Abstract: Agroecosystems are a significant source of nitric oxide (NO) which serves as an air pollutant. There is an urgent need to quantify and control NO emissions from agroecosystems. The NO fluxes were measured in a long-term (since 1990) fertilized winter wheat-maize cropping system for two years (from October 2022 to October 2024). The aims were to quantify the responses of NO emissions to stalk incorporation and to identify the major regulatory factors. The field trials included an unfertilized control (CK), full chemical fertilizers (NPK), and a combination of chemical fertilizers and maize stalk (NPKS). The CK treatment was not fertilized throughout the year. The NPK and NPKS treatments received the same amount of urea, with nitrogen application rates of 165 and 188 kg·hm⁻² in the winter wheat and maize seasons, respectively. Only for NPKS, all stalks (with a nitrogen application rate averaging 40 kg·hm⁻²) were retained at the time of maize harvest. The results showed that the NO fluxes were low in CK, while always peaked following fertilizations in NPK and NPKS. The boundary lines of NO fluxes followed a logistic and a Gaussian model against soil temperature and water-filled pore space, respectively, and linear models against ammonium and nitrate concentrations. The CK, NPK, and NPKS treatments released annual NO emissions of 0.18 ~ 0.19, 0.31~ 0.81, and 0.65 ~ 1.10 kg·hm⁻², respectively. Annual NO emissions of NPKS were 37% ~ 113% higher than those of NPK (P < 0.05). In the two winter wheat seasons, cumulative NO emissions of NPKS were either 60% lower or 28% higher relative to those of NPK (P > 0.05); in the two maize seasons, cumulative NO emissions of NPKS were 60% ~ 231% higher (P < 0.05). The enhanced NO emissions mostly occurred in maize seasons, which were attributed to the 20% higher soil organic matter content of NPKS relative to that of NPK. In maize seasons, the promoting effect of soil organic matter on NO fluxes may be amplified in a warm and humidity environment; while in winter wheat seasons, the effect of soil organic matter may be weakened or overrode by low temperature and stalk incorporation. With long-term stalk incorporation, annual NO emissions from the winter wheat-maize cropping system were significantly enhanced, and mitigation efforts need focus in maize season.