LOCATION MCCLURE SDEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Typic Argiustolls
TYPICAL PEDON: McClure silt loam - on a southwest-facing convex slope of 3 percent in native grass. When described the soil was dry throughout. (Colors are for dry unless otherwise stated.)
A1--0 to 5 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; weak thin platy structure parting to weak fine granular; slightly hard, friable; slightly acid; clear smooth boundary.
A2--5 to 9 inches; dark grayish brown (10YR 4/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak medium and fine subangular blocky structure; slightly hard, friable; slightly acid; clear smooth boundary. (Combined thickness of the A horizon is 5 to 10 inches.)
Bt1--9 to 14 inches; brown (10YR 5/3) silty clay loam, dark brown (10YR 3/3) moist; weak medium prismatic structure parting to moderate fine subangular blocky; hard, firm, sticky and plastic; shiny surfaces on faces of peds; neutral; clear wavy boundary.
Bt2--14 to 19 inches; brown (10YR 5/3) silty clay loam, dark brown (10YR 4/3) moist; weak medium prismatic structure parting to moderate medium subangular blocky; hard, firm, sticky and plastic; shiny surfaces on faces of peds; slightly alkaline; clear wavy boundary. (Combined thickness of the B2t horizon is 10 to 18 inches.)
Bk1--19 to 24 inches; pale brown (10YR 6/3) silty clay loam, brown (10YR 5/3) moist; weak medium prismatic structure parting to moderate medium subangular blocky; hard, firm, sticky and plastic; few fine accumulations of carbonate; strong effervescence; moderately alkaline; clear wavy boundary. (0 to 10 inches thick)
2Bk2--24 to 34 inches; grayish brown (2.5Y 5/2) clay, dark grayish brown (2.5Y 4/2) moist; weak coarse prismatic structure parting to moderate medium subangular blocky; very hard, very firm, sticky and plastic; common medium soft accumulations of carbonate; violent effervescence; moderately alkaline; clear wavy boundary. (0 to 12 inches thick)
2Bk3--34 to 46 inches; grayish brown (2.5Y 5/2) clay, dark grayish brown (2.5Y 4/2) moist; weak medium subangular blocky structure; very hard, very firm, sticky and plastic; common fine accumulations of carbonate; strong effervescence; moderately alkaline; gradual wavy boundary. (0 to 16 inches thick)
2C--46 to 60 inches; light brownish gray (2.5Y 6/2) silty clay, grayish brown (2.5Y 5/2) moist; massive; hard, firm, sticky and plastic; strong effervescence; moderately alkaline.
TYPE LOCATION: Stanley County, South Dakota; about 11 miles south and 14 miles east of Fort Pierre; 1,590 feet west and 90 feet north of the SE corner of sec. 33, T. 109 N., R. 77 W.
RANGE IN CHARACTERISTICS: The depth to carbonates typically is about 20 to 24 inches and ranges from 14 to 30 inches. Thickness of the mollic epipedon ranges from 7 to 18 inches and includes the upper part of the Bt horizon. Depth to contrasting clayey material ranges from 20 to 40 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 is silt loam or silty clay loam and is slightly acid or neutral.
The Bt horizon has hue of 10YR or 2.5Y, value of 4 or 5 and 2 to 4 moist, and chroma of 2 or 3. It is silty clay loam or silty clay averaging between 35 and 45 percent clay and less than 15 percent fine or coarser sand. It is neutral or slightly alkaline. Some pedons have carbonates in the lower part.
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 is silty clay loam or silty clay. The carbonates are dissemenated or accumulated. It is slightly or moderately alkaline.
The 2Bk horizon, when present, has hue of 2.5Y or 5Y, value of 4 to 7 and 3 to 5 moist, and chroma of 2 to 4. It is silty clay or clay. It has common or many, fine to coarse accumulations of carbonate. It is slightly or moderately alkaline.
The 2C horizon has hue of 2.5Y or 5Y, value of 5 to 7 and 4 to 6 moist, and chroma of 2 to 4. It is silty clay or clay and is slightly or moderately alkaline. Bedded shale is between depths of 40 and 60 inches in some pedons.
COMPETING SERIES: These are the Beadle, Carlson, Harney, Kirley, Mento, Peno, Raber, Reliance, and Spearville series in the same family. Beadle, Kirley, Peno, and Raber soils contain more sand in the argillic horizon. In addition, Beadle, Peno, and Raber soils formed in glacial till. Carlson, Harney, Mento, and Spearville soils have annual temperature higher than 52 degrees F. In addition, Carlson soils typically have carbonates at shallower depths and formed in calcareous residuum or alluvium; Harney soils typically have thicker sola; Mento soils have 5 to 15 percent exchangeable sodium in the B and C horizons; and Spearville soils typically contain more clay in the argillic horizon.
GEOGRAPHIC SETTING: McClure soils are on loess-covered uplands that are underlain by clay residuum. Surfaces are plane or convex. Slope gradients typically are less than 6 percent but range from 0 to 9 percent. McClure soils formed in 20 to 40 inches of silty materials overlying clayey materials. The mean annual temperature ranges from 45 to 52 degrees F, and mean annual precipitation ranges from 15 to 24 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Agar, Carter, Hurley, Promise, Onita, and Reliance soils. Agar and Millboro are in similar nearby landscapes. Agar soils have fine-silty control sections. Carter, Hurley, and Promise soils contain more clay in the series control section and are in nearby landcapes. In addition, Carter and Hurley soils contain appreciable amounts of exchangeable sodium in the control section. Onita soils are in swales. Reliance soils are in the same landscapes. Onita soils have mollic epipedons thicker than 20 inches. Reliance soils do not have contrasting clayey material within a depth of 40 inches.
DRAINAGE AND PERMEABILITY: Well drained. Surface runoff is medium or high. Permeability is slow.
USE AND VEGETATION: About equally divided between native range and cropland. Winter wheat, corn, grain sorghum, and alfalfa are the principal crops. Native vegetation consists mainly of western wheatgrass, green needlegrass, needleandthread, sideoats gram, blue grama, sedges, and forbs.
DISTRIBUTION AND EXTENT: South-central South Dakota. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Stanley 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 (A, Bt1 horizons) and an argillic horizon from 9 to 19 inches (Bt1, Bt2 horizons).