Rice Genomics and Genetics 2025, Vol.16, No.3, 116-131 http://cropscipublisher.com/index.php/rgg 123 monoculture. The long-term positioning experiment of Sun et al. (2025) also found that the activities of soil β-glucosidase, cellulolytic enzyme, chitinase and urease in 5-year rice-fish co-cultivation were significantly improved compared with monoculture, and the activities of these enzymes in 30-year co-cultivation were more than 50% higher than the control. The increase in enzyme activity directly leads to an increase in the mineralization rate and turnover rate of soil nutrients, which is manifested in the faster release of nutrients that can be absorbed by plants. For example, the increase in urease activity means that the conversion of organic nitrogen to ammonium nitrogen is faster, and the increase in phosphatase promotes the inorganicization of organic phosphorus. When comparing different models, Meng et al. (2021) pointed out that the comprehensive soil fertility index of all rice field models involving animals is higher than that of the control without animals, among which the enzyme activity contributes outstandingly. It should be noted that the enhancement of microbial activity will also accelerate the rate of decomposition and loss of soil organic matter. Therefore, although integrated farming increases organic matter and nutrients, excessive consumption of nutrients by microorganisms should also be avoided. Fortunately, the ecological balance formed by integrated farming and breeding is generally self-regulating. For example, when organic matter increases, the amount of microorganisms increases and reaches a new balance point, which does not cause nutrient "burning". Integrated rice field farming and breeding significantly stimulates the potential of soil microorganisms by "promoting microorganisms with movement", making the soil nutrient cycle process faster and more efficient. This is also one of the internal motivations for maintaining or even improving soil fertility and crop yields while reducing external inputs. 5 Case Studies 5.1 Xingqing Farm’s rice-duck-saffron rotation model Xingqing Family Farm, located in Deqing, Huzhou, Zhejiang, pioneered a new integrated farming model of "rice-saffron rotation + rice-duck co-cultivation" based on rice-duck co-cultivation (Figure 1; Figure 2). The farm releases about 2 000 ducks in the fields every year during the rice growing season, implements rice-duck co-cultivation, uses ducks to control Cordyceps, and returns manure to the fields; after the rice is harvested, the fields are used to plant precious medicinal materials saffron in the winter, achieving two harvests a year. Figure 1 Panorama of planting base of Deqing Xingqing family farm Co., Ltd. (Photographed by Yuchao Shen) This rotation co-cultivation model has significant ecological and economic benefits: it is reported that the comprehensive income per mu (≈0.067 hectares) can reach more than 20 000 yuan. Rice-duck co-cultivation improves the quality and unit price of rice, and saffron planting brings high added value, making the unit benefit
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