Back to the future – site, science and sustainability

Abstract

Inter-annual rainfall variability across Queensland, Australia, is among the highest in the world. This variability coupled with episodic periods of drought and flood and highly variable forage supply pose major challenges for grazing management in Queensland. Since the mid-1990s, researchers have successfully used historical and current pasture data with the GRASP biophysical model to simulate pasture growth in the grazing lands of northern Australia. The FORAGE online system provides a unique combination of pasture modelling (GRASP model), remote sensing and climate forecasts to support grazing land and environmental management decisions. Here we look ‘back to the future’ to build on previous research, transfer our past knowledge and experience in modelling grazing systems to new researchers, and use the traditional, highly valued but resource-intensive site data to improve the GRASP land type models used in the FORAGE decision support system. Four fenced sites were established in regionally dominant Brigalow softwood scrub and Brigalow blackbutt buffel grass (Cenchrus ciliaris cvv. Biloela, Gayndah) pastures. We use detailed soil, pasture and rainfall measurements collected over three years (2020 – 2022) to represent key biological and physical pasture processes in the GRASP model. Across the years, the sites varied in rainfall (3 – 138% above long-term median), average buffel grass dominance (69 – 98% of total yield), peak pasture yield (2742 – 4343 DM kg ha-1) and sward nitrogen yield (19 – 34 kg N ha-1). We use this data to improve the FORAGE modelled estimates of long-term buffel grass pasture productivity in the broader Brigalow softwood and Blackbutt land type pastures in central Queensland. This will inform grazing and environmental land management decisions that promote both sustainable natural resource use in grazing lands and profitable grazing industries.