RESUMO
The continuous use of KCl may not be sustainable in the long term in agricultural systems. High doses used in crops accumulate in the soil and plants, hindering the metabolic processes of soil organisms. This study assessed the soil microbial activity in response to the application of K sources in banana crop and effects on microbial C. The experimental design was completely randomized with four K sources: potassium nitrate (KNO3), potassium chloride (KCl), potassium sulfate (K2SO4), and monopotassium phosphate (KH2PO4) at 200 mg kg-1of K2O, besides the control (without K) and combinations KCl:K2SO4. KCl application increased microbial activity 7 days after incubation, with gradual reduction over time. The isolated application of K2SO4and the combination KCl: K2SO4at the ratio 60: 40% increased total CO2released by the microbiota. K2SO4source had the highest microbial biomass C (MBC), as well as the 60: 40 combinations. Isolated application of K sources, especially with high chloride concentration, reduces the soil microbial activity and MBC.(AU)