Which type of soil is characterized by a high clay content and poor drainage?

Clay soil is distinguished by its high clay content, which significantly impacts its physical properties. The small particle size of clay particles allows them to pack closely together, creating a dense structure. This density impedes the movement of water and air, resulting in poor drainage and limited aeration. Consequently, clay soil tends to retain moisture rather than allowing it to pass through, which can create waterlogged conditions and affect plant growth.

In terms of agricultural implications, clay soil can be challenging for farming because of its tendency to hold water. This can lead to root rot in plants if they remain submerged for extended periods. On the other hand, while loamy soil, sandy soil, and humus-rich soil have varying compositions and drainage characteristics, they do not possess the same high clay content that defines clay soil. For example, loamy soil is a balanced mixture of sand, silt, and clay, offering good drainage and fertility. Sandy soil, on the other hand, has larger particles that allow for excellent drainage but holds less water and nutrients. Humus-rich soil is known for its organic matter content rather than its clay composition. Therefore, the defining characteristic of clay soil—its high clay content leading to poor drainage—clearly makes it the correct answer.