LOCATION OWANKA SDEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Torrertic Haplustolls
TYPICAL PEDON: Owanka clay loam - on a plane slope of 1 percent in alfalfa-grass hayland. When described the soil was moist throughout. (Colors are for dry soil unless otherwise stated)
A--0 to 6 inches; dark grayish brown (10YR 4/2) clay loam, very dark gray (10YR 3/1) moist; moderate medium and fine granular structure; hard, friable, sticky and plastic; common fine and coarse roots; neutral; clear smooth boundary. (5 to 7 inches thick)
Bw1--6 to 13 inches; dark grayish brown (10YR 4/2) clay loam, very dark grayish brown (10YR 3/2) moist; weak medium prismatic structure parting to weak fine and medium subangular blocky; hard, friable, sticky and plastic; few fine and coarse roots; neutral; clear smooth boundary.
Bw2--13 to 18 inches; dark grayish brown (10YR 4/2) clay loam, very dark grayish brown (10YR 3/2) moist; weak medium and coarse prismatic structure parting to moderate medium and fine subangular blocky; hard, friable, sticky and plastic; few fine roots; slightly alkaline; clear wavy boundary. (Combined Bw horizons is 5 to 14 inches thick.)
Bk1--18 to 27 inches; grayish brown (10YR 5/2) clay loam, dark grayish brown (10YR 4/2) moist; weak coarse prismatic structure parting to moderate medium subangular blocky; hard, friable, sticky and plastic; few fine roots; few fine accumulations of carbonate; slight effervescence; moderately alkaline; gradual wavy boundary.
Bk2--27 to 35 inches; grayish brown (10YR 5/2) clay loam, dark grayish brown (10YR 4/2) moist; weak coarse prismatic structure parting to moderate coarse subangular blocky; hard, friable, sticky and plastic; very few fine roots; few fine and medium accumulations of carbonate; strong effervescence; moderately alkaline; gradual wavy boundary. (Combined Bk horizons is 12 to 25 inches thick.)
C--35 to 60 inches; grayish brown (10YR 5/2) clay loam, dark grayish brown (10YR 4/2) moist; massive; hard, friable, sticky and plastic; few fine accumulations of carbonate; slight effervescence; moderately alkaline.
TYPE LOCATION: Pennington County, South Dakota; about 13 miles east of Rapid City; 2480 feet north and 200 feet east of the southwest corner of sec. 9, T. 1 S., R. 10 E.
RANGE IN CHARACTERISTICS: The depth to carbonates ranges from 10 to 20 inches. The thickness of the mollic epipedon ranges from 9 to 20 inches. Coarse and medium gravels are scattered throughout the pedon and make up less than 10 percent by volume. Thin lens of coarse and medium gravel occur between depths of 40 and 60 inches in some pedons and are less than 4 inches thick. The control section contains 35 to 45 percent clay and less than 15 percent fine sand or coarser.
The A horizon has hue of 10YR or 2.5Y, value of 4 or 5, 2 or 3 moist, and chroma of 1 or 2. It is clay loam, silty clay, or silty clay loam. Reaction is slightly acid to slightly alkaline.
The Bw horizon has hue of 10YR or 2.5Y, value of 4 to 6, 2 to 5 moist, and chroma of 1 to 3. It is clay loam or silty clay loam. Reaction is slightly acid to slightly alkaline.
The Bk and C horizons have hue of 10YR or 2.5Y, value of 5 or 6, 4 or 5 moist, and chroma of 2 or 3. They are clay loam or silty clay loam. They have few to common, fine to medium accumulations of carbonate. Some pedons have accumulations of gypsum and other salts. Reaction is slightly or moderately alkaline.
COMPETING SERIES: These are the Maggin series in the same family. Maggin soils are moderately deep to shale.
GEOGRAPHIC SETTING: Owanka soils are on nearly level to level stream terraces and alluvial fans. Slopes are smooth and plane. Slope gradients range from 0 to 3 percent. Owanka soils formed in clayey sediments. Mean annual air temperature ranges from 43 to 48 degrees F. Mean annual precipitation ranges from 14 to 18 inches. Growing season is about 110 to 140 days, average growing season precipitation ranges from 11 to 16 inches; and growing degree days are about 2400 to 3200.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Arvada, Bridgeport, Colombo, Egas, Haverson, Kyle, and Lohmiller soils. These soils are all on landscapes similar to the Owanka. The Arvada, Haverson, Kyle, and Lohmiller soils do not have a mollic epipedon. In addition, the Arvada soils have a natric horizon; Haverson and Lohmiller soils are stratified within a depth of 40 inches; and Kyle soils have a very fine series control section. Bridgeport soils are fine-silty. Colombo soils are fine-loamy. Egas soils have a SAR of more than 8 throughout the profile, and are poorly or very poorly drained.
DRAINAGE AND PERMEABILITY: Well drained. Runoff is low. Permeability is moderately slow.
USE AND VEGETATION: The primary use of the Owanka soil is irrigated cropland or hayland. Grain sorghum, corn, alfalfa, and smooth bromegrass are the main crops. Native vegetation is principally western wheatgrass, green needlegrass, prairie dropseed, bluegrama, needleandthread, sedges and forbs.
DISTRIBUTION AND EXTENT: Southwest South Dakota. It is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Pennington County, South Dakota, 1986.
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 18 inches (A, Bw1 and Bw2 horizons); ustoll feature - rainfall 14 to 18 inches. This soil has a relatively high organic carbon content at 50 inches but is not considered Fluventic.
ADDITIONAL DATA: See S85SD-103-004.