Why is aggregate stability an important soil health indicator, and how can management improve it?

• A. It measures water content
• B. It predicts erosion risk only after rainfall events
• C. It reflects resistance to breakdown under wetting and drying and traffic
• D. It reflects soil color

Answer: (C)

Aggregate stability is about how well soil aggregates hold together when they’re stressed by moisture changes and physical disturbance. This matters for soil health because stable clumps preserve the pore network that allows water to infiltrate, air to move, roots to grow, and soil organisms to function, while also reducing erosion and crust formation after rain.

The best description is that aggregate stability reflects resistance to breakdown under wetting and drying and traffic. When soils can keep their structure during wetting and drying cycles and under the weight of animals or machinery, they maintain porosity and cohesion that support plant growth and reduce erosion. If aggregates readily crumble, infiltration declines, surface crusts form, and erosion and nutrient losses increase.

Management can improve aggregate stability by boosting organic matter and fostering a living soil. Practices include maintaining soil cover with residue or vegetation to protect the soil surface, reducing tillage and soil disturbance (especially when soils are wet), and minimizing heavy traffic on fragile soils. Additionally, keeping roots in the soil for longer periods—through diverse, perennial or rotation crops and continuous ground cover—promotes soil organisms and root exudates that help bind particles together. In practice, these steps build the “glue” and cementing agents inside soil that enhance stability and overall soil health.