Investigation of Sulfur Oxidation States and Phosphorus Speciation in Soil from a Controlled-Release Fertilizer Based on a Polysulfide with

Controlled-release fertilizers based on the dispersion of eco-friendly P sources – Bayóvar rock and Struvite – on a polysulfide matrix were investigated for improving the delivery of both P and S. The studied polysulfides have a multifunctional role, helping P solubilization and providing S for plants after being oxidized in soil to sulfate. Previous results showed a superior sulfate formation from polysulfides than elemental sulfur (S8), and that P stimulates the oxidation of S. Yet, little is known from literature about the biodegradation of this polymer and the dynamics in soil when in the presence of P sources. The aim of this proposal is to elucidate the S species formed in soil by the oxidation of the polysulfide and S8, to better understand differences in oxidation steps and transformations from both these sources. In addition, we propose to investigate the shifts in P speciation produced when Bayóvar rock and Struvite are associated with the polysulfide in this system.