Bulletin 579 November 1956
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATIONS
JOSEPH R. BECKENBACH, Director
in cooperation with
Agricultural Marketing Service, United States Department of Agriculture
Equipment for Mechanical Harvesting
and Handling of Irish Potatoes
in the Southeast
J. S. NORTON, R. E. L. GREENE AND L. J. KUSHMAN
Assistant Agricultural Engineer and Agricultural Economist, Florida
Agricultural Experiment Station, and Associate Plant Physiologist, Quality
Maintenance and Improvement Section, Agricultural Marketing Service,
U. S. Department of Agriculture, Respectively
Fig. 1.-Interior of bulk body. Note that boards are placed over conveyor
before potatoes are placed in the body. They are removed as the' load
is unloaded to allow the potatoes to roll down on the conveyor chain.
INTRODUCTION .....................------------------ -- -----.----- .....----- -.... 3
SYSTEMS AND EQUIPMENT FOR HARVESTING AND HANDLING POTATOES.-..-.. 4
Conventional System .......-........ --........ --....- ----- ......------ .. 4
Completely Mechanized System ......-..-.......------..--....--..... ... 4
Partially Mechanized System .-.......-------..----.......-------..-. 8
AMOUNT OF USE, RATE AND COST OF HARVESTING, AND QUALITY OF
POTATOES HARVESTED WITH MECHANICAL EQUIPMENT.......................- 9
Use of Equipment in Florida and Alabama in 1953 and 1954..-...---. 9
Investment, Rate of Harvesting, and Cost of Harvesting Potatoes
With Mechanical Equipment ..-...........-.......--.--- ............ 10
Amount of Physical Injuries in Potatoes Harvested Mechanically .. 12
PROBLEMS ENCOUNTERED AND SUGGESTIONS FOR IMPROVING THE
OPERATION OF MECHANICAL EQUIPMENT ..........-......-......-.....-----..--14
Selection of Equipment .---....... --...-......---..------- --- -------- 14
Coordinating Field and Packinghouse Operations .............--..-- ....--.. 15
Obtaining Maximum Rate of Harvesting .......--..-- ..-..--. ........-----.. 15
Clod and Trash Elimination ........................... .. ... ..-- ..------.. 19
Reducing Injuries in Digging, Loading and Hauling Potatoes ......----20
Safety ................... ....... ... .... .------....-. .. 23
Improving Facilities at Packinghouses for Receiving Potatoes
Hauled in Bulk ........--- -.......-.... --..-----------.. 23
SUMMARY ----------------- .......----...--- --...------------................. 30
LITERATURE CITED .......---- ..-....---.-....--..--..------ ...-----------.... 32
Equipment for Mechanical Harvesting
and Handling of Irish Potatoes
in the Southeast*
J. S. NORTON, R. E. L. GREENE AND L. J. KUSHMAN
Assistant Agricultural Engineer and Agricultural Econom'st, Florida
Agricultural Experiment Station, and Associate Plant Physiologist, Quality
Maintenance and Improvement Section, Agricultural Marketing Service,
U. S. Department of Agriculture, Respectively
Growers are mechanizing the harvesting and handling of
potatoes for at least three reasons: (1) to reduce the amount
of labor required, (2) to improve general quality and salability
of the crop and (3) to reduce costs and increase returns from
Idaho, an early leader in the use of potato harvesters, had
1,450 machines in use in 1949 (3)1. However, most of these
were machines that placed the potatoes in bags but still required
manual handling of the bags. Complete mechanization of potato
harvesting probably has made its most rapid gain in the Red
River Valley area of Minnesota and North Dakota. In 1948
less than a dozen harvesters were used in that area; in 1954 over
75 percent of the potato crop was harvested mechanically (1).
At present all of the major potato producing areas are devoting
special attention to the use of mechanical equipment.
Although a few homemade harvesters were used previously (2),
commercially built mechanical harvesters were first used to
an appreciable extent in the Southeast in 1952. During that
year preliminary observations were made on the use of mechani-
cal equipment in Florida and Alabama. In 1953 the Florida
Agricultural Experiment Station began a regional research study
in which special attention was given to mechanical harvesting
and handling of potatoes in Florida and Alabama. This work
was done in cooperation with the Quality Maintenance and Im-
provement Section of the Agricultural Marketing Service, U. S.
Department of Agriculture.
This study was supported by funds provided by the Research and
Marketing Act of 1946 and State research funds. It is a contr-buting
project to Southern Regional Potato Marketing Research Project SM-9.
SItalic figures in parentheses refer to Literature Cited.
4 Florida Agricultural Experiment Stations
Data were obtained on the cost of operating mechanical equip-
ment, some of the changes needed to improve its operation, and
the amount of physical damage to potatoes harvested.
Work was directed toward developing and testing equipment
to be used at the packinghouses to aid in removing clods, vines
and trash from potatoes hauled in bulk. Attention was given
also to the problem of transferring potatoes from bulk trucks
to bins as used by some of the packinghouses in the Hastings,
The purpose of this report is to describe the various systems
and equipment being used to harvest and handle potatoes
mechanically in the Southeast and to present data on amount of
use, performance and cost. Major emphasis is given to describ-
ing problems encountered and suggestions for improving the
operation of mechanical equipment. No effort is made to ana-
lyze cost and quality factors, as these data will be presented in
SYSTEMS AND EQUIPMENT FOR HARVESTING AND
Systems for harvesting and handling potatoes, as used in the
Southeast, may be classified into three groups: (1) conventional
system, (2) completely mechanized system, and (3) partially
In the conventional system of harvesting, a one-row or two-
row tractor-drawn digger is used to dig the potatoes and drop
them back on the ground. They are then picked up by hand
and placed in field containers-bags or boxes. When the potatoes
are hauled from the fields the containers are loaded on trucks
manually and are also unloaded manually at the packinghouse.
