LOCATION ELLOAM MTEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Aridic Natrustalfs
TYPICAL PEDON: Elloam clay loam, in grassland. (Colors are for dry soil unless otherwise noted)
E--0 to 3 inches; light gray (10YR 7/2) loam, brown (10YR 5/3) moist; crusty; strong very thin platy structure; slightly hard, very friable, slightly sticky and slightly plastic; many fine roots; many unstained silt and sand grains on plates; slightly alkaline (pH 7.6); abrupt smooth boundary. (1 to 4 inches thick)
Btn1--3 to 6 inches; pale brown (10YR 6/3) clay, dark brown (10YR 4/3) moist; strong medium columnar structure parting to strong medium angular blocky; very hard, firm, sticky and plastic; common very fine roots; many very fine tubular pores; continuous moderately thick clay film on faces of peds; 5 percent pebbles; moderately alkaline (pH 7.9); clear smooth boundary.
Btn2--6 to 10 inches; pale brown (10YR 6/3) clay, dark brown (10YR 4/3) moist; moderate medium prismatic structure parting to moderate medium angular blocky; very hard, firm, sticky and plastic; common very fine roots; many very fine tubular pores; continuous moderately thick clay film on faces of peds; 5 percent pebbles; moderately alkaline (pH 8.4); clear smooth boundary. (Combined Btn horizons 7 to 18 inches thick)
Bkn--10 to 20 inches; light brownish gray (2.5Y 6/2) clay loam, dark grayish brown (2.5Y 4/2) moist; moderate medium prismatic structure parting to moderate medium angular blocky; common very fine roots; many very fine tubular pores; 5 percent pebbles; strongly effervescent; strongly alkaline (pH 8.6); clear smooth boundary. (5 to 15 inches thick)
Bknyz--20 to 43 inches; gray (10YR 5/1) clay loam, dark gray (10YR 4/1) moist; weak coarse angular blocky; hard, friable, sticky and plastic; few very fine roots; 5 percent pebbles; many seams and masses of gypsum and other salts to a depth of 30 inches and common seams and soft masses of gypsum and other salts below this depth; strongly effervescent; moderately alkaline (pH 8.4); clear smooth boundary. (10 to 30 inches thick)
Cn--43 to 60 inches; light brownish gray (2.5Y 6/2) clay loam, dark grayish brown (2.5Y 4/2) moist; massive; hard, friable, sticky and plastic; few very fine roots; 5 percent pebbles; strongly effervescent; moderately alkaline.
TYPE LOCATION: Valley County, Montana; 50 feet south and 1,700 feet east of the NW corner of sec. 13, T. 27 N., R. 38 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 above.
Depth to Bkn horizon - 8 to 18 inches.
Depth to gypsum and other salts horizon - 16 to 25 inches.
E horizon - Hue: 10YR or 2.5Y
Value: 5, 6, or 7 dry; 4 or 5 moist
Chroma: 2 or 3
Texture: loam or silt loam
Clay content: 20 to 27 percent
Clay content: 30 to 45 percent where mixed to 7 inches and textures are clay loam or clay
Rock fragments: 0 to 30 percent--0 to trace stones, 0 to 5 percent cobbles, 0 to 25 percent pebbles.
EC: 0 to 2 mmhos/cm
Reaction: pH 6.1 to 7.8
The surface layer is crusted in the natural state and is also crusted where cultivated.
Btn horizons - Hue: 10YR or 2.5Y
Value: 4, 5, or 6 dry; 3, 4, or 5 moist
Chroma: 2 or 3
Texture: clay loam or clay
Clay content: 35 to 55 percent
Structure: strong or medium columnar, prismatic or blocky
Rock fragments: 0 to 15 percent--0 to trace cobbles; 0 to 15 percent pebbles
SAR: 8 to 25
EC: 2 to 8 mmhos/cm
Reaction: pH 6.6 to 9.0
Pedons that have less than 15 percent ESP have more exchangeable Mg plus sodium than calcium, plus exchange acidity at pH 8.2.
