Availability and leaching of nutrients after biofilm biofertilizer applications into a Red Yellow Podsolic soil

Nutrient leaching in RYP soils lowers the fertilizer use efficiency in plantation agriculture of Sri Lanka. The study was conducted to determine nutrient leaching and their availability in a rubber (Hevea brasiliensis Mull Arg.) growing RYP soil supplied with biofilm biofertilizers (BFBF). Microorganisms isolated from rubber roots were formulated as BFBF under in-vitro conditions, and applied with or without 50% and 100% recommended chemical fertilizers into rubber seedlings growing in RYP soils packed in PVC columns. Combine use of inorganic fertilizer with BFBF reduced leaching loss of soil organic carbon throughout the experimental period. The application of BFBF had a marginal influence on leaching losses of K but it significantly reduced Mg losses. The leaching loss of N was not affected in the first two months, but from three months onward a significant reduction was observed with combine use of full recommended inorganic fertilizer with BFBF (100%F+BFBF) compare to inorganic fertilizer alone (100%F). Available nutrients, organic carbon and cations exchange capacity (CEC) in these two treatments were also comparable. Reduced leaching losses of some nutrients in the combine use of inorganic fertilizer with BFBF treatments (50%F+BFBF &100%F+BFBF) were not reflected in the nutrient status of the top soil layer (0-5 cm) but high plant dry matter accumulation was observed in BFBF treated plants. There is a possibility to reduce leaching loss of some nutrients and induce dry matter accumulation of rubber plants by BFBF application into RYP (Hapludults) soils.