The concentration of NO−3 in the lower portion of cornstalks at physiological maturity has been proposed as the basis for evaluating the N status of corn (Zea mays L.). Here we refine estimates of the optimal range in NO−3 concentrations for this test by using relevant economic scenarios that include 900 plot‐years of new data as well as 450 plot‐years reported earlier. The results showed that rainfall had little effect on concentrations of NO−3 identified as being optimal. However, calculations showed that optimal concentrations of NO−3 in stalks were influenced by prices of corn and fertilizer. For prices that have prevailed in the Corn Belt during the past decade, an optimal range of 0.7 to 2.0 g NO−3‐N kg−1 was shown to be more appropriate than the range originally reported. When this optimal range is used, the tissue test can be used to identify deficiencies of N as well as excesses of N. Overall, the results show that the end‐of‐season cornstalk test deserves attention as a tool for providing feedback that can be used to compare and refine systems for making N fertilizer recommendations.
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Binford et al. (1992) studied this question.