Which feature is commonly recognized as a restrictive horizon?

A restrictive horizon in soil is characterized by layers that impede water movement and the flow of air within the soil profile, which can affect the performance of onsite wastewater systems. One of the most common features recognized as a restrictive horizon is shallow rock formations. These formations create a barrier that prevents proper drainage and can lead to surface pooling or saturation, which is problematic for septic systems.

While dense root structures can affect soil porosity, they do not necessarily act as a definitive barrier to water movement like shallow rock does. Sandy soil layers, on the other hand, typically allow for good drainage, making them less likely to be classified as restrictive horizons. Aquifer fringes refer to areas where groundwater meets surface water, but they are not directly associated with the properties of the soil profile that restrict movement. Thus, the presence of shallow rock formations is the most significant factor in identifying a restrictive horizon in this context.