Final answer:
The O horizon is rich in organic material with decomposed vegetation and humus, while the A horizon, known as topsoil, contains a mixture of organic and inorganic material and is darker due to organic matter.
Step-by-step explanation:
Difference Between O and A Horizons
The primary difference between the O horizon and A horizon in soil profiles is that the O horizon usually has a higher content of organic matter. The O horizon, also known as the organic layer, is composed primarily of freshly decomposing organic matter, which is termed humus, and decomposed vegetation. This layer enriches the soil with nutrients and enhances its moisture retention capabilities. In contrast, the A horizon, often referred to as the topsoil, is a mixture of organic matter and inorganic products of weathering. While it also contains organic material, the A horizon is primarily known for its role in plant production and is generally darker due to the presence of organic matter mixed with mineral particles. The composition and thickness of these horizons can vary based on environmental factors such as climate, topography, and the presence of plant life.