Farming - Rising fertiliser price does amount to a hill of beans

In the first country-wide field-scale investigation of its kind, Scottish researchers have found that field beans can incorporate more than 400kg of nitrogen per hectare.

The spiralling costs of bagged fertilisers and the search for more carbon efficient methods of supplying crops with nutrients - along with the race to reduce the livestock sector’s reliance on imported soya - have led to a renewed interest in the role which domestically grown field beans and other legume crops can play in fixing nitrogen.

The team of researchers at the James Hutton Institute said that the symbiosis between legume crops and soil bacteria allows the harnessing of naturally occurring atmospheric nitrogen while reducing the need for added inorganic nitrogen fertilisers.

“The crops also provide nitrogen to the production system after harvest and the residual stems, roots, and pods decay into the soil as a natural fertiliser, and general soil improver,” said Prof Euan James, a research leader at the Institute’s Ecological Sciences department and co-author of the study.

The study looked at the levels of nitrogen fixation in a range of different farm types across the country using a range of production systems, from Orkney to the South of England - and was backed up with intensive field-scale investigations the JHI’s Centre for Sustainable Cropping (CSC) at Bulruddery farm on the outskirts of Dundee.

“These results are a first for Scotland and the UK and demonstrate that in addition to their value as a high-protein crop, beans can be used to help reduce costly and environmentally damaging fertiliser nitrogen inputs into arable systems,” said Prof James.

“This demonstrates the huge potential grain legumes such as faba bean could provide in achieving zero-carbon agriculture, as well as meeting Scotland’s ambitious greenhouse gas emissions reduction targets.”

Agroecologist and legume specialist with the Hutton, Dr Pete Iannetta who was also authored the report added: “The ability of beans to fix nitrogen from air presents an opportunity by which the environmental damaging impacts of excessive synthetic nitrogen fertiliser use may be avoided.”

He said that access to long-term whole-system datasets of the CSC, which is managed by Dr Cathy Hawes played an important role in verifying the findings:

“There is nothing like it globally for agroecological studies of arable cropping,” said Iannetta, “This, allied to a fantastic team of collaborators from across the UK, including farmers – has allowed us to achieve a strong foundation for future environmental impact assessments.”

The sustainable cropping facility was established in 2009 to design an integrated cropping system for multiple benefits and test the long-term impacts on biodiversity and whole-system sustainability.

Commenting on the weather driven boom-bust cycle of bean growing in Scotland, Iannetta said that there was no real breeding programme aimed at producing varieties for Scotland’s maritime climate – but he said that the institute assessed varieties for their suitability – adding that seed from a ‘Scottish bean’ which had both early maturing and dwarf characteristics which had been donated to the Institute was currently being multiplied up for further assessment and possible national listing.