Pine sawdust biochar reduces GHG emission by decreasing microbial and enzyme activities in forest and grassland soils in a laboratory experiment.

This study investigated the effects of biochar soil amendment on greenhouse gas (GHG) emissions in soils. Pine (Pinus koraiensis Siebold & Zucc.) sawdust biochar was produced at 300 and 550°C with and without steam activation (coded as BC300-S, BC550-S, BC300 and BC550, respectively). They were applied to forest and grassland soils at 1.5% (w/w) rate in a 100-day laboratory incubation experiment. Application of BC550 significantly reduced cumulative CO2 emission from the forest soil by 16.4% relative to the control (without biochar application), but not from the grassland soil. Biochar application did not have significant effects on CH4 uptake from either soil. Application of BC550 and BC550-S reduced the cumulative N2O emission by 27.5 and 31.5%, respectively, in the forest soil and 14.8 and 11.7%, respectively, in the grassland soil, as compared to the control. The effects of BC300 and BC300-S on cumulative CO2 and N2O emission was not significant in both soils, except for the significant reduction in cumulative N2O emission from the forest soil by BC300-S. The effect of BC550 and BC550-S on N2O emission persisted until the end of the 100-day incubation indicating possible long-term effects of these biochars. We conclude that BC550 and BC550-S had the highest potential to reduce CO2 and N2O emission in the 100-day laboratory incubation experiment. These biochars should be tested in long-term field trials to confirm their potential for mitigating CO2 and N2O fluxes in real ecosystems with a relevant time frame.