LOCATION PENDROY MTEstablished Series
TAXONOMIC CLASS: Very-fine, smectitic, frigid Aridic Haplusterts
TYPICAL PEDON: Pendroy clay, grassland (colors are for dry soil unless otherwise noted).
A--0 to 3 inches; grayish brown (2.5Y 5/2) clay, dark grayish brown (2.5Y 4/2) moist; moderate fine and very fine granular structure; very hard, friable, sticky and very plastic; many very fine roots; many very fine pores; slightly effervescent; slightly alkaline (pH 7.8); clear wavy boundary. (2 to 5 inches thick)
Bss1--3 to 7 inches; grayish brown (2.5Y 5/2) clay, dark grayish brown (2.5Y 4/2) moist; moderate fine angular blocky structure; extremely hard, firm, sticky and very plastic; many very fine roots; many very fine pores; 1 to 3 inch wide vertical cracks that are 2 to 6 inches apart; continuous distinct slickensides that intersect at a 30 to 60 degree angle; slightly effervescent; slightly alkaline (pH 7.8); diffuse wavy boundary.
Bss2--7 to 30 inches; grayish brown (2.5Y 5/2) clay, dark grayish brown (2.5Y 4/2) moist; weak coarse angular blocky structure; extremely hard, firm, sticky and very plastic; common very fine roots; few very fine pores; continuous distinct slickensides that intersect at a 30 to 60 degree angle; slightly effervescent; slightly alkaline (pH 7.8); diffuse wavy boundary. (Combined Bss horizons 15 to 45 inches thick)
Bssy--30 to 42 inches; grayish brown (2.5Y 5/2) clay, dark grayish brown (2.5Y 4/2) moist; weak coarse angular blocky structure; very firm, sticky and plastic; few very fine roots; few very fine pores; few distinct gray (2.5Y 5/0) and dark gray (2.5Y 4/0) moist; bands of clay; continuous distinct slickensides that intersect at a 30 to 60 degree angle; few fine seams of gypsum; slightly effervescent; moderately alkaline (pH 8.2); clear wavy boundary. (0 to 20 inches thick)
BCy--42 to 70 inches, grayish brown (2.5Y 5/2) silty clay, dark grayish brown (2.5Y 4/2) moist; massive; extremely hard, very firm, sticky and plastic; many gray (N 5/ ) and dark gray (N 4/ ) bands of clay below 50 inches; common coarse seams and masses of gypsum; slightly effervescent; moderately alkaline (pH 8.4).
TYPE LOCATION: Cascade County, Montana; 800 feet west and 110 feet north of SE corner of the SW 1/4 of sec. 18, T.22 N., R. 4 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F.
Depth to gypsum accumulations - 20 to 50 inches.
When dry these soils form cracks 1 to 4 inches wide at the surface that extend to depths of 20 inches or more, where they are still 1 cm or more wide. A bedrock substratum phase is recognized.
A horizon - Hue: 10YR or 2.5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 or 3
Texture: clay or silty clay
Clay content: 60 to 75 percent
EC: 0 to 4 mmhos/cm
Reaction: pH 7.4 to 8.4
Bss1, Bss2 horizons - Hue: 10YR or 2.5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture: clay or silty clay
Clay content: 60 to 75 percent
EC: 2 to 4 mmhos/cm
Reaction: pH 7.4 to 8.4
Bssy horizon - Hue: 10YR or 2.5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture: clay or silty clay
Clay content: 60 to 75 percent
Slickensides: few to continuous
EC: 2 to 4 mmhos/cm
Gypsum: 2 to 8 percent
Reaction: pH 7.4 to 8.4
BCy horizon - Hue: 10YR, 2.5Y, or 5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture: silty clay or clay
Clay content: 50 to 65 percent
EC: 2 to 4 mmhos/cm
Gypsum: 2 to 6 percent
Reaction: pH 7.9 to 8.4
COMPETING SERIES:
There are no competing series.
GEOGRAPHIC SETTING:
Landform - alluvial fans; floodplains; stream terraces; lake plains.
Elevation - 2,600 to 4,200 feet.
Slope- 0 to 15 percent.
Parent material - clayey glaciofluvial or glaciolacustrine material or in alluvium from sedimentary plains.
Climate - long, cold winters; moist springs; warm summers.
Mean annual precipitation - 10 to 14 inches.
Mean annual air temperature - 40 to 45 degrees F.
Frost-free period - 100 to 135 days.
DRAINAGE AND PERMEABILITY: Well drained; very slow permeability.
USE AND VEGETATION: Pendroy soils are used for dryland crops and as rangeland. Potential native vegetation is mainly green needlegrass, bluebunch wheatgrass, and western and thickspike wheatgrass.
DISTRIBUTION AND EXTENT: Pendroy soils are extensive on the glaciated plains in northern Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Cascade County, Montana, 1969.
REMARKS: Soil interpretation record: MT0116, MT0848.
Diagnostic horizons and features recognized in this pedon are: ochric epipedon - from the soil surface to 7 inches, mixed (A, Bss1 horizons); intersecting slickensides - between 3 and 42 inches and cracks more than 1 cm wide extending to 30 inches or more (Bss1, Bss2 horizons); particle-size control section - from 10 to 40 inches (Bss2, Bss3 horizons); horizon of gypsum accumulation - from 30 to 70 inches (Bssy, BCy horizons). Pendroy soils have a frigid temperature regime and an ustic moisture regime that borders on aridic.
ADDITIONAL DATA: Laboratory sample S67MT-013-7.