The Chinese rice–fish–duck symbiosis system is one of the globally important agricultural heritage systems, with a history of nearly a thousand years. It embodies the wisdom of the Chinese ancestors and has huge comprehensive value, which has extremely important references for the sustainable development of agriculture. The technological core for the rice–fish–duck symbiosis system lies in the selection of rice, fish, and duck varieties and the coupling of agricultural operation time. In the process of modern agriculture, many varieties with high comprehensive benefits have also been applied to the rice–fish–duck system, and the rice–fish–duck model has been further developed. What is worrying is that the transfer of rural labor, the promotion of modern agricultural technology, the low degree of marketization and industrialization, the weakening of cultural awareness, and the change in climate have posed huge threats and challenges to the traditional Chinese rice–fish–duck system. The protection and development of the system are urgently needed. Therefore, we recommend delimiting active protection areas, establishing scientific research bases, improving relevant systems, developing rural tourism markets, and innovating farming technology, which also provide guidance for protecting and developing other agricultural cultural heritages.

The rice-turtle coculture system is the most special rice-fish integrated farming system. In this study, we selected four paddy fields, including a rice monoculture paddy and three rice-turtle paddies with different planting years, to investigate the soil bacterial community composition with Illumina MiSeq sequencing technology. The results indicated that the contents of soil available nitrogen (AN), soil available phosphorus (AP) and soil organic matter (OM) in 9th year of rice-turtle paddy (RT9) were increased by 5.40%, 51.11% and 23.33% compared with rice monoculture paddy (CK), respectively. Significant differences of Acidobacteria, Desulfobacteria, Crenarchaeota were observed among the different rice farming systems. The relative abundance of Methylomonadaceae, Methylococcaceae and Methylophilaceae in RT9 was significantly higher than that in other treatments. RT9 had significantly lower relative abundance of Acidobacteria, but significantly higher relative abundance of Proteobacteria than other treatments. Redundancy analysis showed that soil AN and AP contents were the major factors influencing the abundance of the dominant microbes, wherein Methylomonadaceae, Methylococcaceae and Methylophilaceae were positively correlated with OM. The findings revealed the rice-turtle coculture system in the 9th year had higher soil nutrients and soil bacterial diversity, but there was also a risk of increasing methane emissions.

Earthworms have been studied in many ecosystems, demonstrating their high ecological value. However, there are few studies on the coupling of earthworms to irrigated paddy fields. On this basis, a symbiotic system of irrigated rice and earthworms was established with a wide-ridge cultivation model, and a combination of field experiments and pot experiments was carried out in Southern China. The results showed that the symbiosis of irrigated rice and earthworms in the pot experiment significantly loosened the soil by 5–10 cm, compacted the soil by 10–20 cm, increased the soil pH value by 0–10 cm, and increased the content of soil organic matter by 5–20 cm compared with rice monoculture. Due to the significant increase in leaf area index and grain weight at the mature stage, the white root at the heading and grain filling stages improved significantly, and the yield of irrigated rice also increased significantly by 15.39%. However, in the field experiment, due to the low survival rate of earthworms, the effect of inoculating earthworms was not significant. This study confirmed the beneficial effect of earthworm inoculation on the paddy field ecosystem, and provided a research basis for introducing earthworms into the paddy field ecosystem, realizing the sustainable development of rice cultivation, and ensuring world food security.