• TABLE OF CONTENTS
HIDE
 Front Cover
 Acknowledgement
 Table of Contents
 Introduction
 Growth rates
 Droppage rates
 Effects on total production
 Summary






Group Title: Agricultural economics report - University of Florida Dept. of Agricultural Economics ; no. 62-2
Title: Size of fruit and droppage rates influence total citrus production
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00074609/00001
 Material Information
Title: Size of fruit and droppage rates influence total citrus production
Physical Description: 19 p. : ; .. cm.
Language: English
Creator: Stout, R.G
University of Florida -- Agricultural Experiment Station. -- Dept. of Agricultural Economics
Publisher: s.n.
Place of Publication: Gainesville
Publication Date: 1961
 Subjects
Genre: non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by R.G. Stout.
 Record Information
Bibliographic ID: UF00074609
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 67642542
clc - 000474557

Table of Contents
    Front Cover
        Front Cover
    Acknowledgement
        Page i
    Table of Contents
        Page ii
    Introduction
        Page 1
    Growth rates
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
    Droppage rates
        Page 10
        Page 11
        Page 12
    Effects on total production
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
    Summary
        Page 18
        Page 19
Full Text




July 1961


Roy G. Stout


Florida Crop and Livestock
Reporting Service
Orlando, Florida


Department of Agricult ciEconomics
Florida Agricultural Ex ir(riinCStation .';
Gainesville, Florida


Agricultural Economics
Report No. 62-2




SIZE OF FRUIT AND DROPPAGE RATES INFLUENCE
TOTAL CITRUS PRODUCTION

by














FOREWORD


Data reported in this report were collected primarily for use in

citrus crop forecasting. These data collections were made possible from

funds provided on a matching basis by the Growers Administrative

Committee and the Agricultural Marketing Service, United States

Department of Agriculture,




ACKNOWLEDGMENTS



Many thanks are extended to the Florida Crop and Livestock

Reporting Service for their assistance and use of data in preparation

of this report. Particularly appreciation is extended to Mr. J. C.

Townsend, Jr., Statistician-ln-Charge and to Mr. Paul E. Shuler,

Citrus Statistician and Mr. J. VV. Todd, Survey Statistician.

















CONTENTS

Page

INTRODUCTION.... .. ....... * .* 1

GROWTH RATES. .............. . ... 2

Average Monthly Growth Rates 3
October to Maturity Date Growth Rates 3

DROPPAGE RATES . ....... .. . 10

Annual Droppage Rates 11
Monthly Droppage Rates 12

EFFECTS ON TOTAL PRODUCTION .. ... .. ... 13

Number of Fruit per Box 14
Change in Total Production 14

SUMMARY.. ....... .. ... 18













SIZE OF FRUIT AND DROPPAGE RATES INFLUENCE
TOTAL CITRUS PRODUCTION

by

Roy G. Stout1


INTRODUCTION


The size of the citrus crop is influenced by many factors such as climatic

conditions, soil type, and cultural practices. In direct relation to these pro-

ductive factors and the size of the citrus crop is the number of fruit set on the

tree, the number of fruit that drops off during the growing season, and the size

of the fruit at picking. For the past several seasons the United States Department

of Agriculture has collected information on growth rates and droppage rates in

connection with forecasting the citrus crop.

These growth and droppage rates and their influence on the total citrus

crop are summarized in this report. All data presented herein relates to esti-

mated averages for the State, Individual growers are cautioned that their groves

may or may not behave in a manner similar to the State averages.

Information on growth rates and droppage rates was collected from approxi-

mately 445 groves throughout the citrus producing counties. The sample in 1960-61

consisted of 135 early and midse.ason groves, 125 Valencia groves, 78 seedy grape-

fruit groves, and 117 seedless grapefruit groves.


Assistant Agricultural Economist, Department of Agricultural Economics.










For collecting growth rate data, 2 trees per grove were randomly selected

and a spot on a limb was tagged. The 10 nearest fruit to this spot was measured

each month. When a sample tree was picked of fruit the next grove on the route

of like variety was substituted. If one of the fruit that was being measured dropped

off, the next closest one to the tagged spot was measured as a substitute.

