Improving Nitrogen Fertilizer Management in Maize with Split Fertilizer Applications: Implications for Precision Agriculture.

The economically optimum nitrogen (N) rate is the amount of N fertilizer that when applied to a maize crop provides the highest economic return to the farmer. This optimum N rate varies from year-to-year, even on the same field, largely in response to variations in weather. Many approaches have been developed to help farmers estimate optimum N rates; these approaches typically rely on an farmer-derived yield goal. But because yield itself is also highly variable from year-to-ear, the efficacy of these approaches are limited. We present a nitrogen (N) fertilizer management strategy that conceptualizes maize grain yield as the result of two recursive, N-mediated processes. First, N uptake throughout vegetative growth, and during the critical period bracketing silking, influences yield potential by regulating potential kernel number (i.e. spikelets). Second, N uptake during grain-filling, especially in the first 2-3 weeks after silking, minimizes kernel abortion and maintains kernel weight throughout grain-fill. This conceptualization supports an N management strategy based on two N applications: an initial N rate (pre-plant or early side-dress) that, for a given season, maximizes yield potential established around silking, and a second N rate that, for a season’s given yield potential, minimizes yield losses during grain-filling. This management strategy eliminates the need for early-season yield goal estimates and creates a niche for precision agriculture approaches by allowing for the second N rate to be tailored based on in-season parameters of yield potential. To demonstrate the feasibility of this approach, this poster also presents the results of a field study which quantifies the interaction between different initial pre-plant N rates, and a second N rate applied at the V13 stage of development. Taking place the Elora Research Station near Guelph, Ontario, this study quantifies N uptake, crop growth rate around silking, radiation use efficiency, kernel abortion and grain yield.