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November 30, 2017 | By: | Agronomy

How to Fit Cover Crops into a Corn-Soybean Rotation



Cover Crops Guest Post from Dr. Abbey Wick – NDSU Extension Soil Health Specialist and Assistant Professor of Soil Health – Extension

Soils are physical, chemical and biological systems that require balanced approaches and inputs to keep them functioning efficiently.  Management of physical and chemical properties are in the form of utilizing reduced tillage and soil testing for fertility. In supporting the biological component, cover crops are a useful tool. Cover crops can add diversity to food, root structures and time of a living root in the soil to existing crops in rotation for better support of microbial growth and habitat.

One approach to incorporating cover crops into a corn-soybean rotation is the five food groups rule. This rule was developed by Lee Briese, an Independent Crop Consultant with Centrol Ag, and is useful when it comes to keeping things simple.

The basis for the five food group rule is to grow a warm season grass, warm season broadleaf, cool season grass, cool season broadleaf and a legume over a period of a couple years. Cash crops count towards the five food groups. Soybeans cover the warm season broadleaf and legume categories and corn fits the warm season grass category. The final piece is choosing cover crops that fit the cool season grass and cool season broadleaf categories to achieve growing all five food groups within two years.

Two of the best options are cereal rye (cool season grass) and daikon radish (cool season broadleaf), which can both be interseeded into corn. There are multiple ways to get this done including seeders, broadcast and highboy units, and flying it on. Cover crops can be interseeded any time after five-to-eight-leaf corn and will not compete for resources after this growth stage.

The goal is to get cereal rye and radish established in the corn. Once the corn starts drying down, the canopy opens up and the cover crops can start putting on some growth. Be sure to turn the chopping head off when harvesting corn to leave the stalks standing and residue mostly attached to the soil. Radish will winter kill, but cereal rye will overwinter and continue growing the following spring.

With the cereal rye growing the following spring, there is the option to “plant green” which means you are planting soybean into a living cover crop. This approach requires management. If it is a dry spring, the cereal rye needs to be terminated with a full rate of herbicide to avoid excess water use.  If it is a wet spring, farmers can use the cereal rye as a tool to manage moisture via transpiration and terminate again with a full rate of herbicide at planting.  Keep in mind that this approach is not RMA approved, so you need to discuss this with your insurance company if you plan to try this.

Cover crops continue to thrive even after corn harvest is complete.

By default, in using this approach with cover crops, you will be reducing tillage.  So plan to get more information and try it only on a small number of acres first to get familiar with this practice. The NDSU Soil Health website is packed full of information and you can also follow me on Twitter (@NDSUsoilhealth) to get more tips.


Dr. Wick received her PhD in 2007 from University of Wyoming and was research faculty at Virginia Tech from 2008 to 2012. She has extensive experience in working with landowners and industry on issues ranging from soil nutrient cycling and physical limitations of soils on crop production to best management practices for reclaiming mined lands.

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