Drainage in paddy systems maintains rice yield and reduces total greenhouse gas emissions on the global scale

Rice sustains the survival of nearly half of humanity, meanwhile, paddy systems are also a significant source of greenhouse gas (GHG) emissions in agriculture. Drainage is widely accepted as a key agricultural management practice (AMP) to reduce CH4 emissions in paddy systems, however, its impact on rice yield and global warming potential (GWP) under different soil and APM conditions remains uncertain. Here, we performed a global meta-analysis of 519 samples from 74 fields in 64 peer-reviewed publications, including measurements of rice yield and at least one of GHG emissions (N2O, CH4, and CO2). Overall, the effects of implementing drainage in paddy systems on yield, N2O emissions, CH4 emissions, CO2 emissions, GWP, and GWP intensity (GWPI) were +0.3% (p = 0.85), +149.9% (p < 0.0001), −57.8% (p < 0.0001), +27.7% (p = 0.12), −44.9% (p < 0.0001), and 57.7% (p < 0.0001), respectively. Drainage in lower total N soils was more capable of maintaining yield (+0.9% vs. −1.4%), and drainage in higher pH and organic carbon soils resulted in greater reductions in CH4 emissions (−46.73% vs. −37.3%, −46.36% vs. −38.12%). Mid-season drainage was superior to early-season and fallow season drainage in CH4 emissions reduction. Extending the duration and increasing the events of drainage would increase N2O emissions but contribute to a better CH4 emissions reduction effect. Implementing drainage in paddy systems with organic amendment can achieve greater GHG emissions reduction (both N2O and CH4) than in that without organic amendment. The GWPI decreased by the installation of drainage system might disappear when the nitrogen fertilizer application rate (N rate) reached over 530 kg ha−1. As for different N rates, single drainage is more suitable for the N rate below 115 kg ha−1, while multi-drainage has more advantages on reducing GWPI in the high N rate (≥ 115 kg ha−1).