Sulfur Response in Midwestern Corn Production

Robert Mullen, Ph.D.

Robert Mullen

Robert Mullen, Ph.D.


Director of Agronomy

To say Dr. Robert Mullen is passionate about agriculture would be an understatement. He holds a Bachelor of Science degree in ag business from Cameron University, along with a Master of Science degree in plant and soil science and a Ph.D. in soil science from Oklahoma State University. In addition, Dr. Mullen has been published in a variety of scientific and trade journals. But it’s not just his academic accomplishments that make him unique. It’s his unwavering ability to take complex data and — in simple terms — explain how it impacts a farmer’s bottom line. Dr. Mullen delivers the kind of insightful observations that can lead to a more profitable business. As a leading agronomy expert, Dr. Mullen has a goal to further educate farmers on best management practices that improve their yields and maximize their return on investment.

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Most of us in the world of soil fertility have talked about increased need for supplemental sulfur due to decreased sulfur emissions from coal-fired power plants. Decreased sulfur emissions translate into less sulfur deposition with rainfall. Based upon the National Atmospheric Deposition Program (available here), which monitors nutrient concentration in rainfall, sulfate-sulfur deposition has decreased from over 24 pounds per acre in the mid-80s across much of the Midwest to less than 12 pounds per acre.

To address this issue, Purdue University conducted field research in 2018 and found that 6 out of 11 experimental sites showed response to side-dress sulfur with yield increases ranging from 4 to 22 bushels per acre (average yield increase was 14 bushels per acre). Side-dress sulfur rates were between 10 and 15 pounds of sulfur per acre. For more information, check the full update from Purdue.