All branches of single-axis apple trees in high-density orchards are subject to limb renewal. Renewal limb management aims to replace overly vigorous and yield inefficient limbs with weaker, balanced limbs of higher yield potential. Recently, producers have adopted the application of long stubs, i.e., 10 cm, when renewing apple limbs despite a dearth of research on the topic. The current multi-year project evaluated the effect of stub length (between 2.5 to 10 cm in 2.5 cm increments) on the number, length and orientation of replacement limbs. The experiment was conducted on 3rd and 4th leaf ‘Honeycrisp’, ‘Gala’ and ‘Fuji’ trees on Budagovsky 9 rootstock, trained to tall spindle. We demonstrate a significant, positive relationship between increasing stub length and limb renewal response (expressed as the number of shoots and total vegetative growth per stub) but observed varying levels of the response in relation to scion vigor. Moreover, stub length did not affect the orientation of replacement limbs nor decrease the length of the longest limb on the stub. The data suggest that different stub lengths should be considered on the basis of cultivar and site vigor and not uniformly applied across cultivars.

中文翻译：

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更新的苹果枝条的存根长度与栽培品种相互作用，并影响替代枝条的数量和质量


高密度果园中单轴苹果树的所有枝条都需要进行枝条更新。更新肢体管理旨在用较弱、平衡但产量潜力较高的肢体取代过于旺盛和产量低下的肢体。最近，生产者在更新苹果肢条时采用了长短茎，即 10 厘米，尽管缺乏关于该主题的研究。目前的多年项目评估了存根长度（在 2.5 至 10 厘米之间，以 2.5 厘米为增量）对替换肢体的数量、长度和方向的影响。该实验是在 Budagovsky 9 砧木上的第 3 和第 4 叶 'Honeycrisp'、'Gala' 和 'Fuji' 树上进行的，训练成高纺锤。我们证明了增加的存根长度与肢体更新反应（表示为每个存根的芽数和总营养生长量）之间存在显着的正相关关系，但观察到与接穗活力相关的反应水平不同。此外，存根长度不会影响替换肢体的方向，也不会减少存根上最长肢体的长度。数据表明，应根据品种和场地活力考虑不同的存根长度，而不是在各个品种之间统一应用。