Book excerpt: This study, based on a literature review and simulations, shows the efficiency of cover crops at catching nitrate in most agriculture situations. It also analyzes both the negative impacts they can have and the ecosystem services they can provide. The introduction of a cover crop between two main crops helps catch the soil mineral nitrogen before the period of drainage and consequently reduces nitrate leaching and nitrate concentration in the drainage water. This study allows quantifying the efficiency of cover crops at catching nitrate and optimizing their implantation conditions over a large range of French pedoclimatic conditions. The presence of high nitrate levels in surface and ground waters, due to excessive nitrogen fertilization and natural production of nitrate by soil organic matter mineralization, is a double challenge for public health and environment protection.