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• A total of 66 species were found to occur in the type (Peabody Appendix 10-1), with 21 of <br />those species encountered in the cover sampling. Only 12 of these species had relative cover <br />values of 1 percent or greater. Of these 12 species, 8 were graminoids and four were (orbs. <br />Though this represents a low level of diversity for native plant communities, irrigated pastures <br />that are in good condition and well managed should have a composition of only a few species <br />(Stewart 1973). <br />The general stocking rate for the irrigated pasture is approximately 1.2 AUM's/acre at a 70 <br />percent utilization rate. Since the production on these pastures can be sustained by irrigation, <br />this stocking rate should apply during the majority of the growing season. Ideally, the forage <br />should achieve a 4-5 inch height in the spring and between pasture recovery periods before <br />grazing with allowance fora 4-5 inch stubble height of vegetation remaining at the end of the <br />growing season (SCS 1985). Observations during 1987 indicate that the trend is to graze <br />early, continuously during the growing season, and late for a number of the operators. <br />Many factors contribute to the composition, utility and appearance of the irrigated pasture type. <br />Soils vary from moderately deep loams to shallow loams and with a number of rock outcrops <br />• (see Section 2.04.9, Soils Resource Information). The deeper soils could be placed in hay <br />production, however the various operators' management objectives dictate a use of these <br />lands for irrigated pasture. At the other extreme, are the areas of shallow soils. These lands <br />normally occur as the remnant sagebrush type or as disturbed areas associated with <br />farmsteads or facilities. In these cases, the operator has chosen to apply irrigation water on <br />seeded pasture species even though the site potential is low. In some cases, the sites are so <br />shallo, that tillage and seeding are not feasible and continued application of irrigation water has <br />allowed for volunteering of species normally found in the irrigated pasture type. These shallo, <br />sites have a lower production potential than the deeper sites, but it is much higher than if left in <br />the dry remnant sagebrush state. Within the irrigated pasture type are small localized areas <br />that receive only limited amounts of supplemental irrigation water because of the natural <br />topography or landform. These areas are too small to stratify out from the type. Land leveling <br />or shaping to overcome these problems has not been done to any great extent within the study <br />area. Ground water seeps and baggy areas from irrigation runoff and irrigation recharged <br />ground water systems contribute to areas of higher production or occur as small inclusions of <br />the swale/drainage vegetation type. <br />• (REVISED 9/99) 2.04.10 - 33 <br />