Maize monoculture systems often cause environmental impacts such as soil erosion, nitrate leaching and pesticide transfer. Conservation tillage and the use of cover crops appear to hold promise for limiting these impacts, but questions about their performance remain, particularly during the transition period after conventional soil tillage ceases. In this study, effects of no-tillage maize and fallow-period management with different cover crop species, either pure or in mixtures, were studied on the agronomic performance of maize and on soil N and water dynamics. The study combined field experiments over three years (2012–2014) and simulation modelling with the STICS model. The biomass of cover crops produced during the fallow period varied from 0.8 to 10.5 t dry matter ha-1 depending on the cover crop species and date of termination. Differences in soil water content were quantified among the treatments studied, with the lowest water content at the beginning of the maize growing season with late termination of a cover crop composed of pure faba bean or a vetch-oat mixture in 2014 (25–50% of plant-water available capacity). Maize grain yields ranged from 8.5 to 13.6 t dry matter ha-1, with the lowest yields in the bare soil treatment. Simulations with STICS were consistent with the observations and indicated a decrease in drainage of 8–38 mm year-1, depending on the year and cover crop. Introducing cover crops into maize systems is a powerful mechanism for maintaining production while improving environmental performances during the transition phase of soil properties in conservation tillage.