LOCATION HARDTRIGGER             ID

Established Series
Rev. ALH/CLM
01/2019

HARDTRIGGER SERIES

The Hardtrigger series consists of very deep, well drained soils with moderately slow permeability that formed in mixed alluvium from volcaniclastic material. Hardtrigger soils are on fan terraces, calderas and structural benches. Slopes range from 1 to 35 percent. The average annual precipitation is about 280 mm and the average annual temperature is about 9.4 degrees C.

TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Xeric Haplargids

TYPICAL PEDON: Hardtrigger gravelly loam -- on a east-facing slope of 3 percent, in native rangeland at 1,495 meters elevation. (When described on June 24, 1980, the soil was dry throughout. Colors are for air-dry soil unless otherwise stated.)

A--0 to 10 cm; pale brown (10YR 6/3) gravelly loam, dark brown (10YR 4/3) moist; weak fine and medium granular structure; soft, very friable, nonsticky and nonplastic; many very fine and fine, few medium roots; common very fine and fine interstitial pores; 15 percent gravel; slightly alkaline (pH 7.8); clear smooth boundary. (5 to 15 cm thick)

Bt1--10 to 20 cm; very pale brown (10YR 7/3) gravelly loam, dark brown (10YR 4/3) moist; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine, few medium roots; few very fine and fine tubular and interstitial pores; many faint clay films on faces of peds; 20 percent gravel; moderately alkaline (pH 8.1); clear smooth boundary. (0 to 13 cm thick)

Bt2--20 to 38 cm; very pale brown (10YR 7/4) clay loam, yellowish brown (10YR 5/4) moist; moderate medium subangular blocky structure parting to moderate fine angular blocky; hard, friable, slightly sticky and slightly plastic; common fine, few very fine and medium roots; few very fine interstitial and tubular pores; common distinct clay films on faces of peds; 10 percent gravel; moderately alkaline (pH 8.4); clear smooth boundary. (10 to 56 cm thick)

Btk--38 to 51 cm; very pale brown (10YR 7/4) gravelly clay loam, light yellowish brown (10YR 6/4) moist; weak medium and fine subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common fine, few medium roots; few very fine tubular and interstitial pores; common faint clay films on faces of peds; 15 percent gravel; strongly effervescent; strongly alkaline (pH 8.5); gradual smooth boundary.
(0 to 18 cm thick)

Bk--51 to 71 cm; white (10YR 8/2) gravelly sandy loam, light yellowish brown (10YR 6/4) moist; massive; hard, firm, nonsticky and nonplastic; few fine and medium roots; few very fine tubular pores; 20 percent gravel; violently effervescent; strongly alkaline (pH 8.7); gradual smooth boundary. (15 to 76 cm thick)

Bkq--71 to 152 cm; white (10YR 8/2) very gravelly loamy sand, very pale brown (10YR 7/4) moist; massive; slightly hard, friable, nonsticky and nonplastic; few fine and medium roots; 40 percent gravel; 10 percent durinodes; violently effervescent; strongly alkaline (pH 8.9).

TYPE LOCATION: Owyhee County, Idaho; about 10 miles north and 4 1/2 miles west of Grasmere; about 500 feet north and 1,700 feet east of the southwest corner of section 28, T. 10 S., R. 4 E.; USGS Wickahoney Crossing 7.5 minute topographic quadrangle; 42 degrees, 31 minutes, 20 seconds North Latitude and 115 degrees, 59 minutes, 43 seconds West Longitude; WGS84 Decimal Degrees 42.5222222 latitude, -115.9952778 longitude.

RANGE IN CHARACTERISTICS:

Depth to base of argillic horizon - 36 to 75 cm.
Depth to calcium carbonates - 25 to 69 cm.
Average annual soil temperature - 8.3 to 12.2 degrees C.
Soil moisture - usually dry late June through October; aridic moisture regime bordering on xeric.

