Heavy Rainfall Stimulates More N2O Emissions from Wheat Fields During Basal and Overwintering Fertilization Phases

Extreme precipitation events have become increasingly prevalent globally. Runoff and leaching losses of nitrogen (N) are commonly observed after heavy rainfall, while post-rainfall N losses, particularly nitrous oxide (N2O) emissions, are often overlooked. In this study, a field-simulated rainfall experiment was conducted under two conditions: with (CF) and without (CK) N fertilizer application, to examine the impact of precipitation on post-rainfall N2O emissions over a continuous 10-day period. Heavy rainfall (90 mm) was simulated on the 7th day after fertilization at basal (BFS), overwintering (WFS), and jointing (JFS) stages, based on CF treatment fertilization timing. Results showed a significant increase in soil nitrate N content after fertilization (F), leading to elevated N loss through runoff and leaching due to precipitation (P). Both P and F had significant effects on post-rainfall N2O emissions, though their interaction was not statistically significant. Average N2O emission intensity (NEI) in the CF treatment increased by 72.73 % relative to CK control, attributed to fertilization. Additionally, rainfall substantially intensified NEI during BFS and WFS stages (P<0.05 or 0.001), while it tended to decrease NEI during the JFS stage. Consequently, average NEI under rainfall conditions doubled compared to no-rainfall controls. Correlation analysis indicated that N2O emissions were primarily influenced by soil nitrate N content, nirS gene abundance, and denitrification potential in middle-lower layers (5-15 cm). Overall, the stimulating effect of heavy rainfall in the early growing period on post-rainfall N2O emissions in fertilized wheat fields warrants attention.