葉面噴施尿素對‘Tifblue’兔眼藍莓休眠期落葉及其後續生長之影響

Abstract

落葉果樹於亞熱帶低海拔地區常因秋冬季低溫不足，而無法順利打破芽體休眠，常用之解決方式為強制落葉。本研究探討於休眠末期以葉面噴施尿素強制‘Tifblue’兔眼藍莓(Vaccinium ashei Reade)落葉，對其後萌芽、生長與結果之影響。於2016年3月1日及2017年2月7日分別以0.5%或3%尿素水溶液，對多年生盆植之‘Tifblue’植株進行葉面噴施，並以葉面噴施清水做對照組。兩年試驗中，3%尿素處理可使藍莓提早落葉，新梢數量及枝條總生長量、枝條停梢後各次梢長度、比葉面積，及SPAD讀值則各處理間無顯著差異。2016年試驗中，0.5%及3%尿素處理植株之累積花芽萌芽率、累積開花率與累積著果率達40%之日期較對照組分別提前15天、13天與12天。2017年試驗中，3%尿素處理較對照組與0.5%尿素處理提早20與29天達30%萌芽率，提早15天與28天達30%開花，提早22天與45天著果率達30%。2016年試驗中，0.5%及3%尿素處理可提早萌芽、開花及著果，但採收期並未提早。3%尿素處理之產量較集中，但總產量、果徑、單果重、果實內可溶性固形物含量均無顯著差異，推測2016年尿素處理組於開花期遇大雨，因而授粉不良，導致產量與其他處理間無顯著差異。2017年試驗中，3%尿素處理提早萌芽、開花及著果，並使產期提前，開花期未遇大雨，因此產量顯著高於對照組，但果徑、單果重、果實之可溶性固形物含量均無顯著差異。此外3%尿素處理，顯著降低果實酸度與增加果實糖酸比，果實品質較佳；而0.5%尿素處理在2017年試驗中無法提早落葉與萌芽，產量與對照組無顯著差異。綜合兩年試驗結果，噴施3%尿素水溶液能提早兔眼藍莓‘Tifblue’落葉、提早花芽萌發、促進異花授粉並增加產量與果實品質，且對樹體無負面影響，為適合推薦農民使用於藍莓之落葉劑。

Insufficient chilling temperatures in the subtropical lowland often results in poor spring budbreak in deciduous fruit trees. Defoliation is a common practice to overcome this problem. In this thesis, the effects of dormant season foliar urea sprays on budbreak, growth, and fruiting in container grown ‘Tifblue’ rabbiteye blueberries (Vaccinium ashei Reade) were studies. On March 1, 2016 and February, 2017, 0.5% or 3% urea solution was sprayed on plants and the control group was sprayed with water. Defoliation of 3% urea spray was earlier than the control. Urea sprays did not affect number of shoots, cumulative shoot growth, length of shoots, specific leaf area, or SPAD value. In 2016, dates of 40% flower budbreak, flowering and fruit set in bushes subjected to urea defoliation were 15 day, 13 day and 12 day, respectively, earlier than the control. In 2017, dates of 30% flower budbreak, flowering and fruit set in bushes subjected to 3% urea defoliation were 20 day and 29 day, 15 day and 28 day, and 22 day and 45 day, respectively, earlier than the 0.5% urea solution sprays and the control. Defoliation treatments resulted in early bloom and fruit set but not early harvest. Total yield, number of berries, berry diameter, berry weight and total soluble solids content were not significant different among treatments within harvest periods. Although in 2016 3% urea spay advanced blooming, the final yield was not affected, possibly due to heavy rainfall during full bloom. In 2017, flower budbreak, flowering and fruit set in bushes of 3% urea sprays were earlier than the control. In addition, no rainfall was encountered during fuall bloom, 3% urea spray also significantly increased final yield. . The number of berries, berry diameter, berry weight and total soluble solids content were not significant different among treatments within harvest periods. 3% urea spay reduced berry acidity and increased suger/acid ratio, thus improving berry quality. In 2017, 0.5% urea spray had little overall effect. In conclusion, 3% urea solution spray on ‘Tifblue’ rabbiteye blueberries in the late dormant season promoted defoliation, flower bud break, cross pollination, yield and fruit quality without noticeable negative effect. It is therefore, recommended for blueberry growers in the subtropical region.