premature bolting in onion bulb crop; effect of

i

PREMATURE BOLTING IN ONION BULB CROP; EFFECT OF

TRANSPLANTING DATES, SEEDLING AGE NITROGEN

FERTILIZER AND CULTIVARS

By

Noor Habib Khan

11-PhD-Agr-S-Hu-4

A dissertation submitted in partial fulfillment for the requirement of degree of

Doctor of Philosophy

In

Agricultural Sciences (Horticulture)

DEPARTMENT OF AGRICULTURAL SCIENCES

THE UNIVERSITY OF HARIPUR

KHYBER PAKHTUNKHWA PAKISTAN

APRIL, 2017

ii


TRANSPLANTING DATES, SEEDLING AGE, NITROGEN FERTILIZER

AND CULTIVARS

BY

Noor Habib Khan

Approved By:

_______________________

Dr. Shah Masaud Khan Chairman, Supervisory Committee

________________________

Prof. Dr. Ayub Khan Co-Supervisor

________________________

Dr. Sher Aslam Khan Member (Major Field)

Associate Professor

________________________

Prof. Dr. Abid Farid Member (Other Field)

________________________

Dr. Naushad Ali Member (Other Field)

Assistant Professor

_______________________

Prof. Dr. Ayub Khan Chairman, Deptt. Of Agri.Sciences

________________________

Prof. Dr. Abid Farid Dean Faculty of Basic and Applied Sciences

________________________

Dr. Shah Masaud Khan Director, Advance Studies and Research Board

DEPARTMENT OF AGRICULTURAL SCIENCES (HORTICULTURE)

THE UNIVERSITY OF HARIPUR, KHYBER PAKHTUNKHWA

PAKISTAN

April, 2017

iii



AND CULTIVARS

BY

Noor Habib Khan

Approved By:

External Examiner

Prof. Dr. Akihiro Isoda

Graduate School of Horticulture

Chiba University Matsudo 648

Matsudo-city

Chiba 271-8510

Japan

E-mail: [email protected]

Phone: +81-47-308-8814

iv



AND CULTIVARS

BY

Noor Habib Khan

Approved By:

External Examiner

Prof. Dr. Mahmud T. Muda Mohamed

Universiti Putra Malaysia

Department of Crop Sciences

43400 UPM Serdang

Selangor Darul Ehsan

E-mail: [email protected]

Phone: +603-8947 4823

v



AND CULTIVARS

BY

Noor Habib Khan

Approved By:

Internal / National Examiner

Prof. Dr. Noor Ul Amin

Department of Horticulture

The University of Agriculture, Peshawar

Dr. Muhammad Sajid

Associate Professor

Department of Horticulture

Hazara University, Mansehra

vi

PREMATURE BOLTING IN ONION BULB CROP; EFFECT OF TRANSPLANTING

DATES, SEEDLING AGE NITROGEN FERTILIZER AND CULTIVARS

ABSTRACT

By

Noor Habib Khan and Shah Masaud Khan

Research trials were conducted at Agricultural Research Institute, Mingora Swat over two consecutive

growing seasons from November to June 2013-14 and 2014-15.

In the first trial seedlings of 45, 60 and 75 days old were transplanted on 5 different dates (30th November,

15th December, 30th December, 15th January and 30th January) to study its effect on premature bolting in

onion. Transplanting dates and seedling age exerted significant effect on different growth and yield

parameters studied. Plant height, number of leaves at bolting, stem thickness, days to maturity, bulb

diameter, bulb weight and total yield (ton ha-1) decreased with delay in transplanting as well as with

increasing seedling age. On the other hand, bolting and cull percentage decreased with delay in

transplanting and increased with increase in seedling age. Maximum marketable yield (ton ha-1) was

recorded when 60 days old seedlings were transplanted on 15th December. The correlation co-efficient

analysis data revealed a positive correlation between marketable yield (0.671 ton/ha) and bulb diameter

(0.381). Non- significant positive correlations of marketable yield were recorded with bulb weight (0.173),

number of leaves at bolting (0.097), stem thickness (0.091) and plant height (0.106). The association of

marketable yield with bolting percentage (-0.381) and % cull (-0.552) was significantly negative.

In the second trial three commercial cultivars ‘Swat-1’, ‘Saryab Red’ and ‘Chiltan-89’ were transplanted

on five different dates at 15 days interval (25th November, 10th December, 25th December, 10th January and

25th January). Cultivars varied in their susceptibility to bolting. Cultivar Swat-1 took significantly

maximum (78.67 days) to bolting initiation and recorded minimum bolting percentage (12.51%) compared

to ‘Saryab Red’(13.75%) and ‘Chiltan-89’ (17.32%). Early transplanting took less (108.06 days) to bolting

initiation. Bolting percentage was maximum (34.52%) at early transplanting and reduced with delay in

transplanting from 25th November to 25th December. Bolting was not recorded at late, (10th and 25th

January) transplanting irrespective of the cultivar. When compared to ‘Saryab Red’ and ‘Chiltan-89’,

‘Swat-1’ had maximum plant height (65.58 cm), number of leaves per plant (10.64), stem thickness

(15.43mm), bulb diameter (60.08 cm), bulb weight (169.08 g), and days to maturity (168.37), total (32.94

vii

ton ha-1 ) and marketable yield (25.07 ton ha-1 ). Plant height (61.24cm), number of leaves per plant (10.96),

stem thickness (17.24 cm), bulb diameter (63.08 cm), bulb weight (149.31g), and days to maturity (167.89),

total yield (31.07 ton ha-1) was maximum at early transplanting and decreased with delay in transplanting.

Cultivar Swat-1 produced maximum marketable yield (25.07 ton ha-1) than ‘Saryab Red’ and ‘Chiltan-89’.

Marketable yield was maximum at mid transplanting date (25th December); attributed to less bolting and

percent cull compared to early transplanting. Unmarketable yield at early transplanting was largely due to

bolting while at late transplanting it was due to small ungraded bulbs.

In the third trial different rates of nitrogen fertilizer (75, 100, 125 and 150 kg ha-1) were applied at different

transplanting dates (15th Nov, 1st Dec, 15th Dec, 1st Jan and 15th Jan) with the objective to determine its

influence on inflorescence development in onion bulb crop. Bolting percentage decreased gradually with

increase in the rate of nitrogen fertilizer. Maximum bolting percentage was recorded in early transplanting

and declined with delay in transplanting. Bolting incidence did not occurre in very late (15th January)

transplanting irrespective of the rate of nitrogen applied. Plant height, stem thickness, bulb diameter, bulb

weight and total yield ton ha-1 increased with increase in nitrogen fertilizer and conversely showed a

downward trend with delay in transplanting. Different rates of nitrogen fertilizer didn’t significantly

influence number of leaves plant-1. However, early transplanting exhibited significantly more leaves than

late transplanting. Early transplanting took maximum 175.88 days to maturity than late transplanting

(163.75) days. Maturity was delayed with increase in nitrogen fertilizer. Percent cull decreased with

increase in the rate of nitrogen fertilizer. Marketable yield ton ha-1 was maximum at mid transplanting date

(15th December) and with maximum rate of nitrogen fertilizer. The correlation co-efficient analysis revealed

that marketable yield ton ha-1 has positive correlation with plant height, number of leaves plant-1, bulb

diameter, bulb weight, total yield ton ha-1 and negative correlation with stem thickness bolting percentage

and percent cull. Bolting percentage has positive association with percent cull.

It can be concluded that bolting resistant cultivar is not available in this country, however, ‘Swat-1’

performed best in the existing cultivars. Research should be initiated to develop bolting resistant cultivars

or produce resistance in available cultivars through phenotypic recurrent selection. Modification in cultural

practices remained the viable option for the growers to mitigate bolting problem. Transplanting should be

delayed in such a way to avoid plants receiving cold temperature at sensitive stage to minimize bolting.

Correct transplant age (50-60 days) and ample nitrogen fertilizer of 125-150 Kg ha-1 also reduced the

incidence of bolting.

viii

ACKNOWLEDGEMENTS

All praises to Almighty Allah, the most beneficent the most merciful for all his blessing conferred upon me.

I have accompanied and supported by many people. It is pleasant opportunity to express my gratitude for

all of them.

I am truly indebted to my supervisor Dr. Shah Masaud Khan Associate professor, The University of Haripur for his

guidance, valuable advice and constructive criticism; refining my arguments and consolidating my resolve to

complete this dissertation. The guidance and encouragement of Professor Dr. Ayub Khan, Chairman Department of

Agricultural Sciences, University of Haripur has been vital in enabling me to reach this stage. Without his motivation

my PhD research would have been unbearably challenging.

I am very grateful to Professor Dr. Abid Farid, Dean Faculty of Basic and Applied Sciences, for his insight and fruitful

criticism during this study. Faculty Members, Dr. Muhammad Saeed and Dr. Sher Aslam Khan deserve many thanks

for their useful suggestions and unforgettable friendly attitude.

I’m very indebted to Dr. Abdul Bari, Director ARI, Mingora, Swat who facilitated me at the institute during the course

of this study.

I would like to thank and wholeheartedly appreciate my colleagues Dr. Ehsan Ullah Principal Research Officer for

sparing his precious time to shape and edit this manuscript to an improved version, Dr. Rahmani Gul Senior Research

Officer, for his valuable suggestions and help in statistical analysis, Dr. Muhammad Naeem, Research Officer, Dr.

Amjad Khan Principal Research Officer and Dr. Fazli Maula Senior Research Officer for frequent help and most

needed moral support.

I wish to record my sincere thanks to Mr. Iqbal Hussain who extended full support in my field research work and data

analysis with patience, commitment and dedication. I also convey my thankfulness to Dr. Muhammad Munir who

accompanied me during my travel and stay during this study.

I am grateful to Mr. Javed Ali and Mr. Jamshid, Field Assistants and field workers of vegetable section for untiring

help in field operations and in data collection.

Last, but utmost thanks to my parents, wife and children whose prayers granted me the courage and devotion to deal

diligently with frequent frustration during this study

Date Noor Habib Khan

ix

LIST OF ABBREVIATION

Abbreviations Full form

% Per cent

@ At the rate of 0C Degree Celsius

Cm Centimeter

Plant-1 Per plant

et al. And co-worker/and others

Fig. Figure

FYM Farm yard manure

Gm Gram

ha-1 Per hectare

Kg Kilogram

m-2 Per Meter square

Mm Millimeter

N Nitrogen

Ns non-significant

RH Relative humidity

S. No. Serial number

Mn Manganese

Zn Zinc

K Potash

VD Vernalization day

RGR Relative growth rate

DATP Days after transplanting

x

TABLE OF CONTENTS

ABSTRACT ............................................................................................................................................... VI

ACKNOWLEDGEMENTS ................................................................................................................ VIII

LIST OF ABBREVIATION ................................................................................................................... IX

LIST OF TABLES ................................................................................................................................... XI

LIST OF FIGURES .............................................................................................................................. XIII

CHAPTER 1: INTRODUCTION ............................................................................................................... I

CHAPTER 2: REVIEW OF LITERATURE ....................................................................................... 8

CHAPTER 3: EXPERIMENT1:EFFECTS OFTRANSPLANTING DATES AND

SEEDLING AGE ON PREMATURE BOLTING IN ONION BULB CROP…………….22

CHAPTER 4:EXPERIMENT 2: BOLTING IN ONION BULB CROP AS INFLUENCED BY

CULTIVARS AND TRANSPLANTING DATES……………………………………………….51

CHAPTER 5: EXPERIMENT 3: EFFECT OF TRANSPLANTING DATES AND NITROGEN

FERTILIZER ON FLOWERING INITIATION IN ONION BULB CROP…………………..73

CHAPTER 6: OVERALL SUMMARY, CONCLUSIONS AND

RECOMMENDATIONS……………………………………………………………………96

CHAPTER 7: LITERATURE CITED .............................................................................................. 101

APPENDICES ......................................................................................................................................... 118

SELECTED PICTURES ...................................................................................................................... 133

xi

LIST OF TABLES Table 1: Nutritional composition of onion (per 100 g) .................................................................................... 2

Table 2: Effect of day length, temperature and variety on bolting in Alliums ................................................... 4

Table3: Physico-chemical properties of the experimental soil. ................................................................................. 26

Table 4: Elaborated planting dates and seedling ages. ............................................................................................... 27

Table 5: Effect of transplanting date and seedling age on plant height during year 2014 and 2015....................... 31

Table 6:Effect of transplanting date and seedling age on number of leaves at Bolting in year 2014 and 2015….32

Table 7: Effect of transplanting date and seedling age on stem diameter during year 2014 and 2015.. ................. 33

Table 8: Effect of transplanting date and seedling age on days to maturity during the year2014 and 2015.. ........ 35

Table 9: Effect of transplanting dates and seedling age on bolting percentage during year 2014 and 2015.. ........ 36

Table 10: Effect of transplanting date and seedling age on bulb diameter (mm) during years 2014 and 2015……39

Table 11: Effect of transplanting date and seedling age on bulb weight (g) during year 2014 and 2015.. ............ 40

Table 12: Effect of transplanting date and seedling age on yield (ton ha-1) during the year 2014 and 2015.. ........ 42

Table 13: Effect of transplanting date and seedling age on percent cull during year 2014 and 2015.. ................... 44

Table 14:Effect of transplanting date and seedling age on marketable yield (ton ha-1) in year 2014 and 2015….46

Table 15: Phenotypic correlation coefficient among yield and yield related characters in onion.. ......................... 48

Table 16: Treatment detail of the experiment………………………………………………………………....53

Table 17:Effect of on transplanting date and cultivars on plant height (cm) during the year 2014 and 2015……55

Table 18: Effect of on transplanting date and cultivars on number of leaves plant-1 in year 2014 and 2015. ........ 56

Table 19: Effect of on transplanting dates and cultivars on stem diameter during the year 2014 and 2015. ......... 57

Table 20: Effect of on transplanting dates and cultivars on bulb diameter during the year 2014 and 2015. .......... 58

Table 21: Effect of transplanting date and cultivars on bulb Weight (g) dduring the year 2014 and 2015............ 60

Table 22:Effect of on transplanting date and cultivars on days to bolting initiation during year 2014 and 2015. . 62

Table 23: Effect of on transplanting date and cultivars on bolting percentage during during 2014 and 2015. ...... 65

Table 24: Effect of on transplanting date and cultivars on days to maturity during the year 2014 and 2015. ....... 67

Table 25: Effect of on transplanting date and cultivars on total yield (ton ha-1) during year 2014 and 2015. ....... 68

xii

Table 26: Effect of on transplanting dates and cultivars on marketable yield (ton ha-1) in year 2014 and 2015. .. 70

Table 27: Treatment details.......................................................................................................................................... 75

Table 28: Effect of on transplanting date and cultivars on plant height (cm) during the year 2014 and 2015. ...... 77

Table 29:Effect of transplanting dates and nitrogen levels on the number of leaves plant-1 in 2014 and 2015. .... 79

Table 30: Effect of transplanting dates and nitrogen levels on stem thickness (cm) year 2014 and 2015. ............ 80

Table 31: Effect of transplanting dates and nitrogen levels on bulb diameter (mm) in year 2014 and 2015. ........ 81

Table 32: Effect of transplanting dates and nitrogen levels on bulb weight (g) in year 2014 and 2015. ................ 83

Table 33: Effect of transplanting dates and nitrogen levels on bolting percentage in year 2014 and 2015. .......... 84

Table 34: Effect of transplanting dates and nitrogen levels on days to maturity in year 2014 and 2015. .............. 86

Table 35: Effect of transplanting dates and nitrogen levels on total yield (ton ha-1) in year 2014 and 2015. ......... 87

Table 36: Effect of transplanting dates and nitrogen levels on percent cull in year 2014 and 2015 ....................... 89

Table 37: Effect of transplanting dates and nitrogen levels on marketable yield ton ha-1 in year 2014 and 2015. 92

Table 38: Phenotypic correlation coefficient among yield and yield related characters in onion………………....84

xiii

LIST OF FIGURES

Figure 1: Bolting problem in onion bulb crop at farmer’s field in Swat-------------------------------------6

Figure 2: Mean monthly temperature at ARI Mingora during the growing season in 2013-14. ............................ 24

Figure 3: Mean monthly temperature during the growing season in 2014-15. ........................................................ 25

Figure 4: Mean data showing interaction transplanting dates and seedling age for bolting percentage. ................ 37

Figure 5: Mean data showing interaction of transplanting dates and seedling age for bulb weight (gm). ............. 41

Figure 6: Mean data showing interaction of transplanting dates and seedling age for yield ton ha-1. .................... 43

Figure 7: Mean data showing interaction of transplanting dates and year for yield ton ha-1. ................................. 43

Figure 8: Mean data showing interaction of transplanting dates and seedling age for percent cull. ....................... 45

Figure 9: Mean data showing interaction of transplanting dates and seedling age for marketable yield ton ha-1...47

Figure 10: Interaction of transplanting dates and cultivars for bulb diameter (mm). ............................................... 59

Figure 11: Interaction of transplanting dates and cultivars for bulb weight (g)........................................................ 61

Figure 12: Interaction of transplanting dates and cultivars for days to bolting initiation. ........................................ 63

Figure 13: Mean data on interaction of transplanting and year for days to bolting initiation. ................................. 63

Figure 14: Mean data on interaction of transplanting, dates and seedling age for Bolting Percentage. ................. 66

Figure 15: Mean data on interaction of transplanting, dates and year for bolting percentage. ................................ 66

Figure 16: Mean data on interaction of transplanting dates and cultivars for yield ton / ha. ................................... 69

Figure 17: Mean data on interaction of transplanting dates and cultivars for marketable yield ton / ha…………71

Figure 18: Mean data on interaction of Transplanting dates and nitrogen fertilizer for bolting percentage. ......... 85

Figure 19: mean data on interaction of transplanting dates and nitrogen level for percent cull. ............................. 90

Figure 20: Mean data on interaction of year and nitrogen level for percent cull...................................................... 90

Figure 21: Mean data on interaction of transplanting dates and N level for marketable yield ton/ha. ................... 91

xiv

Dedicated to my family, wife and children Hishaam, Ayesha and Qasim

1

Chapter 1

INTRODUCTION

Onion (Allium cepa L.) is a bulbus vegetable belonging to family Alliaceae and Central Asia is viewed

to be its center of origin (Vavilov, 1951: Brewster, 1994). It is monocotyledonous and cross pollinated

with diploid chromosome number 2n = 16 (Bassett, 1986; and Khokhar, 2014). It is the most important

spice and vegetable crop all over the world (Brewster, 1994). Onion is only second to tomato in term of

total annual production among the 15 vegetables listed by Food and Agricultural Organization (Pathak,

2000). It has been grown in 175 countries with a world production of about 82 million metric tons (FAO,

2013).

Onion being a biennial vegetable, largely grown as annual vegetable for bulbs, immature stem (Shallot)

or green leaves (Green Bunching Onion). Onions are called “tunicate” bulbs, which mean that the scales

are covered by a thin skin known as tunic. These scales are also called “wrapping scales.” (Sidhu et al.,

2005). Bulb is modified underground shoot or flower bud. The thick scales that protect the bud are in

fact swollen leaf bases. The scales are attached to a tough basal plate from which the roots grow. The

bulb contains nearly everything that the embryonic bud will need to grow and flourish (Sidhu et

al.,2005).

Cultivation of onion dates back to prehistoric times. Mentions of onions can be found in the Bible, Quran

and in the writings of the ancient civilization of Egypt, Rome, Greece, and China. As onion cultivation

spread, cultivars evolved with more diversity in shape, color, flavor, keeping-quality, and with critical

adaptations to new climates. The most important adaptive traits involved is the bulbing response to day

length and high temperature, and conversely bolting response to low temperatures (McCollum, 1976).

Maximum diversity in onion is found in the eastern Mediterranean countries, from Turkmenistan and

Tajikistan to Pakistan and India (Astley et al., 1982).

Onion is a common vegetable grown for its flavorful bulbs and leaves (Shanmugasundaram and Kalb,

2001). It contains carbohydrate, protein, vitamin A, thiamine, riboflavin, niacin, ascorbic acid (Hanen

et al., 2012), beta-carotene and lachrymatic compounds having antioxidant activity that helps to fight

against cancer and chronic diseases (Karadeniz et al., 2005; Jorjandi et al., 2009). Onion has been

reported to have a range of health benefits which include anti-carcinogenic properties, anti-platelet

activity, antithrombotic activity, anti-asthmatic and antibiotic effects (Griffiths et al., 2002). The use of

onion by humans has a long history that can be traced back to the Egyptians. Olympic athletes were fed

onions and garlic to improve performance in track and field events and Europeans have treated blood

clots in horses for centuries with onion. So, these folklores suggested improved blood circulation by

consumption of onion. Internet has become a major source of information in this era of technological

2

advancement. Many websites exist with information on advocating herbal and therapeutic uses of onion

and garlic. Noticeably many of these claims on health benefits of Alliums have not received any

scientific research (Griffiths et al., 2002). Table 1: Nutritional composition of onion (per 100 g)

Nutional composition of onion is presented in

Table 1. Onion is consumed widely in every

household in several forms. It is used in

pickles, curries, salad, chutney, sauces and

dehydrated onion in spices. Onion bulbs are

consumed both cooked and uncooked as

salad. Due to its unique tasteIt is an essential

item of every kitchen and hence, German

called it Queen of the Kitchen.(Pareek et al,

2017)

Onion can be grown on soils ranging from

sandy loam to heavy clay but sandy and silt

loams fertile soil having good retention of

moisture are best suited for its cultivation. It is

very sensitive to water logging. The optimum

pH range is 5.8 to 8.0 (Rana and Hore, 2015).

Onion can be grown under a wide range of climatic condition but it grows well in mild climate without

extreme of high or low temperature. For seed germination a temperature range of 12.5 to 25oc, for

vegetative stage before bulbing 12.8 to 21oc and for bulb formation temperature range 15.5 to 25oc is

considered ideal. It is hardy and can withstand freezing temperatures. It does not grow well in area

having rainfall 75-100 cm in monsoon (Rana and Hore, 2015). High temperature favors bulbing and

curing (Shanmugasundaram and Kalb, 2001).Growth and development of onion is greatly affected by

temperature and photoperiod (Rabinowitch, 1985, Brewster, 1987; Coolong & Randle, 2003; Ansari,

2007; Bosekeng and Coetzer, 2013). These environmental factors and their interaction with genotype

determine the performance of an onion cultivar (Brewster, 1994; Khan et al., 2001, Jilani & Ghaffoor,

2003) and this interaction defines the selection of variety for the specific area (Bosekeng and Coetzer,

2013).

Temperature also plays a key role in bulb initiation and formation in onions. Temperature variations

have been found to influence the degree of vegetative growth (Butt, 1968; Brewster, 1979; Seabrook,

2005), leaf initiation, and emergence (De Ruiter, 1986). Tesfay (2011) found that temperature induce

Constituents Quantity

Water (g) 86.6

Carbohydrate (g) 11.8

Protein (g) 1.5

Fat (g) 0.15

Fibers (g) 0.6

Minerals (g) 0.5

Phosphorus (mg) 55.0

Calcium (mg) 43.5

Potassium (mg) 127.0

Sodium (mg) 4.0

Magnesium (mg) 16.0

Iron (mg) 1.0

Copper (mg) 0.18

Zinc (mg) 0.41

Manganese (mg) 0.18

Molybdenum (mg) 0.03

Thiamine (mg) 0.08

Riboflavin (mg) 0.01

Carotene (µg) 8.0

Niacin (mg) 0.5

Folic acid(mg) 6.0

Ascorbic acid (mg) 11.0

Energy (kcal) 55 Rana and Hore, 2015

3

variations in leaf number, plant height, leaf area, and also influence bulb formation. Providing sowing

on the same dates, temperature probably seems to be the main reason for differences in maturity date

between seasons and between locations at the same latitude. In the tropics, it is temperature rather than

day length which controls the timing of bulbing (Sinclair, 1989).

Low temperature affects plant development in many species (Ritchie, 1991; Wang &Engel, 1998;

Streck, 2003). Exposure to low temperature promotes flowering in many plants including onion is called

vernalization (Pinthus, 1985; Flood & Halloran, 1986).

Vernalization in onion has been of research interest because of the need to prevent bulbs from bolting

in the first growing season and to enhance flowering in second growing season or in seed crop (Brewster,

1987; Streck, 2003). In tropical regions, onion plants neither flower nor produce seed due to lack of cold

temperature (Kimani et al., 1994). This is the reason that many countries in the tropics import onion

seed from sub tropic or temperate countries where winter provide vernalization temperature for

flowering and seed production (Peters, 1990; Khokhar, 2014). The response of plant to vernalization

depends on the combination of two factors, the temperature during vernalization and duration of

vernalization period (Hodges &Ritchie, 1991; Streck, 2003). In relation to temperature response,

vernalization has three basic (minimum, optimum and maximum) temperatures (Wang & Engel, 1998;

Yan and Hunt, 1999) while the duration to vernalization is measured by as effective vernalization day

(VD). Plant receives a vernalization for one VD when exposed to optimum temperature for a period of

24 hours (Streck, 2003).

Onion cultivars differ in their vernalization requirement for flower initiation. Cold temperatures between

5˚C - 13˚C for 20 to 120 days were optimum for flower induction in most cultivars. Yet, bolting resistant

cultivars needed comparatively longer (154 - 185 days) cold stimulus (Brewster, 1983; Peters, 1990;

Khokhar et al., 2007a; Khokhkar, 2008). Peters (1990) reviewed that vernalization temperature of 100C

is adequate to bring almost any cultivar to complete flowering.

Optimal day length and vernalization is not enough to induce flowering. Plants should be old enough to

sense and respond to these environmental stimuli. Some perennial plants flower readily when exposed

to environmental condition such as photoperiod and vernalization. While others cannot flower until pass

the juvenile stage and grown to a certain age or size (maturity). According to Fausey et al., (2006),

juvenility is the early phase of growth during which flowering cannot be induced by any treatment.

Onion differs in their flower initiation response to environmental condition because of differences in

genotypes (Khokhar, 2008; Brewster, 1987) and physiological age (Khokhar, 2008). Dong et al., (2013)

stated that onion seedling must be grown to certain age before they sense the cold temperature and start

4

vernalization process. Low temperature promote flowering in onion only if they have passed the

juvenility stage (Rabinowitch, 1990; Khokhar et al., 2007a). Leaf number rather than chronological time

is the best sign of the plant’s physiological age (Rabinowitch, 1990). Onion, depending on cultivars,

initiate flowering when have a minimum number of 7-10 leaves including leaf initial (Rabinowitch,

1990; Khokhar et al., 2007a).

Photoperiod is refers to the length of the day in which a plant is growing in (Denisen, 1979). Day length

has significant effect on bulb formation in onion and the leaves are considered to be the receptors of this

photoperiodic stimulus (Okporie & Ekpe, 2008). This stimulus helps carbohydrate accumulation passed

on from the leaf blade to the leaf sheath (Mondal et al., 1986; Mettananda & Fordham, 1999), making

the sheath of the leaves to swollen and expand. This thickened leaf sheath will form a storage structure

called bulb. The outer one to four leaf sheaths dry off to make protective skin as the bulb matures

(Brewster, 1994).

The day length requirements for bulbing vary with cultivar, normally ranging from 12-16 hours (Van

Den Berg et al., 1997). Short day onion cultivars need a day length of 11-12 hours for bulbing and can

be successfully cultivated in the tropics on 30°N and S from the equator. (Wiles, 1989; Smith, 2006).

Intermediate day cultivars may be cultivated as a winter or spring crop in regions from 30° and 45°

latitude. They need 12-14 hours day length for bulb formation. Long day cultivars require longer days

16 or more hours for bulb formation and can be planted in the regions between 45° to 60° latitude

(Hemy, 1984; Van Den Berg et al., 1997). Short and intermediate day cultivars like Swat-1, Saryab Red

and Phulkara are grown in Pakistan. Bulbing initiates in these cultivars in March when day length

exceeds 12 hours and harvested in May-June when day length is 14 hours.

Table 2: Effect of daylength, temperature and variety on bolting in Alliums.

Crop Day length Temperature Variety

Onion Slight Major Major

Garlic Slight Major Major

Shallot Slight Major Major

Leek Slight Major Moderate

Bunching onion Slight Major Major

Wien, H. C. (1997)

Bolting is premature seed stalk developments (Voss et al., 1999) that decrease the marketability of onion

bulb (Cramer, 2003). Bolting cuts the storage potential and quality of the bulbs as whole of the energy

5

of the plant is exhausted and nothing is left in the bulbs to accumulate. Thus, bulbs become fibrous and

light weight (Rana and Hore, 2015). Bolting in onion bulb crop is produced due to low temperature (8-

13 0C) when plants have grown enough to initiate bulbing. The sensitivity to cold temperature rises as

plant age increased (Cramer, 2003). When seedlings are transplanted early, the onion plants will grasp

the sensitive size for bulbing when temperature is still low, the plants will bolt instead of making bulbs.

Sowing / transplanting should be adjusted so as to prevent plants receiving a cold spell at sensitive plant

size that cause bolting instead of bulb formation. Cramer (2003) stated that late sowing reduced bolting

incidence, but plants are small yet when bulb formation begins causing small bulbs of a poor quality.

Sowing dates are, therefore, important factor that needs to be optimized to prevent bolting in onion.

Dong et al., (2013) reported significant effect of cultivar, sowing date and transplant location and their

interaction on the initiation and final rate of bolting in Welsh onion. Their results suggested that bolting

can be controlled in Welsh onion by choosing an appropriate cultivar, sowing date and transplant

location.

Seedling age or set size also influences the incidence of bolting. Kanton et al., (2003) reported that older

(30 or 40 days) seedlings take less days to mature than the younger (20 days) seedlings. Dong et al.,

(2013) stated that onion seedling must be grown to certain age before they sense the cold temperature

and start vernalization process. The characteristics of seedling also determine the survival percentage

and their ability to respond to cold temperature (Cremaschi et al., 2012). Gao et al., (2011) found that

older seedling needed less accumulation of low temperature for bolting. Khokhar (2009) reported that

incidence of bolting increased linearly with set-size and curvy-linearly with decreasing storage

temperature.

Other factors affecting bolting in onion include nitrogen and phosphorous fertilizers (Brewester, 1983).

Rabinowitch (1990) termed onion as nitro-neutral plant whose flowering time is unaffected by nitrogen.

A few studies, however, indicates that nitrogen affect the flowering process in onion (Brewester, 1983;

Peterson, 1984). Brewster (1983) found that low nitrogen in nutrient solution speeded up flowering.

Abdissa et al., (2011) reported that percentage of bolters per plot decreased by about 11 and 22% in

response to the application of 69 and 92 kg N ha-1, respectively over the control. According to the

findings of Yamasaki and Tanaka, (2005) low nitrogen enhanced bolting in bunching onion (Allium

fistulosum L.) exposed to low temperature for 35 days. Diaz-Perez et al., (2003) suggested that low

nitrogen fertilizer application increased bolting and reported that bolting incidence decrease steadily

with increase nitrogen fertilization rates up to197 kg.ha1.

Different cultivars showed significant variation in bolting percentage (Mushtaq et al., 2013). This

variation was due to the genetic differences of the tested cultivars. Lancaster et al., (1999) evaluated 32

6

onion cultivars from four geographical regions for three years and found significant difference in bolting

tendency among the cultivars. It is difficult to determine the proper date for fall seeding to minimize

bolting and winter injury while increase yield, as it is cultivar and environment dependent. Bolting

resistance cultivars have less bolting percentage, less winter injury and high yield and can be planted

earlier (Cramer, 2003).

Onion is an important cash crop in Pakistan. It is a source of income and livelihood for small farmers.

An appreciable quantity of onions is also exported earning precious foreign exchange for the country. It

occupies an area of 147.2 thousand ha, with production of 1981.7 thousand tons in 2017-18. (Pakistan

Economic Survey 2017-18).

Malakand Division in Khyber Pakhtunkhwa, plays a vital role in onion seed and bulb production. It is

an important cash crop widely grown in all six districts of Malakand division. It enhances the grower’s

net income and creates the employment opportunities for the landless and owner household families

(Saeed and Nasir, 2001).

Figure 2: Bolting problem in onion bulb crop at farmer’s field in Swat.

Onion has many production constraints like lake of quality seed, lack of more productive cultivars,

diseases & insect pest and premature bolting. Premature bolting poses a serious threat to onion

cultivation. Onions sown for bulb production send seed stalks causing them to be unmarketable. And

this occurred for the last many years and the intensity of the problem is more than 50% in most onion

bulb crop across the country. The climate change particularly shifting of winter rains from January-

February to April-May aggravated the problem.This is a great set back to the onion cultivation in

traditionally onion growing area of Malakand division in Khyber Pakhtunkhwa. This problem not only

7

affects the socio economic condition of the farmers but also the availability of onion in local markets

resultantly leads to price hike.

We cannot control the weather but can re-adjust the cropping season to mitigate the problem. This

problem oriented research trials have been designed to re-adjust transplanting time, use correct seedling

age, adequate amount of N fertilizer and use bolting resistant varieties to prevent onion bulb crop from

bolting. This study aimed to achieve the following objectives.

• Main objective

• To prevent onion bulb crop from premature bolting.

• Specific objectives

• To determine the optimum transplanting dates and seedling age to avoid bolting and increase the

yield simultaneously.

• To find out the effect of cultivars and transplanting dates have any effect on premature bolting in

onion.

• To find out the influence of transplanting dates and nitrogen fertilizer on premature onion bolting,

growth and bulb yield.

8

Chapter 2

REVIEW OF LITERATURE

Temperature and photoperiod are the two environmental factors that largely control the growth and

development in onion. These environmental factors and their interactions with genotype determine the

performance of an onion cultivar (Brewster, 1994; Jilani & Ghaffoor, 2003; Khan et al., 2001). This

interaction defines the selection of variety for the specific area (Bosekeng and Coetzer, 2013).

Cultural practices like sowing dates, seedling age, fertilizers, irrigation and plant population also

influence growth, yield and quality of onion bulbs (Brewster, 2008;Bosekeng and Coetzer, 2013).

In this chapter literature pertaining to climatic requirement of onion, growth stages, plant structure, effect

of sowing dates, seedling age, nitrogen fertilizer and cultivars on yield and associated traits are being

discussed and reviewed.

Climatic Requirements

Temperature

Temperature influence growth and development of onion plant in all stages (Coolong & Randle, 2003;

Ansari, 2007; Bosekeng and Coetzer, 2013). A temperature between 7.5 and 30°C is required to obtain

at least 70% germination percentage (Abu-Rayyan et al., 2012). Comrie, (1997a) stated that optimum

temperature for onion seed germination is 24°C, while minimum temperature for onion is 2°C and

maximum temperatures is 35°C, respectively.

