Pg. 12-14 Litchi High Density Orchard Management

Thinning of overcrowded orchards by removing trees improves yield per tree and orchard yield (t/ha) significantly, due to better light interception and penetration. It is clear that thinning is not the long-term solution. Ultimately we need to control tree size through pruning and other management practices. A new trial, looking at mechanical hedging of overcrowded orchards, will start after the 1998 harvest.

Wind damage is reduced by pruning and by higher planting densities. Girdling of young and or stressed trees can cause trees to die and in this trial girdling did not enhance precocity or increase the yield of five-year-old trees. No significant increase in yield was obtained through pruning, girdling and pruning, girdling or mechanical hedging in comparison with the non-manipulated control during the 1997 season.

A single leader system with well-developed lateral branches has been obtained for young litchi trees.

Summary:

• Traditional planting distances of 12m x 12m for litchi orchards are not optimal due to long times to profitability and large unmanageable trees.
• High-density planting improves soil surface utilization, leads to earlier break-even points, and requires effective tree size management to maintain optimal production.
• Key to high-density orchards is achieving optimal leaf surface area for maximum light interception and penetration, crucial for fruit development and flower initiation.
• Ideal tree shape is conical or pyramidal, with single leader or closed vase systems, well-developed lateral branches starting at knee height, and tree height limited to 80% of row spacing.
• Two pruning cuts are important: heading removes mature branch parts causing vigorous new growth, while tipping removes new growth points and stimulates only localized growth.
• In overcrowded older orchards, thinning by tree removal significantly improves yield per tree and overall orchard yield due to better light availability; however, thinning is not a long-term solution as overcrowding recurs.
• Mechanical hedging and tree thinning trials are planned to manage overcrowding more sustainably; growth inhibitors will also be tested.
• Wind damage is reduced by pruning and higher planting densities, which physically protect trees and improve branch angles.
• Girdling young or stressed trees is not recommended due to tree death risk and did not improve precocity or yield in five-year-old trees.
• No significant yield increase was found from pruning, girdling, or mechanical hedging treatments in the initial production years.
• Training young litchi trees to a single leader system with strong lateral branches shows promise for future orchard management.
• Overall, control of tree size and shape through pruning, pruning systems, and high-density planting is essential for sustained high productivity and manageable orchards.