| Abstract: | Phosphate sorption and desorption in soils are markedly influenced by iron oxides, although little is known on how the common iron oxides differ in their behaviour towards added phosphate. In this study, we investigated phosphate sorption and desorption in the clay fractions of 12 Terre Rosse that ranged widely in Fe oxide content, had very low contents of oxalate-extractable Fe oxides and different hematite/goethite ratios. Phosphate sorption at an equilibrium concentration of 1 mg P 1?1 was correlated with the goethite but not with the hematite content of the clay fractions. When phosphate was desorbed by electro-ultrafiltration, the difference in desorption half-time between untreated and deferrified clays was positively correlated with the goethite but not with the hematite content. These results suggest that goethite is more active than hematite in phosphate sorption and retention by soils. |
