Using stable isotopes to determine water absorption of summer maize under different fertilizer treatments in North China Plain

Fertilization affects water uptake by crops, the study of water transport and water use in maize after the application of organic fertilizer can provide a theoretical basis for sustainable grain production in this area. In this study, dual stable isotopes (δD and δ 18 O) were used to determine seasonal variation in water uptake patterns of summer maize under different fertilization treatments in Shijiazhuang, China, during 2017. The contributions of soil water at different depths to water uptake were quantified using the MixSIAR Bayesian mixing model. The average contribution of soil water from the 0–20, 20–40, 40–70, and 70–120 cm layers was 39.6%, 23.2%, 29.8%, and 7.4%, respectively, and most water was taken up from the upper soil layers (0–70 cm) during the drought season before sowing. Water uptake was mainly sourced from the 0–20 cm depth at the mid filling stage (81.2%), the 0–40 cm depth at the seedling stage (85.0%), and the 0–70 cm depth at the jointing stage (86.2%), 12-leaf stage (91.2%), heading stage (88.8%), tasseling stage (86.7%), early filling stage (95.0%), and mature stage (94.0%). Two fertilization applications led to clear differences in the proportional contribution of soil water from 0–20 cm (average 35.3% and 43.8% for chemical and organic fertilizer, respectively), 20–40 cm (25.4% and 20.9%), and 70–120 cm (9.7% and 5.2%). The contribution from the 0–20cm layer was higher after organic fertilizer treatment than after the use of chemical fertilizer. This was because the manure fertilizer changed the physical properties of the soil, improving water-holding capacity and reducing soil evaporation. Our results have scientific implications for fertilization and irrigation management.