Solubility Curves of Inorganic Phosphorus in the Paddy Soils of Taiwan

The pH-solubility curve of inorganic soil phosphorus of the main soil groups of Taiwan was summarized as follows: (1) In the acid red earth or yellow earth and mudstone alluvial soil, iron and aluminum phosphate may be the principal form of phosphorus. (2) In the slate alluvial soils, schist alluvial soils and saline alluvial soils, calcium phosphate is predominent form of inorganic soil phosphorus. (3) In the sandstone and shale alluvial soils, both calcium phosphate and iron, aluminum phosphates are present in about equal amount. (4) The minimum solubility of phosphorus in the soils of different soil groups are generally in the pH range of 6 to 8.