Studies On The Nitrogen Absorption And Distribution Using ¹⁵N In Different Fertilizer Response Flue-cured Tobacco Varieties At Medium And Low-yield Cropland

Using intolerantly fertilized flue-cured tobacco Yuyan No.5 and tolerantly fertilized flue-cured tobacco Yuyan No.10 as materials, the experiment was carried out in 2013, in experimental field of Xuchang Campus of Henan Agricultural University. With the method of 15 N isotope tracer, we studied the law of absorption and utilization of different genotypes of flue-cured tobacco on nitrogen. The results showed that: 1 The regularity of accumulation and distribution of nitrogen in flue-cured tobacco.In the different growth stages, the total nitrogen content accumulated in various organs of two cultivars shows that leaf owns the largest nitrogen, stem owns the smaller one, and that root owns the smallest one. The nitrogen content of different parts of the leaf exhibits as follows: upper leaf owns the most nitrogen; lower leaf owns the least; the content of nitrogen of middle leaf is between them. The peak of nitrogen uptake focuses on 40 to 60 days after transplanting. While, during this period from post-tip-pruning to premature, the accumulation of nitrogen fertilizer in tobacco plants appears a slight decrease, because tobacco plants basically completes the absorption of nitrogen fertilizer before tip pruning. What’s more, with the transference of the growth center, the largest nitrogen content shall be transferred accordingly in reproductive period. That is, during 40 to 60 days after transplanting, leaf nitrogen content reaches a maximum, after which the content is lower. The nitrogen content of tobacco roots, stems decreases in 60 days after transplanting, after which it increases slightly. In the whole growth period, pistil owns the highest percentage of nitrogen. Mature organs presents negative growth during the late growth period. 2 The regularity of the accumulation of soil nitrogen and fertilizer nitrogen in flue-cured tobacco.The fertilizer nitrogen content in total nitrogen of intolerantly fertilized Yuyan No.5 possesses the largest percentage among the whole reproductive periods in 40 days after transplanting. Compared with intolerantly fertilized Yuyan No.5, tolerantly fertilized Yuyan No.10 reaches its largest percentage in 80 days after transplanting. Both of the two varieties’ fertilizer nitrogen contents in total nitrogen are more than 80% after they enter into their harvesting time. The basal nitrogen utilization of intolerantly fertilized Yuyan No.5 in its growth period is higher than tolerantly fertilized Yuyan No.10. However, the topdressing nitrogen utilization of tolerantly fertilized Yuyan No.10 is higher than intolerantly fertilized Yuyan No.5. In the whole reproductive period, the fertilizer utilization of intolerantly fertilized variety is higher than tolerantly fertilized variety, and both of their basal nitrogen utilizations are higher than topdressing nitrogen utilization.Accumulation of two genotypes of basal and top dressing nitrogen in flue-cured tobacco peaks at different times. That is, after transplanting 60 days, the basal nitrogen accumulation of Yuyan No.5reaches a maximum. While, the basal nitrogen accumulation of Yuyan No.10 reaches its peak after transplanting 80 days.The topdressing nitrogen accumulation of Yuyan No.5reaches a maximum after transplanting 80 days. However, Yuyan No.10 can reach peak after transplanting 60 days. In the whole growth period, the accumulation of fertilizer nitrogen of the two varieties shows that leaf owns the largest nitrogen, root owns the smaller one, and that stem owns the smallest one. The accumulation of fertilizer nitrogen in different parts of the leaf presents different dynamic characteristics. The percentage of fertilizer nitrogen content in total nitrogen of two varieties falls with the raise of leaf parts.