Impact of elevated temperatures on greenhouse gas emissions in rice systems: interaction with straw incorporation studied in a growth chamber experiment

Abstract

Two pot experiments in a “walk-in” growth chamber with controlled day and night temperatures were conducted to investigate the influence of elevated temperatures along with rice straw incorporation on methane (CH4) and nitrous oxide (N2O) emissions as well as rice yield. Three temperature regimes–29/25, 32/25, and 35/30 °C (Exp. I) and 29/22, 32/25, and 35/28 °C (Exp. II), representing daily maxima/minima were used in the study. Two amounts of rice straw (0 and 6 t ha−1) were applied with four replications in each temperature regime. CH4 and N2O emissions as well as soil redox potential (Eh) were monitored weekly throughout the rice-growing period. Elevated temperatures increased CH4 emission rates, with a more pronounced effect from flowering to maturity. The increase in emissions was further enhanced by incorporation of rice straw. A decrease in soil Eh to <−100 mV and CH4 emissions was observed early in rice straw–incorporated pots while the soil without straw did not reach negative Eh levels (Exp. I) or showed a delayed decrease (Exp. II). Moreover, soil with high organic C (Exp. II) had higher CH4 emissions. In contrast to CH4 emissions, N2O emissions were negligible during the rice-growing season. The global warming potential (GWP) was highest at high temperature with rice straw incorporation compared with low temperature without rice straw. On the other hand, the high temperature significantly increased spikelet sterility and reduced grain yield (p < 0.05). Elevated temperature increased GWP while decreased rice yield. This suggests that global warming may result in a double negative effect: higher emissions and lower yields.