Soil oxygen depletion and corresponding nitrous oxide production at hot moments in an agricultural soil

• Published in: Environmental pollution (1987) 2022-01, Vol.292, p.118345-118345, Article 118345
• Main Authors: Song, Xiaotong, Wei, Huanhuan, Rees, Robert M., Ju, Xiaotang
• Format: Article
• Language: English
• Subjects: Extreme weather; Management; Nitrous oxide; Oxygen; Rewetting; Spatial-temporal heterogeneity
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2021.118345

Hot moments of nitrous oxide (N2O) emissions induced by interactions between weather and management make a major contribution to annual N2O budgets in agricultural soils. The causes of N2O production during hot moments are not well understood under field conditions, but emerging evidence suggests that short-term fluctuations in soil oxygen (O2) concentration can be critically important. We conducted high time-resolution field observations of O2 and N2O concentrations during hot moments in a dryland agricultural soil in Northern China. Three typical management and weather events, including irrigation (Irr.), fertilization coupled with irrigation (Fer.+Irr.) or with extreme precipitation (Fer.+Pre.), were observed. Soil O2 and N2O concentrations were measured hourly for 24 h immediately following events and measured daily for at least one week before and after the events. Soil moisture, temperature, and mineral N were simultaneously measured. Soil O2 concentrations decreased rapidly within 4 h following irrigation in both the Irr. and Fer.+Irr. events. In the Fer.+Pre. event, soil O2 depletion did not occur immediately following fertilization but began following subsequent continuous rainfall. The soil O2 concentration dropped to as low as 0.2% (with the highest soil N2O concentration of up to 180 ppmv) following the Fer.+Pre. event, but only fell to 11.7% and 13.6% after the Fer.+Irr. and Irr. events, which were associated with soil N2O concentrations of 27 ppmv and 3 ppmv, respectively. During the hot moments of all three events, soil N2O concentrations were negatively correlated with soil O2 concentrations (r = −0.5, P