Effective root growth zone of apple tree under water storage pit irrigation using stable isotope methodology

ABSTRACTWays of understanding and quantifying the effectiveness of new irrigation methods are required in order to more precisely evaluate them, including the effect of root growth on water storage pit irrigation (WSPI). In this study, the effective root growth zone (ERGZ) of 5-year-old apple trees under WSPI and traditional surface irrigation (CK) treatment was estimated using stable isotope technology during two seasons 2015 and 2016. The stable isotopes of water in stems and different soil depths were analyzed using four analysis methods (namely direct inference, the Romero-Saltos model, the IsoSource model and the coupled model). Results showed that the ERGZ depth under surface irrigation ranged from 10 cm to 60 cm, with the main contribution at 0–40 cm during the growth stage. Under water storage pit irrigation, the ERGZ depth for the apple tree was deeper and ranged from 20 cm to 100 cm, with the main contribution of ERGZ deepened to 20–100 cm after the earlier of shoot rapid-growing stage. The use ...