Fig. 1. Path diagram illustrating the relationship between soil properties and soil P retention capacity. D_ij denotes the direct path; r_ij denotes the correlation coefficient; P retention index (PRI) is the soil P retention capacity; sand is the percentage of sand; Ca_M3, Mg_M3 and Mn_M3 denote Mehlich-3 extractable Ca, Mg, and Mn, respectively; Al_Ox and Fe_Ox are the ammonium oxalate-extractable Al and Fe, respectively; and U is the residual estimated as where R² is the coefficient of determination for the regression model (R² = 0.88).