• We evaluated effects of fungi on N₂O emission in Chinese milk vetch-containing soils.

Fungi play an important role in soil nitrous oxide (N₂O) emission in many agricultural soil systems. However, the effect of fungi on N₂O emission in Chinese milk vetch (CMV)-containing soils has not been examined sufficiently. This study investigated the contribution of bacteria and fungi to soil N₂O emission in CMV-amended soils. We compared soils from an experimental field in the Fujian Academy of Agricultural Sciences that had been treated with 30 000 kg of CMV per 667 m² per year with one that was not treated with CMV. We incubated soil using cycloheximide and streptomycin to differentiate fungal and bacterial N₂O emissions, respectively. Quantitative PCR (qPCR) was performed to investigate bacterial and fungal abundances in the two agricultural soil ecosystems. The contribution of fungi to soil N₂O emission in CMV-amended soils was greater than that in non-CMV-amended paddy soils, with fungi accounting for more than 56% of the emissions in CMV-amended soils. Quantitative PCR showed that the ratio of the internal transcribed spacer to 16S rDNA was significantly higher in CMV-amended soils than in non-CMV-amended paddy soils. Furthermore, soil properties, such as pH (P<0.05) and NH₄⁺ concentration (P<0.05), significantly and negatively affected N₂O emission by fungi in soil, whereas the total organic carbon (P<0.05) and NO₃^- concentration (P<0.05) showed significant positive effects. Fungi may be important contributors to N₂O production in CMV-amended soils, which may create challenges for mitigating N₂O production.