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RESEARCH ARTICLE

Mineralogical properties of sandy podzols on the Swan Coastal Plain, south-west Australia, and the effects of drying on their phosphate sorption characteristics

J. Z. He, R. J. Gilkes and G. M. Dimmock

Australian Journal of Soil Research 36(3) 395 - 410
Published: 1998

Abstract

Very sandy and sometimes seasonally inundated humus podzols of the Bassendean soil association in southwest Australia experience severe leaching of fertiliser P with consequent eutrophication of waterways. P sorption by these soils is mostly minimal and is primarily due to the podzol Bh horizon. The consequence of seasonal drying of profiles under the prevailing Mediterranean climate on the P sorption capacity of these B horizon materials is not known. The effects of air-drying on P sorption were studied for 3 sandy podzols using samples from entire soil profiles collected in winter (wet) and summer (dry). Results confirm that the surface and near surface horizons (i.e. A and E horizons) of these soils have very low P sorption capacities. Only some B horizon materials exhibit substantial P sorption and this is mostly due to allophane, with minor contributions from extractable Fe forms, organic carbon, and clay. Air-drying during summer and in the laboratory increased P sorption of B horizon materials by up to 120% compared with field-moist samples. The difference in P sorption between air-dried samples and the field-moist samples decreased for long reaction times.

Keywords: phosphorus leaching, seasonal change, allophane.

https://doi.org/10.1071/S97061

© CSIRO 1998

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