Group Title: Lake Alfred AREC research report - University of Florida Agricultural Research and Education Center ; AREC-LA-72-18
Title: Shaker-pickup harvest system for early and midseason oranges
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 Material Information
Title: Shaker-pickup harvest system for early and midseason oranges
Series Title: Lake Alfred AREC research report
Physical Description: 29 leaves : ill. ; 28 cm.
Language: English
Creator: Wilson, William Curtis, 1927-
Agricultural Research and Education Center (Lake Alfred, Fla.)
Publisher: University of Florida, Agricultural Research and Education Center
Place of Publication: Lake Alfred FL
Publication Date: 1972
Subject: Oranges -- Harvesting -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: W.C Wilson ... et al..
General Note: Caption title.
General Note: "300-7/14/72-GEC-Lake Alfred, Fla."
 Record Information
Bibliographic ID: UF00072464
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 76805341

Full Text

300-7/14/72-GEC-Lake Alfred, Fla.


W. C. Wilson----Abscission chemical
G. E. Coppock---Shakers
H. R. Sumner
S. L. Hedden----Rake-pickup machine and fruit
transport equipment
J. G. Blair-----Fruit damage determination
D. L. Deason
C. L. Anderson--System evaluation

The shaker-pickup harvest system is one of several systems proposed
for the mechanical harvesting of citrus fruit. Within the system, the fruit
is (a) loosened with an abscission chemical, (b) detached with a shaker
and allowed to drop to the ground, (c) picked up with a rake-pickup
machine, (d) hauled to a roadside semitrailer in a hi-lift grove truck,
and (e) transported to processing plant in a semitrailer. One man follows
the shaker to detach any fruit left on the trees and to rake fruit away
from the tree trunks. The system is referred to in this report as ASPT,
(A)bscission chemical, (S)haker, (P)ickup machine, (T)ruck.

Components of the system have been under development at the AREC-LA
for several years. Their development has progressed to a level where they
will function acceptably in an integrated harvesting system. In the past,
it has been difficult to make meaningful evaluations independently because
the components are dependent on each other.

The purpose of this study was to evaluate the ASPT system and its
separate components while operating under varied grove, fruit, and climatic
conditions during the early and midseason orange season. The criteria for
evaluation were performance and compatibility of components, harvesting costs
and effect on fruit and tree conditions.


A test of the system was conducted at 3 dates, 3 to 4 weeks apart,
over the December to March harvest season. Detailed descriptions of the
components are gven under separate headings in this report. They are listed
Abscission chemical--Acti-Aid at 2 concentrations.
Shakers--2 AREC-LA self-propelled lin 1h s .o
Rake-pickup machine--USDA. HUME LItRARY
Grove truck--Conventional hi-lift tr ck, 60-box capacity.
Semi trailer--Conventional, 500-box ;apacitAUG 15 1972

(A)University of Florida, Florida Department o .A S-,(f l toriL.S
Department of Agriculture cooperating.

Arrangements were made for 3 grove areas (l-'Hamlin' and 2-'Pineapple')
suitable for harvesting with limb shakers and for operating a pickup-
machine. No extensive land preparation or tree pruning was necessary.
The grove areas are described below:

Lynchburg 'Hamlin'--20 X 24-foot square spacing, 18 to 20-
foot high trees, hedged both middles in
one direction, hedged every other middle
in the other direction, fairly level terrain,
3-foot tree skirts, Figure 1.

Florida Gold 'Pineapple'--25 X 25-foot square spacing, 16 to 20-
foot high trees, hedged both middles in both
directions, fairly level terrain, 3-foot tree
skirts, Figure 2.

Winter Garden 'Pineapple'--25 X 25-foot diagonal spacing, 20 to
25-foot high trees, foliage canopied over
in top, fairly level terrain, 8-foot tree
skirts, Figure 3.

Each test consisted of 3 plots, with enough trees to produce approxi-
mately 400 boxes per plot. The number of trees varied with fruit yield.
Two plots were sprayed with Acti-Aid, one with a maximum and the other with
a minimum concentration required for loosening the fruit. The concentrations
were determined by the harvest conditions. The third plot was left unsprayed
for a control.

When it was thought the Acti-Aid had caused peak loosening of the fruit,
the plots were harvested. Usually, one plot was harvested each day for 3
consecutive days. The fruit was delivered to the roadside trailer the same
day it was removed from the tree. In the Lynchburg 'Hamlin' and the Florida
Gold 'Pineapple' tests, the fruit was held on the semitrailer about 24 hours
after loading before it was delivered to the processing plant. In the Winter
Garden 'Pineapple' test, it was delivered about 3 hours after loading.
Fd + Fg + Ft
Average yield per tree =
No trees in plot
Fd =Fruit delivered to processing plant, lbs.
Fg =Fruit left on ground, lbs.
Ft =Fruit left on tree, lbs.
Fd + Fg X 100
Fruit removal efficiency, % = Yiel

The fruit delivered (Fd) to the processing plant was determined by
weighing at the plant. Fruit left on the ground (Fg) and on the tree (Ft)
were determined by weighing the fruit collected in these locations after
harvest from 6 randomly selected trees for each preharvest treatment.

Lynchburg 'Hamlin' grove with AREC-IA limb
shaker in operation.

V Jr **-

Florida Gold 'Pineapple' grove with USDA
rake--pickup machine in operation.

Figure 1.

Figure 2.

Figure 3. Winter Garden 'Pineapple' grove with USDA
rake--pickup machine in operation.

At the processing plant,each trailer load of fruit was graded and the
percentage unwholesome fruit graded out was determined. A double size
sample was taken from the regular State controlled sampler and from it the
percentage of unwholesome fruit was determined by a State Inspector.

The amount of fruit split when it hit the ground was determined by
randomly dropping a 3-foot square wire frame on the ground under a tree
and determining the percentage of split fruit within the frame. At the
same time, the percentage of fruit removed with stems was determined.
This procedure was followed at 4 locations under each of 6 randomly
selected trees in each treatment plot.

