Pg. 18-25 Effect of different management programs on yield and fruit size of litchi, cv. HLH Mauritius

The South African litchi industry is predominantly export orientated and fruit size is of great importance. The aim of this research, therefore, was to establish a management program, which is based on foliar applications of fertilisers and/or plant growth regulators, as well as horticultural techniques like pruning and girdling to promote sustainable litchi production based on increased fruit retention and size. Five management programs were developed and are currently being compared with one another according ta their effects on yield and fruit size. The management programs as well as progress on the project thus far will be discussed.

Summary:

• The study aimed to develop and compare five management programs for litchi production focusing on foliar fertilizers, plant growth regulators, pruning, and girdling to improve fruit retention, size, and yield for sustainable production.
• Conducted in a 3.7 ha commercial orchard near Nelspruit with 19-year-old HLH Mauritius litchi trees, treatments included combinations of urea, potassium nitrate (KNO₃), auxin (Maxim), cytokinin (Kelpak), micronutrients, girdling, and pruning.
• Yield was highest in treatment 1 (16.4 t/ha), followed by treatment 5 (15.9 t/ha) and treatments 3 (15.4 t/ha) and 4 (14.4 t/ha); treatment 2 yielded lowest (12.8 t/ha), likely due to mistimed auxin application causing fruit drop.
• Fruit size was largest in treatment 4 (girdling), followed by treatments 3 (KNO₃) and 5 (combined foliar and girdling), with treatment 2 showing the smallest fruit size.
• Treatments involving girdling at the 2 g fruitlet stage and potassium nitrate applications effectively increased fruit size; auxin effectiveness depended heavily on timing.
• Fruit size class distribution shifted positively in treatments 3, 4, and 5, with more fruits in larger size classes (L and XL), enhancing marketability.
• Economic analysis showed four treatments (1, 3, 4, and 5) increased net income compared to control, with treatment 1 being most profitable (+R13,728/ha), while treatment 2 caused financial loss.
• Soil moisture monitoring revealed irrigation and rainfall patterns critical for litchi production; proper soil knowledge and irrigation management are essential for optimizing water use.
• Phenological observations indicated temperature played a significant role in flowering and bud development; treatments need to consider tree growth stages for timing applications accurately.
• The study suggests a combined approach of fertilization, growth regulators, and horticultural practices can enhance sustainable yield and fruit quality in litchi orchards.
• Continued trials and monitoring are recommended to optimize treatment timing, explore long-term effects, especially of girdling, and improve decision-making tools for growers.