LOCATION ALLENTINE MTEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Torrertic Natrustalfs
TYPICAL PEDON: Allentine clay, in cropland. (Colors are for dry soil unless otherwise noted)
Ap-0 to 10 inches; light brownish gray (2.5Y 6/2) clay, dark grayish brown (2.5Y 4/2) moist; strong very fine granular structure; very hard, firm, sticky and very plastic; moderately alkaline (pH 7.9); abrupt smooth boundary.
Btn-10 to 13 inches; grayish brown (2.5Y 5/2) clay, dark grayish brown (2.5Y 4/2) moist; moderate medium prismatic structure parting to strong medium angular blocky; extremely hard, very firm, very sticky and very plastic; common moderately thick clay films on peds; moderately alkaline (pH 8.0); clear smooth boundary. (3 to 10 inches thick)
Btkn-13 to 23 inches; light yellowish brown (2.5Y 6/4) clay, light olive brown (2.5Y 5/4) moist; weak coarse prismatic structure parting to moderate medium blocky; extremely hard, very firm, very sticky and very plastic; common masses of lime; common faint clay films on peds; moderately alkaline (pH 7.9); gradual wavy boundary. (5 to 15 inches thick)
Bky-23 to 36 inches; light yellowish brown (2.5Y 6/4) clay, light olive brown (2.5Y 5/4) moist; weak coarse blocky structure; extremely hard, very firm, very sticky and very plastic; few masses of lime; few seams of gypsum and other salts; moderately alkaline (pH 8.0); clean wavy boundary. (5 to 14 inches thick)
Byz1-36 to 50 inches; light olive gray (5Y 6/2) clay, olive (5Y 4/3) moist; massive; extremely hard, very firm, very sticky and very plastic; common seams of gypsum and other salts; moderately alkaline (pH 8.0); gradual boundary.
Byz2-50 to 55 inches; olive gray (5Y 5/2) clay, olive gray (5Y 5/2) moist; massive; extremely hard, very firm, very sticky and very plastic; common seams of gypsum and other salts; moderately alkaline (pH 8.4); gradual wavy boundary. (Combined Byz horizons 10 to 25 inches thick)
2Cz-55 to 60 inches; grayish brown (2.5Y 5/2) very gravelly sandy loam; dark grayish brown (2.5Y 4/2) moist; 55 percent pebbles; few seams of salts; moderately alkaline (pH 8.4).
TYPE LOCATION: Yellowstone County, Montana; 35 feet east and 2,550 feet north of the southwest corner of sec. 10, T. 2 N., R. 27 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 47 to 54 degrees F.
Moisture control section - dry in all parts more than half of the time during April through September.
Control section - 40 to 60 percent clay.
Rock fragments - 35 to 60 percent pebbles in 2C horizon.
Depth to Bz - 25 to 40 inches.
Depth to Bk horizon - 10 to 15 inches.
A horizon
Hue; 10YR or 2.5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 or 3
Texture, less than 2 mm: clay loam, silty clay loam, silty clay, or clay
Clay content: 30 to 50 percent
Reaction: pH 7.4 to 8.4
NOTES: Undisturbed areas have a silt loam or very fine sandy loam E horizon 1 to 3 inches thick.
Btn horizon
Hue: 10YR, 2.5Y, or 5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture, less than 2 mm: clay
Clay content: 40 to 60 percent
SAR: 2 to 10
Reaction: pH 7.9 to 9.0
Btkn horizon
Hue: 10Y, 2.5Y or 5Y
Value; 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture, less than 2 mm: clay
Clay content: 40 to 60 percent
Calcium Carbonate Equivalent: 5 to 15 percent
SAR: 2 to 10
Reaction: pH 7.9 to 9.0
Bky horizon
Hue: 2.5Y or 5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture, less than 2 mm: clay
Clay content: 40 to 60 percent
Calcium Carbonate Equivalent: 5 to 15 percent
EC: 4 to 16 mmhos/cm
Reaction: pH 7.9 to 9.0
Byz horizon
Hue: 2.5Y or 5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture, less than 2 mm: clay
Clay content: 40 to 60 percent
EC: 4 to 16 mmhos/cm
Reaction: pH 7.9 to 9.0
NOTES: Common to many seams of gypsum and other salts.
2Cz horizon
Hue: 10YR, 2.5Y, or 5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture, less than 2mm: sandy loam
Clay content: 10 to 18 percent
Rock fragments: 35 to 60 percent pebbles
EC: 8 to 16 mmhos/cm
Reaction: pH 7.9 to 9.0
COMPETING SERIES: This is the Gilt Edge series. Gilt Edge soils have an E horizon more than 5 inches thick.
GEOGRAPHIC SETTING: The Allentine soils are on terraces. Elevations range from 2,500 to 4,000 feet. Slopes are 0 to 8 percent. The climate is characterized by long, cold winters; moist springs; and warm summers. Mean annual precipitation is 10 to 14 inches. Mean annual air temperature is 47 to 54 degrees F. The frost-free period is 110 to 140 days.
DRAINAGE AND PERMEABILITY: Well drained; slow or medium runoff; slow permeability.
USE AND VEGETATION: Allentine soils are used mainly as rangeland and for dryland and irrigated crops. Potential native vegetation is mainly western wheatgrass, green needlegrass, and bluebunch wheatgrass.
DISTRIBUTION AND EXTENT: Allentine soils are of moderate extent in south central Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado.
SERIES ESTABLISHED: Big Horn County (Big Horn Area), Montana, 1970.
REMARKS: Diagnostic horizon features recognized in this pedon are: ochric epipedon - the zone from the surface of the soil to a depth of 10 inches (Ap horizon); argillic horizon - the zone from 10 to 23 inches (Bt and Btk horizon); particle-size control section - zone from 10 to 23 inches (Bt and Btk horizons). The Btk horizon has more exchangeable magnesium plus sodium than calcium plus acidity (pH 8.2).
It appears this series has been mapped in frigid areas and may fit better in that regime. This determination will be made as surveys are updated. Competing series in the frigid regime would include the Gerdrum, Loburn, Thoeny and Weingart series. These soils have an SAR of more than 10 in the Bt horizons. In addition Thoeny soils formed in till and have more rock fragments and a bulk density to more than 1.55 within a depth of 40 inches and Weingart soils are moderately deep to beds.
Soil Interpretations Record: MT0474.