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Cover crops effective at reducing nitrate concentrations in tile-drained water


May 6, 2022
By Drainage Contractor

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Nutrient runoff from tile-drained fields remains a concern in the Midwest and beyond, and many in the industry are always looking to mitigate those effects. Recent research from Iowa State University shows that cover crops were almost as effective as restored prairie at reducing nitrate concentrations in tile-drained water.

The study, led by associate professor Marshall McDaniel, looked to understand how tile drainage water impacts in-stream potential for nutrient enrichment, leading to growth of algae and depletion of vital oxygen in aquatic ecosystems. With subsurface tile drainage used in nearly half of midwestern farm fields and some delivering nutrient-laden water directly to waterways, McDaniel says a complex study process was required to study a complex issue.

“It’s not easy to study streams. They are dynamic biologic systems that tend to vary rapidly over space and time,” McDaniel said in an Iowa State report. “Different types of streams also have unique characteristics, including their own unique history of prior nutrient loadings. This likely affects how streams respond to land-use changes within their watershed – sometimes in surprising ways.”

The study found that tile-drained water from cover crops and restored prairie caused less algal growth. McDaniel says the positive effects of the cover crop were almost as strong as the prairie overall.

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For more detailed results and study methodology, the final report is available through the Iowa Nutrient Research Center website.