Comprehensive evaluation of soil fertility in Sanmenxia tobacco-growing areas.

Nutrient contents of 238 soil samples from Sanmenxia tobacco-growing area in Henan Province were analyzed.Types of membership function and threshold values for each fertility index were determined.Based on methods of multivariate statistical analysis and principles of fuzzy mathematics,the comprehensive evaluation of soil fertility was conducted.The results comprehensive evaluation indicated that there existed significant variation for the soil fertility of Sanmenxia tobacco-growing area.IFI values of the whole soil samples range from0.35 to 0.81,with the mean of 0.52 and the coefficient of variation of 14.93 %.The soil fertility could be classified four ranks of high,higher,medium and low by cluster analysis,which took up 3.86 %,48.51 %,29.18 % and 18.45 % of the total,respectively.The pH value was too high in general,the contents of organic matter,total N,total P and available N were obviously deficient,available P,available K and total K were suitable.It was suggested that increasing and controlling N,supplying and adjusting P,increasing and steadying K for balanced fertilization in Sanmenxia tobacco-growing was suitable.