Bioscience Methods 2025, Vol.16, No.4, 204-217 http://bioscipublisher.com/index.php/bm 210 on the side during mechanical transplanting, and topdressing is applied in time according to the growth of the field in the later stage, supplemented by planting attracting plants such as cosmos and vetiver and placing sex attractants to kill borers, reducing the dependence on chemical pesticides. At the same time, biological pesticides and biological microbial agents are used to control pests and diseases, improve plant health, and enhance their nutrient utilization efficiency (Ren, 2017; Li, 2024). Other studies have tried models such as rice-fish farming and rice-duck farming to increase breeding income while reducing the occurrence of pests, and found that rice-fish farming can also reduce field methane and nitrous oxide emissions, achieving "killing two birds with one stone". The integration of green prevention and control and scientific fertilization can maintain high rice yields under the condition of nitrogen reduction and reduce environmental and health risks. This collaborative management requires agricultural technicians to accurately monitor crop growth and pest occurrence, dynamically adjust fertilizer and pesticide input according to actual conditions, and achieve reduced and efficient agricultural inputs. 4.3 Field trials for fertilizer reduction and efficiency enhancement, and benefit evaluation A large number of field experiments have shown that rice yields can be maintained while reducing nitrogen fertilizer inputs by optimizing fertilization. Generally speaking, reducing nitrogen by 10%-20% in high-yield fields has no significant effect on yield, while nitrogen fertilizer utilization efficiency can be significantly improved (Hu et al., 2019). For example, experiments in South China found that compared with farmers' conventional nitrogen application, rice yields in the treatment of 20% nitrogen fertilizer reduction only decreased slightly or remained basically the same, but the rice produced per kilogram of nitrogen fertilizer increased, and the agronomic efficiency of nitrogen fertilizer was improved. High-yield nitrogen and high-efficiency varieties perform particularly well under nitrogen reduction conditions, with significantly higher biomass and yield than general varieties, and higher nitrogen grain production efficiency (Fu et al., 2023). This shows that through the combination of varieties and fertilization measures, "reducing nitrogen without reducing production" can be achieved. Nitrogen fertilizer reduction also brings environmental and economic benefits. For example, a long-term positioning study showed that compared with the usual amount, reducing nitrogen by about 15% can reduce the risk of nitrogen leaching in rice fields and improve fertilizer utilization without reducing production. In the Jiashan demonstration, the application of side deep fertilization technology reduced the amount of nitrogen fertilizer by about 20% compared with traditional broadcasting, while the average yield per mu remained above 600 kg, which reduced the input of nitrogen fertilizer per kilogram of rice and improved the planting efficiency. Of course, the potential for nitrogen reduction also varies by region and production level. Some studies have used models to evaluate the nitrogen reduction potential in different rice-growing areas. For example, in the black soil area of Northeast China, nitrogen can theoretically be reduced by about 17% with little impact on yield (Yin et al., 2022). Field experiments and economic analysis support the conclusion that it is feasible to reduce fertilizer input without significantly affecting rice yield by optimizing fertilization structure and methods. This is also an effective way to increase fertilizer utilization, reduce costs and environmental costs. 5 Nitrogen Response Characteristics of Superior Rice Varieties 5.1 Nitrogen sensitivity of indica-japonica hybrid rice Indica-japonica hybrid rice varieties usually have higher yield potential, but they often show stronger response sensitivity to nitrogen fertilizer levels. Compared with conventional rice, hybrid rice requires slightly less nitrogen to produce 100 kg of rice (about 1.4-2.0 kg), but due to its high yield and large population biomass, the total nitrogen required per hectare is still higher than that of conventional rice. Hybrid rice is also generally more efficient in absorbing and utilizing nitrogen fertilizer. With reasonable cultivation measures, the nitrogen fertilizer recovery rate of high-yield hybrid rice varieties in the season can reach 40%-45%. Taking the widely planted indica-japonica hybrid rice "Yongyou" series as an example, its population grows vigorously, with large panicles and many grains, and can fully exert its yield potential under high nitrogen conditions; but at the same time, excessive nitrogen is more likely to lead to its late greed for green, lodging and increased risks of diseases and insect pests, so the amount of nitrogen fertilizer in the late stage needs to be strictly controlled. As a representative variety of this series, "Yongyou 33" has a strong nitrogen response ability. The experiment showed that under sufficient nitrogen application, the number of spikelets in the "Yongyou 33" population far exceeded that of
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