LOCATION WILLHILL                ID+NV

Established Series
Rev. PJS/ALH/JVC/JBF
12/2019

WILLHILL SERIES

The Willhill series consists of moderately deep, well drained soils that formed in alluvium and residuum derived from rhyolitic tuff. Willhill soils are on hills and plateaus. Slopes are 3 to 25 percent. The mean annual precipitation is about 280 mm and the mean annual temperature is about 9 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Durinodic Xeric Calciargids

TYPICAL PEDON: Willhill gravelly loam--on a southeast-facing slope of 8 percent at 1,490 meters elevation--rangeland. (When described on May 21, 1980, the soil was dry to 8 cm, slightly moist from 8 to 23 cm, and dry below. Colors are for dry soil unless otherwise noted.) The soil surface has about 1 percent cover of stones.

A--0 to 8 cm; pale brown (10YR 6/3) gravelly loam, brown (10YR 4/3) moist; weak fine and medium subangular blocky structure parting to moderate fine granular; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine, few medium roots; common very fine and fine, few medium vesicular and interstitial pores; 20 percent gravel and 2 percent stones; neutral (pH 7.3); clear smooth boundary. (5 to 15 cm thick)

Bt1--8 to 18 cm; light yellowish brown (10YR 6/4) gravelly clay loam, dark yellowish brown (10YR 4/4) moist; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and moderately plastic; common very fine and fine, few medium roots; common very fine and few fine interstitial pores; common faint clay films on faces of peds; 25 percent gravel; slightly alkaline (pH 7.5); clear wavy boundary. (8 to 20 cm thick)

Bt2--18 to 25 cm; very pale brown (10YR 7/4) very gravelly clay loam, yellowish brown (10YR 5/4) moist; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and moderately plastic; common fine, few very fine and medium roots; common faint clay films on faces of peds; 40 percent gravel; slightly alkaline (pH 7.6); clear wavy boundary. (0 to 13 cm thick)

Bkq1--25 to 38 cm; very pale brown (10YR 7/4) extremely cobbly loam, yellowish brown (10YR 5/4) moist; massive; slightly hard, friable, nonsticky and nonplastic; few very fine and fine roots; 50 percent gravel and 30 percent cobbles; moderately thick (1 to 3 mm) silica and carbonate coatings on bottoms and sides of rock fragments; violently effervescent; moderately alkaline (pH 8.4); clear irregular boundary. (0 to 71 cm thick)

Bkq2--38 to 56 cm; very pale brown (10YR 8/2) extremely cobbly loam, light gray (10YR 7/2) moist; massive; very hard, very firm, nonsticky and nonplastic; brittle; few very fine and fine roots; 30 percent gravel and 50 percent cobbles; discontinuous strong silica cementation with fractures 2 to 14 cm apart throughout a 1 to 3 mm thick laminar cap and 2 to 8 mm long silica and carbonate pendants on all sides of rock fragments; violently effervescent; moderately alkaline (pH 8.4); gradual wavy boundary. (15 to 50 cm thick)

R--56 cm; highly fractured welded rhyolitic tuff.

TYPE LOCATION: Owyhee County, Idaho; about 12.5 miles north and 4.5 miles west of Grasmere; 1,200 feet west and 150 feet south of the northeast corner of section 15, T. 10 S., R. 4 E.; USGS Wickahoney Crossing 7.5 minute topographic quadrangle; latitude 42 degrees 33 minutes 50 seconds N and longitude 115 degrees 58 minutes 01 seconds W;
WGS84 Decimal Degrees 42.5638889 latitude, -115.9669444 longitude.

RANGE IN CHARACTERISTICS:
Soil moisture: Usually dry, moist in winter and spring, dry in summer and fall; aridic soil moisture regime that borders on xeric.
Mean annual soil temperature: 8 to 12 degrees C.
Depth to silica cementation: 20 to 86 cm.
Depth to bedrock: 53 to 100 cm to a lithic contact.

Particle-size control section - Clay content: 27 to 35 percent.
Rock fragments: 35 to 60 percent, mainly gravel. Lithology of fragments is volcanic rocks such as tuff.

A horizon
Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 2 through 4, dry or moist.
Reaction: Neutral or slightly alkaline.

Bt horizons
Value: 5 through 7 dry, 4 or 5 moist.
Chroma: 3 or 4, dry or moist.
Texture: Very gravelly clay loam, gravelly clay loam, or very cobbly clay loam.
Rock fragments: 25 to 50 percent.
Reaction: Neutral or slightly alkaline.

Bkq horizons
Rock fragments: 60 to 80 percent, mainly cobbles and gravel.
Reaction: Moderately alkaline or strongly alkaline.
Effervescence: Slightly effervescent through violently effervescent.

COMPETING SERIES: At present, there are no other series in this family.

GEOGRAPHIC SETTING: Willhill soils are on hills and plateaus. They formed in slope alluvium and residuum derived from welded rhyolitic tuff. Slopes are 3 to 25 percent. Elevations range from 855 to 1,680 meters. The climate is semiarid with cool, moist winters and warm, dry summers. The mean annual precipitation is 250 to 330 mm, the mean annual temperature is 7 to 11 degrees C, and the frost-free period is 85 to 140 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cottle, Hotcreek, Orovada, and Troughs soils. Hotcreek and Cottle soils are on similar landscape positions but are less than 50 cm to a lithic contact. Orovada soils occur on alluvial bottoms, lack an argillic horizon and have less than 18 percent clay in the particle-size control section. Troughs soils occur on bench positions and have an indurated duripan at less than 50 cm.

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

USE AND VEGETATION: Willhill soils are used mainly for rangeland and wildlife habitat. The dominant natural vegetation is Wyoming big sagebrush, Sandberg bluegrass, bluebunch wheatgrass, and bottlebrush squirreltail.

DISTRIBUTION AND EXTENT: Southwestern Idaho. These soils are moderately extensive. MLRA 25.

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

SERIES ESTABLISHED: Elmore County Area Soil Survey, Idaho, 1986.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 8 cm (A horizon).
Argillic horizon - The zone from 8 to 25 cm (Bt1 and Bt2 horizons).
Calcic horizon - The zone from 25 to 56 cm (Bkq1 and Bkq2 horizons).
Duric feature - The zone from 38 to 56 cm (Bkq2 horizon).
Lithic contact - The boundary at 56 cm to underlying hard bedrock (R layer).
Particle-size control section - The zone from 8 to 56 cm (Bt1, Bt2, Bkq1, and Bkq2 horizons).

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National Cooperative Soil Survey
U.S.A.