Responses of soil water-root coupling and coupling effects on grapevines to irrigation methods in extremely arid region

Scarce rainfall and low water productivity (WP) are the primary problems constraining development of the grape industry in the extremely arid region of Xinjiang. Reducing evaporative loss and improving deep soil water use are important measures to solve this problem. In this study, a root zone irrigation (RI) method was introduced and studied in irrigation experiments in Shanshan, Xinjiang, to compare the effects of three types of irrigation emitter burial depths and furrow irrigation (FI) on soil water-root system coupling characteristics, root water uptake strategies, and leaf water physiology, yield, and quality. The results showed that RI optimized the coupling level of the soil water-root system and improved root water uptake strategies. Compared with FI, RI increased the water contribution rate of the middle and deep soil layers, resulting in an increase in the average root water uptake depth by 50.1-74.5 %. RI expanded the root water uptake range, which in turn increased the midday leaf water potential (psi m) and net photosynthetic rate (Pn) by 8.9-15.6 % and 9.9-18.9 %, respectively. Increasing the burial depth of the irrigation emitter under RI could lead to the migration of water, root, and average root water uptake depth to the deep soil, however, the psi m and Pn would also decrease. RI reduced evaporative loss and actual crop evapotranspiration (ETc act), however, the RI yield and WP were higher than those of FI by 8.6-18.7 % and 27.1-52.3 %, respectively. Moreover, RI significantly increased the soluble solid content, berry volume, and berry weight of grapes compared with that of FI. Under RI, increasing the burial depth of the irrigation emitter did not significantly affect WP, however, the yield and grape quality gradually decreased. The results showed that an irrigation emitter burial depth of 0-40 cm under RI in an extremely arid region is a scientific and reasonable irrigation method.