LOCATION LEN MTEstablished Series
TAXONOMIC CLASS: Clayey over loamy-skeletal, mixed, superactive, frigid Typic Argiustolls
TYPICAL PEDON: Len cobbly loam, rangeland (colors are for dry soil unless otherwise stated).
A--0 to 3 inches; dark grayish brown (10YR 4/2) cobbly loam, very dark grayish brown (10YR 3/2) moist; moderate very thin platy structure parting to moderate very fine granular; soft, very friable, slightly sticky and slightly plastic; many very fine roots; 10 percent cobbles and 10 percent pebbles; neutral; clear smooth boundary. (2 to 6 inches)
Bt1--3 to 7 inches; dark grayish brown (10YR 4/2) clay loam, very dark grayish brown (10YR 3/2) moist; strong medium and fine granular structure; slightly hard, friable, moderately sticky and moderately plastic; common very fine roots; many very fine tubular and interstitial pores; many distinct clay films on faces of peds; 5 percent pebbles; neutral; gradual smooth boundary. (3 to 8 inches thick)
Bt2--7 to 17 inches; brown (10YR 5/3) clay, dark brown (10YR 4/3) moist; strong medium prismatic structure parting to strong medium and fine subangular blocky; hard, firm, moderately sticky and moderately plastic; common very fine roots; many very fine tubular and interstitial pores; continuous distinct dark brown (10YR3/3) moist clay films on faces of peds; 5 percent pebbles; neutral; gradual smooth boundary. (6 to 15 inches thick)
2Btk--17 to 22 inches; pale brown (10YR 6/3) very gravelly sandy clay loam, dark brown (10YR 4/3) moist; moderate medium and fine subangular blocky structure; hard, friable, moderately sticky and slightly plastic; common very fine roots; many very fine tubular and interstitial pores; common distinct clay films on faces of peds; 40 percent pebbles and 10 percent cobbles; common fine masses of lime; continuous faint coatings of lime on fragments and continuous faint casts on underside of fragments; strongly effervescent; slightly alkaline; clear smooth boundary. (0 to 5 inches thick)
2Bk1--22 to 40 inches; pale brown (10YR 6/3) very gravelly sandy loam, dark brown (10YR 4/3) moist; weak medium and fine subangular blocky structure; hard, friable, slightly sticky and nonplastic; few very fine roots; common very fine tubular and interstitial pores; 50 percent pebbles and 15 percent cobbles; common fine seams and masses of lime; continuous faint lime casts on undersides of fragments; strongly effervescent; slightly alkaline; gradual smooth boundary. (6 to 20 inches thick)
2Bk2--40 to 60 inches; pale brown (10YR 6/3) very gravelly sandy loam, dark brown (10YR 4/3) moist; weak fine subangular blocky structure; slightly hard, very friable, moderately sticky and slightly plastic; few very fine roots; 50 percent pebbles and 10 percent cobbles; disseminated lime; continuous faint lime casts on underside of fragments; strongly effervescent; slightly alkaline.
TYPE LOCATION: Lewis and Clark County, Montana; 100 feet west and 10 feet north of the SW corner of sec. 25, T. 17 N., R. 6 W.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees.
Moisture control section - between 4 and 12 inches.
Mollic epipedon thickness - 7 to 16 inches.
Control section - 35 to 55 percent clay.
Depth to 2Btk horizon - 11 to 24 inches.
A horizon - Value: 3 or 4 dry; 2 or 3 moist
Chroma: 2 or 3
Texture: loam or clay loam
Clay content: 20 to 35 percent
Rock fragments: 15 to 25 percent--5 to 10 percent cobbles, 10 to 15 percent pebbles
Reaction: pH 6.6 to 7.3
Bt1 horizon - Hue: 10YR or 2.5Y
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 2 or 3
Clay content: 30 to 35 percent
Rock fragments: 5 to 35 percent--0 to 10 percent cobbles, 5 to 25 percent pebbles
Reaction: pH 6.6 to 7.3
Bt2 horizon - Hue: 10YR or 2.5Y
Value: 4 or 5 dry, 3 or 4 moist
Texture: clay loam or clay
Clay content: 35 to 55 percent
Rock fragments: 5 to 35 percent--0 to 10 percent cobbles, 5 to 25 percent pebbles
Reaction: pH 7.4 to 8.4
2Btk Horizon - Hue: 2.5Y, 5Y, or 10YR
Value: 5 or 6 dry, 4 or 5 moist
Texture: sandy clay loam or clay loam
Clay content: 30 to 35 percent
Rock fragments: 35 to 60 percent--5 to 15 percent cobbles, 30 to 45 percent pebbles
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.9 to 8.4
2Bk1 & 2Bk2 Horizons: Hue: 2.5Y, 5Y, 10YR
Value: 5, 6, or 7 dry; 4 or 5 moist
Texture: sandy loam or loam
Clay content: 5 to 10 percent
Rock fragments: 55 to 85 percent--10 to 30 percent cobbles, 45 to 55 percent pebbles
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.9 to 8.4
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - dissected alluvial fans and stream terraces.
Elevation - 3,600 to 5,000 feet.
Slope - 1 to 8 percent.
Parent material - alluvium.
Climate - long, cold winters; moist springs; warm summers.
Mean annual precipitation - 15 to 19 inches.
Mean annual temperature - 40 to 44 degrees F.
Frost-free period - 90 to 110 days.
DRAINAGE AND PERMEABILITY: Well drained; slow permeability.
USE AND VEGETATION: Len soils are used mainly for range. Some are used for irrigated crops of hay and pasture. Potential native vegetation is mainly bluebunch wheatgrass, Idaho fescue, rough fescue, Sandberg bluegrass, sagebrush, and arrowleaf balsamroot.
DISTRIBUTION AND EXTENT: Len series are of minor extent. They are in mountain valleys in central Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Type location moved to Lewis and Clark County, Montana and established by the correlation of Lewis and Clark County Area, Montana, 1991. Series proposed in Granite County Area, Montana, 1967.
REMARKS: Soil interpretation record: MT0560. Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from the soil surface to 7 inches (A, Bt1 horizons); an argillic horizon from 3 to 22 inches (Bt1, Bt2, 2Btk horizons); and a discontinuity from 22 to 60 inches (2Bk1, 2Bk2 horizons). Len soils have a frigid temperature regime and an ustic moisture regime.