<資料・研究ノート>東南アジア低湿地の土壌,その2 : 湿地林下の有機質土壌

Abstract

The vast area of tropical peat land in Southeast Asia represents an impotrant fraction of potentially cultivable land. Tropical peat develops under swamp forest in the freshwater environment of the low coastal zone. Most is deep ombrogenous peat of the raised-bog type, and thus extremely oligotrophic in nutritional status. This paper reviews the process of formation, physical and chemical characteristics, and classification of tropical peat, and discusses in detail problems that these characteristics raise in attempts at reclamation. Continuous land subsidence due to dewatering, compaction and decomposition of peat is particularly serious when deep peat is drained for reclamation. Deficiencies in both major and minor elements of oligotrophic peat are no less a problem than subsidence. After disappearance of peat due to decomposition, moreover, the underlying clay may develop into acid sulfate soil. Another unsolved problem in the utilization of peat is the failure of grain formation of paddy rice, which is otherwise the crop most adapted to peat land. It is tentatively concluded that only a few percent of total tropical peat land may be reclaimed successfully, and the rest should be conserved as natural swamp forest.