Soil Judging Manual
Fall Semester, 2003
Table of Contents
A. Morphology
Horizonation
Horizon Boundary
Texture
Color
Structure
Moist Consistence
Redoximorphic Features
Page Number
2
2
5
9
12
13
15
15
B. Soil Profile Characteristics
Hydraulic Conductivity
Effective Rooting Depth
Water Retention to 1 m
Soil Drainage Class
16
16
17
18
19
C. Site Characteristics
Landform
Parent Material
Slope
Slope Profile
Surface Runoff
20
20
20
21
21
23
D. Soil Classification
Epipedon
Diagnostic Subsurface Horizons and Features
Orders, Suborders, and Great Groups
Family Particle-Size Control Section and Class
24
24
28
33
40
E. Site Interpretations
Appendix - Abbreviations
List of Great Groups
43
47
48
A. Morphology
Horizonation
soil horizon - A layer of soil or soil material approximately parallel to the land surface and
differing from adjacent genetically related layers in physical, chemical, and biological
properties or characteristics such as color, structure,texture, consistency, kinds and number of
organisms present, degree of acidity or alkalinity, etc.
Prefix:
None (dashed) - standard, soil is of same parent material throughout
2, 3, 4, ...
- lithologic discontinuity in parent materials, dramatic change
in color, texture, or rock fragments indicating contrasting
parent materials
Master:
O - organic surface layers
A - mineral surface layers. The surface horizon of a mineral soil having
maximum organic matter accumulation, maximum biological activity,
and/or eluviation of materials such as iron and aluminum oxides and
silicate clays
E - eluviated, stripped or bleached horizon, having less clay content and a
lighter color than horizons above and below.
B - illuviated, accumulation or enrichments or clay, organic matter, or iron
and aluminum oxides and/or blocky or prismatic structure.
C - unconsolidated material underlying the A and B horizons, relatively
unaffected by soil forming processes
R - hard bedrock (not diggable)
2
Subordinate:
(O)
i - slightly decomposed organic matter (fibric)
e - moderately decomposed organic matter (hemic)
a - highly decomposed organic matter (sapric)
(A)
dashed - wavy, uneven boundary, found in uncultivated areas
p- plowed, having a smooth, flat boundary
(E)
dashed - common
g - gleyed, matrix color with chroma of 2 or less, frequently found directly
above a limiting horizon that perches water
(B)
* All B horizons must have a subordinate horizon (i.e. no dashes)
Primary:
t - illuvial accumulation of clay. Illuvial means that the clay moved into the horizon.
h - humus accumulation (black colors)
s - iron accumulation (red colors) – usually for Spodosols
hs - iron and humus accumulation, value and chroma of 3 or less – usually for
Spodosols
Secondary:
x - fragipan - see below
g - gleyed, matrix color with chroma of 2 or less (can be used alone or
following t, x, or tx)
Tertiary:
w - "weak B" - other B horizons that don't have any of above characteristics
(C)
dashed - common
g - gleyed, matrix color with chroma of 2 or less
r - "rotten rock" - slightly weathered or soft bedrock (saprolite)
(R)
dashed
3
Note: b - buried horizon - can be used with any of the above master-subordinate
horizons
' - Bisequal soils - A prime (') is used for the second of two horizons with the
same master-subordinate name that are separated by a different horizon
(rare)
Fragipans
Fragipans are dense, brittle horizons that restrict water and root penetration. The following
properties are generally found in fragipans in Pennsylvania (from Ciolkosz et al., 1995):
 Low organic matter content
 Loamy texture (without high clay or sand content)
 Firm or very firm, brittle consistence (moist state)
 High bulk density
 Low permeability
 Distinctive dark brown color that contrasts with the color of the cambic or argillic
horizon above it (this feature often not observed in red parent materials)
They usually have:
 Prism faces gray in color with a bright yellowish brown zone just inside the gray zone.
4
Horizon Number
Use numbers to distinguish between consecutive horizons with identical master-subordinate
names. Note, the prefix may differ. For example:
Ap
Oi
E
A
Bt1
Bt
Bt2
Btg1
2Bt3
Btg2
Boundary
Depth - the lower depth of the horizon described
Distinctness:
a - abrupt, < 2 cm
c - clear, 2 - 5 cm
g - gradual, 5 - 15 cm
d - diffuse, > 15 cm (generally not used except in tropics - use a transitional
horizon instead)
FOR ORGANIC HORIZONS, ONLY THE BOUNDARY AND COLOR ARE
MEASURED, EVERYTHING ELSE IS DASHED.
Rock Fragment Modifier
Flattened
ch - channery (0.2 - 15 cm)
fl - flaggy (15 - 38 cm)
st - stony (38 - 60 cm)
bd - bouldery (> 60 cm)
< 15%
15 - 35%
35 - 60%
60 - 90%
SIZE AND SHAPE
Not flattened
g - gravelly ( 0.2 - 7.5 cm)
cb - cobbly (7.5 - 25 cm)
st - stony (25 - 60 cm)
bd - bouldery (> 60 cm)
ABUNDANCE
- no modifier
(dashed)
- use size and shape modifier only (e.g., g or gravelly)
- very, (abbreviation is "v")
(e.g., vg or very gravelly)
- extremely, (abbreviation is "e")
(e.g., eg or extremely gravelly)
5
Soil texture - The relative proportions of the various soil separates in a soil as described by
the classes of soil texture. The textural classes may be modified by the addition of suitable
adjectives when rock fragments are present in substantial amounts; for example, "stony silt
loam." The sand, loamy sand, and sandy loam are further subdivided on the basis of the
proportions of the various sand separates present.
