The typical Phragmites australis marsh in the Minjiang estuary was selected as the study object and a field N load experiment was conducted, which included four N load levels (NN, no N treatment, 0 g N m^-2 a^-1; NL, low N treatment, 12.5 g N m^-2 a^-1; NM, medium N treatment, 25 g N m^-2 a^-1; and NH, high N treatment, 75 g N m^-2 a^-1). The marsh soils were sampled in different N load treatments after 9 (December 2021, WT9) and 21 months (December 2022, WT21) of N import and the N₂O production processes of different marsh soils were comparatively assessed through incubation experiments. Results showed that, with increased N loads, the sources of N₂O production varied significantly, with the NM treatment showing the highest total N₂O emissions during both the WT9 and WT21 periods. While the heterotrophic denitrification process significantly reduced N₂O emissions in the soils during the WT9 and WT21 periods, N₂O emissions generally rose with extended N loading durations. Under different N load treatments, the N₂O productions of marsh soils were primarily due to the non-biological process, but its N₂O production generally decreased with increasing N load levels in a short-term period (WT9) and increased in a long-term period (WT21). The higher contributions of non-biological process to N₂O production in different N load treatments mainly depended on the abundant iron (Fe), manganese (Mn) and sulfides in soils and the great alteration of soil pH under enhanced N load conditions. The interactions between N load levels and temperature showed different influences on N₂O production processes in soils of WT9 and WT21 periods. At lower temperature (5.5-11.5 ℃), the N₂O productions in soils of different N load treatments at WT9 period were mainly dependent on non-biological process, while those at WT21 period were predominated by nitrification and non-biological processes. However, at higher temperatures (17.5 ℃), the N₂O productions in soils of WT9 and WT21 periods were predominantly governed by non-biological process and nitrifier denitrification process. This study found that enhanced N load altered the original contribution patterns of biological and non-biological processes to soil N₂O production at WT9 and WT21 periods, which mainly influenced the biological or non-biological processes of N₂O production by altering soil nutrient status. Under low temperature and N load conditions in winter in the Minjiang estuary marsh, the interactions between temperature and N enrichment showed an offset effect on soil N₂O production, which was favorable for reducing the N₂O emissions in winter.