Rex A. Omonode, Dept. of Agronomy., Purdue University, West Lafayette, IN, Tony J. Vyn, 915 W State St., Purdue University, West Lafayette, IN and Cliff Johnston, Purdue University, West Lafayette, IN
Understanding the nitrification kinetics of applied nitrogen (N) fertilizers in long-term tillage systems can help management decisions to improve N use efficiency, and reduce nitrous oxide (N2O) emissions during crop production. Field studies were conducted in 2013 and 2014 near West Lafayette, IN, to determine rate of nitrification and N2O emissions in long-term no-till (NT), strip-till (ST), chisel (CP), and moldboard plow (MP) systems following urea ammonium-nitrate (UAN) application, with and without nitrapyrin (Instinct). Soil samples were taken weekly to the 30cm depth for up 10 weeks, analyzed for ammonium- and nitrate-N concentrations, and appropriate kinetic model fitted to the data. Nitrous oxide emission was measured twice weekly for 8 weeks, and thereafter weekly for additional 12 weeks, using the static vented chamber procedure. Nitrification was best described by 1st order kinetics with and without nitrapyrin, and regardless of tillage system. Without nitrapyrin, N2O emission was greatest under CP and MP, and was smallest for NT. Across tillage systems, N2O emission was reduced by nearly 20% with Instinct application, and magnitude of emission reduction was generally in the order: MP>ST>NT>CP.