LOCATION WILSALL                 MT

Established Series
Rev. GAR-JAL-EMM
01/2014

WILSALL SERIES

The Wilsall series consists of shallow, well drained soils that formed in residuum from interbedded sandstone and shale. These soils are on hills, escarpments and sedimentary plains. Slopes are 2 to 45 percent. The mean annual precipitation is about 19 inches, and the mean annual temperature is about 40 degrees F.

TAXONOMIC CLASS: Clayey, smectitic, frigid, shallow Vertic Argiustolls

TYPICAL PEDON: Wilsall clay loam, in cropland (colors are for dry soil unless otherwise noted).

Ap--0 to 4 inches; dark grayish brown (10YR 4/2) clay loam, very dark grayish brown (10YR 3/2) moist; weak fine granular structure; hard, firm, moderately sticky and moderately plastic; common very fine roots and few fine roots; neutral (pH 6.8); clear smooth boundary. (3 to 8 inches thick)

Bt--4 to 13 inches; dark grayish brown (10YR 4/2) clay, very dark grayish brown (10YR 3/2) moist; moderate medium angular blocky structure; very hard, very firm, very sticky and very plastic; common very fine roots and few fine roots; common distinct clay films on faces of peds and lining pores; 5 percent gravel; neutral (pH 7.0); gradual smooth boundary. (6 to 13 inches thick)

Cr1--13 to 25 inches; brown (7.5YR 4/2) semi-consolidated shale, dark brown (7.5YR 3/2) moist.

Cr2--25 to 36 inches; dark grayish brown (2.5Y 4/2) semi-consolidated shale, very dark grayish brown (2.5Y 3/2) moist; violently effervescent.

Cr3--36 to 60 inches; grayish brown (2.5Y 5/2) semi-consolidated fine grained sandstone, dark grayish brown (2.5Y 4/2) moist; violently effervescent.

TYPE LOCATION: Park County, Montana; 1,200 feet west and 1,900 feet south of the northeast corner of sec. 17, T.4 N., R.8 E.

RANGE IN CHARACTERISTICS:

Mean annual soil temperature - 39 to 45 degrees F.
Moisture control section - between 4 and 12 inches; not dry for 45 consecutive days.
Mollic epipedon thickness - 7 to 16 inches, including all or part of the argillic horizon.
Depth to weakly consolidated shale or sandstone - 10 to 20 inches.

Ap or A horizon
Hue - 5YR, 7.5YR or 10YR
Value - 4 or 5 dry; 2 or 3 moist
Chroma - 2 or 3, dry or moist
Texture - clay loam or clay
Clay content - 30 to 45 percent
Rock fragments - 0 to 15 percent total; 0 to 15 percent gravel, 0 to 10 percent cobbles
Reaction - pH 6.6 to 7.3

Bt horizon
Hue - 5YR, 7.5YR, or 10YR
Value - 4 or 5 dry, 3 or 4 moist
Chroma - 2 or 3, dry or moist
Texture - clay loam, clay or silty clay
Clay content - 35 to 55 percent
Rock fragments - 0 to 15 percent total; 0 to 15 percent gravel, 0 to 5 percent cobbles
Reaction - pH 6.6 to 7.8

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING:

Landform - hills, escarpments, and sedimentary plains.
Elevation - 4,800 to 6,000 feet.
Parent material - residuum from interbedded sandstone and shale.
Slope - 2 to 45 percent.
Climate - long, cold winters; moist springs; warm summers.
Mean annual precipitation - 15 to 22 inches.
Mean annual temperature - 37 to 43 degrees F.
Frost-free period - 80 to 110 days.

GEOGRAPHICALLY ASSOCIATED SOILS: None listed.

DRAINAGE AND PERMEABILITY: Well drained; slow permeability.

USE AND VEGETATION: Wilsall soils are used for rangeland, hayland, and production of small grains. The potential native vegetation is Idaho fescue, bluebunch wheatgrass, and big sagebrush.

DISTRIBUTION AND EXTENT: These soils are extensive in southwestern Montana. MLRA 43B and 44B.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Gallatin County, Montana, 1997; proposed in Park County, Montana, 1995.

REMARKS: Soil interpretation record MT1450.

Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from the soil surface to 13 inches (Ap and Bt horizons)
Argillic horizon - the zone from 4 to 13 inches (Bt horizon)
Paralithic contact - the zone starting at 13 inches (Cr horizons)
Wilsall soils have a frigid soil temperature regime and an ustic soil moisture regime.

The 1/2014 update reflects a reclassification from Typic to Vertic subgroup based on a weighted average linear extensibility greater than 6.0 above the paralithic contact.

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National Cooperative Soil Survey
U.S.A.