The influence of calcium on the growth, yield, quality, and chemical composition of watermelons, Citrullus vulgaris Schrad

MISSING IMAGE

Material Information

Title:
The influence of calcium on the growth, yield, quality, and chemical composition of watermelons, Citrullus vulgaris Schrad
Physical Description:
viii, 112, (1) leaves : ill. ; 28 cm.
Language:
English
Creator:
Waters, Willie Estel, 1931-
Publication Date:

Subjects

Subjects / Keywords:
Melons   ( lcsh )
Plants -- Effect of calcium on   ( lcsh )
Genre:
bibliography   ( marcgt )
theses   ( marcgt )
non-fiction   ( marcgt )

Notes

Thesis:
Thesis--University of Florida, 1960.
Bibliography:
Includes bibliographical references (leaves 90-96).
Statement of Responsibility:
by Willie Estel Waters.
General Note:
Typescript.
General Note:
Vita.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 000414423
notis - ACG1598
oclc - 36813940
System ID:
AA00003575:00001

Full Text









The Influence of Calcium on the Growth, Yield,

Quality, and Chemical Composition of

Watermelons, Citrullus vulgaris Schrad.










By
WILLIE ESTEL WATERS


A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF
THE UNIVERSITY OF FLORIDA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY










UNIVERSITY OF FLORIDA
January, 1960











ACKNOWLEDGEMENTS


The author wishes to express his sincere apprecia-

tion to Dr. V. F. Nettles, Professor of Vegetable Crops,

for guidance and suggestions throughout this study.

The helpful advice and assistance of the other mem-

bers of the supervisory committee, Dr. W. O. Ash, Dr. F. S.

Jamison, Dr. D. F. Rothwell, and Dr. B. D. Thompson, is

gratefully acknowledged.

Appreciation is expressed to all members of the

Vegetable Crops Department for their interests and coopera-

tion during this study.

The author is also indebted to his wife, Mary

Elizabeth Waters, for assistance in the preparation of

the manuscript and for continued devotion and encourage-

ment.


















ii











CONTENTS

Page
LIST OF TABLES . v

LIST OF ILLUSTRATIONS viAi

INTRODUCTION . . 1

REVIEW OF LITERATURE . 3

Mineral Nutrition of Cucurbits . 3

Effects on Yield .... 3
Effects on Quality . # 5
Effects on Sex Expression and Fruit Set. 7
Effects on Blossom-end Rot .. 8

Calcium in Plant Nutrition 10

Role in the Soil .. .. 10
Role in Plants .... 11

Cations in Plant Tissue * 13

Cation Accumulation * 13
Effects of Nitrogen on the Cation Content 17
Distribution of Cations in Plants. *. 18

METHODS AND PROCEDURES ,. ... 20

Greenhouse Phase. . .. 22

Field Phase . 25

Description of Soil Type and Soil Test 25
Field Methods . 26
Tissue Samples . 28

Chemical Analyses .... 29

Statistical Methods .. .. 30

RESULTS OF EXPERIMENTS .. .. 31

Greenhouse Phase *...... 35


iii








Page
Growth Responses . 35
Sex Expression and Fruit Set .. 42
Chemical Composition .. .... 45

Field Phase 0.,, 9 o *. 48

Soil Tests o 48
Growth Responses . 50
Fruit Set . . 58
Chemical Composition 57
DISCUSSION . . 69

Growth Responses e . .. a 69

Sex Expression and Fruit Set .... 77

Chemical Analyses . .. 78

SUMMARY AND CONCLUSION .. . 84

REFERENCES CITED . 90

APPENDICES . . 97

A Detailed Soil Test Results by Plot .. 97

B Analyses of Variance Tables .. 100

BIOGRAPHICAL NOTES 111










LIST OF TABLES


Table Page

1. Calcium levels in greenhouse solution cultures 23

2. The composition of the basic nutrient solution
for greenhouse experiment, .. 24
3. Total bi-monthly rainfall recorded at the
Horticulture Unit March 1 to June 30, 1959 27
4. The percentage of calcium, potassium, magnesium,
and sodium at six-locations within mature
watermelon plants, 1958 . 33
5. Test of significance for the percentage of
potassium, calcium, and magnesium at six
locations within mature watermelon plants. 34
6. The effects of calcium treatments on the dry
weight of vines, roots, fruits, and total
weight in the greenhouse experiment 42
7. The effects of calcium treatments on flower
production and fruit set in the greenhouse
experiment * .. 43
8. Test of significance for the effects of calcium
treatments on flower production in the
greenhouse experiment 44
9. The effects of calcium treatments on the per-
centage of calcium, potassium, and magnesium
in the leaves and tips of plants grown in
the greenhouse .* 48
10. The effects of calcium treatments on the per-
oentage of calcium, potassium, and magnesium
in the roots and fruits of plants grown in
the greenhouse .. 47
11. The pH and pounds per acre of available nutrients
of samples taken from the watermelon beds on
April 1, 1959 .. . 48









12. The pH and pounds per acre of available
nutrients of samples taken from each side
of the melon beds on April 1, 1959 49

13. The influence of more than eight inches of
rainfall on the removal of fertilizer
nutrients in pounds per aer from the
upper eight inches of soil in watermelon
beds * # *. ., 50

14. The effects of calcium and nitrogen on early
vine growth as indicated by the dry weight
of eight hills per plot ....* .* 51
15. The effects of calcium and nitrogen on the
number of early U. S. Number 1 watermelons. *51
16. Effects of calcium and nitrogen on the total
weight in pounds of early U. S. Number 1
watermelons. * 52
17. Effects of calcium and nitrogen on the total
number of U. S. Number 1 watermelons *. .* 53
18. Effects of calcium and nitrogen on the total
weight in pounds of U. S. Number 1
watermelons. . 53
19. The effects of calcium and nitrogen on the
average soluble solids as per cent sucrose
from all marketable melons per plot 54
20. The effects of calcium and nitrogen on the
average thickness of the rind in centi-
meters at the top center and bottom center
of all marketable fruits .. a 55

21. The effects of calcium and nitrogen on the
average thickness of the rind in centi-
meters at the blossom-end of all marketable
fruits # *. . # 55
22. The effects of calcium and nitrogen on the
percentage of blossom-end rot 56
23. The effects of calcium and nitrogen on the
total number of fruits set ... 57
24. The effects of calcium and nitrogen on the per-
centage of calcium, potassium, and magnesium
in the tips of young watermelon plants 58


Table


Page









25. The effects of calcium and nitrogen on the per-
centage of calcium, potassium, and mag-
nesium in the leaves of young watermelon
plants .* # . 59
26. The effects of calcium and nitrogen on the per-
centage of calcium, potassium, and mag-
nesium in the tips of mature watermelon
plants . 62
27. The effects of calcium and nitrogen on the per-
centage of calcium, potassium, and mag-
nesium in the leaves of mature watermelon
plants # . 63
28. The effects of calcium and nitrogen on the per-
centage of calcium, potassium, and mag-
neasiu in U. S. Number 1 watermelon fruits 65
29. The effects of ealcium-and nitrogen on the per-
centage of calcium, potassium, and mag-
nesium in watermelon fruits exhibiting
blossom-end rot 66
30. The average percentage of calcium, potassium,
and magnesium associated with each cal-
cium and each nitrogen level in both vines
and fruits from the field experiment .. 80
31. The pH and the pounds per acre of available
nutrients from soil samples taken in
watermelon beds from all field plots on
April I, 1959 98
32. The pH and the pounds per acre of available
nutrients from soil samples taken on each,
side of the bed from all plots on April 1,
1959 . . 99
33-42, Analyses of variance tables . .101-110


vii


Table


page












LIST OF ILLUSTRATIONS


Figure


1. The twelfth leaf from the-base of the plants
in treatments 2, 3, 4, 7, and 8 from the
greenhouse experiment *. ,. *


2. Representative-root systems from treatments
2, 3, 5, 7, and 8 of the greenhouse
experiment. .* .* .

3. The interaction of calcium and nitrogen
(CaL X NL) on the magnesium content of
the leaves of young watermelon plants .

4. The interaction of calcium and nitrogen
(Ca X NQ) on the potassium content of
U. Number 1 watermelons .* .

5. The interaction of calcium and nitrogen
(CaL X Nq) on the potassium content of
watermelon fruits exhibiting blossom-
end rot . *. *

6. The interaction of calcium and nitrogen
(CaL X NL) on the magnesium content of
watermelon fruits exhibiting blossom-
end rot *# .


S. 41



. 61



61


& 0


. 67


7. The influence of calcium-on the dry weight of
fruits, roots, vines, and total weight per
experimental unit in the greenhouse .

8. The percentage increase in early and total
yield of U. S. Number 1 watermelons from
plots receiving 500 and 1,000 pounds of
hydrated lime over plots receiving no
lime *. . .


viii


Page










INTRODUCTION


The watermelon is one of the most extensively grown

vegetables in the United States, yet little is known about

the nutrition of this plant. Florida alone produced 95,000

acres of watermelons during the 1957 and the 1958 seasons,

which comprised 31 per cent of the southern acreage or 21

per cent of the acreage of the United States (80). Rela-

tively few basic nutrient experiments have been conducted

with watermelons, mainly because the extensive type of vine

growth limits the feasibility of greenhouse culture tech-

niques. However, extensive experimentation has been con-

ducted in the field on the rates, sources, and methods of

application of the major fertilizer elements.

In the South watermelons are planted on light sandy

soils, whirc often have inherently low calcium supplies and

pH. Watermelons have generally been considered to tolerate

relatively acid conditions, and thus the liming of water-

melon fields is not normally a recommended practice. However,

from a literature review, it is obvious that very little

research has been conducted on the effects of differential

calcium levels and soil pH on the yield and quality of water-

melons.

The objective of this study was to evaluate the ef-

fects of the calcium supply on growth responses; yield;







2

quality; sex expression and fruit set; and the concentrations

of calcium, potassium, and magnesium in the tissues of the

Charleston Gray variety of watermelon. The study was con-

ducted in two parts: (1) a greenhouse phase involving eight

calcium levels in nutrient cultures and (2) a field phase

designed to study three levels of calcium in combination with

three levels of nitrogen.

The results of this study may be beneficial in ex-

plaining the occurrence of certain physiological disorders

and poor yields often obtained from watermelon fields re-

oeiving apparently adequate fertilizer. It also emphasizes

the need for additional research on the nutrition of the

watermelon.










REV IEW OF LITERATURE


Mineral Nutrition of Cucurbits

Effects a yzi~Ma

The extent to which the major nutrient elements
affect the yield of watermelons (Citrllus vulgar Schrad.)

is variable, depending upon the element, the environment,
and the chemical properties of the soil. Hartwell and Damon

(34) reported in 1914 that the best yields of watermelons

were obtained on plots made very acid by the application of
sulfate of ammonia. Examination of their data indicated

that liming had no effect on yield. Hartman and Gaylord

(33) reported no significant difference in yield or average

weight of watermelons grown on Princeton or Elk fine sand

ranging in pH from 4.7 to 7.5. However, there was a trend
toward greater yields at the higher pH levels. The pH

range was obtained by the application of up to 1,000 pounds
of elemental sulfur or up to 9,000 pounds of limestone.

Hall, Nettles, and Dennison (28) found no significant
differences in yields in a factorial experiment on Arredonda

fine sand containing three levels of calcium (0, 80, and 160
pounds per acre supplied as calcium sulfate in the row) and
three levels of magnesium (0, 20, and 40 pounds per acre of

magnesium oxide applied in the row). Hall, Nettles, and
Dennison (29) in later work were unable to show benefits from

3








the application of gypsum alone in the row. Jamison and

Nettles (40) reported that the application of soluble mag-

nesium with all inorganic nitrogen increased the yields of

watermelons.

Eisenmenger and Kucinski (20) observed that calcium

hastened maturity of both watermelons and cantaloupes by

nearly two weeks over no-lime treatments. Apparently the

application of lime augments cantaloupe production on soils

with low pH. Carolus and Lorenz (14) concluded that the

application of lime to light acid soils promotes early ma-

turity and increases yields of muskmelons. Hartman and

Gaylord (32) obtained an increase of cantaloupes from 160

bushels to 350 bushels per acre by increasing the soil pH

from 4.7 to 7.2 with limestone. Other cucurbits including

cucumbers, squash, and pumpkins apparently yield more when

grown on soils moderately supplied with calcium and within

the pH range of 5.5 to 7.0 (42, 83).

Considerable research relative to the effect of N-P-K

fertilizers on yields has been reported. Hall, Nettles, and

Dennison (29) concluded after five years of experimentation

at several locations in Florida that 60 pounds per acre each

of potassium and nitrogen were ample to give maximum yields

in seasons with reasonably favorable rainfall. This is, in

general, supported by data presented by Nettles and Halsey(53)

in 1958. Bradley and Fleming (10) observed similar results

on Norfolk fine sand in Arkansas. They stated that 60 pounds





5

each of nitrogen, potassium, and phosphorus was adequate for

good yields. In a somewhat drier area in Texas, Smith and

Mohr (70) concluded after four years tests on Hockley fine

sand that 20 pounds of nitrogen, 40 pounds of phosphorus, and

40 pounds of potassium produced maximum yields. However,

Patterson and Smith (57) reported significant increases in

yield from up to 200 pounds of potassium on Hockley fine

sand in Texas. According to Brantley (11) nitrogen increased

early marketable, total marketable, and total yield of water-

melons in Indiana on Princeton fine sand in a season of

heavy rainfall but not in a moderately dry season. Potassium

did not affect yields in either season.

Effects R quality

It has long been known that the quality of watermelons,

especially the soluble solids, is influenced by both heredity

and environmental factors (60, 85). The effects of these fac-

tors have been established; however, research relative to the

true influence of different nutrient elements is less apparent.

