LOCATION BOBKNOLL UT

Established Series
Rev. CW/JWB
03/2011

BOBKNOLL SERIES

The Bobknoll series consists of moderately deep, well drained soils that formed in slope alluvium from sedimentary rock over residuum derived from sandstone and conglomerate. Bobknoll soils are on plateaus. Slopes range from 2 to 10 percent. Mean annual precipitation is about 35 cm and the mean annual temperature is about 8 degrees C.

TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, mesic Aridic Calciustepts

TYPICAL PEDON: Bobknoll very fine sandy loam, on a west facing, convex, 4 percent slope in rangeland at an elevation of 2,271 meters. (Colors are for dry soil unless otherwise noted.) The surface is covered by 5 percent sandstone gravel.

A--0 to 7 cm; brown (7.5YR 5/3) very fine sandy loam, brown (7.5YR 4/3) moist; 18 percent clay; weak fine granular structure; very friable, soft, slightly sticky, slightly plastic; common medium, fine and very fine roots; common very fine tubular and vesicular pores; 5 percent gravel; slightly effervescent, carbonates are finely disseminated; moderately alkaline (pH 8.0); gradual wavy boundary. (7 cm thick)

Bw--7 to 30 cm; brown (7.5YR 5/3) very fine sandy loam, brown (7.5YR 4/3) moist; 18 percent clay; weak fine subangular blocky structure; very friable, slightly hard, slightly sticky, slightly plastic; common medium, fine and very fine roots; many very fine tubular pores; 5 percent gravel; strongly effervescent, 5 percent distinct threadlike pinkish gray (7.5YR 7/2) carbonate masses throughout; moderately alkaline (pH 8.2); gradual wavy boundary. (15 to 23 cm thick)

Bk1--30 to 81 cm; brown (7.5YR 5/4) gravelly loam, brown (7.5YR 4/4) moist; 19 percent clay; weak fine subangular blocky structure; very friable, slightly hard, slightly sticky, slightly plastic; few medium and fine and common very fine roots; few medium and common very fine tubular pores; 5 percent channers, 15 percent gravel; violently effervescent, 5 percent distinct carbonate coats on bottom surfaces of rock fragments, 10 percent distinct threadlike pinkish gray (7.5YR 7/2) carbonate masses throughout; moderately alkaline (pH 8.3); gradual wavy boundary.

Bk2--81 to 89 cm; pinkish gray (7.5YR 7/2) gravelly loam, light brown (7.5YR 6/3) moist; 17 percent clay; weak fine subangular blocky structure; friable, slightly hard, slightly sticky, slightly plastic; few fine and very fine roots; few fine and very fine tubular pores; 5 percent channers, 25 percent gravel; violently effervescent, 10 percent distinct carbonate coats on rock fragments, 25 percent distinct threadlike white (7.5YR 8/1) carbonate masses throughout; moderately alkaline (pH 8.4); clear smooth boundary. (Combined thickness of the Bk horizons is 21 to 59 cm)

R--89 to 99 cm; indurated sandstone bedrock.

TYPE LOCATION: Emery County, Utah; about 34 kilometers (21 miles) east of Castle Dale, on Cedar Mountain; located about 1,000 feet south and 2,500 feet west of the northeast corner of sec. 11, T. 19 S., R. 11 E.; Bob Hill Knoll USGS quad; lat. 39 degrees 11 minutes 17.22 seconds N. and long. 110 degrees 39 minutes 16.92 seconds W., NAD 83

RANGE IN CHARACTERISTICS:
Soil moisture: The sSoil moisture control section is usually moist in some part during summer and early fall, and intermittently dry in late fall. affected by precipitation that peaks from July to October and falls evenly throughout the remainder of the year; uUstic moisture regime bordering on aridic.
Mean annual soil temperature: 8.3 to 11.1 degrees C
Depth to lithic contact: 51 to 102 cm
Depth to cambic horizon: 7 cm
Depth to calcic horizon: 30 to 48 cm
Thickness of the cambic horizon: 15 to 23 cm
Thickness of the calcic horizon: 21 to 59 cm

