LOCATION BACKSWITCH IDEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, frigid Typic Haploxerepts
TYPICAL PEDON: Backswitch coarse sandy loam, forested -- on a west-facing slope of 43 percent at 4,350 feet elevation. When described on September 11, 2002, the soil was dry throughout. (Colors are for air-dry soil unless otherwise noted.)
Oi--0 to 2 inch; slightly decomposed forest litter.
A--2 to 8 inches; grayish brown (10YR 5/2) coarse sandy loam, very dark grayish brown (10YR 3/2) moist; weak fine and medium subangular blocky structure parting to weak fine granular; soft, very friable, nonsticky and nonplastic; common very fine and fine, few medium roots; many very fine and fine, few medium irregular pores; 10 percent fine gravel; moderately acid (pH 5.7); clear wavy boundary. (2 to 7 inches thick)
Bw1--8 to 14 inches; pale brown (10YR 6/3) fine gravelly coarse sandy loam, brown (10YR 4/3) moist; moderate fine and medium subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; few very fine, fine, medium and coarse roots; few very fine and fine irregular and tubular pores; 20 percent fine gravel; moderately acid (pH 6.0); clear smooth boundary.
Bw2--14 to 25 inches; light yellowish brown (10YR 6/4) fine gravelly coarse sandy loam, dark yellowish brown (10YR 4/4) moist; weak fine and medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; few very fine, fine and medium roots; few very fine and fine irregular and tubular pores; 20 percent fine gravel; slightly acid (pH 6.2); clear smooth boundary. (combined Bw horizon - 12 to 25 inches thick)
C--25 to 35 inches; very pale brown (10YR 7/4) very gravelly loamy coarse sand, yellowish brown (10YR 5/4) moist; massive; soft, very friable, nonsticky and nonplastic; few very fine and fine roots; few very fine and fine irregular pores; 40 percent fine gravel; neutral (pH 6.6); abrupt wavy boundary. (4 to 15 inches thick)
Cr--35 to 38 inches; highly fractured and moderately weathered granodiorite; clear smooth boundary. (2 to 10 inches thick)
R--38 inches; slightly weathered granodiorite.
TYPE LOCATION: Boise County, Idaho; about 1 mile northeast of New Centerville; 2,300 feet south and 2,300 feet west of the northeast corner of section 5, T.6 N., R.5 E.; USGS Placerville Quadrangle; Latitude - 43 degrees, 53 minutes, 13 seconds N. and Longitude - 115 degrees, 53 minutes, 22 seconds W.; NAD 83.
RANGE IN CHARACTERISTICS:
Ochric epipedon thickness - 2 to 8 inches
Depth to paralithic contact- 20 to 40 inches
Reaction - moderately acid through neutral
Particle-size control section - 4 to 12 percent clay; 10 to 35 percent rock fragments
Moisture control section - dry 45 to 75 consecutive days following the summer solstice
Average annual soil temperature - 41to 47 degrees F.
A horizon
Value - 4 or 5 dry, 2 or 3 moist
Chroma - 2 or 3 dry or moist
Rock fragments - 0 to 15 percent gravel
Bw horizon
Value - 6 or 7 dry, 4 or 5 moist
Chroma - 2 through 4 dry or moist
Texture - SL or COSL
Clay content - 5 to 15 percent
Rock fragments - 0 to 25 percent gravel
Base saturation (NH4OAc) - 60 to 85 percent
C horizon
Hue - 10YR or 2.5Y
Value - 6 or 7 dry, 4 or 5 moist
Chroma - 3 or 4 dry or moist
Texture - SL, COSL, LS or LCOS
Clay content - 3 to 10 percent
Rock fragments - 15 to 40 percent gravel, 0 to 20 percent cobbles, 0 to 10 percent stones and 15 to 50 percent total
Base saturation (NH4OAc) - 60 to 85 percent
BA horizons occur in some pedons
COMPETING SERIES: These are the Bouldrock, Selon, Snowshoe, and Stavely series. The Wagontown soils are similar and established in the same geographic area as the Backswitch series. Bouldrock soils are non-forested and do not have an O horizon, have darker values in the Bw and C horizons (4 or 5 dry, 2 or 3 moist), and 0 to 20 percent gravel in the C horizon, and lack a paralithic contact of weathered granodiorite over a lithic contact. Selon, Snowshoe and Stavely soils are 60 inches or more deep. Wagontown soils are sandy-skeletal and 40 to 60 inches deep.
GEOGRAPHIC SETTING: Backswitch soils are on hill and mountain slopes at elevations of 3,800 to 6,500 feet. These soils formed in colluvium and residuum from granitic rocks. Slopes range from 8 to 70 percent. The average annual precipitation is 20 to 28 inches. The average annual temperature is 39 to 45 degrees F. The frost-free period is 50 to 90 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Broad Canyon, Charters, Grousecreek, Shirts and Zimmer soils. Broad Canyon and Grousecreek soils are deep, Charters soils are very deep and Zimmer soils are shallow. These soils have mollic epipedons. They are on similar geomorphic positions.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; medium to very rapid runoff; moderately rapid permeability.
USE AND VEGETATION: Backswitch soils are used mainly for timber production and woodland grazing. Native vegetation is Douglas-fir, ponderosa pine, Geyers (elk) sedge, mountain snowberry, antelope bitterbrush, bluebunch wheatgrass, and in some places dwarf bilberry (huckleberry)or creeping barberry (Oregon grape).
DISTRIBUTION AND EXTENT: West-central Idaho. MLRA 43 and 44. Switchback soils are moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Boise County Area, Idaho, Parts of Ada and Boise Counties, 2005.
REMARKS: This OSD is written to include the Switchback soils as mapped and correlated in Elmore County Area, Idaho (1985). These soils are not Vitrandic as the Switchback soils have since been classified.
Diagnostic horizons and features recognized in this pedon:
Ochric epipedon - zone from 2 to 8 inches (A horizon)
Cambic horizon - zone from 8 to 25 inches (Bw1 and Bw2 horizons)
Particle-size control section - zone from 10 to 35 inches
Paralithic contact - at 35 inches (Cr)
Lithic contact - at 38 inches (R)
Soil moisture regime - xeric
Base saturation is assumed to be greater than 60 percent (NH4Oac) in some horizon between 10 and 30 inches and is based on lab data from the associated Stavely soil in Elmore County, ID.
All depths to diagnostic horizons and features within the range of characteristics are measured from the top of the first mineral horizon.