Sulphur distribution and fractionation in calcareous soils: Impact of long-term organic and inorganic inputs in rice-based systems

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This study examines the long-term effects of organic and inorganic fertilizers on soil sulphur (S) dynamics and fractionation in rice-based cropping systems on calcareous soils, addressing critical gaps in understanding S distribution and availability. The findings reveal that prolonged fertilization significantly influences S content across various soil depths, with the most pronounced increases in available S occurring at 30-45 cm, particularly in plots treated with compost. Compost amendments were especially effective in enhancing S availability, promoting greater S accumulation compared to inorganic fertilizers alone. The fractionation analysis highlighted that fertilization strategies and cropping systems affected different S fractions, with organically bound sulphur being the dominant form. Total S content increased substantially with the application of both organic and inorganic fertilizers, with compost at 5 t ha-1 showing the greatest impact. The study also demonstrated that S concentrations increased with soil depth, influenced primarily by organic inputs such as compost. These results emphasize the crucial role of organic inputs, particularly compost, in improving S availability and its distribution within the soil profile, which is essential for optimizing nutrient management in rice-based cropping systems. The research underscores the importance of adopting long-term fertilization strategies that combine organic and inorganic inputs to enhance soil health, sustain crop productivity, and ensure the efficient cycling of essential nutrients like sulphur. By providing insights into the interplay between fertilization practices and sulphur dynamics, the study offers valuable guidance for sustainable agricultural management in rice based systems, particularly in calcareous soils, where the use of compost can significantly boost available S levels and improve overall soil fertility.