Optimizing the sowing window for direct-seeded rice (Oryza sativa L.) considering high yield and methane emissions in Central China

Abstract

CONTEXTElevated temperatures have had many adverse effects on rice (Oryza sativa L.) production. Methane (CH4) emissions from rice paddy fields can further increase global temperatures and in turn affect rice production. Many adaptations, such as shifting the sowing date, can help rice plants avoid the influences of high temperatures and reduce CH4 emissions by shortening the rice-growth duration. OBJECTIVEThis study explored the optimal sowing window for direct-seeded rice with the highest yield and lowest CH4 emissions. METHODSHere, we used the calibrated Crop Environment Resource Synthesis (CERES)-Rice model and a widely used CH4 estimation equation to determine the optimal sowing window under historical and future scenarios in Hubei Province, China. This province was divided into four zones, and three rice cultivars were selected. Numerical simulations were conducted for sowing dates at three-day intervals across the entire potential sowing window for each cultivar and zone. The simulated rice yields and estimated CH4 emissions for all sowing dates were compared to determine the optimal sowing window. RESULTS AND CONCLUSIONSOur results indicated that due to the lower emergence rate caused by low temperatures during the early stage of the potential sowing window, rice yield gradually increased with sowing date delay and tended to be stable, while CH4 emissions exhibited the opposite pattern. In this study, the optimal sowing window was determined to be when the lowest CH4 emissions and highest rice yields occurred simultaneously. Under heat stress, these two kinds of events often did not overlap, and the optimal sowing window was defined by the highest yields only. In addition, the current sowing date was mostly within the optimal sowing window during the historical period. The optimal sowing window appeared later under future scenarios than in the historical period, suggesting that the sowing date should be delayed in the future. SIGNIFICANCERice plants cultivated in optimal sowing windows can produce high yields and emit the least CH4. This study provides a better understanding of the effects of shifting the sowing date on food security and greenhouse gas emissions, ensuring sustainable rice production.