The climate cost of saving water by different plastic mulching patterns

Abstract

Global water shortage and climate change are two of the most significant challenges for our planet, and how to coordinate their relationship is a problem unsolved. In this study, we proposed the synchronization index of water-saving and CO2 mitigation to evaluate the climate cost of saving water by different plastic mulching patterns and explore way to improve the synchronization. The water-saving performance, carbon footprint, and the synchronization index were analyzed for three typical plastic mulching patterns, namely conventional partial plastic mulching, full plastic mulching, and “one film for two years” mulching. The results indicated that all three types of plastic mulching systems were effective in reducing the water footprint of crop production, with full plastic mulching showing the best performance in terms of improving crop yields and water savings. The application of plastic mulching mainly influences the carbon footprint through increasing indirect greenhouse gas emission, accelerating soil organic carbon decline and increasing N2O emission. Area-scale carbon footprint showed a significant positive relationship with the input amounts of plastic film, and the sort order of yield-scale carbon footprint was partial plastic mulching > full plastic mulching > “one film for two years” mulching. Calculated synchronization index was -0.35 kg CO2-eq m−3, -0.10 kg CO2-eq m−3, and 0.50 kg CO2-eq m−3 for partial plastic mulching, full plastic mulching, and “one film for two years” mulching, respectively. Full plastic mulching and partial plastic mulching resulted in an additional 0.35 and 0.10 kg of CO2-eq for saving one cubic meter of water, and only “one film for two years” mulching resulted in simultaneous water savings and greenhouse gas mitigation. This study suggests that water savings achieved using conventional partial plastic mulching have costs in terms of climate change. Faced with the dual pressure of global water shortages and climate change, controlling input amounts of plastic film and prolonging the lifetime of the film are simple and effective way to coordinate water savings and greenhouse gas mitigation. Moreover, the results of this study suggested that water savings and GHG emission mitigation cannot necessarily be achieved simultaneously and that searching for both water-saving performance and its synchronization with GHG mitigation should become a new paradigm for the development of water-saving technologies in the future.