Class
sic - silty clay
scl - sandy clay loam
sc - sandy clay (very rare)
c - clay
ls - loamy sand - requires sand modifier
s - sand - requires sand modifier
l - loam
cl - clay loam
si - silt
sil - silt loam
sicl - silty clay loam
sl - sandy loam - requires sand modifier
Modifiers for loamy sand, sandy loam, and sand classes:
c - coarse - dominated by very coarse and coarse sand
none - medium - dominated by medium sand
f - fine sand - dominated by fine sand
vf - very fine sand - dominated by very fine sand
examples: vfs, fsl, lcs, lvfs, sl
sand classes:
very coarse sand
2 - 1 mm diameter
coarse sand
medium sand
fine sand
very fine sand
1 - 0.5 mm
0.5 - 0.25 mm
0.25 - 0.1 mm
0.10 - 0.05 mm
Clay Percentage - determined by texturing
9
TEXTURING
Texturing is perhaps the most important skill used in soil investigations. The soil
texture helps determine horizon designation and depths. Soil hydraulic conductivity and root
penetration are most affected by the texture of the underlying soil. While soil texture can be
determined in a laboratory, a soil scientist, who may investigate tens of sites in a day,
textures soil in the field.
There is no one way to texture soil. Many soil scientists texture many different ways.
Enclosed is several different methods for determining texture. Each method has its own
merits; some techniques may work for you and some may not. During the course of this
class, you will probably develop texturing techniques that are unique to you only; that is all
right, as long as it works. A professional soil scientist becomes proficient at texturing
because of repetition; comparing the relative differences between the unknown sample and
known samples that the soil scientist previously textured. It takes time and experience to
become proficient at texturing.
Here are a couple of clues:
1. Always texture with your non-writing hand - if you don't, you'll smudge your
description sheet.
2. Grittiness and/or crunching - presence of sand in the texture
3. Flour-like particles and ruffles in texture - presence of silt
4. Texture takes a long time to moisten and is extremely sticky when moist presence of clay
11
Color - found by using Soil Color Charts Book
Hue - A measure of the chromatic composition of light that reaches the eye. Page of
color book, Y = yellow, R = red, pages range from red to olive green
Value - The degree of lightness or darkness of a color in relation to a neutral gray
scale. On a neutral gray scale, value extends from pure black to pure white.
Numbers read vertically on each page; the higher the number, the lighter the
color.
Chroma - The relative purity, strength, or saturation of a color. For those that like a
technical definition: directly related to the dominance of the determining
wavelength of the light and inversely related to grayness. Or, in simpler
terms, chroma measures the amount of pigment (as opposed to white and
black) in a color. A flourescent color has a very high chroma, a black and
white TV show has zero chroma. Numbers read horizontally on each page;
the higher the number, the brighter the color.
Example: 5 YR 4/6 - hue is 5 YR, value is 4, chroma is 6.
Reading soil color:
- Colors for A horizons are read from a crushed, but not smeared, sample.
- Colors for other horizons are read from the moist interior of a broken ped face.
- Whenever possible, read colors in direct sunlight, preferably with the sun to your
back.
- Many colors are actually between chips or pages in the color book. This doesn't
mean that you are not coloring well, this is reality. Use the closest color possible.
12
Structure
soil structure - The combination or arrangement of primary soil particles into secondary
units or peds. The secondary units are characterized on the basis of size, shape, and grade
(degree of distinctness)
Grade
A grouping or classification of soil structure on the basis of inter- and intraaggregate adhesion, cohesion, or stability
Structureless (0) - no discrete units observable in place or in hand sample (usually in
Weak (1)
Moderate (2)
Strong (3)
C horizons).
- units are barely observable in place or in a hand sample.
- units well-formed and evident in place or in a hand sample.
Usually need to be in the pit to see.
- units are distinct in place (undisturbed soil), and separate cleanly
when disturbed. Usually can see from outside of the pit.
Shape
For grade structureless:
massive (m)
single grained (sg)
- no structural units, material is a coherent mass (not
necessarily cemented. Soil falls out in chunks as they are
dug out with a knife (usually found in C horizons)
- no structural units, entirely noncoherent; e.g., loose sand.
For other grades (also see diagram on following page):
granular (gr)
- small polyhedrals, with curved or very irregular faces
(common in A horizons, rare in subsurface horizons).
angular blocky (abk)
- blocks with faces that intersect at sharp angles, usually
found in textures with high clay content (most often in B
horizons)
subangular blocky (sbk) - blocks with sub-rounded and planar faces, lack sharp
angles.
prismatic (pr)
- vertically elongated units with flat tops
platy (pl)
- thin, horizontally bedded plates (found in E horizons,
fragipans, and compacted A horizons)
13
Moist Consistence
loose (l)
- intact specimen not obtainable
very friable (vfr) - specimen fails under very slight force between fingers.
friable (fr)
- specimen fails under slight force between fingers.
firm (fi)
- specimen fails under moderate force between fingers.
very firm (vfi)
- specimen fails under strong force between fingers.
extremely firm (efi) - specimen fails under moderate force between hands.
