Short-Term Effect of Biochar on Microbial Biomass, Respiration and Enzymatic Activities in Wastewater Irrigated Soils in Urban Agroecosystems of the West African Savannah

Urban Farm DB summary

In a field experiment on irrigated urban agriculture in the Guinea savannah zone of Ghana, this study assessed the transient effect of rice husk biochar (20 t ha-1) and/or mineral fertilizer (NPK 15-15-15) on microbial respiration, microbial biomass carbon (MBC) and enzyme activities in soils irrigated with wastewater and tap water. One year after biochar application, soil organic carbon (SOC) increased by up to 123%, hot water extractable carbon (HWEC) increased by 11-26%, and MBC increased by 34%. Basal respiration increased significantly by up to 46% in mineral-fertilized soil but decreased by 12-45% under wastewater irrigation. The metabolic quotient (qCO2) indicated reduced microbial community stress and higher carbon use efficiency with biochar application and wastewater irrigation. Total enzyme activity increased under wastewater irrigation, and biochar-treated soils showed a more diverse composition of carbon-cycling enzymes and higher aminopeptidase activity. Biochar and wastewater showed positive effects on biological soil properties that contributed to soil fertility, and the results suggest biochar may have beneficial long-term effects on non-biochar SOC stocks.