Pg. 6-14 Progress on the management program to improve yield and fruit size of litchi, cv. HLH Mauritius

The aim of this research is 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 compared with one another according to their effects on yield and fruit size.

The 2005/06 season yielded the first results for the management program. Four out of the five treatments gave higher yields and income, compared to the control.

In the 2006/07 season the same treatments were applied with minor adjustments regarding the application time of Maxim^®, a synthetic auxin. Similar trends in yield and fruit size were obtained as in the first season. Applying Maxim^® after the second fruit drop, as compared to the 2 g stage, proved to be more beneficial.

Starch analysis reflected the same trends as were found previously by other authors. The phenological growth pattern was similar to the 2005/06 season. However, flowering started later and was more extended than in the previous season.

Summary:

• The research aims to develop a management program combining foliar fertilizers, plant growth regulators, and horticultural techniques like pruning and girdling to improve sustainable litchi production by increasing fruit retention and size.
• Five different management programs were tested over two seasons, comparing their effects on yield, fruit size, and economic viability.
• Results showed that four of the five treatments led to higher yields and greater income than the control group.
• Applying the synthetic auxin Maxim later in the fruit development (after the second fruit drop) was more beneficial for fruit size than applying it at the earlier 2 g fruitlet stage.
• Girdling combined with nutrient sprays helped improve fruit set and size, as did specific timings of potassium nitrate (KNO₃) applications.
• Starch analysis in branches indicated that higher starch reserves correlated with better cropping, with reserves being depleted during heavy cropping seasons (on-years) and lower during off-years.
• Phenological observations revealed that flowering started later and lasted longer in the second season compared to the first, influenced by lower winter temperatures.
• Irrigation and soil moisture monitoring showed critical periods of water stress impacting flowering and fruit development.
• Economic analysis indicated that treatments 4 and 1 provided the best net income to growers when considering both yield benefits and treatment costs.
• Controlling alternate bearing remains a challenge; the program aims to manage this through different strategies for on-years and off-years.
• Overall, the orchard is adapting to the new management strategies with improvements in tree production balance and fruit quality.
• Continued research is needed to optimize plant growth regulator application timings, nutrient management, and water stress control to sustain high yields and fruit size.