Long-term research from Scotland found that including field beans in cereal rotations could reduce environmental impacts by about 25%, lower nitrogen fertiliser requirements and improve barley yields in most years studied.
Growing field beans before spring barley could reduce fertiliser use, lower environmental impacts and improve crop yields, according to new research from The James Hutton Institute and the University of Galway.
The study, published in Plant and Soil, examined long-term cropping data from the institute’s Centre for Sustainable Cropping (CSC) at Balruddery Farm near Dundee, Scotland. Researchers compared spring barley grown after field beans with barley grown after barley to assess how crop rotations influence productivity and environmental performance.
Across five two-year cropping periods, growing field beans before barley reduced the environmental impact of barley production in four of the five periods. Overall, environmental impacts were approximately 25% lower across the crop sequences, according to a press release.
Dr. Cathy Hawes, who leads research at the CSC, said the findings demonstrate the value of assessing agricultural practices over multiple growing seasons.
“The CSC was established to test what genuinely regenerative cropping can look like in practice,” Hawes said. “Rather than relying on a single intervention, CSC stacks a series of complementary innovations including reduced tillage, organic matter inputs, cover and companion cropping, more targeted pesticide use, nutrient budgeting and biodiversity-supporting field features with the aim of maintaining productive farming while reducing reliance on external inputs and improving soil condition, biodiversity and wider environmental performance over the long term.
“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.”
Field Beans Reduce Nitrogen Requirements
A major benefit of including field beans in cereal rotations comes from their ability to fix atmospheric nitrogen through a relationship with naturally occurring soil bacteria.
Unlike cereal crops, field beans do not require synthetic nitrogen fertiliser, reducing one of the major sources of environmental impacts associated with crop production. They can also leave residual nitrogen in the soil that benefits subsequent crops.
The study found that barley grown after field beans required an average of 22 kilograms less synthetic nitrogen fertiliser per hectare than barley grown after barley.
Pesticide use could also be substantially lower following field beans, contributing to the reduced environmental footprint of the rotation.
Barley Yields Improve in Most Years
Researchers also identified potential productivity gains from including field beans in cereal rotations.
In four of the five years examined, spring barley grown after beans produced an average of 1.2 tonnes per hectare more than barley following barley.
However, the benefits were not consistent under all growing conditions. During the unusually dry conditions affecting the 2022 barley crop, barley following field beans yielded less than barley grown after barley.
The findings suggest that weather conditions, particularly temperature and humidity, along with the performance of the preceding bean crop, influence how much benefit a subsequent cereal crop receives.
Assessing the Long-Term Benefits of Crop Rotations
The researchers emphasized that evaluating individual crops in isolation can overlook important benefits that emerge across an entire rotation.
“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,” said Professor Pietro Iannetta, co-author of the study.
“The next challenge is to go beyond measuring impact reduction alone and ask whether those reductions are matched by real gains in ecosystem functions, including soil processes, nutrient cycling and biodiversity.”
Additional life cycle assessment research is underway at the CSC to examine how reductions in environmental impacts relate to measurable changes in soil health, nutrient cycling and other ecosystem functions.
“Further advanced life cycle analysis (LCA) work is now underway at the CSC to link reductions in environmental burdens with measured changes in ecosystem functioning. That should help us move from saying a system uses fewer inputs, to demonstrating whether it is genuinely delivering regenerative outcomes.”
The findings have particular relevance for Scotland, where spring barley supports the brewing, distilling and livestock industries.
A theoretical assessment included in the study suggested that wider adoption of bean–barley rotations could deliver substantial greenhouse gas reductions at a national scale. However, researchers cautioned that these estimates require further testing across different soils, farming systems and growing seasons.
The study suggests that incorporating legumes into cereal rotations could help farmers reduce reliance on synthetic fertilisers while maintaining productivity, although the benefits depend on growing conditions and how the rotation is managed.
