Soil-Forming Processes (Pedogenesis) Which pedogenic process is associated with poor drainage and leads to the accumulation of organic matter and the formation of gley features in the upper soil layers?

Introduction / Context:
Pedogenesis encompasses processes that create and modify soils under different environmental conditions. Waterlogging and oxygen deficiency greatly influence soil color, chemistry, and organic matter dynamics. The named process for such poorly drained settings is important in wetland ecology and land-use planning.

Given Data / Assumptions:

• Sustained poor drainage or waterlogging near the surface.
• Accumulation of organic matter due to slow decomposition under anaerobic conditions.
• Characteristic gray/blue gley colors from reduced iron compounds.

Concept / Approach:
Gleisation (or gleying) occurs where prolonged saturation leads to anaerobic conditions, reduction of iron, and organic matter build-up. The result is a gley horizon with mottled gray-blue colors. Other processes—salinisation (salt accumulation), calcification (accumulation of calcium carbonate), and podsolisation (acid leaching producing ash-gray E horizons)—do not match the waterlogging-driven characteristics described.

Step-by-Step Solution:

Verification / Alternative check:
Soil surveys classify many wetland/riparian soils as gleyed. Field indicators such as low chroma matrices and redoximorphic features corroborate gleisation under saturated regimes.

Why Other Options Are Wrong:

• Salinisation: Driven by evaporation and capillary rise of salts in arid/irrigated soils.
• Calcification: Calcium carbonate accumulation typical of semi-arid climates.
• Podsolisation: Acid leaching and translocation of sesquioxides; not primarily a waterlogging product.

Common Pitfalls:
Equating dark surface color with any process; here the key is poor drainage and reduction, which point to gleisation specifically.

Final Answer:
gleisation