LOCATION SAMOIST WYEstablished Series
TAXONOMIC CLASS: Clayey, smectitic, calcareous, frigid, shallow Ustic Torriorthents
TYPICAL PEDON: Samoist clay loam--on a southwesterly facing hillslope of 8 percent under native grassland. (Colors are for dry soil unless otherwise stated.)
A1--0 to 2 inches; dark grayish brown (10YR 4/2) clay loam, very dark grayish brown (10YR 3/2) moist; weak fine granular structure; hard, firm, sticky and plastic; common fine roots; slightly effervescent, lime disseminated; mildly alkaline (pH 8.0); clear smooth boundary. (0 to 4 inches thick)
Bw--2 to 5 inches; grayish brown (10YR 5/2) clay, dark grayish brown (10YR 4/2) moist; weak coarse angular blocky structure; hard, firm, sticky and plastic; common fine roots; strongly effervescent, lime mostly disseminated, few fine soft masses; moderately alkaline (pH 8.2); clear smooth boundary. (0 to 5 inches thick)
C--5 to 12 inches; light brownish gray (2.5Y 6/2) clay, grayish brown (2.5Y 5/2) moist; massive, hard, firm, sticky and plastic; few fine roots; strongly effervescent, lime disseminated; moderately alkaline (pH 8.2); gradual wavy boundary. (6 to 18 inches thick)
Cr--12 inches; light brownish gray clay shale.
TYPE LOCATION: Weston County, Wyoming; 300 feet east and 400 feet south of the NW corner of sec. 7, T. 48 N., R. 62 W.
RANGE IN CHARACTERISTICS: Depth to bedrock ranges from 6 to 20 inches. The family control section contains from 35 to 50 percent clay and is either a heavy clay loam or clay. Coarse fragments, when present, are less than 10 percent and break down with pretreatment. The mean annual soil temperature is 42 to 46 degrees F., and the mean summer soil temperature is 59 to 64 degrees F. The soil is typically dry in some or all parts of the moisture control section from July 20 to September 30 in most years.
The A horizon has hue of 10YR or 2.5Y, value of 4 or 5 moist, 3 or 4 dry, and chroma of 2 or 3. Texture is heavy clay loam or clay with 35 to 45 percent clay. Reaction is mildly through strongly alkaline. EC is less than 2 mmhos.
The Bw horizon, when present, has the same range as the A horizon. Weak or moderate grades of angular blocky structure are common.
The C horizon has hue of 10YR or 2.5Y value of 5 through 7 moist and dry, and chroma of 2 or 3. Texture is most commonly clay with clay loam less common. Clay ranges from 35 to 50 percent. Reaction is moderately to strongly alkaline. EC ranges from 0 to 4 mmhos. The carbonates range from 5 to 13 percent throughout the horizon with only limited evidence in some pedons of segregation.
COMPETING SERIES: These are the Lisam, Moyerson, Wiscow, and Yawdim soils. The Lisam soils have over 50 percent clay in the control section. The Moyerson soils are drier and have mean annual precipitation of 10 to 14 inches. The Wiscow soils have hue of 7.5YR or redder. The Yawdim soils lack soft, coarse fragments in the control section.
GEOGRAPHIC SETTING: Samoist soils are on metastable hillslopes, shoulders, and backslopes on uplands. Slopes are 2 to 30 percent. The soils formed in slopewash alluvium and residual material weathered primarily from calcareous gray clay shale. Elevations are 4,500 to 6,000 feet. The average annual precipitation is about 16 inches but ranges from 15 to 19. Over half the precipitation falls in April, May, and June. The mean annual temperature is 44 degrees F. but ranges from 40 to 45 degrees F. The frost-free season is typically 90 to 110 days but in isolated areas may vary somewhat from the norm.
GEOGRAPHICALLY ASSOCIATED SOILS: This is the Colsavage soil which is deeper to bedrock and normally occurs where slopes are more gentle and weathering occurs more rapidly.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; very slow permeability.
USE AND VEGETATION: These soils are used primarily for grazing. Principal native vegetation is western wheatgrass, sideoats grama, bottlebrush squirreltail, and green needlegrass.
DISTRIBUTION AND EXTENT: Black Hills footslopes in northeastern Wyoming. The series is of minor extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Weston County, Wyoming; 1983.