Use of cover crops for increasing organic matter: spontaneous or sown, in autumn/winter in permanent crops in Mediterranean Agroforestry systems, may improve soil erosion. The composition, technique and management in each farm depend a lot on soils and local conditions, especially in rainfed Mediterranean conditions. Testing and demonstration are needed at a local scale for promoting its use. It increases organic matter and nutrients availability. It fixes carbon at the soil. It improves the soil structure and avoids erosion. Benefits for biodiversity, since it provides food and shelter for useful fauna.