Effect of nitrogen rates on root-shoot balance and nitrogen accumulation and distribution in flue-cured tobacco

A pot-cultured experiment was conducted to study the ratio of root to shoot and nitrogen accumulation and distribution of tobacco under different nitrogen levels by using 15N tracer technique. Tobacco plants were applied N 0 (CK), 5.45 (N1) and 8.18 g (N2) per plant respectively. The results showed that above-ground dry matter accumulation amount increased with the increasing of nitrogen rate, root dry matter accumulation amount of treatment N1 was the most among the three treatments from planting to topping stage. From topping to maturity stage, the above-ground dry matter accumulation amount of treatment N1 was the most and the root dry matter accumulation amount increased with the increasing of nitrogen rate. The ratio of root to shoot decreased with the increasing of nitrogen application rate at topping stage while increased in maturity stage. The nitrogen accumulation amount of total plant of treatment N1 was the most among the three treatments from topping to maturity stage; nitrogen accumulation was observed in each plant organ of treatment N1, whereas in treatment CK and N2, the outputs of nitrogen were observed in lower and middle leaves. The distribution proportion of nitrogen in roots decreased with the increasing of nitrogen application rate at topping stage. With the increasing rate of nitrogen application, the proportion of nitrogen uptake from fertilizer increased while decreased from soil, and the proportion of nitrogen uptake from basal fertilizer increased while decreased from topdressing fertilizer. About this experiment, the treatment of 5.45 g nitrogen applied per plant could accelerate root-shoot balance, and plants grew naturally.