By Stephanie Porter
Soybean growers across Illinois continue to ask whether sulfur applications can reliably deliver a yield bump. In 2025, our Illinois Soybean Association (ISA) On-Farm Trial Network tackled this question head-on by evaluating 16 locations that consisted of a wide range of soils, weather, and management practices. The short answer: sulfur yield response can be real — but it’s complicated.
Why sulfur matters more today
For decades, industrial emissions supplied Midwest soils with 10–30 lb./acre of sulfur through atmospheric deposition. After the 1970 Clean Air Act reduced sulfur dioxide emissions by over 95%, that free nutrient source essentially disappeared.
Sulfur is essential for amino acid formation, nitrogen fixation, chlorophyll production, biomass growth, and seed quality. Soybeans take up about 85% of their sulfur during reproductive stages, making in season availability especially critical.
Inside the 2025 sulfur trials
This year’s sulfur trials included a minimum of 40-acre field scale layouts with replicated strips of spring applied sulfur (ATS or AMS) versus untreated checks. Each participating farmer contributed four years of management data and ISA collected soil samples, tissue tests, field insights, and yield monitor data.
Across the state, results were mixed — and that variation is exactly what makes this dataset valuable.
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