Soil Erodibility Changes in Sloping Chemically Managed Citrus Plantations in Eastern Spain.

Soil erosion in citrus plantations was negligible when they were located on flat areas in the lower parts of watersheds. The increasing demand for citrus resulted in the expansion of the plantations to sloping areas. These new plantations are highly mechanised, chemically managed and on sloping terrain, and therefore the erosion potential is high. In most plantations the soils are left bare due to the use of herbicides and continuous ploughing. These practices persist, even though research has shown the benefits of vegetation cover, mulching or stone cover to prevent erosion.

In a sloping area a 7 year old citrus plantation was assessed for surface cover and soil erosion rates. Crop growth and mulching of the pruned branches increased litter cover from 0 to 11.21 % in 7 years. Rock fragments were the most dynamic soil surface cover; changing from 2.54 to 57.76 % between 2007 and 2014). The soil erosion assessment focused on the detachment of material at the pedon scale (<1 m²). Soil erosion was measured using a portable rainfall simulator in winter and summer from 2007 to 2014. The rainfall simulation experiments allowed comparing soil erodibility as the rainfall properties were constant (55 mm h^-1 for one hour in 0.25 m² microplots). The results showed that soil erosion was very high the year of plantation establishment and was reduced from 3.56 Mg ha^-1 hour^-1 to 0.32 Mg ha^-1 hour^-1 seven years later. Winter always showed higher erosion rates and runoff discharge, although the runoff sediment concentration was higher in summer. The key factor in soil erosion reduction was increased rock fragment cover. Erosion reduction was mainly caused by increase in infiltration due to the rock fragment pavement.

This research received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 603498 (RECARE project).