Gleyed

Gleyed is an adjective used in soil science to describe horizons that have undergone gleying, a redox process that imparts a characteristic gray coloration to the soil matrix. The term is commonly applied to horizons where prolonged water saturation reduces iron and other elements, altering color and structure.

Gleying occurs in soils that are poorly drained or periodically waterlogged. In the anaerobic conditions of saturated soil, ferric iron (Fe3+) is reduced to ferrous iron (Fe2+), along with related chemical changes that suppress vivid iron oxides. This results in gray to bluish-gray colors with low chroma. When the water table fluctuates, oxidation-reduction cycles can create mottling, producing patches or blotches of yellow, olive, or brown within the gray matrix.

Visually, a gleyed horizon appears predominantly gray or blue-gray, often described as “gley,” and may show faint uniform color or contrasting mottles. The low chroma colors indicate reduced conditions, while darker or lighter zones reflect localized oxidation during drying periods. The pattern and intensity of gleying can vary with depth and local drainage conditions.

Gleyed horizons are typical of hydric soils and wetlands, indicating prolonged saturation and poor drainage. They influence soil properties such as aeration, permeability, and rooting patterns, and are important in soil surveys, land-use planning, and wetland delineation. In classification schemes, gleying is a key diagnostic feature used to identify and describe soil horizons and their drainage status.