Distribution of allophane and organic matter in podzol B horizons: reply to Buurman & Van Reeuwijk |
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| Authors: | VC FARMER |
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| Institution: | The Macaulay Institute for Soil Research, Craigiebuckler, Aberdeen AB9 2QJ, Scotland |
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| Abstract: | The macromorphology, micromorphology and chemical nature of illuvial material in podzol B horizons and subsoils can be explained by contributions from two different migrating species: (a) a positively-charged mixed Al2O3-Fe2O3-SiO2-H2O sol incorporating minor amounts of adsorbed organic matter and silicate clay, and (b) negatively charged organic sols and solutions, carrying minor amounts of Al, Fe and clay. These species can also be generated within B horizons of high root activity. An alternative theory, that requires allophane to be formed in situ in the B horizon by microbial decomposition of precipitated organic complexes, fails to predict the observed distribution of allophane. |
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