LOCATION BENTFORT CO
Tentative Series
Proposed LAN
01/2014
BENTFORT SERIES
The Bentfort series consists of very deep, moderately well to well drained soils that formed in stratified alluvium derived from mixed sedimentary materials. Bentfort soils are on flood plains. Slopes range from 0 to 3 percent. Mean annual precipitation is about 305 mm and the mean annual temperature is about 11 degrees C.
TAXONOMIC CLASS: Fine-silty over sandy or sandy-skeletal, mixed, superactive, mesic Oxyaquic Haplustolls
TYPICAL PEDON: Bentfort silty clay loam, on a northeast-facing, linear 1 percent slope in a cultivated field, at an elevation of 1248 meters (4086 feet). (Colors are for dry soil unless otherwise noted.) When described on November 28, 2011 the soil was moist from 0 to 107 cm. The surface was covered by corn stubble.
Ap--0 to 38 cm (0 to 15 inches); dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; strong fine subangular blocky structure; very hard, firm, moderately sticky and moderately plastic; common fine roots;1 percent calcium carbonate equivalent, slightly effervescent; slightly alkaline (pH 7.8); abrupt smooth boundary. (25 to 49 cm thick)
Bk--38 to 84 cm (15 to 33 inches); brown (10YR 5/3) silt loam, brown (10YR 4/3) moist; moderate fine subangular blocky structure; moderately hard, friable, slightly sticky and slightly plastic; common fine roots; 1 percent fine, distinct, spherical, non-cemented carbonate masses in matrix, 8 percent calcium carbonate equivalent, strongly effervescent; 1 percent medium, distinct, strong brown (7.5YR 5/6) iron masses in the matrix; slightly alkaline (pH 7.8); abrupt smooth boundary. (30 to 49 cm thick)
2C1--84 to 107 cm (33 to 42 inches); yellowish brown (10YR 5/4) sand, dark yellowish brown (10YR 4/4) moist; single grain; loose, loose, nonsticky and nonplastic; very slightly effervescent; slightly alkaline (pH 7.6); gradual smooth boundary.
2C2--107 to 200 cm (42 to 80 inches); brownish yellow (10YR 6/6) loamy sand, yellowish brown (10YR 5/6) moist; massive; soft, very friable, nonsticky and nonplastic; slightly effervescent; slightly alkaline (pH 7.6). (combined thickness of the 2C horizons is 100 to 139 cm)
TYPE LOCATION: Otero County, Colorado; about 2 kilometers (1.2 miles) east northeast of Swink; located about 2400 feet east and 2500 feet north of the southwest corner of sec. 30, T. 23 S., R. 55 W.; Cheraw, Colorado USGS topographic quadrangle; UTM zone 13 621849 E, 4208672 N; latitude 38 degrees 1 minutes 3.2 seconds N. and longitude 103 degrees 36 minutes 42.6 seconds W., NAD 83
RANGE IN CHARACTERISTICS:
Soil moisture: The soil moisture control section is moist in some part March through May, intermittently moist June through October. It is driest December through February.
Moisture regime: aridic moisture regime bordering on ustic.
Mean annual soil temperature: 9 to 12 degrees C (49 to 54 degrees F.)
Depth to secondary calcium carbonate: 25 to 51 cm (10 to 20 inches)
Depth to cambic horizon: 25 to 51 cm (10 to 20 inches)
Depth to redox concentrations: 25 to 152 cm (10 to 60 inches)
Thickness of the mollic epipedon: 18 to 51 cm (7 to 20 inches)
Particle-size control section (weighted averages):
Clay content: 18 to 28 percent
Sand content: 10 to 90 percent
Ap horizon:
Hue: 7.5YR or 10YR
Value: 4 or 5 dry, 2 or 3 moist
Chroma: 2 or 3
Texture: clay loam, silty clay loam
Clay content: 27 to 35 percent
Calcium carbonate equivalent: 1 to 4 percent
EC (dS/m): 0 to 2
Reaction: slightly alkaline or moderately alkaline
Bk horizon:
Hue: 7.5YR or 10YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 or 4
Texture: silt loam, loam, clay loam
Clay content: 20 to 35 percent
Rock fragments: 0 to 5 percent
Calcium carbonate equivalent: 5 to 10 percent
EC (dS/m): 2 to 4
Reaction: slightly alkaline or moderately alkaline
2C horizon(s):
Hue: 7.5YR or 10YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 to 6
Texture: sand, loamy sand, sandy loam
Clay content: 1 to 15 percent
Rock fragments: 0 to 25 percent
Calcium carbonate equivalent: 0 to 5 percent
EC (dS/m): 0 to 2
Reaction: neutral or slightly alkaline
COMPETING SERIES: There are presently no competing series.
GEOGRAPHIC SETTING:
Parent material: mixed stratified alluvium derived from sedimentary materials
Landform: flood plain
Slopes: 0 to 3 percent
Elevation: 1158 to 1585 meters (3800 to 5200 feet)
Mean annual temperature: 10 to 12 degrees C (50 to 54 degrees F.)
Mean annual precipitation: 256 to 356 mm (10 to 14 inches)
Precipitation pattern:
Peak period: May through August
Driest period: December through February
Frost-free period: 130 to 170 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cheraw(T),
Glenberg, and
Bankard series. The Cheraw soils are fine textured andmoderately well drained. The Bankard soils have a sandy control section. The Glenberg soils have a coarse-loamy control section. All associated soils are on flood plains.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage: moderately well to well drained
Saturated hydraulic conductivity: moderately low to moderately high in the upper part, high to very high in the lower part.
Occasionally flooded for brief periods during the months of April through August but may occur in any month.
USE AND VEGETATION: Used primarily as irrigated cropland. Principal irrigated crops are, alfalfa, small grains, corn, and truck crop. Native vegetation is dominantly blue grama, alkali sacaton, galleta grass, inland saltgrass, and fourwing saltbush. ESD R069XY030CO: Salt Meadow.
DISTRIBUTION AND EXTENT: Arkansas River Valley, Colorado; LRR G, MLRA 69 and 67B; the series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES PROPOSED: Otero County, Colorado; Otero County Soil Survey Area, Colorado. The name is coined from Bent's Old Fort National Monument.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Series control section: The zone from 0 to 150 centimeters (0 to 59 inches).
Particle-size control section: The zone from 25 to 100 centimeters (10 to 39 inches). (All or part of the Ap, Bk and 2C1 horizons)
Mollic epipedon: The zone from 0 to 38 centimeters (0 to 15 inches). (Ap horizon)
Cambic horizon: The zone from 38 to 84 centimeters (15 to 33 inches). (Bk horizon)
Redoximorphic concentrations: In the zone from 38 to 84 centimeters (15 to 33 inches) (Bk horizon)
Endosaturation: The zone of saturation from 38 to 200 centimeters (Bk, 2C1, and 2C2 horizons)
Lithologic discontinuity: At the upper boundary of the Bk and 2C1 horizon.
Other features: Ustic aridic moisture regime, mesic temperature regime.
The assignment of the cation-exchange activity class is inferred from lab data from similar soils in the surrounding area.
This soil was previously identified as Rocky Ford, sand substratum phase on flood plains that are occasionally flooded. The Bentfort series will replace that phase in the Arkansas River Valley in Colorado.
Taxonomic Version: Classified according to Keys to Soil Taxonomy, Eleventh Edition, 2010.
National Cooperative Soil Survey
U.S.A.