A new study of long-term data from a Hertfordshire pasture, conducted by Rothamsted Research and the University of Reading, suggests that spring hay yields in southern England have reduced by more than a third due to climate change, with further declines forecast.
Published in the Journal of the Royal Society Interface, the research indicates that animal fodder yields from grassland have fallen by 35% over the last century. The data was collected between 1902 and 2016 from the Park Grass experiment at Rpthamsted’s main site at Harpenden.
Furthermore, the study forecasts that climate change will reduce the spring hay yield by between 20% and 50% by 2080.
The statistical modelling takes into account unusual patterns of yield variability, however, the results show a wide forecast range primarily due to uncertainty over future greenhouse gas emissions. The model did confirm that warmer and drier autumns, winters and springs have reduced yields, with optimum spring weather being colder and wetter than what we are seeing now.
Dr John Addy, a statistician at Rothamsted Research and the study’s lead author said: “The precise response of spring hay yield to temperature and rainfall varied during the year but there is an optimum “Goldilocks” spring rainfall and temperature associated with the maximum level of yield. Changes in autumn and winter temperature had more of an effect on yield than autumn and winter rainfall.”
Managed grassland is the UK’s largest crop by area, covering some 12 million hectares. It underpins the livestock sector, which is worth over £13 billion annual, with spring hay and silage being used as winter feed and during summer droughts, as is the case this year.
Professor Richard Ellis of the School of Agriculture, Policy and Development at the University of Reading added: “The one hundred and fifteen years of results from the Park Grass experiment allow us to analyse the consequences of the previous year’s weather on yield. There is a substantial legacy effect in this perennial crop: if the weather in one year is poor for hay yield, then yield in the following year is also reduced to some extent and vice versa. This is highly relevant to the resilience of farming businesses.”
The projections are specific to the Park Grass site, but the design of the experiment means that a range of grassland systems are studied. Plots include high fertiliser inputs, farmyard manures and some with no additional inputs. The effect of climate change was said to be remarkably similar across the treatments.
“Many livestock farmers in the region have already responded to change – the increase in the area of forage maize over the past half-century being but one example, but future investments in milk production from grass are more likely to favour the wetter and cooler regions of the UK,” concluded Professor Ellis.