Vertical Distribution of Extractable Iron and Aluminium in Soil Profiles From a Brown Earth‐peaty Podzol Association

Summary Fe and Al extractable by 3 per cent oxalic acid and by 0.1M potassium pyrophosphate at pH 10 have been determined in horizon samples of two soil profiles of each of three subgroups (Brown Earth, Brown Podzolic Soil, and Peaty Podzol) developed in North Wales on parent materials derived from Silurian shales. The vertical distribution of Fe and Al together with the relationship between pyrophosphate‐extractable (‘fresh’ hydrous oxides) and oxalic‐extract‐able Fe or Al (‘fresh’+‘aged’ hydrous oxides) can assist classification and interpretation of the course of podzolization in these soils. If podzolization is defined as sesquioxide transport, then its degree of development in the soils studied differs according to whether Al or Fe are used as the index element. The evidence supports continued recognition of soils of Brown Podzolic type as an intergrade subgroup.