COMPLETELY MECHANIZED SYSTEM
In complete mechanization, both the harvesting and the hand-
ling are mechanized. Mechanical equipment is used to dig the
potatoes and load them in bulk in special bodies mounted on
trucks or trailers. The bodies are hopper-shaped and have in
the bottom a draper chain (rod) conveyor by which the potatoes
are unloaded (Fig. 1). This conveyor is driven by a detachable
electric motor (Fig. 2).
states handled in bulk at the p' ijnghouse. In
Fig. 2ctUnloading moving down a slide onto an endless belt. Rate of
loading thn be controlled by starting g and stopping the conveyor chain.
Fig. 3.-Two-row direct harvester loading potatoes in bulk.
6 Florida Agricultural Experiment Stations
Direct Harvesting.-Direct harvesting means that the po-
tatoes are dug, vines and trash eliminated and the potatoes
loaded in bulk in one continuous operation. A direct harvester
may be either a one-row or two-row machine; it may be self-
propelled or trailer-type pulled behind a two-row digger (Fig. 3).
Usually a two-row machine is used because the capacity of a
one-row machine is insufficient to warrant the use of bulk trucks.
Indirect Harvesting.-With indirect harvesting, potatoes from
two rows are first dug and placed together in a window by
means of a two-row digger equipped with a windrowing attach-
ment (Figs. 4 and 5). They are then picked up from the wind-
row by a moving chain elevator on an indirect harvester that
loads them in bulk after eliminating vines, clods and trash. No
digger blade is used on the indirect harvester.
Windrowing attachments observed in the Southeast may be
classified into two general types: (1) Single apron, consisting
of one cross conveyor mounted at the rear of one side of the
two-row digger; this conveyor deposits the potatoes from both
sides of the digger into the same row; (2) double apron, consist-
ing of two conveyors, one mounted at the rear of each side of
the digger, which convey the two rows of potatoes together in
the middle. A chute-type windrower has been used in other
areas but has not proved very satisfactory because of the high
clearance necessary to provide sufficient slope for the potatoes
and trash to slide to the center.
Advantages and Disadvantages of Direct and Indirect Methods
of Harvesting.-The choice of method is affected by equipment
available, soil types, harvesting conditions, and marketing pro-
gram. The quality of the work done depends more on the care
in operating the equipment than on the method. Potatoes har-
vested by the direct method move directly from the soil to the
bulk trucks and thus are not damaged by exposure. This method
requires only one tractor for the digging and loading.
Potatoes harvested by the indirect method may be left in the
window for a short period to dry before they are picked up
by the harvester. In some areas it is claimed that drying in
the window helps in eliminating clods, soil, and trash when
extremely adverse conditions caused by wet weather, heavy
soils, or heavy weed growth exist. It is stated also that the
drying of the potatoes helps to set the skins and thus results
in less skinning. It has been impossible to determine the validity
S 4 LA' 's.3A 'i-
Fig. 4.-Digger with window attachment mounted on left side. Note the
drag used for making a wide, flat furrow into which potatoes fall.
Fig. 5.-Windrowing potatoes for the indirect method of harvesting.
8 Florida Agricultural Experiment Stations
of these claims because the indirect method of harvesting has
not been used much in the Southeast. However, since warm
and dry weather usually prevails at harvest time, exposure
may quickly cause desiccation injury (scald spots) at skinned
areas. Mechanical breakdown, causing a delay in picking up
potatoes that have been windrowed, also has resulted in losses
due to sunscald.
Farmers in Florida and Alabama have been reluctant to use
the indirect method because they feel that it is too slow. Under
soil and digging conditions in areas where the machines have
been used, they have not seen any advantage in handling the
PARTIALLY MECHANIZED SYSTEM
Partial mechanization refers to the use of mechanical equip-
ment for only a part of the harvesting operations and the use
of conventional methods for the remainder. That is, the po-
tatoes may be dug with a harvester that places them in field
containers, which are then handled manually in the field and
at the packinghouse in the usually way. On the other hand, the
potatoes may be dug and picked up in the conventional way and
then loaded in bulk mechanically with an elevator into hopper-
type bodies similar to those described above (Fig. 6).
Fig. 6.-Field loader used in bulk loading potatoes from field containers.
Mechanical Harvesting and Handling of Irish Potatoes 9
Bagging potatoes mechanically is usually carried out with a
one-row direct harvester, since volume harvested is limited by
the speed at which the bagging operation can be performed.
With the usual commercial one-row machine, field containers
are set off along the row as they are filled. In the case of a one-
row machine developed at Hastings, Florida, the bags of po-
tatoes are piled on a platform on the harvester and carried to
the end of the row to be unloaded. This reduces exposure of
the potatoes and also requires less labor for loading the field bags.
The field loader used for loading the potatoes from the field
containers in bulk is usually a draper chain elevator mounted
on wheels (Fig. 6). It may be either tractor-drawn with the
elevator chain being driven by the tractor power take-off, or
it may be pulled by the truck by means of a bracket mounted
on the truck, and the elevator driven by an auxiliary engine
mounted on the loader. Field loaders can be obtained with
capacities up to 1,000 bushels per hour.
AMOUNT OF USE, RATE AND COST OF HARVESTING, AND
QUALITY OF POTATOES HARVESTED WITH
USE OF EQUIPMENT IN FLORIDA AND ALABAMA IN 1953 AND 1954
In 1953, 1,125 acres of potatoes were harvested mechanically
in Florida with six farmer-built and two commercially-built har-
vesters. The farmer-built harvesters placed the potatoes in
bags or bushel size boxes. Two growers also field-loaded and
hauled potatoes from 500 acres in bulk after digging and pick-
ing them up in the conventional way. In Alabama, 1,700 acres
of potatoes were harvested with 12 commercially-built harvest-
ers owned by farmers and 350 acres with machines operated
on a custom basis. Of the harvesters owned by the farmers
in Alabama, six were two-row direct and six were indirect. All
the mechanically harvested potatoes were handled in bulk.
In 1954, commercially built harvesters operated in the Fort
Myers and Hastings areas in Florida. During the 1954 season
four farmer-owned and two custom-operated two-row direct har-
vesters that loaded the potatoes in bulk harvested 1,335 acres
in the Fort Myers and Hastings areas. Eleven farmer-built
one-row machines that placed the potatoes in bags were used
to harvest 522 acres in the Hastings area. In addition to the
mechanically harvested potatoes, 746 acres were dug with con-
10 Florida Agricultural Experiment Stations
ventional diggers and picked up by hand, after which they were
field-loaded and hauled in bulk to the packinghouse.
