key to subgroups
IDDA. Cryochrepts that have a lithic contact within 50
cm of the mineral soil surface.

Lithic Cryochrepts

oz


433
DCD, Other Ustox that have both:

1. A clay content of 40 percent or more in the fine-
earth fraction between the soil surface and a depth
of 18 cm, after mixing; and

2. A kandic horizon that has its upper boundary
within 150 cm of the mineral soil surface.
Kandiustox, p. 438

DCE. Other Ustox.
Haplustox, p. 436

Acrustox

Key to subgroups

DCBA. Acrustox that have, within 125 cm of the
mineral soil surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).

Aquic Petroferric Acrustox

DCBB. Other Acrustox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Acrustox

DCBC, Other Acrustox that have, within 125 cm of the
mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).

Aquic Lithic Acrustox

DCBD, Other Acrustox that have a lithic contact within
125 cm of the mineral soil surface.
Lithic Acrustox

DCBE. Other Acrustox that have, within 125 cm of the
mineral soil surface, both:

1, A delta pH (KCI pH minus 1;1 water pH) with
a 0 or net positive charge in a layer 18 cm or more
thick; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).

Anionic Aquic Acrustox


200
FACN. Other Natrargids which have both:

1. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a, In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,

(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.64-(0.038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or

b. In the upper 18 cm of the soil, if there is a

paralithic contact between 18 and 40 om
from the soil surface,

(1) 0.72 or more, with a sand/clay
tatio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between J
and 13; and

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

Ustollic Natrargids

FACO. Other Natrargids which have skeletans on 10
percent or more of the faces of peds that are 2.5 om or
more below the upper boundary of the natric horizon.

Glossic Natrargids
FACP, Other Natrargids.
Typic Natrargids
Paleargids
Key to subgroups

FADA. Paleargids which have:

1, A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, between the soil surface and a depth
of 40 cm as follows:

a. 0.60 or more, with a sand/clay ratio of 1.0
or less; or

b. 0.15 or more, with a sand/clay ratio of 13
‘of more; or

¢. 0.64-(0.038 x sand/clay ratio), or more,
with a sand/clay ratio between 1 and 13; and


378

mollic epipedon and a chroma too high for an
albic horizon; or
2. A glossic horizon, or interfingering of albic
materials into the upper part of the argillic
horizon, or skeletans of clean silt and sand
covering 50 percent or more of the faces of peds in
the upper 5 cm of the argillic horizon,

Ustalfic Argiustolis

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, in one or more
horizons within 100 cm of the mineral soil surface,
redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or
artificial drainage).

Aquic Argiustolls
HFEM. Other Argiustolls that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of

10 years.
Oxyaquic Argiustolls

HFEN. Other Argiustolls which have, if neither
irrigated nor fallowed to store moisture, either:

1. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some or all parts for six
tenths or more of the cumulative days per year
when the soil temperature at a depth of 50 cm
below the soil surface is higher than 5°C; or

2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years,
remains moist in some or all parts for less than 90
consecutive days per year when the temperature at
a depth of 50 cm below the soil surface is higher
than 8°C.

Aridic Argiustolls

HFEO. Other Argiustolls which have, if neither
irrigated nor fallowed to store moisture, either:

1. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for four tenths
or less of the cumulative days per year when the
temperature at a depth of 50 cm below the soil
surface is higher than 5°C; or

2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is dry
in some or all parts for less than 120 cumulative


191

b. In the upper 18 cm of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

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 which have both:

1, A moisture control section that is dry in all its
parts for less than three fourths of the cumulative
days per year in 6 or more out of 10 years when
the soil temperature at a depth of 50 cm from the
soil surface is 5°C or higher; and

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

FAAA, Nadurargids which have, above the duripan, one
or both of the following:

1. Cracks that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick; or

2. A linear extensibility of 6.0 cm or more.
Vertic Nadurargids

FAAB, Other Nadurargids which have both:
1. A duripan that is either not platy or massive, or
not indurated in any subhorizon; and

2. In one or more horizons within 100 cm of the
soil surface, aquic conditions for some time in
most years (or artificial drainage) and one or more
of the following:

a. A chroma of 0, or a hue of 2.5Y or
yellower and a chroma of 1; or

—-2>


"7

3. No lithic or paralithic contact within 50 cm of
the mineral soil surface, and an argillic horizon
which has both:

a. A clayey particle size throughout one or
more subhorizons in its upper part; and

b. At its upper boundary, a clay increase of

either 20 percent or more (absolute) within

a vertical distance of 7.5 cm, or of 15

percent or more (absolute) within a vertical

distance of 2.5 cm, in the fine-earth fraction.
Paleustalfs, p. 124

ICG. Other Ustalfs which have throughout the argillic
horizon a hue of 2.5YR or redder, a color value, moist,
of 3 or less, and a color value, dry, no more than 1 unit

higher than the value, moist.

Rhodustalfs, p. 128
ICH. Other Ustalfs.

Haplustalfs, p. 117
Durustalfs

Durustalfs are the Ustalfs which have a duripan that has
its upper boundary within 100 cm of the mineral soil
surface. They are not known to occur in the United
States, but the great group has been provided for use in
other countries. Subgroups have not been developed.

Haplustalfs

Key to subgroups

ICHA. Haplustalfs that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Haplustalfs

ICHB. Other Haplustalfs which have both:

1. If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for four tenths or less of the
cumulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or

b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, is dry in some or all parts for less
than 120 cumulative days per year when the

temperature at a depth of 50 cm below the
soil surface is higher than 8°C; and


63

of noncemented Spodosols normally does not have a
modifier to indicate 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
are weakly cemented and some are indurated. The
recognition of petrocalcic and petrogypsic horizons is
expected to meet most, if not all, the needs for
recognition of cementation in those horizons. Therefore,
taxa with a petrocalcic or petrogypsic horizon do not
have a family modifier indicating cementation.
Classes of coatings

Despite the emphasis given to particle-size classes in
the taxonomy, variability remains in the sandy particle-
size class, which includes sands and loamy sands. Some
sands are very clean, i.¢., almost completely free of silt
and clay, while others are mixed with appreciable
amounts of finer grains. A total of 5 percent silt plus
clay makes a reasonable division of the sands at the
family level. Two classes of Quartzipsamments are
defined in terms of their silt-plus-clay content, as
follows:

Coated.—The fine-earth fraction contains more than 5
percent (by weight) silt plus clay.

Uncoated.—The fine-earth fraction contains 5 percent
or less (by weight) silt plus clay.

f permanent cr:

Hydraquents consolidate or shrink after drainage and
become Fluvaquents. In the process they form
polyhedrons roughly 12 to 50 om in diameter, depending
on their 7 value and particle size. These polyhedrons are
separated by cracks that range in width from 2 mm to
more than 1 cm. The polyhedrons may shrink and swell
with changes in the moisture content of the soil, but the
cracks are permanent and can persist for several
hundreds of years even though the soils are cultivated.
These cracks permit rapid movement of water through
the soil, either vertically or laterally, But such soils may
have the same particle size, mineralogy, and other
family properties as soils which are not cracked or
which have cracks that open and close with the seasons.
Soils with permanent cracks are very rare in the United
States. They are identified by the following term:

Cracked —This modifier is used only for families of
Fluvaquents, It means that there are continuous,
permanent lateral and vertical cracks 2 mm or more
wide, spaced at average lateral intervals of less than 50
cm. If the family name of a Fluvaquent does not contain
the modifier cracked, permanent cracks are assumed to
be absent.


242
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 with a base saturation (by sum of cations) of 35
percent or more within 100 cm of the mineral soil
surface.

Alfic Xerarents
KBBB. Other Xerarents.
Xerarents
FLUVENTS
Key to great groups

KDA, Fluvents that have a cryic soil temperature
regime.
Cryofluvents, p. 242
KDB. Other Fluvents that have a xeric moisture regime.
Xerofluvents, p. 249

KDC. Other Fluvents that have an ustic moisture
regime.
Ustifluvents, p. 247

KDD. Other Fluvents that have a torric moisture
regime.

Torrifluvents, p. 243
KDE. Other Fluvents that have an isomesic, isothermic,
or isohyperthermic soil temperature regime.

Tropofluvents, p. 246

KDF. Other Fluvents.
Udifluvents, p. 246

Cryofluvents

Key to subgroups

KDAA. Cryofluvents that have, throughout one or more
horizons with a total thickness of 18 cm or more within
75 cm of the mineral soil surface, a fine-earth fraction
with both a bulk density of 1.0 g/cm or less, measured.
at 33 kPa water retention, and aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling more than
1.0.

Andic Cryoftuvents

KDAB. Other Cryofluvents that have, throughout one or
more horizons with a total thickness of 18 cm or more


69

B. OTHER MINERALOGY CLASSES OF SOIL
FAMILIES, IN THE FRAGMENTAL, SANDY,
SANDY-SKELETAL, LOAMY, OR LOAMY-
SKELETAL PARTICLE-SIZE CLASSES

Micaceous: More than 40 percent (by weight)? mica in
the 0.02-to-20-mm fraction.

Siliceous: More than 90 percent (by weight)‘ silica
minerals (quartz, chalcedony, or opal) and other
extremely durable minerals that are resistant to
weathering, in the 0.02-to-20-mm fraction.

Mixed: All others that have less than 40 percent (by
weight) of any single kind of mineral other than quartz
or feldspars, in the 0.02-to-20-mm fraction.

C. OTHER MINERALOGY CLASSES OF SOIL
FAMILIES, IN THE CLAYEY OR CLAYEY-
SKELETAL PARTICLE-SIZE CLASS

Halloysitic: More than one half (by weight) halloysites,
and smaller amounts of allophane or kaolinite, or both,
in the less-than-0.002-mm fraction.

Kaolinitic: More than one half (by weight) kaolinite,
tabular halloysite, dickite, and nacrite, smaller amounts
of other 1:1 or non-expanding 2:1 layer minerals or
gibbsite, and less than 10 percent (by weight)
montmorillonite, in the less-than-0.002-mm fraction.

Montmorillonitic: More than one half (by weight)
montmorillonite and nontronite, or a mixture that
contains more montmorillonite than any other single
kind of clay mineral, in the less-than-0.002-mm
fraction.

Mllitic: More than one half (by weight) illite (hydrous

mica), and commonly more than 4 percent K,O, in the
less-than-0.002-mm fraction.

Vermiculitic: More than one half (by weight)
vermiculite, or more vermiculite than any other single
kind of clay mineral, in the less-than-0.002-mm
fraction.

Chioritie: More than one half (by weight) chlorite, or
more chlorite than any other single kind of clay mineral,
in the less-than-0.002-mm fraction.

Mixed: Other soilss.

3 Percentages by weight are estimated from grain counts. Usually, ‘counting
‘one or two of the dominant grain-size fractions of a conventional mechanical

analysis is sufficient for placement of the soil.

4 See preceding footnote.

5 The halloysite considered here includes only the tubular forms. What is

‘known as tabular halloysite is grouped with kaolinite

6 Sepioline, defined as containng more than one half (by weight) sepiolite,
attapulgite, and palygorskite, should be listed separately 1f identified.

