Nitrogen Uptake And Utilization And Nicotine Accumulation In Nicotiana Tabacum L. Influenced By Transplanting Date And Nitrogen Fertilizer

The area around Shenlongjia is a main flue-cured tobacco(FCT) production area, and the FCT leaves of"Jinshengnong" produced exhibit a character of"faint scent,sweet and refined".However,the soil and climate,the two main ecological conditions,change with the altitude hight,and lead to the difference of the production and the quality of tobacco.Investigating the agricultural techniques of high,stable and good quality of tobacco under different ecological conditions is of great importace for manifestating the characteristics of tobacco leaf and improving production and quality of tobacco in this district.Using FCT cultivar(Nicotiana tabacum L.K326),a field experiment with ¹⁵N isotope tracing micro-plots was carried out to study the effects of different transplanting date,different basal N fertilization time and N fertilizer application on N uptake, utilization and distribution,the yields and market values,the growth and development,the nicotine concentrations and the origin of nicotine～N in different organs of plants FCT plants in two ecological tobacco production areas[Zhaojiashan(N 31°28′,E 111°15′, 903m above sea level) and Laowan(N 31°27′,E 111°14′,1130m above sea level)]of Xiangfan city,Hubei province.The object of this experiment is to work out the best transplanting date and basal N fertilization time,and to provide the scientific and theoretical guidance for production of good quality of tobacco leaves "Jinshengnong". The main results were as follows:1.The results from experiment of different transplanting date showed that in two ecological district,lower altitude and higher altitude,applying N fertilizer significantly increased dry matter accumulation in shoot of FCT plants at different growing stages by 109%～238%fold and 85%～175%respectively,increaced the yield by 29.0%and 19.2%, and the market values by 24.8%and 25.7%for the lower and higher sites,respectively. Compared to the transplanting date at 5^th May,the transplanting date at 15^th～25^th May,dry matter accumulation in the same organs of shoot of FCT plants at the same growing stages increaced gradually by 8.9%～17.8%and 4.6%～11.7%respectively;although there was no significant effect on the yield and market values of tobacco at the lower altitude site,but the yields and market values of tobacco were increased by 10%～30%at the higher altitude.When the transplanting date was put off to 15^th～25^th May,the total N accumulation by tobacco increased by 25%～45%at the lower altitude site,but decreased by 6%～20%at the higher altitued.The use efficiencies of nitrogen fertilizer were 30%(at the lower altitude site) and 21%(at the higher altitude),which were improved significantly at earlier growing stage by delaying the transplanting time.On the contrary to total N accumulation,putting off the transplanting time decreased the use efficiency of N fertilizer by 10%～40%at the lower altitude site and increased by 15%～50%at the higher altitude. 2.The nicotine concentrations of tobacco leaves and the proportion of nicotine N to total N in different parts of FCT plants,increased gradually with the development of the plant and the increasing order of nicotine concentrations was lower leaf＞middle leaf＞upper leaf before the removal of apex,and was upper leaf＞middle leaf＞lower leaf affter the removal of apex.The proportion of nicotine N from fertilizer to total nicotine N decreased with the growing of FCT plants and the rising of leaf position.So,it was inferred that soil N application was the main factor that affected the nicotine concentrations and accumulations in middle and upper leaves(especially the upper ones) of FCT plants,after the removal of apex.Compared to without N fertilizer application, applying N fertilizer significantly increased nicotine concentrations and the proportion of nicotine N to total N by 44%～86%and 3%～286%at lower altitude,and by 26%～33% and 5%～127%at higher altitude,respectively.Compared to the transplanting date of 5^th May,postponing the transplanting date to 15^th～25^th May decreased the nicotine concentrations,the proportion of nicotine N to total N,and the proportion of nicotine N from fertilizer in organs of FCT plants,by 5%～25%,13%～45%,13%～36%at lower altitude,but increased by 10%～85%,5%～110%and 21%～56%at higher altitude, respectively.3.Results of the experiment with different basal N fertilization time showed that in two different FCT ecological districts,supplying N fertilizer significantly increased the dry matter accumulation by 0.78～3.05 fold and 2.10～2.72 fold,respectively;and the yields and market values of FCT plants by 13%～40%and 14%～35%for the experimental site of Zhaojiashan(lower altitude) and Laowan(higher altitude),respectively.Basal fertilization time had no significant effects on the yields of FCT plants at both the two experimental sites,and compared to basal N fertilization time 0d before transplanting, basal N fertilization time 15d～30d before transplanting increased market values by 10%～30%at higher altitude.Early application of basal N fertilizer(30 d before transplanting) increased N uptake by 8%～26%as compared to that of applying basal N fertilizer at 0d or 15d before transplanting at the two ecological areas.There was no significant effects of basal N fertilizer application time on N fertilizer efficiency at lower altitude,but basal N fertilization time 30d before transplanting increased by 3%～6%at higher altitude.The proportion of fertilizer N to total N in FCT plants decreased by 8%～32%at lower altitude,but increased by 25%～32%at higher altitude when basal N fertilizer was supplied 30d before transplanting.These results indicated that properly earlier supplication of basal N fertilizer could improve the N fertilizer efficiency,and thus increase the yields and market values of FCT,especially at higher altitude areas with less sunshine and lower temperature.4.Early basal N fertilization time 15d～30d before transplanting significantly increased nicotine concentrations of lower leaves by 6%～19%at lower altitude and organs of shoot of FCT plants at higher altitude.Compared to the basal fertilization time 0d or 15d before transplanting,applying basal fertilizer 30d before transplanting increased the proportion of nicotine N to total N of organs of shoot of FCT plants at Zhaojiashan site(lower altitude) and that of middle leaves and stem at higher altitude by 11%～34%and 14%～43%,respectively.There was no significant effects of basal N fertilization time on the proportion of nicotine～N from fertilizer to total nicotine～N in organs of FCT plants before and after topping,in Zhaojiashan site and Laowan site respectively.But compared to basal N fertilization time 0d before transplanting,applying basal N fertilizer 15～30d before transplanting increased it that of middle leaves by 38%～43%significantly in Zhaojiashan site.Early basal fertilization time increased the proportion of nicotine～N from fertilizer to total nicotine～N of upper leaves significantly before topping in Laowan site.In summary,N fertilizer application was an important agricultural technique for improving yields and market values of FCT plants.Postponing the transplanting date to 15^th～25^th May was benefiting in promoting N uptake and utilization,growth and development and decreasing nicotine concentrations of FCT plants leaves(especially middle and upper leaves) effectively at lower altitude.Transplanting date at 5^th May or earlier was good for N uptake and utilization of shoot and decreasing nicotine concentrations of tobacco leaves.At two ecological districts,the basal N fertilization time 15d～30d before transplanting was helpful in improving the market values and the N uptake and utilization of FCT plants,which the basal N fertilization time 15d or so before transplanting could specially avoid the contradiction of workforce stress and decreasing nicotine concentrations.