SITE PREPARATION FOR PINUS ESTABLISHMENT IN SOUTH-EASTERN QUEENSLAND .2. EFFECT OF CULTIVATION AND CULTIVATION WIDTH ON GROWTH

The standard site preparation practice used for Pinus plantation estab lishment on well-drained soils in south-eastern Queensland is blade (s ubsurface, wing rip) cultivation to a width of 2.0 m and a depth of 0. 2 m. This operation requires high drawbar power and is difficult to ac hieve in high strength soils, or in soils where roots and stumps hinde r progress of the blade through the soil. The aim of the study reporte d in this paper was to better define cultivation growth relationships for Pinus caribaea var. hondurensis plantations in order to determine if site preparation objectives could be achieved with a reduced cultiv ation effort. A highly significant 'soil type x cultivation' interacti on was observed. In contrast to the growth responses observed on hards etting soils, cultivation did not improve growth on non-hardsetting so ils. There is an opportunity therefore to reduce reforestation site pr eparation costs by only cultivating soils that show a growth response. The cultivation response on hardsetting soils has increased throughou t the study period, and is attributed to a reduction in soil penetrati on resistance. The response however shows diminishing gains with incre asing cultivation widths. Blade cultivation widths of 1.2 m were found to capture 97% of the gains that could be expected from widths of 2.0 m. A significant 'family x soil penetration resistance' interaction w as observed. An opportunity to increase plantation productivity by tar geting better performing families to hardsetting soils is suggested.