Sb


199

(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or

(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; and

3. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soi] temperatures at a
depth of 50 cm from the soi) surface, and an aridic
moisture regime that borders on a xeric regime.
Haploxerollic Natrargids

FACL. Other Natrargids that have an exchangeable
sodium percentage of less than 15 (or a sodium
adsorption ratio of less than 13) in 50 percent or more of
the natric horizon.

Haplic Natrargids
FACM. Other Natrargids which have both:

1. A weighted average percentage of organic
carbon, relative to the weighted average ratio of
sand to clay, as follows:

a, In the upper 40 cm of the soil, if there is
no paralithic contact within 40 cm of the soil
surface,
(1) 0.60 or more, with a sand/clay
ratio of 1.0 or less; or
(2) 0.15 or more, with a sand/clay
ratio of 13 or more; or
(3) 0.64-(0,038 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13; or
b. In the upper 18 cm of the soil, if there is a
paralithic contact between 18 and 40 cm
from the soil surface,
(1) 0.72 or more, with a sand/clay
ratio of 1.0 or less; or
(2) 0.18 or more, with a sand/clay
ratio of 13 or more; or
(3) 0.77-(0.046 x sand/clay ratio), or

more, with a sand/clay ratio between 1
and 13; and

—-DPD

2, A mean annual soi! temperature lower than.
22°C, a difference of 5°C or more between mean
summer and mean winter soi] temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Xerollic Natrargids


306

percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b, In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Dystrochrepts

JDHG. Other Dystrochrepts which have:

1. In one or more horizons within 60 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. Either 0.2 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

3. A slope of less than 25 percent.
Fluvaquentic Dystrochrepts
JDHH. Other Dystrochrepts that have, in one or more
horizons within 60 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial

drainage),
Aquic Dystrochrepts
JDHL. Other Dystrochrepts that are saturated with

water, in one or more layers within 100 cm of the
mineral soil surface, for 1 month or more per year in 6

or more out of 10 years.
Oxyaquic Dystrochrepts
JDHJ. Other Dystrochrepts which have:

1. Either 0.2 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

2. A slope of less than 25 percent; and

3. An Ap horizon with a color value, moist, of 3 or
less and a color value, dry, af 5 or less (crushed
and smoothed sample), or materials between the
soil surface and a depth of 18 cm which have
these color values after mixing.

Fluventic Umbric Dystrochrepts


394

1. Sandy: within 100 cm of the mineral soil
surface; or
2. Loamy: within 60 cm of the mineral soil
surface; or
3. Clayey: within 50 cm of the mineral soil

surface.
Calcic Paleustolls

HFCK. Other Paleustolls that are calcareous throughout
after the soi] has been mixed to a depth of 18 cm.

Entic Paleustolls
HFCL. Other Paleustolls.

Typic Paleustolls
Vermustolis
Key to subgroups

HFFA. Vermustolls that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Vermustolls

HFFB. Other Vermustolls that have a mollic epipedon
75 cm or more thick,
Pachic Vermustolls

HFFC. Other Vermustolls that have, in one or more
horizons within 100 cm of the mineral soil surface,
redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or
artificial drainage).

Aquic Vermustolls

HFFD. Other Vermustolls that have a cambic horizon.
Haplic Vermustolls

HFFE, Other Vermustolls that have a mollic epipedon
Jess than 50 cm thick,

Entic Vermustolls
HFFF. Other Vetmustolls.

Typic Vermustolis
XEROLLS
Key to great groups

HDA. Xerolls that have a duripan within 100 cm of the
mineral soi] surface.
Durixerolls, p. 401

HDB, Other Xerolls which have a natric horizon, but do

not have a petrocalcic horizon that has its upper

boundary within 150 cm of the mineral soil surface.
Natrixerolls, p. 409


332

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Haplumbrepts

JEDE. Other Haplumbrepts that have, in all horizons
within 100 cm of the mineral soil surface, both:

1. A sandy particle size; and
2. More than 90 percent silica and other extremely
durable minerals in the 0.02-to-2.0-mm fraction.
Quartzipsammentic Haplumbrepts
JEDF. Other Haplumbrepts that have a sandy particle
size in all horizons within 100 cm of the mineral soil
surface.
Psammentic Haplumbrepts

JEDG. Other Haplumbrepts which have:

1, An umbric or a mollic epipedon that is 50 cm or
tore thick; and
2. An irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and
3. A slope of less than 25 percent.

Cumulic Haplumbrepts

JEDH. Other Haplumbrepts that have an umbric or a
mollic epipedon that is 50 cm or more thick.
Pachic Haplumbrepts

JEDI. Other Haplumbrepts that have, in one or more
horizons within 50 cm of the mineral soil surface, redox.
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Haplumbrepts
JEDJ. Other Haplumbrepts that are saturated with
water, in one or more layers within 100 cm of the
mineral soil surface, for 1 month or more per year in 6

or more out of 10 years.
Oxyaquic Haplumbrepts

JEDK. Other Haplumbrepts which have both:

1, An irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

2. A slope of less than 25 percent.
Fluventic Haplumbrepts
JEDL. Other Haplumbrepts that do not have a cambic
horizon.
Entic Haplumbrepts


537

Paleaquults
Paleargids .
Paleboralfs
Paleborolls
Palehumults

Paleorthids 205,228
Paleudalfs .. 100,112
Paleudolls . 365,372
Paleudults

Paleustalfs 117,124
Paleustolls . 374,391
Paleustults - 482,488
Palexeralfs - 130,135
Palexerolls 395,409
Palexerults 489,490
Paralithic contact 31

Particle-size classes
choice of 7 or 11



13

1. It contains 15 percent or more CaCO, equivalent, and
its CaCO, equivalent is 5 percent or more (absolute)
higher than that of the C horizon; or

2. It contains 15 percent or more CaCO, equivalent,
including 5 percent or more (by volume) identifiable
secondary carbonates as pendants on pebbles, as
concretions, or as soft powdery lime (see below), if it
rests on limestone, marl, or other very highly calcareous
materials with a CaCO, equivalent of 40 percent or
more, the carbonate content need not decrease with
increasing depth below the calcic horizon; or

3. It may contain a CaCO, equivalent of less than 15
percent if it has less than 18 percent clay in the fine-
earth fraction, a particle size that is sandy, sandy-
skeletal, coarse-loamy, or loamy-skeletal, and a content
of soft powdery secondary CaCO, that is 5 percent or
more (absolute) higher than that of an underlying,
horizon.

Air-dry fragments of a calcic horizon will slake in
water, except for disconnected carbonate concretions
and pendants under rocks. If a horizon enriched with
secondary carbonates is indurated or cemented to such a
degree that its dry fragments do not slake in water, it is
considered a petrocalcic horizon (defined below).

Cambic horizon

The cambic horizon is an altered horizon that does not
have the dark color, organic-matter content, and
structure of a histic, a mollic, or an umbric epipedon,
and has all of the following:

1. A texture of very fine sand, loamy very fine sand, or
finer; and

2. Soil structure, or absence of rock structure, in one
half or more of its volume; and

3. Evidence of alteration in the form of either:

a. Aquic conditions for some time in most years
(or artificial drainage), and both of the following:

(1) Within 50 cm of the mineral soil surface,
either on faces of peds, or in the matrix if
peds are absent, 50 percent or more chroma
as follows:

(a) Two or less, and redox
concentrations; or

(b) Zero, and a color value, moist, of 3
or less; or

(c) One or less, and a color value,
moist, of 4 or more; and

(2) One or more of the following properties:

(a) A regular decrease in the amount
of organic carbon with increasing,


a7

DDBG. Other Acroperox that have, in one or more
horizons within 125 cm of the mineral soil surface,
redox depletions with a color value, moist, of 4 or more
and a chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage).

Aquic Acroperox

DDBH. Other Acroperox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2, Fifty percent or more hue of 2.5YR or redder
and color value, moist, of 3 or less between 25
and 125 cm from the mineral soil surface.

Humic Rhodic Acroperox

DDBI. Other Acroperox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 7.5YR or yellower
and color value, moist, of 6 or more between 25
and 125 cm from the mineral soil surface.

Humic Xanthic Acroperox

DDBJ. Other Acroperox that have 16 kg/m? or more
organic carbon between the mineral soil surface and a
depth of 100 cm,

Humic Acroperox

DDBK. Other Acroperox that have 50 percent or more
hue of 2.5YR or redder and color value, moist, of 3 or
less between 25 and 125 cm from the mineral soil

surface,
Rhodic Acroperox

DDBL. Other Acroperox that have 50 percent or more
hue of 7.5YR or yellower and color value, moist, of 6 or
more between 25 and 125 cm from the mineral soil
surface.

Xanthic Acroperox

DDBM. Other Acroperox.
Typic Acroperox

Eutroperox
ean e
DDCA, Eutroperox that have, within 125 cm of the u

mineral soil surface, both:
1. A petroferric contact; and
2, Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Aquic Petroferric Eutroperox


389

temperature at a depth of 50 cm below the
soil surface is higher than 8°C; and
2. Either do not have a cambic horizon and do not,
in the lower part of the mollic epipedon, meet the
requirements for a cambic horizon except color, or
have carbonates throughout either the cambic
horizon or the lower part of the mollic epipedon.
Udorthentic Haplustolls

HFGxX. Other Haplustolls which have, if neither
irrigated nor fallowed to store moisture, either:

1. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for four tenths
or less of the cumulative days per year when the
temperature at a depth of 50 cm below the soil
surface is higher than 5°C; or

2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is dry
in some or all parts for less than 120 days per year
when the temperature at a depth of 50 cm below
the soil surface is higher than 8°C.

Udic Haplustolis

HFGY. Other Haplustolls that either do not have a
cambic horizon and do not, in the lower part of the
mollic epipedon, meet the requirements for a cambic
horizon except color, or have carbonates throughout
either the cambic horizon or the lower part of the mollic
epipedon.

Entic Haplustolls
HFGZ. Other Haplustolls.

Typic Haplustolls

Natrustolls

Key to subgroups

HFBA. Natrustolls which have one or both of the

following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Natrustolls


623

A“B” horizon that has a significant accumulation of
clay and also shows evidence of a development of color
or structure, or both, is designated Bt (t has precedence
‘over w, s, and h). A “B” horizon that is gleyed or
contains accumulations of carbonates, sodium, silica,
gypsum, salts more soluble than gypsum, or residual
accumulations of sesquioxides, carries the appropriate
symbol: g, k, n, q, y, Z, or o. If illuvial clay is also
present, t precedes the other symbol: Bto.

The suffixes h, s, and w are not used with g, k,n, q, y,
z, or 0, unless needed for explanatory purposes.

VERTICAL SUBDIVISION

Commonly a horizon or layer identified by a single
letter or a combination of letters has to be subdivided.
For this purpose, Arabic numerals are added to the
letters of the horizon designation. These numerals
follow all the letters. Within a C horizon, for example,
successive layers may be designated C1, C2, C3, etc,;
or, if the lower part is gleyed and the upper part is not,
the layers may be designated C1-C2-Cgl-Cg2 or C-Cgl-
Cg2-R.

These conventions apply whatever the purpose of the
subdivision. In many soils, a horizon that could be
identified by a single set of letters is subdivided to
recognize differences in morphological features, such as
structure, color, or texture. These divisions are
numbered consecutively with Arabic numerals, but the
numbering starts again with 1 wherever in the profile
any letter of the horizon symbol changes, e.g.: Bt1-Bt2-
Btk1-Btk2 (not Bt!-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;
¢.g.: Bs]-Bs2-2Bs3-2Bs4 (not Bs1-Bs2-2Bs1-2Bs2).

