Effects Of Transplanting Date And Mulching Method On Growth,Yield And Quality Of Dark Sun-cured Tobacco In Jiaohe

In order to establish the suitable transplanting dates and cultivation methods for dark sun-cured tobacco in Jiaohe City,Jilin Province.In 2019,the effects of three transplanting periods and two mulching methods on soil temperature and humidity,main climatic factors,tobacco plant growth and development,yield and quality of flue-cured tobacco were studied.The relationships between dry matter accumulation,main economic characters and sensory quality of flue-cured tobacco and light,temperature and water were analyzed.The main results are as follows:1.Different transplanting dates and mulching methods have a greater impact on the growth period of the dark sun-cured tobacco.Under naked planting conditions,with the postponement of the transplanting date,the whole growth period of dark sun-cured tobacco has little change,but the root extension period was significantly shortened and the prosperous period was prolonged;under the condition of mulching,as the transplanting date was delayed,the root extension period,maturity period and the entire field growth period of dark sun-cured tobacco were shortened,and the number of days in the peak period was less affected by the transplanting date.In the same transplanting date,mulching cultivation significantly reduced the root extension period and field growth period of dark sun-cured tobacco,transplanting in advance and using mulching prolonged the maturity days of dark sun-cured tobacco,was conducive to the accumulation of substances in tobacco leaves,and lays the foundation for high-quality and high-yield tobacco leaves.2.Different transplanting dates and mulching methods have obvious adjustment effects on the light,temperature and water conditions at each growth stage of sun-cured tobacco.With the postponement of the transplanting date,the number of days in the root extension period was significantly shortened,which led to a downward trend in the accumulated temperature of>10℃,accumulated temperature of>20℃,rainfall,and sunshine hours,under naked planting conditions,these indexes and daily average temperature were higher than those of plastic mulching cultivation.In the prosperous period,with the postponement of the transplanting date,the daily average temperature,the accumulated temperature of>10℃,the accumulated temperature of>20℃,and the rainfall all showed an increasing trend,and these indexes under the naked planting condition were greater than those of the mulching cultivation;but the sunshine hour was opposite to performance was similar to the above indexes.During the maturity period,with the postponement of the transplanting date,the daily average temperature,accumulated temperature>20℃ and the number of days decreased,and the rainfall increased.The two heat indicators of the mulching treatment were significantly higher than that of the naked planting,and the rainfall was lower than that of the naked planting.The sunshine hours of naked planting treatment were lower than that of plastic mulching cultivation.On the whole,transplanting on May 24 and taking plastic film mulching treatment were favorable to the maturity and modulation of tobacco leaves due to sufficient light,abundant heat and less rainfall in the mature period,followed by transplanting on May 29 and taking plastic film mulching treatment.3.Different transplanting dates and mulching methods had a significant impact on the temperature and humidity of the tobacco planting soil.Under the condition of plastic film mulching,the fluctuation range of soil temperature of each soil layer was smaller and obviously higher than that of naked planting treatment,especially when the soil temperature of 5-15cm soil layer was above 25℃,which was conducive to soil nutrient transformation,root development and nutrient absorption,and promote the early growth of tobacco plants.The soil moisture content of different soil layers was 20cm>10cm in the growing period;When mulching,the rainfall was low in the delayed transplanting period,and the soil moisture content of the mulching was higher than that of the bare soil,which showed the remarkable effect of soil moisture conservation.4.Different transplanting dates and mulching methods had significant effects on the agronomic characteristics and dry matter accumulation of dark sun-cured tobacco.Postponing the transplanting date and using plastic mulching significantly increased the plant height,stem circumference and leaf area coefficient of tobacco,and significantly increased the dry matter accumulation of dark sun-cured tobacco.The logistic growth model was established with accumulated temperature>10℃ as independent variable and dry matter accumulation of sun cured tobacco as dependent variable.The fitting coefficients R2 were all above 0.9940.Postponement of the transplanting date and the use of mulching film significantly increase the dry matter accumulation rate of dark sun-cured tobacco;under the condition of film mulching,the peak of dry matter accumulation rate of dark sun-cured tobacco appears to accumulate temperature earlier,shortening the continuous accumulation of temperature during the rapid growth period.Delaying transplanting period and using plastic film mulching significantly increased dry matter accumulation rate of dark sun-cured tobacco.5.Studies have shown that the transplanting date had a very significant impact on the proportion of top-class of dark sun-cured tobacco;the effect of mulching methods on the output value and the proportion of top-class of tobacco reached a significant level,and the impact on the yield reached a very significant level.Early transplanting date and the use of plastic film mulching reduced the yield,but the output value,average price,and the proportion of medium and upper-class tobacco have increased significantly,transplanting from May 24 to 29 and adopting plastic film mulching cultivation has the best comprehensive economic benefits.6.Different transplanting time and mulching methods had significant effects on the chemical components of dark sun-cured tobacco.The results showed that delaying transplanting period significantly reduced the potassium content in different parts of dark sun-cured tobacco,and the plastic film mulching cultivation significantly increased the potassium content of tobacco;Delaying transplanting period reduced nicotine content of dark sun cured tobacco,and plastic film mulching increased nicotine content of dark sun-cured tobacco;Delaying the transplanting period significantly increased the sugar content in the upper leaves of sun cured tobacco,while plastic film mulching decreased the sugar content in the middle and upper leaves and increased the sugar content in the lower leaves.Appropriate early planting and plastic film mulching make the chemical composition of tobacco more harmonious.The content of neutral aroma components and sensory quality of dark sun-cured tobacco were the highest in transplanting on May 24 with plastic film mulching treatment,followed by transplanting on May 29 with plastic film mulching treatment.Correlation analysis shows that the total sensory quality scores of dark sun-cured tobacco were significantly positively correlated with the average daily temperature of maturity,>10℃ accumulated temperature,>20℃ accumulated temperature and the number of days,and were extremely significantly negatively correlated with the relative humidity of the air during the growth period of the field,it showed that the relative humidity of the air during the growing period of the dark sun-cured tobacco field was the limiting factor for the sensory quality,and the heat condition was the gain factor of sensory quality.In summary,Jiaohe dark sun-cured tobacco is more suitable for transplanting from May 24 to 29 and using plastic film mulching for cultivation.