This study presents an investigation of soil chemical properties and microbial community diversity by Biolog ECO analysis in a seven-year field experiment using winter flooded fallow + no straw returning (W), winter flooded fallow + straw returning (WS), and winter flooded fallow + straw returning + crayfish farming (WSC) at soil depths of 0–10 cm and 10–20 cm. Compared with the WS treatment, the WSC treatment had significantly higher total organic carbon (TOC) content in the 0–10 cm layer as well as greater available nitrogen (AN) and total nitrogen (TN) contents and acid phosphatase and sucrase activities in the 10–20 cm layer, while the pH value, total reducing substances, and Fe2+ content in the 0–20 cm layer were considerably lower. The WSC treatment improved the microbial species abundance in the 10–20 cm layer and the utilization rate of carbon sources in the 0–20 cm layer compared with the WS treatment. The soil microbial species abundance, microbial community diversity, and utilization rate of carbon sources in all of the layers examined were significantly higher in the WSC treatment than in the W treatment. The results indicate that straw returning under the rice-crayfish integrated system improves the contents of TOC, TN, and AN, decreases reducing substances properties, increases acid phosphatase and sucrase activities, and improves microbial community functional diversity, thereby contributing to the improvement of soil quality and the long-term sustainable development of the rice-crayfish integrated system.

This study represents the investigation of soil physicochemical properties and microbial diversity by the Biolog ECO analysis in a 7-year field experiment using winter flooded fallow + no straw returning (W), winter flooded fallow + straw returning (WS), and winter flooded fallow + straw returning + crayfish farming (WSC) at soil depths of 0-10 cm and 10-20 cm. Compared with the W treatment, the WS treatment has significantly more total reducing substances in the 0-10 cm layer and sucrase activity in the 0-20 cm layer. The WSC treatment has significantly more available N (AN), total N (TN) contents, acid phosphatase and sucrase activities in the 10-20 cm layer, while the pH value, total reducing substances, and Fe2+ content in the 0-20 cm layer was considerably lower compared with the WS treatment. Biolog ECO analysis reveals that microbial community composition in the WS and WSC treatments differs from that in the W treatment in the 0-20cm layer. The WS treatment increases significantly the diversity of bacterial community and the ability of utilizing carbon sources in the 0-10 cm layer, and the species abundance of bacterial community in the 0-20 cm layer. Meanwhile, in the 10-20 cm soil layer, the WSC treatment improves the species abundance of bacterial community and the ability of utilizing carbon sources compared with the WS treatment. These results indicate that straw returning under the rice-crayfish integrated system improves soil physicochemical properties, decreases reducing substances properties, and increases soil enzyme activity and functional diversity of microbial community, thereby contributing to soil condition.