LOCATION FULCRUM                 ID

Established Series
Rev. ALH/CLM
01/2019

FULCRUM SERIES

The Fulcrum series consists of moderately deep, somewhat excessively drained soils with moderately rapid permeability that formed in residuum and alluvium from vitric tuff and breccia. Fulcrum soils are on extrusive domes. Slopes range from 3 to 15 percent. The average annual precipitation is about 380 mm and the average annual air temperature is about 5.6 degrees C.

TAXONOMIC CLASS: Ashy-skeletal, glassy, frigid Vitrandic Haploxerolls

TYPICAL PEDON: Fulcrum cobbly ashy sandy loam -- on a convex northwest-facing slope of 8 percent, in native rangeland at 1,830 meters elevation. The surface has about 1 percent stone cover. (When described on August 28, 1980, the soil was dry throughout. Colors are for air dry soil unless otherwise stated)

A1--0 to 8 cm; dark brown (10YR 3/3) cobbly ashy sandy loam, black (10YR 2/1) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine and fine, few medium roots; many very fine and fine irregular pores; 10 percent gravel, 5 percent cobbles, 1 percent stones; slightly acid (pH 6.2; clear smooth boundary. (5 to 13 cm thick)

A2--8 to 28 cm; dark brown (10YR 3/3) gravelly ashy sandy loam, very dark brown (10YR 2/2) moist; weak fine subangular blocky structure parting to weak fine granular; soft, very friable, nonsticky and nonplastic; many very fine and fine, few medium roots; few very fine and fine tubular and vesicular pores; 10 percent gravel, 5 percent cobbles; slightly acid (pH 6.3); clear smooth boundary. (0 to 25 cm thick)

Bw--28 to 53 cm; brown (10YR 4/3) very gravelly ashy sandy loam, dark yellowish brown (10YR 3/4) moist; moderate fine subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; common very fine and fine, few medium roots; common very fine and fine tubular and vesicular pores; common faint clay films in pores; 35 percent gravel, 5 percent cobbles; slightly acid (pH 6.3); clear wavy boundary. (25 to 61 cm thick)

C--53 to 71 cm; yellowish brown (10YR 5/4) extremely cobbly loamy sand, brown (10YR 4/3) moist; massive; few very fine and fine roots; 35 percent gravel, 35 percent cobbles, 15 percent stones; neutral (pH 6.6); clear irregular boundary. (8 to 50 cm thick)

Cr--71 cm; moderately weathered vitric tuff.

TYPE LOCATION: Owyhee County, Idaho; about 28 miles southeast of Silver City; about 1,600 feet east and 750 feet south of the northwest corner of section 36, T. 8 S., R. 1 W.; USGS Clover Mountain 7.5 minute topographic quadrangle; latitude 42 degrees 41 minutes 26 seconds N and longitude 116 degrees 24 minutes 28 seconds W; WGS84 Decimal Degrees 42.6905556 latitude, -116.4077778 longitude.

RANGE IN CHARACTERISTICS:

Mollic epipedon thickness - 18 to 38 cm (dark parent material significantly influences colors throughout)
Volcanic glass content (very fine sand fraction) - 45 to 70 percent.
Depth to bedrock - 50 to 100 cm.
Particle-size control section (weighted average) - 10 to 18 percent clay and 35 to 70 percent rock fragments
Reaction (pH) - slightly acid or neutral
Average annual soil temperature - 5.6 to 7.2 degrees C.
Average summer soil temperature - 16.7 to 18.3 degrees C.
Typic xeric moisture regime.

A horizon
Hue - 7.5YR or 10YR
Value - 3 to 5 dry, 2 or 3 moist
Chroma - 2 or 3 dry, 1 to 3 moist

Bw horizon
Hue - 7.5YR or 10YR
Value - 4 to 6 dry, 3 or 4 moist
Chroma - 3 or 4 dry, 2 to 4 moist
Clay content - 12 to 20 percent
Rock fragment content - 35 to 50 percent

C horizon
Hue - 7.5YR or 10YR
Value - 4 to 7 dry, 3 to 6 moist
Chroma - 3 to 6 dry or moist
Texture - CBX-LS, GRV-SL, or GRX-SL
Clay content - 6 to 18 percent
Rock fragment content - 50 to 90 percent

COMPETING SERIES: These are the Lonigan and Stines series. Lonigan soils have Bk horizons and are over soft bedrock. Stines soils are 100 to 150 cm deep over soft bedrock.

GEOGRAPHIC SETTING: Fulcrum soils are undulating to hilly on extrusive domes at elevations of 1,740 to 1,895 meters. Slopes range from 3 to 15 percent. The soils formed in residuum and alluvium from vitric tuff and flow-breccia. The climate is cool and moist in the winter and warm and dry in the summer. Average annual precipitation is 360 to 410 mm, and average annual temperature is 4.4 to 6.1 degrees C. The frost-free period is 65 to 80 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Monasterio and Zola soils. Monasterio soils have argillic horizons and are on similar landscape positions. Zola soils are deeper than 150 cm and on fluvial bottoms.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Somewhat excessively drained; slow to medium runoff; moderately rapid saturated hydraulic conductivity.

USE AND VEGETATION: Fulcrum soils are used mainly for rangeland and wildlife habitat. The dominant natural vegetation is mountain big sagebrush, bluebunch wheatgrass, Idaho fescue, and antelope bitterbrush.

DISTRIBUTION AND EXTENT: Southwestern Idaho. This series is not extensive. MLRA 25.

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

SERIES ESTABLISHED: Owyhee County Area, Idaho, 1992.

REMARKS: Diagnostic horizons and other features recognized in this pedon:

Mollic epipedon - The zone 0 to 28 cm (A1 and A2 horizons).

Cambic horizon - The zone 28 to 53 cm (Bw horizon)

Particle-size control section - The zone 25 to 69 cm (part of the A2, Bw and the C horizons)

Volcanic glass - The zone 0 to 28 cm (A1 and A2 horizons) = 53 percent; the zone 28 to 53 cm (Bw horizon) = 64 percent.
Paralithic contact - The boundary at 71 cm (Cr boundary).

ADDITIONAL DATA: NSSL pedon # 90P-914.

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National Cooperative Soil Survey
U.S.A.