Estimate greenhouse gas emissions from water-saving and drought-resistance rice paddies by deNitrification-deComposition model

Flooded rice fields have been confirmed as a major anthropogenic source of atmospheric methane (CH₄). Avoiding continuous flooding is an effective practice to mitigate the CH₄ emissions originating from paddy fields. However, the contradiction between the high yield and water consumption of paddy rice limits the mitigation potential of greenhouse gas (GHG) emissions through a dramatic reduction in water usage. Recently, a new rice type, water-saving and drought-resistance rice (WDR), has been developed to satisfy both the rice yield and quality with a high water use efficiency and good drought resistance. WDR can be planted under dry cultivation, similar to upland crops. A biogeochemical process model, DNDC (i.e., DeNitrification-DeComposition) was used to evaluate the effect of agricultural practices (F-R as paddy rice under flooding management and D-WDR as WDR under dry cultivation) on GHG emissions from paddy fields in Anhui Province, China. The results are as follows: 1) the DNDC model attained a good performance when simulating the rice yield, seasonal cumulative CH₄ and N₂O emissions, and GWP; 2) the mitigation potential of the D-WDR system was higher than 90% while maintaining a high rice yield; 3) if rice paddies in Anhui can be replaced by D-WDR system, the GHG mitigation potential could reach 16.92 Mt CO₂-eq, and the increased N₂O emissions of the WDR system could offset a small fraction (7.6%) of the GHG radiated forcing benefit gained by the decrease in CH₄ emissions. Shifting rice production from paddy rice to WDR has a remarkable potential to balance the relationship between CH₄ mitigation and rice yield maintenance.