Consistence generally gets firmer with increasing clay content and changing structure from
weak to strong.
Redoximorphic Features (old term was mottles)
redoximorphic features - Soil properties associated with wetness that result from the
reduction and oxidation of iron and manganese compounds in the soil after saturation with
water and desaturation, respectively
redox depletions - Zones of low chroma (2 or less) where Fe-Mn oxides alone or both FeMn oxides and clay have been stripped out of the soil.
redox concentrations - Zones of apparent accumulation of Fe-Mn oxides in soils (bright
colors)
Abundance (see diagram on following pages for visuals of 2 and 20%)
None (dashed)
- no redoximorphic features
Few (f)
- < 2% of soil matrix
Common (c)
- 2 - 20% of soil matrix
Many (m)
- > 20% of soil matrix
Contrast (see table and chart on following pages for more exact measures)
Faint (f)
- generally can only be seen upon close examination
Distinct (d)
- generally can be seen while standing in the pit
Prominent (p)
- generally can be seen from outside of the pit
15
B. Soil Profile Characteristics
Hydraulic Conductivity - an expression of the readiness with which water flows through a
soil in response to a given potential gradient
In the field, saturated HC (Ksat) is estimated from texture, organic matter content,
structure, and consistence:
High (> 3.6 cm/hr)
organic materials
s, ls textures
sl, l textures that are loose because of high organic matter content
fragmental soils: large volume of coarse fragments with insufficient fines
Medium (.036 - 3.6 cm/hr)
materials excluded from high and low classes
Low (< .036 cm/hr)
c, sc, sic textures with moderate (2) or weaker structure
sicl textures with weak structure
fragipans (Bx, Bxg, Btx, Btxg horizons)
dense glacial till (Cd horizons)
hard bedrock (R)
horizontally bedded soft bedrock with few vertical fractures (Cr horizons)
Surface
The surface hydraulic conductivity is based on the first described horizon.
Limiting Layer
The limiting layer is the least conductive layer in the soil profile. Note: the surface
may be the limiting layer. In this area, there often is a fragipan or heavy clay layer in the
subsoil which is more limiting.
16
Effective Soil Depth (Rooting Depth)
Limitations
hard or soft bedrock (R or Cr horizons) fragipans (Bx, Bxg, Btx, Btxg horizons) c, sc,
sic textures with massive structure textures with high amounts of sands and coarse
fragments and insufficient fines
Classes
Deep
100 - 150 cm
Moderately Deep
Shallow
Very Shallow
50 - 100 cm
25 - 50 cm
< 25 cm
17
Water Retention to 1 m
Water Retention to 1 m is the amount of water held between .033 MPa (Field Capacity) and
1.5 MPa (Wilting Point) in the top 100 cm of soil or to a bedrock layer, whichever is
shallower.
Texture- water retention relationship
Texture
sand (s)
cm water/ cm soil
.04
organic materials
loamy sand (ls)
sl, scl, cl, sc, sic, c
sicl, l
sil
.05
.08
.14
.17
.20
*For a coarse or very coarse sand modifier, decrease water content by one class; for a fine or
very fine modifier, increase water content by one class
For fragipans or dense glacial till, reduce water retention values by 1/2 for all horizons from
the top of the fragipan or dense till to 100 cm or bedrock layer.
EQUATION: (horizon depth) x (texture water content value) x (1- % coarse fragments)
Classes
Very Low
Low
Medium
< 5 cm
5 - 10 cm
10 - 15 cm
High
> 15 cm
18
Soil Drainage Class
- a reflection of the frequency and duration of wet periods in the soil. Drainage class
is influenced by landscape position, slope, surface runoff, and hydraulic conductivity.
Drainage class determination is variable from state to state.
Somewhat excessively drained (SED)
water is removed rapidly; high hydraulic conductivity, low water
retention difference, no redox features; sandy or gravelly textures
throughout
Well drained (WD)
water is removed readily, but not rapidly; no redox features
in A or B horizons, or to a depth of 100 cm
Moderately well drained (MWD)
soil is wet for a small period of time; redox features in lower
B or in C horizons
Somewhat poorly drained (SPD)
soil is wet for significant periods; redox features in upper B
horizon
Poorly drained (PD)
soil is wet for a large part of time; thin dark gray or
black surface horizon, all subsurface horizons have a
light gray matrix color (chroma 2 or less, value 4 or
more), usually prominent red redox features below A horizon
Very poorly drained (VPD)
soil is wet most of the time and is frequently ponded;
surface is thick and black with high organic matter
content, often a solid gray matrix below the A horizon
with no iron accumulations
Another way to differentiate between drainage classes:
-No redox features within 100 cm
-Redox features between 50 and 100 cm
-Redox features above 50 cm
-All subsurface horizons have a light gray matrix color
(chroma 2 or less, value 4 or more)
19
- WD
- MWD
- SWPD
- PD
C. Site Characteristics
LANDFORM
Upland - Default landform
Depression - Landform that has no visible or external drainage
Stream terrace - Old stream floodplain. No longer flooded during a 100 year flood.
Floodplain - Landform near stream that is flooded during a 100 year flood.
