The Impact of Major Meteorological Factors in Tobacco Growing Areas on Key Chemical Constituents of Tobacco Leaves

To clarify the relationships between the main chemical components in flue-cured tobacco in Guizhou and field meteorological factors during the tobacco growing period, the contributions of meteorological factors to the chemical composition of flue-cured tobacco and related components were explored in this study. The flue-cured tobacco variety Y87 was used as the experimental material, and tobacco samples and meteorological data were collected from seven typical tobacco-growing areas in Guizhou Province. Using a random forest model and canonical correlation analysis, the impact and contribution of the monthly mean temperature, precipitation, and sunshine duration during the field growing period to the chemical indicators of tobacco leaves were investigated. During the growing period of flue-cured tobacco in Guizhou, meteorological factors showed considerable variation, with the magnitude of change decreasing in the order of precipitation, sunshine duration, and mean temperature. Precipitation in April, mean temperature in June and August, and sunshine duration in April and May had the most significant impacts on the main chemical components of tobacco leaves, particularly nicotine, total sugar, and starch, with coefficients of variation reaching 14.93%, 14.59%, and 24.27%, respectively. The precipitation in May and June, mean temperature in August, and sunshine duration in June played key roles in influencing the nitrogen–nicotine ratio and total–reducing sugar ratio. Moreover, the mean temperature in May, precipitation in July, and mean temperature in July substantially contributed to the nicotine and total nitrogen contents, with contribution rates of 19.17%, 12.19%, and 17.36%, respectively, to the nicotine content. Sunshine duration in May, mean temperature in August, and sunshine duration in July significantly contributed to starch content, with rates of 17.45%, 15.34%, and 13.27%. During the root extension stage, vigorous growth stage, and maturation stage, meteorological factors primarily affected the accumulation of nitrogenous compounds such as nicotine and total nitrogen. The mean temperatures in May and July contributed 19.17% and 17.36% respectively to nicotine accumulation; whereas during the maturation stage and harvest stage, these factors mainly impacted the accumulation of carbohydrates such as starch and total sugars, The mean temperature in August and sunshine duration in July contributed 15.34% and 13.27% respectively to starch accumulation. Therefore, ensuring tobacco seedling transplantation is completed before May and appropriately extending the maturation period can promote the accumulation of carbon-nitrogen compounds in tobacco leaves and improve leaf quality.