Responses of yield, CH4 and N2O emissions to elevated atmospheric temperature and CO2 concentration in a double rice cropping system

Abstract Elevated atmospheric temperature and CO 2 concentration ([CO 2 ]) can strongly affect yield, CH 4 and N 2 O emissions in rice paddies. However, understanding of their response to combined temperature and [CO 2 ] increases under field conditions is still limited. To study this issue further, an open-top chamber (OTC) platform was set up to simulate two levels of atmospheric temperature (ambient and 2 °C elevated) and two levels of [CO 2 ] (ambient and 60 ppm elevated) during two rotations of double rice, including twelve independent OTCs and three un-chambered open field sites as trial plots. The experimental site is located in Hubei Province, Central China, which has a subtropical monsoon climate. In all four rice seasons, elevated CO 2 induced an increment in grain yield by 11.4–19.7%, while also enhancing CH 4 and N 2 O emissions by 19.8–52.6% and 102.4–140.0%, respectively, compared with ambient temperature and [CO 2 ]. Elevated temperature enhanced CH 4 emissions by 4.4–36.0%, and decreased N 2 O emissions by 1.5–10.5% in three rice seasons. Elevated temperature had different effects on grain yield, with a reduction of 1.0–3.2% in early rice and an increase of 6.3–9.2% in late rice. When elevated temperature and [CO 2 ] were combined, there was a positive interaction that further enhanced CH 4 emissions and yield of late rice, and an offsetting effect on N 2 O emissions and yield of early rice. Over the 2-year experiment, warming and CO 2 enrichment caused an increase of 9.3–44.2% in greenhouse gas intensity, suggesting that more greenhouse gas emissions will be emitted to produce a unit mass of rice under projected global warming. These findings provide initial data for the estimation of CH 4 and N 2 O emissions under elevated temperature and [CO 2 ] in double rice cropping system, and stress the need for effective management practices that promote rice yield while reducing greenhouse gas emissions.