Dibbling Machine for ArborGen

Abstract

ArborGen’s nursery, located in Tokoroa, supplies approximately 6 million seedlings per year to the forestry industry (figure 1). The vast majority of seedlings are Pine Radiata but they also supply Plug Plus and Douglas fir. In peak season, they plant up to 120,000 seedlings per day that each require a straight vertical hole of certain depth and spacing, (depending on seedling type). For example the most common seedling, Radiata pine, requires holes of approximately 10mm diameter x 40mm deep (figure 2). The process of making the holes is called dibbling. Dibbling has become a major problem that has resulted in an estimated 400,000 rejections per year. An investigation of the dibbling process identified the following problems: • Existing human dibbling methods too slow and unreliable • Machine methods produce low quality holes that lead to mis-planted seedlings • Lack of flexibility of existing, methods with regard to hole size and spacing • Current methods compact the soil hindering root growth so hole drilling is preferred • Currently, dibbling must be done on the day of planting due to the deterioration of the bed surface