Fate of applied urea 15N in a soil-maize system as affected by urease inhibitor and nitrification inhibitor

A micro-plot field experiment with reduced urea 15N application was conducted to study the effects of urease inhibitor NBPT (N-(n-butyl) thiophosphoric triamide) and nitrification inhibitor DMPP(3,4-dimethyl-1H-pyrazolium dihydrogen) on the fate of applied urea 15N; it aimed to find an efficient way to reduce the urea N application rate while improving the agronomic and environmental benefits. Five treatments were installed, i.e., 180 kg N/ha (N1, conventional application rate), 126 kg N/ha (N2, reduced to 70% conventional application rate), N2 + NBPT, N2 + DMPP, and N2 + NBPT + DMPP. Compared with treatment N1, all the other treatments had a significantly higher total 15N recovery by both soil and plant (P < 0.05 48.20, 41.39, 37.69, 38.85 and 34.83% soil recovery for N2 + NBPT + DMPP, N2 + DMPP, N2 + NBPT, N2 and N1 treatment respectively; and 42.68, 40.86, 40.25, 37.18 and 36.30% plant recovery for N2 + NBPT + DMPP, N2 + DMPP, N2 + NBPT, N2, and N1 treatment, respectively). In the plant 15N recovery, the 15N absorbed in grain/stem was highest in treatment N2 + NBPT + DMPP. The maize biomass and the maize yield had a slight increase in treatment N2 + NBPT + DMPP, compared with those in treatment N1. In sum, for the maize production in study area, N2 + NBPT + DMPP application method would be a feasible way to ensure the normal maize yield while improving yield quality, saving urea fertilizer, and protecting the environment.