Pg. 6-12 A management programme to improve yield and fruit size of litchi, cv. HLH Mauritius – third season’s report

In 2005 an orchard management program was started consisting of irrigation, soil and foliar applications of fertilizers and plant growth regulators, as well as horticultural techniques like pruning and girdling to promote sustainable litchi production. Five management programs were developed and are compared with one another according to their effects on yield and fruit size. In 2005/06 and 2006/07 similar results were achieved regarding tree phenology, yield and fruit size. Results for the 2007 /08 season are presented and discussed.

Summary:

• The study is a 3-year orchard management program conducted on 20-year-old HLH Mauritius litchi trees in Nelspruit, South Africa, aimed at sustainable litchi production by improving yield and fruit size.
• Five management programs were tested, involving irrigation, soil and foliar fertilizers, plant growth regulators, pruning, girdling, and the application of growth inhibitors like Ethapon to reduce alternate bearing and increase fruit set and size.
• Treatments included variations in timing and types of fertilizer, cytokinin Kelpak, potassium nitrate (KNO₃), auxins (Maxim), and girdling applied at specific fruit development stages.
• Yield results showed that after initial alternate bearing years, the orchard adapted to the treatments with an improved on-year yield of up to 16.8 tons/ha in some treatments, although differences between treatments were not always statistically significant.
• Fruit mass and size correlated, with treatments 2 and 5 (which included Maxim) producing the largest fruits and highest percentage of extra-large fruit sizes, while treatment 4 had the highest yield.
• Economic analysis showed treatment 4 achieved the highest net income due to high yield and relatively low treatment costs; treatment 2 was also profitable despite higher costs because of larger fruit size and good yield.
• Irrigation scheduling and soil moisture monitoring emphasized the importance of consistent water supply, particularly during critical flowering and fruit-set periods, as interruptions caused fruit shedding.
• Phenological observations indicated flower panicle emergence and flowering timing were influenced by temperature, with extended flower emergence due to prolonged cold periods below 15°C.
• The use of Ethapon effectively controlled vegetative flushing and helped reduce alternate bearing when applied consistently and at the correct concentrations.
• Overall, general orchard management practices like irrigation, fertilization, and growth regulator application had more impact on orchard performance than foliar sprays alone.
• Maxim application after the second fruit drop was confirmed to significantly increase fruit size.
• The study recommends integrating these management practices for sustainable, improved litchi production.