Agronomic Evaluations of an Arkansas Rock Phosphate

During earlier decades such material was rather widely used as a phosphorus fertilizer. But in modern agriculture only an insignificant percentage of the total phosphorus fertilizer is applied in this form. Most of the commercial phosphorus fertilizer now marketed is manufactured by treating the ground rock phosphate with sulfuric acid, or otherwise processing it, so that the orthophosphate ion exists as the more soluble H2 PO4 or HPO42 rather than as the insoluble PO 4 3