Abstract: With the flue-cured tobacco and soil samples from the Hunan tobacco-growing areas as test materials, this paper studied the relationships between the chemical components in flue-cured tobacco leaf and the content of soil organic matter. The results indicated that in Hunan tobacco-growing areas, soil organic matter content was generally high, with a mean of 39.06 g·kg^-1±11.90 g·kg^-1. The total N and K contents in flue-cured tobacco leaf were relatively high, while the nicotine, total sugar, chlorine, and reducing sugar contents were appropriate. The relationships between the nicotine content in flue-cured tobacco leaf and the organic matter content in soil could be described by linear-flat model, with the turning point at flat stage being 36.25 g·kg^-1 of soil organic matter content, and 3.00% of nicotine content. The nitrate and nitrite contents in tobacco leaf increased with increasing soil organic matter content, while the content of petroleum ether extract seemed to show a decreasing trend. After grouping the soil organic matter contents and by using multiple comparison method, significant differences at 0.05 level were found in the contents of nicotine, total N, nitrate, nitrite, petroleum ether extract, potassium and chlorine, and the ratios of nitrogen to nicotine, reducing sugar to nicotine, and potassium to chlorine in flue-cured tobacco leaf among the groups, but no significant differences were observed in the contents of total sugar and reducing sugar.

Key words: Open holes ratio of plastic mulch, Cumulative evaporation, Perforated rate