夏季修剪方式對兔眼藍莓(Vaccinium virgatum Ait.)生長及果實品質之影響

Abstract

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進行機械式夏季修剪取代以剪定鋏進行之手工夏季修剪對兔眼藍莓(Vaccinium virgatum Aiton)生長及果實品質之影響。試驗以‘Tifblue’ 兔眼藍莓植株為材料，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。2018年經手工、機械修剪處理及對照組平均單株產量分別為798.4 g、691.6 g及917.8 g，平均單果重分別為2.07 g、2.06 g及1.72 g；2019年經手工及機械修剪處理平均單株產量分別為255.6 g及419.9 g，平均單果重分別為1.39 g及1.50 g，產量及單果重處理間均未達顯著差異。連續兩年之試驗結果顯示，兩種修剪方式在葉面積、生長速率指標、新葉佔比、產量、單果重量、果實糖酸皆無顯著差異，但皆有更新營養生長，維持植株健康的效益。兩修剪處理後樹冠發育有所不同，手工夏季修剪後，萌發較多粗壯枝條，而機械修剪後則有較多細短枝條。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140.19秒及2019年完整修剪之603.23秒，因此機械修剪可大幅減少修剪所需之人力成本。然而經機械修剪後，冬季行手工修剪時，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。總合夏冬兩季修剪時間兩修剪方式無顯著差異，機械夏季修剪雖無法顯著降低手工修剪所需年度人力成本，但可輔助栽培者分配人力資源，依照其夏冬季人力多寡決定修剪之方式。

Summer pruning is a recommended practice for blueberry (Vaccinium spp.) cultivation in warm climates. Summer pruning promotes summer flushes and thus bush vigor and quality flower buds. However, conventional hand pruning is labor and time consuming. 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 and fruit quality in rabbiteye blueberries (Vaccinium virgatum Aiton) was studied. Seven-year-old container grown ‘Tifblue’ rabbiteye blueberries were subjected to either hand pruning (HP) or mechanical pruning (MP) on August 4, 2018 and August 8, 2019, and were compared to bushes without summer pruning (CK). In 2018, HP and MP had slightly lower yield (798.4g and 691.6g per bush, respectively) than CK (917.8g). Berry weight was slightly greater in HP and MP (2.07g and 2.06g, respectively) than in CK (1.72g). In 2019, HP had slightly lower yield (255.6g per bush) than MP (419.9g). Berry weight was slightly greater in MP (1.50g) than in HP (1.39g). In the two-year experiment, both pruning treatments showed no significant difference in leaf area, growth rate index, new leaf ratio, yield, average fruit weight, fruit sugar/acid ratio between each other. Either pruning method promoted vegetative growth and maintained plant health. However, the canopy development was different. HP produced more long, thick shoots than MP. On the other hand, MP produced more short, thin shoots than HP. The time required for mechanical summer pruning a bush was 28.1 s 2018 with a backpack hedge trimmer and 78.4 s in 2019 with a handheld hedge trimmer, shorter than the time required for hand pruning in 2018 with a fast pruning approach (140.2s) and in 2019 with a detail pruning approach (603.2 s). Although MP summer pruning saved labor, bushes subject to MP summer pruning required more time for winter pruning (988.7 s) than HP bushes (548.3 s). There was no significant difference in the sum of the time spent in pruning throughout the year between HP and MP treatments. Overall, MP summer pruning did not significantly reduce the annual pruning labor. However, it could still improve the efficiency of seasonal labor management.