Sown grass–legume production paddocks have potential to improve beef enterprise productivity in the seasonally dry monsoonal tropics of northern Queensland

Abstract

The production of tropical cattle breeds for feeder or live export markets is the dominant primary industry in the seasonally-dry monsoonal tropics of northern Queensland. Natural woodlands and grasslands are key feed resources, with smaller cleared areas used for pasture development. Extended dry season feed deficits plus land condition decline limit animal growth and market options for producers. Previous research in northern Queensland using introduced legumes sown into native grass pastures demonstrated that intensively-managed ‘production paddocks’ using well-adapted and productive grasses and legumes could improve weaner and steer nutrition during the early to mid-dry season, enabling earlier sale or higher sale weights of cattle. Promising introduced grasses and legumes were tested at two sites of contrasting fertility in northern Queensland to test suitability for production paddocks. Replicated small-plot combinations of sown grass and legume on fertile and infertile soils resulted in pasture yields up to three times greater than those typically achieved on native pastures. A range of grasses (Bothriochloa, Brachiaria, Digitaria, Panicum, Urochloa) formed dense swards when soil-available phosphorous and sulfur were supplemented with fertiliser. Competitive legumes (Stylosanthes scabra and S. seabrana (on both fertile and infertile soils) and Clitoria ternatea (fertile soil)) increased total herbage yields (up to 14 t DM/ha) when grown with these grasses. The legume component contributed leaf with high feed value (15–20% crude protein and 8–10 MJ/kg metabolisable energy) during the wet and dry seasons, which should enable producers to reduce dietary herd inefficiencies. The most competitive grasses and legumes also suppressed plants (Bothriochloa pertusa, Themeda quadrivalvis, Chamaecrista rotundifolia) of low feed value for cattle, which otherwise dominated the sites. Preliminary economic analyses using the experimental results showed the development of ‘production paddocks’ to be profitable on fertile and infertile land types.