Assessing Management of Nitrapyrin with Urea Ammonium Nitrate Fertilizer on Corn Yield and Soil Nitrogen in a Poorly-Drained Claypan Soil

Use of nitrification inhibitors (NI) in agricultural production systems is considered a risk management strategy for both agricultural and environmental considerations. It can be utilized when risk of reduced nitrogen (N) fertilizer use efficiency or yield, and risk of pollution from mineral N is high which can occur in poorly-drained soils that are vulnerable to waterlogging and runoff. Field research was conducted on corn (Zea mays L.) from 2012 to 2015 in Missouri, USA on a poorly-drained claypan soil. Treatments consisted of two application timings of urea ammonium nitrate (UAN) fertilizer solution [pre-emergence (PRE) and V3 growth stage], two application rates (143 and 168 kg N ha-1) in the presence or absence of nitrapyrin, and a non-treated control. UAN at 143 kg ha-1 with nitrapyrin at the V3 growth stage resulted in the highest yield (8.6 Mg ha-1). Similarly, pre-emergence application of UAN 168 kg ha-1 with nitrapyrin resulted in greater yields (7.7 Mg ha-1). UAN application rates and timings affected soil NO3-N and NH4-N concentrations more than the presence or absence of nitrapyrin during the growing season. A side-dress application of a lower rate of UAN with nitrapyrin at V3 was effective in poorly-drained soils when risk of N losses during the growing season due to unfavorable precipitation events and other environmental variables was high. A pre-emergence application of UAN with nitrapyrin was also effective and it may eliminate the need for split-application of N fertilizer later in the season thereby reducing the workload on growers during the growing season.