LOCATION SORUM SD+MTEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Aridic Natrustolls
TYPICAL PEDON: Sorum fine sandy loam - on a plane slope of less than 1 percent under native grass. (Colors are for dry soil unless otherwise stated.)
A1--0 to 2 inches; grayish brown (2.5Y 5/2) fine sandy loam, very dark grayish brown (10YR 3/2) moist; weak very fine granular structure; loose, very friable; abundant roots; moderately acid; smooth boundary.
A2--2 to 6 inches; grayish brown (10YR 5/2) fine sandy loam, very dark grayish brown (10YR 3/2) moist; weak fine and medium granular structure; soft, very friable; many roots; moderately acid; clear smooth boundary.
A3--6 to 13 inches; grayish brown (10YR 5/2) fine sandy loam, very dark grayish brown (10YR 3/2) moist; weak medium and coarse subangular blocky structure; slightly hard, very friable; common roots; slightly acid; clear smooth boundary. (Combined A horizons is 8 to 16 inches thick.)
E--13 to 15 inches; light brownish gray (2.5Y 6/2) fine sandy loam, dark grayish brown (10YR 4/2) moist; weak medium and thick platy structure; slightly hard, very friable; common roots; slightly alkaline; abrupt smooth boundary. (2 to 4 inches thick)
Btn--15 to 18 inches; grayish brown (2.5Y 5/2) clay loam, dark grayish brown (10YR 4/2) moist; strong medium and coarse columnar structure parting to strong fine and medium blocky; very hard, friable; few roots; moderately alkaline; clear smooth boundary. (3 to 6 inches thick)
Btkn--18 to 25 inches; light brownish gray (2.5Y 6/2) clay loam, grayish brown (2.5Y 5/2) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; very hard, friable; few roots; common medium accumulations of carbonate; strong effervescence; moderately alkaline; clear smooth boundary. (5 to 10 inches thick)
Bk--25 to 33 inches; light brownish gray (2.5Y 6/2) clay loam, grayish brown (2.5Y 5/2) moist; weak coarse prismatic structure parting to weak medium subangular blocky; hard, friable; very few roots; common fine accumulations of carbonate; strong effervescence; moderately alkaline; clear smooth boundary. (5 to 8 inches thick)
C--33 to 60 inches; light brownish gray (2.5Y 6/2) fine sandy loam, grayish brown (2.5Y 5/2) moist; massive; slightly hard, very friable; strong effervescence; moderately alkaline.
TYPE LOCATION: Butte County, South Dakota; about 4 miles north and 5 miles west of Hoover; 790 feet north and 1690 feet west of the southeast corner of sec. 15, T. 14 N., R. 6 E.
RANGE IN CHARACTERISTICS: The thickness of the solum ranges from 23 to 44 inches and depth to free carbonate from 17 to 30 inches. Mollic epipedon is 8 to 16 inches thick.
The A horizon has hue of 10YR or 2.5Y, value of 4 or 5 and 3 moist, and chroma of 1 or 2. It is fine sandy loam, sandy loam, or loam. It is moderately acid to slightly alkaline.
The E horizon has hue of 10YR or 2.5Y, value of 5 or 6 and 4 or 5 moist, and chroma of 1 or 2. It is fine sandy loam, sandy loam, or loamy fine sandy. It is moderately acid to slightly alkaline.
The Btn, Btkn, and Bk horizons have hue of 10YR through 5Y, value of 5 or 6 and 4 or 5 moist, and chroma of 1 or 3. They are clay loam or sandy clay loam estimated to average between 20 and 35 percent clay and more than 15 percent fine sand or coarser. Exchanageable sodium percentage exceeds 15 percent in some part of the Bt horizon. Reaction is slightly alkaline or moderately alkaline. Carbonate is present in the Btk and Bk horizons as few or common, fine or medium accumulations and striations.
The C horizon has hue of 2,5Y or 5Y, value of 5 or 6 and 4 or 5 moist, and chroma of 2 or 3. It typically is fine sandy loam or sandy loam, but sandy clay loam and clay loam strata are in some pedons. It is slightly alkaline or moderately alkaline.
COMPETING SERIES: There are no other soils in the same family.
GEOGRAPHIC SETTING: Sorum soils are on nearly level to gently sloping terraces and fans. Surfaces are dominantly smooth and slope gradients range from 0 to 6 percent. The soils formed in loamy alluvium. Mean annual temperature ranges from 39 to 45 degrees F, and mean annual precipitation ranges from 14 to 15 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Absher, Archin, Assinniboine, and Chinook soils. The Absher and Archin soils are in micro-lows. Absher soils have fine textures. Archin soils do not have a mollic epipedon. The Assinniboine and Chinook soils do not have a natric horizon and are on nearby uplands.
DRAINAGE AND PERMEABILITY: Well drained. Permeability is very slow in the solum and moderately rapid in the underlying material. Runoff is medium or high.
USE AND VEGETATION: Used mainly as rangeland, but a few areas are used for growing alfalfa and small grain. Native vegetation includes prairie sandreed, little bluestem, sand bluestem, needleandthread, western wheatgrass, sedges, and forbs.
DISTRIBUTION AND EXTENT: Northwestern South Dakota. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Butte County, South Dakota, 1970.
REMARKS: Diagnostic horizons and features recognized in this pedon are: mollic epipedon - the zone from the surface of the soil to a depth of about 13 inches (A1, A2, and A3 horizons); albic horizon - the zone from about 13 to 15 inches (E horizon); natric horizon - the zone from a depth of about 15 to 25 inches (Btn and Btkn horizons).