Effects Of Nitrogen And Density Interaction On Quality Formation And Nitrogen Utilization Of Flue-Cured Tobacco Variety NC102

Nitrogen application rate and planting density are two key factors affecting tobacco yield and quality.A reasonable combination of planting density and nitrogen application is beneficial to improving the yield,quality,and industrial availability of flue-cured tobacco.However,the determination of suitable planting density and nitrogen application rate is closely related to climate factors,soil characteristics,main varieties and planting patterns in the production area.In this study,the main flue-cured tobacco variety NC102 in Shandong Province was used as the experimental material.A two factor experiment was conducted in Yishui County,Linyi City,Shandong Province in 2021 and 2022,with nitrogen application rate and planting density.The planting density is set at three levels:12000 plants/hm²（D1）,16000 plants/hm²（D2）,and 20000plants/hm²（D3）.The nitrogen application rate is set at four levels:0（N0）,60（N1）,90（N2）,and 120（N3）kg/hm².To explore the effects of nitrogen density interaction on agronomic traits,photosynthetic characteristics,nitrogen absorption and utilization,economic traits,chemical components,and quality of flue-cured tobacco.With the goal of improving the yield,quality,and nitrogen utilization efficiency of tobacco leaves,the mechanism of the appropriate combination of nitrogen and density interaction to improve the quality of tobacco leaves was revealed.The main research results are as follows:（1）In terms of agronomic traits of tobacco plants,planting density and nitrogen application rate have a significant impact on the agronomic traits of flue-cured tobacco at various stages,and nitrogen application rate is the main factor affecting the agronomic traits of flue-cured tobacco.Within a certain range,with the increase of nitrogen application rate（N0-N2）and planting density（D1-D2）,the plant height and pitch of flue-cured tobacco increased.At maturity,stem circumference,maximum leaf length,maximum leaf width,and maximum leaf area all increased first and then decreased with the increase in planting density and nitrogen application.Appropriate nitrogen application rate and reasonable planting density are conducive to the growth and development of flue-cured tobacco.In summary,the agronomic traits of the nitrogen density combination with a nitrogen application rate of 90 kg/hm² and a planting density of 16000 plants/hm² were better.（2）In terms of photosynthetic characteristics of tobacco leaves,planting density and nitrogen application rate have a significant impact on photosynthetic characteristics parameters of flue-cured tobacco at various stages,and nitrogen application rate is the main factor affecting photosynthetic characteristics parameters and SPAD values of flue-cured tobacco at various stages.At the budding stage,the Pn,Tr,Gs,and SPAD values of flue-cured tobacco leaves increased with the increase in nitrogen application,but decreased with the increase in planting density.During the topping and ripening stages,the Pn,Tr,Gs,and SPAD values of tobacco leaves all showed a trend of first increasing and then decreasing with the increase of planting density and nitrogen application rate,which were N2>N3>N1>N0,D2>D3>D1,respectively.Correlation analysis showed that Pn,Tr,Gs,and SPAD values were significantly positively correlated with yield,while intercellular CO₂ concentration was significantly negatively correlated with yield,indicating that photosynthetic characteristics had a significant impact on yield of flue-cured tobacco.In summary,the photosynthetic characteristics of the nitrogen density combination treated with D2N2,with a nitrogen application rate of 90 kg/hm² and a planting density of 16000 plants/hm²,were the best.（3）In terms of chemical composition and quality of flue-cured tobacco leaves,planting density and nitrogen application rate have significant effects on the chemical composition and quality of flue-cured tobacco,and their interaction has significant effects on sensory quality.Under the same planting density,with the increase of nitrogen application rate,the sugar content of tobacco leaves decreased,while the nicotine and total nitrogen content increased;Under the same nitrogen application rate,total sugar and reducing sugar increased with the increase of planting density,while nicotine content decreased with the increase of planting density,thereby improving the sugar base ratio.With the increase of planting density and nitrogen application,the chloride ion content first decreased and then increased.The potassium ion content and sensory mass fraction first increased and then decreased with the increase of nitrogen application rate and planting density.Appropriate increase in planting density can effectively reduce the nicotine content of flue-cured tobacco,coordinate chemical components,and improve the smoking quality of tobacco leaves.Overall,the chemical composition of the nitrogen density combination with a nitrogen application rate of 90 kg/hm² and a planting density of 16000 plants/hm² is more coordinated.（4）In terms of economic traits,planting density,nitrogen application rate,and their interaction have a significant impact on indicators such as economic traits of flue-cured tobacco.The yield and output value first increase and then decrease with the increase of planting density and nitrogen application rate.The average price and proportion of top grade tobacco decrease with the increase of planting density,and first increase and then decrease with the increase of nitrogen application rate.The yield performance is D2>D3>D1,the output value performance is D2>D1>D3,and the average price and the proportion of top grade cigarettes are D1>D2>D3;The yield,average price,output value,and the proportion of top grade tobacco showed N2>N3>N1>N0.Unreasonable nitrogen application and planting density lead to reduced yield and quality of flue-cured tobacco,thereby affecting the economic benefits of tobacco leaves.Overall,the best economic characteristics of flue-cured tobacco were obtained when the nitrogen application rate was 90 kg/hm² and the planting density was 16000 plants/hm².（5）In terms of nitrogen absorption and utilization of tobacco plants,planting density and nitrogen application rate have significant effects on NA,AEN and PFPN of flue-cured tobacco,and their interaction has significant effects on NA and PFPN.With the increase of planting density and nitrogen application rate,NA and NUE increased first and then decreased.AEN and PFPN decreased with the increase of nitrogen application rate,and first increased and then decreased with the increase of planting density.The NA and NUE of D2N2 treatment were the highest.The NHI treated with D3N1 is the best;The AEN and PFPN of D2N1 treatment were the highest.As a whole,the nitrogen utilization efficiency of flue-cured tobacco was better with the nitrogen application rate of 90 kg/hm² and the planting density of 16000 plants/hm²,which met the production goal of suitable yield,high quality and high efficiency of flue-cured tobacco.