Field Crop 2025, Vol.8, No.5, 238-246 http://cropscipublisher.com/index.php/fc 242 5 Case Study: Implementation in the Mekong Delta, Vietnam 5.1 Background and adoption process In Vietnam's Mekong Delta, many farmers have begun to abandon their original rice-only farming methods and adopt a "rice-fish combination" farming method. This change is mainly because farmers want to make agriculture more sustainable and their family income more stable. Although the original intensive single rice farming has high yields, it also has many problems, such as high fertilizer and pesticide use and high environmental pressure. The promotion of rice-fish symbiosis is not achieved overnight. It is affected by many factors, such as the size of farmers' land, water conditions, whether they have received training, and how much they know about this combination of farming and farming. Generally speaking, farmers with larger fields, more abundant water sources, and who have participated in training are more likely to accept this new method. Participatory promotion and research are also crucial. For example, the promotion of methods such as "integrated pest management" (IPM) allows farmers to not only learn farming techniques, but also know how to use less pesticides (Figure 2). This method is particularly helpful in promoting the popularization of the rice-fish model and can better ensure that this model can develop in the long run (Bosma et al., 2012). Figure 2 Main reasons for applying IPM among 20 rice-fish farmers (RF) and 14 rice farmers (R) in Cai Be (Adopted from Berg et al., 2016) 5.2 Outcomes on fertilizer and pesticide reduction In the Mekong Delta, farmers who use rice-fish farming use less fertilizer and pesticides than traditional rice farmers. Many surveys have found that rice-fish farmers, especially those who use IPM pest management methods, have reduced their pesticide use by almost 65% over three years. On the contrary, those who do not use IPM use more and more pesticides, even up by 40%. Why is this so? Because after raising fish, farmers will pay more attention to the impact of pesticides on fish. If too much pesticide is used, the fish may die, so they will be more cautious. This makes the use of chemical pesticides more reasonable. The amount of fertilizer used is also much less than that of single rice cultivation, but the rice yield has not decreased significantly. This shows that using less fertilizer can still maintain yield, and there is no need to rely on heavy investment to get a good harvest (Rothuis et al., 1998; Berg, 2001; Berg et al., 2016; Berg and Tam, 2018). 5.3 Broader environmental and socioeconomic impacts In addition to reducing the use of chemical fertilizers and pesticides, rice-fish symbiosis has also brought many benefits to the environment and society. For example, the water has become cleaner and there are more organisms in the rice fields. The functions of the ecosystem have become stronger, such as the natural reduction of pests, and the living environment of fish and other aquatic organisms has also become better. Many farmers have reported that they can now see more organisms that are beneficial to the ecology, such as more small animals that can eat pests, and the water quality is clearer. They are not only producing food, but also working with nature. In terms of income, this model of combining farming and breeding is also very cost-effective. Because less fertilizer and pesticides are used, the input cost is naturally lower. Moreover, they can sell not only rice, but also fish, which has a richer source of income. Even if the rice yield is slightly lower, farmers still think it is worthwhile because the overall benefits are better, it can also protect the environment, and it will be more sustainable in the future (Berg, 2002; Bosma et al., 2012; Berg et al., 2023).
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