Keywords: Sulfur cycle, Sulfur fertilizers, Sulfur deposition, Soil analysis, Amendments

The sulfur cycle in the soil has similarities to both nitrogen and phosphorus and, like these nutrients, appropriate soil testing procedures are essential to determine the sulfur fertilizer requirements of crops and pastures. The KCl-40 test, which is used widely in Australia, has been found to be a better predictor of sulfur response than monocalcium phosphate.

Atmospheric inputs of sulfur in rain or as dry deposition can markedly affect fertilizer requirements. A simple cation/anion collection tube has been developed to allow measurement of nutrient additions in rainfall at many locations and this can indicate if fertilizer sulfur is required. In areas near the sea, where appreciable wind speeds carry sea spray onto the coast, sulfur fertilizers may not be required.

The choice of sulfur fertilizer source needs to be based on its agronomic performance in the crop immediately after application, its residual value and cost. Sulfate and elemental forms can be applied directly or added into, or onto, compound fertilizers. The agronomic performance of both sources can be manipulated by altering particle size. A computer program has been developed to determine the optimum particle size of elemental sulfur to be used on specific crops in specified locations.

Prof. Graeme J Blair, Center for Sustainable Farming Systems, Agronomy and Soil Science, University of New England, Armidale, NSW, 2350, Australia.

36 pages, 10 figures, 7 tables, 72 references.