Dynamics and its Control of Soils in Tropical Monsoon Regions

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We have studied the soils in the tropical monsoon regions, mainly the soils distributed in Thailand emphasizing soils classified as "Ultisols" which has been considered to be one of the most degradable soil types in the tropical regions. The ecological fragility in the tropics were considered mainly due to the degrability of the soils in these regions. For elucidating the basic concept involved in the degradation mechanism, firstly, we had to spend our effort to a greater extent in selecting sites for the soil sampling where the type of soil should be identical from the viewpoint of the soil genesis but different in human management as "Cultivated vs Uncultivated". Secondly, we have tried to investigate from the viewpoint of soil properties and crop root morphology which might be involved with the degradation mechanisms of soil.As a result we succeeded in collecting 30 soil samples in 1988, 41 in 1989 and in 1990 mostly from areas of the Ultisols soil type. Furthermore, these soil samples were analyzed for the physical, chemical, microbiological and root morphological properties in order to investigate th possible mechanisms involved in the soil degradation.