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Effect of redox conditions on phosphate exchangeability and iron forms in a soil amended with ferrous iron
Author(s) -
Schärer M.,
De Grave E.,
Semalulu O.,
Sinaj S.,
Vandenberghe R. E.,
Frossard E.
Publication year - 2009
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1111/j.1365-2389.2009.01135.x
Subject(s) - anoxic waters , chemistry , soil water , oxalate , ferrous , dissolution , precipitation , environmental chemistry , solubility , ferrihydrite , phosphorus , iron oxide , phosphate , inorganic chemistry , soil science , geology , physics , organic chemistry , adsorption , meteorology
Summary Application of iron (Fe) ‐rich amendments to soils has been proposed as a means of decreasing phosphorus (P) losses from soils. However, anoxic conditions following soil saturation are known to increase Fe and P solubility in soils, thus cancelling out the potential benefits. Our aim was to evaluate the effects of continuous oxic, continuous anoxic and alternating anoxic/oxic conditions on P exchangeability and Fe forms in soil amended with Ca(OH) 2 and FeSO 4 . We incubated amended and unamended soils under these conditions for 8 weeks and measured Fe forms and P exchangeability. Under oxic conditions, addition of Ca(OH) 2 and FeSO 4 resulted in a strong decrease in P exchangeability and an increase in oxalate‐extractable Fe. Mössbauer analyses suggested that an unidentified Fe oxide (D1oxide) with a strong sorbing capacity for P was precipitated. Under continuously anoxic conditions, P exchangeability and oxalate‐extractable Fe increased with or without the amendments. Mössbauer analyses suggested that there was a partial dissolution of the D1oxide phase, precipitation of another unidentified Fe oxide (S3) and a reduction of structural Fe 3+ in phyllosilicate, thereby increasing soil negative charge. These transformations resulted in a strong increase in rapidly exchangeable P. Alternating anoxic and oxic periods induced the dissolution and precipitation of iron oxides and the increase and decrease in P exchangeability. Implications of the results for limiting P losses from grassland soils are discussed.