LOCATION WILKINS OR+ID

Established Series
Rev. HMV/WEL/RWL
03/2013

WILKINS SERIES

The Wilkins series consists of very deep, somewhat poorly drained soils that formed in loess and minor amounts of volcanic ash over alluvium weathered from basic igneous rocks. Wilkins soils are in concave basins and swales on plateaus and in mountain valleys. Slopes are 0 to 5 percent. The mean annual precipitation is about 24 inches and the mean annual temperature is about 43 degrees F.

TAXONOMIC CLASS: Fine, smectitic, frigid Xerertic Argialbolls

TYPICAL PEDON: Wilkins silt loam, native pasture. (All colors are for moist soil unless otherwise noted.)

A1--0 to 4 inches; black (10YR 2/1) silt loam, very dark gray (10YR 3/1) dry; weak very thin platy and very weak fine granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine roots; many irregular pores; moderately acid (pH 5.9); abrupt smooth boundary. (2 to 6 inches thick)

A2--4 to 10 inches; black (10YR 2/1) silt loam, very dark gray (10YR 3/1) dry; weak medium platy and weak very fine granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots; many irregular pores; few fine faint dark brown (10YR 3/3) redox concentrations as masses; moderately acid (pH 5.9); abrupt wavy boundary. (4 to 9 inches thick)

A3--10 to 19 inches; very dark grayish brown (10YR 3/2) silt loam, brown (10YR 5/3) dry; weak fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine to fine roots; many very fine and common fine tubular pores; few medium distinct brown (7.5YR 4/4) redox concentrations as masses; moderately acid (pH 5.9); abrupt wavy boundary. (0 to 11 inches thick)

E1--19 to 23 inches; grayish brown (10YR 5/2) silt loam, pale brown (10YR 6/3) dry; weak coarse granular structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; many very fine and common fine tubular pores; common thin clean bleached silt and sand coatings; few black and red redox concretions larger than 2 mm; moderately acid (pH 5.8); abrupt wavy boundary. (2 to 5 inches thick)

E2--23 to 25 inches; grayish brown (10YR 5/2) silt loam, light gray (10YR 7/2) dry; massive; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; common very fine and few fine tubular pores; common thin clean bleached silt and sand coatings; few black and red redox concretions larger than 2 mm; moderately acid (pH 5.8); abrupt wavy boundary. (0 to 5 inches thick)

2Bt1--25 to 32 inches; dark brown (10YR 3/3) silty clay, brown (10YR 4/3) dry; moderate medium columnar structure; extremely hard, extremely firm, very sticky and very plastic; common very fine roots; many very fine tubular pores; continuous prominent clay films on ped faces; few clean silt and sand coatings; slightly acid (pH 6.2); clear wavy boundary. (6 to 8 inches thick)

2Bt2--32 to 52 inches; brown (10YR 4/3) silty clay, brown (10YR 5/3) dry; moderate medium prismatic and moderate fine angular blocky structure; extremely hard, extremely firm, very sticky and very plastic; common very fine roots; many very fine tubular pores; continuous distinct clay films on ped faces; few clean silt and sand coatings; neutral (pH 6.6); gradual wavy boundary. (10 to 24 inches thick)

3C1--52 to 70 inches; light olive brown (2.5Y 5/3) loam, light yellowish brown (2.5Y 6/3) dry; massive; hard, friable, slightly sticky and slightly plastic; few very fine tubular pores; few fine faint redox concentrations as masses; moderately acid (pH 5.8); gradual wavy boundary. (0 to 20 inches thick)

3C2--70 to 76 inches; light olive brown (2.5Y 5/3) gravelly clay loam, light yellowish brown (2.5Y 6/3) dry; massive; hard, friable, slightly sticky and slightly plastic; common medium distinct redox concentrations as masses; 20 percent gravel; moderately acid (pH 5.7).

TYPE LOCATION: Wallowa County, Oregon; about 12 miles north of the town of Wallowa at Maxville Meadow; 1,900 west and 600 feet south of the northeast corner of section 16, T. 3 N., R. 42 E. (Latitude 45 degrees, 44 minutes, 54 seconds N. and Longitude 117 degrees, 34 minutes, 15 seconds W.)

