Pomological Descriptors, Phenolic Compounds, and Chemical Monitoring in Olive Fruits Irrigated with Dairy Treated Wastewater

In this work, the pomological characteristics, phenolic composition, and chemical contents modification in response to treated wastewater (TWW) irrigation was studied on olive fruits. The experiment was carried out during two successive years (2016/2017) on olive trees (cv. Chemlali). Three irrigation treatments were adopted and two TWW irrigation levels were applied (T1: 20% ETc; T2: 40% ETc; CT: Control Treatment (rainfed condition)). Results show that TWW irrigation leads to increased fruit fresh weight and water content, whatever the level applied. In addition, fruit oil content remained unaffected by TWW irrigation. Moreover, this agronomic practice preserves some phenolic compound contents like verbascoside, therefore fruits nutritional value. A positive feature was then observed following TWW irrigation. In fact, oleuropein, tyrosol, luteolin-7-glucoside, and pinoresinol amounts were enhanced in treated olive fruits. On the other hand, TWW irrigated trees with a level of 40% ETc (T2) produced olive fruits richer in Mg and K than those cultivated in rainfed conditions (CT). Fruits Zn, Mn, and Pb contents decreased as a result of olive trees TWW irrigation.