LOCATION TRIMAD MT+WY
Established Series
Rev. JB-JJU-RJS
09/2011
TRIMAD SERIES
The Trimad series consists of very deep, well drained soils that formed in alluvium or colluvium. These soils are on alluvial fans, fan remnants, stream terraces, basin floors, hills and escarpments. Slopes are 0 to 60 percent. Mean annual precipitation is about 12 inches, and mean annual air temperature is about 40 degrees F.
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Aridic Calciustolls
TYPICAL PEDON: Trimad cobbly loam, native grassland (colors are for dry soil unless otherwise noted).
A--0 to 2 inches; dark grayish brown (10YR 4/2) cobbly loam, very dark grayish brown (10YR 3/2) moist; moderate very fine granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine and fine irregular pores; 10 percent gravel and 10 percent cobbles; neutral (pH 7.1); clear smooth boundary. (2 to 6 inches thick)
Bw--2 to 6 inches; brown (10YR 5/3) gravelly loam, dark brown (10YR 3/3) moist; moderate medium prismatic structure parting to fine strong subangular blocky; hard, friable, moderately sticky and moderately plastic; many fine roots; many very fine irregular and tubular pores; 15 percent gravel and 10 percent cobbles; neutral (pH 7.2); clear smooth boundary. (0 to 5 inches thick)
Bk1--6 to 9 inches; light gray (10YR 7/2) gravelly loam, grayish brown (10YR 5/2) moist; weak medium prismatic structure parting to moderate fine subangular blocky; slightly hard, friable, slightly sticky and slightly plastic; common fine roots; common very fine irregular and tubular pores; 15 percent gravel and 5 percent cobbles; calcium carbonate coatings on gravel and cobbles, and finely disseminated calcium carbonate; strongly effervescent; slightly alkaline (pH 7.7); clear smooth boundary. (0 to 14 inches thick)
Bk2--9 to 18 inches; light gray (10YR 7/2) very gravelly loam, light brownish gray (10YR 6/2) moist; massive; slightly hard, very friable, nonsticky and nonplastic; common very fine roots; common fine vesicular pores, and few very fine tubular pores; 30 percent gravel and 10 percent cobbles; calcium carbonate coatings on gravel and cobbles, and finely disseminated calcium carbonate; violently effervescent; moderately alkaline (pH 8.0); clear wavy boundary. (6 to 25 inches thick)
Bk3--18 to 60 inches; light brownish gray (10YR 6/2) extremely gravelly sandy loam, grayish brown (10YR 5/2) moist; massive; soft, very friable, nonsticky and nonplastic; few very fine roots; many fine irregular pores; 50 percent gravel and 20 percent cobbles; calcium carbonate coatings on gravel and cobbles, and finely disseminated calcium carbonate; strongly effervescent; slightly alkaline (pH 7.6).
TYPE LOCATION: Madison County, Montana; approximately 400 feet north and 2,000 feet east of the southwest corner of sec. 8, T. 6S, R. 1E.
RANGE IN CHARACTERISTICS:
Soil temperature: 40 to 44 degrees F.
Mollic epipedon thickness: 7 to 10 inches
Depth to calcic horizon: 6 to 12 inches
Note: Calcareous to the surface when mixed to 7 inches.
A horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 4 or 5; dry
Chroma: 2 or 3; dry or moist
Texture: loam or fine sandy loam
Clay content: 10 to 27 percent
Rock fragments: 5 to 50 percent--0 to 30 percent gravel, 0 to 25 percent cobbles and stones
Calcium carbonate equivalent: 0 to 5 percent
Reaction: pH 6.6 to 8.4
Bw horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 4 or 5; dry
Chroma: 2 or 3; dry or moist
Texture: loam, sandy loam or sandy clay loam
Clay content: 10 to 27 percent
Rock fragments: 15 to 50 percent--5 to 30 percent gravel, 0 to 20 percent cobbles and stones
Calcium carbonate equivalent: 0 to 5 percent
Reaction: pH 6.6 to 8.4
Bk1 horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 2 to 4; dry or moist
Texture: loam, sandy loam or sandy clay loam
Clay content: 10 to 27 percent
Rock fragments: 15 to 50 percent--5 to 35 percent gravel, 5 to 20 percent cobbles and stones
Calcium carbonate equivalent: 10 to 25 percent
Reaction: pH 7.4 to 8.4
Bk2 horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 2 to 4; dry or moist
Texture: loam, sandy loam or sandy clay loam
Clay content: 10 to 25 percent
Rock fragments: 35 to 70 percent--25 to 45 percent gravel, 5 to 25 percent cobbles and stones
Calcium carbonate equivalent: 15 to 30 percent
Reaction: pH 7.4 to 8.4
Bk3 horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 6 to 8 dry; 5 or 6 moist
Chroma: 2 to 4; dry or moist
Texture: loam or sandy loam
Clay content: 10 to 18 percent
Rock fragments: 35 to 70 percent--25 to 60 percent gravel, 5 to 20 percent cobbles
Calcium carbonate equivalent: 10 to 25 percent
Reaction: pH 7.4 to 8.4
COMPETING SERIES:
Arle (CO) - are moderately deep to a paralithic contact
Guben (UT) - have an ABt horizon
Spudbar (MT) - are moderately deep to a lithic contact
Tricart (MT) - have a lithologic discontinuity
Tridell (UT) - have lower precipitation in spring and early summer
Whetrock (UT) - are moderately deep to a paralithic contact
GEOGRAPHIC SETTING:
Landform - alluvial fans, fan remnants, stream terraces, basin floors, hills and escarpments
Elevation - 4,000 to 7,600 feet
Slope - 0 to 60 percent
Parent material - alluvium or colluvium
Climate - cool with long, cold winters; moist springs; hot, dry summers
Mean annual precipitation - 10 to 15 inches
Mean annual temperature - 38 to 45 degrees F.
Frost-free period - 70 to 115 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; permeability is moderate to about 20 inches and moderately rapid below.
USE AND VEGETATION: These soils are used mainly as rangeland. Under irrigation these soils are also used for hay and pasture. The potential native vegetation is mainly bluebunch wheatgrass, needleandthread, and prairie junegrass.
DISTRIBUTION AND EXTENT: Moderately extensive in southwestern Montana and north central Wyoming. MLRAs - 43B, 44B, 46, 49, 58A, 67A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Madison County Area, Montana, 1983.
Remarks: Diagnostic horizons and features recognized in this soil are:
Mollic epipedon - from 0 to 7 inches when mixed (A, Bw, part of Bk1 horizons)
Calcic horizon - from 6 to 60 inches (Bk1, Bk2, Bk3 horizons)
Particle-size control section - from 10 to 40 inches (part of Bk2, part of Bk3 horizons)
Trimad soils have a frigid temperature regime and an ustic moisture regime bordering on aridic.
National Cooperative Soil Survey
U.S.A.