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When Joel Mathiowetz started planting corn this spring on his farm near Morton, Minn., he added the usual starter fertilizer to boost plant growth. But then he added something new: bacteria, right there in the soil alongside the corn seeds.

Mathiowetz is one of a handful of farmers in Minnesota who are testing the approach on their corn fields. The bacteria, which have been genetically modified and developed by California-based Pivot Bio, will help the corn plants convert nitrogen from the atmosphere into a form the corn plants can use as fertilizer. The idea is to eventually replace synthetic nitrogen fertilizer with microbes.

They're not commercially available in Minnesota yet, but Mathiowetz is in his second year of testing the microbes on his farm. 

It's a fairly simple process: "I push some fish food-looking material into a solution and activate the microbes prior to applying it to our field," said Mathiowetz, who raises corn, soybeans and peas with several family members on 2,500 acres in southern Minnesota.

Last year, the test plots where he used the microbes produced six bushels of corn more per acre than the fields where he used only fertilizer.

It's a symbiotic relationship. As the corn starts to grow, the bacteria attaches to the roots of the plant. It then feeds on a sugar in the corn roots and converts nitrogen in the air into a form the plant can use as fertilizer.

There's nothing new about this process. Bacteria have evolved over millennia to have these symbiotic relationships with plants. By making sure the plants grow well, the bacteria ensure themselves a food source. 

But agriculture has upset that balance by adding increasing amounts of synthetic nitrogen to the soil, said Sarah Bloch, Pivot Bio's associate director of research.

"The challenge is that nitrogen fixation requires a lot of energy. When there's nitrogen present, the microbe is really efficient at turning off those genes so that it can save that energy," she said.

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So with abundant nitrogen already in the soil, the bacteria feed off the corn roots, but don't help plants use that naturally occurring nitrogen. 

Plants need nitrogen in the soil, which usually comes in the form of fertilizer, to help them thrive. But synthetic nitrogen is a common source of water pollution. 

There's growing interest among farmers and ag industry in finding ways to improve the health of soil and reduce the use of nutrients like nitrogen and phosphorus, which contribute to degraded water quality in lakes and streams.

"We want to solve a specific problem, which is the negative impacts of synthetic nitrogen on the environment," said Bloch.

So, Pivot Bio found a nitrogen-fixing bacteria that had already evolved to live on corn roots, and tweaked its genes so it would not turn off its nitrogen-fixing action, even when there's abundant nitrogen in the soil. The company claims it's the first nitrogen-enhancing microbe of its kind on the market. It's being offered in 25 states — and sold out this year.

Mathiowetz is among a group of farmers who are paid to test the microbe and collect data on the test plots, but he's looking at this product the same way he considers any new technology.

"We're always skeptical of new products that are coming to our farms," he said. "We're always skeptical of new technologies and how they may or may not help us and the consequences or unintended consequences that they may have." 

But he says he sees promise in the microbes. They won't replace nitrogen fertilizer yet, but this year on his test plots, he plans to skip a side-dress fertilizer application — additional nitrogen that's typically added when the corn is a few inches tall. Skipping that step will save him time and money. 

And he's still keeping a close eye on the results. He said: "Is there a cost savings? Is there a nitrogen savings? Is there an application saving? Does this provide an opportunity for our crop to a grow to a greater potential?"

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Bloch and her colleagues at Pivot Bio hope this product is a first step in replacing synthetic fertilizer with microbes. The ultimate goal is to modify microbes that will provide all of the nitrogen crops need.

"We think that we can make a product that can both provide enough nitrogen and maintain profitability enough for a farmer that they will eventually shift to reducing the application of synthetic nitrogen," said Bloch.

She admits such a shift would take some time. The interactions among the billions of microbes in soil are still not well understood — and some skeptics doubt that science can tame the still largely unexplored soil microbiome — but Bloch said she thinks the company will succeed by narrowly focusing on a few microbes that are good at fixing nitrogen.

And Pivot Bio has attracted investors with deep pockets, including Monsanto and the Bill and Melinda Gates Foundation, and Bloch said the company plans to develop nitrogen-fixing bacteria for crops beyond corn.  

Mathiowetz still isn't sure if he'll buy the bacteria to use on his farm when he's done with the testing and it's commercially available in Minnesota. But, he said, if the technology proves it has financial and environmental benefits, he expects to be activating microbes again next season, before he puts his corn seeds in the ground.

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Farmers across the country are putting a genetically modified bacteria in the ground this spring to help corn plants use naturally occurring nitrogen. The goal is to eventually replace synthetic nitrogen fertilizer.

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