Physiological and productive parameters of olive trees (Olea europaea L.) under different irrigation scheduling in central-south Italy

Olive tree is a drought tolerant species withstanding prolonged dry periods using physiological and morphological mechanisms of resistance to water stress. In this work we measured functional and yield changes in olive plants (Olea europaea L. 'Frantoio' and 'Leccino') subjected to different irrigation scheduling. The study was carried out in field trials during the years 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 treatment fully irrigated with 100% of maximum crop evapotranspiration (ETc) and two deficit treatments that received 33 and 66% of ETc. Physiological parameters related to plant water status and nitrogen concentration in leaves were determined regularly during the two growing seasons. Vegetative development was monitored measuring the transverse trunk cross-section area, the crown volume, and the dry mass pruned yearly. Yield parameters (dry mass and oil content) were measured on fruits having similar maturity index. Irrigation levels significantly modified plant physiological conditions and vegetative growth of the two cultivars. Significant changes in xylem water potential, stomatal conductance and leaf nitrogen concentration were observed between irrigation treatments, and changes depended on cultivar and time of measurement. Trunk cross-section area, crown volume and pruned wood increased with the amount of water applied. Fruit and oil yield per plant showed a gradual increase with the amount of water supplied to trees, reaching the highest values in plants irrigated with 100% of ETc.