This is to certify that the

thesis entitled

THE EFFECT OF SIZE, PARTIAL DEFOLIATION, AND USE OF
PROTECTIVE ROW COVERS ON THE QUALITY AND YIELD OF
CHINESE CABBAGE (BRASSICA CAMPESTRIS L. SSP.
PEKINENSIS)

 

 

presented by

Vincent Arthur Fritz

has been accepted towards fulfillment
of the requirements for

 

 

Master's degree in Horticulture

Major professor

Date M64 2/ /fJ/V’
/ / /

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THE EFFECTS OF SIZE, PARTIAL DEFOLIATION, AND USE OF
PROTECTIVE ROW COVERS ON THE QUALITY AND YIELD OF
CHINESE CABBAGE (BRASSICA CAMPESTRIS L. SSP. PEKINENSIS)

 

 

 

BY

Vincent Arthur Fritz

A THESIS

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

MASTER OF SCIENCE

Department of Horticulture

I982

ABSTRACT

THE EFFECT OF SIZE, PARTIAL DEFOLIATION, AND USE OF

PROTECTIVE ROW COVERS ON THE QUALITY AND YIELD OF
CHINESE CABBAGE (BRASSICA CAMPESTRIS L. SSP. PEKINENSIS)
BY

Vincent Arthur Fritz

Protective wax paper tunnels, used in early celery

production in Michigan were utilized to prevent bolting in
ssp. Pekinensis).

(Brassica campestris L.

Chinese cabbage
The transplants were subjected to various degrees of defolia-

to achieve minimal

(0 25, 50% of the foliar length)
7—8 leaf

tion
(3-4, 5-6,

transplant shock. Various plant sizes
stages) were also examined to confirm the report that cold

A.
4' ' . , "z \.
“wk-"V. :3 kl?

temperature sensitivity changes with plant size.
(50%) plants were slow in recovery

’-
\

Severely pruned
from transplant shock as compared to those unpruned and
Unpruned plants showed good early

(in l I"

slightly pruned (25%).

plant growth. Early plant growth under tunnels was more

rapid than without tunnels. The tunnel was effective in
3—4 leaf transplants

preventing vernalization and bolting.
recovered more slowly than larger transplants (5-6 and 7-8
leaves). The 5—6 and 7-8 leaf stage transplants produced
the largest head weights.

DEDICATION

The author wishes to dedicate this thesis to his
wife, Barb, for her endless love, support, and understanding

throughout his graduate studies.

ii

ACKNOWLEDGEMENTS

The author wishes to express sincere appreciation
to Dr. S. Honma for his valuable assistance in experimenta-
tion and in the preparation of the manuscript. Appreciation
is also extended to Dr. H.C. Price and Dr. D. Warncke for

their suggestions and constructive criticism of the manu-

script.

Finally the writer wishes to express gratitude to his

parents for their continuous support and encouragement during

his graduate studies.

iii

TABLE

OF CONTENTS

List of Tables. . . . . . v
List of Figures . . . . . . vi
Introduction. . . . . . . . 1
Literature Review . . . . 3
Materials and Methods . 8
HRC, Spring 1979. . 8
Greenhouse 1979 . 9
HRC, Spring 1980. . . . 10
HRC, Muck Farm, Spring 1981 . . . . . . . . . . . . ll
Results and Discussion. . . 14

Peat Pot and Pruning, Spring 1979 . . . . . . . . . l4

Pruning and Leaf Stage,

Fall 1979 . . . . . . . . . l4

Tunnel, Leaf Stage, Pruning, Spring 1980. . . . . . l9

HRC

I

Nagaoka #2, Spring 1981. . . . . . . . . . . . 23

HRC, Jade Pagoda, Spring 1981 . . . . . . . . . . . 24

Muck Farm, Nagaoka #2,

Muck Farm, Jade Pagoda,
General Conclusions
Appendix,

LlCCLdCUfe Cited.

Spring 1981. . . . . . . . . 28
Spring 1981 . . . . . . . . 34

41

47

iv

 

TABLE

LIST OF TABLES

Effects of partial defoliation and type
of transplant on yield and quality of
Chinese cabbage, (CV- Nagaoka #2), HRC,
1979. . . . . . . . . . . . . . . . .

Effects of transplant leaf stage and
degree of defoliation on head length,
diameter, and weight of Chinese cabbage,
(cv. Nagaoka #2), greenhouse, 1979 .

Effects of transplant leaf stage, degree
of defoliation, and protective covers,
on quality and yield of Chinese cabbage,
(cv. Nagaoka #2), HRC, 1980. . . .

Effects of transplant leaf stage, degree
of defoliation, and protective covers,
on quality and yield of Chinese cabbage,
(cv. Nagaoka #2), HRC, 1981. . . . . .

Effects of transplant leaf stage, degree
of defoliation, and protective covers,
on quality and yield of Chinese cabbage,
(cv. Jade Pagoda), HRC, 1981 . . . . .

Effects of transplant leaf stage, degree
of defoliation, and protective covers,
on quality and yield of Chinese cabbage,
(cv. Nagaoka #2), Muck Farm, 1981. .

Effects of transplant leaf stage, degree
of defoliation, and protective covers,
on quality and yield of Chinese cabbage,
(cv. Jade Pagoda), Muck Farm,198l.

PAGE

15

18

20

26

27

33

36

FIGURE

1

LIST OF FIGURES

The effect of degree of defoliation and
transplant leaf stage, on head diameter of
Chinese cabbage (CV. Nagaoka #2), green-
house, 1979. . . . . . . . . . . . . . .

The effect of transplant leaf stage and
protective covers, on head weight of
Chinese cabbage (CV- Nagaoka #2), HRC,
1980 . . . . . . . . . . . . . . . . . . .

The effect of transplant leaf stage
and protective covers, on percent of
bolters in Chinese cabbage (cv.
Nagaoka #2), HRC, 1981 .

The effect of degree of defoliation and
transplant leaf stage, on head diameter
of Chinese cabbage grown unprotected
(cv. Nagaoka #2), Muck Farm, 1981 .

The effect of degree of defoliation and
transplant leaf stage, on head length
of Chinese cabbage grown unprotected
(cv. Nagaoka #2), Muck Farm, 1981

The effect of degree of defoliation and
transplant leaf stage, on head weight of
Chinese cabbage grown unprotected

(cv. Nagaoka #2), Muck Farm, 1981 . . .