Grove preparation was necessary to allow satisfactory performance of
the ground pickup system for this test. Low hanging limbs were pruned
off when required to let the rake get under the tree canopy and large
hedge trimmings were removed from the grove. Preraking and pickup was
also required in some groves to remove excessive trash and decayed fruit.

Dead wood was hand picked up after shaking to avoid fruit damage and
to reduce trash conveyed to the storage bin. Fruit near the tree trunk
was hand raked out to 2 feet from the tree trunk to avoid being missed by
the machine in this area.

Data from operating under the 3 grove conditions are given in Tables
1, 2, and 3.

Abscission Chemical
The chemical Acti-Aid (CHI or cycloheximide) was applied in the 3
tests conducted during the 1971-72 fruit season to 'Hamlin' and 'Pineapple'
oranges. A summary of these results is shown in Tables 1, 2, and 3.
Pull force measurements were made after the fruit was adjudged to be
sufficiently loose for mechanical harvesting, generally from 5-7 days
following spray applications.

Overall performance of the chemical this season was not nearly as
good as that obtained in the past.

1. In past years, applications of 10-20 ppm of CHI had commonly produced
pull force reductions to 3-5 pounds, but loosening produced this season in
these series of experiments was rarely below 7 pounds (see Tables 1, 2, and
3). Considerable variation in loosening between different parts of single
blocks was not unusual (Table 4).

2. Observed leaf drop was much higher than in past seasons. In some
cases, the final leaf losses were severe. Leaf drop in the Lynchburg
'Hamlin' test (sprayed 12/8/71) was heavy at the time of shaking, particularly
with the 15 ppm concentration. A very peculiar observation was made follow-
ing the test applied at Florida Gold 'Pineapple' grove (sprayed 1/5/72).

Table L Lynchburg 'Hamlin' Tests, 12/13-12/15/71.

Acti-Aid Treatment
15 ppm 10 ppm Control
Number of trees 66 64 63
Fruit delivered--
canning plant, Ibs. 41,580 40,860 36,990
Fruit left on ground, Ibs. 554 335 1,134
Fruit removed from tree, lbs. 42,134 41,195 38,124
Fruit left on tree, lbs. 1,181 1,907 1,940
Fruit yield, lbs. 43,315 43,102 40,064

Fruit yield, boxes/tree 7.29 7.48 7.07
Fruit removed, boxes/tree 7.09 7.15 6.72
Fruit delivered, boxes/tree 7.00 7.09 6.52

Avg. pull force, Ibs. 7.68 9.74 15.38
Standard Dev. 3.56 3.66 1.38
Avg. plugs, % 12.2 33.3 87.7
Fruit drop, No./tree 10-20 5-10 0
Spray material, gal./tree 8.33 8.33 0

Avg. harv. rate, trees/hr. 9.4 9.8 8.6
Avg. harv. rate, boxes/hr. 66.6 70.1 57.8
Fruit removal efficiency, % 97.3 95.6 95.2
Fruit split on ground, % 3.1 4.6 4.3
Fruit w/stems on ground, % 6 14.4 24.3

Pickup machine:
Pickup rate, trees/hr. 42.6 44.4 42.9
Pickup rate,*boxes/hr. 298 315 280

Grove truck:
Hauling rate, boxes/hr. 302 395

Fruit condition at plant:
Culls from grading, % 1.4 1.4 .4
Culls from official sample, % 12.00 13.27 10.10
Brix/acid ratio 16.03 15.81 17.08

Measured performance rate (does not include delays, minor repairs, or
turning time).

Table 2. Florida Gold 'Pineapple' Tests, 1/10-1/12/72.

Number of trees
Fruit delivered--
canning plant, Ibs.
Left on ground, Ibs.
Fruit removed from tree, Ibs.
Left on tree, Ibs.
Yield, Ibs.

Yield, boxes/tree
Fruit removed, boxes/tree
Fruit delivered, boxes/tree

Avg. pull force, lbs.
Standard Dev.
Avg. plugs, %
Fruit drop, no./tree
Spray material, gal./tree

Avg. harv. rate,, tree/hr.
Avg. harv. rate, boxes/hr.
Fruit removal efficiency, %
Fruit split on ground, %
Fruit w/stems on ground, %

Pickup machine:
Pickup rate," trees/hr.
Pickup rate,* boxes/hr.

15 ppm






Acti-Aid Treatment
10 ppm






Grove truck:
Hauling rate, boxes/hr.

Fruit condition at plant:
Culls from grading, %
Culls from official sample, %
Brix/acid ratio



*Measured performance rate
turning time).

(does not include delays, minor repairs, or









Table 3. Winter Garden 'Pineapple' Tests 2/15-2/18/72.

Number of trees
Fruit delivered--
canning plant, Ibs.
Left on ground, Ibs.
Fruit removed from tree, lbs.
Left on tree, Ibs.
Yield, Ibs.

Yield, boxes/tree
Fruit removed, boxes/tree
Fruit delivered, boxes/tree

Avg. pull force, Ibs.
Standard Dev.
Avg. plugs, %
Fruit drop, no./tree
Spray material, gal./tree

Avg. harv. rate, trees/hr.
Avg. harv. rate,' boxes/hr.
Fruit removal efficiency, %
Fruit split on ground, %
Fruit w/stems on ground, %

Pickup machine:
Pickup rate, trees/hr.
Pickup rate, boxes/hr.

20 ppm






Acti-Aid Treatment
10 ppm






Grove truck:
Hauling rate, boxes/hr.

Fruit condition at plant:
Culls from grading, %
Culls from official sample, %
Brix/acid ratio



*Measured performance rate (does not
turning time).

include delays, minor repairs, or








Table 4. A comparison of pull forces which occurred in various portions
of 1-2 acre treated blocks. Chemical used was Acti-Aid (CHI
or cycloheximide) applied at varying concentrations on 3
different dates.

