Corn Grain Yield As Affected By the Nitrification Inhibitor KAS771G77.

Greater awareness of environmental issues related to nitrogen (N) management and potential for greater yields in corn (Zea mays L.) have renewed interest in sidedress N applications. Nitrification inhibitor use may reduce N losses due to leaching and denitrification and therefore potentially increase yields, especially with early sidedress applications of urea ammonium nitrate (UAN). The objectives of this study were to measure the effects of two nitrification inhibitors, KAS 771G77 (Koch Agronomic Services, LLC) and nitrapyrin [2-chloro-6-(trichloromethyl) pyridine], on corn grain yields, N removal in grain and economic optimum N rate on poorly-drained glacial till soils (Aquic Endoaquolls) in Minnesota. Four fertilizer N rates (67, 134, 202 and 269 kg ha^-1) were the main plots in a split-plot arrangement of a randomized complete block design with four replicates. Sub-plots were comprised of four nitrification inhibitor treatments [control, 9.4 and 18.7 L ha^-1 of KAS 771G77 and 2.6 L ha^-1 (0.57 kg ai ha^-1) of nitrapyrin as Instinct™ (Dow AgroSciences)]. A zero N control treatment was included in each replication. Nitrogen as UAN was stream-injected 5-8 cm deep midway between corn rows at the V1 growth stage. Each inhibitor was added to UAN and thoroughly mixed prior to application. In a dry spring (2012), corn grain yields were not affected by nitrification inhibitors; whereas, in a wet spring (2013) corn grain yields were 0.8 – 1.1 Mg ha^-1 greater with nitrification inhibitors. Yields were similar among inhibitor sources (KAS 771G77 and nitrapyrin) and KAS 771G77 rates. In 2013, use of KAS 771G77 reduced economic optimum N rate 27 kg ha^-1, while numerically increasing grain yields 0.5 Mg ha^-1.