Mixing Beans Helps Growers and the Environment

Wed, 1, March, 2023 by Food from Thought

Mixed beans can mean higher yields and reduced risk for farmers and also help the environment, say University of Guelph researchers.

Traditionally, bean farmers have planted only a single variety of bean throughout their fields, says Dr. Peter Pauls, a professor in the Department of Plant Agriculture within the Ontario Agricultural College.

Farmers have looked for ways to increase environmental diversity such as planting hedgerows around their fields, he says.

“But that doesn’t really address the in-field issue. We thought, what about mixing pure bean lines? That would really increase the genetic diversity.”

For the past five years, his team, including post-doc Yarmilla Reinprecht and technicians Thomas Smith and Lyndsay Schram, have combined varieties of navy beans, kidney beans and black beans. They have experimented with planting mixtures within rows and in alternate rows and compared the results with pure lines of beans.

Benefits to farmers

“At the end of it, we concluded there was no penalty in terms of yield for mixing varieties, and sometimes the average yields of the mixtures were better than the pure lines,” says Pauls.

That’s a new idea for many bean plant breeders, who rely mostly on developing and evaluating pure varieties. This Food from Thought project suggests mixing varieties with different architectures and traits may pay off.

To study risk mitigation in one trial, the team planted white and black beans in alternating rows. Flooding killed the black beans but not the white ones.

“Instead of having a total crop failure, the white beans can fill in the rows, producing a pretty decent crop at the end of the day,” says Pauls. “For the farmer, it’s like building in insurance because they don’t know what the growing season will throw at them – it’s essentially hedging their bets.”

Environmental benefits

Greater crop diversity may also benefit the environment in various ways. Researchers are analyzing bean root samples to determine how mixtures affect beneficial soil microbes. Pauls says mixing purple-flowered black beans with white-flowered white beans may attract a wider variety of pollinators.

Increasing genetic diversity supports a broader mixture of organisms on the landscape, he says. “This is a pretty simple way to increase that genetic diversity right in the field.”

Economic benefits

Environmental benefits may also help Canadian exports. Beyond the agronomic and environmental pluses of mixing beans, says Pauls, more markets including the European Commission are demanding that crops they grow and buy are environmentally sustainable.

“Eighty per cent of our beans are shipped overseas,” he says.

Europe’s farm to fork policy currently applies to domestic production, but its parameters – including genetic diversity – may apply to imports from other countries, including Canada.

Pauls has discussed this research with growers at industry conferences and has published the team’s findings in a leading journal.

This story is a part of the 2021-22 Food from Thought Annual Impact Report