Spray Date 12-8-71

CHI 15 ppm (EE)
CHI 15 ppm (C)
CHI 15 ppm (WE)
CHI 10 (EE)
CHI 10 (C)
CHI 10 (WE)
Check (EE)
Check (C)
Check (WE)

Spray Date 1-5-72

CHI 15 ppm
CHI 15 ppm
CHI 15 ppm
CHI 10 ppm
CHI 10 ppm
CHI 10 ppm
Check (WE)
Check (C)
Check (EE)


Spray Date 2-10-72
CHI 10 ppm (SE)
CHI 10 ppm (NE)
Check (SE)
Check (C)
Check (NE)

Pull Force (Avg.)

Pull Force (Avg.)

Pull Force (Avg.)

Standard Dev.

Standard Dev.

Standard Dev.

EE East end of block
C Center of block
WE West end of block

NE North end of block
SE South end of block


Initial leaf drop at the time of shaking appeared not excessive, but
approximately 7 days following the harvesting operation, all trees in
the sprayed area suddenly dropped a large percentage of their leaves,
leaving the entire block looking bare. Leaf drop was minimal with trees
sprayed 2/10/72 in the Winter Garden 'Pineapple' test.

3. Standard deviations of sprayed treatments were generally quite large,
indicating a considerable variable response by the fruit to the chemical.
A computer analysis of pull test data also demonstrated this, and graphically
showed that the loosest fruit on the tree tends to "over loosen" and fall
to the ground, while the tightest fruit tends not to loosen at all.

The relatively poor performance of the chemical was probably due to
the abnormally warm winter season, although our experience with the
chemical over the short time period we have been working with it, is too
limited to make any definite conclusions. Tree dormancy probably never
was completely achieved. Weather records indicate this was the warmest
winter in about 40 years in Florida.

Although part of the problem with the chemical may have been because
of warm weather, it is undoubtedly not the whole reason. The chemical has
certain imperfections even under the best weather conditions. We should
continue to screen for more effective chemicals for future use with the
following considerations taking priority:

1. Find a chemical which is less weather dependent.

2. Work toward finding chemicals with less tendency to cause
leaf drop.

3. Although from an engineering standpoint it would be very desirable
to have a chemical loosen all the fruit to about 5 pounds pull
force, because of natural biological variation which occurs
in every living thing, this is virtually impossible. However,
it is probable that a chemical can be found which will cause a
greater pull force reduction on the portion of the fruit which
is hard to loosen. Finding a chemical which will give the
equivalent of "chemical picking" is also in the realm of


Two self-propelled limb shakers were used in the harvest system,
Figure 1. These shakers were developed on the cooperative Harvesting
Research Project at the AREC-LA (A). One shaker used an 8-inch stroke
and operated at a maximum frequency of 250 cpm. The other one used a
6-inch stroke and operated at 350 cpm. They will be referred to as 6
and 8-inch shakers in this report.

Price information is not available since these machines are not
built commercially. However, it is estimated the cost of materials
and labor to be about $8,000 with a total sales cost of $10,000.

(A) University of Florida, Florida Department of Citrus,and the U. S.
Department of Agriculture cooperating.


The shaker is operated by one man. All positioning movements
are controlled from the handle bar located opposite the clamp end of
the boom. The powered movements are remotely controlled through
solenoid valves. The frequency control is located on the shaker
transport frame for safety purposes. For continuous transport in the grove,
an auxiliary control is provided on the transport unit.

In operation the shaker boom is clamped onto a limb. The transport
unit may be shuttled back and forth to find a convenient opening in the
canopy to insert the boom. After clamping a limb, the operator releases
the handle bar and actuates the frequency control to set the shaker in
operation. The frequency is controlled as desired by the operator for
maximum fruit removal efficiency. To prevent running over fruit which
has already fallen to the ground, the shakers are backed down the tree-
row leaving the fallen fruit behind. In these tests, the shakers were
located so that all limbs were shaken from one side of the tree.

The 6 and 8-inch shakers were compared in all 3 groves. The 8-inch
performed better in the Lynchburg and Florida Gold groves but the 6-inch
performed better in the Winter Garden grove. Trees in the Winter Garden
grove were so tall that the 8-inch stroke could not reach high enough
to clamp onto limbs small enough to get an effective displacement. The
6-inch shaker could clamp on the larger limbs and partially compensate
for poor displacement by increasing frequency.

Time and motion study of the shakers operating under conditions
of these tests is shown in Table 5. Positioning the shaker boom for
shaker clamp attachment required the greatest amount of time. Shaking
limbs followed close second. The greatest potential for increasing harvest
rate is in the reduction of time required for these elements. Time to
position could be reduced by pruning the trees to make the limbs more
accessible. This is evidenced by the wide variation in positioning time
between the 3 groves. The time for shaking each limb was reduced by the
use of the abscission chemical, Acti-Aid. The number of limbs clamped
per tree was not affected by Acti-Aid because this factor is mostly
related to grove condition. It varied from 4 limbs per tree in the
Winter Garden grove to 8 in the Florida Gold grove.

The data in Tables 1, 2, and 3 shows that fruit removal efficiency
was not greatly affected by the Acti-Aid. This was partially caused
by the shaker operator's objective to shake for above 90% removal. The
time of shaking was allowed to vary to achieve this objective. Thus,
the main effect of Acti-Aid is reflected in the harvest rate. Acti-Aid
increased the harvest rate in all three groves but the increase was
greatest in the Winter Garden grove which had much taller trees. Acti-
Aid also reduced the percentage of fruit removed with stems.

The percentage of fruit that was split in being shaken from the trees
and from falling on the ground varied between groves. It was related to
tree height, ground conditions, and fruit type. An average of 4.0% was
split in the Lunchburg 'Hamlin' grove which had a thin skinned fruit and
1.6% was split in the Florida Gold 'Pineapple' grove which had a thicker
skinned fruit. The highest percentage was split (5.7%) in the Winter
Garden 'Pineapple' grove where the trees were tall and the soil compacted


Table 5. Time and Motion of Limb Shaker Under Test-Conditions.

