Studies On Microbial Community Diversity And Activities Of Straw Mulching And White Clover Intercropping Tea Plantation

The field experiments were conducted to study the effects of different mulching measures(straw mulching and intercropping three leaf grass) on soil temperature, soil moisture, soilnutrient, dynamic variation of soil microbial biomass, yield and quality of tea garden inChangsha county in Hunan province. The plot experiments with straw cover and intercroppingthree-leaf grass with different fertilization were settled and microbial population and enzymeactivities were studied. The BIOLOG and DGGE were successfully employed in this study andthe research methods on the microbial ecology of the tea garden were well developed. The mainresults are shown as follows:Mulching measures had double effects on adjusting soil temperature. The s0il temperaturewas adjusted when the air temperature was too low or high, particularly in the surface soil layer.Thus the damage to roots was alleviated. Compared to ck, the changes of soil temperature withmulching were smaller in a year, and the effects decreased wlth the depth of soil layer.Mulching increased soil moisture in tea garden. The effect of mulching on soil moisturediffered in different depth of soils; generally, it was prior in surface soil layer, especially in Julyand August when there was a lack of rainfall. The effect of water storage and conservation wassignificant, compared to ck. The straw mulching increased 20.84 percent, while the grassmulching increased 11.58 percent in the 0-60cm soil.Based on the melioration in tea plantation, grass intercropping and straw, mulchingincreased the earthworm population and biomass evidently. They lessened weed species andrestrained dominant population. Moreover, they diminished weed density, height and biomassremarkably.The monthly dynamics of SMB-C,SMB-N,SMB-P all showed to be higher in summerand lower in winter. It is "low-high-low-high" in the whole year.After straw covering and intercropping three-leaf grass, the amount of organic matter,Alkali-hydrolysable N, available P of surface soil layer increased obviously, the amount ofSoil microbial biomass C,N,P,soil organic C, the whole N, the whole P, available P,Alkali-hydrolysable N also decreased with decreasing of the profile.In the plot experiments the numbers of bacteria increased notably after iritercroppingthree-leaf grasses, while actinomycetes increased after Straw covering and the extent of funginumbers varied tiny.It was found that straw cover and intercropping three-leaf grass with different fertilization can all increased the amount of SMB-C,SMB-N, while those of straw cover with fertilizationincreased notable. Positive correlation was found between SMB-C,SMB-N and organic matter,total N, available N. In addition, SMB-C was much sensitive than SMB-N.The soil enzyme activities and nutrient content were assayed. The results obtained by thecorrelation, path and principal component analysis showed that positive correlation was foundbetween the activities of hydrogen peroxides, phosphates, urease, invertase respiratory intensityand the contents of organic matter, total N and available N. Soil fertility could be evaluatedobjectively by principal component analysis.BIOLOG bacterial identification system plates were used to assess soil microbialcommunity of the tea Plantations. It was found that different treatments could all improve theabundance and diversity. Straw cover with fertilization was the best, followed by intercroppingthree-leaf grass with organic matter.Analysis of multiple indexes indicated that, different treatments have litter significantinfluence on the common species of the soil microorganism, but the microbial communityevenness reduced organic matter. The differentiation to soil microbial community was broughtmainly by the carbohydrate and the carboxylic acid after using the principal componentsanalysis.The use of BIOLOG for microbial identification was subject to the same limitations astraditional isolate characterization, it proved to be a rapid and reproducible method of detectingrelative change in microbial communities. The application of the community-level approach toassays of microbial function would provide a more sensitive and ecologically meaningfulmeasure of heterotrophic microbial community structure.As a new DNA fingerprinting technique, Denaturing Gradient Gel Electrophoresis (DGGE)can be used to analyze the soil microbial diversity. The genomic DNA of soils microbialcommunity was extracted directly from chemical method, then different DNA yields wereobtained, the 16SrRNA genes (V6 region) were amplified by using the specific primers(F954GC~+ and R1369). The result of agarose gel electrophoresis showed that the PCR productswere about 500bp. These amplified DNA fragments were then separated by paralleled DGGEwith the denaturant (urea and formamide) from 40% to 60%. The profile of DGGE showed thatdifferent soils had different bands patterns. The analysis of multiple indexes indicated thatStraw cover with fertilization was the best,(0.8742) followed by Straw cover with organicmatter(0.8035), then followed by intercropping three-leaf grass with fertilization(0.7631). The amplified fragments of 16SrRNA genes (V6 region) of different microbial community in soilswere separated successfully in this study, which made it possible to identify and define these16SrDNA fragments by sequencing. The results showed that DGGE is a new and effectivetechnique in analyzing soil microbial diversity of the tea garden.