LOCATION BOZEMAN MT+ID WYEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive Pachic Argicryolls
TYPICAL PEDON: Bozeman silt loam - pasture. (Colors are for dry soil unless otherwise noted.)
A1--0 to 4 inches; very dark gray (10YR 3/1) silt loam, black (10YR 2/1) moist; moderate thin platy separating to moderate fine crumb structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots and pores; many unstained sand grains on faces of peds; neutral (pH 7.0); clear smooth boundary. (2 to 4 inches thick)
A2--4 to 8 inches; very dark gray (10YR 3/1) light silty clay loam, black (10YR 2/1) moist; moderate medium prismatic separating to moderate medium and fine granular structure; hard, friable, slightly sticky and slightly plastic; many very fine and fine roots and pores; many unstained sand grains on faces of peds; neutral (pH 7.1); clear smooth boundary. (4 to 12 inches thick)
AB--8 to 13 inches; very dark grayish brown (10YR 3/2) silty clay loam, very dark brown (10YR 2/2) moist; moderate medium prismatic separating to strong medium angular blocky structure; hard, friable, moderately sticky and moderately plastic; many very fine and fine roots and pores; thin continuous glazed surfaces on faces of peds; many unstained sand grains on faces of peds; neutral (pH 7.2); clear smooth boundary. (0 to 6 inches thick)
Bt1--13 to 20 inches; dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium prismatic separating to very strong fine subangular blocky structure; very hard, firm, moderately sticky and moderately plastic; common fine and many very fine roots and pores; continuous distinct clay films on faces of all peds; many unstained sand grains on faces of peds; neutral (pH 7.3); diffuse boundary. (4 to 7 inches thick)
Bt2--20 to 28 inches; brown (10YR 5/3) silty clay loam, brown (10YR 4/3) moist; moderate medium prismatic separating to strong fine and medium blocky structure; very hard, firm, moderately sticky and moderately plastic; common fine and many very fine roots and pores; continuous faint clay films on faces of peds and patches of prominent clay films on vertical faces; slightly alkaline (pH 7.5); clear wavy boundary. (5 to 11 inches thick)
Bk--28 to 48 inches; pale brown (10YR 6/3) silt loam, dark grayish brown (10YR 4/2) moist; moderate coarse prismatic separating to weak medium and coarse blocky structure; hard, friable, slightly sticky, slightly plastic; common fine and very fine roots and pores; violently effervescent, common filaments and soft masses of calcium carbonate; strongly alkaline (pH 8.7); gradual smooth boundary. (15 to 30 inches thick)
BCk--48 to 64 inches; pale brown (10YR 6/3) silt loam, brown (10YR 5/3) moist; massive; slightly hard, friable, slightly sticky, slightly plastic; few very fine and fine roots and pores; strongly effervescent, few filaments and soft masses of calcium carbonate; strongly alkaline (pH 8.8).
TYPE LOCATION: Gallatin County, Montana; on Ft. Ellis Livestock Experiment Station; 1,670 feet east, 960 feet south of NW corner sec. 15, T.2S., R.6E.
RANGE IN CHARACTERISTICS: The noncalcareous part is 15 to 40 inches thick. The mollic epipedon is 16 to 30 inches thick and includes part or all of the B2t horizon in some pedons. The solum is neutral or slightly alkaline. Mean annual soil temperature ranges from 41 degrees to 47 degrees F.
The A horizon has hue of 10YR or 7.5YR, value of 3 or 5 dry, 2 or 3 moist, and chroma of 1 through 3. It is silt loam or light silty clay loam.
The Bt horizon has 18 to 35 percent clay, 30 to 70 percent silt, and 10 to 50 percent sand of which less than 15 percent is fine sand or coarser. It has moderate or strong prismatic, blocky or prismatic and blocky structure.
The Bk and BCk horizons are silt loam or light silty clay loam and have faint to prominent accumulations of filaments or soft masses of calcium carbonate with calcium carbonate equivalent ranging from about 2 to 12 percent. It is moderately or strongly alkaline.
COMPETING SERIES: These are the Halfcircle, Lanark, Pinebutte, and Robana series. Halfcircle soils are deep to a paralithic contact. Lanark soils have a calcic horizon. Pinebutte soils are deep to a lithic contact. Robana soils are noncalcareous to depths exceeding 60 inches.
GEOGRAPHIC SETTING: Bozeman soils are on nearly level to moderately sloping plains and dissected sideslopes of mountain valleys. Slope gradients range from 0 to 20 percent. Elevation ranges from 4,000 to 6,000 feet. The soils formed in loess derived from mixed alluvial sources. The climate is cool subhumid. Annual precipitation ranges from 16 to 24 inches. Mean annual temperature ranges from about 38 degrees to 45 degrees F. The average frost-free period is less than 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Amsterdam, Bridger, Huffine, and Robana soils.
DRAINAGE AND PERMEABILITY: Well-drained; slow or medium runoff; moderate permeability.
USE AND VEGETATION: Used as dryland and irrigated cropland, and as rangeland. Principal native vegetation is rough fescue, Idaho fescue, mountain bromegrass, bluegrass, rosebush, snowberry, and sagebrush.
DISTRIBUTION AND EXTENT: Mountain valleys in Montana, Wyoming, and Idaho. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Gallatin County, Montana, 1905.