Long-Term Olive Mill Wastewater Applications on Various Crops Can Improve Productivity

Olive mill wastewater (OMW), a by-product from the olive oil extraction process, is annually produced in huge amounts in olive-growing areas and represents a significant environmental problem in Mediterranean areas. OMW is characterized by high pollutant loads, such as salinity and phytotoxic polyphenols, but it includes relatively high organic compounds and plant mineral nutrients. This study aims to investigate the effects of olive mill wastewater, applied at different rates (50, 100, and 200 m3 ha−1 year−1) of productivity under natural field conditions, namely olive, pear, apple, and tomato crops. These findings suggest that OMW land spreading requires the use of suitable doses, especially in the Mediterranean area where this practice has been extended.