Bkn horizon - Hue: 10YR, 2.5Y, or 5Y
Value: 5, 6, or 7 dry; 4, 5, or 6 moist
Chroma: 2 or 3
Texture: clay loam or clay
Clay content: 30 to 45 percent
Rock fragments: 0 to 15 percent--0 to trace cobbles; 0 to 15 percent pebbles
SAR: 13 to 25
EC: 4 to 8 mmhos/cm
Reaction: pH 7.9 to 9.0
Bknyz, Bkny horizon - Hue: 10YR, 2.5Y, or 5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 1, 2, or 3
Texture: loam or clay loam
Clay content: 25 to 40 percent
Rock fragments: 0 to 15 percent--0 to trace cobbles; 0 to 15 percent pebbles
SAR: 13 to 25
EC: 8 to 16 mmhos/cm
Gypsum: 1 to 3 percent
Reaction: pH 7.9 to 9.0
Cn horizon - Hue: 10YR, 2.5Y, or 5Y
Value: 5, 6, or 7 dry; 4 or 5 moist
Chroma: 1, 2, or 3
Texture: loam or clay loam
Clay content: 25 to 40 percent
Rock fragments: 0 to 15 percent--0 to trace cobbles; 0 to 15 percent pebbles
SAR: 13 to 25
EC: 8 to 16 mmhos/cm
Reaction: pH 7.4 to 7.8
Bulk density: 1.55 grams/cc and greater
COMPETING SERIES:
Absher (MT) - has EC of 8 mmhos/cm and greater in the argillic horizon; dry consistence is extremely hard in the argillic horizon and below.
Creed (MT) - does not have till with a bulk density of 1.5 or greater above a depth of less than 60 inches; has A and E horizons with a combined thickness of 5 to 10 inches.
Gerdrum (MT) - does not have till with a bulk density of 1.5 or greater above a depth of less than 60 inches; has A horizons, and the combined thickness of the A and E horizons is 2 to 5 inches; formed in alluvium.
Oburn (MT) - does not have till with a bulk density of 1.5 or greater above a depth of less than 60 inches; has A and E horizons with a combined thickness of 5 to 10 inches; contrasting substratum of coarser materials above a depth of 40 inches.
Thoeny (MT) - does not have a crusty surface; has SAR of 10 to 13 in the Bt horizons; has accumulations of gypsum below a depth of 22 inches and secondary carbonates below a depth of 10 inches.
Weingart (MT) - has bedrock at depth of 20 to 40 inches.
GEOGRAPHIC SETTING:
Landform - till plains.
Elevation - 2,200 to 4,000 feet.
Slopes- 0 to 15 percent.
Parent material - calcareous till.
Climate - cool with long, cold winters; moist springs; hot, dry summers.
Mean annual precipitation - 10 to 15 inches, most of which falls during spring and early in summer.
Mean annual air temperature - 40 to 45 degrees F.
Frost-free season - 100 to 135 days.
DRAINAGE AND PERMEABILITY: Well drained. Slow or very slow permeability in the solum, and very slow permeability in the underlying till. Runoff is low to very high depending on slope and permeability of the surface.
USE AND VEGETATION: These soils are used as dryland farmland and as rangeland. The potential native vegetation is mainly western wheatgrass, Sandberg bluegrass, green needlegrass, blue grama, Nuttall saltbush, greasewood, and other shrubs and forbs.
DISTRIBUTION AND EXTENT: Elloam soils occur in north-central and northeastern Montana on the till plains. They are extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Blaine County, Montana, 1976.
REMARKS: Soil interpretation record: MT0272, MT0608.
Diagnostic horizons and features recognized in this pedon are: ochric epipedon - the zone from the surface of the to a depth of 3 inches (E horizon); natric horizon - the zone from 3 to 18 inches (Btn1, Btn2 and part of Bkn horizon); natric horizon - the zone from 3 to 10 inches that is also the particle-size control section (Btn1 and Btn2 horizons); horizons of secondary carbonate accumulation - the zone from 10 to 43 inches (Bkn and Bknyz horizons). Elloam soils have a frigid temperature regime and an ustic moisture regime that borders on aridic.
ADDITIONAL DATA: Laboratory data S62-MT-3-8, S62-MT-3-11.