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Fluid Journal : Fluid Journal 1996-1998
Fall 1997 considered an aberration and not included in this report. Grain yield Corn grain yields were improved above control in all three reported years. Optimal yields were produced at the 100-lb/A N rate in two of three years. Note in Figure 1 how the highest three- year average was attained where 100 lbs/A of UAN was spokewheel injected at preemergence into the ridge. No significant differences in grain yield were found between N sources or among methods and times of application in 1987 and 1989. In 1986, spokewheel injection of UAN into the ridge at preemergence produced 19 bu/A more of corn than anhydrous ammonia injected preplant into the valley. Similarly, for reasons unknown, yields from both preemergence spokewheel injections of UAN were higher than for surface band treatments. Split applica- tions of UAN, and UAN plus anhydrous ammonia produced average yields 7.7 bu/A less than single preemergence applications of UAN. This may have been due to an inadequate rate of band- applied N (30 lbs/A) on the row at preemergence when the majority of split- applied N (70 lbs/A) was applied at late sidedress. Therefore, preemergence rate was raised to 40 lbs/A in 1987 and 1989. Economic return As can be seen in Figure 2, the highest net economic return to nitrogen occurred where UAN was spokewheel injected at preemergence into the ridge at the rate of 100 lbs/A. Split applications of N did not result in improved net economic return above single applications. When banding UAN on the ridge, economic return was improved substantially as the N rate increased from 60 to 140 lbs/A. Calculation of net economic return was based on the three-year average of corn grain yield. Corn was priced at $2.75/bu, anhydrous ammonia at $0.20/lb, and UAN at $0.28/lb. Application cost per time for anhydrous was $5/A. For UAN it was $5/A banded, $4/A broadcast, and $6/A for spokewheel. N uptake Total above-ground plant uptake of N was increased above the control in all $/A/YR 100 90 80 70 60 50 40 30 20 10 AA, PP, INJ-V UAN, PE, BR UAN, PE, BDCT UAN, PE, PINJR UAN/UAN, PESDV7, BR/PINJV UAN/UAN, PESDV16, BR/PINJV Figure 2. Net economic return to N as influenced by N rate, source, timing, and application method; three-year average, Randall, et al., University of Minnesota. 100 60 100 140 100 100 100 30+70 30+70 30+70 30+70 N Rate --- lbs/A UAN, PE, PINJV UAN/AA, PESDV7, BR/PINJV BR=Band on Ridge, PP=Preplant, PE=Preemergence, BDCT=Broadcast, PINJR=Point Inject in Ridge, PINJV= Point Inject in Valley, SD=Sidedress
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