Effects of nitrogen in soil and fertilizer on accumulation and distribution of total nitrogen and nicotine in flue-cured tobacco

The 15N isotope was employed to determine effects of deferent nitrogenous sources on accumulation and distribution of total nitrogen and nicotine in flue-cured tobacco.The results showed that the total nitrogen content of different parts(upper leaves,middle leaves,lower leaves,stem and roots) decreased significantly;and the nicotine content of each part increased significantly in the later growth period,65 days after transplanted.At harvest,of the total nitrogen,63.57% came from soil mineralization,while 36.43% from fertilizer,and,68.22% of nitrogen in nicotine came from soil mineralization,while 31.78% from fertilizer.More than 52% of the total nitrogen and nicotine-nitrogen in each part,especially upper leaves,came from soil mineralization,followed by roots and stem,and lower leaves.Approximately 2/3 of the total nitrogen and 3/4 of the nicotine-nitrogen in the leaves came from either fertilizer or soil mineralization,with the greatest proportion in the upper leaves.Three quarters of the nicotine-nitrogen were found in the leaves,with more than 1/2 of it in the upper leaves.