What is a defining feature of Alfisols?

Alfisols are characterized by the presence of an argillic horizon, which is a soil layer enriched with clay translocated from upper horizons. This horizon signifies a process known as illuviation, where clay and nutrients leach downwards through the soil profile, enhancing fertility and contributing to the soil's overall structure. Alfisols typically form in temperate regions and are important for agriculture due to their relatively high nutrient content and good moisture retention.

While other soil horizons, such as cambic or mollic horizons, describe different soil properties or processes, they do not specifically define Alfisols. Cambic horizons indicate weakly developed subsoil characteristics, while mollic horizons are associated with high organic matter and distinctly fertile soils like Mollisols. The limnic horizon, typically associated with sedimentary deposits in aquifer systems, is not relevant to the classification of Alfisols. Thus, the defining feature that uniquely identifies Alfisols within soil classifications is the presence of the argillic or glossic horizon.