The effect of stand age and sampling position on solar drying performance and post-drying quality of oil palm lumber

The solar drying process creates a mild drying condition which might be suitable for oil palm wood. The drying process of a particular wood is also affected by its intrinsic factors, such as age and sampling position within the trunk. A study on solar drying of oil palm wood from various ages and sampling positions in standing trees has not been carried out elsewhere This study was then carried out to investigate the solar drying performance and post-drying qualities of old oil palm wood from different sampling positions. The main materials used were 25-and 32-year-oil palm wood sampled from vertical (from the bottom to the top parts of the trunk) and horizontal positions (along the transversal surface of the trunk, i.e., the inner and outer zones) in the trunk. All samples were prepared as tangential sawn boards, sizing 25 mm (thickness) x 100 mm (width) x 1400 mm (length). The drying process was run in a solar dryer until each board reached a moisture content of 10-11%. Drying rate, time, shrinkage and several post-drying defects were then evaluated. The results show that the stand age and the vertical sampling position (along the trunk length) significantly affected the drying rate, the drying period, and the post-drying shrinkage. The horizontal sampling position (along the transversal surface of the trunk) also significantly affected the post­ drying shrinkage. On average, the 25-year-old oil palm wood had the fastest drying rate (approximately-0.06%/hour) and the shortest drying period (approximately 232 hours). As the stand age increased, the tendency to develop external checks decreased, but the depth of all the distortion defects and the tendency to collapse increased. The inner-zone samples shrank more than the outer-zone samples and were more prone to develop an external check, bowing, cupping, and collapse than the outer-zone samples.