Sulfur Fertilizer Production and Technology.

An awareness of the need for sulfur (S) for plant nutrition is growing as the occurrence of reported deficiencies increases.  Fifty years ago, the major sources of S were geologic deposits of elemental S and S recovered from pyrite minerals.  The major source of S today is from petroleum refineries and natural-gas processing plants, where hydrogen sulfide is removed to avoid air quality issues. China is the largest global S producer, followed by the U.S. and Canada.

Most S is oxidized to sulfuric acid by first burning it in the presence of oxygen, followed by reaction with water.  Over half of the global S production is used in the production of fertilizer, especially for making soluble P fertilizer.  Much of the S used for P fertilizer production ends up as byproduct phosphogypsum and not used for agricultural purposes.

There are many excellent soluble and slowly soluble S-containing fertilizers that are used for plant nutrition.  Their synthesis, chemistry and behavior in soil are described.  A number of elemental S fertilizers are widely used.  The factors controlling the oxidation of elemental S to the plant-available sulfate form include the particle size, the method and time of application, and numerous soil properties.  The use of dispersible elemental S for plant nutrition is growing.  Other uses of S include remediation of alkaline soils and treatment of irrigation water.  The global production and use of S is anticipated to increase for the foreseeable future.