Effect of variable water irrigation supply in olive (Olea europaea L.) cv. Arbequina in Aragon(Spain). I. Fruit and oil production

Results of an irrigation experiment in an olive orchard of the Arbequina variety during 1998 and 1999 are presented. The olive trees were irrigated with a variable water supply using a drip irrigation system. Four irrigation treatments were established. These treatments included: T1 = No irrigation water applied, T2 = Irrigation with 33% of the net irrigation requirements (NIR), T3 = Irrigation with 66% of the NIR and T4 = Irrigation with 100% of the NIR. The seasonal irrigation water applied in treatment T4 was 5100 L tree(-1) year(-1) in 1998 and 6080 L tree(-1) year(-1) in 1999. Total olive production, fruit weight, oil percentage and stage of maturity at three dates of harvest were evaluated in all the irrigation treatments. The olive tree production in T4 was 74% and 91% higher than the driest treatment (T1) in 1998 and 1999 respectively. In the three harvest dates of both years an acceleration of the olive ripening was observed as the irrigation was reduced. The weight of 100 olive fruits increased with the irrigation amount in 1998 but it was not affected by the irrigation treatments in 1999. The oil percentage of the olive fruit extracted in the second harvest of 1998 with the Soxhlet method was higher in the treatment T4 (53.3% in dry matter) than in treatment T1 (39.0% in dry matter).