Productivity and Efficiency of Extracting Small-Sized Eucalyptus Logs by Farm Tractors with Backhoe Grapples in Thailand Short-Rotation Forestry

Identifying effective methods for harvesting wood in short-rotation planted forests has recently become challenging, especially when trying to balance differing perspectives on the issue. In addition, practice in such forests may be highly variable from one place to another, and models are required to better understand the effectiveness of planted forest management and to make better decisions. A simulation experiment was setup in this study to understand how the productive performance of farm tractors, which is a common technical option in Thailand, is affected when extracting small-sized eucalyptus payloads sourced by very short cycles. Two tractors (hereafter T1 and T2) of different class size and fitted with backhoe grapples were selected and monitored via GNSS. Operational events were extracted from GNSS data, and were characterized by their speed, while payload size was estimated based on manual measurement done in the field. Then, simulations were carried out to see how moving speed and payload size may affect the productive performance as a function of extraction distance. Significant differences (α=0.05) in speed and payload size led to substantial variations in performance as the extraction distance increased. For instance, the number of daily work cycles were similar for both machines in a distance range of up to 100 m; daily production (m3), productivity (m3/h), and efficiency (h/m3), on the other hand, have shown important differences, with the higher size class T1 being more performant. Payload size and moving speed had a strong effect on efficiency, tripling the unit time for T2 at a distance of 1000 m. These findings have important consequences, at least for the local practice in South East Asia. Since these machines are frequently used interchangeably, the average extraction distance should be limited to 50 m, a scenario in which the differences in performance are the lowest. T1 maintains higher daily production and a greater number of work cycles at longer distances, highlighting the importance of choosing the appropriate tractor size for varying extraction distances in short-rotation eucalyptus forestry. Furthermore, the extraction distance should also be planned based on the performance of upstream and downstream processes, since the local practice makes use of motor-manual tree felling and cross-cutting, manual delimbing and bunching, and medium capacity trucks.