Aluminum toxicity is a major problem for rice grown on an acid sulfate soil. High exchangeable AI in soil is usually associated with low pH. This is clearly shown by the data given in Table 3; the lowest pH coincides with the highest Al (T5). It shows the opposite in Tl. As seen in Table I, the initial exchangeable Al was extremely high in some samples, reaching a value of 32.43 cmolJkg soil in the subsoil of T3. The lowest value was 2.72, in the topsoil ofT5. In the water in the vicinity of the experimental plots, Al would certainly exceed the critical value for rice production of 1-2 mg/kg. This high Al in the solution can be reduced to an accepted level by applying GML at an appropriate rate. This study suggested that GML application at 4 tlha would be appropriate