Relationship Between Corn Yield, Expressed as a Percentage of Maximum, and the N Percentage in the Grain. II. Diagnostic Use1
- W. H. Pierre,
- Lloyd Dumenil and
- Julio Henao2
The purpose of this study was to develop a procedure for determining the amount of N fertilizer needed by corn (Zea mays L.) for maximum yield and economic optimum yield based on the relationship between the relative yield of corn, expressed as a percentage of maximum yield, and the N percentage in the grain. The three major steps in the procedure are: (a) determining the maximum potential yield and yield increase from the relative yield — percent N relationship and the present yield, (b) determining the N-requirement index (NRI) for different initial relative yields, and (c) calculating the total N requirement.
Two procedures were developed for estimating the NRI, the N required per unit of yield increase, from different initial relative yield levels to maximum or economic optimum yields. One involved simple computations using the treatment means from 13 site-years of experimental data. The other utilized the individual regressions of yield on N fertilizer from the same experiments to calculate the NRI's to the same marginal productivity point on each site-year's regression. Good agreement was obtained between the two procedures.
The average NRI's were found to vary from approximately 7.5 kg/q at 90% of maximum yield to 3.5 kg/q at 45% of maximum yield. Evidence was obtained showing the desirability of using NRI values for comparing the efficiency of N use under different environmental and management conditions.
Factors that may affect the relative yield — percent N and the NRI — initial relative yield relationships are discussed briefly. Also, the need for further research, expecially on the effect of different hybrids, is suggested.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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