Development of mechatronic dibbling machine for improving the quality of forestry seedlings

Abstract

A forestry nursery in Tokoroa, New Zealand grows approximately 3 million Radiata pine seedlings per annum of which about 65% (2 million) are of suitable quality for forestry plantations. The high rejection rate of 35% was attributed to poorly trained, seasonal workers and unsophisticated equipment. It was estimated that about 22% of seedling rejection (approximately 220,000 per year) was due to poorly dibbled holes that caused bends in the stems. The bends occurred when planters pinched the stems of the seedlings in an attempt to make them vertical. A research and development project was undertaken to develop a mechatronic dibbling machine that could produce vertical holes of specified depth. The machine also had to produce 120,000 holes per day and be flexible with regard to spacing and size. The completed mechatronic dibbling machine was tested at the Tokoroa nursery and produced 98% of the holes at the required angle and 100% of useable depth. Harvesting, the following season, showed that the unwanted stem bends had been eliminated with a subsequent reduction in rejects. Furthermore, it was found that worker productivity increased by approximately 10% as they did not have to spend time setting seedlings vertically.