Development and use of models to predict and study the production and the environmental impacts of biomass cropping systems are of great interest for their sustainable development. Improvements were made to the research version of the STICS crop-soil model in order to simulate biomass production and environmental impacts of Miscanthus x giganteus cropping systems in the long term. This research version was then validated on a large database and in various pedoclimatic environments in France and UK. The model accurately simulated biomass production and nitrogen (N) content in aboveground biomass, from planting until 4 to 20 years of cultivation. The model efficiency (EF) was 0.80 and 0.64 for biomass and N content, respectively, and the values of relative RMSE were 23 and 31 %. Soil water and mineral N contents were also satisfactorily predicted (EF = 0.96 and 0.42; relative RMSE = 10 and 72 %). The model accurately reproduced the effect of management practices on the harvested biomass and N export. Yield gap analysis using simulations with and without active stresses revealed that Miscanthus x giganteus biomass production was limited by both water and N availability during the establishment phase but mainly limited by water availability during the post-establishment phase. The STICS crop-soil model can accurately predict Miscanthus x giganteus biomass production and environmental impacts such as water drainage and nitrate leaching and compare strategies with varying N fertilization, irrigation and harvest date.