Sulphur (S) is one of the 17 nutrient elements essential for growth and development of all plants. It is the thirteenth most abundant element in the earth crust with an average concentration of 0.06%. It is now considered as the 4th major plant nutrient after nitrogen (N), phosphorous (P) and potassium (K)(Patel et al., 2013a). It resembles N in its role and function in plant production, is comparable to P in terms of overall crop needs and could be equated with K in terms of per unit cost. Sulphur containing amino acids like cystine, cysteine and methionine and promotes nodulation in legumes (Patel et al., 2013b). The yield attributing characters of crops were greatly affected by sulphur application (Choudhary et al., 2014). Sulphur is one of the constituents of essential oils, imparting flavour, and sharpness in onion, garlic etc.(Havlin et al., 2004).

It is present in soil both in organic and inorganic forms like sulphate (SO4-2) and sulphide (S-2) but is primarily taken up by plants as the SO4-2 ion. The common forms of inorganic sulphur in soils are (1) water soluble sulphate (2) adsorbed sulphate (3) insoluble sulphates of Ca, Ba, Fe etc. and (4) sulphides or other reduced forms of sulphur. Sulphate is present in soil either water-soluble or adsorbed form; the latter depends on soil characteristics such as content of iron oxide/hydroxide and pH. Much of the organic sulphur in soils remains uncharacterized and three broad groups of sulphur compounds are recognized. They are (1) HI-reducible sulphur (2) C-bonded sulphur and (3) residual or inert sulphur. Organic sulphur is a reserve source of sulphur for plants and must undergo mineralization before it becomes available to plants. As sulphur immobilization is microbial process, it depends on factors like moisture, aeration; temperature soil reaction etc. Organic sulphur of the soil has been designated as indicator of reserve sulphur status of soil (Kumar and Singh, 1974).