LOCATION BRIDGESON WAEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Fluvaquentic Endoaquolls
TYPICAL PEDON: Bridgeson silt loam, pasture. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 12 inches; gray (10YR 5/1) silt loam, very dark gray (10YR 3/1) moist; weak fine and medium granular structure; slightly hard, friable, slightly sticky and slightly plastic; many fine roots; neutral (pH 7.0); clear smooth boundary. (10 to 12 inches thick)
Bg1--12 to 20 inches; gray (10YR 6/1) silt loam, dark gray (10YR 4/1) moist; moderate medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common fine roots; common very fine and fine pores; few fine distinct brown (7.5YR 4/4) moist redox concentrations; neutral (pH 7.1); clear wavy boundary. (6 to 8 inches thick)
Bg2--20 to 31 inches; gray (10YR 6/1) light silty clay loam, dark gray (10YR 4/1) moist; moderate fine and medium subangular blocky structure; hard, very firm, moderately sticky and moderately plastic; common fine roots; many very fine, few fine pores; few faint clay films in pores; common medium distinct brown (7.5YR 4/4) moist redox concentrations; neutral (pH 7.0); abrupt smooth boundary. (8 to 12 inches thick)
Bg3--31 to 40 inches; gray (10YR 6/1) silty clay loam, dark gray (10YR 4/1) moist; moderate fine and medium subangular blocky structure; hard, very firm, moderately sticky and moderately plastic; common fine roots; many very fine and few fine pores; common medium distinct brown (7.5YR 4/4) moist redox concentrations; neutral (pH 7.2); clear smooth boundary. (10 to 14 inches thick)
Bg4--40 to 60 inches; gray (10YR 6/1) heavy silty clay loam, dark gray (10YR 4/1) moist; strong medium angular blocky structure; very hard, very firm, moderately sticky and moderately plastic; few roots; common very fine pores; common medium prominent bluish gray (5B 5/1) moist redox depletions; few black stains on peds; neutral (pH 7.0).
TYPE LOCATION: Spokane County, Washington; 200 feet west of Bridge 2907 on Grove Road in the NE1/4 SE1/4 SE1/4 sec. 21, T. 29 N., R. 42 E., W.M.
RANGE IN CHARACTERISTICS: These soils are saturated during the winter and spring. Mean annual soil temperature ranges from 47 to 50 degrees F. The control section has 27 to 35 percent clay on a weight average. The soil averages 5 to 20 percent volcanic glass in the coarse silt and sand fraction.The mollic epipedon is 10 to 12 inches thick. The soil is neutral or slightly alkaline.
The Bg horizon is silt loam or silty clay loam and has 27 to 35 percent clay on a weight average. It has lenses of clay loam in some pedons.
COMPETING SERIES: These are the
Beaucoup,
Blackoar,
Copperas,
Ettrick,
Fella,
Gorham,
Sauvie,
Sepo, and
Wapato series. Beaucoup, Fella, Gorham, and Sepo soils lack a component of volcanic ash. Blackoar soils have 18 to 27 percent clay and have iron and manganese concretions. Copperas soils have a paralithic contact between 40 and 60 inches below the soil surface. Ettrick soils have 18 to 27 percent clay on a weight average in the particle-size control section. Sauvie soils are slightly acid and subject to tidal flooding. Wapato soils are 35 to
50 percent clay in the lower part of the series control section.
GEOGRAPHIC SETTING: Bridgeson soils are in narrow drainageways at elevations of 1,600 to 2,500 feet. Slopes are 0 to 3 percent. The soils formed in alluvium. They are in a climate characterized by relatively dry summers and cool, moist winters. Mean annual precipitation is 18 to 22 inches. Mean January temperature is 26 degrees F., mean July temperature is 66 degrees F., mean annual temperature is 47 degrees F., and average frost-free season is 100 to 125 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Clayton, Laketon, Narcisse, and Peone soils. Clayton and Narcisse soils have a coarse-loamy control section. Peone and Laketon soils are high in volcanic ash.
DRAINAGE AND PERMEABILITY: Poorly drained; slow runoff; moderately slow permeability. Seasonal high water table.
USE AND VEGETATION: Small grains, grass, clover, unimproved pasture; native vegetation is water tolerant grasses, willows, wild rose, reeds, tules and rushes.
DISTRIBUTION AND EXTENT: Eastern Washington. Series is of small extent.
MLRA OFFICE RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Spokane County, Washington, 1964.
REMARKS: Diagnostic horizons and features recognized in this pedon are a mollic epipedon from the surface to 12 inches, a cambic horizon from 12 to 60 inches. The particle-size control section is the zone from 10 to 40 inches (Ap,Bg1,Bg2, and Bg3 horizons). Redoximorphic features of iron accumulation are present from 12 to 60 inches.