Mechanizing the harvesting and orchard handling of fruits

Historic, archived document

Do not assume content reflects current
scientific knowledge, policies, or practices.

MECHANIZING the HARVESTING
and ORCHARD HANDLING of FRUITS

ARS 22-88

February 1964

Agricultural Research Service

UNITED STATES DEPARTMENT OF AGRICULTURE

ABOUT THIS REPORT...

This report discusses the progress that research is making, to mechanize the
harvesting and handling of fruits. It emphasizes the necessity for this research and
how mechanization may save growers time and money and insure for the con-
sumer that which he has always demanded—an abundant supply of quality fruit
and berries at a reasonable price.

Some examples illustrate further the advantages of mechanization: One man
can mechanically harvest as many blueberries as six handpickers and six men can
harvest as many cherries as 33 handpickers. Also, 1 man and an equipped tractor
can carry 1,500 bushels of apples out of an orchard in an 8-hour day—a job that
formerly required 6 men, 3 tractors, and 8 trailers.

This report has been prepared for county agents and other agricultural leaders.

Information in this report was provided by the Agricultural Engineering Research
Division of the Agricultural Research Service.

MECHANIZING THE HARVESTING AND ORCHARD HANDLING
OF FRUITS

Changes are taking place in the harvesting and handling of certain fruits. The
actual picking of the fruit is being mechanized and the harvest is thereafter han-
dled in bulk lots. Aids are also being developed to increase handpicker efficiency.

The Agricultural Engineering Research Division (AERD) of the Agricultural
Research Service, U.S. Department of Agriculture, and the Division’s predecessors,
pioneered this mechanical handling and harvesting of fruit. In 1949, it initiated re-
search to improve handling. Today, over 80 percent of the deciduous fruit har-
vested in Washington, Oregon, Michigan, and California are economically and con-
veniently handled in the orchard by methods worked out and recommended by
AERD.

In 1955, AERD began research designed to mechanize fruit and berry harvest-
ing. While this research is still in its infancy, many of its developments have been
accepted by many growers in Michigan, California, New Jersey, and elsewhere.

Today, AERD, in cooperation with several States, is studying the mechanical
handling and harvesting of the following: Apples in Washington; peaches, apricots,
prunes, and dates in California; citrus fruit in Florida and California; and apples,
sweet and sour cherries, grapes, and blueberries in Michigan.

SIGNIFICANCE OF THIS RESEARCH

Crops that cannot be harvested cannot be utilized. And many fruit and berry
crops in the United States may not be utilized in the future unless research finds
ways to harvest them mechanically. The reason: Scarcity of labor to do the har-
vesting and high costs when labor is available. In 1962, for example, growers re-
ceived 4.7 cents per pound for their cherries but had to pay 214 to 3 cents per
pound to handpickers. Each year thousands of pounds of berries are not harvested
because growers cannot find enough handpickers.

Many fruit and berry growers may be forced out of business before research
can solve their harvesting problems. If this prediction comes to pass, the consumer
will be the ultimate loser.

Since mechanized harvesting usually means faster harvesting than handpick-
ing, methods to improve and speed up harvest handling are imperative—else advan-
tages accruing to speedier harvesting will be lost. Fruit held too long in boxes or
baskets spoil just as rapidly as the unharvested on the bush or tree.

SOME OBJECTIVES AND CONSIDERATIONS

The ultimate objective of this AERD research is to enable one man to do the
work formerly done by many. But the quality of mechanical harvests must equal or
surpass the quality of handpicked harvests and the harvesting must not injure the
tree or bush. In California, Michigan, and elsewhere, where harvests of some fruits
are extensively mechanized, these objectives are being realized.

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Economic considerations are also important. Mechanization must make money
for the grower—enough money so he ¢an afford to invest in the equipment needed.
AERD has estimated savings from mechanically harvesting and handling some
crops and how much a hypothetical grower must market to make mechanization
profitable (see p. 10-13). Individual growers, however, who encounter unusual dif-
ficulty in getting harvesting help may decide to mechanize even though mechaniza-
tion will not increase profits.

Before mechanizing, growers should be certain of their markets. AERD advises
that not all processors and fresh fruit buyers will accept mechanically harvested
fruit. Many of them will, however, and most of them do—after establishing that the
quality of mechanically harvested crops equals or surpasses that of handpicked
crops.

MECHANICAL HARVESTING—EQUIPMENT AND METHODS

The fact that fruit can be dislodged from trees by shaking the trees led AERD
engineers and their collaborators to investigate, test, and develop mechanical shak-
ers and catching frames to mechanize the harvesting of fruit. Today mechanical
shakers and catching frames have been used to harvest thousands of tons of prunes
in California, millions of pounds of cherries and plums in Michigan, and blue-
berries in New Jersey and Michigan. Their use will undoubtedly be extended to
other crops as research learns more about them.

