Mutant Legumes Provide Key to Chemical-Free Fertilizer

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Stanford University Researchers use legumes to find key to reducing chemical fertilizers and greenhouse gassesScientists at Stanford University have come up with another reason to eat your beans, or at least to appreciate them: a study of mutant legumes has yielded an important clue that could help reduce global dependence on chemical fertilizers.  As reported by Louis Bergeron for Stanford, that’s a green twofer: it could help reduce algae blooms caused by fertilizer, and it could reduce greenhouse gasses caused by fertilizer.


Sort of ironic, isn’t it?  We’re used to thinking of legumes like beans as the cause of noxious gasses (for proof, check out that classic scene in Blazing Saddles), but on a global scale they could very well help provide a cure.

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Beans and Fertilizer

If you remember anything about science class from elementary school, you might remember that beans and other legumes capture nitrogen from the air and turn it into ammonia to feed themselves.  As Bergeron reports, the process involves a bacteria that is the only living organism capable of drawing nitrogen from the air.  Farmers have used this property for thousands of years, rotating beans with other crops to keep the soil enriched, but until now the actual mechanics of it have been something of a mystery.

Stanford University and Mutant Legumes

The Stanford researchers conducted their study on an alfalfa-like legume called barrel medic (also called barrel clover).  Specifically, they looked at mutant plants that seemed to have all the right equipment to fix nitrogen but were not getting the job done.  Working from there the researchers found that an enzyme was missing from the end of the process, meaning that the bacteria were not receiving a signal to fix nitrogen.  The next step was to compare the genomes of mutant and normal plants, which revealed that a missing gene was the cause.

Fertilizer, Algae Blooms and Greenhouse Gasses

It’s common knowledge that chemical fertilizers run off into waterways, adding nutrients that cause populations of algae to explode.  The introduction of strains of legumes and possibly other plants that are highly efficient, natural nitrogen fixers could help relieve farmers of the need to add chemical fertilizers.  In developing countries, that would help relieve cash-strapped farmers from the expense of purchasing fertilizer, and it would also reduce the carbon footprint involved in manufacturing, shipping, and spreading fertilizer.  It could also make a significant dent in emissions from decomposing fertilizer, particularly nitrous oxide — a particularly potent greenhouse gas which according to the U.S. EPA has heat trapping effects more than 300 times that of carbon dioxide.  Quick, pass those beans!

Image: Beans by Bohman on

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Tina Casey

Tina specializes in advanced energy technology, military sustainability, emerging materials, biofuels, ESG and related policy and political matters. Views expressed are her own. Follow her on LinkedIn, Threads, or Bluesky.

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