What does the "R horizon" primarily consist of?

The "R horizon," also known as the bedrock layer, primarily consists of consolidated rock. This layer is found beneath all other soil horizons and is considered the parent material from which soil develops over time. It can be composed of various types of rock, such as granite, limestone, or basalt, depending on the geological characteristics of the area. The presence of the R horizon indicates that there are no further soil layers below it, and it plays a critical role in soil formation processes, impacting drainage, root penetration, and the overall soil profile.

This understanding is crucial for soil evaluation and management, as the R horizon can affect land use decisions, construction projects, and ecological assessments. It serves as a natural barrier to water movement and can influence the growth of vegetation above it due to its physical and chemical properties. Therefore, recognizing the characteristics of the R horizon is essential for effective soil assessment and land management practices.