The climate of the UK is predicted to change significantly over the coming decades, notably in terms of temperature and rainfall. These changes will affect the growth of crops, as temperature and moisture availability are controls on growth rates. However, the timing and magnitudes of changes will matter a great deal in how such changes will be expressed.

As part of a larger Soil Policy Programme by ADAS for the Welsh Government, we have used the ADAS Grass Model (AGM) to predict possible changes in ryegrass yields around Wales in the period leading up to 2080. Such changes will be key to the Welsh farming economy, as 78% of Wales is currently covered by managed grasslands or rough grazing.

Uniquely, the AGM uses data from grassland manuring trails performed by ADAS and the Grassland Research Institute in the late 1970s to produce locally calibrated predictions for grass growth rates around the UK. The calibrated model combines soil properties and daily weather data at a site to project grass dry matter yields in modelled harvests throughout a year. For this project, the model was fed with climatological data up to 2080 from the most up to date UKCP18 climate projections for the UK to produce predictions for the harvests under possible climate change scenarios.

The work suggests that although increased summer temperatures and reduced rainfall will lead to more droughtiness in the summer, grasslands may benefit from warmer temperatures earlier in the year and enhance growth rates driven by higher concentrations of CO2 in the atmosphere. Results suggest that in many – though not all – places around Wales, these two effects will approximately cancel out in terms of total annual grass dry matter yield.

Nevertheless, climate change may still have major impact on Welsh farming practices. Yield gains are predicted to occur in Spring only, with major reductions in yield from mid-summer onwards in a typical year. The work highlights possible changes needed to animal management to sustain livestock through future late summer periods in some areas of Wales.


For more information on grass growth modelling, please contact Dan Hobley.