LOCATION COTTONTHOMAS ID+UTEstablished Series
TAXONOMIC CLASS: Ashy, glassy, frigid Vitrandic Haploxerolls
TYPICAL PEDON: Cottonthomas fine sandy loam - rangeland. On a 4 percent concave slope, east aspect, 5,100 feet elevation. (Colors are for air dry soil unless otherwise stated. When described on November 9, 1979, the profile was moist to 11 inches and dry below.
A1--0 to 3 inches; brown (10YR 5/3) fine sandy loam, very dark grayish brown (10YR 3/2) moist; weak thick platy structure parting to weak very fine granular; soft and very friable; many fine and common medium roots; many very fine tubular pores; neutral (pH 7.3) with creosol red, pH 6.8 with sodium flouride; abrupt wavy boundary. (2 to 10 inches thick)
A2--3 to 11 inches; brown (10YR 5/3) loam, dark brown (10YR 3/3) moist; weak medium and coarse subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many fine roots; many very fine tubular pores; slightly alkaline (pH 7.6) with creosol red, pH 7.0 with sodium flouride; clear smooth boundary. (0 to 10 inches thick)
Bw1--11 to 22 inches; very pale brown (10YR 7/3) loam, brown (10YR 4/3) moist; massive; hard, firm, slightly sticky and slightly plastic; few very fine roots; few very fine tubular pores; 15 percent hard, firm nodules; slightly alkaline (pH 7.6) with creosol red, pH 7.0 with sodium flouride; clear smooth boundary. (0 to 20 inches thick)
Bw2--22 to 35 inches; pale brown (10YR 6/3) loam, brown (10YR 4/3) moist; massive; hard, firm and slightly sticky; many very fine roots on faces of nodules; few very fine tubular pores; 40 percent nodules; 10 percent durinodes below 26 inches; slightly alkaline (pH 7.7) with creosol red, pH 6.8 with sodium flouride; gradual smooth boundary. (8 to 17 inches thick)
Bk1--35 to 45 inches; pale brown (10YR 6/3) fine sandy loam, brown (10YR 4/3) moist; massive; hard and firm; common very fine roots; few very fine tubular pores; slightly effervescent matrix; strongly effervescent common fine irregular lime in seams; slightly alkaline (pH 7.8); gradual smooth boundary. (8 to 18 inches thick)
Bk2--45 to 60 inches; very pale brown (10YR 7/3) fine sandy loam, brown (10YR 5/3) moist; hard and firm; few very fine roots; few very fine tubular pores; 10 percent durinodes coated with strongly effervescent lime; slightly effervescent, moderately alkaline (pH 8.2).
TYPE LOCATION: Cassia County, Idaho; about 1850 feet west and 200 feet south of the northeast corner of sec. 30, T. 16S., R. 21E.
RANGE IN CHARACTERISTICS:
Average Annual soil temperature - 43 to 47 degrees F.
Thickness of the mollic epipedon - 10 to 16 inches
Rock fragment content - 0 to 15 percent
Reaction - pH with sodium flouride less than 9.5
A horizons - Chroma - 2 or 3
Reaction - neutral to slightly alkaline
Bw horizons - Color hue - 2.5Y or 10YR
Value - 6 or 7 dry, 4 or 5 moist
Chroma - 2 or 3
Texture - FSL to L
Nodule content - 0 to 50 percent
Durinode content - 0 to 10 percent
Bk horizons - Color hue - 2.5Y or 10YR
Value - 6 through 8 dry, 4 through 6 moist
Chroma - 2 or 3
Texture - FSL, L, LFS
Nodule content - 0 to 50 percent
Durinode content - 0 to 10 percent
Reaction - slightly to moderately alkaline
COMPETING SERIES: There are no competing series. Prior to the change in the classification of the Cottonthomas series from a Vitrandept to a Haploxeroll the Coalbank and Trailcreek series were competing. Coalbank soils lack a Bk horizon. Trailcreek soils are moderately deep to a paralithic contact.
GEOGRAPHIC SETTING: Cottonthomas soils are on fan terraces and hillsides. Slopes range from 0 to 20 percent. Elevation ranges from 5,000 to 6,600 feet. The soil formed in alluvium from ash. The average annual precipitation is about 12 to 16 inches, the average annual air temperature is about 41 to 45 degrees F., and the frost-free season is 80 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bluehill, (T) Hardister and Tomsherry series, and the competing Coalbank series. Bluehill and Hardister soils are mesic. Bluehill soils are moderately deep and do not have a mollic epipedon. Tomsherry soils are moderately deep over a duripan. Bluehill soils are on steep south-facing slopes. Coalbank soils are on steep north-facing slopes. Hardister soils are on valley floors and stream terraces. Tomsherry soils are on fan terraces.
DRAINAGE AND PERMEABILITY: Well drained; slight to medium runoff; moderate or moderately rapid permeability.
USE AND VEGETATION: Cottonthomas soils are used for range. The natural vegetation is Wyoming big sagebrush, needleandthread, bluebunch wheatgrass, and Sandberg bluegrass.
DISTRIBUTION AND EXTENT: South-central Idaho. The soils of this series are moderately extensive.
MLRA OFFICE RESPONSIBLE: Reno, Nevada
SERIES ESTABLISHED: Box Elder County, Utah, 1985.
REMARKS: Name is after a creek.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 11 inches (A1 and
A2 horizons)
Cambic horizon - The zone from 11 to 35 inches (Bw1 and Bw2 horizons)
Particle size control section - The zone from 10 to 40 inches (part of
the A2 horizon and the Bw1, Bw2, and Bk1 horizons)
This soil has greater than 65 percent volcanic ash in the particle size
control section