The onion seedling grows best between 20 and 25°C (Shanmugasundaram & Kalb, 2001). Temperature

between18-22°C is best for optimum vegetative growth, yet plants can grow at low temperatures as

10°C and higher temperature up to 27°C (Comrie, 1997a). A higher temperate between 25 and 28°C is

required from bulb initiation till harvesting. However, lower temperatures of 8 and 13°Cat bulb

initiation, results in bolting instead of bulbing in onion crop (Comrie, 1997a).

Photoperiod

Photoperiod refers to the length of the day in which a plant is growing in (Denisen, 1979). Day length

has significant effect on bulb formation in onion and the leaves are considered to be the receptors of this

photoperiodic stimulus (Okporie and Ekpe, 2008). This stimulus helps carbohydrate accumulation

passed on from the leaf blade to the leaf sheath (Mondal et al., 1986; Mettananda and Fordham, 1999),

making the sheath of the leaves to swollen and expand. This thickened leaf sheath will form a storage

9

structure called bulb. The outer one to four leaf sheath dry out to make protective skin as the bulb

matures (Brewster, 1994).

The day length requirement for bulbing vary with cultivar, ranging from 12-16 hours (Van Den Berg et

al., 1997). Short day onion cultivars need a day length of 11-12 hours for bulb formation and can be

successfully cultivated in in the tropics between 30°N and S from the equator. (Wiles, 1989).

Intermediate day cultivars may be cultivated as a winter or spring crop in regions from 30° and 45°

latitude. They need 12-14 hours day length for bulb formation.Long day cultivars require longer days

16 or more hours for bulb formation and can be planted in the regions between 45° to 60° latitude

(Hemy, 1984; Van Den Berg et al., 1997).

Intermediate day cultivars like ‘Swat-1’,‘Saryab Surkh’ and ‘Pulkara’ can be grown in Pakistan.

Bulbing starts in early march when day length exceeds 12 hours and harvested in May-June when day

length is 14 hrs. Long day cultivars cannot be grown in Pakistan because maximum day length here

never exceeds 14 hours in May-June.

Adaptation of onion cultivar in a specific area is mostly depended on the photoperiod of that area and

photoperiodic requirement of the cultivar (Wiles, 1989). If an onion cultivar is grown in area having day

length shorter than needed, plant will grow forming leaves without bulbing (Wiles, 1994) and maximum

bolting percentage with high stem thickness can also happen (González, 1997). Conversely, when a

cultivar is exposed to the photoperiod longer than what is necessary, premature bulb formation

increased, bulbing and maturity is speeded up and that all causes smaller bulbs and little yield

(Wickramasinghe et al., 2000). Hence, day length of a certain area at the time of bulb initiation influence

the cultivar choice (Bosekeng and Coetzer, 2013).

Growth Stages

Onion has fairly complex life cycle consisted of three main stages (Brewster 1990, Bosch & Casanova,

2000). According to Bosch & Casanova (2000) these stages are the seedling, vegetative and bulbing

stages. In the first growth stage onion seed will begin to germinate after sowing (Brewster, 1994). In the

process of germination, the primary root will start grow downward while the cotyledon rising upward

through the soil surface as hook or loop and this stage is called the loop stage. During this flag leaf stage,

also referred to as first leaf stage, the first true leaf stage appear while the cotyledon still bent in a whip

shape. At this stage cotyledon senescence takes place causing the withering and falling the cotyledon.

Second and third true leaf also appeared at this stage. At the fourth leaf stage also referred to as leek

stage, fourth true leaf appears and the first leaf begin to shrink and the neck of the plant starts to thicken.

As the first leaf falls, the second leaf becomes detached at the sheath and begins to senescence from the

10

tip, simultaneously fifth, sixth and seven leaf appear. This is called the fall of the first leaf stage. During

bulbing stage the bulbs begins to form, second and third leaf desiccate and at the same time leaves eight

to thirteen appear and the plant attain its maximum height (Bosekeng, 2012).

Progressive desiccation of the leaf four to six together with the tips of younger leaves occurred during

the rapid bulbing stage. Leaves begin to bend under their own weight. One or two short leaf blades may

still appear while bulb skin starts to form. During the leaf fall-down or soft neck stage the neck becomes

hollow, lose turgidity and soften causing the falling under its own weight and bulb reaches its maximum

size. In bulb ripening stage the outer skin of the bulb dries out cure and set while the senescence of the

foliage is complete (Bosekeng, 2012).

Effect of Sowing Dates

Temperature and photoperiod play a key role in onion growth and development. Transplanting time is,

therefore, important that every stage of plant growth and development occur in optimum temperature

and photoperiod.

Germination and emergence

Onion is winter vegetable and can withstand frost. According to Abu-Rayyan et al., (2012) a

temperature ranging from 7.5-300C is required for germination and emergence percentage. Kretschmer

(1994) in Germany obtained 90% germination at temperature ranging between 10 to 25°C. According

to Ansari (2007) late sowing speed up the emergence of onion seed. Seed sown in January, February

and March emerge after 22, 10 and 7 days undergoing an average temperature of 77.7, 24.7 and 34.7°C,

respectively. These findings shows that high temperature can shorten the time from germination to

emergence.

Seedling and vegetative growth

The seedling stage of onion (from loop up to the cotyledon senescence stage is a slow and long period

of growth and may continue for 2-3 months (Sullivan et al., 2001; Brewster, 2008). The relative growth

rate (RGR) of onion seedlings (1.00) is temperature dependent and is almost half the other winter

vegetables like lettuce (1.91) and cabbage (1.96). Nevertheless, onion seedlings are the fastest growing

among the edible alliums (Brewster, 2008).

Leaf growth and canopy development during the vegetative stage are closely linked with temperature.

A minimum or base temperature of 6°C is needed for leaf growth and leaf canopy development and leaf

growth stops below this temperature. The relatively growth rate (RLGR) rise linearly with an increase

11

in temperature from 6 to 20°C. Growth rate slow down with further increase in temperature and above

26°C it will end.

At the onset of bulb formation, second and third leaf dries out while leaf eight and thirteen appear, and

the plant attain its maximum height (Brewster, 1994). Late sown onion plants likely to be small at the

start of bulbing due to short growing period (Al-Moshileh, 2007). Bulb formation for early and late

sown plant of the same onion variety will happened at the same time as the plants mainly react to day

length for bulb initiation. The production of new leaves stop when bulbing initiates, suggesting that early

sown plant will develop more and larger leaves and larger leaf area compared to late sown plants

(Brewster, 1994). This will produce higher leaf area index for more light interception assisting in

efficient plant photosynthesis (Mondal et al., 1986; Sobeih and Wright, 1986).

Plant Height

Bosekeng and Coetzer (2013) stated that sowing date did not influence plant height and leaf number

significantly over a period of two years, however, early sowing dates in one year resulted in taller plants.

Brewster (2008) reported that bulbs will be initiated when temperature starts to increase and the

necessary minimum day length of a specific onion cultivar is met. So, when the same cultivars is sown

at different times in the same area, plants will starts bulb formation more or less the same time. Hence,

earlier sown plants will have a longer vegetative growth period and consequently have larger plants with

more leaves (Comrie, 1997a; Bosekeng and Coetzer, 2013). Sawant et al., (2002) found that plant height

and the number of leaves have significantly affected by sowing dates. Early sowing produced the tallest

plants with maximum number of leaves (Rahman et al., 2002; Ibrahim, 2010). Kandil et al., (2013)

found maximum plant height at 90 and 120 days from transplanting and total culls were resulted from

early transplanting date (15th November) in both seasons.

Leaf Area/ Number of Leaves/Plant

Cramer (2003) observed that earlier planting produced larger plants with more leaves compared to later

seeding dated in a growing season. Sawant et al., (2002) found that plant height and the number of

leaves have significantly affected by sowing dates. On the other hand, Bosekeng and Coetzer (2013)

stated that sowing date did not influence plant height and leaf number significantly over a period of two

years, however, early sowing dates in one year resulted in taller plants.

Bolting

Bolting is premature seed stalk development (Voss et al., 1999) that decreases the marketability of onion

bulb (Cramer, 2003). Bolting in onion bulb crop is produced to low temperature (8-13co) when plants

12

have grown enough to start bulbing. The sensitivity to cold temperature rises as plant age increased

Cramer (2003) added. Khokhar et al., (2007b) reported that the number of leaves has been used to define

the critical plant size at which bolting occur when expose to low temperature. They found that 7-10

leaves stage is sensitive plant size (at first leaf fall and the start of bulb formation stage). When seedlings

are transplanted early, the onion plants will grasp the sensitive size for bulbing when temperature are

still low, the plants will form seed stems instead bulbs. Sowing should be adjusted so as to prevent plants

receiving a cold spell at sensitive plant size that cause bolting instead of bulb formation. Cramer (2003)

stated that late sowing reduce bolting incidence, but plants are small yet when bulb formation begins

causing small bulbs of a poor quality. Sowing dates are, therefore, important factor that needs to be pay

heed to while preventing bolting.

Madisa (1994) reported that bolting did not occur when onion plants are sown late in the season as when

cold temperature prevailed plants are still small and not yet grown to minimum plant size for bolting.

Agic et al., (2007) found that bolting was encouraged by early sowing while cultivars differs in bolting

tendency in this study. Jianjun and Yu (2003) found higher premature bolting ratio and abruptly lower

mean bulb weight and plot yield in early sown crop. Dong et al., (2013) reported significant effect of

cultivar, sowing date and transplant location and their interaction on the initiation and final rate of bolting

in Welsh onion. The result suggests that bolting can be controlled in Welsh onion by choosing an

appropriate cultivar, sowing date and transplant location.

Stem Diameter

Both bulb and stem diameter are the two important quality traits in onion. Bulbs with thin necks store

for longer period than bulbs with thick necks (Gautam et al., 2006). (Peters et al., 1994; Wright and

Grant, 1997) reported that thick bulb necks take more time to dry off after harvesting and have a high

risk for infection of post-harvest storage diseases such as bacterial soft rot (Pseudomonas gladioli pv.

alliicola Burkholder). Gonzalez, (1997) found that 81% of the plants produced bulbs with thick necks

when sown late compared to 45.3% when sown early.

Bulb Diameter/Size

According to Bosekeng and Coetzer (2013) bulb diameter was significantly influenced by both cultivar

and sowing dates and earlier sown crop produced the largest bulbs. Consumers prefer medium bulbs

above large bulbs and higher prices are consequently obtained on fresh produce markets for medium

bulbs (Kanton et al., 2002). Early planting produced maximum polar and equatorial diameter and hence,

produced large size bulbs (Sawant et al., 2002). Comrie (1997a) observed that early sown onions will

13

reach bulb formation stage when the temperature is still low and the plants will bolt instead of making

bulbs. This will cause less yield of low quality bulbs (Khokhar et al., 2007a).

Bulb Weight

Planting dates influence single bulb weight and yield in onion. Earlier sown plants will have a longer

vegetative growth period and consequently have larger plants with more leaves (Comrie, 1997b;

Bosekeng and Coetzer, 2013). Sawant et al., (2002) found that plant height and the number of leaves

have significantly affected by sowing dates. Abdissa et al., (2011) found strong and positive correlation

of mean bulb weight with plant height, number of leaves, bulb length and diameter. Bosekeng and

Coetzer (2013) reported that delayed sowing significantly decreased average bulb fresh mass while early

sown plant produced the largest bulbs. This all suggest that planting dates influence single bulb weight

in onion.

Bulb Yield

Bulb yield in onion is influenced by several factors that include cultivar, temperature, and photoperiod,

light interception, sowing dates, plant population, seedling age, irrigation and fertilizer. Ample

vegetative growth before bulb formation is essential (Ibrahim, 2010) to get high yield. When sowing is

delayed, plant starts bulbing before attaining sufficient vegetative growth, resulting in small bulbs and

lesser yield. Late sown crop produce smaller plants with small canopy that intercept less light and

resultantly produce low yield (Bosekeng and Coetzer, 2013). They also found that delayed sowing dates

significantly reduce bulb fresh mass and yield from 40.96 to 28.20 tons ha-1.

According to Cramer (2003) premature onion bolting increased when fall-sown onions were seeded

earlier. In general, less bolting, later maturity and increase in bulb yield were recorded with delay in

seeding. Madisa (1994) reported that late planting (April) produced lower yields than the March planting

due to a reduction in bulb size. Ibrahim (2010) found reduction in bulb yield from 40 tons ha-1 to 20 tons

ha-1 in 2001-02 when transplanting was delayed from November to March and from 48 tons ha-1 to less

than 20 tons ha-1 in 2002-03 when transplanting was delayed from December to March. Asmatullah et

al., (2004) transplanted onion cv. Swat-I at 10-day intervals from 12 November 1994 to 21 January

1995 reported that the nursery transplanted on 12 November produced maximum bulb yield (21.38

t/ha), number and weight of large-sized bulbs, leaves per plant but reduced number of culls. A higher

percentage of bolting and thick neck were recorded at earlier transplanting dates.

Sowing date for a specific onion cultivar should be selected to attain sufficient leaf growth before bulb

initiation to get high yields. However, a too long growth period before bulb initiation can also lead to

14

bolting as this results in large plants exposed to cold temperatures just before bulb initiation and split

bulbs may also occur.

Effect of Seedling Age

Is the seedling age at the time of transplanting influence the growth and development of onion plant?

Literature on seedling age are sparse (Vavrina, 2002). Brewster (1994) reported that one cause for low

yield is the use of seedlings of different age. Transplanting seedling is widely adopted practice in onion

cultivation though work on direct seeding has also been produced. The largest volume of literature on

transplant age is available on vegetables.

Wien (1997) stated that seedling transplanting is a common practice particularly for those vegetable

having small seeds, slow or difficult to germinate and require special care. (Islam, 1981; Saha, 1982)

reported that seedling age at transplanting influence bulb yield. Salter (1985) stated that transplanting

permits more precise control of plant population and spacing, and also make the best use of expensive

seed better than does direct seeding. Mohammadi et al., (2010) reported that transplanting produce quick

and complete stand compared to direct seeding.

Plant Height and Leaf Numbers

Salik and Pervaiz, (2000) transplanted 4, 5 and 6 week old seedling of three cultivar of tomato to find

out best age for transplanting. They found medium age, 5 week old seedling survival percentage of

plants, height of plant, number of fruits and yield. Kanton et al., (2003) found significant effect of

seedling age on plant height and the tallest plants from 40 days old transplants in onion. Gao et al.,

(2011) conducted a trial to determine the influence of accumulated temperature and seedling age on

shallot onion bolting. Results depicts that when plant attained height of 13.8cm with 2.6 leaf and stem

diameter 0.4 cm and active accumulated temperature and the effective accumulated temperature before

winter were 971℃ ( ≥ 5℃)or 777℃ ( ≥ 10℃) and 616℃ ( ≥ 5℃) or 542℃ (≥10℃), respectively, it

reached a critical stage and initiated inflorescences development.

Stem Diameter

According to Bijarniya et al, (2015) seedling age has significant influence on stem thickness.

Older seedling produce thick neck compared to young seedlings. Increase in stem thickness in

older seedlings may be due the vigorous growth due to enough stored foods (Bijarniya et al,

2015).Kumbhekar al el, (2012) reported thin neck bubs of 1.04 cm from 6 week old transplant

compared to 7 and 8 weeks seedlings. Bijarniya et al, (2015) also recorded thick neck from old

seedling compared to young seedlings.

15

Bolting

Onion is a bulb vegetable that needs vernalization for flower induction. Dong et al (2013) stated that

Onion seedling must be grown to certain age before they sense the cold temperature and start

vernalization process. The characteristics of seedling also determine the survival percentage and their

ability to respond to cold temperature (Cremaschi et al., 2012). Gao et al., (2011) found that older

seedling needed less accumulation of low temperature for bolting.

Khokhar, (2009) reported that incidence of bolting increased linearly with set-size and curvy-linearly

with decreasing storage temperature. Seedlings of 30 or 40 days old take less days to mature than

younger (20 days) seedlings (Kanton et al., 2003)

Bulb Diameter/size

Kanton et al (2003) stated that plants grown from 30 and 40-day-old seedlings took less time to mature

than those grown from 20-day-old seedlings. Seedling age influence final plant height, bulb height, bulb

diameter, bulb average weight, harvest index and yield. 40-day-old seedlings produced the tallest plants

with widest and heaviest bulbs (Kanton et al., 2003)

Mean bulb weight and bulb diameter decreased with increasing seedling age. (Kanton et al., 2003,

Aubyn and Abutiate, 1994). Oladiram and Sangodele, (1996) reported that onion cv. Composite 4

produced widest bulbs when six weeks old seedlings were transplanted. Mohanty et al., (1990) and

Herison et al., (1993) reported conflicting results that bulb diameter and yield increased with increasing

seedling age.

Bulb Weight & Bulb Yield

Age of transplants affects bulb yield (Islam, 1981; Saha, 1982). Islam (1981) found that 60 days old

seedling produced more yield than 50 days old transplants while Saha (1982) reported that plants

derived from 50 day transplant had produced the maximum yield with exception of cultivar Patra Red

where 40 days transplant had the highest yield. Aubyn and Abutiate (1994) reported that bulb yield of

fresh onion decreased with increasing age of transplants. If transplanting of seedlings were delayed than

the optimum time in which they are making active growth, then growth after transplanting and yield

would be suffered (NeSmith, 1993). Bulb yield increased with increasing seedlings age up to 7 weeks,

after which it started to decline (Vachhani and Patel, 1988) while Herison et al, (1993) stated that

increase in bulb yield is due to transplant size rather than transplant age. According to Norman, (1992)

that younger seedlings recovered from transplanting shock more quickly than older ones.

16

Kanton et al., (2003) stated in their arguments that higher bulb yields produced for plants developed

from younger transplants could be attributed to better plant growth as revealed in taller plants having the

maximum leaf and bulb dimensions compared to older seedlings. They further reported that younger

seedlings restarted vegetative growth more quickly, which might have contributed to more vigorous

development. Plants derived from younger transplants seemed to be more efficient in conversion of

photosynthate into harvestable bulbs than plants grown from older seedlings.

Lujan-Favela (1992) in Mexico, obtained the highest yield from 7-week-old transplants sown in mid-

September. He correlated yield with transplant size suggesting larger seedlings were better in

performance.

Vavrina (1998) reported that the conflicting results in the literature on transplant age may be due to the

different environmental and cultural conditions that the plants were exposed to, both in the greenhouse

and in the field.

Effect of Nitrogen Fertilizer

Nitrogen is the major plant nutrient required in greater quantities. It is important component of protein,

enzymes, vitamins and chlorophyll (Kokobe et al., 2013). Onions are more susceptible to nutrient

deficiencies than most crop plants because of their shallow and unbranched root system (Brewester,

1994).Onion is heavy feeder and need a sufficient amount of nitrogen. Yet, excess N fertilization effects

undue vegetative growth, delay maturity, rise susceptibility to diseases, cut dry matter contents and

storage life and finally decrease yield and quality of bulbs (Brewster, 1994; Sorensen and Grevsen,

2001).

Vegetative Growth

Rizk (1994) reported that increasing the amount of NPK fertilizer increased the vegetative growth and

yield of onion bulb. According to the findings of Vachhani and Patel, (1993) plant height, number of

leaves/plant, bulb weight, size and onion yield were highest with the application of 150 kg N ha-1.

Nitrogen fertilization, regardless of the rate, prolonged physiological maturity by about 6 days over the

control (Abdissa et al., 2011). They also reported that plant height and leaf length has increased by about

10 and 11.5%, respectively over the unfertilized check with application of 69 kg N ha-1.They also found

an increase of about 8% over the control when 92 kg N ha-1 was applied. According to Vachhani and

Patel, (1993) that plant height, number of leaves/plant, bulb weight, size and onion yield were maximum

with the application of 150 kg N ha-1. Pandey and Ekpo, (1991) reported that application rate of 160 kg

N ha-1 produced maximum plant height of 63.9 cm and high number of leaves/plant (13.0), while 120

kg N ha-1 produced highest average bulb weight and the maximum yield of onion bulb.

17

Plant height and number of leaves plant-1

Plant height and leaf length has increased by about 10 and 11.5%, respectively with application of 69

kg N ha-1over the unfertilized check and further addition of N did not produce significant increase

(Abdissa et al., 2011). The increase in height could be attributed to its involvement in the synthesis of

amino acids, as they link together and form proteins and make up metabolic processes needed for plant

growth (Abdissa et al., 2011). Bungard et al., (1999) argued that N is a constituent of many fundamental

cell components and it plays an essential role in all living tissues of the plant. No other element has such

an effect on promoting vigorous plant growth. Abdissa et al., (2011) claimed that N fertilizers

significantly affect number of leaves per plant in onion. They reported about 8% increase in number of

leaves over check when 92 kg N ha-1 was added. The results of Nasreen et al., (2007) showed that

application of 120 kg N ha-1 significantly increased the number of leaves per plant and further addition

of nitrogen to 160 kg ha-1 inclined to decrease it.

Bolting

Premature seed stalk development (bolting) in onion produces poor quality unmarketable bulbs

(Rabinowitch, 1990). Flowering process in onion is influenced by plant age and several environmental

factors (Brewester, 1997; Rabinowitch, 1990; Roberts et al., 1997; Diaz-Pérez et al., 2003). Though

temperature and photoperiod are two important factors affecting onion bolting (Brewester, 1997;

Roberts et al., 1997) temperature has the major factor influencing the initiation and development of

inflorescence in onion (Rabinowitch, 1990). Flowering, however, occur after the formation of certain

number of leaves followed by exposure to low temperature (Brewester, 1985). Other factors affecting

bolting in onion are nitrogen and phosphorous fertilizers (Brewester, 1983; Diaz-Pérez et al., 2003).

Rabinowitch (1990) termed onion as nitro neutral plant whose flowering time is unaffected by nitrogen.

A few studies, however, indicates that nitrogen affect the flowering process in onion (Brewester, 1983;

Peterson, 1984). Brewester (1983) found that low nitrogen in nutrient solution speeded up flowering.


response to the application of 69 and 92 kg N ha-1, respectively over the control. According to the

findings of Yamasaki and Tanaka, (2005) low nitrogen enhanced bolting in bunching onion (Allium

fistulosum L.) exposed to low temperature for 35 days. Low N fertilizer increases bolting and that bolting

incidence decreases steadily with increasing the level of N fertilizer up to 197 kg ha-1. (Diaz-Pérez et al.,

2003)

18

Bulb diameter

Bulb diameter is an important character that predicts its marketability and usage of crop. Variations in

bulb diameter are mostly due to variation in the genetic makeup of varieties but is also affected by

environment and management practices (Yang et al., 2004). Onion bulb size can be increased by

application of N during the growing period (Rice et al, 1993). Results of a field experiment of Abdissa

et al., (2011) showed that regardless of the rate of application, N fertilization increased bulb diameter

and average bulb weight by about 12 and 21.5%, respectively over the control. According to their

findings nitrogen fertilization significantly increased bulb diameter without affecting bulb length. N

application up to 120 kgha-1increase bulb diameter (Nasreen et al., 2007; Yadav et al., 2003). Bulb

length, however, reported to increase with increased in N fertilization (Yadav et al, 2003; Reddy et al.,

2005). Bulb diameter has strong and positive correlation with the total bulb yield of onion signifying

that an increase in individual bulb size is key to maximize onion productivity per unit area (Abdissa et

al., 2011).

Bulb Weight

Bulb weight is a key parameter that adds towards the yield and also determines the suitability of an

onion variety for salad purpose. Abdissa et al., (2011) reported that N fertilizer significantly increased

bulb weight. Increase in N fertilizer up to 69 kg ha-1 increased bulb weight by about 26% while further

addition did not increase in bulb weight (Abdissa et al., 2011). From the result they concluded that

increase in bulb weight to N could be attributed to the increase in plant height, number of leaves, leaf

length, and extended physiological maturity in response to the fertilization all might have increased

assimilate production and allocation to the bulbs. Their results showed that mean bulb weight was

positively and strongly correlated with bulb length and diameter suggesting that N fertilization increased

bulb weight by improving bulb length and diameter. Resende et al.,(2014) reported thatincrease in the

levels of nitrogen caused a linear increase in fresh mass of the bulbs.

Bulb Yield

Onion bulb yield depends on many factors like planting dates, soil nutrient supply, climate and cultivar.

Kolota et al., (2013) reported that growth, yield and nutritional value of bunching onion is affected by

nutrient supply. Abdissa et al., (2011) found that N significantly increases total and marketable bulb

yield of onion. Total and marketable yield increased by about 5.74 and 4.06 ton respectively at the

application of nitrogen at the rate of 69 kg ha-1. Cizauskas et al., (2003) also reported somewhat similar

results that application of 60 kg N ha-1 gave highest bulb yield of onion. According to Aklilu (1997)

application of 90 to 120 kg N ha-1 compared to the unfertilized crops in sandy loam soil in semiarid

19

region was beneficial. Different researcher at different times reported increase in bulb yield in response

to nitrogen fertilization (Singh et al., 1989; Patel and Patel, 1990; Pandey and Ekpo, 1991; Vachhani

and Patel, 1993b; Patel and Vachhani, 1994). Different growth parameters like plant height and bulb

diameter are reported to increased bulb yield (Nasreen et al., 2007). Abdissa et al., (2011) found that

leaf length and leaf diameter was positively correlated with total bulb and marketable yield. This

indicates that photosynthetic area increases with application of nitrogen application which resulted

production of more assimilates and more onion bulb production.

Pungency

Onion is mostly used to boost the flavor of other foods. The quality of onion is often judged by its

pungency. A distinct group of organo-sulfur compounds governs onion flavor. Hydrolysis of the flavor

precursor compounds, like, S-alk (en)yl-l-cysteine sulfoxides, when the cells are mechanically ruptured,

produced pungent onion flavor. This hydrolysis reaction is catalyzed by allinase and takes about 6

minutes to complete. (Schwimmer & Weston, 1961). During this reaction thiopropanol S-oxide

(lachrymator), pyruvic acid, ammonia and many sulfur volatiles are produced. The measurement of

pyruvate as indicator of pungency is probably the most recognized method to assess pungency in onion

and garlic (Dhuma et al, 2007).

Nitrogen fertilizer improved onion pungency. Nitrogen application increased sulfur availability to plants

which is the main source of pungency in onion. Application of nitrogen @ 138 kg ha-1 increased

pyruvate content by 10.29 % over the control (Tekalign et al., 2012; Nasreen et al., 2007)). Randle and

Ketter (1998) described that pyruvate contents in onions are determined by the genetics of the cultivar.

Yet, the growing environment like sulfate availability, growing temperature, and water availability

affect onion pungency. The more sulphate available for uptake, the more pungent the onion bulbs will

be. Randle (2000) found that when N level increased from 0.22 to 0.97 gl-1 in a hydroponic solution,

enzymatically produced pyruvate increased linearly but then declined at the highest N dose. Conflicting

results to the above studies were reported by Abbey, (2004) that N fertilization significantly reduced

onion bulb pyruvic acid concentration.

Effect of Cultivar

Mushtaq et al, (2013) stated that different onion cultivars had different photoperiod and vernalization

requirements and vary in yield, yield related traits and bolting percentage. Brewster, (1994) and Khan

et al, (2001) reported that genotype and environment are the two factors that defines the performance of

a variety. A variety responds differently in different environmental condition and several varieties of the

same species are vary in performance even grown under the same climatic condition.

http://www.sciencedirect.com/science/article/pii/S0308814605010514#bib9

20

Effect on Plant Height

Bosekeng and Coetzer, (2013) found significant difference in plant height in onion cultivars over a

period of two year study. Haydar et al., (2007) reported that plant height, bulb yield and bulb length

were found to show high broad sense heritability. Bulb yield showed strong positive correlation with

plant height, bulb length, bulb diameter and days to harvest.

2. Effect on Bolting

Different cultivars shows significant variation in bolting percentage (Mushtaq et al., 2013). This

variation was due to the genetic differences of the tested cultivars. Lancaster et al., (1999) evaluated 32

onion cultivars from four geographical regions for 3 years and found significant difference in bolting

tendency among the cultivars. It is difficult to determine the proper date for fall seeding to minimize

bolting and winter injury while increase yield as it is cultivar and environment dependent. Bolting

resistance cultivars have less bolting percentage, less winter injury and high yield and can be planted

earlier (Cramer, 2003).

Effect on Bulb Weight

Bulb weight is a key parameter that contributes towards final yield. Mushtaq et al., (2013) reported

significant difference in bulb weight in different onion cultivars. The differences in bulb weight was due

the genotype and the adaptability of the cultivars in given environment.

Effect on Bulb Diameter/Size

According to (Mushtaq et al., 2013) bulb diameter determines the marketability and use of the bulbs.

They found variation in bulb diameters in different cultivars. Different sizes bulbs produced by different

varieties was due genetic variation of the varieties (Mushtaq et al., 2013 and Yang et al., 2004).

Management practices also influence bulb diameter (Mushtaq et al., 2013). Rahman and Das, (1985)

stated that bulb diameter followed by number of leaves/plant had maximum positive direct effect on

bulb yield in garlic.

Neck Diameter

Neck diameter is an important character that indicates the storage potential of onion. Gautam et al.,

(2006) reported that thin neck varieties have longer shelf life compared to thick neck varieties. Mushtaq

et al., (2013) found significant variation in neck diameter in nineteen varieties evaluated. Brewster,

(1997) stated that stem thickness shows the failure of the plant to complete the bulb formation process

21

and such bulbs do not undergo dormant. This problem arises because of slow growth or short growing

period.

Bulb Yield

Bulb yield is the end product for which the onion bulb crop is grown. A number of factors likeplanting

dates, soil nutrient supply, climate and cultivar influence bulb yield (Kolota et al., 2003). Mushtaq et al.,

(2013) stated that bulb yield in onion crop is a manifestation of collective effect of different yield

components. Many researchers reported wide variations in bulb yield and its quality among onion

cultivars (Kandil et al, 2013).

Mushtaq et al., (2013) and Cheema et al., (2003a) and Cheema et al, (2003b) found significant

difference in bulb yield in different onion varieties. This may be attributed to superiority and suitability

of genotype to the local conditions (Naz and Amjad, 2004). Boyhan et al., (2014) in five year varietal

trial found marketable yield ranged from 23% to 99% of the total yield.

22

Chapter 3

EXPERIMENT 1: EFFECTS OF TRANSPLANTING DATES AND SEEDLING AGE ON

PREMATURE BOLTING IN ONION BULB CROP.

ABSTRACT

By


Department of Agricultural Sciences (Horticulture), University of Haripur

April 2017

Premature bolting reduces the storage life, quality and marketable yield of onion bulbs. Experiments

were arranged in RCB design with the objective to determine the effect of transplanting dates and

seedling age on bolting and marketable yield. Trials were conducted for two consective years from

November 2013-June 2014 and November 2014-June 2015at Agricultural Research Institute, Mingora,

Swat. Seedlings of 45, 60 and 75 days old were transplanted on five different dates (30th November, 15th

December, 30th December, 15th January and 30th January) to study its effect on premature bolting in

onion. Transplanting dates and seedlings age exerted significant effects on different growth and yield

parameters studied. Plant height, number of leaves at bolting, stem diameter, days to maturity, bulb

diameter, bulb weight decreased with delay in transplanting as well as with increasing seedling age. On

the other hand, bolting and cull percentage decrease with delay in transplanting and increased with

increase in seedling age. Maximum marketable yield (ton ha-1) was recorded when 60 days old seedlings

were transplanted on15th December. The correlation co-efficient analysis data revealed positive

correlation between marketable yield (0.671 ton/ha) and bulb diameter (0.381). Non- significant positive

correlations of marketable yield were recorded with bulb weight (0.173 gm), number of leaves at bolting

(0.097), stem thickness (0.091) and plant height (0.106). The association of marketable yield with

bolting percentage (-0.381) and % cull (-0.552) was significantly negative.

INTODUCTION

Onion (Allium cepa L.) is biennial herbaceous vegetable and mostly grown as annul for bulbs

production. It has two stages of growth, a vegetative stage and reproductive stage. In vegetative

stage it grow and produce leaves and bulbs while in reproductive stage it send seed stalk,

produce flowers and seeds. When onions are seeded/transplanted for bulbs and it initiated

inflorescences development, thus, deviating from its normal life cycle, is called bolting. Bolting

makes the bulb hard, fibrous, and lightweight and are discarded in final grading for the market.

Premature bolting, therefore, reduces the quality and marketable yield of onion bulb.

23

Low temperatures affects plant development in many species (Ritchie, 1991; Wang & Engel,

1998; Streck. 2003). Exposure to low temperature promotes flowering in many plants including

onion is called vernalization (Pinthus. 1985; Flood and Halloran. 1986).Vernalization in onion

has been of research interest because of the need to prevent bulbs from bolting in the first

growing season and to enhance flowering in seed crop (Brewster, 1987; Streck, 2003). Some

perennial plants flower readily when exposed to environmental condition such as photoperiod

and vernalization that enhance flowering. While others cannot flower until pass the juvenile

stage and grown to a certain age or size (maturity). According to Fausey et al. (2006) Juvenility

is the early phase of growth during which flowering cannot be induced by any treatment. Low

temperature also induce flowering in onion only if it grown to a certain stage and passed the

juvenility phase (Rabinowitch, 1990; Khokhar et al. 2007a).

Onion cultivars differ in their vernalization requirement for flowering initiation. A cold

temperature of 5-13 0C for 20 to 120 days is enough to bring flowering in any cultivar (Shishido

and Saito. 1977; Brewster. 1983; Khokhar et al. 2007a; Khokhkar. 2008). Peters. (1990) in a

literature review concluded that vernalization temperature of 10 0C is adequate to bring almost

any cultivar to complete flowering. The growth stage at which plants become responsive to low

temperature and switch from vegetative stage to reproductive stage has been studied by many

researchers. According to Brewster, (1983, 1987), leaf initiation is constant in a given

environment and thus, leaf number instead of chronological time is used to decide plant’s

physiological age (Rabinowitch. 1990). Onion require 10-14 leaves before inflorescence

initiation (Gregory. 1936 cited by Cramer. 2003). According to Heath and Mathur, 1944 cited

by Cramer. 2003) 12 leaves with most plants averaging 13.6 leaves required before flower

induction. Depending on cultivars, onion initiate flowering when have a minimum number of

7-10 leaves including leaf initial (Rabinowitch. 1990; Khokhar et al. 2007a).

