A cover crop is established between the harvest of a main crop and the sowing of the next main crop. Cover crops are intended to go back to the soil and not to be exported from the field. They are sown to avoid bare soil between two main crops and to provide multiple services (the term used is Multi-Service Cover Crop). These Multi-Service Cover Crops contribute to improve, among others, soil structure, to reduce soil erosion, and to maintain associated biodiversity.
Above all, Multi-Service Cover Crops minimise losses of mineral nitrogen during the draining winter period (this is called the catch crop effect). This involves “capturing” nitrate from the soil after the harvest of the main crop in order to avoid their leaching by precipitation. Therefore, after destruction of the Multi-Service Cover Crops, the nitrogen contained in the plants is mineralised and partially available for the next main crop (this is called the green manure effect). This process allows to enrich the stock of organic matter in the soil. The green manure effect on the next main crop depends on the nitrogen and carbon content of the Multi-Service Cover Crops.
Therefore, depending on the services expected, the Multi-Service cover crops species will be adapted choosing a single specie or a mixture of a legume (clover, vetch, pea, bean …) and a non-legume (mustard, radish, rape, bristle oat, ryegrass, moharia, phacelia …). In an agro-ecological approach, the destruction of the Multi-Service cover crops will be mechanical or natural (by the frost) and the use of herbicides must be avoided to prevent transfer of these molecules to the environment.