Ammonia volatilization from freshwater fish ponds

NH₃ traps placed in ponds on a weather vane sampler were used to measure NH₃ emissions from June to September 1997 to study such emissions to the atmosphere from fishpond waters and uneaten, floating feed. Channel catfish (Ictalurus punctatus) were stocked at 500/pond in four 400 sq m ponds at the Auburn University Fisheries Research, Auburn, AL, on 5/30/97, and feed (28% crude protein), prepared as floating pellets, was applied daily. Ponds were harvested 10/7-9/97. Also, NH₃ volatilization from wetted catfish feed was measured in a laboratory experiment. Average NH₃ volatilization in ponds was 8.8-71.0 mg NH₃-N sq m/day, and averaged 3.75% of total NH₃ nitrogen (TAN) level in water. Positive linear correlations were found between feed quantity and TAN concentration in the water and between TAN and NH₃ volatilization. Volatilization from wetted feed was not a key loss to the atmosphere. It was suggested that 24 kg/ha N were lost to the atmosphere from 6/23/97 to 9/30/97 from ponds in which 158 kg/ha N were applied. Extrapolation from this work suggested that 1584 ton NH₃ could volatilize from catfish ponds each summer.