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Fluid Journal : Fluid Journal 1993-1995
costs increase as field time increases, making UAN injection more expensive. Nevertheless, when the cost of N and the cost of application are combined, injection still has a total cost advantage because higher application costs are greatly offset by lower N costs when compared to broadcasting. As can be seen in the table, injected UAN has a $12.40/A total cost advantage over broadcast UAN. Table 2 lists estimated yields per acre, total production costs per acre, and break- even prices per bushel for N application methods, using the 1983, 1984, and 1985 yield response functions. Total production costs include all costs except those for land, management, and risk. Differences in total production cost emanate from differences in method of application. Break-even lower, too Break-even prices to land, management, and risk are calculated by dividing the yield level into total cost of production (Table 2). Note that the highest break-even price difference between broadcast and injection of UAN occurs in the year 1983, being $0.72/ bu. As already noted, poor weather account for this skewing. With yields higher in 1984 and 1985, because of more favorable weather, break- even prices in Table 2 decline notably. So do break-even price differences between broadcast and injection application meth- ods. Note in Table 2 that the break-even price for injected UAN is $0.07 below broadcast UAN in 1984 and $0.14 below in 1985. These results reflect the increased efficiency of broadcast UAN, relative to injection, under good and average weather conditions (1984 and 1985) as opposed to poor weather conditions (1983). Thus, risk associated with broadcasting is greatest in poor weather years. Assuming, as we have, a Tennessee no- till corn grower fertilizes for average weather conditions to achieve a yield of 90 bu/A, results show (for 1985 conditions in Table 2) a more favorable return for injected UAN versus broadcast. Using the marketing year average corn price in Tennessee for 1984 through 1993, we'll see how this would work out. Given a price of $2.36/bu, injected UAN would return $0.85/bu ($2.36 - $1.51) while broadcast UAN would return only $0.71/bu. On a per acre basis, with a 90-bu/A yield, injected UAN would return $76.75 (90 bu/A times $2.36/bu, less $135.65/A total costs) to land, management, and risk, while broadcast UAN would return only $63.80. That amounts to a difference of $12.95/A! Differences in break-even prices between application methods are greatest for the poor weather conditions of 1983, as the table so clearly shows, suggesting greatly reduced efficiency of broadcast UAN. For the good and average weather conditions of 1984 and 1985, greater relative efficiency of broadcast UAN is reflected in smaller differences in break-even prices. Thus, risk associated with broadcasting compared to injected UAN is greatly increased in poor weather years. Based on our yield response functions, no-till corn growers should inject rather than broadcast UAN. Risks of negative returns in poor weather years will be reduced, and profits will be enhanced in years with average or better than average weather. Methodology Production costs found in the 90-bushel, no-till corn budget were adjusted for the N application methods. Adjustments to budgets were for the amounts and price of UAN, and for machinery and labor required for application. Application costs were estimated to include fuel, repairs, machinery depreciation and interest, interest on operating capital, and labor associated with application. A 100-horsepower tractor was assumed for both application methods. Tractor time required to pull the fertilizer spreader was assumed to be 0.07 hours/A for broadcast UAN. For injected UAN, tractor hours/A to pull the injector tanks were assumed to be 0.16. For both broadcast and injected UAN, labor hours for application were set at 1.35 times tractor hours. This extra labor was assumed to cover the time associated with preparation and cleanup. Charges for spreader or tank rental were assumed to be included in the price of fertilizer. A common practice in Tennessee is for the fertilizer distributor to supply application equipment at no extra cost to the growers. Dr. Roberts is professor, Dr. Gerloff is associate professor, and Dr. Howard is professor at the University of Tennessee. University of Tennessee, 1985. ! Injected UAN Broadcast UAN Yield - bu/A 140 120 100 80 60 40 20 00 50 100 150 200 72 133 N - lbs/A Figure 1. Estimated yield response functions for UAN applied to no-till corn, comparing broadcast and injection responses, Milan, TN, Roberts, et al., University ofTennessee, 1985. Summer 1995
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