Evaluation of Optimum N Rate for Corn Fertilized with and without Sulfur Grown on Medium and Fine Textured Soils.

Nitrogen (N) and sulfur (S) could potentially interact within the corn (Zea mays L.) plant and could affect optimum N rate when S is not applied. The objectives of this study were to evaluate the potential S×N interaction on the grain yield, and tissue N and S concentrations. A total of eight field locations were studied across Minnesota from 2011 to 2013. Treatments were applied as a complete factorial design. Factor 1 consisted of 0 or 28 kg S ha^-1 and factor 2 consisted of rates of N (0, 56, 112, 168, 224, and 280 kg N ha^-1). Grain yield was affected by a significant S×N interaction only at one site when highest N rates were applied. Grain yield increased with the application of S at this site. Significant S×N interactions occurred on ear leaf N concentration at one site, on ear leaf S concentration at two sites. Both N and S concentrations slightly increased with the application of S. These changes occurred at higher N rates suggesting that when N is deficient application of S will not be a benefit for corn. The decision regarding a need for fertilizer S should be based on potential for increased corn yield. These results indicate that S×N interaction affected agronomic productivity inconsistently and in lower magnitude. Therefore, farmers do not need to change their management practices for corn production.