“Cheat Sheet” for Soil Description and Interpretation (Revised 1/12/09)
Part A: Morphology
Common Subordinate Distinctions
g = chroma < 2 from redox
h = illuvial C and metals
k = pedogenic carbonates
p = disturbed
r = weathered rock
s = illuvial Fe, Al, and C
t = illuvial silicate clay
w = development of color and/or structure
Distinctness of Boundary
Abrupt (a) = < 2 cm
Clear (c) = 2 to 6 cm
Gradual (g) = 6 to 16 cm
Diffuse (d) = > 16 cm
Texture Modifiers
Gravelly (gr) = 15 to 35% fragments between 0.2 and 7.5 cm in size (e.g., gravel-sized)
Very Gravelly (vgr) = more than 35% gravel
Cobbly (cb) = 15 to 35% fragments between 7.5 and 25 cm
Very Cobbly (vcb) = more than 35% cobbles
Texture Class (see textural class estimation chart)
Sand1 (s) = 0.05 to 2.00 mm
Loamy Sand (ls)
Sandy Loam (sl)
Sandy Clay Loam (scl)
Sandy Clay (sc) = > 35% clay
Structure Grade
Structureless (sl)
Weak (wk)
Moderate (mo)
Strong (st)
Loam (l)
Clay Loam (cl)
Clay (c)
Silt (si)
Silt Loam (sil)
Silty Clay Loam (sicl)
Silty Clay (sic)
= no evident planes of weakness
= barely evident after removal or in place
= distinct peds in hand, but not readily evident in place
= durable peds in hand; structure also evident in pit face
Structure Shape (see examples and illustrations)
Single Grain (sg)
= noncoherent structureless
Massive (ma)
= coherent structureless
Granular (gr)
= spheroidal; irregular surfaces; sometimes porous; common in A horizons
Platy (pl)
= plate-shaped
Prismatic (pr)
= vertically elongated peds ("prisms")
Angular Blocky (abk)
= well-defined angles and corners at face intersections
Subangular Blocky (sbk)
= rounded edges and corners
Consistence
Loose (l)
Very Friable (vfr)
Friable (fr)
Firm (fi)
Very firm (vfi)
Extremely Firm (efi)
= noncoherent
= aggregates crush under very gentle pressure
= aggregates crush under gentle to moderate pressure
= resistance to crushing between thumb and forefinger is noticeable
= barely can be crushed between thumb and forefinger
= cannot be crushed between thumb and forefinger
Redoximorphic Features
Enter Yes (Y) or No (N) for : a. Redox Concentrations
* brown or red nodules or concretions (firm)
* brown or red masses (soft)
* Pore linings - zones of brighter colors along root channels
b. Redox Depletions
* Zones of low chroma (≤2) (gray)
c. Reduced Matrix
* Most of the horizon is low chroma (≤2)
Part B: Soil Profile Properties and Interpretations
Infiltration Rate (Maximum rate water enters soil through the uppermost horizon, in cm/hour)
High:
Moderate:
Low:
>7.5 cm/hour = s and ls; sl with > 2% organic matter
0.5 to 7.5 cm/hour = sl with < 2% organic matter; sil, sicl, scl, l, cl with mo or strong structure; sc
and c with strong structure
<0.5 cm/hour = sicl, sic, scl, sc, l, and cl with wk structure; c with wk to mo structure
___________________________________________________________________________________________________
Available Water (Water held between field capacity and permanent wilting point; estimated for top 150 cm)
Available water capacity (AWC), expressed as cm of water per 150 cm of soil, can be estimated from textural class and
coarse fragment content. A weighted average is determined using horizon thicknesses to 150 cm depth; however, if there is a
root-restricting layer use the depth to the top of that layer. Start with the assumed values in the following table:
-------------------------------------------------------------------------------------------cm of water/cm of soil
texture
0.05
s, ls
0.15
sl, scl, cl, l, sic, sc, c
0.20
sil, si, sicl
--------------------------------------------------------------------------------------------Available water capacity classes:
Very low ≤7.5 cm
Low
> 7.5 to 15 cm
Moderate > 15 to 22.5 cm
High
> 22.5 to 30 cm
Very high > 30 cm
Example of available water capacity (AWC) calculation for a soil.
------------------------------------------------------------------------------------------------------------------------------Bottom
ThickCoarse
Hor- Depth
ness
Textural
Fragments
AWC "formula" by horizon
izon
(cm)
(T in cm)
Class
cm/cm
(F in %)
(cm)
------------------------------------------------------------------------------------------------------------------------------T*(cm/cm)*(1-F*0.01)
A
E
B
C
20
50
120
150
20
30
70
30
s
s
scl
sl
0.05
0.05
0.15
0.15
2
5
5
7
20*(0.05)*(1-0.02) = 0.98
30*(0.05)*(1-0.05) = 1.43
70*(0.15)*(1-0.05) = 9.98
30*(0.15)*(1-0.07) = 4.19
--------Total 16.58 cm
Thus AWC for this soil would be Moderate.
Remember: You only go to 150 cm. If the bottom horizon goes deeper, stop at that depth. Also stop at the top of any compact
layer that prevents root growth below that depth.
____________________________________________________________________________________________________
Hydraulic Conductivity
(Rate water flows through soils under saturated conditions; ordinarily expressed in distance/time
units, but for soil judging we only rate as "high, moderate, or slow" based mainly on texture and
consistence)
High
= sand or loamy sand
Moderate = Neither high nor low
Low
= Clayey with wk structure; cemented horizons.
