In Narathiwat, Province in the most southern part of Thailand near the border to Malaysia, acid sulfate soil is a major cause of low yield of rice, and hence improvement of acid sulfate soil is an urgent issue. Application of lime is the most practical and useful means to improve the crop yield in acid soil conditions, but the increasing cost of lime is gradually making it difficult to cultivate rice in this region. A solution to this problem would be to cultivate acid soil-tolerant varieties using a small amount of lime.