Capa-
biltiy
Class

Effective
Soil depth
(inches)1/

Climate Thornthwaite
1948 indices (inches)
Irr.        Dry
ETp 32F 4ETa

Surface Layer Texture

Irrigated     Dryland

Permea-
bility 2/

Drainage
Class 3/

Available
Water
Capacity 4/

Slope
A          B
5/ 6/ 7/

Erosion Hazard

Flooding Hazard

Salinity
ECx1U @
25o C 8/

Alkali
ESP 8/

Toxic
Sub-
stances9/

Frost
Free
Season

1

> 40

> 20        > 20

Sandy Loam thru Clay Loam

Sandy Loam thru Clay Loam

Mod. Rapid
thru
Mod. Slow

Well or Mod. Well >60"

> 7.5 inch av. AWC > 0.13 In/In.

<2%

<2%

None or slight

None or rare

<4 mmhos
(none)

None

None

> 140
Days

2

> 40

> 14        > 16

Loamy
Sand thru
Clay may
be Gravelly

Sandy
Loams thru Clay (may be Gravelly)

Rapid
thru Slow

Somewhat Poorly thru Somewhat Excessively >36"

> 5.0 inch av. AWC > 0.08 In/In.

<5%

None thru Mod.

None thru Occas.

<8 mmhos

< 25

None or Slight

> 100 Days

3

> 20

> 10        > 12

Any, may be Gravelly or Cobbly

Sandy
Loam thru
Clay (may
be Gravelly
or Cobbly)

Rapid thru Very Slow

Poorly thru Excessively > 20"

> 3.5 inch av. AWC > 0.06 In/In.

<8%

<15%

None thru High

None thru Occas.

<16 mmhos

< 50

None thru Mod.

> 80 Days

4

> 10

> 6        > 8

Any, may be Very Gravelly, Very Cobbly or Stony 10/

Loamy Sand thru Clay, Very Gravelly Very Cobbly or Stony 10/

Any

Poorly thru Excessively > 20"

> 2.5 inch av. AWC > 0.04 In/In.

<15%

<25%

Any

None thru Frequent 11/

<16 mmhos

< 50

None thru Mod.

> 50 Days

5

> 20

> 6         > 8

Any, may be Extremely Gravelly, Ext. Cobbly or Very Stony

Any, may be Extremely Gravelly, Ext. Cobbly or Very Stony

Any

Any

>3.0 inch av. AWC

<2%

<2%

None or Slight

Any

<8 mmhos

< 25

None or Slight

Any

6 12/

> 10

> 4          > 6

Any, may be Extremely Gravelly, Ext. Cobbly or Very Stony

Any, may be Extremely Gravelly, Ext. Cobbly or Very Stony

Any

Any

> 2.0 inc hav. AWC

<25%

<50%

Any

Any

Dry Land
<16 mmhos
  Irr. Any 

Dry Land
<25 Irr. <50

Dry Land Slight Irr. Slight thru Moderate

Any

713/

Any

> 2

Any

Any

Any

Any

> 1.0 inc hav. AWC

<50%

<75%

Any

Any

Any

Any

Any

Any

814/

Any

Any          Any

Any

Any

Any

Any

Any

Any

Any

Any

Any

Any

Any

Any

Any

1/ Clay pans with permeabilities less than 0.06 in/hr., will be treated as limiting the effective depth.

8/ For salts and alkali to be a major limitation, there should be other soil limitations, such as slow permeabilities or high water tables.

2/ Permeability of the least permeable subsurface horizon.

9/ Such as boron and magnesium that leach with difficulty.

3/ Depth to water table during growing season.

10/ Coarse fragments interfere with tillage, but do not prevent cropping.

4/ Available moisture between field capacity and wilting point.

11/ Frequent flooding that does not prevent normal cropping.

5/ Use erosion hazard to help determine upper slope percent.

12/ Range & wdlnd. mechanical practices can be applied to class 6 land.

6/ In existing mapping units 9% and 30% can be substituted for 8% and 25%.

13/ Range & wdlnd. mechanical practices are impractical on class 7 land.

7/ Column A is used for soils w/ K factors of 0.37 or greater and soils subject to rill and gully erosion, such as soils formed from granitic parent material or w/ claypans. Other soils are in grp B.

14/ Class 8 lands have limitations that preclude their use for commercial plant production and restrict their use to recreation, water supply or esthetic purposes.