Ammonium enrichment in livestock manure driven by ammonia-abatement practices can reduce nitrous oxide emissions

The sustainable development of livestock production faces challenges due to substantial emissions of ammonia and nitrous oxide, contributing to global warming and ecosystem acidification. Over the past four decades, the global spotlight on reducing livestock ammonia emissions, notably within Europe, has resulted in the heightened accumulation of ammonium ions in manure. Remarkably, the repercussions of ammonium accumulation in manure have been relatively overlooked, notwithstanding the potential conversion of accumulated ammonium into nitrous oxide through microbial processes. Here, we delved into the microbial mechanisms responsible for this phenomenon, utilizing 15N labeling and metagenomic sequencing, and assessed its global implications. Our analysis reveals that ammonium accumulation, driven by upstream ammonia mitigation in manure management, can reduce nitrous oxide emissions, due to bacterial denitrifiers' constraints in carbon acquisition. A global assessment suggests that augmenting the accumulation of ammonium in manure by implementing ammonia abatement can unlock substantial benefits in nitrous oxide mitigation.