Hartman and Gaylord (33) reported that the application of up

to 9,000 pounds of ground limestone did not significantly in-

crease the percentage of sucrose. Hall, Nettles, and Dennison

(28, 29) observed that neither calcium sulfate nor magnesium

oxide had any significant effect on the percentage of soluble

solids, hollow-heart, or white-heart. However, Eisenmenger

and Kucinski (20) stated that cantaloupes and watermelons

grown on land treated with calcium were considerably higher






6

in sugar content, although no data were presented. Mazaeva

(47) observed that magnesium increased the sugar content of

watermelons grown in pots of light sodpodzolized soil. Ac-

cording to Morazov (52) the application of sodium chloride

or sodium sulfate to the soil decreased the monosaccharides

and the total sugar content of both watermelons and musk-

melons.

Work by Brantley (11) and by Kimbrough (41) indicated

that up to 250 pounds of elemental nitrogen had no signifi-

cant effect on the percentage of soluble solids in water-

melons. Bradley and Fleming (10) reported a significant

increase in soluble solids as a result of an interaction be-

tween nitrogen and phosphorus and an interaction between

phosphorus and potassium, but other quality measurements such

as hollow-heart, white-heart, and rind thickness were not

affected by any fertilizer treatment. When yields were not

affected by fertilizer treatments, soluble solids were not

affected; therefore, they concluded that providing adequate

fertilizer assures good quality. In contrast to this, Hall,

Nettles, and Dennison (28) concluded after several experi-

ments that neither potassium nor nitrogen had any significant

effect on soluble solids, white-heart, or hollow-heart.

Brantley (11) found no effect from differential levels of

potassium on the quality of watermelons or cantaloupes.

Woodard (85) demonstrated that the occurrence of white-heart

of watermelons was associated with heredity and not with

nitrogen source.







LEffcs an I Uaression mai fruit RA

The nature of the effect, if any, of the cations on
sex expression and fruit set has not been clearly defined.

Basler and Haurizio (35) reported that insufficient amounts

of potassium as well as nitrogen and phosphorus resulted in

both poor flowering and seed set in winter rape (Brassica
nafus). According to Mazaeva (47), magnesium acts on repro-

ductive organs, tending to increase female flowers in many

crops. Stark and Haut (72) found that flower production

in cantaloupes was inhibited when the potassium level was
dropped to 0.25 milliequivalents per liter (9.15 ppm).

There was a positive response of fruit set to high levels

of calcium: 10 and 15 milliequivalents per liter (200, 300

ppm). A concentration of 0.2 milliequivalents per liter

(2.4 ppm) of magnesium was inadequate for normal fruit set.

After comprehensive literature reviews on the
physiological aspects of sex expression, Loehwing (45) and

Heslop (36) concluded that, with the exception of carbohy-

drates and nitrogen, general nutrition is not a major factor

in sex expression in monoecious and dioecious species.

Furthermore, Loehwing (45) stated that highly localized com-

positional differences are much more significant than general

composition, not only in relation to flowering but also in

determining sexes in various floral parts.

There are numerous reports in the literature to the
effect that increased nitrogen concentrations in the substrate







enhanced female sex expression in plants. Thompson (76)

working with spinach, Tibeau (77) with hemp, and Sabinin (64)

with corn observed that high levels of nitrogen stimulated

the production of pistillate flowers while low nitrogen levels
favored staminate flower formation. Similar observations
have been reported by Tiedjens (78) and Dearborn (18) for

cucumbers (Cucumis sativus), by Hall (30) for gherkins

(Cucumis annuria), by Sabinin (64) and Minina (51) for cu-
cumbers and watermelons, and by Brantley (11) for cantaloupes

and watermelons.

The influence of nitrogen on fruit set is similar to

its effect on yields. In general, increasing increments of

nitrogen up to a critical maximum enhances fruit set while

additional increments tend to decrease fruit set (11, 17).

Work by Jamison and Nettles (40) and by Cunningham (17) indi-

cates that late side-dressing with nitrogen delays and de-

creases fruit set.

Effects IM blossom-end rf1

The precise cause of watermelon blossom-end rot has

not been determined. Blossom-end rot first appears as a

water-soaked area at the blossom-end, later turning brown,

and often invaded by saprophytic and parasitic fungi (56,

73). The disease has been attributed to many factors--includ-

ing pathogenic organisms, disarrangement of internal nutrition,

improper moisture supply, poor pollination and/or fertiliza-

tion. Pathologists (56, 75) have shown that a large number





9
of both saprophytic and parasitic organisms have been asso-

ciated with blossom-end rot. Parris (56) reported that

Plthn~ debarranr and e. aphanidermatum started the infection.

Taubenhaus (75) in 1921 concluded that Dinlodia tubericola

caused blossom-end rot of watermelons. However, Blodgett (8)

was unable to control the disease by use of fungicides.

Stuckey (73) postulated in 1924 that blossom-end rot

is probably a physiological disturbance brought on by rapid

changes in soil moisture as the young fruit start to grow.

He reported it is of little consequence in low-lying loamy

sands where the water table is near the surface. Walker (82)

in 1931 noted that blossom-end rot had been observed in con-

nection with pollination work and that defective pollination

appeared to be the most important factor in initiating it.

He pointed out that considerable decline of the melon occurred

before fungi appeared. Nettles and Halsey (53) were unable

to associate the incidence of blossom-end rot with fertilizer

rates of up to 2,000 pounds of 6-8-8 or with plant spacings

of 3, 6, 9, and 12 feet. Everett and Geraldson (22) obtained

a lower percentage of melons exhibiting blossom-end rot from

plots receiving one-half ton of hydrated lime or gypsum per

acre plus two tons of dolomite than from plots receiving

dolomite alone.

Geraldson (27) has shown similar blossom-end disorders

in tomatoes and peppers may be produced by insufficient cal-

cium in the substrate or by high concentrations of soluble

salts. Taylor and Smith (74) reported significant increases





10
in blossom-end rot of tomatoes as a result of high nitrogen

levels.

Brantley (11) associated the occurrence of blossom-

end rot of watermelons with high nitrogen levels; however,

no data were presented.

Calcium in lan Nutrition


Role in the ail
Soil scientists have vividly demonstrated that the

application of lime affects not only the chemical properties

of the soil but also the biological and physical properties

as well. The beneficial chemical effects of liming acid

soils result from: (1) increased availability of calcium

and possibly certain other nutrient elements and (2) pH

changes which influence the solubility of other elements,

both essential and non-essential.

In work reported by Marshall (46) a considerable part

of the absorbed calcium in kaolinitic type clays became active

at calcium saturation percentages of 39 to 59 while 70 to 80

per cent calcium saturation was necessary in montmorillonitic

type clays. According to Sharpies and Foster (66) maximum

growth of cantaloupes on Arizona desert soil occurred between

50 to 60 per cent calcium saturation with growth decreasing

rapidly on either side of this range. Fried and Peech (25)

in several field and greenhouse experiments have demonstrated

that increasing the calcium supply with gypsum, in contrast

to limestone, failed to increase plant growth of such crops







as barley, alfalfa, and perennial ryegrass.
Many workers have shown that the solubility of alumi-

num, manganese, iron, boron, copper, and zinc increases with

increasing acidity (25, 38, 61, 65, 71, 86). Toxic concentra-

tions of such elements as aluminum, manganese, and iron may

develop below pH 5.5; moreover, such elements as manganese,

iron, and boron may become deficient above pH 6.5.
The soil biological population is influenced by cal-

cium directly as an essential element for metabolism and

indirectly through alterations in the soil reaction (1, 4,
13, 83). Microbiologists have demonstrated that, in general,

fungi thrive when the pH is below 6 and bacteria and acti-
nomycetes prefer media above pH 6 (1, 13, 48, 81). This

points out the necessity for liming acid soils to obtain
maximum benefits from nitrifying bacteria as well as from
other biological processes involving principally bacteria.

Baver and Hall (5) and Meyers (49) have shown that

calcium ions do not affect the physical properties of organic
or inorganic colloids any more than do hydrogen ions. After

reviewing the literature on this subject Bayer (4) concluded

the main effect of lime on the soil physical properties,
especially aggregation, resulted indirectly from its effect
on the production and decomposition of organic matter.


fie l aJR lants
Calcium enters into several important physiological
processes within the plant. One of its most important roles







is the reaction with pectic acids to form calcium pectate,

a constituent of the middle lamella of the cell wall (9, 48,

50). Pectic acid is composed of long chains of galacturonic

acid residues which possess the 6-membered pyranose ring

structure with a carboxyl group on the number five carbon.

This carboxyl group is free to combine with available cations

such as calcium, potassium, and magnesium thereby forming

pectates.

Calcium reacts with certain organic acids, especially

oxalic and malic, to form relatively immobile oxalate com-

pounds (6, 9, 79). According to Meyer and Anderson (48)

these oxalate compounds occur in the cell vacuoles in large

quantities.

Plant physiologists point out that it was once be-

lieved that organic acids were toxic; therefore, calcium and

other cations were absorbed to precipitate these acids.

However, according to Meyer and Anderson (48) and Shear,

Crane, and Meyers (68) cell sap must be electrostatically

neutral; therefore, if greater absorption of cations than

anion occurs the plant cells produce certain organic acids

to precipitate the cations.

Nightingale (54) reported that in the absence of cal-

cium some species are unable to absorb nitrates.

It is generally believe that calcium is necessary for

the continued growth of meristematic tissue. This is appar-

ent by the symptoms of calcium deficient plants. The leaves

of plants grown in media low in calcium, especially the





13

young leaves, often are distorted, dark green in color, and

the margins pointed downward or cupped under (48, 50). In

severe cases a deficiency is manifested by cessation of

terminal growth and the development of chlorosis and necrotic

areas even in the older growth.

Calcium plays another important role in plant growth

by its antagnostic effects on the absorption of other ions

(21, 44, 48, 50, 56, 79). The antagonism apparently works
in at least two ways. First, less toxic ions may depress

the uptake or accumulation of more toxic ions. For example,

sodium, potassium, or magnesium may be toxic in single-salt

solutions; however, this toxic effect is eliminated by the

addition of calcium. Second, proteins may become saturated

with a single salt thereby changing their normal composition.

The addition of other salts tends to balance the protein

colloidal system.


Cations IA Plant liague

Cation accumulation
It has been demonstrated many times that the concen-

tration and type of nutrient elements occurring in plant tis-

sue is dependent upon a number of interrelated environmental

conditions as well as the plant species in question. Numerous

literature reviews point out that the ratio or balance of the

various ions in the substrate has a direct effect on the

chemical composition of the tissue (6, 13, 21, 63, 85, 74).

In a refinement and extension of nutritional theories proposed






14

by earlier workers, Shear and co-workers (67, 68, 69) state

that plant growth is a function of two nutritional variables,

intensity and balance, which are reflected in the composition

of leaves when the plants are in the same stage of growth

and development. Intensity refers to the total equivalent

concentration of all functional nutrient elements in the

plant. They pointed out that there is a definite cation:

anion ratio within the plant; therefore, an accumulation of

one or more nations must be accompanied by an equivalent

decrease in one or more cations at any given anion level.

Likewise, an accumulation of one or more anions at a given

cation level must be accompanied by a decrease in one or

more anions. The simultaneous accumulation of both cations

and anions, either organic or inorganic, in plant tissue has

been observed by many authors (3, 13, 26, 63, 68, 69, 79).

Cooper (16) concluded that the relative rate of ab-

sorption and accumulation of nutrients by plants is propor-

tional to the relative activity (energy properties) of the

nutrients as measured by such means as standard electrode or

ionization potential. This conclusion has been subjected to

extensive criticism. Geraldson (27) explained the occurrence

of blossom-end rot of tomatoes as a calcium deficiency when

the plants were grown in high concentrations of soluble salts

on the basis that as the soluble salt concentrations increase,

the relative activities (effective concentration) of the

divalent salts decrease at a more rapid rate than monovalent

salts. Also, the calcium to soil soluble salts ratio (actual







concentration) varies inversely with concentration.

Shear, Crane, and Meyers (69) working with young
tung nut trees found that increasing the magnesium or potas-

sium in the substrate generally resulted in increased con-

centrations in the tissue; however, the total accumulation

of potassiumemagnesium4calcium was generally decreased.

Moreover, increasing calcium in the substrate not only in-

creased the calcium in the tissue but also increased the

total accumulation of the three cations. This was explained

on the basis that since a large percentage of the absorbed

calcium in many species is inactivated by oxalate precipita-

tion and no longer able to affect the entrance of other

cations, the increased calcium accumulation would result in

an increased total cation accumulation. Pierre and Bower

(59) pointed out that potassium absorption is usually de-
creased in the presence of high concentrationsof other

cations such as calcium and magnesium. However, under rela-

tively high levels of potassium, increasing the concentration

of other cations, especially calcium, may increase potassium

absorption and accumulation in many crops. After a critical

literature review Peech and Bradfield (58) concluded that the

addition of lime to soils may have no effect, may increase,

or decrease the availability of potassium to plants depending

upon the degree of initial soil saturation. They indicated

that calcium aay have little effect on the absorption of the

available potassium, at least at the concentrations found in

most soils. Meanwhile, Geraldson (26) indicated that the








application of excessive amounts of ammonium, potassium,

magnesium, or sodium to sandy soils of Florida limited the

uptake of calcium by tomatoes.

Reports on the specific cation nutrition of cucurbits,

especially watermelons, are limited. Bradley and Fleming

(10) observed that the potassium content of watermelon leaves

was influenced primarily by the addition of potassium to the

soil. The difference in potassium content of the leaves be-

tween treatments grew smaller as the season progressed. The

application of 60 pounds of potassium in the row significantly

reduced the calcium content of the watermelon leaves early

in the season but had no effect toward the end of the season.

In one of two seasons potassium applications significantly

reduced the magnesium content of the leaves early in the

season but had no effect on samples collected toward the end

of the growing season.

Sharples and Foster (66) grew cantaloupes in Arizona

desert sand cultures with calcium saturation percentages of

2.9, 11.9, 36.2, 63.7, 72.5, and 86.6. They found that ex-

tremely high and low saturation percentages tended to restrict

potassium uptake while leaf calcium varied directly and mag-

nesium inversely with the calcium saturation percentages.

