LOCATION LONNA MTEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, frigid Aridic Haplustepts
TYPICAL PEDON: Lonna silt loam, in cropland (colors are for dry soil unless otherwise noted).
Ap--0 to 5 inches; brown (10YR 5/3) silt loam, brown (10YR 4/3) moist; moderate fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine roots; slightly effervescent; slightly alkaline (pH 7.6); clear smooth boundary. (2 to 8 inches thick)
Bw--5 to 10 inches; pale brown (10YR 6/3) silt loam, brown (10YR 5/3) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine roots; many very fine pores; disseminated lime; strongly effervescent; moderately alkaline (pH 8.0); clear smooth boundary. (5 to 8 inches thick)
Bk1--10 to 17 inches; light yellowish brown (2.5Y 6/4) silt loam, light olive brown (2.5Y 5/4) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; many very fine pores; disseminated lime; common fine threads and masses of lime; violently effervescent; moderately alkaline (pH 8.4); gradual smooth boundary. (5 to 17 inches thick)
Bk2--17 to 30 inches; light yellowish brown (2.5Y 6/4) silt loam, light olive brown (2.5Y 5/4) moist; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots; common very fine pores; disseminated lime; common fine threads and masses of lime; violently effervescent; strongly alkaline (pH 8.6); gradual smooth boundary. (6 to 25 inches thick)
BC--30 to 60 inches; pale yellow (2.5Y 7/4) silt loam, light yellowish brown (2.5Y 6/4) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots; few very fine pores; disseminated lime; strongly effervescent; moderately alkaline (pH 8.4).
TYPE LOCATION: Rosebud County, Montana; 500 feet north and 1,400 feet east of the SW corner of sec. 19, T. 12 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.
Control section - 18 to 35 percent clay.
Depth to Bk horizon - 10 to 16 inches.
EC and SAR- below a depth of 30 inches electrical conductivity ranges from 2 to 16 and the sodium adsorption ratio ranges from 10 to 30.
Soil phases - The noncalcareous phase has less than 5 percent calcium carbonate after mixing the surface 7 inches. The calcareous phase has 5 to 10 percent calcium carbonate.
A By horizon is allowed.
A or Ap horizon - Hue: 10YR or 2.5Y
Value: 5 or 6 dry; 3, 4, or 5 moist
Chroma: 2, 3, or 4
Texture: loam, silt loam, silty clay loam
Clay content: 18 to 35 percent
Effervescence: slightly or strongly; it has no effervescence in some uncultivated pedons
Calcium carbonate equivalent: 0 to 10 percent
Reaction: pH 6.6 to 8.4
Uncultivated areas have A horizons 2 to 4 inches thick.
Bw horizon - Hue: 10YR or 2.5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture: silt loam, silty clay loam
Clay content: 18 to 35 percent
Effervescence: slightly or strongly
Calcium carbonate equivalent: 0 to 10 percent
Reaction: pH 6.6 to 8.4
This horizon may be noneffervescent in some pedons.
Bk1 horizon - Hue: 10YR or 2.5Y
Value: 5, 6, or 7 dry; 4, 5, or 6 moist
Chroma: 2, 3, or 4
Texture: silt loam, silty clay loam
Clay content: 18 to 35 percent
Calcium carbonate equivalent: 5 to 12 percent
EC: 0 to 8 mmhos/cm
SAR: 0 to 13
Effervescence: strongly or violently
Reaction: pH 7.9 to 9.0
Bk2 horizon - Hue: 10YR or 2.5Y
Value: 5, 6, 7, or 8 dry; 4, 5, 6, or 7 moist
Chroma: 2, 3, or 4
Texture: silt loam, silty clay loam
Clay content: 18 to 35 percent
Calcium carbonate equivalent: 5 to 15 percent
EC: 0 to 8 mmhos/cm
SAR: 0 to 13
Effervescence: strongly or violently
Reaction: pH 7.9 to 9.0
BC horizon - Hue: 10YR or 2.5Y
Value: 5, 6, or 7 dry; 4, 5, or 6 moist
Chroma: 2, 3, or 4
Texture: very fine sandy loam, loam, silt loam, silty clay loam (may be stratified)
Clay content: 10 to 35 percent
EC: 2 to 16 mmhos/cm
SAR: 10 to 30
Effervescence: strongly or violently
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.9 to 9.0
COMPETING SERIES:
Alona (MT) - is very strongly alkaline below a depth of 13 inches; has a sodium adsorption ratio greater than 13 at a depth of 13 inches; has a horizon of salt accumulation at depths of 22 inches.
Rahworth (MT) - is moderately alkaline in the control section; has a variegated subsoil below a depth of 23 inches that contains gypsum and salt.
GEOGRAPHIC SETTING:
Landform - alluvial fans; stream terraces; lake plains; drainageways; sedimentary plains; hills.
Elevation - 1,900 to 5,200 feet.
Slope- 0 to 25 percent.
Parent materials - alluvium derived from semiconsolidated, loamy sedimentary beds, glaciofluvial and glaciolacustrine deposits.
Climate - long, cold winters; moist springs; hot, dry summers.
Mean annual precipitation - 10 to 14 inches.
Mean annual temperature - 39 to 45 degrees F.
Frost-free period - 90 to 135 days.
GEOGRAPHICALLY ASSOCIATED SOILS:
DRAINAGE AND PERMEABILITY: Well drained, moderate permeability.
USE AND VEGETATION: Lonna soils are used mainly as rangeland, dryland pasture, and cropland. The potential native vegetation is western wheatgrass, needleandthread, green needlegrass, some forbs, and shrubs.
DISTRIBUTION AND EXTENT: Lonna soils are extensive on sedimentary uplands of eastern Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Stillwater County, Montana, 1975.
REMARKS: Soil interpretations record: MT0156. Reaction is by dye indicators. Diagnostic horizons and features recognized in this pedon are: an ochric epipedon from the soil surface to 5 inches (Ap horizon); a cambic horizon from 5 to 17 inches (Bw, Bk1 horizons); accumulation of lime from 17 to 30 inches (Bk2 horizon); a particle-size control section from 10 to 40 inches (Bk1, Bk2, BC horizons). Lonna soils have a frigid temperature regime and an ustic moisture regime that borders on aridic.