LOCATION GERBER MTEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Vertic Argiustolls
TYPICAL PEDON: Gerber silty clay loam, in cropland (colors are for dry soil unless otherwise noted).
Ap--0 to 7 inches; dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; strong fine and very fine granular structure that becomes cloddy when cultivated; hard, friable, sticky and plastic; common fine and very fine roots; neutral (pH 7.0); abrupt wavy boundary. (6 to 9 inches thick)
Bt1--7 to 11 inches, brown (10YR 5/3) silty clay, dark brown (10YR 4/3) moist; moderate medium prismatic structure parting to strong fine and very fine subangular blocky; very hard, friable, sticky and very plastic; common fine and very fine roots; many very fine pores; few fine and medium pores; continuous thin very dark grayish brown (10YR 3/2) moist; clay films on faces of peds; mildly alkaline (pH 7.4); clear wavy boundary. (3 to 5 inches thick)
Bt2--11 to 14 inches, brown (10YR 5/3) silty clay, dark brown (10YR 4/3) moist; strong medium prismatic structure parting to strong fine and very fine subangular blocky; very hard, friable, sticky and plastic; common fine and very fine roots; many fine and very fine pores, few medium pores; continuous thin very dark grayish brown (10YR 3/2) moist, clay films on faces of peds; common pressure faces; mildly alkaline (pH 7.4); clear wavy boundary. (3 to 6 inches thick)
Bk1--14 to 24 inches; grayish brown (2.5Y 5/2) silty clay, dark grayish brown (2.5Y 4/2) moist; strong medium and coarse prismatic structure parting to moderate fine and medium subangular blocky extremely hard, friable, sticky and plastic; few fine and very fine roots; many very fine pores, few fine and medium pores; common masses of segregated lime; strongly effervescent; moderately alkaline (pH 8.0); diffuse wavy boundary.
Bk2--24 to 32 inches; light brownish gray (2.5Y 6/2) silty clay loam, dark grayish brown (2.5Y 4/2) moist; moderate medium and coarse prismatic structure parting to weak thick and very thick platy in the lower part; very hard, friable, sticky and plastic; few fine and very fine roots; common fine and very fine pores, few medium pores; common masses of segregated lime; strongly effervescent; moderately alkaline (pH 8.2); gradual wavy boundary. (The Bk horizons are 12 to 22 inches thick.)
2Bk--32 to 46 inches; grayish brown (2.5Y 5/2) clay loam till, dark grayish brown (2.5Y 4/2) moist; weak thick and very thick platy structure; extremely hard, firm, sticky and plastic; common fine and very fine pores; few masses of segregated lime; strongly effervescent; few pebbles, shale and lignite chips; moderately alkaline (pH 8.2); diffuse wavy boundary. (0 to 18 inches thick)
2C--46 to 60 inches; grayish brown (2.5Y 5/2) clay loam till, dark grayish brown (2.5Y 4/2) moist; weak thick and very thick platy structure; extremely hard, firm sticky and plastic; slightly effervescent; few pebbles, shale and lignite chips; moderately alkaline (pH 8.2).
TYPE LOCATION: Cascade County, Montana; 900 feet east and 100 feet north of SW corner of NW 1/4 of sec. 24, T. 20 N., R 5 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F.
Moisture control section - between 4 and 12 inches.
Mollic epipedon thickness - 7 to 12 inches.
Depth to Bk horizon - 12 to 20 inches.
When dry these soils form cracks that are 1 centimeter or more wide at depths of 20 inches or more. They have few to common pressure faces in the lower part of the Bt horizon.
A or Ap horizon - Value: 4 or 5 dry; 3 moist
Chroma: 2 or 3
Texture: silty clay loam, clay loam, silty clay, or clay
Clay content: 30 to 50 percent
Reaction: pH 6.6 to 7.8
Bt1 and Bt2 horizon - Value: 4 or 5 dry; 3 or 4 moist
Chroma: 2 or 3
Texture: silty clay or clay
Clay content: 45 to 60 percent
Reaction: pH 7.4 to 8.4
A Btk horizon is allowed.
Bk1 and Bk2 horizon - Hue: 10YR or 2.5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 or 3
Texture: silty clay, silty clay loam, clay loam, or clay
Clay content: 35 to 50 percent
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.4 to 8.4
2Bk and 2C horizon - Hue: 10YR or 2.5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture: clay loam, silty clay loam, silty clay, or clay
Clay content: 35 to 50 percent
Rock fragments: 0 to 10 percent pebbles
Calcium carbonate equivalent: 3 to 15 percent
Reaction: pH 7.4 to 9.0
Some pedons have By and C horizons.
COMPETING SERIES:
Ridgeview (SD) - formed in residuum from shale, have accumulations of gypsum, have shale bedrock at depths between 40 and 60 inches, and do not have a discontinuity of till above 60 inches.
Gerbana (MT) - has a paralithic contact between the depths of 20 and 40 inches.
GEOGRAPHIC SETTING:
Landforms - alluvial fans, stream terraces, lake plains, sedimentary plains, till plains, and hills.
Elevations - 3,000 to 4,200 feet.
Slopes- 0 to 15 percent.
Parent material - alluvium, till, glaciofluvial or glaciolacustrine deposits.
Climate - long, cold winters; moist springs, and warm summers.
Mean annual precipitation - 13 to 19 inches.
Mean annual temperature - 40 to 45 degrees F.
Frost-free period - 90 to 130 days.
DRAINAGE AND PERMEABILITY: Well drained; slow permeability.
USE AND VEGETATION: Gerber soils are used mainly for dryland crops. Some areas are used as rangeland. Potential native vegetation is mainly bluebunch wheatgrass, rough fescue, Idaho fescue, western wheatgrass, and Columbia needlegrass.
DISTRIBUTION AND EXTENT: Gerber soils are of moderate extent on the glaciated plains in northern Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Cascade County, Montana, 1975.
REMARKS: Soil interpretation record: MT0098. Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from the soil surface to 7 inches (Ap horizon); an argillic horizon from 7 to 14 inches, that is also the particle-size control section (Bt1, Bt2 horizons); horizons of secondary carbonate accumulation from 14 to 46 inches (Bk1, Bk2, 2Bk horizons); a discontinuity of till at 32 inches (2Bk horizon). Gerber soils have a frigid temperature regime and an ustic moisture regime. The Gerber soils were classified as Udorthentic Chromusterts. They do not have the intersecting slickensides needed for the Vertisol order. They do have pressure faces on ped surfaces and deep cracks to 20 inches.