Global N₂O Emissions From Cropland Driven by Nitrogen Addition and Environmental Factors: Comparison and Uncertainty Analysis

Abstract

Human activities have caused considerable perturbations of the nitrogen (N) cycle, leading to a~20% increase in the concentration of atmospheric nitrous oxide (N 2 O) since the preindustrial era. While substantial efforts have been made to quantify global and regional N 2 O emissions from cropland, there is large uncertainty regarding how climate change and variability have altered net N 2 O fluxes at annual and decadal time scales. Herein, we applied a process-based dynamic land ecosystem model (DLEM) to estimate global N 2 O emissions from cropland driven by synthetic N fertilizer application and multiple environmental factors (i.e., elevated CO 2 , atmospheric N deposition, and climate change). We estimate that global cropland N 2 O emissions increased by 180% (from 1.1 ± 0.2 to 3.3 ± 0.1 Tg N year −1 ; mean ±1 standard deviation) during 1961-2014. Synthetic N fertilizer applications accounted for~70% of total emissions during 2000-2014. At the regional scale, Europe and North America were two leading regions for N 2 O emissions in the 1960s. However, East Asia became the largest emitter after the 1990s. Compared with estimates based on linear and nonlinear emission factors, our results were 150% and 186% larger, respectively, at the global scale during 2000-2014. Our higher estimates of N 2 O emissions could be attributable to the legacy effect from previous N addition to cropland as well as the interactive effect of N addition and climate change. To reduce future cropland N 2 O emissions, effective mitigation strategies should be implemented in regions that have received high levels of N fertilizer and regions that would be more vulnerable to future climate change.

Magnitude and Uncertainty of Nitrous Oxide Emissions From North America Based on Bottom‐Up and Top‐Down Approaches: Informing Future Research and National Inventories

“…For instance, R. Xu et al. (2020) found evident spatial heterogeneity in the three available datasets of N fertilizer use rate, resulting in divergent spatiotemporal patterns of modeled cropland N 2 O fluxes by DLEM. Third, there exists large divergence among NMIP models in attributing soil N 2 O emissions to different driving factors.…”

Global evaluation of inhibitor impacts on ammonia and nitrous oxide emissions from agricultural soils: A meta‐analysis

“…The terrestrial emissions of trace gases such as ammonia (NH 3 ) and nitrous oxide (N 2 O) have drastically increased in the past decades, largely attributed to agricultural activities including increasing nitrogen (N) fertilization in croplands and intensive livestock farming in grasslands (Aneja et al, 2009; Damme et al, 2014; Xu et al, 2020). The deposition of NH 3 induces a cascade of negative environmental perturbations such as soil acidification and eutrophication (Bobbink et al, 2010; Roy et al, 2014).…”

“…The terrestrial emissions of trace gases such as ammonia (NH 3 ) and nitrous oxide (N 2 O) have drastically increased in the past decades, largely attributed to agricultural activities including increasing nitrogen (N) fertilization in croplands and intensive livestock farming in grasslands (Aneja et al, 2009;Damme et al, 2014;Xu et al, 2020).…”

Soil Nitrogen Transformations Respond Diversely to Multiple Levels of Nitrogen Addition in a Tibetan Alpine Steppe

“…However, the direction and magnitude of changes in ecosystem functions might partly depend on the responses of soil N transformations (e.g., N mineralization, nitrification and microbial immobilization) to continuous N input. Increased nitrification rate could accelerate soil N loss because NO 3 − ‐N was vulnerable to be lost via leaching and gas emissions (Isobe et al., 2018; Xu et al., 2020). Enhanced microbial immobilization rate, in contrast, could facilitate soil N retention through microbial assimilation (Li et al., 2021; Mao et al., 2019).…”