Many farmers have realized that they can no longer rely on atmospheric sulfur (S) to meet crop needs, as increased crop yields in recent years have placed a higher demand for sulfur from the soil. Many have started to make sulfur applications from various sources before corn, but what about soybeans?

Our neighboring state of Indiana has reported in-season visual differences and soybean yield responses to sulfur applications in certain years, particularly in heavier soils with a higher organic matter and possibly in earlier planting situations or no-till. This is because these field situations tend to be cooler and wetter, limiting the soil mineralization of the sulfur.

Purdue University has also found that farmers get the most “bang for their buck” if they apply sulfur to soybeans from planting to V2/V3 growth stages. There are sulfur starters or broadcast fertilizers that also contain nitrogen (N), which can provide an additional yield boost in some years, especially in cooler or wetter fields.

To learn more about sulfur management of soybeans, Illinois Soybean Association (ISA) will be conducting on-farm research in 2025 across Illinois. To accomplish this, we are seeking up to 16 farmer cooperators to conduct farm trials to determine the yield impact of soybean sulfur fertilization across different environments in Illinois. A special research focus will be placed upon early planting situations.

The protocol is as follows:

• The farmer will be responsible for sulfur applications and planting the field. The plot layout will be flexible depending on equipment and field dimensions, but a minimum of 40 acres will be needed to conduct the trial.
• Each site will receive a sulfur treatment of 30 lbs/A S applied and compared to a control treatment with no additional sulfur added. Trials will consist of at least four replications of both a control and sulfur treatment (a total of eight plots), each a minimum width of 60 feet.
• The sulfur treatment options can be applied as all applied preplant or as starter with sprayer, starter application, dry broadcast, or drone. The preferred sulfur sources used for these trials are as follows:
  • Broadcast spray application of 115 lb/A of Ammonium Thiosulfate (supplying 30 lb/A of S and 13.8 lb/A of N)
  • Broadcast dry Ammonium Sulfate preplant at a rate of 125 lb/A (Supplying 30 lb/A of S and 27.6 lb/A of N).
• The combine must have a calibrated yield monitor for accurate yield assessment.

Over the past several years, many Illinois farmers have resoundingly voiced to us that they would like to explore the possible benefits for soybeans with sulfur applications on their farm. We have come together as a team to develop a protocol to help farmers answer key questions regarding sulfur fertilization. We would appreciate the opportunity to work directly with farmers and to learn from them.

If you have any interest in participating in this on-farm research to learn more about sulfur management on your farm, please fill out the ISA On-Farm Trial Network Interest Form – https://bit.ly/OFTN_SignUp. 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 Illinois Soybean Association’s On-Farm Trial Network may be eligible for cost-share and program payments. Eligibility requirements and payment amounts will vary based on specific program guidelines. The On-Farm Trial Network is funded by the Illinois Soybean checkoff program.