19 - Nitrogen Assessment and Management in Brackish-Water Aquaculture of India

Abstract

The synthesis of information on nitrogen dynamics in aquaculture ponds and coastal ecosystems indicates uncertainties in our understanding. Coastal water bodies receive external input of reactive N (Nr) from brackish-water aquaculture (BWA) ponds utilizing natural resources, such as land, water, and biological resources such as seed and feed. BWA pond soils contain comparatively lesser amount of available nitrogen compared to freshwater ponds. Nitrogen limits the primary productivity of ponds, and transformation of nutrients in pond soil depends considerably on the widely fluctuating water salinities during different seasons of the year. Nitrogen budgeting studies showed that only 25–30% of the feed N is recovered in the cultured animals at harvest and is the major contributor for deterioration of water quality through discharge water and lost to atmosphere as volatilized ammonia and production of greenhouse gas N2O. Improving N use efficiency through better management practices can reduce N2O emissions. Research on improvements in nitrogen utilization, data on species-level efficiency, and simultaneous reduction of nitrogen loss is highly desirable for sustainable aquaculture development.