LOCATION HILLCREEK IDEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Vitrandic Argixerolls
TYPICAL PEDON: Hillcreek ashy loam -- on a north-facing foothill slope of 57 percent at 4,240 feet elevation in rangeland. When described on August 30, 1995, the soil was dry throughout. (Colors are for air-dry soil unless otherwise noted.)
A1--0 to 2 inches; very dark grayish brown (10YR 3/2) ashy loam, very dark brown (10YR 2/2) moist; strong fine and medium granular structure; slightly hard, very friable, slightly sticky and moderately plastic; many very fine and fine, few medium roots; many very fine, fine and medium irregular pores; neutral (pH 7.0); clear wavy boundary.
A2--2 to 10 inches; very dark grayish brown (10YR 3/2) ashy loam, very dark brown (10YR 2/2) moist; moderate fine subangular blocky structure parting to moderate medium and coarse granular; slightly hard, very friable, moderately sticky and moderately plastic; many very fine and fine roots; many very fine, fine and medium irregular pores; neutral (pH 6.9); clear wavy boundary. (combined A horizon - 8 to 16 inches thick)
AB--10 to 27 inches; very dark grayish brown (10YR 3/2) ashy loam, very dark brown (10YR 2/2) moist; moderate fine and medium subangular blocky structure; slightly hard, very friable, moderately sticky and moderately plastic; many very fine and fine roots; many very fine and fine tubular pores; neutral (pH 6.9); clear wavy boundary. (10 to 20 inches thick)
2Bt1--27 to 43 inches; brown (10YR 4/3) clay loam, dark brown(10YR 3/3) moist; moderate fine and medium subangular blocky structure; slightly hard, very friable, moderately sticky and moderately plastic; many very fine and fine roots; many very fine and fine tubular pores; common distinct clay films on faces of peds; 2 percent gravel; neutral (pH 7.3); gradual wavy boundary. (10 to 20 inches thick)
2Bt2--43 to 59 inches; brown (10YR 5/3) clay loam, brown (10YR 4/3) moist; moderate medium subangular blocky structure; slightly hard, very friable, moderately sticky and moderately plastic; common very fine roots; many very fine and fine tubular pores; many distinct clay films on faces of peds; 5 percent gravel, 5 percent cobbles; neutral (pH 7.3); clear wavy boundary. (10 to 24 inches thick)
2Bt3--59 to 66 inches; yellowish brown (10YR 5/4) gravelly clay loam, dark yellowish brown (10YR 4/4) moist; weak fine and medium subangular blocky structure; slightly hard, very friable, slightly sticky and moderately plastic; common very fine roots; many very fine and fine tubular pores; common distinct clay films on faces of peds; 10 percent gravel, 5 percent cobbles; slightly alkaline (pH 7.4).
TYPE LOCATION: Boise County, Idaho; about 8 miles north of Boise; 300 feet south and 150 feet east of the northwest corner of section 23, T.5 N., R.2 E.; USGS Cartwright Canyon Quadrangle; Latitude - 43 degrees, 45 minutes, 46 seconds N. and Longitude - 116 degrees, 11 minutes, 35 seconds W.; NAD 83.
RANGE IN CHARACTERISTICS:
Mollic epipedon thickness - 20 to 45 inches
Depth to bedrock - greater than 60 inches
Depth to base of vitrandic feature - 20 to 36 inches
Particle-size control section - 27 to 35 percent clay; 0 to 15 percent rock
Moisture control section - dry 60 to 90 consecutive days following the summer solstice
Average annual soil temperature - 47 to 51 degrees F.
A horizon
Value - 3 through 5 dry, 2 or 3 moist
Chroma - 2 or 3 dry or moist
Rock fragments - 0 to 5 percent gravel
Volcanic glass content - 5 to 15 percent
Acid oxalate extract A1+1/2 Fe - 0.5 to 1.0 percent
AB horizon
Value - 3 through 5 dry, 2 or 3 moist
Chroma - 2 or 3 dry or moist
Texture - ASHY-L or ASHY-SIL
Clay content - 20 to 27 percent
Rock fragments - 0 to 10 percent gravel
Volcanic glass content - 5 to 15 percent
Acid oxalate extract A1+1/2 Fe - 0.5 to 1.0 percent
2Bt1 horizon
Value - 4 through 6 dry, 3 or 4 moist
Chroma - 2 through 4 dry or moist
Texture - CL or SICL
Clay content - 27 to 35 percent
Rock fragments - 0 to 10 percent gravel
2Bt2 and 2Bt3 horizons
Value - 5 through 7 dry, 3 through 5 moist
Chroma - 3 or 4 dry or moist
Texture - L, CL or SICL
Clay content - 25 to 35 percent
Reaction - neutral or slightly alkaline
Rock fragments - 5 to 25 percent gravel, 0 to 10 percent cobbles and 5 to 25 percent total
COMPETING SERIES: These are the Buckbay, Georgecreek, Jauriga, Morical, Mozen (T), Pachneum (T), Ralock, Rollinger, Shushuskin (T), Teewee, Tolius, Vanderbilt (T), Volinger (T), Wenner and Wockum soils. Buckbay, Morical and Jauriga soils are moderately deep to a paralithic contact. Georgecreek, Teewee and Wenner soils have mollic epipedons less than 20 inches thick. Mozen and Shushuskin soils are moderately deep to lithic bedrock. Pachneum soils are ashy (vitrandic features) to depths of 13 to 19 inches. Ralock and Rollinger soils contain secondary carbonates above 42 inches and are dry for 100 to 120 consecutive days following the summer solstice. Tolius soils have base saturation of 60 to 70 percent in some part above 30 inches and have C horizons with textures of loam or sandy loam above 60 inches. Vanderbilt soils have a mollic epipedon more than 60 inches thick and are dry for 90 to 100 consecutive days following the summer solstice. Volinger soils have secondary carbonates at 43 to 60 inches. Wockum soils are dry 90 to 100 days and are ashy (vitrandic features) to depths of 7 to 12 inches.
GEOGRAPHIC SETTING: Hillcreek soils are on hill backslopes and fan remnants at elevations of 2,600 to 5,250 feet. These soils formed in colluvium and slope alluvium from basalt mixed with volcanic ash in the upper part. Slopes range from 4 to 65 percent. The average annual precipitation is 14 to 22 inches. The average annual temperature is 45 to 49 degrees F. The frost-free period is 90 to 130 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Hovelton and Hann soils. Hovelton soils are moderately deep to bedrock, loamy-skeletal and on hill backslopes. Hann soils are fine textured and on hill backslopes and footslopes.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; moderately slow permeability.
USE AND VEGETATION: Hillcreek soils are used mainly for rangeland. Native vegetation is xeric big sagebrush, bluebunch wheatgrass and Idaho fescue.
DISTRIBUTION AND EXTENT: West-central Idaho. MLRA 10. Hillcreek soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Boise County Area, Idaho, Parts of Ada and Boise Counties, 2005.
REMARKS: Diagnostic horizons and features recognized in this pedon:
Mollic epipedon - zone from the soil surface to 43 inches (A1, A2, AB and Bt1 horizons)
Vitrandic feature - zone from the soil surface to 27 inches (A1, A2 and AB horizons)
Argillic horizon - zone from 27 to 66 inches (Bt1, Bt2 and Bt3 horizons)
Particle-size control section - zone from 27 to 47 inches
Soil moisture regime - xeric