LOCATION CUSTCO IDEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Calcic Argixerolls
TYPICAL PEDON: Custco gravelly loam - on a northwest-facing slope of 35 percent, rangeland, at 5,300 feet elevation. (Colors are for dry soil unless otherwise stated. When described on November 3, 1980, the soil was dry throughout.)
A--0 to 4 inches; dark grayish brown (10YR 4/2) gravelly loam, very dark grayish brown (10YR 3/2) moist; moderate very fine and fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine and fine roots; many very fine interstitial and common very fine and fine tubular pores; 25 percent pebbles; neutral (pH 7.2); clear wavy boundary. (3 to 8 inches thick)
Bt1--4 to 10 inches; brown (10YR 5/3) very gravelly loam, dark brown (10YR 3/3) moist; moderate very fine and fine subangular blocky structure; slightly hard, firm, slightly sticky and slightly plastic; many very fine, common fine and few medium roots; common very fine interstitial and common very fine and fine tubular pores; 45 percent pebbles; common faint and few distinct clay films lining pores and on faces of peds; neutral (pH 7.2); clear wavy boundary. (5 to 10 inches thick)
Bt2--10 to 17 inches; brown (10YR 5/3) very gravelly loam, dark brown (10YR 4/3) moist; moderate very fine and fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine and few medium roots; many very fine interstitial and common very fine and fine tubular pores; 50 percent pebbles; few faint clay films lining pores and on faces of peds; neutral (pH 7.2); gradual wavy boundary. (3 to 17 inches thick)
Bk1--17 to 40 inches; pale brown (10YR 6/3) extremely gravelly sandy loam, brown (10YR 5/3) moist; massive; soft, very friable, nonsticky and nonplastic; common very fine and fine interstitial and few medium roots; many very fine and fine interstitial and common fine tubular pores; 50 percent pebbles, 10 percent cobbles, 1 percent stones; lime and silica layers 1 to 3 mm thick on undersides of coarse fragments; about 20 percent soft secondary lime in matrix and in pores; violently effervescent; moderately alkaline (pH 8.2); gradual wavy boundary. (15 to 30 inches thick)
Bk2--40 to 60 inches; pale brown (10YR 6/3) extremely gravelly loamy sand, brown (10YR 4/3) moist; single grain; loose; few very fine roots; many very fine interstitial pores; 40 percent gravels, 20 percent cobbles, 5 percent stones; strongly effervescent; moderately alkaline (pH 8.2).
TYPE LOCATION: Lemhi County, Idaho; about 15 miles north of Ellis, Idaho; about 900 feet west and 500 feet south of the northeast corner, sec. 12, T. 18 N., R. 20 E. Latitude - 44 degrees, 54 minutes, 37 seconds North; Longitude - 114 degrees, 02 minutes, 20 seconds West.
RANGE IN CHARACTERISTICS:
Average annual soil temperature - 39 to 45 degrees F.
Mollic thickness - 9 to 15 inches
Control section - percent clay 18 to 27
Rock fragments - 35 to 70 percent
Depth to secondary lime - 15 to 35 inches
Reaction of profile - neutral through moderately alkaline
A horizon
Value - 2 to 5 dry and 2 or 3 moist
Chroma - 2 or 3 dry and moist
Bt horizon
Value - 4 or 5 dry and 3 or 4 moist
Chroma - 3 to 5 dry and moist
Texture - GRV-L, GRX-L
Bk horizon
Value - 6 or 7 dry and 4 to 6 moist
Chroma - 3 to 5 dry and moist
Texture - GRV-SL, GRX-LS, GRV-L, GRX-SL, GRX-L
Rock fragments - 40 to 75 percent
COMPETING SERIES: These are the Drage, Rawnjay, Remount, Searla, and Swampydraw (T) series. Broad soils are moderately deep to weathering fractured bedrock. Drage and Searla soils have 28 to 35 percent clay in the control section and moderately slow permeability. Small and Sheep Creek soils are moderately deep to bedrock. Swampydraw soils are currently very similar and will probably be combined with Custco.
GEOGRAPHIC SETTING: Custco soils are on foothills, fan terraces and mountains and have slopes of 8 to 50 percent. Elevations range from 4,300 to 6,500 feet. The soils formed in slope alluvium from extrusive igneous rock. The climate is cold and moist in winter and dry in summer. Average annual precipitation is 13 to 16 inches and average annual temperature is 37 to 43 degrees F. The frost-free period is 60 to 90 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Dacont, Dawtonia, Siri, Snowslide, Venum, and Whitecloud soils. Dacont soils are on hills and mountains and occur in an aridic moisture regime. Dawtonia and Venum soils are on hills and mountains and lack mollic epipedons. Siri, Snowslide, and Whitecloud soils are on fan terraces and have ochric epipedons.
DRAINAGE AND PERMEABILITY: Well-drained. Runoff is medium. Permeability is moderate in the solum and rapid in the substratum.
USE AND VEGETATION: Rangeland. Vegetation is mainly three-tip sagebrush and Idaho fescue.
DISTRIBUTION AND EXTENT: East-central Idaho. These soils are not extensive.
MLRA OFFICE RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Lemhi County, Idaho, 1999.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from the soil surface to a depth of 10 inches (A and Bt1 horizons).
Argillic horizon - the zone from 4 to 17 inches (Bt1 and Bt2 horizons).
Calcic horizon - the zone from 17 to 40 inches (Bk1 horizon).
Particle-size control section - the argillic horizon.