Effects of root pruning on the vegetative growth and fruit quality of Zhanhuadongzao trees

The effects of root pruning on the vegetative growth and fruit quality of six-year-old Zhanhuadongzao (Ziziphus jujuba Mill.) trees were evaluated. Three root pruning treatments (severe, moderate and light degree) were conducted at the distance of 3,5 and 7 times trunk diameter from trunk on both inter-row sides of the trees, respectively. The results showed that the severe root pruning decreased the length of primary branch by 27.9% and the number of primary branches by 12.1% in contrast to the control of no root pruning. Compared to the control, both severe and moderate root pruning had no apparent effects on nitrogen, phosphorus and potassium contents of leaves after 35 days, but had significant effects after 161 days. Severe root pruning had larger effectiveness of controlling vegetative growth than the moderate one. By root pruning, the contents of vitamin C and total sugar were increased but the content of cypermethrin was decreased in fruits and no effects were found on total acid content of fruit and yield at harvest. In the rhizosphere soil, root pruning decreased the microbial populations and enzymes activities but increased the concentrations of cypermethrin, available nitrogen, phosphorus and potassium. It is proposed that the removal of root at 3 times trunk diameter distance from trunk was feasible to regulate the vegetative growth and fruit quality of Zhanhuadongzao tree.