LOCATION OPNISH WAEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, mesic Vitrandic Argixerolls
TYPICAL PEDON: Opnish loam, drained- irrigated cropland, on a 1 percent slope at an elevation of 1,600 feet. (Colors are for dry soil unless otherwise stated.
Ap--0 to 8 inches; dark gray (10YR 4/1) ashy loam, very dark brown (10YR 2/2) moist; moderate medium granular structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine and common fine roots; many very fine tubular pores; slight effervescence; NaF pH 9.5; moderately alkaline (pH 7.9); abrupt smooth boundary. (7 to 10 inches thick)
ABtk--8 to 13 inches; dark gray (10YR 4/1) ashy clay loam; very dark brown (10YR 2/2) moist; moderate medium subangular blocky parting to moderate medium granular; hard, friable, slightly sticky and slightly plastic; many very fine roots; common very fine tubular and vesicular pores; few faint soft masses of lime throughout; few faint dark yellowish brown (10YR 4/4) clay films in pores and on faces of peds; slight effervescence, moderately alkaline (pH 7.9); clear wavy boundary. (4 to 8 inches thick)
Btk1--13 to 19 inches; dark grayish brown (10YR 4/2) clay loam, very dark gray (10YR 3/1) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; very hard, friable, moderately sticky and moderately plastic; common very fine roots; common fine tubular and vesicular pores; common medium soft masses of lime throughout; few faint clay films lining pores and on faces of peds; slight effervescence, moderately alkaline (pH 8.4); clear wavy boundary.
Btk2--19 to 26 inches; dark grayish brown (10YR 4/2) clay loam, very dark gray (10YR 3/1) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; very hard, friable, moderately sticky and moderately plastic; common very fine roots; common fine tubular and vesicular pores; common distinct soft masses of lime throughout; common distinct clay films lining pores and on faces of peds; 5 percent gravel; slight effervescence, moderately alkaline (pH 8.4); abrupt wavy boundary. (Combined Btk horizon is 10 to 22 inches thick)
2Btk3--26 to 37 inches; dark grayish brown (10YR 4/2) extremely gravelly clay loam, very dark grayish brown (10YR 3/2) moist; few faint mottles throughout; moderate medium subangular blocky structure parting to moderate fine subangular blocky; hard, friable, moderately sticky and moderately plastic; few very fine roots; common fine irregular and tubular pores; common distinct white (10YR 8/1) carbonate coats on faces of peds and on rock fragments; common distinct clay films lining pores and on faces of peds; 65 percent gravel and 10 percent cobbles; slight effervescence, moderately alkaline (pH 8.2); clear wavy boundary. (7 to 12 inches thick)
2Bt1--37 to 47 inches; brown (10YR 4/3) extremely gravelly sandy clay; very dark grayish brown (10YR 3/2) moist; single grain; slightly hard, friable, moderately sticky and moderately plastic; few very fine roots; few very fine tubular pores; common fine iron redox stains on sand and gravel; 60 percent gravel and 15 percent cobbles; slightly alkaline (pH 7.8); abrupt smooth boundary. (8 to 12 inches thick)
2Bt2--47 to 60 inches; brown (10YR 4/3) extremely gravelly sandy clay; very dark grayish brown (10YR 3/2) moist; single grain, slightly hard, friable, sticky and plastic; few very fine roots; few fine tubular and vesicular pores; common fine iron redox stains on sand and gravel; 50 percent gravel and 30 percent cobbles; slightly alkaline (pH 7.6).
TYPE LOCATION: Kittitas County, Washington; about 4 miles southeast of Ellensburg, WA., 700 feet east and 400 feet south of the northwest corner, section 10, T. 17 N., R. 19 E.; USGS Kittitas topographic quadrangle; latitude 46 degrees 59 minutes 05 seconds N. and longitude 120 degrees 27 minutes 08 seconds W.
