| A field experiment was carried out to study the effects of different nitrogen application rate and ratio of base and topdressing on agronomy characters, dry matter accumulation amounts, nitrogen, potassium, phosphate absorption, accumulation, soil inorganic nitrogen contents, medi-leaves quality and yield. The results showed that:1. Basal application of a certain amount of nitrogen fertilizer was excellent acceleration effect at agronomy characters on the rosette stage and the budding stage. On the rosette stage there were significantly effects at the plant height , biggest leaf length, the biggest leaf width of different nitrogen application rate and ratio of base and topdressing, and as the increasing amounts of applied nitrogen, the plant height , biggest leaf length and the biggest leaf width increased, the plant height , biggest leaf length and the biggest leaf of the 50:50 of base and topdressing were larger than those of other treatments. On the budding stage, there were significantly effect at the plant height, effective leaves and distal leaf length, however, there had not an obvious change trend as the changing of applied nitrogen. On the flat-roofed stage, there was a growing trend towards the leaf length and leaf width of different parts as the increasing amounts of applied nitrogen.2. The effects were not obvious in dry matter accumulation amounts in early growth stage of flue-cured tobacco, dry matter accumulation amounts of the whole tobacco plants which were produced primarily for 7 weeks to 13 weeks after transplanting. The difference among the treatments in dry matter accumulation amounts of the organs of flue-cured tobacco appeared in the middle to late of the tobacco growth.3. Reducing nitrogen application rate made soil NO3--N contents in early and late growth stage of flue-cured tobacco decreased obviously. Within rosette stage to budding stage, both of NO3--N and NH4+-N contents sharply declined. The NO3--N contents in the 20-40cm soil significantly less than in the 0-20cm soil, but NH4+-N contents in the 20-40cm soil and in the 0-20cm soil were not statistically different. The effects were not obvious in nitrogen content and nitrogen accumulation amounts of different treatments in early growth stage of flue-cured tobacco, reducing nitrogen application rate and basal dosage reduced nitrogen content and nitrogen accumulation amounts in the mature leaves. The nitrogen content of the roots added as ratio of base and topdressing increased, but there was not obvious change trend at the nitrogen content of leaves and plants, The dynamic variation rule of nitrogen accumulation of different treatment was in conformity with dry matter accumulation amounts.4. The dynamic variation rule of potassium accumulation of different treatment was in conformity with nitrogen and phosphate accumulation, the peaks of the three accumulations all occurred at week 10 and 16, showing "M"-type movements. The potassium accumulation of the roots came earlier than the nitrogen and phosphate accumulation of the roots. On the flat-roofed stage, the phosphate accumulation of the leaves increased as the increasing amounts of applied nitrogen, however, the phosphate accumulation of the roots had not obvious change trend as the increasing amounts of applied nitrogen, which was consistent with the phosphate accumulation of the stalks. 5. As the increasing amounts of applied nitrogen, the reducing sugar contents and the ratio of total sugar to total plant alkaloid contents were reduced, while the total plant alkaloid and total nitrogen contents were increased. Reduce amounts of applied nitrogen appropriately can improve Sensory and smoking quality of drying flue-cured tobacco leaves.6. The treatment of nitrogen application rate 45kg/hm~2 raised average price and ratios of grade A and grade B leaves. The economic characters of using base fertilizer in combination with topdressing fertilizer better than using base fertilize or topdressing fertilizer independently.
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