Responses of Water Fluxes and Water-Use Efficiency of Maize to Warming Based on Water Transformation Dynamical Processes Experimental Device (WTDPED) Experiment

Evaluating the impacts of warming on water balance components in the groundwater⁻soil⁻plant⁻atmosphere continuum (GSPAC) and crop growth are crucial for assessing the risk of water resources and food security under future global warming. A water transformation dynamical processes experimental device (WTDPED) was developed using a chamber coupled with a weighing lysimeter and groundwater supply system, which could simultaneously control both climatic and ground-water level conditions and accurately monitor water fluxes in the GSPAC. Two experiments with maize under increased temperature by 2 °C (T-warm) and ambient temperature (T-control) scenarios were conducted via the WTDPED. The duration of growing season decreased from 125 days under T-control to 117 days under 2 °C warming. There was little difference of total evapotranspiration (ET) (332.6 mm vs. 332.5 mm), soil water storage change (∆W) (−119.0 mm vs. −119.0 mm), drainage (D) (−13.6 mm vs. −13.5 mm) between T-control and T-warm experiments. The average daily ET for maize significantly increased by approximately 6.7% (p < 0.05) in the T-warm experiment, especially during the sixth leaf to tasseling—silking stage with an increase of 0.36 mm with respect to the T-control experiment. There were evident decreases in LAI (leaf area index), whereas non-significant decreases in mean stem diameter, crop height and leaf chlorophyll content under T-warm compared to T-control experiment. However, the chlorophyll content increased by 12% during the sixth leaf to tasseling⁻silking stage under 2 °C warming, which accelerated the photosynthesis and transpiration rate. The grain yield and water-use efficiency (WUE) for maize increased by 11.0% and 11.1% in the T-warm experiment, respectively, especially due to enhanced growth during the sixth leaf to tasseling⁻silking stage. This study provided important references for agricultural planting and water management to adapt to a warming environment