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Bioreactors zap tile line nitrates in pilot project

A good-sized gathering of representatives from the media, farm groups and conservation organizations gathered on June 11 at the Arlo Diest farm, near Webster City, Iowa, to watch the installation of a tile line bioreactor demonstration project.

Sponsoring organizations, including the Iowa Soybean Association, Agriculture's Clean Water Alliance and the Sand County Foundation, are hoping that bioreactors can make a significant contribution in the future to cleaning up streams, rivers, and drinking water supplies in Iowa and other farm states.

A bioreactor consists of a trench filled with a carbon source, in this case wood chips. As tile line water flows through the bioreactor, microorganisms break down the nitrate and expel the substance as a gas.

"The systems are easy to construct, relatively inexpensive, take little or no land out of production, and are believed to require little maintenance," according to a statement from the sponsors.

Farmer concerns about possible adverse effects on drainage and crop production are being addressed by the project, and so far -- in the case of the first installation last year -- no problems have been found, said Keegan Kult, an environmental specialist for the Iowa Soybean Association.

Early research has shown that a bioreactor can remove 25% to 35% of nitrate in tile line water. But, Kult said that the first bioreactor installed in Greene County, last year has cut nitrate concentrations by 60% to 70%.

The 12x100-foot, Boone County project, which is receiving water from a 40-acre tile pattern, will cost about $7,000 -- for the control structures, wood chips, fabric, and contracting work. The practice is being reviewed by USDA for funding eligibility.

Farmers have been "excited and supportive" about the bioreactor project, Kult said. Thus far, the bioreactors have maintained drainage, he says. Managers of the project are still "playing around" with the flow controls and design elements to get the best results.

"This is a pretty progressive step for a farmer to take," Kult said. Practices like terraces, conservation tillage, and grass waterways provide direct benefits for the farmer, he said. "This bioreactor is helping the people downstream."

A good-sized gathering of representatives from the media, farm groups and conservation organizations gathered on June 11 at the Arlo Diest farm, near Webster City, Iowa, to watch the installation of a tile line bioreactor demonstration project.

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