LOCATION ASHLO                   MT

Established Series
Rev. LCB-DRS-JCK
04/2021

ASHLO SERIES


The Ashlo series consists of very deep, well drained soils that formed in gravelly and cobbly alluvium or colluvium. These soils are on stream terraces, alluvial fans, fan remnants, and eroded fan remnants. Slopes are 0 to 15 percent. Mean annual precipitation is about 330 mm, and mean annual temperature is about 6 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, carbonatic, frigid Aridic Calciustolls

TYPICAL PEDON: Ashlo cobbly loam, grassland (colors are for dry soil unless otherwise noted).

A--0 to 8 cm; grayish brown (10YR 5/2) very cobbly loam, very dark grayish brown (10YR 3/2) moist; weak very thin platy structure parting to moderate very fine granular; soft, very friable, slightly sticky and slightly plastic; many very fine roots; 20 percent gravel and 20 percent cobbles; strongly effervescent; moderately alkaline (pH 7.9); clear smooth boundary. (8 to 25 cm thick)

ABk--8 to 15 cm; grayish brown (10YR 5/2) very cobbly loam, very dark grayish brown (10YR 3/2) moist; moderate medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine roots; many very fine tubular and interstitial pores; many faint calcium carbonate coats on bottom surfaces of rock fragments; 15 percent gravel and 20 percent cobbles; strongly effervescent; moderately alkaline (pH 7.9); clear smooth boundary. (0 to 15 cm thick)

Bk1--15 to 25 cm; very pale brown (10YR 7/3) gravelly loam, brown (10YR 5/3) moist; weak medium prismatic structure parting to weak medium and fine subangular blocky; slightly hard, very friable, slightly sticky and slightly plastic; common very fine roots; many very fine tubular and interstitial pores; finely disseminated carbonates; many prominent carbonate coats on bottom surfaces of rock fragments; 20 percent gravel and 10 percent cobbles; violently effervescent; moderately alkaline (pH 8.0); gradual smooth boundary. (10 to 30 cm thick)

Bk2--25 to 51 cm; very pale brown (10YR 8/2) extremely gravelly loam, pale brown (10YR 6/3) moist; weak medium and fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine roots; common very fine tubular and interstitial pores; common fine calcium carbonate masses in the matrix and many prominent platy carbonate-silica concretions and pendular nodules on the bottom of rock fragments; 10 percent petrocalcic fragments, 65 percent gravel, and 5 percent cobbles; violently effervescent; moderately alkaline (pH 8.2); gradual smooth boundary. (13 to 38 cm thick)

Bk3--51 to 76 cm; very pale brown (10YR 8/3) extremely gravelly sandy loam, pale brown (10YR 6/3) moist; weak medium and fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine roots; common very fine tubular and interstitial pores; many prominent carbonate coats on rock fragments; common fine calcium carbonate masses in the matrix and many prominent platy carbonate-silica concretions and pendular nodules on the bottom of rock fragments; 10 percent petrocalcic fragments, 65 percent gravel, and 10 percent cobbles; violently effervescent; moderately alkaline (pH 8.2); clear smooth boundary. (13 to 25 cm thick)

Bk4--76 to 152 cm; pale brown (10YR 6/3) extremely gravelly sand, brown (10YR 4/3) moist; single grain; loose; many prominent platy carbonate-silica concretions and pendular nodules on the bottom of rock fragments; 5 percent petrocalcic fragments, 65 percent gravel, and 10 percent cobbles; violently effervescent; moderately alkaline (pH 8.2).

