Ammonia volatilization from tall fescue pastures fertilized with broiler litter

Ammonia (NH₃) volatilization is an important and often overlooked component of the N budget in many agricultural systems involving land application of animal wastes. We quantified the amount and rate of NH₃ volatilization from broiler litter applied to established tall rescue pastures (Festuca arundinacea Schreb.). Study sites were located in the Coastal Plain (Alabama), Piedmont (Georgia), and Cumberland Plateau (Tennessee) Major Land Resource Areas (MLRA) of the southeast USA. Litter was applied to supply 70 kg of available N ha^-1 based on equations developed by the U.S. Department of Agriculture (USDA) and the U.S. Environmental Protection Agency (USEPA). Measurements of NH₃-N volatilization were taken using a micrometeorological, field-scale technique for 14 d immediately following litter application during the spring of 1995 and 1996. Ammonia flux for the study period ranged from 3.7 to 10.6 kg N ha^-1 in 1995, and from 3.5 to 8.0 kg N ha^-1 in 1996. A sharp increase in volatilization rate occurred 1 to 3 d after litter application at all three sites in both years. However, volatilization rates rapidly decreased to normal levels within 10 d. Volatilization rates peaked at 2.8 kg NH₃-N ha^-1 d^-1 in 1995 and 2.2 kg NH₃-N ha^-1 d^-1 in 1996. Overall, N losses due to NH₃ volatilization were less than expected based on previous studies. These data suggest that for these conditions, NH₃ volatilization was a relatively minor component of the N cycle and was not a major pathway for N loss.