Influence of Land Treatment for Rural Sewage on Soil Environment and Flue-cured Tobacco Quality

In order to explore how the land treatment of rural sewage affects the soil environment and the flue-cured tobacco quality, the pretreated sewage collected from rural areas of south China were directly discharged to the experimental fields and the microbial number, enzymatic activities of soils with different distance away from the outlet and different depth were observed; besides, the sewage were diluted to different proportions and applied for the cultivations of flue-cured tobacco, afterwards, the flue-cured tobacco leaves at maturity were harvested for the quality evaluation and the Principle Component Analysis ( PCA ) method was adopted to select the best dilution proportion (treatment) based on the comprehensive analysis of the quality of tobacco leaves under different treatments. Results showed that: The sewage treatment had little effect on surface soil microbial number, but which significantly increased the number of bacteria, fungus and actinomyce in soils of 20~40 cm and 40~60 cm layer. At the same time, the sewage treatment significantly increased the soil enzymatic activity including the urease activity, catalase activity and polyphenol oxidase activity at all measuring points. Known from the analysis of flue-cured tobacco leaves, treatments with higher sewage proportion obviously increased the content of nicotine, total N and potassium in flue-cured tobacco leaves, but which decreased the content of reducing sugar. According to the calculations of PCA model, the quality sequence from excellent to inferior could be ordered as: T2>T1>T3>T4>CK, therefore, for flue-cured tobaccos, T2 was more conductive for equilibrium absorption of nutrients compared with other treatments.