Department of Soils, Punjab Agricultural University
A greenhouse experiment was conducted on 17 soils having a range in calcium chloride (0.15%) extractable S varying from 4.0 to 39.0 mg kg−1 soil to determine the critical deficiency level of S in medium to coarse-textured, alluvium-derived soils of Punjab for wheat. Among the five extractants used, three extractants viz. 0.15% calcium chloride, mono-calcium phosphate (500 ppm P) and heat soluble S had shown highly significant correlations with Bray's per cent yield. Critical levels of available S in soils extracted with calcium chloride, mono-calcium phosphate and heat soluble were established as 11.2, 13.5 and 15.5 mg kg−1 soil using statistical method of Cate and Nelson. Following the same method, the critical limit of total S in flag leaf of wheat at 80 days growth was worked out to be 0.195 per cent. Soil application of 10 mg S kg−1 soil significantly increased the grain yield of wheat, however, the differences in grain yield between 10 and 20 mg S kg−1 soil were non-significant.
Critical S level, Extractants, Flag leaf, Wheat
