Updated April 4, 2021:
Please see uploaded final report.

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In this experiment we hypothesized that soybean yield and quality would respond positively to sulfur (S) fertilization. We tested S fertilizers applied at 40 lbs/ac S applied to corn in the year before soybean production (2019) to S fertilizers applied in the soybean production year (2020). Our results indicated that there was not an effect of S fertilization on grain yield or crude protein concentration, however, grain S concentration increased as well as the concentration of the S-containing amino acids cysteine and methionine. This suggests that in cases where S doesn’t limit yield, there are still some effects of the addition of S, especially if producers are concerned about the amino acid concentration of their grain. We also sought to describe the depth distribution of S in the soil profile after S application, and did so at three time points: after corn harvest in 2019, prior to soybean planting in 2020, and after soybean harvest in 2020. We found that even after two seasons of crop production, subsoil S content was higher in after soybean harvest in treatments which had received S in 2019 than treatments which received no S in either year. This is an important finding because it illustrates the fact that the subsoil can act as a reservoir to hold S for use by multiple cropping cycles. In addition, our soybean plant rooting depth data and plant tissue testing data indicated that once roots reached the deeper soil layers containing S, plants readily took it up and assimilated it into their tissues. Finally, when considering the potential interaction between N and S, our plant tissue, soil testing, and grain analyses all indicated that gypsum and ammonium sulfate performed equally well. There was no difference in S content between the two treatments at either plant tissue sampling date, there were no differences in yield, and both treatments resulted in increased grain S, methionine, and cysteine concentrations when compared to the control. Therefore, if a producer’s intends to add S to their soybean crop, the cheaper of these two products should be selected, since the results so far indicate similar crop performance. It also appears that if S is added during the corn year of the rotation, producers should be able to rely on excess S stored in clayey subsoils.