EVALUATION OF PASTURE MANAGEMENT-SYSTEMS FOR BEEF-PRODUCTION IN THE SEMIARID TROPICS - MODEL DEVELOPMENT

Beef production in the Australian semi-arid tropics is currently based mainly on extensive grazing of native pastures, where animal performance is limited by the quantity and/or quality of the pastures. Beef producers are interested in production systems to overcome these limitations to animal production. To assist with comparisons of different systems a spreadsheet model was developed and used to evaluate the whole property implications of two forms of pasture development - killing trees to increase grass production, and oversewing the native pastures with introduced legumes and grasses. Four systems (live trees, native pasture; killed trees, native pasture; live trees, sown pasture, killed trees, sown pasture) were compared under a range of seasonal conditions and over a range of stocking rates. Both killing trees and sowing introduced species increased production and net cash flow with the combination of killed trees and sown pasture giving the greatest increase. The relative changes in net cashflow with different growing seasons were less on sown pasture than native pasture systems. Systems where the trees were killed produced near maximal returns over a wider range of stocking rates than systems with live trees. The results suggest that pasture development using legumes can be a profitable investment. However, when using the model to assist with decisions related to pasture development, individual producers will need to provide basic data on their properties, and to be satisfied that the assumptions made in the model are appropriate for their property and circumstances.