LOCATION DURSTON MT
Established Series
Rev. GAR-EWC-RJS
10/2012
DURSTON SERIES
The Durston series consists of very deep, well drained soils that formed in loess and re-worked loess. These soils are on relict stream terraces, alluvial fans, eroded fan remnants and hillslopes. Slopes are 0 to 15 percent. Mean annual precipitation is about 500 mm, and the mean annual air temperature is about 4 degrees C.
TAXONOMIC CLASS: Fine, mixed, superactive, frigid Typic Argiustolls
TYPICAL PEDON: Durston silty clay loam, in hayland (colors are for dry soil unless otherwise noted).
Ap--0 to 15 cm; very dark grayish brown (10YR 3/2) silty clay loam, black (10YR 2/1) moist; weak fine granular structure; slightly hard, friable, moderately sticky and slightly plastic; many very fine, common fine and medium roots; slightly acid (pH 6.2); clear smooth boundary. (15 to 30 cm thick)
Bt1--15 to 36 cm; brown (10YR 4/3) silty clay loam, dark brown (10YR 3/3) moist, weak medium prismatic structure parting to moderate medium subangular blocky; very hard, firm, moderately sticky and moderately plastic; common very fine, fine and medium roots; common distinct clay films on faces of peds and lining pores; neutral (pH 6.8); gradual smooth boundary.
Bt2--36 to 64 cm; yellowish brown (10YR 5/4) silty clay loam, brown (10YR 4/3) moist; moderate medium subangular blocky structure; very hard, firm, moderately sticky and moderately plastic; common very fine, few fine and medium roots; common distinct clay films on faces of peds and lining pores; slightly alkaline (pH 7.4); clear smooth boundary. (combined thickness of Bt horizons - 25 to 70 cm).
Bk1--64 to 100 cm; pale brown (10YR 6/3) silty clay loam, brown (10YR 4/3) moist; weak medium subangular blocky structure; very hard, firm, moderately sticky and moderately plastic; few very fine roots; many medium soft masses of calcium carbonate; violently effervescent; slightly alkaline (pH 7.8); gradual smooth boundary. (60 to 125 cm thick)
Bk2--100 to 152 cm; brown (10YR 5/3) silt loam, brown (10YR 4/3) moist; weak fine subangular blocky structure; very hard, friable, sticky and slightly plastic; few very fine roots; common medium soft masses of calcium carbonate; strongly effervescent; slightly alkaline (pH 7.4).
TYPE LOCATION: Gallatin County, Montana; 610 meters south and 396 meters east of the northwest corner of Sec. 27, T.2S, R.6E.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 4 to 6 degrees C.
Mollic epipedon thickness - 20 to 38 cm
Depth to calcic horizon - 50 to 100 cm
Note: Some pedons may have a BCk horizon present.
Ap horizon
Value: 3 or 4 dry; 2 or 3 moist
Texture: silty clay loam, clay loam or loam
Clay content: 20 to 35 percent
Rock fragments: 0 to 35 percent--0 to 15 percent gravel, 0 to 20 percent cobbles
Reaction: pH 6.1 to 7.3
Bt1 horizon
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 2 to 4; dry or moist
Texture: silty clay loam, silty clay, clay loam or clay
Clay content: 35 to 50 percent
Rock fragments: 0 to 15 percent--0 to 10 percent gravel, 0 to 5 percent cobbles
Reaction: pH 6.1 to 7.3
Bt2 horizon
Value: 4 or 5; dry
Chroma: 3 or 4; dry or moist
Texture: silty clay loam, silty clay, clay loam or clay
Clay content: 35 to 50 percent
Rock fragments: 0 to 15 percent--0 to 10 percent gravel, 0 to 5 percent cobbles
Reaction: pH 6.6 to 7.8
Bk1 horizon
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 to 4; dry or moist
Texture: silty clay loam, clay loam or silt loam
Clay content: 25 to 40 percent
Rock fragments: 0 to 15 percent--0 to 15 percent gravel, 0 to 5 percent cobbles
Calcium carbonate equivalent: 15 to 30 percent
Reaction: pH 7.4 to 8.4
Bk2 horizon
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 2 to 4; dry or moist
Texture: silt loam, silty clay loam or clay loam
Clay content: 25 to 35 percent
Rock fragments: 0 to 15 percent--0 to 15 percent gravel, 0 to 5 percent cobbles
Calcium carbonate equivalent: 15 to 30 percent
Reaction: pH 7.4 to 8.4
BCk horizon (where present)
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 2 to 4; dry or moist
Texture: loam or fine sandy loam
Clay content: 18 to 27 percent
Rock fragments: 0 to 15 percent--0 to 10 percent gravel, 0 to 5 percent cobbles
Calcium carbonate equivalent: 15 to 30 percent
Reaction: pH 7.9 to 8.4
COMPETING SERIES:
Alder (MT) - moderately deep to a paralithic contact
Bacbuster (MT) - moderately deep to a paralithic contact
Bigbear (MT) - has more than 15 percent coarse fragments in the Bk horizon
Billman (MT) - moderately deep to a paralithic contact
Charo (MT) - moderately deep to a lithic contact
Darret (MT) - moderately deep to a paralithic contact
Microy (NM) - moderately deep to a lithic contact
Mishakal (MT) - moderately deep to a paralithic contact
Pino (NM) - moderately deep to a lithic contact
Roaringlion (MT) - does not have a calic horizon
Turkeysprings (NM) - deep to a lithic contact
Wilcoxson (NM) - deep to a lithic contact
GEOGRAPHIC SETTING:
Landform - relict stream terraces, alluvial fans, eroded fan remnants and hillslopes
Elevation - 1,460 to 1,675 feet
Slopes - 0 to 20 percent
Parent material - loess and re-worked loess
Climate - long cold winters; moist springs; warm summers
Mean annual precipitation - 365 to 560 mm
Mean annual air temperature - 2.5 to 6 degrees C.
Frost-free period - 80 to 110 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; slow permeability.
USE AND VEGETATION: Durston soils are used mainly for hayland, pasture and rangeland. Potential native vegetation includes subalpine needlegrasses, Idaho fescue, rough fescue, spike fescues, big bluegrass, sedges, lupine, sticky geranium as well as other forbs, grasses and woody shrubs.
DISTRIBUTION AND EXTENT: Durston soils are of small extent in southwestern Montana. MLRAs - 44A, 44B, 43B.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Gallatin County, Montana, 1997.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 36 cm (Ap, Bt1 horizons)
Argillic horizon - 15 to 64 cm (Bt1, Bt2 horizons)
Calcic horizon - 64 to 152 cm (Bk1, Bk2 horizons)
Particle-size control section - 15 to 64 inches (Bt1, Bt2 horizon)
Durston soils have a frigid temperature regime and an ustic moisture regime.
Additional Information: Soil interpretation record: MT1638.
National Cooperative Soil Survey
U.S.A.