Seasonal Variation in Water Uptake Depth of Jujube Estimated with Stable Isotopes: Comparative Study of Drip and Basin Irrigation

Quantifying seasonal variation of plant root water uptake depth is critical for optimizing irrigation scheduling and improving utilization efficiency of irrigation water in arid region. The stable isotopes (δD and δ18O) in rainfall, stem water, irrigation water and soil water in the jujube (Zizyphus Jujube Mill.) orchard under basin and drip irrigation were investigated to determine the seasonal water uptake patterns of jujube. The jujube mainly acquired water from the upper 40 cm soil layer. The contribution of soil water from the 0–10 cm layer in the basin-irrigated jujube (29.06%) was similar to that of the drip-irrigated jujube (30.15%). However, there were significant differences in the percentage of absorbing soil water from the 10–20 cm, 20–40 cm and 40–100 cm layers between the drip-irrigated jujube (16.61%, 18.35% and 35.74% respectively) and the basin-irrigated jujube (13.79%, 13.69% and 43.26% respectively). Approximately 19.6% and 9.9% of irrigation water and rainwater infiltrated into soil layer below 100 cm for the basin and drip irrigation, respectively. These results suggested that reducing irrigation rate with efficient irrigation method should be recommended to improve irrigation water use efficiency in arid regions.