Soil · Soil type
Gleysol
Also known as: Gley soil, Groundwater-affected soil
A Gleysol is a soil saturated by groundwater for long enough to develop reducing conditions, producing the characteristic grey, blue-grey, and mottled colours of gleying. Wetness and poor aeration are its defining constraints, but with drainage many Gleysols become productive, and undrained they are classic rice soils.
Gleysols are soils that are saturated by groundwater for prolonged periods, so that the profile spends much of the year with little or no oxygen. Under these waterlogged, reducing conditions, iron in the soil is chemically altered, giving rise to the grey, blue-grey, and greenish colours, often with rusty mottles, that are the hallmark of gleying and that signal a history of saturation.
Because their defining feature is wetness rather than a particular parent material or texture, Gleysols occur wherever groundwater sits near the surface, in valley bottoms, floodplains, depressions, and low-lying plains across many climates. Their agricultural behaviour is dominated by drainage: poorly aerated as they are, they can be highly limiting for dryland crops yet well suited to wetland rice, and often become productive once artificially drained.
Overview
A Gleysol is identified by the effects of long-term saturation within the profile: dull grey and blue-grey colours where iron has been chemically reduced, interspersed with rusty mottles where some oxygen periodically penetrates. These colour patterns record recurring waterlogging and distinguish Gleysols from freely drained soils.
Formation and distribution
Gleysols form where the water table is at or near the surface for much of the year, so that the soil is saturated and oxygen is excluded for long periods. In the absence of oxygen, microbial activity draws on iron and other elements instead, chemically reducing them and producing the characteristic gley colours. They occur across climates wherever this groundwater condition prevails, particularly in valley floors, floodplains, deltas, and low-lying depressions.
Physical and chemical properties
- Gley colours
- Grey, blue-grey, and greenish hues with rusty mottles, reflecting reducing conditions from prolonged saturation.
- Aeration
- Poor for much of the year because water fills the pore space, restricting oxygen supply to roots.
- Texture and structure
- Variable, but often fine-textured and prone to structural weakness when wet and to hard-setting on drying.
- Fertility
- Depends on parent material and organic matter; wetness rather than nutrient supply is usually the primary limitation.
Management considerations
Managing Gleysols for dryland cropping centres on controlling excess water so that the root zone is adequately aerated for at least part of the year.
- Install and maintain artificial drainage to lower the water table and improve aeration
- Avoid working or trafficking the soil when wet, as it is highly vulnerable to compaction and structural damage
- Match land use to the drainage that is feasible, using wetter areas for grassland or wetland rice
- Manage organic matter and structure to support workability within the limited window when the soil is not saturated
Crop suitability
In their natural, undrained state Gleysols are classic soils for wetland rice, which tolerates and even depends on saturated, ponded conditions. Where drainage is installed, they can support grassland and a range of arable crops, though their agricultural value remains tied to how well water can be controlled.
Relationships
Evidence-backed connections in the knowledge graph.
Suitable for
Scope & limitations
Geographic scope: Global. Gleysols occur in groundwater-affected positions such as valley bottoms, floodplains, and low-lying plains across many climates; their behaviour depends on local hydrology, texture, and drainage.
Climate context: Gleysols are defined by groundwater saturation rather than climate, and occur in both humid and seasonally wet regions wherever the water table sits at or near the surface for extended periods.
- The behaviour and suitability of Gleysols depend heavily on local hydrology and on whether effective drainage is feasible.
- Draining Gleysols has environmental implications for wetlands and, in organic-rich examples, for stored carbon, which must be weighed against agricultural gains.
- This entry is a general overview; site-specific assessment of the water table, texture, and fertility is needed for management decisions.
Sources
This article draws on the following authoritative sources. See our sources & methodology for how they are selected.
- Authoritative
Cited for: Gleysol Reference Soil Group, formation, and distribution
- Type:
- Intergovernmental organization
- Jurisdiction:
- Global
- Accessed:
- 2026-07-12
- High
Cited for: Global information on Gleysols and gley features
- Type:
- Research institute
- Jurisdiction:
- Global
- Accessed:
- 2026-07-12
- [3]USDA NRCS — Natural Resources Conservation Service (opens in a new tab)Authoritative
USDA Natural Resources Conservation Service (NRCS)
Cited for: Wetness, drainage, and management of gleyed soils
- Type:
- Government agency
- Jurisdiction:
- United States
- Accessed:
- 2026-07-12
- Moderate
Cited for: General overview of gley soils
- Type:
- Reference database
- Jurisdiction:
- Global
- Accessed:
- 2026-07-12