LOCATION RHEA OREstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Calcic Haploxerolls
TYPICAL PEDON: Rhea silt loam, cultivated. (Colors are for moist soil unless otherwise noted.)
Ap--0 to 7 inches; very dark brown (10YR 2/2) silt loam, grayish brown (10YR 5/2) dry; weak fine granular and weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine roots; many very fine irregular and tubular pores; neutral (pH 6.6); abrupt smooth boundary. (5 to 10 inches thick)
A12--7 to 14 inches; very dark grayish brown (10YR 3/2) silt loam, grayish brown (10YR 5/2) dry; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine roots; many very fine tubular pores; neutral (pH 6.8); clear wavy boundary. (2 to 10 inches thick)
B21--14 to 22 inches; dark brown (10YR 3/3) silt loam, pale brown (10YR 6/3) dry; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine roots; many very fine tubular pores; neutral (pH 7.0); clear smooth boundary. (5 to 12 inches thick)
B22--22 to 33 inches; dark brown (10YR 4/3) silt loam, pale brown (10YR 6/3) dry; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine roots; many very fine tubular pores; neutral (pH 7.2); clear wavy boundary. (8 to 15 inches thick)
C1ca--33 to 45 inches; dark brown (10YR 4/3) silt loam, pale brown (10YR 6/3) dry; massive; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; many very fine tubular pores; moderately calcareous seams of soft segregated lime; moderately alkaline (pH 8.0); abrupt wavy boundary. (5 to 12 inches thick)
C2ca--45 to 60 inches; dark brown (10YR 4/3) silt loam, very pale brown (10YR 7/3) dry; massive; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots; many very fine tubular pores; strongly calcareous; mycelial lime; moderately alkaline (pH 8.4).
TYPE LOCATION: Morrow County, Oregon; 300 feet west of gate, 30 feet south of road in NE1/4 SE1/4 SW1/4 section 19, T. 3 S., R. 24 E.
RANGE IN CHARACTERISTICS: In most years the soil is usually moist but is dry between depths of 4 and 12 inches for more than 60 consecutive days within the 3-month period following the summer solstice. The mean annual soil temperature ranges from 49 to 53 degrees F. The mollic epipedon ranges from 7 to 20 inches thick. Thickness of the solum ranges from 20 to 40 inches. Depth to secondary lime ranges from 20 to 43 inches. The control section is silt loam with 18 to 24 percent clay and less than 15 percent coarser than very fine sand. Rock fragments commonly are absent but range up to 2 percent in some lower horizons.
The A horizon has value of 4 or 5 dry, 2 or 3 moist, and chroma of 2 or 3 moist and dry.
The B2 horizon has value of 4 through 6 dry, 3 or 4 moist, and chroma of 2 or 3 moist and dry. It has weak or moderate structure.
The Cca horizon has hue of 10YR or 7.5YR, value of 6 or 7 dry, 4 or 5 moist and chroma of 2 through 6 moist and dry. It is moderately or strongly calcareous and has segregated and myceolial lime.
COMPETING SERIES: These are the Calouse, Hunters, Kearns, Staley, and Valby series. Calouse soils have a mollic epipedon thicker than 20 inches. Hunters soils have free carbonates in the lower part of the solum. Kearns soils have mildly or moderately alkaline sola and lack any influence of ash. Staley soils have secondary carbonates throughout the B horizon and are moderately or strongly alkaline in the B horizon. Valby soils are 20 to 40 inches deep to bedrock.
GEOGRAPHIC SETTING: Rhea soils are on upland slopes at elevations of 1,600 to 3,200 feet. Slopes range from 1 to 50 percent. These soils formed in loess with an appreciable component of volcanic ash. The climate is semiarid with cool moist winters and dry summers. The mean winter temperature is 31 to 35 degrees F., the summer temperature is 62 to 66 degrees F., mean annual temperature is 47 to 51 degrees F., and mean annual precipitation is 10 to 14 inches. The frost-free period (32 degrees F.) is 100 to 150 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bakeoven, Lickskillet, and Wrentham soils and the competing Valby soil. Bakeoven, Lickskillet and Wrentham soils contain more than 35 percent fragments coarser than 2 mm. Also, Bakeoven and Lickskillet soils are less than 20 inches deep to bedrock.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; moderate permeability.
USE AND VEGETATION: Soils are cultivated or used as rangeland. Small grains, hay and pasture are the principal crops. Native vegetation is mainly bluebunch wheatgrass, Idaho fescue, Sandberg bluegrass and forbs such as yarrow, phlox and buckwheat.
DISTRIBUTION AND EXTENT: North-central Oregon. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Morrow County, Oregon, 1977.