Abstract:
Sulfur (S) is increasingly being recognized as the fourth major plant nutrient after
nitrogen, phosphorus and potassium. It is a constituent of amino acids cysteine and
methionine, which act as a precursor for the synthesis of all other compounds containing
reduced sulfur (Scherer, 2001). Sulfur is essential for both plant and animal life. Although
the element is required by plants in amounts comparable to phosphorus, the first field case
of sulfur deficiency was reported only in 1933. In wetland rice, sulfur deficiency was first
reported in 1938. During the last 10 years, sulfur deficiency has been recognized as an
important growth-limiting factor for both dry land crops and wetland rice. In Asia, sulfur
deficiency of wetland rice has been reported in Bangladesh, Burma, India, Indonesia,
Japan, Philippines and Sri Lanka. Responses to sulfur have been reported for 23 crops in 40
tropical countries. This occurrence of sulfur deficiencies has been accentuated by the
increase in use of low sulfur fertilizers, decrease in use of organic manures, intensive
cropping and reduced atmospheric deposition. To alleviate sulfur deficiency, sulfur
fertilizers are invariably added to soils, usually in a reduced form, such as elemental sulfur.
Use of S oxidizers enhances the rate of natural oxidation of S and speed up the production of
sulfates,and makes them available to plants at their critical stages, consequently resulting
in increased plant yield.
