Regional differences in tree - crop competition due to soil, climate and management

Abstract

Large areas of trees are being planted in Australian agricultural lands for a range of environmental, ecological and economic reasons. In the medium to low rainfall zones, these plantings can negatively impact upon adjacent agricultural production through competition for soil moisture. The nature of the tree–crop competition zone and the means of managing it have been studied in the main southern cropping zones. However, the differences in soil, climate and agronomic systems in Australia’s northern dryland cropping zones could lead to differences in the competition processes and the management options needed to minimise them. In this study, the competition for soil moisture and resultant impacts on crop production were studied for a Eucalyptus argophloia windbreak on a farm near Warra, Queensland (26.93°S, 150.93°E). The results indicate well defined inner and outer competition zones, the extents of which agree with those found elsewhere in Australia and overseas. However, while the extent of the competition is comparable with other regions, local agronomic practices developed for variable climatic conditions and deep clay soils allow trees to extract soil water stored during fallow periods resulting in relatively higher production losses.