LOCATION RISWOLD                 ID

Established Series
Rev. PNP-BGD-EMM
07/2013

RISWOLD SERIES

The Riswold series consists of very deep, well drained soils that formed in volcanic ash and loess over material weathered from basalt. Riswold soils are on hills on plateaus and escarpments, and sideslopes and structural benches in canyons and have slopes of 5 to 70 percent. They have moderately slow permeability. The average annual precipitation is about 35 inches and the average annual temperature is about 42 degrees F.

TAXONOMIC CLASS: Fine-silty, mixed, superactive, frigid Andic Hapludalfs

TYPICAL PEDON: Riswold ashy silt loam, forested--on a 62 percent northerly aspect at an elevation of 2,800 feet. When described on August 8, l983, the profile was moist throughout. (Colors are for dry soil unless otherwise stated.)

0i--0 to 1.5 inches; leaves, needles, twigs, moss, and roots. (1 to 3 inches thick)

A--1.5 to 9 inches; yellowish brown (10YR 5/4) ashy silt loam, dark yellowish brown (10YR 3/4) moist; weak fine subangular blocky structure parting to weak fine granular; soft, very friable; slightly sticky and nonplastic; many very fine, fine and medium roots; many very fine irregular pores; 5 percent gravel; neutral (pH 6.8); clear smooth boundary. (1 to 8 inches thick)

Bw--9 to 17 inches; light yellowish brown (10YR 6/4) ashy silt loam, dark yellowish brown (10YR 4/4) moist; weak fine subangular blocky structure; soft, very friable, slightly sticky and nonplastic; many very fine, fine and medium, few coarse roots; many very fine irregular pores; 5 percent gravel; slightly acid (pH 6.5) clear wavy boundary. (4 to 15 inches thick)

2E/Bt--17 to 27 inches; E - pale brown (10YR 6/3) silt loam, brown (10YR 5/3) moist; B - brown (10YR 5/3) silt loam, dark brown (10YR 3/3) moist; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine, fine and medium, few coarse roots; many very fine and fine tubular, many very fine irregular pores; common faint clay films on faces of peds and lining pores; few faint uncoated silt grains on faces of peds; 5 percent gravel; slightly acid (pH 6.4) clear wavy boundary. (0 to 25 inches thick)

2Bt/E1--27 to 37 inches; B - brown (10YR 5/3) silt loam, brown (10YR 4/3) moist; E - very pale brown (10YR 7/3) silt loam, brown (10YR 5/3) moist; weak fine prismatic structure parting to moderate fine subangular blocky; slightly hard, firm, moderately sticky and slightly plastic; common very fine and fine roots; many very fine and fine tubular, common very fine irregular pores; many faint, few distinct clay films on faces of peds and lining pores; 10 percent gravel; few faint uncoated silt grains on faces of peds; slightly acid (pH 6.4); gradual wavy boundary.

2Bt/E2--37 to 44 inches; B - brown (10YR 5/3) gravelly silt loam, brown (10YR 4/3) moist; E - very pale brown (10YR 7/3), gravelly silt loam brown (10YR 5/3) moist; moderate fine prismatic structure; hard, firm, moderately sticky and slightly plastic; common very fine and fine roots; many very fine and fine tubular and common very fine irregular pores; common distinct clay films on faces of peds and lining pores; 15 percent gravel, common uncoated silt grains on faces of peds; slightly acid (pH 6.2); gradual wavy boundary. (2B/E horizons 10 to 24 inches thick)

3Bt1--44 to 60 inches; brown (10YR 5/3) cobbly silty clay loam, brown (10YR 4/3) moist; moderate fine and medium prismatic structure; hard, firm, moderately sticky and moderately plastic; few very fine and fine roots; many very fine, fine, few medium tubular, many very fine irregular pores; many distinct clay films on faces of peds and lining pores; 10 percent gravel and 10 percent cobbles; common uncoated silt grains on faces of peds; slightly acid (pH 6.2); clear smooth boundary. (10 to 33 inches thick)

3Bt2--60 to 72 inches; pale brown (10YR 6/3) very cobbly silty clay loam, brown (10YR 4/3) moist; weak fine subangular blocky structure; slightly hard, firm, moderately sticky and moderately plastic; few very fine, fine and coarse roots; many very fine, fine, few medium tubular, many very fine irregular pores; many distinct clay films on faces of peds and lining pores; 15 percent gravel and 40 percent cobbles, few fine silt coats on faces of peds; moderately acid (pH 5.8).

TYPE LOCATION: Clearwater County, Idaho; about 8.5 miles north of Ahsahka; about 3,000 feet north and 700 feet east of the southwest corner of section 22, T. 38 N., R. 1 E.; Latitude - 46 degrees, 37 minutes, 20 seconds North; Longitude - 116 degrees, 19 minutes, 34 seconds West; USGS Ahsahka Quadrangle.

