Predicting Soil Erosion With RUSLE in Mediterranean Agricultural Systems at Catchment Scale

Accurate assessment of soil loss is essential for sustainable agricultural production, management, and conservation planning, especially in productive rain-fed agroecosystems and protected areas. The European Union considers soil as a nonrenewable resource and identifies that soil degradation has strong impacts on soil and water resources. In this work, the Revised Universal Soil Loss Equation model was applied within a geographic information system in the Estana catchment (Spanish pre-Pyrenees) as representative of a Mediterranean agroecosystem to elaborate a map of soil erosion at high spatial resolution (5 x 5-m cell size). The soil erodibility factor (K) was calculated from three different approaches to evaluate the importance of spatial variations in soil texture, field infiltration measurements (K-fs), and amount of coarse fragments. The average value of estimated soil loss for the whole study area was 2.3 Mg ha(-1) year(-1), and the highest rates were estimated in crops in steep areas (5.8 Mg ha(-1) year(-1)) and trails (18.7 Mg ha(-1) year(-1)). Cultivated soils with high soil erosion rates (>8 Mg ha(-1) year(-1)) represented 20% of the cultivated area. The average value of soil loss in areas with human disturbances (4.21 Mg ha(-1) year(-1)) was 4.4-fold that estimated for areas with natural vegetation (0.96 Mg ha(-1) year(-1)). Field validation with (CS)-C-137 showed that the estimated value of soil loss in barley fields with the K-K-fs-rocks factor improves the model predictions in comparison with those obtained with the K texture and K-K-fs factors. The Revised Universal Soil Loss Equation model predicted a decrease ill soil erosion in fields in accordance with the increase of the age of abandonment. Predicted values of soil erosion and measured soil organic matter and stoniness in old abandoned fields agreed with those in areas of natural forest and indicated the recovery of the original conditions of the soil. Statistical analysis highlights that the C factor contributed most of the variability of the values of predicted soil erosion; the K and LS factors contributed in a similar way. The P factor contributed least to the variability of soil erosion. Cultivated soils developed over clay materials in high slope areas are the most susceptible to soil degradation processes in comparison with soils developed over limestones in gentle and medium slope areas. The recovery of terraces in steep fields and conservation of crop residues are proposed as soil conservation practices to reduce the magnitude of soil loss in the study area.