LOCATION EAKIN SDEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Typic Argiustolls
TYPICAL PEDON: Eakin silt loam in a cultivated field on a south-facing slope of 1 percent. When described the soil was dry throughout. (Colors are for dry conditions unless otherwise stated.)
Ap--0 to 7 inches; dark gray (10YR 4/1) silt loam, very dark brown (10YR 2/2) moist; weak fine granular structure; soft, very friable; neutral; abrupt smooth boundary. (4 to 8 inches thick)
Bt--7 to 13 inches; grayish brown (10YR 5/2) silty clay loam, dark grayish brown (10YR 4/2) moist; moderate medium prismatic structure parting to moderate medium and fine subangular blocky; slightly hard, friable, slightly sticky and slightly plastic; shiny film on the vertical faces of peds; neutral; clear wavy boundary. (5 to 15 inches thick)
Bk1--13 to 27 inches; light yellowish brown (2.5Y 6/3) silt loam, olive brown (2.5Y 4/3) moist; weak medium prismatic structure parting to weak medium subangular blocky; slightly hard, friable; common medium accumulations of carbonate; strong effervescence; moderately alkaline; clear wavy boundary. (5 to 26 inches thick)
2Bk2--27 to 38 inches; gray (5Y 5/1) clay loam, olive gray (5Y 4/2) moist; common fine faint mottles of dark grayish brown (2.5Y 4/2) and reddish brown (5YR 4/4) moist; weak medium and coarse subangular blocky structure; hard, firm, slightly sticky and slightly plastic; common medium and fine accumulations of carbonate; strong effervescence; moderately alkaline; gradual wavy boundary. (8 to 16 inches thick)
2C1--38 to 54 inches; grayish brown (2.5Y 5/2) and dark gray (2.5Y 4/1) clay loam, dark grayish brown (2.5Y 4/2) and dark gray (2.5Y 3/1) moist; common fine distinct relic mottles of light olive brown (2.5Y 5/6) moist; massive; hard, firm, sticky and plastic; strong effervescence; moderately alkaline.
2C2--54 to 62 inches; grayish brown (2.5Y 5/2) and gray (2.5Y 5/1) clay loam, dark grayish brown (2.5Y 4/2) and very dark gray (2.5Y 3/1) moist; common fine distinct relic mottles of light olive brown (2.5Y 5/6) moist; massive; hard, firm, sticky and plastic; common nests and seams of gypsum crystals; strong effervescence; moderately alkaline.
TYPE LOCATION: Sully County, South Dakota; about 1 mile north and 1 mile west of Agar; 550 feet west and 350 feet south (of fence north of trail) of the northeast corner of sec. 16, T. 116 N., R. 77 W.
RANGE IN CHARACTERISTICS: Depth to carbonate typically is about 13 inches but ranges from 10 to 18 inches. The mollic epipedon ranges from 7 to 20 inches in thickness and includes the upper part of the Bt horizon in some pedons. The thickness of the silty mantle overlying the glacial till typically is about 28 inches thick but ranges from 20 to 40 inches; the solum rests on or extends into the glacial till. The solum ranges from slightly acid to slightly alkaline in the noncalcareous part and from slightly alkaline to strongly alkaline in the remainder of the solum and C horizon.
The A horizon has value of 4 or 5 and 2 or 3 moist, and chroma of 1 or 2.
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 averages between 27 and 35 percent clay and less than 15 percent fine sand or coarser.
The Bk horizon has hue of 10YR or 2.5Y, value of 5 to 7 and 4 to 6 moist, and chroma of 2 to 4. It has few to many, fine or medium accumulations of carbonate.
The 2Bk and 2C horizons have hue of 2.5Y or 5Y, value of 5 to 7 and 4 to 6 moist, and chroma of 1 to 4. They are loam or clay loam with more than 15 percent fine sand or coarser. Relic mottles, fragments of shale, small pebbles, and nests of gypsum crystals are in some pedons.
COMPETING SERIES: These are the Agar, Fairlo, Highmore, Holdrege, Monticello, Northdale, and Paka series. The Agar, Highmore and Holdrege soils do not have horizons with more than 15 percent fine sand or coarser above 40 inches. The Fairlo soils are underlain by clayey sediments. The Monticello and Northdale soils have redder hue. The Paka soils have soft siltstone at depths of 40 to 60 inches.
GEOGRAPHIC SETTING: Nearly level to sloping uplands. Slopes are smooth, plane or convex. Slope gradients range from 0 to 9 percent. Eakin soils formed in a silty mantle overlying glacial till. Mean annual temperature ranges from 45 to 48 degrees F, and precipitation ranges from 17 to 21 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Agar, DeGrey, Glenham, Highmore, Mobridge, Onita, Raber, and Walke soils. Agar soils are intermingled in areas where the silty mantle is loess. DeGrey, Highmore, and Walke soils are intermingled mainly on nearly level landscapes. Highmore soils do not have glacial till within a depths of 40 inches. The fine-loamy Glenham soils and the fine textured Raber soils are intermingled where the silty mantle is thinly deposited over glacial till. DeGrey and Walke soils have natric horizons. Mobridge and Onita soils have mollic epipedons more than 20 inches thick and are in swales and drainageways.
DRAINAGE AND PERMEABILITY: Well drained. Surface runoff is slow on nearly level areas and medium on more sloping areas. Permeability is moderate in the solum and moderately slow in the 2C horizons.
USE AND VEGETATION: Mainly cultivated. Small grain, corn, and sorghum are the principal crops. Western wheatgrass, bluegrama, needleandthread, and green needlegrass are the main species in areas of native range.
DISTRIBUTION AND EXTENT: Central and south-central South Dakota east of the Missouri River. It is extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Hand County, South Dakota, 1957.
REMARKS: Diagnostic horizons and features recognized in this pedon are: mollic epipedon - the zone from the surface of the soil t a depth of about 7 inches (Ap horizon); argillic horizon - the zone from about 7 to 13 inches (Bt horizon).