LOCATION AMBOAT ID

Established Series
Rev. DA/CLM
02/2018

AMBOAT SERIES

The Amboat series consists of very deep, well drained soils that formed in colluvium and residuum from welded tuff. They are on summits. Permeability is very slow. Slopes range from 2 to 20 percent. The average annual precipitation is about 380 mm, and the average annual temperature is about 6 degrees C.

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 2,000 meter elevation. (Colors are for dry soil unless otherwise noted.) When described on October 3, 1977, the soil profile was dry.

A--0 to 8 cm; 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. (5 to 13 cm thick)

AB--8 to 20 cm; dark brown (10YR 4/3) gravelly loam, very dark brown (10YR 2/2) moist; weak medium subangular block structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine, fine and coarse roots; many very fine tubular pores; 15 percent gravel; neutral (pH 6.8); clear smooth boundary. (8 to 28 cm thick)

Bt--20 to 43 cm; dark brown (10YR 4/3) gravelly clay, dark brown (10YR 3/3) moist; moderate medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; common fine and medium 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. (13 to 23 cm thick)

2Bt--43 to 152 cm; brown (7.5YR 4/2) extremely stony clay, dark brown (7.5 YR 4/4) moist; very hard, very firm, very sticky and very plastic; strong medium angular blocky structure; common fine and medium 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 5 cm 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. 15 S., R. 16 E.; USGS Magic Hot Springs 7.5 minute topographic quadrangle; latitude 42 degrees 5 minutes 56 seconds N and longitude 114 degrees 36 minutes 36 seconds W; WGS84 Decimal Degrees 42.0988889 latitude, -114.6100000 longitude.

RANGE IN CHARACTERISTICS:

Depth to bedrock - more than 150 cm. Thickness of mollic epipedon - 30 to 50 cm.
Average annual soil temperature - 5 degrees to 6 degrees C. Average summer soil temperature - 15 to 16 degrees C.
Typic xeric moisture regime.

A horizon
Value, dry - 4 or 5
Value, moist - 2 or 3
Chroma - 1 through 3 dry or moist
Structure Type - granular or platy
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

2Bt 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, and Ziram series. Aninto and Ziram soils have Bk horizons, and have an average annual soil temperature warmer than 6 degrees C. 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 100 cm. Secrepass soils have 30 to 65 percent rock fragments in the 2Bt horizon and the base of the argillic is less than 100 cm.

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 1,770 to 2,015 meters. The average annual precipitation ranges from 330 to 410 mm. The average annual temperature is 4 to 7 degrees C. 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 25.

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

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 43 cm (A, AB and Bt horizons).
Argillic horizon - the zone from 20 to 152 cm (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 50 cm of the argillic horizon (Bt and part of the 2Bt horizons.)

National Cooperative Soil Survey
U.S.A.