<資料・研究ノート>東南アジア低湿地の土壌 : その1 マングローブ下の堆積物に由来する土壌

Abstract

The coastal areas of the Southeast Asian tropics are vegetated extensively by mangrove forest. Inland there are areas which were formerly under mangrove, before they were cut off from the marine or brackish environments. These areas together represent an important fraction of the potentially cultivable land for food production in the near future. This paper looks at the soils derived from the sediments deposited under mangrove, to evaluate their potential for cultivation. Mangrove mud contains oxidizable sulfur compounds, mainly in the form of pyrite, which upon exposure to the air is oxidized to sulfuric acid, developing a strong acidity. The resultant soil is called acid sulfate soil. This paper deals first with the processes of pyrite accumulation under mangrove and its oxidation upon reclamation. It then discusses the classification, properties and management of acid sulfate soils on the basis of recent research results. It is concluded that the former mangrove land is probably reclaimable only with difficulty and a high investment. It may, however, be possible to improve soil conditions to some extent by simple means practicable by the small farmer, such as localized phosphate application.