Aquaculture and Agricultural Production in the Mekong Delta and its Effects on Nutrient Pollution of Soil and Water

Abstract

The Mekong Delta (MD) is the most important area for agriculture and aquaculture production in Vietnam, especially in terms of the production of rice, fruits, shrimp and catfish. However, intensification of rice and shrimp production on both alluvial soils and acid sulphate soils (ASS) has resulted in degradation of soil and water environments. Results of the studies on water quality showed that surface water in two branches of the Mekong River had high biological oxygen demand, chemical oxygen demand and nitrate concentrations, which exceeded the limits of the Vietnamese standard for surface water. In ASS areas, water in the canals showed high levels of aluminium, iron and manganese, and toxic metals such as Arsenic, Cadmium, Copper, Nickel, Lead and Zinc. The concentrations of these metals were higher than that in non ASS areas. For shrimp cultivation, rice-shrimp and extensive shrimp systems were more sustainable in-terms of soil and water quality when compared to the intensive shrimp system. In ASS areas, shrimp cultivation had high risk of failure due to low pH and low alkalinity. Based on recent studies, rice rotation with upland crops and compost amendment were the best practices for maintaining soil fertility and improving rice yield in the intensive rice cultivation areas. Organic amendment also improved soil properties and fruit yields in fruit orchards. In intensive vegetable growing areas, soil available phosphate was very high due to high phosphate fertilization, therefore reducing P fertilizer application is a strategy to both save P resources and reduce production costs for farmers. Further studies on the approaches for sustainability in agriculture and aquaculture production in the MD are needed to adapt to climate change.