Effects Of Interaction Of Water And Nitrogen On Uptake And Utilization Of Nitrogen And Yield And Quality Of Flue-Cured Tobacco

Water controlled pot experiment,simulated experiment and field experiments were employed to study the effects of water and nitrogen interaction on nitrogen supply characteristics of tobacco field,nutrients uptake of tobacco plant,water and fertilizer use efficiency,and yield and quality of flue-cured tobacco.The results were as follows:1.The main form of mineralization nitrogen intobacco field was nitrate,and the amount of mineralized nitrogen in early growth stage of flue-cured tobacco was less than that in middle and later stage.The concentration of nitrate and ammonium in tobacco field were affected by nitrogen rate and soil moisture.With the increase of nitrogen rate and soil moisture,the available nitrogen in tobacco field increased.Moreover,the effect of nitrogen rate on improving soil nitrogen supply was greater than that of soil moisture,and significant interaction effects of water and fertilizer coupling were observed.After fertilization,the available nitrogen in tobacco field was mainly centralized in 0～20 cm soil layer depth,the main nitrogen form was nitrate and the main supply stage of nitrogen was at the early and middle growing stage of flue-cured tobacco.The more the nitrogen rate,the greater the nitrogen supply of the soil.2.With the increasing of nitrogen rate,the uptake amount of nitrogen,phosphorus and potassium of flue-cured tobacco increased.Both nitrogen fertilization and irrigation could significantly improve nutrients absorption of tobacco plant,but the effect of nitrogen rate was greater than that of irrigation,and significant interaction effect was found in water and nitrogen coupling.The nitrogen absorbed by tobacco plant was mainly distributed in the leaves,and the accumulation of nitrogen in cutters and upper leaves were more than that of lower leaves.The absorption proportion of soil nitrogen and fertilizer nitrogen changed with the different growth period of flue-cured tobacco.In the condition of field experiment,nitrogen absorbed by tobacco plant was mainly from fertilizers in the early and middle growth stage,and that was mainly from soil nitrogen sources at mature stage.However,in the condition of pot experiment,the nitrogen accumulated in the plant was mainly from fertilizers in all growth period of flue-cured tobacco. Irrigation could promote tobacco plant to absorb nitrogen from fertilizers,and there was significant positive interaction effect between water and nitrogen coupling on uptake of fertilizer nitrogen.The application of nitrogen could speedup the decomposition of soil organic matter, which could produce significant priming effect on flue-cured tobacco to absorb soil nitrogen.3.The contribution rate of soil and fertilizer nitrogen to accumulation of nitrogen in the plant was different at different growth period of flue-cured tobacco.Under field experiment,the contribution rate of soil nitrogen to nitrogen accumulation of tobacco plant was greater than that of fertilizers,especially in the upper leaves in mature stage.Under pot experiment,the contribution rate of fertilizer nitrogen to the accumulation of nitrogen in tobacco plant was greater than that of soil nitrogen in all growth period of flue-cured tobacco,and which was increased with the increase of nitrogen rate and soil moisture,while the contribution rate of soil nitrogen was decreased. Furthermore,the contribution rate of fertilizer nitrogen to lower leaves was greater than that of upper leaves.4.Water and nitrogen interaction could increase water use efficiency of flue-cured tobacco significantly.Compared with pot experiment,water consumption of tobacco plant was more and water use efficiency was lower in field experiment.In the year of different precipitations,water use efficiency of flue-cured tobacco in normal year and the year with high water was lower than that in the year with low water,and it tended to increase with the increasing of nitrogen rate.There was significant effect of interaction between irrigation and nitrogen rate on improving water use efficiency of flue-cured tobacco.Under the condition of low soil moisture,the application of nitrogen could enlarge soil water utilization which showed the effect in raising water use efficiency by increasing fertilization.Under the condition of high nitrogen rate,irrigation could increase the uptake of fertilizers which showed the effect in raising fertilizer use efficiency by irrigation.5.The nitrogen use efficiency of flue-cured tobacco investigated in field experiment was lower than that in pot experiment.In the year of different precipitations,nitrogen use efficiency of tobacco plant in the year with low water was lower than that in the year with high water,and water and nitrogen coupling could increase nitrogen use efficiency significantly.With the increasing of nitrogen rate,the apparent recovery efficiency of nitrogen tended to increase,the agronomic nitrogen efficiency,physiologic nitrogen efficiency and partial factor productivity for applied nitrogen tended to decrease,and the soil nitrogen dependency of flue-cured tobacco reduced,while the fertilizer nitrogen dependency increased.Under the condition of nitrogen rate at 127.5kg/hm~2, the nitrogen use efficiency of flue-cured tobacco was 23.1～31.8%.After harvest of tobacco leaves,the residual ratio of fertilizer nitrogen