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).
The OMW used in this study came from a continuous centrifu- gation system, and its main chemical and physical characteristics are reported in Table 2.
It was used either as received or after a fourfold dilution with freshwater (see Section 2.3). Olive waste compost was obtained by mixing exhausted olive pomace (91% w/w) with straw (2%) and poultry manure (7%), and its composition is reported in Table 3.