Drainage ditch

Achieving Cleaner Water Through Nitrate Loss Reduction

Laura with a pile of wood chipsLaura Christianson

Iowa State University

SARE grant: Producer Education of Nitrate Reduction Strategies and Evaluation of Acceptance (2009)

Where she is now: Assistant Professor of Water Quality, University of Illinois | Illinois SARE Co-Coordinator

The challenge is vast: The Corn Belt includes 38 million acres with tile drainage, and while tiling makes the land easier to farm, it also increases the amount of nitrate leaving fields and ultimately degrades the quality of Midwestern streams, rivers and lakes, and the Gulf of Mexico.

So, Laura Christianson turned her attention to strategies that can make tile drainage cleaner for Midwestern corn and soybean farmers. Using a 2009 SARE Graduate Student grant while at Iowa State University, she evaluated the costs, ecosystem services and farmer perceptions of seven nitrate reduction strategies: wetlands, controlled drainage, cover crops, crop rotation, fertilizer rate reduction, fertilizer timing modification and denitrification bioreactors.

Christianson also compiled cost-efficiency numbers, conducted surveys and held farmer discussion groups, collecting data that continues to inform her water quality work at the University of Illinois, where she is an assistant professor.

For example, the cost-efficiency numbers she compiled were used in the nutrient reduction strategies in Iowa and Illinois. These are research- and technology-based frameworks for coordinating state-level changes that reduce nutrient runoff. She views this as “a huge impact that I am really proud of,” Christianson says. “I did work as a graduate student that became part of state-level strategies impacting policy decisions.”

 

Cost Comparison

In her research, Christianson conducted a cost comparison of practices that reduce nitrate in drainage water, information that was incorporated into state-level nutrient reduction strategies for Iowa and Illinois. She found that although cover crops are more expensive per unit of nitrate treated than some of the other reduction strategies, farmers expressed more willingness to use them. Gaining in popularity nationwide, cover crops provide a wide range of ecosystem services and production benefits that go beyond nitrate loss reduction, such as soil retention, increased biodiversity and weed suppression. Learn about cover crops at www.SARE.org/cover-crops.

“I think a better understanding of the costs of conservation practices helps contribute to sustainable agriculture,” Christianson says. “But a better understanding of what farmers’ perceptions are of certain practices is important, too.”

Wood Chip Bioreactors

cover of woodchip bioreactor publicationChristianson researched denitrification bioreactors, trenches filled with wood chips through which drainage water is routed. She was drawn to this concept because of its simplicity; bacteria in the wood chips convert nitrates into nitrogen gas, and can remove 15-60 percent of the nitrate load from water that comes from fields. Bioreactors can be placed at field edges, requiring no land to be taken out of production. Although denitrification produces nitrous oxide, a greenhouse gas, research suggests it is a small amount of the nitrate entering the system, and through good design and management, emissions may be minimized.

Christianson produced the Iowa State University publication Woodchip Bioreactors for Nitrate in Agricultural Drainage.

Christianson produced the Iowa State University publication Woodchip Bioreactors for Nitrate in Agricultural Drainage.

Christianson's cost comparison of practices that reduce nitrate in drainage water was incorporated into state-level nutrient reduction strategies for Iowa and Illinois.

The Ag Water Management website features much of Christianson's work on wood chip bioreactors, at http://agwatermgmt.ae.iastate.edu/content/denitrifying-woodchip-bioreactors.

See scholarly publications at www.researchgate.net/profile/Laura_Christianson/publications.

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