Effect of one-time olive-mill waste water application on yield and water relations of olive trees

Olive-mill waste water (OMWW) represents an environmental risk in the olive (Olea europaea) growing strip around the Mediterranean. The objective of this study was to investigate the effect of a one-time application of OMWW on the yield, stomatal conductance and leaf water content of mature 'Zeiti' olive trees. Four rates (0, 50, 80, and 100 m(3) ha(-1)) of OMWW were applied in December to trees that were pruned two weeks earlier or not pruned. These rates were referred to as control, low, moderate, and high, respectively. Soil organic matter and micronutrient concentrations increased linearly with application rates, while CEC and pH decreased slightly. Fruit yield was highest for the low application treatment (82 kg tree(-1)) followed by the moderate, high, and control treatments, respectively. Stomatal conductance was generally highest for control treatment, except for pruned trees in the spring, for which the low treatment resulted in highest conductance values. Pruned trees had much higher conductance in the spring compared to non-pruned trees.