Optimization of saline water level for sustainable Barnea olive and oil production in desert conditions

The main aim of the present study is to evaluate the effects of long-term irrigation with water at three different levels of salinity on Barnea olive trees with a view to optimize vegetative growth, productivity and oil quality. The study was carried out on trees growing in the Negev desert of Israel. The intermediate salinity (4.2dSm^-1EC) inhibited growth significantly only in the first year after planting, while from the second year onward retardation of vegetative growth as compared with the control treatment (1.2dSm^-1EC) was slight and non-significant. However, the high salinity (7.5dSm^-1EC) retarded tree growth significantly. Furthermore, the intermediate treatment led to significant increase in tree productivity relative to the other treatments, and also to an increase in olive oil yield. In conformity with the greater number of fruits produced, the olives of the 4.2dSm^-1EC treatment tended to be smaller. No significant differences were found between saline- and control-water irrigated trees in terms of olive oil basic quality parameters, such as free fatty acids, peroxide value, and fatty acid profile. The saline treatments increased the levels of certain antioxidant components (polyphenols and Vitamin E) in the oil extracted from the olives as compared with the control. The data obtained clearly show that, of the three water salinities tried, the moderate level of 4.2dSm ^-1EC is best suited for production of olives and olive oil under the conditions prevailing in the central Negev, at least during the first 9 years from planting. The sustainability of Barnea cultivation under moderately saline water is discussed.