Phosphorus retention in drainage soils of commercial greenhouses

Abstract

Five commercial greenhouses in the central mountainous zone of Puerto Rico were studied in order to identify changes in soil factors that affect P retention. Soils were collected both within and outside drainages at a 0- to 15-cm depth. Soil physicochemical properties varied in samples taken both within and outside drainages. The high Fe and Al content in the soils of this study suggested a high phosphorus retention capacity. Laboratory estimates of P retention parameters indicated differences in P sorption capacity among soils. Phosphorus retention parameters were highly correlated with citrate dithionite extractable Fe. The equilibrium P concentration was also correlated with citrate dithionate Al in soils outside drainages. This finding was due to the higher soil organic matter counterbalancing the soil P retention capability of Al, all of which indicates the importance of clearing all drainages of organic residues in order to avoid excessive movement of P outside the greenhouse premises.