Jaime Cantu and Richard Leno work on one of two Oxbo citrus canopy shakers being used for research.
THE FUTURE: MECHANICAL HARVESTING
Chapter 25: A shrinking role for hands
By Thomas Becnel
Published: Wednesday, December 31, 2008 at 1:00 a.m.
In the world of mechanical citrus harvesting, where agribusiness meets science fiction, there are trunk shakers and canopy shakers. Trunk shakers live up to their name. A machine with a mechanical arm simply grabs the base of an orange tree, jostles fruit loose into a ground-level catch system, then moves on to the next tree. Canopy shakers, though, take harvesting to another level. These machines work in pairs pairs that cost $1 million. In a diesel-powered parade, they roll down both sides of a row of trees. Each carries vertical agitators that look like round hair brushes. The steel bristles on those brushes reach into the canopy of an orange tree and shake branches back and forth.
At top speed -- 1 or 2 mph -- engines whine and brushes rattle to the beat of oranges thumping into plastic containers.
"When you see 'em going down the row, filling those bins, it's impressive," says Will Elliot, general manager of Coe-Collier Citrus Harvesting. "They move some fruit."
For hundreds of years, citrus has been harvested by hand. Field laborers climbed ladders, filled sacks and emptied fruit into bins, which were emptied into larger containers and then wagons or trucks.
Now that is changing.
In 2000, according to the Florida Department of Citrus, fewer than 10,000 acres of fruit were harvested mechanically. For 2005, it was 25,000 acres. By 2010, mechanical harvesting is expected to reach 50,000 acres.
Even 50,000 acres is less than 10 percent of the total crop, but the move toward mechanical harvesting is gaining momentum.
Labor and immigration issues have forced growers to consider harvesting alternatives. Improved machines could make a capital investment pay off.
"It's simple economics now," says Robin Bryant, a former Tropicana researcher who now runs Magnolia Consulting in Palmetto. "The machines will save them money over hand picking."
A move to mechanical harvesting would transform the agricultural landscape in Florida. Instead of thousands of migrant workers picking their way slowly through the groves, hundreds of harvesters would roll down row after row.
Once initial resistance is overcome, a switch to mechanical harvesting could come quickly. That's what happened in Florida's sugar cane industry.
Before 1990, harvesting was done by hand, with hundreds of West Indian migrant workers swinging cane knives in vast fields around Lake Okeechobee. By 1995, those workers were gone, replaced by tall combines that cut sugar cane stalks and fed them into trucks.
Dalton Yancey, a retired spokesman for the Florida Sugar Cane League, remembers change coming gradually, then all at once.
"Once a system was developed that worked," he says, "everybody bought it."
Reza Ehsani, an agricultural engineer, is still new to Lake Alfred, home of the Citrus Research and Education Center for the University of Florida.
At Ohio State, he worked in precision agriculture. In Florida, it is mechanical harvesting.
When Ehsani began studying mechanical harvesters, he was impressed by the creativity shown by decades of engineers.
"Almost anything imaginable, they've tried," he says. "They tried air harvesting, air shaking, using high-velocity air, 120 miles per hour, almost the speed of a hurricane."
Ehsani chuckles.
"They were telling me sometimes the fruit would fly three rows over."
Right now, citrus harvested mechanically is made into orange juice. Tree and canopy shakers are not so good with table fruit, because the orange skin is often bruised or torn in the process.
That's where the citrus industry could get a hand from robots.
Tom Burks, an agricultural roboticist at UF, says it's a daunting task. Robots work best indoors, in a carefully controlled environment, without the variables of a job like picking ripe fruit.
"It's as complex an automation problem as you can get," he says.
Florida engineers have been working with robots, off and on, since the 1980s. There are many different designs for pickers.
"Some of them look like a human hand, some of them look like vacuum cleaners," Burks says. "Some of them look like a medieval glove that grabs hold of the fruit."
Interest in robotics, like mechanical harvesting, goes up and down, following the supply of cheap labor in Florida.
Burks has had to work through funding cuts, which might be why he is wary in dealing with the media or discussing specifics. The university has a "platform" for a citrus robot, but it doesn't have a name other than "automated citrus harvester."
"If we had a cute name, maybe we'd get funding from more sources," Burks says, "but we haven't come up with a cute name for it."
When canopy shakers move down a row of orange trees, they leave behind a green trail of small branches and thick leaves. If it is late in the harvesting season, after May 1, that trail often includes tiny green fruit.
This is a problem.
That fruit is next year's crop.
The trick in mechanical harvesting is to shake loose mature oranges without harming the immature fruit that will grow and ripen next year. One technique is to spray groves with chemicals that help loosen fruit from the base of their stems.
This is called abscission.
A leader in the field -- literally -- is Jackie Burns, a horticulture professor for UF in Lake Alfred. For the last 10 years she has studied the application of agents such as CMNP, short for 5-chloro-3-methyl-4-nitro-1H-pyrazole.
If oranges are already hanging loose, then a machine will not have to shake the branches as hard. This is easier on the fruit and the tree.
"When we do it with less force," Burns explains, "we keep green fruit on the tree and maintain yield for next season."
The California native spends half her time in an air-conditioned office and half in orange groves that are often steaming hot and buzzing with mosquitoes. Even after a decade in the field, she's impressed by the harvesting speed of canopy shakers.
"For such big machines, it's quite awe-inspiring," she says. "With abscission, it's an even better experience."
