Formation of apatite from superphosphate in the soil

The bulk of the phosphate added to soils as fertilizer remains in forms unavailable to plants. In calcareous soils it has been said to form hydroxyapatite. From a study of the reversion of mixtures of superphosphate and liming materials, MacIntire and his associates have recently suggested that the ultimate form of some of the phosphate applied to heavily limed soils may be fluorapatite; but, so far as we have been able to ascertain, no direct evidence has ever been obtained of the actual presence in the soil of apatite formed from fertilizers. RESP-02962