LOCATION PRATHER WAEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, mesic Aquic Palexeralfs
TYPICAL PEDON: Prather silty clay loam - forest. (Colors are for moist soil unless otherwise stated. Profile was moist when described. All textures are apparent field textures.)
A--0 to 7 inches; very dark brown (10YR 2/2) silty clay loam, brown (10YR 5/3) dry; moderate very fine and fine subangular blocky structure; hard, friable, slightly sticky and plastic; many roots; few very fine and fine tubular and many very fine irregular pores; about 10 percent concretions; moderately acid (pH 6.0); clear smooth boundary. (5 to 9 inches thick)
AB--7 to 14 inches; dark brown (10YR 3/3) silty clay loam, yellowish brown (10YR 5/4) dry; moderate medium, fine and very fine subangular blocky structure; hard, friable, slightly sticky and plastic; many roots; common very fine tubular and many very fine irregular pores; few thin clay films on faces of peds and in pores; about 5 percent concretions; moderately acid (pH 5.8); clear smooth boundary. (6 to 8 inches thick)
Bt1--l4 to 26 inches; brown (7.5YR 4/4) silty clay, yellowish brown (10YR 5/8) dry; yellowish brown (10YR 5/6) rubbed dry; moderate medium and fine subangular blocky structure; hard, friable, sticky and plastic; many roots; common very fine tubular pores; common thin clay films on faces of peds and in pores; strongly acid (pH 5.3); gradual smooth boundary.
Bt2--26 to 40 inches; dark brown (7.5YR 4/4) silty clay, yellowish brown (10YR 5/8) dry; common medium faint brown (7.5YR 5/2) mottles, light gray (10YR 7/2) dry; brown (7.5YR 5/4) rubbed, yellowish brown (10YR 5/8) dry; moderate medium and fine subangular blocky structure; hard, friable, sticky and plastic; few roots; common very fine tubular pores; many faint clay films on faces of peds and in pores; strongly acid (pH 5.3); clear irregular boundary.
Bt3--40 to 51 inches; yellowish brown (10YR 5/6) clay, strong brown (7.5YR 5/6) dry; many medium prominent gray (10YR 5/1) and common reddish brown (5YR 4/4) mottles, light brownish gray (10YR 6/2) and reddish yellow (7.5YR 6/8) dry; brown (7.5YR 5/4) rubbed, yellowish brown (10YR 5/6) dry; moderate coarse, medium and fine subangular and angular blocky structure; very hard, firm, sticky and plastic; few roots; common very fine tubular pores; many faint and distinct clay films on faces of peds and in pores; moderately acid (pH 5.6); clear wavy boundary. (Combined thickness of the Bt horizon is 12 to 40 inches)
BCt1--51 to 71 inches; mottled dark reddish brown (2.5YR 3/4), gray (10YR 5/1) brown (7.5YR 5/4) clay, red (2.5YR 4/8), light brownish gray (10YR 6/2), yellowish brown (10YR 5/4) dry; reddish brown (2.5YR 4/4) rubbed, yellowish red (5YR 4/8) dry; moderate coarse medium and fine subangular blocky structure; hard, firm, sticky and plastic; few roots; common very fine tubular pores; continuous faint and distinct thick clay films on faces of peds and in pores; strongly acid (pH 5.4); clear wavy boundary. (0 to 34 inches thick)
BCt2--71 to 78 inches; brown (7.5YR 5/4) rubbed clay, yellowish brown (10YR 5/6) dry; moderate coarse, medium and fine subangular and angular blocky structure; hard, firm, sticky and plastic; few roots; common very fine tubular pores; continuous faint and distinct films on faces of peds and in pores; moderately acid (pH 5.6).
TYPE LOCATION: Lewis County, Washington; near the Logan Hill Grange; 150 feet east and 900 feet north of the south 1/4 corner of sec. 5, T. 13 N., R. 1 W.
