LOCATION PLANKINTON SDEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Typic Argialbolls
TYPICAL PEDON: Plankinton silt loam - in a level upland depression in native grass. When described the soil was moist throughout. (Colors are for moist soil unless otherwise stated.)
A--0 to 4 inches; very dark gray (10YR 3/1) silt loam, dark gray (10YR 4/1) dry; weak very thin platy structure parting to weak fine granular; slightly hard, very friable; many fine and medium roots; slightly acid; clear smooth boundary. (3 to 6 inches thick)
E--4 to 8 inches; dark gray (10YR 4/1) silt loam, light gray (10YR 7/1) dry; common fine distinct yellowish brown (10YR 5/4) mottles; weak thin and medium platy structure parting to weak fine subangular blocky; slightly hard, very friable; common fine roots; few fine vertical pores; few fine dark concretions (iron and manganese oxides); neutral; abrupt smooth boundary. (2 to 5 inches thick)
Bt1--8 to 19 inches; black (10YR 2/1) silty clay, dark gray (10YR 4/1) dry; moderate medium prismatic structure parting to moderate fine and medium subangular blocky; very hard, firm, sticky and plastic; shiny film on faces of peds; few fine roots; common fine dark concretions (iron and manganese oxides); neutral; gradual wavy boundary.
Bt2--19 to 28 inches; black (10YR 2/1) silty clay, dark gray (10YR 4/1) dry; moderate medium and coarse prismatic structure parting to weak medium subangular blocky; very hard, firm, sticky and plastic; shiny film on faces of peds; few fine roots; few fine dark concretions (iron and manganese oxides); moderately alkaline; clear wavy boundary. (Combined Bt horizons is 14 to 35 inches thick.)
Bk--28 to 40 inches; very dark gray (10YR 3/1) and dark gray (N 4/0) silty clay loam, dark gray (10YR 4/1) and grayish brown (2.5Y 5/2) dry; weak medium and coarse prismatic structure parting to moderate fine and medium subangular blocky; hard, firm, slightly sticky and slightly plastic; few fine roots; few fine dark concretions (iron and manganese oxides); common fine accumulations of carbonate on vertical faces of peds; strong effervescence; moderately alkaline; gradual wavy boundary. (5 to 24 inches thick)
C1--40 to 55 inches; grayish brown (2.5Y 5/2) clay loam, light gray (2.5Y 7/2) dry; common fine and medium prominent dark reddish brown (5YR 3/2) mottles and common medium distinct dark gray (N 4/0) mottles; weak medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few fine concretions (iron and manganese oxides); few fine accumulations of carbonate; violent effervescence.
C2--55 to 60 inches; grayish brown (2.5Y 5/2) and light olive brown (2.5Y 5/4) clay loam, light gray (2.5Y 7/2) and light yellowish brown (2.5Y 6/4) dry; common fine prominent strong brown (7.5YR 5/6) mottles; massive; hard, friable, slightly sticky and slightly plastic; common fine dark concretions (iron and manganese oxides); few fine accumulations of carbonate; strong effervescence; moderately alkaline.
TYPE LOCATION: Aurora County, South Dakota, about 1 mile west and 1/2 mile south of Aurora Center, 2,050 feet north and 230 feet east of the southwest corner of sec. 26, T. 101 N., R. 65 W.
RANGE IN CHARACTERISTICS: Depth to carbonate and thickness of the mollic epipedon typically is 24 to 38 inches but ranges from 24 to 50 inches.
The A horizon has hue of 10YR, value of 2 or 3 and 4 or 5 dry, and chroma of 1 or 2. It is medium acid to neutral.
The E horizon has hue of 10YR, value of 4 to 5 and 5 to 7 dry, and chroma of 1 or 2. Few to many, distinct or prominent mottles are in most pedons. It is medium acid to neutral.
The Bt horizon has hue of 10YR or 2.5Y, value of 2 or 3 and 3 to 5 dry, and chroma of 2 or less. It is silty clay, clay, silty clay loam or clay loam. Clay content typically is about 50 percent, but ranges from 38 to 60 percent. It is slightly acid to moderately alkaline.
The Bk horizon has hue of 10YR, 2.5Y, 5Y, or is neutral, value of 3 to 5 and 4 to 6 dry, and chroma of 3 or less. It is silty clay loam, clay loam, clay or silty clay. Some pedons do not have free carbonate. It ranges is neutral to moderately alkaline. BC horizons are in some pedons.
The C horizon has hue of 2.5Y or 5Y, value of 3 to 5 and 4 to 7 dry, and chroma of 1 to 4. It is clay loam, silty clay loam, silty clay or clay. Some pedons are stratified with thin lenses of loam or silt loam. It has few or common, fine to coarse accumulations of carbonate in most pedons. It is slightly alkaline or moderately alkaline. Accumulations of gypsum are in the Bk and C horizons of some pedons. Buried A horizons are between depths of 40 and 60 inches in some pedons.
COMPETING SERIES: These are Barbert, Chauncey, Edina, Fillmore, Goose Lake, Massie, Rolfe, Scott, and Sperry series in the same family. Babert soils formed in lacustrine sediments and have a wetter climate. Chauncey, Edina, Rolfe, and Sperry soils have wetter climates. In addition, Sperry and Edina are leached of carbonate to greater depths and Rolfe soils are more acid in the solum. Fillmore and Scott soils formed in loess and Scott soils are more poorly drained and Fillmore soils have a thicker A horizon. Goose Lake soils formed in sediments weathered from tuff, rhyolite, and basalt. The very poorly drained Massie soils do not have carbonate above depths of 50 inches.
GEOGRAPHIC SETTING: The Plankinton soils are level in depressions and in narrow poorly defined drainageways on glacial till plains. Slopes are less than 1 percent. They formed in local alluvial sediments overlying glacial till. The mean annual temperature ranges from 45 to 52 degrees F, and mean annual precipitation ranges from 16 to 26 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the soils and the Clarno, Dudley, Ethan, Hoven, Houdek, Prosper, Stickney, Tetonka, and Worthing soils. Clarno, Ethan, and Houdek soils are well drained and are on higher parts of the landscape. Dudley, Prosper, and Stickney soils are moderately well drained and are in swales and nearly level upland positions. In addition, Dudley and Stickney soils have natric horizon. Hoven, Tetonka and Worthing soils are on similar landscapes. Hoven soils have a natric horizons. Tetonka soils have thicker A horizons and lack an abrupt textural change from the albic to the argillic horizon. Worthing soils do not have E horizons.
DRAINAGE AND PERMEABILITY: Poorly drained. These soils are ponded after heavy rains and by meltwater from snow. Surface runoff is ponded. Permeability is slow or very slow.
USE AND VEGETATION: Largely cropped when drained. Small grain, tame grasses, corn, and grain sorghum are the most common crops. Native vegetation is mainly western wheatgrass and sedges.
DISTRIBUTION AND EXTENT: Central and south-central South Dakota east of the Missouri River. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Aurora County, South Dakota, 1979.
REMARKS: Diagnostic horizons and features recognized in this pedon aer: mollic epipedon - the zone from the surface of the soil to a depth of about 28 inches (A, E, Bt1, & Bt2 horizon); albic horizon - the zone from about 4 to 8 inches (E horizon); argillic horizon - the zone from about 8 to 28 inches (Bt1 & Bt2 horizons).