Effect of different water and material on inorganic phosphorus transformation in calcareous soil

Incubation experiments indoor were conducted to study on effect of factor of soil constituent on form transformation of inorganic phosphates. The results showed that the applied soluble phosphates rapidly transformed into different inorganic forms, the predominant transformed form is Fe P, then the Ca2-P, Ca8-P, Al-P, and the Ca10-P and O-P were much less than other inorganic phosphates. Soil inorganic phosphates transformation was significantly affected by water content and application of different contents of calcium carbonate, humic acid and straw. Ca8-P、Al-P in light clay soil favorably transformed into Fe-P and Ca10-P under the conditions of low water content (200g/kg), and high water content(200g/kg) was disadvantageous to formation of Ca10-P , however, advantageous to the formation of Fe-P. Application of different content of calcium carbonate accelerate the transformation of Fe-P、Al-P , even Ca2-P into the forms of Ca8-P,Ca10-P. Application of straw and humic acid increased the contents of all inorganic phosphates and total inorganic content, reduced the extent of decreasing of available phosphorus, and raised the level of available P. Al-P,Fe-P transformed into insoluble calcium phosphate (Ca8-P,Ca10-P) with the time prolonging.