Abstract: The investigation of the relationship between soil nitrous oxide (N₂O) emission and environmental factors, as well as its response to management practices, is of great significance for estimating soil greenhouse gas emission potential, improving non-point source pollution, and optimizing citrus orchard management in the Three Gorges Reservoir Area of the Yangtze River. We explored the effects of management practices on the physicochemical properties of citrus orchard soils, N₂O emission fluxes, and microbial characteristics, along with the regulatory mechanisms behind N₂O emissions in the Three Gorges Reservoir Area. Soil samples from 0-10 cm depth were collected under three management practices: fertilization plus smooth vetch cover (V), fertilization plus grass clearing (T), and no fertilization plus smooth vetch cover (NF). The results showed that fertilization increased overall soil enzyme activity by 5.12% and reduced the water stability of soil aggregates by 14.84%. In contrast, the smooth vetch cover reduced overall soil enzyme activity by 10.31% but did not affect aggregate stability. Fertilization stimulated soil N₂O emission, whereas smooth vetch reduced it. There was a weak correlation between soil N₂O and other gas emission fluxes. Greenhouse gas and ammonia emission fluxes were influenced by the ratio of soil carbon to nitrogen and nitrate nitrogen content under T and NF treatments, and by soil pH and water content under V treatment. N₂O emission fluxes were significantly affected by soil total porosity, cation exchange capacity, and the threshold ratio of carbon to phosphorus. Soil microbial growth and metabolism were nitrogen-limited. Both fertilization and smooth vetch cover alleviated nitrogen-limitation. Furthermore, these practices regulated N₂O emission fluxes mainly through the direct effects of soil temperature on soil silt content, mean weight diameter of water-stable aggregates, and nitrate reductase activity, which collectively explained 98.7% of the variation. Implementing sustainable agricultural management strategies can enhance soil aggregate stability, thereby directly regulating soil N₂O emission fluxes.

Key words: Three Gorges Reservoir Area, fertilization, grass mulching, nitrous oxide (N₂O), aggregate stability, microbial nutrient limitation