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3 1293 00908

This is to certify that the
thesis entitled
PRODUCTION OF SPANISH ONION
TRANSPLANTS IN THE GREENHOUSE
presented by

Catur Herison

has been accepted towards fulfillment
of the requirements for

M . S . degree in Horticulture

 

 

Major prof or

DateWZ77/

0-7639 MS U is an Affirmative Action/Equal Opportunity Institution

 

 

 

 

 

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University

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PLACE IN RETURN BOX to remove We checkouI from your record.
TO AVOID FINES return on or before date due.

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DATE DUE DATE DUE DATE DUE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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MSU Is An Affirmative Action/Equal Opportunity Institution
ammo-c1

__—__..—_——

 

PRODUCTION OF SPANISH ONION TRANSPLANT S
IN THE GREENHOUSE

BY

Catur Herison

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Horticulture

1991

(82-5825

ABSTRACT

PRODUCTION OF SPANISH ONION TRANSPLANTS
-IN THE GREENHOUSE

BY

Catur Herison

Studies were conducted-to determine the effect of root
type, plants per cell, and age and N-nutrition of onion
transplants in the greenhouse on yield and quality in the
field. On Houghton muck, cell transplants yielded more and
larger bulbs than did bareroot transplants. Two and three
plants per cell increased total yield by 40% and 65%,
respectively. Total yield and yield of bulbs >76 mm were
greatest with 10- and 12-week old seedlings, and with 150
and 225 ppm N. Bulb storability was slightly better with
younger seedlings, but was not affected by N-nutrition of
seedlings. On Colwood-Brookston loams, root type had no
effect on yield and quality of Spanish onions. Two and
three plants per cell increased total yield by 26% and 50%,
respectively. Yield of bulbs >76 mm was greatest with
single transplants. Age and N-nutrition of seedlings did
not influence yield and quality, and storability of Spanish

onions.

To my wife Rustikawati and my daughter Rieska
for their love, support and understanding.

To my father and mother with all my
gratitude.

iii

ACKNOWLEDGEMENT

I wish to express my sincere appreciation to my major
professor Dr. Bernard H. Zandstra for his patient guidance,
encouragement, and helpful suggestions during the course of
my graduate studies, and to Drs. Darryl D. Warncke and
Lowell C. Ewart, members of my Guidance Committee, for their ‘
advice and constructive criticism.

I wish to thank to the MSU Muck Research Farm and MSU
Horticultural Research Center staff for their help in taking
care of my plants during my research. Many thanks also go
to Ron V. Gruesbeck and Joseph G. Masabni for their help in
the field work. .

iv

TABLE OF CONTENTS

LIST OF TABLES vii
CHAPTER I. REVIEW OF LITERATURE
INTRODUCTION ................................... 1
LITERATURE REVIEW ..................... ......... 5
LITERATURE CITED ............................... 15
CHAPTER II. A COMPARISON OF GROWTH, YIELD AND QUALITY
OF SPANISH ONIONS GROWN FROM BARE ROOT AND CELL
TRANSPLANTS »
Abstract ....................................... 20
Introduction ................................... 21
Materials and Methods .......................... 22
Results ........................................ 27
Discussion and Conclusions ..................... 33

Literature Cited OOOOOOOOOOOOOOOOOOOOOOOOOOOO0.0 37

CHAPTER III. THE EFFECT OF MULTISEEDED CELL TRANSPLANTS
ON GROWTH, YIELD AND QUALITY OF SPANISH ONIONS

Abstract ....................................... 39
Introduction ................................... 40
Materials and Methods .......................... 41
. Results ........................................ 44
Discussion and Conclusions ..................... 54

Literature Cited .0.00000000000000000000000.0... 57

CHAPTER IV. THE EFFECT OF AGE AND NITROGEN NUTRITION
OF SEEDLINGS ON GROWTH, YIELD AND QUALITY OF
SPANISH ONIONS IN THE FIELD
Abstract .............. ..... . ...... .............
IntrOduction 00.0.0000...OOOOOOOOOOOOO...0......
Materials and Methods ...................... ....
Results OOOOOOOOOOOOOOOOOOOOOOO...OOOOOOOOOOOOOO
Discussion and'Conclusions .....................

Literature Cited OOOOOOOOOOOOOOOOOOOOOO0.0......

SUMRYAND CONCLUSIONS .00...OOOOOOOOOOOOOOOOOOOOOO.

vi

58

59

60

63

80

85

86

10.

LIST OF TABLES

page
A comparison of the size of seedlings from bare
roots and cells at transplanting at the MSU Muck
ResearCh Farm. OOOOOOOOOOOOOOOOOOOOO...0.0.0....O. 28

A comparison of plant weight of seedlings from
bare roots and cells at transplanting at the MSU
MuCR ResearCh Farm 0.0000000000000000000000000....

A comparison of plant size and weight of onions
from bare root and cell transplants at 8 weeks
after transplanting in the field, MSU Muck
Research Farm. ...................................

A comparison of the yield and quality of spanish
onions grown from bare root and cell transplants,
MSUMuCk ResearCh Farm. OOOOOIOOOOOOOOOOOOOOOO...O

A comparison of the yield and quality of Spanish
onions grown from bare root and cell transplants,
MSU Horticultural Research Center. ..............

The effect of multiseeded cell transplants on
seedling size of Spanish onions at transplanting,
at 12 weeks after seeding. .......................

The effect of multiseeded cell transplants on
seedling weight of Spanish onions at transplanting,
at 12 weeks after seeding. .......................

The effect of number of seedlings per cell on
plant size and weight of Spanish onions at 8 weeks
after transplanting, MSU Muck Research Farm. .....

The effect of number of transplants per cell on
maturity and yield of Spanish onions, MSU Muck
ResearCh Farm. OOOOOOOOOOOOOOOOOOOOOOOO00.0.0.0...

The effect of number of transplants per cell on
the size of Spanish onions, MSU Muck Research

Farm. O0......OOOOOOOOOOOOOOOOOOOO0.00.0.0... .....

vii

29

30

31

32

45

46

47

49

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

The effect of number of transplants per cell on

time to maturity and yield of Spanish onions,
MSU Horticultural Research Center. .........

The effect of number of transplants per cell on

the size of Spanish onions, MSU Horticultural
ResearCh center. OOOOOOOOOOOOOOOO0.0.00.0...

The effect of age and N-nutrition on size of

Spanish onion seedlings at transplanting at the

MSU Muck Research Farm.......................

The effect of age and N-nutrition on weight of
Spanish onion seedlings at transplanting at the

MSU Muck Research Farm. .....................

The effect of age and N-nutrition of seedlings
on plant size and weight of Spanish onions at 8
weeks after transplanting, MSU Muck Research Farm.

The effect of age and N-nutrition of seedlings
on the yield and quality of Spanish onions, MSU

HuCk ResearCh Fame 00.0.0...00......000000000

The effect of age and N-nutrition of seedlings

on quality of Spanish onions after 15-week
storage, MSU Muck Research Farm. ............

The effect of age and N-nutrition of seedlings
on the yield and quality of Spanish onions, MSU

Horticultural Research Center. .............

The effect of age and N-nutrition of seedlings

on quality of Spanish onions after 15-week
storage, MSU Horticultural Research Center. .

The effect of interaction between cultivar and
age on seedling size and weight at transplanting

at the MSU Muck Research Farm. ..............

The effect of interaction between cultivar and
N-nutrition of seedlings on plant size at 8 weeks

after transplanting, MSU Muck Research Farm.

The effect of interaction between age and N-
nutrition on seedling size and weight at
transplanting at the MSU Muck Research Farm.

52

53

64

65

67

68

69

71

72

75

77

79

CHAPTER I

REVIEW OF LITERATURE
INTRODUCTION

Bulb onions can be grown either from seeds, sets, or
transplants. Each of these methods is extensively used. In
the United States, for instance, northern onions grown
during the summer for storage are usually direct seeded.
Onions for immediate sale are sometimes grown from sets.
Over-winter crops in southern states are usually grown from
transplants (Jones and Mann, 1963). Based on bulb
utilization, direct seeding is the most common method for
pickling onion production. But transplanting is a more
preferred method in fresh market onion production
(Rabinowitch and Brewster, 1990).

In many onion-producing countries, transplanting is
more popular than other methods of establishment. In the
United States, more than 25% of the onions are grown from
transplants. In Egypt, Italy, Spain, India (Jones and Mann,
1963) and Canada (Rabinowitch and Brewster, 1990) most
Spanish type onions are transplanted.

Compared to direct seeding, there are advantages of

transplanting in onion production. First, onion bulbs grown

2
from transplants mature earlier than from seeds (Jones and
Mann, 1963). This means shorter field occupation, with less
pesticides needed. Plants can be sown in greenhouses
several months before the growing season, or be imported
from sourthern transplant production areas.

Second, transplanted crops may yield more than direct
seeded crops (Salter, 1976). This may be due to poor
direct-seeded seedling establishment in early spring
(Rabinowitch and Brewster, 1990). Transplants may be able
to withstand cold temperatures and post-emergence herbicides
better than young seedlings. Finally, transplanted onions
usually produce larger bulbs than seeded onions. It is
difficult to precision-seed raw onion seeds, which may
result in higher population and smaller bulbs. Over-
population leads to competition among plants, resulting in
smaller size bulbs at harvest (McGeary, 1985).

The major disadvantage of using transplants in onion
production is the relatively high cost of labor and planting
material (Naegely, 1986). Another potential problem of
using transplants is the potential to spread diseases from
one region to another on the planting material (Liptay,
1987).

In northern U.S. and southern Canada, most onion
transplants are imported from southern states, such as Texas
and Georgia (Nonnecke, 1989). The transplants are grown in

field beds and hand-pulled for shipping. Roots and shoots

3
are trimmed to facilitate handling and shipping. The
transplants are pulled when leaves and soil are dry to
reduce rot during shipment (Jones and Mann, 1963).

While southern transplants have fulfilled the need of
onion growers in the north for many years, many problems
have arisen. Scheduling of pulling and shipping transplants
in the south with planting time in the north is always a
problem (Liptay, 1987). If the weather condition is
unfavorable for planting, the transplants have to be stored.
These bare-rooted, trimmed and dried transplants may have a
limited storage time. They often rot or dry up, and become
unsuitable for transplanting if stored for extended periods
of time (Zandstra, 1991).

These factors have prompted growers to look for other
sources of transplants. Local greenhouses may be a good
alternative source. Local greenhouse production not only
would reduce losses of stored bare root seedlings, but also
would give growers more control over their own transplants.

There are currently a limited number of growers in
temperate regions, such as in Ontario, Canada, who produce
their own transplants. Some of them raise seedlings on soil
beds in greenhouses. However, these plants may not be
economically competitive with southern transplants (Fisher,
1985).

In recent years, commercial transplant growers have

introduced new methods of producing transplants. They grow

4

seedlings in small plug trays which have commonly been used

in ornamental plant production. In many vegetables, such as

tomato, pepper, celery, and cabbage, this method has been
competitive with bare root transplant production (Anonymous,

1980). Furthermore, plug-tray transplants have been

preferred over bare root seedlings because they facilitate

mechanized transplanting more successfully, and have better
plant establishment and production in the field (Anonymous,

1978; 1980; Fuller, 1981; Liptay, 1987). .However, few

studies have been done on production of onion transplants in

greenhouse trays.

The objectives of this study were to gain better
understanding of the influence of cell transplant production
method, plant density, age and nutritional condition of
transplants on growth, yield and quality of transplanted
onions.

The approaches were:

1. to compare growth, yield and quality of Spanish onions
grown from bare root transplants and from cell
transplants,

2. to determine the effect of multiseeded cell transplants
on growth, yield and quality of Spanish onions,

3. to determine the effect of cell transplant age and N-
nutrition during the seedling stage on growth, yield and

quality and storability of Spanish onions.

LITERATURE REVIEW

Transplanting is an activity of removing growing plants
from one soil or place and resetting them in another place
(Gove, 1981). A transplant is a young growing plant. Onion
transplant condition (Hawthorn, 1938; Baker and Wilcox,
1961) and transplanting methods (Maurer, 1983) have a
profound effect on growth and production of transplanted

onions.

Seed germination is the first step in seedling growth
and development. The germination process of onions is very
distinct. Jones and Mann (1963) and Rabinowitch and
Brewster (1990) illustrated that when germination starts the
cotyledon pushes root and stem out from the seed. The
cotyledon continuously elongates and the stem begins to
thicken. While the primary root starts to grow downward,
the cotyledon forms a sharp bend, the knee. The knee then
unbends and pulls the tip of the cotyledon out from the
soil.

The germination rate of onions is greatly affected by

6
temperature (Bierhuizen and Wagenvoort, 1974). Within the
range of 5°C to 25°C, the germination rate increases almost
linearly as temperature increases (Rabinowitch and Brewster,
1990).

After the seedling is established, the young onion
plant enters its juvenile stage. It continuously produces
new leaves and roots. The short stem elongates and
broadens. The new leaves rise from the apex on the upper
surface of the broad stem. Then, the leaf sheaths form a
firm structure commonly called a false stem. Later in
development, the false stem becomes a storage organ (Jones
and Mann, 1963; Rabinowitch and Brewster, 1990).

Jones and Mann (1963) also mentioned that new roots of
onions always grow from the youngest stem tissue. The onion
root system is one of the most limited among vegetable
crops. Goff in Jones and Mann (1963) reported that the root
system of a mature, growing onion grows about 16 to 18
inches deep and only a foot laterally from the bulb. Weaver
and Bruner (1927) found that the root system of a full grown
onion is about 1.5 feet laterally from its bulb and 2 to 3
feet deep. There are a greater number but less spreading
roots in onions grown in a compact soil compared to those

grown in loose soil.

