Hand-picking can cost growers more than half of their gross returns
By Hank Shaw,
A clutch of olive growers stood around a machine that looked like a mobile, padded skateboard ramp attached to a conveyor and armed with a massive pair of grippers.
The machine’s grippers grabbed the trunk of an olive tree and began to shake it. Olives flew off in all directions, most of them bouncing off the padded shields and rolling into the conveyor, where they were collected into bins.
When the shaking stopped, some growers gathered to check the olives to see if they were bruised. Others looked at the tree to see how many olives remained. A few looked at the tree’s trunk to see if it was scarred.
Researchers have been trying to perfect mechanical harvesting of table olives for about a decade, and while they are closing in, “we still have a ways to go.”
So says Erick Nielsen, who is among the manufacturers working on shaking machines. Others are working on picking heads, which use thick rubber fingers to knock the olives off the tree.
All are trying to mechanize olive harvesting because hand-picking can cost growers more than half of their gross returns, according to Louise Ferguson, a University of California-Davis Cooperative Extension researcher.
“Manually harvesting now is perhaps $450 a ton,” she said. “And on a good year (growers) will get $650 a ton.”
Ferguson, Nielsen, Coe Harvesters, other researchers and local growers met in a test grove near the Sacramento Valley town of Arbuckle last week to conduct the field trial.
Bottom line: Growers will still need to hire human workers for at least another year or two.
Olives destined for the table are devilishly difficult to pick. They bruise easily and bruised olives don’t cure properly. Olive trees tend to be wispy, which limits the ability of shaking machines to clean off a tree that just sways. And olive tree trunks are typically knobby and shakers rub the bark off those knobs, opening the tree to disease.
Ferguson and others are working on new ways to train the trees to make pickers and shakers more efficient.
Her specialty is a wire-trained set-up where the trees are woven vertically in and out of what looks like a giant grape trellis. This keeps most of the fruiting branches facing upright and close to the center of the tree – good for both pickers, which have limited reach, and shakers, which can only shake off olives close to the trunk.
Nielsen said they thought they reached a breakthrough with their harvester recently. With a higher frequency shake, they got 84 percent of the olives off a tree in four seconds.
“We thought, ‘We have arrived!'” Nielsen said. But the high frequency shaking is tough on bearings in the machine and the persistent problem with the tree’s bark returned.
Ferguson says the goal is to get a machine that will not damage the tree while removing at least 80 percent of the olives on one pass.
“You want to be in a position not to have to send in a hand crew,” she said.
One way to get there will be the new pruning and training systems they are working with. Another will be pulling olive trees older than about 25 years, which are too large to harvest by machine.
And what should a grower do who has trees this old?
“Enjoy them for what they are,” she said.
[Source] Click here