LOCATION AUSMUS OREstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, frigid Aquic Natrargids
TYPICAL PEDON: Ausmus ashy silt loam--on a 1 percent slope at an elevation of 1,248 meters--rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 5 cm; light brownish gray (2.5Y 6/2) ashy silt loam, dark grayish brown (2.5Y 4/2) moist; weak fine and medium platy structure; soft, very friable, moderately sticky and slightly plastic; common very fine and few fine roots; many very fine irregular pores; strongly effervescent with disseminated carbonates; 16 percent calcium carbonate; SAR is 18; EC is 3 mmhos/cm; 36 percent volcanic glass; strongly alkaline (pH 8.9); abrupt smooth boundary. (3 to 13 cm thick)
Btkn--5 to 23 cm; light brownish gray (2.5Y 6/2) silty clay loam, dark grayish brown (2.5Y 4/2) moist; strong fine prismatic structure parting to strong fine angular blocky; very hard, very firm, very sticky and very plastic; common very fine and few fine roots; common very fine tubular pores; common faint clay skin coatings on the faces of peds; strongly effervescent with disseminated carbonates; 20 percent calcium carbonate; SAR is 70; EC is 7 mmhos/cm; very strongly alkaline (pH 9.1); clear smooth boundary. (10 to 25 cm thick)
Bkn--23 to 40 cm; light brownish gray (2.5Y 6/2) silty clay loam, olive brown (2.5Y 4/3) moist; weak medium and fine subangular blocky structure; hard, friable, moderately sticky and moderately plastic; few very fine and fine roots; common very fine tubular pores; strongly effervescent with disseminated carbonates; 21 percent calcium carbonate equivalent; SAR is 187; EC is 13 mmhos/cm; very strongly alkaline (pH 9.4); gradual smooth boundary. (13 to 25 cm thick)
Bknz1--40 to 72 cm; light brownish gray (2.5Y 6/2) silt loam, olive brown (2.5Y 4/3) moist; weak fine and medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few fine roots; common very fine tubular pores; strongly effervescent with disseminated carbonates; 22 percent calcium carbonate equivalent; SAR is 401; EC is 25 mmhos/cm; very strongly alkaline (pH 9.7); gradual smooth boundary. (20 to 38 cm thick)
Bknz2--72 to 92 cm; light yellowish brown (2.5Y 6/3) ashy loam, dark olive brown (2.5Y 3/3) moist; weak medium prismatic structure parting to moderate fine subangular blocky; hard, firm, slightly sticky and slightly plastic; few very fine tubular pores; few fine distinct brown (7.5YR 4/4) masses of iron accumulation; strongly effervescent; few fine carbonate threads; 1 percent calcium carbonate equivalent; SAR is 488; EC is 29 mmhos/cm; very strongly alkaline (pH 9.7); gradual smooth boundary.
Bknz3--92 to 174 cm; light yellowish brown (2.5Y 6/3) ashy loam, dark olive brown (2.5Y 3/3) moist; moderate fine prismatic structure parting to strong fine angular blocky; very hard, very firm, slightly sticky and slightly plastic; common very fine and fine tubular pores; common fine distinct brown (7.5YR 4/4) masses of iron accumulation; common prominent black (10YR 2/1) masses of manganese and manganese-iron accumulation; common prominent gray (10YR 5/1) silt coats (skeletans) lining root channels and pores; many fine carbonate threads; strongly effervescent; 3 percent calcium carbonate equivalent; SAR is 449; EC is 27 mmhos/cm; very strongly alkaline (pH 9.7).
TYPE LOCATION: Harney County, Oregon; about 4 miles west-northwest of the New Princeton town site; approximately 1,090 feet north and 1,150 feet west of the southeast corner of section 16, T. 26 S., R. 33 E.; USGS Malheur Lake East 7.5 minute topographic quadrangle; 43 degrees 18 minutes 30.56 seconds north latitude and 118 degrees 38 minutes 46.73 seconds west longitude, NAD83.
RANGE IN CHARACTERISTICS:
Soil moisture - The soil is moist in the moisture control section during winter and spring; dry from July through October; Aridic moisture regime that borders on xeric.
Mean annual soil temperature - 7 to 8.5 degrees C.; the temperature at a depth of 50 cm is above 5 degrees C. from May through November.
Mean summer soil temperature - 15 to 18 degrees C.
Depth to bedrock - More than 152 cm.
Depth to redoximorphic concentrations - 64 to 100 cm.
