Iron Oxides in Relation to Aggregation of Soil Particles

Abstract

Soils from Denmark and Tanzania have been extracted with ammonium acetate (controls), EDTA to dissolve amorphous Fe oxides, and dithionite-EDTA to dissolve crystalline Fe oxides. The particle size distribution of the extracted soils was determined to assess the ability of Fe oxides to cement soil particles into aggregates. Except for a few soils, in which organo-metallic complexes presumably acted as cement, the particle size distribution was unaffected by the pretreatment of the soil. Provided that the Fe oxides of acetate-extracted and original soil are identical, this result confirms that Fe oxides have only negligible effect on aggregation in soil.