TRANSFORMATION OF MINERAL PHOSPHORUS IN A SOD-PODZOLIC SOIL

Phosphorous fertilizers of differing solubility (superphosphate, precipitate, and ground phosphate rock) had varying effects on the content of phosphates extractable with 0.2 M HCl and on the content of the various phosphate groups in a Sod-Podzolic soil. Superphosphate and precipitate applied to the soil were converted into soil aluminum phosphates, and to a lesser extent iron phosphates, as early as in the year of application. When ground phosphate rock was applied, the content of mineral phosphates increased, mainly as calcium phosphates. These calcium phosphates were not really soil phosphates but rather fertilizer phosphates which had not reacted with the soil.