Nitrification inhibitor application at stem elongation stage increases soil nitrogen availability and wheat nitrogen use efficiency under drought stress

One of the practices which could mitigate the negative effects of drought stress is ammonium nutrition. Nitrification inhibitor (DMPP) can keep ammonium concentrations high in the soil for several weeks. Although there are contradictory reports regarding the priority of NH4+ uptake and its toxicity effects on wheat, it is necessary to understand better how to apply DMPP to increase drought tolerance without any negative effects. The field experiment was conducted using N-15 trace technology. The fertilizers treatment included ((NH4)-N-15)(2)SO4 and ((NH4)-N-15)(2)SO4 with DMPP at four drought stress levels. Available soil mineral nitrogen was measured, as well as yield components and N-15 recovery. The results showed that DMPP application at full irrigation and moderate drought stress caused an increase in grain yield of 13% and 10%, respectively. DMPP application at full irrigation, moderate and severe drought stress caused a significant increase in nitrogen use efficiency of 19%, 11%, and 17%, respectively. It seems DMPP application at the stem elongation stage, promoted NH4+ assimilation and transfer to the shoots, which has created relative resistance to drought stress conditions. In conclusion, it is recommended that farmers use DMPP at stem elongation to avoid wheat yield reduction and nitrogen recovery under drought stress.