Post-seasonal effects of water-saving rice production regimes on N2O emissions in an annual rice-barley rotation system

Abstract

Ground cover rice production system (GCRPS)-related water-saving practices have been proposed to alleviate the challenge of increasing water resource scarcity. While water irrigation regime can directly affect nitrous oxide (N2O) emissions in the rice-growing season, it may also have the post-seasonal effects on N2O emissions in the barley-growing season within an annual rice-barley rotation system. A split-plot experiment was conducted to examine the effects of various water-saving rice production regimes on N2O emissions during the following barley-growing season. The abundances of soil N2O-related functional genes (AOA and AOB, and nirS, nirK and nosZ) were simultaneously determined using qPCR. The results showed that, relative to the waterlogged control, GCRPS-film and moisture irrigated rice production system (MRPS) consistently stimulated N2O emissions and associated yield-scaled N2O emissions in the barley-growing season, while they were decreased by 10% and 15% under the GCRPS-straw water-saving system, respectively. Compared with the waterlogged control, the water-saving rice practices increased the abundances of AOA and nosZ genes in the barley-growing season. The abundances of AOA and nirS genes had significant positive correlations with N2O fluxes, as a contrary to the negative correlation of nosZ gene abundances with N2O fluxes. The barley grain yields were slightly increased following water-saving practices but showed no statistical significance among different irrigation systems. Overall, the water-saving ground cover rice production system with rice straw mulching can be encouraged to reconcile high grain yields and low N2O emissions in the following upland cropping seasons.