Rice-crayfish farming enhances soil organic carbon by increasing labile organic carbon and altering microbial functions

In China, rice-crayfish farming (RCF) is a resource-efficient and eco-friendly agricultural model that demonstrates significant potential for soil organic carbon (SOC) storage. However, the impact of RCF on SOC accumulation and its associated microbial characteristics remains unclear. In this study, we conducted an experiment in rice fields with five years of RCF. We investigated surface SOC content and its components, as well as soil microbial community and its functions over two consecutive years. Compared to rice monoculture (RM), SOC in RCF increased by 24.13 % to 32.40 %. Labile organic carbon I (LOC I) and recalcitrant organic carbon (ROC) in RCF increased by 25.84 % to 39.07 % and 30.98 % to 60.87 %, respectively. While RCF reduced dissolved organic carbon (DOC) by 33.24 % to 45.83 %, it increased particulate organic carbon (POC) and easily oxidizable carbon (EOC) by 92.28 % to 132.61 % and 66.42 % to 69.76 %, respectively. The activities of (3-xylanase (BX), (3-glucosidase (BG) were significantly decreased and (3-1,4-N-acetylglucosaminidase (NAG) was significantly increased in RCF. Additionally, RCF decreased the proportion of chemoheterotrophy and aerobic chemoheterotrophy of prokaryotic communities, while increased the proportion of dark sulfide oxidation and the dark oxidation of sulfur compounds. RCF also exhibited a high proportion of wood saprotroph functions of fungal communities. The structural equation models revealed that soil properties and prokaryotic communities were the main factors contributing the accumulation of SOC by enzyme activities in RCF. Overall, the practice of RCF increased the content of LOC I and ROC, altered soil prokaryotic community structure and predicted functions, led to a reduction of soil enzyme activities involved in the decomposition of organic matter, and consequently enhancing the accumulation of SOC.