Modeling CH4 and N2O emissions for continuous and noncontinuous flooding rice systems

Abstract

CONTEXTNoncontinuous flooding irrigation is an important means of reducing water use, mitigating greenhouse gas emission, and maintaining crop yield in rice production systems. Quantifying the CH4 and N2O emissions in continuous and noncontinuous flooding irrigation systems is crucial to the exploration of sustainable water management practices in rice systems. OBJECTIVEIn this study, a simple “anaerobic ball” method was incorporated into the WHCNS (soil Water Heat Carbon Nitrogen Simulator) model to simulate and evaluate the CH4 and N2O emissions under continuous and noncontinuous flooding irrigation conditions. METHODSThis model considers the processes of dissolved organic carbon (DOC) release and transport in the soil profile, CH4 production, oxidation, and transport, and N2O production, reduction, and transport. Three years of field experiment data, including soil and environment variables (e.g., ponding water depth, soil water content, and soil temperature) and daily CH4 and N2O emission fluxes under different irrigation practices were collected to test the improved WHCNS model. RESULTS AND CONCLUSIONSResults show that the model performs well in simulating soil and environment variables, with performance indices IA, NSE, and Pearson's r varying from 0.772 to 0.966, 0.530–0.853, and 0.780–0.934, respectively. Furthermore, the daily dynamics of CH4 and N2O emissions were captured under different rice irrigation systems, with average IA, NSE, and Pearson's r values of 0.857, 0.476, and 0.763, respectively. The observed and simulated results indicate that noncontinuous irrigation reduces CH4 emission but increases N2O emission. Compared with continuous flooding irrigation, noncontinuous flooding irrigation significantly decreased the accumulated CH4 emission by 82.1%, but significantly increased the N2O emission by 129.4%, resulting in the global warming potential reduction of 23.5%. SIGNIFICANCEThe improved model reflects the effects of continuous and noncontinuous flooding practices on CH4 and N2O emissions, and exhibits great potential for the development of sustainable water management for rice production systems.