Microbial activity and metabolic quotient of microbes in soils amended with biochar and contaminated with atrazine and paraquat

The study was conducted to determine how biochar as a soil amendment maintained the microbial community in pesticide contaminated soils. Alfisol (Adenta series – Typic Kandiustalf) and Vertisol (Akuse series – Typic Calciustert) were amended with biochar (0 t/ha biochar, 10 t/ha cocoa husk biochar (CHB), 10 t/ha rice husk biochar (RHB)) and pesticides (atrazine and paraquat at two rates each namely 0 kg/ha pesticide and 10 times the normal recommended rate of pesticide) were applied. The CHB-amended soils stimulated microbial activities such as ammonia and nitrate release more than the RHB-amended soils. Basal respiration was significantly higher in the atrazine polluted soils than in paraquat polluted soil. Significant interaction occurred between soil type and biochar and high microbial biomass carbon was recorded for vertisol amended with CHB. Metabolic quotient was lower in soils amended with biochar and polluted with atrazine than in the un-amended soil. The use of CHB in soil of high clay content (47.5%, i.e. the vertisol) was a more effective management tool in maintaining the microbial community in a pesticide-polluted environment than in soil of lower clay content (22.5%). Soils of high clay content amended with biochar can sustain the soil microbial community even in a disturbed environment.