ABSTRACT
A large proportion of the input of nitrogen (N) that remains unaccounted for during livestock production (up to 90% in grassland systems) is lost through volatilisation of ammonia (NH3) to the atmosphere. Such loss of N has important economic and environmental implications. Particular problems are presented when measuring NH3 loss due to the reactivity of the gas and the dependence of loss on environmental conditions. Unequivocal measurements are obtained only when a micrometeorological method is used. However, recent studies have shown that enclosures suited to experiments using small plots can be designed and operated to have negligible effects on NH3 loss. These enclosures may also be useful in studies of odour emission, a process dependent on factors similar to those affecting NH3 loss. Findings in recent studies of NH3 loss from grassland systems are discussed. These reveal losses of 20 to 30% of the N input during grazing or following land application of slurry. Significant losses of NH3 from winter-housed cattle have also been measured. Methods of reducing NH3 loss, including injection of slurry and the role of zeolites, are discussed.