Qni9n_transplant_nresustion_sxstem

Transplanting is one of the major economic inputs in
transplanted vegetable crop production. High quality
transplants are needed to get good production. The
importance of using high quality transplants in vegetable
crop production was well documented by Loomis (1925) and
Romshe (1954).

Onion transplant establishment in the field correlates
well with the seedling condition prior to transplanting.
Ramtohul and Splittstoesser (1979) proposed the correlation
between the bulbing ratio of the seedlings at transplanting
and plant establishment in the field. They determined that
transplants with a bulbing ratio above 3.37 did not
establish well in the field. Peffley, Ortiz, and Corgan
(1981) mentioned that field survival is also affected by
seedling age. Seedlings 90 days old or older survived
better than younger ones. The criterion of transplant
establishment is the resumption of vegetative growth within
3 weeks after transplanting (Peffley, Ortiz, and Corgan,
1981).

_ There are two reliable methods for vegetable transplant
production: bare root transplants and containerized
transplants (Lorenz and Maynard, 1988). The former method
has been widely used in onion transplant production. The

latter has not been commonly utilized for onions.

W

Bare root production is considered to be the simplest
method for production of onion transplants. Onion seedlings
are grown on raised beds of soil or on ridges in open
fields. After reaching about 7 mm in diameter or 18 to 25
cm high, they are harvested by pulling them out from the
soil bed (Jones and Mann, 1963; Riekels, Tiessen, and
Nonnecks, 1976; Fuller, 1981).

Jones and Mann (1963) and Riekels, Tiessen, and
Nonnecks (1976) also mentioned that with bare-rooted
transplants, pruning both leaves and roots was necessary to
help transplanting. Many reports, however, have shown that
pruning reduces onion yields (Hawthorn, 1938; Davis and
Jones, 1944; Baker and Wilcox, 1961; Lipe and Thomas, 1980;
Sabota and Downes, 1981; Rahim and Farooqe, 1983; Comrie,
1986).

Hawthorn (1938) studied the effect of transplant
pruning on yield of 'Yellow Bermuda' for 5 years. The
transplants were leaf, root, or both leaf and root pruned,
or unpruned. Unpruned transplants yielded more than pruned
transplants. Pruning both leaves and roots reduced yield
more thanonly leaf or root pruning did.

'Similar experiments were done on 'California Early
Red’, 'Stockton Yellow Globe', 'Red 21', 'San Joaquin’ and
’Crystal Grano' (Davis and Jones, 1944). They found that

pruning reduced yields of 'California Early Red', 'Stockton

9

Yellow Globe', and ’Red 21', but there was no significant
reduction in yield with 'San Joaquin' and 'Crystal Grano'.

Lipe and Thomas (1980) demonstrated the effect of
transplant top cutting on onion cultivar 'Yellow Sweet
Spanish Colorado No.6'. The seedlings were top out
retaining 75%, 50%, or 25% of the plant height. Unpruned
transplants were used as a control. They found that severe
leaf pruning decreased yields, but topping, up to one half
of plant height, had no significant effect on the yields.
Severe pruning also resulted in delayed maturity, reduced
bulb size, and increased neck diameter at harvest.

Sabota and Downes (1981) showed the relationship
between transplant pruning and yields of onion cultivar
'White Grano'. The treatments were unpruned, top, root, and
top and root pruned. All pruning treatments produced less
yield than the control did.

In a study of the effect of pre-planting top and root
pruning on growth and yields of 'Faridpuri Bhati’ cultivar,
Rahim and Farooqe (1983) found that yields were reduced with
an increase of top and root pruning.

Comrie (1986) revealed the effect of seedling
defoliation on growth and yield of 'Coledone Globe' and
’Australian Brown' cultivars. Compared to an unpruned
control, defoliation of 25% or 75% caused decreased
marketable bulb size in both cultivars.

The reduction of yields due to pruning was also

10
demonstrated on ’Downing Yellow Globe’ onions (Baker and
Wilcox, 1961). Plants were cut back 0, 30, 60, and 90% at
any age. The authors concluded that any defoliation during
the 6 leaf stage to the maximum leaf develOpment and early

bulb development adversely affected yields.

Containerizgd transplants

In containerized transplant production, seedlings are
raised in containers, such as paper pots, plastic pots, or
multicell plastic trays. This system limits seedling root
extension and helps growers control transplant quality by
managing moisture, nutrients or microenvironment (Carlson,
1990).

Royle (1980) proposed that container shapes influenced
seedling growth and establishment. Inverse pyramid cellular
trays facilitated root air pruning which promoted secondary
root growth resulting in better root growth following
transplanting. However, Cox (1984) found that there was no
effect of container shape on transplant establishment in the
field.

The size of containers dictated root volume of
transplants. Limited root growth in turn affected seedling
growth and development. It was well documented that large
container size ensured better seedling growth of pepper
(Weston, 1988; Bar-Tal, Bar-Yosef, and Kafkafi, 1990),

asparagus (Dufault and Waters, 1984) cauliflower and

11
broccoli (Dufault and Waters, 1985), and tomato (Weston and
Zandstra, 1986). Nevertheless, there has been limited study
done on determining the optimum cell size for field planting
of vegetable crops.

Wood (1982) demonstrated the effect of container size
on the yields of onions. 'Augusta', ’Hyper', ’Gustado',
'Robusta', and 'Buffalo' transplants were raised in
different sizes of peat blocks, trays, and paper pots. He
suggested that marketable bulb production increased when the
block or container size increased. In a study with 5, 14,
or 25 ml cells, Bull (1987) found that the highest yields of
'Elk' onion cultivar was obtained from the transplants with

the largest cells.

l!e! ! 0!. E! . J !

Nitrogen is one of the most important plant nutrients.
Depending on plant species, stage of development, and plant
part, nitrogen constitutes about 2 to 5 percent of plant dry
weight (Harschner, 1986). Vigorous growth and deep green
coloration of plants are associated with a sufficient supply
of nitrogen (Tisdale and Nelson, 1956).

Nitrogen management is one of most important aspects in
transplant production. Weston and Zandstra (1989) found
that a high level of N (400 mg N/liter) increased height,

leaf area, shoot and root dry weight, and reduced root to

12
shoot ratio of cell-grown tomato transplants at 5 weeks
after seeding. Nitrogen status in the plant tissue was
proposed to be an important factor for improving the growth
of transplanted tomato seedlings (Widders, 1989).
Nitrogen supply up to 250 ppm N increased celery

seedling size and quality (Dufault, 1985). However, higher
nitrogen application reduced the quality of celery seedlings

(Tremblay, Yelle, Gosselin, 1987).

arm-mm

Bulb development in onions is a day-length and
temperature dependent process. Bulb initiation and
development require long days even though the day-length
required varies among cultivars (Kate, 1964; Austin, 1972;
Steer 1980). In addition, no bulbing occurs in any onions
in a day-length under 9 hours (Kedar, Levy, Goldschmidt,
1975). At a given day-length, high temperature accelerates
the bulbing process (Rate, 1964; Steer, 1980).

When photoperiod and temperature are favorable, bulbs
begin to develop. The process is initiated by the
thickening of the base of the pseudostem and scale formation
from youngest leaves on the stem apex (Heath and
Hollies, 1965). New leaves produced during this stage,
therefore, have a relatively short blade. Some younger ones

even abort their blade and change their function and become

13
storage sheaths (Jones and Mann, 1963).

There are two indices of bulb initiation in onion:
bulbing ratio (Clark and Heath, 1962) and leaf ratio (Heath
and Hollies, 1965). The former is the ratio of the maximum
diameter of the leaf base to the minimum diameter of the
neck. Kedar gt,a1& (1975) considered a bulb to have formed
when the bulbing ratio is larger than 2. The latter is the
ratio of blade to sheath of a new growing leaf. When the
bulb initiates, the leaf ratio is normally less than 1.
Although leaf ratio is a more sensitive method to
investigate bulb initiation, bulb ratio is a more common
measurement in many studies. This is because leaf ratio is

a destructive method.

: J! J E c! E: !' i 2 !'

Transplant size and plant density are important factors
in onion yield. The yields of transplanted onions
correlated to the size of seedlings at transplanting.
Hawthorn (1938) suggested that medium size transplants
yielded more than larger or smaller transplants did.

Davis andJones (1944) concluded that transplants whose
diameter was between 10 to 13 mm had a greater yield than
smaller or larger transplants. The larger seedlings, above
13 mm in diameter, tended to produce a high percentage of

seed stalks. Sabota and Downes (1981) found that

l4
transplants whose diameter was larger than 0.6 cm produced
more marketable size bulbs than smaller transplants.

With respect to plant density, Mondal, Brewster,
Morris, and Butler (1986) revealed that high plant density
accelerated plant maturity. McGeary (1985) found that
increasing plant densities resulted in reduced plant size,
plant fresh and dry weight, bulb size and days to maturity.
Yield-density relationship of onions was, up to 445 plants
m9, asymptotic (Frappel, 1973) and parabolic when plant
densities were increased up to more than 625 plants m4

(McGeary, 1985).

15

LITERATURE CITED

Anonymous. 1978. Caught Speedling! Amer. Veg. Grower.
26(11):11,49.

Anonymous. 1980. Speedling into the future. Amer. Veg.
Grower. 28(5):12,14,16.

Austin, R.B. 1972. Bulb formation in onions as affected by
photoperiod and spectral quality of light. J. Hort.
Sci. 47:497-504.

Baker, R.S. and G.E. Wilcox. 1961. Effect of foliage
damage and stand reduction on onion yield. Proc. Amer.
Soc. Hort. Sci. 78:400-405.

Bar-Tal, A., B. Bar-Yosef and U. Kafkafi. 1990. Pepper
transplant response to root volume and nutrition in
the nursery. Agron. J. 82:989-995.

Bierhuizen, J.F. and W.A. Wagenvoort. 1974. Some aspect of
seed germination in vegetables. I. The determination
and application of heat sums and minimum temperature
for germination. Scientia Hort. 2:213-219.

Bull, P.B. 1987. Boosting onion. Cell transplants. New
‘Zealand Commercial Grower. 42(5):17. Hort. Abstr.
OC059-01979.

Carlson, W.H. 1990. Controlling transplant height. Amer.
Veg. Grower. 38(4):16-18.

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physiology of the onion plant. V. An investigation
into the growth substance content of bulbing onions.
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Comrie, A.G. 1986. The effect of partial defoliation of
onion seedlings on their subsequent growth, yield and
keeping quality. Acta Hort. 194:125-132.

Cox, E.F. 1984. The effect of shape of compost blocks on
the propagation, transplant establishment and yield of
four vegetable species. J. Hort. Sci. 59:205-212.

16

Davis, G.N. and H.A. Jones. 1944. Experiments with the
transplant onion crops in California. Berkeley Agr.
Expt. Sta. Bul. 628. California.

Dufault, R.J. 1985. Relationship among nitrogen,
phosporus, and potassium fertility regimes on celery
transplant growth. HortScience 20(6):1104-1106.

Dufault, R.J. and L. Waters. 1984. Propagation methods
influence asparagus transplant quality and seedling
growth. HortScience 19(6):866-868.

Dufault, R.J. and L. Waters. 1985. Container size
influences broccoli and cauliflower transplants
growth but not yield. HortScience 20(4):682-684.

Fisher, G.A. 1985. Preliminary report on processing
tomato transplant production 1985. Ontario Ministry of
Agriculture and Food. Chatham. Ontario.

Frappell, B.D. 1973. Plant spacing of onions. J. Hort.
Sci. 48:19-23.

Fuller, D.J. 1981. Propagating and transplanting
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Gove, P.B. 1981. Webster's third new international
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Hawthorn, L.R. 1938. Cultural experiments with Yellow
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Heath, O.V.S. and H.A. Hollies. 1965. Studies in the
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16(46):128-144.

Jones, H.A. and L.R. Mann. 1963. Onion and Their Allies.
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Kato, T. 1964. Physiological studies on the bulbing and
dormancy of onion plant. III. Effects of external
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Soc. Hort. Sci. 33(1):53-61. .

Kedar, N., D. Levy and E.E. Goldschmidt. 1975.
Photoperiodic regulation of bulbing and maturation of
Bet Alpha onions (511133 9gp; L.) under decreasing day-
length conditions. J. Hort. Sci. 50:373-380.

17

Lipe, W.N. and D. Thomas. 1980. Effects of transplant
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Liptay, A. 1987. Preview of transitional development of
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Loomis, W.E. 1925. Studies in the transplanting of
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63 pp.

Lorenz, O.A. and D.N. Maynard. 1988. Knott's Handbook for
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Marschner, H. 1986. Mineral Nutrition of Higher Plants.
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Maurer, A.R. 1983. Soil blocks for transplants. Research
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McGeary, D.J. 1985. The effect of plant density on shape,
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Nonnecke, I.L. 1989. Vegetable production. An AVI book.
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Hort. Abstr. OC054-06144

18

Ramtohul, M. and W.E. Splittstoesser. 1979. The effect of
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Weston, L.A. and B.H. Zandstra. 1986. Effect of root
container size and location of production on growth and
yield of tomato transplants. J. Amer. Soc. Hort. Sci.
111(4):498-501.

Weston, L.A. and B.H. Zandstra. 1989. Transplant age and N
and P nutrition effects on growth and yield of
tomatoes. HortScience 24(1):88-90.

l9
Widders, I.E. 1989. Pretransplant treatments of N and P
influence growth and elemental accumulation in tomato
seedlings. J. Amer. Soc. Hort. Sci. 114(3):416-420.

Wood, M. 1982. Transplant bonuses for the onion crops.
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Zandstra, B.H. 1991. Personal communications.

