Utilization of reclaimed wastewater for olive irrigation: Effect on soil properties, tree growth, yield and oil content

• Irrigation with reclaimed wastewater may affect negatively some soil chemical properties particularly EC, Na% and SAR values.
• Olive tree shoot growth, fruit set, fruit weight and yield were significantly improved by irrigation with reclaimed wastewater or fresh as water compared to rain-fed conditions.
• Oil content in olive fruits based on fresh and dry weight basis was significantly higher in the rain-fed treatment than freshwater and reclaimed wastewater treatments.

The experiment was conducted over four successive years (2008, 2009, 2010 and 2011) on ‘Nabali Muhassan’ olive cultivar at a private olive orchard located in the northern part of Jordan (Ramtha area). Experimental treatments applied were irrigation with fresh water (underground well water) and reclaimed wastewater to be compared with the rain-fed (non-irrigated) treatment. Total quantity of fresh water and reclaimed wastewater applied were similar during the irrigation period. Analysis of irrigation water showed higher EC value for reclaimed wastewater as compared to fresh water. Average values of pH, EC, TSS, cations, anions, N, NO3, B, heavy metals, BOD5, COD and fecal coliform in reclaimed wastewater were within the Jordanian standard for water use in irrigation of fruit trees, however, the values of SAR, Cl and Na were higher than the standard limits. Results of soil analysis indicated that soil chemical properties (pH, EC, Ca, Na, SAR, ESP, P, K, Cu, Mn, Pb and B) in soil irrigated with reclaimed wastewater were significantly higher than in soil irrigated with fresh water. The application of reclaimed wastewater or fresh water showed significant increase in annual shoot length as compared to rain-fed treatment. Average olive tree yield was significantly higher for fresh water treatment than the rain-fed treatment, which was not significantly different from the reclaimed wastewater treatment. Fruit oil content based on fresh weight and dry weight basis were significantly higher in rain-fed treatment than freshwater and reclaimed wastewater treatments.