PARENT MATERIAL
Residuum - soil material is weathered from the underlying rock, rocks in soil profile
will be oriented parallel to the bedding of the bedrock (horizontal), found on uplands
Colluvium - material that moved downslope due to gravity, rocks of all shapes and
sizes are oriented at different angles throughout the profile, found on lower backslope and
footslope positions
Loess - material that is transported and deposited by wind, silty textures with few or
no rock fragments are typical, found on many upland landforms
Glacial Till - unsorted material deposited by glacial ice, soil particles and rocks of all
shapes and sizes are oriented at different angles throughout the profile, extremely variable in
composition
Glacial Outwash - well sorted material deposited by water from a melting glacier,
rounded gravels and sands are present throughout the profile, found on many landforms
20
Lacustrine - material deposited by lakes (slow moving water), silty and clayey
textures with few or no rock fragments are typical, found on many landforms
Old Alluvium - sediments transported and deposited by streams (fast moving water)
in the past, silty to sandy textures throughout the profile are common, occur on stream
terraces
Recent Alluvium - sediments transported and deposited by streams recently, silty to
sandy surface textures with stratified sands and gravels down the profile are common, often a
buried surface horizon is present toward the bottom of the profile, occur on floodplains
SLOPE
Slope - also called "slope gradient" - the angle of the ground surface (in percent)
through the site and in the direction that overland water would flow (e.g., 18%).
SLOPE PROFILE
Also see diagrams on following pages
Summit - a topographic high such as a hill or ridge top. Has relatively constant, flat
slope.
Shoulder - A slope adjacent to the summit that is convexly rounded toward a
drainageway. Tends to be the area of maximum erosion.
Backslope - A mostly linear surface that extends downward from a summit or
shoulder position.
Footslope - A concave slope segment near the base of a hillslope. Tends to the area
of maximum deposition.
None - Slopes less than 2% and where none of the above slope elements can be
distinguished. Includes toeslope positions, broad flat interfluves, and broad flat terraces.
21
SOILS 100 - SOIL CLASSIFICATION
Diagnostic horizons - Combinations of specific soil characteristics that are indicative of
certain classes of soils. Those which occur at the soil surface are called epipedons, those
below the surface, diagnostic subsurface horizons.
Epipedon - Surface layer, may include O, A, or B horizons
*Its depth usually stops at the B horizon
Note: Underlined material is supplemental information from soil taxonomy.
Mollic



The "A" horizon is 3/3 or darker moist and 5/3 or darker dry
Base saturation > 50%
Organic carbon is > .6%
Must be
 > 10 cm if directly over lithic or paralithic contact
 > 18 cm is there is no argillic subsurface horizon
 > 25cm if there is an argillic subsurface horizon
The mollic epipedon consists of mineral soil materials and has the following properties:
1. When dry, either or both:
a. Structural units with a diameter of 30 cm or less or secondary structure with a
diameter of 30 cm or less; or
b. A moderately hard or softer rupture-resistance class; and
2. Rock structure, including fine (less than 5 mm) stratifications, in less than one-half of the
volume of all parts; and
3. One of the following:
a. All of the following:
(1) Colors with a value of 3 or less, moist, and of 5 or less, dry; and
(2) Colors with chroma of 3 or less, moist; and
(3) If the soil has a C horizon, the mollic epipedon has a color value at least 1
Munsell unit lower or chroma at least 2 units lower (both moist and dry) than
that of the C horizon or the epipedon has at least 0.6 percent more organic
carbon than the C horizon; or
b. A fine-earth fraction that has a calcium carbonate equivalent of 15 to 40 percent
and colors with a value and chroma of 3 or less, moist; or
24
c. A fine-earth fraction that has a calcium carbonate equivalent of 40 percent or more
and a color value, moist, of 5 or less; and
4. A base saturation (by NH4OAc) of 50 percent or more; and
5. An organic-carbon content of:
a. 2.5 percent or more if the epipedon has a color value, moist, of 4 or 5; or
b. 0.6 percent more than that of the C horizon (if one occurs) if the mollic epipedon
has a color value less than 1 Munsell unit lower or chroma less than 2 units lower
(both moist and dry) than the C horizon; or
c. 0.6 percent or more; and
6. After mixing of the upper 18 cm of the mineral soil or of the whole mineral soil if its depth
to a densic, lithic, or paralithic contact, petrocalcic horizon, or duripan (all defined below) is
less than 18 cm, the minimum thickness of the epipedon is as follows:
a. 10 cm or the depth of the noncemented soil if the epipedon is loamy very fine sand
or finer and is directly above a densic, lithic, or paralithic contact, a petrocalcic
horizon, or a duripan that is within 18 cm of the mineral soil surface; or
b. 25 cm or more if the epipedon is loamy fine sand or coarser throughout or if there
are no underlying diagnostic horizons (defined below) and the organic-carbon content
of the underlying materials decreases irregularly with increasing depth; or
c. 25 cm or more if all of the following are 75 cm or more below the mineral soil
surface:
(1) The upper boundary of any pedogenic lime that is present as filaments,
soft coatings, or soft nodules; and
(2) The lower boundary of any argillic, cambic, natric, oxic, or spodic horizon
(defined below); and
(3) The upper boundary of any petrocalcic horizon, duripan, or fragipan; or
d. 18 cm if the epipedon is loamy very fine sand or finer in some part and one-third or
more of the total thickness between the top of the epipedon and the shallowest of any
features listed in item 6-c is less than 75 cm below the mineral soil surface; or
e. 18 cm or more if none of the above conditions apply; and
7. Phosphate:
a. Content less than 1,500 milligrams per kilogram soluble in 1 percent citric acid; or
25
b. Content decreasing irregularly with increasing depth below the epipedon; or
c. Nodules are within the epipedon; and
8. Some part of the epipedon is moist for 90 days or more (cumulative) in normal years
during times when the soil temperature at a depth of 50 cm is 5 oC or higher, if the soil is
not irrigated; and
9. The n value (defined below) is less than 0.7.
Umbric- Same as mollic, but base saturation is < 50%.