CHAPTER II

A COMPARISON OF GROWTH, YIELD, AND QUALITY OF SPANISH ONIONS
GROWN FROM BARE ROOT AND CELL TRANSPLANTS

Abstract

Seedlings of three Sweet Spanish onion cultivars,
'Sweet Sandwich', 'Yula', and 'Vega', were grown in either
open trays or 200 cell plastic trays in the greenhouse. All
seedlings were transplanted into the field at 12 weeks after
seeding with a Mechanical Transplanter Model 4000. Seedling
size at transplanting was greater with open trays than 200
cell trays. At 8 weeks after transplanting, plant size was
similar with either bare root or cell transplants. Time to
maturity was not affected by the type of transplants. On
Houghton muck, yield of bulbs >76 mm at harvest was greater
with cell transplants than bare root transplants. On
Colwood-Brookston loams, there was no significant difference
observed in yield or bulb size of onions from cell and bare
root transplants. All cultivars showed similar responses to

the types of transplants.

20

21
introduction

Most onion transplants are grown in the field and
pulled with bare roots. Transplant growers usually sow
seeds in rows at the rate of 19 to 22.5 kg/ha (Jones and
Mann, 1963). They harvest the seedlings by hand after the
plant size is suitable for transplanting, usually 12-14
weeks after seeding.

Onion transplanting was commonly done by hand.
Increasing labor cost has encouraged growers to mechanize
transplanting. The use of mechanized transplanters,
however, requires transplants with certain characteristics.
Using a mechanized celery transplanter to transplant onions
in Texas, for instance, showed the need for severe pruning
to facilitate transplanting (Sabota and Downes, 1981).
However, previous research has shown that pruning reduced
the yield of onions.

Growing transplants of some species in the greenhouse
has allowed growers to avoid leaf pruning while still
producing satisfactory plants (Carlson, 1990). They are
able to control the size of seedlings of some species by
properly managing nutrition, moisture, temperature, and
other factors. Therefore, without pruning, the required
size transplants for mechanized transplanting could be grown
(Fuller 1981).

Compared to bare root production, growing seedlings in

22
containers allows transferring plants with less root
disturbance (McKee, 1981). This method also transfers a
small reservoir of water and nutrients on which the
transplants can draw before new roots are established
(Fuller, 1981). Transplants grown in containers are usually
more uniform because there is sufficient environment to grow
for each individual transplant (Liptay, 1987).

Recently, vegetable transplants grown in cellular
trays have been preferred over the bare root transplants.
Besides their success in facilitating mechanized
transplanting, cell transplants ensure high plant survival
in the field (Anonymous, 1978, 1980). However, very few
studies have been done on the use of multicellular trays in
onion transplant production.

The objective of this study was to compare the growth,
yield and quality of Spanish onions grown from bare root and

from cell transplants.

W

W

.Seeds of cultivars 'Sweet Sandwich', 'Yula', and 'Vega’
were sown in either open trays or 200 cell plastic flats
(Blackmore Transplanter Co, Ypsilanti, Michigan) containing
peat (Baccto Professional Planting Mix, Michigan Peat Co.),

on 17 February 1990, in the MSU Plant Science greenhouse,

23
East Lansing, Michigan. A 200 cell tray is a 27 cm wide, 53
cm long, and 4 cm high consisting of 200 discrete, inverse
pyramidal compartments each with a surface area of 1.8 cm2
and a volume of 4.6 amt In the open trays, seeds were sown
in rows at the rate of 400 seeds per tray, 100 seeds per
row. Three weeks after seeding, the seedlings were thinned
to 50 plants per row. In the 200 cell trays, two seeds were
planted in each cell. When they were 3 weeks old, the
seedlings were thinned to one seedling per cell. There were
four open and four cell trays of each cultivar.

All seedlings were fertilized with solution of 20N-
8.6P-16.6K fertilizer at the rate of 375 mg/liter, equal to
75 ppm N, 32 ppm P and 62 ppm K. Fertilizer was applied
with a watering can weekly, starting 2 weeks after seeding.
Water was applied as needed.

On 14 May 1990, 10 plants from each tray were pulled,
washed, and measured for fresh weight, shoot and root
length, and neck and leaf base diameter. The shoots and
roots were separated and dried in an oven at 49°C for 5 days
and then weighed.

Before being transplanted, the seedlings were topped,
retaining about 10 cm of leaf, so that they would pass
through the transplanter easily. The roots of bare-root
plants were trimmed for the same reason.

The experiment was conducted in the field at the

Michigan State University Muck Research Farm (Muck Farm),

24
Laingsburg, Michigan, from May to September 1990. The soil
type was a Houghton muck (Euic, Mesic, Typic, Medisaprist),
pH 6.3, with 80% organic matter. Plants were transplanted
on 15 May 1991 with a Mechanical Transplanter Model 4000.
It is a machine with four horizontally placed cone-shaped
cups which is driven by an independent drive wheel. The
system is mounted on a tractor, and requires one operator
per unit for a row. The operator puts seedlings into the
cone-shaped cups, which turn and drop the seedlings into an
open furrow precisely behind a small device which ejects the
seedlings into the closing furrow to pass between two
inclined press wheels.

Fertilizer of 80 kg N and 86 kg P per ha as diammonium
phosphate was broadcasted on 27 April, followed by 274 kg K
per ha as potassium chloride on 30 April 1990. On 25 June
1990, plants were sidedressed with 103 kg N per ha as urea.
Pesticides and irrigation were applied as necessary.

The experimental design was a Randomized complete
block, with 4 replications. Cultivar ('Sweet Sandwich',
’Yula' and 'Vega') and transplant type (bare root and cell
transplant) were arranged factorially. Plots were 1.5 m
wide and 7.6 m long. Each plot consisted of two rows, 0.76
m apart. Plant spacing was 15 cm apart in rows.

On 14 July 1990, 10 plants from each plot were
collected. Plant height, neck diameter, bulb diameter and

fresh weight were measured. Plant dry weight was measured

25
after the samples were dried in an oven at 49°C for 7 days.

Plant maturity was determined by the percentage of
plants whose leaves had lied down. It was considered to be
mature when 25% or more plants had fallen down (Jones and
Mann, 1963).

Onions were harvested on 5 September 1990. Five meters
of two rows in each plot were pulled and topped by hand.
Harvest weight was measured in the field. Onions were
graded for size and quality after being cured for 4 weeks in
a ventilated room.

Data was analyzed by Analysis of Variance, using MSTAT.
Mean separation was done with the Least Significant

Difference (LSD) at the 5% level, or higher.

t ' u . se ente .

Seedlings were grown as mentioned earlier. The
experiment was conducted at the Michigan State University
Horticultural Research Center (Hort Farm), East Lansing,
Michigan, from May to September 1990. The soil type was a
Colwood-Brookston loams (Fine-loamy, Mixed, Mesic, Typic,
Argiaquolls), pH 6.1-6.5, with 1.0-3.0% organic matter.
Transplanting was done on 29 May 1990, with a Mechanical
Transplanter Model 4000.

The experimental design was a Randomized complete block
with 3 replications. Cultivar ('Sweet Sandwich', 'Yula' and

'Vega') and type of transplant (bare root and cell

26
transplant) were arranged factorially. Plot size was 0.76 m
wide and 7.6 m long. Each plot consisted of 1 row with
plant spacing 15 cm apart in the row.

Fertilizer was broadcasted on 23 May 1990 at the rate
of 67 kg N, 58 kg P and 111 kg K per ha as 10N-8.6P-16.6K
fertilizer. The field was sidedressed with 18.5 kg N per ha
as ammonium nitrate on 5 and 25 July 1990. Pesticides and
irrigation were applied as necessary.

Plant maturity was evaluated as mentioned above. On 20
September 1990, 5 meters of row in each plot were pulled and
topped. Harvest weight was measured in the field. The
onions were graded for size and quality after curing for 4

weeks.

27

Results
. e o c ' a o eed ' an owth

yield. and quality,

There was no difference between cultivars in plant
size or weight at transplanting or 8 weeks after
transplanting at the Muck Farm (Table 1, 2, 3).

In experiment 1, Muck Farm, 'Yula' matured earliest,
followed by 'Sweet Sandwich', and 'Vega’ (Table 4). 'Sweet
Sandwich' yielded less than the other cultivars. 'Yula’ and
'Vega' yielded similarly. ’Vega’ produced a greater
percentage of large and jumbo bulbs than 'Sweet Sandwich'
and 'Yula'. 'Sweet Sandwich' and 'Yula' produced similar
bulb size at harvest.

In Experiment 2, Hort Farm, 'Yula’ matured earliest at
13.8 weeks after transplanting, while 'Sweet Sandwich' and
'Vega' matured similarly at slightly over 15 weeks after
transplanting (Table 5). 'Vega' yielded the most total
weight but also had the highest percentage of culls. 'Sweet
Sandwich' and 'Yula’ yielded similarly. 'Vega’ produced
more bulbs over 76 mm at harvest. Yields of bulbs >76 mm

were the same for 'Sweet Sandwich' and 'Yula'.

b !;e ’ ' 1°;' '1?! t! 7 O!“ ‘L! .ewd

The height, root length, neck and bulb diameter, shoot

fresh and dry weight of seedlings grown in open trays were

28

Table 1. A comparison of the size of seedlings from bare
roots and cells at transplanting at the MSU Muck
Research Farm.

 

 

Seedling Root Neck Bulb Bulb/neck
height length diam. diam. ratiol
TREATMENT (cm) (cm) (mm) (mm)
011nm
Sweet Sand. 17.7 9.3 4.3 8.7 2.0
Yula 17.9 10.1 4.1 9.3 2.2
Vega 18.5 9.6 4.4 9.3 2.1
F test NS as us as as
W
Bare root 23.9 12.2 4.8 10.4 2.2
Cell 12.2 7.1 3.7 7.8 2.1
F test * * * * NS
C X T us NS us as NS
cv (t) 15.7 15.0 11.0 10.3 10.2

 

1The average of bulb to neck ratio of 8 and 10 plants for
cultivars and types of transplants, respectively.
us, not significant; *, significant at 5% level.

29

Table 2. A comparison of plant weight of seedlings from
bare roots and cells at transplanting at the MSU Muck
Research Farm.l

 

 

Shoot Root Shoot Root Root/shoot
fresh wt. fresh wt. dry wt. dry wt. ratio
TREATMENT (9) (9) (9) (9) (dry wt-)2
m
Sweet Sand. 2.14 0.58 0.20 0.04 0.27
Yula 2.16 0.44 0.19 0.03 0.21
Vega 2.44 0.52 0.20 0.04 0.22
F test NS NS us NS us
W
Bare root 3.30 0.52 0.30 0.04 0.14
Cell 1.23 0.50 0.10 0.03 0.35
F test * us * NS *
C x T NS as us NS NS
CV (t) 12.12 11.81 11.87 15.14 12.43

 

‘Data were transformed by 7; for analysis; actual weights
are presented.

2The average of root to shoot ratio of 8 and 10 plants for
cultivars and types of transplants, respectively.

us, not significant; *, significant at 5% level.

30

Table 3. A comparison of plant size and weight of onions
from bare root and cell transplants at 8 weeks after
transplanting in the field, MSU Muck Research Farm.

 

 

Plant Neck Bulb Bulb/1 Fresh Dry
height diam. diam. neck weight weight
TREATMENT (cm) (mm) (mm) ratio (9) (9)
Sweet Sand. 74.4 21.0 35.0 1.7 129.5 9.4
Yula 76.3 19.4 34.2 1.8 115.9 8.1
Vega 78.3 20.3 32.3 1.6 116.8 8.0
F test us as as as us us
Transplant
Bare root 77.6 20.5 32.4 1.6 126.6 8.8
Cell 75.1 19.9 35.3 1.8 114.6 8.1
F test as ' as us as us us
C X T us us us NS NS us
cv (t) 4.5 6.4 16.9 18.8 14.7 15.3

 

‘The average of bulb to neck ratio of 8 and 10 plants for
cultivars and types of transplants, respectively.
us, not significant.

31

Table 4. A comparison of the yield and quality of Spanish
onions grown from bare root and cell transplants, MSU
Muck Research Farm.

 

Weeks‘ Harvest Bulb size3 Est.yield
to ma- weight (%1by weight) of >76 mm
TREATMENT turity (kg/plot)2 Small’Medium Large Jumbos Cull"’(MT/ha)°

 

Cultivar

Sweet San. 15.0 31.7 1.6 49.5 45.7 1.6 1.6 36.6
Yula 14.0 34.4 1.5 47.0 44.0 3.6 3.9 38.6
Vega 15.7 34.8 2.0 35.7 57.1 2.6 2.6 38.5
F test * * us * * NS NS *

LSD (0.05) 0.8 1.6 - 10.6 7.8 - - 1.7
rans a t '

Bare root 14.8 31.4 3.0 49.8 43.7 2.2 1.3 35.6
Cell 15.0 35.7 0.6 38.3 54.2 2.8 4.0 40.2
F test NS * * * * as t t

C X T NS NS NS NS us NS NS NS
CV (%) 5.0 4.4 29.0 22.6 14.9 49.5 24.4 4.3

 

‘Maturity defined as 25% leaves down.

2Plot size was 7.6 m2

3Bulb size: Small: <76 mm; Medium: 76-102 mm; Large: 102-127 mm
Jumbo: >127 mm in diameter.

‘Cull consisted of rotten, sprouted, and split bulbs.

’Data were transformed by arcsin/Ty+1) for analysis; actual values

are presented; LSD is not presented for transformed data.

‘Yields were estimated by combining medium and large bulb weights

after grading and multiplying by the conversion factor 1.32.

us, not significant; *, significant at 5% level.

32

Table 5. A comparison of the yield and quality of Spanish
onions grown from bare root and cell transplants, MSU
Horticultural Research Center.

