LOCATION JOHNSON IDEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Ultic Argixerolls
TYPICAL PEDON: Johnson loam, on a 37 percent east-facing slope at 3,900 feet elevation in forest. When described on May 8, 1974, the soil was moist throughout. (Colors are for dry soil unless otherwise noted.)
Oi--0 to 1 inch; fresh and partially decomposed needles and twigs.
A1--1 to 3 inches; very dark grayish brown (10YR 3/2) loam, very dark brown (10YR 2/2) moist; moderate fine granular structure; soft, very friable, slightly sticky and slightly plastic; many fine roots; many fine irregular pores; moderately acid (pH 5.8); abrupt smooth boundary. (0 to 4 inches thick)
A2--3 to 8 inches; dark brown (10YR 3/3) loam, very dark brown (10YR 2/2) moist; moderate fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; many fine roots; many fine irregular pores; moderately acid (pH 6.0); gradual smooth boundary. (4 to 8 inches thick)
A3--8 to 20 inches; dark yellowish brown (10YR 4/4) loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure parting to moderate medium granular; hard, very friable, slightly sticky and slightly plastic; many fine roots; many fine irregular pores; moderately acid (pH 6.0); clear smooth boundary. (5 to 15 inches thick)
BA--20 to 28 inches; brown (7.5YR 4/4) loam, dark yellowish brown (10YR 3/4) moist; weak fine subangular blocky structure; very hard, friable, moderately sticky and moderately plastic; common fine roots; many fine tubular pores; few faint clay films; slightly acid (pH 6.2); gradual smooth boundary. (0 to 10 inches thick)
Bt1--28 to 40 inches; brown (7.5YR 4/4) loam, dark brown (7.5YR 3/4) moist; moderate fine and medium subangular blocky structure; very hard, friable, moderately sticky and moderately plastic; common fine and few coarse roots; many fine tubular pores; few distinct clay films; slightly acid (pH 6.4); gradual smooth boundary. (8 to 15 inches thick)
Bt2--40 to 56 inches; brown (7.5YR 4/4) clay loam, dark brown (7.5YR 3/4) moist; moderate fine and medium subangular blocky structure; extremely hard, friable, moderately sticky and moderately plastic; few fine and coarse roots; common fine tubular pores; few distinct clay films; neutral (pH 6.6); gradual smooth boundary. (10 to 20 inches thick)
Bt3--56 to 66 inches; brown (7.5YR 4/4) loam, dark brown (7.5YR 3/4) moist; weak fine subangular blocky structure; extremely hard, friable, moderately sticky and moderately plastic; few fine roots; common fine tubular pores; few faint clay films; neutral (pH 6.6).
TYPE LOCATION: Idaho County, Idaho; about 8 miles east of Riggins; about 100 feet south and 400 feet west of the northeast corner of section 24, T. 24 N., R. 2 E. Latitude - 45 degrees, 24 minutes, 43 seconds North; Longitude - 116 degrees, 08 minutes, 52 seconds West; USGS Riggins Hot Springs Quadrangle.
RANGE IN CHARACTERISTICS:
Thickness of mollic epipedon - 10 to 20 inches
Sand content - 30 to 45 percent sand coarser then very fine sand Depth to bedrock and solum thickness - 40 to 60 inches or more
Base saturation - 50 to 75 percent in some part between 10 and 30 inches
Days dry, moisture control section - 45 to 60 during late summer and autumn. Xeric moisture regime.
Average annual soil temperature - 41 to 47 degrees F. Frigid temperature regime.
Particle-size control section (weighted averages)
Clay content - 20 to 35 percent
Coarse fragment content - 0 to 30 percent
A horizon
Hue - 7.5YR or 10YR moist
Value - 3 through 5 dry, 2 or 3 moist
Chroma - 2 through 4 dry, 2 or 3 moist
Textures - L, SIL
Clay content - 12 to 25 percent
Rock fragments - 0 to 14 percent gravel
Reaction - moderately acid to neutral
AB or BA horizons (present in some pedons)
Hue - 7.5YR or 10YR moist
Value - 3 or 4 moist
Chroma - 3 or 4 dry, 2 to 4 moist
Textures - L, CL, SCL
Clay content - 20 to 31 percent
Rock fragments - 0 to 14 percent gravel
Reaction - moderately acid to neutral
Bt horizons
Hue - 5YR, 7.5YR, or 10YR
Value - 4 to 6 dry, 3 or 4 moist
Chroma - 2 to 6 dry or moist
Textures - L, CL, GR-L, GR-CL, CB-L, CB-CL, SIL, SCL
Rock fragment content - 0 to 30 percent gravel, 0 to 15 percent cobbles, 0 to 30 percent total rock fragment content
Clay content - 18 to 38 percent
Reaction - moderately acid to neutral
Present in some pedons - BC and C horizons
Hue - 7.5YR or 10YR
Value - 5 or 6 dry, 3 or 4 moist
Chroma - 3 through 6, dry or moist
Textures - GR-CL, GR-L, SCL, SL, COSL, CBV-CL
Clay content - 12 to 27 percent
Rock fragments - 10 to 20 percent gravel, 0 to 60 percent cobbles, 10 to 60 percent total rock fragment content
COMPETING SERIES: These are the Carmack, Elkcreek, Middlefork, Mojo, Molyneux, Muldoon, Simonton, Skelter, Suloaf, and Trojan series. Middlefork soils have horizons containing lamellae. Molyneux, Skelter, and Trojan soils are usually dry for more than 60 days in summer and early fall. Carmack and Suloaf soils are less than 30 percent coarser than very fine sand. Elkcreek and Mojo soils are moderately deep. Muldoon soils are deep to a duripan. Simonton soils have a solum less than 40 inches thick.
GEOGRAPHIC SETTING: Johnson soils are on mountains, hill sides, canyon sides, and benches and have slopes of 5 to 75 percent. They formed in residuum from granitic or metamorphic rocks and loess. Elevations are 1,000 to 4,000 feet. The climate is subhumid with cold winters and warm summers. Average annual precipitation is 22 to 30 inches. Average annual temperature is 40 to 46 degrees F. Frost-free season is 80 to 125 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Brownlee, De Masters, and Nazaton soils. Brownlee soils have average annual soil temperature above 47 degrees F. De Masters soils are Pachic. Nazaton soils are Pachic and have less than 18 percent clay in the control section .
DRAINAGE AND PERMEABILITY: Well drained; medium to very rapid runoff; moderate or moderately slow permeability.
USE AND VEGETATION: Used mainly for production of small grains, timber production, and livestock grazing. Vegetation is mainly ponderosa pine, scattered Douglas-fir, snowberry and associated plants.
DISTRIBUTION AND EXTENT: The Johnson series is of moderate extent in north central Idaho.
MLRA OFFICE RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Idaho County, Idaho, 1976.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from 1 to 20 inches (A1, A2, A3 horizons)
Argillic horizon - the zone from 28 to 66 inches (Bt1, Bt2 and Bt3 horizons)
Particle-size control section - the zone from 28 to 48 inches (Bt1 and part of the Bt2 horizons)
The deep phase of Johnson is used only in Clearwater SSA.