In Alabama, 1,755 acres of potatoes were harvested and han-
dled entirely with mechanical equipment. Field loaders and
bulk trucks were used to handle 321 acres of conventionally dug
potatoes from the field to the washer. Although the acreage
harvested mechanically in Alabama in 1954 was less than in
1953, it represented about 9 percent of the crop, whereas the
1953 figure represented only 6 percent. However, of the total
acreage harvested mechanically, only 634 acres, or 36 percent,
were harvested by the indirect method in 1954, whereas 1,055
acres, or 53 percent, were harvested by the indirect method
INVESTMENT, RATE OF HARVESTING, AND COST OF HARVESTING
POTATOES WITH MECHANICAL EQUIPMENT
A unit of equipment for a completely mechanized system nor-
mally consists of a harvester and three to five hopper-type boxes.
The investment in a unit of equipment for the direct method of
harvesting varies from $7,500 to $10,000. This amount does not
include the investment in a tractor for pulling the harvester or
for trucks used in hauling potatoes.
Rate of Harvesting.-The volume of potatoes harvested per
hour varies with yield per acre, digging conditions and other
factors. During the 1954 season, records of daily performance
were kept on a number of harvesters in the Alabama and the
Hastings, Florida, areas. Data were obtained on such factors
as hours operated, acres and volume harvested,2 amount of oper-
ating time lost, and yields per acre. The average rate of harvest-
ing for mechanical harvester B3 in Alabama was 101 packed
bags per hour (Table 1). However, the quantity harvested per
hour averaged only 78 bags for a third of the days when the
rate of harvesting was lowest and 124 bags for the third when
the rate of harvesting was highest.
In the Hastings area the average rate of harvesting for the
make B harvester digging Sebago potatoes was 137 packed bags
"2 "Packed bag" or "bag" as used in this report means a 100 pound
packed bag or its equivalent converted from other measures.
3 Data were obtained for two makes of direct mechanical harvesters.
Since the machines varied considerably in number of laborers required to
operate and other factors, it seemed advisable to not average the data.
The machines were designated as make A and make B. Data for make
B harvester is presented in this report since this was the make of harvester
used most in the two areas.
Mechanical Harvesting and Handling of Irish Potatoes 11
per hour (Table 1). Rate of harvesting varied from 91 bags
for the low group to 192 bags for the high group. Rate of har-
vesting for the one-row machines averaged 63 packed bags per
hour and varied from 49 bags for the low group to 80 bags for
the high group.
TABLE 1.-VARIATION IN AMOUNT OF POTATOES HARVESTED PER HOUR WITH
MECHANICAL HARVESTERS, AVERAGE ACRES HARVESTED, YIELD PER ACRE
AND PROPORTION OF OPERATING TIME LOST, ALABAMA AND HASTINGS
AREA OF FLORIDA, 1954.
Quantity Number Average tion of Average Rate of
Harvested of Obser- Yie.d Operating Harvest.ng per Hour
per Hour nations per Acre Time Lost Quantity Acres
100 Lb. 100 Lb. I 100 Lb.
Packed Bag Bags Percent I Bags Number
Baldwin County, Alabama, Make B Mechanical Harvester
Less than 90 ...... 9 113 4 78 .69
90-109 ............. 7 125 9 99 .79
110 or more ....... 8 131 5 124 .99
Total or average 24 124 7 101 .82
Hastings Area, Florida, Make B Mechanical Harvester
Less than 120 .... 13 155 11 91 .59
120 169 -.........- 13 208 14 150 .72
170 or more ....... 9 227 13 192 .84
Total or average 35 197 12 137 .70
Hastings Area, Florida, One-Row Mechanical Harvester
Less than 55 ...... 16 152 2 49 .32
55-69 .................. 15 193 6 59 .31
70 or more .......... 17 237 7 80 .34
Total or average 48 196 5 63 .32
In 1954 two-row direct make B harvesters averaged about
0.70 acre per hour in Florida and 0.82 acre in Alabama (Table 1).
The one-row machines used in the Hastings area averaged 0.32
acre per hour. In both areas most of the two-row machines
harvested 100 to 125 acres per season, with an occasional ma-
chine harvesting as much as 175 acres.
Using mechanical harvesters is a new experience for most
operators and many have not made the changes necessary for
the most efficient use of the equipment. The average rate of
harvesting should increase as changes and improvements are
12 Florida Agricultural Experiment Stations
made in the machines and as the operators improve their tech-
niques in operating them.
Cost of Harvesting.-Growers using mechanical equipment can
expect to reduce their harvesting and handling costs over present
methods by at least 5 to 10 cents per 100-pound packed bag if
their equipment is operated with reasonable efficiency. A sum-
mary of data obtained in 1954 showed that the average cost of
harvesting and handling potatoes in Alabama with mechanical
equipment was 31.6 cents per 100-pound packed bag.4 In the
Hastings area the average cost was 23.7 cents per packed bag
with complete two-row equipment and 25.8 cents with one-row
machines. These costs included all costs-both operating and
fixed-from removing the vines before digging until the potatoes
were placed on the washing equipment in the packinghouse.
Cost per unit is materially affected by volume harvested per
day and number of acres harvested per season by a unit of equip-
ment. Records from two efficient operators, one each in Florida
and Alabama, showed their cost to be about 15 cents per packed
bag for all operations of harvesting. Included in this amount
was the cost of placing the potatoes on the washer in the packing-
house. Both operators had an average rate of harvesting of
225 packed bags or more per hour. Acres harvested per unit of
equipment were 185 and 225 for the two operators, respectively.
AMOUNT OF PHYSICAL INJURIES IN POTATOES HARVESTED
A very important factor in considering the use of mechanical
harvesting and handling equipment is its effect on the quality
of the potatoes, especially damage due to physical injuries.