During sampling for laboratory analyses, thick soil
horizons are sometimes subdivided even though
differences in morphology are not evident in the field.
These subdivisions, too, are identified by Arabic
numerals which follow the respective horizon
designations, For example, four layers of a Bt horizon
sampled by 10-cm increments are designated Btl, Bt2,
Bt3, and Bté. If the horizon has already been subdivided
because of differences in morphological features, the set
of Arabic numerals that identifies the additional
sampling subdivisions follows the first numeral. For
example, three layers of a Bt2 horizon sampled by 10-
cm increments are designated Bt21, Bt22, and Bt23,
The descriptions for each of these sampling subdivisions
can be the same, and a comment can be added stating
that the horizon has been subdivided for sampling
purposes only.


159

CGFL, Other Hapludands which have, undried, a 1500-
‘kPa water retention of less than 30 percent throughout
one or more layers with andic soil properties that have a
total thickness of 25 cm more within 100 cm either of
the mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Vitric Hapludands

CGEM. Other Hapludands that have both:

1, Undried, a 1500-kPa water retention of 70
Percent or more throughout a layer 35 cm or more
thick within 100 cm either of the mineral soil
surface, or of the top of an organic layer with
andic soil properties, whichever is shallower; and

2, Between 25 and 100 cm either from the mineral
soil surface, or from the top of an organic layer
with andic soil properties, whichever is shallower,
a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic

epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more
that have a color value, moist, 1 unit or more
higher and an organic-carbon content | percent or
more (absolute) lower.

Hydric Thaptic Hapludands

CGEN, Other Hapludands that have, undried, a 1500-
kPa water retention of 70 percent or more throughout a
Jayer 35 cm or more thick within 100 cm either of the
mineral soil surface, or of the top of an organic layer
with andic soil properties, whichever is shallower.
Hydric Hapludands

CHFO. Other Hapludands that have both:

1. A sum of extractable bases of more than 25.0
cmol(+)/kg in the fine-earth fraction throughout
‘one or more horizons with a total thickness of 15
cm or more between 25 and 75 cm either from the
mineral soil surface, or from the top of an organic
layer with andic soil properties, whichever is
shallower; and

2. Between 25 and 100 cm cither from the mineral
soil surface, or from the top of an organic layer
with andic soil properties, whichever is shallower,
a layer 10 cm or more thick with more than 3.0
percent organic carbon and colors of a mollic
epipedon throughout, underlying one or more
horizons with a total thickness of 10 cm or more
that have a color value, moist, 1 unit or more
higher and an organic-carbon content | percent or
more (absolute) lower.

Eutric Thaptic Hapludands

CGFP. Other Hapludands that have, between 25 and
100 om either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, a layer 10 cm or more thick


231

FBBG. Other Paleorthids.
Typic Paleorthids

Salorthids

Key to subgroups

FBAA. Salorthids that have a weighted average
percentage of organic carbon, relative to the weighted
average ratio of sand to noncarbonate clay, between the
soil surface and a depth of 40 cm as follows:

1. 0,60 or more, with a sand/noncarbonate-clay
ratio of 1.0 or less; or

2. 0.15 or more, with a sand/noncarbonate-clay
ratio of 13 or more; or

3. 0.64-(0.038 x sand/noncarbonate-clay ratio), or
more, with a sand/noncarbonate-clay ratio

between 1 and 13,
Aquollic Salorthids

FBAB. Other Salorthids.
Typic Salorthids


348

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower; and

2. Both of the following:

a. A color value, dry, of 5 in the upper 18
om of the mollic epipedon, after mixing, or
in an Ap horizon 18 cm or more thick; and

b. If not irrigated, a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for six tenths or more of the
cumulative days per year when the soil
temperature at a depth of 50 cm from the
soil surface is 5°C or higher.

Torrertic Argiborolls

HEDG. Other Argiborolls which have both:
1. One or both of the following:

a. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through
a thickness of 30 cm or more for some time
in most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either
a depth of 100 cm or a lithic or paralithic
contact, whichever is shallower; and

2. Both of the following:

a. A color value, dry, of 5 or more in the
upper 18 cm of the mollic epipedon, after
mixing, or in an Ap horizon 18 cm or more
thick; and
b. If not irrigated, a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for six tenths or more of the
cumulative days per year when the soil
temperature at a depth of 50 cm from the
soil surface is 5°C or higher.
Ustertic Argiborolls
HEDH. Other Argiborolls which have one or both of the
following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or


percentages (by ammonium oxalate) totaling more than
1.0.
Andic Paleboralfs

IBAB. Other Paleboralfs that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1, More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or
b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Paleboralfs

IBAC, Other Paleboralfs that have, in one or more
horizons within 100 cm of the mineral soil surface,
redox depletions with a chroma of 2 or less, and also
aquic conditions for some time in most years (or
artificial drainage).
Aquic Paleboralfs

IBAD. Other Paleboralfs that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Paleboralfs

IBAE. Other Paleboralfs which have an argillic horizon
that has, in its fine-earth fraction, a clay increase with
depth of 20 percent or more (absolute) within its upper
7.5 om.

Abruptic Paleboralfs

IBAF. Other Paleboralfs that have an Ap horizon with a
color value, moist, of 3 or less and a color value, dry, of
5 or less (crushed and smoothed sample), or materials
between the soil surface and a depth of 18 cm which
have these color values after mixing.

Mollic Paleboralfs

IBAG. Other Paleboralfs.
Typic Paleboralfs


8

more than 40 percent total clay in the fine-
earth fraction; and

b. Ata depth

(1) Between 100 cm and 200 cm from the
mineral soil surface, if the particle-size class
throughout the upper 100 cm is sandy; or

(2) Less than 125 cm from the mineral soil
surface, if the clay content in the fine-earth
fraction of the surface horizon is less than
20 percent and the particle-size class (of
part or all of the upper 100 cm) is finer than
sandy; or

(3) Less than 100 cm from the mineral soil
surface, if the clay content in the fine-earth
fraction of the surface horizon is 20 percent
or more,

3. Has a thickness of either:
a. 30 cm or more; or

b. 15 cm or more if there is a lithic, paralithic, or
petroferric contact within 50 cm of the mineral
soil surface, with the kandic horizon constituting
60 percent or more of the vertical distance
between a depth of 18 cm and the contact.

4, Has a texture of loamy very fine sand or finer.

5. Has a CEC of 16 cmol(+) or less per kg clays (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 50 percent or more of its
thickness between the point where the clay increase
requirements are met and either a depth of 100 cm
below that point, or a lithic, paralithic, or petroferric
contact if shallower.

6. Has a regular decrease in organic-carbon content with
increasing depth, no fine stratification, and no overlying
layers more than 30 cm thick that have fine stratification
and/or organic carbon contents which decrease
irregularly with increasing depth.

Natrie horizon

The natric horizon (NL. natrium, sodium, implying
presence of sodium) is a special kind of argillic horizon.
Tt has, in addition to the properties of the argillic
horizon:

6 The percentage of clay is either measured by the pipette method, or
estimated to be 2.5 tines (percent water retained at 1500 kPa tension minus
percent organic carbon), whichever value is higher, but no more than 100.


47

within that depth are fibric and three fourths or more of
the fiber volume is derived from sphagnum or other
mosses, or (2) the materials have a bulk density of less
than 0.1 g/cm}; otherwise, the surface tier extends from
the soil surface to a depth of 30 cm.

On some organic soils, a surface mineral layer less than
40 cm thick is present as a result of flooding, volcanic
eruptions, additions of mineral materials to increase soil
strength or reduce frost hazard, or other causes, If such a
mineral layer is less than 30 cm thick, it constitutes the
upper part of the surface tier; if it is 30 to 40 cm thick,
it constitutes the whole surface tier and part of the
subsurface tier.

Subsurface tier

The subsurface tier is normally 60 cm thick. If,
however, the control section ends at a shallower depth
(ata lithic or paralithic contact or a water layer, or in
permafrost), the subsurface tier extends from the lower
boundary of the surface tier to the lower boundary of the
control section. It includes any unconsolidated mineral
layers that may be present within those depths.

Bottom tier

The bottom tier is 40 cm thick unless the control section
has its lower boundary at a shallower depth (at a lithic
or paralithic contact or a water layer, or in permafrost).


94

depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.
Vertic Eutroboralfs

IBEC. Other Eutroboralfs that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm? or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Eutroboralfs

IBED. Other Eutroboralfs that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1, More than 35 percent (by volume) fragments
coarser than 2,0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or
b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Eutroboralfs

IBEE. Other Eutroboralfs that have both:

1. In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. A sandy particle size throughout a layer

extending from the mineral soil surface to the top

of an argillic horizon at a depth of 50 to 100 cm.
Aquic Arenic Eutroboralfs

IBEF, Other Eutroboralfs which have both:
1, A glossic horizon; and
2, Redox depletions with a chroma of 2 or less in

layers that also have aquic conditions in most
years (or artificial drainage) either:
a. Within the upper 25 cm of the argillic
horizon if its upper boundary is within 50
em of the mineral soil surface; or

b. Within 75 cm of the mineral soil surface
if the upper boundary of the argillic horizon


416

DDC. Other Perox that have a base saturation (by
NH,OAc) of 35 percent or more in all horizons within
125 cm of the mineral soil surface.

Eutroperox, p. 417
DDD. Other Perox which have both:

1. A clay content of 40 percent or more in the fine-
earth fraction between the soil surface and a depth
of 18 cm, after mixing; and

2. A kandic horizon that has its upper boundary
within 150 cm of the mineral soil surface.
Kandiperox, p.421

DDE, Other Perox.
Haploperox, p. 419

Acroperox

Key to subgroups

DDBA. Acroperox that have, within 125 cm of the
mineral soil surface, both:

1. A petroferric contact; and

2, Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Aquic Petroferric Acroperox
DDBB. Other Acroperox that have a petroferric contact
within 125 cm of the mineral soil surface.
Petroferric Acroperox

DDBC. Other Acroperox that have, within 125 cm of
the mineral soil surface, both:

1. A lithic contact; and

2, Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Aquic Lithic Acroperox
DDBD. Other Acroperox that have a lithic contact
within 125 cm of the mineral soil surface.
Lithic Acroperox
DDBE. Other Acroperox that have a delta pH (KC! pH
minus 1:1 water pH) with a 0 or net positive charge in a
layer 18 cm or more thick within 125 cm of the mineral
soil surface,
Anionic Acroperox
DDBF, Other Acroperox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125
em of the mineral soil surface.
Plinthic Acroperox


238

depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.
Vertic Fluvaquents

KAEC. Other Fluvaquents which have both:

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

2. A difference of less than 5°C between mean
summer and mean winter soil temperatures, either
at a depth of 50 cm from the soil surface or at a
lithic or paralithic contact, whichever is
shallower.

