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This article in SSSAJ

  1. Vol. 49 No. 1, p. 134-139
    Received: Feb 29, 1984
    Accepted: Aug 14, 1984

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Fertilizer Nitrogen and Residual Nitrate-Nitrogen Effects on Irrigated Corn Yield1

  1. A. B. Onken,
  2. R. L. Matheson and
  3. D. M. Nesmith2



Multirate nitrogen studies were conducted for a 6-yr period, on an irrigated clay loam soil, to determine the influence of applied N and residual soil N on the grain yield of corn (Zea mays L.). Soil samples were taken prior to fertilizer application each year in depth increments of 0 to 0.15, 0.15 to 0.30, 0.30 to 0.60 and 0.60 to 0.90 m and analyzed for nitrate-N (NO-3-N). Applied N and residual soil NO-3-N were found to significantly influence grain yields. Regression analyses of the data showed highly significant relationships between (i) quantities of NO-3-N measured in the upper portions and those measured in the lower portions of the soil profile and (ii) grain yield and applied N and residual NO-3-N. Highest coefficients of determination were obtained when residual NO-3-N was included as a separate independent variable in the regression equation. Results indicated that residual NO-3-N measured to 0.15 m would be sufficient for evaluation of residual N effects on irrigated corn grain yield on this soil. Fertilizer N requirements for several combinations of grain yield and residual soil NO-3-N were calculated using the N requirement index (NRI) and a power function, and simple and multiple linear response equations generated by regression analysis. A range of values was obtained, with NRI most frequently predicting the highest N requirement. The marginal rate of substitution of residual soil NO-3-N for applied fertilizer N was variable and influenced by (i) amount of residual NO-3-N, (ii) depth of measurement of residual NO-3-N and (iii) maximum grain yield. Fertilizer use efficiency (FUE) was influenced by grain yield, fertilizer N rate, and amount of residual soil NO-3-N. The greatest reduction in FUE resulted from residual soil NO-3-N. In order to maximize FUE, it is necessary to apply the amount of fertilizer N to achieve a given yield level and simultaneously leave as little as possible in the soil to carry over to the next crop year.

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