The Impact of UAN Fertilizer Solution and Nitrification Inhibitor Management on Soil Nitrogen and Corn Growth.

Effective management of nitrogen (N) fertilization of poorly-drained agricultural soils is important for optimizing crop production and reducing potential environmental N loss.  Among the practices used to improve N use efficiency is changing the rate and timing of N fertilizer application and the use of nitrification inhibitors.  The objectives of this research were to determine the effects of using different application rates and timing of UAN fertilizer solution and nitrification inhibitors on soil N content throughout the growing season with depth and to evaluate these management practices on corn (Zea mays L.) N status and grain production.  Field research was conducted from 2012 to 2015 on a poorly-drained claypan soil in Northeast Missouri with treatments consisting of two timings of UAN fertilizer solution application (pre-emergence and at the V2-V3 growth stage), two application rates (143 and 168 kg N ha^-1), with and without nitrapyrin nitrification inhibitor, and an untreated control.  The treatments were arranged in a randomized complete block design with 4 replications.  Soil samples were collected during the growing season and at harvest at the 0 to 22 and 23 to 46 cm depths to determine soil ammonium and nitrate N as affected by the treatments.  Soil ammonium and nitrate concentrations were affected by the timing of N fertilizer application and were significantly higher than the control.  No consistent effect of the nitrification inhibitor on soil N was observed. In general, no differences in leaf chlorophyll readings were observed among plots receiving N fertilizer with or without the nitrification inhibitor.  Across years, crop grain yields were similarly not affected by differences in UAN management or use of the nitrification inhibitor.  Further analysis of the results for 2015 will be presented to evaluate the efficacy of use of these different N fertilizer management practices.