Rejuvenation of a 60 Year Old Lychee Orchard by Pruning and Fertilizer Applications to Maximize Production
The main objective of the experiment is to learn if a well-established 60-year-old lychee trees would survive severe pruning. A secondary objective is to learn if different quantities and timing of fertilizer would affect the subsequent regrowth and flowering of the tree.
Elisabeth Ladoux, project coordinator, bought her farm 16 years ago from a widow whose children had left the farm years earlier and had neglected the farm’s lychee orchards for at least 20 years. The trees had grown 40 to 60 feet high, and the surrounding jungle had invaded the orchards. Ladoux worked for years to find the trees and clear the encroaching vegetation.
Meanwhile, fruit matured and required picking. But the dangers (two near-fatal accidents, one her own) and difficulties of harvesting from trees so tall persuaded Ladoux to undertake the pruning and fertilization experiment. Another impetus was the large volume of fruit that remained on the tree because it was out of reach.
Despite her doubts and anxieties, none of the trees died from her pruning. Indeed, all that were pruned are now thriving.
The secondary objective of her experiment has yet to yield any conclusions. Fertilizer applications, at 15 pounds an acre on 290 trees, failed to produce results different from the rest of the farm. She adds that her fertility program may have been affected by drought in 2000 and 2001 in the Haiku area.
After rejecting pruning suggestions from professional arborists, owing to the excessive time and labor involved, Ladoux turned to Norman Nagata, University of Hawaii Extension agent on Maui. Nagata recommended making cuts vertical to the ground to avoid water pooling as is common in mature trees grown from air layering. Nagata put Ladoux in touch with Mike Nagao of the UH Extension office on the Island of Hawaii. Nagao, who had severely pruned wind-damaged trees, assured Ladoux her trees would survive major pruning. He also helped her develop a fertility program.
The cutting crew, comprising Ladoux and an experienced tree cutter, began their work July 1, 2000, systematically pruning 107 trees on 5.37 acres over the next 60 days. The massive volume of pruned branches then required nine months to move. However, the newly opened orchard canopy provided the first benefit of the project: light could now penetrate to the ground, which stimulated grass growth and helped to stem erosion.
“Where rain used to cause rivulets through the orchard floor and flood a spot,” says Ladoux, “the new grass stopped that from happening. Opening the orchard to light caused the grass to grow and is saving untold amounts (of soil) from erosion.” The laborious and time-consuming branch cleanup kept Ladoux in the orchard, where she could pay close attention to her trees. She says that by the time she finished cutting all the trees, the first trees were already sprouting new branches.
Pruning involved eliminating any branches unlikely to bear fruit. All branches growing under one another were stripped, and where three branches sprouted from the trunk, only one would be left.
“I took great care to make sure any branch left on the tree had an unhindered shot to light or the top of the tree,” says Ladoux. “Now, almost two years after cutting, branch diameters are from 2 to 3 inches and the trees are 15 to 18 feet tall.”
The fertilizer program has been followed for two years, but results remain inconclusive, in part because of two years of drought.
Ladoux says she has the largest lychee farm in Hawaii, and she anticipates that her methods will be well received by other producers.
FARMER ADOPTION AND DIRECT IMPACT
So far, it’s difficult to gauge whether other lychee producers in Hawaii have adopted the pruning and fertilization methods from this SARE-funded project.
FUTURE RECOMMENDATIONS OR NEW HYPOTHESES
Ladoux is hopeful that rain patterns will change from recent drought years and that she can assess the results of her fertility experiment.
“I would not recommend planting lychee anywhere that does not receive 10 to 12 inches of rain in November or December,” she adds.
DISSEMINATION OF FINDINGS
Because the fertility aspect of the project has yet to draw specific conclusions, the project coordinator has asked for an extension, after which she will disseminate the findings. As for the pruning segment of the experiment, many observers visited and offered comments on the project. Most were aghast at the severity of the pruning. They thought Ladoux had killed her trees, but they have been persuaded otherwise by the lush regrowth.