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Abstract

The aim of this study was to elucidate interactions between soil organic matter, inositol-hexaphosphate (IHP), aluminium (Al), and calcium (Ca) as well as four minerals (kaolinite, illite, smectite, and goethite) at low and high pH. For this purpose, we conducted experiments, in which we quantified the removal of soil-derived, natural organic matter (NOM) and IHP from the solution due to sorption and coprecipitation. The fraction of IHP in solution decreased due to Al addition to less than 2% of the initial amount, in all treatments (with and without minerals). The fraction of organic carbon (OC) of NOM in solution decreased due to Al addition in the absence of minerals to 12% of the initial amount and less strongly in the treatments with minerals to 39% of the initial amount. Aluminium addition decreased the fraction of OC of NOM in solution more strongly than the minerals, both at low and high pH. Addition of Ca and IHP also decreased the fraction of NOM in solution, particularly in the absence of minerals, but their effects were smaller than the effect of Al. Our finding that IHP decreased the fraction of NOM in solution supports the so-called anchor hypothesis stating that IHP can bind organic compounds to minerals and to other organic compounds. The effect of IHP on the fraction of NOM in solution was larger in the absence than in the presence of minerals, suggesting that IHP connects organic compounds to each other. Furthermore, the results show that IHP coprecipitates to a larger extent with Al than organic matter that has a very low phosphorus content. The results are important for understanding the architecture of organo-mineral associations, and specifically the role of organic phosphorus compounds therein, which is relevant for soil organic matter sequestration.

Keywords

aluminium; coprecipitation; organic phosphorus; organo-mineral associations; soil organic carbon; soil organic matter; sorption

Published in

European Journal of Soil Science
2025, volume: 76, number: 6, article number: e70221
Publisher: WILEY

SLU Authors

UKÄ Subject classification

Soil Science

Publication identifier

  • DOI: https://doi.org/10.1111/ejss.70221

Permanent link to this page (URI)

https://res.slu.se/id/publ/144559