Converting farms from livestock to arable would lead to regular crop failures, some of the UK's top agri-scientists have warned.

As society is increasingly invited – or pressured – into shifting towards a more plant-based diet, it is common to hear campaigners claiming that land currently dedicated to grazing could produce much more food if it were instead dedicated to crops.

But a new study by Rothamsted Research, also involving SRUC, has challenged this easy assumption, and highlighted that some soil types and climates will not easily accommodate conventional arable farming.

The Rothamsted-led study focused on the southwest of England, and concluded that the chance of successfully growing winter wheat on fields once used to raise livestock could be as little as 28% in future, as increased rainfall will make field access for machinery impossible.

While forecasts show that in the absence of climate change, yields could be greater than 14 tonnes per hectare – but when the near certain impact of increased future rainfall on sowing and harvest dates were included in the simulation, it fell in some situations to less than three tonnes per hectare.

Lead author Dr Lianhai Wu said: “Adapting to the changing climate and changes in consumer demands will force us to diversify land from its current uses. Livestock grazing is the main type of farming across the west of the British Isles and it has been suggested that grasslands in the region could be converted to other land uses, such as growing cereal crops.

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“However, our simulations suggest that, for the southwest of England and regions under a similar combination of soil types and climates, planting winter wheat between October and December would be impossible in some years because of constraints on soil ‘workability’.”

The study, which also involved SRUC, looked at three soil types common across the southwest, under the current climate and three climate predictions from the Met Office, which show the number of heavy rain days – those with more than 2cm of rain – will increase in the southwest from six, to as many as 17 days a year, by the end of the century.

Delays to sowing and failure to harvest a crop in some years due to wet weather made the idea of conversion to arable a 'non-starter' for livestock farmers in the southwest, said Dr Wu: “But the question still remains – if we are going to eat less meat and rear less livestock, what happens to these farmers and these farming areas?”

The study also looked at the implications for soil carbon storage and greenhouse gas emissions if grassland cut three times a year to provide silage, was converted to winter wheat – and found that, whilst the average greenhouse gas emissions from soil growing ryegrass were higher than from the same land converted to wheat, this was compensated for by the greater amounts of carbon stored within the ryegrass.