Evaluating the effectiveness of four representative land uses in soil and water conservation on a typical rainfed Mediterranean agricultural landscape in La Rioja (Spain)

Mediterranean steep-slope agricultural landscapes are highly vulnerable to soil erosion, exacerbated by climate and land use changes. In Spain, the 1992 EU Common Agricultural Policy reform led to an increase in tilled, unseeded fallow land, altering soil erosion dynamics. However, systematic research comparing the hydrological and soil conservation performance of fallow land versus traditional crops remains limited.

This study addresses this gap by evaluating the hydrological and sedimentary responses of tilled, unseeded fallow land compared to three representative Mediterranean crops—olive, vineyard, and barley—on steep slopes in La Rioja, Spain. We propose a flexible modelling approach (SIMulated Water Erosion model; SMIWE) to determine suitable land use for steep-slope agriculture in the region by simulating water and soil movement during extreme rainfall, which is expected to become more frequent due to climate change.

The analysis examines and compares differences in hydro-sedimentary outputs, including surface water depth, sediment flux, and erosion rates. Results show that fallow land had the lowest surface water depth 0.001 m, but the highest sediment flux 0.04 kg m⁻¹ s⁻¹ and erosion rate (39 % higher than vineyards). Among cultivated lands, vineyards had the lowest sediment flux and erosion rates, with 13 % lower than olive and 2 % lower than barley fields. Total erosion in fallow land was significantly higher than in other land uses, followed by olive, barley, and vineyards. Despite the uncertainty and the limitations of the modelling exercise, these findings highlight the vulnerability of unseeded fallow land to soil erosion and underscore the importance of crop selection and management strategies for improving landscape resilience and sustainability.