Elemental sulfur combinations and regional waste gypsum products as alternative sulfur fertilizer sources

Abstract

The potential of elemental sulfur and gypsum as viable sulfur alternatives to ammonium sulfate were evaluated. Continued concerns regarding poor product performance by elemental sulfur, and the lack of an economically viable gypsum source have restricted large scale usage. Laboratory and field measurement of plant available S release, plant yield, residual soil sulfate, and crop use efficiency suggest advantages to sludge plus elemental sulfur usage rather than application of elemental sulfur alone. Altering elemental sulfur’s physiochemical nature leads to inherent advantages in microbial establishment, which is the initial process critical to the conversion of So to sulfate. The final product is envisioned as a fertilizer pellet or prill utilizing sludge as a binder or carrier agent. The tested waste gypsum products are sulfate alternatives with solubilities that predict short-term to intermediate availability. Waste gypsum products have specific advantages in certain environmental niches wherein readily soluble fertilizers could be lost to leaching and immobilization.