Examination of numerous samples of potatoes shows clearly
that the amount of physical injuries resulting when mechanical
equipment is carefully operated and the packinghouses set up
properly to receive potatoes handled in bulk is as low as or lower
than in those harvested and handled by usual methods. Figure
7 shows the variation in average amount of physical injuries
in samples of mechanically harvested potatoes collected in nine
packinghouses in Florida and Alabama in 1954.5 In each case
the samples were collected from the washer, so the amount rep-
resents all injuries resulting from digging, loading, unloading
and conveying the potatoes to the washer.
'Detailed data on costs will be given in a later report.
Detailed data on amount of physical injuries will be given in another
Mechanical Harvesting and Handling of Irish Potatoes 13
Results for the Hastings area are for potatoes of the Sebago
variety. In Alabama the results are for red varieties only, with
Bliss Triumph predominating. Differences in varieties and ma-
turity of the potatoes account for a large part of the difference
in amount of physical damage between the two areas.
per cwt Hastings Area Alabama
I Non Grade )
Defects ) Total
0- Probable Grade ) Defects 3
Defects ) W 3
20 2 i .")
Good Good Ave. Poor Poor Good Ave. Ave. Poor
Arrangement of Packinghouse for Receiving Potatoes
Fig. 7.-Amount and type of physical injuries in potatoes at end of
washing when harvested and handled with mechanical equipment and packed
in 9 different packinghouses, Hastings area, Florida, and Baldwin County,
Variations in damage in samples collected from different pack-
inghouses in the same area were due partly to type of harvesting
equipment and the care with which it was operated. Principal
factor causing variation in damage, however, was the manner
in which the packinghouses were set up to receive potatoes in
bulk. In a packinghouse in the Hastings area, where total dam-
age averaged only about 3 percent, the harvester used in digging
the potatoes was very carefully operated and the arrangement
of receiving equipment at the packinghouse was very satis-
factory for the prevention of injuries (Fig. 2). However, even
in houses where damage was high, it usually was no more than
14 Florida Agricultural Experiment Stations
in potatoes dug by conventional methods. In Alabama, samples
were taken at random on two different days from washers in
houses packing potatoes harvested by mechanical and conven-
tional methods. These data showed 35 pounds of injured po-
tatoes per 100 pounds for mechanical equipment and 34 pounds
for the conventional method.
Available evidence indicates that at present the amount of
physical injuries in mechanically harvested potatoes is larger
than it need be. Manufacturers are continually improving their
equipment to make it more dependable and to reduce the amount
of damage to the potatoes. However, a number of changes and
improvements often could be made in the operation of present
equipment at little or no additional expense. Suggestions for
reducing injuries to potatoes are discussed on page 20.
PROBLEMS ENCOUNTERED AND SUGGESTIONS FOR
IMPROVING THE OPERATION OF MECHANICAL
Certain of the problems that operators have encountered and
some of the ways to meet them are discussed in this section.
SELECTION OF EQUIPMENT
The selection of equipment depends upon such factors as capi-
tal available, type of equipment already owned, soil type, variety
of potatoes, harvesting conditions and facilities for packing po-
tatoes. A farmer may elect to partially mechanize because of
the high initial cost of complete mechanization, or he may do
so in order to avoid changing the method of hauling the potatoes
or handling them at the packinghouse. On the other hand, if
he has a good digger, he may elect to use an indirect harvester.
In areas where the soil is sandy, the use of direct harvesting
equipment may be the most satisfactory. In areas of heavy
soil, the indirect method may be more satisfactory, provided
the potatoes may be exposed long enough for some drying with-
out causing damage due to exposure.
In the Southeast, narrow headlands, short rows, drainage
ditches and "pot holes" are frequently encountered, making it
particularly important to consider maneuverability in selecting
equipment. It is also important to consider the availability of
parts and repair service in selecting equipment.
Mechanical Harvesting and Handling of Irish Potatoes 15
COORDINATING FIELD AND PACKINGHOUSE OPERATIONS
In the Southeast, harvesting must be geared to the operation
of the packinghouses because potatoes are dug, graded and
shipped in one near-continuous operation. The volume of po-
tatoes needed to supply a packinghouse depends on size and
amount of equipment used. A packing line may be designed
to handle as little as 15,000 pounds of potatoes per hour or as
much as 30,000 pounds or more when operating at capacity.
Packinghouses may also have two or more packing lines. Some
sheds have bins, racks, or other means of providing temporary
storage for potatoes to help in maintaining a continuous supply
for the house. Some houses pack for only one or a few growers,
while others may pack for a number of growers.
Each situation creates a need for a different organization or
management. Frequently the rate of packing is such that one
or two harvesting units will not furnish sufficient volume for
a house but an additional unit will supply an excess volume.
Some packinghouses handle potatoes dug with mechanical equip-
ment and also by the usual method. Under such conditions to
avoid delaying the operation of harvesters, digging and packing
should be coordinated so that the bulk trucks are not tied up
longer than necessary while waiting to unload.
OBTAINING MAXIMUM RATE OF HARVESTING
Some of the factors that should be considered in obtaining
maximum rate of harvesting are:
Efficiency with Which the Harvester Is Operated.-Controls
for raising and lowering the front end of the digger, for running
the belts and chains, and for raising and lowering bulk loaders
should all be placed together in a convenient position where the
operator can readily see all operations. Most operators have
found manually operated controls too slow and have replaced
them with hydraulically powered ones.
Laborers should be assigned to the tasks they perform well.
Rotation from one position to another may reduce fatigue and
thus improve quality of work.
Movement of bulk trucks must be coordinated with the oper-
ation of the harvester. Operators have found that the most
satisfactory method of obtaining coordination is to have one
driver for all trucks while being loaded. Other drivers move
the trucks between the field and the packinghouse. This makes
it necessary to train only one truck driver to work with the
16 Florida Agricultural Experiment Stations
harvester and he becomes accustomed to gearing the truck speed
with the harvester movement.
There should be some means of communication between the
harvester operator, the tractor driver and the driver of the
truck being loaded. The danger of striking the loading con-
veyor against the front or rear of the truck body can be reduced
by painting reference marks on the harvester which define the
position of the conveyor in the truck body. Equipping the truck
with mirrors so the driver can see the truck body makes it
easier to keep the truck in the proper position with the harvester.
