LOCATION LARKIN ID+WAEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Ultic Argixerolls
TYPICAL PEDON: Larkin silt loam, forested; on a 22 percent convex west-facing slope at 3,040 feet elevation. Described on April 28, 1977. (Colors are for dry soil unless otherwise noted.)
Oi--0 to 1 inch; slightly needles, leaves, grass, and twigs. (0 to 2 inches thick)
Oe--1 to 1.5 inches; moderately decomposed needles, leaves, grass, and twigs. (0 to 1 inch thick)
A1--1.5 to 6 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; weak fine subangular blocky structure parting to fine granular; slightly hard, very friable, slightly sticky and slightly plastic; many very fine, fine, and medium and few coarse roots; many very fine and fine irregular pores; worm holes throughout; neutral (pH 6.6); clear wavy boundary. (2 to 8 inches thick)
A2--6 to 11 inches; brown (10YR 5/3) silt loam, very dark grayish brown (10YR 3/2) moist; weak fine and medium subangular blocky structure parting to moderate fine and medium granular; slightly hard, friable, slightly sticky and slightly plastic; many very fine, and medium and common coarse roots; many very fine and fine and few medium continuous tubular pores; worm holes throughout; slightly acid (pH 6.4); clear wavy boundary. (2 to 10 inches thick)
AB--11 to 17 inches; brown (10YR 5/3) silt loam, dark brown (10YR 3/3) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine, fine, and medium and common coarse roots; many very fine and fine and common medium continuous tubular pores; few light gray (10YR 7/2) silt coating on faces of peds; worm holes throughout; slightly acid (pH 6.4); clear wavy boundary. (0 to 10 inches thick)
Bt1--17 to 23 inches; yellowish brown (10YR 5/4) silt loam, dark yellowish brown (10YR 4/4) moist; weak medium prismatic structure parting to moderate fine and medium subangular blocky; hard, firm, slightly sticky and slightly plastic; common very fine and coarse and many fine and medium roots; many very fine and fine and common medium continuous tubular pores; few faint brown (7.5YR 5/4) clay films on faces of peds; light gray (10YR 7/2) silt coating on faces of peds; worm holes throughout; slightly acid (pH 6.2); clear smooth boundary. (5 to 18 inches thick)
Bt2--23 to 37 inches; yellowish brown (10YR 5/4) silt loam, dark yellowish brown (10YR 4/4) moist; moderate medium and coarse prismatic structure parting to strong fine subangular blocky; very hard, very firm, slightly sticky and slightly plastic; many very fine, common fine and medium, and few coarse roots; many very fine and fine and common medium continuous tubular pores; common faint brown (7.5YR 5/4) clay films on faces of peds; common light gray (10YR 7/2) silt coating on faces of peds; worm holes throughout; moderately acid (pH 6.0); clear wavy boundary. (10 to 20 inches thick)
Btc1--37 to 51 inches; yellowish brown (10YR 5/4) silt loam, dark yellowish brown (10YR 4/4) moist; moderate medium and coarse prismatic structure parting to moderate fine subangular blocky; very hard, very firm, sticky and plastic; many very fine and common fine, medium, and coarse roots; many very hard, very firm, moderately sticky and moderately plastic; many very fine and common fine, medium, and coarse roots; many very fine, fine, and medium continuous tubular pores; many distinct reddish brown (5YR 5/4) clay films on faces of peds and in pores; common light gray (10YR 7/2) silt coating on faces of peds; many fine (less than 2 mm) iron and manganese concretions; worm holes throughout; moderately acid (pH 6.0); gradual wavy boundary. (10 to 20 inches thick)
Btc2--51 to 62 inches; yellowish brown (10YR 5/4) silt loam, dark yellowish brown (10YR 4/4) moist; weak coarse prismatic and structure parting to moderate fine subangular blocky; very hard, firm, moderately sticky and slightly plastic; common fine, medium, and coarse and many very fine roots; many very fine, fine, and medium continuous tubular pores; many prominent and distinct reddish brown (5YR 5/4) clay films on faces of peds and in pores; many fine (less than 2 mm) iron and manganese concretions; few light gray (10YR 7/2) silt coating on faces of peds; worm holes throughout; slightly acid (pH 6.2).
TYPE LOCATION: Latah County, Idaho; about 2 1/2 miles north of Viola, Idaho, about 400 feet south and 1,170 feet west of the northeast corner of section 30, T. 41 N., R. 5 W.; (Latitude - 46 degrees, 52 minutes, 22 seconds North and Longitude - 117 degrees, 00 minutes, 19 seconds West; USGS Viola Quadrangle).
