Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 12, 1999
Publication Date: N/A
Technical Abstract: This is a review paper on research on the effects of the oxidation/reduction status on phosphorus (P) chemistry in soils and sediments. Phosphorus mobility and bioavailability is greatly affected by the redox status of soils and sediments, since many of the phosphate minerals contain ferric iron or manganic manganese. Iron phosphate minerals include vivianite (Fe3(PO4)2.8H2O), strengite (FePO4.2H2O) and amorphous ferric phosphate (FePO4), whereas manganese phosphate minerals include reddingite (Mn3(PO4)2.3H2O), hureaulite (Mn5H2(PO4)4.4H2O) and trivalent manganese phosphate (MnPO4.1.5H2O). Ferric and manganic oxides and hydroxides are also important with respect to phosphorus bioavailability, because they have a high phosphate sorption capacity. The solubility of all of these mineral phases is highly dependent on redox potential (Eh) and pH. Under reducing conditions, such as that found in flooded rice fields or in lake sediments, ferric (Fe3+) iron and manganic (Mn4+) manganese can be reduced to the more soluble ferrous (Fe2+) and manganous (Mn3+) forms, releasing phosphorus in the process. This release of phosphorus in paddy rice fields is beneficial because it reduces the need for flooded rice to receive phosphorus fertilizer inputs; however, it can be detrimental in lake systems if eutrophication is a problem.