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Utah State Cooperative Extension Service

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Numerous preliminary simulations are again performed to determine the smallest fertilizer amount, applied througii sprinkler irrigations (chemigation), that should still yield 15.3 tons of potatoes per acre. Applying only 68 lbs/ac of ammonium nitrate fertilizer in the first irrigation on June 28, should be sufficient. Again, total crop N uptake equals potential crop N uptake throughout the growing season. Except for the net income and applied fertilizer N uptake efficiency, all the other results computed by NLEAP (Figure 4 and Table 1) are very similar to results of scenario II. Applied fertilizer N uptake efficiency is the highest (91%) in this case. As a result, only 68 lbs/ac of ammonium nitrate fertilizer need be applied to achieve the same potato yield. Since the amount of fertilizer is 3 lbs/ac less than that of scenario II, the net income is the greatest of all scenarios (Table 1 ).