BM_2025v16n4

Bioscience Methods 2025, Vol.16, No.4, 204-217 http://bioscipublisher.com/index.php/bm 215 redistributed in the phloem in the plant, and later meets the filling demand through leaf-grain nitrogen transport. The coordination between source and sink determines nitrogen utilization efficiency and yield. Nitrogen metabolism and carbon metabolism are coupled to each other, and the C/N balance of the plant is maintained through feedback regulation at the transcriptional and metabolic levels, thereby ensuring normal growth and efficient nitrogen utilization. A number of key genes that control nitrogen efficiency have been identified: OsNRT1.1B and others determine the differences in nitrogen absorption among varieties, OsGS1;1 and others affect nitrogen assimilation and reuse, and OsNAC42, OsNLP4 and others are located upstream of the regulatory network, commanding the expression of nitrogen-responsive genes. These results have built a theoretical framework for efficient nitrogen utilization in rice. The core of rice NUE is to improve the productivity of unit nitrogen, which can be achieved by: enhancing the coordination between root absorption capacity and soil nitrogen supply, promoting efficient nitrogen transport between nutritional organs and reproductive organs, delaying the senescence of functional leaves to extend the assimilation period, and optimizing regulation to match nitrogen supply with crop growth needs. The above mechanism points out the direction for formulating nitrogen-saving and high-yield cultivation strategies and breeding improvements. Promoting green and efficient fertilization technology is an important means to achieve sustainable agricultural development. On the one hand, these technologies can significantly reduce the use of chemical fertilizers, improve resource utilization efficiency, and reduce environmental load. For example, the application of slow-release fertilizers and soil-testing formula fertilization can reduce fertilizer input per unit area by 10%-30%, and nitrogen leaching and nitrous oxide emissions will be reduced accordingly, which will help mitigate agricultural non-point source pollution and greenhouse effect. On the other hand, green fertilization promotes healthy crop growth, soil fertility maintenance and biodiversity by improving the way crops are supplied with nutrients. For example, technologies such as returning straw to the field and replacing organic fertilizers can improve soil fertility while supplementing nutrients, achieving a virtuous cycle of carbon and nitrogen cycles in farmland. Another example is the combination of nitrogen reduction and plant protection technology, which reduces the use of pesticides and ensures the quality and safety of agricultural products and the stability of farmland ecosystems. Facts have proved that relying on scientific and technological innovation and reasonable policy guidance, my country has achieved the goal of zero growth in fertilizers from 2015 to 2020, and the input of fertilizers per unit of output in major grain crops has decreased year by year. This shows that the promotion of green fertilization technology has a significant effect on promoting the transformation of traditional agriculture to resource-saving and environmentally friendly agriculture. It can be foreseen that green fertilization will play a more critical role in the future sustainable development of agriculture: by matching with excellent rice varieties and cultivation patterns, it will support a modern rice farming system that takes into account high yield, high quality and ecological safety. Looking to the future, the research and application of improving rice NUE should focus on the following aspects: First, deepen the study of molecular mechanisms, identify more nitrogen high-efficiency related genes and their action pathways, especially reveal the complex network of crop nitrogen metabolism regulation under different environmental conditions. Functional genomics and systems biology can be used to discover the role of currently unknown regulatory elements, such as non-coding RNA and epigenetic markers in nitrogen high efficiency, providing new ideas for molecular breeding. Second, accelerate the selection and breeding of nitrogen-efficient varieties and the creation of new germplasm. With the help of molecular marker-assisted selection and gene editing technology, excellent alleles are accurately introduced into the main varieties to achieve the directional improvement of low-nitrogen and high-yield traits. At the same time, focus on comprehensive trait cultivation, so that high-NUE varieties have both stress resistance and high quality characteristics to meet production needs. Third, integrate innovative cultivation technology to achieve the "three-in-one" optimization management of crops, soil and inputs. For example, develop intelligent fertilization systems, use sensor monitoring and model decision-making to dynamically supply nitrogen according to the actual needs of crops, and avoid shortages or surpluses. Another example is to improve water-fertilizer integration technology, reduce nitrogen losses while saving water, and improve nutrient utilization efficiency. Fourth, strengthen demonstration and promotion and policy support. In large-scale production, through the radiation and promotion of demonstration areas, let farmers

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