PROFITABILITY OF SITE-SPECIFIC NITROGEN RECOMMENDATIONS FOR MICHIGAN CORN

Site-specific nitrogen application (SSNA) has been considered a potentially more efficient nitrogen (N) management than uniform N application (UNA), because it tailors the N application rate to meet crop needs. However, previous studies on the profitability of SSNA were inconclusive. This study examines the conventional N fertilizer recommendation as a possible reason for the poor profitability of previous SSNA studies. Most previous SSNA experiments followed state-level N recommendations based on yield goals and/or soil nutrient levels that assume corn yield response to N does not vary site-specifically. This study challenges that assumption. It examines a set of six continuous site characteristic variables, more than any previous study, in order to assess a wide range of site factors that could affect corn yield response to applied nitrogen. In examining three years of data on 14 fields in Central Michigan, this work looks at a longer time series and wider cross section than comparable research. For the first time, three years and 13 fields data are pooled together on the basis of irrigation status to provide an SSNA recipe. The results suggest that corn yield response to N does vary site-specifically, but at current prices, SSNA cannot generate enough benefits to cover its costs on most cornfields in this region.