The effect of degree of defoliation and
transplant leaf stage, on internal stalk
length of Chinese cabbage grown unprotected
(cv. Nagaoka #2), Muck Farm, 1981

The effect of degree of defoliation and
transplant leaf stage, on head length of
Chinese cabbage grown unprotected (cv.
Jade Pagoda), Muck Farm, 1981.

vi

PAGE

17

22

25

29

31

32

35

37

FIGURE PAGE

9 The effect of degree of defoliation
and transplant leaf stage, on head
weight of Chinese cabbage grown under

tunnels (CV- Jade Pagoda), Muck Farm,
39
1981. . . . . . . . . . . . . . . . . .
10 The effect of degree of defoliation
and transplant leaf stage, on head
weight of Chinese cabbage grown un—
protected (cv. Jade Pagoda), Muck 4O

Farm,l981 . . . . . . .

INTRODUCTION

Chinese cabbage (Brassica campestris, L. ssp.

 

pekinensis), originated from Brassica campestris and was

 

 

first reported in China between 290 and 307.AD (Kraus, 1940).
Sturtevant (1919) reported that it had been identified in
several art works of agriculture as early as the fifth cen-
tury. It was introduced into Europe in 1751 by missionaries
(Boswell, 1949). Cultivation of Chinese cabbage in the United
States was essentially nonexistent until about 1884 when in-
terest in this vegetable increased. Bailey (1930) imported
several cultivars from Kew in 1893 and from Japan in 1890-
1894. According to Fairchild (1918), there were substantial
plantings of Chinese cabbage in New Jersey for many years
prior to his writing. '

Chinese cabbage production in Michigan is limited,
but may increase with the continuing influx of Asiatic peo—
ple into the United States and the increase in the number of
American consumers. Other reasons for the limited production
of Chinese cabbage may be due to the lacK of knowledge in
culture and its culinary use.

Chinese cabbage requires close attention since it is
extremely sensitive to environmental conditions. It is sus-
ceptible to severe shock at transplanting due to its limited

1

 

2

root system and massive leaf area. The plant's transpiration
rate is escalated when exposed to high temperatures, low rel—
ative humidity, and wind so prOVisions must be made to sup—
ply water. Chinese cabbage is also very sensitive to cold
temperatures and will easily bolt. Approximately two weeks
exposure to temperatures at or below 13°C will induce flower-
ing (Koda et al., 1974). This process inhibits the head for-
mation when the plants are young and decreaess the value of
the crop at maturity. Japanese growers use 91 cm (3 ft.)
wide polyethylene film tunnels for early production. Celery
growers in Michigan use a white plastic or wax paper tunnel
to allow for warming during the day to reverse the vernali—
zation process.

The purpose of this Study was to determine whether the
tunnels used in the production of celery can be applied to
an early crop of Chinese cabbage. Other factors such as
partial defoliation, seedling stage, and methods of growing

transplants were also examined.

LITERATURE REVIEW

Several studies have been conducted relating to early
maturity and increased yields in vegetables. Early maturity
has been accomplished by the use of transplants, however,
there is concern of seedling damage caused by adverse weather
conditions or simply by the physical act of transplanting.
Partial defoliation has been used to reduce transpiration,
thus reducing transplant shock. This allows for root estab—
lishment during the early stages of growth after transplan—
ting. Van Graan (1929) reported that by removing some of
the foilage of a celery seedling, the remaining portion of
the leaves would remain photosynthetically efficient for a
longer period during the day. He also found that pruned cab—
bage and tomato seedlings matured earlier, but only following
exposure to adverse environmental conditions. Zink and Knott
(1965) found that pruned vegetable seedlings were in no in-
stance superior to unpruned plants in terms of earliness or
yield. They also reported that the least pruned seedlings
recovered better from transplanting and there was no signi—
ficant difference in percent survival between the pruned and
unpruned plants. Kraus (1942) working with cauliflower seed—
lings, noted that the total loss of water was greater for the
unpruned than the pruned, but the rate of transpiration was

3

4
greater per unit leaf area for the pruned than the unpruned
plants. He also noted that transplant recovery and subse—
quent root and top growth was correlated with the amount of
carbohydrates present after pruning. This is in agreement
with Aung and Kelly (1966), who reported that young leaf de—
foliation in tomato resulted in a decrease of the net assimi—
lation rate due to the loss of the carbohydrate sink supplied
by the young leaves. Defoliation of mature leaves resulted
in a subsequent increase in new growth. This increase rate
of new growth appeared to be made because of a reduction in
the relative growth of the stem and roots. They suggested
that this was due to a redirection of translocates from the
stem and roots to the apex.

The use of various sizes of transplants at transplant-
ing is also used to overcome the check in growth. Zink and
Knott (1965) reported that extra large and large celery plants
(graded on a fresh weight basis) produced significantly higher
yields than smaller transplants. No significant difference
in plant survival was observed. However, Kratky, Wang and
Kubojiri (1982) found that various transplant ages of Chinese
cabbage had a minimal affect on days to maturity and no af-
fect on yield when grown in an unheated plastic greenhouse.

Seedling stage is very important in preventing pre—
mature flowering in Chinese cabbage. Eguchi et a1. (1963),
Iwama and Serizawa (1953), and Yamasaki (1962) reported that
the susceptibility to low temperatures augments with seedling

age. Wang (1969), and Kagawa and Soda (1957) found that 12

5

day old seedlings of Brassica chinensis when exposed to 10° C

 

for 3 days bolted 10 days later when exposed to high temper—
atures and long daylengths. Lorenz (1946) also reported sim-
ilar results with Chinese cabbage. Nakamura (1976) and Koda
et al., (1974) reported that Chinese cabbage seedlings having
approximately 20—25 outer leaves will form a head even if
vernalized since enough leaves were differentiated to permit
proper head formation prior to bolting. Yamasaki (1956) re—
ported that 30 day or older (7-8 leaves) seedlings, have
enough differentiated leaves to properly form the head fol-
lowing vernalization. Nakamura (1976), Koda et al.(l974),
and Cooley (1979) stress that proper growing conditions must
be maintained to overcome the competition between flower stalk
formation and leaf growth, so that head formation can be com—
pleted.

