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La Plata County Area, Colorado
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<br />potential. Roads should be designed to overcome the
<br />limitations of low soil strength and high shrink-swell
<br />potential. The slow permeability should be considered
<br />when planning septic tank absorption fields. Sewage
<br />lagoons work well.
<br />This map unit is in capability subclasses Ille, irrigates
<br />and Illc, nonirrigated.
<br />27-Falfa clay loam, 3 to 8 percent slopes. This
<br />deep, well drained soil is on mesa tops. It formed in
<br />calcareous loess. Elevation is 6,500 to 7,000 feet. The
<br />average annual precipitation is 15 to 18 inches. The
<br />average annual air temperature is about 48 to 49
<br />degrees F, and the average frost-free period is 100 to
<br />120 days.
<br />Typically, the surface layer is reddish brown clay loam
<br />about 9 inches thick. The upper part of the subsoil is
<br />reddish brown clay loam about 5 inches thick, the next
<br />part is reddish brown clay about 20 inches thick, and the
<br />lower part is reddish brown clay loam about 23 inches
<br />thick. The substratum is yellowish red clay loam that
<br />extends to a depth of 60 inches or more.
<br />Included in this unit are about 10 percent Corta loam,
<br />5 percent soils that are similar to this Falfa soil but have
<br />a dark-colored surtace layer, and small areas of Witt
<br />loam and Simpatico loam.
<br />Permeability of this Falfa soil is slow. Effective rooting
<br />depth is 60 inches or more. Available water capacity is
<br />high. Runoff is medium, and the hazard of erosion is
<br />moderate.
<br />This unit is used mainly for irrigated and nonirrigated
<br />crops and as rangeland and homesites. The main
<br />irrigated crops are corn for silage; small grain such as
<br />. wheat, barley, and oats; pasture; and alfalfa hay. The
<br />.main nonirrigated crops are wheat and pinto beans.
<br />In irrigated areas, the main concerns of management
<br />are controlling water erosion, maintaining the organic
<br />matter content and fertility of the surtace layer, and
<br />.properly using irrigation water. Incorporating crop residue
<br />onto the surtace layer increases the water intake rate,
<br />'improves filth, reduces erosion, and helps to maintain
<br />adequate organic matter content. Realignment of ditches
<br />and irrigation structures is needed in some areas to
<br />~~'e a more uniform distribution of irrigation water.
<br />~, ;~9ation methods suited to this unit are furrow,
<br />~;~g~aUon, and sprinkler systems. Furrow irrigation is
<br />~ rted to row crops. Furrows should run across the
<br />• Sprinkler irrigation is well suited to most crops.
<br />;;~W this method permits the even, controlled
<br />.Icatfon of water, reduces runoff, and minimizes the
<br />b! erosion. Corrugation systems are suited to alfalfa,
<br />e, and small grain. Regardless of the irrigation
<br />Nnoff water should be applied carefully to
<br />~..~to the and control erosion. Returning all crop
<br />soil and using a cropping system that
<br />names, legumes, or grass-legume mixtures
<br />fain the fertility and filth. The use of fertilizer
<br />helps to maintain the fertility of the soil. Grain and
<br />grasses respond to nitrogen, and legumes respond to
<br />phosphorus.
<br />conservermoisturercontrol eaos one and maintaintthe
<br />productivity of the soil. Stubble mulch tillage and
<br />returning crop residue help to reduce runoff and erosion
<br />and to conserve moisture. Chiseling or subsoiling can be
<br />used to break up the tillage pan and thus improve the
<br />water intake rate. Tillage should be kept to a minimum.
<br />Diversions and grassed waterways may be needed to
<br />reduce gully erosion.
<br />The native vegetation of the unit consists of western
<br />wheatgrass, muttongrass, junegrass, Indian ricegrass, big
<br />sagebrush, Gambel oak, serviceberry, Rocky Mountain
<br />juniper, and pinyon. Proper grazing use as part of a
<br />planned grazing system helps to maintain the quality and
<br />quantity of the preferred rangeland vegetation. Seeding
<br />and deferring grazing facilitate revegetation of areas
<br />depleted by heavy grazing, cultivation, and other
<br />disturbances. Developing livestock watering facilities,
<br />fencing, and deferring grazing improve the distribution of
<br />grazing and help to maintain the condition of the
<br />rangeland. The production of forage is limited by low
<br />rainfall in summer. Contour furrowing and pitting increase
<br />the water intake rate and reduce runoff. These practices
<br />are especially effective on rangeland in poor or fair
<br />condition.
<br />environmen9al plantingss It fsdl mited mba nay by lack of
<br />sufficient rainfall in summer. Supplemental irrigation may
<br />be needed when planting and during the early stages of
<br />growth. Cultivation to reduce plant competition
<br />commonly is necessary, particularly while the plantings
<br />are young.
<br />Among the trees that are suitable for planting are
<br />and eastean redcedas~Among theosh ubs are caragana,
<br />lilac, honeysuckle, and sumac. Some areas support
<br />stands of pinyon and juniper. Woodland products such
<br />as firewood, fenceposts, Christmas trees, and pinyon
<br />capab enof p odtucing abouttl8scordsaof firewood per
<br />acre in a stand of trees that average 5 inches in
<br />diameter at a height of 1 foot, if all limbs larger than 2
<br />inches in diameter are used.
<br />to m~ nitme e~rosionrSeeding tonadapted~g asses may be
<br />needed in some areas after harvesting. Low precipitation
<br />and the presence of brushy plants may influence
<br />seedling survival. Areas can be maintained in pinyon and
<br />juniper by selective cutting, leaving small trees and a few
<br />of the larger seed producing trees, and controlling
<br />livestock grazing so that seedlings can become
<br />established.
<br />Wildlife such as cottontail, mule deer, coyote, squirrel,
<br />pheasant, and mourning dove use this unit. Irrigated
<br />13G
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