Site preparation for Pinus establishment in south-eastern Queensland. 2. Effect of cultivation and cultivation width on growth

Abstract

The standard site preparation practice used for Pinus plantation establishment on well-drained soils in south-eastern Queensland is blade (subsurface, 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 achieve in high strength soils, or in soils where roots and stumps hinder progress of the blade through the soil. The aim of the study reported 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 cultivation effort. A highly significant 'soil type x cultivation' interaction was observed. In contrast to the growth responses observed on hardsetting soils, cultivation did not improve growth on non-hardsetting soils. There is an opportunity therefore to reduce reforestation site preparation costs by only cultivating soils that show a growth response. The cultivation response on hardsetting soils has increased throughout the study period, and is attributed to a reduction in soil penetration resistance. The response however shows diminishing gains with increasing 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 was observed. An opportunity to increase plantation productivity by targeting better performing families to hardsetting soils is suggested.