RANGE IN CHARACTERISTICS: The solum thickness ranges from 40 to more than 60 inches and the soil thickness overlying slow or very slowly permeable horizons ranges from 20 to 30 inches. Depth to mottles with chroma of 2 or less ranges from 20 to 30 inches. The average annual soil temperature at a depth of 20 inches ranges from 47 to 55 degrees F. These soils are usually moist but they are dry in all parts between depths of 4 and l2 inches for 45 to 60 consecutive days within the 3 months following the summer solstice. The particle-size control section contains 35 to 60 percent clay and is typically silty clay but is silty clay loam or clay in some pedons. Base saturation, by sum of cations, is 35 to 55 percent at depth of 1.25 meters below the upper boundary of the argillic horizon. These soils have 10YR or 7.5YR hue throughout the A, AB, and upper Bt horizons.
The A and AB horizons have hue of 10YR or 7.5YR, value of 2 or 3 moist, 5 or 6 dry, and chroma of 2 to 4 moist or dry. It has moderate or strong structure. This horizon is slightly acid to strongly acid.
The Bt horizon has hue of 10YR or 7.5YR, value of 3 through 5 moist, 4 or 5 dry, and chroma of 4 through 6 moist, 6 through 8 dry. It is silty clay loam, silty clay, or clay. This horizon is moderately acid or strongly acid. The BC horizon is mottled silty clay, or clay. This B3 horizon contains widely varying amounts of very strongly weathered gravel and cobble size fragments that are rounded and soft. Reaction is strongly acid or moderately acid. The BCt, where present, ranges in hue from 2.5YR to 2.5Y.
COMPETING SERIES: These are the Bow, Coveland, Coweeman, Hardscrabble, Sara, and Scamman series. Bow and Coveland soils have an albic horizon and are slightly acid or neutral throughout. Coweeman soils have an ochric epipedon and have a chroma of 1 or 2 throughout the argillic horizon. Hardscrabble soils have an ochric epipedon and an abrupt increase in clay of 20 to 30 percent at the AB - Bt contact. Sara soils have a perched water table during the winter and early spring and lack mottles in the lower Bt horizon. Scamman soils have an ochric epipedon, an albic horizon, and tonguing of albic material into the argillic horizon.
GEOGRAPHIC SETTING: Prather soils are on nearly level to moderately steep upland terraces and till plains at elevations of 200 to l000 feet. The soils formed in very strongly weathered ancient glacial drift deposits derived from basic and acid igneous rocks. The climate is a marine-type having cool dry summers and mild wet winters. Average annual precipitation is 40 to 60 inches. Average annual temperature is 50 degrees F. The average January temperature is 39 degrees F; average July temperature is 65 degrees F. The frost-free season ranges between l50 and 200 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Galvin, Lacamas, and Scammon soils and the competing Olympic and Salkum soils. Galvin soils have less than 35 percent clay in the control section. Lacamas soils are poorly drained.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow to medium runoff; moderate permeability to the upper 2 feet, slow below about 2 feet. Water stands within 1 and 3.0 feet of the soil surface during the winter.
USE AND VEGETATION About half of the Prather soils are in woodland and half are used for cropland. Small grain, pasture, hay, and corn for silage are common crops. Native vegetation is Douglas-fir, western hemlock, red alder, western redcedar, and bigleaf maple, with an understory of salal, Oregon-grape, western brackenfern, western swordfern, vine maple, red huckleberry, trailing blackberry, trillium, Oregon oxalis, Pacific dogwood, bedstraw, longtube twinflower, creambush oceanspray and deer fern.
DISTRIBUTION AND EXTENT: Southwestern Washington. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Thurston County, Washington, l949.
REMARKS: Diagnostic horizons and features recognized in this pedon are an umbric epipedon from the surface to 14 inches, and an argillic horizon from 14 to 78 inches. National soil survey laboratory data are available. Characterization soil sample numbers S72WA-21-8 and S72WA- 21-9.