LOCATION POISONHOL ID

Established Series
Rev. FRK/GHL/JBF
03/2011

POISONHOL SERIES

The Poisonhol series consists of moderately deep, well drained, soilsthat are formed in mixed alluvium. They are on coalesced fan terraces and hillsides. Slopes are 1 to 15 percent. The average annual precipitation is about 14 inches and the average annual temperature is about 44 degrees F.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Haploxerollic Durixerolls

TYPICAL PEDON: Poisonhol very stony loam, rangeland, on a 3 percent south slope, 5370 feet elevation. When described on October 10, 1984 the soil was dry throughout. (Colors are for air dry soil unless otherwise noted.)

A1--0 to 2 inches; grayish brown (10YR 5/2) very stony loam, very dark grayish brown (10YR 3/2) moist; weak very coarse platy structure parting to moderate very fine and fine granular; soft, very friable, slightly sticky, slightly plastic; many very fine roots; many very fine irregular pores; Class 3 and 4 stones on the surface and about 10 percent pebbles in the horizon; moderately alkaline (pH 8.0); abrupt smooth boundary.

AB--2 to 5 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; moderate very coarse platy structure parting to moderate very fine and fine subangular blocky; slightly hard, very friable, slightly sticky, plastic; common very fine, few fine roots; many very fine tubular pores; moderately alkaline (pH 8.0); clear smooth boundary. (Combined thickness of the A horizons is 2 to 7 inches)

Bw--5 to 12 inches; grayish brown (10YR 5/2) very cobbly clay loam, very dark grayish brown (10YR 3/2) moist; weak coarse prismatic structure parting to moderate fine and medium subangular blocky; slightly hard, very friable, sticky, plastic; common very fine, few fine roots; many very fine tubular pores; 10 percent durinodes; 5 percent stones, 25 percent cobbles, 20 percent pebbles; moderately alkaline (pH 8.0); clear wavy boundary. (5 to 8 inches thick)

Bk1--12 to 21 inches; very pale brown (10YR 7/3) very stony loam, light yellowish brown (10YR 6/4) moist; moderate coarse platy structure parting to strong fine and medium subangular blocky; slightly hard,friable, slightly sticky, slightly plastic; common very fine roots; many very fine tubular pores; strongly effervescent; lime is disseminated; 35 percent stones, 10 percent cobbles, 15 percent pebbles; moderately alkaline (pH 8.2); gradual wavy boundary. (4 to 9 inches thick)

Bk2--21 to 31 inches; very pale brown (10YR 8/3) very stony loam, light yellowish brown (10YR 6/4) moist; strong medium and coarse platy structure; slightly hard, friable; few very fine roots; many very fine tubular pores; violently effervescent; lime is disseminated; 30 percent stones, 15 percent cobbles, 15 percent pebbles; rock fragments coated with lime on all sides; moderately alkaline (pH 8.3); abrupt wavy boundary. (10 to 15 inches thick)

2Bkqm--31 inches; white (10YR 8/2) and light brown (7.5YR 6/4) moist, silica indurated hardpan; strong very coarse and coarse platy structure; extremely hard; extremely firm; violently effervescent; moderately alkaline (pH 8.4); 30 percent stones, 20 percent cobbles, 20 percent pebbles in the upper 5 inches.

TYPE LOCATION: Cassia County, Idaho; about 2 miles northeast of Almo, Idaho, 2200 feet east, 1600 feet north of the southwest corner of section 12, T.15S., R.24E.

RANGE IN CHARACTERISTICS:
Soil moisture: Moist in winter and spring and continuously dry in all parts for significant periods in summer and fall; xeric soil moisture regime bordering on aridic.
Mean annual soil temperature: 45 to 46 degrees F.
Mollic epipedon thickness: 11 to 15 inches
Depth to duripan: 30 to 39 inches
Depth to secondary lime: 7 to 12 inches

Particle-size control section - Clay content: Averages 18 to 27 percent.
Rock fragments: Average 45 to 70 percent.

A horizons
Value:2 or 3 moist
Chroma: 2 or 3
Reaction: Slightly alkaline or moderately alkaline

Bw horizon
Chroma: 2 or 3
Texture: CBV-CL, GRV-CL, CBV-L, GRV-L
Clay content:-25 to 32 percent
Rock fragment content: 45 to 60 percent
Reaction: Slightly or moderately alkaline

Bk horizon
Value: 6 through 8 dry, 5 or 6 moist
Chroma: 2 through 4
Texture: STV-L, CBV-L, GRV-L, CBV-CL, STX-L, CBX-L
Clay content: 10 to 18 percent averaged through horizon
Rock fragment content: 45 to 80 percent
Reaction: Moderately alkaline or strongly alkaline

2Bqkm horizon
Hue: 10YR or 7.5YR
Value: 7 or 8 dry, 4 through 6 moist
Chroma: 2 through 4
Cementation: Continuously indurated
Duripan: Generally contains greater than 35 percent coarse fragments

COMPETING SERIES: There are no other series in this family

GEOGRAPHIC SETTING: Poisonhol soils are on coalesced fan terraces and hillsides. Slopes range from 1 to 15 percent. Elevation ranges from 5300 to 5800 feet. The soil formed in mixed alluvium. The average annual precipitation ranges from 12 to 6 inches, the average annual air temperature is about 43 to 45 degrees F., the frost free season is 80 to 95 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Acord, Chen, Riceton, and Vipont series. Acord, Chen, and Vipont soils have argillic horizons. Acord and Chen soils have a clayey skeletal control section. Riceton soils are pachic and formed in alluvium and residuum of acid igneous rocks. Acord and Riceton soils are very deep. Vipont soils are moderately deep to bedrock. Chen soils are shallow to bedrock. Acord and Riceton soils are on fan terraces. Chen and Vipont soils are on mountainsides.

DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderately permeable above the duripan and very slow through the pan.

USE AND VEGETATION: Poisonhol soils are used for rangeland wildlife habitat. The native vegetation is mountain big sagebrush, bluebunch wheatgrass, Sandberg bluegrass, and rabbitbrush.

DISTRIBUTION AND EXTENT: South central Idaho. The soils of this series are inextensive.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona

SERIES ESTABLISHED: Cassia County, Idaho, 1986.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 12 inches (A1, AB, and Bw horizons).
Cambic horizon - The zone from 5 to 12 inches (Bw horizon)
Calcic horizon - The zone from 12 to 31 inches (Bk1 and Bk2 horizons).
Duripan - The boundary at 31 inches (2Bkqm horizon).
Particle-size control section - The zone from 10 to 31 inches (Bw, Bk1 and Bk2 horizons).

National Cooperative Soil Survey
U.S.A.