In this study

we uses hydrogen and oxygen stable isotope tracer technique to determine the water isotopic compositions of precipitation

soil water at different depth and stalks of summer corn during the growing season in 2015 in Yucheng

Shandong Province. On the base of these measurements

using direct comparison and multivariate linear regression methods

we analyzed the sources of summer corn root water uptake and their contributions

and further discussed field water movement and transference laws in the precipitation-soil-crop continuum. The precipitation isotope measurements showed that the atmospheric precipitation equation was δD=6.55δ18O-3.03 (R2=0.88) for Yucheng area. The analyses of water source during the growing period showed that summer corn mainly used surface (0—15 cm) soil water during the seedling stage and the contribution rate was 73.9%; during the jointing stage

it mainly imbibed water from the 0—50 cm soil layer (81.8%)

and the water from the 30—55 cm soil layer was used relatively more. In addition

the precipitation was also significantly used during this period. In contrast

the water used was mostly from deeper soil layer during the heading stage (30—55 cm

71%). During this period

the evaporation was high and soil water content decreased rapidly in the shallow soil layer

and water that could be used by plants was less. Because the water content in the deeper soil layer (30—100 cm) was less affected by air temperature and soil evaporation

it could provide water for summer corn during the heading stage stably. During the filling stage

the amount of soil water absorbed from each layer was similar (15—100 cm

72%); the precipitation was small

the temperature dropt and the evaporation decreased

and soil water content in each layer was relatively stable. During the mature stage

the summer corn mainly absorbed water from the 30—100 cm soil layer and the contribution rate was 70%

indicating that the absorption of soil water of summer corn mainly relied on deeper soil layers when the precipitation was small. Furthermore

the results showed that the water sources of summer corn were significantly affected by soil water content and soil evapotranspiration

meanwhile

precipitation

air temperature and humidity affected soil water content. The water balance model showed that the evapotranspiration of summer corn during the seedling

jointing

heading and filling stage was 35.62

34.99

32.4

22.31

16.94 mm

respectively. This study presents guidelines for summer corn water-saving irrigation during different growth stage in Yucheng area.