Rice Genomics and Genetics 2025, Vol.16, No.5, 267-281 http://cropscipublisher.com/index.php/rgg 274 ducks are controlled, there is basically no need to apply herbicides separately within a growing season to control weed damage to a level that does not affect yield. This not only saves pesticide expenses, but also avoids herbicide damage and residue problems, which can be said to be "killing two birds with one stone". Second, duck manure is used to replace some chemical fertilizers. Duck manure is a high-quality organic fertilizer with a comprehensive nitrogen, phosphorus and potassium nutrient ratio and good slow-release properties. Rice-duck farming allows duck manure to be directly returned to the field, which is equivalent to continuously applying a small amount of organic fertilizer to rice. It is estimated that each duck can produce about 0.05 kg of nitrogen per day, which is equivalent to applying 0.1 kg of urea. If calculated based on 20 ducks per mu, the nutrients provided by duck manure during a growing period can replace about 30%-50% of the amount of chemical nitrogen fertilizer used. Moreover, the organic matter in duck manure is conducive to improving soil fertility and soil structure, which is incomparable to chemical fertilizers. This "raising instead of applying" organic fertilizer source recycling model improves nutrient utilization, reduces fertilizer input, and is more environmentally friendly. Rice-duck farming has taken a sustainable path to reduce external input and reduce environmental pressure by developing ecological circular agriculture. As Wang (2019) pointed out, a series of rice farming and breeding models (including rice-duck farming) reflect the shift of agricultural input from external dependence to internal potential, making agricultural production more dependent on ecological processes and biological functions rather than simply relying on chemicals. This model is in line with the current direction of green agricultural development and has good prospects for promotion. 5 Case Studies 5.1 Xingqing Family Farm (Deqing): model of rice-duck co-culture As a successful practice case of rice-duck co-cultivation, the experience of Xingqing Family Farm in Deqing County, Zhejiang Province is representative. The family farm began to explore the rice-duck symbiotic breeding model in the 2010s. After years of practice, it has formed a complete set of standardized and large-scale rice-duck co-cultivation operation models (Figure 2). In the planting stage, high-quality rice varieties (such as "Zhehexiang No. 2" and other fragrant japonica rice) are selected for green planting, and chemical pesticides and herbicides are not used during the entire growth period. After the seedlings are planted, about 1 000 mountain ducklings are evenly released into the rice fields according to the fields. The ducks are free to forage for insects and weeds in the rice fields to achieve ecological pest control and weed control. Figure 2 Rice-duck co-cultivation model at Xingqing Family Farm (Photographed by Yuchao Shen) According to farm statistics, after adopting rice-duck co-cultivation, there is basically no need for manual weeding, and the average annual reduction of pesticide application per mu of land is 23 times, and the cost of pesticides is almost zero. This reduces the cost of rice planting by about 17.6%, and the rice produced fully meets the standards
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