| Cotton industry is among the leading industries in Xinjiang, which possesses a large proportion in the whole industrial structure within the region and has important impetus to the regional economic development. The cotton area in Xinjiang is the largest inland irrigated cotton are in China because of its superior climatic conditions and adequate light and heat resources leading the cotton production a unique advantage. Cotton production is an irreplaceable pillar industries in Xinjiang and the major source of farmers'incomes. In recent years, Xinjiang's cotton industry has vigorously developed and plant area is increasingly expanding. However, excessive use of land over a long period of time, common phenomenon of continuous cropping and substantial application of fertilizers, pesticides and plastic mulch have resulted in the soil seriously degradated which are closely related to the changes of soil microbes, and consequently the major negative changes of soil quality. Therefore, how to restore soil quality of cotton field has become a hot research in agrology and has important theoretical and practical significance. Learning the changes of soil microbial characteristics in cotton production can provide scientific data for instruction of cotton soil improvement by using microbial indicators. In this study, according to the current situation of cotton plant distribution in Xinjiang, those representative cotton soils were sampled from No. 31, 44, 122, 125, and 148 Regiments, to reveal the change characteristics of microbial community and its spatial variation, microbial biomass carbon and nitrogen in Xinjiang. The results indicated:1. Bacteria, actinomycetes and fungi are the three major groups of soil microorganisms in cotton fields, composing the main soil microbial biomass, The largest number of bacteria relative in soil fauna, about 77.98% -97.31% of total bacterial counts, actinomycetes times, fungi at least about 0.22% -3.13%.the percentage of Bacteria decrease slightly with the increase of cropping years, the percentage of fungi increase overall, actinomycetes discipline was not obvious; Bacteria, fungi, actinomycetes of drip irrigation cotton field have increase relative Furrow cotton field. Compared with furrow irrigation, the value of B / F of drip irrigation increased significantly; drip irrigation make low-fertilizer"Fungal-type"change to high-fertility"bacterial-type"cotton field. In the three microbial flora, Bacteria and total P,available K were negatively correlated(P<0.05), with available N were positive correlation (P<0.05), actinomycetes with soil total soluble salt were negatively correlated(P<0.05). Fungi with the basic physical and chemical properties of the sample were not correlation.2. With the extension of cropping years, soil microbial biomass carbon and nitrogen showed some variations and significant difference with the increase of cropping years. Soil microbial biomass carbon and nitrogen were increased with the increase of cropping years, about attain maximum at continuous cropping 15 years, then began to decrease thereafter. Compared with furrow irrigation, drip irrigation increased the soil microbial biomass carbon and nitrogen, and two irrigation methods have significant differences. There was very significantly positive correlation (P<0.01) between soil microbial biomass carbon and microbial biomass nitrogen, significant positive correlation (P<0.05) between soil microbial biomass carbon and total N or available N, very significantly positive correlation (P<0.01) between soil microbial biomass nitrogen and total N or available N, and significant negative correlation (P<0.05) between soil microbial biomass nitrogen and soil total soluble salt or available K.3. Geostatistic approaches (GS+,Surfer) were applied in this article to study the biological characteristics (microbial community) of soil in cotton field especially the spatial variability of soil microbes as well to verify the feasibility of such approaches. The spatial variability of topsoil microbes showed a certain trend during different growth periods of cotton, but not quite similar to each microbial flora. In the cotton field, spatial variability of vertical profile also showed a determinate regularity.
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