 

 

 

 

Weeks' Harvest Bulb size3 Est.yield
to ma- weight (2 by t) of >76 mm
TREATMENT turity (kg/plot)’Small Medium Large Jumbo Cull‘-‘(MT/ha)6
Cultim
Sweet San. 15.2 6.9 56.9 43.1 0.0 0.0 7.6
Yula 13.8 6.8 42.0 54.1 3.9 0.0 9.6
Vega 15.3 8.8 25.1 70.9 2.0 2.0 16.3
F test * * * * NS * *
LSD (0.05) 0.9 1.1 16.8 16.5 _ - 3.8
W
Bare root 14.8 7.1 40.1 55.1 3.9 0.9 10.8
Cell 15.0 7.8 42.6 56.9 0.0 0.5 11.5
F test as NS us as us as NS
C X T us NS as us as as us
CV (%) 4.5 11.1 31.7 22.9 57.9 35.8 27.7

 

‘Maturity defined as 25% leaves down.

2Plot size was 3.8 m3.

3Bulb size: Small: <76 mm; Medium: 76-102 mm;
Jumbo: >127 mm in diameter.

‘Cull consisted of rotten, sprouted, and split bulbs.

’Data were transformed by arcsinJIy+1) for analysis; actual values

are presented; LSD is not presented for transformed data.

oYields were estimated by combining medium and large bulb weights

after grading and multiplying by the conversion factor 2.63.

us, not significant; *, significant at 5% level.

Large: 102-127 mm

33
greater than those of seedlings grown in cell trays at
transplanting (Table 1,2). There was no difference in root
fresh and dry weight. The root to shoot ratio of cell
transplants was higher than that of transplants grown in
open trays (Table 2). There was no different in size of
plants at 8 weeks after transplanting (Table 3).

In Experiment 1, Muck Farm, there was no difference in
time to maturity between plants grown from bare root and
cell transplants. However, total yield and yield of bulbs
>76 mm of plants grown from cell transplants was higher than
that of plants grown from bare root transplants (Table 4).
Plants from cell transplants produced slightly more culls
than plants from bare roots.

In Experiment 2, Hort Farm, there was no significant
difference in time to maturity, yield and bulb distribution
between plants grown from bare root and cell transplants.

In both experiments, there was no interaction between

cultivars and types of transplants at any time.

Di 8. i : J .

Plant size of transplants grown in open trays at
transplanting was greater than those in 200 cell flats.
This may be due to greater space and medium in which roots

grow in open trays than in discrete cells. Previous

34
research showed that larger root containers ensured better
transplant growth (Dufault and Waters, 1984, 1985; Weston
and Zandstra, 1986; Weston, 1988; Bar-Tal, Bar-Yosef, and
Kafkafi, 1990). Knavel (1965) mentioned that large
containers provided sufficient medium for root development
to support plants to the transplanting stage. On the other
hand, plants grown in small containers often experienced
nutrient starvation (Knavel, 1965) and were very dependent
on a routine water and nutrient supply (Fuller, 1981).
Those conditions caused a reduction in growth of transplants
raised in cell trays in the greenhouse (Heiden gt_a1.,
1989).

Root to shoot ratio was greater with plants grown in
cells. This was due to less weight of shoots of plants in
cells, while root weight of plants from both types of trays
was the same (Table 2).

At 8 weeks after transplanting, the size of plants from
cells was similar to that from bare-root plants, even though
cell transplants were smaller at transplanting. They were
probably able to catch up with bare-root plants because of
less root disturbance at transplanting. Benoit and
Ceustermans (1987) found that leeks from cells had better
growth than those from bare roots. McKee (1981) reported
that reducing root disturbance and root loss at
transplanting improved plant growth. Plants grown in

discrete modules undergo less transplant shock at

35
transplanting than bare root transplants.

In the Muck Farm experiment, total yield of bulbs >76
mm was greater with cells than bare root transplants. This
result agreed with Maurer (1983) that onions from
containerized transplants had greater yield than bare root
transplants. The lower yield of plants from bare root
transplants was probably related to leaf and root pruning at
transplanting, which had to be done to get them through the
transplanter. Topping and root trimming of transplants may
adversely affect the final yield of onions at harvest.
Previous research showed that pruning reduced yield of
onions (Hawthorn, 1938; Davis and Jones, 1944; Baker and
Wilcox, 1961; Lipe and Thomas, 1980; Sabota and Downes,
1981; Rahim and Farooqe, 1983; Comrie, 1986). McKee (1981)
reported that cell transplants of many crops had greater
yield because they suffered less transplant shock at
transplanting than bare root transplants.

In summary, seedling size at transplanting was greater
with open trays. Plant size at 8 weeks after transplanting
was similar with either bare root or cell transplants. Time
to maturity was not affected by the type of transplants. At
the Muck Farm, total yield and bulb size at harvest were
greater with cell transplants. Yield of bulbs >76 mm was
4.6 MT/ha greater with cells over bare root transplants. At
the Hort Farm, yield and quality of Spanish onions were not

affected by the type of transplants. In both experiments,

36
there was no interaction observed between cultivar and type

of transplants at any time.

37
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Davis, G.N. and H.A. Jones. 1944. Experiments with the
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influences broccoli and cauliflower transplants
growth but not yield. HortScience 20(4):682-684.

Fuller, D.J. 1981. Propagating and transplanting
vegetables. Ministry of Agriculture, Food and Fishery.
,Ref. Book 344. England.

Hawthorn, L.R. 1938. Cultural experiments with ’Yellow
Bermuda' onions under irrigation. Texas Agr. Expt.
Sta. Bul. 561:1-30.

Heiden, R.W., W.N. Carlson, R.D. Heins, and L.W. Ewart.
1989. Producing vegetable transplants as bedding
plants. Mich. State Univ. Ext. Bul. E-2148.

38

Jones, H.A. and L.R. Mann. 1963. Onion and Their Allies.
Interscience Publ. Inc. New York. 283 pp.

Knavel, D.E. 1965. Influence of container, container size,
and spacing on growth of transplants and yields in
tomato. Proc. Amer. Soc. Hort. Sci. 86:582-586.

Lipe, W.N. and D. Thomas. 1980. Effects of transplant
pruning and orientation on plant survival, yield and
size distribution. HortScience 15(1):28-29.

Liptay, A. 1987. Preview of transitional development of
processing tomato transplant production and/or use in
Ontario, Canada. Acta Hort. 220:211-215.

Maurer, A.R. 1983. Soil blocks for transplants. Research
Review. Res. Sta. Agassiz. May-August:10-11. Hort.
Abstr. OC054-03355.

McKee, J.M.T. 1981. Physiological aspect of transplanting
vegetables and other crops. II. Methods used to
improve transplant establishment. Hort. Abstr.
51(6):355-368.

Rahim, H.A. and A.M. Farooqe. 1983. Effect of pre-planting
top and root pruning of onion transplants on the growth
and yield of onions. Punjab Veg. Grower. 17/18:21-24.
Hort. Abstr. OC054-06144

Sabota, C.M. and J.D. Downes. 1981. Onion growth and yield
on relation to transplant pruning, size, and depth of
planting. HortScience 16(4):533-535.

Weston, L.A. 1988. Effect of flat cell size, transplant
age, and production site on growth and yield of pepper
transplants. HortScience 23(4):709-711.

Weston, L.A. and B.H. Zandstra. 1986. Effect of root
container size and location of production on growth and
yield of tomato transplants. J. Amer. Soc. Hort. Sci.
111(4):498-501.

CHAPTER III

THE EFFECT OT NULTISBSDBD CELL TRANSPLANTS
ON GRONTN, YIELD AND QUALITY OF SPANISH ONIONS

ADEEIQEL

The seedlings of three Sweet Spanish onion cultivars,
'Sweet Sandwich', 'Yula', and 'Vega', were.raised in 200
cell trays with 1, 2, or 3 seedlings per cell. Fewer
transplants per cell resulted in larger plants at
transplanting and at 8 weeks after transplanting.
Multitransplants matured slightly sooner and produced
greater total yield, but had smaller bulbs at harvest
compared to single transplants. On Houghton muck, total
yield increased by 40% and 65% with 2 and 3 plants per cell,
respectively. .Yield of bulbs >76 mm was greatest with 2 and
3 transplants per cell. On Colwood-Brookston loams, 2 and 3
plants per cell increased total yield by 26% and 50%,
respectively. Yields of bulbs >76 mm was greatest with
single transplants. In both locations, all cultivars

responded similarly.

39

40
Introduction

Spanish onions are usually transplanted singly 8 to 15
cm apart in rows 45 to 60 cm apart. This gives the onions
sufficient room to expand and form large, spherical bulbs.
Onions have the ability to push out into unused space and
form large bulbs, even when planted very close together
(Jones and Mann, 1963; Rabinowitch and Brewster, 1990).

Onion yields are directly related to plant population.
However, cultural practices and cost of plants limit plant
spacing and population. The components of plant spacing are
plant arrangement and plant density (Peirce, 1987). Plant
arrangement is defined as the ratio of the distance of
plants between and within the row, and plant density is the
number of plants per unit area.

In the optimum plant arrangement, plant density may
control bulb size and production. McGeary (1985) and
Rabinowitch and Brewster (1990) reported that bulb size was
reduced with an increase in plant density. The relationship
of plant density and yield in onions was asymptotic
(Frappel, 1973) or parabolic (McGeary, 1985) depending on
the range of plant population per unit area.

Producing plants in cells in the greenhouse is more
expensive than producing plants in the field. It may be
possible to increase the number of plants per cell and take

advantage of onions' ability to push out into unused space,

41
and thus reduce the number of cells needed per unit area.
The objective of this study was to determine the effect
of the number of seedlings per cell on growth, yield and

quality of Spanish onions in the field.

W

,A!‘ iu-nt nu t -_: 9 .1 : o- z , - . i-sea_ 1
m...

Seeds of cultivars 'Sweet Sandwich', (Yula', and 'Vega’
were sown in 200 cell plastic trays (Blackmore Transplanter
Co., Ypsilanti, Michigan) containing peat (Baccto
Professional Planting Mix, Michigan Peat Co., Michigan) on
18 February 1990, in the MSU Plant Science greenhouse, East
Lansing, Michigan. The rate of seeding was 2, 3, or 5 seeds
per cell. At 3 weeks after seeding, the seedlings were
thinned to 1, 2, or 3 seedlings per cell, respectively.

All seedlings were fertilized with a complete 20N-8.6P-
16.6K fertilizer at the rate of 1.5 g fertilizer diluted in
4 liters water, equal to 75 ppm N, 32 ppm P and 62 ppm X
weekly starting from 2 weeks after seeding, with a watering
can. The seedlings were watered daily. Pesticides were
applied as needed.

On 14 May 1990, plants in 10 cells of each tray were
harvested. The seedlings were washed and measured for plant
height, shoot and root fresh weight, and neck and leaf base

diameter. Shoot and root dry weight were measured after the

42
transplants were dried in an oven at 49° C for 5 days. The
average data was used in analyses.

The experiment was established at the Michigan State
University Muck Research Farm (Muck Farm), Laingsburg,
(Michigan, from May to September 1990. The soil type was a
Houghton muck, pH 6.3, with 80% organic matter. The plants
were transplanted in the field on 15 May 1990, with a
Mechanical Transplanter Model 4000. Fertilizer of 80 kg N,
86 kg P per ha as diammonium phosphate was broadcasted on 27
April, followed by 174 kg K per ha as potassium chloride on
30 April 1990. Plants were sidedressed with 103 kg N per ha
as urea on 25 June 1990. Pesticides and irrigation were
applied as necessary.

The experimental design was a Randomized complete block
with 4 replications. Cultivar (’Sweet Sandwich', 'Yula’ and
'Vega') and the number of transplants per cell were arranged
in factorial order. Plot size was 7.6 m long and 1.5 m
wide. Each plot contained two rows, 0.76 m apart. Plant
spacing was 15 cm apart in the rows.

On 14 July, 10 plants or clusters of onions in each
plot were harvested. Plant height, neck and bulb diameter,
and plant fresh weight were measured. Plant dry weight was
evaluated after the samples were dried in an oven at 49°C:
for 7 days. The average data was used in analyses. Plant
maturity was defined as mentioned earlier. Onions were

harvested on 5 September 1990. Five meters of two rows in

43
each plot were pulled and topped by hand, and weighed. The
onions were stored in a dry building for 4 weeks. They were
then graded for size and quality. Bulbs from each plot were
measured for length and diameter. The shape of bulbs was
determined by the diameter to length ratio of bulbs. The
bulb was spherical when the ratio was 1.0, flat when the
ratio was greater then 1.0, and tall when the ratio was less
than 1.0.

Data analyses were done as mentioned earlier.

A97 'uil fl u- 7!): 0 anti 9; :7 9 2° . - t

B§§§§IQE_QQDE§LL
The experiment was done at Michigan State University
Horticultural Research Center (Hort Farm), East Lansing,
Michigan, from May to September 1990. The soil type was a
Colwood-Brookston loams, pH 6.1-6.5, with 1.0-3.0% organic
matter._ Seedlings were raised and planted with the methods
mentioned above. Transplanting was done on 29 May 1990.

The experimental design was a Randomized complete block
with 3 replications. Cultivar ('Sweet Sandwich', 'Yula’,
and 'Vega’) and the number of seedlings (1, 2, and 3
seedlings) per cell were arranged factorially. Plot size
was 0.76 m wide and 7.6 m long consisting of 1 row. Plant
spacing was 15 cm apart in the row.

Fertilizer of 67 kg N, 58 kg P and 111 kg K per ha as
10N-8.6P-16.6K was broadcasted on 23 May 1990. Nitrogen was

sidedressed at 18.5 kg per ha as ammonium nitrate on 5 and

44
25 July 1990. Pesticides and irrigation were applied as
necessary. Lorsban was used to control onion maggots.
Plant maturity was defined as described earlier. On 20
September 1990, 5 m of onions in each plot were pulled and
topped by hand and were weighed. The onions were graded for
size and quality after being cured for 4 weeks. Bulbs were

selected randomly from each plot and measured for diameter

and length.
Bosnlts
a 2- O 1 _-'.L.°‘ 0 1‘0711‘18 e 0!
s 1 wt e a s
oniontLiLtanioiol

Fewer seedlings per cell resulted in larger size per
plant at transplanting (Table 6). In general, single
seedlings were larger in size than multiseedlings.
Transplant height, neck and leaf base diameter, were greater
with single transplants than with multitransplants per cell.

