Fertilization practices are vital for agricultural productivity and soil health. However, the impact of long-term organic and inorganic fertilization on pore structure and related functions in paddy soil is still under-explored. In this study, macroaggregates approximately 5 mm in diameter were collected from a 20-year long-term experiment with no fertilization (CK), and those treated with chemical fertilizer (NPK), organic fertilizer (RS), and a combination of both (RS+NPK). The pore structure of these macroaggregates was examined using synchrotron radiation-based X-ray tomography, alongside a pore network model and skeleton analysis. The soil functions concerning the pore structure at the aggregate scale were assessed through their physical and topological properties. Results indicated that the pore structure of the macroaggregates responded differently to organic versus inorganic fertilization. Specifically, the application of NPK significantly reduced the connected porosity, accessibility, and network complexity within the macroaggregates, whereas the opposite effects were observed with the RS treatment. Connectivity analysis showed that the critical pores in CK, NPK, and RS+NPK treatments originated from plant roots, while those in the RS treatment were likely formed through the decomposition of rice straw. Compared to CK, the NPK treatment exhibited fewer channels with high hydraulic conductance, indicating impaired transportability of water and nutrients under saturated conditions, while the opposite was true for the RS treatments. Furthermore, skeleton analysis highlighted that the NPK treatment has fewer paths for preferential and capillary flow compared to CK, indicating reduced accessibility of air, water, and nutrients under unsaturated conditions. These findings are essential for understanding the changes in soil functions related to pore structure following organic and inorganic fertilizer applications and for optimizing fertilization strategies to preserve soil structure and health.

中文翻译：

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长期有机和无机施肥后大团聚体孔隙结构的构型及相关功能


施肥做法对农业生产力和土壤健康至关重要。然而，长期有机和无机施肥对稻田土壤孔隙结构及相关功能的影响仍未得到充分探索。在这项研究中，从一项为期 20 年的长期无施肥 （CK） 和化学肥料 （NPK）、有机肥 （RS） 和两者的组合 （RS+NPK） 处理的大团聚体中收集了直径约 5 mm 的大团聚体。使用基于同步辐射的 X 射线断层扫描以及孔隙网络模型和骨架分析来检查这些大聚集体的孔结构。通过物理和拓扑特性评估了骨料尺度上与孔隙结构有关的土壤功能。结果表明，大团聚体的孔隙结构对有机肥和无机施肥的反应不同。具体来说，NPK 的应用显著降低了大团聚体内的连通孔隙率、可达性和网络复杂性，而 RS 处理则观察到相反的效果。连通性分析表明，CK、NPK 和 RS+NPK 处理的临界孔隙来源于植物根系，而 RS 处理的临界孔隙很可能是通过稻草分解形成的。与 CK 相比，NPK 处理表现出较少的通道和高水力传导率，表明在饱和条件下水和养分的运输能力受损，而 RS 处理则相反。此外，骨架分析强调，与 CK 相比，NPK 处理的优先流和毛细流路径较少，表明在不饱和条件下空气、水和营养物质的可及性降低。 这些发现对于了解施用有机和无机肥料后与孔隙结构相关的土壤功能的变化以及优化施肥策略以保持土壤结构和健康至关重要。