The effect of the timing of water deficit on yield components and oil quality of olive trees

An experiment was carried out in an olive (Olea europaea 'Frantoio') orchard over two growing seasons to compare the effect of regulated deficit irrigation (RDI) on yield components and oil (VOO) quality. Fully irrigated trees (FI) received 100% of water needs during the entire irrigation period (from 23-28 to 100-103 days after full bloom, DAFB), whereas deficit irrigated trees (DI-1 and DI-2) were not irrigated from 23-28 through 41-60 DAFB (DI-1) and from 41-60 through 71-85 DAFB (DI-2), respectively. Although fruit yields of DI-1 and DI-2 trees were 70 and 80% those of FI ones, respectively, and oil yields were 66 and 77% (average of two years), there were no differences when yields were expressed on a trunk cross sectional area basis. In 2012 the fruit fresh weight of FI trees was 134 and 123% than that of DI-1 and DI-2 trees, respectively (110 and 99% in 2013). All oils were within the limits of VOO classification. The fatty acids composition was affected only in 2012. VOOs obtained from DI-1 trees had higher total phenols (136 and 121%) and ortho-diphenols (125 and 128%) than those of FI and DI-2 treatments, respectively. Hence, an early water stress seems to be sufficient to induce an increase in the phenolic concentration of olive oil.