Sustainable pasture systems under climate extremes

Summary

The increasing frequency and intensity of climate extremes pose a new challenge for pasture-dependent industries, such as red meat production. Information about how pasture grasses and legumes perform under drought and increased temperatures can support decisions about pasture selection, planting times and management.

In this project, grasses, legumes and grass-legume mixtures were exposed to manipulated rainfall, temperatures, soil and nutrients to mimic extreme winter and spring climate extremes.

There was considerable variation in how different pastures responded to different climate conditions. Most perennial species recovered rapidly when drought conditions were alleviated. During the trials, increased temperatures generally reduced productivity and increased greenhouse gas emissions but had little effect on nutritional quality of pastures.

Objectives

This project had two main aims:

• To produce information to support pasture management under extreme climates.
• To identify opportunities to increase climate resilience and minimise future risks to the grazing industry.

Key findings

• The productivity decline of pasture species varied in response to extreme winter/spring drought conditions:
  • The smallest annual yield reductions were for Rhodes grass (-10%) and Digit (-17%)
  • The biggest declines in yield were Biserrula (-43%) and Fescue (-46%).
• On average, tropical grasses were more productive and had significantly higher crude protein concentrations and digestibility under prolonged winter and spring drought conditions than temperate grasses or legumes.
• Warmer temperatures were generally associated with reduced biomass production across all four seasons.
• Using a mixture of species was more productive and showed more potential for reducing climate risk.
• Plants with longer, thinner root systems and high levels of mycorrhizal fungi infection performed better under drought conditions.

Benefits to industry

This project has made significant advances in understanding how key pasture species respond to climate extremes.

This research provides guidance for selecting pasture species based on their productivity and nutrition qualities in the context of extreme seasonal drought. The research also produced insights into the productivity benefits of using a mixture of species to mitigate the impact of extreme climates.

MLA action

MLA is considering further research to explore the findings generated from this project in order to better inform decision making regarding pasture selection and soil management.

Future research

More research is needed to understand:

• how key pasture legumes will perform – particularly in relation to their N-fixing capacity – under warmer, drier conditions
• which grass-legume combinations offer the best opportunity to optimise multi-season production, and nutrition, under more extreme climate conditions
• how management strategies and plant responses to altered climate will affect the accumulation of soil organic matter and greenhouse gas emissions
• how multi-year climate stress affects perennial species’ productivity, nutrition and persistence.