不同施肥时期对冬枣15N贮藏及翌年分配利用的影响

【目的】保证冬枣树体的正常发育，提高肥料利用效率（包括选择最佳施肥时期），增加树体贮藏氮。【方法】以盆栽冬枣/金丝小枣为试材，研究了冬枣不同追施15N-尿素时期对休眠期贮藏15N及翌年盛花期15N分配利用的影响。【结果】在休眠期测定，萌芽前、果实硬核期、果实速长期3次追肥，植株氮素的利用率分别为2.42%、9.77%、9.01%；翌年盛花期测定分别为5.20%、16.16%、10.30%；休眠期15N主要贮藏于根系和主干，粗根的15N分配率最高，3个处理分别为萌芽前30.43%、果实硬核期38.61%、果实速长期40.62%。翌年盛花期时，枝干和根系中15N向新生器官大量运转，满足其生长发育的需要；萌芽前施肥处理，多年生器官（主干、粗根）中的Ndff%较低，其它器官中的Ndff%差异较小，细根中最高为1.28%；果实硬核期和果实速长期施肥处理，15N在新生器官（新生枣头枝、枣吊、叶片和花）中的Ndff%较高（4.01%～5.25%），而多年生枝中的Ndff%较低（1.49%～2.89%）。【结论】随施肥时期的推迟氮素优先分配到根系，果实硬核期施肥更有利于休眠期贮藏氮的积累和翌年春新生器官的生长发育。

Storage and Remobilization of Nitrogen by Chinese Jujube (Z. jujuba Mill. var. inermis Rehd) Seedling as Affected by Timing of 15N Supply

【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.