Influence of Supplemental Nitrogen Applications on Corn Yield on Two Mississippi River Alluvial Soils.

Nitrogen (N) fertilization is a critical cultural practice required for producing maximum corn yield. Sometimes N applications are delayed or omitted due to inclement weather or other factors. Field experiments were conducted in 2008, 2009, and 2010 to evaluate the timing of supplemental N rates on Mississippi River alluvial soils. Supplemental N rates of 34 and 68 kg ha-1 were applied at the 8-leaf, 12-leaf, or early-silk growth stages in addition to early-season N rates of 168 kg ha-1 (2-leaf growth stage) on Commerce silt loam and 202 kg ha-1 on Sharkey clay and compared to equivalent N rates applied once early season at the Northeast Research Station in St. Joseph, LA. Yields were increased each year on each soil by each supplemental N rates across timings, more so for the 68 kg N ha-1 rate. Generally, yields were greater for the 8- and 12-leaf timings compared to the early silk applications on Commerce and similar across timings on Sharkey. In the Commerce silt loam study, there was little advantage for the supplemental N plus early-season N compared to the equivalent rate applied once early season. In the 2009 Sharkey clay study, yields for the supplemental N application plus early-season N were greater than the equivalent N rate applied at the 2-leaf growth stage, especially for the 8-leaf application. Leaf N and remote sensing data collected at different growth stages will be discussed.