Selected Chamical Properties of Alluvial Soils in Vietnam

In the present study, 16 profiles of alluvial soils of Vietnam were collected throughout the countr and analyzed for some selected chamical propeties. The soil pH was found to be controlled by several factors such as soil forming process, oarent material, landform and land management, and the organic carbon (OC) content was mainly dependent on soil forming processes and land management. Within soil profile, the pH was a little lower at the surface horizon and was remarlably constant throughout the lower horizons in Eutric Fluvisols and Dystric Fluvisols, whereas it decreased with depth in Cambic Fluvisols and Gleyic Fluvisols. The cation exchange capasity (CEC) and the content of exchangeable cations were contorolled by sediment sources and showed the regional variations. As a result, soils were divided into three groups based on the river systems. The variability in CEC of soils in the Mekong River system. Average of CEC was larger for the latter than for the former. Alluvial soils distributed in the large basins of the Red River and the Mekong River systems had the high content of exchangeable basis of the Red River and the Mekong River systems had the high content of Exchangeable cations, especially Ca[2+] and Mg[2+], in comparison with alluvial soils from the small drainage basions of the other rivers system