University of Arkansas, Fayetteville Division of Agriculture


In the Illinois River Watershed, there has been growing concern over elevated phosphorus concentrations in the water column. This study evaluated how much phosphorus is contributed from floodplain soils into surface waters, examining the relationship between the flux of phosphorus released and the amount of phosphorus stored in the soil. This was investigated by artificially inundating soil cores from four sites and determining the soluble reactive phosphorus concentrations of the overlying water and the levels of Water and Mehlich-3 extractable phosphorus in the soil. The flux of phosphorus to the overlying water ranged from 0.43 to 6.61 mg m-2 hr-1 within the short-term (16.5-hr incubation) and 0.06 to 1.26 mg m-2 hr-1 over the long term (282.5-hr incubation). Phosphorus flux to the overlying water was significantly correlated with the amount of phosphorus stored in the soil. This study showed that riparian soils with elevated phosphorus content have the potential to release phosphorus when flooded.