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Growing corn with a cover of grassGrowing corn with a cover of grass

Find best combination of grass cover and corn, when producing stover for biofuel and soil protection.

May 5, 2017

3 Min Read
PERENNIAL GRASS COVER: Where most of the corn stover is removed from a field for cellulosic ethanol production, grass planted in the growing corn crop protects soil from erosion. The ISU study is looking at using a perennial grass cover.

The phrase “a double-edged sword” describes something that is beneficial in some ways but problematic in others. One example is removing corn stover, such as husks, stems and leaves, from fields. Corn stover is used to make cellulosic ethanol, a renewable biofuel. And renewable biofuels are beneficial to the environment. However, removing the stover can harm the environment if it causes soil to erode and lose nutrients.

Taking up this double-edged sword is Cynthia Bartel, a doctoral candidate at Iowa State University. She’s finding a way to lessen the harm and increase the benefits of removing stover.

“While water and wind erosion are substantial problems for stover removal, soil quality preservation is an even greater constraint,” she explains. Bartel needed to find a way to remove the stover but preserve soil quality. So, she turned to previous research for ideas and found that cover crops or companion crops can improve soil quality. Bartel liked the idea of using cover crops, but was curious about a different type of cover crop.

Using perennial ground cover
Instead of annual cover crops, which must be replanted every year, Bartel continued research at ISU involving perennial groundcover, specifically grasses. “We envision that perennial grass seed might need to be purchased and planted only every four to five years, which would greatly reduce expenses compared to planting annual covers.”

Using a perennial groundcover could be a win-win, including natural resources preservation in addition to reducing costs. However, Bartel needed to determine if perennial groundcover and corn are compatible. She also needed to determine if using a perennial groundcover crop is both environmentally and economically beneficial.

To explore these questions, the ISU team conducted a field study at two locations in Iowa. In some areas, they planted Kentucky bluegrass with the corn. In other areas, they planted creeping red fescue with the corn. The team closely monitored and analyzed the crops over two years. “The success of the system largely depends on using a compatible species,” she says. And compatibility depends on several factors.

How the grass affects corn yield
A compatible grass would easily and reliably grow in the area where it is planted. But, it would go dormant in summer during corn’s growing season. The team discovered that the older grass varieties originally selected for the project failed to establish. In addition, the modern grass varieties stayed green too long. Not finding a perfect match on the first try didn’t deter the researchers though. “We identified key challenges in variety selection to ensure that further research efforts are focused effectively,” says Bartel.

In addition to compatibility, Bartel studied the grasses’ impacts on the corn. She found that corn crops did produce less grain in the first year. However, in the second year, the normal control corn and the corn with grass had similar yields. Plus, the grass didn’t negatively impact the quality of the stover in the second year or the quantity of the stover in either year. “Ultimately, there may be some yield penalty for perennial grass establishment in exchange for the natural resources benefits,” Bartel says. “But refining the system further, to ensure compatibility between the row crop and grass cover species, should largely minimize that penalty.”

Bartel’s field study began exploring one possible way to lessen the harm and increase the benefits of removing corn stover. Now future research can build on her work. Read more about Bartel’s work in Agronomy Journal.

Source: American Society of Agronomy

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