What texture must the A or B horizon have to indicate shrink and swell properties?

The identification of shrink-swell properties in soil is primarily linked to the texture of the A or B horizons, particularly those that contain clay. Moderately fine or fine textured soils, which have a higher percentage of clay particles, are critical for this purpose. The small size and flat shape of clay particles allow them to move closer together when dry, resulting in shrinking, and separate when wet, leading to swelling.

This behavior significantly affects the soil's physical characteristics—such as its volume and density—making it an important consideration in land management, construction, and agriculture. In contrast, coarse textured soils do not exhibit significant shrink and swell properties because they contain larger particles, allowing water to drain quickly and reducing the extreme changes in volume associated with moisture fluctuations. Atypical textures or very coarse textures also lack the clay-rich composition necessary for pronounced shrink-swell behavior. Therefore, identifying moderately fine or fine textured soil horizons provides key insights into the potential for shrink-swell properties in a given soil profile.