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November/December 2021 | Muedanyi Ramantswana

Productivity and ergonomics of Patas pruning machine

Stand Tending


Pruning of forest trees is labour intensive silvicultural activity which is often conducted by using pruning or motorized saws. There have been very few mechanised solutions developed and adopted globally even though this activity is widely practiced improving the timber quality and grade.

Overview of research
According to a recent article from Forst&Technik, The Department of Ergonomics and Process Technology at the University of Göttingen scientifically assessed the productivity and ergonomics of using the Patas pruning machine manufactured by advaligno. The pilot study was conducted by Florian Hartsch, Dirk Jaeger, Tim Jordan. For information on how the Patas works visit  or  . The research was conducted on an area of about 1.7 ha planted with 40-year-old larch and stand density of approximately 110 stems per ha.

Key findings of pilot study
The researchers found the Patas could prune almost 30 trees per hour of work with the actual pruning process taking between 8 and 12 seconds. Other time consuming elements assessed as part of the pruning process included searching for tree to be pruned, positioning of tractor and personal recovering during non-working hours. The cost of pruning using a 37kW tractor and two forest workers amounted to € 3.70 per tree. Furthermore, the research also found that the quality of pruning achieved was acceptable, with fine branches, branch stubs greater than 1 cm length (7.9% of all pruned trees with 1 – 4 stubs) and bark damage  more prominent at the height over nine meters. Ergonomically the physical strain of the work process seemed to be relatively high even though within the framework of general forest work.

The research scientifically investigated the productivity, quality and ergonomics of the Patas delimbing machine. The initial findings are important as they provide important and objective information to guide various stakeholders such as foresters and contractors about the machine.

For more information please visit Forst&Technik for the comprehensive research.