Microbially mediated mechanisms underlie N2O mitigation by bio-organic fertilizer in greenhouse vegetable production system

Bio-organic fertilizer substitution for chemical fertilizer is an important action for nature-based solutions to identify optimal management practices at reducing soil N₂O emissions. However, the current understanding of the underlying microbial mechanisms in response to bio-organic fertilizer substitution for chemical fertilizer is primitive, particularly in greenhouse vegetable production system. Herein, we present the field experiment that spans five years and encompasses four treatments, including no fertilizer (CK), chemical fertilizer (CF), bio-organic fertilizer (OF), and chemical fertilizer combined with bio-organic fertilizer (COF) in the greenhouse vegetable production system. We aimed to investigate the effects of replacing chemical fertilizer with bio-organic fertilizer on soil N₂O emissions and nitrogen-cycling microbial communities. The OF and COF treatments reduced soil N₂O emissions by 70.2 % and 32.3 %, respectively, compared with the CF treatment. The substitution of chemical fertilizer with bio-organic fertilizer led to a reduction in residual nitrate and dissolved organic nitrogen levels in the soil. Additionally, it enhanced the abundance of functional genes associated with both soil assimilatory nitrate reduction and dissimilatory nitrate reduction processes. These changes likely facilitated the conversion of nitrate nitrogen to ammonium nitrogen and mitigated soil denitrification. Additionally, bio-organic fertilizer significantly (P < 0.05) decreased the activity of soil-denitrifying microorganisms and increased the abundance of soil nitrogen-fixing genes to reduce N₂O emissions. These results indicate the potential of using bio-organic fertilizer instead of chemical fertilizer to reduce reactive nitrogen emissions in greenhouse vegetable production system, which can contribute to the development of environmentally friendly fertilization strategies.