LOCATION MCKENTON MT
Established Series
Rev. DES-KTS-RJS
05/2011
MCKENTON SERIES
The McKenton series consists of very deep, very poorly drained soils that formed in saline and sodic alluvium derived from mixed rock sources. These soils are on plains, flood-plain steps, stream terraces and drainageways. Slopes are 0 to 2 percent. Mean annual precipitation is about 14 inches, and mean annual air temperature is about 40 degrees F.
TAXONOMIC CLASS: Fine, mixed, superactive, calcareous, frigid Fluvaquentic Endoaquolls
TYPICAL PEDON: Mckenton clay loam, in pasture (colors are for moist soil unless otherwise noted).
Ag1--0 to 2 inches; very dark grayish brown (2.5Y 3/2) clay loam, dark grayish brown (2.5Y 4/2) dry; many faint very dark gray (5Y 3/1) redox depletions; moderate medium subangular blocky structure; slightly hard, very friable, moderately sticky and moderately plastic; many very fine and fine roots; many very fine and fine interstitial and tubular pores; 5 percent gravel; finely disseminated calcium carbonate; strongly effervescent; very strongly alkaline (pH 9.6); clear wavy boundary.
Ag2--2 to 6 inches; very dark grayish brown (2.5Y 3/2) clay loam, dark grayish brown (2.5Y 4/2) dry; many distinct very dark gray (2.5Y 3/1) redox depletions; strong medium prismatic structure parting to moderate medium subangular blocky; hard, very firm, very sticky and very plastic; many very fine and fine roots; many very fine and fine interstitial and tubular pores; 5 percent gravel; strongly effervescent; very strongly alkaline (pH 9.6); clear wavy boundary. (combined thickness of Ag1, Ag2 horizons - 5 to 8 inches)
Bg--6 to 11 inches; very dark grayish brown (2.5Y 3/2) clay loam, grayish brown (2.5Y 5/2) dry; many distinct black (2.5Y 2.5/1) redox depletions; strong coarse prismatic structure; very hard, very firm, very sticky and very plastic; common very fine and fine roots; common very fine and fine interstitial and tubular pores; 5 percent gravel; slightly effervescent; very strongly alkaline (pH 9.2); gradual wavy boundary. (5 to 12 inches thick)
Bkzg1--11 to 17 inches; dark grayish brown (2.5Y 4/2) gravelly clay loam, light brownish gray (2.5Y 6/2) dry; many faint very dark gray (5Y 3/1) redox depletions and few prominent strong brown (7.5YR 5/6) redox concentrations; strong coarse and very coarse prismatic structure; very hard, firm, moderately sticky and moderately plastic; common very fine and fine roots; common very fine and fine pores; 15 percent gravel; finely disseminated calcium carbonate, common medium masses and threads of calcium carbonate, and common distinct calcium carbonate coatings on undersides of gravel; common medium masses and threads of salt; violently effervescent; moderately alkaline (pH 8.2); gradual irregular boundary.
Bkzg2--17 to 28 inches; greenish gray (5GY 5/1) and dark gray (5Y 4/1) gravelly clay loam, olive (5Y 5/3) dry; common faint very dark gray (5Y 3/1) redox depletions and common prominent strong brown (7.5YR 5/6) redox concentrations; massive; hard, firm, moderately sticky and moderately plastic; few very fine roots; common very fine and fine interstitial and tubular pores; 20 percent gravel; finely disseminated calcium carbonate, few fine masses and threads of calcium carbonate, and few faint calcium carbonate coatings on gravel; few fine masses and threads of salt; strongly effervescent; moderately alkaline (pH 8.2); gradual irregular boundary.
Bkzg3--28 to 45 inches; dark gray (5Y 4/1) and greenish gray (5GY 5/1) gravelly clay loam with thin strata of clay and loam, olive (5Y 5/4) dry; common faint very dark gray (5Y 3/1) redox depletions; massive; hard, friable, slightly sticky and moderately plastic; few very fine roots; few very fine interstitial and tubular pores; 30 percent gravel; finely disseminated calcium carbonate and few fine threads of calcium carbonate; few fine masses and threads of salt; slightly effervescent; moderately alkaline (pH 8.2). (combined thickness of 2Bkzg horizons - 10 to 40 inches)
Cg--45 to 60 inches; olive (5Y 4/3) and greenish gray (5GY 5/1) stratified gravelly clay loam and clay, pale olive (5Y 6/3) and greenish gray (5GY 5/1) dry; common distinct very dark gray (5Y 3/1) redox depletions; massive; hard, friable, slightly sticky and moderately plastic; few very fine roots; few very fine interstitial and tubular pores; 30 percent gravel; finely disseminated calcium carbonate; slightly effervescent; moderately alkaline (pH 8.2).
