Fruit and oil quality of olive (Olea europaea L.) under different irrigation regimes and harvest times in south eastern Australia

Olive (Olea europaea L.) fruit growth and oil quality is affected by cultivar, degree of maturation and environmental factors such as water availability.In this study, a field experiment was conducted on 12 year old olive trees cv. Corregiola at Wagga Wagga, NSW (Australia) to determine the effect ofirrigation and harvest time on olive fruit growth and the quantity and quality of oil. Three irrigation treatments during the olive pit hardening periodwere used: rainfed (0% of evapotranspiration), deficit irrigation (50% of evapotranspiration), and full irrigation (100% of evapotranspiration). Fruitwater content decreased during the harvest window (April-July). The rainfed treatment had the highest maturity index, while the irrigated treatmenthad the lowest one. In the first year of this two-year experiment, at the last harvest date, the maturity index of fruits were 4.2, 4.0, and 3.4 for rainfed,deficit irrigation, and full irrigation treatments, respectively. Both extractable oil (mechanical extraction) and total oil (chemical extraction) from therainfed treatments were higher than that of the other two treatments. The amount of oil extracted and extraction efficiency increased during the harvestperiod (April-July). The extraction efficiency was higher for rainfed treatment. Oil acidity increased during fruit ripening. No significant differencewas observed between the peroxide values of the treatments and also polyphenol content. Chemical properties of olive oil are highly influenced byharvest time, while irrigation slows the ripening process of olive fruits.