Summer growth rates and annual yields of perennial ryegrass in the Upper North Island expected to decline as a result of climate change

Evaluating the ability of perennial ryegrass to continue underpinning New Zealand’s low-cost dairy production systems under future climate change scenarios requires a modelling approach. In this study, climate projections for different climate change scenarios were used in the BASGRA pasture model to predict changes in annual yields and seasonal pasture growth rate patterns of perennial ryegrass. These predictions, including uncertainty, were made for the years 2010-2014, 2040- 2044 and 2090-2094 in 14 dairy dominant subregions in the Upper North Island of New Zealand. The suitability of perennial ryegrass is expected to decline in the future across all subregions, with worse outcomes expected under higher atmospheric greenhouse gas levels. Winter is expected to be the season least affected by climate change and summer the most. Late-winter/spring is predicted to become the main growing season, followed by late-autumn/early-winter. The ability of farmers to adapt their farming practices is essential in remaining profitable and internationally competitive.