Soil Organic Carbon Sequestration after Biochar Application: A Global Meta-Analysis

Biochar application to soil has the potential to sequester carbon in the long term because of its high stability and large-scale production potential. However, biochar technologies are still relatively new, and the global factors affecting the long-term fate of biochar in the environment are still poorly understood. To fill this important research gap, a global meta-analysis was conducted including 64 studies with 736 individual treatments. Field experiments covered experimental durations between 1 and 10 years with biochar application amounts between 1 and 100 Mg ha(-1). They showed a mean increase in soil organic carbon (SOC) stocks by 13.0 Mg ha(-1) on average, corresponding to 29%. Pot and incubation experiments ranged between 1 and 1278 days and biochar amounts between 5 g kg(-1) and 200 g kg(-1). They raised SOC by 6.3 g kg(-1) on average, corresponding to 75%. More SOC was accumulated in long experimental durations of >500 days in pot and incubation experiments and 6-10 years in field experiments than in shorter experimental durations. Organic fertilizer co-applications significantly further increased SOC. Biochar from plant material showed higher C sequestration potential than biochar from fecal matter, due to higher C/N ratio. SOC increases after biochar application were higher in medium to fine grain textured soils than in soils with coarse grain sizes. Our study clearly demonstrated the high C sequestration potential of biochar application to agricultural soils of varying site and soil characteristics.

Automated summary

Biochar application to soil has the potential to effectively sequester carbon in the long term, with higher effectiveness in medium to long-term experiments. Organic fertilizer co-applications and biochar from plant material are shown to further increase soil organic carbon levels.