LOCATION ROCKY FORD CO
Established Series
Rev. AJC/LAN
01/2014
ROCKY FORD SERIES
The Rocky Ford series consists of very deep, well drained soils that formed in alluvium Rocky Ford soils are on terraces. The surface horizon formed in clayey alluvium from sediment-rich irrigation water. The subsoil and substratum formed in alluvium from mixed sedimentary materials. Slopes range from 0 to 6 percent. The mean annual temperature is about 11 degrees C (52 degrees F.) and the mean annual precipitation is about 305 millimeters (12 inches).
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Aridic Calciustolls
TYPICAL PEDON: Rocky Ford silty clay loam, on north facing, 1 percent slope in a cultivated field at an elevation of 1,271 meters (4,196 feet). (Colors are for dry soil unless otherwise noted.) When described on August 17, 2011 the soil was slightly moist from 0 to 30 centimeters and moist from 30 to 200 centimeters.
Ap1--0 to 25 centimeters (0 to 10 inches); grayish brown (10YR 5/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; strong fine angular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; common fine roots; strongly effervescent; 6 percent calcium carbonate equivalent; slightly alkaline (pH 7.6); clear smooth boundary.
Ap2--25 to 46 centimeters (10 to 18 inches); grayish brown (10YR 5/2) silty clay loam, dark brown (10YR 3/3) moist; moderate medium subangular blocky structure; moderately hard, firm, moderately sticky and moderately plastic; common fine roots; strongly effervescent; 4 percent calcium carbonate equivalent; slightly alkaline (pH 7.6); abrupt smooth boundary. (Combined thickness of the Ap horizons is 25 to 49 centimeters (10 to 19 inches))
Bk1--46 to 89 centimeters (18 to 35 inches); pale brown (10YR 6/3) silt loam, brown (10YR 5/3) moist; moderate medium subangular blocky structure; common fine roots; 5 medium, distinct, spherical carbonate masses in matrix; violently effervescent; 18 percent calcium carbonate equivalent; moderately alkaline (pH 8.2); clear smooth boundary. (25 to 51 centimeters thick (10 to 20 inches))
Bk2--89 to 122 centimeters (35 to 48 inches); pale brown (10YR 6/3) silt loam, brown (10YR 4/3)moist; moderate medium subangular blocky structure; few very fine roots; 8 percent medium, distinct, spherical carbonate masses in matrix; violently effervescent; 11 percent calcium carbonate equivalent; moderately alkaline (pH 8.2); gradual smooth boundary. (Combined thickness of the Bk1 and Bk2 horizons is 25 to 51 centimeters thick (10 to 20 inches))
Bk3--122 to 200 centimeters (48 to 79 inches); light yellowish brown (10YR 6/4) loam, dark yellowish brown (10YR 4/4) moist; weak medium subangular blocky structure; 20 percent fine, faint, irregular carbonate masses in matrix; violently effervescent; 18 percent calcium carbonate equivalent; strongly alkaline (pH 8.6).
TYPE LOCATION: Otero County, Colorado; approximately 2 miles south and 2 miles west of Swink; 1,950 feet east and 700 feet south of the northwest corner of Sec. 10, T. 24 S., R. 56 W. Sixth Principle Meridian; Hawley, Colorado USGS topographic quadrangle; UTM zone 13 617011 E, 4204468 N; latitude 37 degrees, 58 minutes, 49 seconds N. and longitude 103 degrees, 40 minutes, 3.5 seconds W., NAD 83.
RANGE IN CHARACTERISTICS:
Soil moisture: moist in some part March through May and intermittently moist June through October. It is driest December through February.
Moisture regime: aridic bordering on ustic.
Mean annual soil temperature: 9 to 12 degrees C. (49 to 54 degrees F.)
Mean summer soil temperature: 20 to 24 degrees C (68 to 75 degrees F.)
Depth to secondary calcium carbonate: 25 to 51 centimeters (10 to 20 inches)
Depth to calcic horizon: 25 to 99 centimeters (10 to 39 inches)
Thickness of calcic horizon: 38 to 132 centimeters (15 to 52 inches)
Ap horizons have increases of clay and organic matter content due to prolonged irrigation, cultivation, and fertilization. Phosphorous content is not high enough for an anthropic epipedon.