Stark and Haut (72) reported that the calcium content of

cantaloupe leaves increased in a geometric proportion to the

calcium concentration in the substrate, while potassium and

magnesium increased in arithmetic proportions to the concen-

tration of these respective elements in the substrate.








Concentrations of 4 to 5 milliequivalents per liter (200-

300 ppm) appeared to produce the best growth. When calcium
was supplied at 4, 8, or 16 milliequivalents (80, 160, 220

ppm), Reynolds and Stark (62) obtained maximum top, root,
and fruit yields of cucumbers at the lowest calcium level,
and growth decreased as the calcium level increased.

Efftsa af nitrogen on IIi cation content
It has been established that not only the concentra-

tion of nitrogen in the substrate but also the source
(nitrate or ammonium) will have a profound effect on the
cation content of the tissue (3, 13, 48, 63, 67, 84).

It has been shown repeatedly that increasing the

proportion of nitrate to ammonium nitrogen in the substrate
increases the production of organic acids, especially oxalis

(13). Since oxalic acid precipitates much of the absorbed

calcium, plants growing under high nitrate levels may uti-
lize more calcium (3, 13, 48, 63, 67, 68).
Shear and co-workers (67, 68, 69), Geraldson (26),

and Burrus (13) pointed out that the activity of the ammonium

ion is very similar to the activity of the potassium ion and

will greatly affect the uptake of other cations. Shear and
Crane (67), by supplying the nitrogen as ammonium in contrast

to nitrate, reduced the cation content of tung leaves by the
following percentages: potassium--18 per cent, magnesium--

25 per cent, and calcium--46 per cent.
Bradley and Fleming (10) indicated that the soil






18

application of ammonium nitrate had no consistent effect on

the potassium, calcium, and magnesium content of watermelon

leaves. Sharples and Foster (66) reported that the applica-

tion of ammonium nitrate in sand cultures of cantaloupes

significantly increased the potassium, calcium, and magnesium

content of the leaves and decreased the phosphorus content

under varying calcium and magnesium ratios.

Distribution of nations in plants

Numerous studies have been conducted on the distri-

bution of cations in plant tissue employing both chemical

analyses and radio-isotopes (3, 7, 31, 43, 63). The follow-

ing generalizations may be drawn: (1) a large part of the

calcium is located in the leaves with considerably smaller

amounts occurring in the roots, stem, seeds, and meriste-

matic areas, (2) potassium is distributed more uniformly

throughout the plant than calcium with relatively large

quantities occurring in regions of meristematic division,

translocation, and storage, and (3) magnesium is present in

somewhat smaller amounts than calcium or potassium with

relatively large concentrations occurring in the leaves and

in the seeds of some plants.

Hardh (31) showed with radiographs that calcium ac-

cumulates in cucumbers in clearly separated pits occurring

more frequently in the leaves than in the stems. Wilkins

(83) reported that cucurbit vines, namely, pumpkins, pre-

serving citrons, two types of squash, cucumbers, and canta-
loupes, contained large amounts of calcium ranging from 5






19
to 8.5 per cent calcium oxide, while the fruits at no time

contained over 0.75 per cent calcium oxide. The vines con-

tained up to 5.9 per cent potassium oxide and the fruit up

to 5.4 per cent depending upon the species. The magnesium

content of the vines was much less variable, ranging from

0.46 per cent to 1.30 per cent magnesium oxide, and the

fruit consistently contained even less magnesium than cal-

ciu. Wilkins (83) also found an increase in the percentage

of calcium in the cucurbit vines toward maturity, and the

calcium content of the fruit decreased slightly toward ma-

turity. The opposite trends were true for both potassium

and magnesium.











METHODS AND IFiOCEDURES


The watermelon industry in North Central Florida was

surveyed by making field observations and soil analyses in

30 melon fields during the 1958 growing season. This aided

in familiarization with the fertility problems involved in

watermelon production.

The literature indicated that certain physiological

disorders of watermelons resulted from adverse chemical or

physical conditions of the soil. Therefore, profile exami-

nations were made and soil samples were obtained from plots

devoted to watermelon fertility experiments as described by

Nettles and Halsey (53) in the spring of 1953. Chemical

analyses or the soil samples were made to observe any pos-

sible correlation between the chemical constituents and the

presence of blossom-end rot.

In the spring of 1958 samples of watermelon tissue

were obtained from mature field-grown plants to determine

the distribution of calcium, potassium, magnesium, and

sodium in the various plant parts and the variation of these

elements from plant to plant. The samples for analyses were

taken from six plants grown under similar environmental con-

ditions and were bearing mature fruits. Samples for analyses

from each plant included the following locations: basal

leaves, mid-leaves, vine tips, basal stem, mid-stem, and fruit.

20








Each tissue sample was analyzed for calcium, potassium,

magnesium, and sodium on the Beckman model DU flame spectro-

photometer by using procedures outlined by Breland (12).

In order to evaluate the effect of interfering anions in

the watermelon tissue on the calcium determinations, each

sample was analyzed for calcium, with and without these ions

present. The method of removing the interfering anions from

the samples is given under the heading "Chemical Analyses.*

Preliminary experiments with nutrient solutions and

quartz sand were conducted to determine the feasibility of

these techniques for greenhouse culture of watermelons.

In addition to the major study reported below,

simultaneous exploratory work was conducted in the greenhouse

and field to observe the effects of foliar applications of

calcium chloride on watermelons. Plants grown in field soil

in greenhouse benches were sprayed with 0.25, 0.10, 0.08,

0.06, and 0.04 molar concentrations of calcium chloride to

determine optimum levels for foliar applications. Severe

leaf burning occurred at the 0.25 level and slight burning

was evident at the 0.10 molar concentration. The 0.04 through

0.08 molar levels appeared satisfactory for treatment. A

greenhouse sand culture experiment with 8 replications was

established to observe the effects of bi-weekly applications

of 0.04 molar calcium chloride spray versus no spray on the

watermelon plants. Adequate amounts of a basic nutrient solu-

tion containing 16 ppm calcium was supplied to each pot. A

field experiment containing three levels of a calcium chloride






22

foliar spray arranged in a randomized block design was con-

ducted during the 1959 season. The spray levels were no

spray, 0.04, and 0.08 molar concentrations of calcium chloride

applied every five days.

The major study consisted of two parts--a greenhouse

phase and a field phase. The greenhouse phase was organized

to study the effects of various calcium levels in nutrient

solutions on growth responses; sex expression; fruit set and

quality; and the accumulation of calcium, potassium, and

magnesium in the various plant parts. The field phase was

designed to investigate the effects of three levels of nitro-

gen and three levels of calcium on growth, yield, quality,

and cation composition of the watermelon plant. The Charles-

ton Gray variety of watermelons was used in all experiments.

Greenhouse Phase

A randomized block experiment with four replications

was initiated on April 15, 1959, to study the influence of

eight progressive levels of calcium on watermelon responses.

This test was conducted using a solution culture procedure

in which the calcium levels were supplied by the addition of

calcium chloride to a basic nutrient solution. Young water-

melon seedlings were produced by germinating seeds on wet

filter paper. Two of these seedlings constituted an experi-

mental unit when suspended by a wooden support in a four-

gallon glazed crock. The solution levelsin the crooks were

maintained at 13 liters by daily application of deionized







water with a complete change of solution each week. Ade-

quate aeration was supplied to each crock by means of a

centrally located pump.

The concentration of calcium in the different treat-
ments is given in Table 1. Since it was necessary to use

large volumes of solutions, the concentration is given in

both parts per million(ppm) and milliequivalents per liter

(m.e./L).


TABLE 1
CALCIUM LEVELS IN GREENHOUSE SOLUTION CULTURES

Greenhouse Treatment Calcium Calcium
Number ppm moI../

1 0 0.0
2 4 0.2
3 8 0.4
4 16 0.8
5 32 1.6
6 64 3.2
7 128 6.4
8 256 12.8


The composition of the basic nutrient solution is
shown in Table 2. The iron solution was prepared by dis-

solving 100 grams of sodium-iron versenol (12 per cent iron)

per 2.5 liters of deionized water, and 1/10 millileter of

this solution was used per liter of nutrient solution. The

other elements were prepared by the procedure outlined by

Hoagland and Arnon (37).

The pH of all newly prepared solutions, regardless
of calcium level, was approximately 5.2. At the end of the






24

seven-day period the pH of the solutions ranged from 6.0 to

6.8 depending on the size of the vines; therefore, no pHi

adjustments were necessary.


TABLE 2

THE COMPOSITION OF THE BASIC NUTRIENT SOLUTION
FOR GREENHOUSE EXPnRIMTFNT


Element Source Concentration
(ppm)

Nitrogen KN03 70
Phosphorus KH Pn 32
Potassium KNO f 4 234
Magnesium MgS 48
Boron 13B03 0.5
Manganese MnC12 0.5
Iron ,ai'eEiJiA 0.5
Molybdium H2MoO4 0.05
Zinc ZnSO4 0.05
Copper CuSO4 0.02


Fifteen days after transplanting one plant per pot

was harvested and dry weights were obtained as an early

growth measurement. All flowers were hand-pollinated in

the early morning and the number of both pistillate and

staminate flowers produced per experimental unit was re-

corded daily. All fruits developed blossom-end rot in this

experiment and were harvested individually and oven-dried as

soon as the rot was obvious. Continuous records on growth

responses were maintained throughout the experiments.

The experiment ended June 15 and the following ob-

tained from each experimental unit: leaf, tip, and root

samples and dry weight of fru roots, and vines. The leaf







a5
samples were composed of eight mature leaves per plant. The

tip samples were composed of eight actively growing lateral

tips two inches in length. The root samples were composed

of the entire root system from each experimental unit. All

tissue samples were washed twice in demonized water before

drying, with each washing lasting approximately 10 seconds.




Description a f1i a a j~Ad soil testU

The area used in this experiment was located on the

Horticulture Unit of the University of Florida near Gaines-

ville, Florida. The soil was classified as Kanapaha fine

sand (2). The surface layer is medium gray, loose, acid,

fine sand and underlain by yellowish white, loose, strongly

acid, fine sand. This is underlain by a phosphatic lime

material. Kanapaha fine sand is relatively low in organic

matter, moderately to imperfectly drained, level to slightly

undulating with poor physical structure, and often located

near ponds or lakes.

Two soil samples were taken from each plot on April

1. One sample was taken in the bed and consisted of 5 cores

taken at four locations across the bed. The other sample

was taken from the calcium-treated area on each side of the

bed and consisted of 20 cores. The samples were analyzed for

available CaO, MgO, K20, P205, NO3, and phl by the University

of Florida Soil Testing Laboratory.







Eie2d methods
An experiment containing three levels of calcium and

three levels of nitrogen arranged factorially in a balanced-

lattice design was conducted in the spring of 1959 on Kanapaha

fine sand. The calcium levels tested were at the rate of

0, 500, and 1,000 pounds of hyd.ated lime (Ca(0I)2)per acre.

The nitrogen levels tested were at the rate of 60, 120, and

180 pounds per acre applied as ammonium nitrate. The indi-

vidual plot size was 15 by 80 feet with each calcium treat-

ment being broadcast in a 10-foot band throughout the length

of each plot on February 20. This left an untreated area of

2.5 feet on both sides of each plot. An untreated area of

10 feet was left between the ends of the plots to serve as

a buffer area.

A single bed approximately 8 inches high and 18

inches wide was prepared in the center of each plot. One

half of the total nitrogen and a uniform application of 80

pounds of P205 and 80 pounds of K20 per acre was placed in

two bands in the row on March 12. The remaining half of the

nitrogen was plowed into both sides of the bed May 1, when

the vines began to develop.

Sixteen hills of watermelons were planted per plot

on March 26, and an excellent stand of plants was obtained.

Two weeks after emergence the melons were thinned to two

plants per hill. The methods used for cultivation, insect,

and disease control were in accordance with recommended prac-

tices for the North Central Florida area. The melons were






27
harvested four times (June 17, 22, 26, and July 3) and the

following data obtained on all fruits from each plot: number

and weight of early marketable yield; number and weight of

total marketable yield; mean thickness of rind of each fruit

measured at the top center and bottom center; thickness of

rind at blossom-end; percentage soluble solids; percentage

blossom-end rot; and cutting quality including data on hollow-

heart, white-heart, and other abnormalities. The first three

harvests were considered to represent the early yield, and

all normally shaped melons over 16 pounds in weight were con-

sidered as U. S. number 1. Soluble solids were determined

on a Carl Zeiss water-cooled refractometer.

The amount of rainfall recorded in the immediate area
of the experiment is presented in Table 3.


TABLE 3
TOTAL BI-MONTHLY RAINFALL RECORDED AT THE HORTICULTURE
UNIT MARCH 1 TO JUNE 30, 1959


Date Inches of rain

March 1-14 3.22
March 15-31 8.01
April 1-14 1.73
April 15-30 2.07
May 1-14 0.70
May 15-31 5.93
June 1-14 1.53
June 15-30 2.32


Total 25.51







Since there was an extremely large amount of rain-

fall following the first fertilizer application early in
March, an attempt was made to estimate the fertilizer loss
from the upper 8 inches of soil as a result of more than 8
inches of rain. An extra row was fertilized on April 1 at
the rate of 90 pounds of nitrogen and 80 pounds each of

P205 and K20 per acre. This was located beside a row which
received the same fertilizer treatments before the rains.

Six soil samples were taken on April 1 from each of these

two rows, as well as from a third row receiving no fertilizer,

and analyzed for CaO, MgO, P205, K20, N03, and pH.


Tissue amules
On May 1, just prior to the second application of

nitrogen, every other hill of the young watermelon plants

from each plot was harvested and pooled into one composite

sample, and the oven-dry weight was obtained. Prior to dry-

ing, tip and leaf samples were taken from each composite
sample for chemical analyses. Additional leaf and tip sam-

ples were obtained from each plot for chemical analyses one
week prior to the first harvest of fruit. At this time the
plants were in a vigorous state of growth with little ap-

parent disease or insect damage. The leaf sample from each
plot was composed of the first two normal leaves, including
the petiole, from each plant. The tip samples consisted of

four actively growing vine tips from each plant located in

each plot. These tips were 2 inches in length and included





29

very young leaves and a small end portion of the stem. The
leaf and tip samples were oven-dried and stored.

