Rice Genomics and Genetics 2025, Vol.16, No.5, 267-281 http://cropscipublisher.com/index.php/rgg 270 higher than conventional planting because the rice produced is green, organic and high-quality rice with a higher market price (Gao et al., 2023). In southern rice-growing provinces such as Hunan and Jiangxi, integrated rice farming is seen as an important measure for the structural reform of the agricultural supply side. Some areas in Hunan have combined and promoted the "rice + duck" model with the "rice + fish" and "rice + frog" models to form a regional characteristic ecological agricultural industry. The traditional rice-fish-duck symbiotic system of the Dong ethnic group in Congjiang, Guizhou has been protected and developed, becoming an important carrier of eco-tourism and cultural heritage, attracting a large number of tourists to visit and experience it every year. In the cold and cool rice-growing areas of Northeast China, there have been experiments in recent years to introduce rice-duck co-breeding into organic rice production, but due to climate and growth period restrictions, the model needs to be adjusted, such as selecting cold-resistant duck varieties. In Asian countries such as Japan and South Korea, modern rice-duck farming technology has also been applied as a means of reducing chemical inputs and producing organic rice. When applying rice-duck co-breeding, various places will improve it in combination with their own natural conditions and breeding traditions. For example, in the Erhai Basin in Yunnan, a scientific research team explored the use of organic fertilizers to replace some chemical fertilizers, and used rice-duck co-breeding to control non-point source pollution, achieving good results. The rice-duck symbiotic system has shown broad prospects in my country's rice-growing areas, but the degree of promotion varies from region to region, requiring targeted demonstration and technical optimization to achieve a balance between ecological and economic benefits. 3 Mechanisms Enhancing Ecosystem Services 3.1 Natural pest and weed control Biological control of pests and diseases is one of the most prominent ecological service functions of rice-duck co-cultivation model. After the introduction of ducks into rice fields, ducks eat a considerable part of the pests and weeds in the fields, reducing the base number of pests and diseases from the source. For pests, experiments have shown that the incidence of major rice pests such as rice stem borer, rice planthopper, and rice leaf roller in rice-duck fields has been significantly reduced. For example, the field comparison experiment of Lan et al. (2021) showed that compared with the control field without ducks, the amount of insect traps in the rice-duck co-cultivation field was greatly reduced, and the incidence of diseases such as rice sheath blight and rice blast also decreased (because ducks eat pests and reduce the transmission medium). Ducks keep foraging in the fields during the day, preying on insect larvae, eggs and mollusks in the rice fields, effectively curbing the growth of pest populations. This biological insect control effect can replace or reduce multiple pesticide applications. Studies have shown that under the co-cultivation model, the application of pesticides can be reduced by 1-2 times per season without causing a rebound in insect population density, which reflects the green control advantage of "using ducks to control insects". For weeds, ducks like to eat tender weed seedlings and seeds. In the first few weeks after the seedlings are transplanted and survive, it is the period of rice tillering and weed germination. When ducks search for food in the field, they will peck at most broad-leaved weeds and grass weed seedlings such as barnyard grass and duckweed. Studies have determined that the weed biomass in rice-duck co-cultivation fields is more than 70% lower than that in conventional rice fields, and the weed control effect is comparable to that of chemical herbicides. The disturbance caused by duck activities makes it difficult for weeds to take root. After several years of continuous duck release, the weed seed bank in the rice field soil is greatly reduced. The study of Nayak et al. (2020) also proved that in the integrated rice farming system where ducks or fish are introduced in India and other places, the field weed coverage and density are significantly lower than those in single-plant rice fields. Rice-duck co-cultivation achieves natural control of major pests in rice fields through the feeding and activities of ducks. This ecological regulation function reduces the frequency of pesticide use, not only reduces production costs, but also protects natural enemy insects and biodiversity around rice fields, and maintains the stability of farmland ecosystems. It should be noted that in practice, the release time and density of ducks should be reasonably regulated according to the situation of field pests and weeds to ensure the balance between biological pest control and rice seedling growth.
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