Methane and nitrous oxide emissions from a ratoon paddy field in Sichuan Province, China

Ratoon rice (RR) is a practice that involves achieving a second crop originating from the stubble left after the previous main rice crop (MR) harvest. There has been little previous study on methane (CH₄) and nitrous oxide (N₂O) emissions from ratoon paddy fields. A 3‐year field experiment was conducted to simultaneously measure CH₄ and N₂O emissions from traditional single rice (SR) and MR + RR fields in Sichuan Province, southwest China. The CH₄ and N₂O flux peaks were earlier for MR than SR. The CH₄ emissions from the RR season accounted for 8–30% of total emissions from MR + RR. Compared with SR, MR + RR increased seasonal CH₄ emissions by 3–15%. Correlation analysis showed that the seasonal variation of CH₄ fluxes for MR + RR was significantly related to soil redox potential (Eh). The proportion of emitted N₂O from RR to MR + RR was 11–42%. The average cumulative N₂O emissions from MR and MR + RR were increased by 49 and 110% relative to those from SR plots across the 3 years, respectively. The global warming potential (GWP) of RR occupied 10–27% of MR + RR. The GWP of MR + RR was 7–62% higher than that of SR, and it was chiefly dependent on the contribution of CH₄ emissions, despite the greater increase in N₂O emissions. Grain yield in RR was 11–18% of that in MR + RR. MR + RR significantly increased rice yield by 19%, but the yield‐scaled GWP was comparable to SR. Our results suggest that MR + RR increases the amount of CH₄ and N₂O emissions from rice paddy fields and rice grain yield. The yield gaps of ratoon rice would be narrowed by optimizing field management practices to realize sustainable rice production under future climate change conditions. The CH₄ and N₂O emission peaks of ratoon rice were earlier than those of single rice. The CH₄ and N₂O emissions from ratoon rice fields were significantly higher than from single rice fields. Ratoon rice significantly increased yield and GWP compared to single rice. No significant difference in yield‐scaled GWP was observed between ratoon rice and single rice. HIGHLIGHTS: The CH₂ and N₂O emission peaks of ratoon rice were earlier than those of single rice. The CH₄ and N₂O emissions from ratoon rice fields were significantly higher than from single rice fields. Ratoon rice significantly increased yield and GWP compared to single rice. No significant difference in yield‐scaled GWP was observed between ratoon rice and single rice.