One cultural method that has been used to ensure the
proper environmental conditions for plant growth has been
the use of protective coverings. These are made of plastic,
paper, waxed paper, and nylon mesh. Opena (1981) and Harris
(1965) reported that the interval from seedling to emergence
decreased and the percent emergence increased giving a more
uniform crop when sown under a protective tunnel. Bakhchevanova
(1976) found that by using plastic tunnels for spring cabbage
production, earliness increased 203.1%, overall yield 14.8%,
and total value of the crop 20.4%. O'Dell (1979) obtained

similar results with peppers as did Malakowski (1969) with

 

6
carrots, radishes, cauliflower, cucumbers, and melons. How—
ever, Zink (1954) in California did not obtain a higher yield—
ing or earlier crop of muskmelons and reported that very high
temperatures in the plastic tunnels damaged the plants. This
is in agreement with Wells and Loy (1980) who found that vine
crops perish from excessive transpiration if a decrease in
soil temperature occurs due to cloudy weather followed by
sunny days. The use of perforated or slit tunnels was used
to help alleviate the problem of high temperatures. Slitted
tunnels were preferred because of its superior ability to re-
tain more heat at night when the wind is usually calmer. This
also helps to keep the humidity and.condensatidn: from causing
damage. High air temperature is of concern when growing Chinese
cabbage. Marukawa (1975) found no growth inhibition when tem-
peratures reached 30-32°C, however, Nakamura (1976) and Koda
et al., (1974) warn that high temperatures increases suscep-

tibility to soft rot (Erwinia caratovora).

 

Frost protection is another benefit of protective cover-
ings. Waggoner (1958) and Zink (1965) found that plastic had
both a higher maximum and a lower minimum temperature than the
paper cover. The use of protective coverings in spring Chinese
cabbage production is important in preventing frost as well as
inhibiting vernalization.

Bremer (1935) and Kraus (1940) felt that there were
other factors affecting bolting. Lorenz (1946) found that

exposure for one month to 8°C and long days greatly hastened

7
flowering. According to Nakamura (1976) and Koda et al.,
(1974) many commercial varieties will initiate a flower
primordia if exposed for 14 days to 5°C. Yamasaki (1956)
developed a formula to determine when sufficient vernaliza-
tion has occurred: (13—X) Y2:87°C, X=temperature below 13°C
and Y=number of days with a minimum daily temperature below
13°C. When the heat sum of the low temperature reaches or
exceeds 87°C, flower induction takes place. It follows that
the longer the duration of the cold treatment, the sooner
flowering will occur. Mori et al., (1979), Iwama and Serizawa
(1953), Nakagawa (1957), and Thompson (1929) all reported sim-

ilar results.

 

MATERIALS AND METHODS

Horticulture Research Center, Spring 1979

 

A preliminary study was made to determine the effect
of partial defoliation of the transplant on yield, head
length, head diameter, and flower stalk development. The
transplants were grown in 6 cm Jiffy peat pots and in green—
house soil.

Seeds of Nagaoka #2 were sown in standard wooden flats
(51 x 90 x 8 cm) using a 1:1:1 top soil, peat, sand mixture
on March 23. One week later, the seedlings were thinned to
35 plants per flat. The plants were fertilized weekly with
113.5 gms of 6—24—30 and 113.5 gms of ammonium nitrate in 8
litres of H20 using a 16:1 garden hoSe proportioner. The
experiment consisted of 6 treatments in randomized complete
block design with 9 plants per treatment and 2 replicates.
The treatments were: (a) 3 degrees of defoliation of 0, 33,
and 66% of the foliar length; (b) transplants grown in peat
pots, and bare rooted transplants.

On May 7 the transplants with 7 true leaves were trans—
planted in the field. The 7 leaf stage has been reported to
be at the optimal stage to permit completion of the heading
process prior to flower stalk elongation (Yamasaki, 1956).

8

' -——_~m_ H‘Km‘ ~_~—u.,, ,.." . .- . ... - . ‘ . , ,.

9

Spacing within the rows was 38 cm and between rows was 61 cm.
After transplanting, all plants were watered with 120 ml of
a starter solution and insecticide (Diazinon) mixture. The
plot was irrigated, sprayed, and cultivated as necessary.
A preplant application of 1135 kg per hectare of 12—12—12
was applied. Two side dressings of ammonium nitrate at 113.5
kg per hectare were also applied prior to and during the head—
ing process.

The Chinese cabbage was harvested from June 27 to July
6. Plant yield, head length and diameter, and number of vis-

ible flower stalks were recorded.

Greenhouse, Fall 1979

 

An experiment was conducted in a greenhouse bed to
determine the effect of various number of leaves on the trans-
plants and the amount of defoliation on yield, head length
and diameter. The transplants were grown as in the previous
experiment. Seeds of Nagaoka #2 were sown in flats on 7/23,
7/27, 7/31 and 8/4 to obtain the various leaf numbers neces—
sary. Plants were selected for leaf number rather than chrono-
logical age due to uneven growth within each sowing. The
non-uniformity in plant growth made it necessary to transplant
at various times(8/27, 8/29, and 9/1). The experiment was a
randomized complete block design with 9 plants per treatment
and three replicates. The treatments consisted of three degrees

of defoliation: 0 25 and 50% of the plant foliar length,

I I

10

applied to 4, 5 6

I I

and 7 leaf stages. Spacing was 38 cm
within rows and 61 cm between rows in a greenhouse bed. Two
side dressings of 227 gms of ammonium nitrate in 16 litres

of H20 using a 16:1 garden hose proportioner were applied

in addition to a preplant application of fertilizer based on

a soil test. Daytime temperature was maintained at 20-25°C

at the beginning of the experiment and at 15—18°C towards har—
vest. Chinese cabbage was harvested from 10/27 to 11/7. Head

weight, head length and diamter were recorded.

Horticulture Research Center, Spring 1980

 

Due to the difficulty in obtaining precise leaf stages,
plants with 3—4, 5—6 and 7-8 leaves are used for this experi—
ment. Plants with 0, 25 and 50% of the foliar length removed
were grown with and without protective covering. The pro—
tective covering was a wax paper tunnel which enclosed a sin-
gle row of plants.