The fruits exhibiting blossom-end rot were removed
from the vines at the beginning of the harvest period and

a composite fruit sample was obtained from six representa-

tive fruits from each plot. Three cores, one inch in dia-

meter, were taken through the center of each fruit by use

of a soil sampling tube. These cores were then cut into

sections one-half inch long and mixed thoroughly; after

which, four 90-gram subsamples were weighed from each plot

sample. Two of these were frozen at 00 F. for subsequent

chemical analyses. The remaining two samples were used for

moisture determinations. Similar subsamples for analyses

were obtained from the first six normal fruits harvested

from each plot.

Chemical Analvses

All tissue samples were dried in a forced air oven
for 48 hours at 70C. After which all loaf, tip, root, and

greenhouse fruit samples were ground in a Wiley Mill and
stored in one-pound paper bags. One-gram samples of the

oven dried tissue were ashed in a muffle furnace at 4500C.,

dissolved in 15 milliliters (ml.) of 40 per cent hydrochloric

acid (H01), evaporated to dryness, reheated in the muffle
furnace at 4500C. for 30 minutes to 3 hours (depending on the

amount of black carbon present), dissolved in 1 ml. of








concentrated HC1, evaporated to dryness, and diluted to

volume with 0.1 normal HC1.

Fruit samples collected from the field experiment

were dried in 250 ml. beakers and ashed in the same manner

as the other tissue samples. The entire sample was washed

and calculations were based on the oven dry weight of the

sample less beaker weight.

All samples were analyzed for potassium, calcium,

and magnesium on a Beckman model DU flame spectrophotometer

following the procedure outlined by Breland (12). Before

the calcium and magnesium determinations were made, 10 ml.

aliquots of each sample were passed through a six-inch column

of anion exchange resin (Dowex 1-8X, 50-100 mesh, medium

porosity) to remove interfering anions (39).


Statistical Methods

The data were analyzed by the analysis of variance

methods described by Cochran and Cox (15). Probability

statements of comparisons among means are based on the

Duncan Multiple Range Test (19). Count data were trans-

formed by the square root method and percentage data by the

arcsin transformation before statistical analyses were made.

All growth response data presented from the field experiment

were derived from the adjusted treatment totals of the

balanced-lattice design.










RESULTS OF EXPERIMENTS


Examination of soil test data obtained from the field

survey indicated that, in general, low yields and a high per-

centage of blossom-end rot were associated with low nutrient

levels, especially calcium and magnesium.

Data obtained from fruit counts and soil studies from

fertility experiments described by Nettles and Halsey (53)

revealed that significant differences in the percentage of

blossom-end rot could not be attributed to fertility treat-

ments of differential levels of available soil nutrients.

In two of the three fertility experiments significant dif-

ferences in the percentage of blossom-end rot did result

from replications. Further examination of the data showed

that in one of the experiments the percentage of blossom-

end rot decreased significantly from the higher to the lower

elevation of the field. Examination of the soil profile re-

vealed that the soil in the upper portion of the field was

slightly compact for the first 18 inches then was very loose

to a depth of over 6 feet. The compactness of this upper

portion of the soil decreased from the higher to the lower

elevation of the field. From field examination of the pro-

file, at the lower elevation the soil appeared to have a

more desirable texture, more organic matter, and was darker

in color. Examination of the data from a second experiment





32

indicated that replications located on a soil with a loose

porous profile produced significantly more blossom-end rot

than replications located on a soil with a hard-pan 12 to

24 inches below the surface. In the third experiment no

significant differences resulted from replications. Examina-

tion of this soil profile revealed a uniform, relatively loose

profile with no observable textural or structural differences

throughout the experimental area.

The distribution of calcium, potassium, magnesium,

and sodium in the various parts of mature watermelon plants

grown under similar environmental conditions during the

spring of 1958 is shown in Table 4. By passing the sample

solutions through an anion exchange resin, calcium determi-

nation values were, in general, from 20 to 35 per cent greater

than those obtained from samples in which this step was elimi-

nated. The greatest concentration of calcium, irrespective

of analytical methods, and of magnesium occurred in the older

leaves with the percentages decreasing at the various sampling

locations in the following order: basal leaves, mid-leaves,

tips, stems, and fruits.

Statistical comparisons of the percentage of potassium,

calcium, and magnesium present at different locations in the

plants are shown in Table 5. The concentration of potassium

was significantly less in the leaves than in other plant parts

with the largest concentrations occurring in the stems and

fruits. There was no significant difference between the cal-

cium content of the stem sampling positions; however, the





















la

C4
4 0












E,
0 10
I-I



6
E E
















hill
$. #


0 0
g p

r4 ci
a

d I
a 14

4 x


T
S '


* 4 4.0
W A X
TIE~ca*


0 0 0 00
0 0 0 0 0





S0 0 0 0






il 10 0 0 0
Q c

*OQQ Q rC















10 '00C 0 0 0


4
O
* ,







a



on
* 4


d dt





e a
aO 8

P a
S i
e 0i


4t *







Ml
* o
A *
i-4f
^ |







calcium; percentages of all other sampling locations within

the plant were significantly different from each other. This

was true for the samples passed il rough the anion exchange

columns as well as for those not passed through the columns.

The magnesium content of the sampling positions in the stems

did not differ significantly; however, the magnesium content

of all other sampling locations within the plants differed

significantly.


TABLE 5

TEST OF SIGNIFICANCE FOR THE PERCENTAGE OF POTASSIUM,
CALCPrM, AND ,AG:,SITT: AT SIX LOCATIONS
WITHIN MATURE WATERMELON PLANTSa


Iotassiiur percentage

Mid- Basal Basal Mature Mid-
Locations leaves leaves Tips stem fruits stem





Calciumb and magnesium

Mature Mid- rDasal Mid- Basal
Locations fruit stem stems Tips leaves leaves


aAny two locations underlined by the same line were
not significantly different. Any two locations not under-
lined by the same line were significantly different at the
5 per cent level (See Table 33 for A.O.V.).
bSignificance table for calcium analyses both with
and without anion exchange resins.






35

There was far greater variation in the sodium con-

tent from one plant to another than from sampling locations

within any one plant; consequently, sodium analyses were

eliminated in later work.

Results from exploratory foliar spray experiments

were inconclusive. Vine growth in the greenhouse was not

affected by foliar application of 0.04 molar calcium chlo-

ride. When each plant was allowed to set one fruit, all

eight of the vines receiving no spray produced fruits with

obvious blossom-end rot. Two of the eight plants receiving

bi-weekly sprays of 0.04 molar calcium chloride produced

fruit with obvious blossom-end rot. The remaining six plants

produced fruits vith no external symptoms of rot; however,

examination of the internal tissues revealed that three of

the fruits had a semi-dehydrated, whitish, leathery type of

tissue at the blossom-end. There were no significant dif-

ferences in vine growth, yield, or percentage of blossom-

end rot obtained from the foliar spray treatments of the

field experiment. However, it should be pointed out that

the plants in this experiment were injured considerably by

excessive rains.


Gregnhouse hase

Growth resgonses

All plants grown in solutions void of calcium became

stunted, chlorotie and all but one plant died within two





36

weeks after transplanting. One plant per experimental unit

was harvested from the seven remaining treatments 18 days

after transplanting. The analysis of variance of the data

revealed no significant differences in the dry weights of

roots or tops.

Slight calcium deficiency symptoms became apparent

on newly developing leaves of plants grown in 4 ppm calcium

(treatment 2) on May 8. By May 15, these deficiency symptoms

were very pronounced in both the tops and the roots, and the

symptoms became increasingly more severe as the season prog-

ressed. The leaves of deficient plants were dark green in

color, moderately cupped under at the margins, and severely

restricted especially at the apex forming a more circular

type leaf (Fig. 1, No. 2).

The vine laterals of plants in treatment 2 were

shorter and much more numerous than those of the other treat-

ments. Frequently terminal growth of these short laterals

would cease and more short laterals would appear which would

in turn often produce other short laterals. This type of

growth pattern suggested a retardation or cessation of the

activity of the merstimatic tissue at the apex of each vine

lateral. There were no observable differences in either vine

laterals or leaf formation of plants in treatments 3 through

8. However, the leaves of treatments 7 and 8 were lighter

green in color and appeared to be smaller in size (Fig. 1).

The root systems of plants grown in treatment 2

exhibited a growth pattern similar to the vine laterals with




























Fig. 1.--The twelfth leaf from the
base of the plants in treatments 2, 3, 4,
7, and 8 of the greenhouse experiment.
Treatments 5 and 6 were eliminated to con-
serve space, because they did not appear to
be different from 4.

























































77""

-I





39
the roots being short, dense, very numerous, and often dark

at the apex indicating death (Fig. 2). Root systems of

treatment 3 showed these symptoms in a very limited degree.

The root systems of treatments 4 through 8 appeared to be

normal.

Since the calcium levels used in this experiment were

4, 8, 16, 32, 64, 128, and 256 ppm, that is, increased in

the ratio of 2 to 1, statistical analyses and interpretations

of the data were facilitated by considering all responses as

measured against the logarithms of the calcium concentrations.

Thus, in the analysis of variance of all data pertaining to

the greenhouse experiment and to the discussion of linear and

non-linear effects, the independent variable is always the

logarithm of the amount of calcium added to the nutrient

solutions.

The dry weights of vines, roots, fruits, and the

total dry weight of plants are presented in Table 6. When

the vine growth was measured against the increasing calcium

levels, it was found to decrease in a highly significant

linear trend, while the root growth responded in a signifi-

cant cubic fashion. There were no significant differences

in the dry weight of the entire plants (vines, roots, and

fruits), although it appeared to be curvilinear. Statistical

analysis was not made on the dry weight of the fruits, because

they were harvested whenever external blossom-end rot became

evident.






























4 p
Iii .:""' ,
- ----..


-c
S.,

-I


:~t4KL'~
3C;r~r ~
.4 -


e-~ r --_..

,, c~c; ,,


S


C.' '-~'






'IL -%-~- -.L
1- N


N>


4%

~-u-~---- `r





























Fig. 2.--Representative root systems
from treatments 2, 3, 5, 7, and 8 of the green-
house experiment. Treatments 4 and 6 did not
appear to be different from 5.








TABLE 6
THE EFFECTS OF CALCIUM TREATMENTS ON THE DRY WEIGHT
OF VINES, ROOTS, FRUITS, AND TOTAL WEIGHT
IN THE GREENHOUSE EXPERIMENT

Treatment Dry weight in grams
Number Ca Levels
ppm Vines Roots Fruits Total

2 4 79.60 5.84 0.00 85.44
3 8 91.10 5.80 1.76 98.66
4 16 81.60 5.95 33.23 120.79
5 32 61.13 3.80 39.84 104.78
6 64 60.80 4.12 26.86 91.79
7 128 66.82 3.72 26.91 97.45
8 256 60.05 5.15 32.84 98.16

Effect :b
Linear ** --- N. S.
Quadratic N. S. N. S. --- N. S.
Cubic N. S. --- S.

Significant at the 0.05 level
** Significant at the 0.01 level
N.S. Not significant

aEach figure is the average of four replications
measured in grams.
bThe linear, quadratic, and cubic effects were
determined by using log x as the independent variable,
where x is the concentration of calcium in ppm in the
nutrient solution (see Table 34 for A.O.V.)


Sax ezxreussin and rit L1
The number of pistillate and staminate flowers, the

ratio of staminate to pistillate flowers, and the number of

fruits set are given in Table 7, and the comparisons of the


square root of the means are given in Table 8.








TABLE 7

THE EFFECTS OF CALCIUM TREATMENTS ON FLOWER PRODUCTION
AND FRUIT SET IN THE GREENHOUSE EXPERIMENT

Treatment Ave. No. of flowers produced Total
Number Ca levels Staminate Pistillate Ratio number
ppm S: of fruits
....... .. .. s oe t

2 4 155.1 5.80 27.79 0
3 8 247.2 28.42 8.74 1
4 16 182.4 22.78 8.16 9
5 32 119.3 14.92 8.10 11
6 84 152.6 17.93 8.54 12
7 128 184.7 18.70 10.21 11
8 256 155.4 15,62 11.68 12


Treatment 3 produced significantly more and treatment

5 produced significantly fever staminate flowers than any

other treatments. Treatment 2 produced the least number of

pistillate flowers while treatment 3 produced the largest

number. The ratio of staminate to pistillate flowers was

significantly greater in treatment 2 than in any of the other

treatments. No fruit was set on plants in treatment 2 (4

ppm calcium) and only one fruit was set by plants in treat-

ment 3 (16 ppm calcium). There were no significant dif-

ferences in the number of fruit set from treatments 4

through 8.

Almost all the ovaries produced by plants grown in

treatment 2 turned dark brown to black in color beginning at

the blossom-end, even before the flower parts opened. This

also occurred rather frequently in the plants in treatment

3, but it was not observed in any of the other treatments.








TABLE 8

TEST OF SIGNIFICANCE FOR THE EFFECTS OF CALCIUM
TREATMENTS ON FLOWER PRODUCTION IN
THE GREENHOUSE EXPERIMENT


Staminate flowers


Treatment 5 6 2 8 4 7 3

Mean (sq. 10.92 12.35 12.45 12.46 13.50 13.59 15.75
root) _____......


Pistillate flowers


Treatment 2 5 8 6 7 4 3

Mean (sq. 2.41 3.86 3.95 4.24 4.32 4.77 5.33
root)




Ratio of staminate to pistillate flowers


Treatment 5 4 6 3 7 8 2

Mean (sq. 2.85 2.86 2.92 2.96 3.20 3.42 5.27
root)

Notes:
Any two means underlined by the same line are not
significantly different. Any two not underlined by the same
line are significantly different at the 5 per cent level
(see Table 35 for the A.O.V.).








