Additive effects dominate phosphorus offsetting positive effects of nitrogen to terrestrial ecosystem N2O emissions

• N addition increases N 2 O emissions by 122.5%, while P addition reduces them by 16.3 %. • N and P addition drive additive N 2 O effects, not synergistic or antagonistic. • Ecosystem type modulates N and P effects on N 2 O emissions globally. • Antagonistic effects of N and P on N 2 O emissions are exclusive to cropland. Nitrous oxide (N 2 O) emissions from terrestrial ecosystem significantly contribute to global warming and are substantially influenced by nitrogen (N) and phosphorus (P) additions. Yet, the precise interactive effects of N and P addition on N 2 O emissions remain poorly understood. We synthesized 714 observations from 198 publications to evaluate the response of N 2 O emission rates to N and P addition across terrestrial ecosystems. Our results revealed that N and nitrogen + phosphorus (NP) additions increased N 2 O emissions by 122.5 % and 64.5 %, respectively. In contrast, P addition alone reduced N 2 O emissions by 16.3 %. Akaike mixed model weights identified ecosystem type as a factor commonly influencing N 2 O emissions under added N, P, and NP. Predominantly additive interactions between N and P additions drove N 2 O emission responses, rather than synergistic or antagonistic interactions. Antagonistic effects were exclusively observed in cropland ecosystems. Collectively, these findings demonstrate that N and P addition exhibit independent and additive effects on N 2 O emissions in terrestrial ecosystems. This implies that the stimulatory effect of N and the inhibitory effect of P can be quantitatively combined to improve predictions of N 2 O emissions under nutrient enrichment scenarios.