AVG. MIN/TREE 15 ppm 10 ppm Control

Lynchburg 'Hamlin'
Positioning shaker boom -- -- 2.9
Moving transport unit -- -- 0.7
Raking fruit from wheels -- -- 0.5
Shaking limbs -- -- 2.7
Total operation -- -- 6.8
Avg. No. of clamps per tree -- -- 6

Florida Gold 'Pineapple'
Positioning shaker boom 4.82 3.23 5.64
Moving transport unit 0.99 0.65 0.41
Raking fruit from wheels 0.19 0.45 0.51
Shaking limbs 1.72 1.90 2.88
Total operation 7.72 6.23 9.45
Avg. No. of clamps per tree 8.0 8.0 8.7

Winter Garden 'Pineapple'
Positioning shaker boom 2.00 2.55 3.40
Moving transport unit 0.45 0.50 0.38
Raking fruit from wheels 0.22 0.55 0.83
Shaking limbs 1.25 1.50 1.70
Total operation 3.92 5.10 6.31
Avg. No. of clamps per tree 4.0 4.5 4.0


The following general conclusions were reached regarding limb shaker
1. Acti-Aid increased harvest rate and reduced the number of fruit removed
with stems.
2. There is a good potential for improving-the fruit removal operation.
If the abscission chemical was improved to consistently loosen 100% of the
crop below a 5-pound pull force, a reduction of 75% may be possible in actual
shaking time. This would reflect in a 33% increase in the rate of fruit
removal. Also, improved loosening of the fruit would reduce the shaker
positioning time by reducing the number of limbs that would have to be shaken.
A reduction of 50% in positioning time seems possible. This would reflect
in a 30% increase in fruit removal rate. Thus the potential gain in fruit
removal rate from a near perfect abscission chemical would be 63%. Pruning
the trees to remove water sprouts would increase the fruit removal rate by
reducing the positioning time requirement. Of course, this increase would
have to be justified economically by comparing the value gained against the
pruning cost.
3. Additional development is needed on the shakers to improve reliability
and to reduce the effort required to operate.

Rake-Pickup Machine--Fruit Transport Equipment

Equipment--The equipment used in this series of tests was the USDA
combination rake and pickup machine (Figure 2) which moved the fruit from
under the tree skirt on the right-hand side onto a pickup chain where it
was elevated into a 30-box capacity hopper. When the hopper was full, the
pickup machine was stopped and the hopper raised and dumped into a con-
ventional hi-lift grove truck for transport to the roadside loading area.
A conventional semitrailer hauled the fruit from roadside to the processing

The pickup machine had an effective raking width of 14 feet and could
retract 3 feet to clear low limbs on the tree trunk as it progressed
down the row. The pickup chain allowed sand and much of the trash to
fall through onto the ground again.

Performance--During the 1972 harvest season, fruit was picked up in several
different grove situations. In the Lynchburg 'Hamlin' grove, the sandy soil
was moist but not wet which offered excellent ground conditions. Heavy dew
delayed the pickup operation until approximately 10:30 a.m. each morning.
The 'Hamlin' fruit was thin skinned and quite turgid. The pickup machine
operated at an average rate of 43 trees per hour or 298 boxes per hour
in the Lynchburg 'Hamlin' grove at a continuous "down the row" rate without
delays, Table 1. Rows were 33 trees long and an average of 2.9 minutes were
required to turn around at the end of each row. Including delay and un-
loading time in pickup machine operation, 51.3% of the total operational
time was spent picking up fruit, 15.6% in unloading the fruit hopper, and
33.0% in delays or downtime due to mechanical problems, tree interference,
or sticks and sand clogging the machine.


Conditions at the Florida Gold 'Pineapple' grove were better for
picking up fruit than at Lynchburg. The trees were more widely spaced
(25 x 25 feet), the soil was level and not wet enough to cause a build
up in the machine,and the tree skirts were high enough to cause little
interference with the gathering rake. The pickup machine handled fruit
at an average sustained rate of 289 boxes per hour at a grove speed of
30.3 trees per hour, Table 2. On a total operational basis, fruit was
being picked up 69.3% of the time, unloaded 9.3% of the operating time,
and 21.4% of the time was taken up by delays due to mechanical problems,
dirt and stick buildup, or waiting for the hi-lift truck.

The Winter Garden 'Pineapple' grove was quite different from either
of the previous groves in tree structure and soil characteristics. The
trees were approximately 25 feet tall with skirts 6 to 8 feet above ground.
The soil was firm, moist, and much heavier than the previous groves.
Several heavy rainfalls occurred while this trial was underway which made
the machine clog with wet sand easily and slower ground speeds were

The fruit pickup rate at Winter Garden averaged 183 boxes per hour
for the three treatments and the machine speed was 31 trees per hour,
Table 3. These average figures, however, cover a wide range of 23 to
39 trees per hour and 145 to 229 boxes per hour. The lower figures were
pickup rates after a hard rain shower. Of the total operating time, an
average of 69.3% was spent picking up fruit,'6.8% unloading the fruit
hopper, and 23.9% in delays mostly due to excessive build up of wet sand
in the machine.

It should be noted that the highest pickup rate was achieved in
the Lynchburg grove;but at Florida Gold,97% as much fruit per hour was
picked up while passing 70% as many trees. This is due to the higher
fruit yield of approximately 2.5 more boxes per tree at Florida Gold.

Rake capacity appears to be a limiting feature on the pickup machine
although the machine as a whole was able to keep up with the output of the
two self-propelled limb shakers. Fruit damage occurred at the point where
the retractable portion of the rake overlapped the fixed rake as the rake
retracted to go around a tree trunk. If the ground speed or the fruit
density became too great, fruit was carried over the rake bars and usually
crushed. This condition seldom occurred because of the infinite ground
speed capability of the machine. The low profile, lift hopper worked very
well as a surge bin compared to the large 60-box elevated hopper used on
previous machines. Unloading "on the go" did not seem necessary though
unloading the surge bin required 7 to 15% of the total operating time.
Some of this lost time might be regained if no surge bin were used and fruit
loaded directly into a truck but an additional truck would be required.
Some trash in the form of cans and chopped up portions of hedge trimmings
was loaded along with the fruit and had to be sorted out at the processing
plant. This trash could become a plant disposal problem but was not a
probhm as far as picking it off the sorting belt was concerned.