Particle-size control section (weighted averages):
Clay content: 15 to 24 percent
Carbonate clay content: 2 to 6 percent
Rock fragment content: 15 to 35 percent gravel

A horizon:
Hue: 7.5YR or 10YR
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 to 4 dry or moist
Texture: very fine sandy loam, gravelly very fine sandy loam
Clay content: 12 to 18 percent
Carbonate clay content: 0 to 2 percent
Rock fragments: 0 to 35 percent gravel
Calcium carbonate equivalent: 0 to 10 percent
EC (mmhos/cm): 0 to 4
SAR: 0 to 2
Reaction: 7.4 to 8.4

Bw horizon:
Hue: 7.5YR or 10YR
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 3 to 6 dry or moist
Texture: very fine sandy loam, gravelly loam
Clay content: 12 to 24 percent
Carbonate clay content: 0 to 2 percent
Rock fragments: 0 to 35 percent gravel
Calcium carbonate equivalent: 0 to 10 percent
EC (mmhos/cm): 0 to 4
SAR: 0 to 2
Reaction: 7.9 to 8.4

Bk horizons:
Hue: 7.5YR or 10YR
Value: 6 to 8 dry; 4 to 7 moist
Chroma: 2 to 4 dry or moist
Texture: gravelly loam, gravelly fine sandy loam, very gravelly fine sandy loam
Clay content: 12 to 24 percent
Carbonate clay content: 0 to 7 percent
Rock fragments: 15 to 60 percent gravel
Calcium carbonate equivalent: 5 to 35 percent
EC (mmhos/cm): 0 to 4
SAR: 0 to 3
Reaction: 7.9 to 9.0

COMPETING SERIES: These are the Snilloc, Sweatbee and Tanoan (T) series. These soils are greater than 102 cm deep to bedrock.

GEOGRAPHIC SETTING:
Parent material: slope alluvium derived from sedimentary rock over residuum from sandstone
Landform: plateaus
Slopes: 2 to 10 percent
Elevation: 2,073 to 2,286 meters
Mean annual temperature: 7.2 to 8.9 degrees C
Mean annual precipitation: 30.5 to 40.6 cm
Precipitation pattern: Wettest months areprecipitation peaks from July to October and driest months are December and Junefalls evenly throughout the remainder of the year.
Frost-free period: 110 to 135 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Colskel, Pollow, Stephouse and Wimmer series. The Colskel and Stephouse soils are shallow and are on bench ridges, rims and risers under Utah juniper and pinyon. The Pollow soils have argillic horizons and are on concave areas under mixed shrubs and ponderosa pine. The Wimmer soils are fine-loamy, very deep and are in concave areas intermixed with the Bobknoll soils.

DRAINAGE AND PERMEABILITY: well drained, low runoff, moderate permeability.

USE AND VEGETATION: Grazing, watershed, recreation and wildlife habitat. Native vegetation is Wyoming big sagebrush, Mormon-tea, fourwing saltbush, buckwheat, winterfat, Indian ricegrass, blue grama, western wheatgrass, needleandthread, muttongrass and a few Utah juniper and pinyon pine.

DISTRIBUTION AND EXTENT: Central Utah upland plateaus; LRR D, MLRA 34B; small extent. About 2,450 hectares (6,000 acres) in Emery County, Utah.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Emery County, Emery soil survey area, Utah, 2011. The name is derived from Bob Hill Knoll near the type location.

REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Series control section: The zone from 0 to 89 cm.
Particle-size control section: The zone from 25 to 89 cm. (Bw and Bk horizons)
Ochric epipedon: The zone from 0 to 7 cm. (A horizon)
Cambic horizon: The zone from 7 to 30 cm. (Bw horizon)
Calcic horizon: The zone from 30 to 89 cm. (Bk horizons)
Lithic contact: The contact with indurated sandstone bedrock at 89 cm. (R horizon)

The assignment of the cation-exchange activity class is inferred from lab data from similar soils in the surrounding area.

Taxonomic Version: Classified according to Keys to Soil Taxonomy, Eleventh Edition, 2010.

National Cooperative Soil Survey
U.S.A.