LOCATION LOMA COEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Aridic Argiustolls
TYPICAL PEDON: Loma loam - grassland. (Colors are for dry soil unless otherwise noted.)
A1--0 to 5 inches; brown (7.5YR 5/3) loam, dark brown (7.5YR 3/3) moist; strong fine granular structure; soft, very friable; calcareous; moderately alkaline (pH 8.2); clear smooth boundary. (4 to 6 inches thick)
B1--5 to 9 inches; brown (7.5YR 5/2) heavy silty clay loam, dark brown (7.5YR 3/2) moist; strong fine subangular blocky structure that parts to medium granules; soft, very friable; peds are hard dry; few glossy patches on some faces of peds; calcareous; moderately alkaline (pH 8.2); clear smooth boundary. (3 to 4 inches thick)
B21t--9 to 14 inches; reddish gray (5YR 5/2) light silty clay, dark reddish brown (5YR 3/2) moist; moderate medium prismatic structure that parts to moderate fine angular blocks; slightly hard, very friable; peds are extremely hard; thin nearly continuous wax-like coatings on the surface of the peds; wax-like fillings in root channels and soil pores; calcareous; moderately alkaline (pH 8.2); clear smooth boundary. (0 to 10 inches thick)
B22t--14 to 21 inches; reddish gray (5YR 5/2) light silty clay, dark reddish gray (5YR 4/2) moist; strong medium prismatic structure that parts to strong medium angular blocks; hard, very friable; peds are extremely hard; thin continuous wax-like coatings on the surface of the peds; wax-like fillings in root channels and soil pores; calcareous; moderately alkaline (pH 8.2); gradual wavy boundary.
(5 to 12 inches thick)
B3ca--21 to 28 inches; reddish brown (5YR 5/3) heavy clay loam, reddish brown (5YR 4/3) moist; weak medium prismatic structure that parts to moderate medium subangular and angular blocks; hard, very friable; peds are very hard; common, thin, wax-like patches on both horizontal and vertical faces of peds; some wax-like coatings in root channels; some visible secondary calcium carbonate occurring as concretions or in thin seams and streaks; calcareous; moderately alkaline (pH 8.2); gradual wavy boundary. (3 to 8 inches thick)
Cca--28 to 40 inches; light reddish brown (5YR 6/3) silt loam, reddish brown (5YR 5/3) moist; massive; hard, very friable; some visible secondary calcium occurring as concretions or in thin seams and streaks; calcareous; moderately alkaline (pH 8.2).
TYPE LOCATION: Mesa County, Colorado; NE1/4 Sec. 24, T. 12 S., R. 102 W.
RANGE IN CHARACTERISTICS: The mollic epipedon is 7 to 20 inches thick. The solum is 15 to 40 inches thick. Typically, these soils are calcareous throughout but are leached for a few inches in some pedons. Organic carbon in the mollic epipedon ranges from 0.8 to 2 percent and decreases uniformly with increasing depth. Cation exchange capacity ranges from 60 to 90 milliequivalents per 100 grams of clay. Rock fragments are usually less than 1 percent but range from 0 to 15 percent. Mean annual soil temperature ranges from 47 to 58 degrees F., and mean summer soil temperature ranges from 60 to 78 degrees F.
The A1 horizon has hue of 10YR through 5YR, value of 4 or 5 dry, 2 or 3 moist, and chroma of 2 or 3. Typically, it has fine granular or crumb primary structure but it has weak subangular blocky structure in some pedons. This horizon is soft to slightly hard. It is mildly or moderately alkaline (pH 7.6 to 8.2) and is generally calcareous except for the surface few inches.
The B2t horizon has hue of 5YR through 10YR, value of 5 or 6 dry, 3 or 4 moist, and chroma from 2 through 4. It is usually light silty clay or clay and clay ranges from 35 to 50 percent, silt from 20 to 50 percent, and sand from 10 to 40 percent with less than 15 percent being fine or coarser sand. This horizon has moderate strong prismatic primary structure that parts to angular blocks.
The Cca horizon has hue of 7.5YR or 5YR. It is moderately to strongly alkaline (pH 8.0 to 8.6) and has 4 to 12 percent calcium carbonate equivalent.
COMPETING SERIES: These are the Boneek, Chapin, Collbran, Harney, Nunn, Rednun, Richfield, Sofia, Valmont, and Wormser series. Boneek, Collbran, Harney, Nunn, Richfield, Rednun, and Sofia soils are noncalcareous to depths of more than 9 inches. Chapin soils have a lithic contact at depths of 20 to 40 inches. Collbran, Harney, Nunn, Richfield, Sofia, Valmont, and Wormser soils have lithochromic hue no redder than 7.5YR. Valmont soils have loamy-skeletal substratums at depths of less than 40 inches. Wormser soils have a paralithic contact at depths of 20 to 40 inches.
GEOGRAPHIC SETTING: The Loma soils are on gently to moderately sloping mesa tops and upland hills and ridges. Slopes range from 0 to about 10 percent. The soils formed in eolian or eolian-modified reddish calcareous sediments high in very fine sand and originating from redbed formations. At the type location the average annual precipitation is 16 inches with peak periods of precipitation occurring during the spring and early summer. The average annual temperature is 48 degrees F., and the average summer temperature is 63 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Gibber and Unaweep soils. Gibber soils lack mollic epipedons. Unaweep soils have less than 18 percent clay in the series control section and lack argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; slow permeability.
USE AND VEGETATION: These soils are used principally as native pastureland; however, they are irrigated where water is available. Principal native vegetation is sage, western wheatgrass, and Indian ricegrass.
DISTRIBUTION AND EXTENT: Western slope of Colorado. The series is probably of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Mesa County (Lower Colorado Area), Colorado, 1970.
REMARKS: Last updated by the state 5/73.