Grove truck hauling rates were not obtained in all cases but the one
hi-lift truck kept ahead of the pickup machine most of the time. A round


trip to the road truck averted 8.3 minutes at Lynchburg where the semi-
trailer was 0.7 mile round trip from the grove area. In all other trials
at Florida Gold and Winter Garden, the road truck loading area was located
at the ends of the pickup rows so that no road travel was necessary.
Deducting the Lynchburg road travel time leaves an average time of
approximately 5 minutes required for the grove truck to get out of the
grove, unload, and return to the pickup machine.


General Procedure for Calculating Fixed Machine Costs

The method used for calculating fixed cost uses straight line
depreciation method resulting in an equal depreciation charge for each
year of life of the machine. Total annual fixed costs are first estimated
as a fraction of the purdhase price to facilitate comparisons. Interest,
taxes, housing cost,and insurance costs are estimated as a percent of
the average machine value during its useful life. The complete fixed
cost formula is:

Total annual fixed cost = + -P+ (i + t + h + in) + Lic where:
L 2
P = purchase price $
S = salvage value $ or %/100 P
L = years of life of the piece of equipment for depreciation purposes
i = interest,%/100 of the average value
t = taxes, %/100 of the average value
h = housing (shelters, garage building, etc.), %/100 of the average
in = insurance cost, %/100 of the average value
Lic = annual vehicle license cost, $
Rake-Pickup Machine Costs

Costs were first determined per hour of actual operational time
and later converted to a cost per box, etc. For the pickup machine,
this operational time includes unloading, turning, and minor adjustments.
Data used in subsequent calculations are the best estimates available,
and were generally agreed on by personnel conducting this test.
The following data were used:
P = $20,000 i = .08
S = 0.1P t + h + in = (.01 + .01 + .005) = .025
L = 5 years Base wage rate (operator) = $2.40/hr.
H = 450 hours yearly L. F. (labor use factor) = 1.5


Some discussion on these figures is justified at this point. Cost
of the rake-pickup machine and the shaker in this system represent an
estimated cost of labor and material for production plus 25% mark-up.
Thus the $20,000 price tag represents $16,000 for material, parts, and
labor plus $4,000 (25%). The 5 years life of the machine and only 450
hours use annually are large contributors to high per hour machine cost.
It is believed that the 5-year life is not overly conservative in view
of the nature of the machines in this system and the obsolescence factor
for new machine systems. Annual usage is based on the fact that this
system can presently be used only on early and midseason fruit. Given
a 13-week harvest season, 6-7 working days per week,and 5-6 hours of
actual operation per day, we arrive at 450 hours annual use for the rake-
pickup machine. Fixed costs are:
P S P .1P
Depreciation = 5 .180P
L 5
Interest P + S 1.1P
Inr (.08) 2 (.08) = .044P
2 (.08) 2
(t + h + in) P2 = .025 ( ) = .0138P

Total Annual Fixed Cost = .2378P

The estimation of operating cost for a new machine involves many
hazards. This must include repair cost and labor efficiency of the
machine as part of a system. Historical data is never available for
new machines.

Documented repair costs by Richey and Hunt (B), indicate that for
self-propelled combines, hay balers, and forage harvesters, repair cost
as a percent of initial list price through 1966 were 10%, 35%, and 42%
respectively for the first 1000 hrs. of accumulated use. Information
being gathered at the Lake Alfred Research Center (C) indicate that
average repair costs of groups of grove tractors and air blast sprayers
exceed $1.00 per hour of use. The rake-pickup combination contains an
extensive hydraulic system, and is required to operate in an extremely
dirty environment. A repair cost of .15P for the first 1000 hours use
is deemed reasonable. This includes oil, tires, etc.

Wages are another large item in calculating total cost per hour
of actual operation. This cost is generally underestimated by a large
margin. To a base wage rate must be added cost for social security,
unemployment compensation when applicable, and other fringe benefits.

(B) Richey, C. B. and D. R. Hunt, Determining Usage Cost for Farm
Tractors and Field Machines, Cooperative Extension Service
Publication No. AE-81, Purdue University, 1971.
(C) Deason, D. L. and Charles L. Anderson, Unpublished data being
gathered at the Lake Alfred Research Center on actual labor
and machinery costs for Florida citrus production operations.


For grove production operations, this is in the neighborhood of 11%
of total labor costs (C). A labor factor (L. F.) of 1.5 is assumed (C)
which means the operator will be paid on the average for 1.5 hours of
labor for each hour of machine operation.

Overhead is another operating cost which must be included in the
total cost. For a cooperatively owned harvesting group, this represents
cost of administration, management salaries, and auto expenses, etc.
Records (C) on a large scale cooperatively owned grove production
organization, indicate that overhead amounts to approximately 15% of
total machinery and labor expense.

Fixed Cost: .2378P = .2378($20,000) $/hr.
H 450 10.57

Operating Cost:

(1) Hourly repair cost =
.15 P/1000 hrs.= .15 ($20,000)/1000 hrs. = 3.00

(2) Fuel (gas)
.06 (max. pto hp) ($.26/gal.) = .06(42)(.26)= .65

(3) Labor Cost operator per hour of operation =
base wage (L. F.) = $2.40 (1.5)/.89= 4.05

(4) 1/2 of time for the clean-up man included in
the total system = 1/2 of 1.90(1.5)/.89 = 1.60

Total Fixed and Operating Cost per Hour = 19.87

Overhead Cost:

15% (Total Fixed plus Operating Cost) =
.15 ($19.87) = 2.98

Total Cost per operating hour for rake-pickup machine 22.85

Shaker Costs

The cost per hour of operating time for the shaker is arrived at
similarly to rake-pickup machine. A larger number of annual hours of
usage are assumed as well as a smaller labor factor compared to the rake-
pickup machine. The shakers are not limited by heavy dew and wet fruit
during the early daylight hours as is the rake-pickup machine.

