LOCATION AGENTIA ORTentative Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Vitritorrandic Argixerolls
TYPICAL PEDON: Agentia very stony ashy sandy loam, on a north facing 50 percent slope, rangeland. (Colors are for moist soils unless otherwise noted.)
A-- 0 to 6 inches; very dark grayish brown (10YR 3/2) very stony ashy sandy loam, grayish brown (10YR 5/2) dry; weak very fine granular structure; soft, friable, nonsticky and nonplastic; common very fine and fine roots; many fine vesicular pores; 50 percent sand-size (0.25 to 1.0 mm) pumice, light brownish gray (10YR 6/2) dry; 20 percent stones and 15 percent cobbles; neutral (pH 6.8); clear smooth boundary. (4 to 10 inches thick)
AB-- 6 to 11 inches; very dark grayish brown (10YR 3/2) very stony ashy sandy loam, brown (10YR 5/3) dry; weak medium subangular blocky structure parting to weak very fine granular; slightly hard, friable, nonsticky and nonplastic; common very fine and fine roots; common fine and medium tubular pores; 40 percent sand-size (0.25 to 1.0 mm) pumice, light brownish gray (10YR 6/2) dry; 20 percent stones and 15 percent cobbles; neutral (pH 7.0); clear smooth boundary. (3 to 7 inches thick)
2Bt1-- 11 to 15 inches; brown (10YR 4/3) very stony loam, pale brown (10YR 6/3) dry; moderate medium subangular blocky structure; hard, firm, slightly sticky and slightly plastic; common very fine and fine roots; common fine and medium tubular pores; few patchy faint clay films on faces of peds; 30 percent stones and 10 percent cobbles; neutral (pH 7.2); clear wavy boundary.
2Bt2-- 15 to 22 inches; dark brown (10YR 3/3) very stony clay loam, brown (10YR 5/3) dry; moderate fine and medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; common very fine and fine roots; few fine and medium tubular pores; many continuous prominent clay films on faces of peds and lining pores; 30 percent stones and 10 percent cobbles; slightly effervescent; moderately alkaline (pH 8.0); clear wavy boundary. (Combined thickness of the Bt horizon ranges from 6 to 15 inches.)
2Bk-- 22 to 36 inches; dark grayish brown (10YR 4/2) stony sandy clay loam, light brownish gray (10YR 6/2) dry; massive; hard, firm, slightly sticky and slightly plastic; few very fine and fine roots; few fine tubular pores; 15 percent stones and 5 percent cobbles; strongly effervescent; moderately alkaline (pH 8.2); gradual smooth boundary. (6 to 15 inches thick)
3R-- 36 inches; basalt; strongly effervescent with disseminated lime along rock fractures.
TYPE LOCATION: Crook County, Oregon; located 200 feet north and 1000 feet east of the SW corner of section 6, T. 15 S., R 16 E; about 1 mile southwest of Prineville.
RANGE OF CHARACTERISTICS: The soils are dry for one-half to three-fourths of the time when the soil temperature is above 41 degrees F. They are usually dry, and are dry in the moisture control section for 100 to 120 days following the summer solstice. The mean annual soil temperature is 50 to 54 degrees F. Depth to secondary carbonates is 20 to 30 inches. The mollic epipedon and depth to bedrock is 25 to 40 inches. Depth to the 2Bt horizon is 10 to 15 inches.
The A and AB horizons have value of 2 or 3 moist, 4 or 5 dry and chroma of 2 or 3 moist and dry. It contains 20 to 40 percent stones and 0 to 15 percent cobbles. The sand-size (0.25 to 1.0mm) pumice content is 30 to 60 percent. It has a phosphate retention of 15 to 25 percent, 10 to 30 percent glass and glass coated aggregate and acid oxalate aluminum plus one-half the iron is 0.4 to 0.8 percent.
The 2Bt horizon has value of 3 or 4 moist, 5 or 6 dry and chroma of 2 or 3 moist and dry. It is loam or clay loam and contains 20 to 40 percent stones, 0 to 15 percent cobbles and 25 to 35 percent clay.
The 2Bk horizon has value of 4 or 5 moist, 6 or 7 dry and chroma of 3 or 4 moist and dry. It is sandy clay loam or sandy loam and contains 0 to 30 percent gravel, 10 to 20 stones and 0 to 10 percent cobbles. It is slightly to strongly effervescent, and moderately or strongly alkaline.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Agentia soils are on north-facing side slopes of canyons at elevations of 2800 to 3400 feet. Slopes range from 40 to 70 percent. The soils formed in colluvium derived from basalt with an influence of volcanic ash in the surface. The climate is characterized by cool moist winters and hot dry summers. The mean annual precipitation is 9 to 12 inches, the mean annual temperature is 48 to 52 degrees F., and the frost-free period is 70 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Era, Lickskillet, Redmond and Stukmond soils. Era soils are coarse-loamy, very deep and are in concave positions of north slopes. Lickskillet soils are shallow and are on adjacent south-facing side slopes. Redmond soils are fine-loamy and are on adjacent mesas. Stukmond soils are loamy, shallow and are on adjacent mesas.
DRAINAGE AND PERMEABILITY: Well drained, permeability is moderately slow.
USE AND VEGETATION: Agentia soils are used mainly for livestock grazing and wildlife habitat. The native vegetation is Idaho fescue, bluebunch wheatgrass and mountain big sagebrush.
DISTRIBUTION AND EXTENT: Central Oregon, MLRA 10, pumice zone. The series is not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES PROPOSED: Crook County Area, Oregon; 1999.
REMARKS: Diagnostic horizons and features in this pedon include:
Mollic epipedon - the zone from the surface to a depth of 11 inches (A and AB horizons).
Argillic horizon - from a depth of 11 to 22 inches (2Bt1 and 2Bt2 horizons).
Vitritorrandic feature - the zone from the surface to a depth of 11 inches.