LOCATION POWWAHKEE WA+IDEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Pachic Ultic Argixerolls
TYPICAL PEDON: Powwahkee silt loam - cultivated on a 4 percent northeast facing slope at an elevation of 3,440 feet. (Colors are for dry soil unless otherwise noted)
Ap--0 to 8 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist, weak very fine subangular blocky structure; hard, friable, slightly sticky and slightly plastic, many very fine and few fine roots; common very fine and few fine irregular pores; slightly acid (pH 6.2); abrupt smooth boundary. (6 to 9 inches thick)
A--8 to 22 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; moderate medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; many very fine roots; many very fine irregular and common very fine and fine tubular pores; slightly acid (pH 6.4); clear wavy boundary. (6 to 15 inches thick)
Bt1--22 to 31 inches; brown (10YR 5/3) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium prismatic structure; hard, firm, sticky and plastic; common very fine roots; few thin stress cutans and clay films on faces of peds; neutral (pH 6.8); clear wavy boundary. (5 to 15 inches thick)
Bt2--31 to 39 inches; brown (10YR 5/3) silty clay loam brown (10YR 4/3) moist; moderate medium prismatic structure; hard, firm, sticky and plastic; common very fine roots; few very fine tubular pores; common thin stress cutans and clay films on faces of peds and clay films lining some pores; neutral (pH 7.0); clear wavy boundary. (5 to 15 inches thick)
Bt3--39 to 46 inches, brown (10YR 5/3) silty clay loam, brown (10YR 4/3) moist; moderate medium subangular blocky structure; hard, firm, sticky and plastic; common very fine roots; common very fine tubular pores; continuous thin stress cutans and clay films on faces of peds; and clay films lining some pores; neutral (pH 7.0); clear wavy boundary. (0 to 13 inches thick)
Bt4--46 to 51 inches; yellowish brown (10YR 5/4) silty clay, dark yellowish brown (10YR 4/4) moist; moderate medium angular blocky structure; very hard, firm, very sticky and very plastic; few very fine roots; common very fine tubular pores; continuous moderately thick stress cutans and clay films on faces of peds; neutral (pH 7.0); clear wavy boundary. (0 to 13 inches thick)
Bt5--51 to 55 inches; brown (10YR 5/3) silty clay, brown (10YR 4/3) moist; moderate medium angular blocky structure; very hard, firm, very sticky and very plastic; few very fine roots; few very fine tubular pores; continuous thin stress cutans on faces of peds; neutral (pH 7.2); clear wavy boundary. (0 to 10 inches thick)
Btk--55 to 60 inches; brown (10YR 5/3) silty clay loam, brown (10YR 4/3) moist; moderate medium angular blocky structure; very hard, firm, very sticky and very plastic; few very fine roots; few very fine tubular pores, many thin stress cutans on faces of peds; common lime coatings in pores and on faces of peds; mildly alkaline (pH 7.6).
TYPE LOCATION: Asotin County, Washington; about 5 miles southeast of Anatone; 1,200 feet north and 1,950 feet west of southeast corner of sec. 3, T. 7 N., R. 46 E.
RANGE IN CHARACTERISTICS: The depth to secondary lime is more than 44 inches. The mean annual soil temperature is 47 to 49 degrees F. These soils are usually moist, but are dry in all parts between depths of 4 and 12 inches for 60 to 75 consecutive days during summer and fall. The particle-size control section is 27 to 35 percent clay. The mollic epipedon is 20 to 35 inches thick.
The A horizon has value of 3 or 4 dry and chroma of 1 to 3 dry or moist. Reaction is moderately acid or neutral. The lower part is silt loam or silty clay loam.
The Bt horizon has hue of 7.5YR or 10YR, value of 4 to 6 dry, 3 or 4 moist, and chroma of 2 through 4 dry or moist. It is subangular blocky structure or angular blocky. It is silty clay loam in the upper part and silty clay loam or silty clay in the lower part. It is neutral or mildly alkaline.
The Btk horizon has value of 5 through 8 dry, 3 through 5 moist, and chroma of 2 through 4 dry or moist. It is silty clay loam or silty clay. It is mildly alkaline or moderately alkaline. This horizon is lacking in some pedons.
COMPETING SERIES: This is the Willamette series. Willamette soils are slightly acid or medium acid throughout and have a mean annual soil temperature of about 54 degrees F.
GEOGRAPHIC SETTING: Powwahkee soils are on basalt plateaus and have slopes of 3 to 30 percent. These soils formed in loess. Elevation ranges from 3,200 to 3,800 feet. Summers are warm and dry and winters are cool and moist. The average annual precipitation ranges from 18 to 23 inches. The mean annual air temperature is about 46 degrees F. Frost-free season is 110 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: They are the Ferdinand, Gwinly, Mallory, Neconda, and Rockly soils. Ferdinand, Mallory, and Neconda soils have a lithic contact at depths of 20 to 40 inches. Gwinly and Rockly soils have a lithic contact at a depth of less than 20 inches.
DRAINAGE AND PERMEABILITY: Well drained; slow or medium runoff, moderately slow permeability.
USE AND VEGETATION: Used for cropland and wildlife habitat. The principle crops are small grains and grass. Native vegetation is Idaho fescue, bluebunch wheatgrass, Sandberg bluegrass, and rose.
DISTRIBUTION AND EXTENT: Southeast Washington and northcentral Idaho. Series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Asotin County, Washington, 1984.
REMARKS: Diagnostic horizons and features recognized in this pedon are a mollic epipedon from the surface to 31 inches and an argillic horizon from 21 to 60 inches.