LOCATION MITCHELLPOINT WAEstablished Series
TAXONOMIC CLASS: Ashy over loamy, aniso, glassy over mixed, superactive, mesic Alfic Vitrixerands
TYPICAL PEDON: Mitchellpoint ashy silt loam - on a south facing 3 percent slopes, at 1,820 feet elevation, under a ponderosa pine canopy. (Colors are for dry soil unless otherwise noted).
Oi--0 to 3 inches; needles, leaves, grass, and twigs.
A--3 to 10 inches brown (10YR 5/3) ashy silt loam, dark brown (10YR 3/3) moist; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky and nonplastic; many very fine and common fine and medium roots; slightly acid (pH 6.2); abrupt smooth boundary. (3 to 8 inches thick).
Bw--10 to 17 inches; light yellowish brown (10YR 6/4) ashy silt loam, dark yellowish brown (10YR 4/4) moist; weak fine subangular blocky structure; soft, very friable, slightly sticky and nonplastic; many very fine and common fine and medium roots; slightly acid (pH 6.2); clear smooth boundary. (6 to 13 inches thick).
2B/E--17 to 23 inches; light yellowish brown (10YR 6/4) silt loam (B part), dark yellowish brown (10YR 4/4) moist; very pale brown (10YR 7/4) silt loam (E part), yellowish brown (10YR 5/4) moist; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine, fine, and medium roots; slightly acid (pH 6.4); clear wavy boundary. (6 to 13 inches thick)
2Bt--23 to 29 inches; very pale brown (10YR 7/3) cobbly silt loam, yellowish brown (10YR 5/4) moist; moderate medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine, fine, and few medium roots; common faint dark yellowish brown (10YR 4/4) most clay films on face of peds and lining pores; 10 percent cobbles and 5 percent pebbles; slightly acid (pH 6.2); clear smooth boundary. (0 to 6 inches thick).
3C1--29 to 39 inches; multicolored very cobbly loamy coarse sand; massive; soft, very friable, nonsticky and nonplastic; common very fine and few fine roots; 5 percent stones, 15 percent cobbles, and 30 percent pebbles; neutral (pH 6.6); clear smooth boundary. (0 to 12 inches thick)
3C2--39 to 60 inches; multicolored very gravelly coarse sand; single grained; loose, nonsticky and nonplastic; few very fine roots; 55 percent pebbles; neutral (pH 6.8).
TYPE LOCATION: Colville Indian Reservation; Ferry County, Washington; about 16 miles east of the town of Keller; 1.750 feet north and 300 feet east of the southwest corner of sec. 30, T. 30 N., R. 36 E., W.M.
RANGE IN CHARACTERISTICS: The mean annual soil temperature at a depth of 20 inches is 47 to 49 degrees F. These soils ae usually moist but are dry in all parts between 4 and 12 inches for 75 to 90 consecutive days following the summer solstice. Thickness of the volcanic ash mantle ranges from 14 to 20 inches. Depth to the 3C horizon is 23 to 35 inches. The upper part of the 0 to 40 inch particle-size control section has an estimated moist bulk density of 0.75 to 0.95 g/cc, volcanic glass content of 30 to 60 percent, acid-oxalate extractable aluminum plus one-half of the acid-oxalate extractable iron of 1.0 to 2.0 percent, and 15-bar water retention of 5 to 12 percent for air dried samples. The lower part of the particle-size control section has 18 to 27 percent clay. Reaction is slightly acid or neutral.
The A horizon has chroma of 2 or 3 dry or moist. It contains 0 to 10 percent pebbles.
The Bw horizon has value of 5 or 6 dry, 3 or 4 moist, and chroma of 3 or 4 dry or moist. It is 0 to 10 percent pebbles.
The 2B/E horizon has value of 6 or 7 dry, 4 or 5 moist, and chroma o 3 or 4 dry or moist. It is sandy loam, loam, or silt loam and may be gravelly or cobbly. It is 0 to 20 percent pebbles and 0 to 5 percent cobbles. Some pedons have a 2E/B horizon.
The 2Bt horizon has value of 6 or 7 dry, 4 or 5 moist, and chroma of 3 or 4 dry or moist. It is silt loam or loam and may be gravelly or cobbly. It is 0 to 15 percent cobbles, and 5 to 15 percent pebbles.
The 3C horizon commonly is stratified loamy coarse sand and coarse sand, and is very gravelly or very cobbly. Some subhorizons may be gravelly or extremely gravelly. It has 0 to 5 percent stones, 5 to 20 percent cobbles, and 30 to 55 percent pebbles.
COMPETING SERIES: There are no competing series. Similar soils in other families are the Brusher, Henneway, Nard, and Nahahum series. These soils are fine-loamy.
GEOGRAPHIC SETTING: Mitchellpoint soils are on outwash terraces at elevations of 1,800 to 2,100 feet. These soils formed in glaciofluvial deposits over glacial outwash with a mantle of volcanic ash and loess. Slopes are 0 to 5 percent. The climate is characterized by warm, dry summers and cool, moist winters. The average annual precipitation is 17 to 19 inches. The mean January temperature is about 25 degrees F, the mean July temperature is about 67 degrees F, and the mean annual air temperature is 45 to 48 degrees F. The frost-free season is 100 to 130 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cedonia, Garrison, Hallcreek, Hunters, Inchelium, and Scala soils. Cedonia and Hunters soils are fine-silty. Garrison soils are loamy-skeletal. Hallcreek soils are sandy-skeletal. Inchelium soils are coarse-silty. Scala soils are coarse-loamy.
DRAINAGE AND PERMEABILITY: Well drained; slow runoff; permeability is moderate in the solum and very rapid in the substratum.
USE AND VEGETATION: Grazing, nonirrigated hay and pasture, timber production, wildlife, and watershed are the principal uses. Native vegetation is ponderosa pine, Douglas-fir, pinegrass, creambush oceanspray, Saskatoon serviceberry, white spirea, hawkweed, lupine, and rose.
DISTRIBUTION AND EXTENT: North-central Washington. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Colville Indian Reservation; Ferry County, Washington, 1987.
REMARKS: Diagnostic horizons and features recognized in this soil are an ochric epipedon from the mineral soil surface to 10 inches, an argillic horizon from 17 to 29 inches. The description reflects a change in classification from ashy over loamy, mixed, mesic Alfic Vitrixerands to ashy over loamy, ansio, glassy over mixed, superactive, mesic Alfic Vitrixerands. The 0 to 40 inch particle-size control section has 3 contrasting particle-sizes; ashy over loamy over sandy-skeletal. Ashy over loamy is used to provide the most useful interpretations.