LOCATION ROBSON                  NV+OR

Established Series
Rev: RAF/RLB/JBF
10/2016

ROBSON SERIES

The Robson series consists of shallow, well drained soils that formed in residuum derived from igneous rock. Robson soils are on hill and mountain crests and side slopes. Slopes are 2 to 75 percent. The mean annual precipitation is about 380 mm and the mean annual temperature is about 6 degrees C.

TAXONOMIC CLASS: Clayey-skeletal, smectitic, frigid Lithic Xeric Haplargids

TYPICAL PEDON: Robson cobbly loam--rangeland. (Colors are for dry soil unless otherwise noted.) The soil surface has a partial cover of about 5 percent stones.

A--0 to 25 cm; brown (10YR 5/3) cobbly loam, brown (10YR 4/3) moist; moderate medium granular structure; slightly hard, very friable, slightly sticky and slightly plastic; common medium, fine, and very fine roots; common medium vesicular pores; 10 percent gravel, 10 percent cobbles and 5 percent stones; neutral (pH 7.0); clear smooth boundary. (5 to 25 cm thick)

Bt1--25 to 36 cm; light yellowish brown (10YR 6/4) very cobbly clay loam, dark yellowish brown (10YR 4/4) moist; strong fine angular blocky structure; hard, firm, moderately sticky and moderately plastic; few fine and very fine roots; common fine tubular pores; many distinct pressure faces on peds; 15 percent gravel and 35 percent cobbles; neutral (pH 6.8); abrupt smooth boundary. (8 to 15 cm thick)

Bt2--36 to 48 cm; light brown (7.5YR 6/4) extremely cobbly clay, brown (7.5YR 4/4) moist; strong coarse prismatic structure parting to strong medium and coarse angular blocky; very hard, very firm, very sticky and very plastic; few fine and very fine roots; few fine tubular pores; many prominent pressure faces on peds; 15 percent gravel and 45 percent cobbles; neutral (pH 6.8); abrupt wavy boundary. (8 to 25 cm thick)

R--48 cm; rhyolite.

TYPE LOCATION: Eureka County, Nevada; approximately 34 miles northwest of Eureka; at about the northwest corner of section 15 T., 21 N., R. 48 E.; USGS Shagnasty 7.5 minute topographic quadrangle; latitude 39 degrees 41 minutes 34 seconds N and longitude 116 degrees 34 minutes 17 seconds W; WGS84 Decimal Degrees 39.6927778 latitude, -116.5713889 longitude.

RANGE IN CHARACTERISTICS:
Soil moisture: Usually dry, moist in the winter and spring months and dry late June through October; aridic soil moisture regime bordering on xeric.
Mean annual soil temperature: 7 to 8 degrees C.
Ochric epipedon: 5 to 25 cm.
Depth to bedrock: 30 to 50 cm.
Other features: If colors meet mollic criteria organic carbon is not high enough for a mollic epipedon.

Particle-size control section - Clay content: Averages 40 to 50 percent.
Rock fragments: Average 50 to 75 percent, mainly cobbles, when mixed.

A horizon
Hue: 7.5YR or 10YR.
Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 2 or 3.
Structure: Very thin or thin platy or very fine to medium subangular blocky or granular.
Reaction: Neutral or slightly alkaline.

Bt horizon
Hue: 7.5YR or 10YR.
Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 3 or 4.
Structure: Weak to strong, very fine through coarse prismatic, subangular or angular blocky.
Reaction: Neutral through moderately alkaline.
Other features: In most pedons, the upper few cm of bedrock is commonly fractured into angular cobble or gravel size fragments.

COMPETING SERIES: This is the Locane series. Locane soils have an argillic horizon with 35 to 40 percent clay and 35 to 50 percent rock fragments.

GEOGRAPHIC SETTING: Robson soils are on hill and mountain crests and side slopes. These soils formed in residuum derived from tuffs, basalt, rhyolite, andesite and other related igneous rocks. Slopes are 2 to 75 percent. Elevations are 1,555 to 2,565 meters. The climate is cool, semiarid with warm, dry summers and cool, moist winters. The average annual precipitation is 250 to 450 mm, average annual temperature is 6 to 8 degrees C, and the frost-free season is 50 to 90 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Akerue, Anawalt, Simpark, Softscrabble and Walti soils. Akerue soils are shallow to an indurated duripan above the bedrock. Simpark soils have 18 to 27 percent clay in their particle-size control section and are shallow to an indurated duripan above the bedrock. Anawalt soils are clayey, Softscrabble soils are very deep with a mollic epipedon and 27 to 35 percent clay in their particle-size control section. Walti soils are moderately deep to bedrock, have a mollic epipedon and 5 to 25 percent rock fragments in their particle-size control section.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; rapid runoff; moderately low saturated hydraulic conductivity.

USE AND VEGETATION: Livestock grazing and wildlife habitat. The vegetation is principally low sagebrush, Idaho fescue, bluebunch wheatgrass bottlebrush squirreltail and Sandberg bluegrass. In areas where the A horizon is on the thicker extreme of the range big sagebrush is in the community.

DISTRIBUTION AND EXTENT: Northeastern Nevada and Southeastern Oregon. These soils are not extensive. MLRA 24, 25 and 28B.

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

SERIES ESTABLISHED: Eureka County, Nevada, 1983.

REMARKS: Additional data available from NSSL #81NV-015-301.

Diagnostic horizons and features recognized in this pedons are:
Ochric epipedon - The zone from the surface to 25 cm (A horizon).
Argillic horizon - The zone from 25 to 48 cm (Bt1 and Bt2 horizons).
Lithic contact - The boundary at 48 cm (R layer).
Particle-size control section - The zone from 25 to 48 cm (Bt1 and Bt2 horizons).

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National Cooperative Soil Survey
U.S.A.