"Environment" research area

Repurposing Drainage Ditches to Remove Nitrogen

Principal Investigator - Jeffrey StrockPrimary InvestigatorJeffrey Strock
Co-Investigators: Satoshi Ishii, Hao Wang (Graduate Scholar)
Industry Partners:  Minnesota Drainage Viewers Association, I&S Group, Inc. (ISG), Minnesota Department of Agriculture, Sand County Foundation, and USDA Natural Resources Conservation Service
Award Type: Seed Grant - Graduate Research Scholar

Problem: Drainage ditches on agricultural land improve field drainage efficiency by providing preferred flow paths for excess water. However, the increased flow rates do not allow dissolved nitrogen and phosphorus time to react, bind, or be absorbed by ditch sediment/soil or vegetation. These ditches transport high concentrations of nutrients and other contaminants into nearby streams and rivers, which degrades local and downstream ecosystems.

Solution: If drainage ditches behaved more like natural wetlands (chemically, biologically, and microbiologically), they could remove higher levels of nitrogen from field runoff, both through denitrification and plant uptake. Strock and his team will engineer and install low-grade weirs (aka - low dams) at a field site near Lamberton, with the goal to modestly raise upstream water levels, decrease flow velocity, and thus enhance nitrogen removal. The laboratory component of the project will analyze biological and microbial communities effective for nitrogen uptake within their low-grade weir design, with a focus on cold-climate denitrifiers.

Impact: Each year roughly 60 million pounds of nitrogen flows through drainage ditches leading to the Minnesota River. Improving the ability of drainage ditches to naturally remove more nitrate offers a low-cost solution to one of Minnesota’s most persistent environmental challenges. If successful, not only will this solution decrease the amount of dissolved nitrogen in Minnesota’s major waterways, but it would also decrease the amount of dissolved nitrogen leaving Minnesota via the Mississippi.