Relationship Between Phosphorus Fractions in Paddy Soil and Phosphorus Release to Runoff Amended with Manure

This paper presents a study of the relationship between phosphorus fractions and phosphorus release in the presence of manure. Dynamic changes in the characteristics of total phosphorus in surface water are simulated by waterlogged incubation. The study was carried out by comparing sterilized and non-sterilized treatments to analyze the effect of manure on the dynamics of phosphorus (P) release from soil. Experimental results show that manure application in paddy soil can significantly increase the content of phosphorus fractions (p < 0.05). The concentration of total phosphorus in surface water also increased during incubation. The regression coefficients of moderately resistant organic phosphorus (B = 0.066), occluded P (O-P) (B = 0.012), and calcium phosphate (Ca-P) (B = −0.034) are significantly linear, which suggests possible contributions to total phosphorus. Path analysis indicates that the direct effect of Ca-P on P loss curbs the release of P; the indirect effect of Ca-P via O-P and moderately resistant organic phosphorus involved promotion of P loss. The presence of microorganisms promoted transformation of phosphorus forms; for example, Ca-P can transform into O-P and moderately resistant organic phosphorus.