Nitrogen Fertilizer Management of Temporarily Waterlogged Soils to Improve Nitrogen Availability and Corn Production.

In the Midwestern United States, extreme precipitation events during April to June can often cause decreases in corn (Zea mays L.) grain yields in both upland and low-lying areas. Major problems associated with intense precipitation events in corn production include escalated N loss and abiotic crop stress. The objectives of this study were to determine the effects of different waterlogging durations and pre-plant and rescue N fertilizer applications on N availability and corn production. A two-year field experiment was initiated in 2013 on a poorly-drained claypan soil in Northeast Missouri; with treatments arranged in a split-split plot arrangement in a randomized complete block design with three replications. Pre-plant fertilizer treatments included a non-treated control (CO), urea (NCU), urea plus nitrapyrin (NCU+NI), and polymer coated urea (PCU) applied at a rate of 168 kg N ha^-1. Waterlogging treatments included a non-waterlogged control and one, three and seven days of soil waterlogging when the corn was at the V6 growth stage. A rescue N treatment of 83 kg N ha^-1 of urea plus urease inhibitor (NCU+UI) was applied at the V10 growth stage to half of all treatments. The results for the 2013 growing season showed that in the plots that received no waterlogging, PCU-treated plots had 56.6 kg N ha^-1 greater inorganic soil N content to a depth of 30 cm than that of the NCU-treated plots. During the 2013 growing season, there were no enhanced efficiency pre-plant fertilizer or rescue N treatment effects on grain yield possibly due to residual soil N from the 2012 drought year. However, there were yield reductions after three and seven days of waterlogging when compared to the non-flooded control. Results for the 2014 growing season will also be presented.