Planting peas and other legumes alongside cereal crops could help make farming greener, ecologists at the James Hutton Institute say.
Intercropping, as it’s known, could cut greenhouse gas emissions by reducing dependence on fertiliser, as well as boosting biodiversity, food security and opening up new markets for local food and drinks businesses.
At the British Ecological Society’s annual meeting in Liverpool, Dr Pietro Iannetta of the James Hutton Institute discussed his research on intercropping.
This includes producing impressive crop yields without artificial nitrogen fertiliser – and inventing new ways of brewing and distilling with beans.
In crop trials, Dr Iannetta grew peas and barley together. Despite sowing the intercropped barley and peas each at a 50% rate and using no artificial nitrogen, he found that total yield exceeded that of barley grown alone.
Nitrogen is essential for good crop yields, and cereals are usually grown with added man-made nitrogen at around 110 kg N per hectare. But artificial nitrogen comes from fossil fuels, so has a high carbon footprint.
Emissions could be reduced by 420,000 tonnes CO2 equivalent if the 2016 UK spring barley cropped area (682,000 ha) were to be grown without artificial nitrogen – similar to planting over 420,000 trees a year.
This is because peas and other legumes fix their own nitrogen. And when grown with other crops such as barley, the peas supply the cereal’s nitrogen needs.
Agriculture contributes around 15% of greenhouse gas emissions, so finding new ways to curb this contribution to climate change is important.
Farming also needs to diversify by growing a wider range of crops and develop new markets for local, sustainable food and drinks.
Western agriculture depends on a narrow range of crops, including wheat, barley and potatoes. By adding more legumes to the mix, intercropping would boost diversity, making farming more resilient as well as less dependent on fossil fuels.
To find new markets for a larger legume crop, Dr Iannetta is also developing new ways of turning peas and beans into alcohol.
“Beans are notoriously difficult to ferment, but we have discovered a way of doing this by neutralising the fermentation inhibitors,” he explains.
He has teamed up with enzyme expert Professor Graeme Walker of Abertay University, Barney’s Beer in Edinburgh and Arbikie Distillery in Arbroath, to develop ‘Tundra’ – a beer made from 40% whole faba beans.
“Tundra is a wonderful, heavily hopped American IPA. By turning pulse starch into fermentable sugars and alcohol from 40% beans intercropped with 60% barley – we have produced a beer using 40% less artificial fertiliser,” says Dr Iannetta.
Their research is particularly relevant in Scotland, where 60% of all non-grazing arable land is used to grow barley, around half of which is for malting and distilling.
“Minimising the amount of artificial nitrogen used to grow barley would save carbon, save money and deliver Scottish whisky – the UK’s greatest export and tax revenue resource – in a more sustainable way.”
“The public wants healthier food that is grown more sustainably. It’s great that shops are now selling grain legume-based crisps and bread, but I wish they used more home-grown legumes. There is a huge opportunity for small growers to diversify and shorten their supply chains by developing their own high-quality legume-based products.”
The final benefit of their fermentation process is that it also produces a high-protein by-product, which could be used to make fish farming more sustainable.
In 2017, he hopes to have commercially-available green beers and neutral spirits. “These will have been produced using no man-made fertilisers, and give co-products that provide sustainable and profitable protein production for the food chain,” he concludes.
