LOCATION AKASKA SDEstablished Series
TAXONOMIC CLASS: Fine-silty over sandy or sandy-skeletal, mixed, superactive, mesic Typic Argiustolls
TYPICAL PEDON: Akaska silt loam - on a plane slope of 1 percent under native grass. When described, the soil was moist to 8 inches. (Colors are for dry soil unless otherwise stated.)
A--0 to 6 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; weak fine granular structure; slightly hard, very friable; many fine roots; neutral; clear smooth boundary. (6 to 10 inches thick)
Bt1--6 to 14 inches; grayish brown (10YR 5/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium prismatic structure parting to moderate fine and medium subangular blocky; hard, friable, slightly sticky and slightly plastic; many fine roots; thin patchy clay films; neutral; clear smooth boundary.
Bt2--14 to 17 inches; grayish brown (10YR 5/2) silty clay loam; very dark grayish brown (10YR 3/2) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; hard, friable, slightly sticky and slightly plastic; common fine roots; thin patchy clay films, slight effervescence; slightly alkaline; gradual wavy boundary. (Combined Bt horizons is 10 to 20 inches thick.)
Bk1--17 to 27 inches; light brownish gray (2.5Y 6/2) silt clay loam, dark grayish brown (2.5Y 4/2) moist; weak coarse prismatic structure parting to weak, medium and coarse subangular blocky; hard, friable, slightly sticky and slightly plastic; few fine roots; common fine and medium accumulations of carbonate; strong effervescence; moderately alkaline; gradual wavy boundary.
Bk2--27 to 37 inches; light brownish gray (2.5Y 6/2) silt clay loam, grayish brown (2.5Y 5/2) moist; weak medium and coarse subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few fine roots; common fine accumulations of carbonate; strong effervescence; moderately alkaline; clear smooth boundary. (Combined Bk horizons is 0 to 20 inches thick.)
2C--37 to 60 inches; multicolored sand and gravel, single grained; loose; slight effervescence; neutral.
TYPE LOCATION: Sully County, South Dakota; 12.5 miles west and 4 miles south of Onida; 720 feet north and 2470 feet east of the southwest corner of sec. 27, T. 114 N., R. 79 W.
RANGE IN CHARACTERISTICS: The depth to loose sand and gravel typically is about 37 inches, but ranges from 20 to 40 inches. The depth to carbonates ranges from 14 to 28 inches. The mollic epipedon ranges from 8 to 18 inches in thickness and extends into the Bt horizon in most pedons.
The A horizon has 10YR hue, value of 3 through 5 and 2 or 3 moist, and chroma of 1 or 2. It is slightly acid or neutral.
The Bt horizon has hue of 10YR or 2.5Y value of 4 or 5 and 3 or 4 moist, and chroma of 2 or 3. It typically is silty clay loam, but in some pedons is silt loam averaging between 25 and 35 percent clay and less than 15 percent sand that is fine sand or coarser. It is neutral or slightly alkaline.
The Bk horizon has hue of 10YR or 2.5Y, value of 5 through 7 and 4 or 5 moist, and chroma of 2 through 4. It typically is silty clay loam or silt loam but is gravelly loam or loam in some pedons. Most pedons contain few to common, fine or medium accumulations of carbonate. It is slightly alkaline or moderately alkaline. Some pedons have a C horizon that has colors and textures of the Bk horizon.
The 2C horizon is multicolored, mainly in hue of 10YR or 2.5Y. Coatings of carbonate are on the underside of the pebbles in the upper part. It is slightly alkaline or moderately alkaline.
COMPETING SERIES: There are no other series in this family.
GEOGRAPHIC SETTING: Akaska soils are on glacial outwash plains and stream terraces. Slopes are smooth, plane to slightly convex. Slope gradients are principally 2 percent or less, but range to 6 percent. The Akaska soils formed in silty sediments overlying sand and gravel. The mean annual temperature ranges from 45 to 50 degrees F, and the mean annual precipitation ranges from about 17 to 24 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Agar, Eakin, Fairlo and Highmore soils. Agar, Eakin, Fairlo, and Highmore soils do not have sand and gravel within depths of 40 inches. Agar and Fairlo soils are on similar landscapes as the Akaska soils. Eakin and Highmore soils are slightly higher in the landscape.
DRAINAGE AND PERMEABILITY: Well drained; surface runoff is low to medium. Permeability is moderate through the solum and rapid in the underlying sand and gravel.
USE AND VEGETATION: Mainly cultivated. Small grain, corn, and sorghum are the main crops. Native vegetation includes western wheatgrass, green needlegrass, blue grama and needleandthread.
DISTRIBUTION AND EXTENT: Central South Dakota, mainly east of the Missouri River. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Potter County, South Dakota, 1955.
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 17 inches (A, Bt1, Bt2 horizons); argillic horizon - the zone from about 6 to 17 inches (Bt1, Bt2 horizons).