LOCATION COBBRA UT

Established Series
Rev. RHF/MJD/SSP
12/2022

COBBRA SERIES

The Cobbra series consists of very deep, well drained soils that formed in alluvium over glaciofluvial deposits derived from sedimentary and quartzite rocks. Cobbra soils are on strath terraces. Slopes range from 1 to 3 percent. Mean annual precipitation is about 10 inches and the mean annual temperature is about 45 degrees F.

TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, mesic Ustic Haplocalcids

TYPICAL PEDON: Cobbra loam, on a south facing, linear, 3 percent slope in irrigated cropland at an elevation of 5,710 feet. (Colors are for dry soil unless otherwise noted.)

Ap1--0 to 4 inches; dark yellowish brown (10YR 4/4) loam, brown (10YR 4/3) moist; weak fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine, few fine and medium roots; common very fine, few fine tubular pores; very slightly effervescent (3 percent calcium carbonate equivalent), carbonates are disseminated; moderately alkaline (pH 8.0); abrupt smooth boundary. (2 to 8 inches thick)

Ap2--4 to 16 inches; brown (7.5YR 5/4) loam, brown (7.5YR 4/4) moist; moderate very fine and fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and coarse, few fine and medium roots; common very fine, few fine tubular pores; very slightly effervescent (3 percent calcium carbonate equivalent), carbonates are disseminated; moderately alkaline (pH 8.0); clear smooth boundary. (0 to 2 inches thick)

Bk1--16 to 24 inches; strong brown (7.5YR 5/6) loam, brown (7.5YR 5/4) moist; moderate fine and medium subangular blocky structure; hard, friable, moderately sticky and slightly plastic; common very fine and coarse, few fine and medium roots; many very fine, few fine tubular pores; slightly effervescent (10 percent calcium carbonate equivalent), carbonates are disseminated and segregated as few fine masses; moderately alkaline (pH 8.2); clear smooth boundary. (4 to 11 inches thick)

Bk2--24 to 47 inches; light brown (7.5YR 6/4) loam, brown (7.5YR 5/4) moist; moderate fine and medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine, few fine and medium roots; common very fine, few fine tubular pores; 5 percent gravel; strongly effervescent (21 percent calcium carbonate equivalent), carbonates are disseminated and segregated as common medium masses and 1 mm thick coatings on bottom of rock fragments; moderately alkaline (pH 8.2); clear smooth boundary. (7 to 23 inches thick)

Bk3--47 to 55 inches; light brown (7.5YR 6/4) fine sandy loam, brown (7.5YR 5/4) moist; weak fine and medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine, few fine and medium roots; common very fine, few fine tubular pores; 5 percent gravel, 5 percent cobble; strongly effervescent (12 percent calcium carbonate equivalent), carbonates are disseminated and segregated as 1 mm thick coatings on bottom of rock fragments; moderately alkaline (pH 8.2); clear wavy boundary. (8 to 37 inches thick)

2Bk4--55 to 60 inches; light brown (7.5YR 6/4) extremely cobbly fine sandy loam, brown (7.5YR 5/4) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; common very fine, few fine and medium roots; common very fine, few fine tubular pores; 15 percent gravel, 50 percent cobble; strongly effervescent (10 percent calcium carbonate equivalent), carbonates are disseminated and segregated as 1 mm thick coatings on bottom of rock fragments; moderately alkaline (pH 8.2).

TYPE LOCATION: Uintah County, Utah; about 2.9 miles southeast of Whiterocks; located about 2,200 feet east and 2600 feet south of the northwest corner of sec. 33, T. 1 N., R. 1 E., USBM; Whiterocks, Utah USGS quad; lat. 40 degrees 26 minutes 55 seconds N. and long. 109 degrees 53 minutes 20 seconds W., NAD 27

RANGE IN CHARACTERISTICS:

Soil moisture: The soil moisture control section is affected by precipitation that falls evenly throughout the year, with a slight increase in the late summer and early fall. Aridic moisture regime bordering on ustic.
Mean annual soil temperature: 47 to 52 degrees F.
Depth to calcic horizon: 8 to 24 inches
Depth to lithologic discontinuity: 40 to 57 inches to glaciofluvial deposits

