Effects of oil mill wastes on surface soil properties, runoff and soil losses in traditional olive groves in southern Spain

In Spain, agriculture triggers soil degradation and erosion processes. New strategies have to be developed to reduce soil losses and recover or maintain soil functionality in order to achieve a sustainable agriculture. This experiment was designed to evaluate the effect of two olive mill wastes (olive leaves and “alperujo”) on soil properties and soil erosion in a rain fed olive grove in SE Spain. After three years experiment, oil mill wastes application significantly improved physical and chemical properties of the studied soil with respect to control. The organic matter content, bulk density and porosity were increased, which confirmed the interactions of these properties. Available water capacity increased with olive leaves but decreased when applied “alperujo”. With respect to erosion, after simulated rainfall experiments it was found that the oil mill wastes contributed to increase the roughness and the interception of raindrops, delaying runoff generation and enhancing the infiltration of rainwater. Treatment with oil mill wastes contributed to a reduction in runoff generation and soil losses compared to bare soil, especially when applied olive leaves.