When seedlings are transplanted early, onion plants will grasp the sensitive size when

temperature are still low, the plants induce to bolt instead of making bulbs. Agic et al. (2007)

found that bolting was enhanced by early sowing while cultivars differ in bolting tendency in

their study. Madisa. (1994) reported that onion plants sown late did not bolt because when low

temperatures responsible for bolting prevailed, plants were still in juvenile stage. Cramer.

(2003) stated that late sowing reduce bolting incidence, but plants are small yet when bulb

formation begins causing small bulbs of poor quality. Sowing dates are, therefore, important

factor that needs to be adjusted in such a way to avoid bolting and have maximum marketable

yield.

24

Seedling age or set size also an important factor in onion production. Generally, large seedling

produce higher yield but have more bolting incidence (Boyhan et al. 2009). Kanton et al. (2003)

reported that older (30 or 40 days) seedlings take less days to mature than the younger (20 days)

seedlings. Dong et al. (2013) stated that onion seedling must be grown to certain age before

they sense the cold temperature and start vernalization process. The characteristics of seedling

also determine the survival percentage and their ability to respond to cold temperature

(Cremaschi et al. 2012). Gao et al. (2011) found that older seedling needed less accumulation

of low temperature for bolting. Khokhar et al. (2009) reported that incidence of bolting

increased linearly with set-size and curvy-linearly with decreasing storage temperature. The

objective of this study is to determine correct seedling age and to adjust the transplanting date

in such a way that prevent bolting and produce greater marketable yield at the same time.

MATERIALS & METHODS

Trial was conducted at Agricultural Research Institute, Mingora, Swat in Khyber Pakhtunkhwa

province of Pakistan from November to June 2013-14 and was repeated at the same location in the next

growing season i-e 2014-15. ARI Swat, the experimental site, is 906 m above sea level located in the

Hindu Kush range at 34.3- 35.53° North Latitude and 71.5-72.5° Longitude in the north of west of

Figure 3: Mean monthly temperature at ARI Mingora during the growing season in 2013-14.

0

100

200

300

400

500

600

700

800

0

5

10

15

20

25

30

35

40

To

tal

Rai

nfa

ll

Tem

per

atu

re ̊C

Avg. Min Temp Avg. Max temp Avg. Temp Total Rainfall

25

Pakistan. Climate is warm temperate. Temperature ranges from 25 to 35 oc while it drops in winter as

low as -4oC with snow and frost. In summer mercury rises sometimes above 40oc. Average rainfall

ranges from 740-1200mm. Mean monthly temperature and total rainfall at experimental site during the

two growing seasons of 2013-14 and 2014-15 is given in figures 2 and 3. Soil is silt loam with pH ranges

from 5-5.6. Soil analysis of the site are presented in Table 3.

Experiment Detail

The experiment was carried out in two consecutive growing seasons from November 2013 to June 2014

and November 2014 to June 2015. Nursery of onion variety Swat-1, the commercial variety grown in

Khyber Pakhtunkhwa and Pothohar region, was raised on different dates. Seedlings having age of 45,

60 and 75 days were transplanted on five different dates. First transplanting was done on November,

30th and the subsequent

Figure 4: Mean monthly temperature during the growing season in 2014-15.

transplanting was carried out at 15 days intervals. Seedling were transplanted 10 cm apart within row

and 25 cm between rows in plot size of 1×3 m2 having 120 plants in 4 rows.

0

100

200

300

400

500

600

0

5

10

15

20

25

30

35

Jan

Feb

Ma

r

Apr

Ma

y

Jun

Jul

Aug

Sep

Ave

rag

e

To

tal

Rai

nfa

ll M

m

Tem

per

atu

re O

C

Avg. Min Temp Avg. Max temp Avg. Temp Total Rainfall

26

Table 3: Physico-chemical properties of the experimental soil.

Soil Analysis 2013-14 2014-15

Soil Texture Silt Loam Silt Loam

pH 6.4 6.0

OM % 1.59 1.31

Lime % 2.4 2.6

N % .057 .035

P mg Kg-1 41.0 27.51

K mg Kg-1 54.0 50.0

Cu mg Kg-1 5.48 4.02

Fe mg Kg-1 32.62 34.62

Zn mg Kg-1 6.22 4.90

Mn mg Kg-1 11.25 14.75

Layout and Treatment details

Planting on five different dates and three seedling ages were the two factors making 15 treatment

combinations. These treatment combinations were set in randomized complete block design (RCBD)

with three replications.

Treatments: 1. Transplanting Dates=5 2. Seedling Age =3

Experimental lay out

R

3

D1S

1

D1S

2

D1S

3

D2S

1

D2S

2

D2S

3

D3S

1

D3S

2

D3S

3

D4S

1

D4S

2

D4S

3

D5S

1

D5S

2

D5S

3

R

2

D4S

1

D4S

3

D3S

1

D3S

2

D5S

3

D3S

3

D1S

2

D5S

1

D4S

2

D5S

2

D1S

1

D1S

3

D2S

2

D2S

3

D2S

1

R

1

D4S

2

D2S

3

D5S

1

D3S

1

D5S

2

D1S

1

D4S

3

D1S

3

D5S

3

D2S

2

D2S

1

D4S

1

D1S

2

D3S

2

D3S

3

D = Date of transplanting S = Seedling Age

27

Table 4: Elaborated planting dates and seedling ages.

S.No Sowing/Planting Dates Seedling Age Treatments

1 30th November 45 days old seedlings T1

60 days old seedlings T2


2 15th December 45 days old seedlings T4



3 30th December 45 days old seedlings T7



4 15th January 45 days old seedlings T10



5 30th January 45 days old seedlings T13



Cultural Practices

Nursery preparation

Field was thoroughly ploughed and weeds were removed by hand. Fully decomposed FYM was mixed

with soil. Soil clods were well broken with help of hand hoe. Raised beds with 2×1m length and width

were prepared. Seeds were sown in lines and covered with mixture of fine sand. After sowing jute bags

were spread over the bed and irrigated with hand sprinkle till the seedling emergence. Weeding was

practiced manually. Nursery was raised on different dates in order to prepare 45, 60 and 75 days old

seedlings for each 5 transplanting dates.

Field Preparation

Experimental field was ploughed with cultivator and the weeds, stubbles and residues of the previous

crop, if any, were manually collected and removed. On the next day, soil was pulverized with rotovator

and prepared to a good tilth. Plots were prepared according to experimental design.

Transplanting of Seedlings

Seedling of 45, 60 and 75 days old were uprooted with help of hand hoe and transplanted manually in

prepared experimental plots. Soon after transplanting a pre-emergence weedicide pandymethaline at the

28

rate of 2 ml per litre of water was sprayed to disallow the emergence of weed seeds. On next day

transplanted field was light irrigated.

Manure and Fertilizer Application

Well decomposed FYM @ of 15 tons per hectare was applied during land preparation. Recommended

dose of nitrogen, phosphorus and potash (100: 90:60) were applied based on the soil analysis results

(Table 2 page 37). Total amount of phosphorus and potash was applied and mixed with soil at the time

of sowing while nitrogen was applied in three split doses. Nitrogen was applied in the form of

ammonium sulphate, phosphorus in the form of single super phosphate (SSP) and potash in the form of

potassium sulphate (SOP).

Harvesting

Bulbs were harvested when 80 % of the tops were down. Care was taken to avoid bulb injuries.

Data Collection

To assess the effect of various treatments on bolting and yield in onion, data on different growth

parameters was collected from transplanting of seedlings to the harvesting of bulbs. Data was collected

on 20 randomly selected plants from 2 central rows in each unit plot. The randomly selected plants were

marked and used for succeeding data parameters.

Plant height (cm)

The plant height was measured at the maturity stage on randomly selected 20 plants with the help of

standard ruler and the average was worked out.

Leaf Number

Number of leaves per plant was counted on randomly selected 20 plants and then averaged.

Number of Leaves at Bolting

Number of Leaves per plant was counted when bolting was initiated in 20 plants and then average was

counted.

Stem Diameter(mm)

Neck diameter or stem thickness is an important character in onion that indicates bulb storage ability.

Stem thickness of randomly selected 20 sampled plants was measured with the help of digital Vernier

Caliper in centimeter (mm) and the average was analyzed.

29

Bulb weight (g)

Single bulb weight on randomly selected 20 bulbs from middle rows were measured on electric balance

and average worked out.

Bulb diameter (mm)

Bulb diameter (size) was measured on randomly selected 20 plants with the help of digital Vernier

Caliper in centimeter (mm) and the averaged calculated value was analyzed.

Days to Bolting initiation

Days to bolting initiation were counted from the date of transplanting to the day at which inflorescence

initiation was observed.

Bolting percentage

Total number of plants that developed premature bolting in a unit plot were counted and then percentage

was calculated. The average value of bolting percentage was used for analysis.

Days to Maturity

Days to physiological maturity was calculated from date of transplanting to 80% yellowing of the leaves.

Total Bulb Yield (ton ha-1)

Marketable bulb yield per plot was weighed using an electric balance and then the values were converted

into bulb yield per hectare.

Cull

Bolted, diseased, damaged and double bubs were separated, culled and weighted and the values were

converted to cull per hectare.

Marketable Yield (ton ha-1)

Marketable yield per plot was determined after separating cull from the bulbs. The bulbs weight per plot

was recorded converted to marketable yield ton ha-1.

Statistical Analysis

Data were analyzed by the technique of analysis of variance on all studied parameters using statistical

software “Statistix 8.1”. Significant differences between means of treatments were calculated using

LSD test for the LSD ≤ 0.05.

30

RESULTS & DISCUSSION

The data collected was statistically analyzed to deduce results. The findings of the study are presented

in tables, graphs and figures and are briefly discussed in light of the available litrature.

Plant height (cm)

Data related to plant height in 2014, 2015 and its mean were presented in Table 5. It is evident from the

table that transplanting date and seedling age significantly (p<0.05) affected plant height whereas years

had a non-significant effect for these traits. All interactions were also non-significant at 5% level of

probability. Maximum plant height of 58.80 cm were recorded from early transplanting on 30th

November followed by 57.62 cm transplanted on 15th December whereas, almost two months late

transplanting on 30th January resulted in minimum plant height of 53.77cm. Sawant et al., (2002) found

that plant height and the number of leaves were significantly affected by sowing dates. Early sowing

produced the tallest plants with maximum number of leaves (Rahman et al., 2002; Ibrahim, 2010).

Brewster (2008) reported that bulbs will be initiated when temperature starts to increase and the required

minimum day length of a specific onion cultivar is met. So, when the same cultivar is sown at different

times in the same area, plants will start bulb formation more or less the same time. Hence, earlier sown

plants will have a longer vegetative growth period and consequently have vigorous plants with more

leaves (Comrie, 1997b; Bosekeng and Coetzer, 2013). Vigorous plants with more vegetative growth

produce bigger bulbs and thus more yield.

Seedling age also significantly affected plant height at 5 % level of probability. Maximum plant height

of 57.91cm was recorded when 60 days old seedlings were transplanted while, the minimum plant

height of 55.16cm was recorded when younger seedlings of 45 days old were transplanted. Seedlings

of 60 days age may be in active growth stage and recover from transplanting shock quickly. Very small

seedling have the risk of winter injury while very old seedlings recover from transplanting shock slowly.

If transplanting of seedlings were delayed than the optimum time in which they are making active growth,

31

Table 5: Effect of transplanting date and seedling age on plant height during year 2014 and 2015.

Row Labels 2014 2015 Mean

Transplanting Dates

30th November 58.43 a 59.16 a 58.80 a

15th December 57.06 ab 58.18 ab 57.62 ab

30th December 55.72 b 56.87 bc 56.29 bc

15th January 55.19 b 56.03 c 55.61 c

30th January 52.41 c 55.07 c 53.74 d

LSD 1.19 2.09 1.39

Seedling Age

75 day’s old seedlings 55.32 b 57.02 ab 56.17 b

60 day’s old seedlings 57.86 a 57.95 a 57.91 a

45 day’s old seedlings 54.11 b 56.21 b 55.16 b

LSD 1.75 1.95 1.36

Year 55.04 a 57.02 a

Interactions

D × S ns ns Ns

Year × D - - Ns

Year × S - - Ns

Year × D × S - - Ns

D = Transplanting dates S = Seedling age *- significant at P =0.05

the optimum time in which they are making active growth, the growth after transplanting and yield

would be affected (NeSmith, 1993). Bijarniya et al., (2015) recorded maximum plant height 29.86,

59.61 and 64.00cm from 8 weeks old seedlings 45, 75 and 90 days after transplanting respectively. On

the contrary Kanton et al., (2003) found significant effect of seedling age on plant height and reported

the tallest plants from 40 days old transplants in onion as compared to older transplanting.

Number of Leaves at Bolting Stage

Data for number of leaves at bolting dring 2014, 2015 and its mean was given in Table 6. Analysis of

the data revealed that number of leaves at bolting initiation stage was non-significant in both years, while

transplanting date and seedling age had significant (p<0.05) effect on the number of leaves at the time

of bolting initiation. All the interactions were found non-significant. Maximum number of leaves per

plant 8.29 were recorded, when premature inflorescence initiated, in 30th November transplantings and

the lowest number of leaves 6.29 were recorded in 30th January transplanting. Flowering induction in

onion is caused by low temperature after the juvenile stage of development. Onion plants will form seed

32

stem in the first year if they reach the critical size and then receive cold stimulus. As leaf initiation rate

is constant in a given environment (Brewster, 1983, 1987; Cramer, 2003) leaf number has been used to

determine plant’s age (Rabinowitch, 1990). Khokhar et al., (2007a) reported that the number of leaves

has been used to determine the critical plant size at which bolting occurs when exposed to low

temperature. They found that 7-10 leaves stage is sensitive plant size (at the end of the first leaf fall and

the beginning of bulbing stage). When seedlings are transplanted early, plants reach the reproductive

stage and initiate bolting upon exposure to low temperature. Current study confirm this as early

transplanting produced more leaves 8.29 and were at reproductive stage when temperature was still low

and had maximum bolting percentage 33.63.

Table 6: Effect of transplanting date and seedling age on number of leaves at Bolting in year 2014 and

2015.


Transplanting Date

30th November 8.19 a 8.38 a 8.29 a

15th December 7.50 b 7.58 b 7.54 b

30th December 7.11 bc 7.17 bc 7.13 b

15th January 6.53 cd 6.50 cd 6.51 c

30th January 6.31 d 6.28 d 6.29 c

LSD 0.65 0.69 0.51

Seedling Age


60 day’s old seedlings 7.00 b 7.10 a 7.05 b

45 day’s old seedlings 6.21 c 6.45 b 6.33 c

LSD 0.50 0.53 0.46

Year 7.13 a 7.18 a

Interactions

D × S ns ns Ns

Year × D - - Ns

Year × S - - Ns

Year × D × S - - Ns

D = Transplanting dates S = Seedling age *- significant at P =0.05

Cramer (2003) observed that earlier planted onion produced larger plants with more leaves compared

to later seeding onion. Sawant et al, (2002) found that plant height and the number of leaves were

significantly affected by sowing dates. On the other hand, Bosekeng and Coetzer (2013) stated that

33

sowing date did not influence plant height and leaf number significantly over a period of two years,

however, early sowing dates in one year resulted in taller plants.

Likewise, maximum number of leaves at bolting (8.08 leaves/plant) were reported when 75 days old

seedlings were transplanted, whereas minimum of 6.33 leaves per plant were recorded when 45 days

old seedling were transplanted. These results are in conformity with the findings of Singh and Chaure,

(1999) and Bahadur and Singh (2005). Bijarniya et al, (2015) recorded maximum number of leaves per

plant 5.16, 8.61 and 10.95 from 8-weeks old seedling at 45, 75 and 90 DATP compared to 6 and 7-

weeks old seedling. Thus, early transplanting coupled with aged seedlings completes the juvenile phase

early and become receptive to cold stimulus that induces bolting.

Stem Diameter (mm)

Stem diameter data influence by transplanting date and seedling age during 2014, 2015 and its combined

means is given in Table 7. It is evident from the data that year as a source of variation was not significant

at 5% level of probability. The interactions were also found non-significant. Transplanting date and

Table 7: Effect of transplanting date and seedling age on stem diameter during year 2014 and 2015.


Transplanting Date

30th November 17.21 a 17.24 a 17.22 a

15th December 16.85 ab 16.81 ab 16.83 ab

30th December 16.46 ab 16.55 ab 16.51 bc

15th January 16.11 bc 16.19 bc 16.15 c

30th January 15.20 c 15.28 c 15.24 d

LSD 0.97 0.93 0.66

Seedling Age


60 day’s old seedlings 16.41 ab 16.46 ab 16.43 a


LSD 0.75 0.72 0.51

Year 16.37 16.37

Interactions

D × S ns ns ns

Year × D - - ns

Year × S - - ns

Year × D × S - - ns

D = Transplanting dates S = Seedling age *-significant at P =0.05 ns- non- significant at P =0.05

34

seedling age had significant effect on stem diameter in both the years. Stem diameter declined with

delay in transplanting from 30th November to 30th January.

Maximum stemt diameter 17.22 mm was noted in 30th November transplanting, followed by 16.38 mm

in 15th December transplanting, whereas lowest stem thickness 15.24 mm was recorded when onion

were transplanted on 30th January. Brewster, (1997) stated that stem thickness shows the failure of the

plant to complete the bulb formation process and such bulbs do not undergo dormant. This problem

arises because of slow growth or short growing period. According to Rana and Hore (2015), every

cultivar has specific photoperiodic requirement for bulb initiation. When the minimum photoperiodic

and temperature requirement of the cultivar does not meet, plants continue to grow without bulb

formation which leads to thickening of the stems. Results similar to this study were reported by

Bosekeng and Coetzer (2013) who obtained bulbs with thickest stem from early transplanting compared

to late transplanting. Jilani (2004), also reported that the thickest onion bulb necks was obtained with

early plantings (27th October) compared to late plantings (26th December). Thinner stem with later

planting may be due to early bulb initiation in smaller plants. Asmatullah et al, (2004) reported a higher

percentage of bolting and thick neck from earlier transplanting dates. Likewise, decreasing stem

thickness with decreasing seedling age was also recorded. Maximum stem diameter of 16.87mm was

obtained when 75 days old seedlings were transplanted and minimum stem diameter of 15.87mm was

noted when 45 days old seedling were transplanted. The results of this study are in conformity with the

findings of Bijarniya et al, (2015) who found maximum stem thickness in 8-weeks old transplanting

compared to 6 and 7-week old seedlings.

Days to Maturity/Harvesting

Data regarding maturity for two consective years 2014- 2015 and its combined means are presented in

Table 8. Maturity/harvesting remained non-significant between the two growing seasons. All the

interactions were also non-significant. Transplanting date significantly affected days to harvesting while

the seedling age effect was found to be non-significant (p<0.05). Maximum days to maturity 180.89

were observed for 30th November transplantings, followed by 176.50 in 15th December transplantings.

Whereas minimum days of 152.72 to maturity were recorded in 30th January transplantings. Data in

2014 and 2015 showed a similar trend.

Though the effect of seedling age on maturity was non-significant, however, mean data revealed that

younger seedlings took more days to maturity as compared to older seedlings. The combined means of

two year showed that maximum 167.83 days to maturity were taken by 45 days old seedlings and

minimum 165.73 days to were taken to harvesting when 75 days old seedlings were transplanted. Bulbs

35

normally start to mature when the required minimum photoperiod and temperature requirement of the

specific cultivar is met. Hence a cultivar sown on different dates or having varying seedling ages start

to mature more or less at the same time. Thus late transplanting (30th January) took less days to maturity

than early transplanting. Similar results were reported by Sawant et al, (2002) that early transplanting

took the longest duration (137 days) to maturity than late planting. The findings of Bijarniya et al, (2015)

that older seedling take less days to maturity than younger seedlings also support our results.

Table 8: Effect of transplanting date and seedling age on days to maturity during the year2014 and 2015.


Transplanting Dates

30th November 182.56 a 179.22 a 180.89 a

15th December 177.89 a 175.11 a 176.50 b

30th December 164.00 b 167.11 b 165.56 c

15th January 158.22 c 156.78 c 157.50 d

30th January 153.56 c 151.89 d 152.72 e

LSD 5.63 4.29 3.43

Seedling Age




LSD 4.36 3.32 2.66

Year 167.24 a 166.02 a 166.46

Interactions

D × S ns ns ns

Year × D - - ns

Year × S - - ns


Bolting Percentage

Statistical analysis of the data pertaining to bolting percentage during 2014-2015 and its combined

means are summarized in Table 9 and significant interaction (p < 0.05) of transplanting date and seedling

age is given in Figure 4.Transplanting date and seedling age significantly affected the bolting percentage

while the year effect was non-significant (p < 0.05). Maximum bolting percentage of 33.63% was

recorded in in early transplantin on 30th November and it decreased with delay in transplanting and

completely diminished (0%) in the very late transplanting on 30th January.Thus, bolting was decreased

from 33.63 % to 0% when transplanting was delayed from 30 November to 30 January. Khokhar et al.,

36

(2007a) reported that the number of leaves has been used to determine the critical plant size at which

bolting occur when expose to low temperature. They found that 7-10 leaves stage is sensitive plant size

(at the end of the first leaf fall and the beginning of bulbing stage). When seedlings are transplanted early

in the season, seedlings will achieve enough growth to complete the vegetative phase before the fall of

temperature. And when cold temperature occurs it induces bolting instead of making bulbs. As in our

study early transplanting on 30th November produced 8.29 leaves (Table 5) and were at reproductive

stage when temperature was still low in season which inducecd 33.63 % plants to boltings. Late

transplanted (30th January) seedlings were at juvenile phase having 6.29 leaves and produce 0 % bolting

in spite of low temperature prevailing late in the season. Thus, late transplantings escape the cold spell.

Sowing should be adjusted so as to prevent plants receiving a cold spell at sensitive plant size that cause

bolting instead of bulb formation. .It is difficult to define the exact date for transplanting to reduce bolting

and increase yield at the same time as it is cultivar and environment dependent (Cramer, 2003).

Table 9: Effect of transplanting dates and seedling age on bolting percentage during year 2014 and 2015.


Transplanting Date

30th November 34.55 a 32.72 a 33.63 a

15th December 23.44 b 22.23 b 22.83 b

30th December 12.67 c 12.16 c 12.41 c

15th January 6.03 d 7.14 d 6.57 d

30th January 0.0-e- 0.0-e- 0.0-e-

LSD(0.05) 3.44 3.81 2.47

Seedling Age



45 day’s old seedlings 5.67 c 3.53 c 4.60 c

LSD 2.67 2.95 1.91

Year 15.33 14.85 15.79

Interactions

D × S * * *

Year × D - - ns

Year × S - - ns


37

Temperature later in the season, particularly in March-April when plants have enough leaf numbers to

respond to cold stimulus is vary year after year. In some years climate is cool and favor bolting or vice

versa.In current study though year effect was not significant, 2013-14 season was little colder than 2014-

15 and have more bolting numbers. Boyhan et al, (2009) also reported more bolting occurrence in 2003-

04 season compared to 2004-05 season. Madisa (1994) reported onion plants sown late did not bolt as

when low temperatures responsible for bolting prevailed, the plants were still small and had not yet

reached minimum plant size.

Similarly, highest bolting percentage was noted in older seedlings compared to younger seedlings. The

highest bolting percentage of 30.81% was observed in 75 days old transplantings, followed by 9.86%

in 60 days old transplantings.The lowest bolting percentage 4.60% was noted when 45 days old

seedlings were transplanted.

Transplant size may be an important factor in onion performance. Commonly, large seedling have higher yield

but more bolting occurrence. This may be due to the fact that large seedlings are more stressed and grown enough

to enter the reproductive stage early as reflected in the study of Boyhan et al, (2009) and is also verified by present

study. Dong et al, (2013) stated that onion seedling must be grown to certain age before they sense the cold

temperature and start vernalization process. Gao et al, (2011) found that older seedling needed less accumulation

of low temperature for bolting. Kanton et al (2003) reported that older (30 or 40 days) seedlings take less days to

mature than younger transplants (20 days). Jahromi and Amirizadeh (2015) reported similar results that bolting

percentage increased with increasing seedling age.

Figure 5: Mean data showing interaction of transplanting dates and seedling age for bolting percentage

0

10

20

30

40

50

60

70

D 1 D 2 D 3 D 4 D 5

Bo

ltin

g p

erce

nta

ge

Transplanting dates

S1 S2 S3

38

All the interactions were found non-significant except, transplanting date and seedling age. As per the

two year means interaction results of D×S combination maximum bolting percentage 66.33% was

recorded in D1S1 combination followed by 48.33 % D2S1 (Figure 3). The Lowest bolting percentage of

4.33% was observed in D3S3. No bolting was recorded in D4S3 and D5 irrespective of the seedling age.

Early transplanting of larger seedlings take less time to reach minimum critical size, sense the cold

response and bolt readily instead of making bulbs. Contrary, younger seedlings with late transplanting

take more time to mature and are more likely to escape the cold weather inducing bolting. Brewster

(1994) showed that there is a relationship between sowing date, bulb yield and bolting. Muhammad et

al (2016) also found significant interaction of transplanting dates and seedling age for bolting

percentage.

Bulb Diameter (mm)

Data regarding bulb diameter showed significant differences for transplanting dates and seedling age,

whereas years and all interactions were not significant at 5% level of probability (Table 10). Maximum

bulb diameter of 69.74 mm was recorded for 30th November transplantings. Bulb diameter decreased

as transplanting delayed from November 30 to January 30 and minimum bulb diameter of 47.61mm

was recorded in late transplanting on January 30. Early transplants have sufficient time for vegetative

growth before minimum temperature and day length requirement for bulbing is fulfilled. Thus they

attain maximum plant height with more number of leaves and produce large size bulbs. Sawant et al,

(2002) reported that early planting produced maximum polar and equatorial diameter and hence,

produced large sized bulbs. According to Bosekeng and Coetzer (2013) bulb diameter was significantly

influenced by both cultivar and sowing date and earlier sown crop produced the largest bulbs. The results

of Bijarniya et al., (2015), Hiray (2001), Kumar et al., (1998) and Mosleh and Deen (2008) also support

current study. Similarly, seedling age exerted significant effect on bulb diameter and maximum bulb

diameter of 63.11mm was noted in 60 days old seedling (S2) while minimum bulb size of 56.16 mm

was recorded when 75 days old nursery was transplanted. These results are in conformity with the

findings of Kanton et al, (2003) and Aubyn and Abutiate (1994) that mean bulb weight and bulb

diameter decreased with increasing seedling age. Norman (1992) reported that younger seedlings

recovered from transplanting shock quickly than older seedlings. NeSmith (1993) reported that if

transplanting is delayed after the optimal time in which they are making active growth, then growth after

transplanting and yield would be affected.

39

Table 10: Effect of transplanting date and seedling age on bulb diameter (mm) during the years 2014 and

2015.


Transplanting Dates

30th November 71.34 a 68.14 a 69.74 a

15th December 67.16 a 66.92 a 67.03 a

30th December 58.62 b 59.99 b 59.31 b

15th January 51.43 c 51.53 c 51.48 c

30th January 48.21 c 47.01 c 47.61 d

LSD 4.31 4.58 3.05

Seedling Age




LSD 3.34 3.54 2.36

Year 5.93 5.87

Interactions

D × S ns ns ns

Year × D - - ns

Year × S - - ns


Bulb Weight (g)

Data concerning bulb weight in 2014 and 2015 and its combined means are presented in Table 11.

Statistical analysis of the data revealed that transplanting dates, seedling age and its interaction had

significant (p<0.05) effect on bulb weight while the years effect was not significantly. Maximum bulb

weight of 224.39 g was noted for when seedlings were transplanted early on November 30 followed by

218.39 g in 15th December transplantings. Bulb weight decreased with delay in transplanting and the

minimum bulb weight of 158.89 g was recorded in the late transplanting on January 30. Bosekeng and

Coetzer (2013) reported that delayed sowing significantly decreased average bulb fresh mass while early

sown plant produced the largest bulbs. This all suggest that planting dates influence single bulb weight

in onion.

40

Table 11: Effect of transplanting date and seedling age on bulb weight (g) during year 2014 and 2015.


Transplanting Dates

30th November 221.56 a 226.89 a 224.39 a

15th December 218.00 a 218.78 a 218.39 a

30th December 188.06 b 195.33 b 191.69 b

15th January 168.44 c 171.00 c 169.72 c

30th January 159.56 c 158.22 d 158.89 d

LSD 9.26 8.19 6.05

Seedling Age



45 day’s old seedlings 180.00 b 177.87 c 178.93 c

LSD 7.17 6.35 4.68

Year 189.22 a 193.87 a

Interactions

D × S * * *

Year × D - - ns

Year × S - - ns



Combined means of bulb weight as affected by seedling age showed that maximum bulb weight of

209.55 g was recorded in 60 days old transplants ,while the minimum bulb weight of 178.93g was

recorded in 75 day’s old transplant (S3). A similar trend of decreasing bulb weight with decreasing

seedling age has also been observed in 2014 and 2015. Age of transplants affects bulb yield (Saha,1982).

Islam, (1981) found that 60 days old seedling produced more yield than 50 days old transplants. Aubyn

and Abutiate (1994) reported that bulb yield of fresh onion decreased with increasing age of transplants.

If transplanting of seedlings were delayed than the optimum time in which they are making active

growth, then growth after transplanting and yield would be affected (NeSmith, 1993). Vachhani and

Patel (1988) reported that bulb yield increased with increasing seedlings age up to 7 weeks, after which

it started to decline while Herison et al, (1993) stated that increased bulb yield is due to transplant size

rather than transplant age.

41

Figure 6: Mean data showing interaction of transplanting dates and seedling age for bulb weight (g).

Kanton et al (2003) stated in their arguments that higher bulb yields produced for plants developed from

younger transplants could be attributed to better plant growth as revealed in taller plants having the

maximum leaf and bulb dimensions compared to their older seedlings. They also reported that younger

seedlings restarted vegetative growth more quickly, which might have contributed to more vigorous

development. Plants derived from younger transplants seemed to be more efficient in conversion of

photosynthates into harvestable bulbs than plants grown from older seedlings. The interaction of D×S

was significant while the remaining interaction were not significant.

Data about the interaction of transplanting date and seedling age is given in Figure 4 revealed that

maximum bulb weight 249.50 g was produced by D1S2 combination followed by 237.50 g in D2S2

combination. Bulb weight decline as transplanting delayed and seedling aged decreased. Minimum bulb

weight of 158.83 g was produced in D5S3 combination.

Total Yield (ton ha-1)

Data associated with yield ton ha-1 is shown in Table 12. Transplanting date and seedling age made

significant difference in yield ton ha-1 at 5% level of probability while the year effect on yield ton ha-1

was found non-significant. All the interaction were also found non-significant. Maximum yield 39.90

ton ha-1was obtained from 15th December transplanting followed by 39.71 ton ha-1 from 30th November

transplantings, whereas, minimum yield 15.99 ton ha-1was recorded when transplanting was delayed to

January 30. Ample vegetative growth before bulb formation is essential to get high yield (Ibrahim,

2010). When sowing is delayed, plant start bulbing before attaining sufficient vegetative growth,

resulting in small bulbs and lesser yield. Smaller plant canopy of small plant in late sowing crop

intercepts less light and resultantly produce low yield (Bosekeng and Coetzer, 2013). They also found

that late sowing significantly reduce bulb fresh mass and yield from 40.96 to 28.20 tons ha-1.

0

50

100

150

200

250

300

D1 D2 D3 D4 D5

Bu

lb w

eig

ht

(g)

Transplanting Dates

S1 S2 S3

42

Different age nursery transplanting also found to have significant effect on yield ton ha-1. The highest

yield 32.43 ton ha-1 was produced when 60 days old seedlings were transplanted while lowest yield

27.24 ton ha-1was recorded in 45 days old transplants. Similar results has reported by Kanton et al,

(2003) that higher bulb yields produced

Table 12: Effect of transplanting date and seedling age on yield (ton ha-1) during the year 2014 and 2015.


Transplanting Dates

30th November 38.64 a 40.78 a 39.71 a

15th December 39.81 a 40.00 a 39.90 a

30th December 29.75 b 31.47 b 30.61 b

15th January 20.31 c 23.06 c 21.68 c

30th January 12.78 d 19.19 d 15.99 d

LSD 3.35 2.51 2.05

Seedling Age



45 day’s old seedlings 27.58 b 30.55 b 29.07 c

LSD 2.60 1.95 1.58

Year 28.26 30.90

Interactions

D × S * ns ns

Year × D - - ns

Year × S - - ns


43

Figure 7: Mean data showing interaction of transplanting dates and seedling age for yield ton ha-1.

for plants developed from younger transplants could be attributed to better plant growth compared to

their older seedlings. They further stated that younger seedlings revived vegetative growth more quickly,

which might have contributed to more vigorous development. Plants derived from younger transplants

seemed to be more efficient in conversion of photosynthate into harvestable bulbs than plants grown

from older seedlings. According to Fathi (2009) the optimum seedling age of onion is 60 days and the

60 days-old transplant had the higher yield than other transplant ages. The results of this study are also

matched with the findings of Jahromi and Amirizadeh (2015) who obtained maximum total yield from

60 days old transplants.

Figure 8: Mean data showing interaction of transplanting dates and year for yield ton ha-1.

0

5

10

15

20

25

30

35

40

45

D1 D2 D3 D4 D5

Yie

ld t

on

ha-1

Transplanting Dates

S1 S2 S3

0

5

10

15

20

25

30

35

40

D1 D2 D3 D4 D5

Yiel

d t

on

ha-1

Transplanting dates

Y1 Y2

44

Percent Cull

Statistical analysis of the data regarding percent cull in 2014, 2015 and their means were shown in Table

13. Transplanting date and seedling age caused significant difference in percent cull at 5% level of

probability. Year as a source of variation remained non- significant. Maximum percent cull of 33.85%

was recorded in early transplanting on November 30 followed by 31.15%. in 15th December transplants.

Table 13: Effect of transplanting date and seedling age on percent cull during year 2014 and 2015.


