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Fluid Journal : Fluid Journal 1993-1995
Drs. R. K. Roberts, D. C. Gerloff, D. D. Howard Injecting N Cuts Application R Injecting N Cuts Application R Injecting N Cuts Application R Injecting N Cuts Application R Injecting N Cuts Application Rate in Half? ate in Half? ate in Half? ate in Half? ate in Half? Could be, say University ofTennessee researchers who set up models com- paring broadcasting with injecting UAN in no-till corn. Summary: Results of this research show a reduction of 46 percent in the amount of N required from injected compared to broadcast UAN to achieve a no-till corn yield of 90 bu/A under average weather conditions. A 90-bu/A yield is not chosen as a target yield to which farmers aspire, but rather is representative of average corn yields in Tennessee. Although the cost of application is over two times higher for injection than broadcast, a lower cost of N is more than offsetting, resulting in a reduction in total cost of N fertilization by 39 percent. Furthermore, total production costs (less costs of land, management, and risk) of producing a 90-bushel yield through injection are nine percent lower than those for broadcast. Greatest differ- ences in break-even prices between the two application methods occurred under poor weather conditions. The objective of this study was to evaluate the economic tradeoffs between injection and broadcast methods of apply- ing N to no-till corn. Data were obtained from a three-year experiment that began in 1983 and ended in 1985. Location of the study was the Milan Experiment Station in Milan, Tennessee. Soil was Memphis silt loam. No-till corn followed a wheat cover crop, and N was applied after planting. Weather conditions in 1983 were poor, while in 1984 precipitation was excellent and well timed. In 1985, weather conditions were about average. These data are still applicable in defining cost-efficient N application methods because the same application methods are currently being used, and state average corn yields have not changed appreciably since 1984. The University of Tennessee Agricultural Extension Service prints row-crop budgets annually. These budgets include no-till corn production inputs and machinery comple- ments specified for a 90 bu/A yield. This 90- bu/A yield was not chosen as a target yield to which farmers aspire. Rather it was chosen because it is representative of what typical corn land produced in an average weather year in Gibson County, Tennessee (1985 average yield, 96 bu/A), and in the state as a whole (1984-93 average yield, 92 bu/A). Forty-six percent less N Quadratic yield response functions were estimated by regression using 1983, 1984, and 1985 field data. Assuming a grower fertilizes for an average weather year, the 1985 yield response functions (field yields were 95 bu/A) were chosen to represent conditions necessary to achieve the 90- bushel yield given in the no-till corn budget. The resulting response functions for 1985 (average weather) are given in Figure 1, which shows the amounts of N that would be required to achieve a corn yield of 90 bu/ A for each application method. Note by the curves how injecting UAN, compared to broadcasting, would require significantly less lbs/A of N. Table 1 lists the amounts of N that would be needed to produce yields of 90 bushels using the 1985 function, the price of UAN, and costs of N as well as its application. To achieve a 90-bu/A yield for average weather conditions (1985) would require 133 lbs/A of N from broadcast UAN and 72 lbs/A of N from injected UAN. These findings suggest substantial N reductions can be achieved through injection rather than broadcast. In fertilizing for average weather conditions to achieve a 90-bu/A yield, injecting UAN would require 46 percent less N than broadcasting UAN. Total cost lower Injected UAN has a variable N cost lower than broadcast in Table 1 because of a lower N application rate. The cost of injecting N is higher because more time is required to fertilizer an acre. Both labor and machinery Table 1. Cost comparisons between broadcasting and injecting UAN at rates expected to achieve a 90-bu/A no-till corn yield at Milan, TN, 1985, Roberts, et al. Variable Application Total Cost Method N N Price cost of N cost of N of N1 lbs/A $/lb $/A $/A $/A Broadcast 133.2 0.229 30.50 1.34 31.84 Inject 71.5 0.229 16.37 3.07 19.44 1 Variable cost of N, plus cost of applying N. Does not include interest on operating capital. Table 2. Differences in costs and break-even prices to achieve a 90-bu/A no-till corn yield at Milan, TN, by broadcasting or injecting UAN, Roberts, et al., University of Tennessee. Method Estimated Cost of Break-even Difference in yield production price break-even prices bu/A $/A $/bu $/bu 1983: Broadcast 50.0 148.60 2.97 0.72 Inject 60.2 135.65 2.25 - - 1984: Broadcast 112.8 148.60 1.32 0.07 Inject 108.9 135.65 1.25 -- 1985: Broadcast 90.0 148.60 1.65 0.14 Inject 90.0 135.65 1.51 - - 1 Includes interest on operating capital not included in Table 1. Summer 1995
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