in the field was more than 29%,and the loss rate was beyond 35%.The residue of fertilizer nitrogen was mainly centralized at 0～20 cm soil layer depth, and the eluviations of fertilizer nitrogen in tobacco field increased with the increasing of nitrogen rate and irrigation.6.Under the same application rate of nitrogen,the nitrogen uptake amount of flue-cured tobacco derived from base fertilizer decreased,and increased significantly from top dressing with the increasing proportion of top dressing.The total nitrogen uptake amount of tobacco plant and the ratio of nitrogen absorbed from fertilizers raised,while the ratio of nitrogen absorbed from soil nitrogen sources reduced.With the increasing proportion of top dressing,the nitrogen use efficiency(NUE) of the plant to base fertilizer increased and that of top dressing decreased significantly.However,the NUE to top dressing was significantly higher than that of base fertilizer in all treatments at different growth period of flue-cured tobacco,which resulted in the NUE(base fertilizer+top dressing) of flue-cured tobacco increased.After harvesting of all the leaves of tobacco plant,both base fertilizer and top dressing remained in the soil of tobacco field in various degrees.With the increment of top dressing,the residual ratio of base fertilizer decreased and that of top dressing increased,whereas the total residual nitrogen and the nitrogen loss rate of fertilizers reduced significantly.So,under the determinate application rate of nitrogen,increasing the proportion of top dressing reasonably could enhance NUE of flue-cured tobacco in rainy regions.7.With the increase of nitrogen rate and soil water content,the plant height,stalk circumference,average length and width of leaves and leaf area increased in different degree. Water and nitrogen coupling could promote the growth and development of flue-cured tobacco significantly,and the responses of plant height,leaf length and leaf area to soil moisture were more sensitive than that of leaf width and stalk circumference.With the increase of nitrogen rate,dry matter accumulation in root,stalk,and leaf of the plant increased significantly,and the distribution ratio of dry matter in the leaf was the highest,stalk took the second place,and root was the lowest. With the growth and development of tobacco plant,dry matter distribution ratio in the leaf tended to decrease,and that in root and stalk tended to increase.Water and nitrogen coupling could significantly promote dry matter accumulation of flue-cured tobacco,and the effect of nitrogen was greater than that of watering.There was significant interaction effect of water and nitrogen on dry matter accumulation of the plant.8.The results of pot experiment showed that the effect of nitrogen fertilization on increase production of flue-cured tobacco was greater than that of irrigation,and water and nitrogen coupling could improve yield of the leaves significantly.The effect of drought at different growth period of flue-cured tobacco on yield and quality of the leaves was different.The effect of drought stress on yield was relatively obvious at vigorous growing stage and that on quality of the leaves was more significant at mature stage.The results of field experiment indicated that yield,output value and ratio of superior leaves of flue-cured tobacco increased significantly,the content of total sugar and reducing sugar in the leaves decreased,and the content of nicotine and total nitrogen increased with the increment of nitrogen in a certain range.Both application of nitrogen and irrigation could improve yield,output value and ratio of high class leaves of flue-cured tobacco, and the effect of nitrogen was greater than that of irrigation,and different degrees of water and nitrogen coupling effects were also observed.On the comprehensive analysis of the economic characteristics,chemical components and smoking quality of flue-cured tobacco with different treatments of nitrogen rate,the appropriate nitrogen rate of flue-cured tobacco in Liuyang and Xiangxi was about 127.5 kg/hm~2 and 112.5 kg/hm~2 respectively.9.Based on the results of pot and simulation experiments,the models of water and fertilizers for growth,dry matter accumulation and yield of flue-cured tobacco were put forward.The results showed that there was a linear correlation between soil moisture and plant height and dry matter accumulation of flue-cured tobacco,whereas a conic correlation was found between soil water content and single leaf area under different nitrogen rate.However,a conic correlation was observed between nitrogen rate and plant height,single leaf area and dry matter accumulation respectively under different soil moisture.In different irrigation conditions,the models of the effect of nitrogen and potassium fertilizer for yield,output value and ratio of high class leaf of flue-cured tobacco were all conic,which indicated that with the increment of soil moisture and rate of nitrogen and potassium,the yield,output value and ratio of superior leaf increased,but the effect of water and fertilizers for increasing the yield of flue-cured tobacco tended to decrease in higher application level of nitrogen and potassium.According to the coupling models of water and nitrogen established in the experiment,sufficient supply of water and nitrogen could promote growth and dry matter accumulation of flue-cured tobacco,which resulted in the increase of the yield.