LOCATION POIN MT+WY
Established Series
Rev. JB-JJU-EMM
04/2014
POIN SERIES
The Poin series consists of shallow, well drained soils that formed in colluvium and residuum derived from gneiss-schist, sandstone, rhyolite, granite, quartzite or welded tuff bedrock. These soils are on bedrock floored plains, hills, ridges and mountains. Slopes are 4 to 60 percent. Mean annual precipitation is about 17 inches, and mean annual temperature is about 38 degrees F.
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive Lithic Haplocryolls
TYPICAL PEDON: Poin very flaggy sandy loam, native grassland. (colors are for dry soil unless otherwise noted)
A--0 to 5 inches; grayish brown (10YR 5/2) very flaggy sandy loam, very dark brown (10YR 2/2) moist; moderate very fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine and fine roots; common very fine and fine tubular pores; 25 percent channers and 15 percent flagstones; neutral (pH 7.2); abrupt wavy boundary. (3 to 8 inches thick)
Bw1--5 to 12 inches; brown (10YR 5/3) extremely channery sandy loam, brown (10YR 4/3) moist; weak very fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine and fine roots; common very fine and fine tubular pores; 45 channers and 15 percent flagstones; neutral (pH 7.2); clear smooth boundary.
Bw2--12 to 19 inches; pale brown (10YR 6/3) extremely flaggy sandy loam, brown (10YR 5/3) moist; weak very fine granular structure; soft, very friable, nonsticky and nonplastic; common very fine and fine roots; 20 percent channers and 60 percent flagstones; neutral (pH 7.3); gradual irregular boundary. (combined thickness of Bw1, Bw2 horizons - 7 to 15 inches)
R--19 inches; fractured gneiss-schist bedrock; few fine roots in some cracks.
TYPE LOCATION: Madison County, Montana; approximately 2,500 feet north and 1,900 feet east of the southwest corner of sec. 4, T. 2S, R. 7W.
RANGE IN CHARACTERISTICS:
Soil temperature: 36 to 42 degrees F.
Mollic epipedon thickness: 7 to 15 inches
Depth to a lithic contact: 10 to 20 inches, but mainly 12 to 20 inches
Note: Some pedons may have a thin C horizon overlying the bedrock.
A horizon
Hues: 10YR or 7.5YR; dry or moist
Value: 4 or 5 dry; 2 or 3 moist
Chroma: 2 to 3; dry or moist
Texture: sandy loam, coarse sandy loam or loam
Clay content: 5 to 25 percent
Rock fragments: 5 to 60 percent--5 to 45 percent gravel or channers, 0 to 30 percent flagstones or cobbles, 0 to 5 percent stones
Reaction: pH 5.6 to 7.4
Bw1 horizon
Hues: 10YR or 7.5YR; dry or moist
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 2 to 3; dry or moist
Texture: loam, sandy loam or coarse sandy loam
Clay content: 5 to 18 percent
Rock fragments: 35 to 70 percent--25 to 50 percent gravel or channers, 10 to 35 percent cobbles or flagstones
Reaction: pH 6.1 to 7.8
Bw2 horizon
Hues: 10YR or 7.5YR; dry or moist
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 to 3; dry or moist
Texture: sandy loam or coarse sandy loam
Clay content: 5 to 18 percent
Rock fragments: 60 to 90 percent--45 to 65 percent gravel or channers, 15 to 35 percent cobbles or flagstones
Reaction: pH 6.1 to 7.8
C horizon (where present)
Hues: 10YR or 7.5YR; dry or moist
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 to 3; dry or moist
Texture: sandy loam, coarse sandy loam or loamy sand
Clay content: 5 to 15 percent
Rock fragments: 60 to 90 percent--45 to 65 percent gravel or channers, 15 to 35 percent cobbles or flagstones
Reaction: pH 6.1 to 7.8
COMPETING SERIES:
Arrowpeak (MT) - have an udic moisture regime
Betemer (CO) - have greater than 18 percent clay throughout
Catlinsprings (MT) - have greater than 18 percent clay in the Bw horizon
Cheadle (MT) - have secondary calcium carbonate accumulation
Chokecherry (ID) - have a xeric moisture regime
Clamp (OR) - have a xeric moisture regime
Dalys (MT) - have a lithic contact at less than 10 inches
Dollarhide (ID) - have a xeric moisture regime
Eyre (CO) - do not have a cambic horizon
Irigul (WY) - do not have a cambic horizon
Irson (WY) - do not have a cambic horizon
Jonlake (NV) - have a xeric moisture regime
Labshaft (NV) - have 25 to 35 percent clay in the Bw horizon
Mccadden (UT) - have secondary calcium carbonate accumulation
Rogert (CO) - do not have a cambic horizon
Schwacheim (CO) - have an udic moisture regime
Starley (WY) - have secondary calcium carbonate accumulation
Topeki (NV) - have a xeric moisture regime
Trump (CO) - have secondary calcium carbonate accumulation
Udel (NV) - have a lithic contact at less than 10 inches
GEOGRAPHIC SETTING:
Landform - bedrock floored plains, hills, ridges and mountains
Elevation - 5,500 to 8,500 feet
Slope - 4 to 60 percent
Parent material - colluvium and residuum derived from gneiss-schist, sandstone, rhyolite, granite, quartzite or welded tuff bedrock
Climate - cool with long, cold winters and moist springs
Mean annual precipitation - 14 to 24 inches
Mean annual temperature - 34 to 40 degrees F.
Frost-free period - 30 to 70 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Oro fino and
Sebud soils. These soils are very deep and occur on similar landforms.
DRAINAGE AND PERMEABILITY: Well drained; moderately rapid permeability.
USE AND VEGETATION: These soils are used mainly as rangeland. The potential native vegetation is mainly bluebunch wheatgrass, Idaho fescue, Columbia needlegrass, forbs and shrubs.
DISTRIBUTION AND EXTENT: These soils are of moderate extent in southwestern Montana. MLRAs - 43B, 44B, 46, 48A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Madison County, Montana, 1983.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from 0 to 7 inches mixed (A, part of Bw1 horizons)
Cambic horizon - from 7 to 19 inches (part of Bw1, Bw2 horizons)
Lithic contact - at 19 inches (R horizon)
Particle-size control section - from 10 to 19 inches (part of Bw1, Bw2 horizons)
Poin soils have a cryic temperature regime an ustic moisture regime.
National Cooperative Soil Survey
U.S.A.