The Effects of Crop Load and Irrigation Rate in the Oil Accumulation Stage On Oil Yield and Water Relations of Field-Grown ‘Koroneiki' Olives

The interactions between irrigation rates applied during the oil accumulation stage and crop load were studied in field-grown Koroneiki (Olea europea L.) olives. The experiment was conducted in a six-year old super high density orchard. Five irrigation rates were applied from July 1^st until harvest. Fresh fruit yield increased with increasing irrigation and oil contents (on a fresh weight basis) decreased dramatically with increasing irrigation rate due to higher water content. Fruit oil weight decreased with increasing crop load and with decreasing irrigation rates. Oil yield increased with increasing irrigation rate from ~3 t/ha to ~5.5 t/ha. Oil yield was unaffected by irrigation rate at low crop loads up to ca 2 t/ha and showed augmented positive response with increasing crop load. Our data clearly shows that irrigation affects oil yield on a fruit basis and its effect on a per tree basis is highly dependent on crop load. Stomatal conductance decreased with decreasing stem water potential but a certain level of stomatal aperture was maintained even at extremely low water potentials. Higher stomatal conductance and lower stem water potential were measured in trees with high crop loads and it was more pronounced in lower irrigation rates. While crop load did not affect the relationships between stomatal conductance and stem water potential at the end of June 2009, some effect could be noticed at the end of August, and it was well pronounced in early October.