The umbric epipedon consists of mineral soil materials and has the following properties:
1. When dry, either or both:
a. Structural units with a diameter of 30 cm or less or secondary structure with
a diameter of 30 cm or less; or
b. A moderately hard or softer rupture-resistance class; and
2. All of the following:
a. Colors with a value of 3 or less, moist, and of 5 or less, dry; and
b. Colors with chroma of 3 or less, moist; and
c. If the soil has a C horizon, the umbric epipedon has a color value at least 1 Munsell
unit lower or chroma at least 2 units lower (both moist and dry) than that of the C
horizon or the epipedon has at least 0.6 percent more organic carbon than that of the
C horizon; and
3. A base saturation (by NH4OAc) of less than 50 percent in some or all parts; and
4. An organic-carbon content of:
a. 0.6 percent more than that of the C horizon (if one occurs) if the umbric epipedon
has a color value less than 1 Munsell unit lower or chroma less than 2 units lower
(both moist and dry) than the C horizon; or
b. 0.6 percent or more; and
5. After mixing of the upper 18 cm of the mineral soil or of the whole mineral soil if its depth
to a densic, lithic, or paralithic contact or a duripan (all defined below) is less than 18 cm, the
minimum thickness of the epipedon is as follows:
a. 10 cm or the depth of the noncemented soil if the epipedon is loamy very fine sand
or finer and is directly above a densic, lithic, or paralithic contact or a duripan that is
within 18 cm of the mineral soil surface; or
26
b. 25 cm or more if the epipedon is loamy fine sand or coarser throughout or if there
are no underlying diagnostic horizons (defined below) and the organic-carbon content
of the underlying materials decreases irregularly with increasing depth; or
c. 25 cm or more if the lower boundary of any argillic, cambic, natric, oxic, or spodic
horizon (defined below) is 75 cm or more below the mineral soil surface; or
d. 18 cm if the epipedon is loamy very fine sand or finer in some part and one-third or
more of the total thickness between the top of the epipedon and the shallowest of any
features listed in item 5-c is less than 75 cm below the mineral soil surface; or
e. 18 cm or more if none of the above conditions apply; and
6. Phosphate:
a. Content less than 1,500 milligrams per kilogram soluble in 1 percent citric acid; or
b. Content decreasing irregularly with increasing depth below the epipedon; or
c. Nodules are within the epipedon; and
7. Some part of the epipedon is moist for 90 days or more (cumulative) in normal years
during times when the soil temperature at a depth of 50 cm is 5 oC or higher, if the soil is
not irrigated; and
8. The n value (defined below) is less than 0.7; and
9. The umbric epipedon does not have the artifacts, spade marks, and raised surfaces that are
characteristic of the plaggen epipedon.
Ochric- All other epipedons.
The ochric epipedon fails to meet the definitions for any of the other seven epipedons
because it is too thin or too dry, has too high a color value or chroma, contains too little
organic carbon, has too high an n value or melanic index, or is both massive and hard or
harder when dry . Many ochric epipedons have either a Munsell color value of 4 or more,
moist, and 6 or more, dry, or chroma of 4 or more, or they include an A or Ap horizon that
has both low color values and low chroma but is too thin to be recognized as a mollic or
umbric epipedon (and has less than 15 percent calcium carbonate equivalent in the fine-earth
fraction). Ochric epipedons also include horizons of organic materials that are too thin to
meet the requirements for a histic or folistic epipedon.
The ochric epipedon includes eluvial horizons that are at or near the soil surface, and it
extends to the first underlying diagnostic illuvial horizon (defined below as an argillic,
27
kandic, natric, or spodic horizon). If the underlying horizon is a B horizon of alteration
(defined below as a cambic or oxic horizon) and there is no surface horizon that is
appreciably darkened by humus, the lower limit of the ochric epipedon is the lower boundary
of the plow layer or an equivalent depth (18 cm) in a soil that has not been plowed. Actually,
the same horizon in an unplowed soil may be both part of the epipedon and part of the
cambic horizon; the ochric epipedon and the subsurface diagnostic horizons are not all
mutually exclusive. The ochric epipedon does not have rock structure and does not include
finely stratified fresh sediments, nor can it be an Ap horizon directly overlying such deposits.
Diagnostic Subsurface Horizons & Features - Subsoil, may include E, B, or C horizons.
In a soil profile, there may be more than one.
Albic- Below "A" or "O" horizons (always an E horizon), usually above argillic, cambic,
spodic, or fragipan. Usually lighter in color and "stripped" and lower in clay and iron content
than horizons above and below. For moist colors, a value of 4 or 5, chroma is 2 or less, for
value of 6 or 7, chroma is 3 or less. Has to be > 1 inch (2.5 cm) thick.
