LOCATION KOTO SDEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Argiaquic Argialbolls
TYPICAL PEDON: Koto loam - on a plane slope of less than 1 percent in a depression in a formerly cultivated field. When described the soil was dry to 30 inches and moist below. (Colors are for moist soil unless otherwise stated.)
A--0 to 8 inches; black (10YR 2/1) loam, dark gray (10YR 4/1) dry; weak very fine granular structure; slightly hard, very friable; many fine roots; moderately acid; abrupt smooth boundary. (5 to 10 inches thick)
E--8 to 11 inches; dark grayish brown (10YR 4/2) fine sandy loam, light gray (10YR 7/1) dry; common fine distinct yellowish brown (10YR 5/4) and dark brown (7.5YR 4/4) mottles; weak thin platy structure; soft, very friable; common very fine roots; common fine and very fine pores; slightly acid; clear irregular boundary. (2 to 9 inches thick)
Bt1--11 to 18 inches; very dark grayish brown (10YR 3/2) sandy clay loam, grayish brown (10YR 5/2) dry; few fine prominent light olive brown (2.5Y 5/4) mottles; strong coarse columnar structure parting to moderate coarse and medium blocky; hard, very friable; common very fine roots; common fine pores; thin continuous light gray (10YR 7/1) and gray (10YR 6/1) coatings on prism tops and sides; common medium and fine dark stains (iron and manganese oxides) along faces of peds and along root pores; moderately acid; clear wavy boundary.
Bt2--18 to 27 inches; dark grayish brown (10YR 4/2) sandy clay loam, grayish brown (10YR 5/2) dry; few fine prominent yellowish brown (10YR 5/6) mottles in interiors of peds; strong very coarse and coarse prismatic structure parting to moderate coarse and moderately subangular blocky; hard, friable; common very fine roots; common fine pores; shiny films on faces of peds; common fine dark stains (iron and manganese oxides) in interiors of peds and along root pores; moderately acid; clear wavy boundary. (Combined Bt horizons is 8 to 21 inches thick.)
Btk--27 to 32 inches; grayish brown (2.5Y 5/2) loam, light brownish gray (2.5Y 6/2) dry; common medium and fine prominent yellowish brown (10YR 5/6) mottles; moderate medium and fine blocky structure; slightly hard, very friable; few very fine roots; common fine pores; common tongues 1/4 to 1/2 inch thick of dark grayish brown (10YR 4/2); common fine accumulations of carbonate; violent effervescence; slightly alkaline; clear wavy boundary. (0 to 10 inches thick)
Bk--32 to 42 inches; grayish brown (2.5Y 5/2) sandy loam, light gray (2.5Y 7/2) dry; common medium and fine prominent yellowish brown (10YR 5/6) and common fine distinct gray (10YR 6/1) mottles; weak medium and fine subangular blocky structure; slightly hard, very friable; common fine pores; bedding planes evident; common fine accumulations of carbonate; strong effervescence; moderately alkaline; clear smooth boundary. (Combined Bk horizons is 0 to 20 inches thick.)
2C1--42 to 55 inches; grayish brown (2.5Y 5/2) loam, light gray (2.5Y 7/2) dry; many medium and fine prominent dark brown (7.5YR 4/4) and gray (10YR 6/1) mottles; massive; slightly hard, very friable; few fine pores, 10 percent pebbles; few fine accumulations of carbonate; strong effervescence; moderately alkaline; clear smooth boundary.
2C2-55 to 60 inches; light olive brown (2.5Y 5/4) loam, light yellowish brown (2.5Y 6/4) dry; common fine distinct yellowish brown (10YR 5/6) and gray (10YR 6/1) mottles; massive; slightly hard, very friable; few small pebbles; strong effervescence; moderately alkaline.
TYPE LOCATION: Brown County, South Dakota; about 9 1/2 miles west and 1 mile north of Westport; 1,950 feet east and 290 feet north of the southwest corner, sec. 5, T. 125 N., R. 65 W.
RANGE IN CHARACTERISTICS: The depth to free carbonates is 15 to 40 inches. The mollic epipedon ranges from 7 to 19 inches and includes the upper part of the Bt horizon in some pedons. The underlying material contains up to 15 percent by volume coarse fragments.
The A horizon has hue of 10YR, value of 2 to 4 and 3 to 5 dry, and chroma of 1. It is loam, fine sandy loam, or sandy loam. It ranges from moderately acid to neutral.
The E horizon has a hue of 10YR, value of 3 to 5 and 6 or 7 dry, and chroma of 1 or 2. It is fine sandy loam, sandy loam, loamy fine sand or loamy sand. Mottles range from few to many and faint to prominent. The E horizon extends into the Bt horizon in some pedons and bleached sand and silt coats the surfaces of peds in the Bt horizon. It ranges from moderately acid to slightly alkaline.
The Bt horizon has hue of 2.5Y or 10YR, value of 3 to 5 and 4 to 7 dry, and chroma of 1 or 2. It is clay loam, sandy clay loam, or sandy loam and has 18 to 30 percent clay. There is a wide range in amount and distinctness of mottling. The Bt horizon ranges from moderately acid to moderately alkaline. Some pedons do not have columnar structure.
The Btk horizon has hue of 2.5Y or 10YR, value of 4 to 6 and 5 to 7 dry, and chroma of 1 to 4. It is loam, sandy clay loam, or sandy loam. It is slightly alkaline or moderately alkaline.
The Bk horizon has hue of 5Y to 10YR, value of 4 to 6 and 5 to 8 dry, and chroma of 1 to 4. It is loam, sandy loam, loamy sand, sandy clay loam, or clay loam. It is slightly alkaline to strongly alkaline. Some pedons have a C horizon.
The 2C horizon has hue of 10YR, 2.5Y, or 5Y; value of 4 to 6 and 6 to 8 dry; and chroma of 1 to 4. It is clay loam, or loam. It ranges from slightly alkaline to strongly alkaline. Mottles range from common to many and faint to prominent.
COMPETING SERIES: There are no other series in the same family.
GEOGRAPHIC SETTING: Koto soils are in depressions. Slope gradients are less than 1 percent. The soils formed in loamy glacial outwash sediments over glacial till. Mean annual air temperature ranges from 38 to 45 degrees F, and mean annual precipitation ranges from 16 to 24 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bowbells, Harriet, Letcher, Miranda, Niobell, Nishon, Noonan, Tally, Tonka, and Williams soils. The moderately well drained Bowbells soils are in nearby swales. Harriet, Nishon, and Tonka soils have fine textures and are on similar landscape as the Koto soils. Letcher, Miranda, Niobell, and Noonan soils have a natric horizon and are on slightly higher nearby uplands. The well drained Tally and Williams soils are on nearby uplands. In addition, Tally soils are coarse-loamy.
DRAINAGE AND PERMEABILITY: Poorly drained. Surface runoff is negligible. Permeability is slow. The depth to the water table ranges from 1 to 3 feet in the spring.
USE AND VEGETATION: Used mainly for hay and pasture. Cultivated areas are used mainly for growing small grain, alfalfa, and tame pasture. Native vegetation mainly is big bluestem, prairie cordgrass, switchgrass, and sedges.
DISTRIBUTION AND EXTENT: Northeastern South Dakota. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Brown County, South Dakota, 1987.
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 8 inches (A horizon) and from 11 to 18 inches (Bt1 horizon); albic horizon - the zone from about 8 to 11 inches (E horizon); argillic horizon - the zone from about 11 to 32 inches (Bt1, Bt2, and Btk horizons).