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Highlights • A meta-analysis on GHG emissions and rice yield as affected by water management. • Non-continuous flooding reduced CH 4 emissions by 53%, but it increased N 2 O emissions by 105%. • Severe soil drying reduced rice yield, but mild soil drying did not. • Non-continuous flooding reduced GWP by 44% and yield-scaled GWP by 42%. • IPCC underestimates the impact of multiple (i.e. ≥ 2) drying events on CH 4 emissions. Abstract Rice is a main staple food for roughly half of the world's population, but rice agriculture is also a main source of anthropogenic greenhouse gas (GHG) emissions. Many studies have reported that water management (e.g. alternate wetting and drying, intermittent irrigation, mid-season drain, aerobic rice) affects rice yields and methane (CH 4) and nitrous oxide (N 2 O) emissions from rice paddies. However, these studies span a variety of practices and vary in experimental design and results, making it difficult to determine their global response from individual experiments. Here we conducted a meta-analysis using 201 paired observations from 52 studies to assess the effects of water management practices on GHG emissions and rice yield. Overall, compared to continuous flooding, non-continuous flooding practices reduced CH 4 emissions by 53%, increased N 2 O emissions by 105%, and decreased yield by 3.6%. Importantly, N 2 O emissions were low, contributing, on average, 12% to the combined global warming potential (GWP; CH 4 + N 2 O). As a result, non-continuous flooding reduced GWP (-44%) and yield-scaled GWP (-42%). However, non-continuous flooding practices stimulated N 2 O emissions to a greater degree in soils with high organic carbon or with manure additions. The reduction in CH 4 emissions increased with the number of drying events, soil drying severity, and the number of unflooded days. Currently, Intergovernmental Panel on Climate Change (IPCC) scaling factors for single and multiple (≥ 2) drying events are 0.6 and 0.52. Based on this analysis using actual side-by- side field studies, we suggest changing these to 0.67 for a single event and 0.36 for multiple events. [ABSTRACT FROM AUTHOR]

Abstract: Crop model projections and historical data analyses have shown that global warming may cause serious decrease in crop productivity, however, many uncertainities remain on the impact quantification due to the unclear understanding of actual crop response. Therefore, we performed a three-year field warming experiment with free air temperature increase (FATI) facility to investigate the actual response of midseason rice growth in East China. There were four treatments (AW: all-day warming; DW: daytime warming; NW: nighttime warming; CK: ambient control) with three replicates. This FATI facility presented a good simulation of the local air temperature pattern with an increase in the daily mean temperature of about 1.1–2.0°C during rice whole growth duration compared to the ambient control. Warming shortened the pre-heading phase respectively by 3.3d, 1.7d and 2.0d in the AW, DW and NW plots, while the post-heading phase stayed almost unchanged. During the three years, warming slightly decreased the aboveground biomass by an average of 9.1%, 10.3% and 3.3%, and the grain yield by an average of 0.9%, 6.4% and 6.1% in the AW, DW and NW plots, respectively. Warming tended to decrease rice photosynthesis rate and stimulate the nighttime respiration rate. It also enlarged the flag leaf area and increased its chlorophyll content. No significant difference and interaction in the actual response of rice growth were found between the warming regimes. The above evidences suggest that the expected warming less than 2.0°C may not cause significant decrease in rice productivity in East China. [Copyright &y& Elsevier]