Perennial ryegrass is more sensitive to heat stress and drought than deep-rooted species such as tall fescue. Deep roots are associated with better performance under heat stress and drought conditions because they allow for more water uptake leading to higher leaf water content and photosynthetic activity, reduced stomatal resistance, and transpiration cooling. Understanding the benefits associated with deep-rooted pasture species is critical in determining effective ways to adapt pasture systems to the increasing frequency and severity of heatwaves associated with climate change.
This project aims to determine the potential benefit of switching to deep-rooted pasture species by quantifying the extent to which they outperform perennial ryegrass in response to heatwaves. The research is part of the Forewarned is Forearmed project led by Prof. Richard Eckard and Dr. Ann-Maree Graham at PICCC, University of Melbourne in collaboration with Brendan Cullen, Ruchika Perera, and Alex Sinnett also at the University of Melbourne’s Faculty of Veterinary and Agricultural Science.
Dr. Rachelle Meyer will use a whole-farm system modelling approach to determine the productivity gains and improved performance of a deep-rooted pasture species compared to perennial ryegrass under heat stress conditions. Two sites will be modelled to capture the differences in responses in high and low-rainfall regions of eastern Australian pastures. In addition to the historic climate, used as a baseline, 2 climate scenarios will be used to investigate the performance of the two species. The traditional climate change scenario uses change factors from an RCP 8.5 scenario for 2080. The extreme heat scenarios alter these projections to increase variability of temperature while preserving the mean based on the methodology of Harrison (2016). This results in more severe heatwaves and allows for isolation of the impacts of heat on plant responses.
Results from the biophysical responses and assumptions regarding pasture persistence and establishment will inform an economic analysis performed by Alex Sinnett to determine the likely extra profit from sowing a deep-rooted pasture species, such as tall fescue, instead of perennial ryegrass. The pasture dry matter available for consumption by livestock will be valued using the two-price method of putting a value on extra pasture that is used in a farm system. Stochastic simulation will be used to incorporate price risk volatility and risk of establishment failure.
Links to the resulting publications will be included here when available.
This project is supported by funding from the Australian Government Department of Agriculture and Water Resources as part of its Rural R&D for Profit program in partnership with rural Research and Development Corporations, commercial companies, state departments and universities. Meat &Livestock Australia (MLA) is responsible for the overall management of the project.