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In order to study whether jujube trees can grow normally under rain-fed conditions in loess hilly areas, we planted jujube trees (Ziziphus jujuba Mill.) 4 years after felling a 23-year-old apple orchard. The growth process of the jujube trees and the variation in soil water content (SWC) were monitored for three consecutive years following planting in order to study the effects of the water-saving pruning (WSP) technique. Results showed the following. (1) The soil at a depth of 0–1,000 cm had been desiccated when the area was an apple orchard. (2) Under rain-fed conditions, the jujube trees with the WSP technique were always able to maintain normal growth while the jujube trees with conventional pruning method had a normal growth stage of only 4 years. The water use efficiency of the jujube trees with the WSP technique was much higher than that of the jujube trees with conventional pruning. We recommend WSP in jujube orchard management, because the jujube trees with WSP could maintain normal growth in the deep dried soils of the loess hilly region, as WSP can reduce the water consumption of the jujube trees and may have a positive effect on soil moisture restoration. HIGHLIGHTS We proposed water-saving pruning for the growth of jujube trees planted in dry soil.; Water-saving pruning can significantly improve water use efficiency of jujube trees planted in dry soil.; Water-saving pruning may have a positive impact on the restoration of soil water in dry soil.;

Highlights • Water consumption by jujube can be regulated by the canopy size. • Pruning effectively decreases water consumption and improves the water use efficiency in jujube. • Pruning can reduce soil water consumption and relieve deep soil drying. • Pruning level should be determined based on water consumption and average rainfall. Abstract Aims Soil drying has occurred widely in artificial plantations in the semiarid loess region because the water consumption exceeds the rainfall. Jujube (Ziziphus jujube Mill. CV. Lizao) plantations have been planted to improve the economic income since 2000. In order to prevent soil drying and sustain artificial plantation development, we examined the relationships between the canopy size, water consumption, and water use efficiency in a dry land jujube plantation. Methods Seven treatments were tested comprising native jujube with no pruning and dwarfing jujube under different pruning levels ranging from 1 to 6. Jujube is a popular dwarfing canopy type in this region with a tree height of 2.2 m and this comprised level 1. Jujube received increased intensities of pruning as well as decreases in tree height and canopy size for levels 2–4. Jujube received severe pruning to a tree height of only 1.1 m at level 5, and the canopy was removed with only 30–40 cm of the trunk left for level 6. Soil water was detected using CNC100 neutron tubes. A thermal diffusion probe was used to monitor the sap flow in jujube trees throughout the whole growth period. Results During our study period, 2014 was a wet year with rainfall of 460.4 mm and 2015 was a dry year with rainfall of only 380.8 mm. Transpiration and water consumption by jujube decreased significantly whereas the soil water content increased as the pruning intensity increased in these two years. Compared with 15-year-old native jujube, the annual soil water consumption by 15-year-old dwarfing jujube (pruned at level 1) was 6.54 mm less and the soil water consumption depth moved upward by 2.2 m. The soil water recovered faster for jujube at level 6 and the soil water restoration depth reached 4.6 m after 3 years, with an annual restoration depth of 153.3 cm. Compared with level 1 jujube, at level 5, the height was halved, the transpiration was about 22.1%, and the water use efficiency was significantly improved by 1.1 times, thereby demonstrating that the water consumption could be regulated by the canopy size. Level 2 jujube had the highest water use efficiency with the optimal pruning level in the local region. Conclusions We found that pruning could effectively decrease water consumption, relieve deep soil drying, and improve the water use efficiency in jujube. The pruning level should be determined based on the water consumption rate and average rainfall to obtain high yields. [ABSTRACT FROM AUTHOR]

Aims: 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. Methods: A soil coring method with a LuoYang shovel was used for sampling until no more roots were found. Results: 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. Conclusions: 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. [ABSTRACT FROM AUTHOR]