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Phosphorus and Nitrogen Budgets for Inland, Saline Water Shrimp Ponds in Alabama

Wei Sun and Claude E Boyd

Phosphorus and nitrogen budgets were prepared for ponds at an inland low-salinity shrimp farm in the Black land Prairie region of Alabama. The study was conducted during the first crop in three newly constructed ponds that had never before contained water. The main input of phosphorus and nitrogen was feed and averaged 47 kg/ha and 208.5 kg/ha, respectively. These inputs respectively accounted for 98.9% and 95.5% of total input for phosphorus and nitrogen; other inputs of phosphorus and nitrogen were post larvae, well water, rainfall and runoff, that combined, averaged 0.5 kg/ha and 9.8 kg/ha, respectively. The major output of phosphorus and nitrogen was shrimp harvest that averaged 5.2 kg/ha for phosphorus and 45.7 kg/ha for nitrogen. Only 10.9% of phosphorus and 21% of nitrogen applied in feed were incorporated into shrimp. Other losses of phosphorus and nitrogen were water outflows (seepage and harvest effluent) that accounted for 3.2 kg/ha for phosphorus and 7.8 kg/ha for nitrogen. The difference between the inputs and outputs of phosphorus is thought to represent adsorption by bottom soils. For nitrogen, the discrepancy between input and output apparently was caused by accumulation of organic nitrogen in bottom soil, denitrification and NH3 volatilization.