RANGE IN CHARACTERISTICS:

Base saturation in the argillic - 50 to 60 percent
Average annual soil temperature - 39 to 45 degrees F.
Frigid temperature regime
Soil moisture control section - not dry for 45 consecutive days during 4 months that follow summer solstice.
Udic moisture regime
Thickness of volcanic ash influenced horizons - 10 to 23 inches
Volcanic glass content - 5 to 25 percent
Acid-oxalate extractable Al plus 1/2 Fe - 1.0 to 1.5 percent
Phosphate retention - 60 to 70 percent
15-bar water retention on air dried samples - 7 to 12 percent

A horizon
Hue - 7.5YR or 10YR moist
Value - 3 to 6 dry, 2 to 4 moist
Chroma - 2 to 4 dry or moist
Clay content - 8 to 15 percent
Rock fragments - 0 to 5 gravel
Reaction - moderately acid to neutral
Bulk density - 0.70 to 0.90 g/cc

Bw horizon
Hue - 7.5YR or 10YR moist
Value - 5 or 6 dry, 2.5 to 4 moist
Chroma - 4 to 7 dry, 3 to 7 moist
Textures - ashy-silt loam or ashy-loam
Clay content - 8 to 16 percent
Rock fragments - 0 to 10 percent gravel
Reaction - moderately acid to neutral
Bulk density - 0.90 to 1.20 g/cc

2E/Bt horizons (absent in some profiles)
Color of E -
Hue - 7.5YR or 10YR moist
Value - 6 or 7 dry, 3 to 5 moist
Chroma - 3 or 4 dry, 3 to 6 moist
Color of Bt -
Hue - 7.5YR or 10YR moist
Value - 5 or 6 dry and 3 or 4 moist
Chroma - 3 or 4 dry and 3 to 6 moist
Textures (2E/Bt) - silt loam
Clay content - 16 to 25 percent
Rock fragments - 0 to 15 percent gravel
Reaction - strongly acid to slightly acid

2Bt/E horizons
Color of Bt -
Hue - 7.5YR or 10YR moist
Value - 5 or 6 dry, 3 or 4 moist
Chroma - 3 to 5 dry and 3 to 6 moist
Color of E -
Hue - 7.5YR or 10YR moist
Value - 5 to 7 dry and 4 or 5 moist
Chroma - 3 or 4 dry or moist
Textures - silt loam or silty clay loam
Clay content (2Bt/E horizons) - 18 to 30 percent
Rock fragments - 0 to 20 percent gravel, 0 to 5 percent cobbles, 0 to 20 percent total fragments
Reaction - very strongly acid to slightly acid

3Bt horizons
Hue - 7.5YR or 10YR dry or moist
Value - 5 to 7 dry and 3 or 4 moist
Chroma - 3 to 6 dry or moist
Textures - silty clay loam, clay loam, silt loam or loam
Clay content - 18 to 38 percent
Rock fragments - 5 to 40 percent gravel, 5 to 40 percent cobbles, 0 to 5 percent stones, 10 to 60 percent total fragments
Reaction - very strongly acid to slightly acid

3BC or 3C horizons (when present)
Hue - 7.5YR or 10YR dry or moist
Value - 4 to 8 dry, 3 to 6 moist
Chroma - 1 to 6 dry or moist
Texture - clay loam, loam or silt loam
Clay content - 18 to 28 percent
Rock fragments - 5 to 60 percent gravel, 5 to 40 percent cobbles, 10 to 90 percent total fragments
Reaction - strongly to slightly acid

COMPETING SERIES: These are the Bandmill, Brequito, and Scaler series. Bandmill soils have less than 10 percent rock fragments throughout. Brequito soils have less than 5 percent cobbles in the argillic horizon. Scaler soils have 30 to 85 percent mica in the 3Bt and 3C horizons.

GEOGRAPHIC SETTING: Riswold soils are on canyon sides, hills, plateaus, and structural benches at elevations of 1,600 to 3,800 feet with slopes of 5 to 70 percent. These soils formed in volcanic ash and loess over material weathered from basalt. The average annual temperature ranges from 38 to 44 degrees F. The average annual precipitation ranges from 28 to 55 inches and the frost-free period is 50 to 110 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Elkridge, Grangemont and Kauder series. The Elkridge soils are loamy-skeletal and are on convex positions. Grangemont soils contain fragic material and are on concave positions on plateaus. The Kauder soils have a fragipan and are on plateaus.

DRAINAGE AND PERMEABILITY: Well drained; runoff is medium to very rapid; permeability is moderately slow.

USE AND VEGETATION: This soil is used primarily for timber production, livestock grazing, wildlife habitat, and watershed. The natural vegetation is western red cedar, grand fir, Douglas-fir, western larch, queencup beadlily, goldthread, longtube twinflower, common snowberry and Myrtle pachystima.

DISTRIBUTION AND EXTENT: North-central Idaho; Riswold soils are moderately extensive. MLRA 43A.

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

SERIES ESTABLISHED: Clearwater County, Idaho, 2003.

REMARKS: Diagnostic horizons and features recognized in this pedon are:

Ochric epipedon - The zone from 0 to 9 inches (Oi and A horizons).

Cambic horizon - The zone from 9 to 17 inches (Bw horizon).

Volcanic ash cap - The zone from 1.5 to 9 inches (A horizon).

Argillic horizon - The zone from 17 to 72 inches (2E/Bt, 2Bt/E, and 3Bt horizons).

Particle-size control section - The zone from 17 to 37 inches (2E/Bt, and the 2Bt/E horizons).

The ranges of values listed under the Range In Characteristics for the soil properties Bulk Density, Volcanic glass content, Acid-oxalate Al+1/2 Fe, Phosphate retention and 15-bar water retention are estimates only.

Additional data: This series has laboratory data S92-ID-035-025 (92P963) Clearwater county, Idaho; by NSSL, Lincoln, NE.

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National Cooperative Soil Survey
U.S.A.