Which type of soil structure is characterized by flat peds that lie horizontally?

The type of soil structure characterized by flat peds that lie horizontally is known as a platy structure. This soil formation consists of thin, flat plates, or peds, which can impede water movement and root penetration due to their horizontal alignment. The flat peds create a compacted layer that can restrict the flow of air and water within the soil, potentially leading to drainage issues and affecting plant growth.

In contrast, rock fragments consist of larger pieces of rock and do not exhibit a distinct soil structure like peds. The term "PED" refers generically to soil aggregates or blocks, not specifically to their shape or arrangement. Granular structure consists of round peds that promote good drainage and aeration, which is quite different from the horizontal alignment seen in platy structures. Understanding these distinctions is crucial for effective soil management, particularly in applications like septic system design and maintenance.