Thapto-Histic Tropic Fluvaquents

KAED. Other Fluvaquents which have a buried

Histosol, or a buried histic epipedon, that has its upper

boundary within 100 cm of the mineral soil surface.
Thapto-Histic Fluvaquents

KAEE. Other Fluvaquents which have, throughout one
or more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or more of
the following:

1. A fine-earth fraction with both a bulk density of
1.0 g/cm’ or less, measured at 33 kPa water
retention, and aluminum plus 1/2 iron percentages
(by ammonium oxalate) totaling more than 1.0; or
2. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
3. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0,02-to-2.0-mm fraction, more than

30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent

or more volcanic glass, and in the fine-earth

fraction, aluminum plus 1/2 iron

percentages (by ammonium oxalate) totaling

0.40 or more,

Aquandic Fluvaquents

KAEF. Other Fluvaquents that have both:

1, A difference of less than 5°C between mean
summer and mean winter soil temperatures either
at a depth of 50 cm from the soil surface or at a
lithic or paralithic contact, whichever is
shallower; and

2. In one or more horizons between either the Ap
horizon or a depth of 25 cm from the mineral soil
surface, whichever is deeper, and a depth of 75


505,

EEC. Other Usterts which have a gypsic horizon that
has its upper boundary within 100 cm of the mineral
soil surface.

Gypsiusterts, p. 507

EED. Other Usterts which have a calcic or petrocalcic
horizon that has its upper boundary within 100 cm of
the mineral soil surface.

Calciusterts, p. 505

EEE. Other Usterts.
Haplusterts, p. 508

Calciusterts

Key to subgroups

EEDA. Calciusterts that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Calciusterts

EEDB. Other Calciusterts that have, throughout a layer
15 cm or more thick within 100 cm of the mineral soil
surface, an electrical conductivity of 15 dS/m-or more
(1:1 soil:water) for 6 or more months per year in 6 or
more out of 10 years,

Halic Calciusterts

EEDC. Other Calciusterts that have, in one or more
horizons within 100 cm of the mineral soil surface, an
exchangeable sodium percentage of 15 or more (or a
sodium adsorption ratio of 13 or more) for 6 or more
months per year in 6 or more out of 10 years.

Sodic Calciusterts

EEDD. Other Calciusterts which have a petrocalcic
horizon that has its upper boundary within 100 cm of
the mineral soil surface.

Petrocalcic Calciusterts

EEDE. Other Calciusterts which, if not irrigated during
‘the year, have cracks in 6 or more out of 10 years that
are 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for 210
or more cumulative days per year.

Aridic Calciusterts

EEDF. Other Calciusterts which, if not irrigated during
the year, have cracks in 6 or more out of 10 years that
are 5 mm or more wide, through a thickness of 25 cm or
more within 50 cm of the mineral soil surface, for less
than 150 cumulative days per year.

Udic Calciusterts

EEDG. Other Calciusterts that have a lithic or paralithic
contact, or the upper boundary of a duripan, within 100
cm of the mineral soil surface.

Leptic Calciusterts

EEDH, Other Calciusterts which have a layer 25 cm or
more thick that contains less than 27 percent clay in its


cco)

2. Are 2 mm or more thick between vertical faces of
abutting peds; and

3. Constitute less than 15 percent (by volume) of the
layer which they penetrate.

Linear extensibility (LE)

The linear extensibility (LE) of a soil layer is the
product of the thickness, in centimeters, multiplied by
the COLE of the layer in question. The LE of a soil is
the sum of these products for all soil horizons.

Lithic contact

A lithic contact is the boundary between soil and a
coherent underlying material. Except in ruptic-lithic
subgroups the underlying material must be virtually
continuous within the limits of a pedon, Cracks that can
be penetrated by roots are few, and their horizontal
spacing is 10 cm or more. The underlying material must
be sufficiently coherent when moist to make hand-
digging with a spade impractical, although the material
may be chipped or scraped with a spade. If it consists of
a single mineral, it must have a hardness by Mohs scale
of 3 or more; otherwise, chunks of gravel size that can
be broken out must not disperse during 15 hours of
shaking in water or in a sodium hexametaphosphate
solution. The underlying material considered here does
not include diagnostic soil horizons such as a duripan or
a petrocalcic horizon.

A lithic contact is diagnostic at the subgroup level if it
is within 125 em of the mineral soil surface of Oxisols
and within 50 cm of the mineral soil surface of all other
mineral soils.

nvalue

The » value (Pons and Zonneveld, 1965) characterizes
the relation between the percentage of water in a soil
under field conditions and its percentages of inorganic
clay and humus. The » value is helpful in predicting
whether a soil can be grazed by livestock or can support
other loads, and in predicting what degree of subsidence
would occur after drainage. For mineral soil materials
that are not thixotropic, the n value can be calculated by
the formula:

n=(A-0.2R\M(L + 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; Z is the percentage of clay,
and H is the percentage of organic matter (percent
organic carbon multiplied by 1.724).

Few data are available in the United States for
calculations of the 7 value, but the critical n value of 0.7
can be approximated closely in the field by a simple test
of squeezing a soi! sample in the hand. If the soil flows


167

2. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
redox depletions on faces of peds, or in the matrix
if peds are absent; or

3. Enough active ferrous iron to give a positive
reaction to a.,c.'-dipyridy] at a time when the soil
is not being irrigated.
Aquic Placudands
CGAC. Other Placudands that have both:

1. Extractable bases plus 1N-KCl-extractable AP*
totaling less than 2.0 cmol(+)/kg in the fine-earth
fraction of one or more horizons with a total
thickness of 30 cm or more, between 25 and 100
cm either from the mineral soil surface, or from
the top of an organic layer with andic soil
properties, whichever is shallower; and

2. Undried, a 1500-kPa water retention of 70
percent or more throughout a layer 35 cm or more
thick within 100 cm either of the mineral soil
surface, or of the top of an organic layer with
andic soil properties, whichever is shallower.
Acrudoxic Hydric Placudands

CGAD. Other Placudands that have extractable bases
plus IN-KC1-extractable Al>* totaling less than 2.0
cmol(+)/kg in the fine-earth fraction of one or more
horizons with a total thickness of 30 cm or more,
between 25 and 100 cm either from the mineral soil
surface, or from the top of an organic layer with andic
soil properties, whichever is shallower.

Acrudoxic Placudands

CGAE. Other Placudands that have both:

1. A sum of extractable bases of more than 25.0
cmol(+)/kg in the fine-earth fraction throughout
‘one or more horizons with a total thickness of 15
m or more between 25 and 75 cm either from the
mineral soil surface, or from the top of an organic
layer with andic soil properties, whichever is
shallower; and

2, Undried, a 1500-kPa water retention of less
than 30 percent throughout one or more layers
with andic soil properties that have a total
thickness of 25 cm more within 100 cm either of
the mineral soil surface, or of the top of an organic
layer with andic soil properties, whichever is
shallower,

Eutric Vitric Placudands

OZpP


358

that is moist in some or all of its parts throughout
the year in 6 or more out of 10 years.
Cumulic Udic Haploborolis

HEGI. Other Haploborolls which have:

1. A mollic epipedon 40 cm or more thick, of
which less than 50 percent has a sandy particle
size, and no paralithic contact or sandy contrasting
layer between 40 and 50 cm from the mineral soil
surface; and

2. An irregular decrease in organic-carbon content
from a depth of 25 cm below the mineral soil
surface to a depth of 125 cm, or to a lithic or
paralithic contact if shallower; and

3. A slope of less than 25 percent and a concave
shape.
Cumulic Haploborolls

HEGJ. Other Haploborolls that have both:

1. A mollic epipedon 40 cm or more thick, of
which less than 50 percent has a sandy particle
size, and no paralithic contact or sandy contrasting
layer between 40 and 50 cm from the mineral soil
surface; and

2. Either a chroma of | or less (crushed and
smoothed sample) in the upper 18 cm of the
mollic epipedon, after mixing, or in an Ap horizon
18 cm or more thick, or a moisture control section
that is moist in some or all of its parts throughout
the year in 6 or more out of 10 years.

Pachic Udic Haploborolls

HEGK. Other Haploborolls that have a mollic epipedon
40 cm or more thick, of which less than 50 percent has a
sandy particle size, and no paralithic contact or sandy
contrasting layer between 40 and 50 cm from the
mineral soil surface.

Pachic Haploborolls

HEGL. Other Haploborolls that have:

1. Either 0.3 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

2. In one or more horizons within 100 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and
3. A slope of less than 25 percent.

Fluvaquentic Haploborolls

HEGM. Other Haploborolls that have, in one or more
horizons within 100 cm of the mineral soil surface,


404

a. More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or

b, A fine-carth fraction containing 30

percent or more particles 0.02 to 2.0 mm in
diameter, and either:

(1) In the 0.02-to-2.0-mm fraction,
more than 30 percent volcanic glass;
or

(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more.
Vitritorrandic Haploxerolls

HDFF, Other Haploxerolls that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:

1. More than 35 percent (by volume) fragments
coarser than 2,0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0,02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
of more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling

0.40 or more.
Vitrandic Haploxerolls
HDFG. Other Haploxerolls which have:

1, A mollic epipedon 50 cm or more thick with a
texture finer than loamy fine sand; and

2. An irregular decrease in organic-carbon content
from a depth of 25 cm below the mineral soil
surface to a depth of 125 cm, or to a lithic or
paralithic contact if shallower; and

3. A slope of less than 25 percent; and

4, A base saturation (by sum of cations) of 75
percent or less in one or more horizons between.
either an Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and
either a depth of 75 cm or a lithic or paralithic
contact, whichever is shallower.

Cumulic Ultic Haploxerolls


TORRERTS

Key to great groups

EDA. Torrerts which have a salic horizon that has its
upper boundary within 100 cm of the soil surface,
Salitorrerts, p. 502

EDB. Other Torrerts which have a gypsic horizon that
has its upper boundary within 100 cm of the soil
surface.

Gypsitorrerts, p. 501

EDC. Other Torrerts which have a calcic or petrocalcic
horizon that has its upper boundary within 100 cm of
the soil surface.

Calcitorrerts, p. 500

EDD. Other Torrerts.
Haplotorrerts, p. 501

Calcitorrerts

Key to subgroups
EDCA. Calcitorrerts which have a petrocalcic horizon
that has its upper boundary within 100 cm of the soil
surface.

Petrocalcic Caicitorrerts

EDCB. Other Calcitorrerts that have a lithic or
paralithic contact, or the upper boundary of a duripan,
within 100 cm of the soil surface.

Leptic Calcitorrerts

EDCC, Other Calcitorrerts which have a layer 25 cm or
more thick that contains less than 27 percent clay in its
fine-earth fraction and has its upper boundary within
100 cm of the soil surface.

Entic Calcitorrerts

EDCD. Other Calcitorrerts that have, in one or more
horizons within 30 cm of the soil surface, 50 percent or
more colors as follows:

1. Acolor value, moist, of 4 or more; or
2. A color value, dry, of 6 or more; or

3. A chroma of 3 or more.
Chromic Calcitorrerts

EDCE. Other Calcitorrerts.
Typic Calcitorrerts


132
percentages (by ammonium oxalate) totaling

0.40 or more.
Vitrandic Fragixeralfs

IDCC, Other Fragixeralfs that have an Ap horizon with
acolor value, moist, of 3 or less and a color value, dry,
of 5 or less (crushed and smoothed sample), or materials
between the soil surface and a depth of 18 em which
haye these color values after mixing.