The albic horizon is an eluvial horizon, 1.0 cm or more thick, that has 85 percent or more (by
volume) albic materials (defined below). It generally occurs below an A horizon but may be
at the mineral soil surface. Under the albic horizon there generally is an argillic, cambic,
kandic, natric, or spodic horizon or a fragipan (defined below). The albic horizon may lie
between a spodic horizon and either a fragipan or an argillic horizon, or it may be between an
argillic or kandic horizon and a fragipan. It may lie between a mollic epipedon and an argillic
or natric horizon or between a cambic horizon and an argillic, kandic, or natric horizon or a
fragipan. The albic horizon may separate horizons that, if they were together, would meet the
requirements for a mollic epipedon. It may separate lamellae that together meet the
requirements for an argillic horizon. These lamellae are not considered to be part of the albic
horizon.
Argillic- Accumulation of clay. If clay content is < 15% in A and/or E horizons, argillic must
be 3% higher in total clay for underlying horizon. If overlying horizon is 15-40% in clay,
then argillic must be 20% higher in relative clay percentage (e.g., 24% versus 20%). If
overlying horizon is 40-60% in clay, argillic must be 8% higher in total clay percentage (e.g.,
50% versus 42%). In other words the amount of clay must be 20% higher. However, if 20%
is less than 3 or greater than 8% clay, use the 3 or 8%. (Most always a Bt)
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An argillic horizon is normally a subsurface horizon with a significantly higher percentage of
phyllosilicate clay than the overlying soil material. It shows evidence of clay illuviation. The
argillic horizon forms below the soil surface, but it may be exposed at the surface later by
erosion.
Required Characteristics
1. All argillic horizons must meet both of the following requirements:
a. One of the following:
(1) If the argillic horizon is coarse-loamy, fine-loamy, coarse-silty, fine-silty,
fine, or very-fine or is loamy or clayey, including skeletal counterparts, it
must be at least 7.5 cm thick or at least one-tenth as thick as the sum of the
thickness of all overlying horizons, whichever is greater; (deleted text) or
(2) If the argillic horizon is sandy or sandy-skeletal, it must be at least 15 cm
thick; or
(3) If the argillic horizon is composed entirely of lamellae, the combined
thickness of the lamellae that are 0.5 cm or more thick must be 15 cm or
more; and
b. Evidence of clay illuviation in at least one of the following forms:
(1) Oriented clay bridging the sand grains; or
(2) Clay films lining pores; or
(3) Clay films on both vertical and horizontal surfaces of peds; or
(4) Thin sections with oriented clay bodies that are more than 1 percent of the
section; or
(5) If the coefficient of linear extensibility is 0.04 or higher and the soil has
distinct wet and dry seasons, then the ratio of fine clay to total clay in the
illuvial horizon is greater by 1.2 times or more than the ratio in the eluvial
horizon; and
2. If an eluvial horizon remains and there is no lithologic discontinuity between it and the
illuvial horizon and no plow layer directly above the illuvial layer, then the illuvial horizon
must contain more total clay than the eluvial horizon within a vertical distance of 30 cm or
less, as follows:
a. If any part of the eluvial horizon has less than 15 percent total clay in the fine-earth
fraction, the argillic horizon must contain at least 3 percent (absolute) more clay (10
percent versus 13 percent, for example); or
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b. If the eluvial horizon has 15 to 40 percent total clay in the fine-earth fraction, the
argillic horizon must have at least 1.2 times more clay than the eluvial horizon; or
c. If the eluvial horizon has 40 percent or more total clay in the fine-earth fraction, the
argillic horizon must contain at least 8 percent (absolute) more clay (42 percent
versus 50 percent, for example).
Cambic- If subsoil >18 cm has textures other than loamy sand or sand, and has either:
structure other than prismatic which also differs from surface structure, a redder or oranger
color than the surface horizon, more wetness redox features than the surface horizon, or a
grayer color than the parent material. (Most always a Bw)
A cambic horizon is the result of physical alterations, chemical transformations, or removals
or of a combination of two or more of these processes.
Required Characteristics
The cambic horizon is an altered horizon 15 cm or more thick. If it is composed of lamellae,
the combined thickness of the lamellae must be 15 cm or more. In addition, the cambic
horizon must meet all of the following:
1. Has a texture of very fine sand, loamy very fine sand, or finer; and
2. Shows evidence of alteration in one of the following forms:
a. Aquic conditions within 50 cm of the soil surface or artificial drainage and all of
the following:
(1) Soil structure or the absence of rock structure in more than one-half of the
volume; and
(2) Colors that do not change on exposure to air; and
(3) Dominant color, moist, on faces of peds or in the matrix as follows:
(a) Value of 3 or less and chroma of 0; or
(b) Value of 4 or more and chroma of 1 or less; or
(c) Any value, chroma of 2 or less, and redox concentrations; or
b. Does not have the combination of aquic conditions within 50 cm of the soil surface
or artificial drainage and colors, moist, as defined in item 2-a-(3) above, and has soil
structure or the absence of rock structure in more than onehalf of the volume and one
or more of the following properties:
(1) Higher chroma, higher value, redder hue, or higher clay content than the
underlying horizon or an overlying horizon; or
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(2) Evidence of the removal of carbonates or gypsum; and
3. Has properties that do not meet the requirements for an anthropic, histic, folistic, melanic,
mollic, plaggen, or umbric epipedon, a duripan or fragipan, or an argillic, calcic, gypsic,
natric, oxic, petrocalcic, petrogypsic, placic, or spodic horizon; and
4. Is not part of an Ap horizon and does not have a brittle manner of failure in more than 60
percent of the matrix.
