Comparative Study of Toxicity Attenuation of Phorate & Chlorpyriphos on Eisenia fetida by Rice Straw Biochar.

Biochar is an external organic input added in soil as ameliorative agent against soil pollution. In this study, the impact of biochar on Eisenia fetida's mortality (LC50) of two organophosphates (Phorate and Chlorpyriphos) in the artificial OECD soil was assessed. Acute test was applied to calculate the LC50 of Phorate and chlorpyrifos on the earthworm Eisenia fetida by using artificial soil test. Biochar was derived from rice straw, a major agricultural crop residue at two different pyrolysis temperature 300°C and 500°C with the heating rate of 10°C/min for 3 hours in an inert gas environment with limited supply of oxygen in a tubular muffle furnace. Rice straw biochar was then analyzed physiochemically and morphologically. Results demonstrated that the biochar produced is consistent with available literature. Experiment was set up as per OECD guidelines. Two different biochar RSB300 and RSB500 treatments were applied from 1.5%, 3%, 5%, 6.5%, 8% and 10% application rate for both organophosphates separately to nullify the earthworm's mortality at LC50. The mortality changes were noted after 14 days exposure of treatments at median lethal concentration of pesticides.LC50 of Phorate and CPF were calculated by probit analysis (p value <.005) and found to be 27.436mg/kg and 99.806 mg/Kg respectively. The outcome of correlation analysis between rate of application of biochar vs mortality (LC50) in Eisenia fetida for Phorate and Chlorpyrifos reported that RSB500 Phorate and RSB500 CPF showed statistically significant difference with p values close to 0 and R square values than RSB300 Phorate and RSB300 CPF. [ABSTRACT FROM AUTHOR]