Food security

How does growing corn in perennial groundcover work?

Using perennial groundcovers, farmers can merge high yield agriculture with natural resources conservation, while maintaining or improving profitability. How does it work?

Farmers first seed their acres with a groundcover, such as bluegrass or fescue. Then they plant their row crop. My Iowa State University team and I recently finished a study in which corn was grown into perennial grass groundcovers.

During the first year, the perennial grass grows along with the corn. It remains to protect the soil after corn harvest when the soil is otherwise bare. In following years, so the grass does not get too tall and interfere with corn growth, the groundcover is suppressed in the spring and goes dormant during the corn growing season. The groundcover comes out of dormancy and regrows after the summer heat and drought stress ends.

A key benefit of this system is that its management activities are like those of conventional corn. Conversely, most row crop systems are designed to use the entire growing season leaving little time to establish and remove or suppress an annual winter cover crop.  In addition, other groundcovers, like annual cover crops, have annual planting costs, but perennial groundcovers do not. This saves money, while regenerating the environment.

graphic showing stages of grass and corn in rows with small corn plants on left and larger ones on right; grass stays the same
Changes in the perennial grass and corn system throughout a season. Left, early season, right, corn at mature height. The perennial grass supports soil health and provides conservation benefits without reducing corn yields. Credit: Kenneth J. Moore

Another plus about perennial grass and corn systems is that they fit with the current farming model. Things like existing market forces, infrastructure investments, and federal farm programs all fit with perennial groundcover development. Thus, efforts have been supported by farmer-led groups, rural economic development organizations, and commercial input suppliers.

Variations on this system have been adopted for large-scale production outside the United States. But questions remained for how best to manage perennial grass intercropped with an annual cash crop in the US Corn Belt. That is where my research team at Iowa State comes in.

We created a model based on three years of data. Our data was collected from fields that grew corn in perennial grasses as described above. We use the model to better understand how the corn and grass interacted. We also explored both production and conservation benefits of the perennial grass and corn system.

Our modeling showed these systems can attain multiple conservation efforts while producing competitive corn yield. To achieve these conservation benefits, spring grass suppression is the critical factor affecting corn yield. When grass is well suppressed, the corn yield loss is minimal, and the environmental benefits are significant. Two of the most challenging water quality issues – runoff and nitrate leaching – were reduced. The model also predicted increases in soil carbon. This improves soil structure and retains nutrients and water for corn to use.

Graphic of the perennial grass and corn system. Note the roots of the grass are able to hold soil in place all seasons, without interrupting the growth of corn. Credit: D. Raj Raman.

On the flip side, when grass is not successfully suppressed, it reduces corn growth rates. The perennial grasses compete first with the row crop for light and then water and nutrients. Together, these can translate into substantial corn yield losses at the end of the season.

The primary implication of the modeling work at our research lab is that well-managed perennial groundcover and corn systems can meet both production and natural resources management goals. Yields remain high, and the conservation benefits are also high. We are currently using these findings to refine the management of the grass and to select corn and grasses that pair well and looking at ways that energy and farm program policy can increase perennial groundcover system profitability.

Answered by Cynthia Bartel, Iowa State University

This blog was based in part by Dr. Bartel’s research published in Agronomy Journal “Establishment of Perennial Ground Covers for Maize-based Bioenergy Production Systems.”

About us: This blog is sponsored and written by members of the American Society of Agronomy and Crop Science Society of America. Our members are researchers and trained, certified, professionals in the areas of growing our world’s food supply while protecting our environment. We work at universities, government research facilities, and private businesses across the United States and the world.

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