LOCATION BIGRANT IDEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, calcareous Calcic Cryaquolls
TYPICAL PEDON: Bigrant silty clay loam, pasture--on a 1 percent slightly concave slope at 5,200 feet elevation. When described on September 28, 1987, the soil was moist to 19 inches and wet below with ground water at 29 inches. (Colors are for dry soil unless otherwise noted.)
Oi--0 to 4 inches; slightly decomposed grass. (0 to 5 inches thick)
Ak1--4 to 14 inches; gray (10YR 6/1) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure parting to moderate fine granular; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine, and common medium roots; common very fine tubular pores; violently effervescent (20 percent calcium carbonate equivalent); slightly alkaline (pH 7.7); clear wavy boundary. (3 to 12 inches thick)
Ak2--14 to 23 inches; grayish brown (10YR 5/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine, very fine and few medium roots; common very fine and fine tubular pores; violently effervescent (25 percent calcium carbonate equivalent); moderately alkaline (pH 8.0); gradual wavy boundary. (0 to 10 inches thick)
Bkg1--23 to 29 inches; light brownish gray (2.5Y 6/2) clay loam, dark grayish brown (2.5Y 4/2) moist; many large prominent iron concentrations, dark yellowish brown (10YR 4/6) moist; moderate medium subangular blocky structure parting to moderate fine granular; hard, firm, sticky and plastic; common very fine and fine and few medium roots; many very fine and common fine tubular pores; sand sized soft lime nodules common throughout; violently effervescent (26 percent calcium carbonate equivalent); moderately alkaline (pH 8.3); gradual wavy boundary.
Bkg2--29 to 33 inches; light gray (5Y 7/2) clay loam, olive (5Y 5/3) moist; many large distinct iron accumulations, gray (5Y 5/1) moist; moderate medium subangular blocky structure parting to moderate fine granular; hard, firm, sticky and plastic; few very fine and fine roots; common very fine and fine tubular pores; 20 percent of soil material is soft segregated lime; violently effervescent (20 percent calcium carbonate equivalent); moderately alkaline (pH 8.1); clear wavy boundary. (Combined thickness of the Bkg horizon is 8 to 18 inches.)
Bg--33 to 40 inches; light olive gray (5Y 6/2) loam, olive gray (5Y 4/2) moist; common large prominent iron accumulations, dark greenish gray (5BG 4/1) moist; moderate medium subangular blocky structure parting to moderate fine granular; hard, firm, sticky and plastic; few very fine and fine roots; common very fine and fine tubular pores; moderately alkaline (pH 8.3); gradual wavy boundary. (0 to 10 inches thick)
Cg--40 to 64 inches; pale olive (5Y 6/3) loam, greenish gray (5G 5/1) moist; common large prominent iron accumulations, dark yellowish brown (10YR 4/6) moist; massive; hard, firm, slightly sticky and plastic; few very fine and fine roots; few very fine and fine tubular pores; moderately alkaline (pH 8.1).
TYPE LOCATION: Custer County, Idaho; about 3 miles northeast of Challis; about 180 feet north and 5 feet east of the southwest corner of section 14, T.14N, R.19E.
Latitude - 49 degrees, 35 minutes North; Longitude - 114 degrees, 12 minutes West.
RANGE IN CHARACTERISTICS:
Average annual soil temperature - 35 to 41 degrees F.
Average summer soil temperature - 41 to 45 degrees F.
Depth to high water table - 0 to 18 inches April through July
Depth to the calcic horizon - 3 to 12 inches
Mollic epipedon - 10 to 20 inches thick
Particle size control section
Average percent carbonate free clay - 25 to 35 percent
Average percent total clay - 35 to 45 percent
Ak horizons
Value - 5 through 7 dry
Chroma - 1 or 2 dry or moist
Calcium carbonate equivalent - 15 to 30 percent
SAR - 5 to 10
Reaction - slightly or moderately alkaline
Bkg horizons
Hue - 10YR, 2.5Y or 5Y
Value - 6 or 7 dry, 3 through 5 moist
Chroma - 1 through 3 dry or moist
Texture - SICL, CL or C
Total clay content - 30 to 50 percent
Calcium carbonate equivalent - 20 to 35 percent
Reaction - slightly or moderately alkaline
Bg horizon
Hue - 2.5Y or 5Y
Value - 6 or 7 dry, 4 or 5 moist
Chroma - 1 or 2 dry or moist
Clay content - 20 to 26 percent
Reaction - slightly or moderately alkaline
Calcium carbonate equivalent - 0 to 5 percent
Cg horizon
Hue - 5Y, 5GY, or 5G
Clay content - 20 to 26 percent
Reaction - slightly or moderately alkaline
Calcium carbonate equivalent - 0 to 5 percent
COMPETING SERIES: This is the Thosand series. Thosand soils have contrasting sand and gravel at 40 to 60 inches.
GEOGRAPHIC SETTING: Bigrant soils are on flood plains and stream terraces at elevations of 4,800 to 6,400 feet. Slopes range from 0 to 6 percent. These soils formed in silty alluvium. The climate is cold and moist in winter and spring and cool in summer. The average annual precipitation is 8 to 13 inches. The average annual air temperature is 36 to 42 degrees F. The frost-free season is 35 to 55 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Dickeypeak and the competing Thosand soils. Dickeypeak soils are on fan terraces and stream terraces, are somewhat poorly drained and have coarse-loamy textural control sections.
DRAINAGE AND PERMEABILITY: Poorly and very poorly drained. Slow runoff. Moderately slow permeability. Occasional flooding for brief periods April through September.
USE AND VEGETATION: Pastureland. The natural vegetation is inland saltgrass, tufted hairgrass, sedge, basin wildrye and slender wheatgrass.
DISTRIBUTION AND EXTENT: East central Idaho. These soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Custer County, Idaho, 1999.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from 4 to 14 inches (Ak1, Ak2 horizons); dry value is waved because of over 15 percent calcium carbonate.
Calcic horizon - The zone from 14 to 33 inches (Ak2, Bkg1, and Bkg2 horizons).
Particle-size control section - The zone from 14 to 44 inches (Ak2, Bkg1, Bkg2, Bg horizons, and part of the Cg horizon).
ADDITIONAL DATA: This pedon was sampled by the NSSL, Lincoln, NE, Sample Number S87ID-037-005.