Soil organic matter plays a crucial role in maintaining the stability of soil structure, which is essential for plant growth. Two types of soil aggregates, macro- (greater than 250 micrometers) and micro- (less than 250 micrometers), depend on organic matter to resist disruptive forces from rapid wetting. Clay particles in microaggregates can be dispersed by organic acids produced by plants, bacteria, and fungi, which increase the negative charge on clay surfaces. However, this dispersibility is counteracted by binding agents such as polysaccharides from bacteria, plant roots, and fungal hyphae. Multivalent cations also help stabilize microaggregates by bridging organic colloids and clay particles. Macroaggregates are stabilized by plant roots, both living and decomposing, and are sensitive to management practices. Grass growth and minimal soil disturbance increase macroaggregate numbers, while fallow conditions reduce them. Soil structure is defined by the size and arrangement of particles and pores, which are crucial for water and air movement, root growth, and nutrient availability. A well-structured soil has a range of pore sizes, with most clay particles flocculated into microaggregates and bound into macroaggregates. Stability of this structure is vital, as breakdown on wetting can lead to slaking, which reduces infiltration and hydraulic conductivity. Dispersible clay further worsens these conditions by decreasing porosity and increasing soil strength. Organic matter influences both dispersion and flocculation, as well as macroaggregate stability. In soils developed from basalt, organic matter content affects the point of zero charge (PZC) of clay, influencing its dispersibility. Higher organic matter content near the soil surface reduces water dispersible clay, while lower organic matter content at depth increases it. These findings highlight the importance of organic matter in maintaining soil structure and stability, with implications for soil management practices.Soil organic matter plays a crucial role in maintaining the stability of soil structure, which is essential for plant growth. Two types of soil aggregates, macro- (greater than 250 micrometers) and micro- (less than 250 micrometers), depend on organic matter to resist disruptive forces from rapid wetting. Clay particles in microaggregates can be dispersed by organic acids produced by plants, bacteria, and fungi, which increase the negative charge on clay surfaces. However, this dispersibility is counteracted by binding agents such as polysaccharides from bacteria, plant roots, and fungal hyphae. Multivalent cations also help stabilize microaggregates by bridging organic colloids and clay particles. Macroaggregates are stabilized by plant roots, both living and decomposing, and are sensitive to management practices. Grass growth and minimal soil disturbance increase macroaggregate numbers, while fallow conditions reduce them. Soil structure is defined by the size and arrangement of particles and pores, which are crucial for water and air movement, root growth, and nutrient availability. A well-structured soil has a range of pore sizes, with most clay particles flocculated into microaggregates and bound into macroaggregates. Stability of this structure is vital, as breakdown on wetting can lead to slaking, which reduces infiltration and hydraulic conductivity. Dispersible clay further worsens these conditions by decreasing porosity and increasing soil strength. Organic matter influences both dispersion and flocculation, as well as macroaggregate stability. In soils developed from basalt, organic matter content affects the point of zero charge (PZC) of clay, influencing its dispersibility. Higher organic matter content near the soil surface reduces water dispersible clay, while lower organic matter content at depth increases it. These findings highlight the importance of organic matter in maintaining soil structure and stability, with implications for soil management practices.