Particle-size control section: 10 to 18 percent silicate and 18 to 35 percent total clay; 0 to 15 percent rock fragments (predominantly gravel and cobbles from sandstone and quartzite)

A horizon: (combination of thickness and colors do not meet mollic epipedon criteria)
Value: 4 to 6 dry, 3 or 4 moist
Chroma: 3 to 6 dry, 3 or 4 moist
Rock fragments: 0 to 10 percent gravel and cobbles
Calcium carbonate equivalent: 1 to 10 percent
Reaction: moderately alkaline or strongly alkaline

Bk1 horizon:
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 4 to 6 dry or moist
Texture: loam and clay loam
Rock fragments: 0 to 10 percent gravel and cobbles
Calcium carbonate equivalent: 1 to 25 percent
Reaction: moderately alkaline or strongly alkaline

Lower Bk horizons:
Hue: 7.5YR or 10YR
Value: 5 to 8 dry, 4 to 8 moist
Chroma: 1 to 4 dry, 3 to 6 moist
Texture: fine sandy loam, loam, sandy clay loam, or clay loam
Rock fragments: 0 to 15 percent gravel and cobbles
Calcium carbonate equivalent: 10 to 55 percent (averaging 15 to 40 percent in the particle size control section)
Reaction: moderately alkaline or strongly alkaline

2Bk horizon:
Hue: 7.5Y or 10YR
Value: 4 to 8 dry, 4 to 7 moist
Chroma: 2 to 4 dry, 4 to 6 moist
Texture: very gravelly sandy loam, very gravelly sandy clay loam, very cobbly sandy clay loam, extremely cobbly fine sandy loam, or extremely cobbly sandy clay loam
Rock fragments: 35 to 80 percent gravel and cobbles
Calcium carbonate equivalent: 10 to 35 percent
Reaction: moderately alkaline or strongly alkaline

COMPETING SERIES: Current competitors are the Abracon, ThumbRock, Chugcity, Harvey, Milok, Sazi, and Xenmack series. Competitors prior to the Eighth Edition, 1998 Keys to Soil Taxonomy are the Chupadera and Mivida series.

Abracon, Harvey, Milok, and Mivida: do not have lithologic discontinuities with glaciofluvial deposits.

ThumbRock, Chugcity, Chupadera, Sazi, and Xenmack: are moderately deep to a lithic or paralithic contact.

GEOGRAPHIC SETTING:
Parent material: alluvium over glaciofluvial deposits derived from sedimentary and quartzite rocks
Landform: structural benches
Slopes: 1 to 3 percent
Elevation: 5,400 to 6,700 feet
Mean annual air temperature: 45 to 49 degrees F.
Mean annual precipitation: 8 to 12 inches
Frost-free period: 110 to 140 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Clapper, Hazmaz, Lapoint, and Solirec series.

Clapper soils have a loamy-skeletal particle-size control section and are on fan remnants.

Hazmaz and Lapoint soils are moderately deep to petrocalcic horizons and are on strath terraces.

Solirec soils have argillic horizons and are on fan remnants.

DRAINAGE AND PERMEABILITY: Well drained, low runoff, moderate permeability.

USE AND VEGETATION: The major uses are irrigated cropland, irrigated pasture, and rangeland. Potential native vegetation consists of Wyoming big sagebrush, winterfat, Indian ricegrass, bottlebrush squirreltail, galleta and needleandthread. This soil has been correlated to Semidesert Loam (Wyoming Big Sagebrush) - 034XY212UT range sites in Utah.

DISTRIBUTION AND EXTENT: Northeast Utah. LRR D, MLRA 34. This series is of small extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Uintah County, Uintah Area Soil Survey, Utah. 1998. The name is coined.

REMARKS: Diagnostic horizons and features recognized in this pedon are:

Particle-size control section: The zone from 10 to 40 inches. (Ap2, Bk1, and Bk2 horizons)
Ochric epipedon: The zone from 0 to 16 inches. (A horizon)
Calcic horizon: The zone from 24 to 47 inches. (Bk2 horizon)
Lithologic discontinuity: The presence of glaciofluvial deposits at the top of the 2Bk4 horizon.

The CEC activity class was inferred from laboratory data from similar soils in the Uintah Area Soil Survey.

Taxonomic version: Eighth Edition, 1998.

National Cooperative Soil Survey
U.S.A.