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Appendix C—Storie Soil-Rating Chart
Storie Soil Index rating=factor A x factor
B x factor C
x factor X
These factors are used to rate cropland and rangeland.
Factor A -Rating on character of physical profile | |
I Soils on recent alluvial fans, flood plains, or other secondary deposits having undeveloped profiles |
100 |
x-shallow phases (on consolidated material), 2 feet deep |
50-60 |
x-shallow phase (on consolidate material), 3 feet deep |
70 |
g-extremely gravelly subsoils |
80-95 |
s-stratified clay subsoils |
80-95 |
II Soils on young alluvial fans, flood plains, or other secondary deposits have slightly developed profiles |
95-100 |
x-shallow phases (on consolidated material), 2 feet deep |
50-60 |
x-shallow phases (on consolidated material), 3 feet deep |
70 |
g-extremely gravelly subsoils |
80-95 |
s-stratified clay subsoils |
80-95 |
III Soils on older
alluvial fans, alluvial plains, |
80-95 |
x-shallow phases (on consolidated material), 2 feet deep |
40-60 |
x-shallow phases (on consolidated material), 3 feet deep |
60-70 |
g-extremely gravelly subsoils |
60-90 |
IV Soils on older plains or terraces having strongly developed profiles (dense clay subsoils) |
40-80 |
V Soils on older plains or terraces having hardpan subsoil layers: |
|
at less than 1 foot |
5-20 |
at 1 to 2 feet |
20-30 |
at 2 to 3 feet |
30-40 |
at 3 to 4 feet |
40-50 |
at 4 to 6 feet |
50-80 |
VI Soils on older
terraces and upland areas |
40-80 |
VII Soils on upland areas underlain by hard igneous bedrock: |
|
at less than 1 foot |
10-30 |
at 1 to 2 feet |
30-50 |
at 2 to 3 feet |
50-70 |
at 3 to 4 feet |
70-80 |
at 4 to 6 feet |
80-100 |
at more than 6 feet |
100 |
VIII Soils on upland areas underlain by consolidated sedimentary rocks: |
|
at less than 1 foot |
10-30 |
at 1 to 2 feet |
30-50 |
at 2 to 3 feet |
50-70 |
at 3 to 4 feet |
70-80 |
at 4 to 6 feet |
80-100 |
at more than 6 feet |
100 |
IX Soils on upland areas underlain by softly consolidated material: |
|
at less than 1 foot |
20-40 |
at 1 to 2 feet |
40-60 |
at 2 to 3 feet |
60-80 |
at 3 to 4 feet |
80-90 |
at 4 to 6 feet |
90-100 |
at more than 6 feet |
100 |
Factor B-Rating on basis of surface texture | |
Medium textured: | |
fine sandy loam |
100 |
loam |
100 |
silt loam |
100 |
sandy loam |
95 |
silty clay loam, calcareous |
95 |
silty clay loam, noncalcareous |
90 |
clay loam, calcareous |
95 |
clay loam, noncalcareous |
85-90 |
Heavy or fine-textured: | |
silty clay, highly calcareous |
70-90 |
silty clay, noncalcareous |
60-70 |
clay, highly calcareous |
70-80 |
clay, noncalcareous |
50-70 |
Light or coarse-textured: | |
coarse sandy loam |
90 |
loamy sand |
80 |
very fine sand |
80 |
fine sand |
65 |
sand |
60 |
coarse sand |
30-60 |
Gravelly: | |
gravelly fine sandy loam |
70-80 |
gravelly loam |
60-80 |
gravelly silt loam |
60-80 |
gravelly sandy loam |
50-70 |
gravelly clay loam |
60-80 |
gravelly clay |
40-70 |
gravelly sand |
20-30 |
Stony: | |
stony fine sandy loam |
70-80 |
stony loam |
60-80 |
stony silt loam |
60-80 |
stony sandy loam |
50-70 |
stony clay loam |
60-80 |
stony clay |
40-70 |
stony sand |
10-40 |
Factor C-Rating on basis of slope |
|
A-Nearly level (0 to 2%) |
100 |
AA-Gently undulating (0 to 2%) |
95-100 |
B-Gently sloping (3 to 8%) |
95-100 |
BB-Undulating (3 to 8%) |
85-100 |
C-Moderately sloping (9-15%) |
80-95 |
CC-Rolling (9 to 15%) |
80-95 |
D-Strongly sloping (16 to 30%) |
70-80 |
DD-Hilly (16 to 30%) |
70-80 |
E-Steep (30 to 45%) |
30-50 |
F-Very steep (45% and over) |
5-30 |
Factor X-Rating of conditions other than those in factors A, B, and C |
|
Drainage: |
|
well-drained |
100 |
fairly well drained 1/ |
80-90 |
moderately waterlogged 2/ |
40-80 |
badly waterlogged 3/ |
10-40 |
subject to overflow |
variable |
Alkali: 4/ |
|
alkali-free |
100 |
slightly affected |
60-95 |
moderately affected |
30-60 |
moderately to strongly affected |
15-30 |
strongly affected |
5-15 |
Nutrient (fertility level): |
|
high |
100 |
fair |
95-100 |
poor |
80-95 |
very poor |
60-80 |
Acidity: according to degree 5/ |
80-95 |
Erosion: |
|
none to slight |
100 |
detrimental deposition |
75-95 |
moderate sheet erosion |
80-95 |
occasional shallow gullies |
70-90 |
moderate sheet erosion with: |
60-80 |
deep gullies |
10-70 |
moderate sheet erosion with: |
10-60 |
severe sheet erosion |
50-80 |
severe sheet erosion with: |
40-50 |
deep gullies |
10-40 |
very severe erosion |
10-40 |
moderate wind erosion |
80-95 |
severe wind erosion |
30-80 |
Microrelief: |
|
smooth |
100 |
channels |
60-95 |
hogwallows |
60-95 |
low hummocks |
80-95 |
high hummocks |
20-60 |
dunes |
10-40 |
Soil Grading
For simplification, six soil grades have been set up in California by combining soils having ranges in index rating as follows:
Grade 1 (excellent): Soils that rate between 80 and 100 percent and which are suitable for a wide range of crops, including alfalfa, orchard, truck, and field crops.
Grade 2 (good): Soils that rate between 60 and 79 percent and which are suitable for most crops Yields are generally good to excellent.
Grade 3 (fair): Soils that rate between 40 to 59 percent and which are generally of fair quality, with less wide range of suitability than grades 1 and 2 Soils in this grade may give good results with certain specialized crops.
Grade 4 (poor): Soils that rate between 20 to 39 percent and which have a narrow range in their agricultural possibilities For example, a few soils in this grade may be good for rice, but not good for many other uses.
Grade 5 (very poor): Soils that rate between 10 and 19 percent are of very limited use except for pasture, because of adverse conditions such as shallowness, roughness, and alkali content.
Grade 6 (nonagricultural): Soils that rate less than 10 percent include, for example, tidelands, riverwash, soils of high alkali content, and steep broken land.
Current terminology:
1/ moderately well drained
2/ somewhat poorly drained
3/ poorly to very poorly drained
4/ salinity/sodicity
5/ pH less than 50