LOCATION ARRITOLA ORTentative Series
TAXONOMIC CLASS: Loamy, mixed, superactive, mesic, shallow Xeric Haplodurids
TYPICAL PEDON: Arritola loam, range. (Colors are for dry soil unless otherwise noted.)
A1--0 to 2 1/2 inches; light brownish gray (10YR 6/2) loam, very dark grayish brown (10YR 3/2) moist; moderate thin platy structure; soft, friable, nonsticky, nonplastic; few very fine roots; many very fine pores; mildly alkaline (pH 7.6); abrupt smooth boundary. (2 to 6 inches thick)
B21--2 1/2 to 6 inches; light brownish gray (10YR 6/2) clay loam, dark brown (10YR 3/3) moist; moderate thick platy structure; hard, friable, sticky, plastic; many very fine roots; few very fine tubular pores; mildly alkaline (pH 7.6); abrupt smooth boundary. (2 to 6 inches thick)
B22--6 to 10 inches; yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 3/4) moist; moderate fine angular blocky structure; hard, firm, sticky and plastic; many very fine roots; few very fine tubular pores; mildly alkaline (pH 7.8); abrupt smooth boundary. (3 to 6 inches thick)
B3--10 to 13 inches; light brown (7.5YR 6/4) clay loam, dark brown (7.5YR 4/4) moist; weak fine subangular blocky structure; hard, friable, slightly sticky and slightly plastic; many very fine roots; few very fine irregular pores; mildly alkaline (pH 7.8); abrupt smooth boundary. (0 to 4 inches thick)
Csim--13 to 17 inches; indurated silica cemented duripan.
TYPE LOCATION: Malheur County, Oregon; 10 feet west of abandoned road in the SW1/4 SW1/4 NW1/4 section 31, T. 34 S., R. 40 E.
RANGE IN CHARACTERISTICS: The soils are usually dry and dry in all parts between 4 and 12 inches for more than 90 consecutive days following the summer solstice and are moist for 60 days or more following the winter solstice. The solum is mildly to moderately alkaline throughout. Depth to the duripan ranges from 10 to 20 inches. The profiles lack coarse fragments but some pedons have a desert pavement of pebbles ranging from 1/4 inch to 3 inches in diameter.
The A horizon has values of 6 or 7 dry and 3 or 4 moist, and chromas of 2 or 3 moist and dry. It is very fine sandy loam, silt loam or loam.
The B horizon has hues of 7.5YR and 10YR, values of 5 or 6 dry and 3 or 4 moist, and chromas of 2 to 4 moist and dry. It is silt loam, clay loam or silty clay loam with 25 to 35 percent clay and more than 15 percent fine sand and coarser.
The duripan usually has a weak root mat at the contact surface with some roots following fractures. The top 1/2 inch of the duripan is mostly silica with carbonates increasing with depth.
COMPETING SERIES: These are the Bellavista and Vickery series. Bellavista soils have strongly calcareous A and B horizons. Vickery soils are 20 to 40 inches to the duripan and are calcareous in part above the duripan.
GEOGRAPHIC SETTING: Arritola soils are on nearly level to gently sloping terrace with gradients up to 20 percent but commonly less than 12 percent at elevations of 2,500 to 4,500 feet. The soils are formed in lacustrine materials reworked by wind. The climate is semiarid with a mean annual precipitation of 8 to 11 inches and hot dry summers and cold winters. The mean annual temperature is about 47 to 52 degrees F., mean summer temperature is 66 to 70 degrees F., and the mean winter temperature is 30 to 32 degrees F. The frost-free period ranges from 90 to 140 days.
GEOGRAPHICALLY ASSOCIATED SOILS: Unnamed soils to date.
DRAINAGE AND PERMEABILITY: Well drained; slow to moderate runoff; slow permeability.
USE AND VEGETATION: Principal use is range. Vegetation consists of low sagebrush, Atriplex spp., bud sagebrush, matchweed, squirreltail grass, and associated forbs.
DISTRIBUTION AND EXTENT: Southeastern Oregon. The series is inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES PROPOSED: Malheur County, Oregon, 1971. Source of name is the Arritola ranch.
REMARKS: The soils would have been classified as Sierozem soils.
NSTH 17, RECLASSIFICATION ONLY, 3/95
The superactive cation exchange activity class was added in 03/2003 to the taxonomic classification by the National Soil Survey Center on request of the Reno MLRA office, without review of the soil series property data. The remainder of this document has not been updated.