LOCATION AIKMAN IDEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Leptic Haploxererts
TYPICAL PEDON: Aikman stony clay -- on a north-facing slope of 5 percent, in rangeland at 3,375 feet elevation. (Colors are for air-dry soil unless otherwise stated.)
A--0 to 1 inch; dark reddish gray (5YR 4/2) stony clay, dark reddish brown (5YR 3/2) moist; moderate fine granular structure; very hard, very firm, very sticky and very plastic; common fine roots; many very fine irregular pores; vertical cracks when dry, 1 to 3.5 cm wide and 6 to 12 inches apart; 10 percent fine gravel, 15 percent stones and cobbles; neutral (pH 6.6); abrupt wavy boundary.
(1 to 3 inches thick)
Bss1--1 to 8 inches; weak red (2.5YR 4/2) stony clay, dark reddish brown (2.5YR 3/3) moist; moderate coarse and very coarse prismatic structure parting to moderate fine and medium angular blocky; extremely hard, very firm, very sticky and very plastic; common fine roots; few very fine pores; vertical cracks when dry, as described above; slickensides; 10 percent fine gravel, 15 percent stones and cobbles; neutral (pH 6.8); clear irregular boundary.
(6 to 15 inches thick)
Bss2--8 to 18 inches; weak red (2.5YR 4/2) stony clay, dark reddish brown (2.5YR 3/3) moist; moderate medium and coarse prismatic structure parting to moderate medium angular blocky; extremely hard, very firm, very sticky and very plastic; few fine roots; few very fine pores; vertical cracks when dry, as described for A1 but less than 2 cm wide; slickensides; few faint clay films; 10 percent fine gravel, 20 percent stones and cobbles; neutral (pH 6.9) abrupt irregular boundary. (5 to 12 inches thick)
Bkss--18 to 24 inches; pale red (2.5YR 6/2) and light red (2.5YR 6/6) stony clay, reddish brown (2.5YR 5/4) and red (2.5YR 5/4) moist; massive; very hard, very firm, very sticky and very plastic; few fine roots; few very fine pores; slickensides; vertical cracks when dry, as described above; 5 percent gravel, 25 percent stones and cobbles; slightly effervescent, calcium carbonate segregated in common fine filaments and soft masses; sligtly alkaline (pH 7.4); gradual wavy boundary. (0 to 8 inches thick)
Bk--24 to 30 inches; reddish yellow (5YR 6/6) stony clay, yellowish red (5YR 5/6) moist; massive; very hard, very firm, very sticky and very plastic; few fine roots; few very fine pores; 5 percent gravel, 25 percent stones and cobbles; strongly effervescent, calcium carbonate segregated in many fine and medium filaments, seams and soft masses; slightly alkaline (pH 7.6); abrupt irregular boundary.
(2 to 12 inches thick)
R--30 inches; fractured rhyolite or rhyolitic tuff; some calcium carbonate in fractures.
TYPE LOCATION: Gem County, Idaho; about 10 miles southeast of Emmett; 2000 feet west and 600 feet north of the SE corner of section 20, T.6 N., R.1 E.; 43 degrees, 50 minutes, 17 seconds North Latitude and 116 degrees, 21 minutes, 39 seconds West Longitude.
RANGE IN CHARACTERISTICS:
Cracks- 1 to 3.5 cm wide; 10 to 20 inches deep
Depth to bedrock - 20 to 40 inches
Particle-size control section (weighted average) - 40 to 60 percent clay; 15 to 35 percent rock fragments
Average annual soil temperature - 49 to 52 degrees F
Moisture control section - dry 60 to 90 consecutive days after the summer solstice
A horizon
Hue - 2.5YR or 5YR
Value - 4 or 5 dry, 3 or 4 moist
Chroma - 2 or 3 dry or moist
Reaction (pH) - slightly acid or neutral
Bss horizon
Hue - 2.5YR or 5YR
Value - 4 or 5 dry, 3 or 4 moist
Chroma - 2 through 4 dry or moist
Rock fragments - 15 to 35 percent
Reaction (pH) - neutral or slightly alkaline
Bk horizon
Hue - 10R through 5YR
Value - 4 through 6 dry, 3 through 5 moist
Chroma - 3 through 6 dry or moist
Rock fragments - 15 to 35 percent
Calcium carbonate equivalent - 1 to 15 percent
COMPETING SERIES: These are the Jenny, Lassen, Montague, and Pit series. Jenny and Pit soils lack a lithic contact above depth of 40 inches. Lassen soils have hue yellower than 5YR. Montague soils have dark gray (dry) A horizons, dark grayish brown C horizons, and a thin indurated hardpan over a petrocalcic horizon (massive tuff) at depths of 20 to 40 inches. Pit soils are somewhat poorly or poorly drained.
GEOGRAPHIC SETTING: Aikman soils are nearly level to moderately steep on summits, shoulders and backslopes of structural benches and foothills at elevations of 3,000 to 3,700 feet. Slopes range from 0 to 30 percent. These soils formed in residuum from rhyolite or rhyolitic tuff mixed with alluvium from lacustrine sediments derived dominantly from granite. The climate is cool and moist in the winter and warm and dry in the summer. Average annual precipitation ranges from 12 to 14 inches. Average annual temperature ranges from 47 to 50 degrees F. Frost-free period is 110 to 130 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Haw, Perla and Van Dusen series. All of these soils lack cracks and other characteristics of Vertisols. Haw and Perla soils are on higher landscape positions. Van Dusen soils are on steep north-facing slopes.
DRAINAGE AND PERMEABILITY: Well drained; slow to very rapid runoff; slow permeability.
USE AND VEGETATION: Aikman soils are used mainly for rangeland and wildlife habitat. The dominant natural vegetation is bluebunch wheatgrass, Sandberg bluegrass, Hooker balsamroot and xericensis big sagebrush. Small areas have been used for nonirrigated cropland.
DISTRIBUTION AND EXTENT: Southwestern Idaho. Aikman soils are of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Gem County Area, Idaho, 1962.
REMARKS: This revision (6/95) changes the classification from Typic Chromoxererts to Leptic Haploxererts according to the 1994 edition of Keys to Soil Taxonomy. The remainder of the OSD has not been updated since 9/76.
Diagnostic horizons and other features recognized in this pedon:
Mollic epipedon - zone from the soil surface to 18 inches (A, Bss1, and Bss2 horizons)
Cracks and Slickensides- zone 1 to 24 inches (Bss1, Bss2, Bkss horizons)
Particle-size control section - zone 10 to 30 inches (part of the Bss2, the Bkss, and the Bk horizons)
Lithic contact - hard bedrock at 30 inches (R horizon).