Understanding the Need for Sulfur in Kentucky

Abstract: Understanding the Need for Sulfur in Kentucky Soybean Production Atmospheric deposition of sulfur (S), less residual S found in fertilizers, and continued S removal have increased the area showing S deficiency. Although many of the states bordering Kentucky have some sort of S fertility recommendation, adequately predicting a crop response to S fertilization when and where remains a challenge. Few fields in Kentucky show widespread S deficiency. Sulfur deficiencies are typically seen in small areas within a field on coarse textured soils, eroded side slopes with low soil organic matter, in winter annual crops, or in crops with high sulfur demand and removal. Soil sampling typically is the best approach to identifying the status of a particular nutrient. This is not as well defined for S as with other plant nutrients due to soil S mobility and the limited ability of Mehlich 3 soil test extraction to reliably index seasonal soil S plant availability. A better understanding of available S dynamics and quantification methods could prove useful and profitable to Kentucky soybean producers. We propose to conduct research on multiple sites across the state to provide a better answer to these questions. The project is a multifaceted approach to providing better guidance to producers as to when and where an S need is present, and ultimately, how much S might be needed to ensure a S deficiency is not observed in that crop. We will have intensive S research at the University of Kentucky Research and Education Center (UKREC) that will more fully document landscape positions, along with soil test values at multiple depths. Additionally, on-farm response trials in both small and large plots, based in producers’ fields, will be conducted. We propose between 4 and 8 locations to conduct this research in the upcoming year. Soil samples, plant tissue samples and soybean yield will be collected to determine the S status and need in the fields tested. This information will be added to existing information to provide a better informed approach to soybean S fertilization in Kentucky. We are requesting $35,000 to conduct this research in 2025.