Seed of Nagaoka #2 were sown in flats using a 1:1:1
soil, peat, sand mixture at weekly intervals starting on 4/1.
The seedlings were fertilized as in the previous studies. On
5/5, seedlings were transplanted bare rooted in the field fer-
tilized with 1135 kg per hectare of 16—16-16 and preplant in-
corporated with a herbicide (trifluralin) at 908 gms of active
ingredient per hectare. The experimental design was a split

plot with 20 plants per treatment and 4 replicates. Each leaf

stage was subjected to the 3 degrees of defoliation at the time

 

11
of transplanting. The protective tunnel was applied the fol-
lowing day due to windy conditions. After transplanting, all
plants were treated with a starter solution and insecticide
(Diazinon). The plot was irrigated, sprayed, and cultivated
as necessary. Thermocouples were placed within each plot in
pairs to monitor the rising and falling air and soil temper—
atures within and outside the protective tunnels. The soil
thermocouple was placed 10 cm below the soil surface and the
thermocouple 10 cm above the soil surface. Temperatures were
recorded from 5 a.m. to 10 p.m. and from 12-1 a.m. The tun-
nels were vertically slit every 60 cm due to high internal
air temperatures (>35°C) one week later. Tunnels and the
thermograph were removed on 5/21. The number of visible
leaves were recorded on 5 randomly selected plants in each
treatment of the 4 replicates 2 days after the tunnels were
removed. Harvesting began on 6/26 and continued until 7/1.
Head weight, head length and diameter, internal flower stalk
length, number with visible flower stalks, and percentage of

harvestable plants were recorded.

Horticulture Research Center, Muck Farm, Spring 1981

 

Two experiments were conducted in the spring, one at
the Horticulture Research Center (HRC) and the other at the
Muck Farm. The plants were transplanted on 4/27 at the HRC
and on 4/29—30 at the Muck Farm in order to expose the plants

to cold temperatures for a longer duration than the previous

 

12

spring. The experimental design was similar to that used

in the spring of 1980, except 10 plants per treatment with

3 replicates and 2 varieties were used. The varieties Nagaoka
#2 (Won Bok type) and Jade Pagoda (Chihili type) were selected
for these plantings. The HRC plot (sandy loam) was fertilized
with 1135 kg per hectare of 16—16-16 and preplant incorporated
with a herbicide (trifluralin) at 908 gms active ingredients
per hectare before planting. The Muck Farm plot (organic soil)
was fertilized with 1135 kg per hectare of 5-10—30. No her-
bicide was applied on the organic soil. Two side dressings

of potassium nitrate at a rate of 113.5 kg per hectare were
applied to both plots prior to heading and again two weeks
later.

Since the recording thermograph previously used was
unavailable, minimum—maximum thermometers were placed in the
plots in pairs 10 cm above and below the soil surface. Air
and soil temperatures were recorded both inside and outside
the tunnels until the tunnels were removed on 5/27 at the HRC
and on 5/28 at the Muck Farm. Vertical slits were made to
the wax paper coverings when air temperatures exceeded 35°C.
Harvesting at HRC of Nagaoka #2 began on 6/29-30 and from
7/6-7 for Jade Pagoda. The Muck Farm was harvested from 7/8-
12 for Nagaoka #2 and from 7/15—17 for Jade Pagoda. Data were
obtained for head weight, head length and diameter, internal
flower stalk length, number of visible flower stalk, and per-

centage of harvestable plants. Data from all experiments were

l3
analyzed statistically using analysis of variance, least signi—

ficant difference and trend analysis.

RESULTS AND DISCUSSIONS

Peat Pot and Pruning Study, Spring 1979

 

Harvesting began at the Horticulture Research Center
(sandy loam) on 6/27 and continued until 7/6. There were no
significant differences in head length and diameter due to
the degree of defoliation (0, 33, 66% of the foliar length)
for plants transplanted bare rooted and in peat pots. Head
weight and percentage of bolters were also uneffected by the
treatments. Although main treatment effectsand interactions
were not significant, the data showed the following trendszboth
unpruned peat pot and bare rooted transplants developed heads
that were larger in diameter, higher in head weight, and with
fewer number of bolters than the pruned plants. Within the
defoliation treatments, the peat pot transplants produced
head weights that were slightly larger than or equal to the

bare rooted plants (Table l).

Pruning and Leaf Stage Study, Fall 1979

 

Harvesting began in the greenhouse on 10/27 and con—
tinued until 11/7. Statistical analysis of main treatment
effects (leaf stage and pruning) suggested that head length
was not effected. Head diameter was significantly effected

l4

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16
by a leaf X pruning interaction (P = .001). Trend analysis
of this interaction suggested a quadratic trend at the 6
leaf stage, with the slightly (25%) pruned plants producing
the smallest head diameter (P = .05) (Figure 1). At the 7
leaf stage, head diameter decreased linearly with increased
pruning (P = .001).

Plants that were transplanted at the 7 leaf stage pro—
duced heads smaller in head weight when compared to 4, 5, or
6 leaf stage plants (P = .001) (Table 2). Head weight dif-
ferences between 4, 5 and 6 leaf stage plants were not signi—
ficant. The lower head weights produced by the 7 leaf stage
plants may be attributed to slower transplant recovery due
to root damage and subsequent inadequate water uptake. Loomis
(1925) found that plants seriously injured by transplanting
have a high rate of top growth and slow rate of root replace—
ment. He also noted that transplant injury increased with
advancing maturity. The present study shows that the slightly
(25%) and severely (50%) pruned transplants produced lower
yields than unpruned plants (P = .001) Table 2). This may
be due to reduced photosynthetic efficiency as well as a
decrease in leaf area. The differences in head weight be-
tween slightly (25%) pruned and severely (50%) pruned plants

was not significant.

 

17

O 4|eaves

O 5 leaves

 

16 I bleaves
A 7leaves
O
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5.4
o
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r _ A
11
of
0 25 50
Degree of Defoliation (%)
FIGURE 1: THE EFFECT OF DEGREE OF DEFOLIATION AND TRANS—

PLANT LEAF STAGE, ON HEAD DIAMETER OF CHINESE
CABBAGE (CV. NAGAOKA #2), GREENHOUSE, 1979

l8

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.IBUZWJ Q<mm ZO ZOHB<BHJOmMQ m0 mmmomm QZ< m0<9m m<MJ 92¢Jmmz<m9 m0 mBUmmmm ”N me<B

 

l9

Tunnel, Leaf Stage, and Pruning Study, Spring 1980

 

Protective wax paper tunnels placed over different
size transplants that were pruned at various degrees of de-
foliation (0, 25, 50%) were removed due to extremely high

temperatures two weeks after installation. Leaf stages used

were 3—4, 5-6, and 7—8 leaves. After the tunnels were re-
moved, leaf number count was made from 5 randomly selected
plants in each treatment to determine the effect of the tun-
nel on the growth rate. All 3 main effects (tunnel, leaf
stage, and pruning) significantly affected early plant growth

(P = .01 .001, and .001 respectively) (Table 3).

