Application of biochar and nitrogen influences fluxes of CO2, CH4 and N2O in a forest soil

Abstract

Nitrogen (N) fertilization of forests for increasing carbon sequestration and wood volume is expected to influence soil greenhouse gas (GHG) emissions, especially to increase N₂O emissions. As biochar application is known to affect soil GHG emissions, we investigated the effect of biochar application, with and without N fertilization, to a forest soil on GHG emissions in a controlled laboratory study. We found that biochar application at high (10%) application rates increased CO₂ and N₂O emissions when applied without urea-N fertilizer. At both low (1%) and high biochar (10%) application rates CH₄ consumption was reduced when applied without urea-N fertilizer. Biochar application with urea-N fertilization did not increase CO₂ emissions compared to biochar amended soil without fertilizer. In terms of CO₂-eq, the net change in GHG emissions was mainly controlled by CO₂ emissions, regardless of treatment, with CH₄ and N₂O together accounting for less than 1.5% of the total emissions.

Keywords: Biochar; Carbon sequestration; Forest soil; Global warming potential; Greenhouse gas flux; Nitrogen fertilizer.