Research Seeks a Balance Between Crop Residue Removal and Soil Conservation
When farmers harvest grain crops, plant residue is left behind, and it is anything but trash. In fact, farmers increasingly face a quandary: Leaving residue on the field provides long-term benefits to the soil, but it can also be sold as cattle feed during a drought or on a regular basis to ethanol producers.
To help farmers find the right balance, researchers throughout the Midwest, some supported by SARE grants, are studying the effect of residue removal on yield and soil quality under different field-management practices. Their goal is to identify acceptable residue removal rates that offer both soil protection and increased profitability.
“We need to think about residue removal in terms of the long-term impact on productivity and soil sustainability,” says Iowa State University (ISU) agronomist Mahdi Al-Kaisi. “We’re trying to think ahead to educate farmers and agronomists about potential implications of residue removal.”
The argument for selling corn residue is strong. When the 2012 drought crippled production in many parts of the country, some farmers salvaged what they could by selling their crop as livestock feed. Meanwhile, ethanol derived from corn residue—rather than corn grain—is fast becoming reality. Two commercial-scale cellulosic ethanol refineries in Iowa are scheduled to begin operation in 2014, and another is near completion in Kansas. Combined, the three plants will be able to process nearly 1 million tons of residue each year.
With a 2009 SARE grant, Al-Kaisi and ISU graduate student José Guzmán determined that corn yields were unaffected by one to three years of total residue removal. This held true under both conventional tillage and no-till, and with various fertilization rates. However, soil quality suffered immediately when 25-35 percent of residue was removed, leading to decreased water infiltration and increased erosion.
“This is one important thing to stress to farmers. You might not see a decrease in yields in the first five years, but you will see significant decreases in soil physical properties, and it can take five or 10 years to recover those properties,” says Guzmán, now a post-doctoral researcher at Ohio State University.
Guzmán and Al-Kaisi found that well-drained fields can tolerate repeated residue removal better than poorly drained ones, which, Al-Kaisi says, shows there is no one-size-fits-all recommendation. Farmers should carefully assess field conditions and local weather patterns before deciding how much residue to remove, and how often.
With a 2010 SARE grant, University of Nebraska soil scientist Humberto Blanco established a multi-year study on six farms in western Kansas to look at the effect of residue removal on soil in no-till corn, wheat and sorghum production. He found that the top inch of soil was more vulnerable to erosion after removing more than 75 percent of crop residue.
Blanco says his research was guided largely by farmer inquiries. “All six farmers were very interested in this project because they know the value of residue for their soil. But they were interested in the question of how much can be removed. They said the additional income would be nice, if they have more residue than they need to protect their soil.”
Want more information? See the related SARE grant(s) ENC07-094, Impact of Biomass Removal for Bioenergy on Soil and Water Quality , GNC09-111, Corn Residue Removal Impacts on Soil, Water, and Air Resources for Biofuel Production and LNC10-318, Establishment of Permissible Levels of Residue Removal for Corn, Wheat, and Sorghum Fields as Biofuel Feedstocks .
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