Cations in soil solutions affect soil structural stability and thus soil quality and health. Ca and Mg could alleviate soil clay dispersion by replacing Na, which was the main driver. However, Mg could also cause soil disaggregation and weaken aggregate integrity. Currently, most studies on Ca and Mg mainly examine soil hydraulic characteristics and clay particle dispersion, rather than macropore geometry. We analyzed the impact of Ca and Mg on soil macropore morphology by measuring macropore length, aspect ratio, and area indices. An indoor soil column experiment was set up, and irrigation water was prepared with the same electrical conductivity (4 dS m) and different cation compositions (Na-Ca (NC), Na-Ca-Mg (NCM), Na-Mg (NM) and Na-only (N) were added), and deionized water as the control (CK). The results indicated that N had the highest soil suspension turbidity among all treatments, with NM being higher than NC. The highest percentage of soil macropore aspect ratio < 2.0 was found in N, and the highest percentage of soil macropore aspect ratio for NCM was found in > 2.0. The macropore anisotropy of NM was closer to 1.0, and anisotropy of NC was closer to 0. The soil macropore morphology of NC developed towards a spherical shape, while the macropores of NM might extend along one or several similar directions. For Na-Ca dominated soil, Ca mainly affected the macropore area. However, for Na-Mg dominated soil, Mg primarily influenced the number of macropores. Ca inhibited the negative effects of Na, but Mg promoted unidirectional extension of macropores, posing a risk of soil cracking. This study provided a better understanding to explore the differences in the effects of different cations on soil pore structure and helped to provide guidance for field water management.

中文翻译：

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Na+存在下Ca2+和Mg2+引起的伊利石土壤大孔隙形态差异

土壤溶液中的阳离子影响土壤结构稳定性，从而影响土壤质量和健康。 Ca 和 Mg 可以通过替代 Na 来减轻土壤粘土分散，而 Na 是主要驱动因素。然而，镁也会导致土壤解聚并削弱团聚体的完整性。目前，大多数对Ca和Mg的研究主要考察土壤水力特性和粘土颗粒分散性，而不是大孔隙几何形状。通过测量大孔长度、纵横比和面积指数，分析了 Ca 和 Mg 对土壤大孔形态的影响。搭建室内土柱实验，配制相同电导率（4 dS m）、不同阳离子成分（Na-Ca（NC）、Na-Ca-Mg（NCM）、Na-Mg（NM）的灌溉水。 ）和仅添加Na（N）），以及去离子水作为对照（CK）。结果表明，N处理的土壤悬浮浊度最高，且NM高于NC。土壤大孔纵横比 < 2.0 的最高百分比出现在 N 中，NCM 土壤大孔纵横比最高的百分比出现在 > 2.0 中。 NM的大孔各向异性接近1.0，NC的各向异性接近0。NC的土壤大孔形态向球形发展，而NM的大孔可能沿一个或几个相似的方向延伸。对于Na-Ca为主的土壤，Ca主要影响大孔隙面积。然而，对于以钠镁为主的土壤，镁主要影响大孔的数量。 Ca抑制了Na的负面影响，但Mg促进了大孔隙的单向扩展，造成土壤开裂的风险。该研究为探索不同阳离子对土壤孔隙结构影响的差异提供了更好的认识，并有助于为田间水分管理提供指导。