LOCATION HOBNAIL                 ID

Established Series
Rev. CJW-SHB-JCK
11/2022

HOBNAIL SERIES

The Hobnail series consists of very deep, moderately well drained soils on benches, dissected terraces and hills. They formed in colluvium and tertiary alluvium derived dominantly from shales, quartzite, or mica schist, with a thick mantle of volcanic ash. Permeability is slow. Slopes are 5 to 40 percent. The average annual precipitation is about 38 inches and average annual air temperature is about 44 degrees F.

TAXONOMIC CLASS: Ashy over loamy, amorphic over isotic, frigid Oxyaquic Udivitrands

TYPICAL PEDON: Hobnail ashy silt loam on a south-west facing slope of 30 percent at an elevation of 3,150 feet in a forested area. When described on September 22, 1986, the soil was moist throughout. (Colors are for dry soil unless otherwise noted.)

Oi--0 to 1 inch; slightly decomposed needles, leaves, twigs, and moss.

Oe--1 to 1.5 inches; decomposed organic matter mixed with 1980 Mt. St. Helens volcanic ash.

A--1.5 to 3 inches; grayish brown (10YR 5/2) ashy silt loam, very dark grayish brown (10YR 3/2) moist; weak very fine and fine granular structure; soft, very friable, nonsticky and slightly plastic; many very fine, fine and common medium roots; many very fine, fine and few medium tubular pores; slightly acid (pH 6.5); clear wavy boundary. (1 to 6 inches thick)

Bw1--3 to 8 inches; yellowish brown (10YR 5/4) ashy silt loam, dark yellowish brown (10YR 3/4) moist; weak fine and medium subangular blocky structure parting to weak fine granular; soft, very friable, nonsticky and slightly plastic; many very fine, fine, and common medium and coarse roots; many very fine, fine and few medium tubular pores; slightly acid (pH 6.5); gradual wavy boundary.

Bw2--8 to 16 inches; light yellowish brown (10YR 6/4) ashy silt loam, dark yellowish brown (10YR 4/4) moist; weak medium and coarse subangular blocky structure; soft, very friable, nonsticky and slightly plastic; many very fine and fine, common medium and coarse roots; many very fine, fine, and few medium tubular pores; neutral (pH 6.7); abrupt wavy boundary. (combined thickness of the Bw horizon is 11 to 18 inches)

2E--16 to 23 inches; very pale brown (10YR 7/3) silt loam, brown (10YR 5/3) moist; weak medium and coarse subangular blocky structure; slightly hard, friable, nonsticky and slightly plastic; few very fine and fine roots; common very fine and few fine tubular pores; common faint silt coatings on faces of peds; 5 percent gravel; slightly acid (pH 6.5); gradual wavy boundary. (0 to 10 inches thick)

2Bt/E--23 to 33 inches; mixed light brown (7.5YR 6/4) and very pale brown (10YR 7/3) silt loam, brown (7.5YR 4/4) and brown (10YR 5/3) moist; weak coarse prismatic structure parting to moderate medium and coarse angular blocky; very hard, very firm, slightly sticky and slightly plastic; few very fine and fine roots; common very fine and few fine tubular pores; common faint and distinct clay films on faces of peds and lining pores; 15 to 20 percent E material; 10 percent gravel; moderately acid (pH 6.0); gradual wavy boundary. (0 to 14 inches thick)

2Bt1--33 to 46 inches; light brown (7.5YR 6/4) gravelly silty clay loam, brown (7.5YR 4/4) moist; moderate coarse angular blocky structure; very hard, very firm, moderately sticky and moderately plastic; few very fine roots; common very fine and few fine tubular pores; many distinct clay films on faces of peds and lining pores; common medium manganese stains; common faint silt coatings on faces of peds; 15 percent gravel and 5 percent cobbles; strongly acid (pH 5.5); clear wavy boundary. (7 to 13 inches thick)

2Bt2--46 to 60 inches; reddish yellow (7.5YR 6/6) very gravelly clay loam, strong brown (7.5YR 4/6) moist; weak medium and coarse subangular blocky structure; very hard, very firm, moderately sticky and moderately plastic; common very fine and few fine tubular pores; common distinct clay films on faces of peds and lining pores; few fine manganese stains; common faint silt coatings on faces of peds; 25 percent gravel and 20 percent cobbles; very strongly acid (pH 5.0).

TYPE LOCATION: Benewah County, Idaho; about 4 miles west of Emida; about 1,115 feet west and 500 feet south of the northeast corner of section 34, T. 44 N., R. 3 W. Latitude - 47 degrees, 07 minutes, 17.6 seconds N.; Longitude - 116 degrees, 41 minutes, 45.0 seconds W.; NAD 83; USGS West Dennis quadrangle.

RANGE IN CHARACTERISTICS:
Soil moisture - usually dry for 25 to 35 consecutive days, moist mid-September through July, dry August to September
Average annual soil temperature - 42 to 47 degrees F
Average summer soil temperature - 47 to 50 degrees F with an O horizon
Depth to bedrock - greater than 60 inches
Depth to perched water table - 12 to 24 inches (February to April)
Volcanic ash mantle - 14 to 20 inches thick
Volcanic glass content in the 0.02 to 2.0 mm fraction - 15 to 60 percent
Acid-oxalate extractable Al plus 1/2 Fe - 1.0 to 2.7 percent
Phosphate retention - 55 to 95 percent
15-bar water retention on air dried samples - 7 to 12 percent

