LOCATION YANKTON SDEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Pachic Haplustolls
TYPICAL PEDON: Yankton silt loam, on a convex, south-facing slope of 1 percent, in a cultivated area. When described the soil was moist to a depth of 34 inches. (Colors are for dry conditions unless otherwise stated.)
Ap--0 to 7 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; weak medium subangular blocky structure parting to weak fine and medium granular; slightly hard, friable; slightly acid; abrupt smooth boundary.
A1--7 to 13 inches; dark grayish brown (10YR 4/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak medium and coarse subangular blocky structure; slightly hard, friable; slightly acid; clear smooth boundary.
A2--13 to 18 inches; grayish brown (10YR 5/2) silt loam; dark brown (10YR 3/3) moist; weak medium subangular blocky structure parting to moderate fine and medium granular; hard, friable, slightly sticky and slightly plastic; strongly effervescent; slightly alkaline; clear wavy boundary. (Combined thickness of the A horizon is 10 to 26 inches.)
Bw--18 to 28 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak medium prismatic structure parting to moderate medium blocky and subangular blocky; hard, friable, slightly sticky and slightly plastic; strongly effervescent; slightly alkaline; clear wavy boundary. (6 to 15 inches thick)
BCk--28 to 34 inches; light brownish gray (2.5Y 6/2) silt loam; dark grayish brown (10YR 4/2) moist; weak coarse subangular blocky structure; hard, friable, slightly sticky and slightly plastic; strongly effervescent; common medium accumulations of carbonates; slightly alkaline; gradual wavy boundary. (0 to 8 inches thick)
2C--34 to 60 inches; light gray (2.5Y 7/2) clay loam, light brownish gray (2.5Y 6/2) moist; massive; hard, firm, sticky and plastic; strongly effervescent; common fine accumulations of carbonates; slightly alkaline.
TYPE LOCATION: Bon Homme County, South Dakota; about 3 1/2 miles south and 4 miles west of Tabor; located about 1,850 feet west and 360 feet north of the southeast corner of section 6, T. 93 N., R. 58 W.; USGS Tabor topographic quadrangle; lat. 42 degrees 53 minutes 41 seconds N. and long. 97 degrees 44 minutes 27 seconds W., NAD 83.
RANGE IN CHARACTERISTICS: Thickness of the solum typically is 30 to 40 inches but ranges from 25 to 45 inches. Depth to glacial till typically is 30 to 36 inches but ranges from 25 to 40 inches. Thickness of the mollic epipedon is 20 to 40 inches, and it extends into the B horizon in most pedons. Depth to carbonates ranges from 10 to 20 inches. The control section averages 18 to 27 percent clay.
The Ap and A horizon has hue of 10YR, value of 3 to 5, 2 or 3 moist, and chroma of 1 to 3. It ranges from slightly acid in the upper part to slightly alkaline in the lower part. In most pedons, the upper A horizon averages 15 to 18 percent clay and the lower part contains more than 18 percent clay and has a stronger grade of structure.
The B horizon has hue of 10YR or 2.5Y, value of 4 or 5, 3 or 4 moist, and chroma of 2 or 3. It is neutral or slightly alkaline.
The BCk horizon has hue of 10YR or 2.5Y, value of 5 or 6, 3 or 4 moist, and chroma of 2 or 3. It has few to many, fine or medium accumulations of carbonates. Some pedons lack carbonates in the BC horizon. It is slightly alkaline or moderately alkaline. A 2BC horizon is in some pedons.
The 2C horizon has hue of 10YR or 2.5Y, value of 5 to 7, 4 to 6 moist, and chroma of 2 to 4. It typically is clay loam but is loam in some pedons. It is slightly alkaline or moderately alkaline. Accumulations of carbonates range from few to many. Some pedons have mottles.
COMPETING SERIES: These are the Duroc, Eltree, Graceville, Trent, and Viborg soils in the same family and the Eakin and Egan series. The Duroc, Eltree, and Graceville soils do not have glacial till between depths of 20 and 40 inches. In addition, Duroc soils receive less rainfall, and Graceville soils typically contain more clay and are leached of carbonates to greater depths. Trent and Viborg soils contain more clay and are leached of carbonates to greater depths. In addition, Viborg soils have mottles above 40 inches. The Eakin soils have mollic epipedons less than 20 inches thick and have an argillic horizon. Egan soils have mollic epipedons less than 20 inches thick.
GEOGRAPHIC SETTING: The Yankton soils are nearly level to moderately sloping on uplands. Surfaces are plane or convex, and slope gradients range from 0 to 9 percent but typically are less than 6 percent. Yankton soils formed in calcareous silty sediments underlain by loamy glacial till. The thickness of these silty sediments ranges from about 2 to 3.5 feet. The mean annual air temperature ranges from 47 to 50 degrees F. The mean annual precipitation ranges from 20 to 24 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Eltree soils and Alcester, Clarno, Ethan, and Roxbury soils. Eltree soils typically are on gentle slopes below the Yankton soils. Alcester soils are leached of carbonates to greater depths and are in swales. Clarno and Ethan soils are fine-loamy and are on crests of knolls and ridges. Roxbury soils are stratified and on the flood plains.
DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderate in the solum and slow or moderately slow in the underlying glacial till. Runoff is slow on nearly level areas and medium on sloping areas.
USE AND VEGETATION: These soils are used mainly for cropland. Small grains, corn, alfalfa, and feed grains are the principal crops. Principal native grasses are big bluestem, green needlegrass, little bluestem, needleandthread, sideoats grama, sedges, and forbs.
DISTRIBUTION AND EXTENT: Southeastern South Dakota. This soil is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Bon Homme County, South Dakota, 1981.