Inhibition of phosphorus sorption to goethite, gibbsite, and kaolin by fresh and decomposed organic matter

Summary

This laboratory study examined how dissolved organic matter (DOM) from agricultural residues and model compounds affects phosphorus sorption to three common soil minerals. DOM from decomposed organic materials inhibited phosphorus sorption more effectively than DOM from fresh materials, with inhibition varying by mineral type and DOM chemical composition. The findings suggest that microbial decomposition enhances the phosphorus-mobilising properties of organic matter through changes in DOM chemical characteristics.

Regional applicability

The study employed model minerals and standardised laboratory conditions rather than intact UK soils, limiting direct applicability to field conditions. However, the mechanistic insights into how organic matter chemistry influences phosphorus availability are relevant to UK soil and nutrient management practice, particularly for understanding how decomposition processes affect phosphorus cycling in agricultural systems amended with organic residues.

Key measures

Phosphorus sorption index; Tempkin isotherm parameters; DOM percent hydrophobicity; apparent molecular weight; phenolic acidity; total soluble carbon (TSC) concentration

Outcomes reported

The study measured phosphorus sorption to three soil minerals (goethite, gibbsite, kaolin) in the presence of dissolved organic matter (DOM) from fresh and decomposed agricultural residues. Phosphorus sorption inhibition was quantified using a one-point sorption index and Tempkin isotherm modelling, with DOM chemical properties characterised by hydrophobicity, molecular weight, and phenolic acidity.

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