Effects of long-term application of rice-turtle co-culture on soil bacterial community structure and diversity

【Objective】 To explore the effects of rice-turtle co-cultureon soil fertility, soil bacterial community structure and diversity, and to provide a scientific basis for explaining the mechanism of rice-turtle co-culture on soil microbial diversity in paddy fields.【Method】 Soil samples from paddy fields of 2-year rice-turtle co-culture field(RT2) and 5-year rice-turtle co-culture field(RT5) and 8-year rice-turtle co-culture field(RT8) were collected from 0-10 cm soil layer of each treatment to determine the soil nutrient content. Illumina MiSeq high-throughput sequencing technology was used to explore the soil bacterial community structure, and the differences of soil nutrient content and soil bacterial community diversity in rice-turtle co-culture fields with different application years were compared and analyzed.【Result】 Long-term application of rice-turtle co-culture increased soil total nitrogen, total phosphorus, alkali-hydrolyzable nitrogen and available phosphorus contens and soil p H. The contents of total phosphorus and available phosphorus in 5-year rice-turtle co-culture field were significantly higher than those in 2-year rice-turtle co-culture field(P<0.05, the same below), the contents of total nitrogen, total phosphorus, alkali-hydrolyzable nitrogen and available phosphorus in 8-year rice-turtle co-culture field were significantly higher than those in 2-year field. The contents of organic matter, total potassium and available potassium in 5-year field were the highest, and those in 8-year field were the lowest. The Alpha diversity analysis showed that the Shannon index, PD whole tree index and Chao1 index of soil bacterial community diversity were RT5>RT8>RT2. The bacterial groups detected in each sample belonged to 51 phyla, 136 classes, 192 orders, 337 families, 557 genus and 113 species. The analysis of species community composition showed that Proteobacteria, Bacteroidetes, Acidobacteria and Actinobacteria were the main dominant bacterial communities in paddy soil. The differences of soil bacterial community structure in rice-turtle co-culture in different years were mainly manifested in species evenness. There were significant differences in RT2 in the relative abundance of Proteobacteria, Bacteroidetes, Actinobacteria, Acidobacteria, Deinococcus-Thermus, Firmicutes, Chloroflexi, Planctomycetes and Thaumarchaeota. RT8 treatment only showed significant differences in Proteobacteria, Bacteroidetes, Planctomycetes and Synergistetes.【Conclusion】 Long-term application of rice-turtle co-culture can maintain the contents of soil main nutrients, increase the diversity of soil bacterial community, enlarge the relative abundance of dominant bacterial community, and make soil microenvironment more stable without chemical fertilizer.