LOCATION STIRK SDEstablished Series
TAXONOMIC CLASS: Very-fine, smectitic, calcareous, mesic Vertic Ustifluvents
TYPICAL PEDON: Stirk clay - on a plane slope of less than 1 percent under native grass. When described the soil was dry throughout. (Colors are for dry soil unless otherwise stated.)
A--0 to 1 inch; light gray (10YR 7/1) clay, light brownish gray (10YR 6/2) moist; smooth platy crust on surface, weak fine subangular blocky structure parting to weak fine granular in lower part; hard, friable, sticky and plastic; strong effervescence; moderately alkaline; abrupt smooth boundary. (0 to 4 inches thick)
AC--1 to 7 inches; gray (10YR 5/1) and light brownish gray (10YR 6/2) clay, dark gray (10YR 4/1) and dark grayish brown (10YR 4/2) crushing to grayish brown (10YR 5/2) moist; weak medium and coarse prismatic structure parting to weak coarse through fine subangular blocky; extremely hard, extremely firm, very sticky and very plastic; strong effervescence; moderately alkaline; clear smooth boundary. (0 to 8 inches thick)
C--7 to 60 inches; light gray (2.5Y 7/2) clay, light brownish gray (2.5Y 6/2) moist; weak coarse prismatic structure parting to weak coarse subangular blocky in upper 20 inches and massive below; extremely hard, extremely firm, very sticky and very plastic; stratified with thin lenses of coarser materials; few fine accumulations of salts; strong effervescence; moderately alkaline.
TYPE LOCATION: Mellette County, South Dakota; about 3 miles west of Cedar Butte; 2300 feet east and 690 feet north of the southwest corner of sec. 25, T. 42 N., R. 32 W.
RANGE IN CHARACTERISTICS: The 10- to 40-inch control section averages more than 60 percent clay. Below a depth of 40 inches, strata range from clay to sandy loam. The profile contains free carbonate in all parts between a depth of 10 and 20 inches and typically is calcareous throughout. However, some pedons contain thin lenses that do not have free carbonate. The soil is slightly alkaline or moderately alkaline throughout. During dry periods, cracks 1/2 to 3 inches in width and several feet in length extend downward several feet in depth.
The A horizon has hue of 10YR, 2.5Y, or 5Y; value of 4 to 7 and 3 to 6 moist; and chroma of 1 or 2. It is silty clay or clay.
The AC and C horizons have hue of 10YR, 2.5Y, or 5Y; value of 5 to 8 and 4 to 6 moist; and chroma of 1 or 2. Buried dark colored horizons are in some pedons below depths of 30 inches.
COMPETING SERIES: The Catman series is in the same family. Catman soils are in a somewhat drier and warmer area.
GEOGRAPHIC SETTING: Stirk soils are nearly level on flood plains and alluvial fans. Slope gradients are less than 2 percent. They formed in calcareous clayey sediments derived from clay shale. Frequency of flooding depends on their position with that of the stream. Mean annual temperature ranges from 45 to 49 degrees F, and the mean annual precipitation ranges from 14 to 19 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Glenberg, Haverson, Lohmiller, Opal, Promise, Sansarc, and Stetter soils. The Glenberg, Haverson, Lohmiller, and Stetter soils are on similar landscapes. Glenberg soils are coarse-loamy; Haverson soils are fine-loamy and Lohmiller soils are fine textured. Opal, Promise, and Sansarc soils are on adjoining uplands and these soils are not stratified. The Stetter soils are drier and are leached of carbonate to greater depths.
DRAINAGE AND PERMEABILITY: Well drained and moderately well drained. Runoff is medium. Some areas of Stirk soils are frequently or occasionally flooded or ponded for brief periods. Permeability is very slow.
USE AND VEGETATION: Used entirely for rangeland and native hay production. Native grasses are mostly western wheatgrass, blue grama, green needlegrass, sedges, and forbs. Trees are common immediately adjacent to the stream channels.
DISTRIBUTION AND EXTENT: Of small extent in southwestern South Dakota.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Mellette County, South Dakota; 1971.
REMARKS: Diagnostic horizons and features recognized in this pedon are: ochric epipedon - the zone from the surface of the soil to a depth of about 1 inch (A horizon).