Effect of Different Fertilizers on Functional Diversity of Microbial Flora in Rhizospheric Soil Under Tobacco Monoculture

Continuous cropping obstacle is one the most important problems in tobacco (Nicotiana tabacum L.) production. To alleviate continuous cropping obstacle based on management of soil ecology, the effects of different fertilizers were tested using tobacco cultivar K326 growing in a field with 12-year consecutive cultivation. The rhizospheric soil was sampled to investigate the changes in functional diversity of microbial flora in different treatments. The results showed that the autotoxic allelopathic potential was maximal for the monoculture soil treated with traditional compound fertilizer, and minimal for the soil treated with farmyard manure. According to the result of BIOLOG analysis, traditional compound fertilizer was conducive to the growth of microbial flora feeding on amino acids and amine as carbon sources, the commercial organic fertilizer to the growth of microbial flora using carboxylic acids as a carbon source, and farmyard manure to the growth of microbial flora using carbohydrate, fatty acids, and phenolic acids as carbon sources. Principal component analysis indicated that the first 2 components were related to carbon sources, which accounted for 74.37% and 25.63% of the data variation. The carbon source of carbohydrate, fatty acids, and phenolic acids mainly contributed to the separation of the 2 principal components. The autotoxic allelopathic potential of tobacco rhizospheric soil was positively correlated with the average well color development (AWCD) value of microbial flora feeding on carbohydrate and phenolic acids as carbon sources, and negatively correlated with that of the microbial flora using the carbon source of fatty acids. In addition, for the growth of microbial flora in monoculture soil, farmyard manure was the best, followed by commercial organic fertilizer, and traditional compound fertilizer was the worst.