Distribution of iron oxides forms on a transect of calcareous soils, north-west of Iran

• Published in: Archiv für Acker- und Pflanzenbau und Bodenkunde 2010-04, Vol.56 (2), p.165-182
• Main Authors: Rezapour, Salar, Jafarzadeh, A. A., Samadi, Abbas, Oustan, Sh
• Format: Article
• Language: English
• Subjects: iron oxides forms; pedogenic processes; physiographic units; weathering
• ISSN: 0365-0340; 1476-3567
• DOI: 10.1080/03650340902956660

The iron oxides fractions of four major physiographic units obtained from a transect of calcareous materials were studied to assess the effects of key pedogenic processes and local hydrology conditions as well as physiographic units in controlling iron oxides forms in the north-west of Iran. Samples from different horizons belonging to six pedons were selected and analyzed for soil physicochemical properties, clay minerals, and Fe oxides forms (Fe d , Fe o , Fe p ). In general, the soils indicated some variation in the concentration of iron oxides that could be related to rate of weathering, pedogenic accumulations, geomorphologic conditions (as results of different in physiographic units), wet and dry cycle, and organic matter. A wide relative variation in mean values of Fe d (6.4-9.9 g kg −1 ), Fe o (2.9-4 g kg −1 ), and Fe p (0.68-1.3 g kg −1 ) was observed among physiographic units. On the plateau unit, the presence of the most stable geomorphologic conditions and high rate in situ weathering (reflected in clay content), coupled with minor deposition of sediment suggest that the soils have more dynamic conditions than other units, reflecting in the greatest amount Fe d and the lowest Fe o /Fe d ratio. Fe d content of the soils containing less clay content (15-25%) was significantly different from those with greater clay content (25-35%).