Comprehensive Evaluation of Soil Fertility in Yongshun Tobacco-growing Areas of Hunan Province

Nineteen soil nutrient indexes of 239 soil samples from Yongshun tobacco-growing areas of Hunan province were ana-lyzed. Types of membership function and threshold values for each fertility index were determined. The method of principal component analysis was used to calculate the weight of each fertility index, and the additive and multiplicative theorem was used to estimate the integrated fertility index (IFI) of each soil sample. The results of comprehensive evaluation indicated that there was significant varia-tion in soil fertility among different soil samples from Yongshun tobacco-growing areas, IFI values of the whole soil samples ranged from 0. 341 to 0. 730, with the mean of 0.541, and the variation coefficient of IFI was 5. 14% . The soil fertility of various soil samples could be classified into four grading, namely higher, high, medium and low grade by cluster analysis, which took up 15. 86% , 21.61% , 44. 17% and 18.36% of the total soil samples respectively.