Abstract: 【Objective】Winter jujube orchard nitrogen (N) management should aim at increasing N reserves, meeting the tree growth requirement. Fertilization strategies should maximize the efficiency of fertilizers, including the choice the optimal timing of N supply.【Method】15N-urea was applied to winter jujubes on 'jinsixiaozao' jujubes rootstock to evaluate the effect of application timing on N storage and remobilization in mature trees in pot culture. The treatments consisted of ground application before budding (BB), fruit core-hardening stage (FCH) and fruit rapid-swelling stage (FRS).【Result】Nitrogen use efficiency of treatments were significantly different, which were 2.42% (BB), 9.77% (FCH), 9.01% (FRS) in the dormant and 5.20% (BB), 16.16% (FCH), 10.30% (FRS) in the following full bloom. N supply in the pre-harvest helped to increase trees N reserves and then relocate to the new growth organs following year. The largest amount of 15N was detected in the roots and trunks. In all treatment the partition rates were highest in coarse roots, which were 30.43% (BB), 38.61% (FCH), 40.62% (FRS), respectively. 15N stored in roots and trunks were used by jujube trees to sustain new growth in the following full bloom. 15N applied before budding resulted in lower Ndff% in perennial organs (trunks and coarse roots) sampled in the proceeding full bloom, but fine roots had highest Ndff% (1.28%). Other organs recovered a similar amount of Ndff%. In contrast, FCH and FRS treatment led to higher Ndff% (4.01%-5.15%) in the new growth organs (new branches, deciduous spurs, leaves and followers), but lower Ndff% in perennial branches (1.49%-2.89%).【Conclusion】With the delay of 15N-urea application time, 15N increased the partitioning to roots. FCH treatment increases N storage in perennial organ during winter, which should be remobilized to sustain new growth the following spring.

Key words: Z. jujuba Mill. var. inermis Rehd (Winter Jujube), 15N-Lablled Urea, Storage, Remobilisation