Plastic film mulching (PFM) increases crop yields in semi-arid regions by reducing water losses and increasing soil temperature, while crop production in these areas also serves as a significant source of ammonia (NH₃) emissions.  The effects of PFM on NH₃ emissions are nearly unknow because of interactions between larger N mineralization at higher temperature and film cover preventing NH₃ diffusion.  Therefore, our objectives were to (1) evaluate the effects of PFM on NH₃ emissions under field conditions, and (2) identify the maize yield and NH₃ emissions under climate change and atmospheric N deposition using the DeNitrification-DeComposition (DNDC) model.  The experimental treatments included four treatments: (1) no plastic film mulching without N fertilization (control), (2) plastic film mulching without N fertilization (PFM), (3) N fertilization without plastic film mulching (N), and (4) plastic film mulching with N fertilization (PFM+N).  The PFM increased maize yields by 211% and yield stability across the years when combined with N fertilization.  PFM reduced NH₃ emissions by 35% through three mechanisms: i) high water content under PFM saturates soil pores, hindering NH₃ gas movement to atmosphere, ii) the hot and wet conditions under PFM accelerates nitrification rate, thus increasing pH buffering capacity during urea hydrolysis, and iii) the physical barrier created by PFM reduced NH₃ exchange between soil and air.  Daily NH₃ emissions increased with soil temperature, NH₄⁺ content, and pH, but declined with soil moisture under N fertilization.  The NH₃ emissions under PFM+N increased with NH₄⁺ content.  The parameterised DNDC model simulated very well the yield and daily NH₃ emissions. PFM+N increased yield and reduced NH₃ emissions under the shared socioeconomic pathway (SSP) scenario and the N deposition.  Yield under PFM+N increased with increasing N deposition, while NH₃ emissions under N deposition increased under the high radiative forcing scenario (SSP5-8.5).  Concluding, PFM increase yields and mitigate NH₃ emissions, and it also has the potential to achieve similar benefits under future conditions.