Effects of sugarcane-duck symbiosis on soil microbial community diversity in rhizosphere soil and bulk soil of sugarcane

【Objective】 To study the structure and diversity of rhizosphere soil and bulk soil microbial communities in sugarcane fields under the sugarcane-duck symbiosis mode, and reveal the effects of sugarcane-duck symbiosis on the diversity of soil microbial communities and the main groups of microbes in sugarcane fields, which could provide theoretical reference for scientific promotion of the new mode of sugarcane-duck symbiosis. 【Method】 Two treatments were set up in a field in situ experiment, which were sugarcane monoculture（SM） and sugarcane-duck symbiosis（SDS）. Rhizosphere soil and bulk soil samples were collected from sugarcane fields during the mature stage of sugarcane,and soil physicochemical properties,soil bacteria and fungi community structure and diversity were measured and analyzed. The correlation between soil physicochemical properties and soil microbial communities were also explored. 【Result】 Compared with SM, the application of SDS increased nitrate nitrogen（NN） content in rhizosphere soil and bulk soil significantly（P＜0.05, the same below）,while soil pH,catalase（CAT） activity,urease（URE） activity decreased significantly. Invertase（INV） activity and available phosphorus（AP） content reduced significantly in the rhizosphere soil,but increased significantly in bulk soil. Compared with SM, the abundance of rhizosphere soil fungi decreased, and ACE index and Chao1 index decreased by 16.81% and 16.67% respectively. The bacteria diversity of bulk soil was significantly increased in SDS, and the Simpson index was significantly increased by 128.13% compared with SM. In SDS,the relative abundance of Firmicutes varied greatly,while the relative abundance of Myxococcata,Ascomycota and Basidiomycota in the rhizosphere soil decreased. The relative abundance of Sphingomonas and Trichosporon significantly increased,while the relative abundance of Bacillus,Gaiella and Trichoderma significantly decreased. Sphingomonas,norank_f__JG30-KFCM45,Microvirga,norank_f__norank_o__Acidobacteriales, Bradyrhizobium,unclassified_o_Polyporales,Trechispora,Trichosporon and Chaetomium played an important role in the composition of soil microbial communities in SDS. The difference in soil microbial β diversity between SDS and SM was extremely significant（P＜0.01,the same below）. The redundancy analysis results showed that there was extremely significant influence between soil URE activity,CAT activity,organic matter（SOM） content,pH, total nitrogen（TN） content and soil bacterial community structure. Whereas,the soil AP,SOM and total phosphorus（TP） contents,URE and CAT activities had significant impact on the fungi community structure at genus level. The soil pH,NN and ammonium nitrogen（AN） contents played a major role in the growth of its bacterial differential genera in SDS. The soil pH, INV activity and NN,TN,SOM and AN content played a key role in the growth of its fungal differential genera in SDS. 【Conclusion】 Compared with SM,the application of SDS alters significantly soil pH, contents of NN and AP,and activities of INV,CAT and URE,and affects soil microbial community diversity and richness to improve soil microbial community structure. The activity of URE and CAT,the contents of SOM and TN and soil pH were the main environmental factors affecting changes in the structure of bacteria communities in sugarcane fields. The contents of AP,SOM and TP, and the activities of URE and CAT were the main environmental factors affecting changes in the structure of fungi communities in sugarcane fields.