LOCATION CALLAN COEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Calcidic Argiustolls
TYPICAL PEDON: Callan loam - rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 4 inches; brown (7.5YR 5/3) loam, dark brown (7.5YR 3/3) moist; weak fine crumb and granular structure; soft, very friable, slightly sticky and slightly plastic; neutral; clear smooth boundary. (3 to 6 inches thick)
BA--4 to 8 inches; dark brown (7.5YR 4/3) clay loam, dark brown (7.5YR 3/3) moist; weak medium granular structure; hard, very friable, sticky and plastic; neutral; clear smooth boundary. (0 to 4 inches thick)
Bt--8 to 14 inches; brown (7.5YR 5/4)) clay loam, dark brown (7.5 YR 4/4) moist; moderate fine and medium angular blocky structure; very hard, firm, sticky and plastic; neutral; abrupt smooth boundary. (4 to 8 inches thick))
Btk--14 to 22 inches; brown (7.5YR 5/4) clay loam, dark brown (7.5YR 4/4) moist; strong medium angular blocky structure; very hard, friable, sticky and plastic; calcareous; mildly alkaline; clear smooth boundary. (6 to 10 inches thick))
Bk1--22 to 38 inches; light brown (7.5YR 6/4) clay loam, brown (7.5YR 5/4) moist; moderate medium subangular blocky structure; very hard, friable, sticky and plastic; calcareous; moderately alkaline; clear smooth boundary.
Bk2--38 to 48 inches; light brown (7.5YR 6/4) clay loam, brown (7.5YR 5/4) moist; weak coarse subangular blocky structure; very hard, firm, sticky and slightly plastic; calcareous; moderately alkaline; clear wavy boundary. (Combined thickness of Bk is 20 to 30 inches.)
Btkb--48 to 60 inches; brown (7.5YR 5/4) clay loam, strong brown (7.5YR 4/6) moist; moderate fine and medium subangular blocky structure; hard, friable, sticky and plastic; calcareous; moderately alkaline.
TYPE LOCATION: San Miguel County, Colorado; 1,800 feet west and 700 feet north of the southeast corner, sec. 16, T. 45 N., R. 13 W.
RANGE IN CHARACTERISTICS: Thickness of the mollic epipedon ranges from 7 to 10 inches. The upper 7 inches after mixing are mollic in color. Depth to calcareous material ranges from 10 to 20 inches. Coarse fragments range from 0 to 20 percent. Solum thickness is typically 16 to 26 inches to the base of the argillic horizon but ranges from 13 to 28 inches. The calcium carbonate equivalent ranges from 25 to 50 percent in the calcic horizon. Mean annual soil temperature ranges from 40 to 46 degrees F, and summer soil temperature ranges from 60 to 64 degrees F. The soils are usually dry between 4 and 12 inches during the period that the soil temperature at a depth of 20 inches is above 41 degrees F.
The A horizon has hue of 7.5YR or 5YR, value of 4 or 5 dry, 2 or 3 moist, and chroma of 2 or 3.
The Bt horizon has hue of 7.5YR through 2.5YR, value of 4 or 5 dry, 3 or 4 moist, and chroma of 3 to 6. Clay content ranges from 35 to 45 percent. It has strong or moderate angular blocky structure but has weak prismatic structure in some pedons.
The Bk1 horizon has hue of 5YR or 7.5YR, value of 5 to 7 dry, 4 to 6 moist, and chroma of 4 to 6.
The Bk2 horizon PEs hue of 5YR or 7.5YR, value of 6 to 8 dry, 5 to 7 moist, and chroma of 3 or 4.
Buried Btk horizons are common below depths of 44 inches.
COMPETING SERIES: These are the
Gurley and
Smilo soils. Gurley and Smilo soils have hard bedrock above a depth of 40 inches.
GEOGRAPHIC SETTING: Callan soils are on mesa tops and high terraces. Slopes are 1 to 20 percent. The soil formed in wind-reworked local alluvium derived from sandstones and shales. At the type location, the elevation is 6,920 feet, and the average annual precipitation is 16 inches with nearly equal monthly distribution. Mean annual temperature ranges from 43 to 46 degrees F. The frost-free season is 90 to 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are Skein and the competing Gurley soils. Skein soils have bedrock at 10 to 20 inches and lack an argillic horizon.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; slow permeability.
USE AND VEGETATION: These soils are used principally as rangeland and cropland. Native vegetation is mainly sagebrush and native grasses and scattered to moderately thick pinyon-juniper.
DISTRIBUTION AND EXTENT: Mountainous and plateau areas in the San Miguel Basin area of southwestern Colorado. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: San Miguel County, San Miguel Area, Colorado, 1987.
REMARKS: Soil was characterized under NSSL ID Pedon No. 83P0806 and Soil Survey No. S83CO-113-001. These data classified the soil as fine-silty; however, dispersion was a problem and it is agreed that there is 3 to 5 percent more clay than the 31 percent featured in the lab data. Using more dispersion agent, up to 40 percent clay has been analyzed in the Bt horizon.