LOCATION WILLIS WA+OREstablished Series
TAXONOMIC CLASS: Coarse-silty, mixed, superactive, mesic Haploduridic Durixerolls
TYPICAL PEDON: Willis silt loam - cultivated. (Colors are for dry soil unless otherwise stated).
Ap--0 to 8 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak fine granular structure; soft, very friable, slightly sticky and slightly plastic; many roots; slightly alkaline (pH 7.4); abrupt smooth boundary. (6 to 18 inches thick)
Bw--8 to 24 inches; brown (10YR 5/3) silt loam, dark brown (10YR 3/3) moist; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common roots; few very fine tubular pores; slightly alkaline (pH 7.6); abrupt wavy boundary. (8 to 17 inches thick)
Bk--24 to 29 inches; pale brown (10YR 6/3) silt loam, dark yellowish brown (10YR 4/4) moist; massive; hard, friable, slightly sticky and slightly plastic; common roots; few very fine tubular pores; strongly effervescent; strongly alkaline (pH 8.6); abrupt smooth boundary. (4 to 13 inches thick)
2Bkqm--29 inches; lime-silica indurated duripan, lenses 1 to 12 inches thick that do not break down on acid treatment alone.
TYPE LOCATION: Adams County, Washington; about 500 feet south and 100 feet west of the NE corner of section 18, T. 20 N., R. 36 E.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 49 to 54 degrees F. The soil is usually dry in all parts between depths of 4 and 12 inches for one-half to three-fourths of the time when the soil temperature is above 41 degrees F. The depth to the duripan is 20 to 40 inches. In some pedons the pan grades into alternate layers of duripan and loess or is abruptly over basalt or Ringold sediments. The depth to lime carbonates is 15 to 27 inches. The mollic epipedon is 7 to 18 inches thick. The particle-size control section has 10 to 15 percent clay.
The A horizon has value of 4 or 5 dry, 2 or 3 moist and chroma of 2 or 3 dry. It is silt loam, fine sandy loam or very fine sandy loam. It is neutral or slightly alkaline.
The Bw horizon has value of 5 or 6 dry and 3 or 4 moist, and chroma of 3 or 4 moist or dry. It has subangular blocky or coarse prismatic structure. It is neutral to moderately alkaline.
The Bk horizon has value of 5 to 8 dry and 3 to 6 moist and chroma of 1 to 4 moist or dry. It is moderately or strongly alkaline. It is slightly to strongly effervescent and contains 1 to 10 percent calcium carbonate.
COMPETING SERIES: There are no competing series. The Baker, Burke, and Endicott series are similar. Baker soils are coarse-loamy. Endicott soils are usually moist. Burke soils do not have a mollic epipedon.
GEOGRAPHIC SETTING: The Willis soils are on uplands, alluvial fan terraces, and terraces at elevations of 500 to 3,000 feet. Slopes are 0 to 65 percent. The soils formed in loess containing volcanic ash. The climate is semiarid with warm, dry summers and cool, moist winters. The annual precipitation is 9 to 12 inches with an average January temperature of 29 degrees F, an average July temperature of 71 degrees F, an mean annual temperature of 48 to 52 degrees F., and a frost-free season of 125 to 190 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Esquatzel, Farrell, Mikkalo, and Ritzville soils. Esquatzel soils are deep, are on bottomlands and lack a duripan. Farrell and Ritzville soils are deep upland soils. Mikkalo soils have a lithic contact at 20 to 40 inches.
DRAINAGE AND PERMEABILITY: Well-drained; slow or medium runoff; moderate permeability above the lime-silica cemented layer.
USE AND VEGETATION: Used for production of small grains in a dryland winter wheat-summer fallow rotation and for grazing. The native vegetation is mainly bluebunch wheatgrass, Sandberg bluegrass, arrowleaf, balsamroot, yarrow, and big sagebrush.
DISTRIBUTION AND EXTENT: Eastern Washington and eastern Oregon. The series is of moderate extent.
MLRA OFFICE RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Adams County, Washington, 1973.
REMARKS: Diagnostic horizons and features recognized in this pedon are a mollic epipedon from the surface to 8 inches, a cambic horizon from 8 to 24 inches, a zone of carbonate accumulation from 24 to 29 inches, and a duripan at 29 inches. The zone from 8 to 24 inches has mollic colors but has less than 1 percent organic matter.