Over forty years of prior research in Iowa had rarely noted improved crop yield with sulfur (S) fertilization and S deficiency was not considered an issue for crop production. Statewide and regional studies conducted in Iowa during that time period with corn and soybean found yield increase from S fertilizer application only three times out of nearly 200 trials, with one multi-year study having a small average yield decrease. Research in the early 1980’s had also documented sufficient plant available S in the soil profile for crop production on most Iowa soil associations. Results of recent studies in corn and soybean production in areas of Iowa outside of northeast Iowa (2000-2005) were consistent with results of the historical research.