Ammonia volatilization from freshwater fish ponds

This study evaluated ammonia (NH₃) emissions to the atmosphere from fishpond waters and uneaten, floating feed. Channel catfish (Ictalurus punctatus) were stocked at 550 pond^-1 in four, 400-m² ponds at the Auburn University Fisheries Research (AUFRU), Auburn, AL, on 30 May 1997. Feed (28% crude protein), prepared as floating pellets was applied daily. Ponds were harvested between 7 and 9 Oct. 1997. Ammonia traps were placed in ponds on a weather vane sampler. Ammonia emissions were measured from June through September 1997. In addition, NH₃ volatilization from wetted catfish feed was measured in a laboratory experiment. Average NH₃ volatilization from ponds ranged between 8.8 to 71.0 mg NH₃-N m² d^-1, and averaged 3.75% of total NH₃ nitrogen (TAN) concentration in water. Positive linear correlations were found between the amount of feed applied and TAN concentration in the water and between TAN and NH₃ volatilization. Volatilization from wetted feed was not a major NH₃ loss to the atmosphere. The study suggested that 24 kg ha^{- 1} of N were lost to the atmosphere between 23 June 1997 and 30 Sept. 1997 from ponds into which 158 kg ha^-1 N were applied. In the USA, there are about 66 000 ha of catfish ponds. Extrapolation from this study suggests that 1584 t of NH₃ could volatilize from catfish ponds each summer.