Table 3. Simple linear correlations (r) between selected soil P tests and DRP concentrations in the 0.2µm filtrate at 5 and 240 minute equilibration times for the 200 solution:soil ratio. There were no apparent correlation differences between the 5 and 240 minute samples. The 5 and 240 minute DRP concentrations were highly correlated ( r = 0.94-0.97) as well as the soil P tests (r = 0.55-0.91). This indicates that DRP concentrations can be reasonably estimated from all three soil P tests. All correlations were significant at less than 1% probability level. Only small improvements occurred when all soil variables were considered using stepwise regression.