____________________________________________________________________________________________________
Seasonal High Water Table Depth (based on presence of contemporary redoximorphic features)
>150 cm
100 to 150 cm
50 to <100 cm
25 to < 50 cm
<25 cm
Soil Interpretations
Dwellings with Basement: Adapted from NSSH Table 620-3 but modified to fit guidelines in the Southeast Region
Handbook for Collegiate Soils Contest.
Degree of Limitations
Factors Affecting Use
1. Flooding or Ponding Frequency
2. Slope, %
3. Depth to Seasonally High Water
Table, cm
Slight (1)
Moderate (2)
None
Not a choice
Severe (3)
Rare to Frequent
<6
6 - 20
>20
>100
50 - 100
<50
4. Depth to Soft Rock (Cr), cm
>100
50 - 100
<50
5. Depth to Hard Rock (R), cm
>150
100 - 150
<100
Septic Tank Absorption Fields: Adapted from NSSH Table 620-17 but modified to fit guidelines in the Southeast
Region Handbook for Collegiate Soils Contest.
Degree of Limitations
Factors Affecting Use
1. Flooding or Ponding Frequency
2. Slope, %
Slight (1)
None
<6
Moderate (2)
Not a choice
Rare to Frequent
6 - 20
>20
<100
3. Depth to Seasonally High Water
Table, cm
>150
100 - 150
4. Limiting Hydraulic Conductivity
Moderate
Not a choice
>150
100 - 150
5. Depth to Rock (R or Cr), cm
Severe (3)
Low (percs slowly)
High (poor filter)
<100
Local Roads and Streets: Adapted from NSSH Table 620-5 but modified to fit guidelines in the Southeast Region
Handbook for Collegiate Soils Contest.
Degree of Limitations
Factors Affecting Use
Slight (1)
Moderate (2)
1. Flooding or Ponding Frequency
None
Not a choice
2. Slope, %
<6
3. Depth to Seasonally High Water
Table, cm
>50
50 - 25
<25
4. Depth to Soft Rock (Cr), cm
>100
50 - 100
<50
5. Depth to Hard Rock (R), cm
>150
100 - 150
<100
6 - 20
Severe (3)
Rare to Frequent
>20
Part C: Site Characteristics
Position of Site (Landscape position)
Flood Plain: Nearly level landform adjacent to streams. Parent material is relatively recent stream sediments, or in
other words, young alluvium. Soil horizonation is generally minimal, and often sedimentary stratification is still visible.
Soils classify as Entisols if they have no B horizon; Inceptisols if they have a weakly developed B (cambic); and
Mollisols if they have a dark, thick, alkaline A horizon (Mollic epipedon).
Stream Terrace: Nearly level to gently sloping landform associated with streams but at a higher elevation than the
floodplain. Relative extent of soil development increases as you go up in terrace level within a stream system. High
terraces are "old alluvium", and often classify as Ultisols.
Upland: Higher landforms within a landscape. Examples: hilltops and upper convex sideslopes; can be more clearly
defined in WVA than FL!
Depression: The handbook specifies this to mean essentially a "closed" depression, or basin. Examples would be
sinkholes and "backswamp" areas of floodplains. The surface would be concave. Closed depressions are rare except in
limestone- or glacial areas.
Drainageway: A linear or sinuous depression roughly parallel to the general sloping trend of the landform with which
it is associated. It is "open", such that water could flow through it to the next drainage feature. The latter could be a
stream or another drainageway.
Parent Material
Residuum: Formed from weathering rock, primarily in place.
Colluvium: Material at the foot of steep slopes that has accumulated primarily through the processes of erosion and
gravity. Poorly sorted.
Alluvium: Deposited by flowing water, such as by a stream (Fluvial), ocean (Marine) or local slope runoff. Occupies
floodplains and stream terraces; sometimes in depressions and drainageways. Commonly consists of strata of wellsorted material, though adjacent strata may be contrasting. For example, over-the-bank flooding may deposit finetextured material over much coarser (high-energy flow) material. Fining-upward sequences are also common; this
develops with meandering streams.
Eolian: Deposited by wind. May show stratification. Well sorted (narrow particle size ranges).
Soil Slope
Nearly level
Gently sloping
Sloping
= 0 to 2%
= 2 to 6%
= 6 to 12%
Strongly sloping = 12 to 20%
Moderately Steep = 20 to 30%
Steep
= >30%
Surface Runoff (Relative rate that water flows over the surface of the soil)
-------------------------------------------------------------------------------Runoff Classes
_____________________________________________________
High
Moderate
Low
Slope (% )
Infiltration
Infiltration
Infiltration
Rate
Rate
Rate
__________________________________________________________________________
0 to 1
Very slow
Very slow
Very slow
1 to 2
Very slow
Slow
Slow
2 to 6
Slow
Medium
Medium
6 to 12
Medium
Rapid
Very rapid
> 12
Rapid
Very rapid
Very rapid
________________________________________________________________________________
Erosion Potential*
Surface Runoff
-------S, LS, SC
Texture of Surface Horizon
SL, SCL, CL, C, SiC
---------------L, Si, SiL, SiCL
Ponded
Very Low
Very Low
Very Low
Very slow
Very Low
Low
Medium
Slow
Low
Medium
Medium
Medium
Low
Medium
High
Rapid
Medium
High
Very High
Very Rapid
High
Very High
Very High
* Assumes granular structure in surface horizon. If type of structure in surface horizon is something other than granular, then
increase erosion potential by one class except for "Ponded" Surface Runoff.
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Interpretation "Cheat Sheet"