LOCATION EGAS SDEstablished Series
TAXONOMIC CLASS: Fine, smectitic, calcareous, mesic Vertic Endoaquolls
TYPICAL PEDON: Egas silty clay loam - on a slope of less than 1 percent in native grass. When described the soil was moist throughout. (Colors are for moist soil unless otherwise stated)
A1--0 to 1 inches; very dark gray (10YR 3/1) silty clay loam, gray (10YR 5/1) dry; weak medium granular structure; hard, firm, sticky, plastic; moderately alkaline; clear smooth boundary.
A2--1 to 4 inches; black (2.5Y 2/1) silty clay, dark gray (2.5Y 4/1) dry; moderate fine subangular blocky structure; very hard, very firm, very sticky, plastic; moderately alkaline; clear smooth boundary. (Combined A horizons 2 to 20 inches thick)
ACz--4 to 19 inches; very dark gray (2.5Y 3/1) silty clay, gray (2.5Y 5/1) dry; weak fine subangular blocky structure; very hard, very firm, very sticky, plastic; disseminated salt and common fine salt striations, pedons become encrusted with white salts upon drying; strong effervescence; moderately alkaline; gradual wavy boundary. (5 to 30 inches thick)
Cg1--19 to 36 inches; olive gray (5Y 4/2) silty clay, olive gray (5Y 5/2) dry; common fine distinct yellowish brown (10YR 5/6) redox concentrations; massive; very hard, very firm, very sticky, plastic; disseminated salt and few salt striations, pedons become encrusted with white salts upon drying; strong effervescence; moderately alkaline; gradual wavy boundary.
Cg2--36 to 60 inches; dark gray (5Y 4/1) silty clay, gray (5Y 5/1) dry; common fine distinct yellowish brown (10YR 5/6) redox concentrations; massive; very hard, very firm, very sticky, plastic; disseminated salt and few salt striations, peds become encrusted with white salts upon drying, strong effervescence; moderately alkaline.
TYPE LOCATION: Sully County, South Dakota; 11 miles south and 6 miles east of Onida; 473 feet east and 42 feet north of the southwest corner of sec. 36, T. 113 N., R. 76 W.
RANGE IN CHARACTERISTICS: Thickness of the mollic epipedon, typically is 15 to 20 inches and ranges from 8 to 24 inches. The depth to salt accumulations typically is about 4 to 7 inches, but many pedons have salts at the surface. Conductivity typically is 16 or more mmhos/cm and ranges from 8 to more than 50. When the surface is dry, visible crusts of salt are common on many pedons. Carbonate typically is with salt accumulations, but some pedons have horizons with salt accumulations above horizons that contain carbonate. Depth to carbonate ranges from 0 to 10 inches. Some pedons have gypsum crystals in the solum and C horizons. The control section typically averages about 45 percent clay and contains more than 10 percent sand.
The A horizon has hue of 10YR or 2.5Y, value of 2 or 3, and 4 or 5 dry, and chroma of 1 or 2. It is silty clay or silty clay loam. Some pedons have a surface crust of silt loam. It is slightly alkaline to strongly alkaline.
The ACz horizon has hue of 10YR to 5Y, value of 2 to 4 and 4 to 6 dry, and chroma of 1 or 2. It is silty clay loam or silty clay. Some pedons have few or common distinct redox features throughout. It is slightly alkaline to strongly alkaline. Some pedons have accumulations of gypsum.
The C horizon has hue of 2.5Y or 5Y, value of 4 or 5, and 5 to 7 dry, and chroma of 1 or 2. It commonly is silty clay but is silty clay loam, clay loam or clay in some pedons. It has few to many, distinct or prominent redox features, but some pedons do not have redox features. Thin strata of coarser textured materials are below depths of 40 inches in some pedons. It is moderately alkaline or strongly alkaline.
COMPETING SERIES: These are the Herdcamp, Knoke and Nishna series. These soils have EC's of less than 8 mmhos/cm. In addition, Herdcamp soils have less than 10 percent sand in the series control section.
GEOGRAPHIC SETTING: The Egas soils are on level and nearly level flood plains along the larger drainageways in the glacial till plains. Slope gradients are 2 percent or less. These soils formed in clayey alluvial sediments. Mean annual air temperature ranges from 34 to 48 degrees F, and mean annual precipitation ranges from 14 to 21 inches. Growing season ranges from 130 to 155 days; growing season precipitation is about 13 to 15 inches; and growing degree days are 2800 to 3200.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Herdcamp soils and the Betts, Bon, Durrstein, Java and Ree soils. Herdcamp soils are on similar landscapes. Durrstein soils have a natric horizon and are on similar landscapes. The Bon, Betts, Java and Ree soils have a fine-loamy series control section. The well drained and moderately well drained Bon soils are on slightly higher parts of the flood plain. The well drained Betts and Java soils are on higher upland landscapes. The well drained Ree soils are on higher terraces.
DRAINAGE AND PERMEABILITY: Poorly or very poorly drained. Runoff is low or medium depending on slope. Permeability is slow. These soils are subject to flooding and have a seasonal high water table that fluctuates between depths of 0 and 1 feet.
USE AND VEGETATION: Egas soils are used exclusively as native range. Native grasses are mainly western wheatgrass, inland saltgrass, and cordgrass.
DISTRIBUTION AND EXTENT: Central and south-central South Dakota. The series is moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Hughes County, South Dakota, 1970.
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 19 inches (A1, A2, and ACz horizons).