In mixed cropping-livestock farms, grassland fits both productive and environmental functions. Thus, in the Pays de Caux (Haute-Normandie, France), runoff might be mitigated by the presence of permanent or rotational grassland. The aim of our study was to assess how mixed crop-livestock farms, specifically breeding dairy or suckler cows, integrate grassland into their global functioning and to know the farmers' position about grass management. Livestock farms were surveyed and the collected data were analysed by multidimensional statistical analysis. Even though maize silage is the main fodder resource in this region now, we observed a large diversity of types in the more or less intensive uses of grassland. We identified two main strategies of grassland management. In the first type, farms combine grazed grassland and maize silage considered as forage security. In the second type, the farmers’ choice of including cultivated grassland in crop rotations has both advantageous objectives: improving forage self-sufficiency (intensive use of grass for grazing or hay making) and decreasing the risk of runoff. Considering trade-offs between farm production and environmental benefit, the possibility to develop these sown pastures was assessed with quantitative indicators showing their impact on runoff level and providing economic results at farm scale.