[01] P. Premanandarajah, Department of Agricultural Chemistry, Faculty of Agriculture, Eastern University, Chenkalady, Sri Lanka. [02] W. Shanika, Department of Agricultural Chemistry, Faculty of Agriculture, Eastern University, Chenkalady, Sri Lanka.

Potculture experiments were conducted using different sulphur sources to improve organic carbon content and to maintain a better microbial population in groundnut (Arachis hypogaea) sunflower (Helianthus annuus) cropping system. Four organic sources (farmyard manure, poultry manure, vermicompost and sewage sludge) evaluated in comparison with the standard inorganic source of single superphosphate, all applied on equal S basis at 75 kg S ha-1. The six treatments, including a no-S (control) were replicated four times in a completely randomized design. The main crop of groundnut was followed by the residual crop of sunflower. Post-harvest soil analysis was carried out after groundnut and sunflower. Organic manures increased the organic carbon content, biomass carbon content and microbial population. Poultry manure increased the microbial population and biomass carbon content. However, the microbial biomass carbon content in the post-residual crop soil was lower than that in the post-harvest soil after first crop.

Organic Carbon, Biomass Carbon, Sulphur Source, Organic Manure, Microbial Population

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