抄録
Grey degraded soils of four representative profiles in Viet Nam were examined for particle-size distribution and mineralogical composition. They were different in parent material, landform and land use, but three common characteristic horizons were identified in the field: the light grey surface horizon, the eluviated A2 or AB horizon, and the compacted B horizon accumulated with plinthite or laterite. In the particle-size distribution, the upper horizons were dominated by sand particles with the texture of sand, loamy sand or sandy loam. The clay content was nearly equal to or below 10%, but increased with depth and reached to the level of 30 to 50% in the lower horizons. In the clay fraction, kaolin mineral was found to be predominant. Quartz was another dominant mineral. These results indicate the occurrence of more or less intensive leaching and/or decomposition of clay particles in the upper horizons of grey degraded soils.
