Improved drainage and greater air-filled porosity of raised beds in south-western Victoria

Crop production in south-western Victoria has historically been constrained by waterlogging. As a result raised beds have recently become a popular tillage method on soils prone to waterlogging. Soil water properties, air-filled porosity, plant dry matter, and grain yield were compared for raised beds and conventional cultivation treatments during 2003 and 2004. Although rainfall was less than the long-term average, over the whole period the raised beds had consistently lower water content and drained faster than the conventional cultivation. Air-filled porosity was greater and above the critical value of 10% for longer in the raised beds (e.g. in 2004 air-filled porosity was >10% for 69 days longer in the raised beds). Benefits on the raised bed soil (such as greater soil aeration) were probably due to the increased depth to the B horizon and the soil surface topography created by regular furrows. No waterlogging was observed in 2003 and the crop on the conventional cultivation produced significantly more dry matter. Although visible waterlogging of the crop on the conventional cultivation was observed in 2004, the crop on the raised beds was not affected. Despite the different response in growth for each treatment, there was no significant difference in grain yield in either year. Nevertheless, it is predicted that raised beds should provide a well-drained and aerated soil that maintains crop productivity under average or greater rainfall in south-western Victoria.