When the truck is nearly loaded the tractor driver must be
especially alert to truck stalling.
Opening Lands.-With the row spacing commonly used in the
Southeast it is not possible to straddle two rows of potatoes
with a truck of conventional wheel tread. This creates a prob-
lem in opening up lands with a harvester. Two ways of over-
coming this problem are in common use. A bulk body may be
mounted on a trailer with a wheel tread that matches the row
spacings, or the tread on a truck can be matched to row spacing
by removing the inside wheels from the rear of the truck and
reversing the front wheels so that the space between them is in-
creased. It is necessary to remove the front fenders to make
steering possible when the front wheels are reversed. Changing
the wheel tread of a truck as described puts more strain on
the tires, axles, and spindles of the truck. It is advisable to
use an old truck for this purpose and also refrain from putting
a full load of potatoes in the body.
In areas where the fields are cut up into narrow strips by
irrigation or drainage ditches, operators must develop techniques
for opening lands suited for these conditions. In the Hastings
area, for example, a system that appeared to be satisfactory was
carried out as follows: The pair of rows nearest the center of
a land were dug in one direction and the corresponding pair in the
next land were dug on the return trip. Then the harvester made
its rounds in a counterclockwise direction until all the rows
between the opened rows were dug. The direction of travel
was then reversed and the remaining rows of the two lands
were dug. By skipping the third land and opening the fourth
and fifth lands, five lands could be opened in two rounds in which
the special land opening truck was required. Digging the second
and fourth lands left the third one exposed on both sides, per-
mitting loading of the trucks across the ditches.
Mechanical Harvesting and Handling of Irish Potatoes 17
Mechanical Maintenance.-Daily greasing and oiling of the
machinery (preferably at the end of the day), coupled with a
complete inspection, is recommended. Replacement of seriously
worn parts is particularly important because a harvester is the
key to a large operation, the costs of which largely continue
through a breakdown. It is foolish to attempt to get another
10 cents worth of use out of a part at the cost of $5 to $15 for
Fig. 8.-Split digging blades used to reduce spill-out on the side of the row.
The fact that manufacturers are strengthening chronic weak
points in their machines as they appear should provide more
trouble-free operation in the future. Manufacturers and dealers
should both see that operators are given complete operating
instructions. Bearings have been burned out and motors have
been overloaded because of inadequate instructions or careless-
ness in operating the equipment. The improper adjustment of
slip clutches, chains and sprockets has caused annoying break-
downs and delays. Decreasing mechanical breakdown will make
it easier to coordinate the digging and packing operations. One
man who had three harvesters found it profitable to hire a
mechanic to service the equipment at night so that it would
be in good shape for the next day.
18 Florida Agricultural Experiment Stations
Condition of Fields.-Weedy conditions will materially reduce
the efficiency of operation of some machines. Rotobeating, fol-
lowed by barring-off the rows, helps to reduce the amount of
vegetation that must pass over the machine. The cost of barring-
off usually will be less than the increased cost of harvesting
if the field if weedy. Weedy conditions may also cause spill-out
at the sides of the blades. In sandy areas the spill-out can be
reduced by using split blades on direct harvesters (Fig. 8).
The shape of the blades allows the soil, potatoes, and trash to
feed onto the chain rather than to push off to the side of the row.
Spill-out is prevented with indirect harvesters by means of
shields that extend about 18 inches ahead of the pick-up chain.
Difficulty in Turning.-Most operators tend to keep headlands
narrow to avoid wasting land. This makes it necessary to pull
the harvester across the ends of the rows, which requires more
power and better traction than is needed to pull it down the
Fig. 9.-Equipment for transferring the weight of the front end of the
harvester to the tractor to give more traction at the end of the row.
Mechanical Harvesting and Handling of Irish Potatoes 19
row and also causes injuries to the potatoes. On some machines
the traction problem has been overcome to some degree by pro-
viding means of transferring the weight of the front end of the
harvester to the tractor when more traction is needed (Fig. 9).
At least two makes of harvesters have steering on the rear
wheels which permits turning on narrow headlands. Both of
these improvements permit quicker turning. Time could be
saved also by eliminating the common practice of clearing the
machine of potatoes at the end of the each row.
CLOD AND TRASH ELIMINATION
Various mechanical devices are used to aid in obtaining ade-
quate separation of vines, weeds, grass, clods, and dirt from the
potatoes (Fig 10). Under ideal conditions separation is not
difficult. However, with heavy or cloddy soils and weedy fields,
separation is difficult and trash eliminators are not as effective
as desirable (Fig. 17). Even though the rate of harvesting is
reduced and the number of workers is increased, considerable
dirt and trash often are loaded with the potatoes. Cost of har-
vesting will be less if growers have their fields reasonably free
of weeds and grass at harvest time.
Fig. 10.-Inclined chains to facilitate dirt and trash removal. Two
inclined chains carry many clods, vines and other kinds of trash off the
side of the harvester. Potatoes roll down into the next conveyor.
N z 'j "
20 Florida Agricultural Experiment Stations
REDUCING INJURIES IN DIGGING, LOADING AND
Potatoes harvested and handled with mechanical equipment
may be injured mechanically or by exposure in the field or on the
bulk trucks. However, mechanical injury is the most serious
problem. Considerable injury may occur in windrowing, on the
harvester, or during unloading from the bulk trucks and convey-
ing to the washer at the packinghouse (Fig. 11). Normally very
little damage occurs to the potatoes in loading them in bulk in
Pounds Hastings Area Alabama
50 Legend: Da
Conveying to )
40 Washer ) Total i
Damage in )
30 and Loading
Ave. Poor to Poor Ave. Ave. Poor
Arrangement at Packinghouse for Receiving Potatoes
Fig. 11.-Pounds of potatoes receiving physical injury in harvesting
and loading and in unloading and conveying to washer, selected packing-
houses, Hastings area, Florida, and Baldwin County, Alabama, 1954.
