SOIL SODICITY IN VICTORIA

This paper gives a broad overview of the distribution and agricultural importance of sodic soils in Victoria. Sodic soils are estimated to occupy at least 13.4 Mha, representing at least 73% of Victoria's agricultural land. Most of this land is used for dryland farming; about 85% of the cropped land and 66% of the land sown to dryland pastures occurs on sodic soils. The largest sodicity class is 'alkaline sodic', dominated by a diverse range of soils (red duplex, yellow duplex, calcareous earths and self-mulching cracking clays). Alkaline sodic soils comprise half of the total agricultural land area, or about 24% of the area of land currently used for dryland cropping and 21% of the land under sown pasture. Land degradation problems are recognized as affecting most agricultural land in Victoria, and to be substantially limiting its productivity. The nature, extent and severity of the various forms of land degradation are a consequence of both intrinsic soil properties and of management practices. There is an urgent need to improve current farming practices to prevent further deterioration of the soil resource. Existing knowledge of the behaviour of sodic soils under both dryland and irrigated agriculture is reviewed. It is concluded that substantial gains in productivity are possible, but will require effective collaboration between soil scientists, agronomists, and land managers. Collation and integration of current knowledge on the properties and management of sodic soils in Victoria, and the acquisition of additional relevant information by targeted long-term research is required. Key issues for future research are identified.