Clay spreading on water repellent sands in the south east of South Australia—promoting sustainable agriculture

Abstract

Water repellence is a serious land degradation issue and a constraint to productivity on approximately two million hectares across South Australia. Sandy soils that have poor coverage of pasture and crops lend themselves to the risk of wind erosion and loss of yields. A technique that has once seen highly unproductive pasture country now producing crops is ‘clay spreading’. As with many discoveries, the ability of clay to counteract the effects of water repellent sand was unearthed by accident thirty years ago by Clem Obst, farmer at Mundulla, SE of South Australia. Today, approximately 37,000ha of land in South Australia has been clay spread, of which 32,000ha is in the SE of South Australia. The application of clay to water repellent sand increases the effectiveness of pre-emergent herbicides, amelioration of water repellency, improves the germination, establishment and yields of pasture plants and crops and nutrient and moisture retention in the topsoil. Water repellent sand pastures generally contain little, if any, legume content and produce as little as 400kg/ha dry matter compared to clayed pastures (3250kg/ha) which are sub-clover or lucerne based. Spreading clay has generally doubled cropping yields. The technique of clay spreading is continually being modified to enable landholders to attain maximum economic returns while ensuring the long-term sustainability of agriculture on water repellent sands.