The tunnels may have increased growth over the unpro-
tected plants due to increased air and soil temperatures. The
unprotected plants, which were exposed to the wind, may have
had a higher leaf water deficit than the protected plants.

It has been hypothesized (Winter, 1965) that this reduced
the rate of water loss (because of stomatal closure) but
maybe interfered with gas exchange, photosynthesis, and
growth.

The smaller transplants (3—4 leaves) produced signi-
ficantly smaller size plants than the larger transplants (5-6
and 7-8 leaves) (P = .001). It was noted after tunnel re-
moval that the severely (50%) pruned plants were smaller than
unpruned or slightly (25%) pruned plants (P = .001) (Table 3).

Fifty-two days after transplanting the heads were har-

vested. Head length was not significantly effected by the

 

.m.c mm mu

O.H 5.0H N.m
k

.m.c sa.a oa.a

.m.c m.ma N.mH

m. w m
«we

.m.caa.a .m.c ma.fl

.m.: m.om

.m.c N.mH

Hm>ma RH. mcp um ucmoflmacmflm I kkkk
Ho>ma RH ocp um unmonHcOHm 1 ¥«*
Hm>ma Rm may pm pchHchmHm 1 xx

Ho>ma Rea Gnu um unmoHMcham I k

Hm>ma Rea pm pcmuamacmflm won 1 .m.c

om mo cmumo>umr ucmoumm

ma ma 2.3

xamum Hmcuonca
mm.a mm.a Aussie
panama new:
H.HN w.om Asov
onch Emu:

o.ma m.va AEUV
noboemaa cmmz

a 1mm>mmg as

GNHm ucmam

 

QmJ OZ mm>

 

uo>oo

coabmaaomma a

mmmum wmoq

noumEmumm

 

omma .omm .lma <x0<o<z
m>Heomeomm nz<

.ona<Haomma mo mmmoma

.m0<mm<0 mmmzHEU m0 QJMH> QZ< VBHJ<DO ZO .mmm>OU
.mO<Bm m<MJ BZ<JmmZ<mB m0 meummmm ”m mqm<8

 

21

treatment main effects or interactions and although head dia—
meter was effected by leaf stage (P = .05), the mean differ—
ences between treatments was<Ll cm.

The role of leaf stage in effecting head weight was
dependent on whether the transplants were protected. A tun—
nel X,leaf stage interaction showed a linear—quadratic re-
lationship for the unprotected plants (Figure 2) (P = .005).
The smaller transplants (3-4 leaf stage) were inferior to
the 5-6 and 7-8 leaf stages and the head weight of the 7-8
leaf stage plants was less than the 5—6 leaf plants. The
protected plants showed similar trends but.were not signi—
ficant. The small (3-4 leaves), unprotected plants were
inferior to the 3—4 leaf stage plants under the tunnels. This
may be due to the small plants being more susceptible to trans—
plant shock. This is also discernible from the differences
in percentage of harvestable plants due to leaf stage (Table
3). The 3-4 leaf stage showed a lower percentage of harves-
table plants at the end of the experiment than the other leaf
stages (P = .01). Zink and Knott (1965) found that small
celery transplants recovered more slowly than larger plants.
All other treatment main effects (tunnel and pruning) and
interactions did not affect the harvestable percentages.

Although the protected plants were larger at the time
of tunnel removal, the post tunnel growth rate appeared to be

reduced. This may be due to rapid growth under the tunnels

(kgms)

Head Weight

 

22

o no tunnel

 

 

1.7 O tunnel
1.6 .I“‘---
O
1.5
0‘
‘0
1.4
O
1.3
o
1.2
O
3_4 5-6 7-8
Leaf Stage
FIGURE 2: THE EFFECT OF TRANSPLANT LEAF STAGE AND PROTECTIVE

COVERS, ON HEAD WEIGHT OF CHINESE CABBAGE (CV.
NAGAOKA #2) HRC, 1980

I

-23
which made these plants succulent and sensitive to a more ad-
verse environment. Similar observations were made by Waggoner
(1958) who reported that following cover removal on tomatoes,
the plants became less vigorous and set less fruit. Harris
(1965) reported similar results with corn and beans.

Due to a warm spring, flower stalks were not visible
at harvest. In order to evaluate the effect of the tunnel on
bolting, each harvested head was cut longitudinally, and the
length of the developing stalk was measured. The presence
of the internal flower stalks indicated that the plants re—
ceived the minimal amount of cold temperatures for vernaliza-
tion. The unprotected plants showed a longer internal stalk
than the protected plants (P = .10) (Table 3).

From this experiment, one may conclude that the larger
transplants (5—6 and 7—8 leaf stages) produced heads that
were superior to the 3-4 leaf transplants. In general, prun-
ing the seedlings adversely effected early plant growth but
did not significantly decrease yield. If the plants were
transplanted earlier to new exposed or colder temperatures
for a longer period, the unprotected plants probably would
have produced significantly more bolters than those plants
protected. This would have resulted in decreased tonnage

per hectare.

HRC, Nagaoka #2, Spring 1981

Nagaoka #2 was harvested on 6/29—30. Statistical analy—

sis suggested that none of the main treatment effects (leaf

24

stage, pruning, tunnel) significantly affected head diameter,
head length, or head weight. The percentage of harvestable
plants was effected by leaf stage (3—4, 5-6, 7—8). The 7—8
leaf transplants produced slightly more harvestable heads
than the 3-4 leaf stage plants (P = .10) (Table 4). There
was no significant difference in the number of harvestable
plants between 5-6 and 7-8 or 3—4 and 5-6 leaf stages. The
percentage of bolters was significantly effected by a tunnel
X leaf stage interaction (P = .025). Trend analysis sug-
gested that for the unprotected plants, the percentage of
bolters linearly decreased with increased transplant size

(P = .01) (Figure 3). For the protected plants, the per-
centage of bolters increased with larger transplant size,
however, it was not significant. The unprotected plants had
internal flower stalks that were slightly longer than plants

grown under tunnels (P = .10) (Table 4).

