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Identifying Water Repellent Soil Layers: Depth and Management Effects
Water repellent soil is mostly found in the top 10–15 cm of soil, with repellence usually peaking from 2–5 cm depth, depending on the soil’s history and management. The total depth of the water repellent layer varies with climate and soil type but roughly matches the depth of the organically stained layer. In very pale sands it can extend deeper than the very thin organic layer.
Repellence can start at the surface, but sometimes the top few millimetres of soil are wettable and the repellent soil starts from around 5 mm depth. This happens in bare soil or under fire where heat (from the sun or fire) volatilises the organic compounds in the top few millimetres of soil (making that soil wettable again) but the water repellent soil is still lurking just below.