A similar trend was observed on seedling weight.

Single transplants weighed more than multiplants (Table 7).
Shoot and root fresh weight, and shoot and root dry weight
were reduced with more transplants per cell. Nevertheless,
root to shoot ratio was not affected by the number of
seedlings per cell.

A greater number of transplants per cell resulted in

smaller plants at 8 weeks after transplanting (Table 8).

45

Table 6. The effect of multiseeded cell transplants on
seedling size of Spanish onions at transplanting, 12
weeks after seeding.

 

 

Seedling Neck Bulb Bulb/neck
height diameter diameter ratiol
TREATMENT (cm) (mm) (mm)
Cnltixar
Sweet Sand. 9.3 2.9 6.0 2.0
Yula 11.4 3.2 7.3 2.3
Vega 10.3 3.4 7.3 2.1
F test * * * *
LSD (0.05) 1.1 0.2 0.7 0.1
No, of seedlings .
1/cell 10.7 3.4 7.6 2.2
2/cell 10.3 3.2 6.8 2.1
3/cell 10.0 2.9 6.1 2.1
F test * * *, us
LSD (0.05) 0.6 0.2 0.7 -
C X No . NS NS NS NS
cv (t) 6.7 9.2 8.6 8.0

 

1The average of bulb to neck ratio of 12 plants.
NS, not significant; *, significant at 5% level.

46

Table 7. The effect of multiseeded cell transplants on
seedling weight of Spanish onions at transplanting, 12
weeks after seeding. .

 

 

Shoot Root Shoot Root Root/shoot
fresh wt. fresh wt. dry wt. dry wt. ratio

TREATMENT (9) (9) (g) (9) (dry wt-)‘
Cultivar

Sweet Sand. 0.63 0.33 0.06 0.024 0.42
Yula 0.93 0.34 0.08 0.024 0.32
Vega 0.85 0.35 0.07 0.024 0.35

F test * ns ns us *

LSD (0.05) 0.19 - - - 0.06
N .

l/Cell 1.04 0.47 0.08 0.031 0.38
2/cell 0.77 0.32 0.07 0.023 0.36
3/Ce11 0.59 0.24 0.05 0.018 0.36

F test * * * * NS
LSD (0.05) 0.13 0.04 0.01 0.004 -

C X No. us us as as us

CV (%) 19.17 13.50 21.77 21.99 16.55

 

1The average of root to shoot ratio of 12 plants
NS, not significant; *, significant at 5% level.

Table 8.

The effect of number of seedlings per cell on

plant size and weight of Spanish onions at 8 weeks
after transplanting, MSU Muck Research Farm.

 

 

Plant Neck Bulb Bulb/ Fresh Dry
height diam. diam. neck weight weight
TREATMENT (cm) (mm) (mm) ratio1 (9) (9)
guitar
Sweet Sand. 69.7 18.9 27.3 1.43 95.0 6.7
Yula 74.9 17.2 30.0 1.74 88.2 6.2
Vega 75.1 17.5 24.0 1.36 85.5 5.8
F test * * * * NS NS
LSD (0.05) 2.3 0.3 2.2 0.06 - -
Mjooolinos
1/cell 75.4 20.6 33.2 1.61 122.6 8.7
2/cell 72.5 17.3 25.7 1.59 80.5 5.6
3/cell 71.7 15.7 22.3 1.42 65.7 4.4
F test * * * * * *
LSD (0.05) 2.3 0.8 2.2 0.06 12.0 0.8
C X No. NS Ns NS NS NS NS
CV (%) 3.7 5.5 9.6 4.8 15.9 16.0

 

1The average of bulb to neck ratio of 12 plants.

NS, not significant;

*, significant at 5% level.

48
Plants from single transplants were taller, larger in neck
and bulb diameter, and had greater fresh and dry weight than
those from multitransplants. Bulb to neck ratio declined as
the number of plants per cell increased.

In experiment 3, Muck Farm, plants from fewer seedlings
per cell tended to mature slightly later. Three transplants
per cell reduced time to maturity in the field by 0.9 weeks
compared to single transplants (Table 9).

Single transplants produced the lowest total harvest
weight. Two plants per cell increased harvest weight by
about 40%. Three plants per cell increased total yield by
65%. Single transplants also yielded the least yield of
bulbs >76 mm. The greatest yield was obtained by 2 and 3
transplants per cell (Table 9).

Different bulb shapes were caused by the different
number of seedlings per cell. Bulbs produced from single
transplants were more flat, and those from 2 transplants per
cell were more spherical. Bulbs from 3 transplants tended
to be tall (Table 9).

Fewer number of transplants per cell had larger bulb
size at harvest (Table 10). The proportion of bulbs <76 mm
was least with single and was greatest with 3 transplants
per cell. Conversely, single plants had the largest
proportion of bulbs >102 mm, and 3 plants per cell had the '
least. The greatest proportion of bulbs 76-102 mm was

achieved with 2 plants per cell.

Iahi

m.tswer

Clint

nl‘t

-4|'4.2 3

49

Table 9. The effect of number of transplants per cell on
maturity and yield of Spanish onions, MSU Muck Research

 

 

Farm.
Weeksl Harvest Est.Yield Bulb‘
to ma- weight of >76 mm shape
TREATMENT turity (kg/plot)2 (MT/ha)3 (D/L)
gating:
Sweet Sand. 15.0 47.4 47.8 0.97
Yula 13.6 50.1 51.9 1.00
Vega 15.8 48.3 49.6 0.97
F test * NS * *
LSD (0.05) 0.3 - 3.2 0.02
e in
1/Cell 15.3 35.8 40.5 1.12
2/cell 14.8 50.7 54.6 0.95
3/Cell 14.4 59.2 54.2 0.87
F test 4 4 4 . 4
LSD (0.05) 0.3 2.8 3.2 0.02
C X No . NS NS NS NS
CV (%) 3.0 6.9 7.7 2.80

 

lMaturity defined as 25% leaves down.

2Plot size was 7.6 m2

3Yields were estimated by combining medium and large bulb

weights after grading and multiplying by the conversion

factor 1.32.

4Determined by the Diameter and Length Ratio of bulbs.
D/L < 1: tall; D/L = 1 : spherical ; D/L > 1 : flat.

NS, not significant; *, significant at 5% level.

50

Table 10. The effect of number of transplants per cell on
the size of Spanish onions, MSU Muck Research Farm.

 

 

 

 

811115.13;th
TREATMENT Small Medium Large Jumbo3 Cullz'3
Cnltixar
Sweet Sand. 12.3 76.1 11.1 0.0 0.5
Yula 8.8 58.8 26.6 1.4 4.4
Vega 9.8 66.8 20.5 0.2 2.7
F test * * * Ns *
LSD (0.05) 2.6 6.9 6.5 - -
Eo._of_§ooc_u_i_noo
1/ce11 0.9 48.7 44.2 1.7 4.5
2/cell 7.0 80.8 10.3 0.0 1.9
3/Cell 23(0 72.2 3.7 0.0 1.2
F test * * * us *
LSD (0.05) 2.6 6.9 6.5 - -
C X No. NS NS NS NS Ns
CV(%) 29.7 12.2 39.9 131.1 23.9

 

lBulb size: Small: <76 mm; Medium: 76-102 mm; Large:
102-127 mm; Jumbo: >127 mm in diameter.

2Cull consisted of rotten, sprouted, and split bulbs.

3Data were transformed by arcsinJIy+1) for analysis; actual
values are presented; LSD is not presented for transformed
data.

NS, not significant; *, significant at 5% level.

51

Single transplants produced a greater percentage of
cull bulbs at harvest compared to 2 or 3 seedlings per cell
(Table 10). There was no difference between the use of 2
and 3 plants per cell in the percentage of culls.

In experiment 4, Hort Farm, multitransplants slightly
reduced time to maturity in the field. Time to maturity was
longest with single transplants. The use of 2 and 3
seedlings per cell resulted in the same time to maturity in
the field (Table 11).

Greater number of transplants had greater total yield.
Two and three transplants per cell increased the total yield
by about 26% and 50%, respectively. The greatest harvest
weight was obtained with 3 seedlings per cell. However,
yield of bulbs >76 mm was highest with single transplants.
Bulb shape was slightly flat with single transplants and
tall with either 2 or 3 seedlings per cell (Table 11).

Greater number of seedlings resulted in smaller bulbs
at harvest. Single transplants produced the smallest
proportion of bulbs <76 mm, and the greatest percentage of
bulbs 76-102 mm. There was no difference in the proportion
of bulbs >102 mm and culls among the treatments (Table 12).

There was no interaction observed between cultivars and
the number of seedlings per cell at any time. 'Sweet
Sandwich', 'Yula', and 'Vega' responded similarly with the
same number of seedlings per cell (Table 6, 7, 8, 9, 10, 11,

and 12).

52

Table 11. The effect of number of transplants per cell on
time to maturity and yield of Spanish onions, MSU
Horticultural Research Center.

 

 

Weeks‘ Harvest Est.Yield Bulb‘
to ma- weight of >76 mm shape
TREATMENT turity (kg/plot)‘ (MT/ha)‘ (D/L)
Cnitixor
Sweet Sand. 14.7 10.9 7.3 0.92
Yula 13.7 12.6 11.3 0.98
Vega 15.4 12.5 11.7 0.90
F test * * * *
LSD (0.05) 0.6 1.5 4.3 0.11
d ,
1/Cell 15.3 9.6 17.0 1.09
2/cell 14.3 12.1 8.0 0.91
3/cell 14.1 14.4 5.2 0.80
F test * * * *
LSD (0.05) 0.6 1.5 4.3 0.11
C X No . NS NS NS NS
CV (%) 4.7 12.7 42.5 12.20

 

 

‘Maturity defined as 25% leaves down.

2Plot size was 3.8 m2

3Yields were estimated by combining medium and large bulb
weights after grading and multiplying by the conversion
factor 2.63.

‘Determined by the Diameter and Length Ratio of bulbs.
D/L < 1: tall; D/L = 1 : spherical ; D/L > 1 : flat.
NS, not significant; *, significant at 5% level.

53

Table 12. The effect of number of transplants per cell on
the size of Spanish onions, MSU Horticultural Research

 

 

 

Center.
______§nlb_oizoi_itbx_noioht)
TREATMENT Small Medium Large Jumbo Cun’o3
Sweet Sand. 70.7 27.4 1.1 0.8
Yula 56.5 40.9 0.0 2.5
Vega 57.0 41.9 0.6 0.4
F test * * NS *
LSD (0.05) 10.5 09.3 - -
No, of Seedlings
1/cell 25.2 70.8 1.7 2.3
2/cell 73.3 25.8 0.0 0.9
3/cell 85.7 13.6 0.0 0.6
F test * * NS NS
LSD (0.05) 10.6 10.0 - -
C X No . NS NS NS NS
CV(%) 17.2 26.7 361.3 35.5

 

‘Bulb size: Small: <76 mm; Medium: 76-102 mm; Large:
102-127 mm; Jumbo: >127 mm in diameter.

2Cull consisted of rotten, sprouted, and split bulbs.

3Data were transformed by arcsin/Ty+1)for analysis; actual

values are presented; LSD is not presented for transformed

data. ‘

NS, not significant; *, significant at 5% level.

54

D’ . l E J .

Multitransplants per cell at transplanting were smaller
in size than single tranplants. A greater number of
seedlings per cell caused a competition between plants in an
individual cell resulting in less roots and smaller shoots.
Knavel (1965) reported that limited room for roots to grow
inhibited shoot growth.

Similarly, greater number of plants per cell resulted in
smaller plants at 8 weeks after transplanting. Multiplants
per cell increased plant population per unit area, which was
mentioned by Jones and Mann (1963) as causing plants to
compete for space to grow and smaller plant size.

Smaller plant size of multiplants at 8 weeks after
transplanting may also be due to smaller plant size at
transplanting. Sabota and Downes (1981) found that small
transplants resulted in small plant size at harvest.

Time to maturity in the field was slightly reduced with
the increase in the number of seedlings per cell. The
results agreed with Chung (1989). He found that the use of
multiplants per container reduced time to maturity of onions
in the field. Mondal, Brewster, Morris, and Butler (1986),
and McGeary (1985) reported that increasing plant population
per unit area shortened time to maturity.

A greater number of plants per cell had greater total

yield, but smaller bulbs at harvest compared to single

55
plants. These results agreed with Chung (1989). He found
that the use of 2-5 plants per module increased total yield
but decreased bulb size at harvest. It has been documented
that increasing plant population up to a certain level
increases total yield of onions, but the yield levels off at
greater increases of population (Frappel, 1973), and then
decreases with further increases in population (McGeary,
1985).

Although onions had the ability to push out into unused
space while forming bulbs (Jones and Mann, 1963; Rabinowitch
and Brewster, 1990), bulb size tended to be smaller with the
increase of plant density (McGeary, 1985).

The findings that bulb shape was slightly flat, more
spherical, and slightly tall with 1, 2 and 3 plants per
cell, respectively, disagreed with Chung (1989). He
concluded that bulb shape was not affected by the number of
transplants per module.

