Field beans could boost barley yields by 1.2t/ha, research finds

Growing field beans before spring barley could reduce environmental impacts by around 25%, cut nitrogen fertiliser use and boost cereal yields, new research suggests.

Scientists found that barley grown after beans delivered higher yields in four out of five years studied, while requiring an average of 22kg less synthetic nitrogen fertiliser per hectare.

The findings, from the James Hutton Institute and University of Galway, highlight the potential benefits of incorporating legumes into arable rotations.

Published in the journal *Plant and Soil*, the research analysed long-term cropping data from the institute's Centre for Sustainable Cropping at Balruddery Farm, near Dundee.

Researchers compared spring barley grown after field beans with barley following barley, examining crop productivity, fertiliser requirements and environmental impacts.

Across five two-year cropping periods, the bean–barley rotation reduced the environmental impact of barley production in four of the five periods, with an average reduction of around 25% across the crop sequences.

For arable farmers, the findings suggest that incorporating field beans into rotations could help reduce reliance on purchased fertiliser while maintaining productive cereal crops.

Field beans are legumes that work with naturally occurring soil bacteria to fix atmospheric nitrogen, meaning they do not require synthetic nitrogen fertiliser.

They can also leave residual nitrogen available for the following cereal crop, reducing its fertiliser requirements and potentially lowering production costs.

The research found that barley following beans achieved an average yield advantage of 1.2 tonnes per hectare in four of the five years examined.

However, the benefits were not consistent across every season, with barley following beans producing lower yields during the unusually dry conditions associated with the 2022 crop.

Researchers said temperature, humidity and the performance of the preceding bean crop could all influence the results.

Dr Cathy Hawes, who leads research at the Centre for Sustainable Cropping, said the findings demonstrated how improvements in farming systems could benefit successive crops.

She said: "These results show that the benefits of that approach can carry from one crop into the next, rather than being confined to a single growing season."

The centre's approach combines reduced tillage, organic matter inputs, cover and companion cropping, targeted pesticide use and nutrient budgeting to improve long-term sustainability.

Professor Pietro Iannetta, a co-author of the study, said assessing environmental impacts across entire crop rotations was essential to understanding regenerative agriculture.

He said: "This is an important study because there are still relatively few life-cycle assessments that look properly at crop sequences. That matters because regenerative agriculture is fundamentally about system function across time."

The findings could be particularly significant for Scotland's arable sector, where spring barley supports major brewing, distilling and livestock industries.

A theoretical assessment suggested that wider adoption of bean–barley rotations could deliver substantial reductions in greenhouse gas emissions, although researchers stressed that further testing across different soils, farms and growing seasons is needed.

Additional research is now underway to establish whether reduced environmental impacts are matched by measurable improvements in soil processes, nutrient cycling and biodiversity.