Soils of the northeast plateau, Thailand

Technical bulletin of the Tropical Agriculture Research Center
ISSN 03889394
書誌レコードID(総合目録DB) AA00857848
The undulating plateau, which accounts for about 80% of Northeast Thailand, is known for its extremely low soil fertility. Basement rocks of the plateau consist of sandstone or siltstone of the Mesozoic age, of which the greater part is underlain by rock salt bed. The undulating relief of the plateau has been formed by a denudation process. The sediments covering the land surface are not riverine deposits, but deposits formed by mass movement of the weathered mantle of the bed rock.
The low soil fertility is attributed mainly to the extremely low exchange and buffering capacity, and quasi absence of mineral reserves in the surface soils due to the sandy texture, predominance of quartz in sand fractions and low organic matter status. In addition to these, salinity (saline soils) and presence of an ironstone layer at shallow depths (skeletal soils) aggravate the situation in a considerable part of the Northeast plateau.
1) Sandy surface soils: Although the sandy texture is partly derived from the nature of the parent rocks, it has largely resulted from various secondary processes, e.g. 1) selective loss of clay by percolating and seepage water, 2) selective loss of finer particles by runoff or overflow water (micro-erosion), 3) selective loss of finer particles in association with mass movement. It seems that the clearing of forests and careless soil management have enhanced these processes. Destruction of clay by ferrolysis, if any, can not be a major process in the formation of sandy surface soils. Mulching, minimum- or no-tillage and crop rotation so as to keep the vegetative cover are recommended. Soil improvement to enrich active clay and mineral reserves should be considered seriously.
2) Skeletal soils: It is assumed that ironstones had originally been scattered more sparsely in the profile, and that thick ironstone layers have been formed as a result of the removal of the soil matrix and consequent residual concentration of iron nodules in association with mass movement. Soils with ironstone layers or iron-pans are not suited to the growth of crop plants. Northeast Thailand has already been reclaimed beyond its capability. It seems reasonable to preserve the major part of the skeletal soil areas as forests.
3) Saline soils : Salt source of saline soils is considered to be salt-impregnated sandstone or siltstone instead of deep seated rock salt bed. A major problem, however, is the expansion of salt-affected soils by human activities, including deforestation, salt-making operations, construction of reservoirs and ponds, etc. First of all, the mechanism of salinization must be fully clarified. We must be extremely careful in changing the land use, landform or whatever may affect the existing water balance.
作成者 Masanori Mitsuchi Pichai Wichaidit Saeree Jeungnijnirund
公開者 Tropical Agriculture Research Center
開始ページ 1
終了ページ 66
言語 eng
国名 タイ