Neither farmers nor packinghouse operators have given
enough attention to the problem of mechanical injury. A sub-
stantial reduction could be made in the amount of damage now
occurring if more attention were paid to operating the equipment
in the field and if packinghouses were set up properly to handle
potatoes hauled in bulk. Data collected in this study showed
that often much more injury occurred at the packinghouse in
unloading the potatoes and conveying them to the washer than
was realized. Some of the factors that affect damage in digging,
Mechanical H',, .: /1t;,, and Handling of Irish Potatoes 21
loading, and hauling are discussed in this section. Reducing
damage at the packinghouse is covered in the section beginning
on page 23.
Operation of the Harvester.-The digger blade or the "pick
up" should be maintained at a depth that will not cut or crush
the potatoes but still not pick up excess soil. The speed of the
chains and the degree of agitation should be kept to a minimum
that will provide the optimum amount of separation. The amount
of agitation may be regulated by changing the size and type of
shaker. Some harvesters are equipped with agitators that can
be moved "in" and "out" so that the amount of agitation can
be changed according to conditions. Controls for regulating
the agitators should be conveniently located and should provide
for varying degrees of agitation.
When the indirect system of harvesting is used, the window
must be properly formed, or potatoes will be missed or crushed.
The furrow for the window should be shallow, the bottom level
from side to side, and no pockets be allowed to form that would
permit the "pick-up" chain to pass over the potatoes. The digger
should be operated so that enough soil is carried over the digger
chain to cushion the potatoes. Rubber tubing can be placed
on the high links of the chains and the link ends covered to
reduce the amount of physical injuries.
Protection on the Harvester.-Mechanical injuries that can-
not be controlled by the operator are mainly those due to ex-
cessive drops from one conveyor to the next (Fig. 12). Manu-
facturers are showing more concern about excessive drops and
are reducing the height where practical. They are also provid-
ing varying amounts of protection on the equipment, even to
the extent of rubberizing all of the conveyors. However, the
grower can provide additional protection for the potatoes where
necessary. The side of the conveyors can be padded where the
potatoes are likely to strike with force, links ends of the chains
shielded, and the links covered with rubber tubing (4). How-
ever, to get separation when the soil is wet it may be necessary
to use chains that are not covered with rubber unless a chain
with a wider pitch is used.
Filling the Bulk Trucks.-Normally the amount of injury oc-
curring in loading the bulk trucks is small. However, bulk
loaders are at times carelessly operated so that potatoes are
either dropped an excessive distance or the end of the loader
is allowed to run in the potatoes and crush them. Controls for
22 Florida Agricultural Experiment Stations
operating the loader should be located so the harvester operator
has a good view of the load. Potatoes should not be allowed
to drop more than a foot. This distance is most easily main-
tained if there is a continuous relative motion of the truck back
and forth under the conveyor. It is the responsibility of the
truck driver to maintain this relative motion and it requires
practice to develop a satisfactory technique. This is an im-
portant reason why it is better to use the same person to drive
the trucks while they are being loaded.
Injuries Due to Exposure.-When the indirect method of har-
vesting is used and the weather is hot, considerable damage may
occur due to exposure in the field if the potatoes are allowed to
remain in the window more than 20 to 30 minutes before they
are picked up (3). In a number of lots dug by the indirect
method, considerable desiccation damage was observed.
Desiccation damage may occur also after the potatoes are
loaded if they are hauled a considerable distance or allowed to
stand in the sun too long before they are unloaded. If trucks
Fig. 12.-Excessive drop from one conveyor to another. A relatively
long drop onto a chain like this causes considerable injury, especially to
certain varieties or immature potatoes that are easily bruised. Note the
unprotected upturned link ends and sprocket teeth.
Mechanical Harvesting and Handling of Irish Potatoes 23
are not to be unloaded immediately they should be parked in
shade, or covered.
Many of the commercial harvesters have been built without
adequate protection for workers on the machines. Important
safety precautions are as follows: (1) All rotating shafts, gears,
chains and sprockets should be kept shielded; (2) rollers for
removing trash should be shielded so that laborers cannot get
their hands, feet or clothing caught; (3) workers should not
wear loose or flapping clothing which might get caught in mov-
ing parts of the equipment; (4) safety features for controlling
the operation of moving parts on the machines should be kept
in good working order at all times; (5) guard rails should be
constructed where needed to give support for workers and to
prevent them from being thrown off of the equipment when it
is started or stopped suddenly; and (6) when the equipment
becomes jammed with vines or trash, moving parts should be
stopped before clearing is attempted.
IMPROVING FACILITIES AT PACKINGHOUSES FOR RECEIVING
POTATOES HAULED IN BULK
At present one of the biggest problems in the successful,
efficient operation of mechanical equipment in the Southeast is
the lack of proper facilities to receive potatoes hauled in bulk.
Improvement is needed so that less physical damage is done and
time is not lost in changing from one bulk truck to another
(Fig. 11). Equipment should be designed so that dirt, vines,
weeds and grass can be more easily eliminated. In houses using
bins, better methods for filling are needed. Improving and ob-
taining proper facilities at the packinghouse will do much to
increase the efficiency of the operation of mechanical equipment.
The factors that should be given primary consideration in set-
ting up packinghouses for receiving potatoes hauled in bulk are:
1. Potatoes should be delivered from the bulk bodies on rubber
belts, rubber-covered rod conveyors, or in a flume. They should
not be unloaded directly on an uncovered rod conveyor. When
potatoes are unloaded directly on an uncovered draper chain
(rod) conveyor, mechanical damage is usually high unless meas-
ures are taken to reduce the impact of the falling potatoes (Fig.
13). Using a rubber-covered rod conveyor and keeping the height
of drop to a minimum are the surest ways of keeping injuries low.
The link ends of the conveyor can also be turned down to protect
24 Florida Agricultural Experiment Stations
the potatoes. Rubber belts make an ideal receiving conveyor
but dirt and trash cannot fall through a belt as they do through
a rod conveyor.
Potatoes from bulk trucks may be unloaded into a flume or a
tank of water (Fig. 14). The water provides a means of moving
the potatoes to the conveyor with a minimum of physical injury.
