LOCATION OGLALA SD+NEEstablished Series
TAXONOMIC CLASS: Coarse-silty, mixed, superactive, mesic Aridic Haplustolls
TYPICAL PEDON: Oglala loam - on a southwest-facing slope of 10 percent in grass. When described the soil was dry throughout. (Colors are for dry soil unless otherwise stated.)
A1--0 to 7 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; weak medium subangular blocky structure parting to weak fine granular; slightly hard, friable; neutral; gradual wavy boundary.
A2--7 to 15 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; weak coarse and medium prismatic structure parting to weak medium subangular blocky; slightly hard, friable; neutral; clear wavy boundary. (Combined thickness of the A horizons is 7 to 20 inches.)
Bw--15 to 29 inches; light brownish gray (10YR 6/2) loam, dark grayish brown (10YR 4/2) moist; very weak coarse prismatic structure parting to very weak medium and fine subangular blocky; slightly hard, very friable; slightly alkaline; gradual wavy boundary. (8 to 16 inches thick)
C--29 to 42 inches; light gray (10YR 7/2) loam, brown (10YR 5/3) moist; massive; soft, friable; slightly alkaline; diffuse wavy boundary.
Cr--42 to 60 inches; very pale brown (10YR 7/3) fine-grained sandstone, brown (10YR 5/3) moist; weakly bedded; soft; strong effervescence; slightly alkaline.
TYPE LOCATION: Bennett County, South Dakota; about 5 miles north and 2 miles east of Martin; 85 feet west and 2430 feet north of the southeast corner of sec. 21, T. 38 N., R. 37 W.
RANGE IN CHARACTERISTICS: Depth to bedrock ranges from 40 to 60 inches. Depth to carbonate ranges from 15 to 54 inches. The thickness of the mollic epipedon ranges from 7 to 20 inches.
The A horizon has hue of 10YR, value of 4 or 5 and 2 or 3 moist, and chroma of 1 or 2. It typically is loam but is silt loam or very fine sandy loam in some pedons. It is slightly acid to slightly alkaline.
The Bw horizon has 10YR or 2.5Y hue, value of 5 to 7 and 4 or 5 moist, and chroma of 2 or 3. It typically is loam but is silt loam or very fine sandy loam in some pedons. It is neutral or slightly alkaline. Some pedons have an AC horizon in place of the Bw horizon.
The C horizon has 10YR or 2.5Y hue, value of 6 to 8 and 5 or 6 moist, and chroma of 2 or 3 dry or moist. It is loam, silt loam, very fine sandy loam, fine sand loam or loamy very fine sand. It is slightly alkaline or moderately alkaline.
COMPETING SERIES: These are the McConaughy and Tripp series in the same family. McConaughy soils have carbonates at depths of less than 15 inches. Tripp soils formed in alluvium or loess and do not have bedrock within depths of 60 inches.
GEOGRAPHIC SETTING: The Oglala soils are on nearly level to steep uplands. Surfaces are plain to convex and slope gradients range from 0 to 40 percent. These soils formed in silty or loamy residuum weathered from soft fine grained sandstone. The mean annual temperature ranges from 45 to 53 degrees F, and the mean annual precipitation ranges from 12 to 18 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Alliance, Canyon, Keith, Richfield, and Rosebud soils. Alliance soils are on similar landscapes and have an argillic horizon. Canyon soils are on similar landscapes and have bedrock within depths of 20 inches. Rosebud soils commonly are on less sloping similar landscapes and have bedrock between depths of 20 and 40 inches and have an argillic horizon. Keith and Richfield soils commonly are on higher tablelands. Keith and Richfield soils have an argillic horizon.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained or well drained. Runoff is low to very high. Permeability is moderate.
USE AND VEGETATION: Used mainly as rangeland. Native vegetation is mainly western wheatgrass, green needlegrass, needleandthread, sideoats grama, blue grama, sedges, and forbs.
DISTRIBUTION AND EXTENT: Southwestern South Dakota and western Nebraska. The series is extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Dawes County, Nebraska, 1973.
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 15 inches (A1 and A2 horizons); cambic horizon - the zone from a depth of about 15 to 29 inches (Bw horizon).