A limb on each of the 2 trees with a cross-sectional size of about 2 percent

of the cross-sectional size of the trunk was selected and tagged for collecting

droppage data. The number of fruit on this limb was counted as of September 1 and

each month thereafter. The droppage rate each month was determined by the

difference in the number of fruit on the limb for the current month and the previous

month. When a tree was picked, no replacement was added to the sample.


GROWTH RATES


Each individual fruit was measured by the use of specially built calipers

which measured the circumference of the fruit in inches, These measurements

were converted to volume of fruit in cubic inches. The size of the fruit was

converted to volume basis in order to determine the number of fruit required to

equal a 90 pound box equivalent. Consequently this report considers volume as

the unit of size measurement. These data have been obtained monthly from

September to the end of the season since the 1954-55 production year.










Average Monthly Growth Rates


Oranges.--The 7 year average size per fruit of early and midseason and

Valencia oranges by months is shown in Figure 1. The average size of early and

midseason oranges in September was nearly 7 cubic inches. The average size at

the date of maturity of January 1 was 11.6 cubic inches. Valencia oranges

average larger in size than the earlier varieties; perhaps this is due to the longer

growing season. The average size of Valencias in September was about 6.4 cubic

inches whereas the average was about 13 cubic inches at the date of maturity of

April 1.

Tangerines.--The 7 year average growth of tangerines from September to

December was about 1.4 cubic inches each month (Figure 2). The average size

in September was 2.6 cubic inches and 6.7 inches in December. Growth from

December to January was a very small amount.

Grapefruit.--Seedy grapefruit averaged considerably larger than seedless

grapefruit (Figure 3). September average volume for seedy grapefruit was nearly

28 cubic inches and seedless grapefruit averaged 21.5 cubic inches. March 1

average sizes were 43.6 cubic inches for seedy and 35.2 cubic inches for seedless

grapefruit.


October to Maturity Date Growth Rates


The first forecast of the citrus crop is released on October 10. Consequently

the October 1 size of fruit is the last measurement obtained to estimate the size at

maturity. Tables 1 and 2 show the average fruit size for October 1 and the maturing




























Early and
Midseason


Valencias


- IiI I I


Sept. Oct.


Nov. Dec.


Jan. Feb. Mar. Apr.


Month


Figure 1 .--Growth Rote of Early and Midsoason Oranges,
September-January, and Valencias, September-April,
1954-60 Average


__


























7-

(6)






o 4











January, 1954-60 Average















42


40
/ Seedy

38


36
U
34


8 32

o 30

"5 Seedless
u- 28-


26 -


24 -

22

I I I i l I I .
Sept. Oct. Nov. Dec. Jan. Fob. Mar. Apr.
Month

Figure 3.--Growth Rates of Soedless and Soody Grapefruit, September-
March, 1954-60 Average








Table 1 .--Average Volume per Fruit of Oranges and Tangerines as of October 1
ard Maturing Date, 1954-55 to 1960-61


----------------------. Cubic Inches--------------------


1954-55
1955-56
1956-57
1957-58
1958-59
1959-60
1960-61


10.58
10.64
8.54
10.02
8.06
10.71
8.21


12.11
12.77
11.07
11.36
10.84
12.98
10.24


Average 9.54 11.62


9.79
9,33
7.52
8.77
7.45
9.55
7.75


8.59


13.65
13.93
12.65
12.03
13,26
14.18
12.42


13.16


4.28
4.01
3,63
4.19
3.76
5.02
3.24


4.02


6.31
7.99
6.30
6.30
6.58
7.70
6.21


6.77


aAs of January 1.

As of April 1.

CAs of January 1.


Table 2.--Average


Volume per Fruit of Grapefruit as of October 1
and Maturing Date, 1954-55 to 1960-61


-----. --------------- Cubic Inches---------.------ ------


40.25
31.09
28.48
39.17
29.21
44.70
29.23


Average 34.62


48.65
36.81
36.34
45.48
40.02
54.94
38.34


42.94


32.94
26.67
21.84
29.29
24.44
29.59
24.40


27.02


40.56
32.86
29.95
34.08
32.94
39,03
30.93


34.33


aAs of February 1.