The shaking force that is applied to trees creates an equal and opposite force
(the reaction force) that must be absorbed. This law of physics sometimes limits
the effectiveness of shakers. An important segment of AERD research deals with
this phenomenon.

Hand-held Mechanical Shakers

Hand-held mechanical shakers may be powered hydraulically, by compressed air,
or manually by turning a crank. They are essentially long poles or pipes that trans-
mit the shaking force from the powering mechanism to the tree. They are hooked
to or held against individual limbs and then activated. Their use may be exhausting
because they often have to be held shoulder high and because the operator must
absorb the reaction force.

Hand-held Vibrators for Harvesting Blueberries

Hand-held vibrators for harvesting blueberries are driven by electricity or com-
pressed air. The operator holds the vibrator against the blueberry bush and the
driving force vibrates fingers that separate the berries from the bush. The earliest,
experimental vibrators were converted from electric hoes.

Boom Shakers

Boom shaker units usually consist of a tractor or truck-mounted boom with a
claw (clamp) at the end. They can be maneuvered so the claw can be closed on a
main scaffold limb. Once in position the operator can shake the limb by activating
the eccentric on the powering mechanism that activates the boom. Under favorable
conditions, this is a very effective way of harvesting fruit.

The mass of the truck or tractor, however, has to be greater than the mass of
the tree. If it isn’t, the truck or tractor will shake more than the tree because of the
reaction force.

Inertia Shakers

AERD and State research to increase the effectiveness of shakers has led to the
development of inertia shakers. These are designed in such a way that the shaking
mechanism itself absorbs the reaction force. This is due to the fact that the shaking
mechanism is free to rotate along its main line of motion relative to the claw end,
to the ratios between the masses of the shaker and the claw, and the way in which
the shaker is supported. The supporting attachment is approximately at the balance
point or center of gravity of the shaker and attaches to an extension of the shaker
claw.

Catching Frames

Catching frames for fruit are essentially inclined canvas screens fitted under
the tree. As the fruit shakes from the tree, it falls on the screen and rolls down
into a conveyor that carries it into a box. Some catching frames have manual
cranks to move the conveyor. The earliest conveyors were wooden troughs that
lifted out so the fruit could be poured into boxes. Most later models have a gaso-
line engine that moves the frame from tree to tree, runs the conveyor, and powers
the shaker.

Figure 1 shows a boom shaker and catching frame being used to harvest
peaches.

BN=20572

Figure 1.—Boom shaker and catching frame are being used to experimentally harvest
peaches. Note parallel layers of decelerator strips. These slow the descent of the falling peaches
and keep the peaches from bruising when they strike the catching frame.

3

Collecting frames for blueberries are smaller than those for tree fruit and
have no conveyor. They are moved from bush to bush by hand and the harvested
berries are poured from them into boxes.

Some Operational Notes

AERD research reveals that shaking periods of 3 to 5 seconds give the best
results. Increasing the shaking period does not always increase yields but it does
separate more trash and bruise more fruit. The amount of fruit on a tree does not
materially affect the time it takes to harvest it.

When heavily laden limbs are harvested, shaking intervals of 1 or 2 seconds
should alternate with rest periods of approximately the same duration—to give
the fruit a chance to roll off the collecting surface. This procedure reduces strain
on the collecting unit and minimizes pocketing and bruising.

Shaker claws should normally be attached to trees in such a way that the angle
between them and booms is 90 degrees. To make such an attachment, however, is
not always practical. When the angle deviates from 90 degrees, a force is created
that may cause the claw to slip. Points at which attachments should be made de-
pend on branch size, distribution of fruit, visibility, and the angle the limb makes
with the boom. Best results are usually obtained when attachments are made just
below the lowest major lateral branch ona given scaffold branch.

The use of boom or inertia shakers does not appear to damage root systems.

Various amplitudes and frequencies of shaker strokes have been tested. AERD
obtained best results in experimental cherry harvesting with a stroke of 114 inches
and a frequency of 900 to 1,200 cycles a minute.

Open trees on level ground with high heads and three or four scaffold branches
are the easiest to harvest mechanically. Branches that touch the collecting surface
do not shake enough to dislodge the fruit. Rows should be 20 to 24 feet apart and
vegetative ground cover no higher than 2 or 3 inches so the movement of equipment
will not be impeded. Interplants, especially apple interplants in cherry or plum
orchards, often increase mechanical harvesting difficulties by interfering with the
proper placement of catching frames.

Other factors that affect harvesting efficiency (for which little research data has
been accumulated) include: Spraying, fertilizing, and varietal strains.

