Agro-physiological responses of Koroneiki olive trees (Olea europaea L.) irrigated by crude and treated mixture of olive mill and urban wastewaters

Abstract

Water is one of the most limiting factors in agriculture, especially in arid and semi-arid region. The reuse of treated wastewater (TWW) in crop irrigation is becoming a frequent practice in areas with limited water resources. Olive mill wastewater (OMW) as well as urban wastewater (UWW) could be treated and reused to avoid this very serious environmental issue in Mediterranean areas. OMW is a nutritive and rich water concerning plant growth. However, it should be well treated to reduce toxic phenolic compounds and salinity before its reuse in irrigation. In this study “Koroneiki” olive grove used as a model plant, was planted and irrigated for a period of over than one year with a mixture of olive mill and urban wastewater (OMW + UWW) before and after treatment by a constructed wetland (TMCW) and compared to that irrigated by well water (WW) as a control. During the irrigation period, trunk diameter, plant height, stomatal conductance, the maximum quantum yield of PSII and chlorophyll contents were analyzed each two months of growth in order to assess the effect of irrigation by such effluents on morphological and physiological parameters of the olive grove. Results show that the mixture (OMW + UWW) can have a good fertilizer potential even after treatment by constructed wetland that insures a high reduction of toxic phenolic compounds. In terms of morphological parameters, olive grove irrigated by crude mixture and well water has shown the statistically significant highest efficiency regarding plant height and trunk diameter. However, the treated mixture has shown the statistically significant lowest effect in terms of physiological parameters and has given the highest production of olive fruits and oil yield. The maximum quantum yield of PSII (Fv/Fm) was optimum for all treatments.