Rice farming in Thailand uses relatively low management technique.The water resource constrain particularly in rain-fed environment prevents farmer to adopt the modern rice technologies.In the northeast where the rice area is the largest,farmers still grow a single crop of rice with local varieties.Irrigation water constrain,low responsiveness of the local rice yield to chemical fertilizer and the relatively high fertilizer price comparing to rice price resulted in a slow adoption of chemical fertilizer.The country's average application rate of chemical fertilizer was around 27 kg/ha during 1997-75. The rate has been increased to 60 and 115 kg/ha during 1981-85 and 1991-1995, respectively. Between the wet and dry season, the average application rate of the dry season is higher than that of the wet season as a result of modern rice varieties adoption in irrigated areas