EVALUATION OF THE CUTTING FORCE ON VINE BRANCHES IN WINTER PRUNING

Mechanical pruning, usually integrated with manual finishing, still excites some doubts regarding the quality of the cut which appears not to be the best as precision and cleanliness. This aspect, probably conditioned by the model and the application of pruning machines, might also be affected by the characteristics of the vine branches in particular by their cutting force. In order to evaluate the cutting force on different vine type, laboratory and field trails were carried out. The experiments were set in order to evaluate this parameter during winter pruning in relation to three variables: vine type; branch size; pruning time. The results show how the cutting resistance of vine branches during vegetative rest depends on vine variety (Trebbiano 675 N Cabernet 1175 N), on the diameter of the canes (increase of force from 56 % to 86 % between the classes of diameter) and on the pruning date (26% decrease of the cutting force in the latest period for Trebbiano and Sangiovese, and 32 % for Cabernet Sauvignon). Such variations, which can be considerable, affect directly the pruning results. High values of cutting force can generate tiring of operator in manual pruning or cutting damages on the vegetation during mechanical pruning.