Tropical Grasslands (2007) Volume 41, 174190
Production, economic and environmental benefits of leucaena pastures
MAX SHELTON AND SCOTT DALZELL
School of Land, Crop and Food Sciences & School of Animal Studies, The University of Queensland, Queensland, Australia
The rate of adoption of leucaena (Leucaena leucocephala)-grass pastures is rising rapidly in northern Australia as graziers realise the extent of the triple-bottom-line benefits. Leucaena pastures are suited to >13 M ha of Queensland, with a current estimated 150 000 ha producing 37 500 kg of liveweight gain valued at >$69 M each year. Despite high costs of establishment, this area is expected to expand to 300 000–500 000 ha by 2017. The main factor driving high levels of adoption is the ability of leucaena pastures to meet graziers’ needs for a highly productive and profitable system that meets market requirements for grass-fed beef of superior quality. Production benefits include: increased animal production/ha (up to 4-fold) resulting from a combination of greater animal liveweight gains and increased carrying capacity; longevity (30–40 yr); and potential to intensify production within the constraints of recent changes to the Queensland Vegetation Management Act and escalating land prices. Other benefits are: increased marketing flexibility; superior capital appreciation of leucaena pastures; and positive animal welfare outcomes.
Social factors are also important, with many farmers converting marginal dryland cropping cultivation to leucaena pasture owing to concerns about the impact of drought, global warming, and decreased profitability and sustainability of dryland farming. Importantly, technical information regarding the establishment and management of leucaena pastures is now available to graziers, giving them the confidence to adopt the technology.
Environmental benefits include: dryland salinity mitigation; soil erosion control and improved water quality; improved soil fertility through biological nitrogen fixation; and greenhouse gas mitigation. Given an average season, existing leucaena pastures fix approximately 7500 t N and reduce cattle methane emissions by approximately 91 000 t carbon dioxide equivalent carbon (CO2-e) annually. These pastures also have the potential to sequester >4 M t of CO2-e. However, leucaena is an environmental weed in northern Australia, largely as a result of its historical introduction and use as an ornamental and for slope stabilisation. While most current weed infestations are not due to grazier plantings, a voluntary Code of Practice, where graziers take responsibility for any spread from their properties, has been developed to limit seed production and dispersal. Soil acidification will not be a problem on the alkaline clay soils (high pH buffering capacity) in Queensland where most leucaena pastures are planted. There is need for greater factual appreciation of the environmental aspects of large-scale leucaena plantings, and for a thorough cost:benefit analysis to be conducted.