Determination of Suitable Shearing Conditions for Effective Pruning of Tree Branches

Pruning shears used for tree canopy management are manufactured in various sizes and blade curvatures. This paper reports on the selection of suitable blade curvature of manually-operated pruners for tree branch pruning. Various shears available on the market were examined and three with the highest, lowest and medium curvature radii were selected. These were mounted on a material testing machine and used for shearing tree branches (Morus alba) in a randomized complete block design experiment. Effects of blade curvature radius at three levels (42, 45 and 50.5 mm), cutting speed (200, 400 and 600 mm/min) and Mulberry branch diameter at three levels (thin, medium and thick) on the required cutting force and energy were studied. Analysis of covariance was used to remove the effect of branch moisture content. Statistical analysis of the data showed that the effect of blade-curvature on the required cutting force and energy was significant at the 1% level. Cutting force and energy, which are important in manual pruning due to the strain they place on the worker, significantly increased with blade curvature radius. The best cutting conditions for various branch diameters were found to be: blade-curvature radius of 45 mm for large branches and 42 mm for thin and medium branches all at cutting speed of 400 mm/min.