A horizon
Hue - 10YR or 7.5YR
Value - 3 to 6 dry, 2 to 4 moist
Chroma - 2 to 4, dry or moist
Gravel - 0 to 10 percent
Clay content - 3 to 9 percent
Bulk density - 0.65 to 0.90 g/cc
Reaction - moderately acid to neutral

Bw horizons
Hue - 10YR or 7.5YR
Value - 5 to 7 dry, 3 to 5 moist
Chroma - 3 to 6, dry or moist
Texture - ashy silt loam or ashy loam
Gravel - 0 to 10 percent
Cobbles - 0 to 5 percent
Clay content - 3 to 9 percent
Bulk density - 0.65 to 1.00 g/cc
Reaction - moderately acid to neutral

2E horizon
Hue - 10YR, 7.5YR or 5YR
Value - 6 to 8 dry, 3 to 6 moist
Chroma - 3 to 6 moist, 2 to 6 dry
Texture - loam, ot silt loam
Gravel - 0 to 20 percent
Cobbles - 0 to 10 percent
Clay content - 5 to 12 percent
Reaction - moderately acid to neutral

2BE or EB horizons present in some pedons
Hue - 10YR or 7.5YR
Value - 6 or 7 dry, 4 moist
Chroma - 4 dry or moist
Texture - silt loam or loam
Gravel - 0 to 10 percent
Clay content - 10 to 18 percent
Clay films - none to few, faint, on ped faces and in pores
Reaction - moderately acid or slightly acid

2Bt/E or 2E/Bt horizons
Hue - 10YR, 7.5YR or 5YR
Value - 6 to 8 dry, 4 to 6 moist
Chroma - 3 to 6, dry or moist
Texture - loam, silt loam or silty clay loam
Gravel - 0 to 20 percent
Cobbles - 0 to 10 percent
Clay content - 18 to 30 percent
Reaction - strongly acid to slightly acid
Base saturation (sum) - 35 to 75 percent

2Bt horizon
Hue - 10YR, 7.5YR or 5YR
Value - 4 to 8 dry, 3 to 6 moist
Chroma - 3 to 6, dry or moist
Texture - silt loam, loam, clay loam, sandy clay loam, or silty clay loam
Rock fragments - 5 to 25 percent in the upper part and 30 to 60 percent in the lower part
Clay content - 18 to 34 percent
Reaction - very strongly acid to moderately acid
Base saturation (sum of cations) - 35 to 75 percent

2BC or 2BCt horizon - present in some pedons
Hue - 10YR, 7.5YR , 5YR or 2.5Y
Value - 6 to 8 dry, 5 or 6 moist
Chroma - 3 to 8, dry or moist
Texture - loam, silt loam or sandy loam
Gravel - 15 to 45 percent
Cobbles - 5 to 15 percent
Para fragments - 10 to 35 percent
Total rock fragments - 30 to 70 percent
Clay content - 10 to 25 percent
Reaction - strongly acid to slightly acid

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING: Hobnail soils are on all aspects of dissected terraces and foothills. Slopes range from 5 to 35 percent. These soils formed in colluvium and tertiary alluvium derived dominantly from shale, quartzite, or mica schist, with a thick mantle of volcanic ash. Elevations range from 1,600 to 4,000 feet. The average annual air temperature ranges from 42 to 46 degrees F, and average annual precipitation is 30 to 50 inches. The frost-free period is from 80 to 110 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bouldercreek, Honeyjones, and Hugus soils and the Helmer soils. Bouldercreek and Honeyjones soils are on steeper, convex, north-facing backslopes of mountains and are ashy over loamy-skeletal. Hugus soils are on steeper, north-facing, convex, dissected terrace slopes and foothills, and are loamy-skeletal. Helmer soils are on concave terraces and have a fragipan.

DRAINAGE AND PERMEABILITY: Moderately well drained; medium to very rapid runoff; slow permeability. A seasonally perched water table is present at a depth of 1 to 2 feet, February to April.

USE AND VEGETATION: These soils are used for timber production, livestock grazing, recreation, wildlife habitat, hay and pasture, and homesites. Potential natural vegetation is mainly western hemlock, western redcedar, western white pine, grand fir, Douglas-fir, western larch, and lodgepole pine, with an understory of queencup beadlily, American trailplant, Columbia brome, violet, starry false-Solomon's-seal, sweetscented bedstraw, goldthread, Oregon fairybells, oneleaf foamflower, piper anemone, northern twinflower, and western rattlesnake plantain.

DISTRIBUTION AND EXTENT: Northern Idaho; MLRA 43A. This soil is moderately extensive.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Shoshone County, Idaho, 1993.

REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from 0 to 3 inches (Oi, Oe, and A horizons).
Cambic horizon - the zone from 3 to 16 inches (Bw1 and Bw2 horizons).
Albic horizon - the zone from 16 to 23 inches (2E horizon).
Glossic horizon - the zone from 23 to 33 inches (2Bt/E horizon).
Argillic horizon - the zone from 23 to 60 inches (2Bt/E, 2Bt1, 2Bt2 horizons).
Volcanic ash mantle - the zone from the mineral surface to 16 inches (A, Bw1, and Bw2 horizons).
Particle-size control section - the zone from the mineral surface to 40 inches (A, Bw1, Bw2, 2E, 2Bt/E and part of the 2Bt1 horizon).

Classification revised 1/09 from Ashy over loamy, amorphic over mixed, active, frigid Alfic Udivitrands to Ashy over loamy, amorphic over isotic frigid Oxyaquic Udivitrands.

ADDITIONAL DATA: Soil Survey Sample Number: S89ID-079-004. NSSL Sample Number: 89P748.

Series name was changed as directed by the Chief in November 2022.

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National Cooperative Soil Survey
U.S.A.