| As a terrestrial ecosystem with a high biology diversity,soil ecosystem is too complex to dope out, it is known little by us.Microorganisms are the main biology of the soil ecosystem. The energy and nutrition exchanges can not be implemented without the soil microorganisms, so they play a vital role in ecosystem balance keeping. And they means a lot to the forming, developing, fertility keep of the soil, and the growth of the plants. As the most important organisms of the terrestrial ecosystems, it can represent the quality and the healthiness of the soil, so the study of the soil organisms is significant.In this paper, the diversity of the bacteria and fungi in bulk soil and different size particle fractions were studied in a paddy soil under a long-term fertilizer application trial, including the treatments of chemical fertilizer with straw return (CFS), chemical fertilizer plus pig manure (CFM), chemical fertilizer alone (CF) and no fertilizer application (NF). Particle size fractions (2000-200,200-20,20-2 and<2μm) were obtained by low-energy sonication along with a combination of wet sieving and centrifugation. The main results were as follows:1. In the bulk soil, the content of soil organic carbon and total nitrogen content were highest in the treatments of chemical fertilizer with straw return, and lowest in the treatments of no fertilizer. In the size fractions of 2000-200μm and<2μm, the content of soil organic carbon and total nitrogen were also highest in the treatments of chemical fertilizer with straw return, and lowest in the treatments of no fertilizer.2. Microbial phospholipid fatty acid (PLFA) test showed that combined application of organic manure and chemical fertilizer significantly increased total soil PLFA. In the< 2μm particle size fractions, total PLFA was higher, the application of straw and manure significantly increased total PLFA in 2000-200μm particle size fraction, chemical fertilizer significantly reduced the total PLFA in different sizes of particle size fractions, while in the other particle size fractions, the total content of PLFA groups did not change significantly. 3.The PLFA in different sizes of particle size fractions showed that, the fungi and bacteria biomass were increased with straw return. The chemical plus organic fertilizer could increase the fungi biomass and the proportion of fungi and bacteria significantly. The total content of PLFA was higher comparatively in the size fraction of<2μm, and the application of the chemical fertilizer reduced the total content of PLFA significantly in the size fraction of 2000-200μm. The application of fertilizer did not affect the total PLFA in the other sizes of particle size fractions. Thus it could be seen that, the size fraction of 2000-200 u m was the most susceptive particle size fractions.4. PCR-DGGE results showed that long-term application of chemical fertilizers significantly reduce bacterial diversity, chemical and organic fertilizers in the soil significantly increased bacterial diversity, and the effect of different fertilizer application on soil fungal diversity was not obvious. In sizes of different particle size fractions, in 20-2μm particle size of fraction of bacteria diversity index was the lowest,2000-200μm and<2μm particle size fractions of bacteria diversity index higher fertilizer significantly. The application of chemical fertilizer reduced 200-20μm particle size fractions of bacteria diversity significantly. Fungal diversity was manifested in 2000-200μm particle size fractions were higher,<2μm was in the middle,200-20μm and 20-2μm particle size fractions were relatively lower, larger particle size fractions affected the diversity of soil microorganisms more than the different fertilization. |
PDF Full Text Request