Yield and water use efficiency of potato at different irrigation levels in agro-pastoral ecotone under future climate change

Understanding the impacts of climate change on potato production is critical for future food security in agro-pastoral ecotone (APE) of North China. In this study, the APSIM-Potato model was calibrated and validated at Zhangbei (ZB) and Wuchuan (WC) stations by using filed experimental data. At Zhangbei a long-term (2011-2017) experiment was conducted under rainfed conditions, with Dabaihua' potato cultivar planted in 1000 m2 plots. Potato production at Wuchuan station was under irrigated conditions, 4 irrigation levels of 0, 90, 180 and 360 mm were designed in the experiment and each treatment replicated 3 times. Experimental data in 2011 and 2012 from ZB site and the values for WC site in 2015 were used to calibrate the model. The validation years were 2014 and 2017 for ZB site and 2016 for WC site. The trial-and-error method was used to calibrate the model. The calibrated model was then used to assess the impacts of future climate change on irrigated potato yield and evapotranspiration at the 2 typical sites under different irrigation levels with amount of 60, 120, 180 and 240 mm. The future daily climate data at the 2 sites were statistically downscaled from 33 global climate models (GCMs) under 2 representative concentration pathways (RCP4.5 and RCP8.5). Results showed that APSIM-Potato model accurately simulated potato yield and soil water storage under both of rainfed and irrigated conditions with the relative error of yield not higher than 22.6%. The ensemble of downscaled GCM projections showed significant increase in growing season temperature in the period 2021-2040 (2030s), 2051-2070 (2060s) and 2081-2100 (2090s) compared with the baseline period 1981-2010. Total solar radiation during the growing season of potato had decreased trend in the 2030s under RCP4.5 and RCP8.5 scenarios at the 2 sites, while showed a slight increase in 2060s and 2090s compared with the baseline period 1981-2010. Total precipitation in the growing season of potato showed increase trend in all 3 future periods under RCP4.5 and RCP 8.5 for the 2 sites. Compared with irrigated yield under baseline period (1981-2010), the yield under RCP4.5 in 2030s-2090s could be increased by 4.1%-36.2% and 2.5%-13.6% at Zhangbei and Wuchuan, respectively. For RCP8.5 the values were 3.1%-36.8% and 3.1%-38.5% at Zhangbei and Wuchuan, respectively. The evapotranspiration of potato showed an increase trend under most periods under RCPs, however decreased by 0.12% at Zhangbei under RCP4.5 and by 0.8% at Wuchuan under RCP8.5 in 2090s. Water use efficiency (WUE) of potato showed an increased trend in 2030s-2090s under both RCPs. Our results suggested that future climate change will have more positive effects on irrigated potato production in the APE. © 2020, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.