Mollic Fragixeralfs

IDCD. Other Fragixeralfs that have, in one or more
horizons within 40 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial

drai .
nage) Aquic Fragixeralfs

IDCE, Other Fragixeralfs that do not, above the
fragipan, have an argillic horizon with clay films on
both vertical and horizontal faces of any peds.

Ochreptic Fragixeralfs
IDCF, Other Fragixeralfs,
Typic Fragixeralfs
Haploxeralfs
Key to subgroups

IDGA. Haploxeralfs that have both:

1. A lithic contact within 50 cm of the mineral soil
surface; and

2. A color value, moist, of 3 or less and 0.7
percent or more organic carbon, either throughout
an Ap horizon or throughout the upper 10 cm of
an A horizon,

Lithic Mollic Haploxeralfs

IDGB. Other Haploxeralfs which have both:

1. A lithic contact within 50 cm of the mineral soil
surface; and
2. An argillic horizon that is discontinuous
horizontally in each pedon.
Lithic Ruptic-Xerochreptic Haploxeralfs
IDGC, Other Haploxeralfs that have a lithic contact

within 50 cm of the mineral soil surface.
Lithic Haploxeralfs

IDGD. Other Haploxeralfs which have one or both of
the following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has


14

depth, and an organic-carbon content
of less than 0.2 percent either at a
depth of 125 cm below the mineral
soil surface, or directly above a sandy-
skeletal substratum at a depth of less
than 125 cm; or

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

(c) Permafrost at some depth; or

@ A histic epipedon consisting of
mineral soil materials, or a mollic or
an umbric epipedon; or
b. Either no aquic conditions (or artificial
drainage), or colors different from those defined in
3.a, or both, and one or more of the following:

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

(2) Evidence of removal of carbonates;
particularly, less carbonate than in 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 coated only on the underside,
those in the cambic horizon are free of
coatings), or

(3) If carbonates are absent in the parent
material and in the dust that falls on the
soil, the requirement of evidence of
alteration is satisfied by the presence of soil
structure and absence of rock structure; and

4. Properties that do not meet the requirements for an
argillic, a kandic, an oxic, or a spodic horizon; and

5. No cementation or induration and no brittle
consistence when moist; and

6. A lower boundary at a depth of 25 cm or more from
the mineral soil surface, unless the soil temperature
regime is cryic or pergelic.

Duripan

The duripan (L. durus, hard, meaning hardpan) is a
silica-cemented subsurface horizon in which:

1. Cementation in one or more subhorizons is strong

enough so that dry fragments from these subhorizons do
not slake in water, even during prolonged wetting; and

2. Coatings of silica, insoluble in 1N HC! even during
prolonged soaking but soluble in hot concentrated KOH


296

JADC. Other Fragiaquepts.
Typic Fragiaquepts

Halaquepts

Key to subgroups

JACA. Halaquepts which have one or both of the
following:

1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Halaquepts

JACB. Other Halaquepts which have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or more of
the following:

1. A fine-earth fraction with both a bulk density of
1.0 g/cm? or less, measured at 33 kPa water

retention, and aluminum plus 1/2 iron percentages
(by ammonium oxalate) totaling more than 1.0; or

2. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

3. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or

b. In the 0.02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-carth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Aquandic Halaquepts

JACC. Other Halaquepts that have a chroma of 3 or
more in 40 percent or more of the matrix of one or more
horizons between 15 and 75 cm from the mineral soil
surface.

Aeric Halaquepts

JACD. Other Halaquepts that have a mollic epipedon.
Mollic Halaquepts


at

(absolute) within a vertical distance of 2.5 cm, in
the fine-earth fraction.
Haplic Palexerolls

HDCJ. Other Palexerolls.
Typic Palexerolls



538

Pergelic soil temperature regime

Plinthustults
Powdery lime, sof
Prime, use of.....
Psammaquents
PSAMMENTS



89

Contrasting particle-size families are recognized for
soils in which substitute class names are applicable to
part of the control section. If such substitute terms are
applied only to the upper part, one of the seven particle-
size class names is used to characterize the lower part.
For example, we use the term cindery over loanty (not
cindery over fine-loamy).

Only two subclasses of particle-size classes are applied
to soil families in the Vertisol order, i.e., 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’s fine-earth fraction.

Mineralogy classes
The control section

Mineralogy classes are based on the approximate
mineralogical composition of selected grain-size
fractions of the same segment of a soil (i.¢., the same
control section) that is used to determine particle-size
classes.

ntrasting mins mi
Contrasting mineralogy modifiers are only recognized in
those soil families to which substitutes for particle-size
names have been applied. In naming the contrasting
mineralogy classes for the families of such soils, the set
of seven particle-size classes 1s used to describe the
lower part of the particle-size control section. For
example, a pair of contrasting layers in the control
section 1s characterized as medial over loamy, mixed
(not medial over coarse-loamy, mixed).

If there are layers of contrasting particle sizes in the
control section, the mineralogy class of the upper part
determines the family mineralogy modifier. For
example, if there is fine-loamy material of mixed
mineralogy over siliceous sandy material, the soil family
is described as fine-loamy over sandy, mixed (not fine-
loamy, mixed, over sandy, siliceous).

Key to mineralogy classes

Table 1 provides a key for determining the proper
mineralogy classes of families in all mineral soils
except Oxisols; the mineralogy classes of Oxisol

families are listed in Table 2. These tables contain keys,
not complete definitions,

Important variations in Andisols, in many intergrades to
Andisols, and in many cryic great groups and cryic
subgroups of Spodosols are identified by using the
substitute modifiers listed above which replace names
of particle-size classes, and which include aspects of
texture, consistence, and mineralogy.

Mineralogy classes are not named in families of
Calciaquolls because their amount of carbonates is more
significant than other aspects of their mineralogy, and


216

(3) 0.77-(0.046 x sand/clay ratio), or
more, with a sand/clay ratio between 1
and 13.

Borollic Camborthids

FBFH. Other Camborthids which have both:
1. One or both of the following:

a, Cracks within 125 cm of the soil surface
that are 5 mm or more wide through a
thickness of 30 cm or more for some time in
most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the soil surface; or

b. A linear extensibility of 6.0 cm or more
between the soil surface and either a depth
of 100 cm or a lithic or paralithic contact,
whichever is shallower; and

2. A mean annual soil temperature lower than
22°C, a difference of 5°C or more between mean
summer and mean winter soil temperatures at a
depth of 50 cm from the soil surface, and an aridic
moisture regime that borders on a xeric regime.
Xerertic Camborthids

FBFI. Other Camborthids which have both:
1. One or both of the following:

a. Cracks within 125 cm of the soil surface
that are 5 mm or more wide through a
thickness of 30 cm or more for some time in
most years, and slickensides or wedge-
shaped aggregates in a layer 15 cm or more
thick that has its upper boundary within 125
cm of the soil surface; or

b. A linear extensibility of 6.0 cm or more
between the soil surface and either a depth
of 100 cm or a lithic or paralithic contact,
whichever is shallower; and

2. An aridic moisture regime that borders on an
ustic regime.
Ustertic Camborthids

FBFJ. Other Camborthids which have one or both of the
following:

1. Cracks within 125 cm of the soil surface that

are 5 mm or more wide through a thickness of 30

cm or more for some time in most years, and

slickensides or wedge-shaped aggregates in a

layer 15 cm or more thick that has its upper

boundary within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more
between the soil surface and either a depth of 100


129

temperature at a depth of 50 cm below the soil
surface is higher than 5°C; or
2. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is dry
in some or all parts for less than 120 cumulative
days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8°C.
Udic Rhodustalfs

ICGD. Other Rhodustalfs.
Typic Rhodustalfs

XERALFS

Key to great groups

IDA. Xeralfs which have a duripan that has its upper

boundary within 100 cm of the mineral soil surface. A
Durixeralfs, p. 130 Ll

IDB. Other Xeralfs that have a natric horizon. F
Natrixeralfs, p. 135

IDC. Other Xeralfs that have a fragipan.
Fragixeralfs, p. 131
IDD. Other Xeralfs that have one or more horizons
within 150 cm of the mineral soil surface in which
plinthite either forms a continuous phase or constitutes
one half or more of the volume.
Plinthoxeralfs, p. 138

IDE. Other Xeralfs which have throughout the argillic
horizon a hue of 2.5YR or redder, a color value, moist,
of 3 or less, and a color value, dry, no more than I unit
higher than the value, moist.

Rhodoxeralfs, p. 138

IDF. Other Xeralfs which have one or more of the
following:
1. A petrocalcic horizon that has its upper
boundary within 150 cm of the mineral soil
surface; or
2. No lithic or paralithic contact within 150 cm of
the mineral soil surface, and an argillic horizon
which has both:

a. Within 150 cm of the mineral soil surface,
either
(1) No clay decrease with increasing
depth of 20 percent or more (relative)
from the maximum clay content; or

(2) Five percent or more (by volume)
skeletans on faces of peds in the layer
that has a 20 percent lower clay
content and, below that layer, a clay
increase of 3 percent or more


496

more within 50 cm of the mineral soil surface, for 90 or
tore cumulative days per year.
Ustic Endoaquerts

EAGF. Other Endoaquerts that have, in one or more
horizons between either an Ap horizon or a depth of 25
cm from the mineral soil surface, whichever is deeper,
and a depth of 75 cm, 50 percent or more colors as
follows:

1. A hue of 2,5Y or redder and either:

a. A color value, moist, of 6 or more and a
chroma of 3 or more; or

b. A color value, moist, of 5 or less and a
chroma of 2 or more; or

2. A hue of SY and a chroma of 3 or more; or

3. A chroma of 2 or more, and no redox
concentrations.
Aeric Endoaquerts
EAGG. Other Endoaquerts that have a lithic or
paralithic contact within 100 cm of the mineral soil
surface.
Leptic Endoaquerts
EAGH. Other Endoaquerts which have a layer 25 cm or
more thick that contains less than 27 percent clay in its
fine-earth fraction and has its upper boundary within
100 cm of the mineral soil surface.
Entic Endoaquerts

EAGI. Other Endoaquerts that have, in one or more
horizons within 30 cm of the mineral soil surface, one
or both of the following in more than half of each
pedon:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more.

Chromic Endoaquerts
EAGJ. Other Endoaquerts.
Typic Endoaquerts
Eplaquerts
Key to subgroups

EAFA. Epiaquerts that have, throughout a layer 15 cm
or more thick within 100 cm of the mineral soil surface,
an electrical conductivity of 15 dS/m or more (1:1
soil:water) for 6 or more months per year in 6 or more
out of 10 years.

Halic Epiaquerts

EAFB. Other Epiaquerts that have, in one or more
horizons within 100 cm of the mineral soil surface, an
exchangeable sodium percentage of 15 or more (or a


821
0 Residual accumulation of sesquioxides

This symbol indicates a residual accumulation of
sesquioxides,

p Tillage or other disturbance

This symbol indicates a disturbance of the surface
layer by mechanical means, pasturing, or similar
uses. A disturbed organic horizon is designated
Op. A disturbed mineral horizon is designated Ap
even though it is clearly a former E, B, or C
horizon.

q Accumulation of silica

This symbol indicates an accumulation of
secondary silica.

