Fig. 1. Relationship between water-extractable phosphorus (P_H2O) and degree of phosphorus saturation estimated as the ratio of either Olsen (P_Ols) or Mehlich 3 (P_M3)–extractable P to P sorption indices. Ca_M3, Mehlich 3–extractable Ca; (Ca + Mg)_M3, the sum of Mehlich 3–extractable Ca and Mg; P₁₅₀, P sorption index at 150 mg L^–1 of added P; ES_max, estimated Langmuir adsorption. All relationships are significant at p < 0.01 (n = 112). Three points with P_H2O values of 0.9, 1.1, and 2.3 mmol kg^–1 were statistically shown to be outliers and were eliminated from the regression plot.