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,
or terraces having moderately develop profiles (moderately dense subsoils)

 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
having dense clay subsoils resting on
moderately consolidated or consolidated
material

 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:
shallow gullies

 60-80

deep gullies

 10-70

moderate sheet erosion with:
deep gullies

 10-60

severe sheet erosion

 50-80

severe sheet erosion with:
shallow gullies

 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