LOCATION OBADIA COEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Ustic Natrargids
TYPICAL PEDON: Obadia sandy loam - rangeland. (Colors are for dry soil unless otherwise noted.)
E--0 to 1 inch; light gray (10YR 7/2) sandy loam, dark grayish brown (10YR 4/2) moist; weak medium platy structure; soft, very friable, slightly sticky and slightly plastic; slightly alkaline (pH 7.6); abrupt smooth boundary. (1 to 3 inches thick)
Bt--1 inch to 8 inches; brown (10YR 5/3) clay, brown (10YR 4/3) moist; moderate medium prismatic structure parting to moderate medium angular blocky; very hard, firm, very sticky and very plastic; common prominent clay films on faces of peds; 12 percent exchangeable sodium; slightly alkaline (pH 7.8); clear wavy boundary. (3 to 8 inches thick)
Btn--8 to 13 inches; brown (10YR 5/3) clay, brown (10YR 4/3) moist; moderate coarse prismatic structure parting to moderate medium prismatic; very hard, firm, very sticky and very plastic; common prominent clay films on faces of peds; 16 percent exchangeable sodium; slightly effervescent; strongly alkaline (pH 8.6); clear wavy boundary. (4 to 7 inches thick)
Btkn--13 to 21 inches; light yellowish brown (2.5Y 6/4) clay loam, light olive brown (2.5Y 5/4) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; very hard, firm, very sticky and very plastic; few thin clay films on faces of peds; few distinct threads of calcium carbonate; 16 percent exchangeable sodium; slightly effervescent; strongly alkaline (pH 8.8); clear wavy boundary. (7 to 11 inches thick)
Bkn--21 to 42 inches; light brownish gray (2.5Y 6/2) clay loam, olive gray (5Y 5/2) moist; massive; hard, firm, moderately sticky and moderately plastic; common fine threads of calcium carbonate; 17 percent exchangeable sodium; strongly effervescent; strongly alkaline (pH 9.0); clear wavy boundary. (15 to 23 inches thick)
Bky--42 to 60 inches; light brownish gray (2.5Y 6/2) sandy clay loam, olive (5Y 5/3) moist; massive; hard, firm, moderately sticky and moderately plastic; 10 percent pebbles; common fine gypsum crystals; strongly effervescent; moderately alkaline (pH 8.4).
TYPE LOCATION: Moffat County, Colorado; about 4 miles north of Craig, Colorado; about 1,800 feet east and 2,000 feet south of the northwest corner of Sec. 5, T. 7 N., R. 90 W.; 40 degrees, 35 minutes, 45 seconds north latitude; 107 degrees, 31 minutes, 2 seconds west longitude.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature ranges from 44 to 46 degrees F.
Mean summer soil temperature ranges from 62 to 64 degrees F.
Depth to secondary calcium carbonate: 10 to 20 inches
The soil moisture control section is dry in all parts following July 1 and moist in some part in late September or October. The soil moisture regime is aridic bordering on ustic.
E horizon:
Hue: 7.5YR or 10YR
Value: 7 or 8 dry, 4 through 6 moist
Chroma: 2 or 3.
Bt horizon
Hue: 7.5YR or 10YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 or 4
Texture: clay loam or clay
Reaction: slightly alkaline or moderately alkaline.
Btn horizon
Hue: 7.5YR or 10YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2 or 3
Texture: clay loam or clay
SAR: 10 to 20
Reaction: moderately alkaline or strongly alkaline.
Btkn horizon
Hue: 10YR or 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 or 4
Texture: clay loam or clay
Calcium carbonate equivalent: 3 to 10 percent
SAR: 15 to 20
Reaction: moderately or strongly alkaline.
Bk horizon
Hue: 10YR to 5Y
Value: 6 or 7 dry, 5 or 6 moist
Chroma: 2 through 4
Texture: clay loam or sandy clay loam
Calcium carbonate equivalent: 5 to 10 percent
SAR: 15 to 20
Reaction: moderately alkaline or strongly alkaline.
COMPETING SERIES: These are the Abston and Giarch series. Abston soils have a paralithic contact. Giarch soils have SAR greater than 30 in the natric horizon.
GEOGRAPHIC SETTING: Obadia soils are on toe slopes. These soils formed in alluvium derived from sandstone and shale. Slopes range from 1 to 8 percent. Elevation ranges from 6,400 to 6,800 feet. The mean annual precipitation is 11 to 15 inches, the mean annual temperature is 42 to 45 degrees F., and the frost-free season is 75 to 95 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Abor, Forelle, Gretdivid, and Taffom soils, All of these soils lack a natric horizon. In addition the Abor soil is moderately deep to a paralithic contact. The Forelle and Taffom soils are in the fine-loamy family. The Gretdivid soils are in the sandy family.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; very slow permeability.
USE AND VEGETATION: These soils are used for nonirrigated crops, livestock grazing and wildlife habitat. Native vegetation consists of alkali sagebrush, bluebunch wheatgrass, prairie junegrass, Sandberg bluegrass and western wheatgrass.
DISTRIBUTION AND EXTENT: These soils occur in northwestern Colorado. The series is of small extent. MLRA 34. Total acreage is about 1,600 acres.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Moffat County (Moffat County Area), Colorado, 1991.
REMARKS: The diagnostic horizons recognized in this pedon are:
Ochric epipedon - the zone from 0 to 1 inch
Natric horizon - the zone from 1 to 21 inches
This pedon has more sodium plus magnesium than calcium plus exchangeable acidity in all the Bt horizons.
The precipitation range appears to cross from ustic-aridic to aridic-ustic. However the vegetation is consistent with the ustic-aridic subclass.