Soils pH values

Figure 9.6 illustrates the relative stabilities of several phosphate compounds in soils of various pH values. Soil solution compositions can be plotted on the diagram by measuring soil pH and soluble phosphate concentrations. Data above a compound s isotherm represent supersaturation with respect to the solid, indicating that the compound will precipitate. Data below the isotherm indicate undersaturation of phosphate in the soil solution with respect to that compound, so that the solid, if... 

Jackman, R.H. and Black, C.A. (1951) Solubility of iron, aluminium, calcium and magnesium inositol phosphates at different pH values. Soil Science 72, 1 79-186. 

---