Searching for “Win-Win” solutions for food-water-GHG emissions tradeoffs across irrigation regimes of paddy rice in China

Paddy rice cultivation is an important source of agricultural greenhouse gas emissions in China. The traditional flooded paddy rice fields not only use large amounts of irrigation water, but also produce significant methane (CH₄) emissions. To balance food security with environmental impacts of rice production, many water-saving irrigations technologies have been tested in the field to increase the drainage period during the rice growth cycle. However, whether these management solutions can be implemented at the regional scale needs to be further explored. Because it is too time-consuming and resource-intensive for field experiments to be carried out across large areas, we opt to assess the regional impacts of alternative irrigation schemes via computer modeling, by coupling the well-known DSSAT and DNDC models, which have been extensively validated in China. Irrigation methods tested include the traditional Continuous Flooding (CF), Midseason Drainage (MD) and Alternate Wetting and Drying (AWD). Simulation results show that compared with CF, water-saving irrigation methods can significantly reduce the CH₄ emission from paddy rice field, with slight or no loss in expected rice yields. AWD had the greatest effect in reducing irrigation water amounts and CH₄ emission. Compared with CF, CH₄ emission under the AWD were 60% - 71% lower in Northeast China sites and 34% - 65% lower in South China sites. At the same time, compared to CF, irrigation water use in AWD was reduced by 23% - 34% in northeast China sites and by 18% - 50% in south China sites. Our results suggest that policies that support expansion of AWD in paddy rice cultivation across China can lead to a “win-win” for the food-water-GHG emissions tradeoffs, and offer a viable solution for policy makers and stakeholders in China.