Use of Perennial Grass in Grazing Systems of Southern Australia to Adapt to a Changing Climate

Grasslands and rangelands occupy over 70% of the earth's land area (Holechek et al., 2004; World Resource Institute, 2000), and are a major source of meat, milk and fibre production in the world.The rising demand for meat and milk in the past 30 -40 years and the adverse impact from climate varibility have placed great pressure on the productive and sustainable use of grazing lands (Delgado, 2005;Nie & Norton, 2009).By 2020, it is predicted that developing countries will consume 72 m tons more meat and 152 m tons more milk compared to 2002/03 whereas developed countries' increases will be 9 and 18 m tons for meat and milk, respectively (Delgado, 2005).Australia is the world's driest inhabited continent.Half of its total land area has an average annual rainfall (AAR) of less than 300 mm.Around 60% is used for agriculture, of which over 90% is used for grazing (Peeters, 2008).A particular feature of the continent is the high rainfall variability which makes selecting the right pasture species/cultivars, optimising pasture and grazing management and avoiding overgrazing very challenging.About 5% of Australia's grazing lands have been sown to introduced plant species and these improved pastures support a large proportion of the domestic livestock.The improved pasture species are productive and generally have high nutritive characteristics; however, their persistence is often poor due to the limited capacity to sustain a suite of varying soil, climatic and management conditions.A pasture survey in south west Victoria revealed that the majority of pastures were dominated by low-producing, 'unimproved' grass species (Quigley et al., 1992), and similar results were found in southern New South Wales (NSW; Virgona & Hildebrand, 2007).The main perennial pasture grasses sown in southern Australia are perennial ryegrass (Lolium perenne), phalaris (Phalaris aquatica), tall fescue (Festuca arundinaceum syn.Lolium arundinaceum), and cocksfoot (Dactylis glomerata) (Reed, 1996).These grasses differ in their requirements of rainfall, temperature and soil type and fertility for growth, therefore have a varying degree of adaptation in different regions.Plant breeders have developed new cultivars to improve one or more attributes for each of the grasses.Agronomists working with other specialists such as animal and soil scientists have developed management systems to accommodate the expression of the attributes from the new cultivars.At present there are large variations between cultivars within each species, not to mention between species. www.intechopen.com Climate Change -Research and Technology for Adaptation and Mitigation 432In rangelands and marginal land classes such as steep hill or stony country where improved perennial grasses cannot be sown or do not persist, Australian native grasses are often the dominant perennial species.Native grasses have grown and evolved in Australia for millions of years, and are generally well adapted to the soil and climatic conditions.While there has been debate on the yield and nutritive value of native grasses compared with improved exotic species, there is a general consensus that native grasses are better adapted to low fertility soils and low input farming systems that receive low and unreliable rainfall.Climate change projections for Australia indicate increasing temperatures, varying rainfall patterns across regions, and elevated atmospheric carbon dioxide (CO 2 ) concentrations (CSIRO & BoM, 2007), which are likely to affect the productivity of pasture-based systems, although the overall effect is likely to vary regionally, depending on the combination of those changes (Harle et al., 2007;Howden et al., 2008;McKeon et al., 2009).The predicted long-term (up to 2070) rainfall patterns indicate a higher chance of rainfall reduction in southern than in north, central and eastern Australia (CSIRO & BoM, 2007).The rainfall reductions in southern Australia are projected to be largest in winter and spring.Research into the responses of perennial grasses to climate, soil and management factors has long been a major target for agronomists, breeders and physiologists to improve the resistance/adaptation attributes and management of these plants.The challenge is how we can place these responses and improved attributes in a systems context and achieve production and sustainability goals in practice.This chapter discusses the past and current research on perennial grasses and their management systems that may lead to the development of adaptation strategies to climate change in southern Australia.