Pot trials were conducted to study the effects of NH₄⁺-N, CO(NH₂)₂ and NO₃^--N on the transformation of several synthesized phosphates in light clay calcareous Chao soil. The results indicated that treatment with maize and no added P decreased to different degree the content of all inorganic P species in rhizosphere. DCP, OCP, Al-P applied mostly transformed into other inorganic phosphates other than dicalcium phosphate, octacalcium phosphate, aluminum phosphate respectively. However, Fe-P, especially FA applied, mainly existed in their corresponding forms in soil and the condition in rhizosphere is favorable for their transformation into other inorganic phosphates. The transformation of Al-P and FA applied in soil were significantly affected by forms of nitrogen fertilizer. Al-P coupled with NO₃^--N predominantly transformed into apatite. FA coupled with NH₄⁺-N was more favorable for its transformation into other inorganic phosphates except apatite than coupled with other two N forms. The content of ferric phosphate in rhizosphere and bulk soil significantly increased in all treatments and accumulated in rhizosphere when coupled with NH₄⁺-N and CO (NH₂)₂. Besides dicalcium phosphate and aluminum phosphate content also increased markedly and both of them were lower in rhizosphere than those in bulk soil. Their transformations in soil, especially in rhizosphere, were consistent with their availability.