Iron oxides and particle aggregation in B horizons of some Italian soils

Abstract

The relative importance of iron oxides to the aggregation status of soil has been evaluated for thirteen samples collected from B horizons of Inceptisols and Alfisols. The particle size distributions before and after selective dissolution treatments were performed to assess the capacity of various iron oxides to aggregate soil particles. Iron extractable with NH₄-oxalate was more effective in aggregation than goethite and hematite. The capacity of iron oxides to aggregate clay-sized particles was not significantly different in samples containing goethite and hematite from those having goethite only. Goethite and hematite in clay and in sand fractions had similar Al substitution and mean crystallite dimensions but different reductive dissolution rates in dithionite.