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Sierra Mixe Nitrogen-Fixing Corn

Most corn grows small “prop” roots, but Sierra Mixe corn uses them for nitrogen fixing, too. Photo by Flickr/Ton Rulkens.

A joint research team from the University of California, Davis; the University of Wisconsin, Madison; and Mars, Inc. recently described a landrace of corn in the Sierra Mixe region of Mexico that doesn’t just survive in low-nitrogen soil — it thrives. The cultivar looks quite unfamiliar compared with the mass-produced, conventional cultivars in the United States, growing more than 16 feet tall. It grows much more slowly than conventional corn as well, taking about nine months to reach maturity, rather than conventional corn’s three.

However, the most remarkable thing about the Sierra Mixe corn is how it obtains most of its nitrogen.

Sierra Mixe corn grows 8 to 10 aerial roots — rather than the one or two grown by conventional corn — that secrete a sugar-rich mucilage, which attracts nitrogen-fixing bacteria that then convert aerial nitrogen into a more usable form. In a simplified sense, the corn fixes nitrogen from the air, rather than the soil.

Incredibly fascinating in its own right, this corn also holds some serious potential for sustainable agriculture down the line. Nitrogen fertilizers are often financially inaccessible in developing countries, and producing them requires about 2 percent of the world’s energy supply, which contributes to global greenhouse gas emissions. If the Sierra Mixe corn’s nitrogen-fixing trait could be bred into cheap, conventional cultivars, it could dramatically increase yields in nitrogen-poor areas and eliminate the need for costly nitrogen fertilizers. It would also mean a more sustainable way to grow one of the world’s most mass-produced crops, and greater food security for developing nations.

Published on Feb 26, 2019

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