Effects Of Different Transplanting Periods On The Production Of High-end Characteristic Tobacco Leaves In Dali

Consolidating and improving tobacco leaf quality is an important issue for the sustainable development of tobacco production.Previous research has shown that ecological conditions are important factors affecting tobacco leaf quality,and transplanting period adjustment is an effective means of managing meteorological resources such as light,temperature,and water during the crop’s growth period.In order to better ensure the quality of high-end tobacco leaf production in Dali,this experiment was conducted in two counties,Nanjian(Hong Da)and Yongping(K326),by studying the differences in meteorological resource allocation,crop growth,internal metabolism,yield,and intrinsic quality among four different transplanting periods(T1: April 23,T2: May 2,T3: May 11,T4: May 20)under current climatic conditions.The aim was to re-select the appropriate transplanting time,better match the current climate situation in Dali,improve tobacco leaf quality,and guarantee the demand of cigarette industry enterprises for high-quality tobacco raw materials.Based on the preliminary experimental results from both areas,the main research conclusions are as follows:(1)The overall growth period of tobacco plants was delayed with the delay of transplanting period,while the total field growing period was reduced,and the root elongation period showed the most significant reduction.Overall,T3 treatment was the best,as stable and relatively high temperatures in the early stage were more suitable for tobacco seedling growth,avoiding rainy seasons during maturity period,which is beneficial for tobacco maturation and material accumulation.(2)Regarding the differences in crop growth and economic traits among different transplanting periods,T3 and T4 developed slower than T1 and T2 due to late transplanting,but completed their development at the topping phase,resulting in no significant differences in plant height,stem circumference,maximum leaf length,and maximum leaf width compared to T1 and T2.However,it can increase the number of effective leaves by1-2 to a certain extent.In terms of economic traits,both areas performed best with T3 treatment,with an increase in yield of 8.9% and 17.8%,respectively,compared to T2,and an increase in production value of 6.9% and 11.1%,respectively.(3)For the differences in tobacco leaf quality among different transplanting periods,the external quality score improved with the delay in transplanting period,and the maturity,color,and chromaticity of the roasted tobacco leaves were better,but the oil content was slightly insufficient.The comprehensive score was highest for T3 treatment of C3 F,reaching 81.5 and 85.83 in both counties,respectively.In terms of chemical composition,all indicators except water-soluble sugar and reducing sugar in the upper and middle leaves were higher than the appropriate range,while the overall performance of other indicators was within the suitable range.Regarding coordination,T2 and T3 treatments were generally better in terms of sugar difference,sugar-alkali ratio,and nitrogen-alkali ratio.(4)Regarding the differences in crop metabolism among different transplanting periods,carbon-nitrogen metabolism was more active,and the activity of carbon metabolism enzymes SS sucrose synthase and SPS sucrose phosphate synthase peaked during the vigorous growth period.The activity of nitrogen metabolism enzymes NR nitrate reductase and GS glutamine synthetase showed a trend of high in the early and middle growth stages and low in the later stage.Secondary metabolism enzyme PAL phenylalanine ammonia-lyase and PPO polyphenol oxidase showed a trend of low in the early growth period and high in the mid-late period.Among them,the T3 treatment showed that the SS and SPS activities were low in the early and middle stages but high in the later stage,the NR and GS activities were high in the early and middle stages but low in the later stage,nitrogen metabolism was vigorous in the early stage,carbon metabolism was vigorous in the later stage,and enzyme activity coordination was better compared to other treatments.Its sugar-alkali ratio and nitrogen-alkali ratio were also better.In summary,T3 treatment showed better tobacco leaf growth,better coordinated carbon-nitrogen related enzyme activities throughout the growth period,the best economic traits of tobacco leaves,and relatively coordinated chemical quality.Therefore,it is the most suitable for promotion in the tobacco production areas of Nanjian County and Yongping County in Dali.