Published Apr 16, 2014

Does a cover crop affect corn or soybean yields?

By Stefan Gailans

Practical Farmers of Iowa and Iowa Learning Farms have jointly released a research report 5 years in the making! See the full report here.

Twelve cooperator farmers across the state helped conduct 40 trials between 2009 and 2013 to determine if a winter cereal rye cover crop had any effect on the yields of corn or soybeans. Each farmer established strips the length of their field that either contained a cover crop or laid bare over the winter between years that they grew either corn or soybeans.

Strips at Funcke's

Strips with winter cereal rye cover crop and without cover in spring at Jim Funcke’s farm near Jefferson, Iowa.

Among the key findings:

  • In 19 out of 22 trials, the rye cover crop had little or no negative effect on corn yields.
  • In 4 out of 18 trials, the rye cover crop increased soybean yields, while 13 trials showed little or no negative effect on soybean yields.
  • A properly managed winter cereal rye cover crop can usually be added to a corn-soybean system without significantly affecting yields.

This study will continue in the years to come with 8 cooperators participating in 2014. For more information on this study, contact Stefan Gailans at

The project was made possible by funds provided by the State Soil Conservation Committee and the Iowa Department of Agriculture and Land Stewardship. The full report can be found here.