LOCATION CAVO SDEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Typic Natrustolls
TYPICAL PEDON: Cavo silt loam - on a slope of less than 1 percent in native grass. When described the soil was dry throughout. (Colors are for dry soil unless otherwise stated)
A- 0 to 4 inches; dark gray (10YR 4/1) silt loam, very dark gray (10YR 3/1) moist; weak fine granular structure; soft, very friable; many very fine and few fine roots; neutral, clear smooth boundary. (3 to 6 inches thick)
E- 4 to 8 inches; gray (10YR 5/1) loam, very dark gray (10YR 3/1) moist; weak and moderate thin platy structure; soft, very friable; common very fine and few fine roots; neutral; abrupt smooth boundary. (2 to 4 inches thick)
Btn1- 8 to 10 inches; dark gray (10YR 4/1) clay loam, very dark gray (10YR 3/1) moist; moderate medium columnar structure parting to moderate medium subangular blocky; very hard, firm, sticky and plastic; common very fine and few fine roots; thin continuous gray (10YR 5/1) coatings on tops of columns; continuous shiny films on vertical faces of peds; slightly alkaline; clear smooth boundary.
Btn2- 10 to 14 inches; dark grayish brown (10YR 4/2) clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium subangular blocky structure; very hard, firm, sticky and plastic; few very fine roots; continuous shiny films on vertical faces of peds; moderately alkaline; gradual smooth boundary.
Btn3- 14 to 19 inches; grayish brown (10YR 5/2) clay loam, dark grayish brown (10YR 4/2) moist; moderate medium subangular blocky structure; very hard, firm, sticky and plastic; common very fine roots; continuous shiny films on vertical faces of peds; moderately alkaline; gradual smooth boundary. (Combined Btn horizons 5 to 13 inches thick)
Bkz- 19 to 27 inches; grayish brown (2.5Y 5/2) clay loam, dark grayish brown (2.5Y 4/2) moist; weak medium subangular blocky structure; very hard, friable, sticky and plastic; few very fine roots; few fine masses of carbonate; few fine nests of salts; about 2 percent rock fragments; strong effervescence; moderately alkaline; gradual smooth boundary. (6 to 20 inches thick)
BCkz- 27 to 41 inches; grayish brown (2.5Y 5/2) clay loam, dark grayish brown (2.5Y 4/2) moist; massive; very hard, friable, sticky and plastic; few very fine roots; common fine masses of carbonate; common fine nests of salts; about 3 percent rock fragments; strong effervescence; moderately alkaline; gradual smooth boundary. (0 to 20 inches thick)
C- 41 to 60 inches; light brownish gray (2.5Y 6/2) clay loam, grayish brown (2.5Y 5/2) moist; few fine distinct yellowish brown (10YR 5/6) and very dark brown (10YR 2/2) redox concentrations; massive; very hard, friable, sticky and plastic; few very fine roots; common fine and medium masses of carbonate; few fine nests of salts; about 5 percent rock fragments; strong effervescence; moderately alkaline.
TYPE LOCATION: Buffalo County, South Dakota; about 6 miles west of Gann Valley; 900 feet north and 120 feet west of the southeast corner of sec. 28, T. 107 N., R. 69 W.
RANGE IN CHARACTERISTICS: Depth to carbonates range from 10 to 20 inches. Thickness of the mollic epipedon is less than 20 inches and includes all or part of the Btn horizon. The natric horizon has a SAR of 10 to 20.
The A horizon has value of 4 or 5 and 2 or 3 moist, and chroma of 1 or 2. It is loam or silt loam and is slightly acid or neutral.
The E horizon has value of 5 to 7 and 3 or 4 moist, and chroma of 1 or 2. It is loam or silt loam and is slightly acid or neutral. The A and E horizons are usually mixed, when cultivated.
The Btn horizon has hue of 10YR or 2.5Y, value of 4 or 5 and 3 or 4 moist, and chroma of 1 or 2. It is clay loam or clay averaging 35 to 50 percent clay. It is slightly alkaline or moderately alkaline.
The Bkz and BCkz horizons have hue of 10YR, 2.5Y or 5Y, value of 5 or 6 and 4 or 5 moist, and chroma of 2 or 3. They are clay loam or clay and moderately alkaline or strongly alkaline. They contain few to many, fine or medium masses of carbonates. Few to many concentrations of visible salts or gypsum occur below 16 inches. The horizons contain 1 to 10 percent coarse fragments.
The C 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 typically is clay loam, but is clay in some pedons. It is moderately alkaline or strongly alkaline. Visible salts and gypsum vary between pedons and range from few to common, fine or medium nests or threads. It does not contain masses of carbonates in some pedons. It contains 1 to 10 percent coarse fragments.
COMPETING SERIES: These are the DeGrey, Dudley, Dwight, Farmsworth and Wood River soils. DeGrey soils contain less than 15 percent fine sand and coarser in the control section. Dudley and Farmsworth soils have mollic epipedons more than 20 inches thick. Dwight soils contain less sand in the control section, have a wetter soil moisture control section and have a soil temperature of more than 50 degrees F. Wood River soils contain less sand and typically are leached of carbonates to greater depths.
GEOGRAPHIC SETTING: Cavo soils are on level to gently sloping till plains. Slope gradients typically are less than 2 percent but range from 0 to 6 percent. They formed in glacial till. Mean annual air temperature ranges from 45 to 48 degrees F, and mean annual precipitation ranges from 17 to 21 inches. Growing season is about 130 to 155 days; growing season precipitation ranges from 13 to 17 inches; and growing degree days are about 2800 to 3200.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Demky, Glenham, Hoven, Jerauld, Oko, Onita and Raber soils. Demky and Jerauld soils are on similar landscapes. Demky soils do not have columnar structure and have tonguing of an albic horizon into the natric horizon. Jerauld soils have visible salts within 16 inches of the surface. Glenham, Oko and Raber soils do not have natric horizons and are on similar landscapes and adjacent uplands. Hoven soils are poorly or very poorly drained and are in upland basins. Onita soils do not have natric horizons and are on foot slopes.
DRAINAGE AND PERMEABILITY: Moderately well drained. Runoff is low to high depending on slope. Permeability is slow or very slow.
USE AND VEGETATION: Soils are used for cropland and rangeland. Small grain, sorghum, corn, and alfalfa are the principal crops in cultivated areas. Native vegetation is dominantly western wheatgrass, green needlegrass, blue grama, sedges, and forbs.
DISTRIBUTION AND EXTENT: Central South Dakota. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Hughes County, South Dakota, 1971.
REMARKS: Diagnostic horizons and features recognized in this pedon are: mollic epipedon - the zone from the surface of the soil to a depth of 14 inches (A, E, Btn1, Btn2 horizons); natric horizon - zone from 8 to 19 inches (Btn1, Btn2 and Btn3 horizons).
ADDITIONAL DATA: Reference data - S71-SDak-32-2, Lincoln SSIU, Sample Nos. - 71L360-71L368.