LOCATION BLACKHORSE ID
Established Series
IRD LAR/RGK/CBR
03/2019
BLACKHORSE SERIES
Landscape--hills
Landform--hillslopes
Slope--5 to 50 percent
Parent material--loess-influenced colluvium derived from limestone
Mean annual precipitation--about 450 mm
Mean annual air temperature--about 3 degrees C
Depth class--very deep
Drainage class--well drained
Soil moisture regime--xeric
Soil temperature regime--cryic
TAXONOMIC CLASS: Fine, mixed, superactive Calcic Argicryolls
TYPICAL PEDON: Blackhorse gravelly silty clay loam in an area of rangeland
A--0 to 15 cm; gravelly silty clay loam, very dark grayish brown (10YR 3/2) dry, very dark brown (10YR 2/2) moist; moderate medium and fine granular structure; soft, very firm, slightly sticky and slightly plastic; many very fine and fine and few medium and coarse roots; common very fine and fine tubular pores; 15 percent gravel; slightly alkaline (pH 7.6); clear wavy boundary
Bt--15 to 30 cm; gravelly silty clay loam, dark grayish brown (10YR 4/2) dry, very dark grayish brown (10YR 3/2) moist; strong coarse granular structure; slightly hard, firm, moderately sticky and moderately plastic; common very fine and fine and few medium and coarse roots; common very fine and fine tubular pores; 35 percent faint clay films on ped faces and lining tubular pores; slightly effervescent (4 percent calcium carbonate equivalent); 15 percent gravel; slightly alkaline (pH 7.6); clear wavy boundary
Btk--30 to 56 cm; very gravelly silty clay loam, pale brown (10YR 6/3) dry, brown (10YR 5/3) moist; strong medium and fine angular blocky structure; hard, firm, moderately sticky and moderately plastic; few very fine, fine, medium, and coarse roots; 35 percent faint clay films on ped faces and lining tubular pores; strongly effervescent (40 percent calcium carbonate equivalent); 35 percent gravel; moderately alkaline (pH 8.0); clear wavy boundary
Bk1--56 to 89 cm; silty clay, very pale brown (10YR 7/3) dry, light yellowish brown (10YR 6/4) moist; strong coarse prismatic structure; very hard, very firm, moderately sticky and moderately plastic; few very fine, fine, medium, and coarse roots; common very fine tubular pores; 20 percent masses of calcium carbonate; strongly effervescent (45 percent calcium carbonate equivalent); 5 percent gravel; moderately alkaline (pH 8.2); clear wavy boundary
Bk2--89 to 109 cm; silty clay, very pale brown (10YR 7/3) dry, light yellowish brown (10YR 6/4) moist; strong coarse prismatic structure; hard, firm, moderately sticky and moderately plastic; few very fine and fine roots; common very fine and fine tubular pores; 30 percent masses of calcium carbonate; violently effervescent (25 percent calcium carbonate equivalent); 5 percent gravel; moderately alkaline (pH 8.2); clear wavy boundary
Bk3--109 to 124 cm; gravelly silty clay, very pale brown (10YR 7/3) dry, light yellowish brown (10YR 6/4) moist; strong coarse prismatic structure; hard, firm, moderately sticky and moderately plastic; few very fine roots; common very fine and fine tubular pores; 30 percent masses of calcium carbonate; violently effervescent (50 percent calcium carbonate equivalent); 30 percent gravel; moderately alkaline (pH 8.2); clear wavy boundary
Bk4--124 to 150 cm; silty clay, very pale brown (10YR 8/2) dry, very pale brown (10YR 7/3) moist; weak medium subangular blocky structure, hard, firm, moderately sticky and moderately plastic; few very fine tubular pores; 20 percent masses of calcium carbonate; violently effervescent (65 percent calcium carbonate equivalent); 10 percent gravel; moderately alkaline (pH 8.2)
TYPE LOCATION: Clark County, Idaho; latitude 44.30590 degrees north, longitude 112.64026 west, datum WGS 84
RANGE IN CHARACTERISTICS:
Mean annual soil temperature--3 to 6 degrees C
Thickness of mollic epipedon--23 to 36 cm
Depth to calcic horizon--18 to 60 cm
Particle-size control section (weighted averages)
Clay content--35 to 45 percent
Calcium carbonate equivalent--less than 40 percent
Total rock fragment content--15 to 35 percent
A horizon
Value--3 or 4 dry, 2 or 3 moist
Chroma--1 or 2 dry or moist
Clay content--27 to 35 percent
Gravel content--15 to 25 percent
Reaction--pH 7.4 to 7.8
Thickness--13 to 20 cm
Bt horizon
Hue--10YR or 2.5Y dry or moist
Value--4 to 6 dry
Chroma--1 to 3 dry or moist
Texture (less than 2-mm fraction)--silty clay loam, clay loam
Clay content--27 to 40 percent
Gravel content--15 to 35 percent
Reaction--pH 7.4 to 7.8
Thickness--10 to 15 cm
Btk horizon
Hue--7.5YR to 2.5Y
Value--5 to 7 dry or moist
Chroma--2 to 4 dry or moist
Texture (less than 2-mm fraction)--silty clay loam, clay loam
Clay content--30 to 40 percent
Gravel content--25 to 45 percent
Calcium carbonate equivalent--25 to 40 percent
Reaction--pH 7.9 to 8.4
Thickness--25 to 43 cm
Bk horizon
Hue--7.5YR to 5Y
Value--5 to 8 dry or moist
Chroma--2 to 4 dry or moist
Texture (less than 2-mm fraction)--silty clay, silty clay loam, clay loam
Clay content--30 to 50 percent
Gravel content--5 to 40 percent
Calcium carbonate equivalent--40 to 70 percent
Reaction--pH 7.9 to 8.4
COMPETING SERIES:
Gillum--udic soil moisture regime
Jenksdraw--50 to 100 cm (moderately deep) to lithic contact (limestone, sandstone)
GEOGRAPHIC SETTING:
Elevation--1990 to 2260 m
Mean annual precipitation--400 to 575 mm
Mean annual air temperature--about 2 to 6 degrees C
Frost-free period--30 to 60 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--well drained
Saturated hydraulic conductivity (Ksat)--0.1 to 5.0 um/sec
USE AND VEGETATION:
Major use--livestock grazing
Potential natural vegetation--mountain big sagebrush, Idaho fescue, bluebunch wheatgrass
DISTRIBUTION AND EXTENT: Southeastern Idaho; MLRA 12; small extent
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Clark County, Idaho; 2018
REMARKS:
Diagnostic horizons and other features in this pedon
*Mollic epipedon--zone from the surface to a depth of 30 cm
*Argillic horizon--zone from 15 to 56 cm
*Calcic horizon--zone from 56 to 150 cm
*Particle-size control section--zone from 15 to 56 cm
The soil is not calcareous to the surface after mixing the upper 18 cm.
Taxonomic version--Twelfth Edition, 2014
National Cooperative Soil Survey
U.S.A.