LOCATION POWWATKA OREstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, frigid Vitrandic Argixerolls
TYPICAL PEDON: Powwatka ashy silt loam, cultivated. (Colors are for moist soil unless otherwise noted.)
Ap--0 to 8 inches; dark brown (10YR 2/2) ashy silt loam, dark gray (10YR 4/1) dry; weak very fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine roots; common irregular pores; slightly acid (pH 6.4); abrupt smooth boundary.
A--8 to 14 inches; very dark grayish brown (10YR 3/2) ashy silt loam, dark grayish brown (10YR 4/2) dry; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and plastic; many very fine roots; many very fine tubular pores; neutral (pH 6.6); clear wavy boundary. (Combined thickness of the A horizon is 8 to 22 inches)
Bt1--14 to 18 inches; dark brown (10YR 3/3) silty clay loam, brown (10YR 5/3) dry, weak fine prismatic structure parting to moderate fine and very fine subangular blocky; slightly hard, friable, slightly sticky and plastic; many fine roots; many very fine tubular pores; few faint clay films on ped faces; krotovinas 2 to 4 inches in diameter; neutral (pH 6.8); gradual wavy boundary.
Bt2--18 to 24 inches; dark brown (7.5YR 4/4) silty clay loam, brown (7.5YR 5/4) dry; weak fine prismatic structure parting to moderate fine and very fine subangular blocky; hard, friable, sticky and plastic; common very fine roots; many very fine tubular pores; few faint clay films on ped faces; krotovinas 2 to 4 inches in diameter; neutral (pH 6.8); abrupt wavy boundary. (Combined thickness of the Bt horizon is 10 to 18 inches)
2R--24 inches; fractured basalt.
TYPE LOCATION: Wallowa County, Oregon; about two miles NE of Lostine, 1,650 feet north and 400 feet east of the SW corner of section 1, T. 1 S., R. 43 E. (Latitude 45 degrees, 30 minutes, 15 seconds N, Longitude 117 degrees, 23 minutes, 36 seconds W)
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 44 to 47 degrees F. The soils are usually moist, but are dry in the 4 to 12 inch control section for 60 to 90 consecutive days. The mollic epipedon is 12 to 20 inches thick and may include the upper part of the Bt horizon. The particle-size control section has more than 18 percent clay and less than 15 percent coarser than very fine sand. Depth to basalt bedrock is 20 to 40 inches.
The A horizon has value of 2 or 3 moist, 4 or 5 dry and chroma of 1 or 2 moist and dry. It is ashy silt loam or cobbly ashy silt loam with 18 to 25 percent clay. It has 0 to 30 percent cobbles and 0 to 15 percent gravel. It has 30 to 60 percent volcanic glass and glass coated aggregate and less than 0.1 percent acid oxalate oxalate extractable aluminum plus one-half iron. Soil reaction is slightly acid or neutral.
The Bt horizon has hue of 7.5YR or 10YR, value of 3 or 4 moist, 4 or 5 dry and chroma of 3 or 4 moist and dry. It is silt clay loam with 27 to 35 percent clay. The Bt2 horizon has 0 to 10 percent gravel. Soil reaction is slightly acid or neutral in the upper part and neutral or slightly alkaline in the lower part.
COMPETING SERIES: This is the Hurwal series. Hurwal soils have mollic epipedons more than 20 inches thick and are greater than 40 inches deep to bedrock.
GEOGRAPHIC SETTING: Powwatka soils are on rolling hills and ridgetops. Slope is 2 to 30 percent. The soils formed in loess with an influence of volcanic ash in the surface. Elevation is 3,400 to 5,200 feet. The climate is characterized by cold wet winters and hot dry summers. The mean annual precipitation is 13 to 17 inches. The mean annual temperature is 42 to 45 degrees F. The frost-free period is 60 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Hurwal, and the Harlow, Parsnip, and Snell series. Harlow soils are clayey-skeletal, less than 20 inches to bedrock and occur on south-facing side slopes. Hurwal soils occur in drainageways and on footslopes of north-facing side slopes. Parsnip soils are 10 to 20 inches to bedrock and occur on adjacent plateaus. Snell soils are clayey-skeletal, 20 to 40 inches to bedrock, and occur on north-facing side slopes.
DRAINAGE AND PERMEABILITY: Well drained; moderately slow permeability.
USE AND VEGETATION: The soils are used mainly for dry cropland and livestock grazing. The potential native vegetation is Idaho fescue and bluebunch wheatgrass.
DISTRIBUTION AND EXTENT: Northeastern Oregon, MLRA 9. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Wallowa County, Oregon, 1998.
REMARKS: Diagnostic horizons and features recognized in this pedon include:
Mollic epipedon - from the surface to 18 inches (Ap, A, and Bt1 horizons).
Argillic horizon - from 14 to 24 inches (Bt1 and Bt2 horizons).
Vitrandic feature - from 0 to 14 inches (Ap and A horizons) based on laboratory data from the associated Parsnip soil.
Particle-size control section - from 14 to 24 inches (Bt1 and Bt2 horizons).
This series has been reclassified from Typic Argixerolls to Vitrandic Argixerolls.