1 Weathered or soft bedrock

This symbol is used with C to indicate root-
restrictive layers of saprolite such as weathered
igneous rock, or of soft bedrock such as partly
consolidated sandstone, siltstone, and shale.
Excavation difficulty is low or moderate.

 Illuvial accumulation of sesquioxides and organic
matter

This symbol is used with B to indicate an
accumulation of illuvial, amorphous, dispersible
organic-matter-sesquioxide complexes if both the
organic-matter and sesquioxide components are
significant, and if the color value and chroma,
moist, of the horizon is 4 or more. The symbol is
also used in combination with h as “Bhs” if both
the organic-matter and sesquioxide components
are significant, and if the color value and chroma,
moist, is 3 or less.

ss Presence of slickensides

This symbol indicates the presence of
slickensides, Slickensides result directly from the
swelling of clay minerals and shear failure,
commonly at angles of 20 to 60 degrees above
horizontal. They are indicators that other vertic
characteristics, such as wedge-shaped peds and
surface cracks, may be present.

t Accumulation of silicate clay

This symbol indicates an accumulation of silicate
clay that has either formed and subsequently been
translocated within the horizon or has been moved
into the horizon by illuviation, or both. At least
some part of the horizon should show evidence of
clay accumulation either as coatings on surfaces of
peds or in pores, or as lamellae or as bridges
between mineral grains.


113

thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or
2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Paleudalfs

IEIB. Other Paleudalfs that have anthraquic conditions.
‘Anthraquic Paleudalfs

TEIC. Other Paleudalfs that have both:

1. In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (of artificial drainage);
and
2. Five percent or more (by volume) plinthite in
one or more horizons within 150 cm of the
mineral soil surface.

Plinthaquic Paleudalfs

IEID. Other Paleudalfs which have both:

1. In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. In the upper part of the argillic horizon, one or
more subhorizons that have 5 percent or more (by
volume) clay depletions with a chroma of 2 or
less.

Glossaquic Paleudalfs
TEIE. Other Paleudalfs that have both:

1, In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. A clay increase of 15 percent or more (absolute)
in the fine-earth fraction within a vertical distance
of 2.5 cm at the upper boundary of the argillic
horizon.
Albaquic Paleudalfs
TEIF. Other Paleudalfs that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).
Aquic Paleudalfs


260

days per year when the temperature at a depth of
50 cm below the soil surface is higher than 8°C.
Udic Ustorthents

KEEL. Other Ustorthents that have 50 percent or more
(by volume) wormholes, worm casts, and filled animal
burrows between either the Ap horizon or a depth of 25
cm from the mineral soil surface, whichever is deeper,
and either a depth of 100 cm or a lithic, paralithic, or
petroferric contact, whichever is shallower.

Vermic Ustorthents
KEEJ. Other Ustorthents.
Typic Ustorthents
Xerorthents
Key to subgroups

KECA. Xerorthents that have a lithic contact within 50
cm of the mineral soil surface.
Lithic Xerorthents

KECB. Other Xerorthents which have both:

1. In one or more horizons within 100 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, one or more of the following:

a. A fine-carth fraction with both a bulk
density of 1.0 g/cm? or less, measured at 33
kPa water retention, and aluminum plus 1/2
iron percentages (by ammonium oxalate)
totaling more than 1.0; or

b. More than 35 percent (by volume)
fragments coarser than 2.0 mm, of which
more than 66 percent are cinders, pumice,
and pumice-like fragments; or

c. A fine-earth fraction containing 30

percent or more particles 0.02 to 2.0 mm in
diameter, and either:

(1) In the 0.02-to-2.0-mm fraction,
more than 30 percent volcanic glass;
or

(2) In the 0.02-to-2.0-mm fraction, 5
percent or more volcanic glass, and in
the fine-earth fraction, aluminum plus
1/2 iron percentages (by ammonium
oxalate) totaling 0.40 or more.
Aquandic Xerorthents


352
Cryoborolls

Key to subgroups
HEBA. Cryoborolls which have both:

1, A lithic contact within 50 cm of the mineral soil
surface; and

2. An argillic horizon, and either:

a. Above the argillic horizon, an albic
horizon, or a horizon that has color values
too high for a mollic epipedon and a chroma
too high for an albic horizon; or

b. A glossic horizon, or interfingering of
albic materials into the upper part of the
argillic horizon, or skeletans of clean silt
and sand covering 50 percent or more of the
faces of peds in the upper 5 cm of the
argillic horizon.

Boralfic Lithic Cryoborolls

HEBB. Other Cryoborolls which have both:

1. A lithic contact within 50 cm of the mineral soil
surface; and
2. An argillic horizon.

Argic Lithic Cryoborolls

HEBC. Other Cryoborolls which have both:

1. A lithic contact within 50 cm of the mineral soil
surface; and
2. A mollic epipedon that is discontinuous in each
pedon.
Lithic Ruptic-Entic Cryoborolls
HEBD. Other Cryoborolls which have both:

1. A lithic contact within 50 cm of the mineral soil
surface; and
2. An argillic horizon that is discontinuous in each
pedon.
Lithic Ruptic-Argic Cryoborolls
HEBE. Other Cryoborolls that have a lithic contact

within 50 cm of the mineral soil surface.
Lithic Cryoborolls

HEBF. Other Cryoborolls that have a mean annual soil
temperature of 0°C or less.

Pergelic Cryoborolls
HEBG. Other Cryoborolls which have an argillic
horizon that has, in half or more of its thickness, an
exchangeable sodium percentage of 15 percent or more
(or a sodium adsorption ratio of 13 or more).

Natric Cryoborolls

HEBH. Other Cryoborolls which have an argillic
horizon and one or both of the following:


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 which have both:

1. One or more layers, with a total thickness of 25
em or more, of the subsurface and bottom tiers
consisting of fibric materials, and

2. A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Fibric Terric Medihemists

ACGD. Other Medihemists which have both:

1. One or more layers, with a total thickness of
12.5 cm or more, of the subsurface and bottom
tiers consisting of sapric materials; and

2. A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Sapric Terric Medihemists

ACGE. Other Medihemists which have a mineral layer
30 cm or more thick that has its upper boundary within
the control section below the surface tier.

Terric Medihemists

ACGF. Other Medihemists that have one or more limnic
layers with a total thickness of 5 cm or more within the
control section.

Limnic Medihemists

ACGG. Other Medihemists that have, within organic
materials, either one mineral layer 5 cm or more thick,
or two or more mineral layers of any thickness, in the
control section below the surface tier.

Fluvaquentic Medihemists

ACGH. Other Medihemists that have one or more
layers, with a total thickness of 25 cm or more, of the
subsurface and bottom tiers consisting of fibric
materials.

Fibric Medihemists

ACGL. Other Medihemists that have one or more layers,
with a total thickness of 12.5 cm or more, of the
subsurface and bottom tiers consisting of sapric
materials,

Sapric Medihemists

ACGJ. Other Medihemists.
Typic Medihemists


115

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

Rhodic Paleudalfs

IEIP. Other Paleudalfs that have an Ap horizon with a
color value, moist, of 3 or less and a color value, dry, of
5 or less (crushed and smoothed sample), or materials
between the soil surface and a depth of 18 em which
have these color values after mixing.

Mollic Paleudalfs

IEIQ. Other Paleudalfs.
Typic Paleudalfs

Rhodudaifs

Rhodudalfs are dark red Udalfs that have a thinner
solum than Paleudalfs. Their definition is parallel to
that of other Rhodic great groups. Their parent materials
are basic. These soils are rare in the United States, and
definitions of subgroups have not been developed.

USTALFS

Key to great groups

ICA. Ustalfs which have a duripan that has its upper

boundary within 100 cm of the mineral soil surface.
Durustalfs, p. 117

ICB. Other Ustalfs that have one or more horizons
within 150 cm of the mineral soil surface in which
plinthite either forms a continuous phase or constitutes
one half or more of the volume.

Plinthustalfs, p. 128

ICC. Other Ustalfs that have a natric horizon.
Natrustalfs, p. 123

ICD, Other Ustalfs which:

1, Have a CEC of 16 cmol(+)/kg clay or less (by
IN NH,OAc pH 7) and an ECEC of 12 cmol(+)/kg
clay or less (sum of bases extracted with IN
NH,OAc pH 7, plus 1N-KCl-extractable Al) in 50
percent or more either of the argillic or kandic
horizon if less than 100 cm thick, or of its upper
100 cm; and

2. Do not have a lithic, paralithic, or petroferric
contact within 150 cm of the mineral soi] surface;
and

3. Within 150 cm of the mineral soil surface,
either

a, Do not have a clay decrease with
increasing depth of 20 percent or more

meP>


466

GBCE. Other Kandihumults that have, in one or more
horizons within 75 cm of the mineral soil surface, redox
concentrations, a color value, moist, of 4 or more, and a
hue which is 1OYR or yellower, but which becomes.
redder with increasing depth within 100 cm of the
mineral soil surface.
Ombroaquic Kandihumults
GBCF. Other Kandihumults that have 5 percent or more
(by volume) plinthite in one or more horizons within
150 cm of the mineral soil surface.
Plinthic Kandihumults
GBCG. Other Kandihumults that have an ustic moisture
Tegime.
Ustic Kandihumults
GBCH. Other Kandihumults that have a xeric moisture
regime.
Xeric Kandihumults
GBCI. Other Kandihumults that have an anthropic
epipedon.

Anthropic Kandihumults
GBCJ. Other Kandihumults.
Typic Kandihumults
Kanhaplohumults
Key to subgroups .

GBDA. Kanhaplohumults that have a lithic contact
within 50 cm of the mineral soil surface.
Lithic Kanhaplohumults

GBDB. Other Kanhaplohumults that have both:
1. An ustic moisture regime; and

2. Throughout one or more horizons with a total
thickness of 18 cm or more within 75 cm of the
mineral soil surface, a fine-earth fraction with
both a bulk density of 1.0 g/cm} or less, measured
at 33 kPa water retention, and aluminum plus 1/2
iron percentages (by ammonium oxalate) totaling
more than 1.0.

Ustandic Kanhaplohumults

GBDC. Other Kanhaplohumults that have, throughout
‘one or more horizons with a total thickness of 18 em or
more within 75 cm of the mineral soil surface, a fine-
earth fraction with both a bulk density of 1.0 g/cm? or
less, measured at 33 kPa water retention, and aluminum
plus 1/2 iron percentages (by ammonium oxalate)
totaling more than 1.0.

Andic Kanhaplohumults

GBDD. Other Kanhaplohumults that have, in one or
more subhorizons within the upper 25 cm of the argillic
or kandic horizon, redox depletions with a color value,
moist, of 4 or more and a chroma of 2 or less,


280

2. Never freeze below a depth of 5 cm from the
soil surface but have a mean annual soil

temperature lower than 8°C.
Cryohemists, p. 281

ACE. Other Hemists that have a mean annual soil
temperature lower than 8°C.
Borohemists, p. 280
ACF, Other Hemists that have a difference of less than
5°C between mean summer and mean winter soil
temperatures at a depth of 30 cm below the soil surface.
Tropohemists, p. 283

ACG. Other Hemists.
Medihemists, p. 282

Borohemists

Key to subgroups

ACEA, Borohemists 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 which have both:

1. One or more layers, with a total thickness of 25
cm or mote, of the subsurface and bottom tiers
consisting of fibric materials; and

2. A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Fibric Terric Borohemists

ACED. Other Borohemists which have both:

1. One or more layers, with a total thickness of
12.5 cm or more, of the subsurface and bottom
tiers consisting of sapric materials; and

2, A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Sapric Terric Borohemists

ACEE. Other Borohemists which have a mineral layer
30 cm or more thick that has its upper boundary within
the control section below the surface tier.

