What are soil horizons?

Soil horizons refer to the distinct layers within a soil profile that exhibit differences in composition, texture, color, and other properties. Each horizon forms over time due to various environmental factors, including weathering processes, organic matter decomposition, and the movement of water and nutrients. The identification of these layers is crucial for understanding soil health, fertility, and suitability for various land uses, as they can indicate how well the soil can support plant growth and retain moisture.

In contrast, natural drainage systems within the soil are more related to hydrological features and how water moves through the soil rather than the distinct layers that make up the horizon. Organic layers formed by decaying plant matter are typically found in the topmost horizons but do not encompass the broader concept of all soil horizons. Lastly, while mineral deposits can provide information about soil age and formation, they do not define or describe soil horizons themselves. Thus, the first option accurately captures the essence of what soil horizons are.