Abstract:

To explore the effects and mechanisms of biochar and nitrification inhibitors on the emission of main reactive nitrogen gases (NH₃ and N₂O) in protected vegetable cultivation soil, soil from vegetable greenhouses in Zhejiang was collected, and a pot experiment was conducted using a closed chamber-gas chromatography method to observe the impacts of straw biochar and nitrification inhibitor (DMPP) on soil N₂O and NH₃ emissions during crop growth. Five treatments were set up for the experiment, including CK (control), urea (N), urea + nitrification inhibitor (N+DMPP), urea + biochar (N+C), and urea + biochar + nitrification inhibitor (N+C+DMPP). The results showed that the cumulative N₂O emission of the N treatment was 16.69 mg N/m², and that of the N+C treatment was 14.73 mg N/m², indicating that biochar reduced the cumulative N₂O loss in vegetable field soil by approximately 11.74%. The cumulative N₂O emissions of the N+DMPP, N+C+DMPP, and CK treatments were 8.36, 2.82 and 2.58 mg N/m², respectively, which were significantly lower than those of the N treatment. DMPP inhibited nitrification by suppressing the growth and reproduction of AOB (ammonia-oxidizing bacteria), thereby reducing the cumulative N₂O loss from the nitrification process. The cumulative ammonia volatilization in the soil of the N+C treatment was 45.08 kg N/hm², 59.75% higher than that of the N treatment, and the N+C+DMPP treatment was 24.24% higher than the N treatment. There was no significant difference in ammonia volatilization between the single DMPP addition and the N treatment. The number of nosZ genes in the biochar and nitrification inhibitor combined treatment was 80% higher than that in the single application, indicating that the combined application significantly enhanced soil denitrification, which was conducive to the reduction of N₂O to N₂. Considering the global warming potential (GWP) caused by direct N₂O emissions and indirect N₂O emissions from ammonia volatilization, the N+C treatment reduced N₂O emissions but promoted ammonia volatilization, thereby increasing its GWP. In the protected vegetable cultivation system, compared with single application measures, the combined application of 3, 4-dimethylpyrazole phosphate (DMPP) and biochar can more significantly inhibit greenhouse gas emissions during soil nitrogen transformation, showing the best GWP reduction effect during the critical fertilization period, providing an efficient and feasible technical path for achieving green and low-carbon production in protected agriculture.

Key words: straw, protected vegetables, nitrification inhibitor, greenhouse effect potential, active N