Abstract: By the method of field in situ culture and ¹⁵N isotopic tracer technique, and taking flue-cured tobacco (Nicotiana tobacum) cultivar K326 as test material, a field experiment was conducted in the Nanxiong tobacco-planting area of Guangdong Province to study the characteristics of soil nitrogen (N) mineralization, the patterns of N accumulation and allocation in tobacco plants, and the allocation of plant-absorbed fertilizer N applied in current growth season. In the study area, the amount of soil mineralized N increased with tobacco growth, peaked at 75 days after transplanting, and decreased thereafter. The soil  mineralized N at each tobacco growth stage was significantly higher in the control than in the N fertilization treatment. The N accumulation in tobacco plant organs was in the order of leaf > stalk > root. Tobacco plants mainly absorbed fertilizer N at rosette stage and topping stage, and mainly absorbed soil N at mature stage. The absorbed N in tobacco whole growth period was mainly derived from soil N, and the absorbed soil N and its proportion to the total absorbed N increased evidently with extending growth stage and ascending leaf position. The fertilizer N use efficiency per plant and the residual rate and loss rate of applied fertilizer N were 30.8%, 32.3%, and 36.9%, respectively. In the study area, soil N mineralization rate was relatively high, and soil N had greater effects on the quality of upper tobacco leaves. Under the application rate of 150 kg N·hm^-2, the residual amount and loss amount of applied fertilizer N were relatively high.

Key words: flue-cured tobacco, nitrogen, soil, mineralization, ¹⁵N tracer