Tree crops are a key element of the European agricultural landscape with more than 13 million hectares of permanent tree crops in the EU-28. The majority of them, approximately 80 per cent of the surface, are concentrated in areas with Mediterranean type of climate (Table 1). This is because the majority of these crops in the EU (such as olives, citrus or almonds) are best grown under a Mediterranean type of climate. The only exception among the dominant tree crops are vines. The 3.2 million hectares of vines in the EU-28 are distributed across the continent among 21 countries, from Sweden to Malta, albeit the majority of them are also concentrated in Mediterranean areas.The major reason for that distribution is the favourable conditions in terms of temperature and radiation. Other reasons are the rusticity of some of these tree crops, particularly olives and almonds, which allows cultivation in areas not suitable for other crops or grazing and their double role as a food and cash crop. However, the Mediterranean type of climate is characterized by a limited, and highly variable, precipitation in relation Sustainability using cover crops in Mediterranean tree crops, olives and vines -Challenges and current knowledge
AbstractTree crops cover a large area of European landscape, 13.3 million hectares, with olive, grapes, nuts and almonds been the most extended and mostly concentrated in Mediterranean areas. The cultivation of tree crops in rain limited Mediterranean areas depend on an adequate management of water balance that, been historically mostly based on bare soil, has created severe erosion and offsite contamination problems. Temporary cover crops can be an alternative to control these problems with a larger effect on erosion control than on reducing runoff, and a moderate impact on soil properties. This impact depend strongly on the ability to implement temporary cover crops that achieve a significant development during the rainy season while simultaneously minimizing the competition for soil water with the major crop, which is not always easy in commercial farms. This balance between soil protection and yield has been achieved in some conditions but not in others, and a significant reduction in yield has been reported for some situations. This potential risk of yield decrease, combine with the difficulty to see a collapse in yield due to soil degradation by water erosion in the short/ medium term can explain, partially, the reluctance of farmers for an extensive use of temporary cover crops. The development of improved strategies for using temporary cover crops which could include the use of water balance models, new varieties better adapted to the region, and strategies for restoring ground cover in severely degraded orchards seems to be necessary, coupled with regulations and incentive to their use by farmers. Future research should focus in the less understood elements of this system, among them root development, biomass production, phenology under different microclimate of the cover crops and the main ...