"Residue protects soil from wind and water erosion, so removing it should be based on field-specific conditions and potential soil erosion," says Mahdi Al-Kaisi. Above, crop residue in the foreground. (Credit: CIMMYT/Flickr)

agriculture

Is selling corn residue worth harming soil?

After the corn harvest, farmers still have plant material, called corn residue, left behind.

Farmers considering selling that corn residue to produce cellulosic ethanol should consider carefully, according to new research.

Mahdi Al-Kaisi, a professor of agronomy at Iowa State University, is urging farmers to consider variables such as topography, tillage system, nitrogen application, and the amount of organic matter present in their soil to determine how much corn residue they should part with.

“Residue removal has some real environmental impacts on soil health and water quality,” Al-Kaisi says. “It needs to be approached thoughtfully and on a site-specific condition basis.”

Is the ethanol worth it?

His most recent publication, published in the Soil Science Society of America Journal, shows how a decrease in crop residue can lead to increases in greenhouse gas emissions from the soil.

Al-Kaisi began the study in 2008. The continued development of cellulosic ethanol, a biofuel made from corn residue, motivates the research.

As the technology continues to mature, cellulosic ethanol production will require more and more feedstock. Al-Kaisi says research like his will help to balance the needs of the cellulosic ethanol industry with information that can help farmers safeguard their soil.

More emissions

The research team conducted experiments at two locations, one in central Iowa and one in southwest Iowa, and monitored the effects of removing portions of corn residue from the test plots on yield, soil organic matter, greenhouse gas emissions, and soil quality. The team also tested how various residue removal levels interact with different nitrogen rates and tillage systems such as no-till and conventional tillage.

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The research found a general increase in the emissions of carbon dioxide and nitrous oxide from all residue removal plots as nitrogen application increased. They also found that conventional tillage led to an increase in carbon dioxide emissions regardless of the residue removal level.

As residue is removed, black surface soil is exposed to direct sunlight. The dark surface absorbs heat and results in an increase in the oxidation of organic matter and the release of carbon dioxide, Al-Kaisi says.

A previous paper published as a result of the study noted residue removal results in less organic matter in the soil, which Al-Kaisi says could lead to diminished productivity in the long term. Farmers should also exercise caution when considering the removal of residue from fields prone to erosion.

“Residue protects soil from wind and water erosion, so removing it should be based on field-specific conditions and potential soil erosion,” Al-Kaisi says. “Farmers who are going to remove corn residue should make sure they know how these different factors interact when making these decisions.”

Source: Iowa State University

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