IRRIGATION AND SODICITY

The productivity of irrigated agriculture in Australia is low for most crops and one important factor is the physical and chemical constrain ts caused by sodicity in the rootzone. Over 80% of the irrigated soils are sodic and have degraded structure limiting water and gas transpor t and root growth. Irrigation, without appropriate drainage, leads to the buildup of salts in soil solutions with increased sodium adsorptio n ratio (SAR) and can develop perched watertables due to a very low le aching fraction of the soil layers exacerbated by sodicity. Therefore, irrigation management in Australia is closely linked with the managem ent of soil sodicity. The inevitable consequence of continued irrigati on of crops and pastures with saline-sodic water without careful manag ement is the further sodification of soil layers and concentration of salt in the rootzone. This will increase the possibility of dissolving toxic elements from soil minerals. The yields of crops can be far bel ow the potential yields determined by climate. The cost of continued u se of amendments and fertilizers to maintain normal yields will increa se under saline-sodic irrigation. Most of the irrigated soils in Austr alia need reclamation of sodicity of soil layers at least in the rootz one. The management of these sodic soils involves the application of g ypsum, suitable tillage and the maintenance of structure by the buildu p of organic matter and biological activity aver time. Then artificial drainage, an essential component of the management of irrigated sodic soils, is possible. By following these soil management practices, irr igated agriculture in Australia will become sustainable with increased yields and high economic returns.