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Fluid Journal : Fluid Journal 1996-1998
Winter 1998 return are shown in Figure 1. Using mean values in the response function, economic optimum N rates were similar for point injection and knife banding and greatest for the broadcasting system. N rates represent those that would earn the most profit per acre. These rates are averages over the three- year study, and the optimum would vary under specific environmental conditions. Root/sucrose yield and accompanying gross revenue were greatest under the optimal N rate for point injection, and were least under knife banding. Fertilizer and application costs were similar for point injection and knife banding. Point injection produced superior sugarbeet performance and the greatest gross and net returns of the three placement methods. In spite of considerable equipment costs, point injection produced $67/A more revenue above fertilization and beet hauling costs than broadcasting, and $94/A more than knife banding. Fertilization costs were highest for the broadcasting system because of a higher optimum N rate and high application cost. An increase in N price would increase the advantage of precision placement. Optimal N and associated returns for all production goals are summarized in Table 2. As economic theory would indicate, the optimal N rates required for obtaining maximum root yields, sucrose yields, and recoverable sucrose yields are higher than the rates obtained when maximizing profit. Maximizing recoverable sucrose yield requires more N than the profit maximizing rate, but net returns are similar. Nitrogen fertilization rates under the four management goals were almost always less for point injection and always more for broadcasting, with returns over fertilizer and beet hauling being greatest for point injection. The optimum N rate for each of the four goals changed less under point injection than for knife banding or broadcasting. Range in optimum N rate under the four management goals was 187 to 200 lbs/A for point injection, 187 to 224 lbs/A for knife banding, and 220 to 266 lbs/A for broadcasting. _________________________________ Drs. Van Tassell and Yang are professors, Department of Agricultural Economics, University of Wyoming, and Dr. Blaylock is agronomist, Agrium US, Inc. ! Figure 1. Sucrose yield and gross/net revenues from economic optimum N rate for three placement methods on sugarbeets, Van Tassell et al., University of Wyoming, 1991-93. 10,200 10,000 9,800 9,600 9,400 9,200 Yield -- lbs/A B P K B P K B P K B=Broadcast P=Point Injection K=Knife Banding 1,100 1,050 1,000 950 900 850 Yield Gross Revenue Revenue above fertilization and beet hauling costs $/A Table 2. Associated profit rate for each management goal under alternative fertilization methods, Van Tassell et al., University of Wyoming, 1991-93. Goal Broadcast Point injection Knife banding Root yield N rate--lbs/A 266 202 224 Return--$/A 883 964 859 Sucrose yield N rate--lbs/A 248 200 209 Return--$/A 983 964 867 Recoverable sucrose yield N rate--lbs/A 241 197 205 Return--$/A 896 965 869
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