The importance of adequate sulfur (S) for corn (Zea mays L.) production has been recognized for many years and was recently confirmed by positive yield responses in central IA. We compared a granular S-enhanced fertilizer material [SEF (13-33-0-15S)], granular ammonium sulfate [AMS (21-0-0-24S)], and liquid ammonium thiosulfate [ATS (12-0-0-26S)] on eroded Clarion (Typic Haplaquolls) hill slopes in central Iowa for four years. Applying 34 kg S ha^-1 as SEF significantly (P≤0.05) increased mean V5 plant dry weight each year. AMS and ATS showed a similar but non-significant trend. Whole-plant S concentrations at V5 were generally higher than the control for all S sources. Grain yield and moisture content at harvest were not affected by S in 2006 and 2007. In 2008 and 2009, 34 kg S ha^-1 as SEF significantly increased yield by 0.76 and 0.38 Mg ha^-1, respectively. The agronomic efficiency of S (yield per unit applied) was greatest for SEF in 2006 and 2008 (12.3 and 22.5 kg grain (kg S)^-1, respectively). There was little difference among the S sources in 2007 and 2009. Below-normal precipitation during the 2006 and 2007 growing seasons and inherent soil variability presumably affected our S yield response, but overall we conclude that S may become a limiting nutrient for maize, especially if maize stover is harvested as a bio-energy feedstock.