Agronomic and economic implications of using treated olive mill wastewater in maize production.

Olive mill wastewater (OMWW) is a byproduct of the olive oil extraction process, characterized by high polluting load and polyphenols content. The treatment of OMWW, using microfiltration and XAD4 resin, results in recovery of polyphenols, and also in an effluent (treated OMWW) with decreased organic load and phytotoxic properties, compared to the initial OMWW. The effects of the treated OMWW (T-OMWW) application on maize kernel yield and quality, and soil quality were investigated through a two-year field experiment. T-OMWW was applied by drip irrigation to maize cultivation using two rates of 25–50 t ha−1 year−1, with the addition of mineral fertilization. Furthermore, a treatment of only T-OMWW applied at the rate of 50 t ha−1 year−1and an only mineral fertilization treatment were used. Maize kernel yield and quality were not significantly different between mineral fertilization and T-OMWW application, hence indicating that T-OMWW could fully substitute mineral fertilization under the conditions of our study. Based on the experimental results, an economic analysis was undertaken in order to evaluate the economic implications of T-OMWW application by drip irrigation to maize production. Three scenarios were investigated: (a) mineral fertilization only, (b) T-OMWW application at the rate of 50 t ha−1 year−1only, and (c) T-OMWW application at the rate of 25 t ha−1 year−1combined with reduced mineral fertilization. The cost analysis showed that T-OMWW application at the rate of 50 t ha−1 year−1was the least expensive of the three scenarios investigated, irrespective of the distance between the olive mill and the farm. The use of the farm tractor and tanker for the T-OMWW transportation was more cost effective than hiring a liquid transport company, for distance up to approximately 20 km. For greater distance, hiring a liquid transport company was more economical. [ABSTRACT FROM AUTHOR]