Relative contribution of ammonia-oxidizing bacteria and denitrifying fungi to N 2 O production during rice straw composting with biochar and biogas residue amendments.

Nitrous oxide (N ₂ O) production is associated with ammonia-oxidizing bacteria (amoA-AOB) and denitrifying fungi (nirK-fungi) during the incorporation of biochar and biogas residue composting. This research examined the relative contribution of alterations in the abundance, diversity and structure of amoA-AOB and nirK-fungi communities on N ₂ O emission by real-time PCR and sequence processing. Results showed that N ₂ O emissions showed an extreme relation with the abundance of amoA-AOB (rs = 0.584) while giving credit to nirK-fungi (rs = 0.500). Nitrosomonas and Nitrosospira emerged as the dominant genera driving ammoxidation process. Biogas residue changed the community structure of AOB by altering Nitrosomonadaceae proportion and physiological capacity. The denitrification process, primarily governed by nirK-fungi, served as a crucial pathway for N ₂ O production, unveiling the pivotal mechanism of biochar to suppress N ₂ O emissions. C/N and NH ₄ ⁺ -N were identified as significant parameters influencing the distribution of nirK-fungi, especially Micromonospora, Halomonas and Mesorhizobium.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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