LAUSR

Abstract Warming affects tremendously agricultural water cycle though crop evapotranspiration, soil evaporation, crop water uptake pattern etc. Crop water uptake pattern plays an important role on water cycle of the groundwater-soil-plant-atmosphere continuum (GSPAC). A comprehensive assessment of climatic factors, water sources supply dynamics and crop seasonal water uptake pattern under warming is lacking. Here, climatic factors, water sources supply dynamics during the whole growing stages for summer maize under warming 2 ℃ were monitored by a Water Transformation Dynamical Processes Experimental Device (WTDPED). Isotopic labeling experiments by deuterium oxide (2H2O) were conducted to determine seasonal variations in crop water uptake patterns. The contributions of soil water at different depths to water uptake were quantified by the MixSIAR Bayesian mixing model and dual stable isotopes (δD and δ18O). Results showed that warming enriched the δD values in topsoil (10–20 cm) and depleted the δD values in deep soil (80–270 cm). Warming increased the proportional contributions of soil water at 0–40 cm layer to maize crop uptake by 3.5%, 19.9%, 5.3%, 14.4% and 29.8% during transplanting to maturation stage compared with ambient temperature. It means that deficit irrigation is better applied to reduce root biomass accumulation in the superficial soil layer (0–40 cm) especially at sixth leaf to 12th leaf stage and milk to physiological maturity stage for maize. To some extent, the reduced water infiltration in soil profile offset the increased soil evaporation at 0–80 cm layer under warming. Simultaneously, the maize water uptake for shallow soil layers was greatly induced due to the decrease acclimation of vapor pressure deficit (VPD) especially during tasseling-silking to maturation stage. Smaller water supply and more irrigation times were required for adapting warming condition for summer maize, particularly in water-limited regions. The study gives new perspectives of the effect mechanisms for crop water utilization and agricultural water cycles under future climate change.