Occurrence of iron and aluminum sesquioxides and their implications for the P sorption in subtropical soils

The effect of the pedo-climatic variation in qualitative and quantitative soil sesquioxide contents and soil phosphorus (P) sorption capacities has been studied. In four soils (samples from A horizons) located along a southern Brazilian environmental gradient (EG) shown a decrease in crystallized iron oxides with the increase of altitude. Hematite and goethite were found at low EG altitudes in association with low soil organic carbon content, and goethite-ferrihydrite and gibbsite were found at high altitudes in association with high organic carbon content. The adsorbed soil P (measured by the remaining P) was predicted by the goethite content, and the desorbed P (measured by successive P extractions using anion exchange resin membranes) was predicted mainly by the goethite and clay content. In subtropical soils, even a smooth environmental gradient could determine the qualitative and quantitative iron and aluminum sesquioxide distributions that control soil P sorption capacities. (c) 2014 Elsevier B.V. All rights reserved.