Chuck Woods (352) 392-1773 x 281
IMMOKALEE, FLA.—As the Florida citrus industry ramps up its winter harvesting season — picking a record 252 million boxes of oranges over the next six months — a small but growing number of producers are beginning to use mechanical harvesters that allow one person to collect more than 90 boxes per hour.
The new tree-shaking harvesting systems are nine times more efficient than picking oranges by hand and will help the state’s $9 billion citrus industry compete with low-cost producers such as Brazil, according to researchers with the University of Florida’s Institute of Food and Agricultural Sciences.
“In today’s global citrus market, necessity has become the mother of invention,” said Fritz Roka, an associate professor of food and resource economics at UF’s Southwest Florida Research and Education Center in Immokalee, who is studying the economic aspects of mechanical harvesting.
“With higher labor costs in Florida and strong competition from low-cost producers such as Brazil, mechanical harvesting is becoming a necessity on the state’s 600,000 acres of processed oranges,” Roka said.
“Make no mistake about it, the future economic viability of Florida’s citrus industry will depend on our ability to grow citrus at competitive prices,” Roka said. “And mechanical harvesting offers an excellent opportunity to significantly lower harvesting costs by threefold.”
Ron Muraro, a professor of food and resource economics at UF’s Citrus Research and Education Center in Lake Alfred, has developed cost comparisons between the Brazilian and Florida citrus industries. During the 2000-01 harvesting season, the cost of picking and “roadsiding” fruit into a trailer was $1.60 per 90-pound box of fruit in Florida compared to 38 cents per box for growers in Sao Paulo, Brazil.
And, while the current U.S. tariff on imported Brazilian processed orange juice products eliminates their advantage in the domestic market, tariffs on imported agricultural commodities would be eliminated under the proposed Free Trade Area of the Americas agreement, Muraro said.
Roka said interest in mechanical harvesting dates back to the 1960s when UF research was aimed at helping grove workers hand pick oranges more efficiently. Scientists have tried everything from tree shakers to air-blast machines and water cannons.
He said previous mechanical harvesting research programs were motivated by fears of labor shortages. “The goal of shake-and- catch systems during the 1970s was to help grove workers increase the number of boxes they could harvest from 8 or 10 boxes per hour to 30.
“Today, we’re looking at new tree- shaking and catch-frame harvesting systems that allow one person to collect more than 90 boxes-per-hour. Higher labor productivity should translate to lower harvesting costs,” he said.
Roka said the Florida Department of Citrus (FDOC) in Lakeland has invested more than $9 million since 1995 from grower assessments to develop mechanical harvesting systems.
The FDOC Harvesting Research Advisory Council, which includes growers, harvesters and processors, was established in 1995 to coordinate development of mechanical harvesting technologies. Since then, the council and UF researchers have evaluated six different machine systems from eight manufacturers. Today, two systems are achieving commercial success in Southwest Florida.
“During last year’s harvesting season, the trunk-shake-catch (TSC) and the continuous-canopy-shake-catch (CCSC) systems removed at least 95 percent and recovered 90 percent of the fruit from trees in Southwest Florida,” Roka said. “During the 2003-04 harvesting season, upwards of 25 TSC and CCSC machines could be operating, primarily in Southwest Florida. Mechanical harvesting is also expanding to other areas of the state.”
He said CCSC systems have greater harvesting capacity than TSC systems. One set of CCSC machines can load up to 18,500-box trailers in one day. One set of TSC equipment can fill five trailers in one day. However, a TSC system requires only three operators while the CCSC system requires six people.
“As a result, harvest labor productivity is similar for the two systems,” Roka said. “Hourly labor productivity was measured at more than 90 field boxes per hour, which represents a nine-fold increase in labor productivity over a hand-harvesting crew.”
However, in order for these systems to perform effectively, trees and groves must be well prepared. Tree canopies must be trimmed or “skirted” at least 30 inches from the ground and have at least 12 inches of “clear trunk,” he said. TSC systems are being used in groves with a tree density up to 175 trees per acre and on trees between 10 and 18 years old.
He said the two shake and catch systems are most efficient in the newer groves of Southwest Florida where tree age, height and spacing are more uniform. Older groves in the Ridge area of Central Florida have lots of resets or tree replacements and lack the uniformity needed for efficient machine harvest.
“One of the biggest challenges for growers is overcoming the idea that groves can be planted like they were 50 years ago,” Roka said. “Older groves need to be replanted with smaller trees that are closer together and more uniform, allowing shake-and- catch machines to move down tree rows more efficiently.”
Roka has developed a computer spreadsheet program so that growers can organize information on mechanical harvesting and determine when it is profitable. Key parameters include the system’s fruit recovery percentage, fruit price, crop yield and the cost difference between mechanical and hand harvesting. The model is available at the UF Southwest Florida Research and Education Center Web site: http://www.imok.ufl.edu/economics.
“Growers need to recognize that 100 percent fruit recovery is not necessary for increasing revenues,” Roka said. “A sufficiently large differential between hand and machine costs could more than offset the value of non-recovered fruit.”
Foremost in the minds of growers is how a mechanical harvesting system will affect the long-term health of trees. Jodie Whitney, a retired professor of agricultural and biological engineering at UF’s Lake Alfred center, has been developing and testing mechanical harvesting equipment since the 1970s.
“Our research, coupled with the harvesting experience of commercial growers, indicates that trunk or canopy shaking has no adverse effect on tree yield through seven years of harvesting. With each additional year of experience, uncertainly among growers should diminish,” Whitney said.
Abscission Agents to Loosen Fruit
Another tool for more efficient mechanical harvesting is the use of abscission agents, compounds that help loosen mature fruit from trees, said Jackie Burns, a professor of horticulture at UF’s Lake Alfred center.
“Spraying trees with an abscission agent a few days before harvest increases fruit removal and makes harvesting faster and easier,” she said. “Abscission agents must be non-toxic, selective, cost- effective and environmentally safe.”
Burns, who manages the abscission research team at Lake Alfred, said the selectivity of the abscission agent is especially important on Valencia trees that have young, developing fruit and mature fruit at the same time. Removing too much of the developing fruit with a mechanical harvester decreases the next season’s yield.
Burns and her research team are working on three promising abscission agents – - CMNP (5-chloro-3-methyl-4-nitro-1H- pyrazole), ethephon and coronatine. CMNP and coronatine are at least five to seven years from being commercially available. Ethephon is available for use on some horticultural crops, but not citrus. If ethephon is selected for use as a citrus abscission agent, it may take a few years to get citrus listed on the label for approved use, she said.