RANGE IN CHARACTERISTICS: Mean annual soil temperature at a depth of 20 inches ranges from 47 to 54 degrees F. These soils are usually moist but are dry in the moisture control section for 90 to 100 consecutive days following the summer solstice. Depth to the irrigation-induced water table 24 to 40 inches. The particle-size control section has 35 to 45 percent clay in the fine earth fraction and 10 to 20 percent rock fragments by volume. The upper 7 to 14 inches has an estimated moist bulk density of 1.15 to 1.40 g/cc; acid oxalate extractable Alox plus Feox of 0.25 to 0.7 percent, and volcanic glass of 5 to 20 percent. Depth to a very or extremely gravelly 2Btk horizon is 20 to 40 inches. Organic matter is estimated to range from 1 to 3 percent. Thickness of the mollic epipedon is 40 to 60 inches.
The Ap horizon has value of 4 or 5 dry, 2 or 3 moist, and chroma of 1 or 2 dry or moist.
The ABtk horizon has value of 4 or 5 dry, 2 or 3 moist, and chroma of 1 or 2 dry or moist. Texture is ashy clay loam or ashy loam. Reaction is moderately or strongly alkaline.
The Btk horizons have value of 4 or 5 dry, 2 or 3 moist, and chroma of 1 through 3 dry or moist. Texture is clay loam or sandy clay. Reaction is moderately or strongly alkaline.
The 2Btk and 2Bt horizons have value of 4 or 5 dry, 3 or 4 moist and chroma of 2 or 3 dry or moist. Texture is extremely gravelly clay loam, very gravelly clay loam or extremely gravelly sandy clay. Reaction is slightly alkaline or moderately alkaline.
COMPETING SERIES: This is the Umtanum (T) series. Umtanum soils have a mollic epipedon greater than 60 inches and lack very or extremely gravelly 2Btk horizons with secondary carbonates. The Forseer (T) and Geoconda series are similar. Forseer soils are well drained and have frigid soil temperatures. Geoconda soils 40 to 60 inches deep over lithic contact and have montmorillonitic mineralogy.
GEOGRAPHIC SETTING: Opnish soils are on alluvial fans and have slopes of 0 to 2 percent. They formed in alluvium with an influence of volcanic ash in the surface over flood deposits. Elevation is 1,400 to 2,400 feet. Climate is semiarid with warm, dry summers and cool, moist winters. The mean annual precipitation is 9 to 12 inches. The average January temperature is about 25 degrees F.; and the average July temperature is about 69 degrees F. The mean annual temperature is about 48 to 50 degrees F. The frost-free season is 130 to 150 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Mitta, Nack, Nanum soils. Nack soils are on alluvial fans and contain greater than 35 percent rock fragments in the particle-size control section. Mitta soils are are on terraces and bottomlands, have a mollic epipedon greater than 60 inches thick, and have from 1 to 10 percent exchangeable sodium. Nanum soils are on alluvial fans and terraces and lack a calcic horizon.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow runoff; moderately slow permeability. This soil has an irrigation-induced water table with its uppermost limit occurring at some time betweem the mid-May to mid-October growing season.
USE AND VEGETATION: This soils is used for irrigated crop production and livestock grazing. Native vegetation is greasewood and saltgrass. When irrigated, hay, oats, wheat, corn, potatoes, and peas are among the crops grown.
DISTRIBUTION AND EXTENT: Central Washington; MLRA 8. The soil is of small extent. The name is coined.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Kittitas County, Washington, Yakima Training Center, 1994.
REMARKS: Diagnostic horizons and features recognized in this pedon include:
Mollic epipedon (pachic) - 0 to 60 inches (all horizons)
Argillic horizon - 13 to 60 inches (Btk1, Btk2, 2Btk3, 2Bt1 and 2Bt2 horizons)
Carbonate accumulation - 8 to 37 inches (ABtk, Btk1, Btk2 and 2Btk3 horizons)
Vitrandic feature from 0 to 13 inches
ADDITIONAL DATA: Partial laboratory data available for sample #s S92WA-037-002 and S92WA-037-019, NSSL, Lincoln, NE.