United States Department of Agriculture
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 Hydric soils
 

Criteria for Soils of Local Importance within the Fairbanks Soil and Water Conservation District and the Matanuska-Susitna Borough, Alaska

All soils that properly classify into Land Capability Classes 2 and 3 as established by the Natural Resources Conservation Service (USDA-NRCS-Alaska, 1984).

In addition, all soils that have all of the physical characteristics of Land Capability Class 2 and 3 soils, have a 30 day or greater frost-free season, but also experience less than 1250 growing degree days. These are the soils that would classify in land capability class 4C.

Based on LAND CAPABILITY CLASSIFICATION GUIDE - ALASKA (USDA-NRCS, 1984)

Class Soil Depth 1
-------
T-factor		Minimum AWC to 10”
---or---Top 30” 		Surface Soil (10 Inches) Perme- ability In/hr to 30” Drainage Class
---------
Water Table3 		Flood Hazard 3, 4 Climate 5
-----------
Growing Degree Days
---------
  FFS 		% Slope Water Erosion (KxS) Max. value Wind Erosion (WEG)
Texture 2 Coarse Fragments (any Layer) Stones

 
2> 20“
--------
-
2 - 5

 

2
-------
5		SCL, L, SIL,VFSL, FSL,SL, COSL; SICL, CL w/<35% Clay; < 8” Peat <15% gravel

 

Class 1 < .01%0.2-6.0Well Mod. Well
---------
> 30” 		 None, Rare 3 key crops mature 8 years in 10
--------
> 1500
--------
≥ 90		0-71.5 2-8
3 > 20“

--------
 -
Any T		2
 
-------

3		Above plus
LS, LFS, LVFS, SI, SIC, SC; CL and SICL w>35% clay; C w/<60% clay, < 8”Peat 		<35% gravel Class 1 < .01% 0.06-20 Well Mod. Well Somewhat Poorly

--------

> 20”		None, Rare 2 key crops mature 8 years in 10
--------
> 1250
--------
≥ 80 		0-12 3.0 1-8
4C Meets requirements for classes 2 or 3 1 key crop matures 8 years in 10
-------
-------
≥ 30 		Meets requirements for classes 2 or 3

Footnotes to Criteria for Soils of Local Importance

1 Depth of mineral soil to permafrost, lithic, or paralithic contact; include organic layers only for Histosols

2 Abbreviations for soil texture are:

C - Clay CL – Silty Clay Loam COS – Coarse Sand COSL – Coarse Sandy Loam
FS – Fine Sand FSL – Fine Sandy Loam L – Loam LCOS – Loamy Coarse Sand
LFS – Loamy Fine Sand LS – Loamy Sand LVFS – Loamy Very Fine Sand S – Sand
SC – Sandy Clay SCL – Sandy Clay Loam SI – Silt SIC – Silty Clay
SIL – Silt Loam VFS – Very Fine Sand VFSL – Very Fine Sandy Loam

3 During the growing season

4 Abbreviations for flood Hazard are:
                NONE - < 1% chance
                RARE – 1 – 5% chance
 

5 Check climate data for survey area or sub-area; note frost-free season (FFS) and growing degree-days, determine how many key crops can be grown.

 
Key Crops Required Frost Free Days Required Growing Degree Days
(40 degree base)
Barley 90 1500
Potatoes 80 1250
Grass 30   -


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