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Abstract: In order to alleviate the stress of heavy metal Pb on flue-cured tobacco and reduce the toxicity of Pb,pot experiments were conducted to simulate Pb pollution in soil(200 mg/ kg).The threatments were setted as no fertilizer( CK),single application of compound fertilizer special for tobacco( T1),compound fertilizer special for tobacco and biochar combined application(T2),compound fertilizer special for tobacco,biochar and organic fertilizer(T3),and the effects of combined application of biochar and organic fertilizer on biomass accumulation of flue-cured tobacco,root activity,Pb accumulation of tobacco plant and soil microbial population under Pb stress.The results showed that the biomass of fluecured tobacco treated with T3 was 24.5% higher than that of T1 at 90 d after transplanting,and the biomass showed T3>T2>T1 at the same nitrogen application rate;the root activity of tobacco plant showed T3>T2>T1>CK in general,among which T3 and T2 were 94.9% and 55.1% higher than that of CK at 90 d after transplanting,respectively.At 90 d after transplanting,the available Pb content in soil,Pb content of tobacco stems and tobacco leaf were reduced by 15.8%,40.6% and 25.0% compared with CK,respectively,and the Pb content of tobacco leaves in T3 decreased by 30.0% and 20.9% compared with T1,T2 respectively.Soil pH value and microbial flora of T3 were significantly improved compared with CK and T1.In general,the application of biochar and the combined application of biochar and organic fertilizer could reduce the effect of heavy metal Pb on the growth of flue-cured tobacco,decrease the content of available Pb in the soil and the accumulation of Pb in roots,stems and leaves,and improve soil microorganism quantity.

Key words: Biochar, Organic fertilizer, Combined application, Heavy metal, Pb stress, Flue-cured tobacco, Soil microorganism