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Nfixing-corn-roots800.jpg Jean-Michel Ané
This tropical corn found in Oaxaca, Mexico, grows to 15 feet and has gel-oozing brace roots up and down its stems. The gel helps capture nitrogen that feeds the plant.

Nitrogen-fixing corn is farming’s holy grail. But when?

Groundbreaking research could dramatically lower farmer costs and protect groundwater.

Around the turn of the last century German chemists Fritz Haber and Carl Bosch advanced a moonshot idea that likely saved mankind: converting atmospheric nitrogen in to ammonia fertilizer. That unleashed the age of synthetic fertilizer leading to higher crop yields and bountiful food supplies for a growing world population.

Now, over a century later, scientists are again looking to at another moonshot: making a corn plant that can get much of its own nitrogen from soil and air. Such an invention could save farmers money, keep more fertilizer from running into drinking water, and boost corn yields in places where farmers can’t afford synthetic fertilizers.

Outlandish? They’re working on it right now on at least three fronts, with some products on or nearly ready for market.

Microbial or biological products have been on the market for some time now, mainly to protect soybean roots and ward off disease. More recently microbial-based products have appeared on the market to boost soil fungi mycorrhiza that help corn roots take up moisture and nutrients.

One giant leap

You might say these efforts are one small step for man; what’s coming next will be one giant leap for mankind.

In 2018 field trials for PivotBio’s N-delivering microbes applied in-furrow during planting, users cut applied commercial nitrogen by 35 pounds per acre resulting in yields nearly identical to the traditional check fields. PivotBio’s ‘Proven’ is available commercially this year in selected states (for more, see article).

At Joyn, a biology engineering company that is a joint venture between Bayer and Ginkgo Bioworks, they’re engineering soil microbes that will feed nitrogen to crops from the air and soil, potentially cutting the use of synthetic fertilizers in half and stretching their use much further into the future.

Meanwhile researchers from University of California Davis, University of Wisconsin-Madison and Mars, Inc., last summer discovered a tropical corn in Oaxaca, Mexico that can acquire significant amounts of nitrogen from the air by cooperating with bacteria. The corn secretes mucus-like gel from aerial roots; the gel harbors bacteria that converts atmospheric air into a form usable by the plant.

That corn can acquire up to 80% of its nitrogen needs this way, but the future effectiveness depends on factors such as humidity and rain, and scientists are still a good 5 to 10 years away from breeding that trait into a useful hybrid for the northern hemisphere.

Long-held dream

It has long been a dream for scientists and farmers to find a way to get cereals like corn to fertilize themselves. And the need to do so grows more urgent each day.

“Everybody wants to find alternatives to synthetic chemical fertilizers,” says Joyn’s CEO Mike Miille. “The greenhouse gas to produce it, and environmental effects of runoffs, have gotten to the point where people are concerned. It’s not sustainable.

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“Everybody wants to find alternatives to synthetic chemical fertilizers,” says Joyn CEO Mike Miille. “The greenhouse gas to produce it, and environmental effects of runoffs, have gotten to the point where people are concerned.” Photo by MIke Wilson

“Among growers there’s concern about when regulations are coming - where it will be limiting, all in a world where we’re trying to grow productivity,” he adds.

More than one percent of the world’s total energy production goes to produce nitrogen fertilizer. Developed countries contend with waterways polluted with leaching nitrogen, while adequate fertilizer is often inaccessible or too expensive for farmers in developing countries.

In the case of the Mexican corn, researchers hope it can be developed into a plant that can do a good job hosting microbes, explains Jean-Michel Ané, professor of bacteriology and agronomy at University of Wisconsin-Madison.

“Often when plants associate with nitrogen-fixing microbes, the plant is the limiting partner,” he says. “We have good nitrogen-fixing microbes pretty much anywhere; the problem is, the plants we are using are not good hosts for these microbes. For them to fix nitrogen they need to have energy, to be fed, and be in a low oxygen environment to fix nitrogen.”

The researchers were shocked at what they found in Mexico, where 15-foot high corn plants had 8, 10 or more nodes on several brace roots up and down the stem. These roots make the gel that provide a good environment for nitrogen-fixing bacteria.

“We just weren’t looking for this,” notes Ané. “When people think about having a better host for nitrogen fixation, they think of nodules, and corn doesn’t form nodules. The corn we found had not been well-characterized before and nobody thought nitrogen-fixation could happen so efficiently on these brace roots.”

