Regulated deficit irrigation in olive trees (Olea europaea L. cv. Arbequina) for oil production

Regulated deficit irrigation (RDI) strategies have been used in many fruit trees in order to save water without reducing yield or increasing water use efficiency. To test the viability of using RDI strategies for oil production, four irrigation treatments were applied during 1996-98 in a commercial olive plot (Olea europaea 'Arbequina') located in the area of "Les Garrigues" (Lleida. Spain). Control treatment was irrigated at 100% ETc during the whole season, whereas three RDI treatments were applied between beginning of massive pit hardening (beginning of July) and the end of September, at 75%, 50% and 25% of the dose applied to the Control treatment. Leaf water potential, leaf gas exchange, vegetative growth, fruit growth and oil yield were monitored during three years. Leaf water status in the RDI-25% showed a progressive decrease during RDI period compared to the Control, reducing vegetative growth, fruit growth and fruit yield. Water stress during RDI period forwarded ripening time and seemed to increase the amount of extracted oil. No differences were observed in oil yield between Control and RDI-25%, with RDI-50% reaching the highest yield. Nevertheless, water stress in RDI-50% and RDI-25% reduced net assimilation of the leaf and reduced next year flowering, which could limit yield in future years. Therefore, RDI in olive trees could be a good irrigation strategy for oil production, being RDI-75% treatment the most recommendable.