Using stable isotopes to determine seasonal variations in water uptake of summer maize under different fertilization treatments

- Dual stable isotopes and MixSIAR were coupled to quantify water uptake of maize.
- Maize mainly used soil water in 20-50 cm at milk stage and 0-20 cm at other stages.
- Fertilization treatments led to distinct water uptake pattern at 0-50 cm depth.
- Soil water contribution was significantly linear with proportion of root length.

Fertilization and water both affect root water uptake in the nutrient and water cycle of the Soil-Plant-Atmosphere-Continuum (SPAC). In this study, dual stable isotopes (D and 18O) were used to determine seasonal variations in water uptake patterns of summer maize under different fertilization treatments in Beijing, China during 2013-2014. The contributions of soil water at different depths to water uptake were quantified by the MixSIAR Bayesian mixing model. Water uptake was mainly sourced from soil water in the 0-20 cm depth at the seeding (67.7%), jointing (60.5%), tasseling (47.5%), dough (41.4%), and harvest (43.9%) stages, and the 20-50 cm depth at the milk stage (32.8%). Different levels of fertilization application led to considerable differences in the proportional contribution of soil water at 0-20 cm (6.0-58.5%) and 20-50 cm (6.1-26.3%). There was little difference of contributions in the deep layers (50-200 cm) among treatments in 2013, whereas differences were observed in 50-90 cm at the milk stage and 50-200 cm at the dough stage during 2014. The main water uptake depth was concentrated in the upper soil layers (0-50 cm) during the wet season (2013), whereas a seasonal drought in 2014 promoted the contribution of soil water in deep layers. The contribution of soil water was significantly and positively correlated with the proportions of root length (r = 0.753, p < 0.01). The changes of soil water distribution were consistent with the seasonal variation in water uptake patterns. The present study identified water sources for summer maize under varying fertilization treatments and provided scientific implications for fertilization and irrigation management.

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