Leaf mineral status as influenced by different irrigation strategies in two Italian olive (Olea europaea L.) cultivars

Olive tree (Olea europaea L.) is a typical Mediterranean species adapted to droughty summer seasons; nevertheless, in the last decades irrigation has been applied to olive orchards, to achieve quantitatively and qualitatively better production. In addition to analyzing irrigation effects on fruit production, it is very important to determine its effects on the whole plant's status. In this work, we focused on the influence of different irrigation schedules on mineral nutrition in two Italian olive cultivars ('Frantoio' and 'Leccino'). Field trials were carried out in 2006 and 2007 in a typical hilly olive-growing area of southern Italy. Irrigation treatments were applied from pit hardening to fruit veraison and consisted of a non-irrigated control, a fully irrigated treatment with 100% of maximum crop evapotranspiration (ETc) and two deficit treatments receiving 33% and 66% of ETc, respectively. Pre-dawn leaf water potential and stomatal conductance were measured during the growing seasons, and leaf nitrogen (N), phosphorus (P) and potassium (K) concentrations were determined on a regular basis in both years. Physiological and yield parameters were recorded during each experimental period. Significant changes in xylem water potential, stomatal conductance and leaf N and P concentrations were observed in both years between irrigation treatments, with the changes depending on cultivar and time of measurement. Leaf K concentration appeared to be independent of cultivar and irrigation, and only influenced by sampling period.