Soybean Growth and Yield Response to Starter Sulfur Applied with Nitrogen and Phosphorus.

In Minnesota, sulfur (S) has only been recommended in crops historically showing a need for sulfur application. Soybean is not typically been shown to respond to sulfur but responses demonstrated in corn in areas of the state have growers questioning if soybeans would response as well. The objectives of this study were to determine soybean growth and yield response to S using replicated strip trial methodology and to evaluate various factors for predicting S need, Field strip trials were conducted in 2008 and 2009 at three locations with two different soil types of clay loam (CL) and silt loam (SL). The fertility treatments consisted of N (22 kg N ha-1), P (10 kg P ha-1), and S (28 kg S ha-1), with several combinations (no S (check), S only broadcast pre-plant, N only, N+P, N+S, and N+P+S applied 5 cm besides and below the seed with the planter. Factors evaluated were above ground growth at V5 and R6, grain yield, and grain sulfur removal. Application of sulfur typically increased plant growth at all locations, especially when combined with nitrogen and phosphorus which did not increase growth when applied in combination or alone. Early growth responses were typically still seen with late season samplings. Grain yields were only increased by sulfur in silt loam fields with low organic matter levels. Even when yield was not increased more sulfur was taken up into the soybean grain indicating that it was getting into the plant but was not being utilized to increase yields. We conclude that early plant growth can be enhanced with starter fertilizer combinations with sulfur, but yield effects are likely only going to be seen under isolated circumstance.