Carter soils have more clay in the series control section and are in the lower parts of the landscape. Millboro soils are on nearly similar landscapes and they have fine-textured argillic horizons. Mobridge and Onita soils are in swales and have mollic epipedons greater than 20 inches thick. In addition, Onita soils have fine-textured argillic horizons. Surface runoff is low on nearly level slopes and medium on more sloping areas.
Permeability is moderate in the silty part of the soils and slow in the underlying clayey sediments.
About equally divided between native range and cropland. Small grain, sorghum, corn, and alfalfa are the principal crops. Native vegetation includes green needlegrass, western wheatgrass, needleandthread, blue grama, sideoats grama, bluestems, sedges, and forbs. This series is of small extent. Lyman County, South Dakota, 1984.