Effects of nitrogen application methods combined with urease/nitrification inhibitor on decreasing NH₃ volatilization and N₂O emission in rice season

  Objectives  NH₃ volatilization and N₂O emission from paddy fields were determined under different fertilization methods and urease/nitrification inhibitor addition, to optimize fertilization measures.

  Methods  A two-year paddy field experiment was conducted in the Taihu Lake region. The urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) and nitrification inhibitor methyl 3-(4-hydroxyphenyl) propionate (MHPP) were applied at 1% urea-N. The six treatments include no N application (CK), broadcasted urea N at 300 kg/hm² (conventional fertilization, CN), broadcasted urea N at 225 kg/hm² (RNB), 50% in deep urea N application at 225 kg/hm² (RND), broadcasted urea N application at 225 kg/hm²+NBPT+MHPP (RNB+DI), and 50% in deep urea N placement at 225 kg/hm²+NBPT+MHPP (RND+DI). The dynamic chamber technique was used to monitor NH₃ volatilization flux from the paddy field within two weeks after fertilization. The static chamber-gas chromatography method was used to monitor N₂O emission flux from paddy field across the rice season.

  Results  1) The NH₃ volatilization lasted for 7 days after fertilization. The total NH₃ volatilization after broadcasting basal and tillering fertilizer accounted for 86.63%–91.76% of the total NH₃ volatilization. The N₂O emission flux peaks appeared after fertilization and halfway through aeration. 2) Compared with the CN, RNB decreased total NH₃ volatilization and N₂O emission by 29.69%–39.41% and 13.43%–23.37%, respectively. 3) Compared with the broadcasted urea application (RNB), deep placement of urea (RND) decreased total NH₃ volatilization and N₂O emission by 53.50%–72.05% and 16.66%–23.43%, respectively (P<0.05). 4) Compared with RNB, RNB+DI decreased total NH₃ volatilization and N₂O emission by 9.57%–22.27% and 8.77%–15.67%. 5) Compared with CN, RND+DI (P<0.05) decreased total NH₃ volatilization and N₂O emission by 76.89%–82.29% and 37.98%–48.71%.

  Conclusions  NH₃ volatilization and N₂O emission can be decreased by reducing the N application rate, N-fertilizer deep placement and adding inhibitors in urea, which had a better effect on NH₃ volatilization reduction. The combination of these optimized N fertilization measures can achieve optimum NH₃ and N₂O emissions reduction effects. The comprehensive integration measure is feasible in practice and provides technical support for promoting rice production.