Azoxystrobin and imidacloprid degradation in biobed setup under laboratory conditions

Biobeds are an important tool to check point source of pesticide contamination and treat on-farm generated pesticide waste. The present study reports retention and degradation of azoxystrobin and imidacloprid in the rice straw – compost (RS+C) and corn cob – compost (CC+C) biobeds. Azoxystrobin (10,000 µg) + imidacloprid (10,000 µg) in 100 mL water were co-applied twice at an interval of 45 days. Both biobeds were effective in retaining high amounts of azoxystrobin and imidacloprid, and no pesticide was detected in the leachate. After 45 days of Ist application, no imidacloprid was detected in the surface layer (3–4 cm) of both the biobeds, while 8.24 and 5.36 µg g−1of azoxystrobin were detected in the RS+C and CC+C biomixtures, respectively. After 30 days of IInd application, destructive sampling suggested that imidacloprid was completely degraded in both the biobeds, while only 81.5% and 68.1% of azoxystrobin degradation were observed in the RS+C and CC+C biobeds, respectively. Imidacloprid was mainly restricted to the surface layer in both biobeds. The RS+C biobed was better than the CC+C in degrading azoxystrobin and was attributed to its higher microbial biomass carbon content. The low-cost biomixtures made of easily available materials have the potential of degrading azoxystrobin and imidacloprid containing rinsate.