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SUMMARY The gley podzols of the west coast of South Island, New Zealand, typically exhibit permanent waterlogging extending from the surface to depths of 1–3 m. Their formation is explained by a continuation of processes which give rise to Peaty Podzols with thin iron pan (Ironpan Stagnopodzols; Placaquods). Iron pans initially formed within the upper B horizon are breached by acidic reducing waters and reform at a succession of lower levels down to 3 m or more below the surface.

The definition of an aquic soil moisture regime given in Soil Taxonomy is difficult to understand and, in places, ambiguous. The essence of the definition as written, however, is the requirement for reducing conditions. A soil which is saturated with groundwater or with capillary fringe water may, or may not, have an aquic moisture regime. Reducing conditions are defined in Soil Taxonomy in relation to the virtual absence of dissolved oxygen, though morphological criteria for the differentiation of soil classes are based on the reduction and segregation of iron. The absence of requirements relating to duration of reducing conditions, or to the thickness of reduced soil, suggests that the definition was intended to apply to soil material rather than to a pedon. The aquic moisture regime has a particular depth connotation only when it is applied to the differentiation of soil classes. A simple field test, based on the complexing agent �,�-dipyridyl, is useful for the identification of ferrous ions in soil solutions and hence is potentially useful in the recognition of aquic moisture regimes. The sensitivity of this test limits its usefulness to those soils which contain more than about 0.5% free iron (i.e. iron which can be solubilised as iron(II) under reducing conditions as measured by extraction with dithionite reagent).

SUMMARY Podzols under sessile oak at Yarner Wood National Nature Reserve have extraordinarily hard and compact grey subsurface (Ea) horizons. The parent material is solifluxion debris from sandstones and siltstones of the Culm Measures (Lower Carboniferous) into which small amounts of loess have been incorporated. The general morphological, micro‐morphological and chemical features of these soils, which are classified as hardpan stagnopodzols, are outlined and compared with those of adjoining brown podzolic soils. The evidence shows that the compaction is due only to close packing of particles and not to cementation. The genesis of the hardpan stagnopodzols and their relationship to other hardpan soils elsewhere in the world is discussed and the creation of a‘Densi‐’Great Group within Soil Taxonomy is proposed.

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