Rice Genomics and Genetics 2025, Vol.16, No.5, 267-281 http://cropscipublisher.com/index.php/rgg 273 This reduction effect is more ecologically significant when applied on a large scale: if a region promotes rice-duck farming on a large scale, a considerable amount of total fertilizer and pesticide application can be reduced each year, which will have a far-reaching impact on regional soil and water environment protection. It should be emphasized that reducing the frequency of input does not mean no application at all. When serious pests and diseases outbreaks or soil deficiency occur, appropriate chemical means are still needed. Rice-duck farming has achieved the transformation of rice field production from "high input and high output" to "low input and high efficiency" through biological substitution. This not only improves resource utilization efficiency, but also conforms to the current policy direction of reducing fertilizers and pesticides and sustainable agricultural development. 4.2 Reduced environmental burden on soil and water bodies Rice-duck co-cultivation reduces the pollution and harm of agricultural chemicals to water and soil environment from the source by reducing the use of pesticides and fertilizers. In conventional rice cultivation, a large amount of nitrogen and phosphorus fertilizers are easily lost into field ditches and groundwater, causing eutrophication of water bodies. Frequently sprayed pesticides and herbicides will accumulate in the soil and enter the surrounding waters with farmland runoff, endangering aquatic organisms and ecosystem health. In the rice-duck co-cultivation model, since ducks feed on Cordyceps and return their feces to the fields, there is almost "zero input" of chemical pesticides and herbicides during the planting process, and the demand for chemical fertilizers is also significantly reduced. The study by Xu et al. (2024) specifically measured the water environment and found that in the experimental fields in the Erhai Lake Basin where rice-duck co-cultivation was practiced and 25% of chemical fertilizers were replaced by organic fertilizers, the total nitrogen and total phosphorus concentrations in the field drainage were reduced by more than 30% compared with the conventional fertilized fields. This shows that the co-cultivation model effectively reduces the nutrient load in rice field runoff, which has positive significance for preventing lake eutrophication and protecting regional water quality. Similarly, the study by Li et al. (2020) pointed out that the rice-duck mixed farming model can alleviate agricultural non-point source pollution in rice fields, and can significantly reduce the chemical oxygen demand and pesticide residue concentration in rice field drainage compared with single planting. In terms of soil, reducing the application of pesticides makes the soil ecological environment safer. Long-term excessive use of pesticides will destroy the soil microbial community and lead to soil functional degradation. In rice-duck co-cultivation fields, since biological control replaces chemical control, the diversity and number of beneficial microorganisms (such as actinomycetes, nitrogen-fixing bacteria, etc.) in the soil are often higher than those in conventional rice fields. The survey by Shi and Jiang (2022) also showed that the detection rate of pesticide residues in farmland soil using rice-duck ecological farming was close to zero, and the pesticide concentration in field water was lower than the national environmental standard limit. This means that the rice-duck co-cultivation model can fundamentally avoid the generation of difficult-to-degrade organic pollutants in agricultural non-point sources, which is conducive to maintaining the cleanliness and health of the agricultural ecosystem. Rice-duck farming promotes the circulation of nutrients in the field, allowing more nitrogen and phosphorus nutrients to remain in the crop-soil system instead of being lost. While ensuring agricultural output, rice-duck farming minimizes the negative impact of chemical inputs on the environment, achieving a win-win situation for agricultural production and environmental protection. 4.3 Sustainable transition through eco-friendly inputs Rice-duck farming has explored a feasible path of "replacing chemistry with biology" for sustainable agricultural development, that is, controlling weeds, pests and diseases and providing nutrients through ecological means, partially replacing the functions of herbicides, pesticides and fertilizers. It is specifically reflected in the following two aspects: First, using ducks to weed instead of chemical herbicides. Weed control has always been a difficult problem in rice production. In the past, large-scale spraying of herbicides was not only costly but also polluted the environment. In rice-duck farming, ducks have a significant inhibitory effect on common weeds in rice fields such as barnyard grass and duck tongue grass. Practice has proved that as long as the stocking time and density of
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