Effects of climate change on the extension of the potential double cropping region and and crop water requirements in Northern China

Multiple cropping systems have been widely used in China as smart strategies to address climate change to ensure that increasing food demand is met. In the context of climate warming, the climate-based boundaries of multiple cropping systems are moving northward, and the potential crop yield is projected to increase due to continuous cropping that will be possible with increased light and heat resources. However, increasing demands for crop water have further aggravated the severity of water shortages in Northern China. In this study, we determine the impacts of climate change on the double cropping system (DCS) in Northern China using the annual accumulated temperature above 0 degrees C. The northern climate-based boundaries of the DCS have moved significantly northward and westward in Liaoning, Hebei, Gansu, Shaanxi and Shanxi Provinces. At the same time, the annual crop water requirement has increased by 198-403 mm in the planting areas sensitive to climate change [areas where the cropping system can potentially be transformed from a single cropping system (SCS) to a DCS]. The highest probability of water deficit exceedance was found during the winter wheat growing season. In addition, the difference in crop yields between the two planting patterns was analyzed using the Agricultural Production Systems Simulator (APSIM) model. The annual output per arable land unit in the potential DCS region, which benefited from the increase in winter crops, increased by 11.6-86.2% under different irrigation scenarios. The increase in crop production is related to irrigation. In the water-saving irrigation scenarios of Irrigation-Wheat (180 mm for winter wheat critical growth periods) and Irrigation-Wheat & Maize (180 mm for winter wheat critical growth periods and 50 mm for maize sowing), the annual output reached approximately 74-80% of the potential high yield in the Full Irrigation scenario. Our research provides suggestions for adjusting planting patterns under climate change. In the future, it will be necessary to develop multiple cropping practices that include innovative water-saving techniques and breeding technologies.