Slurry acidification outperformed injection as an ammonia emission-reducing technique in boreal grass cultivation

Abstract

Ammonia (NH3) constitutes the single largest loss of manure nitrogen (N), making measures targeted at reducing its emissions meaningful for the environment and the overall efficiency of manure N use. In this study, the performance of two emission-reducing techniques, acidification and injection, were studied in a field experiment with grass ley over two growing seasons. Emissions of NH3, crop growth, and N use efficiency were determined from plots fertilized with cattle slurry either band spread, injected or band spread after acidification. The approximate cumulative NH3 losses from the plots with band-spread untreated slurry amounted to about 22 kg NH3-N ha−1 over the observation periods in 2017 and 10 kg NH3-N ha−1 in 2018. The injection and acidification reduced the estimated cumulative NH3 emissions by 43 and 95% respectively in 2018, and both by 97% in 2017. In 2017, the emission-reducing techniques had no impacts on crop growth, but in 2018, acidification increased dry matter yield by 29% and apparent N recovery by 65% compared with band-spread untreated slurry. According to the current results, acidification consistently produced the lowest NH3 emissions and a discernible positive yield effect. It can therefore be recommended instead of injection for reducing NH3 emissions in boreal grass cultivation.