Single superphosphate (SSP) and ammonium sulfate are the source of 75% of the 10.5 million tons of S applied to soils worldwide.  The Sulphur Institute (TSI) estimates that only 50% of world demand is being met.  With limited new production and existing facilities for SSP and ammonium sulfate, and with SSP facing economic scrutiny, what sources are likely to be used to correct future sulfur deficiencies? The objectives of this presentation are (1) examine major groups of S-containing fertilizers, their S content and form, and considerations associated with recommending particular sources; and (2) review worldwide and regionally the dominant S fertilizer sources and potential future changes in the use of these fertilizers.

Sulfur fertilizers fall into three categories: those which contain a sulfate carrier, those containing elemental S and products emerging containing both sulfate for immediate plant availability and elemental S to provide reserve availability.  While dominant, little growth if any, is expected with ammonium sulfate (24%S) and SSP (10-14%S), hovering at 4 million tons of S and 4.5 million tons of S equivalent, respectively; these materials are giving way to increased production of sources such as ammonium sulfate plus ammonium nitrate, most commonly 26-0-0-14S, S bentonite (90%S), and compound fertilizers containing a series of nutrients to include N-P-S grades.

The Sulphur Institute has identified more than 15 S-containing fertilizers sold commercially.  Use management of these materials can vary widely to optimize performance and efficiency.  In determining application rates, the S cycle also needs to considered with such variables as organic matter and sulfur dioxide contributing.