2009-11-30_PERMIT FILE - C1981038 (5)

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Volume 7 Exhibit 5 Other Nutrients Dryland Alfalfa Most Colorado soils contain adequate Alfalfa responses to applied P under dryland conditions are most likely levels of available S, and soil tests for on soils with low or medium levels of extractable P. Suggested P rates (Table 5) available S are not routinely performed. are based on broadcast applications related to soil test levels. Alfalfa has a high S requirement; a 4-torVA crop removes 20 lb of S/A, Phosphorus Fertilizer Placement Therefore, levels of available S may Placement of P fertilizers in the root zone is important because P is not decrease, especially on soils low in mobile in soil. Broadcast application followed by incorporation prior: to planting organic matter. Irrigation from is the most efficient placement method for P, and the suggested rates for new most surface waters and some wells seedi rigs in Tables 3 to 5 are for three years of forage production. often contains appreciable SO, S, so Established stands that will be maintained more than three years may irrigated soils usually are adequately need tapdressing of phosphate fertilizer. Test _soils in -early fall, so P fertilizers supplied with S._However, some well waters as. wellas snow -melt water are can be applied prior to winter if needed. While P does not move in soil under lowin SOI -S, so water samples should most conditions, phosphate fertilizers may be washed into cracks in the dry soil be analyzed if soils are low inorganic during the fall and spring, or be incorporated by freezing and thawing during the matter and S deficiency is suspected. winter. Branch roots near the soil surface also may take up applied fertilizer P. The last cutting in the fall should be. early enough, so there is sufficient There have been no confirmed deficiencies of boron (B), copper (Cu), regrowth to reduce the potential for erosion of P- fertilized soils during the fall iron (Fe), manganese (Mn), and zinc and winter months. Base application rates of P fertilizers on new soil test levels, (Zn) in alfalfa, perennial grasses, and but apply about half of the rates suggested for establishing stands. Two important grass - legume mixtures for forage factors should be considered in managing .P fertility in established stands of production in Colorado. alfalfa. First, the probability of forage response to topdressed P is greater on soils testing very low to low in extractable P. Second, the probability of obtaining a yield response to topdressed "P declines as the stands age. Most P fertilizers contain N that may not be needed by the alfalfa, except during stand establishment. However, few alternate P sources are available. Choose a fertilizer based on availability and cost per unit of P Table 6: Suggested K rates for irrigated alfalfa, grass - legume mixtures and perennial gras Potassium Suggestions Irrigated Alfalfa and Grass- Legume Mixtures ppm K in soil Relative Fertilizer rate, lb K AB -DTPA or NH;,OAc level Alfalfa Grass- legume 0-,60 low 200 60 61- -120 medium 100 40 > 120 high 0 0 Suggested rates are for 3 years of production. Table 7: Suggested K rates for dryland alfalfa. Fertilizer rate lb K ppm K in soil Relative New Established AB -DTPA or NH level seedings` stands" 0-60 low 45 30 > 60 high 0 0 `Suggested ratesare for 3 years of production. * "Suggested rates are for 1 year of production. NOTE: Potassium applications are not suggested for grasses and grass- legume mixtures under dryland conditions. Most Colorado soils are relatively high in extractable K, and few crop responses to K fertilizers have been reported. Suggested K rates related to soil test values .for three years of production of alfalfa and grass - legume mixtures under, irrigated conditions are in Table 6. The main K fertilizer is KCl (potash). Broadcast application incorporated into.. the soil prior to planting- is the usual method of application. Potassium fertilizers can be topdressed on :established stands to help maintain stands. Dryland Alfalfa Under dryland conditions, the suggested K rates in Table 7 for new seedings are for three years of production, but those for established stands are for the current.year. Potassium fertilizer applications are not suggested for grass and grass- legume mixture forage production under dryland conditions. • IJ.G. Davis, Colorado State University Cooperative Extension soils specialist-and professor, D. H. Smith, professor and R. L. Colorado State University, U.S. Department of Agriculture, and Colorado counties cooperating. Croissant, crops specialistand professor Cooperative Extension programs are available to all without discrimination. No endorsement of (retired); soil and:crop sciences, products mentioned is intended nor is criticism implied of products not mentioned. pr 1 90 - Noya09