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This study examines the profitability and stability of site‐specific (SS) nitrogen fertilizer recommendations using an empirical model of SS yield response to controlled inputs, stable site characteristics, and time‐varying weather factors. Using a three‐year panel of on‐farm corn yield experiments and new, continuous variables to describe site characteristics, both spatial and ordinary least squares regression models show clear evidence of SS corn yield response to nitrogen fertilizer. Yield response is predictable only on irrigated fields. Even there, bootstrapped confidence intervals for profitability gains on selected fields indicate that SS nitrogen application would rarely cover its costs.
Liu et al. (Wed,) studied this question.