Objectives Exploring the impacts of land use patterns and fertilization on N₂O emissions and their generation processes can deepen our understanding of the emission factors and mechanisms of N₂O in soil, providing a scientific basis for rational fertilization and greenhouse gas reduction.

Methods In this study, a ¹⁵N pair tracer (¹⁵NH₄⁺ and ¹⁵NO₃⁻) indoor soil incubation experiment was carried out under 60% water holding capacity (WHC) at 25℃. The tested soils were collected from a fallow land (FL) and treatment plots of no fertilizer control (CK), nitrogen and phosphorous fertilization (NP), and combined application of NP and organic fertilizer (NPM) in a localized experiment. During the seven days of incubation, the N₂O emission rate and ¹⁵N enrichment of N₂O were investigated every day. The content and ¹⁵N enrichment of NH₄⁺ and NO₃⁻ in soils were measured at 0, 1, 3, 5, and 7 days of incubation for constructing the FLUAZ model, which was used to fit the gross nitrification and mineralization rate, and to investigate N₂O production processes.

Results Land use patterns and fertilization regimes significantly influenced N₂O emissions. The N₂O emission rate of fallow land was N₂O-N 23.9 ng/(kg∙h), which was significantly lower than that of farmland soil. The N₂O emission rate in the NP treatment N₂O-N 146 ng/(kg∙h) was 1.87 times that of the CK treatment N₂O-N 77.9 ng/(kg∙h), while the NPM treatment had the highest N₂O emission rate N₂O-N 222 ng/(kg∙h), which was 2.85 and 1.52 times those of the CK and NP treatments, respectively. The order of N₂O emission ratios among treatments during the incubation period was NPM > NP > CK > FL, with values ranging from 0.012% to 0.029%. N₂O emitted from the soil originated from both nitrification and denitrification processes, but the contribution of nitrification to N₂O emissions ranged from 83.1% to 89.4%. A significant positive correlation was observed between the N₂O emission rate and the gross nitrification rate, indicating that nitrification was the primary pathway for N₂O emissions. The contributions of denitrification to N₂O emissions in FL, CK, and NP treatments were 10.6%, 10.2%, and 13.1%, respectively, while the contribution significantly increased to 16.9% in the NPM treatment.

Conclusions Land reclamation and utilization significantly enhanced the nitrification and denitrification processes of nitrogen in the soil, thereby increasing N₂O emissions. Fertilization significantly promoted N₂O emissions from farmland soil, particularly in the treatment of nitrogen and phosphorus combined with organic fertilizer, where N₂O emissions were significantly higher than those in the no-fertilizer and nitrogen and phosphorus fertilizer treatments. Nitrification was the primary pathway for N₂O emissions from black soil, while the contribution of denitrification could not be overlooked. Fertilization, especially the combination of nitrogen and phosphorus fertilizers with organic fertilizer, significantly increased the contribution rate of denitrification to N₂O emissions. Therefore, controlling nitrification and denitrification processes is crucial for reducing nitrogen fertilizer losses and lowering N₂O emissions.