In recent years, many Illinois farmers have resoundingly told us they want to explore the possible benefits of sulfur applications prior to planting soybeans on their farm. In 2025, the Illinois Soybean Association (ISA) On-Farm Trial Network (OFTN) introduced its first sulfur (S) trial protocol. These sulfur action trials were developed in response to the annual Soybean Production Concerns Survey and direct farmer feedback. We were encouraged by the strong response and appreciated the opportunity to work directly with Illinois farmers. 

In 2025, farmers in more than 15 Illinois counties participated in large-scale, field-ready sulfur trials. Together, the ISA team developed protocols and made field observations to help farmers answer key questions regarding sulfur fertilization. Our team is currently analyzing management and tissue testing data and is eagerly awaiting yield data. We will be sharing findings soon on FieldAdvisor.org.  

ISA's OFTN sulfur research will continue in 2026 with the introduction of a Sulfur 2.0 action trial protocol. This trial will give more Illinois farmers the opportunity to participate and learn about sulfur management of soybeans. To accomplish this, we are seeking farmer cooperators to conduct on-farm trials to determine the yield impact of soybean sulfur fertilization across different environments in Illinois. A special focus will be placed upon early planting and no-till situations. 

The protocol is as follows: 

• The farmer is responsible for sulfur applications and planting the field. Plot layout may vary depending on equipment and field dimensions, but each trial must cover a minimum of 40 acres.  

• Each site will receive a sulfur treatment of 30 lbs/A of actual S and be compared to a control treatment with no additional sulfur. There will be strong emphasis on having the matching amount of nitrogen (N) applied to the control as in the sulfur treatments. 

• Trials will consist of at least four replications of both control and sulfur treatment (a total of eight plots), each with a minimum width of 60 feet. 

• Sulfur treatments may be applied preplant or as starter using a sprayer, starter application, dry broadcast, or drone. The preferred sulfur sources used for these trials are as follows: 

• Ammonium Thiosulfate (ATS)-Broadcast spray application of 115 lb/A (10.4 gallons/A) ATS (supplying 30 lb/A of S and 13.8 lb/A of N)  

• Ammonium Sulfate (AMS)-Broadcast dry preplant application of 125 lb/A AMS (supplying 30 lb/A of S and 27.6 lb/A of N)  

• Gypsum applied at rate of ~176 lb/A (supplying 30 lb/A S, actual lb/A may need to be adjusted based on grade of gypsum fertilizer) NOTE: Gypsum ONLY as additional treatment (i.e. must also have control and ATS or AMS treatment.) 

• Combines must have a calibrated yield monitor for accurate yield assessment to provide post-harvest yield data.  

Read the entire protocol by clicking here.

 If you are interested in participating in this on-farm research to learn more about sulfur management in soybeans on your farm, please fill out the Illinois Soybean Association On-Farm Trial Network Interest Form. If you have questions about participating in this study, contact Deanna Burkhart, Producer and Field Services Administrator, at deanna.burkhart@ilsoy.org or 309-307-9366. 

Qualified farmers participating in ISA's OFTN may be eligible for stipend payments. Program eligibility and payment amounts will vary based on specific guidelines. The OFTN is funded by the Illinois Soybean checkoff program.