LOCATION ALONA MTEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, frigid Aridic Haplustepts
TYPICAL PEDON: Alona silt loam, on stream terrace in grassland. (Colors are for dry soil unless otherwise noted)
A--0 to 2 inches; grayish brown (2.5Y 5/2) silt loam, very dark grayish brown (2.5Y 3/2) moist; moderate fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many fine roots throughout horizon; common fine tubular continuous pores; moderately alkaline (pH 8.2); clear smooth boundary. (2 to 5 inches thick)
Bw1--2 to 5 inches; grayish brown (2.5Y 6/2) silt loam, very dark grayish brown (2.5Y 3/2) moist; moderate medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many fine roots throughout horizon; common fine tubular pores; moderately alkaline (pH 8.2); clear wavy boundary. (0 to 3 inches thick)
Bw2--5 to 13 inches; light brownish gray (2.5Y 6/2) silty clay loam, dark grayish brown (10YR 4/2) moist; moderate medium prismatic structure; slightly hard, friable, slightly sticky and slightly plastic; many fine roots throughout horizon; many fine tubular pores; strongly alkaline (pH 9.0); clear wavy boundary. (4 to 10 inches thick)
Bk--13 to 22 inches; light gray (2.5Y 7/2) silty clay loam, brown (10YR 5/3) moist; moderate medium and coarse prismatic structure; slightly hard, friable, lightly sticky and slightly plastic; many fine roots throughout horizon; many fine tubular pores; common fine masses of lime; violently effervescent; very strongly alkaline (pH 9.6); clear wavy boundary. (5 to 12 inches thick)
Bkz--22 to 54 inches; light gray (2.5Y 7/2) silty clay loam, grayish brown (2.5Y 5/2) moist; weak coarse prismatic structure; slightly hard, friable, sticky and plastic; common grading to few very fine roots throughout horizon; few fine tubular pores; many distinct very fine salt crystals; many distinct calcium carbonate cutans on faces of peds; strongly effervescent; very strongly alkaline (pH 9.2); clear wavy boundary. (0 to 35 inches thick)
Bz--54 to 60 inches; light gray (2.5Y 7/2) silty clay loam, grayish brown (2.5Y 5/2) moist; weak coarse prismatic structure; slightly hard, very friable, sticky and plastic; few very fine roots; few fine tubular pores; many distinct very fine salt crystals; strongly effervescent; very strongly alkaline (pH 9.2).
TYPE LOCATION: McCone County, Montana; 560 feet east and 1,900 feet south of the NW corner of sec. 33, T. 19 N., R. 44 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.
Depth to Bk horizon - 6 to 18 inches.
Soil phases - a saline phase of this soil is recognized. The thin A horizons have mollic colors, but when mixed to a depth of 7 inches do not meet the requirements for a mollic epipedon. When cultivated, the surface may form a vesicular crust 1/2-to 1-inch thick after a rain.
