Pg. 33-39 How important is timing of water stress for consistent litchi yields?

Various studies in literature indicate that flower induction and initiation in litchi is solely triggered by temperature
differences. However, reducing soil moisture by withholding water in autumn and early winter to levels below the water requirements of the trees, can assist them to enter a rest period and indirectly influence flower induction positively. 

Four treatments were applied to litchi trees in the Malelane and Hazyview areas under different soil (clay and sand) and irrigation systems (micro and drip). Water stress was applied either between March and April, between April and May or not at all. Furthermore, Ethapon was applied to three of the treatments during autumn when late flush appeared. One wet treatment was not treated with Ethapon at all.

Although late rains interfered with the trial, results indicate that water stress put a hold on trees, whereas trees with no water stress and no Ethapon reacted faster to temperature changes that are unfavourable for flower induction/initiation, leading to lower yields. When the wet and dry treatments with Ethapon application were compared, it was clear in both locations that water stress increased flowering and yield compared to optimum irrigation. Whether earlier or later water stress would be more beneficial could not be established after the first year. However, the success of correct timing for water stress appears to be closely related to flower induction time. Such a relationship as well as induction periods of the various production areas still need to be investigated further.

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