LOCATION BANCROFT ID+WYEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, frigid Calcic Argixerolls
TYPICAL PEDON: Bancroft silt loam, cropland. (Colors are for dry soil unless otherwise noted.)
A--0 to 7 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak fine platy structure parting to weak fine granular; slightly hard, friable, slightly sticky and slightly plastic; many fine, few medium roots; many very fine interstitial pores; neutral (pH 7.0); clear wavy boundary. (2 to 8 inches thick)
AB--7 to 14 inches; brown (10YR 5/3) silt loam, dark brown (10YR 3/3) moist; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine and medium roots; common medium, many very fine and fine tubular pores; neutral (pH 7.2); clear wavy boundary. (5 to 12 inches thick)
Bt--14 to 27 inches; pale brown (10YR 6/3) silt loam, dark brown (10YR 4/3) moist; moderate medium subangular blocky structure; hard, friable, sticky and plastic; common very fine and fine roots; many fine and medium tubular pores; common thin clay films on faces of peds; slightly alkaline (pH 7.6); abrupt wavy boundary. (9 to 13 inches thick)
Bk--27 to 55 inches; very pale brown (10YR 8/3) silt loam, pale brown (10YR 6/3) moist; massive; hard, firm, moderately sticky and moderately plastic; few fine roots; many fine and medium tubular pores; violently effervescent; strongly alkaline (pH 8.8); gradual irregular boundary. (15 to 28 inches thick)
C--55 to 61 inches; very pale brown (10YR 7/3) silt loam, pale brown (10YR 6/3) moist; massive; hard, firm, moderately sticky and moderately plastic; few fine roots; many fine and medium tubular pores; strongly effervescent; strongly alkaline (pH 8.6).
TYPE LOCATION: Caribou County, Idaho; 3/4 mile east of Bancroft; 1,600 feet east and 2,300 feet south of the northwest corner, sec. 23, T. 8 S., R. 39 E.
RANGE IN CHARACTERISTICS:
Depth to bedrock - 40 to 60 inches or more
Thickness of mollic epipedon - 10 to 19 inches
Particle-size control section - 18 to 32 percent clay
Mean annual soil temperature - 42 to 47 degrees F
Depth to calcic horizon - 19 to 40 inches
Depth to the 2Bk or C horizon is over 40 inches
A horizon
Color value, dry - 4 or 5
Value, moist - 2 or 3
Chroma, dry or moist - 2 or 3
Organic matter - 2 to 3 percent
Reaction - slightly acid to slightly alkaline
Bt horizon
Color hue - 10YR or 7.5YR
Color value, dry - 4 to 6
Value, moist - 3 to 5
Chroma, dry or moist - 2 through 4
Texture - SIL, SICL
Reaction - slightly acid to moderately alkaline
Bk horizon
Color value, dry - 6 through 8
Value, moist - 4 through 7
Chroma, dry or moist - 2 through 4
Reaction - slightly to strongly alkaline
Calcium Carbonate - 15 to 30 percent
C or 2Bk horizon
Color value, dry - 7 or 8
Value moist - 4 to 6
Chroma, dry or moist - 3 or 4
Reaction - slightly to strongly alkaline
Coarse fragments - 0 to 25 percent
Texture - SIL, LS, L
COMPETING SERIES: These are the Chatburn, Elevator, and Thatcher series. Chatburn soils have cartonates at 13 to 19 inches. Elevator soils contain relic mottles and are extremely hard and extremely firm below the argillic horizon. Thatcher soils have hues of 7.5YR in the Bt horizon and are underlain by lake sediments.
GEOGRAPHIC SETTING: Bancroft soils are on fan terraces, mountain footslopes, foothills, and basalt plains. Slopes range from 0 to 30 percent. They formed in loess and silty alluvium from loess. The mean annual precipitation ranges from 12 to 16 inches, and the mean annual temperature ranges from 40 to 45 degrees F. The frost-free season is about 60 to 100 days. Elevation ranges from 4,800 to 6,400 feet.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Joes, Lanoak, Manila, McBiggam and Rexburg series. Joes soils lack argillic horizons and are calcareous to the surface. Lanoak soils lack argillic horizons, have mollic epipedons greater than 20 inches thick, and lack calcic horizons within 40 inches. Manila soils are fine and lack calcic horizons within 40 inches. Rexburg soils are coarse-silty and lack argillic horizons. Joes soils are on south-facing fan terraces. Lanoak soils are on north-facing fan terraces, foothills, and mountain footslopes. Manila soils are on mountain footslopes, foothills, and fan terraces. Rexburg soils are on south and west-facing fan terraces, foothills, and mountain footslopes. McBiggam soils are on adjacent upland sideslopes and lack a Calcic horizon.
DRAINAGE AND PERMEABILITY: Well drained; slow to very rapid runoff; moderate permeability.
USE AND VEGETATION: Used for irrigated and non-irrigated cropland. The potential natural vegetation is mountain big sagebrush, bluebunch wheatgrass, slender wheatgrass, Idaho fescue, and three-tip sagebrush.
DISTRIBUTION AND EXTENT: Southeastern Idaho. The series is of moderate extent.
MLRA OFFICE RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Bannock County, Idaho, 1983.
REMARKS: Diagnostic horizons and features recognized in this series are:
Mollic epipedon - the zone from the surface of the soil to
approximately 14 inches (A and AB horizons)
Argillic horizon - the zone from approximately 14 to 27 inches (Bt horizon)
Calcic horizon - the zone from approximately 27 to 55 inches (Bk horizon)