Effects of rates and methods of N application on growth and N uptake of flue-cured tobacco

Our previous study showed that both changing N applying method and reducing N application rate to 52.5 kg/ha could meet the growth requirement of tobacco plant for N.A field experiment combining with a microplot in Yunnan province was carried out to further study the effects of N fertilization on the growth and N uptake of flue-cured tobacco.Two N application rates of 120 and 52.5 kg/ha were used.The results showed that tobacco supplied N 120 kg/ha mainly utilized soil N after topping,while soil N became the dominant N source after rosette for plants with N 52.5 kg/ha.Nitrogen application with 52.5 kg/ha could assure the growth of plants from the stage of transplanting to topping;but their dry matter gain and N accumulation decreased slightly comparing with the treatment of N 120 kg/ha due to inadequate N supply after topping.Changing N application rates had no effect on dry matter distribution in tobacco plant.The higher the rate of fertilizer N supplied,the more fertilizer N was found in the plant,and the higher the ratio of fertilizer N to total N in different organs and whole plant was.The highest ratio of the fertilizer N to total N in plant was found in rosette stage,and then it declined slowly.In addition,the ratio of the fertilizer N to total N in upper leaves was smaller than that in lower leaves.And the difference of the ratio of fertilizer N to total N between the upper and lower leaves was smaller,when more N(120 kg/ha) was supplied.