LOCATION COTTONTHOMAS ID+UT

Established Series
FRK/FMK/GHL
01/2019

COTTONTHOMAS SERIES

The Cottonthomas series consists of very deep, well-drained, moderately permeable soils that are formed in alluvium from ash. They are on fan terraces and hillsides and have slopes of 0 to 20 percent. The average annual temperature is about 7 degrees C., and the average annual precipitation is about 360 mm.

TAXONOMIC CLASS: Ashy, glassy, frigid Vitrandic Haploxerolls

TYPICAL PEDON: Cottonthomas ashy fine sandy loam - rangeland. On a 4 percent concave slope, east aspect, 1,555 meters 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 8 cm; brown (10YR 5/3) ashy 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 fluoride; abrupt wavy boundary. (5 to 25 cm thick)

A2--8 to 28 cm; brown (10YR 5/3) ashy 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 fluoride; clear smooth boundary. (0 to 25 cm thick)

Bw1--28 to 56 cm; very pale brown (10YR 7/3) ashy 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 fluoride; clear smooth boundary. (0 to 50 cm thick)

Bw2--56 to 89 cm; pale brown (10YR 6/3) ashy loam, brown (10YR 4/3) moist; massive; hard, firm, slightly sticky 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 fluoride; gradual smooth boundary. (20 to 43 cm thick)

Bk1--89 to 114 cm; pale brown (10YR 6/3) ashy fine sandy loam, brown (10YR 4/3) moist; massive; hard, firm, nonsticky and nonplastic; common very fine roots; few very fine tubular pores; slightly effervescent matrix; strongly effervescent common fine irregular carbonate in seams; slightly alkaline (pH 7.8); gradual smooth boundary. (20 to 46 cm thick)

Bk2--114 to 152 cm; very pale brown (10YR 7/3) ashy fine sandy loam, brown (10YR 5/3) moist; hard, firm, nonsticky and nonplastic; few very fine roots; few very fine tubular pores; 10 percent durinodes coated with strongly effervescent carbonates; slightly effervescent, moderately alkaline (pH 8.2).

TYPE LOCATION: Cassia County, Idaho; about 1,850 feet west and 200 feet south of the northeast corner of sec. 30, T. 16 S., R. 21 E.; USGS Ibex Peak 7.5 minute topographic quadrangle; latitude 42 degrees 01 minutes 19 seconds N and longitude 114 degrees 02 minutes 09 seconds W; WGS84 Decimal Degrees 42.0219444 latitude, -114.0358333 longitude.

RANGE IN CHARACTERISTICS:
Average Annual soil temperature - 6 to 8 degrees C.
Thickness of the mollic epipedon - 25 to 41 cm.
Rock fragment content - 0 to 15 percent
Reaction - pH with sodium fluoride less than 9.5.
Typic xeric moisture regime.

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 1,525 to 2,015 meters. The soil formed in alluvium from ash. The average annual precipitation is about 300 to 410 mm, the average annual air temperature is about 5 to 7 degrees C., and the frost-free season is 80 to 100 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bluehill, 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 SATURATED HYDRAULIC CONDUCTIVITY: Well drained; slight to medium runoff; moderate or moderately rapid saturated hydraulic conductivity.

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 25.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California

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 28 cm (A1 and A2 horizons).
Cambic horizon - The zone from 28 to 89 cm (Bw1 and Bw2 horizons).

Particle size control section - The zone from 25 to 100 cm (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

National Cooperative Soil Survey
U.S.A.