One of the most important problems facing production of rice on acid sulfate soils is Fe toxicity. We observed that in the abandoned rice fields, the water was reddish in color, indicating the presence of high amounts of soluble iron. In this study, acid-extractable Fe in the soils was slightly above the critical level, ranging from 0.07 to 0.81 cmoJJkg soil (data not shown). Critical Fe concentration varies from 0.05 to 5.37 cmolclkg soil (Dobermann and Fairhurst, 2000) implying that Fe may not be the only source soil toxicity that causes reduction in yield.