AMES, Iowa — Cereal rye cover crops added to a corn-soybean rotation have little to no negative effect on yield, and actually increased soybean yields in eight site-years and corn yield in two site-years, according to a nine-year study conducted by the Iowa Learning Farms and Practical Farmers of Iowa.
In 2008 and 2009, 12 farmers across Iowa established replicated strips of winter cereal rye cover crop and strips with no cover crop within their corn and soybean rotation. The cover crop was either drilled after harvest or aerially seeded into standing crops each fall. At each site, the cover crop was terminated the following spring by herbicide one to two weeks before planting.
When the project began, the farmers were concerned that the winter cereal rye would impact their corn or soybean yields negatively. But after harvest was completed each year, the farmers reported that this was not the case. When properly managed, cover crops had little to no negative effect and, in some cases, actually improved yields.
For Taylor County farmer Kelly Tobin, the top benefits of adding a cover crop to his operation were reduced soil erosion and improved soil health. “I had put in pattern tile three feet down that never worked until I had a cover crop for three years. The tile now removes standing water after heavy rains thanks to the roots and biological activity underground.” Tobin also noted that although it has taken time, he has been able to achieve an increase in crop yields. In 2016, Tobin reported a 19 bushel per acre advantage for corn, and in 2017, measured an 11 bushel per acre increase in soybeans.
Proper management is key when incorporating cover crops into a corn-soybean rotation. Knowing what cover crop to use, when to plant, and how and when to terminate are the main components to successful implementation. Effective termination with herbicide requires an actively growing plant. Planter settings may also need to be adjusted to handle increased residue.
There are many resources to help farmers with answers to these management details online and in print, as well as the option of contacting a cover crop farmer in your area through the Iowa Learning Farm or Practical Farmers of Iowa network, local Iowa State University Extension and Outreach field agronomist or NRCS field specialist.
The farmers in this study include: Bill Buman, Harlan; Randy Caviness, Greenfield; Jim Funcke, Jefferson; Devan Green, Conrad; Rick Juchems, Plainfield; Whiterock Conservancy, Coon Rapids; Mark Pokorny, Clutier; George Schaefer, Kalona; Jerry Sindt, Holstein; Rob Stout, West Chester; Gary and Dave Nelson, Fort Dodge; and Kelly Tobin, New Market.
The year nine update for this study is available online at the ILF website: https://www.iowalearningfarms.org/content/cover-crop-research.