LOCATION SEVAR WAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Vitrandic Durixerolls
TYPICAL PEDON: Sevar ashy fine sandy loam, cropland on a 6 percent south facing slope at an elevation of 2,900 feet. (Colors are for dry soil unless otherwise noted. All textures are apparent field textures.)
Ap--0 to 5 inches; grayish brown (10YR 5/2) ashy fine sandy loam, very dark grayish brown (10YR 3/2) moist; weak medium granular structure; soft, very friable, nonsticky and nonplastic; few medium and many very fine roots; common fine interstitial pores; 10 percent sand-size ash, 0.5 to 2mm in size; slightly acid (pH 6.2); clear smooth boundary. (5 to 7 inches thick)
A--5 to 10 inches; brown (10YR 5/3) ashy loam, dark brown (10YR 3/3) moist; moderated medium prismatic structure; very hard, friable, nonsticky and slightly plastic; few very fine and fine and few medium roots; common fine and medium interstitial pores; 5 percent sand-size ash 0.5 to 2mm in size; moderately acid (pH 6.0); clear wavy boundary. (2 to 7 inches thick)
2Bt1--10 to 15 inches; yellowish brown (10YR 5/4) silt loam, brown (10YR 4/3) moist; moderate medium prismatic structure; very hard, firm, slightly sticky and slightly plastic; few very fine and fine roots; common fine and medium tubular pores; 5 percent sand-size ash 0.5 to 2mm in size; few faint clay films on faces of peds; neutral (pH 7.2); clear wavy boundary. (4 to 7 inches thick)
2Bt2--15 to 24 inches; brown (7.5YR 5/4) silty clay loam, brown (7.5YR 4/4) moist; strong medium prismatic structure parting to moderate medium subangular blocky; very hard, very firm, moderately sticky and moderately plastic; few very fine roots; few fine tubular pores; common distinct clay films on face of peds; slightly alkaline (pH 7.6); clear wavy boundary. (5 to 10 inches thick)
2Bt3--24 to 28 inches; light brown (7.5YR 6/4) silt loam, brown (7.5YR 4/4) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; very hard, very firm, slightly sticky and slightly plastic; fine and very fine roots; few fine tubular pores; few faint clay films on faces of peds; few fine filaments and soft masses of calcium carbonate, slightly effervescent; moderately alkaline (pH 8.0); abrupt smooth boundary. (3 to 9 inches thick)
3Bkqm1--28 to 32 inches; indurated lime-silica cemented duripan; many distinct pink (7.5YR 8/3) dry and very pale brown (10YR 8/3) dry coatings of silica and carbonates on duripan faces; violently efferevescent; clear wavy boundary.
3Bkqm2--32 to 37 inches; thin stratified layers of weakly and moderately cemented duripans interbedded with thin layers of silt loam and gravelly silt loam; violently effervescent; abrupt wavy boundary.
4R--37 inches; basalt.
TYPE LOCATION: Douglas County, Washington; about 7 miles northwest of Withrow; 1,300 feet south and 950 feet west of the northeast corner of section 6, T.26N., R.24E. (Latitude 47 degrees 47 minutes 00 seconds N, Longitude 119 degrees 52 minutes 13 seconds W)
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 49 to 51 degrees F. These soils are usually moist in the moisture control section but are dry for 90 to 105 consecutive days following the summer solstice. The upper 7 to 14 inches of the profile has an estimated moist bulk density of 1.10 to 1.35 g/cc, volcanic glass content of 30 to 60 percent, including 10 to 20 percent sand-size pumice, 0.5 to 2.0 mm. in diameter, acid-oxalate extractable aluminum plus one-half of the acid-oxalate extractable iron of 0.15 to 0.40 percent, 15-bar water retention of 5 to 10 percent, 0 to 5 percent basalt rock fragments, and an apparent field estimated clay content of 5 to 14 percent.
The upper 20 inches of the argillic horizon averages 18 to 27 percent clay. The particle size control section contains more than 15 percent very fine sand or coarser. Depth to indurated lime-silica cemented duripan ranges from 20 to 40 inches with basalt at depths of 30 inches or more. The mollic epipedon is 7 to 14 inches thick.
The A horizon has chroma of 1, 2 or 3 dry or moist.
The 2Bt1 horizon has value of 5 or 6 dry and 3 or 4 moist. Chroma is 3 or 4 dry and moist. Texture is silt loam or loam. It is neutral or slightly alkaline.
The 2Bt2 horizon has value of 5 or 6 dry, chroma is 4 or 5 dry and 3 or 4 moist. Texture is silt loam or silty clay loam. It is slightly or moderately alkaline.
The 2Bt3 horizon has value of 5 through 7 dry and 4 or 5 moist. Chroma is 3 or 4 dry and 2 through 4 moist. Textures are silt loam or loam.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: The Sevar soils occur at elevations of 2,700 to 3,200 feet and are on nonglaciated plateaus. These soils formed in volcanic ash mixed with loess over older loess. Slopes are 0 to 30 percent. The average annual precipitation is 12 to 15 inches. The semiarid climate is characterized by warm, dry summers and cool, moist winters. Average January temperature is 26 degrees F. and average July temperature is 70 degrees F. Average annual air temperature is 47 to 49 F. Frost-free season is 110 to 165 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Dougville, Dutchenry and the competing Silico soils all of which are on upland positions. Dougville soils are more than 40 inches deep. Dutchenry soils are coarse-loamy.
DRAINAGE AND PERMEABILITY: Well drained, slow to medium runoff; moderately slow permeability above the duripan.
USE AND VEGETATION: Sevar soils are used mainly for dryland crop production with a small amount for livestock grazing and wildlife habitat. Crops are mainly wheat and barley. Potential native vegetation is bluebunch wheatgrass, Idaho fescue, Wyoming big sagebrush, Sandberg bluegrass, biscuitroot, and threetip sagebrush.
DISTRIBUTION AND EXTENT: North Central Washington. Series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Douglas County, Washington, 1998.
REMARKS: Diagnostic horizons and features recognized in this pedon are a mollic epipedon from the surface to 10 inches and an argillic horizon from 10 to 28 inches. Volcanic glass counts of coarse silt and very fine sand are 26 and 19 percent from the surface to 8 inches. With the presence of pumice it is estimated that medium, coarse and very coarse sand is 50 percent or more volcanic glass and fine sand is 35 percent or more volcanic glass. The calculated (weighted) average of volcanic glass in the 0.02 to 2.0 mm. fraction is 32 percent. An indurated duripan occurs at 28 inches. The particle size control section is a zone from 10 to 28 inches (the 2Bt1, the 2Bt2 and the 2Bt3 horizon).
ADDITIONAL DATA: NSSL lab data is available for this pedon, number 90P1013, and for another pedon 89P0207.