Role of sulfur mineralization and fertilizer source in corn and soybean production systems

Abstract

Sulfur (S) is an important nutrient for plant growth and crop yield. In the northern U.S. Corn Belt, a decrease in atmospheric S deposition and an increase in grain harvest have increased the frequency of S deficiency in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. Nevertheless, S deficiency remains difficult to predict owing to complex interactions between the production of plant-available sulfate-S from soil organic matter (SOM) mineralization and sulfate-S losses to leaching. Our objective was to measure corn and soybean yield response to four S fertilizers (ammonium sulfate, elemental S, gypsum, and polyhalite) in the 1st year following fertilizer application and in the 2nd (residual) year following fertilizer application in Iowa. Across 4 site-years, none of the S fertilizer products increased soybean yield. Across 12 site-years in the 1st year following application, sulfate-S based fertilizers increased corn yield in 4 site-years while elemental S had no effect. Across 6 site-years in the second residual year following application, elemental S, polyhalite, and gypsum increased corn yield in 1 site-year while ammonium sulfate had no effect. Laboratory incubations confirmed that there was slower production of plant-available S from elemental compared with sulfate-based fertilizers, potentially explaining the lack of elemental S effect in the 1st year following application. In contrast to our expectations, there was a weak, but positive relationship between corn yield response to S fertilizer and SOM concentration. Overall, the kinetics of S fertilizer mineralization and solubility appear to affect the magnitude and timing of crop response to S fertilizer.