Agricultural Use of Microfiltered Olive Mill Wastewater: Effects on Maize Production and Soil Properties

Abstract

The disposal of olive mill wastewater (OMWW) is considered as one of the most serious environmental problems in the Mediterranean region. This study constitutes part of a holistic OMWW management approach aiming at the production of high added value products from OMWW with zero discharge. OMWW constitutes an organic material that could be recycled back to the soil after its treatment with microfiltration, and used as liquid fertilizer for plant production, thus leading to an environmentally friendly cultivation method with minor carbon footprint, since wastewater would (partially or fully) substitute mineral fertilizers, fresh water savings, and also economic benefits to the farmer. Microfiltered OMWW (MF-OMWW) was applied to maize cultivation in a clay loam soil using two rates of 25 and 50 Mg ha-1, with the addition of mineral fertilization of 200 kg N ha-1. Furthermore, a treatment of only MF-OMWW applied at the rates of 50 Mg ha-1 and an only mineral fertilization treatment were used. The four treatments were replicated four times. The results of the 1st year experiment showed that the different amounts of MF-OMWW used had no significant effect on soil properties. Maize yield, kernel moisture and fat content were not significantly influenced by the different treatments, whereas kernel protein, starch, fiber and ash content were significantly affected. Considering all quality and quantity parameters studied, the treatment with only mineral fertilizer N application gave similar results with the only MF-OMWW treatment, indicating the potential of mineral fertilizer full substitution by MF-OMWW, under the conditions of our study.