Fig. 2. Variation of P fractions with time for untreated Berks high P and Watson low P soils. Lines represent the fit of the power equation to the data. No line represents a nonsignificant fit. Vertical bars represent the percent clay in each sediment sample. DRP, dissolved reactive phosphorus; DURP, dissolved unreactive phosphorus; TDP, total dissolved reactive phosphorus; PP, particulate phosphorus; TP, total phosphorus.