Effect of biochars from sewage sludge on plant growth, soil microorganisms, and nitrogen content in grey forest soils

Summary: The aim of this study was to assess the impact of biochar obtained from sewage sludge at different pyrolysis temperatures on the height and biomass of oat and mustard plants, as well as on the microbiological parameters of gray forest soil. The biochar was obtained at the fast pyrolysis unit FPP02 at a temperature of 300 + 20 °C and 500 + 20 °С. During the laboratory vegetation experiment, 2%, 5% and 10% of biochar from the soil weight were added to the soil. Oat and white mustard plants were grown in vegetational pots for 42 days. The height and biomass of white mustard plants increased compared to the control when adding 2 % and 5% of biochar obtained at 500 °C, and 2 % of biochar obtained at 300 °C. When 10% biochar obtained at 300º was added to the soil, the productivity of oat and mustard plants decreased compared to the control. The introduction of biochar from sewage sludge contributed to an increase in the total nitrogen content in the soil. At that the number of most trophic groups of microorganisms increased, and more significantly -- when biochar obtained at 300º was added. The highest correlation between the concentration of biochar obtained at 300º and the number of microorganisms was observed for microscopic fungi, the lowest -- for the group of pedotrophic microorganisms.