HRC, Jade Pagoda, Spring 1981

Plants were harvested one week later than Nagaoka #2
(7/6-7). The main treatment effects (leaf stage, pruning,
tunnel) had no effect on head diameter, head lenght, inter-
nal stalk length, or head weight, however the use of the
tunnels did significantly reduce the percentage of bolters
(P = .05), (Table 5) resulting in a higher percentage of

harvestable plants (P - .10). The percentage of plants

 

25

 

 

80
0 0 no tunnel
70 O tunnel
O

60

so '

40

1....o

"O 0—7
a: 30
f.)
.4
O
m
o\°

20} o

0 +

3—4 5-6 7—8
Leaf Stage
FIGURE 3: THE EFFECT OF TRANSPLANT LEAF STAGE AND PROTECTIVE
ROW COVERS, ON PERCENT OF BOLTERS IN CHINESE CABBAGE
(cv. NAGAOKA #2) HRC, 1981.

I

 

.am>ma Rea OLD pm acmOHMHCOam : a

 

 

 

a®>®a Rea mca am unmoawacvam Doc I .m.c
.m.c R.mm m.>m .m.c m.am «.mv a.mv Re.ma R.Nm m.>v e.em Umpmm>umz uCOOGOe
.m.c a.me a.mN .m.c a.mv a.ev R.em .m.c R.av m.ev e.>v Umpaom bcouumm
w.a e.ma R.ea .m.c a.ma v.5a v.wa .m.c m.na m.ma e.>a AEOV xampm amcumbca
2.m.c em.a em.a .mfiaamv.a mm.a RN.a .m.c vm.a Nv.a em.a Amemxe unmamz Cam:
.m.c m.aN m.aN .m.c w.am a.aN e.aN .m.c N.aN v.am m.aN AEUV cumcmu Ono:
.m.c m.va a.ma .m.c e.ma m.va a.va .m.c a.va a.ma a.va AEUV Houmemao 0mm:
Owe oz mm» omq em mm o ems min elm vim
um>ou Coaumaaowmm R manpm woos Hoaoemumm

 

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zo .mmm>oo m>HeomeomA aza .oneaHaommo mo mmmoma .moaem mama 9244mmz<me mo meommmm ”a mamas

am>ma Rm orb pm Damoauacoam I .*

 

 

 

am>ma Rea orb um bemoauacmam . *

ao>®a Rea 05a um acmoawacmam DOC I .m.c

m.aa G.Na R.mml&m.m a.am e.va a.mm .m.: a.mm a.mm - m.oa Gmbmm>umz bcmOGmm

Mmimiem e.eR e.wv .m.c N.ae v.00 a.mm .m.c m.>e v.em e.me Oouaom Dcoouoe

.m.c e.em e.am .m.c a.mm e.mm a.mm .m.c e.vm m.am a.mm AEOV xamum amcuouca

.m.c me.a mm.a .m.cam.a vv.a mm.a .m.C em.a mm.a ao.a Ameoxe DCanz 0mm:

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DmJ 02 mm» QmJ om mm 0 am; mlh elm Vim

Hm>oo coaumaaommn R mmmam mums nonmemumm

 

amma .Um: .A<QOO<m mm<h .>UV .mw<mm<0 mmmZHEU m0 QJmHM QZ< NBHJ<DO
ZO .mmm>OU m>HBUMBomm 02¢ .ZOHB<HJOhMQ m0 mmmomm .m0<Bm m<mq BZ<Jmmz<mB m0 mBUmmmm "m mdm<9

28
harvested was also effected by the degree of defoliation.
Unpruned plants produced more harvestable plants than those
slightly (25%) pruned (P = .05) (Table 5). There were no
significant differences in percentage of harvestable plants
between slightly (25%) and severely (50%) pruned plants or

unpruned and severely (50%) pruned plants.

Muck Farm, Nagaoka #2, Spring 1981

 

Harvesting began on 7/8 and continued until 7/12. Head
diameter was effected by the second order interaction, leaf
stage X pruning X tunnel. Trend analysis suggested that only
the head diameter of the unprotected plants were effected by
the interaction: (1) a quadratic trend at the 3—4 leaf stage
with increased pruning in which the slightly (25%) pruned
plants produced heads largest in diameter (P = .01), (2) a
significant linear relationship at the 5—6 leaf stage which
showed a decrease in head diameter with increased pruning

(P = .05) and (3) a linear trend at the 7-8 leaf stage which

showed an increase in head diameter with increased pruning
(P = .005) (Figure 4).

Head length was also effected by the second order in-
teraction (leaf stage X pruning X tunnel). Trend analysis
showed that only the unprotected plants were effected by the

interaction: (1) a linear-quadratic relationship at the 3-4

leaf stage in which the slightly (25%) pruned plants produced

29

 

 

16
n
O
15 o 3-4 leaves
0 5-6 leaves
0 7-8 loaves
" 14
E
8
O
5 a
3 l3 .
E
.,.I o C
e
U 12
m
B’ o
11
O
10
0
0 25 50

Degree of Defoliation (%)

FIGURE 4: THE EFFECT OF DEGREE OF DEFOLIATION AND TRANSPLANT
LEAF STAGE, ON HEAD DIAMETER OF CHINESE CABBAGE
GROWN UNPROTECTED (CV, NAGAOKA #2), MUCK FARM, 1981

30

the longest heads (P = .025— .01), (2) a linear trend at

the 5—6 leaf stage which showed a decrease in head length
with increased pruning (P = .005), and (3) a linear trend

at the 7-8 leaf stage which showed an increase in head length
when plants were more severely (50%) pruned (P = .01) (Figure
5).

Head weight was effected by the leaf stage X pruning
X tunnel interaction. This second order interaction only
effected the head weights of unprotected plants: (1) a
quadratic relationship at the 3-4 leaf stage with increased
pruning; the slightly (25%) pruned plants having produced
the largest head weights (P = .005), (2) a negative linear
trend at the 5-6 leaf stage with increased pruning (P = .05),
and (3) a positive linear trend of head weight at the 7-8
leaf stage as pruning increased (P = .025) (Figure 6).