Fragipan- If subsoil is very firm and brittle with a loamy texture. Occurs in depositional
parent material, either colluvial or glacial. Gray and red streaks running roughly 10 cm or
more apart down through the subsoil. Roots are upturned and water perches above.
Sometimes an E horizon forms above a fragipan as water moves laterally on the fragipan
surface. (Bx)
Required Characteristics
To be identified as a fragipan, a layer must have all of the following characteristics:
1. The layer is 15 cm or more thick; and
2. The layer shows evidence of pedogenesis within the horizon or, at a minimum, on the
faces of structural units; and
3. The layer has very coarse prismatic, columnar, or blocky structure of any grade, has weak
structure of any size, or is massive. Separations between structural units that allow roots to
enter have an average spacing of 10 cm or more on the horizontal dimensions; and
4. Air-dry fragments of the natural soil fabric, 5 to 10 cm in diameter, from more than 50
percent of the horizon slake when they are submerged in water; and
5. The layer has, in 60 percent or more of the volume, a firm or firmer rupture-resistance
class, a brittle manner of failure at or near field capacity, and virtually no roots.
Spodic- Alternating bands of white (E)/ black or dark red (Bhs)/ orange (Bs)/ gray or olive
(C). If plowed, black or dark red (Bhs) band is directly below plowed A horizon. Has to be
greater than 1 inch (2.5 cm) thick. (Bhs with/without Bs)
A spodic horizon is an illuvial layer with 85 percent or more spodic materials (defined
below).
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Required Characteristics
A spodic horizon is normally a subsurface horizon underlying an O, A, Ap, or E horizon. It
may, however, meet the definition of an umbric epipedon. A spodic horizon must have 85
percent or more spodic materials in a layer 2.5 cm or more thick that is not part of any
Ap horizon.
Lithic Contact- Hard bedrock (R)
A lithic contact is the boundary between soil and a coherent underlying material. Except in
Ruptic-Lithic subgroups, the underlying material must be virtually continuous within the
limits of a pedon. Cracks that can be penetrated by roots are few, and their horizontal spacing
is 10 cm or more. The underlying material must be sufficiently coherent when moist to make
hand-digging with a spade impractical, although the material may be chipped or scraped with
a spade. The material below a lithic contact must be in a strongly cemented or more
cemented rupture-resistance class. Commonly, the material is indurated. The underlying
material considered here does not include diagnostic soil horizons, such as a duripan or a
petrocalcic horizon.
A lithic contact is diagnostic at the subgroup level if it is within 125 cm of the mineral soil
surface in Oxisols and within 50 cm of the mineral soil surface in all other mineral soils. In
organic soils the lithic contact must be within the control section to be recognized at the
subgroup level.
Paralithic Contact- Soft, diggable bedrock (Cr)
A paralithic (lithiclike) contact is a contact between soil and paralithic materials (defined
below) where the paralithic materials have no cracks or the spacing of cracks that roots can
enter is 10 cm or more.
None- Textures are loamy sands and sands. Commonly found in floodplains where stratified
sands (C horizons) lie directly below the A horizon, or in extremely sandy parent materials
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Soil Taxonomy - A Simplified Key for Centre County
Soil Orders:
1.) Has a spodic horizon within 2 m of surface
> > > > Spodosols
2.) Has a mollic epipedon
> > > > Mollisols
2.) Has an argillic horizon, and a base saturation of < 35% at the shallowest of the following
depths:
-125 cm below upper boundary of the argillic
-180 cm below mineral soil surface
-at lithic or paralithic contact
If there is a fragipan, then the base saturation of < 35% at the shallowest of the following
depths:
-75 cm below upper boundary of the fragipan
-200 cm below mineral soil surface
-at lithic or paralithic contact
> > > > Ultisols
3.) Other soils with an argillic horizon
> > > > Alfisols
4.) Has a cambic horizon
> > > > Inceptisols
5.) Other soils
> > > > Entisols
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SPODOSOLS
Suborders
-Within 50 cm, redox features in albic or spodic horizon
-Other spodosols
> > Aquods
> > Orthods
Great Groups
For Aquods:
-Has a fragipan
> > Fragiaquods
-Saturation is coming from above, perched water
-Saturation (water) is coming from below
For Orthods:
-Has a fragipan
-Other orthods
> > Epiaquods
> > Endoaquods
> > Fragiorthods
> > Haplorthods
MOLLISOLS
Suborders
-Redox features in the mollic epipedon
-Other mollisols
> > Aquolls
> > Udolls
Great Groups
For Aquolls:
-Has an argillic horizon
-Saturation is coming from above, perched water
-Saturation (water) is coming from below
> > Argiaquolls
> > Epiaquolls
> > Endoaquolls
For Udolls:
-Has an argillic horizon
-Other udolls
> > Argiudolls
> > Hapludolls
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ULTISOLS
Suborders
-Redox features or gray matrix in all layers between the Ap horizon (or depth of 25
cm, whichever is deeper) and above 40 cm and 50% or more low chroma colors (chroma 2 or
less) on faces of peds or in the matrix in upper 12.5 cm of argillic horizon.
