LOCATION MARIAS MT+ND WYEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Aridic Haplusterts
TYPICAL PEDON: Marias clay, in cropland. (Colors are for dry soil unless otherwise noted)
Ap--0 to 6 inches; grayish brown (2.5Y 5/2) clay, dark grayish brown (2.5Y 4/2) moist; strong very fine granules structure; hard, friable, sticky and very plastic; common fine roots; after a rain a thin weak crust consisting of adhering soil granules forms on the soil surface; slightly effervescent; moderately alkaline (pH 7.9); abrupt smooth boundary. (3 to 10 inches thick)
Bw--6 to 11 inches; grayish brown (2.5Y 5/2) clay, dark grayish brown (2.5Y 4/2) moist; strong coarse angular blocky structure parting to moderate very fine angular blocky; very hard, firm, sticky and very plastic; common fine roots; common fine tubular pores; dark grayish brown (2.5Y 4/2) organic coatings on faces of peds; slightly effervescent; moderately alkaline (pH 8.0); gradual smooth boundary. (0 to 15 inches thick)
Bss--11 to 27 inches; grayish brown (2.5Y 5/2) clay, dark grayish brown (2.5Y 4/2) moist; strong coarse angular blocky structure parting to moderate very fine angular blocky; very hard, firm, sticky and very plastic; few fine roots; common very fine tubular pores; common slickensides with intersecting surfaces 20 to 40 degrees from horizontal; slightly effervescent; moderately alkaline (pH 8.0); clear smooth boundary. (10 to 25 inches thick)
Bssy--27 to 60 inches, gray (5Y 5/1) clay, very dark gray (5Y 3/1) moist; moderate very coarse prismatic structure parting to moderate very fine granular; very hard, firm, sticky and very plastic; thick slickensides on faces of prisms; many large (1 inch diameter) masses and threads of gypsum crystals; slightly effervescent; moderately alkaline (pH 8.0).
TYPE LOCATION: Valley County, Montana; 2,000 feet west and 120 feet north of the SE corner of sec. 7, T. 31 N., R. 35 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F.
Moisture control section - between 4 and 12 inches; dry in all parts between four-tenths and five-tenths of the cumulative days per year when the soil temperature at a depth of 20 inches is 41 degrees F or higher.
Depth to accumulation of gypsum - 20 to 45 inches.
Linear extensibility - .06 to .10 in the upper 30 inches of soil; cracks 5 mm or more wide to 50 cm.
Soil phases - bedrock substratum.
A By horizon is allowed.
Ap horizon - Hue: 10YR, 2.5Y, 5Y
Value: 4, 5, or 6 dry; 3, 4, or 5 moist
Chroma: 1, 2, or 3
Texture: clay, silty clay, or silty clay loam
Clay content: 27 to 60 percent
EC: 0 to 4 mmhos/cm
SAR: 1 to 4
Calcium carbonate equivalent: 1 to 10 percent
Reaction: pH 7.4 to 8.4.
Bw horizon - Hue: 10YR, 2.5Y, 5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2 or 3
Texture: clay or silty clay
Clay content: 40 to 60 percent clay
EC: 0 to 4 mmhos/cm
SAR: 1 to 4
Calcium carbonate equivalent: 1 to 10 percent
Reaction: pH 7.9 to 8.4
Bss horizon - Hue: 10YR, 2.5Y, or 5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2 or 3
Texture: clay or silty clay
Clay content: 40 to 60 percent clay
Slickensides: common or many
EC: 0 to 4
SAR: 1 to 4
Calcium carbonate equivalent: 1 to 10 percent
Reaction: pH 7.9 to 9.0
Bssy horizon - Hue: 10YR, 2.5Y, 5Y
Value: 5 or 6 dry; 3, 4, or 5 moist
Chroma: 1, 2, 3 or 4
Texture: clay or silty clay
Clay content: 40 to 60
Gypsum: 1 to 6 percent
EC: 2 to 4 mmhos/cm above a depth of 30 inches and 2 to 8 mmhos/cm below
SAR: 1 to 4 above 30 inches and 4 to 13 below
Calcium carbonate equivalent: 2 to 10 percent
Reaction: pH 7.9 to 9.0
COMPETING SERIES:
There are no competing series.
GEOGRAPHIC SETTING:
Landform - alluvial fans; stream terraces; lake plains; sedimentary plains; hills.
Elevation - 1,900 to 4,850 feet.
Slope- 0 to 15 percent.
Parent material - calcareous alluvium or glaciolacustrine or lacustrine deposits.
Climate - long, cold winters; moist springs; warm summers.
Mean annual precipitation - 10 to 14 inches, most of which falls in the spring and early part of summer.
Mean annual air temperature - 39 to 45 degrees F.
Frost-free period - 90 to 135 days.
DRAINAGE AND PERMEABILITY: Well drained. Very slow permeability. Runoff is medium to very high depending on slope.
USE AND VEGETATION: Marias soils are used mainly for nonirrigated and irrigated crops. Some soils are also used for range. The potential native vegetation is mainly western wheatgrass, green needlegrass, bluebunch wheatgrass, forbs, and shrubs.
DISTRIBUTION AND EXTENT: Marias soils are of moderate extent and are mainly in central and eastern Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Milk River Area, Montana, 1928.
REMARKS: Soil interpretation records: MT0013, MT0815.
Diagnostic horizons and features recognized in this pedon are: ochric epipedon - the zone from the surface of the soil to a depth of 6 inches (Ap horizon); cambic horizon - the zone from 6 to 27 inches (Bw and Bss horizons); accumulation of gypsum - the zone from 27 to 60 inches (Bssy horizon); particle-size control section - the zone from 10 to 40 inches (Bw, Bss and Bssy horizons).
ADDITIONAL DATA: Laboratory data S62MT-105-1, S62MT-105-2, S67MT-13-2.