Terric Borohemists

ACEF, Other Borohemists that have one or more limnic
layers with a total thickness of 5 cm or more within the
control section.

Limnic Borohemists

ACEG. Other Borohemists that have, within organic
materials, either one mineral layer $ cm or more thick,


Family differentiae, Histosols ... 64
Family differentiae, mineral soil 49
Series differentiae within a famil 66

Discontinuities, designations
Duraqualfs

- 129,130
. 511,512
394,401
301,303


248

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Ustifluvents

KDCB. Other Ustifluvents that have anthraquic
conditions.

Anthraquic Ustifluvents
KDCC. Other Ustifluvents that have either:

1. In one or more horizons within 50 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage); or

2. In one or more horizons within 150 cm of the
mineral soil surface, a color value, moist, of 4 or
more and either a chroma of 0 or a hue of SGY,
5G, 5BG, or 5B, and also aquic conditions for
some time in most years (or artificial drainage).
Aquic Ustifluvents
KDCD. Other Ustifluvents that are saturated with
water, in one or more layers within 150 cm of the
mineral soil surface, for ] month or more per year in 6
or more out of 10 years.
Oxyaquic Ustifluvents

KDCE. Other Ustifluvents which, if neither irrigated

nor fallowed to store moisture, have one of the

following:
1. A frigid soil temperature regime, and a
moisture control section which, in 6 or more out of
10 years, is dry in all parts for four tenths or more
of the cumulative days per year when the soil
temperature at a depth of 50 om below the soil
surface is higher than 5°C; or

2. A mesic or thermic soil temperature regime,
and a moisture control section which, in 6 or more
out of 10 years, is dry in some part for six tenths
or more of the cumulative days per year when the
soil temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or
3. A hyperthermic, an isomesic, or a warmer iso
soil temperature regime, and a moisture control
section which, in 6 or more out of 10 years, is
moist in some or all parts for less than 180
cumulative days per year when the temperature at
a depth of 50 cm below the soil surface is higher
than 8°C.

Aridic Ustifluvents

KDCF. Other Ustifluvents which, if neither irrigated
nor fallowed to store moisture, have one of the
following:


308

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Eutrochrepts

JDGD, Other Eutrochrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm? or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Eutrochrepts

JDGE. Other Eutrochrepts that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:
1, More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or

2. A fine-earth fraction containing 30 percent or
more particles 0,02 to 2.0 mm in diameter, and
either:

a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or
b. In the 0,02-to-2.0-mm fraction, 5 percent
or more volcanic glass, and in the fine-earth
fraction, aluminum plus 1/2 iron
percentages (by ammonium oxalate) totaling
0.40 or more.

Vitrandic Eutrochrepts

JDGF. Other Eutrochrepts that have anthraquic
conditions.

Anthraquic Eutrochrepts
JDGG. Other Eutrochrepts that have:

1. In one or more horizons within 60 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and
2. Either 0.2 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and
3. A slope of less than 25 percent.

Fluvaquentic Eutrochrepts

JDGH. Other Eutrochrepts which:


435
Eutrustox

Key to subgroups

DCCA. Eutrustox that have, within 125 cm of the
mineral soil surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Aquic Petroferric Eutrustox
DCCB, Other Eutrustox that have a petroferric contact

within 125 cm of the mineral soil surface.
Petroferric Eutrustox

DCCC. Other Eutrustox that have, within 125 cm of the
mineral soil surface, both:

1. A lithic contact; and

2, Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Aquic Lithic Eutrustox
DCCD. Other Eutrustox that have a lithic contact within
125 cm of the mineral soil surface.
Lithic Eutrustox

DCCE. Other Eutrustox that have, in one or more
horizons within 125 cm of the mineral soil surface,
both:

1. Five percent or more (by volume) plinthite; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage). ,
Plinthaquic Eutrustox
DCCF. Other Eutrustox that have 5 percent or more (by
volume) plinthite in one or more horizons within 125
cm of the mineral soil surface.
Plinthic Eutrustox

DCCG. Other Eutrustox that have, in one or more
horizons within 125 cm of the mineral soil surface,
redox depletions with a color value, moist, of 4 or more
and a chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage).

Aquic Eutrustox

DCCH. Other Eutrustox that have both:

1. A clay content of 40 percent or more in the fine-
earth fraction between the soil surface and a depth
of 18 cm, after mixing; and


Chapter 1

The Soil That We Classify,
and
Buried Soils

THE SOIL THAT WE CLASSIFY

Soil is the collective term used in this text for the
natural bodies, made up of mineral and organic
materials, that cover much of the earth’s surface,
contain living matter and can support vegetation out of
doors, and have in places been changed by human
activity. The upper limit of soil is air or shallow water.
Its horizontal boundaries are where it grades to deep
water or to barren areas of rock or ice. The lower
boundary that separates soil from the not-soil
underneath is most difficult to define. Soil consists of
the horizons near the earth’s surface which, in contrast
to the underlying rock material, have been altered by the
interactions, over time, between climate, relief, parent
materials, and living organisms. In the few places where
it contains thin cemented horizons that are impermeable
to roots, soil is considered to be as deep as the deepest
cemented horizon. More commonly, soil grades at its
lower boundary to hard rock or to earthy materials
virtually devoid of animals, roots, or other marks of
biologic activity. Thus the lower limit of soil is normally
the lower limit of biologic activity, which generally
coincides with the common rooting depth of native
perennial plants. If, however, either 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. For certain soil management
purposes, layers deeper than the lower boundary of the
soil that we classify must also be described if they affect
the content and movement of water and air in the soil of
the root zone,

BURIED SOILS

A soil is considered to be a buried soil if it is covered
with a surface mantle of new soil material that is either
50 cm or more thick, or is 30 to 50 cm thick and has a
thickness that equals at least half the total thickness of
the named diagnostic horizons that are preserved in the
buried soil. A surface mantle of new material less than
30 cm thick is not considered in the taxonomy, but is
considered in establishing a phase if it affects the use of
the soil. In areas where a surface mantle is present, the
soil that we classify therefore has its upper boundary
either at the soil surface or less than 50 cm below the
surface, depending on the thickness of its horizons.

-On


Cryoboralfs

Key to subgroups
IBDA. Cryoboralfs that have both:

1. A lithic contact within 50 cm of the mineral soil
surface; and
2. A color value, moist, of 3 or less (crushed and
smoothed sample) either in an Ap horizon, or
between the soil surface and a depth of 15 cm,
Lithic Mollic Cryoboralfs
IBDB. Other Cryoboralfs that have a lithic contact
within 50 cm of the mineral soil surface.
Lithic Cryoboralfs

IBDC. Other Cryoboralfs which have one or both of the

following:
1. Cracks within 125 cm of the mineral soil
surface that are 5 mm or more wide through a
thickness of 30 cm or more for some time in most
years, and slickensides or wedge-shaped
aggregates in a layer 15 cm or more thick that has
its upper boundary within 125 cm of the mineral
soil surface; or

2. A linear extensibility of 6.0 cm or more
between the mineral soil surface and either a
depth of 100 cm or a lithic or paralithic contact,
whichever is shallower.

Vertic Cryoboralfs

IBDD. Other Cryoboralfs that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm? or less,
measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0.

Andic Cryoboralfs

IBDE. Other Cryoboralfs that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, one or both of
the following:
1. More than 35 percent (by volume) fragments
coarser than 2.0 mm, of which more than 66
percent are cinders, pumice, and pumice-like
fragments; or
2. A fine-earth fraction containing 30 percent or
more particles 0.02 to 2.0 mm in diameter, and
either:
a. In the 0.02-to-2.0-mm fraction, more than
30 percent volcanic glass; or


532



35

water is moving or because the environment is
unfavorable for micro-organisms (e.g., if the
temperature is less than 1°C); such a regime is not
considered aquic.

It is not known how long a soil must be saturated to
have an aquic moisture regime, but the duration must be
at least a few days, because it is implicit in the concept
that dissolved oxygen is virtually absent. Because
dissolved oxygen is removed from ground water by
respiration of micro-organisms, roots, and soil fauna, it
is also implicit in the concept that the soil temperature
is above biologic zero (5°C) for some time while the soil
is saturated.

Very commonly, the level of ground water fluctuates
with the seasons; it is highest in the rainy season, or in
fall, winter, or spring if cold weather virtually | stops
evapotranspiration. There are soils, however, in which
the ground water is always at or very close to the
surface. 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 terms aquic moisture regime and peraquic
are not used as either a criterion or a formative element
for taxa, they are used in taxon 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 is, in 6 or more out of 10 years,

1, Dry in all parts for more than half the cumulative
days per year when the soil temperature at a depth of 50
cm from the soil surface is above 5°C; and

2. Moist in some or all parts for less than 90
consecutive days when the soil temperature at a depth of
50 cm is above 8°C.

Soils that have an aridic or a torric moisture regime
normally occur 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 regimes, and soluble salts accumulate in the
soil if there is a source of them.

The limits set for soil temperature exclude from these
moisture regimes the very cold and dry polar regions
and high elevations. The data available on the soils of

12 Torridus is not a very satisfactory root, but a better one could not be
found, Soils that have a torric moisture regime are hot and dry in summer,
although they may not be hot throughout the year,


426

redox depletions with a color value, moist, of 4 or more
and a chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage).

Aquic Acrudox

DEBI. Other Acrudox that have a base saturation (by
NH,OAc) of 35 percent or more in all horizons within
125 cm of the mineral soil surface.

Eutric Acrudox

DEBJ. Other Acrudox that have both:

1, 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 2.5YR or redder
and color value, moist, of 3 or less between 25
and 125 cm from the mineral soil surface.

Humic Rhodic Acrudox

DEBK. Other Acrudox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 7.5YR or yellower
and color value, moist, of 6 or more between 25
and 125 cm from the mineral soil surface.

Humic Xanthic Acrudox

DEBL. Other Acrudox that have 16 kg/m? or more
organic carbon between the mineral soil surface and a
depth of 100 cm.

Humic Acrudox

DEBM. Other Acrudox that have 50 percent or more
hue of 2.5YR or redder and color value, moist, of 3 or
less between 25 and 125 cm from the mineral soil
surface.

Rhodic Acrudox

DEBN. Other Acrudox that have 50 percent or more hue
of 7.5YR or yellower and color value, moist, of 6 or
more between 25 and 125 cm from the mineral soil
surface.

Xanthic Acrudox
DEBO. Other Acrudox.
Typic Acrudox
Eutrudox
Key to subgroups

DECA. Eutrudox that have, within 125 cm of the
‘mineral soil surface, both:

1. A petroferric contact; and


387

HFGQ., Other Haplustolls that are saturated with water,
in one or more layers within 100 cm of the mineral soil
surface, for 1 month or more per year in 6 or more out of
10 years.

