Potential iron and phosphate mobilization during flooding of soil material

This study shows that mobilization of phosphate from soils under anaerobic conditions can be intimately coupled with reductive dissolution of iron from iron oxides. Among four soil samples from the reclaimed Skjerna estuary in Denmark incubated anaerobically and amended with glucose, 28-39% of the dithionite-citrate-bicarbonate-extractable iron and 10-25% of the oxalate-extractable phosphorus (P-ox) were released to the soil solution after 31 days. Significant correlation (r = 0.992**) between the molar ratio P-ox/(Fe-ox + Al-ox) for the aerobic samples and (P-sol/Fe-sol) (the molar ratio between phosphate and iron in solution during anaerobic incubation), indicates that the phosphate saturation status of the soil is an important determinant of the amount of phosphate released during flooding of moderately acid soils.