Sulfur Species Formed in the Seed-Row of Sulfur Fertilized Soils As Revealed By S K-Edge XANES Spectroscopy.

Sulfur (S) K-edge X-ray absorption near edge structure (XANES) spectroscopy was successfully used for the first time to identify sulfur species formed from S fertilizers in the soil. The synchrotron spectroscopy technique was developed and used to determine S forms present in the seed-row after application of sulfur fertilizers in Saskatchewan soils. Crop grown was canola. Sulfur fertilizers evaluated were ammonium sulfate, gypsum and elemental sulfur and applied in the seed row at rates of 20 kg S ha^-1. Urea N fertilizer was broadcast to provide the same rate of N for all treatments at the rate of 100kg N ha^-1. XANES spectroscopy showed that after fertilizer application, sulfur species present in the seed-row included the initial forms as well as reduced thiols, oxidized organic S (ester sulfur) presumably originating from microbial assimilation, and inorganic sulfate forms. Overall, the combination of chemical techniques (sulfate extraction) and spectroscopic techniques revealed that different sulfur fertilizer behaved differently and eventually transformed into different sulfur forms.