A long-term experiment was established in 2013 to study the responses to nitrogen (N), potassium (K), and sulfur (S) on continuous corn. Research at ISU Southeast Research Farm has looked at the corn yield response to N and K fertilization but not to S application. Results of a study with different N and K fertilization rates for corn at this farm and in northern Iowa have shown a positive interaction between these two nutrients. This means that a deficiency of one nutrient reduces the maximum yield level and also limits the yield response to increasing rates of the other. This type of interaction seldom has been observed between N and P or P and K in Iowa, unless the deficiency is extreme. The study summarized in this report applied several rates of N, K, and S to study the corn responses to these nutrients. No Iowa research has studied the possible interactions among these three nutrients.