In conclusion, multitransplants per cell resulted in
smaller plants at transplanting and 8 weeks after
transplanting. Time to maturity was slightly shortened with
multitransplants. Multitransplants yielded more but had
smaller bulb size than single transplants at harvest. At
the Muck Farm, total yield increased by 40% and 65% with 2
and 3 transplants per cell. Yield of bulbs >76 mm was
greatest with 2 and 3 plants per cell. At the Hort Farm, 2

and 3 plants per cell resulted in increased total yield by

56
26% and 50%, respectively. Yield of bulbs >76 mm was
greatest with single transplants. In both locations, there
was no interaction between cultivars and number of plants

per cell.

57
W

Chung, B. 1989. Multi-plant module transplants of bulb
onions. Acta Hort. 247:187-191.

Frappell, B.D. 1973. Plant spacing of onions. J. Hort.
Sci. 48:19-23.

Jones, H.A. and L.R. Mann. 1963. Onion and Their Allies.
Interscience Publ. Inc. New York. 283 pp.

Knavel, D.E. 1965. Influence of container, container size,
and spacing on growth of transplants and yields in
tomato. Proc. Amer. Soc. Hort. Sci. 86:582-586.

McGeary, D.J. 1985. The effect of plant density on Shape,
size, uniformity, soluble solids content, and yield of
onions suitable for pickling. J. Hort. Sci. 60:83-87.

Mondal, M.F., J.L. Brewster, G.L. Morris and H.A. Butler.
1986. Bulb development in onion (Alligm gap; L.). I.
Effect of plant density and sowing date in field
conditions. Ann. Bot. 58:187-195.

Peirce, L.C. 1987. Vegetables: CharaCteristics,
Production, and Marketing. John Wiley 4 Sons Inc. New
York.

Rabinowitch, H.D. and J.L. Brewster. 1990. Onions and
allied crops. Vol I 8 II. CRC Press Inc. Florida.

Sabota, C.M. and J.D. Downes. 1981. Onion growth and yield
on relation to transplant pruning, size, and depth of
planting. HortScience 16(4):533-535.

CHAPTER IV

THE EFFECT OF AGE AND NITROGEN NUTRITION OF SEEDLINGS
ON GROITE, YIELD AND QUALITY OF SPANISH ONIONS
IN TEE FIELD

Abotraot

Spanish onion cultivars, ’Sweet Sandwich', 'Yula', and
’Vega', were seeded in 200-cell trays at 12, 10, or 8 weeks
before transplanting. All seedlings were fertilized with
75, 150, or 225 ppm N, weekly. In the experiment on
Houghton muck, time to maturity was not affected by age of
seedlings, and negligibly reduced with higher N rate in the
greenhouse. Both greater age and higher N level of
seedlings favored larger onions at harvest. Total yield and
yield of bulbs >76 mm were greatest with 10- and 12-week old
seedlings, and with 150 and 225 ppm N in the greenhouse.
Storability was slightly reduced with greater age, but not
affected by N-nutrition of seedlings. All cultivars
responded similarly. On Colwood-Brookston loams, time to
maturity, yield, and storability were not affected by age
and N-nutrition of seedlings. All cultivars responded
similarly. In both experiments, ’Sweet Sandwich’ had the
best storability, followed by 'Vega' and 'Yula'.

58

59
Introduotion

Many cultural practices implemented in the greenhouse
are known to influence transplant size, quality,
establishment and yielding ability in the field. Nitrogen

nutrition in the greenhouse influenced plant size and weight

'4 MS!

of celery transplants Dufault (1985), and also their yield

n 1."_

in the field (Tremblay, Yelle, and Gosselin, 1987). Weston E

and Zandstra (1989) reported that nitrogen nutrition of

 

tomato transplants influenced transplant size, quality and
marketable yield.

Another cultural practice was age of seedlings at
transplanting. Age of seedlings affected not only
transplant size at transplanting, but also yield of tomatoes
(Weston and Zandstra, 1989) and pepper (Weston, 1988) in the
field.

However, depending on the crops, those cultural
practices applied on transplants in the greenhouse may or
may not influence the yield in the field. There is limited
information available on the effect of age and nitrogen
nutrition of onion seedlings in the greenhouse on growth,
yield and quality in the field.

The objective of this study was to determine the effect
of age and nitrogen nutrition of Spanish onion seedlings in
the greenhouse on onion yield and quality in the field, and

onion storability.

60

A9: u?! 5 a-e ,,. -; 3 'o. o t . s-_.1 - .S Muck

A field experiment was done at the Michigan State
University Muck Research Farm (Muck Farm), Laingsburg,
Michigan, from May to September 1990. The soil type was
Houghton muck, pH 6.3, with 80% organic matter.

Seeds of the onion cultivars 'Sweet Sandwich’, 'Yula',
and 'Vega’ were sown in 200 cell plastic trays on 20
February, 6 March, and 20 March 1990 in the MSU Plant
Science greenhouse. They were 12-, 10-, Or 8-week old
seedlings at transplanting on 18 May 1990. Two seeds were
planted in each cell. At 2 weeks after seeding, the
seedlings were thinned to one seedling per cell.

The seedlings were fertilized with the solution of 1.5
g of 20N-8.6P-16.6K, 1.5 g Of 20N-8.6P-16.6K and 0.65 g of
46N-0P-0K, or 1.5 g of 20N-8.6P-16.6K and 1.3 g of 46N-0P-0K
fertilizer in 4 liters water, which was equal to 75, 150, or
225 ppm N respectively, weekly starting 2 weeks after
seeding. Fertilizing was done with a watering can until all
,cells were saturated. The seedlings were watered everyday.
Pesticides were applied as needed.

On 14 May 1990, 10 samples of each tray were harvested.
Seedling height, neck and bulb diameter, and shoot and root

fresh weight were measured after being washed. The

'!

 

61
seedlings were dried in the oven at 49° C for 5 days for
shoot and root dry weight measurement.

Before being transplanted, the large seedlings were
clipped, retaining 10 cm of plant height, so that they would
pass through the transplanter easily. Field transplanting
was done on 18 May 1990 with a Mechanical Transplanter Model
4000.

The experimental design was a split plot with 4
replications. The main plot was cultivar (’Sweet Sandwich',
’Yula', and 'Vega'), and the sub plots were the combination
of age of seedlings (8, 10, and 12 weeks) and nitrogen
nutrition (75, 150, and 225 ppm). Plot size was 7.6 m long
and 1.5 m wide. Each plot consisted of 2 rows, 76 cm apart.
Plant spacing was 15 cm apart in rows.

Fertilizer of 80 kg N and 86 kg P per ha as diammonium
phosphate was broadcasted on 27 April, followed by 174 kg K
per ha as potassium chloride on 30 April 1990. On 25 June
1990, plants were sidedressed with 103 kg N per ha as urea.
Pesticides and irrigation were applied as needed.

On 16 July 1990, 10 plants from each plot were
harvested and measured for height, neck and bulb diameter,
and fresh weight. Plant dry weight was measured after the
samples were dried in an oven at 49° C for 7 days.

Plants were considered mature when 25% or more of the
population were down (Jones and Mann, 1963).

On 7 September 1990, onions were harvested. Five

 

62
meters of two rows in each plot were pulled and topped by
hand. Harvest weight per plot was measured in the field.
Onions were graded for size and quality after being cured
for 4 weeks.
Thirty bulbs >76 mm diameter from each plot were

weighed and stored in an onion storage at 2° C for 15 ,weeks .
to evaluate storability. The quality of bulbs was

reevaluated after storage. Bulb firmness was evaluated by

 

squeezing the bulbs by hand.

Data analyses were done as mentioned earlier. '
Expegiment é. ege ene N-nueritien ef trensplents. MSU

W

A field experiment was conducted in the Michigan State
University Horticultural Research Center (Hort Farm), East
Lansing, Michigan, from May to September 1990. Soil type
was a Colwood-Brookston loam, pH 6.1-6.5, with 1.0-3.0%
organic matter.

Seedlings were raised and treated similarly as in
experiment 5. Field transplanting was done on 29 May 1990.

The experimental design was a split plot with 4
replications. The main plot was cultivar ('Sweet Sandwich',
'Yula’, and 'Vega') and the sub plots were the combination
of age of seedlings (8, 10, and 12 weeks) and nitrogen
nutrition (75, 150, and 225 ppm). Plot size was 0.76 m wide

and 7.6 m long. Each plot was comprised of 1 row with plant

63
spacing of 15 cm apart in the row.

Fertilizer of 67 kg N, 58 kg P and 111 kg K per he as
10N-8.6P-16.6K was broadcasted on 23 May 1990. Fertilizer
was reapplied at the rate of 18.5'kg N per ha as ammonium
nitrate on 5 and 25 July 1990. Pesticides and irrigation
were applied as needed. Lorsban was used to control onion
maggots.

Plant maturity was determined as mentioned above. On
20 September 1990, onions from 5 meters of row in each plot
were hand pulled and topped, and were weighed. The onions
were graded for size and quality after curing for 4 weeks.

Bulbs of >76 mm in diameter were put in an onion
storage at 1? C for 15 weeks for storability evaluation.
The quality of onions was reevaluated after storage.

Data analyses was done as mentioned earlier.

B§§Bl§§
a. 9: - - -‘ ;-: o; s--d ' . s',- a ,: :-.a ' .
't b' ' ° .

Greater age of seedlings resulted in larger seedlings
at transplanting. Seedling height, neck and bulb diameter,
and bulb to neck ratio were greater with older seedlings
(Table 13). A similar trend was observed on seedling weight

at transplanting (Table 14). Older seedlings possessed

 

64

Table 13. The effect of age and N-nutrition on size of
Spanish onion seedlings at transplanting at the MSU
Muck Research Farm.

 

 

 

Seedling Neck bulb bulb/neck
height diameter diameter ratio‘
TREATMENT (cm) (mm) (mm)
tnltixor
Sweet Sandwich 13.1 . 3.2 6.3 2.0
Yula 14.6 3.4 7.1 2.1
Vega 14.1 3.5 7.1 2.0
F test * * * Ns
LSD (0.05) 0.7 0.2 0.3 -
Aoo_of_oooolinos .

8 weeks 13.1 2.8 5.2 1.9
10 weeks 13.2 3.4 7.0 2.1
12 weeks 15.4 3.9 8.4 2.2
F test * * * *
LSD (0.05) 0.7 0.2 0.3 ' 0.1

Nznntrition

75 ppm 10.7 3.1 6.3 2.0
150 ppm 13.9 3.4 6.9 2.0
225 ppm 17.2 3.6 7.3 2.0
F test * * * NS
LSD (0.05) 1.4 0.1 0.5 -
C X A NS NS * NS
C X N NS NS NS Ns
A X N * NS NS NS
C X A X N NS NS NS NS
CV (%) 10.0 8.8 8.8 7.8

 

‘The average of the bulb to neck ratio of 36 plants.
NS, not significant; *, significant at 5% level.

Table 14.

65

The effect of age and N-nutrition on weight of
Spanish onion seedlings at transplanting at the MSU
Muck Research Farm.

 

 

Shoot Root Shoot Root Root/shoot
fresh wt. fresh wt. dry wt. dry wt. ratio
TREATMENT (9) (9) (9) (9) (dry wt-)‘
giltixar
Sweet Sandwich 1.05 0.41 0.08 0.028 0.35
Yula 1.28 0.41 0.09 0.026 0.32
Vega 1.25 0.43 0.09 0.028 0.32
F test NS NS NS NS NS
LSD (0.05) - - - - -

8 weeks 0.70 0.25 0.05 0.016 0.35
10 weeks 1.12 0.41 0.08 0.027 0.34
12 weeks 1.76 0.59 0.14 0.040 0.31
F test * * * t *
LSD (0.05) 0.09 0.04 0.01 0.003 0.03

H- ! .!.

75 ppm 0.72 0.31 0.06 0.021 0.37
150 ppm 1.20 0.43 0.09 0.029 0.34
225 ppm 1.66 0.51 0.12 0.033 0.33
F test * * * * NS
LSD (0.05) 0.17 0.07 0.01 0.003 -

C X A * NS * NS *
C X N NS NS NS NS NS
A X N * * * NS NS
C X A NS NS NS NS NS
CV (% 16.16 19.47 19.12 22.29 22.74

 

‘The average of root to shoot ratio of 36 plants.

NS, not significant;

*, significant at 5% level.

WE

66
greater shoot fresh and dry weight, root fresh and dry
weight. However, greater age reduced root to shoot ratio.

At 8 weeks after transplanting, older seedlings had
greater plant size and weight. The greatest plant size and
weight was obtained with 12-week old transplants (Table 15).
Plant height, neck and bulb diameter, and plant fresh and
dry weight were the same with 8- and 10-week old seedlings.
The bulb to neck ratio was not affected by age of seedlings.

In the experiment at the Muck Farm, age of transplants
at transplanting had no significant effect on time to
maturity in the field (Table 16). Total yield and yield of
bulbs >76 mm in diameter were greatest with 10- and 12-week
old seedlings.

Older seedlings produced larger bulbs at harvest.
Eight-week old transplants produced the greatest proportion
of small and medium bulbs, and the least large bulbs (Table
16). Conversely, the 12-week old seedlings produced the
least small and medium bulbs, but the most large bulbs.
There was no effect of seedling age on jumbo or cull bulb
production.

Age of seedlings at transplanting did not significantly
influence firmness of bulbs, percent weight loss, and rotten
bulbs after storage (Table 17). However, greater marketable
bulb and smaller sprout percentage were obtained with
younger seedlings. The proportion of marketable bulbs was

greatest with 8-week old transplants.

67

Table 15. The effect of age and N-nutrition of seedlings on
plant size and weight of Spanish onions at 8 weeks
after transplanting, MSU Muck Research Farm.

