In the Upper Mississippi River Basin, cereal rye is still king when it comes to cover crops. Additionally, this winter hearty grain is the focus of most of the water quality research done surrounding cover crops in this region. When it comes to cleaning up nutrient rich water causing Hypoxia in the Gulf of Mexico, state developed Nutrient Reduction Strategies are leaning on cover crops to help reduce nitrogen and phosphorus making it to the Mississippi River. Cereal rye is the “grass-based” cover crop forming the basis of the Nutrient Reduction Strategies for Illinois, Iowa, and Minnesota.
All of that said, cereal rye is not the only player in the game, and improving water quality is not the only reason cover crops are planted. In the 2015-2016 Cover Crop Survey by the Conservation Technology Information Center, Sustainable Agriculture Research & Education and American Seed Trade Association, improvements in soil health was the responding producers’ top pick for cover crop benefits, whereas water quality was quite a way down the list. Even so, grass-based cover crops (including cereal rye) made up about 53% of total acres planted by respondents of this survey with brassicas (like radish) making up about 27% and legumes (like clover) making up around 20%.
Protecting and enhancing our critical soil resource is important, as is reducing the impact of agriculture on the Gulf of Mexico. Can we quantify a water quality benefit associated with the suite of soil health based cover crop decisions producers are making? For example, though minimal water quality information from this part of the country is available for cover crops other than cereal rye, research from other parts of the country suggest that nitrogen fixing legumes, if managed right, might have 35% to 60% the water quality benefit of a cereal rye.
Finally, cover crop mixes are on the rise, with the 2015-2016 Cover Crop Survey showing 51% of respondents considering moving from a single species cover crop to multiple species. We might consider water quality benefits of mixes (if they include a sizeable portion of grass) to be based on how much biomass is produced, though there is likely a bit more work to do on this front.
Reid Christianson, PE, PhD
Senior Water Resources Engineer, Center for Watershed Protection
Reid joined the Center in 2012 and works on a variety of projects including urban stormwater management designs, research on new practices, and strategic watershed planning. Reid made a 3.5 year stay in Maryland before heading west to Illinois, where he works remotely. Dr. Christianson is a Professional Engineer and has over 12 years’ experience in the water resources field. Prior to joining the Center, Reid worked for Iowa State University where he researched the impacts of agricultural best management practices and land use on water quality. In his spare time, Reid enjoys spreadsheet development, light weight programming, and “tinkering.”
