Lime-based materials reduce N2O emissions by regulating soil carbon-nitrogen availability and functional gene abundances in an acidic citrus orchard soil

Global citrus production is expanding rapidly, yet excessive fertilization has triggered severe soil acidification and heightened nitrous oxide (N 2 O) emissions in citrus orchards. Liming effectively alleviates soil acidification and regulates N 2 O release, but its quantitative effect on soil pH and N 2 O mitigation in acidic citrus orchard soils, as well as the associated microbial mechanisms, remain unclear. To fill this gap, controlled incubation experiments were conducted to investigate N 2 O emission dynamics and key regulatory mechanisms under lime-based materials addition. The results showed that both application of lime (0.3 g kg -1 ) and dolomite (0.6 g kg -1 ) achieved obvious reductions in soil N 2 O emission. Relative to the control, both amendments significantly raised soil pH, elevated the levels of soil inorganic nitrogen, and dissolved organic carbon (DOC), thereby inhibiting soil N 2 O production. Soil pH was identified as a crucial factor regulating the abundances of AOA- amoA and AOB- amoA genes following the addition of lime-based materials. Specifically, as pH rose, the copy number of the AOA- amoA gene declined dramatically, but the AOB- amoA gene grew obviously. Moreover, enhanced soil pH exhibited a greater impact on nosZ II-type bacteria compared to nosZ I-type bacteria, both of which play roles in accelerating soil N 2 O reduction. In summary, the application of lime-based materials, particularly with a focus on dolomite, have been shown to significantly mitigate N 2 O emissions from acidic citrus orchard soil by modifying soil chemical conditions and influencing the abundance of functional genes associated with N 2 O production pathways. These findings underscore the importance of considering coupled biochemical regulation mechanisms when developing strategies for N 2 O mitigation in acidic citrus orchards in future management practices.