LOCATION COVELLO WAEstablished Series
TAXONOMIC CLASS: Coarse-silty, mixed, superactive, mesic Cumulic Haploxerolls
TYPICAL PEDON: Covello silt loam - cultivated. (Colors are for moist soil unless otherwise noted.)
Ap--0 to 10 inches, very dark brown (10YR 2/2) silt loam, dark grayish brown (10YR 4/2) dry; moderate fine and medium granular structure; slightly hard, friable, slightly sticky and slightly plastic; common fine and medium roots; moderately alkaline (pH 8.2); abrupt wavy boundary. (6 to 11 inches thick)
A12--10 to 21 inches; very dark brown and very dark grayish brown (10YR 2/2 and 3/2) silt loam, dark grayish brown (10YR 4/2) dry; weak coarse blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine and very fine roots; many fine tubular pores and large worm holes; moderately alkaline (pH 8.3); abrupt wavy boundary. (5 to 18 inches thick)
A13--21 to 30 inches; very dark brown (10YR 2/2) silt loam, dark grayish brown (10YR 4/2) dry; weak medium prismatic structure; soft, very friable, nonsticky and nonplastic; common fine and very fine roots; common medium and many coarse pores (worm holes), black (10YR 2/1) deposits in coarse pores; moderately alkaline (pH 8.3); abrupt wavy boundary. (0 to 10 inches thick)
A14--30 to 36 inches; black (10YR 2/1) silt loam, dark gray (10YR 4/1) dry; weak coarse prismatic structure; hard, firm, slightly sticky, slightly plastic; few fine roots; many very fine pores; common worm holes; strongly effervescent, strongly alkaline (pH 8.5); clear wavy boundary. (6 to 23 inches thick)
A15--36 to 50 inches; same as above, but friable. (8 to 24 inches thick)
IIC1--50 to 68 inches; dark gray (10YR 4/1) very fine sandy loam, gray (10YR 6/1) dry; massive; soft, very friable, nonsticky and nonplastic; moderately alkaline (pH 8.3). (0 to 30 inches thick)
IIC2--68 to 84 inches; gray (10YR 5/1) very fine sandy loam, light gray (10YR 7/1) dry; massive; soft, very friable, nonsticky and nonplastic; moderately alkaline (pH 8.3).
TYPE LOCATION: Columbia County, Washington; 120 feet north of Highway 31, 400 feet southwest of Enger Road; southeast 1/4, northwest 1/4 of section 34, T. 11 N., R. 39 E.
RANGE IN CHARACTERISTICS: Mean soil temperature is about 53 degrees F. The soils are dry in all parts between depths of 4 and 12 inches for 60 to 90 consecutive days in summer and autumn of most years. The Ap and C horizons have value of 2 or 3 and chroma of 1 or 2. The 10- to 40-inch control section contains about 14 to 18 percent clay, and has less than 15 percent coarser than very fine sand. Below depth of 40 inches, the A horizon is very fine sandy loam or silty clay loam in some pedons. Except where drained, there is a permanent water table in the C horizon.
COMPETING SERIES: These are the Cloquato, Hermiston, Mondovi, Onyx, Pasco, Pedigo, and Powder series. Pasco soils are usually dry between depths of 4 and 12 inches, and the upper three feet of Pedigo soils are strongly alkaline and calcareous. All the other competing series lack a water table. In addition, Cloquato soils are neutral to medium acid, and Mondovi and Onyx soils are free of lime above a depth of 43 inches.
GEOGRAPHIC SETTING: Nearly level bottom lands along streams, at an elevation of 1,200 to 2,100 feet. The soils are frequently flooded when streams are high. They formed in alluvium consisting mainly of loess and volcanic ash. Summers are hot and dry, and winters are cool and moist. Annual precipitation is 16 to 23 inches. Average January temperature is 32 degrees F., average July temperature is 71 degrees F., mean annual temperature is 51 degrees F.
ASSOCIATED SOILS: These are the competing Hermiston and Mondovi soils and the Athena, Patit Creek, and Palouse soils. Athena and Palouse soils have a cambic horizon, and occupy upland positions. Patit Creek soils have more than 15 percent coarser than very fine sand in the control section.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; slow runoff; moderate permeability.
USE AND VEGETATION: Used for pasture and grazing unless drained. Vegetation is willows, cottonwood, and water-tolerant grasses.
DISTRIBUTION AND EXTENT: Southeastern Washington. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Columbia County, Washington, 1971.
REMARKS: The soils were formerly classified as Low Humic Gley soils.