Field Crop 2025, Vol.8, No.5, 238-246 http://cropscipublisher.com/index.php/fc 239 The focus of this study is to see whether the practice of "raising fish in rice fields" can reduce the use of fertilizers and pesticides and see if it has a positive impact on the ecological environment. We will combine some recent research results to analyze the differences between the rice-fish symbiotic system and traditional rice cultivation. For example, how do they differ in soil health, nutrient cycling, greenhouse gas emissions, and overall ecosystem services? We will also evaluate whether rice-fish integration can lead to more sustainable agricultural development, improve the rural living environment, and have a positive impact on farmers' economic income and quality of life. 2 Mechanisms of Fertilizer Reduction in Rice-Fish Systems 2.1 Nutrient recycling by fish activity In the rice-fish symbiotic fields, fish are not "supporting roles", they actually play a very important role in the nutrient cycle. Fish will eat organic matter in the rice fields, such as residual plants, plankton, etc. The feces they excrete contain a lot of nutrients such as nitrogen and phosphorus, which will be absorbed by the rice in the rice fields. Simply put, the fish help to circulate nutrients in the process of eating and defecating. In this way, farmers do not need to input so many external fertilizers. Especially nitrogen fertilizer, fish feed and fish feces can provide a lot of alternative nitrogen sources. Studies have found that using fish feed to replace 50% to 75% of the original nitrogen fertilizer input can still make rice grow well, and it can also reduce nutrient waste and reduce water pollution problems (Liu et al., 2024). The relationship between fish and rice is like mutual help, with higher nitrogen utilization and less damage to the environment (Xie et al., 2011). 2.2 Reduced need for synthetic inputs In rice-fish symbiotic farmland, the use of fertilizer is generally much less than that of pure rice fields. Studies have shown that this system can reduce the use of fertilizer by up to 24% without affecting rice yields. In other words, rice still grows well even with almost a quarter of less fertilizer. This system can also use some alternatives, such as compost, organic fertilizer or wastewater from fish ponds, which are all good sources of nutrients, and there is no need to buy fertilizers specifically (Yassi et al., 2023). For example, experiments have found that using fish pond water to irrigate rice fields and reducing the amount of conventional fertilizer by 20% did not reduce rice yields, but improved water quality (Qi et al., 2020). This method is both economical and environmentally friendly. Using less fertilizer not only reduces the cost of farming, but also reduces the risk of pollution caused by excess nutrients in the water (Li et al., 2024). 2.3 Enhanced soil fertility and structure In the rice-fish symbiotic system, the soil condition can also be improved. Because of the participation of fish, the organic matter content in the soil will increase, nitrogen and other nutrients will be richer, and the nutrient cycle efficiency will be improved (Xie et al., 2010). At the same time, the use of fish manure and some organic fertilizers can increase the carbon and nitrogen storage in the soil (Figure 1). The soil structure has also become softer, with more pores, better water and air circulation, and lower bulk density. This structure is more conducive to the growth of rice roots (the soil will not be hardened), making the soil healthier and more suitable for farming (Zhang et al., 2023). Long-term studies have also shown that this method of growing rice and raising fish can not only maintain soil fertility, but also maintain stable yields while reducing fertilizers compared to the method of growing rice alone. In other words, not only is the ecology better, but farmers can continue to make money. These changes make rice fields more sustainable and more resistant to risks, which is good for both the environment and farmers. 3 Reduction of Pesticide Dependence 3.1 Natural pest control by fish Raising fish in rice fields can actually prevent insects. Because fish eat pests and their larvae in the water, there are naturally fewer insects. In this way, farmers do not need to rely on spraying pesticides to deal with pests as before. Studies have found that the use of pesticides can be reduced by up to 68% by using the practice of rice-fish symbiosis (Xie et al., 2011). Moreover, fish can control the number of insects before the pests break out, which is also a kind of protection for the growth of rice. Not only are there fewer insects, but this method can also make
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