LOCATION PASCO WAEstablished Series
TAXONOMIC CLASS: Coarse-silty, mixed, superactive, calcareous, mesic Cumulic Endoaquolls
TYPICAL PEDON: Pasco silt loam, pasture. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 6 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; few fine faint mottles; weak fine and medium granular structure; soft, friable, slightly sticky, slightly plastic; many roots; few fine pores; slight effervescence with dilute HCl; moderately alkaline (pH 8.2); clear smooth boundary. (4 to 12 inches thick)
A1--6 to 20 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; common medium faint mottles; massive; soft, friable, slightly sticky, slightly plastic; common roots; few fine pores; slight effervescence with dilute HCl; moderately alkaline (pH 8.4); clear wavy boundary. (4 to 16 inches thick)
A2--20 to 33 inches; grayish brown (10YR 5/2) heavy silt loam, very dark gray (10YR 3/1) moist; weak medium prismatic structure; slightly hard, friable, sticky, slightly plastic; common roots; common fine pores; slight effervescence with dilute HCl; moderately alkaline (pH 8.0); clear wavy boundary. (4 to 16 inches thick)
AC1--33 to 52 inches; gray (10YR 5/1) very fine sandy loam, very dark gray (10YR 3/1) moist; common medium faint mottles; massive; soft, very friable, slightly sticky, slightly plastic; common roots; slight effervescence with dilute HCl; mildly alkaline (pH 7.8); clear wavy boundary. (4 to 20 inches thick)
AC2--52 to 62 inches; gray (10YR 5/1) heavy silt loam, very dark brown (10YR 2/2) moist; massive; slightly hard, friable, sticky, slightly plastic; few roots; common fine pores; slight effervescence with dilute HCl; mildly alkaline (pH 7.8).
TYPE LOCATION: Benton County, Washington; 1 mile west of the Richland Wye and 700 feet north of Highway U.S. 410, NW1/4 SW1/4 section 24, T.9N., R.28E., WM.
RANGE IN CHARACTERISTICS: The mean annual soil temperature at 20 inches is 47 to 55 degrees F. The mollic epipedon is 24 to more than 40 inches thick. These soils are typically calcareous throughout but may be noncalcareous in the upper 10 inches. They are mildly alkaline to strongly alkaline, becoming less alkaline with depth.
The A horizon has hue of 2.5Y or 10YR, value of 2 or 3 moist and 4 or 5 dry. It has weak fine granular to weak thin platy structure.
The C horizon has hue of 2.5Y or 10YR, value of 2 or 3 moist, 4 or 5 dry, and chroma of 1 or 2 moist or dry. It is weak medium prismatic or weak medium subangular blocky structure. Some pedons are massive. In some pedons the C horizon is stratified with lenses of fine sandy loam about 1 to 3 inches thick. Mottles occur in some pedons below 20 inches.
COMPETING SERIES AND THEIR DIFFERENTIAE: These are the Caldwell, Covello, Hermiston, Keigley, Kittitas, Onyx, Pedigo, Red Rock, and Zillah series. Caldwell, Keigley, Kittitas and Red Rock soils have fine, silty control sections. Covello, Hermiston, Pedigo and Onyx soils lack evidence of wetness associated with Aquolls. Zillah soils are noncalcareous in some parts between 10 and 20 inches.
GEOGRAPHIC SETTING: These soils are in basins and low flat areas adjacent to the Columbia River and its tributaries at elevations of 250 to 700 feet. Slope gradients range from 0 to 3 percent. Pasco soils formed in recent alluvium accumulating under ponded drainage conditions. The climate is arid to semiarid; the mean annual temperature is 54 degrees F.; and the average annual precipitation is 6 to 10 inches. The frost free season is 136 to 190 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Burbank, Esquatzel, and Beverly soils. Burbank and Beverly soils lack mollic epipedons,are underlain by outwash gravels and cobbles at depths of less than 40 inches, and are well drained. Esquatzel soils are noncalcareous to depths of about 24 inches and are well drained.
DRAINAGE AND PERMEABILITY: Somewhat poorly and moderately well drained; very slow runoff or ponded; moderate permeability.
USE AND VEGETATION: Pasture, hay, orchards and wildlife. The native vegetation is sedges, saltgrass, willow, bluebunch wheatgrass, and blue grass.
DISTRIBUTION AND EXTENT: North central and central Washington and Oregon. Pasco series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Franklin County, Washington, 1914.
REMARKS: These soils were formerly classified as Alluvial soils.