FLORIDA STATE HORTICULTURAL SOCIETY, 1971
92
tree shape, mode of shake, and design of foliage
100:
clamp. There was considerable room for improve
ments in all of these factors which would have
affected removal efficiency. Stem count with the
90
tree shaker ranged from 46% down to 22% over
80 U-
the 2-month harvest period with an average of
30% stems removed with the fruit. The foliage
shaker had a narrow range of stems averaging
27%. The effect of the two shakers at the different
harvest dates on subsequent fruit yield for the
▼ v AREC Shaker
3
• •
84
o
ITF Shaker
% Remova I
/
1971 test will be obtained in 1972.
7
/
Selectivity Ratio/ y'
/
Acknowledgements
2
The help and cooperation of the Roper Growers
10
30
20
10
20
30
MAY
APRIL
HARVEST DATE-I97I
Figure 3.—Influence of harvest date on
mature fruit removal in 'Valencia' oranges.
10
20
JUNE
selectivity
and
for all harvest dates when compared with the limb
shaker. The difference was significant at the 1%
confidence level for the May 11 harvest and at
the 10% level for the June harvest. The foliage
shaker selectivity data may be slightly biased be
cause of lower mature fruit removal, 80% average
compared to 88% for the tree shaker. The time
that each machine spent shaking each tree aver
aged 2.4 minutes for the limb shaker and 2.3 min
utes for the foliage shaker. The time did not in
clude that necessary for getting into position,
grasping the tree, or disengaging from the tree.
Total harvest time is dependent on operator skill,
Cooperative in providing a grove area in which
to work and picking labor to obtain 1971 yield data
was sincerely appreciated. The ITF Leasing Corp.
furnished the foliage shaker used in these experi
ments as well as the machine operator and helped
in counting fruit and collecting data. Dr. W. C.
Wilson and his assistants applied the experimental
abscission chemicals for all the harvest trials.
LITERATURE CITED
1. Hedden, S. L , and G. E. Coppock. 1965. A tree shaker
harvest system for citrus. Proc. Fla. State Hort. Soc.
78:302-306.
2. Whitney, J. D. 1968. Citrus fruit removal witji an air
harvest concept. Proc. Fla. State Hort. Soc. 81:43-48.
3. Coppock, G. E. 1967. Harvesting early and midseason
citrus fruit with tree shaker harvest systems. Proc. Fla.
State Hort.
Soc.
80:98-104.
4. Coppock, G. E., S. L. Hedden, and D. H. Lenker. 1969.
Biophysical properties of citrus fruit related to mechanical
harvesting. Transactions of the ASAE 12:561-563.
5. Florida Agricultural Statistics, Citrus Summary 1970.
p. 6-7.
THE EFFECT OF PRECIPITATION ON MATURITY PARAMETERS
OF FLORIDA CITRUS1
Robert D. Carter, Bela S. Buslig, and
John A. Attaway
Florida Department of Citrus
Lake Alfred
Abstract
Annual precipitation records at ten representa
tive U. S. Weather Bureau locations throughout
Florida Agricultural Experiment Stations Journal Series
No. 4191.
Cooperative research of the State of Florida, Department
of Citrus and University of Florida Agricultural Experiment
Station.
the citrus producing area of Florida were studied
from 1952 through 1970. Seasonal averages of
fruit acidity, Brix and yields as reported by the
Florida Department of Agriculture and the Florida
Canners Association were correlated with the pre
cipitation data. Correlation was found between
precipitation and maturity in terms of acids (r =
-.83) and Brix (r = -.83) of grapefruit.
Introduction
There has been scattered evidence that the
acidity and Brix of grapefruit varies inversely with
CARTER, ET AL: PRECIPITATION AND MATURITY
93
precipitation or applied moisture (1, 5, 9), al
though one report relates low moisture application
to low acidity and low solids in citrus on Lakewood
cessed product yields
fine sand (7).
per standard box (90 lbs oranges; 85 lbs grape
It has been demonstrated in a seven year
study that 14 to 28 inches of supplemental irriga
fruit)
tion annually increases production in 'Hamlin',
'Pineapple' and 'Valencia' oranges and 'Marsh*
grapefruit. 'Marsh* grapefruit showed the greatest
effect with an increase of 40% in production and
an increase of 33% in pounds solids per tree (6).
The aldehyde contents, a quality parameter of
and correlation coefficients determined.
orange peel oils and juices has been shown to in
crease in Valencia orange oil with increased total
annual rainfall (4).