1954-55
1955-56
1956-57
1957-59
1958-59
1959-60
1960-61


_ _


_










date for each of the past 7 seasons. The average size of the fruit has varied con-

siderably during the 7 years covered. The October size for early and midseason

oranges, for example, was only 8.06 cubic inches in 1958-59. The following year

the average size on the same date was 10.71 cubic inches. However, the increase

in size from October to harvest is more consistent. Relative to their annual average

sizes, the other kinds of citrus show more variation in comparison between years than

was true for early and midseason oranges.

Table 3 shows the relationship of the October size to the size at picking

time. The size of the fruit at harvest time is pretty well established by October.

Early and midseason oranges averaged an increase of 22 percent from October 1 to

January 1 for the 7.years. The smallest increase was 14 percent in the 1954-55

season and the largest increase was 34 percent in the 1958-59 season.


Table 3.--October 1 Average Volume of Fruit as a Percent of the Average Volume
at Maturity Date, 1954-55 to 1960-61


Oranges Grapefruit Tangerines
Season Tangerines
Early and Midseason Valencias Seedy Seedless

1954-55 114 139 121 123 148
1955-56 120 149 118 123 199
1956-57 130 168 128 137 174
1957-58 113 137 116 116 150
1958-59 134 178 137 135 175
1959-60 121 148 123 132 153
1960-61 125 160 131 127 192

Average 122 153 124 127 168









Valencia oranges at harvest date averaged 153 percent of the October

size -- an increase of 53 percent. In the case of Valencias, there appears to be

2 growth rate patterns that follow from October to harvest. This undoubtedly

is due to whether there has been an early or late bloom and fruit set. During the

7 years, the percentage growth from October until harvest varied from 37 percent

in the 1957-58 season to 78 percent in the 1958-59 season, Part of the small

increase in size during 1957-58 was undoubtedly due to the December freezes.

However, there were other low growth years as in 1954-55 when the percentage

growth was only 39 percent. If the data for Valoncias in Table 2 are divided into

2 groups (those years when the October size was under 8 cubic inches in one

group and over 8 cubic inches in the second group) the percentage growth rate is

very similar within each group. For the small group the average harvest size

was 169 percent of the October size. For the large sized group the average

harvest size was 144 percent of the October size.

Tangerine growth from October to January is considerable, For the

7 years the average increase from October to January was 68 percent, with a

low of 48 in 1954-55 and a high of 99 in 1955-56. Tangerine size, like Valencias,

in October is a factor in determining the percentage growth for the remainder of

the year. If the data for tangerines in Table 2 is divided into two groups (those

years when the October size was under 4.1 cubic inches in one group and those

larger in a second group) the percentage increase from October to January for the

small group was 85 percent and 51 percent for the large group.










Grapefruit sizes are fairly well established by October. The 7 year

average for seedy grapefruit showed an increase of 24 percent from October to

February. Seedless increase averaged 27 percent. The range for seedy was from

a low of 16 percent during the 1957-58 year (year of the freeze) to 37 percent

in 1958-59. The seedless grapefruit range was about the same -- from 16 per-

cent in 1957-58 to 37 percent in 1956-57.


DROPPAGE RATES


The amount of fruit that drops off a tree even after the fruit has passed

the halfway mark in the length of the growth period is considerable. For many

trees, half of the fruit that was on the tree as of September 1 dropped off before

the tree was picked. This rate of droppage has caused considerable alarm to many

people in the industry, particularly those who have been directly affected. Again

it should be pointed out that the droppage rate presented represents only averages

for the State sample and individual groves may show considerable variation from

these averages. It is anticipated that a later publication will include a study of

the variation in droppage rates and growth rates.

Information on droppage rates for the 1959-60 and 1960-61 season was

obtained according to the methods described in the Introduction. For the 3 previous

seasons, droppago data were obtained by clearing the ground under the sample

trees in September and returning each month to count the fruit on the ground. An

average drop per tree was computed for the sample. This was used to adjust the










average number of fruit on the tree as estimated in the fruit count survey. Mechanics

of carrying out the field work plus the advantage of having complete data, that is,

number of fruit on the sample limb and the droppage from these limbs, made it

desirable to change to the tagged limb sample.