Particle size control section (weighted average):
Clay content: 24 to 35 percent
Silt content: 50 to 65 percent
Sand content: 5 to 25 percent, with less than 15 percent fine or coarse sand
Rock fragments: 0 to 5 percent, fine gravel
Ap horizons:
Hue: 10YR
Value: 3 through 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: 0 to 8 percent
Reaction: slightly alkaline or moderately alkaline
Bw horizons: (where present)
Hue: 10YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 or 4
Texture: clay loam, silty clay loam, silt loam
Clay content: 18 to 35 percent
Calcium carbonate equivalent: 5 to 10 percent
Electrical conductivity: 0 to 2 dS/m
Sodium Adsorption Ratio: 0 to 2
Electrical conductivity: 0 to 2 dS/m
Reaction: slightly alkaline or moderately alkaline
Bk1 and Bk2 horizons:
Hue: 10YR or 7.5YR
Value: 5 through 7 dry, 4 or 5 moist
Chroma: 3 or 4
Texture: silt loam, silty clay loam
Clay content: 15 to 27 percent
Rock fragment content: 0 to 5 percent
Calcium carbonate equivalent: 5 to 25 percent with at least one horizon greater than 15 percent above a depth of 100 cm (40 inches)
Electrical conductivity: 0 to 2 dS/m
Gypsum: 0 to 1 percent
Sodium Adsorption Ratio: 0 to 6
Reaction: moderately alkaline
Rock fragment content: 0 to 5 percent
Bk3 horizon:
Hue: 10YR or 7.5YR
Value: 5 through 7 dry, 4 through 6 moist
Chroma: 3 through 6
Texture: silt loam, loam, fine sandy loam
Clay content: 15 to 27 percent
Rock fragment content: 0 to 5 percent
Calcium carbonate equivalent: 5 to 25 percent
Electrical conductivity: 0 to 4 dS/m
Gypsum content: 0 to 1 percent
Exchangeable sodium percentage: typically 0 to 5 percent, but can range to 10 percent in some pedons
Sodium Adsorption Ratio: 1 to 5
Reaction: moderately alkaline or strongly alkaline
Rock fragment content: 0 to 5 percent
COMPETING SERIES: These are the
Cuevoland (NM),
Nepesta (CO),
Sophia (OK+TX), and Timpas (CO) series.
Cuevoland soils: have a mean annual soil temperature of 13 to 14.5 degrees C (55 to 58 degrees C) and average greater than 25 percent calcium carbonate equivalent in the Bk horizons.
Nepesta soils:
Sophia soils: have an ustic moisture regime, a mean annual soil temperature of 13 to 14.5 degrees C (55 to 58 degrees C) and average greater than 25 percent calcium carbonate equivalent in the Bk horizons.
Timpas soils:
Timpas soils: have a paralithic contact at depths of 100 to 152 centimeters (40 to 60 inches)
GEOGRAPHIC SETTING:
Parent material: clayey alluvium from sediment-rich irrigation water over silty alluvium derived from mixed sources.
Landform: terraces and paleoterraces
Parent material: clayey alluvium from irrigation water over silty mixed alluvium.
Slopes: 0 to 6 percent
Elevation: 1,158 to 1,585 meters (3,800 to 5,000 feet)
Mean annual air temperature: 10 to 12 degrees C (50 to 54 degrees F.)
Mean annual precipitation: 254 to 356 millimeters (10 to 14 inches)
Precipitation pattern:
Peak period: May through August
Driest period: December through February
Average annual air temperature: 10 to 12 degrees C (50 to 54 degrees F.)
Frost free season: 130 to 170 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Kornman,
Numa, and Timpas soils.
Kornman soils: have a coarse-loamy control section and are on terraces
Numa soils: have a fine-loamy control section and are on paleoterraces and terraces
Timpas soils: have a paralithic contact at depths of 100 to 152 centimeters (40 to 60 inches) and are on paleoterraces and strath terraces.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage: well drained
Saturated hydraulic conductivity: moderately high or high
Flooding: Non-flooded to occasional, brief flooding during spring snowmelt
USE AND VEGETATION: Used as irrigated cropland. Principal irrigated crops are alfalfa, small grains, sorghum, corn, truck crops, and melons. Native vegetation is mainly blue grama, galleta, and western wheatgrass. Loamy plains (R069XY006CO) ecological site.
DISTRIBUTION AND EXTENT: Arkansas River Valley, Colorado, LRR G, MLRA 69 and 67B. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Prowers County, Colorado 1963.
REMARKS: OSD scanned by NSSQA. Last revised on 10/2013.
Diagnostic horizons and features in this pedon are:
Series control section: 0 to 200 centimeters
Particle size control section: 25 to 100 centimeters (10 to 40 inches).
Mollic epipedon: 0 to 46 centimeters (0 to 18 inches). (Ap1 and Ap2 horizons)
Calcic horizon: 46 to 89 centimeters (18 to 35 inches). (Bk1 horizon)
The assignment of the cation-exchange activity class is inferred from lab data from similar soils in the surrounding area.
LAN 3/2013 The previous classification of calcareous Ustic Torriorthents became obsolete following a field project that indicated soils in the area had mollic epipedons. As a result of this update, the type location has been moved from from Prowers County, Colorado to Otero County, Colorado and taxonomic class changes to Fine-silty, mixed, superactive, mesic Aridic Calciustolls.
Taxonomic Version: Eleventh Edition, 2010.
National Cooperative Soil Survey
U.S.A.