Keywords: Brimstone, Elemental sulfur, Elemental sulfur fertilizers, Frasch, Liquid sulfur fertilizers, Pyrites, Sulfate sulfur fertilizers, Sulfur-containing compound fertilizers, Sulfur in other forms, Sulfuric acid.

Since the start of industrial times, sulfur has been a key raw material for the fertilizer and chemical industries. It is the primary source for sulfuric acid, the world’s most widely used chemical, in a host of manufacturing processes. Sulfuric acid is used by the fertilizer industry to manufacture primarily phosphates or phosphoric acid, and also other fertilizers like ammonium sulfate.

The sulfur industry has undergone major changes during the past four decades. From being essentially a mining industry, the sector has evolved to a non-voluntary co-product of the petroleum and non-ferrous metals sectors. Changes in sulfur consumption have also been marked. Although sulfur is an increasingly important plant nutrient in its own right, its greatest use in the fertilizer industry is as an input for phosphate fertilizer manufacture. In the 1950s and 1960s a shift from low to high concentration phosphate materials signified a sharp increase in sulfur demand. More recently, non-fertilizer sulfur use gained importance resulting from increased use in hydrometallurgical applications.

Sulfur fertilizers can be divided into three groups:
1. Fertilizers containing sulfate;
2. Fertilizers containing elemental sulfur; and
3. Liquid sulfur fertilizers.

Sulfate fertilizers provide most of the fertilizer sulfur applied to soils. Elemental sulfur-based fertilizers are the most concentrated sulfur carrier. Modern technologies have improved their properties and increased their use in direct applications or as additives to various fertilizers. Thiosulfates will continue to gain in popularity for fluid fertilizer applications. Sulfur-modified or enriched compound fertilizers using either sulfate or elemental sulfur have several advantages, including improved chemical and physical properties; and providing multi-nutrients with balanced ratios for plant nutrition for direct application purposes.

The sulfur fertilizer industry has made several advancements with products in recent years. The sector has developed materials adapted to particular crop and management situations. Sulfur fertilizers include a wide range of products, offering versatility for a variety of applications.

D. L. Messick, C. de Brey, and M. X. Fan, The Sulfur Institute, 1140 Connecticut Avenue N.W. Suite 612, Washington, D.C. 20036 USA.

24 pages, 5 figures, 1 table, 12 references.