Significant increases in nitrous oxide emissions under simulated extreme rainfall events and straw amendments from agricultural soil

Pulsed N2O emissions resulting from field management practices (N fertilization addition and straw return) or rainfall events make for a significant proportion of the total annual N2O budget from croplands. However, it remains unclear whether altered rainfall patterns induced by climate change will stimulate the responses of pulsed N2O emissions to various field practices. In this study, we aimed to elucidate the underlying mechanisms driving pulsed N2O emissions in response to extreme rainfall events and examine their interaction with carbon and nitrogen availability. We hypothesized that highly available substrates rapidly induce an anaerobic environment and N2O pulses during extreme rainfall events. A soil column experiment under simulating extreme rainfall events was conducted to investigate the responses of pulsed N2O emissions to three common farming practices: nitrogen fertilization (N), nitrogen fertilization coupled with low straw return (N+LS), and nitrogen fertilization coupled with high straw return (N+HS). We frequently monitored surface emissions and soil concentrations of N2O and CO2, and measured O2, NH4+, NO3 - and DOC concentrations. N and straw amendments together under simulated rainfall events significantly depleted O2, and simultaneously increased pulsed N2O emissions. The N+HS treatment exhibited the highest soil N2O concentration (51.9 mu L L-1) and lowest O2 concentration (4.3 %), along with high soil moisture levels (24.8 %-32.2 %). Correspondingly, the highest cumulative N2O emissions were observed in the N+HS treatment (117.8 mg m- 2), followed by 52.2, 31.9, and 11.0 mg m- 2 for the N+LS, N, and CK treatments, respectively. The promotion of N2O production by highly available substrates confirms our hypothesis. Our work contributes to the refinement of global climate models and field mitigation practices, as pulsed N2O emissions from croplands will increase under future extreme rainfall events owing to climate change.