The study aimed to determine the effects of alternating wetting / drying (AWD) irrigation management on soil available phosphorus (P) and rice yield. The field experiment was conducted on the paddy field which was previously affected by salinity. Irrigation was applied in three strategies: (1) when water level is at around 1 cm on the soil surface, (2) when water level percolated about -15 cm and (3) when water level was at -30 cm from the soil surface. The results showed that saline concentrations in soil solution increased significantly at the heading, flowering stages and at 79 days of sowing of rice growth when soil was irrigated at water level -30 cm (P < 0.05). Applying AWD irrigation did not result in a clear effect on soil P availability as well as P contents in rice biomass. However, applying irrigation when the water level was at 30 cm below soil surface reduced the content of P in rice plant (P < 0.05). Generally, irrigating when water table was at -15 cm was safe for rice yield.

Key words: AWD, available phosphorus, rice yield, salinity.