Sulphur regime of an Arable Soil (Typic ustrochrept) under long-term differential fertilization at various growth stages of wheat

The effect of continuous application of N, P and K to a maize-wheat annual sequence for 22 years was studied on the changes in the chemical pools of sulphur in the soil and their effect on crop yield and sulphur uptake. Out of the S fractions of heat soluble and water soluble S, the former was the dominant one. Application of increasing levels of N and P (up to 40 kg P₂O₅ ha⁻¹) caused a significant increase in the S fractions, but the plots receiving higher doses of P (80 kg P₂O₅ ha⁻¹) and K (40 kg K₂O ha⁻¹) had lower contents of these S forms. During wheat growth, all the S fractions decreased with advancing crop growth. The sulphur concentration of plants also exhibited a decline with increasing age of the plant. The sulphur uptake by the plant continued to increase with plant age. The association between S content in the top layer (0–15 cm) and S concentration and its uptake by wheat was significant at tillering stage whereas the later stages showed significant association in one or the other plant part.