Abstract:In order to improve soil bulk density, the main cultivars of Hunan tobacco growing area Yunyan 87 was selected as testing material, to optimize the use level of biochar. Effects of three different dosage of biochar on soil improvement and tobacco growth in the field were also studied. The results showed that the amount of biochar can significantly reduce soil bulk density and increase field capacity. Soil bulk density was negatively correlated with the amount of biochar, while field capacity was positively correlated with it. Tobacco showed good botany quality traits, great dry matter accumulation, well-developed root system and coordinated root to shoot ratio when the use level of biochar was below 3750kg·hm-2, which can significantly improve nitrogen use efficiency of flue-cured tobacco. But growth of flue-cured tobacco was restrained with the increased usage level of biochar. Therefore, the biochar usage at a level of 3750kg·hm-2 was more appropriate. The results of this study bear a certain theoretical guiding significance on the using of biochar improved soil and promoting high quality tobacco production.