Zn-modified biochar coupled with biological nitrification inhibitors mitigates nitrous oxide emissions from alkaline...

Biochar (BC) has generally been employed to mitigate the nitrous oxide (N₂O) emissions from agricultural soils, but its response is soil-dependent. Thereby, in soil with proficient nitrification tendency, Zn-modified BC coupled with biological nitrification inhibitors (BNIs) could be more effective in mitigating N₂O emissions. The effects of coupled application of Zn-modified biochar and BNIs on N₂O emission and its underlying microbial mechanism remain largely unknown. In our study, a 24-day incubation experiment was established representing nine treatments; with three biochars amendments using three settings of BNIs, referred to as: 1) control (without amendment/inhibitor, 2) control with methyl 3-(4-hydroxyphenyl) acrylate -MHPA, 3) control with methyl 3-(4-hydroxyphenyl) Propionate-MHPP, 4) pristine BC without inhibitor, 5) pristine BC with MHPA, 6) pristine BC with MHPP, 7) Zn-modified BC without inhibitor, 8) Zn-modified BC with MHPA, 9) Zn-modified BC with MHPP, all at agronomically recommended dosage. N dynamics were evaluated following the addition of urea. The inclusion of Zn-modified BC in combination with MHPA and MHPP substantially reduced N₂O emissions by 94.52% and 96.85% relative to control. Quantification of N-cycling genes indicated that the treatment without BC amendment stimulated the growth of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) across the entire incubation period. The input of Zn-BC with MHPA and MHPP substantially inhibited the population of AOA and AOB. LEfSe cladogram elucidated the distinct shift in bacterial assemblage across the treatments. Overall, our results demonstrated that Zn-modified BC + MHPP played a key role in the dynamics of ammonia-oxidizing functional microbiome and N turnover, potentially considerably mitigating N₂O emissions.