Transplanting Dates

30th November 35.85 a 31.84 a 33.85 a

15th December 32.46 b 29.81 b 31.15 b

30th December 12.62 c 11.81 c 12.21 c

15th January 6.89 d 8.35 d 7.62 d

30th January 2.21 e 2.64 e 2.42 e

LSD(0.05) 2.25 1.86 1.43

Age of seedling



45 day’s old seedlings 13.40 c 12.37 c 12.89 c

LSD 1.74 1.44 1.11

Year 14.51 17.17

Interactions

D × S * * *

Year × D - - ns

Year × S - - ns



A reduction of 31.43% in unmarketable yield was recorded when transplanting was delayed from

November 30-January 30. Early transplants complete vegetative phase and reach reproductive stage

early when cold temperature prevails. This low temperature induce bolting which contribute to

unmarketable yield. In early transplanting maximum bolting 33.63% and maximum unmarketable yield

were recorded. The lowest percent cull in late transplanting was due to small ungraded bubs. The results

of this study matched with findings of Bijarniya et al, (2015) who recorded maximum % cull in early

transplanting compared to later transplanting. Kandil et al, (2013) reported similar results stating that

the highest values on total culls were resulted from transplanting seedlings on 15th November (early

45

transplanting date) in2010-11 and 2011-12. Similar results has been reported by Kumar et al, (1998)

and Singh (2006).

In the same way highest cull 21.89% was recorded in 75 days old seedlings (S1) while lowest 12.89 %

cull was noted in 45 days old seedlings ( S3). A similar trend has also been observed in year 1 and year

2. Flowering stem formation started only after the juvenile stage of development (the emergence of

certain number of leaves depending on cultivar) followed by exposure to low temperature (Brewster,

1985; Diaz-Perez, 2003). The sensitivity to low temperature increased with increase plant age.

Figure 9: Mean data showing interaction of transplanting dates and seedling age for percent cull

Older seedling take less time to attain maturity and run to premature bolting instead of making bulbs. In

this study higher % cull in older seedlings was due maximum bolting while in younger seedling small

bulbs contributed to unmarketable yield. Bijarniya et al, (2015) reported highest unmarketable yield

7.66 kg/plot was recorded in 8-weeks old seedling compared to 6-week old seedlings.

The interaction of D × S was found significant (p<0.05) while the remaining. Interactions were non-

significant. The D × S interaction pointed out that percent cull was maximum in D1S1 combination 42.44

and decline consistently as transplanting delayed and seedling age decreased. Minimum cull 1.81% was

recorded in D5S3 combination.


Marketable yield ton ha-1 affected by transplanting dates and seedling age has been presented in Table

14. Statistical analysis of the data revealed that transplanting date and seedling age significantly

42

.44

30

.68

29

.48

22

.72

17

.04

16

.16

12

.72

11

.71

10

.29

7.5

2

5.2

4

2.5

3

2.5

3

2.2

8

1.8

1

0

5

10

15

20

25

30

35

40

45

S 1 S 1 S 2 S 1 S 2 S 3 S 1 S 3 S 2 S 3 S 2 S 2 S 3 S 3 S 1

D 1 D 2 D 1 D 3 D 2 D 1 D 4 D 2 D 3 D 3 D 4 D 5 D 4 D 5 D 5

Per

cen

t C

ull

Transplanting dates & seedling age

46

influenced marketable yield ton ha-1 at 5% level of probability. Year as source of variation was non-

significant (p<0.05). The highest marketable yield 28.50 ton ha-1 was obtained from when transplanting

was done on December 30 , followed by 26.36 ton ha-1 in 15th December transplantings whereas, the

lowest marketable yield 15.64 ton ha-1 was recorded in when transplanting was carried out late on

January 30. According to Cramer (2003) early transplanting and larger seedling resulted in maximum

bolting percentage. Bolters occurred in early transplanting from November 30-January 15 contributed

to unmarketable yield. Bolting and cull both are negatively correlated with marketable yield. Marketable

yield decreased when bolting percentage and percent cull increased. Ibrahim (2010) also found

maximum cured yield ton ha-1 from 3rd date of transplanting.

Table 13: Effect of transplanting date and seedling age on marketable yield (ton ha-1) during the year 2014

and 2015.


Transplanting Dates

30th November 24.81 b 26.82 b 25.81 b

15th December 25.50 b 27.22 ab 26.36 b

30th December 27.29 a 29.70 a 28.50 a

15th January 20.75 c 21.50 c 21.13 c

30th January 14.50 d 16.79 d 15.64 d

LSD(0.05) 2.16 2.78 1.72

Age of seedling




LSD 1.67 2.15 1.33

Year 22.57 24.41 23.49

Interactions

D × S * * *

Year × D - - ns

Year × S - - ns



Bijarniya et al (2015) also reported similar results. There is a tendency of declining total yield with delay

in transplanting but early transplanting have the risk of bolting, splitting and doubles. Thus, later dates

produced medium sized bubs with highest marketable yield (Sinclair (1989).

47

Transplanting should be adjusted to avoid plant to receive enough cold at reproductive stage. Too much

delay will diminished the bolting at the cost of marketable yield. The result of this study is at variance

with Nourai et al., (2007) who reported highest total and marketable yield from early transplanting (15th

Nov) compared to 15th Dec and 15th Jan transplanting.

Similarly, maximum marketable yield 25.50 ton ha-1 was recorded in 60 days old seedlings S2 while the

minimum marketable yield 20.39 ton ha-1 was recorded from 75 days old transplants. Conflicting results

has been reported by Bijarniya et al (2015) who recorded maximum marketable yield from older nursery

transplanting and marketable yield decrease with decrease in seedling age.

Figure 10 Mean data of interaction of transplanting dates and seedling age for marketable yield ton ha-1.

The interaction of D × S was significant (p<0.05) while the rest of interactions were non-significant.

The D × S interaction indicated that marketable yield ton ha-1 was maximum 37.17 ton ha-1 in D2S2

combination followed by 34.47 ton ha-1 D2S3. Marketable yield decreases as with delay in transplanting

as well as decreasing seedling age. Minimum 14.90 ton ha-1 was recorded in D5S3 combination. (Figure

9). Muhammad et al, (2016) also found significant interaction of transplanting dates and seedling age

for marketable yield ton ha-1.

Correlation co-efficient analysis

The correlation co-efficient analysis quantifies the mutual relationship of various characters. The

correlation co-efficient between total and marketable yield with yield contributing parameters is

presented in Table 15. The data revealed that marketable yield ton ha-1 has significant positive

correlation with bulb diameter (0.381) and total yield ton ha-1 (0.671) and non- significant positive

correlation with bulb weight (0.173), number of leaves at bolting (0.097), stem thickness (0.091) and

0

10

20

30

40

50

60

70

80

90

100

D1 D2 D3 D4 D5

Mar

keta

ble

Yie

ld t

on

ha-1

Transplanting Dates

S1 S2 S3

48

plant height (0.106). The association of marketable yield with bolting percentage (-0.381) and % cull (-

0.552) was significantly negative. Marketable yield decreases as bolting and % cull increased (Cramer,

2003) who also found negative correlation of marketable yield with bolting percentage. The table

showed that percent cull has positive correlation with bolting percentage (0.671) and negative

correlation with total yield ton ha-1 (-0.05) and marketable yield ton ha-1 (-0.552). Bolting percentage

contribute to unmarketable yield and increasing in bolting percentage and percent cull is lowering

marketable yield. It is evident from the table that total yield ton ha-1 has positive correlation with plant

height (0.011), bulb diameter (0.397), bulb weight (0.227), marketable yield (0.671) and negative

correlation with total cull (-0.05).

According to Kanton et al., (2003) bulb yield was significantly (P < 0.05) correlated with mean bulb

weight (r = 0.92) and bulb diameter (r = 0.64). Rahman et al (2010) also found significantly positive

correlation of total bulb yield with plant height, number of leaf per plant, bulb diameter and bulb weight.

Haydar et al (2007) in a trial found that bulb yield had highly positive significant association with bulb

length and bulb diameter. Bulb diameter has significantly positive correlation with bulb weight (0.491),

yield ton ha-1 (0.397), marketable yield (0.381)

Table 14: Phenotypic correlation coefficient among yield and yield related characters in onion.

Bolting

percentage

No. of

leaves/plant

at Bolting

Bulb

weight

Bulb

Diameter

Stem

Thickness

Plant

Height

Days to

Maturity

Yield

tons/ha

Percent

Cull

Marketable

Yield(t/h)

Bolting

percentage

1 0.078 0.033 -0.072 0.149 -0.201 0.033 0.105 0.671* -0.381*

No. of

leaves/plant

at Bolting

1 -0.031 0 0.038 -0.064 0.029 0.039 0.037 0.097

Bulb

weight

1 0.491* 0.025 0.243* 0.024 0.248* 0.185 0.173

Bulb

Diameter

1 0.078 0.122 -0.069 0.397* -0.076 0.381*

Stem

Thickness

1 0.043 0.137 0.227* 0.093 0.091

Plant

Height

1 -0.058 0.011 -0.231* 0.106

Days to

Maturity

1 -0.063 0.131 -0.048

Yield

tons/ha

1 -0.05 0.671*

Percent

Cull

1 -0.552*

Marketable

Yield

1

49

and negative correlation with % cull (-0.76).Bolting percentage has positive correlation with number of

leaves at bolting stage (0.078), stem thickness (0.149), bulb weight (0.033), yield ton ha-1 (0.105) and

% cull (0.671) while its association with plant height (-0.201), bulb diameter (-0.72) and marketable

yield (-0.381) was found negative. Plant height has non-significantly positive correlated with bulb

diameter (0.122), bulb weight (0.243), yield ton ha-1 (0.011) and marketable yield ton ha-1 (0.106) while

its correlation is significantly negative with number of leaves at bolting (-0.064) and percent cull (-

0.231).

Summary Conclusios And Recommendations

Summary

Premature flower stalk development in onion bulb crop deviating from normal life cycle is called

bolting. Bolting makes the bulbs fibrous, lightweight and thus reduces its quality. Bolting is one of the

major production constraints in all onion growing areas in Pakistan. This study was conducted with the

aim to prevent onion bulb crop from bolting and produce quality onion bulbs.

This study was conducted to find out the effect of transplanting dates and seedling age on premature

bolting in onion bulb crop. Seedlings of 45, 60 and 75 days in nursery were transplanted on 5 different

dates (30th November, 15th December, 30th December, 15th January and 30th January) Transplanting

dates and seedling age produced significant effect on different growth and yield parameters studied.

Early transplantings produced maximum plant height, number of leaves at bolting, stem diameter, days

to maturity, bub diameter, bulb weight and total yield decreased with delay in transplanting as well as

increasing seedling age. On the other hand bolting and cull percentage decrease with delay in

transplanting and increased with increase in seedling age. Maximum marketable yield (tons ha-1) was

recorded when 60 days old seedlings were transplanted on15th December. The correlation co-efficient

analysis data revealed positive correlation between marketable yield (0.671 ton ha-1) and bulb diameter

(0.381). Non- significant positive correlations of marketable yield were recorded with bulb weight

(0.173 gm), number of leaves at bolting (0.097), stem thickness (0.091) and plant height (0.106). The

association of marketable yield with bolting percentage (-0.381) and percent cull (-0.552) was

significantly negative.

Conclusions

1. A 15 days delay in transplanting from 30th November to 15thDecember caused reduction in bolting

from 33.63% to 22.83 %. Likewise, 15 days delay from 15 December to 30th December decreases

bolting from 22.83% to 12.41%. Moreover, 15 days delay in transplanting from 30th December to

50

15th January reduced bolting percentage from 12.41% to 6.57%. Bolting was not observed on 30th

January transplanting.

2. Younger seedlings take more days to pass the juvenile stage and enter the reproductive stage, thus,

more likely to escape the cold temperature that is responsible for bolting. Older seedlings (more

than 60 days) took less days to transition phase and initiate inflorescence development upon

exposure to low temperature.

3. Bolting percentage decreased from 30.81 to 9.86% when transplant age was reduced from 75 days

to 60 days. Bolting incidence further declined from 9.86% to 4.60% when 45 days old seedlings

were transplanted.

Recommendation

1. Transplanting should be carried out from December 15 to January 15 since it produced

maximum marketable yield with low bolting percentage and minimum cull in the north of West

Pakistan. Very early transplanting increases bolting whilevery late transplanting produces small

bulbs and low yield.

2. Seedling age also influence the incidence of bolting. Larger plants switched from juvenile stage

to reproductive stage earlier when temperature gets low and start bolting instead of bulbing.

Fifty to sixty days old seedlings gave maximum marketable yield and minimum bolting.

51

Chapter 4

EXPERIMENT 2: BOLTING IN ONION BULB CROP AS INFLUENCED BY

CULTIVARS AND TRANSPLANTING DATES.

ABSTRACT

By


Department of Agricultural Sciences (Horticulture) University of Haripur

April 2017

Three commercial cultivars ‘Swat-1’, ‘Saryab Red’ and ‘Chiltan-89’ were transplanted on five different

dates at 15 days interval (25th November, 10th December, 25th December, 10th January and 25th January).

Cultivars varied in their susceptibility to bolting. Cultivar Swat-1 took significantly maximum 78.67

days to bolting initiation and recorded minimum bolting percentage 12.51 compared to ‘Saryab

Red’13.75 and ‘Chiltan-89’ 17.32. Early transplanting took less 108.06 days to bolting initiation.

Bolting percentage was maximum 34.52 at early transplanting and reduced with delay in transplanting

from 25th November to 25th December. Bolting has not been recorded at late, (10th and 25th January)

transplanting irrespective of the cultivar. When compared to ‘Saryab Red’ and ‘Chiltan-89’, ‘Swat-1’

produced maximum plant height 65.58 cm, number of leaves per plant 10.64, stem diameter 15.43 mm,

bulb diameter 60.08 cm, bulb weight169.08 g, and days to maturity 168.37, total yield 32.94 ton ha-1

and marketable yield 25.07 ton ha-1. Plant height 61.24 cm, number of leaves per plant 10.96, stem

thickness 17.24 cm, bulb diameter 63.08 cm, bulb weight 149.31g, and days to maturity 167.89, total

yield 31.07 ton ha-1 and percent cull was maximum at early transplanting and decreased with delay in

transplanting. Cultivar Swat-1 produced maximum marketable yield 25.07 ton ha-1 than ‘Saryab Red’

and ‘Chiltan-89’. Marketable yield was highest at mid transplanting date (25th December); attributed to

less bolting compared to early transplanting. Unmarketable yield at early transplanting was largely due

to bolting while at late transplanting it was due to small ungraded bulbs.

INTRODUCTION

Onion is a biennial vegetable, and its growth and development is greatly affected by temperature and

photoperiod (Brewster, 1983, 1987; Rabinowitch, 1985). These environmental factors and their

interactions with genotype determine the performance of an onion cultivar (Brewster, 1994; Jilani &

Ghaffoor, 2003; Khan et al., 2001) and this interaction defines the selection of variety for the specific

area (Bosekeng and Coetzer, 2013).

52

Onion cultivars differ in their vernalization requirement for flower initiation. Cold temperatures between

5˚C - 13˚C for 20 to 120 days were optimum for flower induction in most cultivars. Yet, bolting resistant

cultivars needed comparatively longer (154 - 185 days) cold stimulus (Peters, 1990; Brewster, 1983;

Khokhar et al., 2007a; Khokhkar, 2008).

Onion differs in their flower initiation response to environmental condition because of differences in

genotypes (Khokhar, 2008; Brewster, 1987) and physiological age (Khokhar, 2008). Dong et al., (2013)

stated that onion seedling must be grown to certain age before they sense the cold temperature and start

vernalization process. Low temperature promotes flowering in onion only if they have passed the

juvenility stage (Rabinowitch, 1990; Khokhar et al., 2007a). Onion, depending on cultivars, initiate

flowering when have a minimum number of 7-10 leaves including leaf initial (Rabinowitch, 1990;

Khokhar et al., 2007a).

Bolting is premature seed stalk development (Voss et al., 1999) that decrease the marketability of onion

bulb (Cramer, 2003). Bolting cuts the storage potential and quality of the bulbs as whole of the energy

of the plant is exhausted and nothing is left in the bulbs to accumulate. Thus, bulbs become fibrous and

lightweight (Rana and Hore, 2015). Bolting in onion bulb crop is produced to low temperature (8-13

0C) when plants have grown enough to initiate bulbing. When seedlings are transplanted early, the onion

plants will grasp the sensitive size for bulbing when temperature is still low, the plants will bolt instead

of making bulbs. Agic et al., (2007) found that bolting was encouraged by early sowing while cultivars

differs in bolting tendency in their study. Cramer (2003) stated that late sowing reduced bolting

incidence, but plants are small yet when bulb formation begins causing small bulbs of a poor quality.

Sowing dates are, therefore, important factor that needs to be optimized to prevent bolting in onion.

Dong et al., (2013) reported significant effect of cultivar, sowing date and transplant location and their

interaction on the initiation and final rate of bolting in Welsh onion. Their results suggest that bolting

can be controlled in Welsh onion by choosing an appropriate cultivar, sowing date and transplant

location. Bolting resistance cultivars have less bolting percentage, less winter injury and high yield and

can be planted earlier (Cramer, 2003). The objective of this trial is to select an appropriate cultivar and

adjust the sowing date to prevent onion bulb crop from bolting and get high marketable yield.

MATERIALS & METHODS

Location

Field trial was conducted at Agricultural Research Institute, Mingora, Swat located in the Hindu

Kush range at 34.3- 35.53° North Latitude and 71.5-72.5° Longitude in the north of west of Pakistan.

Altitude of the site is 906 m above sea level. Climate is warm temperate. Temperature ranges from 25

53

to 35 oc. Average rainfall ranges from 740-1200mm. Soil is silt loam with pH ranges from 5-5.6.

Weather data of 2013-14 (Fig: 1) and 2014-15 (Fig: 2) have been recorded using Remote Automatic

Weather Station-Fire (RAWS-F) of Cambel Scientific. Detail of the physico-chemical properties

of the experimental soil is presented in Table 3.

Experiment Detail

The experiment was carried out in two growing seasons from November 2013 to June 2014 and from

November 2014 to June 2015. Nursery of onion varieties Swat-1, Saryab Red, and Chiltan- 89 were

sown on raised seedbed. First transplanting was done on November, 25 and the subsequent 4

transplanting were carried out at 15 days interval. Plot size was 1×3 m2 with four rows each 25 cm apart

having 30 plants per row. Thus, total numbers of plants in a unit plot were 120.

Layout and Treatment detail

Commercially grown three onion cultivars namely Swat-1, Saryab Red and Chiltan-89 were

transplanted on five different dates making 15 treatment combinations. These treatment combinations

were set in factorial RCB design with three replications.

Table 15: Treatment detail of the experiment.

S.No Cultivars Sowing/Planting Dates Treatments

1 Swat-1 25 the November T1

10 the December T2

25the December T3

10 the January T4

25 the January T5

2 Saryab Red 25 the November T6

10 the December T7

25the December T8

10 the January T9

25 the January T10

3 Chiltan-89 25 the November T11

10 the December T12

25the December T13

10 the January T14

25 the January T15

54

Experimental lay out

R

3

C3D

2

C1D

2

C2D

3

C1D

4

C3D

5

C2D

1

C3D

3

C1D

3

C2D

4

C2D

5

C3D

1

C1D

1

C2D

2

C3D

4

C1D

5

R

2

C3D

2

C2D

5

C3D

1

C3D

5

C1D

3

C3D

3

C1D

1

C1D

4

C1D

2

C3D

4

C1D

5

C2D

1

C2D

3

C2D

4

C2D

2

R

1

C2D

1

C3D

3

C2D

2

C3D

4

C3D

2

C2D

3

C2D

4

C3D

1

C1D

5

C3D

5

C1D

2

C1D

1

C1D

3

C2D

5

C1D

4

D = Transplanting Date C = Cultivar

Cultural Practices

Seeds of cultivars Swat-1, Saryab Red and Chiltan-89 were sown in manure mixed good tilth

soil on raised seed bed to develop nursery. It was sown on the same date in order to achieve the

size seedlings. Nursery of the same size and age was transplanted in already prepared

experimental plots. Soon after transplanting a pre-emergence weedicide pandymethaline was sprayed

to disallow the emergence of weed seeds. FYM, well decomposed @ of 15 tons per hectare was applied

during land preparation. Recommended dose of nitrogen, phosphorus and potash were applied based on

the soil analysis results. Bulbs were harvested when 80 % of the tops were down. Care was taken to

avoid bulb injuries. For detail see chapter 3 page 37-38.

Data Collection

Data was collected from 20 randomly selected plants from 2 central rows in each unit plot. The selected

plants were marked and used for all subsequent data parameters. Data on different parameters were

collected from transplanting of seedlings to the harvesting of bulbs to measure the effect of various

treatments on bolting and yield. For detail see chapter 3 page 38-39.




RESULTS & DISCUSSIONS

Plant Height (cm)

Data pertaining to plant height affected by transplanting dates and cultivars was presented in Table 17.

Both transplanting dates and cultivar significantly affected plant height at 5% level of probability. Year

as a source of variation was not significant (p<0.05). All the interaction for plant height were also non-

significant. Plant height showed a slight and steady decrease with delay in transplanting. Maximum

55

plant height of 61.24 cm was recorded in early transplanting on 25th November while minimum plant

height of 56.08 cm was recorded by almost two months late transplanting on 25th January. Sawant et

al., (2002) found that plant height and the number of leaves were significantly affected by sowing dates.

Kandil et al., (2013) found maximum plant height at 90 and 120 days from transplanting and total culls

were resulted from early transplanting date (15th November) in both seasons. The results of this study

also matched with the findings of Brewster (2008) who reported that earlier sown plants will have a

longer vegetative growth period and consequently have larger plants with more leaves.

Among the cultivars, Swat-1 produced maximum plant height of 65.58cm while Saryab Red and

Chiltan-89 attained plant height of 55.09 cm and 54.10 cm, respectively. Bosekeng and Coetzer (2013)

also found different plant height for different cultivars. Similar result has also been reported by Singh

and Bhonde (2011) from a trial evaluating 15 hybrids and a variety of onion in Maharashtra, India.

Table 17. Effect of on transplanting date and cultivars on plant height (cm) during the year 2014 and 2015.


Transplanting Dates

25 the November 60.33 a 62.16 a 61.24 a

10 the December 58.77 a 61.36 ab 60.06 a

25the December 55.20 b 59.99 bc 57.60 b

10 the January 53.98 b 58.59 c 56.29 b

25 the January 53.47 b 58.68 c 56.08 b

LSD(0.05) 2.74 1.60 1.41

Cultivars

Swat-1 63.97 a 67.18 a 65.58 a

Saryab Red 52.83 b 57.35 b 55.09 b

Chiltan-89 52.25 b 55.94 c 54.10 b

LSD 2.12 1.24 1.20

Year 56.35 60.16 58.25

Interactions

D × Cv ns ns ns

Year × D - - ns

Year × Cv - - ns

Year × D × Cv - - ns

56

Number of Leaves Plant-1

Mean data regarding number of leaves plant-1 influenced by transplanting dates and cultivars is shown

in Table 18. Transplanting dates and cultivars caused significant effect (p<0.05) on the number of leaves

plant-1.The influence of year was significant. Maximum number of leaves plant-1 10.96 were produced

by early transplanting on 25th November .A slight decrease in leaf number was recorded with each 15

days interval delay in transplanting and minimum number of leaves plant -1were noted in late

transplanting on 25th January. Sawant et al., (2002) found that plant height and the number of leaves

were significantly affected by sowing dates. Bijarniya et al., (2015) noted maximum number of leaves

(4.99, 8.74 and 10.90) 45, 75 and 90 DATP in 30th November transplanting. Early seeded yield more

leaves and taller plants (Cramer, 2003).

Table 16 Effect of on transplanting date and cultivars on number of leaves plant-1 in year 2014 and 2015.


Transplanting Dates

25 the November 10.53 a 11.39 a 10.96 a

10 the December 9.83 b 10.86 b 10.34 b

25the December 9.56 bc 10.33 c 9.94 c

10 the January 9.41 bc 9.86 d 9.63 c

25 the January 9.09 c 9.33 e 9.21 d

LSD(0.05) 0.55 0.42 0.34

Cultivars

Swat-1 10.22 a 11.06 a 10.64 a

Saryab Red 9.79 b 10.34 b 10.07 b

Chiltan-89 9.04 c 9.66 c 9.35 c

LSD 0.43 0.33 0.26

Year 9.68 b 10.35 a 10.02

Interactions

D × Cv ns ns ns

Year × D - - ns

Year × Cv - - ns


D = Transplanting dates Cv=Cultivar *-significant at P =0.05 ns- non- significant at P =0.05

Cultivar also varied significantly for number of leaves plant-1 and cultivar ‘Swat-1’ produced maximum

number of leaves plant-1 10.64 followed by ‘Saryab Red’ 10.07 and minimum number of leaves plant-1

9.35 were recorded in ‘Chiltan-89’. All the interaction for number of leaves plant-1 were non-significant.

57

Kandil et al., (2013) also found significant difference in number of leaves plant-1, at 90 and 120 day after

transplanting.

Stem Diameter (mm)

Statistical analysis of the data regarding stem thickness revealed significant differences for transplanting

dates and whereas years as source of variance and the different interactions were non-significant at 5%

level of probability (Table 19). Early transplanting produced plants with maximum stem diameter which

is gradually decrease with delay in transplanting. The maximum stem diameter of 17.24 mm was

recorded in 25th November transplantings and the minimum stem diameter of 14.42 mm was recorded

in late 25th January transplanting. Pandy et al., (1992) found that neck thickness problem was more in

early (June) sowing onion. Results of this study also in conformity with the finding of Boyhan et al.,

(2009) that early transplanting reduced the bulb quality by producing thick neck bulbs. Muhammad et

al., (2016) also reported that early transplanting resulted thick neck of bulbs.

Table 17: Effect of on transplanting dates and cultivars on stem diameter during the year 2014 and 2015.


Transplanting Dates

25 the November 16.97 a 17.52 a 17.24 a

10 the December 16.53 a 17.01 b 16.77 b

25the December 15.38 b 16.37 c 15.87 c

10 the January 14.68 c 15.39 d 15.04 d

25 the January 14.24 c 14.60 e 14.42 e

LSD(0.05) 0.56 0.43 0.34

Cultivars

Swat-1 15.06 b 15.81 b 15.43 b

Saryab Red 15.78 a 16.44 a 16.11 a

Chiltan-89 15.84 a 16.27 a 16.06 a

LSD 0.43 0.33 0.26

Year 15.56 16.18 15.87

Interactions

D × Cv ns ns ns

Year × D - - ns

Year × Cv - - ns



58

Among the cultivars, maximum stem diameter of 16.11mm was noted in ‘Saryab Red’ and minimum

stem diaameter of 15.43 mm was recorded in ‘Swat-1’. Stem thickness is important trait indicating the

storage prospect of an onion cultivar. Gautam et al., (2006) reported that thin neck varieties have longer

shelf life than thick neck varieties. According to Brewester (1997) the problem of thick stem arises

because of slow growth or short growing cycle. The result of this study is similar to the findings of

Mushtaq et al., (2013) who found significant difference in stem thickness in 19 onion cultivars.

Bulb Diameter (mm)

Data regarding bulb diameter as affected by transplanting dates and cultivars is depicted in Table 20.

Transplanting dates and cultivars significantly influenced (p < 0.05) bulb diameter while year as a source

of variation was not significant. The interactions of transplanting dates and cultivars (D×Cv) for bulb

diameter were significant while the remaining interactions were not significant Maximum bulb diameter

of 63.08 mm was recorded in early transplanting on 25th November and it reduced consistently with

Table 20: Effect of on transplanting dates and cultivars on bulb diameter during the year 2014 and 2015.


Transplanting Dates

25 the November 61.26 a 64.90 a 63.08 a

10 the December 55.51 b 59.86 b 57.69 b

25the December 48.72 c 51.47 c 50.10 c

10 the January 41.92 d 43.66 d 42.79 d

25 the January 35.33 e 37.69 e 36.51 e

LSD(0.05) 3.35 3.05 2.22

Cultivars

Swat-1 58.12 a 62.04 a 60.08 a

Saryab Red 45.95 b 48.60 b 47.27 b

Chiltan-89 41.58 c 43.90 c 42.74 c

LSD 2.59 2.37 1.71

Year 48.55 51.52 50.03

Interactions

D × Cv * * *

Year × D - - ns

Year × Cv - - ns



59

delay in transplanting. Minimum bulb diameter of 36.51 mm was noted in late 25th January

transplanting. Sawant et al., (2002) reported that early planting produced maximum polar and equatorial

diameter and hence, produced large size bulbs. According to Bosekeng and Coetzer (2013) bulb

diameter was significantly influenced by both cultivar and sowing date and earlier sown crop produced

the largest bulbs. According to Bijarniya et al., (2015) bulb diameter decreased with delay in

transplanting after 15th November. They recorded maximum bulb diameter from early transplanting i.e.,

15th November.

Among cultivars, maximum bulb diameter 60.08 mm was produced by cultivar ‘Swat-1’. ‘Saryab Red’

and ‘Chiltan 89’ produced bulb diameters of 47.27 mm and 42.74 mm respectively. According to

Bosekeng and Coetzer (2013) bulb size vary with different cultivars. Mushtaq et al., (2013) in trial

evaluating 19 onion varieties for yield and quality found significant difference in bulb diameter.

The interactions of D×Cv indicated that bulb diameter was maximum in early transplanting and ‘Swat-

1’ cultivars. Bulb diameter declined with delay in transplanting irrespective of the cultivars used in the

trial.

Figure 11: Interaction of transplanting dates and cultivars for bulb diameter (mm).

Bulb Weight (g)

Data concerning with bulb weight influenced by transplanting dates and cultivars is summarized in

Table 21. It is evident from the table that transplanting dates and cultivars produced significant effect in

bulb weight at 5% level of probability while the year’s effect was not significant. The interaction of

transplanting dates and cultivars (D×Cv) was significant (p < 0.05) while the rest of the interactions

were found non-significant. Maximum bulb weight 149.31g was produced by early 25th November

0

10

20

30

40

50

60

70

80

D1 D2 D3 D4 D5

Bu

lb D

iam

eter

(m

m)

Transplanting Dates

Swat-1 Saryab Red Chiltan 89

60

transplanting and the weight lessened steadily with each 15 days interval delay in transplanting.

Minimum bulb weight 80.98 g was recorded in very late transplanting on 25th January. Early

transplanting have more time for vegetative growth and produced more leaves and maximum plant

height. Abdissa et al., (2011) found strong and positive correlation of mean bulb weight with plant

height, number of leaves, bulb length and diameter. Plants with more vegetative growth translocated

more photosynthate towards bulb formation. This resultantly produced bigger bulbs than late

transplanting. Bosekeng and Coetzer (2013) reported that late sowing significantly decreased average

bulb fresh mass while early sown plant produced the largest bulbs.

Cultivars also caused significant difference in bulb weight. Cultivar ‘Swat-1’ produced heaviest bulbs

169.08 g compared to ‘Saryab Red’ 100.14 g and ‘Chiltan-89’ 82.35g.

Table 28: Effect of transplanting date and cultivars on bulb Weight (g) dduring the year 2014 and 2015.


Transplanting Dates

25 the November 146.23 a 152.39 a 149.31 a

10 the December 132.63 b 138.38 b 135.50 b

25the December 117.66 c 122.46 c 120.06 c

10 the January 97.51 d 102.68 d 100.09 d

25 the January 79.71 e 82.26 e 80.98 e

LSD(0.05) 9.34 8.44 6.15

Cultivars

Swat-1 166.72 a 171.44 a 169.08 a

Saryab Red 97.69 b 102.59 b 100.14 b

Chiltan-89 79.83 c 84.87 c 82.35 c

LSD 7.24 6.53 4.77

Year 114.75 a 119.63 a 117.19

Interactions

D × Cv * * *

Year × D - - ns

Year × Cv - - ns



The D×Cv interaction showed significant effect (p<0.05) on bulb weight. Bulb weight was maximum

at early transplanting in Swat-1 cultivar and constantly decreased with delay in transplanting. This trend

61

was more prominent in cultivar ‘Swat-1’ than ‘Saryab Red’ and ‘Chiltan-89’. Similar results were

reported by Mushtaq et al., (2013)

who stated that bulb weight is an important yield parameter and found it significant in different cultivars.

Kimani et al., (1993) evaluated 9 onion cultivars in different environment in Kenya and found that bulb

weight differs among cultivar and in different environment.

Figure 11: Interaction of transplanting dates and cultivars for bulb weight (g)

Days to Bolting initiation

Information about days to bolting initiation as influenced by transplanting dates and cultivars is

presented in Table 22. Transplanting dates and cultivars significantly affected days to bolting initiation.

Year as a source of variation was non-significant at 5% level of probability. Early transplanting took

less 108.06 days to bolting initiation which gradually increased with delay in transplanting and 25th

December transplanting took 117.28 days to bolting initiation. Bolting has not been initiated in late 10th

and 25th January transplantings. According to Cramer (2003) bolting in onion bulb crop is produced in

response to low temperature (8-13 0C) when plants have grown enough to start bulbing. The sensitivity

to cold temperature increases with increase in plant age. Khokhar et al (2007a) reported that the number

of leaves has been used to determine the critical plant size at which bolting occur when expose to low

temperature. They found that 7-10 leaves stage is sensitive plant size (at which onion plant become

responsive to cold temperature). When seedlings are transplanted early, plants will reach the sensitive

size for bulbing when temperature is still low, plants initiate bolting instead bulbing. Thus early

transplanting will take less day to bolting initiation compared to late transplants.

21

9.5

20

2.6

6

17

8.8

3

14

1.7

5

12

6.3

6

11

1.9

5

10

2.6

6

10

2.0

7

10

0.9

3

91

.9

86

.03

80

.41

75

.45

72

.51

64

.84

0

50

100

150

200

250

D1 D2 D3 D4 D1 D2 D5 D1 D3 D2 D4 D3 D5 D4 D5

Swat-1 Swat-1 Swat-1 Swat-1 Saryab

Red

Saryab

Red

Swat-1 Chiltan-

89

Saryab

Red

Chiltan-

89

Saryab

Red

Chiltan-

89

Saryab

Red

Chiltan-

89

Chiltan-

89

Bulb

Wei

ght

(g)

Transplanting dates & Cultivars

62

Table 22: Effect of on transplanting date and cultivars on days to bolting initiation during year 2014 and

2015.


