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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]

Arbuscular mycorrhizal fungi (AMF), which form symbiotic associations with 80% of land plants, provide host plants with soil phosphorus (P) and nitrogen (N) in exchange for carbon. The AMF often reduces nitrous oxide (N 2 O) emissions from soils with non-legume plants, as they acquire N from soils to plants. However, the effect of AMF on soil N 2 O emissions is still unknown in the legume system, a major source of this potent greenhouse gas. Therefore, we conducted the field and pot experiments to investigate the effects of AMF on plant growth and soil N 2 O emissions in legume systems. The results showed that AMF significantly increased soil N 2 O emissions from soils with soybean by 39% in the field experiment and by 63% in the pot experiment. The AMF significantly enhanced the root biomass, aboveground biomass, grain yield, plant N uptake, plant P uptake, and the nodule numbers. The AMF increased soil extractable N concentrations and DOC concentrations, but reduced soil available P concentrations. The AMF stimulated the N 2 O-producing microbes (nirS - and nirK -type) whereas they did not affect the N 2 O-consuming (nosZ -type) denitrifiers. The AMF reduced the yield-scaled N 2 O emissions in the field experiment and increased the net ecosystem economic budget. Our findings indicate that AMF increase soil N 2 O emissions from legume system through enhancing P acquisition for biological N 2 fixation and suggest that AMF benefit crop production for higher-yield with less N 2 O emissions. • The first study of N 2 O emissions from legume systems as affected by AMF. • AMF significantly increased soybean yields and soil N 2 O emissions in soybean systems. • AMF increased N 2 O-producing microbes mainly due to higher biological N 2 fixation. • AMF increased net ecosystem economic budget. [ABSTRACT FROM AUTHOR]