Reducing yield-scaled global warming potential and water use by rice plastic film mulching in a winter flooded paddy field

Abstract

Winter flooded paddy fields emit considerable amounts of CH4 and N2O that add to global warming potential (GWP). However, mitigating the GWP and water use without compromising crop yield in the fields is poorly documented. A 3 year-round field experiment was conducted with the use of PM (plastic film mulching cultivation with water-saving irrigation in rice season while drainage in winter season) in comparison of two traditional paddies that were flooded in the winter season but either rain-fed (TC1) or continuously flooded (TC2) in the rice season. Shifting TC1 into PM significantly promoted rice tiller and increased grain yields by 23 %, showing a significant increase in effective number of panicles per m2 (40 %), total filled grains per m2 (55 %) and filled grains percentage (4.2 %). Changing TC2 into PM, however, had little effect on these variables. Compared with TC1 and TC2, the PM reduced annual water use by 20–69 %. Meanwhile, it decreased annual cumulative CH4 emissions by 23–64 % and increased N2O emissions by 56–4.2 %. This change was probably related to the significant decreases in both dissolved organic carbon content (DOC) and CH4 production potential (MPP) for CH4, and much higher NH4+-N concentration at the beginning of the rice season and a more favorable soil water content (SWC) for N2O. Because mean CH4 emission was positively correlated with mean DOC and MPP, and mean N2O emission was negatively related to mean SWC, respectively. Overall, the PM reduced annual GWP by 18–60 % and yield-scaled GWP by 34–60 % relative to TC1 and TC2. The findings suggest that the application of PM in the winter flooded paddy fields substantially mitigates GWP and has a great potential to reduce water use while maintaining high yields.