It was reported (10) without data and refer
ence that preliminary studies of weather and fruit
quality showed a high negative correlation between
the total annual rainfall and the soluble solids
(r = -.960) and acid (r = -.931) content of
'Marsh' and 'Duncan' grapefruit.
In view of the limited literature reports in the
area
of moisture effect
on
citrus fruit quality
parameters
(11) a study was made of rainfall
data over the past eighteen years in the citrus
producing areas of Florida vs. various quality
(2)
fruit juice are reported in No. 2 cans (20 fl. oz.)
of fruit
(11).
The data on precipitation,
acidity, Brix, and yield were statistically analyzed
Discussion of Results
Table 1 shows the 1952-1970 average annual
precipitation data for each of the ten representa
tive U. S. Weather Stations. Lake Alfred had the
least average rain frequency with rain on 28%
of the days per year (102 days). West Palm Beach
had the highest average of 47% of days with rain
or 171 days with rain per year. West Palm Beach
and Bradenton had the highest average of 61.51
and 58.18 inches of rain per year respectively. The
remaining stations averaged in a remarkably nar
row range between 51.72 and 55.91 inches per year.
Table 2 shows annual precipitation data for
the March-February growth years 1952-1970, to
gether with Brix and acid data for grapefruit
delivered to processors during the SeptemberAugust processing season. Visual observation of
parameters of citrus. This data covering precipita
the
tion and frequency of precipitation was related to
acidity and Brix values
acidity, Brix (3) and yield data of grapefruit and
of canned grapefruit
sections, canned orange juice and canned grape
yearly
patterns
of
rainfall
and
(Fig. 1)
grapefruit
for the period
examined indicated an inverse relationship between
oranges delivered to processing plants during the
precipitation and either acidity or Brix. The 1961-
corresponding years 1952 through 1970.
62 growing season had the lowest average pre
cipitation with 38.6 inches with the fourth highest
grapefruit acidity
Experimental Procedure
Monthly precipitation
reports
72.9 inches,
issued
U.S. Weather Bureau for the State of
from
1952
through
1970
were
used
by
the
(1.4%). The highest rainfall,
(1959-60)
grapefruit acid
occurred with the lowest
(1.15%).
Florida
(12).
An
Table 1.
Average Annual Precipitation Data for Ten
arbitrary selection of ten weather stations repre
U. S. Weather Stations Representative of the Citrus
sentative of the citrus producing areas of Florida
Producing Areas of Florida.
are listed in Table 1. It should be noted that in
(1952-1970).
Average IAnnual
1969 the Lake Placid Station was discontinued and
Precipitation
Frequency
replaced by the Archbold Biological Station some
Station
Inchess
ten miles southwest of the original station.
Bradenton
58.18
119
Brooksville
55.91
120
Clermont
51.97
128
Ft.
54.08
159
Daily precipitation data was studied and
monthly tabulations were made of total rainfall
and number of days with
a trace
or more
of
Myers
in Days
precipitation at each station. Monthly totals, an
Lake Alfred
52.62
102
nual totals and averages were developed.
Lake Placid*
52.84
141
Ocala
54.98
121
ginning of the growth year on the basis of a study
Sanford
51.97
139
of citrus bloom patterns (8).
Vero Beach
51.73
142
West Palm Beach
61.51
171
The month of March was selected as the be
Average annual Brix and acid values of grape
fruit and oranges delivered to processing plants
(3) were tabulated for the years 1952-1970. Pro
The Archbold Biological Station replaced the
Lake Placid Station in 1969.
FLORIDA STATE HORTICULTURAL SOCIETY, 1971
94
Table 2.
March Through February Annual Precipitation and Seasonal Average
Processing Grapefruit Brix and Acid,
(1952-1970).
Grapefruit
Total Precipitation
March
Inches
Year
Mar.
Processing
Acid
Brix
Days
130
10.19
1.36
65.8
141
9.95
1.23
49.9
132
10.25
1.36
121
11.11
1.50
48.5
1953
for
Seasonal Average
- February
1952
- Feb.
1953
-
1954
1954
-
1955
1955
-
1956
40.7
1956
-
1957
42.4
116
10.70
1.41
1957
-
1958
63.5
152
9.87
1.25
1958
-
1959
56.7
136
10.58
1.39
9.51
1.15
1959
-
1960
72.9
162
1960
-
1961
1961
-
1962
1963
1964
-
1965
-
1967
-
1968
-
1969
-
65.1
137
10.25
1.33
1962
38.6
112
11.27
1.40
-
1963
54.0
141
9.96
1.26
-
1964
52.2.
