LOCATION SWAUK WAEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, mesic Ultic Palexerolls
TYPICAL PEDON: Swauk loam under wheat on a west-facing slope at an elevation of 2,400 feet. The B horizon was moist when described. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 5 inches; brown (10YR 5/3) loam, dark brown (10YR 3/3) moist; weak fine and medium subangular blocky structure; slightly hard, very friable, slightly sticky, plastic; many fine roots; many very fine irregular pores; 10 percent pebbles; slightly acid (pH 6.2); abrupt wavy boundary. (5 to 6 inches thick)
Bt1--5 to 11 inches; brown (10YR 4/3) clay loam, dark brown (10YR 3/3) moist; moderate coarse subangular blocky structure; hard, friable, sticky, plastic; common very fine roots; many fine tubular pores; common distinct clay films on faces of peds; 10 percent pebbles; slightly acid (pH 6.2); clear wavy boundary.
Bt2--11 to 18 inches; brown (10YR 5/3) gravelly clay loam, dark brown (10YR 3/3) moist, moderate medium and coarse subangular blocky structure; hard, firm, sticky, very plastic; common very fine roots; many fine tubular pores; common distinct clay films on ped faces and in pores; 15 percent pebbles; slightly acid (pH 6.2); abrupt smooth boundary.
Bt3--18 to 28 inches; brown (10YR 5/3) clay, olive brown (2.5Y 4/4) moist; weak coarse prismatic; very hard, very firm, very sticky, very plastic; few fine roots; common fine distinct light brownish gray (10YR 6/2) skeletons; common fine tubular pores; many prominent clay films; 10 percent pebbles; slightly acid (pH 6.2); abrupt smooth boundary.
Bt4--28 to 31 inches; light yellowish brown (2.5Y 6/4) clay. olive brown (2.5Y 4/4) moist; common fine faint yellowish brown (10YR 5/6) moist mottles; weak coarse prismatic structure; very hard, very firm, sticky, very plastic; few fine roots; common fine tubular pores; many moderately thick dark yellowish brown (10YR 4/4) moist clay films on faces of peds, common prominent very dark grayish brown (10YR 3/2) moist clay films on faces of peds and lining pores; 10 percent pebbles; slightly acid (pH 6.2) abrupt smooth boundary. (Combined thickness of the Bt horizon is 17 to 40 inches)
Cd1--31 to 37 inches; light yellowish brown (2.5Y 6/4) dense glacial till that breaks to gravelly clay loam, olive brown (2.5Y 4/4) moist; moderate medium platy structure; hard, extremely firm, sticky, plastic; very few very fine tubular pores; many distinct dark yellowish brown (10YR 4/4) moist and few prominent very dark grayish brown (10YR 3/2) moist clay films on faces of peds; 15 percent pebbles; slightly acid (pH 6.4); clear wavy boundary. (5 to 10 inches thick)
Cd2--37 to 60 inches; light yellowish brown (2.5Y 6/4) dense glacial till that breaks to gravelly clay loam, olive brown (2.5Y 4/4) moist; massive; very hard, very firm, sticky, plastic; few very fine and fine irregular pores; common distinct dark yellowish brown (10YR 4/4) moist and few distinct dark yellowish brown (10YR 4/4) moist and few distinct very dark gray (10YR 3/1) moist clay bridges between mineral grains; 15 percent pebbles; slightly acid (pH 6.4).
TYPE LOCATION: Kittitas County, Washington; about 1 mile east of Verdun Junction on the Swauk Prairie, 810 feet west and 2,160 feet south of the northeast corner of sec. 29, T. 20 N., R. 17 E.
RANGE IN CHARACTERISTICS: Solum thickness is 29 to 40 inches. Thickness of the mollic epipedon is 10 to 20 inches. The average annual soil temperature ranges 48 to 50 degrees F. The soils are usually moist, but are dry in all parts of the moisture control section for 75 to 90 consecutive days during summer and fall. The control section is 40 to 60 percent clay in the fine earth fraction 0 to 15 percent pebbles. The upper part of the argillic horizon is clayey with an increase of at least 15 percent clay absolute, within a distance of 1 inch at the upper boundary. Base saturation (by sum) is assumed to be 50 to 60 percent.
The A horizon has a value of 4 or 5 dry, and chroma of 2 or 3 moist and dry.
The Bt1 and Bt2 horizons have a value of 4 or 5 dry and chroma of 3 or 4 moist or dry. They are gravelly heavy clay loam, heavy clay loam, or clay.
The Bt3 and Bt4 horizons have a hue of 2.5Y or 10YR, value of 4 or 5 moist and 5 or 6 dry. They are clay or gravelly clay. They have common and many distinct and prominent clay films on faces of peds and lining pores. It has weak to strong prismatic or subangular blocky structure.
The Cd horizon has a hue of 10YR or 2.5Y, a value of 6 or 7 dry, 4 or 5 moist and chroma of 3 or 4 dry or moist. The upper part of the Cr horizon is massive or platy. It is dense glacial till that breaks to loam or gravelly clay loam.
COMPETING SERIES: This is the Tekison series in a similar family. Tekison soils are clayey-skeletal.
GEOGRAPHIC SETTING: Swauk soils are on moraines and have slopes of 0 to 15 percent. These soils formed in glacial till deposited as end moraine of the Kittitas Drift and loess. Elevation is 2,100 to 3,400 feet. These soils are in a climate with warm, dry summers and cool, moist winters. The average annual precipitation is 15 to 25 inches. The average January temperature is about 26 degrees F and the average July temperature is about 67 degrees F. The average annual temperature is 46 to 48 degrees F. The frost-free season is about 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Quicksell, Teanaway and Nard soils. Quicksell soils are in swales, are moderately well drained and have an albic horizon. Teanaway and Nard soils are fine-loamy and lack a mollic epipedon.
DRAINAGE AND PERMEABILITY: Well drained, slow to medium runoff; permeability is slow in the argillic and very slow in the dense glacial till substratum.
USE AND VEGETATION: Used for dryland farming. Common crops are winter wheat and pasture. Native vegetation is Idaho fescue, bluebunch wheatgrass, bitterbrush, lupine, and arrowleaf balsamroot.
DISTRIBUTION AND EXTENT: North central Washington. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Kittitas County, Washington, 1936.
REMARKS: Diagnostic horizons and features recognized in this pedon are a mollic epipedon from the surface to 18 inches, an argillic horizon from 5 to 31 inches, and a contact with dense glacial till at 31 inches.