Effect of water management on transformation of inorganic phosphorus in paddy soil in Taihu lake district.

The dynamic changes of inorganic phosphorus in paddy soil and its influential factors under different water and fertilizer conditions were studied by using classification method for inorganic phosphorus in neutral soil.The results indicated that the phosphorus application could significantly increase various forms of inorganic phosphorus content.Under the waterlogged condition,the contents of Ca2-P,Ca8-P and Al-P were gradually decreasing,while the contents of Fe-P and Oc-P were increasing,and the content of Ca10-P was basically stable.The changing trends of all forms of phosphorus content were similar in the 60% field water-holding incubation.In a word,soil incubation increased the fixation ability of soil to phosphorus,and the MNK,MNPK and CNPK treatments fixed more P than C0 and CNK treatments.The changes in the contents of soil crystalloid Fe,chelated Fe and amorphous Fe in the incubation period corresponded with the partial mechanism of soil inorganic phosphorus transformation,but how the reducing iron in the waterlogged soil was oxidized and led to the second fixation of phosphorus still needed further study.