LOCATION LAP MT+CO
Established Series
Rev. DES-JAL-EMM
04/2013
LAP SERIES
The Lap series consists of shallow, well drained soils that formed in residuum and colluvium from limestone. These soils are on bedrock-floored plains, escarpments, structural benches, hills, and mountains. Slopes are 0 to 75 percent. Mean annual precipitation is about 17 inches, and mean annual temperature is about 43 degrees F.
TAXONOMIC CLASS: Loamy-skeletal, carbonatic, frigid Lithic Calciustolls
TYPICAL PEDON: Lap channery loam, grassland (colors are for dry soil unless otherwise noted).
A--0 to 4 inches; dark grayish brown (10YR 4/2) channery loam, very dark grayish brown (10YR 3/2) moist; weak very fine granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine roots; 35 percent channers (flat 1 to 4 inch diameter limestone fragments); slightly alkaline (pH 7.4); clear wavy boundary. (4 to 9 inches thick)
Bk1--4 to 12 inches; light brownish gray (10YR 6/2) very channery loam, dark grayish brown (10YR 4/2) moist; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; 50 percent channers; disseminated lime, continuous prominent lime casts on underside of channers; strongly effervescent; moderately alkaline (pH 8.2); clear wavy boundary. (2 to 8 inches thick)
Bk2--12 to 19 inches; light gray (10YR 7/2) extremely channery loam, brown (10YR 5/3) moist; massive; slightly hard, friable, moderately sticky and moderately plastic; few very fine roots; 65 percent channers; disseminated lime; continuous prominent lime casts on underside of channers; violently effervescent; moderately alkaline (pH 8.4); gradual irregular boundary. (4 to 11 inches thick)
R--19 inches; hard limestone bedrock with some cracks.
TYPE LOCATION: Big Horn County, Montana; 1,200 feet west and 1,200 feet north of the SE corner of sec. 6, T. 6 S., R. 26 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 38 to 47 degrees F.
Moisture control section - between 4 and 12 inches or between 4 inches and the lithic contact if less than 12 inches.
Mollic epipedon thickness - 7 to 12 inches.
Depth to R horizon - 10 to 20 inches.
Surface stones or boulders - 0 to 3 percent
A horizon
Hue: 10YR or 2.5Y
Value: 3, 4 or 5 dry; 2 or 3 moist
Chroma: 1, 2 or 3, dry or moist
Clay content: 15 to 27 percent
Rock fragments: 10 to 60 percent--0 to 40 percent cobbles, flagstones, and stones; 10 to 45 percent channers or gravel
Calcium carbonate equivalent: 0 to 45 percent in less than 2 mm particle-size fraction and more than 40 percent in the less than 20 mm particle-size class.
Reaction: pH 7.0 to 8.2
Bk1 horizon
Hue: 7.5YR, 10YR, or 2.5Y
Value: 5, 6, or 7 dry; 3, 4 or 5 moist
Chroma: 2 or 3, dry or moist
Texture: loam or clay loam
Clay content: 15 to 30 percent
Rock fragments: 35 to 70 percent--0 to 30 percent cobbles, flagstones, or stones; 30 to 55 percent channers or gravel
Calcium carbonate equivalent: 30 to 60 percent in the less than 2 mm particle-size fraction and more than 40 percent in the less than 20 mm soil particle-size fraction
Reaction: pH 7.9 to 9.0
Bk2 horizon
Hue: 7.5YR, 10YR, or 2.5Y
Value: 5, 6, 7, or 8 dry; 4, 5 or 6 moist
Chroma: 2 or 3, dry or moist
Texture: loam or clay loam
Clay content: 15 to 30 percent
Rock fragments: 50 to 70 percent--25 to 35 percent cobbles, flagstones, or stones; 25 to 60 percent channers or gravel
Calcium carbonate equivalent: 30 to 60 percent in the less than 2 mm particle-size fraction and more than 40 percent in the less than 20 mm soil particle-size fraction
Reaction: pH 7.9 to 9.0
COMPETING SERIES:
Pinerid (UT) - has an ustic moisture regime bordering on aridic.
GEOGRAPHIC SETTING:
Landform - bedrock-floored plains, hills, escarpments, structural benches, and mountains.
Elevation - 3,600 to 6,800 feet.
Slope - 0 to 75 percent.
Parent material - residuum and colluvium from limestone.
Climate - long, cold winters; moist springs; warm summers.
Mean annual precipitation - 15 to 22 inches.
Mean annual temperature - 39 to 45 degrees F.
Frost-free period - 70 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.
USE AND VEGETATION: Lap soils are used mainly as rangeland, some of the soils are used for dryland crops where they occur with other kinds of soils. Potential native vegetation is mainly bluebunch wheatgrass, rough fescue, Idaho fescue, needleandthread, western wheatgrass, forbs, and shrubs.
DISTRIBUTION AND EXTENT: Lap soils are extensive in the foothills and mountains of central and southwest Montana. MLRAs 43B, 44B, 46.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Big Horn County, Montana, 1970.
REMARKS: Soil interpretation records: MT0506, MT0804.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from the soil surface to 7 inches, mixed (A, part of Bk horizon)
Calcic horizon - from 4 to 19 inches (Bk1, Bk2 horizons)
Lithic contact - at a depth of 19 inches
Particle-size control section - from 10 to 19 inches (part of Bk1, Bk2 horizons)
Lap soils have a frigid temperature regime and an ustic moisture regime.
National Cooperative Soil Survey
U.S.A.