The effect on N2O emissions of storage conditions and rapid incorporation of pig and cattle farmyard manure into tillage land

The use of additional straw in animal housing and the rapid incorporation of manure into tillage land have been recognised as potential techniques to reduce ammonia (NH3) emissions. However, there is the potential for these management practices to increase nitrous oxide (N2O) emissions, i.e. ‘pollution swapping’. Emissions of N2O were monitored during storage of either pig or cattle farmyard manure (FYM) and after application to tillage land at two UK sites. Losses of N2O from conventionally stored pig and cattle FYM were 2.6% and 4.3% of the total-N into store, respectively. Following land spreading, N2O losses ranged from <0.01% to 0.23% of total-N applied for stored manure, but up to 0.86% from fresh pig FYM. There was no significant (probability P>0.05) effect of extra straw use during housing on N2O emissions following the spreading of pig and cattle FYM. No consistent effect of FYM incorporation on N2O emissions was evident suggesting that rapid incorporation (<4 h) can only reduce both N2O and NH3 losses under site specific conditions. The results suggest that strategies to minimise N2O emissions from solid manure management should focus on storage rather than land spreading, and that there is a need to develop integrated manure management strategies to minimise ‘pollution swapping’.