LOCATION SWINT SDEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Fluventic Haplustolls
TYPICAL PEDON: Swint silt loam - on a plane slope of less than 1 percent in irrigated cropland at 3400 feet elevation. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 8 inches; dark reddish gray (5YR 4/2) silt loam, dark reddish brown (5YR 2/2) moist; moderate fine subangular blocky structure; hard, very friable; few roots; slight effervescence; slightly alkaline; abrupt smooth boundary.
A--8 to 14 inches; dark reddish gray (5YR 4/2) silt loam, dark reddish brown (5YR 2/2) moist; weak medium subangular blocky structure parting to weak fine granular; hard, very friable; common fine reddish brown (5YR 5/4) worm channels, dark reddish brown (5YR 3/4) moist; few roots; slight effervescence; slightly alkaline; clear wavy boundary. (Combined A horizons is 10 to 20 inches thick.)
C1--14 to 27 inches; light reddish brown (5YR 6/4) silt loam, reddish brown (5YR 4/4) moist; weak medium subangular blocky structure; hard, very friable; few roots; dark reddish gray (5YR 4/2) organic coats along common worm channels; strong effervescence; moderately alkaline; clear wavy boundary.
C2--27 to 44 inches; reddish brown (5YR 5/3) silt loam, reddish brown (5YR 4/3) moist; weak coarse subangular blocky structure; hard, very friable; strong effervescence; moderately alkaline; clear wavy boundary.
C3--44 to 60 inches; light reddish brown (5YR 6/4) very fine sandy loam, reddish brown (5YR 4/4) moist; massive; hard, very friable; strong effervescence; moderately alkaline.
TYPE LOCATION: Lawrence County, South Dakota; about 3 miles north and 1 mile west of Spearfish; 1150 feet south and 1100 feet east of the northwest corner of sec. 28, T. 7 N., R. 2 E.
RANGE IN CHARACTERISTICS: Typically this soil has free carbonate at the surface but some pedons are leached to a depth of 8 inches. The control section includes silt loam, loam, or very fine sandy loam; and averages 18 to 24 percent clay. The mollic epipedon ranges from 10 to 20 inches thick. Buried horizons are in some pedons.
The A horizon has hue of 5YR, 7.5YR, or 10YR, value of 3 to 5 and 2 or 3 moist, and chroma of 2 or 3. It is silt loam, loam, or very fine sandy loam and neutral to moderately alkaline. Some pedons have an AC horizons.
The C horizon has hue of 2.5YR, 5YR, or 7.5YR, value of 4 to 6 and 3 to 5 moist, and chroma of 2 to 6. It is loam, silt loam, or very fine sandy loam and commonly is stratified with thin layers of coarser materials. It is slightly alkaline or moderately alkaline. Sand or sand and gravel is between a depth of 40 and 60 inches in some pedons.
COMPETING SERIES: These are Mogollon and Prewitt series. Mogollon soils contain more medium and coarse sand. Prewitt soils contain more clay.
GEOGRAPHIC SETTING: Swint soils are on nearly level flood plains, low terraces, and alluvial fans with slope gradients of 0 to 4 percent. The soils formed in stratified, reddish colored, loamy alluvium. Mean annual temperature is 43 to 48 degrees F, and mean annual precipitation is 15 to 18 inches. Elevations are between 2950 and 5600 feet.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Barnum, Haverson, Nevee, St. Onge, Tilford, and Vale soils. The Barnum, Haverson, and St. Onge soils are on similar landscape positions. Barnum and Haverson soils do not have a mollic epipedon and St. Onge soils have a mollic epipedon thicker than 20 inches. Nevee, Tilford, and Vale soils are on high parts of the landscape. Tilford soils have a regular decrease in organic matter with depth. Nevee soils do not have a mollic epipedon and Vale soils have an argillic horizon.
DRAINAGE AND PERMEABILITY: Well drained or moderately well drained; surface runoff is low or medium. Permeability is moderate. These soils are rarely or occasionally flooded.
USE AND VEGETATION: Soils are used for cropland and rangeland. Alfalfa, corn, and small grain are the principal crops. These soils are irrigated where water is available. The native vegetation is western wheatgrass, green needlegrass, sideoats grama, and big bluestem. Scattered deciduous trees and shrubs are along stream channels in some areas.
DISTRIBUTION AND EXTENT: Of small extent in the foothills of the Black Hills of western South Dakota.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Lawrence County, South Dakota, 1977.
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 14 inches (Ap and A horizons).