A horizon - Hue: 10YR, 2.5Y or 5Y
Value: 5 or 6 dry; 3, 4, or 5 moist
Chroma: 2 or 3
Texture: loam, silt loam, or silty clay loam
Clay content: 18 to 35 percent
Effervescence: none to strongly
Electrical conductivity: 2 to 8 mmhos/cm; saline phase is 4 to 8 mmhos/cm
SAR: 2 to 10
Calcium carbonate equivalent: 0 to 10 percent
Reaction: pH 6.6 to 8.4
Bw1 horizon - Hue: 10YR, 2.5Y or 5Y
Value: 4, 5 or 6 dry; 3, 4 or 5 moist
Chroma: 2 or 3
Texture: loam to silt loam
Clay content: 18 to 27 percent
Effervescence: none to violently
Electrical conductivity: 2 to 8 mmhos/cm; saline phase is 4 to 8 mmhos/cm
SAR: 2 to 10
Calcium carbonate equivalent: 0 to 10 percent
Reaction: pH 6.6 to 8.4
Bw2 horizon - Hue: 10YR, 2.5Y or 5Y
Value: 5 or 6 dry; 3, 4, or 5 moist
Chroma: 2 to 4
Texture: silt loam or silty clay loam
Clay content: 25 to 35 percent
Effervescence: none to violently
Electrical conductivity: 2 to 16 mmhos/cm; saline phase is 8 to 16 mmhos/cm
SAR: 1 to 13
Calcium carbonate equivalent: 0 to 10 percent
Reaction: pH 7.9 to 10; saline phase pH 8.4 to 10
Bk horizon - Hue: 10YR, 2.5Y or 5Y
Value: 6 or 7 dry; 4, 5, or 6 moist
Chroma: 2, 3, or 4
Texture: silt loam or silty clay loam
Clay content: 18 to 35 percent
Effervescence: strongly or violently
Calcium carbonate equivalent: 5 to 15
Electrical conductivity: 2 to 16 mmhos/cm; saline phase is 8 to 16 mmhos/cm
SAR: 13 to 40
Reaction: pH 7.9 to 10.0
Bkz horizon - Hue: 10YR, 2.5Y or 5Y
Value: 6 or 7 dry; 4, 5, or 6 moist
Chroma: 2, 3, or 4
Texture: loam or silty clay loam, silt loam
Clay content: 18 to 35 percent
Effervescence: strongly or violently
Calcium carbonate equivalent: 5 to 15
Electrical conductivity: 8 to 20 mmhos/cm
SAR: greater than 13 to 40
Reaction: pH 8.4 to 10.0
Bz horizon - Hue: 10YR to 5Y
Value: 6 or 7 dry; 4, 5, or 6 moist
Chroma: 2, 3, or 4
Texture: loam, silty clay loam, silt loam
Clay content: 18 to 35 percent
Effervescence: strongly or violently
Electrical conductivity: 8 to 20 mmhos/cm
SAR: 13 to 45
Reaction: pH 8.5 to 10.0
COMPETING SERIES:
Cambeth (MT) - has weakly consolidated bedrock at a depth of 20 to 40 inches.
Lonna (MT) - does not have Bkz or Bz horizons; does not have salt accumulations above a depth of 30 inches; has an SAR of 0 to 13 above 21 to 40 inches.
Rahworth (MT) - has an E horizon; does not have very strongly alkaline Bkz and Bz horizons.
GEOGRAPHIC SETTING:
Landform- stream terraces, alluvial fans or sedimentary plains.
Elevation- 1,900 to 4,500 feet.
Slope- 0 to 15 percent.
Parent material - alluvium derived from calcareous and alkaline sedimentary deposits.
Mean annual precipitation - 12 inches at the type location and ranges from 10 to 14 inches.
Mean annual air temperature - 40 to 45 degrees F.
Frost-free period - 90 to 135 days.
DRAINAGE AND PERMEABILITY: Well drained; moderately slow permeability.
USE AND VEGETATION: These soils are used primarily for range. The potential native vegetation is inland saltgrass, western wheatgrass, green needlegrass, and some salt-tolerant shrubs.
DISTRIBUTION AND EXTENT: Sedimentary uplands of eastern Montana. The series is of moderate extent.
SERIES ESTABLISHED: McCone County, Montana, 1981.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
REMARKS: Soil interpretation records: MT0165, MT0414.
Diagnostic horizons and features recognized in this pedon are: ochric epipedon - the zone from the surface of the soil to a depth of 7 inches (A, Bw1 and part of Bw2 horizons); cambic horizon - the zone from 5 to 13 inches (Bw2 horizon); accumulation of lime - the zone from 13 to 54 inches (Bk, Bkz horizon); accumulation of salts - the zone from 22 to 60 inches (Bkz, Bz horizons); particle-size control section - the zone from 10 to 40 inches (part of Bw2, Bk, and part of Bkz horizons). Alona soils have a frigid temperature regime and an ustic moisture regime that borders on aridic.
Classification changed from Borollic Camborthids to Aridic Ustochrepts in 1993.
ADDITIONAL DATA: Laboratory data S74MT-55-3 is a similar pedon.