The Study Of Microbial Diversity In Rhizosphere Of Cucumber In Greenhouse

Obstacles of continuous cropping have became important factors of decreasing vegetable yield, and it inhibit the sustaining development, soil microbes were considered as the leading one in a lot of factors. Because its change and composing of populations can reflect the health and quality of the soil in some degree. At the same time, it was the key of overcoming the obstacles of continuous cropping and other factors of influencing the soil health. Generally speaking, a soil that having diversified and active microbial populations must have relatively abundant nutrient, what's more, the diversity and evenness of soil microbial populations structure and composing not only enhance the stability and harmony of the soil ecosystem, but also improve the buffering ability for resisting the deterioration of soil entironment.The microbes can decompose the organic matter and then form the humus and release nutrient, and keep the balanceable state of decomposing and synthesizing the organic matters in soil, this kind of state was realized by the vital activity of soil microbes. Therefore, the soil microbes not only transform the soil carbon element and stable inorganic nutrition into microbial biass, but also mineralize the organic matter and transform the hardly dissolved matter that the plant can not absorb directly into soluble matter, by this they can increase the soil fertility, the microbes can produce great influence on soil fertility and fertilizer effect, the determination of soil microbial bioass have gradually became sensitive index of the soil fertility influence by the agricultural management measurement.This experiment studied the number of microbes and the DNA sequence of microbial community in the soil under different fertilization treatment and cropped for different years at different growth periods with traditional isolating and culturing methods and PCR-DGGE molecular marker technology, gained the changes and differences of the number of soil microbe , DNA sequence diversity and evenness index, and analyzed the influencing factors that may change the soil microbial community, try to supply the scientific bases for the eatablishing reasonable farming and manage system by adjusting or even altering the structure of soil microbial community by ourselves, keeping the harmonious, stable and healthy state, which will improve plant yield and quality.By the experiment, we got some conclusions:Firstly, bacteria are predominant among all microbes, and variation of bacteria can represent that of microbes. With the years of continuous cropping of cucumber prolonging, total population of cucumber rhizosphere microbes increased slightly, among them, fungi, bacteria, actinomycete, ammonium-oxidizing bacteria and nitrifying bacteria showed increase, and cellulolytic anaerobicbacteria decrease. Results also showed that growing cucumber and tomato in spring and autumn alternately is beneficial for microbes accumulation in the soil.Secondly, under different fertilization treatment ,the number of bacteria, fungus, actinomycete, ammonium-oxidizing bacteria and nitrifying bacteria were mostly improved, but the number of denitrifying bacteria was decreased in some degree when employ the organic fertilization and the mixture of the organic fertilization and composite fertilization; at the same time, the Shannon-weaver index and evenness index of soil samples which were fertilized with the organic fertilizer or the mixture of the organic fertilizer and composite fertilizer are higher than the soil which were fertilized with composite fertilizer or not fertilized. All these results show that the application of organic fertilizer or the mixture of organic fertilizer and composite fertilizer can improve the environment of cucumber rhizosphere and the transformation of soil nutrient, and have the strong ability for advancing the growth of microbes.