Particle-size control section - Clay content: Averages 25 to 35 percent;
Fine sand or coarser content: 5 to 15 percent.
Effervescence- Strongly effervescent or violently effervescent.
A horizon
Hue: 10YR or 2.5Y.
Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 2 or 3, dry or moist.
Texture: Ashy silt loam or ashy fine sandy loam.
Clay content: 10 to 20 percent.
Reaction: Strongly alkaline or very strongly alkaline.
Sodicity (SAR): 10 to 20.
Volcanic glass content: 30 to 45 percent in coarse silt through fine sand fractions.
Btkn and Bkn horizons
Hue: 10YR through 5Y.
Value: 4 through 7 dry, 3 through 5 moist.
Chroma: 2 or 3, dry or moist.
Texture: Silty clay loam or clay loam.
Clay content: 27 to 35 percent.
Calcium carbonate equivalent: 10 to 20 percent.
Salinity (EC): 4 to 12 mmhos/cm.
Sodicity (SAR): 20 to 200 increasing with depth.
Other features: These horizons have similar volcanic glass contents as the overlying and underlying horizons, but average less than 30 percent particles in the 0.02 to 2.0 mm fraction.
Bknz horizons
Hue: 10YR through 5Y.
Value: 4 through 7 dry, 3 through 5 moist.
Chroma: 2 or 3, dry or moist.
Texture: Silt loam, ashy silt loam, or ashy loam.
Clay content: 20 to 27 percent.
Salinity (EC): 16 to 30 mmhos/cm.
Sodicity (SAR): 300 to 500.
Calcium carbonate equivalent: 1 to 20 percent decreasing with depth.
Redoximorphic features: Redox concentrations of iron and manganese are distinct or prominent.
Volcanic glass content: 15 to 40 percent in coarse silt through fine sand fractions.
COMPETING SERIES: There are currently no other series in this family.
GEOGRAPHIC SETTING: Ausmus soils are on drainageways and depressions on low lake terraces. These soils formed in alluvium and lacustrine deposits derived from volcanic rocks and volcanic ash. Slopes are 0 to 2 percent. Elevations range from 1,219 to 1,372 meters. The climate is semiarid and characterized by cold, moist winters and warm, dry summers. The mean annual precipitation is 200 to 250 mm, the mean annual temperature is 6 to 7 degrees C., and the frost-free period is 50 to 80 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Poujade, Crowcamp, Fury, Lawen, and Lolak soils. Crowcamp, Fury, Lawen, and Lolak soils lack natric horizons. In addition Crowcamp, Lawen, and Fury soils have mollic epipedons. Poujade soils are moderately well drained. Lolak soils are poorly drained. Lolak soils are on low lake terraces. Crowcamp, Lawen and Poujade soils are on high lake terraces. Fury soils are on stream terraces.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained or moderately well drained; moderately slow permeability (moderately high saturated hydraulic conductivity). Endosaturation is present with an apparent seasonal high water table between 76 and 100 cm (moderately deep free water occurrence class) from March through May. Cumulative annual duration class is Common. The soil surface is saturated in the spring. These soils are susceptible to rare ponding from March through May or they are susceptible to frequent ponding for long duration from March through May with water up to 15 cm deep.
USE AND VEGETATION: Ausmus soils are used for livestock grazing and wildlife habitat. The potential native vegetation is basin wildrye, black greasewood, and inland saltgrass.
DISTRIBUTION AND EXTENT: South-central Oregon. These soils are moderately extensive. MLRA 23.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Harney County, Oregon, 1997.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 5 cm (A horizon).
Natric horizon - The zone from 5 to 23 cm (Btkn horizon).
Calcic horizon - The zone from 5 to 72 cm (Btkn, Bkn, and Bkz1 horizons).
Endosaturation feature - The condition of ground water with an upper boundary between 76 and 100 cm at certain times during normal years (parts of the Bknz2 and Bknz3 horizons).
Particle-size control section - The zone from 5 to 100 cm (Btkn, Bkn, Bknz1, and Bknz2 horizons and part of the Bknz3 horizon).
ADDITIONAL DATA: The typical pedon at the series type location has full characterization data by the Soil Survey Laboratory (SSL), Lincoln, NE, as user pedon ID 93OR025005 (pedon # 93P0792). Other characterization data is available for pedon 93OR025003 (pedon # 93P0790) as well as a similar pedon 93OR025004 (pedon # 93P0791) that is sodic but lacks a natric horizon.