suggesting that OMW increased infiltration rate. Such effect could be caused by the generation of preferential flow pathways, due to the border effect at the interface between the soil and the internal wall of the ly- simeters, which occurred since the beginning of the experiment. Over time, the organic matter content of OMW, which is respon- sible for the sealing of soil particles (Mahmoud et al., 2010), enhanced the effect of the preferential flow pathways in lysime- ters amended with olive mill wastes with respect to the control ones. The only exception was treatment