LOCATION SENRA                   OR

Established Series
Rev. CWL-MPK-JVC-JBF
06/2011

SENRA SERIES

The Senra series consists of shallow to a duripan, well drained soils that formed in volcanic ash over residuum derived from basalt or tuff-breccia. Senra soils are on lava plateaus. Slopes are 0 to 20 percent. The mean annual precipitation is about 280 mm and the mean annual temperature is about 7 degrees C.

TAXONOMIC CLASS: Ashy, glassy, frigid, shallow Vitritorrandic Durixerolls

TYPICAL PEDON: Senra ashy fine sandy loam--on a 1 percent slope of a lava plateau at an elevation of 1,529 meters--rangeland. (Colors are for dry soil unless otherwise noted.)

A1--0 to 8 cm; brown (10YR 5/3) ashy fine sandy loam, very dark grayish brown (10YR 3/2) moist; strong thick platy structure parting to weak thin platy; slightly hard, very friable, slightly sticky and slightly plastic; many very fine, and common fine roots; many very fine, common fine, and few medium vesicular pores; 10 percent gravel and 2 percent cobbles; slightly alkaline (pH 7.5); abrupt smooth boundary. (5 or 8 cm thick)

A2--8 to 25 cm; grayish brown (10YR 5/2) ashy loam, dark brown (10YR 3/3) moist; weak medium subangular blocky structure parting to strong medium granular; soft, very friable, slightly sticky and slightly plastic; common very fine, many fine, and few medium roots; common very fine, common fine, and few medium interstitial and tubular pores; many filled cicada burrows; 5 percent gravel and 5 percent cobbles; slightly alkaline (pH 7.5); clear smooth boundary. (10 to 18 cm thick)

Bt1--25 to 38 cm; pale brown (10YR 6/3) ashy sandy clay loam, dark brown (10YR 3/3) moist; moderate coarse subangular blocky structure parting to weak medium angular blocky; slightly hard, very friable, slightly sticky and moderately plastic; common very fine, many fine, and few medium roots; common very fine, common fine, and few medium tubular pores; 5 percent gravel; many filled cicada burrows; common faint clay films on faces of peds; slightly alkaline (pH 7.5); abrupt smooth boundary. (13 or 15 cm thick)

Bt2--38 to 48 cm; pale brown (10YR 6/3) channery ashy clay loam, brown (10YR 4/3) moist; strong medium subangular blocky structure parting to weak medium angular blocky; slightly hard, firm, moderately sticky and moderately plastic; very few roots; few very fine and few fine tubular pores; 5 percent gravel; 15 percent platy duripan fragments; common faint and few distinct clay films on faces of peds; slightly alkaline (pH 7.6); abrupt smooth boundary. (8 to 15 cm thick)

Bqm1--48 to 66 cm; light yellowish brown (10YR 6/4) cemented material, yellowish brown (10YR 5/4) moist; strong thick and very thick platy structure; rigid; very strongly cemented by secondary silica; upper 2 inches of pan is fractured; slightly alkaline (pH 7.7); abrupt smooth boundary. (5 to 18 cm thick)

Bqm2--66 to 81 cm; very pale brown (10YR 7/4) cemented material, light yellowish brown (10YR 6/4) moist; strong thick platy structure; very rigid; indurated by secondary silica; slightly alkaline (pH 7.8); abrupt wavy boundary. (3 to 28 cm thick)

R--81 cm; basalt.

TYPE LOCATION: Lake County, Oregon; about 3 miles southeast of Saddle Butte; approximately 1,600 feet south and 500 feet west of the northeast corner of section 30, T. 23 S., R. 19 E.; USGS Frederick Butte 7.5 minute topographic quadrangle; latitude 43 degrees 33 minutes 12 seconds N and longitude 120 degrees 28 minutes 42 seconds W; NAD 83.

RANGE IN CHARACTERISTICS:
Soil moisture: Usually moist in winter and spring, dry in summer and fall; aridic moisture regime that borders on xeric.
Mollic epipedon thickness; 18 to 33 cm.
Argillic horizon thickness: 20 to 30 cm.
Depth to duripan; 38 to 50 cm.
Depth to bedrock: 50 to 100 cm to a lithic contact.
Volcanic glass content: 40 to 80 percent in coarse silt through fine sand fractions.

Particle-size control section - Clay content: 27 to 35 percent;
Rock fragments: 0 to 30 percent, mainly gravel and channers smaller than 8 cm in diameter. Lithology of fragments are mainly basalt and very strongly cemented to indurated duripan fragments.

A1 horizon
Hue: 10YR or 7.5YR.
Chroma: 2 or 3, dry or moist.
Organic matter content: 1 to 3 percent.

A2 horizon
Hue: 10YR or 7.5YR.
Chroma: 2 or 3, dry or moist.
Clay content: 10 to 20 percent.
Rock fragments: 5 to 15 percent.
Organic matter content: 1 to 3 percent.

Bt1 horizon
Hue: 10YR or 7.5YR
Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 2 through 4, dry or moist.
Clay content: 21 to 28 percent.
Rock fragments: 0 to 10 percent.

Bt2 horizon
Hue: 10YR or 7.5YR.
Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 2 or 3 dry, 3 or 4 moist.
Texture: Channery ashy clay loam or ashy sandy clay loam.
Clay content: 27 to 36 percent.
Rock fragments: 0 to 5 percent basalt gravel and 0 to 25 percent detached fragments of very strongly cemented to indurated platy duripan (channers).

Bqkm horizons
Cementation: Very strongly cemented or indurated.

COMPETING SERIES: This is the Goodtack series. Goodtack soils have 18 to 26 percent clay in the particle-size control section.

GEOGRAPHIC SETTING: Senra soils are on lava plateaus. These soils formed in volcanic ash and residuum derived from basalt or tuff-breccia. Slopes are 0 to 20 percent. Elevations range from 1,280 to 1,540 meters. The climate is semiarid with cold, moist winters and warm, dry summers. The mean annual precipitation is 200 to 300 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 competing Goodtack soil and the Borobey, Dunres, Hayespring, Jacksplace, and Moonbeam soils. Borobey soils are very deep and do not have argillic horizons or duripans. Dunres and Moonbeam soils are clayey. Hayespring soils are moderately deep to duripans. Jacksplace soils are ashy-skeletal and moderately deep to lithic contacts.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; very high surface runoff; moderately high saturated hydraulic conductivity.

USE AND VEGETATION: Senra soils are used for livestock grazing. The vegetation is mainly low sagebrush, antelope bitterbrush, Idaho fescue, and scattered western juniper.

DISTRIBUTION AND EXTENT: South-central Oregon. These soils are moderately extensive. MLRA 23.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.

SERIES ESTABLISHED: Lake County (Northern Part), Oregon, 2006. The name is coined.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 25 cm (A1 and A2 horizons).
Argillic horizon - The zone from 25 to 48 cm (Bt1 and Bt2 horizons).
Vitrandic intergrade feature - The zone from the soil surface to 48 cm (A1, A2, Bt1, and Bt2 horizons).
Duripan - The zone from 48 to 81 cm (Bqm1 and Bqm2 horizons).
Lithic contact - The boundary at 81 cm to underlying hard bedrock (R layer).
Particle-size control section and ashy substitute class with glassy mineralogy - The zone from 25 to 48 cm (Bt1 and Bt2 horizons).

ADDITIONAL DATA: Volcanic glass content determined locally by optical grain counts using a polarizing petrographic microscope.

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National Cooperative Soil Survey
U.S.A.