Effects Of Sugarcane Rationing Cultivation On The Changes Of Microbial Communities In The Rizosphere Soil

Sugarcane (Saccharum officenarum L.) is perennial herb classified into Gramineae Saccharum crops. Sugarcane is an important raw material which produces more than 90% sugar in China. Sugar industry helps the farmers become prosperous and local government get the fiscal revenue. In the process of sugarcane planting, sugarcane ratooning cultivation is an important cultivation system. However, there are some problems in sugarcane ratooning cultivation, such as low yield and diseases, which caused fewer seedlings and the lower number of stems.The causes resulting in continuous cropping obstacles are complex. The conbined effects of factors in the crop and soil systems generate the phenomenon of continuous cropping obstacles. In this study, terminal restriction fragment length polymorphism (T-RFLP) was used to analyze the changes of soil microbial communities in blank soil, new sugarcane planting soil and one year of sugarcane ratooning soil. And it explored molecular ecology mechanism caused by sugarcane ratooning cultivation in the sugarcane rhizosphere soil, and established the theoretical basis for soil remediation. The results were as follows:(1) The changes of bacterial community diversity among the samples of sugarcane rhizosphere soilThere were some changes among the five samples collected from sugarcane rhizosphere soil and blank soil, which exited the same trend. The number of microorganisms in one year of Funong28 ratooning soil was less than that of Funong28 new planting soil and blank soil. On the contrary, the number of microorganisms in one year of Gannan99 ratooning soil was more than that of Gannan99 new planting soil and blank soil. The microbial diversity index and evenness index in one year Funong28 ratooning soil were lower than the other soil samples. There was no significant difference among other soil samples.(2) The difference of bacterial functions in sugarcane rhizosphere soil of different planting patternsIn the new planting soil and one year of ratooning soil, there were same bacterial species and specific bacterial populations containing related ecological functions. The pathogenic bacterial community appeared in one year of Funong28 and Gannan99 ratooning soil. The individual number of microbial populations with the same ecological functions were different in the rizosphere soil of same sugarcane varieties planted under different cropping patterns. In one year of Funong28 ratooning soil, the microbial populations involved in the carbon cycle increased, and the population of beneficial bacteria and biological nitrogen fixation bacteria decreased. The population of bacteria involving in carbon cycle and nitrogen fixation increased in one year of Gannan99 ratooning soil, and the population of beneficial bacteria remained unchanged.(3) The difference of bacterial functions in rhizosphere soil of different sugarcane varieties planted in one year of ratooning cultivationDifferent varieties of the same crop, cultivated in the same cultivation manner and same soil conditions, can produce different rhizosphere microbial communities. The number of bacteria population involving in biological nitrogen fixation, metabolism of alcohol, lactic acid fermentation and beneficial bacteria in one year of Gannan99 ratooning soil were more than that in one year of Funong28 ratooning soil. However, the number of pathogenic population in one year of Gannan99 ratooning soil was less than that in one year of Funong28 ratooning soil.Based various experimental results, it was suggested that under different cropping patterns different sugarcane varieties had different effects on the structure of rhizosphere microbial community. In one year of Funong28 ratooning soil, the diversity of microbial communities decreased, some communities involved in basic metabolic processes and beneficial communities declined and the pathogenic communities emerged. In contrast, the diversity of microbial communities and related ecological functions kept healthy. However, the identification of quality in sugarcane ratooning cultivation must combine with comprehensive study of other factors, such as the study on the changes of microbial communities and soil substance in the different growth period of sugarcane ratooning cultivation, and survey of the agronomic traits. Thus, in the process of sugarcane ratooning cultivation, the sugarcane varieties suitable for ratooning cultivation would be selected from different sugarcane germplasm which was planted around the country. The different tillage practices were used to improve soil microenvironment and structure of soil microbial communities in the sugarcane ratooning cultivation. It can provide some technical support for sugarcane agricultural production.