Long-Term Evaluation of the Influence of Mechanical Pruning on Olive Growing

Abstract

In Portugal, olive (Olea europaea L.) groves with the traditional tree density of around 100 trees ha -1, necessitate increasing pruning costs every year. As a result farmers tend to lengthen pruning intervals. With the purpose of studying a mechanised alternative to the expensive, labor-intensive manual pruning practice, the authors established in 1997 field trials with the following three treatments: i) manual pruning with a chain saw; ii) mechanical pruning, performed by a tractor mounted cutting bar provided with 6 circular disc-saws; and iii) mechanical pruning, as in the mechanical pruning treatment, followed by a manual pruning complement. The effect of the above treatments on olive production and on harvesting efficiency was evaluated every year for 8 yr. The harvesting was performed by a trunk shaker, and the remaining non-detached fruits were collected manually. The pruning rate of mechanical pruning (487 trees hour-1man-1) was substantially higher than the values of manual pruning and mechanical+manual pruning, which were the same (20 trees hour-1man-1). Over the 8-yr period, mechanical pruning had an average yield of 36,4 kg tree-1 year-1 which was significantly higher than the 30,1 kg tree-1 year-1 of manual pruning and no significantly different from the 34,1 kg tree-1 year-1 of mechanical+manual pruning. The shaker efficiency was significantly influenced by the year, ranging from 72% to 96%; no significant differences were found between treatments in terms of harvesting efficiency. These tests indicate that after mechanized pruning (horizontal cut at the uppermost part of the canopy) trees can be kept for at least 8 years without any significant loss in olive yield per tree and no effect in harvesting efficiency, therefore reducing costs. Selective manual complement to the mechanized pruning, performed in the same year, does not provide any further advantages in olive yield nor in shaker performance and consequently increasing production costs.