LOCATION MALHEUR OREstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Xeric Natridurids
TYPICAL PEDON: Malheur silt loam, rangeland. (Colors are for dry soil unless otherwise noted.)
A1--0 to 5 inches; light brownish gray (10YR 6/2) silt loam, very dark grayish brown (10YR 3/2) moist; moderate thin platy structure; soft, friable, slightly sticky and slightly plastic; many roots; many very fine pores; moderately alkaline (pH 8.0); abrupt smooth boundary. (3 to 6 inches thick)
A2--5 to 9 inches; light gray (10YR 7/2) silt loam, dark brown (10YR 3/3) moist; moderate medium prismatic structure; soft, friable, slightly sticky and slightly plastic; many roots; many very fine tubular pores; moderately alkaline (pH 8.0); abrupt smooth boundary. (2 to 5 inches thick)
IIB2t--9 to 17 inches; yellowish brown (10YR 5/4) silty clay loam, dark brown (10YR 3/3, 4/3 crushed) moist; strong fine columnar parting to moderate blocky structure; very hard, firm, very sticky and very plastic; common fine roots; few very fine tubular pores; continuous moderately thick clay films on faces of peds and in pores; moderately alkaline (pH 8.2); clear wavy boundary. (6 to 10 inches thick)
IIB3t--17 to 23 inches; pale brown (10YR 6/3) heavy silt loam, dark brown (10YR 4/3) moist; moderate medium subangular blocky structure; hard, firm, sticky and plastic; common fine roots; many very fine tubular pores; few moderately thick clay films on peds and in pores; moderately alkaline (pH 8.4); clear wavy boundary. (2 to 6 inches thick)
IIC1ca--23 to 31 inches; pale brown (10YR 6/3) silt loam, brown (10YR 4/3) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots; many very fine tubular pores; common 1/4 to 1/2 inch soft lime coated concretions; slightly calcareous; moderately alkaline (pH 8.4); abrupt smooth boundary. (4 to 8 inches thick)
IIC2sicam--31 to 35 inches; white (10YR 8/2) indurated duripan; very pale brown (10YR 7/4) moist; platy; continuous silica laminar capping; strongly calcareous.
TYPE LOCATION: Malheur County, Oregon; 400 feet west of fence corner and 100 feet south of east and west road along the fence in NW1/4 NW1/4 section 7, T. 17 S., R. 47 E.
RANGE IN CHARACTERISTICS: The mean annual soil temperature ranges from 52 to 56 degrees F. These soils are dry in the moisture control section for more than half the time (cumulative) that the soil temperature at depth of 20 inches is above 41 degrees F., and are dry for more than 90 consecutive days within the 3-month period following the summer solstice between depths of 4 and 12 inches, but are moist more than 60 days during the winter. The solum ranges from slightly to strongly alkaline. Depth to the duripan ranges from 20 to 40 inches. Depth to calcareous material ranges from 18 to 26 inches. The soil is underlain by stratified, medium textured lakelaid sediments.
The A horizon has value of 6 or 7 dry, 3 or 4 moist, and chroma of 2 or 3 moist and dry.
The B2t horizon has value of 5 or 6 dry, 3 or 4 moist, and chroma of 3 or 4 moist and dry. It is silty clay loam with 27 to 35 percent clay and less than 15 percent coarser than very fine sand. Some pedons have strong or moderate prismatic or strong fine blocky structure. Exchangeable sodium in the B2t horizon exceeds 15 percent.
The B3t horizon is silty clay loam or heavy silt loam. It has moderate prismatic, subangular or blocky structure.
COMPETING SERIES: These are the Cortez, Ocho, Sebree, and Timpahute series. Cortez, Ocho, and Timpahute soils have more than 15 percent clay in the matric horizon. Sebree soils have a saline layer at 1 to 8 inches in depth.
GEOGRAPHIC SETTING: Malheur soils are on nearly level, undulating or somewhat dissected medium or high terraces at elevations ranging from 2,400 to 2,800 feet. They formed in mixed lakelaid sediments with a surface influence of loess. The climate is semiarid with a mean annual precipitation of 9 to 11 inches; mean annual temperature is about 50 to 54 degrees F., the mean summer temperature is 70 to 74 degrees F., and the mean winter temperature is 31 to 33 degrees F. The frost-free period ranges from 140 to 160 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Nyssa, Owyhee and Virtue soils. Nyssa and Owyhee soils lack argillic horizons. Virtue soils have less than 15 percent exchangeable sodium in the argillic horizon.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderately slow permeability in the B horizon.
USE AND VEGETATION: Used mainly for variegated crops of small grains, hay and pasture. Vegetation is mainly Thurber needlegrass, Sandberg bluegrass, 6 weeks fescue, bluebunch wheatgrass, and big sagebrush.
DISTRIBUTION AND EXTENT: Northeastern Malheur County, Oregon. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Malheur County, Oregon, 1975.
ADDITIONAL DATA: Characterized data for one pedon (S72-Oreg-23-2) by Oregon State University.
NSTH 17, RECLASSIFICATION ONLY, 3/95