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There has been increasing concern about drinking water contamination and accelerated eutrophication of surface water bodies. A field experiment was conducted to assess leaching potential of PO4-P in a Riviera fine sand (loamy, siliceous, hyperthermic ArenicGlossaqualf) under grapefruit (Cirrus paradisi Macfad.) production that received 0 to 30 kg P ha-1 yr-1. The PO4-P concentration was measured in soil solution sampled using suction lysimeters installed above (120 cm) and below (180 cm) the hardpan (argillic horizon). Phosphorus sorption-desorption in soil samples from different depths of the soil profile was determined to understand the transport and leaching of P in the sandy soil. Phosphorus sorption capacity of the argillic horizon was much greater than the soil above and below it. The PO4-P concentrations in soil solution varied from 0.031 to 0.976 and from 0.002 to 0.083 mg P L-1 at the 120- and 180-cm depths, respectively. Solution PO4-P concentrations generally increased with P application rates. The concentrations of P in solution at the 120-cm depth were much greater than those at the 180-cm depths, due to the greater P retention capacity of and restricted flow of P through the hardpan. This study demonstrates that leaching of Pinto groundwater was reduced by thepresence of a hardpan in the Riviera fine sand. However, the water drained from the soil above the hardpan contains phosphorus and could be a potential P source to surface waters. [ABSTRACT FROM AUTHOR]