Ammonia, non-methane volatile organic compounds, and hydrogen sulphide emissions from untreated and acidified pig slurry applied to permanent grassland

Field application of animal slurry contributes to emissions of ammonia (NH 3 ), non-methane volatile organic compounds (NMVOC), and hydrogen sulphide (H 2 S), which are harmful to the environment, and cause odour nuisance. Slurry acidification with sulphuric acid is a proven solution to minimize NH 3 losses; however, lowering the slurry pH could enhance the volatilization of acidic compounds such as volatile fatty acids and H 2 S. While several reliable techniques exist to measure NH 3 emissions, research on NMVOC and H 2 S volatilization from slurry field application is still scarce, and the previous work has relied solely on enclosure measurement methods. This work aimed to measure NH 3 , NMVOC and H 2 S emissions after trailing hose application of untreated pig slurry to permanent grassland using an enclosure (dynamic flux chambers; DFC) and a micrometeorological (backward Lagrangian Stochastic; bLS) method. Moreover, the effect of increasing sulphuric acid dosages on NH 3 and odour emissions was investigated from small replicated plots using DFC. Acidification did not affect NH 3 emissions, while it significantly enhanced volatile fatty acids losses. The low dry matter content of the slurry may have facilitated infiltration into the soil, resulting in low NH 3 fluxes, thereby obscuring the acidification effect on cumulative NH 3 emissions. The DFC and bLS methods yielded similar NH 3 and NMVOC cumulative emissions after untreated slurry application, likely due to comparable air exchange conditions inside the DFC and in the atmospheric boundary layer.