ORIGINAL RESEARCH article
Front. Soil Sci.
Sec. Soil Biogeochemistry & Nutrient Cycling
Competitive adsorption between phosphate and dissolved organic carbon in iron rich soils
Provisionally accepted
- School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Sydney, Australia
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Competitive adsorption between phosphate and dissolved organic carbon (DOC) have been reported in Andosols and podzols. However, the published results are unclear and sometimes contradictory. In addition, the competitive behaviour between phosphate and DOC may be quite different in the surface and subsurface soils. In this study we used surface and subsurface soils with substantial Fe oxides contents from two sites, i.e., Wagga Wagga and Tumbarumba to evaluate the adsorption behaviour of phosphate and DOC. Adsorption data were fitted into linear initial mass (IM) isotherm. The results showed that both surface and subsurface soils from Tumbarumba had a greater phosphate adsorption capacity than the soils from Wagga Wagga. Phosphate adsorption was greater for the subsurface soil (m = 0.72) than the surface soil (m = 0.82) from Tumbarumba, while this trend for was opposite for Wagga Wagga soils, where phosphate adsorption capacity was greater for the surface (m = 0.55) soil than the subsurface (m = 0.37) soil. The DOC adsorption was greater in the subsurface soils from both sites. The addition of mixed solution of P and DOC promoted DOC desorption in soils from Wagga Wagga and Tumbarumba. The results of this study have crucial implications on the sustainability of Fe-rich soils. The adsorption of phosphate promoted DOC desorption in these soils, which may lead to destabilisation of OC and impair OC sequestration and therefore enhance microbial decomposition of OC in these soils.
Keywords: Phosphate, DOC, Soil, Adsorption, desorption, linear initial mass isotherm
Received: 06 Oct 2025; Accepted: 19 Nov 2025.
Copyright: © 2025 Amenkhienan, Dijkstra and Singh. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Bright Ehijiele Amenkhienan, bright.amenkhienan@sydney.edu.au
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