FE STATUS OF BRUNISOLIC AND RELATED SOIL PROFILES

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Abstract
Three pairs of soil profiles developed on calcareous parent materials and two pairs of soil profiles developed on acidic parent materials were chosen morphologically in the field to represent Brunisolic/Luvisolic and Brunisolic/Podzolic features, respectively. Oxalate-, pyrophosphate-, and dithionite-extractable Fe were determined for each horizon. Also, Fe was partitioned into crystalline, "aged" and "gel" amorphous hydrous oxides, and organic forms. Humic acids extracted from each horizon with alkali were characterized by infrared absorption spectroscopy. Soils developed on acidic parent materials contained more extractable Fe than did those developed on calcareous parent materials. Only one horizon fitted the requirements of the chemical definition of a Bf horizon. All three reagents indicated zones of depletion and accumulation of Fe in soils developed on calcareous parent materials; oxalate and pyrophosphate did but dithionite did not show these relationships for soils developed on acidic parent materials. With exceptions, extractable Fe was correlated with clay content on the soils with calcareous parent material but was correlated with organic carbon on the soils with acidic parent materials. Well-crystallized Fe showed horizon differentiation in soils with calcareous parent materials and is therefore a weathering product. In soils with acidic parent materials, crystallized Fe was the source of weathering product forms of Fe. Humic acids of soils with acidic parent materials were more highly oxidized and hence more capable of reacting with Fe than were those of soils with calcareous parent materials.

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