ABSTRACT
There are two types of acid sulfate soils in Thailand: potential and actual acid sulfate soils. Both were formed from marine and brackish water deposit rich in pyrite along the coastal zone. The potential acid sulfate soils are found to occur on the active tidal flat where mangroves occur and comprise about 459,000 ha. They have low agricultural potential and their uses should be restricted to mangrove for conservation. The actual acid sulfate soils generally occur in the former tidal flat or in the middle part of the delta. The soils are more developed and frequently contain jarosite mottles in the lower subsoil. They are extremely acidic, contain high amounts of Fe and Al but are low in available phosphorus. At present, the management of the actual acid sulfate soil in Thailand is successful for growing paddy rice and other crops like fruit trees or fast-growing trees. Also, water management using proper irrigation systems is the key factor for watering, leaching and maintaining a high groundwater table. Lime application is recommended for the correction of acidity as well as using acid tolerant crops to reduce the cost of production. At present, the management of acid sulfate soil in Thailand is successful for growing various crops, especially paddy rice, at a commercial scale. However, crop diversification system needs to be implemented for better market buffer in the future. At the same time, more studies on the dynamics of soil chemical properties are required for precise management. Additionally, proper water management at low cost and economical use is needed for future planning.
