LOCATION PEKAY MTEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Typic Hapluderts
TYPICAL PEDON: Pekay silty clay, cultivated. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 7 inches; very dark gray (10YR 3/1) silty clay, black (10YR 2/1) moist; moderate medium granular structure; hard, firm, moderately sticky and very plastic; common fine and very fine roots; slightly effervescent; slightly alkaline (pH 7.8); clear wavy boundary. (5 to 9 inches thick)
Bw--7 to 29 inches; dark gray (10YR 4/1) silty clay, black (10YR 2/1) moist; moderate medium and coarse prismatic structure; extremely hard, very firm, moderately sticky and very plastic; common fine and very fine roots; common fine and very fine pores; common slickensides; few medium masses of lime; slightly effervescent; moderately alkaline (pH 8.2); gradual boundary. (15 to 24 inches thick)
Bky1--29 to 47 inches; dark gray (10YR 4/1) clay, very dark gray (10YR 3/1) moist; weak fine and medium subangular blocky structure; extremely hard, very firm, moderately sticky and very plastic; common fine and very fine pores; few medium gypsum crystals; common medium soft masses of lime; strongly effervescent; moderately alkaline (pH 8.2); clear wavy boundary. (10 to 24 inches thick)
Bky2--47 to 60 inches; gray (10YR 5/1) silty clay, dark gray (10YR 4/1) moist; few medium faint brown (10YR 4/3) moist mottles; moderate medium and coarse prismatic structure; extremely hard, firm, moderately sticky and very plastic; few fine and very fine roots; few very fine pores; common medium soft masses of lime; few medium masses of gypsum; strongly effervescent; moderately alkaline (pH 8.4); clear wavy boundary. (0 to 6 inches thick)
Cky--60 to 66 inches; gray (10YR 5/1) silty clay, dark gray (10YR 4/1) moist; few medium faint dark yellowish brown (10YR 4/4) moist mottles; massive; extremely hard, firm, moderately sticky and very plastic; few very fine roots; few fine pores; common medium soft masses of lime; common medium masses of gypsum; strongly effervescent; moderately alkaline (pH 8.4).
TYPE LOCATION: Fergus County, Montana; 1247 feet south and 1310 feet west of the center of sec. 14, T. 14 N., R. 19 E.
RANGE IN CHARACTERISTICS:
Soil temperature: 41 to 45 degrees F.
Mollic epipedon thickness: 30 to 47 inches
Depth to k horizon: 12 to 33 inches
Cracking: 1 to 2 mm cracks to 30 inches
A horizon:
Hue: 10YR or 2.5Y
Value, dry: 3 or 4
Value, moist: 2 or 3
Chroma: 1 or 2
Texture: silty clay
Clay content: 40 to 50 percent
Rock fragments: none
Reaction: pH 6.6 to 7.8
Bw and Bky1 horizons:(In some pedons the B horizons
are noncalcareous to 12 inches)
Hue: 10YR or 2.5Y
Value, dry: 3 or 4
Value, moist: 2 or 3
Chroma: 1 or 2
Texture: silty clay or clay
Clay content: 45 to 60 percent
Rock fragments: none
Calcium carbonate equivalent: 3 to 10 percent
Reaction: pH 7.9 to 8.4
Bky2 horizon:(Some pedons lack a Bky2 horizon)
Hue: 10YR or 2.5Y
Value, dry: 4 or 5
Value, moist: 4
Chroma: 1 or 2
Texture: silty clay or clay
Clay content: 45 to 60 percent
Rock fragments: none
Calcium carbonate equivalent: 5 to 10 percent
Reaction: pH 7.9 to 8.4
Cky horizon: (Some pedons lack C horizons)
Hue: 10YR or 2.5Y
Value, dry: 4 or 5
Value, moist: 4
Chroma: 1 to 3
Texture: silty clay or clay
Clay content: 45 to 60 percent
Rock fragments: none
Calcium carbonate equivalent: 5 to 10 percent
Reaction: pH 7.9 to 8.4
COMPETING SERIES: These are the Jokodowski, Sinai, and Wahpeton series. Jokodowski soils do not have horizons of carbonate or gypsum accumulation and are moderately well drained. Sinai soils do not have horizons of gypsum accumulation and are moderately well drained. Wahpeton soils do not have horizons of carbonate or gypsum accumulations, are moderately well drained, and have buried horizons.
GEOGRAPHIC SETTING: Pekay soils are on terraces, fans, and foot slopes and have slope gradients of 0 to 8 percent. Elevations are 4,100 to 5,000 feet. Pekay soils formed in clayey alluvium derived from clay and silty clay shales. The climate is cool, with long cold winters and moist springs and summers. Mean annual temperature is 39 to 43 degrees F. Mean annual precipitation is 18 to 24 inches. The growing season is 90 to 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Burnel, Castle, Hoosan, and Kildor soils. Burnel soils have an argillic horizon. Castle soils are moderately deep to bedrock. Hoosan and Kildor soils are less clayey. Also, Kildor soils are moderately deep to bedrock and are cryic.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; slow permeability.
USE AND VEGETATION: Pekay soils are used for dry cropland, hay, pasture, and rangeland. The potential native vegetation is mainly basin wildrye, rough fescue, Columbia needlegrass, bearded wheatgrass, Idaho fescue, forbs, and shrubs.
DISTRIBUTION AND EXTENT: Central and eastern Montana in foothills area. Pekay soils are inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Fergus County, Montana, 1979.