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“The corn we found had not been well-characterized before and nobody thought nitrogen-fixation could happen so efficiently on these brace roots,” says University of Wisconsin-Madison professor Jean-Michel Ané.

Several factors work against adapting the Mexican hybrids. Besides their tall stature they need a nine-month growing season. Right now, that corn wouldn’t grow well in the northern latitudes, so the researchers will try to breed the N-fixing trait into more conventional varieties.

“That’s going to take at least five, possibly 10 years,” Ané says. The first question will be how much nitrogen can we really save by using that type of corn? And, will you get a nitrogen benefit to the soil, much as you do with soybeans? These are practical agronomic questions.”

Getting that trait to market might go faster with genetic engineering, but the researchers don’t have enough genetic information yet to go that route.

“If we knew right away which genes we need to modify to get the trait, then yes, I would go for gene editing, but we are still figuring out all the genes necessary for the trait,” says Ané. “We are not putting all our money on gene editing because we know breeding works.”

Building a microbe ‘chassis’

The Mexican corn is an exciting story, but there are different approaches that work toward the same goal-- some focused on the host plant, and some on microbes. Joyn’s plan is to engineer microbes with full characterization so that users know exactly what they can do. The Joyn researchers expect these microbes to perform “at significantly higher levels” than products currently on the market.

“We have an idea to go in and engineer the microbe and optimize it to convert nitrogen to a useable form to where we could replace 30% to 40% of commercial fertilizer,” says Miille.

“This is clearly a moonshot, but it’s not totally crazy,” he adds. “We know we have microbes that fix nitrogen and microbes that transfer nitrogen to the plant; the question is, can you engineer a microbe in such a way as to cut commercial fertilizer needs by 30% or more?”

For Joyn that’s just part of the equation. The company wants to engineer several chassis not just for nitrogen but also for other crop needs to ward off disease and pests – all through microbes.

“That microbe becomes a delivery mechanism,” says Miille. “You are programming it to deliver in a highly selected and targeted way."

This would be a whole new way forward for crop disease and insect protection.

“You’re no longer spraying chemicals on a plant. Rather, you’re programing microbes with selected enzymes and proteins, to take care of these crop problems,” he says.

Joyn expects to show data to the world within 2 years. The process will soon move to field trials in corn.

“Eventually we want a grower to say, ‘I can cut my synthetic fertilizer use 50% and get the same yield,” says Miille.

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This unique nitrogen-fixing corn found in Mexico has N-fixing brace roots up and down its stalk. Photo by Jean-Michel Ané
Rethinking food

Because of Europe’s restrictive regulatory approach to biotechnology, Miille says he doesn’t believe the Joyn microbes will ever be sold there. On the other hand, there is a clear path to registration in the U.S., Asia and Latin America.

But, will consumers accept these new approaches, in 5 or 10 years when products are headed to market? Miille is wary, but optimistic.

“Scientifically there’s a significant difference in the use of the acronym GMO in plants and what we’re doing,” he says. “For a lot of people, they are fundamentally opposed to GMO and biotech, and not interested in reasons why there are different types of genetic engineering. Their approach is very emotional.

“If you walk in to that setting using science, you fail.”

It’s better, he adds, to start and end every discussion conveying the benefits. “Once people understand there is a significant benefit – to lower commercial fertilizer and better environment - then their approach and attitude is very different,” he says.

“If we get to market with these products and they substitute for chemicals, people will change their views on what is and is not organic production,” he says. “You can bring the argument back to, were chemicals used in making this crop?

“I do believe ag needs new solutions to their problems,” he adds. “Whether it’s nitrogen fixation, crop protection or food quality – can we imagine a day where some of these microbes are used to minimize spoilage, rot and waste, extend shelf life in the store by fighting bacteria, or allow food to last longer in your refrigerator?

“We believe microbes are going to be a critical part of ag in 2030, 2040, 2050,” he says.

For University of Wisconsin researcher Ané, commercializing an N-fixing corn trait is a dream with worldwide benefits.

“We would use it not only here but everywhere,” he says. “In the U.S. it will be useful to help reduce the environmental impact of commercial fertilizer, and in developing countries it would be good for people who can’t afford or don’t have access to commercial fertilizer.”

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