Sulfur In Australian Agriculture and New Fertilizer Technologies.

World demand for sulfur (S) fertilizers is predicted to increase from 50Mt to 60Mt in the next 5 years, and in Australia growth is likely to occur in many cropping areas. Historically much of the S applied in Australian agriculture was derived from single superphosphate, but with a decline in areas of pastures grown in rotations with crops, and a general decline in the amounts of superphosphate used on pastures, incidences of S deficiency are now more common. At a national scale Australia has a positive S balance (inputs-exports in food) but regional differences in farm-scale S balances indicate several areas with negative farm-gate S balances. In cropping areas, new products that incorporate both sulfate and elemental S are becoming more popular, as there are several benefits that may accrue for combining both elemental and sulfate-S into a phosphatic fertilizer, apart from the nutritional role of S for crop uptake. Changes in solution chemistry around the granule due to dissolution of these combined N:P:S products may affect P and micronutrient chemistry in the dissolution zone, and oxidation of the elemental S may subsequently affect release of nutrients from fertilizer reaction products in and around the granule. The contribution of the sulfate-S and elemental-S components in these products can also be evaluated using dual isotope labelling/dilution methods. It is likely the use of S-enhanced products will increase in Australian cropping industries, but it will be difficult to see single superphosphate being replaced as the dominant pasture fertilizer in Australian agriculture.