Micro-particle biochar for soil carbon pool management: Application and mechanism

Abstract

In this study, the possibility of using biochar for soil carbon pool regulation owing to its unique physical and chemical properties was tested. Specifically, to investigate the effects of different biochar particle sizes (500–2000, 250–500, 20–250, and < 20 μm) on the soil carbon pool structure as well as the associated mechanism, pot culture experiments were performed using peanut shell biochar. The results obtained showed that the chemical properties of the biochar remained unchanged; however, the different particle sizes influenced the porosity properties of the biochar. Smaller-sized biochar particles showed specific surface area (32.91 m2/g), pore volume (0.043 m3/g), and pore size (4.56 nm) that were larger than those corresponding to their larger-sized counterparts. Further, biochar application enhanced the organic carbon content of the treated soil by up to 46.85 % compared with conventional fertilisation. Biochar with particle size < 20 μm improved the mean weight diameter of soil water-stable aggregates by 2.5–12.5 %. Furthermore, the easily oxidisable carbon content of the biochar-treated soil reached 2.22 g/kg, increasing by 80.31–89.58 % compared with that achieved via conventional fertilisation. The average soil dissolved organic carbon content was 356.64 mg/kg, which is 78.86 % higher than that achieved via conventional fertilisation. Additionally, biochar with a particle size < 20 μm also significantly improved the soil carbon pool management index by 186.17 %. Therefore, the results of this study provide a theoretical basis for the scientific application of biochar based on particle size given that micro-particle biochar, in particular, can significantly improve the soil carbon pool management index.