An agro-ecological evaluation of aquaculture integration into farming systems of the Mekong Delta

This study compared ecological sustainability of Integrated Agriculture-Aquaculture (IAA) systems with different forms and intensity of aquaculture integration in the Mekong Delta of Vietnam: orchard-based and low-input fish (O-LF); rice-based and medium-input fish (R-MF); and rice-based and high-input fish (R-HF) farming systems. We monitored eleven IAA-farms from September 2002 to September 2004. ECOPATH models, based on nitrogen flows, produced 19 agro-ecological system attributes that were reduced to four factors by factor analysis (Productivity-Efficiency; Diversity; Maturity; Aquaculture Integration), explaining 76.8% of total variance. In general, R-HF farms scored higher on Productivity-Efficiency, R-MF on Diversity, and O-LF farms on Maturity than the other systems. Within all three farm systems, variability among farms was high, caused by differences in land use, financial and crop disease constraints, market possibilities, and family conditions. The ponds and ditches served as a trap to capture nutrients and re-distribute them to other parts of the farms. Despite the differences in intensity of fish keeping between the three systems, the fish ponds in the rice-based systems and fish in ditches in the orchard-based system contributed to the same extent to the nutrient supply of other components. Differences in nutrient efficiency among the farming systems were caused primarily by the inefficient orchard and rice components on the O-LF farms. Fertilizers were often applied in excess. Nutrient use efficiency should be improved through proper application of fertilizers and promotion of the traditional integration practices.