The Rhizosphere Soil Microbial Diversity Is Changed By Flue-Cured Tobacco Continuous Cropping

Flue-cured tobacco is the main cash crops in China, bring huge benefits to national income. But tobacco is an intolerance continuous cropping crop, continue cropping inevitably in agricultural production has severely restricted the tobacco agriculture sustainable developing. Therefore, researching the mechanism of tobacco continuous cropping obstacle is the most important issues that need to be soluted urgenty. This paper takes Longjing911flue-cured tobacco as material which is planted widely in Heilongjiang Province, using the methods of Biolog Eco microplate detection technology and454pyrosequencing to research the effects of tobacco continuous cropping on structural and functional diversity of soil microbial communities, to analyze species diversity in the molecular biology level of different farming methords, which include species richness, diversity index, identification of the dominant strain, and so on, from the data find out tobacco coutinuous cropping how affect the soil microbial community, which provide the theoretical basis for the continuous cropping obstacles mechanism, to work out a reasonable way of farming to avoid cropping obsracles to ensure the sustainable development of agriculture of tobacco has an important significance.The results were as below.1. With continuously planting tobacco for5years,1year and tobacco rotation (soybean-wheat-tobacco) for the treatment, to study the number of soil microbial changes in10cm and20cm soil layer. The results showed that continuous cropping of flue-cured tobacco decreased the numbers of soil bacteria and actinomyces, increased the numbers of soil fungi. The amount of ammonifying bacteria, aerobic azotobacter and anaerobic cellulose-decomposer decreased for5-year continuous cropping compared to one-year continuous cropping. The soil microbial number of10cm soil layer significantly more than20cm soil layer. It suggested that continuous tobacco cropping changed the number of soil microbial, soil ecosystem imbalance, beneficial soil microbes reduced, leading to the occurrence of continuous cropping obstacles.2. The Soil microbial diversity and community structure under effects of continuously planting tobacco were analyzed using Biolog microplates. The results showed that the average well color development (AWCD) of soil microbes were reduced obviously under continuous tobacco cropping, the indices of richness, Shannon-Wiener and Simpson’s diversity of microbial metabolic diversity indicated significantly lower in the soil of continuous cropping than in rotation, and the functional diversity index of soil microbial community under7years continuous tobacco cropping was lower than under2years continuous tobacco cropping. The carbon sources with lower utilization by soil microbes in continuous cropping than in rotation. It suggested that continuous tobacco cropping reduced the diversity of soil microbial community structure and function, and with the increase of continuous tobacco cropping years, the Soil microbial diversity was reduced. Principal component analysis showed that7years continuous tobacco cropping had significant difference in carbon utilization compared with other treatments, correlation analysis showed this difference was mainly the results of microbial carboxylic acids, carbohydrates, amino acids and amines were choose used.3. Soil bacterial16S rDNA diversity differences in different tobacco cropping patterns were analyzed using454pyrosequencing technology, to explore the influence on structural diversity of soil bacterial communities by flue-cured tobacco contintuous cropping. The sequencing analysis showed that the richness (Chaol and Ace)in two continuous tobacco cropping treatments were significantly lower than the other rotation treatments, while the dibersity index (Shannon and Simpsion)had no significantly difference. In phylum and genus level analysised the bacterial community structure showed that the soil bacterial communities diversity was reduced in tobacco continuous cropping soil.In conclusion, tobacco continuous cropping made the number of soil microbial changed, functional diversity carbon metabolism reduced, bacterial community structure changed and soil microecology imbalance, which were the fundamental reasons for tobacco cropping obstacles. Therefore, through regulate the continuous cropping soil microflora to achieve the purpose of overcome continuous cropping obstacles.