For the shaker:

P = $10,000 t + h + in = .025
S = 0.1P Operator wage rate = $2.40/hour
L = 5 years L. F. (labor factor) = 1.4
H = 550 hours yearly Repair = .15P/1000 hours
i = .08


.2378P .2378(10,000) $/hr.
Fixed Cost: H 550 4.32
H 550 4.32
Operating Cost:
(1) Hourly repair cost = .15P/1000 hrs. = 1.50

(2) Fuel .50

(3) Labor Cost (operator)-effective rate 3.78

(4) Labor for 1/2 of time for the clean-up
man included in the total system 1.60

Total Fixed and Operating Cost per Hour = 11.70

Overhead Cost:

15% (Total Fixed plus Operating Cost)
= .15 (11.70) 1.76

Total Cost per Operating Hour for Shaker 13.46

Truck Costs

It is assumed that the truck used with this operation is
equipped with hi-lift body and hydraulic loader boom and would
have additional usage outside this ASPT system. Performance rate is
limited by the working rate of the rake-pickup machine.

P = $10,000 S = 0.1P L = 8
L. F. = 1.4 Driver wage = $2.00/hr. i = .08
t + h + in = .025 Lic = $75.00 yearly H = 800

Fixed Cost:
(1.0-0.1)P = 1125P
Depreciation = L

Interest = .08(1.0 + 0.1)P/2 = .044P

Taxes, housing,& ins. = .025(.55P) = .0138P

Annually = .1703P
Hourly 1703($10,000) + 75.00 $/hr.
Hourly 800 2.22


Operating Cost:

(1) Repair & lubricant = 1.40

(2) Fuel 4 gal./hr. at $.27/gal. = 1.08

(3) Driver's labor 1.4(2.00)/.89 = 3.15 5.63

Total machine and Labor Cost = 7.85


15% (machine & labor) = .15(7.85) = 1.18

Total Cost per Operating Hour for Truck = 9.03

Sensitivity Analysis of Hourly and Per Box Cost

When a best estimate of machine cost is reached, doubt may still
remain as to the validity of the cost factors used. A sensitivity
analysis will indicate the effect on the total cost picture due to
variation in the individual factors affecting cost. This is accomplished
by variation of the factors which affect cost, one at a time,about the
base figures.

Lynchburg ASPT System Harvesting Cost Dec. 1971

Determination for the component costs of harvesting are shown in
some detail. The first test (Lynchburg) was used for sample calculations.
Every effort has been made to determine each cost component on the basis
of the boxes of fruit delivered to the plant.

1. Abscission Cost (Cents per box):

Applied 15 ppm rate at 750 gal. per acre. Yield delivered to the
plant was 462 field boxes from 66 trees harvested. Tree spacing
was 20 x 24 feet with 90 trees per acre.

750 gal./acre of 15 ppm formulation 1.125 units/acre

Material Cost: 1.125 units/acre X $35./unit 6.25
630 delivered boxes/acre
1.5 tanks/acre X $10.00/tank = ,
Application Cost: 630 delivered boxes/acre 2.38

Total Abscission Chemical Cost per delivered box
of fruit = 8.63V


1-be Pfckiin-Rake Oneration

Dollars per Hour
Cents per Box

Dollars per Hour
Cents per Box

Dollars per Hour
Cents per Box

Dollars per Hour
Cents per Box

Dollars per Hour
Cents per Box

Dollars per Hour
Cents per Box

Dollars per Hour
Cents per Box






0. 1P*










0.15P/1000 hr.*


1.5 men*


* Base value used for "Best Estimate" cost; second and third figures
in each group represent "Best Estimate" cost per hour and per box
at 200 box/hr. capacity.















C! 4 1- 4 i- &-al sI)I Is for the Pickun-Rake Onerat ionL
v L J_ IY

C~onc~rCir; +,~ ~nal~rC;g fnr


Sensitivity Analysis for the Shaking Operation

PURCHASE PRICE 8,000 9,000 $10,000* 11,000 12,000
Dollars per Hour 12.47 12.96 $13.46 13.96 14.46
Cents per Box 19.18 19.94 20.71 21.48 22.25

LIFE-YEARS 7 6 5* 4 3
Dollars per Hour 12.39 12.83 $13.46 14.50 15.97
Cents per Box 19.06 19.74 20.71 22.31 24.57

HOURS ANNUAL USE 825 687 550* 413 275
Dollars per Hour 11.80 12.47 $13.46 15.11 18.44
Cents per Box 18.15 19.18 20.71 23.25 28.37

REPAIRS .05P .10P .15P/1000 hrs.* .20P .25P
Dollars per Hour 12.31 13.19 $13.46 14.03 14.61
Cents per Box 18.94 20.29 20.71 21.58 22.48

BOXES PER HOUR 97.5 81 65* 49 32.5
Dollars per Hour 13.46 13.46 $13.46 13.46 13.46
Cents per Box 13.81 16.62 20.71 27.47 41.42

SALVAGE VALUE 0.IP* 0.2P 0.3P 0.4P 0.5P
Dollars per Hour $13.46 13.04 12.63 12.20 11.79
Cents per Box 20.71 20.06 19.43 18.77 18.14

* Base value used for "Best Estimate" cost; second and third figures
in each group represent "Best Estimate" cost per hour and per box
at 65 boxes/hr. capacity.


For 10 ppm Test:

Material Cost:


Application Cost: 1638.-

Total Abscission Chemical Cost per delivered box of
fruit =

2. Shaker Cost per box of Delivered Fruit:

15 ppm:

10 ppm:


7 hours X $13.46 hour
462 boxes fruit
6.5 X $13.46
7.37 X $13.46





3. Rake-pickup Machine Cost per Box of Delivered Fruit:
Machine Performance

15 ppm

Pickup Time
102.2 min.

