Medium to trace element contents in tobacco leaves and their correlations with leaf appearance quality

To investigate the difference of levels of medium to trace elements in tobacco leaves from different planting areas and their correlations with leaf appearance quality indexes, 264 flue-cured tobacco leaf samples (C3F) were collected from six provinces including Fujian, Guizhou, Henan, Hunan, Sichuan and Yunnan. The appearance quality and the contents of Mn, Fe, Cu, Zn, Ca and Mg in tobacco leaves were analyzed. The results showed that the contents of Mn, Fe, Cu, Zn, Ca and Mg in tobacco leaves ranged from 14.24-452.10 mg/kg, 46.62-613.98 mg/kg, 1.13-72.79 mg/kg, 6.32-123.09 mg/kg, 6.14-48.44 g/kg and 0.88-7.27 g/kg, respectively. There were also significant regional differences in their contents. Mn and Zn contents in leaves from Henan were significantly lower, but the contents of Fe, Cu and Ca were higher; while Fujian's leaf samples had an opposite trend. The contents of the six elements in tobacco leaves from Yunnan, Guizhou and Sichuan were similar. Cu, Fe, Zn, Ca and Mg contents were negatively correlated with most appearance quality indexes, while Mn was positively correlated with these indexes. The grey correlation degree of the six elements with the appearance quality was Cu > Zn > Fe > Ca > Mn > Mg. Cu and Zn had great influences on the appearance quality of tobacco leaves. Therefore, Cu and Zn should be reasonably applied in order to improve the quality of tobacco leaves.