Effects of organic-inorganic compound phosphorus fertilizer on transformation of inorganic phosphorus pool in lime soils

Effects of organic-inorganic compound phosphate fertilizer on the composing and transformation of inorganic phosphorus in lime soil was carried out under laboratory incubation condition. The results show that there are little effects on improving soil available P content through single application of small quantity of organic materials, but the soil available phosphorus contents are significantly increased under the applications of phosphate fertilizers, whether it is MAP or organic-inorganic compound phosphate fertilizer. Besides, the soil available phosphorus contents are increased by 67.5 mg/kg to 80.4 mg/kg under the applications of organic-inorganic phosphate fertilizer compared to the application of MAP (62.3 mg/kg). Moreover, there are little effects of the quantity of organic materials in organic-inorganic compound fertilizers on the soil available P. The increasing trend of Ca2-P content is found through single application of organic materials, and the Ca8-P content is significantly increased as well, while there are little changes in Al-P, Fe-P, O-P and Ca10-P contents; Applications of phosphate fertilizers, whether it is MAP or organic-inorganic compound phosphate fertilizer, improve the soil Ca2-P, Ca8-P, Al-P contents significantly, while the changes of Fe-P, O-P, Ca10-P are small. Comparing with the MAP treatment, the applications of organic-inorganic fertilizers have little affects on the content of Ca2-P, while increases the content of Ca8-P and decreases the Al-P content significantly, and there is a rising trend on Fe-P content and no obvious regularity on O-P and Ca10-P contents. Besides, there is no obvious regularity in the effect of the organic materials proportion on the composing and transformation of soil inorganic phosphorus pool. The changes in Ca2-P and Ca8-P contents are bigger than those of the other phosphorus forms through the phosphate fertilizer application. Compared with the MAP fertilizer application, the applications of organic-inorganic compound fertilizers increase Ca8-P variability and decreases Al-P variability, and there are no differences in the other indicators. Statistical analysis results show that there are positive linear correlations between soil available P and Ca2-P and Ca8-P, and the correlation coefficients reach to 0.9888, 0.9867, respectively, while there are not significant linear correlations between soil available P and Al-P, Fe-P, O-P and Ca10-P content. As a conclude, the variabilities of Ca2-P and Ca8-P pool affect the available P content most after the application of the phosphate fertilizer.