LOCATION PEDIGO WA+OREstablished Series
TAXONOMIC CLASS: Coarse-silty, mixed, superactive, mesic Cumulic Haploxerolls
TYPICAL PEDON: Pedigo silt loam - cultivated. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 8 inches; dark gray (10YR 4/1) silt loam, very dark brown (10YR 2/2) moist; weak fine granular structure; slightly hard, firm, slightly sticky and slightly plastic; common fine roots; many fine tubular pores; calcareous; strongly alkaline (pH 8.8); abrupt smooth boundary. (6 to 10 inches thick)
A1--8 to 15 inches; dark gray (10YR 4/1) silt loam, very dark brown (10YR 2/2) moist; weak fine granular structure; hard, firm, sticky and slightly plastic; common fine roots; many fine tubular pores; black organic stains of peds; strongly calcareous; strongly alkaline (pH 8.9); gradual wavy boundary. (6 to 20 inches thick)
A2--15 to 34 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; massive; hard, friable, sticky and plastic; few roots; common fine tubular pores; strongly calcareous; moderately alkaline (pH 8.4); gradual wavy boundary. (6 to 20 inches thick)
C--34 to 60 inches; pale brown (10YR 6/3) silt loam, very dark grayish brown (2.5Y 3/2) moist; massive; hard, friable, sticky and slightly plastic; few roots; common fine pores; moderately alkaline (pH 8.2).
TYPE LOCATION: Walla Walla County, Washington; 50 feet south of County Road and 1,000 feet west of park boundary; NE1/4 SE1/4 section 32, T. 7 N., R. 35 E.
RANGE IN CHARACTERISTICS: The mean annual soil temperature at a depth of 20 inches ranges from 47 to 55 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 the 3 months following the summer solstice. The mollic epipedon is 20 to more than 40 inches thick. The particle-size control section is dominantly silt loam, but in some pedons there are thin lenses (less than 1 inch) of very fine sandy loam or layers of silty clay loam; however, it averages silt loam with 10 to 18 percent clay and less than 15 percent coarser than fine sand. Reaction is moderately alkaline to very strongly alkaline.
The A horizon has value of 2 or 3 moist, 4 or 5 dry, and chroma of 1 through 3 moist or dry.
The C horizon has hue of 10YR or 2.5Y, value of 3 or 4 moist, 5 or 6 dry, and chroma of 1, 2, or 3 dry or moist.
COMPETING SERIES: These ae the Covello, Hermiston, Mondovi, Onyx, and Powder series. Covello and Hermiston soils are not calcareous in the upper part of the 10- to 40-inch control section. Mondovi soils have a moist value of 2 to a depth of 40 inches or more and are noncalcareous. Onyx soils are noncalcareous. Powder soils have a B2 horizon with segregated lime, are well and moderately well drained and are usually dry.
GEOGRAPHIC SETTING: Pedigo soils are on bottomlands at elevations of 200 to 2,700 feet. Slopes are 0 to 3 percent. The soils formed in silty alluvium from loess and some volcanic ash washed from uplands. Summers are hot and dry and winters are cold and moist. Average annual precipitation is 10 to 18 inches. Average January temperature is about 30 degrees F, average July temperature is about 70 degrees F, and the mean annual temperature ranges from 45 to 53 degrees F. The average frost-free season is about 110 to 180 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ahtanum, Athena, Endersby, Palouse, Tygh, Umapine, and Walla Walla soils and the competing Hermiston, Mondovi, and Onyx soils. Ahtanum and Umapine soils are strongly saline-alkali affected. Also, Ahtanum soils have a duripan at a depth of 20 to 40 inches and Umapine soils lack a mollic epipedon. Athena soils have a regular distribution of organic matter with increasing depth. Walla Walla soils have a mollic epipedon less than 20 inches thick. Endersby and Tygh soils are coarse-loamy.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; very slow runoff; moderate permeability. A water table is at a depth of about 30 to 40 inches during the winter and early spring.
USE AND VEGETATION: These soils are used for the production of small grains, alfalfa, and grass. A few areas are irrigated. Native vegetation was bluebunch wheatgrass, basin wildrye, inland saltgrass, and, in places, willows along the streams.
DISTRIBUTION AND EXTENT: Eastern Washington and northeastern Oregon. This series is moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Walla Walla County, Washington, 1960.
REMARKS: Diagnostic horizons and features recognized in this pedon are a mollic epipedon from the surface to 34 inches with an irregular decrease in organic carbon and calcareous throughout.