Transplanting Dates

25 the November 105.22 b 111.67 c 108.06 c

10 the December 108.56 b 116.56 b 112.22 b

25the December 113.56 a 121.00 a 117.28 a

10 the January 0.00 0.00 0.00

25 the January 0.00 0.00 0.00

LSD(0.05) 3.72 2.74 2.07

Cultivars

Swat-1 76.67 a 81.27 a 78.67 a

Saryab Red 56.80 c 60.60 c 58.47 c

Chiltan-89 63.53 b 67.67 b 65.40 b

LSD 2.88 2.12 1.60

Year 65.18 69.84 67.51

Interactions

D × Cv * * *

Year × D - - *

Year × Cv - - ns

Year × D × Cv - - *


Cultivars also varied for days to bolting initiation. Cultivar ‘Swat-1’ took maximum days 78.67 to

inflorescence initiation and ‘Saryab Red’ and ‘Chiltan-89’ took 58.47 and 65.40 days respectively. The

results indicate that all the three cultivars are prone to bolting, cultivar ‘Swat-1’ is a little better among

them. The mechanism of bolting is not understood (Cramer, 2003). There isn’t complete bolting

resistance variety in the world. As such variety will not flower even at normal condition and cannot be

propagated. According to Cramer, (2003) the resistance to bolting is additive as bolting resistant

varieties have been developed from bolting susceptible germplasms in bolting inducing environment

through phenotypic recurrent selection. According to Cramer, (2003) bolting resistant cultivar may

require either large plant size or longer cold period for bolting.

63

Figure 12: Interaction of transplanting dates and cultivars for days to bolting initiation.

Interaction of D×Cv, Y×D and Y×D × Cv were significant and that of Y×Cv was not

significant(p<0.05). Interaction of D× Cv indicated that early transplanting took less days to bolting

initiation and number of days increased as transplanting delayed. Cultivar ‘Swat-1’ took more days to

bolting initiation compared to ‘Saryab Red’ and ‘Chiltan-89’. Bolting has not been initiated in late 10th

and 25th January transplanting irrespective of the cultivar.

Figure 13: Mean data on interaction of transplanting dates and year for days to bolting initiation.

From the interaction of Y×D it is evident that early transplanting took less days to premature seed stalk

development in both the years compared to late 10th and 25th December transplanting (D2 and D3). As

year 2 was warmer than year 1, number of days to bolting initiation were more in year 2 compared to

year 1. Bolting was not initiated in late transplanting on 10th and 25th January in either year.

0

20

40

60

80

100

120

140

160

D1 D2 D3 D4 D5

Day

s to

bo

ltin

g in

itia

tio

n

Transplanting dates

Swat-1 Saryab Red Chiltan-89

12

1

11

6.5

6

11

3.5

6

11

1.6

7

10

7.8

9

10

4.4

4

0.0

0.0

0.0

0.0

-40

-20

0

20

40

60

80

100

120

140

160

D3 D2 D3 D1 D2 D1 D4 D5 D4 D5

Y2 Y2 Y1 Y2 Y1 Y1 Y1 Y2 Y2 Y2

Day

s to

bo

ltin

g i

nit

iati

on

Transplanting dates & growing seasons

64

Bolting Percentage

Bolting is a physiological disorder in which floral stalk developed in onion plants intended for bulbs

production. It lower the marketability of bulbs as the whole energy of the plant is exhausted and nothing

is left in to accumulate in the bulbs. This make the bulbs fibrous and lightweight.

Data pertaining to bolting percentage affected by transplanting dates and cultivars is presented in Table

23. Both transplanting dates and cultivars made significant difference in bolting percentage while year

as a source of variation remained non-significant at 5% level of probability. The interaction of

transplanting dates and cultivars (D× Cv), year and transplanting dates (Y×D) were significant and the

rest of the interactions were not significant.

Bolting was maximum 34.52% in early in 25th December transplanting and decline steadily with delay

in transplanting. Bolting has not been recorded in late 10th and 25th January transplanting. These results

are in agreement with the findings of Madisa (1994) who reported onion plants sown late did not bolt

because when low temperatures responsible for bolting prevailed, the plants were still small and had not

yet reached minimum plant size. Tendaj and Mysiak (2013) recorded maximum seed stalk development

in early transplanting irrespective of the cultivars in the trial. Earlier transplanting seedlings clench the

critical stage for bulbing sooner when low temperature still prevails and initiate inflorescence instead of

bulb formation. Late transplanting plants will be at juvenile stage when the temperature are low late in

the season. Flowering cannot be induced by vernalization in juvenility stage. Hence, bolting will not

occur in late transplants.

Among the cultivars 17.32% plants developed premature seed stalk in ‘Chiltan-89’ while 13.75 % and

12.51% initiated premature inflorescence development in ‘Saryab Red’ and ‘Swat-1’ respectively.

Brewster and Salter, (1980) reported that cultivars varied evidently in their susceptibility to bolting.

Mushtaq et al (2013) reported that onion cultivars differs in yield and yield related traits and bolting in

specific agro- conditions. Among the nineteen evaluated onion varieties high bolting percentage

(46.67%) was found in Desi Red, while it was the lowest in Faisal Red and VRIO-6 (13.33%).It is

difficult to give the exact date for transplanting to reduce bolting and increase yield at the same time as

it is cultivar and environment dependent. Bolting resistant cultivar have less bolting incidence and can

be seeded/transplanted earlier (Cramer, 2003).

65

Table 23: Effect of transplanting date and cultivars on bolting percentage during 2014 and 2015.


Transplanting Dates

25 the November 36.67 a 32.37 a 34.52 a

10 the December 22.46 b 24.21 b 23.33 b

25the December 15.68 c 13.87 c 14.77 c

10 the January 0.00 d 0.00 d 0.00 d

25 the January 0.00 d 0.00 d 0.00 d

LSD(0.05) 2.96 2.67 1.95

Cultivars

Swat-1 12.90 b 12.12 b 12.51 b

Saryab Red 14.25 b 13.24 b 13.75 b

Chiltan-89 17.73 a 16.91 a 17.32 a

LSD 2.29 2.07 1.51

Year 14.96 14.09 14.53

Interactions

D × Cv * * *

Year × D - - *

Year × Cv - - ns



Flowering is essential for crop production if grown for fruit or seed purpose. The transition from

vegetative to reproductive growth is a key developmental change in flowering plants. Blumel et al,

(2015). Onion initiate floral stalk development after the juvenile phase when receive flower inductive

low temperature. Khokhar et al (2007a) reported that onion plants switch from vegetative phase to

reproductive phase when grown 7-10 leaf stage. Thus, earlier transplants in the season reached

reproductive stage and are more susceptible to bolting when temperature drops latter in the season. The

bolting tendency also varies with cultivars. To our knowledge there is no complete bolting resistance

cultivar.

66

Figure 14: Mean data on interaction of transplanting, dates and cultivars for bolting percentage.

According to Cramer, (2003) the mechanism of bolting resistance is not known. Bolting resistance is

highly additive as it is developed from bolting susceptible germplasms in bolting favorable environment

through phenotypic recurrent selection. According to Cramer, (2003) many theories may explained the

phenomenon of bolting. Bolting resistant cultivars may require more chilling hours than bolting

susceptible cultivars. Bolting resistant cultivars may require larger plant size than bolting susceptible

cultivar to become receptive to cold stimulus. Likewise, bolting resistant plant may be slow in growth

during initial period of low temperature and thus not receptive to cold stimulus.

Figure 15: Mean data on interaction of transplanting, dates and year for bolting percentage.

The interaction of D× Cv indicated that bolting percentage was maximum in early transplanting and

decreased gradually as transplanting was delayed from November 25-December 25 (D1 to D3 ). Bolting

has not been recorded in late 10th and 25th January transplanting regardless of the cultivar. The interaction

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

D1 D2 D3 D4 D5

Bo

ltin

g P

erce

nta

ge

Transplanting Dates


0

5

10

15

20

25

30

35

40

D1 D2 D3 D4 D5

Bo

ltin

g P

erce

nta

ge

Transplanting Dates

Year 1 Year 2

67

of Y×D showed that delaying transplanting from D1 to D3 decrease bolting percentage from 36.67% to

13.87%. Premature bolting has not been noted in late 10th and 25th January transplanting in both years.


Data about days to harvesting affected by transplanting dates and cultivars is given in Table

24.Transplanting dates and cultivars caused significant difference in days to harvesting. Year as a source

of variation was also found significant at 5% level of probability. Interactions for days to maturity were

not significant. Maximum 167.89 days to harvesting were taken by early 25th November transplanting

and days to harvesting decreased with delay in transplanting. Late transplanting on 25th January took

minimum days 158.28 to harvesting. Bulbs normally start to

Table 24: Effect of on transplanting date and cultivars on days to maturity during the year 2014 and 2015.


Transplanting Dates

25 the November 165.67 a 170.11 a 167.89 a

10 the December 164.22 a 168.33 a 166.28 b

25the December 160.00 b 164.56 b 162.29 c

10 the January 156.56 c 161.53 c 159.06 d

25 the January 155.33 c 161.22 c 158.28 d

LSD(0.05) 3.21 2.21 1.07

Cultivars

Swat-1 166.60 a 170.13 a 168.37 a

Saryab Red 160.47 b 165.53 b 163.00 b

Chiltan-89 154.00 c 159.80 c 156.90 c

LSD 2.49 1.72 0.94

Year 160.36 b 165.16 a 163.00

Interactions

D × Cv ns ns ns

Year × D - - ns

Year × Cv - - ns



Cultivar ‘Swat-1’ took maximum 168.37 day to harvesting and ‘Saryab Red’ and ‘Chiltan-89’ took

163.00 and 156.90 day to harvesting in this order. Kimani et al, (1993) evaluated 9 onion cultivars in

Kyneya and found mature when the required minimum day length and temperature of the specific

cultivar is met. Hence the same cultivar sown on different dates or having varying seedling ages will

68

start to mature more or less at the same time. Thus late transplanting tookk less days to maturity than

early transplanting. Similar results have reported by Sawant et al., (2002) that early transplanting had

taken the longest duration (137 days) to maturity than late planting.significant difference in days to

Maturity. Minimum days (144.6-202.0) to maturity was taken by “KON 4” while maximum days

(159.2-215.4).took by “KON 8”. Temperature and photoperiod essentially control the growth and

development in onion. The interaction of these environmental factors with genotype decide the

performance of an onion cultivar (Brewster, 1994; Jilani & Ghaffoor, 2003; Khan et al., 2001). This is

the reason that different genotypes perform differently in the same environment.

Total Yield (ton ha-1)

Data relating to total yield ton ha-1 affected by transplanting dates and cultivars is summarized in Table

25. Transplanting dates and cultivars shaped significantly total yield tonha-1. Year as a source of variance

remained non-significant. All the interaction were non-significant (p<0.05) except D × Cv. Early

Table 25: Effect of on transplanting date and cultivars on total yield (ton ha-1) during year 2014 and 2015.


Transplanting Dates

25 the November 29.44 a 32.71 a 31.07 a

10 the December 27.97 a 31.49 a 29.73 a

25the December 24.67 b 27.09 b 25.88 b

10 the January 21.33 c 23.21 c 22.27 c

25 the January 19.68 c 18.78 d 20.00 d

LSD(0.05) 2.90 2.17 1.54

Cultivars

Swat-1 32.19 a 33.70 a 32.94 a

Saryab Red 22.73 b 25.21 b 23.97 b

Chiltan-89 18.94 c 21.06 c 22.09 c

LSD 2.24 1.68 1.19

Year 24.62 a 26.65 a 26.39

Interactions

D × Cv ns ns *

Year × D - - ns

Year × Cv - - ns



69

transplanting on 25th November produced maximum yield 31.07 ton ha-1 and the yield showed a decline

trend with delay in transplanting and late transplanting on 25th January produced minimum yield 20.00

ton ha-1. A total 60 days delay in transplanting caused reduction in yield from 31.07 to 20.00 ton ha-1

amounting to 11.07 ton ha-1. From this it can be concluded that each 10 day delay in transplanting caused

1.85 ton ha-1 reduction in yield. Ample vegetative growth before bulb formation is essential to get high

yield (Ibrahim, 2010). Bulb formation starts when temperature and day length requirement is fulfilled.

Though when a variety is sown on different dates yet, bulbing will starts more or less at the same time.

Hence, early transplants will have more vegetative growth and high yield. The results of Patil et al.,

(2012) showed that early transplanting (15th November) of onion significantly produced high yield.

Figure 16: Mean data on interaction of transplanting dates and cultivars for yield ton ha-1.

Among the cultivars ‘Swat-1’ produced total yield of 32.94 ton ha-1while ‘Saryab Red’ and ‘Chiltan-

89’ yielded 23.97 and 22.09 tonha-1respectively. Lancaster et al, (1995) evaluating 32 onion varieties

for commercial production in New Zealand found significant difference in yield. The interaction of D ×

Cv revealed a descending trend in yield ton ha-1 with delay in transplanting from November 25-January

25 (D1 to D5 ) in all the three cultivars.

Marketable (Yield ton ha-1)

Data concerning marketable yield ton ha-1affected by transplanting dates and cultivar is presented in

Table 26. Transplanting dates and cultivar produced significant effect (p<0.05) on marketable yield

tonha-1. Year as a source of variation was also significant. Interaction of D × Cv was significant and the

remaining interactions were not significant. Maximum marketable yield 23.45 ton ha-1was recorded in

mid transplanting on 25th December. While the marketable yield of 10th December and 10th January

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

D1 D2 D3 D4 D5

Yiel

d t

on

ha-1

Transplanting Dates


70

transplantings was statistically at par. Very early and very late transplanting produce less marketable

yield of 17.23 and 15.42 ton ha-1 respectively. In very early transplanting 34.52 % plants went to

premature bolting and become unmarketable and were discarded. In very late transplanting small

ungraded bulbs contributed to cull. The result of this study are in conformity with findings of Bijarniya

et al., (2015) and Ibrahim (2010) who reported maximum marketable yield from mid transplanting

dates.

Among the cultivars ‘Swat-1’ produced maximum marketable yield of 25.07 ton ha-1 ‘Saryab Red’ and

‘Chiltan-89’ produced 19.09 and 14.38 ton ha-1 marketable yield. Baliyan (2014) in a trial evaluated six

onion varieties and found that Texas Grano produced the highest total yield of 54.07 ton ha-1, however,

Hanna variety produced the highest marketable yield of 43.01 ton ha-1. Texas Grano produced the lowest

marketable (60%) in Botswana. Cramer (2003) in a five year varietal trial found that marketable yield

ranged from 61-82%. In current study cultivar ‘Swat-1’ produced the highest total and marketable yield

32.94 and 25.07 ton ha-1 respectively.

Table 26: Effect of on transplanting dates and cultivars on marketable yield (ton ha-1) during the year

2014 and 2015.


Transplanting Dates

25 the November 16.73 c 17.72 c 17.23 c

10 the December 19.88 b 22.53 ab 21.21 b

25the December 22.62 a 24.27 a 23.45 a

10 the January 18.56 b 21.97 b 20.27 b

25 the January 14.27 d 16.58 c 15.42 d

LSD(0.05) 1.56 1.98 1.19

Cultivars

Swat-1 24.16 a 25.98 a 25.07 a

Saryab Red 17.96 b 20.22 b 19.09 b

Chiltan-89 13.12 c 15.64 c 14.38 c

LSD 1.21 1.53 0.92

Year 18.41 b 20.61 a 19.51

Interactions

D × Cv * * *

Year × D - - ns

Year × Cv - - ns



71

The interaction of Transplanting dates and cultivars (D× Cv) revealed that marketable yield was

maximum in cultivar “Swat -1” at mid transplanting date. In very early and late transplantin produced

less marketable yiels ton ha-1 Less marketable yield in early transplanting was due to high percentage of

bolting while in late transplantings it was due to small ungraded bulbs

Figure 17: Mean data on interaction of transplanting dates and cultivars for marketable yield (ton ha-1).

Summary conclusios and recommendations

Summary

Three commercial cultivars ‘Swat-1’, ‘Saryab Red’ and ‘Chiltan-89’ were transplanted on five different

dates (25th November, 10th December, 25th December, 10th January and 25th January). Apparently none

of the cultivars showed resistance to bolting however, they varied in their susceptibility to bolting.

Cultivar Swat-1 took significantly maximum 78.67 days to bolting initiation and recorded minimum

bolting percentage 12.51 compared to ‘Saryab Red’13.75 and ‘Chiltan-89’ 17.32. Early transplanting

took less 108.06 days to bolting initiation. Bolting percentage was maximum 34.52 at early transplanting

and reduced with delay in transplanting from 25th November to 25th December. In all cultivars bolting

has not been recorded at late, (10th and 25th January) transplanting irrespective of the cultivar. Compare

to ‘Saryab Red’ and ‘Chiltan-89’, ‘Swat-1’ has maximum plant height 65.58 cm, number of leaves per

plant 10.64, stem thickness 15.43 mm, bulb diameter 60.08 cm, bulb weight 169.08 g, and days to

maturity 168.37, total yield 32.94 ton ha-1 and marketable yield 25.07 ton ha-1. Plant height 61.24 cm,

number of leaves per plant 10.96, stem diameter 17.24 cm, bulb diameter 63.08 cm, bulb weight

149.31g, and days to maturity 167.89, total yield 31.07 ton ha-1 were maximum at early transplanting

and decreased with delay in transplanting. Cultivar Swat-1 produced maximum marketable yield 25.07

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

D1 D2 D3 D4 D5 Mean

Mar

keta

ble

yie

ld t

on

ha-1

Transplanting dates

Swat-1 Saryab Red Chiltan-89 Mean

72

ton ha-1 than ‘Saryab Red’ and ‘Chiltan-89’. Marketable yield was maximum at mid transplanting date

(25th December); attributed to less bolting and percent cull compared to early transplanting.

Unmarketable yield at early transplanting was largely due to bolting while at late transplanting it was

due to small ungraded bulbs.

Conclusions

Cultivar Swat-1 took significantly maximum days to bolting initiation and had minimum bolting

percentage compared to Saryab Red and Chiltan-89. Early transplanting took less days to bolting

initiation. Bolting percentage was maximum at early transplanting and reduced with delay in

transplanting from 25th November to 25thDecember in all cultivars. Bolting was not recorded in late

transplanting (10th and 25th January) irrespective of the cultivar. Compared to Saryab Red and Chiltan-

89, Cultivars Swat-1 produced maximum marketable yield ton ha-1. Marketable yield was maximum at

mid transplanting date (25th December) attributed to less bolting and percent cull compared to early

transplanting. Unmarketable yield at early transplanting was largely contributed by bolting while at late

transplanting it was due to small ungraded bulbs.

Recommendations

1. Transplanting should be done from December 15 to January 15 since it produced low bolting

percentage and maximum marketable yield. Very early transplanting increased bolting and very

late transplanting produced small bulbs and low yield.

2. Bolting resistant variety should be used. Though, there is no bolting resistant variety in Pakistan

‘Swat-1’ has comparatively less bolting incidence among the existing cultivars. Research work

should be initiated to develop bolting resistant variety or produce bolting resistance in existing

cultivars though phenotypic recurrent selection.

73

Chapter 5

EXPERIMENT 3: EFFECT OF TRANSPLANTING DATES AND NITROGEN

FERTILIZER ON FLOWERING INITIATION IN ONION BULB CROP.

ABSTRACT

By

Noor Habib Khan

Department of Agricultural Sciences (Horticulture) University of Haripur

April 2017

Trials were conducted in two consecutive growing seasons from 2013-14 and 2014-15 at Agricultural

Research Institute, Mingora Swat 906 m above sea level. Experiment was planned in RCB design in a

plot size of 2.5 × 0.8 m2 with 5 rows and 25 plants per row. Rows were 20 cm apart and plants were

spaced 10 cm within a row. Different doses of nitrogen fertilizer (75, 100, 125 and 150 kg ha-1)

were applied to onion crop transplanted on five different dates (15th November, 1st December, 15th

December, 1st January and 15th January) with the objective to determine its influence on

inflorescence development in onion bulb crop. Bolting percentage decreased gradually with

increase in the rate of nitrogen fertilizer. Maximum bolting percentage was recorded in early

transplanting and declined with delay in transplanting. Bolting incidence did not occurred in

very late transplanting (15th January) irrespective of the rate of nitrogen applied. Plant height,

stem thickness, bulb diameter, bulb weight and total yield increased with increase in nitrogen

fertilizer and conversely showed a downward trend with delay in transplanting. Different doses

of nitrogen fertilizer didn’t significantly influenced leaves per plant. Early transplanting took

maximum days to maturity than late transplanting. Maturity was delayed with increase in

nitrogen fertilizer. Percent cull decreased with increase in the rate of nitrogen fertilizer.

Marketable yield was maximum at mid transplanting (15th December) and with maximum dose

of nitrogen fertilizer. It can be concluded that 150 Kg N ha-1 should be applied and transplanting

should be delayed up to December 15th to avoid bolting and have maximum marketable yield.

INTRODUCTION

Bolting is the premature seed stem development in some vegetables that reduces storage life

and marketability of the produce (Rana and Hore, 2015). Inflorescence initiated in onion after

74

plants have grown and developed to certain number of leaves, depending on cultivar, followed

by exposure to low vernalizing temperature ( Diaz-Perez, 2003, Dong et al, 2013).

Vernalization in onion has been of research interest because of the need to prevent bulbs from bolting

in the first growing season and to enhance flowering in second growing season (Streck, 2003, Dong et

al, 2013). In tropical regions onion plants neither flower nor produce seed due to lack of cold

temperature (Kimani et al., 1994). This is the reason that many countries in the tropics import onion

seed from sub tropic or temperate countries where winter provide vernalization temperature for

flowering and seed production (Khokhar, 2014). The response of plant to vernalization depends on the

combination of two factors, the temperature during vernalization and duration of vernalization period

(Streck, 2003).

Optimal day length and vernalization is not enough to induce flowering. Plants should be old enough to

sense and respond to these environmental stimuli. Some perennial plants flower readily when exposed

to environmental condition that enhance flowering such as photoperiod and vernalization. While others

including onion cannot flower until pass the juvenile stage and grown to a certain age or size.

(Rabinowitch, 1990; Khokhar et al., 2007a). Leaf number rather than chronological time is the best sign

of the plant’s physiological age (Rabinowitch, 1990). Depending on cultivars, onion plant initiates

flowering when have a minimum number of 7-10 leaves including leaf initial (Rabinowitch, 1990;

Khokhar et al., 2007a).

Other factors affecting bolting in onion are nitrogen and phosphorous (Brewester, 1983). Rabinowitch

(1990) termed onion as nitro-neutral plant whose flowering time is unaffected by nitrogen. A few

studies, however, indicates that nitrogen affect the flowering process in onion (Brewester, 1983).

Brewester (1983) found that low nitrogen in nutrient solution speeded up flowering. According to the

findings of Yamasaki and Tanaka, (2005) Bolting in bunching onion (Allium fistulosum L.) enhanced

by low nitrogen following exposure to low temperature for a period of 35 days. Diaz-Perez et al. (2003)

suggested that low nitrogen fertilizer application increased bolting and reported that bolting incidence

decrease steadily with increase nitrogen fertilization rates up to 197 kg ha-1. This trial was aimed to

investigate the effect of transplanting dates and nitrogen fertilizer on premature bolting in onion.

MATERIALS & METHODS

Location

Field trials were conducted at Agricultural Research Institute, Mingora, Swat located in the Hindu

Kush range at 34.3- 35.53° North Latitude and 71.5-72.5° Longitude in the north of west of Pakistan.

75

Altitude of the site is 906 m above sea level. Climate is warm temperate. Temperature ranges from 25

to 35 oc. Average rainfall ranges from 740-1200 mm. Soil is silt loam with pH ranges from 5-5.6.

Weather data of 2013-14 (Fig: 1) and 2014-15 (Fig: 2) have been recorded using Remote Automatic

Weather Station-Fire (RAWS-F) of Cambel Scientific. Detail of the physico-chemical properties

of the experimental soil is presented in Table 3.

Experiment Detail

The experiments cited above were carried out in two consecutive years from November 2013 to June

2014 and from November 2014 to June 2015. Nursery of onion cultivar “Swat-1”, was sown on different

dates in a raised seedbed. Seedling of the same size and age were transplanted on five different dates.

Plot size was kept 2.5×0.8 m2 with five rows and 25 plants per row. Row to row distance was 20 cm and

plants were spaced 10 cm within a row.

Table 27: Treatment details.

S. No Sowing/Planting Dates Nitrogen Levels Treatments

1 15th November L1 =75 kg/ha T1

L2=100 Kg/ha T2

L3=125 kg/ha T3

L4=150 kg/ha T4

2 30th December L1 =75 kg/ha T5

L2=100 Kg/ha T6

L3=125 kg/ha T7

L4=150 kg/ha T8

3 15th December L1 =75 kg/ha T9

L2=100 Kg/ha T10

L3=125 kg/ha T11

L4=150 kg/ha T12

4 1st January L1 =75 kg/ha T13

L2=100 Kg/ha T14

L3=125 kg/ha T15

L4=150 kg/ha T16

5 15th January L1 =75 kg/ha T17

L2=100 Kg/ha T18

L3=125 kg/ha T19

L4=150 kg/ha T20

76

Experimental Lay out

R3

D3L

4

D1L

3

D2L

1

D2L

4

D4L

3

D2L

3

D5L

1

D4L

4

D5l

2

D1L

1

D4L

1

D5L

3

D4L

2

D3L

2

D1L

2

D2L

2

D5L

4

D1L

4

D3L

1

D3L

3

R2

D5L

3

D5l

2

D4L

2

D3L

2

D2L

2

D3L

4

D5L

4

D1L

4

D1L

2

D2L

1

D3L

3

D2L

3

D4L

3

D3L

1

D4L

4

D5L

1

D1L

3

D1L

1

D4L

1

D2L

4

R1

D4L

4

D2L

3

D5L

1

D1L

1

D4L

1

D3L

3

D5L

3

D5L

4

D4L

2

D3L

2

D2L

2

D2L

4

D1L

4

D3L

4

D2L

1

D5l

2

D3L

1

D1L

2

D4L

3

D1L

3

D = Transplanting dates L= Level of Nitrogen

Layout and Treatment detail

The experiment was planned in RCB Design with factorial arrangement. Cultivar Swat-1 planted on

five different dates and four levels of nitrogen fertilizer were applied. Thus, making total treatment

combinations 20 which were repeated 3 times.

Treatments: 1. Transplanting Dates=5, 2. Nitrogen Level=4, 3. Cultivar=1 (Swat-1)

Cultural Practices

Nursery of cultivars Swat-1, was sown in good tilth soil on raised seed bed on five different

dates to get uniform size and age of seedling transplanting. Nursery of the same size and age

was transplanted in already prepared experimental plots. Soon after transplanting a pre-emergence

weedicide pandymethaline was sprayed to disallow the emergence of weed seeds. FYM, well

decomposed @ of 15 tons per hectare, phosphorus @ 90 kg ha-1 and potash @ 60 Kg ha-1 was applied

during land preparation. Four levels of nitrogen fertilizer 75, 100, 125 and 150 kg ha-1 were applied in

three split doses. Bulbs were harvested when 80 % of the tops were down. Care was taken to avoid bulb

injuries. For detail see chapter 3 page 37-38.

Data Collection

Data was collected from 20 randomly selected plants from 2 central rows in each unit plot. The selected

plants were marked and used for all subsequent data parameters. Data on different parameters were

collected from transplanting of seedlings to the harvesting of bulbs to measure the effect of various

treatments on bolting and yield. For detail see chapter 3 page 38-39.




77

RESULTS & DISCUSSIONS

Plant Height (cm)

Data regarding plant height in 2014 and 2015 and its mean (Table 28) showed that transplanting dates

and nitrogen level significantly (p < 0.05) affected plant height in both years. Year as source of variation

was also found significant. All the interaction were non-significant for plant height. Maximum plant

height of 61.08 cm was recorded when transplanting was done on 15th November. Plant height

decreased when transplanting was delayed and minimum plant height of 57.49 cm were produced in

15th January transplanting. Bulbing started when temperature begin to increase and the required

minimum day length of the specific cultivar is met. Thus when same variety is sown at different times

at the same locality bulbing will start more or less at the same time. Earlier sown plants, therefore, will

have longer vegetative growth, larger plants with more leaves as compared to late sown plants

(Brewster, 2008).

Table 28: Effect of on transplanting date and cultivars on plant height (cm) during the year 2014 and 2015.


Transplanting Date

15th November 58.76 a 63.40 a 61.08 a

30th December 58.15 a 62.04 ab 61.1 b

15th December 56.96 ab 61.38 abc 59.17 bc

1st January 56.06 b 61.06 bc 58.56 c

15th January 55.31 b 59.67 c 57.49 d

LSD(0.05) 1.99 2.13 0.96

Nitrogen Levels

75 kg ha-1 55.32 c 60.16 b 57.74 c

100 kg ha-1 56.38 bc 60.44 b 58.41 c

125 kg ha-1 57.84 ab 61.86 ab 59.85 b

150 kg ha-1 58.65 a 63.57 a 61.11 a

LSD(0.05) 1.78 1.90 0.85

Year 57.04 b 61.51 a 59.26

Interactions

D × N ns ns ns

Year × D - - ns

Year × N - - ns

Year × D × N - - ns

D = Transplanting dates N=Nitrogen levels *-significant at P =0.05 ns- non- significant at P =0.05

78

Likewise, minimum plant height of 57.74 cm was recorded when nitrogen was applied at the rate of 75

Kg ha-1 and was found to increase with increases in nitrogen level. Maximum plant height was noted in

above optimal nitrogen of 150 kg ha-1 application treatment. These results are in conformity with the

finding of Vachhani and Patel (1993) that plant height, number of leavesplant-1, bulb weight, size and

onion yield were maximum with the application of 150 kg N ha-1 while Pandey and Ekpo (1991)

reported that application rate of 160 kg N ha-1 produced maximum plant height of 63.9 cm. Abdissa et

al, (2011) stated that increase in height could be attributed

to its involvement in the synthesis of amino acids, as they link together and form proteins and make up

metabolic processes needed for plant growth.

The correlation coefficient Table 37 revealed that plant height has significant positive correlation with

number of leaves per plant (0.158), bulb diameter (0.310), bulb weight (0.316) non-significant but

positive correlation with bolting percentage (0.064), Stem thickness (0.116), total yield ton/ha (0.054)

and marketable yield (0.089) while its interaction with percent cull was non-significant and negative (-

0.140). Sharma et al (2015) found positive association of plant height with number of leaves/plant, bulb

diameter, bulb weight and total yield ton ha-1.

Number of Leaves Plant-1

Data pertaining to number of leaves per plant in 2014 and 2015 and its mean has been summarized in

Table 29. Different transplanting dates and nitrogen level significantly (p < 0.05) influenced number of

leaves per plant. Year effect on number of leaves per plant was found non-significant. Maximum

number of leaves per plant of 12.46 were recorded in 15th November transplanting and minimum

number of leaves per plant of 10.05 were produced when transplanting was delayed for about two

months on 15thJanuary. Cramer (2003) observed that earlier sowing produced larger plants with more

leaves compared to later seeding in a growing season. Sawant et al., (2002) found that plant height and

the number of leaves have significantly affected by sowing dates. On the other hand, Bosekeng and

Coetzer (2013) stated that sowing date did not influence plant height and leaf number significantly over

a period of two years, however, early sowing dates in one year resulted in maximum plant height.

Similarly, minimum number of leaves per plant were noted when nitrogen was applied at the rate of 75

Kg ha-1 and maximum number of leaves per plant were found in 150 Kg ha-1 nitrogen application

treatment. According to the findings of Vachhani and Patel (1993) plant height, number of leaves plant-

1, bulb weight, size and onion yield were highest with the application of 150 kg N ha-1. Bungard et al,

(1999) argued that nitrogen is a constituent of

79

Table 29: Effect of transplanting dates and nitrogen levels on the number of leaves plant-1 during 2014 and

2015.


Transplanting Date

15th November 12.37 a 12.55 a 12.46 a

30th December 12.31 a 12.52 a 12.41 a

15th December 11.47 ab 11.51 ab 11.49 b

1st January 10.81 bc 10.95 bc 10.88 c

15th January 10.08 c 10.02 c 10.05 d

LSD(0.05) 1.11 1.32 0.54

Rate of N Fertilizer

75 kg ha-1 11.48 a 11.26 a 11.37 b

100 kg ha-1 11.16 a 10.99 a 11.08 b

125 kg ha-1 11.03 a 11.75 a 11.39 b

150 kg ha-1 11.96 a 12.03 a 12.00 a

LSD(0.05) 0.99 1.18 0.42

Year 11.39 11.51 11.45

Interactions

D × N ns ns ns

Year × D - - ns

Year × N - - ns



many fundamental cell components and it plays an essential role in all living tissues of the plant. No

other element has such an effect on promoting vigorous plant growth. Abdissa et al., (2011) claimed

that N fertilizer significantly affect number of leaves per plant in onion. They reported about 8% increase

in number of leaves over check when 92 kg N ha-1 was added. The results of Nasreen et al, (2007)

showed that application of 120 kg nitrogen ha-1 significantly increased the number of leaves per plant

and further addition of N to 160 kg ha-1 inclined to decrease it. The interactions of D × N, Y × N, Y × D

and Y × D × N all were found non-significant.

Stem Thickness (mm)

It is obvious from Table 30 that maximum stem diameter of 17.37 mm were produced in 15th November

transplanting while minimum stem diameter of 15.31 mm produced when transplanting was delayed to

15th January. Muhammad et al., (2016) also reported that early transplanting resulted thick neck of bulbs.

80

Table 30: Effect of transplanting dates and nitrogen levels on stem thickness (cm) year 2014 and 2015.


Transplanting Date

15th November 16.87 a 17.83 a 17.37 a

30th December 16.62 a 17.73 a 17.18 ab

15th December 16.03 ab 17.11 ab 16.57 bc

1st January 15.64 ab 16.52 bc 16.08 c

15th January 14.87 b 15.74 c 15.31 d

LSD(0.05) 1.44 1.19 0.74


75 kg ha-1 14.96 b 16.74 a 15.85 b

100 kg ha-1 15.98 ab 16.83 a 16.41 b

125 kg ha-1 16.00 ab 17.03 a 16.51 b

150 kg ha-1 17.60 a 17.38 a 17.23 a

LSD(0.05) 1.29 1.06 0.66

Year 15.94 17.00 16.47

Interactions

D × N ns ns ns

Year × D - - ns

Year × N - - ns



Pandy et al., (1992) found that neck thickness problem was more in early (June) sowing onion. Results

of this study also confirm the finding of Boyhan et al., (2009) that early transplanting reduces the bulb

quality by producing thick neck bulbs. In the same way minimum stem thickness of 15.85 mm were

recorded when nitrogen was applied at the rate of 75 Kg ha-1 while 150 kg ha-1 nitrogen application

produced the thickest stem of 17.23 mm plants. Stem thickness over the year were found non-

significant. All the interactions for stem thickness were found non-significant. Similar results were

reported by Jilani (2004) and Muhammad et al., (2016) that increasing nitrogen fertilizer increasing

neck thickness. As neck develop from the base of the leaves and early transplanted produce more and

larger leaves compared to later transplanting. Thus, early transplanting produce thick neck.

