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<br />This map unit is in capability subclasses Ille, irrigated, and Illc, nonirrigated. It is in Foothill Swale range site. <br />92-Trembles loam, wet. This deep, moderately well drained soil is on alluvial valley floors, flood plains, and low stream <br />terraces. It formed in mixed alluvium. Slope is 0 to 3 percent. Areas are elongated and are 20 to 200 acres. The native <br />vegetation is mainly low shrubs and grasses and cottonwood trees and willows along major streams. Elevation is 5,800 <br />to 6,200 feet. The average annual precipitation is 14 to 16 inches, the average annual air temperature is 42 to 45 de- <br />grees F, and the average frost-free period is BS to 105 days. <br />Typically, the upper part of the surface layer is light gray loam about 3 inches thick. The lower part is pale brown loam <br />about 5 inches thick. The upper 12 inches of the underlying material is very pale brown fine sandy loam, the next 22 <br />inches is very pale brown fine sandy loam, and the lower part to a depth of 60 inches or more is light gray fine sandy <br />loam that has lenses of sandy loam. In some areas the surface layer is sandy loam or clay loam. <br /> <br />Included in this unit are small areas of Glendive fine sandy loam, Havre loam, Kobar silty clay loam, Patent loam, Redrob <br />loam, and Tisworth fine sandy loam. Also included are small areas of soils that are similar to this Trembles soil, but the <br />underlying material is very cobbly and gravelly sand. Included areas make up about percent of the total acreage. The <br />percentage varies from one area to another. <br />Permeability of the Trembles soil is moderately rapid. Available water capacity is moderate. Effective rooting depth is 60 <br />inches or more. Runoff is slow, and the hazard of water erosion is slight. A seasonal high water table fluctuates between <br />depths of 36 and 60 inches in spring. In low areas along the major river in the area, this soil is subject to brief periods of <br />flooding in spring. <br />• This unit is used for irrigated hay and pasture, livestock grazing, and wildlife habitat. <br />This unit is well suited to hay and pasture. The main limitation is the short growing season. For good establishment of <br />hay and pasture, prepare a seedbed, drill in the seed, and use supplemental irrigation. Furrow, border, corrugation, and <br />sprinkler irrigation systems are suited to this unit. Leveling helps to insure the uniform application of water. <br />Proper stocking rates, pasture rotation, and restricted grazing during wet periods help to keep the pasture in good condi- <br />tion and to protect the soil from erosion. Use of nitrogen and phosphorus fertilizer promotes good growth of forage <br />plants. <br />If this unit is used for irrigated small grain crops, the main limdation is the short growing season. <br />The potential plant community on this unit is mainly western wheatgrass, slender wheatgrass, saltgrass, Kentucky blue- <br />grass, and tall rabbitbrush. Smaller amounts of foxtail, basin wildrye, and some greasewood commonly are also present <br />in the potential plant community. Cottonwood trees, willows, and cattails are common along streambanks and oxbows. <br />The average annual production of air-dry vegetation is about 2,000 pounds per acre. <br />If the range is overgrazed, the proportion of preferred forage plants decreases and the proportion of less preferred for- <br />age plants increases. Therefore, livestock grazing should be managed so that the desired balance of preferred species <br />is maintained in the plant community. <br />Piceance Pit 7/01 <br />