A case study on acid sulfate soils in the Mekong River Delta of Vietnam

Begun in 1992, the IAS/FOS/DTM Project adopted a multiscale approach to conduct research and development activities an the highly heterogeneous acid sulfate soils in the Plain of Reeds, Mekong Delta, Vietnam. Based on secondary data and in collaboration with various organizations, zooming from the Plain of Reeds to the village level made it possible to identify an experimental area covering the major conditions in the Plain of Reeds. Detailed studies and experiments were then conducted in the field, with due attention given to heterogeneity as a source of information. The studies provided important documentation on very acid sulfate soils and practical recommendations for their reclamation. Clear correlations were observed among soil physical and chemical characteristics, natural vegetation, water table, and rnicro-topography. Field characteristics (such as elevation and soil permeability, which decreases with length of cultivation) were used to adapt recommendations to individual fields throughout the Plain of Reeds. Correlations among soil type, elevation, and vegetation can also be used for land surveys and mapping at various scales. Problems in implementing the multiscale research approach arose mainly because of inconsistencies among sources of information, especially with regard to differences in soil classifications used by the various organizations involved in agricultural planning and research. Extrapolation of results to the entire Plain of Reeds is possible due to the detailed knowledge obtained on soils and their variability, genesis, and associated agronomic problems. It was facilitated because these processes are continuous in space and time. In addition, the main key for extrapolation, micro-elevation, can be assessed easily by observing natural vegetation distribution. (Résumé d'auteur