81

Bulb Diameter (mm)

It is clear from the data (Table 31) that maximum bulb diameter of 69.45 mm was recorded in early

transplanting 15th November whereas minimum bulb diameter of 55.68 mm was noted when

transplanting was delayed to 15th January. According to Bosekeng and Coetzer (2013) bulb diameter

was significantly influenced by both cultivar

Table 9: Effect of transplanting dates and nitrogen levels on bulb diameter (mm) in year 2014 and 2015.


Transplanting Date

15th November 65.11 a 73.79 a 69.45 a

30th December 64.53 a 72.16 a 68.34 b

15th December 60.36 b 68.93 b 64.65 c

1st January 55.61 c 65.03 c 60.31 d

15th January 51.17 d 60.19 d 55.68 e

LSD(0.05) 3.62 4.65 1.08


75 kg ha-1 54.70 c 64.27 d 59.38 d

100 kg ha-1 57.65 bc 67.00 c 62.46 c

125 kg ha-1 60.37 b 68.53 b 64.51 b

150 kg ha-1 64.72 a 72.07 a 68.40 a

LSD(0.05) 0.79 1.34 0.96

Year 59.36 a 68.02 a 63.55

Interactions

D × N ns ns ns

Year × D - - ns

Year × N - - ns



and sowing date and earlier sown crop produced the largest bulbs. Sawant et al., (2002) reported that

early planting produced maximum polar and equatorial diameter and hence, produced large size bulbs.

An ascending trend was observed in bulb diameter when the level of nitrogen were increased. Minimum

bulb diameter of 59.38 mm was recorded when nitrogen was applied at the rate of 75 Kg ha-1and the

diameter increased to 68.40 cm when the level of nitrogen was increased to 150 kg ha-1. Bulb diameter

between the years was non-significant. Bulb diameter is a main character that predicts its marketability

and usage of crop. Variations in bulb diameter are mostly due to variation in the genetic makeup of

82

varieties but is also affected by environment and management practices (Yang et al., 2004). Onion bulb

size can be increased by application of nitrogen during the growing period (Rice et al., 1993). Results

of a field experiment of Abdissa et al., (2011) showed that regardless of the rate of application, nitrogen

fertilization increased bulb diameter and average bulb weight by about 12 and 21.5%, respectively over

the control. According to their findings nitrogen fertilization significantly increased bulb diameter

without affecting bulb length. nitrogen application up to 120 kg ha1 increase bulb diameter (Nasreen et

al., 2007; Yadav et al., 2003). Bulb length, however, reported to increase with increased in nitrogen

fertilization (Yadav et al., 2003; Reddy et al., 2005).

The interactions of transplanting dates × N level, year × N level, year × Transplanting dates and year ×

Transplanting dates × N level all were found non-significant.

Bulb Weight (g)

Transplanting dates and nitrogen levels significantly (p < 0.05) affected bulb diameter and weight in

both years. Small difference in the weather elements (Fig 2 and 3). resulted no significant difference

over the two growing seasons (Table 32). It is understandable from the table that early transplanting on

15th November produced maximum bulb weight of 206.17 g whereas 15th January transplanting formed

minimum bulb weight of 166.04 g. More than 80 % of the bulb dry matter is added during the first few

weeks from the start of the bulb formation. The final size of the bulb, however, is closely related to the

size of the plant when it starts bulbing. So anything that affects how large a plant is before bulbing affects

the bulb size and yield after bulbing. In this study early transplanting and increase in the levels of

nitrogen fertilizer produced large size plants at bulbing and hence, resulted maximum bulb diameter and

weight at maturity. .Temperature, irrigation, nutrition, weeds and pest control and environmental factors

also contribute to bulb diameter and weight. Plants gained more height with more numbers of leave and

produced bigger size bulbs because of high temperature in 2014-15 than 2013-14. Sawant et al., (2002)

reported that early planting produced maximum polar and equatorial diameter and hence, produced

large size bulbs. Bosekeng and Coetzer, (2013) reported that delayed sowing significantly decreased

average bulb fresh mass while early sown plant produced the largest bulbs. Correspondingly, minimum

bulb diameter of 177.33 g was observed when nitrogen was applied at the rate of 75 Kgha-1 and

maximum bulb weight of 203.60 g was recorded when nitrogen level was increased to 150 kg ha-1. All

the interactions for bulb weight were non-significant at 5% level of probability. Bulb weight is a key

parameter that adds towards the final yield and also determines the suitability of an onion variety for

salad purpose. Abdissa et al., (2011) reported that nitrogen fertilizer significantly increased bulb weight.

Increase in nitrogen fertilizer up to 69 kg nitrogen ha-1 increased bulb weight by about 26% while further

83

increase did not resulted increase in bulb weight (Abdissa et al., 2011). From the result they concluded

that increase in bulb weight to nitrogen could be attributed

Table 310: Effect of transplanting dates and nitrogen levels on bulb weight (g) in year 2014 and 2015.


Transplanting Date

15th November 203.75 a 208.58 a 206.17 a

30th December 197.08 ab 200.67 ab 198.88 b

15th December 185.50 bc 189.42 bc 187.46 c

1st January 174.83 c 188.58 bc 181.71 c

15th January 158.00 d 174.08 c 166.04 d

LSD(0.05) 14.94 18.72 7.26


75 kg ha-1 172.00 c 182.67 b 177.33 c

100 kg ha-1 177.87 bc 183.13 b 180.50 c

125 kg ha-1 188.73 ab 192.80 b 190.77 b

150 kg ha-1 196.73 a 210.47 a 203.60 a

LSD(0.05) 5.12 12.17 6.49

Year 183.83 192.27 188.05

Interactions

D × N ns ns ns

Year × D - - ns

Year × N - - ns



to the increase in plant height, number of leaves, leaf length, and extended physiological maturity in

response to the fertilization all might have increased assimilate production and allocation to the bulbs.

Increase in the levels of the nitrogen caused a linear increase in fresh mass of the bulbs (Resende et al.,

2014).

Bolting Percentage

Bolting is untimely inflorescence development in onion seeded / transplanted for bulbs departing from

normal life cycle.

Transplanting dates and nitrogen levels significantly (p < 0.05) affected bolting percentage during both

years (Table 33). Though year effect was not significant yet, bolting percentage was higher in 2013-

14 because low winter temperature than 2014-15. It is evident from the results that maximum

84

bolting percentage of 53.92 was recorded in early transplanting on 15th November followed by 50.54 %

on 1st December transplanting. Premature seed stalk development was not observed in 15th January

transplanting. Madisa (1994) reported that onion plants sown late did not bolt because when low

temperatures responsible for bolting prevailed, the plants were still small and had not yet reached

reproductive stage. Agic et al., (2007) found that bolting was enhanced by early sowing while cultivars

differs in bolting tendency in their study. When seedlings are transplanted early, the onion plants will

grasp the sensitive size for bulbing when temperature are still low, the plants will bolt instead of making

bulbs. Both cultivar and environment influence the phenomenon of bolting and, thus, it is challenging

to give the exact date for transplanting to reduce bolting and increase yield at the same time (Cramer,

2003). Sowing should be adjusted in such a way to minimize plants exposure to cold spell at sensitive

plant size to avoid bolting. (Khokharet al., 2007b, Cramer, 2003). Sowing dates are, therefore, important

factor that needs to be considered while avoiding bolting.

Table 33: Effect of transplanting dates and nitrogen levels on bolting percentage in year 2014 and 2015.


Transplanting Date

15th November 54.25 a 53.58 a 53.92 a

30th December 51.41 a 49.67 a 50.54 b

15th December 31.83 b 24.75 b 28.29 c

1st January 20.75 c 16.08 c 18.42 d

15th January 00.00 d 00.00 d 00.00 e

LSD(0.05) 4.52 4.08 2.91


75 kg ha-1 47.47 a 43.40 a 45.43 a

100 kg ha-1 33.07 b 33.07 b 33.07 b

125 kg ha-1 27.33 c 23.73 c 25.53 c

150 kg ha-1 18.73 d 15.07 d 16.90 d

LSD(0.05) 4.04 3.65 2.60

Year 31.65 28.81

Interactions

D × N * * *

Year × D - - ns

Year × N - - ns



85

Likewise, bolting percentage was maximum 45.43% when nitrogen was applied at the rate of 75 Kgha-

1 and decreased as the level of nitrogen increased and was minimum 16.90% when nitrogen was given

at the rate of 150 kgha-1. Thus bolting percentage was decreased 28.53% when nitrogen application was

increased from 75-150 kg ha-1.Bolting percentage between the years was non-significant. Rabinowitch

(1990) termed onion as nitro-neutral plant whose flowering time is unaffected by nitrogen. A few

studies, however, indicates that nitrogen affect the

flowering process in onion (Brewester, 1983; Peterson, 1984). Brewester (1983) found that low nitrogen

in nutrient solution speeded up flowering. Low carbon-to-nitrogen ratio (C/N) favors vegetative growth

and high C/N ratio favors reproductive growth in horticultural plants (Dennis, 1984; Díaz-Pérez et al.,

2003). The C/N ratio determines whether onion plants to be vegetative or initiate flowering

(Rabinowitch, 1990). Díaz-Pérez et al., (2003) found that bulb N content increased with increasing

nitrogen fertilizer and bolting decreased steadily with increasing bulb and shoot N contents. Nitrogen

fertilizer modify plant’s C/N ratio. Increasing N fertilizer rates likely decrease C/N ratio and decrease

the bolting incidence. Appropriate nitrogen fertilizer at the time when onion plant at the transition stage

from vegetative to reproduction stage is very important. Application of second dose of N fertilizer

should be applied just before the onset of bulbing to lower C/N ratio and avoid bolting.

Figure 18: Mean data on interaction of transplanting dates and nitrogen fertilizer for bolting percentage.


response to the application of 69 and 92 kg nitrogen ha-1, respectively over the control. According to the

findings of Yamasaki and Tanaka (2005) low nitrogen enhanced bolting in bunching onion (Allium

fistulosum L.) exposed to low temperature for 35 days. Díaz-Pérez et al., (2003) suggested that low

nitrogen fertilizer application increased bolting and reported that bolting incidence decrease steadily

with increase nitrogen fertilization rates up 197 kg.ha1.

73

66

.5

59

.67

59

.33

51

.67

50

48

.17

36

35

.17

28

.33

26

18

.5

18

14

.67

11

8.6

7

0 0 0 0

-10

0

10

20

30

40

50

60

70

80

90

N1 N1 N2 N2 N1 N3 N3 N1 N4 N2 N4 N3 N2 N4 N3 N4 N1 N2 N3 N4

D1 D2 D2 D1 D3 D2 D1 D4 D1 D3 D2 D3 D4 D3 D4 D4 D5 D5 D5 D5

% B

olt

ing

Nitrogen level & Transplanting dates

86

All the interactions except transplanting dates and nitrogen were found non-significant. It is evident

from the interaction of transplanting dates and nitrogen (Figure 17) that maximum bolting percentage

was in D1 × N1 (73.0) followed by (66.5) in D2 × N1. Minimum bolting percentage of 8.67 was recorded

in D4 × N4. No bolting was observed when transplanting was delayed to 15th January irrespective of the

nitrogen level applied.


Data concerning to physiological maturity/harvesting is depicted in Table 34. Days to harvesting

between the two growing seasons were non-significant at 5% level of probability. The interactions were

found non-significant. Both transplanting dates and nitrogen levels significantly influenced days to

maturity. In this study early transplanting on 15th November took 12.13 more days than almost 2 month

late transplanting on 15th January treatment. However, maturity was earlier in early transplanting.

Table 34: Effect of transplanting dates and nitrogen levels on days to maturity in year 2014 and 2015.


Transplanting Dates

15th November 174.17 a 177.58 a 175.88 a

30th December 171.58 a 175.58 ab 173.58 b

15th December 169.00 ab 172.50 abc 170.75 c

1st January 164.75 bc 169.75 bc 167.25 d

15th January 161.17 c 166.33 c 163.75 e

LSD(0.05) 6.61 6.46 1.27


75 kg ha-1 163.87 b 167.67 b 165.77 d

100 kg ha-1 167.27 ab 172.13 ab 169.70 c

125 kg ha-1 169.60 ab 172.87 ab 171.23 b

150 kg ha-1 171.80 a 176.73 a 174.27 a

LSD(0.05) 5.91 5.77 1.14

Year 168.13 a 172.35 a 170.24

Interactions

D × N ns ns ns

Year × D - - ns

Year × N - - ns



87

According to Salter and James (1975) early sown plant resulted in earlier bulb maturity while later

seeded crop resulted in later maturity of the crop (Almanza-Sandoval and Wall, 2000). Cramer in (2003)

also reported delay in maturity with delay in seeding dates. Minimum days 165.77 to maturity were recorded

when nitrogen was applied at the rate of 75 Kg/ha-1 and the maturity was prolonged for 8.5 days when the rate of

nitrogen was increased from 75 Kg ha-1 to 150 kg ha-1. Abdissa et al., (2011) found that N fertilization, regardless

of the rate, prolonged physiological maturity by about 6 days over the control.

Yield (ton ha-1)

Statistical analysis of the data relating to yield ton ha-1 (Table 35) revealed that transplanting dates and

nitrogen levels significantly (p<0.05) affected yield ton ha-1 in 2014 and 2015. The yield in 2014-15,

though, non-significant was little higher than yield in 2013-14. Because of high air temperature in 2014-

15, plants were taller with more number of leaves that produce large bulbs and more yield.. All the

interaction for yield ton ha-1 were found non-significant at 5% level of probability.

Table 35: Effect of transplanting dates and nitrogen levels on total yield (ton ha-1) in year 2014 and 2015.


Transplanting Date

15th November 36.45 a 39.17 a 37.81

30th December 34.89 a 38.00 a 36.45

15th December 29.74 b 31.79 b 30.77

1st January 23.40 c 26.38 c 24.89

15th January 18.19 d 20.25 d 19.22

LSD(0.05) 2.75 2.86 1.46


75 kg ha-1 23.46 d 25.33 c 24.39 d

100 kg ha-1 26.89 c 29.47 b 28.18 c

125 kg ha-1 29.94 b 31.67 b 30.80 b

150 kg ha-1 33.85 a 38.00 a 35.92 a

LSD(0.05) 2.46 2.56 1.30

Year 28.53 a 31.12 a 29.83

Interactions

D × N ns ns ns

Year × D - - ns

Year × N - - ns



88

Maximum yield of 37.81 ton ha-1 was produced by early transplanting on 15th November. Late

transplanting on 15th January produce minimum yield of 19.22 tonha-1. Similar results has been reported

by Patil et al., (2012) that early transplanting (15th November) of onion significantly produce maximum

yield. They recorded a yield of 37.5 ton ha-1in second season when transplanted on 15th November,

while lowest yield of 14.3 ton ha-1in first season when transplanted on 15th January. In the same way

low nitrogen level at the rate of 75 Kgha-1 produce minimum yield of 24.39 ton ha-1and maximum yield

of 35.92 ton ha-1 was recorded when nitrogen was applied at the rate of 150 kg ha-1. According to the

findings of Vachhani and Patel (1993) plant height, number of leavesplant-1, bulb weight, size and onion

yield were highest with the application of 150 kg N ha-1. Total and marketable yield increased by about

5.74 and 4.06 ton respectively at the application of nitrogen at the rate of 69 kg ha-1. Cizauskas et al., (2003) also

reported somewhat similar results that application of 60 kg N ha-1 gave highest bulb yield of onion. Different

researcher at different times reported increase in bulb yield in response to nitrogen fertilization (Singh et al., 1989;

Patel and Patel, 1990; Pandey and Ekpo, 1991; Vachhani and Patel, 1993b; Patel and Vachhani, 1994).

Percentages of Cull

Cull is split, double, diseased and bolters which is culled and discarded from marketable product. Data

relating to % cull has shown in Table 36. It is clear from the table that transplanting date and N level

significantly (p<0.05) influenced % cull while it remained non-significant between the years. Maximum

cull of 55.71% was recorded in early transplanting on 15th November and minimum produce 12.80%

went to cull in late transplanting on 15th January. Farmers in Malakand division tend to transplant early

in November to capture early market. This practice increased the incidence of bolting and that make the

bulbs unmarketable. Kandil et al., (2013) found maximum total culls were resulted from early

transplanting date (15th November) in both seasons. In this study yield loss in early transplanting was

due to bolting which decrease with delay in transplanting. In very late transplanting very small bubs

contributed to percent cull. Poor crop management and environmental factors also play a part in

unmarketable produce. Bolting incidence was higher in 2013-14 because low winter temperature

than 2014-15.

89

Table 36: Effect of transplanting dates and nitrogen levels on percent cull in year 2014 and 2015.


Transplanting Date

15th November 56.68 a 54.73 a 55.71 a

30th December 45.97 b 44.06 b 45.01 b

15th December 33.92 c 30.43 c 32.18 c

1st January 21.25 d 17.77 d 19.51 d

15th January 13.35 e 12.26 d 12.80 e

LSD(0.05) 5.73 5.85 2.33


75 kg ha-1 55.30 a 48.39 a 51.85 a

100 kg ha-1 35.96 b 33.09 b 34.52 b

125 kg ha-1 25.34 c 27.91 b 26.63 c

150 kg ha-1 20.34 c 18.01 c 19.18 d

LSD(0.05) 5.12 5.23 2.08

Year 34.24 a 31.85 a 33.04

Interactions

D × N * * *

Year × D - - ns

Year × N - - *



The nitrogen application at the rate of 75 Kg ha-1 contributed maximum to percent cull and percent cull

was minimum when nitrogen was applied at the rate of 150 kg ha-1. Similar results has been reported

by Jilani et al., (2004) that % cull was maximum at control treatment while minimum when nitrogen

was applied at the rate of 160 kg ha–1. Díaz-Pérez (2003) reported that loss in marketable yield was a

combination of bolting and bulb decay and was minimum at 162 kg N application ha–1. In this study %

cull in low nitrogen application is due to bolting while in higher nitrogen application is due to bulb

decay. This confirm the finding of Díaz-Pérez (2003) who stated that yield losses at minimum nitrogen

rate was due to bolting while at higher nitrogen rate it was due to bulb decay.

All the interactions except D × N and Y × N were found non-significant. Significant interaction of D ×

N and Y × N has been shown in Figure 18 and 19 respectively.

90

Figure 19: mean data on interaction of transplanting dates and nitrogen level for percentage of cull.

It is concluded from the Figure18 that maximum % cull (79%) has been recorded in D1N1 followed by

D2N1 (66.71%) combination. Minimum produce went to cull in D5N4 combination. Interaction of Y ×

N (Figure 19) showed that maximum produce were culled in Y2N1 (55.3 %) followed by Y1N1 (48.4

%) while minimum (18.0 %) in Y1N4 combination.

The correlation coefficient Table 37 showed that % cull has strong positive correlation with bolting

percentage (0.475) and significantly negative correlation with marketable yield ton/ha (-0.738). Thus,

bolters as occurred in early transplanting and in low N application contributes to cull and as the bolting

increased amount of the cull increased. In late transplanting very small bubs contribute to unmarketable

yield.

Figure 20: Mean data on interaction of year and nitrogen level for percent cull.

79

.58

66

.71

57

.41

57

.05

51

50

.41

37

.49

36

.78

35

.43

30

.22

30

.21

22

.71

19

.18

19

.1

18

.73

14

.8

12

.41

10

.11

9.6

6

7.2

1

0

10

20

30

40

50

60

70

80

90



Per

cen

t C

ull

Nitrogen level & Transplanting dates

0.0

10.0

20.0

30.0

40.0

50.0

60.0

N1 N2 N3 N4

Per

cen

t C

ull

Nitrogen level

Year 1 Year 2

91


Data pertaining to marketable yield ton ha-1 affected by transplanting date and nitrogen levels has

presented in Table 37. Statistical analysis of the data revealed that transplanting date and nitrogen levels

significantly influenced marketable yield tonha-1at 5% level of probability. Year as a source of variation

was not significant. The D× N interaction was significant (p<0.05) while the remaining interactions

were found non-significant. Maximum marketable yield of 21.60 ton ha-1 was recorded in D3 i.e., 15th

December followed by 20.82 ton ha-1 in D2 and minimum 16.95 tonha-1 was recorded in late

transplanting treatment D5. Marketable yield increased with increase in nitrogen application and

maximum 28.46 ton ha-1 was produced when nitrogen was applied at the rate of 150 kg ha-1. Minimum

marketable yield 10.34 tonha-1 was recorded when nitrogen was applied at the rate of 75 kgha1. Abdissa

et al.; (2011) found that nitrogen significantly increased total and marketable bulb yield of onion. Total

and marketable yield increased by about 5.74 and 4.06 ton respectively at the application of nitrogen at

the rate of 69 kg ha-1. Muhammad et al., (2016) also reported increase in marketable yield with increase

in N fertilizer. Similar results has also been presented by Maier et al., (1990) that marketable yield was

significantly increased with increase in nitrogen fertilizer. The results of this study are in agreement with

finding of Díaz-Pérez (2003) who reported that total and marketable yield was minimum at low nitrogen

rate 102 kg ha-1 and highest at 146 kg nitrogen ha-1. Nitrogen application beyond 146 kg ha-1 had no

significant effect on either total or marketable yield.

Figure 20: Mean data on interaction of transplanting dates and N level for marketable yield ton/ha.

32

.28

30

.41

29

.02

28

.14

25

.48

23

.57

22

.45

21

.39

20

.11

19

.39

19

.1

18

.45

17

.07

15

.43

15

.31

12

.92

11

.47

10

.41

10

.36

6.5

6

0

5

10

15

20

25

30

35



Mar

ket

able

yie

ld t

on

ha-1

Transplanting dates & Nirtrogen level

92

Environmental factors also contribute to marketable yield. As bolting incidence and consequently

percent cull was higher in 2013-14 because low winter temperature than 2014-15. This higher

incidence of bolting resulted for lower marketable yield in 2013-14.

The D× N interaction showed that maximum marketable yield was produced by mid transplanting dates

(15th December) and high level of nitrogen application. Early and late transplanting and low nitrogen

application gave low marketable yield. Maximum marketable yield of 32.82 ton ha-1 has been recorded

in D2N4 combination followed by 30.41 ton ha-1 in D3N4 combination, while, minimum of 6.56 tonha-1

was produced by D1N1 combination.

Table 37: Effect of transplanting dates and nitrogen levels on marketable yield ton ha-1 in year 2014 and

2015.


Transplanting Date

15th November 17.25 bc 17.89 b 17.57 b

30th December 20.23 ab 21.42 ab 20.82 a

15th December 21.23 a 21.97 a 21.60 a

1st January 19.57 ab 21.21 ab 20.39 a

15th January 16.06 c 17.83 b 16.95 b

LSD(0.05) 3.27 3.59 1.51


75 kg ha-1 10.56 d 10.13 d 10.34 d

100 kg ha-1 17.03 c 17.78 c 17.40 c

125 kg ha-1 20.65 b 22.67 b 21.66 b

150 kg ha-1 27.24 a 29.67 a 28.46 a

LSD(0.05) 2.93 3.22 1.35

Year 18.87 20.06 19.47

Interactions

D × N ns ns *

Year × D - - ns

Year × N - - ns



93

Correlation co-efficient analysis

The correlation coefficient Table 38 revealed that plant height has significant positive correlation with

number of leaves per plant (0.158), bulb diameter (0.310), bulb weight (0.333) total yield tonha-1 (0.279)

and marketable yield (0.264)non-significant but positive correlation with bolting percentage (0.064),

Stem thickness (0.116), while its association with percent cull was significant and negative (-0.186).

Sharma et al(2015) found positive association of plant height with number of leaves plant-1, bulb

diameter, bulb weight and total yield ton ha-1.Singh et al., (2010), Mahanthesh et al., (2008), Aliyu et

al., (2007), Gurjar and Singh, (2006) all presented the same findings.

Number of leaves per plant showed positive correlation with bolting percentage (0.058), bulb diameter

(0.361), bulb weight (0.024), total yield tonha-1 (0.044) and marketable yield tonha-1 (0.095) while its

association with stem thickness (-0.067) and percent cull (-0.193) was negative. Bulb diameter has

positive correlation with bulb weight (0.505) total yield tonha-1 (0.463) and marketable yield tonha-1

(0.420) while its association with percent cull (-0.118) was negative. Bulb diameter has strong and

positive correlation with the total bulb yield of onion signifying that the increased in individual bulb size

is key to maximize onion productivity per unit area (Abdissa et al., 2011).The results of Abdissa et al.,

(2011) showed that mean bulb weight was positively and strongly correlated with bulb length and

diameter suggesting that N fertilization increased bulb weight by improving bulb length and diameter.

Sharma et al., (2015) reported similar results that total yield had positive and significant correlation with

plant height, number of leaves/plant, equatorial diameter of bulb average weight of bulb and marketable

bulb yield. Bolting percentage has positive correlation with stem thickness (0.149) bulb diameter

(0.092), yield tonha-1 (0.172), percent cull (0.417) and negative correlation with bulb weight (-0.038)

marketable yield (-0.118). Total yield ton ha-1has negative correlation (-0.323) with % cull and positive

correlation (0.809) with marketable yield ton ha-1.Percent cull has strong positive correlation with

bolting percentage (0.475) and significantly negative correlation with marketable yield tonha-1 (-0.738).

Thus, bolters as occurred in early transplanting and at low N application contributes to cull and as bolting

increased amount of unmarketable yield increased. In late transplanting very small ungraded bubs

contribute to unmarketable yield.

94

Table 38: Phenotypic correlation coefficient among yield and yield related characters in onion.

Plant

Heigh

t

No. of

leaves

plant-1

Bolting

percentage

Stem

Thick

ness

Bulb

Diameter

Bulb

weight

Yield

tons/h

a

Percen

t Cull

Marketabl

e Yield(t/h)

Plant Height 1 0.158 0.064 0.116 0.310* 0.333* 0.279* -0.186* 0.264*

No.of leaves

plant-1

1 0.058 -0.067 0.361* 0.024 0.044

-0.193* 0.095

Bolting

percentage

1 0.149 0.092 -0.038 0.172* 0.417* -0.118

Stem

Thickness

1 0.054 -0.212* -0.143 0.279* -0.232*

Bulb

Diameter

1 0.505* 0.463* -0.188* 0.420*

Bulb weight 1 0.694* -0.410* 0.626*

Yield

tons/ha

1 -0.323* 0.809*

Percent Cull 1

-0.791*

Marketable

Yield

1

Summary conclusios and recommendations

Summary

In experiment no. 3 seedlings were transplanting at five different dates (15th Nov, 1st Dec, 15th Dec, 1st

Jan and 15th Jan) four level of nitrogen fertilizer (75, 100, 125 and 150 kg ha-1) were applied with the

objective to determine its influence on inflorescence development in onion bulb crop. Bolting

percentage decreased gradually with increase in the rate of nitrogen fertilizer. Maximum bolting

percentage was recorded in early transplanting and declined with delay in transplanting. Bolting

incidence did not occurred in very late, 15th January, transplanting irrespective of the rate of nitrogen

applied. Plant height, stem thickness, bulb diameter and weight and total yield ton ha-1 increased with

increase in nitrogen fertilizer and conversely showed a downward trend with delay in transplanting.

Different rates of nitrogen fertilizer didn’t significantly influenced number of leaves plant-1. However,

early transplanting exhibited significantly more leaves than late transplanting. Early transplanting took

maximum 175.88 days to maturity than late transplanting (163.75) days. Maturity was delayed with

increase in nitrogen fertilizer. Percent cull decreased with increase in the rate of nitrogen fertilizer.

Marketable yield ton ha-1 was maximum at mid transplanting date (15th December) and with maximum

rate of nitrogen fertilizer. The correlation co-efficient analysis revealed that marketable yield ton ha-1

95

has positive correlation with plant height, number of leaves plant-1, bulb diameter, bulb weight, total

yield ton-1 and negative correlation with stem thickness bolting percentage and percent cull. Bolting

percentage has positive association with percent cull.

Conclusions

1. Bolting percentage decreased gradually with increase in the rate of nitrogen fertilizer. Maximum

bolting percentage was recorded in early transplanting and declined with delay in transplanting.

No bolting was observed in very late, 15th January, transplanting irrespective of the rate of

nitrogen applied. Percent cull decreased with increase in the rate of nitrogen fertilizer.

Marketable yield ton ha-1 was maximum at mid transplanting date, 15th December and with

maximum rate of nitrogen fertilizer. Marketable yield ton ha-1 has positive correlation with plant

height, number of leaves plant-1, bulb diameter, bulb weight, total yield ton ha-1 and negative

correlation with stem thickness, bolting percentage and percent cull.

2. Marketable yield increased from 10.34 to 28.46 ton ha-1 when nitrogen application was

increased from 75 to 150 kg ha-1.

3. Bolting decreased by 28.53% when nitrogen application was increased from 75 to 150 kg ha-1

Recommendations

1. Transplanting should be done from December 15 to January 15 since it will produce maximum

marketable yield with low bolting percentage and minimum cull in the north of West Pakistan.

Very early transplanting increases bolting and very late transplanting produces small bulbs and

low yield.

2. 125-150 Kg nitrogen ha-1 should be applied. Low nitrogen fertilizer increases bolting. Similarly,

avoid over fertilization as it also encourages bulb decay.

3. 90:60:60 Kg ha-1is the common recommendation of NPK for onion here in Pakistan. In current

study 125-150 kg nitrogen ha-1 produced maximum marketable yield and minimum bolting

percentage. Hence, research should be carried out to determine the amount of P and K when N

was increased from 90 Kg ha-1 to 125-150 Kg ha-1.

96

Chapter 6:

OVERALL SUMMARY, CONCLUSIONS AND RECOMMENDATIONS

Summary

Premature flower stalk development in onion bulb crop deviating from normal life cycle was called

bolting. Bolting makes the bulbs fibrous, lightweight and thus reduces its quality. Bolting is one of the

major production constraints in all onion growing areas in Pakistan. Three field trials were conducted

with the aim to prevent onion bulb crop from bolting and produce quality onion bulbs.

Study was conducted at Agricultural Research Institute, Mingora, Swat, a picturesque district in Khyber

Pakhtunkhwa province of Pakistan from November to June 2013-14. Experiments were repeated at the

same location in the next growing season of 2014-15. The experimental site, is 906 m above sea level

located in the Hindu Kush range at 34.3- 35.53° North Latitude and 71.5-72.5° Longitude in the north

of west of Pakistan. Climate is warm temperate. Temperature ranges from 25 to 35 oc. Temperature

drops in winter as low as -4oc with snow and frost. In summer temperature rises sometimes above 40oc.

Average rainfall ranges from 740-1200 mm. Soil is silt loam with pH ranges from 5-5.6.

In the experiment titled “effect of transplanting dates and seedling age on premature bolting in onion

bulb crop” seedlings of 45, 60 and 75 days in nursery were transplanted on 5 different dates (30th

November, 15th December, 30th December, 15th January and 30th January) to study its effect on

premature bolting in onion. Transplanting dates and seedling age exerted significant effect on different

growth and yield parameters studied. Plant height, number of leaves at bolting, stem thickness, days to

maturity, bub diameter, bulb weight and total yield decreased with delay in transplanting as well as

increasing seedling age. On the other hand bolting and cull percentage decrease with delay in

transplanting and increased with increase in seedling age. Maximum marketable yield (tons ha-1) was

recorded when 60 days old seedlings were transplanted on15th December. The correlation co-efficient

analysis data revealed positive correlation between marketable yield (0.671 ton ha-1) and bulb diameter

(0.381). Non- significant positive correlations of marketable yield were recorded with bulb weight

(0.173 gm), number of leaves at bolting (0.097), stem thickness (0.091) and plant height (0.106). The

association of marketable yield with bolting percentage (-0.381) and percent cull (-0.552) was

significantly negative.

In the second study three commercial cultivars ‘Swat-1’, ‘Saryab Red’ and ‘Chiltan-89’ were

transplanted on five different dates (25th November, 10th December, 25th December, 10th January and

25th January). Apparently none of the cultivars showed resistance to bolting however, they varied in

their susceptibility to bolting. Cultivar Swat-1 took significantly maximum 78.67 days to bolting

97

initiation and recorded minimum bolting percentage 12.51 compared to ‘Saryab Red’13.75 and

‘Chiltan-89’ 17.32. Early transplanting took less 108.06 days to bolting initiation. Bolting percentage

was maximum 34.52 at early transplanting and reduced with delay in transplanting from 25th November

to 25th December. In all cultivars bolting has not been recorded at late, (10th and 25th January)

transplanting irrespective of the cultivar. Compare to ‘Saryab Red’ and ‘Chiltan-89’, ‘Swat-1’ has

maximum plant height 65.58 cm, number of leaves per plant 10.64, stem thickness 15.43mm, bulb

diameter 60.08 cm, bulb weight169.08 g, and days to maturity 168.37, total and marketable yield 32.94,

25.07 ton ha-1 respectively. Plant height 61.24cm, number of leaves per plant 10.96, stem thickness

17.24 cm, bulb diameter 63.08 cm, bulb weight 149.31g, and days to maturity 167.89, total yield 31.07

ton ha-1 was maximum at early transplanting and decreased with delay in transplanting. Cultivar Swat-

1 produced maximum marketable yield 25.07 ton ha-1than ‘Saryab Red’ and ‘Chiltan-89’. Marketable

yield was maximum at mid transplanting date (25th December); attributed to less bolting compared to

early transplanting. Unmarketable yield at early transplanting was largely due to bolting while at late

transplanting it was due to small ungraded bulbs.

In the third experiment seedlings were transplanting at five different dates (15th Nov, 1st Dec, 15th Dec,

1st Jan and 15th Jan) four level of nitrogen fertilizer (75, 100, 125 and 150 kg ha-1) were applied to onion

bulb with the objective to determine its influence on inflorescence development in onion bulb crop.

Bolting percentage decreased gradually with increase in the rate of Nitrogen fertilizer. Maximum bolting

percentage was recorded in early transplanting and declined with delay in transplanting. Bolting

incidence did not occurred in very late, 15th January, transplanting irrespective of the rate of nitrogen

applied. Plant height, stem thickness, bulb diameter and weight and total yield ton ha-1 increased with

increase in nitrogen fertilizer and conversely showed a downward trend with delay in transplanting.