Chemical gmenoition

The effects of varying levels of calcium in the sub-

strate on the percentage of calcium, potassium, and magnesium

in the leaves, tips, roots and fruits are presented in Tables

9 and 10. Statistical analyses revealed that as the loga-

rithms of the calcium concentrationswere increased by equal

amounts in substrate the calcium content of the leaves in-

creased in quadratic fashion, the potassium content decreased

in a highly significant linear trend, and the magnesium con-

tent decreased in a highly significant quadratic manner.

The calcium content of the plant tips increased

linearly, the magnesium content decreased in a curvilinear

fashion, and the potassium content was not significantly

affected by increasing increments of calcium in the nutrient

solutions.

As the calcium levels were increased, the percentage

of calcium in the root tissue increased in a highly signifi-

cant cubic manner, and both the potassium and magnesium

percentages decreased linearly.

Analyses of the fruit from treatments 4 through 8

indicated that the potassium content of the fruit was not af-

fected by varying the calcium concentration of the substrate.

However, there was a highly positive linear regression in

the calcium content and a highly negative linear response in

the magnesium content of the fruits when measured against

increasing calcium concentrations in the nutrient solutions.








TABLE 9

THE EFFECTS OF CALCIUM TREATMENTS ON THE PERCENTAGE
OF CALCIUM, POTASSIUM, AND MAGNESIUM IN THE
LEAVES AND TIPS OF PLANTS GROWN
IN THE GREENHOUSEa

Treatment Leaves Tips
Number Ca levels Ca K Mg Ca K Mg
(ppm)

2 4 0.32 5.19 2.07 0.088 4.16 0.557
3 8 0.48 4.79 1.45 .117 3.54 .490
4 16 1.04 4.14 1.89 .270 3.81 .603
5 32 3.12 4.02 2.06 .285 4.04 .575
6 64 3.90 3.54 1.41 .347 3.59 .460
7 128 4.95 3.72 0.89 .303 3.77 .345
8 256 5.01 3.36 0.53 0.385 3.76 0.322

Effect:b
Linear ** ** ** ** N.S. **
Quadratic N.S. N.S. ** N.S. N.S. **
Cubic ** N.S.N.S. NS.S. N.S. N.S.

Significant at 0.05 level
** Significant at 0.01 level
N.S. Not significant


aEach percentage is the average
on the dry weight basis.


of four replications


bLinear, quadratic, and cubic effects were determined
by using log x as the independent variable, where x equals
the concentration of calcium in the nutrient solution in ppm
(see Table 36 for A.O.V.).








TALLr: 10


THE! EFFECTS OF CAMULCIU Tr:\EArTF:NTS ON THE I EILCEIAGE
OF CALCIUM, POTASSIUM, AND MAGNcSI N IN
THE HOOTS A!D FRUITS OF PLANTS
GROWN IN MHE GRI-:NHOUSEa


Treatment ,1oots 'ruits
Number Ca levels Ca K M Ca K MK
(ppm)

2 4 0.19 5.33 0.525 -- -- --
3 8 0.25 4.92 .415 -- -- --
4 16 0.38 4.69 .420 0.095 4.87 0.370
5 32 0.41 3.80 .315 .105 4.40 .320
6 64 0.55 4.01 .312 .175 4.73 .295
7 128 1.39 3.79 .302 .265 4.72 .273
8 256 4.8K 3.76 0.253 0.313 4.53 0.235

Effect:b
Linear ** ** ** ** N.S. **
Quadratic ** N.S. N.S. N.S. N.S. N.S.
Cubic ** N.S N.S. N.S. N.S. N.S.


Significant at 0.05 level.

** Significant at 0.01 level.

N.S. Not significant


aCach percentage is the average of four replications
on the dry weight basis.

bLinear, quadratic, and cubic effects were determined
by using log x as the independent variable, where x equals
the concentration of calcium in the nutrient solution in
ppm (see Tables 36 and 37 for A.O.V.).












The results of the analyses of soil samples taken

within the beds are presented in Table 11. In general, the

results show good correlation with the amount of hydrated

lime applied. The variability within treatments may be

partially attributed to at least two factors: (1) at the

time of sampling small particles of hydrated lime were still

visible in some of the soil samples and (2) replication

number 3 was abnormally high in the various elements; this

tended to increase the average values of all tests (see

Appendix Table 31).

TA LE 11

THE ph AND POUNDS PER ACRE OF AVAILABLE NUTRIENTS
OF SAMPLES TAKEN FROM THE WATERMELON
BEUS ON APHIL 1, 1959a


Treatments pH CaO MgO P205 K20 NO3


Ca N 4.9 234 101 93 263 VL
CaoN1 5.0 147 85 90 227 L
CaoN2 4.8 145 98 86 247 L
Ca-N 5.3 373 73 77 226 L
Cap N 5.4 653 90 89 267 L
CalN2 5.4 629 87 90 226 L
Ca2No 5.8 1316 66 97 262 L
Ca2N1 5.8 1511 65 99 231 M
Ca2N2 5.8 1967 116 91 228 L

aEach value is the average of four replications.
bCa0onone, Ca=:500, and Ca2.1,000 lbs. of Ca(OH)2
per acre; No,60, N=120, and N2. 180 lbs. of N per acre.
Meamedium, Lalow, VLavery low.






49

The data in Table 12 are from soil samples collected

from each side of the bed within the calcium treated area.

There was little difference in the pH and calcium content of

the various treatments. This may be explained by the fact

that the beds were prepared following the lime applications

which tended to concentrate the lime in the beds. The data

in Table 12, excluding calcium, represent the native fertility

of the plots (see Appendix Table 32).


TABLE 12

THE pH AND POUNDS PER ACRE OF AVAILABLE NUTRIENTS
OF SAMPLES TAKEN FROM EACH SIDE OF THE
MELON BEDS ON APRIL 1, 1959a


treatments pH CaO MgO P2 0 K20 N03


Ca0 N 4.9 188 94 50 69 VL
Ca0 1 4.8 85 71 55 69 L
Ca0N2 4.8 94 93 51 77 VL
CalNO 5.0 94 58 49 58 L
CalN1 5.0 188 90 48 53 L
CalN2 4.9 102 75 51 52 L
Ca2NO 5.0 154 62 52 49 L
Ca2N1 5.1 146 57 51 37 L
Ca2N2 5.0 186 80 48 58 VL

aEach value is the average of four replications.


The effects of heavy rains on the removal of ferti-

lizer from the upper eight inches of soil are shown in

Table 13. It is apparent from examination of the data that

all of the nitrates and approximately 50 per cent of the

K20 were leached from the upper eight inches of the soil.





50

The excessive rainfall had very little effect on the levels

of CaO, MgO, and P205.

TABLE 13

THE INFLUENCE OF MORE THAN EIGHT INCHES OF RAINFALL ON
THE REMOVAL OF FERTILIZER NUTRIENTS IN POUNDS
PER ACRE FROM THE UPPER EIGHT INCHES
OF SOIL IN WATERMELON BEDSa

Treatmentab pH CaO MgO P205 K20 NO3c

Fertilizer
plus no rain 4.8 109 86 80 426 VH

Ferlitizer
plus 8" rain 5.0 80 65 90 228 L

No fertilizer
plus 8" rain 4.8 45 43 51 45 L

aEach figure is the average of six determinations.

bThe fertilizer-rate was 90 lbs. N/acre as NH NO3,
80 lbs. KgO/acre as KC1, and 80 lbs. of P205/aere as triple
superphosphate.
oVH-very high, L-low.


Growth responses

The dry weight of plants from eight hills per plot

harvested May I is given in Table 14. There was a signifi-

cant linear increase in dry weight as the calcium levels

were increased. Nitrogen did not significantly affect early

vine growth or any other growth response measured in this

experiment.

The number of U. S. Number 1 watermelons harvested

early is given in Table 15. There was a highly significant








TABLE 14

THE EFFECTS OF CALCIUM AND NITROGEN ON EARLY VINE
GROWTH AS INDICATED BY THE DRY WEIGHT
OF EIGHT HILLS PER PLOT


Pounds of hydrated Pounds of nitrogen cer acre Total
lime per acre 60 120 180

0 196.30 204.00 193.75 594.05
'500 214.05 206.35 237.25 657.65
1,000 208.20 212.35 251.50 672.05

Total 618.55 622.70 682.50


Effect (from A.O.V. in Table 38):
Calcium linear-significant at 0.05 level.
Nitrogen-not significant.



TABLE 15

THE EFFECTS OF CALCIUM AND NITROGEN ON THE NUMBER
OF EARLY U. S. NUMBER 1 WATERMELONS


Pounds of hydrated Pounds of nitrogen per acre Total
lime per acre 60 120 180

0 25 23 18 66
*500 30 32 31 93
1,000 37 28 44 109

Total 92 83 93


Effect (from A.O.V. in Table 38)z
Calcium linear-singificant at 0.01 level.
Nitrogen-not significant.







linear increase in the number of early watermelons as a

result of the calcium treatments.

The total weight of U. S. Number 1 watermelons

which was harvested early are presented in Table 16. There

was a significant linear increase in the early yield, in

pounds, as a result of increasing increments of calcium.


TABLE 16

EFFECTS OF CALCIUM AND NITROGEN ON THE TOTAL WEIGHT
IN POUNDS OF U. S. NUMBER 1 WATERMELONS
HARVESTED EARLY


Pounds of hydrated Pounds of nitrogen per acre Total
lime per acre 60 120 180

0 576.4 568.3 428.6 1573.3
-500 765.6 725.8 779.5 2270.9
1,000 872.9 626.1 1148.5 2647.5

Total 2214.9 1920.2 2356.6


Effect (from A.O.V. in Table 38):
Calcium linear-significant at the 0.05 level.
Nitrogen-not significant.


The total number of U. S. Number 1 watermelons har-

vested is given in Table 17. The total number of watermelons

produced increased in a significant fashion in response to

the calcium treatments.

The total weight in pounds of U. S. Number 1 water-

melons, reported in Table 18, increased in a significant

linear manner in response to the calcium treatments.








TABLE 17

EFFECTS OF CALCIUM AND NITROGEN ON THE TOTAL
NUMBER OF U. S. NUMBER 1 WATERMELONS


Pounds of hydrated Pounds of nitrogen ner acre Total
lime per acre 60 120 180

0 39 35 35 109
-500 52 53 47 152
1,000 58 45 59 162

Total 149 133 141


Effect (from A.O.V. in Table 38):
Calcium linear-significant at the 0.05 level.
Nitrogen-not significant.


TABLE 18
EFFECTS OF CALCIUM AND NITROGEN ON THE TOTAL WEIGHT
IN POUNDS OF U. So NUMBER 1 WATERMELONS

Pounds of hydrated Pounds of nitrogen per acre Total
lime per acre 60 120 180

0 851.8 755.4 778.0 2385.2
-500 1167.0 1140.4 1118.6 3426.0
1,000 1267.8 938.3 1444.7 3650.8

Total 3286.6 2834.1 3341.3


Effect (from A.O.V. in Table 38):
Calcium linear-significant at the 0.05 level.
Nitrogen-not significant.






54

The average of soluble solids as per cent sucrose

of all marketable fruit from each plot is reported in Table

19. The average percentage of soluble solids was not sig-

nificantly affected by either the nitrogen or the calcium

treatments.


TABLE 19

THE EFFECTS OF CALCIUM AND NITROGEN ON THE AVERAGE
SOLUBLE SOLIDS AS PER CENT SUCROSE FROM
ALL MARKETABLE MELONS PER PLOT


Pounds of hydrated Pounds of nitrogen per acre Mean
lime per acre 60 120 180

0 9.97 9.65 10.24 9.95
500 9.78 9.94 10.12 9.95
1,000 9.48 9.46 9.72 9.55

Mean 9.74 9.68 10.03


Effect (from A.O.V. in Table 39):
Not significant.


The average thickness of the rinds measured at the

top and bottom center of all marketable fruits is shown in

Table 20. The average thickness of the rind at these loca-

tions was not affected significantly by any treatment com-

bination.

The average thickness of the rind at the blossom-

end of all marketable fruits per plot is given in Table 21.

A linear reduction in the thickness of the rind at the

blossom-end was associated with increasing increments of

calcium.








TABLE 20

THE EFFECTS OF CALCIUM AND NITROGEN ON THE AVERAGE
THICKNESS OF THE RIND IN CENTIMETERS AT THE
TOP CENTER AND BOTTOM CENTER OF
ALL MARKETABLE FRUITS


Pounds of hydrated Pounds of nitrogen per acre Mean
lime per acre 60 120 180

0 2.006 1.712 1.883 1.867
500 1.797 1.818 1.722 1.779
1,000 1.722 1.709 1.957 1.796

Mean 1.842 1.746 1.854


Effect (from A.O.V. in Table 39):
Not significant.


TABLE 21

THE EFFECTS OF CALCIUM AND NITROGEN ON THE AVERAGE
THICKNESS OF THE RIND IN CENTIMETERS AT THE
BLOSSOM-END OF ALL MARKETABLE FRUITS


Pounds of hydrated Pounds of nitrogen per acre Mean
lime per acre 60 120 180

0 1.548 1.512 1.641 1.567
500 1.008 1.365 0.979 1.117
1,000 0.982 1.053 1.300 1.112

Mean 1.179 1.310 1.307


Effect (from A.O.V. in Table 39):
Calcium linear-significant at the 0.05 level.
Nitrogen-not significant.







The average percentage of blossom-end rot of the

watermelon fruits associated with each treatment combination

is given in Table 22. The analysis of variance of this data

revealed no significant difference among treatments.

TABLE 22

THE EFFECTS OF CALCIUM AND NITROGEN ON THE
PERCENTAGE OF BLOSSOM-END ROT


Pounds of hydrated Pounds of nitrogen per acre Mean
lime per acre 60 120 180

0 46.52 47.27 39.93 44.57
500 48.83 46.46 51.55 48.95
1,000 44.64 49.56 42.10 45.43

Mean 46.66 47.76 44.53


Effect (from A.0.V. in Table 39):
Not significant.


All fruits were examined for hollow-heart, white-

heart, and other abnormalities; however, these disorders

were very limited in occurrence and of no importance in

this experiment.


