To remain profitable the California table olive industry must institute mechanical harvesting. To effectively use the combing head harvester developed for the olive industry the trees must be mechanically hedged and topped. However, the effects of mechanical topping and hedging on current and subsequent years' yield are not known. The objective of this research is to determine the effects of mechanical topping and hedging on yield. A mature 17 year-old Manzanillo orchard spaced at 5.2m in the row and 6.8m between rows was used. After fruit set in June of 1996 and 1998, five, 182 tree row replications of the four treatments were established: a hand pruned control, hedged on both sides 2.2m from the trunk, topped at 3.8m, and a combined hedged and topped treatment. No pruning was done in the interim years, 1997 and 1999. At harvest, each row was individually hand harvested to obtain a calculated yield per tree and hectare, and 10 subsamples per row were graded to obtain calculated value per tree and hectare. All mechanical pruning treatments except hedging in 1996 significantly reduced yield the year of treatment. In 1996 hedged trees yielded 99% of controls whereas topped trees, and hedged and topped trees yielded significantly less at 77% and 76% of controls, respectively. Mechanical pruning in 1998 produced similar results. Hedged, topped, and hedged and topped trees all produced significantly less than hand pruned controls at 88%, 66% and 59% of controls, respectively. These significant differences between hand and mechanically pruned trees dissipated in 1997 and 1999, the year after treatment. Mechanical pruning treatments incorporating topping, alone or combined with hedging, produced a thinning effect which increased per tree calculated gross return. Table olive value is the product of yield per tree and fruit size distribution. Trees topped in 1996 yielded significantly less kg per tree; 77% for topped and 76% for topped and hedged trees relative to controls, but the increase in fruit size produced by the pruning treatments increased value to 80% of controls. Similarly, in 1998 hedging, topping, and hedging and topping combined, significantly reduced yields to 88%, 66% and 59% of controls but calculated fruit values were 77%, 84% and 80% of controls respectively. However, even with increase in the fruit size produced by mechanical pruning, mechanical harvesting costs must decrease significantly to compensate for the significant decreases in yield and value produced by mechanical pruning. If the mechanical harvester is 90% efficient a ranging analysis indicates harvesting costs must be decreased by 50% to compensate for crop losses produced by mechanical pruning. Also, perhaps the mechanical pruning interval could be increased to every third year.
