Significant sulfur (S) deficiency in Iowa crops was first documented about 15 years ago. First identified in alfalfa and then corn and soybean. Since then about 150 trials with corn (along with trials with alfalfa and soybean) have been conducted across the state, with approximately 50% of trials having a statistically significant yield increase. A main reason for the yield response to S in recent years, as compared to many years prior, has been reduction in atmospheric deposition as a result of the Clean Air Act. Other factors for increased S responses include fields with no manure applications, increased crop yields, refinement of phosphate fertilizers, and decreases in soil organic matter levels.
Iowa State University
Sawyer, John E., "Crop Sulfur Fertilization This Spring" (2020). Integrated Crop Management News. 2610.
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