The relation between soil structure and solute transport under raised bed cropping and conventional cultivation in south-western Victoria

This study examined the relationship between soil structure and solute transport in a texture contrast soil under 2 different tillage treatments'raised beds and conventional cultivation'in south-western Victoria. Undisturbed soil samples were collected for resin-impregnation and image analysis. This enabled several descriptive parameters of macropore structure to be calculated. Large, undisturbed soil samples were also collected for a solute transport experiment using a KCl solution. A convective log-normal transfer function was used to model Cl' movement. The assessment of soil structure showed that the raised beds contained a better connected pore network than the conventionally cultivated soil. Solute transport was faster through the raised bed soil when close to saturation (at '5 mm tension). Under these conditions, the solute transport parameters showed a smaller ratio of transport volume to soil water volume in the raised bed than the conventionally cultivated soil. Together, these data strongly indicate that the raised beds had greater pore connectivity and were able to transmit solute faster and more efficiently than the conventionally cultivated soil. It is concluded that raised bed soils are better structured and provide less risk from waterlogging than conventionally cultivated soils. However, there is greater potential for preferential flow of pesticides and solutes in raised bed soils.