Sulphur Fractions Under Soybean–Wheat Cropping System in 50-years Old Long-term Fertilizer Experiment on a Vertisol

Abstract

The present experiment was conducted during rabi season, 2021–22 at Jawaharlal Nehru Krishi Vishwavidyalaya, Jabalpur, Madhya Pradesh, to evaluate the effect of long-term application of inorganic fertilizers and organic manure on sulphur dynamics under a 50-year-old soybean–wheat cropping system in a Vertisol. The results revealed that the application of 100% NPK along with FYM @ 5 t ha^-1 recorded the highest organic carbon content and available nitrogen, phosphorus, and potassium at both 0.0–0.15 m and 0.15–0.30 m soil depths, whereas the lowest values were observed under the control plot. The integrated use of balanced fertilizers and FYM significantly enhanced available sulphur and different sulphur fractions in comparison to the control and sulphur-free treatments (100% N and 100% NPK–S). Among the sulphur fractions, their relative abundance followed the order: Total-S > Organic-S > Heat Soluble-S > Water Soluble-S. Significant positive correlations were observed between soil organic carbon, available N, P, K and S and the various sulphur fractions at both soil depths. Continuous application of sulphur-free fertilizers resulted in depletion of available sulphur compared to its initial status. The study concluded that the conjoint application of balanced fertilizers with organic manure, improved sulphur availability, maintained soil fertility, and sustained crop productivity. Therefore, sulphur application along with balanced fertilization was found essential for the long-term sustainability of the soybean–wheat cropping system.