Investigating the phosphorus (P) sources, pathways, and final sinks are important to reduce P pollution and improve P management. In this study, substance flow analysis (SFA) was performed for P flow analysis from 1995 to 2016 in different crops of Dongying District, a core region of the alluvial delta at the estuary of the Yellow River. The results showed that P input steadily increased from 1.48 × 104 t in 1995 to 2.16 × 104 t in 2007, and then decreased from 1.90 × 104 t in 2010 to 1.78 × 104 t in 2016. Chemical fertilizers made the highest contribution to P input. The cotton with the highest P load was on the top of P load risk ranks. More importantly, this study applied the Partial Least Squares Path Modeling (PLS-PM) model for P flow analysis and established the numerical relationship between the variables (including fertilizers, straws return-to-field, harvested grains, discarded straw, and P erosion and runoff), P use efficiency (PUE) and P load. The analysis revealed that fertilizer and crop production are the key factors affecting the PUE. Therefore, optimizing the use of P-fertilizer whilst maintaining yields can be an effective strategy to improve the local region PUE.
