Dynamics of ammonia volatilisation measured by eddy covariance during slurry spreading in north Italy

During spring 2009 and 2011, dairy slurry was spread in two intensively managed agricultural fields in northern Italy. Ammonia (NH3) fluxes have been measured using the eddy covariance method during the slurry application and the following incorporation into the soil. The measurement system was equipped with a fast sensor for NH3 concentration measurements based on Tunable Infrared Laser Differential Absorption Spectrometry. NH3 volatilisation has been monitored in continuous until the end of the process for both experimental trials, confirming the rapidity of the NH3 losses when slurry is spread on the field. Within 24 hours from the application the volatilisation suddenly decreases, stopping after slurry incorporation. The maximum NH3 emission levels were 138.3 and 245.5 ?g m-2 s-1 and the total losses of NH4+-N were 19.4% and 28.5% after 7 days following the spreading for the first and the second trial, respectively. To explain these observed differences, the relationship between NH3 losses and meteorological conditions has been investigated. In particular, rain during the 2009 trial caused a significant reduction in emissions with respect to the 2011 one, which was characterised by higher air temperatures.