Effects Of Nitrogen Fertigation On Nitrogen Uptake And Utilization Of Flue-cured Tobacco And Soil Nitrogen Characteristics

Nitrogen absorption and utilization of different growth period of flue-cured tobacco is different,as"S"type curve.Nitrogen fertigation can be based on crop demand for nitrogen in a timely manner quantitative supply of crops needed nitrogen.The effects of different nitrogen fertigation treatments on the nitrogen uptake,distribution,utilization of flue-cured tobacco and the temporal and spatial distribution,content and apparent profit and loss of soil inorganic nitrogen were studied by a pot experiment and field experiment,hoping to provide the basis for the use of water and nitrogen in flue-cured tobacco production.The main results were indicated as follows:?1?59.76%-69.27%of the nitrogen uptake of flue-cured tobacco was derived from fertilizer N,30.73%-40.24%was derived from soil N,36.77%-86.77%of fertilizer nitrogen was derived from 28days after transplanting?DAT?.Fertilizer N accumulation amount of different organs increased in an order of leaves to stem to root,and the leaves in an order ofmiddle leaf to upper leaves to lower leaves.The base fertilizer N accumulation amount in the lower leaves was higher than that in the other leaves,and the of topdressing fertilizer N accumulation amount in the middle and upper parts was higher than that of other leaves.28.82%-34.00%of nicotine nitrogen was derived from fertilizer N,66.00%-71.18%was derived from soil nitrogen,and the propertion of nicotine nitrogen derived from base fertilizer N in decreased with the elevation of stalkposition,while the proportion of nicotine nitrogen derived from topdressing fertilizer N increased with thee levation of stalk position.On 28 DAT,among the treatments of nitrogen topdressing once time,the dry weight of different organs,nitrogen content and nitrogen accumulation amount of leaves increased with nitrogen topdressing rate,nitrogen accumulation of root derived from topdressing fertilizer N increased,but that of root and stem from fertilizer N decreased,and that of the leaves from fertilizer N and that from topdressing N both increased.The utilization of fertilizer N of the treatments with topdressing twice was decreased;the ratio of nicotine N to total N of plant and the ratio of fertilizer N of all stalk positions to nicotine N both reduced;Meanwhile,fertilizer Nresidue in the soil decreased,but topdressing fertilizer N nitrogen residue increased.For the treatments of 50%or 30%of the nitrogen fertilizer used as base fertilizer and topdressing twice,fertilizer N accumulation amount of root and stem were lower thanthat of topdressing only once,fertilizer N accumulation amount of leaves were the opposite.Basal nitrogen 50%,the fertilizer N utilization of the treatment of topdressing twice was 1.24 percentage points higher than that of topdressing only once.10%of the nitrogen fertilizer used as base fertilizer,the ratio of nicotine N to total N,and the ratio of base fertilizer N and first topdressing N to nicotine N of the leaves of topdressing twice treatments were lower than that of topdressing only once.?2?Soil NO₃^--N content in the vertical and horizontal directions at different distances from the infusion point,and reduced soil nitrogen apparent budget.Nitrogen topdressing twice applied on 28 and42 DAT led to an decrease in NO₃^--N content in the bottom soil and the possibility of NO₃^--N leaching.50%or 30%of the nitrogen fertilizer used as base fertilizer and topdressing twice,the NO₃^--N content of soil in the horizontal direction of topdressing twice treatments were higher than that of topdressing only once,soil nitrogen apparent budget was the opposite.10%of the nitrogen fertilizer used as base fertilizer,the NO₃^--N contentin the middle and lower soil of topdressing twice treatments were lower that of topdressing only once,soil nitrogen apparent budget was higher than that of topdressing only once.?3?Root dry weight,root-shoot ratio,root surface area in the vertical direction?15-25 cm?and horizontal direction?15-20 cm?distance from the infusion point decreased with the increase of rate of nitrogen topdressing,while the average diameter was increased.Root dry weight,root-shoot ratio and root average of T2 were respectively higher 27.08%,3.61%and 13.79% than T1.30% or 10% of the nitrogen fertilizer used as base fertilizer,root dry weight of topdressing twice treatments were lower than that of topdressing only once,Root length density and root surface area in the vertical direction?20-25 cm?and horizontal direction?15-20 cm?distance from the infusion point of topdressing twice treatments were bigger than that of topdressing only once.On 28 DAT,for the treatments of topdressing only once,single leaf weight,length and width of leaf increased,and the stem ratio first increased and then decreased with increasing topdressing ratio from 30%to 70%.The reducing sugar and total sugar of treatments that 50%of the nitrogen fertilizer used as base fertilizer were higher,and coordination of that was batter.The greater the proportion of topdressing,the greater the yield.The ratio of medium and superior tobacco of trentments 30%of the nitrogen fertilizer used as base fertilizer were the highest.Topdressing twice increased single leaf weight,length and width of leaf and total nitrogen content,and decreased the stem ratio,compared with topdressing only once.Moreover,the yield,the ratio of medium and superior tobacco,the average price and value of output of topdressing twice treatments were higher that of topdressing only once.Considering the nitrogen absorption and utilization,soil mineral nitrogen distribution and surplus,yield,and value of output,50%of the nitrogen fertilizer used as base fertilizer,30%-35%of the nitrogen fertilizer applied on 28 days after transplanting,15%-20%of the nitrogen fertilizer applied on42 days after transplanting could be recommended as the production of nitrogen fertigation system.