10 ppm 92.5

None 92.0

Unload Turning
35.3 8.8





Total Delays &
operate waiting
'146.3 59.2

133.4 67.8

124.3 61.6
404.0* 188.6

* Total operate time was 67.8% of the total.
2.44 hours X $22.85/hour
15 ppm: 462 boxes delivered
2.22 X $22.85
10 ppm: 454


2.07 X $22.85




4. Truck Cost per Box Pickup Machine to Roadside:

The effective hauling rate of the truck
pickup capacity to about 200 boxes per hour.
cost, this is 4.5 cents per box. This value
ASPT tests.

is constrained by the rake-
At $9.00 per hour truck
will be used for all other





5. Cost of Fruit Lost in Grove Due to Nonremoval or Left on Ground:

15 ppm: 554 # left on ground
1181 # left on trees

1735 # 19.28 field boxes cents/box

19.28 boxes X $2.00/box 8.35
462 delivered boxes

24.91 X $2.00 1= 0.97
10 ppm: 454

34.15 X $2.00 16.61
None: -411

6. Cost of Plant Abandoned Fruit:

Regulations require that canning plant may normally accept not more than
10% unwholesome fruit. If the official sample exceeds this level, the load
of fruit may, at the discretion of the inspector, be regraded to achieve the
10% or lower level. For the purpose of this report, the quantity of fruit in
excess of 10% was charged against the harvesting cost at prevailing prices of
$.50 per pound of solids.

15 ppm:

(.12 .10) X 462 delivered boxes X 5.43 Ibs. solids/box X $.50/lb.
= 5.43 cents/box

10 ppm: (.1327 .10) X 548 X .50 8.95

None: (.1050 .10) X 5.57 X .50 =1.4

7. Cost of Plant Labor for Regrading:

Assuming that regrading of loads with excessive unwholesome fruit
is a satisfactory answer, this can be done at the plant for fruit with
10% 15% unwholesome fruit. A rough estimate of this cost assumes that
it will take 4 graders, 1 hour to regrade a 450 box load.
(4 X $2.25/hr.)/450 boxes = 2.0

8. Roadside to Plant Hauling Cost:

Average roadside to plant hauling costs as presented by Spurlock
for the 68-69 and 69-70 season were approximately 12.0 and 13.2V per
box. It is estimated that this cost will be about 15.0U per box for
the 71-72 season.

ASPT harvest cost (cents per box) for the 3 groves is summarized in
Tables 6, 7, and 8.


Table 6. Lynchburg 'Hamlin' Dec. 1971.

Treatment 15 ppm 10 ppm None

Trees 66 64 63

Boxes Delivered 462 454 411

Abscission 8.63 6.46 0

Shaking 20.39 19.27 24.14

Rake-Pickup 12.07 11.17 11.51

Truck 4.5 4.5 4.5

Grove Abandonment 8.35 '10.97 16.61

Plant Abandonment 5.43 8.95 1.40

Plant Grading 2.0 2.0 2.0

Hauling to Plant 15.0 15.0 15.0

Total Cost per 76.714 78.314 75.174
Box ASPT System


Table 7. Florida Gold 'Pineapple' Jan. 1972.

Treatment 15 ppm 10 ppm None

Trees 44 47 42

Boxes Delivered 401 411 452

Abscission 8.26 6.40 0

Shaking 18.13 21.32 20.46

Rake-Pickup 11.60 14.0 13.60

Truck 4.5 4.5 4.5

Grove Abandonment 22.10 12.60 13.11

Plant Abandonment 5.1 3.70 3.80

Plant Grading 0 0 0

Hauling to Plant 15.0 15.0 15.0

Total Cost per 84.69 77.52 70.474
Box ASPT System


Table 8. Winter Garden -'Pineapple'.

Treatment 20 ppm 10 ppm None

Trees 51 57 59

Boxes Delivered 302 304 315

Abscission 12.20 10.30 0

Shaking 16.05 23.11 27.31

Rake-Pickup 15.25 15.25 15.25

Truck 4.5 4.5 4.5

Grove Abandonment 12.75 20.0 17.55

Plant Abandonment 0 0 0

Plant Grading 0 0 0

Hauling to Plant 15.0 15.0 15.0

Total Cost per 75.754 88.164 79.614
Box ASPT System


Discussion of ASPT System Harvest Cost

A short discussion of the results shown in Tables6, 7, and 8 is
offered. The results of the Lynchburg test (Table 6) show large variations
in shaking, grove abandonment,and plant abandonment costs. Test data in
Table 1 indicated that the abscission agent-resulted in a reduction in
average pull force for the treated tests. The higher shaking cost of the
check treatment resulted from more time being required to achieve the de-
sired fruit removal from the tree. The higher grove abandonment cost of
the check treatment resulted from aggressive removal of unwholesome fruit
in the grove as it was picked up. The result was high cost for grove
abandonment and lower plant abandonment cost compared to the abscission

Results of the Florida Gold test (Table 7) indicate a decided
advantage for the treatment receiving no abscission agent application.
The total cost advantage of the check treatment compared to the 10 ppm
treatment was the cost of applying the 10 ppm abscission treatment which
in turn provided no increase in harvest rate or removal efficiency. This
is reflected in Table 2 by a negligible decrease in pull force for the 10 ppm
treatment and essentially the same shaker harvest rate for the 10 ppm treat-
ment and the check. Results are unfairly biased against the 15 ppm treatment
compared to the check. Principally, grove abandonment costs are responsible
for this. Harvest rate for the 15 ppm treatment was 77 boxes per hour
compared to 67 for the no abscission agent treatment. This increased harvest
rate apparently resulted in a reduced percentage removal for this test.
Table 7 also indicates larger amounts of fruit left on the ground and a
decreased percentage of unwholesome fruit in the official plant test when
compared to 10 ppm test and check. Both occurred as a result of grading
out unwholesome fruit in the grove. These factors are reflected in an
approximate 9 cents per box higher grove abandonment cost for the 15 ppm
test compared to the 10 ppm and the no abscission test.

