Corn: No Fertilizer Necessary

Corn: No Fertilizer Necessary

As the demands on the global food supply increase, many commercial farms have switched from natural fertilizers like livestock manure to a synthetic nitrogen fertilizer, ammonium nitrate. Last year, American farmers sprayed more than 6.6 million tons of it. The problem with ammonium nitrate is that crops don’t absorb all of it, and that excess fertilizer has to go somewhere. It typically runs off into our water supply, leading to dangerous algal blooms, or evaporates as nitrous oxide, a greenhouse gas contributing to climate change.

Nitrogen is naturally and readily available in the atmosphere, but cereal crops like rice and corn can’t convert that atmospheric nitrogen into a usable form for fertilizer. The process of conversion is called nitrogen fixation, and it’s only possible for legumes like soybeans and peanuts. That’s because legumes have special structures in their roots where bacteria live, and those beneficial bacteria pull nitrogen from the air and convert it to a form the plant can use. In place of nitrogen fixation, farmers have to apply enormous amounts of chemical fertilizer to grow enough food to meet the growing demand.

In contrast to American farmers’ overuse of nitrogen fertilizer, people from the Sierra Mixe region of southern Mexico have been growing corn for thousands of years with barely any fertilizer, and their corn reaches heights of over 16 feet.

The Sierra Mixe corn looks nothing like the regular corn on the cob you buy at the grocery store. Its roots aren’t in the ground, but in the air, covered in a thick, dripping mucus loaded with bacteria. A collaborative team of researchers from UC Davis, the University of Wisconsin – Madison, and Mars, Inc. discovered the bacteria living in the mucus are capable of nitrogen fixation just like the bacteria in the roots of legumes. As a result, farmers can grow corn without putting any harmful ammonium nitrate into the environment.  

Sierra Mixe corn takes eight months to fully mature, compared to conventional corn’s three month growing period. That’s too long for Sierra Mixe corn to be a commercially viable crop, but researchers are hopeful the corn’s unique ability could potentially be transferred to more conventional varieties of corn through crossbreeding or physically transplanting the mucus from the Sierra Mixe corn to traditional varieties. Using these traditional methods of gene manipulation has the added advantage of avoiding the stigma of genetically modified organisms, which still face distrust from the general public.

The researchers still have a lot of work ahead of them before nitrogen-fixing corn is widely available, but the discovery is a promising development for increasing the global food supply, especially in developing countries where agricultural output is limited by the availability of fertilizer, and reducing the harmful environmental impact of spraying nitrogen fertilizers.

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