LOCATION DARRET MT
Established Series
Rev. CAM-SHB-EMM
07/2012
DARRET SERIES
The Darret series consists of moderately deep, well drained soils formed in material weathered from interbedded shale and sandstone. They are on sedimentary plains and hills. Slopes are 0 to 35 percent. Mean annual precipitation is about 15 inches and mean annual air temperature is about 43 degrees F.
TAXONOMIC CLASS: Fine, mixed, superactive, frigid Typic Argiustolls
TYPICAL PEDON: Darret silty clay loam - native grass (Colors are for dry soil unless otherwise noted.)
A--0 to 4 inches; dark reddish gray (5YR 4/2) silty clay loam, dark reddish brown (5YR 3/2) moist; weak fine granular structure; slightly hard, friable, moderately sticky and moderately plastic; many very fine roots; neutral (pH 7.0); clear smooth boundary. (4 to 6 inches thick)
Bt1--4 to 8 inches; dark reddish gray (5YR 4/2) silty clay loam, dark reddish brown (5YR 3/2) moist; weak medium prismatic structure that parts to moderate medium subangular blocky; hard, friable, moderately sticky and moderately plastic; many very fine roots; continuous distinct clay films on faces of peds; neutral (pH 7.0); clear smooth boundary. (0 to 6 inches thick)
Bt2--8 to 13 inches; weak red (2.5YR 4/2) silty clay, dusky red (2.5YR 3/2) moist; moderate medium and coarse prismatic structure that separates to moderate medium and fine subangular blocky; hard, friable, very sticky and very plastic; continuous distinct clay films on faces of peds; many very fine roots; slightly alkaline (pH 7.4); clear smooth boundary (4 to 11 inches thick)
BC--13 to 19 inches; weak red (2.5YR 4/2) paragravelly clay loam, dusky red (2.5YR 3/2) moist; massive; hard, firm, moderately sticky and moderately plastic; many very fine roots; 20 percent shale and soft sandstone fragments; slightly effervescent; moderately alkaline (pH 8.0); clear smooth boundary. (0 to 10 inches thick)
BCk--19 to 28 inches; weak red (2.5YR 4/2) paragravely clay loam, dusky red (2.5YR 3/2) moist; massive; slightly hard, friable, moderately sticky and moderately plastic; few roots; strongly effervescent; lime coating on underside of most shale and sandstone fragments and continuous coating on some; about 20 percent shale and sandstone fragments; moderately alkaline (pH 8.0); clear wavy boundary. (0 to 10 inches thick)
Cr--28 to 60 inches; reddish interbedded soft sandstone and shale; few roots that extend beyond 19 inches are compressed into a horizontal mat between the shale and sandstone layers; moderately effervescent.
TYPE LOCATION: Judith Basin County, Montana; 20 feet east of center of road; 1,325 feet east and 500 feet north of W1/4 corner of section 28, T.18N., R.8E.
RANGE IN CHARACTERISTICS:
Average annual soil temperature - 43 to 47 degrees F.
Average summer soil temperature - 60 to 64 degrees F.
Depth to paralithic contact - 20 to 40 inches.
A horizon
Hue: 7.5YR to 2.5YR
Value: 4 or 5 dry, 2 or 3 moist
Chroma: 2 or 3
Texture: loam, clay loam or silty clay loam
Clay content: 20 to 35 percent
Reaction: pH 6.6 to 7.8
Bt1 horizon
Hue: 7.5YR to 2.5YR
Value: 4 or 5 dry, 2 or 3 moist
Chroma: 2 or 3
Texture: loam, clay loam or silty clay loam
Clay content: 20 to 35 percent
Reaction: pH 6.6 to 7.8
Bt2 horizon
Hue: 7.5YR to 2.5YR
Value: 4 to 6 dry, 3 to 5 moist
Chroma: 2 to 6
Texture: clay loam, silty clay loam or silty clay
Clay content: 35 to 45 percent
Reaction: pH 6.6 to 8.4
Btk horizon present in some pedons.
BC and BCk horizons
Hue: 7.5YR to 2.5YR
Value: 4 to 6 dry, 3 to 5 moist
Chroma: 2 to 6
Texture: paragravelly clay loam, silty clay loam or silty clay
Clay content: 30 to 45 percent
Rock fragments: 0 to 25 percent soft shale and sandstone
Calcium carbonate equivalent: 5 to 10 percent
Reaction: pH 7.4 to 8.4
COMPETING SERIES:
Alder (MT) - 18 to 24 inch precipitation zone.
Bacbuster (MT) - has a Bk horizon; hues are mostly 10YR or yellower throughout.
Bigbear (MT) - is very deep.
Billman (MT) - does not have horizon of secondary carbonate accumulation.
Charo (NM) - moderately deep to lithic contact of basalt.
Durston (MT) - is very deep.
Microy (NM) - moderately deep to lithic contact of basalt.
Mishakal (MT) - does not have horizon of secondary carbonate accumulation.
Pino (NM) - does not have horizon of secondary carbonate accumulation.
Roaringlion (MT) - does not have a horizon of secondary carbonate accumulation.
Turkeysprings (NM) - do not have a paralithic contact above 60 inches.
Wilcoxson (NM) - is deep to a lithic contact.
GEOGRAPHIC SETTING:
Landform - sedimentary plains and hills
Elevation - 3,000 to 6,000 feet
Slope - 0 to 35 percent
Climate - long, cold winters, moist springs, warm summers
Mean annual precipitation - 12 to 17 inches, with those areas receiving less than 14 inches having cooler temperatures and lower evaporation.
Mean annual temperature - 41 to 45 degrees F.
Frost-free period - 80 to 135 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well-drained; moderately slow or slow permeability.
USE AND VEGETATION: Used for range and for dryland production of small grain. Native vegetation is bluebunch wheatgrass, needle-and-thread, blue grama, and fringed sagewort.
DISTRIBUTION AND EXTENT: Central and southern Montana, adjacent to mountainous areas. Darret soils are moderately extensive. MLRAs 46 and 58A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Reconnaissance Soil Survey of Central Montana, 1946.
REMARKS: Diagnostic horizons and features recognized in this pedon are: Mollic epipedon - from the surface to 8 inches (A and Bt1 horizons)
Argillic horizon - from 4 to 13 inches (Bt1 and Bt2 horizons)
Particle-size control section - from 4 to 13 inches (Bt1 and Bt2 horizons)
Horizon of secondary carbonate accumulation - from 19 to 28 inches (Bk horizon)
Paralithic contact - at 28 inches (Cr horizon)
Darret soils have an ustic moisture regime and a frigid temperature regime.
National Cooperative Soil Survey
U.S.A.