Using weather forecasts to avoid major emission events of N2O in connection with manure application

Choosing the appropriate timing of fertilisation is one of the primary managerial strategies to avoid emissions of nitrous oxide. To minimise odour nuisance and ammonia volatilisation, farmers are advised to apply pig slurry (PS) before light rainfall events. However, application of manure at the time of heavy rain events can pose a high risk of nitrous oxide (N2O) emissions, and analysing weather forecasts to avoid this could be important to mitigate emissions. A controlled field experiment was conducted to assess the effect of rainfall around the time of PS fertilisation on soil N2O emissions. The main findings were: 1) Rainfall treatments showed slight peaks in N2O emissions up to 3.9 mg N2O-N ha−1 day−1 after a rain event, and cumulative N2O emissions were numerically higher compared to the treatment without rainfall, suggesting a higher risk when manure application coincides with rainfall. 2) However, the short duration of elevated soil water content with more than 80 % water-filled pore space (WFPS) lasting only a few days after a rain event, may not have been sufficient to create anoxic conditions necessary for substantial N2O emissions from PS. This study's simulated rain approach can be used for future manipulative studies of field sites to further investigate mitigation options related to rainfall to inform best practices for fertiliser application in relation to weather forecasts.