Abstract Sulfur deficiency in soils has become an increasing concern over the past decades. Despite elemental sulfur (S 8) vast utilization as a commercial fertilizer, S 8 has to be biologically oxidized for plant assimilation, drastically limiting its efficiency. Therefore, we propose a new fertilizer in which S 8 structure is more accessible to oxidizing microorganisms by chemical modification via inverse vulcanization technique, a solvent-free copolymerization method, with soybean oil as comonomer. Sulfur oxidation experiments were performed by A. niger submerged cultivation, confirming that the homogeneous rubbery-like material provides enhanced oxidation, with great potential as multifunctional sulfur-fertilizer. Graphical abstract Image 1 Highlights • Polysulfide fertilizers were synthesized via inverse vulcanization. • The polysulfides achieved superior S-oxidation than elemental sulfur. • The alkene content of the polymer contributed as substrate for biological activity. [ABSTRACT FROM AUTHOR]