Comparing two theories about the nature of soil phosphate

Two theories about the nature of phosphate in soil are current. One holds that soil phosphate is mostly present as particles of iron, aluminium and calcium phosphates: the precipitate‐particulate theory . The other holds that phosphate is mostly adsorbed and penetrates heterogeneous, variable‐charge particles: the adsorption‐penetration theory . This is the only theory that is consistent with and can be deduced from observations. It is my contention that the persistence of the precipitate‐particulate theory leads to: wasted research effort in trying to identify the supposed phosphate fractions; failure to recognize the long‐term changes in soil phosphate due to repeated applications, and thus to over‐fertilisation; and misapprehension about the effects of pH on phosphate availability.