Rice Genomics and Genetics 2025, Vol.16, No.3, 116-131 http://cropscipublisher.com/index.php/rgg 117 2025). The integrated rice farming model introduces animals to achieve multi-level recycling of nutrients within the rice field ecosystem, and is considered an effective way to improve the efficiency of soil nutrient management. Animal activities and metabolism add organic nutrients to the soil, promote soil nutrient turnover, and improve soil physical and chemical properties, which is expected to enhance soil fertility and buffering capacity. A large number of field studies have shown that integrated farming systems such as rice-fish and rice-duck have complex effects on soil nutrient cycles and the environment while increasing yields. This study will systematically sort out the characteristics of soil nutrient content and dynamic changes under the integrated farming model of rice fields, summarize the regulatory role of animal farming on the soil nutrient cycle mechanism, evaluate its sustainable benefits and practical significance, discuss the impact of integrated farming on soil organic matter and major nutrient content, and its regulatory role on nutrient cycles through mechanisms such as manure return to the field, water disturbance, and microbial activation, and analyze it in combination with practical cases, pointing out the current bottlenecks and future development suggestions. This study hopes to provide a scientific basis for a deep understanding of how integrated farming in rice fields regulates soil nutrient dynamics and provide a reference for green agricultural practices. 2 Typical Models of Integrated Rice Farming 2.1 Rice-duck, rice-fish, and rice-crab symbiotic systems Rice-duck farming refers to releasing a moderate amount of domestic ducks during the growing season of rice fields, allowing them to move freely to eat weeds and pests, and excrete feces to fertilize the fields, so as to achieve a mutually beneficial symbiosis between rice and domestic ducks. Ducks "weed and control insects, trample and loosen the soil, and return manure to the fields" in rice fields, which is one of the most widely used ecological farming models in my country. Studies have shown that rice-duck symbiosis can effectively control pests such as barnyard grass and rice leafhoppers, reduce the application of pesticides, and have a positive impact on soil nutrients (Lan et al., 2021). Rice-fish symbiosis has a long history. Fish ditches or fish ponds are dug in rice fields to raise fish (such as carp, crucian carp, etc.). Fish feed on field bait, and their excrement provides nutrients for rice. Rice and fish promote each other, which has the effect of "rice, millet and fish fertilizer". Modern rice-fish farming introduces specialized species such as loach and tilapia, which significantly increases protein output per unit area. Fish farming in rice fields has become a large-scale industry in southern China, which has dual benefits in increasing farmers' income and grain production. Rice-crab farming is the cultivation of crustaceans such as river crabs in rice fields. This model is common in the middle and lower reaches of the Yangtze River. Crabs are raised by digging ditches in rice fields. Crabs prey on fish, insects and snails in the fields, loosen the soil, and their excrement can fertilize the soil. Studies have shown that the soil organic matter and total nitrogen in rice-crab fields are significantly higher than those in monoculture rice fields (Xu et al., 2025). Different integrated farming models are based on the shallow water ecology of rice fields, organically combining rice planting with aquaculture, but the types of animals introduced are different, and the functional emphasis is slightly different. 2.2 Ecological characteristics of integrated cultivation The integrated farming model of rice fields forms a rice-animal symbiotic micro-ecological system with ecological characteristics of integrated farming and recycling. First, the food chain is expanded: rice provides habitats and some biomass (such as Cordyceps) for animals, and animals eat weeds, pests and feed in the field, producing feces that are decomposed and used by rice, forming a material cycle. For example, in the rice-duck farming system, ducks feed on weeds and snails in the field, reducing the consumption of soil nutrients by weeds. At the same time, duck manure contains about 1.0% to 1.5% nitrogen, which directly supplements soil nutrients (Lan et al., 2021). Secondly, diversity is improved: rice fields are transformed from a single rice crop system to a multi-species coexistence system such as rice-fish/duck, and the biodiversity of microorganisms, benthic animals and other organisms in the soil and water bodies increases, which helps maintain ecological balance (Liao et al., 2019). Thirdly, energy utilization efficiency is improved: integrated rice farming converts part of the unused energy (such as aquatic biological resources) in the original rice field monoculture system into aquatic or livestock
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