Rice Genomics and Genetics 2025, Vol.16, No.5, 267-281 http://cropscipublisher.com/index.php/rgg 269 It is reported that duck activities can increase the dissolved oxygen concentration in the surface water of rice fields by about 38%, thereby promoting the development of rice roots and nutrient absorption. The moderate stirring of ducks can also inhibit the anaerobic fermentation of methane-producing bacteria in the surface layer of rice fields, reducing the emission of greenhouse gases such as methane. Third, duck manure is a good organic fertilizer. After decomposition, duck manure and residual feed release nutrients such as nitrogen, phosphorus, and potassium, which are absorbed and utilized by rice plants, realizing the cycle of nutrients between animals and plants. Studies have shown that the total nitrogen content in the 0 cm-10 cm soil layer of rice-duck co-cultivation fields is 8.5%-28.4% higher than that of monoculture rice fields, and the soil organic matter and enzyme activity are also significantly improved (Xu et al., 2017; Wang et al., 2019). Through the above mechanisms, the rice-duck symbiotic system has established a complex food web and nutrient cycle network, with higher energy and material utilization efficiency than the single planting system, and the stability and resistance of the ecosystem have also been enhanced. 2.2 Farming practices and management in integrated systems The field management under the rice-duck symbiotic model needs to be scientifically arranged according to the growth stage of rice and the biological characteristics of ducks. Generally speaking, about 7-10 days after the transplanting of early or mid-season rice, when the seedlings are basically rooted and alive and the plant height reaches 15 cm~20 cm, the appropriate-age ducklings are selected and put into the rice field for stocking. The stocking density depends on the conditions of the rice field. It is usually appropriate to stock 15-30 ducklings per mu (666.7 square meters of paddy field). Too high a duck density may cause trampling damage to the seedlings, while too low a density will make it difficult to fully play the role of controlling weeds and insects. During the symbiotic growth period, farmers need to carry out necessary feeding and management of the ducks. For example, anti-escape nets are set up around the edge of the field, and simple duck sheds are set up in the field for ducks to roost and shelter from rain at night. A small amount of grain feed can be supplemented in the evening to ensure the nutrition of ducks. In the early stage of rice growth, shallow water irrigation is maintained frequently to meet the needs of rice tillering and facilitate duck activities; in the later stage, when the fields are left for baking, the ducks can be transferred to ditches and ponds for short-term foster care or their activity time in the fields can be reduced. The key node is that during the heading period of rice, ducks need to be completely withdrawn from the rice fields to prevent them from eating rice ears or stepping on plants. Generally, ducks are caught about 10 days before rice heading, or they are raised and fattened separately outside the rice fields. Rice is harvested normally after maturity, and duck-rice fields in different seasons can also be connected to the cultivation of other crops and poultry. For example, in some places, green manure or other economic crops are planted in winter after rice and ducks to achieve an efficient rotation of "one rice and one poultry". The entire rice-duck co-cultivation process emphasizes the coordination of the growth rhythm of rice and ducks: ducks help rice in the early stage and ducks give way to rice in the later stage, which not only ensures stable rice production but also cultivates high-quality ducks. In field management, attention should also be paid to disease prevention and control, such as regular water changes and timely disinfection, to ensure the healthy growth of ducks and rice. The operation process of rice-duck co-cultivation is to organically embed duck farming into the rice-growing cycle on the basis of following the laws of rice cultivation, and achieve synchronous increase in production and efficiency through fine management (Vipriyanti et al., 2021). 2.3 Overview of regional applications of co-culture systems The rice-duck co-cultivation model has been put into practice in many rice-growing areas in my country, and various forms have been developed according to local conditions. In the middle and lower reaches of the Yangtze River, such as Huai'an District, Huai'an City, Jiangsu Province, the ecological cultivation and breeding of rice and ducks has been promoted since the 2010s, and many family farms have adopted this model to achieve significant economic and ecological benefits. Research statistics show that although the rice yield under the rice-duck model is slightly lower than that of the conventional machine-planting model, the comprehensive benefits are much
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