Moussadek, R., Mrabet, R., Zante, P., Lamachère, J. M., Pépin, Y., Le Bissonnais, Y., Ye, L., Verdoodt, A. and Van Ranst, E. 2011. Impact of tillage and residue management on the soil properties and water erosion of a Mediterranean Vertisol. Can. J. Soil Sci. 91: 627-635. Soil erosion research on Mediterranean Vertisols under no tillage systems (NT) is still scarce. A rainfall simulator was used on Vertisols to compare water runoff and soil loss in a conventional tillage system (CT), NT system with crop residues removed (NT0), and NT with 50% of crop residues returned to the soil surface (NT50). Runoff and soil loss rates were more than 50% lower under NT50 compared with NT0 and CT. Wet aggregate stability (MWD), soil organic matter (SOM) and soil bulk density (Da) were significantly higher under NT than under CT. A multiple regression analysis showed that when the soil was dry, Da explained 84 and 96% of the variation in water runoff and soil loss, respectively. Under wet soil conditions, MWD explained 47 and 69% of variation in water runoff and soil loss, respectively. Consequently, although NT systems improved soil quality (MWD, SOM) compared with the CT system, returning 50% of crop residues at the soil surface was mandatory under NT to protect these Vertisols against water erosion.