Negative priming effect of three kinds of biochar on the mineralization of native soil organic carbon

Abstract This study was conducted to improve our understanding of the effect of biochar on the degradation of original soil organic carbon (SOC) and the resulting net C sequestration. A 120‐day incubation experiment was conducted to detect the CO 2 evolution from soil amended with three kinds of biochar, namely, rice husk biochar (RH), pecan shell biochar (PS), and bamboo biochar (BB), at biochar to soil ratios of 0% (as control), 1%, 2%, and 5%, as well as 100% pure biochar, and to evaluate their priming effect on SOC mineralization. Results showed that the cumulative mineralized amounts of SOC decreased by 7.95–10.7% with 5% RH, PS, and BB treatments, whereas there were no significant differences in 1% or 2% biochar treatments after 120 days of incubation compared with the control. Biochar had a suppressing influence on native SOC decomposition, and the effect increased with the amount of applied biochar increasing. The negative priming effect of biochar on the mineralization of SOC was mainly observed after 15 days of incubation and increased with incubation time. The negative effects of BB and RH were significantly stronger than that of PS at the 5% application ratio. This was mainly due to the less pores and smaller specific surface area of PS, which resulted in the weaker encapsulation and adsorption protection effect of PS than RH and BB, and inhibited the degradation of the adsorbed native SOC. Therefore, BB and RH have great potential for C sequestration and mitigation, especially in soils with low organic C.