Study finds diverse non-GMO crop system reduces herbicides, enhances soils, increases yields

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By Ken Roseboro
Published: January 31, 2014
Category: Organic/Sustainable Farming

Harvesting alfalfa at Iowa State University’s Marsden Farm.
Photo by David N. Sundberg

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What happens when you add diversity to Iowa’s conventional corn-soybean cropping system? An Iowa State University agronomist has found that you can reduce herbicide inputs, maintain and even improve weed suppression, enhance soil quality by several measures, plus boost grain yields. The study also found that non-GMO crops performed better than genetically modified varieties.

The cropping system research began in 2002, conducted by ISU agronomy professor Matt Liebman at the ISU Marsden Farm in Boone County. This 22-acre field experiment assesses agrichemical input use, yields, weed dynamics, economic characteristics and soil functions of diversified and simpler (two-year) crop rotation systems. The diversified corn-soybean systems are three- and four-year rotations that include oats and organic matter amendments, such as manure. In 2008, the experiment added a comparison of genetically modified and non-GMO corn and soybeans.

Results of this study indicate that the diversified three- and four-year crop rotation systems produced high yields of corn and soybeans and suppressed weeds effectively, while receiving only a fraction of the synthetic nitrogen fertilizer and herbicides used for a conventionally managed corn-soybean rotation. Among the six rotation systems and technology package combinations evaluated during 2008-2012, the highest level of profitability was obtained from the 3-year corn-soybean-oat/red clover rotation that did not employ GM crops.

The study was funded as part of the Leopold Center for Sustainable Agriculture’s long-running competitive grants program.