A 2‐year study of the impact of reduced nitrogen application combined with double inhibitors on soil nitrogen transformation and wheat productivity under drip irrigation

Nitrification inhibitors (NIs) and urease inhibitors (UIs) can decrease the risk of nitrogen (N) loss and extend N uptake by plants. However, there are few case studies about reduced N application combined with double inhibitors (DIs, NI plus UI), especially under drip irrigation systems. A 2-year field experiment was therefore conducted to explore the effect of 80% N application rate combined with NI or DIs on soil N transformation, wheat productivity and N use efficiency (NUE) in a drip-irrigated field. The four treatments included a no-fertilizer control, 100% urea, 80% urea + NI (nitrapyrin) and 80% urea + DIs (nitrapyrin and N-(n-butyl) thiophosphorictriamide (NBPT)).Our results showed that the 80% urea + DIs treatment significantly increased the ratio of NH4+ to NO3- and N content (urea-N, NH4+ -N and NO3- -N) in soil at 0-20 cm depth (P < 0.05) at the heading stage and the filling stage of wheat in both 2013 and 2014, relative to the 100% urea treatment. A total of 80% urea + NI treatment decreased wheat N uptake and wheat productivity (plant biomass and yield) compared to 100% urea treatments (P < 0.05). However, application of 80% urea combined with DIs achieved equivalent wheat productivity with 100% urea treatment. Moreover, the greatest NUE (43.6%) was recorded with the application of DIs.Cutting the N application rate by 20% combined with NBPT and nitrapyrin could provide a sustainable fertilization strategy for wheat production under drip irrigation. © 2020 Society of Chemical Industry.