ABSTRACT
REDUCING ACD) POLLUTION FROM RECLAIMED ACID SULPHATE SOILS: EXPERIENCES FROM THE MEKONG DELTA, VIETNAM
T. P. TUONG Soil and Water Sciences Division, International Rice Research Institute, Los Banos, The Philippines L. Q.MINHandD. V.NI Can Tho University, Can Tho, Viet Nam M.E.F VAN MENSVOORT Department of soil and geology, Wageningen Agricultural University, Wageningen, The Netherlands
Abstract Using innovative land and water management methods, developed by trial and error, farmers have turned vast tracks of the traditionally abandoned acid sulphate soils (ASS) in Southeast Asia into reasonably productive lands. Leaching of ASS however creates environmental hazards. The amounts of acidity released are strongly influenced by the severity of the soil acidity, but also by the type of land use and farmers practices. In the reclaimed ASS of the Mekong Delta, Vietnam, on monthly basis, rice fields with good water management facilities release less than 2 kmol(+) ha"1 of aluminum even on severely acid soils. Corresponding amounts from fields provided with raised beds for upland crop cultivation, or from spoils of newly dug canals can be 8 times higher Through diffusion and mass transport, the pollution can spread to the surrounding, affecting bio-diversity, the food chain... over a large area. Pollution hazard can be reduced by proper land uses, surface soil management, and adjusting the timing of leaching. Rehabilitating natural wetlands by impounding fresh or saline water may help prevent further oxidation and acidic export. Melaleuca forests have a potential as "sinks" for improving water quality drained from the reclaimed soils. The research implications of the above strategies and practices are discussed. Keywords: Acid sulphate soils, aluminium, drainage, land reclamation, oxidation, rice irrigation, water pollution.
