Abstract:Among nutrients necessary for plant growth,nitrogen is both the most unstable in soil,and the most important for the yield and the quality of tobacco leaves.For obtaining high yield of tobacco leaves,over-fertilization of nitrogen in present tobacco production in China was very common,which often caused reduction of the quality of tobacco leaves.The dosage and the time of nitrogen supply according to the present recommendation for the application rate of chemical fertilizer nitrogen can not meet the demand of tobacco plant for nitrogen.Soil nitrogen mineralization at the late growth stage of plant makes it difficult to manage nitrogen during the plant growth,and the suitable method to control the nitrogen status in plant is also lack.The understanding of the reason for the increased nicotine concentration in tobacco leaves is not correct.Accordingly,in this paper,the topics of optimal application rate and time of fertilizer N,rapid plant nitrate test,soil nitrogen mineralization at the late growth stage of plant,and the relations between application rate N fertilizer and nicotine content in tobacco leaves are discussed.