CAN PERENNIAL PASTURES PROVIDE THE BASIS FOR A SUSTAINABLE FARMING SYSTEM IN SOUTHERN AUSTRALIA

Land degradation, associated with farming systems based on annual past ures and crops, is threatening the long-term viability of Australian a griculture. Perennial pastures could play a significant role in reduci ng some forms of land degradation i.e. dryland salinity, erosion, and soil structure decline. In terms of sustainability, the key difference s between perennial and annual pastures relate to rooting depth and th e water uptake pattern throughout the year. Deep-rooted perennials can use water when annual pastures are dead, recover leached nitrate (and reduce acidification), and can provide soil cover and root mass to re strict wind and water erosion. Deeply penetrating roots also create bi opores and improve soil structure and drainage. In addition, problems normally associated with water repellency are reduced as perennials ar e not required to germinate each year. There is an urgent need to bree d plants that can colonise hostile Australian subsoils characterised b y high soil strength, acidity, and high concentrations of toxic elemen ts. In terms of the four perennial grasses considered in this workshop , we believe that the deeper rooting habit of phalaris and tall fescue offer more scope for overcoming degradation than cocksfoot and perenn ial ryegrass. Plant breeders need to consider the considerable benefit s of deep-rooted lines and lines which are able to colonise soils with hostile subsoils.