MANAGEMENT UNIT SIZE AND EFFICIENCY GAINS FROM NITROGEN-FERTILIZER APPLICATION

Efficiency gains of breaking a simulated field into management units s izes from the largest possible (whole field) to the smallest possible were calculated for the application of nitrogen fertilizer to corn. Tw enty-seven alternative field fertility distributions were generated by varying the mean, coefficient of variation and correlation coefficien t for a lognormal distribution that follows an AR(I) process. Average application rate and yield gain increase with decreases in management unit size for high fertility fields as areas in the field requiring mo re fertilizer can be identified. The opposite occurs in low average fe rtility fields since less fertilizer can be applied to those more fert ile areas rather than apply a high rate based on the low average for a larger region. Efficiency gains increase with decreases in management unit size and are enhanced with spatial variability. (C) 1997 Elsevie r Science Ltd. All rights reserved.