夏季修剪方式對兔眼藍莓樹冠發育、果實產量與品質之影響

The Effects of Summer Pruning Methods on Rabbiteye Blueberries’ Canopy Development, Fruit Yield and Quality

夏季修剪是亞熱帶及熱帶地區藍莓（Vaccinium spp.）栽培之必要田間管理。透過回剪結果枝及春季發育之成熟綠枝，刺激強勢夏梢生長，促進植株活力與提昇花芽品質。傳統手工修剪成本高昂，機械修剪可節省人力成本，但不具有枝條選擇性。本試驗探討以修籬機（機械修剪）取代以剪定鋏（手工修剪）進行之夏季修剪對兔眼藍莓（V. virgatum Aiton）生長及果實品質之影響。試驗以兔眼藍莓‘Tifblue’植株為材料，分別於2018年8月4日及2019年8月8日進行修剪，並以未修剪為對照組。夏季修剪每植株所需時間於2018年以背負式修籬機操作及2019年以手持式修籬機操作分別為28.1秒及78.4秒，皆低於2018年快速手工修剪之140.2秒及2019年細部修剪之603.2秒，兩年結果顯示機械修剪可大幅減少夏季人力成本。然而經機械夏季修剪後，冬季行傳統手工修剪時，每植株所需時間為988.7秒，反而高於夏季以手工修剪處理之548.3秒。因此在全年度修剪時間上，兩種修剪方式無顯著差異。兩種修剪方式在各樹冠生長指標上亦無顯著差異，但修剪後樹冠發育形態略有不同，手工修剪有促進萌發較多粗壯枝條之趨勢，而機械修剪後則有較多細短枝條。樹冠光截取率經手工夏季修剪後大幅下降，但也在新生葉片產生後快速回復。2019年兩修剪處理產量略低於對照組但果重稍重，惟差異並不顯著；2020年手工及機械修剪平均單株產量及單果重亦無顯著差異。本研究結果顯示，以機械代替手工修剪對藍莓產量及果實品質影響不大，但可大幅降低夏季修剪所需之時間與人力。

Summer pruning is a recommended practice for blueberry (Vaccinium spp.) cultivation in warm climates. Summer pruning promotes summer flushes which leads to bush vigor and quality flower buds. However, conventional hand pruning is a labor and time-consuming task. Mechanical pruning is a cost-effective alternative but has been criticized for its non-selective nature. In this study, the effect of mechanical pruning with hedge trimmers and hand pruning on the growth, yield and fruit quality in rabbiteye blueberries (Vaccinium virgatum Aiton) were studied. Seven-year-old container grown ‘Tifblue’ rabbiteye blueberries were subjected to either hand pruning (HP) or mechanical pruning (MP) on 4 August 2018 and 8 August 2019, with bushes without summer pruning served as the control (CK). The time required for mechanical per bush with a backpack hedge trimmer was 28.1 s in 2018 with a backpack hedge trimmer and 78.4 s while in 2019 the time required for pruning with a handheld hedge trimmer was 78.4, which was significantly faster than the time required for hand pruning in 2018 (140.2s) and in 2019 (603.2 s). Although MP summer pruning saved time, bushes subjected to MP required more time for winter hand pruning (988.7 s) than HP (548.3 s), resulting in no difference in year-round pruning time. It was observed that there was no difference in canopy development parameters between MP and HP but there were slight slightly differences in canopy structure were observed. HP tended to promote long, thick shoots while MP generated more short, thin shoot. Canopy light interception significantly declined after hand summer pruning but quickly recovered after new leaf development. In 2019, HP and MP had slightly lower yield but greater berry weight than CK, but neither showed significant differences among treatments. In 2020, both pruning methods also generated similar yield and berry weight. The results indicate that mechanical pruning did not compromise yield or berry quality but could significantly save time and labor for summer pruning.