LOCATION ROCKY FORD COEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, calcareous, mesic Ustic Torriorthents
TYPICAL PEDON: Rocky Ford clay loam - cultivated (Colors are for dry soil unless otherwise noted.)
AP--0 to 12 inches; grayish brown (slightly darker than 10YR 5/2) clay loam, dark grayish brown (slightly darker than 10YR 4/2) moist; weak coarse subangular blocky structure that parts to fine and very fine granules; slightly hard, very friable, slightly sticky, slightly plastic; primary peds are hard, firm; moderate amounts of undecomposed and partially decomposed organic materials; calcareous; moderately alkaline (pH 8.0); abrupt smooth boundary. (10 to 20 inches thick)
Cca--12 to 60 inches; pale brown (10YR 6/3) loam, brown (10YR 5/3) moist; massive; hard, friable, slightly sticky, slightly plastic; visible secondary calcium carbonate occurring mostly as small concretions or in seams and streaks throughout the horizon; calcareous; moderately alkaline (pH 8.2).
TYPE LOCATION: Prowers County, Colorado; .3 mile north and 100 feet east of W1/4 corner Sec. 33, T. 22 S., R. 45 W.
RANGE IN CHARACTERISTICS: These soils are usually calcareous throughout, but are leached to depths of 2 or 3 inches in some pedons. Gypsum content of a majority of subhorizons in the control section ranges from 0 to 1.5 percent by weight. Exchangeable sodium ranges from 0 to 14 percent in a majority of subhorizons of the control section and there is no subhorizon as much as 3 inches thick above a depth of 20 inches that exceeds 15 percent. Conductivity ranges from 0 to 14 millimhos in most subhorizons of the control section and there is no subhorizon as much as 3 inches thick above a depth of 20 inches that exceeds 14 millimhos. Continuous subhorizons of genetically concentrated visible secondary calcium carbonate and/or sulfate do not occur above a depth of 40 inches although some visible calcium carbonate and/or sulfate occurs inconsistently at any depth or occurs uniformly throughout the profile as a natural feature of the parent material. The control section is usually loam, clay loam, silt loam or silty clay loam but clay ranges from 18 to 35 percent, silt from 20 to 60 percent, and sand from 10 to 60 percent with less than 15 percent being fine or coarser sand. Rock fragments range from 0 to 5 percent and are mainly 1/2 to 10 inches in diameter. Subhorizons redder than 7.5YR occur in a few pedons but the major part of the control section above a depth of 40 inches has hue of 7.5YR or yellower. Manmade Ap horizons ranging from 10 to 20 inches thick that are medium to moderately fine textured, that border mollic epipedons in color and anthropic epipedons in phosphorous and nitrogen characterize this series. They have resulted from long irrigation with silt laden irrigation water accompanied by intense cropping, heavy fertilization and larger than normal yearly returns of organic matter.
The A horizon has hue of 2.5Y through 7.5YR, value of 5 through 7 dry, 3 through 6 moist, and chroma of 1 through 4. It is moderately or strongly alkaline (1:5 dilution unbuffered organic dye).
The C horizon has hue of 2.5Y through 7.5YR. Subhorizons redder than 7.5YR occur in some pedons. This horizon is moderately or strongly alkaline (1:5 dilution unbuffered organic dye). Calcium carbonate equivalent of the fine earth ranges from about 1 to 10 percent.
COMPETING SERIES: These are the Bainville, Colby, Manvel, and Minnequa series. Bainville and Minnequa soils have a paralithic contact at depths of less than 40 inches. Colby soils lack a thick manmade nitrogen and phosphorous enriched Ap horizon. Manvel soils have a calcium carbonate equivalent of 10 percent or more in most subhorizons above a depth of 40 inches and lack a thick manmade Ap horizon.
GEOGRAPHIC SETTING: Rocky Ford soils are on nearly level to gently sloping terraces and alluvial fans. Slopes typically range from about 0 to 6 percent or more. The soils formed in thick calcareous eolian or silty uniform alluvium containing much very fine sand and modified by long irrigation. At the type location the mean annual precipitation is about 15 inches with peak periods of precipitation in the spring and early summer months. Mean annual temperature is 52 degrees F. and mean summer temperature is 79 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Colby soils and the Nepesta soils. Nepesta soils have an argillic horizon.
DRAINAGE AND PERMEABILITY: Well-drained; slow to very runoff; moderate to slow permeability.
USE AND VEGETATION: Used as irrigated cropland. Principal irrigated crops are alfalfa, small grains, sorghum, corn, truck crops, and melons.
DISTRIBUTION AND EXTENT: Arkansas River Valley, Colorado. The series is of moderate extent.
MLRA OFFICE RESPONSIBLE: Salina, Kansas
SERIES ESTABLISHED: Prowers County, Colorado 1963.
REMARKS: OSED scanned by NSSQA. Last revised by state on 4/73.