LOCATION BROCKWAY MT
Established Series
Rev. GFB-KTS-RJS
03/2011
BROCKWAY SERIES
The Brockway series consists of very deep, well drained soils that formed in silty loess, lake sediments and alluvium. These soils are on alluvial fans, fan remnants, hills and lake plains. Slopes are 0 to 35 percent. Mean annual precipitation is about 12 inches, and mean annual air temperature is about 43 degrees F.
TAXONOMIC CLASS: Fine-silty, mixed, superactive, frigid Aridic Calciustepts
TYPICAL PEDON: Brockway silt loam, cultivated (colors are for dry soil unless otherwise noted).
Ap--0 to 6 inches; grayish brown (10YR 5/2) silt loam, dark grayish brown (10YR 4/2) moist; moderate fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; strongly effervescent; moderately alkaline (pH 8.0); abrupt smooth boundary. (4 to 10 inches thick)
Bk1--6 to 11 inches; light brownish gray (2.5Y 6/2) silt loam, light olive brown (2.5Y 5/4) moist; weak medium prismatic structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine roots; many fine and very fine tubular pores; disseminated calcium carbonate; violently effervescent; moderately alkaline (pH 8.4); abrupt smooth boundary. (4 to 10 inches thick)
Bk2--11 to 18 inches; light gray (2.5Y 7/2) stratified silty clay loam and silt loam; light olive brown (2.5Y 5/4) moist; weak medium prismatic structure parting to weak thin platy; hard, friable, moderately sticky and moderately plastic; many very fine roots; many fine tubular pores; common grayish brown (2.5Y 5/2) moist coatings on faces of peds; disseminated calcium carbonate; many fine and medium coatings and seams of calcium carbonate on faces of peds; violently effervescent; moderately alkaline (pH 8.4); abrupt smooth boundary. (6 to 20 inches thick)
Bk3--18 to 28 inches; light gray (2.5Y 7/2) silty clay loam, grayish brown (2.5Y 5/2) moist; moderate very thin strata of dark grayish brown (2.5Y 4/2) moist silty clay and light olive brown (2.5Y 5/4) moist silt loam; moderate very thin platy structure; hard, friable, moderately sticky and moderately plastic; common very fine roots; common fine tubular pores; disseminated calcium carbonate; many fine and medium coatings and seams of calcium carbonate on faces of plates; violently effervescent; moderately alkaline (pH 8.4); abrupt smooth boundary. (6 to 18 inches thick)
C--28 to 39 inches; light gray (2.5Y 7/2) very fine sandy loam, grayish brown (2.5Y 5/2) moist; massive; soft, very friable, nonsticky and nonplastic; common very fine roots; common fine tubular pores; disseminated calcium carbonate; violently effervescent; moderately alkaline (pH 8.4); abrupt smooth boundary. (6 to 20 inches thick)
Cy--39 to 60 inches; light gray (2.5Y 7/2) very fine sandy loam, grayish brown (2.5Y 5/2) moist with thin strata of light brownish gray (2.5Y 6/2) silty clay, light yellowish brown (2.5Y 6/4) moist; average texture is silty clay loam; thin and very thin varves; very fine sandy loam layers are soft, very friable, nonsticky and nonplastic; silty clay layers are hard, firm, sticky and slightly plastic; many seams and masses of gypsum crystals; violently effervescent; moderately alkaline (pH 8.4).
TYPE LOCATION: Glacier County, Montana; 1,300 feet west and 200 feet south of the northeast corner of sec. 17, T. 34 N., R. 6 W.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F.
Depth to calcic horizon - 4 to 10 inches
Ap horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 or 3; dry or moist
Texture: silt loam or loam
Clay content: 18 to 27 percent
Rock fragments: 0 to 8 percent--0 to 4 percent cobbles, 0 to 4 percent stones
Calcium carbonate equivalent: 5 to 10 percent
Reaction: pH 7.8 to 8.4
Bk1 horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 6 or 7 dry; 4 or 5 moist
Chroma: 2 to 4; dry or moist
Texture: silt loam or loam
Clay content: 18 to 27 percent
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.9 to 8.4
Bk2 and Bk3 horizons
Hue: 10YR or 2.5Y; dry or moist
Value: 6 to 8 dry; 4 to 6 moist
Chroma: 2 to 4; dry or moist
Texture: silt loam or silty clay loam
Clay content: 18 to 35 percent
Calcium carbonate equivalent: 15 to 40 percent
Reaction: pH 7.9 to 9.0
C horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 6 or 7 dry; 5 or 6 moist
Chroma: 2 to 4; dry or moist
Texture: very fine sandy loam, silt loam or silty clay loam (some thin silty clay layers may occur in some pedons)
Clay content: 18 to 35 percent
EC: 0 to 4 mmhos/cm
Calcium carbonate equivalent: 15 to 25 percent
Reaction: pH 7.9 to 9.0
Cy horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 6 or 7 dry; 5 or 6 moist
Chroma: 2 to 4; dry or moist
Texture: very fine sandy loam, silt loam or silty clay loam (some thin silty clay layers may occur in some pedons)
Clay content: 18 to 35 percent
EC: 0 to 4 mmhos/cm
Calcium carbonate equivalent: 15 to 25 percent
Gypsum: less than 1 percent
Reaction: pH 7.9 to 9.0
COMPETING SERIES:
Cambeth (MT) - have a paralithic contact at 20 to 40 inches
Neen (MT) - have horizons of salt accumulation
GEOGRAPHIC SETTING:
Landform - alluvial fans, fan remnants, hills and lake plains
Elevation - 3,000 to 6,200 feet
Parent material - silty loess, lake sediments and alluvium
Slope - 0 to 35 percent
Climate - long, cold winters; moist springs, warm summers
Mean annual precipitation - 10 to 14 inches
Mean annual air temperature - 38 to 45 degrees F.
Frost-free period - 70 to 120 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; moderately slow permeability.
USE AND VEGETATION: Brockway soils are used mainly for rangeland and for irrigated and nonirrigated crops. Potential native vegetation is mainly bluebunch wheatgrass, western wheatgrass, green needlegrass, Sandberg bluegrass, threadleaf sedge, needleandthread, forbs, and shrubs.
DISTRIBUTION AND EXTENT: Brockway soils are of moderate extent in Montana east of the Rocky Mountains. MLRAs - 44B, 46, 52, 54 and 58A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Glacier County, Montana, 1969.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - from 0 to 6 inches (A horizon)
Horizons of secondary carbonate accumulation - from 6 to 28 inches (Bk1, Bk2 and Bk3 horizons)
Calcic horizon - from 11 to 28 inches (Bk2 and Bk3 horizons)
Horizon of gypsum accumulation - from 39 to 60 inches (Cy horizon)
Particle-size control section - from 10 to 40 inches (part of Bk1, Bk2, Bk3, C and part of Cy horizons)
Brockway soils have a frigid temperature regime and an ustic moisture regime bordering on aridic.
ADDITIONAL DATA: Soil interpretations record - MT0635.
National Cooperative Soil Survey
U.S.A.