Annual Droppage Rates


The estimated percentage of the crop that was on the tree as of September 1

that dropped off before the end of the harvest season is shown in Table 4.

Valencia oranges dropped considerably more on a percentage basis than any

other kind of fruit. Again the longer growing season contributes greatly to

this increased droppage. A higher percentage of seedy grapefruit dropped off

the tree than of the seedless variety.

Table 4.--Estimated Percent of Total Crop on Tree as of September 1 that Dropped
During the Seasons 1956-57 to 1960-61


1956-57
1957-58
1958-59
1959-60
1960-61

Average


--------------- ..Percent---------------------

10.3 19.0 14.6 11.1
16.3 40.4 25.6 18.0
12.4 24.7 16.6 16.2
16.6 33.7 12.3 10.4
23.9 41.9 31.9 27.0

15.9 31.9 20.2 15.1











Early and midseason oranges dropped off at an average rate of about 16 per-

cent; Valencias, 32 percent; seedy grapefruit, 20 percent; and seedless grape-

fruit, 15 percent. The 1957-58 freeze in December undoubtedly affected Valencias

and grapefruit the most since much of the early varieties crop was already

harvested. Likewise the September hurricane affected the 1960-61 droppage

even though droppage during the hurricane was estimated as 10 percent and has

been subtracted out of the data in Table 4.


Monthly Droppage Rates


The month-to-month variation in droppage rates is rather variable, con-

sequently it is rather difficult to estimate droppage rates. However, the 5 year

monthly average droppage rates indicate a significant droppage each month

(Table 5). The September droppage for oranges was slightly over 4 percent.

This reduced slightly, percentagewise, as the season advanced to about 3 per-

cent in January and February. Grapefruit averaged about 3 percent droppage

in September and about 2.5 percent in February and March.

In any one year weather conditions, as the freeze in 1957-58 and the

hurricane in 1960-61, can cause large droppage in any one month. In addition

to this unusual and occasional weather effect, there are other factors that cause

some droppage to occur every month of the season.











Table 5.--Average Percent of Fruit on Tree as of the First Day of the Month that
Dropped During the Month, 5 Year Averagea

/ Monthb
Kind of Fruit an
Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May

-....--------------.- -- Percent-- ---------------..

Early and midseason
oranges 4.1 3.7 3.1 2.4 2.9 3.2

Valencias 4.2 4.9 4.6 2.7 3.1 3.2 2.9 3.4 2.0

Seedy grapefruit 3.8 2.5 3.7 3.1 3.1 2.8 2.6

Seedless grapefruit 3.1 1.9 2.6 2,2 2.2 2.5 2.6


aDroppage during 1957-58 after the freeze was not included in computing
these monthly averages.

bMonthly figures are based on the crop remaining on the tree, therefore
the total of the monthly percentage drops is greater than the percent of the total
crop that dropped off the trees.


EFFECTS ON TOTAL PRODUCTION


Droppago rates and growth rates both have a considerable effect on the

size of the total citrus crop. Droppage rates require no explanation as to their

effect on the size of the crop harvest, because if an orange drops off the tree then

it is entirely eliminated from the harvest potential. However, variations in

growth rates are not so straightforward. Variations in the size of the individual

fruit cause variations in the number of fruit required to make a box. That is the

number of fruit required to fill a standard sized box is dependent on the size of

the individual fruit.











Number of Fruit Per Box


Figure 4 shows the relationship between average volume per fruit and

number of fruit per box for oranges. Assuming the average volume per fruit of

oranges is 15 cubic inches, it takes 165 oranges to fill a box; if the average

volume is 17 cubic inches the number of fruit per box is about 141, and if the

volume is 12 cubic inches the number of fruit per box is 204.

Figure 5 shows the relationship between volume per fruit and number of

grapefruit per box. If average volume is 60 cubic inches, it takes about 47 fruit

to fill a box. However, it requires 67 fruit to fill a box if the average volume

per fruit is 40 cubic inches.


