Sustaining yield and mitigating methane emissions from rice production with plastic film mulching technique

Reducing water use and mitigating greenhouse gas (GHG) emissions are two major challenges faced by paddy rice (Oryza sativa L.) cultivation. Water-saving technologies, including controlled irrigation (CI), plastic film mulching (FM), and straw mulching (SM), have been increasingly adopted to improve rice production efficiency. However, few studies have comprehensively evaluated the effects of these practices on grain yield, water consumption, and GHG emissions relative to current farmer’s practice (FP). The objective of this two-year field experiment performed in southwestern China was to quantify the effects of CI, FM, and SM (compared with the FP control) on rice grain yield, irrigation water input, water productivity, methane (CH4) and nitrous oxide (N2O) emissions, global warming potential (GWP), and GHG intensity (GHGI). The FM treatment produced grain yield similar to the FP treatment, but it significantly decreased the irrigation water input by 69.6%, and then markedly increased the water productivity from 5.9 to 7.0 kg ha−1 mm−1 to 12.9–13.1 kg ha−1 mm−1. Furthermore, the FM treatment significantly reduced CH4 emissions (91.0–95.0%), resulting in a great decrease in GWP (36.7–51.4%) and GHGI (36.5–51.9%), although it markedly increased N2O emissions (90.9–206.9%) compared with the FP treatment. The CI and SM treatments also significantly increased water productivity and decreased CH4 emissions by reducing irrigation, but they caused yield reductions (9.5% and 14.5% on average, respectively) and showed no benefit to GHGI mitigation compared with the FP treatment. These results suggest that there is still great potential to further optimize the current FP practice, and FM is a preferable management option to save irrigation water and mitigate GHG emissions while maintaining grain yield in rice production.