Abstract
This study was initiated to observe the performance of yuzu (Citrusjunos Sieb. ex Tanaka) fruit trees when affected by a late freezing in 2018 and to evaluate the recovery of frost-damaged trees during post management under protected cultivation. A—4.9 °C of minimum daily temperature and 40-day drought occurred during dormancy, which then received heavy precipitation between early- and mid-March, with 15 m s−1 more than maximum instantaneous wind speeds frequently observed. This resulted in observed decreases in height, width and volume as well as in fruiting, fruit weight and yield, as well as yield index in 60–90% defoliated yuzu trees, in addition to higher rates of shoot dieback compared to trees that experienced only 0–30% defoliation. Lower performance and recovery rates of trees grown on flat land compared to trees on sloped land were also observed. Tree and net windbreaks did not significantly affect tree vegetative growth and fruit productivity but were found to have lowered shoot mortality in 2018 and 2019. Mulch with an irrigation after freezing or foliar urea application was shown to effectively increase vegetative tree growth and fruit productivity and reduce shoot mortality.
Highlights
Average minimum daily temperature during January and February in the last 20 years mostly declined to −4.9 ◦ C in 2018 and to −4.3 ◦ C in 2011 [26], when severe frost damage was reported in yuzu orchards in southern S
Minimum daily temperatures lower than −10 ◦ C continued over four days at the end of January and in early February (Figure 2A) when the frost resistance of temperate fruit trees was expected to decrease
A higher risk of yuzu trees experiencing freezing was likely caused by extremely low minimum daily temperatures, prolonged drought and temperature fluctuations from
Summary
Ex Tanaka) is an upright evergreen tree 2–7 m tall and has been traditionally grown in South Korea, China and Japan [1]. Yuzu trees annually require higher amounts of sunshine (up to h) and water than other temperate fruit trees during the growing season [1,7]. The trees grow in a warm climate of between 13–38 ◦ C annual average temperature, and are more cold tolerant than most other citrus species, being able to withstand daily minimum temperatures down to −9 ◦ C [1,7,8], and are most extensively cultivated in Goheung-gun, Southern S. With 81.6% of the country’s production [8]
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