Cover crops can be used to prevent nitrogen loss

Cover crop research shows that winter cereal rye may reduce nitrate leaching

Manure in Crop Field
Photo by USDA NRCS South Dakota Colette Kessler, Pierre, SD, 2013

Careful manure management is a principle of farm profitability and environmental stewardship. Livestock farmers are looking for ways to reduce the incidence of nitrogen leaching into groundwater from manure. Farmers have adapted and changed their practices to address  things such as manure, timing of applications, and application methods.  

Minnesota researchers, led by Dr. Les Everman, University of Minnesota Water Resource Center retired, wanted to determine:

  1. Fate of nitrogen in the soil from injected manure with and without a cover crop
  2. Nitrogen needs to the cash crop with and without cover crops are met

Winter cereal rye was planted following corn silage or soybeans during the 2016 and 2017 growing season on 19 farms in central and southern Minnesota. Dairy or swine manure was injected in the 3 replicated plots with a check strip after the rye was established. In the spring, cover crop biomass, nitrogen content of the cover crop, and soil nitrate was checked. Rye was terminated and in most cased incorporated into the field. The fields  were then planted with corn and a starter fertilizer was applied at planting. Corn yield and nitrogen content were determined at harvest.

The research resulted in the following findings:

  1. In both years, adequate growing season existed to establish the rye cover crop after either corn silage or soybean harvest, but above-ground fall growth was limited.
  2. The rye was very resilient to manure injection, however, stand reduction was considerable at two sites where shank injectors or disk coverers were too aggressive.
  3. Spring rye growth was good at most sites with soil nitrate reduced under the cover crop compared to the check strips at all sites.
  4. Rye growth and nitrogen uptake were greater in southern than central Minnesota.
  5. Across sites, there was no significant difference in silage or grain yield between the cover crop and check strips.

Future research is required to assess the effects of cover crop termination methods and timing on nitrogen dynamics and performance of the subsequent corn crop. To obtain the full research report visit this link.

In another study, researchers from Purdue University and Illinois State University found that cover crops reduced the N load in subsurface drainage up to 47%. Adoption of a cover crop management scheme allows for a responsive cover in the event of sudden thaws that characterize winter in Michigan. Cover crops proved to be effective in reducing NO3-N loading through tile-drainage across the spectrum of common nitrogen fertilizer management systems.

If you would like to learn more about cover crops, how they can benefit your farm, or to find a cover crop educator visit the Michigan State University Extension Cover Crop site.

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