Environmental Performance of Wetlands Receiving Non-Point Source Nutrient Loads: Benefits and Limitations of Targeted Wetland Restorations

Iowa Learning Farms hosted a webinar on Wednesday about the results from 15 years of research on Iowa Conservation Reserve Enhancement Program (CREP) wetlands, including nutrient removal, greenhouse gas emissions, and hydrology. The research presented in this webinar is one of the largest and longest running projects of its kind and helps to clarify the potential benefits and limitations of targeted wetland restorations. The research methods are also being used to monitor the impact of in-field practice changes through the Conservation Learning Lab project.

The location of the sites for wetland performance monitoring during this project

Iowa’s landscape used to be covered in wetlands, but these have been extensively drained to allow for agriculture and development. Drainage networks are the primary pathways that nitrate moves across the landscape and into surface water. By routing drainage lines into treatment wetlands, these wetlands can remove nitrate from subsurface drainage, especially when they are constructed in targeted areas.

Targeted wetland restorations have the opportunity to intercept drainage networks to remove nitrogen

William Crumpton, University Professor at Iowa State University, also discussed greenhouse gas emissions from wetlands and the phosphorus removal performance of treatment wetlands that receive non-point source loads during the webinar. He emphasized the importance of targeting wetland restorations. Wetlands that are established for habitat in upland areas do not have the opportunity to intercept tile flow, and therefore can only remove low amounts of nitrate. If wetlands are sited strategically in downslope areas to intercept tile flow, then their removal of nitrate dramatically increases.

Upslope wetland sites only remove about 1.9 metric tons of N, while downslope wetland sites are able to remove about 17 metric tons of N.

To learn more about this research project and the effectiveness of targeted wetlands that receive non-point source nutrient loads, watch the full webinar here.

Join us next week on Wednesday, July 1 for a webinar titled “Optimizing Yields of Corn Planted After a Cereal Rye Cover Crop” presented by Alison Robertson, Professor & Extension Field Crops Pathologist at Iowa State University.

Hilary Pierce