Decelerator Strips and Cushioning Material

Two common sources of bruising during the shaking operations are fruit strik-
ing other fruit and fruit striking hard surfaces of the catching frame. AERD re-
search approaches these problems through experimental use of decelerator strips
and cushioning material.

Decelerator strips are canvas or other woven material, 3 to 6 inches wide, and
the same length as the catching frame. They are placed 4 to 5 inches over conveyors
or collecting surfaces (see fig. 1). If only one layer of strips is used, the strips are
usually angled 30 to 40 degrees similar to venetian blinds. When two or more lay-
ers are used, the strips may be staggered at different elevations. California ex-
periments showed that deceleration strips prevented serious bruises in mechanically
harvested fruit having as much as 24 inch-pounds of energy at impact—a 0.13-pound
fruit falling 151% feet.

In its search for suitable cushioning material, the AERD is looking for a ma-
terial that, like cotton, absorbs energy rather than one such as sponge rubber that
stores energy and then releases it. The latter momentarily holds the harvested fruit
but then propels it upward into the fruit that is falling.

In some studies, AERD subjected over 120 different samples of material to im-
pact of a falling ball from heights of 1 to 22 feet and determined the impact force.
The data collected are still being analyzed.

AIDS FOR HANDPICKERS

Harvesting fruit for the fresh-fruit market has not been extensively mechan-
ized because equipment now available is not entirely satisfactory. AERD feels, how-
ever, that this limitation will eventually yield to research.

Until such equipment is developed, however, AERD is looking for ways to in-
crease picker efficiency so the costs of harvesting for the fresh-fruit market can be
reduced. Time studies, for example, show that the average picker spends about
one-fourth of his time climbing up and down and repositioning his ladder. And
other studies show that a picker can increase his output if he merely picks the fruit
and immediately drops it instead of placing it in a picking bag.

Self-propelled, Orchard, and Boom Platforms

Experimental use of these has demonstrated their superiority over ladders and
has kept the picker in the tree 100 percent of his time. Most platforms have con-
trols that the picker can use to lower or raise himself as he picks—a distinct ad-
vantage over perpetually climbing down, repositioning a ladder, and climbing up
up again. Figure 2 shows a self-propelled platform.

Tractors or other vehicles are needed to move orchard platforms. Platforms
may also be mounted on the end of booms and the booms raised, lowered, or moved
sideways as the picking progresses.

Commercial versions of platforms are available. Currently, however, they are
too expensive to justify their exclusive use for picking. Most in use were purchased
primarily for pruning and thinning.

Pick-and-drop Equipment

AERD and Washington State University are developing pick—and—drop equip-
ment. It consists of a canvas funnel and a chute mounted on a self-propelled plat-
form (see fig. 2). The picker picks the fruit and then drops it immediately into the
funnel. The funnel carries it into the chute that in turn carries it into a bulk box
also carried on the platform. The chute is padded and baffled so the fruit is not
bruised.

Rotating—table Receiver

An experimental table rotates around the picker. The picker, facing any direc-
tion, can pick fruit and place it on the table. As the table rotates, it transfers the
fruit into a chute that leads to a bulk box.

:

BN=20570

ent to

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ick—and—drop equ

Figure 2.—Worker is utilizing a self-propelled platform with p

pick apples.

IMPROVEMENTS IN HANDLING

Before 1949, the fruit and berry harvests were gathered in small “lugs’’, bushel
baskets, or small crates. Each container was then handled separately—lifted and
stacked onto trailers, wagons, or trucks to be carried out of the orchard, and then,
perhaps, lifted and stacked many additional times before being dispatched to market.
To carry 1,500 bushels of apples out of an orchard, for example, required six men,
three trailers, and two tractors.

Today, however, one man operating lift equipment and handling the harvest on
pallets or bulk boxes can move nearly as many apples in an 8-hour day. AERD
is also working on a machine to pick up filled boxes of fruit or produce spotted be-
tween rows, and other devices and systems.

Pallets

Pallets are essentially low, portable, double-faced platforms upon which smaller
containers can be placed. They are made in such a way that lift equipment can pick
them up, and raise, lower, and usually stack them in one continuous operation.
Thirty to 60 containers, each containing 40 pounds of grapes or other fruit, can be
handled simultaneously as a unit on one pallet.

Bulk Boxes!

Bulk boxes are large boxes constructed on pallets. They may hold 15 to 40
bushels and carry between 800 and 1,500 pounds depending on box size and kind
of fruit. They can be lifted, carried, and stacked in one continuous operation, the
same as pallets, with lift equipment operated by one man. Their initial cost is less
than the cost of a pallet and, perhaps, 20 small containers. They seem to be more
durable than small containers and are not easily lost. Special equipment may be
needed to empty them. Only growers who have lift equipment can utilize bulk boxes
advantageously. AERD estimates that an apple grower who produces 8,000 crates
of apples would find investing in lift equipment and bulk boxes feasible.

