LOCATION ROBIN IDEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive Pachic Palecryolls
TYPICAL PEDON: Robin silt loam, native grass. (Colors are for dry soil unless otherwise stated.)
A1--0 to 11 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; moderate very fine, fine, and medium granular structure in upper part and weak very fine and fine granular structure in lower part; slightly hard, very friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine and fine pores; slightly acid (pH 6.2); gradual wavy boundary. (7 to 16 inches thick)
A2--11 to 18 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist and few fine streaks of light brownish gray; lower part is grayish brown dry, and dark brown moist; weak medium prismatic structure that parts to weak medium subangular blocky, thin to weak medium and fine granular; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine and fine pores; few splotches of partially uncoated silt on surfaces of peds; slightly acid (pH 6.4); clear wavy boundary. (6 to 15 inches thick)
AB--18 to 30 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak medium and coarse prismatic structure that parts to moderate medium subangular blocky; hard, friable, slightly sticky and slightly plastic; common very fine and fine, few medium roots; many very fine and fine slightly sticky and slightly plastic; common very fine and fine, few medium roots; many very fine and fine tubular pores; few thin clay films on surfaces of peds and pores; thin coating of light gray (10YR 7/2), nearly clean silt on surfaces of peds; many krotovinas 3 to 4 inches across; neutral (pH 6.6); clear wavy boundary. (8 to 14 inches thick)
Bt1--30 to 48 inches; brown (10YR 5/3) silt loam, dark brown (10YR 4/3) moist; moderate medium and coarse prismatic structure that parts to moderate medium and coarse subangular blocky; hard, friable, sticky and plastic; common very fine and fine roots; many very fine and fine tubular pores; several brown (7.5YR 4/3) silty clay loam bands 1/2 to 1 inch thick; thin patchy clay films on surfaces of peds and thick continuous ones in bands; medium coating of light gray (10YR 7/2) uncoated silt on surfaces of peds and in few 0.5-0.3 inch pockets; neutral (pH 6.6); gradual wavy boundary. (12 to 30 inches thick)
Bt2--48 to 72 inches; pale brown (10YR 6/3) silt loam, dark brown (10YR 4/3) moist; moderate medium and fine prismatic structure parting to weak medium subangular blocky; hard, friable, slightly sticky and slightly plastic; few very fine roots; many very fine and fine tubular pores; medium continuous clay films in some channels and thin patchy clay films on surfaces of peds; thick continuous brown (10YR 4/3) clay films in more clayey bands 1/2 to 1 inch thick; few streaks and medium coating of light gray uncoated silt on surfaces of peds; common soft iron-manganese oxide concretions less than 1 mm. across; neutral (pH 6.6); gradual wavy boundary. (0 to 25 inches thick)
BC--72 to 94 inches; pale brown (10YR 6/3) silt loam, brown (10YR 4/3) moist; massive; hard, very friable, slightly sticky and slightly plastic; few very fine and fine roots; many very fine and fine tubular pores; few thin clay films; thin coating of clean silt; noncalcareous; neutral (pH 7.0); clear wavy boundary. (0 to 25 inches thick)
C--94 to 112 inches; very pale brown (10YR 7/3) silt loam, brown (10YR 5/3) moist; massive; hard, friable, slightly sticky and slightly plastic; few very fine and fine roots; many very fine and fine tubular pores; moderately calcareous; slightly alkaline (pH 7.4). (0 to few feet thick)
TYPE LOCATION: Bingham County, Idaho; 10 miles south of Bone at an elevation of 6,500 feet; 580 feet east and 1,550 feet north of the center of sec. 9, T. 3 S., R. 40 E.
RANGE IN CHARACTERISTICS: The mean annual soil temperature ranges from 35 degrees to 43 degrees F., and the mean summer temperature at a depth of 20 inches ranges from 55 degrees to 59 degrees F. The mollic epipedon is 24 to 32 inches thick. The upper boundary of the argillic horizon is deeper than 24 inches. The solum thickness ranges from 40 inches to 7 feet and is usually greater than 5 feet. The soils are noncalcareous to 5 feet or deeper.
The A horizon has value of 3 through 5 dry, 2 or 3 moist, and chroma of 1 to 3 dry or moist. It has weak very fine to moderate medium granular structure. This A horizon is medium acid to neutral.
The Bt horizon has hue of 10YR or 7.5YR, value of 5 or 6 dry, 3 to 5 moist, and chroma of 2 to 4. It is silt loam or silty clay loam and averages 18 to 35 percent clay. This horizon has thin and patchy to medium and nearly continuous clay films and continuous ones in the bands. It has weak to moderate, medium to coarse prismatic to moderate, medium to coarse subangular blocky structure. Uncoated or partially uncoated silt specking on the surfaces of peds ranges from thin to medium.
COMPETING SERIES: These are the Bozeman, Dranyon, Huffine, Lanark, Red Spur and Rin soils all having the upper boundary of the argillic horizon at depths of less than 24 inches from the soil surface. Bozeman soils are calcareous within 40 inches of the surface. Dranyon and Red Spur soils have more than 15 percent particles coarser than very fine sand in the control section. Huffine and Willow Creek soils have a mollic epipedon thinner than 16 inches. Lanark soils are calcareous within 60 inches of the surface. Rin soils lack an argillic horizon.
GEOGRAPHIC SETTING: The soils are in level to steep loess-covered uplands and mountain, but the dominant slopes are between 3 and 45 percent. The soils formed in loess 3.5 to several feet in depth. Elevations range from 5,400 to 7,500 feet. The climate is cold subhumid continental. Mean annual precipitation is 17 to 25 inches including 6 to 10 feet of snowfall. Average annula air temperature is 35 to 41 degrees F. The average frost-free period ranges from 30 to 90 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Dranyon and Lanark soils and the Gilispie soils. Gilispie soils have bedrock at a depth of 10 to 20 inches.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderate or moderately slow permeability.
USE AND VEGETATION: Most of the area is in native grass, but sizeable areas are used for small grains. The natural vegetation is mainly Idaho fescue, streambank wheatgrass, Columbia needlegrass, Nevada bluegrass, geranium, potentilla, and aspen.
DISTRIBUTION AND EXTENT: High loessal uplands of southeastern Idaho and western Wyoming. Moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Bingham County, Idaho, 1972.
REMARKS: Diagnostic horizon and features recognized in this pedon are:
Mollic epipedon (pachic feature) - The zone from the soil surface to 30 inches (A1, A2 and AB horizons).
Argillic horizon - the zone from 30 to 72 inches (Bt1 and Bt2 horizons).
Pale feature - More than 24 inches to the top of the argillic horizon.
This soil has a xeric soil moisture regime.