Corn Yield and Economic Optima for Nitrogen Treatments and Plant Population Over a Seven‐Year Period¹

Abstract

Response of corn (Zea Mays L.) yield to nitrogen applications at various planting rates were determined for two soil types over a seven‐year period. Regression analysis was used to determine response surfaces, maximum and economic optimal treatments and yields. Response curves and production surfaces were constructed from the regression data. Significant differences in responses and optimal treatments were found from year to year and between sites. Optimal nitrogen treatments varied from 21.4 to 202.1 kg/ha and optimal planting rates from 12,189 to 54,135 plants/ha. A function from data aggregated over seven years indicated that the optimal rates would be 120 kg/ha of N and 37,787 plants/ha.

A Comparison of Annual Versus Average Optima for Fertilizer Experiments

“…Experimental methods and results are discussed in detail by Colyer and Kroth [4]. 2 The same experimental procedure was duplicated at all sites over a seven-year period.…”

“…The problem is analogous to the classic problem in firm theory in which a given output must be produced at a minimum of cost. The estimated variance formula replaces the isocost line under pure competition and the estimated 4 Averaging the annual functions assumes each annual function is equally likely and that the average function is certain. This assumption amounts to restricting the comparisons to the actual seven years that occurred.…”

Effects of Nitrogen Rate, Irrigation Rate, and Plant Population on Corn Yield and Water Use Efficiency

“…Optimum plant population is related to soil moisture availability (Holt and Timmons, 1968; Karlen and Camp, 1985), N fertility, and other environmental factors. Optimum plant population for corn production increases with the increase of available N until plant population at approximately 50000 plants ha −1 (Lang et al, 1956; Colyer and Kroth, 1968; Thomison et al, 1992; Eckert and Martin, 1994).…”

Fertilization Strategy Under Uncertainty*

“…Experiments to obtain data for response curves or surfaces over long time spans and under relatively constant conditions, except for weather, are needed It0 improve the use of such procedures. One set of such experiments has been conducted in Missouri for a period of eight years [3]. Although the length of time is still inadequate, Ithere has been sufficient variation of climatic conditions to initiate the analytic use of the results.…”