Oxyaquic Haplustolls

HFGR. Other Haplustolls which have:

1. If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for six tenths or more of the
cumulative days per year when the soil
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or
b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, remains moist in some or all parts for
less than 90 consecutive days per year when.
the temperature at a depth of 50 cm below
the soil surface is higher than 8°C; and
2. Either 0.3 percent or more organic carbon at a
depth of 125 cm below the mineral soil surface, or
an irregular decrease in organic-carbon content
from a depth of 25 cm to a depth of 125 cm, or to
a lithic or paralithic contact if shallower; and

3. A slope of less than 25 percent.
Torrifluventic Haplustolis

HFGS, Other Haplustolls which:

1. Have, if neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in

some part for six tenths or more of the M
cumulative days per year when the soil fe)
temperature at a depth of 50 cm below the L

soil surface is higher than 5°C; or

b. A hyperthermic, an isomesic, or a warmer
iso soil temperature regime, and a moisture
control section which, in 6 or more out of 10
years, remains moist in some or all parts for
less than 90 consecutive days per year when
the temperature at a depth of 50 cm below
the soil surface is higher than 8°C; and


157

2. In one or more horizons between 50 and 100 cm
either from the mineral soil surface, or from the
top of an organic layer with andic soil properties,
whichever is shallower, aquic conditions for some
time in most years (or artificial drainage) and one
or more of the following:

a, Two percent or more redox
concentrations; or

b. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
redox depletions on faces of peds, or in the
matrix if peds are absent; or

c. Enough active ferrous iron to give a
positive reaction to o.,a'-dipyridyl at a time
when the soil is not being irrigated.

Aquic Duric Hapludands

CGFE. Other Hapludands that have a horizon 15 em or
more thick, with 20 percent or more (by volume)
cemented soil material that does not slake in water after
air-drying, that has its upper boundary within 100 cm
either of the mineral soil surface, or of the top of an
organic layer with andic soil properties, whichever is
shallower.

Duric Hapludands

CGFF, Other Hapludands that have more than 2,0
cmol(+)/kg Al? (by IN KCl) in the fine-earth fraction
of one or more horizons with a total thickness of 10 cm
or more, between 25 and 50 cm either from the mineral
soil surface, or from the top of an organic layer with
andic soil properties, whichever is shallower,

Alic Hapludands

CGFG. Other Hapludands that have, in one or more
horizons between 50 and 100 cm either from the
mineral soil surface, or from the top of an organic layer
with andic soil properties, whichever is shallower, aquic
conditions for some time in most years (or artificial
drainage) and one or more of the following:

1. Two percent or more redox concentrations; or

2. A color value, moist, of 4 or more, and 50
percent or more chroma of 2 or less either in
redox depletions on faces of peds, or in the matrix
if peds are absent; or
3. Enough active ferrous iron to give a positive
reaction to .,a'-dipyridy] at a time when the soil
is not being irrigated.

Aquic Hapludands

CGFH, Other Hapludands that have both:

1. Extractable bases plus 1N-KCl-extractable A+
totaling less than 2.0 cmol(+)/kg in the fine-earth
fraction of one or more horizons with a total
thickness of 30 cm or more, between 25 and 100


124
ICCC. Other Natrustalfs that have both:

1. In one or more horizons within 75 cm of the
mineral soil surface, redox depletions with a
chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage);
and

2. A sandy particle size throughout a layer

extending from the mineral soil surface to the top

of an argillic horizon at a depth of 50 to 100 cm.
Aquic Arenic Natrustalfs

ICCD. Other Natrustalfs that have, in one or more
horizons within 75 om of the mineral soil surface, redox
depletions with a chroma of 2 or less, and also aquic
conditions for some time in most years (or artificial
drainage).

Aquic Natrustalfs
ICCE. Other Natrustalfs that have a sandy particle size
throughout a layer extending from the mineral soil
surface to the top of an argillic horizon at a depth of 50
to 100 cm.

Arenic Natrustalfs

ICCF, Other Natrustalfs which have a petrocalcic
horizon that has its upper boundary within 150 cm of
the mineral soil surface.

Petrocalcic Natrustalfs

ICCG, Other Natrustalfs which have a salic horizon that
has its upper boundary within 75 cm of the mineral soil
surface.

Salorthidic Natrustalfs
ICCH. Other Natrustalfs that have an Ap horizon with a
color value, moist, of 3 or less and a color value, dry, of

5 or less (crushed and smoothed sample), or materials
between the soil surface and a depth of 18 cm which

have these color-values after mixing.

Mollic Natrustalfs
ICCI. Other Natrustalfs.

Typic Natrustalfs
Paleustalfs
Key to subgroups

ICFA. Paleustalfs which have both:

1. If neither irrigated nor fallowed to store
moisture, either:

a. A mesic or thermic soil temperature
regime, and a moisture control section
which, in 6 or more out of 10 years, is dry in
some part for four tenths or less of the
curnulative days per year when the
temperature at a depth of 50 cm below the
soil surface is higher than 5°C; or


Sulfihemists

Key to subgroups

ACBA. Sulfihemists which have a mineral layer 30 cm
or more thick that has its upper boundary within the
control section below the surface tier.

Terric Sulfihemists
ACBB. Other Sulfihemists.

Typic Sulfihemists
Sulfohemists
Key to subgroups
ACAA. All Sulfohemists (provisionally),

Typic Sulfohemists
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 Tropohemists which have both:

1, One or more layers, with a total thickness of 25
cm or more, of the subsurface and bottom tiers
consisting of fibric materials, and

2. A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Fibric Terric Tropohemists

ACFD. Other Tropohemists which have both:

1. One or more layers, with a total thickness of
12.5 cm or more, of the subsurface and bottom
tiers consisting of sapric materials; and

2. A mineral layer 30 cm or more thick that has its
upper boundary within the control section below
the surface tier.

Sapric Terric Tropohemists

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

Terric Tropohemists

ACFF. Other Tropohemists that have one or more
limnic layers with a total thickness of $ cm or more
within the control section.

Limnic Tropohemists



UDALFS

Key to great groups
IBA. Udalfs that have an agric horizon.
Agrudalfs, p. 100

IEB. Other Udalfs that have a natric horizon.
Natrudalfs, p. 112

TEC. Other Udalfs which have:
1, A discontinuous albic horizon, or none, above
the argillic horizon; and
2. An argillic horizon that is discontinuous
horizontally; and
3. In the argillic horizon, discrete nodules 2.5 cm
to 30 cm in diameter with exteriors that (a) are
enriched and cither weakly cemented or indurated.
with iron, and (b) have either a redder hue or a
higher chroma than the interiors.

Ferrudalfs, p. 101

IED. Other Udalfs that have a glossic horizon and a
fragipan.

mc D>

Fraglossudalfs, p. 103

TEE. Other Udalfs that have a glossic horizon.
Glossudalfs, p. 103

IEF, Other Udalfs that have a fragipan.
Fragiudalfs, p. 101

IEG. Other Udalfs which:

1, Do not have a lithic, paralithic, or petroferric
contact within 150 cm of the mineral soil surface;
and

2. Have a CEC of 16 cmol(+)/kg clay or less (by
1N NH,OAc pH 7) and an ECEC of 12 cmol(+)/kg
clay or less (sum of bases extracted with IN
NH,OAc pH 7, plus 1N-KCl-extractable Al) in 50
percent or more either of the argillic or kandic
horizon if tess than 100 cm thick, or of its upper
100 cm; and

3. Within 150 cm of the mineral soil surface,
either

a. Do not have a clay decrease with
increasing depth of 20 percent or more
(relative) from the maximum clay content;
or

b. Have 5 percent or more (by volume)
skeletans on faces of peds in the layer that
has a 20 percent lower clay content and,
below that layer, a clay increase of 3 percent
or more (absolute) in the fine-earth fraction.
Kandiudalfs, p. 110


eB

excess water. 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. Ice wedges and lenses are normal
in such soils in the United States.

Cryic (Gr. kryos, coldness; meaning very cold
soils).—Soils in this temperature regime have a mean
annual temperature higher than 0°C but lower than 8°C.
1, In mineral soils, the mean summer soil temperature
(June, July, and August in the northern hemisphere and
December, January, and February in the southern
hemisphere) either at a depth of 50 cm from the soil
surface or at a lithic or paralithic contact, whichever is
shallower, is as follows:

a. If the soil is not saturated with water during
some part of the summer and

(1) If there is no O horizon: lower than
15°C; or

(2) If there is an O horizon: lower than 8°C;
or

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

(1) If there is no O horizon: lower than
13°C; or

(2) If there is an O horizon or a histic
epipedon: lower than 6°C.
2. In organic soils, the soil is either:
a, Frozen in some layer within the control section
in most years 2 months after the summer solstice;
i.e, the soil is very cold in winter but warms up
slightly in summer; or
b. Not frozen in most years below a depth of 5S cm
from the soil surface; i.e., the soil is cold
throughout the year but, because of marine
influence, does not freeze in most years.

Cryic soils that have an aquic moisture regime
commonly are churned by frost. All isofrigid (see
below) soils without permafrost are considered to have a
cryic temperature regime.

Frigid.—The concept of the frigid soil temperature
regime and of other soil temperature regimes listed
below are used chiefly in defining classes of soils in the
low categories. A soil with a frigid regime is warmer in
summer than a soil with a cryic regime, but its mean
annual temperature is lower than 8°C, and the
difference between mean summer and mean winter soil
temperatures (June-July-August and December-January-
February) is more than 5°C either at a depth of 50 cm
from the soil surface or at a lithic or paralithic contact,
whichever is shallower.


420

DDEC. Other Haploperox that have, within 125 cm of
the mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).
Aquic Lithic Haploperox
DDED. Other Haploperox that have a lithic contact
within 125 cm of the mineral soil surface.
Lithic Haploperox

DDEE. Other Haploperox that have, in one or more
horizons within 125 cm of the mineral soil surface,
both:

1. Five percent or more (by volume) plinthite; and

2. Redox depletions with a color value, moist, of 4
or more and a chroma of 2 or less, and also aquic
conditions for some time in most years (or
artificial drainage).

Plinthaquic Haploperox

DDEF. Other Haploperox that have 5 percent or more
(by volume) plinthite in one or more horizons within
125 cm of the mineral soil surface.

Plinthic Haploperox

DDEG. Other Haploperox that have, in one or more
horizons within 125 cm of the mineral soil surface,
redox depletions with a color value, moist, of 4 or more
and a chroma of 2 or less, and also aquic conditions for
some time in most years (or artificial drainage),

Aquic Haploperox

DDEH. Other Haploperox that have, throughout one or
more horizons with a total thickness of 18 cm or more
within 75 cm of the mineral soil surface, a fine-earth
fraction with both a bulk density of 1.0 g/cm or less,
‘measured at 33 kPa water retention, and aluminum plus
1/2 iron percentages (by ammonium oxalate) totaling
more than 1.0,

Andic Haploperox

DDEI. Other Haploperox that have both:

1. 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and

2. Fifty percent or more hue of 2.5YR or redder
and color value, moist, of 3 or less between 25
and 125 cm from the mineral soil surface,

Humic Rhodic Haploperox

DDEJ. Other Haploperox that have both:

1, 16 kg/m? or more organic carbon between the
mineral soil surface and a depth of 100 cm; and