> > Aquults
-Other ultisols
> > Udults
Great Groups
For Aquults:
-Has a fragipan within 100 cm
-Saturation is coming from above, perched water
-Saturation (water) is coming from below
> > Fragiaquults
> > Epiaquults
> > Endoaquults
For Udults:
-Has a fragipan within 100 cm
-Other udults
> > Fragiudults
> > Hapludults
ALFISOLS
Suborders
-Redox features or gray matrix between Ap or 25 cm (whichever is deeper) and 40
cm and >50% gray matrix (chroma 2 or less) in upper 12.5 cm of argillic horizon
> > Aqualfs
-Other alfisols
> > Udalfs
Great Groups
For Aqualfs:
-Has a fragipan within 100 cm
-Saturation is coming from above, perched water
-Saturation (water) is coming from below
For Udalfs:
-Has a fragipan within 100 cm
-Other udalfs
> > Fragiaqualfs
> > Epiaqualfs
> > Endoaqualfs
> > Fragiudalfs
> > Hapludalfs
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INCEPTISOLS
Suborders
- Horizon below Ap and within 50 cm that has, on faces of peds or in the matrix if
peds are absent, 50% or more low chroma colors (chroma 2 or less)
> > Aquepts
-Other inceptisols
> > Udepts
Great Groups
For Aquepts:
-Has a fragipan within 100 cm
-Saturation is coming from above, perched water
-Saturation (water) is coming from below
> > Fragiaquepts
> > Epiaquepts
> > Endoaquepts
For Udepts:
-Has a fragipan within 100 cm
> > Fragiudepts
-Base saturation is > 60% between 25 and 75 cm from the mineral soil surface
> > Eutrudepts
-Other udepts
> > Dystrudepts
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ENTISOLS
Suborders
-Gray matrix (chroma 2 or less) between 40 and 50 cm or above lithic or paralithic
contact.
> > Aquents
-Textures of loamy sands or sands within the entire particle-size control section and
<35% rock fragments.
> > Psamments
-Irregular decrease in organic Carbon (buried A horizon), found in floodplains
> > Fluvents
> > Orthents
-Other entisols
Great Groups
For Aquents:
-<35% rock fragments and textures loamy sands or sands within the entire particle
size control section.
> > Psammaquents
-0.2% or more organic carbon of Holocene age at a depth of 125 cm below the
mineral soil surface or an irregular decrease in organic carbon content from 25 cm to
125 cm (or to lithic or paralithic contact if shallower)
-Saturation is coming from above, perched water
-Saturation (water) is coming from below
> > Fluvaquents
> > Epiaquents
> > Endoaquents
For Psamments:
-Resistant mineral (e.g, Quartz) content is > 90% within particle-size control section
> > Quartzipsamments
-Other psamments
> > Udipsamments
For Fluvents:
-In eastern US, for all fluvents
For Orthents:
-In eastern US, for all orthents
> > Udifluvents
> > Udorthents
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Family Particle Size Control Section and Class
Particle Size Control Section Upper and Lower Depth:
1) If you don't have an argillic horizon:
The upper depth is 25 cm except if there is an Ap that is deeper than 25 cm. If there is an Ap
deeper than 25 cm, then the upper depth is the bottom of the Ap.
The lower depth is 100 cm except the particle size control section cannot include any of the
following:
 bedrock (R)
 saprolite (Cr)
 fragipan
 Dense horizons (Cd)
If there is one or more of these horizons within 100 cm, then the lower depth is the top of this
(or these) horizons.
2) If you do have an argillic horizon (that is not a part of a fragipan):
The particle size control section upper and lower depths are the top 50 cm of the argillic.
Note, if the argillic is less than 50 cm, than the particle size control section is the entire
argillic horizon. Don't include any of the fragipan in the particle size control section.
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Family Particle-Size Classes:
(also see following pages for triangle - this may be easier for some people)
Once you have determined the PSC, you can now determine the particle-size class.
1) Rock fragments are > 35% volume
a.) all textures are sands and loamy sands
> sandy-skeletal
b.) clay average is > 35%
> clayey-skeletal
c.) clay average is < 35%
> loamy-skeletal
2) all textures are sands and loamy sands
> sandy
3) Lithic contact within 50 cm of surface (lithic), or
50 cm or more loamy fine sand or coarser over argillic (arenic, grossarenic)
a.) clay average is > 35%
> clayey
b.) clay average is < 35%
> loamy
4) Rock fragments are < 35% volume
a. ) clay average is > 60%
1. Ultisol
2. other
b.) clay average is > 35%
1. Ultisol
2. other
c.) clay average is < 35%
2. clay average is > 18%
a. sand average is > 15%
b. sand average is < 15%
3. clay average is < 18%
a. sand average is > 15%
b. sand average is < 15%
> clayey
> very fine
> clayey
> fine
> fine-loamy
> fine-silty
> coarse-loamy
> coarse-silty
Note: For 2 parent materials, there are 2 particle size control sections and classes.
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