Change in Total Production


The effects of an increase in one average size on tree production is

shown in Table 6. If grapefruit growth increased in volume from 37.4 to

42.0 cubic inches, the number of fruit per box decreases from 70 to 64 which

is about 8.5 percent. Assuming an average tree has 500 grapefruit, the number

of boxes per tree increases from 7.1 to 7.8 boxes. There are presently about

6.7 million grapefruit trees in Florida; consequently a change in average fruit

volume from 37.4 to 42.0 cubic inches per fruit would increase total production

by about 4.2 million boxes (assuming 500 fruit per tree).












25




20





U.15




- 10




5-


120 140 160 180 200 220 240 260

Figure 4.-Relationship Between Fruit Size and Number of Fruit per Box
(Valencia Oranges)









80





70




0
S-60

U

a)a
o 50 -


u,


40





30





Figure 5.--Relationship Between Fruit Size and Number of Fruit per Box
(Grapefruit)










Table 6.--Number of Fruit per Box and Number of Boxes by Two Sizes of Fruit


Volume Boxes per Tree Assuming
Kind No. Fruit per 500 Grapefruit and
per Box Fruit 1,000 Oranges per Tree


Grapefruit 70 37.4 7.1
64 42.0 7.8

Oranges 200 12.48 5.01
190 13.05 5.26



If the average volume per fruit of oranges increased from 12.48 to 13.05

cubic inches, the number of fruit per box decreases from 200 to 190, or about

4.6 percent in production. Assuming 1,000 oranges per tree, this would be an

increase from 5.01 to 5.26 boxes. There are presently about 26.5 million orange

trees in Florida, thus an increase in size from 12.48 to 13.05 would mean an

increase in total production of 6.6 million boxes.

According to the data obtained from the limb count survey conducted

in each August and September, the average number of fruit per tree for the past

5 years was slightly above 500 for grapefruit, 866 for Valencias, and 1185 for

early and midseason oranges (Table 7). If these figures are reduced by the

average percent droppage rates shown in Table 4, then the average number of

fruit harvested per tree was 402 for grapefruit, 590 for Valencias, and 997 for


early and midseason.










Table 7.--Estimated Average Number of Fruit per Tree as of September 1a

Kind
Season Oranges Grapefruit
Early and Midseason Valencias Seedy Seedless

1956-57 1,218 934 524 594
1957-58 1,380 1,056 524 543
1958-59 1,099 740 663 458
1959-60 1,005 796 321 453
1960-61b 1,221 805 607 508

Average 1,185 866 528 511


aFrom limb count survey.

bAfter hurricane.


Thus changes in the average size of the fruit could affect the total pro-

duction by as much as 8 to 10 million boxes from one year to the next, even if

the total number of fruit remains the same.


SUMMARY


Data collected during the past 7 years indicate that the eventual size of

an individual fruit of early oranges and grapefruit is pretty well established by

October 1. The individual sizes of tangerines and Valencias vary more between

October size and maturity date size than early oranges and grapefruit. Average

growth rate of early and midseason oranges from October 1 to January 1 was

22 percent, Valencia oranges increased in size by an average of 53 percent from

October to April, tangerines increased by an average of 68 percent from October











to January, seedy grapefruit average increasing in size by 24 percent from

October to February, and seedless grapefruit increased in size by an average

of 27 percent.

Droppage of fruit off the tree after September is considerable and appears

to be on the increase. Valencia droppage is quite a bit higher than the other

kinds of citrus. The 5 year average droppage after September 1 for early and

midseason oranges and seedless grapefruit was about 15 percent; seedy grapefruit,

20 percent; and Valencia oranges, 32 percent.

Research work desperately needs to be conducted to determine the cause

of this heavy droppage. True droppage due to weather conditions cannot be

controlled, but there is considerable droppage due to the splitting of the orange.

If droppage due to this splitting alone could be controlled, citrus production

would be increased by a significant amount.
















RGS: ms 7/61
Agr. Expt. Sta. -- 1,500




University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs