Mechanical site preparation in South Africa: comparing the productivity of pitting machine operators under different site conditions

Pitting is the preparation of a tree planting position. In South Africa, various contractors and grower companies have gradually adopted pitting machines over the past decade, to overcome the challenges of manual pitting, such as low productivity, poor ergonomics, and inconsistent pit quality. Even though most forestry stakeholders understand productivity requirements (e.g. pits/shift) from pitting machines, they are often unaware of productivity differences associated with different operators and work conditions. This study aimed to compare the operational productivity and pit quality achieved by different pitting machine operators under different site conditions. The experiment was conducted in two sub-compartments, with two different post-harvest slash treatments: broadcast burning or mulching (and pre-marking). Then, four operators were tasked to dig pits using the same equipment. Operator productivity was assessed by analyzing time study data, while pit quality was estimated by determining pit depth and diameter. The results indicated that Operator 4 performed significantly better on mulched sites (543 pits/PMH) than on burned sites (430 pits/PMH), while Operator 2 was the least productive with 261 and 253 pits/PMH in mulched and burned sites, respectively. The overall average productivity was 120 pits/PMH higher on mulched sites than on burned sites. Although work quality did not correlate with productivity, there were differences between operators on the mulched site. The proportion of good pits varied, but site preparation technique did not significantly affect pit quality. We conclude that operator experience significantly impacts productivity and that marking the pitting spots is important to ensure that the required number of pits per hectare is achieved.