The internal flower stalk length was significantly
effected by the use of the protective tunnels. The protected
plants had shorten internal stalks than unprotected plants
(P - .05) (Table 6). The leaf stage X pruning X tunnel in-
teraction also had a significant effect on internal stalk
development. Trend analysis suggested that in the unpro—
tected plants, with increased pruning: (l) the 3-4 leaf stage
showed a linear-quadratic relationship in which the slightly
(25%) pruned transplants developed the longest internal stalks
(P — .05— .001), (2) the 5—6 leaf stage showed negative lin-

ear relationship (P = .025), and (3) the 7-8 leaf stage

 

 

0 5-6 loaves

\ i 0 7-3- leaves
0

u
/n o 3-4 lecwos

 

23
22
21
E
3
.C 20
H
O"
C‘.
a)
._‘l
ID 19
ru
0)
:I: /
0
FIGURE 5:

0 25 50

Degree of Defoliation (%)

THE EFFECT OF DEGREE OF DEFOLIATION AND TRANSPLANT
LEAF STAGE, ON HEAD LENGTH OF CHINESE CABBAGE GROWN
UNPROTECTED (CV. NAGAOKA #2 ) , MUCK FARM, 1981

32

1.75
o
- u
1.50
o 3-4 leaves
0 5-6 loaves
1.25 o o 7-8 leaves
a
1:?
1.00
3‘ o
4.)
B
.75
3
C
m
o .50
:1:
O —

 

0 25 50

Degree of Defoliation (%)

FIGURE 6: THE EFFECT OF DEGREE OF DEFOLIATION AND TRANSPLANT
LEAF STAGE, ON HEAD WEIGHT OF CHINESE CABBAGE GROWN
UNPROTECTED (CV. NAGAOKA #2), MUCK FARM, 1981

am>0a Rm mca um ucmoawacmam I R

 

 

 

am>®a Rea ozu um acmoamaCOHO DOC I .m.c
m.em R.mm m.em .m.c R.mm v.mm w.am .m.c m.em m.ae m.mm Coumm>umr ucmoume
«
m.Nm a.me a.ma .m.c N.mm e.vv a.mv .m.c a.mv e.>m a.mw Douaom unmoumm
R
3
3 a.m a.ma N.ma .m.c m.ea m.Ra e.Ra .m.c N.wa a.ma e.ea AEOV xamum amcuobca
#
.m.c Na.a Rm.a .m.caa.a, Rm.a em.a .m.c am.a Re.a ma.a Amemxv ucoaoz Ono:
.m.c v.aN a.aN .m.c R.eN o.aN v.am .m.c e.aN m.em m.aN AEOV camcmq Ono:
.m.c a.ma e.ma .m.c e.ma n.ma v.ma .m.c a.ma w.ma a.ma AEOV Emumemae Ono:
mm; 02 mm» mm; em. mm o mm; ml» elm elm
um>OO coaumaaommo R mmmum wmmq nonmemumm

 

ZO

amma .zm<m mos: .Ame <xo<oaz .>oe .mo<mm<o mmmszo mo mama» eza aeHa<eo
.mmm>oo m>HeomeOmm 62¢ .one<Haomma so mmmomo .mo<em E<ma ez<ammz<me mo meommmm no mamas

34

showed a positive linear trend in stalk length with increased
pruning (P = .025) (Figure 7). The use of protective tunnel
reduced the number Of bolters and resulted in a greater total
percentage of heads harvested than when unprotected (P = .05)

(Table 6).

Muck Farm, Jade Pagoda, Spring 1981

 

Harvesting commenced on 7/15 and continued until 7/17.
Mean head diameter comparisons between leaf stages showed
that the 7—8 leaf transplants significantly produced heads
larger in diameter than the 3—4 leaf stage plants (P = .05)
(Table 7). Head differences were not significant between
the 3-4 and 5-6 or 5-6 and 7—8 leaf stages.

Although main treatment effects (leaf stage, pruning,
tunnel) did not effect head length, the second order inter-
action, leaf stage X pruning X tunnel had a significant ef—
fect on head length of unprotected plants. A negative lin—
ear trend in head length was noted with increased pruning at
the 5—6 leaf stage (P = .005). At the 7-8 leaf stage, a
quadratic relationship was noted in which the slightly (25%)
pruned plants produced the longest heads (P = .025) (Figure
8).

Head weight of Jade Pagoda grown without cover was
greater than when grown protected for all treatments (P = .05)

(Table 7).

 

35

 

23 o
O
22
21
o 3-4 leaves
0 5-6 loaves
20
0 7-8 loaves
A o
S 19 a
V O
S O
*5. 18 °
C
o
a
x 17
H
ru
4.)
m 16
H
2
0
’5 15
4.)
C o
H
14
UL
0 25 50
Degree of Defoliation (%)
FIGURE 7: THE EFFECT OF DEGREE OF DEFOLIATION AND TRANSPLANT

LEAF STAGE, ON INTERNAL STALK LENGTH OF CHINESE CAB-
BAGE GROWN UNPROTECTED (CV. NAGAOKA #2), MUCK FARM,
1981.

ao>ma Rm.m we» um bemoauacmam I III

 

 

 

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am>ma Rea one an quoawaCOam I k
am>0a Rea an quoamaCOam uoc I .m.C
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yo
m.mv a.me N.ea .m.C a.mm e.em a.mm .m.C a.mm m.em a.mm Umpaom_HCoouom
«RR
,Oemhm e.mm R.mm .m.C N.mm N.Rm e.eN .m.C R.mm a.mm a.mm AEOV xamum amCCouCa
3
mm. am.a aa.a .m.c Gm.a sm.a oe.a .m.c am.a mm.a Ga.a Ameoxv Bream: 8mm:
«R
.m.C N.mm a.am .m.C m.mm m.mm e.mm m.C R.Nm m.mm a.mm AEUV CumCOE Ono:
.m.C m.aa m.ea .m.C N.aa m.ea m.aa v..«N.a a.aa a.aa v.ea Asov umuosmae Ono:
emu oz no» emu em mm e om; mIR eIm va
um>OO Coaumaaomme R momum mmma nmumEmumm

 

amma .Zm<m MUD: .A<Q00<m ma<h .>Ov .m0<mm<0 WWMZHZU m0 QJme QZ< >8HJ<DO
ZO .mmm>OU m>HBUmBOmm 024 .ZOHBéHJOhMQ m0 mmmomm .m0<9m m<ma BZ<JmmZ<mB m0 mBUmmhm "h Mdm<8

37

0 3-4 loaves

 

35.5
0 5-6 leaves
‘3 o 7-8 leaves
35.0
34.5
0
34.0 0
o
,. 33.5 o
E
o
V o
E 33.0
o n
C
a)
J 32.5
'0
rt:
0)
E 32.0
n
31.5
31.0
30.5
o
30.0
0L
0 25 50
Degree of Defoliation (%)
FIGURE 8: THE EFFECT OF DEGREE OF DEFOLIATION AND TRANSPLANT

LEAF STAGE, ON HEAD LENGTH OF CHINESE CABBAGE GROWN
UNPROTECTED (cv. JADE PAGODA)

MUCK FARM, 1981

I

-38

It was also determined that the leaf stage X pruning-
X tunnel interaction effected head weight. Trend analysis
suggested that when plants grown under the tunnels, the
larger transplants (7-8 leaves) showed a negative linear
relationship in head weight with increased pruning (P = .05)
(Figure 9). Trend analysis also suggested that with the
unprotected plants, the 7—8 leaf stage plants showed a quad—
ratic trend with increased pruning with the slightly (25%)
pruned plants producing the heaviest heads (P = .10). The
5-6 leaf stage plants showed a negative linear relationship
of head weight with increased pruning (P = .025) (Figure 10).

