Management of nitrogen and nitrification inhibitors for corn and wheat production on claypan soils
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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. Field research was conducted on corn (Zea mays L.) from 2012 to 2015 in Northeast Missouri. 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 ), with and without a NI (nitrapyrin), and a non-treated control which were arranged in randomized complete block design. UAN applied at a rate of 143 kg ha-1 with nitrapyrin at the V3 growth 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 concentration more than nitrapyrin presence or absence during the growing season. A side-dress application of a lower rate of UAN with nitrapyrin at V3 corn growth stage may be useful when risk of N losses during the growing season due to unfavorable precipitation events and other environmental variables is high. A pre-emergence application of UAN with nitrapyrin was useful and it may eliminate the need for split-application of N fertilizer later in the season. Workload on growers soon before planting or during growing season, excessive wet field conditions in early spring, reduced N fertilizer use efficiencies due to uncertain climatic conditions during growing season, and environmental concerns of pollution from - 30 - N escaping from agriculture production systems may give an incentive to growers and policy makers to increase the use of nitrapyrin in the future.