Abstract: To investigate the effects of fertilizer types (organic and chemical fertilizer) on nitrous oxide (N₂O) emissions from soil bacteria and fungi, we conducted a long-term experiment with four treatments, including no fertilization (CK), chemical fertilizer (T1), combined application of chemical and organic fertilizers (T2), and organic fertilizer (T3). We measured soil physical and chemical properties, and the contributions of N₂O emissions from bacteria and fungi. The abundance and structure of bacterial and fungal communities were analyzed by real-time PCR and high-throughput sequencing. The results showed that, compared with T1, T3 significantly increased N₂O emissions from bacteria by 31.34% and decreased N₂O emissions from fungi by 17.11%, while T2 significantly increased overall N₂O emissions by 57.83%, increased N₂O emissions from bacteria by 47.83%, and from fungi by 72.37%. The results of PLS-SEM modeling showed that N₂O emission from bacteria was mainly affected by bacterial community structure rather than their abundance, and by soil pH and electrical conductivity as well. The N₂O emission from fungi was mainly affected by fungal community structure. The proportion of relative abundance of Ascomycota and Basidiomycota was the key to influence the N₂O emission from fungi. Our results highlight that it is necessary to consider not only the characteristics of fertilizer, but also the effects of physicochemical properties such as soil pH and electrical conductivity when studying the effects of fertilizer type on N₂O emissions from bacteria and fungi.

Key words: organic and inorganic combined application, bacteria, fungi, nitrous oxide, microbial community