Effects of Soil Properties on Phosphorus Subsurface Migration in Sandy Soils*1

The soil factors influencing the potential migration of dissolved and particulate phosphorus (P) from structurally-weak sandy subsoils were evaluated by means of soil column leaching experiments. Soil colloids were extracted from two types of soils to make the colloid-bound forms of P solution. Eight sandy soils with diverse properties were collected for packing soil columns. The effects of influent solutions varying in concentrations of colloids, P, and electrolyte, on the transport of P and quality of leachates were characterized. P migration in the soils was soil property-dependent. High soil electrical conductivity values retarded the mobility of colloids and transportability of colloid-associated P (particulate P). Soil electrical conductivity was negatively correlated with colloids and reactive particulate P (RPP) concentrations in the leachates, whereas, the total reactive P (TRP) and dissolved reactive P (DRP) concentrations in the leachates were mainly controlled by the P adsorption capacity and the P levels in the subsoil. The reactive particulate P in the leachates was positively correlated with the colloidal concentration. Increased colloidal concentration in the influent could significantly increase the colloidal concentration in the leachates. Elevated P concentration in the influent had little effect on P recovery in the leachates, but it resulted in significant increases in the absolute P concentration in the leachates.