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

In Portugal, olive (Olea europaea L.) traditional groves 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 an alternative to the expensive, labor-intensive manual pruning practice, field trials were established with three treatments: (i) manual pruning with a chain saw; (ii) mechanical pruning, performed by a tractor mounted circular disc-saws cutting bar; and (iii) mechanical pruning, as in the mechanical pruning treatment, followed by a manual pruning complement. Olive production and harvesting efficiency were evaluated every year for 8 yr. Olives were harvested with a trunk shaker, and the remaining nondetached fruits were collected manually. The pruning rate of mechanical pruning (487 trees h(-1)man(-1)) was substantially higher than the values of manual pruning and mechanical+manual pruning, which were the same (20 trees h(-1)man(-1)). Over the 8-yr period, mechanical pruning had an average yield of 36.4 kg tree(-1) yr(-1) which was significantly higher than the 30.1 kg tree(-1) yr(-1) of manual pruning and no significantly different from the 34.1 kg tree(-1) yr(-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. Results indicate that after mechanical pruning trees can be kept for at least 8 yr without any significant loss in olive yield and no effect in harvesting efficiency, therefore reducing costs. Mechanical+manual pruning, performed in the same year, did not yield further improvement.