Effect of Irrigation with Reclaimed Wastewater on Physical and Chemical Properties of Olives

The present study measured certain chemical and physical properties of olives under two treatments: irrigation with reclaimed wastewater and traditional rain-fed conditions. Each treatment consisted of two 20- to 25-year-old olive trees of the variety Improved Nabali in five replicates. Olive trees were irrigated three times a week with reclaimed wastewater generated from Sir domestic wastewater treatment plant in the northwestern part of the West Bank. Subsequent analysis of reclaimed wastewater revealed high EC values (2636 µS/cm) and average TSS of 41.24 mg/L, within the acceptable Palestinian limits for olive irrigation. Average annual shoot growth in olive trees irrigated with reclaimed wastewater was found to be signif-icantly higher than in the rain-fed trees, whereas no significant differences were found in fruit set between treatments. Moreover, no significant differences were found in the leaf concentrations of Na, Cl, N, Ni, Mo, Cu, Mn and Fe between treatments, while Ca, Mg and Zn concentrations were significantly higher in the rain-fed leaves, and only K concentration was significantly higher in leaves of irrigated trees. Average yield, fruit weight, fruit length and stone length were significantly higher in trees irrigated with reclaimed wastewater, while, no significant differences were found in terms of fruit width or oil content between treatments. The reclaimed wastewater group had significantly higher olive fruit fly infestation compared to the rain-fed group. In addition, oil acidity was significantly higher in the irrigated treat-ment (0.73%) compared to rain-fed (0.30%), whereas no significant differences were found in peroxide values. All 10 oil samples tested from the rain-fed treatment were extra virgin according to International Olive Oil Council standards (COI/T.15/NC No 3/Rev, 2009), while in the reclaimed wastewater treatment, 5 samples were extra virgin, 4 virgin and 1 normal.