Bulk-box handling methods that AERD developed have become standard prac-
tices in all fruit-producing areas of the United States and Canada. During 1962,
over 50 million bushels of apples, pears, peaches, and prunes were handled in bulk
boxes, thereby reducing production costs about $2 million.

Lift Equipment

ARS 42-20 lists seven types of lift equipment, descriptions of which are sum-
marized below.

Industrial Forklift Trucks

These trucks are the most effective of any for lifting, moving, and stacking unit
loads. Growers who pack or store and pack their fruit should provide themselves
with this type of lift equipment for use in and around their packing and storage
areas. Because these units are heavy, have small tires, and have very little clear-
ance, they cannot be operated on the soft, uneven ground usually found in orchards.

*ARS 42-20, “Equipment Used by Deciduous Fruit Growers in Handling Bulk Boxes,” dis-
cusses bulk boxes and lift equipment more fully. This publication is available from the Agricultural
Engineering ‘Research Division, ARS, U.S. Department of Agriculture, Plant Industry Station,
Beltsville, Md. 20705

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Field Forklift Trucks

These trucks can be operated in orchards that are sodded and where grades are
not excessive. Most, however, are too large and expensive for practical orchard use.
They find their maximum, most efficient use around orchard docks and loading areas.

Forklift Tractors

These are effective for orchard use. They are essentially conventional tractors
with the lift mast attached to the rear of the vehicle. The gear box, steering mech-
anism, and driver’s seat are reversed so the driver faces the load. Many manufac-
turers offer new tractors already modified for about $1,200 more than the basic
price of the tractor. Others offer units built on secondhand tractors for about $1,500
complete; a tractor of standard make can be modified for about $1,000. Forklift
tractors cannot be used like conventional tractors (to pull a plow, for example) un-
less they are remodified, which is expensive.

Forklift Attachments for Tractors

These attachments are available for both the front and rear ends of practically
every tractor of standard make (fig. 3). They are serviceable and operate in prac-
tically the same way as those found on industrial lift trucks. They range in price
from $450 to $1,000 or more, depending on capacity, the height to which the forks
can be raised and other features. AERD recommends rear-mounted attachments be-
cause (1) the operator can always see his work, (2) weight of the load is carried
by the heavy rear axle and large tires, and (8) steering is usually not affected since
the load is off the front wheels.

BN=20571

Figure 3.—Tractor equipped with forklift attachments being used to carry apples out of an
orchard. Other types of lift equipment are available.

8

Fork Attachments for Three-point Hydraulic Hitches
Found on Some Tractors

These attachments, costing about $50, can lift a bulk box about 18 inches.
They are quite useful for hauling filled boxes out of an orchard. They cannot be
used for stacking. Overloading these attachments may cause leaks in the tractor’s
hydraulic system.

Fork Attachments for Front-end Loaders

These attachments cost about $50. If used to handle bulk boxes, however, an
added hydraulic cylinder costing an additional $50 between the fork and the lifting
arms of the buckrake or hayloader is desirable so the operator can keep the forks
level. These units have limitations. It is difficult to move the forks smoothly, the
forks are on the front of the tractor so it is sometimes difficult for the operator to
see the load, and the added weight on the front of the tractor makes steering diffi-
cult. When used consistently, AERD recommends (1) that the front axle of the
tractor be reinforced, (2) that oversize tires be used, and (3) that the unit be
equipped with powersteering.

Homemade Lift Units

Growers with well equipped machine shops can make their own lifts—by
shortening a truck chassis, reversing the axle and steering mechanism, and adding a
lift mast. Cost of necessary material is about $1,000. Well built units of this type
operate effectively.

Trailers and Skids

If it takes 20 minutes or less to make a round trip between the orchard and the
packinghouse, storage, or loading area, then bulk boxes can be moved economically
by lift equipment. If the round trip takes longer than 20 minutes, trailers or skids
may be used economically. ARS 42-20 describes a two-wheeled, bulk-box trailer, and
the use of skids.

Straddle Carriers

These vehicles are driven over a load of palletized crates or bulk boxes set on
bolsters. Hydraulically operated raising and lowering shoes pick up the load. Loads
of 5 to 6 tons can be picked up or set down in 10 to 20 seconds. Loaded straddle
carriers can reach speeds of 40 to 50 miles per hour on surfaced roads. Since they
have large wheels they can be driven into fields and orchards. They are expensive,
however, and AERD estimates that they must be used continuously 10 to 16 hours a
day for several weeks before their purchase can be justified. ARS 42—42 illustrates
and describes straddle carriers more fully (see footnote 1, p. 7 and footnote 3, p.14).

