Which of the following increases as a soil's clay content increases?

As soil's clay content increases, the surface area also increases. Clay particles are significantly smaller in size compared to sand and silt particles, which means that a higher clay content results in a greater total surface area for the soil. This increased surface area plays a crucial role in various soil properties, including nutrient and water retention, as well as the soil’s ability to hold onto organic matter and other compounds.

The larger surface area of clay particles allows them to attract and hold more water molecules and nutrients compared to coarser particles like sand. This means that soils with higher clay content are generally more capable of retaining moisture and nutrients, which is beneficial for plant growth.

In contrast, other factors, such as bulk density and sand content, do not increase with clay content; they often decrease or remain unchanged as clay content changes. This understanding is important for effective soil management and crop production strategies.