It also removes some of the dirt and trash and causes some of
the clods to break up that would otherwise have to be picked out
by hand. There is some question about the advisability of using
dumping tanks in the Southeast because there may be danger
of inoculating the potatoes with organisms that produce decay,
but specific data are not available. Tanks are used in certain
other potato-producing areas where water is limited and must
be reused. Dumping potatoes in a large volume of running water
that is not re-used probably minimizes the danger of infection
from decay-producing organisms.
Flumes have worked very satisfactorily in packinghouses in
the Hastings area. In one packinghouse as high as 900 bushels
Fig. 13.-Potatoes being severely damaged in unloading from bulk
truck onto uncovered rod conveyor. Samples of Bliss Triumph potatoes
taken before and after they struck the conveyor showed 35 percent being
injured at this point.
Mechanical Harvesting and Handling of Irish Potatoes 25
of potatoes per hour were carried through a flume with a flow
of about 400 gallons of water per minute. This flume was trapa-
zoidal in cross-section-8 inches wide at the bottom, 26 inches
wide at the top and 24 inches deep. It was constructed of 3/
inch exterior plywood and was 57 feet long, with a fall of four
inches in that distance. In this instance the cost of the flume,
well and pump was comparable to the cost of an 18-inch rubber
belt conveyor installed. Maintenance cost should be very low
because there are no moving parts except the pump.
When flumes are used, the discharge arrangement should be
such that the potatoes do not fall far to the elevator. If the
rods on the elevator are covered with rubber, the potatoes may
fall directly on the elevator without being injured. The water
can run through the elevator chain to the waste channel, facili-
tating the removal of soil and trash. If the channel is narrow,
most of the waste will be washed out.
2. Means should be provided to compensate for the increase
in height of the bulk body as the potatoes are unloaded so that
distance of fall from bulk trucks to the receiving conveyor is
kept to a minimum. Due to decreased weight, the height of
Fig. 14.-Potatoes being unloaded from a bulk truck into a flume.
26 Florida Agricultural Experiment Stations
conveyors in the bulk bodies will increase as much as 8 inches
when the potatoes are unloaded. This increases the length of
fall for the potatoes unless some means is used to compensate
for the change in height. This may be done by using a chute
on the back of the bulk body (Fig. 2), or by raising and lower-
ing the conveyor with a chain hoist (Fig. 15). Piles of dirt
should not be allowed to accumulate where the trucks unload,
as this makes it more difficult to keep the unloading conveyor
and the bulk bodies at the same height.
Fig. 15.-Chain hoist used in raising conveyor to compensate for the change
in height of bulk bodies as potatoes are unloaded.
The problem of keeping the drop from the truck to the receiv-
ing conveyor to a minimum can be reduced by mounting all the
truck bodies the same height above the ground. Wood members,
channels or junior I beams may be used to raise the bodies on
trucks with lower chassis to the same height as those on higher
3. Receiving conveyor should be arranged so that two bulk
trucks can be placed in unloading position at the same time. One
truck can be readied for unloading while another is being un-
Mechanical Harvesting and Handling of Irish Potatoes 27
loaded (Fig. 16). This prevents loss of time and interruption
of the packinghouse operation between loads. It requires three
to five minutes to move one truck out and place another truck
in position and prepare to unload it. Such an interruption each
time a truck unloads results in a loss in the packinghouse of one
to two man-hours for every 20 workers. Since the average posi-
tioning and unloading time is about 20 minutes per load, there
would be a loss of three to six man-hours per hour for every
20 packinghouse workers.
Consideration should be given to setting up receiving con-
veyors separately from permanent installations. If a driver
accidently backs into it and damages a conveyor that is part of
a permanent installation it may put the packinghouse out of
operation for a longer time than if conveyors are separate. The
use of two unloading motors makes it possible to start unloading
the second truck as the first truck is finishing. This also gives
a margin of safety in the case of motor failure.
4. Speed of conveyors in bulk trucks should be adjusted so
that the volume of potatoes unloaded is approximately the same
as the volume needed to supply the packinghouse. This reduces
wear and tear on the motor driving the conveyor, as it need not
Fig. 16.-Extension on back of bulk body to compensate for increase in
height of bodies as potatoes are unloaded.
-_ N ..
28 Florida Agricultural Experiment Stations
be stopped and started so many times. It also makes for higher
efficiency, since more volume can be handled and a better job
done when the potatoes move through the house at a uniform
In unloading the bulk bodies the boards over the conveyor
should be removed regularly at a rate giving an even delivery
suited to the capacity of the various conveyors and elevators.
6. Conveyors and elevators should have adequate capacity to
carry the volume of potatoes needed to supply washing and grad-
ing equipment. Frequently conveyors and elevators are under-
designed with respect to capacity for a reasonable rate of speed.
To make up for the low capacity, the speed is increased, with
a resultant increase in physical injuries. Rod-type conveyors at
the packinghouse should not exceed a speed of 50 feet per minute.
Elevators used for lifting potatoes should be designed to carry
their maximum load with a minimum rollback. Excessive roll-
back causes skinning and bruising; bruising is especially serious
in the tender Bliss Triumph and Red Pontiac potatoes. The
elevators should be padded just as all other conveyors to keep
7. Equipment at the packinghouse should facilitate the re-
moval of dirt, vines, weeds, and grass in bulk loads. Very often,
the rate of harvesting must be reduced by as much as one-half
when bad digging conditions are encountered. Even then con-
siderable extraneous material is often hauled to the packing-
house in the bulk loads (Fig 17). If adequate facilities were
available for removing clods and trash at the packinghouse, more
normal operating speeds could be maintained by the harvester.
Such equipment would also help prevent trash from fouling the
washer and other packing equipment.
If efficiency of separation is to be increased at the packing-
house, new equipment must be developed. In connection with
this study, a variable-speed tilted-table separator for eliminat-
ing dirt and trash was designed and installed and tested in a
commercial packinghouse in the Hastings area (Fig. 18). Bulk
loads of potatoes dug with a mechanical harvester after a three-
inch rain contained very large amounts of dirt, weeds and vines.
It was estimated that 90 to 95 percent of the extraneous material
was removed by the experimental separator as the potatoes
"A separate report giving data on the tests and details for constructing
the separator is being prepared.