Handling Fruit in Water

Handling fruit in water, worked out by AERD and Michigan State University,
is simple and effective. Cherries, for example, come from the picker’s pail onto a
sorting board and from there into tank trucks of water. When filled to capacity, the
tank and contents are cooled to 60 degrees F. or less by additional running water
and the truck then goes to the processing plant. At the plant, the driver attaches
a flume, opens the outlet valve and flushes the cherries out with a hose. No other
handling between orchard and processor is needed. (Tanks may also be fastened to
pallets and handled with lift equipment.)

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The sorting table provides a practical means of removing defective fruit. The
cooling preserves on-the-tree quality. Distances between orchard and processor are
no longer critical—last year cherries in water were transported over 250 miles with
no loss in quality. This system eliminates the need for lugs and the troublesome
problems of lug storage, maintenance, and distribution. By reducing production
costs, it benefits grower, processor, and consumer. Several hundred tons of cherries
were handled this way last year.

AERD has also perfected a water-flotation dumping unit for apples that was
used to empty over 400,000 bushels of apples last year. At least 12 units patterned
after the AERD unit are now in use.

Machine To Pick Up Filled Lugs?

In 1961, AERD investigated the feasibility of a machine to pick up lugs and in
1962 the machine was built and tested. It mounts on a tractor. It has a lifting de-
vice, powered by a hydraulic motor, that exerts enough pressure against the sides
of filled lugs to raise them onto an elevating conveyor as the tractor moves between
rows. The conveyor, powered by the tractor’s power takeoff, moves the lugs back
under the rear axle of the tractor and raises them to a holding platform above a
trailing wagon or trailer bed. A worker on the wagon or trailer bed removes the
filled lugs without stooping and stacks them.

The pickup device can be adjusted to accommodate almost any size or shape
of box so the machine can be used on many crops. The machine also appears to
be especially advantageous in small orchards or fields where it might permit a
family to harvest its fruit or other crops without employing outside help. It should
cost less than forklift equipment. Commercial models are not yet available.

HARVESTING AND HANDLING SPECIFIC CROPS

The fact that shakers and catching frames are practical and commercially ac-
ceptable for mechanically harvesting certain tree fruits and berries is encouraging.
It has prompted AERD to experiment further with this system and to explore
other harvesting methods as well.

Sour Cherries

Domestic production of our sour cherries approaches 130,000 tons yearly, the
“farm value” being about $20 million. It formerly required 45,000 workers to har-
vest Michigan’s crop alone—35,000 of which were nonlocal and had to be recruited
in other States or from foreign countries. New York, Wisconsin, Oregon, and other
States faced similar problems.

Today, under conditions existing in most orchards, 6 men and suitably designed
tree shakers and catching frames can harvest as many sour cherries as 33 hand-
pickers. During 1962, about 2 million pounds of sour cherries were harvested
mechanically at a cost of approximately 14 cent per pound against 3 cents per pound
usually paid handpickers.

*See ARS 42-83, “Machine For Picking Up Filled Grape Boxes,” available from the Agri-
cultural Engineering Research Division, ARS, U.S. Department of Agriculture, Plant Industry Sta-
tion, Beltsville, Md. 20705

10

Cherry harvesting equipment costs between $5,000 and $7,000. AERD esti-
mates that if a grower has at least 2,250 trees (about 25 acres) and harvests about
100 pounds of cherries from each tree, he could pay for the equipment in about 114
years. If the equipment were depreciated for 3 years (it would last much longer
under normal use), a grower who had only 15 acres of cherry trees could normally
afford harvesting equipment.

AERD also found that cherries could be mechanically harvested with no more
bruising than normally occurs when cherries are picked by hand. Undergoing
mechanical shaking, falling through the tree, striking the collecting unit and rolling
over it to the conveyor bruised the cherries very little. Decelerator strips, how-
ever, are necessary over conveyors and desirable over catching surfaces.

In three of six orchards mechanically harvested, about 2 percent of the cherries
retained their stems. In the other three, however, 7 percent retained their stems.
(Stem retention is undesirable in cherries destined for processing.) Causes for this
variation are not definitely known. In some tests, however, attachment was found
to vary with the maturity of fruit and the nature of shaking—the number of at-
tached stems decreased as cherries became riper; mechanical shaking yielded fewer
with stems than manual shaking. AERD is investigating the possibility that a
relationship exists between stem attachment and the amount of nitrogen in the soil
or tree. A small percentage of stemmed cherries does not seriously hamper proc-
essing.