Internal stalk development and the percentage of plants
showing visible flower stalks (bolters) were significantly in-
hibited by the use of the protective tunnel (P = .025) (Table
7). Since fewer bolters were found in the protected plants,
significantly more heads were harvested from the protected

plants than from unprotected plants (P = .10) (Table 7).

1.50

1.40

Head Weight (kgms)
H H H H
'o i—a IV LO
0 O O 0

KO
O

.80

FIGURE 9:

 

 

\

39

U o 3-4 leaves

0 5-6 Leaves

0 778. leaves

 

0 25 50

Degree of Defoliation (%)

THE EFFECT OF DEGREE OF DEFOLIATION AND TRANSPLANT
LEAF STAGE, ON HEAD WEIGHT OF CHINESE CABBAGE GROWN
UNDER TUNNELS (CV. JADE PAGODA), MUCK FARM, 1981

40

9-3-4 loaves
<35-6 have:
u 7—. 8 leaves

(kgms)

 

Head Weight

0 25 50

Degree of Defoliation (%)

FIGURE 10: THE EFFECT OF DEGREE OF DEFOLIATION AND TRANS—
PLANT LEAF STAGE, ON HEAD WEIGHT OF CHINESE
CABBAGE GROWN UNPROTECTED (cv. JADE PAGODA),
MUCK FARM, 1981

 

GENERAL CONCLUSIONS

1. The use of the protective tunnels significantly
reduced the number of bolters and the length of internal
flower stalk.

2. Older seedlings (5-6 and 7-8 leaf stages) produce
a greater percentage of harvestable heads than the smaller
seedlings (3-4 leaves).

3. The protective tunnels hasten early plant growth,
however, subsequent growth after tunnel removal was slowed
down.

4. There appeared to be more uniform growth between
treatments when plants were grown under the tunnels.

5. Pruning decreased early plant growth, however,
harvested head weight was not significantly effected.

6. It appeared that the 5-6 leaf transplants left
unpruned and grown protected produced the best overall yield

and quality.

41

APPENDIX

FIGURE A-l: DIAGRAM OF THE CHINESE CABBAGE .SEEDLING
TUNNEL SYSTEM USED IN JAPAN (BELOW) AND THE
SYSTEM USED IN MICHIGAN (ABOVE).

42

 

 

 

 

 

FIGURE A-Z: MEAN AIR AND SOIL TEMPERATURES WITHIN AND
OUTSIDE THE TUNNEL SYSTEM FROM 5/6 TO 5/11/80

43

2: to as;

 

 

 

3?: 31.5
maeamwxomammamaaaoammxdma
. a a _ . al . _ a a] all T _ A a 1 _ a 4 a D

7,
\ lo
) x
/ >
/ \ //
x M
O// /
4y) I I a
/a/
I ow
.233 is :u OIIIIIIIO
.055. 33 to Cl II I I...
.225. \3 :3 o o
.053. 33 :3 ollllo
- e

 

(3 o) BdanHBcI/Gl

FIGURE A-3: MEAN AIR AND SOIL TEMPERATURES WITHIN AND
OUTSIDE THE TUNNEL SYSTEM FROM 5/11 TO 5/16/80

 

    

 

>58sz
3?: 31.5
Naoammmomemmamaaaoamwmmmao
a 1 la I. . a J . .(a a a _ J . . . _ . .
\\’
/
/
\ r
or \ / .2
//1 \\O\ \ «Illor/
. . /
z \o\ . M.
x
P /
A... // .
4 0
,7
/
. . I . IIOI
-8
.055. \3 :0 .0 O.
.055. a}: :0 cl I II o l R
.055. \3 Zen 0 o

.055. at: :aa OI I I o,

 

(j o) BEHIthBcNSl

FIGURE A-4: MEAN AIR AND SOIL TEMPERATURES WITHIN AND
OUTSIDE THE TUNNEL SYSTEM FROM 5/16 TO 5/21/80

:5 E as;

 

Aide 12.5
Na 2 m w R o m 3 m N a Na aa 2 m m m e m a
\lt
) x
/ \xOIl . IO/I
“ / R o JVIIO

 

.055. \3 .._u o o
.055. at, .._o OII II II II.
.055. \3 :3 OIIIIIIIIO

.055. at: :0» 0| II .| .10

 

ea

(3 o) EHMWEdEi

TABLE A—l: MAXIMUM/MINIMUM AIR AND SOIL TEMPERATURES WITHIN
AND OUTSIDE THE TUNNEL SYSTEM, 1981

46

 

Aamccsp moampsoe na\ma :H\mm R\Ga a\~m R\ma m\oa G\oH :\mfi m\ma o\ma R\Na m\ma

1am223p moamCae ma\am ma\m~ m\am m\om R\Ra m\mm R\ma m\ma o\om m\mm m\ma m\:m

 

 

 

 

 

 

aaom ha aaom ha aaom ha< aaom pa< aaom pa< aaom La<
em I N NNVWIwamw a I a Na (m waume mmwucmm:

 

 

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Aamccsp anamCAV Ga\mm ma\mm aa\mm m\~m m\ma m\mm Ha\oa G\am

 

 

 

 

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oI-I
I—I
-a

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BIBLIOGRAPHY

BIBLIOGRAPHY

Aung, L.H. and Kelly, W.C., 1966. Influence of defoliation
on vegetative, floral, and fruit development in tomatoes.
Proc. Amer. Soc. Hort. Sci. 89:563-570.

Bailey, L.H., 1930. The cultivated Brassicas. Gentes
Herbarium. 2:211-267.

 

Bakhchevanova, S., 1976. The use of polyethylene tunnels
for growing early head cabbage. Gradinarska; Lozarska
Nauka. 13 (5):57-62.

Boswell, V.R., 1949. Our vegetable travelers. National
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