Fruit ul

The total number of fruits set per treatment is

shown in Table 23. There was a significant positive quad-

ratic response to the increasing calcium levels. Nitrogen

treatments had no significant effect on the total number of

fruits set.








TABLE 23

THE EFFECTS OF CALCIUM AND NITROGEN ON THE
TOTAL NUMBER OF FRUITS SET


Pounds of hydrated Pounds of nitrogen per acre Total
lime per acre 60 120 180

0 136.6 124.6 92.2 353.4
500 148.2 160.9 186.4 495.5
1,000 136.8 163.2 163.5 463.5

Total 421.6 448.8 442.1


Effect (from A.O.V. in Table 39)t
Calcium linear-significant at 0.05 level.
Calcium quadratic-significant at 0.05 level.
Nitrogen-not significant.


Chemical composition

The percentage of calcium, potassium, and magnesium

in the tips of young watermelon plants on May 1 is presented

in Table 24. There was a highly significant linear increase

in the calcium content of the tips as the calcium supply

was increased in the soil. The calcium content of the tips

was not affected by the nitrogen treatments. Neither the

potassium nor magnesium content of the young tips was in-

fluenced by the application of nitrogen or calcium to the

soil.

The cation composition of the leaves from young

watermelon plants is shown in Table 25. The calcium con-

tent of the leaves gave a curvilinear response to calcium

treatments, increasing with increasing amounts of lime per

acre. In response to nitrogen treatments, however, the







TABLE 24

THE EFFECTS OF CALCIUM AND NITROGEN ON THE PERCENTAGE
OF CALCIUM, POTASSIUM, AND MAGNESIUM IN THE
TIPS OF YOUNG WATERMELON PLANTS


Pounds of hydrated Pounds of nitrogen .er acre Mean
lime per acre 60 120 180

Calcium Content

0 0.545 0.385 0.340 0.423
500 0.555 0.630 0.713 0.633
1,000 0.713 0.937 0.722 0.791

Mean 0.604 0.651 0.594


Potassium Content

0 5.61 4.69 5.11 5.14
500 5.19 5.02 5.55 5.25
1,000 5.26 5.00 5.51 5.26

Mean 5.35 4.90 5.39


Malnesium Content

0 0.340 0.285 0.300 0.308
-500 0.285 0.323 0.298 0.302
1,000 0.292 0.308 0.288 0.296

Mean 0.306 0.305 0.295


Effect (from A.0.V. in Table 40):
Calcium content-calcium linear (CaL) sig-
nificant at O.ul level.
Potassium content-not significant.
Magnesium content-not significant.








TABLE 25

THE EFFECTS OF CALCIUM AND NITROGEN ON THE PERCENTAGE
OF CALCIUM, POTASSIUM, AND MAGNESIUM IN THE
LEAVES OF YOUNG WATERMELON PLANTS


Pounds of hydrated Pounds of nitrogen ner acre Mean
lime per acre 60 120 180

Calcium Content

0 2.73 2.41 1.96 2.37
6500 4.15 3.81 3.59 3.85
1,000 4.21 4.31 4.06 4.19

Mean 3.70 3.51 3.20


Potassium Content

0 5.75 5.80 5.90 5.82
5500 5.23 5.42 5.35 5.33
1,000 5.24 5.21 5.67 5.37

Mean 5.41 5.48 5.64


Marnesium Content

O 0.623 0.600 0.457 0.560
-500 0.450 0.485 0.428 0.454
1,000 0.410 0.385 0.472 0.422

Mean 0.494 0.490 0.452


Effect (from A.O.V. in Table 40):
Calcium contnent-Ca, calcium quadratic
(Cao), and nitrogen linear (NL) significant
at 0.01 level.
Potassium content-CaL significant at 0.05
level.
Magnesium content-CaL significant at 0.01
level; CaL X NL significant at 0.05 level.






60

calcium content showed a highly significant linear regres-

sion, decreasing as the nitrogen levels were increased.

Potassium content also showed a significant linear regres-

sion, decreasing as the calcium levels were increased in

the soil. The magnesium content of the leaves similarly

decreased in a highly significant linear trend as a result

of increasing the calcium levels. However, a significant

linear interaction was discovered between the linear re-

sponses of calcium and nitrogen, CaL X NL, on the magnesium

content of the leaves of young plants (Fig. 3). The effect

of increasing nitrogen on the linear response to the calcium

treatments was to change the regression from negative to

slightly positive as the nitrogen levels increased from 60

to 180 pounds per acre.

The effect of the calcium and nitrogen treatments

on the cation composition of the tips from the mature water-

melon plants is presented in Table 26. The calcium treat-

ments had no significant effect on the cation composition

of the mature tips. The potassium and magnesium content

of the tips, however, responded in a significant negative

linear fashion to the increasing nitrogen levels.

The cation composition of the leaves from mature

plants is given in Table 27. Nitrogen treatments had no

significant effect on the percentage of potassium, calcium,

or magnesium in the mature leaves. The calcium content of

the leaves was increased in a highly significant quadratic












610 0 lbs. N





180 lbs. N-7


0.7


0.6


0.5

0.4


0.21 i | I
0 500 1,000
POUNDS OF HYDRATED LIME PER ACRE

Fig. 3.--The interaction of calcium and
nitrogen (Ca X NL) on the magnesium content of
the leaves of young watermelon plants


2.1-


60 bs. N
\860 lbs. N


S 180 lbs.



-120 lbs.

N.


1,000


POUNDS OF HYDRATED LIME PER ACRE


Fig. 4.--The interaction of calcium and
nitrogen (Ca X N ) on the potassium content of
U. S. Number 1 watermelons.


O120 Ibs. N


0.3


N.


2.0


1.9


1.8


1.7


1.6


500


___








TABLE 26

THE EFFECTS OF CALCIUM AND NITROGEN ON THE PERCENTAGE
OF CALCIUM, POTASSIUM, AND MAGNESIUM IN THE
TIPS OF MATURE WATERMELON PLANTS


Pounds of hydrated Pounds of nitrogen nor acre Mean
lime per acre 60 120 180

Calcium Content

0 0.285 0.230 0.325 0.280
-500 0.370 0.300 0.325 0.332
1,000 0.365 0.325 0.300 0.330

Mean 0.340 0.285 0.317


Potassium Content

0 3.85 3.84 3.75 3.81
500 4.06 3.35 3.35 3.59
1,000 3.84 3.26 3.56 3.55

Mean 3.92 3.48 3.55


Magnesium Content

0 0.460 0.367 0.380 0.402
500 0.385 0.355 0.333 0.358
1,000 0.400 0.345 0.390 0.378

Mean 0.415 0.356 0.368


Effect (from A.0.V. in TRble 41):
Calcium content-not significant.
Potassium contenL-NL significant at 0.05
level.
Magnesium content-NL significant at 0.05
level.








TABLE 27

THE EFFECTS OF CALCIUM AND NITROGEN ON THE PERCENTAGE
OF CALCIUM, POTASSIUM, AND MAGNESIUM IN THE
LEAVES OF MATURE WATERMELON PLANTS


Pounds of hydrated Pounds of nitrogen per acre Mean
lime per acre 60 120 180

Calcium Content

0 4.21 4.50 4.63 4.45
-500 8.16 8.88 8.72 8.59
1,000 9.90 8.23 9.15 9.09

Mean 7.42 7.20 7.50


Potassium Content

0 3.21 2.79 2.81 2.94
-500 1.96 2.19 1.83 1.99
1,000 1.96 1.79 2.08 1.94

Mean 2.38 2.26 2.24


Magnesium Content

0 1.070 1.111 0.947 1.040
'500 1.020 1.050 0.902 0.991
1,000 0.942 0.850 0.968 0.920

Mean 1.010 1.003 0.939


Effect (from A.O.V. in Table 41)t
Calcium content-CaL* CaQ significant at
0.01 level.
Potassium content-CaLr Caq significant at
0.01 level.
Magnesium content-net significant.






64

fashion and the potassium content was decreased in a highly

significant quadratic manner as the calcium levels were

increased in the soil.

The results of the analyses of the mature marketable
fruit for calcium, potassium, and magnesium are shown in

Table 28. The calcium content increased in a highly sig-

nificant manner as a result of the calcium applications, and
it decreased in a highly significant quadratic fashion as a

result of the nitrogen treatments. The potassium content
showed significant quadratic regressions as a result of

both calcium and nitrogen treatments. However, these rela-

tionships are complicated by a quadratic interaction

(Caq X N ) shown in Fig. 4. The quadratic regression on

calcium changed drastically from "concave upward" for 60

and 180 pounds of nitrogen to "concave downwardR for the

120 pounds of nitrogen applied per acre. The magnesium

content responded to nitrogen only, and this was a quadratic

relationship.
The composition of the fruits exhibiting blossom-

end rot is shown in Table 29. The calcium content of the
fruit showed a strong linear regression, increasing in re-

sponse to increasing increments of applied calcium. The
potassium content responded negatively to the calcium treat-

ments and positively to the nitrogen treatments. However,

a significant interaction (CaL X NQ) is quite evident in

Fig. 5. Here the shape of the linear regression of








TABLE 28

THE EFFECTS OF CALCIUM AND NITROGEN ON THE PERCENTAGE
OF CALCIUM, POTASSIUM, AND MAGNESIUM IN
U.S. NUMBER 1 WATERMELON FRUITS


Pounds of hydrated Pounds of nitrogen per acre Mean
lime per acre 60 120 180

Calcium Content

0 0.106 0.095 0.101 0.101
500 0.163 0.135 0.131 0.143
1,000 0.185 0.135 0.162 0.161

Mean 0.151 0.122 0.131


Potassium Content

0 2.06 1.91 1.93 1.97
'500 1.71 1.76 1.71 1.73
1,000 1.85 1.58 1.84 1.78

Mean 1.87 1.75 1.83


Magnesium Content

0 0.143 0.134 0.146 0.141
-500 0.127 0.120 0.134 0.127
1,000 0.125 0.108 0.143 0.125

Mean 0.132 0.121 0.141


Effect (from A.O.V. in Table 42):
Calcium content-CaL significant at 0.01
level; N, N significant at 0.05 level.
Potassium ontSnt- Car, CaQ singificant at
0.01 level; NQ, CaQX NQ significant at
0.05 level.
Magnesium oontent-Nq significant at 0.05
level.








TABLE 29

THE EFFECTS OF CALCIUM AND NITROGEN ON THE PERCENTAGE
OF CALCIUM, POTASSIUM, AND MAGNESIUM IN
WATERMELON FRUITS EXHIBITING
BLOSSOM-END ROT


Pounds of hydrated Pounds of nitrogen per acre Mean
lime per acre 60 120 180

Calcinum Content

0 0.199 0.180 0.226 0.202
'500 0.243 0.255 0.219 0.239
1,000 0.321 0.233 0.291 0.282

Mean 0.254 0.223 0.245


Potassium Content

0 2.15 2.92 3.01 2.69
'500 2.36 2.54 2.49 2.46
1,000 2.34 1.98 2.48 2.27

Mean 2.28 2.48 2.66


Magnesium Content

0 0.180 0.218 0.238 0.212
"500 0.184 0.154 0.181 0.173
1,000 0.159 0.124 0.156 0.146

Mean 0.174 0.165 0.192


Effect (from A.O.V. in Table 42):
Calcium content-CaL significant at 0.01 level.
Potassium content-Ca significant at 0.01
level; NL, CaL X NQ significant at 0.05
level.
Magnesium content-CaL significant at 0.01
level; CaL X NL significant at 0.05 level.










3.0


2.8


2.6-


2.4-


2.2-


2.0-


0 500 1,000
POUNDS OF HYDRATED LIME PER ACRE
Fig. 5.--The interaction of calcium and
nitrogen (CaL X NQ) on the potassium content of
watermelon fruits exhibiting blossom-end rot.


180 lbs. N


,60 lbs.


(120 lbs. N
^120 lbs. N


0.12' I I


500


1,000


POUNDS OF HYDRATED LIME PER ACRE


Fig. 6.--The interaction of calcium and
nitrogen (CaL X NL) on the magnesium content of
watermelon fruits exhibiting blossom-end rot.


p180 lbs. N

/60 Ibs. N



-120 lbs. N


1.8


0.24


0.22


0.20


0.18


0.16


0.14





68
potassium on calcium changed markedly from positive to

negative in a curvilinear fashion for different levels of

nitrogen. The highly significant linear reduction in the

magnesium content in response to calcium treatments appeared

to be influenced by the nitrogen levels. It is evident by

the linear interaction (CaL X NL) of the magnesium content

on calcium shown in Fig. 6. The graph clearly shows how the

negative slope of the regression becomes steeper as the

nitrogen is increased above 60 pounds of nitrogen per acre.











DISCUSSION


Growth Reglonses

In the greenhouse experiments with watermelons, any

level of calcium in the nutrient solution from 4 to 256 ppm

appeared to produce normal growth of plants the first two

weeks after transplanting. After this, plants grown in

solutions containing 4 ppm of calcium began to develop

deficiency symptoms in the leaves, vines, and roots, and

these symptoms grew increasingly more pronounced as the

season progressed. Within three days all watermelon plants

placed in solutions containing no calcium began developing

deficiency symptoms which resulted in death of the plants in

approximately two weeks. These visible symptoms appeared to

be characteristic of a severe calcium deficiency rather than

toxicity if any other element or elements. No deficiency

symptoms were apparent in the tops of plants grown in 8 ppm

calcium; however, the roots did show obvious deficiency

symptoms at the 8 ppm level but not at 16 ppm of calcium.

Research reported by Biddulph -t al. (7) indicated that Red

Kidney bean plants survived in nutrient solutions containing

as low as 0.05 millimoles (2 ppm) of calcium. Below this

level, the beans developed a severe deficiency or chlorosis

which resulted in death.







The negative linear relationships existing between
the dry weight of vines or the dry weight of the roots and

the calcium concentrations, when expressed logarithmically,
may be explained by the fruit yields (Fig. 7). In solutions
containing 16 through 256 ppm of calcium a considerable

part of the total plant weight was represented by the dry

weight of the fruits. This is apparent by observation of

the non-significant quadratic trend in total weight. The
curvilinear response of root growth is unquestionably mainly

a response to treatments; however, it may be partially
attributed to the amount of the base portion of the main

stem harvested with the root systems. Therefore, the nega-

tive linear pattern appears to describe the data adequately
(Fig. 7).

