Genotype, Environment, and Management Factors Controlling Corn Response to Late Season N Application.

ASA Abstract

“Genotype, Environment, and Management Factors Controlling Corn Response to Late Season N Application”

Late N applications (i.e. those after the V10 stage in corn) are potentially beneficial from an environmental standpoint because they may increase the synchrony between N fertilizer application and the time of maximum crop N uptake. Our review of the literature indicates that there are many G x E x M interacting factors controlling corn yield response to late season N application.  Modern hybrids typically take up proportionally more late-season N than older hybrids, but even similar-maturity modern hybrids can vary widely in the quantity and timing of plant N uptake from soil.  It is, however, quite common for modern hybrids to take up at least 30% of their total N accumulation after silk emergence. The relative proportion of late-season N uptake can also be affected by management factors such plant densities, N source, and N placement, as well as by environmental factors like rainfall/irrigation timing or soil moisture status before and after the late N application.  The relative amount of the total N fertilizer package that is applied pre-plant versus typical side-dress (V4-V6) versus late (post V10) sidedress also has consequences for the probability of a positive corn response. Physiologically, increased whole-plant N uptake and increased ear N allocation have been strongly related to increased ear sink strength.  Prior researchers have demonstrated that N concentration in the reproductive organs is influenced by N availability, and that increased ear shoot N concentration is highly correlated with increased kernel number.  Late-season N application may, therefore, be more warranted in high yield corn situations if it helps to increase ear shoot N concentrations during the critical period. This presentation will provide perspectives on the primary G x E x M factors (and underlying mechanisms) that have been demonstrated to impact corn response to late-season N applications.  

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