Pea and Bean Varieties Could Shape Soil Health and the Next Harvest

New research suggests differences in crop residues could give breeders another selection criterion: how a variety supports soil processes and the crop that follows.

Selecting pea and field bean varieties could influence more than the pulse harvest. New research suggests the stems, leaves and roots left behind can affect soil microbial activity, nitrogen availability and the growth of a subsequent barley crop.

Researchers from The James Hutton Institute and the Universidade Católica Portuguesa in Porto found that these effects depended on the variety, the characteristics of its residues and the amount returned to the soil. The study, published in Plant and Soil, points to potential opportunities to breed pulses for their contribution to the wider crop rotation.

“Understanding genuinely regenerative cropping systems demands more detail regarding the chemical nature of crop residues, how much is returned, when it is returned and how it interacts with soil biology and the crop that follows,” said Professor Pietro Iannetta of The James Hutton Institute, a co-author of the study.

Different Varieties Leave Different Soil Legacies

Peas and beans are already valued for their ability to acquire nitrogen through biological fixation, reducing reliance on manufactured fertilisers. The research suggests their chemical diversity may also influence soil processes after harvest.

Moderate amounts of residue from some varieties increased microbial activity, improved nitrogen availability and supported barley growth comparable to that achieved with synthetic nitrogen fertiliser, according to a press release.

Very large amounts had the opposite effect, reducing microbial activity and nitrogen availability and slowing barley growth. However, the highest amounts tested were far above those typically found on farms and were included to help researchers understand the underlying processes.

The differences between varieties suggest breeders could consider benefits to subsequent crops alongside established selection criteria such as yield and disease resistance.

Plant Compounds Add a Breeding Consideration

Iannetta is particularly interested in phenolics, naturally occurring plant compounds that can play protective roles in soil and gut health.

“Such phytochemicals – the naturally occurring chemicals present in, or extracted from, plants – are being bred out of the most cultivated pulse crop varieties for mainly monogastric (farmed chicken and pig feed) markets. Consequently, we should work to understand the impacts and trade-offs of this major influence.”

Residues rich in phenolics appeared to change how nitrogen was used below ground, making it available to plants over a longer period. The finding highlights the importance of understanding how breeding decisions affect both a crop’s intended market and its role in the rotation.

Field Research Needed to Test Longer-Term Benefits

The study examined only the first eight weeks of barley growth under controlled conditions. Further field research will be needed to establish how the effects develop across growing seasons and under practical residue levels.

The team also wants to investigate impacts on greenhouse gas emissions, soil carbon storage and long-term soil health.

For breeders and growers, the findings suggest that a pulse variety’s value may extend beyond its own yield to the soil conditions and growing opportunities it leaves for the next crop.