Effect of Deficit Irrigation on Quantity and Quality Characteristics of Fruit and Oil of Olive (Olea Europaea L. cv. Koronaiki)

To evaluate deficit irrigation effect on quantity and quality characteristics of olive fruit (Olea europaea L. cv. Koronaiki), this study was carried out in 2009 in Gilvan (49^o 5¢ E longitude, 36^o 47¢ N latitude, and elevation 330 m above sea level) located in Tarom region in Zanjan province, Iran. Soil texture of the farm was loam. The experimental design was randomized complete blocks with 4 replications. The irrigation treatments were T₁, =100% (control treatment), T₂= 75%, T₃= 50%, and T₄= 25 % of olive water requirement (OWR). Trees were watered by drip irrigation system with loop layout. OWR was calculated based on Gilvan synoptic weather station data and FAO Penman-Monteith equation and the FAO-56 recommended crop coefficient.
Based on the results, the effect of deficit irrigation on percentage of fruit oil, ratio of fruit length to diameter, percentage of complete flowers, and percentage of secondary fruits were significant at 1% probability, while the effects on percentage of primary fruits produced were significant at 5% probability. However, deficit irrigation effects on the percentage of fruits dry mass and pulp/pit ratio were not significant. The results showed that the percentage of complete flower produced in T₄ was the least (42%). Deficit irrigation caused significant difference (P=5%) between T₁ and the other treatments in terms of percentage of primary fruits produced (about 31% difference). Also, deficit irrigation caused differences between percentage of the primary and secondary fruits in T₄. Based on the results, difference in ratio of fruit length to diameter between T₁ and deficit irrigation treatments were significant (P=5%). Therefore, deficit irrigation was not suggested for cannery objectives. The maximum content of fruit oil (28.49%) and the least content (22.73 %) were obtained from 75% and 25% OWR treatments, respectively. Therefore, in the research site, to irrigate olive trees cv. Koroneiki, 25% continuous deficit irrigation (irrigation with 75% OWR) is suggested in order to save on water use.