LOCATION POISONCREEK             ID+NV

Established Series
Rev. RDR-ALH-CLM-JBF
10/2019

POISONCREEK SERIES

The Poisoncreek series consists of shallow, well or somewhat excessively drained soils that formed in colluvium and residuum derived from granitic rocks. These soils are on mountain and foothill ridges and sideslopes. Slopes range from 1 to 75 percent. The average annual precipitation is about 380 mm, and the average annual temperature is about 6 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid, shallow Aridic Argixerolls

TYPICAL PEDON: Poisoncreek gravelly coarse sandy loam -- on a convex south-facing slope of 3 percent, in native rangeland at 5,770 feet elevation. (When described on July 29, 1980, the soil was dry throughout. Colors are for air dry soils unless otherwise stated.)

A--0 to 8 cm; grayish brown (10YR 5/2) gravelly coarse sandy loam, very dark gray (10YR 3/1) moist; weak medium and fine subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; many very fine and fine roots; many very fine interstitial pores; 15 percent fine gravel; neutral (pH 7.2); clear smooth boundary. (5 to 13 cm thick)

Bt--8 to 15 cm; brown (10YR 5/3) very gravelly sandy clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium subangular blocky structure; slightly hard, friable, moderately sticky and slightly plastic; many very fine and fine roots; many very fine interstitial and tubular pores; common faint clay films on faces of peds and in pores; 30 percent gravel, 20 percent cobbles; neutral (pH 7.2), clear smooth boundary. (8 to 20 cm thick)

C/Bt--15 to 30 cm; yellowish brown (10YR 5/6) extremely cobbly sandy clay loam in pockets and fractures; dark yellowish brown (10YR 4/4) moist; massive; 60 percent C material and 40 percent B material; hard, friable, moderately sticky and moderately plastic; many very fine and fine, few medium roots; fractures are 1 to 5 mm wide, less than 10 cm apart and contain many distinct and prominent clay films; 45 percent gravel, 40 percent cobbles; neutral (pH 7.0); clear wavy boundary. (0 to 20 cm thick)

Cr1--30 to 41 cm; very pale brown (10YR 8/2) weathered granite with yellowish brown (10YR 5/8) iron staining, light yellowish brown (10YR 6/4) moist; rock structure; fractures are greater than 10 cm apart and contain some illuviated soil material and few very fine and fine roots; gradual wavy boundary. (5 to 25 cm thick)

Cr2--41 cm; weathered and slightly fractured granite.

TYPE LOCATION: Owyhee County, Idaho; about 19 miles south and 13 1/2 miles east of Silver City; about 1,650 feet north and 1,630 feet east of the southwest corner of section 9, T. 8 S., R. 1 W.; USGS Clover Mountain 7.5 minute topographic quadrangle; latitude 42 degrees 44 minutes 28 seconds N and longitude 116 degrees 28 minutes 0 seconds W; WGS84 Decimal Degrees 42.7411111 latitude, -116.4666667 longitude.

RANGE IN CHARACTERISTICS:
Soil moisture control section: Usually moist, dry 70 to 120 days following summer solstice; aridic soil moisture regime bordering on xeric.
Mean annual soil temperature: 5 to 8 degrees C.
Mean summer soil temperature: 16 to 19 degrees C.
Mollic epipedon thickness: 18 to 30 cm.
Depth to paralithic contact: 25 to 36 cm.
Depth to hard bedrock: 36 to 50 cm.

Particle-size control section - Clay content: Averages 20 to 30 percent.
Rock fragments: 35 to 75 percent, dominantly 2 to 5 mm gravel. Lithology of fragments is mainly granitic rocks.

A horizon
Value: 4 or 5 dry.
Chroma: 2 or 3 dry, 1 to 3 moist.
Rock fragments: 5 to 35 percent.

Bt horizon
Hue: 10 YR or 2.5 Y.
Value: 4 to 6 dry, 3 or 4 moist.
Chroma: 2 to 4.
Texture: GRV-SCL, CBV-CL, or GRV-L.
Clay content: 25 to 35 percent.
Rock fragments: 35 to 60 percent.

COMPETING SERIES: These are the Deanran, Dotsolot, Garnel, Lyra and Pinenut series.

Deanran soils have less than 25 percent clay in the argillic horizon. Dotsolot soils are deeper than 36 cm. Garnel soils are intermittently moist in the upper part for 10 to 20 days cumulative due to convection storms between July and September. Lyra soils have fine carbonate coatings on the paralithic bedrock. Pinenut soils have mainly 5 to 75 mm gravel.

GEOGRAPHIC SETTING: The Poisoncreek soils occur on convex ridges and south to west facing mountain and foothill sideslopes at elevations of 1,400 to 2,300 meters. These soils formed in residuum derived from granitic rocks. Slopes range from 1 to 75 percent. The climate is cool and moist in the winter and warm and dry in the summer. The average annual precipitation is 330 to 460 mm, and average annual temperature is 4 to 7 degrees C. The frost-free period is 60 to 95 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Hurryback, Ola, Kanlee, and Takeuchi soils. Hurryback soils are deep, have mollic epipedons greater than 50 cm thick and are on northeast aspects. Ola, Kanlee, and Takeuchi are moderately deep and on slightly concave sideslopes.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well or somewhat excessively drained; medium to very rapid runoff; moderately high saturated hydraulic conductivity.

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

DISTRIBUTION AND EXTENT: Southwestern Idaho and northern Nevada. This series is moderately extensive. MLRA 25 and 24.

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 are:
Mollic epipedon - The zone the surface to 15 cm (A and Bt horizons).
Argillic horizon - The zone 8 to 15 cm (Bt and C/Bt horizons).
Paralithic contact - The contact at 30 cm (Cr1 layer).
Particle-size control section - The zone from the surface to 30 cm (A, Bt, and C/B horizons).

ADDITIONAL DATA: The Cr2 should be verified during a MLRA update to determine if shallow or lithic within 50 cm.

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National Cooperative Soil Survey
U.S.A.