The order of harvest for the Winter Garden (Table 8) treatments were:
check, 20 ppm, and 10 ppm. In this case,the 20 ppm of abscission agent
showed a decided cost advantage for fruit removal and grove abandonment
cost when compared to the 10 ppm test and the check. The canopy of the
trees in this test had many long willowy fruit hangers making a high
percentage of fruit removal virtually impossible without the use of the
abscission agent. On the 10 ppm test, the abscission action was not as
good as desired, resulting in more fruit left on the trees compared to
the 20 ppm test and consequent high grove abandonment costs. This test
indicates that the abscission agent is required to do an excellent job in
order that reductions in shaking cost and grove abandonment cost more than
offset the additional cost of applying this abscission agent. The 10 ppm
test resulting in 88.1 cents per box is a result of such incurred additional
cost with little reduction of total cost for shaking plus grove abandonment
when compared to the check treatment.


Field Capacity and Compatibility of the ASPT System

It should be pointed out again that this system of machines was
tested under selected grove conditions. The groves were moderate to
high yielding early and midseason oranges. Tree skirt clearance was
necessary for operation of the rake-pickup machine. In addition the
grove was required to be relatively flat, and to have only negligible
grass, weeds, and pruning residue.

The rake-pickup machine was limited to fewer hours per day of
operation than the shakers due to wet soil and wet fruit in the early
morning hours. When operating, the rake-pickup machine depended on the
truck being available to allow it to unload. In order to keep the
harvesting system operating then,it is necessary that each subsequent
machine component have more capacity than the previous. In our case,
the truck could have hauled more fruit on a continuous basis than the
rake-pickup averaged; the rake-pickup had more per hour capacity than
the 2 shakers, etc. Allowing for some failures in the system, this
complement of machinery, in similarly selected groves, appears capable
of producing 900-1000 boxes of roadside fruit per 10-hour day. This
is based on 65 boxes per hour average harvest rate for each of 2 shakers
and average rake-pickup capacity of 175-200 boxes per hour.

Quality of Fruit Delivered to Canning Plant

The percentage unwholesome fruit as shown in Tables 1, 2, and 3 was
determined by official sample of the State Inspection Service according
to Department of Citrus regulations. On the basis of unwholesome fruit,
the Lynchburg test was marginal; the Florida Gold and the Winter Garden
tests were well within tolerance. There was more trash in the loads from
the Lynchburg and Florida Gold test than in average loads arriving at the
plant. Trash in the Lynchburg loads was above normal to excessive due to
pruning residue on the ground and lack of cleaning equipment on the rake-
pickup machine. A subjective estimate of internal fruit damage (not
considered in unwholesome fruit count) indicates that this could well be
a major problem area. This type damage results from fruit falling, on
the shaker itself, on compacted soil, or on tree limbs plus damage caused by
the rake-pickup machine. Grove preparation before shaking and improvement
of the raking action to lessen the piling effect in front of rake can be
expected to reduce this damage.

Effect of Fruit Prices on ASPT System Costs

During the 1971-72 period when this test was carried out, prices
of oranges were about $.50 per pound solids, or an average of $2.80
per box through the season up to April 1, 1972 as reported by the Departmentof
Citrus (D). This reflected on tree prices of approximately $2.00 per box
during the period of these tests. Prices existing during a similar period
for the 1970-71 harvest season were much lower; $.25-$.27 per pounds solids,
an average of $1.45 per box value for fruit processed as of April 3, 1971,
an approximate average on tree value of $.60 per box. These price differences
are reflected in the total harvesting cost as differences in grove abandon-
ment cost and at plant abandonment cost of culls.

(D) Weekly Citrus Statistical Report, Florida Department of Citrus, April 1,
1972 and April 3, 1971.


As an example, assume a grove with 550 boxes per acre yield, 95%
removal is obtained, 2% is left on ground, 2% of delivered in fruit is
graded out as culls. All other things being equal, harvesting with the
ASPT System would have cost 86.3 cents per box in the 71-72 season and
73 cents per box in the 70-71 season.


A shaker-pickup harvest system was evaluated for harvesting early
and midseason oranges under several grove conditions.

The cost of harvesting varied from 70 to 88 cents per box. This
cost compares favorably with the average hand harvesting system cost of
75 cents per box.

The abscission chemical (Acti-Aid) increased the harvest rate in
all the groves, but the increase was large enough to compensate for the
additional cost only in the grove with the taller trees. The abscission
chemical was not as effective as had been expected. It did not loosen
all the fruit to a level where it could be removed easily. From 10 to
15% of the fruit crop was still firmly attached which resulted in the
shaker having to shake longer and harder to remove that portion of the
crop. In some cases, this completely negated the gain from the faster
removal of the portion of the crop which did loosen.

Fruit delivered to the processing plant from the shaker-pickup
system contained a larger amount of foreign material and unwholesome
fruit than that normally expected from hand harvesting systems. The
fruit passed the standards set by the State Inspection Service, although
some extra grading was required. Some juice losses were expected in
the processing plant from damaged fruit but it could not be evaluated
under the conventional handling procedures. These losses could become
a problem if a large quantity of this fruit was handled. The fruit was
processed within 36 hours after harvest to prevent it from becoming
too soft.

The harvest system has certain limitations on the conditions under
which it will function properly. It is restricted to fairly level terrain,
not over a 5% slope. The ground must be smoothed, disked to a depth of
2 inches,and cleared of trash. Tree skirts must be at least 3 feet at
the outer edge of the foliage and no side limbs protruding laterally
on the trunk below 2 feet. Trees must be open enough to alow the shaker
operator a view of the main limbs.

AiC i.w !LLi .L L EINTS

The authors wish to acknowledge the excellent cooperation of the
Foods Division of Coca Cola Company and Southern Fruit Distributors in
furnishing grove areas for these tests and in allowing the use of their
fruit receiving facilities for the fruit quality determinations.

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