Different rates of nitrogen fertilizer didn’t significantly influenced number of leaves plant-1. However,

early transplanting exhibited significantly more leaves than late transplanting. Early transplanting took

maximum 175.88 days to maturity than late transplanting (163.75) days. Maturity was delayed with

increase in nitrogen fertilizer. Percent cull decreased with increase in the rate of nitrogen fertilizer.

Marketable yield ton ha-1 was maximum at mid transplanting date (15th December) and with maximum

rate of nitrogen fertilizer. The correlation co-efficient analysis revealed that marketable yield ton ha-1

has positive correlation with plant height, number of leaves plant-1, bulb diameter, bulb weight, total

yield ton-1 and negative correlation with stem thickness bolting percentage and percent cull. Bolting

percentage has positive association with percent cull.

It is challenging to control bolting and increase yield at the same time. Delay transplanting decrease

bolting incidence and yield as well. Bolting resistance cultivars can be planted earlier. Presently, bolting

98

resistant cultivar is not available in this country. Research should be initiated to develop bolting resistant

cultivar or produce resistance in available cultivars through phenotypic recurrent selection.

Transplanting should be delayed in such a way to avoid plants receiving cold temperature at sensitive

stage to minimize bolting. Increasing transplant age at nursery can creased bolting and vice versa.

Likewise, chances of bolting incidence decline with increasing the level of nitrogen fertilizer. Therefore,

correct transplant age (50-60 days) and ample nitrogen fertilizer of 125-150 Kg ha-1also reduced the

incidence of bolting.

Conclusions

1. It is very difficult to give exact date for transplanting to control bolting and increase yield

simultaneously as it is cultivar and environment dependent.

2. A 15 days delay in transplanting from 15th November to 1stDecember caused reduction in

bolting from 53.92% to 33.63 %. A further 15 days delay in transplanting from 30th November

to 15thDecember caused reduction in bolting from 33.63% to 22.83 %. Likewise, 15 days delay

from 15 December to 30th December decreases bolting from 22.83% to 12.41%. Moreover, 15

days delay in transplanting from 30th December to 15th January reduced bolting percentage from

12.41% to 6.57%. Bolting was not observed on 30th January transplanting.

3. Younger seedlings take more days to pass the juvenility and enter the reproductive stage, thus,

more likely to escape the cold temperature responsible for bolting. Older seedlings (more than

60 days) took less days to transition phase and initiate inflorescence development upon exposure

to low temperature.

4. Bolting percentage decreased from 30.81 to 9.86% when age of transplant was reduced from

75 days to 60 days. Bolting incidence further declined from 9.86% to 4.60% when 45 days old

seedlings were transplanted.

5. Marketable yield increased from 10.34 to 28.46 ton ha-1 when nitrogen application was

increased from 75 to 150 kg ha-1.

6. Bolting decreased by 28.53% when N application was increased from 75 to 150 kg ha-1

7. Plant height, number of leaves at bolting, stem thickness, days to maturity, bolting percentage,

bulb diameter, weight and percent cull decreased with delay in transplanting and increasing

seedling age. Early transplanting and older seedling increased the incidence of bolting.

Maximum marketable yield ton ha-1was recorded in mid transplanting date (30th December)

and 60 days old seedlings.

99

8. Cultivar Swat-1 took significantly maximum days to bolting initiation and had minimum

bolting percentage compared to Saryab Red and Chiltan-89. Early transplanting took less days

to bolting initiation. Bolting percentage was maximum at early transplanting and reduced with

delay in transplanting from 25th November to 25th December in all cultivars. Bolting was not

recorded in late transplanting (10th and 25th January) irrespective of the cultivar. Compared to

Saryab Red and Chiltan-89, Cultivars Swat-1 produced maximum marketable yield ton ha-1.

Marketable yield was maximum at mid transplanting date (25th December) attributed to less

bolting and percent cull compared to early transplanting. Unmarketable yield at early

transplanting was largely contributed by bolting while at late transplanting it was due to small

ungraded bulbs.

9. Bolting percentage decreased gradually with increase in the rate of nitrogen fertilizer. Maximum

bolting percentage was recorded in early transplanting and declined with delay in transplanting.

No bolting was observed in very late, 15th January, transplanting irrespective of the rate of

nitrogen applied. Percent cull decreased with increase in the rate of nitrogen fertilizer.

Marketable yield ton ha-1 was maximum at mid transplanting date, 15th December and with

maximum rate of nitrogen fertilizer. Marketable yield ton ha-1 has positive correlation with plant

height, number of leaves plant-1, bulb diameter, bulb weight, total yield ton ha-1 and negative

correlation with stem thickness, bolting percentage and percent cull.

Recommendations

1. Transplanting should be done from December 15 to January 15 since it will produce maximum

marketable yield with low bolting percentage and minimum cull in the north of West Pakistan.

Very early transplanting increases bolting and very late transplanting produces small bulbs and

low yield.

2. Seedling age also influence the incidence of bolting. Larger plants switched from juvenile stage

to reproductive stage earlier when temperature gets low and start bolting instead of bulbing.

Fifty to sixty days old seedlings gave maximum marketable yield and minimum bolting.

3. 125-150 Kg N ha-1 should be applied. Low nitrogen fertilizer increases bolting. Similarly, avoid

over fertilization as it also encourages bulb decay.

4. 90:60:60 Kg ha-1is the common recommendation of NPK for onion here in Pakistan. In this

research 125-150 kg N ha-1 produced maximum marketable yield and minimum bolting

percentage. Hence, research should be carried out to determine the amount of P and K when N

was increased from 90 Kg ha-1 to 125-150 Kg ha-1.

100

5. Further research should be carried out particularly, in controlled environment to confirm finding

of this research.

6. Bolting resistant variety should be used. Though, there is no bolting resistant variety in Pakistan

‘Swat-1’ has comparatively less bolting incidence among the existing cultivars. Research work

should be initiated to develop bolting resistant variety or produce bolting resistance in existing

cultivars though phenotypic recurrent selection.

101

Chapter 7:

LITERATURE CITED

Abbey, L., Joyce, D. C., Aked, J., Smith, B. and Marshall, C., 2004. Electronic nose evaluation of onion

headspace volatiles and bulb quality as affected by nitrogen, Sulphur and soil type. Ann. Appl.

Biol., 145(1): 41-50.

Abdissa, A., Tekalign,T., and Pant, L. M., 2011. Growth, bulb yield and quality of onion (Allium cepa

L.) as influenced by nitrogen and phosphorus fertilization on vertisol I. growth attributes,

biomass production and bulb yield. Afri. J. Agri. Res., 6(14): 3252-3258, 18 July, 2011

Abu-Rayyan, A. M. and Abu-Irmaileh, B. E., 2004. Onion development and yield in response to manual

cultivation, herbicides, or colored mulches. J. Veg. Crop Prod. 10, 37-49.

Abu-Rayyan, A. Akash, M. W. and Gianqinto, G., 2012. Onion seed germination as affected by

temperature and light. Int. J. Veg. Prod., 10: 37-49.

Agic, R., Popsimonova, G., Jankulovski, D. and Martinovski, G., 2007. Winter onion susceptibility to

premature bolting depending on the variety and the sowing date. Acta. Hort. 729, 271-276.

Aklilu, L., 1997. Onion research and production in Ethiopia. Acta Hortic. 433:95-97.

Aliyu, U., Magaji, M. D., Yakubu, A. Y. and Dikko, A. U., 2007. Correlation and path coefficient

analysis for some yield related traits in onion (Allium cepa L.). J. Plant. Sci. 2(3):366-369.

Almaza-Sandoval, J..L. and Wall, M. M., 2000. Maturity date induced by transplant size or sowing date

affects pungency of NuMex of sweet onion.p.189-191. In: W. Randle (ed.) Proc. 3rd Intl. Symp.

Edible Alliaceae.Alliums 2000.Attens, Ga

Al-Moshileh, A. M., 2007. Effects of planting date and irrigation water level on onion (Allium cepa L.)

production under central Saudi Arabian conditions. Sci. J.King Faisal Univ. 8, 75-85.

Ami, E. J., Islam, M. T., Farooque, A. M., 2013. Effect of Vernalization on Seed Production of Onion.

Agr. For. Fish. Vol. 2(6) 212-217.

Ansari, N. A., 2007. Effect of density, cultivars and sowing date on onion sets production. Asian J. Plant

Sci. 6, 1147-1150.

Asmatullah, Mahar, N. A. and Munir, M., 2004. Performance of bulb crop onion as affected by sowing

dates. IndusJ Plant Sci., 3(4): 376-380.

102

Astley, D., Innes, N. L. and van der Meer, Q. P., 1982. Genetic resources of Allium species–a global

report. IBPGR Secretariat, Rome, p.7.

Aubyn, A., and Abutiate,W. S., 1994. Effect of age of transplant on the establishment and yield of onion

cultivar Bawku. Proc. National Workshop of Food and Industrial Crops. Kumasi, 25-27 Oct.

1994. pp. 67-69.

Bahadur, A., Singh, R., 2005. Influence of seedling age on bulb production of Rabi onion. Ann. Agric.

Res.New Series. 26(1):147-148.

Baldwin. S., Revanna, R., Pither-Joyce, M., Shaw, M., Wright, K., Thomson, S., Moya, L., Lee, R.,

McKnight, R. and McCallum, J., 2014. Genetic analyses of bolting in bulb onion (Allium cepa

L.). Theor. Appl. Genet., Vol: 127 (3): 535-547

Baliyan, S. P., 2014. Evaluation of Onion Varieties for Productivity in Performance in Botsowana.

World Journal of Agricultural Research.2(3):129-135.

Baliyan, S. P. and Baliyan, P. S., 2013. Comparative Profitability of Onions Harvested as Green and

Dry (Mature) in Botswana. Intl. J. Agri. Res., Innovation and Technology, 3(1):73-77.

Bassett, M. J., 1986. Breeding Vegetable Crops. AVI Publishing Co., USA, 584pp.

Bijarniya, N., Jat, M., Patel, B.and Bana, M. 2015. Effect of Age of Seedling and Dates of Transplanting

on Growth, Yield and Quality of Onion (Allium Cepa L.) in Rabi under North Gujarat

Condition. The Journal of Rural and Agricultural Research Vol. 15(2) 38-42.

Blümel, M., Dally, N. and Jung, C., 2015. Flowering time regulation in crops—what did we learn from

Arabidopsis? Curr. Opin. Biotechnol. 32, pp.121-129.

Bosekeng, G., 2012. Response of onion (Allium cepa L.) to sowing dates and plant population (Doctoral

dissertation, University of the Free State)

Bosekeng, G. and Coetzer, G. M., 2013. Response of Onion (Allium cepa L.) to sowing dates. Afri. J.

Agri. Res., 8(22): 2757-2764.

Boyhan, G. E., Torrance, R. L., Cook, M. J., Riner, C., Hill, C. R., 2009. Sowing date, transplanting date

and variety effect on transplanted short-day onion production. Hort. Technol., 19(1):66-71.

Boyhan, G. E., Torrance, R. L., Riner, C. M., Cook, IV, M. J., Dollar, M. A., Curry, D. S., Hill, C. R.,

Thigpen, D. R. and Bateman, A.G., 2014. Five-Year Evaluation of Short-Day Onion Varieties,

Intl. J. Veg. Sci., 20(2): 150-184, DOI: 10.1080/19315260.2013.788595

103

Brewster, J. L., and Salter, P. J. 1980. The effect of plant spacing on the yield and bolting of two cultivars

of overwintered bulb onion. J. Hort. Sci. 55(2):97-102

Brewster, J. L., 1983. Effects of photoperiod, nitrogen nutrition and temperature on inflorescence

initiation and development in onion (Allium cepa L.). Ann. of Bot., London, 51(4): 429-440.

Brewster, J. L., 1985. The influence of seedling size and carbohydrate status and photon flux density

during vernalization on inflorescence initiation in onion (Allium cepa L.). Ann. Bot. 55:403-414.

Brewster, J. L., 1987. Vernalization in the onion – a quantitative approach. In: Atherton, J.G.

Manipulation of flowering. London: Butterworths, Cap. 13, p. 171-183

Brewster, J. L., 2008. Onions and other vegetable alliums, 2nd edn. CAB International,Oxford shire,

United Kingdom. pp. 85-150.

Brewster, J. L., 1990. Physiology of crop growth and bulbing. In: Onion and allied crops. Vol.1.

Rabinowitch, H. D., Brewster, J. L., (Ed.). Boca Raton, CRC press Inc.

Brewster, J. L., 1994. Onions and other vegetable alliums. 1st ed., CAB International, Wallingford,

United Kingdom.

Bungard, R. A., Wingler, A., Morton, J. D. and Andrews, M., 1999. Ammonium can stimulate nitrate

and nitrite reductase in the absence of nitrate in Clematis Vitalba. Plant Cell Environ. 22:859-

866

Cheema, K. L., Saeed, A. and Ahmad, M., 2003a. Autumn crop production through sets in eight onion

cultivars. Int. J. Agric. Biol. 4:547-549.

Cheema, K. L., Saeed, A. and Habib, M., 2003b. Effect of sowing date on set size in various cultivars

of onion (Allium cepa L.). Int. J. Agric. Biol. 5:185-187.

Cizauskas, A., Viskelis, P., Dris, R., Oladele, O. I., 2003. Influence of nitrogen rates on onion yield,

quality and storability. Moor J. Agric. Res., 4(1):85-89

Comrie, A. G., 1997a. Climatic and soil requirements for onions. Onions B.1. Agricultural Research

Council, Vegetable and Ornamental Plant Institute, Pretoria, South Africa. pp. 1-2.

Comrie, A. G., 1997b. How to grow onions. Onions D.1. Agricultural Research Council, Vegetable and

Ornamental Plant Institute, Pretoria, South Africa. pp. 1-5.

Coolong, T. W. and Randle,W. M., 2003. Sulfur and nitrogen availability interact to affect the flavor

biosynthetic pathway in onion. J. Amer. Soc. Hort. Sci. 128: 776-783.

104

Coolong, T. W. and Randle,W. M., 2006. The influence of root zone temperature on growth and flavor

precursors in (Allium cepa L.). J. Hort. Sci. and biotech. 81(2):199-204.

Cramer, C. S., 2003. Performance of fall-sown onion cultivars using four seeding dates. J. Amer. Soc.

Hort. Sci. 128: 472-478.

Cramer, C. S., 2006. Onion trait heritability and response from selection. J. Amer. Soc. Hort. Sci. 131(5):

646-650.

Cremaschi, G., Andreau, R., Martinez, S., Garbi, M., Morelli, G. and Bidondo, D., 2012. Effect of

transplanting date on the phenology and production of 4 tomato (Lycopersicon esculentum

Mill.) hybrids grown under greenhouse. Acta Hortic. 927, 301-

308DOI:10.17660/ActaHortic.2012.927.35.

Dhuma, K., Datir, S. and Pandey, R., 2007. Assessment of bulb pungency level in different Indian

cultivars of onion (Allium cepa L.). Food Chem. Vol. (100)4: 1328–1330

Díaz-Pérez, J. C., Purvis, A. C. and Paulk, J. T., 2003. Bolting, yield, and bulb decay of sweet onion as

affected by nitrogen fertilization. J. Amer. Soc. Hort. Sci. 128: 144-149.

Dong,Y., Cheng, Z., Meng, H., Liu, H., Wu, C. and Khan, A. R., 2013. The effect of cultivar, sowing

date and transplant location in field on bolting of welsh onion (Allium fistulosum L.).BMC Plant

Biology; 13; 154.

Fao, F., 2013. Statistical Yearbook 2013: World Food and Agriculture. FAO Food Agric. Organziation

UN Rome Italy (www.fao.org)

Fatema, U. J. 2001. Variability and interrelationship of yield and yield components of onion. M.Sc.

Thesis. Department of Botany. Rajshahi University. Bangladesh.

Fausey, B., Padhye, S., Runkle, E. and Cameron, A., 2006. Vernalization: Life in the cold. Greenhouse

growers, pp: 70-76. www.greenhousegrower.com

Flood, R. G.; Halloran, G. M., 1986. Genetics and physiology of Vernalization response in wheat. Adv.

Agron.New York. 39: 87-125,

Fathi, S. M. R., 2009. The most suitable age for planting onion. Fars News Service (Persian)

Gao, L. M., Ren, Z. W., Chen, Y. Q., Chen, W. and Dong, F., 2011. Effects of Accumulated

Temperature and Seedling Age on Welsh Onion Bolting. Shandong Agric. Sci., 11:011.

105

Gautam, I. P., Khatri,B. and Paudel,G. P., 2006. Evaluation of Different Varieties of Onion and Their

Transplanting Times for Off-Season Production in Mid Hills of Nepal. Nepal Agric. Res. J.7:21-

26

Gessesew, W. S., Woldetsadik,K. and Mohammed,W., 2015. Growth Parameters of Onion (Allium

cepa L. var. Cepa) as Affected by Nitrogen Fertilizer Rates and Intra-row Spacing Under

Irrigation in Gode, South-Eastern Ethiopia. Agri. For. Fish. 4(6): 239-245. Doi:

10.11648/j.aff.20150406.11

González, M. I., 1997. Effect of sowing date on the production of three storage varieties of onion in the

eight regions of Chile. In I International Symposium on Edible Alliaceae. 433: 549-554.

Griffiths, G., Trueman, L., Crowther,T., Thomas, B. and Smith, B., 2002. Onions—a global benefit to

health. Phytotherapy Research. 16(7): 603-615.

Gurjar, R. S. S. and Singhania, D. L. 2006. Genetic variability, correlation and path analysis of yield and

yield components in onion. Indian J. Hort. 63(1):53-58.

Hanen, N., Fattouch, S., Ammar E.and Neffati, M., 2012. Allium species, ancient health food for the

future. Scientific, Health and Social Aspects of the Food Industry. 343-354. INTECH Open

Access Publisher.

Haydar, A., Sharker,N., Ahmed, M. B., Hannan, M. M., Razvy, M. A., Hossain, M., Hoque, A. and

Karim, R., 2007. Genetic variability and interrelationship in onion (Allium cepa L.). Middle-

East J. Sci. Res, 2(3-4):132-134.

Henderson, I. R., Shindo, C. and Dean, C., 2003. The need for winter in the switch to flowering. Annu.

Rev. Genet. 37(1):371-392.

Herison, C., Masabni, J. G. and Zandstra,B. H., 1993. Increasing seedling density, age and nitrogen

fertilization increase onion yield. Hort. Sci. 28:23-25.

Hiray, S. A., 2001. Effect of nitrogen levels, spacing and planting dates on the growth, yield and quality

of onion bulbs (Allium cepa L.) cv. N-53 under heavy rainfall zone – I under South Gujarat

condition. M. Sc. (Agri.) Thesis, Submitted to Gujarat Agricultural University,

Sardarkrushinagar.

Hodges, T. and Ritchie, J. T. The Ceres-Wheat phenology model. In: Hodges, T. Predicting crop

phenology. Boston: CRC Press, 1991. Cap. 12: 133-141.

106

Holdsworth, M., and Heath, O. V. S., 1950. Studies in the Physiology of the Onion Plant: IV. The

influence of day-length and temperature on the flowering of the onion plant J. Exp. Bot. 1 (3):

353-375 doi:10.1093/jxb/1.3.353

Huang, Z., Liu, S., Zhang, Z., Chen, Y., Zhang, Y. and Ma, L., 2011. Effect of Prolonged Photoperiod

on Bolting of Garlic [J]. ActaAgriculturae Boreali-Occidentalis Sinica. 9:021.

Hyun, D. Y., Kim, O. T., Bang, K. H., Kim,Y. C., Yoo, N. H., Kim, C. W. and Lee, J. H., 2009. Genetic

and molecular studies for regulation of bolting time of onion (Allium cepa L.). J. of Plant Biol,

52(6): 602-608.

Ibrahim, N. D., 2010. Growth and yield of Onion (Allium cepa L.) in Sokoto, Nigeria. Agric. Biol. J. N.

Am., 1(4): 556-564.

Ijoyah, M. O., Rakotomavo, H. and Naiken, M.V., 2009. Yield Performance of Four Onion (Allium

Cepa L.) Varieties Compared with the Local Variety under Open Field Conditions at Anse

Boileau, Seychelles. J. Sci. and Technol. (Ghana), 28(3): 28-33.

Islam, M. J., 1981. An investigation into the effect of date of planting and age of seedling for a late crop

of onion. M.Sc. Diss., Dept. of Horticulture, Univ. of Mymensingh, Mymensingh, Bangladesh.

Islam, M. K., Alam, M. F., and Islam, A. K. M. R., 2007. Growth and yield response of onion (Allium

cepa L.) genotypes to different levels of fertilizers. Bangladesh J. Bot. 36(1):33-38.

Jahromi. A. A., Amirzadeh, S. R., 2015. Production potential of onion (Allium cepa.L) as influenced by

different transplant age. Ind. J. Fundam. Appl. life Sci. 5 (2) 118-121.

Jianjun, H. W. H. X. W., Yu, C., 2003. Effects of different sowing dates and post-winter field planting

on growth and yield of onion (Allium cepa L.) [J]. Acta Agriculturae Shanghai, 4: 014.

Jilani, M. S., and Ghafoor, A. 2003.Screening of local varieties of onion for bulb formation. Int. J. Agric.

and Biol, 5(2) 129-133

Jilani, M. S., 2004. Studies on the management strategies for bulb and seed production of different

cultivars of onion (Allium cepaL.). Ph.D. Thesis, p.91 Gomal University, Dera Ismail Khan.

Pakistan.

Jilani, M. S. Ghafoor., A., Waseem, K. and Farooq, J. I., 2004. Effect of different level of nitrogen on

growth and yield of three onion varieties. Int. J. Agric. Biol., 6(3):507-510.

Jilani, M.S., Khan, M. Q. and Rahman, S., 2009. Planting densities effect on yield and yield components

of onion (Allium cepa L.). J. Agri. Res. 47(4).

107

Jorjandi, M., Bonjar,G. H. S., Baghizadeh, A., Sirchi, G. R. S., Massumi, H., Baniasadi, F., Aghighi, S.

and Farokhi, P. R., 2009. Biocontrol of Botrytis allii Munn the causal agent of neck rot, the

postharvest disease in onion, by use of a new Iranian isolate of Streptomyces. Am. J. Agric. Biol.

Sci. 4:72-78.

Kandil, A. A., Sharief, A. E. and Fathalla, F. H., 2013. Effect of transplanting dates of some onion

cultivars on vegetative growth, bulb yield and its quality. ESci, J. Crop Prod. 2(3):72-82.

Kanton, A. L., Abbey, L., Hilla,R.G., Tabil, M. A., Jan, N. D., 2002. Density affects plant development

and yield of bulb onion (Allium cepa L.) in northern Ghana. J. Veg. Crop Prod. 8:15-25.

Kanton. R. A. L, Abbey, L., Hilla,R. G., Tabil, M. A. and Jan, N. D., 2003. Influence of Transplanting

Age on Bulb Yield and Yield Components of Onion (Allium cepa L.), J. Veg. Crop Prod., 8(2):

27-37

Karadeniz, F., Burdurlu, H. S., Koca, N. and Soyer, Y., 2005. Antioxidant activity of selected fruits and

vegetables grown in Turkey. Turk. J. Agric. For. 29: 297-303.

Khan, S. A., Amjad, M., and Khan, A. A., 2001. The extent of inbreeding depression in seven cultivars

of onion (Allium cepa L.). Int. J. Agric. Biol. 3:498-500

Khoda Dadi, M., 2009. Evaluation and comparison of yield, photoperiodic reaction and growth degree

day’s requirement for bulbing in important local population onion. agris.fao.org

Khokhar, K. M., 2014. Flowering and Seed Development in Onion—A Review. Open Access Library

Journal, 1: e1049. http://dx.doi.org/10.4236/oalib.1101049

Khokhar, K. M., Hadley, P., Pearson, S., 2007a. Effect of cold temperature durations of onion sets in

store on the incidence of bolting, bulbing and seed yield. Sci. Hortic. 112:16-22 ISSN: 0304-

4238 DOI: 10.1016/j.scienta.12.038. Elsevier Science

Khokhar, K. M.., Hadley, P., Pearson, S., 2007b. Effect of photoperiod and temperature on inflorescence

appearance and subsequent development towards flowering in onion raised from sets. Scientia

Horticulturae. 112 (1): 9–15.

Khokhar, K. M., Hadley, P., Pearson, S., 2009. Effect of set-size and storage temperature on bolting,

bulbing and seed yield in two onion cultivars. Scientia Horticulturae. 2: 187–194

Khokhar, K. M., 2008. Effect of temperature and photoperiod on the incidence of bulbing and bolting

in seedlings of onion cultivars of diverse origin. J. Hort. Sci. Biotechnology. 83 (4) 488–496

108

Kimani, P. M., Peters, R., Rabinowitch, H. D., 1994. Potential of onion seed production in a tropical

environment. Acta Horticulturae, Wageningen. 358(1): 341-348.

Kolota, E., Adamczewska-Sowinska, K. and Uklanska-Pusz, C., 2013. Response of Japanese bunching

onion (Allium fistulosum L.) to nitrogen fertilization. Acta Sci. Pol. Hortorum Cultus, 12(2):51-

61.

Krontal, Y., Kamenetsky, R. and Rabinowitch, H. D., 2000. Flowering physiology and some vegetative

traits of short-day shallot: a comparison with bulb onion. The J. of Hort. Sci.Biotech, 75 (1):35-

41.

Kumar, H., Singh, J.,V., Kumar, A. and Singh, M., 1998. Influence of time of transplanting on growth

and yield of onion (Allium cepa L) Cv ‘Patna red'. Indian J. of Agric.Res, 32(1), pp.6-10.

Lancaster, J. E., McCartney, E. P., Jermyn, W. A. and Johnstone, J.V., 1995. Identification of onion

cultivars for commercial production in Canterbury New Zealand. New Zealand J.Crop Hort.

Sci. 23(3) 299-306.

Lei, L., Shiqi, L., Li, X., Liandong, Q. and Yunqi, Z., 2006. Studies on the Difference of Bolting and

Unbolting Onions on the Physiological and Biochemical Characteristics [J]. Chinese

Agricultural Science Bulletin, 1:040.

Leskovar, D. I. and Vavrina, C. S., 1999. Onion growth and yield are influenced by transplant tray cell

size and age. Scientia Horticulturae, 80(3):133-143.

Lujan-Favela, M., 1992. Growth and productivity of onions sown and transplanted at different dates,

ages and sizes. Revista-Fitotecia-Mexicana 15(l):51-60 (Spanish).

Madisa, M. E., 1994. The effect of planting date set size and spacing on the yield of onion (Allium cepa

L.) in Botswana. Acta Hort., 358: 353-357.

Mahanthesh, B., Sajjan, M. R. P., Thippesha, D., Harshavardhan, M. and Janardhan, G., 2008. Studies

on multiple correlation between bulb yield, growth and yield attributes in different genotypes of

onion (Allium cepa L.) under irrigated conditions. Res. Crops. 9(1): 90-93.

Maier, N. A., Dahlenburg, A. P. and Twigden, T. K., 1990. Effect of nitrogen on the yield and quality

of irrigated onions (Allium cepa L.) cv. Cream Gold grown on siliceous sands. Animal Prod.

Sci., 30 (6), pp.845-851.

Mallor, C., Carravedo, M., Estopañan, G. and Mallor, F., 2011. Characterization of genetic resources of

onion (Allium cepa L.) from the Spanish secondary Centre of diversity. Spanish J. Agri. Res.

2011 9(1): 144-155.

109

McCallum, J. A., Grant, D. G., McCartney, E. P., Scheffer, J., Shaw, M. L. and R. Butler, C., 2001.

Genotypic and environmental variation in bulb composition of New Zealand adapted onion

(Allium cepa) germplasm, New Zealand J. Crop and Hort. Sci., 29(3): 149-158, DOI:

10.1080/01140671.2001.9514173.

McCollum, G. D., 1976. Onion and allies, Allium (Liliaceae). In Evolution of Crop Plants, ed. N.W.

Simmonds, Longman Press, pp. 186-190.

Mehri, S., Forodi, B. R. and Abdol-Karim K., 2015. Influence of Planting Date on Some Morphological

Characteristic and Seed Production in Onion (Allium cepa L.) Cultivars. Agri. Sci. Develop. 4

(2).

Merrill, D. C., 2009. Development of a Colorimetric Test Kit to Determine Enzymatically Produced

Pyruvic Acid in Sweet Onions. A thesis submitted to Oregon State University for Bachelor of

Science.

Mettananda, K. A. and Fordham, R., 1999. Effects of plant size and leaf number on the bulbing of

tropical short-day onion cultivars (Allium cepa L.) under controlled environments in the United

Kingdom and tropical field conditions in Sri Lanka. J.Hort. Sci.& Biotech, 74(5): 622-631

Milec, Z., Valárik,M., Bartoš, J. and Šafář, J., 2014. Can a late bloomer become an early bird? Tools for

flowering time adjustment. Biotechnol. adv., 32(1): 200-214.

Mohammadi, J., Lamei, J., Khasmakhi-Sabet, A., Olfati, J. A. and Peyvast, G., 2010. Effect of irrigation

methods and transplant size on onion cultivars yield and quality. J. Food, Agri. Environ,

8(1):158-160.

Mohanty, B.K., 2001. Genetic variability, inter-relationship and path analysis in onion. J. Trop. Agri.

39(1):17-20.

Mohanty, B. K., Barik, J. and Dora, D. K., 1990. Effect of time of transplanting and age of seedlings on

yield of onion (Allium cepa L.). Onion Nswl. Tropics.7:41-43.

Mondal, M. F., Brewster,J. L.,Morris, G. E. L. and Butler, H. A., 1986. Bulb development in onion

(Allium cepa L.). III. Effects of the size of adjacent plants, shading by neutral and leaf filters,

irrigation and nitrogen regime and the relationship between the red: far-red spectral ration in the

canopy and leaf area index. Ann. Bot. 58: 207-219.

Mosleh, M. D. and Deen, U. D. 2008. Effect of mother bulb size and planting time on growth, bulb and

seed yield of onion. Bangladesh J. Agric. Res., 33(3): 531-537.

110

Moursi, M. A., El Habbasha, K. M., Nour El Din, N. A. 1975. Effect of sowing date and seed rate on

the growth and yield of direct sown onion (Allium cepa L.) plants. Egyptian J. Hort.

Muhammad, T., Amjad, M., Hayat, S., Ahmad, H. and Ahmed, S. 2016. Influence of nursery sowing

dates, seedling age and nitrogen levels on bulb quality and marketable yield of onion (Allium

cepa L.). Pure Appl. Biol, 5(2): 223-233, June 2016

Mushtaq, S., Amjad, M., Ziaf, K., Cheema, K. L., Raza, M. A. and Hafeez, O. B. A., 2013. Productive

and qualitative evaluation of onion cultivars under agro-climatic conditions of Faisalabad. Pak.

J. Agri. Sci. 50(2):199-203.

Msuya, D. G., Reuben, S. O. W. M., Mbilinyi, L. B., Maerere, A. P., Msogoya, T., Mulungu, L. S. and

Misangu, R. N., 2005. Evaluation of field performance and storage some tropical short-day

onion (Allium cepa L.) cultivars. W. Afr. J. Ecol. 8: 10-18.

Nasreen, S., Haque, M. M., Hossain, M. A. and Farid, A.T. M., 2007. Nutrient uptake and yield as

influenced by nitrogen and Sulphur fertilization. Bangladesh J. Agric. Res., 32(3) 413-420.

Naz, S. and Amjad, M., 2004. Production potential of diverse onion genotypes raised through sets. Pak.

J. Agri. Sci. 41:141-143.

NeSmith, D. S., 1993. Transplant age influences summer squash growth and yield. Hort Science.

28:618-620.

Ngullie, E., Singh,V. B., Singh, A. K. and Singh, H., 2011. Fertilizing for Sustainable Onion Production

Systems. BETTER CROPS, p.10.

Norman, J.C., 1992. Tropical Vegetable Crops. 2nd ed. Stock well London, UK.

Okporie, E.O. and Ekp, I. I., 2008. Effect of photoperiod on the growth and bulbing of two tropical

onion (Allium cepa L.) varieties. W. J. Agric. Sci. 4, 36-39.

Oladiran, J. A. and Sangodele, S. E., 1996. Effect of cultivars and age of transplant on the bulb yield of

onion (Allium cepa L.). Onion Nswl. Tropics. 7:41-43.

Pakistan Economic Survey, 2017-18. Ministry of Finance, Economic advisor’s Wing, Islamabad,

Pakistan.

Pandey, U. C., Epko, U., 1991. Responce of nitrogen on growth and yield of onion (Allium cepa L.) in

Maiduguri region of Borno State, Nigeria. Res. Dev. Reporter, 8(1):5-9.

111

Pandy, V. B., Qadri, S. M. H., Chongule, A. B. and Tripathi, B. P., 1992. The effect of time of sowing

on yield and quality of small onion (Allium cepa L.). Newsletter Associated Agricultural

Development Foundation 12: 1-2.

Pareek, S., Sagar,N., Sharma, S., Yada, V., 2017. Onion ( Allium cepa L.): Chemistry and

human health, 2nd Edition. 10.1002/9781119158042.ch58.

Patel, I. J., Patel, A.T., 1990. Effect nitrogen and phosphorus level on growth and yield of onion (Allium

cepa L.) cultivar Pusa Red. Res. Gujrat. Agric. Univ., 15:1-5.

Patel, Z. G., Vachhani, M.U., 1994. Effect of NPK fertilization on the yield and quality of onion. Hort.

J., 7(1) 75-77.

Patel, N., and Rajput, T. B. S., 2009. Effect of subsurface drip irrigation on onion yield. Irrigation

science, 27(2). 97-108.

Pathak, C. S., 2000. Hybrid Seed Production in Onion, J. New Seeds, 1:3-4, 89-108, DOI:

10.1300/J153v01n03_04

Patil, D. G.; Dhake, A.V., Sane, P.V. andSubramaniam, V.R., 2012. Studies on different genotypes and

transplanting dates on bulb yield of high solid white onion (Allium cepa L.) under short-day

conditions. Acta Hort., 969: 143-148.

Peters, R., 1990. Seed Production in Onions and Some Other Allium Species. In: Rabinowitch, H. D.

and Brewster, J.L. (Eds.), Onions and Allied Crops. Botany, Physiology and Genetics, CRC

Press, Boca Raton.1: 161-176.

Peters, R. J., Kowithayakorn,T., Chalard, T.and Rabinowitch, H.D., 1994. The effect of date of harvest

on shelf life of onions stored by hanging from leaves. Acta Hort. 358, 365-368.

