Macropores are often regarded as preferential paths for root growth to bypass high-strength soil. However, the influence of macropore characteristics on root growth in compacted soils is not clearly understood. In this study, we investigated the effects of macropore diameter, density, wall surface area and porosity in a compacted soil on maize growth and N uptake at the seedling stage. Different diameters (0.5-, 1- and 2-mm) and densities (0, 1750, 3500, 7000 and 28,000 m⁻² indicated by 0, 5, 10, 20, 80 numbers, respectively) of artificial macropores were created in compacted (1.6 g cm⁻³) soil columns (150 mm height × 60 mm internal diameter). The absence of macropores was treated as a Control. After 20 days of maize growth, the 3D root architecture and the interaction between roots and macropores were visualized and quantified using X-ray computed tomography (CT). The nitrogen uptake by plants from the compacted subsoil was determined using ¹⁵N tracer. Our results showed that the presence of 0.5- or 1-mm macropores enhanced maize growth and ¹⁵N uptake relative to the Control, but not the presence of 2-mm macropores. At a given macropore diameter of 0.5-mm, the effect of macropore density on maize growth and ¹⁵N uptake was in the order of 7000 m⁻² > 28,000 m⁻² and 1750 m⁻². Under the same macropore wall surface area conditions (i.e., 2513 mm² in this study), maize growth and ¹⁵N uptake decreased with increasing macropore diameter. Under the same macroporosity (i.e., 0.342% in this study), maize growth and ¹⁵N uptake were more promoted by macropore characteristics of 1-mm diameter with 7000 m⁻² density and 0.5-mm diameter with 28,000 m⁻² density compared with 2-mm diameter with 1750 m⁻² density. CT images showed that the number of macropores colonized by roots and the intersecting area between roots and macropores both increased with increasing macropore density. Our results demonstrate that the presence of macropores can improve crop growth, but its effect depends on macropore characteristics created by appropriate macropore diameter and density (e.g., 0.5 mm diameter and 7000 m⁻² density in this study).

大孔通常被认为是根系生长绕过高强度土壤的优先途径。然而，大孔特征对压实土壤中根系生长的影响尚不清楚。在这项研究中，我们研究了压实土壤中的大孔直径、密度、壁表面积和孔隙率对玉米生长和苗期氮吸收的影响。不同直径（0.5-、1- 和 2-mm）和密度（0、1750、3500、7000 和 28,000 m ^-2分别由 0、5、10、20、80 数字表示）的人造大孔在压实中产生(1.6 克厘米^-3) 土柱（150 毫米高 × 60 毫米内径）。没有大孔被视为对照。在玉米生长 20 天后，使用 X 射线计算机断层扫描 (CT) 对 3D 根结构以及根与大孔之间的相互作用进行可视化和量化。^使用15 N 示踪剂测定植物从压实底土中吸收的氮。我们的结果表明，相对于对照，0.5 或 1-mm 大孔的存在增强了玉米的生长和¹⁵ N 的吸收，但 2-mm 大孔的存在却没有。在给定的 0.5-mm 大孔直径下，大孔密度对玉米生长和¹⁵ N 吸收的影响约为 7000 m ^-2 > 28,000 m ^-2和 1750 m ^-2. 在相同的大孔壁表面积条件下（即本研究中的2513 mm ²），玉米的生长和¹⁵ N 的吸收随着大孔直径的增加而降低。在相同的大孔隙度（即本研究中的 0.342%）下，与 1-mm 直径和 7000 m ^-2密度和 0.5-mm 直径和 28,000 m ^-2密度的大孔隙特征相比，玉米生长和¹⁵ N 吸收更受促进。 2-mm 直径，1750 m ^-2密度。CT图像显示，随着大孔密度的增加，根系定植的大孔数量以及根与大孔的相交面积均增加。我们的研究结果表明，大孔的存在可以改善作物生长，但其效果取决于由适当的大孔直径和密度（例如，本研究中的0.5 mm 直径和7000 m ^-2密度）产生的大孔特征。