Ammonia and nitrous oxide emissions following field-application of manure: state of the art measurements in the Netherlands

Manure application to grassland and arable land is an important source of ammonia and nitrous oxide losses. For both gasses, national and international policies have been developed with the objective of reducing the emissions. Since the early 1990s, measurements have been carried out in The Netherlands to assess the gaseous losses from manure application, especially for ammonia. Measurements of nitrous oxide emissions are relatively scarce. This paper presents the results of these measurements with the objective of providing an updated quantification of the effect of techniques for application and incorporation of manure, and to assess influencing factors. The manure application techniques differ in their spreading or placement of the manure onto the grass or soil surface or into the soil. The following techniques are treated in this paper: surface spreading, narrow-band application, shallow injection with open slots on grassland, and surface spreading, surface incorporation, deep placement on arable land. Low emission techniques such as narrow band application, shallow injection, incorporation or injection on arable land show a significant reduction of ammonia emission compared to surface spreading. On grassland, average emission factors (% of total ammonium nitrogen) were 74% for surface spreading and 16% for shallow injection. On arable land, the emission factors were 69% for surface spreading and 2% for deep placement. However, the nitrous oxide emission factor from manure applied with low ammonia emissions techniques is higher than the emission factor for surface applied manures. In a whole farm context, the higher nitrous oxide emission with shallow injection is partly offset directly by reduced emissions from fertiliser savings and indirectly from lower ammonia losses.