Fig. 2. Correlations between surface runoff concentrations of colloidal molybdate-reactive phosphorus (MRP) (µM) and colloidal Ca (µM) for the Portneuf soil (top), and colloidal Fe (µM) for the Warden soil (bottom). Runoff was generated by simulated sprinkler irrigation. Colloidal fractions were defined as particles between 1 µm and 1 nm in diameter.