Evaluation Of Instinct Nitrification Inhibitor With Spring Applied Urea-Ammonium Nitrate Solution.

Nitrogen loss from applied fertilizer by leaching or denitrification can result in significant economic issues for corn (Zea mays L.) production and water quality.  Instinct [nitrapyrin: 2-chloro-6-(trichloromethyl) pyridine] is a nitrification inhibitor that could potentially help reduce N losses by keeping applied N in the NH₄⁺ form for a longer time period.  The active ingredient (a.i.) in Instinct, nitrapyrin, is microencapsulated to prevent volatilization after surface application.  The objective of this study was to evaluate if Instinct positively affects corn yield when applied spring preplant with urea-ammonium nitrate (UAN) solution.  A field study was conducted from 2010 to 2012 with four replications in a randomized complete block design with UAN fertilizer (28% N) injected and broadcast at six incremental N rates, 0 to 225 kg-N ha^-1, with or without Instinct at the recommended 2.56 L ha^-1 (0.56 kg a.i. ha^-1) label rate.  Broadcast treatments were incorporated within three days after application.  Across years and N rates, mean corn yield was 0.4 Mg ha^-1 lower with use of Instinct, due to lower yield at rates ≤ 135 kg N ha^-1.  The economic optimum N rate (EONR) for treatments with and without Instinct were 178 and 143 kg N ha^-1, respectively.  There was no difference in yield at the EONR for either Instinct treatment (13.0 Mg ha^-1).  Corn canopy sensing at mid-vegetative growth (V10 stage) indicated less crop canopy and greater N stress in treatments with Instinct at low applied N (<120 kg N ha^-1), as well as in treatments where N was injected at the high N rates (>90 kg N ha^-1).  In conclusion, Instinct had no positive effect on corn growth and yield at high N rates, and resulted in reduced growth and yield at low N rates.