Short-Term Effects of Olive Mill Wastewater Land Spreading on Soil Physical and Hydraulic Properties

In this study, we investigated the effect of olive mill wastewater on selected soil physical and hydraulic properties. Olive mill wastewater was added to each column every week at different loading rates (0, 50, 100, and 200 m3 ha−1). Physicochemical and hydraulic properties were determined for surface (0–8 cm) and subsurface layers (8–16 and 16–24 cm). The highest loading rate (200 m3 ha−1) showed an increase in aggregate stability from 18% (control) to 31 and to 38%, penetration resistance from 1.8 kg cm−2 (control) to 3.5 and to 4.5 kg cm−2, hydraulic conductivity from 43 cm day−1 (control) to 15.3 and 3.3 cm day−1, and water repellency from < 5 s (control) to 120 and 261 s in the first and second months for the surface layer, respectively. The opposite was observed for the infiltration rate, where it decreased from 39.01 mm h−1 (control) to 1.26 and 0.42 mm h−1 for the first and second months, respectively. This study showed that application of olive mill wastewater deteriorated the physical and hydraulic properties of soil proportional to loading rates and more specifically at the surface layer.