Pyrolysis Temperature vs. Application Rate of Biochar Amendments: Impacts on Soil Microbiota and Metribuzin Degradation

Biochar-amended soils influence the degradation of herbicides depending on the pyrolysis temperature, application rate, and feedstock used. The objective of this study was to evaluate the influence of sugarcane straw biochar (BC) produced at different pyrolysis temperatures (350 & DEG;C, 550 & DEG;C, and 750 & DEG;C) and application rates in soil (0, 0.1, 0.5, 1, 1.5, 5, and 10% w/w) on metribuzin degradation and soil microbiota. Detection analysis of metribuzin in the soil to find time for 50% and 90% metribuzin degradation (DT50 and DT90) was performed using high-performance liquid chromatography (HPLC). Soil microbiota was analyzed by respiration rate (C-CO2), microbial biomass carbon (MBC), and metabolic quotient (qCO(2)). BC350 & DEG;C-amended soil at 10% increased the DT50 of metribuzin from 7.35 days to 17.32 days compared to the unamended soil. Lower application rates (0.1% to 1.5%) of BC550 & DEG;C and BC750 & DEG;C decreased the DT50 of metribuzin to similar to 4.05 and similar to 5.41 days, respectively. BC350 & DEG;C-amended soil at high application rates (5% and 10%) provided high C-CO2, low MBC fixation, and high qCO(2). The addition of low application rates (0.1% to 1.5%) of sugarcane straw biochar produced at high temperatures (BC550 & DEG;C and BC750 & DEG;C) resulted in increased metribuzin degradation and may influence the residual effect of the herbicide and weed control efficiency.

Automated summary

The degradation of herbicides can be influenced by the type of biochar used, its pyrolysis temperature, and application rate. The study evaluated the impact of sugarcane straw biochar produced at different temperatures (350 °C, 550 °C, and 750 °C) and applied at various rates (0%, 0.1%, 0.5%, 1%, 1.5%, 5%, and 10% w/w) on the degradation of metribuzin and soil microbiota. It was found that lower application rates of biochar produced at higher temperatures decreased metribuzin degradation, while higher application rates of biochar produced at lower temperatures increased metribuzin degradation.