LOCATION ALIBI ID

Established Series
Rev. PS/ALH/CLM
02/2018

ALIBI SERIES

The Alibi series consists of moderately deep, well drained soils with slow permeability that formed in colluvium and residuum from rhyolite and welded rhyolitic tuff. The Alibi soils are on foothill sideslopes. Slopes range from 3 to 35 percent. Average annual precipitation is 360 mm and average annual temperature is 8 degrees C.

TAXONOMIC CLASS: Fine, smectitic, mesic Typic Palexerolls

TYPICAL PEDON: Alibi very gravelly loam -- on a northwest-facing slope of 18 percent, in native rangeland, at 41,375 meter elevation. The surface is covered by 3 percent stones. (Colors are for air-dry soil unless otherwise stated.)

A--0 to 10 cm; brown (10YR 5/3) very gravelly loam, dark brown (10YR 3/3) moist; moderate fine granular structure; soft, very friable, slightly sticky and moderately plastic; common very fine and fine roots; many very fine and fine interstitial pores; 35 percent gravel, 5 percent cobbles, 5 percent stones; slightly acid (pH 6.4); clear smooth boundary. (5 to 18 cm thick)

AB--10 to 18 cm; brown (10YR 5/3) gravelly loam, dark brown (10YR 3/3) moist; moderate fine and medium subangular blocky structure parting to strong fine and medium granular; slightly hard, friable, very sticky and moderately plastic; common very fine and fine roots; many very fine tubular pores; common faint clay films on faces of peds; 15 percent gravel, 2 percent cobbles; slightly acid (pH 6.4); abrupt smooth boundary. (0 to 15 cm thick)

Bt1--18 to 30 cm; yellowish brown (10YR 5/4) gravelly clay, brown (10YR 4/3) moist; moderate medium prismatic structure parting to strong fine and medium angular blocky; very hard, very firm, very sticky and very plastic; few very fine and fine roots; common very fine tubular pores; common pressure faces; many prominent clay films on faces of peds and in pores; 15 percent gravel, 2 percent cobbles; neutral (pH 6.6); clear smooth boundary. (13 to 20 cm thick)

Bt2--30 to 43 cm; brown (7.5YR 5/4) gravelly clay, dark brown (7.5YR 4/4) moist; strong fine and medium angular blocky structure; hard, firm, moderately sticky and very plastic; few very fine and fine roots; common very fine tubular pores; many prominent films on faces of peds; 20 percent gravel, 5 percent cobbles; slightly alkaline (pH 7.4); clear smooth boundary. (10 to 18 cm thick)

Bq--43 to 58 cm; pink (7.5YR 7/4) very gravelly sandy loam, brown (7.5YR 5/4) moist; massive; slightly hard, very friable, nonsticky and nonplastic; few very fine and fine roots; common very fine and fine interstitial and tubular pores; 45 percent gravel, 10 percent cobbles; most rock fragments are coated with secondary silica; slightly alkaline (pH 7.6); gradual smooth boundary. (8 to 25 cm thick)

R--58 cm; fractured moderately weathered rhyolite.

TYPE LOCATION: Owyhee County, Idaho; approximately 11 1/2 miles southwest of Oreana; 2,300 feet west and 1,800 feet south of the northeast corner of section 1, T. 6 S., R. 2 W.; USGS Toy Pass 7.5 minute topographic quadrangle; latitude 42 degrees 55 minutes 59 seconds N and longitude 116 degrees 31 minutes 18 seconds W; WGS84 Decimal Degrees 42.9330556 latitude, -116.5216667 longitude.

RANGE IN CHARACTERISTICS:

Mollic epipedon thickness and depth to abrupt textural change - 18 to 25 cm.
Depth to base of argillic - 43 to 58 cm.
Depth to bedrock - 50 to 75 cm.
Average annual soil temperature - 9 to 11 degrees C.
Typic xeric moisture regime.

A and AB horizons
Value - 4 or 5 dry, 2 or 3 moist
Chroma - 2 or 3 dry or moist
Reaction (pH) - slightly acid to neutral

Bt horizons
Hue - 10YR or 7.5YR
Value - 5 or 6 dry, 4 or 5 moist
Chroma - 3 or 4 dry or moist
Texture - GR-C, C, or GR-CL
Percent clay - 35 to 50
Rock fragments - 10 to 35 percent (mostly gravel)
Reaction (pH) - neutral to mildly alkaline

Bq horizon
Value - 6 or 7 dry, 4 or 5 moist
Chroma - 3 or 4 dry or moist
Texture - GRV-SL, GRV-SCL, or CBV-SCL
Rock fragment content - 35 to 60 percent
Reaction (pH) - neutral to mildly alkaline

COMPETING SERIES: These are the Coleman, Dry Creek, Lasere, Pomponio, Pritchard, Succor, and Tutuilla series. Coleman, Dry Creek, and Pritchard soils are greater than 150 cm to bedrock. Lasere soils have less than 10 percent rock fragment in the Bt horizon and lack layers of silica accumulation. Pomponio soils are moderately deep to a paralithic contact and have chromas of 1 or 2 throughout. Succor soils are very deep. Tutuilla soils have a paralithic contact between 100 and 150 cm.

GEOGRAPHIC SETTING: Alibi soils are undulating to steep on sideslopes of foothills. These soils formed in colluvium and residuum from rhyolite and welded rhyolitic tuff. Slopes range from 3 to 35 percent. Elevations are 1,130 to 1,605 meters. The climate is characterized by hot, dry summers and cool, moist winters. The average annual precipitation ranges from 300 to 380 mm and the average annual air temperature ranges from 7 to 10 degrees C. The frost-free period is 90 to 125 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Chinabutte soils. Chinabutte soils are shallow over bedrock and occur on sideslopes and shoulders of foothills, usually above Alibi soils on the landscape.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; medium to rapid runoff; slow hydraulic conductivity.

USE AND VEGETATION: Alibi soils are used for rangeland and wildlife habitat. The dominant natural vegetation is low sagebrush, Idaho fescue, and bluebunch wheatgrass.

DISTRIBUTION AND EXTENT: Southwestern Idaho. Alibi soils are of small extent. MLRA 23 and 25.

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

SERIES ESTABLISHED: Owyhee County Area, Idaho, 1992.

REMARKS: Diagnostic horizons and features recognized in this pedon:
Mollic epipedon greater than 1/3 the depth to the base of the argillic - zone 0 to 18 cm (A and AB horizons)
Abrupt texture change - the boundary a 17 cm (Bt1 boundary).
Argillic horizon and particle-size control section - zone 17 to 43 cm (Bt1 and Bt2 horizons)
"Siliceous" horizon - zone 43 to 58 cm (Bq horizon).
Bedrock - The boundary at 58 cm (R boundary).

National Cooperative Soil Survey
U.S.A.