RANGE IN CHARACTERISTICS: The soils are usually moist but dry for 45 to 80 consecutive days during the summer months between depths of 4 and 12 inches in most years. The mean annual soil temperature is 41 to 46 degrees F. Depth to bedrock is 60 inches or more. Depth to the argillic horizon is 15 to 30 inches. Black and red concretions 0.5 to 3 mm in size are few to common in the E and 2Bt horizons.

The A horizon has value of 2 or 3 moist, 3 to 5 dry, and chroma of 0 to 1 in the upper part and 1 to 3 in the lower part. It has faint to distinct redox concentrations below depth of 4 inches. This horizon is silt loam and has 18 to 27 percent clay. Reaction is moderately acid to neutral.

The E horizon has value of 4 to 6 moist, 6 to 8 dry, and chroma of 1 or 2 moist in more than half of the matrix and is 4 to 10 inches thick. Reaction is moderately acid to neutral. It is silt loam with 10 to 27 percent clay.

The 2Bt horizon has hue of 10YR or 2.5Y, value of 3 to 6 moist, 4 to 7 dry, and chroma of 1 to 4 moist or dry. It is silty clay or clay and has 40 to 60 percent clay. This horizon has lenses of volcanic ash below 40 inches in some pedons. It has 0 to 10 percent gravel mostly in the lower part. Reaction is moderately acid to neutral.

A BC horizon is present in some pedons.

The C horizon has hue of 2.5Y, 5Y, or 10YR, value of 3 to 6 moist, 4 to 7 dry and chroma of 1 to 4 moist and dry. It is loam, clay loam, or silty clay loam with 15 to 40 percent clay and 0 to 25 percent gravel.

COMPETING SERIES: These are the Cowsly and Morphey series. Morphey soils are well or moderately well drained, lack redox features and have a calcic horizon at a depth of 20 to 30 inches. Cowsly soils are moderately well drained, have redox concentrations within a depth of 20 to 40 inches and have secondary carbonates below 40 inches in some pedons.

GEOGRAPHIC SETTING: The Wilkins soils are in drainageways, swales, and concave drainage basins on plateaus and in mountain valleys. Slopes are 0 to 5 percent. Elevations are typically 2,800 to 5,500 feet but range down to 1,100 feet in northeastern Idaho. The soils formed in loess and minor amounts of volcanic ash over alluvium weathered from basic igneous rocks. The climate is characterized by cold wet winters and hot dry summers. The mean annual precipitation is 17 to 35 inches. The average January temperature is 23 to 25 degrees F; average summer temperature is 61 to 65 degrees F. The mean annual temperature is 40 to 45 degrees F. The frost-free period is 50 to 125 days.

GEOGRAPHICALLY ASSOCIATED SOILS: Wilkins soils are associated with the Klicker, and Tolo series. All of these soils lack an E horizon and the abrupt textural change. Akerite soils are on adjacent footslopes, moderately well drained, and have a volcanic ash mantle. Klicker soils are on adjacent south-facing side slopes, well drained, loamy-skeletal and 20 to 40 inches deep to basalt. Tolo soils are on adjacent footslopes and side slopes, well drained and have a volcanic ash mantle.

DRAINAGE AND PERMEABILITY: Somewhat poorly drained; very slow permeability. A perched water table is at its uppermost limit from December to June. This soils ranges from none to occasional flooding for brief periods occurs from February to May.

USE AND VEGETATION: These soils are used for livestock grazing, hayland, and wildlife habitat. Potential native vegetation is mainly tufted hairgrass, sedge and rush.

DISTRIBUTION AND EXTENT: Blue Mountains of northeastern Oregon and in north-central Idaho, MLRA 9. Series is of small extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon

SERIES ESTABLISHED: Idaho County, Western Part, Idaho, 1976.

REMARKS: Diagnostic horizons and features of this pedon include:

Mollic epipedon - from soil surface to 19 inches (A1, A2, A3 horizons).
Albic horizon - from 19 to 25 inches (E1 and E2 horizons) with an abrupt boundary to the argillic horizon.
Argillic horizon - from 25 to 52 inches (2Bt1 and 2Bt2 horizons).
Xerertic feature - from 25 to 52 inches (2Bt1 and 2Bt2 horizons) having montmorillonitic mineralogy, 40 to 60 percent clay, and a high shrink-swell.

National Cooperative Soil Survey
U.S.A.