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TECHNICAL REPORTS

Dependence of Ammonia Emissions From Housing on the Time Cattle Spent Inside

^a Institute of Grassland and Environmental Research, North Wyke Research Station, Okehampton, Devon, EX20 2SB, UK
^b ADAS Research, Wergs Road, Wolverhampton WV6 8TQ, UK

^* Corresponding author (sarah.gilhespy{at}bbsrc.ac.uk)

Received for publication August 2, 2005. Buildings housing cattle contribute 19% (42 kt NH₃–N yr^–1) of total UK ammonia (NH₃) emissions. In the UK there is not usually an abrupt switch from cattle being kept inside to when they are turned out to graze 24 h a day. Moreover, during the summer dairy cows return to the farm twice a day to be milked and may spend some time inside buildings. Hence, there is uncertainty over the treatment of the transitional and summer periods when inventorying NH₃ emissions. The aim of this study was to measure, under controlled and replicated conditions, the relationship between the number of hours cattle spend in buildings and the NH₃ emissions from those buildings. Our results indicate that NH₃ emissions decrease as the proportion of the day cattle spend in the buildings decreases, although the trend is not linear. Daily emission rates from cattle housed for 2 h ranged from 1.6 to 6.2 g NH₃–N lu^–1 whereas emissions from cattle housed for 24 h ranged from 8.1 to 24.1 g NH₃–N lu^–1. To significantly reduce NH₃ emissions in comparison to those from buildings where cattle are housed for 24 h, the occupancy would have to be reduced to no more than 6 h each day. Thus, the strategy of extending the grazing season by allowing cattle to graze for c. 4 to 12 h during the winter is unlikely to reduce NH₃ emissions from buildings or overall.

Abbreviations: TAN, total ammoniacal-N • lu, livestock unit (500-kg live weight)