LOCATION AHTANUM WA+OREstablished Series
TAXONOMIC CLASS: Coarse-silty, mixed, superactive, calcareous, mesic Typic Duraquolls
TYPICAL PEDON: Ahtanum silt loam, cultivated. (Colors are for dry soil unless otherwise noted.)
Ap1--0 to 4 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; moderate thin platy structure; slightly hard, friable, slightly sticky and slightly plastic; many roots; common fine pores; violent effervescence; very strongly alkaline (pH 9.4); abrupt smooth boundary. (2 to 10 inches thick)
Ap2--4 to 10 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak medium platy structure; slightly hard, friable, slightly sticky and slightly plastic; common roots; common fine pores; violent effervescence; very strongly alkaline (pH 9.4; clear wavy boundary. (0 to 8 inches thick)
Bn--10 to 21 inches; light brownish gray (10YR 6/2) silt loam, dark grayish brown (10YR 4/2) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; common roots; many fine pores; violent effervescence; very strongly alkaline (pH 9.4); gradual wavy boundary. (1 to 24 inches thick)
Bkqm--21 to 31 inches; pale brown (10YR 6/3) silt loam, dark brown (10YR 4/3) moist; massive; weakly cemented lime-silica hardpan; brittle, hard; few roots; many fine pores; some disseminated lime; violent effervescence; abrupt wavy boundary. (1 to 20 inches thick)
C1--31 to 50 inches; pale brown (10YR 6/3) silt loam, dark brown (10YR 4/3) moist; massive; soft, friable, slightly sticky and slightly plastic; many fine pores; moderately alkaline (pH 8.0); abrupt smooth boundary. (Variable thickness)
2C2--50 to 60 inches; very pale brown (10YR 7/3) loamy sand, yellowish brown (10YR 5/4) moist; single grained; loose; mildly alkaline (pH 7.8).
TYPE LOCATION: Yakima County, Washington; 1/4 mile south of Branch Road and 1 mile west of Brownstown, in SE1/4 of the NE1/4 of sec. 36, T.11N., R.17E., W.M.
RANGE IN CHARACTERISTICS: The mean annual soil temperature at a depth of 20 inches ranges from 47 to 55 degrees F. These soils are saturated at some season. They are commonly calcareous in all parts after the upper 7 inches has been mixed. The particle-size control section is 5 to 15 percent clay. The depth to the duripan ranges from 20 to 40 inches.
The A horizon has value of 4 or 5 dry, 2 or 3 moist, and chroma of 2 or 3 moist and dry. It has weak or moderate platy or subangular blocky structure. It is very strongly alkaline to moderately alkaline.
The Bn horizon has hue of 10YR, 2.5Y, or 5Y, value of 5 through 7 dry, and 2 through 6 moist, and chroma of 1 through 4 dry or moist. It is loam in the lower part in some pedons.
The Bkqm horizon commonly is continuously cemented but the range includes fractured weakly cemented to strongly indurated duripans. Reaction is very strongly alkaline to moderately alkaline above the Bqkm horizon. Some pedons have a buried A horizon.
The C horizon has hue of 10YR, 2.5Y or 5Y, value of 5 through 7 dry, 2 through 7 moist, and chroma of 1 through 4 dry or moist. It is silt loam, loam, very fine sandy loam, or loamy sand in the lower part. Reaction ranges from strongly alkaline to mildly alkaline. It is strongly effervescent to noneffervescent.
COMPETING SERIES: These are the Hoopal and Stanfield series in other families. Hoopal soils are coarse-loamy. Stanfield soils lack a mollic epipedon and are usually dry.
GEOGRAPHIC SETTING: Ahtanum soils are on terraces, and in basins at an elevation of 700 to 3,000 feet. Slopes are 0 to 5 percent. These soils formed in loess and mixed alluvium. They are in a climate with warm, dry summers, cool, moist winters and an average annual precipitation of 6 to 14 inches. Average January temperature is about 29 degrees F., average July temperature is about 73 degrees F., and the mean temperature is 51 degrees F. Frost-free season is 110 to 180 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Stanfield soils and the Harana, Kittitas and Toppenish soils. Harana, Kittitas and Toppenish soils lack cemented layers.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; slow runoff to ponded; moderate permeability to the cemented layer and very slow permeability in the cemented layer.
USE AND VEGETATION: Native range and irrigated cropland. The native vegetation is greasewood, basin wild rye, alkali bluegrass, alkali cordgrass, and saltgrass. Irrigated crops are pasture, hay, sugar beets, and corn.
DISTRIBUTION AND EXTENT: Central Washington and eastern Oregon. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Kittitas County, Washington, 1937.
REMARKS: Diagnostic horizons and features recognized in this pedon are a mollic epipedon from the surface to 10 inches, a duripan from 21 to 31 inches, and the soils are sodium affected throughout.