Canopy Shaker Research Articles

Physiological Effects of Mechanical Harvesting in Citrus Trees

Mechanical harvesting of citrus trees by trunk or canopy shakers can cause leaf and twig removal, bark injury and root exposure. Such problems have restricted the adoption of mechanical harvesting in Florida citrus. We assessed physiological responses of citrus trees that were mechanically harvested with a linear-type trunk shaker, operating at 4 Hz, 70.8 kg mass weight, and 6.5 cm displacement, for 10 or 20 seconds. We measured fruit recovery efficiency, leaf and shoot removal, mid-day stem water potential, leaf gas exchange, and leaf fluorescence emission of mature `Hamlin' and `Valencia' orange trees under restricted or normal irrigation. Shaking treatments effectively removed 90% to 94% of fruit without bark damage. Compared to harvesting by hand, trunk shaking removed 10% more leaf area and twigs, and caused some visible exposure of fibrous roots at the soil surface. There were no significant treatment differences on mid-day stem water potential, leaf gas exchange, and leaf photosystem efficiency. Excessively shaken trees for 20-30 seconds can temporary induce stress symptoms resembling that in trees without irrigation. Trees may have benefited from the low levels of leaf and twig loss after trunk shaking that compensated for any root loss. Long-term effects of trunk shaking will be assessed by tree growth, return bloom, subsequent yield, and carbohydrate reserves.

Optimizing Continuous Canopy Shakers for Late Season `Valenica' Harvest

Continuous canopy shakers (CCS) were developed in the late 90's and have been used to commercially harvest citrus in Florida. A viable mechanical harvester in Florida must be able to selectively remove mature `Valencia' fruit. A study was conducted to evaluate the effect of operating conditions on mature and immature fruit removal during the 2003 harvest season. The study was conducted in the southern flat woods and northern ridge areas. The study treatments were completely random and replicated four times. The CCS treatments were 145, 215, 230, and 245 cycles per minute (cpm) and a hand picked control. The harvest occurred on 17 and 19 June at the southern and northern sites, respectively. Mature fruit removal linearly increased from 95.7% to 97.9% between 145 and 245 cpm, respectively. Varying the operating ranges significantly influenced mature fruit removal in the southern flat woods site. The trees at the southern site were taller (>4m), and had a larger crop load. At the northern ridge site where trees were smaller, varying the CCS operating ranges did not significantly influence mature fruit removal. Immature fruit removal was influenced by the operating ranges. Immature fruit removal was increased at least 22% over hand picked controls. The results were interpreted to indicate the frequency of CCS is dependent on tree size. The initial selectivity of the CCS was not equal to hand picking.

FIELD TEST RESULTS WITH MECHANICAL HARVESTING EQUIPMENT IN FLORIDA ORANGES

During the 1996-1997 season, mechanical harvesting tests were conducted with a canopy shaker, a trunk shake-catch harvester, and a fruit pickup machine. The canopy shaker, which moved continuously down one side of the tree row canopy, operated at 1.2 to 2.4 km/h. Orange removals ranged from 55% in larger diameter tree canopies to 95% in smaller tree canopies with machine capacities up to 25 t/h. The trunk shake-catch harvester removed 84 to 94% of oranges shaking 5 to 10 s per tree with machine capacities up to 10 t/h. The fruit pickup machine picked up oranges at 15 to 20 t/h at 97% efficiency and caused 3 to 7% split peels from handling.

MECHANICAL HARVESTER FOR PROCESS ORANGES

An experimental, direct-drive, double-spiked-drum canopy shaker was developed to harvest oranges from highdensity groves. Each drum was 2.44 m (8 ft) in diameter and had six horizontal whorls spaced 300 mm (12 in.) apart on avertical shaft. Each whorl had 16 nylon rods, 32 mm (1.25 in.) in diameter, spaced at equal angles. Maximum rodpenetration into the canopy was 1 m (39 in.), shaking frequency was 4 to 5 Hz, and maximum horizontal displacement ofthe rod tip was of 250 mm (10 in.). The shaker was towed by a tractor along a tree row at travel speeds ranging from 1.4to 3.2 kph (0.9 to 2 mph). In the canopy space penetrated by the shaking rods, mature fruit removal averaged 71 to 91%.These promising results prompted the development of a prototype harvesting system. The shaker drums were enlarged to3.66 m (12 ft) in diameter and increased in height to harvest trees up to 4 m (13 ft) high. Fruit catching and conveyingcomponents were added under the shaker mechanism to collect and transport the detached oranges to the rear, row-centerof the shaker unit. A self-propelled bulk transport unit followed the harvest unit at a synchronized speed. The bulktransport unit had a conveying system that received the oranges from the harvester and transferred them to its rearhopper (6 t capacity). Both the harvester and the bulk transport unit had trash removal devices. Tests during the winterand spring of 1997 demonstrated potential of the system as an effective high-capacity harvesting alternative if compatibletree training and machine design parameters can be achieved. Fruit receiving grade at the processing plant was as goodas hand-harvested fruit.

MECHANCIAL PEACH THINNING

The purpose of these studies was to compare two mechanical means of thinning with hand thinning peaches 40-60 days after full bloom. A spiked-drum canopy shaker and a trunk impacter shaker were used to thin `Loring' peach trained to `Y' shape. Initial studies demonstrated that the spiked-drum shaker removed more fruit from horizontal than vertical branches. The spiked-drum shaker did not preferentially remove larger or smaller fruit. The yield of large fruit was not significantly different for hand or mechanically thinned trees when fruit was thinned 40-60 days after full bloom.

Selective Harvesting of Valencia Oranges with a Vertical Canopy Shaker

Selective Harvesting of Valencia Oranges with a Vertical Canopy Shaker