Sweet Cherries

A considerable portion of the sweet cherry crop is harvested for brining be-
fore the cherries are mature enough to go to the fresh fruit market or to the canner.
Mechanically separating such immature fruit from the tree requires rather violent
shaking and causes considerable bruising. None of 20 or more chemicals that AERD
tested to loosen the cherries before attempts at mechanical harvesting proved to be
satisfactory.

Further AERD investigation, however, reveals that sweet cherries allowed to
reach full maturity increase in size and weight by about 31 percent and that such
mature cherries can be mechanically harvested. Whether they can be successfully
brined remains to be determined.

AERD research also showed that sweet cherries can be handled in bulk boxes
at depths of 16 inches without loss in quality and with savings in time, labor, and
money.

Plums

Equipment used to harvest sour cherries mechanically can be used to harvest
Stanley Prune plums. Many growers in Michigan and elsewhere are profitably ex-
ploiting this fact since the two crops mature at different times.

Compared to handpicking, mechanically harvesting Stanley Prune plums saves
the grower about 23 cents per bushel. About 80 trees yielding 5.1 bushels per tree
would justify spending $90 for the use of mechanical harvesting equipment.

When AERD experimentally harvested 39 Stanley Prune plum trees, 3.1 per-
cent of the plums were severely bruised and an additional 4.2 percent were slightly
bruised. Leaves and twigs that shook off with the plums accounted for 2.7 percent

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of total weight. From 3 to 14 percent came off with stems attached. The quality
of the mechanically harvested plums compared favorably with that of the hand-
picked being received at the same processing plant. The cooperating processor
stated that leaves, twigs, and stems could be removed during processing without
difficulty and that bruised plums were acceptable if processed promptly.

AERD attempts to harvest Damson plums with the same equipment were
abandoned because about 5 percent of the plums came off with spurs attached.
AERD feared that losing so many fruit spurs might reduce the amount of plums
borne in succeeding years.

Prunes

Prune growers in the Sacramento Valley, Calif., have adopted mechanical har-
vesting methods. A three-man crew can harvest up to 70 trees per hour using
equipment and methods that AERD and the University of California developed.
The equipment consists of a conveyor belt 6 feet wide and 22 feet long, suitable
catching surfaces, and a shaker. As the fruit shakes from the tree, it falls or rolls
onto the conveyor and moves directly into bulk boxes.

Labor costs with this equipment are about $2 per ton compared with $12 per
ton for hand harvesting. AERD estimates that a grower would have to harvest
3,200 trees (about 30 acres), four boxes to the tree, before he could afford such
mechanical harvesting equipment—the cost (including interest, taxes, and insur-
ance) amortized over 3 years.

In the Santa Clara Valley, Calif., most of the prunes fall from the tree as
they mature. This phenomenon presents two problems: (1) Shakers and catching
frames could not be utilized efficiently every year because in any given year a large
percentage of the prunes might already be on the ground, and (2) handpicking
the fallen prunes is costly and slow. After studying these problems, AERD con-
cluded that a ground pickup device or a blower-catch operation to harvest many
trees quickly or both would be practical.

The ground pickup device became a machine, self-propelled, 20 inches wide,
and operated by one man walking behind it. The man and this machine replaces
six or seven handpickers and can harvest about 1,000 pounds of prunes an hour.
The operation does not damage the fruit or pick up excessive amounts of soil or
trash. About 20 of these machines were in use last year.

AERD engineers and their collaborators also produced a device to remove
prunes from trees by modifying a commercially available frost protector blower
(6-foot propeller; air velocity, over 100 miles per hour). They installed 9-inch
louvers that could be either rotated or oscillated in front of the air stream, and
harvested 4 plots of 60 trees every 4 or 7 days. Travel speeds of 21% and 114 miles
per hour and oscillation and rotation rates of 60 per minute were used. Results
showed that this method was selective in removing only ripe fruit, but the total
removed was lower than desirable especially on the last harvest. The results were
promising, however, and AERD will conduct more research using this device, per-
haps with supplemental shaking.

Blueberries

Cultivated blueberries are grown commercially in the Middle Atlantic States,
Great Lakes area, and the Pacific Northwest. About 35 percent of Michigan’s
blueberries and 30 percent of New Jersey’s are harvested mechanically by means

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of equipment and methods already described that AERD developed. These harvest-
ing improvements are currently saving growers about 5 cents per pound. Even at
a 4-cent-per-pound savings, AERD estimates that 20,000 pints or 4 acres of blue-
berries would justify a mechanical harvesting unit. Equipment for a four-man crew
costs about $2,000. Amortized over 3 years, the annual cost would be about $800.

