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Machines tackle hard to harvest lettuce, citrus crops

Remarkable progress has been made in the effort to harvest two of California's billion-dollar-plus crops mechanically — citrus and lettuce. If the citrus harvester proves itself useful, it can probably be applied to a range of tree fruits that have persistently defied harvest by machines.

Development of the harvesters for the two primary crops has followed two very different paths. An industry-wide research program has led to the development of the citrus harvesting system. A highly motivated individual effort has brought the lettuce harvester to its current stage of development.

The methods and techniques employed by both are as spectacular as the breakthrough itself, considered all but impossible as recently as 10 years ago. For citrus, newly developed units rely heavily on the latest photoelectric imagery and computer science to map an orchard ready for harvest. Then, sophisticated hydraulic robotics take over, read the map and pluck the fruit from the trees.

The latest lettuce-harvester builds on decades of development through individual and group trial-and-error experiments — boosted by durable metals coupled to workhorse driving units. The basic manufacturer credits his "trash eliminator" as a key to making the unit practical.

Manufacturer Frank Maconachy at Ramsay Highlander Inc. in Salinas said this trash eliminator allows harvested heads of lettuce to be conveyed upward into the machine with their wrapper leaves attached. By removing them mechanically, the machine paves the way for graders and packers riding the machine to complete their tasks efficiently and comfortably.

Both machines are costly — around $350,000 for the citrus system, and nearly $500,000 for the lettuce unit. However, the machines' efficiencies put the costs in perspective, and getting high-value crops picked when hand labor is at a minimum justifies otherwise unsustainable inputs.

Daylight is not required for the citrus-harvesting system to operate. That makes 18-hour days routine. Hand crews often pick for only six hours a day, after waiting for overnight moisture to evaporate, and then harvesting at top speed to avoid the approaching darkness of short winter days.

The apple industry in Washington has been a partner in the research leading to the citrus harvesting system. Others who are watching the development closely include the pear industry in California and the Northwest and California's dynamic tree-fruit industry, centering on peaches, plums and nectarines.

The citrus harvesting unit employs eight mechanical arms programmed to seek out individual fruits on the trees and deposit them in bins to be transported for packing.

If the "scout" unit that precedes the harvester does its job properly, fruit that is misshapen or not adequately colored or not otherwise matured will be left on the trees, minimizing the work that graders must do after the fruit goes to the packinghouse. Ted Batkin at the Citrus Research Center in Visalia has shepherded the development of the citrus unit for years.

He has shared its progress with all those who have contributed to the $7 million research effort as well as those who might be able to take advantage of the machine when it becomes available. He believes commercial application of the harvesting system is at least four years away. The lettuce harvester will see action this summer.

While some outsiders are hung up on the nebulous concept of sustainability in agriculture, the heart of the industry is looking ahead to getting the job done the old-fashioned way through progress, production and profit.


Publication date: 7/3/2007


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