Fertilized cropland is a significant source of ammonia (NH₃) emissions. Urea, the dominant synthetic nitrogen (N) fertilizer, makes the largest contribution to NH₃ volatilization from cropland in China. To improve environmental quality and resource utilization efficiency, stabilized urea (UI: Urea amended with the urease inhibitor Limus®) was tested in an intensive cropping system in the North China Plain (NCP). A two-year field trial and an extensive demonstration experiment at five sites were carried out in Quzhou county, NCP, to quantify the effect of RNUI (Reduced N rate + Urea Inhibitor) technology on NH₃ mitigation from farms. NH₃ emission, crop yield and N use efficiency (NUE) were measured to evaluate the efficacy of UI and a questionnaire-based survey used to investigate farmers’ attitudes to the technology. In the field trial, UI significantly reduced NH₃ emissions by 60.5–62.9% and 39.7–52.3% during wheat and maize growing seasons, respectively, compared to untreated urea applied at the same rate. NUE was significantly increased by 34.6–62.7% in the wheat season and 14.9–66.6% during the maize season. No significant crop yield improvement was observed, but UI significantly reduced yield-scaled NH₃ emissions. Similar results were found at the five demonstration sites in Quzhou, but there was a small yield increase for maize. On average there were 49.0% and 38.5% reductions in NH₃ emissions, and 50.5% and 46.3% reductions in yield-scaled NH₃ emissions for wheat and maize, respectively, compared to typical farmer practice. Farmers’ willingness to adopt RNUI technology depended mainly on crop yield, the convenience of using RNUI and government subsidy to reduce costs. Results emphasized the importance of on-farm demonstration experiments, integrated field management, government subsidies and legislation for the promotion of RNUI technology, achieving sustainable high yields and NUE for mitigating agricultural NH₃ loss at a county level in the NCP.