Soybeans don’t lower nitrate pollution as much as expected
Wide predictions that switching fields from corn to soybeans and back would affect the level of nitrate pollution appear to be off, a study by the University of Iowa and the Iowa Soybean Association found. Iowa Environmental Focus reported that the study, published in the Journal of Soil and Water Conservation, challenges many of these predictions. As corn acres rose and soybean acres dropped, fertilizer applications jumped 24 percent. But nitrate levels either fell slightly or were flat. The study evaluated 7,000 water samples in the Raccoon River Watershed from 1999 to 2014. Researchers had fertilizer data for 700 fields. Typically, little to no fertilizer is applied to soybeans, a legume that adds nitrogen from the atmosphere to the soil. Scientists called the findings counterintuitive and said they may suggest organic material in the soil plays a larger role than previously thought.
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