NH3 emissions from land application of manures and N-fertilisers: a review of the Italian literature
Résumé
One of the major pathways of nitrogen (N) loss from agricultural systems is represented by ammonia (NH3) volatilisation. At the global scale, soil application of livestock manures and N-fertilisers represents one of the main sources of this atmospheric pollutant. A literature review was carried out over 78 field trials in order to collect and summarise the research on NH3 emission from land application of manure and N-fertiliser in Italy. Data availability proved to be still limited in terms of coverage of the national territory, representativeness of the measurement method used, type of fertiliser and application strategies explored. Coherently with their importance as NH3 emission sources, livestock manures and urea have been the most assessed materials. From a methodological perspective, the measurements were mostly performed on non-representative scales and the collected data present large weaknesses due to lacking information on the variables that regulate losses of this gas to the atmosphere. The measured emission factors (EFs) have proved to be consistent with the ranges reported by international literature, showing appreciable differences in magnitude among manures and synthetic N-fertilisers and among different field management practices. This is supported by the ALFAM model estimation, which has also shown a strong dependency upon the simulated measurement methods. The reviewed EFs for the different type of fertilisers were compared with the values used by the European and Italian emission inventories. Despite the agreement between these values, our analysis emphasized that the reviewed EFs cannot be regarded as representative for the national territory, mainly because of inconsistencies in the measurement methods.