 

Plant Neck Bulb Bulb/ Fresh Dry
height diam. diam. neck weight weight

 

TREATMENT (cm) (mm) (mm) ratio‘ (9) (g)
Cultiver
Sweet Sand. 64.4 18.7 27.7 1.5 89.9 6.0
Yula 69.9 18.0 35.6 2.0 101.7 6.9
Vega 70.9 18.1 26.5 1.5 88.2 5.8
F test * NS * * * *
LSD (0.05) 2.1 - 2.5 0.1 12.2 0.7
Aoo_of_§ooolinoo
8 weeks 66.6 17.5 28.1 1.6 82.0 5.4
10 weeks 67.7 17.9 28.7 1.6 87.0 5.9
12 weeks 70.8 19.4 33.0 1.7 110.8 7.3
F test * * * NS * *
LSD (0.05) 1.3 0.6 1.4 - 6.7 0.4
N-gutrigion
75 ppm 66.2 17.2 26.5 1.5 77.5 5.2
150 ppm 68.4 18.4 31.2 1.7 96.8 6.4
225 ppm 70.5 19.1 32.2 1.7 105.5 7.0
F test 4 4 4 4 4 4
LSD (0.05) 1.3 0.6 1.4 0.1 6.7 0.4
C X A NS NS NS NS NS NS
C X N * * NS * NS Ns
A X N NS NS NS NS NS NS
C X A X N NS NS NS NS NS NS
CV (%) 4.1 6.7 9.8 7.8 15.2 14.2

 

‘The average of bulb to neck ratio of 36 plants.
NS, not significant; *, significant at 5% level.

Table 16.

68

The effect of age and N-nutrition of seedlings

on the yield and quality of Spanish onions, MSU Muck
Research Farm.

 

Weeks‘
to ma-

 

 

Est.yield
of >76 mm
TREATMENT turity (kg/plot)‘Small Medium Large Jumbo’ Cull"5(MT/ha)°

 

Oath/Ar
Sweet San. 15.5

Yula 14.5
Vega 16.0
F test *
LSD (0.05) 0.1
Age of eeegl,

8 weeks 15.4
10 weeks 15.3
12 weeks 15.3
F test NS
LSD (0.05) -

N-nutrition

75 ppm 15.6
150 ppm 15.3
225 ppm 15.1
F test *
LSD (0.05) 0.1
C X A NS
C X N - NS
A X N NS
C X A X N NS
CV (%) 2.1

Harvest Bulb size3
weight (% byegeightl,

31.2 1.1 76.0 20.1 0.0 2.8
32.6 1.3 39.8 47.4 1.0 10.4
33.9 1.2 49.8 44.4 0.6 4.1
* NS * * * *
1.7 - 2.9 3.1 - -
31.1 1.7 59.1 33.4 0.5 5.3
33.0 1.1 56.0 36.6 0.4 5.9
33.7 0.7 50.6 41.9 0.7 6.1
* * * * NS NS
0.9 0.4 3.0 2.8 - -
30.8 1.7 60.9 31.7 0.4 5.2
33.0 0.9 53.7 38.9 0.6 5.9
33.8 1.0 51.0 41.3 0.5 6.1
i * * * NS NS
0.9 0.4 3.0 2.8 - -
NS NS NS NS NS Ns
NS NS NS NS NS NS
NS NS NS NS NS NS
NS NS NS NS NS NS
6.1 111.1 16.3 22.8 40.2 32.0

35.1
34.2
37.5

7.4

 

‘Maturity defined as 25% leaves down.
2Plot size was 7.6 m3.

3Bulb size:

Jumbo:

‘Cull consisted of rotten, sprouted, and split bulbs.

’Data were transformed by arcsinJTy+1) for analysis; actual values
are presented; LSD is not presented for transformed data.

Small: <76 mm; Medium: 76-102 mm; Large: 102-127 mm
>127 mm in diameter.

6Yields were estimated by combining medium and large bulb weights
after grading and multiplying by the conversion factor 1.32.
*, significant at 5% level.

NS, not significant;

 

69

Table 17. The effect of age and N-nutrition of seedlings on
quality of Spanish onions after 15-week storage, MSU
Muck Research Farm.

 

 

 

 

t lav 19.19111:
Firm-‘ Weight Marketable2 Sprout3 Rot and
TREATMENT ness loss bulb soft
9311111121:

Sweet Sand. 4.9 2.6 90.7 0.1 9.2
Yula 2.8 4.5 61.3 2.5 36.1
Vega 4.2 2.4 84.1 0.7 15.2
F test * t i i *
LSD (0.05) 0.3 0.9 7.8 - 6.8

8 weeks 4.1 3.2 82.9 0.4 16.7
10 weeks 3.9 3.3 76.0 2.0 22.0
12 weeks 3.9 3.0 77.2 1.0 21.7
F test NS NS * * NS
LSD (0.05) - - 5.4 - -

knntrition

75 ppm 4.0 3.3 78.7 1.2 20.1
150 ppm 3.9 3.1 80.0 1.1 19.0
225 ppm 3.9 3.2 77.4 1.1 21.4
F test NS NS NS NS NS
LSD (0.05) - - - - -
C X A NS NS NS NS NS
C X N NS NS NS NS NS
A X N NS NS NS NS NS
C X A X N NS NS NS NS Ns
CV (%) 13.3 34.8 14.9 44.4 56.3

 

 

‘Firmness ranges from 1 to 5, from the least to the most
firm.

2Marketable bulbs were defined as firm, unsprouted bulbs.
3Data were transformed by arcsinJIy+1) for analysis; actual
values are presented; LSD is not presented for transformed
data.

NS, not significant; *, significant at 5% level.

 

70
In the experiment at the Hort Farm, age of transplants
had no Significant effect on time to maturity in the field,

yield and quality at harvest (Table 18), and storability

(Table 19).
b e - t ' t e e n ouse on eed ' J
' ' ' 't il of S anish 3

onionol

A higher level of N in the greenhouse favored larger

 

 

seedlings at transplanting. Seedling height, neck and bulb L

___Jl

diameter increased with N rate (Table 13). However, bulb to
neck ratio of transplants was not affected by higher N-
nutrition.

Similarly, plant weight at transplanting also increased
with higher nitrogen level in the greenhouse (Table 14).
Shoot fresh and dry weight, and root fresh and dry weight
were greater with higher N level. However, root to shoot
ratio of transplants tended to decrease with the increase in
nitrogen.

A similar trend was evident at 8 weeks after
transplanting. Plant height, neck and bulb diameter, bulb
to neck ratio, and plant fresh and dry weight were greater
with higher N level of seedlings in the greenhouse (Table
15) .

In the experiment at the Muck Farm, time to maturity in
the field was slightly reduced with higher N-nutrition of

seedlings in the greenhouse (Table 16). Total yield and

 

71

Table 18. The effect of age and N-nutrition of seedlings
on the yield and quality of Spanish onions, MSU
Horticultural Research Center.

 

 

 

 

Weeks‘ Harvest Bulb size3 Est.yield
to ma- weight (% bvggeight) of >76 mm
TREATMENT turity (kg/plot)’Small‘ Medium Large°Jumbo Cull‘-‘(MT/ha)7
getive:
Sweet San. 15.0 9.2 29.0 69.0 0.3 - 1.7 15.9
Yula 13.9 9.9 21.8 68.2 5.5 4.5 18.2
Vega 15.8 11.2 17.1 72.6 7.5 2.8 22.0
F test * NS Ns NS * NS *
LSD (0.05) 1.0 - - - - - 3.8
Age of seem.2
8 weeks 15.1 9.8 22.8 70.1 4.4 2.6 18.2
10 weeks 14.8 10.2 24.2 67.3 5.0 2.2 18.5
12 weeks 14.8 10.3 20.8 72.4 3.9 4.3 19.4
F test NS NS NS Ns NS NS NS
LSD (0.05) - - - - - - -
Nznntrition
75 ppm 15.0 9.8 26.1 67.4 3.8 2.7 17.4
150 ppm 15.0 10.2 20.9 73.1 3.9 3.5 19.6
225 ppm 14.7 10.3 20.9 69.3 5.6 2.9 19.1
F test NS NS NS NS ’ NS NS NS
LSD (0.05) - - - - - - -
C X A NS NS NS NS NS Ns NS
C X N NS NS NS NS NS NS NS
A X N NS NS NS NS NS NS NS
C X A X N NS NS NS NS NS NS NS
CV (8) 4.4 13.8 7.0 14.3 58.0 47.4 27.3

 

‘Maturity defined as 25% leaves down.

2Plot size was 3.8 I?

3Bulb size: Small: <76 mm; Medium: 76-102 mm; Large: 102-127 mm
Jumbo: >127 mm in diameter.

‘Cull consisted of rotten, sprouted, and split bulbs.

’Data were transformed by [7 for analysis; actual values are

presented; LSD is not presented for transformed data.

6Data were transformed by arcsinJIy+1) for analysis; actual values

are presented.

7Yields were estimated by combining medium and large bulb weights

and multiplying by the conversion factor 2.63.

NS, not significant; *, significant at 5% level.

72

Table 19. The effect of age and N-nutrition of seedlings
on quality of Spanish onions after 15-week storage, MSU
Horticultural Research Center.

 

 

 

% by weight
Weight Marketable Sprout3

 

Firm-‘ Rot and
TREATMENT ness loss bulb soft
Qeitivar
Sweet Sand. 4.9 2.3 96.3 0.2 3.5
Yula 2.4 6.3 54.9 1.0 44.1
Vega 3.8 3.8 80.5 1.0 18.5
F test * * * NS *
LSD (0.05) 0.3 0.7 10.1 - 8.6
Aoo_of_§ooolinoo
8 weeks 3.8 4.0 77.6 0.7 21.7
10 weeks 3.6 4.2 78.9 0.3 20.8
12 weeks 3.7 4.1 75.2 1.1 23.7
F test NS NS NS 7 NS NS
LSD (0.05) - - - - -
Eznntrition
75 ppm 3.6 3.9 75.3 1.0 23.7
150 ppm 3.7 4.0 79.3 1.0 19.7
225 ppm 3.8 4.5 77.1 0.1 23.0
F test NS NS NS NS NS
LSD (0.05) - - - - -
C X A NS NS NS NS NS
C X N NS NS NS NS NS
A X N NS NS NS NS NS
C X A X N NS NS Ns NS NS
CV (%) 15.7 30.2 18.3 45.3 63.0

 

‘Firmness ranges from 1 to 5, from the least to the most
firm.

2Marketable bulbs were defined as firm, unsprouted bulbs.
3Data were transformed by arcsin/Iy+1) for analysis;
actual values are presented.

NS, not significant; *, significant at 5% level.

 

73
yield of bulbs >76 mm were higher with higher N level. The
greatest yield was obtained with 150 and 225 ppm N in the
greenhouse.

Seedlings treated with higher N produced larger bulbs
at harvest. The N level of 225 ppm favored the greatest
proportion of large bulbs, and the least percentage of small r
and medium bulbs (Table 16). Conversely, 75 ppm N resulted ‘

in the least large bulb and the greatest small and medium

 

bulb percentage. However, the production of jumbo and cull "

bulbs was not affected by N level. '
N-nutrition of seedlings in the greenhouse had no

significant influence on the storability of onions. Bulb

firmness, percent weight loss, marketable, sprout and rotten

bulbs were not significantly different with the increase in

N level of seedlings (Table 17).
In the experiment at the Hort Farm, there was no

significant difference in time to maturity in the field,

yield and quality at harvest (Table 18), and storability of

onions, as result of N nutrition of seedlings in the

greenhouse (Table 19).

v I I I I I I

There was a significant difference in bulb storability
between Spanish onion cultivars. 'Sweet Sandwich' had the
best storability, followed by 'Vega' and 'Yula' (Table 17

and 19).

74

In experiment 5, at the Muck Farm, percent marketable
bulbs was greatest, and weight loss, sprout and rotten bulbs
were least with ’Sweet Sandwich’ and ’Vega’ (Table 17).
Oppositely, ’Yula’ had the fewest marketable bulbs, and the
greatest weight loss, sprout and rotten bulbs after storage.

In experiment 6, at the Hort Farm, ’Sweet Sandwich’ had
the best storability, followed by ’Vega’ and ’Yula’. ’Sweet
Sandwich’ had the least weight loss and rotten bulbs, and
the most marketable bulbs, while ’Yula’ had the greatest
weight loss and rotten bulbs, and the least marketable bulbs
after 15-week storage (Table 19). There was no significant
difference between the three cultivars in the percentage of

sprouted bulbs.

d. 9: - ect . gt- 2 . s .- w--. _'v. ; - d .-e and
N-ngtrition ef eeedlings en eeegiing eize, gregth,

Witt.

Interaction effects between cultivar and age on
seedling size and weight were observed on bulb diameter
(Table 13), and shoot fresh and dry weight, and root to
shoot ratio of seedlings at transplanting (Table 14). Bulb
diameter of ’Sweet Sandwich’ transplants at 8 and 12 weeks
after seeding was the smallest among cultivars at the same
age (Table 20). However, there was no significant
difference at 10 weeks among cultivars.

The increase of shoot fresh and dry weight from 8 to 10

weeks after seeding was the same among cultivars (Table 20).

75

Table 20. The effect of interaction between cultivar and
age on seedling size and weight at transplanting at the
MSU Muck Research Farm.

 

 

Bulb Shoot Shoot Root/shoot
diam. fresh wt. dry wt. ratio
TREATMENT (mm) (9) (9) (dry wto)
intiraLLAoo
Sweet Sand., 8 weeks 4.9a 0.6a 0.05a 0.35bc
10 weeks 6.7c 1.1b 0.08b 0.36bc
12 weeks 7.4d 1.4c 0.12c 0.36bc
Yula, 8 weeks 5.2ab 0.7a 0.05a 0.38c
10 weeks 7.0cd 1.1b 0.08b 0.33bc
12 weeks 9.0e 2.0d 0.15d 0.26a
Vega, 8 weeks 5.5b 0.7a 0.05a 0.33b
10 weeks 7.2cd 1.2bc 0.08b 0.33b
12 weeks 8.7e 1.9d 0.14d 0.31ab
LSD (0.05) 0.5 0.2 0.01 0.05
CV (%) 8.8 16.2 18.19 19.24

 

 

76
Nevertheless, at 12 weeks, shoot fresh and dry weight were
greatest with ’Yula’ and ’Vega’. Root to shoot ratio was
not affected by age of seedlings of ’Sweet Sandwich’ and
’Vega’, but was reduced with greater age of ’Yula’.

