Roles of gibberellic acid and zinc sulphate in increasing size and weight of olive fruit
Olive trees (Olea europaea L. cv. Shengeh) were treated with gibberellic acid (GA3) at 0, 15, 30 and 45 ppm and zinc sulphate at 0, 0.25, 0.5 and 0.75% when fruit were at 70% of their final size in experiments carried out in 2007 season. The effect of GA3 and ZnSO4 treatments on yield and some variables related to fruit characteristics (fruit, pit and pulp weight, pulp/pit weight ratio, fruit length and diameter, pit length and diameter, fruit L/D ratio, pit L/D ratio fruit volume) was analyzed. Fruit weight was significantly increased most by concentrations of GA3 and ZnSO4 treatments with respect to control trees, due to an increase in fruit size. GA3 spray at the 30 ppm concentration was more effective in improving yield than spraying GA3 at other concentrations and control. Thus, these treatments accelerated fruit growth of olive, and also increased both fruit size and total yield per tree, allowing for an increase in its economic value. Use of 0.5% ZnSO4 + 30 ppm GA3 treatments was optimum for improvement of olive fruit yield.