LOCATION SILI CO+UT
Established Series
Rev. JPP-TWH-WWJ-KLS
02/2018
SILI SERIES
The Sili series consists of very deep, well drained soils that formed in alluvium and slope alluvium weathered from shale and sandstone. Sili soils are on valley bottoms, pediments, and alluvial fans, usually below shale hills, with slopes of 1 to 15 percent. The mean annual precipitation is about 356 mm and the mean annual air temperature is about 8.9 degrees C.
TAXONOMIC CLASS: Fine, smectitic, mesic Aridic Haplustepts
TYPICAL PEDON: Sili clay loam, cultivated. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 18 cm; light brownish gray (10YR 6/2) clay loam, dark grayish brown (10YR 4/2) moist; moderate medium granular structure; slightly hard, firm, moderately sticky and moderately plastic; slightly alkaline (pH 7.4); clear smooth boundary. (18 to 25 cm thick)
Bt--18 to 56 cm; light brownish gray (10YR 6/2) clay loam, dark grayish brown (10YR 4/2) moist; moderate medium angular and subangular blocky structure; hard, firm, moderately sticky and moderately plastic; few thin patchy clay films on faces of peds; strongly effervescent; 2 percent calcium carbonate; slightly alkaline (pH 7.6); clear smooth boundary. (25 to 76 cm thick)
C--56 to 152 cm; light brownish gray (10YR 6/2) clay loam, dark grayish brown (10YR 4/2) moist; massive; very hard, firm, moderately sticky and moderately plastic; strongly effervescent; 5 percent calcium carbonate; moderately alkaline (pH 8.0)
TYPE LOCATION: La Plata County, Colorado; 91 meters north and 40 meters west of the southeast corner of Sec. 19, T.33N, R.6W.; Tiffany USGS quad; Lat. 37 degrees, 04 minutes, 59 seconds, N. and Long. 107 degrees, 31 minutes, 57 seconds, W.; NAD 27.
RANGE IN CHARACTERISTICS:
Thickness of the solum: 36 to 152 cm
Depth to calcareous material: 0 to 76 cm
Linear extensibility: 5.0 to 6.0 (estimated)
Mean annual soil temperature: 8.9 to 11.1 degrees C.
Mean summer soil temperature: 17.2 to 20.0 degrees C.
Particle size control section (weighted average):
Clay content: 35 to 45 percent
Rock fragment content: 0 to 10 percent
A horizon
Hue: 7.5YR to 2.5Y
Value: 5 or 6, 3 or 4 moist
Chroma: 2 or 3, dry or moist
Texture: clay loam or silty clay loam
Calcium carbonate equivalent: 0 to 2 percent
Reaction (pH): 6.6 to 8.4
Bt horizon (Bw in some pedons)
Hue: 7.5YR to 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2 to 4, dry or moist
Texture: silty clay loam, clay, or clay loam with 35 to 45 percent clay, 15 to 50 silt and 15 to 45 percent sand
Calcium carbonate equivalent: 0 to 5 percent
Reaction (pH): 7.4 to 8.4
C horizon (Bk in some pedons)
Hue: 7.5YR to 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2 or 3, dry or moist
Texture: silty clay loam, clay loam, or clay
Calcium carbonate equivalent: 1 to 5 percent
Reaction (pH): 7.4 to 8.4
Minor cracking occurs in some pedons. Secondary calcium carbonates are visible in some pedons.
COMPETING SERIES:
Cromack (WY) - are moderately deep to paralithic contact
Sabatka (WY) - are moderately deep to paralithic contact
GEOGRAPHIC SETTING:
Landform - valley bottoms, pediments, and alluvial fans, normally in areas below shale hills.
Elevation - 1,830 to 2,200 meters
Slopes - 1 to 12 percent
Parent material - alluvium and slope alluvium that has weathered from nearby Animas and Wasatch shale and sandstone
Mean annual precipitation - 300 to 410 mm, but can range to 560 mm in some areas
Mean annual air temperature - 8.3 to 11.1 degrees C.
Mean summer air temperature - 16.1 to 19.4 degrees C.
Frost-free period - 110 to 130 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; moderate runoff; moderately slow permeability.
USE AND VEGETATION: These soils are used for irrigated crops and pasture and native range. Native vegetation is big sagebrush, blue grama, western wheatgrass, Indian ricegrass, and widely spaced pinyon and juniper trees.
DISTRIBUTION AND EXTENT: Western Colorado and adjacent parts of Utah; LRR D, E; MLRA 36, 48A; moderate extent.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: La Plata County Area, Colorado, 1982.
REMARKS: Diagnostic horizons and features recognized in this pedon:
Cambic horizon: 18 to 56 cm (Bt horizon)
Particle-size control section: 25 to 100 cm (part of the Bt and C horizons)
Sili soils have a mesic temperature regime and are in an ustic soil moisture regime bordering on aridic.
The 08/2000 revision changed the classification from Ustollic Camborthids to Aridic Haplustepts (change in moisture regime subclass).
National Cooperative Soil Survey
U.S.A.