Mechanical Harcesting and Handling of Irish Potatoes 29
Conveying potatoes to the washer by means of a flume was
a very satisfactory method of removing loose dirt from potatoes
hauled in bulk, but it did not get rid of vines and trash.
Fig. 17.-Dirt and grass in bulk load of potatoes. This condition fre-
quently occurs when ground is wet. Such large quantities of soil and trash
require additional labor for removal and cause breakdowns in the packing-
8. Equipment should be provided for transferring potatoes
from bulk trucks to bins. A house depending on mechanical
harvesters needs a small volume of potatoes in temporary stor-
age to process in case of mechanical breakdown of the harvester.
Bins of the type already in use appear to be satisfactory for the
purpose. Special portable bin fillers that have considerable
flexibility and that can be moved from one bin to another should
be satisfactory and feasible.
For most effective operation, certain features are necessary
in such a bin filler. The section that extends into the bin should
swing down to the floor and rise to a height that will permit
filling the bins to maximum capacity. The receiving hopper
should be designed to compensate for the increase in the height
30 Florida Agricultural Experiment Stations
of the bulk body as it is unloaded. As with all other conveyors,
the bin filler should have the conveyor rods covered with rubber
and all points of impact of the potatoes padded. The capacity
should be 1,000 to 1,500 bushels per hour with a reasonable
chain speed and a minimum rollback. Where several farmers
are hauling their potatoes to the same packing shed, more than
one bin filler should be available.
The main problem encountered in using a bin is the additional
mechanical injury that may occur to the potatoes. This can
be reduced by putting padding in the bin where the potatoes are
likely to strike, and by keeping the end of the conveyor as near
the potatoes as possible. In emptying the bin less injuries will
result if a uniform flow of potatoes from the bin is maintained.
Frequent opening and closing of trap doors should be avoided.
The purpose of this report is to describe the various systems
and equipment being used to harvest and handle potatoes
mechanically in the Southeast, to present some data on the
Fig. 18.-Experimental separator for removing dirt and trash at the
packinghouse. Use of this equipment at the packinghouse will increase
capacity of harvester under adverse weather conditions.
Ui U L"
Mechanical Harvesting and Handling of Irish Potatoes 31
amount of use, performance, and cost of operating equipment
and to make suggestions for improving its operation. Definite
progress is being made in the use of mechanical equipment in
Systems for harvesting and handling potatoes may be classi-
fied into three groups: (1) conventional system, (2) completely
mechanized system and (3) partially mechanized system. In
selecting equipment to partially mechanize, a grower should
keep in mind the system he might ultimately use, since equip-
ment selected for one system might be used later in another
The investment in a unit of equipment for the direct method
of harvesting varies from 87,500 to $10,000. The average rate
of harvesting for two-row machines has been about 100 hundred-
pound packed bags equivalent per hour in Alabama and about
137 packed bags in the Hastings area. Data on cost indicate
that if mechanical equipment is operated with reasonable effi-
ciency, cost of harvesting and handling potatoes is 5 to 10 cents
per packed bag less than with conventional methods. The amount
of physical damage in mechanically harvested potatoes is no
more than in potatoes dug and handled by the conventional
method if the harvesting and hauling equipment is carefully
operated and the packinghouse set up properly to receive potatoes
handled in bulk.
The selection of equipment depends on such factors as capital
available, type of equipment already owned, soil type, variety
of potatoes, harvesting conditions and facilities for packing po-
tatoes. The farmer should select the type of equipment that
best fits his particular situation.
Rate of harvesting can be maintained at a high level by proper
operation of the harvester and by obtaining as good field con-
ditions as economical. Training labor on the harvester for the
most efficient performance, and adequate maintenance to reduce
time loss due to mechanical breakdown, are important factors
in increasing output.
Careful operation of the harvester is essential if the amount
of physical damage in the potatoes is to be kept low. The amount
of agitation should be kept to the minimum that will provide
an optimum amount of separation. Damage can be reduced by
providing protection for the potatoes while on the harvester.
Care must be exercised also in operating the elevator to prevent
32 Florida Agricultural Experiment Stations
excessive drop or crushing potatoes by insufficient clearance in
filling bulk trucks.
The amount of physical damage in potatoes at the packing-
house and also the efficiency of the operations of mechanical har-
vesting and handling equipment are affected to a considerable
extent by the arrangement at the packinghouse for receiving
potatoes hauled in bulk. In setting up packinghouse facilities,
the following are recommended: (1) Unload potatoes from the
bulk trucks onto a rubber belt or rubber-covered rod conveyor
or into a flume; (2) provide means to compensate for the increase
in height of the bulk body as the potatoes are unloaded so that
the distance of fall from the bulk trucks to the receiving con-
veyor is kept to a minimum; (3) arrange receiving conveyors so
that two bulk trucks can be placed in unloading positions at the
same time, and provide two motors for unloading; (4) adjust the
speed of the conveyor in the bulk bodies so that the volume of po-
tatoes unloaded is approximately the same as the volume needed
to supply the packinghouse; (5) have conveyors and elevators of
adequate capacity to carry a volume of potatoes needed to supply
the washing and grading equipment; (6) the equipment at the
packinghouse should be such as to facilitate the removal of dirt,
vines, weeds, and grass in bulk loads; and (7) packinghouses
using bins for temporary storage should provide a satisfactory
method of transferring the potatoes from the bulk bodies to
Many of the problems of mechanical harvesting will be cor-
rected with further research and as more experience is gained.
1. GLAVES, A. H. Research and recent developments in mechanical harvest-
ing of potatoes in the Red River Valley. USDA BPI SAE release,
East Grand Fork, Minnesota; also personal correspondence between
the authors and Mr. Glaves.
2. JOHNSON, J. M., and L. J. KUSHMAN. Marketing southeastern early
Irish potatoes. Va. Agr. Expt. Sta. Processed Report.
3. MARTIN, J. W., and E. N. HUMPHRY. The Idaho potato harvester. Idaho
Expt. Sta. Bul. 283. June 1951.
4. TODD, B. J., and R. E. L. GREENE. Reduction of physical injuries to
early Irish potatoes during digging and picking up. S. C. Expt.
Sta. Bul. 32, Southern Cooperative Series. March 1953.