Effects of soil and climate on photosynthetic characteristics and chemical constituents of strong-flavor flue-cured tobacco in different ecological subregions

Objective  To investigate the effects of main ecological factors on feature formation of strong-flavor flue-cured tobacco.

Method  ‘Yueyan 97’ was chosed as test material. According to the small differences on ecological condition and territory between two ecological subregions (Maozifeng and Gushi) in Nanxiong tobacco-growing area, four treatments by interchanging soil with the same texture were setted to study the effects of soil and climate on photosynthetic characteristics, chemical constituent contents and coordinations of strong-flavor flue-cured tobacco in different ecological subregions.

Result  On the 50th day after transplanting, compared with tobacco planted in Gushi with local sandy soil and climate condition (T2), the net photosynthetic rate of tobacco planted in Gushi with Maozifeng sandy soil (T1) increased by 3.66%; the contents of total sugar, reducing sugar and starch in middle leaves decreased by 5.74%, 4.77% and 10.73% respectively, and the contents of nicotine, K⁺ and total nitrogen increased by 6.49%, 11.07% and 11.34% respectively. Meanwhile, compared with tobacco planted in Maozifeng with local sandy soil and climate condition (T4), the net photosynthetic rate of tobacco planted in Maozifeng with Gushi sandy soil (T3) increased by 1.81%, the contents of reducing sugar and nicotine in middle leaves decreased by 10.02% and 13.14% respectively, and starch content increased by 9.30%. The climate had significant impacts on the contents of total sugar, reducing sugar, nicotine , total nitrogen and starch, nitrogen-nicotine ratio, stomatal conductance, transpiration rate, intercellular CO₂ concentration and net photosynthetic rate; soil and climate interaction had significant impacts on the contents of reducing sugar, nicotine, total nitrogen and starch, nitrogen-nicotine ratio and stomatal conductance; soil had significant impacts on the contents of K⁺ and total nitrogen and sugar-nicotine ratio.

Conclusion  Climate is the main factor affecting the feature formation of strong-flavor flue-cured tobacco, especially precipitation amount and mean temperature at root spreading and fast growing stages, followed by the interaction of soil and climate, and soil has the minimal role. The climate of Gushi is more suitable for production of superior strong-flavor tobacco leaves.