Projection of the climate change effects on soil water dynamics of summer maize grown in water repellent soils using APSIM and HYDRUS-1D models

Soil water repellency greatly affects crop growth and soil water movement. The aim of this study was to estimate dynamics of soil water storage (SWS), actual evapotranspiration (ETa), root water uptake (RWU) and actual evaporation (Ea) under an annual crop grown in water repellent (WR) soils at future climate scenarios. The soil hydraulic parameters were calibrated and validated for HYDRUS-1D based on the experimental data in 2016 and 2017. The summer maize growth periods and irrigation schedules were generated with Agricultural Production Systems Simulator (APSIM). The daily SWS, ETa, RWU and Ea values from five water repellent treatments were simulated for summer maize growth periods during 1981-2000, 2030-2059 and 2060-2089 using eight selected global climate models under two representative concentration pathways (RCP 4.5 and RCP 8.5). Due to the increased temperature, the growth period reduced by 12-27 days, the total SWS, ETa, RWU and Ea decreased by 8.1%-21.1%, 2.2%-11.1%, 0.5%-9.7% and 0.8%-9.6% compared to the baseline period, respectively. Changes of total SWS, ETa, RWU and Ea during the whole summer maize growth periods under RCP 4.5 were greater than RCP 8.5 during the same period. Values of total SWS, ETa, RWU and Ea in 2030-2059 were higher than 2060-2089 for the same RCP scenario. With increasing initial water droplet penetration time, total SWS and Ea increased, while ETa and RWU decreased. The global circulation model (GCM) and Period contributed greatly to uncertainty. The results implied that it is necessary to adjust the planting date of summer maize.