LOCATION SCOBEY MTEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Aridic Argiustolls
TYPICAL PEDON: Scobey clay loam, cropland (colors are for dry soil unless otherwise noted).
Ap--0 to 6 inches; grayish brown (10YR 5/2) clay loam, very dark grayish brown (10YR 3/2) moist; strong fine granular structure; hard, friable, sticky and plastic; many fine roots; 5 percent pebbles; neutral (pH 6.8); clear wavy boundary. (5 to 8 inches thick, uncultivated areas have an A horizon 2 or 3 inches thick.)
Bt--6 to 12 inches; brown (10YR 5/3) clay, dark brown (10YR 4/3) moist; strong fine and medium prismatic structure parting to strong fine angular blocky; hard, friable, sticky and plastic; many fine roots; many fine and very fine tubular pores; continuous faint dark grayish brown (10YR 4/2) clay films on faces of peds; 5 percent pebbles; neutral (pH 7.0); clear wavy boundary. (5 to 12 inches thick)
Bk1--12 to 19 inches; grayish brown (2.5Y 5/2) clay loam, dark grayish brown (2.5Y 4/2) moist; strong medium prismatic structure parting to strong fine subangular blocky; very hard, friable, sticky and plastic; common fine roots; many fine and very fine tubular pores; common faint clay films on vertical faces of peds; 5 percent pebbles; few fine masses of lime; strongly effervescent; slightly alkaline (pH 7.8); gradual wavy boundary. (3 to 12 inches thick)
Bk2--19 to 42 inches; light brownish gray (2.5Y 6/2) clay loam, dark grayish brown (2.5Y 4/2) moist; weak coarse and very coarse prismatic structure parting to weak medium subangular blocky; very hard, firm, sticky and plastic; few fine and very fine roots; common fine and very fine pores; 5 percent pebbles; many fine masses of lime; violently effervescent; moderately alkaline (pH 8.4); gradual wavy boundary. (20 to 30 inches thick)
Bky--42 to 60 inches; grayish brown (2.5Y 5/2) clay loam, dark grayish brown (2.5Y 4/2) moist; weak thick platy structure; very hard, firm, sticky and plastic; 5 percent pebbles; common fine masses of lime; common fine masses of gypsum; strongly effervescent; moderately alkaline (pH 8.2).
TYPE LOCATION: Blaine County, Montana; north of road, about 500 feet west and 100 feet north of SE corner of sec. 5, T. 34 N., R. 24 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F.
Moisture control section - between 4 and 12 inches; dry in all parts between four-tenths and five-tenths of the cumulative days per year when the soil temperature at a depth of 20 inches is 41 degrees F or higher.
Mollic epipedon thickness - 7 to 16 inches.
Depth to Bk horizon - 10 to 18 inches.
Depth to Bky or By horizon - 30 to 55 inches.
Btk, By, or BC horizons are allowed.
Phases- stony, shaley substratum.
Scobey soils have air dry bulk density greater than 1.35 g/cc above 40 inches and a moist bulk density greater than 1.35 g/cc at depths as shallow as 20 inches.
Ap, A horizons - Hue: 10YR or 2.5Y
Chroma: 2 or 3
Texture: loam, clay loam, fine sandy loam, or sandy loam.
Clay content: 10 to 35 percent
Rock fragments: 0 to 60 percent--0 to 25 percent cobbles and stones; trace to 40 percent pebbles
Reaction: pH 6.1 to 7.8
Pedons with sandy loam surfaces are in areas which have a thin sandy eolian mantle.
Bt horizon - Hue: 10YR or 2.5Y
Value: 4, 5, or 6 dry; 3 or 4 moist
Chroma: 2 or 3
Texture: clay loam or clay
Clay content: 35 to 45 percent
Rock fragments: 0 to 15 percent--0 to 5 percent cobbles; trace to 10 percent pebbles
Reaction: pH 6.6 to 8.4
Bk1 and Bk2 horizons - Hue: 10YR or 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2, 3, or 4
Clay content: 30 to 40 percent
Rock fragments: 0 to 15 percent--0 to 5 percent cobbles; trace to 10 percent pebbles
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.4 to 8.4
Bky horizon - Hue: 10YR or 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2, 3 or 4
Clay content: 30 to 40 percent
Rock fragments: 0 to 15 percent--0 to 5 percent cobbles; trace to 10 percent pebbles
Calcium carbonate equivalent: 5 to 12 percent
SAR: 1 to 8
Gypsum: 1 to 6 percent
Reaction: pH 7.4 to 9.0
COMPETING SERIES:
Ethridge (MT) - does not have till above a depth of 40 inches that has a bulk density of 1.35 gr/cc or greater.
Holderness (CO) - has carbonates at a depth of 40 inches and deeper.
Morop (CO) - has 15 to 35 percent coarse fragments in the Bk horizons.
Nilrap (WY) - has hues of 7.5YR and redder in the control section.
Nunnston (WY) - does not have horizons that have accumulations of gypsum.
Tanna (MT) - has a paralithic contact at depths of 20 to 40 inches.
Ulric (WY) - has 15 to 35 percent rock fragments below a depth of 20 inches; has bedrock between a depth of 40 and 60 inches.
GEOGRAPHIC SETTING:
Landform - till plains; hills; moraines.
Elevation - 2,400 to 4,000 feet.
Slope- 0 to 15 percent.
Parent material - clay loam till.
Climate - long, cold winters; moist springs; warm summers.
Mean annual precipitation - 10 to 14 inches.
Mean annual air temperature - 40 to 45 degrees F.
Frost-free period - 100 to 135 days.
DRAINAGE AND PERMEABILITY: Well drained; slow permeability.
USE AND VEGETATION: Scobey soils are used mainly for dryland crops. Some areas are used as rangeland. Potential native vegetation is mainly bluebunch wheatgrass, western wheatgrass, green needlegrass, and needleandthread.
DISTRIBUTION AND EXTENT: Scobey soils are extensive in the till plains of northern Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Milk River Area, Montana, 1928.
REMARKS: Soil interpretation record: MT0124, MT0675, MT0240.
Diagnostic horizons and features recognized in this pedon are: mollic epipedon - from the soil surface to 7 inches (mixed); argillic horizon - from 6 to 12 inches (Bt horizon); particle-size control section - from 6 to 12 inches (Bt horizon); horizons with secondary carbonate accumulation - from 12 to 42 inches (Bk1, Bk2 horizons); a horizon with secondary carbonate accumulation from 12 to 42 inches (Bk1, Bk2 horizons); horizon with secondary carbonate accumulation and gypsum accumulations - from 42 to 60 inches (Bky horizon). Scobey soils have a frigid temperature regime and an ustic moisture regime bordering on aridic.
ADDITIONAL INFORMATION: Laboratory samples S62MT-005-015, S62MT-005-014, S62MT-013-006, S82MT-073-001, W88MT-051-003.