LOCATION AHLSTROM UTEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Calcidic Paleustalfs
TYPICAL PEDON: Ahlstrom silt loam--rangeland. (Colors are for air-dry soil unless otherwise stated.)
A--0 to 7 inches; brown (7.5YR 5/4) silt loam, dark brown (7.5YR 3/4) moist, crushed; moderate very thin platy with pockets of moderate thin platy structure that parts to moderate very fine granular; slightly hard, friable, slightly sticky and slightly plastic; many very fine and common fine and medium roots; many fine and very fine and common medium pores; slightly effervescent; slightly alkaline (pH 7.4); abrupt smooth boundary. (3 to 9 inches thick)
Bt1--7 to 10 inches; brown (7.5YR 5/4) silty clay loam, dark brown (7.5YR 3/4) moist, crushed; moderate fine and medium prismatic structure that parts to moderate fine subangular blocky; hard, firm, moderately sticky and moderately plastic; few very fine and medium roots; common fine and few very fine pores; few thin clay films on faces of peds; strongly effervescent; slightly alkaline (pH 7.4); clear smooth boundary. (3 to 12 inches thick)
Bt2--10 to 14 inches; brown (7.5YR 5/4) silty clay loam, brown (7.5YR 4/4) moist, crushed; moderate medium prismatic structure that parts to moderate fine and medium angular blocky and moderate very fine angular blocky; hard, firm, moderately sticky and moderately plastic; common fine, few very fine and medium roots; few fine pores; few thin clay films on faces of peds; strongly effervescent; slightly alkaline (pH 7.5); abrupt smooth boundary. (4 to 20 inches thick)
Btk1--14 to 20 inches; reddish yellow (7.5YR 6/6) silty clay loam, reddish brown (5YR 4/4) moist, crushed; weak medium angular blocky structure that parts to moderate fine angular blocky; hard, firm, moderately sticky and moderately plastic; few fine and very fine roots; many very fine pores; few thin clay films in pores; violently effervescent; slightly alkaline (pH 7.5); clear smooth boundary. (5 to 15 inches thick)
Btk2--20 to 60 inches; reddish yellow (5YR 6/6) silty clay, reddish yellow (5YR 6/8) moist, crushed; moderate very coarse angular blocky structure that parts to moderate medium and fine angular blocky; very hard, very firm, moderately sticky and moderately plastic; few very fine and medium roots; many very fine pores; few thin clay films in pores; violently effervescent; slightly alkaline (pH 7.8).
TYPE LOCATION: Garfield County, Utah; Daves Hollow; in northwest 1/4 sec. 25, T. 36 S., R. 4 W.
RANGE IN CHARACTERISTICS: The mean annual temperature is about 42 to 47 degrees F. The mean summer soil temperature is about 59 to 64 degrees F. These soils have an ustic moisture regime bordering on an aridic regime.
The A horizon is slightly effervescent to strongly effervescent. It is brown to strong brown, reddish brown or yellowish brown, and has hue of 5YR or 10YR, value of 4 or 5 dry, 3 or 4 moist, an chroma of 2 to 4.
The A horizons that have values less than 3.5 moist and chromas less than 4 moist are less than 10 inches thick or less than 1/3 the thickness of the solum.
The Bt horizon ranges from brown to strong brown, yellowish brown or reddish yellow, and has hue of 5YR, 7.5YR or 10YR, value of 5 to 8 dry, 3 to 6 moist, and chroma of 3 to 6. The particle size control section averages silty clay loam with about 35 to 45 percent clay but the particle size control section is stratified and texture of individual strata includes loam, silt loam, silty clay loam, and silty clay.
The Bk horizon ranges from reddish yellow to reddish brown or yellowish brown and has hue of 5YR, 7.5YR or 10YR, value of 6 to 8 dry, 4 to 6 moist; and chroma of 4 to 8. It averages silty clay loam, but is stratified loam, silt loam, silty clay loam, silty clay and has loamy sand or gravel lenses. This horizon has 15 to 40 percent calcium carbonate equivalent.
COMPETING SERIES: This is the Widen series. It has bedrock of soft siltstone or shale at depths of 20 to 40 inches.
GEOGRAPHIC SETTING: Ahlstrom soils are on flood plains and valley slopes at elevations of 7,600 to 8,400 feet. Slopes range from 0 to 12 percent, but are usually 2 to 3 percent. These soils formed in mixed alluvium from limestone and shale. The average annual precipitation is 14 to 18 inches and the freeze-free period ranges from 70 to 80 days. The mean annual temperature is 40 to 45 degrees F. and the average summer temperature is 59 to 64 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Brycan, Kade and Osote soils. Brycan soils have less than 35 percent clay in the particle size control section. Kade soils lack a cambic horizon and are saturated with water below a depth of 1 to 3 feet in most years.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; slow permeability.
USE AND VEGETATION: Rangeland. Native vegetation is big sagebrush, rabbitbrush, black sagebrush, and forbs.
DISTRIBUTION AND EXTENT: South-central Utah. These soil are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Paunsaugunt Survey Area, Utah, 1969. The typical pedon is in the Panguitch Area soil survey.
REMARKS: Diagnostic horizons and features recognized in this pedon::
Ochric epipedon: 0 to 7 inches (Ap horizon)
Argillic horizon: 7 to 60 inches (Bt1, Bt2, Btk1, and Btk horizons)
Pale- feature: an argillic horizon with reddish color and no clay decrease.
Calcic horizon 14 to 60 inches (Btk1 and Btk horizons)
This series was formerly classified as Typic Ustochrepts. In 1999 it was decided as described this soil had an argillic horizon. This needs to be confirmed in the field. On floodplain landforms the clay films are particularly questionable.