Effects of long term irrigation with treated wastewater on leaf mineral element contents and oil quality in Olive cv. Chemlali

Water is one of the most limiting factors in agriculture, particularly in arid areas such as Tunisia. Olives are the most important tree fruit in the country and are cultivated over 1.6 million hectares. An olive grove of cv. Chemlali was irrigated either by using treated wastewater (TWW) or fresh water (FW) from 2002 to 2012. The aim of this 10-year study was to investigate the effects of irrigation with TWW on both quality parameters (i.e. K232, total phenols, free fatty acids, etc.) and content of mineral elements in the leaves. Data obtained indicated no effects of the irrigation on parameters such as oil content and K270, either by using TWW or FW, and significant effects only after 10 years on free acidity and K232. Instead, palmitoleic and stearic acid contents significantly decreased after 10 years of irrigation with TWW with respect to FW irrigation. TWW irrigation also increased the content of total phenols, chlorophyll, and minor and major nutrients in the leaves.