Irrigation schedule impact on greenhouse gas mitigation, carbon sequestration, and yield improvement of double rice-cropping systems in southern China

Abstract

The development of water-saving irrigation in paddy soils is crucial because of the increasing demand for water resources. There is a need to improve the understanding of water use strategies that save water and reduce greenhouse gas (GHG) emissions without causing yield losses in double rice-cropping systems. The current study was conducted to examine the net global warming potential (NGWP) and net greenhouse gas intensity (NGHGI) based on the net GHG emissions, including soil organic carbon (SOC) change and indirect emissions (IEs). An experiment was conducted under flood irrigation (FI), shallow irrigation (SI), and intermittent irrigation (II) conditions. The average double rice yields under the SI and II treatments were significantly higher than those under FI by 4.7% and 12.1%, respectively. The SI and II treatments could save 44% and 67% of irrigation water in the entire double-cropping rice-growing season, respectively. However, the SOC sequestration rate over 4 years was not significantly different among the three irrigation regimes. Compared to FI, the annual methane (CH4) emissions decreased by 34% and 45% under SI and II, respectively. In contrast, nitrous oxide (N2O) emissions under SI and II increased by 27% and 50%, respectively. IEs were nearly the same among the three irrigation regimes, with fertilizer use as the top contributor, and followed the order FI > SI > II. The NGWP and NGHGI decreased by 37% and 44%, respectively, under II compared to FI. In conclusion, water-saving irrigation strategies, especially the II practice, are an effective method that can simultaneously achieve great success in saving water, increasing rice production, and reducing GHG emissions.