Corn Response to Urea–Ammonium Nitrate Solution Treated with Encapsulated Nitrapyrin

CORE IDEAS: Instinct nitrification inhibitor either did not affect or reduced grain yield.Instinct did not positively influence early growth plant height or mid‐vegetative canopy normalized difference vegetative index (NDVI).Broadcasting or injecting urea–ammonium nitrate solution (UAN) did not change corn response to Instinct. The use of nitrification inhibitors with fertilizer N application is an attempt to improve corn (Zea mays L.) N use efficiency while reducing environmental and economic concerns associated with N losses. The objective of this study was to evaluate if the encapsulated formulation of nitrapyrin [2‐chloro‐6‐(trichloromethyl) pyridine], Instinct nitrification inhibitor, would influence corn growth and production when applied with spring preplant urea–ammonium nitrate solution (UAN). A 3‐yr field study was conducted in a randomized complete block design with four replications of a factorial combination consisting of UAN at six incremental N rates (0–225 kg N ha⁻¹), broadcast‐incorporated and injected, and with and without 2.56 L ha⁻¹ (0.56 kg a.i. ha⁻¹) Instinct. In 1 of 3 yr, as well as for the means across years, Instinct applied with UAN had a negative effect of reduced early growth plant height and lower mid‐vegetative canopy normalized difference vegetative index (NDVI) compared with UAN without Instinct. Corn grain yield also had a lower across N rate mean yield with Instinct application in 2 of 3 yr and across all 3 yr. The economic optimum N rate (EONR) with Instinct was 32 kg N ha⁻¹ higher than without Instinct, applied either broadcast or injected. Because Instinct did not provide positive effects on corn growth and yield, the study results indicate that Instinct use with spring preplant applied UAN solution would not be an effective nitrification inhibitor to enhance fertilizer N supply or corn production.