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Rio Blanco County Area, Colorado
<br />pasture in good condition and to protect the soil from
<br />erosion.
<br />If this unit is used for irrigated crops, the main
<br />limitation is slow permeability. In summer, irrigation is
<br />needed for maximum production of most crops. Irrigation
<br />water can be applied by the border, corrugation, and
<br />furrow methods. The method used generally is .governed
<br />by the crop grown. Water needs to be applied at a slow
<br />rate over a long period to insure that the root zone is
<br />properly wetted. To avoid overirrigating and leaching of
<br />plant nutrients, applications of irrigation water should be
<br />adjusted to the available water capacity, the water intake
<br />rate, and the crop needs. Leveling helps to insure the
<br />uniform application of water. Compaction and excessive
<br />cloddiness occur if the soil is cultivated when it is too
<br />moist. Annual applications of nitrogen and phosphorus
<br />fertilizer are needed to maintain production of high
<br />quality irrigated pasture.
<br />If this unit is used for nonirrigated small grain, the main
<br />limitations are slow permeability and low precipitation.
<br />Because precipitation is not sufficient for annual
<br />cropping, a cropping system that includes small grain
<br />and summer fallow is most suitable.
<br />Returning crop residue to the soil or regularly adding
<br />other organic matter improves fertility, reduces crusting,
<br />and increases the water intake rate. Crop residue left on
<br />or near the surface helps to conserve moisture, maintain
<br />tilth, and control erosion. Tillage should be kept to a
<br />minimum. Compaction and excessive cloddiness occur if
<br />the soil is cultivated when it is too moist. Crops respond
<br />to small applications of nitrogen fertilizer.
<br />The potential plant community on this unit is mainly
<br />western wheatgrass, Letterman needlegrass,
<br />muttongrass, slender wheatgrass, and big sagebrush.
<br />Smaller amounts of serviceberry, rabbitbrush, and
<br />greasewood commonly are also present in the potential
<br />plant community. The production of forage is limited by
<br />slow permeability and strong alkalinity. The average
<br />annual production of air-dry vegetation is about 2,000
<br />pounds per acre.
<br />If the range is overgrazed, the proportion of preferred
<br />forage plants decreases and the proportion of less
<br />preferred forage plants increases. Therefore, livestock
<br />grazing should be managed so that the desired balance
<br />of preferred species is maintained in the plant
<br />community.
<br />Management practices suitable for use on this unit are
<br />proper range use, deferred grazing, rotation grazing, and
<br />brush management. Grazing should be delayed until the
<br />soil in this unit has drained sufficiently and is firm enough
<br />to withstand trampling by livestock. Brush management
<br />improves deteriorated areas of range that are producing
<br />more woody shrubs than were present in the potential
<br />plant community.
<br />Range seeding is also suitable if the range is in poor
<br />condition. The main limitations for seeding are low
<br />precipitation and slow permeability. For successful
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<br />seeding, prepare a seedbed and drill in the seed.
<br />Compaction and excessive cloddiness occur if the soil is
<br />cultivated when it is too moist. The plants selected for
<br />seeding should meet the seasonal requirements of
<br />livestock or wildlife, or both.
<br />If this unit is used for urban development, the main
<br />limitations are the potential for shrinking and swelling
<br />and slow permeability. Because standard septic tank
<br />absorption fields will not function properly on the soil in
<br />this unit, other sewage systems or designs are needed.
<br />Buildings and roads should be designed to offset the
<br />limited ability of the soil to support a load. The effects of
<br />shrinking and swelling can be reduced by maintaining a
<br />constant moisture content around the foundation and by
<br />backfilling excavations with material that has low shrink -
<br />swell potential.
<br />This map unit is in capability subclasses Ille, irrigated,
<br />and IIIc, nonirrigated. It is in Deep Clay Loam range site.
<br />48—Kobar silty clay loam, 3 to 8 percent slopes.
<br />This deep, well drained soil is on alluvial valley floors
<br />and on fans. It formed in calcareous alluvium derived
<br />dominantly from shale. Areas are elongated and are 20
<br />to 300 acres. The vegetation in areas not cultivated is
<br />mainly low shrubs and grass. Elevation is 5,800 to 7,200
<br />feet. The average annual precipitation is 15 to 18 inches,
<br />the average annual air temperature is 42 to 45 degrees
<br />F, and the average frost -free period is 85 to 105 days.
<br />Typically, the surface layer is grayish brown silty clay
<br />loam about 3 inches thick. The next layer is grayish
<br />brown silty clay loam about 9 inches thick. The
<br />underlying material to a depth of 60 inches or more is
<br />light brownish gray silty clay that has some gypsum
<br />crystals. In some areas the surface layer is clay loam or
<br />silty clay.
<br />Included in this unit are small areas of Absher loam,
<br />Dollard silty clay loam, Havre loam, Patent loam, and
<br />Tisworth fine sandy loam. Also included are small areas
<br />of soils that are similar to this Kobar soil but are saline.
<br />Included areas make up about 15 percent of the total
<br />acreage. The percentage varies from one area to
<br />another.
<br />Permeability of the Kobar soil is slow. Available water
<br />capacity is high. Effective rooting depth is 60 inches or
<br />more. Runoff is medium to rapid, and the hazard of
<br />water erosion is moderate.
<br />This unit is used mainly as irrigated and nonirrigated
<br />cropland and for livestock grazing. It is also used for
<br />urban development and wildlife habitat.
<br />If this unit is used for hay and pasture, the main
<br />limitations are slow permeability, slope, and rapid runoff.
<br />For good establishment of hay and pasture, prepare a
<br />seedbed, drill in the seed, and use supplemental
<br />irrigation. Irrigation water can be applied by the sprinkler
<br />or controlled flooding methods. Leveling helps to insure
<br />the uniform application of water.
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