Soil Loss and Runoff Reduction in Olive-Tree Dry-Farming with Cover Crops

Soil erosion constitutes a major problem in the dry-farming agriculture of Mediterranean areas. The coincidence of fall showers falling over bare soils after a long, hot, dry summer, steep slopes, and intensive tillage, or the occurrence of large uncultivated patches like in tree-cropping, aggravate the problem. Among several soil conservation practices, cover crops are being adopted by olive farmers as a promising method to reduce soil and water losses. This report summarizes the results of 2 yr from a network of microplots installed in olive orchards in the olive-growing area of Southern Spain to improve the technique of soil management and extend it to farmers. The cover crop diminished soil losses in all the experimental plots with an average of 76%. Water loss was also reduced, although to a lesser extent, in six of the eight fields, with an average of 22%. Additionally, the results showed the great influence of the cover percentage in the decrease in soil loss and in the concentration of sediments in the runoff. However, it should be taken into account that plant cover consumes water, and that the advantages of the decrease in runoff in the water balance with the cover could be eliminated if it is not managed appropriately. Therefore, more years of experimentation covering different climate conditions are necessary.