Australian experience with cool season annual legumes - the challenge to develop environmentally sustainable farming systems

Abstract

Australian farming systems have traditionally relied on annual legumes such as subterranean clover (Trifolium subterraneum) and annual medics (Medicago spp.) in either short-term pastures in rotation with crops or permanent pastures to provide low cost biologically fixed N and a high quality forage for livestock. The role of legumes in farming systems is now being reassessed because of the recognition that their extensive use is associated with widespread soil acidification, loss of species diversity in native pastures and increasing dryland salinity. In the future, annual legumes are more likely to be sown in mixtures with deep-rooted perennial pasture species, both in permanent pastures and in rotation with crops, to improve hydrological balance in the landscape. As a result, there is a change of direction in annual legume selection and breeding programs within Australia with a greater focus on the ability of legumes to coexist with perennial species, as well as on characteristics such as an extended growing season and deeper rooting habit to exploit subsoil water. There is also a trend towards increasing the diversity of annual legume species sown in pasture mixes to better exploit paddock variation and variable seasonal conditions.