There were no significant interactions between cultivar
and age on plant size and weight at 8 weeks after
transplanting, time to maturity in the field, yield and
quality at harvest, and storability of onions, at any time
(Table 15, 16, 17, 18, and 19).

Significant interactions between cultivar and N-
nutrition of seedlings were evident in plant height, neck
diameter, and bulb to neck ratio at 8 weeks after
transplanting at the Muck Farm (Table 15). Seedlings of
’Sweet Sandwich’ treated with 75 ppm N had the shortest
plants among treatments (Table 21). Higher N level of
seedlings in the greenhouse resulted in taller plants in
’Sweet Sandwich’ and ’Vega’, but had no significant effect
on ’Yula’ at 8 weeks after transplanting in the field.
Plant height was greatest with Vega treated with 225 ppm N
in the greenhouse.

Higher N level of seedlings resulted in greater neck
diameter of ’Sweet Sandwich’ and ’Vega’, but had no effect
on ’Yula’ at 8 weeks after transplanting. Neck diameter was
greatest with ’Sweet Sandwich’ treated with 150 and 225 ppm,
and ’Vega’ fertilized with 225 ppm N in the greenhouse.

There was no significant difference in bulb to neck

77

Table 21. The effect of interaction between cultivar and N-
nutrition of seedlings on plant size at 8 weeks after
transplanting, MSU Muck Farm.

 

 

Plant Neck Bulb/
height diameter neck
TREATMENT cm) (mm) ratio
intixorLIL-nntrit'mn
Sweet Sandwich, 75 ppm 60.8a 17.0a 1.4a
150 ppm 65.6b 19.4c 1.5a
225 ppm 66.8bc 19.6c 1.5a
Yula, 75 ppm 69.1d 17.7ab 1.8b
150 ppm 70.0d 17.9ab 2.1c
225 ppm 70.6d 18.2b 2.1c
Vega, 75 ppm 68.9cd 17.0a 1.4a
150 ppm 69.7d 18.0ab 1.5a
225 ppm 74.0e 19.4c 1.5a
LSD (0.05) 2.1 1.0 0.1

CV (%) 4.1 6.6 7.8

 

78
ratio of ’Sweet Sandwich’ and ’Vega’ treated with different
N levels. However, in ’Yula’, bulb to neck ratio was
slightly increased with higher N in the greenhouse.

There were no significant interactions between cultivar
and N-nutrition observed on seedling size and weight at
transplanting, time to maturity in the field, yield and
quality at harvest, and storability (Table 13, 14, 16, 17,
18, and 19).

Interactions between age and N-nutrition were observed
on seedling height (Table 13), shoot fresh and dry weight
and root fresh weight at transplanting (Table 14). Seedling
height increased with higher N level, at all ages (Table
22). There was no difference in height of seedlings of 8-
and 10-week old plants at the same level of N. The tallest
seedlings were obtained at 12-weeks treated with 225 ppm N.

Shoot fresh and dry weight increased with both greater
age and N-nutrition (Table 22). The increase of shoot fresh
and dry weight due to higher N was greater on older
seedlings at transplanting. Shoot fresh and dry weight was
greatest with 12-week old seedlings fertilized with 225 ppm
N. On 8-week old seedlings, higher N rate did not
significantly affect root fresh weight. However, root fresh
weight increased with higher N level on 10-and 12-week old
transplants.

There was no significant age and N-nutrition

interaction observed on plant height and size at 8 weeks

79

Table 22. The effect of interaction between age and N-
nutrition on seedling size and weight at transplanting
at the MSU Muck Research Farm.

 

 

Seedling Shoot Shoot Root
height fresh wt dry wt. fresh wt.
TREATMENT (cm) (9) (9) (9)
- i
8 weeks, 75 ppm 10.7ab 0.4a 0.03a 0.2a
150 ppm 13.2c 0.7b 0.05b 0.3ab
225 ppm 15.5de 1.0c 0.06b 0.3ab
10 weeks, 75 ppm 10.0a 0.7b 0.05b 0.3ab
150 ppm 13.1c 1.2c 0.08c 0.4bc
225 ppm 16.4e 1.5d 0.11d 0.5cd
12 weeks, 75 ppm 11.3b 1.0c .0.09c 0.5cd
150 ppm 15.2d 1.7d 0.14e 0.6de
225 ppm 19.7f 2.5e 0.18f 0.7e
LSD (0.05) 1.1 0.2 0.01 0.1
CV (%) 10.0 16.2 18.19 19.5

 

 

80
after transplanting, time to maturity in the field, yield
and quality at harvest, and storability, at any time (Table
15, 16, 17, 18, and 19).
In either experiment 5 or 6, there were no significant
interactions observed between cultivar and age and N-
nutrition of transplants at any time (Table 13, 14, 15, 16,

17, 18, and 19).

88' o

Older seedlings were greater in size and weight at
transplanting. Seedlings 12-weeks old were taller, larger
in neck and bulb diameter, had a higher bulb to neck ratio,
and had greater shoot fresh and dry weight, and root fresh
and dry weight than did younger seedlings. This was most
likely due to longer growing period before being
transplanted.

At 8 weeks after transplanting, older transplants
produced larger plants in the field. Twelve-week old
seedlings had the largest plants, while seedlings of 8-weeks
old caught up the neck and bulb diameter, and plant fresh
and dry weight of plants 10-weeks old. The greater age
resulted in greater size of transplants, thus larger plants
in the field. Sabota and Downes (1981) believed that larger

seedlings produced larger plants in the field.

81

Time to maturity was not affected by age of seedlings.
Eight, 10-and 12-week old seedlings resulted in similar time
to maturity.

Greater age of transplants slightly increased total
yield and yield of bulbs >76 mm in diameter. The yields
were greatest with 10- and 12-week old seedlings. These
results disagreed with Singh and Singh (1979) who concluded
that 5- and 6-week old onion transplants produced better
yield than did younger or older seedlings.

Older seedlings tended to produce larger bulbs at
harvest. They produced a greater proportion of large bulbs,
and smaller percentage of small and medium bulbs than did
younger transplants. The greater yields and larger bulbs of
plants from older seedlings may be related to plant size in
the field. Kato (1964) reported that bulb size and yield of
onions was significantly correlated with the plant size at
the beginning of bulb development.

Storability of onions was slightly improved with
younger transplants. Although 8-week old seedlings had the
lowest yield at harvest, they produced bulbs with better
storability. This may be related to the bulb size at
harvest. Smaller bulbs was usually harder and had better
storability (Zandstra, 1991).

Higher N-nutrition in the greenhouse.significantly
influenced seedling size and weight at transplanting.

Higher N levels favored greater plant height, neck and bulb

82
diameter, shoot fresh and dry weight, and root fresh and dry
weight. Research on the influence of N-nutrition in the
greenhouse in many vegetables, such as celery (Dufault,
1985; Tremblay, Yelle, and Gosselin, 1987), pepper (Bar-Tal,
Bar-Yosef, and Kafkafi, 1990), tomato (Weston and Zandstra,
1989) showed similar results. Nitrogen fertilization was
the primary factor promoting accelerated shoot growth of
seedlings (Marschner, 1986; Widders, 1989).

However, root to shoot ratio tended to decrease with
higher N levels. A similar result was observed on celery
(Dufault, 1985; Tremblay, Yelle and Gosselin, 1987).
Marschner (1986) believed that higher N promoted greater
relative growth of shoots than that of roots resulting in a
smaller root to shoot ratio.

Plant size and weight at 8 weeks after transplanting
was increased with higher N of seedlings. Plant height,
neck and bulb diameter, plant fresh and dry weight were
greater with higher N rate in the greenhouse. N-nutrition
effect in the greenhouse was most likely carried through on
the plant size at 8 weeks after transplanting.

Time to maturity was slightly reduced with higher N of
seedlings in the greenhouse. However, the reduced time to
maturity by 0.5 weeks was negligible biologically, in onion
production (Zandstra, 1991).

Total yield and yield of bulbs >76 mm and bulb size

were greater with higher N rate of seedlings. This may be

83
associated with seedling size at transplanting and plant
size in the field. Previous research has shown that
transplant Size was positively correlated with yields and
bulb size at harvest (Sabota and Downes, 1981). Kato (1964)
mentioned that plant size at the beginning of bulb
development greatly influenced bulb size and yields at
harvest.

Onion storability was slightly reduced with greater
age, but not affected by higher N rate in the greenhouse.
However, storability varied greatly among cultivars. ’Sweet
Sandwich’ showed the best storability, followed by ’Vega’
and ’Yula’. Jones and Mann (1963) also mentioned that
storability was an inherent character of cultivars.

In conclusion, plant size and weight at transplanting
and 8 weeks after transplanting were greater with greater
age and higher N-nutrition in the greenhouse. At the Muck
Farm, time to maturity in the field was not affected by
seedling age, and negligibly reduced by higher N rate of
seedlings. Greater age and higher N favored larger bulbs at
harvest. Total yield and yield of bulbs >76 mm were highest
with 10 and 12-week old seedlings, and 150 and 225 ppm N in
the greenhouse. Bulb firmness after storage was not
affected by seedling age and N-nutrition of seedlings in the
greenhouse. Storability was Slightly reduced with older
transplants, but not affected by N nutrition of seedlings.
At the Hort Farm, time to maturity in the field, yield and

84
quality at harvest, and storability were not affected by
seedling age and N-nutrition in the greenhouse. ’Sweet

Sandwich’ had the best storability, followed by ’Vega’ and

’Yula’.

 

85
Litoratnro_9itoo

Bar-Tal, A., B. Bar-Yosef and U. Kafkafi. 1990. Pepper
transplant response to root volume and nutrition in
the nursery. Agron. J. 82:989-995.

Dufault, R.J. 1985. Relationship among nitrogen,
phosporus, and potassium fertility regimes on celery
transplant growth. HortScience 20(6):1104-1106.

Jones, H.A. and L.R. Mann. 1963. Onion and Their Allies.
Interscience Publ. Inc. New York. 283 pp.

Kato, T. 1964. Physiological studies on the bulbing and
dormancy of onion plant. III. Effects of external
factors on the bulb formation and development. J. Jpn.
Soc. Hort. Sci. 33(1):53-61.

Marschner, H. 1986. Mineral Nutrition of Higher Plants.
Academic Press. London. 674 pp.

Sabota, C.M. and J.D. Downes. 1981. Onion growth and yield
on relation to transplant pruning, size, and depth of
planting. HortScience 16(4):533-535.

Singh, D.P. and R.P. Singh. 1974. Studies on the effect of
time of sowing and age of seedlings on growth and yield
of onions (Ailing gene L.). Indian J. Hort. Sci.
31(1):69-76. Hort. Abstr. OC045-03125

Tremblay, N., S. Yelle and A. Gosselin. 1987. Effects of
CO2 enrichment, nitrogen and phosporus fertilization on
growth and yield of celery transplants. HortScience
22(5):875-876.

Weston, L.A. 1988. Effect of flat cell size, transplant
age, and production site on growth and yield of pepper
transplants. HortScience 23(4):709-711.

Weston, L.A. and B.H. Zandstra. 1989. Transplant age and N
and P nutrition effects on growth and yield of
tomatoes. HortScience 24(1):88-90.

Widders, I.E. 1989. Pretransplant treatments of N and P
influence growth and elemental accumulation in tomato
seedlings. J. Amer. Soc. Hort. Sci. 114(3):416-420.

Zandstra, B.H. 1991. Personal communications.

SUMMARY AND CONCLUSIONS

SUNNARY AND CONCLUSIONS

In conclusion, on Houghton muck, type of transplant had
no significant effect on time to maturity of Spanish onions.
Cell transplants produced higher yield and larger bulbs at

harvest than did bare root transplants. Multitransplants

 

reduced time to maturity in the field. Total yield
increased by 40% and 65% with two and three transplants per
cell. Yields of bulbs >76 mm was greatest with two and
three plants. Time to maturity was not affected by seedling
age, and was negligibly reduced by higher N level. Greater
age and higher N of seedlings favored larger bulbs at
harvest. Yields of bulbs >76 mm was greatest with 10- and
12-week old seedlings, and with 150 and 225 ppm N in the
greenhouse. Bulb storability was slightly better with
younger transplants, but was not affected by N level.

On Colwood-Brookston loams, type of transplant had no
significant effect on time to maturity, yield and quality of
Spanish onions. Time to maturity was slightly reduced by
multitransplants. Two and three plants per cell increased
total yield by 26% and 50%, respectively. Yield of bulbs
>76 mm was greatest with single transplants. There was no

significant effect of age and N-nutrition of seedlings on

86

 

87
time to maturity, yield and quality, and storability of
Spanish onions.

In both locations, there was no interaction between
cultivar and type of transplants, cultivar and number of
seedlings per cell, cultivar and age of seedlings, cultivar
and N-nutrition of seedlings, or cultivar and age and N-
nutrition of seedlings at any time.

The results of these experiments suggested that local
greenhouses are a good alternative source of transplants for
transplanted onion production. Cell transplants were better
than bare-roots because they produced higher yield and
larger bulbs. The use of two plants per cell was
recommended because they not only produced high yield but
also more spherical bulbs resulting in the most packed out
onions. Seedlings of eight weeks old treated with 225 ppm N
were also suggested because they occupied greenhouse for a
shorter time while still producing satisfactory yields in
the field.

 

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