TRANSFORMATION OF MINERAL PHOSPHORUS IN A SOD-PODZOLIC SOIL

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