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La Plata County Area, Colorado
<br />by selective cutting, leaving small trees and a few
<br />larger seed produclng trees, end controlling
<br />pk grazing so that seedlings Can become
<br />Wildlife uch as mule deer, coyote, cottontail, squirrel,
<br />and moumi dove use this unit They obtain their food
<br />from areas o upland and native vegetation. Areas of
<br />pinyon and juni and rengeland provide cover and
<br />nesting areas. Su' le management for wildlife should
<br />include providing pro lion from overgrazing and wildfire
<br />and maintaining adequ a plant cover, including areas of
<br />pirryon and juniper. Inc and areas favorable habitat
<br />can be developed by main ing plant cover along
<br />fences and ditches and in ce ors of fields.
<br />ff this unit is used for ho development, the main
<br />limitations are the bw soil stre moderate shrink-
<br />swell potential. Buildings should be rigid to offset
<br />the effects of shrinking and swelling. should be
<br />designed to overcome the limitations of soil strength.
<br />The moderatety slow permeability should considered
<br />when designing septic tank absorption fields sewage
<br />lagoons. Absorption fields may need to be larger
<br />than normal. Sewage lagoons can he sealed to r e
<br />seepage.
<br />This map unit is in capability subclasses Ille, iniga
<br />and Illc, nonirrigated.
<br />7~WItf loam, S to 8 percent slopes This deep,
<br />well drafried"sal'is on uplands-arid rnes`as: It funned in
<br />calcareous loess. Elevation is 620o to 7,500 feet The
<br />average annual precipitation is about 14 to 17 inches.
<br />The average annual air temperature is 45 to 50 degrees
<br />F, and the average frost•free period is 110 to 130 days.
<br />Typically, the upper pert of the surface layer is brown
<br />loam about 7 incites thick and the lower part is reddish
<br />brown loam about 3 inches thick. The upper part of the
<br />subsoil is reddish brown silty cloy loam about 9 inches
<br />thick, the next pert is reddish blown silty day loam about
<br />15 inches thick, and the lower part is light reddish brown
<br />loam about 14 inches thick The substratum is yelbwish
<br />red loam that extends to a depth of 60 inches or mare.
<br />Included in this unit is abut 5 percent Pulpit loam.
<br />Also included are small areas of eroded Witt loam and of
<br />Simpatico loam.
<br />Permeability of this Witt soil is modaratety slow.
<br />Effective rooting depth is 60 inches a more. Available
<br />water capacity is high. Runoff is medium, and the hazard
<br />of erosion is moderate.
<br />This unit is used mainly for irrigated and nonirrigated
<br />crops and as rangeland. The main irtigeted crops are
<br />alfalfa, barley, and oats. The main nonirrigated pops are
<br />wheat, pinto beans, and aBaRa
<br />The main management concerns in irrigated areas are
<br />controlling water erosion, maintaining the organic matter
<br />content and fertility of the surface layer, end property
<br />using imgation water. Furrow, oortugetion, and sprinkler
<br />irrigation systems are suited to this unit Furtaw irrigation
<br />73
<br />is best suited to row crops, and corrugation irrigation is
<br />best suited to alfalfa, pasture, and small grain. Sprinkler
<br />irrigation is suited to most crops. Use of this method
<br />permits the even, controlled application of water,
<br />reduces runoff, and minimaes the risk of erosion.
<br />Irrigation water should be applied at a rate that ensures
<br />optimum production without excessive runoff, deep
<br />percolation, and erosion. Furtows should run across the
<br />slope. Returning all crop residue to the soil and using a
<br />cropping system that includes grasses, legumes, or
<br />grass•legume mbctures help to maintain the fertility and
<br />filth of the soil. Grain and grasses respond to nitrogen,
<br />and legumes respond to phosphorus.
<br />This unit is well suited to nonirrigated sops. The main
<br />concerns are reducing runoff and erosion, conserving
<br />moisture, and maintainng ttte producOviry of the soil.
<br />Practices that can be used to control erosion include
<br />stubble mulch tillage, contour farming, and construction
<br />o} terraces, diversions, and grassed waterways.
<br />Maintaining crop residue on or near the surface layer
<br />increases the water intake rate, reduces runoff and
<br />erosion, and helps to maintain soil filth and organ
<br />matter ceMent Tertaces reduce runoff and erosion arW
<br />conserve moisture. Chiseling or subsoiling can be used
<br />to break up the tillage pan and thus improve the water
<br />intake rate. Tillage should be kept to a minimum.
<br />Diversbns and grassed waterways may lie needed to
<br />reduce gutty erosion.
<br />The native vegetation in most areas used as
<br />rangeland is mainly big sagebrush, western wheatgrass,
<br />pinyon, and Rocky Mountain juniper. Other important
<br />plants that characterize this unR are Indian ricegrass,
<br />blue grams, muttongrass, junegrass, needleandthread,
<br />Gambol oak, and serviceberry. If the range is
<br />overgrazed, the proportion of preferted forage plants
<br />decreases and the proportion of less preferred forage
<br />plants increases; therefore, livestock grazing should be
<br />managed So that the dewed balance of species is
<br />maintained in the plats community.
<br />The production a- forage is limited by low rainfall in
<br />summer. Proper grazing use as part of a planned grazing
<br />system helps to maintain the quality and quantity of the
<br />preferted rangeland vegetation. Mechanical or chemkal
<br />brush control followed by seeding to adapted grasses
<br />improves areas that support dense stands of sagebrtsh.
<br />Seeding facllitates revegetation of areas depleted by
<br />heavy grazing, cultivation, and other disturbances.
<br />Developing livestock watering facilities, fencing, and
<br />deferring grazing help to improve the distribution of
<br />grazing and to maintain the condition of the rangeland.
<br />Contour furrowing and pitting increase the water intake
<br />rate and reduce runoff. These practices are especialty
<br />effective in rangeland areas in poor to fair condition.
<br />This unit generally is suited to windbreaks and
<br />environmental plantings. It is limited mainy by a lack of
<br />suffxrent rainfall in summer. Supplements! irrigation may
<br />be needed when planting and during the early stages of
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