LOCATION POKEMAN WYEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Ustic Haplargids
TYPICAL PEDON: Pokeman loam-rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 3 inches; brown (7.5YR 5/4) loam, dark brown (5YR 4/2) moist; moderate fine granular structure; soft, very friable, slightly sticky and slightly plastic; common fine and very fine roots; mildly alkaline (pH 7.6); clear smooth boundary. (2 to 5 inches thick)
Bt--3 to 10 inches; reddish brown (5YR 5/4) clay loam, reddish brown (5YR 4/4) moist; weak medium prismatic structure parting to fine and medium subangular blocky; hard, very friable, sticky and plastic; common fine and very fine and few coarse roots; common thin clay films on faces of peds and in root channels; mildly alkaline (pH 7.6); clear smooth boundary.
(5 to 7 inches thick)
Btky--10 to 13 inches; light reddish brown (5YR 6/4) clay loam, reddish brown (5YR 4/4) moist; weak medium subangular blocky structure; hard, very friable, sticky and plastic; few fine roots; few thin clay films on faces of some peds; strongly effervescent, carbonates as common soft masses; gypsum as common fine and medium nests of crystals; moderately alkaline (pH 8.4); clear smooth boundary. (0 to 10 inches thick)
Bky--13 to 30 inches; pinkish gray (5YR 7/2) loam, pinkish gray (5YR 6/2) moist; massive; hard, very friable, slightly sticky and slightly plastic; violently effervescent, carbonates as common soft masses and disseminated; gypsum as common fine and medium nests of crystals; moderately alkaline (pH 8.4); abrupt wavy boundary. (10 to 30 inches thick)
Cr--30 to 60 inches; semiconsolidated gypsum bedrock (alabaster). Hardness is less than 3.
TYPE LOCATION: Johnson County, Wyoming; NW1/4, NE1/4 of sec. 30, T. 41 N., R. 84 W.
RANGE IN CHARACTERISTICS: Depth to bedrock and the paralithic contact ranges from 20 to 40 inches. Depth to the base of the argillic horizon ranges from 7 to 16 inches. The mean annual soil temperature ranges from about 47 to 53 degrees F. EC is less than 4 mmhos throughout. Coarse fragments range from 0 to 15 percent pebbles throughout the soil but are typically less than 5 percent.
The A horizon has hue of 7.5YR or 5YR, value of 4 through 6 dry, 3 through 5 moist, and chroma of 2 through 4. Reaction is neutral or mildly alkaline.
The Bt horizon has hue of 5YR or 2.5YR, value of 4 through 6 dry, 3 through 5 moist, and chroma of 3 through 5. Texture is clay loam or loam with 18 to 35 percent clay and more than 15 but less than 35 percent fine sand or coarser. The Bt is typically noncalcareous, but some pedons are calcareous due to recharge. Reaction is neutral or mildly alkaline.
The Btky horizon, when present, has the same color and textural range as the Bt horizon. Pedogenetic accumulations of carbonates and gypsum occur as soft masses, filaments, and nests of crystals, respectively. Reaction is typically mildly or moderately alkaline, but some pedons may be strongly alkaline when not buffered by excess gypsum.
The Bky horizon has hue of 2.5YR through 7.5YR, value of 5 through 7 dry, 5 or 6 moist, and chroma of 2 through 4. Texture is loam or clay loam with 18 to 30 percent clay. Pedogenetic accumulations of carbonates and gypsum occur as common soft masses, filaments, and as nests of crystals. Calcium carbonate equivalent ranges from 6 to 15 percent. Gypsum ranges from 2 to 6 percent. Reaction is moderately or strongly alkaline.
COMPETING SERIES: These are the Balon, Bowbac, Buckle, Cambria, Cerrillos, Clovis, Cushman, Decolney, Fattig, Fernando, Forkwood, Fort Collins, Frisite, Gaddes, Hagerman, Harbord, Hiland, Los Alamos, Maysdorf, Millet, Olney, Penistaja, Potts, Progresso, Pugsley, Rauzi, Scholle, Spangler, Splendo, Stoneham, Sundance, Threetop, Topia, Toluca, Tuweep, and Yenlo series. The Balon, Buckle, Cambria, Cerrillos, Clovis, Decolney, Fernando, Forkwood, Fort Collins, Frisite, Harbord, Hiland, Maysdorf, Millet, Olney, Penistaja, Potts, Rauzi, Scholle, Spangler, Splendo, Stoneham, Sundance, Topia, Taluca, and Yenlo soils are deep. Bowbac and Cushman soils have hue of 7.5YR or yellower in the Bt horizon and have a paralithic contact to soft sandstone. Pugsley soils have more than 35 percent fine or coarser sand in the Bt horizon. Fattig, Hagerman, Progresso, and Threetop soils have a lithic contact at 20 to 40 inches. Gaddes soils lack gypsum and have granite bedrock at 20 to 40 inches. Los Alamos soils have pumice and ash at 20 to 40 inches and pumice gravel throughout the soil.
GEOGRAPHIC SETTING: Pokeman soils are on bedrock controlled uplands. They formed in residuum and colluvial slopewash derived from gypsiferous bedrock. Slopes are 2 to 15 percent. Elevations are 5,000 to 6,300 feet. The mean annual precipitation ranges from 10 to 14 inches with about half falling as snow and rain in April, May, and early June. The mean annual air temperature is 43 to 46 degrees F. The frost-free season is estimated to range from 100 to 130 days depending upon elevation, aspect, and air drainage.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Gystrum, Rekop, and Spearfish soils and the competing Threetop series. Gystrum soils have gypsic mineralogy and a cambic horizon. Rekop and Spearfish have bedrock at less than 20 inches and have no diagnostic subsurface horizons.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderate permeability.
USE AND VEGETATION: Rangeland and wildlife habitat. Native vegetation consists of western wheatgrass, needleandthread, blue grama, green needlegrass, and smooth phlox.
DISTRIBUTION AND EXTENT: North central and central Wyoming. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Johnson County, Wyoming, South Part; 1971.