TYPE LOCATION: Jefferson County, Montana; 1,800 feet north and 2,400 feet west of the southeast corner of sec. 13, T. 4N, R. 3W.
RANGE IN CHARACTERISTICS:
Soil Temperature - 40 to 46 degrees F.
Mollic epipedon thickness - 7 to 11 inches
Depth to secondary calcium carbonate accumulation - 11 to 15 inches
Depth to a seasonally high water table - 0 to 12 inches for extended periods during spring and summer
Note: Some pedons may have a thin organic layer at the surface.
Ag1, Ag2 horizons
Hue: 10YR, 2.5Y or 5Y; dry or moist
Value: 3 to 5 dry; 2 or 3 moist
Chroma: 1 or 2; dry or moist
Texture: clay loam, silty clay loam or silt loam
Clay content: 22 to 40 percent
Rock fragments: 0 to 5 percent gravel
Electrical conductivity: 8 to 20 mmhos/cm
Sodium adsorption ratio: 4 to 16
Calcium carbonate equivalent: 0 to 5 percent
Reaction: pH 7.9 to 9.6
Note: Some pedons may have a thin crust at the surface.
Bg horizon
Hue: 2.5Y or 5Y; dry or moist
Value: 4 or 5 dry; 2 or 3 moist
Chroma: 1 or 2; dry or moist
Texture: clay loam, silty clay loam or clay
Clay content: 35 to 45 percent
Rock fragments: 0 to 10 percent gravel
Electrical conductivity: 4 to 16 mmhos/cm
Sodium adsorption ratio: 4 to 16
Calcium carbonate equivalent: 0 to 10 percent
Reaction: pH 7.9 to 9.6
Bkzg1, Bkzg2, Bkg3 horizons
Hue: 2.5Y, 5Y or 5GY; dry or moist
Value: 4 to 6 dry; 4 or 5 moist
Chroma: 1 to 4; dry or moist
Texture: clay loam, clay or silty clay loam
Clay content: 35 to 45 percent
Rock fragments: 5 to 35 percent gravel
Electrical conductivity: 2 to 16 mmhos/cm
Sodium adsorption ratio: 2 to 13
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.9 to 9.6
Cg horizon
Hue: 5Y, 5GY or 2.5Y; dry or moist
Value: 5 to 7 dry; 3 to 5 moist
Chroma: 1 to 3; dry or moist
Texture: clay loam or silty clay loam
Clay content: 35 to 40 percent
Rock fragments: 15 to 45 percent gravel
Electrical conductivity: 2 to 16 mmhos/cm
Sodium adsorption ratio: 2 to 13
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.9 to 9.6
COMPETING SERIES:
Klayent (MT) - have a seasonally high water table at depths of greater than 12 inches
GEOGRAPHIC SETTING:
Landform - flood plains, flood-plain steps, stream terraces and drainageways
Elevation - 3,800 to 5,000 feet
Slope - 0 to 2 percent
Parent material - saline and sodic alluvium derived from mixed rock sources
Climate - long, cold winters; moist springs; warm summers
Mean annual precipitation - 10 to 19 inches
Mean annual air temperature - 38 to 44 degrees F.
Frost-free period - 70 to 115 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Very poorly drained; slow permeability.
USE AND VEGETATION: Mckenton soils are primarily used for rangeland and pasture. The potential native vegetation is mainly alkali sacaton, basin wildrye, inland saltgrass, western wheatgrass, sedges, rushes and greasewood.
DISTRIBUTION AND EXTENT: Mckenton soils are of small extent on floodplains of rivers and streams in southwestern Montana. MLRA - 44B.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Jefferson County, Montana, 1998.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from 0 to 11 inches (Ag1, Ag2, Bg horizons)
Secondary calcium carbonate accumulation - from 11 to 45 inches (Bkzg1, Bkzg2, Bkzg3 horizons)
Particle-size control section - from 10 to 40 inches (part of Bg, Bkzg1, Bkzg2, part of Bkzg3 horizons)
Mckenton soils have a frigid temperature regime and an aquic moisture regime.
ADDITIONAL DATA: Soil interpretation record - MT1572.
National Cooperative Soil Survey
U.S.A.