LOCATION HARKNESS IDEstablished Series
TAXONOMIC CLASS: Fine, smectitic Vertic Haplocryalfs
TYPICAL PEDON: Harkness silt loam - on a 35 percent north facing slope under Douglas-fir and subalpine fir at 6,800 feet elevation. (Colors are for air dry soil unless otherwise stated. When described, the soil was moist throughout.)
Oi--0 to 1 inch; slightly decomposed needles, leaves, twigs, and grasses. (0 to 4 inches thick)
Oe--1 to 2 inches; moderately decomposed needles, leaves, twigs, and grasses. (0 to 2 inches thick)
A1--2 to 5 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; weak coarse and medium subangular blocky structure parting to weak medium granular; soft, very friable, slightly sticky and slightly plastic; many very fine and fine and common medium and coarse roots; many very fine interstitial pores; about 10 percent pebbles; moderately acid (pH 5.6); abrupt smooth boundary. (3 to 5 inches thick)
A2--5 to 10 inches; brown (10YR 4/3) silt loam, very dark brown (10YR 2/2) moist; weak coarse and medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine and fine and common medium and coarse roots; many very fine tubular and common very fine interstitial pores; about 10 percent pebbles and cobbles; strongly acid (pH 5.5); clear wavy boundary. (0 to 5 inches thick)
E--10 to 16 inches; pale brown (10YR 6/3) very cobbly loam, dark yellowish brown (10YR 4/4) moist; weak medium subangular blocky structure parting to weak fine subangular blocky; hard, very friable, slightly sticky and slightly plastic; common very fine, fine and medium and few coarse roots; many very fine tubular and few very fine interstitial pores; 20 percent pebbles and 15 percent cobbles; strongly acid (pH 5.5); clear wavy boundary. (5 to 15 inches thick)
B/E--16 to 23 inches; light yellowish brown (10YR 6/4) clay loam, dark yellowish brown (10YR 4/6) moist; coatings of pale brown (10YR 6/3) E material on faces of peds, dark yellowish brown (10YR 4/4) moist; moderate medium and fine subangular blocky structure; hard, firm, moderately sticky and moderately plastic; common very fine, fine, and medium and few coarse roots; common very fine tubular pores; few faint clay films on faces of peds and in pores; about 10 percent pebbles and cobbles; very strongly acid (pH 5/3); gradual wavy boundary. (7 to 17 inches thick)
Bt1--23 to 36 inches; light yellowish brown (10YR 6/4) silty clay loam, dark yellowish brown (10YR 4/6) moist; strong coarse and medium angular blocky structure; hard, firm, moderately sticky and moderately plastic; common very fine and fine and few medium roots mostly along faces of peds and in cracks; common very fine tubular pores; many strong brown (7.5YR 4/6) prominent clay films on faces of peds and in pores; about 10 percent pebbles and cobbles; strongly acid (pH 5.2); diffuse wavy boundary.(19 to 26 inches thick)
Bt2--36 to 62 inches; light yellowish brown (10YR 6/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; strong coarse and medium angular blocky structure; hard, firm, moderately sticky and moderately plastic; common very fine and fine roots mostly along faces of peds and in cracks; few very fine tubular pores; common strong brown (7.5YR 5/6) distinct clay films on faces of peds and in pores; about 10 percent pebbles and cobbles; strongly acid (pH 5.2).
TYPE LOCATION: Bannock County, Idaho; about 11 miles east and 2 miles north of Downey; 1,000 feet south and 200 feet east of the northwest corner of sec. 21, T. 11 S., R. 39 E.
RANGE IN CHARACTERISTICS:
Moisture regime - udic
Average annual soil temperature - 36 to 40 degrees F
Solum thickness - 60 inches or more
Particle-size control section - 35 to 55 percent clay (upper 20 inches
of the argillic horizon)
A Horizon
Color value, dry - 4 or 5
Value, moist - 2 or 3
Chroma, dry or moist - 2 or 3
Reaction - strongly acid to moderately acid
E Horizon
Color value, dry - 6 through 8
Value, moist - 4 or 5
Chroma, dry or moist - 2 through 4
Texture - very cobbly loam, stony silt loam
Clay - 15 to 25 percent
Rock fragments - 15 to 40 percent
Reaction - strongly acid to moderately acid
Bt Horizon
Color hue, dry or moist - 7.5YR through 10YR
Value, dry - 5 through 7
Value, moist - 4 through 6
Chroma, dry or moist - 3 through 6
Texture - clay loam, silty clay loam, cobbly silty clay
Clay - 35 to 55 percent
Rock fragments - 5 to 30 percent
Reaction - very strongly acid to slightly acid
COMPETING SERIES: These are the Goldhill and Herd series. Goldhill soils have a calcic horizon and a xeric soil moisture regime. Herd soils lack and O and E horizons and are cobbly or gravelly in the surface 20 inches.
GEOGRAPHIC SETTING: Harkness soils are on mountainslopes. Slopes range from 20 to 50 percent. They formed in colluvium from a variety of sedimentary and metasedimentary rocks, dominantly sandstone and quartzite. The average annual precipitation ranges from 22 to 32 inches and the average annual temperature ranges from 35 to 39 degrees F. The frost-free period is less than 50 days. Elevation ranges from 6,000 to 8,000 feet.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Beaverdam, Broadhead, Hades, Mikesell, Sedgway, Toponce, and Valmar series. The Beaverdam, Toponce, and Broadhead soils have mollic epipedons. Hades soils have a mollic epipedon and a fine-loamy control section. Mikesell soils have moist color value of 4 or more in their upper horizons, after mixing to a depth of 6 inches. Sedgway soils have a mollic epipedon and a loamy-skeletal control section. Valmar soils have a mollic epipedon, a loamy-skeletal control section, and have bedrock at 20 to 40 inches. Beaverdam soils occur on similar landforms at lower elevations and slightly warmer and drier positions. Broadhead soils occur on footslopes and fan terraces at lower elevations and generally have slopes of less than 30 percent. Hades and Valmar soils are on south and west-facing mountainslopes. Mikesell soils are found in concave positions on the same landscape as Harkness. Sedgway soils occupy nearby landscapes and are generally higher on the slope near the shoulder or in convex slope positions. Toponce soils are on footslopes at the lower limit of the elevation range of Harkness and generally have slopes less than 30 percent.
DRAINAGE AND PERMEABILITY: Well drained; runoff is rapid or very rapid; permeability is slow.
USE AND VEGETATION: Used for timber production and grazing. The principal native plants at climax are an overstory dominated by subalpine fir and an understory dominated by pine reedgrass.
DISTRIBUTION AND EXTENT: Southeastern Idaho; MLRA 13. This series is inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Bannock County, Idaho, 1983.