LOCATION OBNOT IDEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Typic Haploxererts
TYPICAL PEDON: Obnot cobbly silty clay loam, rangeland; on a 12 percent slope. When described on Sept. 6, 1979, the soil was dry to 19 inches. (Color is for dry soil unless otherwise noted.)
A1--0 to 5 inches; dark grayish brown (10YR 4/2) cobbly silty clay loam, very dark brown (10YR 2/2) moist; weak fine subangular blocky structure; soft, friable, moderately sticky and moderately plastic; few very fine and fine roots; many very fine and fine tubular pores; 1.5 to 3 cm wide cracks; 10 percent cobbles and 5 percent stones; slightly acid (pH 6.2); clear smooth boundary.
A2--5 to 12 inches; dark grayish brown (10YR 4/2) silty clay, very dark grayish brown (10YR 3/2) moist; moderate medium subangular blocky structure parting to weak medium and fine subangular blocky; hard, firm, moderately sticky and moderately plastic; few very fine and fine roots; many very fine and fine tubular pores; 1.5 to 3 cm wide cracks; 5 percent cobbles; neutral (pH 6.6); clear wavy boundary. (Combined thickness of the A horizons is 8 to 14 inches)
AB--12 to 19 inches; brown (7.5YR 5/4) silty clay, dark brown (7.5YR 3/4) moist; moderate medium subangular blocky structure parting to weak fine angular blocky; very hard, very firm, very sticky and very plastic; few very fine roots; common very fine and fine tubular pores; 1.5 to 3 cm wide cracks filled with surface material; 5 percent gravel; slightly acid (pH 6.2); clear smooth boundary. (4 to 9 inches thick)
Bss1--19 to 24 inches; brown (7.5YR 5/4) silty clay, brown (7.5YR 4/4) moist; moderate coarse subangular blocky structure parting to moderate fine angular blocky; extremely hard, very firm, very sticky and very plastic; few very fine roots; few very fine tubular pores; 1.5 to 3 cm wide cracks; few intersecting slickensides; neutral (pH 7.2); clear smooth boundary.
Bss2--24 to 31 inches; light brown (7.5YR 6/4) silty clay, brown (7.5YR 4/4) moist; very dark brown (10YR 2/2) stainings along side of peds and black (10YR 2/1) iron and manganese concretions in lower part of horizon; weak coarse angular blocky structure parting to moderate medium platy; extremely hard, extremely firm, very sticky and very plastic; few very fine roots; few very fine tubular pores; 1.5 to 3 cm wide cracks; common intersecting slickensides; few wedge shaped aggregates; 5 percent gravel; neutral (pH 7.0); clear smooth boundary. (Combined thickness of the Bss horizons is 8 to 16 inches)
Bk1--31 to 34 inches; light brown (7.5YR 6/4) clay loam, brown (7.5YR 4/4) moist; moderate coarse subangular blocky structure; extremely hard, extremely firm, very sticky and very plastic; few very fine tubular pores; 5 percent gravel; slightly effervescent; slightly alkaline (pH 7.6); clear smooth boundary. (3 to 8 inches thick)
Bk2--34 to 60 inches; pink (7.5YR 7/4) cobbly clay loam, brown (7.5YR 5/4) moist; massive; extremely hard, extremely firm, very sticky and very plastic; common very fine tubular pores; 10 percent cobbles and 5 percent stones; strongly effervescent; slightly alkaline (pH 7.8).
TYPE LOCATION: Oneida County, Idaho; about 6 miles north of Malad City; about 500 feet east and 100 feet south of the northwest corner of section 19, T. 13 S., R. 37 E. Latitude - 42 degrees, 17 minutes, 7 seconds North; Longitude - 112 degrees, 11 minutes, 15 seconds West.
RANGE IN CHARACTERISTICS:
Cracks 1.5 to 3 cm wide extending to 31 inches
Thickness of the mollic epipedon - 12 to 23 inches
Depth to secondary lime - 30 to 39 inches
Average annual soil temperature - 44 to 47 degrees F.
Moisture control section - dry 80 to 100 days in late summer and fall
Control section averages - 40 to 55 percent clay and 0 to 10 percent coarse fragments
A horizons
Value - 4 or 5 dry, 2 or 3 moist
Chroma - 2 to 4 dry, 2 or 3 moist (when chroma of 3 or more is present in the surface 12 inches, it accounts for less than 50 percent of the horizon color)
Bss horizons
Hue - 10YR or 7.5YR
Value - 5 or 6 dry, 4 or 5 moist
Chroma - 3 or 4 dry or moist
Reaction - slightly acid or neutral
Bk horizons
Hue - 10YR or 7.5YR
Value - 6 or 7 dry, 4 or 5 moist
Chroma - 3 or 4 dry or moist
Texture - CB-CL, CL
Calcium carbonate equivalent - 5 to 15 percent
Reaction - slightly or moderately alkaline
COMPETING SERIES: These are the Bagval (T), Frenchollow (T), Hawkins, and Obray series. Bagval soils have argillic horizons and have mollic epipedons that are 30 to 60 inches thick. Frenchollow soils do not have secondary carbonates within 39 inches of the soil surface and have clay films in the cambic horizon. Hawkins soils are dry for less than 80 days. Obray soils have mollic epipedons more than 30 inches thick.
GEOGRAPHIC SETTING: Obnot soils are on fan terraces and mountain footslopes at elevations of 5,000 to 6,000 feet. They formed in alluvium from quartzite. Slopes are 4 to 12 percent. The average annual precipitation ranges from 15 to 18 inches. The average annual air temperature is 42 to 45 degrees F. The frost-free period is 80 to 95 days.
GEOGRAPHICALLY ASSOCIATED SOILS: Broadhead, Manila, and Yago soils. Broadhead soils are in draws and lack vertic soil properties. Yago soils are clayey-skeletal and are on sides of draws.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; very slow permeability.
USE AND VEGETATION: Obnot soils are used for nonirrigated cropland and rangeland. The native vegetation is mountain big sagebrush and bluebunch wheatgrass.
DISTRIBUTION AND EXTENT: Southeastern Idaho. These soils are of small extent. MLRA 13.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Oneida County, Idaho, 1994.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 12 inches (A1 and A2 horizons)
Cambic horizon and slickensides - The zone from 19 to 31 inches (Bss1 and Bss2 horizons)
Particle-size control section - The zone from 10 to 40 inches (part of the A2, the AB, Bss1, Bss2, Bk1 and part of the Bk2 horizons)