Effects of drip irrigation mode and NaCl concentration on hydraulic resistance and water use of young apple tree

This research investigated the effect of four NaCl levels (0% (CK), 0.2% (S1), 0.3% (S2) and 0.4% (S3)) and three drip irrigation modesalternate partial rootzone drip irrigation(ADI: alternate watering on both sides of the root-zone), fixed partial rootzone watering (FDI: fixed watering on one side of the root-zone ) and conventional watering(CDI: Simultaneous watering on both sides of the root-zone) on the physiological characteristic, hydraulic resistance and water use of young apple tree (Malus pumila) under greenhouse condition. The results show that the relationship between leaves hydraulic resistance (Rl+p) and leaf water use efficiency (WUEl), the total hydraulic resistance (Rt) and irrigation water use efficiency (WUEi) were described as a logarithmic correlation. Compared with the CDI, water-saving up to 50 percent for ADI, but the average root dry matter and root hydraulic resistance (Rr) only decreased by 8.7% and 0.53%, respectively, and WUEl, WUEi, Rl+p, shoot hydraulic resistance (Rsh) and Rt were increased by 7.6%, 16.96%, 74.85%, 35.33% and 15.22% under the same NaCl concentration. and the Rl+p and WUEi increased by 50.5% and 78.07% for ADI, respectively, but the Rr decrease by 1.34% and 9.96% under the higher NaCl concentration as S2 and S3 treatment. This shows ADI treatment has an obvious promoting effect on the root growth of young apple tree, meanwhile, increased Rl+p and decreased Rr, so these are some important reasons for improving water use efficiency of ADI treatment, and not only to improve the control and regulation plant water ability, but also to be strengthened resistance stability to salt-stress.