132
10.67
1.35
1965
52.4
125
11.02
1.33
1966
55.1
131
10.35
1.35
1967
52.8
138
10.25
1.26
1968
44.4
126
10.83
1.46
1969
57.9
125
9.83
1.23
1970
67.0
138
9.82
1.24
1966
Correlation coefficients (r)
Total inches vs Brix and Acid
Total days vs Brix and Acid
-.83
-.83
-.80
-.75
precipitation values, the negative correlations in
tween grapefruit acid and the total inches precipi
tation falling in the four month period of June,
July, August, and September. Other combinations
dicating as rainfall increased, grapefruit acidity
of months showed poorer correlations between pre
decreased. Grapefruit acid values also correlated
well (r = -.75) with the average number of days
cipitation and acid or Brix, indicating the import
precipitation in the citrus producing area of Flor
Sept. in determining the quality of the forthcoming
ida. Grapefruit Brix also showed
with annual precipitation (r =
number of days precipitation (r
There was poor correlation
crop.
Annual average grapefruit acidity values cor
related well (r = -.83) with the average annual
good correlation
-.83) and with
= -.80).
between either
orange Brix or orange acid and
either of the
average precipitation values.
There was also poor correlation between aver
age annual grapefruit section yields, canned orange
juice and canned grapefruit juice yields reported
in No. 2 cans per box of fruit (2).
There was a fair correlation (r = -.642) be
ance of the rainfall during the period June through
LITERATURE CITED
1. Calvert, D. V., R. C. J. Koo and H. W. Ford. 1967.
Flood irrigation studies with citrus. Proc. Fla. State Hort.
Soc. 80:79-85.
2.
Florida
Canners
Association.
Statistical
Summary
1969-70 Season.
3. Florida Department of Agriculture, Division of Fruit
& Vegetable Inspection Reports 1952-53 through 1969-70.
4. Kesterson, J. W. and R. Hendrickson. 1966. Aldehyde
content of Valencia orange oil as related to total rainfall.
American Perfumer and Cosmetics 81: (2), 39-40.
5. Koo, R. C. J. 1963. Effects of frequency of irrigation
on yield of orange and grapefruit. Proc. Fla. State Hort.
Soc. 76:1-B.
95
CARTER, ET AL: PRECIPITATION AND MATURITY
SEASON VS. GRAPEFRUIT BRIX. ACIDITY, & RAINFALL
A
a^"\
§
1.50
BRIX4
<I.3O
ACID
1.20
II.Oo
A
10.5 |
\
10.0 go
9.5
A
A
170 S
1.10
Z
<
CO
X
80
70
6O
5O
*^S» /
A
/
\
\
150 <
/
/ ^
I
^
"V
INCHES
40
52
53
53
54
54
55
55 56 57 58
56 57 58 59
130 K
,^Av A-A/
59 60 61
60 61 62
62 63
63 64
64 65 66 67 68
65 66 67 68 69
69
70
SEASONS
Figure 1.-Variation in maturity indices with rainfall.
6. Koo, R. C. J. 1969. Evaportranspiration and soil
moisture determination as guides to citrus irrigation. Proc.
First Int. Citrus Symp. p. 1725-30.
7. Koo, R. C. J., and G. T. Hurner, Jr. 1969. Irrigation
requirements of citrus grown on Lakewood fine sand. Proc.
Fla. State Hort. Soc. 82:69-72.
8. Simanton, W. A. 1969. Seasonal patterns of citrus
bloom. Proc. Fla. State Hort. Soc. 82:96-98.
9. Sites, J. W. 1947. Internal fruit quality as related to
production practices. Proc. Fla. State Hort. Soc. 60:55-62.
10.
Sites, John W., Herman J. Reitz, and E. J. Deszyck.
1951. Some results of irrigation research with Florida citrus.
Proc. Fla. State Hort. Soc. 64:71-79.
11. Soule, J., W. Grierson, and J. G. Blair. 1967. Quality
Tests for Citrus Fruit. What every grower should know.
Fla. Agr. Expt. Sta. Circ. 315.
12. U. S. Dept. of Commerce, Weather Bureau and TJniv.
of Fla. Agr. Expt. Stations, Lakeland, Fla. 1952-1970. The
Seasons Report of the Federal-State Frost Warning Service.