Legacy effects cause systematic underestimation of N2O emission factors
Haoyu Qian, Zhengqi Yuan, Nana Chen, Xiangcheng Zhu, Shan Huang, Changying Lu, Kailou Liu, Feng Zhou, Pete Smith, Hanqin Tian, Qiang Xü, Jianwen Zou, Shuwei Liu, Zhenwei Song, Weijian Zhang, Songhan Wang, Zhenghui Liu, Ganghua Li, Ziyin Shang, Yanfeng Ding, Kees Jan van Groenigen, Yu Jiang
Abstract
Agricultural soils contribute ~52% of global anthropogenic nitrous oxide (N2O) emissions, predominantly from nitrogen (N) fertilizer use. Global N2O emission factors (EFs), estimated using IPCC Tier 1 methodologies, largely rely on short-term field measurements that ignore legacy effects of historic N fertilization. Here we show, through data synthesis and experiments, that EFs increase over time. Historic N addition increases soil N availability, lowers soil pH, and stimulates the abundance of N2O producing microorganisms and N2O emissions in control plots, causing underestimates of EFs in short-term experiments. Accounting for this legacy effect, we estimate that global EFs and annual fertilizer-induced N2O emissions of cropland are 1.9% and 2.1 Tg N2O-N yr−1, respectively, both ~110% higher than IPCC estimates. Our findings highlight the significance of legacy effects on N2O emissions, emphasize the importance of long-term experiments for accurate N2O emission estimates, and underscore the need for mitigation practices to reduce N2O emissions. N fertilization increases N2O emissions over time by raising soil N availability, lowering pH, and stimulating N2O-producing microbes, making global fertilizer induced N2O emissions from cropland ~110% higher than IPCC estimates. Peer review information Nature Communications thanks the anonymous reviewer(s) for their contribution to the peer review of this work. A peer review file is available.