Multiple sources characteristics of root water uptake of crop under oasis farmlands in hyper-arid regions

Understanding the water use strategy of crops is important for maintaining the stability of agricultural production and improving water use efficiency (WUE). Affected by a variety of water sources and hyper-arid climate, the characteristics of root water uptake (RWU) in seed maize are extremely complicated but underestimated in oasis farmlands with shallow groundwater. We hypothesized that isotope (δ2H and δ18O) measurements over three years coupled with a MixSIAR model would reveal the characteristics of RWU in maize. Stable water isotopes in oasis farmlands were continuously observed from 2019 to 2021. Over the growing season, the soil matrix potential increased with soil depth. The isotopes in stem water had high similarity to groundwater, irrigation water, and soil water. The contributions of soil water in 0–20 cm, 20–40 cm, 40–60 cm, and 60–100 cm soil layers to RWU in maize were 29.7%, 12.2%, 14.8%, and 43.3%, respectively. From the jointing stage to the dough stage, the depth of RWU in maize was from shallow to deep; but after the dough stage, the depth of RWU in maize was from deep to shallow. Crops might prefer to absorb more groundwater and irrigation water in oasis farmlands with shallow groundwater. This study provides insights into crop water uptake and agricultural water management in hyper-arid regions.