LOCATION UHLORN IDEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Typic Argixerolls
TYPICAL PEDON: Uhlorn silt loam, on a 10 percent east-facing slope at 3,890 feet elevation in a cultivated field. When described on June 7, 1962 the soil was moist throughout. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 6 inches; very dark gray (10YR 3/1) silt loam, black (10YR 2/1) moist; moderate fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; many fine roots; many fine irrregular pores; neutral (pH 6.6); abrupt smooth boundary. (6 to 7 inches thick)
A--6 to 13 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; weak medium and coarse prismatic structure parting to weak fine subangular blocky; slightly hard, very friable, slightly sticky and slightly plastic; common fine roots; common tubular pores; few worm holes and krotovinas filled with browner soil material; slightly acid (pH 6.3); clear smooth boundary. (6 to 8 inches thick)
BAt--13 to 18 inches; brown (10YR 5/3) silt loam, dark brown (10YR 3/3) moist; moderate fine subangular blocky structure; hard, friable, slightly sticky and plastic; common fine roots; common fine tubular pores; few faint clay films; few uncoated silt grains mostly on vertical faces of peds; slightly acid (pH 6.3); clear smooth boundary. (4 to 6 inches thick)
Bt1--18 to 33 inches; yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; moderate medium and fine subangular blocky structure; very hard, firm, slightly sticky and plastic; common fine roots; common fine tubular pores; continuous distinct clay films; common uncoated silt grains coating most vertical surfaces of peds; slightly acid (pH 6.4); gradual smooth boundary. (12 to 16 inches thick)
Bt2--33 to 42 inches; yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; moderate medium and fine subangular blocky structure; very hard, very firm, sticky and plastic; few fine roots; common fine tubular pores; continuous distinct clay films; many uncoated silt grains on all surfaces of peds; slightly acid (pH 6.2); clear smooth boundary. (8 to 10 inches thick)
2Bt3--42 to 60 inches; brown (7.5YR 5/3) silty clay loam, dark brown (7.5YR 3/4) moist; moderate fine angular block structure; very hard, very firm, sticky and plastic; few fine roots; few fine tubular pores; continuous prominent clay films; slightly brittle; few fine black iron-manganese concretions; 10 percent weathered fine gravel, increasing in number with increasing depth; neutral (pH 6.9).
TYPE LOCATION: Idaho County, Idaho; about 2 miles south of Ferdinand; in a road cut, south side of road; 1,360 feet north and 1,480 feet west of the southeast corner of section 12, T.32 N., R.1 W. Latitude - 46 degrees, 07 minutes, 32 seconds North; Longitude - 116 degrees, 23 minutes, 41 seconds West; Craigmont USGS topographic quadrangle.
RANGE IN CHARACTERISTICS:
Thickness of mollic epipedon - 10 to 20 inches
Organic matter content in the mollic epipedon (weighted average) - 3 to 6 percent
Base saturation - 75 to 90 percent between depths of 10 and 30 inches Depth to bedrock - greater than 60 inches
The soil is usually moist between depths of 4 and 12 inches but is dry for 45 to 60 days in late summer
Average summer soil temperature - 60 to 64 degrees F
Average annual soil temperature - 47 to 51 degrees F
Particle-size control section
Clay content - averages 30 to 35 percent
A horizon
Value, upper part - 3 through 5 dry, 2 or 3 moist
Chroma, upper part - 1 through 3, dry or moist
Reaction - moderately acid through neutral
Bt horizon
Hue - 10YR or 7.5YR
Value - 5 or 6 dry, 3 through 5 moist
Chroma - 3 through 6 dry, 3 or 4 moist
Texture, upper part - SIL, SICL
Texture, lower part - SICL with minor amounts of CL
Clay content, upper part - 24 to 32 percent
Clay content, lower part - 28 to 35 percent
There are few to many uncoated silt grains on peds.
The lower parts contain up to 10 percent gravel, and contain lime in veins in some pedons.
Reaction - slightly acid through mildly alkaline
Present in some pedons - Btb horizon
COMPETING SERIES: This is the Darrah (T) series. Darrah soils have Btb horizons with 35 to 50 percent clay in the lower part of the series control section and would have and arid soil moisture regime if not for additional moisture received from run-on.
GEOGRAPHIC SETTING: The soils are on hills on plateaus, mainly on north-facing slopes. Slopes are 2 to 65 percent. The elevation ranges from 2,600 to 4,200 feet. The soils formed mostly in loess. The average annual precipitation is 21 to 24 inches. Average annual temperature is 44 to 49 degrees F. The frost free season ranges from 100 to 140 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Meland, Nez Perce and Riggins soils. Meland soils are moderately deep and fine-loamy, and are on hillsides. Nez Perce soils have albic horizons and clayey Bt horizons, and are on convex slopes and drier aspects. Riggins soils are shallow to bedrock, and are on canyon rims.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; moderately slow permeability.
USE AND VEGETATION: Uhlorn soils are used mostly for production of dryland wheat, peas, alfalfa, and grass. The natural vegetation is mainly Idaho fescue, bluebunch wheatgrass, arrowleaf balsamroot, silky lupine, geranium, cinquefoil and wild rose.
DISTRIBUTION AND EXTENT: The loessial prairies near Grangeville, Nezperce, and Craigmont, Idaho. The series is moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Idaho County, Idaho, 1976.
REMARKS: This revision (6/93) changes the classification from fine-silty, mixed, mesic Ultic Argixerolls.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the surface to 18 inches (the Ap, A, and BAt horizons).
Argillic horizon - The zone from 18 to 60 inches (the Bt1, Bt2, and 2Bt3 horizons).
Particle-size control section - The zone from 18 to 38 inches (the Bt1 and part of the Bt2 horizons).
ADDITIONAL DATA: This series has been sampled in Lewis County, Idaho, for analysis at the NSSL. Laboratory sample number 86P 877; soil survey sample number S86ID-061-002.