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

Abstract

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.