The positive linear response of early vine growth

to calcium treatments in the field (Table 14) is in general
agreement with data obtained from a preliminary sand-pot

experiment. Pots of Leon fine sand receiving 600 pounds of
hydrated lime per acre produced significantly more vine

growth than pots receiving no lime, but vine growth was not

significantly different in pots receiving 600; 1,200; 1,800;

or 2,400 pounds of hydrated lime per acre. Field application
of nitrogen did not influence the early vine growth signifi-
cantly. This may be explained on either of the following

assumptions: (1) the excessive rains following application

partially eliminated the nitrogen variable or (2) sufficient



















DuY WEIGHT IN GRAMS FOR THE ROOTS


4 -< 0
- i-i


0 oo In l m 0 r't


I I f I I I I I


'-4
C,


\






m
U)
C0
1-1


N


b I


o 0 0 0 0 0 e 0 .
0 Oi C C- tO L0 0


DRY WEIGHT IN GRAMS FOR VINES, FRUITS
AND TOTAL


I e
0
Q










-4






0
1


"ir

(X)


.4


eja






Q
r-4 4)
I C










rot
Of







0 M
C 0)
0:



!- OIL<









f*rf


I


A







nitrogen remained at all nitrogen levels after the exces-

sive rains to give maximum growth in the early stages.

The percentage increase in early and total yields

both in pounds and numbers are shown in Fig. 8. On an

acre basis the application of 500 and 1,000 pounds of

hydrated lime increased the number of early harvested water-

melons by 80 and 129 respectively. These figures represent

a percentage increase over the no lime treatment of 40 and

60 per cent respectively. On an acre basis the application

of 500 and 1,000 pounds of hydrated lime increased the

pounds of watermelons harvested early by 2,092.8 and

3,222.6 or 44 and 68 per cent respectively over the no lime

treatment. The percentage increase in the number of pounds

was slightly larger than the percentage increase in the ac-

tual number of watermelons. This indicates that the average

weight per melon was slightly greater as a result of the

lime treatments; however, statistical analysis based on the

average weight per plot showed no significant difference.

When the total yield of U.S. Number 1 watermelons

per acre is considered, the application of 500 and 1,000

pounds of hydrated lime increased the yields by 127 and 156

watermelons (39 and 48 per cent) respectively. A compari-

son of the percentage increase in the total number with the

percentage increase in total pounds again indicates that the

melons were larger in size, and this is supported by statis-

tical significance based on the average weight per plot. It

should be pointed out, however, that the average weight per















































LI~TiTHTflIBThlihII1


m
I. m
S00
t o

as


0
O
40 0

0 bP
+) r. bL

c4 > G-
t t4) V4



4).)


0 0
Oim
)o





P4 10
O o
4)4) 01-4

0) 0

I c















4 C 4)
^0 *

hOE


a)k a c





oo
I 9 I S '
arr
on 3







pt(
>i rt-


o 0 0 0 0 0 0 0
P oo E CEN'r IC eE e

PER CENT INCREASE






74

plot was based on unequal numbers; therefore, the analysis

of variance may be biased,

Since these yield increases were obtained from rows

spaced 15 feet apart and the hills 10 feet apart in the row,

even greater total yields were probable by spacing the rows

or the hills closer together. In commercial watermelon

fields rows are usually spaced 8 to 10 feet apart. Nettles

and Halsey (53) reported significant increases in the number

of watermelons produced as the number of hills per row were

increased. Plants spaced 3 feet apart in rows 10 feet apart

produced 1,260 marketable watermelons per acre, and plants

spaced 12 feet apart in 10-foot rows produced 660 marketable

watermelons per acre. The average weight did not differ

significantly, but it tended to be greater at the wider

spacings.

From the literature review and from examination of

all soil and tissue analytical data it appears that the

beneficial effects of calcium resulted from both an in-

creased supply of calcium and pH changes, which may have

directly or indirectly affected the availability of certain

other elements. In general, investigators agree that the

calcium to magnesium ratio in the soil should be in the

range 6 to 10:1. Data in Table 11 and 31 indicate the cal-

cium to magnesium ratios associated with the three treatments

(0, 500, and 1,000 pounds of hydrated lime per acre) were

approximately 1:1, 6:1, and 15:1, respectively. Likewise,

more favorable calcium to potassium ratios existed in the








plots receiving lime. The importance of these ratios is
exemplified by the data on the cation composition of the

plants shown in Tables 24 through 30. In general, the cal-
cium content of the plant increased from 50 to 100 per cent

in response to added calcium, and the potassium and mag-

nesium content generally decreased. Moreover, Wilkins (83)

pointed out that cucurbits accumulate large quantities of

calcium, and suggested that it may be desirable to plant

these crops on soils containing an abundant supply of cal-

cium.

Another undoubtably important factor contributing

to the increased yields is the soil pH. From data in

Table 11, it may be seen that the average pH corresponding

to the three calcium levels were 4.9, 5.4, and 5.8.

Fiskell and co-workers (23, 24) have shown that toxic con-

centrations of aluminum ions are present in many of the

Florida soils, including Kanapaha, with a low pH. Further-

more, it has been established that the rate of nitrification

as well as organic matter decomposition is greatly in-

fluenced by the soil pH (13, 81).

Nitrogen had no significant effect on any of the

yield data from the field experiment. This may be attributed

in part to excessive rainfall following both nitrogen ap-

plications. Over eight inches of rain fell the first 15

days following the initial application of nitrogen. Over

seven inches of rain fell the first 30 days following the

second application of nitrogen. Data in Table 13 indicated








that almost all of the nitrates and approximately 50 per

cent of the potassiur was leached from the upper eight

inches of the soil by slightly more than eight inches of

rainfall. Since ammonium occupies a lower position in the

lyotrophic series than potaseiuL it follows that at least

50 per cent of the am.monlui. nitrogen also was lost.

Io definite relationship was established between

blossom-end rot and calcium treatments in the greenhouse

or the field. In all greenhouse w'or!k using rntrient cul-

tures, all the fruits set developed blossom-end rot.

Geraldsou (2O) observed that Ilack-heart of celery, a cal-

clum deficiency, occurred in nutrient solutions in the green-

house regardless of the calcium levels. Elack-heart was

controlled by foliar applications of 0.04 molar calcium

chloride. A similar control has been developed for blos-

som-end rot of tomatoes (37).

In the exploratory work in the greenhouse with water-

melons, a lower incidence of blossom-end rot was observed

with treatments receiving foliar sprays of 0.04 molar calcium

chloride tihani fom pots receiving no spray. This does not

necessarily establish the disorder as a calcium deficiency;

however, it does support the theory that blossom-end rot is

a physiological disorder. This is further substantiated by

the fact that a large percenta.;e of the ovaries of plants

grown in four and eight ppm calcium decayed beginning at

the blossorn-enri even before the floral parts opened. It is

suggested, therefore, that future examinations into the







77

causes of blossom-end rot of watermelons may be more prof-

itable if attempted under controlled environmental condi-

tions.

The differential calcium treatments tested in the

field did have an effect on the rind thickness at the

blossom-end of the watermelon but not on the average thick-

ness of the top and bottom center of the rind. At the

blossom-end the rind thickness decreased as the calcium

levels were increased. At least two possible explanations

exist for this: it is possible that calcium enhanced ma-

turity; however, this is not supported by a significant

increase in the soluble solids, and observations have shown

that fruits affected with blossom-end disorders tend to have

a thick whitish rind at the blossom-end; therefore, increas-

ing the calcium supply may have reduced these disorders. It

should also be pointed out that the calcium content of the

fruit generally increased linearly in response to calcium

treatments.


sx Expression and Fruit Set
Calcium treatments had a profound effect on sex ex-

pression in nutrient solutions containing relatively low

amounts of calcium (Table 7). Plants grown in 13 liters of

a solution containing 4 ppm calcium had an average ratio of

staminate to pistillate flowers of 27.79:1. When the calcium

level was raised to 8 ppm the ratio dropped to 8.74:1 and did

not differ significantly as the calcium level was increased








from 4 to 256 ppm; however, at the higher calcium levels

the ratio tended to increase. From data presented in Tables

9 and 10 it may be assumed that this drastic increase in

the flower ratio was due to either a deficiency of calcium,

an excess of potassium and magnesium in the nutrient solu-

tion, or any combination of the latter with a calcium de-

ficiency.

Apparently calcium concentrations greater than 8

ppm are necessary for fruit set. Since a large number of

the ovaries of plants in solutions containing 4 and 8 ppm

calcium decayed, it is assumed that insufficient quantities

of calcium were present for normal cellular development.

The parabolic response in the number of fruits set to cal-

cium treatments in the field may be explained on the basis

that the liming applications enhanced vine growth thereby

increasing the actual numbers of fruits set (Table 23).

Chemical Analyses

In the greenhouse experiment, the increase in the

calcium content of the tips and fruits was linear as the

logarithms of the calcium treatments increased, however, a

positive curvilinear response occurred in the leaves and

roots. It is generally agreed that increasing the concen-

tration of any element in the substrate usually results in

increased absorption of that element by the plant (44, 59).

The linear decrease in the potassium content of the leaves

and roots probably was produced by a cation antagonism








resulting from an increase in the calcium content. The

failure of potassium to decrease significantly in the tips

and fruits may be explained on the basis that potassium is

a very mobile element and occurs in relatively large quan-

tities in areas of high metabolic activity (48, 50). Ap-

parently cation antagonism between calcium and magnesium

resulted in a linear decrease in the magnesium content of

the leaves and roots and a quadratic decrease in the tips

and fruits.

Conversion of the data in Table 10 to equivalents

per 100 grams indicated that the calcium-equivalent in-

crease in the plants at the various treatments was con-

siderably greater than the accumulative equivalent decrease

of potassium and magnesium. This may be attributed to

inactivation of much of the absorbed calcium by organic

acid precipitation thereby causing a continuous build-up

of the total cation equivalents in the tissue as calcium

increased in the substrate.

The influence of calcium and nitrogen on the aver-

age percentage of calcium, potassium, and magnesium of

tissue samples from the field experiment is shown in Table

30. The linear increase in the calcium content in response

to calcium applications occurred in the leaves of both

young and mature plants. The significant decrease in the

calcium content of the leaves at the first sampling date

as a result of nitrogen treatments failed to occur at the

second sampling date. This may be the consequence of








TABLE 30

THE AVERAGE PERCENTAGE OF CALCIUM, POTASSIUM, AND MAGNESIUM
ASSOCIATED WITH EACH CALCIUM AND EACH NITROGEN
LEVEL IN BOTH VINES AND FRUITS FROM
THE FIELD EXPERIMENTa

Treatment Composition of young Composition of mature
levels plants plants
(May 1, 1959) (June 10, 1959)

Leaves Leaves
Ca K Mg Ca K Mg
Calcium
0 2.37 5.82 0.560 4.45 2.94 1.04
500 3.85 5.33 .454 8.59 1.99 0.99
1,000 4.19 5.37 .422 9.09 1.94 0.92

Nitrogen
60 3.70 5.41 .494 7.42 2.38 1.01
120 3.51 5.48 .490 7.20 2.26 1.00
180 3.20 5.64 .452 7.50 2.24 0.94


Tins Tips
Ca K Mg Ca K Mg
Calcium
0 0.423 5.14 0.308 0.280 2.81 0.402
-500 .633 5.25 .302 .332 3.59 .358
1,000 .791 5.26 .296 .330 3.55 .378

Nitrogen
60 .604 5.35 .306 .340 3.92 .415
120 .651 4.90 .305 .285 3.48 .356
180 0.594 5.39 0.295 0.317 3.55 0.368

Composition of fruits
Composition of U, S. exhibiting
number 1 fruits blossom-end rot
Ca K Mg Ca K Mg
Cal cium
0 0.101 1.97 0.141 0.202 2.69 0.212
,500 .143 1.73 .127 .239 2.46 .173
1,000 .161 1.76 .125 .282 2.27 .146

Nitrogen
60 .151 1.87 .132 .254 2.28 .174
120 .122 1.75 .121 .223 2.48 .165
180 0.131 1.83 0.141 0.245 2.66 0.192

aOven dry weight basis.






81

retardation in growth and less antagonism between ammonium

and calcium through leaching and oxidation of the ammonium.

The concentration of calcium in the leaves, regardless of

treatments, approximately doubled from the first to the

second sampling date. This is probably due to the precipi-

tation of a large percentage of the calcium by certain

organic acids.

The potassium content of the leaves at both sampling

dates decreased in response to calcium applications; al-

though, nitrogen had no effect on the potassium percentage

of the leaves at either sampling period. The leaf samples

taken early in the season contained more than twice as much

potassium on a percentage basis as those collected late in

the season. Perhaps the best explanation of this is a com-

bination of the mass action effect of the potassium applied

early in the season with luxury consumption by the plant,

and a dilution effect later in the season induced by heavy

vine growth.

The interaction between calcium and nitrogen on the

magnesium content of the leaves at the first sampling may be

attributed to varying degrees of antagonism between the ap-

plied calcium and ammonium nitrogen when the level of either

was changed along with differential growth responses. At

maturity this decrease in the magnesium percentage of the

leaves was not statistically significant. The relative in-

crease in the magnesium percentage of the leaves as the

season progressed, regardless of treatment, was approximately





82

proportional to the relative increase in the calcium per-

centage.

The equivalent shift of the nation composition of

the leaves in response to treatments at either sampling

time is in agreement with the greenhouse findings. That is,

the calcium-equivalent increase in the tissue in response

to calcium applications is much greater than the total mag-

nesium and potassium equivalent decrease in the tissue.

The linear increase in the calcium content of the

tips at the first sampling date in response to the calcium

levels had disappeared by the second sampling date (Tables

21, 26, 30). Perhaps the best explanation of this is that

the young plants were in a more vigorous state of growth

and assimilation than the mature plants. Also, this would

account for the greater percentage of calcium in the tips

of young plants.

