Sulphur -a General Overview and Interaction with Nitrogen (Report‪)‬

Introduction With the improvement of crop productivity through the adoption of high-yielding varieties and multiple cropping systems, fertilizer use has become more and more important to increase crops yield and quality. S is an essential plant nutrient for crop production. For oil crop producers, S fertilizer is especially important because oil crops require more S than cereal grains. For example, the amount of S required to produce one ton of seed is about 3-4 kg S for cereals (range 1-6); 8 kg S for legume crops (range 5-13); and 12 kg S for oil crops (range 5-20). In general, oil crops require about the same amount of S as, or more than, phosphorus for high yield and product quality. In intensive crop rotations including oil crops, S uptake can be very high, especially when the crop residue is removed from the field along with the product. This leads to considerable S depletion in soil if the corresponding amount of S is not applied through fertilizer. S is increasingly being recognized as the fourth major plant nutrient after nitrogen, phosphorus and potassium. The importance of S in agriculture is being increasingly emphasized and its role in crop production is well recognized (Jamal et al., 2005, 2006a; 2006b; 2006c; 2009; 2010; Scherer, 2009). S is best known for its role in the formation of amino acids methionine (21% S) and cysteine (27% S); synthesis of proteins and chlorophyll; oil content of the seeds and nutritive quality of forages (Tandon, 1986; Jamal et al., 2005, 2006a; 2009). Although S is one of the essential nutrients for plant growth with crop requirement similar to phosphorus, this element received little attention for many years, because fertilizers and atmospheric inputs supplied the soil with adequate amounts of S. Now, areas of S deficiency are becoming widespread throughout the world due to the use of high-analysis low S fertilizers, low S returns with farmyard manure, high yielding varieties and intensive agriculture, declining use of S containing fungicides and reduced atmospheric input caused by stricter emission regulation. An insufficient S supply can affect yield and quality of the crops, caused by the S requirement for protein and enzyme synthesis as well it is a constituent of the amino acids, methionine and cysteine. To overcome the problems associated with S deficiency a number of S-containing fertilizers as well as other S containing by-products from industrial processes are available. The information on impact of S-fertilization and S in general has been reviewed and presented under the following heads: The function of S, Soil organic S, Soil inorganic S, S deficiency in soil, Sulphur and nitrogen interaction in soil, Sulphur and nitrogen interaction in plant , Sulphur and nitrogen interaction in relation to yield and quality of crop, Sulphur and nitrogen interaction in relation to uptake and assimilation of sulphur and nitrogen, N:S ratio in relation to sulphur and nitrogen interaction.