LOCATION UCOLO UTEstablished Series
TAXONOMIC CLASS: Fine, mixed, active, mesic Fluventic Haplustolls
TYPICAL PEDON: Ucolo silty clay loam, rangeland. (Colors are for moist soil unless otherwise noted )
A1--0 to 2 inches; very dark grayish brown (10YR 3/2) silt loam, grayish brown (10YR 5/2) dry; weak medium platy structure that parts easily to weak fine granular; slightly hard, friable, slightly sticky and slightly plastic; few fine roots; vesicular pores; strongly calcareous; moderately alkaline (pH 8.2); abrupt smooth boundary. (0 to 3 inches thick)
A2--2 to 10 inches; very dark grayish brown (10YR 3/2) silty clay loam, dark grayish brown (10YR 4/2) dry; weak thick platy structure that parts to medium platy; slightly hard, friable, sticky and plastic; few fine roots; few fine pores; strongly calcareous; moderately alkaline (pH 8.2); gradual smooth boundary. (4 to 10 inches thick)
C1--10 to 30 inches; dark grayish brown (10YR 4/2) silty clay, grayish brown (10YR 5/2) dry; very weak medium prismatic structure that parts to weak subangular blocky; very hard, firm, sticky and plastic; many fine roots; common fine pores; strongly calcareous; strongly alkaline (pH 8.6); gradual smooth boundary. (12 to 24 inches thick)
C2--30 to 53 inches; dark grayish brown (10YR 4/2) clay, grayish brown (10YR 5/2) dry; massive; very hard, very firm, sticky and plastic; many fine roots; strongly calcareous; veins of gypsum and other soluble salts; moderately alkaline (pH 8.3); clear smooth boundary. (15 to 25 inches thick)
C3--53 to 72 inches; grayish brown (2.5Y 5/2) clay, light brownish gray (2.5Y 6/2) dry; massive; extremely hard, very firm, sticky and plastic; very strongly calcareous, with fine veins of lime; strongly alkaline (pH 8.5).
TYPE LOCATION: San Juan County, Utah; 2.5 miles north of Highway 160 on west side of west Summit Point road; SE1/4 section 25, T.33S., R.25E.
RANGE IN CHARACTERISTICS:
Thickness of the mollic epipedon: 7 to 12 inches
Depth to shale: 48 to 60 inches or more
Mean annual soil temperature: 47 to 49 degrees F.
Organic matter: decreases irregularly with depth
Soil moisture: The soils are moist in some part of the moisture control section for 45 to 60 days during the summer. Aridic ustic moisture regime.
A horizon
Value: 4 or 5 dry, 3 to 3.5 moist
Chroma: 2 or 3
Texture: silty clay loam, heavy silt loam or clay loam
Calcium carbonate: moderately or strongly calcareous
Reaction: moderately or strongly alkaline
Thickness: 7 to 12 inches
C horizon
Hue: 10YR or 2.5YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2 or 3
Texture: silty clay, clay, heavy silty clay loam or heavy clay loam
Calcium carbonate: strongly or very strongly calcareous
Reaction: moderately alkaline or strongly alkaline
Soluble salt: 0.5 to 2.0 percent
Gypsum: contains common veins of gypsum
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Ucolo soils are on alluvial fans and narrow intermittent stream valleys, at elevations, of 6,500 to 6,800 feet. Slopes are mainly 0 to 10 percent. These soils formed in alluvium weathered mainly from shale. The mean annual temperature ranges from 46 to 48 degrees F. The mean summer temperature is 63 to 66 degrees F. The average annual precipitation is 13 to 15 inches. The frost-free season is 105 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Hovenweep soils and the competing Lockerby soils. Hovenweep soils are fine-loamy and have a calcic horizon.
DRAINAGE AND PERMEABILITY: Moderately well drained; medium runoff; slow or very slow permeability.
USE AND VEGETATION: Used mainly for rangeland. Some are used for irrigated or nonirrigated crops. Irrigated crops are mainly small grains, alfalfa and pasture. Nonirrigated crops are pinto beans and small grains. Native vegetation is dominantly western wheatgrass, greasewood, big sagebrush, and black sagebrush.
DISTRIBUTION AND EXTENT: Southeastern Utah and southwestern Colorado. This series is inextensive. MLRA 36.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: San Juan Area, Utah, 1952.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 10 inches (A horizons)
Fluventic subgroup - irregular decrease in organic matter with depth
Classified according to Soil Taxonomy Second Edition, 1999; Keys to Soil Taxonomy Tenth Edition, 2006.