| Tobacco-specific nitrosamines(TSNA) are the nitrogen compounds that could cause cancers strongly. The nitrate, nitrite and alkaloids are precursor to form TSNA in tobacco leaves. Factors that influence the precursor of TSNA could affect the accumulation of TSNA. Soil is the basis of growth of tobacco plants. Therefore, it is of great importance to decrease the TSNA content and produce high quality and low harmful tobacco leaves by controlling soil nutrition conditions to reduce the accumulation of nitrate and nitrite in tobacco leaves. This experiment was conducted on the farm of 29 Counties (towns), Hunan Province in 2002. More than 2320 soil samples and 256 flue-cured tobacco leaf samples were tested and analyzed to study the relationship between nitrate and nitrite content and soil nutrients and quality characters in flue-cured tobacco leaf. The results were as follows:(1) Descriptive statistics indicated that the soil fertility is high as a whole in Hunan. In the all soil samples, the rang of content of organic matter is 17.25-77.00g/kg, and the average is 38.52 ± 12.46g/kg; the rang of content of total N is 1.02~4.26g/kg, and the average is 2.31 ?.7lg/kg; the rang of content of hydrolytic N is 91.10~380.50mg/kg, and the average is 194.66 ±60.77mg/kg; the rang of content of ammonia N is 7.20-33.95mg/kg, and the average is 17.61 ± 8.37mg/kg. According to variation coefficients, contents of the soil nutrients are unbalanced in Hunan tobacco-growing areas, and the nitrate nitrogen content in flue-cured tobacco was different for different leaf positions, which showed the trend of C3F>B2F>X2F. For same tobacco leaf rank,variation coefficient of nitrite content is bigger than that of nitrate content.(2) Bavaria statistics indicated that positive correlation coefficients of contents of nitrate and nitrite were significant at 1% level with contents of organic matter, total N, hydrolytic N and ammonia N, and were not significant at 5% level with contents of total P, total K, pH value, available P, available K, and other nutrient elements. For different tobacco leaf rank, positive correlation coefficients of contents of nitrate and nitrite were significant at 1% level with contents of nicotine and total N; negative correlation coefficients of contents of nitrate and nitrite were significant at 1% level with contents of reducing sugar, total sugar and petroleum ether extract; the positive or negative correlation coefficients of contents of nitrate and nitrite were not significant at 5% level with contents of available P, available K, and other nutrient elements of tobacco-leaf. Stepwise regression statistics indicated that the major factors influencing nitrate and nitrite content in different grade flue-cured tobacco were soil organic matter, soil total N, soil hydrolytic N and ammonia N.(3) Canonical correlation statistics indicated that the relation is close between soil nitrogen nutrients and nitrate contents of flue-cured tobacco. Content of nitrate showed the increasing trend with the increasing of soil nitrogen nutrients and decreasing of soil total P in a certain range. The relation of soil nitrogen nutrients to nitrate contents is closer than that of soil nitrogen nutrients to nitrite content, which also explained the fact that nitrite content was produced in the process of flue curing.For chemistry components of different grade flue-cured tobacco leaves, canonical correlation statistics indicated the first canonical correlation coefficient of the contents of nitrate and nitrite was significant at 1% level with contents of other nitrogen components (nicotine, total N). The correlation information of the first canonical correlation coefficient accounts for 75.41%~86.92% of the total. The significant canonicalcorrelation was mainly caused by correlation between contents of nitrate and other nitrogen compounds (nicotine, total N). Similarly, the first canonical correlation coefficient of the contents of nitrate and nitrite were significant at 1% level with contents of reducing...
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