Effect of GA3 and Zinc Sulfate on Fruit Yield and Oil Percentage of ‘Shengeh’ Olive Trees

This study was conducted on ten-year-old ‘Shengeh’ olive trees at the Kazerun Olive Research Station, Iran to investigate the effect of gibberellic acid (GA3) and zinc sulfate (ZnSO4) sprays on fruit yield and oil production. A factorial experiment (4 × 4 × 4) was arranged in a randomized complete block design. The plants were sprayed with 0, 15, 30, and 45 ppm GA3 and 0, 0.25, 0.50, and 0.75% ZnSO4 in August, which was about halfway through the fruit growth period. Maximum fruit retention (90%) was obtained by spraying with 0.5% ZnSO4 and 45 ppm GA3. The greatest fruit weight (3.25 g/fruit) was achieved with 30 ppm GA3 and 0.75% ZnSO4. The highest oil % on a dry weight basis (34.75) was produced with 0.50% ZnSO4 + 30 ppm GA3. The results showed that appropriate spraying with GA3 in combination with ZnSO4 increases oil production by increasing both fruit oil and fruit retention.