Red Seal Landscape Horticulturist Practice Exam

Which type of soil has the highest water retention capacity?

1. Sandy soil

2. Clay soil

3. Silty soil

4. Loamy soil

The correct answer is: Clay soil

Clay soil has the highest water retention capacity due to its very small particle size and the way particles are arranged. The tiny clay particles create a large surface area that can hold onto water molecules through cohesion. This means that even though clay may become compacted, preventing drainage, it still retains a significant amount of moisture. In contrast, sandy soil, characterized by larger particles with more space between them, allows water to drain quickly, leading to lower water retention. Silty soil, while it can hold moisture better than sandy soil, cannot retain as much water as clay due to its intermediate particle size. Loamy soil, which is a mixture of sand, silt, and clay, offers a balance between water retention and drainage, making it ideal for many plants, but it still does not surpass the water holding capacity of clay soil. Therefore, clay soil's properties effectively position it as the type with the highest capacity for retaining water.