The texture is sandy loam for both soils. According to the FAO system of soil Classification (ISSS-ISRIC-FAO, 1994) the soil S1 is classified as Luvisols-Phaeozems, and the S2 as Phaeozems- Cambisols. Although S1 and S2 belong to the same texture class, the different percentages of gravel and sand affect their hydraulic properties such as porosity and hydraulic conductivity. In partic- ular, the soil S2 allows much more drainage than the soil S1, due to the high percentage of gravel that makes its behaviour more similar to that of a gravel soil (40% of gravel).