Physiological and productive responses of Olea europaea L. cultivars Frantoio and Leccino to a regulated deficit irrigation regime

Olive is a drought-tolerant species and it is known that it responds efficiently to any additional water up to a limit. A fieldexperiment was planned with the following aims: to provide estimates of crop evapotranspiration (ETc) to improve water useefficiency during the growing season; to present guidelines for efficient management of irrigation scheduling; and tocharacterize the relationship between plant water status and optimum fruit yield. These relationships were monitored duringfour years by analysing the influence of deficit irrigation strategies on mature modern-trained olive trees of cultivars Frantoioand Leccino. Treatments were a non-irrigated control (rain-fed) and three treatments that received a seasonal water amountequivalent to 33, 66 and 100% of ETc, from the beginning of pit hardening to early fruit veraison. Results of the relationshipbetween leaf water potential and maximum stomatal conductance (Cpd vs. gsmax) showed that the stomatal apparatus inFrantoio was more sensitive to water deficit than that of Leccino. Differences in yield between treatments were mainlyrelated to mean fruit weight, indicating that water availability might have affected growing conditions before flowering orduring the early stages of fruit growth rather than later in the summer season. Vegetative development was a function of wateravailable to plants. Frantoio achieved the highest crop production per unit of water consumption. Oil quality was scarcelyaffected by deficit irrigation. Regulated deficit irrigation of olive trees after pit hardening could be recommended, at leastunder the experimental conditions of this study. Given the different long-term watering response of Frantoio and Leccino, acultivar-specific irrigation scheduling is advisable.