In-vitro evaluation of rice straw biochars' effect on bispyribac-sodium dissipation and microbial activity in soil

Dissipation of bispyribac-sodium was estimated in an unamended sandy loam soil and soil amended with rice straw and its biochars in pot culture experiment. Effect of herbicide and amendments on abundance and activity of soil microbial parameters was also assessed by determining soil biological parameters. Amendment type, application rate and soil moisture had differential influence on bispyribac-sodium dissipation and soil's microbial parameters. Amendment of soil with rice straw and its biochars enhanced the dissipation of bispyribac-sodium (DT₅₀ = 7.55-18.44 days) as compared to unamended soil (DT₅₀ = 23.13-28.60 days) and dissipation decreased in this order: rice straw >350BC > 550BC > CBC amended soil > unamended soil. Dissipation of bispyribac-sodium decreased with increase in amendment level of rice straw and its biochars in soil. Irrespective of amendment type and application rate, bispyribac sodium was more persistent under submerged conditions than at field capacity and its DT₅₀ was 10.13 to 28.60 and 7.55-27.14 days, respectively. Dehydrogenase, alkaline phosphatase activity and bacterial population indicated that application of the organic amendment decreased negative effects of the herbicide on soil enzymatic activities. These findings prove that biostimulation using rice straw and its biochars has the potential to decrease the persistence of bispyribac-sodium and minimize its environmental hazards.