Effect of Sulfur-Enriched Biochar in Combination with Sulfur-Oxidizing Bacterium (Thiobacillus Spp.) on Release and Distribution of Phosphorus in High Calcareous P-Fixing Soils

Reducing the reliance on hazardous agrochemicals (i.e., chemical fertilizers) that damage agro-ecosystems represents great challenges in modern agriculture. Sulfur-enriched biochar derived from organic wastes in the presence of sulfur-oxidizing bacteria could be a promising alternative to inorganic phosphorus fertilizers for sustainable P use in highly calcareous soils. This incubation experiment examined the impacts of applying a mixture of bone-wood chips biochar and sulfur at different rates with sulfur-oxidizing bacteria as well as incubation periods on availability and fraction changes of P in high P-fixing soil as calcareous sandy soil. In this study, 100 g air-dried soil was placed in plastic jars. It contains 3 treatments: control is unamended soil, soil amended with 0.25 g of biochar amendment jar(-1), and soil amended with 0.50 g of biochar amendment jar(-1). Soil in all treatments was inoculated by sulfur-oxidizing bacteria (Thiobacillus spp.). The results revealed that applying biochar amendment improved significantly phosphorus availability compared with control. Olsen-P increased with increasing incubating periods for bone char treatments and control. The value of Olsen-P was highest when 0.25 g and 0.50 g of biochar amendments jar(-1) were added (32 and 34 mg kg(-1), respectively) and the lowest in the control treatment (29 mg kg(-1)). Applying biochar amendments to calcareous sandy soil significantly enhanced labile P and P associated with calcium fractions compared to control. Based on those obtained results, using sulfur-enriched biochar in calcareous sandy soil is beneficial because it can be a slow-release fertilizer, has a low cost, and is a clean alternative to mineral phosphate fertilizers.