GLEYS

INTRODUCTION

The name gley is derived from the Russian words glei = compact bluish-grey.

Gleys are widespread throughout Scotland, being developed under conditions of intermittent or permanent waterlogging. The greyish or bluey-grey colours and orange mottling are characteristic of gley soils are generally of secondary origin, replacing those inherited from the parent material. They result from the absence or very low levels of oxygen when iron compounds are changed chemically from their usual brown colours (reduction of ferric iron compounds to (mobile) ferrous compounds). Gleys are often confined to depressed or receiving sites where anaerobic conditions result from the periodic or long-term waterlogging, either a direct result of surface water collection or groundwater conditions. They also occur where the soil is dense and water is prevented
from moving through the soil. They are found at all elevations. Where the upper soil horizons
are wet for much of the year, they are generally rich in organic matter with intergrades to
shallow peat (peat >50cm) being widespread.

PROFILE CHARACTERISTICS OF NONCALCAREOUS GLEYS

Ag	Mineral surface horizon often with high organic matter content (in the case of peat formation the Ag becomes an O horizon) and drab colours.
Bg	Subsoil mineral horizon with variable texture but generally blue-grey, grey colours due to waterlogging; if waterlogging is intermittent, drab colours with distinct orange mottling is a feature.
Cg	Blue-grey colour where groundwater is present, may be compact and responsible for surface-water gleying. It is generally the Bg horizon that is responsible for surface water gleying not the Cg.

UTILISATION

Require adequate drainage for proper
agricultural use and some form of
drainage/remediation for satisfactory tree growth. In humid upland areas gley soils
with peaty topsoils develop under moorland or blanket bog vegetation and rough grazing or forestry are the principal forms of land use.

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Gley soil with very poor drainage
and significant peat development on
surface often referred to as a peaty gley.