コーンベルトの土壌が凍結、融解する際に排出される亜酸化窒素が急増(Nitrous oxide emissions from Corn Belt soils spike when soils freeze, thaw)

2022-08-23 イリノイ大学アーバナ・シャンペーン校

＜関連情報＞

• https://aces.illinois.edu/news/nitrous-oxide-emissions-corn-belt-soils-spike-when-soils-freeze-thaw
• https://www.sciencedirect.com/science/article/abs/pii/S0168192322002957

米国中西部における非生育期のN2O排出の異なる駆動メカニズムによる空間特異的な緩和戦略の必要性 Distinct driving mechanisms of non-growing season N2O emissions call for spatial-specific mitigation strategies in the US Midwest

Yufeng Yang,Licheng Liu,Wang Zhou,Kaiyu Guan,Jinyun Tang,Taegon Kim,Robert F.Grant,Bin Peng,Peng Zhu,Ziyi Li,Timothy J.Griffis,Zhenong Jin
Agricultural and Forest Meteorology  Available online: 3 August 2022
DOI:https://doi.org/10.1016/j.agrformet.2022.109108

Highlights

•NGS N₂O emissions accounted for 6–60% of the annual fluxes in the US Midwest.

•NGS N₂O emissions were controlled by distinct drivers in the southeast and northwest.

•NGS precipitation 300 mm line was found to be a threshold for the divergence.

•Intensive freezing effect is the dominant driver of NGS N₂O emissions in the southeast.

•The thawing effect is the dominant driver of NGS N₂O emissions in the northwest.

Abstract

Agricultural N₂O emission is a growing concern for climate change. Recent field evidence suggests that non-growing seasons (NGS) may contribute one-third to half of the annual N₂O emissions, but implications on management adaptations remain unclear. Here we used an advanced process-based model, ecosys, to investigate the magnitude and drivers of NGS N₂O emissions from the US Midwest. Results showed that simulated NGS N₂O emissions accounted for 6–60% of the annual fluxes under continuous corn systems, peaking in counties with NGS precipitation (P_NGS) around 300 mm. Divergent patterns of spatial-temporal correlations between NGS N₂O emissions and environmental variables were shown in the southeast (P_NGS > 300 mm) and the northwest (P_NGS < 300 mm) of the study area by simulations. Causal analysis indicates that more intensive freezing caused by decreased air temperature (T_a) is the dominant driver that leads to NGS N₂O emissions increasing within the southeast of the study area, while increased P_NGS and increased T_a cooperatively result in soil moisture decreasing at soil thaws that enhances NGS N₂O production within the northwest of the study area. Scenario simulations suggest that annual N₂O emissions in the US Midwest are likely to reduce under climate change primarily due to the reduction of NGS N₂O emissions. Our estimates on monetized social benefits inform the necessity to implement spatial-specific mitigation strategies, i.e. determining fertilizer timing and use of nitrification inhibitors (NI). Spring fertilizer application is more beneficial than fall fertilizer application for most counties, however, the latter can bring extra benefits to some counties in the west of the study area. Introducing NI with either spring or fall applications can greatly increase social benefits by reducing N₂O emissions and N leaching. This study addresses possibly effective adaptations by providing seasonal- and spatial-explicit mitigation potentials.