EVALUATION OF THE USE OF A DISC-SAW MACHINE IN WINTER PRUNING 'ROCHA' PEARS ORCHARDS - AN ACCOUNT OF FIVE YEARS

Manual pruning with pneumatic shears is a current practice used by ‘Rocha’ pear farmers in Portugal. However, it is labour-intensive and therefore expensive. Work started in 2008 to study a mechanised alternative based on a discs-saw pruning machine mounted on a front loader of an agricultural tractor. The following three treatments were compared: T1 – manual pruning performed annually using pneumatic shears; T2 – mechanical pruning, performed annually, topping the canopy parallel to the ground; in 2008 and 2010 topping was followed by mechanical hedging of both sides of the canopy; in 2011 mechanical topping was complemented with manual pruning; T3 – mechanical pruning, performed annually, topping the canopy parallel to the ground followed by a manual pruning complement; in 2008, prior to the manual complement, trees were hedged on both sides of the canopy. A randomised complete block design was used, with three replications, leading to 9 plots with three lines of 10 trees per plot. In each plot only the central line was used in the evaluation. Trials were performed in a 20-year-old commercial orchard, planted in an array of 4×2 m with trees trained as central leader system. The following data were collected: tree height and canopy width, before and after pruning interventions; weight of biomass removed; fruit yield and working rates. Results show that yield in treatment 2 was always lower than in treatment 1; yield in treatment 3, except once, was always lower than in treatment 1. Mechanical pruning leads to a more uniform orchard when compared to manual pruning.
Although not beneficial in terms of yield, the use of the tractor mounted cutting bar prior to manual pruning interventions result in a reduction of time required by this expensive operation. However, further field work at a real scale is needed to validate the economic value of the strategy of performing mechanical pruning, based on a disc-saws pruning machine, followed by a manual complement.