A horizon
Value - 5 through 7 dry, 3 through 5 moist
Chroma - 2 or 3 dry or moist
Reaction (pH) - neutral through slightly alkaline

Bt horizon
Value - 4 through 7 dry, 3 through 5 moist
Chroma - 3 or 4 dry or moist
Texture - CL, GR-CL, GR-SCL, GR-L
Clay content - 22 to 34 percent
Rock fragments (gravel) - 5 to 25 percent
Reaction (pH) - neutral through moderately alkaline

Bk horizon
Value - 6 through 8 dry, 4 through 7 moist
Chroma - 2 through 4 dry or moist
Texture - SL, GR-SL, or GR-COSL
Clay content - 10 to 20 percent
Rock fragments (gravel) - 10 to 35 percent
Calcium carbonate equivalent - 5 to 15 percent
Reaction (pH) - moderately or strongly alkaline

Bkq horizon (when present)
Value - 7 or 8 dry, 3 or 4 moist
Chroma - 2 through 4 dry or moist
Texture - GRV-LS, GR-SL, or GRV-SL
Clay content - 4 to 12 percent
Rock fragments (mainly gravel) - 15 to 50 percent
Reaction (pH) - strongly or very strongly alkaline
Calcium carbonate equivalent - 5 to 15 percent
Cementation - commonly 5 to 20 percent durinodes or weak discontinuous duripan

COMPETING SERIES: These are the Abgese, Ackelton, Ackley, Blacknest, Colbar, Greenbrae, Harsan, Hoosegow, Lankbush, Morfitt, Paulville, Sevy, Shawave, Sidlake, Turria, Windypoint and Zane series. Abgese soils have argillic horizons that extend to depths of 75 to 100 cm and have greater than 35 percent rock fragments in the lower part (Btk horizon). Ackelton soils have a calcic horizon and a duripan. Ackley, Greenbrae, Hoosegow and Lankbush soils are noncalcareous above 86 cm. Blacknest soils are 50 to 100 cm to sand and gravel. Colbar and Sidlake soils have lithic or paralithic contacts at depths of 50 to 100. Harsan soils have moderately fine textured Bk horizons in the lower part of the profile. Paulville and Turria soils have less than 35 percent fine sand and coarser in the control section. Sevy and Zane soils have hue of 7.5YR or redder. Shawave soils have massive Btk horizon with noneffervescent matrix and Bk horizons that have less than 10 percent clay with noneffervescent matrix. Windypoint soils lack secondary silica and are 64 to 100 cm deep to sand and gravel.

GEOGRAPHIC SETTING: Hardtrigger soils are gently sloping to moderately steep on fan terraces, calderas and structural benches at elevations of 2,350 to 5,400 feet. Slopes range from 1 to 35 percent. These soils formed in mixed alluvium from volcaniclastic materials. The climate is cool and moist in the winter and hot and dry in the summer. Average annual precipitation ranges from 8 to 13 inches. Average annual temperature ranges from 45 to 52 degrees F. Frost-free period is 90 to 150 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Arbidge, Briabbit, Bruncan, Cottle, Scism and Snowmore series. Briabbit and Scism soils lack an argillic horizon and are on similar landscape positions. Arbidge, Bruncan and Snowmore soils have indurated duripans and are on similar landscape positions. Cottle soils are shallow to bedrock on summits.

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

USE AND VEGETATION: Hardtrigger soils are used mainly for rangeland and wildlife habitat. The dominant natural vegetation is Wyoming big sagebrush, Indian ricegrass, Thurber needlegrass, and at higher elevations bluebunch wheatgrass.

DISTRIBUTION AND EXTENT: Southwestern Idaho. Hardtrigger soils are of moderate extent. MLRA 25.

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

SERIES ESTABLISHED: Owyhee County Area, Idaho, 1992.

REMARKS: This revision (8/95) changes the classification from Xerollic Haplargids to Xeric Haplargids according to the 1994 edition of Keys to Soil Taxonomy. The remainder of the OSD has not been updated since 5/93.

Diagnostic horizons and other features recognized in this pedon:
Ochric epipedon - The zone from the soil surface to 10 cm (A horizon).
Argillic horizon and particle-size control section - The zone from 10 to 51 cm (Bt1, Bt2 and Btk horizons).

The superactive cation exchange activity class was added in 03/2003 to the taxonomic classification by the National Soil Survey Center on request of the Reno MLRA office, without review of the soil series property data. The remainder of this document has not been updated.

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National Cooperative Soil Survey
U.S.A.