RANGE IN CHARACTERISTICS:
Thickness of mollic epipedon - 10 to 20 inches
Base saturation - 50 to 75 percent in some part between 10 and 30 inches
Days dry in soil moisture control section - 45 to 75
Mean annual soil temperature - 47 to 54 degrees F
Particle-size control section (weighted average) clay content - 20 to 35 percent
A or Ap horizon
Hue - 10YR or 7.5YR
Value - 4 or 5 dry, 2 or 3 moist
Chroma - 2 or 3, dry or moist
Texture - SIL, SICL, ASHY SIL
Clay content - 15 to 27 percent
Rock fragments - 0 to 5 percent
Reaction - moderately acid to neutral
AB horizon (present in some pedons)
Hue - 10YR or 7.5 YR
Value - 4 to 6 dry, 2 to 4 moist
Chroma - 2 or 3 dry, 3 or 4 moist
Texture - SIL or SICL
Clay content - 15 to 27 percent
Rock fragments - 0 to 5 percent
Reaction - moderately acid to neutral
Bt and Btc horizons:
Hue - 10YR or 7.5YR
Value - 4 to 6 dry, 3 to 5 moist
Chroma - 3 to 6 dry or moist
Texture - SIL, SICL
Clay content - 20 to 35 percent
Rock fragments - 0 to 5 percent
Reaction - moderately acid to neutral
2Bt/E horizons (present in some pedons):
Bt part
Hue - 10YR or 7.5YR
Value - 3 or 4, dry or moist
Chroma - 3 or 4 moist
Clay content - 20 to 24 percent
Rock fragments - 0 to 5 percent
E part
Value - 5 to 7, dry or moist
Chroma - 3 or 4, dry or moist
Reaction - slightly acid or neutral
2Bt horizons (present in some pedons):
Value - 5 or 6 dry, 3 or 4 moist
Chroma - 3 to 6, dry or moist
Clay content - 27 to 35 percent
Rock fragments - 0 to 5 percent gravel
Reaction - moderately acid to neutral
COMPETING SERIES: This is the Hillsboro series. Hillsboro soils have mean annual soil temperature of 54 to 56 degrees F. and has stratified loamy and sandy material below 40 inches.
GEOGRAPHIC SETTING: The soils are on hills, plateaus and structural benches. Slopes are 0 to 60 percent. Elevation is 1,200 to 3,700 feet in Idaho and up to 4,500 feet in Washington. The soils formed dominantly in loess. In some areas, it formed from loess over residuum from basalt or loess mixed with minor amounts of volcanic ash in the surface. The mean annual precipitation is 18 to 30 inches. The mean annual temperature is 45 to 52 degrees F. The frost-free period is 90 to 180 days (9 years in 10 to 1 year on 10, respectively).
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Driscoll, Latahco, and Southwick soils. Driscoll soils on summits and sholder slopes are moderately well drained and have an albic horizon. Latahco soils formed in alluvium and are in bottomlands. Southwick soils on south or west-facing backslopes have an albic horizon.
DRAINAGE AND PERMEABILITY: Well drained; medium through very rapid runoff; moderately slow permeability.
USE AND VEGETATION: These soils are dominantly used for cropland. Some are used for woodland. The potential natural vegetation is mainly ponderosa pine, mallow ninebark, common snowberry, elk sedge, and bluebunch wheatgrass.
DISTRIBUTION AND EXTENT: Northern Idaho and eastern Washington. MLRA9. The series is moderately extensive.
MLRA OFFICE RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Latah County, Idaho, 1944.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from 1.5 to 17 inches (the A1, A2, and AB horizons)
Argillic horizon - the zone from 17 to 62 inches (the Bt1, Bt2 Btc1, and Btc2 horizons)
Particle-size control section - the zone from 17 to 37 inches (the Bt1 and Bt2 horizons)
Depths to diagnostic horizons and features recognized in this pedon are measured from the top of the first mineral horizon.
When this soil is recognized over loess and residuum from basalt, 2B/E and 2Bt horizons are present. This occurs in Clearwater County, Idaho.
In Spokane County, Washington this soil is recognized as a taxadjunct and meets vitrandic subgroup criteria. Further investigation is needed to check the extent of this taxadjunct in other counties.