Effects of drip irrigation on deep root distribution, rooting depth, and soil water profile of jujube in a semiarid region

Aimed to understand how soil water was depleted by deep roots, the effects of drip irrigation and stand age on the deep root distribution, rooting depth, and soil water profile dynamics were investigated in a jujube (Ziziphus jujube Mill. CV. Lizao) plantation. A soil coring method with a LuoYang shovel was used for sampling until no more roots were found. It showed that the maximum fine rooting depth (< 2 mm in diameter) increased with stand age and it extended deep into the soil rapidly during the first 4 years, but more slowly in the subsequent 4 years. The maximum rooting depth reached 5 m in a 9-year-old jujube plantation, but it stabilized and did not increase thereafter. However, it was 10 m in a 12-year-old jujube plantation that lacked irrigation. We found that the application of 33.3 mm of irrigation water (equivalent to 7 % of the local annual precipitation) could halve the maximum rooting depth, thereby reducing deep soil water depletion. Our results showed that a low-volume water supply reduced the maximum rooting depth in jujube and prevented the depletion of the deep soil water. Appropriate drip irrigation is an effective water management strategy for sustainable artificial forest development in semiarid regions.