MEASURING AMMONIA VOLATILIZATION BY THE A ERODYNAMIC METHOD UNDER ACTUAL FIELD CONDITIONS

Up to now nitrogen losses through ammonia volatilization after organic fertilization have only been studied over small plots and with time-s cales greater than several hours. In this study, a dairy cattle slurry was spread over a 2 ha field in Brittany. Ammonia emissions were moni tored with micrometeorological methods, aerodynamic and mars balance m ethods. They made possible a direct estimate of ammonia emissions unde r actual field conditions. Comparison with an independent indirect met hod, the labelled N recovery method, pointed out the interest of estim ating emissions under real agricultural practices, and with a direct m easurement The aerodynamic method has moreover the advantage of measur ing hourly fluxes, which allows better understanding of the influence of environmental factors on volatilization.