The Effect Of Amount And Form Of Nitrogen Topdressing On Growth Of Flue-cured Tobacco And Inorganic Nitrogen In Soil

In the process of tobacco cultivation, nitrogen topdressing has important implications to tobacco at later stages. Determining appropriate amount and form of nitrogen topdressing is of great significance to optimizing tobacco cultivation and improving quality and yield of tobacco.In this paper, the effect of amount and form of nitrogen topdressing on plant height, leaf area, stem circumference, chlorophyll, and photosynthetic rate, dry weight, yield of per plant, and inorganic nitrogen in soil is studied through field and pot experiments, and eventually the following conclusions are got.Experiment of amount of nitrogen topdressing (urea):(1) Tobacco plant height, leaf area, net photosynthetic rate during whole period first increased and then decreased with the adding of amount of nitrogen topdressing. Chlorophyll content at the root extending stage increased with the adding of amount of nitrogen topdressing. On the whole, the better amount of nitrogen topdressing was13.91g / per plant ( T₃ ).(2) Stem circumference and yield of per plant increased with the adding of amount of nitrogen topdressing. Dry weight under different treatments showed the same trend with net photosynthetic rate, plant height, and leaf area. On the whole, the better amount of nitrogen topdressing was13.91g / per plant ( T₃ ).(3) Increasing of amount of nitrogen topdressing played a certain role in upgrading of ammonium nitrogen in 0-80cm soil layer, but the effect was small. Amount of ammonium nitrogen under different treatments maintained a low level, and the difference between different treatments was small. Increasing of amount of nitrogen topdressing did help the amount of nitric nitrogen in 0-80cm soil layer increase, but the help had limit, the amount of nitric nitrogen would decrease while amount of nitrogen topdressing exceeding a certain threshold. In this experiment, threshold of amount of nitrogen topdressing is between 13.91g / per plant ( T₃ ) and 18.91g / per plant( T₄ ).Experiment of form of nitrogen topdressing (calcium nitrate and urea):(1) For tobacco leaf area, Stem circumference, Chlorophyll content at the root extending stage, net photosynthetic rate during whole period, dry weight and yield of per plant, the effect of the form of nitrogen topdressing in which amount of nitric nitrogen accounting for 80% was better.(2) The form of nitrogen topdressing had effect on amount of ammonium nitrogen in 0-20cm soil layer, which increased with decrease of nitric nitrogen in form of nitrogen topdressing, and the effect mainly displayed at the root extending stage. As for the amount of ammonium nitrogen in 20-80cm soil layer, the form of nitrogen topdressing had no effect. The form of nitrogen topdressing did effect the amount of nitric nitrogen in 0-80cm soil layer increase, the amount of nitric nitrogen in soil increased with increase of nitric nitrogen in form of nitrogen topdressing, and the effect mainly displayed at root extending and vigorous growing stages.