Influence of Weather on Year-to-Year Yield Response of Corn to Ammonia Fertilization
1986
Hollinger, S. E. | Hoeft, R. G.
Multi-year N studies have shown large year-to-year variation in the yield response of corn (Zea mays L.) to N fertilization. The objectives of this study were to (i) determine which normally predicted and measured weather variables account for this year-to-year variability; and (ii) to suggest a climate forecast design that will provide the most flexibility in planning N fertilization programs. Relative yield responses to N treatments were obtained from 6 yr of field research on a fine, silty, mixed mesic Typic Haplaquolls. Relative yields and spring N treatments were transformed using natural logarithms (In). The transformed N treatments accounted for more than 95% of the transformed yield responses in 5 of the 6 yr. The only year the regression failed to fit accurately was a very hot, dry year when there was a negative response to N. The analog of the equation was used to obtain α and β coefficients, where α is the fraction of maximum yield expected if no N is applied, and β is the rate of yield increase with each additional unit of applied fertilizer. The α and β values were then related to the ratio of precipitation/evaporation (P/E) from the 11 June to 15 July period in each of the 6 yr. The quadratic relationship explained 99% of the variation in α and 95% of the variation in β. When P/E is less than optimum, water is limiting and the plant is unable to use the applied nitrogen efficiently. When P/E is greater than optimum, N may be lost through denitrification and/or leaching and is thus, unavailable to the plant.
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