LOCATION AMBOAT IDEstablished Series
TAXONOMIC CLASS: Clayey-skeletal, smectitic, frigid Typic Palexerolls
TYPICAL PEDON: Amboat gravelly loam-on a NW facing slope of 3 percent under native vegetation at 6,550 feet elevation. (Colors are for dry soil unless otherwise noted.) When described on October 3, 1977, the soil profile was dry.
A-0 to 3 inches; dark brown (10YR 4/3) gravelly loam, very dark grayish brown (10YR 3/2) moist; weak fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine, fine and coarse roots; many very fine tubular pores; 20 percent gravel; neutral (pH 6.8); clear smooth boundary. (2 to 5 inches thick)
AB-3 to 8 inches; dark brown (10YR 4/3) gravelly loam, very dark brown (10YR 2/2) moist; weak medium subangular block structure; slightly hard, friable, sticky and plastic; many very fine, fine and coarse roots; many very fine tubular pores; 15 percent gravel; neutral (pH 6.8); clear smooth boundary. (3 to 11 inches thick)
Bt1--8 to 17 inches; dark brown (10YR 4/3) gravelly clay, dark brown (10YR 3/3) moist; moderate medium subangular blocky structure; hard, firm, sticky and plastic; common roots; common very fine tubular pores; common distinct clay films on faces of peds and in pores; 30 percent gravel; neutral (pH 6.8); abrupt smooth boundary. (5 to 9 inches thick)
2Bt2--17 to 60 inches; brown (7.5YR 4/2) extremely stony clay, dark brown (7.5 YR 4/4) moist; strong medium angular blocky structure; common roots; few very fine tubular pores; many prominent clay films on faces of peds and in pores; 85 percent gray (10YR 5/1) fractured vesicular welded tuff, very dark gray (10YR 3/1) moist; fractures are 1/2 to 2 inches wide and run perpendicular to the surface; within the fractures are seams of clay; neutral (pH 6.8).
TYPE LOCATION: Twin Falls County, Idaho; about 8 miles south of Rogerson, Idaho; in the NE 1/4, NW 1/4, NW 1/4, section 29, T.15S., R.16E.
RANGE IN CHARACTERISTICS:
Depth to bedrock - more than 60 inches
Thickness of mollic epipedon - 12 to 20 inches
Average annual soil temperature - 41 degrees to 43 degrees F. Average summer soil temperature - 59 to 60 degrees F.
A horizon
Value, dry - 4 or 5
Value, moist - 2 or 3
Chroma - 1 through 3 dry or moist
Structure Type - granular or platy
Gravel - 10 to 20 percent
Cobbles - 0 to 10 percent
Stones - 0 to 5 percent
pH - slightly acid or neutral
Bt1 horizon
Value, dry - 4 or 5
Value, moist - 2 or 3
Chroma - 2 or 3 dry or moist
Texture - GR-CL, GR-SICL, or GR-C
Clay content - 35 to 55 percent
Gravel - 15 to 30 percent
Cobbles - 0 to 5 percent
2Bt2 horizon
Color hue - 7.5YR or 10YR
Value, dry - 4 or 5
Value, moist - 3 through 5
Chroma - 2 through 4 dry or moist
Clay content - 60 to 85 percent
Cobbles - 0 to 5 percent
Stones - 60 to 85 percent
COMPETING SERIES: This is the Aninto, Durfee, Ebic, Secrepass (T), and Ziram series. Aninto and Ziram soils have Bk horizons, and have an average annual soil temperature warmer than 43 degrees F. Durfee soils do not have a 20 percent clay decrease in the lower part of the argillic horizon and have less than 60 percent stones. Ebic soils have bedrock at depths of less than 40 inches. Secrepass soils have 30 to 65 percent rock fragments in the 2Bt horizon and the base of the argillic is less than 40 inches.
GEOGRAPHIC SETTING: Amboat soils are on summits. Slopes range from 2 to 20 percent. The soils formed from colluvium and residuum of weathered welded tuff. Elevations are 5,800 to 6,600 feet. The average annual precipitation ranges from 13 to 16 inches. The average annual temperature is 40 to 44 degrees F. The frost free season is 70 to 90 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Brose, Congle, Doodlelink, Eep, Forvic, Hogmalat, Keman, and Oshone soils. Brose soils are shallow to welded tuff, and are not skeletal. Congle and Doodlelink occur on sideslopes, footslopes, and breaks, and are pachic. Eep soils occur on breaks and scarp faces, and are ashy-skeletal. Forvic and Oshone soils occur on terraces, and are moderately deep to a hardpan. Hogmalat soils occur on higher summit shoulders, are shallow to welded tuff, and are cryic. Keman soils occur on summit backslopes, are cryic and loamy-skeletal.
DRAINAGE AND PERMEABILITY: Well drained, medium runoff; very slow permeability.
USE AND VEGETATION: Amboat soils are used for rangeland. Native vegetation is Idaho fescue, bluebunch wheatgrass, Nevada bluegrass, lupine, mountain big sagebrush, antelope bitterbrush, serviceberry and snowberry.
DISTRIBUTION AND EXTENT: Amboat soils are of moderate extent in south central Idaho.
MLRA OFFICE RESPONSIBLE: Reno, Nevada
SERIES ESTABLISHED: Twin Falls County, Idaho, 1992.
REMARKS: Diagnostic horizons and features recognized in the pedon are:
Mollic epipedon - the zone from the surface to 17 inches (A, AB and Bt horizons.)
Argillic horizon - the zone from 8 to 60 inches (the Bt and 2Bt horizons.)
Palexeroll feature - has a clay increase greater than 15 percent absolute within a distance of 2.5 cm at the upper boundary of the argillic horizon and has a clayey particle size class.
Particle size control section - the upper 20 inches of the argillic horizon (Bt and part of the 2Bt horizons.)