AERD and Michigan State University have also done considerable work on
a continuous blueberry harvester that could reduce blueberry harvesting costs to
14 cent per pound by enabling 3 men to do the work of 120 handpickers. This
experimental unit, under development for about 4 years, has harvested over 90
percent of the ripe berries from experimental plots without damaging the plants
and without picking an excessive amount of unripe berries.

The machine is self-propelled and has two large rotating spindles mounted ver-
tically on a steel frame. Each spindle has 160 wooden horizontal “fingers.” In
operation, the machine straddles a row of blueberry plants with a spindle on
either side of the plants. The spindles rotate, and the fingers vibrate against the
plants, shaking the berries off into boxes that are at the base of the machine.

Commercial models of this machine are not yet available.

Dates

Date palm trees are 30 to 60 feet high. Growers are finding it increasingly
difficult to get handpickers willing to work at such height. AEKRD, however, is
rapidly developing mechanical harvesting methods for dates that should relieve this
harvesting crisis. Although experimental, the methods were used last year to har-
vest commercially more than 114 million pounds of dates. AERD achieved harvest
rates of 0.96 acres per hour (46 palms per hour) where at least one-half the
bunches on each palm were mature.

One method utilizes a moving tower from which mature bunches from oppo-
site palms are harvested simultaneously. Workers, using specially designed vi-
brators, shake mature dates directly into bulk boxes as the tower moves between
the rows.

The other method utilizes a smaller tower. One-half a palm is bunch harvested
at a time and the bunches are hauled in a trailer to a central point for shaking.

The vibrators deliver a 314-inch stroke at 600 to 1,100 cycles per minute and
can remove all the dates from a bunch in about 2 seconds. Two men feeding and
operating one vibrator can shake 450 bunches per hour.

AERD made time studies of the two harvesting methods and concluded: (1)
Bunch harvesting is feasible, and (2) either method reduces total harvesting costs
relative to the handpicking method.

Apples

Preliminary studies by AERD and Michigan State engineers showed that it
might be feasible to mechanize the harvest of apples destined for processing. The
engineers mechanically harvested several hundred bushels of apples and placed them
in crates at a cost of approximately 3 cents per crate. Apples apparently shake
off the tree very easily. One grower shook off 200 bushels in an hour last year.

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But the significant savings made by mechanically harvesting apples instead of
handpicking them are now more or less offset by increased processing costs because
of bruising and other factors. The aim of present research is to reduce these in-
creased costs—for example, from a possible $7.05 a ton to less than $1.00 per ton.

Apples for the fresh-fruit market are mostly handpicked—again because ma-
chine picking causes too much bruising and the consumer won’t buy excessively
bruised apples.

Peaches, Pears, and Apricots

Engineers at the California Agricultural Experiment Station studied the feasi-
bility of shaking peaches and Bartlett pears onto a catching frame. More than 75
percent of the peaches and an average 68 percent of the pears were free from
visible defects. The fall through the trees damaged more fruit than the falling
onto and over the catching frame. The taller the tree, the more fruit was injured.

AERD attained a degree of selectivity (harvesting only mature fruit) in har-
vesting apricots by using an inertia shaker. Frequencies of 250 to 400 cycles per
minute and a stroke of 1-3/4 inches at the limbs gave the best results. Similarly
harvesting peaches gave only limited selectivity and AERD concluded that such
a method of harvesting would not be satisfactory for commercial operations. These
studies further showed that the use of decelerator strips and proper padding is
mandatory to reduce fruit injury.

Grapes

In 1962, six States in the United States produced 286,250 tons of Concord
grapes, which were mostly picked by hand and handled in boxes, lugs, and trays
that hold from 32 to 42 pounds each. Thus, about 15 million containers had to
be picked up by hand and moved out of vineyards on trailers or wagons. Grapes
are harvested late in the season and it is difficult to find workers to do the harvest-
ing.

The efforts of AERD’s engineers to relieve this situation began in 1958.° They
initially found that very little experimental work had been done to improve the har-
vesting and orchard handling of Concord grapes. They also found that overfilling
the lugs, and other accepted harvesting and handling practices, accelerated quality
deterioration. Other AERD findings are summarized below:

Mechanical Harvesting

AERD engineers experimentally harvested two 14-vine rows of Concord grapes
using the same equipment used to harvest blueberries mechanically. They harvested
at the rate of 318 pounds per man-hour—about twice the rate of handpickers. But
the vibrators cracked between 45 and 50 percent of the grapes during separation; no
damage resulted when the grapes fell on the collecting fame.

Shaker equipment can be designed to harvest muscadine grapes when the acre-
age warrants.

