Indigenous biobed to limit point source pollution of imidacloprid in tropical countries

Point pollution of pesticides originating from the washing of spraying machines could be controlled by biobed system and it is in use in temperate countries. The biobed system is yet to be established in tropical countries. An indigenous biobed system was prepared using local resources like rice straw, farm yard manures (FYM) and paddy field soil to suit the tropical climate. Lowermost 3 cm layer of the biobed system was filled with rice husk biochar to prevent leaching of pesticides from the system. This model system was tested with high doses of imidacloprid (178 mg/column), a commonly used pesticide against number of insect-pests in different crops, for its degradation. The bio-mix trapped a major part of the imidacloprid on the top most layer of the biobed column and only a very small part of imidacloprid recovered from the leachate. The biobed system could degrade 70.13% of applied imidacloprid within 15 days of the experiment and only 5.27% of the total pesticide recovered 90 days after incubation. Addition of biochar layer adsorbed imidacloprid from the outgoing leachate from the biobed column. Biomixture boosted microbial activity more particularly fungal population, which might be responsible for imidacloprid degradation. Microbial biomass carbon, and soil enzymes indicated faster dissipation of imidacloprid from the top layer of the biobed. This simple but efficient biobed system using local resources can fulfill the need of the small and marginal farmers of Asian countries for pesticide decontamination. [Display omitted] •The biomixtures contain rice straw, manures, soil and rice husk biochar.•Top 10 cm of the column adsorbed and degraded imidacloprid.•The system could degrade 70.13% of applied imidacloprid within 15 days.•Fungi might be responsible for imidacloprid degradation.