Objective   Effects of applying tobacco stalk biochar- or bamboo biochar-based fertilizer on the carbon, nitrogen, and microorganisms in soil of tobacco-growing fields were compared.

  Method  In a field experimentation, treatments using no fertilizer as control (CK), a fertilizer designed for tobacco farming (TF), a tobacco stalk biochar-based fertilizer (TBF), or a bamboo biochar-based fertilizer (BBF) were conducted. pH, carbon, nitrogen, enzyme activity, and microbial community of the soil samples were monitored.

  Result   Compared to TF, either TBF or BBF raised by more than 0.5 on soil pH and on microbial biomass carbon by more than 30%; on soluble organic carbon, TBF did by 21.4% and BBF by 30.7%; on oxidizable organic carbon, TBF did by 32.4% and BBF by 17.9% (p＜0.05); on soluble organic nitrogen, TBF did by 50.7% and BBF by 37.7%; on particulate organic nitrogen, TBF did by 28.0% and BBF by 12.7%; and on invertase activity, TBF did by 9.4% and BBF by 3.6%. The Chao1 index of the microbial community in the TBF-treated soil was significantly higher than that of TF-treated counterpart by 5.4% and that of BBF-treated soil by 3.2%. However, there were no significant differences on the observed species or Shannon index of the microbial communities in soils under different treatments. Both TBF and BBF significantly affected the structure of the microbial community in the soil. Notably, the Proteobacteria population decreased by 5.0% under TBF treatment and by 3.4% under BBF treatment in comparison to CK. Even when TF was applied, BBF still managed to generate 18.3% greater abundance on Firmicutes, while TBF 64.8% on Curvularia, in the soil.

  Conclusion  Either TBF or BBF treatment could increase the content of carbon, nitrogen, enzyme activity, and microbial abundance in the tobacco field soil. It helped optimize the structure of the microbial community as well. However, TBF seemed to benefit the improvements more than BBF did.