”

*See ARS 42-42, “A Progress Report on Harvesting and Handling Concord Grapes,” available
from the Agricultural Engineering Research Division, ARS, U.S. Department of Agriculture, Plant
Industry Station, Beltsville, Md. 20705

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Drop Tests

Bunches of grapes should not be dropped more than 6 inches. Single grapes
may be dropped as much as 18 inches without causing significant injury.

Pressure and Piling

Bunch grapes may be piled to a depth of 18 inches; shelled grapes (grapes that
fall from the bunches) to a somewhat lesser depth.

Settling Tests

Ten inches of freshly picked bunch grapes allowed to stand for 48 hours settled
very little. Twenty-four inches of similar lots carried approximately 7 miles in a
pickup truck settled about 214 inches or about 10 percent. Other transporting
studies showed that bunches of grapes piled to a depth of 18 inches can be handled
without appreciable damage.

Other Properties

Fruit accounts for 97 percent of the weight of bunched grapes; stems for the
other 3 percent. Shelled grapes occupy only about 75 percent of the volume taken
up by bunch grapes.

Pallet Handling

Handling lugs of grapes on pallets with forklift trucks increased the rate of
handling from 40 lugs per hour to 59 in one instance and to 79 in another. These
figures indicate that one forklift unit can handle up to 40 tons of grapes in an 8-
hour day. AERD estimates that growers with 30 or more acres of grapes can
justify the purchase of lift equipment. Less than 30 acres may also merit lift equip-
ment because it makes the work easier—even though profits may not be increased.

Bulk-box Handling

Emptying filled lugs into bulk boxes, accumulating the boxes until 15 were filled,
and then carrying the bulk boxes to the plant with a straddle truck increased the
handling rate from 40 to 60 lugs per man-hour. These trials were so promising that
the cooperating processor asked that the work be continued and expanded.

Citrus

Last year growers paid $50 million to have their citrus fruit picked. Expecta-
tions are that this production cost will increase as the supply of handpickers
dwindles and until research can develop mechanical harvesting methods.

AERD has already tested shakers and catching frames to harvest grapefruit.
In preliminary trials, AERD and the Citrus Experiment Station, Lake Alfred, Fla.,
achieved from 50 to 70 percent removal using strokes of 1 to 114 inches. Additional
work may reveal that the proper combination of frequency and amplitude of stroke
will remove at least 90 percent of the fruit. The experimenters also tested oscillat-
ing air blasts at velocities up to 125 miles per hour. They achieved 99 percent re-
moval but felt they also removed too many leaves.

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Also tested were a catching frame and a frame-mounted inertia shaker. The
frame had a conveyor and elevator to handle fruit in unusually large amounts. A
severe freeze halted this work in December 1962. Other work in Florida includes in-
strumentation of a shaker to measure removal forces and the screening of chemi-
cals to find an efficient fruit loosener.

In California, AERD and State engineers are studying the physical properties
of citrus fruit in order to utilize these properties to achieve efficient mechanical har-
vesting of the fruit. Preliminary tests performed on navel oranges indicate (1) that
more than 75 percent of the oranges detached with a pull applied in line with the
stem were removed without stem or calyx, and (2) that oranges detached by spin-
ning separated with or without stem or calyx depending on the orientation of the
spin axis with the axis of the fruit core. Limited studies of citrus trees and fruit
failed to reveal any electrical or thermal properties that could be utilized in me-
chanical harvesting.

Drop tests in California are being evaluated. Additional work is planned in both
Florida and California.

Other Approaches and Applications

AERD, in collaboration with the Michigan and Washington Agricultural Experi-
ment Stations, is also planning research to improve equipment and methods for har-
vesting apples and pears from trees of different sizes and shapes and at different
planting distances—for example, tree walls and tree hedges of standard, semidwarf,
and dwarf trees; trees on trellises; and trees topped and in box shapes at different
distances apart. Where orchards with the desired tree size, shape, and spacing are
not available, trees will be grown for the study by the Michigan and Washington
State Experiment Stations.

The University of California, Michigan State, and Cornell Universities are
working on machines to harvest and handle grapes. The California machines neces-
sitate training the vines so the grape clusters hang uniformly under holding wires.
The machine then clips the clusters with a moving knife and loads them into a
trailer. The Michigan State and Cornell machines are applications of the shaker
method of mechanical harvesting.

The University of Florida has been working for many years on equipment to
pick oranges and grapefruit. One unit tested uses spindles to twist the fruit off the
tree. Although experimental, this unit appears to be promising.

Others who have fruit harvesting projects either active or being planned are
Pennsylvania State University, Rutgers University, Oregon State University, Ohio
State University, and the University of Connecticut. Equipment manufacturers are
also conducting research. Any promising technique developed by these and other
experimenters will presumably find immediate application in the Nation’s vineyards
and orchards.

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