Fig. 1. The summed concentrations of inorganic P extracted using deionized H₂O (H₂O-Pi), 0.5 M NaHCO₃ (NaHCO₃–Pi), 0.1 M NaOH (NaOH-Pi), and organic P extracted using 0.1 M NaOH (NaOH-Po) in relation to ammonium oxalate extractable P(AMOX-P) measured in soils collected in the spring 2004 (**, p value < 0.001).