Transformation of Phosphorus Forms in Calcareous Soils with Manure Application

Manure application is an important management practice to improve soil fertility. In order to understand the phosphate chemistry in manure-amended calcareous soil, the extractant of NaOH-EDTA and31P nuclear magnetic resonance(31P-NMR)spectroscopy were conducted to study and compare phosphorus forms and contents in poultry manure, cattle manure and manure-amended soils. Moreover, effects of manure application on soil available phosphorus were also investigated. The results showed that large percentage of the phosphorus in manure was in the inorganic form. The two manures differed in their P composition. Much more phytate was detected in poultry manure compared with cattle manure. Application of manure changed the organic phosphorus forms in soil. Additionally, transformation of phosphorus forms in soils was observed with incubation time. Content of orthophosphate monoester such as phytate decreased while orthophosphate diesters such as nucleic acid increased obviously. With incubation time, the content of soil available phosphorus increased in poultry manure treatment while it declined in cattle manure treatment. Different variations of soil available phosphorus after manure application might be the synthesis results of phosphorus fixation-precipitation, mineralization and immobilization.