- S A Oosthuyse
- HortResearch SA, PO Box 3849, Tzaneen 0850, South Africa
- 2004
The main scaffold branches of bearing HLH Mauritius (Tai So) litchi trees were either girdled (cinctured) or left. To girdled or non-girdled trees, low-biuret urea, potassium nitrate, or amino acid complex were sprayed in mid-June 2003, prior to flowering in July. Furthermore, paclobutrazol was applied to the soil under the canopy in mid-March, 2003, the roots were pruned in early June, 2003, or the terminal branches were headed back by 30 to 45 cm in mid-June, 2003. The winter conditions (temperatures) were strongly inductive, this presumably masking any treatment benefit of stimulating bud-development and increasing flowering intensity. Winter pruning or girdling delayed bud development, reduced flowering intensity, and increased flowering stage variance. These effects were pronounced following winter pruning. Girdling markedly increased the number of fruits set per inflorescence and tree yield. Headed branched terminated by more leaves showed a greater propensity to initiate inflorescences as opposed to a new shoots. Flowering was more intense, set per inflorescence better, and the initiation of bud-development earlier on the sun-exposed as opposed to the more shaded side of the trees, this indicating the importance of canopy sun-exposure for increased tree performance. Potassium nitrate spraying increased inflorescence stage of development variance. Soil paclobutrazol application was ineffective in influencing inflorescence development stage or variance, or flowering intensity or fruit set. An effect in this regard would be expected when environmental conditions are less effective in inducing flowering. Repeating the study when winter conditions are less inductive was deemed necessary.
Summary:
The study investigated how scaffold branch girdling and various bud-growth stimulatory treatments influence flowering time, intensity, variance, and fruit set in Mauritius litchi (Tai So) trees.
Treatments applied included scaffold branch girdling, sprays of low-biuret urea, potassium nitrate, amino acid complex, soil paclobutrazol application, root pruning, and terminal branch heading.
The trees were studied under strongly inductive winter conditions in South Africa where flowering was intense and synchronous, possibly masking some treatment effects.
Winter pruning and girdling delayed bud development, reduced flowering intensity, and increased variance in flowering stages. These effects were most pronounced with winter pruning.
Girdling notably increased the number of fruits set per inflorescence and overall tree yield despite slightly reducing flowering intensity.
Branches headed back with more leaves showed a higher tendency to initiate inflorescences rather than new shoots, indicating the importance of leaf number near bud development sites.
Flowering was more intense and fruit set better on the sun-exposed side of the tree canopy compared to shaded side, highlighting the importance of canopy sun exposure for performance.
Spraying potassium nitrate increased variance in flowering stage development, while soil paclobutrazol had no significant impact on flowering intensity, variance, or fruit set, likely due to already favorable environmental conditions.
Winter pruning greatly reduced the proportion of branches producing inflorescences and thus flowering intensity, though fruit set per inflorescence was not reduced, possibly due to favorable leaf-to-fruit ratios after pruning.
Girdling decreased the proportion of branches flowering but greatly increased fruit set per inflorescence, contributing to higher yields after natural fruit drop.
The study notes the importance of canopy management and leaf retention near buds for successful flowering and fruit set.
Given intense natural flowering due to cold winter conditions, the study suggests repeating under less inductive conditions to better assess treatment efficacy.
Overall, girdling was effective for increasing fruit number per inflorescence and yield but delayed bud development and increased flowering stage variance, while winter pruning reduced flowering intensity.
Further research on timing, environmental conditions, and combination with canopy management practices is recommended to optimize flowering and yield in Mauritius litchi.