TYPE LOCATION: Lewis & Clark County, Montana; 671 meters west and 396 meters north of the SE corner of sec. 21, T.20 N., R. 6 W.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 5.6 to 8.0 degrees C
Mollic epipedon thickness - 18 to 25 cm
Rock fragments - 60 to 80 percent in the particle-size control section
Depth to sandy-skeletal material - 51 to 102 cm

A horizon
Hue: 10YR or 2.5Y
Value: 4 or 5 dry, 3 moist
Chroma: 1, 2, or 3
Texture: loam, clay loam, or sandy clay loam
Clay content: 15 to 30 percent
Rock fragments: 20 to 70 percent--10 to 40 percent gravel; 10 to 30 percent cobbles and stones
Reaction: pH 7.8 to 8.4

ABk horizon (where present)
Hue: 10YR or 2.5Y
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 2 or 3
Texture: loam, clay loam, sandy clay loam
Clay content: 15 to 30 percent
Rock fragments: 20 to 70 percent--10 to 40 percent gravel; 10 to 30 percent cobbles and stones
Reaction: pH 7.8 to 8.4

Bk1 horizon
Hue: 10YR, 2.5Y, or 5Y
Value: 7 to 8 dry; 5 or 6 moist
Chroma: 2, 3, or 4
Texture: loam or sandy clay loam
Clay content: 10 to 25 percent
Rock fragments: 30 to 70 percent--20 to 55 percent gravel; 10 to 15 percent cobbles and stones
Calcium carbonate equivalent: 15 to 40 percent
Reaction: pH 8.0 to 8.4

Bk2 and Bk3 horizons
Hue: 10YR, 2.5Y, or 5Y
Value: 8 dry, 6 or 7 moist
Chroma: 2 or 3
Texture: loam or sandy loam
Clay content: 10 to 20 percent
Rock fragments: 60 to 85 percent (includes petrocalcic fragments)--50 to 65 percent gravel; 5 to 20 percent cobbles and stones
Calcium carbonate equivalent: 40 to 60 percent
Reaction: pH 8.2 to 8.6

Bk4 horizon
Hue: 10YR, 2.5Y, or 5Y
Value: 6 or 7 dry, 4 or 5 moist
Chroma: 2 or 3
Texture: sand or loamy sand
Clay content: 0 to 10 percent
Rock fragments: 60 to 80 percent (includes petrocalcic fragments)--50 to 65 percent gravel; 10 to 20 percent cobbles and stones
Calcium carbonate equivalent: 40 to 50 percent
Reaction: pH 8.0 to 8.

COMPETING SERIES:
Grapit (CO) - have hues redder than 10YR; do not have sandy-skeletal material in lower part of the subsoil

GEOGRAPHIC SETTING:
Landform - stream terrace, alluvial fans, fan remnants, and eroded fan remnants
Elevation - 1,067 to 1,524 meters
Slope - 0 to 15 percent
Parent material - alluvium or colluvium
Climate - long, cold winters; moist springs; warm, dry summers
Mean annual precipitation - 254 to 356 mm
Mean annual temperature - 4.4 to 8 degrees C
Frost-free period - 90 to 120 days

GEOGRAPHICALLY ASSOCIATED SOILS: None listed.

DRAINAGE AND PERMEABILITY: Well drained; moderate permeability to 51 cm, moderately rapid and very rapid below.

USE AND VEGETATION: Ashlo soils are used mainly for rangeland. Potential native vegetation is mainly bluebunch wheatgrass, needleandthread, western wheatgrass, prairie junegrass, forbs, and shrubs.

DISTRIBUTION AND EXTENT: Ashlo soils are of small extent in in west-central Montana. MLRA 46.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Lewis & Clark County Area, Montana, 1991.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon (mixed) - from 0 to 18 cm (A, ABk, and part of the Bk1 horizon)
Calcic horizon - from 15 to 152 cm (Bk1, Bk2, Bk3, and Bk4 horizons)
Particle-size control section - from 25 to 100 cm (Bk2, Bk3, and part of the Bk4 horizon)

Ashlo soils have a frigid temperature regime and an ustic moisture regime bordering on aridic.

ADDITIONAL DATA: Soil interpretations record - MT0426.


National Cooperative Soil Survey
U.S.A.