Short-term CO2 and N2O emissions and microbial properties of biochar amended sandy loam soils

► Addition of 4 biochars to sandy loam soil, monitoring of CO2 and N2O emissions and soil chemical and biological measures. ► Low temperature biochars highest GHG emissions, N mineralization and microbial stimulation. ► Reduction of emissions due to high temperature biochar additions. ► Volatile matter content important biochar property explaining short-term CO2 and N2O emissions.