Neither the potassium nor the magnesium content in

the tips at the first sampling date was significantly in-

fluenced by any treatment. However, nitrogen treatments

decreased the potassium and magnesium content of the tips

at the second sampling time. This may be attributed to a

combination of a number of factors, including a retardation

of the physiological activity of the merstimatic tissues,

differential build up of ammonium ions in the tissue, and a

dilution effect resulting from differential vine growth and

fruit yields.





93

In general, the normal fruits contained considerably

less calcium, potassium, and magnesium than fruits exhibiting

blossom-end rot. The most logical explanation of this is a

dilution effect, since the mature fruits were approximately

four to five times larger than the ones exhibiting blossom-

end rot (Table 28, 29, 30).

The calcium content of both types of fruit samples

increased linearly in response to calcium treatments. The

curvilinear response of calcium in the mature fruits to

nitrogen may be attributed to antagonism between ammonium

and nitrogen and differential vine growth.

The curvilinear interactions of the calcium and ni-

trogen treatments on the potassium content of both types of

fruits may have resulted from mass action effect of the

hydrated lime, antagonism between ammonium and potassium,

and dilution due to differential growth responses (Figs. 4

and 5). The same explanation may be given for the inter-

action of treatments on the magnesium content of fruits

showing blossom-end rot (Fig. 6).











SUMMARY AND CONCLUSION


Research was conducted in both the greenhouse and
the field to evaluate the effects of varying calcium levels

on vine growth, yields, quality, sex expression and fruit

set, and the calcium, potassium, and magnesium content of

plant tissues of the Charleston Gray variety of watermelons.

In the greenhouse, plants grown in a basic nutrient solution

containing no calcium developed severe calcium deficiency

symptoms and died within two weeks following transplanting.

Plants grown in 4 ppm calcium began to develop calcium de-

ficiency symptoms in both the tops and roots three weeks

following transplanting, and they grew increasingly more

severe as the season progressed. Plants grown in 8 ppm

calcium showed no deficiency symptoms in the tops, although

slight deficiency symptoms were present in the roots. Plants

grew normally in nutrient solutions ranging from 16 to 256

ppm calcium.

The leaves of deficient plants were dark green in

color, moderately cupped under at the margins, and severely

restricted especially at the apex forming a more circular

type leaf, and the vine laterals were short and very nu-

merous. The root systems of calcium deficient plants were

short, dense, very numerous, and often dark at the apex

indicating death.








The dry weight of the vines and the roots, when

analyzed separately, decreased linearly as the logarithms

of the calcium concentration increased in the nutrient solu-

tion. However, total dry weight (vines, roots and fruit)

did not differ significantly among calcium levels.

In the field experiment testing three levels of

calcium (0, 500, and 1,000 pounds of hydrated lime per acre)

and three levels of nitrogen (60, 120, and 180 pounds per

acre), the dry weight of early vine growth increased sig-

nificantly in a linear pattern in response to increasing

calcium levels. Nitrogen did not affect early vine growth

or any other growth measurements taken in this experiment.

Explanations are suggested based on soil test and rainfall

data.

There was a significant linear increase in early

and total yield in both pounds and numbers of marketable

watermelons as a result of increased calcium levels. The

average weight per melon of the early yield was not affected

by treatments; however, the average weight per melon of the

total yield was increased significantly by increasing the

calcium levels. The environmental factors possibly respon-

sible for these yield increases are discussed. It appeared

that the beneficial effects of calcium resulted from both

an increased supply of calcium and pH changes which may

have directly or indirectly affected the availability of

other elements.





86

Calcium levels in the greenhouse nutrient solutions

had a profound effect on sex expression and fruit set at

the lower concentrations. The ratio of staminate to pistil-

late flowers in solutions containing 4 ppm calcium was

27.79:1. When the calcium concentration was increased to

8 ppa the flower ratio dropped to 8.74:1, and it did not

differ significantly as the calcium levels were increased

to 256 ppm. At least 16 ppm of calcium in the nutrient

solutions were necessary for fruit set. In the field the

total number of fruits set increased in a quadratic fashion

as the calcium levels were increased. Nitrogen had no ef-

fect on the numbers of fruit set in the field. A large per-

centage of the ovaries produced by plants grown in nutrient

solutions containing 4 or 8 ppm calcium turned dark brown

to black in color beginning at the blossom-end, even before

the floral parts opened. All fruits set in the greenhouse,

regardless of the admixture of the nutrient solutions, de-

veloped blossom-end rot within three weeks after flowering.

The percentage of blossom-end rot in the field experiments

could not be associated with treatments. However, the rind

thickness at the blossom-end of marketable fruits decreased

linearly as the calcium treatments increased.

Analyses of data from three fertility experiments

during the 1958 season revealed that the occurrence of

blossom-end rot could be associated with the soil profile

characteristics but not with the different fertility treat-

ments.








In the field experiment, the different fertility

treatments tested resulted in no significant influence on

the soluble sugars, hollow-heart, white-heart, or average

thickness of the rind measured at the center of the fruit.

Analyses of tissue samples from various plant parts

indicated that watermelons absorb relatively large quanti-

ties of calcium, potassium, and magnesium. The greatest

concentration of calcium or magnesium occurred in the older

leaves with the percentages decreasing in the following

order: basal leaves, mid-leaves, tips, stems and fruits.

The potassium percentages decreased in the following order:

fruits, stems, tips, leaves.

Analyses of the tips, leaves, roots and fruits from

the greenhouse experiment indicated, in general, that as

the calcium concentration was increased logarithmically in

the nutrient medium the calcium content in the tissues in-

creased and the potassium and magnesium content decreased.

The increase in the percentage of calcium in the tips and

fruits was linear and the increase in the calcium content

of the leaves and roots was curvilinear, when measured

against the logarithms of the calcium concentrations in the

nutrient solution. Significant negative linear regressions

in the potassium content occurred in the leaves and roots

but not in the tips and fruits in response to calcium levels.

The negative regression in the magnesium content induced by

the calcium levels was linear in the roots and fruits and

quadratic in the leaves and tips.








Analyses of tip and leaf samples from both young
and mature watermelon plants from the field indicated that

the calcium percentage generally increased, and the mag-

nesium and potassium content decreased as the calcium sup-

ply was increased in the soil. The influence of nitrogen

on the cation composition of the leaf and tip samples was

at variance for the two sampling dates; however, any sig-

nificant effect of nitrogen treatments on the cation com-

position of the tissues generally resulted in a decrease

of the particular element as the nitrogen levels were in-

creased in the soil.

On a percentage basis the calcium and magnesium

content of the leaves of mature plants, regardless of

treatment, was approximately double that of the leaves of

the young plants, while the potassium content was approxi-

mately 50 per cent less in the older plants. The calcium

or potassium percentage of the tips of mature plants was

50 per cent less, while the magnesium percentage remained

fairly constant from the first to the second sampling.

Analyses of U. S. Number 1 watermelons and those

exhibiting blossom-end rot revealed that the calcium content

generally increased and the potassium and magnesium content

generally decreased in response to increasing calcium levels.

Increasing nitrogen levels, however, resulted in a reduction

of both the calcium and magnesium content of the U. S. Number

1 watermelon fruits. The magnesium content of the fruits








exhibiting blossom-end rot and the potassium content of

both types of fruits was influenced by calcium and nitrogen

interactions.

The calcium, potassium, and magnesium content of the

U. S. Number 1 fruits were generally lover than the con-

centration of these cations in the fruits exhibiting blossom-

end rot*

It is believed that results of this study may be of

value in evaluating and explaining the occurrence of certain

physiological disorders and poor growth and yield often ob-

tained in many of the commercial watermelon fields in North

Central Florida.











REFERENCES CITED


1. Andrews, W. B. 1937. The effect of ammonium sulfate
on the response of soybeans to lime and artificial
innoculation and the energy required of soybean nodule
bacteria. Jour. Amer. Soc. Agron. 29:681-689.

2. Anonymous. 1954. Soil survey, Alachua County, Florida.
USDA and Fla. Agr. Expt. Sta. 233-235.

3. Arnon, D. I. 1943. Mineral nutrition of plants. Ann.
Rev. Biochem. 12:493-528.

4. Baver, L. D.- 1956. Soil Physics, New York: John
Wiley & Sons, Inc. 3rd. Ed.

5. and Hall, N. S. 1937. Colloidal properties
of soil organic matter. Mo. Agr. Expt. Sta. Res. Bull.
267.

6. Bernstein, L. and Hayward, H. E. 1958. Physiology
of salt tolerance. Ann. Rev. Plant Physiol. 9:1-25.

7. Biddulph, O., Cory, R., and Biddulph, Susann. 1959.
Translocation of calcium in the bean. Plant Physiol.
34:512-519.

8. Blodgett, F. H. 1915. Plant pathology and physiology.
Texas Agr. Expt. Sta. Ann. Rept. 18.

9. Bonner, James and Galston, Arthur W. 1952. Principles
of Plant Physiology. San Francisco: W. H. Freeman and
Co.

10. Bradley, G. A. and Fleming, J. W. 1959. Fertilization
and foliar analysis studies on watermelons. Ark. Agr.
Expt. Sta. Bull. 610.

11. Brantley, B. B. 1958. Effects of nutrition and other
factors on flowering, fruiting, and quality of water-
melons and muskmelons. Unpublished Dissertation,
Purdue Univ., Dept. of Hort.

12. Breland, H. L. 1957. Methods of analyses using soil
testing. Fla. Agr. Expt. Sta. Dept. Soils Memo. Rept.
No. 58-3.







13. Burrus R. H. 1959. Nitrogen nutrition. Ann. Rev.
Plant Physiol. 10:301-328.

14. Carolus, R L. andLorenz, 0. A. 1938. The inter-
relation of manure, lime, and potash on the growth
and maturity of the muskmelon. Proc. Amer. Soc. Hort.
Sel. 36:518-522.

15. Cochran, W. G and Cox, Gertrude M. 1957. Experi-
mental Designs. New York: Wiley Publications in
Statistics.

18. Cooper, H. P. 1950. Effects of energy properties of
some plant nutrients on availability, on rate of
absorption, and on intensity of certain oxidation-
reduction reactions. Soil Sci. 69:7-39.

17. Cunningham, Clyde R. 1939. Fruit set in watermelons.
Proc. Ameri. Hort, Set. 37:811-814.
18. Dearborn, R. B. 1936. Nitrogen nutrition and chemi-
cal composition in relation to growth and fruiting
of the cucumber plant. Cornell Univ. Agr. Expt. Memo.
192.

19. Duncan, D. B. 1955. Multiple range and multiple F
test. Biometries. 11:1-42.
20. Eisenmenger, W. S. and Kucinski, K. J. 1939. Mag-
nesium requirements of plants. Mass. Agr. Expt. Sta.
Ann. Rept. 10.
21. Epstein, E. 1956. Mineral nutrition of plants;
mechanisms of uptake and transport. Ann. Rev. Plant
Physiol. 71t-24.
22. Everett, P. H. and Geraldson, C. M. 1958. Fertilizer
requirements of watermelons. Fla. Agr. Expt. Sta. Ann.
Rept. 326-328.

23. Fiskell, ,3 G. A., Hortenstine, C. C., Carver, H. L.,
and Lundy, H. W. 1958. Aluminum studies on some north
and central Florida soils. The Soil and Crop Scit. Soo.
of Fla., Proc, 18M166-178.
24. and Robertson, W. K. 1957. Comparison of
broadcast and row fertilization for potatoes on Kanapaha
fine sand. Fla. State Hort. Soe. 70:96-103.
25. Fried, M. and Peech, M. 1946. The comparative effects
of gypsum upon plant growth in acid soils. Jour. Amer.
Soe. Agron. 38:614-623.








26. Geraldson, C. M. 1957. Symptoms of nutritional dis-
orders in vegetable plants. Fla. Agr. Expt. Sta. Ann.
Rept. 296.

27. 1957. Control of blossom-end rot of toma-
toes. Proc. Amer. Soc. Hort. Sci. 69:309-317.

28. Hall, C. B., Nettles, V. F., and Dennison, R. A.
1951. Fertilizer requirements for watermelons. Fla.
Agr. Expt. Sta. Progress Rept. (Misc.).

29. ___, _, and 1955. Fertilizer
requirements for watermelons. Fla. Agr. Expt. Sta.
Ann. Rept. 113.

30. Hall, W. C. 1949. Effects of photoperiod and nitro-
gen supply on growth and reproduction in the gherkin.
Plant Physiol. 24:753-769.

31. Hardh, J. E. 1957. On the calcium uptake of glass-
house cucumbers. Maataloust Aikakausk. 29:238-242
(Hort. Abs. Vol. 28, No. 1419).

32. Hartman, John D. and Gaylord, F. C. 1940. Soil
acidity for muskmelons and sweetpotatoes on sand. Proo.
Amer. Soc. Hort. Sci. 37:841-845.

33. Hartman, John D. and Gaylord, F, C. 1941. Soil acidity
for watermelons on sand. Proc. Amer. Soc. Hort. Sci.
38:623-625.

34. Hartwell, B. L. and Damon, S. C. 1914. The comparative
effect on different kinds of plants of liming an acid
soil. R. I. Agr. Expt. Sta. Bull. 160.

35. Hasler, A. and Maurizio, A. '1951. The influence of
various nutrients on budding, nector secretion, and
yield of seeds of honey plants, especially winter rape
Brassica namus). Schweiz. Bienen-Z. 74:208-219
C. A. 7ol. 49, No. 4091g).

36. Heslop, Harrison J. 1957. The Experimental Modifica-
tions of Sex Expression in Flowering Plants. Biol.
Review. 32:38-90.

37. Hoagland, D. R. and Arnon, D. I. 1950. The Water-
culture Method for Growing Plants without Soil. Calif.
Agr. Expt. Sta. Cir. 347.

38. Holmes, R. S. 1943. Copper and zinc content of cer-
tain United States soils. Soil Sci. 56:359-370.