Peterson, D. R., 1984. Influence of nitrogen and phosphorus fertilizer on respiration rate, premature

seedstalk formation and yield of yellow granex onion. J. Rio. Grande.Valley Hort. Soc., 37:33-

41

Piñeiro, M., Gómez-Mena, C., Schaffer, R., Martínez-Zapater, J. M. and Coupland, G., 2003. Early

Bolting In Short Days Is Related to Chromatin Remodeling Factors and Regulates Flowering in

Arabidopsis by Repressing FT. The Plant Cell, Vol. 15, 1552–1562, July 2003,

www.plantcell.org © 2003 American Society of Plant Biologists.

Pinthus, M. J., Triticum. In: HALEY, H. C. CRC Handbook of flowering. Volume IV. Boca Raton:

CRC Press, 1985. p. 418- 443.

112

Qasem, J. R., 2006. Response of onion (Allium cepa L.) plants to fertilizers, weed competition duration,

and planting times in the central Jordan Valley. Weed Biology and Management, 6(4):212-220.

Rabinowitch, H. D., 1990. Physiology of Flowering.pp.113-134. In. H. D. Rabinowitch and J. L.

Brewester (ed.,). Onion and Allied Crops. CRC press. Boca Ranton, Florida, USA.

Rabinowitch, H. D., 1985. Onions and other edible Alliums. In: HALEY, H.C. CRC Handbook of

flowering. Volume I. Boca Raton: CRC Press, p. 398-409.

Rafique, E., Mahmood-ul-Hassan, M., Khokhar, K. M., Nabi, G. and Tabassam, T., 2008. Zinc nutrition

of onion: Proposed diagnostic criteria. J. of plant nutr. 31(2):307-316.

Rahman, A.K. M. M. and Das, M. K., 1985. Correlation and path analysis in garlic. Bangladesh J. Agric.

Res., 10 (1): 50-54.

Rahman, M. A., Saha,S. R., Salam, M. A., Masum, A. S. M. H. and Chowdhury, S. S., 2002. Correlation

and path coefficient Analysis in onion (Allium cepa L.). Online J. Biologic Sci. 2 (8): 533-534

Rana, M. K. and Hore, J. K., 2015.Onion. In: Technology for vegetable production. Rana, M.K.,

(ed.,)Kalyani publishers, New Delhi, India

Randle, W.M. and Ketter, C. A., 1998. Pungency assessment in onions. In Proceedings of the 19

workshop conference of the Association for Biology Laboratory Education(ABLE). pp (pp.

177-196).

Randle, W. M. and Bussard, M. L., 1993. Pungency and sugars of short-day onions as affected by sulfur

nutrition. J. Amer. Soc. Hort. Sci., 118(6):766-770.

Randle, W. M., 2000.increasing nitrogen concentration in hydroponic solution affects onion flavor and

bulb quality. J. Amer. Soc. Hort. Sci., 125: 254-259.

Report of a Joint FAO/WHO Expert Consultation. Geneva, World Health Organization, 2003 (WHO

Technical Report Series, No. 916).

Resende, G. M. D. and Costa, N. D., 2014. Effects of levels of potassium and nitrogen on yields and

post-harvest conservation of onions in winter. Revista Ceres, 61(4): 572-577.

Rice, R. P., Rice, L.W., Tindall, H. D., 1993. Fruit and vegetable production in warm climate. The

Macmillan press Ltd. London and Basingstoke.

Ritchie, J. T., 1991. Modeling Plant and Soil Systems. Madison: ASA, CSSA, and SSSA. Cap. 3, p. 31-

54.

113

Roberts, E. H., Summerfield, R. J., Ellis, R. H., Craufurd, P.Q. and Wheeler, T. R.,. 1997. The induction

of flowering. p. 69-99.In: H.C. Wien (ed.) The Physiology of vegetable crops. CAB Intl. Ithaca,

N.Y.

Saeed, I. and Nasir, M., 2001. Onion Seed Production and Marketing in Malalkand Division: Division:

Opportunities and Constraints of Certified Growers. Directorate of Agribusiness Relations,

Social Sciences Division, Pak. Agric. Res. Council, Islamabad.

Saha, M. C., 1982. Effect of age of seedling on the two cultivars of onion. Ph.D. Diss., Dept. of

Horticulture, Univ. of Mymensingh, Mymensingh, Bangladesh.

Salik, M. R., Pervez, M. A., 2000. Relationship between ages of seedling on productivity of tomato

(Lycopersicon esculentum L.). Pak. J. Biol. Sci., (Pakistan).

Salter, P. J. 1985. Crop establishment: recent research and trends in commercial practices.

Sci.Hortcult.36:32-47.

Salter, P. J and James, J. M., 1975. The performance of Japanese and European cultivars of onion from

autumn sowing for early production. J. Natl. Inst. Agr. Bot. 13:367-379.

Sawant, S.V., Inciavale, M. T., Manciave, K. K., Wxih, B. K. and Biiat, N. R., 2002. Effect of date of

planting on growth, yield and quality of onion (allium cepa L.). Veg. Sci. 29 (2): 164-166 (2002)

Schwimmer, S. and Weston, W., 1961. Enzymatic development of pyruvic acid in onion as a measure

of pungency. J.Sci. food. chem. 9:301-304.

Seabrook, J. E. A., 2005. Light effects on the growth and morphogenesis of potato (Solanum tuberosum)

in vitro: A review. Am. J. Potato Res. 82: 353-367.

Shanmugasundaram, S. and T. Kalb., 2001. Suggested Cultural Practices for Onion." AVRDC Training

Guide, Asian Vegetable Research and Development Center, Taiwan.

Sharma, A., Chandrakar, S. and Thakur, D. K., 2015. Character association and path co-efficient

analysis in Kharif onion (Allium Cepa L.) genotypes. Intl. J. Plant Sci., 10(1), pp.70-73.

Sharma, K., Nile, S. H. and Park, S.W., 2015. Importance of growth hormones and temperature for

physiological regulation of dormancy and sprouting in onions, Food Rev. Intl. just-accepted

(2015) DOI: 10.1080/87559129.2015.1058820

Shiraiwa, N. 2008. Physiological studies on the bolting control for stable production of early summer

harvest in bunching onion (Allium fistulosum L.). Special Bulletin of the Tottori Horticultural

Experiment Station (Japan).

114

Sidhu, A. S., Bal, S. S. and Mamta Rani., 2005. Current trends in onion breeding. J. New Seeds 6 (2-3):

223-245.

Sinclair, P., 1989. Physiology of the onion. Australian Onion Grower, Vol. 6, November, 1989

Singh, T., Singh, S. B. and Singh, B. N., 1989. Effect of nitrogen, Potassium and green manuring on

growth and yield of rainy season onion (Allium cepa L.). Narenda Deva. J. Agric. Res., 4(1):57-

60.

Singh, J., Chaure, N. K., 1999. Effect of age of seedlings and nitrogen levels on growth and yield of

onion (Allium cepa L.) Advances-in-Horticulture and Forestry. 6:73-77.

Sing, R. K., Dubey, B. K., Bhonde, S. R. and Gupta, R. P., 2010. Estimate of genetic variability and

correlation in red onion (Allium cepa L.) advance lines. Ind. J. Agric. Sci. 80(2):160-163.

Singh, R. K and Bhonde, S. R., 2011. Performance studies of exotic onion (Allium cepa L.) hybrids in

the Nashik region of Maharashtra. Ind. J. Hill Farming. 24(2): 29-31.

Smith, B., 2006. The farming handbook. University of KwaZulu-Natal Press, Pietermaritzburg, South

Africa. pp. 352-353.

Sobeih, W.Y., Wright, C. J., 1986. The photoperiodic regulation of bulbing in onion (Allium cepa L.).

2. Effect of plant-age and size.J. Hortic. Sci.61(3):337-342

Sorensen, J. N., and Grevsen, K., 2001. Sprouting in bulb onion (Allium cepa L.) as influenced by

nitrogen and water stress. J. Hort. Sci. Biotech., 76:501-506.

Streck, N. A., 2003. A Vernalization model in onion (Allium cepa L). R. bras. Agrociência. 9(2): 99-

105.

Sung. S., and Amasino, R. M., 2004. Vernalization and epigenetics: how plants remember. Curr. Opin.

Plant. Biol. 2004, 7 (1):4–10.www.Sciencedirect.com.

Tabor, G., Stuetzel, H. and Zelleke, A., 2006. Influence of planting material and duration of bulb

Vernalization on bolting of shallot (Allium cepa L. var. ascalonicum Backer). J. Hort.

Sci.&biotech. 81(5):797-802.

Tabor. G., Stuetzel, H. and Zelleke, A., 2005. Juvenility and bolting in shallot (Allium cepa L. var.

ascalonicum Backer). J. Hort. Sci. and Biotech. 80 (6):751-759

Tekalign, T., Abdissa, Y. and Pant, L. M., 2012. Growth bulb yield and quality of onion (Allium cepa

L.) as influenced by nitrogen phosphorus fertilization on vertisol. II: bulb quality and storability.

Afr. J. Agric. Res. 7(45): 5980-5985.

115

Tendaj, M. and Mysiak, B., 2013. The effect of summer seedling planting dates on the development of

seed stalks in shallot (Allium cepa L. var. ascalonicum Backer). Acta Sci. Pol., Hortorum Cultus,

12(6).57-66.

Tesfay, S. Z., Bertling, I., Odindo, A. O., Greenfield, P. L. and Workneh, T. S., 2011. Growth responses

of tropical onion cultivars to photoperiod and temperature based on growing degree days. Afr.

J. Biotechnol. 10(71): 15875-15882.

Vachhani, M.U. and Patel, Z.G., 1988. Studies on growth and yield of onion as affected by seedling age

at transplanting.Progressive Hort.20(3-4):279-289

Vachhani, M. U. and Patel Z. G., 1989. Effect of age of seedling on yield of bulb onion.Indian. J.

Agron.34:433-434.

Vachhani, M. U. and Patel, Z. G., 1993a. Growth and yield of onion (Allium cepa L.) as influenced by

level of nitrogen, phosphorus and Potash under south Gujrat condition.Progressive

Hort.25(3):166-167

Vachhani, M. U. and Patel, Z. G., 1993b. Effect of nitrogen, phosphorus and Potash on bulb yield and

quality of onion (Allium cepa L.).Indian. J. Agron. 3:333-334.

Van Den Berg, A. A., De Wet, H. and Coertze, A. F., 1997. Onion cultivars. Onions C.1. Agricultural

Research Council, Vegetable and Ornamental Plant Institute, Pretoria, South Africa: 1-2.

Vavilov, N. I., 1951. The origin, variation, and immunity and breeding of cultivated plants. Chron. Bot.

13: 1-6

Vavrina, C. S., 2002. Transplant age in vegetable crop. Hort. Technology, 8(4) 550-555.

Vianney, M.T.W., Albert, R. and Zoumbiessé, T., 2011. Effects of Seasons of Bulb and Seed Production

on the Early Bolting of Onion (Allium cepa L.) cv. Violet de Galmi. J. Appl. Biosci., (40): 2652-

2658.

Voss, R. E., Murray, M., Mayberry, K.S. and Miller, I., 1999. Onion seed production in California.

University of California, Division of Agriculture and Natural Resources. California. United

States of America.

Wang, C., Zhang, T., and Wu, S., 2002. Study on the method screening for bolting resistance in spring

cabbages. J. Northeast Agric. Uni., 34(2):129-132.

Wang. E.; Engel, T., 1998. Simulation of phenological development of wheat crops. Agric. Syst.

Amsterdam.58 (1): 1-24.

116

Wickramasinghe, U. L., Wright, C.J. and Currah, L., 2000. Bulbing responses of two cultivars of red

tropical onions to photoperiod, light integral and temperature under controlled growth

conditions. J. Hort. Sci. Biotechnol. 75:304-311.

Wiebe, H. J., 1994. Effects of temperature and daylength on bolting of leek (Allium porrum L.).Scientia

Horticulturae. 59(3–4):177–185

Wien, H. C., 1997.Transplanting, pp. 37-67.In: H.C. Wein (ed.). The Physiology of Vegetable Crops.

CAB. International, Wallingford, England.

Wiles, G. C., 1989. The effect of light and temperature on bulb initiation and development in tropical

cultivars of onion (Allium cepa L.). Ph.D. thesis, Wye College University of London, London.

Wiles, G. C., 1994. The effect of different photoperiods and temperatures following bulb initiation on

bulb development in tropical onion cultivars. Acta Hort. 358: 419-427.

Wright, P.J. and Grant, D.G., 1997. Effects of cultural practices at harvest on onion bulb quality and

incidence of rots in storage. N. Z. J. Crop Hort. Sci. 25: 353-358.

WU, X.H. and GAO, J., 2013. Research into the Change Rule about Soluble Sugar and Soluble Protein

of the Bolting Onions and the Normal Ones by Means of Vernalization [J]. Xinjiang Agric. Sci.,

2:021.

Yadav, R. L., Sen, N. L. and Yadav, B. L., 2003. Response of onion to nitrogen and Potassium

fertilization under semi-arid condition. Indian. J. Hort., 60(2) 176-178.

Yamasaki, A., Miura, H., and Tanaka, K., 2000. Effect of photoperiods before, during and after

Vernalization on flower initiation and development and its varietal difference in Japanese

bunching onion (Allium fistulosum L.). The J.Hort. Sci.Biotech.75 (6): 645-650

Yamasaki, A, Tanaka, K., 2005. Effect of nitrogen on bolting of bunching onion (Allium fistulosum L).

Hort. Res. (Japan), 4(1): 51-54.

Yan, W., and Hunt, L. A., 1999. Reanalysis of Vernalization data of wheat and carrot. Annals of Botany,

London. 84 (5): 615-619.

Yang, J., Meyers, K. J., Heide, J. V.D. and Liu, R. H, 2004. Varietal differences in phenolic contents

and antioxidant and anti-proliferative activities of onion. J. Agric. Food Chem. 52: 6787-6793.

Yohannes, K.W., Belew, D. and Debela, A., 2013. Effect of farm yard manure and nitrogen fertilizer

on growth, yield and yield component of onion (Allium cepa L.) at Jimma southwest Ethopia.

Asian Journal of Plant Sciences, 12(6): 228

117

Zhang, L.G., Kong, X. P., Hu, I. and Zhang, M. K., 2008. The low temperature, light and seedling age

requirement for seedling Vernalization in Chinese cabbage. Acta Hort. Sin, 35:1676-1680.

Zheng, J., Huang, G., Wang,J., Huang,Q., Pereira, L.S, Xu, X.and Liu, H., 2013. Effects of water deficits

on growth, yield and water productivity of drip-irrigated onion (Allium cepa L.) in an arid region

of Northwest China. Irrigation Science, 31(5): 995-1008.

118

APPENDICES

Experiment wise ANOVA tables are given below:

Experiment 1: Effects of Sowing dates and seedling age on premature bolting in onion bulb crop.

Appendix 1.1 Analysis of Variance Plant Height.

Source DF SS MS F P

Year 1 87.75 87.754 2.53 ns

Error Year*Rep 4 138.59 34.647

DOS 4 251.77 62.944 9.06 *

AOS 2 232.43 116.216 16.72 *

DOS*AOS 8 2.03 0.254 0.04 ns

Year*DOS 4 5.69 1.423 0.20 ns

Year*AOS 2 59.42 29.712 4.27 ns

Year*DOS*AOS 8 5.92 0.739 0.11 ns

Error Year*Rep*DOS*AOS 56 389.22 6.950

Total 89 1172.83

CV (Year*Rep) 10.51,

CV (Year*Rep*DOS*AOS) 4.71

Appendix 1.2 Analysis of Variance Table for Number of leaves at bolting stage

Source DF SS MS F P

Year 1 0.069 0.0694 0.26 Ns


DOS 4 46.767 11.6917 24.27 *

AOS 2 46.439 23.2194 48.19 *

DOS*AOS 8 1.200 0.1500 0.31 ns

Year*DOS 4 0.153 0.0382 0.08 ns

Year*AOS 2 0.622 0.3111 0.65 ns

Year*DOS*A

OS

8 1.781 0.2226 0.46 ns

Error

Year*Rep*DO

S*AOS

56 26.981 0.4818

Total 89 125.072

CV (Year*Rep) 7.20,


119

Appendix 1.3 Analysis of Variance Table for Leaf Area.

Source DF SS MS F P

Year 1 146.23 146.230 1.37 ns

Error Year*Rep 4 426.75 106.688

DOS 4 2555.54 638.885 12.58 *

AOS 2 128.56 64.280 1.27 ns

DOS*AOS 8 114.53 14.316 0.28 ns

Year*DOS 4 442.76 110.689 2.18 ns

Year*AOS 2 158.05 79.024 1.56 ns

Year*DOS*AOS 8 179.74 22.467 0.44 ns

Error

Year*Rep*DOS*AOS

56 2843.55 50.778

Total 89 6995.71

CV (Year*Rep) 14.17,


Appendix 1.4 Analysis of Variance Table for Bulb Diameter.

Source DF SS MS F P

Year 1 0.0903 0.0903 0.32 ns


DOS 4 65.9449 16.4862 79.18 *

AOS 2 7.9075 3.9538 18.99 *

DOS*AOS 8 2.4875 0.3109 1.49 ns

Year*DOS 4 0.5223 0.1306 0.63 ns

Year*AOS 2 0.3093 0.1547 0.74 ns

Year*DOS*AOS 8 0.7348 0.0919 0.44 ns

Error

Year*Rep*DOS*A

OS

56 11.6594 0.2082

Total 89 90.7965

CV (Year*Rep) 9.04


120

Appendix 1.5 Analysis of Variance Table for Days to Physiological Maturity.

Source DF SS MS F P

Year 1 33.6 33.61 0.93 ns


DOS 4 10416.1 2604.02 98.70 *

AOS 2 70.2 35.10 1.33 ns

DOS*AOS 8 79.5 9.93 0.38 ns

Year*DOS 4 116.6 29.14 1.10 ns

Year*AOS 2 48.8 24.41 0.93 ns

Year*DOS*AOS 8 106.2 13.27 0.50 ns

Error

Year*Rep*DOS*AOS

56 1477.5 26.38

Total 89 12492.9

CV (Year*Rep) 3.61


Appendix 1.6 Analysis of Variance Table for Stem thickness.

Source DF SS MS F P

Year 1 0.053 0.0532 0.07 ns


DOS 4 41.029 10.2573 10.60 *

AOS 2 15.234 7.6168 7.87 *

DOS*AOS 8 8.666 1.0833 1.12 ns

Year*DOS 4 0.047 0.0117 0.01 ns

Year*AOS 2 0.001 0.0004 0.00 ns

Year*DOS*AOS 8 0.038 0.0048 0.00 ns

Error

Year*Rep*DOS*AOS

56 54.186 0.9676

Total 89 122.288

CV (Year*Rep) 5.31


121

Appendix 1.7 Analysis of Variance Table for Bolting Percentage.

Source DF SS MS F P

Year 1 5.2 5.23 0.23 ns


DOS 4 12799.2 3199.81 234.30 ns

AOS 2 11540.4 5770.19 422.51 *

DOS*AOS 8 6542.5 817.82 59.88 *

Year*DOS 4 23.6 5.91 0.43 ns

Year*AOS 2 80.5 40.27 2.95 ns

Year*DOS*AOS 8 161.3 20.16 1.48 ns

Error

Year*Rep*DOS*AOS

56 764.8 13.66

Total 89 32007.6

CV (Year*Rep) 31.41


Appendix 1.8 Analysis of Variance Table for yield ton ha-1.

Source DF SS MS F P

Year 1 100.28 100.28 1.38 ns


DOS 4 7552.17 1888.04 189.08 *

AOS 2 303.23 151.61 15.18 *

DOS*AOS 8 93.43 11.68 1.17 ns

Year*DOS 4 50.33 12.58 1.26 ns

Year*AOS 2 8.72 4.36 0.44 ns

Year*DOS*AOS 8 69.00 8.63 0.86 ns

Error

Year*Rep*DOS*AOS

56 559.20 9.99

Total 89 9027.94

CV (Year*Rep) 28.42


122

Appendix 1.12 Analysis of Variance Table for Cull Per ha.

Source DF SS MS F P

Year 1 1.38 1.375 0.22 ns


DOS 4 1360.38 340.095 220.19 *

AOS 2 374.16 187.080 121.12 *

DOS*AOS 8 258.56 32.321 20.93 *

Year*DOS 4 15.45 3.863 2.50 ns

Year*AOS 2 3.59 1.797 1.16 ns

Year*DOS*AOS 8 12.16 1.520 0.98 ns

Error

Year*Rep*DOS*AOS

56 86.49 1.545

Total 89 2137.24

CV (Year*Rep) 52.11


Appendix 1.13 Analysis of Variance Table for Marketable Yield ton ha-1.

Source DF SS MS F P

Year 1 64.99 64.994 2.22 ns


DOS 4 1966.68 491.670 74.03 *

AOS 2 459.07 229.534 34.56 *

DOS*AOS 8 337.18 42.148 6.35 *

Year*DOS 4 6.03 1.508 0.23 ns

Year*AOS 2 8.66 4.329 0.65 ns

Year*DOS*AOS 8 78.07 9.759 1.47 ns

Error

Year*Rep*DOS*AOS

56 371.94 6.642

Total 89 3409.60

CV (Year*Rep) 22.96


123

Experiment 2: Bolting in onion bulb crop as influenced by Cultivars and transplanting dates

Appendix 2.1 Analysis of Variance Table for Plant Height.

Source DF SS MS F P

Year 1 326.04 326.04 8.19 *


VAR 2 2427.16 1213.58 223.89 *

DOS 4 382.87 95.72 17.66 *

VAR*DOS 8 22.18 2.77 0.51 ns

Year*VAR 2 6.51 3.25 0.60 ns

Year*DOS 4 40.54 10.14 1.87 ns

Year*VAR*DOS 8 21.24 2.66 0.49 ns

Error

Year*Rep*VAR*DOS

56 303.55 5.42

Total 89 3689.33

CV (Year*Rep) 10.83

CV (Year*Rep*VAR*DOS) 4.00

Appendix 2.2 Analysis of Variance Table for Number of Leaves Plant-1.

Source DF SS MS F P

Year 1 10.0668 10.0668 8.87 *


VAR 2 25.0642 12.5321 48.40 *

DOS 4 32.4084 8.1021 31.29 *

VAR*DOS 8 1.7069 0.2134 0.82 ns

Year*VAR 2 0.3496 0.1748 0.68 ns

Year*DOS 4 1.8093 0.4523 1.75 ns

Year*VAR*DOS 8 0.2927 0.0366 0.14 ns

Error

Year*Rep*VAR*DOS

56 14.4996 0.2589

Total 89 90.7379

CV (Year*Rep) 10.63


124

Appendix 2.4 Analysis of Variance Table for Days to Physical Maturity.

Source DF SS MS F P

Year 1 518.40 518.400 6.75 ns


VAR 2 1974.96 987.478 296.81 *

DOS 4 1309.07 327.267 98.37 *

VAR*DOS 8 20.60 2.575 0.77 ns

Year*VAR 2 20.07 10.033 3.02 ns

Year*DOS 4 8.49 2.122 0.64 ns

Year*VAR*DOS 8 13.71 1.714 0.52 ns

Error

Year*Rep*VAR*DOS

56 186.31 3.327

Total 89 4358.62

Grand Mean 162.76, CV (Year*Rep) 5.38, CV (Year*Rep*VAR*DOS) 1.12

Appendix 2.5 Analysis of Variance Table for Days to bolting initiation.

Source DF SS MS F P

Year 1 490 490.0 16.11 *

Error Year*Rep 4 122 30.4

VAR 2 6321 3160.6 329.20 *

DOS 4 274228 68557.0 7140.76 *

VAR*DOS 8 4404 550.5 57.34 *

Year*VAR 2 3 1.7 0.18 ns

Year*DOS 4 332 83.0 8.65 *

Year*VAR*DOS 8 178 22.2 2.31 *

Error

Year*Rep*VAR*DOS

56 538 9.6

Total 89 286616

Grand Mean 67.512,

CV (Year*Rep) 8.17,


125

Appendix 2.6 Analysis of Variance Table for Stem thickness.

Source D

F

SS MS F P

Year 1 8.513 8.5131 15.64 *


VAR 2 8.515 4.2574 15.68 *

DOS 4 98.863 24.7157 91.05 *

VAR*DOS 8 2.066 0.2582 0.95 ns

Year*VAR 2 0.405 0.2024 0.75 ns

Year*DOS 4 1.042 0.2606 0.96 ns

Year*VAR*DOS 8 0.961 0.1202 0.44 ns

Error

Year*Rep*VAR*DOS

56 15.201 0.2714

Total 89 137.744

CV (Year*Rep) 4.65



Source D

F

SS MS F P

Year 1 17.1 17.12 0.91 ns


VAR 2 374.4 187.21 21.93 *

DOS 4 16188.9 4047.21 474.13 *

VAR*DOS 8 393.2 49.16 5.76 *

Year*VAR 2 0.2 0.11 0.01 ns

Year*DOS 4 94.6 23.66 2.77 *

Year*VAR*DOS 8 6.6 0.83 0.10 ns

Error

Year*Rep*VAR*DOS

56 478.0 8.54

Total 89 17628.6

CV (Year*Rep) 29.91


126


Source DF SS MS F P

Year 1 198.0 198.00 0.45 ns


VAR 2 4852.8 2426.41 219.68 *

DOS 4 8353.2 2088.31 189.07 *

VAR*DOS 8 308.5 38.57 3.49 *

Year*VAR 2 10.7 5.35 0.48 ns

Year*DOS 4 19.4 4.86 0.44 ns

Year*VAR*DOS 8 41.1 5.14 0.47 ns

Error

Year*Rep*VAR*DOS

56 618.5 11.05

Total 89 16164.9

CV (Year*Rep) 41.96


Appendix 2.9 Analysis of Variance Table for Bulb Weight.

Source D

F

SS MS F P

Year 1 537.045 537.0 2.49 ns


VAR 2 125918 62959.1 740.80 *

DOS 4 53613.3 13403.3 157.71 *

VAR*DOS 8 15070.8 1883.8 22.17 *

Year*VAR 2 0.40372 0.2 0.00 ns

Year*DOS 4 35.7016 8.9 0.11 ns

Year*VAR*DOS 8 48.3554 6.0 0.07 ns

Error

Year*Rep*VAR*DOS

56 4759.34 85.0

Total 89 200846

CV (Year*Rep) 12.53


127

Appendix 2.10 Analysis of Variance Table for yield ton ha-1.

Source DF SS MS F P

Year 1 93.23 93.23 2.91 ns


VAR 2 2638.11 1319.06 248.57 *

DOS 4 1778.21 444.55 83.77 *

VAR*DOS 8 95.94 11.99 2.26 *

Year*VAR 2 3.63 1.82 0.34 ns

Year*DOS 4 56.19 14.05 2.65 ns

Year*VAR*DOS 8 17.41 2.18 0.41 ns

Error

Year*Rep*VAR*DOS

56 297.17 5.31

Total 89 5107.87

CV (Year*Rep) 22.06


Experiment 3: Flowering initiation in onion bulb crop as influenced by transplanting dates and nitrogen

fertilizer

Appendix 3.1 Analysis of Variance Table for Plant height.

Source DF SS MS F P

Year 1 597.19 597.194 8.32 *


DOS 4 183.61 45.901 16.44 *

N 3 203.70 67.902 24.32 *

DOS*N 12 20.02 1.669 0.60 ns

Year*DOS 4 3.94 0.984 0.35 ns

Year*N 3 5.30 1.767 0.63 ns

Year*DOS*N 12 13.36 1.113 0.40 ns

Error

Year*Rep*DOS*N

76 212.20 2.792

Total 119 1526.42

CV (Year*Rep) 14.29

CV (Year*Rep*DOS*N) 2.82

128

Appendix 3.2 Analysis of Variance Table for Number of Leaves Plant-1.

Source DF SS MS F P

Year 1 0.305 0.3050 0.01 ns

Error Year*Rep 4 106.475 26.6188

DOS 4 101.509 25.3773 28.64 *

N 3 13.353 4.4511 5.02 *

DOS*N 12 1.534 0.1278 0.14 ns

Year*DOS 4 0.297 0.0743 0.08 ns

Year* N 3 4.325 1.4418 1.63 ns

Year*DOS* N 12 1.858 0.1548 0.17 ns

Error Year*Rep*DOS*

N

76 67.350 0.8862

Total 119 297.006

CV (Year*Rep) 45.02


Appendix 3.3 Analysis of Variance Table for Leaf Area.

Source DF SS MS F P

Year 1 265.19 265.192 2.75 ns


DOS 4 488.90 122.225 44.01 *

N 3 208.09 69.362 24.98 *

DOS* N 12 38.93 3.244 1.17 ns

Year*DOS 4 16.17 4.041 1.46 ns

Year* N 3 20.67 6.891 2.48 ns

Year*DOS* N 12 18.64 1.553 0.56 ns

Error Year*Rep*DOS*

N

76 211.06 2.777

Total 119 1653.80

CV (Year*Rep) 14.11

CV (Year*Rep*DOS* N) 2.39

129

Appendix 3.4 Analysis of Variance Table for Stem Thickness.

Source DF SS MS F P

Year 1 29.512 29.5120 1.46 ns

Error Year*Rep 4 80.766 20.1914

DOS 4 67.946 16.9864 10.23 *

N 3 28.546 9.5154 5.73 *

DOS* N 12 1.962 0.1635 0.10 ns

Year*DOS 4 0.308 0.0769 0.05 ns

Year* N 3 8.147 2.7156 1.64 ns

Year*DOS* N 12 1.827 0.1523 0.09 ns

Error Year*Rep*DOS*

N

76 126.157 1.6600

Total 119 345.170

CV (Year*Rep) 27.23


Appendix 3.5 Analysis of Variance Table for Days to Maturity.

Source DF SS MS F P

Year 1 533.41 533.41 0.46 ns

Error Year*Rep 4 4644.33 1161.08

DOS 4 2262.03 565.51 115.22 *

N 3 1125.09 375.03 76.41 *

DOS*N 12 28.37 2.36 0.48 ns

Year*DOS 4 16.30 4.08 0.83 ns

Year* N 3 15.09 5.03 1.02 ns

Year*DOS* N 12 28.37 2.36 0.48 ns

Error Year*Rep*DOS*

N

76 373.00 4.91

Total 119 9025.99

CV (Year*Rep) 20.02


130


Source DF SS MS F P

Year 1 2249.87 2249.87 5.08 ns

Error Year*Rep 4 1772.62 443.15

DOS 4 3151.44 787.86 222.66 *

N 3 1287.83 429.28 121.32 *

DOS* N 12 29.79 2.48 0.70 ns

Year*DOS 4 10.68 2.67 0.75 ns

Year* N 3 24.61 8.20 2.32 ns

Year*DOS* N 12 35.80 2.98 0.84 ns

Error Year*Rep*DOS*

N

76 268.92 3.54

Total 119 8831.57

CV (Year*Rep) 33.05


Appendix 3.7 Analysis of Variance Table for Bulb Weight.

Source DF SS MS F P

Year 1 2133.6 2133.63 0.40 ns

Error Year*Rep 4 21602.5 5400.62

DOS 4 23287.9 5821.97 36.49 *

N 3 12631.0 4210.32 26.39 *

DOS*N 12 2340.5 195.04 1.22 ns

Year*DOS 4 862.0 215.51 1.35 ns

Year* N 3 466.3 155.43 0.97 ns

Year*DOS* N 12 2019.7 168.31 1.06 ns

Error Year*Rep*DOS*

N

76 12124.2 159.53

Total 119 77467.7

CV (Year*Rep) 39.08


131


Source DF SS MS F P

Year 1 240.8 240.8 4.05 ns


DOS 4 48738.9 12184.7 476.20 *

N 3 13168.1 4389.4 171.54 *

DOS*N 12 4867.8 405.7 15.85 *

Year*DOS 4 211.9 53.0 2.07 ns

Year* N 3 81.2 27.1 1.06 ns

Year*DOS* N 12 344.0 28.7 1.12 ns

Error Year*Rep*DOS*

N

76 1944.6 25.6

Total 119 69835.5

CV (Year*Rep) 25.52


Appendix 3.9 Analysis of Variance Table for Yield ton ha-1

Source DF SS MS F P

Year 1 200.08 200.08 1.83 ns


DOS 4 5885.99 1471.50 229.27 *

N 3 2110.13 703.38 109.59 *

DOS*N 12 53.73 4.48 0.70 ns

Year*DOS 4 6.05 1.51 0.24 ns

Year* N 3 27.74 9.25 1.44 ns

Year*DOS* N 12 16.90 1.41 0.22 ns

Error Year*Rep*DOS*

N

76 487.79 6.42

Total 119 9226.24

CV (Year*Rep) 35.08


132

Appendix 3.10 Analysis of Variance Table for Percent Cull.

Source DF SS MS F P

Year 1 170.6 170.57 0.25 ns


DOS 4 30013.2 7503.31 456.20 *

N 3 17674.1 5891.36 358.19 *

DOS*N 12 2741.6 228.47 13.89 *

Year*DOS 4 27.2 6.79 0.41 ns

Year*N 3 338.9 112.96 6.87 *

Year*DOS*N 12 108.9 9.08 0.55 ns

Error

Year*Rep*DOS*N

76 1250.0 16.45

Total 119 55021.5

CV (Year*Rep) 78.58


Appendix 3.11 Analysis of Variance Table for Marketable Yield ton ha-1.

Source DF SS MS F P

Year 1 42.64 42.64 0.20 ns


DOS 4 412.55 103.14 14.97 *

N 3 5194.66 1731.55 251.27 *

DOS*N 12 365.23 30.44 4.42 *

Year*DOS 4 6.22 1.56 0.23 ns

Year*N 3 37.84 12.61 1.83 ns

Year*DOS*N 12 20.88 1.74 0.25 ns

Error Year*Rep*DOS*N 76 523.73 6.89

Total 119 7469.08

CV (Year*Rep) 75.56


133

SELECTED PICTURES

Figure 21 Bolting problem at farmer's field in Swat

134

Figure 22 View of a field trial

Figure 23 View of field trial

135

Figure 24 The author collecting the data

Figure 25 Three seedling ages 45, 60 and 70 days used in the trial

136

Figure 26 Harvesting and collecting the data

Figure 27 Harvesting the bulbs

137

Figure 28 harvesting and collecting data

Figure 29 Weighing single bulb weight

premature bolting in onion bulb crop; effect of

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